CN101928362A - Method for preparing polyethylene-vinyl acetate-vinyl alcohol terpolymer by non-catalytic hydrolysis of polyethylene vinyl acetate in near critical water - Google Patents

Abstract

The invention discloses a method for preparing a polyethylene-vinyl acetate-vinyl alcohol terpolymer by hydrolyzing polyethylene and vinyl acetate in near-critical water without a catalyst, comprising the following steps: 1) adding deionized water, polyethylene and vinyl acetate with mass ratio of 1:1-40:1 to a high-pressure reactor, stirring the mixture, heating the mixture under normal pressure until the mixture boils and opening an exhaust valve for 2-5min; 2) raising the temperature to 200-290 DEG C and carrying out hydrolysis for 0.5-20h; 3) cooling the hydrolysate, releasing pressure from the cooled hydrolysate and filtering the hydrolysate; and 4) washing the product with the deionized water and vacuum-drying the product to obtain the polyethylene-vinyl acetate-vinyl alcohol terpolymer. The method dispenses with any catalyst during hydrolysis, solves the difficult problem of environmental pollution caused by acid and alkali catalytic hydrolysis and is simple in reaction process, controllable in degree of hydrolysis and environment-friendly. The hydrolysate can be used for packaging coating, food and drugs and carry out blending modification with other resins, etc.

Description

Method for preparing polyethylene-vinyl acetate-vinyl alcohol terpolymer by non-catalytic hydrolysis of polyethylene vinyl acetate in near critical water

technical field

The invention relates to a method for preparing polyethylene-vinyl acetate-vinyl alcohol terpolymer by non-catalytic hydrolysis of polyethylene vinyl acetate in near-critical water. the

Background technique

Polyethylene-vinyl acetate-vinyl alcohol copolymer [P(E-VA-VOH)] is a highly crystalline thermoplastic resin obtained by hydrolysis of polyethylene vinyl acetate (EVA), with a chemical structure of

Where m, x, n-x are the degrees of aggregation. Due to the introduction of highly polar and highly reactive hydroxyl groups on the EVA molecular chain, its performance has been greatly improved (such as high barrier performance, affinity for polar materials, etc.), and its broadened application range. On the one hand, a series of products with different ethylene, vinyl alcohol and vinyl acetate contents and their sequence distribution can be prepared by hydrolysis. The P(E-VA-VOH) products prepared have different properties due to different group components, and can be applied in different It has been used in packaging materials such as hot melt adhesives, food, and drugs; on the other hand, it can react with a variety of functional groups, such as copolymerization with hydropropidine and isocyanate substances, or polyisocyanate and unsaturated Acid grafting modification can obtain coatings with good alkali resistance, weather resistance and heat resistance. In a word, P(E-VA-VOH) has been widely used in actual production and life. However, the existing EVA hydrolysis process is carried out under acid-catalyzed or base-catalyzed conditions, usually using sodium hydroxide as a catalyst, methanol as a solvent, and hydrolyzing in the presence of benzene or other swelling agents. This hydrolysis reaction has the following disadvantages: on the one hand, the degree of hydrolysis of the hydrolyzate cannot be controlled, and it can only be deeply hydrolyzed, that is, directly hydrolyzed into polyethylene-vinyl alcohol copolymer; Alkali neutralization and serious pollution problems. the

Near-critical water usually refers to compressed liquid water with a temperature between 200°C and 350°C. Water in this area has the following three important properties:

1) It has the functions of acid catalysis and base catalysis: under the saturated vapor pressure, the ionization constant of near-critical water has a maximum value of about 10 ^-11 (mol kg) ² near 275 ° C, and its value is normal temperature and pressure It is 1000 times that of water, and the ionization constant increases with the increase of pressure. [H ₃ O ⁺ ] and [OH ^- ] in near-critical water are close to weak acid or weak base, and they have the functions of acid catalysis and base catalysis, so they can Some acid-base catalyzed reactions do not need to add acid-base catalysts, so as to avoid acid-base neutralization, salt treatment and other processes;

2) Dissolve organic and inorganic substances at the same time: under saturated vapor pressure, the dielectric constant of water at 20°C is 80.1, but only 23.5 at 275°C. Although the dielectric constant of near-critical water is still large enough to dissolve and even ionize salts, it is small enough to dissolve organic matter, and the density of near-critical water is high (the density of water at 275°C saturated vapor pressure is 0.76g·cm ³ , The dielectric constant and density of near-critical water are similar to those of acetone), so near-critical water has very good solubility properties and can dissolve both organic and inorganic substances. This enables many synthesis reactions in near-critical water media to be carried out in a homogeneous phase, thereby eliminating mass transfer resistance and increasing reaction speed. At the same time, wax-water separation can be achieved by simply cooling down after the reaction, and the water phase can be recycled;

3) Adjustability of physical properties: The physical and chemical properties of near-critical water, such as dielectric constant, ion product constant, density, viscosity, diffusion coefficient, solubility, etc., can be continuously adjusted in a wide range with temperature and pressure, that is, the near-critical water The physical properties are adjustable, so as a reaction medium, near-critical water has different solvent properties and reaction performance in different states. the

The application research of reactions in near-critical water includes organic synthesis, waste treatment, synthesis of inorganic materials, coal liquefaction, and biomass resource utilization. get expanded. the

The present invention applies the near-critical water medium to the field of polymer modification, and utilizes the characteristics of near-critical water to realize the non-catalytic hydrolysis of EVA to prepare a series of polyethylene-vinyl acetate with different ethylene, vinyl alcohol and vinyl acetate contents and sequence distributions - Vinyl alcohol terpolymers. Since there is no need to add any catalyst during the hydrolysis process, the pollution problem of acid and alkali catalyzed hydrolysis is solved. The degree of hydrolysis is controllable, the process is simple, and it is green. The hydrolyzed products can be used in hot melt adhesives, food packaging, pharmaceutical packaging and other fields. And it can be modified by reaction with a variety of functional groups, which improves the application range of the material. the

Contents of the invention

The object of the present invention is to provide a method for preparing polyethylene-vinyl acetate-vinyl alcohol terpolymer by non-catalytic hydrolysis of polyethylene vinyl acetate in near-critical water. the

The steps of the method are as follows:

1) Add deionized water and polyethylene vinyl acetate into the autoclave, the mass ratio of deionized water to polyethylene vinyl acetate is 1:1~40:1, start stirring, heat up to boiling under normal pressure, open Exhaust valve for 2 to 5 minutes;

2) Heat up to 200-290°C and hydrolyze for 0.5-20 hours;

3) The hydrolyzate is cooled, depressurized, and filtered to obtain a solid product;

4) The solid product is rinsed with deionized water and vacuum-dried to obtain a polyethylene-vinyl acetate-vinyl alcohol terpolymer. the

The purpose of "heating to boiling under normal pressure and opening the exhaust valve for 2 to 5 minutes" in step 1) of the present invention is to utilize water vapor to take away the oxygen in the still, avoiding to accelerate polymer degradation due to the presence of oxygen; The rotating speed is 200 rev/min. the

The mass ratio of deionized water to polyethylene vinyl acetate in step 1) of the present invention is preferably 3:1-20:1; the hydrolysis temperature in step 2) is preferably 230-270°C. the

The present invention does not need to add any catalyst in the hydrolysis process, utilizes the self-acid-base catalytic characteristics of near-critical water and the characteristics of dissolving organic matter to hydrolyze polyethylene vinyl acetate in near-critical water to generate a series of different ethylene, vinyl alcohol and vinyl acetate The polyethylene-vinyl acetate-vinyl alcohol terpolymer with content and its sequence distribution solves the problem of environmental pollution caused by acid and alkali catalyzed hydrolysis. The reaction process is simple, the degree of hydrolysis is controllable, and the speed is fast. Polyethylene Greening of polyvinyl acetate hydrolysis process. The hydrolyzed products can be used as coatings, food and drug packaging, etc., and can be blended with other resins for modification. the

Description of drawings

Fig. 1EVA and its hydrolyzate infrared spectrogram;

Fig. 2 is a process flow diagram for preparing polyethylene-vinyl acetate-vinyl alcohol terpolymer by non-catalytic hydrolysis of polyethylene vinyl acetate in near critical water. the

Detailed ways

In the present invention, the EVA (VA content is respectively 18%, 33%, 42%, 62%, 86%) raw material that adopts is purchased from DuPont Company of the United States, and the weight-average molecular weight M _W is respectively: 75,000, 84,000, 10.6 million, 112,000 and 146,000.

The analysis method is as follows:

Use Flash EA-1112 elemental analyzer (Italy) to determine the composition of EVA raw materials; according to the literature [Liang Xiuli, Wang Aiping, Liu Lijun, You Yusheng, Sun Hongyan. Discussion on the determination method of vinyl acetate content in ethylene/vinyl acetate copolymer, chemical analysis and measurement, 2001,10 (3): 23-24] method, measure vinyl acetate content in the hydrolyzate; The amount of vinyl acetate is obtained by the difference between the total amount of vinyl acetate and the content of vinyl acetate in the hydrolyzate; Nicolet 550 Fourier transform infrared spectrometer (USA) is used for infrared characterization. The molecular weight and distribution width of EVA and hydrolyzate were determined by WATERS-515 gel chromatograph (USA). the

Fig. 1 is EVA (VA molar content is 42%) and its hydrolysis product infrared absorption spectrogram, and wherein reaction temperature is 250 ℃, the proportioning of EVA and deionized water is 1: 20, a, b, c, d are respectively Unhydrolyzed and hydrolyzed time is 1 hour, 2 hours and 4 hours infrared spectrograms, in the figure 1731cm ^-1 and 1240cm ^-1 are the characteristic absorption peaks of ester groups, and there is an obvious hydroxyl absorption peak at 3385cm ^-1 . The intensity of the absorption peak of the ester group gradually weakened as the hydrolysis progressed, and on the contrary, the intensity of the absorption peak of the hydroxyl group gradually increased. This shows that in near-critical water, EVA has undergone hydrolysis modification under non-catalytic conditions, generating free hydroxyl groups on the side chains, and generating the hydrolysis product P(E-VA-VOH).

Table 1 shows the influence of reaction conditions on the weight-average molecular weight and distribution of the hydrolyzed product ethylene-vinyl acetate-vinyl alcohol terpolymer, wherein the ratio of EVA (VA content is 33%) to deionized water is 1:10. It can be seen from Table 1 that as the hydrolysis reaction progresses, the weight-average molecular weight does not decrease significantly, and the molecular weight distribution width is around 3.1, indicating that no polymer degradation occurs within the selected temperature range. However, as the degree of hydrolysis increases, the weight-average molecular weight increases instead. The possible reason is that a new chemical bond -OH is generated through hydrolysis, and the polymer undergoes chemical crosslinking. The higher the temperature in the same hydrolysis time, the number of hydroxyl chemical bonds is generated. The more, the more obvious the cross-linking phenomenon. the

Table 1 The influence of reaction conditions on EVA (VA content is 33%) hydrolysis product ethylene-vinyl acetate-vinyl alcohol terpolymer weight-average molecular weight and its distribution

product Hydrolysis time/h Hydrolysis temperature/℃   Degree of hydrolysis% M _W P _d 1 4 210°C 4.5 8.9×10 ₄ 3.1 2 4 250℃ 34.2 9.1×10 ⁴ 3.1 3 4 290°C 86.6 12.2×10 ⁴ 3.1

Note: The M _W of the raw material EVA (33% VA content) is 8.4×10 ⁴ , and the P _d is 3.1.

Example 1

Add 300 g of deionized water and 7.5 g of EVA (VA-18%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 40:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 200°C for 20 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 5.8g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 9.6%, and the vinyl alcohol content is 8.4%. The average molecular weight was 8.2×10 ⁴ , and the distribution width was 3.1.

Example 2

Add 300 g of deionized water and 10 g of EVA (VA-33%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 30:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 3 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 220°C for 20 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 7.58g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 8.2%, and the vinyl alcohol content is 24.8%. The average molecular weight was 12.2×10 ⁴ , and the distribution width was 3.1.

Example 3

Add 300 g of deionized water and 15 g of EVA (VA-42%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 20:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 4 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 240°C for 10 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 11.48g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 14.9%, and the vinyl alcohol content is 27.1%. The average molecular weight was 16.5×10 ⁴ , and the distribution width was 3.1.

Example 4

Add 300 g of deionized water and 20 g of EVA (VA-62%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 15:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 250°C for 8 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 14.43g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 24.6%, and the vinyl alcohol content is 37.4%. The average molecular weight was 17.6×10 ⁴ , and the distribution width was 3.2.

Example 5

Add 300 g of deionized water and 30 g of EVA (VA-86%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 10:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 260°C for 6 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 19.29g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 14.1%, and the vinyl alcohol content is 71.9%. The average molecular weight was 21.2×10 ⁴ , and the distribution width was 3.1.

Example 6

Add 300 g of deionized water and 60 g of EVA (VA-18%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 5:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 280 ° C for 4 hours for hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 53.92g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 8.2%, and the vinyl alcohol content is 9.8%. The average molecular weight was 18.2×10 ⁴ , and the distribution width was 2.9.

Example 7

Add 300 g of deionized water and 100 g of EVA (VA-33%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 3:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 4 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 290°C for 0.5h of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered Obtain a solid product; the solid product obtains 86.54 g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 28.5%, and the vinyl alcohol content is 4.5%. The weight average molecular weight was 10.1×10 ⁴ , and the distribution width was 3.2.

Example 8

Add 300 g of deionized water and 300 g of EVA (VA-42%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 1:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 200°C for 15 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 252.28g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 37.1%, and the vinyl alcohol content is 4.9%. The average molecular weight was 11.2×10 ⁴ , and the distribution width was 3.4.

Example 9

Add 300 g of deionized water and 7.5 g of EVA (VA-62%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 40:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 210°C for 12 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 4.49g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 45.2%, and the vinyl alcohol content is 16.8%. The average molecular weight was 11.4×10 ⁴ , and the distribution width was 3.1.

Example 10

Add 300 g of deionized water and 15 g of EVA (VA-86%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 20:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 3 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 220°C for 10 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 8.95g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 52.1%, and the vinyl alcohol content is 33.9%. The average molecular weight is 23.8×10 ⁴ , and the distribution width is 3.

Example 11

Add 300 g of deionized water and 15 g of EVA (VA-18%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 20:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 4 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 230°C for 8 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 12.71g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 9.2%, and the vinyl alcohol content is 8.8%. The average molecular weight was 12.6×10 ⁴ , and the distribution width was 3.1.

Example 12

Add 300 g of deionized water and 20 g of EVA (VA-33%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 15:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 240°C for 8 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 16.27g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 15.2%, and the vinyl alcohol content is 17.8%. The average molecular weight was 16.5×10 ⁴ , and the distribution width was 2.9.

Example 13

Add 300 g of deionized water and 30 g of EVA (VA-42%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 10:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 250°C for 4 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 24.06g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 26.2%, and the vinyl alcohol content is 15.8%. The average molecular weight was 16.4×10 ⁴ , and the distribution width was 3.1.

Example 14

Add 300 g of deionized water and 60 g of EVA (VA-62%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 5:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 260°C for 3 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 43.99g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 25.2%, and the vinyl alcohol content is 36.8%. The average molecular weight was 17.2×10 ⁴ , and the distribution width was 3.2.

Example 15

Add 300 g of deionized water and 100 g of EVA (VA-86%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 3:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 4 minutes, use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 270°C for 6 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 65.02g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 10.2%, and the vinyl alcohol content is 75.8%. The average molecular weight was 25.8×10 ⁴ , and the distribution width was 3.1.

Example 16

Add 300 g of deionized water and 300 g of EVA (VA-18%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 1:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 280°C for 6 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 274.81g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 3.4%, and the vinyl alcohol content is 14.6%. The average molecular weight was 22.2×10 ⁴ , and the distribution width was 3.1.

Example 17

Add 300 g of deionized water and 300 g of EVA (VA-33%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 1:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 290°C for 2 hours for hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 258.23g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 15.6%, and the vinyl alcohol content is 17.4%. The average molecular weight was 18.2×10 ⁴ , and the distribution width was 3.

Example 18

Add 300 g of deionized water and 15 g of EVA (VA-42%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 20:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 260°C for 12 hours of hydrolysis; the hydrolyzate is cooled, decompressed, and filtered to obtain Solid product; The solid product obtains 10.38g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 4.8%, and the vinyl alcohol content is 37.2%. The average molecular weight was 23.2×10 ⁴ , and the distribution width was 3.

Example 19

Add 300 g of deionized water and 15 g of EVA (VA-62%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 20:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 250°C for 42 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 13.13g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 26.6%, and the vinyl alcohol content is 35.4%. The average molecular weight was 15.2×10 ⁴ , and the distribution width was 3.1.

Example 20

Add 300 g of deionized water and 30 g of EVA (VA-86%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 10:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 4 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 240°C for 15 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 18.19g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 8.6%, and the vinyl alcohol content is 77.4%. The average molecular weight was 26.4×10 ⁴ , and the distribution width was 3.4.

Example 21

300 g of deionized water and 42.86 g of EVA (VA-18%) were added into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate was 7:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 230°C for 20 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 37.72g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 2.3%, and the vinyl alcohol content is 15.7%. The average molecular weight was 18.4×10 ⁴ , and the distribution width was 3.1.

Example 22

Add 300 g of deionized water and 75 g of EVA (VA-33%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 4:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 220°C for 15 hours of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 61.58g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 12.2%, and the vinyl alcohol content is 20.8%. The average molecular weight was 23.1×10 ⁴ , and the distribution width was 3.1.

Example 23

Add 300 g of deionized water and 15 g of EVA (VA-42%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 20:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 3 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 210°C for 2 hours for hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains 11.38g of polyethylene-vinyl acetate-vinyl alcohol terpolymer after being rinsed with deionized water and vacuum-dried. After analysis, the vinyl acetate content is 40.7%, and the vinyl alcohol content is 1.3%. The average molecular weight was 9.6×10 ⁴ , and the distribution width was 3.1.

Example 24

Add 300 g of deionized water and 20 g of EVA (VA-62%) into a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 15:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 4 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 290 ° C for 4 hours for hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 15.13g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 9.66%, and the vinyl alcohol content is 52.34%. The average molecular weight was 24.4×10 ⁴ , and the distribution width was 3.1.

Example 25

Add 300 g of deionized water and 30 g of EVA (VA-86%) in a 500 mL batch type autoclave, and the mass ratio of deionized water to polyethylene vinyl acetate is 10:1. Turn on stirring, heat up to boiling under normal pressure, open the exhaust valve for 5 minutes, and use water vapor to remove the air in the kettle; close the exhaust valve, continue to heat up to 280°C for 1 hour of hydrolysis; the hydrolyzate is cooled, depressurized, and filtered to obtain Solid product; The solid product obtains polyethylene-vinyl acetate-vinyl alcohol terpolymer 19.19g after washing with deionized water and vacuum drying. After analysis, the vinyl acetate content is 64.4%, and the vinyl alcohol content is 21.6%. The average molecular weight was 12.6×10 ⁴ , and the distribution width was 3.1.

Claims (3)

1. a method for preparing polyethylene-vinyl acetate-vinyl alcohol terpolymer by non-catalytic hydrolysis of polyethylene vinyl acetate in near critical water, is characterized in that, the steps of method are as follows: 1) Add deionized water and polyethylene vinyl acetate into the autoclave, the mass ratio of deionized water to polyethylene vinyl acetate is 1:1~40:1, start stirring, heat up to boiling under normal pressure, open Exhaust valve for 2 to 5 minutes; 2) Heat up to 200-290°C, hydrolyze for 0.5-20 hours; 3) The hydrolyzate is cooled, depressurized, and filtered to obtain a solid product; 4) The solid product is rinsed with deionized water and vacuum-dried to obtain a polyethylene-vinyl acetate-vinyl alcohol terpolymer. 2. the method for preparing polyethylene-vinyl acetate-vinyl alcohol terpolymer by non-catalytic hydrolysis of polyethylene vinyl acetate in a kind of near-critical water according to claim 1, is characterized in that in step 1) deionized water and The mass ratio of polyethylene vinyl acetate is 3:1-20:1. 3. a kind of non-catalytic hydrolysis of polyethylene vinyl acetate in near critical water according to claim 1 prepares the method for polyethylene-vinyl acetate-vinyl alcohol terpolymer, it is characterized in that the hydrolysis temperature in step 2) is 230～270℃.

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