A biomass-degrading foamed film pouch and a method for preparing the same

Abstract

The application discloses a biomass degradable foamed film bag and a preparation method thereof. According to weight parts, the biomass degradable foamed film bag comprises 100 parts of degradable polymer, 10-30 parts of biomass foaming agent, 1-10 parts of auxiliary foaming agent and 1-5 parts of surface modifier; wherein raw materials of the biomass foaming agent comprise biomass straw and sodium silicate. In the application, a self-developed biomass foaming agent is added into a degradable polymer matrix, and a simple double-screw melt extrusion processing mode is used, so that a physical foaming process of water molecules is completed, the amount of generated bubbles is sufficient, and bubble holes are not easy to collapse, and then the product density can be reduced, the resource utilization rate is improved, and compared with a traditional foaming agent, the biomass foaming agent is more in line with the requirements of environmental protection and energy saving, and has important significance for replacing the traditional foaming agent.

Description

Technical Field

[0001] This invention relates to the field of fully biodegradable membrane technology. More specifically, it relates to a biomass-degradable foamed membrane bag and its preparation method. Background Technology

[0002] With plastic pollution becoming increasingly serious, biodegradable plastics have emerged as a solution. However, the current high price of biodegradable raw materials has led to biodegradable film bags being more than twice as expensive as non-biodegradable ones, thus hindering their market application. Previous research has often attempted to reduce the cost of biodegradable film bags by adding inexpensive components to the polymer matrix to partially replace the high-cost biodegradable plastics, sacrificing usability such as mechanical properties. Therefore, effectively reducing costs without compromising performance remains a key research focus.

[0003] Foaming materials can maintain mechanical properties while reducing specific gravity, thus lowering costs and providing better thermal insulation and cushioning. Traditional foamed plastics are made from non-renewable petroleum derivatives, such as polyethylene and polypropylene. Although widely used, their non-degradability and the large amounts of toxic and harmful gases produced during incineration pose a significant threat to the environment. Developing new biodegradable foamed materials is therefore crucial. Currently, foamed materials are mainly prepared using three methods: physical foaming, chemical foaming, and agitation foaming. The foaming agents used are often petroleum-based small-molecule compounds (such as butane) and crosslinking agents. There are almost no reports on foaming biomass straw, which is more environmentally friendly. This is because, firstly, the technology of using water molecule evaporation from biomass straw for foaming is difficult to control; secondly, the stability of the air bubbles is poor, and they are prone to collapse, thus limiting its development in the field of foamed materials. However, from the perspective of green, biodegradable, recyclable, and renewable properties, developing biomass foamed materials to replace traditional foamed plastics is of great significance. Summary of the Invention

[0004] One objective of this invention is to provide a biodegradable foamed film bag. By adding a biomass foaming agent, which is formed by the reaction of biomass straw and sodium silicate, to a biodegradable polymer, and using a simple twin-screw melt extrusion process, the physical foaming process of water molecule evaporation can be completed. In this process, the cellulose, lignin, and sodium silicate in the biomass foaming agent jointly support the air bubbles formed inside the material, making them less prone to collapse. This results in a biodegradable foamed film bag with characteristics such as low cost, low density, environmental friendliness, energy saving, and good mechanical properties.

[0005] Another objective of this invention is to provide a method for preparing the biomass biodegradable foamed film bag as described above. This preparation method is based on physical foaming, is simple to operate, and the entire preparation process is safe, environmentally friendly, and energy-saving.

[0006] To achieve the first objective mentioned above, this invention discloses a biomass-degradable foamed film bag, comprising, by weight, parts of...

[0007]

[0008] The raw materials for the biomass foaming agent include biomass straw and sodium silicate.

[0009] This invention employs a physical foaming process, directly utilizing the pressure difference between the inside and outside of the material when the moisture contained in the material is extruded at the die head of a twin-screw extruder, causing it to vaporize instantly and form bubbles. The cellulose, lignin, and sodium silicate in the biomass straw work together to support the bubble pores formed inside the material, preventing them from collapsing easily.

[0010] Furthermore, the weight ratio of biomass straw to sodium silicate is 100:5-15; exemplaryly, the weight ratio of biomass straw to 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 found that if only biomass straw is added without sodium silicate, or if the amount of sodium silicate introduced is too small, the reinforcing effect of cellulose and lignin in the biomass straw is insufficient to achieve the desired bubble strength.

[0011] Furthermore, the biomass straw comprises cellulose, hemicellulose, lignin, protein, and minerals. Cellulose and hemicellulose are the main components of the straw, accounting for over 70% of the total mass. Cellulose is an undigested carbohydrate composed of multiple glucose molecules and is an important raw material for maintaining the digestive system of animals. Hemicellulose includes xylan, fructooligosaccharides, and xylo-oligosaccharides, which are commonly used food additives in various food processing processes. Besides cellulose and hemicellulose, straw also contains a large amount of lignin, a major component of plant cell walls and a water-insoluble organic compound that enhances the structural strength of plant cells. In foaming materials, both cellulose and lignin can support the air bubbles. Therefore, in this invention, biomass straw can be used as both a biomass filler and a foaming agent to prepare degradable products with controllable foaming ratios. This reduces costs by lowering the proportion of the degradable product, and the foamed film also provides better thermal insulation and elastic cushioning. In one specific embodiment, the biomass straw includes, but is not limited to, one or more ultrafine powders of 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 this invention, upon encountering moisture in biomass straw, can increase the consistency of the biodegradable polymer matrix. Furthermore, it forms silicate crystals within the biodegradable polymer matrix, thereby increasing its strength. These two effects combined enhance the strength and stability of the bubble pores. In one specific embodiment, the sodium silicate includes, but is not limited to, one or more of sodium metasilicate anhydrous, sodium metasilicate pentahydrate, and sodium metasilicate nonahydrate.

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

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

[0015] A foaming agent is a substance that regulates the foaming action of biomass, increasing material flowability and improving the uniformity of air bubbles. In one specific embodiment, the foaming agent includes, but is not limited to, one or more of the following: mica, talc, hydrotalcite-like substances, 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 duranate, stearamide, and N,N'-ethylenebisstearamide.

[0017] Furthermore, the biomass foaming agent is obtained by pretreating the raw materials of the biomass foaming agent, wherein the pretreatment process is as follows:

[0018] Biomass straw and sodium silicate are mixed evenly in a certain proportion to obtain the raw materials for biomass foaming agent reaction;

[0019] Under stirring, the raw materials for the biomass foaming agent reaction are heated to 85-90℃. The stirrer is sealed, and the reaction is carried out for 2-5 hours. The straw, rich in carboxyl and hydroxyl groups, as well as moisture, will react with sodium silicate. Then, the top cover of the stirrer is opened, and stirring continues under heating to evaporate some of the moisture. When the moisture content of the material in the stirrer reaches 2-5%, heating and stirring are stopped, and the material is allowed to cool naturally to obtain the biomass foaming agent. If the moisture content of the material in the stirrer exceeds 5%, the foaming volume will be too large, the bubble pore size will be larger, and the membrane bag will be prone to rupture. If the moisture content of the material in the stirrer is too low, foaming will be difficult.

[0020] To achieve the second objective mentioned above, this invention discloses a method for preparing the biomass degradable foamed film bag as described above, comprising the following steps:

[0021] S1: Add 100 parts by weight of biodegradable polymer, 10-30 parts by weight of biomass foaming agent, 1-10 parts by weight of foaming aid, and 1-5 parts by weight of surface modifier to a mixer, mix at room temperature for 10-30 minutes, then heat to 80-120℃ and continue mixing 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℃, the stirring speed can be increased to 500-600 rpm.

[0023] S2: Add the premixed material to a twin-screw extruder and melt-extrude it at a screw speed of 60-90 rpm and a temperature of 120-150℃ to obtain a special material for biomass degradable foamed film bags;

[0024] S3: Use a blown film machine to blow film the special material for biodegradable foamed film bags. At a screw speed of 15-30 rpm and a blown film temperature of 155-180℃, biodegradable foamed film bags are prepared.

[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℃.

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

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

[0028] This invention discloses a biodegradable foamed film bag. By adding a self-developed biomass foaming agent (biomass straw + sodium silicate) to a biodegradable polymer matrix, and using a simple twin-screw melt extrusion process, a physical foaming process involving water molecule evaporation can be completed. This results in a sufficient amount of bubbles and prevents bubble collapse, thereby reducing product density and improving resource utilization while maintaining the mechanical properties of the biodegradable foamed film bag. Furthermore, the biomass foaming agent selected in this invention is more environmentally friendly and energy-efficient than traditional foaming agents. During the pretreatment of the biomass foaming agent raw materials, it was found that a water content of 2-5% in the mixed materials is beneficial for obtaining bubbles with moderate foaming amount and appropriate bubble size, reducing problems such as film bag punctures or insufficient foaming.

[0029] This invention also provides a method for preparing biomass degradable foamed film bags. This preparation method is based on physical foaming, is simple 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 Implementation

[0030] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0031] Unless otherwise specified, all raw materials used in this invention are commercially available. Any range described in this invention includes end values, any values ​​between end values, and any subranges formed by end values ​​or any values ​​between end values.

[0032] Example 1

[0033] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0034]

[0035] The raw materials for the biomass foaming agent consist of reed stalks and sodium silicate in a weight ratio of 100:12.

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

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

[0038] S2: Under stirring, heat the obtained biomass foaming agent reaction raw materials to 85°C, seal the stirrer, stir and react for 5 hours, then open the top cover of the stirrer and continue stirring under heating to evaporate some water vapor. When the moisture content of the material in the stirrer reaches 3%, stop heating and stirring, and let it cool naturally to obtain the biomass foaming agent.

[0039] S3: Add 100 parts PBAT, 10 parts of the obtained biomass foaming agent, 2 parts talc and 1 part oleamide to a mixer. Mix at room temperature at 100 rpm for 30 minutes, then heat to 80-120℃ and continue mixing at 500 rpm for 30 minutes to obtain the premix.

[0040] S4: Add the premixed material to a twin-screw extruder and melt-extrude it at a screw speed of 90 rpm and a temperature of 150°C to obtain unfoamed biomass biodegradable foamed film bag material;

[0041] S5: Use a blown film machine to blow film the special material for biodegradable foamed film bags. The screw speed is 30 rpm and the blowing temperature is 180℃ to prepare biodegradable foamed film bags.

[0042] Example 2

[0043] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0044]

[0045] The raw materials for the biomass foaming agent consist of corn stalks and sodium silicate in a weight ratio of 100:12.

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

[0047] Example 3

[0048] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0049]

[0050] The raw materials for the biomass foaming agent consist of reed stalks and sodium silicate in a weight ratio of 100:12.

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

[0052] Example 4

[0053] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0054]

[0055]

[0056] The raw materials for the biomass foaming agent consist of reed stalks and sodium silicate in a weight ratio of 100:12.

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

[0058] Comparative Example 1

[0059] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0060]

[0061] The raw material for the biomass foaming agent is reed stalks.

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

[0063] Comparative Example 2

[0064] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0065]

[0066] The raw materials for the biomass foaming agent consist of reed stalks and sodium silicate in a weight ratio of 100:20.

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

[0068] Comparative Example 3

[0069] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0070]

[0071] The raw materials for the biomass foaming agent consist of reed stalks and calcium carbonate in a weight ratio of 100:12.

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

[0073] Comparative Example 4

[0074] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0075]

[0076] The raw materials for the biomass foaming agent consist of reed stalks and sodium silicate in a weight ratio of 100:12.

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

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

[0079] S2: Under stirring, heat the obtained biomass foaming agent reaction raw materials to 85°C, seal the stirrer, stir and react for 5 hours, then open the top cover of the stirrer and continue stirring under heating to evaporate some water vapor. When the moisture content of the material in the stirrer reaches 1%, stop heating and stirring, and allow it to cool naturally to obtain the biomass foaming agent.

[0080] S3: Add 100 parts PBAT, 10 parts of the obtained biomass foaming agent, 2 parts talc and 1 part oleamide to a mixer. Mix at room temperature at 100 rpm for 30 minutes, then heat to 80-120℃ and continue mixing at 500 rpm for 30 minutes to obtain the premix.

[0081] S4: Add the premixed material to a twin-screw extruder and melt-extrude it at a screw speed of 90 rpm and a temperature of 150°C to obtain unfoamed biomass biodegradable foamed film bag material;

[0082] S5: Use a blown film machine to blow film the special material for biodegradable foamed film bags. The screw speed is 30 rpm and the blowing temperature is 180℃ to prepare biodegradable foamed film bags.

[0083] Comparative Example 5

[0084] Biomass-degradable foamed film bags are composed of the following components in parts by weight:

[0085]

[0086] The raw materials for the biomass foaming agent consist of reed stalks and sodium silicate in a weight ratio of 100:12.

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

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

[0089] S2: Under stirring, heat the obtained biomass foaming agent reaction raw materials to 85°C, seal the stirrer, stir and react for 5 hours, then open the top cover of the stirrer and continue stirring under heating to evaporate some water vapor. When the moisture content of the material in the stirrer reaches 6%, stop heating and stirring, and let it cool naturally to obtain the biomass foaming agent.

[0090] S3: Add 100 parts PBAT, 10 parts of the obtained biomass foaming agent, 2 parts talc and 1 part oleamide to a mixer. Mix at room temperature at 100 rpm for 30 minutes, then heat to 80-120℃ and continue mixing at 500 rpm for 30 minutes to obtain the premix.

[0091] S4: Add the premixed material to a twin-screw extruder and melt-extrude it at a screw speed of 90 rpm and a temperature of 150°C to obtain unfoamed biomass biodegradable foamed film bag material;

[0092] S5: Use a blown film machine to blow film the special material for biodegradable foamed film bags. The screw speed is 30 rpm and the blowing temperature is 180℃ to prepare biodegradable foamed film bags.

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

[0094] Table 1 shows the test results of Examples 1-4 and Comparative Examples 1-5 of the present invention: Since the thickness of the membrane bag is generally 20-50 μm, the property parameters of the biomass degradable foamed membrane bags of Examples 1-4 all meet the following 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, the absence of sodium silicate in the biomass foaming agent resulted in insufficient strength of the foamed pores in the prepared biomass biodegradable foamed film bag, leading to easy collapse. In Comparative Example 2, excessive sodium silicate addition caused the prepared biomass biodegradable foamed film bag to be too stiff, significantly reducing its elongation at break. In Comparative Example 3, the combined effect of biomass straw and calcium carbonate was still insufficient to support the strength of the foamed pores, resulting in easy collapse. Comparative Examples 4 and 5 revealed that the moisture content of the biomass foaming agent must be neither too high nor too low during preparation. Too low a moisture content hinders foaming, or may even prevent foaming altogether, while too high a moisture content leads to excessive foaming, reducing the mechanical properties of the biomass biodegradable foamed film bag.

[0096] Table 1. Property parameters of biomass-degradable foamed film bags

[0097]

[0098] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A biomass-degradable foamed film bag, characterized in that, By weight, including 100 parts of biodegradable polymer; 10-30 parts of biomass foaming agent; 1-10 parts of foaming agent; 1-5 parts of surface modifier; The raw materials for the biomass foaming agent include biomass straw and sodium silicate; The weight ratio of the biomass straw to sodium silicate is 100:5-15; The biomass foaming agent is obtained by pretreating the raw materials of the biomass foaming agent. The pretreatment process is as follows: Biomass straw and sodium silicate are mixed evenly in a certain proportion to obtain the raw materials for biomass foaming agent reaction; Under stirring, the raw materials for biomass foaming agent reaction are heated to 85-90℃, 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 allow some water vapor to evaporate. When the moisture content of the material in the stirrer reaches 2-5%, heating and stirring are stopped, and the biomass foaming agent is obtained after natural cooling. Biodegradable foamed film bags are prepared using a physical foaming process.

2. The biomass degradable foamed film bag according to claim 1, characterized in that, The biomass straw is selected from one or more of the following: reed straw, corn straw, cotton straw, peanut straw, wheat straw, rice straw, tree branches and leaves, and coconut fiber materials, and is made into an ultrafine powder with a D90 of 300-800 mesh and a moisture content controlled at 5-30%. The sodium silicate is selected from one or more of sodium metasilicate anhydrous, sodium metasilicate pentahydrate, and sodium metasilicate nonahydrate. The biodegradable polymer is selected from one or more of polybutylene adipate terephthalate, polybutylene succinate, polybutylene adipate, polyvinyl alcohol, polylactic acid, polyglycolic acid, and polycaprolactone.

3. The biomass degradable foamed film bag according to claim 1, characterized in that, The biomass-degradable foamed film bag has a bubble pore size of 2-8μm, a foaming ratio of 2-4 times, a tensile strength of >20MPa, and an elongation at break of >250%.

4. The biomass degradable foamed film bag according to claim 1, characterized in that, The foaming agent is selected from one or more of the following: 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.

5. The biomass degradable foamed film bag according to claim 1, characterized in that, The surface modifier is selected from one or more of oleamide, erucamide, calcium stearate, zinc duranate, stearamide, and N,N'-ethylenebis-stearamide.

6. The method for preparing biomass degradable foamed film bags according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Add 100 parts by weight of biodegradable polymer, 10-30 parts by weight of biomass foaming agent, 1-10 parts by weight of foaming aid, and 1-5 parts by weight of surface modifier to a mixer, mix at room temperature for 10-30 minutes, then heat to 80-120℃ and continue mixing for 20-30 minutes to obtain a premix. S2: Add the premixed material to a twin-screw extruder and melt-extrude it at a screw speed of 60-90 rpm and a temperature of 120-150℃ to obtain a special material for biomass degradable foamed film bags; S3: Use a blown film machine to blow film the special material for biodegradable foamed film bags. At a screw speed of 15-30 rpm and a blown film temperature of 155-180℃, biodegradable foamed film bags are prepared.

7. The preparation method according to claim 6, 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℃.

8. The preparation method according to claim 6, characterized in that, In step S3, when the blown film machine is running, the screw speed is 20-25 rpm and the blown film temperature is 160-170℃.

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