JPH04154807A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To obtain the subject polymer having high thermal stability while suppressing the formation of coarse particles by polymerizing vinyl chloride under specific condition using a perester polymerization initiator having a specific 10hr-half life temperature, in the presence of a suspending agent such as dispersing agent and surfactant. CONSTITUTION:The objective polymer can be produced by polymerizing vinyl chloride in the presence of a suspending agent such as dispersing agent or surfactant, in an aqueous medium using one or more perester initiators having a 10hr half-life temperature of 34-50 deg.C (e.g. 2,4,4-trimethylpentylperoxy-2- neodecanoate) as a polymerization initiator. The amount of the perester initiator is >=50wt.% based on the total amount of initiators. The net stirring power per 1m<2> of the liquid in the polymerizer is controlled within the range of 1.0-3.0kW/m<2> during the time from the start of the polymerization to the time when the polymerization conversion reaches 30%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a vinyl chloride resin having excellent quality. More specifically, the present invention relates to a method for producing high-quality vinyl chloride resin with high efficiency.

[Conventional technology]

Vinyl chloride resin is a useful resin with excellent physical and mechanical properties, and is generally processed industrially in an aqueous medium using a hatch-type polymerization reactor equipped with a jacket for heating and cooling and a stirring device. Manufactured by suspension polymerization method. While efforts are being made to improve the quality of resins so that they can be suitably used in a variety of fields such as hard and soft products, various improvements in manufacturing methods have recently been introduced to cope with the rapidly increasing demand. Improvements are being made.

In order to improve productivity when manufacturing vinyl chloride resin, it is necessary to complete the polymerization in a short time by increasing the polymerization rate to the limit of heat removal capacity, and to increase the production volume per hatch by increasing the size of the polymerization vessel. It is important to increase the temperature and to increase the ability of the polymerization vessel to remove the heat of the polymerization reaction.

Regarding the high-speed polymerization method to shorten the polymerization time, for example, a method using a highly active initiator as a polymerization initiator (Japanese Patent Laid-Open No. 53
Various polymerization methods have been proposed, including a method in which the polymerization rate is made uniform by combining initiators with different activities (Japanese Patent Application Laid-open No. 1-31810). However, all of these methods not only reduce the thermal stability and hue of the resulting resin, but also make particle formation during polymerization unstable, resulting in coarse particles or an increase in fish eyes. There was a problem in that it was not possible to obtain products with commercial value.

In addition, a method using tertiary octyl peroxyneodecanoate, which has high activity as a polymerization initiator and provides a good hue of the resulting resin (Japanese Patent Laid-Open No. 58-120
No. 613) was proposed. Although this method does give the resin a good hue, it has the disadvantage that the particles become coarser and the fins increase, and even when applied to high-speed polymerization, chlorination The quality of the vinyl resin was not necessarily high enough and was insufficient.

On the other hand, increasing the size of the polymerization vessel means that the jacket area per unit volume of the polymerization vessel becomes relatively small. 1) In order to reduce the capacity, the material of the polymerization vessel should be made of a material with good thermal conductivity (Special Publication No. 8405), the flow rate of the cooling water flow in the jacket should be increased, or the flow path of the pipe should be improved. Although it is possible to improve the heat removal ability to some extent by devising methods such as the method of For this reason, there is a method of adding a reflux condenser to a large polymerization vessel with a length of 40 m or more and performing high-speed polymerization within 6 hours (Japanese Patent Publication No. 1) 8082.
However, this method requires increasing the heat removal capacity of the condenser, resulting in clogging of the condenser due to foaming during polymerization, increase in fish eyes in the product, and decrease in bulk specific gravity. There are many operational and quality problems such as deterioration.

It is also possible to improve the heat removal ability of the polymerization reactor by passing pre-cooled low-temperature cooling water through the jacket, but this is not economical as it increases the running cost of the cooling equipment.

It is known that the so-called internal jacket type polymerizer, which has a heating and cooling jacket built into the polymerizer body, has a larger heat transfer coefficient than the conventional external jacket type polymerizer, and can be suitably used for the polymerization of vinyl chloride. (Unexamined Japanese Patent Publication No. 57-1.
No. 17502).

However, even if this internal jacket type polymerization vessel is used and the polymerization rate is increased simply by selecting and increasing the amount of initiator,
Due to the above-mentioned problems of coarsening of particles and increase in fish eyes, it was not possible to obtain a resin that was satisfactory in terms of quality. However, a method for producing high-quality vinyl chloride through high-speed polymerization within 6 hours using an internal jacket type polymerization vessel of 40 m or more had not been technically established.

[Problem to be solved by the invention]

The inventors of the present invention have conducted extensive research to solve the above problem, and have found that a polymerization initiator with a specific structure having a specific activity is used in a specific ratio, and stirring during the particle formation process at the initial stage of polymerization is used. By controlling the power within a specific range and performing high-speed polymerization using a large polymerization device with improved heat removal capacity, the particles do not become coarse, there is less finshuai, and the product has good thermal stability. We have discovered that high-quality vinyl chloride resin can be produced with high efficiency, and have completed the present invention.

[Means for Solving the Problems] Thus, according to the present invention, when vinyl chloride is polymerized in an aqueous medium in the presence of a suspending agent such as a dispersant or a surfactant, the polymerization initiator has a half-life of 10 hours. Temperature is 34-5
one or more bar ester initiators at 0°C,
50 weight or more of the total amount of initiator used in polymerization is used, and the content liquid of the polymerization vessel is 1r+? from the start of polymerization to a polymerization conversion rate of 30%. The net stirring power per unit is 1.0 to 3.0kW.
/n? Provided is a method for producing a vinyl chloride polymer, characterized in that the polymerization is controlled within the range of .

Furthermore, in the above manufacturing method, the internal volume of 40n? By applying the present invention to the above large-scale polymerization vessel and completing the polymerization within 6 hours, the object of the present invention can be achieved more effectively.

The present invention will be explained in detail below.

In carrying out the method for producing a vinyl chloride polymer of the present invention, a polymerization initiator with a specific structure having a specific activity is used in a specific ratio, and stirring is carried out at the initial stage of polymerization when the skeleton of the particle structure of the polymer is formed. The polymerization initiator in the present invention is a polymerization initiator that is highly effective by controlling the power within a specific range. It is essential to use one or more initiators having an ester structure in an amount of 50% by weight or more, preferably 65% by weight or more of the total amount of initiators used in the polymerization. Here, 10 hours are cut in half! The IJl temperature is the temperature at which 0.1 molar concentration of initiator decomposes in a benzene solvent and it takes 10 hours for the concentration to decrease to half of the initial concentration, and it is the temperature at which the initiator decomposition rate is large. In other words, it is an index representing activity.

If the 10-hour half-life temperature is outside the above range, the suspension stability of the particles will be impaired even in a specific stirring power range,
As a result, the resulting vinyl chloride resin becomes coarse particles or has an irregular particle shape, leading to an increase in fish eyes and a decrease in bulk and specific gravity.

In addition, if the amount of the bar ester initiator in the above range is less than 50% by weight of the total amount of initiators used in the polymerization, the thermal stability and hue of the resulting vinyl chloride resin will decrease. The purpose of the invention cannot be achieved.

Examples of the polymerization initiator having a bar ester structure used in the present invention include 2,4.4-1-limethylbentylperoxy-2-neodecanoate, tert-butylperoxyneodecanoate, (α,α-bis-2-neodecanoate, Common examples include, but are not limited to, neodecanoylperoxy)diisopropylbenzene, cumylperoxyneodecanoate, tert-hexylperoxyneodecanoate, and the like.

Other initiators that can be used as a mixture with the bar ester initiator of the present invention include di-2-ethylhexyl peroxydicarbonate and (2-ethoxyethyl)
Peroxycarbonate-based initiators such as peroxydicarbonate, diacyl peroxide-based initiators such as 3.5.5-)limethylhexanoyl peroxide, α
Azo compound-based initiators such as -α-azobis-2,4-dimethylvaleronitrile and the like are generally mentioned, but are not particularly limited to these initiators.

In the present invention, the net stirring power per content liquid IM of the polymerization vessel from the start of polymerization to a polymerization conversion rate of 30% is 1.0 to 3.
It is essential to control the power within a range of 0 kW/d, preferably 1.2 to 2.5 kW/d. Even if a polymerization initiator having a specific structure and having a specific activity as described above is used in a specific ratio, the net stirring power is 1. If it is less than OIW/lrr, the frequency of dispersion and coalescence of suspended oil droplets of vinyl chloride monomers will be low, the porosity of the generated polymer particles will be small, and the distribution will be wide, and the particles may become coarse. ,
Problems such as deterioration of plasticizer absorption and increase in fins eye occur. On the other hand, if it exceeds 3.0 kW/i, the frequency of coalescence of oil droplets becomes too high, and oil droplets and polymer particles collide with each other, resulting in agglomeration, resulting in coarse particles, or depending on other polymerization conditions, dispersion may occur. If this progresses too much, the particle size becomes fine and the bulk specific gravity decreases, making it impossible to achieve the object of the present invention.

When the polymerization conversion rate exceeds 30%, dispersion and aggregation of oil droplets do not occur, so the stirring power after the polymerization conversion rate of 30% is not particularly limited, and it is sufficient as long as the interior of the polymerization vessel is uniformly stirred.

As a method of controlling the stirring power of a polymerization vessel, for example, [Kagaku Kogyo Kyokai Line: Chemical Kogaku Handbook, Revised 3rd Edition, 1065-1]
), page 15, 1962, Maruzen Co., Ltd., using empirical formulas and diagrams that express the relationship between the Ray nozzle number Re and the power number Np of the stirring system for various shapes of stirring devices. Alternatively, Np as an apparatus constant can be experimentally determined by actually measuring the power under certain stirring conditions, and the power can be arbitrarily adjusted by changing the rotational speed of the stirring blade.

That is, the density of the contents of the polymerization vessel is ρ (kg/n?),
The viscosity coefficient is μ (kg/m-5ec), the rotation speed of the stirring blade is n (1/5ec), the blade length is d (m), the gravity conversion coefficient is gc (k+”m/Kg-sec2), the speed reduction mechanism P(
Kg-m/5ec), Re and Np are each defined as Re-ρnd2/μ Np=P-gc/ρn3d5, and Np is determined from known literature or experiments.
can be found. The NpO value of the stirring device of a large polymerization vessel generally employed in the suspension polymerization method of vinyl chloride monomers is approximately in the range of 0.2 to 2. If the liquid volume in the polymerization vessel is V (m), the net stirring power Pv (kW/n?) per unit volume of the polymerization vessel is expressed by the following formula.

Pv=Np・ρn” d5/102・V・g.

Therefore, when adjusting the net stirring power using a specific stirring device, since the power is proportional to the cube of the rotational speed of the stirring blade, it is easy to control the power by the rotational speed.

The stirring rotation speed may be constant during the polymerization period, or may be changed during the polymerization period, but it must be within a range that satisfies 1.0 to 3.0 kW/rr+ during the period from the start of polymerization to the polymerization conversion rate of 30%. Must be. The stirring blades of the stirring device used in the present invention include Faudler type swept blades, pull margin blades, turbine blades, fan turbine blades, paddle blades, etc., but the Faudler type swept blades are more suitable. Further, as the baffle, a pipe (rod type) baffle, a D type hasofle, 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, such as those described above.
"Chemical Engineering Handbook" or "Koji Saeki: Bolimer Manufacturing Process, pages 157-159.

This is explained in the 1971 Industrial Research Association.

According to the production method of the present invention, high-quality vinyl chloride resin can be produced even when applied to high-speed polymerization with a polymerization time of 6 hours or less, and heating and The objects of the present invention can be achieved more effectively by carrying out the above-described high-speed polymerization using an internal jacket type polymerization vessel that includes a jacket for cooling.

Internal volume 40r+? If it is below, the heat transfer area of the jacket per unit volume of the polymerization vessel is large, so high-speed polymerization is possible even in a normal external jacket type polymerization vessel, and an internal jacket type polymerization vessel is not necessarily required. but,
Such a small polymerization vessel is not economical because it requires a large number of polymerization vessels because the production amount per hatch is small. When performing high-speed polymerization, the amount of polymerization initiator charged varies depending on the type of initiator used and polymerization conditions such as polymerization temperature, but is usually 0 per 100 polymerized parts of monomer.
．． By adding 01 to 2 parts by weight, polymerization can be completed within 6 hours.

In the present invention, the polymerization time refers to the pressure in the polymerization vessel from the time when the internal temperature of the polymerization vessel becomes suitable for a predetermined polymerization reaction temperature due to heating and temperature increase after the completion of the preparation.After the natural pressure at that reaction temperature has changed for a while, no reaction The pressure starts to drop as the monomer decreases, and it is defined as the time until the drop 1) reaches 2 kg/cJ. In this case, the polymerization conversion rate is usually 83 to 86
%.

The vinyl chloride resin of the present invention is preferably a vinyl chloride homopolymer, but within the range where the above production method is effective, for example, 10% by weight or less of other vinyl monopolymers copolymerizable with vinyl chloride may be used. May include the body. Other vinyl monomers that can be copolymerized with vinyl chloride include fats such as vinyl acetate! Examples include vinyl ester, acrylic acid, acrylic acids such as methyl acrylate, methacrylic acids such as methacrylic acid and methyl methacrylate, α-olefins such as ethylene and propylene, styrene, etc., and one or more of these are used. .

Suspending agents such as dispersants and surfactants used in the present invention include partially oxidized polyvinyl acetate, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, which is usually used in suspension polymerization of vinyl chloride,
Water-soluble cellulose ethers such as hydroxypropyl methyl cellulose, acrylic acid polymers, water-soluble polymers such as gelatin, oil-soluble polymers such as sorbitan monolaurate, sorbitan monostearate, glycerin tristearate, ethylene oxide propylene oxide bronc copolymer, etc. Examples of emulsifiers include water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate, which may be used alone or in combination of two or more. The entire amount of these may be used from the beginning of the polymerization, or a portion thereof may be added during the polymerization.

In the present invention, any method used in ordinary suspension polymerization can be adopted as a method for introducing water, a vinyl chloride monomer, a suspending agent, an initiator, and other auxiliary agents. For example, a method in which water, a suspending agent, an initiator, and a vinyl chloride monomer are sequentially added to a polymerization vessel, a method in which they are continuously charged at the same time, and a method in which a vinyl chloride monomer is dissolved in an aqueous suspension agent solution and an initiator. It is possible to introduce the polymers sequentially or simultaneously. The weight ratio of water and vinyl chloride monomer is generally water/vinyl chloride monomer - 1
/1 to 1.6/1.

In the present invention, chain transfer agents such as mercaptoalkanol and thioglycolic acid alkyl ester, and PH regulators such as sodium polyphosphate can be added as necessary, and polymerization is usually carried out at a temperature of 35 to 70°C. It will be held in

〔Effect of the invention〕

Thus, according to the present invention, by using an initiator with a specific activity under a specific stirring intensity, a high-quality vinyl chloride resin that does not coarsen the particles, has few fish eyes, and has good thermal stability can be produced. It has become possible to manufacture with high efficiency.

In carrying out the method for producing vinyl chloride resin of the present invention, the object of the present invention can be further achieved by carrying out high-speed polymerization using a large-scale polymerization device with an internal jacket having an internal volume of 40 mm or more and improved heat removal ability. This is the first time that it has been found that this can be achieved effectively.

The mechanism by which the method for producing vinyl chloride resin of the present invention exhibits the above effects is not clear, but by using an initiator with a specific activity under a specific stirring intensity, the effect is due to the behavior of particle formation during the polymerization process. It is presumed that some kind of effect worked to improve the quality of the vinyl chloride resin obtained.

Moreover, the vinyl chloride resin obtained by the vinyl chloride resin manufacturing method of the present invention can be suitably used in both hard and soft fields.

〔Example〕

EXAMPLES The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited only to these Examples. Note that the percentages in Examples and Comparative Examples are based on weight unless otherwise specified. Further, the physical property values of the vinyl chloride polymer shown in each Example and Comparative Example were measured by the following method.

(1) A mixture of 100 parts of fisheye polyvinyl chloride, 60 parts of di-2-ethylhexyl phthalate, 2 parts of Ba-Zn stabilizer, and 3.5 parts of pigment was heated at 135°C for 7 minutes. Roll kneading is performed to form a sheet with a thickness of 0.35 mm and a size of 5 cm x IQ (2), and the number of fish eyes present on the sheet surface is counted.

(2) A mixture of 100 parts of heat-stable polyvinyl chloride, 60 parts of di-2-ethylhexyl phthalate, 2 parts of 13a-Zn stabilizer, and 2 parts of epoxy stabilizer was heated at 160°C for 5 minutes. The roll-kneaded and formed sheet was put into a gear open machine at 190° C., and changes in hue over time were observed. To judge whether the thermal stability is good or bad, the time it takes for the sheet to start turning black is
Ranked as follows:

Rank A: Blackening time 120 minutes or more Rank B: 〃 120 minutes to 105 minutes Rank C:
〃 I05 minutes ~ 90 minutes Rank D: 〃 90
Minutes or less (3) Average particle diameter The 50% passing diameter was determined by sieve analysis using a wire mesh according to JIS standards.

(4) Bulk specific gravity Measured by the method specified in JIS K672]-1977.

Actual difference ↓ Faudler type 4 swept wings with a wingspan of 1.7m and an outer diameter of 0
．． 22m pipe baffle diameter 3.2m with 4 wood
, after degassing an internal jacketed stainless steel polymerization vessel with an internal volume of 45N, 450 kg of water, 450 kg of partially saponified polyvinyl acetate with a saponification degree of 80 mol%, and an average degree of polymerization of 2500.
% aqueous solution 2501, vinyl chloride monomer 16,500 kg
, 2, 4.4. Trimethylpentylperoxy-2
- 6°6 kg of neodecanoate was charged. Subsequently, the net stirring power Pv at the start of polymerization was 1.6 kHz/m.
Stir at a rotation speed of 1) 2 rpm to bring the internal temperature to 56.
．． The temperature was raised to 5°C, and polymerization was allowed to proceed while maintaining this temperature and rotation speed. Next, the pressure in the polymerization vessel was increased to 2.0+
When r/cd decreased, unreacted monomers were collected and the contents were dehydrated and dried. The net stirring power gradually increased as the polymerization progressed, but after the conversion reached 30%, it decreased to 1.7%.
It showed a constant value of kW/M. The polymerization time was 5.3 hours, and the conversion rate was 85%.

2.4.4- of the polymerization initiator in Example 1
The polymerization initiator listed in Table 1 was used instead of l-dimethylbentylperoxy-2-neodecanoether 1~, the net stirring power was set as the stirring power listed in Table 1, and the polymerization temperature was set as listed in Table 1. Polymerization was carried out under the same conditions as in Example 1 except for the temperature.

The physical properties of the vinyl chloride polymer thus obtained were as 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 through high-speed polymerization.

Claims (4)

[Claims] (1) When polymerizing vinyl chloride in an aqueous medium in the presence of a suspending agent such as a dispersant or a surfactant, one or more types having a 10-hour half-life temperature of 34 to 50°C are used as a polymerization initiator. The bar ester initiator is used in an amount of 50% by weight or more of the total amount of initiators used in polymerization, and the net stirring power per 1 m^3 of the content of the polymerization vessel from the start of polymerization to a polymerization conversion rate of 30% is 1. A method for producing a vinyl chloride polymer, which comprises controlling the polymerization to a range of 0 to 3.0 kW/m^3. (2) The method for producing a vinyl chloride polymer according to claim 1, characterized in that the polymerization is completed within a range of 6 hours or less. (3) Claims 1 or 2 characterized in that a large polymerization vessel with an internal volume of 40 m^3 or more is used, which is equipped with a stirrer and has a heating/cooling jacket enclosed in the polymerization vessel body. A method for producing a vinyl chloride polymer. (4) The agitator is a Faudler-type swept blade, and the baffle is a pipe baffle, an E-type baffle, or a D-type baffle.
4. A method for producing a vinyl chloride polymer according to item 3.