Acid salts of amine-functionalized SMA imide resins

Benefit of provisional patent application 60/391,856 filed Jun. 26, 2002 is claimed.

This invention relates to the field of copolymers of styrene and maleic anhydride (SMA) and to methods of preparation of SMA derivatives, methods of use, and compositions prepared from SMA.

Saturated carboxylic acid salts of imidized SMA copolymers were previously suggested for cationic polymerization systems. For example, Pratt, U.S. Pat. No. 3,941,808, disclosed SMA copolymers having pendant tertiary amine groups containing a salt-forming tertiary nitrogen atom neutralized to the extent of at least 75% with saturated mono-carboxylic acids having at least eight carbon atoms such as stearic, lauric, or behenic acid to form salts which lower the surface tension at oil-water interfaces. Dehm et al., U.S. Pat. No. 4,618,655, disclosed polymers containing styrene moieties and cyclic imide moieties reacted with saturated anhydrides. However, no one had previously suggested ethylenically unsaturated imidized SMA salts which are curable, promote cure speed, function as dispersants of pigments and fillers, as emulsifying agents, and are especially useful in radiation cure applications where they improve cure speed, hardness, and adhesion properties of polymer compositions.

In one aspect, the invention comprises a composition comprising an unsaturated carboxylic acid salt of an amine-functionalized styrene-maleic anhydride imide.

In another aspect, the invention comprises a method of preparing such salts comprising reacting an amine functionalized styrene-maleic anhydride imide copolymer with an unsaturated carboxylic acid to form a salt.

In yet another aspect, the invention comprises compositions which have been prepared from such salts and methods of using such salts as dispersing agents, emulsifying agents, crosslinking agents, hardeners, and adhesion promoters.

Compositions comprising a solution of the salt in water, in an organic solvent or in polymerizable organic monomers and/or oligomers, such as UV/EB-curable monomers and/or oligomers are another aspect of the invention.

The compositions of the invention may be in the form of a pigment dispersion, ink, varnish, wood coating or metal coating comprising the salt. In the form of a pigment dispersion, the composition further comprises pigment, water, defoamer and a non-ionic surfactant.

A method of using the salts as polymeric surfactants to disperse pigments or fillers, or as an emulsifying agent or as a hard resin additive are another aspect. More particularly, such a method may comprise dispersing, emulsifying, crosslinking, hardening or conferring adhesion properties to a polymer, oligomer or monomer composition by simply adding the salt of the invention to the said polymer, oligomer or monomer composition. Another aspect of the invention is a coating or a paint obtained by curing a composition of the invention, comprising the unsaturated imide salt.

The salts of the invention react under radiation such as UV or EB cure conditions, free radical polymerization conditions, and via Michael reactions and provide enhanced properties such as cure speed, hardness, and adhesion to finished products.

The salts can homopolymerize or copolymerize with other ethylenically unsaturated monomers and/or oligomers.

The salts can be used in coatings, inks, adhesives, paper applications such as paper coatings, paper sizing, paper making, electronic applications such as photoresists, carpet treatment, overprint varnishes, and other applications where other SMA resins have been used.

FIG. 1 is an example of a reaction to prepare the SMA imide salts of the invention.

The compositions of the invention comprising the salt of the unsaturated carboxylic acid and the amine-functionalized styrene-maleic anhydride imide copolymer can be prepared in most cases by simply mixing an amine functionalized styrene-maleic anhydride imide polymer with an unsaturated carboxylic acid in a solvent or carrier. The preferred solvent is water, but other suitable solvents can be used instead of, or in combination with, water. Such other suitable solvents can be, for example, organic solvents such as acetone or ethyl acetate, photo-polymerizable monomers, or monomer/oligomer mixtures. Suitable monomer/oligomer mixtures can include water soluble monomers such as polyether acrylates or polyacrylates. Some examples of suitable oligomers are epoxy acrylates, urethane acrylates, acrylated acrylics, and polyether acrylates which are water soluble.

A salt of the invention can be isolated as a solid from such a solution by removal of the solvent, and such solid can be added directly to a formulation, or the solid can be redissolved in a solvent which is different from that used during preparation of the salt. For example, the salt can be prepared in water, isolated, and redissolved in radiation curable monomers such as polyethylene glycol 400 acrylate.

Suitable unsaturated carboxylic acids for preparation of the salts of the invention are mono or poly unsaturated and include, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, unsaturated hemi-esters of dicarboxylic anhydrides, butyl maleate, and cinnamic acid. The unsaturated carboxylic acids preferably have one to six carboxyl groups. Acrylic and methacrylic acids are preferred carboxylic acids. A mixture of a 1,2-unsaturated carboxylic acid and a saturated carboxylic acid and/or inorganic acid can be used in some embodiments, for example a mixture of acrylic acid and acetic acid can be used in some cases.

The amount of carboxylic acid used to prepare the salt can be determined by the amount of amine functionality on the SMA imide precursor. A molar ratio of carboxylic acid/SMA imide amine of about 0.5 to 1.5 is preferred, and a molar ratio of about 1.0 is most preferred.

The amine-functionalized styrene-maleic anhydride imide resin can be prepared reacting a styrene-maleic anhydride copolymer with a polyamine compound which contains a primary amine group and at least one tertiary amine group according to conventional methods.

Suitable diamines include, for example, N,N-dialkylaminoalkyl amines. A preferred diamine is N,N-dimethylaminopropyl amine. Among other amines that could be used are diethyl amino propyl amine (DEAPA), dimethyl amino butyl amine (DMABA), dimethyl amino ethyl amine (DMAEA), amino propyl morpholine, and diisopropyl amino propyl amine (DIAPA). SMA imides which can also be prepared from a mixture of a diamine and a monoamine. Suitable monoamines that could be used in combination with diamines include alkyl amines such as n-butyl amine, isopropyl amine, cycloaliphatic amines such as cyclohexyl amine, polyoxyalkylene amines such as methoxypolypropyleneoxy/polyethyleneoxy amines, and aromatic amines such as aniline.

Suitable styrene-maleic anhydride copolymers to be reacted with diamine or mixture of diamine and monoamine to form imides are those wherein the ratio of styrene to maleic anhydride in the copolymer is about 1/1 to 6/1, with a preferred ratio being about 2/1 by weight. The resultant SMA imide polymers may be of any suitable molecular weight, although a weight average molecular weight (Mw) of about 5,000 to 100,000 is preferred. The preferred range of repeating units is about 8 to 100.

The salts of the invention can be used in a wide variety of applications due to their combination of hydrophobic styrene and hydrophilic ammonium salt structural groups and having the ethylenic unsaturation. For example, the salts can be used as reactants in UV/EB cure formulations, as polymeric surfactants cure formulations, as dispersing agents for pigments or fillers, and as emulsifying agents to prepare acrylate emulsions, for example overprint varnishes. The salts can also be used in water based pigment dispersions used in making water-based UV/EB curable inks such as ink jet inks.

Such water based pigment dispersions can be used in the pH 4–7 range and therefore should have improved stability versus the conventional acrylated monomers and oligomers used in water based UV ink jet inks. Pigment dispersions prepared using conventional salts of polyacrylate resins typically have a pH of 8–9.5, which contributes to the instability of certain water based UV ink jet inks derived from them.

The salts can be cured by any type of reaction in which other ethylenically unsaturated monomers react, for example by Michael addition, radiation, and free radical polymerization.

Free radical polymerization of the salts can be in the presence of conventional peroxy initiators. The salts can be homopolymerized or copolymerized with other unsaturated monomers or with oligomers, for example styrene and styrene derivatives, acrylates, methacrylates, and acrylamide monomers, epoxy- or urethane-acrylate or methacrylate oligomers, and unsaturated polyester resins.

Among the radiation curing methods, the salts will participate in the UV or EB cure reactions.

The use of the salts in such curing reactions contributes to desirable curing kinetics and to enhanced properties in finished products.

The preferred salts contain, on average, 8–100 acid salt functional groups per resin molecule and therefore should increase cure speed when added to UV/EB cure formulations. The salts have a high Tg compared to typical monomers and resins that are used in water-based UV/EB formulations which involve low-Tg polyether chemistry. Thus, in combination with their multifunctional characteristics which increase cross-link density, the salts contribute to higher hardness and higher thermal properties in radiation cured compositions.

The following examples in which all parts and percentages are by weight unless otherwise indicated illustrate a few embodiments of the invention.