Biomass degradable foaming film bag and preparation method thereof

Abstract

The invention discloses a biomass degradation foaming film bag and a preparation method thereof. The biomass degradable foaming film bag comprises the following components in parts by weight: 100 parts of a degradable polymer, 10-30 parts of a biomass foaming agent, 1-10 parts of an auxiliary foaming agent and 1-5 parts of a surface modifier, wherein the raw materials of the biomass foaming agent comprise biomass straws and sodium silicate. According to the invention, a self-developed biomass foaming agent is added into a degradable polymer matrix, and a simple double-screw melt extrusion processing mode is matched, so that the physical foaming process of water molecule volatilization can be completed, the quantity of generated bubbles is sufficient, and bubble holes are not easy to collapse; further, on the premise that the mechanical property of the biomass degradable foaming film bag is guaranteed, the product density is reduced, the resource utilization rate is increased, and compared with a traditional foaming agent, the used biomass foaming agent better meets the requirements for environmental protection and energy conservation and has important significance for replacing the traditional foaming agent.

Description

Technical Field

[0001] The present invention relates to the technical field of fully biodegradable films, and more specifically, to a biomass degradable foaming film bag and a preparation method thereof. Background Art

[0002] Plastic pollution is becoming increasingly serious, and biodegradable plastics have come into being. However, the price of degradable raw materials is too high, resulting in the price of degradable film bags being more than twice that of non-degradable film bags, which in turn affects market promotion and application. In previous research, in order to reduce the cost of biodegradable film bag products, cheap components are often added to the polymer matrix to partially replace high-cost biodegradable plastics, sacrificing mechanical properties and other usability to reduce costs. For this reason, how to effectively reduce costs without affecting performance remains a hot issue for researchers.

[0003] Foaming the material can not only maintain the mechanical properties, but also reduce the specific gravity, thereby reducing the cost, and has better thermal insulation and elastic buffering functions. Traditional foam plastics are made of non-renewable petroleum derivatives, such as polyethylene, polypropylene, etc. Although they are widely used, they are directly harmful to the environment due to their non-degradability and the large amount of toxic and harmful gases produced during incineration. The development of new biodegradable foam materials has become the key. In the current preparation process of foam materials, they are mainly achieved by three methods: physical foaming, chemical foaming and stirring foaming. The foaming agents used are often petroleum-based small molecule compounds (such as butane) and cross-linking agents. There are almost no reports on the foaming of more environmentally friendly biomass straw. This is because on the one hand, the technology of foaming by the volatilization of water molecules in biomass straw is not easy to control, and on the other hand, the stability of the bubble pores is not good and easy to collapse, thereby limiting its development in the field of foam materials. However, from the perspective of green, biodegradable, recyclable and renewable, it is of great significance to develop biomass foam materials to replace traditional foam plastics. Summary of the invention

[0004] One object of the present invention is to provide a biodegradable foaming film bag. By adding a biomass foaming agent formed by the reaction of biomass straw and sodium silicate into a degradable polymer, and cooperating with a simple twin-screw melt extrusion processing method, a physical foaming process of water molecule volatilization can be completed, wherein the cellulose, lignin and sodium silicate in the biomass foaming agent jointly support the bubble holes formed inside the material and are not easy to collapse, so that the obtained biomass degradable foaming film bag has the characteristics of low cost, low density, environmental protection, energy saving, good mechanical properties, etc.

[0005] Another object of the present invention is to provide a method for preparing the biomass degradable foaming film bag as described above. The preparation method is based on a physical foaming method, is easy to operate, and the entire preparation process is safe, environmentally friendly, and energy-saving.

[0006] In order to achieve the first object, the present invention discloses a biomass degradable foam film bag, which comprises

[0007]

[0008] Wherein, the raw materials of the biomass foaming agent include biomass straw and sodium silicate.

[0009] The present invention adopts a physical foaming process, which directly utilizes the internal and external pressure difference when the water contained in the material is extruded at the die head of the twin-screw extruder, and instantly vaporizes to form bubbles. The cellulose, lignin and sodium silicate in the biomass straw jointly support the bubble holes formed inside the material and are not easy to collapse.

[0010] Further, the weight ratio of the biomass straw to the sodium silicate is 100:5-15; illustratively, the weight ratio of the biomass straw to the sodium silicate can be 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100:13, 100:14, 100:15, etc. Studies have shown that if only biomass straw is added without sodium silicate, or the amount of sodium silicate introduced is too small, the strengthening effect of cellulose and lignin in the biomass straw is not enough to achieve the effect of bubble pore strength.

[0011] Furthermore, the components of the biomass straw include cellulose, hemicellulose, lignin, protein, minerals, etc. Among them, cellulose and hemicellulose are the main components of the straw, accounting for more than 70% of the total mass. Cellulose is an undigested carbohydrate composed of multiple glucose molecules and is an important raw material for maintaining the operation of the digestive system of animals. Hemicellulose includes xylan, oligofructose, xylooligosaccharide, etc., which are commonly used food additives in various food processing processes. In addition to cellulose and hemicellulose, the straw also contains a large amount of lignin, which is one of the main components of plant cell walls and is a water-insoluble organic compound that can enhance the structural strength of plant cells. In the foaming material, cellulose and lignin can both play a supporting role in the bubble pores. Therefore, in the present invention, the biomass straw can be used as a biomass filler and as a foaming agent component to prepare a degradable product with a controllable foaming ratio, thereby reducing the specific gravity of the degradable product to achieve the purpose of reducing costs, and the foaming film has better thermal insulation and elastic buffering functions. In a specific embodiment, the biomass straw includes but is not limited to ultrafine powder of one or more biomass materials such as reed straw, corn straw, cotton straw, peanut straw, wheat straw, rice straw, tree branches and leaves, and coconut palm materials, with a D90 of 300-800 mesh and a moisture content controlled at 5-30%.

[0012] The sodium silicate introduced in the present invention can improve the consistency of the degradable polymer matrix after encountering the moisture in the biomass straw, and on the other hand, form silicate crystals in the degradable polymer matrix to improve the strength of the degradable polymer matrix. The above two aspects work together to improve the strength of the bubble pores and the stable retention time. In a specific embodiment, the sodium silicate includes but is not limited to one or more of zero-hydrate sodium metasilicate, pentahydrate sodium metasilicate and nonahydrate sodium metasilicate.

[0013] Furthermore, the degradable polymer includes but is not limited to one or more of polybutylene adipate-terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate-adipate (PBSA), polyvinyl alcohol (PVA), polylactic acid (PLA), polyglycolic acid (PGA), and polycaprolactone (PCL).

[0014] Furthermore, the bubble pore size of the biomass-degradable foaming film bag is 2-8 μm, the foaming ratio is 2-4 times, the tensile strength is greater than 20 MPa, and the elongation at break is greater than 250%.

[0015] The foaming agent is a substance that has the function of regulating the foaming agent of biomass, can increase the fluidity of the material, and improve the uniformity of the bubble pores. In a specific embodiment, the foaming agent includes but is not limited to one or more of mica, talc, hydrotalcite, glass microspheres, calcium carbonate, calcium oxide, calcium hydroxide, magnesium hydroxide, zinc oxide, aluminum oxide, silicon dioxide, zinc borate, barium sulfate, sodium sulfate, wollastonite, kaolin, chlorite, and serpentine.

[0016] Furthermore, the surface modifier includes, but is not limited to, one or more of oleamide, erucamide, calcium stearate, zinc stearate, stearic acid amide, and N,N'-ethylenebisstearamide.

[0017] Further, the raw material of the biomass foaming agent is pretreated to obtain the biomass foaming agent, wherein the pretreatment process is as follows:

[0018] The biomass straw and sodium silicate are mixed evenly according to a certain proportion to obtain a biomass foaming agent reaction raw material;

[0019] Under stirring, the raw materials of the biomass foaming agent reaction are heated to 85-90°C, and the stirrer is sealed and stirred for 2-5 hours. The carboxyl, hydroxyl and water in the straw will react with the sodium silicate, and then the top cover of the stirrer is opened, and stirring is continued under heating to evaporate part of the water vapor. When the water content of the material in the stirrer reaches 2-5%, the heating and stirring are stopped, and the biomass foaming agent is obtained after natural cooling. If the water content of the material in the stirrer exceeds 5%, the foaming amount will be too large, the bubble hole size will be larger, and the film bag will be prone to holes. If the water content of the material in the stirrer is too low, it will be difficult to foam.

[0020] In order to achieve the second object, the present invention discloses a method for preparing the biomass degradable foam film bag as described above, comprising the following steps:

[0021] S1: adding 100 parts by weight of a degradable polymer, 10-30 parts by weight of a biomass foaming agent, 1-10 parts by weight of an auxiliary foaming agent and 1-5 parts by weight of a surface modifier into a stirrer, mixing at room temperature for 10-30 minutes, then heating to 80-120° C. and continuing to mix for 20-30 minutes to obtain a premix;

[0022] When mixing at room temperature, the stirring speed is relatively low, generally 100-120 rpm. When the temperature is raised to 80-120°C, the stirring speed can be increased to 500-600 rpm.

[0023] S2: adding the premix to a twin-screw extruder, and performing melt extrusion at a screw speed of 60-90 rpm and 120-150° C. to obtain a special material for biomass-degradable foaming film bags;

[0024] S3: Using a film blowing machine to blow film on the special material for biomass degradable foaming film bags, at a screw speed of 15-30 rpm and a film blowing temperature of 155-180° C., to prepare biomass degradable foaming film bags.

[0025] Furthermore, in step S2, when the twin-screw extruder is running, the screw speed is 70-80 rpm and the melt extrusion temperature is 130-140°C.

[0026] Furthermore, in step S3, when the film blowing machine is running, the screw speed is 20-25 rpm and the film blowing temperature is 160-170°C.

[0027] The beneficial effects of the present invention are as follows:

[0028] The present invention discloses a biomass degradable foaming film bag. By adding a self-developed biomass foaming agent (biomass straw + sodium silicate) into a degradable polymer matrix and cooperating with a simple twin-screw melt extrusion processing method, the physical foaming process of water molecule volatilization can be completed, so that the amount of bubbles generated is sufficient and the bubble holes are not easy to collapse, thereby reducing the product density and improving the resource utilization rate under the premise of ensuring the mechanical properties of the biomass degradable foaming film bag. In addition, the biomass foaming agent selected by the present invention is more environmentally friendly and energy-saving than traditional foaming agents. When pretreating the biomass foaming agent raw material, it is found that when the water content of the stirred and mixed material is 2-5%, it is conducive to obtaining bubbles with moderate foaming amount and moderate bubble hole size, reducing the problem of film bag holes or insufficient foaming amount.

[0029] The present invention also provides a method for preparing a biomass-degradable foaming film bag. The preparation method is based on a physical foaming method, is easy to operate, and the entire preparation process is safe, environmentally friendly, and energy-saving, which is of great significance for replacing traditional foam materials. DETAILED DESCRIPTION

[0030] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0031] Unless otherwise specified, the raw materials used in the present invention can be obtained commercially. Any range recorded in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0032] Example 1

[0033] The biodegradable foam film bag is composed of the following components by weight:

[0034]

[0035] The raw materials of the biomass foaming agent are composed of reed stalks and sodium silicate in a weight ratio of 100:12;

[0036] The biomass degradable foam film bag is prepared according to the following steps:

[0037] S1: mixing reed stalks and sodium silicate in a weight ratio of 100:12 to obtain a biomass foaming agent reaction raw material;

[0038] S2: heating the obtained biomass foaming agent reaction raw material to 85°C under stirring, sealing the stirrer, stirring and reacting for 5 hours, then opening the stirrer cover, continuing to stir under heating to evaporate part of the water vapor, and stopping heating and stirring when the water content of the material in the stirrer reaches 3%, cooling naturally to obtain the biomass foaming agent;

[0039] S3: 100 parts by weight of PBAT, 10 parts by weight of the obtained biomass foaming agent, 2 parts by weight of talc and 1 part by weight of oleic acid amide are added to a stirrer, first mixed at room temperature at a speed of 100 rpm for 30 minutes, then heated to 80-120° C., and continued to mix at a speed of 500 rpm for 30 minutes to obtain a premix;

[0040] S4: adding the premix to a twin-screw extruder, and performing melt extrusion at a screw speed of 90 rpm and a temperature of 150° C. to obtain an unfoamed biomass-degradable foaming film bag special material;

[0041] S5: using a film blowing machine to blow film on the special material for biomass degradable foaming film bags, at a screw speed of 30 rpm and a film blowing temperature of 180° C., to prepare a biomass degradable foaming film bag.

[0042] Example 2

[0043] The biodegradable foam film bag is composed of the following components by weight:

[0044]

[0045] Among them, the raw materials of the biomass foaming agent are composed of corn straw and sodium silicate in a weight ratio of 100:12.

[0046] The preparation process of the biomass degradable foam film bag is the same as that in Example 1.

[0047] Example 3

[0048] The biodegradable foam film bag is composed of the following components by weight:

[0049]

[0050] Among them, the raw materials of the biomass foaming agent are composed of reed stalks and sodium silicate in a weight ratio of 100:12.

[0051] The preparation process of the biomass degradable foam film bag is the same as that in Example 1.

[0052] Example 4

[0053] The biodegradable foam film bag is composed of the following components by weight:

[0054]

[0055]

[0056] Among them, the raw materials of the biomass foaming agent are composed of reed stalks and sodium silicate in a weight ratio of 100:12.

[0057] The preparation process of the biomass degradable foam film bag is the same as that in Example 1.

[0058] Comparative Example 1

[0059] The biodegradable foam film bag is composed of the following components by weight:

[0060]

[0061] Among them, the raw material of biomass foaming agent is reed stalk.

[0062] The preparation process of the biomass degradable foam film bag is the same as that in Example 1.

[0063] Comparative Example 2

[0064] The biodegradable foam film bag is composed of the following components by weight:

[0065]

[0066] Among them, the raw materials of the biomass foaming agent are composed of reed stalks and sodium silicate in a weight ratio of 100:20.

[0067] The preparation process of the biomass degradable foam film bag is the same as that in Example 1.

[0068] Comparative Example 3

[0069] The biodegradable foam film bag is composed of the following components by weight:

[0070]

[0071] Among them, the raw materials of the biomass foaming agent are composed of reed stalks and calcium carbonate in a weight ratio of 100:12.

[0072] The preparation process of the biomass degradable foam film bag is the same as that in Example 1.

[0073] Comparative Example 4

[0074] The biodegradable foam film bag is composed of the following components by weight:

[0075]

[0076] The raw materials of the biomass foaming agent are composed of reed stalks and sodium silicate in a weight ratio of 100:12;

[0077] The biomass degradable foam film bag is prepared according to the following steps:

[0078] S1: mixing reed stalks and sodium silicate in a weight ratio of 100:12 to obtain a biomass foaming agent reaction raw material;

[0079] S2: heating the obtained biomass foaming agent reaction raw material to 85°C under stirring, sealing the stirrer, stirring and reacting for 5 hours, then opening the stirrer cover, continuing to stir under heating to evaporate part of the water vapor, and stopping heating and stirring when the water content of the material in the stirrer reaches 1%, cooling naturally to obtain the biomass foaming agent;

[0080] S3: 100 parts by weight of PBAT, 10 parts by weight of the obtained biomass foaming agent, 2 parts by weight of talc and 1 part by weight of oleic acid amide are added to a stirrer, first mixed at room temperature at a speed of 100 rpm for 30 minutes, then heated to 80-120° C., and continued to mix at a speed of 500 rpm for 30 minutes to obtain a premix;

[0081] S4: adding the premix to a twin-screw extruder, and performing melt extrusion at a screw speed of 90 rpm and a temperature of 150° C. to obtain an unfoamed biomass-degradable foaming film bag special material;

[0082] S5: using a film blowing machine to blow film on the special material for biomass degradable foaming film bags, at a screw speed of 30 rpm and a film blowing temperature of 180° C., to prepare a biomass degradable foaming film bag.

[0083] Comparative Example 5

[0084] The biodegradable foam film bag is composed of the following components by weight:

[0085]

[0086] The raw materials of the biomass foaming agent are composed of reed stalks and sodium silicate in a weight ratio of 100:12;

[0087] The biomass degradable foam film bag is prepared according to the following steps:

[0088] S1: mixing reed stalks and sodium silicate in a weight ratio of 100:12 to obtain a biomass foaming agent reaction raw material;

[0089] S2: heating the obtained biomass foaming agent reaction raw material to 85°C under stirring, sealing the stirrer, stirring and reacting for 5 hours, then opening the stirrer cover, continuing to stir under heating to evaporate part of the water vapor, and stopping heating and stirring when the water content of the material in the stirrer reaches 6%, cooling naturally to obtain the biomass foaming agent;

[0090] S3: 100 parts by weight of PBAT, 10 parts by weight of the obtained biomass foaming agent, 2 parts by weight of talc and 1 part by weight of oleic acid amide are added to a stirrer, first mixed at room temperature at a speed of 100 rpm for 30 minutes, then heated to 80-120° C., and continued to mix at a speed of 500 rpm for 30 minutes to obtain a premix;

[0091] S4: adding the premix to a twin-screw extruder, and performing melt extrusion at a screw speed of 90 rpm and a temperature of 150° C. to obtain an unfoamed biomass-degradable foaming film bag special material;

[0092] S5: using a film blowing machine to blow film on the special material for biomass degradable foaming film bags, at a screw speed of 30 rpm and a film blowing temperature of 180° C., to prepare a biomass degradable foaming film bag.

[0093] The biomass degradable foam film bags prepared in Examples 1-4 of the present invention and Comparative Examples 1-5 were subjected to performance tests, wherein the bubble pore size was measured under a scanning electron microscope (SEM), and the foaming ratio was calculated according to the formula: foaming ratio = volume after foaming / volume before foaming, the density of the sample was tested according to GB / T 6343-2009, and the mechanical properties (tensile strength and elongation at break) of the sample were tested according to GB / T 6344-2008.

[0094] Table 1 shows the test results of Examples 1-4 of the present invention and Comparative Examples 1-5: Since the thickness of the film bag is generally 20-50 μm, the property parameters of the biomass-degradable foaming film bags of Examples 1-4 all meet the requirements: bubble pore size 2-6 μm, foaming ratio 2-4 times, tensile strength > 20 MPa, and elongation at break > 250%.

[0095] In Comparative Example 1, due to the absence of sodium silicate in the biomass foaming agent, the foaming pores in the prepared biomass degradable foaming film bag are not strong enough and are prone to collapse. In Comparative Example 2, due to the excessive addition of sodium silicate, the prepared biomass degradable foaming film bag is too hard and the elongation at break is significantly reduced. In Comparative Example 3, the combined action of biomass straw and calcium carbonate is still insufficient to support the strength of the foaming pores and is prone to collapse. Comparative Examples 4 and 5 were respectively found when preparing biomass foaming agents that the water content of the biomass foaming agent should be neither too large nor too small. Too small a water content is not conducive to foaming and may even result in no foaming. Too large a water content will result in excessive foaming, which will reduce the mechanical properties of the biomass degradable foaming film bag.

[0096] Table 1 Properties of biodegradable foam film bags

[0097]

[0098] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A biomass degradable foam film bag, characterized in that: By weight, including Wherein, the raw materials of the biomass foaming agent include biomass straw and sodium silicate.

2. The biodegradable foam film bag according to claim 1, characterized in that: The weight ratio of the biomass straw to the sodium silicate is 100:5-15.

3. The biodegradable foam film bag according to claim 1, characterized in that: The biomass straw is selected from one or more ultrafine powders of reed straw, corn straw, cotton straw, peanut straw, wheat straw, rice straw, tree branches and leaves, and coconut palm materials, with a D90 of 300-800 mesh and a moisture content of 5-30%; The sodium silicate is selected from one or more of sodium metasilicate zero water, sodium metasilicate pentahydrate and sodium metasilicate nonahydrate; The degradable polymer is selected from one or more of polybutylene adipate-terephthalate, polybutylene succinate, polybutylene succinate-adipate, polyvinyl alcohol, polylactic acid, polyglycolic acid, and polycaprolactone.

4. The biodegradable foam film bag according to claim 1, characterized in that: The bubble pore size of the biomass-degradable foaming film bag is 2-8 μm, the foaming ratio is 2-4 times, the tensile strength is greater than 20 MPa, and the elongation at break is greater than 250%.

5. The biodegradable foam film bag according to claim 1, characterized in that: The auxiliary foaming agent is selected from one or more of mica, talc, hydrotalcite, glass microspheres, calcium carbonate, calcium oxide, calcium hydroxide, magnesium hydroxide, zinc oxide, aluminum oxide, silicon dioxide, zinc borate, barium sulfate, sodium sulfate, wollastonite, kaolin, chlorite, and serpentine.

6. The biodegradable foam film bag according to claim 1, characterized in that: The surface modifier is selected from one or more of oleamide, erucamide, calcium stearate, zinc stearate, stearic acid amide, and N,N'-ethylenebisstearamide.

7. The biodegradable foam film bag according to claim 1, characterized in that: The raw material of the biomass foaming agent is pretreated to obtain the biomass foaming agent, wherein the pretreatment process is as follows: The biomass straw and sodium silicate are mixed evenly according to a certain proportion to obtain a biomass foaming agent reaction raw material; Under stirring, the raw materials of the biomass foaming agent reaction are heated to 85-90°C, the stirrer is sealed, and the reaction is stirred for 2-5 hours, then the top cover of the stirrer is opened, and stirring is continued under heating to evaporate part of the water vapor. When the water content of the material in the stirrer reaches 2-5%, the heating and stirring are stopped, and the biomass foaming agent is obtained after natural cooling.

8. The method for preparing a biomass degradable foam film bag according to any one of claims 1 to 7, characterized in that: The steps include: S1: adding 100 parts by weight of a degradable polymer, 10-30 parts by weight of a biomass foaming agent, 1-10 parts by weight of an auxiliary foaming agent and 1-5 parts by weight of a surface modifier into a stirrer, mixing at room temperature for 10-30 minutes, then heating to 80-120° C. and continuing to mix for 20-30 minutes to obtain a premix; S2: adding the premix to a twin-screw extruder, and performing melt extrusion at a screw speed of 60-90 rpm and 120-150° C. to obtain a special material for biomass-degradable foaming film bags; S3: Using a film blowing machine to blow film on the special material for biomass degradable foaming film bags, at a screw speed of 15-30 rpm and a film blowing temperature of 155-180° C., to prepare biomass degradable foaming film bags.

9. The preparation method according to claim 8, characterized in that: In step S2, when the twin-screw extruder is running, the screw speed is 70-80 rpm and the melt extrusion temperature is 130-140°C.

10. The preparation method according to claim 8, characterized in that: In step S3, when the film blowing machine is running, the screw speed is 20-25 rpm and the film blowing temperature is 160-170°C.

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