US3176437A - Fiber product - Google Patents

Description

United States Patent O 3,176,437 FIBER PRDUCT Charles E. Lanyon, Troy, N.Y., assignor to John A. Manning Paper Co., Inc., Troy, N.Y. Filed July 12, 1962, Ser. No. 209,383 14 Claims. (Cl. 51-408) This invention relates to an improved coated abrasive. More particularly, it relates to a coated abrasive Incorporating a backing which resists the distortion often resulting from application of the various coatings. The finished product also displays an improved resistance to the curling which, in prior products of this type, ensues from differential expansion of the coating and the backing under varying humidity conditions.

A coated abrasive sheet, or sandpaper as it is commonly known, is made by applying to one side of a paper backing a heavy coating or adhesive, known as the making coat, usually, but not always, a hot concentrated solution of hide glue in Water- While the adhesive coat is .still hot and fluid, the abrasive grain is applied and the coated sheet festooned in racks and partially dried. A second adhesive coat, known as the sizing coat, is then put on to anchor the abrasive grain. The sizing coat may be the same as the previous coat, i.e., a hot solution of hide glue in water, although more dilute. It

may also be of a different nature such as a synthetic resin. The composite is then festooned, dried and taken down in rolls for further processing or converting.

`While the material is hanging festooned in the racks, the water in the adhesive coat or coats penetrates through the backing, softening it so that, because of the weight of the coated material hanging in the loops, it tends to distort. Stresses in the backing are relieved by the r dampening action of the water, which may cause the backing to pucker, cockle, or welt. These defects usually carry through to the finished roll, resulting in increased waste and scrap.

The trend in the coated abrasive industry is to coat wider and wider sheets, but the difculties enumerated increase out of proportion to the increase in width.

y Therefore, an improved product which would overcome these difficulties would find a ready sale.

It has been suggested in the prior art to apply a waterimpermeable coating on the side of the paper designed to receive a subsequent coating, in order to prevent strikethrough of adhesive or to reduce curl. However, this f expedient forms a surface to which the making coat adheres with difliculty, causing shedding of the abrasiveadhesive coating from the backing during use.

Accordingly, a principal object of my invention is to provide an improved coated abrasive and an improvedV and will in part appear hereinafter.

The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects yof the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing in which:

FIG. 1 is a fragmentary cross section of sheet material ICC used as a backing for a coated abrasive embodying my invention,

FIG. 2 is a fragmentary cross section of a coated abrasive incorporating the sheet material of FIG. 1 as a backing,

FIG. 3v is a schematic view of apparatus which may be used in manufacturing the sheet material of FIG. 1, and

FIG. 4 is a fragmentary cross section of another coated abrasive embodying the invention.

In general, a coated abrasive embodying my invention includes as a backing a multiply brous sheetkor web of pervious material with an impervious resin or plastic film disposed between a pair of the plies and preferably located substantially closer to the coated surface of the sheet than to the other surface. The film is suitably bonded to the plies engaging it. Thus, when the surface close to the film is exposed to the glue coats, the glue travels only a short distance through the sheet, the film preventing further penetration. Most of the sheet is therefore unaffected and the sheet as a whole retains its strength and other desirable properties which would otherwise be affected by the wet coats.

The impervious film is preferably a plastic, since many such materials do not interfere with the desirable properties of the final product. In order to obtain suflicient strength in the sheet it is generally necessary that the plastic film be well bonded to the plies on both sides of it. For this and other reasons, in the case of paper and other water-laid products we prefer to use the manufacturing process disclosed by J. Welch et al. in copending application Serial No. 233,508, filed October 25, 1962, for Improved Laminated Fiber Product and Method of Making It. However, other well-known bonding techniques, e.g., ofi-machine lamination of paper and preformed resin film, may in many instances be used.

It should be noted that the invention is applicable to thermosetting as well as thermoplastic materials, and the erms plastic and resin, as used herein, include both types. Plastic and resin are used interchangeably herein because most plastics are resins. However, it will be understood that other materials having plastic properties, e.g., cellulose derivatives, are within the scope of the invention and are therefore included within these terms.

FlG. l illustrates in cross section a 5-ply cylinder sheet 8, used in my invention. By way of example, the paper sheet may be in a weight basis of 130 pounds per ream (480 X 24 inch X 36 inch), which is a popular weight in the coated abrasives field. The sheet comprises plies 16, l2, 14, 16 and 18, with an impermeable film 20 disposed between and bonded to the plies 10 and 12. In further manufacturing processes, the upper surface 10a of the ply 10 is coated with a water solution of adhesive, the moisture being prevented by the film 20 from reaching the percent of the sheet comprising the four plies 12-18.

For example, as shown in FIG. 2, the abrasive layer may be added to the sheet 8 by first applying a making coat 22 to the surface 10a. The water in the coat 22 saturates the ply fil and thereby weakens it. However, the film 29 prevents it from reaching the bulk of the paper in the sheet, and with the strength of the sheet preserved, distortion thereof during the later drying operation is largely eliminated. Moreover, the surface to which the abrasive coating is to be applied is paper. Hence, problems of adhesion of the abrasive coating to my improved sheet are no different than they are with conventional paper.

Following the making coat 22, abrasive grain illustrated at 24 is added, and the grain 24 is covered by a sizing Patented Apr. 6, 1965 of a dandy roll 64, which Y `ond'ply 1'2:is"added at'the i Y y. j 3,176,437...Y

coat Finally, the sheet ishung'to dryas'described above:

The preferred-process Yfor,1nanufacturing the sheet 8 In this Way, a vvetv sheet is produced witha layer ofldiscrete particles of resin between two wet plies.` The'vvfet Y n method4 should be of aV type {vi/laich,` after it startsl to sheet is-wet pressed and drieidjaccording to well known n etermined t-,ovbeV` adequate for.V softening and cansingin-A Vcipient ovv in the particular resin used.V It'is'th'en mimediatelycalendered,k whereupon theresin flows and formsf a continuous nlm internally laminating the Atwo'sheets Y papermakizng 'techniquev The dried sheet, still on the L paper, machine, Yis heated to` a temperature previouslyV lt willbe apparentthat Ythe resin particles' need not be appliedv at kthe wetend of the paper machine, although this is preferred for reasonsofweconorn'y and also because ra somewhat betterquality product is obtained.

*.Thus, they 'may be appliedto already formed and dried paper webs, which are lthen heated and pressed into a lcontinuous lm. Also, as mentionedpabove, a pre-formed l resin iilrn may be used.

The; resin Aused, to form the film Ztl in theY preferred soften, Vremains very viscous overl a rather extensive'temperaturerrange. That is,'the fused resin should retain Y substantial body and Aviscosity after heating, since, .if it with a bond strength exceeding `the internalstrength of the two adjacent plies. f Y Y Y FIG. 3 is a 'diagrammatic representation of a 5 -Ymold cylinder machinewhichrnay be used in applying the preferredr manufacturing techniquelto multiply vpaper ernbodying the invention; The machine includes va rseries of vats Si), 32, 34,. 36 and/48. lSince'the vats rnayhavev an4 identical. construction, Vonlythe'vat y Stlwill be described in detail. Y

Stock consisting of a dilutesuspension 40 of*p'aperf making fibers andWater is introduced into thevat V3f) atV an inlet 42. ltithen ows through an arcuate passageway` 44 -arounda' cylinder 46 andv out through an overflowf 48;@ The cylinder, which is hollowand covered with fine wire meshSi), turns with theow of the stock. n y

below the'level 54 vof the stock on the outside by Vmeans of an Youtflow opening 56'. Hence, alpr'essure gradient j exists whichrforces the stock torow froinvtheoutside of, the cylinder to the'inside'. The ber in the'stock is trapped n on the wire mesh, thus Vforming the Vply 10, whichnrmoves-f Vout of thevat 30 and is transferred to the' underside of 62.- The resin The roll 64 ordinarily takes the Aform of a hollow cylinder:

whose surface isv comprisedof cylinder or Fourdrinier Wire (30480 mesh). i

a traveling wetfelt60 by meanslof a `pressure roll (couch)y f kdispersion is applied at point `by means revolvesin a troughY 66 con- Y A becomesV too fluid, it'wills'trik'e into the paper anda continuous lmmay not be produced. Preferably, the temperature at which it becomes iluid is substantially above the Vboiling pointgof lwater, so'that drying ofthe paper lcan be readily'accomplished without liquefying the resin.

The particle size is also of importance. The particles `should not be too fine. Otherwisethey will penetrate the LuV/e'tvveb andnot-form auniform coating of discrete 'resinparticles lfltheyfare too coarse, they may not flow y out under heat andy pressure to develop thev film.

Y organicjperoxidq eg., ldicurnyl peroxidezMixtures of Y v The levelv 52 `of water inside thV Cylin'der46 islrrerritl` Vepoxy resinsswith. polyethylene or Ymirrtures of nylon and Amongthe' resins whichf'inaybe'used for'the 2l) are polyethylene, polypropylene, nylon, ,fluorhalocarbona j polycarbonate and epoxy. Mixtures'of these' resins can `also be. employed. vHow/ever, 'while' a' larger number of :resins are-usable, we prefer to use, partlybecause of their `low'cost,"pf'clyole'finsA such as polyethylene orpolyprOpylene, extended. with Vfillers and cross-linked with polypropylene vare also 'among the preferred materials.

' The preferred;materialsvhave'the addedradvantagesofA producing. flexible, tough sheets which vdo notfrequire The iilinV should notvbe so thin asY to be susceptible to rupture lor so thick as toV cause undue stiffness in the sheet 3; VA thickness rangejof from y0.5 to 5 mils is generally acceptable, althoughh we prefer a rangefof V0.5 'to l2 'mils for sandpaper. j Y 'Y l While itis preferable, for the reasons given above, that theVV resin lrn be Vclose to the coatedV surfacefof the backing, it is not necessary that this be so. Forexample, if

After theapplicationof the resin particles 6:8, theesec-A web 70. Theweb 70, in which the paper'plies 10 and 12 sandwich af layer of the particles, then continues to. Y the vats 34,36 and. 38pwherethe plies 14, 16, and 1S are l. l

vat32j' to form a composite.

added. From the Vvat 38, the: webcontinues varound the.'V l

roll 6 2 vassociated therewith and. on to thc-.subsequent papermaking.V operations. v e erations, including wet pressing, :drying Vand calendering.

Prior to 'calendering Vthe web The latter are conventional op? bonded to the plies 10andl2. The strength of the bondj Aformed in thisrnanner is'due in large part'to 'thef fact that the i'lbers ofthe plies 19 .and 12 penetrate into thel vplastic film 20 (FIG. l) and are gripped by the film which is,"in essence, `formed around them.

VIf'desired, the resin suspension rnay'also bevfappliedsat point X by means of a spraying device or other suitable method.` Thearnountof resin that is appliedcan be conf Y trolled byV varying the concentration of the suspension in the trough 66; by Vchanging the characteristics of the Y dandy'roll 64, if this is used; by changing the spraying pressure, if'uthis method of application is preferred; or A by other means which are obvious to' those skilled in the' art. e

the -film is centrally Alocated within the sheet, over 50 percentofrthey dry strength ofthe backing is retained when thecoating is applied. Y n *l Y Y Insome cases it Will be advantageous .to incorporate a second resin film near the uncoatedv surface of the back ing. Thisprovides a means of controlling therate of Vmoisturev vapor penetration'intoy the sheet and regulating its curling propensities;` `FIG. 4 shows` a coatedabrasive utilitzing'lsuch a sheet '74 'incorporating a second resin film 76'near the'surfacek 74a remote from the abrasive grains `2'4".. Specifically, 'the coated abrasive, which isvsimilar tothecoated abrasive of FIG. 2,1`comprisesvplies 1G, 12,' lala and 18 with' the tilm 20 between the plies 1t? and 12 andtheV film 16 disposed between and bonded to the plies E aud 13. The'nialring coaty 22 and the sizing coat Ze'anch'or the abrasive grains 24 to the 4outer ksurface of the ply lli). v

.Arjs'peciiic' exampleof a.' coated abrasive, embodying myinventicnrwill now be described in detail, it being understood,thatnrthis exampleris givenby vwayvof illustrationand not limitationlof the invention. i

VThe iiber'furni'sh for thebackingrnay consist of rope, jute, wood pulp,V cotton orfmixtures of these. Therevquired lamounts of the fibrous constituents are introduced into a beaterA and beaten to the requisite degree.V In the Ybeaterr thejber 'may also beV dyedV and additives such as resin size, elastomers, etc., maybe-added. After beating, 4the material "is droppedV to storage chests and` passed s, 17e/asv through Jordans to a paper machine which may be a 5- mold cylinder machine as illustrated in FIG. 3.

'The paper machine is adjusted to provide a backing sheet weighing 130 pounds per ream (48() sheets, 24 inch x 36'inch). In the vat 30, the consistency of the stock is set so that, at the speed selected, a ply weighing about 26 pounds is formed. This constitutes about 20 percent 'of the total weight of the fiber furnish. At the point X,

a water suspension of finely divided resin particles 68 is applied in the manner described above. The particles are of polyethylene resin manufactured by United States lndustrial Chemical Co. and marketed under the trade designation Microthene 700. They are ground to pass through a screen having 150 openings per lineal inch, and the concentration of the finely divided polyethylene in the water is about 9 percent. At the speed selected, this concentration results in the application of about 1.8 grams of resin per square foot of paper. A

After drying, the web 70 is heated to a temperature of 275 F. and then calendered under a pressure of 100 lbs. per lineal inch. Under the calendering pressure, the resin particles fuse and form a film about 0.8 mil thick.

The paper is then slit to width and coated with abrasive. To accomplish this, a heavy coat of hot concentrated hide glue is first applied to the coat side of the backing (i define the coat side as that surface (10a) of the sheet S closest to the impermeable film While the glue is still hot and fluid, abrasive grain is applied by conventional methods. The composite is then festooned in racks and partially dried. A more dilute solution of hot hide glue is then applied to the abrasive coat to anchor and hold the grain in place, after which the composite is again festooned in racks and dried. Finally, it is taken down in rolls for further processing.

Coated abrasives made according to the present invention are handled with much less trouble through the coating operation, during drying and through subsequent operations. The bulk of the backing remains dry and retains body and stiffness. Distortion, wrinkling and puckering are noticeably less with the improved backing than with conventional paper.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above article without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.

I claim:

l. A coated abrasive comprising abrasive grains anchored by an adhesive to a fibrous backing comprised of multiple fibrous layers and a resin film between and bonded to first and second ones of said layers said adhesive being contiguous with a fibrous layer of said back-- ing and anchoring said grains directly thereto.

2. The article defined in claim l in which said film is substantially closer to a first surface of said backing to which said grains are anchored than to a second surface opposite said first surface.

3. The article defined in claim 1 in which the fibers in said first and second layers penetrate into said film.

4. The article defined in claim 3 in which said first and second layers are integral.

5. The article defined in claim l including at least five fibrous layers, said first layer being adjacent to said grams.

6. The articie defined in claim l including at least three of said layers, said layers having substantially equal thicknesses, there being a fewer said layers on the side of said film facing said grains than 0n the other side of said film.

7. A coated abrasive comprising abrasive grains anchored by an adhesive directly to a fibrous layer of a backing comprised of multiple fibrous layers, said backing including a first resin film close to a surface of said backing to which said grains are anchored and a second resin film close to the opposite surface of said backing, each of said films being disposed between and bonded to an adjacent pair of said layers.

8. The article defined in claim 7 in which said backing is comprised of paper.

9. The articie defined in claim 8 in which the fibers in the layers adjacent to said film penetrate into said film.

10. In a coated abrasive of the type comprising abrasive grains anchored to a paper backing by a glue having a paper-weakening base of water or the like, the improvement in which said backing comprises a plurality of paper layers and a resin film disposed between and bonded to first and second ones of said layers, said glue being contiguous with said first fibrous layer of said paper backing and anchoring said abrasive grains directly thereto.

1l. The article defined in claim l0 in which said film is substantially closer to a first surface of said backing to which said grains are anchored than to a second surface opposite said first surface.

12. The article defined in claim ll including a second resin film disposed between and bonded to a pair of said v layers, said second film being substantially closer to said second surface than to said first surface.

13. The article defined in claim 10 in which a substantial portion of the fibers in said first and second layers penetrate into said film.

14. The article defined in claim 13 in which said first and second layers are integral with each other.

FRANK H. BRONAUGH, LESTER M. SWINGLE,

Examiners.

Claims (1)

1. A COATED ABRASIVE COMPRISING ABRASIVE GRAINS ANCHORED BY AN ADHESIVE TO A FIBROUS BACKING COMPRISED OF MULTIPLE FIBROUS LAYERS AND A RESIN FILM BETWEEN AND BONDED TO FIRST AND SECOND ONES OF SAID LAYERS SAID ADHESIVE BEING CONTIGUOUS WITH A FIBROUS LAYER OF SAID BACKING AND ANCHORING SAID GRAINS DIRECTLY THERETO.

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