CN-118420826-B - Ethylene-vinyl alcohol copolymer resin composition and preparation method thereof

Abstract

The invention discloses an ethylene-vinyl alcohol copolymer (EVOH) resin composition, which is prepared by ethylene-vinyl acetate copolymerization, wherein the content of polyvinyl alcohol in the EVOH resin composition is less than 5000ppm. The invention can reduce the content of polyvinyl alcohol in the EVOH resin composition, thereby improving the yellowing resistance and the processing stability of the EVOH resin composition in the melt processing process, and the prepared multilayer sheet, film, container and the like are not easy to have defects such as crystal points, stripes and the like.

Inventors

• QIN QINGWEI
• DOU YUQIN
• LI YUAN
• WANG QINGQUAN
• HU LAMEI
• LI YUHONG

Assignees

• 中国石油化工股份有限公司
• 中国石化集团重庆川维化工有限公司

Dates

Publication Date

20260508

Application Date

20230131

Claims (4)

1. 1. A preparation method for preparing an EVOH resin composition comprises carrying out alcoholysis reaction after ethylene-vinyl acetate copolymerization reaction, and is characterized in that after ethylene-vinyl acetate copolymerization reaction, reducing the temperature to 10-30 ℃, adding a terminator, decompressing and flashing, and then introducing a solvent for distillation to obtain an alcohol solution of ethylene-vinyl acetate copolymer; The content of polyvinyl alcohol in the EVOH resin composition is <5000ppm; The content of the terminator is 1000-1500ppm of the ethylene-vinyl acetate copolymer.
2. 2. The process according to claim 1, further comprising adding an alcoholic solution of the EVOH obtained by alcoholysis to the additive solution, extruding the resulting EVOH solution into an aqueous solution at 0-10 ℃, cutting the resulting solution into pellets, and washing the pellets.
3. 3. The method of claim 2, wherein the additive is a heat stabilizer and/or an antioxidant.
4. 4. The method of claim 3, wherein the additive is one or more of carboxylic acid, alkali metal salt, alkaline earth metal salt, boric acid and its salt, and phosphoric acid and its salt.

Description

Ethylene-vinyl alcohol copolymer resin composition and preparation method thereof Technical Field The invention relates to the field of ethylene-vinyl alcohol copolymer, in particular to an ethylene-vinyl alcohol copolymer resin composition and a preparation method thereof. Background Ethylene-vinyl alcohol copolymer (EVOH), especially EVOH with ethylene content of 20-50mol%, has excellent gas barrier property, about 10,000 times that of common polyethylene, and has transparency, processability, solvent resistance and antistatic property, so that it is widely used in the fields of packaging materials, automobile fuel tanks, oxygen-blocking floor heating pipes, textile materials, medical materials and the like. The Chinese patent document CN114426753A discloses an ethylene-vinyl alcohol copolymer composition and a preparation method thereof, wherein the composition comprises an ethylene-vinyl alcohol copolymer, a carboxyl-containing substance, potassium salt and sodium salt, the carboxyl-containing substance comprises acetic acid and carboxylic acid containing carbon-carbon double bonds, and the preparation method of the composition comprises the following steps of carrying out alcoholysis on an ethylene-vinyl acetate copolymer obtained by polymerization by sodium hydroxide, then forming and granulating, then cleaning, adding acetic acid and carboxylic acid containing carbon-carbon double bonds in the cleaning process, washing, and then adding the potassium salt. The prior art has the disadvantage that defects such as crystal points, stripes and the like are easily generated in multilayer sheets, films, containers and the like prepared from the EVOH resin composition. Disclosure of Invention In one aspect, the present invention provides an EVOH resin composition prepared by ethylene-vinyl acetate copolymerization, wherein the EVOH resin composition has a polyvinyl alcohol content of <5000ppm. Further, the method also comprises the step of carrying out pressure relief flash evaporation after the ethylene-vinyl acetate copolymerization reaction and the temperature reduction termination reaction, so that defects such as crystal points, stripes and the like can not be generated in multilayer sheets, films, containers and the like prepared from the prepared EVOH resin composition. Further, the temperature is reduced to 10-30 ℃, so that the multilayer sheet, film, container and the like prepared from the EVOH resin composition can be further prevented from generating defects such as crystal points, stripes and the like. Further, the termination is performed by adding a terminator, so that the multilayer sheet, film, container and the like produced from the EVOH resin composition can be further prevented from generating defects such as crystal points and stripes. Further, the terminator content is 100 to 5000ppm of EVOH, so that the multilayer sheet, film, container and the like produced from the EVOH resin composition can be further prevented from generating defects such as crystal points and stripes. In a second aspect, the present invention provides a method for preparing the EVOH resin composition of the present invention, comprising conducting an alcoholysis reaction after an ethylene-vinyl acetate copolymerization reaction, reducing the temperature to 10-30 ℃ after the ethylene-vinyl acetate copolymerization reaction, adding a terminator, decompressing and flashing, and then introducing a solvent for distillation to obtain an alcohol solution of the ethylene-vinyl acetate copolymer. Further, the method comprises the steps of adding an additive solution into an alcohol solution of the EVOH obtained by alcoholysis to obtain an EVOH solution, extruding the EVOH solution into an aqueous solution at 0-10 ℃, cutting the aqueous solution into particles, and cleaning the particles, so that defects such as crystal points, stripes and the like can not be generated in multilayer sheets, films, containers and the like prepared from the prepared EVOH resin composition. Further, the additives are heat stabilizers and/or antioxidants, so that the multilayer sheet, film, container and the like prepared from the prepared EVOH resin composition can be further free from defects such as crystal points, stripes and the like. Further, the additive is one or more of carboxylic acid, alkali metal salt, alkaline earth metal salt, boric acid and its salt, and phosphoric acid and its salt, so that the multilayer sheet, film, container, etc. produced from the EVOH resin composition can be further free from defects such as crystal points and stripes. In a third aspect, the present invention provides the use of the EVOH resin composition of the present invention in films, multilayer sheets and containers. The invention has the following beneficial effects: 1. The EVOH resin composition disclosed by the invention can eliminate active free radicals in a polymerization system in the processing process, and can reduce the self-polymerization