JPH1135607A - Production of vinyl chloride-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain the subject resin without coarsening particles, by controlling the polymerization reaction of a vinyl chloride-based monomer by using a polymerization initiator having specific activity and a polymerization inhibitor. SOLUTION: A vinyl chloride-based monomer (VC for short) is polymerized at 40-65 deg.C by a polymerizer which is equipped with a reflux condenser so as to communicate with a vapor phase part in the polymerizer and has >=40 m<3> inner volume in an aqueous medium (e.g. water) by adding 0.02-5 pts.wt. based on 100 pts.wt. of VC of a polymerization initiator (preferably α-cumylperoxy neodecanoate) at 30-55 deg.C of half-life temperature of 10 hours, a polymerization initiator [e.g. 2,2-di-(4'-hydroxyphenyl)propane, etc.], is added in the midst of the polymerization and the polymerization is completed within 6 hours to give the objective resin. The weight ratio of water to VC is 1/1 to 1.7/1. In the polymerization method, a suspension (e.g. methyl cellulose) such as a dispersant or a surfactant is used.

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.

In recent years, in the production of PVC, the polymerization time has been shortened by increasing the size of the polymerization vessel and increasing the polymerization rate in order to improve productivity. For that purpose, it is important to increase the ability of the polymerization vessel to remove the heat of the polymerization reaction.

With respect to the high-speed polymerization method for shortening the polymerization time, for example, a method using a highly active polymerization initiator as a polymerization initiator (Japanese Patent Application Laid-Open No. 53-73280), or
Various polymerization methods have been proposed, such as a method of making the polymerization rate uniform by a combination of polymerization initiators having different activities (JP-A-1-31810). However, any of these methods not only decreases the thermal stability and hue of the obtained resin, but also causes unstable particle formation during polymerization, resulting in coarsening of particles or increase of fish eyes. There was a problem that high quality products could not be obtained.

[0005] As the size of the polymerization vessel increases, the jacket area per unit volume of the polymerization vessel becomes relatively small, and the heat removal capacity is reduced. JP-B-58-8405) is disclosed, but although the heat removal ability is improved, its effect is slight and insufficient.

Therefore, a reflux condenser (hereinafter referred to as "RC") is attached to a large-sized polymerization vessel of 40 m ³ or more in order to efficiently remove reaction heat, and a high-speed polymerization is performed within a polymerization time of 6 hours or less. (Japanese Patent Publication No. 1-10882), however, according to this method, it is necessary to increase the heat removal load of RC.

However, when the heat removal load of the reaction heat by the RC is increased, the foaming becomes remarkable especially in the early stage of the polymerization, so that the foam of the polymerization suspension containing the polymerization initiator forms the wall of the gas phase portion of the polymerization tank or the like. It adheres to the inner wall of RC, etc., and becomes a scale, which significantly inhibits the efficiency of heat removal and adversely affects the particle formation at the initial stage of polymerization, so that particles without internal voids called glass balls are generated, However, there is a problem that polymerization proceeds and coarse polymer particles are formed.

It is also possible to improve the heat removal capability of the polymerization vessel by passing low-temperature cooling water, which has been cooled beforehand, through the jacket, but the running cost of the cooling equipment is high and it is not economical.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and has been made by using a polymerization initiator having a specific activity and controlling a polymerization reaction by using a polymerization inhibitor. An object of the present invention is to provide a highly efficient method for producing PVC, in which the obtained PVC particles are not coarsened.

[0010]

According to the method of polymerizing VC of the present invention, VC is polymerized in an aqueous medium in a polymerizer having an internal volume of 40 m ³ or more equipped with RC to complete the polymerization within 6 hours. It is characterized by using a polymerization initiator having a 10-hour half-life temperature of 30 to 55 ° C. and adding a polymerization inhibitor during the polymerization reaction.

In the present invention, a reactor equipped with a RC and a jacket is used. RC is for cooling and condensing a gas vaporized from a liquid layer to return to a liquid state to remove polymerization heat. 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.

The polymerization initiator of the present invention has a 10-hour half-life temperature of 30 to 55 ° C., preferably 30 to 55 ° C.
It is in the range of 50 ° C. Here, the 10-hour half-life temperature is a temperature at which the polymerization initiator is decomposed in a benzene solvent and it takes 10 hours for its concentration to be reduced to half of the initial concentration. It is an index indicating the size, ie, the activity.

When a polymerization initiator having a 10-hour half-life temperature of less than 30 ° C. is used, the decomposition rate of the polymerization initiator is too high, so that the polymerization reaction cannot be sufficiently controlled and the polymerization stability is impaired. When a polymerization initiator having a 10-hour half-life temperature of 55 ° C. or more is used, the effect of the polymerization inhibitor increases, polymerization is delayed, and productivity is reduced.

Examples of the polymerization initiator include, for example, t-butyl peroxyneocanoate, (α, α'-bis-
Neodecanoyl peroxy) diisopropylbenzene,
Isobutyl peroxide, α-cumylper-oxyneodecanoe, t-hexylpa-oxyneodecanoe
G, di-2-ethylhexyl par-oxydica-bone-
And di- (2-ethoxyethyl) peroxydica-bonate, which may be used alone.
Two or more kinds may be used in combination. In particular, among the above-mentioned polymerization initiators, α-cumylper-oxyneodecanoate has a relatively high decomposition rate, and is suitable for controlling a polymerization reaction using a polymerization inhibitor in a polymerization vessel provided with RC.

The amount of the polymerization initiator to be added varies depending on the type used, the polymerization temperature and other conditions, but is preferably 0.02 to 5 parts by weight per 100 parts by weight of VC. At this time, high-speed polymerization is performed, and the calorific value of the polymerization per unit time becomes larger than the appropriate heat removal capability of RC. Therefore, by appropriately adding a polymerization inhibitor during the polymerization, the polymerization can be completed within 6 hours. Required.

The time for adding the polymerization inhibitor is preferably such that the amount of heat generated per unit time in the polymerization reaction of VC is large and the polymerization conversion is 30 to 80% by weight. By adding the polymerization inhibitor at this time, the reaction can be controlled, so that the particles are not coarsened and good PVC can be produced with high efficiency. When the polymerization inhibitor is added at a polymerization conversion of VC of less than 30% by weight, the polymerization reaction is slowed down. When the polymerization conversion is over 80% by weight, the polymerization reaction cannot be controlled, and the obtained PVC has coarse particles. Become

As the polymerization inhibitor (also referred to as a polymerization inhibitor), conventionally known phenol compounds, sulfur compounds, N-oxide compounds and the like are used. For example, 2,2-di- ( 4'-hydroxyphenyl) propane, hydroquinone, p-methoxyphenol, t-butylhydroxyanisole, n-octadecyl-3-
(4-hydroxy-3,5-di-t-butylphenyl)
Propionate, 2,5-di-t-butylhydroquinone, 4,4'-butylidenebis- (3-methyl-6-t
-Butylphenol), 3,5-di-t-butyl-4-
Hydroxytoluene, 2,2 'methylene-bis- (4-
Ethyl-6-t-butylphenol), triethylene glycol, bis [3- (3-t-butyl-5-methyl-
4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], t-
Butyl catechol, 4,4'-thiobis- (6-t-butyl-m-cresol), tocopherol and the like. These may be used alone or in combination of two or more.

The amount of the polymerization inhibitor to be added is not particularly limited because it is determined by the type and amount of the polymerization initiator and the heat removal ability of RC. The addition method may be divided addition or continuous addition, but is preferably added continuously. Various methods may be employed as the addition means, and for example, a solution or dispersion prepared by dissolving in an appropriate solvent or suspending in water may be added.

In the present invention, the polymerization time is defined as the pressure in the polymerization reactor at the reaction temperature from the time when the internal temperature of the polymerization reactor reaches a predetermined polymerization reaction temperature by heating and raising the temperature after charging the raw materials such as VC. After a while, unreacted V
With the decrease in C, a pressure drop starts, and the pressure drop width is 2
It is defined as the time to reach kg / cm ² .

According to the production method of the present invention, R
Using a polymerization vessel with an internal volume of 40 m ³ or more provided with C, the particle size is stable even when the polymerization time is high-speed polymerization within 6 hours.
VC can be manufactured. A small polymerization reactor having an internal volume of less than 40 m ³ requires a large number of polymerization reactors because the production amount per batch is small, and is not economical.

The PVC used in the present invention may contain VC alone or other vinyl monomers copolymerizable with VC as long as the above-mentioned production method 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 acrylate and ethyl (meth) acrylate; olefins such as ethylene and propylene, (meth) acrylic acid, maleic anhydride,
Examples include, but are not limited to, acrylonitrile, styrene, and the like.

In the polymerization method of the present invention, a suspending agent such as a dispersant and a surfactant is used. Examples of the suspending agent include those usually used for suspension polymerization of vinyl chloride. For example, partially saponified polyvinyl acetate; water-soluble cellulose such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose; polyethylene oxide Water-soluble polymers such as polyacrylic acid and gelatin, oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan monostearate, glycerin tristearate, ethylene oxide propylene oxide block copolymer, and polyoxyethylene sorbitan monolau. And water-soluble emulsifiers such as polyoxyethylene glycerin oleate and sodium laurate. These may be used alone or in combination of two or more. The suspending agent may be used in its entirety from the beginning of the polymerization, or a part thereof may be added during the polymerization.

As a method for charging water, VC, a suspending agent, a polymerization initiator and other auxiliaries in the present invention, a method used in ordinary suspension polymerization is suitably employed.
A method of sequentially adding water, a suspending agent, a polymerization initiator, and VC to a polymerization vessel, a method of continuously and simultaneously charging them, and a method of sequentially or simultaneously charging an aqueous solution of a suspending agent and VC in which a polymerization initiator is dissolved, and the like. No. The weight ratio of water to VC is preferably in the range of 1/1 to 1.7 / 1.

In the present invention, if necessary, a chain transfer agent such as mercaptoalkanol and alkyl thioglycolate, and a PH adjuster such as sodium polyphosphate may be added. The polymerization temperature of the present invention is 40 to 65 ° C.
Is preferred.

[0025]

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 stainless steel polymerization vessel equipped with a 50 m ³ jacket and an RC, 23,800 kg of deionized water and partially saponified polyvinyl acetate (average polymerization of saponification degree 72 mol%) Degree 800) 10.5k
g, 2.3 kg of hydroxypropyl methylcellulose,
18,000 kg of VC, 5.0 kg of α-cumylper-oxyneodecanoate and 2.7 kg of di-2-ethoxyethylperoxydica-bonate were charged as polymerization initiators. The temperature in the polymerization vessel was raised to 56 ° C., and after reaching 56 ° C., the operation of RC was started gradually. 2.3 hours after reaching 56 ° C., 0.5 kg of a polymerization inhibitor hydroquinone
It was added to control the polymerization reaction. Thereafter, the pressure of the polymerization vessel was increased to 2.
Unreacted VC was collected at the time of the decrease of 0 kg / cm ² , and the obtained PVC was dehydrated and dried. The polymerization time was 5.1 hours.

(Examples 2 to 6, Comparative Examples 1 and 2) The polymerization initiator and the polymerization inhibitor were of the kind and amount indicated in the table, and the polymerization temperature and the timing of the addition of the polymerization inhibitor were described in Table 1. The procedure was performed in the same manner as in Example 1, except that

The following evaluations were performed on the PVCs obtained in the above Examples and Comparative Examples, 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.

[0029]

[Table 1]

[0030]

The process for producing PVC according to the present invention is as described above. When high-speed polymerization is carried out using a large-sized polymerization vessel of 40 m ³ or more provided with RC, a polymerization initiator and a polymerization inhibitor having a specific activity are provided. By using, the particles are not coarsened and PVC with little fish eyes can be produced with high efficiency.

Claims (3)

[Claims] 1. When a vinyl chloride monomer is polymerized in an aqueous medium in a polymerization vessel having an inner volume of 40 m ³ or more equipped with a reflux condenser, the polymerization is completed within 6 hours.
A method for producing a vinyl chloride resin, comprising using a polymerization initiator having a 0-hour half-life temperature of 30 to 55 ° C. and adding a polymerization inhibitor during the polymerization reaction. 2. The method according to claim 1, wherein the polymerization initiator comprises at least α-cumyl par-
2. The method for producing a vinyl chloride resin according to claim 1, wherein the method comprises oxyneodecanoate. 3. The method for producing a vinyl chloride resin according to claim 1, wherein the polymerization inhibitor is added at a stage when the polymerization conversion of the vinyl chloride monomer is 30 to 80% by weight.