JPS6412221B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of bonding polyurethane elastomer and metal. Urethane elastomers are used as a variety of engineering plastics because of their superior physical properties compared to other synthetic resins and rubbers. In particular, in recent years, we have focused on the physical properties of polyurethane elastomer and coated the surface of metal with urethane elastomer.
Methods are being developed to improve the durability of metals. Conventionally, when bonding a cast polyurethane elastomer and metal, certain types of phenolic resins or epoxy resins are known as adhesives. These are used to bond cast polyurethane elastomers to metals, but when casting, 100%
The urethane is cured for a long time (several hours to a day) at a temperature of 150°C to 150°C to improve the physical properties of the urethane and to improve its adhesive properties. However, in producing cast polyurethane elastomers, it is uneconomical in terms of energy to maintain the cast material at high temperatures for long periods of time, and productivity does not improve. Therefore, it is being considered to obtain a product with a short handling time at a low temperature, but when obtaining a cast polyurethane elastomer at a temperature of 20°C to 80°C, it is necessary to use the above-mentioned phenolic resin or epoxy resin to bond it to metal. Even if you try to do so, you will only get very low values of intensity. The inventors of the present invention investigated a method of obtaining sufficient adhesion between a metal and a cast polyurethane elastomer even at low temperatures, and found that a composition containing a specific urethane prepolymer, chlorinated rubber, phenolic resin, etc. was used as an adhesive. The inventors have discovered that sufficiently strong adhesion can be obtained even at low temperatures, and have thus arrived at the present invention. That is, the present invention has an isocyanate group concentration of 15 to 30
% by weight of a urethane prepolymer, one or more resins selected from polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, chlorinated rubber, and phenolic resin, and a solvent are applied to the metal, and a mixture is applied onto the metal. A method for bonding a urethane elastomer to a metal, characterized by injecting and curing a urethane elastomer stock solution. The present invention will be explained in detail below. The urethane prepolymer used as one of the adhesive components of the present invention is a prepolymer having terminal isocyanate groups obtained by reacting a polyol with an excess amount of polyisocyanate.
It preferably has a content of 15 to 30% by weight (hereinafter % refers to % by weight unless otherwise specified), preferably 20 to 30%.
If this NCO is less than 15%, strong adhesion to metal cannot be obtained, and if it exceeds 30%, the adhesive becomes brittle when solidified, and sufficient adhesive strength cannot be obtained. The isocyanate component of the urethane prepolymer used as one of the adhesive components of the present invention is as follows:
2,4-Toluene diisocyanate (2,4-
TDI), 2,6-toluene diisocyanate (2,
6-TDI), or mixtures thereof, methylene bis-4-phenyl isocyanate (MDI), crude methylene bis-4-phenyl isocyanate (C-MDI), xylylene diisocyanate (XDI), naphthalene diisocyanate (NDI),
Triphenylmethane triisocyanate, hexamethylene diisocyanate, methylene bis-4-
Examples include polyisocyanates such as cyclohexyl isocyanate and isophorone diisocyanate. Among them, aromatic polyisocyanates such as MDI or C-MDI are used to increase the adhesion speed.
It is preferable to use The polyol component of the prepolymer used as one of the adhesive components of the present invention includes polypropylene ether polyol, which is obtained by adding propylene oxide to ethylene glycol, propylene glycol, glycerin, pentaerythritol, sorbitol, sucrose, etc., and other polytetramethylene ether. Polyol (PTMG)
Polyether polyols such as polycaprolactone diol, polycaprolactone triol obtained by adding caprolactone to glycerin, secondary acids such as adipic acid, succinic acid, and phthalic acid, and ethylene glycol, 1,4-butanediol, and hexylene glycol. , polyester polyols obtained from glycols such as diethylene glycol and triethylene glycol. In order to obtain strong adhesion, it is preferable to use a polyol with a molecular weight of 700 or more. Solvents are non-reactive with isocyanates such as acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene,
xylene, ethyl acetate, dimethylformamide,
N-methylpyrrolidone, etc., and these are used in combination according to the work process. The resin added as one of the adhesive components of the present invention is one or more resins selected from polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, chlorinated rubber, and phenolic resin. As the polyvinyl chloride, vinyl chloride powder for base resin is preferred. As the vinyl chloride-vinyl acetate copolymer, powder for paste resin is also preferred. Chlorinated rubber is natural rubber with chlorine added and usually has the molecular formula (C ₅ H ₇ Cl _{3 )}
(C ₅ H ₆ Cl ₄ ) _Y (C ₁₀ H ₁₁ Cl ₄ ) Molecular weight indicated by _Z approx.
5,000 to 100,000 and preferably has a chlorine content of 60% or more. Additionally, synthetic rubber with chlorine added can also be used. Examples of the phenolic resin include alkylphenol resins that are often used in chloroprene adhesives. Chlorinated rubber is preferred in terms of solution stability, viscosity, adhesiveness, etc. The amount added is 5 to 40%, preferably 10 to 35%, based on the total of urethane prepolymer and resin. The cast polyurethane elastomer as used in the present invention is a urethane group-containing prepolymer liquid obtained by reacting a polyoxyalkylene polyol or polyester polyol with an isocyanate compound, a polyoxyalkylene polyol or polyester polyol, a chain extender, and a catalyst. It is preferable to use a system that can be obtained by reacting with a liquid consisting of, etc., and that can obtain sufficient strength even at temperatures below 100°C. The polyoxyalkylene polyol is polyoxypropylene diol, polyoxypropylene-oxyethylene copolymer, or polyoxytetramethylene diol having an average molecular weight of 1,000 to 4,000, and may be a mixture thereof. Polyester polyol is a polyester polyol with an average molecular weight of 1,000 to less than 3,000 obtained by the condensation reaction of low molecular weight glycols such as ethylene glycol, 1,4-butanediol, and diethylene glycol with dicarboxylic acids such as adipic acid, succinic acid, and azelaic acid. It is a compound with hydroxyl group. Isocyanate compounds include polyisocyanate compounds such as tolylene diisocyanate and 4,4'-diphenylmethane diisocyanate.
The isocyanate concentration of the prepolymer liquid is 2% to 25
% is preferred. The preferred NCO concentration is 2 to 15% in view of the reaction rate and properties of the cast product. Chain extenders are ethylene glycol, short-chain diols such as 1,4-butanediol, diamines such as methylene-bis-O-chloroaniline, methylene dianiline, etc., and catalysts are diazabicyclooctane, etc., which are generally used for urethane reactions. or organic tin compounds commonly used in urethane foams, such as dibutyltin octoate and dibutyltin laurate. The urethane elastomer stock solution, that is, the solution consisting of the prepolymer solution, polyglycol, chain extender, etc., is thoroughly removed under reduced pressure to prevent bubbles from entering the cast product, and then the two are mixed to form an elastomer. The adhesive of the present invention is generally used with the above composition, but if it is used where the adherend comes into contact with water, trialkoxyalkylsilane can be added as necessary to improve water resistance. . A preferred trialkoxyalkylsilane is gamma-glycidoxypropyltrimethoxysilane. The preferred bonding method between elastomer and metal is
Do as follows. The adhesive of the present invention is applied to an iron plate, and the solvent is allowed to evaporate for 10 to 60 minutes at room temperature. A urethane elastomer stock solution, that is, a prepolymer solution and a polyol mixture solution sufficiently mixed to form a uniform solution, is poured onto the solution and hardened. If left as is for about a week at room temperature, the strength of the elastomer will stabilize and sufficient adhesive strength will be obtained.
When curing the urethane elastomer stock solution,
If heating is necessary, heating may be performed as appropriate. As described in detail above, according to the present invention, when a urethane elastomer stock solution that can be cured at a relatively low temperature is used, a product with good adhesion can be obtained at a low temperature without taking the trouble of heating as in the conventional method. Example 1 (Production of room temperature curable urethane elastomer stock solution) 1 kg of polytetramethylene ether glycol with an average molecular weight of 1000 and 500 g of tolylene diisocyanate (80 g of 2,4 isomer and 20% of 2,6 isomer) were added.
React at 70°C for 4 hours to prepare a prepolymer solution with terminal isocyanate. The isocyanate group concentration of this prepolymer liquid was 10.5%. On the other hand, 750 g of polytetramethylene ether glycol with an average molecular weight of 1000, 250 g of methylenebis-O-chloroaniline, and 3 g of diazabicyclooctane.
were heated and mixed to produce a glycol mixture. (Manufacture of adhesive) Mix 18 g of polytetramethylene ether glycol (manufactured by Mitsubishi Kasei Corporation) with an average molecular weight of 1000 to 100 g of PAPI-135 (trade name, C-MDI with isocyanate group concentration of 31%, manufactured by Updillon Co., Ltd.), and hold the mixture at 80°C. The mixture was kept for 2 hours to react, and urethane prepolymer A was obtained. The isocyanate group concentration of urethane prepolymer is 24
It was %. 84 g of urethane prepolymer A, 16 g of chlorinated rubber CR-5 (trade name, manufactured by Asahi Denka Co., Ltd.), and 150 g of toluene were mixed to obtain an adhesive. (Adhesion between urethane elastomer and metal) After applying the adhesive [ ] to the iron plate and drying the solvent, stir the urethane elastomer stock solution, that is, the prepolymer and glycol mixture, under a reduced pressure of 20 mmHg to dissolve them in the liquid. After expelling the air, 100g of the prepolymer liquid and 70g of the glycol mixture were mixed and stirred for 1 minute under 20mmHg.
Pour the liquid onto an iron plate coated with adhesive and leave it to harden. The elastomer was left in an atmosphere at 25°C and 50% humidity for one week, and after the physical properties of the elastomer had stabilized, the adhesion was examined. A single-sided elastomer-coated plate with a width of 25 mm and a length of 150 mm was cut out, and the adhesive strength was examined by peeling it at a rate of 180° at a speed of 50 mm/min according to JIS K-6301. Examples 2-20 In the production of the adhesive of Example 1, the types and amounts of the isocyanate component and polyol component were changed as shown in Table 1, and the types, amounts and solvents of the resins to be added were changed as shown in Tables 2-4. Adhesives were manufactured with the following changes, coated with an elastomer in the same manner as in Example 1, and examined for adhesion. The results are shown in Table 5. Comparative Example 1 PAPI-135 100g, PTMG as in Example 1
A urethane prepolymer was produced using 115 g of -1000. NCO% was 10%. 16 g of chlorinated rubber CR-5 and 150 g of toluene were mixed with 84 g of this urethane prepolymer to obtain a uniform solution. This liquid was applied as an adhesive to an iron plate in the same manner as in Example 1, an elastomer was cast thereon, and after being left at room temperature for 7 days, the adhesiveness was examined. The results are shown in Table 5. Comparative Examples 2 and 3 Examples will be shown in which only urethane prepolymer is used as the adhesive and no resin is added (Comparative Example 2), and when only chlorinated rubber is used as the additive resin and no urethane prepolymer is added (Comparative Example 3). The results are shown in Table 5. As is clear from Table 5, good adhesion cannot be obtained even when the isocyanate concentration of the urethane prepolymer used in the adhesive is 15% or less, and adhesion cannot be obtained with each raw material alone. Comparative example 4 Phenol adhesive Chemlok
218 (manufactured by Hughson Chemical) was applied to the metal and cured by heating to 100°C. The room temperature curable urethane elastomer used in Example 1 was coated on this board and the adhesive strength was measured, but only low strength was obtained (Table 5) Values other than NCO% in Tables 1 to 4 below indicates g number.

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Claims (1)

[Claims] 1. A urethane prepolymer with an isocyanate group concentration of 15 to 30% by weight, chlorinated rubber, polyvinyl chloride,
Urethane elastomer and metal, characterized in that a mixture consisting of one or more resins selected from vinyl chloride-vinyl acetate copolymer and phenolic resin and a solvent is applied to the metal, and then a urethane elastomer stock solution is injected and cured thereon. Adhesion method. 2. A bonding method according to claim 1, characterized in that the amount of resin is 5 to 40% by weight based on the total of the urethane prepolymer and the resin.