JPH0618912B2 - How to coat reactive injection molded products - Google Patents

Description

The present invention relates to a method for coating a reactive injection molded article.

[Conventional technology]

A reactive injection molded product is a resin molded product obtained by simultaneously curing and molding a thermosetting resin inside a molding die, and for example, urethane RIM (React
Ion Injection Molding) has been put to practical use, and is mainly useful in the field of automobile parts because of its excellent strength, flexibility, and freedom in designing the shape during molding.

Urethane RIM is basically a molded product that is foamed inside or has a smooth surface, but it is often found that the surface is partially porous due to molding conditions. Especially immediately after molding, the porosity is usually extremely large. In coating such molded articles,
In order to prevent the fine pores, a paint and a coating method which can be rapidly cured and can form a coating film having flexibility that can follow the flexibility of a molded product are required.

For conventional urethane RIM coating, (1) post-curing after urethane RIM molding to further reduce the fine pores on the surface, then apply a two-component polyurethane resin paint at a temperature close to room temperature, or add a catalyst, etc. There is also known a method of applying a low temperature curing type polyurethane resin paint, or (2) a method of applying a low temperature type polyurethane resin paint after the surface of the urethane RIM has been left for several days and then smoothed. Also (3)
As a simple urethane RIM coating method, JP-A-58-7
No. 8737 is known.

On the other hand, (4) JP-A-60-31533 and JP-A-58-5345 are known as coating methods for preventing foaming of a coating film such as a sheet-shaped molded product (SMC) and a bulk molded product (BMC) as a porous material. Has been.

Further, (5) a method for curing a coating film of a polyurethane coating in an amine atmosphere is disclosed in JP-A-59-21661 and JP-A-58-104.
No. 922 and the like are known.

[Problems to be solved by the invention]

However, in the above-mentioned methods (1) and (2), it takes a long time before coating, and post-treatment after molding is required.
Low-temperature polyurethane resin coatings have the disadvantages that the pot life is short, they are complicated or difficult to handle in the field, and there is a big loss in the work process.The coating film obtained is also urethane RIM compatible. It did not have a property sufficiently suitable for flexibility.

In addition, the effect of preventing the pinhole of urethane RIM is not described in the above method (3), and the purpose is different from the present invention.

In addition, the method (4) above does not have flexibility because it is an SMC or BMC that is the object to be coated or originally a hard molded product, and therefore urethane RIM
It is not suitable for the coating of molded articles having excellent flexibility as described above in terms of performance.

The method (5) is a general curing method for polyurethane paints, and the adhesion and flexibility of coating and coating film on flexible molded products such as urethane RIM are taken into consideration. No consideration is given to the prevention of bottleholes in the molded product and the coating film formed.

Therefore, the object of the present invention relates to the coating of reactive injection molded products, for example, urethane RIM, which eliminates the handling defects due to the pot life, can be cured at low temperature in a short time, and has a coating film appearance caused by the surface defects of urethane RIM. It is an object of the present invention to provide an improved coating method for urethane RIM capable of forming a coating film having excellent flexibility and excellent adhesion, by eliminating the above defects.

[Means for solving problems]

The present inventors have conducted extensive research on reactive injection molded products, particularly urethane RIM coating methods, and as a result of coating urethane RIM with a urethane resin coating, a specific polyhydroxy compound and a specific hydroxy group were used. By coating with a paint containing polymer resin and polyisocyanate that does not contain it and curing it in an amine atmosphere, a coating film with excellent flexibility and adhesion can be formed, and it can be cured at low temperature in a short time It was found that the present invention has been completed.

The present invention is a coating method of coating a reactive injection molded article with a urethane resin coating, and then curing the coating in an amine atmosphere in a vapor phase state, wherein the urethane resin coating is (a) T
g: -40 ° C to 60 ° C, number average molecular weight: 1000 to 10
Polyhydroxy compound of 000, (b) Tg: -40 ° C
It is a method of coating using a coating resin containing a hydroxyl group-free polymer resin having a number average molecular weight of 2,000 to 60,000 and a polyisocyanate (c) of -10 ° C.

The reactive injection molded product used in the present invention is as described above, and examples thereof include urethane RIM and fiber reinforced urethane RIM.

As the polyhydroxy compound as the component (a) used in the present invention which is cured in an amine atmosphere in a gas phase, polyols such as acrylic follyol, polyester polyol, alkyd polyol, polyolefin polyol and polyether polyol are used. , Acrylic polyols, polyester polyols, and polyolefin polyols are particularly suitable. Among them, Tg: -40 ° C
Polyols having a number average molecular weight of 1,000 to 10,000 at -60 ° C are suitable. Particularly, a polyol having a Tg of −30 ° C. to 40 ° C. and a number average molecular weight of 3000 to 6000 is preferable.

When Tg is higher than 60 ° C, the flexibility of the formed coating film is insufficient, and when it is lower than -40 ° C, the surface hardness is insufficient, and when the number average molecular weight is more than 10,000, the spray workability is poor and the coating is poor. The appearance of the film becomes poor, and when it is less than 1000, the physical properties such as low temperature physical properties and the chemical performance such as moisture resistance and hot water resistance become poor.

As the polymer resin containing no hydroxy group of the component (b) used in the present invention, an acrylic resin, a polyester resin, an alkyd resin or the like can be used, and among them, Tg: -4
A polymer resin having a temperature of 0 ° C. to 10 ° C. and a number average molecular weight of 2000 to 60,000 is suitable. Above all, Tg: -30 ° C to 5 ° C,
A polymer resin having a number average molecular weight of 4000 to 40,000 is preferable.

If Tg is higher than 10 ° C, the low temperature physical properties are insufficient, and if it is lower than -40 ° C, the drying property of the coating film becomes poor. On the other hand, the number average molecular weight is 60
When it is more than 000, spraying workability is poor and the appearance of the coating film is poor, and when it is less than 2000, the chemical performance such as hot water resistance of the coating film is poor and the mixing effect is poor.

In the present invention, the weight ratio of the polyhydroxy compound as the component (a) to the hydroxy group-free polymer resin as the component (b) is 95: 5 to 40:60, preferably 90:10 to 5
It is 0:50. When the ratio of the component (b) is less than 5, the effect of improving the physical properties of the coating film, especially the low temperature physical properties, is lost,
When it is greater than 0, the effect of suppressing pinholes in the coating film is lost, and the chemical performance such as hot water resistance becomes poor.

Suitable polyisocyanates for use in the polyurethane resin coatings of the present invention include toluylene diisocyanate (TD
I), diphenylmethane diisocyanate, methylene diisocyanate, xylylene diisocyanate (XD
I), hexamethylene diisocyanate, isophorone diisocyanate, triphenyl methane diisocyanate, phenylene diisocyanate, lysine diisocyanate and their methylol adducts or trimers to pentamers, and mixtures thereof.

The mixing ratio of the OH group and the NCO group is preferably 0.6: 1 to 1: 0.6, and preferably 0.8: 1 to 1: 0.8. When the OH group is less than 0.6, the flexibility and low temperature physical properties of the coating film deteriorate. Further, if the NCO group is less than 0.6, the chemical performance such as hot water resistance deteriorates.

In the present invention, the above-mentioned polyurethane resin coating is cured after coating in an amine atmosphere in a gas phase state. As an amine that can be used at this time, a tertiary amine is preferable, for example, trimethylamine, triethylamine, tripropylamine, Aliphatic tertiary amines such as tributylamine and triallylamine, aromatic amines such as dimethylaniline, diethylaniline and tribenzylamine, N-
Alkanolamines such as methylmorpholine, N-ethylmorpholine or triethanolamine, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, dibutylethanolamine, di (2-ethylhexyl) ethanolamine, ethyldiethanolamine, triisopropanolamine, dibutylisopropanolamine. Can be used, and among them, triethylamine and dimethylethanolamine (DMEA) are preferable.

The atmosphere of the amines is such that the amine concentration in the gas phase is 10 to 3000 ppm, preferably 300 to 1200 p.
pm is suitable. The temperature is 0 to 80 ° C, preferably 20 to
40 ° C is suitable. The curing time in the amine atmosphere is
Although it varies depending on the resin composition, the film thickness to be formed, the type of tertiary amine, the temperature, the concentration, etc., it is generally 0.5 to 10 minutes, preferably 1 to 4 minutes. After the treatment in the amine atmosphere, if necessary, at a temperature of 100 ° C. or lower for 3 to
You may heat-process for 15 minutes.

The polyurethane resin coating material to be cured in the amine atmosphere used in the present invention includes various known additives, pigments such as coloring pigments and extender pigments, surfactants, defoaming agents, leveling agents and the like, and further esters, ketones, It may contain an aliphatic or aromatic hydrocarbon solvent or the like.

According to the method of the present invention, when a coating film formed by coating with a urethane resin paint and then cured in an amine atmosphere is in a state where it is not completely cured in the amine atmosphere, a high temperature heat curing treatment may be performed thereafter. At this time, it was found that no abnormality such as foaming was observed in the coating film even when exposed to high temperature.

In the present invention, a known coating method such as air spraying, airless spraying or electrostatic coating is applied as a method for coating the polyurethane resin coating material which is cured in an amine atmosphere.

The polyurethane resin coating film formed by the method of the present invention,
Further, another thermosetting resin paint or polyurethane resin paint can be applied thereon.

[Action]

According to the method of the present invention, a coating film can be cured even at room temperature in a short time, and since the coating film has flexibility and also has a Rucker tendency, a reactive injection molded article such as urethane RI can be used.
Foaming due to the porosity of M can be prevented and urethane RIM
It is possible to obtain a coating film which can follow the flexibility of and has excellent adhesion.

〔Example〕

The present invention will be described below with reference to examples. Unless otherwise specified, "parts in the text" means "parts by weight".

Example 1 (1) Preparation of polyhydroxy compound: 35.0 parts of methyl methacrylate as a monomer, 36.0 parts of butyl acrylate, 13.9 parts of ethyl acrylate and 15.1 parts of 2-hydroxyethyl methacrylate. (Total 100 parts of monomers) was used, 3.4 parts of azobisisobutyronitrile was used as a weight initiator, and 66 parts of xylol was used as a solvent to carry out polymerization by an ordinary method to obtain an acrylic polyol. The solid content of this solution was 60% by weight.

The characteristics of the obtained acrylic polyol were Tg: 5 ° C. and number average molecular weight: 4,500.

(2) Preparation of hydroxy group-free polymer resin: 34.0 parts of methyl methacrylate, 44.7 parts of butyl acrylate and 21.3 parts of ethyl acrylate (100 parts of total monomers) were used as monomers. Then, 1.8 parts of azobisisobutyronitrile as a polymerization initiator and 66 parts of xylol as a solvent were used to carry out polymerization by an ordinary method to obtain an acrylic polymer resin. The solid content of this solution was 60% by weight.

The characteristic number of the obtained polymer resin containing no hydroxy group is Tg: -1.
It was 0 ° C. and the number average molecular weight was 15,000.

(3) Preparation of polyurethane resin coating: 100 parts of the acrylic polyol prepared in the above (1) and 40 parts of the hydroxy group-free acrylic polymer resin prepared in the above (2) were mixed with titanium oxide powder (manufactured by Ishihara Sangyo Co., Ltd., Product name Taipek CR-90) 120 parts, cellosolve acetate 30
Part, xylol 10 parts, and a curing agent, tolylene diisocyanate (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name Sumidiur 75) 20 parts, a two-component polyurethane resin paint was prepared. The ratio of acrylic polyol to hydroxy-free acrylic polymer resin of this product is 7
It was 2:28.

(4) Coating: After degreasing urethane RIM by a conventional method, spray coating the coating prepared in (3) above and setting at room temperature for 2 minutes, then in an atmosphere of dimethylethanolamine 900ppm, the air velocity 1.2m. / Sec at a temperature of 20 ° C. for 2 minutes. After that, it is dried at 30 ℃ for 10 minutes and the thickness is
A coating film of The test results of the obtained coating film are shown in Table 2.
From the results in Table 2, it can be seen that a coating film free from pinholes and excellent in flexibility and adhesion was obtained.

Examples 2 to 4 A polyhydroxy compound and a polymer not containing a hydroxy group according to the method described in (1) and (2) of Example 1 using the monomers, curing agents and solvents shown in Table 1 below. A resin was prepared (note that Table 1 also shows the case of Example 1).

The characteristics and proportions of the (a) polyhydroxy compound and the (b) hydroxy group-free polymer resin used in each of the above-mentioned examples, and the urethane RIM
Table 2 shows the test results of the coating film obtained by coating All of the obtained coating films had no pinholes and were excellent in flexibility and adhesiveness.

Example 5 A urethane RIM was applied in the same manner as in Example 1 except that xylylene diisocyanate (Takenate D-110N, manufactured by Takeda Pharmaceutical Co., Ltd.) was used instead of the curing agent tolylene diisocyanate. The results obtained are shown in Table 3.

Example 6 A urethane was prepared in the same manner as in Example 1 except that the ratio of (1) polyhydroxy compound to (2) hydroxy group-free polymer resin was (1) :( 2) = 96: 4. RIM painted.
The results obtained are shown in Table 3.

Example 7 In Example 2, the ratio of (1) polyhydroxy compound and (2) hydroxy group-free polymer resin was (1) :( 2) = 30: 70.
The following was applied with urethane RIM in the same manner as in Example 2. The results obtained are shown in Table 3.

Comparative Example 1 Urethane obtained by degreasing the coating prepared in Example 1 by a conventional method.
After coating on the RIM material, it was heated and dried at 80 ° C. for 40 minutes to form a cured coating film. The resulting coating film had many pinholes. The results are shown in Table 3.

Comparative Examples 2 to 5 Urethane RIM was coated according to the coating method described in Example 1 using the polyhydroxy compound and the hydroxy group-free polymer resin shown in Table 2. All of the obtained coating films had defective pinholes or lack flexibility. The results are shown in Table 3.

(Effect of the invention) According to the method of the present invention, when coating urethane RIM, there is an effect that the coating film formed is rapidly cured at room temperature, and there is no defect such as pinholes in the formed coating film. A coating film having excellent flexibility, adhesion and warm water resistance can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fumitaka Nakayama 2-7-30-1004 Sakasedai, Takarazuka-shi, Hyogo

Claims (2)

[Claims] 1. A method for coating a reactive injection-molded article with a urethane resin coating, and then curing the coating in a gas phase amine atmosphere, wherein the urethane resin coating is
(a) Tg: −40 ° C. to 60 ° C., number average molecular weight: 1000 to
10000 polyhydroxy compound, (b) Tg: -4
Hydroxyl group-free polymer resin having 0 ° C. to 10 ° C. and number average molecular weight of 2000 to 60,000, and (c)
A method for coating a reactive injection-molded article, which comprises a polyisocyanate. 2. The coating method according to claim 1, wherein the weight ratio of the polyhydroxy compound of (a) to the polymer resin of (b) is 95: 5 to 40:60.