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
2001-02-20
2003-08-26
Harlan, Robert D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S026000, C526S250000, C526S255000, C526S348600
Reexamination Certificate
active
06610788
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an aqueous dispersion of a fluorocopolymer and a composition for water-based coating material.
BACKGROUND ART
Heretofore, a vinylidene fluoride type resin is widely used as a baking-type coating material, since it is excellent in weather resistance, heat resistance and chemical resistance and it is soluble in a solvent at a high temperature. As such a vinylidene fluoride type resin, a homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride with a fluoroolefin (such as tetrafluoroethylene, hexafluoropropylene or chlorotrifluoroethylene), has been proposed. Further, it is known that a copolymer of a fluoroolefin with cyclohexyl vinyl ether and other various monomers, is soluble in an organic solvent even at room temperature, and when used as a coating material, it gives a coating film which is transparent and has high gloss and which further has excellent characteristics such as high weather resistance, water and oil repellency, stain resistance and non-tackiness (JP-A-55-44083), and its use is increasing in the field of weather resistant coating materials for interior and exterior of e.g. buildings.
On the other hand, in recent years, restriction on use of problematic organic solvents has been increased from the viewpoint of the environmental protection against e.g. air pollution or the safety to human bodies, and social demand for an aqueous coating material or a powder coating material employing no organic solvent, has increased. Also with respect to a fluororesin, an aqueous dispersion type has been studied, and with respect to a vinylidene fluoride type resin, a method for emulsion polymerization of an acrylic monomer in the presence of vinylidene fluoride resin particles, has been proposed (JP-A-3-8884, JP-A-4-325509).
Further, also with respect to a copolymer of a fluoroolefin with a cyclohexyl vinyl ether and other various monomers, an aqueous dispersion type has been studied, and it has been reported that such can be prepared by emulsion polymerization (JP-A-57-34107, JP-A-61-231044). Further, an aqueous dispersion has been proposed in which a fluorine-containing copolymer having, as an essential constituting component, polymer units based on a macro monomer having a hydrophilic moiety, is dispersed in water. This aqueous dispersion is excellent in the film-forming properties and presents a coating film having good mechanical strength, and it is reported further that it can be produced even without using an emulsifier or a hydrophilic organic solvent.
However, with an aqueous dispersion of a vinylidene fluoride type resin, the stability of the aqueous dispersion is not necessarily good, and the transparency of the coating film is poor due to the crystallizability of the resin, and if the crystallizability is lowered in an attempt to improve the transparency, there has been a problem that the glass transition temperature of the coating film tends to be so low that the stain resistance tends to deteriorate. By seed polymerization of an acrylic monomer, there has been some improvement over the problems, but such has not been adequate. Further, there has been a problem also with respect to the film-forming properties. Furthermore, the vinylidene fluoride type resin is composed solely of a fluoroolefin, and the cost tends to be high. A copolymer of a fluoroolefin with cyclohexyl vinyl ether and other various monomers is practically useful as the transparency of the coating film and the film-forming properties are good, but since a liquid monomer is employed, the coating film tends to be slightly tacky, and a further improvement in this respect, has been desired.
The present inventors have found that these problems can be solved by an aqueous dispersion obtained by seed polymerization. of an acrylic monomer in the presence of particles of a copolymer of a fluoroolefin with an &agr;-olefin such as ethylene or propylene. Such an aqueous dispersion has a practical level of adhesion to various substrates, but the adhesion to a glass or cement substrate has not yet been fully satisfactory. Further, contaminants are likely to deposit thereon, and when it is used at a place where no rain will fall thereon, the surface deterioration of the coating film will be little due to high weather resistance, and as compared with a coating film which is susceptible to surface deterioration, a stain once deposited, tends to be scarcely removed by a slight force of rain water. Accordingly, there has been a problem that as compared with a coating film which is susceptible to surface deterioration due to inadequate weather resistance, it is susceptible to staining on appearance. Further, under severe weather conditions, as a non-crosslinked type coating material, blistering or peeling of the coating film is likely to result due to rain or sunshine outdoors, and further, there has been a problem that the solvent resistance is inadequate.
DISCLOSURE OF THE INVENTION
The present invention is to solve the above described problems of the prior art and has an object to present an aqueous dispersion of a fluorocopolymer and a composition for water-based coating material, whereby the aqueous dispersion is excellent in stability and film-forming properties, and the fluorocopolymer coating film is excellent in mechanical strength and improved in weather resistance, water resistance, solvent resistance, adhesion and stain resistance.
The present invention has been made to solve the above described problems, and according to the present invention, the following inventions are presented.
(1)
An aqueous dispersion characterized in that a fluorocopolymer which is a copolymer comprising (a) polymer units based on a fluoroolefin, (b) polymer units based on propylene, and (c) polymer units based on ethylene and/or (d) polymer units based on butylene and which has a melting point within a range of from 40 to 150° C., is dispersed in water.
(2)
An aqueous dispersion characterized in that a fluorocopolymer which is the fluorocopolymer as defined in (1) and which has a glass transition temperature within a range of from −20° C. to +80° C., is dispersed in water.
(3)
An aqueous dispersion characterized in that a fluorocopolymer which is the fluorocopolymer as defined in (1) and which has a value Q as an index of its molecular weight within a range of from 0.1 to 10,000, is dispersed in water, provided that the value Q is a value defined by a volume extruded in a unit time (mm
3
/sec), when, using a flow tester, the fluorocopolymer is filled in a cylinder having an inner diameter of 11.3 mm and then extruded from a nozzle having an inner diameter of 2.1 mm and a length of 8 mm under a load of 7 kg at 140° C.
(4)
An aqueous dispersion characterized in that a fluorocopolymer which is the fluorocopolymer as defined in (1) and which has a content of fluorine atoms within a range of from 20 to 65 wt %, is dispersed in water.
(5)
An aqueous dispersion characterized in that a fluorocopolymer which is the fluorocopolymer as defined in (1) and which has a particle size within a range of from 50 nm to 300 nm, is dispersed in water.
(6)
An aqueous dispersion obtained by emulsion polymerization, in the presence of 100 parts by weight of particles of the fluorocopolymer as defined in any one of (1) to (5), of from 100 to 10,000 parts by weight of a mixture of the same combination of monomers as for said particles.
(7)
An aqueous dispersion characterized in that composite particles obtained by emulsion polymerization of from 5 to 200 parts by weight of a radical polymerizable monomer mixture comprising, as the main component, an alkyl (meth)acrylate having a C
1-18
alkyl group, in the presence of 100 parts by weight of particles of the fluorocopolymer as defined in any one of (1) to (6), are dispersed in water.
(8)
A composition for water-based coating material, comprising the aqueous dispersion of the fluorocopolymer as defined in any one of (1) to (6) and from 0.1 to 100 parts by weight, per 100 parts by weight of the solid content of the fluorocopolymer,
Ichikuni Naomi
Ishida Toru
Takakura Teruo
Asahi Glass Company Limited
Harlan Robert D.
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