CA2011862A1

CA2011862A1 - Coating compositions containing chemically modified amorphous polyolefins, a process for coating plastics with these compositions and the coated plastics produced therefrom

Info

Publication number: CA2011862A1
Application number: CA002011862A
Authority: CA
Inventors: Kirkor Sirinyan; Reinhold Dederichs; John L. Williams
Original assignee: Bayer AG; Mobay Corp
Current assignee: Bayer AG; Bayer Corp
Priority date: 1989-03-21
Filing date: 1990-03-09
Publication date: 1990-09-21
Also published as: JPH02284931A; EP0397974A3; EP0397974A2; DE3909217A1

Abstract

Mo3331 LeA 26,718 COATING COMPOSITIONS CONTAINING CHEMICALLY MODIFIED AMORPHOUS POLYOLEFINS, A PROCESS FOR COATING PLASTICS WITH THESE COMPOSITIONS AND THE COATED PLASTIC
PRODUCED THEREFROM
ABSTRACT OF THE DISCLOSURE

The present invention relates to a coating composition which contains a one- or two-component binder and, in addition, an adhesion promoter which is based on a chemically modified, amorphous polyolefin having an average molecular weight Mw (weight average) in the range from 10,000 to 100,000 g/mol, a non-uniformity Un of 1.0 to 6.5, a chlorine content of about 2.5 to 50% by weight and a total content of nitrogen, oxygen, sulfur and silicon, in the form of chemically incorporated functional groups, of about 2.5 to 15.0% by weight.
The present invention also relates to a process for coating plastic substrates with this coating composition and to the coated plastic substrates obtained in accordance with this process.

Mo3331

Description

~3~L~l~36 Mo3331 LeA 26,718 CQATING ccMæosITqGNs CONTAINTNG CHEM~cPIJJY M~DIFIED AM~RPHOUS pOT,y-OLEFINS, A EROCESS EOR OQAT:~IG PL~STICS WIlff IHESE COMPOSITIONS AND
THE CQ~TED PIASTICS PROWOE3~ I~(~M
-BACKGROUND OF THE INVENTION
Field of the Invention The present invention rela~es to new coating compositions containing chemically modified, amorphous polyolefins, particularly polypropylenes; a process for coating plastic substrates wi~h these coating compositions; and to the lo coated plastics thus obtained.
Description of the Prior Art To apply firmly adhering paint coatings to plastics, particularly to polypropylene tPP) injection-molded parts, the substrate surfaces have to be chemically or physically modified.
5 Reference is made in this regard to flame treatment (cf. for examplP F. Garbassi et al, J. Mater. Sci.~ 22, pages 207 to 212 (1987)), corona treatment (cf. for example F. La~son, Rubber Chem. and Technol., 60, 102 (1987)), plasma treatment (cf. for example L H. Coopes et al, J. Macromol. Chem~, 17, pages 217 to 20 226 (1982) and EP-A-O 282 Q94) and pickling with chromosulfuric acid (cf. for example M. Salkauskas, J. Appl. Polym. Sci., 26, pages 2097 to 2098 (1981)). It is also known from the literature that plastic parts based on polypropylene and polye~hylene can be painted with firmly adhering coatings by the use of primers based on clorinated pol~olefins (US-PS 3 676 391) or polyolefins which are modified with maleic acid anhydride (DE-OS 1 546 982).
These methods are expensive and, in addit~on~ cannot be applied to injection-molded parts of complicated geometry. Apart from the hlgh handling costs attributable to their low solids 30 content, application of the primer coatings mentioned aboYe additionally involves environmental problems. In addition, their use is limited to certain paint systems.
According to publ~shed PCT application WO 88/05346, ~he primer coatings are modified by addit~onal measures, such as UV
35 irradiation, which involves additional expense.
Mo3331 35158q~WR0432 ,, The add;tion of standard chlor;nated polypropylenes, to plastics paints, as recommended in US-PS 27468,480, is attended by the disadvantage that chlorinated polyolefins of this type are not compatible with conventional plastics p~ints. In addition, 5 their solubility in typical paint solvents is very poor~ which adversely affects their processib;lity.
Accord;ngly, the problem addressed by the presen~
;nvention is to provide a new process for painting plastics which, through the use of new adhesions pr~Toters~ is suitable for the 10 production of l~igh-quality coatin~ compositions without being attended by any of the disadvantages of the prior art processes mentioned above.
It was possible to solve this problem ;n accordance with the present invention by ~he use of certain adhesion promoters as described 15 in detail hereinafter.
SUMMARY OF THE INVE_TION
The present inven~ion relates to a coating composition w~ich contains a one- or two-oomponent binder and, in addition an adhesion pro~oter ~hich is based on a chemlcally modified, amorphous 20 polyolef;n having an average molecular weight Mw (weight average) in the range from 10,000 to 100,000 g/mol, a non-uniformity Un of 1.0 to 6.5, a chlorine content of about 2.5 to 50~ by weight and a total content of nitrogen, oxygen, sulfur and silicon, in the for~ of chemically incorporated functional groups~ of about 2.5 25 to 15.0% by weight.
The present invention also relates to a process for coating plastic substrates with this coating composition and to the coated plastic substrates obtained in accordance with this process.

The adhesion promoters crucial b~ the invention are chemically m~dified, chlorine-oontaining amDrph~us poly~lefins, preferably chemically m~dified, amorphous polypropylenes, having an average molecular weight (Mw) detenmined by gel permeation chrom~tography Mo3331 ~ :
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of about 10,000 to 100,000, preferably about 15,000 to 60,000 and more preferably about 17,000 to 40,000 g/mol; a non-uniformity of 1.0 to 6.5, preferably from 1.~ to 4.~; a content of chemically bound chlorine of about 2.5 to 50% by weight, preferably about 15 5 to 40~ by weight and more preferably about 20 to 35~ by weight;
and a total content o~ ni~rogen, oxygen, sulfur and silicon, in the form of functional groups con~aining these elemen~s, of about 2.~ to 15~ by weight, preferably about 2.5 to 7.5% by weigh~.
These functional groups in particular are responsible for the 10 excellent compatibility of the additives according to ~he invention with standard paint systems and for their ready solubility in standard paint solvents. In addition, these functional groups provide for good physical fixing of the additive in the paint matrix.
Sui-table functional groups include carboxyl, carboxylic anhydride, carboxylic acid ester, carboxylic acid amide, amino, carboxylic acid imide, aldehyde, ketone, sulfonic acid ester, hydroxyl, hydroperoxide and alkoxysilane groups; heterocyclic groups such as imidazole~ carbazole or pyridinyl groups;
20 activated double bonds such as vinylsulfonyl or vinylam;no groups; and lastly mercapto groups. Particularly su;table functional groups are hydroxyl, hydroperoxide (H-0-0-) carboxyl9 carboxylic anhydride, carboxylic acid amide, carboxylic acid imide, carboxylic acid ester, amino and alkoxysilane groups, 25 preferably trimethoxysilane yroups.
The above-mentioned functional groups which are suitable should not enter into any reactions either among themselves or with the paint components w1th which they are blended under typical storage conditîons, i.e. in the presence of atmospheric 30 moisturel oxygen and elevated temperatures of up to 120C.
Preferred starting materials for the production of the chemically modified adhesion prcmDters ar~ amorphcus polypropylenes or polyethylenes having a molecular weight in the range from 10,000 to 120,000 glmol and a non-un~formlty of 1.0 to 7.5. However, it Mo3331 :
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2 ~3~L~36 is also possible to use as "polyolefins" the corresponding amorphous copolymers of propylene with other olefinically unsaturated monomers, such as ethylene, isoprene, 192-butadiene and/or 1,4-butadiene, in positive amoun~s of up to 25% by weight, 5 based on the weight of all the monomers.
Chlorine is introduced in known manner by chlor;nation of the amorphous polyolefins used as s~arting material (cf. Houben-Weyl, Methoden der Organischen Chemie, Vol. V/3, pages 511-551, Georg Thieme Yerlag, Stuttgart (1962)). For the 10 product;on of the additives according to ~he invention, the chlorination is carried out at temperatures of about -10C to the boiling point of the particular solvent used.
The functional groups may be incorporated by reaction with typical peroxides (incorporation of hydroperoxide or 15 carboxyl groups) or by a radically initiated grafting reactions with monomers containing ~unctional groups according to the invention. Suitable initiators for this grafting reaction are any of the peroxides or azo compounds which are known for this purpose. The modification reactions are also known and are 20 described, for example, in the following literature references:
G.A. Russel, J. Am. Chem. Soc., 79, 3871 (1957); M. Iring et al, Polymer Degradat;on and Stability, 5, 467 (1983); N.6. Gaylord, Journal of Polymer Science, Polymer Letters Edition, ~ol. 21, 23-30 (1983); A. Neyishi et al, ~. of Appl. Poly. Sci. 22, 2953 25 (1978); and A. Hoff, J. of Appl. Poly. Sci.~ 29, 465 (1984).
Suitable initiators include potassium penoxodisulfate, azo-bis-lsobutyronitrile, t-butyl perbenzoate, t-amyl perneodecanoatel p-benzodines, t-butyl perisononanoate, di-2-ethylhexyl peroxydicarbonate or di-n-butyl 30 peroxydicarbonate.
Suitable monomers contalning functional groups include allylamine; allyl alcohol; trimethoxy vinyl silane; triethoxy Yinyl silane; ethyl allyl ether; cyclohex-1-ene-4-dicarboxylic anhydride; maleic anhydride; maleic acld dimethyl, diethyl, Mo3331 .
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, ~ 3L8 dipropyl and dibutyl ester and acid am;des thereof (such as maleic acid d;methyl amide, etc.); n-alkyl maleic acid imides (such as n propyl maleic acid imide or n-butyl maleic acid imide); fumaric acid; fumaric acid dimethyl, diethyl, dipropyl 5 and dibutyl ester and acid imides or amides thereof;

3-trimethoxysilyl-1-chloropropane; N-[2-(trimethoxysilyl~-ethyl]-ethylene-diamine; 3-trimethoxysilyl-1-chloropropane, mercapto-ethyl, mercaptopropyl and ~ercaptobutyl trimethoxy and ~riethoxy silane; vinylene carbonate, vinyl sulfone; 3-trimethoxy-silyl 10 propyl-l-imidazole; and carbazole. Suitable monomers include those which generally do not react with the polyolefins to form block copolymers.
Functional groups may be incorpora~ed ei~her 1~ in the melt by extrusion or other standard injection-molding techniques 15 at temperatures in the range from approximately 140C to 300C, but preferably at temperatures above the melting range of the particular polyolefins used (cf. G.M. Gale, Applied Organometallic Chemistry, 2, pages 17-31 (1988)) or 2) in a suitable solvent (cf. DE-OS 1 546 982). For the incorporation of 20 functional groups in solution, the grafting reaction is generally carried ou~ at elevated temperatures of approxima~ely 40C up to the boiling point of the particular solvent. Suitable solvents include xylene, carbon tetrachlor~de, ~oluene, chlorobenzene~
tetralin, cresol and mixtures of these solven~s.
The sequence of the reactions (chlorination and incorporation of the functional groups) is not oritical.
The additives, which are critical to the invention, are preferably used in solvent-c:onta~nlng coating compositions in quantities of about 0.1 to 15% by weight, 30 preferably about 1 to 10% by we~ght and more preferably about 2 to 5% by weight, based on the weight of the solvent-free binder.
Suitable coating compositions include those containing one- or two-component polyurethane systems, alkyd res~ns~
melamine resins, saturated or unsaturated polyester resins, Mo3331 ,. ~ .~ .

nitrocellulose, rubbers or polyamide resins as binders. These coating compositions are preferably solvent-based paints containing the known paint solvents such as butyl acetate, methyl ethyl ketone, methyl ;sobutyl ketone, methoxypropyl acetate, 5 toluene9 xylene and mixtures of these solvents. However, it is also pnssible to use low-solvent, solventless or aqueous coa~ing compos;tions in which the primers crucial to the invention are present in the quantities mentioned above. Suitable coating compositions are described, for example, ln H. Kittel9 10 Lehrbuch der Lacke und Beschichtungen, Yol. IY, pages 76 to 3069 Yerlag W.A. Cclomb (1~86) or in the same textbook, 1976 Edition9 Vol. IV, pages 328 to 358.
Preferred coating compositions are one-component and, in particular, two-component polyurethane systems.
Preferred one-component polyurethane coating compositions are those based on predominantly linear, fully reacted polyurethanes which are soluble in organic paint solvents of the type previously mentioned and which no longer contain reactive centers, i.e., which dry physically ~cf. for example9 20 Kunststoff-Handbuch, Vol 79 "Polyurethane," edited by Gunter Oertel, Carl Hanser Verlag, Munchen/Wien (1983) page 551).
Suitable physically drying lacquers of this type include those wherein the binders are based on a fully reacted linear polyurethane prepared from (i~ a polyester diol, (ii) a 25 chain-extending agent and (iii) a diisocyanate. Sui~able polyester diols (i) for the production of such polyurethanes include adipic acid/alkanediol/polyester diols having molecular weights of about 600 to 3,000. The alkanediols include 1,4-butanediol, 1,6-hexanediol, neopentyl glycol or mixtures of 30 such glycols. Suitable chain-extending agents (ii) include diols of the type used for the production of the polyester diols and also diamines, such as hexamethylenediamine or isophoronediamine Suitable diisocyanates (iii) include 4,4'-diisocyanatodiphenyl methane or isophorone di~socyanate~ The polyurethanes are Mo3331 .

;~3~L~L8 6 produced in known manner by reacting the starting materials at an equivalent ratio of isocyanate groups to isocyanate-reactive ~roups of about 0.9:1 to 1.1:1.
The particularly preferred ~wo-componen~ polyurethane 5 paints are those wherein the binder ;s a two-component polyurethane system of ~he type described, for example~ nn pages 541 to 544 of "Polyurethane," (cited in the preceding paragraph). The two-component binders of ~hese lacquers are generally based on a polyisocyanate component and a polyol 10 component; these components are presen~ in quankities which correspond to an equivalent ratio of NCO:OH of about 0.5:1 to 2:1, preferably about 0.8:1 ~o 1.5:1. Suitable polyisocyanates include the known paint-quality polyisocyanates, for example, biuret-, isocyanurate- or urethane-modified derivatives of simple 15 diisocyanates such as 2,4-diisocyanatotoluene or mixtures thereof with 2,6-diisocyanatotoluene and, tn particular, 1,6~diiso-cyanatohexane. The derivatives mentioned generally contain about 10 ~o 25% by weight o~ isocyanate groups.
Preferred polyols are polyester polyols, polyether 20 polyols and polyacrylate polyols. The polyester polyols have a molecular weight (Mn) of 500 to 5,000 and contain at least 2, preferably 2 to 6 hydroxyl groups per molecule. The polyether polyols have a molecular weight (Mn) of about 500 to 5~000 and contain from 2 ~o 3 hydroxyl groups per molecule. The acrylate 25 polyols have a molecular weight (Mn) of about 500 to 5,000 and contain 1 to 12% by weight of hydroxyl groups.
To increase their compatibility with paint solvents, neutral, cationic or anionic surfactants may also be added to the primers according to the invention. ~he surfactants are used in 30 quantities of about 0.1 to 2.5% by weight, preferably about 0.1 to 1.0% by weight, based on the total solids content of the coattng compositions. Preferred surfactants are neutral oligomeric or polymer1c compounds based on ethoxylated alkanols containing 5 to 18, pre~erably 5 to 15 carbon atoms tn the alkyl Mo3331 . ., ~ ..
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2~a~L~3~i 2 radical of the alcohol and having a degree o~ ethoxylation of 1 to 40. Other suitable surfactants include ammonium salts of oleic acid such as the diethyl ammonium sal~ of maleic acid;
alkali alkyl sulfona~es particularly sodium alkyl sulfonates 5 containing 5 to l8 carbon atoms in the alkyl radical; alkali, preferably sodium, salts of alkyl benzenesulfonic acids containing 5 to 18 carbon atoms in the alkyl radical, dibutyl naphthelenesulfonates; lauryl alcoho7 sul~ate; and dioctyl glycerol ether sulfate.
The coating compositions used may also contain other auxiliaries and additives such as catalys~s, pigments, the previously mentioned solvents, flow control agents, fillers, etc.
When they are used in two-component polyurethane coating composition~, the auxiliaries and additives, particularly the adhesio~
15 prcmoters according to the invention, are generally added to the polyol component.
The coating compositions containing the aahesion promoters according to the invention are eminently suitable for coating thermoplastics or thermosets of various types. They are 20 particularly suitable for coating polyolefins having a surface tension of at least 35 mN/m which are often difficult to paint with firmly adhering coatings. These polyolefins include modified and unmodified, partly crystalline or amorphous polypropylenes and polyethylenes. Polypropylene moldings are 25 particularly pr~ferred substrates for the coating compositions according to the invention. Other examples of suitable substrates include polyvinylidene ~luoride, polytetrafluoro-ethylene, ethylene-propylene-norbornadiene plastics, acrylonltrile-butadiene-styrene copolymers, polycarbonates, 30 polyamide plastics, polyesters, polybutadienes, polysilicones and cellulose esters.
The coating ccmpositions oontaining the adhesion pr~Dters which are critical bo the present invention, are generally applied in a dky film thickness of about 0.5 bo 100 ~m, preferably from 20 to Mo3331 ' . ' '~ - .

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~3~L~L~36 50 ~m by any of the methods used for painting plastics. In the case of multicoat painting, the base coat naturally contains the additive crucial to the invention. While the use of the same or analogous additives in the other paint coats is optional, 5 improved intermediate paint adhesion can be obtained in this way.
In this case, the primers are added in the quantities indicated above, even to those paint coats which do not come into direct contact with the plastics material to be painted.
The plastics painted in accordance with ~he invention 10 may be used for various everyday applications, including ~or example the interiors and exteriors of automobiles, electrical and electronic appliances and domestic appliances of various kinds.
The invention is further illustrated but is not intended 15 to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.
EXAMPLES
Example 1 100 9 amorphous polypropylene having an average 20 molecular weight ~ of 60,000 g/mol were dissolved in 2000 9 carbon tetrachloride. 12 9 trimethoxy vinyl silane and 1 9 t-butyl perbenzoate were then added dropwise to the resulting solution under nitrogen oYer a period of 1 hour a~ 70C. The solution was cooled to 10C and pure chlorine was introduced with continuous UY irradiation until the weight increased by 48 9. The modified polymer was then precipitated in 5,000 9 ethanol 9 washed 5 times with pure e~hanol and dried overnight. An additlve having an average molecular weight of approximately 40,000 g/mol was obtained. It contained 30 ~% by weight oxygen, 2.2X by weight silicon and 30% by weight chlorine. It was soluble in xylene, toluene, butyl asetate, etc.
and was distinguished by its excellent compatib1lity with typical solvents for plastics paints.

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A 100 x 100 ~m, commercially available modified polypropylene sheet (Hostalen PPN 8018, Hoechs~ AG) was discharged and ~reed from dust particles by blowing with ionized air and then spray-coated with a two-component polyurethane 5 coating composition.
Component I of the coating composit1On was based on a mixture of 100 parts by weight o~ a polyacrylate resin containing hydroxyl groups; hydroxyl group content 2.8% by weight tDesmophen A 365, a 10 product of Bayer AG), 20 parts by weight of a 25% by weight solution of the above-mentioned additive in xylene, 49.3 parts by weight talcum~
3.2 parts by weight black pigment (carbon black), 15 65.6 parts by weight titanium dioxide pigment ~rutile), 4.8 parts by wei~ht of a 10% solution in xylene of a commercially available antisettling agent (Bentone, a product of Kronos Titan GmbH, D-5090 Leverkusen~ and 155 parts by weight of a solvent mix~ure of butyl acetate and 20 xylene in a ratio by weight of 1:1.
Component II of the coating composition was based on a 75% solution in 1-methoxypropyl-2-acetate/xylene t 1:1 ) of a biuret polyisocyanate based on 1,6-diisocyanatohexane; NC0 content of the solution 16.5~ by weight (Desmodur N 759 a product 25 of Bayer AG).
After application, the coating composition was aired for 10 minutes and dried at 70C.
The coat~ng obtained was characterized by a paint adhesion accordin~ to DIN 53 151 of Gt 0 (Gt crosshatch).
30 Com~ar~
When Example 1 was repeated without the critical additivè accordin9 to the present invention results, the result~ng coating had an adhesion value according to DIN 53 151 of Gt 5. The coating was easy to remove from the substrate 35 surface.
Mo3331 ..
- .,, ~ . . . ,. i ,., Example 2 A 100 x 100 mm, carbon black-filled and glass fiber-reinforced polypropylene sheet (Hoechst AG) was provided with a coating as in Example 1.
A coate~ sheet characterized by excellent adhesion of the coating was obtained. The coating had an adhesion value according to DIN 53 151 of Gt 0 and easily passed both the weathering text (DIN 50017-KK) and the alternating temperature test(AS~ D1211 Conparison EY~ample 2 Exampl~ 2 was repeated without the cr~tical additive according to the present invention. The coating had an adhesion value of Gt 5. The coating was easy to remove from the substrate surface.
Example 3 100 9 amorphous polypropylene having an average molecular weight Mw of 100,000 g/mol were dissolved in 2,000 9 carbon tetrachloride. 5 9 azo-bis-isobutyronitrile in 100 ml carbon tetrachloride were then added dropwise to the resulting solution over a period of 120 minutes, followed by stirring for 20 3 hours at 75C. Chlorine gas was then introduced into the solution with UV irradiation over a period of 60 minutes at 0C;
the weight of the polypropylene increased by 21.8 9. The carbon tetrachloride was then replaced by pure xylene. A clear polymer solution was obtained. The solution had a solids conten~ of 25 25 by weight. The modified polypropylene had an oxygen content of 3.5% by weight in the form of hydroxyl, hydroperoxy9 carboxyl and chlorocarbonyl groups and, in addition, contained 17.5% by weight chemically-bound chlorine.
A 100 x 100 cm polypropylene sheet was pressure-coated 30 with a two-component polyurethane coating composition in a dry film thickness of about lS ~m.
Component I of the coating composition was based on a mixture of Mo3331 ,: :

~ L~L~3~2 100 parts by weight of a polyester polyol having a hydroxyl group content of 2.7% (Desmophen A 565, a produc~ of Bayer AG), 10 parts by weight of the above-mentioned solution of the additive to the invention, 5 50 parts by weight talcum9 3~7 parts by weight black pigment, 65.6 parts by weight titanium dioxide pigment (ru~ile) and 4.8 parts by weight of the solution of the anti-settling agent described in Example 1.
Compone~t II of the coating composi~ion was based on 40 par~s by weight of the solution of a biuret polyisocyanate described in Example l.
After airing and drying as described in Example 1, a coating having a paint adhesion of Gt O was obtained.
Further investigations demonstrated that the additive used does not adversely affect ~he properties of paint component I e~en after storage for several months. The pot life of the coating composition also remained unchanged.
Comparison Example 3 When Example 3 was repeated without the critical additive according to the present invention, a paint adhesion of Gt 5 was obtained.
Example 4 100 9 amorphous polypropylene having an average 25 molecular weigh~ of 40,000 g/mol was modified with N-~2-(trimethoxysilyl)-ethyl]-ethylenediamine in accordance with G.M. Gale, Applied Organometallic Chemistry, 2, 17 (1988). 3 9 dir2-ethylhexyl peroxydicarbonate in 50 9 carbon tetrachloride was then added under nitrogen to the modified polypropylene at a 30 temperature of 70C, followed by chlorinat~on at 0C under UY
irradiation. The modified polymer was precipitated in ethanol and dried under vacuum overnight at 80C. The additive obta~ned had an average molecular weight of 22~000 g/mol and a nitrogen content of 1.4% by welght? an oxygen content of 4.5X by weight, a Mo3331 .. . .

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13 ~ L~8 silicon content of 1.4% by weight and a chlorine content of 24.8%
by weight. It was soluble both in polar solvents, such as butyl acetate, and apolar solvents and was distinguished by high compatibility and miscibili~y with known coating compositions.
A two-component polyurethane coating compositio~ was prepared as in Example 1 with the exception tha~ 3.5% by weight of the addi~ive described above was used instead of the add;~ive used in Example 1. A coating was prepared in accordance w;th the process described in Example 1 (coating of a polypropylene 10 sheet). The coating had a paint adhesion of Gt 0.
Example S
50 9 amorphous polypropylene having an average molecular weight of 30,000 g/mol were dissolved in 1000 ~ ~oluene. 7.5 9 allylamine in 75 9 ~oluene and 1.0 g t-amyl perneodecanoate in 15 50 9 toluene were then added dropwise under nitrogen to the resulting solution over a period of 2 hours at 80C. The solvent was then removed from the polymer under vacuum. The polymer was dissolved in 250 9 carbon tetrachloride and chlorinated at 0C by UV irradia~ion.
A modified polymer containing 3% by weight nitrogen, 2%
by weight oxygen and 18% by weight chlorine was obtained. The modified polymer was readily soluble in coa~ing compositions and solvents therefor.
A two-component polyurethane coating composition was 25 prepared as in Example 1 with the except;on that 2~ by weight of the additive described above was used instead of the additive used in Example 1. A coating was prepared ;n accordance with the process described ~n Example 1 (coating of a polypropylene sheet). The coating had a paint adhesion of Gt 0.
30 ~
Amorphous polypropylene (250 9) havlng an average molecular weight of 90,000 g/~l was ~fie~ with maleic acid anhydride in accordance with the N.G. Gaylord, J.Pol~qn.Sci. ,Polym.J.eet.Ed. 9 21, pages 23-30 (1983)~ dissolved in 5000 9 carbon tetrachloride, Mo3331 chlorinated under nitrogen with UV irradiation and then precipitated in ethanol. A polypropylene containing 0 0 and Il 11 -C -O-C --CH2-0-OH- groups with an oxygen content of ~.8% by weight, a 5 chlorine content of 10% by weight and average molecular weight of 40,000 g/mol was obtained.
A two-component polyurethane coating composition was prepare~ as in Example 1 with the excep~ion that a 25% by solution of the additive described above was used instead of the additive used in Example 1. A coating was prepared in accordance with the process described in Example 1 (coating of a polypropylene sheet3. The coating had a paint adhesion of Gt 0.
Example 7 A polypropylene sheet was coated in accordance with the process of Example 1 with an elastic two-component polyurethane coating composition in a dry film thickness of about 20 um.
Component I of the elastic paint was based on a mixture of 15.1 parts by weight of a polyester resin con~aining hydroxyl groups; hydroxyl group content 4.3% by weigh~ tDesmophen 670, a product of Bayer AG), 18.5 parts by weigh~ of a polyacryla~e resin containing hydroxyl groups; hydroxyl group content 2.8~ by weight (Desmophen A 365, a product of Bayer AG), ~5 0.8 part by weight of a 10% solution of 1,4-dia~ab~cyclo-(2,2,2)-octane in butyl acetate~
3.8 parts by weight UV stabilizer (Tinuvin 292, a product of Ciba-Geigy AG), 10% solution in xylene, 22.8 parts by weight TiO2 ~Bayertitan R-KB 4, a product of Bayer AG), 3.$ parts by weight of a 10X solution in xylene of a com~ercially available antl-settling agent (Bentone, a product of Kronos Titan GmbH) and Mo3331 , ~ .'' . ~
, 2 ~L3~8 ~?, 16.6 parts by weight of a 30% by weight solution in xylene of the additive mentioned in Example 1.
Component II of the coating composition was based on a 75% solution in l-methoxypropyl-2-acetate/xylene (1:1) of a 5 biuret polyisocyanate (Desmodur N 75, a product of Bayer AG, cf.
Example 1).
After application, the coating composition was aired for 20 minutes and dried at 80C.
An optically satisfactory transparent coating having a 10 paint adhesion ~ccording to DIN 53 151 of Gt 0 was obtained.
Although the invention has been descr~bed in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art 15 without departing from the spirit and scope of the ;nvention except as it may be limited by the claims.

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Claims

1. A coating composition which comprises a one- or two-component binder and, in addition, an adhesion promoter comprising a chemically modified, amorphous polyolefin having an average molecular weight (Mw) of about 10,000 to 100,000 g/mol, a non-uniformity Un of 1.0 to 6.5, a chlorine content of 2.5 to 50%
by weight and a total content of nitrogen, oxygen, sulfur and silicon, in the form of chemically incorporated functional groups, of about 2.5 to 15.0% by weight.

2. The coating composition of Claim l wherein said chemically modified, amorphous polyolefin comprises chemically modified, amorphous polypropylene.

3. The coating composition of Claim 1 wherein said binder comprises a two-component polyurethane.

4. The coating composition of Claim 2 wherein said binder comprises a two-component polyurethane.

5. A process for coating a plastic substrate which comprises applying to said plastic substrate a coating composition which comprises a one- or two-component binder and, in addition, an adhesion promoter comprising a chemically modified, amorphous polyolefin having an average molecular weight (Mw) of about 10,000 to 100,000 g/mol, a non-uniformity Un of 1.0 to 6.5, a chlorine content of 2.5 to 50% by weight and a total content of nitrogen, oxygen, sulfur and silicon, in the form of chemically incorporated functional groups, of about 2.5 to 15.0% by weight.

6. The process of Claim 5 wherein said chemically modified, amorphous polyolefin comprises chemically modified, amorphous polypropylene.

7. The process of Claim 5 wherein said binder comprises a two-component polyurethane.

8. The process of Claim 6 wherein said binder comprises a two-component polyurethane.

9. The process of Claim 5 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.
Mo3331

10. The process of Claim 6 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.

11. The process of Claim 7 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.

12. The process of Claim 8 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.

13. A coated plastic substrate which is prepared by a process which comprises applying to a plastic substrate a coating composition which comprises a one- or two-component binder and, in addition, an adhesion promoter comprising a chemically modified, amorphous polyolefin having an average molecular weight (Mw) of about 10,000 to 100,000 g/mol, a non-uniformity Un of 1.0 to 6.5, a chlorine content of 2.5 to 50% by weight and a total content of nitrogen, oxygen, sulfur and silicon, in the form of chemically incorporated functional groups, of about 2.5 to 15.0% by weight.

14. The coated plastic substrate of Claim 13 wherein said chemically modified, amorphous polyolefin comprises chemically modified, amorphous polypropylene.

15. The coated plastic substrate of Claim 13 wherein said binder comprises a two-component polyurethane.

16. The coated plastic substrate of Claim 14 wherein said binder comprises a two-component polyurethane.

17. The coated plastic substrate of Claim 13 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.

18. The coated plastic substrate of Claim 14 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.

19. The coated plastic substrate of Claim 15 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.

Mo3331

20. The coated plastic substrate of Claim 16 wherein said plastic substrate is amorphous or partly crystalline polypropylene or polyethylene.

Mo3331