JPH07329099A - Manufacture of polyurethane resin molded product - Google Patents

Abstract

PURPOSE:To manufacture efficiently in a short cycle a polyurethane resin molded product whose surface is coated with a coating, by a method wherein an outer mold release agent to be applied to a mold beforehand is taken as a room temperature curing silicone rubber. CONSTITUTION:After an in-mold coating agent is applied to a mold to which an outer mold release agent is applied beforehand, a polyurethane resin molded product is manufactured by a reaction injection molding method by introducing polyurethane raw materials constituted of polyisocyanate, polyol and a chain extending agent and a catalyst, inner mold release agent, foaming agent, reinforcement agent and the other auxiliary agent when need arises. The room temperature curing silicone rubber of the outer mold release agent has the curing temperature of 20-90 deg.C on the surface of the mold, preferably 60-80 deg.C and surface tension of a cured film is 15-25dyne/cm, preferably 18-20dyne/cm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyurethane resin molded product whose surface is coated with a coating film, such as a steering wheel, a console box, a glove box and the like. Used for automobile interior materials and office chairs.

[0002]

2. Description of the Related Art Conventionally, a polyurethane resin molded article has been produced by introducing a polyurethane raw material such as polyisocyanate, a polyol and a chain extender into a mold which can be closed by a reaction injection molding method.

Polyurethane raw material is cured by reaction in a mold,
Taken out as a polyurethane resin molded product. In order to control the reaction temperature, the mold is made of a material having high thermal conductivity, and a metal mold (hereinafter referred to as a mold) is usually used.

If the in-mold coating agent is applied to the mold to which the release agent has been applied in advance and the polyurethane raw material is introduced,
The polyurethane raw material can be cured by reaction in a mold to produce a polyurethane resin molded product in which the surface of the molded product is coated with a coating film. According to this method, the coated molded article provides a stable molded article surface and avoids coating problems, so that it is possible to substitute for the undercoat of the coated molded article. In this case, in order to prevent the in-mold coating agent from sticking to the mold surface, wax, metal soap,
A mold release agent such as oil is applied on the mold surface in advance.

[0005]

However, in this method, each time molding is performed, a mold release agent must be newly applied to the surface of the mold, and an in-mold coating agent must be applied to the mold. Furthermore, it is necessary to remove the old mold release agent remaining on the mold surface every fixed number of moldings, which requires considerable manpower and time.
It's a big challenge.

As one solution, it has been considered to coat the surface of the mold with a fluororesin having excellent non-adhesiveness. In order to form a film of the fluororesin on the surface of the mold,
It is necessary to bake the mold at a high temperature of 250 to 400 ° C. Not only is it difficult to expose a large mold to high temperatures, but it may cause deformation of the mold, which is not possible with a mold that includes a drive part, a hydraulic device, and electric parts inside.

Further, even if it is a fluororesin, the releasability gradually decreases, so that it is necessary to repaint with the fluororesin at a constant frequency. In this case, it is necessary to remove the damaged old film and fire it again, and in combination with the fact that the fluororesin is expensive, it has not been practically used so far except in the case of a small mold.

The inventors of the present invention, in order to solve such a problem,
As a result of extensive studies, a method for producing a polyurethane resin molded product by a reaction injection molding method using a mold coated with a certain type of external release agent was found, and the present invention was completed.

[0009]

Means for Solving the Problems The present invention is to apply a polyisocyanate, a polyol, a chain extender, and a catalyst, if necessary, after applying an in-mold coating agent to a molding die to which an external release agent has been applied in advance. In a method of producing a polyurethane resin molded article by a reaction injection molding method by introducing a polyurethane raw material consisting of an internal mold release agent, a foaming agent, a reinforcing agent and other auxiliary agents, an external mold release applied beforehand to a molding die. The agent has a curing temperature of 20 to 90 ° C. on the surface of the mold, and the surface tension of the cured film is 15 to 25 dyne / c.
The present invention relates to a method for producing a polyurethane resin molded article which is m and is a room temperature curable silicone rubber.

Examples of the polyisocyanate used in the present invention include diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, a modified product obtained by reacting these polyisocyanates with a polyol, and a carpoimidized product. There is a mixture of these.

As the polyol, polyfunctional hydroxyl group-containing compounds such as propylene glycol, diethylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol and sucrose or compounds containing amino groups and hydroxyl groups such as triethanolamine and diethanolamine, or Polyether polyols having 2 to 6 hydroxyl groups obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to a polyfunctional amino group-containing compound such as ethylenediamine and diaminotoluene, and having an average hydroxyl equivalent of 100 to 3000 or their A polymer polyol obtained by polymerizing a vinyl group-containing compound in a polyether polyol is used. Further, a polyester polyol obtained by reacting a polycarboxylic acid with a low-molecular weight polyfunctional hydroxyl group-containing compound, a polycarbonate polyol obtained by ring-opening polymerization of caprolactone, an amination of hydroxyl groups of a polyether polyol, or a polyether polyol Polyether polyamines obtained by hydrolyzing the isocyanate prepolymer of (1) and having an average active hydrogen equivalent of 100 to 3000 may also be used.

As the chain extender, a polyhydric alcohol such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, trimethylolpropane, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, Polypropylene glycol or polyvalent amine, for example, diethyltoluenediamine, t-butyltoluenediamine, diethyldiaminobenzene, triethyldiaminobenzene, tetraethyldiaminodiphenylmethane, or the like, or a polyol having a molecular weight of 106 to 1500 added with an alkylene oxide is used. Japanese Patent Publication No. 54-17359, Japanese Patent Publication No. 1-34527, and Japanese Patent Laid-Open No. 57-74.
No. 325 and Japanese Patent Publication No. 63-47726.

Examples of the catalyst include tertiary amines such as triethylenediamine, dimethylbenzylamine and tetramethylhexamethylenediamine, alkanolamines such as diethanolamine and dimethylaminoethanol, dibutyltin dilaurate, tin octoate and dibutyltin diacetate. Organometallic compounds are used as needed.

As the internal release agent, a mixture of a carboxylic acid metal salt and an amine (see Japanese Patent Publication No. 63-52056), a reaction product of polysiloxane and polyisocyanate (see Japanese Patent Publication No. 58-1139), Mixture of amine, aliphatic carboxylic acid salt and carboxylic acid ester (see Japanese Patent Publication No. 55-42091), hydrogenated castor oil (see Japanese Patent Publication No. 4-20925), transesterification of fatty acid polyester and lower alkyl acetoacetate. A product (see JP-A-5-155969) is used as necessary.

The blowing agent is carbon dioxide gas generated from the reaction of water or acid with polyisocyanate, low boiling point hydrocarbon, halogenated hydrocarbon, nitrogen gas, air, etc.,
Used as needed.

The reinforcing agent is a fiber such as glassy material, inorganic material or mineral material such as milled glass fiber, wollastonite fiber, processed mineral fiber or flakes such as mica or glass flake, and is used as necessary. . It is also possible to set a glass mat, a glass cloth, etc. in a mold in advance, and introduce a polyurethane raw material thereon to produce a molded product.

As other auxiliaries, a cell regulator, 2,6
-Di-t-butyl-4-methylphenol, tetrakis [methylene 3- (3 ', 5'-di-t-butyl-4'
Stabilizers such as -hydroxyphenyl) propionate] methane, discoloration preventing agents, flow improvers, and colorants are used as necessary.

The in-mold coating agent used in the present invention is a one-component or two-component polyurethane coating material, an acrylic coating material, etc., and is required to be hardened on the surface of the die to give a certain strength. Polyurethane coatings modified or modified with acrylics are mainly used. Polyurethane paints are based on polyester polyols, acrylic polyols, and other polyisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate.
It is composed of a hardener composed of its modified product, a pigment, a weatherproofing agent and a solvent such as toluene and ethyl acetate.
When an in-mold coating agent is used in combination with an internal release agent, the life of the external release agent used in the present invention can be extended and the number of continuous demolding can be increased.

The external release agent used in the present invention is room temperature curable silicone rubber. Room temperature curable silicone rubber is liquid before curing and is at room temperature or a relatively low temperature, for example, 9
It reacts and cures at 0 ° C or lower to become a rubber elastic body, and there are one-pack type and two-pack type. From the mechanism of the curing reaction, dealcohol type, deoxime type, deacetic acid type, dehydroxylamine type or diorganopolysiloxane having a functional group, which causes a condensation reaction by moisture in the air or a catalyst, is used as a trifunctional catalyst. There is an addition reaction type silicone rubber which is crosslinked and cured with the above silane or siloxane. These room temperature-curable silicone rubbers are widely used as coating agents, potting agents, sealing agents or release agents for release paper. Among these room temperature curable silicone rubbers, the curing temperature on the mold surface is 20 to 90 ° C, preferably 60 to 80 ° C, and the cured film has a surface tension of 15 ° C.
~ 25 dyne / cm, preferably 18-20 dyne
What is / cm is used in the present invention. Room temperature curable silicone rubbers used in the method of the present invention include PRX305 and SD72 manufactured by Toray Dow Corning Silicone Co., Ltd.
24, SD7333, SH7020, SRX202M,
SRX290 / SRX242AC, SRX357, etc.
Shin-Etsu Chemical Co., Ltd. KM2002T, KN202A, K
NS204B, KNS303, KNS305, KS70
0, KS701, KS737, KS774, KS77
8, KS779H, KS837, KS841, etc., TSM6281, TSR144, YS manufactured by Toshiba Silicone Co., Ltd.
R3022, YSR6209, YSR6209B and the like.

This silicone rubber is diluted with a solvent such as toluene, xylene, industrial gasoline, solvent naphtha or water into a solution or emulsion having a viscosity of 30 to 300 mPa.s, and uniformly applied to the surface of the mold from which oil and dirt have been removed in advance. Spray or apply on. A more uniform film surface can be obtained by spraying and wiping after application. A surface treatment agent may be used to improve the adhesion between the mold and the film. This film is included in the in-mold coating agent as the curing reaction proceeds by simply leaving it for a few tens of minutes to several tens of hours, for example, 3 hours on a mold adjusted to 20 to 90 ° C. without undergoing a baking process. It is possible to form a film having a film thickness of 3 to 10 μ which can withstand a solvent. Then,
After the in-mold coating agent is applied to the mold to a thickness of 5 to 30 μm, the polyurethane raw material is introduced into the mold and reaction-cured, and then the molded product is released from the mold.

Thereafter, the production of the polyurethane resin molded article is continuously continued without spraying or coating the mold with the diluent of room temperature-curable silicone rubber as a release agent. This continuous demolding is continued several tens times, for example, 50 times or more.

When the cured film deteriorates and loses the mold releasability, a new film is to be formed on the mold surface. At this time, the old film is not removed and a new film is overlaid thereon. After being formed, a molded product can be manufactured continuously. During the continuous demolding, the film thickness of the film is gradually reduced, and even if a new film is applied thereon, the film thickness of the film does not always double. The new film adheres to the old film to form a new surface, and exhibits the same releasability as the original film. The method of producing a molded product by superimposing a new film on the old film without removing the old film can be continued until the total film thickness of the film becomes large and the appearance of the molded product is adversely affected. The coating can then be washed away with an alkaline solution, for example a 20% aqueous sodium hydroxide solution.

[0023]

【Example】

Example 1 Width 30 cm, length 90 cm, thickness 3 adjusted to 80 ° C.
After the surface of the iron mold made of mm was washed with N-methylpyrrolidone, a room temperature-curable silicone rubber PRX305 manufactured by Toray Dow Corning Silicone Co., Ltd. was diluted 5 times with toluene and sprayed. When the surface of the mold was checked after standing for 3 hours, PRX305 was cured and showed no fluidity or tackiness even when touched with a finger. The thickness of the cured film is
It was about 8μ. The surface tension of the separately prepared PRX305 cured film was measured by the contact angle method to find that it was 19 dyne.
Was / cm.

On the lower mold of this mold, an in-mold coating agent "Epicoaton" manufactured by Tanabe Chemical Co., Ltd. (main agent: curing agent:
Solvent = 100: 15: 30) was applied to a thickness of about 10μ. Using this mold, OH value of 28 mgKO obtained by adding propylene oxide and ethylene oxide to glycerin
80 parts of H / g polyether polyol, 18 parts of diethyltoluenediamine, 2 parts of OH value 630 mg KOH / g polyether polyol obtained by adding propylene oxide to ethylenediamine, 33% of triethylenediamine
A polyol mixture in which 0.1 part of a dipropylene glycol solution and 0.1 part of dibutyltin dilaurate are well mixed;
A reaction injection molding machine MC manufactured by Polyurethane Engineering Co., Ltd. with a urethane modified product of diphenylmethane diisocyanate having an NCO group content of 23% at a ratio of 100: 52.
Mixed injection was performed in 1.5 seconds using -106R, and a molded product was taken out after 30 seconds. Repeated application and molding of in-mold coating agent without spraying a new release agent.
The molding was repeated once. Since the mold was beginning to feel a little heavy, the toluene diluted solution of PRX305 was sprayed on the mold again. When the surface of the mold was checked after standing for 3 hours, PRX305 was cured and showed no fluidity or tackiness even when touched with a finger. After that, application and molding of the in-mold coating agent were repeated, and molding was further performed 80 times continuously. No abnormality was found on the surface of the molded product.

Example 2 Width 30 cm, length 90 cm, thickness 3 adjusted to 60 ° C.
After cleaning the surface of the iron die of mm with N-methylpyrrolidone, SRX2 manufactured by Toray Dow Corning Silicone Co., Ltd.
90 / SRX242AC was mixed at 25/1 and further diluted with toluene 5 times and then sprayed. When the surface of the mold was checked after standing for 3 hours, the release agent was cured and showed no fluidity or tackiness even when touched with a finger. The film thickness of the cured film was about 8μ. The surface tension of the separately prepared cured film of the release agent was measured by the contact angle method, and it was 19 dy.
It was ne / cm.

Using this mold, the application and molding of the in-mold coating agent was repeated under the same conditions as in Example 1 to perform continuous demolding 80 times. Then, a toluene diluent of a release agent was sprayed, and continuous demolding was further performed 50 times. No abnormality was found on the surface of the molded product.

Example 3 Width 30 cm, length 90 cm, thickness 3 adjusted to 80 ° C.
After the surface of the iron mold of mm was washed with N-methylpyrrolidone, KM-2002T manufactured by Shin-Etsu Chemical Co., Ltd. was sprayed with a solution diluted 5 times with toluene. When the surface of the mold was checked after standing for 3 hours, KM-2002T was cured and showed no fluidity or tackiness even when touched with a finger. The film thickness of the cured film was about 8μ. Separately prepared KM-2
The surface tension of the cured film of 002T was measured by the contact angle method and found to be 19 dyne / cm.

Using this mold, continuous demolding was carried out 50 times under the same conditions as in Example 1. After that, KM-2002
A toluene diluted solution of T was sprayed, and continuous demolding was further performed 50 times. No abnormality was found on the surface of the molded product.

Comparative Example 1 Width 30 cm, length 90 cm, thickness 3 adjusted to 80 ° C.
After the surface of the iron die of mm was washed with N-methylpyrrolidone, SEPA-COATH manufactured by Shin-Etsu Chemical Co., Ltd. was sprayed. After leaving it for 3 hours and checking the mold surface,
SEPA-COAT H was cured and did not show fluidity or tackiness when touched with a finger. The film thickness of the cured film was about 8μ. The surface tension of the separately prepared cured film of SEPA-COATH was measured by the contact angle method.
It was dyne / cm. Using this mold, Example 1
Attempts were made to apply and mold the in-mold coating agent under the same conditions as above, but at the eighth time, the molded product stuck to the mold and could not be demolded.

Comparative Example 2 Fluorine resin varnish "Lumiflon 200" 10 manufactured by Asahi Glass Co., Ltd. 10
0 g, xylene 50 g, n-butanol 50 g, p-toluenesulfonic acid 0.25 g and butylated melamine 3 g were mixed and applied to the upper die of the same size as in Example 1,
It was baked at 140 ° C. for 1 hour. After confirming that the film was completely cured, the mold was adjusted to 80 ° C. using this upper mold and the lower mold obtained by treating PRX305 in the same manner as in Example 1, and molding was carried out in the same manner as in Example 1. It was The molded product adhered to the upper mold in the third continuous demolding and could not be demolded.

Comparative Example 3 A silicone oil release agent SH200 manufactured by Toray Dow Corning Silicone Co., Ltd. was applied to a mold having the same size as in Example 1 adjusted to 70 ° C. The mold surface was checked after standing for 3 hours, but no curing of the release agent occurred. Using this mold, the in-mold coating agent was applied and molded under the same conditions as in Example 1. At the third time of continuous demolding, the molded product was stuck to the lower mold and could not be demolded.

[0032]

According to the method of the present invention, a polyurethane resin molded product whose surface is coated with a coating film can be produced very efficiently in a short cycle.

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Claims (1)

[Claims] 1. A molding die preliminarily coated with an external release agent,
After applying the in-mold coating agent, introduce a polyurethane raw material consisting of polyisocyanate, polyol, chain extender and, if necessary, catalyst, internal release agent, foaming agent, reinforcing agent and other auxiliary agents, and carry out reaction injection. Depending on the molding method,
In the method for producing a polyurethane resin molded article, the external mold release agent previously applied to the molding die has a curing temperature of 20 to 90 ° C. on the surface of the die, and the surface tension of the cured film is 15 to 25 dyne / A method for producing a polyurethane resin molded article, which is a room temperature curable silicone rubber having a size of cm.