JPS648036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel epoxy resin adhesive, and more specifically, to a block copolymer consisting of an epoxy resin, a monovinyl-substituted aromatic compound polymer block, and a conjugated diolefin polymer block, or a hydrogenated product thereof. The present invention relates to a novel epoxy resin adhesive with excellent adhesive strength, which is composed of a modified product grafted with an unsaturated carboxylic acid or a derivative thereof and a curing agent for epoxy resin. Conventional general epoxy resins are condensation products of bisphenol A and epichlorohydrin, which are cured with amines or acid anhydrides, and exhibit a number of excellent mechanical and chemical properties, making them suitable for adhesives. Although it has excellent shear adhesive strength, it has a weak peel adhesive strength. Attempts have been made to address this drawback by adding copolymerized nylon, liquid rubber having a carboxyl group, or the like to impart flexibility to the epoxy resin, thereby improving the peel adhesion strength. When using copolymerized nylon as a modifier,
It must be used in large quantities, which makes it moisture resistant,
There is a problem with heat resistance. In addition to not being able to obtain sufficient adhesive strength with liquid rubber, there are also problems with heat resistance. Also disclosed is an adhesive composition comprising an unmodified block copolymer and an epoxy resin. (Special Publication No. 52-20491). Since the block copolymer in such adhesives is unmodified, it has poor compatibility with epoxy resins and does not exhibit sufficient adhesive strength. As a result of intensive research into an adhesive that overcomes the drawbacks of epoxy resin adhesives and has excellent shear adhesive strength and peel adhesive strength, the inventors of the present invention discovered that epoxy resin, a monovinyl-substituted aromatic compound polymer block, and a conjugated diolefin polymer block have been developed. It has been found that an adhesive consisting of a modified block copolymer consisting of a combined block or a hydrogenated product thereof, to which an unsaturated carboxylic acid or its derivative is grafted, and an epoxy resin curing agent can achieve the object. Based on this knowledge, the present invention was made. That is, the present invention uses 100 parts by weight of an epoxy resin and general formulas A-B-A, (A-B) _o , B(-A-B)
_o , (A _- B) _-o A or (A-B) n , X is a polyfunctional residue having m bonds, m is an integer of 3 to 7, and n is an integer of 2 to 10. ], the monovinyl-substituted aromatic compound content is 10 to 70% by weight, and the number average molecular weight is
5 parts by weight of a modified block copolymer obtained by grafting an unsaturated carboxylic acid or a derivative thereof in a range of 0.01 to 30% by weight to at least one type of block copolymer having a molecular weight of 5,000 to 500,000 or a hydrogenated product thereof. The present invention provides an adhesive characterized by comprising less than 100 parts by weight of an appropriate amount of an epoxy resin curing agent. The present invention will be explained in detail below. The epoxy resin used in the present invention is a bisphenol type epoxy resin, a novolak type epoxy resin, etc., and examples thereof include bisphenol A/epichlorohydrin adduct, bisphenol A/methylepichlorohydrin adduct, bisphenol F/epichlorohydrin adduct, and tetrachlorohydrin adduct. Examples include bromobisphenol A/epichlorohydrin adducts, novolac/epichlorohydrin adducts, etc., and are not limited as long as they can be used as adhesives. A modified block copolymer (hereinafter referred to as a "modified block copolymer") in which an unsaturated carboxylic acid or a derivative thereof is grafted onto a monovinyl-substituted aromatic compound-conjugated diolefin block copolymer or its hydrogenated product, which is an important component in the present invention. "polymer")
Let's talk about. The monovinyl-substituted aromatic compound-conjugated diolefin block copolymer (hereinafter referred to as "block copolymer"), which serves as the base of such a modified block copolymer, has the general formula A-B-A, (A-
B) _o , B(-A-B) _o , (A-B)- _o A, (A-B
) _n
It is represented by X (A, B, X, m and n in the formula have the same meanings as above) and can be obtained by a living anionic polymerization method using an alkali metal-based initiator. Such block copolymers can be produced by sequentially polymerizing monomers block by block in the presence of the initiator, or by simultaneously charging two types of monomers with different copolymerization reactivity ratios. It can be obtained by a method of obtaining a living block copolymer or by a method of coupling a living block copolymer prepared using the above-mentioned initiator. The block copolymer represented by (A-B) _nX can be obtained by coupling the living block copolymer A-B with a polyfunctional coupling agent. In this case, it is possible to use, for example, tetrafunctional coupling agents such as tin tetrachloride and silicon tetrachloride. Monovinyl-substituted aromatic compounds include styrene, α-methylstyrene, O- or P-vinyltoluene, ethylstyrene, vinylxylene, isopropylstyrene, ethylvinylstyrene, tertiary-butylstyrene, diethylstyrene, vinylnaphthalene, etc. Also, a mixture of two or more of these can be selected. Examples of the conjugated diolefin include 1,3-butadiene, 1,3-pentadiene, isoprene, and 2,3-dimethylbutadiene, and mixtures of two or more of these can be selected. Preferred combinations are styrene and 1,3-butadiene and styrene and isoprene. Furthermore, hydrogenated block copolymers obtained by hydrogenating these block copolymers can be produced by methods well known to those skilled in the art. Various hydrogenation catalysts, such as reaction products of nickel or cobalt carboxylates and halides or nickel or cobalt alksides with alkyl aluminum compounds, copper dichromate, molybdenum sulfide and fine grinding on low surface area carriers. This can be done using platinum or other noble metals. Hydrogenation can be carried out at any temperature, pressure, and time, typically between 25 and 300°C,
It can be carried out at 7 to 70 Kgf/cm ² for 0.2 to 12 hours. The number average molecular weight of the block copolymer is 5000~
500,000, preferably in the range of 20,000 to 400,000. If it is less than 5,000, the adhesive strength of the resulting adhesive will be poor, and if it exceeds 500,000, the difference in viscosity will result in non-uniform mixing, making it impossible to obtain sufficient adhesive strength. The content of the monovinyl-substituted aromatic compound in the block copolymer can be selected within the range of 10 to 70% by weight, preferably 10 to 55% by weight, based on the total polymer. Outside this range, the adhesive strength will be affected. It is not possible to obtain a good adhesive. Examples of unsaturated carboxylic acids or derivatives thereof that can be grafted onto the block copolymer of the present invention or its hydrogenated product to form a modified block copolymer include maleic acid, fumaric acid, itaconic acid, and acrylic acid. , methacrylic acid, crotonic acid, cis-4
-cyclohexene-1,2-dicarboxylic acid, endo-cis-bicyclo[2,2,1]-5-heptene-2,3-dicarboxylic acid, etc. These derivatives include acid anhydrides of these carboxylic acids. ,
Examples include esters, acid amides, dicarboxylic acid imides, and among these, dicarboxylic acid anhydrides are preferred, and maleic anhydride is particularly preferred. The content of unsaturated carboxylic acid or its derivative in the modified block copolymer of the present invention is from 0.01 to
30% by weight, preferably 0.05-10% by weight. If it is less than 0.01%, there is almost no improvement in compatibility with the epoxy resin due to grafting, resulting in low adhesive strength. Even if it exceeds 30% by weight, the effect will not become large. The modified block copolymer of the present invention can be produced by combining the block copolymer or its hydrogenated product and an unsaturated carboxylic acid or its derivative in a molten state or a solution state, with or without the use of a radical initiator. , can be obtained by grafting an unsaturated carboxylic acid or a derivative thereof to the block copolymer. The method for producing these modified block copolymers is not particularly limited in the present invention, but the modified block copolymers obtained may contain undesirable components such as gels, or have a significantly reduced melt viscosity, resulting in poor processability. A manufacturing method that causes deterioration is not preferred. A preferred method is, for example, a method in which the block copolymer or its hydrogenated product is grafted with an unsaturated carboxylic acid or its derivative in an extruder under melt-mixing conditions that substantially do not generate radicals. preferable. The modified block copolymer is used in an amount of 5 parts by weight or more and less than 100 parts by weight, preferably 5 to 70 parts by weight, based on 100 parts by weight of the epoxy resin. Further, as the curing agent for curing the epoxy resin in the present invention, amine curing agents such as aliphatic amines and aromatic amines, acid anhydride curing agents, and the like can be used, and are not particularly limited. The curing agent may be used in an amount of 0.1 to 10% by weight based on the total amount of the modified block copolymer and epoxy resin. Mixing of the modified block copolymer, epoxy resin, and curing agent for epoxy resin does not require any special equipment or method, and can be done at a temperature and for a time that does not substantially cure the epoxy resin due to the curing agent being mixed. . For example, roll mixing, kneader mixing, extrusion mixing, solution mixing, etc. can be used. The bonding method using the adhesive of the present invention does not require any special equipment or method, and may be a conventional and simple method. That is, after applying a solution prepared by dissolving a modified block copolymer, an epoxy resin, and a curing agent for epoxy resin in an appropriate solvent to an adherend, the other adherend is placed on top of the other adherend, and the temperature and time required for the epoxy resin to harden are adjusted. Remove the solvent and cure the adhesive. After coating on one adherend, the solvent is removed at a temperature and time that does not cure the epoxy resin, and then another adherend is stacked and curing bonding is performed at a temperature and time that the epoxy resin hardens. Alternatively, a method using a solution can be used, such as sandwiching a film obtained by casting a solution between adherends and performing curing and adhesion at a temperature and time at which the epoxy resin is cured. In addition, modified block copolymers,
A roll mixture, kneader mixture, etc. of epoxy resin and curing agent for epoxy resin is made into a thin uncured film using a press, calendar roll, etc., and is sandwiched between adherends, and the adhesive is cured at the temperature and time required to cure the epoxy resin. Any other method may be used. Antioxidants, stabilizers, ultraviolet absorbers, etc. can be added to the modified block copolymer used in the present invention, and various thermoplastic additives can be added to the modified block copolymer, as long as they do not deteriorate the adhesive properties of the resulting adhesive mixture. It is also possible to blend resins, unvulcanized rubber, tackifiers, plasticizers, fillers and other additives. On the other hand, in the present invention, examples of adherends that form an adhesive together with the adhesive of the present invention include metals such as aluminum, tin, brass, lead, and iron;
Paper, cellophane, wood, polyester cloth, polyamide cloth, cotton cloth, aramid cloth, etc., as well as thermoplastic materials such as polyolefin polymers such as polyethylene and polypropylene, polystyrene, high-impact polystyrene, AS resin, ABS resin,
Polystyrene polymers such as MBS resin, polyamide resins such as nylon-6, nylon-6, 6, nylon-6, 10, nylon-11, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyvinyl chloride, Vinyl chloride resins such as polyvinylidene chloride, methacrylic resins such as polymethyl methacrylate, polycarbonate resins, polyphenylene ether resins,
Examples include nitrile resins such as ethylene-vinyl acetate resin, polyvinyl alcohol resin, and acrylonitrile-methyl acrylate resin. Other examples include thermosetting resins such as epoxy resins, phenolic resins, and unsaturated polyester resins, and vulcanized rubber. Examples are shown below. The examples are representative of the invention but are not intended to limit the scope of the invention. Examples 1 to 4 Butadiene-styrene-butadiene-styrene block, styrene content 38% by weight,
A modified block copolymer in which maleic anhydride was grafted onto a styrene-butadiene copolymer having a number average molecular weight of 60,000 was obtained by the method shown below. 1.5 parts by weight of maleic anhydride and 0.2 parts by weight of phenothiazine were added to 100 parts by weight of the above styrene-butadiene copolymer, and these were mixed uniformly using a mixer. This mixture was supplied to a screw type extruder (single screw, screw diameter 40 mm, L/D=24, full flight type screw) under a nitrogen atmosphere, and a maleation reaction was carried out at a cylinder temperature of 200°C. Unreacted maleic anhydride was removed from the obtained polymer under reduced pressure. The analysis results are calculated using the melt index (G
Conditions) 7.2, toluene insoluble content was 0.05% by weight, and maleic anhydride adduct was 0.70% by weight. 10 to 80 parts by weight of the obtained modified block copolymer and Asahi epoxy resin AER 661R (epoxy equivalent
450 to 500, manufactured by Asahi Kasei Industries, Ltd.) were kneaded using a pressure kneader at 120°C for 15 minutes, and to 100 parts by weight of the resulting kneaded product, 3 parts by weight of dicyandiamide as an epoxy resin curing agent, Using an oven roll, add 0.2 parts by weight of benzylmethylamine.
The mixture was kneaded at 60°C for 10 minutes to obtain an adhesive composition. Next, use a heat press to heat these for 5 minutes at a temperature of 100℃.
After preheating for 2 minutes, pressurize (50Kgf/cm ² ) for 2 minutes, and
An uncured sheet of 0.2 mm was obtained. This sheet is 0.2mm
Sandwiched between thick, unpolished, 1,1,1-trichloroethane degreased aluminum plates (using a 0.1 mm aluminum plate spacer), heat-bonded at 170℃ for 30 minutes (pressure 25Kgf/
cm ² ) to obtain an adhesive. This adhesive was cut to a width of 25 mm to provide a test piece for a peel test. In addition, the uncured sheet was 1.6 mm thick, unpolished, 1, 1,
1- Place scissors (0.1
mm aluminum plate spacer) was heat-pressed at 170° C. for 30 minutes (pressure: 25 Kgf/cm ² ) to obtain a test piece for shear testing. Peeling test and shear test are conducted at 20℃ and 120℃.
The test was carried out under temperature conditions of 0.degree. C. at a peeling rate of 200 mm/min and a shearing rate of 10 mm/min. The results are shown in Table 1. Comparative Example 1 Unmodified block copolymer 30 before modification of Example 1
Parts by weight of Asahi epoxy resin AER 661R, 100 parts by weight, and the same type and amount of curing agent as in Example 1 were kneaded in the same manner as in Example 1 to obtain an uncured sheet. Adhesion was carried out in the same manner as in Example 1, and the same tests were carried out, and the results are shown in Table 1. Comparative Example 2 The epoxy resin AER 661R used in Example 1 was used alone, and the same type and amount of curing agent as in Example 1 was kneaded at 60°C for 15 minutes using a pressure kneader.
Thereafter, an uncured sheet was obtained by heat pressing (80°C for 10 minutes). This product was bonded and tested in the same manner as in Example 1, and the results are shown in Table 1. Comparative Examples 3 to 4 Instead of the modified block copolymer of Example 2, copolymerized nylon (manufactured by Zytel 61 Du Pont), liquid terminal carboxylic acid 1,2-polybutadiene (NISSO-
An adhesive was produced in the same manner as in Example 1, except that PB C-1000 (manufactured by Nippon Soda) was used, and the same tests as in Example 1 were conducted. The results are shown in Table 1.

[Table] As can be seen from Table 1, adhesives made by mixing epoxy resin with a modified block copolymer at a specific ratio exhibit higher adhesive strength than those using unmodified block copolymers. Moreover, compared to the product using epoxy resin alone, the peel adhesion strength was significantly improved, and the shear adhesion strength was also equal to or higher than that, and was sufficiently usable for practical use. Example 5 It has a styrene-butadiene-styrene block, the styrene content is 30% by weight, and the number average molecular weight is 30% by weight.
A modified block copolymer in which maleic anhydride was grafted onto a hydrogenated styrene-butadiene copolymer of 80,000 was obtained by the method shown below. For 100 parts by weight of the above hydrogenated block copolymer,
2.0 parts by weight maleic anhydride, 0.03 parts by weight 2,
5-dimethyl-2,5-di(t-butylperoxy)hexane was added and mixed uniformly using a mixer. This mixture was fed to an extruder in the same manner as in Example 1, and a maleation reaction was carried out. Unreacted maleic anhydride was removed from the obtained polymer under reduced pressure.
The analysis results are melt index (G condition) 5.1,
The toluene insoluble content was 0.06% by weight, and the amount of maleic anhydride added was 1.20% by weight. 30 parts by weight of the obtained modified block copolymer and 100 parts by weight of Asahi Epoxy AER 661R were kneaded in the same manner as in Example 1, and the same type and amount of epoxy resin curing agent as in Example 1 was mixed. An adhesive composition was obtained by kneading in the same manner. Using this composition, Example 1
An adhesive test piece similar to that was prepared and the same test was conducted. Shear adhesive strength at 20℃ 256Kgf/cm ²
Shear adhesive strength at 120℃ 64Kgf/cm ² , 20℃
It exhibited a high adhesive strength of 9.6 Kgf/25 mm at 120° C. and 5.4 Kgf/25 mm at 120° C., and was sufficiently usable for practical use. Comparative example 5 100 parts by weight of Asahi epoxy resin AER 661R and
In the same manner as in Example 1, 30 parts by weight of a graft polymer obtained by graft polymerizing 39% by weight of methyl methacrylate and 38% by weight of styrene in the presence of 33% by weight of emulsion polymerized SBR containing 10% by weight of styrene. kneading,
The composition was mixed, test pieces were prepared, and an adhesive strength test was conducted. Shear adhesive strength at 20℃ is 205Kgf/
cm ² was good, but the peel adhesion strength at 20° C. was low at 2.5 Kgf/25 mm.

Claims (1)

[Claims] 1. 100 parts by weight of epoxy resin and general formula A-B-
A, (A-B) _o , B(-A-B) _o , (A-B)- _o A
or (A-B) _n
is a block substantially consisting of a conjugated diolefin polymer, X is a polyfunctional residue having m bonds, m
is an integer of 3 to 7, and n is an integer of 2 to 10. ], and the monovinyl-substituted aromatic compound content is 10
~70% by weight, and at least one type of block copolymer having a number average molecular weight in the range of 5,000 to 500,000, or a hydrogenated product thereof, is grafted with an unsaturated carboxylic acid or a derivative thereof in a range of 0.01 to 30% by weight. An epoxy resin adhesive characterized by comprising 5 parts by weight or more and less than 100 parts by weight of a modified block copolymer and an appropriate amount of an epoxy resin curing agent.