Coating compounds, a process for their production and their...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...

Reexamination Certificate

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Reexamination Certificate

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06319981

ABSTRACT:

This invention relates to a new water-containing coating compound based on a polyol component in solution and/or dispersion in an aqueous medium and consisting of a relatively high molecular weight polycondensation resin or of a mixture of a polycondensation resin with a polymerization resin and a polyisocyanate component emulsified therein, to a process for the production of this coating compound and to its use for the production of coatings.
Water-based lacquer systems are acquiring increasing significance for economic and ecological reasons. However, the replacement of conventional lacquer systems is progressing more slowly than had initially been expected.
There are many reasons for this. Thus, water-based dispersions still have disadvantages in terms of processing by comparison with lacquer systems dissolved in organic solvents. By contrast, water-based solutions are attended by the problem of adequate solubility in water on the one hand and the—paradoxically—lower resistance of the coatings to water by comparison with conventionally dissolved lacquer systems. There are also processing problems in this regard which often arise out of the high viscosity and viscosity anomaly and which, hitherto, have been overcome by the use of organic auxiliary solvents. However, the quantity of auxiliary solvent used is limited because otherwise the ecological sense of water-based systems would been obscured.
It is only recently that water-based two-component polyurethane systems have become known (DE-OS 3 829 587) in which the binder consists of a polyacrylate resin dissolved or dispersed in water in combination with a polyisocyanate containing free isocyanate groups emulsified in this dispersion or solution. The systems in question are substantially solventless systems as can be seen from the fact the solvents used in the production of the polymer resins are removed before the production of the water-based preparation.
One of applicants' earlier proposals (German patent application P 41 01 527.4) relates to water-based two-component polyurethane systems based on urethane-modified polyester resins dissolved or dispersed in water and polyisocyanates emulsified in these solutions or dispersions.
It has now surprisingly been found that analogous systems based on polycondensation resins free from urethane groups, more particularly polyester resins, are also suitable as binders for water-based or water-containing organic lacquers;
The present invention relates to coating compounds of which the binder consists essentially of a combination of
a) a polyol component dissolved and/or dispersed in water or a water/solvent mixture and
b) a polyisocyanate component emulsified in the solution and/or dispersion of the polyol component a) with a viscosity at 23  C. of 50 to 10,000 mPa.s
in quantities corresponding to an equivalent ratio of isocyanate groups of component b) to alcoholic hydroxyl groups of component a) of 0.5:1 to 5:1, characterized in that component a) consists essentially of
a1) a water-dilutable, hydroxyfunctional polycondensation resin free from urethane and sulfonate groups and having a molecular weight Mn above 500 or
a2) a mixture of such a polycondensation resin with up to 100% by weight, based on the weight of the polycondensation resin, of at least one water-dilutable, hydroxyfunctional polymerization resin having a molecular weight Mn above 500.
The present invention also relates to a process for the production of these coating compounds which is characterized in that a polyisocyanate component b) having a viscosity at 23° C. of 50 to 10,000 mPa.s and consisting of at least one organic polyisocyanate is emulsified in an aqueous or aqueous organic solution or dispersion of a relatively high molecular weight polyol component a) consisting essentially of
a1) a water-dilutable, hydroxyfunctional polycondensation resin free from urethane and sulfonate groups and having a molecular weight Mn above 500 or
a2) a mixture of such a polycondensation resin with up to 100% by weight, based on the weight of the polycondensation resin, of at least one water-dilutable, hydroxyfunctional polymerization resin having a molecular weight Mn above 500,
the quantitative ratios between the individual components corresponding to an equivalent ratio of isocyanate groups to alcoholic hydroxyl groups of component a) of 0.5:1 to 5:1 and any auxiliaries and additives used being incorporated in the system before addition of the polyisocyanate.
The present invention also relates to the use of these coating compounds for the production of coatings.
The relatively high molecular weight polyol component a1) consists essentially of water-dilutable, i.e. water-soluble or water-dispersible, hydroxyfunctional polycondensation resins free from urethane and sulfonate groups and having a molecular weight Mn above 500.
The expression “polycondesation resins ” is intended in particular to encompass (i) polyester resins free from fatty acids and oils and (ii) fatty-acid- or oil-modified polyester resins, so-called “alkyd resins ”.
Polycondensation resins suitable as component a1) are, in particular, those having a molecular weight above 500 and up to 10,000, molecular weights of up to 5,000 being determined by vapor pressure osmometry in dioxane and acetone (in the event of differing values, the low value is regarded as correct) and molecular weights above 500 being determined by membrane osmometry in acetone. The polycondensation resins generally have hydroxyl values of 30 to 300 and preferably 50 to 200 mg KOH/g and acid values of 25 to 70 and preferably 35 to 55 mg KOH/g. The acid value is based both on the free carboxyl groups and on the carboxyl groups present in neutralized form as carboxylate groups which—particularly where they are neutralized with tertiary amines—are also included in the titration with potassium hydroxide. Tertiary amines, such as for example triethylamine, N,N-dimethyl ethanolamine or N-methyl diethanolamine, are used for the at least partial neutralization of the carboxyl groups present in the polycondensation resins. The polycondensation resins generally contain 50 to 150 milliequivalents—per 100 g solids—of carboxylate groups.
The polyester resins and alkyd resins are produced in known manner by polycondensation of alcohols and carboxylic acids as defined, for example, in Römpp's Chemielexikon, Vol. 1, page 202, Frankh'sche Verlagsbuchhandlung, Stuttgart, 1966, or in D. H. Solomon, The Chemistry of Organic Filmformers, pages 75-101, John Wiley & Sons Inc., New York, 1967.
Starting materials for the production of the polycondensation resins are, for example,
1- to 6- and preferably 1- to 4-hydric alcohols having a molecular weight in the range from 32 to 500, such as ethylene glycol, propylene glycol, butanediols, neopentyl glycol, 2-ethylpropane-1,3-diol, hexanediols; ether alcohols, such as di- and triethylene glycol; ethoxylated bisphenols; perhydrogenated bisphenols, also trimethylol ethane, trimethylol propane, glycerol, pentaerythritol, dipentaerythritol, mannitol and sorbitol, monohydric chain-terminating alcohols, such as methanol, propanol, butanol, cyclohexanol and benzyl alcohol;
polybasic carboxylic acids or carboxylic anhydrides having a molecular weight of 100 to 300, such as phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic acid (anhydride) hexahydrophthalic acid, trimellitic anhydride, pyro- mellitic anhydride, maleic anhydride, adipic acid or succinic anhydride;
aromatic or saturated aliphatic monocarboxylic acids, such as for example benzoic acid, hexahydrobenzoic acid, tert. butyl benzoic acid, coconut oil fatty acids or &agr;-ethylhexanoic acid;
olefinically unsaturated fatty acids and derivatives of olefinically unsaturated fatty acids, such as for example linseed oil, soybean oil, wood oil, safflower oil, ricinene oil, sunflower oil, cottonseed oil, peanut oil or tall oil fatty acid, synthetic olefinically unsaturated C
12-22
fatty acids and derivatives obtained by conjugation, isomerization or dimerization o

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