JPH07173203A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To improve the efficiency of heat removal from a polymerizer to thereby supplement the cooling capacity of the whole polymn. apparatus in the production process of a vinyl chloride polymer. CONSTITUTION:A vinyl chloride polymer is produced by subjecting vinyl chloride or a vinyl monomer mixture mainly comprising vinyl chloride to suspension polymn. in an aq. medium in the presence of an oil-sol. polymn. initiator under conditions that a combination of a compd. having a 10-hr half-life temp. lower than 40 deg.C in a concn. of 0.1mol/d in benzene with a compd. having a 10-hr half-life temp. of 40-60 deg.C is used as the oil-sol. polymn. initiator and that the polymn. is carried out while continuously elevating the polymn. temp. at least by 10 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a vinyl chloride polymer by a suspension polymerization method.

[0002]

2. Description of the Related Art Conventionally, suspension polymerization of vinyl chloride-based monomers requires an aqueous medium, a vinyl chloride-based monomer, a polymerization initiator, a dispersant and a necessary amount in a polymerization vessel equipped with a jacket and a reflux condenser. It has been carried out by charging various other additives according to the circumstances, heating the mixture to a desired temperature, and then passing cooling water through a jacket and a reflux condenser to remove the heat of polymerization and controlling the reaction system at a constant temperature.

However, with the recent increase in the size of the polymerization vessel, the ratio of the heat transfer area to the polymerization reaction product decreases, which causes a problem that the time required for temperature rise becomes longer and the cooling capacity becomes insufficient. occured.

In order to avoid the above problems, either or both of the aqueous medium and the monomer are preheated and charged into the polymerization vessel (so-called hot charge), or the reflux condenser is made large. Measures have been taken such as increasing the amount of heat removed or forcing the cooling water passing through the jacket of the polymerization vessel through a refrigerator to perform strong cooling.

[0005]

However, according to the above-mentioned hot charge method, when the polymerization initiator is charged into the polymerization vessel, the polymerization initiator is rapidly decomposed, so that the polymerization is started during the charging of the raw materials. Therefore, it is extremely difficult to control the polymerization, the fish eyes of the obtained polymer remarkably increase, coarse particles are generated, and the scale adhesion to the wall of the polymerization vessel also increases.

Further, in the method of increasing the size of the condenser to enhance cooling, scale is attached to the inside of the vessel due to carryover accompanying foaming of the polymerization reaction product, and fish eyes in the polymer product are increased, so that the removal is eliminated. There is a restriction that this cannot be used as a heat removal means from the stage at the initiation of the polymerization, because the heat capacity is lowered, and if the condenser is used at a stage where the polymerization rate is low, the particle size of the polymer becomes coarse.

Further, the method of strengthening the cooling power of the cooling water by using a refrigerator is too costly and economically disadvantageous, and in the case of producing a vinyl chloride polymer having a high degree of polymerization, the polymerization temperature is high. There is a problem in that it is not possible to compensate for the lack of cooling capacity because the temperature difference between the cooling water temperature and the cooling water temperature cannot be large.

On the other hand, a method is known in which suspension polymerization is carried out while continuously raising the polymerization temperature (Japanese Patent Publication No.
46-18483, Japanese Patent Publication No. 49-20627, Japanese Patent Publication No. 3-57121
No.). This polymerization method is excellent in that part of heat generated by the reaction is used to raise the temperature of the contents, and therefore the heat load is reduced from the jacket or the condenser, but as the reaction temperature rises. The reaction rate also increases and the amount of heat generated increases. Therefore, the higher the reaction temperature, the higher the heat removal load, and it is difficult to sufficiently compensate for the insufficient cooling capacity of the polymerization vessel.

Accordingly, an object of the present invention is to effectively utilize the heat of polymerization reaction during the polymerization reaction and efficiently remove the heat of reaction to produce a high-quality vinyl chloride polymer with high productivity. To provide a possible method.

[0010]

According to the present invention, a vinyl chloride monomer or a mixture of vinyl-based monomers mainly containing the vinyl chloride monomer is suspended in an aqueous medium in the presence of an oil-soluble polymerization initiator. In the method for producing a vinyl chloride polymer by polymerizing, as the oil-soluble polymerization initiator, (A) a compound having a 10-hour half-life temperature lower than 40 ° C. at a concentration of 0.1 mol / liter in benzene, B) A step of using the compound having a 10-hour half-life temperature of 40 to 60 ° C. in combination and conducting the polymerization while continuously increasing the polymerization temperature in a range of at least 10 ° C. or more. A method for producing a vinyl chloride polymer is provided.

That is, the present invention provides a compound (A) having an 10-hour half-life lower than 40 ° C. as an oil-soluble polymerization initiator.
And a compound having a temperature of 10-60 hours of 40 to 60 ° C.
A remarkable feature is that suspension polymerization is carried out in combination with (B). That is, by using the oil-soluble polymerization initiator in such a combination, it is possible to effectively control the increase in the amount of heat generated due to the increase in the polymerization temperature, and for example, the heat generated by the polymerization at the end of the polymerization when the reaction temperature increases. It is possible to reduce the heat removal load of the jacket or the condenser because it is suppressed, and it has succeeded in supplementing the cooling capacity of the polymerization vessel.

Oil-Soluble Polymerization Initiator In the present invention, the oil-soluble polymerization initiator (A) having a 10-hour half-life temperature at a concentration of 0.1 mol / liter in benzene lower than 40 ° C. is, for example, acetylcyclohexylsulfonyl peroxide ( 26.5 ° C), isobutyryl peroxide (32.5 ° C), α-cumylperoxyneodecanoate (36.6 ° C), 2,4,4-trimethylpentylperoxy-2-neodecanoate (36 ° C), etc. These may be used alone or in combination of two or more.

Further, the temperature of the 10-hour half-life is 40 to 60 ° C.
Examples of the oil-soluble polymerization initiator (B) are diisopropylperoxydicarbonate (41 ° C), di-n-propylperoxydicarbonate (41 ° C), di-2-ethoxyethylperoxydicarbonate (43). C), di-
2-ethoxyhexyl peroxydicarbonate (43
C) etc., percarbonate compounds, t-hexyl peroxy neohexanoate (49 ° C.), t-butyl peroxy neodecanoate (46 ° C.), t-butyl peroxy neohexanoate (49 ° C.) , T-hexyl peroxypivalate (45 ° C.), t-butyl peroxypivalate (55 ° C.) and the like can be exemplified. These can be used alone or in combination of two or more kinds. can do. Of these, perester compounds are preferable.

In the present invention, the above oil-soluble polymerization initiator
It is preferable that (A) and (B) are selected so that the temperature difference between their 10-hour half-lives is 7 ° C or more. If this temperature difference is smaller than 7 ° C., the exothermic peak is concentrated at a specific time, which is not preferable. In addition, the combination ratio of these varies depending on the reaction conditions, but in general, (A) /
It is preferable that the ratio (B) is 1/9 to 2/3.
When the above ratio is lower than 1/9, the heat generation amount remarkably increases in the latter half of the high polymerization temperature, and when it is higher than 2/3,
Since the exothermic peak is reached in the first half of polymerization, it tends to be difficult to efficiently remove heat in both cases.
Further, the total amount of the above oil-soluble polymerization initiators is appropriately 0.03 to 0.3 parts by weight per 100 parts by weight of the charged monomers.

The addition of both of these polymerization initiators to the polymerization system is
It may be diluted with a solvent or dispersed in water to form an emulsion or suspension, and then it may be carried out together with water and / or a suspending agent or after these are charged, and a reactor after charging a vinyl chloride monomer. You may make it press-fit inside.

Examples of the monomer used in the monomer present invention method, in addition to vinyl chloride alone, as a main component a vinyl chloride, a mixture comprising a copolymerizable therewith vinyl monomer (usually a vinyl chloride
50% by weight or more) is preferably used. Examples of the comonomer copolymerized with vinyl chloride include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-
Α-Olefin such as undecene, 1-dodecene, 1-tridecene, 1-tetradecene; acrylic acid such as acrylic acid, methyl acrylate, ethyl acrylate or its ester; methacrylic acid such as methacrylic acid, methyl methacrylate or its ester Maleic acid or its ester; vinyl ester such as vinyl acetate and vinyl propionate; vinyl ether such as lauryl vinyl ether and isobutyl vinyl ether; maleic anhydride;
Acrylonitrile; styrene; vinylidene chloride; other monomers copolymerizable with vinyl chloride, and the like. These can be used alone or in combination of two or more.

Dispersants Suspension polymerization of these monomers in an aqueous medium according to the present invention is carried out by dispersing aids which are usually used in the polymerization of vinyl chloride monomers, such as methylcellulose and hydroxy. Ethyl cellulose, hydroxypropyl cellulose,
Water-soluble cellulose ethers such as hydroxypropylmethyl cellulose; water-soluble or oil-soluble partially saponified polyvinyl alcohol; acrylic acid polymers; water-soluble polymers such as gelatin; sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide propylene. Oil-soluble emulsifiers such as oxide block copolymers; polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate,
One or a combination of two or more water-soluble emulsifiers such as sodium laurate may be used.

Polymerization Conditions In the present invention, the above-mentioned two oil-soluble polymerization initiators are used and at least 10 ° C. or higher, particularly 10 to 40 ° C.
Suspension polymerization can be carried out by a method known per se except that the polymerization temperature is continuously increased within a range of, for example, an aqueous medium to the polymerization vessel, a vinyl chloride-based monomer, a dispersion aid, etc. The charging method, charging ratio, etc. may be the same as in the conventional case.

If the increase in the polymerization temperature is less than 10 ° C., the heat load on the jacket, condenser, etc. cannot be sufficiently reduced, and the heat removal effect becomes unsatisfactory. Further, it is preferable that the temperature rise width is set so that the temperature at the start and end of the rise falls within the range of 35 to 80 ° C.

The rate of increase of the polymerization temperature varies depending on the combination of the polymerization initiators used, but it is generally carried out at a rate of temperature increase of 5 to 20 ° C. per hour, and the temperature is gradually increased depending on the state of heat generation. It can be changed. In addition, since the degree of polymerization of the obtained vinyl chloride-based polymer is roughly determined by the reaction temperature, it is possible to obtain a chloride obtained by providing a step of controlling the polymerization temperature at a constant temperature before, during, or after the increase of the polymerization temperature. It is also possible to adjust the degree of polymerization of the vinyl polymer.

Further, in this polymerization system, if necessary, a polymerization regulator, a chain transfer agent, a pH regulator, a gelation improving agent, an antistatic agent, a cross-linking agent, which are appropriately used for vinyl chloride-based polymerization,
It is also optional to add stabilizers, fillers, antioxidants, buffers, scale inhibitors and the like.

[0022]

【Example】

Example 1 A jacketed stainless steel polymerization vessel having an internal volume of 2 m ³ was charged with 850 kg of deionized water, and 206 g of partially saponified polyvinyl alcohol and 137 g of cellulose ether were dissolved in 1 kg of water to obtain 1343 g of an aqueous solution. Was charged into the polymerization vessel. After degassing the inside of the polymerization vessel to 50 mmHg,
Charge 685 kg of vinyl chloride monomer, stir,
Isobutyryl peroxide (10-hour half-life temperature 32.5 ° C)
103 g, α-cumyl peroxy neodecanoate (at the same temperature of 36.6 ° C.), 137 g, and t-butyl peroxy neodecanoate (at the same temperature of 46 ° C.) 240 g were pumped into the polymerization vessel.

Next, the jacket is charged with hot water,
The temperature of the mixture was raised to 40 ° C to initiate polymerization. After the initiation of the polymerization, the temperature of the charged mixture was continuously raised to 57 ° C. in 1.5 hours while utilizing the heat of polymerization reaction generated and controlling the temperature of the water passing through the jacket. Then, polymerization was carried out for an additional 1 hour while maintaining the temperature of the charged mixture at 57 ° C.

Thereafter, the temperature of the charged mixture was continuously raised to 70 ° C. in 1.5 hours while utilizing the heat of polymerization reaction again generated and controlling the temperature of the water passing through the jacket. Kept at. The pressure in the polymerization vessel is 8.5 (kgf /
The reaction was stopped when it reached (cm ² G). After that, the unreacted monomer was recovered from the inside of the polymerization vessel, and the obtained polymer was taken out of the vessel in a slurry form and dehydrated and dried.

Further, the time from the addition of the polymerization initiator to the termination of the polymerization, the ratio of the amount of heat of polymerization used for heating the polymerization to the total amount of heat of the polymerization reaction, and the minimum jacket temperature when cooling water was passed through the jacket were measured. The results are shown in Table 1. Further, the obtained vinyl chloride polymer was measured for average polymerization degree, bulk specific gravity, particle size distribution, and plasticizer absorption amount by the following methods. The results are shown in Table 1.

(1) Average degree of polymerization: Measured according to JIS K6721. (2) Bulk specific gravity: Measured according to JIS K6721. (3) Particle distribution: Sieving was performed using # 60, # 100, and # 200 sieves according to JIS Z-8801, and the passing amount (% by weight) was measured. (4) Absorption amount of plasticizer: Glass fiber is packed in the bottom of an aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm, and 10 g of a sample vinyl chloride polymer is sampled and charged. To this, 15 cc of dioctyl phthalate (hereinafter referred to as DOP) is added and left for 30 minutes to allow the DOP to sufficiently penetrate the polymer. Then 1500G
Excess DOP was centrifuged under the acceleration of 10 g, and the amount of DOP absorbed in 10 g of the polymer was measured and converted to 100 g of the polymer.

Comparative Example 1 In Example 1, hot water was passed through the jacket to start the polymerization to 57 ° C. to raise the temperature, and then cooling water was passed through the jacket to keep the temperature to continue the polymerization.
Polymerization was performed in the same manner except that the polymerization was stopped when the amount reached 0 kg / cm ² G to obtain a polymer. Furthermore, in the same manner as in Example 1, the ratio of the amount of heat of polymerization used for heating the polymerization, the measurement of the minimum jacket temperature, and the obtained vinyl chloride polymer, the average degree of polymerization, the bulk specific gravity, the particle size distribution, the plasticizer absorption amount. Was measured. The results are shown in Table 1.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that 480 g of t-butylperoxyneodecanoate was used alone as a polymerization initiator, and the ratio of the amount of heat of polymerization used for raising the temperature of the polymerization,
The minimum jacket temperature was measured, and the obtained vinyl chloride polymer was measured for average polymerization degree, bulk specific gravity, particle size distribution, and plasticizer absorption amount. The results are shown in Table 1.

[0029]

[Table 1] The amount of heat of polymerization used was indicated by the ratio (%) of the amount of heat of polymerization reaction used to raise the temperature of polymerization to the total amount of heat of polymerization reaction.

[0030]

INDUSTRIAL APPLICABILITY In the present invention, by using two kinds of polymerization initiators having a specific half-life in combination and conducting the polymerization while raising the polymerization temperature, the heat removal efficiency of the polymerization vessel is improved and the polymerization apparatus in general. It becomes possible to make up for the lack of the cooling capacity, and it is particularly effective when the polymerization time is within 5 hours.

Claims (1)

[Claims] 1. A vinyl chloride polymer is obtained by suspension-polymerizing a vinyl chloride monomer or a mixture of vinyl monomers mainly composed of this in an aqueous medium in the presence of an oil-soluble polymerization initiator. In the method for producing, as the oil-soluble polymerization initiator, (A) a compound having a 10-hour half-life temperature at a concentration of 0.1 mol / liter in benzene lower than 40 ° C., and (B) the 10-hour half-life temperature are 40
A method for producing a vinyl chloride polymer, which comprises using a compound having a temperature of up to 60 ° C. in combination and performing the polymerization while continuously increasing the polymerization temperature in a range of at least 10 ° C. or more.