JP6606387B2 - Dispersion aid for suspension polymerization, aqueous liquid thereof, and method for producing vinyl resin using them - Google Patents

Description

  The present invention relates to a polyvinyl alcohol polymer that can be suitably used as a dispersion aid for suspension polymerization of vinyl compounds, an aqueous liquid containing the polyvinyl alcohol polymer, and the polyvinyl alcohol polymer as a dispersion aid. The present invention relates to a method for producing a vinyl resin.

In general, a vinyl chloride resin (or sometimes referred to as a vinyl chloride polymer) is generally a suspension weight in which a vinyl chloride monomer is dispersed in an aqueous medium together with a polymerization initiator and a dispersion stabilizer. Manufactured legally.
The dispersion stabilizer used at that time is a so-called “dispersion stabilizer” added to stabilize the dispersibility of the vinyl chloride monomer and adjust the particle size of the vinyl chloride resin produced. There is a so-called “dispersion aid” added to increase the porosity in the vinyl chloride resin particles.

Conventionally, polyvinyl alcohol (PVA), hydroxypropylmethylcellulose, and the like have been used as a “dispersion stabilizer” (or sometimes referred to as a primary dispersant hereinafter) (see Patent Documents 1 to 3). Further, as the “dispersion aid”, PVA having a saponification degree lower than that of the primary dispersant (dispersion stabilizer) described above is used (see Patent Document 4).
For example, in the method for producing a vinyl chloride polymer described in Patent Document 4, PVA having a saponification degree of 75 to 85 mol% is used as the dispersion stabilizer, and the saponification degree is 20 to 57 mol as the dispersion aid. % PVA is used.
In addition, as disclosed in Patent Documents 5 to 7, various proposals have been made to improve the performance of the dispersion aid, for example, to improve the porosity of the vinyl chloride resin particles.

  However, when the dispersion aids described in Patent Documents 4 to 7 are used, the porosity, which is the original purpose of using the dispersion aid, can be sufficiently improved. Due to the lack of water dispersibility, there is a drawback that an organic solvent such as alcohol must be used in combination for use as a solution or dispersion.

  Thus, since PVA with a saponification degree lower than 60 mol% has low affinity with water, there exists a fault that it cannot be used as aqueous solution and aqueous liquid. In order to compensate for the drawbacks, as in Patent Documents 8 to 19, ken groups in which an ionic group such as a carboxylic acid group, a sulfonic acid group or an amino group or a hydrophilic group other than polyvinyl alcohol such as polyoxyalkylene is introduced into the molecule. A method for producing a vinyl chloride resin using PVA having a low degree of conversion as a dispersion aid has been proposed.

JP 2002-003510 A JP 2003-327607 A JP 2003-238606 A JP 2005-281680 A Japanese Patent Laid-Open No. 04-85303 Japanese Patent Laid-Open No. 2004-115821 Japanese Patent Laid-Open No. 04-93301 Japanese Patent Laid-Open No. 04-154810 JP 05-345805 A JP-A-10-168128 JP-A-4-154810 JP 10-259213 A WO91 / 15518 JP-A-9-77807 JP-A-10-152508 Japanese Patent Laid-Open No. 9-100301 JP-A-10-152508 JP-A-9-183805 JP 2002-37807 A

However, the dispersion aids introduced with ionic groups as described in Patent Documents 8 to 19 are improved in water solubility and water dispersibility, but the amount of buffer used during suspension polymerization, the buffer The range of pH value (3-8) in the polymerization system may change depending on the timing of charging, the oxygen concentration in the polymerization system, etc., or its characteristics (improvement of porosity, uniformity of porosity distribution, demonomerization and plasticizer There are cases in which the improvement in absorption capacity and the like cannot be sufficiently exhibited, and there are concerns that the polymerization stability becomes poor and the adhesion of the scale becomes remarkable.
In addition, a dispersion aid improved by introducing an ionic group to improve water solubility and water dispersibility can obtain an aqueous liquid having a content of 10% by mass or less. There was a problem that the agent aggregated and an aqueous liquid could not be obtained.

  Further, in recent years, from the viewpoint of environmental considerations and workability improvement, water can be made into an aqueous liquid without using an organic solvent such as alcohols, and a high concentration aqueous liquid can be obtained. There has been a demand for the development of a dispersion aid that is excellent in polymerization stability and excellent in the effect of increasing the porosity of the vinyl chloride resin that is originally intended for use.

An object of the present invention is to provide a dispersion aid useful for the polymerization of vinyl compounds, which can obtain a high concentration aqueous liquid having good stability and easy-to-handle viscosity.
Another object of the present invention is to provide a dispersion aid that, when used for suspension polymerization of a vinyl compound, stably provides a good polymer (vinyl resin) under a wide range of polymerization conditions. .
In particular, an object of the present invention is to provide a dispersion aid for suspension polymerization that can obtain a vinyl resin (particularly, vinyl chloride resin) having a high porosity and excellent plasticizer absorbability. And
Another object of the present invention is to provide a method for producing a vinyl resin having excellent plasticizer absorbability by using the dispersion aid.

Since the aqueous liquid containing PVA having a high degree of polymerization has a high viscosity, when it is a high concentration PVA aqueous liquid, the viscosity becomes particularly high and handling properties are poor. By increasing the randomness of the functional fatty acid group (for example, acetic acid group, etc.), the hydrophobic group is randomly arranged in the PVA molecular chain, thereby reducing the interaction between the PVA molecules, It was found that even if it is an aqueous liquid containing a high concentration of PVA having a high degree of polymerization, an aqueous liquid having a low viscosity and excellent handleability can be obtained because of improved water dispersibility.
In addition, although the PVA having a low degree of polymerization has a low ability to disperse a vinyl monomer, the present inventors have increased the blocking property of hydrophobic fatty acid groups (eg, acetate groups) contained in the PVA having a low degree of polymerization. By doing so, each block chain of a hydrophobic block (that is, a block formed by a structural unit containing a fatty acid group) and a hydrophilic block (that is, a block formed by a structural unit containing a hydroxy group) in the PVA molecular chain It has been found that sufficient vinyl monomer dispersion ability can be obtained even with PVA having a small degree of polymerization, because the length becomes longer and the surface activity of PVA is improved.

Specifically, when using the PVA having a high degree of polymerization, the present inventors increase the randomness of the fatty acid group contained in the PVA (that is, set the fatty acid group block character to a value close to 1). Thus, it has been found that even an aqueous liquid containing a high concentration of PVA having a high degree of polymerization can reduce the viscosity of the aqueous liquid.
On the other hand, when using the PVA having a low degree of polymerization, the present inventors increase the block property of the fatty acid group contained in the PVA (that is, set the fatty acid group block character to a value close to 0). It has been found that even an aqueous liquid containing PVA having a small degree of polymerization can obtain a sufficient vinyl monomer dispersion ability.

  And from these, the present inventors do not merely specify the polymerization degree of PVA or the block character of the fatty acid group contained in PVA, but by making these ratios within a certain range, handling properties and vinyl It has been found that an aqueous liquid excellent in the dispersing ability of the system monomer can be obtained.

That is, as a result of further diligent research to solve the above problems, the inventors of the present invention are polyvinyl alcohol polymers having a saponification degree of 45 to 65 mol%. Is adjusted to the range of the following (formula 1), a high-concentration aqueous liquid capable of containing 30 to 50% by mass of the polyvinyl alcohol-based polymer can be obtained, and the polyvinyl alcohol-based polymer is used. As a result, it was found that a vinyl chloride resin excellent in porosity can be obtained by suspension polymerization of a vinyl chloride monomer, and the present invention was completed through further research.
(Formula 1) 250 <= X / Y <= 400
(Here, X represents the degree of polymerization of the polyvinyl alcohol polymer, and Y represents the block character of the polyvinyl alcohol polymer.)

That is, the present invention relates to the following dispersion aids and the like.
[1] A dispersion aid for suspension polymerization of a vinyl compound, which is a polyvinyl alcohol polymer having a saponification degree of 45 to 65 mol% and satisfying the following (formula 1).
(Formula 1) 250 <= X / Y <= 400
(Here, X represents the degree of polymerization of the polyvinyl alcohol polymer, and Y represents the block character of the polyvinyl alcohol polymer.)
[2] Dispersion aid for suspension polymerization of vinyl compound, which is a polyvinyl alcohol polymer having a polymerization degree of 160 to 400, a block character of 0.6 to 0.9, and a saponification degree of 45 to 65 mol% Agent.
[3] The dispersion aid for suspension polymerization according to the above [1] or [2] for suspension polymerization by being present in a polymerization system together with a water-soluble polymer.
[4] The dispersion aid for suspension polymerization according to [3], wherein the water-soluble polymer is polyvinyl alcohol having a saponification degree of 65 to 90 mol%.
[5] The dispersion aid for suspension polymerization according to any one of the above [1] to [4] for use in polymerization of a vinyl compound containing vinyl chloride.
[6] An aqueous liquid containing the dispersion aid for suspension polymerization according to any one of [1] to [5], wherein the aqueous liquid contains 30 to 50% by mass of the polyvinyl alcohol polymer.
[7] A method for producing a vinyl resin in which a vinyl compound is suspension-polymerized in an aqueous solvent in the presence of the dispersion aid for suspension polymerization according to any one of [1] to [5].
[8] The production method of the above-mentioned [7], wherein suspension polymerization is further performed in the presence of a water-soluble polymer.
[9] The production method of the above-mentioned [8], wherein the water-soluble polymer is polyvinyl alcohol having a saponification degree of 65 to 90 mol%.
[10] The production method according to any one of [7] to [9], wherein the vinyl compound includes vinyl chloride.

The present invention can provide a high-concentration aqueous liquid having good stability and easy-to-handle viscosity, and can provide a dispersion aid useful for suspension polymerization of vinyl compounds. By using an aqueous liquid with good stability and easy-to-handle viscosity, the performance of the dispersion aid (for example, improvement in the porosity and plasticizer absorption of vinyl resins obtained by suspension polymerization) is fully demonstrated. can do.
In addition, according to the present invention, a high concentration aqueous liquid can be obtained without using an organic solvent, and a dispersion aid useful for suspension polymerization of vinyl compounds can be provided.
In addition, according to the present invention, when used for suspension polymerization of a vinyl compound, a dispersion aid capable of stably obtaining a good polymer under a wide range of polymerization conditions can be provided.
In particular, according to the present invention, a dispersion aid for suspension polymerization that can obtain a vinyl resin (particularly a vinyl chloride resin) having a high porosity and excellent plasticizer absorbability, de-monomer property, etc. An agent can be provided.
Moreover, according to this invention, the manufacturing method of the vinyl resin excellent in plasticizer absorptivity etc. can be provided by using this dispersing aid.

Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.
The dispersion aid (additive, dispersant) for suspension polymerization of the vinyl compound (or vinyl monomer or vinyl monomer) of the present invention is a specific polyvinyl alcohol polymer.

[Polyvinyl alcohol polymer]
Examples of the polyvinyl alcohol polymer used in the dispersion aid of the present invention (hereinafter, the polyvinyl alcohol polymer may be abbreviated as PVA polymer) include, for example, a saponification reaction of a vinyl ester polymer. The PVA polymer (A) obtained by this can be used.
The vinyl ester polymer can be obtained by polymerizing a vinyl ester monomer. The polymerization method is not particularly limited and may be a conventionally known method. Examples include bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and the like, and a saponification reaction performed after controlling the polymerization degree or after polymerization. In view of the above, solution polymerization using methanol as a solvent, or suspension polymerization using water or water and methanol as a dispersion medium is preferable, but is not limited thereto.

  The vinyl ester monomer that can be used for the polymerization is not particularly limited, and examples thereof include fatty acid vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl caprylate (vinyl octoate), and vinyl versatate. These vinyl ester monomers can be used alone or in combination of two or more. Among these, vinyl acetate is preferable from an industrial viewpoint.

When the vinyl ester monomer is polymerized, the vinyl ester monomer may be copolymerized with other monomers as long as the effects of the present invention are exhibited.
Examples of other monomers that can be used include, but are not limited to, for example, α-olefins (eg, ethylene, propylene, n-butene, isobutylene, etc.), acrylic acid and salts thereof, and acrylate esters [eg, acrylic Acid alkyl esters (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, _C1-20 alkyl acrylates such as dodecyl acrylate and octadecyl acrylate)], methacrylic acid and salts thereof, methacrylic acid esters [for example, alkyl methacrylates (for example, methyl methacrylate, ethyl methacrylate, methacrylic acid) n-propyl, methacrylic acid i-propi , Methacrylic acid n- butyl, i- butyl methacrylate, butyl t- methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, _{C 1-20} alkyl such as octadecyl methacrylate), acrylamide, acrylamide derivative ( For example, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt or its quaternary salt, N-methylolacrylamide, etc.) Methacrylamide, methacrylamide derivatives (eg, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propane sulfonic acid and salts thereof, methacrylamide propylene Dimethylamine and its salts or quaternary salts thereof, N-methylol methacrylamide, etc.), vinyl ethers (for example, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, C _1-20 alkyl vinyl ethers such as t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, etc.), nitriles (eg, acrylonitrile, methacrylonitrile, etc.), vinyl halides (eg, vinyl chloride, vinyl fluoride, etc.), Vinylidene halides (for example, vinylidene chloride, vinylidene fluoride, etc.), allyl compounds (for example, allyl acetate, allyl chloride, etc.), unsaturated dicarboxylic acids (for example, maleic acid, itaconic acid, fluoric acid, etc.) Le acid) and its salts or its esters, vinyl silyl compounds (e.g., vinyl trimethoxysilane, etc.), fatty acid alkyl esters (e.g., isopropenyl acetate and the like) and the like. These other monomers can be used alone or in combination of two or more.
However, for the purpose of the present invention, it is preferable not to copolymerize ionic monomers such as carboxylic acid and sulfonic acid.

  Content of a vinyl ester monomer is 60-100 mass% etc. with respect to the total amount of a vinyl ester monomer and another monomer, for example.

  When the other monomer is used, the content of the other monomer is, for example, 0.1 to 20% by mass with respect to the total amount of the vinyl ester monomer and the other monomer. .

In the polymerization of the vinyl ester monomer, a chain transfer agent may be allowed to coexist for the purpose of adjusting the degree of polymerization of the resulting vinyl ester polymer.
Examples of the chain transfer agent include, but are not limited to, aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde, and benzaldehyde; ketones such as acetone, methyl ethyl ketone, hexanone, and cyclohexanone; mercaptans such as 2-hydroxyethanethiol and dodecyl mercaptan. And organic halogens such as carbon tetrachloride, trichlorethylene and perchloroethylene, among which aldehydes and ketones are preferably used. These chain transfer agents can be used alone or in combination of two or more.
The addition amount of the chain transfer agent is determined according to the chain transfer constant of the chain transfer agent to be added and the degree of polymerization of the target vinyl ester polymer, but is generally 0.1% relative to the vinyl ester monomer. -10 mass% is desirable.

A PVA polymer (A) can be produced by saponifying the vinyl ester polymer obtained as described above.
The saponification reaction method of the vinyl ester polymer is not particularly limited and may be a conventionally known method. For example, a conventionally known basic catalyst such as sodium hydroxide, potassium hydroxide, sodium methoxide, hydrochloric acid, An alcoholysis or hydrolysis reaction using an acidic catalyst such as sulfuric acid or p-toluenesulfonic acid can be applied.
Examples of the solvent used in the saponification reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene; These can be used alone or in combination of two or more.

  Regarding the saponification degree of the PVA polymer (A), the saponification degree of the PVA polymer determined by the method for measuring the saponification degree of PVA defined in JIS K 6726 is usually 45 mol% to 65 mol%. , Preferably 45 mol% to 60 mol%. If the saponification degree is 45 mol% or more, the viscosity of the aqueous liquid containing the PVA polymer will not be too high, and the stability of the aqueous liquid will be excellent. If the saponification degree is 60 mol% or less, the stability of the suspension polymerization of the vinyl compound is excellent.

Moreover, the PVA polymer used for this invention normally satisfies the following (Formula 1).
(Formula 1) 250 <= X / Y <= 400
(Here, X represents the degree of polymerization of the polyvinyl alcohol polymer, and Y represents the block character of the polyvinyl alcohol polymer.)

If the value of (Formula 1) is 400 or less, the fluidity of the aqueous liquid containing the PVA polymer is improved, or the stability of the aqueous liquid is excellent.
Further, if the value of (Formula 1) is 250 or more, the suspension polymerization stability of the vinyl compound is excellent, and a high porosity vinyl resin [particularly, vinyl chloride resin (hereinafter, PVC type). It may be called resin)].

In Formula 1, the polymerization degree X is a polymerization degree calculated | required by the average polymerization degree measuring method of PVA prescribed | regulated by JISK6726.
Although the polymerization degree of a PVA polymer (A) is not specifically limited, Preferably it is 160-400, More preferably, it is 180-350.
If the degree of polymerization of the PVA polymer (A) is 160 or more, the stability of suspension polymerization of the vinyl compound is excellent, and if the degree of polymerization is 400 or less, the PVA polymer weight during suspension polymerization of the vinyl compound is excellent. Precipitation of the coalescence (A) can be prevented, and the original performance as a dispersion aid can be easily developed.

Further, the block character Y is a block character (η) of the residual fatty acid group of the PVA polymer (A), and is an index indicating the distribution of the residual fatty acid group of the PVA polymer, and is in the ¹³ C-NMR spectrum. It is obtained by analyzing three peaks appearing in the methylene region. The three peaks correspond to three two-unit chain structures corresponding to (OH, OH), (OH, OR), and (OR, OR), and the absorption intensity is proportional to the three structures. ing. The block character (η) is expressed by the following (formula 2). The residual fatty acid group (OR group) is a fatty acid group contained in a fatty acid vinyl ester unit (that is, a unit derived from a fatty acid vinyl ester). For example, when vinyl acetate is used as the fatty acid vinyl ester, an acetoxy group is used. (OAc group) is shown.

(Formula 2) η = (OH, OR) / [2 (OH) (OR)]
[In the formula, (OH, OR) represents the ratio of the two-unit chain structure (OH, OR) in which the OH group and the OR group are adjacent to each other, and is determined from the intensity ratio of methylene carbon in the ¹³ C-NMR spectrum. In the formula, (OH) represents the degree of saponification, and (OR) represents the ratio of residual fatty acid groups, each represented by a mole fraction. ]

In (Formula 2), (OH, OR) represents the ratio of (OH, OR) to the total amount of (OH, OH), (OH, OR) and (OR, OR).
Moreover, (OH) and (OR) represent the ratio of (OH) and (OR) to the total amount of (OH) and (OR) contained in the PVA polymer (A).

  This block character usually takes a value of 0-2, the closer to 0, the higher the blockiness of the residual fatty acid group distribution, the closer to 1, the higher the randomness, and the closer to 2, the alternation. Indicates high. The blockiness of the residual fatty acid group affects the dispersibility of vinyl monomers such as vinyl chloride monomers. As for this block character, its measurement method and the like are described in detail in “Poval”, pp. 246 to 249 of Macromolecules Publication (published in 1981) and Macromolecules, 10, 532 (1977).

Although the block character of a PVA polymer (A) is not specifically limited, It is preferable that it is 0.6-0.9, More preferably, it is 0.6-0.8.
If a block character is 0.9 or less, the porosity of vinyl resin, such as PVC resin obtained, will improve. If the block character is 0.6 or more, the fluidity of the aqueous liquid containing the PVA polymer is improved, and the handleability of the aqueous liquid is improved.

In the present invention, the block character of the residual fatty acid group of the PVA polymer (A) is the type of saponification catalyst and solvent used when the vinyl ester polymer is saponified to produce the PVA polymer (A). Etc. can be adjusted.
In order to obtain a block character of 0.6 or more, a method of acid saponification using an acidic catalyst such as sulfuric acid, hydrochloric acid, paratoluenesulfonic acid and the like is simple.
There is also a method of adjusting the obtained PVA polymer (A) by heating to increase the block character.

  In the present invention, a particularly preferable PVA polymer (A) includes a PVA polymer having a polymerization degree of 160 to 400, a block character of 0.6 to 0.9, and a saponification degree of 45 to 65 mol%. And a PVA polymer having a polymerization degree of 180 to 350, a block character of 0.6 to 0.8, and a saponification degree of 45 to 60 mol%.

[Aqueous liquid]
The dispersion aid of the present invention may be used as it is or as an aqueous liquid.
What is necessary is just to make it disperse | distribute or melt | dissolve in an aqueous solvent by making said polyvinyl alcohol-type polymer (A) into a dispersoid when setting it as an aqueous liquid.

Although the aqueous solvent used for an aqueous liquid is not specifically limited, Usually, it is water.
The aqueous solvent may contain a water-soluble organic solvent from the viewpoint of improving the standing stability.
Examples of water-soluble organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol; esters such as methyl acetate and ethyl acetate; ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl Glycol derivatives such as ether; and the like. These organic solvents may be used alone or in combination of two or more.

  Content of the PVA-type polymer in an aqueous liquid is not specifically limited, For example, it is 30-50 mass% with respect to an aqueous liquid. If the proportion of the PVA polymer is 30% by mass or more, the standing stability of the aqueous liquid is improved, and if it is 50% by mass or less, the fluidity of the aqueous liquid is excellent. It is easy to prevent becoming.

In the aqueous liquid, the content of water in the aqueous solvent is, for example, 50 to 100% by mass.
When the aqueous solvent includes a water-soluble organic solvent, the content of the water-soluble organic solvent is 3.0% by mass or less (for example, 0.1%) with respect to the aqueous liquid from the viewpoint of environmental considerations and workability improvement. It is preferable that it is -3.0 mass%).

The method for obtaining such an aqueous liquid is not particularly limited, and is a method in which the alcohol used for saponifying a vinyl ester polymer is replaced with an aqueous solvent by blowing steam or the like. Examples thereof include a method in which the coalesced (A) is charged and subsequently stirred, and a method in which heating is used in combination.
Even if the content of the polyvinyl alcohol polymer (A) is 30 to 50% by mass, the aqueous liquid of the present invention can be satisfactorily stable for more than one year without using an organic solvent, a dispersant or an emulsifier. (For example, standing stability at room temperature) is obtained.

  The viscosity of the aqueous liquid containing the dispersion aid of the present invention is, for example, 1 to 10,000 mPa · s from the viewpoint that the viscosity at 20 ° C. measured using a B-type rotational viscometer is excellent in handling properties.

[Method for producing vinyl resin]
A suspension polymerization method of a vinyl compound using the dispersion aid of the present invention will be described.
A vinyl resin can be produced by suspension polymerization of a vinyl compound in the presence of the dispersion aid of the present invention.

  Suspension polymerization is usually performed by adding the dispersion aid of the present invention to an aqueous solvent and dispersing the vinyl monomer. The suspension polymerization is usually performed in the presence of a polymerization initiator. The aqueous solvent is usually water and may be heated water. Suspension polymerization may be carried out in the presence of a dispersion stabilizer in the polymerization system.

The vinyl compound (or vinyl monomer or vinyl monomer) to be subjected to suspension polymerization is not particularly limited as long as it is a vinyl compound.
Examples of the vinyl compound include vinyl chloride, vinylidene halide, vinyl ether, vinyl ester (for example, vinyl acetate, vinyl benzoate, etc.), (meth) acrylic acid, (meth) acrylic acid ester (for example, (meth) acrylyl). Acid alkyl esters, etc.), styrenic monomers (eg styrene etc.), unsaturated dicarboxylic acids (eg maleic acid etc.) or anhydrides thereof, olefins (eg ethylene, propylene etc.) etc., but at least vinyl chloride It is preferable to contain. These vinyl monomers can be used alone or in combination of two or more.

  A vinyl chloride resin can be obtained by suspension polymerization of a vinyl compound containing vinyl chloride. In the production of the vinyl chloride resin, it is preferable that 50 to 100 mol% (or 50 to 100 mass%) is vinyl chloride with respect to the total amount of the vinyl compound to be used.

Examples of the dispersion stabilizer include water-soluble polymers (for example, cellulose derivatives such as methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, gelatin, polyvinyl alcohol, polyvinylpyrrolidone, etc.).
Among these, PVA is preferable. The PVA may be any PVA that does not belong to the category of the PVA polymer (A), and the degree of saponification of such PVA may be 65 to 90 mol%. Among these, polyvinyl alcohol having a saponification degree of 65 to 90 mol% and polyvinyl alcohol having a polymerization degree of 500 to 3500 are preferably used.

  The addition amount of the dispersion stabilizer cannot be generally specified depending on the type of the dispersion stabilizer or the like, but is usually 5 parts by mass or less, preferably 0.005 to 1 part by mass with respect to 100 parts by mass of the vinyl monomer, 0.01-0.5 mass part is further more preferable.

  In the suspension polymerization of the vinyl monomer, the amount of the dispersion aid of the present invention is not particularly limited, but the PVA system contained in the dispersion aid is 100 parts by weight of the vinyl monomer. The mass of the polymer is usually 1 part by mass or less (for example, 0.001 to 1 part by mass), preferably 0.001 to 0.5 part by mass, and more preferably 0.005 to 0.2 part by mass. .

The mass ratio of the addition amount of the dispersion stabilizer and the PVA polymer contained in the dispersion aid of the present invention cannot be generally described depending on the type of the dispersion stabilizer, but the range of 90/10 to 30/70 80/20 to 50/50 is particularly preferable.
The dispersion stabilizer and the dispersion aid may be charged all at once in the polymerization system at the initial stage of polymerization, or may be charged separately during the polymerization.

  The dispersion aid of the present invention may be added to the vinyl monomer polymerization system in the form of a powder, or as an aqueous liquid (preferably as an aqueous liquid of 30 to 50% by mass of a PVA polymer). ) You may use it after preparing. Further, the dispersion aid of the present invention may be charged into the polymerization system when or after the vinyl monomer is charged into the polymerization system, but before the vinyl monomer is charged into the polymerization system. It is preferable to charge in the inside.

  In addition, the polymerization initiator is not limited, but may be particularly oil-soluble, for example, a percarbonate compound (for example, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate). Etc.), peroxyester compounds (for example, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-hexylperoxypivalate, α-cumylperoxyneodecanoate, t- Hexyl neohexanoate, 2,4,4-trimethylpentyl-2-peroxy-2-neodecanoate, etc.), azo compounds [eg, azobis (2,4-dimethylvaleronitrile), azobisisobutyronitrile, etc.], Peroxide compounds (eg lauryl peroxy) , Benzoyl peroxide, cumene hydroperoxide, 2,4,4-trimethylpentyl-2-peroxy phenoxy acetate, and the like) and the like.

It is preferable that the addition amount of a polymerization initiator is 0.02-0.2 mass part with respect to 100 mass parts of vinyl monomers or a monomer mixture containing the same.
Further, the polymerization initiator may be added either before or after the aqueous solvent or monomer is charged into the polymerization system. Alternatively, an aqueous emulsion may be added in advance to the polymerization tank.

  As long as the effects of the present invention are not inhibited, a cationic, anionic or nonionic surfactant or the like may be added during suspension polymerization.

  In addition, a well-known technique can be used for the various conditions in the manufacturing method of the vinyl resin of this invention. For example, the charging conditions of each raw material compound, the charging ratio of the monomer and the aqueous solvent, the polymerization temperature, the polymerization conversion rate, the stirring rotation speed, and the like are not particularly limited. Further, if necessary, various known additives such as an antifoaming agent, a polymerization degree adjusting agent, a chain transfer agent, an antioxidant, and an antistatic agent may be used in combination.

[Vinyl chloride resin]
The present invention also includes a specific vinyl chloride resin. The method for producing the vinyl chloride resin is not particularly limited, but it can usually be produced by suspension polymerization of the vinyl compound described above.

  The optimal value of the vinyl chloride resin varies depending on the use of the vinyl chloride resin, but the dioctyl phthalate used as a plasticizer for the vinyl chloride resin is usually 10 parts by mass or more with respect to 100 parts by mass of the vinyl chloride resin. Preferably it is 13-40 mass parts, More preferably, 15-40 mass parts can be absorbed. A higher plasticizer absorption is preferable because fish eyes are reduced when a vinyl chloride resin molded product is obtained. However, when the amount of plasticizer absorption increases, the bulk specific gravity decreases, so when used in hard vinyl chloride resin applications that do not require much plasticizer, such as pipe applications and window frame applications, plasticizer absorption The amount need not be so high and is preferably 10 parts by mass or more, but when used in soft vinyl chloride resin applications that need to contain a large amount of plasticizer such as sheets and films, the amount of plasticizer absorbed is It is preferably 20 parts by mass or more. The dispersion aid is mainly used to increase the plasticizer absorption amount, and the level of the plasticizer absorption amount can be adjusted by increasing or decreasing the addition amount. The dispersion aid of the present invention may be used for both hard vinyl chloride resin applications and soft vinyl chloride resin applications. The measuring method of the plasticizer absorption amount is not particularly limited, and for example, it can be measured using the method described in Examples described later.

  The average particle diameter of the vinyl chloride resin is, for example, 100 to 200 μm, preferably 110 to 190 μm, and more preferably 120 to 180 μm. The measuring method of an average particle diameter is not specifically limited, For example, it can measure by measuring a particle size distribution using a low tap type vibration sieve (using a JIS sieve).

The maximum particle size of the vinyl chloride resin is usually 250 μm or less. In the vinyl chloride resin, the amount of particles that cannot pass through a JIS standard # 60 sieve is preferably less than 0.1% by mass. The particle size distribution of the vinyl chloride resin is preferably in the range of 60 to 250 μm.
The vinyl chloride resin preferably has an amount of particles passing through a JIS standard # 250 sieve of less than 0.1% by mass.
The measuring method of the maximum particle size and the particle size distribution is not particularly limited, and can be measured, for example, by measuring the particle size distribution using a low-tap vibration sieve (using a JIS sieve).

The bulk specific gravity (bulk density) of the vinyl chloride resin is, for example, 0.35 to 0.65 g / ml, preferably 0.4 to 0.6 g / ml, more preferably 0.5 to 0.6 g / ml. .
The bulk specific gravity is preferably higher because the extrusion speed can be improved. The bulk specific gravity can be measured according to JIS K 6721.

  Further, the vinyl chloride resin of the present invention has a high porosity, an excellent de-monomer property and a plasticizer absorbability, and has excellent properties such as less generation of fish eyes.

EXAMPLES The present invention will be described more specifically with reference to examples below, but the present invention is not limited to these examples.
In the following Examples and Comparative Examples, “%” and “part” mean “% by mass” and “part by mass” unless otherwise specified.

First, the evaluation method of the polyvinyl alcohol polymer (PVA polymer) aqueous liquid in this example is shown below.
(Characteristic evaluation of PVA polymer aqueous liquid)
About the obtained polyvinyl alcohol-type polymer aqueous liquid, stability, a viscosity, and fluidity | liquidity were each confirmed and measured by the following method.
a) Stability: 200 g of an aqueous liquid was placed in a 200 ml tall vicat and left standing at 20 ° C. for one day, and the state was visually observed. ○: Uniform (no precipitation or phase separation) ×: Non-uniform (precipitation or phase separation)
b) Viscosity: The viscosity at 20 ° C. of the aqueous liquid was measured using a B-type rotational viscometer.
c) Fluidity: The fluidity of the aqueous liquid was evaluated according to the following criteria.
○: Viscosity = 10000 mP · s or less, X: Viscosity = 10000 mP · s or more

Next, the evaluation method of the vinyl chloride polymer (vinyl chloride resin) in this example is shown below.
(Evaluation of vinyl chloride polymer)
For the vinyl chloride polymer, the average particle size, coarse particle content, bulk specific gravity, and plasticizer absorbability were evaluated as follows.

<Average particle size, coarse particle content>
The particle size distribution was measured with a low tap type vibrating sieve (using a JIS sieve), and the average particle size was determined. The average particle diameter of the vinyl chloride polymer is generally in the range of 100 μm to 200 μm.
From the measured particle size distribution, the content of coarse particles of 60 mesh-on (that is, the particle size is 250 μm or more) was expressed in%. The smaller the content, the smaller the coarse particles, the sharper the particle size distribution, and the better the polymerization stability. In Table 1 described later, the content is indicated as # 60 on.

<Bulk specific gravity>
It measured based on JISK6721. It shows that extrusion rate can be improved and workability is so good that bulk specific gravity is large.

<Plasticizer absorbability>
Put the obtained resin in a cylindrical container filled with glass fiber at the bottom, add an excess of dioctyl phthalate (hereinafter abbreviated as DOP), and let it stand for 30 minutes. After removing excess DOP by centrifugation, the weight of the resin was measured, and the amount of DOP absorption per 100% by mass of the polymer was calculated. The larger the DOP absorption amount, the better the plasticizer absorbability and the better the moldability. Moreover, it shows that the porosity of a vinyl chloride polymer is so high that plasticizer absorptivity is high.

<Example 1>
(Synthesis of PVA polymer)
A reactor equipped with a stirrer, a condenser, a nitrogen gas inlet and an initiator inlet is charged with 10 parts by mass of vinyl acetate, 67 parts by mass of methanol and 0.02 parts by mass of azobisisobutyronitrile in advance in a polymerization vessel. After the substitution, the mixture was heated to the boiling point. And when reaction liquid temperature became 60 degreeC or more, 140 mass parts of vinyl acetate was dripped little by little over 13 hours from the superposition | polymerization can upper part. One hour after the completion of the dropping, the system was cooled when the polymerization rate reached 95%, and the polymerization was stopped.
Next, unreacted vinyl acetate was removed by a conventional method, and 2 parts by mass of 50% methanol solution of paratoluenesulfonic acid was added to 100 parts by mass of 50% methanol solution of polyvinyl acetate, and mixed well. A saponification reaction was performed at 50 ° C., and 4.5 parts by mass of a 5% by weight methanol solution of sodium hydroxide was added to neutralize the saponification reaction to obtain a solution of the PVA polymer (A). The obtained solution was dried to obtain a PVA polymer having a saponification degree of 55.0 mol%, an average degree of polymerization (PA) of 210, a block character of 0.70, and a value obtained from the above-mentioned formula 1 of 300. .

(Creation of aqueous liquid)
The obtained PVA polymer was poured into water so as to contain 40% by mass as a solute, dissolved by stirring at 80 ° C. for 1 hour, and cooled to room temperature to obtain an aqueous liquid. The evaluation results of the obtained aqueous liquid are shown in Table 1.
The obtained aqueous liquid was stable without precipitation and phase separation, had a viscosity of 1380 mPa · s, and had good fluidity.

(Suspension polymerization of vinyl chloride)
In a polymerization machine (pressure autoclave) with an internal volume of 100 liters, 0.056 parts by mass of partially saponified polyvinyl alcohol (saponification degree 80 mol%, degree of polymerization 2500) with respect to 100 parts by mass of vinyl chloride monomer. Polyvinyl alcohol (saponification degree 72 mol%, polymerization degree 800) 0.014 parts by mass was dissolved in 112.5 parts by mass of deionized water, and the aqueous liquid of the present invention obtained above was 0.0625 parts by mass. Parts (0.025 parts by mass in terms of contained dispersion aid (PVA polymer)) and 0.05 parts by mass of t-butylperoxyneodecanoate were added.
Next, after degassing the inside of the polymerization apparatus to 40 mmHg, 100 parts by mass of vinyl chloride monomer was charged and stirring was started. The polymerization temperature was 57 ° C., and this temperature was maintained until the polymerization was completed.
When the polymerization conversion rate reached 80%, the reaction was terminated and unreacted monomers in the polymerization machine were collected, and then the polymer slurry was taken out of the system and dehydrated and dried to obtain a vinyl chloride polymer. The evaluation results of the vinyl chloride polymer are shown in Table 1.
A vinyl chloride resin (PVC resin) having no porosity and a sufficiently high plasticizer absorption amount and a high porosity was obtained.

<Examples 2-9, Comparative Examples 1-5>
A PVA polymer was prepared in the same manner as in Example 1 except that the saponification degree, the polymerization degree, the block character, and the value obtained from Equation 1 were as shown in Table 1, and the same as in Example 1. An aqueous liquid having a PVA polymer content shown in Table 1 was prepared by the method.
Further, using the aqueous liquid, the amount of the aqueous liquid charged under the same conditions as in Example 1 (the amount of the dispersion aid of the present invention added is 0.025 parts by mass in terms of (PVA polymer)). And suspension polymerization of vinyl chloride was performed to obtain a vinyl chloride resin.
Table 1 shows the evaluation results of the aqueous liquid and the evaluation results of the obtained vinyl chloride resin.

<Comparative Example 6>
A vinyl chloride resin was obtained by suspension polymerization of vinyl chloride in the same manner as in Example 1 except that the PVA polymer of the present invention was not used.
The evaluation results of the obtained vinyl chloride resin are also shown in Table 1.

From Table 1, it can be seen that the example is superior to the comparative example. The results are described as follows.
Examples 2 to 9: The obtained aqueous liquid was stable without precipitation and phase separation, and had good fluidity. In addition, a PVC resin having no porosity and a sufficiently high plasticizer absorption amount and a high porosity was obtained.
Comparative example 1: Since the value calculated | required from Formula 1 is larger than 400, the fluidity | liquidity of the aqueous liquid was remarkably low. As a result, the original performance of the dispersant could not be exhibited, the plasticizer absorption amount of the PVC resin was slightly lowered, and the average particle size was slightly enlarged.
Comparative example 2: Since the value calculated | required from Formula 1 is larger than 400, the fluidity | liquidity of the aqueous liquid was remarkably low. As a result, the original performance of the dispersant could not be exhibited, and PVC particles could be blocked due to the suspension polymerization of PVC, and an evaluable PVC resin could not be obtained.
Comparative Example 3: Since the value obtained from Formula 1 is less than 250, the stability of the suspension polymerization of vinyl chloride is deteriorated, and the PVC resin has an increased average particle size and a low porosity. The plasticizer absorbability was inferior.
Comparative Example 4: Since the degree of saponification was too low, the stability of the aqueous liquid was poor, the PVA polymer was precipitated from the aqueous liquid, and the aqueous liquid could not be produced.
Comparative Example 5: Since the degree of saponification is too high, the value obtained from Formula 1 is larger than 400, so that the PVC resin has an average particle size that is enlarged, the porosity is low, and the plasticizer absorption is low. It was.
Comparative Example 6: Since the PVA polymer of the present invention was not used, the obtained PVC resin had a very low porosity and a very low plasticizer absorption.

  Like these results, Examples 1-9 are excellent in the stability of an aqueous liquid and fluidity | liquidity compared with Comparative Examples 1-6, and the porosity of a vinyl chloride resin is high, As a result, plasticizer absorption It can be seen that excellent properties such as that the average particle diameter of the vinyl chloride resin does not increase due to its high properties and little adverse effect on the primary dispersant.

  The dispersion aid of the present invention can provide a high-concentration aqueous liquid having good stability and easy-to-handle viscosity, and is stable under a wide range of polymerization conditions when used for suspension polymerization of vinyl compounds. In particular, it is industrially very useful since a vinyl polymer having a high porosity and excellent plasticizer absorbability, demonomerization property and the like can be obtained.

Claims (10)

Dispersion aid for suspension polymerization of vinyl compound which is a polyvinyl alcohol polymer satisfying the following (formula 1) having a saponification degree of 45 to 65 mol% (formula 1) 250 ≦ X / Y ≦ 400
(Here, X represents the degree of polymerization of the polyvinyl alcohol polymer, and Y represents the block character of the polyvinyl alcohol polymer.)
However, the case where the polyvinyl alcohol polymer is the following (i) or the following (ii) is excluded.
(I) having an aliphatic hydrocarbon group at the terminal (ii) polymerization degree is 250, saponification degree is 55 mol%, and block character is 0.687 .   The dispersion aid for suspension polymerization according to claim 1, which is a polyvinyl alcohol polymer having a polymerization degree of 160 to 400 and a block character of 0.6 to 0.9.   The dispersion aid for suspension polymerization according to claim 1 or 2 for suspension polymerization by being present in a polymerization system together with a water-soluble polymer.   The dispersion aid for suspension polymerization according to claim 3, wherein the water-soluble polymer is polyvinyl alcohol having a saponification degree of 65 to 90 mol%.   The dispersion aid for suspension polymerization according to any one of claims 1 to 4, which is used for suspension polymerization of vinyl compounds containing vinyl chloride.   An aqueous liquid containing the dispersion aid for suspension polymerization according to any one of claims 1 to 5, wherein the aqueous liquid contains 30 to 50% by mass of the polyvinyl alcohol polymer.   A method for producing a vinyl resin, comprising subjecting a vinyl compound to suspension polymerization in an aqueous solvent in the presence of a dispersion aid for suspension polymerization according to any one of claims 1 to 5.   The production method according to claim 7, further comprising suspension polymerization in the presence of a water-soluble polymer.   The method according to claim 8, wherein the water-soluble polymer is polyvinyl alcohol having a saponification degree of 65 to 90 mol%.   The manufacturing method in any one of Claims 7-9 in which a vinyl type compound contains a vinyl chloride.