The method of processing the prepolymer of methyl methacrylate and removal of free monomer

 

(57) Abstract:

The method of processing the prepolymer of methyl methacrylate and removal of free monomer by turning it into a polymer involves the heating of the prepolymer. According to the invention as prepolymer using a prepolymer with conversion 50-85%. The heat produced above the glass transition temperature of the prepolymer, but below the temperature of transition into a plastic state and depolymerization of poly-free monomer. The conversion of monomer in the polymer is carried out at the extrusion of the prepolymer. 4 C.p. f-crystals.

The invention relates to a method of processing synthetic polymers (prepolymers), in particular of polymethyl methacrylate. The method can be used, in particular, in the production of organic glass.

A method of refining the prepolymer of methyl methacrylate and removal of free monomer by turning it into a polymer comprising heating the prepolymer (SU 987939). As the prepolymer using a prepolymer with conversion 25-26%. Such a prepolymer is difficult to be subjected to extrusion due to its relatively low viscosity. As a consequence, can not be implemented mainly those who men requires at least enough additional time-consuming steps. This method does not allow for it continuously. The resulting product has insufficient for a number of applications of physico-mechanical properties.

The task was to create such a method the same destination, which would allow it continuously, could be characterized by less complexity in obtaining the finished products and would enable the extrusion of high molecular weight methyl methacrylate, having good physical and mechanical properties.

This problem was solved by the present invention.

In the recycling method of the prepolymer of methyl methacrylate and removal of free monomer by turning it into a polymer comprising heating the prepolymer according to the invention as prepolymer using a prepolymer with conversion 50-85%, the heat produced above the glass transition temperature of the prepolymer, but below the temperature of transition into a plastic state and depolymerization of poly-free monomer, and the conversion of monomer in the polymer is carried out at the extrusion of the prepolymer.

After extruding the resulting product may be the one to copolymerization with methyl methacrylate with the formation of cross-linked polymer.

The method preferably takes place continuously.

It was found experimentally that if the heat produced above the glass transition temperature of the prepolymer, but below the temperature of transition into a plastic state and depolymerization of poly-free monomer, the polymerization ostchega monomer occurs with sufficient speed and to produce a product of desired molecular weight. If you try to produce polymerization of the residual monomer below the glass transition temperature of the prepolymer, its speed according to kinetic reasons will be low. If you increase the temperature above the glass transition temperature of the polymer, it is possible to quickly achieve polymerization-depolymerization balance and to achieve a degree of conversion of up to 50-85%. A further increase in the degree of conversion is possible after lowering the temperature of polymerization necessary to shift polymerization-depolymerization the equilibrium towards the formation of high molecular weight polymer. The degree of conversion can reach close to 100%.

If the processing of the prepolymer to be carried out during extrusion, mixing processes facilitate polymerization, increase CA what are free radicals, initiating the polymerization process and, therefore, conducive to polymerization of the residual monomer in the prepolymer.

After extruding the resulting product can be subjected to orientation, which contributes to the improvement of performance characteristics of the resulting organic glass (temperature rise operation and reduce shrinkage during heating above the glass transition temperature). In addition, increases the strength of the final product.

The presence of the initiator in the prepolymer facilitates the implementation of the method, as in viscous system is difficult to enter initiator and then spread it on the system. This can be accomplished, for example, the following trick. In the monomer (methyl methacrylate) is administered as an initiator mixture of two initiators to initiate the polymerization at different temperatures, for example a mixture of peroxide of Laurel and peroxide and tert-butyl. In addition, the monomer can be entered bifunctional initiator initiating the polymerization of methyl methacrylate at two different temperatures. Then from the resulting reaction mixture get prepolymer: when heated to the decomposition temperature of the first initiator, he begins to work, and polymerization takes place at this temperaturerange initiator) remains unreacted and thus, it can be used in the implementation of the declared here.

Composition for the preparation of the prepolymer may contain, for example, 100 wt.h methylmethacrylate, 0.01 to 0.2 wt.h cyclohexyloxycarbonyl or peroxide of Laurel and 0.02 to 0.4 wt.% peroxide of tertbutyl.

The presence of a bifunctional monomer allows you to get custom made end product (as in the case of using the extruder - extrusion sewn polymethylmethacrylate), which further improves the operational characteristics of the final product, in particular raises the temperature of operation, and leads to the almost complete disappearance of shrinkage during heating above the glass transition temperature. As a bifunctional polymer can be used, for example, at least one of the monomers selected from the group comprising diallylamine, alismataceae, triallylisocyanurate, illimitability ether of monoethylene glycol, illimitability ether of diethylene glycol, illimitability ether of triethylene glycol, cialissoftlf, dimethacrylates ether of monoethylene glycol, dimethacrylate ether of triethylene glycol, dimethacrylate ester of isophthalic acid.

While it is preferable to use at least one retacrit.

This method can be carried out continuously. It is possible, in particular, to apply the device containing the reactor for polymerization at elevated pressure, the nodes in the preparation of the initial components and unloading of the finished product. This device has associated with the reactor outlet additional capacity for carrying out the depolymerization. The claimed method thus is actually in this capacity.

As an additional capacitance device may contain an extruder.

The presence associated with reactor outlet additional capacity for carrying out the depolymerization can continuously maintain in this capacity conditions for the implementation stage of depolymerization, which ultimately makes possible a continuous process.

If the additional capacitance device comprises an extruder, it allows to obtain high molecular weight polymer extrusion with the degree of conversion is close to 100%, which cannot be done in another way and in another apparatus design.

The method is as follows.

In site preparation polymerization mixture serves Monomeric mixture and Nord-polymerization. In the reactor-polymerizate carry out the polymerization to a conversion of 50-85%, and the polymer-monomer mixture of (prepolymer) comes in depolymerization capacity, which supports a lower temperature than the reactor-polymerizate. In copolymerizations capacity is the exhaustion of residual monomer to the extent of 99%, and the resulting polymer melt using known devices (pumps, extruders and other) is fed to the forming device, and then into the receiving tank.

The implementation of the method is also illustrated by the following examples.

Example 1.

According to the above prepared mixture of methyl methacrylate (MMA) and 0.3 wt.% the initiator as an initiator using the initiator with two working temperatures - bis-1-(hydroperoxyalkyl-1)-peroxide. The polymerisation process is carried out by heating the mixture, while the temperature in the jacket of the reactor-polymerizate support at the level of the 230S. The conversion in the reactor-polymerizate upon receipt of the prepolymer 85%, a molecular weight of about 90 thousand units Temperature in copolymerizations capacity is 110S. Conversion after depolymerization capacity - more than 99%, a MM - about 100 thousand units

Example 3.

The polymerisation process is carried out as in example 1, but as an initiator mixture contains 0.3 wt.% TBPB and 0.1 wt.% peroxide di-tert-butyl (PTB), as depolymerization capacity using an extruder with a forming device. Get extruded polymer with a molecular weight of about 250 thousand units, which cannot be achieved by other known methods.

Example 4.

The polymerisation process is carried out as described above, as an initiator mixture contains 0.3 wt.% TBPB and 0.1 wt.% peroxide di-tert-butyl (PTB), as a monomer mixture, a mixture of 85% MMA and 15% vinyl acetate. Temperature regimes obtain a copolymer similar to that described in example 1. Conversion upon receipt of the prepolymer is 50%. After depolarizer, the claimed invention makes it easy to implement a method of processing the prepolymer of methyl methacrylate and removal of free monomer to a conversion close to 100%, including continuously.

1. The method of processing the prepolymer of methyl methacrylate and removal of free monomer by turning it into a polymer comprising heating the prepolymer, characterized in that the prepolymer is used, the prepolymer with the conversion of 50-85%, the heat produced above the glass transition temperature of the prepolymer, but below the temperature of transition into a plastic state and depolymerization of poly-free monomer, and the conversion of monomer in the polymer is carried out at the extrusion of the prepolymer.

2. The method according to p. 1, wherein after extrusion the resulting product is subjected to orientation.

3. The method according to p. 1, characterized in that the prepolymer contains the initiator.

4. The method according to p. 1, characterized in that the prepolymer contains a bifunctional monomer capable of copolymerization with methyl methacrylate with the formation of cross-linked polymer.

5. The method according to p. 1, characterized in that it is carried out continuously.

 

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