JPS60158207A - Suspension polymerization of vinyl chloride - Google Patents

Abstract

PURPOSE:To shorten a production time and to produce PVC of improved quality, by premixing all of the materials at a specified temperature or below, quickly preheating the mixture to a reaction temperature, charging an autoclave with the preheated mixture and polymerizing it at once. CONSTITUTION:In the suspension polymerization of vinyl chloride, deionized water is premixed with a suspending agent, a polymerization initiator and vinyl chloride or a mixture thereof with a monomer copolymerizable therewith at 50 deg.C or below and the obtained mixture is quickly preheated to a reaction temperature, placed in an autoclave and polymerized at once. It becomes possible to enhance the production rate by shortening a charging time and a reaction time markedly and to produce PVC improved in fish eye content and particle diameter distribution.

Description

[Detailed Description of the Invention] In the suspension polymerization method of a monomer mixture copolymerizable with this (hereinafter referred to as vinyl chloride, etc.), the preparation time and temperature raising time before the start of polymerization are shortened. , relates to a suspension polymerization method that improves the productivity of the polymerization process and also improves fish eye and particle size distribution.

Suspension polymerization of vinyl chloride is usually carried out in a batch process. After charging deionized water, a suspending agent, a polymerization initiator, and other additives to an autoclave, the system is degassed and vinyl chloride, etc. is charged. , Pass hot water circulation or steam through the jacket of the autoclave while stirring to raise the temperature to the polymerization temperature to start the polymerization reaction, and from the time the heat of the polymerization reaction is released, cool water to the jacket of the autoclave to maintain the polymerization temperature, A series of polymerization operations are carried out in which the reaction is continued until a predetermined polymerization rate is reached, and then monomer gas such as vinyl chloride is recovered and the polymer is discharged from the autoclave.

However, in the conventional method as described above, the time required to start polymerization is as much as 5 to 30% of one cycle of polymerization operation, which is a cause of decreased productivity.

Various methods can be considered to solve this problem.

Water heated to the polymerization temperature or higher, a suspending agent, vinyl chloride, etc., and a polymerization initiator are charged all at once into an autoclave.
There is a method to immediately start the polymerization reaction, but this method uses vinyl chloride at around the polymerization humidity.

Since the water 1 comes in contact with the turbidity agent, the particle size becomes unstable, resulting in a particularly large number of coarse particles. Furthermore, there is a quality defect in that the number of fish gourds increases significantly, which is not a good idea.

Furthermore, in the method described in JP-A No. 54-47785, in which water at room temperature and a suspending agent are charged into an autoclave, vinyl chloride is then charged, the mixture is stirred, and heated water is charged to initiate polymerization. This method is complicated, requires a long preparation time, and has the disadvantage of lacking particle size stability due to uneven contact with high-temperature water.

The inventors of the present invention have carried out intensive studies to solve these drawbacks and shorten the cycle time of the polymerization process. As a result, the temperature and the ratio of vinyl chloride to water at the time of contact between vinyl chloride, water, and suspending agent have been determined. It was discovered that this is an important factor, leading to the present invention.

In the present invention, vinyl chloride containing a polymerization initiator and water containing a suspending agent are premixed at 50°C or below to create a stable suspended state, and the mixture is quickly heated to the reaction temperature using a heat exchanger. This is a suspension polymerization method for vinyl chloride, which is characterized by charging it into an autoclave and starting polymerization.

According to the method of the present invention, it is possible to significantly shorten the time for charging the autoclave and the time for raising the temperature, and at the same time, it is possible to improve productivity without damaging the fish eye or other physical properties. It is.

The present invention will be explained in more detail.

As the hexamer used in the present invention, vinyl chloride or a mixture containing vinyl chloride as a main component and a monomer copolymerizable with vinyl chloride can be used. Examples of components copolymerizable with vinyl chloride include ethylene, vinyl acetate, methyl acrylate, acrylonitrile, and vinylidene chloride. Examples of the polymerization initiator include isobutyl peroxide, cumyl peroxy neodecanate, diisopropyl peroxy dicarbonate, di-2-ethylhexyl oxydicarbonate, 1-butyl peroxy neodecanate, and t-butyl peroxy bicarbonate. organic peroxides and αα′-azobis4-
Dimethylvaleronitrile.

These are azo compounds such as αα′-azobisisobutyronitrile and the like.

Examples of the suspending agent include cellulose derivatives such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose, partially saponified polyvinyl alcohol, acrylic acid polymers, gelatin, sorbitan esters, and polyether polymers. It can be used singly or in combination of two or more.

In carrying out the present invention, when using a polymerization initiator with extremely low water solubility that dissolves in vinyl chloride, etc., it is not necessary to dissolve the polymerization initiator in vinyl chloride, but rather to raise the temperature to prevent scale formation. It is preferable to add it later. PVC containing a polymerization initiator, suspending agent, and water at 50℃
In the following, a stable dispersion state can be obtained by sufficiently stirring and mixing in a premixer preferably at 45° C. or lower.

It is preferable to carry out the above-mentioned mixing at a temperature below the cloud point or thermal gelation temperature of the suspending agent; if the temperature exceeds 50°C, a large amount of coarse particles will be formed;
Furthermore, since the decomposition of the polymerization initiator also increases, scale formation rapidly increases. Also, the premixer can be used batchwise or continuously. Furthermore, instead of the preliminary mixing tank, a static mixer having the same stirring and mixing ability as this tank can also be used.

The premix is continuously passed through a heat exchanger and heated to reach the reaction temperature at the time it is charged into the autoclave, thereby shortening/omitting the charging time and the heating time.

Temperature raising and charging are integrated, and in order to minimize the residence time for temperature raising, it is preferable to use a heat exchanger with a large heat transfer coefficient, such as a plate heat exchanger or a spiral heat exchanger. It is also better to keep the residence time in the piping from the heat exchanger to the autoclave to a minimum. In addition, as a heating source,
Hot water or steam at 60-100°C is used.

The residence time of the series of heating/preparation is 5 minutes or less, preferably 1
minutes or less.

In carrying out the present invention, there are no restrictions regarding the polymerization temperature (usually 40 to 70.degree. C.) or other conditions.

The present invention will be explained in more detail with reference to Examples below.

(Example-1) 1 for static mixer (inner diameter 53 mm, length 5000 mm)
- 100 parts of vinyl chloride (2,000 k
y) 12,000 ky/H (D speed, 4 containing partially saponified polyvinyl alcohol α06 parts (9 in 1 and 2)
130 parts (9 in 2,600) of deionized water at 5°C.
600 and 97H17), stirred and mixed, and then passed through a spiral heat exchanger (30/) to a degassed autoclave with CtB port c60'C,)7d at a temperature of 57°C. At a controlled polymerization temperature of 57°C, the internal pressure of the can was 2. Polymerization was stopped when OIcgZcIl decreased, and unreacted monomers were collected, dehydrated, and dried to obtain a vinyl chloride polymer. In addition, in order to prevent scale formation in the line, the line was washed with water after the preparation of vinyl chloride and deionized water was completed. Table 1 shows the particle size distribution of the obtained polymer and the results of the fish eye test.

(Example-2) All conditions were the same as in Example-1 except that in the method of Example-1, the temperature of 30'Q vinyl chloride was changed to 40°C, and the temperature of 45°C deionized water was changed to 40°C. A vinyl chloride polymer was obtained.

Similar to Example-1, the test results are shown in Table-1.

(Example-3) IW in place of the static mixer in the method of Example-1? Stirring mixing tank (with cylindrical vertical paddle type stirrer 101)
A vinyl chloride polymer was obtained by processing under the same conditions as in Example-1 except that 000 rpm was used.

Table 1 shows the test results similar to those in Example-1.

(Comparative Example-1) Partially saponified polyvinyl alcohol o, o6g (1,21
130 parts of deionized water at 30°C (2600k
g) to 7W? After being placed in an autoclave and degassed,
0.02 part of t-butyl peroxyneodecanate (α4
100 parts of vinyl chloride (20001 kg) at 30°C
A vinyl chloride polymer was obtained by treating under the same conditions as in Example 1, except that c9) was prepared and Jahut was heated with 80° C. hot water.

Table 1 shows the test results similar to those in Example-1.

(Comparative Example-2) A vinyl chloride polymer was obtained by processing under the same conditions as in Example-1 except that the static mixer was omitted in the method of Example-1.

Table 1 shows the test results similar to those in Example-1.

Table 1 1) Fischer eye test method Vinyl chloride polymer 100 parts Dioctyl 7-talate 50 parts Calcium stearate 1.5 parts Barium stearate 1.5 parts Ultramarine 3 parts were mixed and kneaded for 5 minutes at a roll temperature of 150°C. A sheet with a thickness of 0.55 era is prepared and a 25 m fisheye measurement is performed.

Patent applicant: Toyo Soda Kogyo Co., Ltd.

Claims (4)

[Claims] (1) In the suspension polymerization method of hinyl mide, a mixture of deionized water, a suspending agent, a polymerization initiator, and vinyl chloride and a monomer copolymerizable with vinyl chloride, which is mainly composed of vinyl chloride, is added at 50°C or less. A suspension polymerization method for vinyl chloride, which is characterized in that after premixing, the mixture is immediately preheated to a reaction temperature, charged into an autoclave, and polymerized immediately. (2) A method for suspension polymerization of vinyl chloride according to claim 1, in which a static mixer or a mixer with an agitator is used for premixing. (3) The suspension polymerization method for vinyl chloride according to claim 1 or 2, wherein the residence time between heating the premix to the reaction temperature and charging it into the autoclave is 3 minutes or less. (4) A method for suspension polymerization of vinyl chloride according to claim 1.2 or 3, in which a spiral heat exchanger or a plate heat exchanger is used to preheat the premix to the reaction temperature.