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
2001-04-20
2003-05-13
Yoon, Tae H. (Department: 1714)
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...
C524S845000, C528S295000, C528S300000, C528S302000
Reexamination Certificate
active
06562899
ABSTRACT:
CONTINUING DATA
This application claims priority of European Patent Application No. 00201423.1 filed on Apr. 20, 2000.
FIELD OF THE INVENTION
The invention relates to a branched hydroxyl-functional polyester resin having an average hydroxyl functionality of >2, a hydroxyl number of 25 to 300 mg KOH/g, and a number average molecular weight within the range of from 500 to 3,000, which polyester resin comprises polyalkylene oxide groups and, optionally, sulphonate groups.
BACKGROUND OF THE INVENTION
Polyester resins and their use in two-component aqueous-based coating compositions are known from, int. al., EP-A-0 537 568 and WO 94/28043. The water-dilutable polyesters disclosed therein contain both sulphonate and hydroxyl groups. Though high-quality coating layers can be obtained with the known aqueous-based coating compositions, the solids content of the aqueous polyester dispersions used in the known compositions is too low to be competitive in a great many applications, such as coating compositions to be used in automotive refinishing shops. The concentration of the polyester particles in the examples of both prior art publications does not exceed 35 wt. %. Furthermore, the storage stability of the aqueous polyester dispersions is inferior. Moreover, in order to emulsify the hydrophobic polyisocyanates in EP-A-0 537 568, frequently use has to be made of an external emulsifier, whereas in the examples of WO 94/28043 always use is made of polyisocyanate modified with polyethylene oxide glycol.
A disadvantage of high water content is that the elimination of said water after the composition has been formed into, int. al., a coating layer requires a lot of time and energy. A further disadvantage of the known coating compositions is that the binder compositions exemplified in WO 94/28043 are said to have a gel time of 3 to 6 hours, whereas on the other hand the curing speed of the binder compositions exemplified in WO 94/28043 is rather low (>12 hrs at 50° C.).
SUMMARY OF THE INVENTION
The invention now provides a branched hydroxyl-functional polyester resin having an average hydroxyl functionality of >2, a hydroxyl number of 25 to 300 mg KOH/g, and a number average molecular weight within the range of from 500 to 3,000, which polyester resin comprises polyalkylene oxide groups and, optionally, sulphonate groups, characterised in that the polyester resin comprises the reaction product of
1) a mixture of carboxylic acids comprising
50 to 80 mole % of an m- and/or p-aromatic and/or cycloaliphatic dicarboxylic acid,
20 to 50 mole % of an aliphatic dicarboxylic acid and/or aliphatic monocarboxylic acid with more than 6 carbon atoms, and, optionally, a tri- or higher-functional acid, and
2) a mixture of alcohols comprising
an aliphatic diol with at least 4 carbon atoms and/or a cycloaliphatic diol with at least 4 carbon atoms, a C
1
-C
4
alkoxy polyalkylene oxide glycol and/or C
1
-C
4
alkoxy polyalkylene oxide 1,3-diol having a number average molecular weight of 500 to 3,000, and, optionally, a tri- or higher-functional polyalcohol, wherein
the polyester resin has a carboxylic acid number of ≦20 mg KOH/g (≦0.357 meq COOH groups per g of resin) and, optionally, a sulphonate number of ≦4 mg KOH/g (≦0.070 meq sulphonate groups per g of resin), the acid groups being at least partly neutralised.
DETAILED DESCRIPTION OF THE INVENTION
Also provided according to the invention is an aqueous dispersion comprising the branched hydroxyl-functional polyester resin and an aqueous cross-linkable binder composition comprising the branched hydroxyl-functional polyester resin and a organic hydrophobic polyisocyanate. Further provided according to the invention is the use of the aqueous cross-linkable binder composition in coating compositions, lacquer compositions, and adhesives. Finally, the present invention provides the use of such aqueous coating compositions in car refinish applications.
The storage stability of the branched hydroxyl-functional polyester resin according to the invention is excellent. Aqueous dispersions comprising the branched hydroxyl-functional polyester resin may have a solids content of more than 45 wt. % at a viscosity of up to 5 Pa·s. The branched hydroxyl-functional polyester resin is able to disperse organic hydrophobic polyisocyanates in the absence of external emulsifiers. Aqueous cross-linkable binder compositions comprising a branched hydroxyl-functional polyester resin and an organic hydrophobic polyisocyanate have an acceptable pot life and cure speed. Aqueous coating compositions comprising the aqueous cross-linkable binder composition according to the present invention provide coatings having excellent properties like gloss, hardness, and distinctness of image (DOI).
The branched hydroxyl-functional polyester resin can be prepared using conventional polymerisation procedures known to be effective for polyester resin synthesis. The reaction to form the polyester resin may be conducted in one or more stages. In order to obtain a branched polyester resin, the condensation reaction is carried out in the presence of a branching agent, which may be a tri- or higher-functional acid and/or alcohol. For the tri- or higher-functional acid preference is given to an acid selected from the group of trimellitic acid and pyromellitic acid or the anhydride thereof. For the tri- or higher-functional polyalcohol preference is given to a polyalcohol selected from the group of 1,1,1-trimethylol propane, 1,1,1-trimethylol ethane, 1,2,3-trimethylol propane, pentaerythritol, and mixtures thereof. More preferred is the use of a tri- or higher-functional polyalcohol. Most preferred is the use of 1,1,1-trimethylol propane.
If desired, the polyester resin may contain a proportion of carbonylamino linking groups —C(═O)—NH— (i.e. amide linking group) by including an appropriate amino-functional reactant as part of the “hydroxyl component” (such amide linkages are in fact useful in that they are more hydrolysis-resistant and more hydrophilic.)
In order to achieve hydroxyl functionality in the resulting polyester resin, a stoichiometric excess of the hydroxyl component should be used. Furthermore, in order to achieve an average hydroxyl functionality of >2, preferably ≧2.3, more preferably ≧2.5, the polyester resin must have a branched structure.
The mixture of carboxylic acids may comprise m-aromatic dicarboxylic acids, p-aromatic dicarboxylic acids, cycloaliphatic dicarboxylic acids, aliphatic dicarboxylic acids with more than 6 carbon atoms, and aliphatic monocarboxylic acid with more than 6 carbon atoms.
Suitable dicarboxylic acids for obtaining excellent hydrolytic stability as well as excellent mechanical properties are m-aromatic dicarboxylic acids such as isophthalic acid, p-aromatic dicarboxylic acids such as terephthalic acid and dimethyl terephthalate, and cycloaliphatic dicarboxylic acids such as 1,4-cyclohexane dicarboxylic acid and hexahydrophthalic anhydride. Mixtures of these dicarboxylic acids may also be used.
Suitable aliphatic dicarboxylic acids with more than 6 carbon atoms include azelaic acid and sebacic acid. Suitable aliphatic monocarboxylic acids with more than 6 carbon atoms include isononanoic acid, decanoic acid, 2-ethylhexyl carboxylic acid, and dodecanoic acid. Mixtures of these aliphatic dicarboxylic acids and/or aliphatic monocarboxylic acids may also be used.
Furthermore, the mixture of carboxylic acids may contain a small amount of an alkali salt of a sulphonic acid-substituted mono- or dicarboxylic acid or ester. Preferably, an alkali salt of a sulphonic acid-substituted dicarboxylic acid or ester is used, such as sodium sulphosuccinic acid and 5-(sodium sulpho)isophthalic acid.
The mixture of alcohols may comprise aliphatic diols with at least 4 carbon, atoms, cycloaliphatic diols with at least 4 carbon atoms, C
1
-C
4
alkoxy polyalkylene oxide glycols and/or C
1
-C
4
alkoxy polyalkylene oxide 1,3-diols having a number average molecular weight of 500 to 3,000.
Suitable (cyclo)aliphatic diols for the preparation of the hyd
Buter Roelof
Geurink Petrus Johannes Arnoldus
Scherer Taco
Steenbergen Andre
Akzo Nobel N.V.
McGillycuddy Joan M.
Yoon Tae H.
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