AU636770B2 - Adhesive for low temperature applications - Google Patents

Description

AUSTRALIA

Patents Act 6367 370 CceqPLgl SPECIFICATPION

(ORIGINAL)

Class Int. Class Application Number: Lo.Qdged: Complete Specification Lodged: Accepted: Published: Priority Related Art: t SName of Applicant: 4491 t t *Illinois Tool Works Inc.

*,Actual Inventor(s): Danald E. Gosiewski Paul C. Briggs Address for, Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: ADHESIVE FOR LOW TEMPERATURE APPLICATIONS .4 4 k 441 :Our Ref :217766 POF Code: 77887/1431 The following statement is a full description of this invention, the best method-of performing it known, to applicant(s): including 1 6006 Expre Mail Certificate No.: B10080413 Docket No. P-254B ADHESIVE FOR LOW TEMPERATURE APPLICATIONS Cross Reference This is a continuation-in-part o Se'No. 07/238,302, filedAugust 29 1 kground of the Invention The field of art to which this invention pertains is structural acrylic adhesives.

Structural acrylic adhesives are rubber-toughened adhesive systems that cure rapidly at room temperature to give excellent adhesive properties. Such adhesives are characterized by high peel strength, shear strength and chemical resistance. They are also tolerant of a variety of substrate surface contaminants, such as oil.

q Fast curing adhesives are described in U.S. Patent No.

3,832,274. These adhesives are made from elastomers having Tg's of less than 15 0 F, acrylic monomers and a redox catalyst.

Structural adhesives which contain chlorosulfonated polyethylene or sulfonyl chloride and chlorinated polymers are disclosed in such patents as U.S. 3,890,407, 3,962,372 and 4,287,106.

U.S. Pttents Nos. 4,126,504, 4,348,503 and 4,451,615 b a, disclose various combinations of elastomers, acrylic minomers, catalysts and other additives.

Adhesives based on diene polymers, such as polybutadienes, polyisoprenes, butadiene-styrene copolymers and ABS graft polymers, plus vinyl monomers, adhesion promoters and the like are described in U.S. Patent No. 4,287,106.

Methacrylate based adhesives which contain chlorinated or chlorosulfonated polyethylene polymers and graft copolymers of the core-shell type are disclosed in U.S. Patent No. 4,536,546.

With the use of more and more plastics in structures, automobiles, there is a continuing and even increasing need for adhesives which can be used on plastics as well as metals to form bonds which will hold up under a wide variety of adverse conditions.

There is a particular need for structural ahesives which not only have high adhesive bond impact strength but also have high bulk tensile elongation when measured at low temperatures.

According to this invention there is provided an adhesive composition comprising: a methacrylate ester monomer; an elastormeric polymer selected from the group consisting of nitrile rubber; polychloroprene; copolymers of butadiene or isoprene with styrene; copolymers of butadiene or styrene with acrylate esters; copolymers of butadiene or styrene with methacrylate esters; copolymers of ethylene and o-25 acrylate ethers; homopolymers of epichlorohydrin; and copolymers of epichlorohydrin and ethylene .oxide, wherein said elastomeric polymer is soluble in the ester monomer and has a Tg below -25 0

C;

a core-shell graft copolymer which swells in the monomer but does not dissolve therein; and S a free radical producing catalyst.

S3 39 -2i~ir~p i I B) an elastomeric polymer soluble in the ester mo mer, said polymer having a Tg below about C) a core-shell graft copolymer which wells in the monomer but does not dissolv herein; and D) a free radical produci catalyst.

The adhesive compositi s of this invention, when used in bonded assemblies, ex i'it a combination of high adhesive bond impact strength at least 15 ft-lb/sq.in.) and high bulk tensile elongatio greater than 10 percent) when measured at or below.

The monomers useful in this invention are methacrylate ester S*monomers wherein the alcohol portion of the ester group contains one to eight carbon atoms. Examples of such ester monomers are methyl methacrylate, ethyl methacrylate, 2-ethyhexyl methacrylate, cyclohexyl methacrylte and mixtures thereof. The i*'t preferred ester monomer is methyl methacrylate.

Additional monomers which can be used in combination with I the methacrylate monomers are acrylate esters wherein the alcohol portion of the ester contains 1 to 8 carbon atoms, examples of which are methyl acrylate, ethyl acrylate, butyl acrylate and 2-ethyhexyl acrylate. Other useful monomers are acrylonitrile, methacrylonitrile, styrene, vinyl toluene, and the like.

The useful monomer composition contains at least about weight percent methacrylate monomer and, preferably, at least ai

-MWMI

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a g l i^ir^*'SJ-^ about 50 weight percent methyl methacrylate monomer.

Additional monomers which are used in combination with the *ethacrylate ester monomers are free radical polymerizable ethylenically unsaturated mono or polycarboxylic acids. Acrylic acid, methacrylic acid, crotonic acid, maleic acid and fumaric acid are examples of such acids. The preferred acid is methacrylic acid.

The elastomers useful in this invention have a second order glass transition temperature (Tg) of less than -25° and are soluble in the monomers described hereinabove. Useful elastomers are synthetic high polymers which exhibit plastic flow. The preferred elastomers are those which are supplied commercially as adhesive or cement grades.

S'A preferred class of elastomers for use in this invention are polychloroprene and copolymers of butadiene or isoprene with styrene, acrylonitrile, acrylate esters, methacrylate esters, and the like. Additional usefal elastomers are copolymers of .I ethylene and acrylate esters, homopolymers of epichlorohydrin and copolymers of epichlorohydrin and ethylene oxide.

SSpecific examples of useful polymers using their letter designation according to ASTM D1418, their trade or common name and chemical description are: CR-Neoprene-polychloroprene; NBR-Nitrile rubber-butadiene acrylonitrile copolymer containing about 25 to about 45 weight percent acrylonitrile; COX Hycar 1072-butadiene-acrylonitrile copolymer modified with carboxylic groups; SBR-GR-S-styrene-butadiene copolymer containing about i -4to about 30 weight percent styrene; ABR Acrylic rubber acrylate butadiene copolymer; and CO, ECO-Hydrin 100 and 200-homopo3ymer or a copolymer of epichlorohydrin and ethylene oxide. Additional useful elastomers are copolymers of ethylene and acrylate esters, such as methyl acrylate and ethyl acrylate, wherein the copolymer contains at least 30 weight percent acrylate ester which elastomers are sold commercially by duPont under the Vamac trademark.

Elastomers useful in this invention are described in detail in the "Handbook of Plastics and Elastomers" pages 1-106-119, (1975) McGraw-Hill, Inc., which is hereby incorporated by reference.

Particularly useful elastomers are polychloroprene and block copolymers of styrene and butadiene or isoprene, such block copolymers being sold under the trademark Kraton by Shell Oil 4 ttt Company. Block copolymers of styrene and diene monomers are described in detail in U.S. Patents No. 4,041,103 and 4,242,470 which are hereby incorporated by reference.

Other elastomeric polymers having a Tg below -25 C and oo solubility in the methyl methacrylate monomer can be employed since, other than the low Tg and solubility characteristics, there are no other limitations on the identity of the elastomers except for the specific requirements of the particular adhesive being formulated, such as suitable molecular weight, viscosity characteristics and compatibility with the other ingredients of the adhesive.

4 t Useful elastomers are those which are soluble in the monomers used in the adhesives of this invention. These elastomers can form solutions of from about 10 to about 35 weight percent elastomer in methyl methacrylate. As used herein the term "solution is intended to cover not only true solutions but colloidal dispersion which exhibit normal or substantially newtonian rheology characteristics.

The core-shell graft copolymers useful in this invention have a "rubbery" core, a "hard" shell, and swell in the monomer compositions but do not dissolve therein. The "core" or backbone polymer of the graft copolymers has a glass transition temperature substantially below ambient temperatures. The ~t "shell" polymer which is grafted onto the backbone polymer has a glass transition temperature substantially above ambient temperatures. Ambient temperature is defined as the temperature range in which the adhesive is used.

Examples of useful core-shell graft copolymers are those where "hard" monomers, such as styrene, acrylonitrile or methyl methacrylate, are grafted onto a rubbery core made from polymers of "soft" or "elastomeric" monomers, such as butadiene or ethyl acrylate.

U.S. Patent No. 3,985,703, which is hereby incorporated by reference, describes useful core-shell polymers, the cores of which are made preferably from butyl acrylate but can be based on ethyl, isobutyl, 2-ethylhexyl, or other alkyl acrylates or mixtures thereof. The core polymer, optionally, can contain up -6-

E

1 to 20 percent of other copolymerizable monomers, such as styrene, vinyl acetate, methyl methacrylate, butadiene, isoprene and the like. The core polymer optionally, can contain up to 5 percent of a crosslinking monomer having two or more nonconjugated double bonds,of approximately equal reactivity, such as ethylene glycol diacrylate, butylene glycol dimethacrylate and the like. It also optionally can contain up to 5 percent of a graft-linking monomer having two or more nonconjugated double bonds of unequal reactivity, such as diallyl maleate and allyl methacrylate.

The shell stage is preferably polymerized from methyl methacrylate and optionally other lower alkyl methacrylates, such as ethyl, butyl, or mixtures thereof. Up to about 40 percent by weight of the shell monomers can be styrene, vinyl acetate, vinyl S. .chloride, and the like.

Additionally useful core-shell graft copolymers are described in U.S. Patents No. 3,984,497, No. 4,096,202, and No.

4,034,013, which are hereby incorporated by reference.

Still other useful core shell polymers are the "MBS" ~polymers such as those described in U.S. Patent No. 4,304,709 which is hereby incorporated by reference. The MBS polymers are made by polymerizing methyl methacrylate in the presence of polybutadiene or a polybutadiene copolymer rubber.

Other patents which describe various useful core-shell graft t copolymers are U.S. Patents No. 3,944,631, No. 4,306,040 and No.

4,495,324, each of which is hereby incorporated by reference.

The core-shell graft polymers used in this invention swell -7in size in the adhesive formulation but do not dissolve. The adhesives, so formulated, exhibit improved spreading and flow properties which are highly desirable in many adhesive applications. For example, when an adhesive is applied to an article by means of a syringe-type application, many adhesives "string-out" between the point where the applicator was applied and the next position of the applicator. With the present invention, a small drop of adhesive can be applied to the article to be bonded with no adhesive string forming.

Additional components of the composition of this invention are polymerization catalysts with or without other components which enhance the reactivity of the catalysts. The catalysts are free radical generators which trigger the polymerization of acrylate and methacrylate compounds. Such catalysts are |peroxides, hydroperoxides, peresters, peracids, radiant energy, ultrav'olet light, and heat. Examples of these catalysts are benzoyl peroxide, cumene hydroperoxide, tertiary butyl hydroperoxide, dicumyl peroxide, tertiary butyl peroxide acetate, tertiary butyl perbenzoate, ditertiary butyl i azodiisobutyronitrile and the like. These free radical producing catalysts are used in amounts of about 0.01 to about 10 weight percent based on the weight of the adhesive composition.

Preferably, the catalysts will be used in the amount of about 0.05 to about 3 weight percent.

Other components which enhance the reactivity of the catalysts are initiators or activators and promoters. Initiators and activators, which terms are used interchangeably, include tertiary amines and aldehyde-amine reaction products. Useful tertiary amines include N,N-dimethylaniline, N,N-dimethyltoluidine, N,N-diethylaniline, N,N-diethyltoluidine and the like.

Aldehyde-amine reaction products include such compositions as butyraldehyde-aniline and butyraldehyde-butylamine compositions.

A promoter is an organic salt of a transition metal, such as cobalt, nickel, manganese or iron naphthenate, copper octoate, copper acetylacetonate, iron hexoate, or iron propionate.

The initiators or activators, if used, are added in the amount of up to about 15 weight percent based on the weight of the adhesive. Preferred amounts are 0.01 to about 5 percent.

Promoters are used in amounts up to about 0.5 weight percent, preferably about 1 part per million to about 0.5 weight percent.

The compositions of this invention are usually prepared in two parts wherein 1 part contains the free radical catalysts and the other part contains the initiator or activator and the promoter if it is used. Just, prior to use, the two parts are S. mixed together and the mixture is applied to at least one of the surfaces to be bonded. Alternatively, the part containing the catalyst can be applied to one surface and the part containing the activator can be applied to the other-surface. When pressed I together, the two parts mix together and polymerization with resultant adhesive bonding takes place.

js pr rr<{ q f fet 4oeaadhesive compositions of this invention -w;43 contain about 55 to about 75 weight percent methacrylate ester monomer, 0 r -9" to about 15 weight percent acid monomer, about 5 to about weight percent elastomer and about 10 to about 30 weight percent core-shell graft copolymner, said weight percents being based on the total weight of the components. Preferably, the compositions contains about 60 to about 70 weight percent methacrylate ester monomer, about 2 to about 10 weight percent acid monomer, about 8 to about 15 weight percent elastomer and about 15 to about weight percent core-shell graft copol *ymer..

Adhesive compositions in accordance with a preferred form of this invention have high adhesive bond impact strength (>l5ft-lb/sq.in) and high bulk tensile elongation (>10 percent) when measured at -10 0 (-23 0

C)

or below. The bulk tensile elongation of these compositions is largely reversible even at low test temperatures. This reversible high elongation contributes to0 the superior performance of these adhesives in structures which undergo impacts at low temperatures.

The compositions of this invention are particularly useful for bonding thermoplastic automobile bumpers which must pass simulated crash impact tests at -l0' to -20'~F (-230 to -290C).

in these tests, which measure energy nianagement capability, bumpers are mounted horizontally and are impacted at various :positions and angles with a pendulum or hydraulic ram at a rate 99' that simulates a 2.5 or a 5 mile per hour crash. in this test, the bumper and the adhesive bondline experience both high impact forces and a deflection of as much as 3 or 4 inches at the center. After the test, the bumper springs back to its original 1 1 4 shape. The high impact strength and high elongation, especially reversible elongation at low temperatures, of the compositions of this invention are clearly advantageous in this bumper application.

'The combination of relatively high modulus up to temperatures of 180 F (82 0 C) and high impact strength and elongation at temperatures of -10°F (-23 0 C) or below is very advantageous for bumpers and other structural applications which require hiqh stiffness and structural integrity together with resistance to impact and other high stresses.

In the following examples, the elastomers were dissolved in the monomers by mixing until a uniform solution was obtained and no visible rubber particles were present. The other components, the core-shell polymers were then added to the elastomer II solution and were stirred until a coarse paste was formed.

Further mixing with a high shear dispersion apparatus was continued until a smooth paste was obtained.

Adhesive strength tests were performed by mixing the k4 formulations with a peroxide catalyst paste, or by combining two adhesive polymer-in-monomer solutions, one of which contained a peroxide, the other a catalyst activator.

The adhesives were tested as follows: Lap, Shear Strength (ASTM D-1002) The adhesive shear strength of bonds formed between substrates, a polycarbonate/polyester thermoplastic resin (Xenoy, obtained from General Electric Company), was measured by applying sufficient adhesive to one end of a 25 mm x 76 mm x 6.3 mm coupon of the substrate to completely fill a 25 mm x 12.5 mm x mm bond gap. A 0.25 mm wire shim or washer was used to control bond thickness. A second coupon was placed over the coupon coated with adhesive to provide the proper lap shear configuration in a mold designed to properly align the specimen.

After a cure time of 24 to 48 hours at room temperature, the bonds were tested at a separation rate of 1.27 mm per minute.

Impact Strength (ASTM D-950) The impact strength of the adhesives was tested using the procedure of ASTM D-950 except that steel bars or rods having diameters of 12.7 mm and lengths of 76.2 mm and 9.5 mm, I l respectively, were used instead of the test specimens having dimensions specified in the ASTM testing method. Surfaces to be bonded together were first solvent cleaned and then grit blasted.

After being bonded, the specimens were conditioned for two days at room temperature prior to testing.

e04! Bulk Adhesive Stress Strain (ASTM B-638) Sufficient adhesive components were mixed to form a sheet of S, cured adhesive approximately 2.5 mm in thickness from which 4 t4 tensile test "dumbbells" were cut using a metal die as specified in the ASTM testing method. Unless otherwise specified, the stress-strain tests were performed at the indicated temperatures using a separation rate of 5 mm per minute.

Cold Impact Test on Plastic Substrates This test was devised to simulate the impact and deflection forces that bonded structural assemblies, such as bumpers, -12experience under test conditions. This test was useful in evaluating the effect of "squeeze-out" at bond edges on the impact performance of the overall bonded assemblies. If the cured adhesive is not sufficiently elastic to relax under impact and elongation conditions, a crack can initiate in the adhesive bead and propagate through the bonded assembly, leading to failures.

In conducting the tests, a 15.2 cm long 5 gram bead of mixed adhesive was applied lengthwise on the centerline of a 15.2 cm x cm plastic coupon. A 2.5 cm length of 1.3 mm diameter stainless steel wire was placed approximately 6 mm from each end parallel to the plastic and perpendicular to the bead of adhesive. A 15.2 cm x 1.3 cm plastic strip was pressed down onto 1 *t the adhesive until it made contact with the wire. The bonded assembly was allowed to cure at room temperature for at least 24 4 hours.

Before testing, the assembly was placed in a -10 0 F (-23 C) freezer for at least 15 hours. The cold sample was tested by Splacing it in a modified National Forge Model TM 52004 t Izod-Charpy impact tester fitted with a 10 ft/lb hammer. A fixture was used to hold the sample at each end with the 2.5 cm plastic strip facing the impact hammer and the hammer was allowed to impact the plastic. The area of the hammer which contacts the 41 2 plastic is approximately 1 cm At the lowest point in the swing where the assembly is impacted, the hammer is travelling at 11 feet per second. If, after the hammer impacts the cold plastic, -13- S1 6006 r -i-

I

i

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~I =r I- 0 W the hammer rebounds and the test specimen remains intact, the result is recorded as a pass. If the plastic breaks at the point of impact, the result is recorded as a failure. Occasionally, the hammer impacts the plastic and rebounds, but the end of the plastic in the fixture cracks. This is recorded as an "end crack". It is considered a qualified pass, since the action of the fixturing assembly against the plastic imposes extraordinary stresses on the bonded assembly at these fulcrum points.

The components used in the examples are identified as follows: t* t ct

C

C

1: C t

II

*i~

MMA

MAA

BMA

2-EHMA Neoprene Nitrile Rubber Hypalon Paraloid KM 753 Paraloid KM 330 Geloy 1020 Methyl methacrylate monomer containing 22-28ppm of hydroquinone inhibitor Methacrylic acid containing 250 ppm of hydroquinone inihibitor S Butyl methacrylate S 2-Ethylhexyl methacrylate S Polychloroprene homopolymer having a Brookfield solution viscosity (5 weight percent in toluene) of about 20 to 35 mPa as measured on Model LVT visometer with UL adaptor S Carboxy modified butadiene-acrylonitrile elastomer with medium acrylonitrile content, specific gravity of 0.98 and Mooney viscosity ML-4, 212 F of 30-45 S Chlorosulfonated polyethylene containing 43 percent chlorine and 1.1 percent sulfur duPont S Core-shell polymer of methacrylate-butadiene styrene with high butadiene content Rohm Haas All acrylic core-shell polymer Rohm Haas S Core-shell polymer of acrylate rubber core and styrene-acrylonitrile shell -14- -Al 1- 0 1- Hydrin Liquid epichlorohydrin hSmopolymer with 5 a x 1 Brookfield viscosity (27 C) of 2.5 x 10 cps, a Tg of -25 C and a number average molecular weight of 4,000.

DMT N,N-dimethyl-p-tolidine ZMTI Zinc 2-mercaptotoluimidazole VAMAC ethylene-methyl acrylate copolymer gum-duPont KRATON styrene-isoprene branched copolymer- D 1320x Shell Oil Co.

TYRIN Chlorinated polyethylene containing 42% chlorine, Dow Chemical Co.

DPESC Diphenyl ether disulfonyl chloride BHT 2,6-Di-tert butyl p-cresol oP CHP Cumene hydroperoxide, 80 weight percent in cumene BPO Paste A paste.of 55 percent benzoyl peroxide in benzyl butyl phthalate plasticizer eo. VANAX 808 Butyraldehyde-aniline condensation product R..

oaB Vanderbilt Co.

The Peroxide Paste used in the examples was prepared as follows: Hydrin 10x1, 25 parts by weight, and trioctyl trimellitate plasticizer, 25 parts by weight, were placed in a 0 t" plastic container and were heated to 1100F (43 0 KM 753, 6 parts was gradually added as the mixture was sheared with a laboratory Hochmeyer high shear mixture. After all the KM 753 had been added, shearing was continued for 5 minutes. The mixture was then placed in a 1100F (43 0 C) oven for one hour and was again sheared until a smooth paste was obtained. After cooling, the BPO paste, 40 parts, was added and the mixture was again sheared until a uniform smooth paste was obtained.

i n~ The following tables list components used to formulate adhesive compositions and show test results of cured adhesives.

In preparing the adhesives, the Neoprene, nitrile rubber and Hypalon elastomer were dissolved in MMA to give solutions of and 40 weight percent, respectively. All other ingredients were combined by direct addition and were mixed as described hereinbefore.

The examples which have A and B parts are two part adhesives which are combined in a 1:1 weight ratio just prior to use. In the other examples (the 1 part adhesives), the Peroxide Paste was added prior to use, the mix ratio being 1:10 paste to adhesive.

Table I illustrates greatly improved cold elongation of the compositions of this invention, Ex 1 and 2, compared to a prior V* C A art example, Ex 3.

4 4 1-46- 4'* 4 4 -16- TABLE I Example 1 2 3 A B Composition parts by wt MA62.85 60.25 54.40 74.65 MAA 5.0 5.0 9.7 Neoprene 11.4 Nitrile rubber 14.0 Hypalon 30 23.3 Paraloid KM 753 20.0 20.0 12.05 Parajloid R4 330 8.2 Geloy 1020 9.6 DMT 0.75 0.75 CUP 0.3 BHT 0.25 Vanax 808 7.55 Peroxide Paste 10 Stress/Strain at -11 +1 0

F

(-24 lt Tensile strength at break, psi 5300 4800 6000 I Elongation at break9 Average 23 309 Maximum 26 44 12 00 Tg, C of elastomer -39 -20 -30 10 C k4 t r 4 4 Table II illustrates the improvement in impact resistance at low temperatures of plastic assemblies bonded with the compositions of this invention, Ex 4 and 5, compared with a prior art composition, Ex 6. The steel impact test results show that Ex 4,.5 and 6 have similar impact strengths when measured by conventional methods.

It t 4144 1 44 i 4 0 4.i #8 t 4

I

It 4* 4 ;t *4 4 4t 0 t.t I 1 *44 4 -18- TABLE II Exarntle 4 5 6 Compos itionl part by w

MMA

MAA

Neoprene Hypalon 30 Paraloid KM 753 Para3.oid KM 330 Geloy 1020

DMT

cliP

BH-T

ZMT I Vanax 808 Peroxide Paste BPO Paste Lap Shear Stgth, on Xenoy 1102 62.5 5.0 3.1.35 19 .9 0.75 61.05 9.6 11 .05 72.05 11.25 54.40 9.7 23.3 14.45 1.4.75 1.2.05 74.65 8.2 9.6 1.95 .3 7.55 3.85 1.595 psi 1555 1460 ~t I j ~I #4 I '9I Cold Impact. Test on Xenov 1.102 -12 2 F (-24.5 1 C) Steel Impact Stgth.

Pass Fai 2.

crack 4 23.1.

0 22.0 19.5 it I

I

Iii; .91 9.

9**

I

.9 1.9 6* -19- Yt a I,, r Table III lists additional examples of adhesive compositions which provide adhesives with high elongation and resistance to low temperature impact failures when used to bond plastic.

Examples 7 and 8 are made using elastomers having Tg's of less than 25 C, Example 9 uses an elastomer having a Tg higher than -250C.

Itft;

V

t 44 44 4 1* 41YC 4a 14 1 a* TABLE III Example 7 8 9 A B A B A B Compos it ion parts by weight !4MA

BMA

2 -EUMA

MAA

VAMAC G

KRATON

TYRIN

Paraloid KM 753

DMT

BPO PASTE Elongation0 at -11 1 (-24 35.5 73.5 14 10 11.5 11.5 35.5 73.5 14 14 10 11.5 11.5 15 15 2 4 35.5 14 14 73.5 i5 15 2 4 11.5 11.5 15 2 4 Ii 414£ 4144 4.

#1 4 44

S

Steel impact Tes 8 ft-lb/in4 at -20 F 24.4 Cold impact test on Xenov 1102, -12 20 F (-24 .5 C passed Tg, C of Elastomer 83 -27 .8 21.0 100 -56 8.9 17 #1444 4 i II 44 4 ~441 '4 #4 .4 4 14 4* -21-

F

The examples listed in Table IV show additional adhesive tested at low temperatures. The Example 10 adhesive contains a core-shell polymer but no low Tg elastomer. Example 11 has a core-shell polymer and an elastomer having a Tg above Example 12 has a low Tg elastomer but no core-shell polymer.

Example 13 contains a low Tg elastomer and no core-shell polymer.

This adhesive exhibits decreased bonding strength on Xenoy plastic as shown in Table V. Example 14 contains both a low Tg elastomer and a core-shell polymer.

a (2 9.p .1, 9999 0r 1* 9 rn 0 9b 9i 994w t, -22- I I TABLE IV Zxample 10 11 12 13 14, A B Composition loart by weight

IMA

MAA

Neoprene Nitrile rubber Elypalon 30 Paraloid KM 753

:DMT

OCP

IBET

'Vanax 808

JDPESC

F'Peroxide Paste 62 .85 5.0 31.4 0.75 10 62.85 69.27 5.0 5.0 24.98 62.85 62.60 5.0Q 9.68 11.15 31.4 66.74 11.15 11.4 20.0 0.75 10 14.56 14.56 0.75 0.75 10 0.25 1.46 7 Stress/S train at-113 1 F

C

Tens ille Stgth at break, psi 6031 Eldnghtion at bre ak AVG <5% 4 1444 MAX <5% Tg C of elastomer 6980 3029 5025 4975 <5% <8% +10 6% 6% 34.3 52% 70% -20 -30 11 16% -34.3 9.

*9 9 4 h 4, 9 94 -23- I The examples listed in Table V illustrate the decrease in adhesion to Xenoy plastic with increasing levels of nitrile rubber. Example 15 which contains the highest amount of nitrile rubber and no core shell polymer has the lowest Lap Shear Strength on Xenoy plastic. Examples 16 and 17, which contain elastomer and core-shell polymer within the limits of the invention, have good tensile strength elongation at break and adhesion to Xenoy plastic. Example 18 which contains less elastomer than claimed in the invention has good tensile strength and adhesion but poor elongation at break.

#1 -24- TABLE V Exam~le 15 16 17 18 Composition parts by weight 14MA M4A A Nitrile rubber Paraloid YN 753

DMT

70.9 5 23. 6 .5 60.3 5 14.1 20.1 .5 58 5 30 .5 63.4 29.8 Stress/Stz 8 in at -11. I F (-23 Tansi14 Strength at break, psi Elongation at break %AVG

%MAX

Lap Shear Strength, psi 965 4590 18 25 1480 5040 15 i5 1615 6400 4 1663 t ;it

I

4* ti 25 TABLE V1 Examo1e 15 16 17 18 Composition parts by weight M14A

MAA

Nitrile rubber Paraloid KM 753

DMT

70.9 5 23. 6 .5 60.3 5 14.1 20.1 .5 58 5 6.5 30 .5 6-3.4 1.3 29 .8 Stress/Strain at -11. I. F (-23 .5 0

C)

Tensile Strength at break, psi Elongation at break AVG

MAX

Lap Shear Strength, psi 965 4590 18 25 1480 5040 15 1615 6400 4 1663

I

I

4 lii

II

I

it I *1

I

Lca~-

A-

The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.

I

t t t i -26-

Claims (8)

1. An adhesive composition comprising: a) a methacrylate ester monomer; b) an elastomeric polymer selected from the group consisting of nitrile rubber; polychloroprene; copolymers of butadiene or isoprene with styrene; copolymers of butadiene or styrene with acrylate esters; copolymers of butadiene or styrene with methacrylate esters; copolymers of ethylene and acrylate ethers; homopolymers of epichlorohydrin; and copolymers of epichlorohydrin and ethylene oxide, wherein said elastomeric polymer is soluble in the ester monomer and has a Tg below c) a core-shell graft coplymer which swells in the monomer but does not dissolve therein; and d) a free radical producing catalyst.

2. The adhesive composition of claim 1 wherein the copolymer of butadiene or isoprene with styrene is a block copolymer.

3. The adhesive composition of claim 1 or claim 2 which contains a free radical polymerizable ethylenically unsaturated mono or polycarboxylic acid.

4. The adhesive composition of claim 3 wherein the acid is methacrylic acid.

The adhesive composition of any one of claims 1 to 4 wherein the methacrylate ester monomer is at least weight percent methyl methacrylate.

6. The adhesive composition of any one of claims 1 to i *wherein the elastomeric polymer is soluble in the monomer I in the amount of from 10 to 35 weight percent based on the weight of the solution. 39 -27- GD

7. The adhesive composition of any one of claims 1 to 6 wherein the core of the core-shell graft copolymer is rubbery and the shell of the core-shell graft copolymer is hard in the temperature ranges in which the adhesive is used.

8. The adhesive composition of claim 1, substantially as herein described with reference to any one of the examples. DATED: 26 February 1993 PHILLIPS ORMONDE FITZPATRICK Attorneys for: 010t4A.tI ILLINOIS TOOL WORKS INC. Ii 2t ft i ft. ft t 3 29 2994b 28 IrJ~I- 4C Abstract of the Disclosure Adhesive compositions are made from methacrylate ester monomers, elastomeric polymers having a Tg below -25 C and which are soluble in the monomers, core-shell polymers which swell in the monomers but do not dissolve therein, and free radical producing catalysts. These adhesive compositions when used in bonded assemblies exhibit a combination of high adhesive bond impact strength and high bulk tensile elongation. 'I t 4 4 4r 4 444 t te HPP:jf pat/hpp/p254b. 4 4 Ii *4 t tt I;F I $I $1 I 44i 4 44e -29-