Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1997-12-18
2001-01-16
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S129000, C528S143000, C528S158000, C528S242000, C528S248000, C526S062000, C526S344000, C526S344100, C526S344200, C525S398000, C525S404000, C525S412000
Reexamination Certificate
active
06174986
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the invention
This invention relates to a process for improved homopolymerization or copolymerization of vinyl chloride; in particular, to a process for preventing adhesion of polymer to an inner wall of a polymerization apparatus such as a polymerization tank and to a polymer adhesion inhibitor therefor.
2) Prior Art
When vinyl chloride is subjected to homopolymerization or copolymerization with a monomer copolymerizable with vinyl chloride, or graft polymerization (hereinafter, collectively referred to as “polymerization”), polymer may adhere to parts of an apparatus such as an inner wall of a polymerization tank, a reflux condenser, a stirring blade, a baffle and various types of pipe connections, in contact with monomer(s) during a polymerization process, causing problems such as reduction of coolability of the polymerization tank and degradation in quality of the homopolymer or copolymer of vinyl chloride (hereinafter, referred to as “the product”) due to contamination with peeled polymer which has been adhered to some surface.
It is therefore usual that after every polymerization process, the inside of the polymerization tank is cleaned prior to a next polymerization process, which requires an enormous amount of labor and time, leading to reduction in productivity rate of the polymerization tank or increase in the cost for the product.
To solve the problem, there have been proposed processes for preventing a polymer adhesion to an inner wall of a polymerization tank and/or other parts by applying some agent; for example, JP-B 61-843 (U.S. Pat. No. 4,355,141) has disclosed a process comprising application of a cocondensation product of resol with a nitrogen-containing compound such as nitrophenols, nitrobenzoic acids, aminophenols and aminobenzoic acids, and JP-A(KOHYO) 2-500845 (PCT-US-88-02462, WO-89-00993) and JP-A (KOHYO) 5-501892 (PCT-US-90-05829, WO-91-06576) have proposed processes comprising application of a condensation product of phenothiazine with an aldehyde.
However, the process according to JP-B 61-843 does not sufficiently prevent scale adhesion, and a more effective method is desired. For the processes described in JP-A 2-500845 and JP-A 5-501892, since the adhesion inhibitor used can be dissolved only in an organic solvent, a particular type of organic solvent should be used as a solvent for a coating liquid, making the apparatus and/or the operation more complex in the light of safety in handling and due to need for recovery of the solvent from the polymerization system. Furthermore, there are practical problems; for example, inadequate recovery of the solvent adversely affects the quality of the product.
3) Object of the Invention
Thus we have investigated for making it possible to quite effectively prevent polymer adhesion in, e.g., a polymerization tank, in polymerization of a vinyl chloride monomer, without affecting a polymerization rate or physical properties of the product; to apply an adhesion inhibitor as a coating liquid containing no or a very small amount of organic solvents; to eliminate the need for removing adhered polymer after every polymerization process; and to realize closed polymerization in which a manhole should not be opened for every polymerization process.
SUMMARY OF THE INVENTION
We have intensively investigated to solve the above problems and have found that in polymerization of a vinyl chloride monomer, polymer adhesion to a polymerization apparatus may be significantly reduced and a small amount of polymer adhered may be readily removed, e.g., with water, by applying a coating liquid comprising a particular wall-adhesion inhibitor prior to polymerization, to parts of a polymerization apparatus and polymerization ancillaries in contact with the monomer during the polymerization process, such as an inner wall of a polymerization tank. Thus, this application discloses the following invention and embodiments;
(a) A process for (co)polymerizing a vinyl chloride monomer wherein the vinyl chloride monomer is subjected to homopolymerization or copolymerization with a monomer copolymerizable with the vinyl chloride monomer in an aqueous solvent or bulk (co)polymerization of vinyl chloride monomer or the monomers, comprising applying in advance a coating liquid containing a cocondensation product obtained by reacting either a phenothiazine derivative and an aldehyde or a phenothiazine derivative, a naphthol derivative and an aldehyde to give an initial condensation product and then reacting the initial product with a polyphenol, to an inner wall of a polymerization tank and parts of an apparatus in contact with the monomers during the polymerization process;
DETAILED DESCRIPTION OF THE INVENTION
(b) A process according to (a), wherein the above cocondensation product is prepared by reacting either a phenothiazine derivative and an aldehyde or a phenothiazine derivative, a naphthol derivative and an aldehyde in the presence of an acidic catalyst to give an initial condensation product and then reacting the initial product with a polyphenol by portionwise or continuously adding the polyphenol;
(c) Aprocess according to (a) or (b), wherein the above coating liquid is an aqueous solution of an alkali metal hydroxide or alkaline earth metal hydroxide containing the above cocondensation product;
(d) A cocondensation product with a weight-average molecular weight in the range of 500 to 5,000 prepared by reacting either a phenothiazine derivative and an aldehyde or a phenothiazine derivative, a naphthol derivative and an aldehyde to give an initial condensation product and then reacting the initial product with a polyphenol;
(e) A cocondensation product according to (d) prepared by reacting either a phenothiazine derivative and an aldehyde or a phenothiazine derivative, a naphthol derivative and an aldehyde in the presence of an acidic catalyst to give an initial condensation product and then reacting the initial product with a polyphenol by portionwise or continuously adding the polyphenol;
(f) A cocondensation product according to (d), wherein the polyphenol is pyrogallol;
(g) A wall-adhesion inhibitor for a (co)polymerization of vinyl chloride, prepared by reacting either a phenothiazine derivative and an aldehyde or a phenothiazine derivative, a naphthol derivative and an aldehyde in the presence of an acidic catalyst to give an initial condensation product and then reacting the initial product with a polyphenol by portionwise or continuously adding the polyphenol;
(h) A wall-adhesion inhibitor for a polymerization of vinyl chloride according to (g), wherein the polyphenol is pyrogallol;
(i) A process according to (c), wherein the concentration of the reaction product in the aqueous alkali metal or alkaline earth metal hydroxide solution is 0.1 to 10.0 wt %, and the concentration of the alkali metal or alkaline earth metal hydroxide is 0.05 to 5.0 wt %;
(j) A process for preventing scale adhesion, during polymerization wherein a vinyl chloride monomer is homopolymerized or copolymerized with a monomer copolymerizable with the vinyl chloride monomer, to an inner wall of a polymerization apparatus in contact with the monomers, by applying in advance a coating liquid to the inner wall, wherein the coating liquid comprises a cocondensation product by reacting either a phenothiazine derivative and an aldehyde or a phenothiazine derivative, a naphthol derivative and an aldehyde to give an initial condensation product and then reacting the initial product with a polyphenol.
A cocondensation product used in this invention may be prepared by reacting either a phenothiazine derivative and an aldehyde or a phenothiazine derivative, a naphthol derivative and an aldehyde to give an initial condensation product and then reacting the initial product with a polyphenol.
The phenothiazine derivative is generally phenothiazine, but its derivative such as the one shown in the following formula may be also used.
The naphthol derivative may be &agr;- or &bgr;-naphthol or its alkylated derivative, preferably &agr;- or &
Nakamura Ichisaburo
Ozawa Masaaki
Takahashi Akihiko
Burns Doane Swecker & Mathis L.L.P.
Mitsui Chemicals Inc.
Truong Duc
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