POLYISOPRENE TOUGHENED ADHESIVE COMPOSITION

Abstract: A structurally toughened heat resistant adhesive com­ position comprising a solution of polyisoprene elastomer in polymerizable acrylate ester monomers. The adhesive com­ position also contains an adhesion promoter, a cross-linking agent, a free-radical generator and a free-radical accelerator. The adhesive compositions are generally used as two-part systems, and yield bonds with improved heat and solvent resistant properties. The polymerizable acrylate ester monomers may be monofunctional or a combination of mono- and polyfunc­ tional monomers. Among the useful classes of monomers are alkyl and cycloalkyl acrylates, alkyl and cycloalkyl methacry­ lates, alkoxy acrylates and methacrylates, alkylene diacrylates and dimethacrylates. A few of the preferred monomers are methyl methacrylate, lauryl methacrylate, isobornyl meth­ acrylate, and tetrahydrofurfuryl methacrylate. The preferred polyisoprene rubbers are generally copolymers (or block copolymers) of (i) isoprene with styrene, acrylonitrile, or methacrylonitrile; (ii) homopolymers of polyisoprene; or (iii) copolymers of either (i) or (ii) with a functional monomer; or (iv) mixtures of the above. Most pre­ ferred are the homopolymers of isoprene.

Description: Tbis invention relates to a polyisoprene tougbened adhesive composition. BACKGROUND bF THE INVENTION Disclosed in the prior art are adhesive compositions based on solutions of elastomeric polymers in polymerizable vinyl monomers. The compositions usually exhibit reasonably good storage stability and cure rapidly to strong, tougb bonds. The compositions cure in the presence of air at room temperature, usually with the aid of various polymerization catalysts; e.g., free-radical generators, initiators, promoters, and accelerators. Examples of such adhesive compositions can be found in United States Patent Nos. 3,810,407, 3,962,372, 4,112,013, 4,118,436, 3,994,764, 3,832,274, and 4,138,449. Adhesive compositions formulated from these patents have several shortcomings which make them ineffective in applications which involve extreme environmental conditions. One major disadvantage is their inability to maintain their structural properties such as tensile shear strengths, T-peel and impact after significant exposure to high temperature aging. The chlorosulfonated polyetbylene, polycbloroprene and polyuretbane rubber based adhesive compositions are limited, with respect to their maximum useful service, to temperatures less than 110 O C. All of these adhesives require the addition of reasonably large amounts of epoxy resins to improve high temperature resistance. However, high temperature improvements in this manner are not always substantial enough to meet the requirements of many high temperature applications, and often are merely temporary. A particular disadvantage of the poly(butadiene) based adhesive compositions is that they are soluble in relatively few monomers. Recent legislation regarding hazardous organic solvents has focused on the need to replace high volatile monomers with low volatility, high boiling-point monomers. The prior art rubbers (elastomers) are generally not sufficiently soluble in low volatility methyl methacrylate monomers to allow a useful product to be forumlated. It is evident that there is a need for an adhesive composition which when cured, provides excellent bond strengths and exbibits tougbness and resistance to environmental conditions, particularly high temperature, for extended periods of time. The adhesive compositions of this invention are designed to overcome these traditional problems of the prior art. SUMMARY OF THE INVENTION This invention relates to fast curing, free-radical catalyzed structural adhesive, which form bonds of high tensile shear strength and high T-peel strength when cured. The adhesives described herein are generally formulated as two-part adhesive, the first part comprising at least one polymerizable acrylate ester monomer, and at least one isoprene rubber soluble in the monomer, an adhesion promoter, and a free radical initiator system; the second part comprising an activator. More particularly, this invention relates to two-part adhesive compositions of the polymer-in-monomer type, wherein the polymer is dissolved in the monomer, along with the adhesion promoter and the free radical catalyst system. This solution serves as the first part of the adhesive composition. The second part of the composition is an activator, which is usually applied as a primer or coating to a substrate prior to bonding. The polymer-in-monomer solution can either be applied directly over the activated surface of the substrate or on another substrate to be mated with the first. These adhesive compositions are essentially 100% reactive and do not rely in any way on the loss or evaporation of organic solvents or water to cure. One advantage of these adhesive compositions is that they exhibit excellent resistance to high temperature heat aging and do not require the addition of large amounts of expensive epoxy resins, as does the prior art. The adhesive compositions retain their high tensile shear strength and high T-peel strengths after exposure to temperatures of up to 1800C for periods of a week or more. Sucb improvements are of particular importance in applications which involve high temperature exposure for long periods of time, e.g., automobile applications wbere adhesive bonded car components must withstand paint baking cycles of 150 C for periods of up to several hours. Another object of this invention is to provide an ultraviolet curing, toughened adhesive composition which has resistance to sunligbt, UV radiation, adverse weather conditions and solvents. The invention further provides adhesive compositions that upon cure yield bonds which can witbstand high impact shock and peeling forces, at room temperature as well as at temperature extremes. The instant adhesive compositions are fast curing, easy to use compositions which exhibit excellent shelf-life stability, and are capable of bonding a wide variety of substrates. When cured, these compositions provide excellent resistance to temperatures ranging from about -40 0C to about 205 C, oils at elevated temperatures (including sulfur bearing types), moisture and humidity, oxidation and ozonation. DETAILED DESCRIPTION OF THE INVENTION AND ITS PREFERRED EMBODIMENTS The polymerizable acrylate ester monomers may be monofunctional or a combination of mono- and polyfunctional monomers. Generally, the monomers are exemplified but not limited to those selected from the class consisting of alkyl acrylates, cycloalkyl acrylates, alkyl methacrylates, cycloalkyl methacrylates, alkoxy acrylates, alkoxy metbacrylates, alkylene diacrylates and alkylene dimethacrylates. Among the preferred monofunctional monomers are methyl methacrylate, lauryl methacrylate, 2-ethyl bexyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate and t-butyl methacrylate. The most preferred are those monomers which have high boiling points and low volatility characteristics, including such monomers as tetrabydrofurfuryl metbacrylate, cyclobexyl methacrylate, isobornyl methacrylate, hydroxoethyl methacrylate and hydroxypropyl methacrylate. The monofunctional monomers mentioned above may generally be represented by the formula: EMI4.1 wherein R1 is H, CH3 or lower alkyl, R2 is H, alkyl, alkoxy, cocloalkyl, or alkylene group. The effective range of the polymerizable acrylate ester monomer to be used in the instant compositions may vary somewhat depending on the specific properties desired, but generally 10-90% by weight of the composition desired, and preferably within the range of 15-80% by weight and most preferably 15-40% by weight, Adjustments within these ranges are easily made within the skill of the art. It may be desirable to add a polyfunctional monomer: to the composition as well. Wben this is done, it generally should be in the range of about 1-40% by weight, depending on the specific polyfunctional monomer. The preferred polyfunctionals are dimetbacrylates of various glycols. These monomers are disclosed in U.S. Patent No. 3,218,305, and are of the general formula: EMI5.1 wherein R3 is H, C14 alkyl or hydroxyalkyl or R5OCH2-; R6 is H, halogen or C4 -4 alkyl; R4 is H, OH or R5O-; R5 is CH2=CR C=O-; m is an integer, preferably 1 to 8; k is an integer, preferably 1 to 20; and p is 0 or 1. Examples of some preferred glycol dimethacrylates of this formula are polyetbylene glycol dimethacrylate and dipropylene glycol dimethacrylate, to name a few. Otber suitable polymerizable acrylate ester monomers which may be employed are desicibed in U.S. Patent No. 4,018,851, having the general formula: EMI6.1 wherein R8is selected from the class consisting of hydrogen, chlorine, and methyl and ethyl radicals; R7 is a bivalent organic radical selected from the group consisting of lower alkylene of 1-8 carbon atoms, phenylene, and naphthylene; W is a polyisocyanate radical; E is an aromatic, heterocyclic or cycloaliphatic polyol or polyamine radical, preferably a diol, and more preferably a diol of a cycloaliphatic compound; d is eitber 1 or 0; i is 0 when d is 0, and otherwise equal to one less than the number of reactive hydrogen atoms of E; wherein Z is a (i) polymeric or copolymeric grafted alkylene ether polyol radical or (ii) polymeric or copolymeric methylene ether polyol radical; z is an integer equal to the valency of Z wherein an asterisk indicates a urethane (-NH-CO-O-) or ureide (-NH-CO-NH-) linkage. Z may also be a polymeric or copolymeric methylene ether polyol radical, giving a group of polymerizable monomers disclosed in U.S. Patent No. 3,993, 815. Monomers generally characterized as polyurethanes or polyureides, as disclosed in U.S. Patent No. 3,425,988 may also be used effectively. These monomers are formed from the reaction of an organic polyisocyanate and an acrylate ester having an active hydrogen in the non-acrylate portion of the ester. These monomers may be represented by the general formula: EMI7.1 wherein X is -O- or -R9 N-; R9 is selected from a group consisting of H or lower alkyls of 1 through 7 10 10 carbon atoms; A is CH2=CR .CO.O-; R is H or CH3; n is an integer from 2 to 6 inclusive; and B is a polyvalent substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkyloxy-alkylene, aryloxy-arylene or heterocyclic radical. Finally, polymerizable urethane-acrylate monomers disclosed in U.S. Patent Application No. 356,679 to O'Sullivan, filed May 2, 1973, now abandoned, particularly Example 3 thereof, may be employed. Typical monomers of this type have the general formula of: EMI7.2 wherein R11 is H, CH3, C2H5 or C1; R12 is C2 20 alkylene, alkenylene or cycloalkylene radical or a C640 arylene, alkarylene, aralkarylene, alkyloxyalkylene or aryloxyarylene radical which may be substituted by 1-4 chlorine atoms or by 1-3 amino or mono- or di-C13 13 alkylamino or C1-3 alkoxy groups. R is one of the following less one hydrogen atom: (a) a C18 hydroxy alkyl or aminoalkyl group, (b) a C16 alkylamino-C1-8 alkyl group; or (c) a hydroxyphenyl, an aminophenyl, a bydroxynaphthyl or an aminonaphthyl group which may be further substituted by an alkyl, alkylamino or dialkylamino group, each alkyl group in this subpart (c) containing up to about 3 carbon atoms. Of these, the preferred compositions contain eitber monomer VI., of formula: EMI8.1 or monomer VII , of formula: EMI8.2 or both, (PR represents a propylene triol oligomer residue). Mixtures of some or all of the above polymerizable acrylate ester monomers are also helpful. The polyisoprene rubbers of the instant invention may be selected from a wide range of suitable materials. Most frequently rubbers used are eitber: (i) bomopolymers of natural or synthetic polyisoprene; (ii) random or block copolymers of isoprene with styrene, acrylonitrile or methacrylonitrile; (iii) a copolymer of (i) or (ii) with a functional monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, itaconic acid, acrylic acid ester and methacrylic acid ester. Also contemplated in the instant invention is a random or block copolymer of synthetic isoprene with a polymerizable acrylate or methacrylate ester monomer. The preferred rubbers include the bomopolymers of natural and synthetic polyisoprenes. Syntbetic bomopolymers of polyisoprene that have been found particularly useful are marketed by Shell Cbemicals under the trade name Cariflex IR-305, and by Goodyear under the tradename Natsyn 2200. One grade of naturally occurring polyisoprene rubber is obtainable from the Malaysian Rubber Producers under the trade name SMR-5L. Natural polyisoprene is found in rubber producing trees such as the species Hevea Brasiliensis. Another preferred polyisoprene rubber is the copolymer of isoprene and acrylonitrile. This rubber is sold by Polysar International S.A. under the trade name Krynac 833. The rubbers of the instant invention are generally present in the adhesive composition in the amount of about 5 to about 80% by weight, and preferably about 5 to 40% by weight. The average molecular weight of the rubber preferably sbould not be less than 5000, with an upper limit not greater than, a value compatible with the solubility in the cbosen monomer-. The choice of the polyisoprene rubber will, to a large degree, dictate various properties and characteristics of the adhesive composition and such choices are easily determined through general experimentation and known methods within the art. It is-preferred, However, that the rubbers of the instant invention bave.a glass transition temperature not exceeding 15 C. In the case of a block copolymer, the glass transition temperature of the various block portions may be different. In the case of isoprene-styrene block copolymers, for example, styrene block has a glass transition temperature of -1000C and the isoprene block which has a glass transition temperature of '-720C. This demonstrates a gradation of glass transition with the block copolymer is present. The adhesion promoters of this invention may be chosen from any of those commonly known to the person reasonably skilled in the art. Two types of promoters are preferred. The first type consists of mono- and dicarboxylic acids which are capable of copolymerizing with the acrylate ester monomer. The preferred species of these classes are metbacrylic and acrylic acid. Such acids are used in proportions of 1-20% by weight of the composition, preferably in proportion of 1-15%. The second preferred type of adhesion promoter is of the well-known silane type, present in the composition in proportions of 1-10% by weight of the composition. The free-radical initiator system consists of a free-radical initiator and an accelerator of free radical polymerization, both of which serve to effect rapid polymerization. The free-radical initiators may be of the organic peroxy or hydroperoxy type, perester or peracid type. Especially useful are the perester and peroxide type, among which t-butyl perbenzoate and cumene bydroperoxide are preferred. Useful initiators include those that can be decomposed by the action of heat or UV light to produce free radicals. They also include other redox polymerization catalysts or any compound capable of generating free radicals. Sucb compounds can easily be selected from those skilled in the art. For a more detailed discussion, see U.S. Patent Nos. 3,043,820, 3,591,438, 3,616,640 and 3,832,274. Those free-radical initiators of the photoinitiator type are preferably selected from the group consisting of acetophenones, benzophenones and 1- and 2- acetonaphthones. Additional initiators may be selected from the class consisting of (a) C1 to C6 alkyl diones; (b) metal carbonyls of the formula Mx(CO)y wherein M is a metal atom, x is 1 or 2, and y is an integer determined by the total valence of the metal atoms; and (c) carbonyl compounds of the 14 15 14 general formula R (CO)R wherein R is an alkyl, aryl, aralkyl or alkaryl group containing up 15 . 14 to about 10 carbon atoms, and R is R or hydrogen; or R14 and R15 taken together with carbonyl group form an aromatic or heterocyclic ketone containing up to'about 16 carbon atoms. The initiators are usually employed in amounts of about 1% to about 10% by weight of the composition. The accelerators of free-radical polymerization of the above-mentioned catalyst system are generally used with good results in concentrations of less tha 10% by weight, the preferred range being about 0.1% to about 0.75%. Sulfimides are the preferred group of free-radical accelerators, with the preferred species being 3-oxo-2, 3-dihydrobenz[d]isothiazole-l, l-dioxide, commonly known as benzoic sulfimide or saccharin. Tertiary amines may also be employed as accelerators for free-radical production with the preferred amine being N,N-dimethyl-paratoluidine. The final essential ingredient in the instant adhesive composition is an activator, which generally comprises the second part of the adhesive composition, the first part being the curable portion of the composition. These activators are intended to be applied on the surface of a substrate to be bonded, usually as a coating or a primer prior to application of the first part of the adhesive composition. However, it is also feasible for the curable portion of the composition to be put on a substrate and the activator applied over it. The preferred activators are generally aldehyde-amine condensation products, the preferred being butyraldehyde-aniline. Activators of the type are sold commercially by Uniroyal under the name Beutene, or by DuPont under the name DuPont 808. The condensation products are usually in a solvent solution such as trichlorerethane, or similar solvents, for easy application. In another embodiment, a two-part composition is contemplated wherein each part has a polymerizable portion of the adhesive composition, and wherein one part contains the free-radical initiator and the accelerator of free-radical polymerization, and the other part contains the activator. It is optional, but recommended, that chelatqrs, cross-linking agents, and inhibitors be present in the adhesive composition for optimum performance. Chelators and inhibitors are effective in amounts of about 0.1 to about 1% by weight of the composition. Ethylenediamine tetra-acetic acid, 2,2-ethylenebis-nitril methylidyne dipyridine and the class of Beta-diketones are generally the most effective and are preferred. Cross-linking agents, optionally present in amounts from about zero to about 10% by weight of the composition, include such compounds as copolymerizable dimethacrylates. The inhibitor concentration left over in the monomers from manufacture is often high enough for good stability. However, to insure maximum shelf life, the proportions mentioned above about 0.1 to about 1% by weight of the composition) are recommended. Of those inhibitors which have been found of adequate utility is the group consisting of hydroquinones, benzoquinones, naphthoquinones, pbenantbraquinones, anthraquinones, and substituted compounds of any of the foregoing. Additionally, various phenols can be employed as inhibitors, the preferred one being 2,6-di-tert-butyl-4-methyl phenol. The amount of thickness, viscosity or thixoetropy desired can be varied in accordance with the particular application required. Thickeners, plasticizers, diluents, and various other agents common to the art can be employed in any reasonable manner to produce the desired characteristics. The invention will be appreciated further from the examples to follow, which are not meant in any way to restrict the effective scope of the invention. EXAMPLES Example 1 The table below shows three adhesive formulations, two of which are of instant polyisoprene rubber-containing compositions (1 and 2), and one which does not have the rubber (control 3). Formulation No Ingredient 1 2 3 (control) Percent by Weight Cariflex IR-305 (polyisoprene homopolymer) 25 20 Methyl Methacrylate 60.5 - 46 Cyclohexyl Metbacrylate - 65.5 Butylene glycol dimethacrylate 2 2 2 Methacrylic Acid 10 10 10 t-butyl perbenzoate 2 2 2 Saccbarin 0.5 0.5 0.5 Elvacite 2009 (polymetbyl- methacrylate) - - 40 *Tensile Strength (psi) 3579 3564 4723 **T-Peel Strength (psi) 26 33 6.0 *Measured according to ASTM D1002-64; tested at room temperature. **Measured according to ASTM D1876-69; tested at room temperature. Cariflex IR-305 is an isoprene bomopolymer which is a synthetic isoprene and is marketed by Shell Chemicals. Metbyl methacrylate and cyclohexyl methacrylate are monofunctional polymerizable methacrylate ester monomers and butylene glycol dimethacrylate is a difunctional polymerizable acrylate ester monomer. Metbacrylic acid serves as the adhesion promoter. The initiator system is represented by the perester- free-radical initiator, t-butyl perbenzoate, and the accelerator of free-radical polymerization, saccharin. Elvacite 2009 is a trade name for polymethyl methacrylate which was added to the control to increase the viscosity to a satisfactory value. Steel, grit-blasted laps were coated with the activator Beutene, an amine-aldehyde condensate in trichloretbane marketed by Uniroyal, and the polymerizable part of the adhesive composition (formulations 1, 2, and 3) was applied and the lap shear specimens allowed to fully cure at room temperature. The lap sbears were then tested at room temperature for tensile shear and T-peel strengths. As indicated in the table, the T-peel strengths of the instant polyisoprene rubber-tougbened compositions are significantly better than the control composition. Example 2 This example is intended to demonstrate the ability of the instant polyisoprene toughened compositions to withstand high temperatures for substantial periods of time. Formulation 4 in Table II, is representative of the first part of the two-part instant composition and formulation 5 is a control, using the chlorosulphonated polyetbylene (Hypalon 20) of the prior art. Table II Formulation No. Ingredients 4 5 (control) Percent by Weight Krynac 833 (acrylonitrile/isoprene copolymer) 20 Hypalon 20 - 35.0 Methyl methacrylate 65.5 48.25 Butylene glycol dimethacrylate 2.0 1.0 Methacrylic acid 10.0 10.0 t-butyl perbenzoate 2.0 Saccharin 0.5 - Cumene hydroperoxide - 0.5 Epoxy - 5.0 Stabilizer - 0.25 Krynac 823 is a copolymer of acrylonitrile and isoprene and is a preferred rubber in the instant composition. As mentioned above, Hypalon is a chlorosulphonated polyethylene rubber used in the prior art. The polymerizable acrylate ester monomers are methyl metachrylate and butylene glycol dimethacrylate. The initiator system is comprised of the perester free-radical initiator, t-butyl perbenzoate, and the sulfimide accelerator of free radical polymerizable, saccharin. Cumene hydroperoxide is a peroxy free-radical initiator. Lap shear specimens were prepared as in Example 1, and those specimens using Formulation 4 were primed with amine-aldehyde activator, Bentene and those specimens using Formulation 5 were primed with DuPont 808, an amine-aldehyde activator. Part one of the adhesive compositions (Formulations 4 and 5) was applied to the primed laps and allowed to fully cure at room temperature). The results of the testing are indicated below. Heat aging - tested at room temperature Formulation No. 4 5 *Tensile Shear (psi) initial (room temp.) 4390 4660 after 1 hour at 180 C 4202 3912 after 6 hours at 1800C 4695 2890 after 24 bours at 180 C 4680 2101 *tested according to ASTM D1002-64 The results above demonstrate an improvement in w heat resistant properties of the instant compositions; (Formulation 4) over those of the prior art (Formulation 5).

Claims: WE CLAIM: 1. An adhesive composition comprising, (i) At least one polymerizable acrylate ester monomer; (ii) at least one polyisoprene rubber soluble in the monomer of (i); (iii) at least one adhesion promoter; (iv) a free radical catalyst system; and (v) an activator. 2. 2. The adhesive composition of Claim 1, wherein the polymerizable acrylate ester monomer is selected from the class consisting of alkyl acrylates, cycloalkyl acrylates, alkyl methacrylates, cycloalkyl methacrylates, alkoxy acrylates, alkoxy methacrylates, alkylene diacrylates and alkylene dimethacrylates, and preferably comprises a mixture of mono- and poly-functional acrylates in the amounts of about 90-60=/o to about 1-403/o, respectively. 3. The composition of Claim 2, wherein the monofunctional polymerizable ester monomers can be represented by the formula: EMI18.1 wherein R is H, CH3, or lower alkyl, R2 is H, alkyl, cycloalkyl alkoxy or alkylene group; or is methyl methacrylate or lauryl methacrylate, tetrabydrofurfuryl methacrylate, isobornyl methacrylate, hydroxyethyl or hydroxypropyl methacrylate, cyclohexyl methacrylate, 2-ethyl hexyl methacrylate or ethyl methacrylate, n-butyl, iso-butyl or t-butyl methacrylate, or is represented by the formula: EMI19.1 wherein R3 is H, C1 14 alkyl or hydroxyalkyl or R5OCH2-; R6 is H, halogen or C4 alkyl; R is H, OH or R5O-; R5 is CH2=CR C=O-; m in an integer, preferably 1 to 8; k is an integer, preferably 1 to 20; and p is 0 or 1, and preferably is selected from the class consisting of glycol dimethacrylates or diacrylates, preferably polyethylene glycol dimethacrylate, or butylene glycol dimethacrylate. 4. The composition of Claim 1, wherein the polymerizable acrylate ester monomers may be represented by the formula: EMI19.2 wherein R8is selected from the class consisting of hydrogen, chlorine, and methyl and ethyl radicals; R is a bivalent organic radical selected from the group consisting of lower alkylene of 1-8 carbon atoms; phenylene, and naphtbylene; W is a polyisocyanate radical; E is an aromatic, heterocyclic or cycloaliphatic polyol or polyamine radical, a diol of cycloaliphatic compound, d is eitber 1 or 0; i is 0 when d is 0, and otherwise equal to one less than the number of reactive hydrogen atoms of E; wherein Z is (i) a polymeric or copolymeric grafted alkylene ether polyol radical or (ii) polymeric or copolymeric methylene ether polyol radical; z is an integer equal to the valency of Z; wherein an asterisk indicates a urethane (-NH-C-O) or ureide (-NH-CO-NH-) linkage; Z may also be a polymeric or copolymer metbylene ether polyol radical; or EMI20.1 wherein X is -0- or -R9N-; R9 is selected from the group consisting of H or lower alkyls of 1 through 7 carbon atoms; A is CH2=CR10.CO.O-; R is H, or CH3; n is an integer from 2 to 6 inclusive; and B is a polyvalent substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, aralkyl, alkyloxy-alkylene, aryloxy-arylene or heterocyclic radical. 5. The composition of Claim 1, wherein the polymerizable acrylate ester monomer may be represented by the general formulas of: EMI21.1 wherein R is H, CH3, C2H5 or C1; R is a C2 20 alkylene, alkenylene or cycloalkylene radical or a C6 40 arylene, alkarylene, aralkarylene, alkyloxyalkylene or aryloxyarylene radical which may be substituted by 1-4 chlorine atoms or by 1-3 amino or mono- or di-C13 alkylamino or C13 alkoxy groups; R13 is one of the following less one hydrogen atom: (a) a C18 hydroxy alkyl or aminoalkyl group, (b) a C16 alkylamino-C1-8 alkyl group; or (c) a hydroxphenyl, an aminophenyl, a hydroxynaphthyl or an aminonaphthyl group which may be further substituted by an alkyl, alkylamino or dialkylamino group, each alkyl group in this subpart (c) containing up to about 3 carbon atoms, and wherein the polymerizable monofunctional acrylate ester ether preferably has the formula: VI. EMI21.2 or monomer VII, of formula: EMI21.3 inhere PR represents a propylene triol oligomer residue. 6. The adhesive composition of any of claims 1 to 5, wherein the polyisoprene rubber is a homopolymer of natural or synthetic isoprene. 7. The adhesive composition of any of claims 1 to 5, wherein the polyisoprene rubber is a random or block copolymer of isoprene and at least one polymerizable monomer selected from the group consisting of styrene, acrylonitrile and metbacrylonitrile. 8. The adhesive composition of any of claims 1 to 5, wherein the polyisoprene rubber is a random or block copolymer of natural or synthetic isoprene and a polymerizable monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic anhydride, fumaric acid and itaconic acid. 9. The adhesive composition of Claim 8 and further characterized by one or more of the following features: (1) the molecular weight of the rubber has a glass transition temperature (Tg) less than about 15 C; (2) the adhesion promoter is acrylic or methacrylic acid, or is a silane; (3) the free radical catalyst system comprises a free radical initiator and a free-radical accelerator, preferably selected from the group consisting of organic peroxides, hydroperoxides, peresters, or peracids, preferably t-butyl perbenzoate; ; (4) the free radical initiator is cumene hydroperoxide, (5) the free radical accelerator is a sulfimide or a tertiary amine, preferably 3-oxo-2,3-dihydrobenz[d] isothiazole-l,l-dioxide or N, N-dimethyl-paratoluidine, (6) the activator is an aldehyde-amine condensation product, preferably butyraldehyde-aniline, and wherein the composition optionally contains an inhibitor in the amount of about 0.1 to about 1% by weight, selected from the group consisting of hydroquinones, benzoquinones, naphtboquinones, phenanthraquinones, anthraquinones and a substituted compound of any of the foregoing, (7) the inhibitor is 2,6-di-tert-butyl-4 -methyl pbenol; ; (8) wherein the composition optionally contains a cbelator in the amount of about 0.1 to about 1% weight, preferably ethylenediaminetetraa acetic acid, or its sodium salt, or 2,2-ethylene-bis-nitril methylidyne dipyridine, or a Beta-diketone; (9) the free radical initiator is of the pbotoinitiator-type and is present in concentrations from about 0.1% to about 10% by weight and is selected from the group consisting of acetophenones, benzophenones, and 1- and 2acetonaphthones. 10. The adhesive composition of Claim 9, wherein the free radical initiator is selected from the class consisting of (a) C1 and C6 alkyl diones; (b) metal carbonyls of the formula Mx(CO)y wherein M is a metal atom, x is 1 or 2, and y is an integer determined by the total valence of the metal atoms; and (c) carbonyl compounds of the general formula R14(CO)R15 wherein R14 is R15 14 and 15 or hydrogen; or R and R taken together with the carbonyl group form an aromatic or heterocyclic ketone containing up to about 16 carbon atoms, and wherein the composition optionally contains a cross-linking agent, preferably a dimetbacrylate compound.

Inventors: CHARNOCK, RONALD SCOTT
Applicants: LOCTITE CORPORATION
Application year: 1981
Main classification: C09J3
IPC codes: C09J4, C08F279