A kind of HDPE resin composition for degradable packaging bottle and preparation method thereof

Abstract

The present invention belongs to the technical field of degradable materials, and specifically relates to a HDPE resin composition for degradable packaging bottles and a preparation method thereof. The HDPE resin composition for degradable packaging bottles provided by the present invention includes 40-50 parts of modified high-density polyethylene, 20-30 parts of modified starch, 10-15 parts of degradation aids, 5-8 parts of antioxidants, 8-12 parts of nano-silicon dioxide, and 5-8 parts of oleamide. The present invention uses naringin and N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane to carry out composite modification of corn starch, effectively improves the tensile strength and elongation at break of the starch film, and blends the modified starch with glycerol, effectively solving the technical problem of poor water resistance of starch-based biodegradable resins; high-temperature calcined oyster shell powder and silane coupling agent are used to modify high-density polyethylene, effectively improving the mechanical properties of high-density polyethylene materials, while providing microbial pores for the degradation of high-density polyethylene materials, and improving the degradation rate.

Description

Technical Field

[0001] The invention belongs to the technical field of degradable materials, and particularly relates to a HDPE resin composition for degradable packaging bottles and a preparation method thereof. Background Art

[0002] High-density polyethylene (HDPE) is a highly crystalline, non-polar thermoplastic resin with good heat resistance and cold resistance, good chemical stability, high rigidity and toughness, and high mechanical strength. It is often used to make plastic bags, plastic bottles, plastic containers and other packaging products. Among them, high-density polyethylene packaging bottles have been widely used in food, medicine, chemicals, construction, agriculture, automobiles and many other fields.

[0003] Most of the biodegradable plastics reported so far are low-crystalline polymers, such as PBAT, but the molecular chain of high-density polyethylene is very stable, and its hydrophobicity and chemical inertness of the alkyl chain further hinder its biodegradation, and it exists in the environment for a long time, endangering biodiversity. Therefore, it is urgent to develop a degradable HDPE resin for packaging bottles.

[0004] The Chinese patent application document with the publication number CN112876761A discloses a degradable polyethylene plastic and a processing technology, wherein the formula includes: 50-60 parts of polyethylene, 20-25 parts of polyvinyl alcohol, 15-18 parts of starch, 6-8 parts of nano-silicon dioxide, 4-6 parts of silane coupling agent, and 2-5 parts of calcium stearate; the production process of the degradable polyethylene plastic includes the following steps: 1) weighing the above-mentioned polyethylene, polyvinyl alcohol, starch, nano-silicon dioxide, silane coupling agent and calcium stearate in proportion for standby use; 2) putting all the weighed raw materials into a mixing device through a feeder for mixing; 3) opening the material valve on the mixing device and putting the mixture into an extrusion film blowing machine for extrusion film blowing, and then cooling the plastic bag by the cold air blown out by the wind disc. This method is to spray a layer of degradation liquid on the surface of the polyethylene plastic after the film is blown to improve the degradation performance of the polyethylene plastic, but the polyethylene plastic obtained by this method is not completely degraded, and the compatibility of starch and polyethylene is poor, and the tensile strength of the modified polyethylene plastic is reduced.

[0005] The Chinese patent application document with publication number CN111471233A discloses a polyethylene-based degradable plastic, including 40-50 parts of polyethylene, 30-50 parts of starch, 0-30 parts of a degradation aid, 0.2-0.5 parts of a degradation promoter, 5-10 parts of a modifier, 3.5-8.5 parts of a plasticizer, 3-5 parts of a lubricant, 0.15-0.25 parts of an antioxidant, and 0.2-0.3 parts of titanium dioxide. This polyethylene degradable plastic achieves degradation by adding a degradation aid, and because starch is added to the formula components, the water resistance of this polyethylene degradable plastic is poor. Summary of the invention

[0006] In order to solve the technical problems in the prior art that high-density polyethylene cannot be degraded, degrades incompletely, and has poor mechanical properties and water resistance, the purpose of the present invention is to provide a HDPE resin composition for degradable packaging bottles and a preparation method thereof.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] A HDPE resin composition for degradable packaging bottles, comprising the following components and their mass fractions:

[0009] 40-50 parts of modified high-density polyethylene, 20-30 parts of modified starch, 10-15 parts of degradation aid, 5-8 parts of antioxidant, 8-12 parts of nano-silicon dioxide, 5-8 parts of oleamide;

[0010] The preparation method of the modified starch comprises the following steps: adding corn starch, naringin, deionized water, tetraethyl silicate and N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane into a reaction kettle, heating the water area to 95-100° C. under stirring, keeping the temperature for reaction for 4.2-5 hours, adding glycerol, stirring, ultrasonicating, cooling, filtering and drying to obtain the modified starch.

[0011] The present invention uses naringin and N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane to carry out composite modification of corn starch. The primary amino and secondary amino functional groups contained in the molecular chain of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane can cross-link with naringin and hydroxyl groups in starch, so that naringin and starch undergo a cross-linking reaction, and the molecular chain segments are entangled together, which effectively improves the tensile strength and elongation at break of the starch film, and improves the compatibility of starch with high-density polyethylene. In addition, in the present invention, the modified starch is blended with glycerol, and the hydroxyl groups between glycerol molecules form a dense hydrogen bond structure, which can effectively hinder the invasion of water molecules to a certain extent, thereby improving the water resistance of the modified starch, and the structure can also effectively improve the tensile strength and elongation at break of the modified starch.

[0012] Furthermore, the mass fractions of the components in the preparation method of the modified starch are: 20-30 parts of corn starch, 8-12 parts of naringin, 70-80 parts of deionized water, 4-6 parts of tetraethyl silicate, 5-10 parts of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and 5-8 parts of glycerol.

[0013] Furthermore, in the method for preparing modified starch, the frequency of ultrasound is 120-140 kHz, and the ultrasound time is 25-30 min.

[0014] Furthermore, the preparation method of the modified high-density polyethylene is: high-temperature calcined oyster shell powder, silane coupling agent and high-density polyethylene are melt-mixed at 170-180° C. and 120-130 rpm using a torque rheometer to obtain modified high-density polyethylene.

[0015] In the present invention, high-temperature calcined oyster shell powder and a silane coupling agent are used to modify high-density polyethylene. Studies have found that the high-temperature calcined oyster shell powder has a porous structure, is coupled with high-density polyethylene through a silane coupling agent, and is uniformly dispersed in the high-density polyethylene, which can not only effectively improve the mechanical properties of the high-density polyethylene material, but also provide microbial pores for the degradation of the high-density polyethylene material, thereby effectively improving the degradation rate of high-density polyethylene products.

[0016] Furthermore, the preparation method of the high-temperature calcined oyster shell powder in the preparation method of modified high-density polyethylene is: wash and dry the oyster shells, perform air flow crushing, and then sieve to obtain the oyster shell powder; calcine the oyster shell powder at 1200-1300°C for 2-3h in a box-type calcining furnace to obtain the high-temperature calcined oyster shell powder.

[0017] Furthermore, in the preparation method of modified high-density polyethylene, the silane coupling agent is one of γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

[0018] Furthermore, the degradation aid is composed of lactose, sodium nitrate and calcium carbonate in a mass ratio of 15-18:7-11:2-5.

[0019] In the present invention, lactose, sodium nitrate and calcium carbonate are selected together as degradation aids to provide corresponding carbon sources and nitrogen sources for the survival of microorganisms, thereby effectively promoting the degradation of the HDPE resin composition for degradable packaging bottles.

[0020] Furthermore, the antioxidant is one of 2,6-di-tert-butyl-p-cresol, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol).

[0021] The present invention also provides a method for preparing the HDPE resin composition for degradable packaging bottles, comprising the following steps:

[0022] S1: uniformly mixing modified high-density polyethylene, modified starch, degradation aid, nano-silicon dioxide and oleic acid amide, adding the mixture into a high-speed mixer for low-speed mixing, and then heating the mixture to 175-185° C. for high-speed mixing to obtain a mixture I;

[0023] S2: Cooling the mixed material I obtained in step S1 to 120-130° C. and then mixing at a low speed, adding an antioxidant, and mixing evenly to obtain a mixed material II;

[0024] S3: adding the mixed material II obtained in step S2 into a twin-screw extruder for extrusion, pelletizing, centrifugal drying, and cooling to obtain a HDPE resin composition for degradable packaging bottles.

[0025] Furthermore, in the method for preparing the HDPE resin composition for degradable packaging bottles, the rotation speed of the low-speed mixing in step S1 and step S2 is 300-500 rpm, and the time is 0.5-2h; the rotation speed of the high-speed mixing in step S1 is 1200-1400 rpm, and the time is 0.5-1h.

[0026] Compared with the prior art, the HDPE resin composition for degradable packaging bottles and the preparation method thereof provided by the present invention have the following technical advantages:

[0027] (1) The HDPE resin composition for degradable packaging bottles provided by the present invention has a simple formula, readily available raw materials, and the finished product has low odor, excellent mechanical properties, and can be biodegraded;

[0028] (2) The present invention uses naringin and N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane to perform composite modification on corn starch, effectively improving the tensile strength and elongation at break of the starch film. The modified starch is blended with glycerol, effectively solving the technical problem of poor water resistance of starch-based biodegradable resins.

[0029] (3) In the present invention, high-temperature calcined oyster shell powder and silane coupling agent are used to modify high-density polyethylene, which effectively improves the mechanical properties of the high-density polyethylene material and provides microbial channels for the degradation of the high-density polyethylene material, thereby increasing the degradation rate. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the embodiments. In the following detailed description, only certain exemplary embodiments of the present invention are described by way of illustration. Needless to say, those of ordinary skill in the art will appreciate that the described embodiments may be modified in a variety of ways without departing from the spirit and scope of the present invention. Therefore, the description is illustrative in nature and is not intended to limit the scope of protection of the claims.

[0031] In this specific embodiment, in the preparation method of the HDPE resin composition for degradable packaging bottles, the parameters of the twin-screw extruder are: the temperature of zone 1 is 100°C, zone 2 is 180°C, zone 3 is 210°C, zone 4 is 210°C, zone 5 is 200°C, the residence time is 2 min, and the pressure is 14 MPa.

[0032] Example 1

[0033] A HDPE resin composition for degradable packaging bottles, comprising the following components and their mass fractions:

[0034] 40g of modified high-density polyethylene, 30g of modified starch, 10g of a degradation aid, 5g of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 8g of nano-silica, and 5g of oleamide; the degradation aid is composed of lactose, sodium nitrate and calcium carbonate in a mass ratio of 15:7:2.

[0035] The preparation method of the modified starch is as follows: 20g corn starch, 8g naringin, 80g deionized water, 4g tetraethyl silicate and 5g N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane are added into a reaction kettle, a condensation reflux tube is connected, the water is heated to 95°C under a stirring state at a rotation speed of 350rpm, the reaction is kept warm for 5h, 5 parts of glycerol are added, the reaction is stirred for 30min under a rotation speed of 350rpm, ultrasonication is performed at 120kHz for 30min, cooling, suction filtration and drying are performed to obtain the modified starch.

[0036] The preparation method of the modified high-density polyethylene is as follows: high-temperature calcined oyster shell powder, γ-aminopropyl triethoxysilane and high-density polyethylene are melt-mixed at 170° C. and 120 rpm using a torque rheometer to obtain the modified high-density polyethylene. The preparation method of high-temperature calcined oyster shell powder is as follows: oyster shells are washed and dried, air flow crushed, and then sieved to obtain oyster shell powder; the oyster shell powder is calcined at 1200° C. for 3 hours in a box-type calcining furnace to obtain high-temperature calcined oyster shell powder.

[0037] The method for preparing the HDPE resin composition for degradable packaging bottles comprises the following steps:

[0038] S1: Modified high-density polyethylene, modified starch, degradation aid, nano-silica and oleic acid amide were mixed uniformly and added into a high-speed mixer for low-speed mixing at a rotation speed of 300 rpm for 2 h, then the temperature was raised to 175° C. and high-speed mixing was performed at a rotation speed of 1200 rpm for 1 h to obtain a mixture I;

[0039] S2: cooling the mixed material I obtained in step S1 to 120° C., mixing at a low speed of 300 rpm for 2 h, adding an antioxidant, and mixing uniformly to obtain a mixed material II;

[0040] S3: adding the mixed material II obtained in step S2 into a twin-screw extruder for extrusion, pelletizing, centrifugal drying, and cooling to obtain a HDPE resin composition for degradable packaging bottles.

[0041] Example 2

[0042] A HDPE resin composition for degradable packaging bottles, comprising the following components and their mass fractions:

[0043] 50g of modified high-density polyethylene, 20g of modified starch, 15g of a degradation aid, 8g of 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 12g of nano-silica, and 8g of oleamide; the degradation aid is composed of lactose, sodium nitrate and calcium carbonate in a mass ratio of 18:11:5.

[0044] The preparation method of the modified starch is as follows: 30g corn starch, 12g naringin, 70g deionized water, 6g tetraethyl silicate and 10g N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane are added into a reaction kettle, a condensation reflux tube is connected, the water area is heated to 100°C under a stirring state at a rotation speed of 350rpm, the reaction is kept warm for 4.2h, 8 parts of glycerol are added, the reaction is stirred for 30min under a rotation speed of 350rpm, ultrasound is performed at 140kHz for 25min, cooling, suction filtration and drying are performed to obtain the modified starch.

[0045] The preparation method of the modified high-density polyethylene is as follows: high-temperature calcined oyster shell powder, vinyl triethoxysilane and high-density polyethylene are melt-mixed at 180° C. and 130 rpm using a torque rheometer to obtain the modified high-density polyethylene. The preparation method of high-temperature calcined oyster shell powder is as follows: oyster shells are washed and dried, air flow crushed, and then sieved to obtain oyster shell powder; the oyster shell powder is calcined at 1300° C. for 3 hours in a box-type calcining furnace to obtain high-temperature calcined oyster shell powder.

[0046] The method for preparing the HDPE resin composition for degradable packaging bottles comprises the following steps:

[0047] S1: Modified high-density polyethylene, modified starch, degradation aid, nano-silica and oleic acid amide were uniformly mixed and added into a high-speed mixer for low-speed mixing at a rotation speed of 500 rpm for 0.5 h, then the temperature was raised to 185° C., and high-speed mixing was performed at a rotation speed of 1400 rpm for 0.5 h to obtain a mixture I;

[0048] S2: cooling the mixed material I obtained in step S1 to 130° C., mixing at a low speed of 500 rpm for 0.5 h, adding an antioxidant, and mixing uniformly to obtain a mixed material II;

[0049] S3: adding the mixed material II obtained in step S2 into a twin-screw extruder for extrusion, pelletizing, centrifugal drying, and cooling to obtain a HDPE resin composition for degradable packaging bottles.

[0050] Example 3

[0051] A HDPE resin composition for degradable packaging bottles, comprising the following components and their mass fractions:

[0052] 46 g of modified high-density polyethylene, 27 g of modified starch, 13 g of a degradation aid, 7 g of 2,6-di-tert-butyl-p-cresol, 11 g of nano-silica, and 7 g of oleamide; the degradation aid is composed of lactose, sodium nitrate and calcium carbonate in a mass ratio of 17:9:4.

[0053] The preparation method of the modified starch is as follows: 25g corn starch, 10g naringin, 76g deionized water, 5g tetraethyl silicate and 8g N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane are added into a reaction kettle, a condensation reflux tube is connected, the water is heated to 98°C under stirring at a speed of 350rpm, the reaction is kept warm for 4.8h, 7 parts of glycerol are added, stirring is carried out for 30min under the condition of a speed of 350rpm, ultrasonication is carried out at 130kHz for 28min, cooling, suction filtration and drying are carried out to obtain the modified starch.

[0054] The preparation method of the modified high-density polyethylene is as follows: high-temperature calcined oyster shell powder, γ-methacryloxypropyltrimethoxysilane and high-density polyethylene are melt-mixed at 175° C. and 125 rpm using a torque rheometer to obtain the modified high-density polyethylene. The preparation method of high-temperature calcined oyster shell powder is as follows: oyster shells are washed and dried, air flow crushed, and then sieved to obtain oyster shell powder; the oyster shell powder is calcined at 1250° C. for 2.5 hours in a box-type calcining furnace to obtain high-temperature calcined oyster shell powder.

[0055] The method for preparing the HDPE resin composition for degradable packaging bottles comprises the following steps:

[0056] S1: Modified high-density polyethylene, modified starch, degradation aid, nano-silica and oleic acid amide were mixed uniformly, added into a high-speed mixer, and mixed at a low speed of 400 rpm for 1 hour, then heated to 180° C., and mixed at a high speed of 1300 rpm for 0.7 hour to obtain a mixture I;

[0057] S2: Cooling the mixed material I obtained in step S1 to 125° C., mixing at a low speed of 400 rpm for 0.9 h, adding an antioxidant, and mixing uniformly to obtain a mixed material II;

[0058] S3: adding the mixed material II obtained in step S2 into a twin-screw extruder for extrusion, pelletizing, centrifugal drying, and cooling to obtain a HDPE resin composition for degradable packaging bottles.

[0059] Comparative Example 1

[0060] The formula and preparation method of the HDPE resin composition in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that starch is used instead of modified starch in this comparative example.

[0061] Comparative Example 2

[0062] The formula and preparation method of the HDPE resin composition in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that in the preparation method of the modified starch in this comparative example, an equal amount of naringin is used instead of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane.

[0063] Comparative Example 3

[0064] The formula and preparation method of the HDPE resin composition in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that an equal amount of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane is used instead of naringin in the preparation method of the modified starch in this comparative example.

[0065] Comparative Example 4

[0066] The formula and preparation method of the HDPE resin composition in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that an equal amount of deionized water is used instead of glycerol in the preparation method of the modified starch in this comparative example.

[0067] Comparative Example 5

[0068] The formula and preparation method of the HDPE resin composition in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that the oyster shell powder used in the preparation method of the modified high-density polyethylene in this comparative example is not subjected to high-temperature calcination.

[0069] Comparative Example 6

[0070] The formula and preparation method of the HDPE resin composition in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that an equal amount of high-density polyethylene is used instead of modified high-density polyethylene in this comparative example.

[0071] Comparative Example 7

[0072] The formula and preparation method of the HDPE resin composition in this comparative example are similar to those in Example 3. The difference between this comparative example and Example 3 is that the degradation aid in this comparative example is composed of lactose, sodium nitrate and calcium carbonate in a mass ratio of 3:9:13.

[0073] Test example

[0074] In this test example, the HDPE resin compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were put into a film blowing machine for film blowing molding with a film thickness of 30 μm, and were cut into 10×10 cm resin films as test samples.

[0075] Degradation performance test: The resin films prepared in Examples 1 to 3, Comparative Examples 1 to 3, and Comparative Examples 5 to 7 were buried in soil under natural conditions, and the degradation rate was calculated by weighing them at regular intervals. Degradation rate = (weight before burial - weight after burial for n days) / weight before burial × 100%. The test results are shown in Table 1.

[0076] Mechanical properties test: According to ASTM / D 638 “Test method for tensile properties of plastics”, the resin films prepared in Example 1 to Example 3, Comparative Example 1 to Comparative Example 2, and Comparative Example 4 to Comparative Example 6 were tested for tensile strength and elongation at break. The test results are shown in Table 2.

[0077] Water resistance test: The resin films prepared in Examples 1 to 3 and Comparative Example 4 were immersed in deionized water at room temperature, and the water absorption rate of the resin films at 20 h, 50 h, and 100 h was calculated by weighing the weight of the resin films. Water absorption rate = (weight after immersion - weight before immersion) / weight before immersion × 100%. The test results are shown in Table 3.

[0078] Table 1 Degradation performance test results

[0079]

[0080] It can be seen from Table 1 that the HDPE resin composition for degradable packaging bottles provided by the present invention can be completely degraded within 30 days, among which the resin film of Example 3 group degrades the fastest, which is the best example of the present invention.

[0081] Compared with Example 3, in Comparative Example 1, starch was used instead of modified starch, but the degradation rate of the resin film was significantly slowed down. This was due to the incomplete degradation of the resin film caused by the uneven distribution of starch in the resin film. In Comparative Example 2, an equal amount of naringin was used instead of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and in Comparative Example 3, an equal amount of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane was used instead of naringin, but the degradation rate of the resin film was slowed down. This shows that naringin and N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane have a significant effect on the degradation of corn starch. The composite modification of powder is better than the modification of corn starch by a single modifier; in Comparative Example 5, the oyster shell powder is not calcined at high temperature, and Comparative Example 6 uses an equal amount of high-density polyethylene instead of modified high-density polyethylene, but the degradation rate of the resin film is slowed down, which shows that the oyster shell powder after high-temperature calcination can provide microbial pores for the degradation of high-density polyethylene materials, and effectively improve the degradation rate of high-density polyethylene products; Comparative Example 7 changes the mass ratio of the various components of the degradation aid, but the degradation rate of the resin film is slightly reduced, which shows that the degradation aid provided by the present invention has been optimized.

[0082] Table 2 Mechanical properties test

[0083]

[0084] As can be seen from Table 2, the resin film prepared from the HDPE resin composition for degradable packaging bottles provided by the present invention has a tensile strength of 23-26 MPa and an elongation at break of 367-432%, and has good mechanical properties.

[0085] Compared with Example 3, in Comparative Example 1, starch was used instead of modified starch, but the mechanical properties of the obtained resin film were significantly deteriorated, which indicates that the modification of starch in the present invention can effectively improve the mechanical properties of the starch film and improve its compatibility with high-density polyethylene; in Comparative Example 2, an equal amount of naringin was used instead of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, but the mechanical properties of the obtained resin film were deteriorated, which indicates that the modification of starch in the present invention can effectively improve the mechanical properties of the starch film and improve its compatibility with high-density polyethylene. together, thereby improving the mechanical properties of the starch film; in Comparative Example 4, an equal amount of deionized water was used instead of glycerol, but the mechanical properties of the obtained resin film became worse, which indicates that the hydroxyl groups between glycerol molecules form a dense hydrogen bond structure, thereby improving the mechanical properties of the starch film; in Comparative Example 5, the oyster shell powder was not calcined at high temperature, and Comparative Example 6 used an equal amount of high-density polyethylene instead of modified high-density polyethylene, but the mechanical properties of the obtained resin film became worse, which indicates that high-temperature calcination of oyster shell powder can effectively improve the mechanical properties of high-density polyethylene materials.

[0086] Table 3 Water resistance test results

[0087]

[0088] As shown in Table 3, the water absorption rate of the resin film prepared from the HDPE resin composition for degradable packaging bottles provided by the present invention is 0.001-0.002% for 100 hours, which indicates that the HDPE resin composition for degradable packaging bottles provided by the present invention has good water resistance. Compared with Example 4, in the preparation process of modified starch, deionized water is used instead of glycerol in Comparative Example 4, but the water resistance of the prepared resin composition is significantly deteriorated, which indicates that the hydroxyl groups between glycerol molecules form a dense hydrogen bond structure, which can effectively hinder the invasion of water molecules to a certain extent, thereby improving the water resistance of the modified starch.

[0089] The above embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any person skilled in the art shall not modify the above embodiments without violating the spirit and scope of the present invention. Therefore, any modification, equivalent substitution and improvement made by those skilled in the art under the technical concept of the present invention shall still be covered by the claims of the present invention.

Claims

1. A HDPE resin composition for degradable packaging bottles, characterized in that: Includes the following components and their mass fractions: 40-50 parts of modified high-density polyethylene, 20-30 parts of modified starch, 10-15 parts of degradation aid, 5-8 parts of antioxidant, 8-12 parts of nano-silicon dioxide, 5-8 parts of oleamide; The preparation method of the modified starch comprises: adding corn starch, naringin, deionized water, tetraethyl silicate and N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane into a reaction kettle, heating the water area to 95-100° C. under stirring, keeping the temperature for reaction for 4.2-5 hours, adding glycerol, stirring, ultrasonicating, cooling, filtering and drying to obtain the modified starch; The preparation method of the modified high-density polyethylene is as follows: high-temperature calcined oyster shell powder, silane coupling agent and high-density polyethylene are melt-mixed at 170-180° C. and 120-130 rpm using a torque rheometer to obtain the modified high-density polyethylene; The degradation aid is composed of lactose, sodium nitrate and calcium carbonate in a mass ratio of 15-18:7-11:2-5.

2. The HDPE resin composition for degradable packaging bottles according to claim 1, characterized in that: The mass proportions of the components in the preparation method of the modified starch are: 20-30 parts of corn starch, 8-12 parts of naringin, 70-80 parts of deionized water, 4-6 parts of tetraethyl silicate, 5-10 parts of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and 5-8 parts of glycerol.

3. The HDPE resin composition for degradable packaging bottles according to claim 1, characterized in that: The ultrasonic frequency in the preparation method of modified starch is 120-140kHz, and the ultrasonic time is 25-30min.

4. The HDPE resin composition for degradable packaging bottles according to claim 1, characterized in that: The preparation method of the high-temperature calcined oyster shell powder comprises: washing and drying the oyster shells, air flow crushing, and then sieving to obtain the oyster shell powder; calcining the oyster shell powder at 1200-1300° C. for 2-3 hours in a box-type calcining furnace to obtain the high-temperature calcined oyster shell powder.

5. The HDPE resin composition for degradable packaging bottles according to claim 1, characterized in that: The silane coupling agent is one of γ-aminopropyltriethoxysilane, vinyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane.

6. The HDPE resin composition for degradable packaging bottles according to claim 1, characterized in that: The antioxidant is one of 2,6-di-tert-butyl-p-cresol, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol).

7. The method for preparing the HDPE resin composition for degradable packaging bottles according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: uniformly mixing modified high-density polyethylene, modified starch, degradation aid, nano-silicon dioxide and oleic acid amide, adding the mixture into a high-speed mixer for low-speed mixing, and then heating the mixture to 175-185° C. for high-speed mixing to obtain a mixture I; S2: Cooling the mixed material I obtained in step S1 to 120-130° C. and then mixing at a low speed, adding an antioxidant, and mixing evenly to obtain a mixed material II; S3: adding the mixed material II obtained in step S2 into a twin-screw extruder for extrusion, pelletizing, centrifugal drying, and cooling to obtain a HDPE resin composition for degradable packaging bottles.

8. The method for preparing the HDPE resin composition for degradable packaging bottles according to claim 7, characterized in that: The rotation speed of the low-speed mixing in step S1 and step S2 is 300-500 rpm, and the time is 0.5-2 h; the rotation speed of the high-speed mixing in step S1 is 1200-1400 rpm, and the time is 0.5-1 h.

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