JPH07292005A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To obtain a vinyl chloride polymer resin having a low degree of polymerization, having a small content of fine particles and having good processability by adding an alpha-olefin as a substitute for a chain transfer agent in the production of the resin by suspension-polymerizing vinyl chloride in an aqueous medium. CONSTITUTION:This production process is the one for producing a vinyl chloride polymer of an average degree of polymerization as low as 850 or below by suspension-polymerizing vinyl chloride or a monomer mixture based thereof in an aqueous medium without using any chain transfer agent, which process comprises adding 0.1-2wt.% 4-10C alpha-olefin to the polymerization system, and performing the reaction under conditions including an inside pressure of 8-9.5kg/ cm<2>.G and a temperature of 60 deg.C or below. Desirable examples of the alpha-olefins include 1-butene, isobutylene, and cis-2-butene. This process can be carried out under conditions of low temperature and low atmosphere and therefore requires no highly-pressure-resistant vessel. The polymer obtained by this process has a sharp viscosity distribution, good workability and good heat resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a vinyl chloride polymer having a low polymerization degree and a good average polymerization degree of 850 or less at a low temperature and a low pressure. Specifically, there are very few fine particles, the particle size distribution and polymerization degree distribution are sharp,
Adhesion to the roll surface does not occur easily during roll forming, processability (melt flowability) and thermal stability are good, and average degree of polymerization is 850.
The following vinyl chloride-based polymers having a low degree of polymerization were used without using a chain transfer agent, and the internal pressure of the polymerization vessel was 8 to 9.5 kg / cm ² G and the polymerization temperature was 6
The present invention relates to a manufacturing method which can be easily obtained under a low temperature and low pressure condition of 0 ° C. or lower.

[0002]

2. Description of the Related Art Usually, in order to obtain a vinyl chloride polymer having a low degree of polymerization by suspension polymerization or the like, the polymerization temperature must be set high. When combined, the thermal stability deteriorates. Further, also in the production, since the pressure in the polymerization vessel increases as the polymerization temperature increases, a polymerization vessel having high pressure resistance is required. Therefore, in order to obtain a vinyl chloride polymer having a low polymerization degree by setting the polymerization temperature low, a method of adding a chain transfer agent has been carried out.

Common chain transfer agents include chlorinated hydrocarbons such as carbon tetrachloride and totichloroethylene, and aldehydes such as n-butyraldehyde. However, since it is difficult for the effect of these to be exhibited even in a small amount, it is necessary to increase the amount used, so that a large amount of gas and sewage which are unfavorable to environmental hygiene are generated in the drying step after the completion of the polymerization reaction.

Further, as a chain transfer agent effective in a small amount, an organic compound having a mercapto group and a hydroxyl group or a carboxyl group (hereinafter referred to as mercaptoethanol etc.), that is, alcohols such as mercaptoethanol and thiopropylene glycol, Carboxylic acids such as thioglycolic acid and thiohydroacrylic acid are known. However, if such a compound is present in the polymerization system from the beginning of the polymerization, it may have a high solubility in water.
The suspended dispersant and the like are adversely affected to produce a large amount of fine particle polymer, which deteriorates the work environment and workability due to dust and the like. In addition, when the polymer is used for extrusion processing, defective molding frequently occurs due to uneven gelation.

Therefore, mercaptoethanol or the like is not added before the polymerization reaction step, and after the polymerization reaction proceeds to some extent, that is, after the dispersion state of the monomer in the aqueous medium becomes stable (the temperature reaches the polymerization temperature). One hour after the start), a method of adding to the polymerization system was devised. As a result, the amount of fine particles of the polymer was reduced, and the particle size distribution of the obtained polymer particles was sharpened. However, in this method, the chain transfer agent (such as mercaptoethanol) is subjected to the polymerization reaction in the absence of the chain transfer agent until it is added to the polymerization system. It means that a polymer having a high degree of polymerization is produced, and a polymer having a low degree of polymerization is produced after the addition of the chain transfer agent (mercaptoethanol or the like). Therefore, the obtained polymer has a broad degree of polymerization distribution. As the average degree of polymerization is set lower, a larger amount of chain transfer agent (such as mercaptoethanol) is required, and the resulting polymer contains a large amount of a polymer having a low degree of polymerization. The degree of distribution is extremely broad, and the resulting polymer has poor mechanical properties and processability (melt flowability) relative to the average degree of polymerization of the polymer, and sticks to the roll surface during kneading during roll forming. There is a problem that occurs. Further, a large amount of chain transfer agent to be used (mercaptoethanol etc.) is required, and the mercaptoethanol etc. remains in the polymer or bonds to the molecular chain end, so that the obtained polymer is Becomes unstable. In manufacturing, the operation of removing the mercaptoethanol and the like is troublesome.

[0006]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to reduce the number of fine particles to a minimum.
The particle size distribution and degree of polymerization distribution are sharp, adhesion to the roll surface does not occur easily during roll forming, and the low polymerization degree vinyl chloride polymer with good processability (melt flowability) and thermal stability can be easily used at low pressure. It is to provide a manufacturing method which can be obtained.

[0007]

As a result of intensive studies to solve these problems, the present inventors did not add a chain transfer agent but instead added a specific α-olefin in a specific amount, The present invention has been completed by finding that it can be easily obtained by polymerizing vinyl chloride at low temperature and low pressure.

The present invention has the following configuration. Suspension polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous medium without using a chain transfer agent to produce a vinyl chloride polymer having an average polymerization degree of 850 or less and a low polymerization degree. At this time, an α-olefin having 4 to 10 carbon atoms was added to the polymerization system at 0.
1 to 2.0% by weight is added, and the inner pressure of the polymerization vessel is 8 to 9.5 kg / cm ^2.
G, a method for producing a vinyl chloride-based polymer, wherein the polymerization reaction is carried out at a polymerization temperature of 60 ° C. or lower.

The monomer mixture used in the present invention is a mixture of vinyl chloride and a polymerizable compound copolymerizable with vinyl chloride. The polymerizable compound is not particularly limited,
Specifically, vinyl acetates such as vinyl acetate and vinyl propionate, unsaturated monocarboxylic acids such as acrylic acid and α-alkylacrylic acid, and their alkyl esters, amides, unsaturated nitriles such as acrylonitrile. And unsaturated dicarboxylic acids such as maleic acid and fumaric acid, alkyl esters thereof, and vinyl alkyl ethers such as vinyl ethyl ethers.

The α-olefin having 4 to 10 carbon atoms according to the present invention includes 1-butene, isobutylene and cis-2.
Butene is preferred. When the α-olefin has more than 10 carbon atoms, it is difficult to obtain a vinyl chloride polymer having a low degree of polymerization, resulting in poor efficiency. On the other hand, when the number of carbon atoms is less than 4, the internal pressure of the polymerization vessel becomes high, and the polymerization cannot be performed at low pressure. α
The -olefin may be used alone or as a mixture of two or more kinds, but when it is used as a mixture, the average carbon number of the α-olefin must be in the range of 4 to 10. The amount of the α-olefin used is determined by the desired average degree of polymerization of the vinyl chloride polymer, but if the amount used is too large, the action of delaying the reaction becomes large. Must be used in the range of.

In the present invention, except that a chain transfer agent is not added and a specific α-olefin is added in a specific amount, a suspension agent, an initiator and other additives used in ordinary suspension polymerization are It can be used freely as long as the effects of the invention are not impaired. Specific examples of the suspending agent include polyvinyl alcohol, methyl cellulose, polyethylene oxide, polyvinylpyrrolidone, and the like, and examples of the initiator include benzoyl peroxide, lauroyl peroxide, dioctyl peroxydicarbonate, cumyl peroxyneodecanoate. , T-butyl peroxy neodecanoate, t-butyl peroxypivalate, acetylcyclohexyl sulfonyl peroxide, 2,
4,4-Trimethylpentylperoxy-2-neodecanoate, t-butylperoxyneohexanoate, t
-Amyl peroxy neohexanoate, 2,2'-azobis- (2,4-dimethylvaleronitrile), bis-3,5,5-trimethylhexanoyl peroxide,
Examples thereof include diisopropyl peroxydicarbonate and di-3-methoxybutyl peroxydicarbonate.

In the present invention, the polymerization reaction temperature is 60.
It must be below ℃. When the polymerization reaction temperature exceeds 60 ° C., the thermal stability of the obtained vinyl chloride polymer deteriorates. Further, in the present invention, the polymerization is carried out at a polymerization vessel internal pressure of 8.
It is performed in the range of 0 to 9.5 kg / cm ² . Generally, a vinyl chloride polymer having a low degree of polymerization is produced under the condition that the internal pressure exceeds 9.5 kg / cm ^2. However, in the present invention, the vinyl chloride polymer having a low degree of polymerization is 9.5 kg / cm 2. ^Since it is possible to manufacture at a low internal pressure of the polymerization vessel of ² or less, it is not necessary to use a polymerization vessel having high pressure resistance, and fatigue of the polymerization vessel can be extremely reduced. Such effects of the present invention are
It cannot be effectively used under conditions where the internal pressure exceeds 9.5 kg / cm ² . Further, under the condition that the internal pressure is less than 8.0 kg / cm ² , it is necessary to increase the amount of α-olefin used to obtain a vinyl chloride polymer having a low degree of polymerization. Delay effect becomes large, so it is not preferable in terms of economic efficiency

[0013]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto. The evaluation methods carried out in Examples and Comparative Examples were based on the following methods.

(1) Average Degree of Polymerization It was carried out according to JIS K-6721. (2) Particle size distribution The particle size was measured by dry sieving analysis using a wire mesh based on Tyler mesh. (3) Thermal stability To 100 parts by weight of the vinyl chloride polymer obtained in each of the examples, 3 parts by weight of a tin stabilizer, 2 parts by weight of an acrylic processing aid, and 1.7 parts by weight of a lubricant were blended. The mixture was kneaded with a heating roll set at a temperature of 150 ° C. for 5 minutes to obtain a sheet having a film thickness of 0.5 mm, and the blackening time and the color tone of the molded product, which are the following evaluation items, were examined. A) Blackening time The above sheet was hung in a gear oven adjusted to a temperature of 180 ° C. and the time until blackening was examined. B) Color tone of molded product The above sheet was press-molded at a temperature of 160 ° C. and a pressure of 120 kg / cm ² , and the color tone of the pressed film was visually observed and judged based on the following criteria. A: Very good B: Slightly yellow discolored C: Yellow discolored (4) Workability The sheet obtained in the heat stability test was cut into 2 × 2 mm square,
The melt flow rate of the cut pieces was measured under the following conditions. (According to JIS K-7210.) Measurement temperature: 20
0 ° C, sample filling: 5 g, preheating: 5 minutes, load: 5 kg, L
/ D: 8/2 mm, manual cutting (method A) (5) Adhesion to rolls 3 parts by weight of DOP, 2 parts by weight of tin stabilizer to 100 parts by weight of the vinyl chloride polymer obtained in each of the examples. 1 part by weight of a processing aid and 1 part by weight of a lubricant were mixed, and the mixture was kneaded with a heating roll set at a temperature of 185 ° C. to a film thickness of 0.3 mm. The time during which the film was stuck to the roll surface and the film could not be taken out was measured. The longer this time, the better the moldability. (6) Using a powder fluidity bulk specific gravity measuring device (JIS K-6721),
Put a certain amount (100g) of vinyl chloride polymer into the funnel made of stainless steel plate, then pull out the damper and measure the time until all the sample falls from the lower part of the funnel (hole with a diameter of 8mm) to measure the powder fluidity. evaluated. The smaller the measured value, the better the powder fluidity and the workability. (7) Angle of repose A sample with a constant mass (100 g) is dropped from a funnel with a constant height (10 cm) without shaking. The angle between the horizontal plane of the falling conical deposit and the generatrix was measured and used as the angle of repose. The smaller the angle of repose, the better the powder fluidity.

(Examples 1 to 3) Internal volume with stirrer 20
The inside of the 0 L polymerization vessel was replaced with nitrogen gas, and then water 55
0.057 parts by weight of polyvinyl alcohol having a saponification degree of 72% as a suspending agent (the amount is based on 100 parts by weight of vinyl chloride; the same applies hereinafter), polyvinyl alcohol having a saponification degree of 68%, 0.057 parts by weight, And the types and amounts of α-olefins and vinyl chlorides 4 shown in Table 1 as α-olefins.
4 kg (100 parts by weight) and 0.04 parts by weight of tert-butyl peroxyneohexanoate as a polymerization initiator were charged, the content was heated to 59.0 ° C., and then a polymerization reaction was performed to carry out polymerization at the time of polymerization. The difference from the maximum value of the internal pressure is 1.0 kg / c
When the internal pressure of the polymerization vessel dropped to m ² , unreacted monomer was discharged out of the system to obtain a vinyl chloride polymer. The obtained polymer was used for the evaluation test described above, and the results are shown in Table 1.

Comparative Examples 1 to 4 Mercaptoethanol was used in place of the α-olefin, and the amount of mercaptoethanol shown in Table 1 was added at the time shown in Table 1 except that
A vinyl chloride polymer was obtained in the same manner as in Example 1. The obtained polymer was used for the evaluation test described above, and the results are shown in Table 1.

(Comparative Example 5) Without using α-olefin,
A vinyl chloride polymer was obtained in the same manner as in Example 1 except that the polymerization reaction was carried out at 67 ° C. The obtained polymer was used for the evaluation test described above, and the results are shown in Table 1.

(Examples 4 to 6) Internal volume with stirrer 20
The inside of the 0 L polymerization vessel was replaced with nitrogen gas, and then water 55
kg, 0.045 parts by weight of polyvinyl alcohol having a saponification degree of 72% as a suspending agent, and α-olefin of the type and amount shown in Table 2 as α-olefin, vinyl chloride 44 kg
(100 parts by weight), 0.04 parts by weight of tert-butyl peroxyneodecanoate as a polymerization initiator and 0.04 parts by weight of tert-butyl peroxyneohexanoate were charged, and the content was heated to 59 ° C. After that, the polymerization reaction was carried out, and the difference from the maximum value of the internal pressure of the polymerization vessel during the polymerization was 1.0 kg / c.
When the internal pressure of the polymerization vessel dropped to m ² , unreacted monomer was discharged out of the system to obtain a vinyl chloride polymer. The obtained polymer was used for the above-mentioned evaluation test, and the results are shown in Table 2.

(Comparative Examples 6 to 9) Mercaptoethanol was used in place of the α-olefin, and at the time shown in Table 2, Table 2
A vinyl chloride polymer was obtained in the same manner as in Example 4 except that the amount of mercaptoethanol shown in (4) was charged. The obtained polymer was used for the above-mentioned evaluation test, and the results are shown in Table 2.

[0020]

As is apparent from Tables 1 and 2, according to the present invention, the heat stability is good, the particle size distribution is sharp, and the amount of fine powder is small, so that the workability is good, and the roll tackiness is improved. It has become possible to manufacture a vinyl chloride polymer with a low degree of polymerization in a low-pressure specification polymerizer, which is advantageous in terms of construction cost.

[0021]

[Table 1]

[0022]

[Table 2]

Claims (1)

[Claims] 1. A vinyl chloride-based vinyl chloride having a low degree of polymerization of 850 or less obtained by suspension polymerization of vinyl chloride or a monomer mixture mainly containing vinyl chloride in an aqueous medium without using a chain transfer agent. When producing a polymer, the polymerization system has 4 to 10 carbon atoms.
0.1 to 2.0% by weight of α-olefin is added, and the polymerization reaction is carried out at a polymerization vessel internal pressure of 8 to 9.5 kg / cm ² G and a polymerization temperature of 60 ° C. or less. Production method.