Low odor reactive coalescent

Details Low odor reactive coalescent Low odor reactive coalescent

2000-02-23

2003-01-21

Killos, Paul J. (Department: 1625)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C560S224000, C106S014130

Reexamination Certificate

active

06509494

ABSTRACT:

This invention relates to compositions which are useful as reactive coalescents. In particular, the invention relates to compositions which are useful as reactive coalescents which are substantially free from odor, their method of preparation, and their use in aqueous coating compositions.
Water based polymers are used extensively in coating compositions. Many applications, such as gloss paint and semigloss paint formulations, require the properties of a hard polymer, i.e. a polymer with a glass transition temperature significantly above the ambient temperature. For the hard polymer to form a film at ambient temperature, the hard polymer is typically formulated with volatile coalescent. The volatile coalescent swells the hard polymer and lowers the glass transition of the hard polymer to allow film formation. After formation of the film, the volatile coalescent evaporates, leaving a hard polymer film. The use of volatile solvents including volatile coalescents, is coming under increased scrutiny as they are a source of volatile organic compounds (VOC's) which can contribute to atmospheric pollution. Recent legislation is mandating the use of coating compositions with lower levels of VOC including VOC free coatings. Further, volatile coalescents are sources of residual odors which may be bothersome, particularly in enclosed environments.
Attempts have been made to use “reactive coalescents” to replace volatile coalescents. Reactive coalescents are compounds which aid in film formation in a similar manner as conventional coalescents but have low volatility and react to become part of the final coating.
One class of reactive coalescents is vinyl reactive coalescents such as dicyclopentenyl esters which include dicyclopentenyloxymethacrylate (DCPOMA), also known as dicyclopentenyl methacrylate, dicyclopentenyloxyacrylate (DCPOA), also known as dicyclopentenyl acrylate, dicyclopentenyloxyethylmethacrylate (DCPOEMA), and dicyclopentyloxyethylacrylate (DCPOEA). These dicyclopentenyl esters have low volatility, and are believed to react through reaction of their vinyl groups to increase the hardness and toughness of coated films. However, DCPOMA and DCPOA, although having low volatility, have objectionable odors which limit their use as reactive coalescents in coating applications, particularly in applications which require baking at elevated temperatures. U.S. Pat. No. 4,141,868 to Emmons et al. teaches the use of DCPOEMA and DCPOEA as vinyl reactive coalescents for aqueous film-forming coating dispersions. Emmons discloses that in contrast to DCPOMA and DCPOA, compositions containing DCPOEMA and DCPOEA do not have an objectionable or even a detectable odor. However, the detection and perception of odor is known to be highly subjective. Further, the standards as to what constitutes a low or no odor composition have changed since the disclosure of Emmons. I have found that despite the disclosure of Emmons, DCPOEMA prepared by the method taught in Emmons still has levels of odor which are objectionable and limit the use of DCPOEMA as a reactive coalescent in coating compositions. There exists a need to provide vinyl reactive coalescents such as DCPOEMA and DCPOEA preparations with lower levels of odor or in particular, no discernible odor, to meet current low odor expectations for coating compositions. A current problem is that DCPOEMA and DCPOEA preparations produced by existing processes have detectable levels of odor that is objectionable to personnel who prepare the coating compositions and/or persons who use them under most conditions of preparation and use. Further, these odors from the DCPOEMA and DCPOEA preparations are more noticeable as modifications to coating compositions have been made to remove other odor causing components such as cosolvents or ammonia which may mask odoriferous smells from the DCPOEMA and DCPOEA preparations. The objectionable smell attributed to DCPOEMA and DCPOEA preparations has limited the use of these preparations in coating compositions.
I have discovered that the odor is not a property of the DCPOEMA, but rather the source of the objectionable odor in the DCPOEMA preparations which are produced by disclosed processes is trace levels of DCPOMA. The DCPOMA is a byproduct of the reactions to prepare DCPOEMA and is not removed by disclosed distillation processes. I have identified a distillation process which is adaptable to an industrial scale process that prepares DCPOEMA and DCPOEA which are substantially-free of DCPOMA and DCPOA and have no objectionable odor. These new preparations of DCPOEMA and DCPOEA are particularly useful as reactive coalescents for aqueous film-forming dispersions.
The distillation process of this invention involves the collection of a first distillation fraction which is rich in the DCPOMA and DCPOA impurities followed by the collection of a second distillation fraction containing DCPOEMA and DCPOEA which is substantially-free of DCPOMA and DCPOA. Since the DCPOMA and DCPOA are distilled into the first distillation fraction, distillation processes without fractional collection of the distillate are not capable of decreasing the concentrations of DCPOMA and DCPOA in DCPOEMA and DCPOEA. Rather, distillation processes without fractional collection of the distillate may be increasing the concentrations of DCPOMA and DCPOA in the distilled DCPOEMA and DCPOEA compared to the concentrations in the distillation mixture, as a fraction of DCPOEMA and DCPOEA often remains undistilled.
In the first aspect of this invention, a composition is provided including at least one dicyclopentenyl ester selected from the group of dicyclopentenyl esters having formula I:
where R represents a H or methyl group and R
1
represents a C
2
-C
12
alkylene group or a C
2
-C
12
oxyalkylene group containing one or more oxygen atoms joining alkylene segments of the groups, each such segment having a chain length of at least two carbon atoms extending between the oxygen atoms and a level of dicyclopentenyloxy(meth)acrylate in the range of from 0 to 0.2 weight % based on the weight of the at least one dicyclopentenyl ester.
In the second aspect of this invention, a process for preparing a low odor composition of a dicyclopentenyl ester selected from the group of dicyclopentenyl esters having formula I:
wherein R represents a H or methyl group and R
1
represents a C
2
-C
12
alkylene group or a C
2
-C
12
oxyalkylene group containing one or more oxygen atoms joining alkylene segments of the groups, each such segment having a chain length of at least two carbon atoms extending between the oxygen atoms, including the steps of preparing a distillation mixture containing the dicyclopentenyl ester and from 10 to 10,000 parts per million by weight based on weight of the dicyclopentenyl ester, of at least one inhibitor selected from the group consisting of phenothiazine, 4-hydroxy-2,2,6,6-tetramethyl piperidinyloxy free radical, 4-methacryloyloxy-2,2,6,6-tetramethyl piperidinyloxy free radical, 4-hydroxy-2,2,6,6-tetramethyl N-hydroxy piperidine, cupric acetate, cupric chloride, 2,6-dichlorobenzoquinone, 2-nitrophenol, p-phenylenediamine, and 1,4-naphthoquinone; distilling the distillation mixture at a temperature in the range of 140° C. to 250° C.; collecting at least one first distillation fraction containing from 2 to 30 weight % of the dicyclopentenyl ester, based on the weight of the dicyclopentenyl ester in the distillation mixture; and collecting at least one second distillation fraction containing from 98 to 70 weight % of the dicyclopentenyl ester, based on the weight of the dicyclopentenyl ester in the distillation mixture; wherein the level of dicyclopentenyloxy(meth)acrylate in the second distillation fraction is in the range of 0 to 0.2 weight %, based on the weight of the dicyclopentenyl ester in the second distillation fraction, wherein the second distillation fraction is the low odor composition of the dicyclopentenyl ester.
In the third aspect of this invention, a composition is provided including at least one compound selected from the

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