JPH0535748B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a thermoplastic polyurethane solvent-based adhesive composition. (Prior art) Thermoplastic polyurethane-polyisocyanate-based solvent-based adhesives lose their tackiness within a short time at room temperature after being applied to the object to be adhered, so they are usually used when bonding. It was necessary to heat the adhesive layer to 80°C or higher. In order to make the above polyurethane adhesive usable at room temperature, the present inventors have confirmed that, for example, when used in combination with a tackifier resin such as Coumaron resin, it is possible to form an adhesive layer that retains its tackiness at room temperature. . However, it has been found that in this case, there are disadvantages such as poor heat deterioration resistance, insufficient initial adhesive strength, and a long period of 3 to 7 days required for final adhesive strength to develop. (Problems to be Solved by the Invention) In view of the above-mentioned drawbacks of thermoplastic polyurethane solvent-based adhesives, the purpose of the present invention is to improve tackiness at room temperature, initial adhesive strength, period until final adhesive strength is developed, and heat resistance. It is an object of the present invention to provide a thermoplastic polyurethane solvent-based adhesive composition in which various physical properties such as deterioration properties are improved in a well-balanced manner. (Means for Solving the Problems) The solvent-based adhesive composition of the present invention contains a base material containing 50 to 300 parts by weight of a urethane-modified epoxy resin based on 100 parts by weight of a thermoplastic polyurethane resin, and a polyisocyanate. It is characterized by comprising a curing agent, thereby achieving the above object. The thermoplastic polyurethane resin in the present invention refers to a polyurethane resin that is a high molecular weight linear polymer and exhibits thermoplastic properties, but it also includes not only fully thermoplastic resins but also slightly partially cross-linked incomplete thermoplastic resins. Although its molecular weight is not specified, it generally has a weight average molecular weight of 10,000 to 10,000.
100,000, preferably 10,000 to 30,000. This is because if the molecular weight is too low, the cohesive force of the adhesive itself will be low and the initial adhesive strength will be low, while if the molecular weight is too high, solvent solubility will be poor and coating workability will tend to be reduced. Such a thermoplastic resin uses, for example, a bifunctional active hydrogen compound such as a polyester or polyether having hydroxyl groups at both ends, and a urethane polymer having an NCO group at the end obtained from a diisocyanate or a diisocyanate and a polyol.
It can be obtained by reacting equivalent amounts of active water hydrogen groups and isocyanate groups in the entire reaction system. As the bifunctional active hydrogen compound, for example, a polyester polyol having a hydroxyl group at the end obtained by reacting adipic acid with ethylene glycol or 1,4-butanediol is preferably used. Urethane-modified epoxy resin means an epoxy resin having a urethane bond, and is generally an epoxy resin containing about 5 to 40 parts by weight of a urethane prepolymer (preferably molecular weight 250 to 5000) having an isocyanate group at the end of the molecule and a hydroxyl group in the molecule. It is obtained by reacting with about 100 parts by weight. As the epoxy resin, bisphenol A type is often used. This urethane-modified epoxy resin is used as a main ingredient together with a thermoplastic polyurethane resin, and the amount added is 50 to 300 parts by weight per 100 parts by weight of the thermoplastic polyurethane resin. The reason is that if it is less than 50 parts by weight, it will not develop adhesion and will not be able to maintain so-called contact properties, and if it exceeds 300 parts by weight, the adhesiveness of thermoplastic polyurethane resin to a wide range of adherends will be impaired. It is from. In addition, polyisocyanate used as a curing agent is a compound having two or more isocyanate groups in one molecule, and specific examples thereof include tolylene diisocyanate (TDI), methylene bis P phenylene diisocyanate (MDI), and triphenylmethane. Examples include triisocyanate and hexamethylene diisocyanate, and aromatic polyisocyanate is preferably used. The mixing amount of the main agent and curing agent is not particularly limited, but generally the content of polyisocyanate is 5 to 85 parts by weight per 100 parts by weight of the total amount of thermoplastic polyurethane resin and urethane-modified epoxy resin. . Although the curing mechanism in the adhesive composition of the present invention is not fully clear, the polyisocyanate reacts with the urethane-modified epoxy resin to harden the resin, and also reacts with the thermoplastic polyurethane resin to produce allophanate crosslinks, resulting in heat resistance. This is thought to increase deterioration. Solvents used to prepare adhesives include good solvents for polyurethane such as methylene chloride, methyl ethyl ketone, acetone, ethyl acetate, and butyl acetate, as well as poor solvents for polyurethane such as toluene, xylene, and hexane that are mixed with these solvents. can be mentioned. Although the blending amount of the solvent is not specified, it is preferable from the viewpoint of adhesive application workability that the solid content in the base resin is 5 to 50% by weight. To prepare the adhesive, the thermoplastic polyurethane resin and urethane-modified epoxy resin are generally dissolved in the solvent, and the polyisocyanate is added immediately before use. Of course, polyisocyanate dissolved in a solvent in advance may be added. (Example) Hereinafter, parts simply refer to parts by weight. Example 1 Desmocol 500 as a thermoplastic polyester polyurethane resin was added to 400 parts of methyl ethyl ketone.
(manufactured by Sumitomo Bayer Urethane Co., Ltd., adivic acid-ethylene glycol/tolylene diisocyanate system)
100 parts of ACR as urethane-modified epoxy resin
A base solution was obtained by mixing and dissolving 200 parts of epoxy X-1427 (manufactured by A.C.R., bisphenol type, epoxy equivalent: 523). To this solution, 85 parts of aromatic polyisocyanate (manufactured by Sumitomo Bayer Urethane Co., Ltd., methylene bis P phenylene diisocyanate) was added as a curing agent, and the pot life (expressed as the number of days until the viscosity became 2.5 times the value immediately after adjustment) was added. The solvent-based adhesive was prepared for 3 days at 20°. This adhesive was applied to the cotton canvas with a brush, and after an open time of 30 minutes, both cotton canvases were bonded by applying pressure with a hand roller twice, and the peel strength was measured in accordance with JISK-6854-1977. In addition, it was confirmed that it was sticky to the touch. The peel strength (represented by a circle in Table 1) was as shown in Table 1. Example 2 An adhesive was prepared in the same manner as in Example 1, except that 100 parts of ACR epoxy R-1362 (manufactured by ACR Corporation, bisphenol type, epoxy equivalent: 230) was used as the urethane-modified epoxy resin. Physical properties were measured. The results were as shown in Table 1. Example 3 Takenate A as aromatic polyisocyanate
An adhesive was prepared in the same manner as in Example 1 except that 250 parts by weight of -447 (manufactured by Takeda Pharmaceutical Co., Ltd., humidity curing type) was used, and its physical properties were measured. The results were as shown in Table 1. Example 4 Desmocol as thermoplastic polyurethane resin
530 (manufactured by Sumitomo Bayer Urethane Co., Ltd., adipic acid-ethylene glycol/tolylene diisocyanate system, slightly lower melt flow index than Desmocol 500) was used, except for using "ACR Epoxy R-1362" as the urethane-modified epoxy resin. An adhesive was prepared in the same manner as in Example 1.
Its physical properties were as shown in Table 1. Example 5 An adhesive composition having the formulation shown in Table 1 was prepared and its physical properties were measured. The results were as shown in Table 1. Comparative Examples 1 to 4 Solvent-based adhesives having the formulations shown in Table 1 were prepared according to the procedure of Example 1, and their physical properties were measured, and the results were as shown in Table 1.

[Table] * Indicates that it was not adhered.
(Effects of the Invention) The solvent-based adhesive composition of the present invention has the above-mentioned structure, and after being applied to an object to be adhered, it maintains tackiness at room temperature, has sufficient initial adhesive strength, and has resistance to heat deterioration. It has various effects such as good adhesive properties and a short period of time until the final adhesive strength is developed.

Claims (1)

[Claims] 1. A solvent-based adhesive comprising a main ingredient containing 50 to 300 parts by weight of a urethane-modified epoxy resin based on 100 parts by weight of a thermoplastic polyurethane resin, and a curing agent containing a polyisocyanate. Composition. 2. The solvent-based adhesive composition according to item 1, wherein the content of polyisocyanate is 5 to 85 parts by weight based on 100 parts by weight of the total amount of the thermoplastic polyurethane resin and the urethane-modified epoxy resin. 3. The solvent-based adhesive composition according to item 1 or 2, wherein the polyisocyanate is an aromatic polyisocyanate.