Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-02-13
2004-07-06
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S080000, C524S543000, C524S577000, C526S329200
Reexamination Certificate
active
06759455
ABSTRACT:
BACKGROUND OF THE INVENTION
Standard mineral spirits used in making typical interior and exterior paint formulations normally contain about 20 percent aromatic compounds. For various reasons, including environmental and ecological concerns, there is a current demand for paint resins that are soluble in paraffinic solvents which do not contain aromatic compounds. However, it is also important for the resin used in such applications to maintain a high level of hardness and ultra-violet light resistance. This desirable combination of properties has heretofore been elusive. More specifically, in the past it has only been possible to improve solubility in paraffinic solvents by compromising hardness and/or ultra-violet light (UV) resistance.
U.S. Pat. Nos. 5,496,905 and 5,504,143 disclose a resin for paints which is highly soluble in paraffinic solvents and which has good resistant to ultra-violet light. These resins contain from about 10 weight percent to about 55 weight percent para-tertiary-butyl styrene (PTBS). These resins also contain about 20 weight percent to about 80 weight percent of at least one alkyl methacrylate monomer, from about 2 weight percent to about 25 weight percent alkyl acrylate monomer, and optionally up to about 40 weight percent of a vinyl aromatic monomer in addition to the PTBS. However, despite the fact that the resin described in U.S. Pat. Nos. 5,496,905 and 5,504,143 has good resistance to ultra-violet light coatings made therewith tend to yellow and discolor over time with exposure to ultra-violet light.
SUMMARY OF THE INVENTION
This invention disclose a resin for paints which is highly soluble in paraffinic solvents and which has excellent resistance to ultra-violet light. Coatings made with these resins are highly resistant to yellowing and discoloration on exposure to ultra-violet light over long periods of time. These resins are comprised of repeat units which are derived from (a) about 5 to about 60 weight percent tertiary-butyl cyclohexyl methacrylate, (b) 0 to about 40 weight percent vinyl aromatic monomers, (c) about 20 to about 80 weight percent alkyl methacrylate monomers, and (d) about 1 to about 30 weight percent alkyl acrylate monomers.
This invention more specifically discloses a resin which is particularly useful in making paraffinic solvent based paints, said resin being comprised of repeat units which are derived from (a) about 5 to about 60 weight percent tertiary-butyl cyclohexyl methacrylate, (b) 0 to about 40 weight percent vinyl aromatic monomers, (c) about 20 to about 80 weight percent alkyl methacrylate monomers, and (d) about 1 to about 30 weight percent alkyl acrylate monomers.
The subject invention further discloses a paint formulation which is comprised of (a) a paraffinic solvent; (b) a resin which is comprised of repeat units which are derived from (i) about 5 to about 60 weight percent tertiary-butyl cyclohexyl methacrylate, (ii) 0 to about 40 weight percent vinyl aromatic monomers, (iii) about 20 to about 80 weight percent alkyl methacrylate monomers, and (iv) about 1 to about 30 weight percent alkyl acrylate monomers; and (c) one or more pigments.
DETAILED DESCRIPTION OF THE INVENTION
The paint resins of this invention are synthesized utilizing free radical emulsion polymerization techniques. This is carried out by adding a tertiary-butyl cyclohexyl methacrylate (TBCHMA), optionally vinyl aromatic monomers, an alkyl methacrylate monomer, and an alkyl acrylate monomer to water to form an aqueous polymerization medium. The aqueous polymerization medium will also normally contain a required amount of a surfactant. Polymerization of the monomers is then initiated with a free radical generator to produce a latex of the resin. The latex made is subsequently coagulated to recover the resin.
In synthesizing the resins of this invention generally from about 5 weight percent to about 60 weight percent TBCHMA, from about 20 weight percent to about 80 weight percent alkyl methacrylate monomers, from about 2 weight percent to about 30 weight percent alkyl acrylate monomers, and from 0 to about 40 weight percent vinyl aromatic monomers are polymerized. It is generally preferred to limit the quantity of vinyl aromatic monomers in the resin since they normally lead to a reduced level of ultra-violet light resistance. For instance, vinyl aromatic monomers can be totally eliminated from the resin. In any case, these resins can be used in manufacturing paints for interior and exterior coatings.
In making resins for interior coatings normally from about 5 weight percent to about 40 weight percent TBCHMA, from about 25 weight percent to about 80 weight percent alkyl methacrylate monomers, from about 5 weight percent to about 25 weight percent alkyl acrylate monomers, and from 0 to about 40 weight percent vinyl aromatic monomers are polymerized. Resins for interior paints preferably contain from about 15 weight percent to about 35 weight percent TBCHMA, from about 30 weight percent to about 70 weight percent alkyl methacrylate monomers, from about 10 weight percent to about 25 weight percent alkyl acrylate monomers, and from 0 to about 35 weight percent vinyl aromatic monomers.
In making resins for exterior coatings normally from about 10 weight percent to about 60 weight percent TBCHMA, from about 30 weight percent to about 80 weight percent alkyl methacrylate monomers, from about 1 weight percent to about 20 weight percent alkyl acrylate monomers, and from 0 to about 15 weight percent vinyl aromatic monomers are polymerized. Resins for exterior paints preferably contain from about 10 weight percent to about 30 weight percent TBCHMA, from about 50 weight percent to about 80 weight percent alkyl methacrylate monomers, from about 2 weight percent to about 10 weight percent alkyl acrylate monomers, and from 0 to about 10 weight percent vinyl aromatic monomers.
The alkyl acrylate monomers that can be used in the resins of this invention generally have the structural formula:
wherein R represents an alkyl group containing from 1 to 10 carbon atoms. The alkyl group in such alkyl acrylate monomers will preferably contain from 2 to 8 carbon atoms with alkyl groups that contain 8 carbon atoms being most preferred. Accordingly, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, and 2-ethyl hexyl acrylate are preferred alkyl acrylate monomers with 2-ethylhexyl acrylate being the most preferred. The alkyl groups in such alkyl acrylate monomers can be straight chained or branched. Thus, normal-propyl acrylate, isopropyl acrylate, normal-butyl acrylate, or tertiary-butyl acrylate can be employed.
The vinyl aromatic monomers which can optionally be included include all of those which are known to polymerize in free radical systems. Such vinyl aromatic monomers typically contain from 8 to 20 carbon atoms. Usually, the vinyl aromatic monomer will contain from 8 to 14 carbon atoms. Some representative examples of vinyl aromatic monomers that can be utilized include styrene, 1-vinyl napthalene, 2-vinyl napthalene, 3-methyl styrene, 4-propyl styrene, 4-cyclohexyl styrene, 4-dodecyl styrene, 2-ethyl-4-benzyl styrene, 4-(phenylbutyl) styrene, para-tertiary-butyl styrene, and the like. Styrene, para-methyl styrene, and mixtures of para-methyl styrene and ortho-methyl styrene are generally the most preferred vinyl aromatic monomers.
The alkyl methacrylate monomers that can be used have the structural formula:
wherein R represents an alkyl group containing from 1 to 10 carbon atoms (R═C
n
H
2n+1
with n being an integer from 1 to 8). The alkyl groups in such alkyl methacrylate monomers can be straight chained or branched. Methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobutyl methacrylate, and n-butyl methacrylate are representative examples of alkyl methacrylate monomers that can be used. The alkyl group in the alkyl methacrylate monomer will preferably contain from 1 to 4 carbon atoms with alkyl groups which contain 4 carbon atoms being most preferred. Accordingly, isobutyl methacrylate is a highly pr
Hu Henry
Wu David W.
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