Water Reducible Phenolic Modified Alkyd Resin

The invention is directed to a new and improved water reducible phenolic modified alkyd resin for use as a binder in coating compositions. More specifically, this invention relates to an alkyd coating resin which is a water reducible alkyd resin for use as a binder in a coating composition which alkyd resin is modified by an alkylated phenolic resin, the modified alkyd resin being a water reducible binder which provides a non-lifting recoatable coating composition.

Environmental concern has become increasingly important in recent years. This concern not only extends to preservation of the environment for its own sake, but extends to safety for the public as to both living and working conditions. Volatile organic emissions resulting from coating compositions which are applied and used by industry and by the consuming public are often not only unpleasant, but contribute to photochemical smog. Fire and health hazards of organic solvents also are well known. Governments may or have established regulations setting forth guidelines relating to volatile organic compounds (VOCs) which may be released to the atmoshpere. The United States Environmental Protection Agency (EPA) has established guidelines relating to the amount of VOCs released to the atmosphere, such guidelines being scheduled for adoption by the states of the United States. Guidelines relating to VOCs, such as those of the EPA, and environmental concerns are particularly pertinent to the paint and industrial coating industry which uses organic solvents which are emitted into the atmosphere.

With respect to coating compositions, and in response to environmental concern, organic coating resings, and most particularly alkyd coating resins have been developed and are known to reduce organic emissions with the use of water or an organic solvent water combination in lieu of using volatile organic solvents without water.

Moving from organic solvents to water or a water organic solvent combination not only changes the constituents of the alkyd, but frequently changes the curing and/or solvent retention characteristics of the coating compositions which contain the alkyd coating resin or binder. Often water as a solvent in these coating compositions will lengthen the drying times of films of these coating compositions. Generally air-drying alkyd films on metal will blister such films if they are recoated within about a three day period. This is thought to be caused by solvent penetration into the base coat and probably relates to incomplete cure or a fast cure on the surface of the coat and/or solvent retention in the base coat. Where second and third coats are required there is an obvious efficiency advantage in being able to add these additional coats of coating composition as soon as possible after applying the base coat.

In conventional organic solvent alkyd coating resin systems, the incorporation of certain phenol-formaldehyde resins into the binder resin is known to help alleviate blistering in coating compositions. These organic solvent systems, however, do not use a trifunctional acid or anhydride such as trimelletic anhydride to achieve water solubility. In water reducible alkyd systems, however, such a component generally is needed to partially react with the alkyd with residual reactive groups forming salts permitting water solubility. As is known, a water reducible alkyd resin is dispersed in water by mixing the resin with an amine or ammonia to form a salt which is then solubilized in water. The use of phenolic resins to minimize lifting with water reducible alkyd binders has heretofore been unknown.

Phenolic resins have been used with water soluble or reducible alkyd coating resins. These resins or binders, however, have required amine cross-linking agents, forced cures, and large amounts of tricarboxylic acids when formulated into coating compositions. Moreover, the literature relating to such compositions has not suggested that the use of phenolic coating resins will alleviate or have any effect on the recoatability or blistering proclivities of water reducible alkyd coating resins.

U.S. Pat. No. 4,347,335 to Thomas describes a water reducible polyester resin modified with a phenolic resin, which modified resin the patent states provides coatings with good thermal ratings, bond strengths and a coating composition with a good shelf life. The coating compositions and binders described in Thomas, however, require forced cures, aminoplast cross-linking agents, and substantial amounts of tricarboxylic acids. Moreover, the recoatability of the coating composition and blistering problem inherent with coating compositions with alkyd coating resins is not recognized or even discussed.

U.S. Pat. No. 4,196,109 to Laganis et al. describes an alkyd resin modified with a phenolic resin with carboxyl substituents and a triazine derivative in combination with water and organic solvent. The coating compositions of Laganis et al., however, require aminoplast cross-linkers and use forced cures. Recoatability and blistering are not discussed.

It has been found that by incorporating an alkylated phenolic resin into a water reducible alkyd resin in an amount from about 4 to about 20 percent by weight based upon the total weight of the phenolic modified alkyd resin, an alkyd coating resin which provides a non-lifting recoatable coating composition is obtained. Moreover, the coating compositions of the invention are curable by oxidative cross-linking and have improved metal adhesion and corrision resistance.

As used herein alkyd resin generally means a condensation product involving a polybasic acid with a polyhydric alcohol with the addition of modifying agents such as higher fatty acids. As used herein, phenolic resin generally means a phenol-formadehyde resin which is the reaction product of formaldehyde with a hydroxy substituted aromatic ring including phenol which ring has one or more hydroxyl groups on it.

In respect to the invention described herein, the alkyd resin used in the composition of the invention is the esterification product of dibasic acids with polyols, monobasic carboxylic acids or vegetable oil precursers thereof including saturated and unsaturated fatty acids having between 10 and 22 carbon atoms and monobasic aromatic acids, and a tricarboxylic acid or anhydride thereof. Esterification catalysts generally are used in preparing the alkyd. Aromatic dicarboxylic acids that can be used to prepare the alkyd resin are isophthalic acid, terephthalic acid, and phthalic acid. Polyhydric alcohols that can be used to prepare alkyd resins may have two or more hydroxyl groups and include ethylene glycol, propylene glycol, 1,3-butylene glycol, pentanediol, neopentyl glycol, hexylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, glycerol, trimethylolethane, trimethylol propane, pentaerythritol, methylglucoside, dipentaerythritol, and sorbitol with neopentyl glycol, trimethyol ethane and trimethylol propane being preferred. Tricarboxylic acids or their anhydrides that can be used to prepare the alkyd resin are trimelletic acid, trimelletic anhydride, trimesic acid and the like with trimelletic anhydride being preferred. Fatty or other carboxylic acids that are used to prepare alkyd resins are capric acid, linoleic acid, benzoic acid, dehydrated castor oil fatty acids, heat-bodied soya oil fatty acids, tung oil fatty acids, linseed oil fatty acids, safflower oil fatty acids, soya oil fatty acids, tall oil fatty acids and the like. Esterification catalysts that are used in the process for preparing alkyd resins are butyl stannoic acid, barium oxide, barium hydroxide, barium naphthenate, calcium oxide, calcium hydroxide, calcium naphthenate, lead oxide, lithium hydroxide, lithium naphthenate, lithium recinollate, sodium hydroxide, sodium naphthenate, zinc oxide, and lead tallate with butyl stannoic acid being preferred.

The phenolic modified alkyd coating resin of the invention is produced by adding the alkylated phenolic resin to the reaction mixture during or after preparation of the alkyd, preferably after substantially completing the esterification reaction between the dibasic acids and polyols. The addition and reaction of the triacid, to the reaction product, however is after the esterification reaction and preparation of the alkyd.

In respect to the invention described herein, an alkylated phenolic resin is a reaction product of an alkylated phenol and formaldehyde wherein the alkyl substitution is at the paraposition on the aromatic ring which substitution is with straight or branched alkyl groups having from 1 to 18 carbon atoms, preferably the alkylation being tertiary butyl. The alkylated phenolic resin is non-heat reactive and made under acid conditions.

By using a non-heat reactive alkylated phenolic resin it would be expected to obtain a product which is a simple physical blend of alkylated phenolic resin and alkyd. While not intending to be bound by any theory, it appears that an interreaction between the alkyd and alkylated phenolic resin occurs to render an alkylated phenolic modified coating resin which has improved recoatability characteristics wherein the coating composition containing the coating resin is fast drying, non-lifting and does not require aminoplast cross-linking agents. Additional to improved recoatability, the coating resin of the invention without amino cross-linking agents provides coating compositions with improved corrosion resistance, improved early water resistace and improved metal adhesion.

It is an object of the invention to provide a water reducible alkyd coating resin modified with an alkylated phenolic resin which will provide a non-lifting, recoatable coating composition which is fast drying and which may be free of aminoplasts or amino cross-linking agents.

It is another object of the invention to provide a method of making a new alkylated phenolic resin modified alkyd which will provide a non-lifting, recoatable coating compositions.

These and other objects of the invention will become more apparent with reference to the following detailed description.

Generally the alkylated phenolic modified alkyd coating resin is made by first obtaining a first ester by reacting with heat from about 20 to about 50 parts by weight polyol per 100 weight of the resulting alkyd coating resin of the invention (hereafter "parts by weight" unless otherwise indicated) with from about 15 to about 60 parts by weight fatty acid and from about 0.005 to about 0.05 parts by weight of an esterification catalyst such as a butyl stannoic acid catalyst sold under the name Fascat 4100 by M&T Chemicals, Inc. When the latter reaction mixture containing the first ester has an acid value of less than 15 and preferably less than 3, the reaction mixture is cooled and from about 15 to about 50 parts by weight of a dibasic acid or anhydride thereof is added thereof; the resulting reaction mixture being heated to form an intermediate polyester with an acid value of less than about 25 and preferably between 11 to 12. The reaction mixture containing the intermediate polyester is cooled and the alkylated phenolic resin is added thereto with agitation and heated to form an alkylated phenolic modified polyester resin with an acid value of about 5 to about 35, preferably about 18. The alkylated phenolic modified polyester resin is mixed with heat with from about 3 to about 15 parts by weight of a tricarboxylic acid of anhydride thereof which yields and alkylated phenolic modified alkyd resin with an acid value of from about 30 to about 60 and preferably about 35 to about 45. The prereaction of the polyol is preferred. Further, the alkylated phenolic resin may be mixed with the alkyd after the formation of the alkyd or with its prereacted components with the addition after the formation of the alkyd being preferred. The trimelletic anhydride or its equivalent, however, must be charged after the formation of the alkyd. At 50% solids in xylene an alkylated phenolic modified alkyd resin, according to the invention, can have a viscosity in the range of S to U and preferably about T on the Gardner-Holdt scale as measured by ASTM method D1545-76.

The modified alkyd resin may be thinned with from about 50 to about 80 parts by weight of an organic solvent such as butoxyethanol, secondary butanol, propoxypropanol, pent-oxone or 4 methoxy-4-methylpentanone-2, or diacetone alcohol. From about 5 to about 60 parts by weight (based upon the weight of the coating composition) of the modified alkyd may then be ground or dispersed with pigments, solvent and metal driers to provide a coating composition with a pigment binding ratio of from about 0.05 to about 1.5.

The following examples are provided to illustrate the invention more fully; however, they should not be construed as limiting the scope of the invention, many variations of which are contemplated.

24.12 parts by weight of a C.sub.18 synthetic fatty acid derived from tall oil (commercially available from Hercules Chemical Company as Pamolyn 327-B) and 14.86 parts by weight trimethylol propane is charged into a reaction vessel fitted with a distillation column under nitrogen and heated to 280.degree. F. whereupon 0.01 parts by weight of a butyl stannoic acid esterification catalyst (Fascat 4100) is added to the reaction mixture which is heated to 360.degree. F. where distillation begins. The reaction mixture then is heated to 440.degree. F. for over 11/2 hours with a water loss of about 1.52 parts by weight to attain an acid value less than 3. When the latter acid value is attained, the reaction is cooled to 325.degree. F. and 8.01 parts by weight of neopentylglycol (1% excess), 23.22 parts by weight isophthalic acid, 2.10 parts by weight terephthalic acid and 0.01 parts by weight Fascat 4100 are added to the coooled reaction mixture which then is heated to about 390.degree. F. at which temperature distillation resumes. From 390.degree. F. the reaction mixture is heated to 440.degree. F. for over 2 hours with the loss of 5.37 parts by weight water and 0.08 parts by weight glycol, to attain an acid value of 11.0-12.0 and a Gardner-Holdt viscosity of Y at 70% solids in xylene. After the reaction mixture has an acid value between 11.0-12.0 the reaction mixture is cooled rapidly to 410.degree. F., the nitrogen reduced to blanket, agitation increased and 5.99 parts by weight of an oil soluble tertiary butyl phenolic resin having a softening point of 235.degree.-250.degree. F. (available from Union Carbide Corporation as CK2500) is added to the reaction mixture. After the addition of the phenolic, the reaction mixture is held at 390.degree.-400.degree. F. for 1/2 hour with the phenolic being dissolved. The reaction mixture with the dissolved phenolic then is cooled to 350.degree.-355.degree. F. and is sampled such that the reaction mixture should have an acid value of 15 to 20 and a Gardner-Holdt viscosity of Z at 70% solids in xylene. After the addition of the phenolic and the acid value of 18 is reached, 3.65 parts by weight of trimellitic anhydride is added to the reaction mixture which is reacted at about 345.degree.-350.degree. F. for 15 minutes to attain an acid value of 42, and a Gardner-Holdt viscosity of N at 50% solids in xylene. After the addition of the trimellitic and the reaction mixture is sampled for an acid value of 42, heating is continued at 345.degree.-350.degree. F. which heat is held until the reaction mixture is sampled for a Gardner-Holdt viscosity of Q-R at 50% xylol; at which time the heat is reduced to 330.degree. F. which is held until the reaction mixture is sampled for a viscosity of T-T 1/2 at 50% xylol. After a viscosity of T-T 1/2 is reached, the resulting phenolic modified alkyd is cooled to 300.degree. F. and 12.50 parts by weight of 2-butoxyethanol is added thereto with agitation. After addition of the 2-butoxyethanol, 12.50 parts by weight of secondary butanol is added to the phenolic modified alkyd resin, both the butyl cellosolve and secondary butanol being added to thin the alkyd for handling and drumming.

The same procedure of Example 1 with the following reactants.

Reactants 1-5 are charged and reacted as in Example 1 to an acid value less than 3. The reaction mixture then is cooled to 325.degree. F. and reactants 7 to 10 are added with the mixture being heated to 440.degree. F. for over 2 hours, with the water and glycol loss as indicated, to an acid value of 8. After the latter acid value is obtained, the reaction mixture is cooled to 410.degree. F. and reactant 11 is added and held at temperature for 30 minutes then cooled to 350.degree. F. After cooling reactant 12 is added under nitrogen blanket and the temperature held at 340.degree.-345.degree. F. for 15 minutes whereupon it is cooled to 310.degree.-320.degree. F. and held at that temperature until a viscosity of V 1/2-W at 50% nonvolatiles in xylene is attained. Then the reaction is cooled to 200.degree. F. and 13 is added. With further cooling to 170.degree. F.14 is added.

The following unmodified alkyd resin was prepared pursuant to the procedures set forth in Examples 1 and 2.

The acid value after reactants 7-10 are added is 16-17; thereafter the reaction is cooled to 350.degree. F. and reactant 11 is added. The reaction then is held at 345.degree.-350.degree. F. for 15 minutes, then cooled to 300.degree. F. and held at that temperature for a viscosity of X at 50% nonvolatiles in xylene. Then 12 and 13 are added while cooling the reaction to 170.degree. F.

Reactants 1-6 are charged into a reactor equipped with a heat and cooling source, stirrer, inert gas sparge line, fractionating column, and heated to 480.degree. F. under an inert gas sparge and agitation. The reactants are held at 480.degree. F. for an acid value of about 7 and a viscosity of about V on the Gardner-Holdt scale when reduced to 75% non-volatile in xylene. The reaction is cooled to about 415.degree. F. and 7 is added. The reactants are held at 415.degree. F. for about 30 minutes and then cooled to 350.degree. F. Reactant 8 is added and the reaction mixture held at 350.degree.-360.degree. F. for an acid value of 42-46 and a viscosity of about Z5 when reduced to 75 percent non-volatile with equal parts of butoxyethanol and secondary butanol. The reaction then is cooled to 300.degree. F. Reactant 9 is added, then reactant 10 is added.

This product is a clear solution having the following physical properties:

The reactants were mixed and reacted as described in Example 4.

This product is a clear solution having the following physical properties.

The performance of the resins of Examples 1 and 3 were compared by compounding a coating composition with pigments, pigment extenders, thickeners, defoamers, surfactants and anti-skimming agents and other additives that was a low gloss black enamel with the binders of Examples 1 and 3 at 75% non-volatiles and additives as identified below.

The above ingredients are mixed by first mixing all of the pigment grind components except the deionized water. After the latter pigment grind components are completely mixed, the viscosity of the mix is adjusted to 65-70 Kreb units using the withheld deionized water. This pigment grind mixture is put into a steel ball mill and ground to a N. S. grind of 7.5 on the Hegman scale.

The secondary butanol, metal driers and Active-8 components of the grind let-down are premixed. This premix and the remainder of the components of the grind let-down are mixed in the order shown with the water being withheld for the final viscosity adjustment. The grind let-down is mixed into the grind. The viscosity of the grind and grind let-down mix is adjusted to 60-80 seconds #4 Ford Cup with the withheld water from the let-down charge.

The performance of the resins of Examples 2 and 3 were compared by compounding a coating composition that was a red oxide primer with the binders of Examples 2 and 3 at 75% non-volatiles, the pigments and solvents as identified below.

Charge the components of the pigment grind to a pebblemill and grind to a N.S. Grind (Hegman) of 7.5.

Premix the butoxyethanol, metal driers and Activ 8 components of the grind let-down.

Add all but the last let-down components and the above premix in the order shown and mix well by stirring.

Adjust the pH to 8.0-8.5 with additional ammonium hydroxide.

Adjust the viscosity to 75 to 80 Kreb units using the remaining component (water).

The primers are sprayed onto cold-rolled steel Parker test panels to obtain a 1 mil thickness of dry film.

The coated panels are permitted to dry for seven days before evaluation.

The alkyd resins of Examples 4 and 5 were evaluated in red oxide primers prepared from the following formulation:

These enamels were prepared by the process described as to the primers prepared from the resins of Examples 1 to 3.

The enamels have the following physical properties.

It should be understood that while certain preferred embodiments of the present invention have been illustrated and described, various modifications thereof will become apparent to those skilled in the art. Accordingly, the scope of the present invention should be defined by the appended claims and equivalents thereof.

Various features of the invention are set forth in the following claims.