JP2000001505A - Production of vinyl chloride resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a vinyl chloride resin whereby the polymerization cycle can be shortened by using a large polymerizer, the formation of coarse particles of the obtained vinyl chloride resin can be prevented, and the formation of fish eyes in a molding can be reduced. SOLUTION: In polymerizing a vinyl chloride monomer in the presence of a polymerization initiator and a dispersant in an aqueous medium, the vinyl chloride monomer and the aqueous medium are fed into the polymerizer while they are being mingled with each other in the upper space of the reactor. It is desirable that the polymerization is performed by using a polymerizer having an internal volume of 40 m3 or above and provided with a reflux condenser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a suspension polymerization method for a vinyl chloride monomer (hereinafter referred to as "VC") or a monomer mixture containing VC as a main component and copolymerizable therewith.
The present invention relates to a method for producing a vinyl chloride resin (hereinafter, referred to as “PVC”) that shortens a charging time before the start of polymerization, improves productivity in a polymerization step, and also improves fish eyes and particle size.

[0002]

2. Description of the Related Art Conventionally, polymerization of vinyl chloride is usually carried out by a batch type water suspension polymerization method in a polymerization vessel equipped with a jacket for heating and cooling and a stirring device. That is, the aqueous medium and the dispersant were charged into the polymerization vessel, then the polymerization initiator was charged, and then the inside of the polymerization vessel was evacuated to vacuum and charged with VC. From the time point, maintain the polymerization temperature by passing cooling water through the polymerization vessel jacket,
Next, a series of polymerization operations for recovering VC and discharging PVC from the polymerization vessel are performed.

However, in the above-mentioned conventional methods, it takes a long time to start the polymerization, which is one of the causes of a decrease in productivity. In order to solve such a problem, various methods have been considered.

There is a method in which water, a dispersant, VC and the like and a polymerization initiator are charged into a polymerization vessel at once and a polymerization reaction is immediately started. In this method, water, a dispersant, VC and the like are charged at the same time. Since each raw material is dispersed non-uniformly in the polymerization vessel, the particle size becomes unstable, and the number of products with coarse particles in particular increases. Further, it has a disadvantage in quality that the number of fish eyes is remarkably increased, which is not an ideal solution. Further, as described in Japanese Patent Publication No. 4-12721, a method is described in which premixing is performed using a static mixer or a mixer equipped with a stirrer and charged into a polymerization vessel. When mixed, the specific heat is different, so that the temperature difference causes foaming, which causes a sudden pressure fluctuation, which poses a safety problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made to reduce the cycle time of the polymerization step by using a large-sized polymerization vessel having a reflux condenser (hereinafter referred to as "RC"). It is an object of the present invention to provide a method for producing PVC, which can reduce the length of the obtained PVC, prevent generation of coarse particles of the obtained PVC, and generate less fish eyes when molded.

[0006]

The polymerization method of the present invention comprises the steps of:
When performing a polymerization reaction in the presence of a polymerization initiator and a dispersant in an aqueous medium, C is mixed and charged in a polymerization vessel space while charging VC and the aqueous medium into the polymerization vessel. It is a manufacturing method. At that time, as the polymerization vessel, R
A polymerization vessel provided with C and having an inner volume of 40 m ³ or more is preferable.

The present invention will be described in more detail.

In the present invention, a polymerization vessel provided with a RC and a jacket is used. RC is for cooling the vaporized gas from the liquid layer, condensing it, returning it to a liquid state, and removing the heat of polymerization. Therefore, the RC needs to be provided so as to communicate with the gas phase portion in the polymerization reactor. The RC has a known structure as a cooler, and a refrigerant is passed through the RC to cool the gas in the RC. Further, in order to efficiently mix the VC and the aqueous medium in the polymerization vessel, a large-sized polymerization vessel is preferable, and a polymerization vessel having 40 m ³ or more is particularly preferable.
It is necessary to consider the form of the polymerization vessel. In order to increase the mixing efficiency, the form of the body is preferably as long as possible.
As in (a) and (b), the ratio (L / D) of the length (L) of the straight body portion to the inner diameter (D) is preferably 1.1 or more.

The VC used in the present invention may be VC alone or a mixture containing VC as a main component (usually VC 50% by weight).
Above). Further, another vinyl monomer copolymerizable with VC may be contained as long as the production method of the present invention exerts its effects. Other vinyl monomers copolymerizable with VC include, for example, vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylates such as methyl (meth) acrylate and ethyl (meth) acrylate; In addition to olefins such as ethylene and propylene, (meth) acrylic acid; maleic anhydride; acrylonitrile;
Styrene; vinylidene chloride, and the like, but are not limited thereto.

[0010] When suspension polymerization is carried out in an aqueous medium using the above VC, a dispersant is generally used. The type of the dispersant is not particularly limited, and examples thereof include those usually used for suspension polymerization of vinyl chloride. For example, partially saponified polyvinyl acetate; aqueous solutions of methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, etc. Water-soluble polymers such as polyethylene oxide, polyacrylic acid, and gelatin; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan monostearate, glycerin tristearate, and ethylene oxide propylene oxide block copolymer; Oxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate
And water-soluble emulsifiers such as sodium laurate. These may be used alone or in combination of two or more.

As the above-mentioned polymerization initiator, an initiator generally used for suspension polymerization of VC is preferably used. Examples of such a polymerization initiator include peroxycarbonate compounds such as diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, and diethoxyethylperoxydicarbonate; α-cumylperoxyneodecanate; t-butyl peroxyneodecanate, t-butyl peroxypivalate,
Peroxyester compounds such as t-hexylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2
Peroxides such as peroxyphenoxy acetate; azobis-2,4-dimethylvaleronitrile, azobis (4
Azo compounds such as -methoxy-2,4-dimethylvaleronitrile); potassium persulfate, ammonium persulfate, hydrogen peroxide and the like, which may be used alone or in combination of two or more. .

Further, a polymerization regulator, a chain transfer agent, a pH regulator, a gelling improver, an antistatic agent, a polymer scale adhesion inhibitor and the like, which are conventionally used in polymerization, may be added.

In the present invention, the polymerization initiator may be charged at the same time as the VC is charged. However, it is preferable to add the polymerization initiator after the temperature is raised to prevent the formation of scale. Also, the dispersant may be any time as long as the aqueous medium is charged,
In order to stabilize the dispersibility of VC, it is preferable that the aqueous medium is charged at the same time as the aqueous medium, and that the aqueous medium is charged in about 1/3 of the time required for completing the charging.

As a method of mixing the VC and the aqueous medium while charging them in the polymerization vessel, there is a method in which the VC and the aqueous medium are charged from different charging ports facing the upper part of the polymerization vessel and mixed and charged in the space above the polymerization vessel. Further, a mixing section may be provided so that mixing can be performed in a mixing space in the space above the polymerization vessel. The charging speed is not particularly limited as long as it can be mixed in the space above the polymerization vessel. The shape of the mixing portion is not particularly limited, as long as the mixing portion can sufficiently mix the VC and the aqueous medium, such as a baffle plate or a net. However, a structure as simple as possible is preferable in consideration of the adhesion of the scale.

Regarding the temperature of the aqueous medium, foaming occurs due to the temperature difference during simultaneous charging with VC, but foaming occurs at the time of mixing in the upper part of the polymerization vessel. Since the temperature of the medium only needs to be 35 ° C. or higher, the time for raising the temperature can be shortened.

A general suspension polymerization method such as VC by the production method of the present invention will be specifically described. First, after degassing the inside of the polymerization vessel, the aqueous medium and VC are simultaneously charged from the top of the polymerization vessel and charged while mixing at the top. At that time, a dispersant is also charged at the same time, and after completion of the charging, a predetermined reaction temperature (normally 40 to 80)
C.) and the initiator is added, and the polymerization is carried out while maintaining the reaction temperature. After that, the pressure of the polymerization vessel was 2.0 kg / c.
Unreacted VC was recovered at the time when m ^{2 was} reduced.
Is dehydrated and dried. The aqueous medium charged during the polymerization, the dispersant and the polymerization initiator are usually 50 to 250 parts by weight of the aqueous medium, 0.02 to 2 parts by weight of the dispersant with respect to 100 parts by weight of VC,
The polymerization initiator is preferably used in an amount of 0.01 to 0.5 parts by weight.

The production method of the present invention can reduce the cycle time of the polymerization step, prevent the generation of coarse particles of the obtained PVC, and further reduce the generation of fish eyes when molded. In addition, safety can be ensured by carrying out simultaneous charging in the polymerization reactor, so that it is particularly effective in a large polymerization reactor of 40 m ³ or more provided with an RC and a jacket.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically by way of examples, but the present invention is not limited to these.

(Embodiment 1) As shown in FIG. 1 (a), an inner volume having a jacket 6 and a RC2, a VC3 and a deionized water 4 inlet are provided at the upper part, and the inlets face each other. After degassing the inside of the 50 m ³ stainless steel polymerization vessel 1, 25700 kg of deionized water at 50 ° C. and VC1
5800 Kg were simultaneously charged from the charging port and mixed and charged in the upper part of the polymerization vessel. In this case, 9.8 Kg of partially saponified polyvinyl acetate and hydroxypropyl methylcellulose were added.
1 kg was added at the same time. After completion of the charging, the temperature in the polymerization vessel was continuously raised to 56 ° C., and after reaching 56 ° C., 6.7 kg of di-2-ethylhexyl peroxydicarbonate was added as a polymerization initiator, and the operation of RC2 was started gradually. .
Polymerization was carried out while maintaining the temperature at 56 ° C. with RC2 and jacket 6. Thereafter, when the pressure in the polymerization vessel 1 dropped by 2.0 kg / cm ² , unreacted VC was recovered, and the obtained PVC was dehydrated and dried. (Example 2) As shown in FIG. 1 (b), when VC and deionized water are simultaneously charged, a stainless steel porous disc 7 having a diameter of 1.2 m is installed as a mixing part in a place where the VC and the deionized water are mixed.
^The procedure was performed in the same manner as in Example 1 except that the stainless steel polymerization vessel 10 was used. (Comparative Example 1) Inner volume 40 m with jacket and RC
^{3 is} a stainless steel polymerization vessel having a structure in which the VC and deionized water inlets are at the top and the inlets face downward (not facing each other). 20000 Kg of deionized water at ℃ and VC1300
At the same time, 8.0 kg of partially saponified polyvinyl acetate and 3.2 kg of hydroxypropylmethylcellulose were simultaneously added. After completion of the charging, the temperature in the polymerization vessel was raised to 56 ° C, and after reaching 56 ° C, di-
2-ethylhexyl peroxydicarbonate 5.4K
g was added and the RC run was started slowly. Polymerization was carried out while maintaining the temperature at 56 ° C. with RC and a jacket. After that, when the pressure in the polymerization reactor drops by 2.0 kg / cm ² , unreacted VC
Was recovered, and the obtained PVC was dehydrated and dried. (Comparative Example 2) 20,000 kg of deionized water at 50 ° C was charged, and 8.0 kg of partially saponified polyvinyl acetate and 3.2 kg of hydroxypropylmethylcellulose were added at the same time. Next, 5.4 kg of a polymerization initiator di-2-ethylhexyl peroxydicarbonate was charged, and after degassing the inside of the polymerization vessel, 13,000 kg of VC was charged, and the temperature was raised to 56 ° C. . Other than that, it carried out similarly to the comparative example 1.

The physical properties of the PVCs obtained in the above Examples and Comparative Examples were evaluated and the time required for preparation was as follows. The results are shown in Table 1. (1) Coarse Grain Degree According to JIS Z 8801, it was sieved using a standard 42-mesh sieve, and indicated by the weight% of the particles remaining on the sieve. (2) Fisheye To 100 parts by weight of the obtained PVC, 50 parts by weight of dioctyl phthalate (plasticizer), 0.5 parts by weight of barium stearate (stabilizer), and 0.5 parts by weight of zinc stearate (stabilizer)
Parts by weight, 0.5 parts by weight of titanium dioxide (filler) and 0.1 parts by weight of carbon black (filler) were mixed, and the mixture was kneaded on a 6-inch roll at 140 ° C. for 5 minutes. A sheet having a thickness of 0.3 mm was prepared, and the number of transparent particles in 100 cm ^{2 of the} sheet was counted to determine the number of fish eyes. (3) Time required for charging Time from the start of charging to the start of heating (minutes)

[0021]

[Table 1]

[0022]

The method for producing PVC of the present invention is as described above. By simultaneously charging deionized water and VC and mixing them in a polymerization vessel, the time required for charging is reduced, and the productivity is improved. Safety is ensured, and P
The generation of coarse particles in the VC is also suppressed, and the fisheye when the obtained PVC is formed into a sheet or the like is reduced.

[0023]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a system in which water and VC are mixed in a polymerization vessel space, and FIG. 1B is a schematic diagram showing a system in which a perforated disk is installed in a place where water and VC are mixed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polymerizer 2 RC 3 VC 4 Aqueous medium 5 Stirrer blade 6 Jacket 7 Perforated disk

Continued on the front page F term (reference) 4J011 AA01 AA03 AA05 AA08 AC06 BB09 BB11 DB18 DB23 JA06 JA07 JA08 JB09 JB26 4J100 AA02Q AA03Q AB02Q AC03P AC04Q AG02Q AG04Q AJ02Q AK32Q AL03Q AM02Q CA01 FA04 FA03

Claims (2)

[Claims] When a vinyl chloride monomer is subjected to a polymerization reaction in an aqueous medium in the presence of a polymerization initiator and a dispersant, the vinyl chloride monomer and the aqueous medium are charged into a polymerization vessel. A method for producing a vinyl chloride resin, which comprises mixing and charging in a polymerization vessel space. 2. The method for producing a vinyl chloride resin according to claim 1, wherein the polymerization is carried out using a polymerization vessel having a reflux condenser and having an inner volume of 40 m ³ or more.