JPH1025307A - Production of vinyl chloride-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a vinyl chloride-based polymer having excellent heat stability and low fisheye-generating property. SOLUTION: In this method for producing a vinyl chloride-based polymer by an aqueous suspension polymerization, (a) a partially saponified polyvinyl alcohol having 65-85 mole % degree of saponification and 400-1000 average degree of polymerization, (b) a partially saponified polyvinyl alcohol having 75-85 mole % degree of saponification and 1500-3000 average degree of polymerization, (c) a partially saponified polyvinyl alcohol having 15-54 mole % degree of saponification and 100-1200 average degree of polymerization and (d) a water soluble cellulose ester are used together as dispersion stabilizers. After finishing the polymerization, 0.01-0.2 pt.wt., based on 100 pts.wt. of the polymer, of the partially sponified polyvinyl alcohol (a) is added in a slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD [0001] The present invention has excellent thermal stability,
The present invention also relates to a method for producing a vinyl chloride polymer having less fish eyes by a suspension polymerization method.

[0002]

2. Description of the Related Art Vinyl chloride food packaging films are:
In general, a non-toxic composite metal soap-based heat stabilizer is blended with a vinyl chloride-based polymer and molded. The vinyl chloride-based polymer used for this purpose has particularly excellent heat stability and fish eye. Characteristics are required.

As a technical means for obtaining a vinyl chloride-based polymer having such properties, a specific polyvinyl alcohol-based dispersion stabilizer (a saponification degree of 70 to 90 mol%, an average polymerization degree of 300 to 90%) is used.
A suspension polymerization method in which 1000 partially saponified polyvinyl alcohols are added to the polymerization system during the polymerization (JP-A-6-2119).
09) or a partially saponified polyvinyl alcohol having a degree of saponification of 70 to 90 mol% and an average degree of polymerization of 1500 to 3000, a partially saponified polyvinyl alcohol having a degree of saponification of 70 to 90 mol% and an average degree of polymerization of 300 to 1000 as a dispersant. Polymerization method in which a specific ratio of a secondary dispersant and a water-soluble cellulose ether are used in combination (JP-A-6-27093)
0) etc. have been proposed.

According to the above-mentioned method, a certain level of thermal stability and fisheye characteristics can be attained, but it is still not practically sufficient. Accordingly, an object of the present invention is to provide a method for producing a vinyl chloride polymer having excellent heat stability and a fisheye level in a molded product by a suspension polymerization method.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, the present invention relates to a method for producing a vinyl chloride polymer by suspension polymerizing vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable with vinyl chloride in an aqueous medium, wherein (a) ) Partially saponified polyvinyl alcohol having a degree of saponification of 65 to 85 mol% and an average degree of polymerization of 400 to 1000; (b) partially saponified polyvinyl alcohol having a degree of saponification of 75 to 85 mol% and an average degree of polymerization of 1500 to 3000; ) A partially saponified polyvinyl alcohol having a degree of saponification of 15 to 54 mol% and an average degree of polymerization of 100 to 1200 and (d) a water-soluble cellulose ether are used in combination. After the polymerization is completed, the obtained polymer slurry is added to the slurry. Characterized by adding 0.01 to 0.2 parts by weight of the above partially saponified polyvinyl alcohol (a) per 100 parts by weight of the polymer It is a manufacturing method of the united. Hereinafter, the present invention will be described in detail.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The amount of a dispersion stabilizer (hereinafter, simply referred to as a dispersant) used for stabilizing suspension polymerization in the present invention is based on 100 parts by weight of a vinyl chloride monomer. (A) is 0.005 to 0.1 part by weight, dispersant (b) is 0.005 to 0.05 part by weight, dispersant (c) is 0.005 to 0.1 part by weight, and dispersant ( d) is 0.0
It is preferably from 0.05 to 0.05 part by weight. Further, the total used amount of these dispersants is preferably 0.05 to 0.2 parts by weight on the same basis. If the total amount of the dispersant is less than 0.05 part by weight, the polymerization becomes unstable, while if it exceeds 0.2 part by weight, the fishy property tends to deteriorate.

In the present invention, when the unreacted monomer is preferably recovered after completion of the polymerization, a partially saponified polyvinyl alcohol of the dispersant (a), that is, a saponification degree of 65 to 85 mol%, is added to the polymer slurry. Average polymerization degree 400-1000
Is added in an amount of 0.01 to 0.2 parts by weight per 100 parts by weight of the vinyl chloride polymer. If the amount is less than 0.01 part by weight, the thermal stability is insufficient, while if it exceeds 0.2 part by weight, the fishiness is poor.

As the dispersant (d), known water-soluble cellulose ethers such as methylcellulose and hydroxypropylcellulose can be used, and hydroxypropylmethylcellulose is preferable. Particularly preferably, the degree of hydroxypropoxyl group substitution (the number of hydroxypropoxyl groups per glucose ring of cellulose)
Is 0.15 to 0.25, and the degree of methoxyl group substitution (the number of methoxyl groups per glucose ring of cellulose)
Is 1.4 to 1.9 hydroxypropyl methylcellulose.

Examples of monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylates such as methyl (meth) acrylate and ethyl (meth) acrylate; And olefins such as propylene; maleic anhydride, acrylonitrile, styrene and vinylidene chloride.
It is preferable that the upper limit of the copolymerizable monomer be 50% by weight based on the total amount of the copolymerizable monomer and the vinyl chloride monomer.

Examples of the oil-soluble polymerization initiator include peroxydicarbonates such as diisopropylperoxydicarbonate, di-1-methylheptylperoxydicarbonate di-2-ethylhexylperoxydicarbonate and diethoxyethylperoxydicarbonate. Compounds, diacyl peroxide compounds such as isobutyl peroxide, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, α, α′-bis (neodecanylylperoxy) diisopropylbenzene, cumylperoxyneodecan Ethate, 2,4,4-trimethylpentyl-2-peroxyneodecanoate, t-
Peroxyester compounds such as hexylperoxyneodecanate and t-butylperoxyneodecanate, α, α′-azobisisobutyronitrile, α, α ′
-Azobis (2,4-dimethylvaleronitrile), α,
There are azo compounds such as α′-azobis (4-methoxy-2,4-dimethylvaleronitrile), and these can be used alone or in combination of two or more.

For the production of the vinyl chloride polymer according to the present invention
Where necessary, surfactants, scale inhibitors, p
Use H regulators, antioxidants and chain transfer agents
Can also. Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
Will be described in more detail. The vinyl chloride obtained in each example was
Eye and Thermal Stability of Nyl-Based Polymers
The evaluation was performed by the following method. Fisheye: 100 parts by weight of vinyl chloride polymer, di
50 parts by weight of octyl phthalate, 3 parts by weight of tribasic lead sulfate
Parts, 1 part by weight of lead stearate and 0.08 weight of carbon
After mixing the parts, the mixture was rolled at 155 ° C. for 4 minutes and 5 minutes.
100cm of the sheet obtained by kneading for 6 minutes Two
The number of fish eyes present was counted.

Thermal stability test: vinyl chloride polymer 100
Parts by weight, 35 parts by weight of diisononyl adipate, Ca-Z
1 part by weight of a composite metal soap-based stabilizer and 0.5 part by weight of tris (nonylphenyl) phosphite were mixed, and the mixture was rotated at 30 rpm using a plastograph tester.
Under the condition of 160 ° C., after 100 g of the mixture is charged, from the time when the maximum torque is reached, after the torque has decreased and shows a constant torque, the time when the torque starts to increase again due to decomposition of the resin The difference between the times was defined as the pyrolysis time.

[0013]

Example 1 200 kg of deionized water and a vinyl chloride monomer 13 were placed in a polymerization vessel made of stainless steel and having a capacity of 400 liters.
5 kg, as a dispersant, 70 mol% of a partially saponified polyvinyl alcohol having an average degree of polymerization of 0.04 parts by weight, and 70 parts by weight of a partially saponified polyvinyl alcohol having an average degree of polymerization of 2000; Saponification degree 5
0.01 mol part of a partially saponified polyvinyl alcohol having an average polymerization degree of 0 mol% of 500 parts by weight of a 2 wt% aqueous solution at 20 ° C. and a viscosity of 50 cps of hydroxypropylmethylcellulose (hydroxypropoxyl group substitution degree; 0.26, methoxyl group substitution degree; 1.9) 0.01 parts by weight of an aqueous solution was charged, and polymerization was carried out at a temperature of 56 ° C. using 0.02 parts by weight of di-2-ethylhexyl peroxydicarbonate as an initiator. After the polymerization was stopped at a conversion of 85% and the unreacted monomer was recovered, the degree of saponification was 70 mol%, and the average degree of polymerization was 5%.
0.1 part by weight of the partially saponified polyvinyl alcohol of No. 00 was added as an aqueous solution. Thereafter, a dried polymer was obtained from the vinyl chloride polymer slurry according to a conventional method, and the above-mentioned physical property test was performed on the dried polymer.

[0014]

Example 2 After recovering the unreacted monomer, the saponification degree was 70
The procedure was performed in the same manner as in Example 1 except that 0.05 parts by weight of a partially saponified polyvinyl alcohol having an average degree of polymerization of 500 and a molar percentage of 500 were added as an aqueous solution.

[0015]

Example 3 After recovering unreacted monomers, the degree of saponification was 78.
The procedure was performed in the same manner as in Example 1 except that 0.1 part by weight of a partially saponified polyvinyl alcohol having an average degree of polymerization of 600 was added as an aqueous solution.

[0016]

Example 4 Using the following compound as a dispersant, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1. Hereinafter, the partially saponified polyvinyl alcohol is abbreviated as PVA. PVA having a saponification degree of 78 mol% and an average polymerization degree of 600:
0.04 parts by weight PVA having a degree of saponification of 80 mol% and an average degree of polymerization of 2000:
0.01 parts by weight PVA having a saponification degree of 50 mol% and an average polymerization degree of 500:
0.01 parts by weight Hydroxypropylmethylcellulose having a viscosity of 50 cps at 20 ° C. of a 2% by weight aqueous solution (hydroxypropoxyl group substitution degree; 0.26, methoxyl group substitution degree;
9): 0.01 parts by weight After completion of the weight, PVA having a degree of saponification of 78 mol% and an average degree of polymerization of 600 was added to the polymer slurry from which the unreacted monomer was recovered.
0.1 part by weight was added as an aqueous solution. Hereinafter, Example 1
The same operation was performed.

[0017]

Comparative Example 1 After the unreacted monomer was recovered, the saponification degree was 70
The procedure was performed in the same manner as in Example 1 except that a partially saponified polyvinyl alcohol having an average polymerization degree of 500% by mol was not added as an aqueous solution.

[0018]

Comparative Example 2 After the unreacted monomer was recovered, the saponification degree was 80
The procedure was performed in the same manner as in Example 1 except that 0.1 part by weight of a partially saponified polyvinyl alcohol having an average degree of polymerization of 2,000 by mole was added as an aqueous solution.

[0019]

Comparative Example 3 After the unreacted monomer was recovered, the substitution degree of hydroxypropoxyl group was 0.26 and the substitution degree of methoxyl group was 1.
Example 9 was carried out in the same manner as in Example 1 except that 0.1 part by weight of hydroxypropylmethylcellulose having a viscosity of 50 cps at 20C of a 9% or 2% by weight aqueous solution was added as an aqueous solution. Table 1 shows the measurement results of the above Examples and Comparative Examples.

[0020]

[Table 1]

[0021]

According to the present invention, a vinyl chloride polymer having excellent heat stability and fish eye level can be obtained.

Claims (1)

[Claims] 1. A method for producing a vinyl chloride polymer by suspension polymerizing vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable with vinyl chloride in an aqueous medium, wherein (a) Saponification degree 65-85 mol%, average polymerization degree 40
0 to 1000 partially saponified polyvinyl alcohol,
(B) Degree of saponification 75 to 85 mol%, average degree of polymerization 1500
~ 3000 partially saponified polyvinyl alcohol, (c)
Saponification degree 15-54 mol%, average polymerization degree 100-120
0 and partially (d) a water-soluble cellulose ether, and after completion of the polymerization, the obtained polymer slurry was mixed with the polymer 100 in the slurry.
A method for producing a vinyl chloride polymer, comprising adding 0.01 to 0.2 parts by weight of the above partially saponified polyvinyl alcohol (a) per part by weight.