JPH0411607A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To obtain the title polymer having a low fish eye content and excellent plasticizer absorptivity by the suspension polymerization of a vinyl chloride monomer (mixture) in an aqueous medium, by adding a plurality of specified oil-soluble polymerization initiators divided in portions to the system under specified conditions. CONSTITUTION:A process for suspension-polymerizing a vinyl chloride monomer or a vinyl monomer mixture based thereon in an aqueous medium, wherein 50-90% of the total weight of at least one oil-soluble polymerization initiator selected from among a percarbonate compound, a diacyl peroxide compound, a peroxydicarbonate compound and an azo compound (e.g. di-2-ethylhexyl peroxydicarbonate) is added to the system before the start of the polymerization, and the remaining 10-50% of the oil-soluble initiator as a peroxyester compound (e.g. t-butyl peroxyneodecanoate) is added to the system during the period from the start of the polymerization to the time when the polymer conversion is 5-50%.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing vinyl chloride polymers, and in particular to a method for producing vinyl chloride polymers, which have a wide range of applications and have low fish eyes and excellent plasticizer absorption. This relates to a manufacturing method.

(Prior art) Vinyl chloride polymers produced by suspension polymerization are useful resins with excellent physical properties and are widely used as hard and soft materials. Since there are electric points in the absorption of plasticizer, the progress of uniform gelation, and the formation of fish eyes, improvements in these characteristics are desired.

(Problems to be Solved by the Invention) Therefore, as a method for obtaining a vinyl chloride polymer with excellent plasticizer absorption, for example, partially saponified polyvinyl alcohol (A) with a saponification degree of 70 to 85 mol% is mixed with monomer 100%. Partially saponified polyvinyl alcohol (B) with a saponification degree of 70 to 95 mol% when the polymerization is started in the presence of 0.005 to 0.05 parts by weight per part by weight and the polymerization conversion rate is 0.1 to 2% by weight. A method of adding A/B in a weight ratio of 1720 to 2/1 (Japanese Unexamined Patent Publication No. 53-35784),
A method of using a partially saponified polyvinyl alcohol with a saponification degree of 60 to 90 mol% in combination with a partially saponified polyvinyl alcohol with a saponification degree of 20 to 55 mol% (JP-A-53-136
A method in which suspension polymerization is carried out by changing the type and timing of addition of the suspending agent (Japanese Patent Publication No. 089), and a method in which a reflux condenser is used in combination and two types of polymerization initiators are used in combination (Japanese Patent Publication No. 1605/1989) Public bulletin) etc. were proposed.

However, using a special suspension agent requires the installation of a new conduit to the polymerization system, which complicates the equipment and increases costs, and the resulting product also has insufficient plasticizer absorption and fish eye suppression. Met.

Therefore, the object of the present invention is to provide a suspension polymerization method that can produce vinyl chloride polymer particles with a wide range of applications, which have less fish eyes and excellent plasticizer absorption even when conventionally known suspending agents are used. It provides:

(Means for Solving the Problems) The present invention has been achieved as a result of intensive research to solve this problem, and uses vinyl chloride monomers or a mixture of vinyl monomers mainly composed of vinyl chloride. When performing suspension polymerization in an aqueous medium, at least one oil-soluble polymerization initiator selected from percarbonate compounds, diacyl peroxide compounds, peroxydicarbonate compounds, and azo compounds is added in the total amount used before starting polymerization. 50-90% added 1
After the start of polymerization, when the polymerization conversion rate is 5 to 50%, the oil-soluble initiator as a peroxyester compound is added to the remaining 10 to 5%.
It is an object of the present invention to provide a method for producing a vinyl chloride polymer, the gist of which is to add 0% of the vinyl chloride polymer.

To explain this, in the present invention, a vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride is subjected to suspension polymerization in an aqueous medium in the presence of a dispersion stabilizer and an oil-soluble polymerization initiator. In this case, the oil-soluble polymerization initiator that is first added is at least one selected from percarbonate compounds, diacyl peroxide compounds, peroxydicarbonate compounds, and azo compounds, and the oil-soluble polymerization initiator is at least one kind selected from percarbonate compounds, diacyl peroxide compounds, peroxydicarbonate compounds, and azo compounds, and the amount of the oil-soluble polymerization initiator added is at least one selected from percarbonate compounds, diacyl peroxide compounds, peroxydicarbonate compounds, and azo compounds. 0.0 per monomer charge equivalent to 90%
It is used in a proportion of 5 to 0.27% by weight.

Specific examples of the oil-soluble polymerization initiator include diisopropyl peroxydicarbonate, di-2-ditylhexyl oxydicarbonate, jetoxyethyl peroxydicarbonate, and other bakacarbonate compounds; decanoyl peroxide, lauroyl peroxide, etc. , benzoyl peroxide, 3,5.5-trimethylhexanoyl peroxide, isobutyryl peroxide, and other diacyl peroxide compounds; diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-2-ethoxyethylperoxy peroxydicarbonate compounds such as dicarbonate, acetylcyclohexylsulfonyl peroxide, dimethoxyisopropyl peroxydicarbonate; α, α′-
Azobisisobutyronitrile, α,α′-azobis(2
, 4-dimethylvaleronitrile), α,α′-azobis(4-methoxy-2,4-dimethylvaleronitrile), and these compounds are used alone or in combination of two or more. be able to.

Furthermore, after the start of polymerization, a peroxyesterified metal is added as an oil-soluble initiator when the polymerization conversion rate is 5 to 50%, but this is usually equivalent to the remaining 10 to 50% of the charged monomer. The proportion is 0.001 to 0.15% by weight.

If this oil-soluble initiator is added before the polymerization conversion rate reaches 5%, the initiator concentration and polymerization rate in the suspended oil droplets will become uneven, resulting in many fish eyes and polymerization. If it is added when the conversion rate exceeds 50%, it is not preferable because a polymerization degree with high plasticizer absorption cannot be obtained.

Note that the polymerization conversion rate at this time can be estimated almost accurately based on the elapsed time from the start of the polymerization.

The oil-soluble initiators added thereafter include 1-butylperoxyneodecanoate, t-butylperoxypivalate, t-hexylperoxypivalate, α-cumylperoxyneodecanoate, t- Perester compounds such as hexyl neohexanoate and 2,4°4-trimethylpentyl-2-peroxy-2-neodecanoate, which can be used alone or in combination of two or more.

In the method for producing a vinyl chloride polymer of the present invention, monomers that are preferably used include vinyl chloride monomers, as well as mixtures of vinyl monomers that are mainly composed of vinyl chloride and copolymerizable with vinyl chloride monomers. (usually vinyl chloride is 50% by weight or more), and comonomers copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; acrylic esters such as methyl acrylate and ethyl acrylate; Examples include methacrylic acid ester; olefins such as ethylene and propylene; maleic anhydride; acrylonitrile; styrene; and vinylidene chloride.

The suspending agent used in this suspension polymerization may be those commonly used in the past, such as water-soluble cellulose ethers such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose; partially saponified polyvinyl alcohol, acrylic acid Coalescence: Examples include water-soluble polymers such as gelatin. These can be used alone or in combination of two or more, and together with the above suspending agents, nonionic compounds such as sorbitan monolaurate, sorbitan triolate, glycerin tristearate, ethylene oxide propylene oxide block copolymer, etc. It is also possible to use a combination of one or more types of emulsifiers, anionic emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerol oleate, and sodium laurate.

Further, if necessary, polymerization regulators, chain transfer agents, pH regulators, gelling improvers, antistatic agents, scale inhibitors, etc., which are appropriately used in vinyl chloride polymerization, may be added.

Other conditions during this polymerization, such as the method of charging the aqueous medium, vinyl chloride monomer, other comonomers, suspending agent, etc. , polymerization conditions such as polymerization temperature may also be the same.

(Example) A specific embodiment of the present invention will be explained below using Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 900 kg of deionized water, 180 g of partially saponified polyvinyl alcohol (average degree of polymerization: 2,000, degree of saponification: 80 mol%), and hydroxyl Propyl methylcellulose (degree of methoxy substitution: 29.2% by weight)
, degree of hydroxypropoxy substitution = 8.9% by weight, viscosity:
49 cps) and 300 g of di-2-ethylhexyl peroxydicarbonate were charged.

Next, after degassing until the internal pressure of the polymerization vessel became 50 mnHg, 600 kg of vinyl chloride monomer was charged. While stirring the inside of the vessel, hot water was passed through the jacket to raise the temperature to 57°C, and then polymerization was carried out while maintaining that temperature. When the polymerization conversion rate reached 35%, 200 g of t-butyl peroxyneodecanoate was added to continue the polymerization.

After the unreacted monomers were collected when the internal pressure of the polymerization vessel decreased to 6.0 kg/cntG, the slurry, which was the reaction mixture, was taken out from inside the polymerization vessel and dehydrated and dried to obtain a vinyl chloride polymer.

Regarding the obtained polymer, the bulk specific gravity and particle size (mesh) distribution according to JIS K-6721, as well as the amount of plasticizer absorption and the amount of fish eyes were measured according to the following method.

・Plasticizer absorption amount 20 g of DOP was added to 10 g of polymer, and after standing for 1 hour, unabsorbed DOP was removed in a centrifugal separator for 20 minutes, and the amount of DOP absorbed by the polymer (% by weight) was expressed.

・Fisheye weight Polymer: 50g, DOP: 25g, Tribasic lead sulfate:
0.3g, lead stearate: 1. Og, titanium oxide 20
゜01g and carbon black: Mix and prepare 0.005g of each component, take out 25g from the resulting mixture, knead it for 5 minutes at 140°C using a 6' roll, and mix it with a width of 1o.
(1) It was molded into a sheet with a thickness of 0.2 ma.

The number of transparent particles per 100 J of area of the obtained silt was counted, and this was used as an index of the amount of fish eyes.

Example 2゜The oil-soluble initiator added first was 400 g of diisopropyl peroxydicarbonate, and the oil-soluble initiator added next was 28 g of α-cumyl peroxyneodecanoate.
A vinyl chloride polymer was obtained in the same manner as in Example 1, except that 0 g was added when the polymerization conversion rate reached 12% by weight. The same measurements as in the previous example were performed on this polymer.

Example 3 The oil-soluble initiator added first was 350 g of jetoxyethyl peroxydicarbonate, and the oil-soluble initiator added next was 350 g of t-amyl peroxypivalate.
Polymerization was carried out in the same manner as in Example 1, except that it was added when the polymerization conversion rate reached 7% by weight, and the obtained vinyl chloride polymer was measured in the same manner as in the previous example.

Example 4゜Polymerization was carried out in the same manner as in Example 1, except that the timing of addition of t-butyl peroxyneodecanoate to be additionally used was set at the time when the polymerization conversion rate reached 17% by weight, and the obtained chloride The same measurements as in the previous example were carried out on vinyl polymers.

Example 5゜The oil-soluble initiator added first was 400 g of di-2-ethylhexyl peroxydicarbonate, and the oil-soluble initiator added next was 200 g of t-hexyl peroxypivalate, so that the polymerization conversion rate was 10. Polymerization was carried out in the same manner as in Example 1, except that it was added when the weight % was reached, and the obtained vinyl chloride polymer was measured in the same manner as in the previous example.

Example 6゜The oil-soluble initiator added first was 560 g of jetoxyethyl peroxydicarbonate, and the oil-soluble initiator added next was 140 g of t-butyl peroxypivalate.
Polymerization was carried out in the same manner as in Example 1, except that it was added when the polymerization conversion rate reached 20% by weight, and the obtained vinyl chloride polymer was measured in the same manner as in the previous example.

Comparative Example 1° Polymerization was carried out in the same manner as in Example 1, except that the oil-soluble initiator was not added during the polymerization, and the obtained polymer was measured in the same manner as in the previous example.

Comparative Example 2゜Polymerization was carried out in the same manner as in Example 1, except that the oil-soluble initiator was added at the time when the polymerization conversion rate reached 3%, and the obtained polymer was subjected to the same measurements. .

Comparative Example 3 Polymerization was carried out in the same manner as Actual Example 1, except that the oil-soluble initiator was added when the polymerization conversion rate reached 65%.
Similar measurements were performed on the obtained polymer.

The above results are shown in the numerical table.

(Effect of the invention) According to the present invention, without changing bulk specific gravity or particle size distribution,
It is possible to obtain a vinyl chloride polymer with excellent plasticizer absorption and a small amount of fish eye.

Claims (1)

[Claims] 1. When a vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride is subjected to suspension polymerization in an aqueous medium, percarbonate compounds, diacyl peroxide compounds, peroxydicarbonate compounds and At least one oil-soluble polymerization initiator selected from azo compounds is added in an amount of 50 to 90% of the total amount used before the start of polymerization, and after the start of polymerization, the peroxyester compound is added at a polymerization conversion rate of 5 to 50%. 1. A method for producing a vinyl chloride polymer, which comprises adding an oil-soluble initiator to the remaining 10 to 50%.