Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-09-20
2002-05-28
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S308000, C525S330300, C523S412000, C523S201000, C524S560000, C524S561000
Reexamination Certificate
active
06395836
ABSTRACT:
The present invention relates to a copolymer. More particularly, the present invention relates to a film-forming copolymer having excellent physical properties and the process for forming the copolymer.
BACKGROUND OF THE INVENTION
It is often necessary to heat and dry a coated film to fully reveal the physical properties of a polymer of conventional technology. Generally, the physical properties, such as a strength and elongation, of the film dried at an elevated temperature are superior to those of the film dried at ambient temperature. A film dried at atmospheric temperature has poorer water resistance and blister resistance, especially after long term exposure under humid conditions than a comparable film dried at an elevated temperature. Furthermore, some conventional polymers show poorer film forming ability at low temperature than a comparable film dried at an elevated temperature and are unusable in certain applications. As used herein, the term “ambient temperature” usually means a temperature above 0° C. and, more specifically, from 5° C. to 35° C.
The object of the present invention is to provide a copolymer that can provide a film having excellent physical properties even when coated and dried at a low temperature. The film prepared from the coating compositions containing the copolymer of the present invention have excellent physical properties, such as a strength and elongation, as well as an excellent water resistance, weather resistance and thermal stability.
The inventor of the present invention has found that the above problem can be solved by using a copolymer prepared by a multi-step polymerization process and which contains at least two acrylic copolymer portions each having a specific range of glass transition temperatures.
SUMMARY OR THE INVENTION
The present invention relates to a core/shell copolymer, comprising:
(a) an acrylic copolymer portion A having a Tg of from 30° C. to 70° C., preferably 30° C. to 60° C.; and
(b) an acrylic copolymer portion B having a Tg of from 5° C. to −30° C., preferably 5° C. to −20° C.;
wherein said acrylic copolymer portion A is present at a level of from 5 weight % to 40 weight %, based on a total weight of said acrylic copolymer portions A and B;
wherein said acrylic copolymer portion B is present at a level of from 60 weight % to 95 weight %, based on a total weight of said acrylic copolymer portion A and B;
wherein said acrylic copolymer portions A and B contain units derived from same said hard monomer and same said soft monomer,
wherein the total amount of said units derived from said hard monomer and soft monomer in each of said acrylic copolymer portion is at least 70 weight %, based on the weight of each acrylic copolymer portion; and
wherein said core/shell copolymer is prepared by a multi-step polymerization process.
The present invention further relates to a process for preparing a core/shell copolymer, comprising the steps of:
(1) preparing an acrylic copolymer portion B having a Tg of from 5° C. to −30° C. from a monomer mixture (b); and
(2) preparing an acrylic copolymer portion A having a Tg of from 30° C. to 70° C. from a monomer mixture (a) in the presence of said acrylic copolymer portion B;
wherein monomer mixture (a) is present at a level of from 5 to 40 weight % based on a total weight of the monomer mixtures (a) and (b);
wherein monomer mixture (b) is present at a level of from 60 to 95 weight %, based on a total weight of the monomer mixtures (a) and (b);
wherein said monomer mixtures (a) and (b) contain the same hard monomer and the same soft monomer; and
wherein the total amount of said hard monomer and said soft monomer in each mixtures (a) and (b) is at least 70 weight %, based on the weight of the mixture.
REFERENCES:
patent: 3454516 (1969-07-01), Victorius
patent: 4097553 (1978-06-01), Novak
patent: 4150005 (1979-04-01), Gehman et al.
patent: 5185387 (1993-02-01), Klesse et al.
patent: WO 94/04581 (1994-03-01), None
Asinovsky Olga
Falk Stephen T.
Rohm and Haas Company
Seidleck James J.
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