阅读说明：本技术 聚乙烯包装材料 (Polyethylene packaging material ) 是由 张燕丹 葛铁军 肖尚雄 于 2020-12-21 设计创作，主要内容包括：本发明公开了一种聚乙烯包装材料。该聚乙烯包装材料由以下原料组成：40-100重量份低密度聚乙烯、25-45重量份填料、2-8重量份麦芽糖醇、1-5重量份铝酸酯偶联剂、5-15重量份降解促进剂、10-20重量份助剂。本发明的聚乙烯包装材料,生产工艺简单,填料及功能添加剂均采用的是可降解物质,而且与聚乙烯树脂的相容性好,不仅具有聚乙烯包装材料本身的优势,而且能够改善聚乙烯包装材料的降解性能,整体性能优异,对聚乙烯包装材料的应用和推广,具有十分重要的社会经济价值。(The invention discloses a polyethylene packaging material. The polyethylene packaging material is composed of the following raw materials: 40-100 parts of low-density polyethylene, 25-45 parts of filler, 2-8 parts of maltitol, 1-5 parts of aluminate coupling agent, 5-15 parts of degradation accelerator and 10-20 parts of auxiliary agent. The polyethylene packaging material disclosed by the invention is simple in production process, the filler and the functional additive are both degradable substances, and the polyethylene packaging material has good compatibility with polyethylene resin, not only has the advantages of the polyethylene packaging material, but also can improve the degradation performance of the polyethylene packaging material, has excellent overall performance, and has very important social and economic values for application and popularization of the polyethylene packaging material.)

1. The polyethylene packaging material is characterized by comprising the following raw materials: low-density polyethylene, filler, maltitol, aluminate coupling agent and degradation accelerator.

2. The polyethylene packaging material as claimed in claim 1, which is prepared from the following raw materials in parts by weight: 40-100 parts of low-density polyethylene, 25-45 parts of filler, 2-8 parts of maltitol, 1-5 parts of aluminate coupling agent and 5-15 parts of degradation accelerator.

3. The polyethylene packaging material as claimed in claim 2, which is prepared from the following raw materials in parts by weight: 40-100 parts of low-density polyethylene, 25-45 parts of filler, 2-8 parts of maltitol, 1-5 parts of aluminate coupling agent, 5-15 parts of degradation accelerator and 10-20 parts of auxiliary agent.

4. A polyethylene packaging material as claimed in claim 2 or 3, wherein the filler is one or a mixture of more than two of corn starch, tapioca starch, modified tapioca starch, potato starch.

5. The polyethylene packaging material according to claim 4, wherein the filler is modified tapioca starch, and the preparation method of the modified tapioca starch comprises the following steps: 1) and (3) oxidation reaction: adding 30-70 parts by weight of cassava starch into 60-140 parts by weight of water, uniformly mixing, adjusting the pH to 8-9 by using 0.1-0.5mol/L potassium hydroxide solution, then adding 6-10 parts by weight of sodium perborate, reacting for 2-6 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A; 2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 80-120 parts by weight of 0.02-0.1mol/L phosphate buffer solution, uniformly mixing, heating to 95-105 ℃, stirring for 40-60min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 58-63 ℃, adding 2-6 parts by weight of pullulanase, incubating for 6-10h, performing low-temperature recrystallization at 2-6 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain cassava starch B; 3) graft modification: adding the cassava starch B obtained in the step 2) into 90-115 parts by weight of 100 ℃ water, stirring and heating for 40-60min until complete gelatinization, stopping heating, then cooling to 25 ℃, adding 3-8 parts by weight of sodium hexametaphosphate, reacting for 1-3h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

6. The polyethylene packaging material according to claim 2 or 3, wherein the degradation promoter is a mixture of polybutylene adipate/terephthalate and polydioxanone; the mass ratio of the polybutylene adipate/terephthalate to the poly (p-dioxanone) is 1: 1.

7. The polyethylene packaging material according to claim 2 or 3, wherein the auxiliary agent is a polylactic acid/polyurethane elastomer.

8. The polyethylene packaging material according to any one of claims 1 to 7, prepared by a process comprising:

(1) weighing the filler and the maltitol according to the parts by weight, mixing the filler and the maltitol in a high mixing machine at the rotating speed of 400-600rpm for 5-15min, and then adding the aluminate coupling agent and the degradation promoter for blending for 15-30 min;

(2) adding low-density polyethylene and an auxiliary agent into the mixture prepared in the step (1), blending at the rotating speed of 700-1000rpm for 25-40min, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the rotation speed of the screw is 150-300rpm, and the working temperature of the extrusion section is 140-180 ℃.

Technical Field

The invention relates to the technical field of packaging materials, in particular to a polyethylene packaging material.

Background

The packaging material, namely the material used for meeting the product packaging requirements, mainly comprises four materials of paper, plastic, metal and glass, and plays a significant role in the whole packaging industry. Plastics have been widely used as packaging materials for most products because of their good properties and low processing costs.

Polyethylene (PE) is a general thermoplastic resin with multiple structures and properties produced by using ethylene as a monomer through various process methods. The packaging material prepared by using polyethylene as a raw material has the characteristics of good toughness, low temperature resistance, low water permeability, processability, light weight, no odor, no toxicity and the like, and becomes one of the most widely applied plastic packaging materials in production and life at present. However, the main raw material of the polyethylene packaging materials used in daily life is polyethylene from petroleum resources, which is increasingly deficient due to unlimited exploitation; in addition, polyethylene has a long degradation time and is prone to "white contamination".

With the development of economic society and the improvement of environmental awareness of people, people not only require that the packaging material has good performance and novel and beautiful appearance, but also require that the packaging material has little pollution to the environment and is easy to decompose.

Therefore, the research on the degradable polyethylene packaging material has very important social and economic values.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a polyethylene packaging material.

In order to solve the technical problems, the invention adopts the technical scheme that:

a polyethylene packaging material is composed of the following raw materials: low-density polyethylene, filler, maltitol, aluminate coupling agent and degradation accelerator.

Preferably, the polyethylene packaging material is composed of the following raw materials in parts by weight: 40-100 parts of low-density polyethylene, 25-45 parts of filler, 2-8 parts of maltitol, 1-5 parts of aluminate coupling agent and 5-15 parts of degradation accelerator.

Preferably, the polyethylene packaging material is composed of the following raw materials in parts by weight: 40-100 parts of low-density polyethylene, 25-45 parts of filler, 2-8 parts of maltitol, 1-5 parts of aluminate coupling agent, 5-15 parts of degradation accelerator and 10-20 parts of auxiliary agent.

In the invention, the coupling agent is nontoxic and has small smell, and the inorganic end and the organic end of the coupling agent can respectively chemically react with the surface of the inorganic filler and the polyethylene resin or form an entangled structure, so that the interface compatibility of the filler and the polyethylene resin is enhanced, the filler is uniformly dispersed, the product quality is improved, and the production cost is reduced.

The filler is one or a mixture of more than two of corn starch, tapioca starch, modified tapioca starch, sawdust and potato starch.

Preferably, the filler is modified tapioca starch. The preparation method of the modified cassava starch comprises the following steps: 1) and (3) oxidation reaction: adding 30-70 parts by weight of cassava starch into 60-140 parts by weight of water, uniformly mixing, adjusting the pH to 8-9 by using 0.1-0.5mol/L potassium hydroxide solution, then adding 6-10 parts by weight of sodium perborate, reacting for 2-6 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A; 2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 80-120 parts by weight of 0.02-0.1mol/L phosphate buffer solution, uniformly mixing, heating to 95-105 ℃, stirring for 40-60min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 58-63 ℃, adding 2-6 parts by weight of pullulanase, incubating for 6-10h, performing low-temperature recrystallization at 2-6 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain cassava starch B; 3) graft modification: adding the cassava starch B obtained in the step 2) into 90-115 parts by weight of 100 ℃ water, stirring and heating for 40-60min until complete gelatinization, stopping heating, then cooling to 25 ℃, adding 3-8 parts by weight of sodium hexametaphosphate, reacting for 1-3h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

In the invention, the modified cassava starch is used as the filler of the polyethylene packaging material, and the amylopectin content of the cassava starch is up to 83%, and after oxidation and enzymolysis treatment, more short-chain starch is generated, so that on one hand, a large number of hole structures are generated on the surface of starch granules, the specific surface area is increased, the dispersibility is improved, on the other hand, after oxidation reaction, the carboxyl content of the cassava starch is increased, then the carboxyl content is subjected to enzymolysis treatment, the hydroxyl content in the cassava starch is increased, and both the carboxyl hydroxyl and the hydroxyl can be combined with metaphosphate to form a phosphate ester bond, so that the polarity of the starch is reduced, the compatibility with a nonpolar polymer is improved, and the processing is facilitated.

The degradation promoter is one or the mixture of more than two of polycaprolactone, polyhydroxybutyrate, polybutylene adipate/terephthalate, polyhydroxyvalerate, polyhydroxycaprylate, polyhydroxybutyrate caproate copolyester and poly-p-dioxanone.

Preferably, the degradation promoter is a mixture of polybutylene adipate/terephthalate and poly-dioxanone; the mass ratio of the polybutylene adipate/terephthalate to the poly (p-dioxanone) is 1: 1.

The auxiliary agent is one or the mixture of more than two of polyethylene/polyoctene elastomer, polylactic acid/polyurethane elastomer and polypropylene/polystyrene elastomer.

Preferably, the auxiliary agent is a polylactic acid/polyurethane elastomer. The preparation method of the polylactic acid/polyurethane elastomer comprises the following steps: stirring 40-50 parts by weight of polylactic acid, 18-25 parts by weight of polyethylene glycol-400, 2-5 parts by weight of trimethylolpropane and 4-10 parts by weight of glycerol at the speed of 80-150rpm for 10-15min, uniformly mixing, then stirring and reacting at the temperature of 120-160 ℃ for 1 hour, cooling to 95-105 ℃, adding 10-18 parts by weight of isocyanate, continuing stirring and reacting at the temperature of 95-105 ℃ for 5-8 hours, after the reaction is finished, pouring the reaction product into deionized water for settling and suction filtration, and freeze-drying the obtained product to obtain the polylactic acid/polyurethane elastomer.

The isocyanate is one or a mixture of more than two of toluene diisocyanate, hexamethylene diisocyanate, lysine methyl ester diisocyanate and 4,4' -diphenylmethane diisocyanate.

Preferably, the isocyanate is a mixture of hexamethylene diisocyanate and lysine methyl ester diisocyanate, and the mass ratio of the hexamethylene diisocyanate to the lysine methyl ester diisocyanate is 1 (1-3).

In the preparation process of the assistant polylactic acid/polyurethane elastomer, polyethylene glycol is used as a soft segment, isocyanate is used as a hard segment, then trifunctional monomer glycerol and trimethylolpropane are added to promote the hydroxyl of the soft segment to be combined with the isocyanate group of the hard segment to generate polyurethane with high crosslinking density, and then the polyurethane reacts with the terminal hydroxyl of polylactic acid, so that the interface compatibility of the blend is greatly improved; the polymer structure contains a large number of oxygen atoms, has good dispersibility and flexibility, and can be well combined with other blends to form a net structure to promote microbial decomposition. On the one hand, trimethylolpropane of a trifunctional monomer can cooperate with glycerol to promote soft and hard segments to combine to generate high-density polyurethane, on the other hand, the moisture absorption of the trimethylolpropane is about 50 times that of the glycerol, and the proper amount of the trimethylolpropane is added to improve the water absorption performance of a system and further promote the decomposition of microorganisms.

As can be seen from the foregoing, the present invention achieves the purpose of easy degradation of the polyethylene packaging material by adding a large amount of starch-based filler to the main raw material, but results in a decrease in mechanical properties of the polyethylene packaging material; the inventor finds that the mechanical property of the polyethylene packaging material can be maintained and the degradation property of the polyethylene packaging material can be improved by adding the auxiliary agent polylactic acid/polyurethane elastomer into the raw materials in the test process.

The polyethylene packaging material is characterized by being prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing the filler and the maltitol in a high mixing machine at the rotating speed of 400-600rpm for 5-15min, and then adding the aluminate coupling agent and the degradation promoter for blending for 15-30 min;

(2) adding low-density polyethylene and an auxiliary agent into the mixture prepared in the step (1), blending at the rotating speed of 700-1000rpm for 25-40min, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the rotation speed of the screw is 150-300rpm, and the working temperature of the extrusion section is 140-180 ℃.

The invention has the following beneficial effects:

the polyethylene packaging material has simple production process, adopts degradable substances as the filler and the functional additive, has good compatibility with the polyethylene resin, not only has the advantages of the polyethylene packaging material in the prior art, but also can improve the degradation performance of the polyethylene packaging material, has excellent overall performance, ensures that the polyethylene packaging material is easy to degrade, and has very important social and economic values for the application and popularization of the polyethylene packaging material.

Detailed Description

The above summary of the present invention is described in further detail below with reference to specific embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples.

Introduction of some raw materials in this application:

low Density Polyethylene (LDPE), density 0.916g/cm³The No. MB9500 is provided by Shanghai super cyclone chemical technology Co., Ltd.

The cassava starch is prepared from commercially available food-grade cassava starch, wherein the product number is as follows: 612, available from Xiamen orange Pont happy Xuan Biotech Co., Ltd.

Maltitol, CAS number: 585-88-6, available from Shanghai Michelin Biochemical technology, Inc.

An aluminate coupling agent, LD-B-1, with a density of 0.88g/mL, a thermal decomposition temperature of 300 ℃ was purchased from Cilida resin, Inc., of Yangzhou.

Sodium perborate, CAS No.: 7632-04-4, available from Beijing coupled technology, Inc.

Pullulanase, CAS No.: 9075-68-7, enzyme activity: 1u/mg, purchased from Shanghai-derived leaf Biotech, Inc.

Sodium hexametaphosphate, CAS number: 10124-56-8, available from Dainichi chemical Co., Ltd, of the Qingzhou city.

Polylactic acid, CAS No.: 26100-51-6, molecular weight 60000, available from Shanghai Allan Biotechnology Ltd.

Polyethylene glycol 400, CAS No.: 25322-68-3, molecular weight 400, available from Yipu crude drug industry Co., Ltd.

Polyethylene polyoctene elastomer, brand Spanish Dow, designation DE2300, density 1.16g/cm³Purchased from Ruisheng plastics Co., Ltd, of Foshan City.

Trimethylolpropane, CAS No.: 77-99-6, available from Pan (Shanghai) International trade, Inc.

Hexamethylene diisocyanate, CAS No.: 822-06-0, available from Shanghai Michelin Biochemical technology, Inc.

Lysine methyl ester diisocyanate, CAS No.: 4460-02-0, available from Bailingwei technologies, Beijing.

Poly-p-dioxahexanone, CAS No.: 31621-87-1, molecular weight: 10000, purchased from Wuhan, a Co-creation science and technology Co.

Poly (butylene adipate/terephthalate), density: 1.25g/cm³And the brand number: C1200F, cat number: 11078 available from Kadaler plastics materials Co., Ltd, Dongguan.

Example 1

A polyethylene packaging material is composed of the following raw materials in parts by weight:

65 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent and 10 parts by weight of degradation accelerator.

The filler is cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene into the mixture prepared in the step (1), blending at the rotating speed of 800rpm for 30min, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Comparative example 1

A polyethylene packaging material is composed of the following raw materials in parts by weight:

100 parts by weight of low-density polyethylene, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent and 10 parts by weight of degradation accelerator.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

A polyethylene packaging material is prepared by the following method:

(1) weighing maltitol, an aluminate coupling agent and a degradation promoter according to the parts by weight, and blending for 20min in a high-speed mixer at the rotating speed of 500rpm to obtain a mixture;

(2) adding low-density polyethylene into the mixture prepared in the step (1), blending at the rotating speed of 800rpm for 30min, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Example 2

A polyethylene packaging material is composed of the following raw materials in parts by weight:

65 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent and 10 parts by weight of degradation accelerator.

The filler is modified tapioca starch.

The preparation method of the modified cassava starch comprises the following steps:

1) and (3) oxidation reaction: adding 50 parts by weight of cassava starch into 100 parts by weight of water, uniformly mixing, adjusting the pH to 8 by using 0.1mol/L potassium hydroxide solution, then adding 8 parts by weight of sodium perborate, reacting for 3 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A;

2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 100 parts by weight of 0.05mol/L phosphate buffer solution, uniformly mixing, heating to 100 ℃, stirring for 50min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 60 ℃, adding 4 parts by weight of pullulanase, incubating for 8h, recrystallizing at a low temperature of 4 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain the cassava starch B;

3) graft modification: adding the cassava starch B obtained in the step 2) into 100 parts by weight of 100 ℃ water, stirring and heating for 50min until the cassava starch B is completely gelatinized, stopping heating, then cooling to 25 ℃, adding 5 parts by weight of sodium hexametaphosphate, reacting for 2h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene into the mixture prepared in the step (1), blending at the rotating speed of 800rpm for 30min, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Example 3

A polyethylene packaging material is composed of the following raw materials in parts by weight:

65 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent and 10 parts by weight of degradation accelerator.

The filler is modified tapioca starch.

The preparation method of the modified cassava starch comprises the following steps:

1) and (3) carrying out enzymolysis reaction: adding 50 parts by weight of cassava starch into 100 parts by weight of 0.05mol/L phosphate buffer solution, uniformly mixing, heating to 100 ℃, stirring for 50min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 60 ℃, adding 4 parts by weight of pullulanase, incubating for 8h, recrystallizing at a low temperature of 4 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain pretreated cassava starch;

2) graft modification: adding the pretreated cassava starch obtained in the step 2) into 100 parts by weight of 100 ℃ water, stirring and heating for 50min until the cassava starch is completely gelatinized, stopping heating, then cooling to 25 ℃, adding 5 parts by weight of sodium hexametaphosphate, reacting for 2h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene into the mixture prepared in the step (1), blending at the rotating speed of 800rpm for 30min, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Example 4

A polyethylene packaging material is composed of the following raw materials in parts by weight:

50 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent, 10 parts by weight of degradation accelerator and 15 parts by weight of auxiliary agent.

The filler is modified tapioca starch.

The preparation method of the modified cassava starch comprises the following steps:

1) and (3) oxidation reaction: adding 50 parts by weight of cassava starch into 100 parts by weight of water, uniformly mixing, adjusting the pH to 8 by using 0.1mol/L potassium hydroxide solution, then adding 8 parts by weight of sodium perborate, reacting for 3 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A;

2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 100 parts by weight of 0.05mol/L phosphate buffer solution, uniformly mixing, heating to 100 ℃, stirring for 50min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 60 ℃, adding 4 parts by weight of pullulanase, incubating for 8h, recrystallizing at a low temperature of 4 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain the cassava starch B;

3) graft modification: adding the cassava starch B obtained in the step 2) into 100 parts by weight of 100 ℃ water, stirring and heating for 50min until the cassava starch B is completely gelatinized, stopping heating, then cooling to 25 ℃, adding 5 parts by weight of sodium hexametaphosphate, reacting for 2h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

The auxiliary agent is polylactic acid/polyurethane elastomer.

The polylactic acid/polyurethane elastomer is prepared by the following method: stirring 48 parts by weight of polylactic acid, 23 parts by weight of polyethylene glycol-400, 4 parts by weight of trimethylolpropane and 6 parts by weight of glycerol at the speed of 100rpm for 12min, uniformly mixing, stirring and reacting at 150 ℃ for 1 hour, cooling to 100 ℃, adding 13 parts by weight of isocyanate, continuously stirring and reacting at 100 ℃ for 6 hours, pouring a reaction product into deionized water for settling and suction filtering after the reaction is finished, and freeze-drying the obtained product to obtain the polylactic acid/polyurethane elastomer.

The isocyanate is hexamethylene diisocyanate.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene and an auxiliary agent into the mixture prepared in the step (1), blending for 30min at the rotating speed of 800rpm, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Example 5

A polyethylene packaging material is composed of the following raw materials in parts by weight:

50 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent, 10 parts by weight of degradation accelerator and 15 parts by weight of auxiliary agent.

The filler is modified tapioca starch.

The preparation method of the modified cassava starch comprises the following steps:

1) and (3) oxidation reaction: adding 50 parts by weight of cassava starch into 100 parts by weight of water, uniformly mixing, adjusting the pH to 8 by using 0.1mol/L potassium hydroxide solution, then adding 8 parts by weight of sodium perborate, reacting for 3 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A;

2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 100 parts by weight of 0.05mol/L phosphate buffer solution, uniformly mixing, heating to 100 ℃, stirring for 50min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 60 ℃, adding 4 parts by weight of pullulanase, incubating for 8h, recrystallizing at a low temperature of 4 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain the cassava starch B;

3) graft modification: adding the cassava starch B obtained in the step 2) into 100 parts by weight of 100 ℃ water, stirring and heating for 50min until the cassava starch B is completely gelatinized, stopping heating, then cooling to 25 ℃, adding 5 parts by weight of sodium hexametaphosphate, reacting for 2h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

The auxiliary agent is polylactic acid/polyurethane elastomer.

The polylactic acid/polyurethane elastomer is prepared by the following method: stirring 48 parts by weight of polylactic acid, 23 parts by weight of polyethylene glycol-400, 4 parts by weight of trimethylolpropane and 6 parts by weight of glycerol at the speed of 100rpm for 12min, uniformly mixing, stirring and reacting at 150 ℃ for 1 hour, cooling to 100 ℃, adding 13 parts by weight of isocyanate, continuously stirring and reacting at 100 ℃ for 6 hours, pouring a reaction product into deionized water for settling and suction filtering after the reaction is finished, and freeze-drying the obtained product to obtain the polylactic acid/polyurethane elastomer.

The isocyanate is lysine methyl ester diisocyanate.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene and an auxiliary agent into the mixture prepared in the step (1), blending for 30min at the rotating speed of 800rpm, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Example 6

A polyethylene packaging material is composed of the following raw materials in parts by weight:

50 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent, 10 parts by weight of degradation accelerator and 15 parts by weight of auxiliary agent.

The filler is modified tapioca starch.

The preparation method of the modified cassava starch comprises the following steps:

1) and (3) oxidation reaction: adding 50 parts by weight of cassava starch into 100 parts by weight of water, uniformly mixing, adjusting the pH to 8 by using 0.1mol/L potassium hydroxide solution, then adding 8 parts by weight of sodium perborate, reacting for 3 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A;

2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 100 parts by weight of 0.05mol/L phosphate buffer solution, uniformly mixing, heating to 100 ℃, stirring for 50min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 60 ℃, adding 4 parts by weight of pullulanase, incubating for 8h, recrystallizing at a low temperature of 4 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain the cassava starch B;

3) graft modification: adding the cassava starch B obtained in the step 2) into 100 parts by weight of 100 ℃ water, stirring and heating for 50min until the cassava starch B is completely gelatinized, stopping heating, then cooling to 25 ℃, adding 5 parts by weight of sodium hexametaphosphate, reacting for 2h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

The auxiliary agent is polylactic acid/polyurethane elastomer.

The polylactic acid/polyurethane elastomer is prepared by the following method: stirring 48 parts by weight of polylactic acid, 23 parts by weight of polyethylene glycol-400, 4 parts by weight of trimethylolpropane and 6 parts by weight of glycerol at the speed of 100rpm for 12min, uniformly mixing, stirring and reacting at 150 ℃ for 1 hour, cooling to 100 ℃, adding 13 parts by weight of isocyanate, continuously stirring and reacting at 100 ℃ for 6 hours, pouring a reaction product into deionized water for settling and suction filtering after the reaction is finished, and freeze-drying the obtained product to obtain the polylactic acid/polyurethane elastomer.

The isocyanate is a mixture of hexamethylene diisocyanate and lysine methyl ester diisocyanate, and the mass ratio of the hexamethylene diisocyanate to the lysine methyl ester diisocyanate is 1: 2.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene and an auxiliary agent into the mixture prepared in the step (1), blending for 30min at the rotating speed of 800rpm, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Comparative example 2

A polyethylene packaging material is composed of the following raw materials in parts by weight:

50 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent, 10 parts by weight of degradation accelerator and 15 parts by weight of auxiliary agent.

The filler is modified tapioca starch.

The preparation method of the modified cassava starch comprises the following steps:

1) and (3) oxidation reaction: adding 50 parts by weight of cassava starch into 100 parts by weight of water, uniformly mixing, adjusting the pH to 8 by using 0.1mol/L potassium hydroxide solution, then adding 8 parts by weight of sodium perborate, reacting for 3 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A;

2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 100 parts by weight of 0.05mol/L phosphate buffer solution, uniformly mixing, heating to 100 ℃, stirring for 50min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 60 ℃, adding 4 parts by weight of pullulanase, incubating for 8h, recrystallizing at a low temperature of 4 ℃ to obtain a suspension, centrifuging, washing, and freeze-drying to obtain the cassava starch B;

3) graft modification: adding the cassava starch B obtained in the step 2) into 100 parts by weight of 100 ℃ water, stirring and heating for 50min until the cassava starch B is completely gelatinized, stopping heating, then cooling to 25 ℃, adding 5 parts by weight of sodium hexametaphosphate, reacting for 2h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

The auxiliary agent is polyethylene/polyoctene elastomer.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene and an auxiliary agent into the mixture prepared in the step (1), blending for 30min at the rotating speed of 800rpm, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Comparative example 3

A polyethylene packaging material is composed of the following raw materials in parts by weight:

50 parts by weight of low-density polyethylene, 35 parts by weight of filler, 5 parts by weight of maltitol, 3 parts by weight of aluminate coupling agent, 10 parts by weight of degradation accelerator and 15 parts by weight of auxiliary agent.

The filler is modified tapioca starch.

The preparation method of the modified cassava starch comprises the following steps: 1) and (3) oxidation reaction: adding 50 parts by weight of cassava starch into 100 parts by weight of water, uniformly mixing, adjusting the pH to 8 by using 0.1mol/L potassium hydroxide solution, then adding 8 parts by weight of sodium perborate, reacting for 3 hours, centrifuging, washing, and freeze-drying to obtain cassava starch A; 2) and (3) carrying out enzymolysis reaction: adding the cassava starch A obtained in the step 1) into 100 parts by weight of phosphate buffer solution, uniformly mixing, heating to 100 ℃, stirring for 50min until the cassava starch A is completely gelatinized, stopping heating, naturally cooling to 60 ℃, adding 4 parts by weight of pullulanase, incubating for 8h, performing low-temperature recrystallization at 4 ℃ to obtain suspension, centrifuging, washing, and freeze-drying to obtain cassava starch B; 3) graft modification: adding the cassava starch B obtained in the step 2) into 100 parts by weight of 100 ℃ water, stirring and heating for 50min until the cassava starch B is completely gelatinized, stopping heating, then cooling to 25 ℃, adding 5 parts by weight of sodium hexametaphosphate, reacting for 2h, centrifuging, washing, and freeze-drying to obtain the modified cassava starch.

The degradation promoter is a mixture formed by mixing poly (butylene adipate)/terephthalate and poly (p-dioxanone) according to the mass ratio of 1: 1.

The auxiliary agent is polylactic acid/polyurethane elastomer.

The polylactic acid/polyurethane elastomer is prepared by the following method: stirring 48 parts by weight of polylactic acid, 23 parts by weight of polyethylene glycol-400 and 10 parts by weight of glycerol at the speed of 100rpm for 12min, uniformly mixing, stirring at 150 ℃ for reaction for 1 hour, cooling to 100 ℃, adding 13 parts by weight of isocyanate, continuing stirring at 100 ℃ for reaction for 6 hours, after the reaction is finished, pouring a reaction product into deionized water for settling and suction filtration, and freeze-drying the obtained product to obtain the polylactic acid/polyurethane elastomer.

The isocyanate is a mixture of hexamethylene diisocyanate and lysine methyl ester diisocyanate, and the mass ratio of the hexamethylene diisocyanate to the lysine methyl ester diisocyanate is 1: 2.

A polyethylene packaging material is prepared by the following method:

(1) weighing the filler and the maltitol according to the parts by weight, mixing for 10min in a high-speed mixer at the rotating speed of 500rpm, and then adding the aluminate coupling agent and the degradation accelerator for blending for 20min to obtain a mixture;

(2) adding low-density polyethylene and an auxiliary agent into the mixture prepared in the step (1), blending for 30min at the rotating speed of 800rpm, placing the mixture into a double-screw extruder for extrusion granulation, and carrying out die pressing on the granulated master batch to prepare a product, so as to obtain the polyethylene packaging material, wherein the extrusion process conditions are as follows: the screw speed was 200rpm and the extrusion section operating temperature was 160 ℃.

Test example 1

And (3) testing tensile property: the national standard is adopted: GB/T1040.2-2006 section 2 for determination of tensile Properties of plastics: test conditions for molded and extruded plastics.

The specific experimental method comprises the following steps: preparing a dumbbell-shaped sample, wherein the type is IV, the total length is 115mm, the total width of two ends is 19mm, the width of a middle narrow part is 6mm, the length of the narrow part is 33mm, the thickness is 1.5mm, the gauge length is 25mm, and the stretching speed is 5 mm/min; the test is carried out under the conditions that the humidity is 23 +/-2 ℃ and the relative humidity is 50 +/-5%, and each group of performance of each formula is tested for 5 times and the average value is obtained. The polyethylene packaging materials prepared in the examples and comparative examples were tested, and the specific results are shown in Table 1.

Table 1: mechanical property of polyethylene packaging material

	Tensile strength, MPa	Elongation at break,%
			Example 1	51.3	200.1
Comparative example 1	55.4	221.7
			Example 2	53.1	214.5
Example 3	52.2	208.6
			Example 4	58.6	232.9
Example 5	59.2	234.2
			Example 6	62.8	245.6
Comparative example 2	57.9	229.7
			Comparative example 3	61.5	242.8

Test example 2

And (3) testing the degradation performance: the soil landfill test method is used in reference to GB/T19275-2003 evaluation of potential biological decomposition and disintegration capability of materials under the action of specific microorganisms.

The specific experimental method comprises the following steps: cutting the polyethylene packaging materials prepared in the examples and the comparative examples into samples with the size of 3cm multiplied by 2mm, weighing 5 samples in each group, drying to constant weight (W)₀) The sample (2) is marked and buried in the same active soil under the same conditions of 60 wt% of soil water retention capacity and 36 wt% of soil humidity, corresponding sample strips are taken out at 6 months and 12 months after the burying, respectively, the samples are cleaned, dried and weighed, wherein (Wn) n is 6 and 12, and the weight loss ratio (%) is calculated as (W is 12)₀-Wn)/W₀X 100. Degradation capability of materialThe average weight loss rate (%) of the mass change was used as an evaluation criterion, and the higher the value, the better the degradability. The results of the experiments are shown in the following table.

TABLE 2 degradation Properties of polyethylene packaging materials

	6 month weight loss rate%	12 month weight loss rate%
			Example 1	49.8	71.3
Comparative example 1	45.6	67.8
			Example 2	62.5	83.6
Example 3	52.3	76.5
			Example 4	66.7	90.4
Example 5	67.1	91.2
			Example 6	70.2	94.9
Comparative example 2	47.4	69.1
			Comparative example 3	68.9	93.5

In the invention, the used filler and functional additive are both degradable substances and have good compatibility with polyethylene resin, so that the degradation performance of the polyethylene packaging material prepared in the embodiment is improved compared with the prior art.

Examples 2 and 3 compared with example 1 and comparative example 1, the modified tapioca starch has better degradability, because the tapioca starch adopted in examples 2-3 is modified tapioca starch, wherein example 2 has better degradability, because the tapioca starch adopted in example 2 is modified tapioca starch through oxidation, enzymolysis and grafting, more short-chain starch is generated, on one hand, a large amount of pore structures are generated on the surface of starch granules, the specific surface area is increased, the dispersity is improved, on the other hand, after oxidation reaction, the carboxyl content of the tapioca starch is increased, the enzymatic treatment is performed on the tapioca starch, the hydroxyl content in the tapioca starch is increased, and both the carboxyl hydroxyl and the hydroxyl can be combined with metaphosphate to form a phosphate ester bond, so that the polarity of the starch is reduced, and the compatibility with non-polar polymers is better, in the degradation process, the large polyethylene is easily split into small polyethylene blocks, and the degradation rate is accelerated.

However, in the invention, in order to realize the purpose that the polyethylene packaging material is easy to degrade, a large amount of starch-based filler is added into the main raw material, so that the mechanical property of the polyethylene packaging material is reduced; the inventor finds that the mechanical property of the polyethylene packaging material can be maintained and the degradation property of the polyethylene packaging material can be improved by adding the aid, namely polylactic acid/polyurethane elastomer, into the raw materials in the test process.

Examples 4-6 are more excellent in degradation than example 2, probably because the introduction of the polylactic acid/polyurethane elastomer containing a large number of oxygen atoms into the polyethylene packaging material can release oxygen during degradation, provide a good living environment for aerobic organisms, increase the amount of aerobic microorganisms or improve the viability of the aerobic microorganisms, and make the rate of microbial degradation faster; in addition, the elastomer additive also has good dispersibility and flexibility, and can be well combined with other blends to form a net structure to promote microbial decomposition.

The polyethylene/polyoctene elastomer which is the most common elastomer for improving the mechanical property in the prior art is added in the comparative example 2, so that the mechanical property is improved, but the degradation rate is slowed down due to the fact that the polyethylene/polyoctene elastomer has a long alkyl chain and the degradation difficulty is increased.

Compared with the embodiment 6, the comparative example 3 has no trimethylolpropane added, so that the trimethylolpropane of the trifunctional monomer can be synergistic with the glycerol to promote the combination of soft and hard segments to generate high-density polyurethane on one hand, and on the other hand, the moisture absorption of the trimethylolpropane is about 50 times that of the glycerol, and the proper amount of the trimethylolpropane is added to improve the water absorption performance of the system and further promote the decomposition of microorganisms.

Further comparison of examples 4-6 shows that the use of a mixture of hexamethylene diisocyanate and lysine methyl ester diisocyanate as the isocyanate for the preparation of polylactic acid/polyurethane elastomers is more effective than either hexamethylene diisocyanate or lysine methyl ester diisocyanate alone.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.