JPS6047035A - Painting of polyolefin resin molding - Google Patents

Abstract

PURPOSE:To form a paint film of good adhesion even on an article of a complicated shape without its deformation during painting, by painting the titled molding after plasma treatment with a specified coating and drying it under exposure to an amine vapor. CONSTITUTION:Use is made of a coating containing a free isocyanato group- containing compound comprising (A) a base (e.g., acrylpolyol), (B) about 0.5- 3mol (in terms of isocyanato groups), per mol of hydroxyl groups of the base, curing agent (e.g., 2,4-tolylene diisocyanate), (C) a pigment and (D) a solvent (preferably, a two-component polyurethane coating). Namely, a polyolefin resin molding is treated with a plasma (preferably, a low-temperature plasma generated by the excitation of oxygen), then with the above coating. The paint film is dried in a stream of air containing a vapor of an amine (e.g., dimethylethanolamine) to cure the paint film.

Description

[Detailed description of the invention] This relates to mounting method 4.

BACKGROUND ART Polyolefin resin molded articles have traditionally been used in various fields including interior and exterior parts of automobiles, and the demand for them is on the rise.

Painting these polyolefin resin molded articles is important for aesthetics and functionality, but polyolefin thread resins generally have high crystallinity and low polarity, so the paintability is extremely poor, and in particular, they do not adhere well to paint. It is difficult to ensure good adhesion. In recent years, a primer with good adhesion to polyolefin thread resin has been developed, and a two-coat method of the primer and top coat paint has been adopted, and improvements have been made in terms of adhesion, but this two-coat method still remains. It has the following drawbacks. That is, in the case of a molded article with a complicated shape, the required film thickness of the primer may not be ensured in some parts, and the adhesion in those parts may be poor. Additionally, primers generally have poor gasoline resistance. Furthermore, since it is a two-coat method, the process is long and productivity is high! I! ．． 4. Even further
Top coatings are generally dried by heating, but the heating causes the molded article to form a thermal rhombus shape, which causes a decrease in product yield. Drying at room temperature to avoid thermal deformation takes time and reduces productivity. For this reason, when painting polyolefin resin molded articles, strong adhesion is ensured even for articles with complex shapes, and there is no deformation during the coating process.
The development of coating methods that require shorter process times is still being sought.

Therefore, an object of the present invention is to provide a coating method for coating polyolefin resin molded articles, which ensures strong adhesion even for articles with complex shapes, eliminates deformation during the coating process, and shortens process time.

More specifically, the present invention involves plasma-treating a polyolefin resin molded article, coating it with a paint containing a compound having an isocyanate group of MXli in a vehicle, and then exposing it to an atmosphere containing amine vapor to apply the paint. A method of coating a polyolefin resin molded article by drying it.

The plasma treatment carried out in the present invention is carried out to improve the adhesion of paint to polyolefin resin molded articles, and is performed to improve the adhesion of paint to polyolefin resin molded articles.
．． A polyolefin molded article is exposed to a low-temperature plasma atmosphere obtained by excitation of gas molecules by microwave discharge, corona discharge, etc. under a pressure of 1 to 10 + mi'Hg, or plasma is blown onto the surface of the molded article. I will do it based on what I can hear. The gas used at this time is oxygen, one part nitrogen, one part argon, one part helium, or a mixture thereof. Of these, oxygen is the most effective. The treatment time is 5 seconds to 30 minutes, preferably 10 seconds to 10 minutes.

The polyolefin resin molded article treated with plasma in this manner may be coated within about two weeks after treatment, but it is preferable to coat it immediately after treatment.

Paints that can be used in the present invention are paints that contain compounds having free isocyanate groups in the vehicle. Such paints are generally referred to as polyurethane paints, and specifically include two-component polyurethane paints and moisture-cured polyurethane paints, with two-component polyurethane paints being more preferred.

A two-component polyurethane paint consists of a paint component (base) containing a resin with two or more hydroxyl groups in the molecule, and a monomer or prepolymer (curing agent) having two or more free isocyanate groups in the molecule. ) are used by mixing them in a specified amount before painting.

Examples of the resin used as the base include acrylic polyol, polyester polyol, polyether polyol, alkyd polyol, and epoxy polyol, and various types of these are commercially available. These may be used alone or in combination of 2 fth or more. The base material is manufactured by adding pigments, solvents, and various additives to these resins as desired.

Examples of BR agents include anchor color pigments such as titanium dioxide, carbon black, yellow lead, and Bengara; extender pigments such as talc,
Clays, silicas, calcium carbonates; and other materials may be used, but are not particularly limited. As a bath agent, any solvent can be used as long as it has no reactivity with the curing agent; examples include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethyl acetate, 1F butyl, amyl acetate,
Cellosolve acetate shield esters; aromatic hydrocarbons such as toluene and xylene are used. There is no problem in using these alone or in combination of two or more. As additives, for example, antioxidants, flow control agents, ultraviolet absorbers, viscosity modifiers, etc. can be used in small amounts.

Next, curing agents that can be used include diisocyanate compounds or prepolymers thereof. Examples of diisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate), 1. ．．
6-hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate-1.
, inphorone diisocyanate 1,4,4'-diphenylmethane diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, trimethylhexamethylene diisocyanate 1 dimer Examples include diisocyanates. Prepolymers are diisocyanate monomers, evaporated ethylene glycol, propylene glycol 11,
2F alcohols such as 4-butanediol, 6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, and bisphenol dihydroxypropyl ether; examples include glycerin, trimethylolpropane, and 1,2,6-hexane. Trihydric alcohols such as doliol; for example, adducts having incyanate groups at the terminals obtained by reacting tetrahydric alcohols such as pentaerythritol at a molar ratio such that incyanate groups are in excess; biuret compounds; and polyisocyanate having an oxadiazinetrione ring obtained by the reaction of a diisocyanate group with km gas. These diisocyanenite compounds or prepolymers may be used alone or in combination of 2 or more.

The curing agent is used by mixing in such a proportion that the inocyanate group is 0.5 to 3.0 moles, preferably 08 to 1.2 moles, per mole of hydrated groups in the base. less than 0.05 mole or 3.0
Exceeding the molar amount is undesirable because it adversely affects the physical properties and durability of the coating film.

The coating method is not particularly limited and can be applied by commonly used air spray, airless spray, or roll coater.

The drying of the coating film carried out in the present invention is carried out by exposing the molded article coated with the coating material described in (11) to an atmosphere containing amine vapor.

The temperature of the atmosphere containing amine vapor is not the normal temperature, that is, 1
The temperature is good at 0 to 30°C, and no heating is required. Therefore, it is possible to avoid heating the object to be coated, and furthermore, it is possible to reduce the energy cost required for drying.

The vine amine used here is especially I'Ji! However, tertiary amines having a vapor saturation concentration of 5 Q PPM or more at room temperature are preferred. Examples of such amines are trimethylamine, triisopropylamine, tri-n-butylamine, triisobutylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, dimethylpropanolamine, tetramethylethylenediamine. , tetraethylethylenediamine, tetramethylpropylenediamine, tetraethylpropylenediamine, N-methylmorpholine, N-ethylmorpholine'4.

The preferred concentration of amine vapor is from 5 Q PPM to the saturation concentration of the amine vapor used, but more preferably from 200 to 2000 PPM.

If it is less than 50 PPM, the time required for drying becomes long, which is not preferable in terms of the process.

The time for exposure to the atmosphere containing amine vapor varies depending on the paint used and the film thickness, but is usually 15 seconds to 10 minutes. At this time, if the atmosphere containing amine vapor is stagnant, only the human blood on the coating will dry and the inside of the coating will tend to dry out. To avoid this, the atmosphere containing amine vapor should be kept at a constant wind speed. It is desirable that the airflow has a

The wind speed may be approximately 0.3 to 5 m/sec.

The coating method of the present invention is suitable for application to polyolefin thread resin molded articles, which have poor adhesion and are susceptible to thermal deformation using conventional degreasing and painting methods.

Examples of polyolefin resins that can be used in dud filJ include low-density polyethylene, high-density polyethylene, polypropylene, ethylene, propylene, butene, etc. Examples include methacrylic acid or their synergy with m> conductors (coalescence), or combinations of these polyolefin resins.These may contain fillers, colorants, antioxidants, and other additives. Good. These polyolefin-based (1D) resins are molded by injection molding, extrusion molding, etc. into various manufactured products, such as automobile parts such as bumpers, pillars, etc.; housings of household electrical appliances such as telepil code players, etc. are suitable for applying the coating method of the present invention, and by coating with the coating method of the present invention, a coating film with good adhesion can be formed in one coat at room temperature in a short time.

The present invention will be described in further detail with reference to Examples below.
Moths are not limited to these.

Note that all examples referred to as "Example Chubu" refer to Juasahibu.

Reference example 1: Manufacture of paint (1) Acrylic polyol (manufactured by Dainippon Ink Chemical Co., Ltd., trade name Acrytic A-800. Solid content 50%, hydroxyl value 50)
), 50 parts of titanium dioxide and 25 parts of a mixed solvent of xylene/cyclohexanone (1:1) were added and dispersed in a ball mill for 10 hours. 0.2 part of a flow control agent was added to 99.8 parts of this material to form a base.

Add a prepolymer of 1,6-hexamethylene diisocyanate (manufactured by Sumitomo Peyer Uretashi Co., Ltd., trade name Sumidur N-75, solid content 75%, Nool) to 100 parts of the base.
After mixing 13 parts of 3%), cellosolve acetate was added for 20 seconds to obtain a viscosity of Ford Cup #4 to form a W-conditioned paint.

Example 1 and Comparative Examples 1 to 3 Polypropylene (manufactured by Sumitomo Chemical Co., Ltd., trade name Noblen H3O1) was injection molded to a size of 70 m x 150 m x 2.5 mm to prepare a test piece.

Two test pieces were degreased and cleaned with chlorocene vapor, and the other two were subjected to low-temperature plasma treatment under the following conditions. .

(7) Equipment (a) Processing conditions Processing gas Oxygen gas pressure 0.5wn/g Output 2 KW Time 20 seconds Air spray the paint of Reference Example 1 on these four test pieces to a film thickness of 20 μm. The coating was coated, and as shown in Table 1 below, it was dried at room temperature (20°C) or dried in an atmosphere containing an amine vapor (conditions below).

Amine used Dimethylethanolamine Amine concentration 1
000 PPM Sowing time: 5 minutes Humidity: 20°C Air flow speed: 1 m 1 secrii Drying Bζ-question and adhesion of B-no'y are shown in Table-1.
As shown in Figure 1, it was proved that the method of this example can form a coating film with good adhesion in a short time without heating.

Table-1 Reference example 2: Production of paint (2) Polyester polyol (manufactured by Dainippon Ink Chemical Co., Ltd., trade name Burnock D-161, solid content 100%, hydroxyl value 1)
70) 7.5 parts of carbon black and 80 parts of a mixed solvent of toluene/edyl carbitol acetate (1:1) were added to 100 parts, and the mixture was dispersed in a hole mill for 12 hours. 0.3 parts of Flow Control IO was added to 99.7 parts of Konomo (7) to prepare a base.・Next, a prepolymer of tolylene diisocyanate (manufactured by Sumitomo Bayer Urethane, trade name Sumidur L-75, solid content 75%, NOo 13%) 52 was added to 100 parts of the base.
Add 20 parts of shunmetogishibbutyl acetate mixed with
The mixture was adjusted to have a viscosity of 1.5 seconds (Ford Oup #4) and used as a room material.

Examples 2 to 4 and Comparative Example 4 Four pieces of polypropylene sample 1, which had been treated with low-humidity plasma as in Example 1, were coated with airs gray from Reference Example 2 to a film thickness of 20μ. It was dried according to the method shown.

All of the obtained specimens reached hardening and drying in 4 to 15 minutes after mounting, and the bud adhesion properties were all 100/100.However, deformation of the test specimens did not occur at all in Examples 2 to 4. On the other hand, in Hiei Example 4, the two test [phase] pieces were warped, and the degree of curvature was as slow as 7M at the extreme end.

Examples 5 to 7 The individual polyolefin resins shown in Table 3 were injection molded in the same manner as in Example 1 to prepare test pieces.

Table 3 These trial pieces were subjected to plasma treatment in the same manner as in Example 1.
When painting and drying in amine vapor, both cases reached hardening and drying within 5 minutes after painting, and the 5d adhesion was LOO
/100. Moreover, no deformation of the test piece was observed.

Patent applicant Shinto Paint Co., Ltd. E, °nu1 Same as Adachi Chibo>, IX +γ・Fn top

Claims (1)

[Claims] 1. After plasma-treating a polyolefin resin molded article, coating it with a paint containing a compound having a free incyanate group in a vehicle and then drying the paint by exposing it to an atmosphere containing amine vapor. A method for coating a polyolefin resin molded article. 2. The coating method according to claim 1, wherein the plasma is a low-temperature plasma generated by exciting chlorine. 3. The coating method according to claim 1, wherein the paint is a two-part polyurethane paint.