TW202005988A - Method for producing vinyl-based polymer - Google Patents

Abstract

A method for producing a vinyl polymer, in which a vinyl compound is subjected to suspension polymerization in the presence of a dispersion stabilizer, and which is configured such that: the dispersion stabilizer contains a modified PVA (A), a PVA (B) and a PVA (C); the modified PVA (A) has double bonds in side chains in an amount of 0.05% by mole or more but less than 0.5% by mole; the modified PVA (A) has a saponification degree of 68% by mole or more but less than 77% by mole and a viscosity-average polymerization degree of 500 or more but less than 1,500; the PVA (B) has a saponification degree of 30% by mole or more but less than 60% by mole and a viscosity-average polymerization degree of 150 or more but less than 600; and the PVA (C) has a saponification degree of 77% by mole or more but less than 90% by mole and a viscosity-average polymerization degree of 1,700 or more but less than 3,000. According to this production method, a polymerization reaction is stabilized, and the formation of coarse particles is suppressed. In addition, the present invention is able to suppress the occurrence of fish eyes in a molded article that is formed from a vinyl polymer, and is also able to improve the plasticizer absorbency and the bulk specific gravity of a vinyl polymer.

Description

Method for manufacturing vinyl polymer

The present invention relates to a method for producing an ethylene-based polymer by suspension polymerization of a vinyl compound in the presence of a dispersion stabilizer containing polyvinyl alcohol.

Polyvinyl alcohol (hereinafter abbreviated as "PVA") has been used for the suspension of adhesives, paper coating agents, polarizing films, water-soluble films, pharmaceutical and cosmetic compositions, and vinyl compounds (for example, vinyl chloride). Dispersion stabilizer for turbid polymerization and other products. It is known that by the presence of reactive groups such as double bonds on PVA, various properties will be improved, or special effects may be obtained.

As a dispersion stabilizer used in the suspension polymerization of ethylene compounds, PVA is widely used (Patent Documents 1 to 5). Although there have been demands for improvements in polymerization stability, plasticizer absorbency, and volumetric specific gravity, it is difficult to say that in the prior art, each is fully satisfied. In particular, the relationship between plasticizer absorbency and volume specific gravity is basically a trade-off relationship, so it is difficult to improve on both sides. Therefore, it is considered that it is difficult to obtain an ethylene-based polymer having excellent plasticizer absorbability and a high volume specific gravity.

In order to improve the stability (polymerization stability) during the polymerization of vinyl chloride, there have been proposals to use heat-treated PVA for polymerization (Patent Documents 1 to 3). However, when these PVAs are used as dispersion stabilizers for suspension polymerization of vinyl chloride, satisfactory effects may not be obtained in terms of polymerization stability, plasticizer absorbency, and volume specific gravity.

Patent Document 4 describes a dispersion stabilizer for suspension polymerization, which is characterized in that it contains: a monoaldehyde having an olefin-based unsaturated double bond, and the side chain obtained by acetalizing polyvinyl alcohol Polyvinyl alcohol with double bonds. When the dispersion stabilizer for suspension polymerization described in Patent Document 4 is used for the polymerization reaction, it is difficult to say that the polymerization stability and the plasticizer absorbability and volume specific gravity of the obtained ethylene-based polymer are sufficient.

In addition, when manufacturing the polyvinyl alcohol contained in Patent Document 4, since acid is used, there is also a problem that expensive equipment having acid resistance is required. In addition, the monoaldehyde with double bonds used in the production of the polyvinyl alcohol is expensive, unstable in the air, is a specified poison, has an irritating odor, has poor handling properties, and has poor raw material supply, etc. problem.

Patent Document 5 describes a dispersion stabilizer composed of a vinyl alcohol having a double bond in a side chain, which is obtained by esterifying polyvinyl alcohol with a carboxylic acid or a salt having an unsaturated double bond. The polyvinyl alcohol used in the dispersion stabilizer can be obtained by a simple method using an inexpensive carboxylic acid.

However, when the dispersion stabilizer composed of this polyvinyl alcohol is used for suspension polymerization of ethylene compounds, in addition to the large amount of fish eyes occurring on the molded product composed of the obtained ethylene-based polymer, the polymerization stability, There are also problems with plasticizer absorption and volume specific gravity.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Unexamined Patent Publication No. 51-45189

[Patent Document 2] Japanese Patent Laid-Open No. 10-67806

[Patent Document 3] Japanese Patent Laid-Open No. 2004-250695

[Patent Literature 4] International Publication No. 2015/182567

[Patent Literature 5] International Publication No. 2007/119735

The present invention has been completed to solve the above-mentioned problems, and its object is to provide a method for producing an ethylene-based polymer which is excellent in polymerization stability when the ethylene compound is suspension polymerized, and allows the obtained ethylene-based polymer to be polymerized The plasticizer absorbability and volumetric specific gravity of the material have been improved, and at the same time, the fisheye of the molded product composed of the ethylene-based polymer can be suppressed.

The above-mentioned problems can be solved by providing a manufacturing method as follows: a manufacturing method which is a manufacturing method of an ethylene-based polymer for suspension polymerization of an ethylene compound in the presence of a dispersion stabilizer, wherein the dispersion The stabilizer contains modified polyvinyl alcohol (A), polyvinyl alcohol (B), and polyvinyl alcohol (C). The modified polyvinyl alcohol (A) has a side chain of 0.05 mol% or more and less than 0.5 mol% The double bond is derived from at least one selected from the group consisting of itaconic acid and its derivatives, methacrylic acid and its derivatives, and the degree of saponification of modified polyvinyl alcohol (A) is 68 mole% or more and less than 77 mole%, the average viscosity polymerization degree is more than 500 and less than 1500, the saponification degree of polyvinyl alcohol (B) is more than 30 mole% and less than 60 mole%, the average viscosity polymerization degree is 150 or more and less than 600, the degree of saponification of polyvinyl alcohol (C) is 77 mol% or more and less than 90 mol%, the average viscosity degree of polymerization is 1700 or more and less than 3000; and relative to modified polyvinyl alcohol (A) , Polyvinyl alcohol (B) and polyvinyl alcohol (C) total 100 parts by mass, the content of modified polyvinyl alcohol (A) is 10 to 45 parts by mass, and the content of polyvinyl alcohol (B) is 1 to 45 parts by mass Parts, the content of the polyvinyl alcohol (C) is 10 to 89 parts by mass.

In this case, it is preferable that the dispersion stabilizer contains 0.001 parts by mass or more and less than 5 parts by mass of the compound (D) relative to 100 parts by mass of the modified polyvinyl alcohol (A). More than one phenolic hydroxyl compound, its salt or its oxide.

Furthermore, it is preferable that the modified polyvinyl alcohol (A) has a double bond derived from itaconic acid in the side chain.

According to the production method of the present invention, the polymerization reaction is stable, and the formation of coarse particles is reduced. In addition, it is possible to suppress the fisheye of the molded product composed of the ethylene-based polymer, and at the same time, it is possible to improve the plasticizer absorbability and volume specific gravity of the ethylene-based polymer.

[Form for carrying out the invention]

The present invention relates to a method for producing an ethylene-based polymer by suspension polymerization of an ethylene compound in the presence of a dispersion stabilizer. In order to solve the above-mentioned problems, the present inventors conducted careful research and review, and as a result completed the use of modified polyvinyl alcohol (A) (hereinafter, referred to as "modified PVA (A)"), polyvinyl alcohol (B) ( Hereinafter, a method for producing an ethylene-based polymer with a dispersion stabilizer of polyvinyl alcohol (C) (hereinafter referred to as "PVA(C)") and polyvinyl alcohol (C) (hereinafter referred to as "PVA(C)").

In the manufacturing method of the present invention, it is important to use a dispersion stabilizer containing a specific amount of modified PVA (A), PVA (B), and PVA (C). According to the production method of the present invention, it is possible to obtain an ethylene-based polymer having improved stability of the ethylene compound during polymerization, a small average particle diameter, and few coarse particles. In addition, fish eyes of the obtained molded product can also be suppressed. It is also surprising that the ethylene polymer plasticizer obtained by the production method of the present invention is excellent in absorbency and has a high volume specific gravity.

[Modified PVA(A)]

The modified PVA (A) used in the present invention has a double bond on the side chain, which is derived from the group selected from the group consisting of itaconic acid and its derivatives, methacrylic acid and its derivatives At least one.

The manufacturing method of the modified PVA (A) used in the present invention is not particularly limited. The preferred manufacturing method is in the presence of the above-mentioned specific carboxylic acid (iconic acid or methacrylic acid) and its derivatives. A method of heating and reacting polyvinyl alcohol (E) (hereinafter, abbreviated as "PVA(E)"). In this case, the specific carboxylic acid and its derivative system may be used alone or in combination of two or more. The reaction temperature and reaction time are not particularly limited. The reaction temperature is preferably from 30 to 200°C. The reaction time is usually 10 minutes to 24 hours. Here, PVA(E) is a PVA having no double bond in the side chain.

In the present invention, examples of the derivatives of itaconic acid include itaconic acid alkyl esters and itaconic anhydride. In addition, examples of methacrylic acid derivatives include alkyl methacrylate and methacrylic anhydride. These carboxylic acids and their derivatives can also be salts.

Among the above-mentioned specific carboxylic acids (iconic acid or methacrylic acid) and derivatives thereof, it is preferably itaconic acid in terms of performance when used as a dispersion stabilizer based on reactivity with PVA (E). That is, the modified PVA (A) of the present invention preferably has a double bond derived from itaconic acid on the side chain.

The above-mentioned PVA (E) system can be produced by a conventional polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, and the like using a vinyl ester monomer. From an industrial point of view, preferred polymerization methods are solution polymerization, emulsification polymerization, and dispersion polymerization. In the polymerization operation, any polymerization method of batch method, semi-batch method and continuous method can also be used.

Examples of the vinyl ester-based monomers used for polymerization include vinyl acetate, vinyl formate, vinyl propionate, vinyl octoate, and vinyl tertiary carbonate. Among these, from the industrial point of view, preferred It is vinyl acetate.

When the vinyl ester-based monomer is polymerized, the vinyl ester-based monomer may be copolymerized with other monomers within a range not detracting from the gist of the present invention. Examples of usable monomers include α-olefins such as ethylene, propylene, n-butene, and isobutene; acrylic acid and its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, and isopropyl acrylate Acrylates such as n-butyl acrylate, isobutyl acrylate, third butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc.; methacrylic acid and its salts; methacrylic acid Methyl ester, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, third butyl methacrylate, 2-methacrylate Methacrylates such as ethylhexyl ester, dodecyl methacrylate, octadecyl methacrylate, etc.; acrylamide, N-methacrylamide, N-ethylacrylamide, N,N- Dimethacrylamide, diacetone acrylamide, propylene amide propane sulfonic acid and its salt, propylene amide propyl dimethylamine and its salt or its grade 4 salt, N-hydroxymethyl acrylamide and Acrylamide derivatives such as its derivatives; methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propanesulfonic acid and its salts, methyl Acrylamidopropyl dimethylamine and its salts or their fourth-grade salts, N-hydroxymethylmethacrylamide and its derivatives, and other methacrylamide derivatives; methyl vinyl ether, ethyl Vinyl ethers such as vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, third butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, etc. ; Acrylonitrile, methacrylonitrile and other nitriles; vinyl chloride, vinyl fluoride, and other halogenated vinyls; vinylidene chloride, vinylidene fluoride, and other dihalide vinylenes; allyl acetate, allyl chloride Allyl compounds such as bases; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid and their salts or their esters; vinylsilyl compounds such as vinyl trimethoxysilane; isopropylene acetate Base etc. The copolymerization amount of such other monomers is usually 10 mol% or less.

In addition, during the polymerization of the vinyl ester-based monomer, a chain transfer agent may be coexisted for the purpose of adjusting the degree of polymerization of the obtained polyvinyl ester. Examples of the chain transfer agent include aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde, and benzaldehyde; ketones such as acetone, methyl ethyl ketone, hexanone, and cyclohexanone; and 2-hydroxyethane sulfide Mercaptans such as alcohol and dodecyl mercaptan; halogenated hydrocarbons such as trichloroethylene and perchloroethylene, among which aldehydes and ketones are preferably used. The addition amount of the chain transfer agent is determined according to the chain transfer constant of the added chain transfer agent and the degree of polymerization of the polyvinyl ester as the target. Generally speaking, it is 0.1 to 10 relative to the vinyl ester monomer. Quality% is better.

For the saponification reaction of polyvinyl ester, alcoholysis or hydrolysis reaction using a conventional alkaline catalyst such as sodium hydroxide, potassium hydroxide, sodium methoxide, or an acid catalyst such as p-toluenesulfonic acid can be applied . Examples of the solvent used in the chemical reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; benzene and toluene. These aromatic hydrocarbons can be used alone or in combination of two or more. Among them, methanol or a mixed solution of methanol and methyl acetate is used as a solvent, and the reaction is carried out in the presence of sodium hydroxide which is an alkaline catalyst, which is relatively simple and preferable.

In the present invention, it is important that the modified PVA (A) has a double bond of 0.05 mol% or more and less than 0.5 mol% on the side chain, which is derived from the inclusion of itaconic acid and its derivatives , At least one selected from the group of methacrylic acid and its derivatives. In addition, the aforementioned double bond system means a carbon-carbon double bond.

When a dispersion stabilizer containing a modified PVA (A) containing less than 0.05 mol% of double bonds is used to suspend polymerization of an ethylene compound, the following problems will occur: the stability of the polymerization will be reduced, and a large amount of coarse particles will be formed 1. A large amount of fisheyes occur on the molded product composed of ethylene-based polymers, and the volumetric specific gravity of ethylene-based polymers is low. The amount of the double bond is preferably 0.08 mol% or more, preferably 0.10 mol% or more, and more preferably 0.12 mol% or more.

On the other hand, when a dispersion stabilizer containing a modified PVA (A) containing a double bond in an amount of 0.5 mol% or more is used for suspension polymerization of an ethylene compound, a large amount of molded products composed of ethylene-based polymers occur At the same time, the absorbency of the plasticizer of the ethylene-based polymer will be low. The amount of double bonds is preferably less than 0.45 mole %, preferably less than 0.40 mole %, and more preferably less than 0.35 mole %.

The amount of the double bond can be measured by a known method. Specifically, measurement by ¹ H-NMR is relatively simple. When measuring the amount of the double bond, it is preferable to remove the unreacted carboxylic acid or its derivative in advance and purify it.

The purification method is not particularly limited, and examples include a method of washing with "a solution that can dissolve unreacted carboxylic acid or its derivative without dissolving modified PVA (A)." After the modified PVA (A) is made into an aqueous solution with a concentration of about 1 to 20% by mass, the aqueous solution is dropped into a solution that can dissolve the modified PVA (A) but can dissolve unreacted carboxylic acid or its derivative, so that the modified Precipitation of sexual PVA (A), and the re-precipitation method by which purification is carried out, is relatively simple and therefore preferable.

The saponification degree of the modified PVA(A) is more than 68 mol% and less than 77 mol%. When the degree of saponification is less than 68 mol%, the water solubility decreases, so that the following problems occur: the handleability decreases, the polymerization becomes unstable, and the coarse particles increase. The saponification degree of modified PVA(A) should be more than 70 mol%. On the other hand, when the saponification degree of the modified PVA (A) is 77 mol% or more, the following problems occur: large amounts of coarse particles are formed, and a large number of fisheyes and vinyls occur on molded products composed of ethylene-based polymers The plasticizer of the polymer has low absorption. The saponification degree of modified PVA (A) is preferably less than 75 mole %. The degree of saponification is a value obtained by measuring in accordance with JIS-K6726 (the degree of saponification described below is also the same measurement method).

The average viscosity degree of polymerization of the modified PVA (A) (sometimes only referred to as "degree of polymerization") is 500 or more and less than 1500. When the degree of polymerization is less than 500, the following problems occur: the stability of the polymerization is reduced, a large amount of coarse particles are formed, a large amount of fisheyes occur in the molded product composed of an ethylene-based polymer, and the volume specific gravity of the ethylene-based polymer is low. The degree of polymerization of the modified PVA (A) is preferably 600 or more. On the other hand, when the degree of polymerization is 1500 or more, the following problems occur: a large amount of coarse particles are formed, a large amount of fisheyes occur in a molded product composed of an ethylene-based polymer, plasticizer absorbability of a vinyl-based polymer, and a volume specific gravity low. The degree of polymerization of the modified PVA (A) is preferably less than 1000, more preferably less than 900. When the degree of saponification is less than 99.5 mol%, for PVA that has been saponified to a degree of saponification of 99.5 mol% or more, the limit viscosity [η] (L/g) measured in water at 30°C is used, by the following formula, The average viscosity degree of polymerization (P) is determined.

P=([η]×10 ⁴ /8.29) ^(1/0.62)

(PVA(B))

The PVA (B) of the present invention is a PVA that does not have a double bond on the side chain, and the preparation method is the same as PVA (E).

The saponification degree of PVA(B) is more than 30 mol% and less than 60 mol%. When the degree of saponification is less than 30 mol%, the polymerization stability when used as a dispersion stabilizer for ethylene compounds will decrease. The degree of saponification is preferably more than 35 mol%. On the other hand, when the degree of saponification of PVA (B) is 60 mol% or more, the following problem occurs: a large amount of fish eyes and plasticizer absorption of the vinyl polymer occur in the molded product composed of the vinyl polymer Sex is low. The degree of saponification is preferably less than 57 mol%, more preferably less than 54 mol%.

The average polymerization degree of viscosity of PVA (B) is 150 or more and less than 600. When the degree of polymerization is less than 150, the following problems will occur: when used as a dispersion stabilizer for ethylene compounds, the polymerization stability will be reduced, large particles will be formed in large amounts, and fisheyes will occur in molded products composed of ethylene-based polymers. The volumetric specific gravity of ethylene-based polymers is low. The degree of polymerization is preferably 200 or more. On the other hand, when the degree of polymerization is 600 or more, there may be a problem that a molded product composed of an ethylene-based polymer has a large amount of fish eyes, and the plasticizer absorption of the ethylene-based polymer is low. The degree of polymerization is preferably less than 550.

(PVA(C))

The PVA (C) of the present invention is a PVA that does not have a double bond on the side chain, and the preparation method is the same as PVA (E).

The saponification degree of PVA(C) is 77 mol% or more and less than 90 mol%. When the degree of saponification is less than 77 mole %, the following problems will occur: when used as a dispersion stabilizer for ethylene compounds, the polymerization stability will decrease, and the volume specific gravity of the ethylene-based polymer will be low. The saponification degree is preferably 78 mol% or more. On the other hand, when the degree of saponification of PVA(C) is 90 mol% or more, the following problem occurs: a large amount of fish eyes and plasticizer absorption of the vinyl polymer occur in the molded product composed of the vinyl polymer Sex is low. The degree of saponification is preferably less than 85 mole %.

The average polymerization degree of viscosity of PVA(C) is more than 1700 and less than 3000. When the degree of polymerization is less than 1700, the following problems will occur: when used as a dispersion stabilizer for ethylene compounds, the polymerization stability will decrease, large particles will form in large amounts, and the volume specific gravity of the ethylene-based polymer will be low. The degree of polymerization is preferably 1800 or more. On the other hand, when the degree of polymerization is 3,000 or more, the following problems occur: molded products composed of ethylene-based polymers have a large amount of fish eyes, and the plasticizer of the ethylene-based polymers has low absorbability. The degree of polymerization is preferably less than 2700.

(Compound (D))

The dispersion stabilizer used in the production method of the present invention preferably further contains the compound (D). In this case, the compound (D) is preferably a compound having two or more phenolic hydroxyl groups, a salt thereof, or an oxide thereof. Examples of compounds having two or more phenolic hydroxyl groups include hydroquinone, catechol, resorcinol, tertiary butyl hydroquinone, di-tertiary butyl hydroquinone, and the like. Phenoltriol, hexahydrobenzene, gallic acid and other phenol carboxylic acids such as alcohol, gallophenol, phloroglucinol, 1,2,4-pyrogallol, etc.; phenol carboxylic acid such as gallic acid alkyl ester Ester; epicatechin, epigallocatechin, epigallocatechin-3-epicatechin and other catechins. Examples of the alkyl gallate include methyl gallate, ethyl gallate, propyl gallate, octyl gallate, and dodecyl gallate. These salts or oxides can also be used in the same way.

Among them, benzenediol, gallic acid, and gallic acid alkyl ester are preferred, benzenediol or gallic acid alkyl ester is more preferred, benzenediol is even more preferred, and particularly preferred is third Butyl hydroquinone.

(Dispersion stabilizer)

For the dispersion stabilizer of the present invention, it is important that the content of the modified PVA (A) is 10 to 45 parts by mass relative to 100 parts by mass of the modified PVA (A), PVA (B), and PVA (C). Copies.

When the content of the modified PVA (A) is less than 10 parts by mass, the following problems may occur: in the suspension polymerization of the ethylene compound, the polymerization stability is reduced, a large amount of coarse particles are formed, and a molded product composed of an ethylene-based polymer A large number of fisheyes and ethylene-based polymers have a low volume specific gravity. The content of the modified PVA (A) is preferably 20 parts by mass or more. On the other hand, when the content of the modified PVA (A) exceeds 45 parts by mass, the following problem occurs: the molded product composed of the ethylene-based polymer has a large amount of fisheyes and the absorbability of the plasticizer of the ethylene-based polymer low. The content of modified PVA (A) is preferably 43 parts by mass or less.

In the present invention, it is also important that the content of PVA (B) is 1 to 45 parts by mass relative to 100 parts by mass of the modified PVA (A), PVA (B), and PVA (C).

When the content of PVA (B) is less than 1 part by mass, the following problems may occur: a large amount of fish eyes occur in the molded product composed of the ethylene-based polymer, and the plasticizer absorption of the ethylene-based polymer is low. The content of PVA (B) is preferably 5 parts by mass or more. On the other hand, when the content of PVA (B) exceeds 45 parts by mass, the following problems will occur: the polymerization stability in suspension polymerization of ethylene compounds is reduced, large particles are formed in large amounts, and the moldings made of ethylene-based polymers A large amount of fisheyes and vinyl polymers have a low volume specific gravity. The content of PVA (B) is preferably 40 parts by mass or less.

In the present invention, it is important that the content of PVA (C) is 10 to 89 parts by mass with respect to the total of 100 parts by mass of modified PVA (A), PVA (B), and PVA (C).

When the content of PVA(C) is less than 10 parts by mass, the following problems will occur: polymerization stability is reduced, large particles are formed in large amounts, and a large amount of fisheyes and the volume of ethylene-based polymers occur on the molded product composed of ethylene-based polymers The proportion is low. The content of PVA (C) is preferably 15 parts by mass or more. When the content of PVA(C) exceeds 89 parts by mass, the following problem occurs: a large amount of fisheyes occur in a molded product composed of an ethylene-based polymer, and the volume specific gravity of the ethylene-based polymer is low. The content of PVA (C) is preferably 75 parts by mass or less.

In the present invention, the dispersion stabilizer is preferably 0.001 parts by mass or more and less than 5 parts by mass relative to 100 parts by mass of the modified PVA (A). When the content of the compound (D) is less than 0.001 parts by mass, there is a tendency for fish eyes to easily occur in the molded product composed of the ethylene-based polymer. The content of the compound (D) is preferably 0.01 parts by mass or more. On the other hand, when the content of the compound (D) is 5 parts by mass or more, the polymerization stability in the suspension polymerization of the ethylene compound decreases, a large amount of coarse particles are formed, and the molded product composed of the ethylene-based polymer is easy Fisheye tendencies occur. The content of the compound (D) is preferably less than 3 parts by mass.

(Manufacturing method of vinyl polymer)

The present invention is a method for producing an ethylene-based polymer by suspension polymerization of an ethylene compound in the presence of a dispersion stabilizer. Then, the dispersion stabilizer contains a certain amount of modified PVA (A), PVA (B) and PVA (C). By using this dispersion stabilizer, an ethylene-based polymer having a small average particle size and few coarse particles can be obtained. In addition, it is also possible to obtain an ethylene-based polymer in which the fisheye of a molded product composed of an ethylene-based polymer is suppressed. Furthermore, it is possible to obtain an ethylene-based polymer that is also excellent in plasticizer absorption and has a high volume specific gravity.

In this case, the total content of the modified PVA (A), PVA (B), and PVA (C) is preferably 0.01 to 1 part by mass relative to 100 parts by mass of the ethylene compound. When the total content of the modified PVA (A), PVA (B), and PVA (C) is less than 0.01 parts by mass, there is a tendency that the polymerization stability is low and the vinyl polymer particles cannot be obtained. The total content of modified PVA (A), PVA (B), and PVA (C) is preferably 0.02 parts by mass or more relative to 100 parts by mass of the ethylene compound. On the other hand, when the total content of the modified PVA (A), PVA (B), and PVA (C) exceeds 1 part by mass, the economy tends to deteriorate. The total content of modified PVA (A), PVA (B), and PVA (C) is preferably 0.5 part by mass or less relative to 100 parts by mass of the ethylene compound.

The above-mentioned dispersion stabilizer is within a range not detracting from the gist of the present invention, and may contain various additives. Examples of the additives include polymerization regulators such as aldehydes, halogenated hydrocarbons, and thiols; polymerization stoppers such as benzene compounds, sulfur compounds, and N-oxide compounds; pH adjusters; crosslinking agents; Antiseptic; anti-mold agent, anti-caking agent, defoaming agent, compatibility agent, etc. The content of various additives in the dispersion stabilizer is preferably 10% by mass or less, and more preferably 5% by mass or less relative to the amount of the dispersion stabilizer.

The method of adding the above-mentioned dispersion stabilizer is not particularly limited. Examples of the method of addition include the following methods (i) to (iv).

Method (i): After mixing the modified PVA(A), PVA(B) and PVA(C) in a powder state, a method of making an aqueous solution and adding it to the polymerization tank

Method (ii): After the modified PVA (A), PVA (B) and PVA (C) are separately prepared into separate aqueous solutions, these are mixed, and the obtained aqueous solution is added to the polymerization tank

Method (iii): After preparing the modified PVA (A), PVA (B) and PVA (C) into separate aqueous solutions, do not mix these into the aqueous solution and add them to the polymerization tank separately

Method (iv): Method of directly adding modified PVA(A), PVA(B) and PVA(C) in powder state

From the viewpoint of uniformity in the polymerization tank, any of the above methods (i), (ii), and (iii) is preferred.

In addition, as described above, in the present invention, it is preferable that the dispersion stabilizer further contains a compound (D). The method of adding the dispersion stabilizer to the polymerization tank at this time is not particularly limited, but the method described below is preferred. First, it is preferable to react PVA (E) with the above-mentioned specific carboxylic acid or its derivative in the presence of compound (D) to obtain a composition containing modified PVA (A). In this composition, the PVA (E) before the reaction will react with the above-mentioned specific carboxylic acid or its derivative to become a modified PVA (A), and the compound (D) will directly remain. Then, the method of adding this composition, PVA(B) and PVA(C) as a dispersion stabilizer to a polymerization tank is preferable. The addition method at this time is not particularly limited, and examples thereof include the above methods (i) to (iv).

Examples of the ethylene compound used in the production method of the present invention include vinyl chloride and other halogenated ethylene; vinyl acetate and vinyl propionate and other vinyl esters; acrylic acid, methacrylic acid, esters and salts thereof ; Maleic acid, fumaric acid, esters and salts of these; styrene; acrylonitrile; vinylidene chloride; vinyl ether, etc. Among them, the dispersion stabilizer of the present invention is particularly preferably used for suspension polymerization, using vinyl chloride alone, or vinyl chloride and monomers copolymerizable with vinyl chloride. Examples of monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic acid such as methyl (meth)acrylate and ethyl (meth)acrylate Esters; α-olefins such as ethylene and propylene; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile; styrene; vinylidene chloride; vinyl ether, etc.

基過氧新癸酸酯等之過氧酯化合物；乙醯基環己基磺酸基過氧化物、2,4,4-三甲基戊基-2-過氧苯氧基乙酸酯、3,5,5-三甲基己醯基過氧化物、月桂醯基過氧化物等之過氧化物；偶氮雙-2,4-二甲基戊腈、偶氮雙(4-2,4-二甲基戊腈)等之偶氮化合物等。作為水溶性之聚合起始劑，例如可列舉有：過硫酸鉀、過硫酸銨、過氧化氫、氫過氧化

等。該等之油溶性或水溶性之聚合起始劑係可單獨使用或組合2種以上使用。 For suspension polymerization of ethylene compounds, it has conventionally been used for polymerization of vinyl chloride. Oil-soluble or water-soluble polymerization initiators can be used. Examples of the oil-soluble polymerization initiator include diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, etc. Peroxycarbonate compound; third butyl peroxyneodecanoate, third butyl peroxytrimethylacetic acid, third hexylperoxytrimethylacetic acid, α-

Peroxyester compounds such as peroxyneodecanoate; acetylcyclohexylsulfonate peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, 3 ,5,5-trimethylhexyl peroxide, lauryl peroxide and other peroxides; azobis-2,4-dimethylvaleronitrile, azobis(4-2,4 -Azo compounds such as dimethylvaleronitrile). Examples of water-soluble polymerization initiators include potassium persulfate, ammonium persulfate, hydrogen peroxide, and hydroperoxide

Wait. These oil-soluble or water-soluble polymerization initiators can be used alone or in combination of two or more.

In the suspension polymerization of an ethylene compound, the polymerization temperature is not particularly limited, and it can be adjusted to a low temperature of about 20°C or a high temperature exceeding 90°C. In addition, in order to improve the heat dissipation efficiency of the polymerization reaction system, a polymerization apparatus with a reflux condenser may also be used.

In the suspension polymerization of ethylene compounds, in addition to the above-mentioned dispersion stabilizers, it can also be used in combination with suspension polymerization of ethylene compounds in an aqueous medium: methyl cellulose, hydroxyethyl cellulose, hydroxy Water-soluble cellulose ethers such as propyl cellulose and hydroxypropyl methyl cellulose; water-soluble polymers such as gelatin; sorbitol monolauryl ester, sorbitol trioleate, glycerol tristearate Oil-soluble emulsifiers for esters, ethylene oxide and propylene oxide block copolymers; water-soluble emulsifiers for polyoxyethylene sorbitol monolaurate, polyoxyethylene glycerol oleate, sodium laurate, etc. Wait. The amount of addition is not particularly limited, and it is preferably 0.01 parts by mass or more and 1.0 parts by mass or less relative to 100 parts by mass of the vinyl compound.

The ethylene-based polymer obtained by the production method of the present invention can be appropriately blended with a plasticizer or the like and used in various molded products.

[Example]

Hereinafter, the present invention will be described in further detail through examples. In the following examples and comparative examples, "parts" and "%" represent mass parts and mass %, respectively, unless otherwise specified.

[Average degree of polymerization of viscosity of PVA]

The average polymerization degree of viscosity of PVA is measured in accordance with JIS-K6726 (1994). Specifically, when the degree of saponification is less than 99.5 mol%, for PVA saponified until the degree of saponification becomes 99.5 mol% or more, the limit viscosity [η] (L/g) measured at 30°C in water is used. The viscosity average polymerization degree (P) is determined by the following formula.

P=([η]×10 ⁴ /8.29) ^(1/0.62)

[Saponification degree of PVA]

The saponification degree of PVA is determined according to the method described in JIS-K6726 (1994). In addition, the saponification degree of the modified PVA (A) is a value obtained by reprecipitating and purifying the powder composed of the obtained composition (C), and measuring the separated modified PVA (A).

[Amount of double bond introduced into modified PVA(A)]

Prepare 10% aqueous solution of modified PVA(A). In a solution of 500 g of methyl acetate/water = 95/5, 5 g of this aqueous solution was dropped to precipitate the modified PVA (A), recovered, and dried. Regarding the separated modified PVA (A), using ¹ H-NMR, the amount of double bonds introduced into the modified PVA (A) was measured. In addition, the amount of this double bond is relative to the amount of double bonds of all monomer units of the modified PVA (A).

Manufacturing Example 1 (Manufacture of PVA (A1))

A solution in which 6.5 parts of itaconic acid was dissolved in 120 parts of methanol was prepared, and 100 parts of PVA (average viscosity polymer 700 as PVA (E), 72 mole% of saponification degree) and third butyl compound (D) were added to it 0.1 parts of hydroquinone, and methanol was removed under reduced pressure. Thereafter, heat treatment was performed at a temperature of 110° C. for 7 hours to obtain PVA (A1) having a double bond derived from itaconic acid on the side chain. Table 1 shows the production conditions of PVA (A1).

The PVA (A1) system can confirm the peak of the double bond introduced in the vicinity of 5.6 to 6.0 ppm, and the amount of the double bond is 0.23 mole %. In addition, the above-mentioned PVA (A1) has an average viscosity polymerization degree of 700 and a saponification degree of 72 mole %. Table 2 shows the production results of PVA (A1).

Manufacturing Examples 2 to 12 (Manufacture of PVA (A2 to A12))

Except for changing the heat treatment conditions such as the type and amount of raw materials used, heat treatment temperature, heat treatment time, etc., the same operation as the production of PVA (A1) was carried out to produce PVA (A2 to A12). The manufacturing conditions are shown in Table 1, and the manufacturing results are shown in Table 2.

[Table 1]

[Table 2]

Example 1

PVA (A1) was dissolved in deionized water, and 100 parts of the filtrate filtered with a 200-mesh nano sieve was added to the autoclave as a dispersion stabilizer. The amount of PVA (A1) used in the filtrate was 0.04 parts by mass (400 ppm) relative to 100 parts by mass of the vinyl chloride addition. Next, PVA (BVA), which has a viscosity average polymerization degree of 250 and a saponification degree of 40 mole %, was dissolved in a solution of deionized water/methanol = 1/1 at a concentration of 40% to make a dispersion stabilizer. Add to the autoclave. The amount of PVA (B) added was 0.02 parts by mass (200 ppm) relative to 100 parts by mass of vinyl chloride. Next, dissolve PVA(C), which has a viscosity average polymerization degree of 2000 and a saponification degree of 80 mol%, as PVA(C) in deionized water, and use 100 parts of the filtrate after filtering through a 200 mesh nanosieve as the The dispersion stabilizer is added to the autoclave. The amount of PVA (C) added was 0.04 parts by mass (400 ppm) relative to 100 parts by mass of vinyl chloride. Next, deionized water is added and added so that the total amount of deionized water becomes 1200 parts.

Next, 0.65 parts of a 70% toluene solution of amyl peroxyneodecanoate and 1.05 parts of a 70% toluene solution of tert-butyl peroxyneodecanoate were added to the autoclave so that the pressure became 0.2 MPa Nitrogen is introduced into the autoclave. After that, a total of 5 operations of nitrogen purging were carried out, and after replacing nitrogen in the autoclave to remove oxygen, 940 parts of vinyl chloride were added. The contents of the autoclave were heated to 57°C, and polymerization of vinyl chloride was started with stirring. The pressure in the autoclave at the start of polymerization was 0.80 MPa. About 3.5 hours after the start of polymerization, the polymerization was stopped when the pressure in the autoclave became 0.70 MPa, and after removing unreacted vinyl chloride, the polymerization reaction product was taken out and dried at 65°C for 16 hours to obtain an ethylene-based resin ( Vinyl chloride polymer particles). Then, the obtained particles were evaluated by the method shown below. The evaluation results are shown in Table 3.

(Evaluation of vinyl chloride polymer particles)

With respect to the obtained vinyl chloride polymer particles, (1) average particle diameter, (2) particle size distribution, (3) volume specific gravity, (4) plasticizer absorbability, and (5) fish eye were evaluated according to the following methods. The evaluation results are shown in Table 3.

(1) Average particle size

Using a gold screen based on a Taylor sieve, the particle size distribution was measured according to the dry sieve method described in JIS-Z8815 (1994). Using the Rosin-Rammler diagram, the average particle diameter was calculated from this result.

(2) Particle size distribution

The content of sieve openings of JIS standard sieve 42 is expressed in mass %.

A: less than 0.5%

B: more than 0.5% and less than 1%

C: more than 1%

The content of sieve openings of JIS standard sieve 60 is expressed in mass %.

A: less than 5%

B: more than 5% and less than 10%

C: more than 10%

In addition, the content of 42 mesh and the content of 60 mesh showed that the smaller the value, the smaller the coarse particles, the sharper the particle size distribution, and the better the stability of polymerization.

(3) Volumetric specific gravity

Measured according to JIS-K6720-2 (1999).

(4) Absorbability of plasticizer

The mass (Ag) of a 5 mL syringe filled with 0.02 g of absorbent cotton was measured, 0.5 g of vinyl chloride polymer particles were added thereto, the mass (Bg) was measured, and 1 g of dioctylphthalate (DOP) was added thereto. After standing for 15 minutes, centrifugation was performed at 3000 rpm for 40 minutes, and the mass (Cg) was measured. Then, the plasticizer absorbency (%) was determined from the following calculation formula. It shows that the higher the absorbency of the plasticizer, the easier the processing, and the less likely it is that defects generated in appearance such as protrusions are generated when the sheet is processed.

Plasticizer absorption (%)=100×[{(C-A)/(B-A)}-1]

(5) Fisheye

At 150°C, 100 parts of the obtained vinyl chloride polymer particles, 50 parts of DOP, 5 parts of tribasic lead sulfate and 1 part of zinc stearate were subjected to roller kneading for 7 minutes to prepare a thin sheet with a thickness of 0.1 mm and measured every 1000 cm. ^2. The number of fisheyes.

Example 2~12

Except that the types and amounts of modified PVA (A), PVA (B), and PVA (C) used as dispersion stabilizers were changed as shown in Table 2, the same procedure as in Example 1 was performed to carry out vinyl chloride. The suspension polymerization. The conditions and results are shown in Table 2 and Table 3.

Comparative example 1

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (A8) was used as the modified PVA (A) as shown in Table 2. Table 3 shows the results. Since the degree of polymerization of PVA (A8) is too low, the polymerization is unstable, the average particle size of the obtained vinyl chloride polymer particles is large, the proportion of coarse particles is also large, the volume specific gravity is low, and there are also many fish eyes.

Comparative example 2

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (A9) was used as the modified PVA (A) as shown in Table 2. Table 3 shows the results. Since the degree of polymerization of PVA (A9) is too high, the volume specific gravity, plasticizer absorption is low, and there are many fish eyes.

Comparative Example 3

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (A10) was used as the modified PVA (A) as shown in Table 2. Table 3 shows the results. Since the degree of saponification of PVA (A10) is too high, the average particle diameter of the obtained vinyl chloride polymer particles is large, the plasticizer absorption is low, and there are many fish eyes.

Comparative Example 4

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (A11) was used as the modified PVA (A) as shown in Table 2. Table 3 shows the results. Since the side chain of PVA (A11) does not have a double bond derived from at least one selected from the group consisting of itaconic acid and its derivatives, methacrylic acid and its derivatives, the polymerization is unstable, so The obtained vinyl chloride polymer particles have a large average particle size, a large proportion of coarse particles, a low volume specific gravity, and a large number of fish eyes.

Comparative example 5

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (A12) was used as the modified PVA (A) as shown in Table 2. Table 3 shows the results. Since the amount of double bonds of PVA (A12) on the side chain is too large, the plasticizer has low absorption and many fish eyes.

Comparative Example 6

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that modified PVA (A) was not used as shown in Table 2. Table 3 shows the results. Since the modified PVA (A) is not used, the polymerization is unstable, the average particle size of the obtained vinyl chloride polymer particles is large, the proportion of coarse particles is also large, the volume specific gravity is low, and the number of fish eyes is also large.

Comparative Example 7

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (B) was not used as shown in Table 2. Table 3 shows the results. Since PVA (B) is not used, the plasticizer has low absorption and many fish eyes.

Comparative Example 8

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that the amounts of modified PVA (A), PVA (B), and PVA (C) were changed as shown in Table 2. Table 3 shows the results. Due to the large amount of PVA (B) and the small amount of PVA (C), the polymerization is unstable, the average particle size of the vinyl chloride polymer particles obtained is large, the proportion of coarse particles is also large, the volume specific gravity is low, fish There are also many eyes.

Comparative Example 9

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that the amounts of modified PVA (A), PVA (B), and PVA (C) were changed as shown in Table 2. Table 3 shows the results. Due to the large amount of PVA(A) used, the plasticizer has low absorption and many fish eyes.

Comparative Example 10

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (B) with a high degree of saponification was used as shown in Table 2. Table 3 shows the results. Since PVA (B) has a high degree of saponification, the plasticizer has low absorbency and many fish eyes.

Comparative Example 11

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (C) with a high degree of saponification was used as shown in Table 2. Table 3 shows the results. Since the degree of saponification of PVA(C) is too high, the absorbency of plasticizer is low and there are many fish eyes.

Comparative Example 12

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (C) having a low degree of polymerization was used as shown in Table 2. Table 3 shows the results. Since the degree of polymerization of PVA(C) is too low, the polymerization is unstable, the average particle size of the obtained vinyl chloride polymer particles is large, the proportion of coarse particles is also large, the volume specific gravity is low, and the number of fish eyes is also large.

Comparative Example 13

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (B) having a low degree of polymerization was used as shown in Table 2. Table 3 shows the results. Since the degree of polymerization of PVA (B) is too low, the polymerization is unstable, the average particle size of the obtained vinyl chloride polymer particles is large, the proportion of coarse particles is also large, the volume specific gravity is low, and there are also many fish eyes.

Comparative Example 14

The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that PVA (B) and PVA (C) were not used and the amount of modified PVA (A) was changed as shown in Table 2. Table 3 shows the results. Since PVA (B) and PVA (C) are not used, the plasticizer has low absorption and many fish eyes.

[table 3]

As shown in the examples, when a vinyl compound such as vinyl chloride is suspended and polymerized to produce an ethylene-based polymer, modified PVA(A), PVA(B) and PVA(PVA(B) and PVA( C), can improve the stability of polymerization. As a result, it is possible to provide an ethylene-based polymer in which coarse particles are generated, the molded product has less fish eyes, and has both plasticizer absorbability and volume specific gravity. Therefore, the industrial utility of the present invention is extremely high.

Claims (3)

A manufacturing method, which is a method for manufacturing an ethylene-based polymer in which a vinyl compound is suspension polymerized in the presence of a dispersion stabilizer, wherein, The dispersion stabilizer contains modified polyvinyl alcohol (A), polyvinyl alcohol (B) and polyvinyl alcohol (C), The modified polyvinyl alcohol (A) has a double bond of 0.05 mol% or more and less than 0.5 mol% in the side chain. The double bond is derived from the group consisting of itaconic acid and its derivatives, methacrylic acid and its At least one selected from the group of derivatives, The saponification degree of the modified polyvinyl alcohol (A) is 68 mole% or more and less than 77 mole %, and the average viscosity polymerization degree is more than 500 and less than 1500, The degree of saponification of polyvinyl alcohol (B) is 30 mol% or more and less than 60 mol%, and the average degree of viscosity polymerization is 150 or more and less than 600, The degree of saponification of polyvinyl alcohol (C) is 77 mol% or more and less than 90 mol%, and the average viscosity polymerization degree is 1700 or more and less than 3000; and The content of modified polyvinyl alcohol (A) is 10 to 45 parts by mass relative to 100 parts by mass of modified polyvinyl alcohol (A), polyvinyl alcohol (B) and polyvinyl alcohol (C). The content of (B) is 1 to 45 parts by mass, and the content of polyvinyl alcohol (C) is 10 to 89 parts by mass. The manufacturing method according to claim 1, wherein the dispersion stabilizer further contains 0.001 parts by mass or more and less than 5 parts by mass of the compound (D) relative to 100 parts by mass of the modified polyvinyl alcohol (A), The compound (D) is a compound having two or more phenolic hydroxyl groups, a salt thereof, or an oxide thereof. The manufacturing method according to claim 1 or 2, wherein the modified polyvinyl alcohol (A) has a double bond derived from itaconic acid on the side chain.