JPH0216345B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for adhering a novel thermosetting adhesive. More specifically, the present invention relates to a method for adhering a novel thermosetting adhesive. The present invention relates to an adhesion method for obtaining an adhesive with excellent adhesive strength at high temperatures through partially crosslinked adhesion of a modified product grafted with a derivative thereof. Conventionally, various solution type, hot melt type and pressure sensitive type adhesives are widely known, which are made of block copolymers consisting of a monovinyl-substituted aromatic compound polymer block and a conjugated diolefin polymer block. No. 44-17037, No. 45-
No. 41518, No. 46-40872, No. 49-330, etc.). Furthermore, adhesives made of modified block copolymers in which unsaturated carboxylic acids or derivatives thereof are grafted to the block copolymers are also widely known (Japanese Patent Laid-Open No.
55-13720, 55-25315, 55-87551).
Adhesives made of such block copolymers and modified products thereof have come to form a category among various adhesives, but adhesives made of such block copolymers and modified products thereof are Adhesive strength is excellent near room temperature, but poor at high temperatures, which limits commercial applications. In order to improve adhesive strength at high temperatures, a technique has been disclosed in which monovalent or divalent metal oxides are added to modified block copolymers to introduce ionic bonds (Japanese Patent Application Laid-open No. 13720/1983). , No. 55-25315). Even in modified block copolymers into which such ionic bonds are introduced, adhesive strength at high temperatures (approximately 120° C.) is insufficient. As a result of extensive research into an adhesive method for producing an adhesive with excellent adhesive strength at high temperatures that overcomes the drawbacks of the block copolymer and its modified products described above, the inventors have discovered a monovinyl-substituted aromatic compound polymer block. We have discovered that this objective can be achieved by partially cross-linking a modified block copolymer grafted with an unsaturated carboxylic acid or its derivative to a block copolymer consisting of a conjugated diolefin polymer block, and based on this knowledge. Based on these findings, the present invention has been completed. That is, the present invention has the general formula 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], and the monovinyl-substituted aromatic compound content is 10 to 70% by weight. , number average molecular weight is 5000
A modified block copolymer obtained by grafting 0.01 to 30% by weight of an unsaturated carboxylic acid or a derivative thereof to at least one block copolymer in the range of ~500,000, and an organic peroxide, sulfur, sulfurs, or sulfur. After mixing the containing compound with a crosslinking agent and applying it between the adherends, the swelling degree of the polymer forming the adhesive (toluene, 25°C
This adhesion method is characterized by partially crosslinking the adhesive until the adhesive strength (immersion for 22 hours) reaches 5 to 100 c.c./g. The present invention will be explained in detail below. In the present invention, a modified block copolymer (hereinafter referred to as "modified block copolymer") in which an unsaturated carboxylic acid or a derivative thereof is grafted to a monovinyl-substituted aromatic compound-conjugated diolefin block copolymer forming the adhesive layer is used. Let's talk about. The monovinyl-substituted aromatic compound-conjugated diolefin block copolymer (hereinafter referred to as "block copolymer") that 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 X (A, B, X,
m and n 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 polymerizing two monomers having different copolymerization reactivity ratios.
It can be obtained by a method of simultaneously charging and polymerizing various monomers to obtain a block copolymer, or by a method of coupling a living block copolymer prepared using the above-mentioned initiator. Said (A-
B) The block copolymer represented by _nX is AB
It can be obtained by coupling a living block copolymer 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. The number average molecular weight of the block copolymer is
It can be selected in the range of 5,000 to 500,000, preferably 20,000 to 400,000. If it is less than 5,000, the resulting adhesive will have poor adhesive strength, and if it exceeds 500,000, the fluidity of the adhesive will be poor and sufficient adhesive strength will not be obtained. The monovinyl-substituted aromatic compound content in the block copolymer is 10 to 70% by weight based on the total polymer.
It can be selected preferably within the range of 10 to 55% by weight; outside this range, a bonded product with excellent adhesive strength cannot be obtained. Examples of unsaturated carboxylic acids or derivatives thereof that can be grafted onto the block copolymer of the present invention to form a modified block copolymer include maleic acid, fumaric acid, itaconic acid, acrylic acid, methacrylic acid, and crotonic acid. acid, cis-4-cyclohexene-1,2-dicarboxylic acid, endo-cis-bicyclo[2,2,1]-5-heptene-2,3-dicarboxylic acid, and derivatives of these include:
Examples include acid anhydrides, esters, acid amides, dicarboxylic imides, etc. of these carboxylic acids, 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. At less than 0.01%, there is almost no improvement in adhesive strength due to grafting, and therefore the adhesive strength at high temperatures is low. 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 above block copolymer and an unsaturated carboxylic acid or a derivative thereof in a molten state or a solution state.
It can be obtained by grafting an unsaturated carboxylic acid or a derivative thereof onto the block copolymer, with or without the use of a radical initiator. Regarding the manufacturing method of these modified block copolymers,
Although not particularly limited in the present invention, production methods in which the obtained modified block copolymer contains undesirable components such as gel, or in which the melt viscosity thereof is greatly reduced and processability is deteriorated are not preferred. A preferred method is, for example, a method in which the above-mentioned block copolymer is grafted with an unsaturated carboxylic acid or a derivative thereof under melt-mixing conditions that substantially do not generate radicals in an extruder. The modified block copolymer, which is an important requirement of the present invention, has a swelling degree (toluene, 25°C x 22h immersion) of 5 to 5.
The crosslinking agent that partially crosslinks to form a polymer of 100 c.c./g is an organic peroxide such as hydroperoxides, dialkyl peroxides, ketone peroxides, peroxy esters, diacyl peroxides, etc. Combinations of these and curing accelerators, sulfur, sulfur-containing compounds, sulfurs, and vulcanization accelerators, etc. can be arbitrarily selected, and the amount added, crosslinking temperature and time are limited as long as these requirements are met. It is not something that will be done. The swelling degree here is a value determined by the following formula. Swelling degree = sample weight after soaking - sample weight before soaking / sample weight before soaking × 1 / toluene density It must be partially crosslinked so that the swelling degree is 5 to 100 c.c./g polymer, and the swelling degree is 5 c.c./g. If it is less than c./g polymer, the adhesive strength of the resulting adhesive will be significantly lower than that of an uncrosslinked adhesive, which is not preferred.
Moreover, if it exceeds 100 c.c./g of polymer, the adhesive strength at high temperatures will be poor like uncrosslinked adhesives, which is not preferable. Mixing of the modified block copolymer and the crosslinking agent does not require any special equipment or method, as long as the temperature and time do not substantially decompose the crosslinking agent to be mixed. For example, roll mixing, kneader mixing, extrusion mixing, solution mixing, etc. can be used. In the method of the present invention, the adhesion method itself, which is carried out using a mixture of a modified block copolymer and a crosslinking agent, does not require any special equipment or method, and can be carried out by a conventional and simple method.
That is, a solution prepared by dissolving a modified block copolymer and a crosslinking agent in a suitable solvent is applied to an adherend, then the other adherend is placed on top of the adherend, and the solvent is removed and partial crosslinking is performed by heating. Further, after coating on one adherend, the solvent is removed, and then another adherend is placed on top of the other adherend, and partial crosslinking adhesion is performed by heating and pressurizing. Alternatively, a method using a solution of an equimodified block copolymer and a crosslinking agent can be used, in which a film obtained by casting a solution is sandwiched between adherends and partially crosslinked and bonded by heating and pressure. In addition, a roll mixture, a kneader mixture, etc. of a modified block copolymer and a crosslinking agent, etc. are made into a thin film using a press or a calendar roll, and the film is sandwiched between adherends, and partial crosslinking is performed by heating and pressurizing. Any method may be used. The modified block copolymer used in the present invention may contain antioxidants, stabilizers, ultraviolet absorbers, etc., and various thermoplastic additives may be added to the modified block copolymer as long as they do not deteriorate the adhesive properties of the modified block copolymer. It is also possible to blend resins, unvulcanized rubber, tackifiers, plasticizers, fillers and other additives. On the other hand, in the present invention, any adherend that forms an adhesive together with the partially crosslinked modified block copolymer can be used as long as it contains a material that can be bonded to the modified block copolymer. Examples of materials that can be bonded to such modified block copolymers include metals such as aluminum, tin, brass, lead, and iron, paper, cellophane, wood, cloth such as polyester cloth, polyamide cloth, cotton cloth, and aramid cloth; Thermoplastic substances include polyolefin polymers such as polyethylene and polypropylene, polystyrene polymers such as polystyrene, impact-resistant polystyrene, AS resin, ABS resin, and MBS resin, nylon-6, nylon-6,6, and nylon-6. 6,
10. Polyamide resins such as 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, ethylene-vinyl acetate resins, polyvinyl alcohol resins, and nitrile resins such as acrylonitrile-methyl acrylate resins. Examples include 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 7, Comparative Examples 1 to 11 It had a butadiene-styrene-butadiene-styrene block, and the styrene content was 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 showed that the melt index (G conditions) was 7.2, the toluene insoluble content was 0.05% by weight, and the amount of maleic anhydride added was 0.70% by weight. For 100 g of modified block copolymer, digimyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,2,5
0.001 mol and 0.005 mol of -dimethylhexane-2,5-dihydroperoxide were mixed at 100°C for 10 minutes using a mixing roll. next,
These mixtures were preheated for 7 minutes at 120° C. using a hot press, and then pressed for 3 minutes (50 Kgf/cm ² ) to produce an uncrosslinked sheet with a thickness of 0.4 mm. This sheet was sandwiched between 0.2 mm thick unpolished, 1,1,1-trichloroethane degreased aluminum plates (using a 0.2 mm aluminum plate spacer), preheated at various temperatures for 30 seconds, and then heat-pressed for various times (pressure 25 Kgf/ cm ² ), an adhesive was obtained. This adhesive was cut to a width of 25 mm to provide a test piece for a peel test. The peel test is
Peeling speed 200mm/under temperature conditions of 20℃ and 120℃
It was carried out in minutes. The results are shown in Table 1. Toluene immersion test (25
℃×22hrs) results are also shown in Table 1.

【table】

[Table] As can be seen from Table 1, adhesives in which a partially crosslinked modified block copolymer with a specific degree of swelling exists as an adhesive layer have excellent peel strength at 20°C and 120°C. , which could be put to practical use. Example 8 A 30% by weight toluene solution of the modified block copolymer used in Example 1 was prepared, 0.001 mol/100 g of benzoyl peroxide was added to the solution, and a toluene solution of the modified block copolymer containing a crosslinking agent was added. Obtained. Wet on the same aluminum plate as in Example 1.
Apply to a thickness of 0.75mm, open time 20
After a few minutes, #10 regular cotton canvas was layered and crimped twice with a roller weighing 2 kg. After standing for one day and night, it was heated in an oven at 130°C for 10 minutes to cause partial crosslinking. The swelling degree of this product is 25 c.c./g polymer, and the peel strength at 20℃ is 17.4Kgf/25mm, which is almost the same as 18.2Kgf/25mm before oven crosslinking, and the peel strength at 120℃ is 4.6Kgf. /25mm, which was sufficient for practical use. Example 9, Comparative Example 12 30 parts by weight of α-pinene polymer (YS Resin A1150, manufactured by Yasukawa Oil Co., Ltd.) was blended with 100 parts by weight of a mixture consisting of the modified block copolymer of Example 1 and 0.001 mol of digimyl peroxide. An adhesive sheet was obtained in the same manner as in Example 1. An aluminum plate was bonded under the same crosslinking conditions as in Example 1 using this adhesive sheet. The peel strength of this adhesive at 20℃ is 21.4Kg
At f/25 mm and 120°C, it was excellent at 5.3 Kgf/25 mm, but in the same manner as in Example 9, α - A contact sheet was prepared by blending 30 parts by weight of a pinene polymer.
An aluminum plate was bonded under the same crosslinking conditions as in Comparative Example 5.
The peel strength of this adhesive at 20℃ is 5.4Kg
At f/25 mm and 120°C, it was inferior to 0.5 Kgf/25 mm and could not be put to practical use.

Claims (1)

[Claims] 1 General formula A-B-A, (A-B) _o , B(-A-B)
_o , (A _- B) _-o A, or (A-B) n block, X is a polyfunctional residue having m bonds, m is an integer of 3 to 7, n is an integer of 2 to 10], and the monovinyl-substituted aromatic compound content is 10 to 70. Weight%, number average molecular weight is 5000
A modified block copolymer obtained by grafting 0.01 to 30% by weight of an unsaturated carboxylic acid or its derivative onto a block copolymer having a molecular weight of 500,000 and a crosslinking agent containing an organic peroxide, sulfur, sulfurs, or a sulfur-containing compound. After applying this between the adherends, the mixture is heated and pressed, and the degree of swelling of the polymer forming the adhesive layer (toluene, 25°C x 22hrs immersion) is 5 to 100 c.c./g.
An adhesion method characterized by partially crosslinking until .