CA2185150A1

CA2185150A1 - Curable polymeric composition and use in protecting a substrate

Info

Publication number: CA2185150A1
Application number: CA002185150A
Authority: CA
Inventors: James A. Rinde; George Pieslak; Leon C. Glover
Original assignee: Individual
Current assignee: Raychem Corp
Priority date: 1994-03-11
Filing date: 1995-03-08
Publication date: 1995-09-14
Also published as: AU1989795A; CN1137180C; AU691587B2; EP0749449A1; PL179652B1; US6294597B1; BR9507026A; PL316205A1; JP3742102B2; MX9604003A; JPH09510248A; CZ292938B6; KR970701744A; CN1149302A; RU2146272C1; WO1995024433A1; US6224710B1; CZ267496A3

Abstract

A curable poymeric composition (6) which is a liquid at 20°C and which comprises 25 to 60 % by weight of a resin component which comprises an epoxy, 5 to 25 % by weight of a curing agent which comprises two components, a first component which is a cycloaliphatic amine or an aromatic amine, and a second component which is a polyamide amine, and 20 to 65 % by weight of an inert inorganic filler.
The curable composition (6) can be used in a method of protecting a substrate such as a pipe (4) or a pipe joint from corrosion or mechanical damage. In the method, the curable composition (6) is first applied to the substrate (4), a polymeric covering layer (2) is applied over the curable composition with an innermost layer of a heat-activatable sealant (8) in intimate contact with the curable composition, and the curable composition is then cured. During the curing process, the heat-activatable sealant, e.g. a hot melt adhesive, remains in contact with the curable composition and interacts therewith.

Description

W095/24433 2 1 8~ 15~ PCT/USg5/03072 CURABLE POLYMERIC COMPOSITION AND
USE IN PROTECTING A SUBSTRATE

BACKGROUND OF THEINVENTION

Field of the Invention This invention relates to a curable polymeric composition and the use of the 10 composition in plo~ g a substrate, in particular a mçt~llic pipe.

Introduction to the Invention To protect substrates such as metallic pipes, pipe joints, and pipelines from corrosion, mechanical damage resulting from abrasion, or degradation due to exposure to sun, soil, moisture, or other elc...~ , a prl~lecLi~e coating may be applied to the exterior of the pipe.
The ~rul~i~i~/e layer is often polymeric and may be in the form of a polymer tape which is coated with a mastic layer and is then applied to the pipe, a polymer layer which is sprayed or painted onto the pipe, or a fusion bonded epoxy coating which has been applied in the 2 0 factory. ~ltçrn~tively~ the plutc;~;~ive layer may be in form of a heat-recoverable article, i.e. a heat-~hrink~ble polymeric article such as a sleeve, sheet, or tape, which is recovered onto a pipe or substrate. Such heat-recoverable articles are particularly useful in providing protection to pipe welds or joints which are created when pipe is repaired or lcllufilled, e.g.
when two pieces of pipe are ~tt~hed to one another. Using a heat-recoverable article allows 2 5 protection to be applied in the field without the need for difficult, time-c-)ns~lming, and craft-sensitive procedures.

In order to çnh~nce the ~lh~osion between the pipe and the heat-recoverable article, it is co~,lon to use a heat-activatable sealant or a mastic which can bond to both the pipe and 3 0 the heat-recoverable article. The sealant or mastic is often in the form of a layer which is applied to the surface of the article which is in contact with the substrate. When heat is applied to the article, generally by means of a torch or other heat source, the heat-activatable sealant is activated and the article recovers. A strong bond is thus fc~nned between the polymeric article and the substrate. Altçrn~tely or in addition to the heat-activatable sealant, a 3 5 primer layer, often in the form of a curable polymeric composition such as an epoxy, may be applied to the substrate to improve the adhesion of the heat-recoverable layer to the substrate.

Curable epoxy primers for pipe coating are known. U.S. 3,876,606 (Kehr), the disclosure of which is incorporated herein by reference, discloses a thermosetting epoxy resin W095/24433 21 8 51 5 0 2 PcTlussslo3o72 which comprises a polyglycidyl ether of polyhydric phenol, a dihydrazide, and a filler such as barium sulfate, calcium carbonate, or mica. The coating has good adhesion to the substrate when subjected to boiling water and also exhibits good cathodic disbonding pelrc llllance at room ~ ~ldlUl~ and at 60C. However, the coating is in the form of a 5 powder which is applied to a preheated substrate. Uniform application of such a powder onto a pipe or a pipe joint in the field is .lifflcult~ requiring complex e luiplllelll and relatively high lelllp~ tures.

U.S. Patent Nos. 4,732,632 and 4,997,685 (Pieslak et al), the disclosures of which 10 are incol~ d herein by reference, disclose a method of applying a protective coating onto a substrate. The method comprises applying to the substrate a curable polymeric composition which is a liquid at about 20C, comprises a resin component and a curing agent, and cures to a substantial extent within 24 hours at a le~ ture of not more than about 80C. A
polymeric covering layer having an innermost layer of a heat-activatable sealant is applied 15 over the curable colllpo~ilion and the curable composition is then cured while in intim~te contact with the inner~nost layer. The resulting covering has good adhesion to both the substrate and the heat-recoverable article and exhibits good cathodic disbonding pelrc,lmance.
It is necess~ry, however, that the curable composition be selected to meet the specific requil~,lllellts for each application; a single composition cannot be used for a wide variety of 2 0 l~ ,ldlUIG applications.

SUMMARY OF THE INVENTION

We have now discovered a com~o~ilion that is suitable for use as a primer on a 2 5 substrate under a variety of telllpel~ conditions which can be prepared by incorporating a particular ~ c; of amines in the curing agent. Furthermore, unlike some conventional compositions, the composition of the invention contains a relatively nonvolatile curing agent and thus is not subject to evaporation during curing. This means that special precautions need not be taken during shipping, h~nr1ling, and use. In a first aspect, this invention 3 0 discloses a curable polymeric co,ll~osition which is a liquid at 20C and which comprises (1) 25 to 60% by weight of a resin colllponelll which cc,lll~ises an epoxy;

(2) 5 to 25% by weight of a curing agent which comprises (a) a first com~onenl which is a cycloaliphatic amine or an aromatic amine, and (b) a second colll~onenl which is a polyamide amine; and wo 95/24433 2 1 8 5 1 5 o PCT/US95,3072 (3) 20 to 65% by weight of an inert inorganic filler.

Compositions of the invention are particularly useful when used in conjunction with a polymeric covering to provide envuo~ t~l protection to a substrate such as a pipe. The composition serves to provide excellent adhesion between the substrate and the protective covering which is applied to the curable composition while it is subst~nti~lly uncured. The inn~rmost layer of the plvle~ e covering, generally an adhesive, is held in illti...~lt contact with the curable composition while the curable composition is cured. As a result of the 10 intim~te contact, the curable composition of the invention and the adhesive layer are able to interact. Thus the second aspect of the invention provides a method of applying a protective covering to a substrate, said method comprising (A) applying to the substrate a curable polymeric composition according to the first aspect of the invention;

(B) applying a m~lltiple-layer polymeric covering having an innermost layer and an oul~l,no~l layer over the curable composition in a manner such that said innermost layer is in i ~ te contact with said co~ osilion, the innermost 2 0 layer compri~ing uncured polymeric heat activatable sealant capable of interacting with said curable composition; and (C) allowing the curable co~ osilion to cure while ~ ing intimate contact between said innerrnost layer and said composition.
In a third aspect, this invention provides an assembly for p~lecling a substrate, the assembly comprising (A) a substrate;
(B) a first layer in contact with the substrate which comprises a cured composition of the first aspect of the invention;

(C) a second layer which contacts the first layer and interacts with it and which 3 5 comprises a hot melt adhesive; and (D) a third layer which contacts the second layer and which is a polymeric covering.

wo 95/24433 2 1 8 5 1 5 0 ~ PCT/US95/03072 BREF DESCRIPTION OF THE DRAWING

The invention is illustrated in the drawing in which Figure 1 shows a perspective view of an assembly of the invention in which a heat-recoverable article is positioned on a 5 substrate after recovery; and Figure 2 shows a cross-sectional view of the article of the invention along line 2-2 of Figure 1.

DETAILED DESCRI~ION OF T~E INVENTION

The colnposilion of the invention is a liquid at 20C in its uncured state so that it can be readily applied to a substrate by any appl~liate means, e.g. brushing, painting, spraying, or dipping. The viscosity of the uncured composition, as measured at 25C according to ASTM-D1084, the disclosure of which is incorporated herein by l~;Ç~, ence, is 30,000 to 70,000 cenli~oise. In this application, the "curable composition" is also referred to as a "primer".

In this speçifi~tion~ all references to ~ c~ ges by weight of the curable 2 o composition refer to the uncured cc,.llposilion.

The curable composition comprises 25 to 60%, preferably 30 to 55%, particularly 35 to 50% by weight of the curable colllposition of a resin co~ )onent which comprises an epoxy. Appl.,pliale epoxies include bisphenol A epoxies and novolak epoxies, or blends 2 5 thereof. Particularly plefell~d is a modified epoxy which is a mixture of a bisphenol A
diglycidyl ether polyrner and a~ Ailllalely 10% of a multifunctional resin based on 4-glycidyloxy-N-N-diglycidyl aniline. Such a ~l~;rell~d m~ten~l is sold by Ciba-Geigy under the tr~1en~m~ AralditelM XIJLY 366. It is l,lcr~llGd that the resin cc.lllponent and the epoxy be a liquid at 20C. In addition to the epoxy, the resin coll,ponent can contain non-volatile 30 plasticizers, e.g. dibutyl phth~l~t~, functionalized epoxy Ailll~nt~ or a Illi~lwe of epoxy resins.

The curable colllposilion also compri~es 5 to 25%, preferably 10 to 20% by weight of a curing agent which cclll~lises at least two coll~ponellb. The first collll~onel-t is a 3 5 cyclo~liph~tic amine or an ar~n~ic amine. E~mples of a~lo~liate cycloaliphatic amines are 4,4'-methylene-bis-(2-ethyl-6-methylcyclohexylamine), 1,3-diaminocyclohexane, isophol~one ~ mine, and m~nth~ne tli~mine Colllll~luially available cyclo~liph~tic amines are dicyclohexyl ...e~ e-4,4'-~i~mine, available from Pacific Anchor as AmicureTM
PACM, and other cycloaliphatic amines available from Pacific Anchor under the tr~ n~mes ~n~ztmineTM 1770, 2049, 2167X, and 2264X. Examples of ap~.op,iate aromatic amines are 4,4'-methylene-bis-(2,6-diethylaniline), 4,4'-methylene-bis-(2-isopropyl-6-methylaniline), 4,4'-methylene-bis-(2,6-diisopropylaniline), 4,4'-methylene dianiline, m-phenylene-diamine, and 4,4'-methylene-bis-(2-ethyl-6-methylaniline), as well as blends of these ~min~s 5 Co...l..~.cially available aromatic amines include CMDrM 8401, available from Rhone-Poulenc, and TonoxTM 60-40, available from Uniroyal Chemi~stl~ Whether a cycloaliphatic amine or an aromatic amine is used depends on the available curing conditions and the desired pl~pcllies of the cured composition. For example, aromatic amines will cure epoxies well only at elevated Icll~eld~ul~s, i.e. generally more than 125C, while unm~lified1 0 cycloaliphatic amines will cure epoxies well at only slightly elevated lCnl~,l dLUrCS, e.g. 50 to 80C. In general, the first component is the majority component, i.e. greater than 50%, preferably greater than 60%, in the curing agent on an equivalence basis.

The second co---pol-cnl is a polyamide amine. This component serves to provide 1 5 good adhesion to the polymeric heat activatable sealant, e.g. a hot-melt adhesive, which forms the innermost layer of a polymeric covering. Polyamide amines generally cure at relatively low temp~.dlure, e.g. room t~,ntpcldtulc. Suitable polyamide amines are available from Henkel under the trad.on~mç Versamid, e.g. VersamidTM 140, 125, 115, and 150, and from Pacific Anchor under the tradçn~mç Anc~mide, e.g. AncamidelM 260A, 350A, 375A, and 400. The second co---~onel~t generally comprises 10 to 45%, preferably 15 to 40%, particularly 25 to 40% of the total curing agent on an equivalence basis.

Both the first and the second co --ponents are reactive curing agents. To ensure that the composition will cure even if a less than o~lhllulll mixing ratio has been used, the curing 2 5 agent often comprises a third cc, ponent which is a catalytic curing agent. Examples of suitable catalytic curing agents are anionic catalysts such as metal alkoxides, isocyanurates, and m~teri~l~ conl~i-lh~g free amine groups. A particularly prerc..cd catalytic curing agent is a tertiary amine. Examples of suitable tertiary amines are pyridine, 2,4,6-tris(dimethyl-~minomethyl) phenol, ben_yldimethyl amine, triethylene tli~mine, and l-methyl imi~lzt7ole. A
30 com,nclcially available tertiary amine (2,4,6-tris(dimethylaminomethyl) phenol) is available from Pacific Anchor under the traden~mç ~nc~mine K54. It is plcrell~d that the tertiary amine be present in the composition at a relatively low loading, i.e. less than 10%, preferably less than 5%, particularly less than 3%, especially less than 2%, more especially less than 1 %
by weight of the curable composition. Fu Ih~,lll~o~e, to ...it-;...;,e the adverse effects of the 3 5 volatility of the tertiary amine, it is p-er~ ,d that any tertiary amine which is present be one with relatively low volatility, e.g. have a relatively high molecular weight and/or low vapor pressure.

wo 95/24433 2 1 8 5 1 5 0 6 PCT/USg5l03072 The amount of curing agent is selected so that the stoichiometric ratio of the epoxy to the curing agent is in the range of 1:0.8 to 1:1.5, preferably in the range of 1:0.9 to 1:1.3, particularly 1:1. In addition, the amount of curing agent and the curing agent blend are selected so that the curable col"po~ilion can be cured to a substantial extent within about 24 5 hours at a ~ lUIG of not more than 80C. By "curable to a substantial extent" is meant that the composition has cured to at least 50%, preferably at least 55%, particularly at least 65%, espec~ ly at least 80% of its fully cured state. It is preferred that compositions of the invention cure to a substantial extent in less than one hour, e.g. 2 minutes to 30 minl1tes, at a lc.llpclalulG of 80C. This relatively rapid cure is advantageous in ensuring that a good bond 10 is achieved to the substrate in a short time, a feature which is illlpC~ tnt in the field.

It is often ~-Gr~ ,d that the curing agent comprise at least one substance which is a Bronsted base. A Bronsted base is a molecular substance capable of accepting a proton, i.e.
a hydrogen ion. It has been found that strong bonds and recist:~n~e to cathodic disbonding 15 are achieved when the curable polymeric composition results in a composition which is basic.
To ensure basicity of the cured composition, excess Bronsted base, i.e. an amount in excess of that required to effect curing of the composition, is preferably used. For compositions of the invention, the Bronsted base is generally added in an amount of at least 0.01 moles in excess of that necess~ry to effect cure of the composition, preferably 0.01 to 2 moles in 2 0 excess. The amount of Bronsted base must be controlled to avoid producing a cured polymeric cc-"po~ilion which does not have adequate hardness orrçcict~nce to cathodic disbonding, two qualities which may be adversely affected by the presence of too much Bronsted base. In addition, because the presence of excess Bronsted base decreases the Tg of the cured polymeric composition, it is necessary to ensure that the excess be limited to an 2 5 amount that achieves the enh~nced bonding and cathodic disbonding resistance but does not decrease the Tg below that required for the application. For most applications, it is plGrell~l that the Tg be at least 80C, preferably at least 90C, especi~lly at least 100C. In general, a curable composition with a higher Tg gives better pelrc,l"~ance at high tempcld~ ;s.

3 0 Also present in the curable composition is an inert inorganic filler which is present in an amount of 20 to 65%, preferably 25 to 60%, particularly 30 to 55% by weight of the total curable col"~osition. In general, the higher the loading of inert filler, the better cathodic disbonding resict~n-~e is achieved. A limiting factor on the amount of filler in the composition is the viscosity of the composition. The inorganic filler may comprise one or more of barium 3 5 sulfate, lithopone (i.e. a Illi~LIUle of barium sulfate, zinc sulfate, and zinc sulfide), mica, and ni~-n~ dioxide. In order to achieve good mixing, it is l IcÇell~d that the particle size of the filler be less than S ~lm, preferably less than 3 ~lm, particularly less than 2 ~m, e.g. 1 to 2 ~m. In order to assist in dispersing the inert filler, it may be coated with a coupling agent or a dispersing agent.

The curable composition may also comprise other additives in an amount up to 10%, preferably up to 8%, particularly up to 6% by weight of the curable composition. Such additives include thixotropic agents (e.g. clay), pigment~ (e.g. carbon black or titanium dioxide), coupling agents (e.g. silanes), surfactants, dispersing agents, stabilizers, processing aids, metal deactivators, t~r~ifl~rs~ adhesion plomo~cl~, hydroxy compounds (e.g. an aliphatic alcohol or water), and otherreagents. In addition, up to 5% by weight of the curable composition can be a solvent. It is ~lcrellcd that there be less than 5%, particularly less than 3%, especially less than 2% by weight of the curable collll)osilion, e.g.
1 0 0 to 2% by weight, of a solvent in order to ~ e the time required to evaporate the solvent when it is being cured. For some applications, however, it is necess~ry to use solvent in order to achieve an appl~liate viscosity for applying the curable composition.

The curable composition is mixed prior to applying to the substrate. Mixing may be 1 5 achieved by any convenient technique. To Ill~inlize the useful shelf life of the curable co~ o~ition, it is often preferred that the curable composition be supplied in two-part form.
The two parts, usually comprising the epoxy in one part (i.e. Part A) and the curing agents in the second part (i.e. Part B), can be colllbilled in the field, just prior to application onto the substrate. Either or both parts may comprise inert inorganic filler and other additives. For 2 0 ease of mixing, it is often plcr~ ,d that the two parts have relatively equal viscosities. In addition, the two parts may contain dirr~ pigments so that it is easy to see when a uniform Illi~Lu~; of the two parts is achieved, e.g. when the mixed composition is a uniform color.
When the composition does comprise two parts, the mixing ratio between the two parts can be adjusted depending on the application but is generally between 40 parts: 100 parts and 100 parts:10 parts, preferably between 100 parts:100 parts and 100 parts:25 parts of part A to part B, measured by weight. Whether in one, two, or more parts the curable composition in the uncured state has a flash point of more than 60C (l~L0F), preferably more than 93C
(200F), as measured according to ASTM D-93 (closed cup method), the disclosure of which is incol~ ted herein by reference, or an equivalent method. This high flash point allows the 3 0 curable colll~osilion to be shipped without special l~lccau~ions.

Substrates to be protected by the compositions of the invention are preferably elongate substrates, particularly cylindrical substrates such as pipelines or tubing. It is ~lerellcd that the substrate be met~llic, e.g. iron, steel, or steel alloys. The method of the invention can be 3 5 used to adhere to a polymeric coating on the substrate as well as protect the exposed metallic substrate. The curable composition can be applied to the substrate in one or more coats.
Subsequent coats may be applied direcdy to the previous coat or be applied to the polymeric layer which is to come into ir~ contact therewith. The curable composition is applied in an amount to provide a coating after curing of 0.05 to 0.76 mm (0.002 to 0.030 inch), WO 95/24433 2 1 8 5 1 5 0 8 PCT/I~S95/03072 preferably 0.05 to 0.64 mm (0.002 to 0.025 inch), particularly 0.05 to 0.25 mm (0.002 to 0.010 inch), especially 0.08 to 0.18 mm (0.003 to 0.007 inch).

Before applying the curable composition, the substrate may be preheated to a temperature of at most 120C, preferably at most 100C, particularly at most 90C, especially at most 80C. Higher preheat tem~l~lul~s are not desirable because the rate of cure of the curable composition will be too rapid, limiting the extent to which the curable composition can interact with the innermost layer of the polymeric covering. The preheating may be achieved by means of a torch or other external heat source, or, if the substrate is a filled pipeline, by means of a hot fluid or other substance in the pipeline.

The curable composition is covered by a polymeric covering comprising one or more polymeric layers before it is l,e~ led to cure to a substantial extent, i.e. while it is substantially uncured. The polymeric covering may be applied by any a~l~l~fiate method, e.g. extrusion, spraying, wrapping, shrinking, pressing, painting, dipping, or electrostatic depositing.

Although a single polymeric layer might be ap~ ,liate for some applications, it is pl~r~,.lGd, particularly for providing protection to substrates such as pipelines, that the 2 0 polymeric covering comprise two or more layers. When there are two layers, the innermost layer will be in contact with the curable con~position. The layers comprising the polymeric covering may be the same or dirr~ t materials and may have the same or different physical and ch~ mic~l pl~ ies. It is generally plGrell~,d that the layers be different in order to achieve different results. For example, the innermost layer is generally an uncured polymeric 2 5 heat-activatable sealant capable of interacting with the curable composition. A plGÇC~ll~ heat-activatable sealant is a hot melt adhesive. The hot melt adhesive can be any sealant typically used to bond corrosion protection coAtingc to metal and particularly those generally used to bond a coating to a pipeline which is catho~i~Ally protected to protect the pipeline from corrosion, abrasion, or impact d~m~g~. Such hot melt adhesives include those based on thermoplastic poly~mi-les, polyolefins, polyesters, polyurethanes, polys-llfi(les. Especially plc;r~ d are polyamide-, ethylene copolymer-, or ethylene terpolymer-based hot melt adhesives. Particular ~ler~ d are hot melt adhesives col~lAil~ing ethylene copolymers or ethylene terpolymers, e.g. copolymers or terpolymers of ethylene with one or more of vinyl acetate, maleic anhydride, acrylic acid, m.~thAt~rylic acid or alkyl acrylate such as ethyl 3 5 acrylate. When protection is required at relatively high l~,m~ tule, e.g. more than 100C, it is prerell._d that the adhesive comprise polypropylene or modified polypropylene, as ed in U.S. Patent Application No. 07/984,806 (Pieslak et al, filed December 3, 1992) and ~ntern~tional Patent Application No. PCI/US93/11686 (Raychem Corporation, filed Decelllbcl 2, 1993), the disclosures of which are inc~ ula~ed herein by reference. The 21~5150 WO 95/24433 ~3 PCT/US95/03072 adhesive may also contain various additives, e.g. waxes, rubbers, stabilizers, and pigments.
The innennost layer is generally applied, e.g. by painting, spraying, or other convenient means, onto one surface of the oute~most layer.

The oul~.. o~l layer is preferably a l~cfolmed shaped article. It is particularly p,~r~i.,~ that the oUt~,lllDSt layer be a heat-recoverable polymeric article, generally in the form of a sleeve, sheet, tube, or tape. The polymeric material of the article has been crosclink~A during the production process so as to enhance the desired rlim~oncional recovery.
One method of producing a heat-recoverable article comprises shaping the polymeric material 10 into the desired heat-stable form, subse luently crosslinking the polymeric material, heating the article to a t~lll~lature above the crystalline melting point of the polymer (or, for amorphous m~teri~lc, the soft~,.-i,-g point of the polymer), deforming the article, and cooling the article while in the deformed state so that the deformed state of the article is retained. In use, because the deformed state of the article is heat-unstable, application of heat, by means 15 of a torch or other heat source, will cause the article to assume its original heat-stable shape, and, for many applications, the article is designed to shrink down onto the substrate. The outermost layer acts as an environmenS~l protection layer over the substrate, and it is impo, ~nl that the curable cc,l,lpo~ition be allowed to cure at a temperature which does not cause the outermost layer to melt or flow. The outermost layer preferably comprises a 2 0 polyolefin such as polyethylene or polypropylene, although for some applications elastomers or rubbers such as acrylic rubber, EPDM, nitrile rubber, or butyl rubber may be used. As with the inne- ~ O~L layer, the oul~,l,lo~l layer may comprise additives, e.g. waxes, rubbers, stabilizers, crocslinking p~umotel~, and pigments.

2 5 The curable compositions of the invention are particularly useful in providing good resic~nce to cathodic disbonding. Cathodic disbonding occurs as a result of the impressed electric current that is applied to the pipe to prevent corrosion of the iron in the steel pipe.
Many adhesive compositions which are used to bond a protective coating onto a pipe are adversely affected by the impressed electric current. As a result, the bond weakens and the 3 0 adhesive pulls away from the pipe, leaving segments of the pipe surface exposed to the corrosive conditions of the env~

The curable compositions of the invention can be used to prepare an assembly of the invention. A ~ubsLI~e, often an elongate substrate such as a pipe or a pipe joint, is coated at 3 5 least partially with a first layer which comprises a curable composition of the invention. The first layer is in contact with, and preferably completely surrounded or covered by, a second layer which is a heat-activatable sealant such as a hot-melt adhesive. The second layer inLe~ with the first layer to form a strong bond, generally due to interaction occurring during the curing of the curable composition. The second layer is in contact with, and preferably completely surrounded or covered by, a third layer which is a polymeric covering.
The polymeric covering may be in the form of a tape, sleeve, tube, sheet, film or other self-supporting layer. Often the polymeric covering is a heat-recoverable article which has been preshaped and which is capable of conforming to the shape of the substrate on recovery. For ease of use, the second layer is often attached to the third layer, e.g. by painting or brushing, prior to bringing the second layer into contact with the first layer.

The invention is illustrated by the drawing in which Figure 1 shows an assembly of the invention. A heat-recoverable article 2 in the form of a polymeric tube has been recovered onto substrate 4 which is a pipe. The pipe is coated with a primer layer formed from a curable composition 6. Adhesive layer 8 which may be part of the heat-recoverable article 2 lies between the curable composition 6 and the backing layer 10 of heat-recoverable article 2.

Shown in Figure 2 is a cross-sectional view along line 2-2 of Figure 1. Visible in this view are the primer layer 6, the adhesive layer 8, and the polymeric backing layer 10.

The invention is illustrated by the following ex~mrlçs.

Examples 1 to 8 The ingredients listed in Table I for each example were mixed by blending 100 grams of the epoxy (Part A) with the specified amount of the premixed ~ g ingredients (Part B) to produce curable compositions in the ratio given as weight percent. Each of the colll~)osilions was painted onto a ~ubs~ e and allowed to cure for 7 days at room temperature (25C), 16 hours at 80C, or 16 hours at 120C before measuring the glass transition lG11I~1~lUIG by means of a thermal mechanical analyzer (I~MA).

The ~Çc.lll~a~lce of each of the curable compositions was measulGd for resistance to catho lic disbonding following the procedure of ASTM G-42, the disclosure of which is incoll,ol~led herein by reference. In that test, a freshly shot-blasted steel pipe with an outer tli~metçr of 57 mm (2.25 inches) and a length of 0.3 meter (12 inches) was preheated to 80C
and the curable composition was painted onto the surface of the pipe. A heat-shrinkable outer layer made from a colll~osilion compri~ing high density polyethylene, ethylene/methyl acrylate copolymer, ethylene-propylene diene rubber (EPDM), carbon black, and antioxidants 3 5 was coated with a hot melt adhesive compri~ing a terpolymer of ethylene, ethyl acrylate, and acrylic acid, was applied to the coated pipe and recovered by heating with a propane torch.
The end of the pipe which was to be illllll~,l sed was sealed with a watertight end cap. A 6 mm (0.24 inch) hole (holiday) was drilled through the backing and the adhesive (but not through the pipe) in the center of the pipe to expose the metal surface of the pipe at that point.

wo 95/24433 1 ~ 2 1 8 5 1 5 o PCT/US95l03072 The pipe was then iml~ ed in an electrolyte solution comrcing water and 1% by weight of each of sodium chloride, sodium sulfate, and sodium carbonate. A potential of 1.5 volts was applied to the pipe, thus making the pipe a cathode in the electrolyte solution which also cnnt~inPA a sacrificial anode. The sample and electrolyte solution were m~int~ined at 80C for 5 30 days. The pipe was then removed and the area around the holiday inspected to determine the extent of disbol-d~ nt The app~ illla~e radius of the disbondment area surrounding the holiday was measured in milli~ (mm) and recorded.

Those co~ Jositions comprising high levels of inert filler had good cathodic 10 disbonding perform~nce, i.e. a disbonding radius of less than 25 mm.

TABLE I

Material~Test Exa-nple 2 3 _ 5 _ 7 8 Epoxy 1 45.1% 67.9% 63.2% 48.8% 66.2% 46.5% 50.0% 61.2 Amine 1 6.1% 3.2% 3.9% 5.1% 6.9% 2.9% 2.4% 8.3 Amine2 14.3% 18.2% 22.1% 11.9% 16.1% 16.2% 13.4% 19.4 Filler 1 30.9% 6.1% 6.6% 31.0% 6.3% 30.7% 30.9% 7.0 Additives 3.6% 4.6% 4.2% 3.2% 4.5% 3.7% 3.3% 4.1 Stoich. Ratio 1:1.3 1:1 1:1.3 1:1 1:1 1:1.3 1:1 1:1.3 PartB (grams) 121.5 47.3 58.3 105.0 51.0 114.9 100.0 63.4 CD at 80C (mm) 19.5 55.5 73.5 14 37 22.5 17.5 62.5 T~ (7 day/25C) 44.3 46.3 49.4 41.0 42.8 45.8 44.1 47.5 T~ (16 hr/80C) 94.2 98.2 97.7 95.5 94.9 94.9 95.9 96.4 T~(16hr/120C) 96.2 144.4 113.9 135.1 138.8 111.9 141.4 106.6 Notes to Table I:
Epoxy 1 is IlliX~Ul~ of a bisphenol A diglycidyl ether polymer and a~u~illlately 10%
of a multifilnction~l resin based on 4-glycidyloxy-N-N-diglycidyl aniline, sold by Ciba-Geigy under the tr~den~me AralditeTM XULY 366. This is part A.
Amine 1 is a polyamide amine, sold by Henkel under the tr~(len~me VersamidTM 140.
Amine 2 is an aromatic amine, sold by Rhone-Poulenc under the tradename CMD
8401.
Filler 1 is barium sulfate (barytes) with a particle size of less than 5 ~lm, sold by Whittaker, Clark & Daniels.
Additives are a Illi~lUl~ of a thixotrope, carbon black, an amino silane, a flow controVleveling agent, and reagent alcohol.

WO 95/24433 2 1 8 5 1 5 0 ~ 2 PCT/I~S95/03072 Stoich. Ratio is the stoichiometric ratio of the epoxy to the curing agent.
Part B is the total amount of part B in grams added to 100 grams of part A.
CD at 80C is the radius in mm of tests run to determine cathodic disbonding at 80C.
Tg represents the glass transition ~ yel~ture of the composition after curing under dirr~,enl conditions.

Example 9 (Cul~y~ e Example) In order to test the perfi rmAnce of cc~,,,yosilions of the invention colllyale;l to conventional fusion bonded epoxy powders, an composition was yl~,lJA~,d in accordance with Example 1 of U.S. Patent No. 3,876,606 (Kehr, April 8, 1975), the disclosure of which is inco,yul~ted herein by reference. A composition con~ ing about 42.6% by weight polyglycidyl ether, 0.4% flow control agent, 0.4% catalyst (2,4,6-tris(dimethylamino methyl)phenol), 2.1 % pigment (c}~llliulll oxide and titanium dioxide), 0.1 % halogenated phthalocyanine, 51.1% by weight barium sulfate, and 3.3% azelaic dihyrazide was prepared in a powder form and coated onto a pipe which had been preheated to 230C. The powder imm~-Ai~tely fused to form a solid coating. The pipe was tested following the procedure of ASTM G-42, described above, under three different conditions: at 60C and 6 volts for 6 days; at 60C and 1.5 volts for 30 days; and at 80C and 1.5 volts for 30 days. The results, 2 0 shown in Table II, indic~ted that the coating degraded under all three conditions, blistering so badly that the coating could be completely peeled off the pipe.

Examples 10 to 13 2 5 Following the procedure of Examples 1 to 8, curable compositions as shown in Table III were prepared. Example 12 was a co"~d~ e example. Each of the con,yo~i~ions comprised two parts, Part A which contained the epoxy, and Part B which contained the curing agents. The co,llyosilions were coated onto pipe preheated to 60C for the 60C tests and to 80C for the 80C tests, and covered with an adhesive-coated polyethylene covering 3 0 layer as described above. For the tests at 60C, the adhesive layer compri ~e~l a teryolymer of ethylene, vinyl acetate, and methacrylic acid; for the tests at 80C, the a&esive comprised a terpolymer of polyethylene, ethyl acrylate, and acrylic acid. The cathodic disbonding p~,rO- " Ance was then measured under the same conditions as Example 9. The results, shown in Table II, in(lic~ted that the compositions of the invention had generally good 3 5 y~.r,, . . .~n~e at 60C and 80C. A cathodic disbonding radius of less than 25 mm was considered good yclrullll~lce.

For Examples 10 and 13, the peel strength at 23C, 60C, and 80C was measured following the disclosure of ASTM D-1000, the disclosure of which is inco,yo~aled herein by WO 9S/24433 ~ 3 2 1 8 5 1 5 0 PCT/US95/03072 cr~l~nce. In addition, for Example 10, a test was done at 110C using a polypropylene-based adhesive and polypropylene covering layer as described in U.S. Patent Application No. 07/984,806 and International Patent Application No. PCT/US93/11686. In the peel test, the pipe with the curable composition and the recovered adhesive-coated polymeric covering 5 layer was cut into test specimens with a width of 25 mm (1 inch). Each ~eci,llell was cut parallel to the direction of the pipe to create a free end which was clamped in the jaw of an InstronTM tester. After allowing the sample to equilibrate to the desired Ic.ll~ldture (23C, 60, 80, or 110C) in the the~nal chamber of the tester, the jaw separation speed of the InstronrM tester was set at 51 mm/minute (2 inches/minute). The amount of force required to 1 0 peel the layer from the pipe was recorded as poundstlinear inch (pli). The results are shown in Table IV. In all cases but one there was adhesive failure to the polymeric covering layer.
The one exception, in~licaterl by "AP", showed an adhesive failure to the primer.

TABLE II
1 5 Results of Cathodic Disbonding (Radius in mm) Test Condition Exarr~le 2 10 11 12~ 13 60C/6 voltst6 days B, D* 6 AP* 11 60Ctl.5 volts/30 days B, D 7 AP 12 11 80C/1.5 volts/30 days TD 13 20 TD 16 *Notes to Table II:
B intlicates blistering of the coating.
D in~lic~tes some degradation of the coating.
TD in~lic~tes total degradation of the coating and complete disbonding from the pipe.
AP in(iic~tes adhesive failure to the primer.
t infii~tes a co~ )~d~i~/e example.

TABLE m Formulations in Weight Percent M~t~i~l Exarnple Epoxy 1 50.0 50.0 47.8 Epoxy2 51.3 Aminel 5.0 11.6 4.6 Arnine 2 5.0 Arnine 3 23.7 Amine4 4-9 AmineS 9.8 9.0 Amine 6 1.0 0.9 Filler 1 30.4 30.3 31.9 Filler2 15.7 3.8 Additivel 3.8 3.1 2.0 Additive 2 4.4 Filler 1 ~ n 100% B 100% B 34.2% A
65.8% B
Filler 2 ~ oc~tic~n 100% A 100% A
A/B Mix Ratio 100/100 100/100 100/40 100/60 5 Notes to Table III:
Epoxy 1 is mixture of a bisphenol A diglycidyl ether polymer and a~n~ ately 10%
of a multifunctional resin based on 4-glycidyloxy-N-N-diglycidyl aniline, sold by Ciba-Geigy under the tr~den~me AralditelM XULY 366.
Epoxy 2 is a bisphenol A epoxy, sold by Shell under the tr~ n~m~ EponTM 828.
Amine 1 is a polyamide amine, sold by Henkel under the tr~ien~ne VersamidTM 140.Amine 2 is an aromatic amine, sold by Rhone-Poulenc under the tradename CMDTM
8401.
Amine 3 is a polyamide amine, sold by Henkel under the tr~len~me VersamidTM 125.Amine 4 is DMAPA (dimethylaminopropyl amine).
Amine 5 is a cycloaliphatic amine, dicyclohexyl l~ e-4,4'-diamine, sold by Pacific Anchor under the tr~den~m~ AmicureTM PACM.
Amine 6 is a tertiary amine,2,4,6-tris(dimethylaminomethyl) phenol, sold by Pacific Anchor under the tr~den~me ~nc~mineTM K54.
Filler 1 is barium sulfate (barytes) with a particle size of less than 5 ~m, sold by Whittaker, Clark & Daniels.

WO 95/24433 ~ 5 ~ PCT/US95/03072 Filler 2 is lithopone with a particle size of less than 5 ~m, sold by Sachtleben Chemie GmbH.
Additive 1 is a ~ ule of a thixotrope, carbon black, an amino silane, a flow controVleveling agent, and reagent alcohol.
Additive 2 is a l~ ule of carbon black, a silane, and a flow control/leveling agent.
Filler 1 Location in~ tes whether Filler 1 was in Part A or Part B of the two-part curable cc,lll~,osilion.
Filler 2 Location inrlicates whether Filler 2 was in Part A or Part B of the two-part curable colll~osilion.
A/B Mix Ratio means the parts by weight of Part A mixed with the parts by weight of Part B.

TABLE IV
Peel Strength (pounds/linear inch) Fxample 60C Sampl- s 80C Sampl--s 110C Samples 2~ 60C 23C 80C 23C 1 10C
22.5 AP 1.1 14.5 2.2 20.2 0.7 14 25.0 0.7 1 8.7 1 .2 - -

Claims

What is claimed is:

1. A curable polymeric composition which is a liquid at 20°C and which comprises (1) 25 to 60% by weight of a resin component which comprises an epoxy;

(2) 5 to 25% by weight of a curing agent which comprises (a) a first component which is a cycloaliphatic amine or an aromatic amine, and (b) a second component which is a polyamide amine; and (3) 20 to 65% by weight of an inert inorganic filler.

2. A composition according to claim 1 wherein the curing agent further comprises a third component which is a tertiary amine.

3. A composition according to claim 1 or claim 2 wherein the curing agent further comprises a Bronsted base.

4. A composition according to claim 1, claim 2, or claim 3 wherein the inorganic filler (a) has an average particle size of less than 5 µm, and (b) comprises barium sulfate, lithopone, titanium dioxide, mica, or a mixture thereof.

5. A composition according to claim 1 or claim 2 wherein the stoichiometric ratio of the epoxy to the curing agent is in the range of 1:0.8 to 1:1.5, preferably 1:1.

6. A composition according to claim 1, claim 2, or claim 3 wherein the composition has a flash point of more than 60°C (140°F).

7. A method of applying a protective covering to a substrate, said method comprising (A) applying to the substrate a curable polymeric composition according to cliam 1;

(B) applying a multiple-layer polymeric covering having an innermost layer and an outermost layer over the curable composition in a manner such that said innermost layer is in intimate contact with said composition, the innermost layer comprising uncured polymeric heat activatable sealant capable of interacting with said curable composition; and (C) allowing the curable composition to cure while maintaining intimate contact between said innermost layer and said composition.

8. A method according to claim 7 wherein the heat activatable sealant comprises a hot melt adhesive, preferably a hot melt adhesive based on a polyamide, an ethylene copolymer, or an ethylene terpolymer.

9. A method according to claim 7 wherein the polymeric covering is a heat-recoverable article.

10. An assembly for protecting a substrate, the assembly comprising (A) a substrate;

(B) a first layer in contact with the substrate which comprises a composition according to claim 1 which is cured and which prior to curing is a liquid at 20°C;

(C) a second layer which contacts the first layer and interacts with it and which comprises a hot melt adhesive; and (D) a third layer which contacts the second layer and which is a polymeric covering.