WO2018096937A1

WO2018096937A1 - Modified vinyl alcohol polymer and production method therefor

Info

Publication number: WO2018096937A1
Application number: PCT/JP2017/040464
Authority: WO
Inventors: 渡辺　亘
Original assignee: デンカ株式会社
Priority date: 2016-11-24
Filing date: 2017-11-09
Publication date: 2018-05-31
Also published as: JPWO2018096937A1; TWI752115B; JP6505328B2; TW201829479A

Abstract

Provided is a dispersion stabilizer which is suitable for use in suspension-polymerizing a vinyl compound to obtain resin particles that are fine and have high evenness in particle size, high plasticizer-absorbing properties, and a proper bulk specific gravity. The dispersion stabilizer comprises a modified vinyl alcohol polymer having carbonyl terminals represented by general formula (I) and formyl terminals represented by general formula (II), wherein the content of the carbonyl terminals represented by general formula (I), the content of the formyl terminals represented by general formula (II), and the total content of these two kinds of terminals are 10-40 mol%, 1-25 mol%, and 15-45 mol%, respectively, with respect to the total content of terminal glycol groups, terminal methylol groups, terminal carboxylic acid salt groups, the carbonyl terminals represented by general formula (I), and the formyl terminals represented by general formula (II). (In formula (I), R represents a C_2-9 alkyl group.)

Description

Modified vinyl alcohol polymer and process for producing the same

The present invention relates to a modified vinyl 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 polymerization of vinyl compounds represented by vinyl chloride.

When producing vinyl resins such as vinyl chloride resins industrially, vinyl compounds such as vinyl chloride are dispersed in an aqueous medium in the presence of a dispersion stabilizer, and polymerization is performed using an oil-soluble catalyst. Suspension polymerization is widely practiced. In general, factors governing the quality of vinyl resins include polymerization rate, water-monomer ratio, polymerization temperature, type and amount of catalyst, type of polymerization tank, stirring speed, and type of dispersion stabilizer. In particular, the influence of the type of dispersion stabilizer is very large.

The performance required for dispersion stabilizers for suspension polymerization of vinyl compounds is to make the particle size distribution of the resulting vinyl resin particles as sharp as possible, and to increase the absorption rate of the plasticizer to improve processability. In order to facilitate the removal of monomers such as vinyl chloride remaining in the resin particles, and to prevent the formation of fish eyes and the like in the molded product, each resin particle has a function of making it porous. For example, it has a function of forming resin particles having a large specific gravity.

Conventionally, as a dispersion stabilizer for suspension polymerization of vinyl compounds, cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, partially saponified polyvinyl alcohol, and the like have been used alone or in combination. Among these, polyvinyl alcohol (PVA) has excellent properties and is most commonly used. However, it is known that even though polyvinyl alcohol is a bite, it has a subtle effect on the properties of the vinyl resin due to its physical and chemical properties such as the degree of polymerization and saponification. An aldehyde-derived carbonyl group is introduced into the mixture, and an unsaturated double bond is introduced by undergoing a dehydration reaction or a deacetic acid reaction at the time of saponification (see, for example, Patent Document 1), and heat treatment is performed in a specific oxygen concentration atmosphere Various modified vinyl alcohol polymers have been proposed, such as introducing a carboxyl group (see, for example, Patent Document 2).

JP-A-8-208724 Japanese Patent No. 3093351

However, these methods are not sufficiently compatible with various types of polymerization cans such as large polymerization cans used in recent years. That is, it becomes coarse vinyl resin particles with poor dispersion power and low plasticizer absorbability, becomes too fine with high dispersion power and becomes too small in bulk specific gravity, or with fine vinyl resin particles. However, it was insufficient to obtain vinyl resin particles that were stably satisfied, such as low plasticizer absorbability.

Therefore, the present invention is suitable for obtaining resin particles having a fine, high uniformity of particle size, high plasticizer absorbability, and proper bulk specific gravity when suspension polymerization of vinyl compounds such as vinyl chloride. An object is to provide a dispersion stabilizer.

As a result of intensive studies to solve the above problems, the present inventors have obtained a modified vinyl alcohol polymer having a predetermined carbonyl terminal and a predetermined formyl terminal, each terminal (terminal glycol group, terminal methylol). Group, terminal carboxylate group, carbonyl terminal represented by general formula (I) and formyl terminal represented by general formula (II)), the content of carbonyl terminal represented by general formula (I) is 10 mol. A modified vinyl alcohol polymer having a formyl terminal content of 1 to 25 mol% and a total content of 15 to 45 mol% in the general formula (II) Has been found to be effective as a dispersion stabilizer for suspension polymerization of vinyl compounds.

Accordingly, in one aspect, the present invention is a modified vinyl alcohol polymer having a carbonyl terminal represented by the general formula (I) and a formyl terminal represented by the general formula (II), which comprises a terminal glycol group, a terminal methylol group, a terminal carboxyl group. The content of the carbonyl terminal represented by the general formula (I) is from 10 mol% to 40 mol% based on the total content of the acid base, the carbonyl terminal represented by the general formula (I) and the formyl terminal represented by the general formula (II). And a modified vinyl alcohol polymer having a formyl terminal content of 1 mol% to 25 mol% and a total content of 15 mol% to 45 mol% shown in the general formula (II).

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)

In one embodiment, the modified vinyl alcohol polymer according to the present invention has a viscosity average polymerization degree of 500 to 1000, and an absorbance at a wavelength of 320 nm of a 0.2 mass% aqueous solution of 0.2 or more.

In another embodiment, the modified vinyl alcohol polymer according to the present invention has a saponification degree of 60 mol% to 80 mol%.

In still another embodiment, the modified vinyl alcohol polymer according to the present invention has a terminal glycol group, a terminal methylol group, a terminal carboxylate group, a carbonyl terminal represented by the general formula (I), and a general formula (II). The content of the terminal carboxylate group is 2 mol% to 8 mol% with respect to the total content of the formyl terminals.

In another aspect, the present invention is a dispersion stabilizer for suspension polymerization containing the modified vinyl alcohol polymer according to the present invention.

In yet another aspect of the present invention, using the dispersion stabilizer for suspension polymerization according to the present invention, a vinyl compound monomer, or a vinyl compound monomer and a monomer copolymerizable therewith, This is a method for producing a vinyl-based resin, which comprises carrying out suspension polymerization by dispersing a mixture in water.

In yet another aspect of the present invention, a process of obtaining a vinyl ester polymer by polymerizing a vinyl ester monomer while introducing a gas containing oxygen and in the presence of an aldehyde represented by the general formula (III). This is a method for producing a modified vinyl alcohol polymer.

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)

In still another aspect of the present invention, a vinyl ester monomer is subjected to suspension polymerization in an aqueous medium while introducing a gas containing oxygen and in the presence of an aldehyde represented by the general formula (III). It is a manufacturing method of the modified vinyl alcohol polymer including the process of obtaining a polymer.

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)

When the dispersion stabilizer for suspension polymerization of the present invention is used for suspension polymerization of vinyl compounds, it is possible to obtain resin particles that are fine and have high uniformity in particle size, high plasticizer absorbability, and appropriate bulk specific gravity. It becomes possible. As described above, the dispersion stabilizer for suspension polymerization of the present invention can have the required performance which is difficult to achieve with the prior art. Moreover, when the particle size uniformity of the resin particles is high and the plasticizer absorbability is high, it is possible to expect a reduction in fish eye and further excellent demonomerization. Therefore, the dispersion stabilizer for suspension polymerization according to the present invention is extremely advantageous industrially.

Hereinafter, the present invention will be described in detail. The dispersion stabilizer for suspension polymerization of the present invention contains a modified vinyl alcohol polymer (modified PVA) having a carbonyl terminal represented by the following general formula (I) and a formyl terminal represented by the general formula (II).

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)

The content of the carbonyl terminal shown in the general formula (I) in the modified PVA is as follows: each terminal (terminal glycol group, terminal methylol group, terminal carboxylate group, carbonyl terminal shown in the general formula (I) and general formula (II). It should be 10 mol% to 40 mol% with respect to the total content of the formyl end shown). When the content of the carbonyl terminal represented by the general formula (I) is less than 10 mol%, the unsaturated double bond starting point due to the carbonyl terminal is decreased or the protective colloid property is decreased. A vinyl resin having a diameter cannot be obtained. Therefore, the content of the carbonyl terminal represented by the general formula (I) needs to be 10 mol% or more, preferably 15 mol% or more, and preferably 20 mol% with respect to the total content of each terminal. % Or more is more preferable. In addition, in order to obtain a modified PVA in which the content of the carbonyl terminal represented by the general formula (I) exceeds 40 mol% with respect to the total content of each terminal, a terminal glycol group or vinyl acetate which is a heterogeneous bond terminal is used. The terminal methylol group derived from the monomer must be controlled by precision polymerization or the like, which is disadvantageous for industrial production. Therefore, the content of the carbonyl terminal represented by the general formula (I) is required to be 40 mol% or less, preferably 38 mol% or less, and preferably 35 mol% based on the total content of each terminal. % Or less is more preferable.

In the present invention, the terminal glycol group means 1,2 glycol terminal (—CH ₂ —CH (OH) —CH (OH) —CH ₃ ), and the terminal methylol group means —CH ₂ CH ₂ OH. The terminal carboxylate group refers to —CH ₂ COOX (X is a metal atom such as an alkali metal such as Na).

It is important that R at the carbonyl terminal shown in the general formula (I) in the modified PVA is an alkyl group having 2 to 9 carbon atoms. There is a method using acetaldehyde having 1 carbon atom at the carbonyl terminal represented by formula (I), but since the boiling point is low, it is difficult to control the polymerization, and in the suspension polymerization method, acetic acid is used because of high water solubility. The affinity with vinyl monomer droplets is low, and there are drawbacks of poor polymerization stability, which is not industrially suitable. Therefore, the carbon number of R is preferably 2 or more, and more preferably 3 or more. On the other hand, if the number of carbons in R exceeds 9, the boiling point is high, so that it is difficult to remove unreacted components and modified PVA with poor dispersion performance, and the required physical properties are not sufficiently developed. Accordingly, the carbon number of R is preferably 9 or less, more preferably 8 or less, even more preferably 6 or less, and even more preferably 5 or less. R may be linear or branched. Specific examples of preferred R include ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, t- Examples thereof include a pentyl group, hexyl group, isohexyl group, heptyl group, octyl group and the like.

The content of the formyl terminal shown in the general formula (II) in the modified PVA is as follows in each terminal (terminal glycol group, terminal methylol group, terminal carboxylate group, carbonyl terminal shown in the general formula (I) and general formula (II). It should be 1 mol% to 25 mol% with respect to the total content of the formyl end shown). When the content is less than 1 mol%, the unsaturated double bond starting point due to the formyl end is reduced or the protective colloid property is lowered, and as a result, a vinyl resin having an appropriate particle size cannot be obtained. . Therefore, the content of the formyl terminal represented by the general formula (II) is required to be 1 mol% or more, preferably 2 mol% or more with respect to the total content of each terminal. % Or more is more preferable. Further, when the modified PVA is a modified PVA having a content of the formyl terminal represented by the general formula (II) exceeding 25 mol% with respect to the total content of the respective terminals, the vinyl system is used when used as a dispersant. Affects resin coloration. Moreover, it may become chemically unstable, and the viscosity of the aqueous solution may increase or gelate. Therefore, the content of the formyl terminal represented by the general formula (II) needs to be 25 mol% or less, preferably 23 mol% or less, and preferably 20 mol with respect to the total content of each terminal. % Or less is more preferable.

The terminal glycol group, terminal methylol group, and terminal carboxylate group of the vinyl alcohol polymer are described in Shigetoshi Aiya, “PVA Fine Structure”, Polymer Processing, 38 (8), P388-396, 1989. As shown, it can be identified and quantified from the peak position of proton NMR and its integrated value. The carbonyl terminal shown in the general formula (I) and the formyl terminal shown in the general formula (II) can also be obtained from the peak position of proton NMR and its integrated value.

A procedure for measuring the content of the terminal glycol group, terminal methylol group, terminal carboxylate group, carbonyl terminal represented by general formula (I), and formyl terminal represented by general formula (II) will be described. The vinyl alcohol polymer is completely saponified to a saponification degree of 99.95 mol% or more, and then thoroughly washed with methanol to prepare a vinyl alcohol polymer for analysis. However, when measuring the formyl terminal shown in the general formula (II), saponification is unnecessary, and the analysis is performed as it is. The prepared vinyl alcohol polymer for analysis was dissolved in each solvent shown in Table 1 according to the functional group to be measured, and after adding several drops of NaOH aqueous solution to pH = 14, it was shown in Table 1. A ¹ H-NMR spectrum with the number of integrations shown in Table 1 at the measured temperature was obtained. The content of any terminal is calculated from the integrated value of the peak indicating each terminal described in Table 1, with the integrated value of the peak of the methylene group (1.2 to 2.0 ppm) of the main chain of PVA as a reference. Specifically, in the ¹ H-NMR spectrum for measuring each terminal, when the integral value of the methylene group of the main chain of the modified PVA is b and the integral value of each terminal is a, the number of protons (methylene group is 2, Each terminal is X (carbonyl terminal and terminal glycol groups are X = 3 since the peak seen is a methyl group, terminal carboxylate groups and terminal methylol groups are X = 2 because the peak seen is a methylene group, and the formyl end is X = In view of 1)), the modification rate (%) is calculated as (a / X) / (b / 2) × 100.

The terminal carboxylate group is in chemical equilibrium with the terminal γ-lactone structure. Since proton NMR measurement is performed at pH 14 as described above, even when a terminal γ-lactone structure is present in the modified PVA, all of them are changed to terminal carboxylate groups. Therefore, in the present invention, the content of the terminal carboxylate group means the total content of the terminal carboxylate group and the terminal γ-lactone structure.

In the modified PVA according to the present invention, the total content of each terminal (terminal glycol group, terminal methylol group, terminal carboxylate group, carbonyl terminal represented by general formula (I) and formyl terminal represented by general formula (II)) The content of the terminal carboxylate group is preferably from 2 mol% to 8 mol%. By making the content of the terminal carboxylate group 2 mol% or more, desirably 3 mol% or more, the affinity of the modified PVA for the vinyl compound is improved, the voids are increased, and the plasticizer absorption amount is increased. This is because improvement in physical properties can be seen. Further, when the content of the terminal carboxylate group is 8 mol% or less, desirably 6 mol% or less, the protective colloid properties are enhanced and the dispersibility is improved.

The viscosity average degree of polymerization of the modified PVA according to the present invention can be 200 to 3500, which is generally used, but the viscosity average degree of polymerization is preferably 500 to 1000. When the viscosity average degree of polymerization is 500 or more, there is an advantage that the protective colloid property is enhanced and the secondary particles are easily refined. Moreover, the porosity of the vinyl-type resin particle produced | generated by setting a viscosity average polymerization degree to 1000 or less can increase, and plasticizer absorptivity can be improved.

Viscosity average polymerization degree is measured in accordance with JIS K6726: 1994. That is, it is obtained from the intrinsic viscosity [η] measured in water at 30 ° C. after completely saponifying and purifying the modified PVA.

The saponification degree of the modified PVA according to the present invention is preferably 60 mol% or more from the viewpoint of water solubility and water dispersibility, more preferably 65 mol% or more, and even more preferably 70 mol% or more. preferable. In addition, the degree of saponification of the modified PVA according to the present invention is preferably 80 mol% or less, and more preferably 75 mol% or less, from the viewpoint of increasing the porosity of the vinyl resin particles to be produced.

The degree of saponification of the modified PVA is measured according to JIS K6726: 1994. That is, it can be determined by quantifying the residual acetic acid group (mol%) in the sample with sodium hydroxide and subtracting it from 100.

The modified PVA according to the present invention is proportional to the double bond amount of the polymer (modified PVA) from the viewpoint of promoting the refinement of the generated vinyl particles and easily increasing the porosity of the generated vinyl particles. The absorbance at a wavelength of 320 nm of the 0.2% by mass aqueous solution is preferably 0.2 or more, more preferably 0.3 or more, and still more preferably 0.4 or more. The modified PVA according to the present invention preferably has an absorbance at a wavelength of 320 nm of a 0.2 mass% aqueous solution of 2.0 or less from the viewpoint of increasing the amount of double bonds and decreasing the stability of the polymer (modified PVA). More preferably, it is 1.5 or less.

In the present invention, the absorbance at a wavelength of 320 nm of a 0.2 mass% aqueous solution of modified PVA is measured as follows. A modified PVA to be measured is dissolved in water to prepare a 0.2 mass% aqueous solution at 25 ° C. Next, the said aqueous solution is put into a cell (optical path length 10mm), and the light absorbency in wavelength 320nm is measured. In the examples, the absorbance was measured using an absorptiometer “UV-1800” manufactured by Shimadzu Corporation.

The method for producing the modified PVA according to the present invention is not particularly limited, but is represented by the following formula (III) while introducing (typically blowing) a gas containing oxygen when radically polymerizing the vinyl ester monomer. The resulting polymer is dissolved in alcohols and treated with an alkali such as sodium hydroxide or ammonia, or with an acid such as hydrochloric acid or paratoluenesulfonic acid to obtain a vinyl ester polymer. The saponification method is simple and efficient. In the present invention, the concept of “introducing a gas containing oxygen” refers to additionally sending oxygen from outside the reaction system into the reaction system, and oxygen due to air or the like initially exists in the reaction system. However, the oxygen is not treated as introduced oxygen.

Although it is not intended that the present invention be limited by theory, when a vinyl ester monomer is polymerized in the presence of an aldehyde represented by the formula (III), the terminal proton of the aldehyde is extracted and chain-transferred. As a result, a carbonyl terminal represented by the general formula (I) is produced in the modified PVA. Moreover, since it is thought that the terminal carboxylate group is generated by cutting the branch of the vinyl ester monomer by the saponification treatment, the content can be controlled by the polymerization rate or the polymerization method (the higher the polymerization rate, the higher the polymerization rate). Branching increases and terminal carboxylate groups increase).

General formula (III):

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)

Specific examples of R are as described in formula (I). Specific examples of the aldehyde represented by the formula (III) include propionaldehyde, butyraldehyde, pentylaldehyde, pentylaldehyde, hexylaldehyde, heptylaldehyde, octylaldehyde, nonylaldehyde, and decanaldehyde. The aldehyde represented by the formula (III) may be used alone or in combination.

Vinyl ester monomers include vinyl acetate, vinyl formate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, saturated branched fatty acid vinyl, and versa Examples thereof include vinyl tick acid.

The polymerization method of the modified PVA according to the present invention is not particularly limited, and a known polymerization method such as solution, emulsification, suspension, and bulk polymerization can be arbitrarily used. A method of producing by a polymerization method having a high concentration of vinyl ester monomer and a high concentration of aldehyde as a modified species is preferable because a carbonyl group is easily introduced at the terminal, and a suspension polymerization method is preferred.

As a method for generating a formyl end, there are a method in which PVA is oxidatively cleaved with an oxidizing agent (Patent Document: JP-A No. 2000-86992), a method in which formaldehyde is allowed to coexist, and the like. However, the number of steps such as the treatment of the oxidizing agent and the dissolution of PVA is increased, and it is difficult to control the polymerization degree distribution. Regarding the latter, since formaldehyde is a low boiling point compound, it is difficult to handle by itself, and polymerization control becomes difficult. On the other hand, according to the results of the study by the present inventors, the formyl end is formed when saponifying polyvinyl acetate obtained by polymerization in the presence of oxygen, and this method is simple and preferable.

The method of introducing oxygen can be arbitrarily selected, but it is preferable to introduce a gas diluted with an inert gas such as nitrogen, argon or helium so that the oxygen concentration becomes 1 to 9% by mass. When the oxygen concentration is less than 1% by mass, a sufficient amount of oxygen is not introduced into the reaction field, and it becomes difficult to obtain a target PVA having a formyl end. If it exceeds 9% by mass, the explosion limit oxygen concentration of vinyl acetate (9 to 10% by mass) is exceeded, which raises a safety concern.

Although introduction of oxygen into the reaction system can be arbitrarily selected, the method of performing polymerization while bubbling directly into the polymerization solution can increase the contact area between the reaction system and oxygen, so that introduction efficiency is good.

The amount of oxygen to be introduced can be arbitrarily selected, but the amount of oxygen based on the monomer amount is preferably in the range of 0.02 mol% to 20 mol%. If it exceeds 20 mol% or more, it reacts with radicals during polymerization and polymerization does not proceed, which is not preferable in production. On the other hand, when it is 0.02 mol% or less, it becomes difficult to obtain a modified PVA having a sufficient formyl end.

The polymerization initiator for radical polymerization of the vinyl ester monomer 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-2 Peroxides such as peroxyphenoxy acetate, percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, t-butyl Over oxy neodecanate, alpha-cumylperoxy neodecanate, t- butyl perester compounds such peroxyneodecanoate and the like may be used singly or in combination. Further, the polymerization reaction temperature is not particularly limited, but can usually be set in a range of about 30 to 90 ° C.

In the present invention, the polymerization rate refers to a value measured by a polymer concentration measurement method. In other words, the polymerization solution is sampled during the polymerization, the weight is measured, the polymer concentration of the polymerization solution is calculated based on the weight of the polymer obtained by distilling off the monomer and the solvent, and the amount of polymer relative to the monomer is determined for polymerization. Calculate the rate.

The dispersion stabilizer for suspension polymerization of the present invention is a monomer that can be copolymerized with a vinyl ester monomer, for example, an unsaturated monoester such as acrylic acid, methacrylic acid, crotonic acid, etc., within the range that does not impair the spirit of the present invention. Carboxylic acids or alkyl esters of these unsaturated monocarboxylic acids, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid or alkyl esters of these unsaturated dicarboxylic acids, nitriles such as acrylonitrile, methacrylonitrile, acrylamide and methacrylamide Alternatively, olefin sulfonic acid such as amide, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or salts thereof, vinyl ether, vinyl ketone, α-olefin, vinyl halide, vinylidene halide, etc. can be copolymerized. . The mixing ratio of such monomers is 10 mol% or less, preferably 5 mol% or less, based on the total number of moles of the vinyl ester monomer.

Saponification can be performed by dissolving the vinyl ester polymer obtained above in an alcohol and in the presence of an alkali catalyst or an acid catalyst. Examples of the alcohol include methanol, ethanol, butanol and the like. The concentration of the polymer in the alcohol is selected from the range of 20 to 70% by weight. Alkali catalysts such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and other alkali metal hydroxides and alcoholates can be used as the alkali catalyst, and as the acid catalyst, hydrochloric acid, An inorganic acid aqueous solution such as sulfuric acid and an organic acid such as p-toluenesulfonic acid can be used. The amount of such a catalyst used must be 1 to 100 mmol equivalents relative to the vinyl ester monomer. In such a case, the saponification temperature is not particularly limited, but is usually in the range of 10 to 70 ° C., preferably 30 to 50 ° C. The reaction is usually carried out over 1 to 3 hours.

The dispersion stabilizer for suspension polymerization of the present invention may contain PVA other than the above modified PVA and other various additives as long as the gist of the present invention is not impaired. Examples of the additive include a pH adjuster, a crosslinking agent, an antiseptic, an antifungal agent, an antiblocking agent, and an antifoaming agent. From the viewpoint of exhibiting the effects of the present invention significantly, the dispersion stabilizer for suspension polymerization of the present invention preferably contains 10% by mass or more of modified PVA, more preferably contains 30% by mass or more, and 70% by mass. It is still more preferable to contain more than%.

The dispersion stabilizer for suspension polymerization of the present invention can be suitably used particularly for suspension polymerization of vinyl compounds. As monomers of vinyl compounds, 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, and esters thereof And anhydrides; styrene, acrylonitrile, vinylidene chloride, vinyl ether and the like. Among these, the dispersion stabilizer for suspension polymerization of the present invention is particularly preferably used in suspension polymerization when vinyl chloride is used alone or together with a monomer capable of copolymerizing vinyl chloride with vinyl chloride. Used. Monomers that can be copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylic 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 is suitable for the production of soft vinyl chloride in terms of producing vinyl chloride particles having excellent plasticizer absorbability, but from the point of excellent particle size distribution, etc. It can also be applied to vinyl production. In addition, the fact that vinyl chloride particles having excellent plasticizer absorbability can be produced means that there are many voids in the resulting vinyl chloride particles, so that the dispersion stabilizer for suspension polymerization of the present invention also has demonomerization properties. It can be expected that it is excellent and that the resulting vinyl chloride particles have less fish eyes.

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 porous resin particle and a uniform particle size distribution can be obtained even when suspension polymerization is carried out by a high temperature water charging polymerization method. Hereinafter, examples of the polymerization method of the vinyl compound will be described in detail, but the method is not limited thereto.

In the case of producing resin particles such as vinyl chloride resin particles, the above-mentioned dispersion stabilizer for suspension polymerization is 0.01% by mass to 0.3% by mass with respect to the vinyl compound monomer, preferably 0.8%. 04 mass% to 0.15 mass% is added. Further, the ratio of the vinyl compound to water can be vinyl compound: water = 1: 0.9 to 1: 3, and preferably 1: 1 to 1: 1.5 in terms of mass ratio.

The polymerization initiator may be one conventionally used for the polymerization of vinyl compounds, such as diisopropylpropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate, etc. Perester compounds such as percarbonate compounds, t-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, t-butylperoxyneodecanoate, acetylcyclohexylsulfonyl peroxide, 2,4,4 -Peroxides such as trimethylpentyl-2-peroxyphenoxyacetate, azo compounds such as azobis-2,4-dimethylpareronitrile, azobis (4-methoxy-2,4-dimethylpareronitrile), and further Potassium sulfate, ammonium persulfate, hydrogen peroxide, etc. alone or It can be used in conjunction look.

Furthermore, it is also optional to add a polymerization regulator, a chain transfer agent, a gelation improver, an antistatic agent, a PH regulator and the like that are used as appropriate for the polymerization of the vinyl compound.

The charging ratio of each component and the polymerization temperature for carrying out the polymerization of the vinyl compound may be determined in accordance with the conditions conventionally employed in the suspension polymerization of the vinyl compound, and there is no particular limitation.

By using the dispersion stabilizer for suspension polymerization of the present invention, it is possible to obtain resin particles that are fine and have high uniformity in particle size, high plasticizer absorbability, and appropriate bulk specific gravity.

In one embodiment, the resin particles obtained using the dispersion stabilizer for suspension polymerization of the present invention can have an average particle size of 140 μm or less, preferably 130 μm or less, typically 110 μm to 140 μm. According to JIS Z8815: 1994, the average particle size is 60 mesh (aperture 250 μm), 80 mesh (aperture 180 μm), 100 mesh (aperture 150 μm), 150 mesh (aperture 106 μm), 200 mesh (aperture) This refers to the particle diameter (D50) having a cumulative frequency of 50% (mass basis) when the particle size distribution is determined using a sieve having an opening of 75 μm.

In one embodiment, the resin particles obtained using the dispersion stabilizer for suspension polymerization according to the present invention have a particle size (D80) having a cumulative frequency of 80% (mass basis) when the particle size distribution is determined by the above method. And the difference in particle diameter (D20) with a cumulative frequency of 20% (mass basis) can be 60 μm or less, preferably 55 μm or less, and typically 40 μm to 60 μm.

In one embodiment, the resin particles obtained using the dispersion stabilizer for suspension polymerization of the present invention can have a plasticizer absorption of 23 phr or more, and preferably have a plasticizer absorption of 30 phr or more. Typically having a plasticizer uptake of 23 phr to 35 phr. In the present invention, the plasticizer absorption amount of the resin is measured by the following procedure. Glass fiber is packed in the bottom of an aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm, and 10 g of resin is charged. To this, 15 mL of a plasticizer (dioctyl phthalate, hereinafter referred to as DOP) is added and left for 30 minutes to allow the DOP to sufficiently penetrate into the resin. Thereafter, excess DOP is centrifuged at an acceleration of 1500 G, and the mass of DOP absorbed by the resin is measured and converted to DOP mass parts (phr) per 100 mass parts of the resin.

In one embodiment, the resin particles obtained using the dispersion stabilizer for suspension polymerization of the present invention are 0.40 g / mL or more, preferably 0.42 g / mL or more, and typically 0.40 g / mL to It can have a bulk specific gravity of 0.45 g / mL. The bulk specific gravity is measured according to JIS K6720-2: 1999.

Hereinafter, the present invention will be described in more detail with reference to examples.
Unless otherwise specified, “parts” and “%” mean “parts by mass” and “mass%”.

Example 1
<Production of dispersion stabilizer>
A polymerization can was charged with 100 parts of vinyl acetate (monomer), 120 parts of water, 0.087 part of polyvinyl alcohol as a dispersant, 1.5 parts of modified normal butyraldehyde, and 0.026 part of azobisisobutyronitrile. Then, an oxygen-nitrogen mixed gas (oxygen concentration 4%, total oxygen amount 0.11 mol% with respect to vinyl acetate) was heated while being blown into the gas phase immediately above the polymerization solution to polymerize at 60 ° C, and the polymerization rate reached 90%. At that time, the polymerization was stopped. Next, unpolymerized vinyl acetate is removed by a conventional method, and the resulting polymer is dissolved in methanol, saponified with sodium hydroxide by a conventional method, and methanol is separated by filtration, and then in a gear oven at 90 ° C. for 80 minutes. By drying, a powdery modified vinyl alcohol polymer (dispersion stabilizer) was obtained. Viscosity average degree of polymerization, degree of saponification of the obtained modified vinyl alcohol polymer, absorbance at a wavelength of 320 nm of 0.2 mass% aqueous solution, each terminal (terminal glycol group, terminal methylol group, terminal carboxylate group, general formula (I) The content of the terminal carboxylate group in the total content of the carbonyl terminal and the formyl terminal shown in the general formula (II), the content of the carbonyl terminal shown in the formula (I), and the formyl terminal shown in the formula (II) The viscosity average polymerization degree was 600, the saponification degree was 71 mol%, the absorbance was 0.29, the terminal carboxylate group content was 3.7 mol%, and the general formula was measured. The carbonyl terminal shown in (I) was 26.3 mol%, and the formyl terminal shown in general formula (II) was 3.7 mol%.

<Suspension polymerization of vinyl chloride>
In a 30 L stainless steel autoclave equipped with a stirrer, 12 kg of water at 30 ° C. with stirring, 9.5 g of the dispersion stabilizer obtained above, 4.6 g of t-butylperoxyneodecanoate as a polymerization initiator, 1 g of α-cumyl peroxyneodecanoate was charged. The autoclave was degassed under vacuum, 5 kg of vinyl chloride monomer was added, and polymerization was carried out at 57 ° C. for 4 hours.

<Evaluation of vinyl chloride resin>
The average particle diameter, particle size distribution, plasticizer absorption, and bulk specific gravity of the obtained vinyl chloride resin were evaluated by the following methods. The results are shown in Table 2 (Tables 2-1 and 2-2).

The average particle size is measured according to JIS Z8815: 1994, 60 mesh (aperture 250 μm), 80 mesh (aperture 180 μm), 100 mesh (aperture 150 μm), 150 mesh (aperture 106 μm), 200 mesh ( Using a sieve with a mesh opening of 75 μm, the particle diameter (D50) with a cumulative frequency of 50% (mass basis) is the average particle diameter, the particle diameter (D80) with a cumulative frequency of 80% (mass basis) and a cumulative frequency of 20% (mass) The difference in the particle size (D20) of the “standard” was defined as the particle size distribution.

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

The plasticizer absorption was measured by the following procedure. Glass fiber was packed in the bottom of an aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm, and 10 g of vinyl chloride resin was charged. To this, 15 mL of a plasticizer (dioctyl phthalate, hereinafter referred to as DOP) was added and allowed to stand for 30 minutes to allow the DOP to sufficiently penetrate into the vinyl chloride resin. Thereafter, excess DOP was centrifuged at an acceleration of 1500 G, and the mass of DOP absorbed in 10 g of vinyl chloride resin was measured and converted to DOP mass parts (phr) per 100 mass parts of vinyl chloride resin.

(Examples 2 to 4, 6, 8, 9)
Table 2 shows the modified species and the amount charged, the total amount of oxygen supplied by the oxygen-nitrogen mixed gas, the oxygen concentration of the oxygen-nitrogen mixed gas, the location where the oxygen-nitrogen mixed gas was blown, the polymerization rate, the degree of polymerization, and the degree of saponification. A modified vinyl alcohol polymer (dispersion stabilizer) was obtained in the same manner as in Example 1 except that the conditions were changed. Regarding the location where the oxygen-nitrogen mixed gas is blown in Table 2, “gas phase” is a method in which the oxygen-nitrogen mixed gas discharge port is placed in the gas phase directly above the polymerization liquid and blown in the same manner as in Example 1. “Liquid phase” refers to a method (bubbling) in which an oxygen-nitrogen mixed gas discharge port is inserted into a polymerization solution.
Subsequently, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the modified vinyl alcohol polymer (dispersion stabilizer) and the vinyl chloride resin in the same manner as in Example 1.

(Example 5)
The modified vinyl acetate polymer obtained in Example 2 was saponified by adjusting the amount of sodium hydroxide to obtain a modified vinyl alcohol polymer having a saponification degree of 80%. A suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the dispersion stabilizer and the vinyl chloride resin in the same manner as in Example 1.

(Example 7)
The modified vinyl alcohol polymer obtained in Example 6 was heat treated at 120 ° C. for 4 hours to obtain a resin with increased absorbance. A suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the dispersion stabilizer and the vinyl chloride resin in the same manner as in Example 1.

(Example 10)
100 parts of vinyl acetate, 1.3 parts of modified normal butyraldehyde and 0.083 parts of azobisisobutyronitrile were charged into a polymerization vessel, and an oxygen-nitrogen mixed gas (oxygen concentration of 3%, total amount of oxygen with respect to vinyl acetate was 0). .05 mol%) was heated to 65 ° C. while blowing into the gas phase directly above the polymerization solution, and the polymerization was stopped when the polymerization rate reached 70%. Thereafter, saponification was performed in the same procedure as in Example 1, and a powdery modified vinyl alcohol polymer (dispersion stabilizer) was obtained after separation operation. A suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the dispersion stabilizer and the vinyl chloride resin in the same manner as in Example 1.

(Comparative Example 1)
The modified vinyl alcohol polymer was changed in the same manner as in Example 1 except that the charged amount of the modified species was changed to the conditions shown in Table 2, and the reaction system was changed to nitrogen atmosphere by nitrogen substitution and polymerization was performed while introducing nitrogen from the gas phase. (Dispersion stabilizer) was obtained. Subsequently, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the dispersion stabilizer and the vinyl chloride resin in the same manner as in Example 1. In this case, since the average particle diameter of the obtained vinyl chloride resin particles is large and the particle size distribution is wide, the dispersion stabilizer has insufficient dispersibility.

(Comparative Example 2)
The polymerization rate and the degree of saponification were changed to the conditions shown in Table 2, and the reaction system was liquid-sealed without replacing with nitrogen, and air introduction from the outside was shut off. Other conditions were modified in the same manner as in Example 1. A vinyl alcohol polymer (dispersion stabilizer) was obtained. Subsequently, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the dispersion stabilizer and the vinyl chloride resin in the same manner as in Example 1. In this case, since the average particle diameter of the obtained vinyl chloride resin particles is large and the particle size distribution is wide, the dispersion stabilizer has insufficient dispersibility. In Comparative Example 2, some formyl ends are formed, which is considered to be caused by air originally present in the reaction system.

(Comparative Example 3)
100 parts of vinyl acetate and 120 parts of methanol are charged into a polymerization vessel, and heated to 65 ° C. while blowing an oxygen-nitrogen mixed gas (oxygen concentration 6%, oxygen total amount 0.10 mol%) into the gas phase directly above the polymerization solution. The polymerization was stopped when the polymerization rate reached 90%. Thereafter, saponification was performed in the same procedure as in Example 1, and a powdery modified vinyl alcohol polymer (dispersion stabilizer) was obtained after separation operation. Subsequently, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the dispersion stabilizer by the same method as in Example 1. In this case, the vinyl chloride resin was blocked and could not be measured.

(Comparative Example 4)
100 parts of vinyl acetate, 68 parts of methanol, 10.7 parts of modified dodecyl aldehyde and 0.083 part of azobisisobutyronitrile were charged into a polymerization vessel, and the reaction system was placed in a nitrogen atmosphere by nitrogen substitution, followed by heating. The temperature was raised to 70 ° C., and the polymerization was stopped when the polymerization rate reached 85%. Thereafter, saponification was performed in the same procedure as in Example 1, and a powdery modified vinyl alcohol polymer (dispersion stabilizer) was obtained after separation operation. Subsequently, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion stabilizer was used. Table 2 shows the results of evaluating the properties of the dispersion stabilizer and the vinyl chloride resin in the same manner as in Example 1. In this case, since the average particle diameter of the obtained vinyl chloride resin particles is large and the particle size distribution is wide, the dispersion stabilizer has insufficient dispersibility.

Claims

A modified vinyl alcohol polymer having a carbonyl end represented by general formula (I) and a formyl end represented by general formula (II), wherein a terminal glycol group, a terminal methylol group, a terminal carboxylate group, The content of the carbonyl terminal represented by the general formula (I) is 10 mol% to 40 mol% with respect to the total content of the carbonyl terminal and the formyl terminal represented by the general formula (II). A modified vinyl alcohol polymer having a formyl terminal content of 1 mol% to 25 mol% and a total content of both of 15 mol% to 45 mol%.

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)
2. The modified vinyl alcohol polymer according to claim 1, wherein the viscosity average polymerization degree is 500 to 1000, and the absorbance at a wavelength of 320 nm of a 0.2 mass% aqueous solution is 0.2 or more.
The modified vinyl alcohol polymer according to claim 1 or 2, wherein the saponification degree is 60 mol% to 80 mol%.
The content of the terminal carboxylate group is 2 mol with respect to the total content of the terminal glycol group, terminal methylol group, terminal carboxylate group, carbonyl end represented by formula (I) and formyl end represented by formula (II). The modified vinyl alcohol polymer according to any one of claims 1 to 3, wherein the content is from 8 to 8 mol%.
A dispersion stabilizer for suspension polymerization containing the modified vinyl alcohol polymer according to any one of claims 1 to 4.
Using the dispersion stabilizer for suspension polymerization according to claim 5, 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 resin, comprising performing suspension polymerization.
5. The method according to claim 1, comprising a step of polymerizing a vinyl ester monomer in the presence of an aldehyde represented by the general formula (III) while introducing a gas containing oxygen to obtain a vinyl ester polymer. A method for producing a modified vinyl alcohol polymer as described in 1 above.

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)
The method includes the step of suspension polymerization of a vinyl ester monomer in an aqueous medium in the presence of an aldehyde represented by the general formula (III) while introducing a gas containing oxygen to obtain a vinyl ester polymer. 5. The method for producing a modified vinyl alcohol polymer according to any one of 4 above.

(In the formula, R represents an alkyl group having 2 to 9 carbon atoms.)