JP3880558B2 - Dispersant for suspension polymerization of vinyl compound and suspension polymerization method - Google Patents

Description

  The present invention relates to a dispersant for suspension polymerization of a vinyl compound. More specifically, the bulk density is high and porous, the plasticizer has high absorption performance, the particle size distribution is sharp, and the undissolved content derived from the dispersant is included when the suspension polymer is dissolved in a solvent. The present invention relates to a dispersant for suspension polymerization of a vinyl compound and a suspension polymerization method, which can produce vinyl polymer particles having no polymer.

  In the industrial production of vinyl polymers such as vinyl chloride resins, there is a suspension polymerization method in which a vinyl compound is dispersed in an aqueous medium in the presence of a dispersant and polymerization is carried out using an oil-soluble catalyst. Widely implemented. In general, factors governing the quality of the resin include polymerization rate, water-monomer ratio, polymerization temperature, amount and timing of polymerization initiator, type of polymerization tank, stirring speed or type and amount of dispersant. However, among these, it is said that the influence of the dispersant is great.

  The performance required for a suspension for suspension polymerization of vinyl compounds is as follows: (1) The suspension polymerization stability is remarkably excellent with a small amount of use, and the particle size distribution of the resulting vinyl polymer particles is as sharp as possible. (2) Increase the plasticizer absorption rate to facilitate processability, facilitate removal of monomers such as vinyl chloride remaining in polymer particles, and fish eyes in molded articles, etc. In order to prevent the formation of polymer particles, making the polymer particles as uniform and porous as possible, (3) having the function of forming polymer particles having a large bulk density, and (4) a polymerization tank, etc. In particular, in the case of vinyl chloride resin, the dispersant is an important factor.

  As such a dispersant, main dispersants such as polyvinyl alcohol resins (hereinafter sometimes abbreviated as PVA), cellulose derivatives, and gelatin are used. Among them, PVA having a saponification degree of 65 to 99 mol% is used as a main dispersant, and PVA having a saponification degree of less than 65 mol% is frequently used as a dispersion aid, but the above (1) to (4 ) Is still not sufficient, and various attempts have been made for the main dispersant and the dispersion aid to enhance the performance of the vinyl chloride resin.

For example, a dispersion aid for suspension polymerization of a vinyl compound having a vinyl ester polymer having an amino group, an ammonium group, a carboxyl group, or a sulfonic acid group in the side chain as a dispersoid may be used in combination with the main dispersant. Specifically, (I) a carboxyl group or a sulfonic acid group is substituted with 0. A method in which a vinyl ester polymer having a saponification degree of 01 to 10 mol% and a saponification degree of 70 mol% or less is used in combination with a conventionally known main dispersant as a dispersion aid for suspension polymerization (see, for example, Patent Document 1) or (II) It consists of PVA having an ionic group at the side chain and / or terminal, a saponification degree of 70 mol% or less, and a saponification degree (Y mol%) and a block character (η) satisfying specific conditions. A method of simultaneously improving productivity and quality of a vinyl chloride resin by using a dispersion aid for suspension polymerization of vinyl chloride together with a conventionally known main dispersant (see, for example, Patent Document 2) As another method, (III) the ethylene unit content is 0. 5 to 20 mol%, a saponification degree of 60 mol% or more, a vinyl alcohol polymer (A) having a polymerization degree of 600 or more, and a content of ethylene units of 0. A method using a dispersant for suspension polymerization of a vinyl compound comprising a vinyl alcohol polymer (B) having 5 to 20 mol%, a saponification degree of 20 to 80 mol%, and a polymerization degree of 100 to 600 (for example, patents) Document 3) has been proposed.
JP-A-4-154810 (Claim 1) JP 2001-233904 A (Claim 1) JP 2002-97208 A (Claim 1)

  However, in the above-mentioned methods (I) to (III), in the suspension polymerization of vinyl monomers, particularly vinyl chloride, the problem of the scale adhering to the polymerization tank and the productivity are slightly improved, but the resulting chloride is obtained. The plasticizer absorptivity of vinyl resins and the sharpness of particle size distribution do not always reach satisfactory levels. In addition, when a vinyl monomer polymer suspension-polymerized using a water-soluble resin such as polyvinyl alcohol or cellulose is used as a thickener or binder for an ink, when dissolved in an organic solvent, the polymer is not dissolved. Things may be generated, causing quality problems.

  As a result of intensive studies, the inventors have found that the viscosity of a 4% by mass aqueous solution at 20 ° C. is 1.5 mPa · s or more, and preferably 0.5 to 50 mol% of oxyalkylene group units in the terminal or molecular chain ( More preferably, a compound comprising a vinyl ester resin containing 1 to 25 mol%) and 5 to 50 mol% of a 2-pyrrolidone group is used as a dispersant for suspension polymerization. The present invention has been found to be effective in achieving the object, and the present invention has been completed. The suspension polymerization dispersant in the present invention may be a so-called dispersion aid, and may be used in combination with other suspension polymerization dispersants.

（式中、Ｒ_１〜Ｒ_６は、同一又は異なって、水素原子又は置換基を示す）
で表される２−ピロリドン基であることを特徴とする上記（１）記載の分散剤、 That is, the present invention
(1) A vinyl compound having a viscosity of 1.5 to 80 mPa · s at 20 ° C. and containing a polyvinyl ester resin containing an oxyalkylene group and a lactam group in the terminal or molecular chain. A dispersant for suspension polymerization of
(2) The lactam group is a formula

(Wherein R _{1 to} R ₆ are the same or different and each represents a hydrogen atom or a substituent)
The dispersant according to (1) above, which is a 2-pyrrolidone group represented by:

[但しｎは１〜５０の整数]
で示されるオキシエチレン基又は一般式

[但しｎは１〜５０の整数]
で示されるオキシプロピレン基であり、かつ、オキシアルキレン基単位を０．５〜５０モル％含有する水溶性ポリビニルエステル系樹脂からなることを特徴とする上記（１）又は（２）記載の分散剤、
（４） ポリビニルエステル系樹脂が、脂肪族ビニルエステルとオキシアルキレン基を有する不飽和単量体とＮ−ビニル−２−ピロリドンとを共重合することにより得られ、ピロリドン基を５〜５０モル％含有することを特徴とする上記（２）又は（３）記載の分散剤、 (3) The oxyalkylene group has the general formula

[N is an integer from 1 to 50]
An oxyethylene group represented by the general formula

[N is an integer from 1 to 50]
The dispersant according to (1) or (2) above, wherein the dispersant is a water-soluble polyvinyl ester resin containing 0.5 to 50 mol% of oxyalkylene group units. ,
(4) A polyvinyl ester-based resin is obtained by copolymerizing an aliphatic vinyl ester, an unsaturated monomer having an oxyalkylene group, and N-vinyl-2-pyrrolidone. A dispersant as described in (2) or (3) above, which contains

(5) A suspension polymerization method of a vinyl compound, characterized by using the dispersant according to any one of (1) to (4) above as a main dispersant or dispersion aid for a vinyl compound,
(6) Vinyl-based resin obtained by the method described in (5) above,
About.

  By using the dispersant for suspension polymerization according to the present invention, the polymerization can be stably performed. As a result, the bulk density is high, the porosity is high, the particle size distribution is sharp, and the processability is high. It is possible to stably produce a vinyl chloride polymer having an average degree of polymerization of 400 to 850 which is excellent in the above. In addition, even when dissolved in an organic solvent, a problem that a portion that does not dissolve in an organic solvent, such as a water-soluble dispersant, does not occur.

  Hereinafter, the present invention will be described in detail. The viscosity of a 4 mass% aqueous solution at 20 ° C. of the polyvinyl ester resin used in the present invention is 1.5 mPa · s or more, preferably 2 mPa · s or more. When the viscosity is 1.5 mPa · s or more, the dispersion stabilizing effect is large, and particularly when used as a dispersion stabilizing aid, the function of sharpening the particle size distribution of the vinyl polymer particles is large. The upper limit of the viscosity cannot be generally specified, but is usually preferably 80 mPa · s or less for handling.

［但しＲ_ａ、Ｒ_ｂは水素またはアルキル基Ｘは水素、アルキル基、アルキルエステル基、アルキルアミド基又はカルボキシル基、カルボキシレート基、スルホ基、スルホン酸塩基等の酸基若しくは中和された酸基、ｎは１〜１００の整数を示す］で表される構造を有するものであり、なかでもｎが１〜５０、好ましくは３〜５０のオキシエチレン基もしくはオキシプロピレン基が好適である。アルキル基、アルキルエステル基、アルキルアミド基におけるアルキル基としては、炭素数１〜２０、好ましくは炭素数１〜８の直鎖状、分岐状又は環状のアルキル基が挙げられる。オキシアルキレン基を有する単位の含有量は０．５〜５０モル％、好ましくは１〜２５モル％である。オキシアルキレン基単位の量が０．５モル％未満の場合にはポリビニルエステル系樹脂の水溶性が低下して分散剤として使用できない。また、オキシアルキレン基単位の量が５０モル％を超える場合にはポリビニルエステル系樹脂の水溶性は向上するが曇点が無くなるため分散剤としての効果が小さくなる場合もある。 The oxyalkylene group referred to in the present invention is a general formula.

[Wherein R _a and R _b are hydrogen or an alkyl group X is hydrogen, an alkyl group, an alkyl ester group, an alkylamide group, an acid group such as a carboxyl group, a carboxylate group, a sulfo group, a sulfonate group, or a neutralized acid Group, n represents an integer of 1 to 100]. Among them, an oxyethylene group or an oxypropylene group in which n is 1 to 50, preferably 3 to 50 is preferable. Examples of the alkyl group in the alkyl group, the alkyl ester group, and the alkylamide group include linear, branched, or cyclic alkyl groups having 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms. Content of the unit which has an oxyalkylene group is 0.5-50 mol%, Preferably it is 1-25 mol%. When the amount of the oxyalkylene group unit is less than 0.5 mol%, the water-solubility of the polyvinyl ester resin is lowered and cannot be used as a dispersant. When the amount of the oxyalkylene group unit exceeds 50 mol%, the water-solubility of the polyvinyl ester resin is improved, but the effect as a dispersant may be reduced because the cloud point disappears.

[式中、Ｒ_１〜Ｒ_６は、同一又は異なって、水素原子又は置換基を示す]で表される。置換基としては、上記した置換基が挙げられる。好ましくはＲ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５およびＲ_６はそれぞれ独立して水素原子またはアルキル基を表す。Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５およびＲ_６がそれぞれ表すことがあるアルキル基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ペンチル基、オクチル基などの炭素数１〜８のアルキル基が好ましいが、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５およびＲ_６はそれぞれ独立して水素原子またはメチル基であることがより好ましく、いずれも水素原子であることが特に好ましい。かかる一般式（１）で示される基としては、２−オキソピロリジン−１−イル基、３−プロピル−２−オキソピロリジン−１−イル基、５−メチル−２−オキソピロリジン−１−イル基、５，５−ジメチル−２−オキソピロリジン−１−イル基などが好ましい。２−ピロリドン基を有する不飽和単量体単位の含有量は５〜５０モル％、好ましくは１〜２５モル％である。２−ピロリドン基を有する不飽和単量体単位の量が５モル％以上の場合にはポリビニルエステル系樹脂の水溶性が低下せず分散剤として好適に使用できる。また、５０モル％以内の場合にはポリビニルエステル系樹脂の水溶性は向上しても曇点が無くなることがないため分散剤としての効果が大きく、好都合である。 The lactam group in the present invention means a group obtained by removing a hydrogen atom from the NH group of a cyclic lactam compound, and the lactam group includes, for example, a halogen atom, a hydroxyl group, a carboxyl group, an amide group, the above-described alkyl group, alkyl It may be substituted with an appropriate substituent such as an ester group, an alkylamide group, or a nitro group. Examples of such cyclic lactam compounds include N-vinyl-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-methyl-2-pyrrolidone, N-vinyl-3- Methyl-2-piperidone, N-vinyl-3-methyl-2-caprolactam, N-vinyl-4-methyl-2-pyrrolidone, N-vinyl-4-methyl-2-piperidone, N-vinyl-4-methyl- 2-caprolactam, N-vinyl-5-methyl-2-pyrrolidone, N-vinyl-5-methyl-2-piperidone, N-vinyl-5-methyl-2-caprolactam, N-vinyl-3-ethyl-2- Examples include pyrrolidone, N-vinyl-4,5-dimethyl-2-pyrrolidone, N-vinyl-3,3,5-trimethyl-2-pyrrolidone and the like. The 2-pyrrolidone group referred to in the present invention is the general formula (1).

[Wherein, R _{1 to} R ₆ are the same or different and each represents a hydrogen atom or a substituent]. Examples of the substituent include the above-described substituents. Preferably, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ each independently represent a hydrogen atom or an alkyl group. Examples of the alkyl group that each of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ may represent include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, octyl group R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently more preferably a hydrogen atom or a methyl group. Is particularly preferably a hydrogen atom. Examples of the group represented by the general formula (1) include 2-oxopyrrolidin-1-yl group, 3-propyl-2-oxopyrrolidin-1-yl group, and 5-methyl-2-oxopyrrolidin-1-yl group. 5,5-dimethyl-2-oxopyrrolidin-1-yl group and the like are preferable. Content of the unsaturated monomer unit which has 2-pyrrolidone group is 5-50 mol%, Preferably it is 1-25 mol%. When the amount of the unsaturated monomer unit having a 2-pyrrolidone group is 5 mol% or more, the water-solubility of the polyvinyl ester resin does not decrease and can be suitably used as a dispersant. Moreover, in the case of 50 mol% or less, since the cloud point does not disappear even if the water-solubility of the polyvinyl ester resin is improved, the effect as a dispersant is great and convenient.

  The polyvinyl ester resin containing an oxyalkylene group and a lactam group of the present invention, preferably a 2-pyrrolidone group, is an unsaturated monomer having an aliphatic vinyl ester and an oxyalkylene group and an unsaturated monomer having a 2-pyrrolidone group. It is obtained by copolymerizing with a monomer. Examples of the aliphatic vinyl ester used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl stearate. Vinyl acetate is particularly preferable from the viewpoint of cost.

  Examples of unsaturated monomers having an oxyalkylene group include polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylic amide, polyoxypropylene (meth) acrylic amide, poly Examples thereof include oxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, and the like, but are not particularly limited as long as they are unsaturated monomers having oxyalkylene. Examples of unsaturated monomers having a 2-pyrrolidone group include N-vinyl-2-pyrrolidone, N-vinyl-3-propyl-2-pyrrolidone, N-vinyl-5-methyl-2-pyrrolidone, and N-vinyl-5. , 5-dimethyl-2-pyrrolidone, N-vinyl-3,5-dimethyl-2-pyrrolidone, N-allyl-2-pyrrolidone, etc., among which N-vinyl-2-pyrrolidone is particularly preferred. Not limited to.

  In addition, when copolymerizing an aliphatic vinyl ester with an unsaturated monomer having an oxyalkylene group and an unsaturated monomer having a 2-pyrrolidone group, the aliphatic vinyl ester Copolymerizable unsaturated monomers, for example, unsaturated dibasic acid monoalkyl esters such as monomethyl maleate and monomethyl itaconate, amide group-containing monomers such as acrylamide, dimethylacrylamide and N-methylolacrylamide, lauryl Alkyl vinyl ethers such as vinyl ether and stearyl vinyl ether, hydroxyl-containing monomers such as allyl alcohol, dimethylallyl alcohol, and isopropenyl allyl alcohol, acetyl group-containing monomers such as allyl acetate, dimethylallyl acetate, and isopropenyl allyl acetate, methacryl Acrylic esters such as methyl, ethyl methacrylate, acrylic acid-2-ethylhexyl, acrylic acid-n-butyl, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, trimethoxyvinylsilane, tributylvinylsilane, It may be further copolymerized with vinylsilanes such as diphenylmethylvinylsilane, α-olefins such as ethylene and propylene, diacetone acrylamide and the like.

The copolymerization method may be a known method, and it is polymerized by addition polymerization or radical polymerization method such as bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc., among others, in a solvent such as methyl alcohol, Polymerization initiators used for the following vinyl chloride polymerizations, preferably azo series such as α, α′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile) or the like In general, polymerization is performed using a peroxide-based initiator such as benzoyl peroxide, peracetic acid, or di-n-propyl peroxydicarbonate. Of course, instead of using an initiator, the copolymerization reaction may be carried out using heating, visible light or ultraviolet irradiation. In the copolymerization, mercaptans, aldehydes, halogen-containing compounds and the like can be added to adjust the degree of polymerization, and the molecular chain terminals can be modified. In addition, a method for removing unreacted monomers and a method for drying and pulverizing may be known methods, and there is no particular limitation.
The thus produced polyvinyl ester resin is excellent in water solubility or water dispersibility. The viscosity of the polyvinyl ester resin of the present invention is such that the polyvinyl ester resin is dissolved or dispersed in water so that the concentration is 4% by mass, and then left in a constant temperature water bath at 20 ° C. to adjust the liquid temperature to 20 ° C. Thereafter, the viscosity is measured with a B-type rotational viscometer.

  The polyvinyl ester resin of the present invention is used as a main dispersant or dispersion aid for suspension polymerization. It is used by dissolving or dispersing in a solvent in the same manner as ordinary dispersing agents. Examples of the solvent include water or a water-organic solvent mixture. Examples of the organic solvent include methanol, ethanol, benzene, toluene, xylene and the like. When used as a main dispersant, those having a viscosity of 4 mass% aqueous solution at 20 ° C. of about 25-60 mPa · s are often used, and when used as a dispersion aid, the viscosity of 4 mass% aqueous solution at 20 ° C. is 2-10 mPa. -Although the thing of about s is generally used well, it is not restricted to this. The polyvinyl ester resin of the present invention may be used alone, or other commonly used dispersants such as partially or fully saponified polyvinyl alcohol having a polymerization degree of 200 to 3500 and a saponification degree of 60 to 95 mol%, In addition, cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide propylene oxide block copolymer, poly You may use together with water-soluble emulsifiers, such as oxyethylene sorbitan monolaurate, polyoxyethylene glycerol oleate, and sodium laurate. Moreover, there is no restriction | limiting in particular about the addition amount of these other dispersing agents, However 0.01-1.0 mass part is preferable per 100 mass parts of vinyl type compounds.

The suspension polymerization of the vinyl compound is performed in the presence of the polyvinyl ester resin of the present invention.
As a vinyl compound monomer that can be subjected to suspension polymerization using the dispersant of the present invention, a monomer mixture containing vinyl chloride alone and a comonomer mainly composed of vinyl chloride and copolymerizable with vinyl chloride (usually , Containing 50% by mass or more of vinyl chloride) can also be used. Such comonomers include vinyl esters such as vinyl acetate and vinyl propionate, (meth) acrylic acid esters such as methyl acrylate and ethyl acrylate, olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, styrene, vinylidene chloride, and the like. Can be illustrated.

  In addition, when performing suspension polymerization, a polymerization initiator conventionally used for vinyl chloride polymerization can be used. Specifically, t-butyl peroxyneodecanate, t-butyl peroxypivalate. , T-hexyl peroxyneodecanoate, t-hexyl neohexanoate, t-hexyl peroxypivalate, α-cumyl peroxyneodecanate, 2,4,4-trimethylpentyl-2-peroxy-2 -Perester compounds such as neodecanate; diisopropyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, dimethoxyisopropyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, etc. Percarbonate compounds; deca Ile peroxide, benzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, 2,4-dichlorobenzoyl peroxide, p-methane hydroperoxide, isobutyryl peroxide, acetylcyclohexylsulfonyl peroxide, 2, 4, 4- Peroxides such as trimethylpentyl-2-peroxyphenoxyacetate, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate; α, α ′ Oils such as azo compounds such as azobisisobutyronitrile, α, α′-azobis (2,4-dimethylvaleronitrile), α, α′-azobis (4-methoxy-2,4-dimethylvaleronitrile) 1 of soluble polymerization initiator Alone or in combination of two or more can be used, further can be used in combination of potassium persulfate, and ammonium persulfate, water-soluble polymerization initiators such as hydrogen peroxide.

  The polymerization initiator may be added during or after the preparation of water or monomer, or it may be mixed with the monomer in advance and charged together with the monomer, and further an aqueous medium as an aqueous emulsion or aqueous solution. You may charge together.

  In the present invention, there is no particular limitation on suspension polymerization, but the polymerization temperature is usually in the range of 50 to 80 ° C. In the polymerization, a chain transfer agent may be used. Specifically, mercaptans such as 2-mercapto-2-thiazoline and 2-mercaptoethanol, 9,10-dihydro-9-oxa-10-phosphafe An organophosphorus compound such as nanthrene-10-oxide is used. The other polymerization conditions can be normal conditions. For example, the amount of aqueous medium used for suspending and dispersing the monomer polymer component is determined by the ratio of monomer to water (water / unit 1). 0 to 1. 5 may be added, and water can be added during the polymerization as needed. Polymerization regulator, pH regulator, gelation improver, antistatic agent, crosslinking agent, stabilizer, filler, antioxidant It is also optional to add agents, buffers, scale inhibitors, and the like.

  Hereinafter, the present invention will be described in more detail with specific examples, but the present invention is not limited to these examples. In the following examples, “%” and “part” mean “% by mass” and “part by mass” unless otherwise specified.

"Analysis of polyvinyl ester resin"
<Viscosity of 4% aqueous solution at 20 ° C>
The polyvinyl ester resin was dissolved in water so as to have a concentration of 4%, and then allowed to stand in a constant temperature water bath at 20 ° C. to bring the liquid temperature to 20 ° C. Then, the viscosity was measured with a B-type rotational viscometer.

"Polymerization of vinyl monomers and characterization of the resulting vinyl polymers"
(1) Particle size distribution The particle size distribution was measured by dry sieve analysis using a Tyler mesh standard wire mesh.
(2) Bulk density The bulk density of the vinyl chloride polymer was measured according to JIS K6721.
(3) CPA (Cold Plasticizer Absorption: Cold Plasticizer Absorption) The amount of dioctyl phthalate absorbed at 23 ° C. was measured by the method described in ASTM-D3367-75.

Example 1
<Manufacture of polyvinyl ester resin>
A reactor equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and pressure gauge was purged with nitrogen, and then deoxygenated 2000 parts by weight of vinyl acetate monomer, 1700 parts of N-vinyl-2-pyrrolidone, and 800 parts by weight of methanol. , 450 parts by mass of polyethylene glycol butyl vinyl ether (addition number of EO: 8 units) was charged, and the temperature was raised under stirring. When the internal temperature reached 60 ° C., 250 parts by mass of methanol was separately added with an initiator (azobisiso). A solution in which 3.5 parts by mass of butyronitrile) was dissolved was added to initiate polymerization. After polymerization at 60 ° C. for 6 hours, the polymerization was stopped by cooling. The solid content concentration in the polymerization solution at this time was 63%. The obtained polymerization solution was supplied to a demonomer tower having a multi-stage perforated plate in the tower, and methanol vapor was blown from the bottom of the tower to come into contact with the polymerization solution to remove unreacted vinyl acetate monomer. The solid content concentration of the polyvinyl ester resin-methanol solution at this time was 65%. The polyvinyl ester resin-methanol solution was dried with an extrusion dryer and then pulverized to obtain the polyvinyl ester resin of the present invention. The resin of the present invention was dissolved in water so as to have a concentration of 4%, then left in a constant temperature water bath at 20 ° C. to adjust the liquid temperature to 20 ° C., and then the viscosity was measured with a B-type rotational viscometer. It was 6.2 mPa · s.

<Suspension polymerization of vinyl chloride>
In a glass-lined autoclave, 50 parts of deionized water and 70% toluene solution of diisopropyl peroxydicarbonate in which the obtained dispersant of the present invention and the dispersant shown in Table 1 were dissolved were dissolved. 05 parts are charged, and the inside of the autoclave is 0. After deaeration to remove oxygen until reaching 0065 MPa, 38 parts of vinyl chloride monomer was added, and the temperature was raised to 57 ° C. with stirring to carry out polymerization. At the start of polymerization, the pressure in the autoclave was 0. 86 MPa, but 0. At 48 MPa, the polymerization was stopped, the unreacted vinyl chloride monomer was purged, the contents were taken out and dehydrated and dried. The polymerization yield of the vinyl chloride polymer was 87%, and the average degree of polymerization was 1030. Polymerizability and characteristics of the vinyl chloride polymer were evaluated by the above methods. The evaluation results are shown in Table 2.

(Example 2)
<Manufacture of polyvinyl ester resin>
The amounts of vinyl acetate, N-vinyl-2-pyrrolidone, polyethylene glycol butyl vinyl ether, and methanol in Example 1 were changed to prepare polyvinyl ester resins having the modified amounts shown in Table 1. This resin was dissolved in water to a concentration of 4%, left in a constant temperature water bath at 20 ° C. to bring the liquid temperature to 20 ° C., and the viscosity was measured with a B-type rotational viscometer to find 5.1 mPa.・ It was s.

<Suspension polymerization of vinyl chloride-vinyl acetate copolymer>
In a glass-lined autoclave, 30 parts of deionized water and 20 parts of methanol in which the obtained dispersant of the present invention and the dispersant shown in Table 1 were dissolved, 70% toluene solution of diisopropyl peroxydicarbonate, 0. 05 parts are charged, and the inside of the autoclave is 0. After deaeration until the pressure became 0065 MPa to remove oxygen, 20 parts of vinyl chloride monomer and 18 parts of vinyl acetate were charged, and the temperature was raised to 57 ° C. with stirring to perform polymerization. At the start of polymerization, the pressure in the autoclave was 0. 66 MPa, but 0. When the pressure reached 38 MPa, the polymerization was stopped, the unreacted vinyl chloride monomer was purged, the contents were taken out and dehydrated and dried. The polymerization yield of the vinyl chloride-vinyl acetate copolymer was 87%, and the average degree of polymerization was 910. Polymerizability and properties of vinyl chloride-vinyl acetate copolymer were evaluated by the above methods. The evaluation results are shown in Table 2.
Further, this vinyl chloride-vinyl acetate copolymer was dissolved in methyl ethyl ketone to prepare a 10% solution, and after standing at 20 ° C. for 24 hours, it was visually confirmed whether or not there was an undissolved precipitate. Undissolved sediment was not generated.

(Examples 3 to 5)
Several kinds of dispersants were prepared by changing the charging composition of vinyl acetate monomer and methanol into the reactor and the modified monomer species. Table 1 shows the physical properties of the modified monomer species and the dispersant. Table 2 shows the evaluation results when vinyl chloride was subjected to turbid polymerization in the same manner as in Example 1 using the dispersion stabilizer shown in Table 1.

(Comparative Example 1)
Example 1 was prepared by blending unmodified (not copolymerized with a modified monomer) polyvinyl alcohol having a 4% aqueous solution viscosity at 20 ° C. of 46 mPa · s and a saponification degree of 80 mol% as shown in Table 1. Similarly, the properties of the vinyl chloride polymer obtained by polymerization of vinyl chloride were evaluated. The evaluation was stopped because a considerable mass was generated in the polymerization machine.

(Comparative Example 2)
4% aqueous solution viscosity at 20 ° C. is 14.3 mPa · s, saponification degree is 80 mol% unmodified (not copolymerized with modified monomer) polyvinyl alcohol, and 4% aqueous solution viscosity at 20 ° C. is 5 mPa · s. Polyvinyl alcohol having a saponification degree of 70 mol% was blended as shown in Table 1, and the properties of the vinyl chloride polymer obtained by polymerization of vinyl chloride were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

(Comparative Example 3)
Vinyl chloride was obtained in the same manner as in Example 2 except that hydroxypropylmethylcellulose having a viscosity of 4% aqueous solution at 20 ° C. of 180 mPa · s and a gel point of 4% aqueous solution of 60 ° C. was used instead of the dispersant of Example 2. A vinyl acetate copolymer was polymerized. The evaluation results of the vinyl chloride vinyl acetate resin are shown in Table 2. In the same manner as in Example 2, the copolymer was dissolved in methyl ethyl ketone to prepare a 10% solution, and after standing at 20 ° C. for 24 hours, it was visually confirmed whether or not there was an undissolved precipitate. Undissolved sediment was settled at the bottom of the solution.

［評価基準］
粒度分布 ；６０メッシュパス〜１５０メッシュオンが９０％以上
かさ密度 ；０．５ｇ／ｃｃ以上
可塑剤吸収性；２５質量％以上
総合評価 ○；粒度分布、かさ密度、可塑剤吸収性ともに優れている。
△；粒度分布、かさ密度、可塑剤吸収性のうちどれかが悪い。
×；粒度分布、かさ密度、可塑剤吸収性のうち２つ以上悪い。

[Evaluation criteria]
Particle size distribution: 60 mesh pass to 150 mesh on 90% or more Bulk density: 0.5 g / cc or more Plasticizer absorbency: 25% by weight or more Overall evaluation: Excellent particle size distribution, bulk density, and plasticizer absorbability .
Δ: Any of particle size distribution, bulk density, and plasticizer absorbability is bad.
X: Two or more of particle size distribution, bulk density, and plasticizer absorbability are bad.

The polyvinyl ester resin of the present invention is useful as a dispersant for suspension polymerization in suspension polymerization of vinyl compounds.

Claims (5)

  Suspension of a vinyl compound characterized in that the viscosity of a 4% by mass aqueous solution at 20 ° C. is 1.5 to 80 mPa · s and contains a polyvinyl ester resin containing an oxyalkylene group and a lactam group in the terminal or molecular chain. Polymerizing dispersant. Lactam group is formula

(Wherein R _{1 to} R ₆ are the same or different and each represents a hydrogen atom or a substituent)
2. The dispersant according to claim 1, which is a 2-pyrrolidone group represented by the formula: Oxyalkylene group is general formula

[N is an integer from 1 to 50]
An oxyethylene group represented by the general formula

[N is an integer from 1 to 50]
The dispersant according to claim 1 or 2, comprising a water-soluble polyvinyl ester resin having an oxypropylene group represented by formula (II) and containing 0.5 to 50 mol% of oxyalkylene group units.   The polyvinyl ester resin is obtained by copolymerizing an aliphatic vinyl ester, an unsaturated monomer having an oxyalkylene group, and N-vinyl-2-pyrrolidone, and contains 5 to 50 mol% of a pyrrolidone group. The dispersant according to claim 2 or 3, wherein: A suspension polymerization method for a vinyl compound, wherein the dispersant according to any one of claims 1 to 4 is used as a main dispersant or a dispersion aid for the vinyl compound.