JP2023137813A - Method for producing vinyl chloride-based polymer - Google Patents

Abstract

To provide a method for producing a vinyl chloride-based polymer having less decrease in conversion rate in a polymerization of a vinyl chloride-based polymer having a low degree of polymerization.SOLUTION: There is provided a method for producing a vinyl chloride-based polymer which comprises a polymerization step of suspension polymerizing a mixture containing a vinyl chloride monomer and a monomer copolymerizable with a vinyl chloride monomer in the presence of an aldehyde having a specific structure, wherein in the polymerization step, suspension polymerization is carried out with a specific amount of aldehyde added and at a specific polymerization temperature.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a vinyl chloride polymer.

Vinyl chloride polymers have excellent properties and are therefore used in various fields, and various methods have been proposed to date to produce them. When dissolved in a solvent and used, lowering the degree of polymerization of vinyl chloride polymers is being considered in order to meet the demand for lowering the viscosity of the solution.

In order to obtain a vinyl chloride polymer with a relatively low degree of polymerization, a method is known in which a chain transfer agent is used during polymerization. Patent Document 1 describes that mercapto compounds such as 2-mercaptoethanol, thio compounds, or aldehydes can be used as chain transfer agents. Moreover, Patent Document 2 discloses a polymer of a mixture of vinyl chloride monomer and vinyl acetate monomer using propionaldehyde as a polymerization regulating substance in order to control the molecular weight.

Special Publication No. 2-25923 Special table 2006-519884 publication

However, the method for producing a vinyl chloride polymer using a chain transfer agent has a problem in that the conversion rate decreases in the polymerization of a vinyl chloride polymer with a low degree of polymerization. Therefore, in the polymerization of vinyl chloride-based polymers with a low degree of polymerization, a technique is desired to improve the decrease in the conversion rate of the polymer.

An object of one aspect of the present invention is to provide a method for producing a vinyl chloride polymer in which the conversion rate of the polymer is less reduced in the polymerization of a vinyl chloride polymer with a low degree of polymerization.

As a result of extensive studies, the present inventors have found that when producing a vinyl chloride polymer with a low degree of polymerization by suspension polymerization, under conditions in which an aldehyde with a specific structure is present in a specific amount, The present inventors have discovered that the reduction in conversion can be suppressed by carrying out suspension polymerization under temperature conditions, and have completed the present invention. That is, one embodiment of the present invention includes the following configuration.

[1]
A polymerization step of suspension polymerizing a mixture containing a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer in the presence of an aldehyde represented by the following general formula (I). , the amount of the aldehyde added is 0.1 parts by weight to 4 parts by weight based on 100 parts by weight of the mixture, and the polymerization temperature in the polymerization step is 65°C to 85°C. Production method.

(In the formula, R represents a saturated alkyl group having 2 to 4 carbon atoms.)

[2]
The method for producing a vinyl chloride polymer according to [1], wherein the aldehyde represented by the general formula (I) is an aldehyde represented by the following general formula (II) or (III).

[3]
The method for producing a vinyl chloride polymer according to [1] or [2], which comprises an isolation step of isolating vinyl chloride polymer particles having an average particle size of 50 μm to 400 μm.

[4]
The method for producing a vinyl chloride polymer according to any one of [1] to [3], wherein the aldehyde represented by the general formula (I) is used as a chain transfer agent.

[5]
In the polymerization step, the vinyl chloride polymer according to any one of [1] to [4], wherein the mixture further contains a polymerization initiator, and the polymerization initiator is an oil-soluble polymerization initiator. manufacturing method.

[6]
The method for producing a vinyl chloride polymer according to [5], wherein the oil-soluble polymerization initiator is (3,5,5, trimethylhexanoyl) peroxide or benzoyl peroxide.

According to one aspect of the present invention, it is possible to provide a method for producing a vinyl chloride polymer in which the conversion rate is less reduced in the polymerization of a vinyl chloride polymer with a low degree of polymerization.

An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various changes can be made within the scope of the claims, and technical means disclosed in different embodiments and examples can be applied. Embodiments and examples obtained by appropriately combining them are also included in the technical scope of the present invention. All documents mentioned herein are incorporated herein by reference. In this specification, when a numerical range is described as "A to B", the description is intended to be "above A (including A and greater than A) and less than or equal to B (including B and less than B)".

Hereinafter, a method for producing a vinyl chloride polymer according to an embodiment of the present invention will be described in detail.

A method for producing a vinyl chloride polymer according to an embodiment of the present invention (hereinafter simply referred to as "manufacturing method") is a method for producing a vinyl chloride monomer in the presence of an aldehyde represented by the following general formula (I). , comprising a polymerization step of suspension polymerizing a mixture containing a vinyl chloride monomer and a copolymerizable monomer, and the amount of the aldehyde added is 0.1 parts by weight to 100 parts by weight of the mixture. 4 parts by weight, and the polymerization temperature in the polymerization step is 65°C to 85°C.

(In the formula, R represents a saturated alkyl group having 2 to 4 carbon atoms.)

With such a configuration, the production method according to an embodiment of the present invention can produce a vinyl chloride polymer with little reduction in conversion rate in polymerization of a vinyl chloride polymer with a low degree of polymerization.

<Vinyl chloride polymer>
In the production method according to one embodiment of the present invention, a mixture containing a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer is subjected to suspension polymerization.

Monomers that can be copolymerized with the vinyl chloride monomer are not limited, and include, for example, vinyl esters (e.g., vinyl acetate, vinyl propionate, vinyl stearate), vinyl ethers (e.g., methyl vinyl ether, ethyl vinyl ether). , octyl vinyl ether, lauryl vinyl ether, isobutyl vinyl ether), acrylates (e.g. 2-ethylhexyl acrylate, butyl methacrylate, hydroxyalkyl acrylate), unsaturated carboxylic acid esters (e.g. methyl (meth)acrylate, (meth) ethyl acrylate, propyl (meth)acrylate, butyl (meth)acrylate, monomethyl maleate, dimethyl maleate, butylbenzyl maleate), unsaturated carboxylic acids and their salts (e.g. acrylic acid, methacrylic acid, maleic acid) , fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride), and crosslinking monomers (eg, diallyl phthalate). From the viewpoint of reducing the solution viscosity when dissolved in a solvent, monomers copolymerizable with vinyl chloride monomers are selected from the group consisting of vinyl acetate, vinyl propionate, and vinyl stearate. At least one of these is preferred.

(vinyl chloride monomer)
The content of vinyl chloride monomer in the mixture is preferably 50 to 98 parts by weight, more preferably 70 to 90 parts by weight, and 75 to 85 parts by weight, based on 100 parts by weight of the entire mixture. Part is more preferable. By setting the content of the vinyl chloride monomer in the mixture within this range, there is an advantage that the solution viscosity of the resulting vinyl chloride polymer when dissolved in a solvent is reduced.

(Monomer copolymerizable with vinyl chloride monomer)
The content of the monomer copolymerizable with the vinyl chloride monomer in the mixture is preferably 2 to 50 parts by weight, and 10 to 30 parts by weight, based on 100 parts by weight of the entire mixture. is more preferable, and even more preferably 15 parts by weight to 25 parts by weight. By setting the content of the monomer copolymerizable with the vinyl chloride monomer in the mixture within this range, there is an advantage that the solution viscosity of the resulting vinyl chloride polymer when dissolved in a solvent is reduced.

(other monomers)
The mixture may contain monomers other than the vinyl chloride monomer and monomers copolymerizable with the vinyl chloride monomer (hereinafter referred to as "other monomers"). As the other monomers, monomers having a hydroxy group or a carboxy group are preferred since vinyl chloride polymers used in inks, paints, etc. can be obtained. The monomer having a hydroxy group is preferably hydroxyalkyl acrylate, and the monomer having a carboxy group is preferably fumaric acid.

(degree of polymerization)
The K value is used as an indicator of the degree of polymerization. The K value is calculated by the following method. A vinyl chloride polymer produced by the production method of an embodiment of the present invention is dissolved in cyclohexane, and the flow time of the resulting solution is measured using a capillary viscometer in an atmosphere of 25°C. Furthermore, the K value corresponding to the viscosity ratio (solution flow time ratio to cyclohexanone: solution flow time/cyclohexane flow time) is calculated using the conversion table of JIS K7367-2-1999.

Although the K value is not limited, vinyl chloride polymers used for inks, paints, etc. usually have a K value of 30 to 50, preferably 35 to 45. By setting the K value of the vinyl chloride polymer within the numerical range, the vinyl chloride polymer can have a low degree of polymerization, and as a result, when dissolved in a solvent, the viscosity of the solution can be reduced. Can be done.

(conversion rate)
The conversion rate can be calculated by the following method. A slurry of a vinyl chloride polymer produced by the production method of an embodiment of the present invention is dried, and the vinyl chloride polymer from which unreacted vinyl chloride monomers have been removed is weighed. The conversion rate is calculated by dividing the weight of the vinyl chloride polymer by the amount of vinyl chloride monomer charged.

The conversion rate is not limited, but is preferably 60 to 100%, more preferably 70 to 100%, more preferably 80 to 100%, and most preferably 85 to 100%. By setting the conversion rate of the vinyl chloride polymer within this numerical range, a vinyl chloride copolymer with a stable particle shape can be obtained, and a polymerization method with excellent productivity can be achieved.

(solvent solubility)
Solvent solubility can be calculated by the following method. The solvent solubility (viscosity) of the vinyl chloride polymer produced by the production method of one embodiment of the present invention is determined by the solvent solubility (viscosity) of methyl ethyl ketone (MEK), toluene (TOL), and butyl acetate (BAC), ethyl acetate ( Measuring the viscosity at 25°C of a solution obtained by dissolving a vinyl chloride polymer in a solvent consisting of EAC) or a solvent consisting of butycell acetate (BGA) using a B-type viscometer. Accordingly, the solubility of the vinyl chloride polymer in a solvent can be evaluated. The lower the viscosity, the higher the solubility in the solvent, so the viscosity of the solution can be lowered.

The viscosity of the solution is not limited, but when dissolved in MEK/TOL/BAC solvent at a solid content of 25%, it is preferably 60 mPa·S to 100 mPa·S, more preferably 70 mPa·S to 80 mPa·S. be. When dissolved in an EAC solvent with a solid content of 20%, the pressure is preferably 20 mPa·S to 50 mPa·S, more preferably 30 mPa·S to 40 mPa·S. When dissolved in a BGA solvent with a solid content of 15%, the pressure is preferably 40 mPa·S to 70 mPa·S, more preferably 50 mPa·S to 60 mPa·S. When the viscosity of the solution is within this range, the vinyl chloride polymer produced by the production method of one embodiment of the present invention can be suitably used as an ink resin or a paint resin.

<Aldehyde>
In the production method according to one embodiment of the present invention, a mixture of monomers is subjected to suspension polymerization in the presence of an aldehyde represented by the following general formula (I) (hereinafter simply referred to as "aldehyde I").

R is a saturated alkyl group having 2 to 4 carbon atoms.

Examples of R include ethyl group, 1-methylethyl group, propyl group, 1-methylpropyl group, 2-methylpropyl group, and butyl group.

By carrying out suspension polymerization of a mixture of monomers in the presence of aldehyde I, it is possible to produce a vinyl chloride polymer with little reduction in conversion rate in the polymerization of a vinyl chloride polymer with a low degree of polymerization.

Further, aldehyde I is preferably an aldehyde represented by the following general formula (II) or (III) (hereinafter simply referred to as "aldehyde II" or "aldehyde III"). Aldehyde II is butyraldehyde (NBD) and aldehyde III is propionaldehyde.

By using aldehyde II or aldehyde III, it is possible to produce a vinyl chloride polymer with a particularly small reduction in conversion rate in the polymerization of a vinyl chloride polymer with a low degree of polymerization.

In one embodiment of the invention, aldehyde I is preferably used as a chain transfer agent. By using it as a chain transfer agent, it is possible to produce a vinyl chloride polymer with little reduction in conversion rate in the polymerization of a vinyl chloride polymer with a low degree of polymerization. In addition, when used as a chain transfer agent, aldehyde II or aldehyde III can be used in the polymerization of a vinyl chloride polymer with a low degree of polymerization, from the viewpoint of producing a vinyl chloride polymer with a particularly small reduction in conversion rate. It is preferable that there be.

<Other raw materials>
In one embodiment of the present invention, the mixture subjected to suspension polymerization during production of the vinyl chloride polymer may contain other raw materials than the monomer and aldehyde I. The components include, but are not particularly limited to, solvents, dispersants, antioxidants, polymerization initiators, and the like.

(solvent)
Examples of the solvent used in one embodiment of the present invention include an aqueous solvent and a water solution in which a water-insoluble organic solvent is added.

The aqueous solvent is not limited to water, and may be one in which an organic solvent that is miscible with water, such as methyl alcohol or ethyl alcohol, is added to water.

Examples of water-insoluble organic solvents include chloroform, halogenated hydrocarbons, aromatic hydrocarbons, and ketones. Examples of halogenated hydrocarbons include carbon tetrachloride. Examples of halogenated hydrocarbons include benzene and toluene. Examples of aromatic hydrocarbons include benzene and toluene. Examples of ketones include methyl ethyl ketone and methyl isobutyl ketone.

(dispersant)
The dispersant used in one embodiment of the present invention is not limited, and examples thereof include methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, partially saponified polyvinyl alcohol, polyethylene oxide, and the like.

From the viewpoint of polymerization stability, among the above-mentioned dispersants, hydroxypropyl methylcellulose and partially saponified polyvinyl alcohol are preferred.

(Antioxidant)
Examples of the antioxidant used in one embodiment of the present invention include hindered phenol-based, thiodipropionic acid ester, aliphatic sulfide, and disulfide-based antioxidants.

(Polymerization initiator)
Examples of the polymerization initiator used in one embodiment of the present invention include oil-soluble polymerization initiators and water-soluble polymerization initiators. From the viewpoint of increasing reaction efficiency and improving productivity by reducing scaling, it is preferable to use an oil-soluble polymerization initiator as the polymerization initiator.

Examples of the oil-soluble polymerization initiator include (3,5,5, trimethylhexanoyl) peroxide, diacyl peroxides (for example, dilauroyl peroxide, di-3,5,5, trimethylhexanoyl peroxide) , peroxydicarbonates (e.g. diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate), organic peroxide initiators (e.g. benzoyl peroxide, t-butyl peroxypivalate, t- butyl peroxyneodecanoate, peroxy esters), azo initiators (e.g. 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile)) can be mentioned. From the viewpoint of suppressing polymerization delay and improving reaction efficiency, the oil-soluble polymerization initiator is preferably (3,5,5, trimethylhexanoyl) peroxide or benzoyl peroxide.

Examples of the water-soluble polymerization initiator include ammonium persulfate, potassium persulfate, sodium persulfate, and aqueous hydrogen peroxide. In addition, when using a water-soluble polymerization initiator, a reducing agent (for example, sodium sulfite, sodium thiosulfate, formaldehyde sodium sulfoxylate dihydrate, ascorbic acid, sodium ascorbate) may be used in combination as necessary. good.

It is preferable to select a polymerization initiator that exhibits an appropriate half-life temperature for the polymerization temperature.

<Polymerization process>
In the polymerization step, a mixture of vinyl monomers including a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer is subjected to suspension polymerization (for example, suspension polymerization) in the presence of the above-mentioned aldehyde. polymerization, fine suspension polymerization, seed fine suspension polymerization). More specifically, the polymerization step involves, in the presence of the above-mentioned aldehyde, a mixture of vinyl monomers containing a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer. This is a process of suspension polymerization. By performing suspension polymerization, (1) vinyl chloride polymer particles having a specific average particle size (for example, 50 μm to 400 μm) can be easily produced; (2) productivity is higher than emulsion polymerization. , which has the advantage of being able to be prototyped at low cost.

The polymerization temperature in the polymerization step is 65°C to 85°C. By setting the polymerization temperature within this range, it is possible to reduce the decrease in conversion rate. The polymerization temperature is preferably 75°C to 85°C, more preferably 75°C to 80°C, since the reduction in conversion can be particularly reduced.

In the polymerization step, the amount of aldehyde added is 0.1 parts by weight to 4 parts by weight, preferably 0.5 parts by weight to 2 parts by weight, and 0.7 parts by weight, based on 100 parts by weight of the mixture. More preferably, the amount is 1 part by weight. By adding such an amount, it is possible to produce a vinyl chloride polymer with little reduction in conversion rate in the polymerization of a vinyl chloride polymer with a low degree of polymerization.

Aldehyde I may be added to the mixture in the polymerization step, or may be added in advance to the vinyl chloride monomer and/or the monomer copolymerizable with the vinyl chloride monomer.

The polymerization time in the polymerization step (specifically, the time from the time when the polymerization temperature is reached to the time when the polymerization is terminated) is not limited and can be set depending on the heat removal ability. The polymerization time in the above polymerization step is preferably 240 minutes to 420 minutes.

In the polymerization process, it is preferable that among the monomers, the monomer with the slowest polymerization rate is initially charged into the polymerization vessel at once, and the monomer with the fastest polymerization rate is dividedly charged into the polymerization vessel. . In the polymerization process, when using only vinyl chloride monomers and monomers copolymerizable with vinyl chloride monomers, monomer A, which has a slower polymerization rate, is placed in the polymerization vessel all at once. It is preferable to initially charge monomer B, which has a faster polymerization rate, into the polymerization vessel in divided doses. Here, among the vinyl chloride monomer and the monomer polymerizable with the vinyl chloride monomer, one corresponds to monomer A and the other corresponds to monomer B. With this configuration, it is possible to prevent monomer B, which has a high polymerization rate, from polymerizing preferentially, and thereby the content ratio of monomer A and monomer B is the desired ratio. A copolymer can be efficiently produced. In this specification, "initial charging" is intended to mean "adding a monomer into the polymerization vessel by the time heating is started to adjust the internal temperature of the polymerization vessel to the polymerization temperature." do.

When the monomer is divided and charged into the polymerization vessel, the timing of charging the monomer is not limited. For example, a part of the monomer may be initially charged into the polymerization vessel, and then (preferably after the polymerization temperature is reached), the remaining monomer may be charged all at once or in portions into the polymerization vessel.

“The monomer with the slowest polymerization rate,” “the monomer with the fastest polymerization rate,” “the monomer with the slower polymerization rate,” and “the monomer with the faster polymerization rate” are vinyl chloride-based monomers. It is not limited because it varies depending on the type of monomer used for producing the polymer. Examples of the "monomer with the highest polymerization rate" and the "monomer with the highest polymerization rate" include vinyl chloride monomer. In this case, examples of the "monomer with the slowest polymerization rate" and the "monomer with the slower polymerization rate" include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl stearate. Can be done.

The polymerization vessel used in the polymerization step is not limited, and a synthetic can commonly used in the production of vinyl chloride polymers may be used.The lower limit of the capacity of the polymerization vessel is not limited, for example, 1L or more, 10L. or more, 100L or more, or 1000L or more. The upper limit of the volume of the polymerization vessel is not limited, and may be, for example, 1.0×10 ⁵ L.

<Other processes>
The manufacturing method according to one embodiment of the present invention may include steps other than the polymerization step.

(Raw material supply process)
The raw material supply step is a step of supplying each raw material into the polymerization vessel. Before the polymerization process, for example, aldehyde I, a solvent, a dispersant, a polymerization initiator, etc. are introduced into the deoxidized polymerization vessel. This is the step of adding the mixture. The mixture may be introduced in the form of a slurry, for example. The order in which the raw materials are added is not particularly limited.

(Dehydration process)
The dehydration step is a step of dehydrating the solvent from the slurry when the vinyl chloride polymer obtained in the polymerization step is in the form of a slurry, and is performed after the polymerization step. For example, a slurry of a vinyl chloride polymer is separated into a vinyl chloride polymer and a filtrate by suction filtration to obtain a dehydrated vinyl chloride polymer.

(drying process)
The drying step is a step in which the vinyl chloride polymer is taken out from the polymerization vessel after the dehydration step and dried in a dryer.

The drying temperature is, for example, preferably 40°C or more and 100°C or less, more preferably 40°C or more and 80°C or less, and even more preferably 40°C or more and 60°C or less.

The drying time is preferably, for example, 1 hour or more and 16 hours or less, and more preferably 1 hour or more and 10 hours or less.

(Isolation process)
The production method according to an embodiment of the present invention includes an isolation step of isolating vinyl chloride polymer particles having an average particle size of 50 μm to 400 μm after the polymerization step, after the dehydration step, or after the drying step. obtain.

EXAMPLES Below, Examples of the present invention will be shown and the present invention will be explained in more detail. Of course, the present invention is not limited to the following embodiments, and it goes without saying that various modifications can be made to the details.

[Examples 1-2]
In a stainless steel polymerization vessel equipped with a stirring blade and an external jacket, ion-exchanged water was used as a solvent, polyethylene oxide (manufactured by Sumitomo Seika Co., Ltd.) was used as a dispersant, and benzoyl peroxide (manufactured by NOF Corporation) was used as a polymerization initiator. and (3,5,5-trimethylhexanoyl) peroxide (manufactured by NOF Corporation) were charged.

Subsequently, the inside of the polymerization vessel was deoxidized using a vacuum pump. After that, stirring was started, and vinyl acetate monomer, vinyl chloride monomer, and butyraldehyde (NBD) as a chain transfer agent (manufactured by Tokyo Chemical Industry Co., Ltd., CAS number: 123-72-8) were added to the polymerization vessel. , molecular weight 72.1) or propionaldehyde (manufactured by Tokyo Chemical Industry Co., Ltd., CAS number: 123-38-6, molecular weight 58.08) (initial charging).

Next, the temperature of the internal solution was raised using the polymerization vessel external jacket. The time when the temperature in the polymerization vessel reached 75°C was defined as the polymerization start time, and the remaining vinyl chloride monomer was continuously charged (additional charge). The temperature inside the polymerization vessel was maintained at 76°C, and the polymerization was terminated when 6.5 hours had elapsed from the polymerization start time (polymerization temperature: 76°C). The obtained slurry was stirred at 80° C. for 1 hour to remove unreacted vinyl acetate monomer, vinyl chloride monomer, and aldehyde, and then the obtained slurry was dried to obtain a vinyl chloride polymer. Ta. The amount of each raw material charged was in accordance with Table 1.

[Comparative example 1]
A vinyl chloride polymer was obtained in the same manner as in Example 1 except that no chain transfer agent was used.

[Comparative Examples 2-3]
As a chain transfer agent, 2-ethylhexyl thioglycolate (EHTG) (manufactured by Tokyo Chemical Industry Co., Ltd., CAS number: 7659-86-1, molecular weight 204.1) or 2-ethylhexyl mercaptopropionate (EHMP) (manufactured by Tokyo Chemical Industry Co., Ltd., CAS number: 7659-86-1, molecular weight 204.1) A vinyl chloride polymer was obtained in the same manner as in Example 1, except that a vinyl chloride polymer (manufactured by Co., Ltd., CAS number: 50448-95-8, molecular weight 218.4) was used.

The K value, conversion rate, solvent solubility (viscosity), and vinyl acetate monomer content of the obtained vinyl chloride polymer were measured by the following methods. The results are shown in Table 2.

(conversion rate)
The weight of the obtained vinyl chloride polymer was measured. The conversion rate was calculated by dividing the weight of the vinyl chloride polymer by the amount of vinyl chloride monomer charged.

(K value)
0.25 g of the obtained vinyl chloride polymer was dissolved in 50 mL of cyclohexanone, and the flow time of the obtained solution was measured using a capillary viscometer in an atmosphere of 25°C. Furthermore, the K value corresponding to the viscosity ratio (solution flow time ratio to cyclohexanone: solution flow time/cyclohexane flow time) was calculated using the conversion table of JIS K7367-2-1999.

(solvent solubility)
Solvent solubility in three types of solvents was calculated.

MEK/TOL/BAC Solvent 50 parts of a vinyl chloride polymer was dissolved in 30 parts of MEK, 30 parts of TOL, and 90 parts of BAC by stirring at 2000 rpm for 20 minutes at 30°C. The viscosity of the obtained solution at 25°C was measured using a B-type viscometer.

EAC Solvent 20 parts of vinyl chloride polymer was dissolved in 80 parts of EAC by stirring at 2000 rpm at 30° C. for 20 minutes. The viscosity of the obtained solution at 25°C was measured using a B-type viscometer.

BGA Solvent 15 parts of a vinyl chloride polymer was dissolved in 85 parts of BGA (CAS number: 112-07-2) by stirring at 2000 rpm for 120 minutes at 50°C. The viscosity of the obtained solution at 25°C was measured using a B-type viscometer.

(Content of vinyl acetate monomer in vinyl chloride polymer)
The content of vinyl acetate monomer in the vinyl chloride polymer was calculated by FT-IR (FT/IR4700 manufactured by JASCO Corporation) measurement. A cast film was prepared on a KBr plate using a 5% tetrahydrofuran (THF) solution, and after drying the cast film at 120° C., FT-IR was measured. The content of vinyl acetate monomer in the vinyl chloride polymer was calculated based on the absorption ratio of CH and C=O.

(Measurement of average particle diameter)
The vinyl chloride polymers obtained in Examples 1 to 2 and Comparative Examples 1 to 3 were sieved (stainless steel sieve 200Φ×60 manufactured by Sanpo Co., Ltd.) to obtain vinyl chloride polymers with an average particle size of 50 μm to 400 μm. An attempt was made to obtain polymer particles.

The average particle diameter of the obtained vinyl chloride polymer particles was measured according to the method of JIS K-6721. Using sieves of 42, 60, 80, 100, 120, 145, and 200 mesh, sieving was performed with a sieve shaker, and the diameter passing 50% by weight was defined as the average particle diameter. The particle size distribution was determined by measuring the weight of the vinyl chloride polymer remaining in each mesh, and expressed as a percentage. Of these, the amount of polymer remaining on the 42 mesh was defined as the coarse particle portion, and the amount that passed through the 200 mesh was defined as the pass portion.

As a result, in Examples 1 and 2, many vinyl chloride polymer particles having an average particle diameter of 50 μm to 400 μm could be obtained.

As shown in Table 2, the K value was smaller in Examples 1 and 2 than in Comparative Examples 1 to 3. That is, compared to Comparative Examples 1 to 3, in Examples 1 and 2, vinyl chloride polymers with a lower degree of polymerization could be produced.

As shown in Table 2, in Comparative Examples 2 and 3 in which a thio-based compound was used as a chain transfer agent, the conversion rate was small. On the other hand, in Examples 1 and 2, the conversion ratio values were large. The conversion rates in Examples 1 and 2 were large values, similar to the conversion rate in Comparative Example 1 in which no chain transfer agent was used.

In other words, it has been found that the production method according to one embodiment of the present invention can produce a vinyl chloride polymer with a small reduction in conversion rate in the polymerization of a vinyl chloride polymer with a low degree of polymerization.

Furthermore, as shown in Table 2, the values of solvent solubility (in other words, viscosity) were smaller in Examples 1 and 2 than in Comparative Examples 1 to 3. This shows that the production method according to one embodiment of the present invention can produce a vinyl chloride polymer that can be used for various purposes (for example, resin for ink and resin for paint).

INDUSTRIAL APPLICATION This invention can be utilized for an ink, a paint, etc.

Claims (6)

A polymerization step of suspension polymerizing a mixture containing a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer in the presence of an aldehyde represented by the following general formula (I). ,
The amount of the aldehyde added is 0.1 parts by weight to 4 parts by weight based on 100 parts by weight of the mixture,
A method for producing a vinyl chloride polymer, wherein the polymerization temperature in the polymerization step is 65°C to 85°C.
(In the formula, R represents a saturated alkyl group having 2 to 4 carbon atoms.) The method for producing a vinyl chloride polymer according to claim 1, wherein the aldehyde represented by the general formula (I) is an aldehyde represented by the following general formula (II) or (III).
The method for producing a vinyl chloride polymer according to claim 1 or 2, comprising an isolation step of isolating vinyl chloride polymer particles having an average particle size of 50 μm to 400 μm. The method for producing a vinyl chloride polymer according to any one of claims 1 to 3, wherein the aldehyde represented by the general formula (I) is used as a chain transfer agent. In the polymerization step, the mixture further includes a polymerization initiator,
The method for producing a vinyl chloride polymer according to any one of claims 1 to 4, wherein the polymerization initiator is an oil-soluble polymerization initiator. The method for producing a vinyl chloride polymer according to claim 5, wherein the oil-soluble polymerization initiator is (3,5,5, trimethylhexanoyl) peroxide or benzoyl peroxide.