JPH057832A - Coating method of polypropylene resin molded product - Google Patents

Abstract

PURPOSE:To provide a coating method to efficiently form a polyurethane resin coating film having excellent adhesion property on the surface of a polypropylene resin molded product. CONSTITUTION:A primer containing chlorinated polyolefin resin as a binder is applied on the surface of a polypropylene resin molded product, and then a two-liquid reaction type polyurethane resin coating material comprising polyol compd. and polyisocyanate compd. is applied. This method features in that both of the primer and polyurethane resin coating material contain a urethane hardening catalyst which partly or wholly consists of a metal compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for efficiently forming a polyurethane resin coating film having excellent adhesiveness on the surface of a polypropylene resin molded article.

[0002]

2. Description of the Related Art Polypropylene resin has the following properties: workability, strength,
Because it is superior in terms of price, it is processed into various molded products and used in a wide range of applications such as automobiles, electric appliances, building materials, medical equipment, office equipment, daily sundries, and in many cases The surface of these molded products is coated with a top coat for the purpose of improving surface characteristics and imparting design or decorative properties.

However, since polypropylene resin has high crystallinity and is non-polar in chemical structure, it has a problem that a coating film is difficult to adhere. Therefore, when a polypropylene resin molded article is overcoated, it is generally used. Specifically, the problem of poor adhesion is improved by applying a primer using a chlorinated polyolefin resin having a polarity similar to that of the molded article substrate as a binder, and then applying a top coat thereon. .

On the other hand, among the paints used for the above-mentioned top coating, the two-component reactive polyurethane resin paint composed of a polyol compound and a polyisocyanate compound forms a coating film excellent in gloss and feeling of holding. Since it has excellent mechanical properties such as abrasion resistance, flexibility, etc.,
It is particularly suitable for top coating and is often used for coating the above-mentioned polypropylene resin molded product. However, when the polyurethane resin coating is applied on a primer using chlorinated polypropylene as a binder, the polyurethane resin coating cures. However, there is a problem in that it takes a long time before the molded product can be handled after coating.

The problem of delayed curing of the polyurethane resin coating film can be improved to some extent by increasing the amount of a urethane curing catalyst that is generally used as a curing accelerator for the polyurethane resin coating material. This is a new problem in that the pot life of polyurethane resin paints is significantly shortened, which hinders the painting work.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the current situation as described above, and a polyurethane resin coating film having excellent adhesion is formed on the surface of a polypropylene resin molded article.
It is an object of the present invention to provide a coating method that can be efficiently formed in a short time without being restricted by coating work.

[0007]

A method for coating a polypropylene resin (hereinafter referred to as PP resin) molded article provided by the present invention is a chlorinated polyolefin resin (hereinafter referred to as chlorinated PP) on the surface of a PP resin molded article. ) As a binder, and then a two-component reactive polyurethane resin coating composition comprising a polyol compound and a polyisocyanate compound is applied onto the primer. Both or both of the resin paints are characterized by containing a urethane curing catalyst which is a metal compound in whole or in part.

The primer used in the present invention is prepared by dissolving a binder containing chlorinated PP in a suitable organic solvent for paints, and using it as a urethane curing catalyst and, if necessary, various paints commonly used for paints. The above-mentioned additive, for example, a coloring material such as a pigment or a dye, a filler, a leveling agent, a thickener, a diluent and the like are blended.

The chlorinated PP used as the binder of the above-mentioned primer is not particularly limited and can be appropriately selected and used from those commonly used as a binder for paints. As an example, the chlorine content is Two
0-40% by weight, weight average molecular weight (Mw) is 4,000
It is preferable to use one having a molecular weight of 0 to 250,000, and it is particularly preferable for Mw to be 5,000 to 70,000.

The chlorinated PP may form the entire binder, or may form a part by combination with other resins. When the chlorinated PP constitutes a part of the binder, it is preferable that the chlorinated PP accounts for 10% by weight or more in the binder.

The urethane curing catalyst that can be contained in the above-mentioned primer is made of a metal compound in whole or in part, and specific examples of the metal compound include dibutyltin dilaurate (hereinafter referred to as DBTDL),
In addition to organic tin compounds such as dibutyltin di (2-ethylhexoate), dibutyltin dioctate, tin octoate, zinc octate (hereinafter referred to as Zn-O), zinc compounds such as zinc naphthenate, calcium octate (Hereinafter referred to as Ca-O), 2-ethylhexoate lead, o-phenylsoda, potassium oleate, bismuth nitrate, 2-ethylhexyl titanate, 2-ethylhexoate iron, 2-ethylhexoate Metal compounds such as cobalt and antimony trichloride.

The above metal compounds may be used alone or in admixture of two or more, and among these metal compounds, it is preferable to use an organic tin compound having a high catalytic activity with respect to the polyurethane resin. When another metal compound other than the above is used, it is preferable to use the metal tin compound in combination with an organic tin compound.

Further, in the urethane curing catalyst to be contained in the primer, when a part of the urethane curing catalyst is composed of the metal compound and the rest is an amine compound, the catalytic activity is further improved and, for example, it is coated on the primer. Even if the amount of urethane curing catalyst in the polyurethane resin coating material is small or the catalyst activity is low, the polyurethane resin coating material can be efficiently cured, so that the pot life of the polyurethane resin coating material is extended. It is also possible to do so. Therefore, in the present invention, it is particularly preferable to use such a mixed catalyst of a metal compound and an amine compound as the urethane curing catalyst contained in the primer.

Specific examples of the amine compound that can be used in combination with the above metal compound catalyst include monoamines such as triethylamine and N, N-dimethylcyclohexylamine, N, N, N ', N'-tetramethylethylenediamine, N, N, N ', N'-tetramethylpropane-1,
Examples thereof include polyamines such as 3-diamine, N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, cyclic amines such as triethylenediamine, alcohol amines and ether amines.

The metal compound contained in the primer is preferably added in an amount of 0.05 to 0.5 part by weight based on 100 parts by weight of the chlorinated polyolefin resin in the primer. When an amine compound is used in combination, the compounding amount is 0.05 to 0.5 with respect to 100 parts by weight of the chlorinated polyolefin resin in the primer.
It is preferably in the range of 5 parts by weight.

The two-component reactive polyurethane resin coating used in the method of the present invention comprises a polyol compound and a polyisocyanate compound. Specific examples of preferable polyol compounds include polyester polyols, polyether polyols and acryl. Polyols and the like, and these polyol compounds are generally 3
Those having a hydroxyl value of 0 to 400 are preferably used.

Specific examples of the polyisocyanate compound include hexamethylene diisocyanate (HMDI).
System, isophorone diisocyanate (IPDI) system, bis (isocyanate methylcyclohexane (HXDI)
System, trimethylhexamethylene diisocyanate (TM
A non-yellowing type polyisocyanate compound such as DI) is preferably used.

The above-mentioned polyurethane resin coating composition is prepared by separately preparing a component containing a polyol compound and a component containing a polyisocyanate compound, and immediately before coating, a predetermined ratio, for example, -OH group 1 in the polyol compound.
The -NCO group in the polyisocyanate compound is mixed and used in an amount of 0.8 to 1.8 mol per mol. Further, in the same manner as in the case of the above-mentioned primer, the polyurethane resin coating material is blended with a urethane curing catalyst and, if necessary, various coating additives, and the urethane curing catalyst or the like is a component containing a polyol compound. It is preferable to mix it in.

The urethane curing catalyst that can be blended in the polyurethane resin coating material is the same metal compound as in the case of the above primer, but if an organotin compound having a high catalytic activity is used, for example, the pot life of the polyurethane resin coating material is improved. Therefore, when using the organic tin compound, it is preferable that the compounding amount thereof be as small as possible or that the organic tin compound be used in combination with a metal compound having a relatively low catalytic activity. Particularly in the present invention, it is preferable to use a zinc compound.

The amount of the metal compound catalyst contained in the polyurethane resin coating material is the amount of the polyurethane resin 1 in the coating material.
The amount of metal is preferably in the range of 0.003 to 0.3 parts by weight, particularly 0.003 to 0.06 parts by weight, based on 00 parts by weight.
It is preferably in the range of parts by weight.

Particularly, in the method of the present invention, when a mixture of an organic tin compound and an amine compound is used as the urethane curing catalyst to be contained in the primer and the urethane curing catalyst to be contained in the polyurethane resin coating is a zinc compound, the polyurethane resin coating is used. It is particularly preferable because it can effectively cure the coating film without causing any trouble to the pot life of the above.

The coating of the above-mentioned primer and polyurethane resin paint is carried out by various coating methods known in the coating industry, for example,
It can be carried out by spray coating, dip coating, roller coating, curtain flow coating, electrostatic coating or the like. The thickness of the coating film formed is generally 5 to 50 μm in the case of a primer and in the case of a top coating film. Is preferably 15 to 150 μm. Further, the coating film after coating may be cured at either room temperature or heating, and a preferable example of heating is a two-coat and two-bake method or a two-coat and one-bake method at a temperature condition of 50 to 120 ° C. Can be done in a manner.

Since the method of the present invention is constituted by incorporating a urethane curing catalyst into the primer applied for improving the adhesion, the primer itself contributes to the acceleration of the curing of the polyurethane resin coating film. Therefore, the drawback that the curing of the polyurethane resin coating film as the top coating material is delayed by the chlorinated PP-containing primer as the lower layer is effectively prevented.

[0024]

【Example】

The present invention will be described in more detail based on the following examples. In addition, the compounding amounts of the respective components in the compounding compositions in the examples are shown in parts by weight unless otherwise specified.

Example 1

Preparation of primer : Chlorinated PP (manufactured by Sanyo Kokusaku Pulp Co., Ltd., trade name: Super Clone 832L, chlorine content 27%, nonvolatile content 30%, Mw 50,000) 1
00 g, xylene 30 g, and DBTDL (manufactured by Yoshitomi Pharmaceutical Co., Ltd., trade name; PLUS GUARD L-101, tin content 1
8%) 0.4g was mixed uniformly to prepare a chlorinated PP-containing primer.

Preparation of top-coat paint ; Polyol compound (Sumitomo Bayer Urethane Co., trade name; Desmophen 1
700 (hydroxyl value 40) / desmophen 1200 (hydroxyl value 172) = 6 parts / 4 parts) 100 g, pigment (titanium dioxide / carbon black = 8 parts / 2 parts) 55 g, DB
TDL 0.14 g, zinc octate (manufactured by Nippon Kagaku Sangyo Co., Ltd., trade name; Nikka Octix zinc, Zn content 8
%) 0.28 g and organic solvent (xylene / butyl acetate /
Ethylene glycol monoethyl ether acetate = 6 parts / 5
(1 part / 1 part) 240 g is uniformly mixed to obtain a polyol component, and the polyisocyanate component (manufactured by Sumitomo Bayer Urethane Co., trade name; Sumidule N) 4 is added to the polyol component.
A polyurethane resin paint was prepared by mixing 2 g.

Coating on PP resin molded product; spray coating on the surface of the PP resin molded product (Ube Industries, Ltd., trade name; Ube 32) so that the coating film thickness after curing is 20 to 25 μm. Then, after setting for 3 minutes, the above polyurethane resin paint is further spray-coated so that the coating film thickness after curing is about 70 μm, and the coating is performed at 80 ° C. for 4 minutes.
It was heated for 0 minute to form a cured coating film on the surface of the PP resin molded product.

Evaluation of cured coating film : The coating film formed as described above was evaluated by the following test methods for pencil hardness, work gloves contamination and adhesion, and for the top coating film, pot life was evaluated and evaluated. The results are shown in Table 2 below.

(1) Pencil hardness: JIS K 5400, 6.
According to the 14 "pencil scratch test" method, the coating film after 2 hours from the heat curing is tested.

(2) Work gloves contamination: A fingertip with work gloves is pressed against the surface of the coating film 2 hours after the heat curing (acupressure of about 8).
Observe the presence or absence of work gloves. Also, the surface of the coating film is rubbed with work gloves and observed for scratches.

(3) Adhesion: JIS K 5400, 6.
15 Test according to the “cross-cut test” method.

(4) Pot life: The change in viscosity of the top coating composition (after mixing the polyol component and the polyisocyanate component) at 30 ° C. is measured, and the pot life is evaluated by the time during which the coatable viscosity is maintained.

Examples 2 to 6

Using the components of Example 1 above, a primer and a polyurethane resin coating material were prepared in the same manner as in Example 1 according to the formulation shown in Table 1 below, coated on a PP molded article, and then evaluated. The evaluation results are shown in the table below. Shown in 2.

[0037]

[Table 1]

[0038]

[Table 2]

Examples 7, 8 and Comparative Examples 1, 2

Using each component of Example 1 above and an amine catalyst [1,4-diaza (2,2,2) bicyclooctane] as a urethane curing catalyst, a primer and a primer were prepared in the same manner as in Example 1 with the formulation shown in Table 3 below. Prepare polyurethane resin paint,
The PP molded article was coated and then evaluated. The evaluation results are also shown in Table 3.

[0041]

[Table 3]

[0042]

EFFECT OF THE INVENTION The method of the present invention is a simple method in which a urethane curing catalyst that accelerates the curing of the top coating film is added to the primer applied to improve the adhesion. The drawback of delayed curing of the resin coating can be effectively eliminated, and in the present invention, since it is not necessary to increase the amount of the urethane curing catalyst in the top coating,
There is no need to consider the problem of pot life, and it is an excellent method for coating PP resin molded products.

Claims (5)

[Claims] 1. A surface of a polypropylene resin molded article is coated with a primer containing a chlorinated polyolefin resin as a binder, and then a two-component reactive polyurethane resin coating comprising a polyol compound and a polyisocyanate compound is coated thereon. In the method for coating a polypropylene resin molded article, the polypropylene resin molded article is characterized in that both the primer and the polyurethane resin coating material contain a urethane curing catalyst which is a metal compound in whole or in part. How to paint. 2. In the urethane curing catalyst, all or part of the metal compound contained in the primer is an organic tin compound, and all or part of the metal compound contained in the polyurethane resin coating is a zinc compound. A method for coating a polypropylene resin molded article according to. 3. The metal compound contained in the primer is chlorinated polyolefin resin 100 in the primer.
The method for coating a polypropylene resin molded article according to claim 1 or 2, wherein the amount of the metal is 0.05 to 0.5 part by weight based on the weight. 4. The method for coating a polypropylene resin molded article according to claim 1, wherein the urethane curing catalyst contained in the primer contains an amine compound. 5. The polypropylene resin according to claim 1, wherein the urethane curing catalyst contained in the primer is a mixture of an organic tin compound and an amine compound, and the urethane resin curing catalyst contained in the polyurethane resin coating is a zinc compound. How to paint molded products.