GB2099001A - Coating composition comprising acrylic copolymer and chlorinated polyolefin - Google Patents

Abstract

A coating composition suitable for painting onto a polyethylene or polypropylene article comprises by weight:- (a) 100 parts of an acrylic copolymer containing 0.3 to 30 wt.% of an acrylic monomer containing basic nitrogen, e.g. in an amino ester of (meth)acrylic acid, and 99.8 to 30 wt.% of another monomer, (b) 0.5 to 30 parts of an epoxy compound having three or more epoxy radicals, which bridge reacts with copolymer (a), and (c) 1 to 100 parts of a chlorinated polyethylene or polypropylene, of 20 to 40 molar % chlorination. An organic solvent is also included. The composition can be prepared in two solutions containing respectively (i) the component (a) and preferably a pigment, and (ii) components (b) and (c). The composition adheres well. It can be overpainted if desired.

Description

SPECIFICATION Coating composition comprising acrylic copolymer and polyolefin This invention relates to compositions for forming an acrylic copolymer coating on a polyethylene or polypropylene article.

It is often desired to treat a polyethylene or polypropylene article so as to ornament or protect it.

Polyolefins are non-polar (hydrophobic) and it has been necessary to surface treat a polyolefin article, e.g. by flame or chromic acid, to render its surface polar so that an applied coating of a polar substance will adhere thereto. However, such treatments are troublesome and may not be fully effective.

No such surface treatment is needed to ensure adhesion before applying a chlorinated polyolefin or a mixture of cyclic rubber and a petroleum resin. However, such coatings lack resistance to solvents other than alcohols and also have unsatisfactory hardness and weather resistance, and need to be overcoated.

Therefore it has been proposed to coat polypropylene articles with a thermosetting coating material comprising a chlorinated polyolefin and boiled polybutadiene resin, which is heated and dried.

However, such coatings also have poor weather resistance and are difficult to be hardened and pigmented.

We have devised a new coating composition for polyethylene and polypropylene articles which has excellent solvent and weather resistance, long storage life and can be easily applied and hardened.

According to the invention we provide a coating composition, suitable for coating a polyethylene or polypropylene article, which comprises, by weight: (a) 100 parts of an acrylic copolymer having a functional group capable of bridge-reaction with the epoxy component (b) and containing 0.3 to 30 wt.% of an acrylic copolymer containing a basic nitrogen atom, and 30 to 99.8% of copolymerizable monomer(s).

(b) 0.5 to 30 parts by an epoxy compound containing three or more epoxy radicals per molecule, and (c) 1 to 100 parts of a polyethylene or polypropylene which has been chlorinated, to a degree of 20 to 40 molar %, our a copolymer thereof with copolymerizable monomer(s).

Suitable components (a) are acryliccopolymers of hard or soft type, suitable for use respectively in coating of hard or soft polypropylene articles (having respectively high rigidity and heat resistance or cold resistance). These are described in Japanese Laid Open Patent Applications Nos. 76,338/1977, 97,030/1978 and 114,838/1978 and in the two Preparations given below.

The monomer containing basic nitrogen is usually amino compound, and can be, e.g. an amino ester of acrylic and/or methacrylic acid, such as dimethyl or diethyl or tert-butyl aminoethyl acrylate or methacrylate. Examples of the other monomer are styrene, acrylic or methacrylic acid and other esters of these acids such as alkyl esters.

Examples of the epoxy compound are bisphenol A or a glycidyl ether of a polyhydric alcohol, such as of ethylene glycol, propylene glycol, diglycerol or sorbitol. The gram atomic ratio of the basic nitrogen atoms of copolymer (a) to oxygen atoms of the epoxy compound (b) is preferably 0.5 to 3; these atoms react in the bridge copolymerization.

The epoxy compound also should be soluble in any ratio in the chlorinated polyolefin resin (c), and in cooperation with an amino radical of the copolymer (a) protects the chlorinated polyolefin (c) from deterioration due to sunlight or heat and reduces its sol-forming temperature. As the amount of epoxy compound increases, the copolymer (a) becomes more soluble in or miscible with the polyolefin (c), whereby the ease of coating, lustre and flexibility of the coating layer are improved and any adverse effect of the polyolefin (c) is countered.

The degree of chlorination of the polymer (c) is 20 to 40%, especially for isotactic polypropylene, and preferably 20 to 35%. Below 20% the solubility of the polymer is decreased and it tends to become a colloidal solution. The polymer (c) provides adhesion of the coating to the surface of the article to be coated, and the amount of polymer should be selected (within the limits of 1 to 100 parts) to give adequate adhesion but without adversely affecting the ease of coating or the properties of the coating.

Any copolymerizable monomer can be used to make a copolymer therewith.

In use of the composition, chlorinated polyethylene or polypropylene should be selected respectively for a polyethylene or polypropylene substrate.

Suitable solvents for the aforesaid three components are xylene, toluene, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, solvent naphtha, 2-methoxy ethyl acetate and 3-methoxy butyl acetate.

The composition is preferably prepared in two separate solutions respectively (i) the acrylic copolymer (a) and a pigment, and (ii) the epoxy compound (b) and chlorinated polyolefin (c). These two solutions can separately be stably stored, and mixed together just before use, and diluted then with further solvent if necessary. In solution (i) the pigment may be dispersed, not dissolved.

The composition may also include 1 to 50 parts by weight, per 1 00 parts of the acrylic copolymer (a), of a hard resin such as a petroleum resin, natural rosin, a maleic acid or phenolic resin which has been denatured with rosin, ketone resin, xylene resin, ester gum, terpene resin or coumarone-indene resin, in order to improve adhesion, hardness and lustre and weather resistance of the coating.

Other additives such as a pigment dispersing agent, antiflooding agent, precipitation preventing agent, antioxidant, ultraviolet ray absorber and abrasion preventing agent may be added to the solution (i).

The paint composition of the invention, e.g. prepared by mixing the solutions (i) and (ii), may be coated on a polyolefinic article by a coating device such as air spraying device or airless spraying device, and can be dried at a temperature of atmospheric temperature to 100 C. On this coating a conventional final coating may then be formed if desired.

The invention has the following advantages.

Treatment of the polyolefinic resin article before being coated is not required and since the product of the invention has good adhesion to the article a good appearance can be obtained as well as a paint for an ABS resin even though only one coating layer is applied on the polyolefinic resin article.

Also, the coating layer formed by the product of the invention has excellent solvent resistance, weather resistance and distinction. The coating may be dried either at atmospheric temperature or at a temperature of less than 1 000C in accordance with the use of the product This allows inexpensive and light polypropylene to be used in place of metal or other synthetic resin as interiors and exteriors of various equipments such as cars, househould articles, audio instruments, containers, toys and stationery.

The following preparations and examples illustrate the invention.

Preparations 1 and 2-Acrylic Copolymers Parts by weight in Preparation No. 1 No. 2 monomers: dimethylamino ethyl methacrylate 6 10 2-hydroxyethyl methacrylate 6 methyl methacrylate 40 30 styrene 20 20 n-butyl acrylate 20 50 n-butyl methacrylate 14 n-dodecyl mercaptan 1 azo-bis-isobutyronitrile (ABN) 1 1 solvents:: toluene 80 80 isobutanol 20 20 Preparation 7:The specified ingredients were placed in a fiask having a cooler, thermometer and agitator and agitated for two hours at a temperature of 800C, thereafter 0.2 parts of ABN were added five times every two hours. After 1 6 hours polymerization was completed, to produce a solution of acrylic copolymer of hard grade and of glass transition temperature 700 C.

Preparation 2: The above procedure was repeated except that the-addition of ABN was of 0.3 parts three times every two hours, and the polymerization was completed after 12 hours, the resultant soft grade acrylic copolymer had a transition temperature of 300C.

EXAMPLE 1 A first white enamel solution (Solution A) was prepared from the following components: parts Acrylic copolymer from Preparation 1 100 Titanium dioxide (pigment) 50 Antiflooding agent of extender:"Disparlon No.201" 0.3 which were mixed together in a sandmill and then dispersed in a solvent.

Seven samples of a Solution B were prepared by dissolving:- a chlorinated polypropylene (of 30% degree of chlorination, 30% non-volatility and viscosity 1 5 to 30 poise at 250C), sold under the trade name "Haldlen 15 L" by Tokyo Kasei Co., Ltd., Japan, and an epoxy compound (sold under the trade name "Denacol Ex. 412" by Nagase Industries Ltd., Japan, in toluene.

The proportion of the components of these samples of Solution B were varied as shown in Table I below.

Each sample was then mixed with Solution A at a weight ratio of A:B of 2:1, and each resultant mixture, and a control sample (no. 1) of Solution A alone, was diluted with a mixture ofL toluene 40 parts xylene 40 parts cyclohexanone 20 parts in a Ford Cup No. 4 in 1 3 to 1 5 seconds to obtain a desired viscosity suitable for spraying.

Each white coating composition sample was sprayed onto a polypropylene board of size 2.5 x 70 x 150 mm, dried by heating at a temperature of 600C for 20 minutes and kept at room temperature (200C) for 72 hours. Test results are given in Table TABLE I

Sample No. 1 2 3 4 5 6 7 8 Chlorinated Components of polypropylene - 0 100 100 100 100 100 100 Solution B Epoxy cpd. - 10 0 1 5 10 15 20 (parts by wt.) Toluene - 200 100 100 100 100 100 100 Storage stability of SolutionBat-200C * a e e c b b b Properties of sprayed coatings Effectiveness a a c c b-c b b b Appearance a a c c - b a a b 60 mirror surface reflectivity 89 97 50 52 70 78 84 87 Scratching by pencil of hardness B F B B HB F F HB Adhesion: resistance to peeled adhesive tape lattice** e e a a a a a a Adhesion to tin plate on bending test (5 mmi e b e e c a a a Resistance to petroleum spirit for 30 mins. * * e d c a a c Resistance to water at 40"C for 48 hours * * d d a a b b Resistance to light (Sunshine Machine, 200 hours) (i) lustre * * 14 21 50 52 55 55 (ii) change in whiteness * * 3.3 3.0 1.5 1.7 1.5 1.8 (iii) adhesion t * a a a a a a ** cellulose tape applied in lmm square lattice.

In this and subsequent tables, qualities which were visually estimated were graded on the scale: a = good, b = fairly good, c = moderate, d = inferior, e = very bad condition.

* indicates that the property was not measured on that sample.

In Example 1, Samples 4 to 8 were in accordance with the invention.

EXAMPLE 2 Seven samples of a black Solution A of the composition in parts by weight shown in Table 2 were prepared by dispersion in a sand mill, and seven samples of the specified Solution B were prepared. The solutions were mixed in the specified weight ratio and then mixed with further solvent to obtain a desired spraying viscosity.

Each black coating composition sample and two known commercial paints for comparison, each were sprayed onto a board as in Example 1, dried at a temperature of 600C for 30 minutes and kept at 200C for 72 hours. Test results are given in Table II.

TABLE II

Sample No. 1 2 3 4 5 1 6 7 Soln. Acrylic Copolymer from Preparation 1 100 100 100 100 100 100 A from Preparation 2 100 parts Rosin-denatured maleic acid 0 15 15 15 15 0 15 Carbon black (FW-200, Degussa) 4 4 4 4 4 4 4 "Disparlon No. 201" agent 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Toluene 40 40 40 40 40 40 40 Solon. Chlorinated polypropylene "Hadlen" "15L", 300 B chlorination degree 100 100 100 100 parts "17L" 35 chlorination degree 100 "1 it" 23 chlorination 8 degree 100 "CPE-2" 259 chlorination degree 100 Epoxy compound, "Denacol Ex911" 5 "Denacol Ex 421" 10 10 20 10 10 5 10 Toluene 100 100 100 100 100 100 100 Ratio by weight of Soln. A:B 2:1 2:1 4:1 2:1 2:1 2:1 2:1 Sample 8: Paint containing polybutadiene, for one-coat coating of polypropylene, "Micron No. 1050", Cashew Co.

Sample 9: Commercial one-coat paint for polypropylene. TABLE lIA

Sample No. 1 2 3 4 5 6 7 8 9 Nature of Boards coated * A A A A A B C A A Properties of Coatings Appearance a a a a c a a a a 60 mirror surface reflectivity 75 80 92 90 50 85 70 90 65 Scratching by pencil of hardness HB F F F F HB HB F F Resistance immersed for to 30 min a a a a a b a a e petroleum (Rerg. G) immersed for 4 hr c b a-b b a e b d * Moisture coated surface a a a a a a a d b resistance 40"C, 99% RH adhesion b-c a a-b d a a a c b-c 240 hr Resistance coated surface a a a a a a a b b to light light lustre 35 32 40 36 24 45 30 2 10 Sunshine lustre 35 32 40 36 24 45 30 2 10 Heat cycle coated surface a a a a a a a a a -20 x 2 hr +80 x 2 hr adhesion b a b c a a a a a (10 cycles) Boiling coated surface b a a b a a a b d water test, 2 hr adhesion c a b c-d a b b c d Erichsen test (10 mm extruded crack) e e e e e a c e e Shock test 300 g a a a a a a a a a 1/4 50 cm Du Pont Impact 10009 c b c c b b b d b tester * Boards A, B and C are as follows: A polypropylene (K-1016, manufactured by Tisso Sekiyu Kagaku).

B rigid polypropylene (BU-H, manufactured by Mitsubishi Yuka).

C surface flame treated polyethylene board (containing carbon black).

EXAMPLE 3 A polypropylene board ("Showaramer PC-i ", made by Showa Denko) was coated first with the composition of the present invention of Sample 3 of Example 2 as an undercoating layer which was dried at 800C for 30 minutes. Thereupon there was coated, on four respective samples of the board, (1) Japanese lacquer, which forms a very black layer, (2) Paint containing Cashew nut shell liquid and No. 91 black formaldehyde resin, (3) Uniace No.1000 black (polyurethane resin paint manufactured by Cashew), and (4) Cashew Art. No. 200 black (denaturated epoxy resin paint manufactured by the Cashew Co.); the final coatings were dried by heating under the drying conditions indicated in Table III and then dried naturally. After seven days, the quality of the coatings was tested and the test results are given in Table Ill.

TABLE ill

Sample No. 1 2 3 4 Final coating paint (details above) (1) (2) (3) (4) Final drying conditions 20 C 20 C 80 C 80^C 7 days 7 days 30 hr 30 hr Appearance of coating layer a a a a Adhesion against cellulose adhesive tape in 1 mm sq.

lattice a a a a Pencil hardness 2H H 2H 2H (Mitsubishi Uni) 1~ to 2H 60 angle mirror surface reflectivity 99 100 94 80 Resistance coated surface a a a a to water at 40OC for 12 hr adhesion a a a a Resistance coated surface a a a a to moisture, 50C, 99% RH, 96 hr adhesion a a a a Resistance coated surface a a a a to boiling water # adhesion a a a a Temperature coated surface a a a a cycle test adhesion a a a a boiling water for 60 minutes followed by room temperature for 30 minutes, for five cycles.

iX -20"C x 2 hr, and 80 JC r 2 hr., for 10 cycles.

EXAMPLE 4 The three types of board (A), (B), (C) used in Example 2 were coated with one of Samples 2, 4 or 5 of Example 2 and dried as indicated respectively in Table IV. Each board was then further coated under the conditions shown in the table, with one of the following paints as a final coat: (1) Stronace YE-70 White (acrylic resin paint manufactured by Cashew Co.), (2) Stronace YE-80 White (acrylic urethane resin paint manufactured by Cashew Co.), (3) Cashew Coat White phthalic acid resin paint (JISK--5572), and (4) Prepared paint White (JISK--5512).

Test results are indicated in Table IV.

TABLE IV

Sample No 1 2 3 4 5 Undercoat composition (Sample No. of Table II) 2 4 5 5 5 Undercoating method spray spray brush brush brush Coating Undercoating drying 20 C 2000 2000 20'C 20 C conditions conditions 5 min 5 min 72 hr 72 hr 72 hr Final coating paint (see above) (1) (2) (1) (3) (4) Final coating method spray spray brush brush brush Board used A B C C C Appearance of coating layer a a a a a Adhesion (against tape) a a a a a Pencil hardness (Mitsubishi Uni) F F F B B 60 mirror reflectivit) 90 92 90 92 85 Resistance tests:: Petroleum spirit 4 hr at 20 C 16 hr a-b e b d d Engine oil spot 18 hr a c * * Wax remover coated surface a a * * * (ST-7 Yushiro clom) 45-C, 50mm adhesion a a * * * Moisture, coated surface a a b c d 50"C, 99% RH, 1000 hr adhesion a a a a-b a-b Light coated surface a b b c d (sunshine machine), 1000 hrs lustre 48 Z5 45 5 2 color change 1.5 92 1 1.6 5.6 7.8 adhesion a a a a b TABLE IV (Continued)

Sample No. 1 2 3 4 5 High coated surface a a a a a Temperature 800C, 400 hr adhesion a a a a a Heat cycle coated surface a d a a a as Table IIA adhesion a a a a a Bending test tin plate 5cm + 1800C, 1 sec d a c c c Shock test 500 g a a b b b as Table IIA 10009 c a l . *

Claims (9)

1. A coating composition, suitable for coating a polyethylene or polypropylene article, which comprises, by weight: (a) 100 parts of an acrylic copolymer having a functional group capable of bridge-reaction with the epoxy component (b) and containing 0.3 to 30 wt.% of an acrylic monomer containing a basic nitrogen atom, and 30 to 99.8% of copolymerizable monomer(s), (b) 0.5 to 30 parts of an epoxy compound containing three or more epoxy radicals per molecule, and (c) 1 to 100 parts of a polyethylene or polypropylene which has been chlorinated, to a degree of 20 to 40 molar %, or a copolymer thereof with copolymerizable monomer(s).

2. A composition as claimed in Claim 1, wherein the basic nitrogen is present in an amino compound monomer.

3. A composition as claimed in Claim 2, wherein the amino monomer is an amino ester of acrylic and/or methacrylic acid.

4. A composition as claimed in any preceding claim, wherein the monomer copolymerized with the acrylic copolymer is styrene, acrylic or methacrylic acid or an ester of one of these acids.

5. A composition as claimed in any preceding claim, wherein the epoxy compound is bisphenol A or a glycidyl ether of polyhydric alcohol.

6. A composition as claimed in any preceding claim, which also includes 1 to 50 parts by weight, per 100 parts of the acrylic copolymer (a), of a petroleum resin, natural rosin, a maleic acid or phenolic resins which has been denatured with rosin, a ketone resin, xylene resin, ester gum, terpene resin or coumarone indene resin.

7. A composition as claimed in any preceding claim, which is in the form of separate solutions, to be mixed before use, respectively of (i) the acrylic copolymer (a) and (ii) the epoxy compound (b) and chlorinated polyolefin (c).

8. A composition as claimed in Claim 7, wherein a pigment is dissolved or dispersed in solution (i).

9. A coating composition as claimed in Claim 1, substantially as hereinbefore described with reference to any of the samples of the invention of the Examples.

j 0. A method of coating a polyolefin article, which comprises applying thereto a coating of a composition as described in any preceding claim and drying the applied coating.