Plastic sealing strip easy to degrade and differentiate

[0021] Example: The present invention provides a plastic sealing strip that is easy to degrade and differentiate, which is made of the following components in parts by weight: 25 to 38 parts of polyethylene, 15 to 30 parts of borax, 15 to 32 parts of urea, and 5 parts of glycerin. ~12 parts, 16~28 parts of plant fiber, 16~30 parts of modified starch, 25~52 parts of ethanol aqueous solution, 14~26 parts of dialdehyde starch, 15~25 parts of polyvinyl alcohol, 11~20 parts of chitosan, 10 to 24 parts of sodium carboxymethyl cellulose, 9 to 28 parts of acetic anhydride, 10 to 22 parts of sorbitol ester, 5 to 18 parts of formamide, 6 to 12 parts of crosslinking agent, and some liquid paraffin;

[0022] The specific preparation steps are as follows:

[0023] S1: According to parts by weight, 16-30 parts of modified starch are prepared with 1% NaOH solution into a modified starch solution with a concentration of 30% g/ml, and 1 to 1.5 parts of polyvinyl alcohol solution are added as modifier , Get solution A; add 0.5% span80 emulsifier to liquid paraffin to get solution B, add solution A to solution B, the weight ratio of solution A to solution B is 1:20, and then emulsify by shearing machine at high speed. The emulsification speed is 500rpm and the time is 20min; after the emulsification is completed, 6-12 parts of crosslinking agent are added, and the crosslinking reaction is carried out by stirring at room temperature for 5 hours. After completion, it is allowed to stand, wash, and dry to obtain particles C;

[0024] S2: In parts by weight, add 16-28 parts of plant fiber, particles C16-30, 11-20 parts of chitosan, 9-28 parts of acetic anhydride, and 6-12 parts of crosslinking agent into water at a temperature of 48℃ Stir uniformly to obtain a paste under the conditions of ~72°C and a pH of 6.2 ~ 6.8; add the paste mixture to the autoclave, and react at 2.7 ~ 4.3 MPa for 35 ~ 50 minutes to obtain mixture D;

[0025] S3: In parts by weight, add mixture D with 25 to 38 parts of polyethylene, 15 to 30 parts of borax, 15 to 32 parts of urea, 5 to 12 parts of glycerin, and 10% to 35% of ethanol aqueous solution by volume fraction, Among them, the ethanol aqueous solution is 25 to 52 parts; the temperature is 70℃~78℃, and the pH is 8.5~10 to make a paste evenly; the paste mixture is added to the autoclave at 2.7~4.3MPa After reacting for 35-50 minutes, modified polyethylene can be obtained after the reaction is completed;

[0026] S4: In parts by weight, add 12 to 23 parts of dialdehyde starch, 13 to 21 parts of polyvinyl alcohol, 9 to 18 parts of chitosan and 8 to 22 parts of sodium carboxymethyl cellulose into the reactor at 100°C React at ~150℃ for 50~70min under the sealed condition; add 23~39 parts of modified polyethylene to the upper tank, the temperature of the upper tank is maintained at 85℃~132℃, while maintaining the temperature of the reactor at 90℃~126℃ ; Start dropping the modified polyethylene in the high-position tank, and finish dropping in 2.5-4 hours. During the dropping, the temperature of the high-position tank and the reactor remains unchanged. After the addition, the temperature of the reactor is increased to 157℃~176 After the temperature is kept for 1 to 2 hours, the degradable modified polyethylene plastic can be prepared.

[0027] S5: Put the degradable modified polyethylene plastic obtained in step S4 into an extruder for extrusion molding.

[0028] As a preferred technical solution of the present invention, the optimal proportion of the following components in parts by weight is: 32 parts of polyethylene, 24 parts of borax, 28 parts of urea, 8 parts of glycerin, 22 parts of plant fiber, and 20 parts of modified starch. Parts, 35 parts of ethanol aqueous solution, 20 parts of dialdehyde starch, 21 parts of polyvinyl alcohol, 16 parts of chitosan, 18 parts of sodium carboxymethyl cellulose, 16 parts of acetic anhydride, 15 parts of sorbitol ester, 14 parts of formamide, 9 parts of crosslinking agent and some liquid paraffin.

[0029] Further, the crosslinking agent is one of divinyl sulfone and sodium tetraborate decahydrate, which has a fast reaction speed and high crosslinking efficiency.

[0030] Further, in step S1, the modified starch is cationic starch, and the weight ratio of polyvinyl alcohol to cationic starch is 1:20.

[0031] Furthermore, the optimum temperature is 66°C, the optimum pH is 6.5, the optimum pressure is 3.7MPa, and the optimum reaction time is 42min.

[0032] Further, the optimum temperature in step S3 is 72°C, and the optimum pH is 9.2.

[0033] Further, as a preference, add 20 parts of dialdehyde starch, 20 parts of polyvinyl alcohol, 16 parts of chitosan and 18 parts of sodium carboxymethyl cellulose into the reaction kettle, and react at 143°C for 65 minutes under sealed conditions; Add 35 parts of polyethylene to the high tank. The temperature of the high tank is maintained at 120°C and the temperature of the reactor is maintained at 115°C. The modified polyethylene in the high tank is started to drip in 3.3 hours. The temperature of the high-level tank and the reaction kettle was kept unchanged. After the dripping, the temperature of the reaction kettle was increased to 170°C and kept for 1.3 hours.

[0034] Working principle: The present invention uses cationic starch as the raw material. The molecular weight of ordinary vegetable starch is high, gelatinization is difficult, and the cross-linking modification reaction is not easy to occur in the crystallization area. Cationic starch can make the modified starch gelatinized easily due to the improvement of the molecular structure. The gelatinization temperature is reduced, the viscosity is greatly reduced, the stability is high, the condensation is weak, the fluidity is high, the transparency is high, the adhesive force is strong, and the film-forming property is good; adding a proper amount of polyvinyl alcohol solution, due to the polyvinyl alcohol itself The presence of a large number of hydroxyl groups and its viscosity make it easier to form stable cross-linked starch particles in the next inverse suspension cross-linking reaction, and more cross-linking reactions are more likely to occur at the same time, which makes the prepared modified starch mechanical strength better. The high-speed emulsification method of the shearing machine is adopted, and the appropriate emulsifier is used to realize the rapid and uniform dispersion of the starch solution, which is beneficial to shorten the crosslinking reaction time and improve the performance of the final product. Polyvinyl alcohol has excellent transparency and gloss, is a non-charged material, and has the advantages of greater tensile strength and tear strength, good oil resistance, gas barrier properties, heat sealability and adhesion. However, the water resistance of polyvinyl alcohol is poor. The present invention uses the synergistic effect of the emulsified modified starch and plant fiber to modify the speed of polyvinyl alcohol, improve its mechanical properties, and overcome the brittle, hard, and The disadvantage of high water solubility improves the degradability of modified polyethylene; the synergistic effect of polyvinyl alcohol, chitosan and modified polyethylene is used to improve the degradability and water resistance of polyethylene plastic. The resulting sealing strip has good degradation and differentiation performance.