RU2393176C1 - Emulsion polymerisation method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to polymer synthesis and specifically to a polyamide synthesis method through emulsion polymerisation of caprolactam. The method involves preparation a reaction mass in form an emulsion of caprolactam and an initiator in liquid polyethylsiloxane, heating, holding, cooling and separation of the polymer granules formed. The reaction mass is heated in two steps - first to 90-100°C for 1.5-2 hours, subsequently holding for 3-4 hours, and then to 210-215°C for 1.5-2 hours and holding the reaction mass for 18-22 hours at that temperature before cooling.

EFFECT: method enables to obtain polyamide in form of granules right away and the polyamide can be processed into fibre.

1 cl, 8 ex, 1 tbl

Description

The invention relates to the chemical industry, and in particular to methods for producing polymers by emulsion polymerization.

State of the art

Various polymers are obtained by emulsion polymerization - polystyrene, polymethyl methacrylate, rubbers.

A known method of producing polymethylmethacrylate by emulsion polymerization (Lebedev A.V., Eliseev V.I. and others. Emulsion polymerization and its use in industry. M., Chemistry, 1976, 205-214 S.).

It includes the following operations: loading components into the reactor in a certain sequence - water, surfactant, buffer, monomer. Then for 15-30 minutes an inert gas is passed through the mixture until the air is completely displaced from it and the reactor. Then add the components of the redox system - ferrous salt, potassium persulfate, reducing agent. After the induction period, which lasts 1-30 minutes, the polymerization process begins. In this case, after 15-45 minutes the temperature reaches its maximum value - 95-97 ° C and does not change for some time, and then slowly decreases to the initial value. The one-stage redox process is usually used to prepare latexes with a dry matter content of 25-30%.

There is also a method of producing rubbers based on chloroprene (Lebedev A.V., Eliseev V.I. and others. Emulsion polymerization and its use in industry. M., Chemistry, 1976, 225-227 S.).

Before use, chloroprene must be thoroughly rectified to ensure the desired product quality. The initial emulsion is prepared in a special apparatus with a circulation pump, and the main emulsifier is prepared by introducing rosin into the monomer and alkali into water. This ensures sufficient standardization of the emulsion in droplet size - about 3 microns. In addition to the main emulsifier, to ensure the stability of the latex in the subsequent stages of the process, up to the release of rubber, surfactants based on a strong acid such as daxad or STEC (sodium salt of petroleum sulfonic acids) are introduced into the aqueous phase.

If the plasticity of the polymer is controlled by sulfur, then after polymerization and distillation of the unreacted monomer, an additional operation is introduced - “alkaline maturation” at 20-30 ° C for at least 8 hours in the presence of a destructuring agent, for example, tetraethylthiuramide sulfide. Finally, coagulation by freezing on the surface of a cooling drum is almost universally used to isolate polychloroprene from latex.

There is also a method of producing polystyrene (Lebedev A.V., Eliseev V.I. and others. Emulsion polymerization and its use in industry. M., Chemistry, 1976, 187-191 pp.), Which is the closest to the invention in terms of essential signs. The method includes the following operations:

- obtaining the reaction mass in the form of an emulsion of styrene and initiator in an immersion liquid. To do this, water is loaded into the reactor as an immersion liquid and an emulsifier;

- heating the reaction mass to ≈100 ° C. In this case, the temperature range is limited, on the one hand, by the decay temperature of the initiators, and on the other, by the temperature of polymer degradation;

- exposure of the reaction mass at this temperature to achieve a given degree of conversion;

- cooling the reaction mass;

- coagulation of the polymer;

- separation of the formed polymer granules. To do this, the mass is washed with water and squeezed in centrifuges or vacuum filters;

- drying.

However, the method has the following disadvantages:

- the inability to obtain polyamide-6;

- the inability to obtain fiber-forming polyamide-6.

SUMMARY OF THE INVENTION

An inventive task is to find a method of emulsion polymerization, which includes obtaining the reaction mass in the form of an emulsion of a monomer and initiator in an immersion liquid, heating, cooling and separating the formed polymer granules, which would make it possible to obtain polyamide-6, and fiber-forming.

The inventive task is solved by the method of emulsion polymerization, which includes obtaining the reaction mass in the form of an emulsion of a monomer and initiator in an immersion liquid, heating, holding, cooling and separating the formed polymer granules, in which caprolactam is used as a monomer, polyethylsiloxane liquid is used as an immersion liquid, heating the reaction mass is carried out in two stages - first to 90-100 ° C for 1.5-2 hours, followed by exposure for 3-4 hours, then to 210-215 ° C, so e for 1.5-2 hours, and extract the reaction mass at that temperature before cooling is carried out for 18-22 hours.

The invention allows to obtain polyamide-6, and capable of being processed into fibers.

In addition, the invention also provides the following advantages:

- receive polyamide-6 directly in the form of granules, i.e. without the use of special equipment both for casting polymer vein from melt and for chopping it into granules, which increases the efficiency of the invention compared to the method currently used in industry;

- increasing the strength of the threads due to the ability to process the polymer at a low temperature, which provides less depolymerization of polyamide-6;

- the uniformity of the physico-mechanical properties of the formed filaments, since the granules have a uniform molecular weight due to the same residence time of the entire reaction mass in the apparatus.

Information confirming the ability to reproduce the invention.

To implement the method using:

- as a monomer - caprolactam - GOST 7850-86;

- as immersion liquid - polyethylsiloxane liquid GOST 13004-77;

- as an initiator - distilled water

TT 46-05-2003.

The method is as follows. A reaction mixture consisting of caprolactam and water taken in calculated amounts (2 mass% water from the mass of caprolactam) is loaded into an autoclave having a mixing device, then a polyethylsiloxane liquid (module 1: 4) is added and heated to a temperature of 90-100 ° С for 1.5-2 hours, followed by exposure for 3-4 hours, then the reaction mass is heated to 210-215 ° C, also for 1.5-2 hours, include stirring and incubated at 210-215 ° C for another 18-22 hours. Then the reaction mass is allowed to cool to about 60-70 ° C. The resulting granules of polyamide-6 are separated, for example, in a centrifuge.

The fiber-forming ability of the obtained polyamide-6 was judged by the degree of polymerization of the prepolymer, calculated by the well-known formula using the value of relative viscosity, determined in accordance with GOST 18249-72.

The properties of polyamide-6 obtained in various modes of the claimed method are shown in the table.

Properties of polyamide-6 obtained in various modes of the claimed method.

Table No. p / p 1st stage of heating 2nd stage of heating Exposure before cooling, h Degree of polymerization Heating time, h t, ° C exposure τ, h Heating time, h t, ° C one 1,5 90 3 1,5 210 eighteen 52 2 2 90 four 2 210 22 56 3 1,5 one hundred 3 1,5 210 eighteen 54 four 2 one hundred four 2 210 22 56 5 1,5 90 3 1,5 215 eighteen 52 6 2 90 four 2 215 22 57 7 1,5 one hundred 3 1,5 215 eighteen 54 8 2 one hundred four 2 215 22 57

Claims (1)

The method of emulsion polymerization, including obtaining the reaction mass in the form of an emulsion of a monomer and initiator in an immersion liquid, heating, holding, cooling and separating the formed polymer granules, characterized in that caprolactam is used as a monomer, polyethylsiloxane liquid is used as an immersion liquid, reaction heating the masses are carried out in two stages - first up to 90-100 ° C for 1.5-2 hours, followed by exposure for 3-4 hours, then up to 210-215 ° C also for 1.5-2 hours, and exposure reaction mass sys at this temperature before cooling is carried out for 18-22 hours