GB2306489A - Alkyd resins - Google Patents

Abstract

A water dispersible alkyd resin is derived from the polycondensation of: (i) a fatty acid component; (ii) a polycarboxylic acid component; (iii) a polyhydric alcohol component; and, optionally (iv) a monofunctional component comprising one or more monohydric alcohols or monocarboxylic acids (other than the fatty acid component); in which at least one component is a sulphonated component; and at least a part of the polyhydric alcohol component (iii) and/or the monohydric alcohol component (iv) comprises a polyethoxylated polyhydric and/or monohydric alcohol.

Description

ALKYL US INS This invention is concerned with improvements in and relating to alkyd resins and, more particularly, to alkyd resins suitable for use in water-based coating compositions.

Whilst it is often desirable, for example from environmental considerations, to formulate coating compositions using water as sole or principal liquid carrier in place of the more conventional volatile organic solvents/diluents, this often leads to problems in formulation.

Alkyd resins have been used as resinous binder components of coating compositions, such as paints and varnishes, for many years and have generally been formulated in conjunction with volatile organic solvents. It is, however, known to produce water-dilutable ("water-reducible") alkyd resins, typically by incorporating in the alkyd resin a hydrophilic component such as polyethyleneoxy chains or neutralised carboxylic acid groups.

Nevertheless, known water-reducible alkyd resins often prove difficult to disperse or emulsify in aqueous media with the result that the preparation of uniform, reproducible products therefrom can be difficult.

It has now been found, in accordance with the present invention that readily emulsifiable or dispersible alkyd resins may be produced from components producing both polyethoxy chains and aromatic sulphonic acid groups.

According to the invention, therefore, there is provided an alkyd resin derived from the polycondensation of: (i) a fatty acid component; (ii) a polycarboxylic acid component; (iii) a polyhydric alcohol component; and, optionally, (iv) a monofunctional component comprising one or more monohydric alcohols or monocarboxylic acids (other than the fatty acid component); in which preferably at least part of the carboxylic acid component (ii) and/or at least part of the monocarboxylic acid component (iv) comprises a sulphonated carboxylic acid; and at least a part of the polyhydric component (iii) and/or monohydric component (iv) comprises a polyethoxylated polyhydric and/or monohydric alcohol and, optionally, one of the monohydric components may contain a sulphonate group.

The alkyd resin of the invention is preferably an air-drying alkyd or modified alkyd resin and may be a short, medium or long oil resin, e.g. may be derived from 10 to 95% by weight, preferably 20 to 85% by weight of long chain fatty acid. Suitable fatty acids include unsaturated C12-C22 carboxylic acids such as oleic, ricinoleic, linoleic, and linolenic and eleostearic acids; typically employed in the form of mixtures of fatty acids derived from natural or synthetic oils such as linseed oil, sunflower oil, say flower oil, cottonseed oil, soya bean oil, tall oil fatty acid, dehydrated castor oil or conjugated fatty acids. The fatty acid mixtures may be used in the form of their naturally occurring triglycerides.

In addition to the fatty acid, the alkyd will also be derived from one or more polyhydric alcohols, such as glycerol, pentaerythritol, trimethylol propane (TMP), neopentyl glycol, ethylene glycol, diethylene glycol, di-trimethylolpropane (di-TMP), dipentaerythritol; propylene glycol and 1,3-butane-diol; and one or more polycarboxylic acids such as phthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, adipic acid, maleic acid, fumaric acid, and abietic acid.Other components which can be commonly used in the manufacture or modification of long oil alkyd resins may also optionally be included, namely rosin esters, phenolic resins, maleic-rosin condensates, isocyanates such as toluene diisocyanate (used as a mixture of 2:4 and 2:6 isomers), isophorone diisocyanate, hexamethylene diisocyanate and trimethyl xylene di-isocyanate and one or more vinyl monomers such as styrene, vinyl toluene, and alkyl (meth) acrylates.

Alkyd resins and their modified derivatives are described, for example, in "The Chemistry of Organic Film Formers, D.H. Solomon, Robert E. Kreiger Publishing Company, 2nd Edition, 1977, e.g. at pages 75-124. For convenience, in the following description, reference will be made only to "alkyd resins" which term is intended to refer to both modified and unmodified alkyd resins.

It is an essential feature of the present invention that a part of one of the components comprises a sulphonated component and it is preferred that a part of the polycarboxylic acid or monocarboxylic acid component be a sulphonated aromatic mono- or poly-carboxylic acid, containing a group -SO3M in which M is a hydrogen or metal ion, e.g. of sodium, lithium, potassium, calcium, copper or iron. The S03M group is suitably attached to an aromatic nucleus such as a benzene, naphthalene, anthracene, diphenyl, oxydiphenyl, sulphonydiphenyl or methylene diphenyl group.

Examples of suitable such acids are 5-sodiosulphoisophthalic acid, lithium 5-sulphoisophthalic acid, 5-sodiosulphoterephthalic acid, 5-sodiosulphophthalic acid or 4-sulphonaphthalene2,7-dicarboxylic acid (or derivatives of such acids e.g.

dimentyl-5-sodiosulphoisophthalate, dimethyl lithium 5-sulphoisophthalate and potassium 5-sulphoisophthalic acid).

Aliphatic sulphonic acids are also suitable, an example being hydroxyethane sulphonic acid.

Other difunctional monomers containing an SO3M group attached to an aromatic nucleus include metal salts of aromatic sulphonic acids (or esters thereof).

These monomers have the general formula:

wherein X is a trivalent aromatic hydrocarbon radical, Y is a divalent aromatic hydrocarbon radical, R is a hydrogen or an alkyl group of 1 to 4 carbon atoms, M is hydrogen, sodium, lithium or potassium ions. Examples of such monomers are 4-sodiosulphophenyl-3,5 dicarbomethoxybenzenesulphonate, 4-sodiosulphophenyl3,5-dicarbomethoxybenzenesulphonate and 6-sodiosulpho 2-naphthyl-3,5-dicarbomethoxybenzenesulphonate.

Other effective difunctional monomers containing an S03M group attached to an aromatic nucleus include metal salts of sulphodiphenyl ether dicarboxylic acids (or esters thereof). These monomers have the general formula:

where R is hydrogen, an alkyl group of 1 to 8 carbon atoms, or phenyl and M is hydrogen, potassium, sodium or lithium ions. Examples are dimethyl 5-[4-(sodiosulpho)phenoxy]isophthalate, dimethyl 5-[4-sodiosulpho)phenoxy]terephthalate and 5-[4-(sodiosulpho)phenoxy]isophthalic acid.

The amount of sulphonic acid groups employed is suitably such as to provide the end alkyd resin with from 0.1 to 100 meq of sulphonate groups/lOOg of alkyd resin, preferably from 0.5 to 20 meq of sulphonate groups/lOOg of alkyd resin.

A second component from which the alkyd resin of the invention are obtained comprises a polyethoxylated mono or polyhydric alcohol, that is an alcohol, the hydroxyl group(s) of which have been reacted with ethylene oxide to form polyethyleneoxy chains. Suitable monohydric alcohols are aliphatic alcohols such as methanol and ethanol an aromatic alcoloh such as nonylphenol.

Suitable polyhydric alcohols are aliphatic alcohols having from 2 to 6 hydroxyl groups per molecule.

Typical examples of such polyhydric alcohols include trimethyolpropane and pentaerythritol. Suitably the polyethoxylated alcohol contains an average of from 1 to 25, more especially 3 to 20, ethyleneoxy groups per molecule. Examples of suitable commercially available material are polyethoxylated derivatives of trimethylolpropane. By nature of their manufacturing process, the polyethoxylated polyhydric alcohol may contain unmodified polyhydric alcohol.

The amount and nature of the polyethoxylated alcohol are suitably such as to introduce from 0.1 to 50wt.%, preferably 0.5 to 30 wt.%, ethyleneoxy groups into the alkyd resin.

The alkyd resin may be prepared by the usual processes namely a solvent process or a dry fusion process. In the well established solvent process the components of the alkyd (which in the case of the (poly)basic acids, may suitably be used in the form of their anhydrides where such exist) are reacted in the presence of a water-immiscible solvent which forms an azeotropic mixture with the water of reaction from the polycondensation process. The water is separated and the solvent returns to the reactor. Typically the amount of the azeotropic solvent added to the reaction mass will comprise 3% - 10% of the total mass in the reaction vessel. Commonly used solvents are xylene, toluene and, higher boiling aromatic solvents including mixtures of alkyl benzenes. The reaction is carried out at elevated temperatures eg. 200 to 2700C.Alkyd resins manufactured by this process may then be further modified with isocyanates or vinyl monomers as described above. The process solvent may optionally be removed, either before or after further modification, in this instance coatings with an aromatic solvent content of less than 16 by weight of the total coating solution may be produced.

The alkyd resin may also be prepared by a dry fusion process, i.e. by reacting the various components (which, in the case of the acids, may suitably be used in the form of their anhydrides where such exist) at elevated temperature, eg. 200 to 2700C, in the absence of added solvent.

In accordance with a preferred feature of the invention, the alkyd resin may be prepared in three stages, either a first stage comprising condensing the sulphonated monomer with non-ethoxylated polyhydric polyol with stoichiometric excess of polyol, a second stage comprising condensing fatty acid with nonethoxylated polyhydric polyol and a third stage, which involves reacting the products from stage 1 to stage 2 with further polycarboxylic acids and polyethoxylated polyhydric alcohol(s) to give an alkyd that contains ethyleneoxy groups and sulphonate groups.

Another preparation method involves three stages, a first stage condensing polyethoxylated polyhydric polyol and sulphonate containing monomer with stoichiometric excess of polyol, a second stage involving reacting the product of stage 1 with fatty acid and non-ethoxylated polyhydric alcohol until desired acid value is achieved, whereby, in the third stage, the product from stage 2 is reacted with further polycarboxylic acid to give an alkyd resin containing both ethyleneoxy groups and sulphonate groups.

In accordance with a further embodiment of the invention, therefore, there is provided a coating composition comprising: (i) an alkyd resin as defined above; (ii) water as carrier/diluent; and, optionally, (iii) a colorant.

The optional colorant component of the composition of the invention comprises one or more pigments and suitable examples of those can be taken from any of the well known inorganic and organic pigment chemical types such as titanium dioxide, antimony oxide, calcium carbonates, barium sulphates, calcite, china clay, iron oxides, chromates, ferrocyanides,, carbon black, azo pigments, phthalocyanines, anthraquinones.

Pigments are suitably used in amounts of from 0.1 to 400% by weight, based on the weight of alkyd resin binder.

In addition to the above components, air-drying compositions in accordance with the invention will almost always contain one or more so-called "driers", that is organic solvent-soluble salts or soaps (e.g.

octoates, naphthenates or linoleates) of various metals such colbalt, manganese, iron, lead, calcium, zinc, lithium, strontium and zirconium. Primary driers, such as cobalt or manganese salts, are suitably used in amounts of from 0.01 to 0.36 by weight of metal and secondary driers (such as calcium, barium, zirconium, lithium, zinc and strontium salts) are suitably used in amounts of from 0.01 to 2.06 by weight of metal, based on the weight of solid alkyd resin binder.

Further components which may be present in compositions in paints according to the invention include antiskinning agents such as methyl ethyl ketoxime (MEKO) clohexanone ketoxime, biocides such as Troysan Polyphosphates AF3, Acticide EP and Algon 100, and silicone oils.

In the preparation of the composition of the invention, the alkyd may be dispersed in the water carrier simply by stirring, i.e. without high emulsification, and in the absence of any additional surfactant material.

In order that the invention may be well understood the following Examples are given by way of illustration only. In the Examples all parts are by weight unless otherwise stated.

Examples Alkyds A and B were prepared, from the components listed in Table A below and had the properties listed in Table B below.

TABLE A Alkyd A Alkyd B B Neopentyl glycol 9.038 5-sodiosulphoisophthalic 1.146 1. 112 acid (SSIPA) Tall oil fatty acid 35.448 40.287 Trimethylolpropane 18.407 26.619 Isophthalic acid 16.725 28.423 Adipic acid 14.726 Ethoxylated 4.510 3.559 trimethylolpropane 100.000 100.000 Alkyd A was prepared by a three stage process as follows.

Stave 1 Charge 37.0g neopentyl glycol and 4.7g 5-sodiosulphoisophthalic acid, 0.5g Fascat 4102 (catalyst) and 0.5g trisnonylphenylphosphite (antioxidant). Heat to 2300C. Nitrogen sparge. Hold at 2300C until acid value is 4 mgKOH/g(max). Cool and discharge. Product yield = 98.5%.

Stave 2 Charge 145.4g tall oil fatty acid and 75.5g trimethylolpropane. Heat to 200-2300C and nitrogen sparge. Hold for acid value 10 mgKOH/g(max). Cool to 1500C. Product yield = 95.7%.

Stave 3 At 1500C, charge 41g reaction product from Stage 1, 211.5g reaction product from stage 2, 68.6g isophthalic acid, 60.4g adipic acid and 18.5g polyethoxylated trimethylol propane. Heat to 2300C and hold for acid value = 20-30 mgKOH/g. Product yield - 92.5%.

Alkyd B was prepared by a three stage process, as follows.

Stage 1 Charge 228.6g polyethoxylated trimethylol propane 5-sodiosulphoisophthalic acid, 0.5g Fascat 4102 (catalyst) and 0.5g trisnonylphenylphosphite (antioxidant). Heat to 2300C. Nitrogen sparge. Hold at 2300C until acid value is 4 mgKOH/g(max). Cool and discharge. Product yield = 96.8%.

Stave 2 Charge 163g tall oil fatty acid, 107.7g trimethylolpropane and 279.1g reaction product from stage 1. Heat to 200-2300C, nitrogen sparge. Hold for acid value 15 mgKOH/g(max). Cool to 1500C. Product yield = 96.4%.

Stave 3 At 1500C, charge 115g isophthalic acid to 279.lg reaction product from stage 2. Heat to 2300C and hold for acid value - 15-20 mgKOH/g. Product yield = 93.6%.

TABLE B Alkyd A Alkyd B % fatty acid by weight 39.2 44.2 % SSIPA by weight 1.27 1.22 % EO by weight 4.18 2.75 meq SSIPA/100g alkyd 4.73 4.55 Hydroxyl excess: mgKOG/g 35.07 77.10 Viscosity: 1000C 3.6 poise 14.5 poise Acid value:mgKOH/g 24.8 17.0 Hydroxyl value: mgKOH/g 59.8 94.1 These alkyds were converted to alkyd emulsion using the following process: 1. Heat the alkyd to 800C.

2. Add water (70-800C) to the alkyd whilst stirring at 7-8000 rpm using a Dispermat type stirrer, until inversion occurs.

The alkyd emulsions so produced, had solids contents of 20-806 and a defined particle size distribution and were free from external surfactant.

Claims (1)

1. CLAIMS:

   1. An alkyd resin derived from the polycondensation of: (i) a fatty acid component; (ii) a polycarboxylic acid component; (iii) a polyhydric alcohol component; and, optionally (iv) a monofunctional component comprising one or more monohydric alcohols or monocarboxylic acids (other than the fatty acid component); in which at least one component is a sulphonated component; and at least a part of the polyhydric alcohol component (iii) and/or the monohydric alcohol component (iv) comprises a polyethoxylated polyhydric and/or monohydric alcohol.

   2. An alkyd resin as claimed in claim 1 in which at least a part of the polycarboxylic acid component (ii) and/or at least a part of the monocarboxylic acid component (iv) comprise a sulphonated aromatic carboxylic acid.

   3. An alkyd resin as claimed in claim 1 or claim 2 containing from 0.1 to 100 meq of sulphonate group per 100 gm of alkyl.

   3. An alkyd resin as claimed in any one of the preceding claims containing from 0.5 to 10 wt.% of ethylenoxy groups.

   5. A coating composition comprising: (i) an alkyd resin as claimed in any one of the preceding claims; (ii) water as carrier/diluen; and, optionally, (iii) a colourant.