JPH0873512A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE: To produce a high-quality vinyl chloride polymer which has a high bulk density, thus giving a compsn. with a high bulk density, is excellent in free-flowing properties, removability of monomers, gelling properties, plasticizer absorption, etc., and hardly gives a product with fish eyes. CONSTITUTION: A process for producing a vinyl chloride polymer by subjecting vinyl chloride or a vinyl monomer mixture contg. vinyl chloride to suspension polymn. in an aq. medium, which comprises using a partially saponified polyvinyl alcohol having a degree of saponification of 60-80mol%, an average degree of polymn. of 500-1,000, a viscosity of the 4% aq. soln. at 20 deg.C of 15cP or lower, and an absorbance of the 1% aq. soln. at a wavelength of 280nm of 4 or higher as the dispersion stabilizer, and adding a partially saponified polyvinyl alcohol having a degree of saponification of 20-55mol% and an average degree of polymn. of 150-600 in an amt. of 0.005-0.5wt.% of the fed monomer to the polymn. system when the conversion is 20-60%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing high quality vinyl chloride polymers, especially for pipe extrusion.

[0002]

2. Description of the Related Art Vinyl chloride polymers are useful resins having excellent physical properties and are widely used as hard and soft materials.

As a molding method of this vinyl chloride polymer, calender molding, extrusion molding, injection molding and the like are generally used. In recent years, however, in the molding method by the hard extrusion molding method, the extrusion amount of a molding machine is used. From the viewpoint of increasing the polymer content, there is a demand for the development of a vinyl chloride polymer having a high bulk specific gravity and a good gelling property.

Therefore, various methods for producing a vinyl chloride polymer having a high bulk specific gravity have been investigated in the method for producing a vinyl chloride polymer by suspension polymerization in an aqueous medium. For example, during the polymerization of a monomer. Method (JP-A-59-16800), a method using highly saponified polyvinyl alcohol (JP-A-57-7600), and a method of adding a suspending agent during polymerization (JP-A-5-3).
Many methods have been proposed, such as Japanese Patent No. 9309).

However, according to these methods, a polymer having a high bulk specific gravity can be obtained to some extent, but the porosity of the obtained polymer is poor, so that the fish eyes of the molded product increase and the gelling property is increased. There are problems such as inferiority. Also, if the porosity is poor, the demomerization property will also deteriorate, so
The concentration of unreacted monomer remaining in the particles becomes high, impairing the working environment in the polymer manufacturing process or molding process,
Since unreacted monomer may remain in the molded body,
There may be a serious impact depending on the application such as food.

On the other hand, polyvinyl alcohol as a suspending agent has recently been improved, and so-called oil-soluble type having low polymerization degree and low saponification degree and those having various modified groups introduced therein have been developed. The oil-soluble type is recognized as having a monomer removal property and an effect of improving fisheye, but has a problem that the bulk specific gravity is lowered and the free-flow property is lowered by charging. In addition, in the case of introducing various modifying groups, the stability of the suspension system is poor in the usual method, and there are problems that scales are attached and the particle size varies.

The present invention has been made in view of the above circumstances, and has a high bulk specific gravity, a free flow property, a demonomer property,
A method for producing a vinyl chloride-based polymer capable of producing a high-quality vinyl chloride-based polymer having good gelling property, plasticizer-absorbing property, etc., and less fish eyes with less scale adhesion in the reaction system. The purpose is to provide.

[0008]

Means and Actions for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that a vinyl chloride monomer or a mixture of vinyl-based monomers mainly containing vinyl chloride is aqueous. Upon suspension polymerization in a medium, as a result of repeated studies on the type of dispersant, addition timing, stirring conditions, etc., a saponification degree of 60 to 8 was obtained as a dispersion stabilizer used at the start of polymerization.
0 mol%, average degree of polymerization 500-1000, viscosity of 4% aqueous solution 15 cps or less (20 ° C.), wavelength of 1% aqueous solution 28
By using a specific partially saponified polyvinyl alcohol having an absorbance at 0 nm of 4 or more, and further adding a specific partially saponified polyvinyl alcohol having a saponification degree of 20 to 55 mol% and an average degree of polymerization of 150 to 600 during the polymerization, It has a high specific gravity, good free-flow property, demonomerizing property, gelling property, plasticizer absorbability, etc., and it gives a good quality vinyl chloride polymer with few fish eyes and is It was found that it can be manufactured without scale attachment.

Therefore, according to the present invention, when suspension polymerization of vinyl chloride or a vinyl-based monomer mixture containing vinyl chloride in an aqueous medium is performed, (A) at the start of polymerization, a saponification degree of 60 to 80 is used as a dispersion stabilizer. Mol%, average degree of polymerization 500 to 100
Viscosity of 0, 4% aqueous solution at 20 ° C. is 15 cps or less, 1
% Partially saponified polyvinyl alcohol having a saponification degree of 20 to 55 mol% and an average degree of polymerization of 150 to 600 while having a polymerization rate of 20 to 60% is used. The present invention provides a method for producing a vinyl chloride polymer, which comprises adding 0.005 to 0.5% by weight to the charged monomer.

The present invention will be described in more detail below. In the method for producing a vinyl chloride polymer of the present invention, as described above, vinyl chloride or a vinyl monomer mixture containing vinyl chloride is suspended in an aqueous medium. It undergoes turbid polymerization.

In this case, the raw material may be vinyl chloride alone or a mixture of vinyl chloride and a vinyl-based monomer (comonomer) copolymerizable therewith (50% by weight or more of vinyl chloride). As the comonomer, vinyl acetate, vinyl ester such as vinyl propionate, methyl acrylate, acrylic ester or methacrylic ester such as ethyl acrylate, ethylene, olefin such as propylene, lauryl vinyl ether, vinyl ether such as isobutyl vinyl ether, Other examples include monomers copolymerizable with vinyl chloride such as maleic anhydride, acrylonitrile, styrene and vinylidene chloride, and one of these may be used alone or two or more of them may be used in combination with vinyl chloride.

Further, the polymerization initiator may be one conventionally used for vinyl chloride-based polymerization, and specifically, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate. Percarbonate compounds such as carbonate, t-
Butyl peroxy neodecanoate, t-butyl peroxypivalate, t-hexyl peroxypivalate, α
-Perester compounds such as cumylperoxy neodecanoate and 2,4,4-trimethylpentyl-2-peroxy-2-neodecanate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxy Acetate, 3,5,5-
Peroxides such as trimethylhexanoyl peroxide and lauroyl peroxide, azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile), and further potassium persulfate, Cumene hydroperoxide and the like can be exemplified, and one of these can be used alone or two or more can be used in combination.

The amount of the polymerization initiator added to the reaction system is 0.03 to 0.2 per 100 parts by weight of the total amount of the vinyl chloride monomer or the vinyl monomer mixture mainly containing vinyl chloride.
It can be used in a ratio of parts by weight. In addition, as a method of adding, a method of charging the above-mentioned monomer and then diluting it with a solvent, or injecting it as an aqueous emulsion into a reaction system by a pump can be adopted.

In the present invention, other conditions such as a charging method, a charging ratio and a polymerization temperature at the time of the polymerization can be usual conditions. However, the ratio of the charged water and the monomer is water / monomer. The range of monomer = 0.9 to 1.5 is preferable. Further, water may be added during the polymerization. Furthermore, in order to shorten the heating time and stabilize the suspension system, deionized water is added to 40-
It is preferable to charge with warm water at 50 ° C.

Thus, in the present invention, as a dispersion stabilizer from the start of polymerization, a viscosity of a 4% aqueous solution having a saponification degree of 60 to 80 mol% and an average polymerization degree of 500 to 1000 and 4% is 15 cps or less, 1 % Partially-saponified polyvinyl alcohol having an absorbance of 4 or more at a wavelength of 280 nm is used.

When partially saponified polyvinyl alcohol which does not satisfy this value is used, not only the bulk specific gravity does not increase, but fish eyes increase or gelation becomes slow,
The object of the present invention cannot be achieved.

The amount of such partially saponified polyvinyl alcohol charged is 0.02 to 0.
The range of 08% by weight is preferable, and the charging method is preferably such that the compound is dispersed and dissolved in a solvent such as water and charged into the polymerization vessel.

After charging the vinyl monomer, the above dispersion stabilizer, etc., stirring is started in order to uniformly disperse the charged contents. In this case, in the present invention, the power required for stirring at that time is 80 to The pressure is set to 150 kg · m / s · ton, preferably 90 to 130 kg · m / s · ton, and is maintained.

In the present invention, the polymerization rate is 20 to 6
Between 0%, saponification degree 20-55 mol%, average degree of polymerization 1
50 to 600 partially saponified polyvinyl alcohol is added in an amount of 0.005 to 0.5% by weight based on the charged monomers.

When the addition time is lower than the polymerization rate of 20%,
The particle size becomes finer, the bulk specific gravity decreases, and the free flow property deteriorates. If it is added when the polymerization rate exceeds 60%, the effect of improving gelation cannot be expected.

The average degree of polymerization is less than 150 and the degree of saponification is 2
If a partially saponified polyvinyl alcohol content of less than 0 mol% is used, the suspension system becomes unstable, coarse particles increase, and scale easily adheres. If a partially saponified polyvinyl alcohol having an average degree of polymerization of 600 and a degree of saponification of 55 mol% or more is used, the effect of improving gelation becomes insufficient.

Further, if the addition amount is less than 0.005% by weight, the gelling property improving effect does not occur, and if the addition amount is more than 0.5% by weight, the effect is saturated, which is economically disadvantageous. Become.

In the present invention, a polymerization regulator, a chain transfer agent, a pH regulator, a gelation improver, an antistatic agent, a cross-linking agent, a stabilizer, which is appropriately used for vinyl chloride-based polymerization, if necessary. It is also optional to add a filler, an antioxidant, a buffer, a scale inhibitor, etc. at a normal time.

[0024]

EFFECTS OF THE INVENTION According to the method for producing a vinyl chloride polymer of the present invention, the bulk specific gravity is high, and the bulk specific gravity is particularly high when it is made into a compound, and the free flow property, the demomer property, the gelling property, and the plasticizer are obtained. It is possible to produce a high-quality vinyl chloride polymer having good absorbability and the like and less fish eyes with less scale adhesion in the reaction system.

When the vinyl chloride polymer obtained by the production method of the present invention is used for pipe extrusion molding, the extrusion amount is high and the appearance of the obtained molded article is good.

[0026]

EXAMPLES Hereinafter, the present invention will be specifically shown by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 and 2, Comparative Examples 1 to 5] Internal volume
2.1m³ 45 ° C deionized water in a stainless steel polymerization can
976 kg and the dispersion stabilizer shown in Table 1 in the amount shown in the same table.
After charging, the inside of the can was degassed to 50 mmHg. Next
Into the above, 650 kg of vinyl chloride monomer was charged and stirred.
At the same time to start raising the temperature by passing hot water through the jacket
Di-2-ethylhexyl peroxydicarbonate 52
Polymerization was initiated by press-fitting 0 g into the polymerization vessel.

Thereafter, the polymerization reaction was carried out while maintaining the temperature of 51.5 ° C., and the suspending agents shown in Table 1 were added during the polymerization.

When the pressure in the polymerization vessel reaches 5.5 kg / cm ² G, unreacted monomers are recovered, the polymer is taken out of the vessel in a slurry state, dehydrated and dried to obtain a vinyl chloride polymer. Obtained.

With respect to the obtained vinyl chloride polymer, the bulk specific gravity, particle size distribution, plasticizer (DO
P) The absorption amount, fish eye, and gelling property were measured, and the scale adhesion inside the polymerization vessel was visually observed. The results are also shown in Table 1. Bulk specific gravity was measured according to JIS K-6721. Particle size distribution According to JIS Z-8801. # 60, # 80, # 1
The sieves were sieved using each of 00, # 120, # 150, and # 200 sieves, and the passing amount (% by weight) was measured. A 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 the obtained vinyl chloride polymer is collected and charged. Add 15 cc of dioctyl phthalate (DOP) to this and leave it for 30 minutes
Allow P to penetrate the resin well. After that, the excess DOP was centrifuged under an acceleration of 1500 G, and the D absorbed by the resin was absorbed.
The amount of OP was calculated as a value per 100 parts by weight of the resin. Fish Eye 100 parts by weight of vinyl chloride polymer obtained, 50 parts by weight of DOP, 0.1 part by weight of barium stearate, 0.1 part by weight of cadmium stearate, 0.8 part by weight of cetanol,
2.0 parts by weight of tin stabilizer, 0.5 parts by weight of titanium dioxide, and 0.1 parts by weight of carbon black were mixed and kneaded for 5 minutes with a 6-inch roll at 140 ° C. to obtain a sheet having a thickness of 0.3 mm. The number of white transparent particles in 100 cm ^{2 of} this sheet was shown. 0.5 parts by weight of Sn mercapto stabilizer, 3.2 parts by weight of complex lubricant, impact modifier methyl methacrylate / butadiene / styrene terpolymer graft copolymer (MBS) per 100 parts by weight of gelled vinyl chloride polymer. (Resin) 5.8 parts by weight are put into a Henschel mixer and mixed with stirring, and when the resin mixture in the Henschel mixer reaches 120 ° C., the mixture is cooled to obtain a compound, and 65 g of this compound is put into a Brabender plastic coater. 200 ℃, 40 rp
The time until the kneading was performed at m and the maximum torque was exhibited was taken as the gelation time.

Bulk specific gravity of the above compound, dry life
The low property was measured by the following method.Compound specific gravity It was measured according to JIS K-6721. Dry flow of compound Compound 1 obtained by the method of JIS K-6721
00cc in the funnel used in JIS K-6721
Put it back in. Complete 100cc of compound from the funnel
The time (seconds) until it completely fell was measured.Scale adhered inside the polymerization can After the slurry is taken out of the vessel, the scale inside the polymerization vessel
The adhered state of the roll was observed and evaluated according to the following criteria. ⊚: There is no adhesion of scale and the metallic mirror surface has gloss. ◯: The metal mirror surface has some cloudiness. X: There is a film-like scale on the entire metal surface.Dispersant A Saponification degree 72.4 mol%, average degree of polymerization 770, 4% water soluble
Viscosity of liquid is 5.7 cps, wavelength of 1% aqueous solution is 280 nm
Partially saponified polyvinyl alcohol with an absorbance of 6.5
Was prepared into a 4% aqueous solution and used.Dispersant B Saponification degree 80.2 mol%, average degree of polymerization 2600
Prepared 6% aqueous solution of polyvinyl alcohol and used
It wasDispersant C Methoxy substitution degree is 29.2% by weight, hydroxypropoxy
Si substitution degree is 8.9% by weight, and its 2% by weight aqueous solution
Hydroxy with a viscosity of 49.5 cps at 20 ° C
Propyl methyl cellulose prepared in 3% aqueous solution and used
It wasDispersant D Partial saponification degree of saponification 48.5 mol% and average degree of polymerization 250
Polyvinyl alcohol dissolved in water / methanol = 1/1
It was dissolved in a medium to prepare a 30% solution for use.

[0032]

[Table 1]

From the results shown in Table 1, according to the production method of the present invention, the bulk specific gravity is high, the amount of fine powder is small, the fish eyes are small, and the gelation property and the plasticizer absorbability are excellent. It is recognized that a vinyl chloride polymer having a high specific gravity can be obtained and that the scale adheres to the inside of the can.

On the other hand, if the dispersant of the present invention is not added in the same manner as in the present invention, not only the bulk specific gravity does not increase, but also fine powder and fish eyes increase, gelation delay and plasticizer absorption decrease. It is recognized that more scale adheres to the inside of the can.

Next, the vinyl chloride polymers obtained in Example 1 and Comparative Example 1 were compounded in the same formulation as in the above gelation measurement to form a compound. Cincinnati Miraculon's conical twin extruder (CM
T-58 tip diameter 60m / m), VP under the conditions of Table 2
A -75 pipe was extruded, and the extrusion amount and the physical properties of the pipe were measured. The results are also shown in Table 2. Charpy impact strength A test measurement sample was cut out from an extruded pipe, and measured according to JIS K-7111. Tensile test A sample for test measurement was cut out from an extruded pipe, and measured and measured according to JISK-7113.

[0036]

[Table 2]

From the results shown in Table 2, under the TEST-1 conditions, there is a difference between the vinyl chloride polymer of Example 1 and the vinyl chloride polymer of Comparative Example 1 in the results of the extrusion amount, the Charpy impact strength and the tensile test. However, it is recognized that the vinyl chloride polymer of Example 1 is excessively kneaded because of slow gelation, resulting in a poor pipe appearance. On the other hand, TES
Under the condition of T-2, the barrel temperature was lowered and the screw rotation speed was further increased in order to adjust the excessive kneading of the vinyl chloride polymer of Example 1. As a result, in the polymer produced in Comparative Example 1, the Charpy impact strength is lowered due to insufficient gelation, whereas in the vinyl chloride polymer of Example 1, the extrusion amount is increased and the Charpy impact strength and the tensile strength are increased. It was confirmed that mechanical properties such as strength were improved and the appearance of the pipe was also good.

Claims (1)

[Claims] 1. When (A) is used for suspension polymerization of vinyl chloride or a vinyl-based monomer mixture containing vinyl chloride in an aqueous medium.
At the start of polymerization, a saponification degree of 60 to 80 is used as a dispersion stabilizer.
Mol%, average degree of polymerization 500-1000, 4% aqueous solution of 2
Viscosity at 0 ° C is 15 cps or less, wavelength of 1% aqueous solution 28
Using partially saponified polyvinyl alcohol having an absorbance at 0 nm of 4 or more, (B) the degree of saponification is 20 to 55 mol% and the average degree of polymerization is 150 to 6 while the degree of polymerization is 20 to 60%.
A method for producing a vinyl chloride-based polymer, characterized in that the partially saponified polyvinyl alcohol of No. 00 is added in an amount of 0.005 to 0.5% by weight based on the charged monomers.