JPH048452B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a polyurethane molded article, and more specifically, a method for producing a polyurethane molded article that can prevent discoloration of the polyvinyl chloride resin skin coated on the polyurethane molded article. It is related to. [Prior art] In recent years, automobile interior parts such as seats, dart boards, armrests, headrests, sun visors, etc. have been coated with a polyvinyl chloride resin skin or an ABS resin skin containing polyvinyl chloride resin on the surface of a foamed polyurethane molded body. Many are coated with . When molding a foamed polyurethane molded product, a tertiary amine is generally used as a catalyst to improve the reaction rate, and the polyvinyl chloride resin skin is integrally molded or the polyurethane foam molded product is molded and then the polyurethane foam is molded. It is manufactured by coating it with a vinyl chloride resin skin. [Problem to be solved by the invention] Temperatures inside automobile cabins sometimes reach over 100°C in summer, and the action of this heat and light causes the polyvinyl chloride resin skin of interior parts to deteriorate and discolor. There was a problem. It is known that this discoloration of the epidermis is significantly accelerated when foamed polyurethane is present inside than when the epidermis is alone. The cause of this is presumed to be that the tertiary amine catalyst remaining in the foamed polyurethane molded article migrates into the skin and causes a reaction with the polyvinyl chloride resin. Conventionally, methods of reducing the amount of tertiary amine used have been proposed to solve the above-mentioned problems to some extent.
A method that uses a metal catalyst such as a tin catalyst instead of a tertiary amine, or an amine compound such as dimethylethanolamine or dimethylaminopropylamine that has active hydrogen that reacts with isocyanate instead of a tertiary amine. A method of trapping the amine compound in the amine compound, a method of adding a third substance such as epichlorohydrin that chemically bonds with the tertiary amine, or a method of adding a tertiary amine compound between the polyvinyl chloride resin skin and the urethane foam molding. There are known methods such as providing a film or the like to prevent the migration of . However, the method of reducing the amount of tertiary amine used takes time to mold polyurethane foam, which reduces the number of production cycles, and the effect of preventing discoloration is low, and the method of using a metal catalyst reduces the molding performance of the molded product. There is a problem that the molded product becomes unstable and the defective rate of the molded product increases. Furthermore, when an amine compound having active hydrogen is used, although it is effective to some extent, it cannot be said to be satisfactory. In addition, in the method of adding a third substance that chemically bonds with the tertiary amine catalyst, the third substance may remain in the resulting molded product and deteriorate the physical properties or worsen the moldability. Therefore, there is a limit to the amount of the tertiary amine catalyst added, and if the amount of the third substance is small, a large amount of the tertiary amine catalyst may remain. Also the third
Since the reaction between the substance and the tertiary amine catalyst and isocyanate proceeds gradually during storage, storage stability may deteriorate. Furthermore, the third substance reacts with the tertiary amine catalyst and reduces the catalytic performance of the tertiary amine catalyst, making it difficult to adjust the catalytic performance and making it difficult to control the utane reaction between polyol and polyisocyanate. There are also some defects. Further, the method of providing a film or the like that does not transmit tertiary amine between the skin and the molded article has the disadvantage that the number of steps increases, leading to an increase in cost. The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a polyurethane molded product that reduces the amount of tertiary amine remaining in the polyurethane molded product and prevents discoloration of the polyvinyl chloride resin skin. With the goal. [Means for Solving the Problems] The method for producing a polyurethane molded body of the present invention includes a molding step in which a polyol and a polyisocyanate are reacted in the presence of a tertiary amine catalyst to form an original molded body, and a molding step in which a raw molded body is obtained. By holding the original molded body in a vapor atmosphere of an amine catching agent for a certain period of time, the tertiary amine remaining in the original molding is reacted with the amine catching agent and inactivated. The method is characterized by a post-treatment step in which the residual amount of the tertiary amine is reduced. The molding step is a step in which a polyol and a polyisocyanate are reacted in the presence of a tertiary amine catalyst to form an original molded body. The polyol has a plurality of hydroxyl groups and serves as the main ingredient in the reaction, and conventionally used polyols such as polyether polyols, polyester polyols, and acrylic polyols can be used as they are. Polyisocyanates have multiple isocyanate (NCO) groups and act as curing agents that cure by reacting with the hydroxyl groups of polyols, including tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and xylylene diisocyanate. Conventional polyisocyanates such as (XDI) and hexamethylene diisocyanate (HMDI) can be used. The polyol and polyisocyanate are rapidly reacted in the presence of a tertiary amine catalyst. This tertiary amine catalyst includes triethylenediamine (for example, DABCO-33LV, manufactured by Nippon Nyukazai Co., Ltd.), etc.
Various conventionally known tertiary amines can be used. The most important feature of the present invention is that a post-treatment step is carried out in which the raw polyurethane molded product reacted and cured in the above-mentioned molding step is held in a vapor atmosphere of an amine catcher agent for a certain period of time. Through this post-treatment step, the tertiary amine remaining in the original molded body is inactivated, thereby reducing the amount of tertiary amine remaining in the obtained molded body. The amine catching agent used is one that reacts with tertiary amines and converts them into inactive compounds.
Conventionally known ethylene bromide, 1, 1,
1-trichloroethane, tetrachloroethane, 1
- Using halogen-containing compounds such as bromo-2chloroethane, 1-bromo3chloropropane, tetramethylene bromide, allyl bromide, epichlorohydrin, epibromohydrin, bromochlorohexane, α-bromoethylbenzene, 1,6-dibromohexane, etc. I can do it. The post-treatment step is carried out by holding the original molded body in the vapor of the amine catcher for a certain period of time. Since it is a vapor, it can penetrate deeply into the molded body and react reliably with the remaining tertiary amine. Moreover, this effect is particularly remarkable when the original molded body is foamed urethane. In the post-treatment step, if the amine catching agent is a gas at room temperature, it can be kept at room temperature. However, in this case, it may take a long time, so it is desirable to increase the reaction rate between the tertiary amine and the amine catching agent by holding the reaction under heat. The higher the temperature at which the original molded body is heated, the more the amine catching agent will be vaporized and the reaction rate will be faster. Furthermore, the tertiary amine itself is vaporized and released from the inside of the original molded body, so that the reaction rate becomes even higher. However, since there is a risk that the molded product may deteriorate, it is generally preferable to keep the temperature within the range of 180°C or lower. The heating and holding time can be variously selected depending on the type of amine catcher, heating temperature, amount of remaining tertiary amine, shape of the molded product, etc., but trial and error is required to avoid deterioration of the original molded product. It is necessary to decide accordingly. Note that it is also preferable that the post-treatment step is carried out under reduced pressure. By carrying out the reaction under reduced pressure, the vaporization of the amine catcher agent and the tertiary amine is promoted, and the gas phase reaction is further promoted. Furthermore, since the heating temperature can be lowered, problems such as deterioration of the molded product can be prevented. The manufacturing method of the present invention can be used for either a solid integral molded product or a foamed foam molded product, but a foamed molded product with a large number of internal spaces is more suitable for amine-based molded products. Penetration of the tying agent and release of the tertiary amine are accelerated, making it particularly effective. The molded article obtained by the production method of the present invention can be made into a product by covering it with a polyvinyl chloride resin skin or the like. [Operations and Effects of the Invention] According to the production method of the present invention, the tertiary amine reacts with the amine catching agent and changes into an inactive compound in the post-treatment step. Therefore, when covering the polyvinyl chloride resin skin, it is necessary to
The residual amount of grade amine is extremely small, making it possible to prevent discoloration of the polyvinyl chloride resin skin even when the temperature reaches high temperatures during use inside a vehicle. Further, the manufacturing method of the present invention is characterized in that the molded article after the reaction between the polyol and the polyisocyanate is treated in an amine catcher agent vapor atmosphere in a post-treatment step. Therefore, compared to a method in which a third substance that reacts with the tertiary amine catalyst is mixed before the reaction of the polyol and polyisocyanate, this method has almost no effect on the moldability and physical properties of the molded article. Furthermore, since there is almost no limit to the amount of amine catching agent used, it is possible to reliably convert the entire amount of the remaining tertiary amine catalyst into an inert compound. Furthermore, the storage stability of the stock solution of the molded body is not impaired. Since the reaction between the polyol and polyisocyanate is carried out in an atmosphere in which no third substance is present, the catalytic action of the tertiary amine catalyst is maximized and the reaction can be easily controlled. [Example] The present invention will be specifically explained below using Examples. As a polyol component, 100 parts by weight of polyether polyol (Sumifuen 3063, manufactured by Sumitomo Bayer Urethane) with an OH value of 28, 3.0 parts by weight of distilled water as a foaming agent, and a silicone foam stabilizer (SZ-1306, 1.0 part by weight of Nippon Unicar Co., Ltd.), and triethylenediamine (DABCO-33LV, Nippon Nyukazai Co., Ltd., boiling point 214°C) as a tertiary amine catalyst.
1.5 parts by weight was taken and stirred for 10 minutes using a small stirrer to adjust the main ingredient. Apart from the above, crude diphenylmethane diisocyanate (44V-
20, manufactured by Sumitomo Bayer Urethane Co., Ltd.) and 350 parts by weight,
150 parts by weight of tolylene diisocyanate (TDI-80, manufactured by Sumitomo Bayer Urethane) was taken and stirred for 5 minutes using a small stirrer to adjust the curing agent component. The temperature of the two liquids obtained above was set at 20℃.
Adjust the temperature to 94 parts by weight of the main component and 41 parts by weight of the curing agent component (NCO/OH = 1.05).
Stir for 8 seconds with a small stirrer and pre-regulate the temperature to 40℃.
100 g of the above mixture was poured into a mold having a cavity of 300 mm x 300 mm x 15 mm. In this state, the mold was held in an oven at 70° C. for 5 minutes to produce an original molded product made of foamed polyurethane. The obtained original molded body was cut into a size of 60 mm x 60 mm x 15 mm to prepare a test piece. This test piece was placed in a constant temperature bath in which epichlorohydrin maintained a vapor-liquid equilibrium state at 70°C, and a post-treatment process was performed in which it was held at 70°C for 1 hour, 2 hours, 5 hours, and 10 hours, respectively. . In addition, as a comparison, the above test pieces were not treated with anything, and were simply exposed to air at 70°C for 1 hour and 10 hours, respectively, without using epichlorohydrin.
A sample that was kept for 24 hours was also created at the same time. After that, 0.4mm
Place a polyvinyl chloride resin sheet with a thickness of
An accelerated test was conducted in which the sample was heated and held in an oven for 24 hours. After taking it out, the color difference (△E according to Hunter's Lab) between each polyvinyl chloride resin sheet and the standard polyvinyl chloride resin sheet before being placed on the test piece was measured using a color difference meter (manufactured by Suga Test Instruments Co., Ltd.). It was measured. The results are shown in the table. (Evaluation) It is clear from the table that the color difference in the samples heated and held in epichlorohydrin vapor is smaller than that in the samples simply heated in the air. This is explained by the fact that the reaction between epichlorohydrin and tertiary amine changes the tertiary amine into an inactive compound, and the amount of tertiary amine remaining during the accelerated test decreases. In addition, regardless of the presence or absence of epichlorohydrin, the color difference of the sheet placed on the heat-treated molded body is smaller than that of the sheet placed on the untreated original molded body that is not heat-treated.

[Table] The longer the retention time, the smaller the color difference. That is, it is clear that the effect of the tertiary amine being separated from the original molded body by heating the original molded body is also added.

Claims (1)

[Scope of Claims] 1. A molding step in which a polyol and a polyisocyanate are reacted in the presence of a tertiary amine catalyst to form an original molded product, and the resulting original molded product is exposed to a vapor atmosphere of an amine catching agent. The tertiary amine remaining in the original molded body is reacted with the amine catching agent to inactivate the tertiary amine by holding it there for a certain period of time. A method for producing a polyurethane molded article, characterized in that the residual amount is reduced. 2. The method for producing a polyurethane molded article according to claim 1, wherein the post-treatment step is carried out under heating. 3. The method for producing a polyurethane molded body according to claim 2, wherein the heating of the original molded body is carried out at a temperature of 180°C or lower.