Aqueous dispersion of a hybrid polymer and coating composition therefrom

Abstract: A water-dispersible hybrid polymer of a core/shell structure is provided which is based upon (A) a polymer (core) of a mercaptofunctionalized poly(epoxyester) onto which (B) at least one addition polymer-based chain (shell) has been grafted via the addition polymerization of free-radically polymerizable monomers in the presence of the mercapto-functionalized poly(epoxyester). Also provided are aqueous dispersions of these hybrid polymers and coating compostions therefrom, which coating compositions are especially suited for use as clearcoats and surfacers.

Description: Background of the Invention The present invention relates generally to a water-dispersible hybrid polymer of a core/shell structure, which comprises (A) a polymer (core) onto which (B) at least one addition polymer-based chain (shell) has been grafted. The present invention also relates generally to aqueous dispersions of these hybrid polymers and coating compostions based thereon, which coating compositions are especially suitable for use as primers/surfacers, clear coatings and pigmented coatings. Hybrid polymers comprising a polymer backbone onto which at least one addition polymer-based chain has been grafted are, in a general sense, known in the art, as is their use in coating compositions. See, for example, DE-A-2304680, US3932562 and US4025471. Aqueous versions of such coating compositions are also known. See, for example, BE854523, EP-A-0116225, EP-A-0287144, US4028294, US4116901, US4212776, US4212781, US4285847, US4297261, US4308185, US4443568, US4564648, JP-A-63309516 and Bauer, Ronald S., "Recent Developments in Water Borne Epoxy Resins," Journal of Waterborne Coatings , 5 (1982), pp.5-17. Summary of the Invention A particular type of such hybrid polymer has now been discovered which, when dispersed in an aqueous medium, produces stable dispersions with relatively low viscosities even at concentrations of 50% by weight and higher. The hybrid polymers themselves possess a relatively low acid number which is comparable to polymers used in organic solvents. Further, aqueous coating compositions based upon these aqueous dispersions may be formulated at quite high solids contents, and films produced from these coating compositions display a good combination of physical and mechanical properties as well as good chemicial and water resistance. Such advantageous hybrid polymers, aqueous dispersions and coating compositions thereof are neither specifically known from nor suggested by the aforementioned prior art. In accordance with the present invention, there is provided a hybrid polymer which comprises (A) a polymer (core) onto which (B) at least one addition polymer-based chain (shell) has been grafted, characterized in that: i. the polymer (A) comprises a mercapto-functionalized poly(epoxyester), which is the reaction product of (1) an epoxy-terminated poly(epoxyester) and (2) a compound containing (a) a primary mercapto group and (b) a group more reactive with an epoxy group than is a primary mercapto group; ii. the addition polymer-based chain (B) comprises an acid number of from about 20 to about 100; and iii. the at least one addition polymer-based chain (B) is grafted onto the polymer (A) via the addition polymerization of free-radically polymerizable monomers in the presence of the mercapto-functionalized poly(epoxyester). It is preferred that the hybrid polymer comprises A) from about 40 wt% to about 90 wt% of the polymer (core) and B) from about 10 wt% to about 60 wt% of the addition polymer-based chains (shell), based upon the total weight of the hybrid polymer. Within these boundaries it has been found that the hybrid polymers possess the best mixture of advantageous properties from the individual components. Advantageous properties of poly(epoxyesters) include, for example, good adhesion to many substrates, good mechanical resistance and a good balance of hardness and flexibility. Advantageous properties of addition polymers include, for example, good chemical resistance. The hybrid polymers in accordance with the present invention are readily water dispersible upon at least partial neutralization of the acid groups of the addition polymer-based chains (B). Aqueous dispersions of such are produced by at least partially neutralizing the acid groups and dispersing the so-neutralized hybrid polymers in an aqueous medium. The aqueous dispersions of the hybrid polymers in accordance with the present invention are suitable for a variety of uses but especially as aqueous coating compositions. Preferred fields of application include clear coatings, pigmented coatings and primers/surfacers. These and other features and advantages of the present invention will be more readily understood by those skilled in the art from a reading of the following detailed description with reference to the specific examples contained therein. Detailed Description of the Preferred Embodiments As indicated earlier, the present invention concerns a particular hybrid polymer, aqueous dispersion of such hybrid polymer and coating composition based thereon. The hybrid polymer comprises (A) a polymer (core) onto which (B) at least one addition polymer-based chain (shell) has been grafted via the addition polymerization of free radically polymerizable monomers in the presence of the polymer (core). The polymer (A) comprises a mercapto-functionalized poly(epoxyester), which is the reaction product of (1) an epoxy-terminated poly(epoxyester) and (2) a compound containing (a) a primary mercapto group and (b) a functional group more reactive with an epoxy group than is a primary mercapto group. The epoxy-terminated poly(epoxyester) preferably comprises the reaction product of n moles of a bisepoxide having a number average molecular weight (Mn) in the range of from about 150 to about 2000, and n-1 moles of a dicarboxylic acid having 4-40 carbons atoms, wherein n = 2-10. The Mn of the resulting poly(epoxyester) should preferably range from about 400 to about 20000. As suitable bisepoxides may be mentioned a wide variety of aliphatic, aromatic, araliphatic and cycloaliphatic bisepoxides as well as mixtures thereof. A number of suitable specific examples may be found by reference to Epoxy Resins - Chemistry and Technology, 2d ed., Dekker Inc., New York (1988), pages 212-31, which is specifically incorporated by reference herein for all purposes. As preferred examples may be mentioned the diglycidyl ethers of bisphenol A; epoxy oligomers from epichlorohydrin and bisphenol A having oxirane end groups and an Mn in the range of about 300 to about 2000; 1,3-bis(2,3-epoxyprop-1-oxy) benzene; 1,4-butanediol diglycidyl ether; a diglycidyl ether of polypropylene glycol; a diglycidyl ether of dimerized linoleic acid; epoxydicyclopentyl phenyl glycidyl ether; bis(2,3-epoxycyclopentyl) ether; bis(2,3-epoxy-6-methylcyclohexylmethyl) adipate; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate and dicyclopentadiene dioxide. Especially preferred of these are the aforementioned diglycidyl ethers of bisphenol A, and epoxy oligomers from epichlorohydrin and bisphenol A. As examples of preferred dicarboxylic acids having from 4-40 carbon atoms may be mentioned adipic acid, isophthalic acid, phthalic acid, napthalene-2,6-dicarboxylic acid, hexahydrophthalic acid, succinic acid, sebacic acid, dodecane dicarboxylic acid, azaleic acid and dimerized fatty acids. Especially preferred are those having from 10 to 40 carbon atoms, particularly the dimerized fatty acids e.g. those containing from 18 to 36 carbon atoms. The epoxy-terminated poly(epoxyester) is mercapto-functionalized via the reaction of at least a portion of the epoxy group, with a compound containing a primary mercapto group and a functional group which is more reactive with an epoxy group than is a primary mercapto group. Preferred of these compounds may be mentioned those represented by the general formula (I) HS - R - X (I). R in formula (I) represents a hydrocarbon group having from 1 to 24 carbon atoms, more preferably an alkylene group having from 1 to 11 carbon atoms, and especially an alkylene group having from 1 to 4 carbon atoms. X in formula (I) represents the other functional group, which is preferably a carboxyl or amino group, most preferably a carboxyl group. Especially preferred are mercaptomonocarboxylic acids. As particularly preferred examples may be mentioned mercaptoacetic acid, mercaptopropionic acid and mercaptovaleric acid. A portion of the primary mercapto group-containing compound may be replaced with a monofuctional compound of the general formula (II) R¹ - X¹ (II). R¹ in formula (II) represents a hydrocarbon group having from 1 to 40 carbon atoms, more preferably an alkyl, aralkyl, aryl or cycloalkyl group having from 1 to 24 carbon atoms. X¹ represents a functional group which is more reactive with an epoxy group than is a primary mercapto group, preferably an amino or carboxyl group, and especially a carboxyl group. Especially preferred are the monocarboxylic acids. As suitable monocarboxylic acids may be mentioned a wide variety of aromatic, araliphatic, aliphatic and cycloaliphatic monocarboxylic acids, preferably with from 2 to 24 carbon atoms. As particularly preferred examples may be mentioned pivalic acid, propionic acid, benzoic acid and stearic acid. The primary mercapto group-containing compound should be reacted with the epoxy-terminated poly(epoxyester) in an equivalence ratio of X groups/epoxy groups of at least about 1/4, preferably at least about 1/2. The combination of the primary mercapto group-containing compound and monofunctional compound is utilized in an equivalence ratio of X+X¹ groups/epoxy groups of from about 1/4 to 1/1, preferably 1/2 to 1/1, and especially 1/1 (stoichiometric) so as to result in essentially no residual epoxy functionality. The mercapto-functionalized poly(epoxyester) may be produced in a conventional manner by reacting the bisepoxide, dicarboxylic acid, primary mercapto group-containing compound and optional monofunctional compound in the amounts described above. Preferably, the reaction should take place in an organic solvent (10-30 wt%) at a temperature of between about 60°C and about 200°C. The organic solvent for the reaction should be water miscible. As suitable examples may be mentioned glycol ethers and propyleneglycol ethers, such as methoxypropanol, butoxyethanol, isopropoxypropanol, propoxypropanol, diethyleneglycol dimethylether and N-methyl pyrrolidone. Small amounts of non-water miscible organic solvents may also be utilized, such as ethylmethyl ketone and methylisobutyl ketone. A catalyst may also be utilized for the reaction between the epoxy groups, and the carboxyl and other functional groups. As suitable examples may be mentioned acid catalysts such as p-toluene sulfonic acid; basic amine, ammonium and phosphonium catalysts such as tetramethylammonium chloride, benzyltrimethylammonium methoxide and triphenylbenzyl phosphonium chloride; and other well-known catalysts such as Cr(III)-2-ethylhexanoate, zinc chloride and zinc acetylacetonate. The hybrid polymer is formed by the addition polymerization of free-radically polymerizable monomers in the presence of the above-described mercapto-functionalized poly(epoxyester). It is believed that the mercapto groups thereof act as chain transfer agents, resulting in the grafting of one or more addition polymer-based chains onto the core polymer. A wide variety of free-radically polymerizable monomers are suitable for use in producing the addition polymer-based chains. As specific examples may be mentioned ethylenically unsaturated monocarboxylic acids, such as (meth)acrylic acid and crotonic acid; (cyclo)alkyl(meth)acrylates with 1-12 carbon atoms in the (cyclo)alkyl group, such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl(meth)acrylate, isobornyl(meth)acrylate, dodecyl(meth)acrylate and cyclohexyl(meth)acrylate; dicarboxylic acids such as maleic acid (and anhydride), fumaric acid and itaconic acid (and anhydride); the (cyclo)alkylesters of such dicarboxylic acids with 1-12 carbon atoms in the (cyclo)alkyl groups, such as dimethylmaleate, diethylmaleate, diethylfumarate, dipropylmaleate, dibutylmaleate, dibutylfumarate, 2-ethylhexylmaleate, 2-ethylhexylfumarate, octylmaleate, isobornylmaleate, dodecylmaleate and cyclohexylmaleate; (meth)acrylates with ether groups, such as 2-methoxy-ethylmethacrylate, 2-ethoxy-ethylmethacrylate and 3-methoxy-propylmethacrylate; hydroxyalkyl(meth)acrylates, such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 4-hydroxybutylacrylate, 6-hydroxyhexylacrylate, p-hydroxycyclohexyl(meth)acrylate, hydroxypolyethyleneglycol(meth)acrylates, hydroxypolypropyleneglycol(meth)acrylates and the alkoxy derivative thereof; monovinyl aromatic compounds, such as styrene, vinyltoluene, α-methylstyrene and vinylnapthelene; other substituted (meth)acrylic compounds, such as (meth)acrylamide, (meth)acrylonitrile, N-methylol(meth)acrylamide and N-alkyl(meth)acrylamides; and other monounsaturated compounds such as vinylchloride, vinylacetate, vinylpropionate and vinylpyrrolidine. Especially preferred monomer mixtures for use in producing the addition polymer-based chains are those disclosed in EP-B-0000601 (US4245074), which is incorporated by reference herein for all purposes. As a first specific example may be mentioned the following monomer mixture: 35-55 mol% of styrene and/or α-methylstyrene; 20-50 mol% of a compound of the general formula (III) wherein R² is an H atom or a methyl group, and R³ is an alkyl group with 4-10 carbon atoms; and 0-30 mol% of one or more other free-radically polymerizable monomers, such as described above. As a second specific example may be mentioned the following monomer mixture: 35-55 mol% of styrene and/or α-methyl styrene; 20-50 mol% of acrylic acid and/or methacrylic acid; and 0-30 mol% of one or more other free-radically polymerizable monomers, such as described above, wherein the reaction product during or after the polymerization is reacted with a glycidyl ester of a carboxylic acid, having the general formula (IV) wherein R³ is as defined above. The particular monomers and/or monomer mixtures should be chosen in a manner and in an amount so as to result in an addition polymer-based chain having an acid number of between about 20 and about 100 (mg KOH/g). It has been generally found stable dispersions cannot readily be produced when the acid number of the addition polymer-based chains is below about 20, and when the acid number is above about 100 the water-resistance becomes unacceptable. It is especially preferred that the acid number should be in the range of from about 30 to about 80. The monomers and/or monomer mixtures should also be chosen in a manner and in an amount so as to result in the hybrid polymer comprising: (A) from about 40 wt% to about 90 wt% of the polymer (core) and (B) from about 10 wt% to about 60 wt% of the addition polymer-based chains (shell), based upon the total weight of the hybrid polymer. As mentioned earlier, within these boundaries it has been found that the hybrid polymers possess the best mixture of advantageous properties from the individual components. Of course, the particular choice of monomers and/or monomers mixtures will also depend on a wide variety of other factors such as, for example, the particular end use of the hybrid polymer. These and other factors will be appreciated by one skilled in the art, who can further adjust the choice of monomers accordingly. The copolymerization of the ethylenically unsaturated monomers in the presence of the mercapto-functionalized poly(epoxyester) is in general conducted under an inert (e.g., nitrogen) atmosphere and in the presence of a radical initiator. The polymerization temperature may generally range from about 60°C to about 200°C, and preferably from about 100°C to about 160°C. As suitable radical initiators may be mentioned dibenzoyl peroxide, dicumyl peroxide, methylethyl ketone peroxide, cumene hydroperoxide, tert.butyloxy-2-ethylhexanoate, tert.butylperbenzoate, tert.butylcumylperoxide, di-tert.butylperoxy-3,5,5-trimethylcyclohexane, 1,3-bis(tert.butyl)peroxyisopropylbenzene and azobisisobutyronitrile. Mixtures of the above are also suitable. In general are the radical initiators utilized in amounts of from about 0,05 wt% to about 10 wt%, and preferably from about 1 wt% to about 5 wt%, based upon the total weight of the monomer mixture. The so-produced hybrid polymers are readily dispersible in an aqueous medium upon at least partial neutralization of the carboxyl groups of the addition polymer-based chains. Suitable neutralizing agents for carboxyl groups include a wide variety of organic and inorganic bases, for example, tertiary amines. The preferred degree of neutralization ranges from about 50% to about 130% on an equivalent basis. After neutralization, the hybrid polymers may readily be dispersed in an aqueous medium by conventional means, preferably at elevated temperatures from about 50°C to about 100°C. When hybrid polymers according to the present invention are utilized, in many cases stable aqueous dispersions of 50 wt% and even higher may be produced. Typically, the aqueous dispersions in accordance with the present invention will comprise a solids content of from about 30 wt% to about 60 wt%, and preferably in the range of from about 35 wt% to about 55 wt%. As indicated earlier, a preferred use of these aqueous dispersions is in the formulation of coating compositions. When so utilized, the coating compositions may also contain a curing agent for the hydroxyl groups of the hybrid polymer. As suitable hydroxyl group-reactive curing agents may generally be mentioned N-methylol and/or N-methylol ether containing animoplasts. Especially favorable results can be obtained by using a methylol melamine having 4-6 methylol groups per molecule, with at least three of the methylol groups being etherified with methanol, butanol and/or a methanol or butanol condensation product of formaldehyde and N,N'-ethylene diurea. Other suitable curing agents include water dispersible blocked isocyanates, such as those blocked with methylethylketoxime, and isocyanate group-containing adducts of a polyisocyanate and a hydroxycarboxylic acid, for instance, dimethylolpropionic acid. The curing agents reacting with the hydroxyl groups are generally utilized in amounts such that the ratio of the hydroxyl groups of the hybrid polymer to the reactive groups of the curing agent is in the range of from about 0,7 to about 1,5. Depending upon the field of application, the coating compositions may also contain a variety of other additives common to the paint industry such as pigments, coloring agents, pigment dispersing agents, and thixotropic and other rheological agents. The coating may, if desired, also contain accelerators for the curing reaction, for example, acid compounds such as p-toluene sulfonic acid and blocked derivatives thereof. The coating compositions may be applied onto any number of well-known substrates such as wood, synthetic materials and metals. Suitable application methods include rolling, spraying, brushing, sprinkling, dipping and electrostatic spraying. The coating compositions may be dried and cured under a variety of conditions, for example, at ambient temperatures. Accelerated curing may also be accomplished by baking at elevated temperature of generally from 100°C to 160°C for from 20 to 60 minutes. As mentioned earlier, these coating compositions are suitable for use in a wide variety of applications. They are, however, especially suited for use as surfacers and clear coats. The foregoing more general discussion of the present invention will be further illustrated by the following specific examples. EXAMPLES Preparation of Dispersions In the following Examples 1-23, a number of stable aqueous polymer dispersions were prepared in accordance with the present invention. Various properties of these dispersions were measured, and the results are present below in Table I. In these examples, the mean particle size of the dispersions was determined by dynamic light scattering, the dispersions being diluted with water to a solids content of about 0,1% by weight. The viscosity of the dispersions was determined with a Brookfield viscometer. The solids content of the dispersions was determined in accordance with ASTM method 1644-59, with heating at 130°C over a period of 30 minutes. Example 1 In a 2 liter reaction flask fitted with a stirrer, a thermometer, a reflux condenser and a dropping funnel were homogenously mixed: 132,3 g of a dimerized fatty acid (commercially available under the trade designation Pripol 1009 from Unilever), 100,6 g of a diglycidyl ether of bisphenol A (commercially available under the trade designation Epikote 828 from Shell), 8,2 g of 3-mercaptopropionic acid, 82,9 g of 1-methoxy propanol-2 and 0,3 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 34,5 g of acrylic acid, 49,8 g of styrene, 71,9 g of the glycidyl ester of 1,1-dimethyl-1-heptane carboxylic acid (commercially available under the trade designation Cardura E from Shell) and 2,4 g of dicumyl peroxide. After ventilating, the reaction flask and dropping funnel were brought under a nitrogen atmosphere. The contents of the reaction flask were then heated to 140°C and maintained at that temperature for 3 hours, after which the contents of the dropping funnel were added and the reaction mixture temperature maintained at 140°C for another three hours. The contents of the reaction flask were then cooled to 95°C and 17,1 g of dimethylethanolamine added after which, over a period of two hours, 552 g of demineralized water were also added. Example 2 Example 1 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 115,0 g of the dimerized fatty acid, 112,5 g of the epoxy resin, 21,2 g of 3-mercaptopropionic acid, 46,0 g of 1-methoxy propanol-2 and 0,3 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 36,0 g of acrylic acid, 52,0 g of styrene, 75,0 g of the glycidyl ester, 1,8 g of dicumyl peroxide and 27,0 g of 1-methoxy propanol-2. After the cooling of the contents of the reaction flask to 95°C, 17,8 g of dimethylethanolamine were added after which, over a period of two hours, 529 g of demineralized water were also added. Example 3 Example 1 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 142,7 g of the dimerized fatty acid, 108,5 g of the epoxy resin, 8,8 g of 3-mercaptopropionic acid, 85,0 g of 1-methoxy propanol-2 and 0,4 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 30,4 g of acrylic acid, 44,0 g of styrene, 63,4 g of the glycidyl ester and 2,2 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 15,1 g of dimethylethanolamine were added after which, over a period of two hours, 500 g of demineralized water were also added. Example 4 Example 1 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 153,7 g of the dimerized fatty acid, 116,9 g of the epoxy resin, 9,4 g of 3-mercaptopropionic acid, 87,2 g of 1-methoxy propanol-2 and 0,4 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 26,1 g of acrylic acid, 37,7 g of styrene, 54,4 g of the glycidyl ester and 1,8 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 12,9 g of dimethylethanolamine were added after which, over a period of two hours, 500 g of demineralized water were also added. Example 5 Example 1 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 124,0 g of the dimerized fatty acid, 91,0 g of the epoxy resin, 2,9 g of 3-mercaptopropionic acid, 3,3 g of benzoic acid 80,8 g of 1-methoxy propanol-2 and 0,3 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 38,8 g of acrylic acid, 56,1 g of styrene, 80,9 g of the glycidyl ester and 2,7 g of dicumyl peroxide. After ventilating, the reaction flask and dropping funnel were brought under a nitrogen atmosphere. The contents of the reaction flask were then heated to reflux (about 130°C-140°C) and maintained at reflux for 3 hours, after which the contents of the dropping funnel were added. The temperature of the reaction mixture was maintained at 130°C for three hours, and increased to 140°C for one additional hour. The contents of the reaction flask were then cooled to 95°C and 19,2 g of dimethylethanolamine added after which, over a period of two hours, 611 g of demineralized water were also added. Example 6 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 123,4 g of the dimerized fatty acid, 90,5 g of the epoxy resin, 2,8 g of 3-mercaptopropionic acid, 3,3 g of benzoic acid, 75,8 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,3 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 37,6 g of acrylic acid, 54,4 g of styrene, 84,9 g of the glycidyl ester and 3,1 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 16,3 g of dimethylethanolamine were added after which, over a period of two hours, 712 g of demineralized water were also added. Example 7 Example 5 was repeated in its entirety except for the following. The dropping funnel was filled with a homogenous mixture of: 37,7 g of acrylic acid, 10,5 g of methyl methacrylate, 43,5 g of styrene, 85,1 g of the glycidyl ester and 3,2 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 16,3 g of dimethylethanolamine were added after which, over a period of two hours, 643 g of demineralized water were also added. Example 8 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 134,6 g of the dimerized fatty acid, 98,7 g of the epoxy resin, 3,1 g of 3-mercaptopropionic acid, 3,6 g of benzoic acid, 77,6 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,4 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 33,6 g of acrylic acid, 9,3 g of methylmethacrylate, 38,7 g of styrene, 75,6 g of the glycidyl ester and 2,8 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 14,5 g of dimethylethanolamine were added after which, over a period of two hours, 526 g of demineralized water were also added. Example 9 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 145,8 g of the dimerized fatty acid, 107,0 g of the epoxy resin, 3,3 g of 3-mercaptopropionic acid, 3,9 g of benzoic acid, 79,4 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,3 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 29,3 g of acrylic acid, 8,1 g of methylmethacrylate, 33,9 g of styrene, 66,2 g of the glycidyl ester and 2,5 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 12,7 g of dimethylethanolamine were added after which, over a period of two hours, 500 g of demineralized water were also added. Example 10 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 157,0 g of the dimerized fatty acid, 115,2 g of the epoxy resin, 3,6 g of 3-mercaptopropionic acid, 4,2 g of benzoic acid, 81,2 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,4 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 25,1 g of acrylic acid, 7,0 g of methylmethacrylate, 29,1 g of styrene, 56,7 g of the glycidyl ester and 2,1 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 10,9 g of dimethylethanolamine were added after which, over a period of two hours, 452 g of demineralized water were also added. Example 11 Example 10 was repeated in its entirety except for the following. The dropping funnel was filled with a homogenous mixture of: 15,4 g of acrylic acid, 12,2 g of methacrylic acid, 7,1 g of methylmethacrylate, 29,65 g of styrene, 53,55 g of the glycidyl ester and 2,10 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 11,4 g of dimethylethanolamine were added after which, over a period of two hours, 430 g of demineralized water were also added. Example 12 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 168,2 g of the dimerized fatty acid, 123,4 g of the epoxy resin, 3,9 g of 3-mercaptopropionic acid, 4,5 g of benzoic acid, 83,0 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,5 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 20,95 g of acrylic acid, 5,80 g of methylmethacrylate, 24,20 g of styrene, 47,30 g of the glycidyl ester and 1,75 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 9,1 g of dimethylethanolamine were added after which, over a period of two hours, 351 g of demineralized water were also added. Example 13 Example 12 was repeated in its entirety except for the following. The dropping funnel was filled with a homogenous mixture of: 12,80 g of acrylic acid, 10,20 g of methylacrylic acid, 5,95 g of methylmethacrylate, 24,70 g of styrene, 44,55 g of the glycidyl ester and 1,80 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 9,5 g of dimethylethanolamine were added after which, over a period of two hours, 351 g of demineralized water were also added. Example 14 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 179,4 g of the dimerized fatty acid, 131,7 g of the epoxy resin, 4,1 g of 3-mercaptopropionic acid, 4,8 g of benzoic acid, 84,8 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,5 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 16,8 g of acrylic acid, 4,7 g of methylmethacrylate, 19,3 g of styrene, 37,8 g of the glycidyl ester and 1,4 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 7,3 g of dimethylethanolamine were added after which, over a period of two hours, 300 g of demineralized water were also added. Example 15 Example 14 was repeated in its entirety except for the following. The dropping funnel was filled with a homogenous mixture of: 10,25 g of acrylic acid, 8,15 g of methacrylic acid, 4,75 g of methylmethacrylate, 19,80 g of styrene, 35,65 g of the glycidyl ester and 1,40 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 7,6 g of dimethylethanolamine were added after which, over a period of two hours, 300 g of demineralized water were also added. Example 16 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 190,7 g of the dimerized fatty acid, 139,9 g of the epoxy resin, 4,4 g of 3-mercaptopropionic acid, 5,0 g of benzoic acid, 86,7 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,5 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 12,60 g of acrylic acid, 3,50 g of methylmethacrylate, 14,50 g of styrene, 28,35 g of the glycidyl ester and 1,05 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 5,4 g of dimethylethanolamine were added after which, over a period of two hours, 284,7 g of demineralized water were also added. Example 17 Example 5 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 260,8 g of the dimerized fatty acid, 191,3 g of the epoxy resin, 6,0 g of 3-mercaptopropionic acid, 6,9 g of benzoic acid, 125,3 g of 1-methoxy propanol-2, 12,0 g of methylisobutylketone and 0,6 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 17,30g of acrylic acid, 13,80 g of methacrylic acid, 8,00 g of methylmethacrylate, 33,35 g of styrene, 60,15 g of the glycidyl ester and 2,40 g of dicumyl peroxide. After the cooling of the contents of the reaction flask to 95°C, 12,85 g of dimethylethanolamine were added after which, over a period of two hours, 500 g of demineralized water were also added. Example 18 In a 2 liter reaction flask fitted with a stirrer, a thermometer, a reflux condenser and a dropping funnel were homogenously mixed: 126,4 g of a dimerized fatty acid of Example 1, 68,4 g of a 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate (commercially available under the trade designation Araldite CY-179 from Ciba-Geigy), 5,2 g of 3-mercaptopropionic acid, 40,0 g of methylisobutylketone and 0,4 g of Cr(III) 2-ethylhexanoate. The dropping funnel was filled with a homogenous mixture of: 75,5 g of styrene, 51,5 g of butylmethacrylate, 36,3 g of methylmethacrylate, 31,2 g of methacrylic acid, 5,5 g of dicumyl peroxide and 60,0 g of dipropyleneglycol monoisopropylether. After ventilating, the reaction flask and dropping funnel were brought under a nitrogen atmosphere. The contents of the reaction flask were then heated to 100°C and maintained at that temperature for 4 hours, after which the contents of the dropping funnel were added. The temperature of the reaction mixture was then brought to 130°C, and this temperature maintained for another four hours. The contents of the reaction flask were then cooled to 100°C and 25,8 g of dimethylethanolamine added after which, over a period of two hours, 808 g of demineralized water were also added. Example 19 In a 2 liter reaction flask fitted with a stirrer, a thermometer, a reflux condenser and two dropping funnels (A and B) were homogenously mixed: 138,80 g of the dimerized fatty acid of Example 1, 75,10 g of the epoxy resin of Example 18, 3,25 g of benzoic acid, 33,00 g of 1-methoxy propanol-2 and 0,40 g of Cr(III) 2-ethylhexanoate. Dropping funnel A was filled with a homogenous mixture of: 2,85 g of 3-mercaptopropionic acid and 10,00 g of methylisobutylketone, and dropping funnel B was filled with a homogenous mixture of: 64,2 g of styrene, 69,1 g of butylacrylate, 22,2 g of 2-hydroxypropylmethacrylate, 19,9 g of methacrylic acid, 4,6 g of dicumyl peroxide and 40,0 g of 1-methoxy propanol-2. After ventilating, the reaction flask and dropping funnel were brought under a nitrogen atmosphere. The contents of the reaction flask were then heated to 100°C and maintained at that temperature for 2 hours, after which the contents of the dropping funnel A were added and the reaction mixture maintained at 100°C for another two hours. The contents of dropping funnel B were then added, and the temperature of the reaction mixture raised to 125°C and maintained at that temperature for four hours. The contents of the reaction flask were then cooled to 100°C and 16,5 g of dimethylethanolamine added after which, over a period of two hours, 791 g of demineralized water were also added. Example 20 Example 19 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 126,15 g of the dimerized fatty acid, 68,25 g of the epoxy resin, 3,00 g of benzoic acid, 33,00 g of dipropyleneglycol dimethylether and 0,40 g of Cr(III) 2-ethylhexanoate. Dropping funnel A was filled with a homogenous mixture of: 2,6 g of 3-mercaptopropionic acid and 7,0 g of dipropyleneglycol dimethylether, and dropping funnel B was filled with a homogenous mixture of: 72,55 g of styrene, 98,22 g of butylacrylate, 24,00 g of methacrylic acid, 5,23 g of dicumyl peroxide and 60,00 g of dipropyleneglycol dimethylether. After the cooling of the contents of the reaction flask to 100°C, 19,9 g of dimethylethanolamine were added after which, over a period of two hours, 731 g of demineralized water were also added. Example 21 Example 19 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 176,99 g of the dimerized fatty acid, 95,76 g of the epoxy resin, 16,00 g of methylethylketone, 20,00 g of 1-methoxy propanol-2 and 0,40 g of Cr(III) 2-ethylhexanoate. Dropping funnel A was filled with a homogenous mixture of: 7,25 g of 3-mercaptopropionic acid and 8,00 g of 1-methoxy propanol-2, and dropping funnel B was filled with a homogenous mixture of: 25,1 g of acrylic acid, 7,0 g of methylmethacrylate, 29,1 g of styrene, 56,7 g of the glycidyl ester of Example 1, 2,1 g of dicumyl peroxide and 45,2 g of 1-methoxy propanol-2. After the cooling of the contents of the reaction flask to 100°C, 10,9 g of dimethylethanolamine were added after which, over a period of two hours, 591 g of demineralized water were also added. Example 22 Example 19 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 177,94 g of the dimerized fatty acid, 94,22 g of the epoxy resin, 4,20 g of benzoic acid, 16,00 g of methylethyl ketone, 20,00 g of 1-methoxy propanol-2 and 0,40 g of Cr(III) 2-ethylhexanoate. Dropping funnel A was filled with a homogenous mixture of: 3,64 g of 3-mercaptopropionic acid and 8,00 g of 1-methoxy propanol-2, and dropping funnel B was filled with a homogenous mixture of: 25,1 g of acrylic acid, 7,0 g of methylmethacrylate, 29,1 g of styrene, 56,7 g of the glycidyl ester, 2,1 g of dicumyl peroxide and 45,2 g of 1-methoxy propanol-2. After the cooling of the contents of the reaction flask to 100°C, 10,9 g of dimethylethanolamine were added after which, over a period of two hours, 553 g of demineralized water were also added. Example 23 Example 19 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 267,18 g of the dimerized fatty acid, 141,46 g of the epoxy resin, 3,15 g of benzoic acid, 30,00 g of propyleneglycol dimethylether, 26,24 g of dipropyleneglycol dimethylether and 0,63 g of Cr(III) 2-ethylhexanoate. Dropping funnel A was filled with a homogenous mixture of: 8,21 g of 3-mercaptopropionic acid and 17,25 g of dipropyleneglycol dimethylether, and dropping funnel B was filled with a homogenous mixture of: 37,65 g of acrylic acid, 10,50 g of methylmethacrylate, 43,65 g of styrene, 85,05 g of the glycidyl ester, 3,15 g of dicumyl peroxide and 60,33 g of dipropyleneglycol dimethylether. After the cooling of the contents of the reaction flask to 100°C, 16,34 g of dimethylethanolamine were added after which, over a period of two hours, 641 g of demineralized water were also added. Comparative Example 1 Example 10 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 156,4 g of the dimerized fatty acid, 114,8 g of the epoxy resin, 4,6 g of dimethylolpropionic acid, 4,2 g of benzoic acid, 81,2 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,4 g of Cr(III) 2-ethylhexanoate. The resulting aqueous dispersion was unstable as phase separation occurred. Comparative Example 2 Example 10 was repeated in its entirety except for the following. In the reaction flask were homogenously mixed: 157,6 g of the dimerized fatty acid, 115,7 g of the epoxy resin, 2,5 g of propionic acid, 4,2 g of benzoic acid, 81,2 g of 1-methoxy propanol-2, 8,0 g of methylisobutylketone and 0,4 g of Cr(III) 2-ethylhexanoate. The resulting aqueous dispersion was unstable as phase separation occurred. Preparation of Coating Compositions In the following Examples 24-48, a number of unpigmented (Examples 24-46) and pigmented (Examples 47-48) coating compositions in accordance with the present invention were prepared by homogenously mixing the dispersion, melamine hardener, optionally demineralized water and optionally titanium dioxide (pigment) as set forth in Table II. The melamine hardener used in these Examples 24-48 was a 90% solids melamine resin commercially available under the trade designation Cymel 327 from American Cyanamid. The demineralized water was added to adjust the coating compositions to a spray viscosity of about 0,1 Pa.sec. (run-out viscosity of 30 sec. in a Ford Cup No. 4). The solids contents of these coating compositions were measured in the same manner as described above for the dispersions, and the results are also presented in Table II. Each of these coating compositions was applied onto a zincphosphate pretreated steel panel (Bonder 132) and cured in a baking oven for 30 minutes at a temperature of 140°C. Various properties of the so-obtained coatings were measured, and the results are presented below in Table III. The Persoz hardness was determined in accordance with French industrial standard NF T30-016, and the results are expressed in seconds. An acceptable minimum for automotive paint is about 180 seconds. The flexibility of the coatings was determined with a ball impact tester in accordance with ASTM D2794-69 using a ball weight of 0,908 kg, a ball diameter of 15,9 mm and an aperture of 16,3 mm, the results being expressed in kg.cm. An acceptable minimum flexibility for the coat side is about 35 kg.cm, with the maximum measurable value being 85 kg.cm. The coatings were also tested via the Erichsen indentation test with the results being expressed in mm. A test value of higher than 6 is indicative of a flexible coating, and a value of 2 a brittle coating. The gloss of the coating was determined in accordance with U.S. industrial standard ASTM D-523 at 60° and 20°. A gloss value on a steel substrate of above 80 at 60° is considered high. Only a limited number of preferred embodiments of the present invention have been described above. One skilled in the art, however, will recognize numerous substitutions, modifications and alterations which can be made without departing from the spirit and scope of the invention as limited by the following claims.

Claims: A hybrid polymer which comprises (A) a polymer (core) onto which (B) at least one addition polymer-based chain (shell) has been grafted, characterized in that: i. the polymer (A) comprises a mercapto-functionalized poly(epoxyester), which is the reaction product of (1) an epoxy-terminated poly(epoxyester) and (2) a compound containing (a) a primary mercapto group and (b) a group more reactive with an epoxy group than is a primary mercapto group; ii. the addition polymer-based chain (B) comprises an acid number of from about 20 to about 100; and iii. the at least one addition polymer-based chain (B) is grafted onto the polymer (A) via the addition polymerization of free-radically polymerizable monomers in the presence of the mercapto-functionalized poly(epoxyester). The hybrid polymer according to claim 1, characterized in that it comprises from about 40 wt% to about 90 wt% of the polymer (A) and from about 10 wt% to about 60 wt% of the addition polymer-based chains (B), based upon the total weight of the hybrid polymer. The hybrid polymer according to claim 1, characterized in that the epoxy-terminated poly(epoxyester) comprises the reaction product of n moles of a bisepoxide having a number average molecular weight (Mn) in the range of from about 150 to about 2000, and n-1 moles of a dicarboxylic acid having 4-40 carbon atoms, wherein n = 2-10. The hybrid polymer according to claim 3, characterized in that the poly(epoxyester) comprises an Mn in the range of from about 400 to about 20000. The hybrid polymer according to claim 3, characterized in that the bisepoxide is selected from a diglycidyl ether of bisphenol A, and epoxy oligomers from epichlorohydrin and bisphenol A. The hybrid polymer according to claim 3, characterized in that the dicarboxylic acid comprises a dimerized fatty acid. The hybrid polymer according to claim 1, characterized in that the primary mercapto group-containing compound comprises a compound of the general formula (I) HS - R - X (I) wherein R is a hydrocarbon group having from 1 to 24 carbon atoms, and X is the group more reactive with an epoxy group than is a primary mercapto group. The hybrid polymer according to claim 7, characterized in that R is an alkylene group having from 1 to 11 carbon atoms, and X is an amino or carboxyl group. The hybrid polymer according to claim 7, characterized in that the primary mercapto group-containing compound comprises a mercaptomonocarboxylic acid. The hybrid polymer according to claim 7, characterized in that a portion of the primary mercapto group-containing compound is replaced with a monofuctional compound of the general formula (II) R¹ - X¹ (II) wherein R¹ is a hydrocarbon group having from 1 to 40 carbon atoms, and X¹ is a functional group which is more reactive with an epoxy group than is a primary mercapto group. The hybrid polymer according to claim 10, characterized in that R¹ is alkyl, aralkyl, aryl or cycloalkyl group having from 1 to 24 carbon atoms, and X¹ is an amino or carboxyl group. The hybrid polymer according to claim 11, characterized in that the monofunctional compound comprises a monocarboxylic acid. The hybrid polymer according to claim 10, characterized in that the primary mercapto group-containing compound is utilized in an equivalence ratio of X groups/epoxy groups of at least about 1/4. The hybrid polymer according to claim 13, characterized in that the primary mercapto group-containing compound is utilized in an equivalence ratio of X groups/epoxy groups of at least about 1/2. The hybrid polymer according to claim 13, characterized in that the combination of the primary mercapto group-containing compound and monofunctional compound is utilized in an equivalence ratio of X+X¹ groups/epoxy groups of from about 1/4 to 1/1. The hybrid polymer according to claim 1, charaterized in that addition polymer-based chains are produced from a monomer mixture comprising 35-55 mol% of styrene and/or α-methylstyrene; 20-50 mol% of a compound of the general formula (III) wherein R² is an H atom or a methyl group, and R³ is an alkyl group with 4-10 carbon atoms; and 0-30 mol% of one or more other free-radically polymerizable monomers. The hybrid polymer according to claim 1, characterized in that the addition polymer-based chains are produced from a monomer mixture comprising 35-55 mol% of styrene and/or α-methyl styrene; 20-50 mol% of acrylic acid and/or methacrylic acid; and 0-30 mol% of one or more other free-radically polymerizable monomers, wherein the reaction product during or after the polymerization is reacted with a glycidyl ester of a carboxylic acid, having the general formula (IV) wherein R³ is an alkyl group with 4-10 carbon atoms. The hybrid polymer according to any one of claims 1-17, characterized in that the acid groups of the hybrid polymer are at least partially neutralized. An aqueous dispersion based upon the at least partially neutralized hybrid polymer according to claim 18. An aqueous coating composition based upon the aqueous dispersion according to claim 19. The aqueous coating composition according to claim 20, characterized in that the coating composition further comprises a hydroxyl group-reactive curing agent. A process of producing the hybrid polymer of any one of claims 1-18, comprising the step of grafting the at least one addition polymer-based chain (B) onto the polymer (A) via the addition polymerization of free-radically polymerizable monomers in the presence of the mercapto-functionalized poly(epoxyester).

Inventors: BUTER ROELOF, ROELOFS ANDREAS HENRICUS JOHAN, WEMMENHOVE ALETTA, BUTER, ROELOF, ROELOFS, ANDREAS HENRICUS JOHANNES, WEMMENHOVE, ALETTA
Applicants: AKZO NOBEL NV, AKZO NOBEL N.V.
Application year: 1991
Main classification: C08F283
IPC codes: C09D151, C08F283