JPH09227606A - Production of vinyl chloride resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a vinyl chloride resin excellent in particle shape with high voids and also excellent in processability by a process wherein vinyl chloride monomer is subjected to suspension polymerization in a large polymerizer provided with a reflux condenser and which is free from abnormal foaming after the beginning of polymerization reaction even if the reflux condenser is operated from the time at which the vinyl chloride monomer is charged into the polymerizer. SOLUTION: In the suspension polymerization of a vinyl chloride monomer by using a polymerizer provided with a reflux condenser, the temperature in the reflux condenser is controlled to be 1-50 deg.C lower than the temperature of liquid in the polymerizer from the step of initiating the charging of the monomer, and the temperature in the reflux condenser is controlled to be 1-50 deg.C lower than the temperature of liquid in the polymerizer during the temperature raising step and the polymerization step.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a vinyl chloride resin.

[0002]

2. Description of the Related Art Conventionally, the polymerization of vinyl chloride-based monomers is usually carried out by a batch type water suspension polymerization method. That is, a method in which an aqueous medium and a dispersant are charged into a polymerization vessel, then a polymerization initiator is charged, and then a vinyl chloride monomer is charged after vacuum degassing the inside of the polymerization vessel, and the temperature is raised to carry out a polymerization reaction. Is.

By the way, in recent years, in the production of vinyl chloride-based polymers, enlargement of the polymerization vessel and reduction of the polymerization time have been studied in order to improve the productivity. For that purpose, it is necessary to efficiently remove the heat of the polymerization reaction, and for example, a method in which a reflux condenser is attached to the polymerization vessel is used.

Generally, in a large-scale polymerization vessel equipped with a reflux condenser, the polymerization reaction heat generated when polymerizing vinyl chloride-based monomers is preferentially removed by the polymerization vessel-side jacket and completely removed by the polymerization vessel-side jacket. The heat of reaction which cannot be removed in a supplementary manner is supplementarily removed by a reflux condenser.

However, when it is attempted to remove the heat of the polymerization reaction by the reflux condenser, remarkable foaming occurs especially at the initial stage of the polymerization, so that the foam of the polymerization suspension containing the polymerization initiator is generated on the wall surface of the gas phase portion of the polymerization tank. Attached to the inner wall of the reflux condenser,
This becomes a scale and significantly hinders the efficiency of heat removal, and adversely affects the particle formation in the initial stage of polymerization, so particles such as glass beads that do not have internal voids are generated, or the polymerization proceeds in the form of bubbles and coarse particles are generated. There was a problem such as formation of coalesced particles. Further, when the scale adheres, it takes a lot of time to remove it, and there is a problem that productivity is reduced.

For this reason, the heat removal by the reflux condenser is gradually started after a certain polymerization rate is reached after the initiation of the polymerization. For example, in Japanese Patent Publication No. 1-18082, the polymerization reaction is performed. A method is disclosed in which the heat removal amount of the reflux condenser is 35% or less of the total heat value of polymerization until the rate of polymerization reaches 5% after the initiation.

Further, a method of removing heat from the reflux condenser from the initial stage of polymerization has also been studied, and in order to control foaming, for example, in Japanese Patent Laid-Open No. 2-180908, the reflux condenser removes heat from the start of polymerization. A method has been proposed in which heat is applied to add a defoaming agent at a polymerization rate of 10% or less. Also, for example,
JP-A-6-136010 proposes a method of operating a reflux condenser from the start of polymerization by using polyethylene oxide having a molecular weight of 100,000 to 4.8 million as a dispersant.

As described above, various methods have been studied to operate the reflux condenser after the initiation of the polymerization reaction and prevent abnormal foaming at that time. However, the temperature of the reflux condenser is controlled before the initiation of the polymerization reaction. Nothing is said about controlling.

[0009]

The present invention has been made in view of the above-mentioned drawbacks, and an object thereof is to carry out suspension polymerization of a vinyl chloride resin in a large-sized polymerization vessel equipped with a reflux condenser. Even when the reflux condenser is operated from the time of charging the vinyl chloride monomer in the polymerization vessel, there is no abnormal foaming after the start of the polymerization reaction, the resin particle shape is excellent and the porosity is high, and the processability is also excellent. Another object of the present invention is to provide a method for producing a vinyl chloride resin.

[0010]

Means for Solving the Problems The method for producing a vinyl chloride resin according to the present invention is a method in which a vinyl chloride monomer is suspension-polymerized by using a polymerization vessel equipped with a reflux condenser. The temperature of the reflux condenser is controlled so as to be 1 to 50 ° C. lower than the liquid temperature in the polymerization vessel from the charging start step of, and the temperature of the reflux condenser is further controlled during the temperature raising step and the polymerization step. The temperature is controlled to be 1 to 50 ° C. lower than the temperature.

The vinyl chloride-based monomer referred to in the present invention includes vinyl chloride monomer alone, vinyl chloride monomer and a mixture of monomers copolymerizable with the vinyl chloride monomer.

Examples of the monomer copolymerizable with the vinyl chloride monomer include vinyl esters such as vinyl acetate and vinyl propionate; and (meta) such as methyl (meth) acrylate and ethyl (meth) acrylate. ) Acrylic acid ester: In addition to olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, styrene, vinylidene chloride, and other monomers copolymerizable with vinyl chloride are included, but are not limited to these. .

In the production method of the present invention, a polymerization vessel having a reflux condenser and a heating and cooling jacket on the polymerization vessel side is used.

The suspension polymerization operation in the production method of the present invention is carried out by the following procedure. First, a predetermined amount of water in the polymerization vessel,
A dispersant is charged and the inside of the polymerization vessel is deaerated in vacuum. The temperature of the charged water is not particularly limited, but it is preferable to heat it in order to shorten the subsequent temperature raising step, and the temperature is 30 ° C.
To a predetermined polymerization temperature range is preferred. The temperature of the jacket is preferably controlled to be equal to or higher than the temperature of the charged water. In the process of vacuum degassing, the reflux condenser may be activated or deactivated.

Next, the process of charging the vinyl chloride monomer is started, but before this, the reflux condenser is operated and the temperature of the reflux condenser is controlled to be 1 to 50 ° C. lower than the liquid temperature in the polymerization vessel. However, the temperature is preferably 3 to 10 ° C. lower than the liquid temperature. Then, a predetermined amount of vinyl chloride monomer is charged. After the completion of charging the vinyl chloride-based monomer, a polymerization initiator is press-fitted to raise the temperature of the jacket on the polymerization vessel side to raise the liquid temperature in the polymerization vessel to a predetermined polymerization temperature. In the above, the temperature of the reflux condenser is always controlled to be 1 to 50 ° C. lower than the liquid temperature in the polymerization vessel, but it is preferably 3 to 10 ° C. lower than the liquid temperature.

After reaching the predetermined polymerization temperature, the temperature of the jacket is controlled to be equal to or lower than the liquid temperature in the polymerization vessel, and the temperature of the reflux condenser is controlled to be 1 to 50 ° C. lower than the liquid temperature in the polymerization vessel.
The temperature is preferably 5 to 40 ° C. lower than the liquid temperature. The rate of heat removal by the reflux condenser is preferably 10 to 100% of the total calorific value.

Further, in order to shorten the charging time, a method of charging water and a monomer at the same time is also possible. That is, after degassing the inside of the polymerization vessel under vacuum, the temperature of the jacket side of the polymerization vessel and the temperature of the reflux condenser are kept constant, and then water and vinyl chloride monomer are simultaneously charged into the polymerization vessel. Is. In this method, it is preferable to keep the temperature of the jacket within a predetermined polymerization temperature range of ± 5 ° C. before charging, but it is not particularly limited.

The temperature of the reflux condenser is 1 to 5 depending on the temperature of the mixture of water and vinyl chloride-based monomer obtained by charging at the same time.
The temperature is controlled to be 0 ° C. lower, but preferably 3 to 20 ° C.
Low temperature. Here, as a method of charging at the same time, a method of starting the introduction of water and a vinyl chloride monomer at the same time and ending the introduction at the same time; starting the introduction of water first and charging the vinyl chloride monomer during the introduction Examples thereof include, but are not limited to, methods. The temperature of the mixed solution of water and the vinyl chloride-based monomer at the end of charging is usually preferably equal to or lower than the predetermined polymerization temperature.

Then, after the completion of charging the above-mentioned water and monomer, a polymerization initiator is injected under pressure to raise the jacket temperature on the side of the polymerization vessel to raise the liquid temperature in the polymerization vessel. Is controlled to be 1 to 50 ° C. lower than the liquid temperature in the polymerization vessel, but is preferably 3 to 20 ° C. lower.

Even after the liquid temperature in the polymerization vessel reaches a predetermined polymerization temperature, the jacket temperature is kept below the liquid temperature in the polymerization vessel to carry out the polymerization reaction. The temperature of the reflux condenser at the time of polymerization is controlled to be 1 to 50 ° C. lower than the liquid temperature in the polymerization device, but preferably 5 to 40 ° C. lower. The rate of heat removal by the reflux condenser is preferably 10 to 100% of the total calorific value.

In the above polymerization reaction, the dispersant is added, but the dispersant may be added at the same time as or after the addition of water and the monomer. The dispersant may be added either collectively or separately.

Examples of the above-mentioned dispersant include those used in ordinary suspension polymerization of vinyl chloride. Examples thereof include water-soluble cellulose such as methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose; Polyvinyl alcohol, polyethylene oxide, acrylic acid, water-soluble polymers such as gelatin; sorbitan monolaurate, water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate and the like, these may be used alone, Two or more kinds may be used in combination.

The amount of the dispersant used is preferably 0.005 to 2% by weight based on the vinyl chloride monomer.

The polymerization initiator used in the present invention includes
Examples include oil-soluble polymerization initiators used for ordinary vinyl chloride suspension polymerization, for example, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, α-cumylperoxyneodecanate,
t-butyl peroxy neodecanoate, t-butyl peroxypivalate, t-butyl peroxy-3,5,5
-Trimethylhexanoate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, lauroyl peroxide, etc. may be used, and these may be used alone, and two or more kinds thereof may be used. You may use together.

Further, if necessary, a polymerization regulator, a polymerization inhibitor, which is usually used for the polymerization of vinyl chloride type monomers,
Chain transfer agents, pH adjusters, stabilizers, scale inhibitors and the like may be added.

The above-mentioned polymerization reaction is preferably stopped when the internal pressure of the polymerization reactor decreases from the pressure during operation by a predetermined pressure, or when a certain time has elapsed from the start of polymerization. After stopping the reaction, the jacket and the reflux condenser are cooled, the remaining unreacted monomer is discharged as an exhaust gas, and the resulting slurry is dehydrated and dried to obtain a vinyl chloride polymer.

As described above, in the production method of the present invention, the porosity is maintained by maintaining the temperature of the reflux condenser lower than the liquid temperature in the polymerization vessel from the time of charging the vinyl chloride-based monomer until the polymerization reaction. It is possible to obtain polymer particles having high processability. Further, it is preferable that the present production method can prevent abnormal foaming even if heat is rapidly removed by the reflux condenser after the initiation of the polymerization reaction, and therefore abnormal polymerization such as coarsening of polymer particles can be prevented.

The rate of heat removal by the reflux condenser can be calculated by the following formula. -Ratio of heat removal by the reflux condenser = heat removal amount of the reflux condenser /
Total calorific value-Removal condenser heat removal amount = Reflux condenser cooling water inlet / outlet temperature difference x cooling water flow rate-Total calorific value = Vinyl chloride-based monomer weight x Monomer unit weight calorific value ( Reference value) x Polymerization rate (measured value)

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Jacket and heat transfer area
Using a stainless steel polymerization vessel with an internal volume of 600 liter equipped with a reflux condenser of 5 m ² , the jacket was heated to 50 ° C., then 250 kg of ion exchanged water at 40 ° C., and a saponification degree of 7
200 g of 2 mol% partially saponified polyvinyl alcohol (“Gosenol KZ-05” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 40 g of polyethylene oxide having an average molecular weight of 4.3 million (“PEO-18” manufactured by Sumitomo Seika Chemical Co., Ltd.) were charged and placed in a polymerization vessel. 13
A vacuum was applied up to kPa. Next, the reflux condenser was operated to adjust the temperature to 30 ° C., and then 250 kg of vinyl chloride monomer was charged into the polymerization vessel. The temperature of the suspension after charging is 38 ° C.
Met. Further, 300 g of a polymerization initiator di-2-ethylhexyl peroxydicarbonate (“Perloyl OPP” manufactured by NOF CORPORATION) was press-fitted with nitrogen, and then the jacket temperature was raised to raise the liquid temperature in the polymerization vessel to 57 ° C. did.
Along with this, the temperature of the reflux condenser was also raised, but the temperature was controlled so that it was always 5 ° C. lower than the liquid temperature in the polymerization vessel.

The polymerization reaction was carried out while maintaining the temperature of the liquid in the polymerization vessel at 57 ° C. At this time, the temperature of the jacket was 57 ° C.
The temperature of the reflux condenser was controlled at 30 ° C., and the heat removal rate in the reflux condenser was 100%. After 4 hours, the pressure inside the polymerization vessel dropped to 0.6 MPa. Therefore, the jacket and the reflux condenser were cooled, unreacted monomers were recovered, and the polymerization reaction was stopped. The resulting polymer slurry was dehydrated and dried to obtain a vinyl chloride resin. During the polymerization step, changes over time in the temperature of the reflux condenser and the liquid temperature in the polymerization vessel are shown in FIG.

(Examples 2 to 5, Comparative Examples 1 to 4) Except that the temperature of the reflux condenser at the time of charging and the temperatures of the jacket and the reflux condenser at the time of the polymerization reaction were changed as shown in Tables 1 and 2. Was subjected to a polymerization reaction in the same manner as in Example 1 to obtain a vinyl chloride resin. During the polymerization step of Comparative Example 1,
Fig. 2 shows the changes over time in the temperature of the reflux condenser and the liquid temperature in the polymerization vessel.
It was shown to.

[0033]

[Table 1]

[0034]

[Table 2]

Example 6 Jacket and heat transfer area
Using a stainless steel polymerization vessel having an internal volume of 600 liters equipped with a 5 m ² reflux condenser, the jacket was heated to 65 ° C. and the reflux condenser was heated to 40 ° C., and then the inside of the polymerization vessel was evacuated to 13 kPa. Then, 250 kg of vinyl chloride monomer preheated to 55 ° C. and 250 kg of ion-exchanged water preheated to 55 ° C. were simultaneously charged into the polymerization vessel. further,
At the same time, a partially saponified polyvinyl alcohol having a saponification degree of 76 mol% (“Poval L-8” manufactured by Kuraray Co., Ltd.) 12
5 g, 30 g of polyethylene oxide having an average molecular weight of 8 million (“PEO-28” manufactured by Sumitomo Seika Chemical Industries, Ltd.) and 125 g of hydroxypropylmethyl cellulose (“Metrose 65SH50” manufactured by Shin-Etsu Chemical Co., Ltd.) were charged to the polymerization vessel. The liquid temperature in the polymerization vessel after charging was 56 ° C.

Then, 300 g of a polymerization initiator di-2-ethylhexyl peroxydicarbonate ("Perloyl OPP" manufactured by NOF CORPORATION) was pressured with nitrogen, and then the polymerization temperature was controlled at 57 ° C to carry out the polymerization reaction. Started. At this time, the temperature of the jacket is 57 ° C and the temperature of the reflux condenser is 30 ° C.
The heat removal rate in the reflux condenser was set to 100%.
After 4 hours, the pressure inside the polymerization vessel dropped to 0.6 MPa, so the jacket and the reflux condenser were cooled, unreacted monomers were recovered, and the polymerization reaction was stopped. The resulting polymer slurry was dehydrated and dried to obtain a vinyl chloride resin.

(Examples 7 to 10 and Comparative Examples 5 to 8) Other than changing the temperature of the reflux condenser during charging, and the temperatures of the jacket and the reflux condenser during the polymerization reaction as shown in Tables 5 and 6. Was subjected to a polymerization reaction in the same manner as in Example 6 to obtain a vinyl chloride resin.

[0038]

[Table 3]

[0039]

[Table 4]

The vinyl chloride resins obtained in the above Examples and Comparative Examples were evaluated as follows, and the results are shown in Tables 5-8.
It was shown to. (1) Degree of polymerization Measured in accordance with JIS K6721. (2) Particle size distribution Measured according to JIS K8801. (3) Bulk specific gravity Measured according to JIS K6721. (4) Porosity Using a mercury intrusion porosimeter, the volume of mercury injected per 100 g of the vinyl chloride resin at 196 MPa was measured to determine the porosity. (5) Glass bead-shaped resin particles Sifted through a 42-mesh standard sieve, the particles remaining on the sieve were observed with a microscope, and the number of semitransparent particles was calculated. (6) Gelation time 100 g of the obtained vinyl chloride resin was added with 2 g of dibutyltin mercapto (“JF-10B” manufactured by Sankyo Machine Gosei Co., Ltd.) and an ester wax (“WAX-OP” manufactured by Hoechst).
A resin composition was prepared by adding 0.5 g, and 65 g of this resin composition was added to Haake Plastograph “Reo Code 90”.
Then, the time until gelation was measured at 190 ° C. and a rotation speed of 50 rpm.

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

[Table 7]

[0044]

[Table 8]

[0045]

The constitution of the method for polymerizing a vinyl chloride resin of the present invention is as described above, and when a suspension polymerization of a vinyl chloride resin is carried out in a large-scale polymerizer equipped with a reflux condenser, Even if the reflux condenser is operated from the time when the vinyl chloride monomer is charged, the slurry does not scatter due to foaming of the monomer, and it is possible to prevent abnormal polymerization such as adhesion of scale and coarsening of particles. it can. Therefore, the obtained vinyl chloride-based resin particles, compared with the vinyl chloride-based polymer obtained by operating the reflux condenser after the start of the conventional polymerization, does not generate glass bead-shaped resin, and has a high bulk specific gravity. High porosity, good particle size distribution, and excellent workability.

[Brief description of drawings]

FIG. 1 is a graph showing changes over time in the temperature of a reflux condenser and the liquid temperature in a polymerization vessel during the polymerization process of Example 1.

2 is a graph showing changes over time in the temperature of the reflux condenser and the liquid temperature in the polymerization vessel during the polymerization step of Comparative Example 1. FIG.

Claims (1)

[Claims] 1. When suspension-polymerizing a vinyl chloride-based monomer using a polymerization vessel equipped with a reflux condenser, the temperature of the reflux condenser is adjusted from the starting step of charging the monomer to the liquid inside the polymerization vessel. 1 from warm
The temperature of the reflux condenser is controlled to be lower by -50 ° C, and the temperature of the reflux condenser is controlled to be lower than the liquid temperature in the polymerization reactor by 1-50 ° C during the temperature raising step and the polymerization step. Method for producing a base resin.