JP2622040B2 - Method for producing vinyl chloride polymer - Google Patents

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 polymer, and more particularly, to an industrial method for producing a vinyl chloride polymer for producing a high quality vinyl chloride polymer with high efficiency.

[0002]

2. Description of the Related Art Conventionally, when a vinyl chloride polymer is produced by a batch suspension polymerization method, water, a suspending agent,
Charge polymerization initiator, monomer and other additives,
The polymerization is carried out by elevating the content to a predetermined polymerization temperature by means such as circulating warm water through the jacket. However, especially in a large-sized polymerization vessel, the charging time is long due to a large amount of charging, and a long time is required to raise the temperature because the heat transfer area of the jacket is relatively small with respect to the capacity of the polymerization vessel. This was one of the factors that hindered the operation rate of the polymerization reactor.

[0003] As a method of solving such a problem,
A method in which a pre-warmed aqueous medium (a mixture in which a suspending agent is dissolved in water) and a uniform mixture of a monomer and a polymerization initiator are simultaneously charged (Japanese Patent Publication No. 62-39601). A method in which the polymerization temperature is adjusted to a predetermined polymerization temperature at the end of the preparation of the total amount of both the water in which is dissolved and the monomer in which the polymerization initiator is dissolved (Japanese Patent Publication No. 60-26488). There is known a method in which an agent is charged and uniformly mixed, and then water heated and degassed at 50 to 80 ° C. in advance (JP-A-58-21408).

However, the method of heating water (water solution of a suspending agent) in which a suspending agent is dissolved as in Japanese Patent Publication No. 60-26488 is thought to be because the surface activity of the suspending agent is reduced by heating. However, not only does a large amount of scale adhere to the inner wall surface of the polymerization vessel and the fish eyes increase, but the polymer particles obtained become coarse and, in extreme cases, solidify in a lump and are discharged from the polymerization vessel. There was a disadvantage that it became difficult.

[0005] In particular, similar inconveniences are remarkable in suspensions having a low cloud point, and it is difficult to use them. The cloud point serves as an index of the degree to which the surface active ability of the suspending agent is reduced by heating, and is the temperature at which the aqueous solution of the suspending agent starts to become cloudy when the temperature is raised.

On the other hand, Japanese Patent Publication No. 58-50603 discloses a method for preventing the formation of coarse particles and an increase in fish eyes by adding a suspending agent and a part of water to be present in a polymerization system in a state of cold water. There has been proposed a method of charging, then charging a monomer, and finally charging heated water. However, according to this method, there is an effect that formation of coarse particles and increase of fish eyes can be prevented, but the charging time cannot be shortened because water and monomer are charged sequentially. In addition, there is a drawback in that the preparation operation is complicated since cold water or hot water is used for the preparation water.

On the other hand, a method of charging a mixture in which a polymerization initiator is dissolved in a monomer in advance (Japanese Patent Publication No. 62-39601)
No. 60-26488) requires equipment such as a tank and a mixer for preparing the mixture, which not only complicates the preparation operation but also prevents the polymerization from starting during the preparation. Therefore, there is a restriction that the mixture is kept at a low temperature, the charge ratio of the polymerization initiator to the monomer is reduced, or only a polymerization initiator having a high decomposition temperature can be used. Further, it is considered that during the charging, the polymerization is rapidly started at the same time as the mixture is brought into contact with the warm water before being uniformly suspended and stabilized in the aqueous medium as oil droplets in the polymerization vessel. Has a disadvantage that it has a large amount of coarse particles and increases fish eyes, and a part of the mixture adheres to the inner wall surface of the polymerization vessel to increase the scale and decrease the heat removal ability for removing heat of polymerization reaction. Had the disadvantage of doing so.

[0008] Further, as in the method according to JP-A-58-21408, a method in which a monomer and a polymerization initiator are charged into a polymerization vessel, and the resulting mixture is uniformly mixed, and then heated water is charged is also used. During the charging, there is a drawback that the scale is remarkably increased because of direct contact with the inner wall surface of the polymerization vessel and the polymerization is started therein, and that only low-quality polymer particles having poor particle size and fish eye are obtained.

[0009] These drawbacks are that the higher the concentration of the polymerization initiator dissolved in the monomer, that is, the shorter the polymerization time, and the higher the temperature of the pre-heated water, that is, the temperature rise to a predetermined polymerization temperature. The shorter the time required, the more remarkable.

Any of these known methods has the advantage that the charging time and / or the time for raising the temperature can be shortened, but since the scale adheres to the wall of the polymerization vessel, the ability to remove the heat of the polymerization reaction is reduced. It became difficult to shorten the polymerization time, and the effect of increasing the operation rate of the polymerization vessel was insufficient. In addition, there is also a disadvantage that the obtained polymer particles are coarsened, resulting in a decrease in quality such as an increase in fish eyes.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the scale from adhering to the inner wall surface of a polymerization vessel and to initiate polymerization without causing coarsening of polymer particles and increase of fish eyes. In addition to shortening the charging time and heating time of the reactor, the operation rate of the polymerization reactor is greatly improved by completing the polymerization in a short time using a large polymerization reactor with enhanced heat removal capacity for the polymerization reaction heat. It is an object of the present invention to provide a production method for producing a high-efficiency and high-quality vinyl chloride polymer.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
In suspension polymerization of a vinyl chloride monomer in an aqueous medium in the presence of an oil-soluble polymerization initiator, 70% by weight of the total charged amount of each of the monomer and pre-warmed water in a polymerization vessel. At the same time, the above components were simultaneously charged and (A) the degree of saponification was 75 to 90 mol% and the average degree of polymerization was 10
(B) a saponification degree of 65 to 75 mol%, and an average polymerization degree of 50
(C) a saponification degree of 15 to 54 mol%, and an average degree of polymerization of 10
0-1200 partially saponified polyvinyl acetate,
The total amount of (A) and (B) per 100 parts by weight of vinyl chloride is 0.03 to 0.15 parts by weight, and the amount of (C) is 0.01 to 100 parts by weight.
0.1 parts by weight, weight ratio of (A) and (B) (A) / (B)
Is used in an amount of 1/5 to 4/5 , and at least 20% by weight of the total charged amount of the suspending agent is charged during the charging of the monomer, and the charged amount of the monomer is 30% of the total charged amount. % And thereafter until it reaches 100% and when the weight ratio of the monomer to water in the polymerization vessel is 1.5 or less, the entire amount of the polymerization initiator is charged, and the monomer, water, After charging all of the turbidity agent and the polymerization initiator, the contents of the polymerization vessel are allowed to reach the polymerization temperature, the polymerization is subsequently carried out, and the polymerization is completed within a polymerization time of 6 hours or less. .

Hereinafter, the present invention will be described in detail. In carrying out the present invention, first, 70% by weight or more of the total charged amount of each of the monomer and the preheated water is simultaneously charged into the degassed polymerization vessel. The remaining charge of less than 30% by weight of each of monomer and water need not necessarily overlap. If the above-mentioned simultaneous charging amount is less than 70% by weight, the charging time is not shortened, so that it is difficult to achieve the object of the present invention. In the charging of both, the charging of water may be started first, and the charging of the monomer may be started during the charging, or vice versa.

The feed water used in the polymerization in the present invention is:
At the end of the charging of water and the total amount of the monomers, the temperature inside the polymerization vessel (t) is increased in advance outside the polymerization vessel so that T-10 ≦ t ≦ T + 5 (° C.) with respect to the predetermined polymerization temperature (T). It is preferable to keep it warm. If the internal temperature is lower than (T-10) ° C., the effect of shortening the temperature raising time is insufficient, and if the internal temperature exceeds (T + 5) ° C., the pressure in the polymerization vessel rises sharply and the polymerization reaction runs away, so it is dangerous. It is. The temperature of the water is usually carried out in the range of about 40-80 ° C. It is desirable that the water be degassed before heating.

The suspending agents used in the present invention are three partially saponified polyvinyl acetates having the following characteristics. (A) The degree of saponification is 75 to 90 mol%, and the average degree of polymerization is 10
(B) a partially saponified polyvinyl acetate having a cloud point of 40 ° C. or higher, (B) a saponification degree of 65 to 75 mol%, and an average polymerization degree of 500 to 900;
(C) The degree of saponification is 15 to 54 mol%, and the average degree of polymerization is 10
0-1200 partially saponified polyvinyl acetate.

The suspending agent (A) is used for stabilizing the monomer oil droplets and the monomer oil droplets and polymer particles during the polymerization during suspension in an aqueous medium. ,
If the degree of saponification and the average degree of polymerization are out of the above ranges, a stable suspension cannot be obtained, and as a result, the polymer particles become coarse and fish eyes increase. The cloud point of the suspending agent (A) needs to be 40 ° C. or higher. If the cloud point is lower than 40 ° C., the polymer particles become coarse, and a large amount of scale adheres to the inner wall of the polymerization can.

The cloud point of the partially saponified polyvinyl acetate is determined by raising the temperature of an aqueous solution having a concentration of 1% by weight at a rate of 1 ° C./min from 20 ° C. to a total light transmittance of 90% of the value at 20 ° C.
It is obtained as a temperature that becomes a value.

The suspending agent (B) is used to increase the porosity of the polymer particles and to produce particles having a porous internal structure. The suspending agent and the average degree of polymerization are as described above. If the ratio is out of the range, the porosity of the polymer particles becomes small, so that the absorbability of the plasticizer decreases and the fish eyes increase.

The suspending agents (A) and (B) are used for suspending monomer oil droplets and polymer particles in an aqueous medium during the preparation and polymerization of the monomer as described above. It is used for producing particles having a porous internal structure while preventing scale from adhering to the inner wall surface and appropriately adjusting the particle size and bulk specific gravity. Therefore, it is essential to strictly specify the amounts and ratios of these two components, and the total amount of (A) and (B) charged per 100 parts by weight of the monomer is 0.03 to 0.15 parts by weight. is the preferably charged as feed weight ratio in 0.04 to 0.1 parts by weight, and the (a) (B) is (a) / (B) = 1 / 5~4 / 5.

If the total amount of (A) and (B) is less than 0.03 parts by weight, the suspension stability of monomer oil droplets and polymer particles during polymerization is impaired and coarse particles are formed. If the amount increases, the porosity decreases, and if it exceeds 0.15 parts by weight, the particle size becomes fine and the bulk specific gravity decreases. Further, the charged weight ratio (A) / (B) of (A) and (B) is 1 /
If it is less than 5, the suspension stability during the monomer preparation is impaired,
As a result, the scale generation on the inner wall surface of the polymerization vessel increases, and the bulk specific gravity of the polymer particles decreases or the polymer particles are coarsened. When (A) / (B) is more than 4/5 , the porosity is impaired, and the quality such as fish eye and plasticizer absorption is reduced, so that the object of the present invention cannot be achieved.

The suspending agent (C), which is the remaining component of the suspending agent system of the present invention, prevents the formation of a skin layer on the surface of the polymer particles and has the basic particles of the order of 1 to several μm inside the particles. Is essential to obtain a resin that is porous, has little fisheye, and has good plasticizer absorption. When the degree of saponification and the average degree of polymerization of the suspending agent (C) are out of the above-mentioned ranges, and when the charged amount of (C) per 100 parts by weight of the monomer is less than 0.01 part by weight, , These effects cannot be exhibited. On the other hand, if the amount exceeds 0.1 part by weight, the particle size becomes fine, and the specific gravity decreases.

It is necessary that at least 20% by weight of the total amount of the suspending agent used in the present invention be charged during the charging of the monomer. When the above value is less than 20% by weight, the suspension system in which the monomer is oil droplets cannot be stabilized during the preparation, and adverse effects such as scale formation, coarsening, and an increase in fish eyes are not obtained. Occurs. It is preferable that the suspension liquid is adjusted and mixed at a ratio and a charge amount specified in advance, and the suspension is dissolved or dispersed in water and directly charged into a polymerization vessel as a normal temperature liquid.

It is well known that a suspending agent has a property that it becomes hardly soluble when heated and its surface activity is reduced, and the suspending agent is also heated in the suspension polymerization of vinyl chloride. By doing so, the effect of suspending and stabilizing the monomer oil droplets decreases, so that the charging method in which the suspending agent is brought into contact with warm water outside the polymerization vessel is inappropriate. The suspending agent is used as a separate liquid from the charged water.
The most preferred embodiment is that the weight% is continuously charged simultaneously with the monomers while forming a suspension under stirring.

The oil-soluble polymerization initiator used in the present invention is used in a period from when the charged amount of the monomer reaches 30% to 100% of the total charged amount, and in a single amount in the polymerization vessel. It is necessary to charge the entire amount of the polymerization initiator when the weight ratio of the body to water is 1.5 or less. If the polymerization initiator is charged when the charged amount of the monomer is less than 30%, the distribution of the polymerization initiator to the individual monomer oil droplets after the charging of the entire amount of the monomer becomes inhomogeneous, and the scale is reduced. This is not preferred because fish eyes deteriorate.

In the method in which the polymerization initiator is charged after the entire amount of the monomer has been charged, the charging time becomes long and the start of the polymerization reaction is delayed, which is disadvantageous in achieving the object of the present invention. The polymerization initiator is charged at the end of the charging of the monomer, preferably at the time when 70 to 100% by weight of the monomer is charged and almost the suspension is completed, and the entire amount thereof is charged at once to obtain a single monomer. The most preferred embodiment is to uniformly adsorb and dissolve in body oil droplets.

On the other hand, if the weight ratio of the monomer present in the polymerization vessel to water exceeds 1.5, a so-called phase-inverted suspension having the monomer as a continuous phase is formed. At this point, if the polymerization initiator is added, it is considered that the monomer in which the polymerization initiator is dissolved becomes a continuous phase and directly contacts the inner wall surface of the polymerization vessel, where polymerization is performed. The object of the present invention cannot be achieved because the heat removal capability of the polymerization vessel is reduced.

After the components are charged into the polymerization reactor to start the polymerization in this way, the internal temperature of the polymerization reactor is maintained at a predetermined polymerization temperature while removing the heat of reaction to complete the polymerization. with the like advances in driving skills improvement and reflux condenser jacket structure of the polymerization vessel, by the removal capability of the polymerization reaction heat of the polymerization vessel was greatly improved, the internal volume 40 m ³ or more being employed on an industrial scale With regard to the large-sized polymerization vessel, high-speed polymerization capable of completing the polymerization within 6 hours in terms of heat removal capability has become possible.

In the present invention, when performing high-speed polymerization within 6 hours, heat transfer is performed by providing a passage for a cooling medium on the inner surface of the inner jacket type polymerization vessel described in Japanese Patent Publication No. 3-4249. It can be advantageously carried out by using a polymerization vessel with improved performance. Of course, it is also possible to adopt a method in which a reflux condenser is attached to the polymerization vessel to additionally remove the heat of the polymerization reaction.

In the present invention, as a method for completing the polymerization, the pressure in the polymerization vessel is about 0.5 to about 0.5 to a steady pressure during the polymerization.
A method may be used in which a polymerization inhibitor is added when 5 kg / cm ² has fallen, or an unreacted monomer is recovered from the polymerization vessel.
In the present invention, the time to complete the polymerization, that is, the polymerization time, after charging the monomer, the polymerization initiator, the suspending agent and water, the contents of the polymerization vessel reached a predetermined polymerization temperature. From the point in time, the pressure in the polymerization reactor changes for a while at the natural pressure at the reaction temperature, then begins to drop as the unreacted monomer decreases, and is defined as the time until the drop becomes 2 kg / cm ² I do.

In the present invention, the vinyl chloride monomer is mainly composed of vinyl chloride, but may contain another monomer copolymerizable with vinyl chloride. Examples of such a monomer include alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, α-monoolefins such as ethylene and propylene, and alkyl acrylates such as methyl acrylate and methyl methacrylate. But are not limited to these.

The polymerization initiator used in the present invention is not particularly limited, but one having a 10-hour half-life temperature of 30 to 60 ° C. is preferably used alone or in combination of two or more. The amount of the polymerization initiator charged varies depending on the polymerization conditions such as the type of polymerization initiator used and the polymerization temperature, but is usually within 6 hours by charging 0.01 to 2 parts by weight per 100 parts by weight of the monomer. The polymerization can be completed. Examples of such a polymerization initiator include 2,4,4-trimethylpentyl-2-peroxyneodecanoate and di-2.
-Ethylhexyl peroxydicarbonate, di (2-
Ethoxyethyl) peroxydicarbonate, α-cumylperoxyneodecanoate, t-butylperoxyneodecanoate, t-butylperoxypiparate,
Organic peroxides such as 3,5,5-trimethylhexanoyl peroxide and acetylcyclohexylsulfonyl peroxide and α, α′-azobisisobutyronitrile and α, α′-azobis-2,
One or a mixture of two or more azo compounds such as 4-dimethylvaleronitrile is exemplified.

Other auxiliary additives optionally used in the present invention include chain transfer agents such as mercaptoalkanols and alkyl thioglycolates, and nonionic surfactants such as glycerin esters and sorbitan esters of higher fatty acids. Agents, pH adjusters and polymerization inhibitors. The above-mentioned other additives may be added to the polymerization system all at once at the start of the charging, or may be added continuously or decomposed during the polymerization. The polymerization is usually carried out at a temperature of 35 to 80 ° C. with stirring.

[0033]

As described above, according to the present invention, it is possible to produce a porous vinyl chloride resin excellent in fisheye, plasticizer absorption and particle size characteristics with high productivity.
Extremely useful.

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples. The percentages and parts in Examples and Comparative Examples are based on weight unless otherwise specified, and the physical properties of the vinyl chloride polymer were measured by the following methods.

(1) Average particle diameter The average particle diameter was shown as a 50% passage diameter by sieve analysis using a JIS standard wire mesh.

(2) Bulk specific gravity A value measured according to the method specified in JIS K6721 is shown.

(3) Fisheye 100 parts of polyvinyl chloride, 60 parts of di-2-ethylhexyl phthalate, 2 parts of Ba-Zn based stabilizer, pigment 3.5
Part of the mixture was roll-kneaded at 135 ° C. for 7 minutes to obtain a mixture having a thickness of 0.1 mm.
A sheet of 35 mm, 5 cm × 10 cm is formed, and the number of fish eyes present on the sheet surface is counted.

(4) Absorbency of plasticizer 400 g of a vinyl chloride resin and a polyester polymer plasticizer (ADEKA Argus) were placed in a container having a jacket temperature of 85 ° C., using a Labo Plastomill manufactured by Toyo Seiki Seisaku-sho, Ltd. 240 g of PN250 (manufactured by Kagaku Co., Ltd.) was charged, and the torque was recorded while stirring at a rotation speed of 60 rpm.

The scale adhesion state on the polymerization vessel wall shown in each of the examples was shown based on the following criteria. ：: Almost no scale adhered Δ: Locally adhered scale ×: Adhered matter was generated on the entire inner wall

Example 1 An inner jacket type stainless steel polymerization vessel having an inner volume of 45 m ³ was degassed and then heated to 61 ° C. water 21.5.
m ³ was continuously charged at a rate of 45.0 m ³ / hour, stirring was started 10 minutes after the start of water supply, and 16.5 tons of vinyl chloride was continuously charged at a rate of 85 m ³ / hour.

Further, 11.8 kg of a 70% toluene solution of di- (2-ethoxyethyl) peroxydicarbonate (polymerization initiator) and partially saponified polyvinyl acetate previously shown in Table 1 were mixed and added to water. 400 L of the dispersed liquid (suspension agent) was charged at the time shown in Table 1 from the start of water charging. The polymerization initiator was continuously charged at a rate of 6 L / min for 2 minutes, and the suspending agent was continuously charged at a rate of 40 L / min for 10 minutes.

The internal temperature of the polymerization vessel, which was 52 ° C. at the end of charging all the components, was raised to 57 ° C., and the polymerization reaction was allowed to proceed while maintaining the temperature. Then, the pressure of the polymerization vessel was 2.0 kg / cm.
The unreacted monomer was recovered ^{when 2} drops and the contents were dehydrated and dried. Table 1 shows the polymerization time, the physical properties of the vinyl chloride polymer, and the scale adhesion state on the polymerization vessel wall.

Examples 2 to 4, Comparative Examples 1 to 5 The suspending agent and the polymerization initiator in Example 1 were changed to the suspending agent and the polymerization initiator shown in Table 1, and the suspension agent and the polymerization initiator were changed. Polymerization was carried out under the same conditions as in Example 1 except that the preparation method described in Table 1 was used.

The physical properties, polymerization time, and scale adhesion of the vinyl chloride polymer thus obtained were as shown in Table 1. From Table 1, it can be seen that the method for producing a vinyl chloride polymer of the present invention produces a high-quality vinyl chloride resin having excellent fisheye and plasticizer absorbency and harmonizing physical properties such as bulk specific gravity and particle size characteristics. It's clear what you can do.

[0045]

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tamio Yamato 1-2-2 Harumi-cho, Tokuyama-shi, Yamaguchi Prefecture Inside Sun Arrow Chemical Co., Ltd. (72) Inventor Yasumichi Ishii 2767 Niihama, Kojima-Shiohama (72) Inventor Masahisa Okawa 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Industries, Ltd. (72) Inventor Isao Ouchi 16 Nishimachi Ochiai, Iwaki-shi, Fukushima Kureha Chemical Industry (72) Inventor Hideki Wakamori 16 Nishimachi Ochiai, Iwaki-shi, Fukushima Prefecture Kureha Chemical Industry Co., Ltd. (56) References JP-A-1-172407 (JP, A) JP-A-62-263206 (JP, A )

Claims (3)

(57) [Claims] When a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator, all of the monomer and preheated water are charged into a polymerization vessel. At the same time, and as a suspending agent, (A) a saponification degree of 75 to 90 mol% and an average polymerization degree of 10
(B) a saponification degree of 65 to 75 mol%, and an average degree of polymerization of 50;
(C) a saponification degree of 15 to 54 mol%, and an average degree of polymerization of 10
0-1200 partially saponified polyvinyl acetate, the total amount of (A) and (B) per 100 parts by weight of vinyl chloride is 0.03-0.15 parts by weight, and the amount of (C) is 0.01 to 0.1 parts by weight, the weight ratio (A) / (B) of (A) / (B) is 1/5 to 4/5 , and At least 20% by weight of the total charged amount of the suspending agent is charged, and when the charged amount of the monomer reaches 30% of the total charged amount and thereafter until it reaches 100%, and the amount of the monomer in the polymerization vessel is increased. At the time when the weight ratio to water is 1.5 or less, charge the entire amount of the polymerization initiator, charge the total amount of the monomer, water, the suspending agent, and the polymerization initiator, and then reach the polymerization reactor contents to the polymerization temperature. Producing a vinyl chloride polymer, wherein the polymerization is carried out, and the polymerization is completed within a period of 6 hours or less. Law. 2. The internal temperature (t) of the polymerization vessel at the end of the charging of the total amount of the monomer and water is adjusted so that T-10 ≦ t ≦ T + 5 (° C.) with respect to a predetermined polymerization temperature (T). The method for producing a vinyl chloride polymer according to claim 1, wherein the water is heated in advance. 3. The polymerization reactor according to claim 1, wherein the polymerization reactor is an internal jacket type having a cooling medium passage provided on the inner surface of the polymerization reactor main body and has a large internal volume of 40 m ³ or more.
The method for producing a vinyl chloride polymer according to any one of the above.