JPH1149808A - Production of vinyl chloride-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce fisheyes in good productivity when molding the resultant resin by blowing steam from a reflux condenser into a polymerizer at the time of charging a reactional mixture when polymerizing a vinyl chloride-based monomer in an aqueous medium. SOLUTION: When a vinyl chloride-based monomer (hereinafter referred to as VC) is polymerized in an aqueous medium, a polymerizer having a reflux condenser (hereinafter referred to as RC) is used and, e.g. the interior of the polymerizer is initially evacuated. Steam is then blown from the RC into the polymerizer and the temperature in the polymerizer is preferably increased to 50-90 deg.C. The aqueous medium (preferably at >=35 deg.C), a dispersing agent, a polymerization initiator and other auxiliaries are charged into the polymerizer, stirred and uniformized. VC is subsequently charged thereinto. Hot water or steam is then passed through a jacket to increase the temperature. When a prescribed reactional temperature attains (preferably 50 90 deg.C), cooling water is passed through the jacket to carry out the (co)polymerization while removing the heat of reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride resin (hereinafter referred to as "PVC"), and more particularly, to a method for producing PVC for producing with high efficiency.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride monomers (hereinafter referred to as "V
C) is usually carried out by a batch water suspension polymerization method in a polymerization vessel equipped with a jacket for heating and cooling and a stirring device. That is, a method in which an aqueous medium and a dispersant are charged into a polymerization vessel, then a polymerization initiator is charged, then the inside of the polymerization vessel is evacuated to vacuum, VC is charged, and the temperature is raised to carry out a polymerization reaction.

[0003] In recent years, in the production of PVC, as one of the methods for increasing the size of a polymerization vessel and increasing the polymerization rate in order to improve productivity, shortening of the time required for charging a reaction mixture and raising the temperature is required. It is planned. For example, a method has been proposed in which at least one of an aqueous medium and VC is preliminarily heated and charged (so-called hot charge method) (Japanese Patent Publication No. 62-1987).
No. 39601). This hot charging method is also excellent in that it compensates for an increase in the size of the polymerization vessel and insufficient heating capacity of the polymerization vessel due to the use of a reflux condenser (hereinafter referred to as RC).

However, this hot charge method is
Since the polymerization initiator is rapidly decomposed at the same time as the polymerization initiator is charged, coarse particles are generated in the obtained polymer, and adhesion of the polymer scale to the inner wall of the polymerization vessel and the like increases. Was. Further, there is a problem that fish eyes when the obtained polymer is formed into a sheet or the like are remarkably increased.

Further, a method has been proposed in which steam is blown into a polymerization vessel when the temperature is raised (JP-A-6-93006). In this method, the productivity is not significantly contributed only by shortening the time at the time of raising the temperature. Further, when steam is blown into the liquid phase, the added polymerization initiator is rapidly decomposed, and coarse particles are formed in the obtained polymer. This has caused a problem that fish eyes are remarkably increased.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to reduce the time required for charging VC and the like and increasing the temperature by using a large-sized polymerization reactor having an RC. It is possible to prevent the generation of coarse particles of the obtained polymer, to effectively prevent the adhesion of the polymer scale in the polymerization vessel, and to reduce the generation of fish eyes when molded, It is to provide a manufacturing method.

[0007]

The polymerization method of the present invention comprises the steps of:
When polymerizing C in an aqueous medium, the reaction mixture is charged using a polymerization vessel equipped with RC, and in a method of producing PVC for performing a polymerization reaction, when the reaction mixture is charged, steam is blown from the RC into the polymerization vessel when the reaction mixture is charged. Features.

[0008] The charging step of the present invention, that is, the charging step is a step of charging an aqueous medium, a dispersant, a polymerization initiator, other auxiliaries and VC into a polymerization vessel from a step of raising the temperature to a predetermined reaction temperature. Indicates that In some cases, degassing and stirring may be performed before the addition of the aqueous medium, the dispersant, or the like.

The production of PVC by the production method of the present invention
For example, the following method is used. First, after the inside of the polymerization vessel was degassed, steam was blown from the RC, the temperature was raised to a predetermined reaction temperature or higher, an aqueous medium, a dispersant, a polymerization initiator, and other auxiliaries were charged, and the mixture was stirred and uniformly mixed. After that, VC is charged.
At this time, the temperature of the aqueous medium is preferably 35 ° C. or higher, more preferably 40 to 80 ° C., in order to shorten the temperature rising time. Further, in order to shorten the charging time, it is possible to simultaneously charge the aqueous medium and the VC.

Next, the temperature is raised by passing hot water or steam through the jacket, and when a predetermined reaction temperature is reached, polymerization is carried out while cooling water is removed through cooling water through the jacket. At that time, in order to prevent adhesion of the polymer scale to the steam blowing nozzle, clogging of the polymer, and the like, it is preferable to perform water flushing by injecting water through the nozzle.

It is preferable to use a plurality of steam nozzles in order to blow the steam from the RC so that the steam can be uniformly dispersed in the gas phase of the polymerization reactor. Further, the steam blowing may be continuous or intermittent. The temperature in the polymerization reactor by steam must be equal to or higher than the predetermined reaction temperature as described above, and is preferably 50 to 90 ° C.

As the steam nozzle, a steam silencer, a mixing nozzle, a tank mixing eductor and the like are suitably used. Although a commonly used spray nozzle or the like can be used, it is not preferable because noise during use is large.

[0013] The temperature in the vapor phase of the polymerization reactor when steam is blown may be raised to a predetermined reaction temperature or higher as described above in order to shorten the time. Preferably, the temperature is raised to a predetermined reaction temperature. It is kept above its predetermined reaction temperature until it reaches. The steam pressure may be higher than the maximum pressure in the polymerization vessel, and for safety, 1 kgf is higher than the maximum pressure in the polymerization vessel.
/ Cm ² or more.

The VC used in the present invention may be VC alone or a mixture containing VC as a main component (generally, 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) acrylate esters such as methyl (meth) acrylate and ethyl (meth) acrylate; In addition to olefins such as ethylene and propylene, (meth) acrylic acid, maleic anhydride, acrylonitrile,
Examples include, but are not limited to, styrene and vinylidene chloride.

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 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. .

The polymerization initiator may be added during or after charging water or VC, or may be uniformly mixed with VC in advance and charged together with VC. further,
A polymerization adjuster, a chain transfer agent, a pH adjuster, a gelling improver, an antistatic agent, a polymer scale adhesion preventive, and the like appropriately used for polymerization of VC or the like may be added.

A general suspension polymerization method such as VC according to the production method of the present invention will be specifically described. First, after the inside of the polymerization vessel is degassed, steam is blown from RC to raise the temperature to a predetermined reaction temperature or higher, and an aqueous medium, a dispersant, a polymerization initiator, and other auxiliaries are charged, and VC is charged after stirring and mixing. . Alternatively, stirring may be performed after steam is blown in, and an aqueous medium, a dispersant, a polymerization initiator, other auxiliaries and VC may be simultaneously charged. The temperature is raised to a predetermined reaction temperature (usually 40 to 80 ° C.), and polymerization is performed while maintaining the reaction temperature. After that, when the pressure of the polymerization reactor dropped by 2.0 kg / cm ² , unreacted V
C is recovered, and the obtained PVC is dehydrated and dried. The aqueous medium, the dispersant, and the polymerization initiator to be charged at the time of the polymerization are usually 50 to 250 parts by weight of the aqueous medium, 0.02 to 2 parts by weight of the dispersant, and 0.02 to 2.0 parts by weight based on 100 parts by weight of VC.
5 parts by weight are preferred.

The production method of the present invention can reduce the time required for raising the temperature, prevent the generation of coarse particles of the polymer, and effectively prevent the adhesion of the polymer scale in the polymerization vessel. This is particularly effective in a large-sized polymerization vessel having a size of 40 m ³ or more.

[0020]

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

(Example 1) After degassing a 50 m ³ stainless steel polymerization vessel equipped with a jacket and RC, R
After steam was blown from C to raise the inside of the polymerization vessel to 80 ° C., 25,700 kg of 50 ° C. deionized water, 9.8 kg of partially saponified polyvinyl acetate, 4.1 kg of hydroxypropylmethyl cellulose, and di-2 as a polymerization initiator. After charging 6.7 kg of -ethylhexylperoxydica-bonate, stirring and charging 15,800 kg of VC, the temperature inside the polymerization vessel was raised to 56 ° C, and after reaching 56 ° C, the RC operation was gradually started. . Polymerization was carried out while maintaining the temperature at 56 ° C. with RC and a jacket. Then the pressure of the polymerization vessel is 2.0kg
The unreacted VC was recovered at the time of the decrease in / cm ² , and the obtained PVC was dehydrated and dried.

(Example 2) The same operation as in Example 1 was carried out except that steam was blown from RC and the inside of the polymerization reactor was raised to 60 ° C.

(Example 3) Steam was blown from the RC, the inside of the polymerization vessel was heated to 80 ° C, and stirring was started.
The same operation as in Example 1 was carried out except that deionized water at 0 ° C., a dispersant, a polymerization initiator and VC were simultaneously charged.

(Comparative Example 1) The same operation as in Example 1 was carried out except that steam was not blown from RC, deionized water at 50 ° C, a dispersant, and a polymerization initiator were charged and VC was charged after stirring.

(Comparative Example 2) The same operation as in Example 1 was carried out except that steam was not blown from RC, deionized water at 30 ° C, a dispersant, and a polymerization initiator were charged, and VC was charged after stirring.

The physical properties of the PVC obtained in the above Examples and Comparative Examples were evaluated as follows, and 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) Bulk specific gravity Measured according to JIS K6721. (3) 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. (4) Scale attached state After the polymerization was completed, the scale attached state in the polymerization vessel was visually observed. ○: No scale attached, ×: Scale attached.

[0027]

[Table 1]

[0028]

The PVC production method of the present invention is as described above. By blowing steam from RC, the time required from preparation to temperature rise is shortened, productivity is improved, and coarse particles in PVC are improved. Is also suppressed, and the obtained P
Fish eyes when VC is formed into a sheet or the like are reduced.

Claims (3)

[Claims] When a vinyl chloride-based monomer is polymerized in an aqueous medium, a reaction mixture is charged using a polymerization vessel equipped with a reflux condenser, and a polymerization reaction is carried out. A method for producing a vinyl chloride resin, wherein steam is blown from a reflux condenser into a polymerization vessel when a reaction mixture is charged. 2. The method for producing a vinyl chloride resin according to claim 1, wherein the internal volume of the polymerization vessel is 40 m ³ or more. 3. The method for producing a vinyl chloride resin according to claim 1, wherein the temperature of the aqueous medium at the time of charging is 35 ° C. or higher.