JPH07110882B2 - Method for producing vinyl chloride polymer - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a vinyl chloride polymer having excellent quality. More specifically, the present invention relates to a production method for producing a high-quality vinyl chloride polymer with high efficiency by using a large-sized polymerization vessel equipped with a reflux condenser.

[0002]

2. Description of the Related Art Vinyl chloride resin is a useful resin having excellent physical and mechanical properties, and is industrially used in a batch type polymerization vessel equipped with a jacket for heating and cooling and a stirrer. It is produced by a suspension polymerization method in an aqueous medium. In addition to improving the quality of the resin so that it can be suitably used in various fields such as hard and soft products, recently, various manufacturing method improvements have been introduced to meet the rapidly increasing demand, and productivity is improved. ing.

In order to improve the productivity in the production of vinyl chloride resin, the heat removal capacity of the polymerization reaction heat of the polymerization vessel is increased and the polymerization rate is increased to the limit of the heat removal capacity to carry out the polymerization in a short time. It is important to complete and enlarge the polymerization vessel to increase the production amount per batch.

Regarding the high-speed polymerization method for shortening the polymerization time, for example, a method of using a highly active initiator as a polymerization initiator (Japanese Patent Laid-Open No. 53-73280) and a uniform polymerization rate by combining initiators having different activities Method (Japanese Patent Application Laid-Open No. 1-
No. 31810), various polymerization methods have been proposed. However, in any of these methods, not only the thermal stability and hue of the resulting resin are lowered, but also the particle formation during polymerization becomes unstable, resulting in coarsening of the particles or an increase in fish eyes. However, there was a problem that a product with commercial value could not be obtained.

Further, there has been proposed a method (Japanese Patent Laid-Open No. 58-120613) which uses, as a polymerization initiator, tertiary octyl peroxy neodecanoate which is a highly active initiator having a good hue of the obtained resin. However, according to this method, the hue of the resin is certainly good, but there is a disadvantage that the fish eyes increase with coarsening of the particles, and the quality of the vinyl chloride resin can be improved even when applied to the high-speed polymerization method. It was not always possible to achieve high quality, and it was not satisfactory.

On the other hand, in order to increase the size of the polymerization vessel, the jacket area per unit volume of the polymerization vessel is made relatively small and the heat removal capacity is reduced, so that the polymerization vessel is made of a material having good thermal conductivity ( It is possible to improve the heat removal capacity to some extent by devising a method such as JP-B-58-8405) or a method of increasing the flow rate of the cooling water flow of the jacket or improving the flow path of the baffle (JP-A-58-160241). However, its effect is slight.

It is also possible to improve the heat removal capability of the polymerization vessel by passing low-temperature cooling water that has been cooled in advance through the jacket, but this is not economical because of the running cost of the cooling equipment. Therefore, a method (Japanese Patent Publication No. 1-18082) in which a reflux condenser is added to a large-scale polymerization vessel of 40 m ³ or more and high-speed polymerization is carried out within 5 hours has been proposed. According to this method, after the middle stage of polymerization,
In particular, since the heat removal rate is large immediately before the pressure inside the polymerization vessel begins to drop, a remarkable foaming phenomenon occurs, causing operational problems such as polymer adhesion to the condenser or clogging of the condenser due to accumulation, or foaming suspension. Contamination by polymer particles contained in the suspension causes quality problems such as an increase in fish eyes of the product.

Further, a polymerization initiator for preventing the foaming suspension from overflowing to the reflux condenser is used (Japanese Patent Publication No. 62-1605).
No.) method has been proposed. However, according to this method, the suspension stability is impaired by the rapid progress of the polymerization at the initial stage of the polymerization in which polymer particles are formed, resulting in coarsening of the product particles, There are quality problems such as increased fish eyes or reduced bulk specific gravity.

In order to solve such a problem, a polymerization prescription,
Various methods have been proposed for the device and the method of operation. For example, as for a polymerization formulation, nonionic surfactants are selected and added to suppress foaming and increase in fish eyes (JP-A-61-207410).
No.), a suspension agent is selected to obtain a resin having a high bulk specific gravity and rapid gelation (JP-A-1-268702), and a resin having a high bulk specific gravity and a small fish eye is obtained by polymerizing while adding water ( JP-A-61-111307) and the like.

Further, regarding the apparatus and the operating method, foaming is suppressed by devising a method of applying a load to the condenser, and adverse effects on quality are reduced (Japanese Patent Laid-Open No. 57-1460).
No. 8), a bubble cutting blade is provided in the gas phase portion in the polymerization vessel to mechanically break the bubbles (Japanese Patent Laid-Open No. 58-49710), but none have been perfected and condensed. At present, it is inferior in terms of quality and operation compared to the case where no vessel is used.

That is, when a reflux condenser for improving the heat removal capacity of a large-scale polymerization vessel of 40 m ³ or more is added to carry out high-speed polymerization within a polymerization time of 6 hours, simply select a polymerization initiator or Even if the polymerization rate was increased by increasing the amount, there was a problem in quality in the above-mentioned operation, and a polymer of satisfactory quality could not be obtained, which was technically unestablished.

[0012]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to solve the above-mentioned drawbacks, and as a result, used a polymerization initiator having a specific structure and having a specific activity in a specific ratio, and By controlling the stirring power of the liquid to a specific range and performing high-speed polymerization using a large-scale polymerization device with a reflux condenser added to improve heat removal capacity, high-quality vinyl chloride resin can be produced with high efficiency. The inventors have found that they can be manufactured and have completed the present invention.

That is, an object of the present invention is to use a large-sized polymerization vessel having an internal volume of 40 m ³ or more, and to use a vinyl chloride resin which does not cause quality problems in terms of coarse particles, fish eyes, bulk specific gravity and thermal stability. The present invention provides a method for producing a high efficiency.

[0014]

Thus, according to the present invention, vinyl chloride is used as a dispersant and a surface active agent by using a large-scale polymerizer having an internal volume of 40 m ³ or more equipped with a stirrer, a heating / cooling jacket and a reflux condenser. When polymerization is carried out in an aqueous medium in the presence of a suspending agent such as an agent, 10
One or two or more perester initiators having a time half-life temperature of 34 to 50 ° C. are used in the polymerization in an amount of 50
Using at least 10% by weight, and controlling the net stirring power per 1 m ³ of the content liquid of the polymerization vessel within the range of 1.0 to 3.0 kW / m ³ ,
Provided is a method for producing a vinyl chloride polymer in which the polymerization is completed within a range of 6 hours.

The present invention will be described in detail below. In the present invention, the internal volume of the polymerization reactor equipped with a reflux condenser is 4
A polymerization vessel of 0 m ³ or more is used. If the inner volume is 40 m ³ or less, the reflux condenser is not always necessary because the heat transfer area of the jacket per inner volume is large. However, in this case, since the production amount per batch is small, a large number of polymerization reactors are required, which is not economical.

The reflux condenser used in the present invention is connected to the gas phase portion of the polymerization vessel by a conduit. The structure is not particularly limited as long as it has a heat removal capacity corresponding to a desired polymerization rate. Generally, a multi-tube reflux condenser is used.

In the present invention, JP-A-57-14750
The present invention can be more advantageously carried out by using the inner jacket type polymerization vessel in which the jacket for heating / cooling described in 2 is included in the inner surface of the polymerization vessel body to improve the heat transfer performance. You can That is, since the heat removal capacity is larger than that of a normal external jacket polymerization device, the polymerization can be completed in a shorter time, and the load on the reflux condenser can be reduced.

In carrying out the present invention, a vinyl chloride monomer, an aqueous medium, a dispersant, a suspending agent such as a surfactant, and a polymerization initiator are charged in a degassed polymerization vessel. The polymerization initiator has a 10-hour half-life temperature of 34 to
It should be an initiator having a perester structure in the range of 50 ° C., preferably 36-48 ° C., one or more of which is 50% by weight or more, preferably 50% by weight or more of the total amount of the initiator used for the polymerization. It is essential to use 65% by weight or more. Here, the 10-hour half-life temperature is a temperature at which it takes 10 hours for the initiator to decompose at a molar concentration of 0.1 in a benzene solvent and to reduce the concentration to half the initial concentration. It is an index showing the magnitude of the decomposition rate of, that is, the activity.

When the 10-hour half-life temperature is less than 34 ° C., the reaction rapidly progresses at the initial stage of the polymerization and the heat removal rate of the reflux condenser increases, so that the reflux disturbance is violent and the suspension of particles becomes stable. Property is impaired, the resulting vinyl chloride polymer becomes coarse particles, and the particle shape becomes irregular, leading to an increase in fish eyes or a decrease in bulk specific gravity. Further, when the 10-hour half-life temperature exceeds 50 ° C, the reaction proceeds rapidly at the end of the polymerization, so that the heat removal rate of the reflux condenser becomes large, and as a result, the weight of the condenser due to a remarkable foaming phenomenon increases. Contamination by polymer particles contained in the coalesced or foamed suspension causes an increase in product fish eyes.

When the amount of the perester initiator used in the above range is less than 50% by weight of the total amount of the initiator used for the polymerization, the thermal stability and hue of the obtained vinyl chloride resin are lowered or the polymerization is performed. There are similar disadvantages such as remarkable foaming phenomenon in the final stage and deterioration of polymer quality due to reflux disturbance in the initial stage of polymerization, and the object of the present invention cannot be achieved.

The polymerization initiator having a perester structure used in the present invention includes 2,4,4-trimethylpentylperoxy-2-neodecanoate, tert-butylperoxyneodecanoate, (α, α-
Common examples include, but are not limited to, bis-neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, tertiary-hexylperoxyneodecanoate, and the like. Other initiators that can be used in admixture with the perester initiator of the present invention in less than 50% by weight of all initiators used for polymerization include di-2-
Ethylhexyl peroxydicarbonate, di- (2-
(Ethoxyethyl) peroxydicarbonate-based initiator such as peroxydicarbonate, diacyl peroxide-based initiator such as 3,5,5, -trimethylhexanoyl peroxide, α, α-azobis-2,4- An azo compound-based initiator such as dimethylvaleronitrile is generally used, but the initiator is not particularly limited thereto.

In carrying out the method for producing a vinyl chloride polymer of the present invention, the above-mentioned polymerization initiator having a specific structure and having a specific activity is used in a specific ratio, and the stirring power of the content liquid in the polymerization vessel is in a specific range. The effect is exhibited for the first time when the content is controlled within a range of 1.0 to 3.0 kW / m ³ , preferably 1.2 to 2.5 kW / m ³ per 1 m ³ of content liquid in the polymerization vessel. ³ , more preferably 1.5-2.
Polymerization is carried out at 0 kW / m ³ .

When the net stirring power is less than 1.0 kW / m ³ , the frequency of dispersion coalescence of suspension oil droplets of vinyl chloride monomer is low, and the porosity of the produced polymer particles is small and its distribution is small. Becomes larger, the particles become coarser, the plasticizer absorbability deteriorates, and the fish eyes increase. Also, when the net stirring power is less than 1.0 kW / m ³ , polymer adhesion to the condenser occurs. It is considered that this is because the foaming phenomenon in which the polymer particles float as a cream layer above the polymerization suspension becomes more prominent particularly in the middle and later stages of the polymerization.

On the other hand, if it exceeds 3.0 kW / m ³ , the coalescence of the oil droplets becomes too frequent, and the oil droplets or polymer particles tend to agglomerate due to collisions with each other, resulting in coarse particles, or other polymerization conditions. In some cases, the particle size becomes fine due to excessive dispersion, which causes problems such as a decrease in bulk specific gravity. Further, since the agitation power is large, the entrainment of air bubbles is severe, the foaming phenomenon in the polymerization vessel is increased, and the adhesion of the polymer to the condenser occurs, so that the object of the present invention cannot be achieved.

The method of controlling the stirring power of the polymerization vessel is described in detail, for example, in "Chemical Engineering Association, Japan: Handbook of Chemical Engineering, Revised Third Edition, pp. 1065-1115, 1968, Maruzen Co., Ltd." As described above, by using an empirical formula and a diagram showing the relationship between the Reynolds number Re and the power number Np of the stirring system for the stirring devices of various shapes, or by measuring the power under a certain stirring condition The power can be arbitrarily adjusted by experimentally obtaining Np as a constant and changing the rotation speed of the stirring blade.

That is, the density of the contents of the polymerization vessel is ρ (kg /
m ³ ), viscosity coefficient μ (kg / m · sec), stirring blade rotation speed n (1 / sec),) blade length d (m), gravity conversion coefficient g _c (k
g · m / Kg · sec ² ), and P (Kg / m · sec) is the net agitation power that does not include loss in the reduction mechanism and shaft seal part,
e and Np are defined as Re = ρnd ² / μ Np = P · g _c / ρn ³ d ⁵ , respectively, and Np is determined from known literature or experiments.
Can be asked.

The Np value of the stirrer of a large-scale polymerization vessel which is generally adopted in the suspension polymerization method of vinyl chloride type monomers is in the range of about 0.2 to 2. The amount of liquid in the polymerization vessel is V
If it is (m ³ ), the net stirring power Pv (kW / m ³ ) per unit volume of the polymerization vessel is expressed by the following equation. Pv = Npρn ³ d ⁵ / 102Vg _c Therefore, when the net stirring power is adjusted using a specific stirring device, the power is proportional to the cube of the rotation speed of the stirring blade, The method of controlling the power by the number is easy. The stirring speed may be constant during the polymerization period or changed during the polymerization, but the net stirring power is 1.0 to 3.0 kW.
It must be within the range that satisfies / m ³ .

The stirring blade of the stirring device used in the present invention includes a Faudler blade, a bull margin blade, a turbine blade, a fan turbine blade, a paddle blade, and the like, and the Faudler blade can be preferably used. As the baffle, a pipe (bar type) baffle, a D type baffle, and an E type (finger type) baffle are preferable. These stirring blades and baffles may be those commonly used in the polymerization of vinyl chloride, for example, the above "Handbook of Chemical Engineering".
Or "Koji Saeki: Polymer Manufacturing Process, 157-
159, 1971, Industrial Research Council, "and so on.

According to the production method of the present invention, the above-mentioned high-speed polymerization is carried out by using an inner jacket type polymerization vessel having an inner volume of 40 m ³ or more and a jacket for heating / cooling which has improved heat removal ability. By doing so, the object of the present invention can be achieved more effectively. When carrying out high-speed polymerization, the amount of the polymerization initiator charged varies depending on the type of the initiator used and the polymerization conditions such as the polymerization temperature, but usually 0.01 to 2 parts by weight per 100 parts by weight of the monomer is added. The polymerization can be completed within 6 hours.

In the present invention, the term "polymerization time" means that the temperature inside the polymerization vessel reaches a predetermined polymerization temperature by heating and raising the temperature after completion of the charging, and the pressure in the polymerization vessel drops to a predetermined pressure to complete the polymerization reaction. It is defined as the time to do. Generally, a polymerization inhibitor is added at a polymerization conversion of 75 to 95%, or unreacted monomers are recovered from the polymerization vessel to complete the polymerization.

The vinyl chloride resin of the present invention is preferably a vinyl chloride homopolymer, but other vinyl monomer copolymerizable with vinyl chloride in an amount of 10% by weight or less, for example, within the range in which the above-mentioned production method is effective. It may include a quantity. Examples of the other vinyl monomer copolymerizable with vinyl chloride include fatty acid vinyl esters such as vinyl acetate, acrylic acid, acrylic acids such as methyl acrylate, methacrylic acid such as methacrylic acid and methyl methacrylate, ethylene, Examples include α-olefins such as propylene, and styrene, and one or more of these are used.

As a suspending agent such as a dispersant or a surfactant used in the present invention, partially saponified polyvinyl acetate, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, which are usually used for suspension polymerization of vinyl chloride, Water-soluble cellulose ethers such as hydroxypropylmethyl cellulose, acrylic acid polymers, water-soluble polymers such as gelatin, sorbitan monolaurate, sorbitan monostearate, glycerin tristearate, oil-soluble emulsifiers such as ethylene oxide propylene oxide block copolymers. Examples thereof include water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate. These are used alone or in combination of two or more. All of these may be used from the beginning of the polymerization, or a part thereof may be added during the polymerization.

Water, vinyl chloride type monomer in the present invention,
As a method for charging the suspending agent, the initiator, and other auxiliary agents, any method used in ordinary suspension polymerization can be adopted. For example, a method of sequentially adding water, a suspending agent, an initiator and a vinyl chloride-based monomer to a polymerization vessel, or a method of continuously charging these at the same time, a vinyl chloride-based single amount in which an aqueous suspension agent and an initiator are dissolved. Either method of charging the body sequentially or simultaneously is possible. The weight ratio of water and vinyl chloride monomer charged is generally 1/1 to 1.6 / 1.
Done in degrees.

In the present invention, a chain transfer agent such as a mercaptoalkanol or a thioglycolic acid alkyl ester, and a pH adjusting agent such as sodium polyphosphate can be added, if necessary. The polymerization is usually carried out at a temperature of 35 to 70 ° C.

[0035]

As described above, according to the present invention, a high-quality vinyl chloride resin can be produced with high efficiency for the first time by using an initiator having a specific activity under a specific stirring strength by using a large-sized polymerization vessel. It has become possible. Although the mechanism by which the method for producing a vinyl chloride resin of the present invention exerts the above-mentioned effect is not clear, the use of an initiator having a specific activity under a specific stirring strength results in the behavior of particle formation in the polymerization process. It is presumed that the vinyl chloride resin obtained was improved in quality by some action. Moreover,
The vinyl chloride resin obtained by the method for producing a vinyl chloride resin of the present invention can be suitably used in the fields of hard and soft.

[0036]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition,% in the examples and comparative examples is based on weight unless otherwise specified. The physical properties of the vinyl chloride polymers shown in each of the examples and comparative examples were measured by the following methods.

(1) Fish eye 100 parts of polyvinyl chloride, 60 parts of di-2-ethylhexyl phthalate, 2 parts of Ba—Zn stabilizer, 3.5 of pigment
Part of the mixture was roll kneaded at 135 ° C. for 7 minutes to give a thickness of 0.
A 35 cm 5 cm x 10 cm sheet is formed and the number of fish eyes present on the sheet surface is counted. (2) Thermal stability A mixture of 100 parts of polyvinyl chloride, 60 parts of di-2-ethylhexyl phthalate, 2 parts of a Ba-Zn stabilizer and 2 parts of an epoxy stabilizer is roll-kneaded at 160 ° C for 5 minutes, The formed sheet was heated in a gear oven at 190 ° C., and changes in hue with time were observed. In order to judge whether the thermal stability was good or bad, the time at which the sheet started to turn black was ranked as follows.

Rank A: Blackening time 120 minutes or more Rank B: 〃 120 minutes to 105 minutes Rank C: 〃 105 minutes to 90 minutes Rank D: 〃 90 minutes or less (3) Average particle size Tyler mesh standard wire mesh is used. By the sieve analysis
It was shown as a 50% passage diameter. (4) Bulk specific gravity It was measured by the method defined in JIS K6721-1977.

Example 1 A shell-and-tube reflux condenser having a heat transfer area of 100 m ² and a blade length of 1.7
m Faudler type 4 retreating blades and 4 pipe baffles with an outer diameter of 0.22 m, diameter 3.2 m, internal volume 4
After degassing the inner jacket type stainless steel polymerization vessel of 5 m ³ , water of 21,450 kg, 4% aqueous solution of partially saponified polyvinyl acetate having an average degree of polymerization of 2500 with a degree of saponification of 80 mol% 250
kg, vinyl chloride monomer 16,500 kg, 2,4,4, trimethylpentylperoxy-2-neodecanoate 1
0.56kg was charged.

Subsequently, the net stirring power P at the start of the polymerization
Stirring at 112 rpm to raise v to 1.6 kW / m ³ , the internal temperature was raised to 57.0 ° C to start polymerization, and cooling water was passed through the reflux condenser to adjust the load factor. While operating, the polymerization was allowed to proceed. Then, the pressure in the polymerization vessel was 6.0.
When the amount reached kg / m ² G, unreacted monomer was recovered, and the content was dehydrated and dried. The net stirring power gradually increased as the polymerization proceeded, but at the end of the polymerization, it showed a value of 1.9 kw / m ³ . The polymerization time was 3.5 hours, and the conversion rate was 87%.

Examples 2 to 4 and Comparative Examples 1 to 6 The polymerization initiators shown in Table 1 were used instead of the polymerization initiator 2,4,4, trimethylpentylperoxy-2-neodecanoate in Example 1. Polymerization was carried out under the same conditions as in Example 1, except that the net stirring power was set to the value shown in Table 1 and the polymerization temperature was set to the temperature shown in Table 1.

The physical properties of the vinyl chloride polymer thus obtained are shown in Table 1. From Table 1, it is clear that according to the method for producing a vinyl chloride polymer of the present invention, a high-quality vinyl chloride resin can be produced with high efficiency by high-speed polymerization.

[0043]

[Table 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tamio Yamato, No. 1 Harumi-cho, Tokuyama City, Yamaguchi Prefecture, Sun Aro Kagaku Co., Ltd. (72) Yasumichi Ishii, 2767, Niihama Shiojima, Shiojima, Kurashiki City, Okayama Prefecture Day 1 Zeon Co., Ltd. (72) Inventor Masahisa Okawa 5-1 Sokai-cho, Niihama, Ehime Prefecture Sumitomo Chemical Co., Ltd. (72) Inventor Isao Ouchi 16 Ochiai Nishiki-cho, Iwaki-shi, Fukushima Kureha Chemical Industry Co., Ltd. In-house (72) Inventor Hideki Wakamori 16 Ochiai Nishiki-cho, Iwaki City, Fukushima Prefecture Kureha Chemical Industry Co., Ltd.

Claims (3)

[Claims] 1. Vinyl chloride is used in the presence of a suspending agent such as a dispersant and a surfactant by using a large-scale polymerization vessel having an internal volume of 40 m ³ or more equipped with a stirrer, a heating / cooling jacket and a reflux condenser. When polymerizing in a medium, one or more perester initiator having a 10-hour half-life temperature of 34 to 50 ° C. is used as a polymerization initiator in an amount of 50% by weight or more of all initiators used for the polymerization, and the polymerization is performed. A vinyl chloride polymer characterized by controlling the net stirring power per 1 m ³ of the content liquid in the vessel to a range of 1.0 to 3.0 kW / m ³ to complete the polymerization within a range of 6 hours. Manufacturing method. 2. The method for producing a vinyl chloride polymer according to claim 1, wherein the heating / cooling jacket is of an inner jacket type. 3. The method for producing a vinyl chloride polymer according to claim 1, wherein the stirrer is a Faudler blade and the baffle is a pipe baffle, an E type baffle or a D type baffle.