DK146340B - METHOD FOR PREPARING POLYVINYL CHLORIDE - Google Patents

Description

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DIRECTORATE OF THE PATENT-00 LABEL MARKET

(21) Patent Application No. 079577 (51) lnt.Cl.3; C 08 F114 / 06 (22) Filing Date: 23 Feb 1977 C 08 F 2/18 (41) Aim. available: 27 Aug 1977 (44) Submitted: 12 sap 1983 (86) International Application No: - (30) Priority: 26 lab 1976 SU 2328148 (71) Applicant: JULIA ALEXANDROVNA 'ZVEREVA; Dzerzhinsk, SU, EVGENY PAVLOVICH 'SHVAREV;

Dzerzhinsk, SU, MIKHAIL ALEXANDROVICH 'KARPACHEV; Dzerzhinsk, SU, BORIS GRIGORIEVICH 'MOISEEV; Dzerzhinsk, SU, VALERY YAKOVLEVICH 'KOLESNIKOV; Dzerzhinsk, SU, JURY PAVLOVICH 'FOKIN; Dzerzhinsk, SU.

(72) Inventor: Same.

(74) Plenipotentiary: International Patent Office (54) Process for the production of polyvinyl chloride

The invention relates to a process for preparing polyvinyl chloride for use in the manufacture of soft and hard products such as tubes, hoses or films.

A process for preparing polyvinyl chloride is known by suspension polymerization of vinyl chloride in combination with "in situ" synthesis of active percarbonate type initiators directly in an autoclave polymerization reactor (cf. US Patent No. 3,022. 281). Instead of using a finished polymerization initiator, starting materials are used for the initiator's synthesis, namely chloroformate, hydrogen peroxide, and an alkaline buffer. The initiator used in said process is diethyl peroxydicarbonate. The advantage of said method is the safety of working with the active polymerization initiators

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(the staff is not in direct contact with the initiator), and also its high efficiency, because the initiator synthesis and isolation, as a separate step, are avoided.

However, in said process, the rate of polymerization is slower than with the same catalyst used in the final form.

Particles of polyvinyl chloride obtained by said process are not granules but fibers. Furthermore, the polymer is deposited on the inner walls of the polymerization reactor.

The process has subsequently been improved. It was found that the rate of polymerization could be increased if an additional finished initiator, e.g. lauroyl peroxide (German Patent No. 2,039,010).

Later, methods for in situ synthesis of diisopropyl peroxydicarbonate (Swedish Patent No. 315,404) and of diethyl peroxydicarbonate (UK Patent No. 1,262,706) have been proposed which ensure higher polymerization rate of vinyl chloride which rates correspond to polymerization rates that can is obtained with the same concentrations of the initiators used in finished form. This was achieved by maintaining the equimolar ratio of chloroformate, hydrogen peroxide and alkaline agent, with the pH being a maximum of 7.0 at the beginning of the polymerization process.

Later, another method has been proposed that improved the quality of polyvinyl chloride produced in the form of uniform granules (U.S. Patent No. 3,799,916).

This was achieved by conducting the polymerization process, and the synthesis of the initiator, in an acidic medium (pH lower than 7.0). However, by this known polymerization method for vinyl chloride, the polymer was also deposited on the inner wall of the reactor ("crust formation").

Thus, all of the known improvements in the vinyl chloride polymerization methods, including synthesis of the initiator in situ, have aimed to increase the rate of polymerization and improve the quality of polyvinyl chloride, while the problem of preventing polymer deposition on the inner walls of the reactor is not solved.

The present invention aims to reduce the deposition of polyvinyl chloride on the reactor walls while maintaining the high polymerization rate and the high quality of the polymer.

In particular, the present invention aims to improve the suspension polymerization method for preparing polyvinyl chloride comprising synthesis of the polymerization initiator in situ so as to reduce the deposition of polyvinyl chloride during the polymerization process.

Said object is achieved by providing a process for the preparation of polyvinyl chloride by polymerization of vinyl chloride in aqueous suspension in the presence of a chloroformate, hydrogen peroxide and alkali, which process according to the invention is characterized by the use of 2-ethylhexyl as chloroformate. chloroformate, cyclohexyl chloroformate or 2-butoxyethyl chloroformate in an amount of 0.01 to 0.1 parts by weight per 100 parts by weight of vinyl chloride, wherein the molar ratio of chloroformate, hydrogen peroxide and alkali is between 2: 1: 3 and 2: 1: 20, and the pH is at least 10.

Vinyl chloride is effectively polymerized at the molar ratio of chloroformate, hydrogen peroxide and alkali between 2: 1: 3 and 2: 1: 8 and pH 10 to 12.

The prescribed process virtually eliminates (90 to 100%) the formation of polyvinyl chloride deposition on the reactor walls during the polymerization process. The rate of polymerization is high, practically as high as when using a complete initiator, e.g. the final 2-ethylhexyl peroxydicarbonate, cyclohexyl peroxydicarbonate and 2-butoxyethyl peroxydicarbonate.

The procedure proposed here is easy to follow. Water, emulsifier, alkali and hydrogen peroxide are placed in a polymerization reactor. The apparatus is evacuated, and chloroformate and. vinyl chloride is finally added. The polymerization process is carried out at a temperature of 45-65 ° C. The initiator is effectively synthesized while the reaction mixture is heated to the desired polymerization temperature over 0.5 to 1.0 hour.

Said effect can be obtained only on condition that the said regulations for the process are strictly observed, namely if said chloroformates, hydrogen peroxide and alkali are used in the molar ratio of 2: 1: 3 to 2: 1: 20 and if the pH of the medium is at least 10. If these requirements are not met, that effect cannot be achieved. This will be shown in the examples below.

The process of the invention is further described by the following Examples, Examples 1-6 illustrating the process of the invention for the preparation of polyvinyl chloride, Example 7 illustrating the process for preparing polyvinyl chloride with the finished initiator, and Examples 8, 9 and 10 illustrating the process for producing polyvinyl chloride under conditions where the required requirements are not met.

Example 1 In a 195 liter reactor and equipped with an agitator and an automatic heat exchange system, 200 parts by weight of water, 0.06 parts by weight of an emulsifier (thawing cell 65 GH-50), 0.0165 parts by weight were introduced. (3 moles) of NaOH, pH = 10.6, and 0.0185 parts by weight (1 mole) of 28% hydrogen peroxide. The reactor was evacuated and 0.05 parts by weight (2 moles) of 2-ethylhexyl chloroformate and 100 The reaction mixture was heated to 53 ° C over 40-50 minutes Ga. 0.04 parts by weight of di-2-ethylhexyl peroxydicarbonate was thereby formed The process was continued at this temperature for 6 hours and 30 minutes. the polymer was 90 parts by weight No polymer was deposited on the walls of the reactor.

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Example 2

The procedure was the same as described in Example 1 except that 0.042 parts by weight (2 moles) of cyclohexyl chloroformate was added. The process was continued for 5 hours and 45 minutes. The yield of polyvinyl chloride was 90 parts by weight.

Example 3

The procedure was the same as described in Example 1 except that 0.047 parts by weight (2 moles) of 2-butoxyethyl chloroformate was added. The process was continued for 6 hours and 40 minutes. The yield of polyvinyl chloride was 90 parts by weight.

Example 4

The procedure was the same as described in Example 1 except that 0.0033 parts by weight (3 moles) of NaOH, pH = 10.2, 0.0037 parts by weight (1 mole) 28% hydrogen peroxide and 0.01 parts by weight ( 2 moles of 2-ethylhexyl chloroformate were added. The process was continued for 16 hours. The yield of the polymer was 90 parts by weight.

Example 5

The procedure was the same as described in Example 1 except that 0.033 parts by weight (3 moles) of NaOH, pH 11.6, 0.037 parts by weight (1 mole) of 28% hydrogen peroxide and 0.1 parts by weight (2 moles) of ethyl hexyl chloroformate was added. The process was continued for 3 hours. The yield of the polymer was 90 parts by weight.

Example 6

The procedure was the same as in Example 1 except that 0.11 parts by weight (20 moles) of NaOH, pH 13.8, 0.0185 parts by weight (1 mole) of 28% hydrogen peroxide and 0.05 parts by weight (2 moles) 2 -ethylhexyl chloroformate was added.

The process was continued for 6 hours and 35 minutes. The yield of polyvinyl chloride was 90 parts by weight.

Polyvinyl chloride was also not deposited on the reactor walls of Examples 2-6.

Example 7 (Comparison) In the reactor described in Example 1, 200 parts by weight of water and 0.06 parts by weight of "Methocel-65 GH-50 'emulsifier were introduced, then the reactor was evacuated and 0.04 parts by weight of finished di-2-ethylhexyl were added. -Peroxydicarbonate and 100 parts by weight of vinyl chloride. The reactor content was heated to 53 ° G over 40-50 minutes. The polymerization process at this temperature was continued for 6 hours and 25 minutes. The yield of polyvinyl chloride was 90 parts by weight.

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mounted on the reactor walls.

Comparison of Examples 1 and 7 shows that the rate of polymerization with di-2-ethylhexyl peroxydicarbonate synthesized in situ was practically the same as with the same concentration of the final di-2-ethylhexyl peroxydicarbonate.

Example 8 (Comparison)

The procedure was the same as in Example 1 except that 0.011 parts by weight (2 moles) of NaOH, pH = 9.0, 0.0185 parts by weight (1 mole) of 28% hydrogen peroxide and 0.05 parts by weight (2 moles) of 2 ethylhexyl chloroformate was added. The polymerization time was 10 hours. The temperature of the polymerization was 53 ° C. The yield of the polymer was less than 15 parts by weight.

Example 9 (Comparison)

The procedure was the same as in Example 1 except that 0.0165 parts by weight (3 moles) of NaOH, pH = 10.6, 0.0185 parts by weight (1 mole) of 28% hydrogen peroxide and 0.034 parts by weight (2 moles) of isopropyl chloroformate was added. The polymerization was continued for 10 hours and the yield of the polymer was 10 parts by weight.

Example 10 (Comparison)

The procedure was the same as in Example 1 except that 0.0165 parts by weight (3 moles) of NaOH, pH = 10.6, 0.0185 parts by weight (1 mole) 28% hydrogen peroxide and 0.0235 parts by weight (2 moles) ethyl chloroformate was added. The polymerization was continued for 10 hours and the yield of the polymer was 12 parts by weight.

Examples 8, 9 and 10 serve to compare and illustrate the results when deviating from the method prescribed by the invention.

In Example 8, alkali, hydrogen peroxide and chloroformate are used in the known molar ratio, but the prescribed 2-ethylhexyl chloroformate is used as chloroformate. In this case, the rate of polymerization was very slow and the process practically did not proceed.

In Examples 9 and 10, the known chloroformates were used and the components were used in the molar ratio prescribed for the process of the present invention. The rate of polymerization was slow in this case too, and the process practically did not proceed.