JP2001262042A - Polyolefin resin coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition showing no coating film discoloring at a high temperature seen in a chlorinated polyolefin resin composition, being in a liquid state different from a conventional non-chlorinated polyolefin resin composition which is in a dispersed or a gel state, and keeping fluidity even if stored at a low temperature. SOLUTION: This coating composition for a polyolefin resin comprises an acid modified noncrystalline polyolefin which is obtained by graft copolymerizing 0.1-10 wt.% α,β-unsaturated carboxylic acid or its derivative to a noncrystalline propylene/butene copolymer having a weight average molecular weight of 5,000-60,000 and at least a hydrocarbon selected from the group consisting of an alicyclic and an aromatic hydrocarbons.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for coating a surface of a molded article of a polyolefin resin such as polypropylene.
Also, the present invention relates to a coating composition used for the purpose of improving adhesion and adhesion when bonding another substrate such as aluminum to a polyolefin resin.

[0002]

BACKGROUND OF THE INVENTION Polyolefin resins such as polypropylene have been used in large quantities in automobile parts and the like because of their excellent properties and low cost. However, unlike synthetic resins having a polarity such as a polyurethane resin, a polyamide resin, an acrylic resin, and a polyester resin, they have a problem that painting and bonding are difficult because they are nonpolar and crystalline.

[0003] In order to solve this problem, conventionally, the surface of a polyolefin resin molded article is activated by plasma treatment or gas flame treatment to improve the adhesion. It has drawbacks that the process is complicated and involves a large amount of equipment cost and time loss, and that the surface treatment effect varies due to the complexity of the shape of the molded article and the influence of pigments and additives.

As a method of coating without such a surface treatment (pretreatment), various methods using a primer composition such as those found in the coating of polypropylene bumpers for automobiles have been proposed (for example, Japanese Patent Publication No. Hei 6-2771). ).

In general, as such a primer composition, a primer composition mainly composed of a chlorinated polyolefin resin obtained by modifying a polyolefin with an unsaturated carboxylic acid and / or an acid anhydride thereof and chlorinating the same is used. (For example, Japanese Patent Publication No. 1-161414). However, these chlorinated polyolefin-based resin compositions are excellent in adhesion, but have problems in weather resistance and heat resistance. For example, under high temperature (150 ° C. or higher), dehydrochlorination proceeds in a short time, and coloring of a coating film occurs. Could happen.

As conventional non-chlorinated polyolefin resin compositions, Japanese Patent Publication No. 61-11250 and Japanese Patent Publication No.
Although a system proposed in JP-A-2-21027 can be mentioned, a system having a crystallinity alone became a dispersed state or a gel state. In addition, the dispersion state loses fluidity during low-temperature storage, so that handling is complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to eliminate the coloring of a coating film due to high temperatures found in a chlorinated polyolefin-based resin composition. An object of the present invention is to provide a coating composition which is present in a solution state, not in a dispersed state or a gel state, and is not lost in fluidity even when stored at a low temperature.

[0008]

The present inventors have made various studies and found that the weight average molecular weight was 5,000 to 60,000.
An acid-modified amorphous polyolefin obtained by graft copolymerizing an α, β-unsaturated carboxylic acid or a derivative thereof to an amorphous propylene-butene copolymer of 0.1 to 10% by weight, and an alicyclic hydrocarbon And a composition containing at least one selected from aromatic hydrocarbons have been found to have excellent properties, and have completed the present invention.

That is, the present invention provides a coating composition for a polyolefin resin as described below. Item 1. Acid-modified amorphous polyolefin obtained by graft copolymerizing an α, β-unsaturated carboxylic acid or a derivative thereof with 0.1 to 10% by weight of an amorphous propylene-butene copolymer having a weight average molecular weight of 5,000 to 60,000. And at least one selected from alicyclic hydrocarbons and aromatic hydrocarbons. Item 2. Item 1 wherein the amorphous propylene-butene copolymer has a propylene component of 55 to 80 mol% and a heat of crystal fusion of 0 to 2 J / g based on thermal analysis by a differential scanning calorimeter. 3. The coating composition for a polyolefin resin according to item 1. Item 3. The solid content concentration of the acid-modified amorphous polyolefin is 1
Item 3. The coating composition for a polyolefin-based resin according to Item 1 or 2, wherein the coating composition is 0 to 50% by weight. Item 4. The solid content concentration of the acid-modified amorphous polyolefin is 1
Item 5. The coating composition for a polyolefin-based resin according to any one of Items 1 to 3, wherein the coating composition is 5 to 30% by weight.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The amorphous propylene-butene copolymer used in the present invention is a binary copolymer of propylene and butene. As butene, 1-butene is preferable. The weight average molecular weight of the amorphous propylene-butene copolymer is 5,000 to 60,000, preferably
000 to 50,000. The weight average molecular weight is GPC
(Gel permeation chromatography).

The proportion of the propylene component in the amorphous propylene-butene copolymer is preferably from 55 to 80 mol%, more preferably from 60 to 70 mol%. When the proportion of the propylene component is less than 55 mol%, the adhesion to the polyolefin tends to decrease.
If it exceeds 0 mol%, the stability of the resulting solution tends to decrease.

The heat of crystal fusion of the amorphous propylene-butene copolymer based on thermal analysis by a differential scanning calorimeter (DSC) is preferably from 0 to 2 J / g. In this case, the crystallinity of the amorphous propylene-butene copolymer by X-ray diffraction is about 0 to 1%. The heat of crystal fusion is more preferably 0 to 1.5 J / g.

An α, β-unsaturated carboxylic acid or a derivative thereof which is graft-copolymerized with an amorphous propylene-butene copolymer refers to α, β-unsaturated carboxylic acid in addition to α, β-unsaturated carboxylic acid. Acid anhydrides and esters, etc.
For example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and citraconic acid, anhydrides of unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride and citraconic anhydride, methyl acrylate ,
Examples include unsaturated carboxylic esters such as methyl methacrylate and dimethyl maleate. Among these, maleic acid, itaconic acid and their acid anhydrides are preferred.
The amount of graft copolymerization is 0.1 to 10% by weight.
It is preferably from 5 to 5% by weight, more preferably from 1 to 3% by weight.

[0014] The graft copolymerization is carried out by a known method. For example, an organic peroxide is added to a molten mixture of the above-mentioned amorphous propylene-butene copolymer and an unsaturated carboxylic acid component, or to a mixed solution using a solvent such as toluene and xylene. The graft copolymerization is preferably carried out under an atmosphere of an inert gas such as nitrogen gas, preferably avoiding air or oxygen. Examples of the organic peroxide include acetylcyclohexylsulfonyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide and the like.

The coating composition for a polyolefin resin of the present invention contains the acid-modified amorphous polyolefin obtained as described above and at least one selected from alicyclic hydrocarbons and aromatic hydrocarbons. Do it.

The alicyclic hydrocarbon used as a solvent in the coating composition of the present invention includes cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, methylethylcyclohexane, and the like.
Examples of the aromatic hydrocarbon include benzene, toluene, xylene, ethylbenzene, isopropylbenzene, and aromatic solvent naphtha. Besides, ethyl acetate,
Ester solvents such as butyl acetate, methyl ethyl ketone,
A ketone solvent such as methyl isobutyl ketone may be used in combination.

The solid content concentration of the acid-modified amorphous polyolefin in the coating composition of the present invention is preferably from 10 to 50% by weight, and more preferably from 15 to 30% by weight, from the viewpoint of solubility and handleability. Is more preferred. With such a solid concentration, the coating composition of the present invention can be in the form of a solution. In particular, the solid content concentration is 30% by weight.
In the following cases, the solution state can be stably maintained even at a low temperature of 5 ° C. or lower.

The coating composition of the present invention can be used by adding and mixing a pigment. As the pigment, inorganic pigments such as carbon black, titanium dioxide, talc, zinc white, and aluminum paste, and organic pigments such as an azo pigment can be used.

[0019]

The coating composition for a polyolefin resin of the present invention exists in a solution state and does not lose its fluidity even when stored at a low temperature. Further, the solubility of the acid-modified amorphous polyolefin used in the present invention in an organic solvent is improved, so that the solid content concentration of the resin in the coating composition can be increased, and it can be applied to a high solid paint.

The coating composition for a polyolefin resin of the present invention has excellent adhesion to polyolefins as well as a conventional chlorinated polyolefin resin composition, and also has good adhesion to polar coating resins. Show. Further, the coating composition for a polyolefin-based resin of the present invention has no coloring of the coating film due to high temperature.

[0021]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Production Example 1 In a 1000 ml autoclave, amorphous propylene
Butene (propylene component 70 mol%, 1-butene component 3
0 mol%, weight average molecular weight of 30,000, heat of crystal fusion of 1.4 J / g based on thermal analysis by a differential scanning calorimeter, crystallinity of 0% by X-ray diffraction) 200 parts by weight were mixed with purified toluene and acetone. Dissolved in 500 parts by weight of a solvent (acetone 5% by weight), added 50 parts by weight of industrial maleic anhydride, heated to 140 ° C., dissolved for 1 hour, and 5 parts by weight of industrial di-t-butyl peroxide Was added. Stirring was continued for 5 hours while maintaining the temperature, and then cooled to room temperature. The obtained resin solution was subjected to acetone 300 as a reprecipitation solvent.
After adding to 0 parts by weight, the precipitated resin was filtered by suction. After drying, the resulting acid-modified amorphous resin had a maleic anhydride modification ratio (graft copolymerization amount) of 1.5% by weight.

Production Example 2 Using the same amorphous propylene-butene copolymer as used in Production Example 1 except that the weight average molecular weight was 50,000, acid-modified amorphous A resin was obtained.
The resulting resin had a maleic anhydride modification ratio (graft copolymerization amount) of 1.0% by weight.

Comparative Production Example 1 A crystalline propylene-butene copolymer (76 mol% of a propylene component, 24 mol% of a 1-butene component, a weight average molecular weight of 125) was used instead of the amorphous propylene-butene copolymer.
An acid-modified resin was obtained in the same manner as in Production Example 1 except that the heat of crystal fusion was 21 J / g based on the thermal analysis of a differential scanning calorimeter and the crystallinity was 25% by X-ray diffraction. The resulting resin had a maleic anhydride modification rate (graft copolymerization amount) of 3.5% by weight.

Comparative Production Example 2 Instead of the amorphous propylene-butene copolymer, a crystalline propylene-butene copolymer (a propylene component of 76 mol%, a 1-butene component of 24 mol%, a weight average molecular weight of 350)
An acid-modified resin was obtained in the same manner as in Production Example 1 except that the heat of crystal fusion was 28 J / g based on the thermal analysis of a differential scanning calorimeter and the crystallinity was 35% by X-ray diffraction. The maleic anhydride modification rate (graft copolymerization amount) of the obtained resin was 1.5% by weight.

Example 1 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in purified toluene to prepare a resin solution having a solid content of 50% by weight. 23 ° C for resin solution
And flowed uniformly.

Example 2 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in purified xylene to prepare a resin solution having a solid content of 40% by weight. 23 ° C for resin solution
And flowed uniformly.

Example 3 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in purified cyclohexane to prepare a resin solution having a solid content of 30% by weight. The resin solution flowed uniformly at 23 ° C.

Example 4 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 2 was dissolved in purified toluene to prepare a resin solution having a solid content of 30% by weight. 23 ° C for resin solution
And flowed uniformly.

Example 5 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in purified toluene to prepare a resin solution having a solid content of 20% by weight.

Example 6 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in a mixed solvent of purified toluene and cyclohexane (mixing weight ratio: 64:16), and the solid content was adjusted to 20. A weight percent resin solution was prepared.

Example 7 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in a mixed solvent of purified toluene and cyclohexane (mixing weight ratio: 40:40), and the solid content was adjusted to 20. A weight percent resin solution was prepared.

Example 8 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in a mixed solvent of purified toluene and cyclohexane (mixing ratio by weight: 16:64), and the solid content was 20%. A weight percent resin solution was prepared.

Example 9 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in purified cyclohexane to prepare a resin solution having a solid content of 20% by weight.

Example 10 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 2 was dissolved in purified ethylcyclohexane to prepare a resin solution having a solid content of 20% by weight.

Example 11 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 2 was dissolved in a mixed solvent of purified toluene and butyl acetate (mixing weight ratio: 75: 5), and the solid content was determined. 20
A weight percent resin solution was prepared.

The solution stability of the resin solutions obtained in Examples 5 to 11 was measured by the following method. [Solution Stability] After each solution was stored at 23 ° C. for 30 days, the fluidity of the solution was confirmed. [Solution stability at low temperature]
After storage at 5 ° C. for 10 days, the fluidity of the solution was confirmed.

The resin solutions obtained in Examples 5 to 11 flowed uniformly at all of 23 ° C., 5 ° C. and -5 ° C.

Comparative Example 1 The maleic anhydride-modified crystalline propylene-butene copolymer obtained in Comparative Production Example 1 was mixed with purified toluene so as to have a solid content of 20% by weight, but was completely dissolved. Did not.

Comparative Example 2 The maleic anhydride-modified crystalline propylene-butene copolymer obtained in Comparative Production Example 1 was mixed with purified cyclohexane so as to have a solid content of 20% by weight, but was completely dissolved. Did not.

Comparative Example 3 The maleic anhydride-modified crystalline propylene-butene copolymer obtained in Comparative Production Example 2 was mixed with purified toluene so as to have a solid content of 20% by weight, but was completely dissolved. Did not.

Test Example 1 The maleic anhydride-modified amorphous propylene-butene copolymer obtained in Production Example 1 was dissolved in purified toluene to prepare a resin solution having a solid content of 20% by weight. The following various properties were evaluated for this resin solution. [Interlayer adhesion] A 20% by weight toluene solution was applied to a polypropylene plate with a bar coater, dried at 80 ° C for 10 minutes, and then a urethane paint for plastic repair (manufactured by Kansai Paint Co., Ltd., trade name: A urethane PG80III (two-pack type urethane paint) was applied and baked at 80 ° C. for 40 minutes to produce a coated piece. Cuts were made on the painted surface of the painted piece with a cutter to make 100 grids reaching the substrate at 1 mm intervals, and a cellophane adhesive tape was adhered thereon and peeled off in a 180 ° direction 10 times. The case where there was no change even after peeling 10 times was scored as 10 points. [Warm water resistance] A coated piece was prepared in the same manner as above,
The coated pieces were immersed in warm water and allowed to stand for 10 days, then pulled up from the warm water, and the appearance of the coating film surface and interlayer adhesion were confirmed. The appearance of the coating film surface was checked for the presence of blisters (swelling of the coating film), and the interlayer adhesion was checked in the same manner as described above. [Gasoline resistance] A coated piece was prepared in the same manner as described above.
The coated piece was immersed in regular gasoline at 0 ° C., and the time (min) until wrinkles (wrinkles) entered the coating film surface was confirmed. It took up to 120 minutes.

The evaluation results were as follows. Regarding the interlayer adhesion, 10 points were obtained in both cases of immersion in hot water and immersion in warm water. No blisters were observed after immersion in warm water.
No wrinkle was observed even after immersion in gasoline for 120 minutes.

For reference, a chlorinated polypropylene resin solution was prepared and various properties were evaluated in the same manner as described above. The same results as above were obtained.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Susumu Ohno 2900 Sone-machi, Takasago-shi, Hyogo Toyo Chemical Industry Co., Ltd. Chemical Term Research Institute F-term (reference) PB07 PC08

Claims (4)

[Claims] (1) a weight average molecular weight of 5,000 to 60,000;
An acid-modified amorphous polyolefin obtained by graft copolymerizing an α, β-unsaturated carboxylic acid or a derivative thereof to an amorphous propylene-butene copolymer of 0.1 to 10% by weight, and an alicyclic hydrocarbon And at least one member selected from aromatic hydrocarbons. 2. An amorphous propylene-butene copolymer,
The coating composition for a polyolefin-based resin according to claim 1, wherein the propylene component is 55 to 80 mol% and the heat of crystal fusion is 0 to 2 J / g based on thermal analysis of a differential scanning calorimeter. . 3. The solid content of the acid-modified amorphous polyolefin is 10 to 50% by weight.
Or the coating composition for a polyolefin resin according to 2. 4. An acid-modified amorphous polyolefin having a solid content concentration of 15 to 30% by weight.
4. The coating composition for a polyolefin-based resin according to any one of items 3 to 3.