JPS63275606A - Manufacture of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To obtain a vinyl chloride polymer which is prevented from fish-eye formation and which contains less residual vinyl chloride without any complicated manufacturing process, by using a suspension dispersant comprising a combination of two specific compounds in aqueous suspension polymerization by vinyl chloride. CONSTITUTION:The following compounds (1) and (2) are used together as suspension dispersants in the suspension polymerization of vinyl chloride or a mixture of vinyl chloride with a comonomer polymerizable therewith in an aqueous medium. Component (1): a partially saponified polyvinyl acetate which has a degree of saponification of 65-75mol.% and the viscosity of a 4wt.% aqueous solution of which is 5-6cps at 20 deg.C; component (2): hydroxypropyl cellulose which has a hydroxypropoxy group content of 50-80% and the viscosity of a 2% aqueous solution of which is 6.0-10.0cps at 20 deg.C. The compounds (1) and (2) are used in a total amount of 0.04-0.15wt.% for the monomer, and it is preferred that the ratio of (1):(2)=1:1-150:1(by weight).

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention is directed to a vinyl chloride polymer with improved moldability, especially fish eyes! ! Regarding the method of sending.

``Prior Art'' Vinyl chloride polymers have excellent mechanical properties, flame retardance, and chemical resistance, and are therefore used in a wide range of fields ranging from soft to hard polymers.

The most commonly used vinyl chloride polymers are usually obtained by suspension polymerization of vinyl chloride monomers in an aqueous medium containing a dispersant in the presence of an oil-soluble polymerization initiator.

However, in general, vinyl chloride polymers produced by suspension polymerization tend to produce undissolved particles called fish eyes during processing, which is undesirable for the appearance and mechanical properties of extruded and calendered products. The drawback was that it had no impact. In addition, there is a trace amount of unreacted vinyl chloride monomer in the vinyl chloride polymer, and there is a problem of environmental pollution due to this vinyl chloride monomer.
There has been a strong desire to produce vinyl chloride polymers with a low residual vinyl chloride monomer content.

Conventionally, as a method for producing vinyl chloride polymers with less fisheye formation and less residual vinyl chloride monomer, the following methods were used: ■ Partially saponified polyvinyl acetate with a low degree of saponification and partially saponified polyvinyl acetate with a high degree of saponification as a dispersant. A method of using polyvinyl acetate or a specific cellulose ether (Japanese Patent Publication No. 1244-1983)
No. 4) ■ A method of using partially saponified polyvinyl acetate with a low degree of saponification as a dispersant in combination with other dispersants (Japanese Patent Laid-Open No. 53-4379)
(No. 2, JP-A No. 54-3187) (1) A method in which partially saponified polyvinyl acetate having a specific degree of saponification and cellulose ether are used in combination as a dispersant (JP-A No. 52-5886) has been proposed.

However, depending on the method described above, the effects on improving fish-eye properties and removing residual monomers were not so great.

Furthermore, improvement of fish eye characteristics and residual vinyl chloride J
Although a technique related to a method for producing a vinyl chloride polymer for the purpose of removing one form of ILi has been proposed in JP-A-61-152703, the invention of this application is based on two types of partially saponified polyvinyl acetate and methyl having different physical properties. It is essential to use the three components of hydroxypropyl cellulose together as a dispersant, and it is necessary to focus on the management of the vinyl chloride polymerization process, including the preparation of the dispersant, making the production of vinyl chloride polymers complicated. Met.

"Problems to be Solved by the Invention" The present inventor omitted the complexity of the manufacturing process as much as possible,
As a result of intensive research into a manufacturing method that has good fish-eye properties and extremely low residual vinyl chloride monomer, we found that by using a specific hydroxypropyl cellulose and one type of partially saponified polyvinyl acetate with specific physical properties, a special It was discovered that a polymer having the same quality as the vinyl chloride polymer obtained in the invention of 1982-152703 could be obtained, and the present invention was completed.

That is, an object of the present invention is to provide a method for producing a vinyl chloride polymer that eliminates the complexity of the production process, has excellent fisheye properties, and has little residual vinyl chloride.

Means for Solving Problem E] Therefore, the essence of the present invention is to provide a method for suspension polymerizing vinyl chloride or a mixture of vinyl chloride and a comonomer copolymerizable therewith in an aqueous medium. As a suspending and dispersing agent, (1) partially saponified polyvinyl acetate having a degree of saponification of 65 to 75 mol% and a viscosity of a 4% aqueous solution thereof at 20° C. of 5 to 6 cps, and (2) a hydroxypropoxy group content of 50 ~80% and 20% of its 2% aqueous solution
9 of a vinyl chloride-based polymer characterized in that it is used in combination with hydroxypropyl cellulose having a viscosity of 6 to 10 eps at °C.
There is one method of construction.

Hereinafter, to explain the method of the present invention in detail, examples of comonomers copolymerizable with vinyl chloride include vinyl acetate, ethylene, propylene, furkyl vinyl ether, acrylic ester, methacrylic ester, acrylonitrile, and vinylidene chloride. These comonomers are used in an amount of 30% or less, preferably 15% or less based on vinyl chloride, but are not limited thereto.

The partially saponified polyvinyl acetate which is the suspension stabilizer used in the method of the present invention has a degree of saponification of 65 to 75 mol%, preferably 70 to 72 mol%, and has a 4% by weight aqueous solution thereof. Those having a viscosity of 5 to 6 cps, preferably 5.5 to 6 ocps are used.

The hydroxypropyl cellulose to be used in combination with partially saponified polyvinyl acetate has a hydroxypropoxy group content of 50 to 80%, preferably 60 to 65%, and a 2% by weight aqueous solution thereof has a viscosity of 6 to 80%. 10cp
s, preferably 7.8 to B, 5 cps.

If the above components (1) and (2) are not used together as a dispersant system, the effects of improving fisheye properties and reducing residual bulk will not be achieved. However, if a dispersant system with saponification degree, viscosity, etc. outside the ranges described in 1. is used, the above-mentioned effects of the present invention will still not be fully achieved.

The amount used in the above and
．． 03-0.3% by weight, preferably 0.04-0.15
It is preferable that the amount is in the range of % by weight, and the ratio of the amount used is preferably 1/1 to 150/1 in weight ratio (■/■). If the total amount of (1) and (2) is too small, the dispersion stabilizing effect tends to be insufficient, while if it is too large, the resulting vinyl chloride polymer particles tend to become fine and difficult to handle.

Furthermore, if the usage ratio (■/■) is too large, the effect of improving fish eyes will be small, and if it is too small, the thermal stability of the vinyl chloride polymer obtained will tend to deteriorate.

In the method of the present invention, dispersants and surfactants other than those mentioned above may be used, such as acrylic acid copolymers, maleic anhydride copolymers, gelatin, polyoxyethylene derivatives,
Although higher fatty acid metal salts and the like may be used as supplements, the effects of the present invention cannot be achieved even if they are used alone.

As the polymerization initiator, oil-soluble polymerization initiators generally used for vinyl chloride polymerization, such as benzoyl peroxide,
Organic peroxides such as lauroyl peroxide, t-butylperoxybivalate, quarctylberoxydicarbonate, diisopropylperoxycabonate, t-butylperoxyneodecanoate, a-cumylperoxyneodecanoate, azo Azo compounds such as bisisobutyronitrile and dimethylvaleronitrile are used, but in particular, t-butylperoxybeverley), 1-
Organic peroxides such as butylperoxyneodecanoate and a-cumylperoxyneodecanoate are preferred.

The amount of these polymerization initiators used is generally in the range of 0.01 to 1% based on the amount of vinyl chloride monomer.

Furthermore, in the polymerization reaction of the present invention, generally known polymerization aids such as chain transfer agents such as trichlorethylene, dodenlumerbutane, 2-mercaptoethanol 1-propionaldehyde, antioxidants, etc. may be used as appropriate. There is no problem.

In addition, as an additive to the above-mentioned dispersant, higher alcohols such as cetyl alcohol and octadecanol, higher fatty acids such as stearic acid and palmitic acid, or sorbitan monostearate, glycerin more stearate,
When higher fatty acid (partial) ester of polyhydric alcohol such as sorbitan-sorbit mixed partial stearate is added in a range of 0.01 to 0.1% by weight based on vinyl chloride monomer, It acts synergistically with the above-mentioned dispersant and further improves the effect of the present invention, so it is preferable ~1°. In this case, if the amount added is too small, no synergistic effect with the dispersant can be obtained, and the above-mentioned Even if the amount is increased more than the above amount, the synergistic effect with the dispersant will not particularly improve.

In carrying out the present invention, the vinyl chloride monomer can be charged all at once before the start of polymerization, or a part of the vinyl chloride monomer can be charged at the start of polymerization and the rest after the start of polymerization. It may be prepared all at once or in parts.

The polymerization temperature varies depending on the type of polymerization initiator used, the polymerization method, etc., but is usually in the range of 0 to 90°C, especially 40 to 70°C.
It is preferable to carry out the reaction at a temperature in the range of 0°C.

Conventional methods such as dehydration and drying of the resulting vinyl chloride polymer slurry are employed, and the vinyl chloride polymer slurry is processed by ordinary drying methods without being treated at high temperatures for a particularly long time. The residual vinyl chloride monomer content in
A vinyl chloride polymer with a pp export or less and excellent fisheye properties can be obtained.

1 Example” Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

In the following examples, the physical properties of the vinyl chloride polymer obtained were evaluated using the following physical property measuring method.

Average degree of polymerization and bulk specific gravity Measured according to the method shown in JIS K-6721.

■ Fisheye (hereinafter abbreviated as FE) (i)
Dioctyl 7-talate method Each vinyl chloride polymer (hereinafter abbreviated as PVC) 100
Parts by weight, 50 parts by weight of a plasticizer dioctyl 7-talate (hereinafter abbreviated as DOP), and 3 parts by weight of a calcium-based powder stabilizer were mixed, and then kneaded with rolls at 160° C. for 3 minutes and 5 minutes, respectively. The number of FEs observed in 25 cm'' of the obtained rolled sheet was counted and determined as the number of FEs.

(ii) 70 parts by weight of polyester plasticizer per 100 parts by weight of polyester PVC
Using part by weight as a plasticizer, the crosstalk time was 5 minutes and 7 minutes, respectively.
It was carried out in the same manner as the dioctyl heptatarate method described in (i), except that the heating time was set for 1 minute.

■ Thermal stability: 1 part by weight of pvcioo, 50 parts by weight of DOP, and 3 parts by weight of barium-zinc stabilizer were kneaded.
It was heated in an open gear at 90° C. and the time until it turned black was measured.

(2) Internal pore volume Using a mercury porosimetry porosimeter (manufactured by Kalkuchi Elba), the volume of 75,000 internal pores with a pore size of 75 was measured and converted to the pore volume per PVCl.

■ Residual vinyl chloride monomer content After dehydrating the slurry of each vinyl chloride polymer, it was heated at 65°C for 24 hours.
A certain amount of the dried material was collected, dissolved in a solvent tetrahydrofuran (THF) in a volumetric flask, and after making up 1 iffll to a certain volume, a chromatograph equipped with a flame ionization detector (FID) was used. A predetermined amount of the solution was injected as a sample, and a peak corresponding to vinyl chloride monomer was obtained.

Separately, the concentration of vinyl chloride monomer in the sample was determined from a calibration curve prepared from a standard sample, and converted to the concentration in PVC (lower limit of detection: 0.2 ppm).

Examples 1 to 6 and Comparative Examples 1 to 2 In a stainless steel polymerization vessel with an internal volume of 400 ml, vinyl chloride monomer (HOOkg, hereinafter abbreviated as VCM) was dispersed in 150 ml of deionized water as shown in Table 1. An aqueous solution of the agent and a polymerization initiator were charged, and the reaction was carried out under stirring and at the reaction temperature shown in Table 1 to a softening rate of 85%.

After the reaction, unreacted VCM was collected, the system was replaced with vacuum and nitrogen, and the resulting PVc slurry was taken out.
After dehydration and drying, analysis and evaluation were performed according to the method described above. (However, each sample for measuring the residual VCM content was separately taken out from the slurry and analyzed.) The results are shown in Table 2.

The following is clear from Table-2.

The vinyl chloride resin obtained by the method of the present invention has low FE and residual VCM, and other physical properties show performance equivalent to or better than that obtained by the conventional method (Comparative Examples 1 and 2).

In addition, as in Comparative Examples 1 and 2, in the method of the present invention in which (1) and (2) are not used together, the FE and VC removal results are obtained when only nooctyl heptatalate, which has good compatibility, is used as a plasticizer.
Although it shows an effect similar to that of the present invention in terms of M properties, the effect of the present invention cannot be obtained with respect to FE when a polyester plasticizer with poor compatibility is used.

"Effects of the Invention" According to the method of the present invention, in the suspension polymerization reaction of vinyl chloride monomer or a mixture of vinyl chloride and fumonomer in an aqueous medium, By using partially saponified polyvinyl acetate and (1) hydroxypropyl cellulose with a specific hydroxypropoxy group content and a specific viscosity, the manufacturing process was simplified, and the invention of Katmachi-no-Sho No. 61-152703 made it possible. It is possible to obtain a vinyl chloride polymer which has a residual vinyl chloride monomer content as low as that of the vinyl chloride P polymer and which has improved fish-eye characteristics.

The vinyl chloride polymer obtained by the method of the present invention has a low FE content, so it can improve productivity during processing and can be used to produce molded products with excellent appearance, such as calendar films, t-shirts, etc.
The process ends with obtaining a molded product with excellent transparency, such as a rubber sheet.

In addition to the above-mentioned dispersant system, when a higher fatty acid ester of a polyhydric alcohol is used in combination, the bush eye properties can be further improved.

Patent applicant: Mitsubishi Kasei Vinyl Co., Ltd. Representative patent attorney for long diameter - (1 other person)

Claims (1)

[Claims] (1) When carrying out suspension polymerization of vinyl chloride or a mixture of vinyl chloride and a comonomer copolymerizable therewith in an aqueous medium, a suspension dispersant having [1] a degree of saponification of 65 to 75 mol%, and Part 4
Partially saponified polyvinyl acetate whose viscosity at 20° C. in a weight% aqueous solution is 5 to 6 cps and [2] a hydroxypropoxy group content of 50 to 80% and whose 2% aqueous solution has a viscosity of 6.0 to 6.0 cps at 20°C. A method for producing a vinyl chloride polymer, characterized in that it is used in combination with hydroxypropyl cellulose having a concentration of 10.0 cps.