KR100251022B1 - A method for the suspension polymerization of a vinyl compound - Google Patents

Abstract

PURPOSE: To obtain a dispersion stabilizer which, when used in the suspension polymerization of a vinyl compound, shows low foaming properties and is excellent in the capability of making the obtained polymer particles uniform and porous. CONSTITUTION: This stabilizer comprises a mercapto-terminated polyvinyl alcohol polymer (A) having a degree of saponification of 60mol% or above or comprises a mixture of component A with a polyvinyl ester polymer (B) having a degree of saponification of below 60mol% in an (A)/(B) weight ratio of 40/60 to 95/5.

Description

A method for the suspension polymerization of a vinyl compound

The present invention relates to a suspending agent for suspension polymerization of a vinyl compound. More specifically, the present invention relates to a suspending agent that is very excellent in the effect of lowering foaming for suspension polymerization of vinyl compounds such as vinyl chloride.

In the industrial production of vinyl compounds such as vinyl chloride, suspension polymerization methods have been widely practiced in which vinyl compounds such as vinyl chloride are suspended in an aqueous medium in the presence of a suspending agent and polymerized using a catalyst soluble in oil. .

In general, factors that determine the quality of a vinyl polymer include conversion to polymer, water to monomer ratio, polymerization temperature, catalyst type, catalyst amount, type of polymer vessel, stirring speed, type of suspending agent and amount of suspending agent, and the like. do. Among these, the type of suspension has a great effect.

The performance of the suspending agent required for the suspension polymerization of the vinyl compound is (1) the ability to make the particle size distribution of the vinyl polymer granules as narrow as possible, (2) the vinyl chloride moiety in the polymer granules to increase the absorption of the plasticizer to facilitate the operation. To easily remove monomers such as and prevent the formation of fish eyes and the like during molding, and to make each polymer granule porous, and (3) to produce polymer granules of higher bulk density. .

As suspending agents for suspension polymerization of vinyl compounds, cellulose derivatives such as methyl cellulose or carboxymethyl cellulose or partially hydrolyzed polyvinyl alcohol and the like have been used alone or in mixed form until now. However, conventional suspending agents have a problem that they do not satisfy the above-mentioned necessities (1) to (3).

Suspension polymerization of vinyl compounds, such as vinyl chloride, is generally carried out by a batch process, which generally introduces an aqueous medium, a suspending agent, a polymerization initiator, a vinyl compound and the like into the polymerization vessel, and then adds the necessary additives, and then This is done by raising the temperature of the polymer.

In recent years, shortening of polymerization time in a batch has been required for productivity improvement. Therefore, during suspension polymerization of the vinyl compound, the removal efficiency of the heat of polymerization is improved by mounting a reflux condenser or the like, and a method of introducing a pre-heated aqueous medium to shorten the time required for temperature rise (hot-charge method: hot-charge method). ) Has been adopted.

However, conventional suspending agents for suspension polymerization of vinyl compounds, when using a polymerization vessel equipped with a reflux condenser, violently foam during polymerization, thereby reducing the effective volume of the polymerization vessel and making temperature control impossible, thereby improving productivity. There is a serious disadvantage of lowering and reducing the porosity of the vinyl polymer granules when a high temperature introduction method is used.

Or, in order to prevent foaming, the addition of a defoaming agent or the like has the disadvantageous effect of reducing the thermal stability of the vinyl polymer granules.

Literature (a); The Poval Book, issued by Polymer Press, 1984], a polyvinyl alcohol having a polymerization degree of 2,000 and a hydrolysis degree of 80 mol% and a polyvinyl alcohol having a polymerization degree of 700 to 800 and a hydrolysis degree of 70 mol% as a suspension for suspension polymerization of vinyl chloride. Phosphorus polyvinyl alcohols are described respectively. WO 91/15518 [Previous Document (b)] discloses a vinyl compound comprising a polyalcohol having a degree of polymerization of 100 or more, a degree of hydrolysis of 50 to 90 mol% and a polyalcohol having an amino group, an ammonium group, a carboxyl group or a sulfonic acid group at the terminal. Suspending agents for suspending polymerizing are described. However, the suspending agents described in the prior documents (a) and (b) have the disadvantage of causing a vigorous foaming phenomenon during the polymerization.

Japanese Laid-Open Patent Publication No. 110797/1977 (Previous Document (c)) describes a secondary suspending agent for suspension polymerization of vinyl chloride containing polyvinyl acetate having a degree of hydrolysis of 30 to 60 mol%. Japanese Laid-Open Patent Publication No. 145208/1994 (prior art (d)) discloses a secondary suspending agent for suspending polymerization of a vinyl compound comprising a water-insoluble polymer having a mercapto group at its terminal, wherein Illustrative examples of insoluble polymers are polyvinyl esters having a degree of hydrolysis of less than 50 mol% and a mercapto group terminally. However, the secondary suspending agents described in the prior documents (c) and (d) do not stably suspension polymerize the vinyl compound when used alone. On the other hand, when the secondary suspending agent is used in admixture with conventional partially hydrolyzed polyvinyl alcohol, a vigorous foaming phenomenon occurs in the polymerization vessel.

Literature (e); Polyvinyl Alcohol-Development (CA Finch, Wiley, 1992) discloses a method of emulsion polymerization of methacrylate ester or styrene by using polyvinyl alcohol having a degree of polymerization of 1,500, a degree of hydrolysis of 88 mol% and a mercapto group at the end. However, emulsion polymerization is suitable for melt molding from an aqueous emulsion since a water-soluble initiator is used and the polymer obtained is in the form of an aqueous emulsion having a particle size of about 0.1 to 2 [mu] m in the emulsion polymerization described in the prior art (e). There is a difficulty in obtaining a suitable powdered polymer.

The object of the present invention is the conventional suspension of vinyl compounds which introduce an aqueous medium at room temperature as well as in the process of using a polymerization vessel equipped with a condenser, in a high temperature introduction process, and in a high temperature introduction process using a polymerization vessel equipped with a condenser. Also in the polymerization method (low temperature introduction method) and the method of controlling the polymerization temperature by a jackkit or coil mounted in the polymerization vessel, the suspension is excellent in foaming effect in the polymerization vessel and at the same time satisfies the necessary performances (1) to (3). To provide the first.

As a result of intensive studies by the present inventors to solve the above problems, a suspending agent for suspension polymerization of a vinyl compound comprising a polyvinyl alcohol polymer (A) having a degree of hydrolysis of not less than 60 mol% and having a mercapto group at its end (1st invention); And a polyvinyl ester polymer (B) having a hydrolysis degree of less than 60 mol% with the polyvinyl alcohol polymer (A) such that the weight ratio of component (A) / component (B) is 40/60 to 95/5. A suspending agent (second invention) for suspension polymerization of a compound was found. Thus, the present invention has been completed.

First, the first invention is described.

The polyvinyl alcohol polymer (A) of the present invention is a polyvinyl alcohol polymer having a degree of hydrolysis of at least 60 mol% and having a mercapto group at one end (preferably at one end). The degree of hydrolysis of the polyvinyl alcohol polymer (A) is at least 60 mol%, preferably 65 to 95 mol%, most preferably 68 to 80 mol%. The viscosity average degree of polymerization (hereinafter, abbreviated as 'polymerization degree') of the polyvinyl alcohol polymer (A) is not particularly limited, but is preferably 200 to 3,500, more preferably 600 to 1,500, most preferably 680 to 1,000 to be.

The polyvinyl alcohol polymer (A) of the present invention can be increased in water solubility by introducing ionic groups into the polymer, in which case the degree of hydrolysis can be calculated only from the amounts of vinyl ester groups and vinyl alcohol groups, where the introduction The degree of hydrolysis of the resulting ionic groups is not included in the degree of hydrolysis.

The polyvinyl alcohol polymer (A) of the present invention can stably suspension polymerize a vinyl compound even when the polymer (A) alone is used, and the polymer (A) is 5 to 100 ° C (preferably 10 to Water-soluble at 90 ° C).

The method for producing the polyvinyl alcohol polymer (A) of the present invention is not particularly limited, but a compound having a thioester and a thiol group or a thiol carboxylic acid in a molecule such as 2-acetylthioethylthiol, 10-acetylthiodecane thiol Radical polymerization of the vinyl ester monomer in the presence and treatment of the obtained vinyl ester polymer with an alkali such as sodium hydroxide or ammonia to hydrolyze the vinyl ester polymer while simultaneously hydrolyzing the thioester at its end, thereby thiol groups The process for preparing the polymer having the polymer is simple and efficient.

Such vinyl esters include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl lactate, vinyl isolactate, vinyl pivalate, vinyl versatate. Vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate and the like.

The polyvinyl alcohol polymers of the present invention may be modified with less than 10 mole percent of ionic groups (eg ammonium groups, carboxyl groups, sulfonic acid groups, etc.), nonionic groups or (long chain) alkyl groups.

The manufacturing method of a polyvinyl alcohol polymer (A) is described in detail in Japanese Patent Application No. 61746/1983 (Unexamined-Japanese-Patent No. 187003/1984).

Next, the second invention of the present invention will be described. The polyvinyl alcohol polymer (A) used in the second invention is the same as the polyvinyl alcohol polymer used in the first invention.

The degree of hydrolysis of the polyvinyl ester polymer (B) of the second invention is less than 60 mol%, preferably 20 to 55 mol%, more preferably 25 to 45 mol%. The weight ratio of component (A) / component (B) is 40/60 to 95/5, preferably 50/50 to 90/10, more preferably 60/40 to 80/20.

When the weight ratio of component (A) / component (B) is 95/5 or more, the effect of improving porosity may sometimes not be observed, and when this ratio is less than 40/60, polymerization stability may be lost. Although the polymerization degree of the polyvinyl ester polymer (B) of this invention is not specifically limited, Preferably it is less than 1,000, More preferably, it is 200-550, Most preferably, it is 230-400.

The polyvinyl ester polymer (B) of the present invention is water insoluble or water dispersible. By introducing ionic groups or the like into the polymer, the polymer can be made self-emulsifying.

In the present invention, the suspending agent of the first invention mixed with the polyvinyl ester polymer (B) as the secondary suspending agent is referred to as suspending agent.

The manufacturing method of the polyvinyl ester polymer (B) of this invention is not specifically limited, A conventionally well-known polymer can also be used. Polyvinyl ester polymers having ionic groups in the side chain described in Japanese Patent Application Laid-Open No. 95103/1989; Polyvinyl esters having ionic groups at the ends described in WP 91/15518; And known polyvinyl ester polymers having less than 10 mol% of nonionic groups or (long chain) alkyl groups are preferably used.

Next, a method for producing a vinyl polymer by suspension polymerization of a vinyl compound using the suspending agent of the present invention is described.

The temperature of the aqueous medium used in the production method of the vinyl polymer is not particularly limited, and cold water of about 20 ° C as well as hot water of 90 ° C or more may be preferably used.

The medium for the heated aqueous medium may be exemplified by an aqueous medium containing an organic solvent or an aqueous solution containing various additive components, in addition to pure water. The amount of heated aqueous medium introduced into the polymerization system may be an amount sufficient to raise the temperature of the polymerization system to the required level.

And, a polymerization vessel equipped with a reflux condenser may be preferably used to improve the efficiency of removing the heat of polymerization.

The amount of the suspending agent used in the production method of the vinyl polymer is not particularly limited, but it is generally less than 5 parts by weight, preferably 0.01 to 1 part by weight, more preferably 0.02 based on 100 parts by weight of the vinyl compound. To 0.2 part by weight. Suspending agents of the present invention may be used alone or in polyvinyl alcohol, water soluble cellulose ethers (e.g. methyl cellulose, hydroxy ethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose), water soluble polymers (e.g. gelatin), fat soluble emulsifiers (E.g. sorbitan monolaurate, sorbitan trioleate, glycerin tristearate and ethylene oxide-propylene oxide block copolymers), and aqueous emulsifiers (e.g. polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oli) And sodium laurate), which are generally used for suspension polymerization of vinyl compounds such as vinyl chloride in an aqueous medium. The amount of the above-mentioned components is not particularly limited, but is preferably 0.01 to 1.0 parts by weight based on 100 parts by weight of a vinyl compound such as vinyl chloride.

If desired, various other additives may be added. Various additives include polymerization regulators such as acetaldehyde, butyl aldehyde, trichloroethylene, perchloroethylene or mercaptan, and polymerization inhibitors such as phenolic compounds and N-oxide compounds. In addition, pH adjusting agents, anti-scale agents, crosslinking agents and the like may be added. Multiple additives described above can be used in combination.

Next, conventional polymerization initiators for polymerizing vinyl compounds such as vinyl chloride may be used, which may include percarbonate compounds such as di-isopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxy Ethyl peroxydicarbonate), perester compounds (e.g. t-butyl peroxyneodecanate, α-cumyl peroxyneodecanate and t-butyl peroxyneodecanate), peroxides (e.g. acetylcyclohexylsulfonyl Peroxides and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate), azo compounds such as 2,2'-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile and Azobis (4-methoxy-2,4-dimethylvaleronitrile)) can be exemplified. Such initiators may be used in admixture with potassium persulfate, ammonium persulfate and hydrogen peroxide.

Vinyl compounds used for suspension polymerization using the suspending agent of the present invention may be exemplified by vinyl chloride alone or a monomer mixture containing mainly vinyl chloride (content of vinyl chloride of at least 50% by weight), together with vinyl chloride. Comonomers to be copolymerized include vinyl esters such as vinyl acetate and vinyl propionate, (meth) acrylate esters such as methyl (meth) acrylate and ethyl (meth) acrylate, olefins such as ethylene and propylene ], Maleic anhydride, acrylonitrile, itaconic acid, styrene, vinylidene chloride, vinyl ether, and further monomers copolymerizable with vinyl chloride. In addition, the suspending agents of the present invention can be used to polymerize and copolymerize the above-mentioned vinyl compounds without using vinyl chloride.

In suspension polymerization using the suspending agent of the present invention, the ratio of each component to be introduced, the polymerization temperature and the like can be determined according to the conventional conditions used for suspension polymerization of a vinyl compound such as vinyl chloride.

In addition, the order and proportion of introduction of the vinyl compound, polymerization initiator, suspending agent, heated aqueous medium and other additives is not particularly limited.

A method is preferably used in which the vinyl compound is preheated prior to introducing the compound into the polymerization vessel and at the same time using heated water.

The present invention is described in detail in the following examples, but the present invention is not limited to these examples. Herein, '%' and 'parts' in the following examples are '% by weight' and 'parts by weight', unless otherwise specified.

Preparation Example

[Polyvinyl alcohol polymer having mercapto group at the end]

2800 parts of vinyl acetate (hereinafter abbreviated as 'VAc') and 670 parts of methanol are introduced into the reaction vessel and the interior of the reaction vessel is sufficiently replaced with nitrogen. When the internal temperature of the reaction vessel reached 60 ° C by raising the external temperature of the reaction vessel to 65 ° C, 10 parts of methanol containing 0.243 parts of thioacetic acid previously replaced with nitrogen was added to the reaction vessel, and then 2,2'- 20 parts of methanol solution containing 1 part of azobisisobutyronitrile are added. Immediately followed by 18 parts of methanol containing 1.8 parts of thioacetic acid for 4 hours. After 5 hours the conversion to polymer is 64.7%.

After 5 hours, the vessel was cooled and further methanol was added while removing residual VAc from the system under reduced pressure with methanol to obtain a methanol solution of polyvinyl ester having a concentration of 62% (hereinafter abbreviated as 'PVAc'). do. A portion of the methanol solution is separated and the concentration of PVAc is adjusted to 30%. A solution of NAOH in methanol is added to the adjusted PVAc solution to give a water content of 3% and a ratio of [NaOH] / [VAc] of 0.02 (molar ratio), followed by hydrolysis at 40 ° C. for 1 hour. The hydrolysis reaction is then terminated by adding acetic acid to neutralize the residual NaOH. The degree of hydrolysis measured is 72 mol%.

By the same method as described above, when the hydrolysis reaction of PVAc is carried out with a ratio (molar ratio) of [NaOH] / [VAc] to 0.05, polyvinyl alcohol (PVA) is obtained, followed by It is purified by the Sletlet extraction method. The degree of hydrolysis measured thereafter is 98.9 mol%. In addition, the intrinsic viscosity is measured in water at 30 ° C., and a polymerization degree 820 is obtained.

The content of the mercapto group (hereinafter abbreviated as 'SH group') contained in PVA is measured by the iodine oxidation method using the purified PVA. An SH group of 4.0 × 10 ⁵ equivalents is identified based on 1 g-PVA.

The purified PVA was reacetylated by a conventional method to obtain reacetylated PVAc, and the GPC measurement of the reacetylated PVAc was performed in THF at 40 ° C. using polystyrene as an index to give a Pw / Pn of 2.1. It is confirmed as

The polyvinyl alcohol polymer (A) of the suspending agent of the present invention obtained by the same method is shown in Table 1. These suspending agents are all soluble in water or hot water.

[Polymerization of Vinyl Chloride]

In a glass-lining autoclave equipped with a reflux condenser, 1 g of deionized water was supplied while dissolving the suspending agents shown in the table (Examples 1 to 10 are listed in Table 1; Examples 11-21 are shown in Table 2; Comparative Examples 1-7 are shown in Table 3]. Subsequently, 0.04 parts of a 70% solution of di-isopropyl peroxydicarbonate in toluene are fed to the autoclave and then evacuated under reduced pressure of 50 mmHg to remove oxygen. Subsequently, 39 parts of warm water at 80 ° C. and 30 parts of vinyl chloride monomer are fed to the autoclave with stirring. After completion of the supply the liquid level is 60% of the vessel from the bottom of the polymerization vessel and the internal temperature is 50 ° C. The polymerization is continued while maintaining the internal temperature at 50 ° C. The pressure in the autoclave, which was 7.0 kg / cm ² G at the start of the polymerization, dropped to 4.0 kg / cm ² G after 6 hours after the start of the polymerization, and the polymerization was stopped. The unreacted vinyl chloride monomer is then removed and the contents are recovered from the autoclave and then dehydrated to dryness.

The properties of the vinyl chloride resin obtained were evaluated by the following method, and the evaluation results are shown in the table. Vinyl chloride polymers have a polymerization yield of 85% and an average degree of polymerization of 1,300.

(1) plasticizer absorbency

400 g of vinyl chloride polymer granules are fed into a plate mixer connected with a platograph and the polymer granules are preheated to 88 ° C. with stirring at 60 rpm for 4 minutes. Then 200 g of dioctyl phthalate are fed. Plasticizer absorbency is expressed in kneading time (minutes) until kneading torque falls.

(2) CPA (Low Temperature Plasticizer Absorbency)

The absorbance of dioctyl phthalate is measured at 23 ° C. according to the method described in ASTM-D3367-75.

(3) foamability measurement

After the polymerization is terminated, the foaming state in the polymerization vessel is visually observed. The results are shown in the following representation.

◎: Not foamed.

(Circle): A bubble is observed below the height of 62-65% of it from the bottom of a polymerization vessel.

(Triangle | delta): A bubble is observed below the height of 66-70% of it from the bottom of a polymerization vessel.

▲: Bubbles are observed below the height of 90 to 100% of them from the bottom of the polymerization vessel.

X: A bubble was observed below its 100% height from the bottom of the polymerization vessel, and the reflux condenser was further filled with a plurality of bubbles.

The suspending agent of the present invention can increase the effective volume of the polymerization vessel in order to improve productivity, and when suspended polymerization using a polymerization vessel equipped with a reflux condenser, when the suspension polymerization by a high temperature introduction method, or equipped with a reflux condenser Even when the suspension polymerization is carried out by a high temperature introduction method using the prepared polymerization vessel, the temperature of the polymerization vessel can be easily controlled during the polymerization. This means that the suspending agent of the present invention has an excellent effect of reducing the foaming during the polymerization compared to the conventional suspension. Because.

When using the suspending agent for suspension polymerization of the present invention, the obtained vinyl polymer granules have a large particle size with a narrow particle size distribution and less scattering when handling, and also a strike-through into a molding machine. ) Vinyl polymer having excellent) properties, high porosity, high plasticizer absorption, and high bulk density. Therefore, the suspending agent for suspension polymerization of the present invention has a great industrial value.

Claims (1)

As a suspending agent, based on 100 parts by weight of the vinyl compound, vinyl in a suspension polymerization medium containing from 0.02 to 0.2 parts by weight of a polyvinyl alcohol polymer (A) having a degree of hydrolysis of 60 to 95 mol% and having a mercapto group at the end. A method of polymerizing a vinyl compound under suspension polymerization conditions, including polymerizing the compound.