JPH0782304A - Method for producing vinyl chloride polymer - Google Patents

Abstract

(57) [Summary] [Structure] In a method for producing a polymer by suspension polymerization of vinyl chloride or a monomer mixture containing vinyl chloride in a polymerization vessel equipped with a reflux condenser, heat removal by the reflux condenser There is a step of charging a highly active oil-soluble polymerization initiator with a 10-hour half-life temperature of 40 ° C or less at a concentration of 0.1 mol / L in benzene until the polymerization conversion rate reaches 60% after the initiation. The amount of polymerization initiator charged is monomer 1
0.0001 to 0.02 part by weight per 00 parts by weight, and the charging speed of the oil-soluble polymerization initiator is 0.5% of the charging amount per minute.
~ 5% by weight of the method for producing a polymer. [Effects] Heat can be efficiently removed during polymer production, and the time required for one batch of polymerization can be shortened, so that productivity is improved. Further, when the obtained polymer is molded into a sheet or the like, a molded product having few fish eyes and good initial colorability can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polymer by suspension polymerization of vinyl chloride or a monomer mixture containing vinyl chloride.

[0002]

2. Description of the Related Art Generally, suspension polymerization of vinyl chloride or a monomer mixture containing vinyl chloride (hereinafter referred to as vinyl chloride etc.) is carried out, for example, in an aqueous medium, dispersion in a polymerization vessel equipped with a jacket and a reflux condenser. Agent (suspension agent) and polymerization initiator are charged, then the interior of the polymerization vessel is evacuated and vinyl chloride, etc. are charged, and other various additives are further charged if necessary, and hot water is passed through the jacket to pass the polymerization vessel. The inside is heated to a predetermined polymerization reaction temperature, and then cooling water is passed through the jacket and the reflux condenser to remove the heat of the polymerization reaction, thereby performing the polymerization reaction while maintaining the inside of the polymerization vessel at the predetermined reaction temperature. It is carried out by the method.

In recent years, the polymerization time has been shortened in order to improve productivity. As one of methods for shortening the polymerization time, there is a method for increasing the charged amount of the polymerization initiator to increase the polymerization reaction rate. In the case of such a method, the amount of heat generated by the polymerization reaction increases from the initial stage of the polymerization, so it is necessary to enhance the heat removal capacity at this stage. However, when the heat is removed by the reflux condenser in the initial stage of the polymerization, that is, when the polymerization conversion rate is low after the initiation of the polymerization reaction (usually, the polymerization conversion rate is less than 15%), coarse particles are generated in the obtained polymer. The reflux condenser cannot be used at this time because of the inconvenience such as formation of a block polymer.
Therefore, the heat removal in the initial stage of the polymerization must be performed only by the jacket, which causes a problem that the heat removal ability is insufficient.

[0004]

In order to avoid the above problems, a low activity polymerization initiator is used in combination, and the polymerization initiator is used twice before initiation of the polymerization reaction and after reaching a predetermined polymerization conversion rate. Control the polymerization reaction rate in the initial stage of polymerization, such as dividing into two parts, to reduce the amount of heat generation so as not to exceed the heat removal capacity of the jacket, and increase the polymerization reaction rate after starting heat removal by the reflux condenser. Measures have been taken to allow it.

By the way, in order to shorten the polymerization time,
It is also necessary to remove heat efficiently. However, according to the above method, since the polymerization reaction rate is increased after the heat removal by the reflux condenser is started, the exothermic peak is reached in the latter half of the polymerization reaction. Therefore, immediately after the heat removal by the reflux condenser is started, it cannot be said that the efficiency of the heat removal is high because there are many unused portions of the heat removal ability by the reflux condenser.

Coloring peculiar to the polymer, which occurs when the polymer is processed into a molded article such as a sheet without adding a coloring agent or the like, is called initial coloration, and the smaller the color, the more preferable.

However, in the above-mentioned method, the low-activity polymerization initiator remains in the polymer, and in the above-mentioned method, the polymerization time after reaching the predetermined polymerization conversion rate is short. The initiator remains in the polymer.
Therefore, according to the above method, there is a disadvantage that the initial colorability when the obtained polymer is molded into a sheet or the like is deteriorated.

Therefore, an object of the present invention is to provide a method for producing a polymer by suspension-polymerizing vinyl chloride or the like in a polymerization vessel equipped with a reflux condenser. It is an object of the present invention to provide a production method capable of shortening the time, and further capable of producing a polymer having good initial colorability of the obtained molded product when molded into a sheet or the like.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have solved the above problems. The present invention relates to a method for producing a polymer by suspension polymerization of vinyl chloride or a monomer mixture containing vinyl chloride in a polymerization vessel equipped with a reflux condenser, wherein the conversion rate after the initiation of heat removal by the reflux condenser is converted. Has a step of charging a highly active oil-soluble polymerization initiator having a 10-hour half-life temperature of 40 ° C or less at a concentration of 0.1 mol / L in benzene until the concentration reaches 60%. Amount charged is 0.00 per 100 parts by weight of monomer
It is 01 to 0.02 part by weight, and the method for producing a polymer is characterized in that the charging rate of the oil-soluble polymerization initiator is 0.5 to 5% by weight of the charging amount per minute.

Highly Active Oil-Soluble Polymerization Initiator As the highly active oil-soluble polymerization initiator used in the present invention and having a 10-hour half-life temperature of 40 ° C. or less at a concentration of 0.1 mol / L in benzene, acetylcyclohexylsulfonyl peroxide is used. (10-hour half-life temperature at a concentration of 0.1 mol / L in benzene: 26.5 ℃), isobutyryl peroxide
(At 32.5 ° C), α-cumylperoxy neodecanoate
(At 36.6 ° C), diisopropylbenzene (at 36.4 ° C),
Examples thereof include diallyl peroxycarbonate (at the same temperature of 38.3 ° C.), and these may be used alone or in combination of two or more kinds. Among these highly active oil-soluble polymerization initiators, preferred are isobutyryl peroxide and α
-Cumylperoxy neodecanoate.

A predetermined amount of the highly active oil-soluble polymerization initiator is
After the start of heat removal by the reflux condenser, the polymerization is carried out at a predetermined charging rate until the polymerization conversion rate reaches 60%, preferably 50%. As a result, the polymerization time can be shortened, and a polymer having a good initial colorability can be obtained. If the addition of the highly active oil-soluble polymerization initiator is started before the start of heat removal by the reflux condenser, the heat removal capacity of the jacket will be exceeded due to the increase in heat of polymerization reaction, and the temperature inside the polymerization vessel will be maintained at a predetermined temperature. It is difficult to do so, and the fisheyes in the resulting polymer increase. On the other hand, when the polymerization conversion exceeds 60% and the highly active oil-soluble polymerization initiator is added, the residual amount of the initiator in the polymer increases,
When the polymer is molded, the initial colorability is deteriorated.

The amount of the highly active oil-soluble polymerization initiator charged is 0.0001 to 0.02 part by weight per 100 parts by weight of the monomer,
It is preferably 0.001 to 0.01 parts by weight. If the charged amount of the highly active oil-soluble polymerization initiator is too large, the residual amount of the initiator in the obtained polymer is increased to reduce the initial colorability when molding such a polymer, and it is too small. The polymerization time cannot be shortened so much.

The charging rate of the above-mentioned highly active oil-soluble polymerization initiator is 0.5 to 5% by weight, preferably 1 to 3% by weight, of the charged amount per minute. If the charging rate of the highly active oil-soluble polymerization initiator is too high, the amount of heat generated by the polymerization reaction will rapidly increase, and the heat removal capacity of the jacket and the reflux condenser will be insufficient, so that the temperature inside the polymerization vessel can be controlled to be constant. It causes inconvenience such as difficulty. Further, if the charging speed is too low, the unused portion of the heat removal capacity of the condenser immediately after the start of heat removal by the reflux condenser increases, and the heat removal efficiency is poor and the polymerization time cannot be shortened so much. Occurs.

Polymer Production Method The production of a polymer by suspension polymerization of vinyl chloride or the like in the present invention is carried out, for example, as follows. First, a polymerization vessel equipped with a jacket and a reflux condenser is charged with an aqueous medium and a dispersant, then, after evacuation of the inside of the polymerization vessel, vinyl chloride or the like is charged, and further, it is generally used.
A polymerization initiator other than the above-mentioned highly active oil-soluble polymerization initiator and, if necessary, other additives are charged. Then, the inside of the polymerization vessel is heated to a predetermined polymerization temperature to start the polymerization reaction. After starting the polymerization reaction, pass cooling water through the jacket,
The heat of the polymerization reaction is removed to start the reaction while keeping the temperature in the polymerization vessel constant. Next, when the polymerization conversion rate of the charged monomers reaches 15% or more, the heat removal by the reflux condenser is started. If the start time of heat removal by the reflux condenser is too early, the particle size of the obtained polymer may become coarse, or a block polymer may be produced. If it is too late, the polymerization time cannot be shortened. After the heat removal by the reflux condenser is started and before the polymerization conversion rate reaches 60%, a predetermined amount of the highly active oil-soluble polymerization initiator is charged at a predetermined charging rate as described above. After completion of the polymerization, unreacted monomers are recovered and the produced polymer is taken out of the polymerization vessel.

Monomers to be polymerized by applying the production method of the present invention include vinyl chloride alone, and a monomer mixture mainly composed of vinyl chloride (usually, 50% by weight or more of vinyl chloride), Examples of the comonomer copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid esters and methacrylic acid esters such as methyl acrylate and ethyl acrylate; olefins such as ethylene and propylene. Maleic anhydride; acrylonitrile; styrene; vinylidene chloride;
Other monomers that can be copolymerized with vinyl chloride are exemplified.

Further, as the polymerization initiator other than the above-mentioned highly active oil-soluble polymerization initiator which is initially charged in the polymerization vessel in the above-mentioned production method, benzene at a concentration of 0.1 mol / L is used.
A low activity polymerization initiator having a 10-hour half-life temperature of more than 40 ° C and 55 ° C or less is used. Examples of such a low activity polymerization initiator include diisopropyl peroxydicarbonate.
(10-hour half-life temperature at a concentration of 0.1 mol / L in benzene: 40.5 ° C), peroxycarbonate compounds such as di-2-ethylhexylperoxydicarbonate (43.4 ° C), t-hexylperoxypivalate (53.2 ° C). ℃), t-
Peroxy ester compounds such as butyl peroxy neodecanoate (at 46.5 ° C) and t-hexyl peroxy neodecanoate (at 49.7 ° C), 2,2-azobis-2,4-dimethylvaleronitrile (at 51.0 ° C) ℃) etc., and these can be used alone or in combination of two or more kinds. The amount of the low activity polymerization initiator charged may be appropriately set within a range that does not exceed the heat removal capability of the jacket alone before the heat removal by the reflux condenser is started, and preferably 0.03 to 100 parts by weight of the charged monomer. It is 0.12 parts by weight, and more preferably 0.05 to 0.08 parts by weight.
If the charged amount of this polymerization initiator is too large, it will cause deterioration of initial colorability when the obtained polymer is molded into a sheet or the like, and if too small, the polymerization time cannot be shortened,
This causes a decrease in productivity.

The amount of the aqueous medium charged in the above production method is usually 100 per 100 parts by weight of the charged monomers.
To 200 parts by weight, preferably 110 to 160 parts by weight.

Further, the dispersant charged in the above production method may be a conventionally known dispersant, for example, a water-soluble cellulose ether such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose; partially saponified polyvinyl alcohol; Acrylic acid polymer; water-soluble polymers such as gelatin. These may be used alone or in combination of two or more. Further, together with the above-mentioned dispersant, sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide-
It is also possible to use nonionic emulsifiers such as propylene oxide-block copolymers, anionic emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate and sodium laurate. The amount of the dispersant charged is usually 0.03 to 2.0 parts by weight, preferably 0.03 to 100 parts by weight of the charged monomers.
It is from 04 to 0.15 parts by weight.

Further, if necessary, as other additives, polymerization regulators, chain transfer agents, pH regulators, gelation improvers, antistatic agents, scale inhibitors, etc., which are appropriately used for vinyl chloride polymerization. Is also optional.

Other conditions for this polymerization, for example, a method of charging an aqueous medium, a vinyl chloride monomer, and in some cases other comonomers, a dispersant, etc. to the polymerization vessel may be carried out by a conventionally known method, and the polymerization temperature The polymerization conditions such as may be those conventionally known.

[0021]

EXAMPLES The polymer production method of the present invention will be described below with reference to specific examples. Example 1 As a polymerization vessel, a jacket (maximum heat removal capacity: 70 Mcal / H
r) and reflux condenser (maximum heat removal capacity: 50 Mcal / Hr)
A stainless steel polymerization vessel having an internal volume of 2 m ³ equipped with the above was used.
Considering the safety of the experiment, the heat removal capacity of the jacket is 55 M
The experiment was performed by setting cal / hr and the heat removal capacity of the reflux condenser to 45 Mcal / hr. In the polymerization vessel, deionized water 856k
g, 206 g of partially saponified polyvinyl alcohol and 137 g of cellulose ether were charged, and the inside of the polymerization vessel was degassed to 50 mmHg, and then 685 kg of vinyl chloride monomer was charged.
Then, while stirring the reaction mixture in the polymerization vessel, di-2-ethylhexyl peroxydicarbonate (0.1% in benzene as a low activity polymerization initiator was further used as a polymerization initiator (1)).
10 hours half-life temperature at mol / L concentration: 43.4 ℃) 190g
Then, 190 g of t-butyl peroxy neodecanoate (same half-life temperature: 46.5 ° C.) was press-fitted with a pump. Then, hot water was passed through the jacket to raise the temperature in the polymerization vessel to 57 ° C., and then cooling water was passed through the jacket to keep the temperature in the polymerization vessel at 57 ° C. for polymerization.

When the polymerization conversion rate reaches 15%, heat removal by the reflux condenser is started, and at the same time, isobutyryl peroxide is added as a polymerization initiator (2) in the polymerization vessel.
(Same half-life temperature: 32.5 ° C) was started to be added. The charging amount of isobutyryl peroxide was 60 g, and the charging speed was 1 g per minute. The polymerization conversion rate at the end of the addition of isobutyryl peroxide was 40%.

Polymerization is carried out continuously, and the internal pressure of the polymerization vessel is increased.
When it falls to 6.0 kgf / cm ² · G, the polymerization reaction is stopped,
After recovering the unreacted monomer, the slurry as the reaction mixture was taken out from the polymerization vessel and dehydrated and dried to obtain a vinyl chloride polymer. Table 1 shows the time (polymerization time) required from the start of temperature increase to the termination of the polymerization reaction.

In order to evaluate the initial colorability when the obtained vinyl chloride polymer was formed into a sheet, the chromatechnique index (b value) was measured by the following method. The results are shown in Table 1.

Measurement of b value 100 parts by weight of the obtained vinyl chloride polymer, 1 part by weight of stannous laurate stabilizer (TS-101, manufactured by Akishima Chemical Co., Ltd.), cadmium stabilizer (C, manufactured by Katsuta Kako Co., Ltd.) -100 J) 0.5 part by weight and 50 parts by weight of dioctyl phthalate as a plasticizer are mixed, and 2
After kneading for 5 minutes at 150 ℃ using this roll mill,
A 0.8 mm sheet was formed. Next, this sheet is cut and piled up, and it is put in a 4 cm x 4 cm x 1.5 cm (thickness) formwork and put in 150
A measurement sample was prepared by heating at 65 ° C. and 65 to 70 kgf / cm ² and pressure molding. For this measurement sample, using a photoelectric colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd.), obtain the chroma techness index b value in the color difference formula of Hunter described in JIS Z 8730 (1980). It was evaluated that the fineness was small, that is, the initial colorability was good.

The b value is obtained as follows. JIS Z 8722
According to the description, using standard light C, photoelectric colorimeter (Nippon Denshoku Industries Co., Ltd., Z-1001 DP colorimetric color difference meter), the stimulus values Y and Z of the XYZ color system are measured by the stimulus value direct reading method. Ask. The geometric conditions for illumination and light reception are JIS Z 8722.
The condition d described in Section 4.3.1 is adopted. From the obtained stimulation values Y and Z, the formula described in JIS Z 8730 (1980): b =
The b value is calculated by 7.0 (Y−0.87Z) / Y ^1/2 .

The number of fish eyes when the obtained polymer was molded into a sheet was measured by the following method.
The results are shown in Table 1.

Measurement of fish eye 100 parts by weight of the obtained vinyl chloride polymer, 50 parts by weight of dioctyl phthalate, 0.5 part by weight of lead tribasic acid sulfate, 1.5 parts by weight of lead stearate, 0.1 part by weight of titanium oxide and carbon black 25 g of a mixture prepared with a compounding ratio of 0.05 parts by weight
Was kneaded with a 6-inch roll for kneading at 140 ° C for 5 minutes, and then formed into a sheet with a width of 10 mm and a thickness of 0.2 mm. The number of transparent particles per 100 cm ^{2 of the} obtained sheet (fish eye)
Were counted.

Comparative Example 1 In Comparative Example 1, polymerization was carried out in the same manner as in Example 1 except that isobutyryl peroxide was not added after the heat removal by the reflux condenser was started. The polymerization time is shown in Table 1. The b value was measured in the same manner as in Example 1 in order to evaluate the initial colorability when the obtained vinyl chloride polymer was molded into a sheet. The results are shown in Table 1. The number of fish eyes when the obtained vinyl chloride polymer was molded into a sheet was measured by the same method as in Example 1.
The results are shown in Table 1.

Comparative Example 2 In Comparative Example 2, polymerization was carried out in the same manner as in Example 1 except that the charging rate of isobutyryl peroxide was 10 g per minute. The polymerization time is shown in Table 1. The polymerization conversion rate at the end of addition of isobutyryl peroxide was 25%.

Further, in this Comparative Example 2, since the charging rate of isobutyryl peroxide was high, the polymerization reaction rate rapidly increased and the calorific value rapidly increased, and the heat removal by the jacket and the reflux condenser was polymerized. 30% conversion
Temporarily lost time in the vicinity, and the temperature in the polymerization vessel was reduced to 57
Since the temperature could not be controlled to 0 ° C, the temperature in the polymerization vessel increased by about 3 ° C.

In order to evaluate the initial colorability when the obtained vinyl chloride polymer was molded into a sheet, the b value was measured by the same method as in Example 1. The results are shown in Table 1. The number of fish eyes when the obtained vinyl chloride polymer was molded into a sheet was measured by the same method as in Example 1. The results are shown in Table 1.

Comparative Example 3 In Comparative Example 3, in addition to 190 g of di-2-ethylhexyl peroxydicarbonate and 190 g of t-butyl peroxy neodecanoate as a polymerization initiator (1), a polymerization initiator (1) was further added.
3,5,5-Trimethylhexanoyl peroxide (10-hour half-life temperature at a concentration of 0.1 mol / L in benzene: 59.5 ℃)
Polymerization was carried out in the same manner as in Example 1 except that 80 g was used and that isobutyryl peroxide was not added after the heat removal by the reflux condenser was started. The polymerization time is shown in Table 1. The b value was measured in the same manner as in Example 1 in order to evaluate the initial colorability when the obtained vinyl chloride polymer was molded into a sheet. The results are shown in Table 1. The number of fish eyes when the obtained vinyl chloride polymer was molded into a sheet was measured by the same method as in Example 1.
The results are shown in Table 1.

Comparative Example 4 In Comparative Example 4, the polymerization initiator (1) was replaced by 190 g of di-2-ethylhexyl peroxydicarbonate and 190 g of t-butyl peroxy neodecanoate, and
2-184 g of ethylhexyl peroxydicarbonate and 184 g of t-butyl peroxyneodecanoate were used. Moreover, after the heat removal was started by the reflux condenser, the polymerization initiator (2) was replaced with dibutyryl peroxide instead of dibutyryl peroxide.
-2-46 g of ethylhexyl peroxydicarbonate and
46 g of t-butyl peroxy neodecanoate was used, and each of them was added simultaneously at a charging rate of 1 g per minute (that is, as a polymerization initiator (2), it was added at a charging rate of 2 g per minute). Polymerization was carried out in the same manner as in Example 1. The polymerization time is shown in Table 1. The polymerization conversion rate at the end of the addition of 46 g of di-2-ethylhexyl peroxydicarbonate and 46 g of t-butyl peroxy neodecanoate was
It was 45%. The b value was measured in the same manner as in Example 1 in order to evaluate the initial colorability when the obtained vinyl chloride polymer was molded into a sheet. The results are shown in Table 1.
The number of fish eyes when the obtained vinyl chloride polymer was molded into a sheet was measured by the same method as in Example 1. The results are shown in Table 1.

Comparative Example 5 In Comparative Example 5, in addition to 190 g of di-2-ethylhexyl peroxydicarbonate and 190 g of t-butyl peroxyneodecanoate as a polymerization initiator (1), isobutyryl peroxide was further added. Polymerization was carried out in the same manner as in Example 1 except that 40 g was used and isobutyryl peroxide was not added after the heat removal by the reflux condenser was started. The polymerization time is shown in Table 1. The b value was measured in the same manner as in Example 1 in order to evaluate the initial colorability when the obtained vinyl chloride polymer was molded into a sheet. The results are shown in Table 1. The number of fish eyes when the obtained vinyl chloride polymer was molded into a sheet was determined in Example 1.
It measured by the method similar to. The results are shown in Table 1.

[0036]

[Table 1]

[0037]

According to the production method of the present invention, heat can be efficiently removed during the production of the polymer, and the time required for one batch of polymerization can be shortened, so that the productivity is improved. Further, when the polymer obtained by applying the production method of the present invention is molded into a sheet or the like, there are few fish eyes,
A molded product having good initial colorability can be obtained.

Claims (1)

[Claims] 1. A method for producing a polymer by subjecting vinyl chloride or a monomer mixture containing vinyl chloride to suspension polymerization in a polymerization vessel equipped with a reflux condenser, wherein polymerization conversion after initiation of heat removal by the reflux condenser is carried out. 60% rate
By the time it reaches, the process has a step of charging a highly active oil-soluble polymerization initiator having a 10-hour half-life temperature of 40 ° C or less at a concentration of 0.1 mol / L in benzene, and the charged amount of the oil-soluble polymerization initiator is The method for producing a polymer is characterized in that it is 0.0001 to 0.02 part by weight per 100 parts by weight of the monomer, and the charging rate of the oil-soluble polymerization initiator is 0.5 to 5% by weight of the charged amount per minute.