Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymerizing in tubular or loop reactor
Patent
1986-07-28
1988-01-26
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymerizing in tubular or loop reactor
526272, 526273, 5263186, 526320, 526329, C08F 242, C08F21002
Patent
active
047217618
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an improved process for the preparation of an ethylene copolymer. More particularly, the present invention relates to a process for prolonged, stable and continuous preparation of a high-quality ethylene copolymer by prevention of polymerization of comonomers in an ultrahigh pressure pump which compresses the comonomers to a reaction pressure and in a conduit and improvement in diffusion of the comonomers into ethylene gas in a reaction vessel.
BACKGROUND TECHNIQUE
Polyethylene is a crystalline, non-polar thermoplastic resin. Polyethylene is also easier to mold and has higher strength and elongation, flexibility and chemical resistance than other thermoplastic or thermosetting resins. Thus, polyethylene has excellent properties and is one of the most important general-purpose resins. However, polyethylene is disadvantageous in that its lack of polar groups causes poor adhesion, oil resistance, dyeability, and heat resistance.
Various studies have been made to improve polyethylene so that it is given characteristic properties without deteriorating the above inherent properties thereof to be developed for formation of composite materials with other materials.
In particular, copolymerization of ethylene and a vinyl compound having polar groups is widely industrially conducted because it is advantageous in that it enables the introduction of polar groups in a high concentration and the production thereof in the same plant as used.
However, high-pressure radical copolymerization of ethylene and such a comonomer having polar groups involves a problem of reactivity of the comonomer. That is, comonomers having a relatively small polymerization reactivity (i.e., the Q value is less than 0.1) such as vinyl acetate and vinyl propionate are generally introduced into a system at a line having a pressure of lower than the reaction pressure, such as, for example, at an inlet line of an ultrahigh pressure compressor, compressed together with ethylene by the ultrahigh pressure compressor to the reaction pressure, and then introduced into the reaction vessel. On the other hand, in the case where comonomers having a high reactivity are used, when a mixture of ethylene and such a comonomer is compressed by an ultrahigh pressure compressor, a copolymer of ethylene and the comonomers or a homopolymer of the comonomer may be produced in an interior of the compressor, an outlet conduit of the compressor, and other apparatus due to compression heat. The polymer thus produced attaches to the interior of the compressor, the outlet conduit of the compressor and other apparatus, causing not only an increase in the amount of leaking gas from a cylinder of the compressor and an increase in pressure loss between the compressor outlet and the reaction vessel which will increase the discharge pressure of the compressor but also a cause to clog the conduits, whereby it causes a very dangerous condition in operation. In order to avoid these troubles, when comonomers having a high reactivity are used, the comonomers are compressed to the reaction pressure by an ultrahigh pressure pump, singly or together with a solvent, and then carried to the reaction vessel.
In general, as such comonomers there are used those which are liquid or solid at ordinary temperature and at atmospheric pressure. A plunger type pump is used as the ultrahigh pressure pump to compress the comonomer to the reaction pressure and carry it to the reaction vessel. As a packing for this type of a pump there is generally used a self-bound V-shaped packing. However, when a comonomer having a high polymerization reactivity enters and accumulates in a V-shaped groove on the packing, heat polymerization takes place in a relatively short period of time due to sliding heat generated in sliding portions of the plunger and the packing. This causes a loss of degree of freedom of the packing, resulting in leakage therefrom. Furthermore, the attachment of the polymer thus produced may even lead to breakage of the pump.
Moreover, the p
Kondo Akira
Okada Takayuki
Omae Tadayuki
Yamaguchi Noboru
Schofer Joseph L.
Sumitomo Chemical Company Limited
Teskin F. M.
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