JP2000086708A - Production of vinyl chloride-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing, by suspension polymerization, a vinyl chloride-based polymer having high bulk density, good gelling characteristics and excellent moldability in which scale is hard to adhere to the inside wall of a polymerizer. SOLUTION: When producing a vinyl chloride-based polymer by suspension polymerization of vinyl chloride monomer or a monomer mixture consisting of vinyl chloride as a principal component and a comonomer in aqueous medium in the presence of a suspending agent and an oil soluble polymerization initiator, the method of this invention is to add a nonionic surfactant having <=10 HLB in a quantity of 50-5,000 ppm based on the charged weight of the monomer(s) during 5-60% polymerization conversion ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

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 in which scale does not easily adhere to the inner wall of a polymerization can and has a large bulk density and a good gelling property. The present invention relates to a method for producing a vinyl chloride polymer by suspension polymerization to obtain vinyl chloride polymer particles having excellent characteristics.

[0002]

2. Description of the Related Art A vinyl chloride monomer or a mixture of a vinyl chloride-based monomer and a monomer copolymerizable therewith (hereinafter referred to as a vinyl chloride-based monomer, and the resulting polymer is referred to as a vinyl chloride-based polymer). In the suspension polymerization, the monomers are dispersed as oil droplets in an aqueous medium by a surface shearing action of a suspending agent and a mechanical shearing action by stirring, and a polymerization initiator dissolved in the oil drops is used. The polymerization starts and proceeds. The viscosity of the liquid monomer oil droplets increases with the progress of polymerization, and eventually converts to resinous polymer particles. In the process until the polymerization conversion rate reaches about 5%, oil droplet units are reduced. Merging and dispersion are repeatedly performed, and at this stage, the basic skeleton of the particle structure is formed. Polymer particles finally obtained as a vinyl chloride resin are aggregates composed of a plurality of oil droplet units, and have voids therein. Therefore, in the suspension polymerization of a vinyl chloride monomer, the formulation of the suspending agent such as the type and amount of the suspending agent, the stirring conditions such as the stirring speed and power, and the conversion of the liquid monomer to the resinous polymer The conversion rate, that is, polymerization conditions such as the polymerization reaction rate are important factors in determining the particle structure, these conditions are the quality characteristics due to the particle structure of the resin, for example, particle size, bulk specific gravity, It is known to control the formability and the like.

Hitherto, high extrusion rates in hard extrusion molding of pipes and resin plates using vinyl chloride polymers, and gelation rates due to plasticizers in soft applications such as sheets for agricultural greenhouses. It has been demanded for the production of vinyl chloride polymers from the viewpoint of resin processing that high processability is good. Also, in the production of vinyl chloride polymers, good polymerization productivity is required, and the polymerization reaction time can be shortened by increasing the size of the polymerization vessel and improving the removal of reaction heat by using a reflux condenser and internal jacket. I have been. However, the polymer scale adhering to the inner wall of the polymerization can lowers the heat transfer coefficient of the jacket and causes the polymerization can to be stopped for scale removal cleaning. Further scale reduction is required.

A nonionic surfactant of HLB 2 to 10 or a sorbitan higher fatty acid ester of HLB 3 to 10 is used together with a suspending agent from the beginning of the polymerization reaction, and a vinyl chloride system having a large bulk density and an improved gelling property. A method for obtaining polymer particles has been proposed (JP-A-5-29500).
No. 8, JP-A-10-101713), these do not improve the amount of adhered scale. In addition, a nonionic surfactant having an HLB of 10 or less is present together with a suspending agent from the beginning of polymerization, and in the course of the polymerization reaction, a nonionic surfactant or a suspending agent having an HLB of 10 or more is added. A method of producing vinyl chloride polymer particles having good gelling properties by additional addition has also been proposed (JP-A-60-228508 and JP-B-5-86408). The amount is not improved, and there is a disadvantage that a polymer having a low bulk density and a high hygroscopicity can be obtained.

[0005]

Under such circumstances, the present invention is intended to prevent scale from adhering to the inner wall of a polymerization can,
An object of the present invention is to provide a method for producing a vinyl chloride-based polymer which has a large bulk density and a large pore diameter in a particle, so that polymer particles having good processability can be obtained in both hard extrusion molding and soft calendar molding. Things.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that by adding a specific nonionic surfactant during a specific period of the polymerization reaction, the occurrence of polymerization can scale is extremely reduced. The present inventors have found that a vinyl chloride polymer obtained by polymerization has a large bulk density and a good gelling property, and this finding has led to the completion of the present invention. That is, the present invention suspends a mixture of a vinyl chloride monomer or a monomer mainly composed of vinyl chloride and copolymerizable therewith in an aqueous medium in the presence of a suspending agent and an oil-soluble polymerization initiator. When a vinyl chloride polymer is produced by polymerization, a nonionic surfactant having a hydrophilic-lipophilic balance (HLB) of 10 or less is charged in a period of polymerization conversion of 5 to 60%, and the monomer weight is reduced. An object of the present invention is to provide a method for producing a vinyl chloride polymer characterized by adding 50 to 5000 ppm.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The monomer used in the present invention is vinyl chloride alone or a mixture of vinyl chloride at 50% by weight or more and a monomer copolymerizable therewith. In the present invention, monomers copolymerizable with vinyl chloride include, for example, alkyl vinyl esters represented by vinyl acetate and vinyl propionate; alkyl vinyl ethers represented by octyl vinyl ether and cetyl vinyl ether; ethylene, propylene and the like. α-monoolefins; alkyl (meth) acrylates such as methyl acrylate and methyl methacrylate; and other examples include vinylidene chloride and styrene, but are not limited thereto as long as they copolymerize. The suspending agent used in the suspension polymerization method of the present invention may be one generally used for suspension polymerization of a vinyl chloride monomer, and is not limited. For example, partially saponified polyvinyl acetate (polyvinyl alcohol) having an average degree of saponification of 15 to 99 mol% and an average degree of polymerization of 100 to 2000; cellulose derivatives such as methylcellulose and hydroxypropylmethylcellulose; one or two kinds of gelatin and the like The above is used in an amount of 0.03 to 0.15 parts by weight per 100 parts by weight of the charged monomers.

The oil-soluble polymerization initiator used in the present invention comprises:
What is generally used for suspension polymerization of a vinyl chloride type monomer may be used, and it is not limited. For example, 2,2,4-
Trimethylpentyl-2-peroxyneodecanoate, di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate, α-
Organic peroxides such as cumyl peroxy neodecanoate, t-butyl peroxy neodecanoate, t-butyl peroxy pivalate, 3,5,5-trimethylhexanoyl peroxide and acetylcyclohexylsulfonyl peroxide , Α, α′-azobisisobutyronitrile and α, α′-azobis-2,4
Azo compounds such as -dimethylvaleronitrile, and one or a mixture of two or more of these. The amount of the initiator used varies depending on the type of the initiator and the polymerization temperature, but is usually 0.02 per 100 parts by weight of the monomer.
~ 2 parts by weight.

[0009] The hydrophilic-lipophilic balance used in the polymerization method of the present invention.
Nonionic surfactants having an ilic balance (HLB) of 10 or less include polyoxyethylene nonyl phenyl ether (HLB 7.8, which depends on the amount of polyoxyethylene added), sorbitan monostearate (HLB 4.7), and sorbitan mono Laurate monopalmitate (HLB6.7), sorbitan monolaurate (HLB8.6), sorbitan distearate (HLB)
4.4), sorbitan tristearate (HLB2.
1), glycerol monostearate (HLB2.
8), di (glycerin) = borate = monostearate (HLB7.8), polyglycerin fatty acid ester, propylene glycol fatty acid ester, pentaerythritol fatty acid ester, and polyoxyethylene adduct thereof. One or a mixture of two or more of these can be used.

[0010] The form of addition may be the nonionic surfactant alone, a dispersion dispersed in water, or an emulsifier for another auxiliary material such as a chain transfer agent. HLB is 1
The addition time of the nonionic surfactant of 0 or less is a period when the polymerization conversion is 5 to 60% by weight, preferably 10 to 50% by weight.
Weight percent period. The amount of the nonionic surfactant to be added is 50 to 5000 ppm, preferably 100 to 4000 ppm, based on the weight of the initially charged monomer or the weight of the monomer charged up to then. H in the manner described above
The addition of a nonionic surfactant having an LB of 10 or less significantly reduces the scale adhesion on the inner wall of the polymerization can. In addition, the obtained vinyl chloride-based polymer particles have a large amount of voids inside the particles, have a good plasticizer absorbency and therefore have a good gelling property, and have a large bulk density, and have excellent moldability. Become.

When the HLB of the nonionic surfactant is larger than 10, a large amount of scale tends to adhere to the inside of the polymerization vessel, and the bulk density of the obtained vinyl chloride polymer particles tends to decrease. When the addition time of the nonionic surfactant having an HLB of 10 or less is a time when the polymerization conversion rate is less than 5%,
There is almost no scale reduction effect on the wall surface of the polymerization can, and the bulk density of the obtained vinyl chloride polymer particles becomes small. On the other hand, when the addition time is later than the point of the polymerization conversion rate of 60%, the pore diameter of the voids inside the obtained polymer particles becomes small, and the gelling property becomes poor. When the added amount of the nonionic surfactant having an HLB of 10 or less is less than 50 ppm of the charged monomer weight, the effect of improving the bulk density and processability is difficult to appear. Conversely, if the addition amount is more than 5000 ppm, the stability of the polymerization reaction is reduced, and coarse particles and scale are easily formed. In the present invention,
The polymerization reaction is usually performed in a range of 40 to 75 ° C. The amount of water in the medium and the amount of the chain transfer agent or the like added as necessary may be under conventional conditions, and is not particularly limited.

[0012]

The present invention will be described more specifically with reference to the following examples. The percentages and parts in Examples and Comparative Examples are based on weight unless otherwise specified. The physical properties of the vinyl chloride resin were measured by the following methods. (1) Average Particle Diameter The dried vinyl chloride polymer particles were shown as a 50% passage diameter by sieve analysis using a JIS standard wire mesh. (2) Bulk specific gravity Measured by the method specified in JIS K6721. (3) Average pore size The dried vinyl chloride-based polymer particles were subjected to MICROMERI
TIPS Co., Ltd., Intra-particle air gap measuring instrument Autopore III 942
Measured by mercury intrusion method using 0. (4) Gelation time 100 parts of a vinyl chloride-based polymer, 4.5 parts of an organic tinmalate-based stabilizer, and 1.0 part of butyl stearate were blended, and the blended powder was mixed with a mixer R of Labo Plastomill manufactured by Toyo Seiki Co., Ltd. After charging 56 g to -60 and preheating at 150 ° C. for 5 minutes, kneading was performed at 80 rpm under the same temperature conditions, and the time until the maximum torque was reached was defined as the gel time. It is determined that the shorter the gelation time, the better the workability. (5) Scale Amount The scale attached to the inner wall of the polymerization vessel, the baffle, and the stirring blade was scraped off with a scraper, dried, and the measured weight was divided by the total internal area to be converted per unit area.

EXAMPLE 1 Deionized water (1000 kL) was placed in a stainless steel polymerization vessel equipped with a stirrer having a capacity of 2000 liters and a jacket.
g, tertiary hexyl peroxy neodecanoate (70% strength in toluene solution), 150 g, tertiary hexyl peroxy pivalate (70% strength in toluene solution), 250 g, and partially saponified PVA as a suspending agent
(Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gohsenol K
H-20 ") and 0.07 parts per 100 parts of vinyl chloride monomer. Then, the polymerization vessel was degassed, 850 kg of vinyl chloride monomer was charged, and polymerization was carried out at a temperature of 61.5 ° C. Started. While maintaining the reaction temperature at 61.5 ° C., an aqueous solution of a chain transfer agent 2-mercaptoethanol was charged and 0.01 part was added to 100 parts of the vinyl chloride monomer. When the polymerization conversion reached 40%, sorbitan monostearate (HLB4.7) was charged and vinyl chloride monomer 100 was added.
0.07 parts were added per part. Polymerization vessel pressure is 0.6kg
The polymerization was terminated at the time when the pressure decreased to 9 kg / cm2G. After completion of the polymerization, the unreacted monomer was recovered, and then the polymer dispersion water was dehydrated and dried. Table 1 shows the evaluation results of the obtained vinyl chloride polymers.

Example 2 In Example 1, sorbitan monostearate was replaced with polyoxyethylene nonyl phenyl ether (HLB7.
8), and the same procedure as in Example 1 was carried out except that the addition time was changed to a point of time when the polymerization conversion rate was 20%, to produce a vinyl chloride polymer. Table 1 shows the evaluation results of the polymer.
Shown in Comparative Example 1 In Example 1, except that the addition time of sorbitan monostearate was changed before degassing and drying before charging the monomer,
It carried out similarly to Example 1 and manufactured the vinyl chloride polymer. Table 1 shows the evaluation results of the polymer.

Comparative Example 2 A vinyl chloride polymer was produced in the same manner as in Example 1, except that the time of addition of sorbitan monostearate was changed to a point at which the polymerization conversion was 65%. . Table 1 shows the evaluation results of the polymer. Comparative Example 3 A vinyl chloride polymer was produced in the same manner as in Example 1, except that sorbitan monostearate was changed to polyoxyethylene lauryl ether (HLB 13.6). Table 1 shows the evaluation results of the polymer.

[0016]

[Table 1]

From Table 1, it can be seen that Examples 1 and 2 according to the method of the present invention have a small amount of scale adhered to the wall of the polymerization can.
Further, it can be seen that the obtained polymer particles have a large bulk density, a large pore diameter, and a good gelling property. Sorbitan monostearate is added at a polymerization conversion rate of 5%
If it is earlier, there is no scale reduction effect of the polymerization can wall,
The obtained polymer particles have a low bulk density (Comparative Example 1). On the other hand, when the addition time is later than the point of the polymerization conversion rate of 60%, the pore diameter in the obtained polymer particles is small and the gelation time is long (Comparative Example 2). The nonionic surfactant H
When the LB having a high LB of 12.5 is used, many scales adhere to the inside of the polymerization can and the bulk density is small (Comparative Example 3).

[0018]

According to the present invention, it is possible to obtain vinyl chloride-based polymer particles which are less likely to adhere to the inner wall of the polymerization can, have a high bulk density, have a good gelling property, and are therefore excellent in workability.

Continued on the front page F term (reference) 4J011 AA01 AA08 DA03 EA03 EA06 JA13 JB24 JB26 PA22 PB40 PC03 PC07 4J100 AA02Q AA03Q AB02Q AC03P AC04Q AE02Q AG02Q AG04Q AL03Q CA01 CA04 FA02 FA03 FA21

Claims (1)

[Claims] 1. A suspension polymerization of a vinyl chloride monomer or a mixture of a vinyl chloride-based monomer and a monomer copolymerizable therewith in an aqueous medium in the presence of a suspending agent and an oil-soluble polymerization initiator. When a vinyl chloride-based polymer is produced, a nonionic surfactant having a hydrophilic-lipophilic balance (HLB) of 10 or less is charged in a period of a polymerization conversion of 5 to 60%, and 50% by weight of monomer is charged. A method for producing a vinyl chloride-based polymer, characterized by adding 5,000 ppm. [0001]