JPH11130804A - Production of vinyl chloride-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject high-quality resin capable of preventing coarse particles and fisheyes from forming, having high productivity and excellent in operating efficiency by carrying out a polymerizing reaction of a vinyl chloride-based monomer in the presence of a polymerization initiator and a dispersing agent in an aqueous medium using a polymerizer equipped with a specific reflux condenser for a specific time. SOLUTION: A polymerizing reaction of a vinyl chloride-based monomer is carried out in the presence of a polymerization initiator (e.g. diisopropyl peroxydicarbonate or potassium persulfate) and a dispersing agent in an aqueous medium by using a polymerizer equipped with a reflux condenser and having >=40 m<3> internal volume to complete the polymerizing reaction within 5 hr. Thereby, the objective resin is produced. The ratio A/B of the heat transfer area A (m<2> ) of the reflux condenser to the heat transfer area B (m<2> ) of the polymerizer is (1/2) to (5/1). A partially saponified polyvinyl alcohol having 65-85 mol.% degree of saponification and 700-3,000 degree or average polymerization is preferably used as the dispersing agent.

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 resin (hereinafter referred to as "PVC"), and more particularly, to a method for producing high quality PVC with high productivity and excellent operability. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride monomers (hereinafter referred to as "V
C) is usually carried out by a batch water suspension polymerization method in a polymerization vessel equipped with a jacket for heating and cooling and a stirring device. That is, a method in which an aqueous medium and a dispersant are charged into a polymerization vessel, then a polymerization initiator is charged, then the inside of the polymerization vessel is evacuated to vacuum, VC is charged, and the temperature is raised to carry out a polymerization reaction.

[0003] The polymerization reaction of VC is an exothermic reaction, and the reaction heat generated during the polymerization is circulated through a cooling medium in the jacket of the polymerization vessel or a reflux condenser (hereinafter referred to as RC) attached to the gas phase of the polymerization vessel. ), And the method of controlling the internal temperature of the polymerization vessel is generally adopted.

In recent years, in the production of PVC, one of the methods for increasing the size of a polymerization vessel and increasing the polymerization rate in order to improve productivity is to shorten the time required for charging a reaction mixture and increasing the temperature. It is planned. At that time, it is important that the polymerization reaction, which usually takes 5 hours or more, is performed at a high speed to complete the polymerization in a short time.

However, when such a high-speed polymerization is carried out, the heat generation rate increases. Therefore, it is necessary to enhance the heat removal capability of the polymerization apparatus. For example, heat removal is performed by using a heat transfer medium cooled in advance by a refrigerator. A method of using a material having excellent thermal conductivity as a material of a polymerization vessel and having little scale adhesion (Japanese Patent Publication No. 58-8405), and reducing the thickness of the jacket by installing the jacket on the inner surface of the polymerization vessel body. Method for improving heat removal efficiency by thinning (Japanese Patent Laid-Open No. 57-147502)
Publication) and the like. However, any of these methods has insufficient heat removal ability to perform high-speed polymerization within 5 hours using a large-sized polymerization vessel having an internal volume of 40 m ³ or more, which is currently employed on an industrial scale. There have been problems such as difficulty in control and increase in costs for installation and operation of the equipment.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and uses a polymerization apparatus comprising a large jacket-type polymerization vessel and an RC to remove heat of polymerization reaction by the jacket and the RC. It is an object of the present invention to provide a method for producing a vinyl chloride-based resin capable of producing high-quality PVC with low fish eyes and less coarse particles with high productivity by molding while completing polymerization. .

[0007]

The polymerization method of the present invention comprises the steps of:
C was subjected to a polymerization reaction in an aqueous medium in the presence of a polymerization initiator and a dispersing agent using a polymerization vessel having an internal volume of 40 m ³ or more equipped with RC, and the polymerization reaction was completed within 5 hours.
C of the heat transfer area A (m ²⁾ and the polymerization reactor heat transfer area B (m ²⁾
Is in the range of 1/2 to 5/1. Hereinafter, the present invention will be described in detail.

[0008] The polymerization apparatus used in the present invention has an inner volume of 40 provided with a jacket and RC for heating and cooling.
The total heat transfer coefficient of the jacket during polymerization in a polymerization reactor of m ³ or more, preferably in a jacket polymerization reactor, is 500 kcal /
Those having a heat transfer performance of at least m ² · hr · ° C. are preferred. The structure of the RC is not particularly limited, but generally a multi-tube RC is exemplified. The method of using RC is not particularly limited, and a known method is applied.

In the present invention, the heat transfer area A of the RC
(M ²⁾ and by the use of polymerizer 1 / 2-5 / 1 ratio A / B of the polymerization vessel in heat transfer area B and (m ^2), to effectively achieve the object of the present invention Can be. If the A / B ratio is less than 1/2, it becomes difficult to remove the polymerization reaction heat, and
When the ratio exceeds / 1, the cost of installation of the RC increases, the space for the equipment is restricted, the cleaning operation and maintenance / inspection require much time and labor, and the RC during polymerization is not only required.
A problem arises in that the temperature control in the inside becomes complicated.

In the practice of the present invention, as a method for charging water, VC, a dispersant, an initiator and other auxiliaries, a method used in ordinary suspension polymerization is suitably used. For example, a method in which water, a dispersant, an initiator, and VC are sequentially added to a polymerization vessel, a method in which these are continuously and simultaneously charged, a method in which a dispersant aqueous solution and VC in which an initiator is dissolved are sequentially or simultaneously charged, and the like. Method is also acceptable. The weight ratio of water to VC is generally water / VC = 0.7 /
It is performed at about 1 to 1.6 / 1. Next, the heat of reaction generated during the polymerization is removed by the jacket of the polymerization reactor and the RC, and the polymerization is continued and completed while controlling the temperature of the contents of the polymerization reactor at a predetermined polymerization temperature.

In this way, the polymerization vessel jacket and R
The heat of the polymerization reaction is removed by C, and the content of the polymerization vessel is polymerized while controlling the content at a predetermined polymerization temperature to complete the reaction.The time until the polymerization is completed, that is, the polymerization time is set to achieve high productivity. It is limited to 5 hours or less in terms of safety such as temperature control and pressure management of the polymerization reactor. The polymerization time in the present invention is defined as the natural pressure at the polymerization temperature when the internal temperature of the polymerization vessel reaches a predetermined polymerization temperature by raising the temperature after charging VC or the like. After a transition for a while, the pressure drop starts with the decrease of the unreacted VC, and is defined as the time until the drop width becomes 2 kg / cm ² .

The VC used in the present invention may be VC alone or a mixture containing VC as a main component (usually VC 50% by weight).
Above). Further, another vinyl monomer copolymerizable with VC may be contained as long as the production method of the present invention exerts its effects. Other vinyl monomers copolymerizable with VC include, for example, vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylate esters such as methyl (meth) acrylate and ethyl (meth) acrylate; In addition to olefins such as ethylene and propylene, (meth) acrylic acid, maleic anhydride, acrylonitrile,
Examples include, but are not limited to, styrene and vinylidene chloride.

When suspension polymerization is carried out in an aqueous medium using the above-mentioned VC, a dispersant is generally used. The type of the dispersant is not particularly limited, and examples thereof include those usually used for suspension polymerization of vinyl chloride. Examples thereof include polyvinyl alcohol; water-soluble cellulose such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose; Synthetic polymer substances such as maleic acid-vinyl acetate copolymer;
Water-soluble polymers such as polyethylene oxide, polyacrylic acid, and gelatin; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan monostearate, glycerin tristearate, and ethylene oxide propylene oxide block copolymer; polyoxyethylene sorbitan Monolaurate, polyoxyethylene glycerin oleate
And water-soluble emulsifiers such as sodium laurate and sodium dodecylbenzenesulfonate. These may be used alone or in combination of two or more.

Among the above dispersants, the saponification degree is from 65 to 85.
Partially saponified polyvinyl alcohol having an average degree of polymerization of 700 to 3000 in mol% is preferred. The amount of the dispersant used is preferably 0.02 to 1 part by weight based on 100 parts by weight of VC.

[0015] The polymerization initiator used in the present invention includes:
In general, a polymerization initiator used for suspension polymerization of VC is preferably used. As such a polymerization initiator, for example,
Peroxycarbonate compounds such as diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate; α-cumylperoxyneodecanate;
Peroxyester compounds such as t-butylperoxyneodecanate, t-butylperoxypivalate, and t-hexylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl- 2-peroxyphenoxyacetate
Azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile); potassium persulfate, ammonium persulfate, hydrogen peroxide and the like. These may be used alone or in combination of two or more.

Further, a polymerization regulator, a chain transfer agent, a pH regulator, a gelling improver, an antistatic agent, a polymer scale adhesion inhibitor and the like which are appropriately used for polymerization of VC or the like may be added.

Further, as the stirring blade of the stirring device used, there are a Faudler type retreating blade, a blue margin blade, a turbine blade, a fan turbine blade, and the like. Baffle, E
A type baffle (finger type) baffle and the like are preferably used.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.

(Embodiment 1) Heat transfer area 8 with internal volume 60 m ³
Using a polymerization apparatus consisting of a 0 m ² polymerization vessel and a multi-tubular RC having a heat transfer area of 120 m ² connected to the gas phase of the polymerization vessel, the vinyl chloride monomer 19,200 k
g, 25,000 kg of deionized water, 10 kg of partially saponified polyvinyl alcohol having a degree of saponification of 78 mol% as a dispersant and an average degree of polymerization of 1700, partially saponified polyvinyl alcohol having a degree of saponification of 73 mol% and an average degree of polymerization of 700 9
kg and 9.6 kg of di-2-ethylhexylperoxyoxycarbonate as a polymerization initiator, and then the inside of the polymerization vessel was heated to 57 ° C. with stirring to initiate polymerization. 8.
The pressure of the polymerization reactor, which was 5 kg / cm ² , was 6.5 kg / c.
At the time of drop to m ² , unreacted vinyl chloride monomer was recovered from the polymerization vessel to complete the polymerization, and the obtained PVC was dehydrated and dried. The polymerization time was 4.1 hours.

Example 2 Same as Example 1 except that 14.4 kg of partially saponified polyvinyl alcohol having a degree of saponification of 73 mol% and an average degree of polymerization of 700 and 7.7 kg of hydroxypropylmethylcellulose were charged as dispersants. Carried out.

Comparative Example 1 The same operation as in Example 1 was carried out except that 17.3 kg of hydroxypropyl methylcellulose was charged as a dispersant.

(Comparative Example 2) A heat transfer area of 7 with an internal volume of 50 m ³
Using a polymerization apparatus consisting of a 0 m ² polymerization vessel and a multi-tubular RC having a heat transfer area of 30 m ² connected to the gas phase of the polymerization vessel, 16,000 kg of vinyl chloride monomer was added to the polymerization vessel degassed in advance.
20,800 kg of deionized water, saponification degree 7 as dispersant
8 mol%, partially saponified polyvinyl alcohol having an average degree of polymerization of 1700 8.8 kg, partially saponified polyvinyl alcohol having a degree of saponification of 73 mol% and an average degree of polymerization of 11.4 k
g, and di-2-ethylhexyl par-
After charging 3.5 kg of oxydica carbonate, the temperature in the polymerization vessel was raised to 57 ° C. with stirring to start polymerization. 8.5
kg / pressure cm ² at a polymerization vessel is 6.5 kg / cm
At the time of drop to ² , the unreacted vinyl chloride monomer was recovered from the polymerization vessel to complete the polymerization, and the obtained PVC was dehydrated and dried. The polymerization time was 7.5 hours.

The physical properties of the PVC obtained in the above Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1. (1) Coarse Grain Degree According to JIS Z 8801, it was sieved using a standard 42-mesh sieve, and indicated by the weight% of the particles remaining on the sieve. (2) Bulk specific gravity Measured according to JIS K6721. (3) Fisheye To 100 parts by weight of the obtained PVC, 50 parts by weight of dioctyl phthalate (plasticizer), 0.5 parts by weight of barium stearate (stabilizer), and 0.5 parts by weight of zinc stearate (stabilizer)
Parts by weight, 0.5 parts by weight of titanium dioxide (filler) and 0.1 parts by weight of carbon black (filler) were mixed, and the mixture was kneaded on a 6-inch roll at 140 ° C. for 5 minutes. A sheet having a thickness of 0.3 mm was prepared, and the number of transparent particles in 100 cm ^{2 of the} sheet was counted to determine the number of fish eyes.

[0024]

[Table 1]

[0025]

The method for producing PVC of the present invention is as described above. By removing the heat of the polymerization reaction using a specific polymerization apparatus, high-speed polymerization within a polymerization time of 5 hours or less can be achieved, and high productivity can be realized. However, the problem of shortening the time, which was difficult to achieve with a conventional large-scale polymerization reactor, was solved. Moreover, coarsening and fish-eye of PVC obtained by using a specific dispersant in combination can be prevented.

Claims (2)

[Claims] 1. A polymerization reaction of a vinyl chloride monomer in an aqueous medium in the presence of a polymerization initiator and a dispersant by using a polymerization vessel having an inner volume of 40 m ³ or more equipped with a reflux condenser. When the polymerization reaction is completed within an hour, the ratio A / B between the heat transfer area A (m ² ) of the reflux condenser and the heat transfer area B (m ² ) of the polymerization vessel is 1/2 to 5/1. A method for producing a vinyl chloride resin. 2. A saponification degree of 65 to 85 mol% as a dispersant.
The method for producing a vinyl chloride resin according to claim 1, wherein a partially saponified polyvinyl alcohol having an average degree of polymerization of 700 to 3000 is used.