JPH1087708A - Production of vinyl chloride polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a vinyl chloride polymer which has a high bulk density and is suitable for high-speed extrusion molding in no need of special operation on polymerization. SOLUTION: In the suspension polymerization of vinyl chloride monomer or that selected from a mixture thereof containing monomers copolymerizable with the same in the presence of an oil-soluble polymerization initiator in an aqueous medium, at least one kind of polyvinyl alcohol with a saponification degree of >=85mol% is used as a dispersant in an amount of 20-60wt.% based on the whole amount of the dispersants. In addition, an acidic component is added to the polymerization system in an amount of 2.0×10<-5> to 1.0×10<-2> mole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer, and more particularly to a method for stably obtaining a vinyl chloride polymer having a high bulk specific gravity, excellent porosity, and good moldability. To possible manufacturing methods.

[0002]

2. Description of the Related Art As a method for obtaining a vinyl chloride polymer having a high bulk specific gravity, when a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium, for example, a vinyl chloride monomer is added during the polymerization. (Japanese Unexamined Patent Publication No. Sho 59-168008), a method of carrying out polymerization while increasing the polymerization temperature during a period of 50% or more of the entire period in which the polymerization reaction proceeds (Japanese Unexamined Patent Publication No. Sho 61-126112), and the like. A method has been proposed.

[0003] However, these methods make the polymerization process more complicated than conventional methods. Further, there are problems that the amount of unreacted monomer remaining in the vinyl chloride polymer after polymerization increases, and it becomes difficult to remove the heat of reaction if the increase in the polymerization temperature is too large. .

JP-A-53-6392 discloses a method for producing a vinyl chloride polymer having a large plasticizer absorption rate by polymerizing vinyl chloride at a pH of 3 to 8.

[0005] Japanese Patent Application Laid-Open No. 7-70211 discloses that when vinyl chloride is polymerized in an aqueous medium, the pH of water becomes 2.
A method for producing polyvinyl chloride with less scale attached to the polymerization vessel by charging the polymerization vessel in the state of 5 to 5 with less fisheye and less initial coloring is disclosed.

JP-A-53-6392 and JP-A-Hei-7
No. 70211 does not disclose that the bulk specific gravity is improved, and the bulk density of the vinyl chloride obtained by the disclosed method is insufficient.

JP-A-57-76008 discloses, as dispersants, (A) a partially saponified polyvinyl alcohol having a polymerization degree of 1500 or more and a saponification degree of 97 mol% or more, (B) a polymerization degree of 700 or more and a saponification degree of 70 or more. Combined use of three kinds of dispersants of hydroxypropyl methylcellulose and / or hydroxypropylcellulose having a surface tension of 50 dyne / cm or less at 25 ° C. of a partially saponified polyvinyl alcohol of ８５85 mol% or more and a 0.1% by weight (C) aqueous solution at 25 ° C. A method for obtaining a vinyl chloride polymer having a high bulk specific gravity is disclosed. According to this method, a vinyl chloride polymer having a high bulk specific gravity can be obtained, but it has been difficult to always stably produce a vinyl chloride polymer having a high bulk specific gravity.

[0008] In the case of manufacturing a rigid molded product such as a pipe, a processor usually weighs the vinyl chloride resin by volume, mixes additives such as a stabilizer and mixes the processed product at a constant speed. Molding. Therefore, when the bulk specific gravity of the vinyl chloride resin changes, the compounding ratio of the stabilizer changes, and further, the amount of resin supplied to the molding machine per unit time changes, thereby changing the quality of the molded product. Therefore, supplying a vinyl chloride resin whose bulk specific gravity does not fluctuate is an extremely important industrial issue.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for stably producing a vinyl chloride polymer which is always stable, has a high bulk specific gravity, and has good moldability.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a method for producing a vinyl chloride polymer by suspension polymerization in an aqueous medium has been described. By using a dispersant, by controlling the content of the acid component in the polymerization system to a specific amount, found that a vinyl chloride polymer having a large bulk specific gravity can be obtained stably, to complete the present invention Reached. That is, the present invention includes the following inventions.

With vinyl chloride monomer or vinyl chloride
Salts selected from monomer mixtures containing copolymerizable monomers
Existence of oil-soluble polymerization initiator in vinyl medium
When performing suspension polymerization in the presence, the degree of saponification as a dispersant
85 mol% or more of partially saponified polyvinyl alcohol
Use at least one of 20 to 60% by weight of the total dispersant,
And the polymerization acid content is 2.0 × with respect to the vinyl chloride monomer.
10^-Five~ 1.0 × 10 ^-2Characterized by the presence of mole%
For producing a vinyl chloride polymer.

An acid content of 2.0 in the vinyl chloride monomer
× 10 ^-5 ~1.0 × 10 manufacturing method of a vinyl chloride polymer according to use vinyl chloride monomer containing ² mol%.

[0013] The vinyl chloride polymer as described above, wherein a vinyl chloride monomer containing 2.0 × 10 ^{−5 to} 1.0 × 10 ⁻² hydrogen chloride in the vinyl chloride monomer as an acid component is used. Manufacturing method.

As a dispersant, in addition to partially saponified polyvinyl alcohol having a degree of saponification of 85 mol% or more, a degree of saponification of 7
The method for producing a vinyl chloride polymer according to the above-mentioned, wherein a partially saponified polyvinyl alcohol having an average degree of polymerization of 700 to 2500 and 0 to 85 mol% is used in combination.

[0015] The method for producing a vinyl chloride polymer according to the above-mentioned, wherein hydroxypropoxymethylcellulose and / or hydroxypropylcellulose are used in combination with the partially saponified polyvinyl alcohol as the dispersant.

The method for producing a vinyl chloride-based polymer according to any one of the above aspects, wherein the vinyl chloride-based monomer is repeatedly polymerized to obtain a vinyl chloride-based polymer having a high bulk specific gravity stably between batches.

The present invention is characterized in that the effect of the present invention is exhibited by selecting and using a specific dispersant when a polymerization acid component is present.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, a vinyl chloride monomer selected from a vinyl chloride monomer or a monomer mixture containing a monomer copolymerizable with vinyl chloride is prepared in an aqueous medium. When performing suspension polymerization in the presence of an oil-soluble polymerization initiator, the acid content of the polymerization system is 2.0 × with respect to the vinyl chloride monomer.
10 ^{-5 to} 1.0 × 10 ^-2 mol%, preferably 2.0 × 1
0 ^{-5 to} 5.0 × 10 ^-3 mol%, more preferably 2.0
X 10 ^{-5 to} 2.0 X 10 ^-3 mol% is present.

The inventor of the present application has studied to obtain a vinyl chloride resin having a high bulk specific gravity and a stable bulk specific gravity. The amount of hydrochloric acid in an industrially obtained vinyl chloride monomer is alkaline (water). 0 in terms of sodium oxide.
Fluctuates from 5 wtppm) to 150 wtppm,
The bulk specific gravity of a vinyl chloride-based polymer (specifically, using the dispersant of Example 1 of the present specification) polymerized using the three types of dispersants described above fluctuates by 0.025 in standard deviation. It was found that the amount of hydrochloric acid or the acid content of the polymerization system was strictly adjusted to the above range, so that the bulk specific gravity was high and stable. It has been found that a vinyl chloride resin having a bulk specific gravity can be obtained, and the present invention has been achieved.

In the method of the present invention, the method of adding the acid component is not particularly limited as long as the acid component of the polymerization system is present, but it is preferable that the acid component be present in the vinyl chloride monomer.

In the step of producing a vinyl chloride monomer from ethylene as a raw material, usually, an ethylene dichloride is produced by a chlorine direct addition step and an oxychlorination step, and further, an ethylene dichloride purification step, a thermal decomposition step of ethylene dichloride, It is roughly divided into five steps of a vinyl monomer purification step. In the above process, the vinyl chloride monomer is obtained by thermally decomposing ethylene dichloride. At this time, hydrogen chloride (hydrogen chloride is used in the specification of the present application including hydrochloric acid) is a by-product of vinyl chloride. In the monomer purification step, separation and purification of vinyl chloride monomer and hydrogen chloride are performed, but since a small amount of hydrogen chloride is present in the separated vinyl chloride monomer, usually a wet process is used to remove this. In the caustic tower, a very strict neutralization treatment is performed to remove a trace amount of hydrogen chloride.

In the present invention, even if a small amount of hydrogen chloride is contained in the vinyl chloride monomer, it can be used as long as the content of hydrogen chloride is controlled, and strict removal of hydrogen chloride is required. And not.

In the present invention, the acid content of the polymerization system may be derived from hydrogen chloride by-produced during the production of the vinyl chloride monomer, or may be an organic acid such as acetic acid or an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid. Can be adjusted by post-addition, but the most preferable method is to adjust the removal rate of hydrogen chloride in the step of purifying the vinyl chloride monomer.

The monomers copolymerizable with vinyl chloride used in the present invention include, for example, vinyl esters such as vinyl acetate and vinyl propionate, methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate. And olefins such as ethylene and propylene, and vinyl ethers such as lauryl vinyl ether and isobutyl vinyl ether. Also, maleic anhydride,
Copolymerizable materials such as acrylonitrile, styrene, and vinylidene chloride are exemplified. These can be used alone or in combination of two or more.

As the dispersant used in the present invention, a saponification degree of 85 mol% or more, preferably 85 to 98 mol%,
More preferably, the polymerization degree is 88 to 98 mol% and the polymerization degree is 1500 to 1500.
At least one of 3000, preferably 1800 to 2500 partially saponified polyvinyl alcohols is used. The amount of the dispersant used is 20 parts of the total amount of the dispersant used for the polymerization.
-60% by weight, preferably 25-55% by weight, more preferably 30-55% by weight. If the amount is less than 20% by weight, the effect of increasing the bulk specific gravity is not exhibited, and if it exceeds 60% by weight, fine particles in the suspension after polymerization increase and the wastewater becomes cloudy.

In the present invention, the degree of saponification is 70 to 85 mol%, preferably 75 to 8 mol%, together with the above dispersant.
It is preferable to use a partially saponified polyvinyl alcohol having 5 mol% and an average degree of polymerization of 700 to 2500, preferably 1000 to 2500. The amount of the dispersant used is 20 to 80% by weight, preferably 30 to 70% by weight, more preferably 35 to 6% by weight of the total amount of the dispersant used for the polymerization.
5% by weight is suitable. When the amount is more than 20% by weight, the polymer particles are not coarsened, and when the amount is less than 80% by weight, the bulk specific gravity is high, which is preferable.

Further, as a third dispersant, 0.1% by weight
It is preferable to use hydroxypropoxymethylcellulose and / or hydroxypropylcellulose having an aqueous solution having a surface tension of 5 to 50 dyne / cm at 25 ° C.

When this dispersant is used as a third dispersant in addition to the above two dispersants, it is used in an amount of 1 to 30% by weight, preferably 1 to 20% by weight of the total amount of the dispersant used in the polymerization. % By weight is appropriate. If it is more than 1% by weight, the fish eye is good, and if it is 30% by weight or less, the bulk specific gravity is high.

In the present invention, it is particularly preferable to use the above three kinds of dispersants in combination.

The amount of the total dispersant used in the present invention is usually from 0.02 to 100 parts by weight of the vinyl chloride monomer.
0.2 parts by weight, preferably 0.04 to 0.18 parts by weight, more preferably 0.06 to 0.15 parts by weight.
If the amount is more than 0.02 parts by weight, the particles do not coarsen,
Below the weight part, the bulk specific gravity becomes high.

In addition to the above three dispersants, partially saponified polyvinyl alcohol, cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, and maleic anhydride other than those described in the claims of the present application. A dispersant such as a synthetic polymer compound such as a vinyl acetate copolymer and a natural polymer substance such as starch and gelatin may be used in combination. Further, the dispersant used for the polymerization may be added all at once or may be added in portions, and the addition time is not limited.

The oil-soluble polymerization initiator used in the present invention includes, for example, diisopropyl peroxydicarbonate, dioctyl peroxydicarbonate, dilauryl peroxydicarbonate, dimyristyl peroxydicarbonate, dicetyl peroxydicarbonate. , Di (tert-butyl) peroxydicarbonate, di (ethoxyethyl) peroxydicarbonate, di (methoxyisopropyl) peroxydicarbonate, di (3methoxybutyl) peroxydicarbonate, di (3methoxy-3-methylbutyl) peroxydi Carbonate, di (butoxyethyl) peroxydicarbonate,
Di (2 isopropoxyethyl) peroxydicarbonate, di (2ethylhexyl) peroxydicarbonate, di (2isopropoxyethyl) peroxydicarbonate, dibenzylperoxydicarbonate, dicyclohexylperoxydicarbonate, ditertiary butyl Percarbonate initiators such as cyclohexyl peroxy dicarbonate, tertiary butyl peroxy neodecanoate, tertiary hexyl peroxy neodecanoate, amyl peroxy neodecanoate,
Tertiary octyl peroxy neodecaneate, α-
Cumyl peroxyneodecanate, 1-cyclohexyl-1-methylethyl peroxyneodecanate, tert-butyl peroxypivalate, amyl peroxypivalate, tertiary octyl peroxypivalate, tertiary hexyl peroxypivalate , Α-
Cumyl peroxypivalate, perhexyl oxalate, ditertiary butyl peroxy oxalate, acetylcyclohexylsulfonyl peroxide,
1.1.3.3. Perester initiators such as tetramethylbutylperoxyphenoxyacetate, lauroyl peroxide, diisobutyl peroxide, 2ethylhexanoyl peroxide, 3.5.5 diacyl peroxide initiators such as trimethylhexanoyl peroxide, 2 .2 'azobisisobutyronitrile,
2.2 'azobis-2.4 dimethylvaleronitrile,
2.2 Azo-based initiators such as 2 'azobis-4methoxy-2.4 dimethylvaleronitrile; water-soluble peroxides such as potassium persulfate and ammonium persulfate; 2.2'-azobis (2-amidinopropane) hydrochloride 2.
Water-soluble azo compounds such as 2'-azobis (NN'-dimethyleneisobutylamidine) hydrochloride and the like are mentioned. In order to make the polymerization reaction rate uniform, a polymerization initiator having a different half-life of 10 hours is used. It may be used in combination of more than one kind. These polymerization initiators may be used as they are, may be used as a water emulsion or a water suspension, or may be used after being dissolved in a solvent such as toluene.

The amount of the initiator used is 100 vinyl chloride monomers.
It is usually 0.01 to 0.1 part by weight, preferably 0.02 to 0.08 part by weight based on part by weight.

The suspension polymerization method of the vinyl chloride monomer mixture in the present invention is carried out by a conventionally known suspension polymerization method.
Additives such as an antioxidant and a chain transfer agent may be added as needed, and the amount of addition, the order of charging to the polymerization vessel, and the like are not particularly limited. The polymerization temperature is set according to the type of the oil-soluble polymerization initiator to be used.
It is in the range of 70 ° C.

[0035]

(Physical property measurement)

(1) Bulk specific gravity: according to JIS K6721 (2) Fisheye: The following components are mixed well and the diameter is 8
145 inch rolls with 15/21 rpm
C. and kneaded for 5 minutes, and the sheet is taken out from a 0.3 mm roll interval. Thereafter, the number of fish eyes existing in an area of 15 × 10 cm was counted. (Resin: 100
g, plasticizer DOP: 50 g, Cd—Ba-based stabilizer: 3
g, Dainichi Seika carbon black (Grade: GY-
3): 1 g) (3) Particle size distribution: JIS standard 60, 80, 100, 1
Sieve analysis was performed using a 50, 200, and 270 mesh wire mesh, and the particle size distribution was measured.

Example 1 A polymerization vessel having an internal volume of 150 m 3 equipped with a Faudler blade was
52 t of degassed ion water and 0.058 parts of partially saponified polyvinyl alcohol (A) having a saponification degree of 98 mol% and an average degree of polymerization of 2500 (viscosity of a 4 wt% aqueous solution at 20 ° C. is 54 cps) as a dispersant. (Weight based on 100 parts of vinyl chloride monomer, the same applies hereinafter), (B) a saponification degree of 80 mol%,
0.055 parts of partially saponified polyvinyl alcohol having an average degree of polymerization of 2000, (C) substitution degree of methoxy group of 28% by weight, substitution degree of hydroxypropoxy group of 10% by weight, 0.1% by weight
0.004 part of hydroxypropoxymethylcellulose having a surface tension of the aqueous solution of 48 dyne / cm was charged. While stirring the polymerization vessel, 58 t of a vinyl chloride monomer having an acid content of 1.5 × 10 ⁻⁵ mol% was charged (when converted assuming that all of the acid content was derived from hydrogen chloride, vinyl chloride monomer was used). 0.088 weight ppm with respect to the monomer.) In this polymerization, the acid content of the polymerization system was equivalent to 2.6 × 10 ^-5 mol% of vinyl chloride monomer because the acid content was present in the water used for the polymerization (this value was also used in the following experiments). And calculate Table 1
No. 2 ).

As the polymerization initiator, (1) di-2-ethylhexyl peroxydicarbonate water emulsion was used.
032 parts by weight and (2) 0.015 parts by weight of an aqueous emulsion of cumyl peroxy neodecanoate were added, and the temperature in the polymerization vessel was set at 57.5 ° C. to carry out polymerization. When the internal pressure reached 6.5 kg / cm 2 -G, the reaction was stopped, unreacted vinyl chloride monomer was recovered, and the slurry was dehydrated and dried to obtain a vinyl chloride polymer. The polymerization time was 6 hours. The polymerization under the same conditions was performed a total of 5 times, and the bulk specific gravity of the obtained vinyl chloride polymer was measured.
Its average value was 0.580 g / ml and its standard deviation was 0.003. Table 1 shows the results.

Examples 2 to 5 Polymerization was carried out five times under the same conditions as in Example 1 except that the acid content in the vinyl chloride monomer and the acid content of the polymerization system were changed to the values shown in Table 1. Was. Table 1 shows the results.

Example 6 A vinyl chloride monomer having an acid content of 1.5 × 10 ⁻⁵ mol% was used, degassed ion water and a dispersant were charged, and hydrochloric acid was charged at the same time. Polymerization was carried out five times under the same conditions as in Example 1 except that the acid content was adjusted to 1.0 × 10 ⁻⁴ mol%. Table 1 shows the results.

Comparative Example 1 Using a vinyl chloride monomer having an acid content of 2.41 × 10 ⁻⁸ , polymerization was carried out five times under the same conditions as in Example 1. The bulk specific gravity of the obtained vinyl chloride polymer varied, and the average value was as low as 0.524 g / ml. Table 2 shows the results.

Comparative Example 2 Polymerization was carried out five times under the same conditions as in Example 1 except that the vinyl chloride monomer adjusted to the acid content shown in Table 2 was used. The bulk specific gravity of the obtained vinyl chloride polymer varied, and the average value was as low as 0.514 g / ml. Table 2 shows the results.

Comparative Example 3 Polymerization was carried out five times under the same conditions as in Example 4 except that the dispersants shown in Table 2 were changed. The average value of the bulk specific gravity of the obtained vinyl chloride polymer was as low as 0.522 g / ml.
Table 2 shows the results.

Comparative Example 4 Polymerization was carried out five times under the same conditions as in Example 4 except that the amount of the dispersant shown in Table 2 was changed. The average value of the bulk specific gravity of the obtained vinyl chloride polymer was as low as 0.529 g / ml. Table 2 shows the results.

Comparative Example 5 Polymerization was carried out five times under the same conditions as in Example 4 except that the amount of the dispersant was changed as shown in Table 2. The average value of the bulk specific gravity of the obtained vinyl chloride polymer was 0.558 g / ml,
Fisheye got worse. Further, the amount of fine particles in the suspension increased, and the wastewater became cloudy. Table 2 shows the results.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

According to the present invention, a vinyl chloride polymer having a high bulk specific gravity and suitable for high-speed extrusion molding can be stably produced without requiring any special operation at the time of polymerization.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Akira Yamamoto 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemicals Co., Ltd.

Claims (5)

[Claims] 1. A vinyl chloride monomer selected from a vinyl chloride monomer or a monomer mixture containing a monomer copolymerizable with vinyl chloride in an aqueous medium in the presence of an oil-soluble polymerization initiator. In carrying out suspension polymerization, a saponification degree of 85 is used as a dispersant.
Mol% or more of partially saponified polyvinyl alcohol is used in an amount of 20 to 60% by weight of the total dispersant, and the acid content of the polymerization system is 2.0 × 10
^A process for producing a vinyl chloride-based polymer, characterized by being present in an amount of from ^{-5 to} 1.0 x 10 ^-2 mol%. 2. An acid content of 2.0 × in a vinyl chloride monomer.
The method for producing a vinyl chloride polymer according to claim 1, wherein a vinyl chloride monomer containing from 10 ^{-5 to} 1.0 x 10 ^-2 mol% is used. 3. An acid content in the vinyl chloride monomer of 2.
0 × 10 ^-5 ~1.0 × 10 ^-2 production method of a vinyl chloride polymer according to claim 1, wherein the use of vinyl chloride monomer containing hydrogen chloride. 4. In addition to a partially saponified polyvinyl alcohol having a degree of saponification of 85 mol% or more as a dispersant, a degree of saponification of 70% is used.
The method for producing a vinyl chloride polymer according to any one of claims 1 to 3, wherein a partially saponified polyvinyl alcohol having an average degree of polymerization of 700 to 2500 and an average degree of polymerization of 700 to 2500 is used in combination. 5. The process for producing a vinyl chloride polymer according to claim 1, wherein hydroxypropoxymethylcellulose and / or hydroxypropylcellulose are used in combination as the dispersant in addition to partially saponified polyvinyl alcohol.