JP5236250B2 - Dispersant for polymerization, method for producing vinyl chloride resin using the same, vinyl chloride resin and molded product - Google Patents

Description

  The present invention relates to a dispersing agent for polymerization, a method for producing a vinyl chloride resin using the same, a vinyl chloride resin, and a molded product. More specifically, the present invention relates to a vinyl chloride resin having a high bulk specific gravity.

  In general, increasing the bulk specific gravity of vinyl chloride resin can contribute to volume reduction. For example, it contributes to saving space in storage warehouses for molded products using vinyl chloride resin and increasing transport efficiency. it can. In addition, since a resin having a high bulk specific gravity has a large amount of processing per unit time at the time of extrusion molding, it can contribute to an improvement in productivity at the production processing site.

  In order to increase the bulk specific gravity of a vinyl chloride resin, for example, a technique of polymerizing a combination of a plurality of polyvinyl alcohols (PVA) and hydroxypropyl methylcellulose as a dispersant is known (for example, Patent Documents 1 and 2). reference). The applicant previously provided a technique relating to modified polyvinyl alcohol having an unsaturated double bond in the molecular chain as a dispersant (see Patent Document 3).

JP2003-238606A. JP-A-2005-281680. JP2007-63369A.

  However, even when a dispersant is used, control of the bulk specific gravity of the resulting vinyl chloride resin is not sufficient. Also, combining a plurality of dispersants is undesirable because it leads to an increase in the amount of dispersant used. When the amount used is large, not only the production cost increases, but also a problem that the dispersant remaining in the product of the vinyl chloride resin causes a drop in fish eyes may occur. For example, when hydroxylpropylmethylcellulose is used as a dispersant, there is a significant problem that it is not economical because it is expensive. Moreover, even when the modified polyvinyl alcohol shown in the cited document 3 is used as a dispersant, it is desired to further improve the bulk specific gravity of the resulting vinyl chloride resin.

  Therefore, the present invention mainly provides a dispersing agent for polymerization capable of obtaining a vinyl chloride resin having a higher bulk specific gravity, a method for producing a vinyl chloride resin using the same, a vinyl chloride resin and a molded product. With a purpose.

In the modified polyvinyl alcohol having a specific molecular structure, the inventors have efficiently focused on the monomer particle formation process during suspension polymerization of the vinyl chloride resin by paying attention to the aqueous solution viscosity and the average saponification degree. I found out that it can be controlled. As a result of earnest research based on this knowledge, it was found that a vinyl chloride resin having a high bulk specific gravity can be obtained efficiently, and the present invention has been completed.
First, the present invention has a bonding unit represented by the following chemical formula (1), and the viscosity at a temperature of 20 degrees of an aqueous solution having a concentration of 4% by mass is 30 mPa · s or more and less than 400 mPa · s, and the average saponification degree There Ri der less 75 mol% or more 90 mol%, the backbone unsaturated double bond starting from the carboxyl group to provide a polymerization dispersing agent containing at least a modified polyvinyl alcohol introduced structure randomly. The polymerization dispersant according to the present invention not only introduces a reactive unsaturated double bond in the molecule, but also has a predetermined aqueous solution viscosity and average degree of saponification, and this is used as a polymerization dispersant. By using it, a vinyl chloride resin having a large bulk specific gravity can be obtained.
In the present invention, the polyvinyl chloride resin refers to a resin obtained by polymerizing a vinyl chloride monomer or a monomer mixture containing vinyl chloride.
Further, X ₁ and X ₂ in the following chemical formula (1) is an alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal atom, which may be identical or different, g is an integer of 0 to 3.

Subsequently, the present invention provides a method for producing a vinyl chloride resin, wherein the polymerization dispersant is used to perform suspension polymerization by dispersing a vinyl chloride monomer or a monomer mixture containing the same in water. . By using the polymerization dispersant, a vinyl chloride resin having a large bulk specific gravity can be produced.
In the present invention, the polymerization dispersant is subjected to suspension polymerization by being charged so as to be 0.01% by mass or more and 0.1% by mass or less with respect to the total monomer of the vinyl chloride resin. A method for producing a resin is provided. By using the polymerization dispersant, the amount of the dispersant used for suspension polymerization can be reduced .

In the present invention, the viscosity of an aqueous solution having a bond unit represented by the chemical formula (1) and having a concentration of 4% by mass at a temperature of 20 degrees is 30 mPa · s or more and less than 400 mPa · s, and the average saponification degree There Ri der less 75 mol% or more 90 mol%, with an unsaturated double bond starting from the carboxyl group in the main chain of the modified polyvinyl alcohol introduced structures randomly as a dispersant, a vinyl chloride monomer or it Disclosed is a vinyl chloride resin obtained by dispersing a monomer mixture in water and subjecting it to suspension polymerization.
The present invention provides a molded product using this vinyl chloride resin.

  According to the present invention, a vinyl chloride resin having a high bulk specific gravity can be obtained.

  Hereinafter, the present invention will be described in detail. However, the following is an example of the present invention and should not be construed as being limited thereto.

  The monomer used as the raw material for the vinyl chloride resin is a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and another monomer copolymerizable therewith. In the case of a mixture, it is desirable to contain 50% by mass or more of vinyl chloride monomer. There are no limitations on the types of other monomers copolymerizable with the vinyl chloride monomer, such as vinyl acetate, methyl propionate, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic acid. , Ethylene, propylene, maleic anhydride, acrylonitrile, styrene, vinylidene chloride, and the like can be used.

  The vinyl chloride resin according to the present invention can be obtained by suspension polymerization. The polymerization initiator used in the suspension polymerization is not limited, and examples thereof include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, and t-butyl peroxy. Neodecanoate, t-hexylperoxyneodecanoate, t-hexylperoxypivalate, α-cumylperoxyneodecanoate, t-hexylneohexanoate, 2,4,4-trimethylpentyl- Peroxyester compounds such as 2-peroxy-2-neodecanoate, azo compounds such as azobis (2,4-dimethylvaleronitrile), azobisisobutyronitrile, lauryl peroxide, benzoyl peroxide, cumene hydroperoxide, 2, 4, 4 Peroxide compounds such as trimethyl pentyl-2-peroxy phenoxy acetate.

  The polymerization initiator may be added either before or after the water or monomer is charged. Alternatively, the aqueous emulsion may be added in advance to the polymerization tank. 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 chloride monomers or a monomer mixture containing the same.

In the present invention, a modified polyvinyl alcohol represented by the following chemical formula (2) is used as a dispersant for suspension polymerization. This modified polyvinyl alcohol is a carbonyl group-containing polyvinyl alcohol and has one of the structural features that an unsaturated double bond starting from a carboxyl group is randomly introduced into the main chain.
Incidentally, X ₁ and X ₂ in the following chemical formula (2) is an alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal atom, it may be well or be the same or different. Moreover, g in following Chemical formula (2) represents the integer of 0-3.

This modified polyvinyl alcohol can be obtained by copolymerizing a monomer having an ethylenically unsaturated double bond and a monomer having a vinyl ester unit and then saponifying the copolymer. it can. As the monomer having an ethylenically unsaturated double bond, for example, a compound represented by the following chemical formula (3) can be suitably used. Incidentally, X ₃ and X ₄ in the following chemical formula (3) is an alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal atom, it may be well or be the same or different.

Examples of the compound represented by the chemical formula (3) include dimethyl maleate, monomethyl maleate, diethyl maleate, monoethyl maleate and the like.

Or the compound represented by following Chemical formula (4) can also be used suitably. Incidentally, X ₅ and X ₆ in the chemical formula (4) is an alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal atom, it may be well or be the same or different.

Examples of the compound represented by the chemical formula (4), for example, dimethyl fumarate, monoethyl fumarate, fumaric acid diethyl Le like.

Moreover, the compound represented by following Chemical formula (5) can also be used suitably.

Examples of the compound represented by the chemical formula (5), anhydrous maleic acid.

  The amount of copolymerization of the monomer having an ethylenically unsaturated double bond is not particularly limited, but from the viewpoint of ensuring the amount of unsaturated double bonds in the molecule and water solubility, etc. 0.1 mol% or more and less than 50 mol% is preferable, and 0.1 mol% or more and less than 10 mol% is particularly preferable.

  The monomer having a vinyl ester unit is not particularly limited, but vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, pivalin. Vinyl acetate and vinyl versatate are available, and vinyl acetate is most preferred from the viewpoint of stable polymerization.

  If necessary, another monomer copolymerizable with the monomer may be copolymerized. The copolymerizable monomer is not particularly limited, and examples thereof include olefins such as ethylene, propylene, 1-butene, and isobutene, acrylic acid, methacrylic acid, crotonic acid, phthalic acid, maleic acid, and itacon. Unsaturated acids such as acids, or salts thereof, monoalkyl esters or dialkyl esters having 1 to 18 carbon atoms, acrylamide, N-alkyl acrylamides having 1 to 18 carbon atoms, N, N-dialkyl acrylamide, diacetone acrylamide Acrylamides such as 2-acrylamidopropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt or quaternary salt thereof, methacrylamide, N-alkylmethacrylamide having 1 to 18 carbon atoms, N, N-dialkylmethacrylamide , Diacetone methacrylate Methacrylamides such as luamide, 2-methacrylamide propanesulfonic acid and salts thereof, methacrylamide dimethyldimethylamine and salts thereof or quaternary salts thereof, alkyl vinyl ethers having an alkyl chain length of 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers, Vinyl ethers such as alkoxyalkyl vinyl ethers, N-vinyl amides such as N-vinyl pyrrolidone, N-vinyl formamide, N-vinyl acetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl fluoride , Vinyl halides such as vinylidene fluoride, vinyl bromide, vinylidene bromide, vinyl silanes such as trimethoxyvinyl silane, allyl acetate, allyl chloride, allyl alcohol, dimethylallyl alcohol Allyl compounds such as vinyl silyl compounds such as vinyltrimethoxysilane, isopropenyl acetate and the like. Although the usage-amount of these other copolymerizable monomers is not specifically limited, It is preferable that they are 0.001 mol% or more and less than 20 mol% with respect to the monomer total.

  The aqueous solution viscosity (concentration of 4% by mass, aqueous solution viscosity at 20 ° C.) of the modified polyvinyl alcohol of the present invention is 30 mPa · s or more and less than 400 mPa · s. The lower limit of the aqueous solution viscosity is preferably 40 mPa · s or more. The upper limit of the aqueous solution viscosity is preferably less than 100 mPa · s. When the aqueous solution viscosity is less than 30 mPa · s, the dispersion performance of the modified polyvinyl alcohol is lowered. When the aqueous solution viscosity is 400 mPa · s or more, the dissolution rate in water becomes slow, and the workability when dissolving the dispersant in water may be reduced.

  By using a modified polyvinyl alcohol having a reactive double bond introduced into the molecule as a dispersant, the hydrophilic part and the hydrophobic part in the solution during suspension polymerization can be more reliably controlled. That is, although it is not certain, the performance of the modified polyvinyl alcohol according to the present invention as a dispersant is mainly influenced by structural factors such as the balance of hydroxyl groups and vinyl acetate ester groups, reactive double bonds, and degree of polymerization. it is conceivable that.

  First, the hydroxyl group of the hydrophilic group is easily drawn into the aqueous phase, and the vinyl acetate group of the lipophilic group is easily drawn into the oil phase (for example, inside the oil droplets of the vinyl chloride monomer). When the saponification degree is up to 90 mol%, if the saponification degree is increased to increase the number of hydroxyl groups, the hydrophilicity is increased and the dispersion performance is improved. However, when the degree of saponification exceeds 90 mol%, it is considered that the lipophilic group necessary for the dispersant to adhere to the oil droplets becomes too small and the dispersion performance is lowered. Based on such findings, it is considered that the balance between hydrophilicity and lipophilicity can be controlled by adjusting the amount of hydroxyl group and vinyl acetate vinyl ester group by the degree of saponification.

  In addition, if a reactive double bond is introduced in the molecule of the dispersant, a covalent bond point between the monomer and the dispersant is generated, and the dispersant can be efficiently fixed to the oil droplets. Can be expected.

  And control of a polymerization degree is important. The higher the degree of polymerization, the larger the area in which one dispersant molecule can cover the oil droplets, so that it becomes possible to efficiently disperse with a small addition amount. Further, in the present invention, the knowledge is further advanced, and the modified polyvinyl alcohol having a large amount of modified species introduced will be insolubilized in part when the pretreatment necessary for measuring the degree of polymerization is performed, and the degree of polymerization will be accurately determined. It has also been found that there are cases where it cannot be measured. Also from such a viewpoint, the present inventors paid attention to aqueous solution viscosity and average saponification degree.

  Based on such knowledge, it discovered that bulky vinyl chloride resin could be manufactured by using the dispersing agent for polymerization according to the present invention. Since these are findings and are based on expectations to the last, even if a predetermined polymerization reaction proceeds by an action other than these findings, it is of course included in the scope of the present invention. .

  The aqueous solution viscosity is measured by a rotational viscometer method defined in JIS K6726. In JIS K6726, the method for measuring the degree of polymerization is also defined. However, since the dispersing agent for polymerization of the present invention is a modified polyvinyl alcohol having a modified species in the molecule, this degree of polymerization should be evaluated by this method. Is not appropriate.

  The average saponification degree of the modified polyvinyl alcohol is 75 mol% or more and less than 90 mol%. Particularly preferably, the lower limit is desirably 76 mol% or more. The upper limit is preferably less than 85 mol%. When the average saponification degree is less than 75 mol%, the bulk specific gravity cannot be sufficiently increased. When the average saponification degree is 90 mol% or more, the dispersion performance of the modified polyvinyl alcohol may be insufficient.

  Although the polymerization method of the monomer used as the raw material of the modified polyvinyl alcohol is not particularly limited, a known polymerization method can be employed. Usually, solution polymerization is performed using an alcohol such as methanol, ethanol or isopropyl alcohol as a solvent. Alternatively, bulk polymerization, emulsion polymerization, suspension polymerization, or the like may be used. When solution polymerization is performed, continuous polymerization or batch polymerization may be performed, and the monomers may be charged all at once, may be charged separately, or may be added continuously or intermittently.

  The polymerization initiator used in the solution polymerization is not particularly limited, but azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile, azobis (4-methoxy-2,4-dimethylpareronitrile). ) And other azo compounds, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, peroxides such as 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, and diisopropylpropyloxy Percarbonate compounds such as dicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, t-butylperoxyneodecanate, α-cumylperoxyneodecanate, t-butylperoxyneo Decanate The perester compound, azobisdimethylvaleronitrile can be used a known radical polymerization initiator such as azo-bis-methoxy valeronitrile. The polymerization reaction temperature is not particularly limited, but can usually be set in the range of about 30 to 90 ° C.

Saponification conditions for producing the modified polyvinyl alcohol are not particularly limited, and can be saponified by a known method. In general, a monomer having an ethylenically unsaturated double bond, a copolymer of a monomer having a vinyl ester unit, in alcoholic solution such as methanol in the presence of an alkali catalyst or an acid catalyst Then, it can be carried out by hydrolyzing the ester part in the molecule. The concentration of the copolymer in the alcohol at this time is not particularly limited, but is preferably 10 to 80% by mass.

  Examples of the alkali catalyst that can be used include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, and potassium methylate, alcoholates, and the like. As the acid catalyst, for example, an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used, but sodium hydroxide is preferably used.

  The temperature of the saponification reaction is not particularly limited, but is preferably 10 to 70 ° C, more preferably 30 to 40 ° C. Although reaction time is not specifically limited, It is desirable to carry out in 30 minutes-3 hours.

  The modified polyvinyl alcohol used in the present invention has a double bond in the molecule (see Formulas 3 to 5). The double bond is generated during a saponification reaction and heat drying described below. The double bond amount can be evaluated, for example, by measuring an ultraviolet absorption spectrum. In the present invention, the absorbance at a wavelength of 270 nm in an aqueous solution having a concentration of 0.2% by mass or a water-methanol mixed solution is preferably 0.05 or more. This absorbance can be appropriately adjusted to a desired value by adjusting saponification conditions such as the amount of catalyst used in the saponification reaction, reaction time, and saponification temperature.

The ultraviolet absorption spectrum of the modified polyvinyl alcohol will be described. According to JP 2004-250695 A and the like, the absorption at 215 nm is attributed to the structure of —CO—CH═CH— of the modified polyvinyl alcohol, and the absorption at 280 nm is the —CO— (CH═CH) ₂ — of the modified polyvinyl alcohol. The absorption at 320 nm is attributed to the structure of —CO— (CH═CH) ₃ — of the modified polyvinyl alcohol.

  The addition amount of the modified polyvinyl alcohol used in the suspension polymerization of the vinyl chloride resin is 0.01% by mass or more and 0.1% by mass or less with respect to the total of the raw material monomers of the vinyl chloride resin. desirable. As a result, a vinyl chloride resin having a high bulk specific gravity can be produced while a small amount of the dispersant is added.

  The modified polyvir alcohol of the present invention may be used in combination with polyvinyl alcohol having a different saponification degree, if necessary. It is desirable to use unmodified polyvinyl alcohol having an average saponification degree of 70 mol% or more and less than 90 mol%. The change in the particle diameter with respect to the change in the amount of the dispersant added can be moderated.

  Known techniques can be used for various conditions in suspension polymerization to obtain a vinyl chloride resin. For example, the charging method of each raw material compound, the charging ratio of the monomer and water, the polymerization temperature, the polymerization conversion rate, the polymerization conditions such as the stirring rotation speed are not particularly limited. Moreover, you may use an antifoamer, a polymerization degree regulator, a chain transfer agent, antioxidant, an antistatic agent etc. as needed.

  Since the vinyl chloride resin of the present invention has a high bulk specific gravity, it can be efficiently stored and transported, and the workability at the processing site can be improved. It is expected to improve the productivity and quality of products such as pipes, joints, cables and window frames, which are general uses of vinyl chloride resin.

Hereinafter, the present invention will be described in more detail with reference to examples. First, various polyvinyl alcohol resins were produced. Subsequently, suspension polymerization of the vinyl chloride resin was performed using these polyvinyl alcohols as a dispersant, and the physical properties of the obtained vinyl chloride resin were evaluated.
Unless otherwise specified, “part” and “%” are based on mass.

<Production of modified polyvinyl alcohol A>
3000 g of vinyl acetate, 616.3 g of methanol, 40.8 g of dimethyl maleate, and 2.5 g of azobisisobutyronitrile were charged into a polymerization vessel, heated with nitrogen, heated to the boiling point, and the polymerization rate reached 70%. At that time, the polymerization was stopped. Subsequently, unreacted vinyl acetate was removed by a conventional method, and the resulting polymer was saponified with sodium hydroxide by a conventional method. Then, the modified polyvinyl alcohol A was obtained by drying with hot air at 90 ° C. for 90 minutes.

<Production of modified polyvinyl alcohol B>
3000 g of vinyl acetate, 76.7 g of methanol, 50.1 g of dimethyl maleate and 2.5 g of azobisisobutyronitrile were charged into a polymerization vessel, heated to a boiling point after substitution with nitrogen, and the polymerization rate reached 46%. At that time, the polymerization was stopped. Subsequently, unreacted vinyl acetate was removed by a conventional method, and the resulting polymer was saponified with sodium hydroxide by a conventional method. Then, the modified polyvinyl alcohol B was obtained by drying with hot air at 90 ° C. for 90 minutes.

<Production of modified polyvinyl alcohols C to J>
2289 g of vinyl acetate, 71.0 g of methanol, 5.0 g of dimethyl maleate, and 2.5 g of azobisisobutyronitrile were charged into a polymerization vessel, heated to a boiling point after substitution with nitrogen. When the temperature of the reaction solution reached 60 ° C. or higher, a mixture of vinyl acetate 711.0 g, methanol 15.0 g and dimethyl maleate 45.1 g was added dropwise little by little over 4 hours from the top of the polymerization vessel. One hour after the completion of the dropping, the polymerization was stopped when the polymerization rate reached 44%. Subsequently, unreacted vinyl acetate was removed by a conventional method, and the resulting polymer was saponified with sodium hydroxide by a conventional method. The saponification reaction temperature, the reaction time, and the amount of sodium hydroxide were adjusted to allow the saponification reaction to proceed, followed by drying with hot air at 90 ° C. for 90 minutes to obtain modified polyvinyl alcohols C to J.

<Production of modified polyvinyl alcohols K to Q>
By adjusting the amount of methanol and the polymerization rate of the modified polyvinyl alcohol C, modified polyvinyl alcohols K to Q having different aqueous solution viscosities were obtained.

The aqueous solution viscosity, average saponification degree, and absorbance at a wavelength of 270 nm of the obtained modified polyvinyl alcohol were measured by the following methods.
Aqueous solution viscosity: Measured according to JIS K6726.
Average degree of saponification: Measured according to JIS K6726.
Absorbance: An aqueous sample solution having a concentration of 0.2% by mass is placed in a quartz cell having an optical path length of 10 mm, and an ultraviolet spectrum at a temperature of 20 ° C. is measured using an ultraviolet-visible spectrophotometer UV-1650PC (manufactured by Shimadzu Corporation). Then, the absorbance at a wavelength of 270 nm was examined.

<Suspension polymerization of vinyl chloride monomer (Examples 1 to 16, Comparative Examples 1 to 10)>
[Example 1]
In Example 1, modified polyvinyl alcohol A was used as a dispersant. In a reactor having a capacity of 30 liters equipped with a paddle stirring blade having a blade width of 37.5 mm, 12000 g of water and the amount of dispersant shown in Table 1 were added and dissolved. Next, 0.5 g of cumylperoxyneodecanoate and 2.3 g of t-butylperoxyneodecanoate were charged as polymerization initiators, and after nitrogen substitution in the system, 5000 g of vinyl chloride monomer was charged. The mixture was reacted at a temperature of 57.5 ° C. for 4 hours while stirring at a rotation speed of 650 rpm. When the internal pressure became 0.78 MPa or less, the polymerization reaction was terminated, the resin slurry was taken out from the reactor, and dehydrated and dried to obtain a resin powder.

The average particle diameter and bulk specific gravity of the obtained vinyl chloride resin were measured. The results are shown in Table 1.
Bulk specific gravity: Measured according to JIS K6720-2.
Average particle diameter: Among test sieves specified in JIS Z8801, sieves with nominal sizes of 300 μm, 250 μm, 180 μm, 150 μm, 106 μm and 75 μm are attached to a low-tap sieving device, and 100 g of a resin sample is gently put in the uppermost stage. After shaking for 10 minutes, the mass of the sample remaining on each sieve was measured, and the percentage (A to F) relative to the total mass (100 g) shown in the following formula was obtained. The average particle size was calculated by substituting the obtained sieving rate and sieving rate for each sieve into the following equation.

[Examples 2 to 16]
In Examples 2 to 16, modified polyvinyl alcohols shown in Table 1 were used as dispersants. Then, under the conditions shown in Table 1, suspension polymerization of the vinyl chloride monomer was performed by the same operation procedure as in Example 1. Table 1 shows the bulk specific gravity and average particle diameter of the vinyl chloride resin thus obtained.

[Comparative Example 1]
The modified polyvinyl alcohol A of Example 1 was modified with a modified polyvinyl alcohol R (an aqueous solution having a double bond only at the molecular end and a concentration of 4% by mass at 20 ° C., a viscosity of 5.5 mPa · s, an average saponification degree of 70.2 mol). %, The vinyl chloride monomer was subjected to suspension polymerization in the same procedure as in Example 1 except that the absorbance was changed to 1.3) at a wavelength of 270 nm. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 2]
The modified polyvinyl alcohol A of Example 1 was modified with polyvinyl alcohol S (viscosity of 10.8 mPa · s at 20 ° C. in an aqueous solution having a double bond in the molecule and a concentration of 4% by mass, and an average saponification degree of 72.0 mol%. The vinyl chloride monomer was subjected to suspension polymerization in the same procedure as in Example 1 except that the absorbance was changed to 1.0) at a wavelength of 270 nm. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 3]
The modified polyvinyl alcohol A of Example 1 was modified with the modified polyvinyl alcohol T (a viscosity of 6.2 mPa · s at 20 ° C. in an aqueous solution having a double bond only at the molecular end and a concentration of 4% by mass, and an average saponification degree of 72.0 mol). %, The vinyl chloride monomer was subjected to suspension polymerization in the same procedure as in Example 1 except that the absorbance was changed to 0.7) at a wavelength of 270 nm. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 4]
The modified polyvinyl alcohol A of Example 1 was modified with a modified polyvinyl alcohol T and Denkapoval B-24 (manufactured by Denki Kagaku Kogyo Co., Ltd., a 4 mass% aqueous solution having a viscosity of 47 mPa · s at 20 ° C., an average saponification degree of 88.2 mol%. The vinyl chloride monomer was subjected to suspension polymerization in the same operating procedure as in Example 1 except that the polyvinyl alcohol having no double bond in the molecule was changed. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 5]
The modified polyvinyl alcohol A of Example 1 was modified with a modified polyvinyl alcohol T and Denkapoval W-20N (manufactured by Denki Kagaku Kogyo Co., Ltd., an aqueous solution having a concentration of 4% by mass, a viscosity of 40 mPa · s at 20 ° C., an average saponification degree of 79.5 mol). %, Except that it was changed to polyvinyl alcohol having no double bond in the molecule). Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 6]
The modified polyvinyl alcohol A of Example 1 was changed to modified polyvinyl alcohol K, and suspension polymerization of the vinyl chloride monomer was performed under the conditions shown in Table 2. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 7]
The modified polyvinyl alcohol A of Example 1 was changed to modified polyvinyl alcohol L, and suspension polymerization of the vinyl chloride monomer was performed under the conditions shown in Table 2. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 8]
The modified polyvinyl alcohol A of Example 1 was changed to modified polyvinyl alcohol Q, and suspension polymerization of the vinyl chloride monomer was performed under the conditions shown in Table 2. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 9]
The modified polyvinyl alcohol A of Example 1 was changed to modified polyvinyl alcohol D, and suspension polymerization of the vinyl chloride monomer was performed under the conditions shown in Table 2. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

[Comparative Example 10]
The modified polyvinyl alcohol A of Example 1 was changed to modified polyvinyl alcohol J, and suspension polymerization of the vinyl chloride monomer was performed under the conditions shown in Table 2. Table 2 shows the bulk specific gravity and average particle diameter of the obtained vinyl chloride resin.

As can be seen from Tables 1 and 2, the vinyl chloride resins of Examples 1 to 16 have a higher bulk specific gravity than the vinyl chloride resins of Comparative Examples 1 to 10. And a small particle size means that the amount added can be reduced. Furthermore, it was shown that in the production of a vinyl chloride resin, a small amount of a dispersant may be contained with respect to the total monomers of the vinyl chloride resin.
Further, when a modified polyvinyl alcohol resin having a double bond only at the molecular terminal was used as a polymerization dispersant, a vinyl chloride resin having a large bulk specific gravity could not be obtained (for example, Comparative Examples 1, 3 and 3). 5).
From the above, it was shown by this example that a vinyl chloride resin having a high bulk specific gravity can be obtained and a vinyl chloride resin having a small particle diameter can be obtained by using the dispersant according to the present invention.

Claims (5)

A dispersing agent for polymerization used in suspension polymerization of a vinyl chloride monomer or a monomer mixture containing the same,
The viscosity of an aqueous solution having a bond unit represented by the following chemical formula (A) and having a concentration of 4% by mass at a temperature of 20 degrees is 30 mPa · s or more and less than 400 mPa · s, and the average saponification degree is 75 mol% or more and 90 mol%. less der is, the main chain polymerization dispersant unsaturated double bond contains at least a modified polyvinyl alcohol introduced structures randomly starting from the carboxyl group.

  A method for producing a vinyl chloride resin, wherein the polymerization dispersant according to claim 1 is used to perform suspension polymerization by dispersing a vinyl chloride monomer or a monomer mixture containing the same in water.   The suspension for polymerization is prepared by adding the polymerization dispersant to 0.01% by mass or more and 0.1% by mass or less with respect to the total monomer of the vinyl chloride resin. The manufacturing method of vinyl chloride-type resin of description. The viscosity of an aqueous solution having a bond unit represented by the following chemical formula (A) and having a concentration of 4% by mass at a temperature of 20 degrees is 30 mPa · s or more and less than 400 mPa · s, and the average saponification degree is 75 mol% or more and 90 mol%. using der is, the modified polyvinyl alcohol in the main chain unsaturated double bond starting from the carboxyl group is introduced at random structure than as a dispersing agent,
A vinyl chloride resin obtained by dispersing a vinyl chloride monomer or a monomer mixture containing it in water and subjecting it to suspension polymerization.

  A molded product using the vinyl chloride resin according to claim 4.