CS254452B1 - The process of polymerizing and copolymerizing vinyl chloride - Google Patents

Abstract

A process for the polymerization and copolymerization of vinyl chloride with a single or repeated dispensing of at least one initiator into a polymerization mixture during polymerization, wherein the initiator or initiators are dispensed in a solid phase.

Description

The invention relates to a process for the polymerization and copolymerization of vinyl chloride.

The kinetics of the polymerization and copolymerization reactions of the monomers is generally dependent primarily on the type and concentration of the initiator system, the temperature or the composition of the starting monomer mixture. The reaction temperature essentially determines the molecular weight, which is one of the basic quality parameters of polymeric materials. In the case of copolymerization, the composition of the starting monomer mixture generally influences the various utility properties of the copolymers. From the foregoing, it will be appreciated that the reaction cycle time, or the polymerization and copolymerization yields following the preparation of polymers and copolymers of certain parameters, can be influenced by the application of a particular initiation system by using an appropriate amount thereof. Thus, the initiator charge used for the reaction is directly related to the economics of the process, not only in terms of yield and reaction times, but also to the cost of the feedstock, since the cost of the initiators is relatively high.

A standard embodiment of polymerization or copolymerization is to dispense the initiator into the reaction system before starting the actual reaction. Upon addition of the other components of the reaction mixture and heating of the reactor contents to the reaction temperature, the initiator decomposes to form radicals which initiate polymerization. The initiator disintegration rate at a given temperature is defined by its half-life, which is an important indicator of its activity and hence its usefulness. Depending on the specific conditions and type of polymerization, a stationary radical concentration in the system is established soon after the start of the reaction. However, in subsequent phases of the reaction, the concentration of radicals decreases over time, mainly due to the loss of initiator, which is gradually consumed by the initiation reaction.

This results in a lower reaction rate of the monomers at the corresponding times. Analogous problems also occur in a number of non-radical polymerizations and copolymers.

This unfavorable situation is confronted by standard procedures, in particular by the application of a plurality of initiators or combinations thereof, and an extension of the reaction time is also possible. However, both approaches are associated with negative economic consequences - either with higher feedstock costs or with reduced plant yields.

The principle of another possible solution is to dispense the initiators during the reaction. However, the application of the initiators in solution creates a risk of negatively affecting the kinetic progression and possibly the product properties of the solvent used. If initiators are used in suspension or emulsion, large volumes of transport and handling must be taken into account.

SUMMARY OF THE INVENTION The present invention provides a process for the polymerization and copolymerization of vinyl chloride with a single or multiple feed of at least one initiator into a polymerization mixture during polymerization, wherein the initiator or initiators are dosed in solid phase. The vinyl chloride polymerization and copolymerization process of the present invention has the following advantages over the standard process. The additional charge of the initiator into the reaction system during the reaction allows more efficient use of the initiator. This allows either a smaller amount of initiator to be used without loss of yield, or with the same amount of initiator to achieve standard conversion in a shorter reaction time, or to obtain higher yields with an unchanged amount of initiator and retained reaction time. When dosing solid-phase initiators, there is no risk of negatively affecting the reaction kinetics and product properties by the solvent used, as well as the transport and handling of large volumes, as is the case with suspension initiators.

The process according to the invention can advantageously be carried out by means of the apparatus of art. AO No 253 970.

Description of the polymerization process

The process of polymerization and copolymerization of vinyl chloride according to the invention, based on additional dosing of initiators into the reaction system during the reaction, can be advantageously used without pressure and pressure polymerizations and copolymers in homogeneous and heterogeneous reaction systems at different temperatures without negatively affecting the product properties.

In the following, the invention is illustrated by the following examples.

The individual components of the reaction mixture are dosed into the polymerization reactor according to the chosen operating procedure, including the initial amount of initiator (s).

At a certain time, an additional dose of initiator is added so that the total amount of initiator applied is more efficiently utilized and the reaction has the desired kinetic progression. The initiator can be added to the system repeatedly in different doses.

He did

Vinyl chloride homopolymerization initiated by a two-component initiation system

10.12 g of 2-hydroxypropyl methylcellulose solution (3.8% solution), 578 g of distilled water, 0.172 56 g of dilauroyl peroxide and 0.087 49 g of dicetylperoxydicarbonate were charged to a 1 dm reactor. After the reactor was inertized, 289.0 g of vinyl chloride was added.

The polymerization was performed at 68.5 ± 0.1 ° C for 6.3 hours; the stirrer speed was set to 500 min. The addition of solid dicetyl peroxydicarbonate during the reaction resulted in a conversion of 90.5%. This value is 10.3% higher than the standard procedure, whereby the total amount of both initiators was present in the reaction mixture from the very beginning of the reaction.

Example 2

Vinyl chloride homopolymerization initiated by a one-component initiation system

15.10 g of a solution of 2-hydroxypropyl methylcellulose (3.8% solution), 595 g of distilled water and 0.345 g of dicetyl peroxydicarbonate were charged to the 1 dm reactor. After the reactor was inerted, 297.7 g of vinyl chloride was added.

Polymerization was carried out for 6 hours at 51.5 + 0.1 ° C and a stirrer speed of 500 min. The addition of solid dicetyl peroxydicarbonate during the reaction resulted in a conversion of 88.4%. The increase in conversion compared to the standard procedure, which used the same total amount of initiator but from the start of the reaction, was 8.4%.

Example3

Copolymerization with vinyl chloride with propene

6.6 g of 2-hydroxypropylmethylcellulose (3.8% solution), 487 g of distilled water and 1.011 of 36 g of dicetyl peroxydicarbonate were charged to a 1 dm reactor. After reactor inertization, 240.8 g of vinyl chloride and 19.2 g of propene were added.

The copolymerization was carried out at 48.0 + 0.1 ° C for 15 hours. The stirrer speed was set to 500 min. Dosing of dicetyl peroxydicarbonate in the solid phase during the reaction gave the copolymer in a yield of 81.0%. The standard procedure, which is to dispense a total of the same amount of initiator into the system before co-polymerization, corresponds to a conversion of 7.1% lower.

Claims (1)

SUBJECT OF THE INVENTION Process for the polymerization and copolymerization of vinyl chloride with a single or repeated feed of at least one initiator to the polymerization mixture during the polymerization, characterized in that the initiator or initiators are dosed in solid phase.