AU669297B2 - Process for the preparation of copolymers containing OH-groups, and their use in high-solids coating compositions - Google Patents

Abstract

Copolymers comprising from 5 to 50 % by weight of one or more glycidyl esters of saturated aliphatic C4-C30-monocarboxylic acids containing a tertiary or quaternary alpha -carbon atom and from 95 to 5 % by weight of at least two olefinically unsaturated, copolymerisable monomers, of which at least one contains at least one carboxyl group. The copolymers are characterised by an OH number of from 50 to 250 mg of KOH/g, a solution viscosity of from 15 to 2000 mPa s (50 % strength solution at 23 DEG C), a mean molecular weight (weight average Mw) of less than 8600 g/mol and a nonuniformity of less than 3.4. The copolymers according to the invention are particularly suitable as binder components for high-solids coating compositions.

Description

V10031cll 1 AU

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: PROCESS FOR THE PREPARATION OF COPOLYMERS CONTAINING OH-GROUPS, AND THEIR USE IN HIGH-SOLIDS COATING

COMPOSITIONS

The following statement is a full description of this invention, including the best method of performing it known to us 1 PPOCESS FOR THE PREPARATION OF COPOLYMERS CONTAINING OH- GROUPS, AND THEIR USE IN HIGH-SOLIDS COATING COMPOSITIONS Background of the Invention The present invention relates to copolymers for use in high-solids coating composition, and to a process for preparation of such copolymers.

An advantage of high-solids acrylate resins coating formulations is that they have a reduced emission of organic compounds when the coating material is applied.

In order to obtain these high-solids coating formulations it is necessary to employ appropriate acrylate resins having low viscosities, low molar masses, and having narrow molar mass distributions.

It is well known that in order to prepare lowviscosity polymers it is possible to employ free-radical solution polyrrerization. See EP 408,858, EP 398,387, and U.S. Patent 4,145,513. The disadvantage of this process is that the properties of the polymers are adversely affected by use during the process of considerable 20 quantities of polymerization initiators and polymerization regulators. In addition, the production of secondary products, some of which are not inuorporated into the polymer chain is disadvantageous. Also, the polymerization regulators used, for example, thiols, can have a foul odor or may even be toxic.

The polymers obtained by free-radical solution polymerization at high pressure and/or at high temperature in high-boiling solvents do not have these disadvantages but, because of their inadequate molar masses, they have glass transition temperatures which are too low to permit their use as binders for coating. This becomes evident in the coatings by these materials having dust-dry times and tack-free drying times which may be of indeterminate length. In addition, some systems have a processing time which is inadequate for commercial application.

1 on the other hand, bulk polymcrization is also known. The great advantage of a bulk polymerization is that only monomer, polymer and initiator are present in the reaction mixture with the consequence that highly pure, solvent-free products are formed. In practice, examples of such bulk polymerization are few, because the liberation of very large quantities of heat in a short reaction time means that the polymerization is difficult to control.

EP 0 027 931 describes such a process for the preparation of low-viscosity copolymers, containing OH groups, by free-radical reaction of from 10 to 30% by weight of glycidyl esters, containing 12 to 14 carbon atoms, of aliphatic saturated monocarboxylic acids having 15 a tertiary or quaternary a carbon atom and from 90 to 70% by weight of at least two unsaturated copolymerizable monomers, at least one of which contains at least one COOH group.

The process comprises initially charging component 20 and reacting it, at 130 to 200 0 C, with component (B) and a free-radical initiator by bulk polymerization until a degree of conversion of at least 95%, preferably at least 98%, has been reached, component containing at least 3.3% by weight of a monomer containing COOH groups.

25 The principal advantage of this process is in the efficient and rapid dissipation of the heat of reaction, during the reaction, by employing component as initial charge. Component the glycidyl ester, acts initially as a solvent and is incorporated completely into the copolymerization product during the reaction, so that no troublesome unreacted components remain present in the end product.

Most organic peroxides, especially those derived from tertiary t-butyl hydroperoxides and used in the examples of the above-mentioned patent, have a very high reactivity which results from the corresponding radicals.

The free radicals derived from hydroperoxides of the t-butyl type, especially di-t-butyl peroxide, are able to abstract hydrogen from the acrylate polymer, which may 3 leod to instances of branching and therefore to a broadening or multimodality in the molar mass distribution. This is observed for the products in EP 0 027 931. By this process the solution viscosities of the products are increased. These effects occur preferentially in interaction with the solvents and solvent mixtures which are conventionally used.

It is known that, in solution polymerizations, highsolids acrylate polymers of monomodally narrow distribution can be prepared by using organic peroxides which are derived from t-amyl hydroperoxide Kamath and J.D. Sargent Jr., Paintindia 41 17-22 (Eng.) 1991; P.A. Callais, V.R. Kamath and M.G. Moskal, "Proc.

Water-Borne, Higher-Solids, Powder Coat. Symp." (New Orleans), 19th, 156-70 (Eng.) 1992]. However, there is no indication that acrylate polymers of this kind can be prepared with this initiator system even without the presence of a solvent.

Summary of the Invention 20 Therefore, an object of the present invention is to provide a bulk copolymerization process which provides solvent-free, low-viscosity acrylate resin polymers of monomodally narrow distribution, which can be carried out within a broad temperature range. It is also an object of the invention to provide a copolymer having these desired properties and coating compositions containing these desired copolymers.

In accordance with these objects, there has been provided a copolymer having an OH number of from 50 to 250mg KOH/g, a solution viscosity (50% strength, 23 0 C) of to 2000 mPa.s, a weight average molar mass M w of less than 8600 g/mol and a polydispersity of less than 3.4.

In accordance with a second aspect of the invention, there has been provided a copolymer of one or more glycidyl esters of saturated aliphatic monocarboxylic acids having a tertiary or quaternary a carbon atom, and

Y

4 at least two unsaturated copolymerizable monomers, one of which at least contains at least one COOH group wherein the polymer has a low viscosity in solution and a monomodal, narrow molar mass distribution.

In accordance with a third aspect of the present invention, there has been provided a copolymer of from 5 to 50% by weight of one or more glycidyl esters of saturated aliphatic monocarboxylic acids having a tertiary or quaternary a carbon atom which acids contain from 4 to 30 carbon atoms, and from 95 to 50% by weight of at least two unsaturated copolymerizable monomers, one of 15 which at least contains at least one COOH group.

In accordance with another aspect of the present invention there has been provided a process for producing a copolymer as set forth above, comprising the freeradical reaction in bulk of components and In accordance with another aspect of the present invention, there has been provided coating compositions comprising a copolymer as described above and a substrate coated with such a composition.

Further objects, features, and advantages of the present invention will become apparent from the detailed description of preferred embodiments which follows.

Detailed Description of the Preferred Embodiments The invention relates to acrylate copolymers which have a low viscosity in solution and have a monomodal, narrow molar mass distribution. By a low viscosity is meant a viscosity of less than 2 Pa.s, measured on a 50 strength solution at 23 °C and by a monomodal, narrow molar mass distribution is meant a polydispersity of less than 3.4. The copolymers generally have an OH number of from 50 to 250 mg of KOH/g, a low solution viscosity of from 15 to 2000 mPa.s (50% strength, 23 0 a weight

M

5 average molar mass M w of less than 8600 g/mol and a polydispersity Mw/Mn [weight-average molar mass over number-average molar mass] of less than 3.4. By means of the process described herein, such copolymers are obtainable for the first time.

These low-viscosity, uniform, OH group-containing copolymers of monomodally narrow distribution can be prepared by the free-radical reaction of one or more glycidyl esters of saturated aliphatic monocarboxylic acids containing a tertiary or quaternary a carbon atom, and at least two unsaturated copolymerizable monomers, one of which at least contains at least one COOH group.

Advantageous products in the context of the invention are obtained in particular by the free-radical copolymerization of from 5 to 50 preferably 7 to 45 more preferably 9 to 40 by weight of glycidyl 20 esters, of aliphatic saturated monocarboxylic acids containing 4 to 30 carbon atoms and containing a tertiary or quaternary a carbon atom and from 95 to 50 preferably 93 to 55 more 25 preferably 91 to 60 by weight of at least two unsaturated copolymerizable monomers, one of which at least contains at least one COOH group, wherein component the glycidyl ester, is initially charged and reacted, preferably at from 100 to 210 0

C,

preferably 120 to 200 oC, with component and at least one specific free-radical initiator, by bulk polymerization, until a degree of conversion of at least preferably at least 97.5%, has been reached. It is also preferred that component contain at least by weight of a monomer containing COOH groups.

The monomers containing COOH groups are preferably available in a quantity such that the reaction with component proceeds to completion and results in an 6 acid number of at least 2 mg of KOH/g, preferably 3 to in the product prepared.

To produce the copolymers of the invention, specific, free radical-forming peroxy compounds are suitable as polymerization initiators. These specific peroxy initiators possess at least one tertiary carbon atom which is adjacent to the peroxy group and carries three linear or branrchd alkyl or aralkyl groups, at least one of which possesses more than 1 carbon atom.

Compounds of this kind are described by the formula

RI-O-O-R

2 where

R

1 is hydrogen, a linear or branched aliphatic acyl radical of 2 to 15 carbon atoms or R 2 and 15 R 2 satisfies the formula

R

3 C- R 4 e

R

3 is a linear or branched alkyl or aralkyl radical of at least 2 carbon atoms, and

R

4 and R 5 are identical or different and are a linear or branched alkyl or aralkyl radical of 1 to 15 carbon atoms.

Examples of such peroxy compounds are t-amyl peroxy- 2-ethylhexanoate, 1,1-di(t-amylperoxy)cyclohexane, t-amyl peroxyacetate, ethyl 3,3-di(t-amylperoxy)butyrate, di-t-amyl peroxide, 3-ethylpent-3-yl peroxy-2'-ethylhexanoate and di(3-ethylpent-3-yl) peroxide.

The proportion of initiator may be varied to give the desired product, and is, for example, from 0.5 to by weight, preferably 0.5 to 4% by weight and in 7 particular 0.5 to 3% by weight, based on the total weight of the starting components.

As component any desired glycidyl ester can be used. Glycidyl esters of a-alkylalkanemonocarboxylic acids and/or a,a-dialkylalkanemonocarboxylic acids are preferably used, alone or as a mixture. The a-alkylalkanemonocarboxylic acids and a,a-dialkylalkanoic acids are isomer mixtures of the corresponding monocarboxylic acids containing 4 to 30, preferably 5 to 20 carbon atoms.

Component is a mixture of at least two kinds of olefinically unsaturated copolymerizable monomers, at least one of which contains a carboxyl group. Any combination of monomers having these characteristics can be used.

Examples of suitable olefinically unsaturated acidic monomers in the case of component include acrylic and/or methacrylic acid and/or monoesters of maleic, fumaric or itaconic acid, maleic acid, fumaric acid, 20 itaconic acid themselves and crotonic, isocrotonic and vinylacetic acid, and also unsaturated fatty acids of 8 to 22 carbon atoms, for example, linolenic acid, linoleic acid, oleic acid, arachidonic acid and ricinenic acid.

Examples of suitable olefinically unsaturated monomers without carboxyl groups include acrylic and/or methacrylic esters of monohydric alcohols of 1 to carbon atoms and the hydroxyalkyl esters of these acids, and also acrylonitrile. Particularly suitable acrylic esters are, for example, the methyl, ethyl, propyl, 2-ethylhexyl, butyl, isobutyl, tert-butyl, hexyl, nonyl, lauryl and stearyl esters of acrylic and methacrylic acid.

Examples of other useful monomers include hydroxyalkyl esters of a,f-unsaturated carboxylic acids containing a primary hydroxyl group such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate and the corresponding methacrylates. Examples of hydroxyalkyl esters containing a secondary hydroxyl I I 8 group which can be used are 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, trimethylolpropane diacrylate and the corresponding methacrylates. It is also possible to employ the corresponding esters of other a,3-unsaturated carboxylic acids, for example, those of crotonic acid and of isocrotonic acid. Particular preference is given to hydroxyethyl, hydroxypropyl and hydroxybutyl acrylates and methacrylates. Other suitable monomers are the products of reaction of one mole of hydroxyethyl acrylate and/or hydroxyethyl methacrylate and on average two moles of E-caprolactone.

Other suitable olefinically unsaturated monomers include vinyl-aromatic hydrocarbons such as styrene, (alkylphenyl)ethenes, a-methylstyrene, a-chlorostyrene and the various vinyltoluenes.

In the initial monomer mixture, component (B) preferably comprises a mixture of (Bl) from 3.3 to 20% by weight, preferably from 3.3 to 15% by weight, of an a,f-unsaturated monocarboxylic acid, preferably acrylic or methacrylic acid or mixtures thereof, (B2) from 0 to 43% by weight, preferably from 16 to 43% by weight, of a hydroxyalkyl ester of 25 acrylic acid or methacrylic acid or mixtures thereof, (B3) from 0 to 57% by weight, preferably from 5 to by weight, of an ester of acrylic or methacrylic acid with a monohydric alcohol of 1 to 20 carbon atoms, or mixtures thereof, (B4) from 0 to 72% by weight, preferably from 15 to by weight, of at least one aromatic vinyl compound, the sum of components always being 100 and the sum of the esters (B2) and (B3) preferably being not more than by weight.

During the polymerization reaction, the acidic monomers and the initial charge of glycidyl ester react to form a product which is present in the copolymer 9 obtained in accordance with the invention, in general, in a proportion of from 6 to 60% by weight, preferably from to 55% by weight.

The polymerization is preferably carried out as a bulk polymerization. The term "bulk polymerization" refers a polymerization which is generally carried out without solvents. In some cases, however, the presence of a small proportion of solvent, namely up to 20% by weight, preferably up to 10 and in particular up to 8% by we ijht, based on the starting components, is also possible. However, working without solvent is preferred.

By working without solvent, solvent-solute interactions can be excluded which generally lead to chemical non-uniformity in copolymers.

15 A particularly preferred procedure is one in which, S. initially, at least one component is initially charged at the beginning of the polymerization and, subsequently, at least two unsaturated copolymerizable monomers are added, at least one of which contains a 20 COOH group. Component is preferably completely incorporated into the copolymer during the polymerization. This is effected by ring-opening esterification of the glycidyl groups in component A and the carboxylic acid groups in component B.

25 The hydroxyl group-containing copolymers of the present invention can be further modified in a subsequent step, for example by reacting them with isocyanate compounds which, for example, which contain per molecule on average from 0.8 to 1.5 free NCO groups and at least one tertiary amino group. In this case, the solvent employed in the polymerization, the preparation of the polymers, should be inert with respect to these isocyanate compounds.

These isocyanate compounds also include, for example, all low molecular weight urea derivatives which, in the paint industry, lead to "sag controlled" acrylate resins.

The polymers according to the invention can be identified by their content of OH groups. They generally I I II 10 have an OH number of from 50 to 250 mg of KOH/g, r-eferably from 80 to 200 and in particular from 90 to 180 mg of KOH/g. Furthermore, the polymers possess a particularly low solution viscosity. This viscosity is generally in the range from 15 to 2000 mPa.s, preferably from 20 to 700 and in particular from 25 to 500 mPa.s (measured for e 50% strength solution in butyl acetate or in a mixture of 3 parts of butyl acetate and 4 parts of xylene at 23 0 C in accordance with DIN 53 018). The polymers according to the ii rention generally possess weight average molar masses of less than 8600 g/mol, preferably less than 8500 g/mol, and a polydispersity of less than 3.4, in particular less than 3.2, especially preferred, less than 3.1.

One of the essential differences between a synthetic high polymer and a monomeric substance is the fact that it is not possible to assign a polymer an exact molar mass. This is a consequence of the length of the chain formed during polymerization reactions being determined 20 solely' by random events. Because of the random nature of the growth process, it is unavoidable that chains of different length will be formed; in other words, the. will be a distribution of chain lengths.

Gel permeation chromatography (abbreviated as GPC) 25 has in recent years become a frequently used method for determining molar masses and their distributions. T. s method, which is usually calibrated using polystyrene, yields a number-average M n and a weight-average M w molar mass. The breadth of the distribution can often be estimated by calculating the polydispersity Mw/M n The nearer this quotient is to 1, the more physically uniform is the polymer. Polymers of greater uniformity, such as the copolymers of the present invention, from the coatings technology point of view, have advantages in terms of drying and hardness.

The copolymers according to the invention are particularly suitable for coatings applications in 2-component systems, especially for so-called high-solids ~711rr 11 systems: for solvent-containing mixtures with a high solids content.

Examples of suitable solvents fu: coating using the copolymer obtained in accordance with the invention include any known solvents and particularly are aliphatic, cycloaliphatic and/or aromatic hydrocarbons, such as alkylbenzenes, for example, xylene or toluene; esters, such as ethyl acetate, butyl acetate, acetates with longer alcohol residues, butyl propionate, pentyl propionate, ethylene glycol monoethyl ether acetate, the corresponding methyl ether acetate; ethers, such as ethylene glycol acetate monoethyl, monomethyl or monobutyl ether; glycols; alcohols; ketones, such as methyl amyl ketone or methyl isobutyl ketone; lactones, 15 or the like, as well as mixtures of these solvents.

The present invention relates furthermore to coating compositions which contain the copolymers according to the invention as a binder component. The copolymers may be cured in the presence of suitable crosslinking agents 20 without heat or at elevated temperature. Any desired crosslinkers can be used.

Suitable curing components in these coating compositions are amino resins, polyisocyanates or compounds which contain anhydride groups, alone or in 25 combination. Generally, the crosslinking agent is added in a quantity such that the molar ratio of the OH groups of the copolymer to the reactive groups of the crosslinking agent is between 0.3:1 and 3:1.

Amino resins which are suitable as the curing component are preferably urea, melamine and/or benzoguanamine resins. These are etherified condensation products of urea, melamine or benzoguanamine with formaldehyde. Suitable mixing ratios generally are in the range from 50:50 to 90:10 in terms of copolymer/amino resin crosslinking agent, based on solid resin.

Appropriate phenolic resins and their derivatives also can be employed as curing agents. In the presence of acids, for example, p-toluenesulfonic acid, these crosslinking agents lead to full curing of the coating.

12 Heat curing can be undertaken conventionally at temperatures of from 90 to 200 0 C over, for example, from to 30 minutes.

Polyisocyanates are suitable for curing the products according to the invention accompanied by crosslinking, especially at moderate temperatures (10 to 80 oC) or a' room temperature. Suitable polyisocyanate components are, in principle, all aliphatic, cycloaliphatic or aromatic polyisocyanates which are known from polyurethane chemistry, alone or in the form of mixtures.

Particularly suitable examples are low molecular weight polyisocyanates such as, for example, hexamethylene diisocyanate, 2,2,4- and/or 2,4,4-trimethyl- 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, tetramethyl-p-xylylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato- 3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), and 4,4'-diisocyanatodicyclohexylmethane, 2,4'and/or 4,4'-diisocyanatodiphenylmethane or mixtures of these isomers with their higher homologs, as are accessible in a manner known per se by phosgenization of aniline/formaldehyde condensation products, and also 2,4and/or 2,6-diisocyanatotoluene, or any mixtures of such compounds.

Derivatives of these simple polyisocyanates are :preferably employed, as are conventional in coating technology. These include polyisocyanates which contain, for example, biuret groups, uretdione groups, isocyanurate groups, urethane groups, carbodiimide groups and/or allophanate groups, as are described, for example, in EP 0 470 461 which is hereby incorporated by reference.

The particularly preferred modified polyisocyanates include N,N',N"-tris(6-isocyanatohexyl)biuret and its mixtures with its higher homologs, as well as N,N',N"-tris(6-isocyanatohexyl) isocyanurate and its mixtures with its higher homologs containing more than one isocyanurate ring.

13 The crosslinking can be catalyzed by adding an organometallic compound, such as a tin compound and, if desired, a tertiary amine, preferably diethylethanolamine. Examples of appropriate tin compounds are dibutyltin dilaurate, dibutyltin diacetate and dibutyloxotin. Compounds suitable for curing at elevated temperature, in addition, include blocked polyisocyanates, polycarboxylic acids and their anhydrides.

The copolymers according to the invention are particularly suitable for the production of high-solids more than 50 solids content), solvent-containing clearcoats. In addition, they are well-suited to producing powder coatings, particularly in conjunction with polycarboxylic anhydrides. The copolymers can be employed for reaction with polycarboxylic anhydrides and for the subsequent use of the resulting products as curing agents for various synthetic resins, especially epoxy resins. The use of the copolymers according to the 20 invention by reaction with specific partial esters of polycarboxylic acids, or with derivatives of polycarboxylic acids or their anhydrides or ester anhydrides, is of particular interest.

Examples of preferred polycarboxylic acid 25 derivatives are polyanhydrides derived from at least :tetrahydric carboxylic acids, with which polyanhydrides the products according to the invention can be reacted.

These systems are of particular advantage for cold curing, because of their high reactivity.

In coating compositions prepared using the copolymers according to the invention it is also possible for other auxiliaries and additives, conventional in coating technology, to be present, although not mentioned hitherto. These include, in particular, catalysts, levelling agents, silicone oils, plasticizers such as phosphates and phthalates, pigments such as iron oxides, lead oxides, lead silicates, titanium dioxide, barium sulfate, zinc sulfide, phthalocyanine complexes, and the like, and fillers such as talc, mica, kaolin, chalk, 14 ground quartz, ground asbestos, ground slate, various silicic acids, silicates etc., viscosity-controlling additives, flattening agents, UV absorbers and light stabilizers, antioxidants and/or peroxide scavengers, antifoams and/or wetting agents, active diluents and the like.

The coating compositions can be applied to the respective substrate by any known methods, for example by brushing, dipping, flow coating or using rollers or blades, but in particular by spraying. They may be applied under heated conditions and, if desired, can be brought into a form in which they are ready for application by the injection of supercritical solvents C0 2 Automotive refinishes with excellent properties can be obtained with binders prepared using the copolymers according to the invention. These binders can be employed for the preparation of both intermediate coats and pigmented or unpigmented topcoats. Express reference 20 is made to the preferential suitability of these binder combinations in two-component automotive refinishes. For this purpose the coating materials are generally cured within the temperature range from -20 to +100 0

C,

preferably from -10 to +60 0

C.

25 The invention is illustrated in more detail in the examples which follow. In the embodiment examples, all percentages are by weight.

Examples: Preparation of the copolymers In a reactor fitted with a stirrer, inert gas inlet, a heating and cooling system and an addition device, the glycidyl ester of an a,a-dialkylalkanemonocarboxylic acid glycidyl ester of Versatic 10 acid (trade name Cardura® E 10, Shell Chemicals)] (in some cases with solvent or solvent mixtures) is initially charged and heated to the desired temperature under inert gas.

Subsequently, nver a period of 6 hours, the monomer 15 mixture (in some cases with solvent or solvent mixtures) is metered in at a uniform rate, together or separately, with the specific initiator (in some cases in solvent or solvent mixtures). Polymerization is subsequently carried out for 2 hours until a conversion of at least has been reached.

The copolymers are dissolved in suitable solvents or solvent mixtures.

The following copolymers are prepared. The precise batches in terms of parts by weight, reaction conditions and product characteristics can be taken from the tables which follow.

e: eeoe 16 Table 1: Preparation and properties of copolymers A Mixture (parts) organic compounds Glycidyl ester Acrylic acid Hycroxyethyl methacrylate Methyl methacrylate.

Styrene comparison 13.03 4.14 28.08 7.58 47.17 1 13.03 4.14 28.08 7.58 47. 17 2 13.02 4.14 28.08 7.58 47.17 di -t-wyL peroxide 1.84 I n tiator di -t-IiityL peroxide~ 1.51 t-myt peroxy- 2- ethythexaroatc 2.47 Po lymeri zat ion temperature 185 SC ()after polymerization SC ()SF (in butyl acetate) Acid number (mg KOH/g SR) Hydroxyl numbe (mg KOH/g SR) Viscosity (mPa.s), 23 0 C (SF) Viscosity (mPa.s), 23 0

C

strength in BuAc/xylene 3:4) 98.4 70.3 8.1 143 10820 177 185 98.2 69.4 5.9 140 8300 145 185 97.9 5.8 136 4440 106 GPC (PS calibration) DM, (g/mol) Mn (g/mol) U ,M 8700 2560 3.4 6830 2530 2.7 5450 2260 2.4 Hazen color number (Lovibond) Appearance SC: solids content SE: Solid resin SF: Supply form trarsparent trcmporent tran-mrmnt 17 Initiators: A di-t-butyl peroxide: Trigonox® B (AKZO) B t-amyl peroxy-2-ethylhexanoate: Trigonox® 121 (AKZO) C di-t-amyl peroxide: Interox® DTAP (Peroxid-Chemie) GPC: M n Millipore® Waters Chromatography System 860 Pump: Waters model 590, RI detector: Waters model 410 Column packing: Waters Ultrastyragel 1 x 1000 A 1 x 500 A 1 x 100 A (Angstrom) Solvent: tetrahydrofuran at 40 0

C

Flow rate: 1 ml/min, concentration: 1% based on solids content Calibration: polystyrene (PSS, Mainz) Determination of characteristics: Acid number, hydroxyl number and viscosity (for standards see "Analytische Bestimmungsmethoden" [Analytical determination methods] (brochure: Synthetic resins Hoechst AG, 1982 edition)). Hazen color number Lovibond) according to DIN 53 409.

The copolymers Al and A2 prepared have relatively low weight-average molar masses. The gel permeation chromatograms show no high molar mass "shoulders", which is evident in a relatively low nonuniformity.

In accordance with the lower molar masses and the higher degree of uniformity, there is a reduction in the supply form viscosity as measured in an Ubbelohde viscosimeter.

18 Table 2: Preparation and properties of copolymers B Mixture (parts) CoMarison 1 2 organic con-pounds Glycidyl ester 19.70 19.70 19.70 Acrylic acid 6.87 6.87 6.87 Hydroxyethyl methacrylate 16.26 16.26 16.26 Methyl methacrylate 24.34 24.34 24.34 Styrene 32.83 32.83 32.83 Initiator A B C peroxicde 2-ethvthexate peroxide 1.50 2.41 1.78 Polymerization temperature (O)160 160 160k 15 SC() after polymerization 98.5 97.6 98.8 SF (in butyl acetate) 70.4 69.7 69.8 Acid number (mg KOH/g SR) 13.0 11.2 10.8 Hydroxyl number (mg KOH-/g SR) 112 115 110 Viscosity (mPa.s), 23 0 C (SF) 13540 10650 9130 20 Viscosity (mPa.s), 23 0

C

strength in BuAc) 172 137 118 GPC (PS calibration) (g/mol) 11750 8440 7870 5M, (g/mol) 3180 2910 2890 25U='Dn3.7 2.9 2.7 Hazen color number (LoDvibond) 150 80 Appearance tr-wspent trwisparet trwqmpront 19 Initiators: A di-t-butyl peroxide: Trigonox® B (AKZO) B t-amyl peroxy-2-ethylhexanoate: Trigonox® 121 (AKZO) C di-t-amyl peroxide: Interox® DTAP (Peroxid-Chemie) GPC: M n Millipore® Waters Chromatography System 860 Pump: Waters model 590, RI detector: Waters model 410 Column packing: Waters Ultrastyragel 1 x 1000 A 1 x 500 A 1 x 100 A (Angstrom) Solvent: tetrahydrofuran at Flow rate: 1 ml/min, concentration: 1% based on solids content Calibration: polystyrene (PSS, Mainz) Determination of characteristics: Acid number, hydroxyl number and viscosity (for standards see "Analytische Bestimmungsmethoden" [Analytical determination methods] .:(brochure: Synthetic resins Hoechst AG, 1982 edition)). Hazen color number Lovibond) according to DIN 53 409.

20 The copolymers B1 and B2 prepared have relatively low weight-average molar masses. The gel permeation chromatograms show no high molar mass "shoulders" which is evident in a relatively low nonuniformity.

In accordance with the lower molar masses and the higher degree of uniformity, there is a reduction in the supply form viscosity as measured in an Ubbelohde viscosimeter.

20 Table 3: Preparation and properties of copolymers C Mixture (parts) Comparison 1 Glycidyl ester 20.71 20.

Acrylic acid 6.19 6.

Hydroxyethyl mnethacrylate 13.30 13.: Methyl mnethacrylate 21.02 21.' Styrene 38.78 38.

*with a very small amount of solvent: butyl acetate 71 19 30 02 78 2 20.71 6.19 13.30 21.02 38.78 Initiator A di t-butyl peroxic& 1.50

B

tZKytI peroxy- 2-ethythexaroate 2.36

C

di -t-mi>' peroxic6e 1.79 Polymerization temperature SC ()after polymerization SC ()SF (in butyl acetate) Acid number (mg KOH/g SR) Hydroxyl number (mg KOH/g SR) Viscosity (mPa.s), 23 0 C (SF) Viscosity (mPa.s), 23 0

C

strength in BuAc) GPC (PS calibration) M, (g/mol) M, (g/mol) U =M/Y Hazen color number (Lovibond) Appearance 185 97.2 69.4 4.5 ill 7620 135 8920 2550 3.5 185 97.9 70.8 3.4 106 4810 185 98.0 70.5 3.1 108 2790 5480 2430 2.3 3600 1710 2.1 tr1r~prent tr~~a-rnt trorqpmr1t 21 s Initiators: A di-t-butyl peroxide: Trigonox® B (AKZO) B t-amyl peroxy-2-ethylhexanoate: Trigonox® 121 (AKZO) C di-t-amyl peroxide: Interox® DTAP (Peroxid-Chemie) GPC: Mn Millipore® Waters Chromatography System 860 Pump: Waters model 590, RI detector: Waters model 410 Column packing: Waters Ultrastyragel 1 x 1000 A 1 x 500 A 1 x 100 A (Angstrom) Solvent: tetrahydrofuran at 40 0

C

Flow rate: 1 ml/min, concentration: 1% based on solids content Calibration: polystyrene (PSS, Mainz) Determination of characteristics: Acid number, hydroxyl number and viscosity (for standards see "Analytische Bestimmungsmethoden" [Analytical determination methods] (brochure: Synthetic resins Hoechst AG, 1982 edition)). Hazen color number (Lovibond) according to DIN 53 409.

The copolymers C1 and C2 prepared have relatively low weight-average molar masses. The gel permeation chromatograms show no high molar mass "shoulders", which is evident in a relatively low nonuniformity.

In accordance with the lower molar masses and the higher degree of uniformity, there is a reduction in the supply form viscosity as measured in an Ubbelohde viscosimeter.

22 Table 4: Preparation and properties of copolymers D Mixture (parts) Glycidyl ester Acrylic acid Hydroxyethyl methacrylate Methyl methacrylate Styrene comparison 9.51 3.03 24.87 27.20 35.39 1 9.51 3.03 24.87 27.20 35.39 2 9.51 3.03 24. 87 27.20 35.39 with a very small amount of solvent: buty! acetate Initiator A peroxice 1. i0

B

t-apyt peroxy- 2-ethythexanoate 1.73

C

di -t-wylt peroxide 1.31 Polvmeri zation temoe-rature

(OC)

SC ()after polymerization SC(% SF (in butyl acetate) Acid number (mrg KOH/g SR) Hydroxyl number (mcj KOH/g SR) Viscosity (rnPa.s), 23 0 C (SF) Viscosity (mPa.s), 23 0

C

strength in BuAc) 175 98.2 69.0 5.2 129 18210 253 175 98.9 69.4 4.5 116 15840 182 175 98.6 69.5 4.3 129 6840 GPC (PS calibration) DL (g/mol) Mn (g/mol) U V~ Hazen color number (Lovibond) Appearance 10010 2910 3.4 8320 2720 3.1 4620 1770 2.6 trrsporent tra-6parent tra-sparent 23 Initiators: A di-t-butyl peroxide: TrigonoxQ B (AKZO) B t-amyl peroxy-2-ethylhexanoate: Trigonox® 121 (AKZO) C di-t-amyl peroxide: Interox® DTAP (Peroxid-Chemie) GPC: M n Millipore® Waters Chromatography System 860 Pump: Waters model 590, RI detector: Waters model 410 Column packing: Waters Ultrastyragel 1 x 1000 A 1 x 500 A 1 x 100 A (Angstrom) Solvent: tetrahydrofuran at 40 0

C

Flow rate: 1 ml/min, concentration: 1% based on solids content Calibration: polystyrene (PSS, Mainz) 15 Determination of characteristics: Acid number, hydroxyl number and viscosity (for standards see "Analytische Bestimmungsmethoden" [Analytical determination methods] (brochure: Synthetic resins Hoechst AG, 1982 edition)). Hazen color number (Lovibond) according to DIN 53 409.

20 The copolymers D1 and D2 prepared have relatively low weight-average molar masses. The gel permeation chromatograms show no high molar mass "shoulders", which is evident in a relatively low nonuniformity.

In accordance with the lower molar masses and the higher degree of uniformity, there is a reduction in the supply form viscosity as measured in an Ubbelohde viscosimeter.

24 II.) Preparation of the coating materials To prepare the curable coating compositions according to the invention, the components comprising a copolymer according to the invention or a mixture of two or more copolymers according to the invention with the auxiliaries and additives, solvents and crosslinking agents in the mixing ratio described in Tables 5 and 6 are mixed and are adjusted using further diluent to the spray viscosity of from 21 to 22 seconds with a flow cup (DIN 52 211, 4 mm, 23 0 Binder as supplied (supply form, and additives are mixed to yield 100 parts by weight in total. Curing agent (isocyanate) is added then.

For components of low viscosity this can be carried out :I in bulk, with heating to higher temperatures being o carried out if desired. Products of higher viscosity are dissolved or dispersed, prior to mixing, in the diluents mentioned, unless the curable mixtures are to be employed as a powder coating.

In the case of pigmented systems a pigment paste is first produced in one dispersion step from the appropriate pigments together with the copolymer according to the invention, or a mixture of two or more copolymers according to the invention, with the optional addition of an appropriate, specific grinding resin in a 21 dispersion apparatus of appropriate construction. This paste is mixed as it is, or with the addition of another binder based on the components, or on a mixture thereof, or alternatively with the addition of a different resin, which is compatible with the other components of the coating system concerned, and this mixture is made up with the addition of further diluents or additives typical for coatings.

The pot life and the properties of the resulting films depend in this context on the process conditions, in other words on the nature and quantity of the starting materials, the metering of the catalyst, the temperature control, etc.; curing can be carried out discontinuously 25 or continuously, for example, using an automatic coating apparatus.

S

26 Table 5: Preparation of High-Solids Clearcoats Copolymer A Copolymer B Mixture Comparison 1 2 Comparison 1 2 Appearance: transparent transparent transparent transparent transparent transparent SC% 70.3 69.4 70 70.4 69.7 69.8 OH number/%OH 143/4.3 140/4.2 136/4.1 112/3.4 115/3.5 110/3.3 Viscosity mPa.s 50% 177 145 106 172 137 118 Binder SF parts 82 82 82 82 82 82 Tinuvin® 292 0.5 0.5 0.5 0.5 0.5 Tinuvin® 1130 1.5 1.5 1.5 1.5 1.5 Si oil Lo 50% "1 1 1 1 1 1 Solvesso® 100 "1.5 1.5 1.5 1.5 1.5 Xylene 2.5 2.5 2.5 2.5 2.5 BuAc 11 11 11 11 11 11 Desmodurs 3390 31.4 30.4 29.9 24.9 25.4 24.0 Flow cup (DIN 53 211) seconds 21.0 21.8 21.5 21.5 22.0 21.8 Designation of coating material AV Al A2 BV B1 B2

L

27 Table 6: Preparation of High-Solids Clearcoats Copolymer C Copolymer D Mixture Comparison 1 2 Comparison 1 2 Appearance: transparent transparent transparent transparent transparent transparent SC% 69.4 70.8 70.5 69.0 69.4 69.5 OH number/%OH 111/3.4 106/3.2 108/3.3 129/3.9 116/3.5 129/3.9 Viscosity mPa.s 50% 135 71 48 253 182 Binder SF parts 82 82 82 82 82 82 Tinuvin® 292 0.5 0.5 0.5 0.5 0.5 Tinuvin® 1130 "1.5 1.5 1.5 1.5 1.5 Si oil Lo 50% 1 1 1 1 1 1 Solvesso® 100 "1.5 1.5 1.5 1.5 1.5 Xylene 2.5 2.5 2.5 2.5 2.5 BuAc 11 11 11 11 11 11 Desmodur® 3390 24.7 23.3 24.0 28.4 25.4 28.3 Flow cup (DIN 53 211) seconds 21 21 21 21 21 21 Designation of coating material CV C1 C2 DV D1 D2 28 Tinuvin® 292 "HALS" (Ciba Geigy, Basle) Tinuvin® 1130 UV absorber (Ciba Geigy, Basle) Si oil LO 50% Leveling agent (silicone oil from Wacker GmbH, Burghausen) Desmodur® N 3390 Polyisocyanate containing isocyanurate groups (Bayer AG, Leverkusen) BuAc Butyl acetate III.) Performance testing The coating systems prepared as in II were applied to clean ed glass panels using a 100 pm doctor blade and were S 15 tested under the conditions of air drying and of forced drying (45 minutes at 60 0

C).

The results can be taken from Tables 7 and 8.

Coatings based on DTAP-initiated products are notable for a solids content which is about 2-4% higher, a dust-dry S' 20 time which is just as good or even shorter, a reduced tack-free drying time and comparable or improved film hardness. The gasoline resistance corresponds to the known, high level.

Testing is performed after drying at room temperature 25 for 24 hours, 2 days etc., or under forced conditions minutes at 60 OC in an oven) and subsequent storage.

Pendulum hardness is measured according to Knig.

Solids content is measured after drying at 125 OC for 1 hour (DIN 53 216).

Gasoline resistance is tested by application of a soaked cotton pad on to the coated surface. The time during which the appearance does not change is stated in the table.

29 Table 7: Performance testing of the high-solids clearcoats Designation of the AV Al A2 BV Bl B2 coating material Appearance: transparent transparent transparent transparent transparent transparent Initial/pot life 8h 8h 8h 8h 8h 8h Dust-dry time 8' 8' 8' 16' 13' 13' Tack-free drying 220' 190' 190' 285' 225' 255' SC-1 h 125 0 C 54.10% 54.20% 57.30% 52.50% 52.90% 54.30% Pendulum hardness after 24 h 159 104 91 54 75 2 d 212 150 193 131 174 174 d 191 151 210 201 207 218 d 226 193 214 204 213 218 Premium-grade 30 30 30 30 30 gasoline after 10 d in min Pendulum hardness after 45' 60 0

C

drying 24 h 166 178 170 140 138 126 2 d 194 200 199 186 186 182 d 207 204 221 220 214 214 60°C drying 30 30 30 30 30 Premium-grade gasoline after 5 d in min 30 ,le 8: Performance testing of the high-solids clearcoats Designation of the CV Cl C2 DV D1 D2 coating material Appearance transparent transparent transparent transparent transparent transparent Initial/pot life 8 h 8 h 8 h 8 h 8 h 8 h Dust-dry time 17' 16' 15' 16' 12' 13' Tack-free drying 120' 109' 105' 70' 48' 44' SC-1 h 125 0 C 53.10% 54.80% 57.90% 51.50% 52.60% 55.10% Pendulum hardness after 24 h 69 53 31 76 54 51 2 d 91 73 61 102 110 98 3 d 123 125 98 148 159 155 7 d 190 188 194 205 197 201 d 200 196 203 207 208 210 Premium-grade 30 30 30 30 30 gasoline after 10 d in min Pendulum hardness after 45' 60 0 C drying 24 h 87 90 54 143 129 92 2 d 116 130 91 180 191 162 4 d 189 192 172 211 222 205 600C drying 30 30 30 30 30 Premium-grade gasoline after 4 d in min

Claims (16)

1. A copolymer of one or more glycidyl esters of saturated aliphatic monocarboxylic acids having a tertiary or quaternary a carbon atom, and at least two unsaturated copolymerizable monomers, at least one of which contains at least one COOH group, wherein the copolymer has a viscosity in solution of less than 2,000 mPa.s and a monomodal, narrow molar mass distribution such that the nonuniformity is less than 3.4.

2. A copolymer as claimed in claim 1, wherein the copolymer has a viscosity in solution from 15 to 2,000 mPa.s and an OH number of from 50 to 250 mg KOH/g and a weight average molar mass of less than 8600 g/mol.

3. A copolymer as claimed in claim 1, of from 5 to 50% by weight of one or more glycidyl esters of saturated aliphatic monocarboxylic acids having a tertiary or quaternary a carbon atom wherein the acid contains from 4 to 30 carbon atoms, and from 95 to 50% by weight of at least two unsaturated copolymerizable monomers, one of which at least contains at least one COOH group, i"wherein the copolymer has an OH number of from 50 to 250 mg KOH/g, a solution viscosity (50% strength, 230C) of 15 to 2,000 mPa.s, a weight average molecular mass Mw of less than 8600 g/mol and a nonuniformity of less than 3.4.

4. A copolymer as claimed in claim 1, which is prepared by initially charging component to a vessel and then reacting it with component in the presence of at least one free radical-forming initiator. 32 A copolymer as claimed in claim 1, which is prepared using one or more free radical-forming initiators of the formula R 1 -O-O-R 2 where R 1 is hydrogen, a linear or branched aliphatic acyl radical of 2 to 15 carbon atoms or is R 2 and R 2 satisfies the formula R, Rs 1 to 15 carbon atoms.

6. A copolymer as claimed in claim 1, wherein e Rcomponent is a linear or branched alkyof one or mor araylic monomers havingcal of at least one COOH group and of one or R 4 and R 5 are identical or different and are a linear or branched alkyl or aralkyl radical of S1 to 15more vinyl-aromatic hydrocarbon atos. 6. A copolymer as claimed in claim 1, wherein component comprises a mixture of one or more acrylic (Bl) from 3.3 to 20% by weight acrylic or methacrylic acid, (B2) from 0 to 43% by weight of at least one hydroxyalkyl ester of acrylic and/or methacrylic acid, (B3) from 0 to 57% by weight of at least one ester of acrylic and/or methacrylic acid with a monohydric alcohol of 1 to 20 carbon atoms, and (B4) from 0 to 72% by weight of at least one aromatic vinyl compound, the sum of (B3) and (B4) being 100. 33

8. A copolymer as claimed in claim 1, which comprises the reaction products of acrylic and/or methacrylic acid with component A in a proportion of from 6 to 60% by weight, based on the weight of the copolymer.

9. A copolymer as claimed in claim 1, which is prepared using one or more free radical-forming initiators of the formula R 1 -O-O-R 2 where R 1 is hydrogen, a linear or branched acyl radical of 2 to 15 carbon atoms or is R 2 and R 2 is t-amyl or 3-ethylpent-3-yl radical.

10. A copolymer as claimed in claim 4, where the initiator comprises at least one t-amyl group.

11. A copolymer as claimed in claim 1, which is modified by reaction with an isocyanate compound.

12. A copolymer as claimed in claim 11, wherein the isocyanate compound contains on average from 0.8 to free NCO groups and at least one tertiary amino group.

13. A copolymer as claimed in claim 1, which has an acid number of at least 3 mg of KOH/g.

14. A process for producing a copolymer as claimed in claim 1, which comprises the free-radical reaction of components and A process as claimed in claim 14, comprising bulk polymerizing components and with a free- radical initiator at from 100 to 210 0 C until a degree of conversion of at least 95% is reached.

16. A process as claimed in claim 15, wherein no more than 20% of solvents based on the weight of the starting materials is used. 34

17. A coating composition comprising a copolymer as claimed in claim 1.

18. A coating composition as claimed in claim 17, wherein the copolymer is cured using a polyisocyanate.

19. A powder coating composition comprising a copolymer as claimed in claim 1. A substrate coated with a coating composition as claimed in claim 17. DATED this 21st day of July 1994. HOECHST AKTIENGESELLSCHAFT es WATERMARK PATENT TRADEMARK ATTORNEYS "THE ATRIUM" 290 BURWOOD ROAD HAWTHORN. VIC. 3122. 35 Abstract of the Disclosure Copolymers of one or more glycidyl esters of saturated aliphatic monocarboxylic acids having a tertiary or quaternary a carbon atom and at least two olefinically unsaturated copolymerizable monomers, at least one of which contains at least one carboxyl group are particularly suitable as binder components for high- solids coating compositions. e