Degradable fresh produce tray and method of making the same

Abstract

The present application relates to a kind of degradable fresh tray and its preparation method, belong to degradable plastic technical field.The present application is by selecting anthocyanin as photodegradation agent protective agent, selecting iron stearate as photodegradation agent, selecting chitosan solution, aluminum acetate solution and silicon dioxide are mixed as curing agent according to proportion, selecting polyvinyl alcohol and polyethylene wax as dispersing agent, and according to the proportion with PP powder, modified bamboo powder is jointly made to obtain degradable fresh tray, so that even being abandoned in the open air by human can be photodegraded into small molecular compounds harmless to environment, reduce the pollution to environment, and will not affect the strength and performance when normal use.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of degradable plastics, and relates to a degradable fresh food tray and a preparation method thereof. BACKGROUND

[0002] Traditional fresh food trays widely use petroleum-based plastics such as polyethylene (PE), polypropylene (PP) or foamed polystyrene (EPS) materials. Although these materials have the advantages of low cost and convenient processing, their non-degradability leads to a serious "white pollution" problem. According to the statistics of the United Nations Environment Programme, about 8 million tons of plastic waste enters the ocean every year, of which food packaging materials account for more than 40%. In recent years, the research on biodegradable materials has gradually become a hot spot. As representative polyester degradable materials, polylactic acid (PLA) and polyhydroxyalkanoate (PHA) are difficult to be applied on a large scale due to their raw material prices being about 2-3 times those of traditional plastics, and their degradation rate is unstable. Under non-industrial composting conditions, the degradation period of PLA can be up to several decades.

[0003] Most plastics only contain C-C, C-H, C-O, C-N and C-Cl bonds and do not absorb light with a wavelength greater than 200 nm, while the tail end of the near ultraviolet region of sunlight is at 290 nm. Therefore, sunlight cannot initiate the photooxidation chain reaction of pure plastics. However, due to some accidental or artificial factors, some ultraviolet-absorbing chromophores are mixed in, such as dyes, impurities (such as catalyst residues Ti, oxidation products generated during processing and storage, etc.) and atmospheric pollution introduced compounds. These impurities or chromophores can initiate photooxidative chain scission. Similarly, if the polymer contains a photosensitive chromophore, a photosensitive degradation process will occur, which is an important degradation mode of the polymer. There are two methods for its preparation: one is a copolymer type photodegradable plastic, which introduces photosensitive groups (such as carboxyl groups and double bonds) into the polymer molecular chain by copolymerization to endow the material with photo-degradation properties. The advantage of this material is that it has photosensitive properties, and the photo-degradation is uniform and complete. However, the disadvantage is that the synthesis conditions are complex, the cost is high, and it is difficult to promote at present: the other is an additive type photodegradable plastic, which adds a photosensitizer to ordinary plastic materials, so that free radicals are generated after absorbing ultraviolet light, inducing oxidative degradation of the polymer material to achieve degradation. This method has the advantages of simple preparation process, low photosensitizer addition amount and low cost, and is easy to promote. However, due to the fact that the light exposure time of plastic waste is usually insufficient, there is the disadvantage of incomplete degradation. In recent years, as polymer photosensitive degradation can be used as a method to solve the environmental pollution caused by waste plastics, it has been increasingly valued, and extensive research has been carried out. The photo-degradable plastics developed and used at home and abroad are based on this principle, that is, introducing photosensitive groups such as carbonyl groups into the main chain of the polymer, or adding photosensitizers to the plastic to endow the main chain of the polymer with photo-degradation, forming a structure that is easily decomposed by light.

[0004] As a natural cellulose material, bamboo powder has the advantages of wide source, low cost and complete biodegradability. However, the packaging material prepared from pure bamboo powder has the following defects: low mechanical strength: the tensile strength is usually less than 10 MPa, which cannot meet the load bearing requirement; high water absorption: the water absorption of unmodified bamboo powder can reach more than 20%, which easily leads to deformation or mildew of the tray; poor interfacial compatibility: the bamboo powder is not firmly combined with the polymer matrix, and interface defects are easily generated.

[0005] Therefore, it is urgent to develop a biodegradable fresh food tray with high strength, biodegradability and low cost. SUMMARY

[0006] The purpose of the present application is to provide a biodegradable fresh food tray with the characteristics of high strength, natural biodegradability and fast biodegradation speed.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A biodegradable fresh food tray is composed of a base tray, a photodegradation agent protective agent and a curing agent.

[0009] The raw material of the base tray comprises a photodegradation agent, PP powder, modified bamboo powder and a dispersing agent.

[0010] The photodegradation agent is iron stearate.

[0011] The photodegradation agent protective agent is anthocyanin.

[0012] The raw material of the curing agent comprises chitosan solution, aluminum acetate solution and silicon dioxide.

[0013] As a preferred technical solution of the present application, the modified bamboo powder is bamboo powder sprayed with silane coupling agent KH-550 and ball milled to 2000 mesh; the spraying amount of the silane coupling agent KH-550 is 0.5%-1.5% of the mass of the bamboo powder.

[0014] As a preferred technical solution of the present application, the anthocyanin is at least one of pelargonidin, cyanidin, delphinidin, peony pigment, morning glory pigment and malvein.

[0015] As a preferred technical solution of the present application, the mass ratio of the photodegradation agent, PP powder, modified bamboo powder, photodegradation agent protective agent, dispersing agent and curing agent is 7-9:70-90:10-20:1-3:1-3:4-6.

[0016] As a preferred technical solution of the present application, the base tray is prepared by the following steps:

[0017] W1. Put the photodegradation agent, PP powder, modified bamboo powder and dispersant into a high-speed blender and stir to obtain a mixed raw material;

[0018] W2. Add the mixed raw material into a twin-screw extruder for melt extrusion, cold drawing and pelletizing, and injection molding to obtain a base tray.

[0019] As a preferred technical solution of the present application, the dispersant is composed of polyvinyl alcohol and polyethylene wax.

[0020] As a preferred technical solution of the present application, the mass ratio of polyvinyl alcohol to polyethylene wax is 8-10:1-3.

[0021] As a preferred technical solution of the present application, the preparation method of the curing agent comprises the following steps:

[0022] X1. Prepare a chitosan solution with a concentration of 3-5%;

[0023] X2. Prepare an aluminum acetate solution with a concentration of 6-8%;

[0024] X3. Mix the chitosan solution, aluminum acetate solution and silicon dioxide in proportion, and adjust the pH value to 4-6 to obtain the curing agent.

[0025] As a preferred technical solution of the present application, the mass ratio of the chitosan solution, aluminum acetate solution and silicon dioxide is 20-25:30-35:3-7.

[0026] As a preferred technical solution of the present application, the degradable fresh food tray is prepared by the following steps:

[0027] Y1. Mix the curing agent and the photodegradation agent protective agent in proportion to obtain a mixed solution;

[0028] Y2. Submerge the base tray in the mixed solution for 30-45 seconds, and then take it out. After the mixed solution is dried and solidified on the surface of the base tray, a degradable fresh food tray is obtained.

[0029] The present application has the following advantages:

[0030] (1) The present application selects anthocyanin as the photodegradation agent protective agent, selects iron stearate as the photodegradation agent, selects the mixture of chitosan solution, aluminum acetate solution and silicon dioxide in proportion as the curing agent, selects polyvinyl alcohol and polyethylene wax as the dispersant, and prepares the degradable fresh food tray together with the PP powder and modified bamboo powder according to the proportion, so that it can be degraded by light into harmless small molecular compounds when abandoned outdoors, reducing the pollution to the environment.

[0031] (2) The anthocyanin is selected as the photodegradation agent protective agent in the application, can effectively absorb ultraviolet light, effectively reduces the degradation of PP caused by the direct absorption of ultraviolet light by the iron stearate to generate macromolecular free radicals, and can effectively ensure the strength and performance of the degradable fresh food tray during use.

[0032] (3) The curing agent in the application fixes the photodegradation agent protective agent on the outer surface of the base tray, effectively reduces the abrasion and hydrolysis of the photodegradation agent protective agent during normal use, and when the degradable fresh food tray is discarded outdoors by human, the curing agent is rapidly decomposed by microorganisms due to its good biodegradability, thereby exposing the photodegradation agent protective agent to the air, and further promoting the photodegradation reaction.

[0033] (4) The anthocyanin, the photodegradation agent protective agent in the application, has good water solubility, can hydrolyze with moisture in the air in a short time when exposed to the air, thereby exposing the photodegradation agent to the air, further promoting the photodegradation reaction, and finally degrading the PP plastic into small molecular compounds in a certain period of time. DETAILED DESCRIPTION

[0034] In order to further illustrate the technical means and effects adopted by the application to achieve the predetermined purpose, the specific embodiments, structures, features and effects according to the application are described in detail as follows in combination with the embodiments.

[0035] Some raw materials in the embodiments of the application are as follows:

[0036] PP powder: HP500P of Shandong Guangchuan Plastic Co., Ltd.

[0037] Bamboo powder: 11292 of Hebei Zhunkun New Material Technology Co., Ltd.

[0038] Polyvinyl alcohol: 2488 of Zhengzhou Ruichang Chemical Product Co., Ltd.

[0039] Polyethylene wax: HONEYWELL AC-6A of Dongguan Kangjin New Material Technology Co., Ltd.

[0040] Chitosan: Henan Huaxing Biological Technology Co., Ltd.

[0041] Example 1

[0042] A degradable fresh food tray, the raw materials of the degradable fresh food tray are composed of a base tray, a pelargonidin and a curing agent.

[0043] The preparation method of the base tray comprises the following steps:

[0044] W1. Iron stearate, PP powder, modified bamboo powder, and polyvinyl alcohol and polyethylene wax with a mass ratio of 8:1 were placed in a high-speed blender and stirred at a speed of 1200 r / min for 20 min to obtain a mixed raw material; the modified bamboo powder was bamboo powder sprayed with silane coupling agent KH-550 and then ball milled to 2000 mesh; the spraying amount of the silane coupling agent KH-550 was 0.5% of the mass of the bamboo powder;

[0045] W2. The mixed raw material was fed into a twin-screw extruder for melt extrusion at a screw speed of 120 r / min and a temperature of 220℃, and then cold-drawing, granulating, and injection molding to obtain a base tray.

[0046] The preparation method of the curing agent comprises the following steps:

[0047] X1. A chitosan solution with a concentration of 3% was prepared;

[0048] X2. An aluminum acetate solution with a concentration of 6% was prepared;

[0049] X3. The chitosan solution, the aluminum acetate solution, and the silicon dioxide were mixed in a mass ratio of 20:30:3, and the pH value was adjusted to 4 to obtain a curing agent.

[0050] The preparation method of the degradable fresh food tray comprises the following steps:

[0051] Y1. The curing agent and the pelargonidin were mixed in a certain proportion to obtain a mixed solution;

[0052] Y2. The base tray was immersed in the mixed solution for 10 seconds, and then taken out; after the mixed solution was dried and solidified on the surface of the base tray, a degradable fresh food tray was obtained.

[0053] The mass ratio of the iron stearate, the PP powder, the modified bamboo powder, the dispersant, the pelargonidin, and the curing agent is 7:70:10:1:1:4.

[0054] Example 2

[0055] A degradable fresh food tray, wherein the raw materials of the degradable fresh food tray consist of a base tray, pelargonidin, and a curing agent;

[0056] The preparation method of the base tray comprises the following steps:

[0057] W1. Iron stearate, PP powder, modified bamboo powder, and polyvinyl alcohol and polyethylene wax with a mass ratio of 9:2 were placed in a high-speed blender and stirred at a speed of 1200 r / min for 20 min to obtain a mixed raw material; the modified bamboo powder was bamboo powder sprayed with silane coupling agent KH-550 and then ball milled to 2000 mesh; the spraying amount of the silane coupling agent KH-550 was 1.0% of the mass of the bamboo powder;

[0058] W2. The mixed raw materials are fed into a twin-screw extruder for melt extrusion at a screw speed of 120 r / min and a temperature of 220℃, and then cold-drawing, granulating, and injection molding to obtain the base tray.

[0059] The preparation method of the curing agent comprises the following steps:

[0060] X1. A chitosan solution with a concentration of 4% is prepared;

[0061] X2. An aluminum acetate solution with a concentration of 7% is prepared;

[0062] X3. The chitosan solution, the aluminum acetate solution, and the silicon dioxide are mixed in a mass ratio of 23:32:5, and the pH value is adjusted to 5 to obtain the curing agent.

[0063] The preparation method of the degradable fresh food tray comprises the following steps:

[0064] Y1. The curing agent is mixed with the cyanin in a certain proportion to obtain a mixed solution;

[0065] Y2. The base tray is immersed in the mixed solution for 13 seconds, and then taken out. After the mixed solution is dried and solidified on the surface of the base tray, the degradable fresh food tray is obtained.

[0066] The mass ratio of the iron stearate, the PP powder, the modified bamboo powder, the dispersing agent, the cyanin, and the curing agent is 8:80:15:2:2:5.

[0067] Example 3

[0068] A degradable fresh food tray, wherein the raw materials of the degradable fresh food tray are composed of a base tray, a peony pigment, and a curing agent in a mass ratio of 9:30:3:3:6;

[0069] The preparation method of the base tray comprises the following steps:

[0070] W1. The iron stearate, the PP powder, the modified bamboo powder, and polyvinyl alcohol and polyethylene wax in a mass ratio of 10:3 are placed in a high-speed blender and stirred at a stirring speed of 1200 r / min for 20 min to obtain mixed raw materials; the modified bamboo powder is bamboo powder that is sprayed with a silane coupling agent KH-550 and then ball-milled to 2000 meshes; the spraying amount of the silane coupling agent KH-550 is 1.5% of the mass of the bamboo powder;

[0071] W2. The mixed raw materials are fed into a twin-screw extruder for melt extrusion at a screw speed of 120 r / min and a temperature of 220℃, and then cold-drawing, granulating, and injection molding to obtain the base tray.

[0072] The preparation method of the solidifying agent comprises the following steps:

[0073] X1. preparing a chitosan solution with a concentration of 5%;

[0074] X2. preparing an aluminum acetate solution with a concentration of 8%;

[0075] X3. mixing the chitosan solution, the aluminum acetate solution and the silicon dioxide in a mass ratio of 25:35:7, and adjusting the pH value to 6 to obtain the solidifying agent.

[0076] The preparation method of the degradable fresh food tray comprises the following steps:

[0077] Y1. mixing the solidifying agent and the peony pigment in a proportion to obtain a mixed solution;

[0078] Y2. immersing the base tray in the mixed solution for 15 seconds, and obtaining the degradable fresh food tray after the mixed solution is dried and solidified on the surface of the base tray.

[0079] The mass ratio of the iron stearate, the PP powder, the modified bamboo powder, the dispersing agent, the peony pigment and the solidifying agent is 9:90:20:3:3:6.

[0080] Comparative Example 1

[0081] No photodegradation agent protector is added, and the remaining operations refer to Example 1.

[0082] Comparative Example 2

[0083] No photodegradation agent protector and no solidifying agent are added, and the remaining operations refer to Example 1.

[0084] Comparative Example 3

[0085] No solidifying agent is added, and the remaining operations refer to Example 1.

[0086] Comparative Example 4

[0087] No photodegradation agent protector and no iron stearate are added, and the remaining operations refer to Example 1.

[0088] Comparative Example 5

[0089] No photodegradation agent protector, no solidifying agent and no iron stearate are added, and the remaining operations refer to Example 1.

[0090] Comparative Example 6

[0091] No solidifying agent and no iron stearate are added, and the remaining operations refer to Example 1.

[0092] Comparative Example 7

[0093] No bamboo powder is added, and the remaining operations refer to Example 1.

[0094] Comparative Example 8

[0095] The bamboo powder was not modified, and the remaining operations were according to Example 1.

[0096] Performance test

[0097] Test method:

[0098] 1. Strength test

[0099] Pure PP plastic was used as a blank control group, and the degradable fresh food trays obtained in Examples 1-3 were used as experimental groups 1-3, respectively, and the products obtained in Comparative Examples 1-8 were used as control groups 1-8, respectively.

[0100] The tensile properties of experimental groups 1-3, control groups 1-6, and the blank control group were tested according to the test method in GB / T1040.2-2022, with a tensile rate of 200 mm / min, and the results are shown in Table 1.

[0101] As can be seen from Table 1, the strength of the degradable fresh food tray prepared from the formula provided by the application has no obvious difference from that of pure PP plastic, and can provide the required strength for daily use.

[0102] Table 1 Tensile strength (Mpa) test results

[0103]

[0104] 2. Degradation capacity test

[0105] The products obtained in Examples 1-3 and Comparative Examples 1-8 were cut according to the specifications of 50mm x 50mm x 2mm, and were used as experimental groups 1-3 and control groups 1-8, respectively, and the following experimental operations were performed in turn:

[0106] Test 1:

[0107] Z1. Weighed separately as the initial weight m1;

[0108] Z2. Soaked in deionized water for 5 min;

[0109] Z3. Placed in a non-sealed acrylic box of 800mm x 300mm x 200mm, with air humidity of 65%, UV index 7, and continuously irradiated for 12 months;

[0110] Z4. Weighed every 4 months after the start of the test as m2, and the degradation rate was calculated according to: degradation rate = (m1-m2) / m1 x 100%, and recorded as shown in Table 2.

[0111] As can be seen from Table 2, the degradation rates of the control groups 2-3 without the addition of the curing agent are relatively high and close, and the possible reason is that the photodegradation agent protective agent in the control group 3 is hydrolyzed and dissolved in water in step Z2, causing the photodegradation agent to directly absorb ultraviolet rays and initiate a photodegradation reaction; the possible reason for the relatively high degradation rate of the control group 1 is that the absence of the photodegradation agent protective agent causes the photodegradation agent to directly absorb ultraviolet rays and initiate a photodegradation reaction. Compared with the control groups 1-3, the possible reason for the relatively low degradation rate of the experimental groups 1-3 after 4 months is that the reaction performed at the beginning of this stage is microbial degradation of the curing agent in the air.

[0112] Table 2 degradation rate (%) test results

[0113]

[0114] The above description is only the preferred embodiments of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any modification, equivalent change and modification of the above embodiments, which does not depart from the technical solution of the present application, is still within the scope of the technical solution of the present application.

Claims

1. A degradable fresh produce tray, characterized in that, The base tray, the photodegradation agent protective agent and the curing agent are used to prepare the biodegradable fresh food tray. The raw material of the base tray comprises the photodegradation agent, PP powder, modified bamboo powder and dispersant. The photodegradation agent is iron stearate. The photodegradation agent protective agent is anthocyanin. The raw material of the curing agent comprises chitosan solution, aluminum acetate solution and silicon dioxide. The modified bamboo powder is obtained by spraying silane coupling agent KH-550 on the bamboo powder and ball milling to 2000 mesh. The spraying amount of the silane coupling agent KH-550 is 0.5-1.5% of the mass of the bamboo powder. The anthocyanin is at least one of pelargonidin, cyanidin, delphinidin, mucroniatin, petunidin and malvidin. The mass ratio of the photodegradation agent, PP powder, modified bamboo powder, photodegradation agent protective agent, dispersant and curing agent is 7-9:70-90:10-20:1-3:1-3:4-6. The base tray is prepared by the following steps: W1. The photodegradation agent, PP powder, modified bamboo powder and dispersant are stirred in a high-speed mixer to obtain mixed raw material. W2. The mixed raw material is fed into a double-screw extruder for melt extrusion, cold-pulling pelletization and injection molding to obtain the base tray. The dispersant comprises polyvinyl alcohol and polyethylene wax. The mass ratio of the polyvinyl alcohol and polyethylene wax is 8-10:1-3. The preparation method of the curing agent comprises the following steps: X1. Chitosan solution with a concentration of 3-5% is prepared. X2. Aluminum acetate solution with a concentration of 6-8% is prepared. X3. The chitosan solution, aluminum acetate solution and silicon dioxide are mixed in a certain proportion, and the pH value is adjusted to 4-6 to obtain the curing agent. The mass ratio of the chitosan solution, aluminum acetate solution and silicon dioxide is 20-25:30-35:3-7.

2. The degradable fresh produce tray of claim 1, wherein, The biodegradable fresh food tray is prepared by the following steps: Y1. The curing agent and the photodegradation agent protective agent are mixed in a certain proportion to obtain a mixed solution. Y2. The base tray is immersed in the mixed solution for 30-45 seconds, and the biodegradable fresh food tray is obtained after the mixed solution is dried and solidified on the surface of the base tray.

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