Antibacterial biodegradable plastic bag and preparation method thereof

Abstract

This invention belongs to the field of plastic preparation technology, specifically relating to an antibacterial and biodegradable plastic bag and its preparation method. The antibacterial and biodegradable plastic bag comprises the following components: 70-90 parts polylactic acid, 20-30 parts polybutylene succinate, 5-10 parts modified diatomaceous earth, 4-12 parts potato starch, 1-5 parts glucose, 0.5-1 part lubricant, and 0.1-0.5 parts antioxidant. The modified diatomaceous earth is obtained through two chemical modifications. The biodegradable plastic bag made using this modified diatomaceous earth possesses both excellent antibacterial properties and strong mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic preparation, and in particular relates to an antibacterial biodegradable plastic bag and a preparation method thereof. Background Art

[0002] Plastic bags are bags made of plastic as the main raw material. Due to their advantages of being cheap, extremely light, large in capacity, and easy to store, they are often used to carry other items and are one of the essential items in people's daily lives. With people's concern about environmental issues, the impact of discarded plastic bags on human life has also attracted much attention. A large number of studies have found that discarded plastic bags, due to their non-degradability, have brought white pollution to the human living environment. General plastic bags generally take hundreds of years to degrade, which causes long-term harm to the soil, affects the growth of crops, and leads to reduced crop yields; at the same time, scattered plastics can also cause animals to eat them by mistake and die. Based on the above problems, China officially implemented a plastic restriction order in 2008, that is, a paid use system for plastic shopping bags was implemented in all supermarkets, shopping malls, bazaars and other commodity retail places, and plastic shopping bags were not allowed to be provided free of charge. The production, sale and use of plastic shopping bags with a thickness of less than 0.025 mm were banned nationwide. Based on this, biodegradable plastics came into being.

[0003] Biodegradable plastics are plastics that are degraded by the action of bacteria, fungi, algae, etc. that exist in nature. They have the advantages of being completely decomposed by environmental microorganisms after being discarded. At present, in the field of plastic preparation technology, natural biopolymer materials are used as raw materials for the preparation of plastic products. This is because natural biopolymers are inexhaustible renewable resources, with a wide variety of varieties, low production costs, and no pollution to the environment. However, the degradable plastic bags in the prior art have problems such as poor antibacterial ability and poor mechanical properties, so it is necessary to further improve the performance of plastic bags. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, one of the purposes of the present invention is to provide an antibacterial biodegradable plastic bag having excellent antibacterial properties.

[0005] The second object of the present invention is to provide a method for preparing an antibacterial biodegradable plastic bag, which is simple and easy to produce and practice.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] An antibacterial biodegradable plastic bag comprises the following ingredients: 70-90 parts of polylactic acid, 20-30 parts of polybutylene succinate, 5-10 parts of modified diatomaceous earth, 4-12 parts of potato starch, 1-5 parts of glucose, 0.5-1 parts of lubricant, and 0.1-0.5 parts of antioxidant;

[0008] The preparation process of the modified diatomite is as follows:

[0009] 1) adding diatomaceous earth to an acidic solution, heating and stirring for a period of time, and then washing to neutrality to obtain pre-modified diatomaceous earth;

[0010] 2) mixing the pre-modified diatomaceous earth prepared in step 1) with birch sap, and calcining the mixture under nitrogen protection to obtain secondary modified diatomaceous earth;

[0011] 3) adding the secondarily modified diatomaceous earth in step 2) into a solvent, adding a surfactant and an antibacterial agent into the solvent, heating and stirring for a period of time, standing to collect the precipitate, and drying to obtain the modified diatomaceous earth.

[0012] Preferably, the acidic solution in step 1) is a nitric acid solution with a mass concentration of 10-20%, the mass concentration of the diatomaceous earth in the acidic solution is 20-30%, the heating temperature is 70-80° C., and the heating time is 1-2 h.

[0013] Preferably, in step 2), the mass ratio of the pre-modified diatomaceous earth to birch sap is 1:0.05-0.1, the calcination temperature is 400-500° C., and the calcination time is 1-2 h.

[0014] Preferably, in step 3), the mass ratio of the secondary modified diatomaceous earth, surfactant and antibacterial agent is 1:0.5-1:0.1-0.3.

[0015] Preferably, in step 3), the solvent is water, the surfactant is sodium lauryl sulfonate, and the antibacterial agent is gallic acid.

[0016] Preferably, the heating temperature in step 3) is 40-50° C. and the heating time is 2-5 h.

[0017] Preferably, the lubricant is paraffin or stearyl stearate.

[0018] Preferably, the antioxidant is selected from one of antioxidant 1010, antioxidant 1076 and antioxidant 168.

[0019] The second object of the present invention is achieved by adopting the following technical solution:

[0020] The method for preparing the antibacterial biodegradable plastic bag comprises the following steps: mixing polylactic acid, polybutylene succinate, modified diatomaceous earth, potato starch, glucose, lubricant and antioxidant, melting and granulating through a twin-screw extruder, blowing film and making bags to obtain the product.

[0021] Preferably, the twin-screw extrusion temperature is 180-200°C.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Improve the performance of diatomite

[0024] The invention firstly adopts nitric acid solution to pre-modify diatomite, then adopts birch sap to perform secondary modification on the pre-modified diatomite, and finally prepares the modified diatomite capable of improving the stability of gallic acid.

[0025] (2) The preparation method is simple and concise

[0026] The present invention also provides a method for preparing an antibacterial biodegradable plastic bag, which has simple steps and is easy to operate and practice. The biodegradable plastic bag prepared by the method has both excellent antibacterial properties and strong mechanical properties. DETAILED DESCRIPTION

[0027] The technical scheme of the present invention is further described below in conjunction with specific embodiments. However, it should be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0028] Example

[0029] Example 1

[0030] The present embodiment provides an antibacterial biodegradable plastic bag, which is composed of 75 parts of polylactic acid, 26 parts of polybutylene succinate, 8 parts of modified diatomaceous earth, 9 parts of potato starch, 3 parts of glucose, 0.6 parts of paraffin, and 0.4 parts of antioxidant 1010.

[0031] Among them, the specific preparation process of modified diatomite is as follows:

[0032] 1) adding diatomaceous earth to a nitric acid solution with a mass concentration of 15%, wherein the mass concentration of diatomaceous earth in the nitric acid solution is 24%, heating and stirring at 75° C. for 1.6 h, and then washing with water until neutral, to obtain pre-modified diatomaceous earth;

[0033] 2) Drill holes in the birch tree and use a catheter to draw out the sap to obtain birch sap;

[0034] According to the mass ratio of pre-modified diatomite to birch sap of 1:0.08, the pre-modified diatomite prepared in step 1) and birch sap were mixed, and then calcined at 450° C. for 1.2 h under nitrogen protection to obtain secondary modified diatomite;

[0035] 3) Weighing each component according to the mass ratio of the secondary modified diatomaceous earth, sodium lauryl sulfate and gallic acid of 1:0.9:0.2, adding the secondary modified diatomaceous earth in step 2) into water, then adding sodium lauryl sulfate and gallic acid, heating and stirring at 45° C. for 3 h, standing to collect the precipitate, and drying to obtain modified diatomaceous earth.

[0036] The specific process of the preparation method of the antibacterial biodegradable plastic bag is as follows:

[0037] Polylactic acid, polybutylene succinate, modified diatomaceous earth, potato starch, glucose, paraffin and antioxidant 1010 are mixed and stirred, melt-extruded and extruded into granules by a twin-screw extruder (the temperature of the twin-screw extruder is 190° C.), and then successively subjected to film blowing and bag making to obtain the product.

[0038] Example 2

[0039] The present embodiment provides an antibacterial biodegradable plastic bag, which is composed of 70 parts of polylactic acid, 30 parts of polybutylene succinate, 5 parts of modified diatomaceous earth, 4 parts of potato starch, 1 part of glucose, 0.5 parts of stearyl stearate, and 0.1 parts of antioxidant 1076.

[0040] Among them, the specific preparation process of modified diatomite is as follows:

[0041] 1) adding diatomaceous earth to a nitric acid solution with a mass concentration of 10%, wherein the mass concentration of diatomaceous earth in the nitric acid solution is 20%, heating and stirring at 70° C. for 2 h, and then washing with water until neutral, to obtain pre-modified diatomaceous earth;

[0042] 2) Drill holes in the birch tree and use a catheter to draw out the sap to obtain birch sap;

[0043] The pre-modified diatomite and birch sap are mixed in a mass ratio of 1:0.05, and then calcined at 500° C. for 2 h under nitrogen protection to obtain secondary modified diatomite;

[0044] 3) Weighing each component according to the mass ratio of the secondary modified diatomaceous earth, sodium lauryl sulfate and gallic acid of 1:0.5:0.1, adding the secondary modified diatomaceous earth in step 2) into water, then adding sodium lauryl sulfate and gallic acid, heating and stirring at 40° C. for 2 h, standing to collect the precipitate, and drying to obtain modified diatomaceous earth.

[0045] The specific process of the preparation method of the antibacterial biodegradable plastic bag is as follows:

[0046] Polylactic acid, polybutylene succinate, modified diatomaceous earth, potato starch, glucose, stearyl stearate and antioxidant 1076 are mixed and stirred, melt-extruded and extruded into granules by a twin-screw extruder (the temperature of the twin-screw extruder is 200°C), and then successively subjected to film blowing and bag making to obtain the product.

[0047] Example 3

[0048] The present embodiment provides an antibacterial biodegradable plastic bag, which is composed of 90 parts of polylactic acid, 20 parts of polybutylene succinate, 10 parts of modified diatomaceous earth, 12 parts of potato starch, 5 parts of glucose, 0.1 parts of paraffin, and 0.5 parts of antioxidant 168.

[0049] Among them, the specific preparation process of modified diatomite is as follows:

[0050] 1) adding diatomaceous earth to a nitric acid solution with a mass concentration of 20%, wherein the mass concentration of diatomaceous earth in the nitric acid solution is 30%, heating and stirring at 80° C. for 1 hour, and then washing with water until neutral, to obtain pre-modified diatomaceous earth;

[0051] 2) Drill holes in the birch tree and use a catheter to draw out the sap to obtain birch sap;

[0052] According to the mass ratio of pre-modified diatomite to birch sap of 1:0.1, the pre-modified diatomite in step 1) and birch sap are mixed, and then calcined at 400° C. for 1 hour under nitrogen protection to obtain secondary modified diatomite;

[0053] 3) Weighing each component according to the mass ratio of the secondary modified diatomaceous earth, sodium lauryl sulfate and gallic acid of 1:1:0.3, adding the secondary modified diatomaceous earth in step 2) into water, then adding sodium lauryl sulfate and gallic acid, heating and stirring at 50° C. for 5 h, standing to collect the precipitate, and drying to obtain modified diatomaceous earth.

[0054] The specific process of the preparation method of the antibacterial biodegradable plastic bag is as follows:

[0055] Polylactic acid, polybutylene succinate, modified diatomaceous earth, potato starch, glucose, paraffin and antioxidant 168 are mixed and stirred, melt-extruded and extruded into granules by a twin-screw extruder (the temperature of the twin-screw extruder is 180°C), and then successively subjected to film blowing and bag making to obtain the product.

[0056] Comparative Example

[0057] Comparative Example 1

[0058] This comparative example provides a biodegradable plastic bag, which is composed of 75 parts of polylactic acid, 26 parts of polybutylene succinate, 8 parts of diatomaceous earth, 9 parts of potato starch, 3 parts of glucose, 0.6 parts of paraffin, and 0.4 parts of antioxidant 1010. Other components are the same as those in Example 1.

[0059] Comparative Example 2

[0060] This comparative example provides a biodegradable plastic bag, which is composed of 75 parts of polylactic acid, 26 parts of polybutylene succinate, 8 parts of modified diatomaceous earth, 9 parts of potato starch, 3 parts of glucose, 0.6 parts of paraffin, and 0.4 parts of antioxidant 1010. Other parts are the same as those in Example 1.

[0061] Among them, the specific preparation process of modified diatomite is as follows:

[0062] 1) adding diatomaceous earth to a nitric acid solution with a mass concentration of 15%, wherein the mass concentration of diatomaceous earth in the nitric acid solution is 24%, heating and stirring at 75° C. for 1.6 h, and then washing with water until neutral, to obtain pre-modified diatomaceous earth;

[0063] 2) calcining the pre-modified diatomaceous earth in step 1) at 450° C. for 1.2 h under nitrogen protection to obtain calcined diatomaceous earth;

[0064] 3) Weighing the components according to the mass ratio of calcined diatomaceous earth, sodium lauryl sulfate and gallic acid of 1:0.9:0.2, adding the calcined diatomaceous earth in step 2) into water, then adding sodium lauryl sulfate and gallic acid, heating and stirring at 45° C. for 3 h, standing to collect the precipitate, and drying to obtain modified diatomaceous earth.

[0065] Comparative Example 3

[0066] This comparative example provides a biodegradable plastic bag, which is composed of 75 parts of polylactic acid, 26 parts of polybutylene succinate, 7.4 parts of diatomaceous earth, 0.6 parts of birch sap, 9 parts of potato starch, 3 parts of glucose, 0.6 parts of paraffin, and 0.4 parts of antioxidant 1010. Other ingredients are the same as those in Example 1.

[0067] Comparative Example 4

[0068] This comparative example provides a biodegradable plastic bag, which is composed of 75 parts of polylactic acid, 26 parts of polybutylene succinate, 6.7 parts of diatomaceous earth, 1.3 parts of gallic acid, 9 parts of potato starch, 3 parts of glucose, 0.6 parts of paraffin, and 0.4 parts of antioxidant 1010. Other ingredients are the same as those in Example 1.

[0069] Test example

[0070] Test Example 1

[0071] This test example explores the various properties of the biodegradable plastic bags of Examples 1-3 and Comparative Examples 1-4. The specific test process is as follows:

[0072] ① Tensile properties: The tensile test was carried out on a universal material testing machine in accordance with the plastic tensile properties test standard GB / T 1040.3-2006. The tensile rate was 2 mm / min. Each group was tested 5 times and the average value was taken.

[0073] ② Elongation at break: According to the plastic tensile properties test standard GB / T 1040.3-2006, a tensile test was carried out on a universal material testing machine. The tensile rate was 2 mm / min. Each group was tested 5 times and the average value was taken.

[0074] ③ Biodegradation performance: The biodegradation performance of the plastic bags obtained in each embodiment after 60 days of landfill was tested according to GB / T20197-2006. Each group was tested 5 times and the average value was taken. The test results are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] It can be seen from Table 1 that the biodegradable plastic bags of Examples 1-3 and Comparative Examples 1-4 have excellent biodegradability. Compared with Examples 1-3, the tensile strength and elongation at break of the biodegradable plastic bags of Comparative Examples 1-4 are reduced to varying degrees. Among them, the biodegradable plastic bag of Comparative Example 1 uses diatomaceous earth instead of modified diatomaceous earth, the biodegradable plastic bag of Comparative Example 2 does not add birch sap when preparing the modified diatomaceous earth, the biodegradable plastic bag of Comparative Example 3 uses a mixture of diatomaceous earth and birch sap instead of modified diatomaceous earth, and the biodegradable plastic bag of Comparative Example 4 uses diatomaceous earth and gallic acid instead of modified diatomaceous earth. It can be seen that the biodegradable plastic bag prepared using the modified diatomaceous earth of the present invention has strong mechanical properties.

[0079] Test Example 2

[0080] This test example explores the antibacterial properties of the biodegradable plastic bags of Examples 1-3 and Comparative Example 4. The specific test process is as follows:

[0081] According to the test method specified in the standard "QB / T2591-2003 Test Method for Antibacterial Performance and Antibacterial Effect of Antibacterial Plastics", the antibacterial properties of the biodegradable plastic bags of Examples 1-3 and Comparative Example 4 against Staphylococcus aureus ATCC 6538, Escherichia coli ATCC25922, and Candida albicans ATCC 10231 were tested. The test results are shown in Table 2.

[0082] Table 2

[0083]

[0084] It can be seen from Table 2 that the antibacterial performance of the biodegradable plastic bag in Comparative Example 4 is reduced compared with Examples 1-3. Analysis shows that the biodegradable plastic bag in Comparative Example 4 uses diatomaceous earth and gallic acid instead of modified diatomaceous earth. It can be seen from the above that the modified diatomaceous earth prepared by the method of the present invention can improve the stability of gallic acid.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. On the basis of the present invention, some modifications or replacements may be made thereto, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of protection claimed by the present invention.

Claims

1. An antibacterial biodegradable plastic bag, characterized in that: The invention comprises the following ingredients: 70-90 parts of polylactic acid, 20-30 parts of polybutylene succinate, 5-10 parts of modified diatomaceous earth, 4-12 parts of potato starch, 1-5 parts of glucose, 0.5-1 parts of lubricant and 0.1-0.5 parts of antioxidant; The preparation process of the modified diatomite is as follows: 1) adding diatomaceous earth to an acidic solution, heating and stirring for a period of time, and then washing to neutrality to obtain pre-modified diatomaceous earth; 2) mixing the pre-modified diatomaceous earth prepared in step 1) with birch sap, and calcining the mixture under nitrogen protection to obtain secondary modified diatomaceous earth; 3) adding the secondarily modified diatomaceous earth in step 2) into a solvent, adding a surfactant and an antibacterial agent into the solvent, heating and stirring for a period of time, standing to collect the precipitate, and drying to obtain the modified diatomaceous earth.

2. The antibacterial biodegradable plastic bag according to claim 1, characterized in that: In step 1), the acidic solution is a nitric acid solution with a mass concentration of 10-20%, the mass concentration of the diatomaceous earth in the acidic solution is 20-30%, the heating temperature is 70-80° C., and the heating time is 1-2 hours.

3. The antibacterial biodegradable plastic bag according to claim 1, characterized in that: In step 2), the mass ratio of the pre-modified diatomaceous earth to birch sap is 1:0.05-0.1, the calcination temperature is 400-500° C., and the calcination time is 1-2 hours.

4. The antibacterial biodegradable plastic bag according to claim 1, characterized in that: The mass ratio of the secondary modified diatomaceous earth, surfactant and antibacterial agent in step 3) is 1:0.5-1:0.1-0.

3.

5. The antibacterial biodegradable plastic bag according to claim 1, characterized in that: In step 3), the solvent is water, the surfactant is sodium lauryl sulfonate, and the antibacterial agent is gallic acid.

6. The antibacterial biodegradable plastic bag according to claim 1, characterized in that: The heating temperature in step 3) is 40-50°C and the heating time is 2-5h.

7. The antibacterial biodegradable plastic bag according to claim 1, characterized in that: The lubricant is paraffin or stearyl stearate.

8. The antibacterial biodegradable plastic bag according to claim 1, characterized in that: The antioxidant is selected from one of antioxidant 1010, antioxidant 1076 and antioxidant 168.

9. The method for preparing an antibacterial biodegradable plastic bag according to any one of claims 1 to 8, characterized in that: The following steps are involved: The product is obtained by mixing polylactic acid, polybutylene succinate, modified diatomaceous earth, potato starch, glucose, lubricant and antioxidant, and then melting and granulating the mixture through a twin-screw extruder, blowing film and making bags.

10. The method for preparing the antibacterial biodegradable plastic bag according to claim 9, characterized in that: The twin-screw extrusion temperature is 180-200°C.

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