JPH1180213A - Method for producing vinyl chloride polymer - Google Patents

Abstract

(57) [Problem] To provide a method for producing a vinyl chloride polymer having a polymerization time of 4 hours or less, a fine particle diameter, a high bulk specific gravity, and a good fishy eye. SOLUTION: In a method in which a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer to polymerize the vinyl chloride polymer in 4 hours or less, A method for producing a vinyl chloride-based polymer, wherein the volume fraction of the vinyl chloride-based monomer in droplets forming a skin is 70% or more by 5.0%.

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 shortening the polymerization time to increase the productivity of the vinyl chloride polymer, The present invention relates to a method for producing a vinyl chloride polymer having a small diameter, a high bulk specific gravity, and a small fish eye.

[0002]

2. Description of the Related Art In the production of polymers, techniques for improving productivity by shortening the polymerization time have been studied in various fields.

However, in the production of a vinyl chloride polymer, quality deterioration such as coarsening, a decrease in bulk specific gravity, and deterioration of fish eyes, which are considered to be caused by an increase in polymerization rate at the very beginning of polymerization, occurs. It is known. And
As a method for preventing such a decrease in quality, Japanese Patent Application Laid-Open
No. 295008 discloses a saponification degree of 15 to 55 mol%.
It describes that a partially saponified polyvinyl alcohol (hereinafter referred to as PVA) or a nonionic surfactant having an HLB of 2 to 10 is used as a dispersion stabilizing aid. Also, generally, in order to prevent such quality degradation,
There is a method of increasing the amount of the dispersant.

[0004]

In general, if the polymerization time is shortened, the amount of heat generated by polymerization per hour increases, and it is necessary to increase the load ratio of a reflux condenser or the like.

When the dispersion stabilizing aid described in JP-A-5-295008 is used or when the amount of the dispersing agent is increased, vigorous foaming of the suspension in the polymerization reactor occurs, and as a result, the gas-liquid interface Of the scale increases, and the fish eyes deteriorate due to the peeling of the scale.

Accordingly, an object of the present invention is to provide a method for producing a vinyl chloride polymer having excellent quality in a reduced polymerization time.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the total conversion of the vinyl chloride-based monomers in the suspension until a specific conversion was reached. Completed the present invention by finding that a vinyl chloride monomer having a specific ratio can be present in the droplets forming the skin to produce a high quality vinyl chloride polymer even when the polymerization time is 4 hours or less. I came to.

That is, the present invention provides a method for polymerizing a vinyl chloride polymer in 4 hours or less by subjecting a vinyl chloride monomer to suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer. , A vinyl chloride monomer having a volume fraction of 70% or more of the total vinyl chloride monomer in the suspension until the conversion of the vinyl chloride monomer into a vinyl chloride polymer reaches 5.0%. It is another object of the present invention to provide a method for producing a vinyl chloride polymer, wherein a vinyl monomer is present in vinyl chloride monomer droplets forming a skin.

Hereinafter, the present invention will be described in detail.

According to the present invention, a conversion rate of a vinyl chloride monomer into a vinyl chloride polymer (hereinafter, referred to as a conversion rate) is 5.0.
% Of the total vinyl chloride-based monomer in the suspension, at least 70% by volume fraction of vinyl chloride-based monomer is present in the vinyl chloride-based monomer droplets forming the skin. By polymerizing a vinyl monomer, a vinyl chloride polymer having excellent quality can be produced in a short time. Here, 70% of the vinyl chloride-based monomer present in the vinyl chloride-based monomer droplets forming the skin having a conversion rate of up to 5.0% was used.
If it is less than 1, the obtained vinyl chloride polymer is unfavorably unfavorable because coarsening, deterioration of fish eyes and the like occur, resulting in poor quality.

In the present invention, any method may be used for measuring the volume fraction of the vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin in the suspension. The suspension can be obtained by taking out the suspension in the middle, directly observing the droplet with a microscope, and inserting the result into the following general formula (1).

Φ = ΣDsi ³ / (ΣDsi ³ + ΣDNi ³ ) × 100 (1) (where φ is a vinyl chloride monomer present in a vinyl chloride monomer droplet forming a skin in a suspension) The volume percentage of the body, Ds is the diameter of the vinyl chloride monomer droplet forming the skin, and DN is the diameter of the vinyl chloride monomer droplet not forming the skin.) The aqueous solution used in the present invention The medium is water or a medium containing water as a main component, and may include any medium without departing from the object of the present invention. The aqueous medium preferably has a temperature of 30 ° C. or higher, since a vinyl chloride polymer having excellent production efficiency and excellent quality can be obtained.

Examples of the vinyl chloride monomer used in the method of the present invention include a vinyl chloride monomer and a mixture comprising a copolymerizable monomer of a vinyl chloride monomer and a vinyl chloride monomer. Can be

Here, the monomer copolymerizable with the vinyl chloride monomer may be any monomer as long as it can be copolymerized with the vinyl chloride monomer, and examples thereof include olefins such as ethylene and propylene. , Vinyl esters such as vinyl acetate and vinyl stearate, vinyl ethers such as ethyl vinyl ether and cetyl vinyl ether, acrylate esters such as methyl acrylate and ethyl acrylate,
Esters or anhydrides such as maleic acid and fumaric acid,
Examples include aromatic vinyl compounds such as styrene, acrylonitrile, and the like. The copolymerizable monomer is preferably used in a proportion of usually 20% by weight or less based on the vinyl chloride monomer.

The oil-soluble polymerization initiator used in the method of the present invention is not particularly limited, and may be those generally used as oil-soluble polymerization initiators, such as diisopropyl peroxydicarbonate and di-2-carbonate. Peroxycarbonate compounds such as ethylhexylperoxydicarbonate and diethoxyethylperoxydicarbonate; peroxyester compounds such as t-butylperoxyneodecanate and α-cumylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide and the like Peroxides: azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and azobis (4-methoxy-2,4-dimethylvaleronitrile); Use in combination of two or more It is also possible. In addition, the polymerization time is 4
In order to perform the reaction in less than the time, it is desirable to use the oil-soluble polymerization initiator in an amount of 0.05 part by weight or more based on 100 parts by weight of the vinyl chloride monomer.

The dispersion stabilizer used in the method of the present invention is not particularly limited, and those generally used as suspension stabilizers for suspension polymerization may be used. Examples thereof include methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylcellulose, and the like. Cellulose derivatives such as propylmethylcellulose, PVA, acrylic acid polymer,
Examples thereof include a water-soluble polymer such as gelatin, a nonionic surfactant, and an anionic surfactant. These can be used alone or in combination of two or more. In the present invention, since a vinyl chloride polymer excellent in quality can be obtained stably with a particularly short polymerization time, (A) a saponification degree of 75 to 90 mol% as a dispersion stabilizer, and PVA having an average degree of polymerization of 2000 to 4000
(Hereinafter referred to as dispersion stabilizer A) and (B) saponification degree 6
Using PVA having a polymerization degree of 0 to 85 mol% and an average degree of polymerization of 300 to 1500 (hereinafter referred to as dispersion stabilizer B), the total amount of the dispersion stabilizer relative to 100 parts by weight of the vinyl chloride monomer. From 0.04 to 0.08 parts by weight of the dispersion stabilizer A /
It is preferable to use the dispersion stabilizer B (weight ratio) in the range of 5/1 to 20/1.

In the method of the present invention, the net stirring power is not particularly limited. However, since a vinyl chloride-based polymer of high quality can be obtained efficiently, the polymerization of the vinyl chloride-based monomer and the aqueous medium can be performed. The net stirring power at the time of charging the reactor is in the range of 2.00 to 4.00 kw / m ³ , and the conversion rate is in the range of 0.5% to 3.0%, and the net stirring power is 1.
It is particularly preferable to set the range of 50 to 2.00 kw / m ³ .

In the present invention, it is preferable to use a polymerization reactor provided with a reflux condenser because the amount of heat generated by polymerization heat generated during the polymerization reaction can be efficiently removed.

According to the present invention, a skin is formed of a vinyl chloride monomer having a volume fraction of 70% or more of all the vinyl chloride monomers in the suspension up to a conversion rate of 5.0%. The present invention is intended to produce a vinyl chloride polymer having excellent quality in a short time by causing the vinyl chloride monomer to be present in the vinyl chloride monomer droplets and polymerizing the vinyl chloride monomer.

As in the present invention, by causing a vinyl chloride monomer having a volume fraction of 70% or more to be present in a vinyl chloride monomer droplet forming a skin up to a conversion rate of 5.0%, Even when the polymerization time is 4 hours or less, the mechanism of the effect of obtaining a vinyl chloride polymer having good quality such as a fine particle diameter and a high bulk specific gravity is not clear, but it is considered as follows.

In the polymerization of the vinyl chloride monomer, a skin is formed on the surface of the vinyl chloride monomer droplet during the conversion of 0.3 to 3.0%. The viscosity of the monomer droplet surface increases, and the droplets aggregate with each other. However, when the polymerization time is 4 hours or less, the polymerization proceeds before the initiator concentration in the vinyl chloride monomer droplets becomes uniform, and thus uneven polymerization occurs between the vinyl chloride monomer droplets. It is considered that as a result, coarsening and an increase in fish eyes were caused. In the present invention, a vinyl chloride-based monomer having a volume fraction of 70% or more is present in a vinyl chloride-based monomer droplet forming a skin by a conversion rate of 5.0%, so that vinyl chloride is obtained. Uniform polymerization occurs between the system monomer droplets, resulting in a polymerization time of 4
It is considered that a vinyl chloride polymer having good quality, such as a fine particle diameter and a high bulk specific gravity, was obtained even when the time was shorter than the above.

In the method of the present invention, the vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer to polymerize the vinyl chloride polymer in 4 hours or less. A vinyl chloride monomer having a volume fraction of 70% or more in the vinyl chloride monomer droplets forming a skin out of all the vinyl chloride monomers in the suspension until the conversion rate reaches 5.0%. Other polymerization conditions, except for the presence in the reactor, such as aqueous medium to the reactor, vinyl chloride monomer, polymerization initiator,
The method of charging the dispersion stabilizer, the polymerization temperature conditions, and the like may be the same as those in the conventional method, and are not particularly limited. Further, if necessary, a pH adjuster, a polymerization degree adjuster and the like may be used within a range not affecting the object of the present invention.

[0023]

EXAMPLES Hereinafter, the production method of the present invention will be described based on examples and comparative examples, but the present invention is not limited to these.

The obtained vinyl chloride polymer was evaluated by the following method.

Average Particle Diameter of Polymer The size (μm) of a sieve through which 50% of the polymer particles of the obtained vinyl chloride polymer pass was defined as the average particle diameter.

-Bulk specific gravity-Measured according to the method described in JIS K-6721.

~ Fisheye ~ 100 parts by weight of the obtained vinyl chloride polymer, Ca-Zn
1.5 parts by weight of a powder-based composite stabilizer, 0.5 parts by weight of an organic phosphorus-based stabilizing aid, 3 parts by weight of ultramarine blue and 50 parts by weight of DOP (dioctyl phthalate) were mixed with a roll at 150 ° C. to a thickness of 0.1 part. The mixture was kneaded at 35 mm and kneaded for 5 minutes, and a 0.35 mm sheet was taken out and indicated by the number of transparent particles in 50 cm ^{2 of} the sheet.

-Measurement of conversion rate of vinyl chloride monomer at the time of temperature rise- A dispersant and 150 parts by weight of water (1430 g) were charged into a stainless steel polymerization vessel having an inner volume of 3 liters equipped with stirring blades, and then evacuated. 100 parts by weight of vinyl chloride monomer (980
g) was charged, the mixture was stirred at 35 ° C., and the mixture was stirred and heated at the same rate of temperature increase as in Examples and Comparative Examples, that is, from 35 ° C. to 57 ° C. over 40 minutes to carry out polymerization. As the initiator, 0.045 parts by weight of cumyl peroxy neodecanoate and 0.045 parts by weight of t-butyl peroxy neodecanoate were used. Then, for a predetermined time (2.5 minutes after the start of heating, 5 minutes,
At 10 minutes, 20 minutes, 30 minutes, 40 minutes (attained the constant temperature), and 50 minutes (10 minutes after the constant temperature was reached), the polymerization was stopped using a hindered phenol-based polymerization inhibitor. Then, the conversion was measured from the weight of the obtained vinyl chloride polymer.

The conversion was 2.5 minutes after the start of heating, 5 minutes, and 1
The measurement was performed at 0, 20, 30, 40 (at a constant temperature), and 50 minutes (10 minutes after a constant temperature was reached). Table 1 shows the results.

[0030]

[Table 1]

-Droplet Change During Polymerization- For the polymerization of Examples and Comparative Examples, the suspension in the polymerization vessel was withdrawn under the condition of a pressure difference of 0.5 kg / cm ³ , and this suspension was diluted. Put into a pressure-resistant cell,
Photographs were taken using a microscope under magnification. From this photograph, the vinyl chloride monomer droplets with the skin formed and the vinyl chloride monomer droplets without the skin were identified,
The droplet size was measured. The presence or absence of skin formation was judged from the transparency of the droplets in the photograph. The number of droplets was 500 or more. From these results, the volume ratio of the vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin was derived from the following equation.

Φ = ΣDsi ³ / (ΣDsi ³ + ΣDNi ³ ) × 100 φ; volume percentage of vinyl chloride-based monomer present in vinyl chloride-based monomer droplets forming a skin in suspension Ds; skin Diameter of the vinyl chloride monomer droplets formed by the particles; diameter of the vinyl chloride monomer droplets without the skin formed 0.1%, 0.4%, 0.7%, 1.1% , 1.
The droplet diameters of the droplets at 4%, 2.8%, 4.8%, and 5.8% were measured.

Example 1 In a polymerization reactor equipped with a backflow condenser having an internal volume of 1.6 m ³ , (A) a saponification degree of 80 mol% was used as a dispersion stabilizer.
0.05 parts by weight of PVA having an average degree of polymerization of 2600 and (B) P having an average degree of polymerization of 850 and a saponification degree of 73 mol%.
0.010 parts by weight of VA, 0.045 parts by weight of cumyl peroxy neodecanoate and 0.045 parts by weight of t-butyl peroxy neodecanoate as polymerization initiator, 100 parts by weight of vinyl chloride monomer (603 kg) 110 parts by weight (663 kg) of water at 40 ° C. and 1.75 net stirring power.
The reactor was charged with stirring at kw / m ³ . The temperature of the suspension at that time was 35 ° C. Thereafter, the temperature was raised to 57 ° C. in 40 minutes while the net stirring power was 1.75 kw / m ³ . At that time, the conversion reached 4.8%, and the amount of vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin was 84%. Then, after reaching 57 ° C., polymerization was carried out for 3.0 hours. Thereafter, unreacted vinyl chloride monomer was recovered, the polymer slurry was taken out, and dehydrated and dried to obtain a vinyl chloride polymer. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a high bulk specific gravity, a small particle size, and a small fish eye.

Example 2 The net stirring power was 2.00 kW / m ³ and the conversion was 4.8.
% (At the time of reaching 57 ° C.), the vinyl chloride polymer was prepared in the same manner as in Example 1 except that the amount of the vinyl chloride monomer present in the vinyl chloride monomer droplet forming the skin was 92%. Obtained. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a high bulk specific gravity, a small particle size, and a small fish eye.

Example 3 A dispersion stabilizer was prepared by using a saponification degree of 80 mol% and an average polymerization degree of 2,600.
0.05 parts by weight of PVA and a net stirring power of 2.25
kw / m ^3, and the amount of vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin at a conversion of 4.8% (at the time of reaching 57 ° C.) was 72%. A vinyl chloride polymer was obtained in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a high bulk specific gravity, a small particle size, and a small fish eye.

Example 4 A dispersion stabilizer was prepared by using a saponification degree of 88 mol% and an average polymerization degree of 2,600.
0.05 parts by weight of PVA and a net stirring power of 2.50
kw / m ³ and the amount of vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin at a conversion of 4.8% (at the time of reaching 57 ° C.) was 76%. A vinyl chloride polymer was obtained in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a high bulk specific gravity, a small particle size, and a small fisheye.

Example 5 A dispersion stabilizer was prepared by using (A) a saponification degree of 80 mol% and an average polymerization degree of 2.
0.05 parts by weight of PVA of 600 and (B) a saponification degree of 7
A vinyl chloride monomer present in a vinyl chloride monomer droplet forming a skin at a conversion rate of 4.8% (at the time of reaching 57 ° C.) with 3 mol% of PVA having an average degree of polymerization of 850 and 0.010 parts by weight of PVA. A vinyl chloride polymer was obtained in the same manner as in Example 1 except that the amount was changed to 92%. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a high bulk specific gravity, a small particle size and a small fish eye.

Example 6 A dispersion stabilizer was prepared by using a saponification degree of 80 mol% and an average polymerization degree of 2,600.
0.05 parts by weight of PVA, a net stirring power of 2.50 kw / m ³ at the time of charging the vinyl chloride monomer and water, and a net stirring power of 0.7% (10 minutes after the start of heating). 1.75 kW / m ³ and the amount of vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin at a conversion of 4.8% (at the time of reaching 57 ° C.) was 86%. A vinyl chloride polymer was obtained in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a high bulk specific gravity, a small particle size, and a small fish eye.

Example 7 A dispersion stabilizer was prepared by using a saponification degree of 80 mol% and an average polymerization degree of 2,600.
Of 0.05% by weight of PVA, a net stirring power of 4.00 kw / m ³ at the time of charging vinyl chloride monomer and water, and a net stirring power of 0.7% (10 minutes after the start of heating). 1.75 kw / m ³ and the amount of vinyl chloride monomer present in the vinyl chloride monomer droplet forming the skin at a conversion of 4.8% (at the time of reaching 57 ° C.) was 93%. A vinyl chloride polymer was obtained in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a high bulk specific gravity, a small particle size, and a small fish eye.

Comparative Example 1 The net stirring power was 1.25 kw / m ³ and the conversion was 4.8.
% (At the time of reaching 57 ° C.), the vinyl chloride polymer was prepared in the same manner as in Example 1 except that the amount of the vinyl chloride monomer present in the vinyl chloride monomer droplet forming the skin was 27%. Obtained. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a low bulk specific gravity, a coarse particle size, and a large number of fish eyes. Comparative Example 2 A dispersion stabilizer having a saponification degree of 80 mol% and an average polymerization degree of 2,600
And the amount of vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin at a conversion of 4.8% (at the time of reaching 57 ° C.) is 36 parts by weight. %, A vinyl chloride polymer was obtained in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a low bulk specific gravity, a coarse particle size, and a large number of fish eyes. Comparative Example 3 A dispersion stabilizer was prepared with a saponification degree of 80 mol% and an average polymerization degree of 4000.
0.05 parts by weight of partially saponified polyvinyl alcohol, the net stirring power was 3.0 kw / m ³ , and the conversion was 4.
8% (at the time of reaching 57 ° C.) 37% of the amount of the vinyl chloride monomer present in the vinyl chloride monomer droplets forming the skin
A vinyl chloride polymer was obtained in the same manner as in Example 1, except that Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a coarse particle size and a large amount of fish eyes. Comparative Example 4 Dispersion stabilizer (A): 80 mol% of saponification degree, average polymerization degree: 2
600 parts by weight of PVA, a net stirring power of 1.90 kW / m ^3, and a chloride present in vinyl chloride monomer droplets forming a skin at a conversion of 4.8% (at the time of reaching 57 ° C.). A vinyl chloride polymer was obtained in the same manner as in Example 1 except that the amount of the vinyl monomer was changed to 51%. Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

The obtained vinyl chloride polymer had a low bulk specific gravity, a coarse particle size, and many fish eyes.

[0052]

[Table 2]

[0053]

According to the present invention, the volume fraction of the vinyl chloride polymer in the vinyl chloride monomer droplets having the skin formed up to the conversion rate of 5.0% is set to 70% or more. Even if the polymerization time is 4 hours or less, it is possible to produce a vinyl chloride polymer having good quality such as a fine particle diameter and a high bulk specific gravity, so that the industrial effect is extremely large.

Claims (4)

[Claims] 1. A method for subjecting a vinyl chloride monomer to suspension polymerization in an aqueous medium in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer to polymerize the vinyl chloride polymer in 4 hours or less. Up to 5.0% conversion of vinyl monomer to vinyl chloride polymer, vinyl chloride monomer having a volume fraction of 70% or more of all vinyl chloride monomers in suspension A method for producing a vinyl chloride-based polymer, wherein the body is present in vinyl chloride-based monomer droplets forming a skin. 2. As the dispersion stabilizer, (A) a saponification degree of 75 to
90 mol%, partially saponified polyvinyl alcohol having an average degree of polymerization of 2000 to 4000, and (B) 60 to 85 mol% of saponification degree, and 300 to 1500 average degree of polymerization
Using partially saponified polyvinyl alcohol, the total amount of the dispersion stabilizer was 0.04 to 0.08 parts by weight, based on 100 parts by weight of the vinyl chloride monomer, and the dispersion stabilizer (A) /
The method for producing a vinyl chloride polymer according to claim 1, wherein the dispersion stabilizer (B) (weight ratio) is used in a range of 5/1 to 20/1. 3. The net stirring power when charging the vinyl chloride monomer and the aqueous medium into the polymerization reactor is 2.00 to 4.00 k.
w / m ³ , and a net stirring power of 1.50 to 2.00 kW / m ^{3 in} the range of 0.5% to 3.0% of conversion of vinyl chloride monomer to vinyl chloride polymer. The method for producing a vinyl chloride-based polymer according to claim 1 or 2, wherein: 4. The method for producing a vinyl chloride polymer according to claim 1, wherein a polymerization reactor provided with a reflux condenser is used.