Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2001-06-21
2003-02-11
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S073000, C528S075000, C528S288000, C528S392000, C525S123000, C525S440030, C525S453000, C427S384000, C428S423100
Reexamination Certificate
active
06518388
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to coating compositions, their preparation and use.
BACKGROUND
Coatings used for the original painting of motor vehicles and for their repair are required to have very good physical properties such as hardness and resistance to water and solvents. The coating compositions are also required to have good application and appearance properties so that they are easy to apply to a substrate using spray application and result in final films having good gloss.
One class of coating compositions which is known for use in painting motor vehicles comprises a hydroxyl functional polymer, such as a polyester or acrylic polymer, and a polyisocyanate. These two components react together after application to the substrate to form a polyurethane coating. These compositions are often thus referred to as ‘polyurethane coating compositions’ although strictly the polyurethane is only formed when the coating hardens.
These polyurethane coating compositions have been widely used in the vehicle refinish industry for many years but suffer from the disadvantage that polyisocyanates are known respiratory sensitisers and so considerable care must be taken in their use, particularly to prevent inhalation of the paint spray by the operator during spraying. This usually requires the operator to wear an air-fed breathing mask. Clearly, an alternative type of paint is desirable.
We have now discovered a surprising alternative class of coating compositions which can give application and final film properties which are equal to or better than those of polyurethane coatings. These alternative coating compositions comprise a polymer incorporating uretdione groups and acrylate, maleic or fumaric groups, which polymer of cross linked with a polyamine cross linker. This represents a total departure from the last 25 years of developments in refinish coating compositions which have virtually all focused on polyurethane compositions.
GB-1409496 and U.S. Pat. No. 5,814,689 disclose uretdione containing polyurethanes cross linked with polyamines. There is however no reference to the use of polyesters or mixed polyesters having acrylate, maleic or fumaric groups.
EP-424745 discloses a maleic or fumaric containing polyurethane polyester for UV of four radical core. There is however no mention of amine cross-linking.
SUMMARY OF THE INVENTION
According to the present invention there is provided a coating composition comprising:
i) a polymer having uretdione groups, and
ii) a polyamine cross linker,
said polymer being a polyester, or a mixed polyester-polyurethane, which polyester or mixed polyester-polyurethane has other groups capable of reacting with the polyamine cross linker, which other groups are acrylate, maleic or fumaric groups.
DETAILED DESCRIPTION OF THE INVENTION
The uretdione groups can be pendant, but preferably they are in the polymer backbone. The polymer is preferably a polyester.
Suitable polyesters are derived from a polybasic acid, a polyhydroxy compound and a compound having uretdione groups and reactive groups.
Polybasic acids are compounds having two or more carboxylic acid groups. Such polybasic acids are well known in the polyester art. Examples of suitable polybasic acids are C
1-6
alkane dioic acids such as succinic acid, glutaric acid, adipic acid or hexanedioic acid, cycloaliphatic acids such as hexahydrophthalic acid, unsaturated alkane dioic acids such as fumaric or maleic acids, dimer acids, and aromatic acids such as phthalic acid, isophthalic acid and trimellitic acid. Ester-forming derivatives of such acids can also be used in place of the free acids. Ester-forming derivatives include anhydrides and lower alkyl, for example methyl or ethyl, esters. Mixtures of two or more acids or their ester-forming derivatives can be used.
The polyester may have other amine-reactive groups capable of, reacting with the polyamine crosslinker such as acetoacetate or epoxy. More preferably, the polyester has units of formula (I);
in which the carbonyl groups can be cis or trans. These units also react with amine groups on the polyamine crosslinker and provide additional sites for crosslinking of the polyester. These units can be derived from maleic acid or fumaric acid, or from ester-forming derivatives of these acids such as maleic anhydride and the lower alkyl, for example methyl or ethyl, esters of these acids. Preferably, these units are derived from maleic acid or maleic anhydride.
Preferably at least 25% of the groups on the polymer which will react with the polyisocyanate crosslinker are uretdione groups.
Polyhydroxy compounds are compounds having two or more hydroxyl groups and are well known in the polyester art Examples of suitable polyhydroxy compounds are diols such as ethylene glycol, propylene glycol, 1,3-propane diol, butylene glycol, 1,4-butane diol, 1,6-hexane diol, neopentyl glycol, triols such as trimethylol propane, and glycerol, tetrols such as pentaeryatritol and higher polyols such as sorbitol. Mixtures of two or more of these polyols can be used.
Uretdione groups are groups of formula (I)I;
in which R and R′ are the residues of the polyester polymer backbone.
These uretdione groups can be incorporated into the polyester backbone by use of a compound having uretdione groups and also reactive groups which will react with the other components of the polyester so as to become incorporated into the polyester backbone. Examples of reactive groups are hydroxyl groups, acid groups, epoxy groups, and isocyanate groups. One example of a compound having uretdione groups and reactive groups is the uretdione of a diisocyanate, such as hexamethylene diisocyanate uretdione (available as HD100™ which also comprises a proportion of higher adducts, from Arco) of Formula (III);
In this case the reactive groups are isocyanate groups which will react with hydroxyl groups on the polyols and so become incorporated into the backbone of the polyester.
Mixed polyester-polyurethanes can be made in a similar way to polyeters but using a di- or polyisocyanate instead of some of the polybasic acid. Suitable diisocyanates are tetramethylxylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and toluene diisocyanate. Suitable polyisocyanates include the isocyanurate trimers, allophanates and uretdiones of diisocyanates such as those described above as well as the reaction products of these diisocyanates with polyols. Polyols are compounds having two or more hydroxyl groups. Suitable polyols include trimethylol propane, glycerol and pentaeryatritol. Many such polyisocyanates are commercially available, for example under the Desmodur trade mark from Bayer or the Tolonate trade mark from Rhodia.
Preferably the polyester has 0.5 to 4 mols/kg uretdione groups based on the weight of the polyester. Preferably the polyester has a number average molecular weight of 600 to 4000, more preferably 600 to 2000.
The polyamnine is a compound with two or more amine groups per molecule, preferably 2 to 6. Preferred diamines, having two amine groups, are aliphatic and cycloaliphatic diamines. Examples of suitable aliphatic and cycloaliphatic diamines are ethylene diamine, propylene diamine, 1,6-hexanediamine and cycloaliphatic diamines of the formulas;
Also useful are polyamines containing three or more primary amine groups. Examples of such polyamines include tris-(2-aminoethyl) amine, N(CH
2
CH
2
NH
2
)
3
and the products of the Jeffamine™ series manufactured by Jefferson Chemical Company having the general structure
where A is the residue of an aliphatic triol, such as glycerol or trimethylol propane, and x, y and z are integers, the sum of which is between 5 and 85. Suitable compounds containing three or more amine groups can be made by joining together compounds with fewer amine groups. For example diethylene triamine can be converted to its bis diketimiine by reaction with methyl diisobutyl ketone and then the remaining secondary amine group can be reacted with a diisocyanate or a diepoxide to give a polyamine having four amine groups or with a triisocy
Gorr Rachel
Miles Jacques B.
PPG Industries Ohio Inc.
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