JPH0278469A - Method for coating reaction injection-molded article - Google Patents

Abstract

PURPOSE:To improve the durability of a reaction injection-molded article by coating the article with black polyurethane resin paint having a specified compsn., curing the resulting coated film in an amine atmosphere and further coating part of the article with thermosetting resin paint. CONSTITUTION:Black polyurethane resin paint is prepd. with polyurethane resin having -40 to 30 deg.C Tg, 20-160 hydroxyl group value and 1,000-10,000 number average mol. wt. and contg. polyols and polyisocyanates including >=30mol% aliphat. polyisocyanate in 0.5:1-2:1 equiv. ratio between OH and isocyanato groups. A reaction injection-molded article is coated with the black polyurethane resin paint and the resulting coated film is cured in an amine atmosphere. Part of the article is further coated with thermosetting resin paint or polyurethane resin paint and the resulting coated film is cured.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a coating method for reactive injection molded articles.More specifically, the present invention relates to a coating method for reactive injection molded articles. The present invention relates to a method for coating reactive injection molded products to obtain a coated film. [Prior Art] A reactive injection molded article is a resin molded article obtained by simultaneously curing and molding a thermosetting resin inside a molding mold. Urethane old M
(Reaction Injection Moldi
ng) is in practical use, and due to its excellent strength, flexibility, and freedom in shape design during molding,
It is mainly useful in the field of automobile parts. In principle, urethane RIM is a molded product that is black in color and has a foamed interior with a smooth surface, but depending on the molding conditions, the surface is often partially porous. Particularly immediately after molding, it is normal that the material is highly porous. In coating such molded products, there is a need for paints and coating methods that can be rapidly cured to prevent micropores and form a coating film with flexibility that can follow the flexibility of the molded product. Conventional painting on urethane RIM is (1) 912281M
After molding, post-curing is performed to further reduce the micropores on the surface, and then a two-component polyurethane resin paint is applied at a temperature close to room temperature, or a low-temperature curing polyurethane resin paint containing a catalyst, etc. is applied. 2) Urethane R
A known method is to leave it for several days after IM molding, and then apply a low-temperature polyurethane resin paint after the surface becomes smooth. On the other hand, when painting urethane RIM, it is often seen that (1) partial painting or (2) two-color painting is applied in order to provide more design. Partial painting in (1) above takes advantage of the original black color of urethane RIM, temporarily covering a part of the base with a masking material of your choice, and then removing the masking material after painting with a paint different from the color of the base. It is done by In addition, the above (
In 2) two-color painting, after painting the first paint on the urethane RIM substrate, a part of the coating film of the first paint is temporarily covered using any masking material, and the first paint is different from the first paint. This is done by removing the masking material after applying a second paint of a different color. [Problems to be Solved by the Invention] However, according to the above-mentioned partial painting method (1),
Even after painting, a part of the urethane RIM base remains unpainted and exposed. Since urethane RIM substrates are black and generally have poor weather resistance, urethane RIM articles having unpainted exposed areas will have reduced long-term durability. In order to avoid this drawback, another method is to use the coating method (2) above, that is, after the first coating is finished, a part of the substrate is coated with urethane R.
A painting method is used in which a second paint having the same color as the IM substrate is applied to create a design that looks as if it had been partially painted. As this second paint, a black paint is used since the substrate is generally black. According to this method, the entire surface of the urethane RIM substrate is coated with paint, so the durability of the article is improved compared to the above-mentioned partial coating method. This results in increased costs and is an industrially disadvantageous method. Furthermore, the coating methods (1) and (2) above require a long time to dry, low-temperature type polyurethane resin paints have a short pot life, are complicated or difficult to handle on site, and are difficult to process. The resulting coating film also did not have properties sufficiently suited to the flexibility of Urethane R and IM. In addition, the present inventors proposed an improvement method on October 2, 1988.
A patent application (Japanese Patent Application No. 62-267414) was filed on the 3rd date. The prior application describes a method that can form a flexible coating film that is free from poor coating film appearance due to surface defects of urethane RIM, such as pinholes, can be cured at low temperatures in a short time, and is flexible. There is no mention of improvement in design through color painting, and if partial painting is performed, urethane R11,
No solution has been found to the above-mentioned drawbacks caused by exposed parts of the substrate. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reactive injection molded article, such as a urethane RIM, with a coating having a design similar to a partial coating, to improve the durability of the urethane RIM article, and to improve the durability of the urethane RIM article. It eliminates defects in the appearance of the paint film caused by
It is an object of the present invention to provide a further improved coating method for urethane RIM that forms a flexible coating film. [Means for Solving the Problems 1] The present invention involves coating a reactive injection molded article with a black polyurethane resin paint (hereinafter also referred to as the first paint), and then coating the coated film in an amine atmosphere in a gas phase. After curing, a method for coating a reactive injection molded article comprises applying a thermosetting resin paint or a polyurethane resin paint (hereinafter also referred to as a second paint) to a part of the reactive injection molded article and curing it, the method comprising: The polyurethane resin paint (first paint) that is cured in an amine atmosphere has (a) Tg: -40°C ~
30°C1 hydroxyl value = 20-160, number average molecular weight +
1000-10000 Vault, (b)
(c) 30 mol% or more of the polyisocyanate is an aliphatic polyisocyanate, and (d) the ratio of OH equivalent to isocyanate equivalent is 0.5:
1 to 2:1 is a method for coating reactive injection molded articles. The reactive injection molded article used in the present invention is as described above, and includes urethane RIM, WA fiber-reinforced urethane RIM, and the like. In addition, the polyols of the black polyurethane resin paint (first paint) that is cured in a gas phase amine atmosphere include acrylic polyol, polyester polyol,
Polyols such as alkyd polyols and polyolefin polyols are used, but acrylic polyols and polyester polyols are particularly suitable. Among these, Tg: -0 to 30°C, hydroxyl value: 20 to 160, number average molecular i: 1000 to 10000. polyols are suitable. Especially Tg: -20~20℃, hydroxyl value: 40~
145, number average molecular ii: acrylic polyols and polyester polyols of 1500 to 600° are desirable. If Tg is higher than 30°C, flexibility will be insufficient, and if Tg is higher than -40°
If the hydroxyl value is lower than C, surface hardening will be insufficient, if the hydroxyl value is higher than 160, flexibility will be insufficient, and if it is lower than 20, chemical performance such as moisture resistance and hot water resistance will be inferior, and the number average molecular weight will be If it is greater than 10,000, the appearance of the paint film will be poor, and
If it is less than 000, chemical properties such as moisture resistance and hot water resistance will be inferior. In the present invention, the polyisocyanate used in the first coating material cured in the above amine atmosphere is a total polyisocyanate of 93%.
0 mol% or more, 30 to 100 mol%, is aliphatic polyisocyanate. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate (IIMDI
), isophorone diisocyanate) (IPDI),
These include lysine diisocyanate, methylene diisocyanate, methylol adducts or tri-pentamers thereof, and mixtures thereof. If the aliphatic polyisocyanate is less than 30 mol % of the total polyisocyanate, the weather resistance of the coating film will deteriorate, which is undesirable. In addition to the above-mentioned aliphatic polyisocyanate, the polyisocyanate used in the present invention may include 7
Toluylene diisocyanate (TD) in an amount of 0 mol% or less
I), diphenylmethane diisocyanate (MDI),
Xylylene diisocyanate (XDI), triphenylmethane triisocyanate, phenylene diisocyanate, and their methylol adducts or 3-5 isomers can be used. The aliphatic polyisocyanate and other polyisocyanates when used are each 2f! ! There is no harm in using a mixture of the above. The polyol and polyisocyanate mentioned above are
The ratio of 11 equivalents to isocyanate equivalents is 065 = 1 to 2:
Use it so that it becomes 1. If the equivalent weight is less than 0.5, the adhesion and flexibility will be reduced, and if it is larger than 2, the water resistance and hot water resistance will be reduced, and the crosslinking density will be reduced, thereby reducing the pinhole suppressing effect. For the black polyurethane resin paint (first paint) that is cured in an amine atmosphere and used in the present invention, a black pigment is used to color it black, such as carbon black. The black pigment may be used alone or in combination of two or more, and depending on the desired hue, a small amount of a coloring pigment other than black may also be used. Also,
In addition to color pigments, extender pigments of 111 or 2 II or more may be used. The black polyurethane resin paint that is cured in an amine atmosphere used in the present invention contains additives such as various known fm matting agents, leveling agents, and anti-color separation agents, as well as esters, ketones, aliphatic or It can contain aromatic hydrocarbon solvents, etc. In the present invention, after the above-mentioned black polyurethane resin paint is applied, it is cured in an amine atmosphere in a gas phase.The amine that can be used at this time is preferably a tertiary amine, such as trimethylamine, triethylamine, tripropylamine, tributylamine,
Aliphatic tertiary amines such as triamylamine, aromatic amines such as dimethylaniline, diethylaniline, tribenzylamine, N-methylmorpholine, N-ethylmorpholine or triethalamine, methyljetanolamine, dimethylethanoamine, diethyl Alkanolamines such as ethanolamine, dibutylethanolamine, di(2-ethylhexyl)ethanolamine, ethyljetanolamine, triisopropanolamine, and dibutylisopropanolamine can be used, with dimethylethanolamine being preferred. The atmosphere with the above amines has an amine concentration in the gas phase of about 10 to 3000 ppm, preferably 300 to 120 ppm.
0 ppm is suitable. A suitable temperature is 0 to 80°C, preferably 20 to 40'C. The curing time in an amine atmosphere varies depending on the resin composition, the thickness of the film to be formed, the type of tertiary amine, temperature, concentration, etc., but is generally 1 to 10 minutes, preferably 2 to 4 minutes. Note that after the treatment in the amine atmosphere, if necessary, a heat treatment may be further performed at a temperature of 100° C. or less for 5 to 15 minutes. In the present invention, after the above-mentioned black polyurethane resin paint (first paint) is applied and cured in an amine atmosphere in a gaseous state, a part of the substrate is masked, and then a thermosetting resin paint or Apply polyurethane resin paint (second paint). Among the thermosetting resin paints or polyurethane resin paints used as the second paint in the present invention, acrylic melamine resin paints, alkyd melamine resin paints, etc. can be used as the thermosetting resin paints. These cured coatings are obtained by condensation of melamine resins and acrylic resins or alkyd resins contained in paints by heating, and various acrylic resins, alkyl resins, and melamine (δ) resins are used depending on the desired physical properties of the coating. You can choose. The heating temperature is 100°C to 140°C. Further, as the polyurethane resin paint, various one-component or two-component polyurethane resin paints can be used. One-component polyurethane resin paint contains a blocked polyisocyanate resin and a resin with hydroxyl groups in the paint, and when heated to 120 to 140°C, the blocked compound dissociates to produce free isocyanate groups, and inocyanate This is a paint that generates urethane bonds through the reaction of groups and hydroxyl groups to form a cured coating. 2
Liquid-type polyurethane resin paint is a paint that is applied after mixing a main agent containing a resin with hydroxyl groups and a curing agent containing a resin with isocyanate groups, and is usually cured by heating at 100°C for 20 to 60 minutes. Obtain a coating. The resin having an isocyanate group used here is preferably a non-yellowing type incyanate-containing resin, and for example, a hexamethylene diisocyanate-based isocyanate-containing resin is used. These second paints, thermosetting resin paints or polyurethane resin paints, contain various coloring pigments, various additives such as antifoaming agents, leveling agents, fluidity regulators, ultraviolet absorbers, light stabilizers, etc., and esters and ketones. , aromatic hydrocarbons, and other solvents. As the coating method for the polyurekne resin first coating material and second coating material which are cured in an amine atmosphere used in the present invention, known methods such as air spraying, airless spraying, electrostatic coating, etc. are applied. In addition, various commercially available masking materials can be used, and by using the masking material as a curing agent for the second paint, such as a thermosetting resin paint or a polyurethane resin paint, or by removing it later, it is possible to use a masking material as a curing agent for the second paint, such as a thermosetting resin paint or a polyurethane resin paint, or by removing it later. Painting with a design is done. [Function] According to the method of the present invention, when painting a reactive injection molded article, the urethane R
The durability of IM articles is improved. In addition, since the method of the present invention allows the coating film made of the first paint to be cured at room temperature for a short time, it is possible to suppress foaming of the coating film caused by the porosity of the urethane RIM, and to improve the flexibility of the urethane RIM. It is possible to form a coating film with performance that can follow. Furthermore, in addition to these features, the method of the present invention has the advantage that it can be cured at room temperature, resulting in economical savings in terms of energy, and that it can maintain a long pot life. [Example] In order to explain the present invention more specifically, the present invention will be described below with reference to Examples. Note that the present invention is not limited to these Examples. Furthermore, in the examples, all parts mean parts by weight. Example 1 (1) Preparation of polyol As monomers, 35.0 parts of methyl methacrylate, 36.0 parts of butyl acrylate, 13.9 parts of ethyl acrylate, and 15.1 parts of 2-hydroxyethyl methacrylate (monomer 100 parts in total), 66 parts of quidylole as a solvent, and 3.4 parts of azobisisobutyronitrile as a polymerization initiator.
Polymerization was carried out in a conventional manner using the above-mentioned parts to obtain an acrylic polyol. The solids content of this solution was 65% by weight. The obtained acrylic polyol had a Tg of 5° C., a hydroxyl value of 65, and a number average molecular weight of 4,500. (2) Preparation of polyurethane resin paint To 100 parts of the acrylic polyol solution prepared in (1) above, add 4 parts of capobon black powder (manufactured by Degussa, trade name: Special Black #6), and 4 parts of silica powder (manufactured by Degussa, trade name: Special Black #6).
Product name 0K-412) 4 parts, Cellosolve Acetate 37
A base containing 10 parts of Quijirol, 10 parts of hexamethylene diisocyanate (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name Sumidur N-75) and tolylene diisocyanate (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name Sumidur L-). 75) A two-component polyurethane resin paint was prepared consisting of 12 parts of a curing agent. Kano/NCO
The ratio was 1/1. (3) After degreasing the painted urethane RIM using a conventional method, spray paint the paint prepared in (2) above (first paint) to a film thickness of 25μ, and set at 25°C for 2 minutes. It was left to stand at a temperature of 20°C for 2 minutes in an atmosphere containing 600 ppm of dimethylethanolamine at a wind speed of 1.2 parts per second, and then dried for 10 minutes at 30°C in air not containing dimethylethanolamine. Next, after masking half of this urethane RIM, white urethane resin paint (manufactured by Kagura Paint Co., Ltd., trade name: Bolin NQ, I R5 White) (second paint)
The coating was spray coated to a film thickness of 30 μm and heated at 100° C. for 30 minutes. The obtained coated urethane RIM had an appearance as if a black base material had been partially painted white. Further, the test results of the coating film are shown in Table 2 below, and it can be seen from the results of Table 2 that a coating film with no pinholes and excellent flexibility, adhesion, and weather resistance was obtained. Comparative Example l The polyurethane resin first paint used in Example 1 was used in Example 1.
After painting in the same manner as above, 100% was applied without amine atmosphere treatment.
After drying at ℃ for 30 minutes, the second paint was applied in the same manner as in Example 1. As shown in Table 3, many pinholes were observed in the formed coating film. Comparative Example 2 In Example 1, diphenylmethane diisocyanate (manufactured by Sumitomo Bayer Nirethane Co., Ltd., trade name Sumidur E-21-1) was used as the curing agent during the preparation of the polyurethane resin paint.
The same procedure was carried out except that the section was changed. As shown in Table 3, the resulting coating film was free of pinholes and had excellent flexibility and adhesion, but had poor weather resistance. Examples 2 to 4 Three types of polyols were prepared in the same manner as in Example 1 using the monomers, initiators, and solvents shown in Table 1. □□□−□−□□ Table 111 3+ of Examples 2 to 4 above! ! These three types of polyurethane resin paints were prepared in the same manner as in Example 1, except that the following polyols were used and those shown in Table 2 were used as curing agents. Table 2 shows the characteristics of the polyol used in each of the above examples and the test results of the coating film obtained by coating urethane RIM using the polyol in the same manner as in Example 1. All of the obtained coated articles had coating films with no pinholes and excellent flexibility, adhesion, and weather resistance. Comparative Examples 3 to 5 Polyurethane resin paints were prepared using polyols and curing agents as shown in Table 3. Table 3 shows the results of coating urethane RIM using these in the same manner as in Example 1. The resulting coating film had defects as shown in Table 3. Comparative Example 6 Example 1 was changed so that masking was performed before applying the prepared first polyurethane resin paint, and then a second paint was applied in the same manner as in Example 1. In the obtained coated article, a portion of the urethane RIM substrate was exposed, and significant chalking occurred in the exposed portion after the weather resistance test. (1) The hydroxyl value is determined by acetylating with acetic anhydride, quantifying free acetic acid with caustic potassium, and expressing the number of mg of caustic potassium equivalent to the hydroxyl group contained in 1 g of resin. (2) Curing agent indicates the type of polyisocyanate used and the mole % in the total polyisocyanate. (3) Adhesiveness was determined using the burrow test method (JIS-K-54
00), and is expressed as the remaining number for 100 gobbles at 1 mm intervals. (4) Flexibility at -20°C was determined by keeping the test piece at -20°C.
It is 180 of n and bendability. (5) Appearance is the result of visual inspection of the paint film for shrinkage, unevenness, gloss, etc. However, pinholes are explained in a separate section. (5) f#j Warm water resistance shows the results of a cross-cut test after being immersed in water for 24 hours at 40°C. (7) Opponent is Sunshine Weather Roster 800
Figure 3 shows chalking and gloss retention after time test. (8) The pot life is expressed as the time when the viscosity does not exceed 3 seconds from the initial temperature using a #4 Four Cup at 30°C. ○, △, and X in the table are defined as follows. [Effects of the Invention] According to the method of the present invention, when painting a reactive injection molded article, a coating film of the first polyurethane resin paint can be formed by rapid curing, thereby eliminating coating film such as pinholes on the reactive injection molded article. Defects can be prevented, a coating film with flexibility that can follow the flexibility of reactive injection molded articles can be obtained, and coated articles with excellent durability and a design similar to partial coating can be obtained.

Claims (1)

[Claims] 1. After coating a reactive injection molded article with a black polyurethane resin paint and then curing the coating film in an amine atmosphere in a gaseous state, one of the reactive injection molded articles A method for coating a reactive injection molded article in which a thermosetting resin paint or a polyurethane resin paint is applied and cured on a part thereof, the polyurethane resin paint being cured in the above-mentioned amine atmosphere: (a) Tg: -40°C to 30°C; °C, hydroxyl value: 20-16
0, a polyol having a number average molecular weight of 1,000 to 10,000, (b) a polyisocyanate, (c) 30 mol% or more of the polyisocyanate is an aliphatic polyisocyanate, and (d) a ratio of OH equivalent to isocyanate equivalent. Ratio is 0.5:1
A method for coating a reactive injection molded article, characterized in that the coating ratio is 2:1.