CS260081B1 - A process for the suspension polymerization and / or copolymerization of vinyl chloride - Google Patents

Abstract

A method of suspension polymerization and/or copolymerization of vinyl chloride, in which polymerization additives are first dosed, vinyl chloride is added together with a portion of water of 2 to 20% by weight, and only at the end is the remaining amount of preheated water at a temperature of 50 to 170 °C added under an overpressure of 0.8 to 1.6 MPa.

Description

The invention relates to a process for the suspension polymerization and/or copolymerization of vinyl chloride (hereinafter referred to as VCM).

Suspension polymerization of VCM is carried out discontinuously on an industrial scale. Usually, the necessary additives, such as dispersants, surfactants, etc., are dosed into the polymerization reactor with the water supplied, a polymerization initiator and monomeric vinyl chloride are added. After or during the dosing of VCM, the reactor is heated to the polymerization temperature (heating is carried out by a jacket or directly by steam), and the polymerization itself occurs. The described process has a relatively low productivity. One of the limiting factors is the long heating time of the reactor.

The above-mentioned disadvantages are eliminated by the method of suspension polymerization and/or copolymerization of vinyl chloride according to the invention, the essence of which consists in that polymerization additives and other components are first dosed into the polymerization reactor with stirring, together with a small amount of water, i.e. 2 to 20% by weight of the total amount of water, and VCM with possible other monomers, and only then is the remaining part of the water added under an overpressure of 0.8 to 1.6 MPa, preheated to a temperature of 50 to 170 °C. If necessary, the reactor is further heated to the polymerization temperature by means of a jacket. In this case, it is possible to start heating the reactor jacket after the start of the dosing of hot water.

The main advantage of the method according to the invention is a significant shortening of the polymerization cycle, thereby significantly increasing the productivity of the entire process. In addition, the method according to the invention brings energy savings and reduced formation of adhesions in the reactor while maintaining the quality parameters of the resulting product. Waste heat can be advantageously used for preheating water.

The following examples illustrate the method according to the invention. The first example describes the prior art and is given for comparison.

Example 1

Into a reactor with an internal volume of 8 liters equipped with a stirrer and a duplicator, 4,200 g of an aqueous phase at a temperature of 20 °C containing demineralized water with 3.4 g of a mixture of methylhydroxypropylcellulose and hydroxypropylcellulose were added. The other components required for the polymerization mixture and initiators were then added. The reactor was closed and, after flushing the free space with nitrogen, it was evacuated to 1.866 kPa. 2,400 g of vinyl chloride were then added while stirring.

After the vinyl chloride dosing was completed, the reactor was heated using a duplicator jacket to a polymerization temperature of 59 °C. The polymerization was terminated after a pressure drop of 0.2 MPa, cooling the reactor and discharging the unreacted monomer.

Example 2

500 ml of deionized water at 20 °C was added to a reactor with an internal volume of 8 l,

3.4 g of cellulose derivatives (dispersants). The procedure was then carried out according to Example 1 with the difference that after the addition of 2,400 g of VCM, 3,700 g of water at 82 °C was added to the reactor under a pressure of 1.25 MPa. When 3,500 g of water was added, when the temperature in the reactor rose by 21 °C, heating was started using the duplicator jacket of the reactor to a polymerization temperature of 59 °C.

The procedure was then carried out according to example 1.

Example 3

The procedure is the same as in example 2, with the difference that the reactor jacket was heated to 58 °C (i.e. 1 °C below the polymerization temperature of 59 °C) at the beginning of the dosing of 80 °C hot water.

During dosing, the temperature in the reactor rose by 27 °C, then the reactor temperature was adjusted to 59 °C. The procedure is the same as in example 1.

and

Example 4

The procedure was as in example 2, with the difference that after adding 1/2 the amount (i.e. approx. 1,800 g) of 75°C warm water, heating was started using the reactor jacket.

Example 5

Into a reactor with an internal volume of 60 l equipped with a stirrer and a duplicator were dosed 28 kg of demineralized water, 22 kg of VCM, 0.0194 kg of dispersants and other components required for the polymerization mixture by the procedure described in Example 1, with the difference that the polymerization temperature was 66 °C.

Example 6

Into the reactor with an internal volume of 60 l was added 1.4 l of demineralized water at 18 °C, 0.019 4 kg of dispersants and other components of the polymerization system. The procedure was then as in example 1 with the difference that after adding 22 kg of VCM, 26.6 kg of demineralized water at 75 °C under a pressure of 1.5 MPa was added to the reactor at a rate of 0.7 1/min. After the addition of hot water, when the temperature in the reactor had risen by 25 °C, the reactor was heated using a duplicator reactor jacket to a polymerization temperature of 66 °C. The polymerization was completed according to example 1.

Table

Example 1 2 3 4 5 6 K value 65.5 65.3 65.2 according to CSN 64 0325 65.4 60.1 60.2 SH (g/D 545 541 bulk 527 531. weight according to CSN 64 623 0804 627 0.250 (%) sieve 0.5 0.5 footprints 0.1 0.3 0.5 0.063 (») 90 97 rest 97 on the net about 98 98 given mesh size 98 (mm) 64 CSN 0212 stickers (g) 0.7 0.3 0.4 0.4 - - RO (pcs/g) - number fish eyes ' according to CSN 2 64 3200 2

SUBJECT OF THE INVENTION

Claims (3)

A process for the suspension polymerization and / or copolymerization of vinyl chloride, characterized in that first the polymerization additives, then the other components together with 2 to 20% by weight of the total amount of water and vinyl chloride with a possible addition of 2 to 20 wt. and then the remainder of the water is metered under an overpressure of 0.8-1.6 MPa preheated to 50-170 ° C. 2. Process according to claim 1, characterized in that the reactor is finally heated to the polymerization temperature. 3. A process as claimed in claim 1 or claim 2, characterized in that the additional heating of the reactor to the polymerization temperature is initiated after the start of dosing of the remaining amount of water heated to 50-170 [deg.] C.