WO2022259658A1

WO2022259658A1 - Resin composition containing modified polyvinyl alcohol polymer, method for producing said resin composition, dispersion stabilizer for suspension polymerization, and method for producing vinyl resin

Info

Publication number: WO2022259658A1
Application number: PCT/JP2022/009813
Authority: WO
Inventors: 真典松本; 聡渡辺
Original assignee: デンカ株式会社
Priority date: 2021-06-07
Filing date: 2022-03-07
Publication date: 2022-12-15
Also published as: JPWO2022259658A1

Abstract

Provided is a resin composition that contains a modified polyvinyl alcohol polymer useful as a dispersion stabilizer suitable for obtaining resin particles having minute and highly uniform particle sizes, few coarsened particles, and a high bulk specific gravity when suspension-polymerization of a vinyl compound such as vinyl chloride is carried out. The resin composition contains, in a main chain, a modified polyvinyl alcohol polymer having the structural unit shown in general formula (I) and a homopolymer of polyvinyl alcohol. The mass percentage of the homopolymer of polyvinyl alcohol in a total of 100 mass% of the modified polyvinyl alcohol polymer and the homopolymer of polyvinyl alcohol is 0 to 5 mass%. (In the formula, X and Y represent a lower alkyl group having 1 to 12 carbon atoms, a hydrogen atom, or a metal atom, and may be the same or different. Z represents the number of repeating units and is an integer from 0 to 3.)

Description

Resin composition containing modified polyvinyl alcohol polymer, method for producing resin composition, dispersion stabilizer for suspension polymerization, and method for producing vinyl resin

The present invention relates to a resin composition containing a modified polyvinyl alcohol polymer and a method for producing the same. The present invention also relates to a dispersion stabilizer for suspension polymerization, particularly a dispersion stabilizer suitable for suspension polymerization of vinyl compounds, especially vinyl chloride.

In the suspension polymerization of a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith, it is essential to use various dispersion stabilizers, such as polyvinyl alcohol, methylol Dispersion stabilizers such as cellulose are used, among which polyvinyl alcohol (PVA) has excellent properties and is most commonly used. For example, as a dispersion stabilizer for suspension polymerization of vinyl compounds, an aldehyde-derived carbonyl group is introduced at the end of a polyvinyl alcohol polymer, and an unsaturated double bond is formed by undergoing a dehydration reaction or a deacetic acid reaction during saponification. (see, for example, Patent Document 1), and a method of introducing an unsaturated double bond derived from a specific monomer into the main chain of the vinyl alcohol polymer molecule has been proposed (see, for example, Patent Documents 2 and 3). ). Patent Document 2 describes that the content of unmodified PVA in modified PVA into which unsaturated double bonds are introduced is preferably 25% by mass or less. It is stated that the content was in the range of 10-45%.

JP-A-8-208724 WO2006/095462 WO2012/114441

These methods are not adequately compatible with various types of polymerization cans, such as the large polymerization cans that have been used in recent years. That is, vinyl resin particles with non-uniform particle diameters increase the adhesion of scale, or vinyl resin particles with strong dispersing power but poor protective colloid properties are obtained and become coarse, resulting in a decrease in workability. Since vinyl resin particles have poor dispersing power and low plasticizer absorbability, and there are problems such as low bulk specific gravity despite being fine vinyl resin particles, the performance required by users is stably satisfied It was insufficient to stably obtain vinyl resin particles.

Therefore, in one embodiment of the present invention, when a vinyl compound such as vinyl chloride is subjected to suspension polymerization, resin particles that are fine and highly uniform in particle size, have few coarse particles, and have a high bulk specific gravity are obtained. An object of the present invention is to provide a resin composition containing a modified polyvinyl alcohol-based polymer useful as a dispersion stabilizer suitable for

As a result of intensive studies to solve the above problems, the present inventors have found a modified polyvinyl alcohol polymer having a dicarboxylic acid monomer unit and a conjugated double bond in the main chain of polyvinyl alcohol, and polyvinyl alcohol wherein the homopolymer of polyvinyl alcohol accounts for 5% by mass of the total 100% by mass of the modified polyvinyl alcohol-based polymer and the homopolymer of polyvinyl alcohol We have found that it is effective to use the following resin composition.

Patent Document 2 describes that in modified PVA into which unsaturated double bonds are introduced, the content of unmodified PVA is preferably 25% by mass or less. However, in Patent Literature 2, even the lowest content of unmodified PVA is 10% by mass. Patent document 2 does not describe a method for reducing the content of unmodified PVA to 5% by mass or less, nor does it describe an advantageous effect as a dispersion stabilizer obtained thereby.

In one aspect of the present invention, there is provided a resin composition containing a modified polyvinyl alcohol-based polymer having a structural unit represented by general formula (I) in the main chain and a polyvinyl alcohol homopolymer, wherein the modified polyvinyl In the resin composition, the proportion by mass of the homopolymer of polyvinyl alcohol is 0 to 5% by mass in the total 100% by mass of the alcohol-based polymer and the homopolymer of polyvinyl alcohol.

(Wherein, X and Y represent a lower alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal atom, and may be the same or different. Z represents the number of repeating units and is an integer of 0 to 3. )

In one embodiment of the resin composition according to the present invention, the UV absorbance (Abs) of a 0.2% by mass aqueous solution at a wavelength of 280 nm and an optical path length of 10 mm is 0.1 or more and 5.0 or less.

In another embodiment of the resin composition according to the present invention, the UV absorbance (Abs) of a 0.2% by mass aqueous solution at a wavelength of 325 nm and an optical path length of 10 mm is 0.01 or more and 1.0 or less.

In still another embodiment of the resin composition according to the present invention, the resin composition has a saponification degree of 65 to 99.9 mol%.

In still another embodiment of the resin composition according to the present invention, the resin composition contains 0.1 to 5.0 mol % of dicarboxylic acid monomer units.

In another aspect of the present invention, there is provided a method for producing a resin composition according to the present invention, comprising a vinyl ester monomer and an unsaturated monomer deriving a dicarboxylic acid monomer unit represented by general formula (I) a step of obtaining a modified vinyl ester polymer by copolymerizing with a monomer, and a step of saponifying the obtained modified vinyl ester polymer. , intermittently or continuously adding a dicarboxylic acid monomer until a conversion of 90% or more is achieved.

Another aspect of the present invention is a dispersion stabilizer for suspension polymerization containing the resin composition according to the present invention.

In still another aspect of the present invention, a vinyl compound monomer or a mixture of a vinyl compound monomer and a monomer copolymerizable therewith is added to water using a dispersion stabilizer for suspension polymerization. A method for producing a vinyl-based resin including dispersion and suspension polymerization.

When suspension polymerization of a vinyl compound is carried out using the dispersion stabilizer for suspension polymerization of the present invention, resin particles with high uniformity in particle size are obtained with little formation of coarse particles. Since the formation of coarse particles is small, blocking during polymerization is suppressed, and particles having a highly uniform particle size are obtained, thereby reducing scale adhesion. Moreover, a resin having a high bulk specific gravity can be obtained, and the productivity at the time of resin processing is improved. Thus, the dispersion stabilizer for suspension polymerization of the present invention can have the required properties that have been difficult to achieve with the prior art.

In one embodiment of the dispersion stabilizer for suspension polymerization of the present invention, a carbon having a conjugated double bond in a structural unit represented by the following general formula (I), that is, a dicarboxylic acid monomer unit in the main chain of polyvinyl alcohol A resin composition containing a modified polyvinyl alcohol polymer (modified PVA) having chain-linked structural units and a polyvinyl alcohol homopolymer (unmodified PVA), wherein the modified polyvinyl alcohol polymer and It contains a resin composition in which the homopolymer of polyvinyl alcohol accounts for 0 to 5% by mass of the total 100% by mass of the homopolymer of polyvinyl alcohol.

The unsaturated monomer from which the dicarboxylic acid monomer unit in general formula (I) is derived is not particularly limited, but dimethyl maleate, monomethyl maleate, diethyl maleate, monoethyl maleate, and dipropyl maleate. , monopropyl maleate, dibutyl maleate, monobutyl maleate, dipentyl maleate, monopentyl maleate, dihexyl maleate, monohexyl maleate, dioctyl maleate, monooctyl maleate, dimethyl fumarate, monomethyl fumarate, fumaric acid Diethyl, monoethyl fumarate, dibutyl fumarate, monobutyl fumarate, dipentyl fumarate, monopentyl fumarate, dihexyl fumarate, monohexyl fumarate, diheptyl fumarate, monoheptyl fumarate, dioctyl fumarate, monooctyl fumarate, maleic acid , maleic anhydride, fumaric acid and the like.

In general formula (I), Z is preferably 0 to 3, more preferably 1 to 3, even more preferably 1 to 2.

In the resin composition according to the present invention, it is preferable that the content of the modified polyvinyl alcohol-based polymer (modified PVA) having the structural unit represented by the following general formula (I) in the polyvinyl alcohol main chain is large. Specifically, the mass ratio of the modified polyvinyl alcohol polymer in the total 100% by mass of the modified polyvinyl alcohol polymer and the polyvinyl alcohol homopolymer (also referred to as "modified PVA content") is preferably It is 95% by mass or more, more preferably 96% by mass or more, still more preferably 97% by mass or more, and even more preferably 98% by mass or more.

In the resin composition according to the present invention, a homopolymer of polyvinyl alcohol, i.e., an unmodified structural unit that does not contain structural units such as those represented by the general formula (I) and structural units derived from other copolymerizable monomers Polyvinyl alcohol (unmodified PVA) is an impurity, and its content is desirably small. Specifically, the mass ratio of the homopolymer (also referred to as "homopolymer content") in the total 100% by mass of the modified polyvinyl alcohol-based polymer and the polyvinyl alcohol homopolymer is preferably 5% by mass or less. , more preferably 4% by mass or less, and still more preferably 3% by mass or less. Polyvinyl alcohol includes both completely saponified polyvinyl alcohol obtained by completely saponifying a vinyl ester polymer and partially saponified polyvinyl alcohol in which vinyl ester units partially remain. If the homopolymer content is more than 5% by mass, the content of components with low protective colloid properties increases, and thus the vinyl-based resin particles may increase in size. The lower limit of the homopolymer content is not particularly limited, and may be 0% by mass, but from the viewpoint of purification cost, it is typically 0.1% by mass or more, more typically 0.3% by mass or more. be. When the resin composition according to the present invention contains the above homopolymer, the resin composition is a mixture of a modified polyvinyl alcohol-based polymer having a structural unit represented by general formula (I) and a homopolymer of polyvinyl alcohol.

In the resin composition according to the present invention, the mass ratio of the homopolymer in the total 100% by mass of the modified polyvinyl alcohol-based polymer and the homopolymer of the polyvinyl alcohol is measured by the following procedure. After completely saponifying the resin composition to a degree of saponification of 99.95 mol % or more, it is sufficiently washed with methanol to prepare a resin composition for analysis. The prepared resin composition for analysis is dissolved in pure water and measured by HPLC (high performance liquid chromatograph). Based on the peak area ratio of the obtained HPLC results, the content of the homopolymer in the total 100% by mass of the modified polyvinyl alcohol-based polymer and the homopolymer of the polyvinyl alcohol is calculated. For example, when HPLC is measured under the following conditions or equivalent conditions, a modified polyvinyl alcohol polymer shows a peak at 3.5 to 7.0 minutes, and a homopolymer at 7.5 to 10.0 minutes. Since peaks are detected in , the mass ratio of the homopolymer is calculated from these peak area ratios. Specifically, the ratio (%) of the peak area of 7.5 to 10.0 minutes to the total of the peak area of 3.5 to 7.0 minutes and the peak area of 7.5 to 10.0 minutes, the denaturation It is the mass ratio (% by mass) of the homopolymer in the total 100% by mass of the polyvinyl alcohol-based polymer and the homopolymer of the polyvinyl alcohol. Also, the ratio (%) of the peak area of 3.5 to 7.0 minutes to the total of the peak area of 3.5 to 7.0 minutes and the peak area of 7.5 to 10.0 minutes, the modified polyvinyl alcohol It is defined as the mass ratio (% by mass) of the modified polyvinyl alcohol polymer in the total 100% by mass of the poly(vinyl alcohol) polymer and the homopolymer of the polyvinyl alcohol.
<HPLC measurement conditions>
Column: MCI (registered trademark) GEL CK08EH (manufactured by Mitsubishi Chemical Corporation)
Eluent: pure water Mobile phase flow rate: 0.6 ml/min
Temperature: 40°C
Injection concentration: 0.01 wt%
Injection volume: 20 μL
Detector: RI

In one embodiment of the resin composition according to the present invention, the total mass ratio of the modified polyvinyl alcohol-based polymer and the homopolymer of polyvinyl alcohol is 90% by mass or more, typically 95% by mass or more, More typically, it is 98% by mass or more. In the present specification, the total mass ratio (also referred to as "the total content of modified PVA and unmodified PVA in the resin composition") is measured by HPLC as described above, and the peak area of 0 to 20 minutes It is defined as the ratio (%) of the sum of the peak area from 3.5 to 7.0 minutes and the peak area from 7.5 to 10.0 minutes to the total of .

The resin composition according to the present invention preferably has a UV absorbance (Abs) of 0.1 or more and 5.0 or less at a wavelength of 280 nm of a 0.2% by mass aqueous solution measured using a quartz cell with an optical path length of 10 mm. . The UV absorbance (Abs) is more preferably 0.3 or more and 3.0 or less, and still more preferably 0.5 or more and 2.0. This UV absorption at a wavelength of 280 nm corresponds to a double chain of conjugated double bonds (Z = 1). As a result, it is difficult to obtain a vinyl resin having an appropriate particle size. Moreover, when this UV absorbance (Abs) exceeds 5.0, coloring becomes conspicuous, and when used as a dispersant, the coloring of the resulting vinyl resin may be affected. In addition, it may become chemically unstable, resulting in an increase in the viscosity of the aqueous solution or gelation.

The resin composition according to the present invention preferably has a UV absorbance (Abs) of 0.01 or more and 1.0 or less at a wavelength of 325 nm of a 0.2% by mass aqueous solution measured using a quartz cell with an optical path length of 10 mm. . The UV absorbance (Abs) at a wavelength of 325 nm is more preferably 0.03 or more and 0.5 or less, and still more preferably 0.05 or more and 0.25 or less. This UV absorption at a wavelength of 325 nm corresponds to a triple chain of conjugated double bonds (Z = 2). As a result, it is difficult to obtain a vinyl resin having an appropriate particle size. Moreover, when this UV absorbance (Abs) exceeds 1.0, coloring becomes conspicuous, and when used as a dispersant, the coloring of the obtained vinyl resin may be affected. In addition, it may become chemically unstable, resulting in an increase in the viscosity of the aqueous solution or gelation.

The degree of saponification of the resin composition of the present invention is preferably 65 mol% or more, more preferably 68 mol% or more, and even more preferably 70 mol% or more, from the viewpoint of improving water solubility and facilitating handling. . In addition, the degree of saponification of the resin composition of the present invention should be 99.9 mol % or less in order to increase the porosity of the particles obtained when the vinyl compound is subjected to suspension polymerization to increase the absorbability of the plasticizer. is preferred, 90 mol % or less is more preferred, and 80 mol % or less is even more preferred.

The degree of saponification of the resin composition of the present invention is measured according to JIS K6726:1994. That is, it can be obtained by quantifying the remaining acetic acid group (mol%) in the sample with sodium hydroxide and subtracting it from 100.

The dicarboxylic acid monomer unit of the resin composition of the present invention is preferably 0.1 to 5.0 mol%, more preferably 0.3 to 3.0 mol%, and 0.5 to 2 0 mol % is more preferred. If it is less than 0.1 mol%, the conjugated double bond portion (-C=CH-(CH=CH)z-) linked to the dicarboxylic acid monomer unit is reduced, resulting in a moderate particle size. It is difficult to obtain a vinyl resin. Moreover, it becomes a vinyl-type resin with a low bulk density. If it exceeds 5.0 mol %, the physical properties change greatly with changes in pH, so that the protective colloid property of the vinyl compound during suspension polymerization decreases, or it becomes chemically unstable and insoluble. It may gel.

The content of dicarboxylic acid monomer units in the resin composition of the present invention is substantially equal to the total number of moles of monomer units constituting the modified polyvinyl alcohol-based polymer and the polyvinyl alcohol homopolymer. It is equal to the ratio (mole %) of the number of moles of the monomer. The method for determining the content of dicarboxylic acid monomer units is not particularly limited, and it can be determined by acid value or the like, but it is convenient to determine by carbon NMR ( ¹³ C-NMR). Specifically, the resin composition is completely saponified to a degree of saponification of 99.95 mol % or more, and then thoroughly washed with methanol to prepare a resin composition for analysis. The prepared resin composition for analysis is dissolved in heavy water, and several drops of NaOH heavy aqueous solution are added to adjust the pH to 14. Then, the pH is measured at 80° C. and ¹³ C-NMR is measured. Based on the integrated value of the methylene group (25 to 50 ppm) peak of the resin composition in the obtained spectrum, the peak is calculated from the 178 to 185 ppm peak of the carbon atom of the carboxyl group. For example, if the integrated value of the methylene group in the resin composition is b and the integrated value of the carbon atom of the carboxyl group is a, the content of the dicarboxylic acid monomer unit is (a/2)/(a/2+b)× Calculated as 100 (mol%). For example, when a=2 and b=99, it is calculated as 1.0 mol %.

The viscosity-average degree of polymerization of the resin composition of the present invention is preferably 400 or more, more preferably 500 or more, in order to improve the dispersion stability during suspension polymerization of the vinyl resin. Further, the viscosity average degree of polymerization is preferably 4000 or less, more preferably 3000 or less, even more preferably 2000 or less, and even more preferably 1500 or less so as not to reduce the dispersing power. .

The viscosity average degree of polymerization is measured according to JIS K6726:1994. That is, it is obtained from the intrinsic viscosity [η] measured in dimethyl sulfoxide (DMSO) at 30° C. after completely saponifying and purifying the resin composition.

The method for producing the resin composition according to the present invention is not particularly limited. A production method comprising a step of copolymerizing a modified vinyl ester polymer with a polymer and a step of saponifying the resulting modified vinyl ester polymer is easy and economical, and is preferably used. Vinyl ester monomers include vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate. is mentioned. The unsaturated monomer from which the dicarboxylic acid monomer unit represented by formula (I) is derived is as described above.

If necessary, monomers copolymerizable with vinyl ester monomers, such as unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, or alkyl esters of these unsaturated monocarboxylic acids, fumaric acid, and itacones. Unsaturated dicarboxylic acids such as acids or alkyl esters of these unsaturated dicarboxylic acids, nitriles or amides such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, olefin sulfonic acids such as ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid Alternatively, these salts, vinyl ethers, vinyl ketones, α-olefins, vinyl halides, vinylidene halides, etc. can be copolymerized singly or in combination. The mixing ratio of the copolymerizable monomers is a total of 10 mol% or less, preferably less than the total number of moles of the vinyl ester monomers and the unsaturated monomers from which the structural units represented by the general formula (I) are derived. A total of 5 mol % or less is appropriate.

The method for introducing a structural unit containing a dicarboxylic acid monomer unit and a conjugated double bond as shown in general formula (I) is not particularly limited, but (i) an aldehyde or ketone containing a carbonyl group, etc. (ii) a modified vinyl ester polymer obtained by polymerizing a vinyl ester monomer in the presence of a chain transfer agent, or (ii) an unsaturated derivative that induces a vinyl ester monomer and a dicarboxylic acid monomer unit After saponifying a modified vinyl ester polymer obtained by copolymerizing with a saturated monomer, a dehydration reaction or deacetic acid reaction is caused in a drying step to introduce a conjugated double bond into the main chain of polyvinyl alcohol. method. In order to further develop conjugated double bonds in the drying step, drying is performed while heating at 90° C. or higher for 1 hour or longer, preferably 100° C. or higher for 1 hour or longer, and more preferably 120° C. or higher for 2 hours or longer. is preferred. Although no upper limit is set for the heating temperature during drying, from the viewpoint of preventing gelation, it is desirable to carry out drying while heating at 180°C or lower, preferably 160°C or lower, more preferably 150°C or lower. Therefore, the heating conditions for introducing the conjugated double bond by the drying process are preferably, for example, 90 to 180° C. for 1 to 5 hours, more preferably 100 to 160° C. for 1 to 5 hours.

Any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization may be used as the polymerization method employed to produce the resin composition according to the present invention. As the polymerization method, any method can be adopted from known methods such as bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method. Among them, a solution polymerization method in which polymerization is performed in the presence of an alcoholic solvent or a bulk polymerization method in which polymerization is performed without using a solvent is preferable, instead of a suspension polymerization method and an emulsion polymerization method that require control of the polymer particle size. Adopted. Methanol, ethanol, isopropanol and the like can be used as the alcoholic solvent used in the solution polymerization method, but the solvent is not limited to these. These solvents may be used alone, or two or more of them may be used in combination.

Although the polymerization temperature for obtaining the resin composition of the present invention is not particularly limited, it is preferably 0°C or higher and 200°C or lower, more preferably 30°C or higher and 150°C or lower. If the temperature for copolymerization is lower than 0°C, it is not preferable because a sufficient polymerization rate cannot be obtained. Further, when the polymerization temperature is higher than 200° C., it is difficult to obtain the desired modified polyvinyl alcohol polymer. As a method for controlling the temperature in the range of 0° C. or higher and 200° C. or lower, a method of controlling the temperature by an external jacket using a suitable heat medium such as water can be mentioned.

The polymerization initiator used in obtaining the resin composition of the present invention is not particularly limited, but azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2, 4-dimethylvaleronitrile), azo compounds such as azobisdimethylvaleronitrile, azobismethoxyvaleronitrile, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl- Peroxides such as 2-peroxyphenoxyacetate, peroxydicarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, t-butyl peroxyneodecanoate , α-cumyl peroxyneodecanoate and the like can be used alone or in combination of two or more. Moreover, it is preferable to add the polymerization initiator intermittently or continuously for the purpose of making the polymerization rate constant. Keeping the polymerization rate constant contributes to lowering the mass ratio of the polyvinyl alcohol homopolymer in the resin composition.

When obtaining the resin composition of the present invention, the total amount of vinyl ester monomers, dicarboxylic acid monomers, and other copolymerizable monomers may be charged at the initial stage of polymerization for polymerization. In order to make the mass ratio of 5% by mass or less, the dicarboxylic acid monomer is first added to the reaction vessel in an amount of 1 to 30% by mass, preferably 5 to 20% by mass, and the rest is preferably added intermittently or continuously from the initial stage of polymerization (the stage where the polymerization rate is 0 to 1% with respect to the final polymerization rate). Furthermore, in order to make the mass ratio of the homopolymer 5% or less, the intermittent or continuous addition of the dicarboxylic acid monomer is continued until the final polymerization rate reaches 90% or more. It is preferable to continue until the polymerization rate reaches 93% or more of the final polymerization rate, and it is even more preferable to continue until the polymerization rate reaches 95% or more of the final polymerization rate.

The final polymerization rate when obtaining the resin composition of the present invention is preferably 30% by mass to 97% by mass, more preferably 50% by mass to 94% by mass, and still more preferably 70% by mass to 93% by mass. is. If the final polymerization rate is less than 30%, unreacted raw materials must be discarded or recovered and purified, which is not economically efficient. If the final polymerization rate exceeds 97% by mass, the modified vinyl ester polymer tends to have a branched structure, which may increase the particle size of the vinyl resin.

For the polymerization rate, measure 5.0 g of the polymerization liquid, dry it at 150° C. for 30 minutes, and determine the concentration of the polymerization liquid from the mass of the dry matter after volatilization of unreacted monomers and solvent. The mass of the polymer polymerized at that time is calculated, and the rate of polymerization is calculated from the ratio of the polymer to the total charged amount of the monomers.

Also, when polymerization is carried out at a high temperature, coloring of polyvinyl alcohol due to decomposition of vinyl ester monomers may be observed. In that case, for the purpose of preventing coloration, an antioxidant such as citric acid may be added to the polymerization system in an amount of 1 ppm or more and 100 ppm or less (based on the weight of the vinyl ester monomer).

The saponification method for producing the resin composition of the present invention is not particularly limited. It is preferable to use it in combination. Alcohols include methanol, ethanol, butanol, and the like. The concentration of the modified vinyl ester polymer in alcohol can be selected from the range of 20 to 50 mass %. Alkali catalysts such as hydroxides and alcoholates of alkali metals such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate can be used as alkali catalysts, and acid catalysts such as hydrochloric acid, An aqueous inorganic acid solution such as sulfuric acid, and an organic acid such as p-toluenesulfonic acid can be used. The amount of these catalysts used is preferably 1 to 100 millimol equivalents relative to the vinyl ester monomer. Although the saponification temperature is not particularly limited, it is usually in the range of 10 to 70°C, preferably in the range of 30 to 50°C. The reaction is usually carried out over 0.5-3 hours.

The dispersion stabilizer for suspension polymerization of the present invention may be the resin composition of the present invention alone, and has a structural unit represented by general formula (I) in the main chain within a range that does not impair the gist of the present invention. The modified polyvinyl alcohol-based polymer, polyvinyl alcohol-based polymers other than the homopolymer of polyvinyl alcohol, and other various additives may be contained. Examples of such additives include polymerization modifiers such as aldehydes, halogenated hydrocarbons and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds and N-oxide compounds; pH adjusters; cross-linking agents; antifungal agents, antiblocking agents; antifoaming agents and the like. From the viewpoint of significantly exhibiting the effects of the present invention, the dispersion stabilizer for suspension polymerization of the present invention preferably contains the modified polyvinyl alcohol polymer in an amount of 10% by mass or more, and preferably 30% by mass or more. More preferably, it is contained in an amount of 70% by mass or more.

The dispersion stabilizer for suspension polymerization of the present invention can be suitably used particularly for suspension polymerization of vinyl compounds. Therefore, according to another aspect of the present invention, a vinyl compound monomer or a mixture of a vinyl compound monomer and a monomer copolymerizable therewith using a dispersion stabilizer for suspension polymerization is dispersed in water to carry out suspension polymerization.

Vinyl compounds include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, esters and salts thereof; maleic acid, fumaric acid, esters and anhydrides thereof; Styrene, acrylonitrile, vinylidene chloride, vinyl ether and the like. Among these, the dispersion stabilizer for suspension polymerization according to one embodiment of the present invention is particularly suitably suspended with vinyl chloride alone or with a monomer capable of copolymerizing vinyl chloride with vinyl chloride. Used for turbidity polymerization. Examples of monomers that can be copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylate esters such as methyl (meth)acrylate and ethyl (meth)acrylate; ethylene, α-olefins such as propylene; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile, styrene, vinylidene chloride, vinyl ether and the like.

The dispersion stabilizer for suspension polymerization of the present invention can be used alone or in combination with other stabilizers such as cellulose derivatives and surfactants.

By using the dispersion stabilizer for suspension polymerization of the present invention, a vinyl chloride resin having a high bulk specific gravity of resin particles, a uniform particle size distribution, and excellent physical properties can be obtained. Hereinafter, the polymerization method of the vinyl compound will be specifically described with examples, but the method is not limited to these.

When producing vinyl resin particles such as vinyl chloride resin particles, the dispersion stabilizer for suspension polymerization described above is added in an amount of 0.01% by mass to 0.3% by mass, preferably 0.3% by mass, based on the vinyl compound monomer. 0.04% by mass to 0.15% by mass is added. In addition, the ratio of the vinyl compound to water can be vinyl compound:water=1:0.9 to 1:3, preferably vinyl compound:water=1:1 to 1:1. 5.

The polymerization initiator may be one conventionally used for the polymerization of vinyl compounds, including peroxydicarbonate such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate. compounds, perester compounds such as t-butyl peroxyneodecanoate and α-cumyl peroxyneodecanoate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate Peroxides, azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis(4-methoxy-2,4-dimethylvaleronitrile), potassium persulfate, ammonium persulfate, hydrogen peroxide, etc. alone or in combination can be used

Furthermore, it is also optional to add polymerization modifiers, chain transfer agents, gelation modifiers, antistatic agents, pH adjusters, etc. that are appropriately used in the polymerization of vinyl compounds.

The charging ratio of each component, the polymerization temperature, etc. in carrying out the polymerization of the vinyl compound may be determined according to the conditions conventionally used in the suspension polymerization of the vinyl compound, and there is no particular reason for limitation.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Example 1)
1410 g of vinyl acetate, 700 g of methanol, 1.8 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was continuously added at a rate of 38.3 g per hour over 11.5 hours, and 16.7 g of dimethyl maleate was added at a rate of 1.45 g per hour for 11.5 hours. Simultaneously, 2.0 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.2 g per hour over 10 hours to effect polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Table 1 shows the polymerization rate at the end of the continuous addition of the dicarboxylic acid monomer, the final polymerization rate, and the polymerization rate at the end of the continuous addition of the dicarboxylic acid monomer relative to the final polymerization rate.
Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA1 was obtained by drying at 110° C. for 2 hours.

<Characteristic evaluation of modified PVA>
Modification rate (dicarboxylic acid monomer unit content), saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, and The viscosity average degree of polymerization was measured by the analytical method previously described. Table 1 shows the results.

A 0.2% by mass aqueous solution of PVA1 is placed in a sample container (quartz cell) with an optical path length of 10 mm, and an ultraviolet-visible-near-infrared spectrophotometer (spectrophotometer UV1800 manufactured by Shimadzu Corporation) is used to measure wavelengths of 280 nm and 325 nm. , the UV absorbance of a 0.2% by mass aqueous solution of PVA1 was measured. Table 1 shows the results. Here, the absorption at a wavelength of 280 nm represents a double chain of conjugated double bonds (in general formula (I), Z = 1), and the absorption at 325 nm represents a triple chain of conjugated double bonds (in general formula (I), Z = 2).

<Suspension polymerization of vinyl chloride>
In a 30 L stainless steel autoclave equipped with a stirrer, 10 kg of water at 30 ° C. is stirred, 5.6 g of PVA1 as a dispersion stabilizer, 4.6 g of t-butyl peroxyneodecanoate as a polymerization initiator, α - 1 g of cumyl peroxyneodecanoate was charged. After the autoclave was degassed by vacuum, 7 kg of vinyl chloride monomer was added and polymerized at 53° C. for 4 hours. In this suspension polymerization, the ratio of the vinyl chloride monomer to water was increased and the polymerization was carried out at a low temperature, so that the particles of the vinyl chloride resin were easily coarsened.

<Evaluation of vinyl chloride resin>
The average particle size, the ratio of particles having a diameter of 250 μm or more, and the bulk specific gravity of the obtained vinyl chloride resin were evaluated by the following methods.

The average particle size was measured in accordance with JIS Z8815: 1994, 60 mesh (250 µm opening), 80 mesh (180 µm opening), 100 mesh (150 µm opening), 150 mesh (106 µm opening), 200 mesh ( Using a sieve with an opening of 75 μm), the average particle diameter (D50) at a cumulative frequency of 50% (based on mass) and the mass ratio of particles of 250 μm or more were determined.

Bulk specific gravity was measured according to JIS K6720-2:1999.

Further, after taking out the polymer slurry from the autoclave, the state of scale adhesion in the reactor was visually observed, and the degree of scale adhesion was evaluated according to the following criteria.
A: There is almost no adhesion of scale inside the autoclave.
B: 100 g or more of scale adheres to the agitator and inner wall of the autoclave, but can be easily removed by washing with water.
C: A large amount of scale weighing 100 g or more, which is difficult to remove by washing with water, adheres to the agitator and inner wall of the autoclave.

(Example 2)
1410 g of vinyl acetate, 700 g of methanol, 3.1 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was continuously added at a rate of 38.3 g per hour over 11.5 hours, and 27.9 g of dimethyl maleate was added at a rate of 2.43 g per hour for 11.5 hours. Simultaneously, 2.4 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.24 g per hour over 10 hours to effect polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA2 was obtained by drying at 110° C. for 2 hours. The modified rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA2 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA2 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 1 shows the results.

(Example 3)
1410 g of vinyl acetate, 700 g of methanol, 3.1 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was added continuously over 11 hours at a rate of 40.0 g per hour, and 27.9 g of dimethyl maleate was added continuously over 11 hours at a rate of 2.54 g per hour. Simultaneously, 2.4 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.24 g per hour over 10 hours to carry out polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA3 was obtained by drying at 110° C. for 2 hours. The modified rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA3 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA3 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 1 shows the results.

(Example 4)
1410 g of vinyl acetate, 700 g of methanol, 4.3 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.15 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was continuously added at a rate of 38.3 g per hour over 11.5 hours, and 38.7 g of dimethyl maleate was added at a rate of 3.37 g per hour for 11.5 hours. Simultaneously, 3.0 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.3 g per hour over 10 hours to effect polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA4 was obtained by drying at 110° C. for 2 hours. The modification rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA4 were compared with Example 1. It was measured by the same method. In addition, the physical properties of vinyl chloride obtained by carrying out suspension polymerization of vinyl chloride under the same conditions as in Example 1 were measured, except that PVA4 was used. Table 1 shows the results.

(Example 5)
1410 g of vinyl acetate, 700 g of methanol, 5.6 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.2 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was continuously added at a rate of 38.3 g per hour over 11.5 hours, and 50.1 g of dimethyl maleate was added at a rate of 4.36 g per hour for 11.5 hours. Simultaneously, 3.6 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.36 g per hour over 10 hours to effect polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA5 was obtained by drying at 110° C. for 2 hours. Modification rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA5 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA5 was used, and physical properties of the resulting vinyl chloride resin were measured. Table 1 shows the results.

(Example 6)
1410 g of vinyl acetate, 700 g of methanol, 7.4 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.25 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was continuously added at a rate of 38.3 g per hour over 11.5 hours, and 66.8 g of dimethyl maleate was added at a rate of 5.81 g per hour for 11.5 hours. Simultaneously, 4.2 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.42 g per hour over 10 hours to effect polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA6 was obtained by drying at 110° C. for 2 hours. Modification rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA6 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA6 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 1 shows the results.

(Example 7)
1410 g of vinyl acetate, 700 g of methanol, 9.3 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.3 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was continuously added at a rate of 38.3 g per hour over 11.5 hours, and 83.7 g of dimethyl maleate was added at a rate of 7.28 g per hour for 11.5 hours. Simultaneously, 5.4 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.54 g per hour over 10 hours to effect polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA7 was obtained by drying at 110° C. for 2 hours. The modified rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA7 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA7 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 1 shows the results.

(Example 8)
1410 g of vinyl acetate, 700 g of methanol, 3.7 g of diethyl maleate as a modified species (dicarboxylic acid monomer), and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, diethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was continuously added at a rate of 38.3 g per hour over 11.5 hours, and 33.3 g of diethyl maleate was added at a rate of 2.90 g per hour for 11.5 hours. Simultaneously, 2.4 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.24 g per hour over 10 hours to effect polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA8 was obtained by drying at 110° C. for 2 hours. Modification rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA8 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA8 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 1 shows the results.

(Comparative example 1)
1410 g of vinyl acetate, 700 g of methanol, 1.8 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was added continuously over 8 hours at a rate of 55.0 g per hour, and 16.7 g of dimethyl maleate was added continuously over 8 hours at a rate of 2.09 g per hour. At the same time, 2.0 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.2 g per hour over 10 hours to carry out polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA9 was obtained by drying at 110° C. for 2 hours. The modification rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA9 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA9 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 2 shows the results.

(Comparative example 2)
1410 g of vinyl acetate, 700 g of methanol, 3.1 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was added continuously over 8 hours at a rate of 55.0 g per hour, and 27.9 g of dimethyl maleate was added continuously over 8 hours at a rate of 3.49 g per hour. Simultaneously, 2.4 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.24 g per hour over 10 hours to carry out polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA10 was obtained by drying at 110° C. for 2 hours. The modification rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA10 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA10 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 2 shows the results.

(Comparative Example 3)
1850 g of vinyl acetate, 700 g of methanol, 31.0 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., 2.4 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.24 g per hour over 10 hours to carry out polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed by a conventional method, and a methanol solution of sodium hydroxide was added to the resulting polymer under the same heating conditions as in Example 1, and the polymer was saponified at 40°C for 1 hour. Then, it was neutralized and dried at 110° C. for 2 hours to obtain PVA11. The modified rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA11 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA11 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 2 shows the results.

(Comparative Example 4)
1410 g of vinyl acetate, 700 g of methanol, 4.3 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.2 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was added continuously over 8 hours at a rate of 55.0 g per hour, and 38.7 g of dimethyl maleate was added continuously over 8 hours at a rate of 4.84 g per hour. At the same time, 3.0 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.3 g per hour over 10 hours to carry out polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed by a conventional method, and a methanol solution of sodium hydroxide was added to the resulting polymer under the same heating conditions as in Example 1, and the polymer was saponified at 40°C for 1 hour. Then, it was neutralized and dried at 110° C. for 2 hours to obtain PVA12. The modified rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA12 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA12 was used, and physical properties of the resulting vinyl chloride resin were measured. Table 2 shows the results.

(Comparative Example 5)
1410 g of vinyl acetate, 700 g of methanol, 18.5 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 0.5 g of di-2-ethylhexylperoxydicarbonate were charged in a polymerization vessel, and the system was purged with nitrogen for 30 minutes. It was replaced and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, dimethyl maleate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 g of vinyl acetate was added continuously over 8 hours at a rate of 55.0 g per hour, and 167.1 g of dimethyl maleate was added continuously over 8 hours at a rate of 20.89 g per hour. At the same time, 9.0 g of di-2-ethylhexylperoxydicarbonate was continuously added at a rate of 0.9 g per hour over 10 hours to carry out polymerization. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA13 was obtained by drying at 110° C. for 2 hours. The modified rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA13 were compared with Example 1. It was measured by the same method. Further, the physical properties of the vinyl chloride resin obtained by suspension polymerization of vinyl chloride under the same conditions as in Example 1 were measured, except that PVA13 was used. Table 2 shows the results.

(Comparative Example 6)
1670 g of vinyl acetate, 1160 g of methanol, 2.5 g of dimethyl maleate as a modified species (dicarboxylic acid monomer), and 2.0 g of azobisisobutyronitrile were charged into a polymerization vessel, and the inside of the system was replaced with nitrogen for 30 minutes. Heating was started. When the liquid temperature reached 60° C., continuous addition of vinyl acetate, methanol and dimethyl maleate was started to carry out polymerization. Specifically, 520 g of vinyl acetate was continuously added over 5 hours at a rate of 104 g per hour, 270 g of methanol was continuously added over 5 hours at a rate of 54 g per hour, and 23 g of dimethyl maleate was added continuously. was added continuously over 5 hours at a rate of 4.60 g per hour. After 6 hours had passed since the liquid temperature reached 60° C., the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, a methanol solution of sodium hydroxide is added to the obtained polymer by a conventional method, saponification is performed at 40° C. for 1 hour, and then neutralization treatment is performed. PVA14 was obtained by drying at 110° C. for 2 hours. The modification rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA14 were compared with Example 1. It was measured by the same method. In addition, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA14 was used, and physical properties of the obtained vinyl chloride resin were measured. Table 2 shows the results.

(Comparative Example 7)
1,410 g of vinyl acetate, 700 g of methanol, and 0.1 g of di-2-ethylhexylperoxydicarbonate were charged into a polymerization vessel, the inside of the system was replaced with nitrogen for 30 minutes, and the temperature was started to rise. When the liquid temperature reached 60° C., continuous addition of vinyl acetate and di-2-ethylhexylperoxydicarbonate was started to carry out polymerization. Specifically, 440 grams of vinyl acetate was added continuously over 8 hours at a rate of 55.0 grams per hour while simultaneously adding 1.8 grams of di-2-ethylhexylperoxydicarbonate at 0.8 grams per hour. Polymerization was carried out by continuous addition over 10 hours at a rate of 18 g. After 12 hours had passed since the liquid temperature reached 60°C, the polymerization was stopped by cooling. Next, unreacted vinyl acetate is removed by a conventional method, and a sodium hydroxide methanol solution is added to the obtained polymer by a conventional method, saponified at 40° C. for 1 hour, and then neutralized. C. for 2 hours to obtain PVA15. The modified rate, saponification degree, modified PVA content, homopolymer content, total content of modified PVA and unmodified PVA in the resin composition, viscosity average degree of polymerization and UV absorbance of the obtained PVA15 were compared with Example 1. It was measured by the same method. Suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that PVA15 was used, and the physical properties of the obtained vinyl chloride resin were measured. Table 2 shows the results.

In Comparative Examples 1 to 6, since the homopolymer content in the resin composition was high, the vinyl chloride resin particles were coarsened, the amount of coarse particles was large, and scale adhesion was large. Since Comparative Example 7 did not contain the structure represented by the general formula (I), the vinyl chloride resin particles were coarsened, the amount of coarse particles was large, and scale adhesion was large. On the other hand, when the resin compositions shown in Examples 1 to 8 are used, the formation of coarse particles in the vinyl chloride resin is small, particles having a highly uniform particle size are obtained, the bulk specific gravity is high, and scale Adhesion was also low. Therefore, the dispersion stabilizers (PVA1 to PVA8) according to Examples 1 to 8 are industrially extremely advantageous.

Claims

A resin composition containing a modified polyvinyl alcohol-based polymer having a structural unit represented by general formula (I) in the main chain and a homopolymer of polyvinyl alcohol, wherein the modified polyvinyl alcohol-based polymer and the polyvinyl A resin composition in which the proportion by mass of the homopolymer of polyvinyl alcohol is 0 to 5% by mass in a total of 100% by mass of the homopolymer of alcohol.

(Wherein, X and Y represent a lower alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal atom, and may be the same or different. Z represents the number of repeating units and is an integer of 0 to 3. )
The resin composition according to claim 1, wherein the UV absorbance (Abs) of a 0.2% by mass aqueous solution at a wavelength of 280 nm and an optical path length of 10 mm is 0.1 or more and 5.0 or less.
The resin composition according to claim 1 or 2, wherein the UV absorbance (Abs) of the 0.2% by mass aqueous solution at a wavelength of 325 nm and an optical path length of 10 mm is 0.01 or more and 1.0 or less.
The resin composition according to any one of claims 1 to 3, wherein the degree of saponification of the resin composition is 65 to 99.9 mol%.
The resin composition according to any one of claims 1 to 4, wherein the resin composition contains 0.1 to 5.0 mol% of dicarboxylic acid monomer units.
A method for producing a resin composition according to any one of claims 1 to 5, wherein a vinyl ester monomer and an unsaturated monomer deriving a dicarboxylic acid monomer unit represented by general formula (I) a step of obtaining a modified vinyl ester polymer by copolymerizing with a monomer, and a step of saponifying the obtained modified vinyl ester polymer. , intermittently or continuously adding a dicarboxylic acid monomer until a conversion of 90% or more is achieved.
A dispersion stabilizer for suspension polymerization containing the resin composition according to any one of claims 1 to 5.
Using the dispersion stabilizer for suspension polymerization according to claim 7, a vinyl compound monomer or a mixture of a vinyl compound monomer and a monomer copolymerizable therewith is dispersed in water. A method for producing a vinyl-based resin, comprising performing suspension polymerization.