CN107746559A - Biodegradable plastic and preparation method thereof - Google Patents

Abstract

The present invention relates to plastics arts, and in particular to a kind of biodegradable plastic and preparation method thereof.Biodegradable plastic provided by the invention includes particles of polylactic acid, soyabean protein powder, soy meal, water, glycerine and polyethylene glycol, the production cost of polylactic acid plastic can be reduced, improve the mechanical property and water resistance of plastic of soybean protein, make biodegradable plastic that there is good biodegradability, water resistance, mechanical property and processing characteristics, while safety non-pollution.The preparation method of the biodegradable plastic of the present invention, by the mixture of each raw material successively by mediating, extruding and be granulated, technique is simple, easy to process, and cost is cheap, has broad application prospects.

Description

Biodegradable plastic and its preparation method

technical field

The invention relates to the technical field of plastics, in particular to a biodegradable plastic and a preparation method thereof.

Background technique

Plastic products have been widely used in people's daily life, providing great convenience for people's life. Statistics show that the world's total annual plastic consumption is 400 million tons, and China consumes more than 60 million tons. In other words, my country's plastic consumption accounts for 15% of the world's total consumption. However, only a small percentage of plastics are recycled. With the rapid development of the production and application of plastic products, the growing amount of plastic waste is increasingly threatening the human ecological environment. The current methods of processing waste plastics, such as landfill and incineration, require a large processing space and a large amount of capital investment, and also bring environmental problems.

With the enhancement of people's awareness of environmental protection, it is more and more prominent to solve the problem of the coordinated development of plastic materials and environmental protection. Degradable plastics refer to plastics that add a certain amount of additives (such as starch, modified starch or other cellulose, photosensitizers, biodegradants, etc.) The emergence of degradable plastics not only expands the functions of plastics, but also alleviates the contradiction with the environment to a certain extent, saves and replaces petroleum resources, effectively eliminates white pollution, and protects the environment. Polylactic acid (PLA) is a new type of biodegradable material, which is made from starch raw materials proposed by renewable plant resources (such as corn). The starch raw materials are fermented into lactic acid, and then converted into polylactic acid by chemical synthesis. Although polylactic acid has good biodegradability, polylactic acid still has problems such as high production cost, and its mechanical and processing properties need to be further improved.

As a natural material, soybean protein contains a variety of functional groups, such as amino groups, hydroxyl groups, phenolic groups, carboxyl groups, etc. These active groups can be used as chemical modification or cross-linking sites to synthesize polymers with various functions . Because soybean protein has the advantages of large output, low cost and renewable, it has become a research hotspot in the field of plastics. However, soybean protein plastics have the characteristics of high hardness, high brittleness and poor fluidity, which are not easy to process and have poor water resistance.

In view of this, the present invention is proposed.

Contents of the invention

The purpose of the present invention is to provide a biodegradable plastic, which can reduce the production cost of polylactic acid plastics and improve the mechanical properties of soybean protein plastics by blending polylactic acid particles, soybean protein powder and soybean powder to prepare biodegradable plastics And water resistance, the biodegradable plastic has good biodegradable performance, mechanical properties and processing performance, safe and pollution-free, it is a biodegradable plastic with relatively ideal comprehensive performance.

Another object of the present invention is to provide a method for preparing biodegradable plastics, which is simple in process, easy to process, low in cost and has broad application prospects.

To achieve the above object, the technical solution adopted in the present invention is:

A biodegradable plastic, mainly made of the following raw materials in parts by weight: 80-120 parts of polylactic acid particles, 40-60 parts of soybean protein powder, 40-60 parts of soybean powder, 55-75 parts of water, 15-15 parts of glycerin 30 parts, 15-25 parts of polyethylene glycol, and optional auxiliary agents.

Further, the biodegradable plastic is mainly made of the following raw materials in parts by weight: 90-110 parts of polylactic acid particles, 45-55 parts of soybean protein powder, 45-55 parts of soybean powder, 60-70 parts of water, glycerin 20-25 parts, 18-22 parts of polyethylene glycol, and optional auxiliary agents.

Preferably, the biodegradable plastic is mainly made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 65 parts of water, 22.5 parts of glycerin, 20 parts of polyethylene glycol parts, and optional auxiliaries.

Further, the auxiliary agent includes one or a combination of at least two of a coupling agent, a reducing agent or an antibacterial agent.

Preferably, the auxiliary agent is a combination of coupling agent, reducing agent and antibacterial agent,

Further preferably, the auxiliary agent is 6-9 parts of coupling agent, 0.5-1.5 parts of reducing agent and 0.5-1.5 parts of antibacterial agent.

Further, the coupling agent is phthalic anhydride or maleic anhydride, preferably phthalic anhydride.

Further, the reducing agent is sulfite or bisulfite, preferably bisulfite, more preferably sodium bisulfite.

Further, the antibacterial agent is an organic antibacterial agent, preferably potassium sorbate or sodium benzoate, more preferably potassium sorbate.

The biodegradable plastic is mainly made of the following raw materials in parts by weight: 90-110 parts of polylactic acid particles, 45-55 parts of soybean protein powder, 45-55 parts of soybean powder, 60-70 parts of water, 20-25 parts of glycerin 18-22 parts of polyethylene glycol, 7-8 parts of phthalic anhydride, 0.8-1.2 parts of sodium bisulfite and 0.8-1.2 parts of potassium sorbate;

Preferably, the biodegradable plastic is mainly made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 65 parts of water, 22.5 parts of glycerin, 20 parts of polyethylene glycol 7.5 parts of phthalic anhydride, 1 part of sodium bisulfite and 1 part of potassium sorbate.

The preparation method of the above-mentioned biodegradable plastics comprises the following steps:

The mixture of raw materials is sequentially kneaded, extruded and granulated to obtain biodegradable plastics.

Further, the raw materials are firstly mixed, and when the temperature of the mixture rises to 100-105° C., the mixture is kept for 8-15 minutes to obtain a mixture of the raw materials.

Preferably, first put soybean protein powder, soybean powder, water, glycerin and additives into the mixer, heat to 45-55°C, add polylactic acid particles and polyethylene glycol, and wait until the temperature of the mixture rises to 100-105 ℃, after 8-15 minutes of heat preservation, a mixture of raw materials is obtained.

Further preferably, first put soybean protein powder, soybean powder, water, glycerin and additives into a mixer, heat to 50°C and then add polylactic acid particles and polyethylene glycol, and when the temperature of the mixture rises to 102°C, After 10 minutes of incubation, a mixture of the raw materials was obtained.

Further, during the mixing process of each raw material, the rotation speed of the mixer is 400-500 rpm, preferably 420-480 rpm, more preferably 450 rpm.

Further, the kneading temperature is 105-115°C, preferably 108-112°C, more preferably 110°C.

Further, an extruder is used for extrusion granulation, and the temperature at the feeding port of the extruder is 90-110°C, preferably 95-105°C, more preferably 100°C;

And/or, the temperature in the middle compression zone is 120-135°C, preferably 125-130°C, more preferably 128°C;

And/or, the extrusion molding zone temperature is 90-110°C, preferably 95-105°C, more preferably 100°C;

And/or, the screw speed of the extruder is 250-350 rpm, preferably 280-320 rpm, more preferably 300 rpm.

Compared with prior art, the beneficial effect of the present invention is:

1. The biodegradable plastic of the present invention prepares the biodegradable plastic by blending polylactic acid particles, soybean protein powder and soybean powder, which can reduce the production cost of polylactic acid plastics on the one hand, and improve the quality of soybean protein plastics on the other hand. Mechanical properties and water resistance, and by adding water, glycerin and polyethylene glycol, the overall mechanical properties and processing properties are improved, and then a biodegradable plastic with ideal comprehensive properties is obtained. The biodegradable plastic has good biodegradable properties , mechanical properties and processing performance, low production cost, safe and pollution-free.

2. The preparation method of the biodegradable plastic provided by the present invention is simple in process, easy to process, low in cost, and has broad application prospects.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Both polylactic acid plastic and soybean protein plastic have good biodegradability, but the production cost of polylactic acid plastic is high, and soybean protein plastic has high hardness, high brittleness and poor water resistance. The present invention prepares biodegradable plastics by blending polylactic acid, soybean protein powder and soybean powder. On the one hand, the production cost of polylactic acid plastics can be reduced, and on the other hand, the mechanical properties and water resistance of soybean protein plastics can be improved. Add water, glycerin and polyethylene glycol to improve the overall mechanical properties and processing properties, and then obtain biodegradable plastics with ideal comprehensive properties.

The invention provides a biodegradable plastic, which is mainly made of the following raw materials in parts by weight: 80-120 parts of polylactic acid particles, 40-60 parts of soybean protein powder, 40-60 parts of soybean powder, and 55-75 parts of water , 15-30 parts of glycerin, 15-25 parts of polyethylene glycol, and optional auxiliary agents.

Polylactic acid (PLA), also known as polylactide, belongs to the family of polyesters. Polylactic acid is a polymer obtained by polymerizing lactic acid as the main raw material. The source of raw material is sufficient and renewable, the production process is pollution-free, and the product is biodegradable. Polylactic acid is made from starch raw materials extracted from renewable plant resources such as corn, wheat, sugarcane and other natural crops. The raw materials can be fermented into lactic acid, and then chemically synthesized to obtain polylactic acid. Polylactic acid is fully biodegradable under composting conditions, is a completely green material, and is considered to be the most competitive renewable plastic.

In the present invention, the typical but non-limiting content of polylactic acid particles in parts by weight is: 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, 110 parts, 115 parts or 120 parts.

Soybean protein powder is a protein powder obtained by extracting soybeans through a series of processing steps. Soybean flour, which is made from soybeans, is also rich in soy protein, with a content of up to 40%. Soybean protein is a molecule composed of one or more polypeptide chains combined in their own special way. It contains a variety of active side groups such as amino, carboxyl and hydroxyl groups, which can chemically react with many substances and have specific primary structures and advanced spatial structures. . Soybean protein is a kind of biodegradable polymer, which is renewable and low in cost. The plastics produced have the advantages of excellent mechanical properties, water resistance and biodegradability. In addition, soybean flour also contains natural polymers such as cellulose and starch, which can improve the toughness of the material through hydrogen bonding.

In the present invention, the typical but non-limiting content of soybean protein powder in parts by weight is: 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 parts, 49 parts , 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60.

In the present invention, in parts by weight, the typical but non-limiting content of soybean flour is: 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 parts, 49 parts, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 or 60.

The purpose of polymer blending modification is to comprehensively balance the properties of the polymer components, learn from each other, eliminate the weaknesses in the performance of each single component, and improve the performance of the material. Blending polylactic acid particles with soybean powder and soybean protein powder to prepare biodegradable plastics can reduce the production cost of polylactic acid plastics on the one hand, and improve the mechanical properties and water resistance of soybean protein plastics on the other hand.

Glycerin, also known as glycerol. On the one hand, the polar group of glycerin interacts with the polar group of the polymer molecule to make the polymer swell, and the non-polar part of the glycerol shields the polarity of the polymer molecule and increases the size of the macromolecule. The distance between starch molecules and hydroxyl groups penetrate into starch molecules to form a physical and chemical interaction, which reduces the amount of original hydroxyl groups in the system, thereby gradually reducing the water absorption rate of the material. On the other hand, glycerin can effectively penetrate between polylactic acid and protein molecules, reduce the force between polylactic acid and protein molecules, have a plasticizing effect on polylactic acid and protein molecules, and improve the toughness and ductility of materials. Therefore, adding glycerin to plastics can reduce the water absorption rate of plastic products and increase the tensile strength of plastic products at the same time.

In the present invention, by weight, the typical but non-limiting content of glycerol is: 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts servings, 26 servings, 27 servings, 28 servings, 29 servings or 30 servings.

Water contains hydroxyl groups, which can enter between polylactic acid molecules or protein molecules, weaken the intermolecular force, improve the melt flow performance, and reduce the brittleness of the final product, thereby improving the toughness and ductility of the material, and changing accordingly. Mechanical properties and processing properties of materials.

In the present invention, by weight, the typical but non-limiting content of water is: 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, 60 parts, 61 parts, 62 parts, 63 parts, 64 parts, 65 parts parts, 66 parts, 67 parts, 68 parts, 69 parts, 70 parts, 71 parts, 72 parts, 73 parts, 74 parts or 75 parts.

Polyethylene glycol can reduce the melting temperature of polylactic acid particles. Since the melting temperature of polylactic acid is higher than that of soybean protein, adding polyethylene glycol can adjust the melting temperature of polylactic acid, so that polylactic acid particles, soybean protein powder and soybean powder can be better melt blended, and at the same time reduce the processing temperature . Moreover, polyethylene glycol can also reduce the degradation of soybean protein at high temperature. Polyethylene glycol also has a certain plasticizing effect. In addition, polyethylene glycol can also be used as a lubricant to facilitate the extrusion of plastics.

In the present invention, the typical but non-limiting content of polyethylene glycol in parts by weight is: 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts servings or 25 servings.

The present invention selects polylactic acid, soybean protein powder and soybean powder as basic raw materials, and at the same time water, glycerin and polyethylene glycol improve the overall mechanical properties and processing properties, so that the prepared biodegradable plastics have good biodegradability Performance, its waste can be completely decomposed into low-molecular compounds under the action of microorganisms, avoiding environmental pollution, and at the same time has good mechanical properties and processing properties, low production cost, safe and pollution-free.

In order to better increase the biodegradable plastic of the present invention, additives can be added to the raw materials.

In an optional embodiment of the present invention, the auxiliary agent includes one or a combination of at least two of a coupling agent, a reducing agent or an antibacterial agent, such as a coupling agent, a reducing agent, an antibacterial agent, a coupling agent and Combination of reducing agent, combination of coupling agent and antibacterial agent, combination of reducing agent and antibacterial agent, combination of coupling agent, reducing agent and antibacterial agent.

In an optional embodiment of the present invention, the auxiliary agents are 6-9 parts of coupling agent, 0.5-1.5 parts of reducing agent and 0.5-1.5 parts of antibacterial agent.

The coupling agent can make the polylactic acid particles and the protein disperse easily, reduce the interfacial tension between the two components, and increase the compatibility. In an optional embodiment of the present invention, the coupling agent is phthalic anhydride or maleic anhydride. Phthalic anhydride or maleic anhydride can cause the dissociation of the subunits of the protein molecule, making the molecule stretch and increase the flexibility. to reduce water absorption. In a preferred embodiment of the present invention, the coupling agent is phthalic anhydride.

In an optional embodiment of the present invention, the reducing agent can reduce disulfide bonds in protein molecules or polypeptide molecules to form sulfhydryl groups (-SH groups), and can also be used to improve the solubility and emulsification properties of soybean protein. In an alternative embodiment of the present invention, the reducing agent is sulfite or bisulfite. In a preferred embodiment of the present invention, the reducing agent is sodium bisulfite.

Antimicrobial agents can inhibit microbial pathogenic bacteria during plastic processing and increase the safety of plastic use.

In an alternative embodiment of the present invention, the antibacterial agent is potassium sorbate or sodium benzoate. In a preferred embodiment of the present invention, the antibacterial agent is potassium sorbate.

In an optional embodiment of the present invention, the biodegradable plastic is mainly made of the following raw materials in parts by weight: 90-110 parts of polylactic acid particles, 45-55 parts of soybean protein powder, 45-55 parts of soybean powder, 60 parts of water -70 parts, 20-25 parts of glycerin, 18-22 parts of polyethylene glycol, 7-8 parts of phthalic anhydride, 0.8-1.2 parts of sodium bisulfite and 0.8-1.2 parts of potassium sorbate.

In a preferred embodiment of the present invention, the biodegradable plastic is mainly made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 65 parts of water, and 22.5 parts of glycerin , 20 parts of polyethylene glycol, 7.5 parts of phthalic anhydride, 1 part of sodium bisulfite and 1 part of potassium sorbate.

The present invention selects polylactic acid, soybean protein powder and soybean powder as basic raw materials, and at the same time water, glycerin and polyethylene glycol improve the overall mechanical properties and processing properties, so that the prepared biodegradable plastics have good biodegradability Performance, its waste can be completely decomposed into low-molecular compounds under the action of microorganisms, avoiding environmental pollution, and at the same time has good mechanical properties and processing properties, low production cost, safe and pollution-free.

It should be noted that the good degradable performance, mechanical properties and processing performance of the biodegradable plastic of the present invention are determined by its specific raw material components and proportions. If the components and their proportions are not coordinated with each other, a single The beneficial effects brought by the components are likely to be reduced or even eliminated by other components, and the overall comprehensive effect cannot be achieved. Through a lot of research and repeated verification, the present invention has obtained the optimal combination and ratio of biodegradable plastics, so that multiple components are integrated and coordinated with each other to produce positive synergies, and can make the final biodegradable plastic Plastic, with good degradability, mechanical properties and processing properties.

The invention also provides a preparation method of the biodegradable plastic, which comprises the following steps: kneading, extruding and granulating the mixture of various raw materials in sequence to obtain the biodegradable plastic.

The preparation method of the biodegradable plastic of the present invention includes the process steps of mixing materials, kneading and extruding, and the process is simple, easy to process and low in cost.

In an optional embodiment of the present invention, the raw materials are firstly mixed, and when the temperature of the mixture rises to 100-105° C., the mixture of the raw materials is kept for 8-15 minutes.

In a preferred embodiment of the present invention, first put soybean protein powder, soybean powder, water, glycerin and additives into the mixer, add polylactic acid particles and polyethylene glycol after heating to 50°C, and wait for the mixture to When the temperature was raised to 102°C, a mixture of the raw materials was obtained after holding the temperature for 10 minutes. Since the melting temperature of polylactic acid particles is higher than that of soybean protein powder and soybean powder, adding polyethylene glycol while adding polylactic acid particles can reduce the melting temperature of polylactic acid, so that various substances can be blended better.

In an optional embodiment of the present invention, the rotation speed of the mixer is 400-500 rpm. Typical but non-limiting speeds of the mixer are: 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, 460 rpm, 470 rpm min, 480 rpm, 490 rpm or 500 rpm. In a preferred embodiment of the present invention, the rotation speed of the mixer is 450 rpm. Within the rotational speed range provided by the invention, the materials are blended evenly and the time is short.

In an alternative embodiment of the present invention, the kneading temperature is 105-115°C. Typical but non-limiting kneading temperatures are: 105°C, 106°C, 107°C, 108°C, 109°C, 110°C, 111°C, 112°C, 113°C, 114°C or 115°C. In a preferred embodiment of the present invention, the temperature during kneading is 110°C. The kneading temperature has a certain influence on the molding of plastics. The higher the temperature, the easier it is for the reaction raw materials to agglomerate or agglomerate, and it is not easy to disperse evenly.

In an optional embodiment of the present invention, an extruder is used for extrusion granulation, and the temperature at the feeding port of the extruder is 90-110°C. Typical but non-limiting temperatures at the feed port of the extruder are: 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C or 110°C. In a preferred embodiment of the present invention, the temperature at the feeding port of the extruder is 100°C. If the temperature of the feeding port is too low, the raw materials cannot enter the extruder smoothly; if the temperature of the feeding port is too high, the raw materials are not easy to form.

In an optional embodiment of the present invention, the temperature in the middle compression zone is 120-135°C. Typical but non-limiting temperatures in the central compression zone are: 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, 131°C, 132°C, 133°C, 134°C or 135°C. In a preferred embodiment of the present invention, the temperature in the middle compression zone is 128°C. The temperature in the central compression zone is too low, the melt viscosity is high, and it is not easy to compress and form; the temperature in the central compression zone is too high, and the stability of raw material molding is poor.

In an optional embodiment of the present invention, the temperature in the extrusion molding zone is 90-110°C. Typical but non-limiting temperatures in the extrusion molding zone are: 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C , 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C or 110°C. In a preferred embodiment of the present invention, the temperature in the extrusion molding zone is 100°C. When the temperature in the forming area is low, the plasticization is not complete, and when the temperature in the forming area is high, it is easy to age.

In an optional embodiment of the present invention, the screw speed of the extruder is 250-350 rpm. Typical but non-limiting screw speed temperatures for extruders are: 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, 300 rpm, 310 rpm, 320 rpm RPM, 330 RPM, 340 RPM or 350 RPM. In a preferred embodiment of the present invention, the screw speed of the extruder is 300 rpm. Screw speed is an important parameter to control extrusion rate and output. The screw speed of the extruder increases, and the output increases; but the screw speed is too high, the motor load is too large, the melt pressure is too high, the shear rate is too high, the die expansion is increased, the surface is deteriorated, and the extrusion volume is unstable .

The preparation method of the biodegradable plastic provided by the invention has the advantages of simple process, easy processing, low cost and wide application prospect.

The present invention will be specifically explained below in conjunction with specific embodiments.

Example 1

The biodegradable plastic of Example 1 is made from the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 65 parts of water, 22.5 parts of glycerin and 20 parts of polyethylene glycol .

Example 2

The biodegradable plastic of Example 2 is made from the following raw materials in parts by weight: 90 parts of polylactic acid particles, 55 parts of soybean protein powder, 45 parts of soybean powder, 70 parts of water, 20 parts of glycerin and 22 parts of polyethylene glycol .

Example 3

The biodegradable plastic of Example 3 is made from the following raw materials in parts by weight: 110 parts of polylactic acid particles, 45 parts of soybean protein powder, 55 parts of soybean powder, 60 parts of water, 25 parts of glycerin and 18 parts of polyethylene glycol .

Example 4

The biodegradable plastic of Example 4 is made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 65 parts of water, 22.5 parts of glycerin and 20 parts of polyethylene glycol , 7.5 parts of phthalic anhydride, 1 part of sodium bisulfite and 1 part of potassium sorbate.

Example 5

The biodegradable plastic of Example 5 is made of the following raw materials in parts by weight: 80 parts of polylactic acid particles, 60 parts of soybean protein powder, 40 parts of soybean powder, 75 parts of water, 15 parts of glycerin, and 25 parts of polyethylene glycol , 6 parts of maleic anhydride, 1.5 parts of sodium bisulfite and 0.5 parts of potassium sorbate.

Example 6

The biodegradable plastic of Example 6 is made of the following raw materials in parts by weight: 120 parts of polylactic acid particles, 40 parts of soybean protein powder, 60 parts of soybean powder, 55 parts of water, 30 parts of glycerin, and 15 parts of polyethylene glycol , 9 parts of phthalic anhydride, 0.5 parts of sodium sulfite and 1.5 parts of sodium benzoate.

Example 7

The preparation method of the biodegradable plastic of embodiment 7, comprises the steps:

(a) Mixing: first put soybean protein powder, soybean powder, water, glycerin and additives into the mixer, keep the speed of the mixer at 450 rpm, heat to 50°C and add polylactic acid particles and Polyethylene glycol, when the temperature of the mixture rises to 102°C, after 10 minutes of heat preservation, a mixture of the raw materials is obtained;

(b) kneading: the mixed material obtained in step (a) is sent into a kneader, and the mixed material is kneaded at 110°C;

(c) Extrusion: Send the kneaded mixture into the extruder, set the temperature at the feeding port of the extruder to 100°C, the temperature in the middle compression zone to 128°C, and the temperature in the extrusion molding zone to 100°C, and keep the speed Be 300 rev/mins, make granule, promptly obtain biodegradable plastics.

The biodegradable plastics of Examples 1-6 were all prepared according to the preparation method of Example 7.

Example 8

The preparation method of the biodegradable plastic of embodiment 8, comprises the steps:

(a) Mixing: first put soybean protein powder, soybean powder, water, glycerin, and additives into the mixer, keep the speed of the mixer at 400 rpm, heat to 45°C, and then add polylactic acid particles and Polyethylene glycol, when the temperature of the mixture rises to 100°C, after 15 minutes of heat preservation, a mixture of various raw materials is obtained;

(b) kneading: the mixed material obtained in step (a) is sent into a kneader, and the mixed material is kneaded at 1°C;

(c) Extrusion: Send the kneaded mixture into the extruder, set the temperature at the feeding port of the extruder to 90°C, the temperature in the middle compression zone to 120°C, and the temperature in the extrusion molding zone to 90°C, and keep the speed Be 250 rev/mins, make granule, promptly obtain biodegradable plastics.

Example 9

The preparation method of the biodegradable plastic of embodiment 9, comprises the steps:

(a) Mixing: first put soybean protein powder, soybean powder, water, glycerin, polylactic acid particles, polyethylene glycol and additives into the mixer, keep the speed of the mixer at 500 rpm, and wait for the mixture to When the temperature rises to 105°C, after 8 minutes of heat preservation, the mixture of each raw material;

(b) kneading: the mixed material obtained in step (a) is sent into a kneader, and the mixed material is kneaded at 115°C;

(c) Extrusion: Send the kneaded mixture into the extruder, set the temperature at the feeding port of the extruder to 110°C, the temperature in the middle compression zone to 130°C, and the temperature in the extrusion molding zone to 110°C, and keep the speed Be 350 rev/mins, make granule, promptly obtain biodegradable plastics.

Comparative example 1

The biodegradable plastic of Comparative Example 1 is made of the following raw materials in parts by weight: 60 parts of polylactic acid particles, 80 parts of soybean protein powder, 80 parts of soybean powder, 50 parts of water, 10 parts of glycerin and 30 parts of polyethylene glycol .

Comparative example 2

The biodegradable plastic of Comparative Example 2 is made of the following raw materials in parts by weight: 150 parts of polylactic acid particles, 30 parts of soybean protein powder, 30 parts of soybean powder, 80 parts of water, 40 parts of glycerin and 10 parts of polyethylene glycol .

Comparative example 3

The difference between Comparative Example 3 and Example 1 is that it does not contain polylactic acid particles.

Comparative example 4

The difference between Comparative Example 4 and Example 1 is that it does not contain soybean protein powder and soybean powder.

Comparative example 5

The difference between Comparative Example 5 and Example 1 is that it does not contain soybean protein powder.

Comparative example 6

The difference between Comparative Example 6 and Example 1 is that it does not contain soybean flour.

Comparative example 7

The biodegradable plastic of Comparative Example 7 is made of the following raw materials in parts by weight: 40 parts of polylactic acid particles, 80 parts of soybean protein powder, 70 parts of soybean powder, 65 parts of water, 22.5 parts of glycerin and 20 parts of polyethylene glycol .

Comparative example 8

The difference between Comparative Example 8 and Example 1 is that it does not contain glycerin.

Comparative example 9

The difference between Comparative Example 9 and Example 1 is that it does not contain water.

Comparative example 10

The difference between Comparative Example 10 and Example 1 is that it does not contain polyethylene glycol.

Comparative example 11

The biodegradable plastic of Comparative Example 11 is made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 80 parts of water, 22.5 parts of glycerin and 20 parts of polyethylene glycol .

Comparative example 12

The biodegradable plastic of Comparative Example 12 is made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 65 parts of water, 60 parts of glycerin and 20 parts of polyethylene glycol .

Comparative example 13

The biodegradable plastic of Comparative Example 13 is made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean powder, 65 parts of water, 22.5 parts of glycerin and 50 parts of polyethylene glycol .

The degradable plastics described in Comparative Examples 1-13 were prepared by the preparation method of the degradable plastics described in Example 7.

Test case

(1) Water immersion test

Make the biodegradable plastic sample material into strips with a length of 76.2mm, a width of 25.4mm, and a height of 3.2mm, and put the sample in a drying oven for drying at 50°C. After drying for 24 hours, take it out and store it at room temperature. Cool at (20-25°C) and perform initial weighing; then immerse in distilled water, weigh again after soaking for 24 hours, record the weight change, and calculate the water absorption rate. When weighing, you need to wipe off the moisture on the surface, dry the water and The weighing process should not exceed 2 minutes.

(2) tensile test

The tensile strength test uses the ASTM638 standard. The biodegradable plastic sample material is made into strips with a length of 165mm, a width of 12.7mm and a thickness of 3.2mm. The tensile speed is 50mm/min. During the stretching process, the specimen Stretch until it breaks, record the maximum tensile force and the change in length after breaking, and calculate the tensile strength and elongation at break.

(3) Biodegradation rate of sample material

Using the method of soil burial, measure the mass loss of the sample material after 30 days and 60 days, and calculate the biodegradation rate of the sample material.

The test results are shown in Table 1.

Table 1 Test results

As can be seen from Table 1, the tensile strength of the biodegradable plastics provided by Examples 1-6 is more than 11MPa, the elongation at break is more than 140%, and the water absorption is lower than 4%. The degradation rate was higher than 28%, and the 60-day biodegradation rate of the sample material was higher than 68%. At the same time, the study also found that under the action of microorganisms, the biodegradable plastic of the present invention can be completely degraded into low-molecular compounds within 3-6 months to avoid environmental pollution.

Through the comparison of Comparative Examples 1-13 and Example 1, it is found that the tensile strength of Comparative Examples 1-6 is far lower than that of Example 1, the elongation at break is far lower than that of Example 1, and the water absorption is much higher than that of Example 1. , the biodegradation rate of sample material 30 days and 60 days is all lower than embodiment 1, and the mechanical properties of biodegradable plastics, water resistance and biodegradability depend on raw material component and proportioning, it can be seen that the biodegradable plastic provided by the present invention Plastic has good mechanical properties, water resistance and biodegradability, and is a biodegradable plastic with ideal comprehensive properties. By comparison of Comparative Examples 3-7 and Example 1, it can be seen that the blending of polylactic acid, soybean protein powder and soybean powder can significantly improve the tensile strength of biodegradable plastics, reduce water absorption, and improve biodegradation. Performance, the ratio of polylactic acid, soybean protein powder and soybean powder also has a great influence on the tensile strength, water absorption and biodegradability of biodegradable plastics. By comparing Examples 8-13 with Example 1, it can be seen that water, glycerin and polyethylene glycol also have a greater impact on the tensile strength, water absorption and biodegradability of biodegradable plastics.

In summary, the biodegradable plastic with the raw material composition and ratio provided by the present invention has mechanical properties, water resistance and biodegradability, and is a biodegradable plastic with relatively ideal comprehensive properties.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. A biodegradable plastic, characterized in that it is mainly made of the following raw materials in parts by weight: 80-120 parts of polylactic acid particles, 40-60 parts of soybean protein powder, 40-60 parts of soybean powder, 55-55 parts of water 75 parts, 15-30 parts of glycerin, 15-25 parts of polyethylene glycol, and optional auxiliary agents. 2. The biodegradable plastic according to claim 1, characterized in that it is mainly made of the following raw materials in parts by weight: 90-110 parts of polylactic acid particles, 45-55 parts of soybean protein powder, 45-55 parts of soybean powder 60-70 parts of water, 20-25 parts of glycerin, 18-22 parts of polyethylene glycol, and optional auxiliary agents; Preferably, it is mainly made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean flour, 65 parts of water, 22.5 parts of glycerin, 20 parts of polyethylene glycol, and optionally Auxiliary. 3. The biodegradable plastic according to claim 1, characterized in that, the auxiliary agent includes one or a combination of at least two of a coupling agent, a reducing agent or an antibacterial agent, preferably a coupling agent, a reducing agent A combination of agent and antibacterial agent, more preferably 6-9 parts of coupling agent, 0.5-1.5 parts of reducing agent and 0.5-1.5 parts of antibacterial agent. 4. The biodegradable plastic according to claim 3, wherein the coupling agent is phthalic anhydride or maleic anhydride, preferably phthalic anhydride; And/or, the reducing agent is sulfite or bisulfite, preferably bisulfite, more preferably sodium bisulfite; And/or, the antibacterial agent is an organic antibacterial agent, preferably potassium sorbate or sodium benzoate, more preferably potassium sorbate. 5. The biodegradable plastic according to claim 1, characterized in that it is mainly made of the following raw materials in parts by weight: 90-110 parts of polylactic acid particles, 45-55 parts of soybean protein powder, 45-55 parts of soybean powder 60-70 parts of water, 20-25 parts of glycerin, 18-22 parts of polyethylene glycol, 7-8 parts of phthalic anhydride, 0.8-1.2 parts of sodium bisulfite and 0.8-1.2 parts of potassium sorbate; Preferably, it is mainly made of the following raw materials in parts by weight: 100 parts of polylactic acid particles, 50 parts of soybean protein powder, 50 parts of soybean flour, 65 parts of water, 22.5 parts of glycerin, 20 parts of polyethylene glycol, 7.5 parts of phthalic anhydride, 1 part sodium bisulfite and 1 part potassium sorbate. 6. A preparation method of the biodegradable plastic according to any one of claims 1-5, characterized in that, comprising the following steps: The mixture of raw materials is sequentially kneaded, extruded and granulated to obtain biodegradable plastics. 7. The preparation method according to claim 6, wherein the raw materials are firstly mixed, and when the temperature of the mixture rises to 100-105° C., the mixture of the raw materials is obtained after being kept warm for 8-15 minutes; Preferably, first put soybean protein powder, soybean powder, water, glycerin and additives into a mixer, heat to 45-55°C, add polylactic acid particles and polyethylene glycol, and wait until the temperature of the mixture rises to 100-105 At ℃, after insulated for 8-15 minutes, the mixture of each raw material is obtained; More preferably, put soybean protein powder, soybean powder, water, glycerin and additives into the mixer, heat to 50°C, add polylactic acid particles and polyethylene glycol, and when the temperature of the mixture rises to 102°C, After 10 minutes of incubation, a mixture of the raw materials was obtained. 8. preparation method according to claim 7, is characterized in that, in each raw material mixing process, the rotating speed of mixer is 400-500 rev/min, is preferably 420-480 rev/min, is more preferably 450 rev/min point. 9. The preparation method according to claim 6, characterized in that the kneading temperature is 105-115°C, preferably 108-112°C, more preferably 110°C. 10. The preparation method according to claim 6, characterized in that an extruder is used for extrusion granulation, and the temperature at the feeding port of the extruder is 90-110° C., preferably 95-105° C., more preferably 100° C. ℃; And/or, the temperature in the middle compression zone is 120-135°C, preferably 125-130°C, more preferably 128°C; And/or, the extrusion molding zone temperature is 90-110°C, preferably 95-105°C, more preferably 100°C; And/or, the screw speed of the extruder is 250-350 rpm, preferably 280-320 rpm, more preferably 300 rpm.