CA2073090A1

CA2073090A1 - Polymer scale preventive agent, polymerization vessel effective in preventing polymer scale deposition, and process of producing polymer using said vessel

Info

Publication number: CA2073090A1
Application number: CA 2073090
Authority: CA
Inventors: Toshihide Shimizu; Minoru Shigemitsu
Original assignee: Individual
Current assignee: Shin Etsu Chemical Co Ltd
Priority date: 1991-07-03
Filing date: 1992-07-03
Publication date: 1993-01-04
Also published as: JP2623383B2; JPH059206A

Abstract

ABSTRACT OF DISCLOSURE

A polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising (A) a water-soluble basic polysaccharide and (B) a phenothiazine. The agent is used for forming a coating on the inner wall, etc. of a polymerization vessel, and highly safe for operators. Deposition of polymer scale can be effectively prevented, and polymeric product with high whiteness or a low initial coloration is obtained.

Description

209sp Polymer scale preventive agent, Pol~merization vessel effective in preventing polymer scale deposition, and Process o~ producing polymex using said vessel BACKGROUND OF THE _NVENTION

. Field of the Invention The present invention relates ~o a polymer scale preventive agent useful in pol~merization of a monomer having an ethylenically unsaturated double bond, a polymerization vessel effective in preventing polymer scale deposition, and a process of producing polymer using said vessel.

2. Description of :the Prior Art In processes of preparing polymers by polymerizing a monomer in a polymerization vessel, the problem that polymer deposits on the inner wall surface and so forth in the form of scale, is known. The deposition of the polymer scale on the inner wall results in disadvantages that ~he yield of the polymes and cooling capacity o the polymerization vessel are lowered; that the polymer scale may peel and mix into a polymeric product, thereby impairing the quality of the polymeric product; and that removal of such polymer scale is laborious and hence time-consuming. Fur~her, since the polymer scale contains unreac~ed monomers and operators may be exposed thereto, which may cause physical disorders in the operators.
Heretofore, as methods for preventing polymer scale deposition on the inner wall surface and so forth of a ,: , . . . . . ..
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polymerization vessel in polymerization of a monomer having an ethylenically unsaturated double bond, methods in which substances exemplified below are coated on the inner wall surface, etc. as a scale preventive agent, have been known.
~or example, particular polar organic compounds (Japanese Patent Publication (KOKOKU) No.45-30343(1970)), a dye or pigment (Japanese Patent Publication (KOKOKU) Nos.45-30835(1970) and 52-24953(1977~), an aromatic amine compound (Japanese Pre-examination Patent Publication (XOK~I) No.51-50887(1~76)) and a reaction product of a phenolic compound and an aromatic aldehyde (Japanese Pre-examination Patent Publication (KOKAI) No.55-54317(1980)) are disclosed.
In the meantime, vinyl chloride pol~mers obtained by polymerization are required to have a good whiteness. That is, when poly~eric produc~s such as vinyl chloride polymers are formed or molded with no addi~ion of a coloring agent, the resulting formed or molded product is colored more or less. This coloration is called initial coloration, which is required to be as low as possible. Specifically, for example, the formed or molded produc~s are required to have an L value according to the Xunter's color difference equation, described in JIS Z 8730 [1980), of 70 or more.
The prior art polymer scale preventive agent~ generally include a great number of colored substances as exemplified typically by the dyes and pigments described in Japanese Patent Publication tKOKOKU) Nos.45-30835(1970) and 52-24953(1977), the aromatic amine compounds described in Japanese Pre-examination Patent Publication (KOK~I) No.51-5088~l(1976), and the reaction products of a phenolic compound and an aromatic aldehyde described in Japanese Pre-examination Patent Publication (KOKAI) ~o.55-54317(1980).
Presumably, for this, a colored polymer i5 obtained in suspension polymerization and the like of vinyl chloride, etc. in a polymerization vessel which has a coating comprising the polymer scale preventive agent described above formed on its inner wall. That is t according to :

.' ~ . ' . , measurement of the lightness L described above, the L may be measured to be 65 or less, and coloration is thereby confirmed. Presumably, the coloration is caused by incorporation of components of the coating which has dissolved or peeled into the polymerization mass.
Improvement is required for producing a polymer of high quality.
Moreover, the prior art polymer scale preventive agents generally include poisonous substances as exemplified t~pically by terrible substances such as aniline/
nitrobenzene, formaldehyde, etc. among the polar compounds described in Japanese Patent Publication (KOKOKU) No.45-30343(1970), and pigments containing a heavy metal such as chromium or lead among the pigments described in Japanese Patent Publication ~KOKOKU~ No.45-30835(1970). The dyes described in Japanese Patent Publication (KOKOKU~ Nos.45-30835(1970) and 52-24953(197i) include some dyes that involve concern about carcinogenesis. Therefore, use of these substances may cau~e problems in safety of operators.
In the U.S. Patent Application Serial No. 07/705,554 filed on Nay 24, 1991 by T. Shimizu et al., is disclosed a polymer scale preventive agent, as one which is safe and effective in producing polymeric products with a low initial coloration, comprising a water-soluble basic polysaccharide such as chitosans. The present invention relates to an improvement of the agent above described in the U.S.
application in prevention of polymer scale deposition~

SUMMARY_OF THE INVENTION

An object of the present invention is to provide a polymer scale preventive agent which is capable of preventing polymer scale deposition effectively, puts no color to a polymeric product to thereby produce the polymeric product with a low initial coloration , and axe not poisonous and therefore causes no concern with respect to safety or sanitation, a polymerization vessel effective in preventing polymer scale deposition using the same preventive agent, and a process of producing a polymer using the polymerization vessel.
Thus, the present invention provides, as a means of attaining said object, a polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising:
(A) a water-soluble basic polysaccharide, and (B~ a phenothiazine.
Further the present invention provides a pol~merization vessel having on its inner wall surfaces a coating preventing deposition of polymer scale, wherein said coating comprises the components (A~ and (B) above.
Furthermore, the present invention provides a process of producing a polymer by polymeriza~ion of a monomer having an ethylenically unsaturated double bond in a polymerization vessel, comprising the step of carrying out said polymerization in said polymerization vessel having on its inner surfaces, the coating comprising the components (A) and (B), whereby the deposition of polymer scale is prevented.
According to the present invention, polymers with an ~
value of 70 or more, which has a low initial coloration or a high whiteness, can be prepared. Moreover, the ~cale preventive agent used in the present invention is not poisonous and is highly safe; hence there is no problem about safety or sanitation of operators.
Further, according to the present invention, polymer scale deposition can be effectively prevented, irrespectively of polymerization conditions such as the kind of a monomer or a polymerization initiator, polymerization type, the kind of material constituting the inner wall of polymerization vessels, etc.

DETAILED DESCRIPTION OF PREFERRED EMBODIM~NTS

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~ : ` , PolYmer scale preventive aqent (A~ Water-soluble_basic E~l~saccharide The water-soluble basic polysaccharide used in the present invention includes, for example, chitosans, water-soluble chitosan derivatives, polygalactosamines, water-soluble polygalactosamine derivatives and water-soluble chitin derivatives.
Chitosans are a straight chain polysaccharide, i.e., poly-1,4-~-glucosamine, formed by polymerization through ~-1,4 linkage of D-glucosamine. It can be obtained by deacetylization of chitin contained in the carapace of the Crustacea such as prawns, shrimps and crabs. Recently a chitosan can be produced by culturing a mold, and the chitosan thus produced can be used in the same manner as those naturally occurring. The chitosans are insoluble in water under the neutral conditions, but soluble under the acidic conditions; hence the chitosans are used under a pH
of less than 7O
The water-soluble chitosan derivatives which may be used in the present invention include the following:
(1) Organic acid salts and inorganic acid salts of chitosans. The organic acid specifically includes, for example, acetic acid, glycollic acid, malic acid, citric acid, and ascorbic acid. The inorganic acid includes, for example, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. Chitosans preferably have a deacetylization degree of 40 to 100~.
(2) Water-soluble low molecular products obtained by decomposition of chitosan~, i.e., water-soluble glucosamine oligomers. Normally, 5 to 20-mers of glucosamine are preferred. Such oligomers can be produced by conventional depolymerization methods, for example, the hydrochloric acid hydrolysis method (Japanese pre-examination patent publication(KOKAI) No. 61-21102(1986), the nitrate decomposition method (Japanese pre-exa~ination patent publication (KOKAI) No. 62-184002(1987), the chlorine 3~D9¢:~

decomposition method (Japanese pre-examination patent publication (KOKAI) No. 60-186504(198~), the pho~phoric acid decomposition method and decomposition methods using an enzyme or microorganism.
(3) Water-soluble derivatives of chitosans prepaxed by introducing a hydrophilic group therein~o. Examples are described in Japanese pre-examination patent publication tKOKAI) No. 63-14714(1988) and include polyoxyethylene chitosans, polyoxypropylene chitosans, phosphated chitosans, N-glycidyltrimethylammonium chitosans, dihydropropylchitosans, glycol chitosan and methylglycol chitosan.
~ he polygalactosamines which may be used in the present invention are insoluble in water under neutral conditions, but soluble under a pH of 7 or less and therefore used under such conditions. Polygalactosamines can be produced by culturing a mold (APPLIC:ATION OF CHITIN AND CHITOSAN pp. 24-26, Edited by Society for Research of Chitin and Chitosan, 1990, published by Giho-do Shuppan).
The water-soluble polygalactosamine derivatives include the following:
(1) Organic acid salts and inorganic acid salts of polygalactosamines including salts of organic acids such as acetic acid, formic acid or the like, and salts of inorganic acids such as hydrochloric acid, nitric acid or the like;
(2) Water-soluble low molecular products obtained by deco~position of polygalactosamines. Normally, 5 to 20-mers of galactosamine are preferred. Such oligomers can be produced by decomposition methods using an enzyme or microorganism.
The water-soluble chi~in derivatives which may be used in the present invention, include the following:
(1) Water-soluble N-acetylglucosamine oligomers obtained by decomposition of chitins. Normally, 5 to 20-mers are preferred. Such oligomers can be produced by conventional depolymeri2ation methods, for example, the nitrous acid . .

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deromposition method, the formic acid decomposition me~hod, the chlorine decomposition method ~Japanese pre-~xamination patent publication (KOKAI) No. 60-186504(1987)) or decomposition methods using an enzyme (e.g., chittinase) or a microorganism.
(2) Water soluble derivatives of chi~ins prepared by introducing a hydrophilic group thereinto. Examples are described in Japanese pre-examination patent publication (KORAI) No. 63-14714(1988) and include polyoxyethylene chitins, polyoxypropylene chitins, phosphated chitins and dihydropropylchitins.
Among the watex-soluble basic polysaccharides de~cribed above, preferred ~re the inorganic acid salts and organic acid salts of chitosans, having a deace~ylization degree of lS 65~ or more and a viscosity at 20C in the form of an aqueous solution containing 0.5~ by weight of the chitosan and 0.5% by weight of acetic acid of 30 cP or more when measured with a B-type viscometer, and the organic or inorganic sal~s of polygalactosamines with a molecular weight of 10,000 or more.
The water-soluble basic polysaccharides may be used singly or in combination of two or more.
(B) Phenothiazine The phenothiazine, the component (B) of the polymer scale preventive agent of the present invention, is typically represented by, for example, the following general formula:

~ S ~ (R)n wherein R may be the same or different where there exist two or more R's and each represent a hydrogen atom, -OH, -Cl, -CH3, -C2H5, -COCH3, -COC2H5, -SO2CH3, -SO2C2H5, or NO2, is an integer of 1 to 4, preferably 1 or 2.
The examples of the phenothiazine include phenothiazine, 2-acetylphenothiazine, 2-propylphenothiazine, . :
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2-nitrophenothiazine, 2-methylsulfonylphenothiazine, 3,7-dihydroxyphenothiazine, 3,7-diaminoph~nothiazine, 3-chlorophenothiazine and the like.
The preferred combinations of the components ~A) and (B) include those specifically described in Examples later.
The amount of the phenothiazine (B) in ~he polymer scale preventive agent of the presen~ invention ranges normally from 0.1 to 1,000 parts by weight! preferably 1 to 600 parts by weight, per 100 parts by weight of the component (A). If the amount of th~ phenothiazine (B) is too small or too large relative to the component (A), improvement in scale preventing effect due to the combined use of the components (A) and (B) is hardly attainedc Other components To the scale preventive agent, for example, a solvent, a cationic surfactant, a nonionic surfactant, an anionic surfactant, and so forth c~n be optionally added as long as the scale preventing effect is not impaired.
Further, inorganic compounds can be optionally added to the coating liquid as long as the high whiteness, safety or the scale preventing effect is not impaired. The inorganic compounds which may be added include, for example, silicic acids or silicates such as or~hosilicic acid, metasilicic acid, mesodisilicic acid, mesotrisilicic acid, mesotetrasilicic acid, sodium metasilicate, sodium orthosilicate, sodium disilica~e, sodium tetrasilicate and water glass; metallic salts such as oxygen acid salts, acetates, nitrates, hydroxides or halides of a metal selected from alkali earth metals such as magnesium, calcium, and barium, zinc family metals such as zinc, aluminum family metals such as aluminum, and platinum family metals such as ruthenium, rhodium, palladium, osmium, iridium and platinum; and inorganic colloids such as ferric hydroxide colloid, colloidal silica, colloid of barium sulfate, and colloid of aluminum hydroxide. The above-mentioned inorganic colloids may ~e those prepared, for ~.

example, by mechanical crushing, irradiation with ultra~onic wave, electrical dispersion or chemical methods.
The polymer scale preventive agent is used for forming a coating, for example, on the inner wall surfaces of a polymerization vessel, so that scale deposition in the vessel can be pre~en~ed. Normally, in forming said coating on the inner wall surfaces, etc. of a polymerization vessel, the polymer scale preventive agent is used in a liquid state, i.e., as a coating liquid.
~E~E~ration of a coatinqLliquid The coating liquid mentioned above is prepared by dissolving or dispersing said components (A) and (B) in a solvent.
The solvents used for preparation of the coating liquid include, for example, water; alcohols such as methanol, ethanol, propanol, butanol, 2-butanol, 2~methyl-1-propanol, 2-methyl-2-propanol, 3-methyl-1-butanol, 2-methyl-2-butanol~
2-pentanol, etc.; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.; esters such as methyl formate, ethyl formate, methyl ace~ate, methyl acetoacetate, etc.; ethers such as 4-methyldioxolane5 ethylene glycol diethyl ether, etc.; furans; and aprotic solvents such as dimethylformamide, dimethyl sulfoxide, acetonitrile, etc.
~hese solvents may be used singly or as a mixed solvent of two or more thereof as appropriate.
The total concentration of the components (A) and (B) is not limited as long as the coating weight described later can be obtained, and it is normally in the range from 0.005 to 10~ by weight, preferably from 0.01 to 5% by weight. The Ph of the coating liquid is not particularly limited.
Asuitable acid or alkali may be used for adjusting the pH.

Formation of coatinq When the coating liquid prepared as described above is used for forming a coating on the inner wall surface of a polymerization vessel, first, khe coating liquid is applied ::
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to the inner wall surface and then dried sufficien~ly, e.g., at a temperature of room temperature ~o 100C, followed by washing with water if neces6ary. ~ coating is formed by these operations on the inner wall surfaca of the polymerization vessel; hence the polymer scale deposition thereon can be prevented.
The above-mentioned coating is preferably formed on not only the inner wall surfaces of a polymeri~ation vessel but also other parts with which khe monomer comes into contact during polymerization. For example, it is preferred to form the coating by applying said coating liquid on a stirring shaft, stirring blades, baffles, condensers, headers, search coil, bolts, nuts, etc.
Nore preferably, the coating is formed on not only the parts with which the monomer comes into contact during polymerization but also o~her parts on which polymer scale may deposit, for example, such as the inner surfaces of equipment and tubing of recovery system for unreacted m~nomer. These parts, more specifically, are exemplified by the inner wall surfaces of monomer dis~illation columns, condensers, monomer stock tanks and valves, etc. in said recovery system.
The method of applying the coating liquid on the inner wall surface, etc. of a polymeri~ation vessel is not particularly limited, and includes, for example, the brush coating, spray coating, the method of filing the polymerization vessel, etc. with the coating liquid followed by withdrawal thereof, and automatic coating methods as disclosed in Japanese Pre-examination Patent Publication (KOKAI) Nos.57-61001(1982) and 55-362B8(1980), and Japanese Pàtent Publication (KOHYO) Nos.56-501116(1981) and 56-501117(1981), and Japanese Pre-examination Publication (KOKAI) No.59-11303(1984), etc.
The method of drying wet coated surface provided by application of the coating liquid, is not limited, either.
The drying is conducted preferably at a temperature within .
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the ran~e from room temperature to 100C, typically 30C to 80C. Specifically, a me~hod in which, after the liquid is applied, hot air with a suitable elevated temperature is blown to the coated surface, and a method in which the inner wall surface of a polymerization vessel and the surfaces of other parts to be coated are previously heated at, e~g., 30-80C and ~he coating liquid is directly applied to the - heated surfaces, etc. After dried, the coa~ed surfaces are washed with water if necessary.
The coating thus formed has normally a coating weight of 0.001 g/m2 or more, preferably from 0.05 to 2 g/m2 The above coating operation may be conducted every l to ten-odd batches of polymerization. The formed coating has fairly good durability and retains the polymer scale~
preventing action; therefore the coating operation is not necessarily performed for every batch of pol~merization.
Hence, the productivity of the manufactured polymer is improved.
Polvmerization After forming the coating on the inner wall surfaces of a polymerization vessel and other parts with which monomer may come into contact by application of the coating liquid, polymerization is carried out in accordance with conventional procedures therein. That is, a monomer having an ethylenically uns~turated double bond and a polymerization initiator (catalyst) are chaxged, and then, a polymerization medium such as water, etc. and, optionally, a dispersing agent such as suspension agents, solid dispersing agents, and nonionic and anionic emulsifying agents, etc.
are charged, followed by carrying out polymerization according to conventional methods.
The monomer having an ethylenically unsaturated double bond to which the method of this invention can be applied includes, for example, vinyl halides such as vinyl chloride;
vinyl esters such as vinyl acetate and vinyl propionate;
acrylic acid, methacrylic acid, and esters and salts ;~7~9~

thereof; maleic acid, fumaric acid, and esters and anhydrides thereof; and diene monomers such as butadiene, chloroprene and isoprene; aromatic vinyl compounds such as styrene; as well as acrylonitrile, halogenated vinylidenes, and vinyl ethers.
There are no particular limitations on the type of polymerization to which the method of this invention can be applied. The presen~ invention is effective in any types of polymerization such as suspension polymerization, emulsion polymerization, solution polymerization, bulk polymerization, and gas phase polymerization. Particularly, the present method is suitable to polymerizations in an aqueous medium such as suspension or emulsion polymerization.
Specifically, in the case of suspension polymerization and emulsion polymerization, polymerization is generally performed as follows, for instance.
First, water and a dispersing agent are charged into a polymerization vessel, and thereafter a polymerization initiator is charged. Subsequently, the inside of the polymerization vessel is evacuated to a pressure of from about 0.1 to about 760 mm~g, and a monomer is then charged (whereupon the pressure inside the polymerization vessel usually becomes from 0.5 to 30 kgf/cm2.G). Then, the polymerization is normally carried out at a temperature of from 30 to 15QC. During the polymerization, one or more of water, a dispersing agent and a polymerization initiator may be optionally added, if necessary. Reaction temperature during the polymerization is different depending on the kind of monomer to be polymerized. For example, in the case of polymerizing vinyl chloride, polymerization may be carried out at 30 to 80C; in the case of polymerizing styrene, polymerization may be carried out at 50 to 150C. The polymerization may be judged to be completed when the pressure inside the polymerization vessel falls ~o from about 0 to 7 kgf/cm2.G or when cooling water which passes ~?~3 through a jacket provided around the polymerization vessel indicates almos~ the same temperature a~ the inlet where it is charged and at the outlet where it i~ discharged (i.e., when liberation of heat due to polymerization reac~ion has been completed). The water, dispersing agent and polymerization initiator charged for the polymerization are used in amounts of about 20 to 500 parts by weight, about 0.01 to 30 parts by weigh~, and about 0.01 ~o 5 parts by weight, respectively, per 100 parts by weight of the monomer.
In the case of solution polymerization, an organic solution such as toluene, xylene, pyridine and the like is used as a polymerization medium in place of water. A
dispersing agent is optionally used. The other conditions are generally the same as those described for suspension and emulsion polymerizations.
In the case of bulk polymerization, after the inside of a polymerization vessel is evacuated to a pressure of from about 0.01 mmHg to about 760 mmHg, a monomer and a polymerization initiator are charged, and then polymerization is carried out at a temperature of from -10C
to 250C. For example, in the case of polymerizing vinyl chloride, polymerization is carried out at a temperature of from 30C to 80C; and in the case of polymerizing styrene, polymerization may be carried out at 50C to 150C.
The present invention is effective in preventing polymer scale from depositing, independent of materials constituting the inner wall, etc. of a pol~merization vessel. For example, this invention is effective in preventing polymer~ scale from depositing in polymerization vessels made of a stainless steel or other steels or vessels lined with glass.
Any additive materials that have been added in a polymerization system can be used without any limitation.
More specifically, the method of this invention can effectively prevent polymer scale from depositing, even in polymerization systems containing the ~ollowing addi~ives:
or example, polymerization initiat~rs such as t-butyl peroxyneodecanoate, bis(2-ethylhexyl) peroxydicarbonate, 3,5,5-trimethylhexanoyl peroxide, a-cumyl peroxyneodecanoate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl peroxypivalate, bis(2-ethylhexyl) peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate, a,a'-azobisisobutyronitrile, a,a'-azobis-2,4-dimethylvaleronitrile, potassium peroxodisulfate, ammoniumperoxodisulfate, p-methane hydroperoxide; suspension agents comprised of natural or synthetic polymeric compounds such as partially saponified polyvinyl alcohols~ polyacrylic acids, vinyl aceta~e/maleic anhydride copolymer, cellulose derivatives such as hydroxypropylmethyl cellulose, and gelatin; solid dispersing agents such as calcium phosphate and hydroxyapatite; nonionic emulsifying agents such as sorbitan monolaurate, sorbitan trioleate and polyoxyethylene alkyl ether; anionic emulsifying agents such as sodium lauryl sulfate, sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dioctylsulfosuccinate;
fillers such as calcium carbonate and titanium oxide;
stabiliæers such as tribasic lead sulfatel calcium stearate, dibutyltin dilaurate and dioctyltin mercaptide; lubricants such as rice wax, stearic acid and cetyl alcohol;
plasticizers such as DOP and DBP; chain transfer agents such as trichloroethylene and mercaptans as exemplified by t-dodecyl mercaptans; and pH adjusters.
Addition to Polvmerization mass The polymer scale preventive agen~ of the present invention may be added into a polymerization medium preferably in the form of a solution like the coating liguid mentioned above in addition to the formation of the coating, so that the scale preventing effect is further improved.
The amount of the polymer scale preventive agent to be added into the polymerization medium, preferably ranges from about `

, . , 5 ppm to 1,000 ppm based on the whole weight of the monomer charged. The addition should be conducted so that it may not affect the quality of polymeric product to be obtained with respect to fish eyes, bulk density, particle size distribution, etc.

EXAMPLES
The present invention is now described in detail by way of working examples and comparative examples. In each of the tables below, Experiments of Nos. marked with * are comparative examples, and the other Experiments working examples of the present invention.
Chitosans used as the component (A) in Examples 1 and 2 below are those described in Table 1.

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Table 1 -Deacetylization Chitosan (3~ Viscosity(1) deqree (2) _ Manufacturer Chitosan (CLH) 100 cP or 80.0% or more Yaizu more Suisankagaku Koqyo K.K.
Chitosan (PSH) 100 cP or 80% or more Yaizu less Suisankagaku Ko~yo KoK~
Chitosan (PSL) 100 cP or 80% or more Yaizu less Suisankagaku ~ogyo R.K.
15Chitosan t90M) 100 to 85.0% to WakoJunyaku 300 cP 94.9% Kogyo K.X.
Chitosan (lOOL) 30 to 99.0% or more WakoJunyaku 100 cP Kogyo R.X.
Chitosan (70H) 300 to 65.0% to WakoJunyaku 500 cP 79.4% Kogyo K~R.
Chitosan (80H) 300 to 75.0% to WakoJunyaku 500 cP 84.9% Kogyo K.K.
.
Remarks:
(1) Viscosity : Measured at 20C with a B-t~pe viscometer ~o.r a 0.5 wt.~ chitosan solution whîch was prepared by--dissolving a chi~osan in an aqueous 0.5 wt.% acetic acid solution.
(2) Deacetyli~ation degree : Measured by the PVSK colloid solution titration method.
~3) Tradenames are indicated in parentheses.
Example l Polymerization was carried out in the following manner using a polymerization vessel with an inner capacity of 1,OQ0 liters and having a stirrer.
In each experiment, firs~, a component (A? and a component (B) were dissolved in a solvent so that the total concentration thereof might become the value gi~en in Table 2, to prepare a coating liquid. The coating liquid was applied to the inner wall and other parts with which a monomer comes into contact including the stirring shaft, stirring blades and baffles, followed by drying under heating at 60C for 15 min. to form a coating, which was then washed with water.
Experiment of No. 101 to 103 are comparative examples in which no coating liquid was applied or a coating liquid containing either a component (A) or a component ~B) was applied.
In preparation of coating liquids containing a water-soluble basic polysaccharide, the wa~er-soluble polysaccharide was completely dissolved in an aqueous glycollic acid solution with a pH of 4 to form a polysaccharide solution, which was then used for preparation of the coating liquids.
The water-soluble basic polysaccharide (A), the kind of the phenazine (B), the total concentration of khe components (A) and (B), the weight ratio of (A)/(B), and the solvent used in each experiment are given in Table 2.
Subsequently, in the polymerization vessel in which a coating had been formed by the coating operation as above, were charged 400 kg of water, 200 kg of vinyl chloride, 250 g o a partially saponified polyvinyl alcohol, 25 g of hydroxypropylmethyl cellulose and 75 g of bis(2-ethylhexyl) peroxydicarbonate. Then, polymerizatioll was carried out at 57C with stirring for 6 hours. After the completion of the polymerization, the amount of polymer scale depositing on the inner wall of the polymerization vessel and the whiteness or initial coloration of the polymer obtained were measured according to the following methods.
- Measurement of the amount of polymer scale deposition ~ he scale depositing on the inner wall surface in an area of 10 cm square was scraped off with a stainless steel spatula as completely as possible to be confirmed with naked eyes, and then the scraped scale was weighted Oll a balance.
Thereafter, the amount of the~deposited scale per area of l m2 was obtained by multiplying the measured value by 100.

- Measuremen~ of initial coloration of polymer A hundred par~s by weight of a polymer, one part by weight of a tin laurate stabilizing agen~ (trade name: TS-101, product of Akishima Chemical Co.) and 0.5 part by weight of a cadmium stabilizing agent (trade name: C-lOOJ, product of Katsuta Kako Co.), and 50 parts by weight of a plasticizer DOP were kneaded at 160C for 5 min. with a twin roll mill, and then formed into a sheet 1 mm thick.
Sùbsequently, this sheet was placed in a mold measuring 4 cm x 4 cm x 1.5 cm (thickness), and molded under heating at 160C and under a pressure of 65 to 70 kgf/cm2to prepare a test specimen. This test specimen was measured for luminosity index L in the Hunter's color difference equation described in JIS Z 8730 (1980). Initial coloration is evaluated to be lower with increase in L value.
The L value was determined as follows. The stimulus value Y of xYæ color system was determined according to the photoelectric tristimulus colorimetry using the s~andard light C, a photoelectric colorimeter (Color measuring color difference meter Model Z-lOOlDP, prodllct of Nippon Denshoku Kogyo K.K.) in accordance with JIS Z 8722. As the geometric condition for illumination and being illuminated, the condition d defined in section 4.3.1 of JIS Z 8722 was adopted. Next, L was calculated based on the equation:
L=lOYl/2 described in JIS Z 8730(1980).
The results are givèn in Table 2.

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In each experiment, the coating procedure of Example 1 was repeated for a stainless steel polymerization vessel having an inner capacity of 20 liters and equipped with a stirrer, except that a coating liquid in which the water-soluble basic polysaccharide (A), the phenazine (B), the total concentration of the components (A)+(B), the weight ratio of (A~/(B), and the solvent were as given in Table 3, was used. Experiment of No. 201 to 203 are comparative experiments in which no coating liquid was applied or a coating liquid containing either a component (A) or a component (B) was applied.
In preparation of coating liquids containing a water-soluble basic polysaccharide, the water-soluble polysaccharide was dissolved in an aqueous ascorbic acid solution with a pH of 4 to form a polysaccharide solution, which was then used for preparation of the coating liquids.
In the polymerization vessel in which the coating was thus formed, were charged 9 kg of water, 225 g of sodium dodecylbenzenesulfonate, 12 g of t-dodecyl mercaptan, and 13 g of potassium peroxodisulfate. ~fter the inner atmosphere was replaced with a nitrogen gas, 1.3 kg of styrene and 3.8 kg of butadiene were char~ed, followed by polymerization at 50C for 20 hours.
After completion of the polymerization, the amount of polymer scale depositing on the inner wall surface was measured.
The results are given in Table 3.

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Claims

1. A polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising:
(A) a water-soluble basic polysaccharide, and (B) a phenothiazine.

2. The agent according to Claim 1, wherein said water-soluble basic plysaccharide (A) is selected from the group consisting of chitosans;
organic acid salts of chitosans;
inorganic acid salts of chitosans;
glucosamine oligomers having about 5 to 20 mers of glucosamine;
polyoxyethylene chitosans;
polyoxypropylene chitosans;
phosphated chitosans;
N-glycidyltrimethylammonium chitosans;
dihydropropylchitosans;
polygalactosamines;
organic acid salts of polygalactosamines;
inorganic acid salts of polygalactosamines;
galactosamine oligomers having about 5 to 20-mers of galactosamine;
N-acetylglucosamine oligomers having about 5 to 20-mers;
polyoxyethylene chitins;
polyoxypropylene chitins;
phosphated chitins; and dihydropropylchitins.

3. The polymer scale preventive agent according to Claim 1, wherein the polysaccharaide (A) is selected from the group consisting of the inorganic acid salts and organic acid salts of chitosans.

4. The polymer scale preventive agent according to Claim 1, wherein the phenothiazine (B) is represented by the general formula:

wherein R may be the same or different where there exist two or more R's and each represent a hydrogen atom, -OH, -Cl, -CH3, -C2H5, -COCH3, -COC2H5, -SO2CH3, -SO2C2H5, or NO2, and n is an integer of 1 to 4.

5. The polymer scale preventive agent according to Claim 1, wherein said component (B) comprises at least one member selected from the group consisting of phenothiazine, 2-acetylphenothiazine, 2-propylphenothiazine, 2-nitrophenothiazine, 2-methylsulfonylphenothiazine, 3,7-dihydroxyphenothiazine, 3,7-diaminophenothiazine, and 3-chlorophenothiazine.

6. The polymer scale preventive agent according to Claim 1, which further comprises a solvent in which the components (A) and (B) have been dissolved or dispersed to form a liquid state.

7. The polymer scale preventive agent according to Claim 6, wherein the total concentration of the components (A) and (B) is in the range of from 0.005 to 10 % by weight.

8. A polymerization vessel for use in polymerization of a monomer having an ethylenically unsaturated double bond, having on its inner wall surfaces a coating for preventing polymer scale deposition, said coating comprising:
(A) a water-soluble basic polysaccharide, and (B) phenothiazine.

9. The polymerization vessel according to Claim 8, wherein said coating has been formed further on the parts with which the monomer comes into contact during polymerization other than the inner wall surface of the polymerization vessel.

10. The polymerization vessel according to Claim 8, wherein said coating has been formed further on parts of the recovery system for unreacted monomer with which unreacted monomer comes into contact.

11. The polymerization vessel according to Claim 8, wherein, after dried, said coating has a coating weight of 0.001 g/m2 or more.

12. A process of producing a polymer by polymerization of a monomer having an ethylenically unsaturated double bond in a polymerization vessel, comprising the step of carrying out said polymerization in a polymerization vessel having on its inner wall surfaces a coating for preventing polymer scale deposition, wherein the coating comprises:
(A) a water-soluble basic polysaccharide, and (B) a phenothiazine.

13. The process according to Claim 12, wherein said polymerization is carried out as suspension polymerization, emulsion polymerization, solution polymerization, bulk polymerization, or gas phase polymerization.

14. The process according to Claim 12, wherein said monomer is selected from the group consisting of vinyl halides;
vinyl esters; acrylic acid, methacrylic acid, and esters and salts thereof; maleic acid and fumaric acid, and esters and anhydrides thereof; diene monomers; aromatic vinyl compounds; acrylonitrile; halogenated vinylidenes; and vinyl ethers.