JP2008255225A - Dispersion stabilizer for suspension polymerization of vinyl monomer and vinyl polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion stabilizer which exhibits the performance of stabilizing the suspension polymerization of a vinyl chloride monomer in a small use amount to the excellent dispersion force of the vinyl chloride monomer in an aqueous medium and fully satisfies a function required for an dispersion stabilizer in the suspension polymerization to obtain a vinyl chloride resin due to reduced deterioration of the resin properties, although the vinyl chloride monomer remains in the vinyl chloride resin obtained by polymerization and a high quality vinyl chloride resin produced by using the same. <P>SOLUTION: A dispersing stabilizer for the suspension polymerization of a vinyl monomer comprises a modified polyvinyl alcohol resin containing a structural unit having chlorine in the side chain whose content is 0.1-20 mol%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a dispersion stabilizer for use in suspension polymerization of vinyl monomers, particularly polymerization of vinyl chloride monomers or copolymerization of vinyl chloride monomers with other vinyl monomers. More specifically, the dispersion stabilizer used in suspension polymerization, and more specifically, the dispersion stabilizer for suspension polymerization in which a vinyl chloride resin having good physical properties and excellent physical properties can be obtained, and the chlorination produced using the dispersion stabilizer. The present invention relates to a vinyl resin.

  The industrial production method of vinyl chloride resins such as vinyl chloride resin, vinyl chloride-vinyl acetate copolymer and saponified product thereof is based on the use of vinyl monomers such as vinyl chloride in the presence of a dispersion stabilizer in an aqueous medium. In general, it is carried out by batch suspension polymerization in which a body (monomer) is dispersed and polymerization is carried out using an oil-soluble polymerization initiator. Factors in the polymerization process that govern the quality of vinyl chloride resin include polymerization rate, ratio of aqueous medium to monomer, polymerization temperature, type and amount of polymerization initiator, type of polymerization tank, stirring speed, and type of dispersion stabilizer. Among them, the influence of the dispersion stabilizer is very large.

The role of the dispersion stabilizer in suspension polymerization to obtain a vinyl chloride resin is to disperse the monomer in an aqueous medium to form stable droplets, and to uniformize the size of the droplets that repeat dispersion and coalescence. The purpose is to control the cohesiveness of the polymerized particles. For this reason, as performance required for such a dispersion stabilizer,
<1> Sharpening the particle size distribution of the obtained vinyl resin particles,
<2> Making the resulting vinyl-based resin particles porous, increasing plasticizer absorbability and improving moldability,
<3> Making the porosity of the vinyl chloride resin particles within a certain range to facilitate the removal of residual monomers,
<4> Increase the bulk specific gravity of the vinyl chloride resin particles and improve the processability of the vinyl chloride resin.
Is mentioned.

Further, the dispersion stabilizer is indispensable for carrying out the polymerization, but it remains in the resin after the completion of the polymerization. Therefore, in addition to the above performances <1> to <4>, the dispersion stabilizer is further required. As the performance
<5> Do not adversely affect the processability of the vinyl chloride resin particles and do not cause fish eyes when molded into sheets,
<6> Do not adversely affect the hue and transparency of the vinyl chloride resin,
Is mentioned.

  That is, to summarize the performance required for the above dispersion stabilizer, it exhibits excellent dispersing power in a small amount, and controls the particle diameter, particle shape, etc. of the vinyl chloride resin to an appropriate state (active performance) Even if it remains in the vinyl chloride resin, it is broadly classified as having no adverse effect during subsequent processing or use (passive performance).

  As the dispersion stabilizer, polyvinyl alcohol resins (hereinafter, polyvinyl alcohol is abbreviated as PVA), cellulose derivatives and the like are generally used alone or in combination, and PVA resins are most widely used. Although it is used, it cannot be said that the above-mentioned required performance is sufficiently satisfied, and various studies are being continued.

  For example, Non-Patent Document 1 discloses a dispersion stabilizer for suspension polymerization of vinyl chloride having a viscosity average polymerization degree of 2000, a saponification degree of 88 mol% or 80 mol%, PVA having a high emulsifying power, and a viscosity. A method is described in which PVA is used which has an average degree of polymerization of 600 to 700 and a degree of saponification of about 70 mol%, and precipitates at the polymerization temperature of the vinyl chloride resin.

  Further, Patent Document 1 discloses a polymerization degree obtained by adding sodium acetate to PVA obtained by saponifying polyvinyl acetate obtained by polymerization in the presence of aldehydes and the like, followed by heat treatment. A method of using PVA having a saponification degree of not more than 1500 and a saponification degree of not more than 90 mol% and having a carbonyl group and a vinylene group in two or three chains as a dispersion stabilizer for suspension polymerization of vinyl chlorides is shown. Yes.

  Furthermore, Patent Document 2 discloses that the absorbance at a wavelength of 280 nm and a wavelength of 320 nm of a 0.1 wt% aqueous solution, which is an index representing the vinylene group content in the molecule, is a certain value or more, and the ratio is a certain value or more. Certain PVAs are indicated as dispersion stabilizers for suspension polymerization of vinyl chlorides.

  Other examples include ethylene-modified PVA (Patent Document 3), PVA having 1,2-diol in the side chain (Patent Document 4), PVA having a C2-C20 hydroxyalkyl group (Patent Document 5), and the like. As described above, various modified PVAs have been studied as dispersion stabilizers.

  For actual suspension polymerization of vinyl chloride monomers, they are used in combination. Particularly, the average polymerization degree is 2000 or more as described in Non-Patent Document 1, and the saponification degree is about 80 mol. % Of unmodified PVA and a PVA having a vinylene group as described in Patent Document 1, having a polymerization degree of 1000 or less and a saponification degree of around 70 mol% are generally used in combination. is there.

Prior art document information related to the invention of the present application cited above is as follows.
Japanese Patent Publication No.58-2962 JP 2004-189889 A JP-A-8-259609 JP 2006-241448 A JP-A-9-77807 “Poval”, published by Kobunshi Publishing, 1989.

  Among those disclosed as dispersion stabilizers in the above prior art information, the PVA described in Non-Patent Document 1 basically has insufficient dispersion power, which causes a problem in the stability of suspension polymerization. There is a tendency that coarse particles tend to be generated, and the particle size distribution of the obtained vinyl chloride resin is not sharp and the plasticizer absorbability is poor. In the PVA described in Patent Documents 1 and 2, the dispersibility of the vinyl chloride monomer is improved as compared with the PVA described in Non-Patent Document 1, but the PVA remaining in the vinyl chloride resin is reduced. There was a problem of adversely affecting the hue and transparency of the vinyl chloride resin. Moreover, also in various modified PVA represented by PVA of patent documents 3-5, what satisfy | fills all the required performance of <1>-<6> is not obtained.

  After all, PVA as proposed as a conventional dispersion stabilizer is essentially insufficient in dispersing power for vinyl chloride monomers, and therefore, when used in a small amount, the above <1> to <4 The required performance (active performance) of> cannot be fully satisfied. On the other hand, when the amount of PVA used is increased, suspension polymerization of the vinyl chloride monomer is stabilized and can satisfy the required performances of <1> to <4>. A large amount of PVA remains, which causes a problem that the required performance (passive performance) of <5> to <6> cannot be satisfied. That is, in suspension polymerization, in order to sufficiently disperse a vinyl chloride monomer in an aqueous medium, it is necessary to increase the amount of dispersion stabilizer added. Residues in the vinyl resin particles adversely affect the physical properties of the resin, and this adverse effect becomes significant as the amount of dispersion stabilizer added increases.

  In particular, among vinyl chloride resins produced by suspension polymerization using a dispersion stabilizer, resins made of vinyl chloride-vinyl acetate copolymer or a saponified product thereof are dissolved in a solvent such as a ketone and used as an ink or paint. When used as a binder, there is a problem that the dispersion stabilizer remaining in the resin and the grafted product thereof are not dissolved in the solvent, and the solution becomes turbid, leading to a decrease in quality.

  In order to solve such a trade-off problem, a dispersion stabilizer having essentially high dispersibility that can disperse a vinyl chloride monomer in a small amount is used, and suspension polymerization is performed. It is necessary to use a dispersion stabilizer having a structure that does not adversely affect the physical properties of the resin even if it remains in the resulting vinyl chloride resin. However, PVA or modified PVA used as a conventional dispersion stabilizer is a polymer having a completely different structure from vinyl chloride resin and lacks the dispersion power of vinyl chloride monomers. There has been a problem that deterioration of physical properties of the resin due to remaining in the vinyl resin cannot be avoided.

  That is, the object of the present invention is extremely excellent in the dispersibility of the vinyl chloride monomer in an aqueous medium, and thus exhibits the ability to stabilize suspension polymerization of the vinyl chloride monomer with a small amount of use. And a dispersion stabilizer in suspension polymerization for obtaining the vinyl chloride resins of the above <1> to <6>, because even if they remain in the vinyl chloride resin obtained by polymerization, the physical properties of the resin are small. The present invention is to provide a dispersion stabilizer that sufficiently satisfies the functions required for the present invention, and to provide a high-quality vinyl chloride resin produced using the dispersion stabilizer.

  However, in view of such circumstances, the present inventor has conducted extensive research and as a result, has included a structural unit having chlorine in the side chain, and the modified PVA resin having a content of 0.1 to 20 mol% is vinyl-based. The present inventors have found that the above-mentioned problems can be solved by using a dispersion stabilizer for suspension polymerization of a monomer, and further researched to complete the present invention.

That is, the present invention
[1] For suspension polymerization of a vinyl monomer, comprising a modified polyvinyl alcohol resin containing a structural unit having chlorine in the side chain and a content of 0.1 to 20 mol% Dispersion stabilizer,
[2] The dispersion stabilizer for suspension polymerization according to [1] above, wherein the modified polyvinyl alcohol resin is a saponified product of vinyl chloride-vinyl acetate copolymer,
[3] The dispersion stabilizer for suspension polymerization as described in [1] above, wherein the modified polyvinyl alcohol resin is a saponified product of vinylidene chloride-vinyl acetate copolymer,
[4] The suspension according to any one of [1] to [3], wherein the modified polyvinyl alcohol resin has a saponification degree of 50 to 95 mol% and an average polymerization degree of 400 to 5000. Dispersion stabilizer for turbid polymerization,
[5] Any one of [1] to [4] above, wherein the vinyl monomer is a mixture of a vinyl chloride monomer or another monomer copolymerizable therewith. A dispersion stabilizer for suspension polymerization as described in
[6] A vinyl polymer characterized by suspension-polymerizing a vinyl monomer using the dispersion stabilizer for suspension polymerization described in any one of [1] to [5] above. Production method and [7] Chlorination produced by suspension polymerization of a vinyl monomer using the dispersion stabilizer for suspension polymerization described in any one of [1] to [5] above. Vinyl resin or vinyl chloride-vinyl acetate copolymer or saponified product thereof,
About.

  The dispersion stabilizer for suspension polymerization of vinyl monomers of the present invention is extremely excellent in the dispersion power of vinyl chloride monomers in an aqueous medium, so that suspension polymerization is excellently stabilized with a small amount of use. Can be made. For this reason, the resulting vinyl chloride resin has a sharp particle size distribution, a high bulk specific gravity, and is porous, so that it has good plasticizer absorbability, and the amount of dispersion stabilizer used is small. The remaining amount is small. Moreover, the residual dispersion stabilizer is similar in structure to the vinyl chloride resin, so there is little adverse effect on the quality of the vinyl chloride resin, no fish eye is produced, and there is no deterioration in hue or transparency. It is extremely useful for producing quality vinyl chloride resins.

The present invention is described in detail below.
The modified PVA resin used as a dispersion stabilizer for suspension polymerization of the vinyl monomer of the present invention (hereinafter sometimes abbreviated as “dispersion stabilizer of the present invention”) is a vinyl acetate structural unit of PVA. In addition to the vinyl alcohol structural unit, it is essential to contain a structural unit having chlorine in the side chain, and the content of the structural unit having chlorine is 0.1 to 20 mol%, preferably It is 0.5-15 mol%, More preferably, it is 1-10 mol%. If the content of the structural unit having chlorine is too small, the dispersion performance (meaning the performance of dispersing the vinyl chloride monomer in the aqueous medium) becomes low and the intended effect of the present invention cannot be obtained. On the other hand, if the content exceeds 20 mol%, the modified PVA resin becomes poor in water solubility, and cannot be used as a dispersion stabilizer for suspension polymerization.

  Examples of the structural unit having chlorine in the side chain include structural units such as vinyl chloride, vinylidene chloride, allyl chloride, vinyl monochloroacetate, vinyl dichloroacetate, vinyl trichloroacetate, methacrylic acid chloride, acrylic acid chloride, and methallyl chloride. Among them, vinyl chloride and vinylidene chloride are preferable. Accordingly, examples of a preferred modified PVA resin used as the dispersion stabilizer of the present invention include a saponified product of vinyl chloride-vinyl acetate copolymer and a saponified product of vinylidene chloride-vinyl acetate copolymer. The modified PVA-based resin may contain only one type of structural unit having chlorine in the side chain, and may contain two or more types at the same time.

  The degree of polymerization of the modified PVA resin used as the dispersion stabilizer of the present invention is not particularly limited, but the degree of polymerization determined by the average polymerization degree measurement method of PVA specified in JIS K 6726 is 400 to 5000. Is more preferable, and 500 to 3000 is more preferable. If the degree of polymerization of the modified PVA resin is too low, the dispersion performance as the dispersion stabilizer of the present invention may be lowered. If the degree of polymerization is too high, the aqueous solution viscosity when dissolved in water is high. Therefore, it becomes difficult to handle and the viscosity of the dispersion medium becomes too high during suspension polymerization, which may adversely affect the polymerization.

  The saponification degree of the modified PVA resin used as the dispersion stabilizer of the present invention is not particularly limited, but the saponification degree required by the method for measuring the saponification degree of PVA defined in JIS K 6726 is 50 to 50. It is preferably 95 mol%, more preferably 70 to 90 mol%. If the degree of saponification is too low, it is difficult to dissolve in water and may not function as a dispersion stabilizer in an aqueous medium. On the other hand, if the degree of saponification is too high, the dispersion performance as a dispersion stabilizer of the present invention May decrease. The water solubility of the resin in the present invention is affected not only by the degree of saponification but also by the content of structural units having chlorine in the side chain, the degree of polymerization, and the type of aqueous medium used for suspension polymerization. Therefore, the saponification degree, the polymerization degree, and the content of the structural unit having chlorine may be appropriately selected within a range that dissolves in the aqueous medium to be used.

The modified PVA resin used as the dispersion stabilizer of the present invention was obtained by, for example, (1) copolymerizing a fatty acid vinyl ester and an ethylenically unsaturated monomer having chlorine in the side chain. A method of saponifying the copolymer,
(2) A method in which a PVA resin and an ethylenically unsaturated monomer having chlorine in the side chain are heated and mixed in the presence of an appropriate solvent and a polymerization initiator, and graft copolymerized.
(3) A method of adding a known chlorine compound having a functional group having reactivity with a hydroxyl group of PVA resin or other functional groups such as chlorobenzaldehyde, chlorobenzoic acid or epichlorohydrin to PVA resin,
However, the method (1) is preferably employed from the viewpoint of uniformity of quality and manufacturing cost.

  Examples of the ethylenically unsaturated monomer having chlorine in the side chain used in the production methods (1) and (2) described above include vinyl chloride, vinylidene chloride, allyl chloride, vinyl monochloroacetate, vinyl dichloroacetate, Examples thereof include vinyl trichloroacetate, methacrylic acid chloride, acrylic acid chloride, and methallyl chloride, and vinyl chloride and vinylidene chloride are preferable from the viewpoint of stability of the compound, polymerizability, and cost.

  Examples of the fatty acid vinyl ester used in the production method (1) include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, and industrially preferred is vinyl acetate.

  When copolymerization is performed by the production methods of (1) and (2), an ethylenically unsaturated monomer other than a monomer having chlorine in the side chain is used for copolymerization within a range not impairing the effects of the present invention. May be. Examples of the ethylenically unsaturated monomer other than the monomer having chlorine in the side chain include α-olefins such as ethylene, propylene and 1-butene, acrylic acid, methacrylic acid and salts thereof, acrylic acid and methacrylic acid. Esters, acrylamides such as acrylamide and N-methyl acrylamide, diacetone acrylamide, methacrylamides such as methacrylamide and N-methyl methacrylamide, vinyl ethers such as methyl vinyl ether, nitriles such as acrylonitrile, methacrylonitrile, Non-chlorinated vinyl halides such as vinyl fluoride, allyl compounds such as allyl acetate, unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid and salts or esters thereof, vinyltrimethoxysilane, etc. Although Nirushiriru compounds and the like are exemplified, but not limited thereto.

  In the production method of (1), examples of the polymerization method for obtaining the copolymer include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, and the saponification reaction performed after controlling the polymerization degree or after polymerization. In view of the above, solution polymerization using methanol as a solvent or suspension polymerization using water or water / methanol as a dispersion medium is advantageous, but is not limited thereto.

  Further, the saponification method of the copolymer is not particularly limited, and known acid saponification and alkali saponification can be applied. Among them, a methanol solution of the copolymer or methanol and water, methyl acetate and benzene A method of adding an alkali hydroxide to a mixed solvent solution with one or more solvents selected from the group and subjecting to alcoholysis is industrially preferable.

In the production method (2), as a method for obtaining a graft copolymer, a known homogeneous or heterogeneous graft copolymerization method can be used. For example, PVA is dissolved in water and an azo-based initiator is started. In the presence of an agent, an ethylenically unsaturated monomer having chlorine in the side chain is added, and the mixture is heated and stirred to obtain a graft copolymer. And a method for removing a homopolymer of an ethylenically unsaturated monomer having chlorine in the chain.

  In addition, in the production method of (3), a known reaction is used as a method of adding a chlorine compound having a functional group reactive to the hydroxyl group or other functional group of the PVA resin to the PVA resin. For example, a method of adding a chlorine-containing compound having an aldehyde group such as chlorobenzaldehyde to an aqueous PVA solution and reacting the hydroxyl group of PVA with an aldehyde group under an acidic condition can be mentioned.

  In the above production methods (1) to (3), the degree of polymerization of the modified PVA resin in the present invention can be controlled. That is, in the production method of (1), the degree of polymerization of the resin is controlled by changing the monomer blending ratio and polymerization yield at the time of polymerization or by using a known chain transfer agent as necessary. In the production methods (2) and (3), the degree of polymerization of the resin can be controlled by making the PVA resin used as a raw material have a desired degree of polymerization.

  In addition, the degree of saponification of the modified PVA resin in the present invention can be controlled. That is, in the production method (1), the saponification degree of the resin can be controlled by changing the amount of acid or alkali used in the saponification reaction, temperature, concentration, reaction time, solvent composition, or the like. In the production methods (2) and (3), the saponification degree of the modified PVA resin can be controlled by making the PVA resin used as a raw material have a desired saponification degree.

  Next, the use of the dispersion stabilizer of the present invention composed of the above-described modified PVA resin or a method for producing a vinyl polymer by suspension polymerization of a vinyl monomer using the same will be described.

  The suspension polymerization in the present invention is to form minute droplets made of a vinyl monomer by adding an insoluble vinyl monomer and an oil-soluble polymerization initiator to an aqueous medium and stirring them. This is a polymerization mode in which polymerization is performed in the droplets. Examples of the aqueous medium that can be used here include water, an aqueous solution containing various additive components, and a mixed solvent of water and an organic solvent having compatibility with water.

  The above modified PVA resin in the present invention can be used as a dispersion stabilizer when carrying out suspension polymerization of a vinyl monomer. Vinyl chloride, vinylidene chloride, styrene, acrylic ester, methacrylic ester In particular, vinyl monomers such as vinyl acetate and acrylonitrile to which suspension polymerization is generally applied are targeted, and among these, vinyl chloride monomers are suitable for suspension polymerization. Examples of the vinyl chloride monomer include a vinyl chloride monomer, and a mixture of a vinyl chloride monomer and another monomer copolymerizable therewith. Other monomers that can be copolymerized with the vinyl chloride monomer include, for example, vinylidene chloride, vinyl acetate, ethylene, propylene, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, styrene, vinyl alkoxysilane, Examples thereof include monomers such as maleic acid, hydroxyalkyl acrylate, allyl sulfonic acid, and vinyl sulfonic acid.

  Therefore, the dispersion stabilizer of the present invention can be suitably used for homopolymerization of vinyl chloride by suspension polymerization, and one kind selected from known monomers copolymerizable with vinyl chloride by suspension polymerization. It can also be used in binary or higher multi-component copolymerization of the above and vinyl chloride, and can be preferably used as a dispersion stabilizer in copolymerization of vinyl chloride and vinyl acetate by suspension polymerization. .

  The polymerization initiator in the suspension polymerization of the vinyl monomer may be a known one, for example, a percarbonate such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate. Compounds, benzoyl peroxide, t-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, perester compounds such as t-butylperoxydecanoate, acetylcyclohexylsulfonyl peroxide, 2,4, Peroxides such as 4-trimethylpentyl-2-peroxyphenoxyacetate, 2,2′-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis (4-methoxy-2,4-dimethyl Azo compounds such as valeronitrile) And benzoyl peroxide, lauroyl peroxide and the like, further, can also be used in combination of potassium persulfate thereto, ammonium persulfate, hydrogen peroxide and the like.

The main role of the dispersion stabilizer in the suspension polymerization of vinyl monomers is to stabilize the droplets made of the vinyl monomer and its polymer, and the polymer particles produced by the droplets The dispersion stabilizer of the present invention is excellent in dispersion performance, so that stable droplets can be formed with a small amount of use. It is possible to prevent the formation of lumps by the above fusion.
The phrase “droplet is stable” means that fine and almost uniform droplets are stably dispersed in a dispersion medium for suspension polymerization.

  The amount of the dispersion stabilizer of the present invention is not particularly limited, but is usually 5 parts by weight or less with respect to 100 parts by weight of the vinyl monomer, preferably 0.005 to 1 part by weight, More preferably, the content is 01 to 0.2 parts by weight. The dispersion stabilizer of the present invention is generally used in the form of a preliminarily dissolved dispersion medium for suspension polymerization before the vinyl monomer is charged, as in the case of a normal dispersion stabilizer.

  As the dispersion stabilizer in suspension polymerization, the dispersion stabilizer of the present invention may be used alone, but other dispersion stabilizers may be used in combination, and as such other dispersion stabilizers, Known dispersion stabilizers used in suspension polymerization of vinyl monomers such as vinyl in an aqueous medium, such as PVA having an average polymerization degree of 100 to 4500 and a saponification degree of 30 to 100 mol%, and the present invention Other modified PVA resins, water-soluble cellulose ethers such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, water-soluble polymers such as gelatin, sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide propylene oxide block polymer, etc. Oil-soluble emulsion, polyoxyethylene glycerol oleate, sodium laurate Such as water-soluble emulsifiers such as helium, and the like. Of these other dispersants, one of them may be used, or two or more of them may be used simultaneously.

  In the present invention, it is preferable to use a combination of two or more PVA resins having different degrees of polymerization and saponification as the dispersion stabilizer, and one or more of them are the dispersion stabilizer of the present invention. It is preferable to use a modified PVA resin. More preferably, a PVA resin having a high emulsifying power having a polymerization degree of 1700 or more and a PVA resin of a type having a polymerization degree of 900 or less and precipitated at a high temperature are used in combination, and one or more of them are used as side chains. A modified PVA-based resin containing a structural unit having chlorine is used.

  In the suspension polymerization using the dispersion stabilizer of the present invention, various known dispersion aids can be used in combination, and such dispersion aids have an average polymerization degree of 30 to 60 mol% saponification degree. A low saponification degree PVA of 180 to 900 is preferably used. It is more preferable to use a modified PVA having a saponification degree of 30 to 50 mol%, an average polymerization degree of 200 to 500 and containing a structural unit having chlorine in the side chain as a dispersion aid.

  In addition to the dispersion aid, various known additives may be used in combination in the suspension polymerization of vinyl compounds such as a chain transfer agent, a polymerization inhibitor, a pH adjuster, a scale inhibitor, and a crosslinking agent.

  There is no restriction | limiting in the polymerization temperature in suspension polymerization, Although it can select arbitrarily according to the kind of vinyl monomer to be used, polymerization conditions, the target polymerization yield, etc., it is preferable that it is 30-80 degreeC. . The polymerization time is not particularly limited, and may be set as appropriate according to the degree of polymerization of the target polymer.

  The vinyl chloride resin obtained by the production method of the present invention has a sharp particle size distribution of polymer particles, a high bulk specific gravity, and good plasticizer absorbability, so that it can be easily processed into various molded products. When formed, there are few fish eyes, and hue and transparency are good. The vinyl chloride-vinyl acetate copolymer produced by the method of the present invention is highly transparent even when dissolved in a solvent such as a ketone, and is suitable as a binder for inks and paints.

EXAMPLES The present invention will be described more specifically with reference to examples below, 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.

Synthesis Example 1 (Production of modified PVA containing a structural unit having chlorine in the side chain)
A pressure reactor equipped with a stirrer, a condenser, a nitrogen gas inlet, a monomer inlet and an initiator inlet was charged with 150 parts of methanol and 850 parts of vinyl acetate monomer in advance, heated to 60 ° C., and then nitrogend for 30 minutes. After the gas was blown and the inside of the system was purged with nitrogen, the inside of the system was pressurized to 1.0 kg / cm ² with nitrogen. Next, 1 part of a 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) previously substituted with nitrogen was added as an initiator, and at the same time, a vinyl chloride monomer was added and polymerized. Started.
During polymerization, the system was maintained at 60 ° C., nitrogen pressure was maintained, and 3.5 parts of a 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) was started. Immediately after that, it was continuously added over 2 hours, and 10.5 parts of vinyl chloride monomer was continuously added over 2.5 hours from the start of polymerization.
Three hours after the start of polymerization, when the reaction yield of vinyl acetate reached 52%, the system was cooled to complete the polymerization. While methanol vapor was added to the obtained reaction product, the remaining vinyl acetate monomer and vinyl chloride monomer were distilled off to obtain a 40% methanol solution of vinyl chloride-vinyl acetate copolymer.

Next, to 500 parts of the 40% methanol solution of the vinyl chloride-vinyl acetate copolymer obtained above, 120 parts of methanol, 20 parts of benzene, and 40 parts of 1% methanol solution of sodium hydroxide were added and mixed well. A saponification reaction was performed at 40 ° C., and the resulting gel-like material was pulverized, washed with methanol and then dried to obtain vinyl chloride-modified PVA.
This modified PVA had a vinyl chloride unit content of 3.1 mol%, a saponification degree of 82.6 mol%, and an average polymerization degree of 2470.

The content of the structural unit having chlorine in the modified PVA is determined by decomposing a precisely weighed sample by an oxygen flask combustion method, absorbing the generated chlorine gas in hydrogen peroxide solution, and titrating with a silver nitrate aqueous solution. The chlorine content was determined, and the content was calculated in terms of mol% from the unit molecular weight of the structural unit containing chlorine (the same applies to Synthesis Examples 2 to 7 and Comparative Synthesis Examples 1 to 4 below).
The saponification degree and average polymerization degree of the modified PVA were measured according to JIS K 6726 (the same applies to the following Synthesis Examples 2 to 7 and Comparative Synthesis Examples 1 to 4).

Synthesis Examples 2 to 5 (Production of modified PVA containing a structural unit having chlorine in the side chain)
Table 2 below shows the same as in Synthesis Example 1 except that the amounts of methanol, vinyl acetate monomer and vinyl chloride monomer used, the polymerization initiator, the polymerization time, and the amount of sodium hydroxide used for the saponification reaction were appropriately changed. A vinyl chloride-modified PVA having such a vinyl chloride unit content, saponification degree and average polymerization degree was obtained.

Synthesis Example 6 (Production of modified PVA containing a structural unit having chlorine in the side chain)
A pressure reactor equipped with a stirrer, condenser, nitrogen gas inlet, monomer inlet and initiator inlet was charged with 150 parts of methanol and 850 parts of vinyl acetate in advance, heated to 60 ° C., and then nitrogen gas for 30 minutes. Then, the inside of the system was purged with nitrogen, and then the inside of the system was pressurized to 0.7 kg / cm ² with nitrogen. Next, 1 part of a 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) previously substituted with nitrogen as an initiator was added, and at the same time, a vinylidene chloride monomer was added and polymerization was performed. Started.
During the polymerization, the system was maintained at 60 ° C., the nitrogen pressure was maintained, and 4 parts of 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) was added immediately after the start of the polymerization. It was continuously added over 2.5 hours, and 16 parts of vinylidene chloride monomer was continuously added over 3 hours from the start of polymerization.
After 3.5 hours from the start of polymerization, when the reaction yield of vinyl acetate reached 54%, the system was cooled to complete the polymerization. While methanol vapor was added to the resulting reaction product, the remaining vinyl acetate monomer and vinylidene chloride monomer were distilled off to obtain a 40% methanol solution of vinylidene chloride-vinyl acetate copolymer.

Next, to 500 parts of 40% methanol solution of vinylidene chloride-vinyl acetate copolymer obtained above, 100 parts of methanol, 20 parts of benzene, 60 parts of 1% methanol solution of sodium hydroxide were added and mixed well. A saponification reaction was performed at 40 ° C., and the resulting gel-like material was pulverized, washed with methanol, and dried to obtain vinylidene chloride-modified PVA.
This modified PVA had a vinylidene chloride unit content of 3.0 mol%, a saponification degree of 83.5 mol%, and an average polymerization degree of 2450.

Synthesis Example 7 (Production of modified PVA containing a structural unit having chlorine in the side chain)
As shown in Table 2 below, in the same manner as in Synthesis Example 8, except that the amount of methanol, vinyl acetate monomer and vinylidene chloride monomer charged, the polymerization initiator, the polymerization time, and the amount of sodium hydroxide used for the saponification reaction were changed. A vinylidene chloride-modified PVA having a vinyl chloride unit content, a saponification degree and an average polymerization degree was obtained.

The polymerization conditions in the above synthesis examples are shown in Table 1 below.

Comparative Synthesis Example 1 (Production of PVA resin)
A reactor equipped with a stirrer, condenser, nitrogen gas inlet and initiator inlet is charged with 140 parts of methanol and 860 parts of vinyl acetate monomer in advance, and the temperature is raised to 60 ° C. while nitrogen gas is circulated in the system. 0.5 parts of a 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) was added as an agent to initiate polymerization.
During the polymerization, the system is maintained at 60 ° C., and a normal pressure is passed while flowing nitrogen gas through the system. Further, a 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) is used. 5 parts were added continuously over 2 hours immediately after the start of polymerization. 2.5 hours after the start of polymerization, when the reaction yield of vinyl acetate reached 55%, the system was cooled to complete the polymerization. While methanol vapor was added to the obtained reaction product, the remaining vinyl acetate monomer was distilled off to obtain a 40% methanol solution of polyvinyl acetate.

  Next, 120 parts of methanol, 20 parts of benzene and 15 parts of 1% methanol solution of sodium hydroxide are added to 500 parts of the 40% methanol solution of polyvinyl acetate obtained above and mixed well, and saponified at 40 ° C. The reaction was carried out, and the resulting gel-like material was pulverized, washed with methanol and dried to obtain PVA having a saponification degree of 80.2 mol% and an average polymerization degree of 2530.

Comparative Synthesis Examples 2-3 (Production of PVA resin)
Saponification as shown in Table 2 below in the same manner as in Comparative Synthesis Example 1 except that the amount of methanol and vinyl acetate monomer used, the polymerization initiator, the polymerization time, and the amount of sodium hydroxide used for the saponification reaction were changed. PVA having a degree of polymerization and an average degree of polymerization was obtained.

Comparative Synthesis Example 4 (Production of PVA resin)
A reactor equipped with a stirrer, condenser, nitrogen gas inlet and initiator inlet was charged with 90 parts of methanol, 880 parts of vinyl acetate and 30 parts of acetaldehyde in advance, and the temperature was raised to 60 ° C. while circulating nitrogen gas in the system. Then, 0.5 part of a 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) was added as an initiator to initiate polymerization. During the polymerization, the system is maintained at 60 ° C., and a normal pressure is passed while flowing nitrogen gas through the system. Further, a 1% methanol solution of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) is used. 5 parts were continuously added over 2 hours immediately after the start of polymerization. 2.5 hours after the start of polymerization, when the reaction yield of vinyl acetate reached 85%, the system was cooled to complete the polymerization. While methanol vapor was added to the obtained reaction product, the remaining vinyl acetate monomer was distilled off to obtain a 50% methanol solution of polyvinyl acetate.

  Next, to 500 parts of 50% methanol solution of polyvinyl acetate obtained above, 120 parts of methanol and 12 parts of 1% methanol solution of sodium hydroxide were added and mixed well, and a saponification reaction was performed at 40 ° C., The obtained gel was pulverized to obtain partially saponified PVA having a polymerization degree of 790 and a saponification degree of 71.1 mol%.

  1 part of sodium acetate was added to 100 parts of this partially saponified PVA and mixed well, followed by heat treatment at 127 ° C. for 2 hours to obtain a PVA resin equivalent to that described in Patent Document 1. The analysis values of this PVA resin are a saponification degree of 71.4 mol% and a polymerization degree of 790, the absorbance at a wavelength of 280 nm of a 0.1% aqueous solution is 0.26, and the absorbance at a wavelength of 320 nm is 0.13. The ratio of absorbance at 320 nm to absorbance at 280 nm was 0.50.

The properties of the modified PVA obtained in the above synthesis example and the PVA resin obtained in the comparative synthesis example are shown in Table 2 below.

  In the following examples and comparative examples, any of the modified PVA obtained in the above synthesis examples and the PVA resins obtained in the comparative synthesis examples (hereinafter collectively referred to as PVA resins) is dispersed. Using it as a stabilizer, suspension polymerization of vinyl chloride was carried out.

Examples 1-9 and Comparative Examples 1-4
In a pressure resistant stainless steel polymerizer, 900 parts of deionized water and the PVA resin obtained in the synthesis examples or comparative synthesis examples were charged in the types and amounts shown in Table 2 below. Next, the inside of the polymerization vessel was depressurized to 50 mmHg with a vacuum pump, degassed, charged with 700 parts of vinyl chloride monomer, and 0.42 parts of t-butylperoxyneodecanoate as a polymerization initiator. After stirring, the mixture was stirred and the temperature was raised. Suspension polymerization is carried out while maintaining the temperature of the contents of the polymerization vessel at 57 ° C., and polymerization is performed when the internal pressure of 7.0 kg / cm ^{2 at the} initial stage of polymerization drops to 6.0 kg / cm ² (both gauge pressures). The reaction was stopped. And after recovering the unreacted monomer with a vacuum trap, the polymer slurry was extracted from the polymerization vessel, dehydrated and dried to obtain a polymer (vinyl chloride resin).

  The composition of the dispersion stabilizer used in the above Examples and Comparative Examples is shown in Table 3 below. In each of the above Examples and Comparative Examples, two types of PVA-based resins are used in combination, and the type of PVA-based resin is represented by the number of the synthesis example or the comparative synthesis example from which it was obtained. Moreover, the usage-amount of PVA-type resin is represented by the mass% when the mass of a vinyl chloride monomer is 100%.

Further, various physical properties (particle size distribution, bulk specific gravity, plasticizer absorbability, fish eye, transparency and initial colorability) of the obtained vinyl chloride resin were evaluated as follows.
<Particle size distribution>
From the particle size distribution measured with a low-tap vibration sieve (using a JIS sieve), the content of coarse particles of 60 mesh on and fine particles of 200 mesh pass was expressed in%. The smaller the content of coarse particles and fine particles, the sharper the particle size distribution.
<Bulk specific gravity>
It measured based on JIS K-6721. It shows that extrusion rate improves and workability is so good that bulk specific gravity is large.
<Plasticizer absorbability>
Put the obtained resin in a cylindrical container filled with glass fiber at the bottom, add an excess of dioctyl phthalate (hereinafter abbreviated as DOP), and let it stand for 30 minutes. After excess DOP was removed by centrifugation, the weight of the resin was measured, and the amount of DOP absorbed per 100 parts of the polymer was calculated. The larger the DOP absorption amount, the better the plasticizer absorbability and the better the moldability.
<Fisheye>
100 parts of the obtained resin, 30 parts of dioctyl phthalate, 1 part of tribasic lead sulfate, 1.5 parts of lead stearate, 0.2 part of titanium dioxide, and 0.1 part of carbon black are melt-kneaded at 150 ° C. for 3 minutes. Then, a sheet having a thickness of 0.3 mm was prepared, and the number of fish eyes (transparent particles) per 100 mm × 100 mm was measured.
<Transparency and initial colorability>
100 parts of the obtained resin, 2 parts of a Ba—Zn composite stabilizer, 2 parts of epoxidized soybean oil, and 38 parts of DOP were melt-kneaded at 150 ° C. for 10 minutes to prepare a sheet having a thickness of 0.8 mm. Next, seven sheets of this sheet were stacked and pressed at 180 ° C. for 5 minutes to obtain a laminated sheet having a thickness of 5 mm. The transparency and initial colorability of this laminated sheet were measured using a chromaticity / turbidity measuring device (COH-300A, manufactured by Nippon Denshoku Industries Co., Ltd.), and evaluated by haze and yellowness (YI), respectively.

  The evaluation results are shown in Table 4 below.

Examples 10-13, Comparative Examples 5-6
A pressure resistant stainless steel polymerizer was charged with 500 parts of deionized water, 0.6 part of sodium carbonate, and the PVA resin obtained in the synthesis example or comparative synthesis example in the types and amounts shown in Table 5 below. Next, the inside of the polymerization vessel was depressurized to 50 mmHg with a vacuum pump, degassed, charged with 220 parts of vinyl chloride monomer and 1.5 parts of dodecyl mercaptan, heated to 65 ° C. while stirring, Polymerization was started by adding 5 parts of vinyl acetate monomer and 1 part of t-butyl peroxide as a polymerization initiator. During polymerization, while maintaining the temperature of the content of the polymerization vessel at 65 ° C. and stirring, 25 parts of vinyl acetate monomer was continuously added, and the internal pressure of the polymerization vessel was reduced to 0 within 8 hours from the start of polymerization. When the pressure reached 5 kg / cm ² (gauge pressure), the polymerization reaction was stopped at that time. When the internal pressure of the polymerization vessel did not reach 0.5 kg / cm ² after 8 hours from the start of polymerization, the polymerization reaction was stopped at that point, and the polymerization rate was judged to be very slow, and the polymerization was poor. . And after recovering the unreacted monomer, the polymer slurry was extracted from the polymerization vessel, dehydrated and dried to obtain a vinyl chloride-vinyl acetate copolymer resin.

  The composition of the dispersion stabilizer used in the above Examples and Comparative Examples is shown in Table 5 below. In addition, the kind of PVA-type resin is represented by the synthesis example from which it was obtained, or the comparative synthesis example, and the usage-amount is a mass when the total mass of a vinyl chloride monomer and a vinyl acetate monomer is 100%. Expressed as a percentage.

Moreover, as a physical property of the obtained vinyl chloride-vinyl acetate copolymer resin, transparency when dissolved in a solvent was evaluated as follows.
<Transparency of solution>
40 parts of the obtained vinyl chloride-vinyl acetate copolymer resin, 20 parts of methyl ethyl ketone, 20 parts of methyl isobutyl ketone and 20 parts of toluene were mixed and dissolved with stirring at 20 ° C. for 1 hour. The transparency of the obtained solution was visually determined according to the following criteria.
○: Not turbid and transparent ×: Cloudy (opaque)

  The evaluation results are shown in Table 6 below.

  As shown in the above examples, the dispersion stabilizer composed of a modified PVA resin containing a structural unit having chlorine in the side chain of the present invention in an amount within a predetermined range is a small amount of vinyl monomer. Since the suspension polymerization can be stabilized, the vinyl chloride resins obtained in the examples have a sharp particle size distribution, high bulk specific gravity, good plasticizer absorbability, and when processed into a sheet shape, It was found that there were few eyes, and transparency and hue were excellent. In addition, in the vinyl chloride-vinyl acetate copolymer resin obtained in Examples using the dispersion stabilizer of the present invention, the physical properties of the dispersion stabilizer remaining in the resin such as the solution becoming cloudy when dissolved in a solvent It was found that there was no decline.

Claims (7)

  Dispersion stabilizer for suspension polymerization of vinyl monomers comprising a modified polyvinyl alcohol resin containing a structural unit having chlorine in the side chain and a content of 0.1 to 20 mol% .   2. The dispersion stabilizer for suspension polymerization according to claim 1, wherein the modified polyvinyl alcohol resin is a saponified product of vinyl chloride-vinyl acetate copolymer.   The dispersion stabilizer for suspension polymerization according to claim 1, wherein the modified polyvinyl alcohol resin is a saponified product of vinylidene chloride-vinyl acetate copolymer.   The dispersion stabilizer for suspension polymerization according to any one of claims 1 to 3, wherein the saponification degree of the modified polyvinyl alcohol resin is 50 to 95 mol% and the average degree of polymerization is 400 to 5000. .   The suspension polymerization according to any one of claims 1 to 4, wherein the vinyl monomer is a mixture of a vinyl chloride monomer or another monomer copolymerizable therewith. Dispersion stabilizer for use.   A method for producing a vinyl polymer, wherein the vinyl monomer is subjected to suspension polymerization using the dispersion stabilizer for suspension polymerization according to any one of claims 1 to 5.   A vinyl chloride resin or vinyl chloride-vinyl acetate copolymer produced by suspension polymerization of a vinyl monomer using the dispersion stabilizer for suspension polymerization according to any one of claims 1 to 5. Combined or saponified product.