CA1088383A - Extrusion coating method with polyolefin foam - Google Patents
Extrusion coating method with polyolefin foamInfo
- Publication number
- CA1088383A CA1088383A CA280,792A CA280792A CA1088383A CA 1088383 A CA1088383 A CA 1088383A CA 280792 A CA280792 A CA 280792A CA 1088383 A CA1088383 A CA 1088383A
- Authority
- CA
- Canada
- Prior art keywords
- foam
- coating
- core material
- hollow core
- resin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
- B29C44/32—Incorporating or moulding on preformed parts, e.g. linings, inserts or reinforcements
- B29C44/322—Incorporating or moulding on preformed parts, e.g. linings, inserts or reinforcements the preformed parts being elongated inserts, e.g. cables
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/15—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor incorporating preformed parts or layers, e.g. extrusion moulding around inserts
- B29C48/151—Coating hollow articles
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S138/00—Pipes and tubular conduits
- Y10S138/09—Cellular
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
- Y10S264/05—Use of one or more blowing agents together
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
- Y10S264/14—Plastic and nonmetallic article shaping or treating: processes forming integral skin on a foamed product
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
- Y10T428/1355—Elemental metal containing [e.g., substrate, foil, film, coating, etc.]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249987—With nonvoid component of specified composition
- Y10T428/249988—Of about the same composition as, and adjacent to, the void-containing component
- Y10T428/249989—Integrally formed skin
Abstract
ABSTRACT OF THE DISCLOSURE A procedure is disclosed for continuous extrusion coating by the use of a coating die of a hollow core material with a highly expanded polyolefin composition containing a volatile organic liquid blowing agent, the improvement comprising externally, cooling the outer surface of the extruded molten mass of expandable polyolefin resin, at the point at which the molten mass begins to foam, by by contacting the surface with a cooling gas or water to allow the pressure of foaming to be exerted inwardly and also to cause the growth of foam to proceed in the direction of the internal core for thereby enabling the poly-olefin foam to adhere fast to the hollow core and giving rise to a coating hav-ing a smooth surface condition, wherein the expanded polyolefin foam has an ex-pansion ratio of not less than 3. This thereby enhances the fastness of ad-hesion of the highly expanded polyolefin foam with the hollow core material and at the same time facilitates the release of the two materials thus joined.
Description
~ 1~88383 miS in~ention relates generally to a process for the continu-ous extxusion coating of a hollow core material with a polyolefin foam, ¦
and particularl~ to a process for the continuously extrusion coating of ~`
a hollow core material in a state ~herein such hollcw core material and a polyolefin foam e~panded to a high ratio ~ore than three times~ are joined fast with each other.
Conventional hollow core materials coated with foamed plastics enjoy thermal insulation, lightness of weight and waterprcofness. Par-ticularly pipes coated with highly expanded foams e.g. of polyethylene, polyurethane, etc. are characterized by possessing excellent the~mal insulation and the ability to peLmit practical applications without re-quiring any advanced technique or skill. Because of the advantageous properties, these pipes are extensively used for hot water systems, city water systems, air conditioning systems and fuel distribution systems in residences, hotels, hospitals, multistory buildings, and the like.
However, these highly expanded plastic foams are invariably torn open ^ along a longitu~inally inserted slit after they have been formed as if they are deposited in the form of tubes round core pipes. ~hen the core pipes are put to use in the site of installation, the torn tubes of plastic foams are closed up again tightly round the core pipes. The finishing of these coated pipes, therefore, inevitably requires the jobs of taping and coating. Moreover, these pipes have a disadvantage that they suffer from inferior field w~rkability and inefficient plumbing operation in spaces of limited di~ensions. As a measure for the con- j .; ~
- tinuous manufacture of metallic or plastic pipes and electric wires coated with foamed plastics, continuous integral coating methods are pre-; sently known whereby the core materials are coated at the same time that the plastics are extrusion foamed. According to this ~ethod, the extxu-;, .
~` sion coating with the foam of a polyolefin ha~ing low expandability can be carried out as effectively as with a non-g~panlable plastic substance, without any difficulty. Where the extrusion coating of a given core ma-texial by this method is caxried out with the foam of a poly~lefin which '~
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~ossesses an expansiQn ratio of 3 or more and suits ad~antageously to uses as a therm~l msulator, a shock absorber or a noise absorber, when the polyolein resin o~ntaining a volatile foaming agent therein is ex- _ truded through the coating die into the atmosphere and therefore is caused to undergo foaming the tukular polyolefin foam which consequently occurs around the core material is inflated in both inside diameter and outside diameter. As the result, the inside diameter of the tubular polyolefin foam becomes greater than the outside diameter of the core material. miS ~eans that a gap is caused to intervene between the core material and the polyolefin foam coating and thus substantially prevent L
them fmm forming fast ad~esion.
~"~.' The method adopted as above has an inevitable disadvantage r that the core material i5 left to slide freely within the polyolefin foam coating, the polyolefin foam coating fcLms an uneven outer surface and the characteristic feature, i.e. theLm~l insulation, of the hollow core material covered with the foamed coating is degraded.
Intimate adllesion of the polyolefin foam coating to the hollow co~e material, therefore, is an indispensable requirement for the sub_ ,~
stantial elimination of these disadvantages. In this respect, methods have been proposed for the forced establishment of tight adhesion be-`tween the core material and the foamed coating. Examples of such methods include: a method whereby the intimate adhesion of the core material and the foamed o~ating is effected by reducing the internal pressure of the ` gap occurring therebetween (Japanese Patent Publication No. 4869/1973;
a method whereby the intimate adhesion is obtained by releasing excess foaming gas from the interspace occurring between the oore material and the foamed coating (Japanese Patent Publicatian No. 24577/1974; and a ,, i ,~ method whereby intImate adhesion bet~een the core material and the ~ foamed coating is ensured by application of an adhesive a~ent to the .,i ~
surface of the core ~aterial.
mese ~ethods inyariahly necessitiate the use of special dies.
' In the case of a product obtained by effecting forced adhesion with the ~ . .
, . , , , _ 1~88383 aid of an adhesiYe agent, since the core ~terial and the foamed ooating are joined strongly to each other, partial remcNal of the foamed coating fr~m the core material which is frequently found necessary for the pur-pose of directly joining two oore materials at the site of field w3rk cannot easily be aco~mplished but calls for much time and labor. Even after the rem~val, some of the coating persists on the surface of the core material and impedes perfect union of the two core materials. Par-ticularly when the core material happens to be a metal pipe or metal wire, since such join}ng is obtained by welding, soldering or other similar treatment, imperfect rem~val of the foamed coating may possibly entail defective union.
It is therefore desirable to provide a method which is sub-stantially free from such drawbacks and which enables a highly expanded poly31efin foam and a hollow core material to be brought into fast mu-tual adhesion simply by use of an ordinary coating die. It has thus been found that the fastness of a & esion between the polyolefin foam and the hollow oore material depends an the extent to which the extruded poly31efin resin containing the ~31a '1e foaming agent is cooled and on the guality, particularly dependence of melt viscosity on tèmperature, which the polyolefin resin containing the volatile foaming agent posses-ses and also that the surface temperature which the hollow core material has at the time the expandable Folyolefin resin is brought into oontact with the hollow core naterial constitutes a critically imp3rtant factor governing the ease with which the foamed coating is released from the h311ow core mater;~l. It has been found that fast adhesion between the highly expanded polyolefLn foam and the hollow core material is success-fully attained by carrying out a continuous extrusion ooating with these factors coordinated to the optimum combination.
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By one broad aspect of this invention a process is provided for the continuous extrusion coating by the use of a coating die of a hollow core ma-terial with a highly expandable polyolefin resin composition containing a vola-tile organic liquid blowing agent, the improvement comprising externally, cool-ing the outer surface of the extruded molten mass of expandable polyolefin resin, at the point at which the molten mass begins to foam, by by contacting the surface with a cooling gas or water to allow the pressure of foaming to be exerLed inwardly and also to cause the growth of foam to proceed in the direction of the internal core for thereby enabling the polyolefin foam to ad-here fast to the hollow core and giving rise to a coating having a smooth sur-face condition, wherein the expanded polyolefin foam has an expansion ratio of not less than 3.
- By a variant thereof, the process comprises keeping the surface - temperature of the hollow core material being continuously supplied at a level below the softening point of the expandable polyolefin resin being extruded through the coating die and thereby allowing a uniform skin layer to be formed of the polyolefin resin along the interface between the core material and the molten mass when they are brought into mutual contact, whereby the . "
uniform skin layer maintains fast adhesion of the foamed coating to the core i~ 20 material and yet permits ready release of the foamed coating fxom the core ~i material.
By a variation thereof, the polyolefin resin is a low-density poly-ethylene having a density of not more than 0.930 g/cc.
, By yet another variant, the polyolefin resin is z mixture consist-ing of from 30 to 90% by weight of a low-density polyethylene having a density of not more than 0.930 glcc and 70 to 10% by weight of a high-density ' polyethylene having a density of not less than 0.940 g/cc.
~; By still another variant, the hollow core material is made of a metallic or synthetic resin substance.
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By another variant, this method comprises applying the expandable polyolefin resin coating to the hollow core as the resin leaves the die.
In more general terms, and in one aspect, this invention provides a process for the continuous extrusion coating of a hollow core material with a highly expanded polyolefin foam by continuous extrusion foaming by means of a volatile organic solvent by use of a coating die. The process comprises first causing the molten mass of the expandable polyolefin extruded through the coat-ing die to be cooled on the surface .
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at the point at which t~e molten ~ass begins to foam, then following the pressure of foamir.g to be exerted inwardly and then causmg the ~
growth of foam to proceed in the direction of the internal core, there- ~ ;by enabling the polyolefin foam to adhere fast to the hollow core and giving rise to a smooth surface coating. FurthermDre, in another aspect, the process comprises keeping the surface temperature of the hollow core ~ -~h~
material being continu~usly supplied at a level below the softening ~
point of the m~lten mass of the ~xpanlable polyolefin resin being ex- _ truded through the coating die, thereby allcwing a uniform skin layer to be formed of said polyolefin resin~along the interface between the core material and the molten mass when they are brought into mutual contact, ~
whereby such uniform skin layer maintains fast adhesi~n of the foamed _ coating to the core material and yet permits ready release of the foamed coating from the core material.
; - Cne of the requirements for fast adhesion between the highlyexpanded polyolefin foam and the hollow core material contemplated by an aspect of the present invention, namely the cooling of the surface of ¦
the m~lten resin of thé expandable polyolefin containing the volatile .
foaming agent extruded through the coating die, has its origin in the manufacture of a highly exEanded polyolefin pipe by the continuous ex-trusion foaming by means of a volatile organic solvent. It has been discovered that, when the cooling of the surface of the molten resin is started at the point at which the extruded molten resin of expandable polyolefirl begins to foam, the melt viscosity in the surface layer of the molten resin sharply increases owing to the cooling to give rise to a skin layer on the surface and consequently produce a smD~th surface. r The outward inflation of the foam is also inhibited and the growth of the foam is allowed to prcceed in the direction of the center of the core m~terial, with the result that the inward inflation of the foam is accelerated and the inside diameter of the highly expanded poly~lefin pipe is decreased.
It has been established that desired fast adhesion of the ~: .
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1~88383 ', highly expanded polyolefin foam and the hollow core material is suc-cessfully attained when this phenomenon is applied to the continuous extrusion coating of the hollow core material ~rith the highly expanded polyolefin foam effected by the continuous extrusion foaming by means of a v~latile organic solvent, so that the pressure of foam is caused to be exerted in the direction of the hollow core m~terial and the expand-ing foam eventually is wrapped up tightly around the hollow core material. The present invention in yet another aspect also provides fast adhesion between the polyolefin foam and the hollow core material 1~ and yet permits ready release of the foamed coating from the hollow core material when the release is found necessary such as in the field works involving use of the finished products. This technical achievement is believed to be ascribable to the fact that a uniform skin layer of said polyolefin resin is formed along the interface between the hollow oore - material and the polyolefin foam when the molten resin of the expandable F~
polyolefin extruded through the die is caused, before it begins to in-flate because of foaming, to come into contact with the hollow core material whose surface temperature is kept at a level below the soften- ~
;~' ~ ing point of said polyolefin resin. Specifically, the skin layer of the s 20 polyolefin foam occurs because the corresponding surface portion of the ; polyolefin foam is suddenly cooled and othe~wise possible foaming of ';
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1~883~33 the resin in said surface portion ls lnhibited owing to local loss of heat.
In the case of the process of an aspect of this invent~on such a skin layer is formed in the inner surface portion of the polyolefin foam because the surface portion of the polyolefin foam is suddenly cooled when the molten resin of the expandable polyolefin extruded through the die is brought into contact with the hollow core material being supplied with the surface tem-perature thereof kept below the softening point of said polyolefin resin.
The formation of the skin layer on the inner surface coupled with the effect of the inward exertion of the ~ressure of foraming brought about by thc surface cooling provideæ effective inhibition of the inflation, so that the foamed layer assumes a structure wherein it is held in fast ad-hesion with the hollow core material throughi,the medium of the non-foamed skin layer. In the finished product, the hollow core material is not per-mitted to slide freel~ within the foamed coating. Whcn the foamed coating is desired to be removed from the core materiai, since ready release is obtained along the interface between the skin layer and the hollow core material, the skin of the hollow core =aterial can be completely exposed.
Where the hollow core material happens to be a metallic pipe, therefore, welding,.soldering and other forms of joining of two or more materials can be carried out rapidly and safely in thè field work involving use of the finished core materials. Here, the rcquirement that the surface tempera-ture of the hollow core material being supplied should be kept at a level lower than the softening point of the expandable polyolefin resin in the molten mix consisting of the expandable polyolefin resin : .
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. , ' '` 1(~88383 and the volatile foaming agent is based on the following reason.
Generally in the integral extrusion coating, as a measure for improving the fastness of adhesion, a method is adopted wherein the core material being supplied is heated in ordor that the elevated temperature of the surface ensures intimate union of the core material with the surface extruded molten resin. In case where the extrusion coating is effected with a foam of high expansion ratio as in aspects of the present invention, if the surface temperature of the hollow core material being supplied is higher than the softening point of said expandable polyolefin resin, then the foaming proceeds also in the surface portion of the polyethylene foam which comes into contact with the hollow core material. If the hollow core material happens to be a flexible pipe made of a plastic material, then the hollow core tends to be deformed by the pressure of foaming which is caused to be exerted inwardly. Further, since strong adhesion occurs in the in-terface between the foam layer and the hollow core material, the field ` work involving use of finished products tends to entail a disadvantage that the foam layer will not readily come off the surface of the hollow core j material.
In an aspect of the present invention, therefore, the surface temperature of the hollow core material being supplied is kept at a level I below the softening point of the expandable polyolefin resin so that the -~ -skin layer formed along the interface between the expandable polyolefin resin and the hollow core material will provide fast adhesion therebetween and, at the same time, give a solution to the problem ~,, .
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mentioned above. l The thickness of the sk~n layer thus formed is determined by ~ -the thickness of the expandable polyolefin resin from the surface on which the resin is cooled for the purpose of inhibiting the foaming.
Generally, the thickness of the skin layer so formed increases with the decreasing surface temperature of the hollow core material. It is, 1 therefore, desirable that the surface temperature of the hollow core ma-,~
terial being supplied should be suitably selected in the range below the softening point of the expandable polyQlefin resin by taking into due consideration a particular specification of the caated product such as, I
: for example, the magnitude of curvature appropriate for the intended ~ ~-bending work.
; m e polyolefin resins which are usable in the process f ~ r aspects of the present invention include crystalline polyolefin resins e.g. of low-density polyethylene, high-de~sity polyethylene, polypropy~
lene and polybutene-l, the resins of copolymers thereof and mixtures of two or more of such copolymer resins. From the standpoint of foamabili-ty, low-density polyethylenes and mixtures of low-density polyethylenes ¦-~
with high-density polyethylenes are advant ageous. Particularly, a t -mixture consisting of from 30 to 90% by weight of a low-density poly-ethylene having a density of not more than 0.930 g/cm3 and fr~m 70 to 10~ by weight of a high-density polyethylene having a density of not less than 0.940 g/cm3 is advantageous for the following reason:: When ~; the cooling of the surface of the molten mixed polyethylene resin is started at the point at which the resin begins to foam, the melt viscos-ity in the surface layer of the molten ~ i !.' ' ` ~; :
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resin rises so abruptly that the resulting mixed polyethylene foam is in-hibited from attaining outward inflation, the pressure of foaming is caused to be exerted inwardly and the growth of foam is made to proceed in the direction of the center of the core material, with an overall result that the inflation of the foam tends to be accelerated inwardly to enhance the fastness of the adhesion of the foam with the hollow core material held in-side.
The coolants which are used advantageously for the cooling in-volved in the process of aspects of the present invention are air, water, and various kinds of gases. The surface of the resin foam is cooled by air-ing or by use of a water bath, for example.
The hollow core materials which are advantageously usable for the coating by the process of aspects of this invention are those hollow bodies made of metallic or plastic materials and used for distribution of hot water and steam in the hot-water supply system, space heating system and centra-lized heating system, for supply of city water, for distribution of coolants in the space cooling system and refrigeration system and for supply of fuel.
The cross-sectional shape of the hollow core material is not critical in-sofar as the finished product obtained after the extrusion coating has a simple cross-sectional shape e.g. a circle or square.
As the volatile foaming agent for the polyolefins, there can be used any of the various volatile foaming agents which are generally accepted i as useful in the continuous extrusion foaming by means of a volatile organic solvent. Examples of the volatile foaming agents which can be used include low boiling point aliphatic hydrocarbons, e.g. propane, butane, pentane and hexane, halogenated hydrocarbons .. , . ~ . .' ,, . , .:, , .:: . : : , - , , . . . . :
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: . : ' , , ...... ' : ' ' 1~88383 e.g. dichlorodifluor,~methane, 1,2-dichlorotetrafluoroethane and mono-chlorodifluorcmethane and ~xtures of tw~ or more of such hydrocar~ons.
As the coating die, there can be used any of the cross-head type c~ating dies designed for die interior joining and die exte~rior ¦
joining.
In the accompanying drawings, Figure 1 is a central longitudinal cross-section of an appara-tus for the continuous extrusion coo~ing of a hollow core material ac-cording to the process of one aspect of the present invention; and Figure 2 is a transverse cross-sectional view of an extruded ~ coated hGllow core material produced by the process of one aspect of ~
,~ this invention. ~,,, -One preferred enbodlment of the continuous extrusion coating of a core material with a polyethylene foam of a high ~xpansion ratio by h', the process of an aspect of the present invention will be described be-low with reference to Figure 1. A mixture of tw~ kinds of polyethylenes and a foaming aid is supplied to a first extruder which is not shGwn in the drawing. At the portion of the extruder interior at which the mix-ture is being melted, a foaming agent in a compressed state is injected ` 20 via an inlet bored thorugh the cylinder barrel of the extruder to be mixed substantially uniformly with the molten mixture. Within the se-7! cond extruder 1, the mixture is adjusted in tem~erature so as to assume ~r'~ a proper viscosity for foaming. Then the mixture at a controlled temperature is forced through a breaker plate 2 into a cross-head die coating. me cross-head die is broadly divided into an inside mandrel , 3, outside mandrel 4 and an adjusting ring 5. me mixture now con-~:; taining the foaming agent is extruded through the gap formed among the ; inside mandrel 3, the outside mandrel 4 and the adjusting ring 5.
i/ In the meantime, a hollow core material 7 which is depicted ~ -,: ~,. .
as a pipe in the drawing is supplied to the inside m,Indrel through the r v~id thereof in the same direction as that of the flow of the molten resin. As the mixture containing the foaming agent is extruded into the atm~spheric , .
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1`~88383 pressure, the foaming agent is abruptly vaporized by the agency of the foam-ing aid to initiate the foaming of the mixture. At this point, cobling air is blown against the outer boundary of the foam through a cooling air ring 6 disposed ad~acent the discharge outlet of the die, to cool the surface of the polyethylene foam and consequently inhibit outward inflation and accelerated inward inflation of the polyethylene foam 8. Thus, fast ad-hesion is established between the hollow core material 7 and the highly ex-panded polyethylene foam 8 having an expansion ratio of not less than 3.
The polyethylene foam-coated material to be obtained by process of an aspect of the present invention (as shown in Fi~ure 2) has a hollow core material coated with a polyethylene foam of a high expansion ratio de-posited to a uniform thickness in fast adhesion with the surface of said core material. Thus, the foamed coating has a smooth surface and keeps firm hold of the hollow core material so that the core material is not left to slide freely inside the coating.
Further.in the preferred embodiment described above, the hollow core material is supplied with its surface temperature kept at a level below the softening point of thc expandable polyethylene resin and the applica-tion of the molten polyethylene resin to the hollow core material is -~ 20 effected within the die interior, with the result that a skin layer of a uniform thickness is formed of said polyethylene resin along the interface between the polyethylene foam and the hollow core material. The polyethylene fl, foam-coated material thus produced, therefore, enjoys fast adhesion between . the foam and the core and provides ready . ~ .
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release of the foamed coating from the core material when the separation isfound necessary in the field work involving use of the finished product.
To summarize the advantages of various aspects of the present in-vention, the usefulness of the invention is recognized in numerous respects as shown below.
As the molten polyolefin resin is extruded through the die, the cooling of the surface of thc extruded molten resin is started at the point at which the molten resin beging to foam so as to heighten abruptly the melt viscosity of the surface portion of the molten resin, inhibit outward in-flation of the resin, cause the pressure of foaming to be exerted inwardly and enable the growth of foam to proceed in the direction of the center of the hollow core material. The advantages derived from the surface cool-ing are:
(1) The foamed coating is permitted to adhere with the hollow core material with ample fastness, without reference to the degree of expandability of the polyolefin resin and the thickness of the layer formed of the foam.
and particularl~ to a process for the continuously extrusion coating of ~`
a hollow core material in a state ~herein such hollcw core material and a polyolefin foam e~panded to a high ratio ~ore than three times~ are joined fast with each other.
Conventional hollow core materials coated with foamed plastics enjoy thermal insulation, lightness of weight and waterprcofness. Par-ticularly pipes coated with highly expanded foams e.g. of polyethylene, polyurethane, etc. are characterized by possessing excellent the~mal insulation and the ability to peLmit practical applications without re-quiring any advanced technique or skill. Because of the advantageous properties, these pipes are extensively used for hot water systems, city water systems, air conditioning systems and fuel distribution systems in residences, hotels, hospitals, multistory buildings, and the like.
However, these highly expanded plastic foams are invariably torn open ^ along a longitu~inally inserted slit after they have been formed as if they are deposited in the form of tubes round core pipes. ~hen the core pipes are put to use in the site of installation, the torn tubes of plastic foams are closed up again tightly round the core pipes. The finishing of these coated pipes, therefore, inevitably requires the jobs of taping and coating. Moreover, these pipes have a disadvantage that they suffer from inferior field w~rkability and inefficient plumbing operation in spaces of limited di~ensions. As a measure for the con- j .; ~
- tinuous manufacture of metallic or plastic pipes and electric wires coated with foamed plastics, continuous integral coating methods are pre-; sently known whereby the core materials are coated at the same time that the plastics are extrusion foamed. According to this ~ethod, the extxu-;, .
~` sion coating with the foam of a polyolefin ha~ing low expandability can be carried out as effectively as with a non-g~panlable plastic substance, without any difficulty. Where the extrusion coating of a given core ma-texial by this method is caxried out with the foam of a poly~lefin which '~
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~ossesses an expansiQn ratio of 3 or more and suits ad~antageously to uses as a therm~l msulator, a shock absorber or a noise absorber, when the polyolein resin o~ntaining a volatile foaming agent therein is ex- _ truded through the coating die into the atmosphere and therefore is caused to undergo foaming the tukular polyolefin foam which consequently occurs around the core material is inflated in both inside diameter and outside diameter. As the result, the inside diameter of the tubular polyolefin foam becomes greater than the outside diameter of the core material. miS ~eans that a gap is caused to intervene between the core material and the polyolefin foam coating and thus substantially prevent L
them fmm forming fast ad~esion.
~"~.' The method adopted as above has an inevitable disadvantage r that the core material i5 left to slide freely within the polyolefin foam coating, the polyolefin foam coating fcLms an uneven outer surface and the characteristic feature, i.e. theLm~l insulation, of the hollow core material covered with the foamed coating is degraded.
Intimate adllesion of the polyolefin foam coating to the hollow co~e material, therefore, is an indispensable requirement for the sub_ ,~
stantial elimination of these disadvantages. In this respect, methods have been proposed for the forced establishment of tight adhesion be-`tween the core material and the foamed coating. Examples of such methods include: a method whereby the intimate adhesion of the core material and the foamed o~ating is effected by reducing the internal pressure of the ` gap occurring therebetween (Japanese Patent Publication No. 4869/1973;
a method whereby the intimate adhesion is obtained by releasing excess foaming gas from the interspace occurring between the oore material and the foamed coating (Japanese Patent Publicatian No. 24577/1974; and a ,, i ,~ method whereby intImate adhesion bet~een the core material and the ~ foamed coating is ensured by application of an adhesive a~ent to the .,i ~
surface of the core ~aterial.
mese ~ethods inyariahly necessitiate the use of special dies.
' In the case of a product obtained by effecting forced adhesion with the ~ . .
, . , , , _ 1~88383 aid of an adhesiYe agent, since the core ~terial and the foamed ooating are joined strongly to each other, partial remcNal of the foamed coating fr~m the core material which is frequently found necessary for the pur-pose of directly joining two oore materials at the site of field w3rk cannot easily be aco~mplished but calls for much time and labor. Even after the rem~val, some of the coating persists on the surface of the core material and impedes perfect union of the two core materials. Par-ticularly when the core material happens to be a metal pipe or metal wire, since such join}ng is obtained by welding, soldering or other similar treatment, imperfect rem~val of the foamed coating may possibly entail defective union.
It is therefore desirable to provide a method which is sub-stantially free from such drawbacks and which enables a highly expanded poly31efin foam and a hollow core material to be brought into fast mu-tual adhesion simply by use of an ordinary coating die. It has thus been found that the fastness of a & esion between the polyolefin foam and the hollow oore material depends an the extent to which the extruded poly31efin resin containing the ~31a '1e foaming agent is cooled and on the guality, particularly dependence of melt viscosity on tèmperature, which the polyolefin resin containing the volatile foaming agent posses-ses and also that the surface temperature which the hollow core material has at the time the expandable Folyolefin resin is brought into oontact with the hollow core naterial constitutes a critically imp3rtant factor governing the ease with which the foamed coating is released from the h311ow core mater;~l. It has been found that fast adhesion between the highly expanded polyolefLn foam and the hollow core material is success-fully attained by carrying out a continuous extrusion ooating with these factors coordinated to the optimum combination.
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By one broad aspect of this invention a process is provided for the continuous extrusion coating by the use of a coating die of a hollow core ma-terial with a highly expandable polyolefin resin composition containing a vola-tile organic liquid blowing agent, the improvement comprising externally, cool-ing the outer surface of the extruded molten mass of expandable polyolefin resin, at the point at which the molten mass begins to foam, by by contacting the surface with a cooling gas or water to allow the pressure of foaming to be exerLed inwardly and also to cause the growth of foam to proceed in the direction of the internal core for thereby enabling the polyolefin foam to ad-here fast to the hollow core and giving rise to a coating having a smooth sur-face condition, wherein the expanded polyolefin foam has an expansion ratio of not less than 3.
- By a variant thereof, the process comprises keeping the surface - temperature of the hollow core material being continuously supplied at a level below the softening point of the expandable polyolefin resin being extruded through the coating die and thereby allowing a uniform skin layer to be formed of the polyolefin resin along the interface between the core material and the molten mass when they are brought into mutual contact, whereby the . "
uniform skin layer maintains fast adhesion of the foamed coating to the core i~ 20 material and yet permits ready release of the foamed coating fxom the core ~i material.
By a variation thereof, the polyolefin resin is a low-density poly-ethylene having a density of not more than 0.930 g/cc.
, By yet another variant, the polyolefin resin is z mixture consist-ing of from 30 to 90% by weight of a low-density polyethylene having a density of not more than 0.930 glcc and 70 to 10% by weight of a high-density ' polyethylene having a density of not less than 0.940 g/cc.
~; By still another variant, the hollow core material is made of a metallic or synthetic resin substance.
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By another variant, this method comprises applying the expandable polyolefin resin coating to the hollow core as the resin leaves the die.
In more general terms, and in one aspect, this invention provides a process for the continuous extrusion coating of a hollow core material with a highly expanded polyolefin foam by continuous extrusion foaming by means of a volatile organic solvent by use of a coating die. The process comprises first causing the molten mass of the expandable polyolefin extruded through the coat-ing die to be cooled on the surface .
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at the point at which t~e molten ~ass begins to foam, then following the pressure of foamir.g to be exerted inwardly and then causmg the ~
growth of foam to proceed in the direction of the internal core, there- ~ ;by enabling the polyolefin foam to adhere fast to the hollow core and giving rise to a smooth surface coating. FurthermDre, in another aspect, the process comprises keeping the surface temperature of the hollow core ~ -~h~
material being continu~usly supplied at a level below the softening ~
point of the m~lten mass of the ~xpanlable polyolefin resin being ex- _ truded through the coating die, thereby allcwing a uniform skin layer to be formed of said polyolefin resin~along the interface between the core material and the molten mass when they are brought into mutual contact, ~
whereby such uniform skin layer maintains fast adhesi~n of the foamed _ coating to the core material and yet permits ready release of the foamed coating from the core material.
; - Cne of the requirements for fast adhesion between the highlyexpanded polyolefin foam and the hollow core material contemplated by an aspect of the present invention, namely the cooling of the surface of ¦
the m~lten resin of thé expandable polyolefin containing the volatile .
foaming agent extruded through the coating die, has its origin in the manufacture of a highly exEanded polyolefin pipe by the continuous ex-trusion foaming by means of a volatile organic solvent. It has been discovered that, when the cooling of the surface of the molten resin is started at the point at which the extruded molten resin of expandable polyolefirl begins to foam, the melt viscosity in the surface layer of the molten resin sharply increases owing to the cooling to give rise to a skin layer on the surface and consequently produce a smD~th surface. r The outward inflation of the foam is also inhibited and the growth of the foam is allowed to prcceed in the direction of the center of the core m~terial, with the result that the inward inflation of the foam is accelerated and the inside diameter of the highly expanded poly~lefin pipe is decreased.
It has been established that desired fast adhesion of the ~: .
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1~88383 ', highly expanded polyolefin foam and the hollow core material is suc-cessfully attained when this phenomenon is applied to the continuous extrusion coating of the hollow core material ~rith the highly expanded polyolefin foam effected by the continuous extrusion foaming by means of a v~latile organic solvent, so that the pressure of foam is caused to be exerted in the direction of the hollow core m~terial and the expand-ing foam eventually is wrapped up tightly around the hollow core material. The present invention in yet another aspect also provides fast adhesion between the polyolefin foam and the hollow core material 1~ and yet permits ready release of the foamed coating from the hollow core material when the release is found necessary such as in the field works involving use of the finished products. This technical achievement is believed to be ascribable to the fact that a uniform skin layer of said polyolefin resin is formed along the interface between the hollow oore - material and the polyolefin foam when the molten resin of the expandable F~
polyolefin extruded through the die is caused, before it begins to in-flate because of foaming, to come into contact with the hollow core material whose surface temperature is kept at a level below the soften- ~
;~' ~ ing point of said polyolefin resin. Specifically, the skin layer of the s 20 polyolefin foam occurs because the corresponding surface portion of the ; polyolefin foam is suddenly cooled and othe~wise possible foaming of ';
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1~883~33 the resin in said surface portion ls lnhibited owing to local loss of heat.
In the case of the process of an aspect of this invent~on such a skin layer is formed in the inner surface portion of the polyolefin foam because the surface portion of the polyolefin foam is suddenly cooled when the molten resin of the expandable polyolefin extruded through the die is brought into contact with the hollow core material being supplied with the surface tem-perature thereof kept below the softening point of said polyolefin resin.
The formation of the skin layer on the inner surface coupled with the effect of the inward exertion of the ~ressure of foraming brought about by thc surface cooling provideæ effective inhibition of the inflation, so that the foamed layer assumes a structure wherein it is held in fast ad-hesion with the hollow core material throughi,the medium of the non-foamed skin layer. In the finished product, the hollow core material is not per-mitted to slide freel~ within the foamed coating. Whcn the foamed coating is desired to be removed from the core materiai, since ready release is obtained along the interface between the skin layer and the hollow core material, the skin of the hollow core =aterial can be completely exposed.
Where the hollow core material happens to be a metallic pipe, therefore, welding,.soldering and other forms of joining of two or more materials can be carried out rapidly and safely in thè field work involving use of the finished core materials. Here, the rcquirement that the surface tempera-ture of the hollow core material being supplied should be kept at a level lower than the softening point of the expandable polyolefin resin in the molten mix consisting of the expandable polyolefin resin : .
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. , ' '` 1(~88383 and the volatile foaming agent is based on the following reason.
Generally in the integral extrusion coating, as a measure for improving the fastness of adhesion, a method is adopted wherein the core material being supplied is heated in ordor that the elevated temperature of the surface ensures intimate union of the core material with the surface extruded molten resin. In case where the extrusion coating is effected with a foam of high expansion ratio as in aspects of the present invention, if the surface temperature of the hollow core material being supplied is higher than the softening point of said expandable polyolefin resin, then the foaming proceeds also in the surface portion of the polyethylene foam which comes into contact with the hollow core material. If the hollow core material happens to be a flexible pipe made of a plastic material, then the hollow core tends to be deformed by the pressure of foaming which is caused to be exerted inwardly. Further, since strong adhesion occurs in the in-terface between the foam layer and the hollow core material, the field ` work involving use of finished products tends to entail a disadvantage that the foam layer will not readily come off the surface of the hollow core j material.
In an aspect of the present invention, therefore, the surface temperature of the hollow core material being supplied is kept at a level I below the softening point of the expandable polyolefin resin so that the -~ -skin layer formed along the interface between the expandable polyolefin resin and the hollow core material will provide fast adhesion therebetween and, at the same time, give a solution to the problem ~,, .
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mentioned above. l The thickness of the sk~n layer thus formed is determined by ~ -the thickness of the expandable polyolefin resin from the surface on which the resin is cooled for the purpose of inhibiting the foaming.
Generally, the thickness of the skin layer so formed increases with the decreasing surface temperature of the hollow core material. It is, 1 therefore, desirable that the surface temperature of the hollow core ma-,~
terial being supplied should be suitably selected in the range below the softening point of the expandable polyQlefin resin by taking into due consideration a particular specification of the caated product such as, I
: for example, the magnitude of curvature appropriate for the intended ~ ~-bending work.
; m e polyolefin resins which are usable in the process f ~ r aspects of the present invention include crystalline polyolefin resins e.g. of low-density polyethylene, high-de~sity polyethylene, polypropy~
lene and polybutene-l, the resins of copolymers thereof and mixtures of two or more of such copolymer resins. From the standpoint of foamabili-ty, low-density polyethylenes and mixtures of low-density polyethylenes ¦-~
with high-density polyethylenes are advant ageous. Particularly, a t -mixture consisting of from 30 to 90% by weight of a low-density poly-ethylene having a density of not more than 0.930 g/cm3 and fr~m 70 to 10~ by weight of a high-density polyethylene having a density of not less than 0.940 g/cm3 is advantageous for the following reason:: When ~; the cooling of the surface of the molten mixed polyethylene resin is started at the point at which the resin begins to foam, the melt viscos-ity in the surface layer of the molten ~ i !.' ' ` ~; :
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resin rises so abruptly that the resulting mixed polyethylene foam is in-hibited from attaining outward inflation, the pressure of foaming is caused to be exerted inwardly and the growth of foam is made to proceed in the direction of the center of the core material, with an overall result that the inflation of the foam tends to be accelerated inwardly to enhance the fastness of the adhesion of the foam with the hollow core material held in-side.
The coolants which are used advantageously for the cooling in-volved in the process of aspects of the present invention are air, water, and various kinds of gases. The surface of the resin foam is cooled by air-ing or by use of a water bath, for example.
The hollow core materials which are advantageously usable for the coating by the process of aspects of this invention are those hollow bodies made of metallic or plastic materials and used for distribution of hot water and steam in the hot-water supply system, space heating system and centra-lized heating system, for supply of city water, for distribution of coolants in the space cooling system and refrigeration system and for supply of fuel.
The cross-sectional shape of the hollow core material is not critical in-sofar as the finished product obtained after the extrusion coating has a simple cross-sectional shape e.g. a circle or square.
As the volatile foaming agent for the polyolefins, there can be used any of the various volatile foaming agents which are generally accepted i as useful in the continuous extrusion foaming by means of a volatile organic solvent. Examples of the volatile foaming agents which can be used include low boiling point aliphatic hydrocarbons, e.g. propane, butane, pentane and hexane, halogenated hydrocarbons .. , . ~ . .' ,, . , .:, , .:: . : : , - , , . . . . :
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As the coating die, there can be used any of the cross-head type c~ating dies designed for die interior joining and die exte~rior ¦
joining.
In the accompanying drawings, Figure 1 is a central longitudinal cross-section of an appara-tus for the continuous extrusion coo~ing of a hollow core material ac-cording to the process of one aspect of the present invention; and Figure 2 is a transverse cross-sectional view of an extruded ~ coated hGllow core material produced by the process of one aspect of ~
,~ this invention. ~,,, -One preferred enbodlment of the continuous extrusion coating of a core material with a polyethylene foam of a high ~xpansion ratio by h', the process of an aspect of the present invention will be described be-low with reference to Figure 1. A mixture of tw~ kinds of polyethylenes and a foaming aid is supplied to a first extruder which is not shGwn in the drawing. At the portion of the extruder interior at which the mix-ture is being melted, a foaming agent in a compressed state is injected ` 20 via an inlet bored thorugh the cylinder barrel of the extruder to be mixed substantially uniformly with the molten mixture. Within the se-7! cond extruder 1, the mixture is adjusted in tem~erature so as to assume ~r'~ a proper viscosity for foaming. Then the mixture at a controlled temperature is forced through a breaker plate 2 into a cross-head die coating. me cross-head die is broadly divided into an inside mandrel , 3, outside mandrel 4 and an adjusting ring 5. me mixture now con-~:; taining the foaming agent is extruded through the gap formed among the ; inside mandrel 3, the outside mandrel 4 and the adjusting ring 5.
i/ In the meantime, a hollow core material 7 which is depicted ~ -,: ~,. .
as a pipe in the drawing is supplied to the inside m,Indrel through the r v~id thereof in the same direction as that of the flow of the molten resin. As the mixture containing the foaming agent is extruded into the atm~spheric , .
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1`~88383 pressure, the foaming agent is abruptly vaporized by the agency of the foam-ing aid to initiate the foaming of the mixture. At this point, cobling air is blown against the outer boundary of the foam through a cooling air ring 6 disposed ad~acent the discharge outlet of the die, to cool the surface of the polyethylene foam and consequently inhibit outward inflation and accelerated inward inflation of the polyethylene foam 8. Thus, fast ad-hesion is established between the hollow core material 7 and the highly ex-panded polyethylene foam 8 having an expansion ratio of not less than 3.
The polyethylene foam-coated material to be obtained by process of an aspect of the present invention (as shown in Fi~ure 2) has a hollow core material coated with a polyethylene foam of a high expansion ratio de-posited to a uniform thickness in fast adhesion with the surface of said core material. Thus, the foamed coating has a smooth surface and keeps firm hold of the hollow core material so that the core material is not left to slide freely inside the coating.
Further.in the preferred embodiment described above, the hollow core material is supplied with its surface temperature kept at a level below the softening point of thc expandable polyethylene resin and the applica-tion of the molten polyethylene resin to the hollow core material is -~ 20 effected within the die interior, with the result that a skin layer of a uniform thickness is formed of said polyethylene resin along the interface between the polyethylene foam and the hollow core material. The polyethylene fl, foam-coated material thus produced, therefore, enjoys fast adhesion between . the foam and the core and provides ready . ~ .
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release of the foamed coating from the core material when the separation isfound necessary in the field work involving use of the finished product.
To summarize the advantages of various aspects of the present in-vention, the usefulness of the invention is recognized in numerous respects as shown below.
As the molten polyolefin resin is extruded through the die, the cooling of the surface of thc extruded molten resin is started at the point at which the molten resin beging to foam so as to heighten abruptly the melt viscosity of the surface portion of the molten resin, inhibit outward in-flation of the resin, cause the pressure of foaming to be exerted inwardly and enable the growth of foam to proceed in the direction of the center of the hollow core material. The advantages derived from the surface cool-ing are:
(1) The foamed coating is permitted to adhere with the hollow core material with ample fastness, without reference to the degree of expandability of the polyolefin resin and the thickness of the layer formed of the foam.
(2) The foamed coating has a smooth surface without reference to the degree of expandability of the polyolefin resin used.
(3) Since the foamed coating has such a-smooth surface, application of an additional coating to the surface and other similar treatments can be effected with great ease.
j The hollow core material is supplied to the die with its surface temperature kept at a level below the softe~ning point of the expandable poly-olefin resin which is extruded through the die, so as to give rise to a skin layer ', ':
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fin resin and the hollow core material. ~ -The advantages derived from the formation of such a skin layer include:
j The hollow core material is supplied to the die with its surface temperature kept at a level below the softe~ning point of the expandable poly-olefin resin which is extruded through the die, so as to give rise to a skin layer ', ':
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fin resin and the hollow core material. ~ -The advantages derived from the formation of such a skin layer include:
(4) me foamed coating and the hollow core material can be held in tight im~ovable union with substantially no stickiness, so that desired re-lease of the foamed coating from the hollow core material can be ob-tair.ed with great ease.
(5) me ease of the release of the foamed coating contributes greatly to lessening the work burden and ensuring the safety in the field work ~` involving use of the finished product. ~
(6) Even if the hollow core material happens to be made of a flexible r---substance, the pressure of foaming will not cause substantial deform~-tion in the core material.
Now the present invention in its various aspects will be de-scribed with reference to working examples, which are purely illustrative of aspects of the invention. ¦;
~ In a kneading extruder (50 mm in b~rrel interior diameter, i i , :~
L/D = 24), a mixture consisting of 70% by weight of a pelletized poly-propylene having a density of 0.91 g/cm3 and a melt index of 2.0 and 30% by weight of a pelletized polybutene-l having a density of 0.905 g/cm3 and a melt index of 2.0 was kneaded at 180C to produce a sub-stantially ho~ogenous mixture. With 100 parts of the mixture were dry blended 0.5 part by weight of sodium bicarbonate and 0.4 part by weight of citric acid as nucleus-forming agents , i ,,'` .
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serving to control the size of individual cells of the foam. Consequentl~, there was obtained a compound for extrusion foaming.
The extrusion foam coating system adopted consisted of two extruders and a cross-head die, with the leading end of the first extruder (50 mm in barrel interior diameter, L/D = 23) joined into the rear end of the second extruder (40 mm in barrel interior diameter, L/D =20). The second r extruder was provided at the leading end thereof with a coating cross-head die llke the one illustrated in Figure 1. The compound was fed to the f.rst extruder kept at 180C at a feed rate of 7.2 kg/hour. At the portion of F
the extruder interior at which the compound was melted _ and kneaded, dichlorodif`luoromethane compressed to a - 15 pressure of 130 kg/cm2 was injected as a foaming agent via an lnlet bored through the cylinder barrel of the extruder at a rate of 0.52 kg/hour. The mixture emanating from the first extruder was fed to the second extruder, then adjusted toa temperature of 148C and extruded through the cross-head die. Through the cavity in the inside mandrel of the cross-head die, a copper pipe 1/2 inch (15.88 mm in outside diameter) was supplied at a rate of 1 m/min. in the same direction as that of the extrusion of the mixture. The mixture was forced through the annular gap formed between the inside mandrel 20 mm in outside diameter and the adjusting ring 24 mm in inside diameter r into the atmosphere. Upor. exposure to the atmospheric ~ressure, the mixture began to foam. At this point, cool-ing air kept at 15C was blown against the outer boundary 3 Or the extruded molten mixture through of the die as -` 11 88383 illustrated in ~igure 1, so as to inhibit outward inflation and accelerate inward inflation of the foam and produce a foamed coating on the copper pipe.
~; The polyolefin foam-coated pipe thus obtained had an outside diameter of 28 mm! had the polyolefin foam coating held fast against the copper pipe and possessed a smooth surface. The polyolefin foam coating represented an expan-sion ratio of 4.5 and was shown to possess relatively high ` rigidity and hi~h thermal resistance.
Example 2:
With 100 parts of a mixture obtained by dry blending 70% by weight of pelletized polyethylene having a density of 0.921 g/cm3 and a melt index of 2.0 with 70%
` by weight of pelletized polyethylene having a density of 0.967 g/cm3 and a melt index of 5.7, 0.5 part by weight of sodium bicarbonate and 0.4 part by weight of citric acid serving to control the size of individual cells of the foam ~
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were dr~ blended. Consequently, there was obtained a compound for extruslon foami~g. The ext~usion foam coating system adopted consisted of two extruders and one cross-head die. The leading end of the first extruder ~50 mm ~, in barrel interior diameter, L/D = 23) was joined into the rear end o~ the second extruder (40 mm in barrel interior diameter, L/D = 20). The leading end of the second extruder was fitted wlth a coating cross-head die as illustrated in Figure 1. To the first extruder kept at 160C, said poly-ethylene mixture was fed at a rate of 6.5 kg/hour. At the portion of the extruder interior at which the mixture was .~ melted and kneaded, dichlorodifluoromethane compressed to a pressure of 110 kg/cm2 was injected as a foaming agent ' I
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via an inlet bored through the cylinder barrel of the extruder at a rate of 0.52 kg/hour. The resultant mixture was fed to the second extruder, adjusted to a temperature ~__ of 130C and forced out of the cross~head die. Through .~; . , .
the cavity in the inside mandrel of the cross-head die, a copper pipe 1/2 inch (15.88 mm in outside diameter) was ~-supplied at a rate of 1 mjmin. in the same direction as the extrusion of the mixture. The mixture was extruded through an annular gap formed between the inside mandrel 20 mm in , . . .
outside diameter and the adjusting rin~ 24 mm in inside diameter into the atmosphere. Upon exposure to the atmospheric pressure, the molten mixture began to foam. ~
At this point cooling air kept at 150C was blown against r the outer boundary of the extruded molten mixture through a cooling air ring disposed adjacent the outlet of the die as shown in Figure 1, so as to inhibit outward inflation :
~ and accelerate inward inflation of the polyethylene foam j-~, .
and produce a foamed coating on the copper pipe. ~r~
The polyethylene foam-coated pipe thus obtained ~ -had an outside diameter of 32 mm,had the polyethylene foam ii~ coating held fast aFainst the copper pipe,and possessed a ' smooth surface. The polyethylene foam coating represented an expansion ratio of 6.5 and was shown to possess relatively high rigidity and high thermal resistance.
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`- 25 Example 3:
-~ The extrusion foaming system used in Example 1 r was fitted with a cross-head type coating die designed for ,." .
inner joining. In a super mixer, 100 parts by weight of a low-density polyethylene having a density of 0.921 g/cm3, ~.
~; 3 a melt index of 2.0 and a Vica' softening point of 92C
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1~88383 was mixed ~ith 0.5 part by weight of sodium bicarDonate and 0.4 part by weight of citric acid boti, serving as nucleus-forming agents.
The resultant mixture was fed to the first extruder kept at 155C at a feed rate of 7.0 kg/hour. Through the inlet for the foaming agent, dichlorodifluoromethane com- ~-pressed in advance to a pressure of 100 kg/cm2 with a reciprocating pump was fed at a rate of 1.0 kg/hour. The mixture discharged in a molten plasticized form from the first extruder was led throu~h a connecting tube into the second extruder with the pressure adjusted to 40 kg/cm2 by control of the revolution number of the screw of the second extruder. The mixture was adjusted to 103C and extruded via the coating die. Through the cavity in the inside mandrel of the cross-head coating die, a copper pipe 8 mm in outside diameter kept at 15C of surface temperature was supplied at a rate of 2 m/min. in the same I-direction as the extrusion of the mixture.
The mixture was applied to the copper pipe in ~0 the die interior 5 mm inwardly from the discharge outlet of the die. The mixture and the pipe were extruded in an integrally joined form through the dischar~e outlet of the die 11 mm in outside diameter into the atmosphere. IJpon exposure to the atmospheric pressure, the mixture on the pipe began to foam.
At this point, cooling air kept at 20C was blown r against the outer boundary of the foam through a slit of the air ring 70 mm in diameter disposed adjacent the dis-charge outlet of the die, to inhibit outward inflation and accelerate inward inflation of the polyethylene foam and ., ,, , . ~ - :
''' '. ' . ~ ' ' ' ~ " .' . . ' ~
883~3 ensure uniform union between the copper pipe and the polyethylene foam coating. Consequently, there was obtained a polyethylene foam-coated pipe.
The polyethylene foam-coated plpe thus produced was found to possess a uniform skin layer 0.1 mm ln thick-ness along the interface between the copper pipe and the foamed coating. The polyethylene foam having a density of ~ o.o8 g/cm3 (representing an expansion ratio of 11.5) and a - coating thickness of 10 mm was found to be held in tight ¦ ;
contact with the copper pipe through the medium of said skin layer. When a cut was inserted with a knife in the ~- coating layer of the polyethylene foam-coated pipe through- ~
out the entire depth and one portion of the coating layer r was pulled off the copper pipe, it was removed yery easily ~`' and absolutely no part of the foamed resin was seen to . remain sticking to the surface of the copper pipe. Thus, i the pipe was shown to enjoy high workability. r :
.
Example 4: ' ,.j .
~ The extrusion foaming system used in Example 1 ,h~ 20 was fitted with a cross-head type coating die designed for ':~ inner joining. In a super mixer, 100 parts by weight of a 1 mixture (having a Vicat sof'tening point of 117.5C) `~; obtained by dry blending 70% by weight of a low-density ,~ polyethylene having a melt index of 2.0 g/10 minutes~ a specific gravity of 0.921 and a Vicat softening point Or ~-~; 92C and 30% by weight of a high-density polyethylene having a melt index of 5.7 g/10 minutes, a specific ` gravity of 0.467 and a Vicat softening point of 127C
~i was mixed with 0.5 part by weight of sodium bicarbonate '~ 30 and 0.4 part by weight of citric acld both serving as ,,; ~
~ ' .
.- ' .. . . .
~ 20 i. .
nucleus-forming agents.
The resulting mixture was fed at a feed rate Or
Now the present invention in its various aspects will be de-scribed with reference to working examples, which are purely illustrative of aspects of the invention. ¦;
~ In a kneading extruder (50 mm in b~rrel interior diameter, i i , :~
L/D = 24), a mixture consisting of 70% by weight of a pelletized poly-propylene having a density of 0.91 g/cm3 and a melt index of 2.0 and 30% by weight of a pelletized polybutene-l having a density of 0.905 g/cm3 and a melt index of 2.0 was kneaded at 180C to produce a sub-stantially ho~ogenous mixture. With 100 parts of the mixture were dry blended 0.5 part by weight of sodium bicarbonate and 0.4 part by weight of citric acid as nucleus-forming agents , i ,,'` .
:,..................................................................... ..
.,. ' ~
~ 30 r .
~ - 15 -' ,,~
, , ~
-" .. . _ .: I
serving to control the size of individual cells of the foam. Consequentl~, there was obtained a compound for extrusion foaming.
The extrusion foam coating system adopted consisted of two extruders and a cross-head die, with the leading end of the first extruder (50 mm in barrel interior diameter, L/D = 23) joined into the rear end of the second extruder (40 mm in barrel interior diameter, L/D =20). The second r extruder was provided at the leading end thereof with a coating cross-head die llke the one illustrated in Figure 1. The compound was fed to the f.rst extruder kept at 180C at a feed rate of 7.2 kg/hour. At the portion of F
the extruder interior at which the compound was melted _ and kneaded, dichlorodif`luoromethane compressed to a - 15 pressure of 130 kg/cm2 was injected as a foaming agent via an lnlet bored through the cylinder barrel of the extruder at a rate of 0.52 kg/hour. The mixture emanating from the first extruder was fed to the second extruder, then adjusted toa temperature of 148C and extruded through the cross-head die. Through the cavity in the inside mandrel of the cross-head die, a copper pipe 1/2 inch (15.88 mm in outside diameter) was supplied at a rate of 1 m/min. in the same direction as that of the extrusion of the mixture. The mixture was forced through the annular gap formed between the inside mandrel 20 mm in outside diameter and the adjusting ring 24 mm in inside diameter r into the atmosphere. Upor. exposure to the atmospheric ~ressure, the mixture began to foam. At this point, cool-ing air kept at 15C was blown against the outer boundary 3 Or the extruded molten mixture through of the die as -` 11 88383 illustrated in ~igure 1, so as to inhibit outward inflation and accelerate inward inflation of the foam and produce a foamed coating on the copper pipe.
~; The polyolefin foam-coated pipe thus obtained had an outside diameter of 28 mm! had the polyolefin foam coating held fast against the copper pipe and possessed a smooth surface. The polyolefin foam coating represented an expan-sion ratio of 4.5 and was shown to possess relatively high ` rigidity and hi~h thermal resistance.
Example 2:
With 100 parts of a mixture obtained by dry blending 70% by weight of pelletized polyethylene having a density of 0.921 g/cm3 and a melt index of 2.0 with 70%
` by weight of pelletized polyethylene having a density of 0.967 g/cm3 and a melt index of 5.7, 0.5 part by weight of sodium bicarbonate and 0.4 part by weight of citric acid serving to control the size of individual cells of the foam ~
::, .
were dr~ blended. Consequently, there was obtained a compound for extruslon foami~g. The ext~usion foam coating system adopted consisted of two extruders and one cross-head die. The leading end of the first extruder ~50 mm ~, in barrel interior diameter, L/D = 23) was joined into the rear end o~ the second extruder (40 mm in barrel interior diameter, L/D = 20). The leading end of the second extruder was fitted wlth a coating cross-head die as illustrated in Figure 1. To the first extruder kept at 160C, said poly-ethylene mixture was fed at a rate of 6.5 kg/hour. At the portion of the extruder interior at which the mixture was .~ melted and kneaded, dichlorodifluoromethane compressed to a pressure of 110 kg/cm2 was injected as a foaming agent ' I
... . .
~ ~ - 17 -: . , .
' ~ : .. ' . ' ~
--` 1088383 t ~
via an inlet bored through the cylinder barrel of the extruder at a rate of 0.52 kg/hour. The resultant mixture was fed to the second extruder, adjusted to a temperature ~__ of 130C and forced out of the cross~head die. Through .~; . , .
the cavity in the inside mandrel of the cross-head die, a copper pipe 1/2 inch (15.88 mm in outside diameter) was ~-supplied at a rate of 1 mjmin. in the same direction as the extrusion of the mixture. The mixture was extruded through an annular gap formed between the inside mandrel 20 mm in , . . .
outside diameter and the adjusting rin~ 24 mm in inside diameter into the atmosphere. Upon exposure to the atmospheric pressure, the molten mixture began to foam. ~
At this point cooling air kept at 150C was blown against r the outer boundary of the extruded molten mixture through a cooling air ring disposed adjacent the outlet of the die as shown in Figure 1, so as to inhibit outward inflation :
~ and accelerate inward inflation of the polyethylene foam j-~, .
and produce a foamed coating on the copper pipe. ~r~
The polyethylene foam-coated pipe thus obtained ~ -had an outside diameter of 32 mm,had the polyethylene foam ii~ coating held fast aFainst the copper pipe,and possessed a ' smooth surface. The polyethylene foam coating represented an expansion ratio of 6.5 and was shown to possess relatively high rigidity and high thermal resistance.
~;~
`- 25 Example 3:
-~ The extrusion foaming system used in Example 1 r was fitted with a cross-head type coating die designed for ,." .
inner joining. In a super mixer, 100 parts by weight of a low-density polyethylene having a density of 0.921 g/cm3, ~.
~; 3 a melt index of 2.0 and a Vica' softening point of 92C
"~, , - 18 - I
J.~
: . , , . . .. _.. __ _ ___ :;;,'~,. . . . .
.''~': : ' . ,' ;"'. ~' . . ,. ' . ~,,~;, "
~; '' ' ' ' ' :.
J'~ .: ~ '::
1~88383 was mixed ~ith 0.5 part by weight of sodium bicarDonate and 0.4 part by weight of citric acid boti, serving as nucleus-forming agents.
The resultant mixture was fed to the first extruder kept at 155C at a feed rate of 7.0 kg/hour. Through the inlet for the foaming agent, dichlorodifluoromethane com- ~-pressed in advance to a pressure of 100 kg/cm2 with a reciprocating pump was fed at a rate of 1.0 kg/hour. The mixture discharged in a molten plasticized form from the first extruder was led throu~h a connecting tube into the second extruder with the pressure adjusted to 40 kg/cm2 by control of the revolution number of the screw of the second extruder. The mixture was adjusted to 103C and extruded via the coating die. Through the cavity in the inside mandrel of the cross-head coating die, a copper pipe 8 mm in outside diameter kept at 15C of surface temperature was supplied at a rate of 2 m/min. in the same I-direction as the extrusion of the mixture.
The mixture was applied to the copper pipe in ~0 the die interior 5 mm inwardly from the discharge outlet of the die. The mixture and the pipe were extruded in an integrally joined form through the dischar~e outlet of the die 11 mm in outside diameter into the atmosphere. IJpon exposure to the atmospheric pressure, the mixture on the pipe began to foam.
At this point, cooling air kept at 20C was blown r against the outer boundary of the foam through a slit of the air ring 70 mm in diameter disposed adjacent the dis-charge outlet of the die, to inhibit outward inflation and accelerate inward inflation of the polyethylene foam and ., ,, , . ~ - :
''' '. ' . ~ ' ' ' ~ " .' . . ' ~
883~3 ensure uniform union between the copper pipe and the polyethylene foam coating. Consequently, there was obtained a polyethylene foam-coated pipe.
The polyethylene foam-coated plpe thus produced was found to possess a uniform skin layer 0.1 mm ln thick-ness along the interface between the copper pipe and the foamed coating. The polyethylene foam having a density of ~ o.o8 g/cm3 (representing an expansion ratio of 11.5) and a - coating thickness of 10 mm was found to be held in tight ¦ ;
contact with the copper pipe through the medium of said skin layer. When a cut was inserted with a knife in the ~- coating layer of the polyethylene foam-coated pipe through- ~
out the entire depth and one portion of the coating layer r was pulled off the copper pipe, it was removed yery easily ~`' and absolutely no part of the foamed resin was seen to . remain sticking to the surface of the copper pipe. Thus, i the pipe was shown to enjoy high workability. r :
.
Example 4: ' ,.j .
~ The extrusion foaming system used in Example 1 ,h~ 20 was fitted with a cross-head type coating die designed for ':~ inner joining. In a super mixer, 100 parts by weight of a 1 mixture (having a Vicat sof'tening point of 117.5C) `~; obtained by dry blending 70% by weight of a low-density ,~ polyethylene having a melt index of 2.0 g/10 minutes~ a specific gravity of 0.921 and a Vicat softening point Or ~-~; 92C and 30% by weight of a high-density polyethylene having a melt index of 5.7 g/10 minutes, a specific ` gravity of 0.467 and a Vicat softening point of 127C
~i was mixed with 0.5 part by weight of sodium bicarbonate '~ 30 and 0.4 part by weight of citric acld both serving as ,,; ~
~ ' .
.- ' .. . . .
~ 20 i. .
nucleus-forming agents.
The resulting mixture was fed at a feed rate Or
7.2 kg/hour to the first extruder fixed at 170C. Via the inlet for introduction of the foaming agent, a mixture of - 5 dichlorodifluoromethane with trichlorofluoromethane (mixingratio at 7 : 3) compressed in advance to a pressure of 110 ~j-kg/cm2 with a reciprocating pump was fed at a ratio of o.8 kg/hour. The mixture discharged in a molten plasticized form from the first extruder was led through a connecting tube into the second extruder with the pressure adjusted to about 40 kg/cm2 through control of the revolution number of the screw. Then the mixture was adju3ted to 130C and ;~ forced out of the cross-head coating die designed for inner _ joining. Through the cavity at the center of the inside mandrel of the cross-head coating die, a copper pipe 8 mm in outside diameter kept at a surface temperature of 25C
was supplied at a rate of 2 m/min. in the same direction as the extrusion of the mixture.
The application of the mixture to the copper pipe was effected in the die interior 5 mm inwardly from the ¦
discharge outlet of the die. The mixture and the pipe were extruded in an integrally joined form through the discharge outlet of the die 11 mm in outside diameter into the atmosphere. Upon exposure to the atmospheric pressure, the mixture began to foam.
At this point, cooling air kept at 15C from a r slitted air ring 70 mm in diameter and cooling water kept at 10C from a perforated rlng 80 mm in diameter, both disposed adjacent the discharge outlet of the die, were blown against the outer boundary of the foam to inhibit ., , r 1- ~ 21 ~
. ~ ~
~:, . . .
. -. . ~ , .
. ~
.
outward inflation Or the polyethylene foam and ensure uniform union of the copper pipe and the polyethylene foam.
Consequently, there was obtained a polyethylene foam-coated r pipe.
The polyethylene foam-coated pipe thus produced - was found to possess a uniform skin layer 0.15 mm in thick- ~-~
ness along the interface between the copper pipe and the polyethylene foam coating. The polyethylene foam having a density of 0.13 g/cm3 (representing an expansion ratio of 7.2) and a coating thickness of 7 mm was found to be held in tight contact with the copper pipe through the medium of said skin layer. When a cut was inserted with a knife in the coating layer of the polyethylene foam-coated pipe through the entire depth and one portion of the coating layer was pulled out of the copper pipe, it was removed very easily and no part of the foamed resin was seen to remain sticking to the surface of the copper pipe. The pipe, thus, was found to enjoy high workability. ~;!, Example 5:
The procedure of Example 4 was faithfully repeated, except the copper pipe as a hollow core material was substituted by a Nylon pipe 8 mrn in outside diameter and kept at a surface temperature of 30C. Consequently, there ` was obtained a polyethylene foam-coated nylon pipe.
The polyethylene foam-coated pipe thus produced was found to possess a uniform skin layer of polyethylene r r' resin 0.1 mm in thickness along the interface between the ,; foam layer and the Nylon pipe. The polyethylene foam coating having a density of 0.11 g/cm3 (representing an 3 expansion ratio of 8.5) and a coating thickness of 8 mm was r ;, , , '~
, - 1~88383 ~ found to be held in tight contact with the Nylon pipe through the medium :::
of said skin layer. When a cut was inserted with a knife in the coating layer of the polyethylene foam-coated pipe through the-entire depth and one portion of the coating layer was pulled out of the Nylon pipe, it was re-moved very easily and absolutely no part of the foamed resin was seen to re-main sticking to the surface of the Nylon pipe. The pipe, thus, was shown to en~oy high wor~ability.
To demonstrate the operation and effect of the method of aspects . of this invention, the procedures of the above described working examples were repeated by using the same extrusion foaming system, except the cooling , of the surface of the polyethylene foam was omitted as described in the following comparison example.
Comparison Example:
'. !
By following the procedure of Example 2, extrusion coating was carried out while the blowing of cooling air to the outer boundary of the foam through the air ring disposed adjacent the outlet of the die was sus-.,~,, , ,,~ pended. The polyethylene foam-coated pipe was found to have an uneven sur-face with the outside diameter varying in the range of from 34 mm to 39 mm.
The foamed coating had its inside diameter also varying in the range of '`i `I 20 from 18 mm to 19 mm (compared with the outside diameter 15.88 mm of the ~,''! copper pipe.) Thus, the foamed coating was not held in tight contact with '''! the copper pipe. The product was found rejectable because it permitted ~, the copper pipe to slide freely inside the polyethylene foam coating.
,, .
.:,, .
., ~ .
!~
. .
r ~ ~ ' .
~ - 23 -,-:
.;" ' .
.. :, ,. ,, ,, : . . :, : , , ' .: . . : . ~ , . : , . : .
. ~, . ~ , : . : . ' :: . ' . : , . . ..
was supplied at a rate of 2 m/min. in the same direction as the extrusion of the mixture.
The application of the mixture to the copper pipe was effected in the die interior 5 mm inwardly from the ¦
discharge outlet of the die. The mixture and the pipe were extruded in an integrally joined form through the discharge outlet of the die 11 mm in outside diameter into the atmosphere. Upon exposure to the atmospheric pressure, the mixture began to foam.
At this point, cooling air kept at 15C from a r slitted air ring 70 mm in diameter and cooling water kept at 10C from a perforated rlng 80 mm in diameter, both disposed adjacent the discharge outlet of the die, were blown against the outer boundary of the foam to inhibit ., , r 1- ~ 21 ~
. ~ ~
~:, . . .
. -. . ~ , .
. ~
.
outward inflation Or the polyethylene foam and ensure uniform union of the copper pipe and the polyethylene foam.
Consequently, there was obtained a polyethylene foam-coated r pipe.
The polyethylene foam-coated pipe thus produced - was found to possess a uniform skin layer 0.15 mm in thick- ~-~
ness along the interface between the copper pipe and the polyethylene foam coating. The polyethylene foam having a density of 0.13 g/cm3 (representing an expansion ratio of 7.2) and a coating thickness of 7 mm was found to be held in tight contact with the copper pipe through the medium of said skin layer. When a cut was inserted with a knife in the coating layer of the polyethylene foam-coated pipe through the entire depth and one portion of the coating layer was pulled out of the copper pipe, it was removed very easily and no part of the foamed resin was seen to remain sticking to the surface of the copper pipe. The pipe, thus, was found to enjoy high workability. ~;!, Example 5:
The procedure of Example 4 was faithfully repeated, except the copper pipe as a hollow core material was substituted by a Nylon pipe 8 mrn in outside diameter and kept at a surface temperature of 30C. Consequently, there ` was obtained a polyethylene foam-coated nylon pipe.
The polyethylene foam-coated pipe thus produced was found to possess a uniform skin layer of polyethylene r r' resin 0.1 mm in thickness along the interface between the ,; foam layer and the Nylon pipe. The polyethylene foam coating having a density of 0.11 g/cm3 (representing an 3 expansion ratio of 8.5) and a coating thickness of 8 mm was r ;, , , '~
, - 1~88383 ~ found to be held in tight contact with the Nylon pipe through the medium :::
of said skin layer. When a cut was inserted with a knife in the coating layer of the polyethylene foam-coated pipe through the-entire depth and one portion of the coating layer was pulled out of the Nylon pipe, it was re-moved very easily and absolutely no part of the foamed resin was seen to re-main sticking to the surface of the Nylon pipe. The pipe, thus, was shown to en~oy high wor~ability.
To demonstrate the operation and effect of the method of aspects . of this invention, the procedures of the above described working examples were repeated by using the same extrusion foaming system, except the cooling , of the surface of the polyethylene foam was omitted as described in the following comparison example.
Comparison Example:
'. !
By following the procedure of Example 2, extrusion coating was carried out while the blowing of cooling air to the outer boundary of the foam through the air ring disposed adjacent the outlet of the die was sus-.,~,, , ,,~ pended. The polyethylene foam-coated pipe was found to have an uneven sur-face with the outside diameter varying in the range of from 34 mm to 39 mm.
The foamed coating had its inside diameter also varying in the range of '`i `I 20 from 18 mm to 19 mm (compared with the outside diameter 15.88 mm of the ~,''! copper pipe.) Thus, the foamed coating was not held in tight contact with '''! the copper pipe. The product was found rejectable because it permitted ~, the copper pipe to slide freely inside the polyethylene foam coating.
,, .
.:,, .
., ~ .
!~
. .
r ~ ~ ' .
~ - 23 -,-:
.;" ' .
.. :, ,. ,, ,, : . . :, : , , ' .: . . : . ~ , . : , . : .
. ~, . ~ , : . : . ' :: . ' . : , . . ..
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method for the continuous extrusion coating by the use of a coating die of a hollow core material with a highly expandable polyolefin resin composition containing a volatile organic liquid blowing agent, the improve-ment comprising externally, cooling the outer surface of said extruded molten mass of expandable polyolefin resin, at the point at which said molten mass be-gins to foam, by by contacting said surface with a cooling gas or water to allow the pressure of foaming to be exerted inwardly and also to cause the growth of foam to proceed in the direction of the internal core for thereby enabling the polyolefin foam to adhere fast to the hollow core and giving rise to a coating having a smooth surface condition, wherein said expanded polyole-fin foam has an expansion ratio of not less than 3.
2. The method according to claim l, comprising keeping the surface temperature of the hollow core material being continuously supplied at a level below the softening point of the expandable polyolefin resin being extruded through the coating die and thereby allowing a uniform skin layer to be formed of said polyolefin resin along the interface between the core material and the molten mass when they are brought into mutual contact, whereby said uniform skin layer maintains fast adhesion of the foamed coating to the core material and yet permits ready release of the foamed coating from the core material.
3. The method according to claim 2, wherein the polyolefin resin is a low-density polyethylene having a density of not more than 0.930 g/cc.
4. The method according to claim 2, wherein the polyolefin resin is a mixture consisting of from 30 to 90% by weight of a low-density poly-ethylene having a density of not more than 0.930 g/cc and 70 to 10% by weight of a high-density polyethylene having a density of not less than 0.940 g/cc.
5. The method according to claim 2, wherein the hollow core material is made of a metallic or synthetic resin substance.
6. The method of claim 1 comprising applying the expandable poly-olefin resin coating to the hollow core as the resin leaves the die.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP51074061A JPS6017692B2 (en) | 1976-06-22 | 1976-06-22 | Continuous extrusion coating method with polyethylene foam |
| JP74061/76 | 1976-06-22 | ||
| JP10303276A JPS5328669A (en) | 1976-08-27 | 1976-08-27 | Process for continuous extrusion coating with polyethylene foam |
| JP103032/76 | 1976-08-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1088383A true CA1088383A (en) | 1980-10-28 |
Family
ID=26415198
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,792A Expired CA1088383A (en) | 1976-06-22 | 1977-06-17 | Extrusion coating method with polyolefin foam |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4146562A (en) |
| CA (1) | CA1088383A (en) |
| DE (1) | DE2728130A1 (en) |
| FR (1) | FR2355645A1 (en) |
| GB (1) | GB1542585A (en) |
| SE (1) | SE425365B (en) |
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| USD693148S1 (en) | 2010-03-03 | 2013-11-12 | Noel Group Llc | Mattress bed cushion |
| WO2012177321A2 (en) | 2011-04-29 | 2012-12-27 | Nomaco Inc. | Unitary composite/hybrid cushioning structures(s) and profile(s) comprised of a thermoplastic foam(s) and a thermoset material (s) and related mothods |
| US20130186869A1 (en) * | 2012-01-23 | 2013-07-25 | Csx Transportation | Coupler installation device |
| USD691400S1 (en) | 2012-02-10 | 2013-10-15 | Nomaco Inc. | Stackable base for mattress assembly |
| USD693146S1 (en) | 2012-04-27 | 2013-11-12 | Noel Group Llc | Mattress bed cushion |
| USD694552S1 (en) | 2012-04-27 | 2013-12-03 | Noel Group Llc | Mattress bed cushion |
| USD693147S1 (en) | 2012-04-27 | 2013-11-12 | Noel Group Llc | Mattress bed cushion |
| USD693149S1 (en) | 2012-04-27 | 2013-11-12 | Noel Group Llc | Mattress bed cushion |
| USD692693S1 (en) | 2012-04-27 | 2013-11-05 | Noel Group Llc | Mattress bed cushion |
| EP2847508A4 (en) | 2012-05-11 | 2016-01-20 | Nomaco Inc | Insulation systems employing expansion features to insulate elongated containers subject to extreme temperature fluctuations, and related components and methods |
| USD697337S1 (en) | 2012-07-03 | 2014-01-14 | Nomaco, Inc. | Stackable base for mattress assembly |
| USD690536S1 (en) | 2012-07-26 | 2013-10-01 | Nomaco Inc. | Motion isolation insulator pad |
| USD692694S1 (en) | 2012-09-28 | 2013-11-05 | Noel Group Llc | Mattress bed cushion |
| USD694041S1 (en) | 2012-09-28 | 2013-11-26 | Noel Group Llc | Mattress bed cushion |
| USD688069S1 (en) | 2012-09-28 | 2013-08-20 | Noel Group Llc | Mattress bed cushion |
| USD709301S1 (en) | 2012-11-09 | 2014-07-22 | Noel Group Llc | Mattress bed cushion |
| USD707467S1 (en) | 2012-11-09 | 2014-06-24 | Noel Group Llc | Mattress bed cushion |
| USD707468S1 (en) | 2012-11-09 | 2014-06-24 | Noel Group Llc | Mattress bed cushion |
| USD701713S1 (en) | 2012-11-09 | 2014-04-01 | Noel Group, Llc | Mattress bed cushion |
| US10045633B2 (en) | 2013-04-26 | 2018-08-14 | Noel Group Llc | Cushioning assemblies with thermoplastic elements encapsulated in thermoset providing customizable support and airflow, and related methods |
| USD704962S1 (en) | 2013-09-09 | 2014-05-20 | Noel Group Llc | Mattress bed cushion |
| CN109203502A (en) * | 2018-07-09 | 2019-01-15 | 浙江双林环境股份有限公司 | A kind of foaming composite pipe production line |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2994327A (en) * | 1955-04-26 | 1961-08-01 | Caronelle Inc | Articles of reinforced foam material |
| US3030623A (en) * | 1957-11-21 | 1962-04-17 | Us Rubber Co | Method for making blown rubber |
| US3029476A (en) * | 1957-12-16 | 1962-04-17 | Us Rubber Co | Method for making blown rubber |
| US3068532A (en) * | 1958-12-09 | 1962-12-18 | Union Carbide Corp | Method of preparing insulated electrical conductors |
| DE1230551B (en) * | 1963-07-09 | 1966-12-15 | Reifenhaeuser Kg | Device for the continuous extrusion of molded bodies |
| FR94389E (en) * | 1966-09-07 | 1969-08-08 | Ugine Kuhlmann | Process and device for the extrusion of expandable plastic materials. |
| DK126094A (en) * | 1966-09-07 | 1900-01-01 | ||
| DE1629716C3 (en) * | 1967-09-29 | 1983-06-01 | Benteler-Werke Ag Werk Neuhaus, 4790 Paderborn | Method and device for the continuous application of a heat and sound insulating jacket layer on a metal pipe |
| CA863712A (en) * | 1968-10-07 | 1971-02-16 | Union Carbide Canada Limited | Tubular insulation formed by an extrusion process |
| FR2033555A5 (en) * | 1969-02-27 | 1970-12-04 | Vallourec | Insulated household hot-water pipe |
| JPS5016921Y2 (en) * | 1971-06-06 | 1975-05-26 | ||
| BE789774A (en) * | 1972-02-18 | 1973-02-01 | Sinclair Koppers Co | PROCESS AND APPARATUS FOR THE MANUFACTURE OF FOAM PROFILES |
| US3860686A (en) * | 1972-06-07 | 1975-01-14 | Western Electric Co | Method of and apparatus for extruding plastic materials |
| US3790436A (en) * | 1972-08-10 | 1974-02-05 | Armstrong Cork Co | Extruded cellular slab of varying densities |
| DE2420608A1 (en) * | 1974-04-27 | 1975-11-20 | Wieland Werke Ag | METHOD AND DEVICE FOR MANUFACTURING A METAL PIPE COVERED WITH A FOAMED PLASTIC COAT |
-
1977
- 1977-06-16 GB GB2529277A patent/GB1542585A/en not_active Expired
- 1977-06-17 CA CA280,792A patent/CA1088383A/en not_active Expired
- 1977-06-20 US US05/808,385 patent/US4146562A/en not_active Expired - Lifetime
- 1977-06-21 SE SE7707185A patent/SE425365B/en not_active IP Right Cessation
- 1977-06-22 FR FR7719181A patent/FR2355645A1/en active Granted
- 1977-06-22 DE DE19772728130 patent/DE2728130A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2728130C2 (en) | 1987-01-15 |
| FR2355645B1 (en) | 1980-04-25 |
| SE425365B (en) | 1982-09-27 |
| US4146562A (en) | 1979-03-27 |
| FR2355645A1 (en) | 1978-01-20 |
| GB1542585A (en) | 1979-03-21 |
| SE7707185L (en) | 1977-12-23 |
| DE2728130A1 (en) | 1978-01-05 |
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| MKEX | Expiry | ||
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