GB2074589A

GB2074589A - Polymerisation of Vinyl Chloride

Info

Publication number: GB2074589A
Application number: GB8107827A
Authority: GB
Original assignee: Kureha Corp
Current assignee: Kureha Corp
Priority date: 1980-04-21
Filing date: 1981-03-12
Publication date: 1981-11-04
Also published as: AU538443B2; FR2480758A1; GB2074589B; FR2480758B1; AU6910381A; JPS56149407A; DE3113560A1

Abstract

A suspension polymerization of vinyl chloride or a mixture of a main component of vinyl chloride and a comonomer is carried out in the presence of 0.05 to 0.15 wt. part of mixed catalysts of alpha -cumyl peroxyneodecanoate and a dialkyl peroxydicarbonate having a C2-C8 alkyl group at a molar ratio of 1:0.1 to 0.8 per 100 wt. parts of said monomer.

Description

SPECIFICATION Process for Polymerizing Vinyl Chloride Type Monomer Background of the Invention: Field of the Invention: The present invention relates to a production of a polymer having high quality with industrial advantages by a novel suspension polymerization of vinyl chloride or vinyl type monomers containing vinyl chloride as a main component.

Description of the Prior Arts: Vinyl chloride resins as commonly used resins have been produced by a mass production because of low costs and excellent physical properties. Various improvements for producing vinyl chloride resins with industrial advantages have been proposed.

As a method of improving productivity of vinyl chloride resins, certain shortening of duty cycle can be considered. In order to attain the purposes, effort for saving labour and time for cleaning under reducing scaling in a polymerization reactor and effort for shortening polymerization time in heat removal limitation have been made.

The polymerization time for the production of vinyl chloride resins has been usually in a range of 7 to 1 2 hours in practical operations. It may be possible to attain the polymerization for shorter than 5 hours by selecting a kind of a catalyst and increasing an amount of the catalyst. The following problems have been usually found.

1) When an amount of the polymerization catalyst is increased for shortening the polymerization time, severe gellation is resulted in the last stage of the polymerization to cause serious rising of temperature. A large cooling equipment is required to cause large loss for efficiency of the cooling equipment because the cooling function of the polymerization reactor is depending upon the heating in the last stage.

2) The increase of the amount of the polymerization catalyst causes lowering of catalytic efficiency and increasing an amount of the residual catalyst, whereby heat stability of the resulting polymer is remarkably reduced.

In order to overcome these problems, it has proposed to combine a catalyst having high catalytic activity with short half-value period of catalyst-decomposing velocity and a catalyst having low catalytic activity with long half-value period of catalyst-decomposing velocity to reduce the heating in the last stage of the polymerization under uniforming polymerization velocity with a small amount of the catalyst.

In Japanese Examined Patent Publication No. 14670/1971 , the combination of catalysts having relatively higher catalytic activities as a combination of acetylcyclohexylsulfonyl peroxide (ACS) as a catalyst having short half-value period and dialkyl peroxydicarbonate as a catalyst having long half-value period has been proposed. It is not preferable to use a large amount of ACS because of deterioration of heat stability of vinyl chloride resins.

In Japanese Examined Patent Publication No. 18852/1972, a combination of t-butyl peroxyneodecanoate as a catalyst having short half-value period and lauroyl peroxide as a catalyst having long half-value period has been proposed. However, t-butyl peroxyneodecanoate still has relatively long half-value period (the temperature for the half-value period of 10 hours is in a range of 46-51 OC). It is difficult to shorten the polymerization time to shorter than 5 hours with a small amount of the catalysts even though said combination of the catalysts is employed.

Summary of the Invention: It is an object of the present invention to provide a process for polymerizing a vinyl chloride type monomer under uniforming polymerization velocity; cooling easily polymerization heat and completing the polymerization for a shorter time (shorter than 5 hours) with a small amount of catalysts.

Another object of the present invention is to provide a process for polymerizing a vinyl chloride type monomer wherein most of catalysts are substantially decomposed in the polymerization and heat stability of the resulting vinyl chloride resin is not inferior to the heat stability of vinyl chloride resins obtained by the polymerization for a long polymerization time.

The foregoing and other objects of the present invention have been attained by providing a process for polymerizing a vinyl chloride type monomer in the presence of 0.05-0.1 5 wt. parts of mixed catalysts of cz-cumyl peroxyneodecanoate and a dialkyl peroxydicarbonate having a C2-C8 alkyl group at a molar ratio of 1:0.1 to 0.8 per 100 wt. parts of said monomer in a suspension polymerization of vinyl chloride or a mixture of a main component of vinyl chloride and a comonomer.

Detailed Description of the Preferred Embodiments: The dialkyl peroxydicarbonates used as a cocatalyst are the peroxydicarbonates having a C2-C8 alkyl group which have relatively high catalytic activity such as dibutoxyethyl peroxydicarbonate, diisopropyl peroxydicarbonate and di-2-ethylhexyl peroxydicarbonate. The temperature for the halfvalue period of 10 hours is about 43+30C.

It has been considered that the optimum polymerization temperature for producing a vinyl chloride resin having an average polymerization degree of about 1,000 as a commonly used grade is in a range of about 57 to 580C in the polymerization of vinyl chloride monomer. In order to complete the polymerization for 7 to 1 2 hours at the polymerization temperature, the dialkyl peroxydicarbonate is the desired catalyst to attain the polymerization under relatively uniform polymerization velocity with less than 0.05 wt. part of the catalyst.However, if the content of the catalyst is increased to shorten the polymerization time, the heating in the last stage of the polymerization is increased by the gellation depending upon the content of the catalyst not to attain uniformity of the temperature and moreover, the heat stability of the polymer is remarkably inferior because of the residual catalyst.

On the other hand, the a-cumyl peroxyneodecanoate as the main component of the catalysts in the process of the invention is the catalyst having higher catalytic activity than the dialkyl peroxydicarbonate. The temperature for the half-value period of 10 hours is about 380C. When only 0.1 wt. part of the catalyst is used for a polymerization of vinyl chloride monomer at a polymerization temperature of 57 to 580 C, the polymerization performs at relatively uniform polymerization velocity.

However, in the last stage of the polymerization, the polymerization velocity becomes remarkably slow by the consumption of the catalyst whereby the polymerization time can not be shortened. The acumyl peroxyneodecanoate is described in detail in Japanese Examined Patent Publication No.

3847/1979.

It has been found that when 0.05 to 0.1 5 wt part of the mixed catalysts containing sg-cumyl peroxyneodecanoate as the main component and the dialkyl peroxydicarbonate as the cocatalyst are incorporated per 100 wt. parts of the monomer, the polymerization of vinyl chloride monomer performs at a uniform polymerization velocity to complete the polymerization for shorter than 5 hours and to obtain the polymer having excellent heat stability.

The heat stability of the polymer is depending upon an amount of the residual catalyst. Therefore, it is advantageous to combine such cataiyst consuming in the initial stage as the main catalyst and the catalyst having slightly lower catalytic activity (the temperature for the half-value period of 10 hours is higher for 4 to 1 00C) as a cocatalyst The a-cumyl peroxyneodecanoate and the dialkyl peroxydicarbonate are preferably combined at a molar ratio of 1:0.1 to 0.8.

The total amount of the catalysts and the ratio of the catalysts used in the present invention are depending upon the polymerization temperature of the vinyl chloride monomer. The total amount of the catalysts is usually in a range of 0.05 to 0.15 wt. part per 100 wt. parts of the monomer at the polymerization temperature of 50 to 650C. When the amount of the catalysts is too small, the polymerization can not be completed within a short time whereas when it is too much, the severe heating is resulted in the last stage of the polymerization and the heat stability of the polymer is inferior.

When the ratio of the dialkyl peroxydicarbonate is too low, the polymerization velocity is too slow in the last stage of the polymerization as the polymerization with only a-cumyl peroxyneodecanoate, whereas when it is too high, the amount of the residual dialkyl peroxydicarbonate in the resulting polymer is too much and the heat stability of the polymer is inferior.

In accordance with the process of the present invention, the polymerization can be carried out under the conditions of the conventional suspension polymerizations except using the combination of the catalysts. For example, into an autoclave made of stainless steel or glass lining equipped with a stirrer, an aqueous solution of a suspending agent at a ratio of 100 to 400 wt.% based on the total monomers is charged, and the autoclave is purged with nitrogen gas and the monomer containing the catalysts of the present invention is fed under pressure to carry out the polymerization with stirring at a specific polymerization temperature of 50 to 650C.The temperature in the polymerization system can be raised for 5 to 1 00C in the last stage of the polymerization to shorten the polymerization time and to reduce the amount of the residual catalysts and to improve the heat stability of the resulting polymer. It is aiso preferable to add a catalyst-decomposing agent such as dialkyl thiodipropionate, trisnonylphenylphosphite and 2,6-ditertiarybutyl hydroxytoluene at the completion of the polymerization since the heat stability of the polymer can be improved.

The suspending agents used in the process of the present invention can be the known suspending agents such as cellulose derivatives e.g., methyl cellulose; and partially hydrolyzed polyvinyl alcohol, polyvinyl alcohol, copolymers of maleic acid and styrene; copolymers of maleic acid and vinyl acetate and polyethyleneoxides. The other additives such as buffer agents, molecular weight regulators, scaling inhibitors etc. can be also incorporated.

The process of the present invention can be applied for a homopolymerization of vinyl chloride monomer or a compolymerization of a mixture of vinyl chloride monomer and less than 30 wt.% of a comonomer. The comonomers can be ethylene, propylene, vinyl acetate, vinylidene chloride, acrylonitrile etc.

The present invention will be further illustrated by certain examples and references which are provided for purposes of illustration only and are not intended to be limiting the present invention.

Example 1: Into a 10 liter stainless steel autoclave equipped with a blade type stirrer, a solution of 1.8 g. of partially hydrolyzed polyvinyl alcohol in 6,000 g. of deionized water was charged and the autoclave was purged with nitrogen gas, and then, 3,000 g. of vinyl chloride monomer containing 2.25 g.

(0.0074 mol) of ct-cumyl peroxyneodecanoate and 0.75 g. (0.0023 mol) of dibutoxyethyl peroxydicarbonate (molar ratio of 1:0.311) was fed under pressure. The mixture was heated to 57 0C during about 10 minutes with stirring and the temperature was maintained by controlling the temperature of the bath. After 3 hours from the heating, the pressure in the polymerization system was reduced for 4.5 kg./cm2 from the equilibrium pressure. At this time, the residual monomer was discharged and the polymer slurry was discharged. The resulting polymer was washed with water and dehydrated and dried. The conversion was 91%.

The curve of Figure 1 shows the relation of bath temperature for maintaining the polymerization temperature at 570C and polymerization times. The results of Example 1 are shown by the curve 1. As it is clearly understood by the curve 1 , the heating was substantially uniform after the initiation of the polymerization and excess heating caused by the gellation in the last stage of the polymerization was not found.

The following composition was prepared by blending the resulting polyvinyl chloride, by a rollkneading operation to prepare a sheet. The heat stability was tested by the initial coloring and Geer's oven test. The results are shown in Table 1.

Table 1

Conversion for Polymerization polymerization Heatstability time lhr.l lO/ol 10 (al Example 1 3/6 91 2 2 3/6 91 1 2 3/6 91 3 3/6 91 1 Reference 1 3/4 91 5 2 3/6 85 2 3 3 3/4 90 4 (a) Composition for Heat Stability Test: Polyvinyl chloride 100 wt. parts Calcium stearate 2.5 wt. parts Barium stearate 0.7 wt. parts Tribasic lead sulfate 0.5 wt parts Roll temperature: 1 6O0C Roll kneading time: 7 minutes Heat stability:Initial colorings of the sheet and colorings in Geer's oven at 1 800C are rated from 1 (good) to 5 (bad).

Example 2: Into the apparatus of Example 1, a solution of 1.8 g. of partially hydrolyzed polyvinyl alcohol in 6,000 g. of deionized water was charged and the system was purged with nitrogen and then, 3,000 g.

of vinyl chloride containing 3.3 g. (0.01-1 mol) of cg-cumyl peroxyneodecanoate and 0.6 g. (0.0019 mol) of dibutoxyethyl peroxydicarbonate (molar ratio of 1:0.1 73) was fed under pressure. The mixture was heated to 520C during about 10 minutes with stirring and the temperature was maintained by controlling the temperature of the bath. After 3 hours 10 minutes from the heating, the pressure in the polymerization system was reduced for 3.7 kg./cm2 from the equilibrium pressure. At this time, a solution of 0.6 g. of nonylphenyl phosphite as a catalyst-decomposing agent in 30 g. of methanol was fed under pressure. In accordance with the process of Example 1, the polymer was separated. The heating was substantially uniform after the initiation of the polymerization and excess heating caused by the gellation was not found.The heat stability of the polymer is shown in Table 1.

Example 3: Into the apparatus of Example 1, a solution of 1.8 g. of partially hydrolyzed polyvinyl alcohol in 6,000 g. of deionized water was charged at 650C and the system was purged with nitrogen, the temperature in the system reached to 580C, and 3,000 g. of vinyl chloride monomer was fed under pressure and a solution of 2.25 g. (0.0074 mol) of a-cumyl peroxyneodecanoate and 0.48 g. (0.023 mol) of diisopropyl peroxydicarbonate (molar ratio of 1 :0.31) in 2,700 g. of vinyl chloride was fed with stirring during about 5 minutes. The temperature was maintained to 570C by controlling the temperature of the bath to carry out the polymerization. After 3.0 hours from the heating, the pressure in the polymerization system was reduced for 4.5 kg./cm2 from the equilibrium pressure.At this time, a solution of 0.3 g. of nonylphenyl phosphite and 0.3 g. of 2,6-ditertiarybutyl hydroxytoluene (BHT) in 30 g. of methanol was fed under pressure. After the polymerization, the polymer was separated.

The bath temperature during the polymerization is shown by the curve 2 of Figure 1. The heat stability of the polymer is shown in Table 1.

Reference 1: In accordance with the process of Example 1 except using only 3.0 g. (0.0093 mol) of dibutoxyethyl peroxydicarbonate as the catalyst, the polymerization was carried out. After 3 hours 5 minutes from the heating, the pressure in the polymerization system was reduced for 4.5 kg./cm2 from the equilibrium pressure. At this time, the polymer was discharged. The heat generation in the last stage of the polymerization was severe as shown by the curve 3 of Figure 1. The heat stability of the polymer is shown in Table 1. The heat stability was inferior because of the residual catalyst.

Reference 2: In accordance with the process of Example 1 except using only 3.0 g. (0.0098 mol) of a-cu myl peroxyneodecanoate as the catalyst, the polymerization was carried out. After 3 hours from the heating, the pressure in the polymerization system was reduced only for 2.5 kg./cm2. At this time, the conversion of the monomer was only 85%.

The heat generation is shown by the curve 4 of Figure 1. The heat stability of the polymer is shown in Table 1. The heat generation by the polymerization was reduced at relatively early stage and the polymerization velocity became slow because of consumption of the catalyst.

Reference 3: In accordance with the process of Example 1 except using 1.63 g. (0.0075 mol) of acetylcyclohexylsulfonyl peroxide having higher catalytic activity instead of a-cumyl peroxyneodecanoate, the polymerization was carried out. After 3 hours 5 minutes from the heating, the pressure in the polymerization system was reduced for 4.5 kg./cm2. At this time, the polymer was discharged and separated. The heat generation during the polymerization was shown by the curve 5 of Figure 1. In this case, the heat generation in the initial stage of the polymerization and the heat generation in the last stage as two peaks are found not be uniform heat generation. The heat stability of the polymer is inferior as shown in Table 1.

In Figure 1 (the curve 5), the relations of temperatures of each bath for maintaining the polymerization temperature at 570C and times of each polymerization are shown.

Claims

1. A process for polymerizing a vinyl chloride type monomer in the presence of 0.05 to 0.1 5 wt.

part of mixed catalysts of a-cu my peroxyneodecanoate and a dialkyl peroxydicarbonate having a C2- C, alkyl group at a molar ratio of 1 :0.1 to 0.8 per 100 wt. parts of said monomer in a suspension polymerization of vinyl chloride or a mixture of a main component of vinyl chloride and a comonomer.

2. The process according to Claim 1 wherein said monomer is vinyl chloride or a mixture of vinyl chloride and less than 30 wt.% of a comonomer based on the total monomers.

3. The process according to Claim 2 wherein said comonomer is ethylene, propylene, vinyl acetate, vinylidene chloride or acrylonitrile.

4. The process according to Claim 1 wherein the polymerization is completed for shorter than 5 hours.

5. The process according to Claim 1 wherein the polymerization temperature is maintained at a specific temperature in a range of 50 to 650C or raising for 5 to ? OOC in the last stage of the polymerization.

6. The process according to Claim 1 wherein a catalyst-decomposing agent is added after the completion of the polymerization.

7. A process according to Claim 1 substantially as herein described with reference to the examples.