Alkyd resin emulsions for coating varnishes
Disclosed are alkyd resin emulsions for coating varnishes, containing a water-insoluble alkyd resin A and a water-soluble alkyd resin B that is used as an emulsifying resin and represents an esterification product of an alkyd resin Ba which can be homogeneously mixed with the alkyd resin A at a weight ratio (Ba to A) ranging between 2:98 and 50:50, alkyd resin A being the resin that is to be emulsified, and an adduct Bb of a C 1 -C 4 alkoxy polyethylene glycol Bba and a cycloaliphatic dicarboxylic acid anhydride Bbb at a mole ration (Bba to Bbb) ranging between 09.95:1.05 mol/mol and 1.05:0.95 mol/mol. Also disclosed is a method for the production thereof, the use thereof for coating substrates selected among textiles, mineral materials, metals, and wood.
1. Alkyd resin emulsions for topcoats comprising a water-insoluble alkyd resin A and a water-soluble alkyd resin B, which is used as an emulsifying resin and is an esterification product of an alkyd resin Ba, which has a hydroxyl number of at least 30 mg/g, and is homogeneously miscible with the alkyd resin A to be emulsified at least in a mass ratio range of Ba to A of from 2:98 to 50:50, and an adduct Bb of a C 1 -C 4 -alkoxypolyethylene glycol Bba and a cycloaliphatic dicarboxylic acid anhydride Bbb in a ratio of amounts of substance of Bba to Bbb of from 0.95:1.05 mol/mol to 1.05:0.95 mol/mol.
2. Alkyd resin emulsions according to claim 1 , characterised in that they comprise in their solids content a mass fraction of
70% to 95% of the water-insoluble alkyd resin A and
5% to 30% of the water-soluble alkyd resin B employed as an emulsifying resin.
3. Alkyd resin emulsions according to claim 1 , characterised in that the alkyd resin B is an esterification product of mass fractions of from 25% to 60% of the alkyd resin Ba and 40% to 75% of the adduct Rb.
4. Alkyd resin emulsions according to claim 1 , characterised in that the alkyd resin A has an oil content of from 25% to 75% and an acid number of up to 20 mg/g.
5. Alkyd resin emulsions according to claim 1 , characterised in that the acid number of the alkyd resin B is not more than 3 mg/g.
6. Process for the preparation of alkyd resin emulsions according to claim 1 , characterised in that
in the first step mass fractions of
70% to 95% of a C 1 -C 4 alkoxypolyethylene glycol Bba having a weight-average molar mass M w of from 500 g/mol to 4,000 g/mol, and
5% to 30% of a cycloaliphatic dicarboxylic acid anhydride Bba are mixed in a substance amounts ratio of from 0.95:1.05 mol/mol to 1.05:0.95 mol/mol, and are reacted in the presence of a catalyst, with opening of the acid anhydride, to form an adduct Bb,
in the second step a mass fraction of from 40% to 75% of the adduct Bb is esterified with a mass fraction of from 25% to 60% of an the alkyd resin Ba which has a hydroxyl number of at least 30 mg/g and is homogeneously miscible with the alkyd resin A to be emulsified at least in a mass ratio range of Ba to A of from 2:98 to 50:50, the sum of the said mass fractions in the reaction mixture giving 100%, to form an alkyd resin B,
in the third step the alkyd resin B is mixed with water, a mass fraction of the alkyd resin of from 30% to 60% being present in the mixture, and the mixture having a dynamic viscosity, measured at 23° C. and a shear gradient of 100 s −1 ,of from 5 Pa·s to 50 Pa·s, and
in the fourth step an alkyd resin A is mixed with the mixture of water and the alkyd resin B from the third step at a temperature of below 100° C. and the resulting alkyd resin emulsion is diluted to a solids mass fraction of from 40% to 75% and a dynamic viscosity of from 200 mPa·s to 3,000 mPa·s by addition of water.
7. Process according to claim 6 , characterised in that in the second step the amount of the reactants is chosen such that the acid number of the alkyd resin B is not more than 3 mg/g.
8. Process according to claim 6 , characterised in that the ratio of the mass of the alkyd resin A to the mass of the alkyd resin B is 70:30 kg/kg to 95:5 kg/kg.