NO175905B - Coating agent comprising an anhydride and a hydroxy component - Google Patents

Description

The present invention relates to coating agents comprising an anhydride and a hydroxy component.

US patent no. 4452948 describes a two-component coating composition comprising a hydroxy component and an anhydride component, where the hydroxy component is a copolymer containing at least two free hydroxy groups per molecule and which also contain amine groups in the molecule to accelerate the curing reaction between the hydroxy groups and the anhydride groups, and the anhydride component is a polymer that contains at least two cyclic carboxylic acid anhydride groups per molecule. In a less preferred embodiment, the amine groups are present in a separate amine compound rather than on the molecule of the hydroxy component. The coatings according to US patent no. 4452948 have the advantage that they are room temperature-hardening without the use of toxic isocyanates and have been used successfully as finish coatings for cars, especially in re-finishing, and as paint for yachts.

European Patent Publication 134691 describes a three-component coating agent comprising a compound containing at least two hydroxy groups, a compound containing at least two anhydride groups and a compound containing at least two epoxide groups.

European patent publication 259172 describes a coating composition comprising an anhydride polymer and a polymer containing hydroxyalkylamino, hydroxyalkylamino, hydroxy-substituted acyloxyalkylamino, hydroxy-substituted polyacyloxyalkylamino, mercaptoalkylamino or oxazolidino groups. One of the polymers includes a flexible polymer chain and has its functional groups present as terminal groups at the end of the flexible polymer chain.

US Patent No. 3984382 describes a modified cationic vinyl polymer suitable for electroplating and prepared by reacting a copolymer of maleic anhydride, styrene and an alkyl acrylate with an amino alcohol and/or a difunctional amine until the modified polymer has no remaining anhydride rings, and reacting the product with a monoepoxy compound.

US patents 3449250 and 3329658 describe an additive which gives stability and detergency to mineral oil. The additive includes a copolymer of maleic anhydride and an α-olefin which is partially esterified with an aliphatic alcohol to make the copolymer oil soluble and in which substantially all of the remaining carboxyl groups are imidized.

German Patent No. 1595333 discloses water-soluble polyelectrolytes which are useful as flocculants and retention aids in papermaking and are prepared by reacting a copolymer of an ethylenically unsaturated carboxylic anhydride with a polyamine containing a primary or secondary amino group, and reacting the reaction product with an epihalohydrin and /or a diepoxide.

The present invention consequently provides a coating agent including (A) a hydroxy component containing at least two free hydroxy groups per molecule and (B) an anhydride component containing at least two cyclic carboxylic acid anhydride groups per molecule, where at least one of (A) and

(B) is a film-forming polymer, where the coating agent contains a catalytically effective amount of tertiary

amine groups to accelerate the curing reaction between the hydroxy groups in (A) and anhydride groups in (B), and where the ratio between amine groups and cyclic carboxylic acid anhydride groups is a maximum of 4:1, the ratio between anhydride groups in (B) and hydroxy groups in (A) being 0 ,5:1 to 2:1. The coating agent is characterized by the fact that the anhydride component (B) contains the tertiary amine groups as neighboring groups in its molecules.

In the invention, a polyanhydride can be used which contains at least two cyclic carboxylic acid anhydride groups per molecule, where the polyanhydride contains adjacent amine groups, the proportion of amine groups to carboxylic acid anhydride groups is not greater than 4:1 and the content of free carboxylic acid groups, if any are present, is less than 200 mol-% based on the amine groups.

The proportion of amine groups to cyclic carboxylic acid anhydride groups in the polyanhydride is preferably at least 0.01:1 and no more than 1.5:1, most preferably 0.01:1 to 1:1. The content of free carboxylic acid groups is preferably less than 100 mol% based on the amine groups; most preferably, free carboxylic acid groups are substantially absent or are present at less than 20 mol-# based on amine groups.

The coating agent according to the invention has advantages compared to those described in US patent no. 4452948 and European patent publication 259172. The polyanhydrides mentioned above can be used in coating compositions with a wide range of hydroxy-functional polymers, including unmodified commercial polymers. The coating agents also have improved stability against photodegradation compared to many of the coatings according to European patent publication 259172. The coating agents according to the invention avoid the possibilities of environmental hazard and stickiness of the cured coatings, which can occur when using a free amine compound as a catalyst.

The amine groups present in the polyanhydride are tertiary amine groups, which are the most effective in catalyzing the reaction between the hydroxy and anhydride groups without giving rise to side reactions.

A preferred type of polyanhydride is a polymer containing cyclic carboxylic acid anhydride groups and N-(dialkylaminoalkyl)-substituted imide groups. Such a polyanhydride can be formed by the reaction of a polymer containing cyclic carboxylic acid anhydride groups with a less than stoichiometric amount of a polyamine containing a primary amine group and at least one tertiary amine group. Said polymer containing cyclic carboxylic anhydride groups is preferably derived from an olefinically unsaturated cyclic carboxylic anhydride.

The polymer containing cyclic carboxylic acid anhydride groups can e.g. be a copolymer of an olefinically unsaturated cyclic carboxylic acid anhydride, such as maleic, itaconic, citraconic or vinyl succinic anhydride or vinyltrimellitan anhydride with one or more olefinically unsaturated comonomers, such as an α-olefin, e.g. ethylene or propylene, a vinyl comonomer, e.g. styrene or a substituted styrene, vinyl acetate or vinyl chloride, or an ester of acrylic or methacrylic acid, e.g. butyl acrylate, ethyl acrylate, methyl methacrylate or butyl methacrylate. Preferred copolymers contain 10-40 wt-#, most preferably 20-35 wt-#, of maleic or itaconic anhydride groups and have a molecular weight of 1500-30000, e.g. 4000-12000. If the coating is to be used as a decorative top coating, it may be preferred to use a vinyl comonomer at a molar ratio of at least 1:1 with regard to the anhydride monomer, as described in US patent no. 4798745.

The polymer containing cyclic carboxylic anhydride groups may alternatively be an adduct of an unsaturated cyclic carboxylic anhydride and a diene polymer, such as maleinized polybutadiene or a maleinized copolymer of butadiene, e.g. a butadiene/styrene copolymer. The maleinized diene polymer is preferably hydrogenated to remove residual unsaturation. Terpene/maleic anhydride copolymer resins are a further alternative. The anhydride adduct of an unsaturated fatty acid ester, e.g. a styrene/allyl alcohol copolymer esterified with an unsaturated fatty acid and maleinized can also be used. The polymer containing cyclic carboxylic anhydride groups can alternatively be formed by the reaction of a polymer containing thiol groups with an olefinically unsaturated cyclic carboxylic anhydride, such as maleic anhydride or itaconic anhydride. The polymer containing thiol groups is preferably thiol-terminated; it can e.g. be a multi-membered telechelic polymer formed by reacting a corresponding hydroxy-terminated polymer with mercaptoacetic acid.

Alternative anhydride-containing polymers can be formed from hydroxy-containing polymers, e.g. copolymers of hydroxyethyl acrylate or hydroxyethyl methacrylate or styrene/allyl alcohol copolymers, by reaction with a tricarboxylic compound capable of introducing anhydride groups, e.g. as described in European Patent Publication 259172. A further alternative type of polymer containing anhydride groups is an adduct of trimellitic anhydride and a polyol, as described in European Patent Publication 134691.

The polyamine which is reacted with the polymer containing anhydride groups is preferably a primary/tertiary diamine, e.g. N,N-dimethylpropane-1,3-diamine ((CH3)2NCE2CH2CE2NH2), N,N-dimethylethylenediamine, 4-amino-1-(diethylamino)-pentane, N,N-diethylpropane-1,3-diamine, 2- amino-pyridine, 3-amino-pyridine, 4-amino-pyridine or N-(3-aminopropyl)-morphol in. The primary amine group reacts with the anhydride group to form an imide group that has the tertiary amine group in a neighboring organic group attached to the imide nitrogen atom. The substituted imide groups formed generally have the formula

where each Z represents a polymer residue and X is an organic group containing a tertiary amine group and is linked to the imide nitrogen atom by a carbon-nitrogen bond. The group X can e.g. be an aminoalkyl group of the form -A-NRg» where -A- is a straight or branched alkylene group preferably containing 2 to 8 carbon atoms and each group R is an alkyl group preferably containing 1 to 4 carbon atoms; a heterocyclic ring containing a tertiary nitrogen atom such as 4-pyridyl; or an alkyl group substituted with a heterocyclic ring containing a tertiary nitrogen atom, such as a pyridine or morpholine ring. For example, when using N,N-dimethylpropane-1,3-diamine

where each Z stands for a polymer residue.

The reaction between the polymer containing anhydride groups and the diamine can e.g. is carried out by heating under reflux in an organic solvent which has a boiling point significantly higher than that of water (e.g. 120-180°C) or forms an azeotrope with water, where water is removed by distillation during the reaction. Examples of solvents are esters such as butyl acetate or methoxypropyl acetate, ketones such as methyl isobutyl ketone or aromatic hydrocarbons such as xylene. The anhydride and amine initially react to form an acid amide which may have limited solubility, particularly in hydrocarbon solvents. It may be preferred to add the diamine gradually during the reaction. Alternatively, the reaction can be carried out as a two-step reaction where the acid amide is formed in an initial step and heated in a solvent, while removing water, or with a dehydrating agent such as acetic anhydride or a carbodiimide such as dicyclohexylcarbodiimide.

The proportion of polyamine reacted with the polymer containing anhydride groups is generally not greater than 0.8 mol of polyamine per mol of anhydride groups in the polymer and is preferably not greater than 0.5 mol/mol so that the resulting polyanhydride contains at least as many anhydride groups as N-(aminoalkyl)-substituted imide groups. Preferably, the molar ratio between diamine and anhydride groups is 0.05-0.5:1, most preferably 0.1-0.33:1.

An alternative form of polyanhydride is the reaction product of a polymer of an olefinically unsaturated tricarboxylic acid such as acetonic acid or an anhydride thereof with an amino alcohol, preferably a tertiary amino alcohol such as N,N-dimethylethanolamine. The reaction is carried out under conditions to remove water, e.g. by refluxing in an organic solvent with a higher boiling point than water and/or which forms an azeotrope with water, e.g. by using butyl acetate as solvent.

This product containing anhydride groups and adjacent amino alkyl ester groups may have increased reactivity with hydroxy groups.

A polymer containing cyclic carboxylic anhydride groups and adjacent amine groups cannot generally be formed by the copolymerization of an unsaturated cyclic carboxylic anhydride such as maleic anhydride or itaconic anhydride and an unsaturated amine such as a dialkylaminoalkyl acrylate or methacrylate. Such polymerization forms either a polyacid or a "black charge-transfer" complex as described by Taylor and Woodward in J. Polymer Science, Part A., Vol. 1, pp. 1473-1482 (1963). However, a polymer containing anhydride groups and adjacent amine groups can be formed by addition copolymerization of an olefinically unsaturated dicarboxylic acid and an olefinically unsaturated amine, preferably a tertiary amine, such as a dialkylaminoalkyl acrylate or methacrylate under conditions to remove water, e.g. at a temperature above 100°C and/or by azeotropic distillation. The most preferred olefinically unsaturated dicarboxylic acid is itaconic acid, which may be dissolved in a polar organic solvent such as tetrahydrofuran. The unsaturated dicarboxylic acid solution is preferably added to the polymerization vessel separately from the amine monomer such as e.g. can be diethylaminoethyl or dimethylaminoethyl acrylate or methacrylate. The amine monomer may be dissolved in an organic solvent such as an aromatic hydrocarbon, ester or ketone, preferably together with one or more olefinically unsaturated comonomers. The solvent for the unsaturated dicarboxylic acid can be removed by distillation during the polymerization; the copolymer is more soluble in organic solvents than the acid monomer.

A further alternative type of polyanhydride is a graft copolymer of a polymer containing cyclic carboxylic anhydride groups and a polymer containing amine groups. Such a graft copolymer can be formed if one of the polymers contains olefinic unsaturation (which is due, for example, to the polymerization of a diene) and grafting is carried out using a free radical catalyst, such as a peroxide. The polymer containing unsaturation is conveniently a maleinized diene polymer, preferably maleinized polybutadiene, containing residual unsaturation.

The hydroxy-functional component (A) to be reacted with the amine-containing anhydride-functional component (B) is preferably a film-forming polymer and can be selected to provide the desired properties in the cured coating. For example, it may be an addition copolymer having adjacent hydroxy groups, such as an acrylic copolymer containing 5-80% by weight, preferably 10-50% by weight, of a hydroxy-containing ester of an olefinically unsaturated carboxylic acid, e.g. a hydroxyalkyl acrylate or methacrylate, such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate or hydroxypropyl acrylate. The hydroxy-containing ester may contain further ester linkages or ether linkages, e.g. 2-(p-hydroxyethoxy)-ethyl acrylate or methacrylate or an adduct of hydroxyethyl acrylate or methacrylate with caprolactone. Examples of olefinically unsaturated monomers which can be copolymerized with the hydroxy ester are acrylic esters such as butyl acrylate, methyl methacrylate, butyl methacrylate, ethyl acrylate and hexyl acrylate and vinyl compounds such as styrene, vinyl acetate and vinyl chloride. The hydroxy component (A) can be a copolymer containing a polyester segment, e.g. a graft copolymer of acrylic monomers on an unsaturated polyester. The acrylic monomers are preferably selected from those mentioned above and include a hydroxy-containing monomer, such as a hydroxyalkyl acrylate or methacrylate. The polyester segment is preferably a low molecular weight polyester (below 1000) derived from a polyol such as methylene glycol, propylene glycol or trimethylolpropane and an acid or an anhydride such as phthalic anhydride, isophthalic acid or adipic acid with a minor amount of an unsaturated acid or an anhydride, such as maleic anhydride. The polyester can e.g. form up to 50 wt.#, preferably 5-25 wt.#, of the graft copolymer. Coatings prepared using an acrylic hydroxy functional component or an acrylic polyester graft copolymer hydroxy functional component have excellent gloss, flow and appearance after spraying.

An alternative method for preparing an addition copolymer having adjacent hydroxy groups for use as the hydroxy component (A) is to prepare a copolymer having amide groups, e.g. acrylamide or methacrylamide units, and to form N-methylol groups on the amide by reaction with the formaldehyde.

The hydroxy functional component (A) can alternatively be a telechelic polymer having hydroxy groups at each end of a polymer chain, such as a polyether, aliphatic polyester, silicone, diene polymer, hydrogenated diene polymer, polyurethane, polyisobutylene or polyacrylate. The use of such a telechelic polymer can provide hardened coatings that have high impact and abrasion resistance. Such a telechelic polymer preferably contains more than 2 hydroxy groups per molecule, e.g. it may be a polyester or polyether containing 3 or 4 arms, each terminated with a hydroxy group. An example of such a hydroxy-terminated polyester sold commercially is a polycaprolactone tetraol of molecular weight approx. 1000. Alternative hydroxy functional polyesters can be prepared from polyols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, dipropylene glycol or neopentyl glycol with dicarboxylic components such as phthalic anhydride, isophthalic acid, maleic anhydride and/or adipic acid, azelaic acid or sebacic acid and a trifunctional compound such as trimethylolpropane, trimethylolethane, glycerol or trimellitic anhydride, using an excess of the polyol to obtain a hydroxy-terminated polymer . A lactone such as caprolactone or a hydroxy acid such as hydroxycaproic acid or dimethylolpropionic acid may be included in the polyester forming reaction. The hydroxy functional polyester may be an alkyd polyol containing fatty acid units. Another suitable hydroxy functional polyester can be prepared by reacting an epoxide, such as ethylene oxide or a glycidyl ether or ester, with a dicarboxylic acid. Various hydroxy-terminated polyethers are marketed commercially, e.g. under the trade names "Teracol" and "Terathane", which typically have molecular weights in the range 600-2400. These are generally formed by reacting a polyol such as glycerol, trimethylolpropane or a higher polyol with propylene oxide and/or ethylene oxide or with tetrahydrofuran. Hydroxy-terminated addition polymers, e.g. hydroxy-terminated polybutadienes or butadiene/styrene or butadiene/acrylonitrile polymers can also be used. Hydroxy-terminated polyurethanes can alternatively be used, formed e.g. from a polyisocyanate and an excess of a polyol component which may include a polyether or polyester polyol and a low molecular weight polyol.

Alternative hydroxy functional polymers suitable for use as hydroxy component (A) include amide-containing polyols prepared by the reaction of a polycarboxylic acid or an anhydride with a polyol and a diamine or an amino alcohol, epoxy polyols prepared by the reaction of glycidyl ethers of polyphenols, such as diglycidyl ethers of bisphenol A with a bisphenol or an aliphatic diol, polyvinyl alcohol, an allyl alcohol polymer such as styrene/allyl alcohol copolymer optionally containing allyl ether units, cellulose or a cellulose derivative, or a hydroxy-functional polyurethane.

The hydroxy functional component (A) may alternatively be a non-polymeric polyol or may include a non-polymeric polyol such as ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2-dimethyl-3-hydroxypropyl 2 ,2-dimethyl-3-hydroxypropionate, diethylene glycol or an alkoxylated bisphenol A.

The coating agent according to the invention is generally a two-component coating where the hydroxy component (A) and the polyanhydride (B) are stored separately and mixed shortly before use. The coating can be applied to a substrate by means of spraying, e.g. conventional airless spray or double-fed spray where the polymers (A) and (B) are not mixed before the spray head, or by rolling or coating. The coating composition generally has a shelf life of at least 15 minutes when applied by double feed spraying or at least half an hour after mixing when applied by other techniques. The coating is preferably a room temperature curing coating which is capable of curing at room temperature, e.g. 10-40°C, on the substrate so that a hard film is obtained which is adhesive-free and resistant to solvent so that it can be covered over within 24 hours. Maximum hardness, solvent resistance and impact resistance are generally developed within a number of days at room temperature, e.g. 5-20 days. Curing can be carried out at temperatures above room temperature, e.g. in the range 40-180°C, especially 100-150°C, for shorter times if this is more appropriate, e.g. when coating under factory conditions.

The proportion of anhydride groups in the anhydride component (B) to hydroxy groups in the hydroxy component (A) is 0.5:1-2:1.

The anhydride component and the hydroxy component are preferably each dissolved in a solvent, such as a hydrocarbon and/or a polar organic solvent, e.g. xylene or toluene or trimethylbenzene or mixtures thereof with an ester such as butyl acetate or ethoxyethyl acetate or methoxypropyl acetate or with a ketone such as methyl isobutyl ketone or methyl isoamyl ketone. For most applications, the polymers (A) and (B) are preferably compatible both in solution and in the absence of solvent so that a clear coating is obtained. For some applications where toughness of the coating is more important than appearance, the polymers may be less compatible so that some phase separation occurs when the coating is dried, leading to domains of a mixture rich in one polymer in a matrix rich in the other polymer . This can provide increased impact resistance, albeit with less complete curing because the anhydride and hydroxy components are not stoichiometrically balanced in each phase.

The coating agent usually contains additives, such as pigments or fillers, e.g. opaque or transparent pigments or pigments with metallic flakes, fillers, plasticizers, antioxidants, UV stabilizers, surfactants or flow control agents including additives to provide thixotropy or sign resistance or pigment orientation. These additives may be included in any or both of the components of the paint, although it is preferred to include any pigments or fillers that may contain significant amounts of absorbed water with the hydroxy component (A) to avoid reaction with the anhydride.

The coating agent according to the invention can be applied to a wide range of substrates, especially to rigid substrates, such as metal, wood, glass or plastic. The coatings can be applied over most commercially sold primers. They can be applied by means of spray, which is generally preferred, coating or roller, or by dip or float coating. The coating agents according to the present invention are very useful as top coat paints and are particularly useful as automotive paints, including paints for refinishing. They can be applied in "clear on base" coating systems in which a pigmented coating is covered with a translucent clear coating. The coating agent according to the present invention can be used as either the base coating or the clear coating in such coating systems, or preferably as both. They can also be applied as clear coats over known base coats, such as polyurethane, acrylic or polyester base coats.

The coating agent according to the invention can alternatively be formed as a powder coating in certain cases, provided that both the hydroxy component (A) and the anhydride component (B) are solids at temperatures up to 50°C, and provided that at least one of (A) and (B) is a synthetic resin having a glass transition temperature in the range of 0-120<*>C, preferably 40-90°C. For use in powder coatings, the anhydride component (B) preferably does not contain an olefinically unsaturated double bond in the ti,<g-> or <g>,7-position with regard to any anhydride groups, and if the anhydride component (B) is an addition polymer, the anhydride groups are preferably separated from the addition polymer chain by at least one intervening carbon atom. It may be derived from a polyanhydride of this type described in European Patent Publication 209377, e.g. by reaction with a primary/tertiary diamine.

Examples

The invention is illustrated by means of the following examples, where all parts and percentages are expressed by weight. Examples 1-3, 7, 10, 12, 14 and 17 are examples of the production of the amine-functional polyanhydride. Examples 4-6, 8, 9, 11, 13, 15, 16 and 18 are examples of coating agents according to the invention.

Example 1

l( a) Preparation of itaconic anhydride copolymer

Butyl acetate solvent (142 g) was placed in a 5 liter container equipped with a mechanical stirrer, addition funnel, reflux condenser and gas inlet. The addition funnel contained itaconic anhydride (150.0 g), methyl methacrylate (75.0 g) and styrene (275.0 g). 2,2'-Azobismethylbutyronitrile 1 (25.0 g) was added to the above mixture and the whole was dissolved in butyl acetate (500 g). The solvent in the reaction vessel was heated to reflux under a nitrogen atmosphere and the contents of the funnel were slowly added with stirring over a period of 3 hours. After the addition was complete, stirring and heating were maintained for an additional 1.5 hours to complete the polymerization. The resulting polymer, polymer A, had a number average molecular weight Mn of 8000, relative to polystyrene, as determined by gel permeation chromatography, and an anhydride equivalent weight of 389.

l( b) Preparation of amine function. ionic polyanhydride Polymer A (92.0 g) was placed in a 500 ml vessel equipped with a mechanical stirrer, addition funnel, Dean and Stark trap and gas inlet, and the addition funnel was filled with N,N-dimethylpropane-1,3-diamine (12.1 g). The contents of the vessel were heated to reflux under a nitrogen atmosphere, and the contents of the funnel were added dropwise with stirring over 2 hours, during which water of reaction was removed azeotropically. Heating and stirring were maintained for an additional 0.5 hours. A total of 2.1 g of water was collected. The resulting polymer, POLYMER B, had an Mn of 8500 by gel permeation chromatography, an amine equivalent weight of 856, and an anhydride equivalent weight of 851.

Example 2

2(a) Preparation of maleic anhydride copolymer A maleic anhydride copolymer was prepared by following the procedure from example 1(a) but using an equal weight of maleic anhydride instead of the itaconic anhydride. The resulting polymer, POLYMER D, had a Mn of 8200 by gel permeation chromatography and an anhydride equivalent weight of 368.

2( b) Preparation of amine function. ionic polyanhydride In an equivalent manner to Example 1(b), polymer D (75.0 g) in butyl acetate solvent (75.0 g) was reacted with N,N-dimethylaminopropylamine (10.2 g). The resulting polymer, POLYMER E, had a Mn of 8700 by gel permeation chromatography, an amine equivalent weight of 1010, and an anhydride equivalent weight of 979.

Example 3

3(a) Preparation of anhydride-functional polymer Dipentaerythritol (1 mol, 254 g), epsilon-caprolactone (6 mol, 684 g) and dibutyltin dilaurate (1.0 g) were heated together in xylene (1000 g) at reflux for 4 hours. Mercaptoacetic acid (6 mol, 552 g) was added, and reflux was continued with a water trap until 108 g of water was collected. Isopropenyl acetate (100 g) was added and total reflux continued for 1 hour to remove any remaining hydroxy groups.

Solvent and unreacted ester were removed under vacuum leaving 1380 g of a relatively mobile pale yellow oil. Maleic anhydride (588 g, 6 mol) and triethylamine catalyst (0.6 g) were added and the mixture was kept below 30°C with stirring for 4 hours.

3( b) Preparation of amine-functional polyanhydride

Xylene (1500 g) was added to the above reaction product, followed by 4-aminopyridine (2 mol, 188 g) over a period of 1 hour. The mixture was refluxed and water (36 g) collected over 7 hours. Volatiles were removed under vacuum to give 2120 g of polyanhydride, POLYMER F, as a yellow oil, with an anhydride equivalent weight of 530.

Examples 4-6

Pentaerythritol (79.9 g) suspended in xylene solvent (1400 g) containing dibutyl dilaurate (0.75 g) was placed in a 5 liter vessel equipped with a mechanical stirrer, reflux cooler, addition funnel and gas inlet, and the addition funnel was filled with dry epsilon- caprolactone (665.7 g). The container contents were stirred at reflux under a nitrogen atmosphere, and the contents of the addition funnel were added slowly over the course of 1 hour. Heating and stirring were maintained for an additional 2 hours, and the solvent was removed under vacuum. The resulting polymeric tetraol, POLYMER C, had an Mn of 1272 and a hydroxy equivalent weight of 318.

Example 4

Polymer B (Example 1) (2.67 parts) in butyl acetate solvent (4.01 parts) was mixed with polymer C (1.00 parts) in butyl acetate (1.00 parts) and cast on glass. It cured at room temperature and produced a hard, strong, glossy film within 16 hours. After 7 days at room temperature, the film had good resistance to methyl ethyl ketone (MEK).

Example 5

A mixture of polymer E (Example 2) (3.08 parts) in butyl acetate solvent (4.62 parts) and polymer C (1.00 part) in butyl acetate solvent (1.00 part) was cast on glass and cured at room temperature. After 7 days at room temperature, the film had good MEK resistance.

Example 6

Polymer F (Example 3) (5.30 parts) was mixed with polymer C (3.18 parts) in butyl acetate solution and cast on glass. The coating cured at room temperature to a hard but very flexible coating.

Comparative example

A copolymer of itaconic anhydride was prepared in the same way as example 1(a), but with a monomer composition itaconic anhydride 13%, methyl methacrylate 20% and styrene b7%. The resulting polymer had approximately the same anhydride equivalent weight as polymer B.

It was mixed with hydroxy-functional polymer C and coated on a glass plate as in Example 4. After 7 days at room temperature, the coating was soft and dissolved after brief contact with solvents such as xylene or MEK.

Example 7

Production of anhydride polymers

Itaconic anhydride (300 g), styrene (570 g), methyl methacrylate (130 g), "Vazo 67" free radical initiator (50 g) and a solvent mixture of xylene (300 g) and N-methylpyrrolidone (100 g) were premixed and introduced in a refluxing mixture of xylene (450 g) and N-methylpyrrolidone (150 g) during 4 hours. The mixture was refluxed for an additional 1 hour and cooled to provide a polyanhydride solution with a solids content of 46.6%, an Mn of 3800 and a weight average molecular weight (Mw) of 7700 (relative to polystyrene).

Preparation of amine-functional polyanhydride N,N-dimethylpropane-1,3-diamine (9.2 g, equivalent to one third of the available anhydride groups) was added dropwise over 15 minutes to the refluxing anhydride polymer solution (215 g) in a container equipped with a water separator. Reflux distillation was continued for another 7 hours, after which 1.7 g of water had been collected. The product had a solids content of 50.0$ and an anhydride equivalent weight of 1204.

Example 8

Production of acrylic polyol

Hydroxyethyl acrylate (193.5 g), methyl methacrylate (403.5 g), styrene (403.5 g) and "Vazo 67" initiator (40 g) were premixed and added dropwise to refluxing butyl acetate (1000 g) in within 3 hours. Reflux was continued for 1 hour to give a polymer solution with a solids content of 50$, a Mn of 5200, a Mw of 10300 (relative to polystyrene) and a hydroxy equivalent weight of 600.

Coating agent

24.1 g of the amine-functional polyanhydride solution from Example 7 and 12.0 g of the acrylic polyol solution prepared above were mixed and cast as a film on glass at a dry film thickness of 60 µm. The coating was cured by heating to 150°C for 3 minutes. The solvent resistance of the cured coating was tested by rubbing with a cloth soaked in MEK; the coating was essentially unaffected by 200 MEK double rubs.

Example 9

Production of polyester polyol

Trimethylolpropane (1 mol, 134 g), caprolactone (6 mol, 684 g) and xylene (407 g) were heated at reflux in the presence of tetrabutyl titanate (0.4 g) for 4 hours. The xylene was then removed by vacuum distillation to provide a polymer with a solids content of 97$, a Mn of 814 and a hydroxy equivalent weight of 271.

Coating agent

24.1 g of the amine functional polyanhydride solution from Example 7 and 2.8 g of the polyester polyol prepared above were mixed, cast as a film and heat cured as described in Example 8. The solvent resistance of the cured coating was 150 MEK double rubs.

Example 10

Preparation of polymeric anhydride

Aconitic acid (223 g), styrene (800 g) and "Vazo 67" (50 g) were dissolved in tetrahydrofuran (780 g) and added dropwise to refluxing butyl acetate over 3 hours. Azeotropic reflux was continued for an additional 8 hours, removing tetrahydrofuran and water through a packed column while topping up butyl acetate as needed to avoid high viscosity development.

The product was a polymer with a solids content of 50$, a Mn of 3400 and a Mw of 8500 (relative to polystyrene). It showed strong anhydride peaks in the infrared spectrum and its acid value after precipitation and methanolysis was determined to be 43.6, indicating mainly the incorporation of aconitine residues.

The calculated anhydride equivalent weight was 780.

Preparation of amine function. ionic polyanhydride Dimethylethanolamine (11.4 g) was added dropwise to the refluxing polymeric anhydride solution prepared above (200 g) over 15 minutes. Azeotropic reflux was continued until 2.3 ml of water had been removed and no hydroxy signal was visible in the infrared spectrum (8 hours). The resulting polymer had a solids content of 73%. Its amine equivalent weight after precipitation was determined to be 783, and its anhydride equivalent weight was 851.

Example 11

11.7 g of the amine-functional polyanhydride solution from Example 10 and 2.8 g of the polyester polyol from Example 9 were mixed and cast as a film on glass at a dry film thickness of 60 µm. The coating film was allowed to cure at room temperature (approx. 20°C). The solvent resistance of the coating was examined after 7 days and was found to be 95 MEK double rubs.

Example 12

Production of amln function. ionic polyanhydride Diethylaminoethyl methacrylate (100 g), styrene (630 g), neopentyl glycol dimethacrylate (70 g), and "Vazo 67" (50 g) were dissolved in xylene (400 g) and used as raw material 1.

Itaconic acid (232 g) was dissolved in tetrahydrofuran (1000 g) as raw material 2.

Raw materials 1 and 2 were separately added dropwise to refluxing xylene (466 g) and N-methylpyrrolidone (200 g) over the course of 3 hours while at the same time tetrahydrofuran was removed by distillation through a packed column. Azeotropic distillation was continued for another 8 hours, topping up the solvent mixture with butyl acetate as needed, until the infrared spectrum showed strong anhydride bands and very weak signals due to free carboxylic acid.

The resulting polymer solution was adjusted to 50% solids content. The polymer had an amine equivalent weight of 1850 and an anhydride equivalent weight of 560.

Example 13

11.2 g of the amine-functional polyanhydride solution from Example 12 and 2.8 g of the polyester polyol from Example 9 were mixed, cast as a film and allowed to cure at room temperature as described in Example 11. The solvent resistance of the coating after 7 days was 100 MEK double rubs.

Example 14

Preparation of polymeric anhydride

A commercially available maleinized anhydride functional polybutadiene of calculated anhydride equivalent weight 490 (available from Revertex as "Lithene PM25MA") (200 g), xylene (400 g) and palladium metal (0.4 g) was treated with hydrogen at a pressure of 80 atmospheres and a temperature of 100°C for 12 hours in a shaking autoclave. The vessel was cooled, vented and emptied to provide a solution, after recovery of the palladium by filtration, having a solids content of 33%, an anhydride equivalent weight of 490 and essentially no unsaturation.

Preparation of amine function. ionic polyanhydride N,N-dimethylpropane-1,3-diamine (1.37 g, equivalent to 10$ of the available anhydride) was added dropwise over 15 minutes to the hydrogenated polyanhydride solution prepared above (200 g). The mixture was azeotroped for 8 hours and a portion of the solvent was removed by vacuum distillation to provide a polymer with a solids content of 50%, an amine equivalent weight of 5000 and an anhydride equivalent weight of 555.

Example 15

Production of acrylic polyol

Hydroxyethyl methacrylate (130.0 g), methyl methacrylate (435 g), styrene (435 g) and "Vazo 67" (50 g) were premixed and added dropwise to refluxing butyl acetate (1000 g) over 3 hours. Reflux was continued for 1 hour to give a polymer solution with a solids content of 54%, a Mn of 4800, a Mw of 9000 (relative to polystyrene) and a hydroxy equivalent weight of 1000.

11.1 g of the amine functional polyanhydride solution from Example 14 and 18.5 g of the acrylic polyol solution prepared above were mixed, cast as a film and heat cured as described in Example 8. The solvent resistance of the cured coating was greater than 200 MEK double rubs .

Example 16

11.1 g of the amine functional polyanhydride solution from Example 14 and 12.0 g of the acrylic polyol solution from Example 8 were mixed, cast as a film and heat cured as

described in Example 8. The solvent resistance of the cured coating was greater than 200 MEK double rubs.

Example 17

Production of amln functions. ionic polyanhydride

Ethyl acrylate (47.1 g), diethylaminoethyl methacrylate (52.9 g) and "Vazo 67" (5.0 g) were mixed and added in refluxing butyl acetate (100 g) over 3 hours. The resulting polymer had an amine equivalent weight of 349. "Lithene PM25MA" (125.9 g) was then added, and benzoyl peroxide (11.3 g) added portionwise over 4 hours. The mixture was kept at reflux for another 4 hours to form a graft copolymer, cooled and emptied. It had a solids content of 70%, an amine equivalent weight of 789 and an anhydride equivalent weight of 879. Although grafting was probably not complete, it was sufficient to ensure compatibility.

Example 18

The grafted polymer from Example 17 (12.6 g) was mixed with the acrylic polyol solution from Example 15 (18.5 g) and cast onto steel plates. Heat curing (20 minutes at 150"C) produced a hard film, resistant to 70 MEK double rubs. Such a coating can be used as a fire primer.

Claims (6)

1. Coating agent including (A) a hydroxy component containing at least two free hydroxy groups per molecule and (B) an anhydride component containing at least two cyclic carboxylic acid anhydride groups per molecule, wherein at least one of (A) and (B) is a film-forming polymer, wherein the coating agent contains a catalytically effective amount of tertiary amine groups to accelerate the curing reaction between the hydroxy groups of (A) and the anhydr i d groups of (B), and wherein the ratio between amine groups and cyclic carboxylic acid anhydride groups is a maximum of 4:1, the ratio between anhydride groups in (B) and hydroxy groups in (A) being 0.5:1 to 2:1, characterized in that the anhydride component (B) contains the tertiary amine groups as adjacent groups in its molecules. 2. Coating agent according to claim 1, characterized in that the anhydride component (B) is a polymer containing cyclic carboxylic acid anhydride groups and N-(dialkylamino-alkyl)-substituted imide groups. 3. Coating agent according to claim 2, characterized in that the anhydride component (B) is the reaction product of a polymer containing cyclic carboxylic acid anhydride groups with a less than stoichiometric amount of a polyamine containing a primary amine group and at least one tertiary amine group. 4. Coating agent according to claim 2, characterized in that the anhydride component (B) is the reaction product of a polymer of an olefinically unsaturated tricarboxylic acid or an anhydride thereof with an amino alcohol. 5 . Coating agent according to claim 1, characterized in that the anhydride component (B) is an addition polymer containing cyclic carboxylic acid anhydride groups and dialkylaminoalkyl groups. 6. Coating agent according to claim 1, characterized in that the anhydride component (B) is a graft copolymer of a polymer containing cyclic carboxylic acid anhydride groups and a polymer containing amine groups.