JPH08295701A - Production of vinyl chloride resin by suspension polymerization - Google Patents

Abstract

PURPOSE: To provide a process for producing a vinyl chloride resin by suspension polymerization whereby the deposition of polymer scales on the inside wall of the polymerizer can be reduced even when the various components are added at one time in the production process, and the obtained vinyl chloride resin particles are highly porous and have a narrow particle size distribution and excellent processability. CONSTITUTION: In suspension-polymerizing a vinyl chloride monomer in the presence of an oil-soluble polymerization initiator in an aqueous medium, at least either a partially saponified polyvinyl acetate of a degree of saponification of 70-90mol% or a cellulose derivative, an anionic emulsifier, an 8-25 C higher fatty acid and a thickener having a Brookfield viscosity of 10-200cP as measured in a 0.1wt.% aqueous solution are added to the reaction system.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a suspension polymerization method for vinyl chloride resins.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride resins have been used in many applications as materials having excellent mechanical strength, weather resistance and chemical resistance. However, the vinyl chloride resin does not have good processability, and further improvement is demanded. Generally, as a method for evaluating the moldability of a vinyl chloride resin, a plasticizer absorption amount is measured, and a plastomill torque and gelation time are measured. Regarding the plasticizer absorbability, the one in which the plasticizer penetrates into the interior of the vinyl chloride resin in a short time has good processability, and the plastomill has the lower maximum torque and the shorter the gelation time, the better the processability. There is.

There are several possible factors that impede the processing characteristics. Among them, the major factor is the presence of the skin on the surface of the vinyl chloride resin particles. The skin means a skin layer existing on the surface of the vinyl chloride resin particles, the components of which are the dispersant (partially saponified polyvinyl acetate, cellulose derivative) mainly used for polymerization and a part of the vinyl chloride resin. Is considered to be a strongly grafted layer.

Originally, the skin is considered to have the role of protecting the surface of the oil droplets in the polymerization system, regulating the splitting and coalescence of the oil droplets, and stabilizing the polymerization system. However, on the other hand, when processing the obtained vinyl chloride resin, it is necessary to crush individual particles to submicron units (primary particles or less), and in that process, a strong skin of the vinyl chloride resin surface Presence is considered to be a major obstacle.

From the above, as the particle structure of the vinyl chloride resin having excellent processing characteristics, it can be mentioned that the skin on the surface is absent or little even if it is present. Further, it is considered that the uniform and large pores between the primary particles of the resin are an important factor so that the liquid stabilizer, the plasticizer and the like taken in the vinyl chloride resin particles can be easily diffused and absorbed. ing.

Conventionally, various proposals have been made as a method for producing a vinyl chloride resin having less skin portion, uniform pore distribution, and excellent workability. For example, Japanese Patent Publication Sho 3
6-22445 discloses a suspension polymerization method in which a sorbitan higher fatty acid ester and a polyoxyethylene sorbitan higher fatty acid ester are used in combination. However, this method has a problem that the obtained vinyl chloride resin has poor porosity and a large amount of polymer scale adheres to the inner wall of the polymerization vessel.

In order to solve the above problems, for example, Japanese Patent Publication No. 53-13395 discloses a combination of a lipophilic sorbitan higher fatty acid ester and a hydrophilic polyoxyethylene sorbitan higher fatty acid ester in the presence of an alkaline compound. A method of using a dispersant and adding a water-soluble cellulose derivative when the polymerization conversion rate of vinyl chloride reaches 5 to 40% is disclosed. Further, for example, in Japanese Examined Patent Publication (Kokoku) No. 5-86408, sorbitan higher fatty acid ester is used as a dispersant, polymerization is started under stirring with a Faudler blade, and when the polymerization conversion rate reaches 5 to 40%, the aqueous solution is dissolved. A method of adding a dispersant is disclosed.

However, in the above two polymerization methods,
Certainly, during the polymerization reaction, it has the effect of preventing the polymer scale from adhering to the inner wall of the polymerization vessel, and it is rich in porosity and gives a vinyl chloride resin with a narrow particle size distribution, but it has a low bulk density. Since the dispersant is added afterward, a large amount of the dispersant remains on the surface of the resin particles, so that various physical property values decrease. Further, in the manufacturing process, it is necessary to add the dispersant in two steps in order to prevent the adhesion of polymer scale, which causes a problem that the operation becomes complicated.

Further, for example, Japanese Patent Laid-Open No. 5-295008.
In the publication, as a system utilizing a nonionic surfactant,
There is disclosed a method in which a known suspension dispersant, a low saponification degree partially saponified polyvinyl acetate, and a nonionic surfactant such as monosorbitan laurate are added in a specific ratio to carry out polymerization. However, although there are cases in which the skin on the resin surface is certainly reduced by this method, the operation becomes complicated because it is necessary to control the power required for stirring at the initial stage of polymerization, gelation, plasticizer absorption, etc. In terms of workability, the effect was still insufficient.

On the other hand, when an anionic emulsifier is added to the polymerization of vinyl chloride resin, it is difficult to control the particle size of the resin, and a large amount of scale adheres to the wall of the polymerization vessel, so that it is generally difficult to use. there were. As described above, at present, by adding various components at once in the presence of an anionic emulsifier, it is rich in porosity, has a narrow particle size distribution, and has less polymer scale adhered to the inner wall of the polymerization vessel, and is excellent in processability. Vinyl chloride resin has not been obtained.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a polymer scale on the inner wall of a polymerization vessel even if various components are added all at once in the manufacturing process. It is intended to provide a method for suspension-polymerizing a vinyl chloride-based resin, which has less adherence to the vinyl chloride resin particles, has a high porosity, has a narrow particle size distribution, and has excellent processability.

[0012]

The method for suspension polymerization of a vinyl chloride resin according to the present invention comprises the steps of reacting a vinyl chloride monomer in suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator. It is characterized in that (a) partially saponified polyvinyl acetate or (b) cellulose derivative, (c) anionic emulsifier, (d) higher fatty acid and (e) thickener are added to the system.

The vinyl chloride resin referred to in the present invention includes
Examples thereof include a homopolymer of a vinyl chloride monomer and a copolymer of a vinyl chloride monomer and a monomer other than vinyl chloride which can be copolymerized with the vinyl chloride monomer. Monomers other than vinyl chloride that can be copolymerized with the vinyl chloride monomer include alkyl vinyl esters such as vinyl acetate; α-monoolefins such as ethylene and propylene, vinylidene chloride,
Examples thereof include styrene, but are not particularly limited as long as they can be copolymerized with a vinyl chloride monomer.

In the production method of the present invention, at least one of the above partially saponified polyvinyl acetate (a) and the above cellulose derivative (b) is used as a suspension dispersant.

The above partially saponified polyvinyl acetate (a) is
When the saponification degree is low, the oil solubility is high and the dispersibility is insufficient, so the resulting resin has many coarse particles, and when the saponification degree is high, the protective colloid property is strong and a strong skin is formed on the surface of the resin. Since the chemical conversion becomes worse,
60 to 90 mol% is preferable, and 70 to 8 is more preferable.
It is 5 mol%.

When the average degree of polymerization of the partially saponified polyvinyl acetate (a) is low, it tends to be coarse particles or blocks due to lack of dispersion ability, and when the average degree of polymerization is high, the skin layer of the obtained resin particles is thick and the average porosity is high. Since the moldability is insufficient and the moldability is deteriorated, 500 to 3,000 is preferable,
More preferably, it is 700-1,500.

Examples of the cellulose derivative (b) used in the present invention include methyl cellulose, ethyl cellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose and the like.

Regardless of whether the partially saponified vinyl acetate (a) and the cellulose derivative (b) are used alone or in combination of both, the resin droplets become blocky because the oil droplets become unstable as the amount decreases. Since the skin part of the obtained resin surface becomes thick and the moldability becomes poor when it increases, it becomes 150 to 2,000 with respect to the vinyl chloride monomer.
ppm is preferred.

Examples of the anionic emulsifier (c) used in the present invention include fatty acid salts such as sodium stearate soap; alkyl sulfate ester salts such as sodium lauryl sulfate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; octylnaphthalene. Alkylnaphthalene sulfonate such as sodium sulfonate; Alkyl sulfosuccinate such as sodium didodecylsulfo succinate, alkyl diphenyl ether disulfonate, alkyl phosphate, polyoxyethylene alkyl sulfate ester salt, naphthalene sulfonic acid formalin condensation Stuff,
Specific polycarboxylic acid type polymer surfactants, polyoxyethylene alkyl phosphates, reactive surfactants, etc. may be mentioned, and these may be used alone or in combination of two or more.

The amount of the anionic emulsifier (c) added is
When the amount decreases, the skin part of the resin is formed thicker and the porosity is insufficient, so the molding processability is not improved.When the amount increases, the particle size distribution of the resin becomes wider and the amount of polymer scale attached to the inner wall of the polymerization vessel increases. However, since it sometimes becomes a block and the resin cannot be obtained, it is preferably from 5 to 1,000 ppm, more preferably from 25 to 750 ppm, based on the vinyl chloride monomer.

When the number of carbon atoms of the higher fatty acid (d) used in the present invention is small, it has a water-soluble property, so that it is not distributed into oil droplets during polymerization and the gelation promoting effect is not exhibited, and when it is large, the melting point is high. Since it becomes higher, the gelation promoting effect cannot be exhibited at the molding temperature, so that it is limited to 8 to 25, and preferably 11 to 22.

Examples of the higher fatty acid (d) having 8 to 25 carbon atoms include isostearic acid, stearic acid, and n.
-Heptadecanoic acid, palmitic acid, n-pentadecanoic acid, myristic acid, aragic acid, nonadecanoic acid, n-tridecanoic acid, lauric acid, undecyl acid, etc.,
These may be used alone or in combination of two or more. As the higher fatty acid (d), the effect is not deteriorated due to the degree of unsaturation of the main chain and branching, but linear saturated fatty acids are particularly preferable.

When the amount of the higher fatty acid (d) added is small, the effect is not obtained, and when it is large, the gelling time is delayed, so that it is 300 to 2,000 with respect to the vinyl chloride monomer.
ppm is preferred.

The thickener (e) used in the present invention is used for imparting a thickening effect to the reaction system,
If the Brookfield viscosity (hereinafter referred to as “η”) of the 0.1% by weight aqueous solution is low, the thickening effect is insufficient, resulting in poor particle size distribution, and if it is high, the average molecular weight is high and the dispersibility in water is poor. Therefore, the effect of improving the particle size distribution is reduced, so that it is limited to 10 to 200 cps, and preferably 11 to 140 cps.

The above η is 10 cps (1 at room temperature and normal pressure).
Examples of the thickener (d) having a viscosity of 0 mPa · s) or more include polyethylene oxide (η = 12 cps, average molecular weight of preferably 1.7 million to 5.5 million, more preferably 4.3 million to 4.8 million), polyvinylpyrrolidone, poly Other than acrylamide (in all cases, η = 51 cps, average molecular weight is preferably 8,000,000 to 14,000,000, more preferably 12,000,000 to 14,000,000), polyacrylamide copolymer, crosslinked (meth) acrylic acid Examples of the polymer include methyl cellulose calcium, sodium starch glycolate, sodium starch phosphate, sodium alginate, propylene glycol alginate, sodium carboxymethyl cellulose, and calcium carboxymethyl cellulose.

When the added amount of the above-mentioned thickening agent (e) is small, a sufficient thickening effect is not exhibited in the reaction system, so that the particle size distribution of the resin is not improved, and when it is large, the resin surface is covered with a strong skin layer. Therefore, the gelation rate becomes slower, so that it is preferably from 5 to 2,000 ppm, more preferably from 25 to 900 ppm, based on the vinyl chloride monomer.

As the above-mentioned oil-soluble polymerization initiator, known ones generally used for the polymerization of vinyl chloride resins can be used, for example, t-butylperoxy neodecanoate, t-hexylperoxy. Neodecanoate,
Perester compounds such as t-hexyl peroxypivalate, α-cumyl peroxy neodecanoate, t-hexyl neohexanoate, 2,4,4-trimethylpentyl-2-peroxy-2-neodecanoate; diisopropylper Percarbonate compounds such as oxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate and dimethoxyisopropyl peroxydicarbonate; decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, Cumene hydroperoxide, cyclohexanone peroxide, 2,4-dichlorobenzoyl peroxide, p-methane hydroperoxide, 3,5,5-trimethylhexanoyl peroxide, isobutyri Peroxide compounds such as peroxide; alpha,. Alpha .'- azobisisobutyronitrile, alpha,. Alpha .'- azobis (2,4-dimethylvaleronitrile), α, α'-
Examples thereof include azo compounds such as azobis (4-methoxy-2,4-dimethylvaleronitrile), and these may be used alone or in combination of two or more kinds.

In the suspension polymerization method of the present invention, deionized water to the reaction system, partially saponified polyvinyl acetate (a), cellulose derivative (b), higher fatty acid (c), anionic emulsifier (d), The method for charging the thickener (e), vinyl chloride monomer and other monomers may be the same as the conventional method, and depending on the polymerization conditions, a polymerization regulator, a chain transfer agent, Antistatic agents, cross-linking agents, stabilizers, fillers, scale inhibitors and the like may be added.

The structure of the polymerization vessel (pressure autoclave) used in the above suspension polymerization method is not particularly limited,
What is conventionally used for the polymerization of vinyl chloride is used. In addition, the stirring blades include a Faudler blade, a paddle blade,
A generally used blade such as a turbine blade, a fan turbine blade or a bull margin blade may be used, but a Faudler blade is particularly preferable. There is no particular limitation on the combination with the baffle.

[0030]

Embodiments of the present invention will be described below. (Examples 1 to 3 and Comparative Examples 1 to 6) 50 kg of deionized water was placed in a polymerization vessel (pressure resistant autoclave) having an internal volume of 100 liters.
Is added to the vinyl chloride monomer, and the degree of saponification and average degree of polymerization shown in Table 1 is partially saponified polyvinyl acetate 75.
0 ppm, 120 ppm of anionic emulsifier shown in Table 1,
1400 ppm of the higher fatty acid shown in Table 1, 150 ppm of the thickening agent shown in Table 1 and 500 ppm of t-butylperoxy neodecanoate were added. Next, after degassing the inside of the polymerization vessel to 45 mmHg, vinyl chloride monomer 33k
g was charged and stirring was started. The temperature in the polymerization vessel was raised to 57 ° C. to start the polymerization, and this temperature was maintained until the completion of the polymerization reaction.
The reaction was terminated when the conversion of polymerization reached 90%, the unreacted monomer in the polymerization vessel was recovered, the polymer was taken out as a slurry, and dehydrated and dried to obtain a vinyl chloride resin.

(Examples 4 to 6, Comparative Examples 7 to 11) Internal volume 1
50 kg of deionized water was placed in a polymerization vessel (pressure autoclave) of 00 liters, and further, 500 ppm of the cellulose derivative shown in Table 2 with respect to the vinyl chloride monomer, Table 2
Anionic emulsifier 450 ppm, higher fatty acid 1400 ppm shown in Table 2, thickener 150 ppm shown in Table 2
And t-butyl peroxy neodecanoate 500
ppm was added. Then, after degassing the inside of the polymerization vessel to 45 mmHg, 33 kg of vinyl chloride monomer was charged and stirring was started. The temperature in the polymerization vessel was raised to 57 ° C. to start the polymerization, and this temperature was maintained until the completion of the polymerization reaction. The reaction is terminated when the polymerization conversion rate reaches 90%, the unreacted monomer in the polymerization vessel is recovered, and then the polymer is taken out in a slurry state,
It was dehydrated and dried to obtain a vinyl chloride resin.

In any of the above examples, adhesion of polymer scale to the inner wall of the polymerization vessel was not observed. Further, in Comparative Example 2, a block-like aggregate was formed and a granular vinyl chloride resin could not be obtained.

The following performance evaluations were performed on the vinyl chloride resins obtained in the above Examples and Comparative Examples, and the results are shown in Table 1.
It was shown to. (1) Porosity Using plasticizer absorbency as an index of porosity, 5 g of vinyl chloride resin was weighed into a centrifuge tube with a glass filter, and an excessive amount of DOP (dioctyl phthalate) plasticizer with respect to the resin 1
After adding 0 ml and mixing well, the mixture was left for 1 hour. Then, excess DOP was separated for 30 minutes by a centrifuge (“H-200N” manufactured by Domestic Centrifuge Co., Ltd., rotation speed: 3000 rpm), and DOP absorption amount (phr) per 100 parts by weight of resin.
I asked.

(2) Particle size distribution 60, 100 and 15 according to JIS Z8801
The amount of passage (% by weight) was calculated by sieving using a 0 mesh sieve.

(3) Workability The gelation time of the resin composition was measured under the following conditions using a Plastomill (“Rheo Cord 90” manufactured by Haake). Resin input amount 60g, rotation speed 50rpm, 190
The gelation time until the torque rises at a constant temperature of ℃ was measured, and the shorter the time, the better the workability. As the resin composition, 100 parts by weight of vinyl chloride resin was used as a lubricant, and a montanic acid ester (“W” manufactured by Hoechst Co., Ltd.) was used.
AX OP ") 0.5 part by weight and dibutyltin mercapto (" JF-10B "manufactured by Sankyo Machine Gosei Co., Ltd.) as a stabilizer 2
120 parts by weight with a super mixer (Mitsui Miike)
The mixture was heated to 40 ° C, mixed and then cooled to 40 ° C.

(4) Surface condition Vinyl chloride resin particles were observed with a scanning electron microscope ("FE-SEM S-4200" manufactured by Hitachi Ltd.) at a magnification of 130.
Take a photograph at 2x and trace the particle outline, skin part, and non-skin part (the part where the primary particles are exposed, hereafter referred to as "skin-free part") to tracing paper (or O
It was copied on the HP sheet). Next, a tracing paper (or OHP sheet) is attached to the image analysis device (Pierce's "P
IAS-III ”) was incorporated into the screen, and the total area of the particles and the area of the skin-free portion were calculated by the following formula, and was defined as the skin-free rate. In the table, the average value of the measured values of 50 particles is shown. Skin-free rate = (area of skin-free portion / total area of particles) × 100 (%) The conditions for using the scanning electron microscope are: accelerating voltage 2 KV,
The magnification was 130 times.

[0037]

[Table 1]

[0038]

[Table 2]

In Tables 1 and 2, the following components were used. (Partially saponified polyvinyl acetate, "PVA" in the table
(A) Average saponification degree 76 mol%, polymerization degree 1,000 (b) Average saponification degree 83 mol%, polymerization degree 1,500 (c) Average saponification degree 72 mol%, polymerization degree 800 (Cellulose derivative) (d) Hydroxypropyl methylcellulose ("H" in the table
(E.g., MC)) (e) Methylcellulose (indicated by "MC" in the table) (anionic emulsifier) -Polyoxyethylene alkyl phosphate ester: "Prysurf A212C" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "A" in the table -Polyoxyethylene alkyl sulfate ester salt: "Hitenol N-08" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., indicated by "S" in the table) (Higher fatty acid) -Stearic acid (18 carbon atoms, in the table) "S")-Lauric acid (12 carbons, indicated by "L" in the table) 1-Pyreneic acid (26 carbons, indicated by "P" in the table) (Thickener) -Polyethylene Oxide (indicated by "PEO" in the table)
Weight average molecular weight 430 to 4.8 million, η = 12 cps Polyacrylamide (indicated by “PAA” in the table) (f) Weight average molecular weight 11 to 12 million, η
= 51 cps (g) Weight average molecular weight 19 to 22 million, η
= 250 cps (h) Weight average molecular weight 2.3 million to 4.5 million, η = 9 cp
s

[0040]

The structure of the method for producing a vinyl chloride resin of the present invention is as described above, and in the production process, polymer scale is less adhered to the inner wall of the polymerization vessel, and the vinyl chloride resin obtained is porous. Rich, narrow particle size distribution, and excellent workability.

Claims (1)

[Claims] 1. A reaction system for suspension polymerization of a vinyl chloride monomer in an aqueous medium in the presence of an oil-soluble polymerization initiator,
At least one of (a) partially saponified polyvinyl acetate and (b) cellulose derivative, (c) anionic emulsifier, (d) higher fatty acid having 8 to 25 carbon atoms, and (e) 0.1 weight. % Aqueous solution having a Brookfield viscosity of 10 to 200 cps is added to the suspension polymerization method of vinyl chloride resin.