GB2155488A - Adhesive compositions comprising halodiene polymers - Google Patents

Abstract

Adhesive compositions comprising at least one 2,3-dihalo-1,3-butadiene polymer, at least one aromatic nitroso compound, at least one lead salt of phosphorous acid or of dicarboxylic acids, and at least one maleimide compound, have been found to be unexpectedly effective as storage-stable, single- package, one-coat adhesive systems for bonding a variety of elastomer materials, including vulcanizable and vulcanized natural and synthetic elastomer compositions, to themselves and other structural substrates. The compositions generally include a solvent or diluent but may also be used in the form of an adhesive tape or film.

Description

SPECIFICATION Adhesive compositions This invention relates to adhesive compositions. More particularly, the invention relates to adhesive compositions suitable for bonding elastomeric materials, including both vulcanizable and vulcanized natural and synthetic elastomer compositions, at elevated temperatures to themselves and other solid structural substrates.

It is well-known to employ adhesive compositions for bonding elastomeric materials to various substrates, including elastomeric, fabric, metal and other solid structural substrates. In the as yet unconsummated search for the ideal all-purpose adhesive, there have been developed a variety of adhesive compositions which have been utilized with varying degrees of success in bonding elastomeric materials to themselves or to other substrates to form laminates and other composite articles. Such bonding has been effected over a wide range of conditions including temperature, pressure and length of bonding cycle, and has included both vulcanizable and vulcanized elastomer compositions. While obviously providing commercially acceptable results, the known prior art compositions are not without their deficiencies.For example, as a general rule, the known adhesives which have been effective as single-coat, i.e., primerless, rubber-to-metal bonding agents are quite often only useful in bonding specific elastomers to specific substrates, and thus are sadly lacking in versatility. This lack of versatility which is characteristic of the general class of one-coat adhesive systems can be partially alleviated by the use of two-coat adhesive systems, which utilize a primer coat applied over the metal substrate and a cover coat (which adheres well to the elastomer) interspersed between the elastomer and the primer.In addition to the problem of versatility, both the one-coat and two-coat adhesive systems suffer from one or more other disadvantages, including a general inability to afford optimum adhesion, particularly at elevated service temperatures; poor storage stability at room and/or elevated temperatures; poor precure heat tolerance, that is, the amount of exposure (at a certain time and temperature), prior to bonding, that a cure activated adhesive system can tolerate without significant impairment to its adhesion potential; and the resistance of the adhesive bond to environmental conditions such as solvents, moisture and the like, is too often poorer than is normally desired in many commercial applications.The variety of prior adhesive systems available at any point in time has never precluded continued research toward the development of more acceptable adhesive materials; indeed, existing adhesive systems have generally inspired such research, particularly as new materials are developed which simply cannot be effectively bonded with existing adhesive compositions or new techniques are developed which require adhesive characteristics not found in existing adhesives.

Adhesive compositions which have been employed in the past have included admixtures of chlorinated rubber and polyalkylene polyamine adhesion promoter; mixtures of halogenated ethylene-propylene copolymer and sulfur; mixtures of chlorosulfonated polyethylene, organic isocyanates and dinitrosobenzene; chlorinated rubber-epoxylated novolak-epoxy resin curing agent admixtures; mixtures comprising chlorine-containing polymers, polyisocyanates, epoxy resins, organosilanes and dinitrosobenzene; and the like.

Adhesive compositions which have been widely used commercially are disclosed in Coleman et al U.S.A. Patent No. 3,258,388, which provides for the incorporation of poly-C-nitroso aromatic compounds into conventional rubber-to-metal adhesives to improve rubber-to-metal adhesion. The conventional adhesives include compositions containing thermosetting condensation polymers; polymers and copolymers of polar ethylenically unsaturated materials, halogenated rubbers, and polyisocyanates. The Coleman et al adhesive compositions provide good to excellent primary adhesion values with a wide variety of elastomers; however, such compositions do not by themselves provide desired levels of environmental resistance as measured by exposure to boiling water, salt spray or high humidity conditions.To obtain at least reasonable levels of environmental resistance, it has been necessary to employ primers such as phenoliccontaining compositions; or incorporate additives such as silanes, silane-isocyanate adducts, phenolic materials, and the like, into the adhesive system.

Findley et al U.S.A. Patent No. 3,640,941 disclose adhesive systems containing as necessary components a graft copolymer of polybutadiene and cyclopentadiene monomer, dibasic lead phosphite, and resorcinol. While excellent adhesives for some natural and synthetic rubbers, they are not effective with non-polar rubbers such as butyl rubber, EPR and EPT rubbers, and the like, nor with vulcanized stock. In addition to the limited versatility, less then optimum characteristics, particularly with respect to precure heat tolerance, layover of adhesive-coated parts prior to bonding, and can stability, have been observed.

Jazenski et al U.S.A. Patent No. 4,119,589 disclose adhesive systems comprising halogencontaining polymer, aromatic nitroso compounds and inorganic/organic acid salts such as dibasic lead phosphite. The preferred halogen-containing polymers include a mixture of chlorosulfonated polyethylene and chlorinated natural rubber. While excellent adhesives, in order to bond to low durometer, natural rubber stock, the Jazenski et al chlorosulfonated polyethylene-containing adhesives require a level of aromatic nitroso compound which not only results in fuming but also contributes to premature vulcanization of the rubber stock and premature curing of the adhesive.

The search continues for more effective adhesive formulations which can be employed to bond elastomeric materials, including both vulcanizable and vulcanized elastomer compositions to themselves and other substrates over a broad spectrum of bonding conditions; which are shelf-stable for extended periods of use; which can be employed with a variety of elastomers, including low durometer natural rubber, and substrates; and which exhibit good precure heat tolerance, good layover and are resistant to degradation from environmental factors.

It is an object of this invention to provide adhesive compositions for bonding a variety of elastomers at elevated temperatures to various substrates, particularly metal substrates.

It is another object of this invention to provide adhesive compositions which are effective to bond low durometer, natural rubbers at elevated temperatures to various substrates.

It is another object of this invention to provide adhesive compositions which afford strong elastomer-substrate adhesive bonds which are resistant to environmental degradation.

These and other objects, aspects, and advantages of the invention, including a method for bonding elastomeric materials to substrates, and adhesively-joined elastomer-substrate composites, will be readily apparent from a consideration of the specification and the appended claims.

In accordance with the present invention, it has been discovered that compositions containing as essential ingredients at least one 2,3-dihalo-1,3-butadiene polymer, such polymer being more specifically defined hereinafter; at least one aromatic nitroso compound; at least one lead salt of certain organic and inorganic acids; and at least one maleimide compound, are unexpectedly effective as adhesive materials for bonding a variety of elastomers, including vulcanizable and vulcanized natural and synthetic rubber compositions, to themselves or other solid substrates. If desired, additives conventionally employed with adhesive compositions, such as fillers, dyes, pigments, extenders, dispersing agents, auxiliary film forming materials and the like, can be incorporated into the novel compositions of this invention.The compositions of this invention are characterized by the unexpected ability to provide strong rubber-to-substrate bonds with good to excellent environmental resistance without the necessity of first priming the substrate surface; however, they can be used with conventional substrate primer compositions if one so desires. The compositions provide excellent adhesion for both unvulcanized and vulcanized elastomer compositions without requiring treatment, such as chlorination, of the rubber surface.

In addition to affording one-coat adhesive systems characterized by excellent primary adhesion and environmental resistance, the compositions of the invention exhibit excellent shelf-life stability, resistance to sweep, that is, movement of the adhesive during the bonding process before the adhesive is set which is caused by frictional forces imposed on the adhesive by the hot rubber compound flowing onto and along the exposed surface of the adhesive, precure heat tolerance, good layover characteristics, that is, adhesively-coated parts, after the adhesive is dried, can be stored for an indefinite period without a noticeable loss of adhesion performance, and are effective over a broad spectrum of bonding temperatures, e.g., from about 90"C to over 1 80 C.

The 2,3-dihalo-1,3-butadiene polymer which is essential to the practice of this invention is selected from the group consisting of the elastomeric homopolymers of 2,3-dihalo-1 ,3- butadiene; copolymers of 2,3-dihalo-1,3-butadiene and at least one monomer selected from the group consisting of a-haloacrylonitrile, a-haloacrylic acid, a-haloacrylic ester, a-halovinyl ketone, a-halovinyl acetate, vinyl halide, vinylidene halide and monoalkenyl aromatic alkyl halides having the formula

wherein X is hydrogen, chlorine, bromine or iodine; R is an alkyl group having from 1 to 4 carbon atoms, the carbon atom of said alkyl group which is attached directly to the aromatic nucleus being substituted with from I to 3 halogen atoms selected from the group consisting of chlorine, bromine or iodine; A is 1 or 2, b is 0, 1 or 2, and at least one b is at least 1; and including such homopolymers and copolymers which have been halogenated subsequent to their polymerization. Chlorine is currently the preferred halogen substituent of the halogen-containing monomers, including the 2,3-dihalo-1,3-butadiene, with bromine being the preferred halogen for post-halogenating the elastomeric polymeric materials. It should be noted that the term "copolymers" is intended to encompass polymers of 2,3-dihalo-1 3-butadiene and two or more monomers which are interpolymerizable with the diene, such as the terpolymer of 2,3-dichloro 1 ,3-butadiene, vinyl benzyl chloride and acrylic acid.The amount of halogen does not appear critical and can range from as low as 3 weight percent to more than 70 weight percent with a halogen content in the range from 55 to 69 weight percent being currently preferred. The elastomeric 2,3-dihalo-1 3-butadiene polymeric materials and their preparation are well-known in the art and no need is seen to elucidate in any detail on these materials or their manufacture.

The aromatic nitroso compounds which are suitable for use in the practice of the present invention can be any aromatic hydrocarbon, such as benzenes, napthalenes, anthracenes, biphenyls, and the like, containing at least two nitroso groups attached directly to non-adjacent ring carbon atoms. More particularly, such nitroso compounds are described as poly-C-nitroso aromatic compounds having from 1 to 3 aromatic nuclei, including fused aromatic nuclei having from 2 to 6 nitroso groups attached directly to non-adjacent nuclear carbon atoms. The presently preferred poly-C-nitroso materials are the di-nitroso aromatic compounds, especially the dinitroso-benzenes and dinitroso-naphthalenes. The nuclear hydrogen atoms of the aromatic nucleus can be replaced by alkyl, alkoxy, cycloalkyl, aryl, aralkyl, alkaryl, arylamine, arylnitroso, amino, halogen, and the like groups.The presence of such substitutents on the aromatic nucleus has little effect on the activity of the poly-C-nitroso compounds in the present invention.

As far as is presently known, there is no limitation as to the character of the substituent, and such substituents can be organic or inorganic in nature. Thus, where reference is made herein to poly-C-nitroso or di-C-nitroso "aromatic compound", "benzenes", or "naphthalenes", it will be understood to include both substituted and unsubstituted nitroso compounds, unless otherwise specified.

Particularly preferred poly-C-nitroso compounds are characterized by the formula (R )m-Ar-(NO)2 wherein Ar is selected from the group consisting of phenylene and naphthalene; R0 is a monovalent organic radical selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl, arylamine and alkoxy radicals having from 1 to 20 carbon atoms, amino, or halogen, and is preferably an alkyl group having from 1 to 8 carbon atoms; and m is zero, 1, 2, 3 or 4 and preferably is zero.

A partial non-limiting listing of suitable poly-C-nitroso compounds which are suitable for use in the practice of the invention include m-dinitroso-benzene, p-dinitrosobenzene, m-dinitrosonaphthalene, p-dinitrosonaphthalene, 2, 5-dinitroso-p-cymene, 2-methyl-1 ,4-dinitrosobenzene, 2 methyl-5-chloro- 1 ,4-dinitrosobenzene, 2-fluoro-l ,4-dinitrosobenzene, 2-methoxy-1 -3-dinitroso-- benzene, 5-chloro-1 ,3-dinitrosobenzene, 2-benzyl-1,4-dinitrosobenzene, and 2-cyclohexyl-1,4dinitrosobenzene.

The lead salts which are suitable for use in the present invention can be described broadly as polybasic lead salts of phosphorous acid and saturated and unsaturated organic dicarboxylic acids and acid anhydrides. The lead salts are well-known articles of commerce and need not be discussed here in detail. At the present time, particularly preferred lead salts include dibasic lead phthalate, monohydrous tribasic lead maleate, tetrabasic lead fumarate, and dibasic lead phosphite; and including mixtures thereof. The effectiveness of the herein-described lead salts, particularly with respect to environmental resistance, is not fully understood. It is known that lead salts are effective acid acceptors for acidic materials which may undesirably be present.

However, other chemical materials which are more effective as acid acceptors than the hereindescribed lead salts do not provide as good results as those obtained with the lead salts.

Maleimide compounds which are suitable for use in the present invention include all of the maleimide, bismaleimide and related compounds which are described in U.S. Patents Nos.

2,444,536 and 2,462,835, which disclosures are herein incorporated by reference. Preferred maleimide compounds include the N,N'-linked bis-maleimides which are either joined directly at the nitrogen atoms without any intervening structure or in which the nitrogen atoms are joined to and separated by an intervening divalent radical such as alkylene, cycloalkylene, oxydimethylene, phenylene (all 3 isomers), 2,6-dimethylene-4-alkylphenol, or sulfonyl. m-Phenylene-bismaleimide is a presently preferred compound, and is available as "HVA-2" from E. I. duPont de Nemours and Co., (Inc.).

With respect to the essential components of the adhesive compositions of this invention, the aromatic nitroso component will be present in the range from 1 to 200, preferably 10 to 100 parts by weight; the lead salt will be present in an amount in the range from 10 to 200, preferably 25 to 100, and most preferably 35 to 75, parts by weight; and the maleimide component will be present in an amount in the range from 0.5 to 100, preferably 2 to 50 parts by weight; with the amounts of each component being on a basis of 100 parts of 2,3-dihalo1 ,3-butadiene polymer. In each case, the amounts of aromatic nitroso component, lead salt component or maleimide component can be outside the recited ranges, but is generally not economically advisable.For example, the use of maleimide compound at 150-200 parts by weight will exhibit better environmental resistance than at 25-75 parts by weight but the resulting increased cost negates its use at the higher levels except in particularly aggressive environments, where cost is a lesser factor. The herein-described adhesive compositions can be compounded with an appropriate inert solvent or diluent to provide an adhesive lacquer having a total solids conftent (TSC) in the range from 5 to 80, preferably 10 to 40, percent.

Alternatively, the adhesive compositions can be provided at 100 percent TSC in the form of an adhesive film or tape. If desired, conventional additives which are normally used in adhesive compositions, such as fillers, colorants, extenders, auxiliary film-forming polymers and the like, can be included in the formulations of the invention, with the amount of such additives being within the ranges conventionally employed. Some degree of experimentation with respect to blending all of the ingredients in particular compositions to ensure their mutual compatibility.

This is particularly true when auxiliary film-forming materials, such as other and different natural synthetic elastomers are compounded with the essential ingredients of the compositions. For example, particularly preferred auxiliary film-forming materials are chlorinated natural rubber and chlorosulfonated polyethylene, which materials can be used separately or together. When used above, the chlorinated natural rubber is used, preferentially, in the the range of 1 to 300 parts by weight per 100 parts by weight of 2,3-dihalo-1 ,3-butadiene polymer and the chlorosulfonated polyethylene is used, preferentially, in the range of 1 to 50 parts by weight per 100 parts by weight of 2,3-dihalo-1 ,3-butadiene polymer.When both are compounded into the adhesive formulations, the chlorinated natural rubber is present in the range from 50 to 300 parts by weight and the chlorosulfonated polyethylene is used in the range from I to 20 parts by weight, per 100 parts by weight of 2,3-dihalo-1 ,3-butadiene polymer.

As noted previously, in addition to halogen-containing polymer, aromatic nitroso compound, polybasic lead salt, and maleimide compound the adhesive compositions of the invention can include conventional additives such as inert filler material, polymeric film-forming adjuncts, pigments, solvent, diluent and the like, with the amount of such additives being within the range customarily employed.

The adhesive compositions of this invention are prepared by conventional means. For ease of application, as is conventional in this art, the components will be mixed and dispersed in an inert liquid carrier which, once the composition has been applied, can be reaily evaporated.

Examples of suitable carriers are aromatic and halogenated aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, dichlorobenzene, and the like; halogenated aliphatic hydrocarbons such as trichloroethylene, perchloroethylene, propylene dichloride, and the like; ketones such as methyl ethyl ketone, methyl, isobutyl ketone, and the like; ethers, naphthas, etc., including mixtures of such carriers. The amount of carrier is not critical and will ordinarily be such as to provide a total solid content range from about 5 to about 80, preferably about 1 5 to about 40, percent by weight. Alternatively, the adhesives can be compounded as 100 percent TSC systems which contain no solvent or diluent and provided in the form of an adhesive tape or film.

The adhesive compositions of the present invention have been found to be particularly suitable for bonding a wide variety of elastomeric materials, including both vulcanized and vulcanizable elastomeric materials, to themselves or to other substrates, particularly inorganic substrates. Elastomers which can be bonded include natural rubber, polychloroprene rubber, styrenebutadiene rubber, nitrile rubber, and the like. Substrates other than the elastomers per se which can be effectively bonded include fabrics such as fiberglass, polyamides, polyesters, aramids, e.g., Kevlar, a trademark of E.I. duPont de Nemours and Co., (Inc.), Wilmington, Delaware, and the like; and metals and their ailoys such as steel, stainless steel, lead, aluminum, copper, brass, bronze, Monel metals, nickel, zinc, and the like, including treated metals such as phosphatized steel, galvanized steel, and the like; glass; ceramics; and the like.

The adhesive compositions are applied to substrate surfaces in a conventional manner such as by dipping, spraying, brushing, and the like. Preferably, the substrate surfaces are allowed to dry after coating before being brought together. After the surfaces have been pressed together with the adhesive layer in between, the assembly is heated in accordance with conventional practices. The exact conditions selected will depend upon the particular elastomer being bonded and whether or not it is cured. If the rubber is uncured, and curing is to be effected during bonding, the conditions will be dictated by the rubber composition and will generally be at a temperature of from about 1 40 C to about 200"C for from about 5 to about 60 minutes.If the rubber is already cured, the bonding temperature may range from about 90"C to above 1 80on for from about 1 5 to about 1 20 minutes. Alternatively, in situations where applicable, the adhesives can be interspersed between the surfaces to be joined as a solid film or tape (100 percent TSC adhesive system) with bonding being accomplished as before.

The following examples are provided for purposes of illustrating the invention, it being understood that the invention is not limited to the examples nor to the specific details therein enumerated. In the examples, amounts are parts by weight, unless otherwise specified.

In the several examples, the substrate to which the elastomeric material was bonded was not primed, unless otherwise noted. The composite assembly was cured at conventional conditions of time and temperature for the specific elastomer. The bonded assemblies are tested for environmental resistance according to the boiling water test. In this test, bonded assemblies, after having been scored at the bond line and prestressed by bending the rubber body back from the substrate, are immersed in boiling water for two hours. The assemblies so treated are tested for relative bond strength by pulling the rubber body from the substrate.In the data reported in the examples, failure is expressed in terms of percent of failure in the rubber body, e.g., 95 R means that 95 percent of the failure occurred in the rubber body, with the remaining failure being between the adhesive composition and the metal, or the like.

EXAMPLE I Adhesive compositions are prepared by dispersing in a KD mill the following ingredients.

Adhesive Composition 1-A 1-B 1-C Ingredients: Brominated poly (2,3-dichloro-1,3-butadiene) 160.0 45.0 45.0 Chlorinated poly (ethylene-propylene) 0.0 65.0 65.0 Chlorinated natural rubber 0.0 50.0 50.0 Chlorosulfonated polyethylene 0.0 0.0 5.0 p-Dinitrosobenzene 20.0 20.0 20.0 Dibasic lead phosphite 40.0 40.0 40.0 N,N'-m-phenylene-bis-malemide 5.0 5.0 5.0 Carbon black 35.0 35.0 35.0 Titanium dioxide 10.0 10.0 10.0 Silica 5.0 5.0 5.0 Epoxy Resin 2.0 2.0 2.0 Toluene/Chlorotulene11,1,1- to 29 percent TSC trichloroetane The compositions are employed to bond unvulcanized low durometer (soft) and high durometer (hard) natural rubber to grit-blasted and phosphatized steel.The assemblies are cured at 1 54 C for 1 5 minutes with precure heat exposure times ranging from zero to 10 minutes.

Boiling water (b H2O) on phosphatized steel and peel adhesion (ASTM D-429, Method B, modified to 45 ) on grit blasted steel tests are made with the following results: Pre-cure heat exposure Peel Adhesion H20 Resistance Elastomer time, min.; temp, OC lblin; failure 2 Hours Adhesion Comoositions 1-A High Durometer 0; NA 66; 100R 100R 5; 153 60; 100R 100R 10; 153 38; 75TR Low Durometer 0; NA 51; 100R 3; 153 41; 100R 6; 153 32; 100R Adhesive Comoosition 1-B High Durometer 0; NA- 64; 100R- 87R, 13 CM 2-1/2; 153 54; lOOR 5; 153 52; 100R 90R, 10 CM 7-112; 153 51; 100R Low Durometer 0;NA 31; 100R 3; 153 31; 100TR 6; 153 23; 100VTR Adhesive Composition 1-C High Durometer 0; NA 64;-100R 88R, 12 CM 2-1/2; 153 54; 100R 5; 153 50; 100R 932, 7 CM 7-112; 153 50; 100R Low Ourometer 0; NA 34; 100R 3; 153 33; 100R 6; 153 24; 100VTR EXAMPLE II Adhesive compositions are prepared by mixing in a KD mill the following ingredients: Adhesive Composition II-A Il-B II-C II-D Ingredients Brominated poly (2,3-dichloro-1,3-butadiene 15.0 15.0 130.0 45.0 Chlorinated poly (ethylene-proplyene) 15.0 130.0 15.0 65.0 Chlorinated natural rubber 130.0 15.0 15.0 50.0 Chlorosulfonated polyethylene a.o 5.0 5.0 5.0 p-Dinitrosobenzene 20.0 20.0 20.0 20.0 Dibasic lead phosphite 40.0 40.0 40.0 40.0 N,N'-m-phenylene-bis-maleimide 5.0 5.0 5.0 5.0 Carbon black 35.0 35.0 35.0 35.0 Titanium dioxide 10.0 10.0 10.0 10.0 Silica 5.0 5.0 5.0 5.0 Epoxy resin 2.0 2.0 2.0 2.0 The compostions are applied to grit-blasted cold-rolled steel substrates.After drying, the steel substrates are bonded to unvulcanized low durometer natural rubber stock, employing a cure cycle of 1 54 C for 1 5 minutes, with pre-cure heat exposure times of 0 and 5 minutes. The bonded assemblies are tested for peel adhesion following the procedure of Example I.The results are as follows: Pre-Cure Heat Exposure Peel Adhesion, Adhesive time, min.; temo, OC lblin; failure II-A O; NA 62; 100R 5; 153 38; 6R, 94RC II-B 0; NA 63; 100R 5; 153 38; 67vTR, 33RC II-C 0; NA 64; 100R 5; 153 58; 100R II-D 0;NA 55; 100R 5; 153 52; 100R EXAMPLE 111 Following the procedure of Example I, the following adhesive compositions are prepared: Adhesive Composition III-A III-B III-C III-D Brominated poly (2,3-lichloro-1,3-butadiene) 45.0 45.0 45.0 as.o Chlorinated poly (ethylene-propylene) 65.0 65.0 65.0 65.0 Chlorinated natural rubber 50.0 50.0 50.0 50.0 Chlorosulfonated polyethylene 5.0 5.0 5.0 5.0 p-Dinitrosobenzene 30.0 30.0 30.0 30.0 Dibasic lead phosphite 0.0 0.0 50.0 50.0 N,N'm-phenyiene-bi sinaleimide 0.0 20.0 0.0 20.0 Carbon black 35.0 35.0 35.0 35.0 Titanium dioxide 10.0 10.0 10.0 10.0 Silica 5.0 5.0 5.0 5.0 Epoxy resin 2.0 2.0 2.0 2.0 The compositions are applied to grit-blasted cold-rolled steel and acid-etched 41 6 stainless steel substrates. After drying, the adhesive-coated metal parts are bonded to unvulcanized low durometer natural rubber stock, employing a cure cycle of 1 54 C at 15 minutes. The bonded assemblies are tested for 2 hour boiling water resistance, with the following results: Boiling Water Resistance, 2 Hour Exposure Pre-Cure Heat Exposure Adhesive Substrate time, min.; temo, C Failure III-A CRS 0; NA 14R, 86 CM III-A CRS 5; 153 25R, 75 CM III-A SS 0; NA 44R, 56 CM Ill-A SS 5; 153 56R, 44 CM III-B CRS 0; NA 26R, 74 CM 111-8 CRS 5; 153 24R, 76 CM Ill-B SS 0; NA 38R, 62 CM III-B SS 5; 153 22R, 78 CM III-C CRS 0;NA 65R, 35 CM III-C CRS 5; 153 56R, 44 CM Ill-C SS 0; NA 80R, 20 CM Ill-C SS 5; 153 93R, 7 CM III-D CRS 0; NA 83R, 17 CM III-0 CRS 5; 153 82R, 18 CM III-D SS 0; NA 96R, 4 CM III-D SS 5; 153 96R, 4 CM EXAMPLE IV Adhesive Il-D from Example II Coleman/Alstadt Covercoat-Commercial Embodiment A" Coleman/Alstadt Covercoat-Commercial Embodiment Ba a adhesives based on teachings of Coleman et al U.S.A. Patent 3,258,388.

The adhesives are applied to phosphatized steel and 304 stainless steel substrates. After drying, the adhesive-coated substrates are bonded to unvulcanized high durometer natural rubber and unvulcanized neoprene rubber stocks. The assemblies are cured at 1 53 C for 15 minutes and tested for boiling water resistance (2 hours exposure) and salt spray resistance (48 hours exposure) with the following results: Boiling Water Resistance Salt Spray Resistance Adhesive Substrate Failure Failure A Phosphatized 29R, 71 CM OR, 100 CM B Phosphatized Il-D Phosphatized 98R 1 00R A Stainless B Stainless OR, 100 CM 53R, 47 CM Il-D Stainless 93R, 7 CM 92R, 8 CM

Claims (20)

1. An adhesive composition consisting essentially of (a) at least one 2,3-dihalo-1 ,3-butadiene polymer; (b) from 1 to 200 parts by weight, per 100 parts by weight of said 2,3-dihalo-1 3-butadiene polymer, of at least one aromatic nitroso compound.

(c) from 10 to 200 parts by weight, per 100 parts by weight of said 2,3-dihalo-1 3-butadiene polymer, of at least one lead salt of an acid selected from the group consisting of phosphorus acid and organic dicarboxylic acids and acid anhydrides; (d) from 0.5 to 100 parts by weight, per 100 parts by weight of said 2,3-dihalo-1,3butadiene polymer, of at least one maleimide compound; and (e) an inert diluent, said diluent being present in an amount to provide a lacquer composition suitable for use as an adhesive, said lacquer having a total solids content in the range from 5 to 80 percent.

2. A composition according to claim 1 having incorporated therein at least one inert additive.

3. An adhesive composition according to claim 1 wherein said lead salt is selected from the group consisting of dibasic lead phthalate, monohydrous tribasic lead maleate, tetrabasic lead fumarate, and dibasic lead phosphite.

4. An adhesive composition according to claim 3 wherein the amount of said aromatic nitroso compound is in the range from 10 to 100 parts by weight and the amount of said lead salt is in the range from 50 to 100 parts by weight.

5. An adhesive composition according to claim 1 wherein the amount of said maleimide compound is in the range from 0.5 to 50 parts by weight.

6. An adhesive composition according to claim 3 wherein the amount of said maleimide compound is in the range from 0.5 to 50 parts by weight.

7. An adhesive composition according to claim 4 wherein the amount of said maleimide compound is in the range from 0.5 to 50 parts by weight.

8. An adhesive composition according to claim 1 wherein said component (a) comprises brominated poly (2,3-dichloro-1,3-butadiene).

9. An adhesive composition according to claim 8 wherein said lead salt comprises dibasic lead phosphite.

1 0. An adhesive composition according to claim 9 wherein the amount of maleimide compound is in the range from 0.5 to 50 parts by weight.

11. An adhesive composition according to claim 1 having incorporated therein from 1 to 300 parts by weight, per 100 parts by weight of said 2,3-dihalo-1,3-butadiene polymer, of at least one halogenated natural rubber.

1 2. An adhesive composition according to claim 1 having incorporated therein from 1 to 50 parts by weight, per 100 parts by weight of said 2,3-dihalo-1,3-butadiene polymer, of at least one chlorosulfonated polyethylene.

1 3. An adhesive composition according to claim 1 having incorporated therein from 50 to 300 parts by weight, per 100 parts by weight of said 2,3-dihalo-1 3-butadiene polymer, of at least one halogenated natural rubber and from 1 to 20 parts by weight, per 100 parts by weight of said 2,3-dihalo-1,3-butadiene polymer, of at least one chlorosulfonated polyethylene.

1 4. An adhesive composition consisting essentially of (a) at least one homopolymer or copolymer of 2,3-dichlorol 3-butadiene; (b) from 1 to 200 parts by weight, per 100 parts by weight of component (a), of at least one aromatic nitroso compound; (c) from 5 to 200 parts by weight, per 100 parts by weight of component (a), of at least one lead salt of an acid selected from the group consisting of phosphorous acid and organic dicarboxylic acids and acid anhydrides; and, (d) from zero to 100 parts by weight, per 100 parts by weight of component (a), of at least one maleimide compound.

1 5. A composition according to claim 14 having incorporated therein at least one inert additive.

1 6. A composition according to claim 14 wherein said lead salt comprises dibasic lead phosphite.

1 7. A composition according to claim 15 having incorporated therein at least one halogenated natural rubber.

18. A composition according to claim 1 7 wherein the maleimide compound is present in an amount in the range from 0.5 to 100 parts by weight, per 100 parts by weight of component (a).

1 9. A composition according to claim 1 6 having incorporated therein at least one chlorosulfonated polyethylene.

20. A composition substantially as hereinbefore described with reference to any one of Examples I to IV.