Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-06-04
2002-12-03
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C524S544000, C526S242000
Reexamination Certificate
active
06489417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for producing a fluorine-containing acrylic or methacrylic polymer.
2. Description of the Related Art
In order to impart good surface properties such as releasability, stainproofing, water repellency and oil repellency to the surfaces of various adherends, it is common to apply coating agents containing a fluorine-containing acrylic or methacrylic polymer.
Such a fluorine-containing acrylic or methacrylic polymer is known to include polymers obtained by polymerizing fluorine monomers such as acrylic or methacrylic acid esters (both herein inclusively “acrylate or methacrylate”) having a polyfluoroalkyl group or perfluoroalkyl group having 6 to 16 carbon atoms. In this instance, the fluorine monomers are mostly copolymerized with non-fluorine monomers, and their copolymerization is widely carried out by solution polymerization or emulsion polymerization making use of general-purpose solvents.
Such copolymerization of fluorine monomers with non-fluorine monomers can make resultant copolymers highly soluble in the general-purpose solvents and also can achieved a low material cost, but on the other hand tends to make greatly poor the properties such as releasability and stainproofing that are inherent in fluorine-containing polymers.
Accordingly, when importance is attached to the properties inherent in the fluorine-containing polymers, the fluorine monomer must be used in a large proportion in the total monomer. Usually, the fluorine monomer must be in a proportion of at least 70% by weight in the total monomer.
Now, when polymerization is carried out under such conditions that the proportion of fluorine monomer in the total monomer exceeds 70% by weight, it is not preferable to employ emulsion polymerization which makes use of a surface-active agent in a large quantity. This is because the surface-active agent used may bleed to coating film surfaces to cause a deterioration of surface properties of coating films formed of fluorine-containing polymers.
One may contemplate employing bulk polymerization as one of polymerization methods, which, however, has a problem on the controllability of polymerization reaction, and also has a problem that the polymer is obtained as a hard mass that is difficult to handle, and is apt to turn into a gel when dissolved in a fluorine type solvent. Thus, it is not practical to employ the bulk polymerization.
Accordingly, it follows that solution polymerization is employed when polymerization is carried out under the conditions that the proportion of fluorine monomer in the total monomer exceeds 70% by weight.
In the solution polymerization, it is necessary to use a solvent capable of dissolving the fluorine monomer and also dissolving the fluorine-containing polymer formed. Such a solvent can not be any commonly available general-purpose solvents not capable of dissolving the fluorine-containing polymer, and fluorine type (PFC) or chlorine-fluorine type (CFC) solvents such as trichlorotrifluoroethane, metaxylene hexafluoride, tetrachlorohexafluorobutane and FC-726 (available from 3M) are used (see Japanese Patent Application Laid-open No. 61-23656 and Japanese Patent Publication No. 1-42983).
Since, however, the fluorine type or chlorine-fluorine type solvents are very expensive solvents compared with commonly available general-purpose solvents, there is a problem that they hinder the reduction of production cost for fluorine-containing polymers. To solve this problem, one may contemplate using the fluorine type solvent in a relatively small quantity (e.g., in an amount not more than 200 parts by weight) based on 100 parts by weight of the total monomer. This, however, may cause an increase in solution viscosity with progress of polymerization to not only make agitation very difficult but also make it very difficult to take out the resultant polymer from the reaction vessel.
The fluorine type or chlorine-fluorine type solvents have another problem that they are considered to destroy the ozone shield present in the sky on the earth and cause a rise of the earth s surface temperature. Thus, it is strongly required not to use them for the purpose of the conservation of terrestrial environment.
SUMMARY OF THE INVENTION
The present invention intends to solve the above problems the prior art has had. Accordingly, an object of the present invention is to make it possible to produce a fluorine-containing polymer having the fluorine monomer in a high proportion, by the use of commonly available general-purpose solvents without use of fluorine type solvents and chlorine-fluorine type solvents.
The present inventors have discovered that, when a non-halogen type solvent is used, a polymer-containing liquid phase comprised of (i) a fluorine-containing acrylic or methacrylic polymer formed with progress of polymerization and (ii) an organic solvent, with which the polymer is saturated, can be separated from the solution phase by controlling the type and amount of the solvent used, and when so polymerized as to cause such phase separation the reaction mixture containing the fluorine-containing polymer can be well stirred even when polymerized without use of any fluorine type solvent or chlorine-fluorine type solvent, so that the fluorine-containing polymer can be produced in a good efficiency. Thus, they have accomplished the present invention.
More specifically, the present invention provides a process for producing a fluorine-containing acrylic or methacrylic polymer, which comprises polymerizing a fluorine-containing acrylate or methacrylate in a solution phase formed of an organic solvent and dissolved therein a monomer containing a fluorine-containing acrylate or methacrylate having a polyfluoroalkyl group, wherein;
a non-halogen type solvent is used as the organic solvent and the fluorine-containing acrylate or methacrylate is so polymerized that a polymer-containing liquid phase comprised of the fluorine-containing acrylic or methacrylic polymer formed with progress of polymerization and the organic solvent is separated from the solution phase.
This and other objects, features and advantages of the present invention are described in or will become apparent from the following detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below in detail.
The process for producing a fluorine-containing acrylic or methacrylic polymer according to the present invention is a process comprising polymerizing a fluorine-containing acrylate or methacrylate in a solution phase formed of an organic solvent and dissolved therein a monomer containing a fluorine-containing acrylate or methacrylate having a polyfluoroalkyl group.
In this process, a non-halogen type solvent is used as the organic solvent. Hence, the problem on production cost and the problem on terrestrial environment do not occur which may occur when the fluorine type or chlorine-fluorine type solvents are used.
In the production process of the present invention, the fluorine-containing acrylate or methacrylate is so polymerized that a polymer-containing liquid phase comprised of the fluorine-containing acrylic or methacrylic polymer formed with progress of polymerization and the organic solvent is separated from the solution phase which is uniform at the initial stage of the polymerization. Hence, the polymerization reaction can be made to progress in a good efficiency while keeping the polymer from turning into a gel during the reaction. The reason therefor is unclear, and is presumed as follows:
Because of the controlling of the type and amount of the non-halogen type solvent, the reaction mixture that forms a uniform solution phase at the initial stage of the polymerization is separated into two phases, a lower-layer phase and an upper-layer phase. The lower-layer phase is a polymer-containing liquid phase in which the resultant fluorine-containing acrylic or methacrylic polymer is contained in a large quantity and the organic solvent and fluorine monomer st
Sony Chemicals Corporation
Zitomer Fred
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