JPS6361961B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for suspension polymerizing vinyl chloride alone or a mixture with other monomers copolymerizable with vinyl chloride in an aqueous medium, and in particular, it relates to a method for suspension polymerizing vinyl chloride alone or a mixture with other monomers that can be copolymerized with vinyl chloride.
The purpose is to obtain a polymer having good initial colorability and thermal stability of a molded product after kneading and molding. The coloring of vinyl chloride polymers can be broadly classified into two types: coloring of the polymer at a relatively small thermal history, so-called initial coloring, and blackening of the polymer at a time of a large thermal history.
Of these, the latter is due to the formation of conjugated double bonds due to thermal decomposition of the vinyl chloride polymer, and is suppressed by adding a metal soap or an organic tin compound as a stabilizer. However, regarding the former initial coloring, the coloring mechanism has not yet been fully elucidated, and therefore some methods have been proposed to prevent this, such as adding some additives during polymerization. Depending on the type of stabilizer, the coloring may become more pronounced, and it is not yet sufficient. In recent years, as new uses and processing techniques have been developed for vinyl chloride polymers, there has been a demand for higher quality vinyl chloride polymers, and in particular, there is a strong demand for vinyl chloride polymers with good initial coloring and thermal stability. In view of such demands, the present inventors have studied various protective colloids and surfactants in order to obtain a vinyl chloride polymer with good initial coloring and thermal stability. By using an epoxidized alkyl ester of alcohol in combination, a vinyl chloride polymer with extremely good initial coloring and thermal stability can be obtained without impairing various properties such as plasticizer absorption, gelling properties, and fixity. I found out that it can be done. That is, in the present invention, when vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith is subjected to suspension polymerization in an aqueous medium in the presence of a polymerization initiator, the epoxidized alkyl of the suspending agent and alcohol This is a method for suspension polymerization of vinyl chloride, which is characterized in that an ester is used in combination. Polymerization initiators used in the present invention include diacyl peroxides such as lauroyl peroxide; peresters such as tert-butyl perpivalate; and di-2-ethylhexyl peroxydicarbonate. Examples include organic peroxides such as percarbonates and azo compounds such as azobisisobutyronitrile, but are not limited to these. Furthermore, as the protective colloid used in the present invention, any commonly known suspending agent can be used without any restriction. Particularly preferred are partially saponified polyvinyl acetates having various degrees of saponification, water-soluble cellulose derivatives such as hydroxymethyl cellulose, and the like. Generally, the suspending agent is added in an amount of 0.01 to 1.0% by weight of the vinyl chloride monomer or monomer mixture, and is used singly or in combination in various compositions. In the present invention, it is important to use an epoxidized alkyl ester of alcohol in combination with the above-mentioned suspending agent. Conventionally, when carrying out suspension polymerization of vinyl chloride polymers, various combinations of suspending agents such as partially saponified polyvinyl acetate and cellulose derivatives are used as suspending agents, and further processing for plasticizer absorption, gelling properties, etc. In order to improve the properties, it has been proposed to use alkyl esters such as sorbitan, sutucarose, and glycerin in combination. On the other hand, according to the present invention, by using an epoxidized alkyl ester of alcohol together with a suspending agent, the above-mentioned properties such as plastic absorption, gelling properties, and other processability are not impaired. , a vinyl chloride polymer with good initial coloring and thermal stability can be obtained. The epoxidized alkyl ester of alcohol in the present invention is an ester with a monohydric or polyhydric alcohol having one or more epoxidized alkyl groups having 8 to 18 carbon atoms and having one or more epoxy rings. In the case of the above-mentioned monohydric alcohols, those with more than 8 carbon atoms can coexist in the polymerization system and be polymerized, but since they have almost no function as a surfactant, their effect as a suspension stabilizer is insufficient. I can't. Therefore, epoxidized alkyl esters of alcohols having 1 to 8 carbon atoms such as methyl alcohol, butyl alcohol, and octyl alcohol are desirable. Examples of the polyhydric alcohol include propylene glycol, glycerin, polyglycerin, pentaerythritol, sorbitan, and saccharides such as sutucarose. In the case of an epoxidized alkyl ester of a polyhydric alcohol, mono-, di-, or tri-esterification can be used, and it is necessary that at least one of them is an epoxidized alkyl group. Furthermore, in order not to lose its function as a surfactant, it is desirable to have at least one unesterified hydroxyl group. These monoesters,
Diesters or triesters can also be used as mixtures. In the present invention, the amount of the epoxidized alkyl ester of alcohol to be used varies depending on the type and amount of the protective colloid to be combined, but is generally 0.01 to 1.0 with respect to the vinyl chloride monomer or monomer mixture.
It may be used preferably in a range of 0.02 to 0.5% by weight. The effect of the present invention is that by using a suspending agent and an epoxidized alkyl ester of alcohol in combination, physical properties such as initial coloration and thermal stability of the vinyl chloride resin obtained are significantly improved.
It can also be added during or at the end of polymerization. The polymerization method of the present invention includes not only homopolymerization of vinyl chloride, but also polymerization of a mixture with copolymerizable monomers,
Furthermore, it can also be applied to polymerization in the coexistence of vinyl chloride and graftable rubbers. Monomers copolymerizable with vinyl chloride include fatty acid vinyl esters such as vinyl acetate; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and their esters or salts; acrylonitrile unsaturated nitriles such as; aromatic vinyl compounds such as styrene; and halogenated olefins other than vinyl chloride such as vinylidene chloride. Examples of rubbers that can be grafted include ethylene-propylene rubber, propylene oxide rubber, and chlorinated polyethylene and ethylene-vinyl acetate copolymers. Of course, it can also be applied to polymerization of vinyl chloride or vinyl chloride and a monomer mixture copolymerizable with vinyl chloride in the coexistence of inorganic substances such as powders such as titanium oxide and carbon black, or glass fibers and carbon fibers. . In the present invention, the combined use of known surfactants conventionally used in the polymerization of vinyl chloride or the use of known additives (antioxidants, chelators, etc.) will not have any adverse effects. It can be selected and used as necessary. EXAMPLES In order to explain the present invention more specifically, Examples and Comparative Examples will be described below, but the present invention is not limited to these Examples. In addition, the measurement method and judgment method in the Examples and Comparative Examples were carried out by the following methods. Test method 1 Initial coloring and oven heat stability (1) Compounding (A) Vinyl chloride polymer tin stabilizer *1 Tin stabilizer *2 100 parts 2.0 parts 2.0 parts (B) Vinyl chloride polymer calcium - Zinc stabilizer *3 Calcium - zinc stabilizer *4 Epoxy plasticizer *5 100 parts 0.3 parts 1.2 parts 4.0 parts *1: Made by Nitto Kasei Co., Ltd., product name N2000E *2: Same, product name E101 *3 : Manufactured by Tokyo Fine Chemical Co., Ltd., product name
TMF309G *4: Same, product name
TMF125 *5: Same, product name W-
100EL (2) Testing and judgment of initial coloring and thermal stability The above composition was kneaded for 5 minutes with oil-heated rolls at 150°C to create a 1mm thick sheet. For initial coloring, stack 5 roll sheets and press at 175℃ for 15 minutes.
After preheating for a minute, the plate was further pressurized to 50 kg/cm ² for 15 minutes to form a plate, and the hue of the plate was evaluated. Oven thermal stability is 25% from the rolled sheet.
Take a section of mm x 50 mm and place it in a gear oven at 180℃.
The hue of the section after minutes was classified into three levels A to C, and for formulation (B), the time (minutes) until the entire surface of the section turned black was shown. The oven thermal stability of formulation (A) was evaluated as 2.5 on the JIS standard color chart because the hue of the sheet section produced by this formulation changes continuously from pale yellow to orange to black in the oven. Grade A, 10YR5/ for those with a slightly yellow hue than around Y6/8.
Those with a hue around 6 are grade B, 10YR4/4 to
Those around 7.5YR4/4 are classified into three stages as stage C. 2.Fish eye measurement Compounded vinyl chloride polymer Dioctyl phthalate Ultramarine Cadmium stearate Barium stearate 100 parts 40 parts 3.0 parts 1.0 parts 1.0 parts After kneading the above composition for 7 minutes with an oil-heated roll at 145°C, a 0.35 mm sheet was made. , the number of fish eyes present in the 50 cm ² sheet. 3 Measurement of gelation time Compounded vinyl chloride polymer Lead stearate Tribasic Lead sulfate Calcium stearate 57.6 g 1.0 〃 0.5 〃 0.35 〃 0.25〃 The above mixture was kneaded using a Brabender blast graph to cause gelation. The time (minutes) required to reach the accompanying maximum torque was determined. Jacket temperature is 190℃, rotor rotation speed is
It is 60rpm. Examples 1 to 10, Comparative Examples 1 to 5 In a stainless steel polymerization can with an internal volume of 65 liters, 26 kg of deionized water, 4.5 g of tertiary butyl perpivalate as a polymerization initiator, and the suspending agent and alcohol shown in Table 1 were added. After adding the epoxidized alkyl ester and purging the system with nitrogen, the pressure was reduced to 100 mmHg, and 20 kg of vinyl chloride monomer was introduced. after that,
Polymerization was carried out by raising the temperature to 67.5℃ with stirring, and when the pressure inside the polymerization vessel decreased by 2.0Kg/cm ² from the equilibrium pressure,
The unreacted monomer in the polymerization reactor was purged to complete the polymerization. After dehydrating and drying the obtained polymer slurry,
The test samples listed in Table 1 were used.

【table】

[Table] In Table 1, Examples 1, 2 and 9 are epoxidized stearic acid esters of monohydric alcohols, and Examples 3 to 8 and 10 are epoxidized fatty acid esters of polyhydric alcohols. In addition, Comparative Examples 1 and 4 are examples in which polymerization was performed using only a suspending agent, and Comparative Examples 3 and 5 are examples in which the same amount of sorbitan monostearate as a surfactant is added to the formulations of Comparative Examples 1 and 4, respectively. This is an example. Comparative Example 2 is an example in which epoxidized soybean oil, which is a tri-epoxidized fatty acid of glycerin, which is a trihydric alcohol, was added. From these examples, each example has a sharper and finer particle size distribution than Comparative Examples 1 or 4, in which polymerization was performed using only a suspending agent, and Comparative Example 3 in which sorbitan monostearate, a known surfactant, was added. or 5
It shows similar or even better results. However, when the epoxy soybean oil shown in Comparative Example 2 was added, the particle size distribution was broader and coarser than in Comparative Example 1, which was polymerized with only a protective colloid, and it was found that the dispersibility was actually inhibited. it is obvious. In addition, the bulk density of each example was higher than that of each comparative example in which polymerization was performed using only a suspending agent, and was comparable to that of sorbitan monostearate, which is a well-known surfactant, but when epoxy soybean oil was added. It can be seen that it is actually getting lower. It is also clear that both the fisheye and the gelation time are significantly better than those obtained by polymerization using only a suspending agent, despite the higher bulk density. Next, when comparing the initial coloring and thermal stability, Comparative Example 2 in which epoxy soybean oil was added in formulation (B)
In addition to the fact that the oven thermal stability of Blend (A) and Blend (B) is close to that of the corresponding example group, the initial coloration and thermal stability of both formulation (A) and formulation (B) are lower than those of the corresponding example group in each comparative example. It is clear that the effect of the present invention is significant. Example 11, Comparative Example 6 Add 32% deionized water to the polymerization can used in Examples 1 to 10.
Kg, 10 g of diisopropyl peroxydicarbonate as a polymerization initiator and 8 g of partially saponified polyvinyl acetate (Gosenol, GH-17), hydroxypropyl methylcellulose (Metrose 60SH-50)
After adding 8 g of sorbitan-mono-epoxidized stearate and purging the inside of the polymerization reactor with nitrogen,
The pressure was reduced to mmHg, and 14.5 kg of vinyl chloride and 0.9 kg of propylene (8 mol%) were introduced. Then under stirring
Polymerization was started by raising the temperature to 57.0°C, and when the pressure inside the polymerization vessel decreased by 3.0 Kg/cm ² from the maximum pressure, the unreacted monomer mixture was purged and polymerization was completed. Comparative Example 6 was an example in which sorbitan monostearate was used instead of sorbitan monoepoxidized stearate. The results are listed in Table-2. Table-2
As is clear from the above, by replacing the stearic acid in sorbitan monostearate with epoxidized stearic acid, the initial coloration and thermal stability are significantly improved while maintaining physical properties such as particle size.

【table】

Claims (1)

[Claims] 1. When vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable with vinyl chloride is subjected to suspension polymerization in an aqueous medium in the presence of a polymerization initiator, an epoxy resin of a suspending agent and an alcohol is used. 1. A method for suspension polymerization of vinyl chloride, which comprises using alkyl ester in combination. 2. The method according to claim 1, wherein the epoxidized alkyl group is an alkyl ester of an alcohol having 8 to 18 carbon atoms and being an aliphatic hydrocarbon residue having one or more epoxy rings. 3. The method according to claim 1, wherein the alcohol is an epoxidized alkyl ester of an alcohol selected from monohydric alcohols having 1 to 8 carbon atoms. 4. The method according to claim 1, wherein the alcohol is an epoxidized alkyl ester of an alcohol selected from dihydric or higher polyhydric alcohols. 5. Claim 4, characterized in that the epoxidized alkyl ester of the alcohol carries at least one unesterified hydroxyl group.
The method described in section. 6. The method according to claim 4, wherein the epoxidized alkyl ester of alcohol is a mono-, di- or tri-epoxidized alkyl ester of alcohol, or a mixture thereof. 7. The method of claim 4, wherein the epoxidized alkyl ester of alcohol is a di- or tri-ester or a mixture thereof containing at least one epoxidized alkyl group. 8. The method according to claim 1, wherein the epoxidized alkyl ester of alcohol is added in an amount of 0.01 to 1.0% by weight based on the monomer.