Environment-friendly degradable plastic food packaging bag and preparation method thereof

Abstract

The application discloses an environment-friendly degradable plastic food packaging bag and a preparation method thereof. The food packaging bag comprises the following raw materials in parts by weight: PBAT 90-100 parts, PLA 10-20 parts, antibacterial modified nano calcium carbonate 15-20 parts, polyethylene wax 1-2 parts, and titanium dioxide 1-2 parts. PBAT and PLA are used as the base material in a large proportion and a small proportion respectively. When the component ratio is greatly different, the intermolecular force between PBAT and PLA is stronger, and the miscibility is better. The two base materials are first mixed to prepare base particles. When the base particles are mixed with other components, better compatibility is achieved. The prepared degradable plastic food packaging bag has more excellent mechanical properties. When the antibacterial modified nano calcium carbonate is melted with other components of the plastic food packaging bag, better compatibility is achieved, and the fluidity of the material during melting is better. Meanwhile, the prepared plastic bag is not easy to precipitate, and the antibacterial performance of the plastic food packaging bag can be maintained for a long time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plastics, and particularly relates to an environment-friendly degradable plastic food packaging bag and a preparation method thereof. BACKGROUND

[0002] The utility and portability of plastic products have brought great convenience to people's life. With the increasing use of plastic products, the environment has been seriously polluted. The production and use of degradable materials can reduce the dependence on fossil fuels such as petroleum, which is conducive to promoting the process of sustainable development and reducing environmental pollution.

[0003] PBAT is one of the most widely used base materials for preparing degradable plastics. It is a polymer material copolymerized by butylene glycol adipate and butylene glycol terephthalate. Its chain segment structure contains rigid aromatic groups and flexible aliphatic chains, which endow it with good ductility and thermal stability. In addition, PBAT has good degradability and can be decomposed into harmless substances in the natural environment. PLA is a natural polymer material mainly derived from plant starch and is often used as a base material for preparing degradable plastics. It has excellent biodegradation performance and can be biologically recycled, making it an environmentally friendly degradable material. The plastic bags made of PLA are soft and transparent, and have good plasticity and processing performance, so they are widely used in the production of degradable plastics. Since PLA has excellent strength and modulus, it is also an ideal choice for reinforcing PBAT. By combining the advantages of PBAT and PLA, two kinds of degradable plastics, the material prepared by blending can overcome their respective disadvantages, thereby achieving more ideal performance. PBAT and PLA have good complementarity in chemical structure, and the material formed after blending has good ductility and thermal stability of PBAT, and excellent strength and modulus of PLA. PLA / PBAT blends can inherit the high strength of PLA and the high elasticity of PBAT, and can still be degraded. At the same time, this PLA / PBAT blend is still a degradable material, avoiding pollution to the environment and waste of resources.

[0004] Plastic food packaging bags are involved in various aspects of our life. With the improvement of living quality, people pay more attention to health and have higher requirements for these close-contact daily plastic packaging bags. They require to be non-toxic and antibacterial. Elemental silver has broad-spectrum and high-efficiency bactericidal capacity and is a very good antibacterial agent. Nano-silver is often added to antibacterial plastics to increase antibacterial performance, but inorganic nano-silver has poor dispersibility and is easy to precipitate, which cannot maintain antibacterial performance for a long time.

[0005] Calcium carbonate is the most commonly used inorganic filler in plastic processing filling modification, blending with PBAT can not only reduce the production cost of products, but also improve the processing performance of PBAT. However, calcium carbonate is easy to agglomerate, so it is difficult to disperse uniformly in the polymer, and the compatibility with PBAT is poor, so it is necessary to modify the calcium carbonate to solve the compatibility problem. SUMMARY

[0006] The purpose of the application is to provide an environmentally friendly degradable plastic food packaging bag and a preparation method thereof.

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

[0008] The environmentally friendly degradable plastic food packaging bag comprises the following raw materials by weight: PBAT 90-100 parts, PLA 10-20 parts, antibacterial modified nano calcium carbonate 15-20 parts, polyethylene wax 1-2 parts, and titanium dioxide 1-2 parts.

[0009] Further, the preparation method of the antibacterial modified nano calcium carbonate is:

[0010] S1, weigh 11-mercapto undecanoic acid into a reaction bottle, add 80-100ml of anhydrous ethanol, place the reaction bottle in a constant temperature water bath with magnetic stirring, stir at a water bath temperature of 45-55℃ for 20-30min, and obtain a modified solution;

[0011] S2, weigh nano calcium carbonate into the reaction bottle, then add 400-500ml of 20-30% ethanol aqueous solution, place the reaction bottle in a heating jacket with magnetic stirring, heat to a temperature of 65-70℃ while stirring, then slowly add the prepared modified solution, and add it within 20-30min, then keep the temperature at 65-70℃ and continue stirring for 2-4h, after the reaction is completed, cool to room temperature, filter, and wash the filter cake with anhydrous ethanol;

[0012] S3, then immerse the filter cake in a silver antibacterial solution, place it in a constant temperature water bath with magnetic stirring, stir at a water bath temperature of 45-55℃ for 2-3h, take it out, filter, wash with purified water, then put the filter cake into an oven and dry it at 100-105℃ for 10-16h, grind it and obtain the modified nano calcium carbonate.

[0013] Further, the mass of 11-mercapto undecanoic acid is 0.7-1.0g.

[0014] Further, the particle size of the nano calcium carbonate is 1-100nm.

[0015] Further, the mass of the nano calcium carbonate is 15-20g.

[0016] Further, the preparation of the silver antibacterial solution is:

[0017] 8-10 mg of silver nitrate, 45-50 mg of sodium citrate and 200 ml of purified water are weighed into a beaker, after complete dissolution, 3-5 ml of 0.03-0.05% mass fraction of sodium borohydride aqueous solution is added, then 10-20 mol / L of sodium hydroxide aqueous solution is added dropwise to adjust the pH of the solution to 10.0-13.0, and then stirred and mixed uniformly, aged for 2-3 h, and finally centrifuged, washed with water, and dried to obtain the silver antibacterial agent, which is dissolved in deionized water to prepare a silver antibacterial solution with a mass concentration of 0.5%-0.8%.

[0018] Further, the volume of the silver antibacterial solution is 400-500 ml.

[0019] The preparation method of the environment-friendly degradable plastic food packaging bag comprises the following steps:

[0020] Firstly, the formula amount of PBAT and PLA are placed in an oven and vacuum dried at 50-55 DEG C for 8-10 h, then added to a twin-screw extruder for melt mixing, extruded and granulated to obtain plastic base particles for standby;

[0021] Secondly, the plastic base particles prepared in the first step and the component amount of antibacterial modified nano calcium carbonate, polyethylene wax and titanium dioxide are added to a high-speed mixer and mixed at room temperature for 3-5 min; Thirdly, the mixed materials of the second step are added to a twin-screw extruder set for mixing and extrusion, and then the extruded strip samples are cut into particles, and then added to a blow molding machine for extrusion molding to obtain the environment-friendly degradable plastic food packaging bag.

[0022] The beneficial effects of the present application are:

[0023] The present application provides an environment-friendly degradable plastic food packaging bag which has good biodegradability and persistent antibacterial performance, and takes PBAT in a large proportion and PLA in a small proportion as a base material, and the intermolecular force between PBAT and PLA is stronger when the component ratio is relatively large, and the mixing melting property is better, the two base materials are first mixed to prepare base particles, and when mixed with other components, the compatibility is better, and the mechanical properties of the prepared degradable plastic food packaging bag are more excellent.

[0024] The surface of nano calcium carbonate as a filler contains a large number of hydroxyl groups, and the 11-mercapto undecanoic acid is used for modification. The carboxyl group on the 11-mercapto undecanoic acid can react with the hydroxyl group on the surface of nano calcium carbonate. The modified nano calcium carbonate is immersed in a silver antibacterial solution. The mercapto group with adsorption performance can adsorb silver atoms and coordinate with them, and then fix them on the calcium carbonate. When the antibacterial modified nano calcium carbonate is melted with other components of the plastic food packaging bag, it has better compatibility and better flowability of the material during melting. At the same time, the silver is not easy to precipitate, and the antibacterial performance of the plastic food packaging bag can be maintained for a long time.

[0025] Of course, it is not necessary for any product implementing the present application to achieve all the advantages mentioned above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 The infrared spectra of 11-mercapto undecanoic acid, antibacterial modified nano calcium carbonate and nano calcium carbonate;

[0028] Figure 2 The calcium element distribution map of EDS energy spectrum analysis of Comparative Example 1 (Figure a) and Example 3 (Figure b). DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] In the following examples

[0031] The preparation method of the antibacterial modified nano calcium carbonate is as follows:

[0032] Preparation of the modification solution: 0.8g of 11-mercapto undecanoic acid is weighed and added to a reaction bottle, 100ml of anhydrous ethanol is added, the reaction bottle is placed in a constant temperature water bath containing magnetic stirring, and stirring is carried out at a water bath temperature of 50℃ for 30min to obtain a modification solution;

[0033] Preparation of antibacterial modified nano-calcium carbonate: 20g of nano-calcium carbonate (particle size of 1-100nm) was weighed and added to a reaction flask, followed by adding 500ml of 30% ethanol aqueous solution by mass, placing the reaction flask in a heating mantle with magnetic stirring, heating to 70°C while stirring, then slowly adding the prepared modified solution, adding it all within 30 minutes, then maintaining the temperature at 70°C and continuing stirring for 4 hours. After the reaction is completed, it was cooled to room temperature, filtered, and the filter cake was washed with anhydrous ethanol. Then, the filter cake was immersed in 500ml of silver antibacterial solution, placed in a constant temperature water bath with magnetic stirring, stirred at 50°C for 2 hours, removed, filtered, washed with purified water, and then placed in an oven and dried at 105°C for 15 hours. After grinding, the modified nano-calcium carbonate was obtained.

[0034] like Figure 1 As shown in the infrared spectrum of modified nano calcium carbonate, at 2933 cm -1 ,2860cm -1 The peak at 1759 cm is the methylene stretching vibration peak in 11-mercaptoundecanoic acid. -1 The peak at the center is the ester stretching vibration peak, indicating that 11-mercaptoundecanoic acid forms a bond on nano-calcium carbonate.

[0035] The preparation method of the antibacterial modifier is:

[0036] 10 mg of silver nitrate, 50 mg of sodium citrate and 200 ml of purified water were weighed and added to a beaker. After complete dissolution, 3 ml of a 0.05% sodium borohydride aqueous solution was added, and then a 15 mol / L sodium hydroxide aqueous solution was added dropwise to adjust the pH of the solution to 10.0-13.0. The mixture was stirred and mixed uniformly, aged for 3 h, and finally centrifuged, washed with water, and dried to obtain a silver antibacterial agent, which was dissolved in deionized water to prepare a silver antibacterial solution with a mass concentration of 0.8%.

[0037] Example 1

[0038] The present invention is an environmentally friendly degradable plastic food packaging bag, comprising the following raw materials in parts by weight: 100 parts of PBAT, 15 parts of PLA, 20 parts of antibacterial modified nano-calcium carbonate, 1 part of polyethylene wax, and 1 part of titanium dioxide;

[0039] The PBAT melt flow index is 5.6g / 10min (190℃ / 2.16kg) and the density is 1.26g / cm 3 ;

[0040] The PLA melt flow index is 6.2g / 10min (190℃ / 2.16kg) and the density is 1.24g / cm 3 ;

[0041] The preparation method of the environment-friendly degradable plastic food packaging bag comprises the following steps:

[0042] In the first step, the formula amount of PBAT and PLA is placed in an oven and vacuum dried at 55 DEG C for 8h, and then added to a twin-screw extruder for melt mixing, extrusion granulation, to obtain plastic base particles for standby;

[0043] In the second step, the plastic base particles prepared in the first step and the component amount of antibacterial modified nano calcium carbonate, polyethylene wax and titanium dioxide are added to a high-speed mixer and mixed at room temperature for 5min;

[0044] In the third step, the mixed materials of the second step are added to a twin-screw extruder set for mixing and extrusion, and then the extruded long strip samples are cut into particles, and then added to a blow molding machine for extrusion molding, to obtain the environment-friendly degradable plastic food packaging bag.

[0045] Example 2

[0046] The environment-friendly degradable plastic food packaging bag comprises the following raw materials by weight: PBAT 90 parts, PLA 20 parts, antibacterial modified nano calcium carbonate 16 parts, polyethylene wax 1.5 parts, and titanium dioxide 1.5 parts;

[0047] The PBAT has a solubility flow index of 5.6g / 10min (190 DEG C / 2.16kg) and a density of 1.26g / cm 3 ;

[0048] The PLA has a solubility flow index of 6.2g / 10min (190 DEG C / 2.16kg) and a density of 1.24g / cm 3 ;

[0049] The preparation method of the environment-friendly degradable plastic food packaging bag comprises the following steps:

[0050] In the first step, the formula amount of PBAT and PLA is placed in an oven and vacuum dried at 55 DEG C for 10h, and then added to a twin-screw extruder for melt mixing, extrusion granulation, to obtain plastic base particles for standby;

[0051] In the second step, the plastic base particles prepared in the first step and the component amount of antibacterial modified nano calcium carbonate, polyethylene wax and titanium dioxide are added to a high-speed mixer and mixed at room temperature for 3min;

[0052] In the third step, the mixed materials of the second step are added to a twin-screw extruder set for mixing and extrusion, and then the extruded long strip samples are cut into particles, and then added to a blow molding machine for extrusion molding, to obtain the environment-friendly degradable plastic food packaging bag.

[0053] Example 3

[0054] The application is an environment-friendly degradable plastic food packaging bag, which comprises the following raw materials by weight: PBAT 95 parts, PLA 10 parts, antibacterial modified nano calcium carbonate 18 parts, polyethylene wax 2 parts, and titanium dioxide 2 parts.

[0055] The PBAT has a melt flow index of 5.6 g / 10 min (190℃ / 2.16 kg) and a density of 1.26 g / cm 3 ;

[0056] The PLA has a melt flow index of 6.2 g / 10 min (190℃ / 2.16 kg) and a density of 1.24 g / cm 3 ;

[0057] The application also provides a preparation method of the environment-friendly degradable plastic food packaging bag.

[0058] Firstly, the formula amount of PBAT and PLA are placed in an oven for vacuum drying at 50℃ for 10h, and then are added into a double-screw extruder for melt mixing, extrusion granulation, to obtain plastic base particles for standby use.

[0059] Secondly, the plastic base particles prepared in the first step and the component amount of antibacterial modified nano calcium carbonate, polyethylene wax, and titanium dioxide are added into a high-speed mixer for mixing at room temperature for 4 min.

[0060] Thirdly, the mixed materials in the second step are added into a double-screw extruder set for mixing and extrusion, and then the extruded long strip samples are cut into particles, and then are added into a blow molding machine for extrusion molding, to obtain the environment-friendly degradable plastic food packaging bag.

[0061] Comparative Example 1

[0062] The application is an environment-friendly degradable plastic food packaging bag, which comprises the following raw materials by weight: PBAT 95 parts, PLA 10 parts, nano calcium carbonate 18 parts, nano silver oxide 2 parts, polyethylene wax 2 parts, and titanium dioxide 2 parts.

[0063] The PBAT has a melt flow index of 5.6 g / 10 min (190℃ / 2.16 kg) and a density of 1.26 g / cm 3 ;

[0064] The PLA has a melt flow index of 6.2 g / 10 min (190℃ / 2.16 kg) and a density of 1.24 g / cm 3 ;

[0065] The application also provides a preparation method of the environment-friendly degradable plastic food packaging bag.

[0066] In the first step, the formulated amount of PBAT and PLA is placed in an oven and vacuum-dried at 50°C for 10 hours, then added to a twin-screw extruder for melt mixing and extrusion granulation to obtain plastic base particles for later use;

[0067] In the second step, the plastic base particles prepared in the first step and the component amounts of nano calcium carbonate, nano silver oxide, polyethylene wax, and titanium dioxide were added to a high-speed mixer and mixed at room temperature for 4 minutes;

[0068] In the third step, the mixture obtained in the second step is added to a twin-screw extruder unit for mixing and extrusion, and then the extruded long strip sample is pelletized and then added to a blow molding machine for extrusion molding to obtain an environmentally friendly degradable plastic food packaging bag.

[0069] like Figure 2 As shown in the EDS energy spectrum analysis of calcium element distribution diagrams of Comparative Example 1 (Figure a) and Example 3 (Figure b), the modified nano-calcium carbonate is more evenly distributed in the degradable plastic system (Example 3).

[0070] Comparative Example 2

[0071] The present invention is an environmentally friendly degradable plastic food packaging bag, comprising the following raw materials in parts by weight: 95 parts of PBAT, 10 parts of PLA, 18 parts of antibacterial modified nano-calcium carbonate, 2 parts of polyethylene wax, and 2 parts of titanium dioxide;

[0072] The PBAT melt flow index is 5.6g / 10min (190℃ / 2.16kg) and the density is 1.26g / cm 3 ;

[0073] The PLA melt flow index is 6.2g / 10min (190℃ / 2.16kg) and the density is 1.24g / cm 3 ;

[0074] A method for preparing an environmentally friendly degradable plastic food packaging bag comprises the following steps:

[0075] In the second step, the raw materials of the component amounts were added into a high-speed mixer and mixed at room temperature for 4 minutes;

[0076] In the third step, the mixture obtained in the second step is added to a twin-screw extruder unit for mixing and extrusion, and then the extruded long strip sample is pelletized and then added to a blow molding machine for extrusion molding to obtain an environmentally friendly degradable plastic food packaging bag.

[0077] The mechanical properties of the degradable plastic food packaging bags of Examples 1-3 and Comparative Examples 1-2 were tested, and the results are shown in Table 1:

[0078] Tensile property test: WDW type universal tensile testing machine was used, and the tensile test was carried out according to the national standard GB / T 1040.1-2018.

[0079] Impact strength test: XJJD-5J electronic impact testing machine was used, and the test was carried out according to the national standard GB / T1843-2008.

[0080] Table 1

[0081] Tensile strength (Mpa) Elongation at break (%) Impact strength (KJ / m 3 ) Example 1 44.8 659.4 48.5 Example 2 46.3 692.7 51.2 Example 3 45.7 668.3 49.3 Comparative Example 1 25.4 253.6 21.5 Comparative Example 2 39.6 571.1 41.6

[0082] From Table 1, it can be seen that the degradable plastic food packaging bag prepared in the application has good mechanical properties. The packaging bag prepared in Comparative Example 1 has poor mechanical properties because no modified nano calcium carbonate is used. The food packaging bag prepared in Comparative Example 2 has slightly weaker mechanical properties than that of Example 3 because the components are directly mixed and melted, which may have slightly poor compatibility.

[0083] Degradation performance test

[0084] The samples of Examples 1-3 and Comparative Examples 1-2 were buried in the test field by natural burying method, with a burying depth of about 15 cm, and light shielding. After burying for 3 months, the samples were taken out, and the degradation degree was visually observed. The results are shown in Table 2:

[0085] Table 2

[0086]

[0087] Antibacterial performance test: The test standard is QB / T 2591-2003A "Antibacterial performance test method and antibacterial effect of antibacterial plastics", and the results are shown in Table 3:

[0088]

[0089] From Table 3, it can be seen that the degradable plastic food packaging bag prepared in the application has good and durable antibacterial properties, and stable performance.

[0090] The above content is only an example and description of the concept of the application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the concept of the application or exceed the scope defined by the present claims, and should belong to the protection scope of the application.

Claims

1. Environmentally friendly degradable plastic food packaging bag, characterized by: The invention comprises the following raw materials in parts by weight: 90-100 parts of PBAT, 10-20 parts of PLA, 15-20 parts of antibacterial modified nano-calcium carbonate, 1-2 parts of polyethylene wax, and 1-2 parts of titanium dioxide; The preparation method of the antibacterial modified nano calcium carbonate is: S1. Weigh 11-mercaptoundecanoic acid and add it to a reaction flask. Add 80-100 ml of anhydrous ethanol, place the reaction flask in a constant temperature water bath with magnetic stirring, and stir at a water bath temperature of 45-55°C for 20-30 minutes to obtain a modified solution. S2, weigh nano-calcium carbonate and add it to the reaction flask, then add 400-500ml of 20-30% ethanol aqueous solution by mass, place the reaction flask in a heating mantle with a magnetic stirrer, heat to 65-70 ° C while stirring, then slowly add the prepared modified solution, adding it within 20-30 minutes, then maintain the temperature at 65-70 ° C and continue stirring for 2-4 hours. After the reaction is completed, cool to room temperature, filter, and wash the filter cake with anhydrous ethanol; S3, then immersing the filter cake in a silver antibacterial solution, placing it in a constant temperature water bath with magnetic stirring, stirring it at a water bath temperature of 45-55°C for 2-3 hours, taking it out, filtering it, washing it with purified water, and then placing the filter cake in an oven, drying it at 100-105°C for 10-16 hours, and grinding it to obtain modified nano-calcium carbonate; The preparation of the silver antibacterial liquid is as follows: Weigh 8-10 mg of silver nitrate, 45-50 mg of sodium citrate and 200 ml of purified water into a beaker, and after complete dissolution, add 3-5 ml of a 0.03-0.05% sodium borohydride aqueous solution, then add a 10-20 mol / L sodium hydroxide aqueous solution dropwise to adjust the pH of the solution to 10.0-13.0, stir and mix evenly, age for 2-3 hours, and finally centrifuge, wash with water, and dry to obtain a silver antibacterial agent, which is dissolved in deionized water to prepare a silver antibacterial solution with a mass concentration of 0.5%-0.8%; The preparation method of the environmentally friendly degradable plastic food packaging bag, The following steps are involved: In the first step, the formulated amount of PBAT and PLA is placed in an oven and vacuum-dried at 50-55°C for 8-10 hours, then added to a twin-screw extruder for melt mixing and extrusion granulation to obtain plastic base particles for later use; In the second step, the plastic base particles prepared in the first step and the component amounts of antibacterial modified nano-calcium carbonate, polyethylene wax, and titanium dioxide are added to a high-speed mixer and mixed at room temperature for 3-5 minutes; In the third step, the mixture obtained in the second step is added to a twin-screw extruder unit for mixing and extrusion, and then the extruded long strip sample is pelletized and then added to a blow molding machine for extrusion molding to obtain an environmentally friendly degradable plastic food packaging bag.

2. The environmentally friendly degradable plastic food packaging bag according to claim 1, characterized in that: The mass of the 11-mercaptoundecanoic acid is 0.7-1.0 g.

3. The environmentally friendly degradable plastic food packaging bag according to claim 1, characterized in that: The particle size of the nano calcium carbonate is 1-100 nm.

4. The environmentally friendly degradable plastic food packaging bag according to claim 1, characterized in that: The mass of the nano calcium carbonate is 15-20g.

5. The environmentally friendly degradable plastic food packaging bag according to claim 1, characterized in that: In step S3, the volume of the silver antibacterial solution is 400-500 ml.

6. A method for preparing the environmentally friendly degradable plastic food packaging bag according to claim 1, characterized in that: The following steps are involved: In the first step, the formulated amount of PBAT and PLA is placed in an oven and vacuum-dried at 50-55°C for 8-10 hours, then added to a twin-screw extruder for melt mixing and extrusion granulation to obtain plastic base particles for later use; In the second step, the plastic base particles prepared in the first step and the component amounts of antibacterial modified nano-calcium carbonate, polyethylene wax, and titanium dioxide are added to a high-speed mixer and mixed at room temperature for 3-5 minutes; In the third step, the mixture obtained in the second step is added to a twin-screw extruder unit for mixing and extrusion, and then the extruded long strip sample is pelletized and then added to a blow molding machine for extrusion molding to obtain an environmentally friendly degradable plastic food packaging bag.

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