A biodegradable composite sheet and a method for preparing the same

Abstract

The application relates to the technical field of biodegradable materials, in particular to a biodegradable composite sheet and a preparation method thereof, wherein the composite sheet comprises a base material, modified raw materials and powder materials, and also comprises an additive; the base material is PHB and other PHAs; the biodegradable material prepared by the application has a special three-layer structure, has the characteristics of good processability, temperature resistance, low cost and high production efficiency, improves the shortcomings of PHA materials, simultaneously has the original advantages of the PHA materials, can meet the requirements of application fields such as food containers, agricultural materials, medical materials or packaging materials and other materials with biodegradable performance.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, specifically to a biodegradable composite sheet and its preparation method. Background Technology

[0002] The advancement of the internet has spurred the rapid development of the express delivery industry, particularly in the food delivery sector. Calculations show that a single plastic bowl and lunchbox weighs between 40g and 60g. Research by the environmental organization "Nature University" indicates that each food delivery order consumes an average of 3.27 lunchboxes, generating approximately 160g of plastic. Adding the average of two plastic bags per order, totaling 170g per order, and considering the use of plastic straws, timely delivery orders will generate a demand for 1.006 million tons of biodegradable plastic by 2025. Furthermore, market demand forecasts for supermarket fresh produce trays and seedling pots for flower cultivation in agriculture and forestry indicate that fresh produce trays (3-5g each) will have an annual demand of 20 billion, equivalent to 60,000-100,000 tons of material. Seedling pots (3-6g each) will have an annual demand of 10 billion, equivalent to approximately 30,000-60,000 tons of material. Therefore, there is a need for biodegradable resin materials and their products that possess excellent biodegradability, are cost-effective, and meet usage requirements, replacing existing non-biodegradable disposable blister packaging products.

[0003] Polyhydroxyalkanoates (PHA) are a novel bio-based and renewable biodegradable material. Compared to traditional non-recyclable plastics such as petroleum, PHA's biggest advantage is that its production substrates are all recyclable carbon sources (e.g., starch sugars, food waste, and hydrolyzed straw sugars). Furthermore, the entire polymerization process of PHA is biopolymerization rather than chemical polymerization, significantly reducing carbon emissions during production, which is of great significance in responding to the goals of "carbon neutrality" and "carbon peaking." In addition, PHA has excellent biodegradability. While most biodegradable materials require composting conditions to degrade, PHA is spontaneously biodegradable, degrading naturally in a controlled manner without composting. It ultimately produces carbon dioxide and water, without polluting the environment, making it a recognized environmentally friendly material.

[0004] However, while PHAs possess numerous advantages, they also have their own drawbacks, such as the brittleness and hardness of PHBs, post-crystallization of PHBV, narrow processing window, and high cost. These disadvantages significantly limit their applications. Therefore, it is necessary to modify these PHA materials to ensure that the final composite material combines the advantages of each material, resulting in an ideal specialty compound. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing PHA materials by modifying them to improve their processing performance. This achieves the goal of lightweighting disposable lunch boxes, trays, seedling pots, and other related products to reduce costs, while also making degradation time controllable.

[0006] In a first aspect, a biodegradable composite sheet is provided, wherein the composite sheet comprises, from top to bottom, an upper structure, a middle structure, and a lower structure, wherein...

[0007] The superstructure includes a surface layer;

[0008] The central structure includes a foamed core layer;

[0009] The lower structure includes a surface layer;

[0010] The material of the surface layer and / or the foamed core layer includes a substrate, which includes PHB and other PHAs.

[0011] Preferably, each of the aforementioned structures includes at least one layer.

[0012] Preferably, the surface layer is obtained by extrusion molding machine through melting and plasticizing, extrusion through T-die, and the extruded melt is obtained by three-roll calendering, cooling, shaping, trimming, traction and winding.

[0013] Preferably, the foamed core layer is obtained by supercritical carbon dioxide foaming.

[0014] Preferably, the apparent density of the surface layer is 1.23-1.34 g / cm³ (e.g., 1.23, 1.24, 1.25, 1.30, 1.31, 1.32, 1.33, 1.34). 3 .

[0015] Preferably, the apparent density of the foamed core layer is 0.30-0.45 g / cm³ (e.g., 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45). 3 .

[0016] Preferably, the thickness ratio of the surface layer to the foamed core layer is (0.25-0.5):(0.5-0.75), for example (0.25, 0.3, 0.35, 0.4, 0.45, 0.5):(0.5, 0.55, 0.6, 0.65, 0.7, 0.75).

[0017] Preferably, the composite sheet has a resilience of 35-50% (e.g., 35, 40, 45, 50)%.

[0018] Preferably, the impact strength of the composite sheet is 7.9-10.7 KJ / m (e.g., 7.9, 8.0, 8.2, 8.4, 8.5, 8.7, 8.9, 9.0, 9.2, 9.5, 9.7, 10.0, 10.3, 10.5, 10.6, 10.7). 2 .

[0019] Preferably, the material of the surface layer and / or the foamed core layer further includes modified raw materials.

[0020] In one specific embodiment of the present invention, the materials of the surface layer and / or foamed core layer, by weight, comprise 30-80 (e.g., 30, 40, 50, 60, 70, 80) parts of base material and 10-60 (e.g., 10, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, 50, 60) parts of modified raw material.

[0021] The modified raw materials include PBAT and / or PPC. For example, the materials of the surface layer and / or foamed core layer include 30-80 (e.g., 30, 40, 50, 60, 70, 80) parts of total PHA and / or 5-20 (e.g., 5, 10, 13, 15, 20) parts of PBAT and 5-20 (e.g., 5, 8, 10, 15, 20) parts of PPC.

[0022] Preferably, the modified raw material further includes plant fibers, and more preferably, the plant fibers include, but are not limited to, one or more combinations of castor fiber, jute fiber, ramie fiber, flax fiber, lignin, and coconut shell fiber.

[0023] Preferably, the material of the surface layer and / or the foamed core layer comprises 0-15 (e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 parts) of plant fiber.

[0024] Preferably, the modified raw material further includes one or more of PLA, PBS, carboxymethyl cellulose, or PGA.

[0025] Preferably, the mass ratio of the substrate to the modified raw material is any value in the range of (1.5-3):1, and more preferably (1.5-2):1. For example, the mass ratio can be 70:(23, 25, 29, 31, 36, 45, 46).

[0026] Preferably, the material of the surface layer and / or the foamed core layer further includes powder.

[0027] Preferably, when the total PHA is 30-80 parts by weight, the material of the surface layer and / or foamed core layer contains 10-60 (e.g., 10, 15, 18, 20, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, 50, 60) parts of powder.

[0028] The powder includes inorganic powders and / or starch.

[0029] Preferably, the inorganic powder includes, but is not limited to, calcium carbonate and / or talc.

[0030] Preferably, the starch includes, but is not limited to, corn starch, tapioca starch, potato starch, or sweet potato starch, and one or more combinations thereof, as well as their modified starches.

[0031] For example, the powder comprises 5-30 (e.g., 5, 10, 15, 20, 25, 30) parts of inorganic powder and 5-30 (e.g., 5, 8, 9, 10, 15, 20, 25, 30) parts of starch.

[0032] Preferably, the mass ratio of the substrate, modified raw material, and powder is any value in the range of (50-80):(15-40):(15-30), and more preferably (65-75):(20-36):(18-23). ​​For example, the mass ratio can be 70:29:25, 70:36:18, 70:31:23, or 70:31:23.

[0033] In one specific embodiment of the present invention, the materials of the surface layer and / or foamed core layer, by weight, comprise 30-80 (e.g., 30, 40, 50, 60, 70, 80) parts of base material, 10-60 (e.g., 10, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, 50, 60) parts of modified raw material, and 10-60 (e.g., 10, 15, 18, 20, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, 50, 60) parts of powder.

[0034] The materials of the surface layer and / or foamed core layer also include additives.

[0035] The total amount of PHA added is any value between 30% and 70% of the material of the surface layer and / or the foamed core layer, for example, 30, 35, 40, 45, 50, 52, 52.4, 52.6, 55, 60, 65, or 70% by mass ratio.

[0036] The amount of the modified material added is any value between 10% and 30% of the material of the surface layer and / or the foamed core layer, for example, 10, 15, 20, 21.8, 23.2, 23.3, 25, 26.9, or 30% by mass.

[0037] The amount of powder added is any value between 5% and 25% of the material of the surface layer and / or the foamed core layer, for example, 5, 10, 13.5, 15, 17.2, 17.3, 18.8, 20, 25% by mass.

[0038] The amount of the additive added is any value from 0 to 10% of the material of the surface layer and / or the foamed core layer, preferably 6 to 8%, for example 0, 1, 2, 3, 4, 5, 6, 6.7, 6.9, 7, 7.2, 7.3, 8, 9, 10% by mass.

[0039] Preferably, when the total PHA is 30-80 parts by weight (e.g., 30, 40, 50, 60, 70, 80), the material of the surface layer and / or foamed core layer contains 0.2-10 parts by weight (e.g., 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 8.5, 8.9, 9, 9.2, 9.5, 9.6, 9.7, 9.8, 9.9, 10) of additives.

[0040] In the composite sheet, the mass ratio is: substrate: modified raw material: powder: additive = (65-75): (20-36): (18-23): (8-9.7).

[0041] The additives include, but are not limited to, one or more combinations of chain extenders, hydrolysis stabilizers, compatibilizers, melt reinforcing agents, coupling agents, solubilizers, plasticizers, antioxidants, heat stabilizers, and lubricants.

[0042] Preferably, the chain extender includes, but is not limited to, one or a combination of two or more of epoxy-functionalized, oxazoline-type, and isocyanate-type chain extenders.

[0043] Preferably, the hydrolysis stabilizer includes, but is not limited to, one or a combination of two or more of carbodiimide, isocyanate, epoxy, oxazoline and acid anhydride hydrolysis stabilizers.

[0044] Preferably, the compatibilizer includes, but is not limited to, one or a combination of two or more of vinyl acetate polymer, maleic anhydride grafted polymer, and glycidyl methacrylate.

[0045] Preferably, the melt reinforcing agent includes, but is not limited to, one or two of acrylate melt reinforcing agents and methacrylic acid-butadiene-styrene copolymers.

[0046] Preferably, the coupling agent includes, but is not limited to, one or a combination of two or more of silane, titanate and aluminate coupling agents.

[0047] Preferably, the solubilizer includes, but is not limited to, one or a combination of two or more of polyethylene glycol, polydiethylene glycol, and glycerin.

[0048] Preferably, the plasticizer includes, but is not limited to, one or more combinations of tributyl citrate, trioctyl citrate, acetylated tributyl citrate, acetylated trioctyl citrate, epoxidized soybean oil, castor oil derivatives, and isosorbide diesters.

[0049] Preferably, the antioxidants include, but are not limited to, one or both of B215 and 1010.

[0050] Preferably, the heat stabilizer includes, but is not limited to, one or both of calcium stearate and zinc stearate.

[0051] Preferably, the lubricant includes, but is not limited to, one or a combination of two or more of stearic acid, monoglyceride, oleic acid, erucamide, and ethylene bis-stearamide.

[0052] Preferably, the other PHAs include homopolymers or copolymers of monomers constituting polyhydroxyalkanoates.

[0053] The monomers comprising the polyhydroxy fatty acid ester include one or more of the following: 2-hydroxypropionic acid, 3-hydroxypropionic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvalerate, 5-hydroxyvalerate, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, and 3-hydroxydodecanoic acid.

[0054] Preferably, the other PHAs include one, two or more of P(HA-LA), P3HP, P4HB, PHV, PHO, PHN, PHD, PHBV, P34HB, PHBHHp, PHBHHx, P3HB4HB3HV or P3HB4HB5HV.

[0055] In P(HA-LA), HA is selected from one or more of 3-hydroxypropionic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvalerate, 5-hydroxyvalerate, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, and 3-hydroxydodecanoic acid; LA is 2-hydroxypropionic acid.

[0056] Preferably, the other PHAs include P34HB, PHBHHx, and / or PHBV.

[0057] Preferably, the molar content of 3HV in PHBV is any value between 5% and 30%, such as 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, or 30%.

[0058] Preferably, the molar content of 4HB in P34HB is any value between 5% and 30%, such as 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, or 30%.

[0059] Preferably, the molar content of HHx in PHBHHx is any value between 5% and 30%, such as 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, or 30%.

[0060] Depending on the specific implementation requirements, the substrate can be a single type or a combination of two or more types.

[0061] Preferably, the mass ratio of the PHB to other PHAs is (1-25):(1-15), and more preferably any value in (3-24):(1-5), such as 9:5, 4:3, 3:2 or 24:11.

[0062] In one specific embodiment of the present invention, the total PHA includes any one of the following groups:

[0063] A) PHB and P34HB, wherein the weight ratio of PHB to P34HB is (1.5-2.5):1, preferably (1.8-2.2):1;

[0064] B) PHB and PHBV, wherein the weight ratio of PHB to PHBV is (1-2):1, preferably (1.3-1.5):1; or,

[0065] C) PHB and PHBHHx, wherein the weight ratio of PHB and PHBHHx is (0.5-3):1, preferably (1-2):1, for example 1.5:1.

[0066] In one specific embodiment of the present invention, the composite sheet comprises the following components in parts by weight:

[0067] Total PHA: 30-80 units, for example, 30, 40, 50, 60, 70, or 80 units;

[0068] Inorganic powder: 5-30 parts, for example, 5, 10, 15, 20, 25, or 30 parts;

[0069] Starch: 5-30 parts, for example, 5, 8, 9, 10, 15, 20, 25, or 30 parts;

[0070] PBAT: 5-20 copies, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 copies;

[0071] PPC: 5-20 portions, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 portions;

[0072] Plant fiber: 0-15 parts, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 parts;

[0073] PLA: 0-50 portions, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 21, 25, 30, 40, 41, 45, 50 portions;

[0074] PBS: 0-20 samples, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 samples;

[0075] Carboxymethyl cellulose: 0-9 parts, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 parts;

[0076] PGA: 0-15 portions, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 portions.

[0077] In one specific embodiment of the present invention, the composite sheet is composed of a substrate, modified raw materials, powder and additives.

[0078] In one specific embodiment of the present invention, the auxiliary agent comprises the following components in parts by weight:

[0079] Chain extender: 0.2-1.5 parts, for example 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.3, 1.4, 1.5;

[0080] Hydrolysis stabilizer: 0.2-1.0 parts, e.g., 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0; Compatibilizer: 0.5-1.5 parts, e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5;

[0081] Melt enhancer: 1.0-2.0 parts, for example 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0;

[0082] Coupling agent: 0.4-2.0 parts, for example 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0;

[0083] Solubilizer: 0.5-1.0 parts, for example 0.5, 0.6, 0.7, 0.8, 0.9, 1.0;

[0084] Plasticizer: 0.5-2.5 parts, for example 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5;

[0085] Antioxidant: 0.4-1.0 parts, for example 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0;

[0086] Heat stabilizer: 0.5-1.0 parts, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0;

[0087] Lubricant: 0.1-0.5 parts, for example 0.1, 0.2, 0.3, 0.4, 0.5.

[0088] Preferably, the overall apparent density of the composite sheet is 0.5-0.9 g / cm³. 3 Any value in the range, such as 0.5, 0.6, 0.7, 0.8, 0.9 g / cm³. 3 .

[0089] Preferably, the foamed core layer is obtained by foaming the material through supercritical carbon dioxide micropores.

[0090] Secondly, a method for preparing the aforementioned composite sheet is provided, wherein the method includes mixing the various materials, melting, and shearing to obtain granules.

[0091] Preferably, the method for preparing the foamed core layer includes microporous foaming of granules using supercritical carbon dioxide, and preparing a composite sheet with a three-layer foamed structure by continuous extrusion.

[0092] Preferably, the surface layer preparation method includes feeding the material into a sheet extrusion molding machine, melting and plasticizing it, extruding it through a T-die, and then cooling, shaping, trimming, traction, and winding the extruded melt into a finished product through a three-roll calender.

[0093] Preferably, the preparation method includes: 1) drying a selected amount of powder by weight and then activating it by adding a coupling agent;

[0094] 2) Cool the activated powder from step 1), and add the selected weight parts of the base material, modified raw material, and additives other than the coupling agent for mixing;

[0095] 3) The material mixed evenly in step 2) is fed into a twin-screw extruder for melting, shearing, mixing, plasticizing and granulation to obtain biodegradable granules.

[0096] Preferably, the drying temperature of the powder in step 1) is any value between 80-110℃, such as 80, 85, 90, 95, 100, 105, or 110℃.

[0097] Preferably, the cooling temperature in step 2) is below 40°C.

[0098] Preferably, in step 3), the length-to-diameter ratio of the twin-screw extruder is any value in the range of (48-60):1, for example (48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60):1.

[0099] Preferably, the shearing, mixing and plasticizing temperature is any value between 140-240℃, such as 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240℃.

[0100] Preferably, the die pressure of the twin-screw extruder is any value between 3 and 6 MPa, such as 3, 4, 5, or 6.

[0101] Preferably, the screw speed of the twin-screw extruder is any value between 300-460 r / min, such as 300, 350, 360, 400, 450, and 460 r / min.

[0102] In the preparation method described above, the extrusion is carried out under high temperature, high shear and high pressure, followed by air cooling and granulation to obtain the biodegradable material.

[0103] In one specific embodiment of the present invention, the preparation method includes:

[0104] (1) Add the powder to the high-speed mixer and run it for 10-15 minutes at a temperature of 95°C inside the mixer. At the same time, add the coupling agent to mix and activate the surface of the powder.

[0105] (2) Use a high-speed mixer at 200 r / min and stir slowly to ensure that the coupling agent fully coats the surface of the powder. Then put the activated powder into a cooling mixer and cool it to below 40°C in the mixer. Add other components and additives as needed and mix evenly.

[0106] (3) Mix at 300 r / min for 4 min to achieve uniform mixing.

[0107] (4) The uniformly blended raw materials are fed into a twin-screw extruder for melt shearing plasticization and granulation. The screw speed of the twin-screw extruder is 360 r / min, the melt temperature is 150-180℃, and the process involves vacuum degassing, pressure extrusion, air-cooled strip shearing and granulation.

[0108] Thirdly, a biodegradable material or composite sheet obtained by the above preparation method is provided.

[0109] Fourthly, the invention provides an application of the above-described composite sheet or the composite sheet obtained by the above-described preparation method in products where the material needs to have biodegradable properties.

[0110] Preferably, the products include, but are not limited to, food containers, agricultural materials, medical materials, or packaging materials. Food containers include, for example, lunch boxes, trays, cups, food packaging bags, etc.

[0111] Preferably, the product is a plastic product.

[0112] In one specific embodiment of the invention, the application includes its use in the preparation of biodegradable controllable containers, the controllable containers including seedling containers, such as seedling pots.

[0113] Preferably, the biodegradable controllable seedling container is prepared from the following components in parts by weight: 20-60 parts PHB, 10-20 parts P3HB4HB, 5-15 parts starch, 10-20 parts PBAT, 5-15 parts PGA and 0.2-10 parts additives.

[0114] Through the above technical solution, the present invention has the following advantages:

[0115] 1. The modified material of the present invention has the characteristics of good processability, temperature resistance, low cost and high production efficiency. At the same time, it improves the shortcomings of PHA material while retaining the original advantages of PHA material.

[0116] 2. Compared with other similar products, the products prepared by the modified materials of this invention can reduce the overall density, making the material cost close to that of traditional plastic products, thus giving them a competitive advantage.

[0117] 3. This invention can prepare layered material structures such as three-layer foamed sheets by modifying materials. For example, three-layer foamed sheets can make full use of the characteristics of each layer of materials, which not only ensures the smoothness and tight fit of the surface (for example, it solves the problem of the lid and bottom of the blister packaging not being properly fastened), but also achieves lightweighting and reduces costs.

[0118] 4. The advantages of using modified materials to prepare three-layer co-extruded foam sheets and products include:

[0119] 1) The core layer has a foam structure, which has a good heat insulation effect. When made into products (such as bowls and cups), it can hold high-temperature liquids (70-100℃) without burning your hands.

[0120] 2) PHA three-layer co-extruded foamed sheets are thermoformed by a vacuum forming machine, which improves the crystallinity of the product, has good heat resistance, and does not deform when filled with high-temperature liquids (70~100℃).

[0121] 3) PHA three-layer co-extruded foam sheets and products are lightweight, weighing 50%-60% of ordinary PLA products, thus reducing costs.

[0122] 4) Scrap materials can be reused. Using 50% scrap materials as raw materials during the production process can ensure stable production.

[0123] 5. Advantages of physical carbon dioxide foaming: Stable equipment and process, consistent product quality, online adjustment of foaming ratio, convenient operation, simple raw materials, no need for complex additives, environmentally friendly and non-toxic, high closed-cell rate, uniform cell size, smooth and flat sheet surface, and low formulation cost, requiring only 5-10 yuan of CO2 per ton of product. Therefore, the overall processing cost is low, but the return is high.

[0124] The term "and / or" as used in this invention encompasses all combinations of items connected by the term, and should be considered as if each combination had been individually listed herein. For example, "A and / or B" includes "A", "A and B", and "B". As another example, "A, B and / or C" includes "A", "B", "C", "A and B", "A and C", "B and C", and "A and B and C".

[0125] The use of "comprising" or "including" in this invention is an open-ended description, encompassing the specified ingredients or steps described, as well as other specified ingredients or steps that do not materially affect them.

[0126] Table 1 shows the English abbreviation and the full Chinese name of this invention.

[0127] Table 1: Comparison of English Abbreviations and Full Chinese Names

[0128] English abbreviations Full Chinese name PHB Poly-3-hydroxybutyrate PHBV Copolymer of 3-hydroxybutyric acid and 3-hydroxyvalerate PHBHHx Copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid P3HB4HB or P34HB Copolymer of 3-hydroxybutyric acid and 4-hydroxybutyric acid PHV Poly-3-hydroxyvalerate P3HP Poly-3-hydroxypropionic acid PHO Poly-3-hydroxyoctanoate PHN Poly-3-hydroxynonanoate PBAT Poly(butylene adipate) / Trepotassium terephthalate PBS Polybutylene succinate PLA Polylactic acid PPC Polypropylene carbonate PGA Polyglycolic acid Attached Figure Description

[0129] Figure 1 The structure is a three-layer co-extruded foamed sheet of PHA, in which 1 and 2 are the smooth upper and lower layers, and 3 is a low-density microporous foam layer. Detailed Implementation

[0130] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0131] Unless otherwise specified, all materials used in the embodiments of this invention are commercially available.

[0132] Unless otherwise specified, the parts, percentages or proportions mentioned in the embodiments of this invention are based on weight.

[0133] The detection criteria for the parameters in this embodiment are as follows:

[0134] 1. MFI (g / 10min) (melt index), MFI test conditions: 190℃ / 2.16kg, refer to GB / T 3682-2000.

[0135] 2. Tensile strength (MPa), refer to GB / T 1040.2-2006.

[0136] 3. Elongation at break (%), refer to GB / T 1040.2-2006.

[0137] 4. Notched impact strength of cantilever beam (KJ / m) 2 GB / T 1843-2008.

[0138] 5. Bending strength (MPa), refer to GB / T 9341-2008.

[0139] 6. Vicat softening point temperature (°C), GB / T 1634-2019.

[0140] 7. Low-temperature performance (°C): Performed by dynamic thermomechanical analysis (DMA) using a DMA Q850 instrument (TAInstrument, USA) in tensile mode. All tests were conducted at a frequency of 1 Hz and a heating rate of 3°C / min, from -60°C to 30°C.

[0141] 8. Thermal conductivity, W / (m·K), GB / T 10295-2008. The lower the thermal conductivity, the better the thermal insulation effect. Generally, materials with a thermal conductivity less than 0.23 W / (m·K) are called thermal insulation materials, materials with a thermal conductivity less than 0.14 W / (m·K) are called thermal insulation materials, and materials with a thermal conductivity not greater than 0.05 W / (m·K) are called high-efficiency thermal insulation materials.

[0142] 9. Rebound performance, i.e., rebound rate, %, refer to Method A in GB / T 6670-2008.

[0143] 10. Apparent density, g / cm³ 3 Refer to the method in GB / T 6343-2009.

[0144] Example 1: PHA(PHB+P34HB) / PBAT / PPC / Plant Fiber Composite Biodegradable Modified Special Material

[0145] The biodegradable modified special material described in this embodiment is made from the following components: 45 parts by weight of PHB, 25 parts by weight of P34HB (4HB content 15 mol%), 15 parts by weight of talc, 5 parts by weight of cassava starch, 5 parts by weight of modified potato starch, 13 parts by weight of PBAT, 8 parts by weight of PPC, 3 parts by weight of castor fiber, 2 parts by weight of ramie fiber, 3 parts by weight of coconut shell fiber, 0.5 parts by weight of epoxy functionalized chain extender, 0.3 parts by weight of carbodiimide anti-hydrolysis agent, 0.2 parts by weight of isocyanate anti-hydrolysis agent, 0.5 parts by weight of vinyl acetate polymer, 1.5 parts by weight of acrylate melt reinforcing agent, 1 part by weight of titanate coupling agent, 1 part by weight of polyethylene glycol, 1.5 parts by weight of tributyl acetylacetonate, 1 part by weight of castor oil-derived ester plasticizer, and antioxidant 1010. 0.4 parts by weight, calcium stearate 0.5 parts by weight, ethylene bis-stearamide 0.5 parts by weight.

[0146] Example 2: Special biodegradable modified material of PHA(PHB+PHBV) / PBS / PGA / PBAT / PPC composite

[0147] The biodegradable modified special material described in this embodiment is made from the following components: 40 parts by weight of PHB, 30 parts by weight of PHBV (3HV content 20mol%), 10 parts by weight of PBS, 5 parts by weight of PGA, 13 parts by weight of PBAT, 8 parts by weight of PPC, 10 parts by weight of calcium carbonate, 4 parts by weight of corn starch, 4 parts by weight of modified corn starch, 0.8 parts by weight of isocyanate chain extender, 0.2 parts by weight of carbodiimide anti-hydrolysis agent, 0.2 parts by weight of epoxy anti-hydrolysis agent, 1 part by weight of maleic anhydride graft polymer, 1.5 parts by weight of methacrylic acid-butadiene-styrene copolymer, 0.5 parts by weight of silane coupling agent, 1.2 parts by weight of titanate coupling agent, 0.8 parts by weight of polydiethylene glycol, 0.5 parts by weight of tributyl citrate, 0.8 parts by weight of trioctyl acetyl citrate, 0.7 parts by weight of epoxidized soybean oil, and antioxidant B215. 0.4 parts by weight, zinc stearate 0.6 parts by weight, stearic acid 0.5 parts by weight.

[0148] Example 3: PHA(PHB+PHBHHx) / PLA / Plant Fiber / PBAT / PPC Composite Biodegradable Modified Special Material

[0149] The biodegradable modified special material described in this embodiment is made from the following components: 42 parts by weight of PHB, 28 parts by weight of PHBHHx (3HHx content 20 mol%), 5 parts by weight of PLA, 4 parts by weight of carboxymethyl cellulose, 3 parts by weight of jute fiber, 2 parts by weight of flax fiber, 2 parts by weight of lignin, 10 parts by weight of PBAT, and PPC. 5 parts by weight, talc powder 15 parts by weight, potato starch 3 parts by weight, modified cassava starch 5 parts by weight, epoxy functionalized chain extender 0.6 parts by weight, oxazoline chain extender 0.4 parts by weight, acid anhydride anti-hydrolysis agent 0.6 parts by weight, vinyl acetate polymer 0.5 parts by weight, glycidyl methacrylate 0.7 parts by weight, acrylate melt reinforcing agent 1.6 parts by weight, titanate coupling agent 0.6 parts by weight, aluminate coupling agent 0.4 parts by weight, glycerol 0.7 parts by weight, trioctyl citrate 1 part by weight, isosorbide diester plasticizer 1 part by weight, antioxidant 1010 0.4 parts by weight, calcium stearate 0.6 parts by weight, monoglyceride 0.2 parts by weight, erucamide 0.3 parts by weight.

[0150] Example 4: PHA(PHB+P34HB) / Plant Fiber / PGA / PBAT / PPC Composite Biodegradable Modified Special Material

[0151] The biodegradable modified special material described in this embodiment is made from the following components: 48 parts by weight of PHB, 22 parts by weight of P34HB (4HB content 20 mol%), 10 parts by weight of PBAT, 5 parts by weight of PPC, 6 parts by weight of PGA, 3 parts by weight of castor fiber, 3 parts by weight of ramie fiber, 4 parts by weight of coconut shell fiber, 15 parts by weight of calcium carbonate, 2 parts by weight of sweet potato starch, 6 parts by weight of modified sweet potato starch, 0.5 parts by weight of epoxy functionalized chain extender, 0.4 parts by weight of isocyanate anti-hydrolysis agent, 0.3 parts by weight of oxazoline anti-hydrolysis agent, 1 part by weight of maleic anhydride graft polymer, 1.5 parts by weight of methacrylic acid-butadiene-styrene copolymer, 1 part by weight of titanate coupling agent, 1 part by weight of polyethylene glycol, 1.5 parts by weight of tributyl acetyl citrate, 0.5 parts by weight of epoxidized soybean oil, and antioxidant B215. 0.5 parts by weight, zinc stearate 0.5 parts by weight, oleic acid 0.2 parts by weight, ethylene stearamide 0.3 parts by weight.

[0152] The preparation method of the biodegradable modified special material described in Examples 1-4 above includes the following steps: Add powder (inorganic powder and / or starch) to a high-speed mixer and run it for 10-15 minutes at an internal temperature of 95°C. Simultaneously, add a coupling agent for blending to activate the powder surface. The high-speed mixer rotates at 200 r / min, and the mixture is slowly stirred to ensure the coupling agent fully coats the powder surface. Then, place the activated powder into a cooling mixer and cool it to below 40°C. Add other appropriate components and additives and blend evenly. The high-speed mixer rotates at 300 r / min and stirs for 4 minutes to achieve uniform blending. Feed the uniformly blended material into a twin-screw extruder for melt shearing and granulation. The twin-screw extruder has a screw speed of 360 r / min and a melt temperature of 150-180°C. Vacuum exhaust, devolatilization, pressurized extrusion, and air-cooled shearing granulation are then performed to obtain the biodegradable modified special material.

[0153] The biodegradable modified special material is fed into a sheet extruder and processed into sheets of the required specifications. The sheet processing includes two methods:

[0154] (1) One method involves using supercritical carbon dioxide foaming to obtain the foamed core layer in a three-layer co-extruded sheet. The sheet has a three-layer structure: surface layer + foamed core layer + surface layer, with a PHA resin density of 1.18-1.30 g / cm³. 3 The overall apparent density of the three-layer co-extruded sheet is 0.5-0.9 g / cm³. 3 Adjustable; can reduce weight by 40-50%. The carbon dioxide foaming process is mature, product quality is stable, the foaming ratio can be adjusted online at any time, and operation is convenient.

[0155] (2) A method for obtaining a surface layer by using non-foamed extruded sheet. The processing technology is as follows: the granules are fed into the sheet extrusion molding machine, melted and plasticized, extruded through a T-die, and the extruded melt is cooled, shaped, trimmed, drawn and wound into a finished product by three-roll calendering.

[0156] The materials prepared through the above embodiments ultimately yield a three-layer co-extruded foamed sheet, such as... Figure 1 As shown, the three-layer co-extruded foam sheet has the following characteristics and advantages:

[0157] 1. Three-layer structure: PHA surface layer + PHA foam core layer + PHA surface layer. The layered material structure makes full use of the characteristics of each layer, which not only ensures the smoothness of the surface and tight adhesion, but also achieves lightweighting and reduces costs.

[0158] 2. Sheet density: PHA resin density 1.18-1.30 g / cm³ 3 The overall apparent density of the three-layer co-extruded sheet is 0.5-0.9 g / cm³. 3Adjustable; weight reduced by 40-50%. The overall density is reduced, making the material cost close to that of traditional plastic products, giving it a competitive advantage.

[0159] 3. Advantages of PHA three-layer co-extruded foam sheets and products:

[0160] 1) The core layer has a foam structure, which has a good heat insulation effect. When made into products (such as bowls and cups), it can hold high-temperature liquids (70-100℃) without burning your hands.

[0161] 2) PHA three-layer co-extruded foamed sheets are thermoformed using a vacuum forming machine, which improves the crystallinity of the product, has good heat resistance, and does not deform when filled with high-temperature liquids (70-100℃);

[0162] 3) PHA three-layer co-extruded foam sheets and products are lightweight, weighing 50%-60% of ordinary PLA products, thus reducing costs.

[0163] 4) Scrap materials can be reused. Using 50% scrap materials as raw materials during the production process can ensure stable production.

[0164] 4. Advantages of physical carbon dioxide foaming: Stable equipment and process, consistent product quality, online adjustment of foaming ratio, convenient operation, simple raw materials, no need for complex additives, environmentally friendly and non-toxic, high closed-cell rate, uniform cell structure, smooth and flat sheet surface, and low formulation cost, requiring only 5-10 yuan of CO2 per ton of product. Therefore, the overall processing cost is low, but the return is high.

[0165] The biodegradable modified special materials and their products prepared in Examples 1-4 of this invention were subjected to the following performance tests according to the relevant national standards for plastic performance testing methods. The performance of each sample met the national standards, and the specific results are shown in Tables 2 and 3.

[0166] Table 2: Main performance parameters of the biodegradable modified special materials prepared in this invention in Examples 1-4

[0167]

[0168]

[0169] Table 3: Hygiene test data of various embodiments of the biodegradable modified special material prepared in this invention.

[0170]

[0171] As can be seen from the results in Tables 2 and 3, the biodegradable modified special materials prepared by the method of the present invention in Examples 1-4 have excellent properties and low density due to the use of the specific components and specific combination contents of the present invention. Moreover, the present invention has low cost, simple production process, and is easy to industrialize.

[0172] Comparative Example 1: Biodegradable Modified PHA Material at Too Low a Proportion

[0173] The biodegradable modified special material described in this comparative example is made from the following components: PLA 45 parts by weight, P3HB4HB (4HB content 15 mol%) 25 parts by weight, talc powder 15 parts by weight, cassava starch 5 parts by weight, modified potato starch 5 parts by weight, PBAT 13 parts by weight, PPC 8 parts by weight, castor fiber 3 parts by weight, ramie fiber 2 parts by weight, coconut shell fiber 3 parts by weight, epoxy functionalized chain extender 0.5 parts by weight, carbodiimide anti-hydrolysis agent 0.3 parts by weight, isocyanate anti-hydrolysis agent 0.2 parts by weight, vinyl acetate polymer 0.5 parts by weight, acrylate melt reinforcing agent 1.5 parts by weight, titanate coupling agent 1 part by weight, polyethylene glycol 1 part by weight, acetylthiol tributyl citrate 1.5 parts by weight, castor oil derived ester plasticizer 1 part by weight, antioxidant 1010 0.4 parts by weight, calcium stearate 0.5 parts by weight, ethylene bis-stearamide 0.5 parts by weight (compared to Example 1, PHB is replaced with PLA, that is, the main material is replaced by PLA instead of PHB).

[0174] The preparation method is the same as in Examples 1-4.

[0175] The test results are shown in Table 4.

[0176] Table 4: Test data for Comparative Example 1

[0177]

[0178]

[0179] Comparative Example 2: A biodegradable modified material of PLA in which both PBAT and PPC were replaced.

[0180] The biodegradable modified special material described in this comparative example is made from the following components: 45 parts by weight of PHB, 25 parts by weight of P3HB4HB (4HB content 15 mol%), 15 parts by weight of talc, 5 parts by weight of cassava starch, 5 parts by weight of modified potato starch, 21 parts by weight of PLA, 3 parts by weight of castor fiber, 2 parts by weight of ramie fiber, 3 parts by weight of coconut shell fiber, 0.5 parts by weight of epoxy functionalized chain extender, 0.3 parts by weight of carbodiimide anti-hydrolysis agent, 0.2 parts by weight of isocyanate anti-hydrolysis agent, 0.5 parts by weight of vinyl acetate polymer, 1.5 parts by weight of acrylate melt reinforcing agent, 1 part by weight of titanate coupling agent, 1 part by weight of polyethylene glycol, 1.5 parts by weight of tributyl acetylacetonate, 1 part by weight of castor oil-derived ester plasticizer, and antioxidant 1010. 0.4 parts by weight, calcium stearate 0.5 parts by weight, ethylene bis-stearamide 0.5 parts by weight (compared to Example 1, PBAT and PPC are replaced with PLA).

[0181] The preparation method is the same as in Examples 1-4.

[0182] The test results are shown in Table 5.

[0183] Table 5: Test data for Comparative Example 2

[0184]

[0185]

[0186] Comparative Example 3: Biodegradable modified special material without added talc and starch

[0187] The biodegradable modified special material described in this comparative example is made from the following components: 45 parts by weight of PHB, 25 parts by weight of P3HB4HB (4HB content 15 mol%), 13 parts by weight of PBAT, 8 parts by weight of PPC, 3 parts by weight of castor fiber, 2 parts by weight of ramie fiber, 3 parts by weight of coconut shell fiber, 0.5 parts by weight of epoxy functionalized chain extender, 0.3 parts by weight of carbodiimide anti-hydrolysis agent, 0.2 parts by weight of isocyanate anti-hydrolysis agent, 0.5 parts by weight of vinyl acetate polymer, 1.5 parts by weight of acrylate melt reinforcing agent, 1 part by weight of titanate coupling agent, 1 part by weight of polyethylene glycol, 1.5 parts by weight of acetylated tributyl citrate, 1 part by weight of castor oil-derived ester plasticizer, 0.4 parts by weight of antioxidant 1010, 0.5 parts by weight of calcium stearate, and 0.5 parts by weight of ethylene bis-stearamide (compared to Example 1, talc and starch were not added).

[0188] The preparation method is the same as in Examples 1-4.

[0189] The test results are shown in Table 6.

[0190] Table 6: Test data for Comparative Example 3

[0191] Measurement items Measurement results <![CDATA[Particle density (g / cm 3 )]]> 1.33 Tensile strength (MPa) 35.4 Bending strength (MPa) 29.1 Low temperature resistance (°C) -14 Thermal conductivity, W / (m·K) 0.067

[0192] Comparative Example 4: PHA-free biodegradable modified special material

[0193] The biodegradable modified special material described in this embodiment is made from the following components: 15 parts by weight of talc, 5 parts by weight of tapioca starch, 5 parts by weight of modified potato starch, 50 parts by weight of PLA, 23 parts by weight of PBAT, and PPC. 18 parts by weight, 3 parts by weight of castor fiber, 2 parts by weight of ramie fiber, 3 parts by weight of coconut shell fiber, 0.5 parts by weight of epoxy functionalized chain extender, 0.3 parts by weight of carbodiimide anti-hydrolysis agent, 0.2 parts by weight of isocyanate anti-hydrolysis agent, 0.5 parts by weight of vinyl acetate polymer, 1.5 parts by weight of acrylate melt reinforcing agent, 1 part by weight of titanate coupling agent, 1 part by weight of polyethylene glycol, 1.5 parts by weight of tributyl acetyl citrate, 1 part by weight of castor oil-derived ester plasticizer, 0.4 parts by weight of antioxidant 1010, 0.5 parts by weight of calcium stearate, 0.5 parts by weight of ethylene bis-stearamide (compared to Example 1, it does not contain PHA, and the balance is supplemented with PLA, PBAT, and PPC).

[0194] The preparation method is the same as in Examples 1-4.

[0195] The test results are shown in Table 7.

[0196] Table 7: Test data for Comparative Example 4

[0197]

[0198]

[0199] Comparative Example 5: Biodegradable modified material with PPC replaced by PLA

[0200] The biodegradable modified special material described in this comparative example is made from the following components: 45 parts by weight of PHB, 25 parts by weight of P3HB4HB (4HB content 15 mol%), 15 parts by weight of talc, 5 parts by weight of cassava starch, 5 parts by weight of modified potato starch, 13 parts by weight of PBAT, 8 parts by weight of PLA, 3 parts by weight of castor fiber, 2 parts by weight of ramie fiber, 3 parts by weight of coconut shell fiber, 0.5 parts by weight of epoxy functionalized chain extender, 0.3 parts by weight of carbodiimide anti-hydrolysis agent, 0.2 parts by weight of isocyanate anti-hydrolysis agent, 0.5 parts by weight of vinyl acetate polymer, 1.5 parts by weight of acrylate melt reinforcing agent, 1 part by weight of titanate coupling agent, 1 part by weight of polyethylene glycol, 1.5 parts by weight of tributyl acetylacetonate, 1 part by weight of castor oil-derived ester plasticizer, and antioxidant 1010. 0.4 parts by weight, calcium stearate 0.5 parts by weight, ethylene bis-stearamide 0.5 parts by weight (compared to Example 1, PPC is replaced with PLA).

[0201] The preparation method is the same as in Examples 1-4.

[0202] The test results are shown in Table 8.

[0203] Table 8: Test data of Comparative Example 5

[0204]

[0205] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A biodegradable composite sheet, characterized in that, The composite sheet comprises, from top to bottom, an upper structure, a middle structure, and a lower structure, wherein, The superstructure includes a surface layer; The central structure includes a foamed core layer; The lower structure includes a surface layer; The surface layer and the foamed core layer are made of a substrate, which is PHB and other PHAs. The materials of the surface layer and the foamed core layer also include modified raw materials and powders. The modified raw materials include PBAT and PPC. The materials of the surface layer and the foamed core layer, by weight, include 30-80 parts of PHB and other PHAs, 5-20 parts of PBAT, 5-20 parts of PPC, and 10-60 parts of powders. The other PHAs mentioned include one, two or more of P(HA-LA), P3HP, P4HB, PHV, PHO, PHN, PHD, PHBV, P34HB, PHBHHp, PHBHHx, P3HB4HB3HV or P3HB4HB5HV. The apparent density of the surface layer is 1.23-1.34 g / cm³. 3 The apparent density of the foamed core layer is 0.30-0.45 g / cm³. 3 The thickness ratio of the surface layer to the foamed core layer is (0.25-0.5):(0.5-0.75).

2. The composite sheet according to claim 1, characterized in that, The surface layer is obtained by extrusion molding machine through melting and plasticizing, extrusion through T-die, and the extruded melt is obtained by three-roll calendering, cooling, shaping, trimming, traction and winding. The foamed core layer is obtained through supercritical carbon dioxide foaming.

3. The composite sheet according to claim 1, characterized in that, The modified raw materials also include one or more of the following: plant fiber, PLA, PBS, carboxymethyl cellulose, or PGA.

4. The composite sheet according to claim 3, characterized in that, The plant fiber is selected from one or more of castor fiber, jute fiber, ramie fiber, flax fiber, lignin, and coconut fiber.

5. The composite sheet according to claim 1, characterized in that, The powder includes inorganic powder and starch.

6. The composite sheet according to claim 5, characterized in that, The inorganic powder is selected from calcium carbonate and / or talc.

7. The composite sheet according to claim 5, characterized in that, The starch is selected from one or more of corn starch, tapioca starch, potato starch or sweet potato starch and their modified starches.

8. The composite sheet according to claim 1, characterized in that, The composite sheet has a resilience of 35-50% and an impact strength of 7.9-10.7 KJ / m. 2 .

9. The composite sheet according to claim 1, characterized in that, The materials of the surface layer and the foamed core layer also include additives; wherein the materials of the surface layer and the foamed core layer contain 0.2-10 parts of additives.

10. The composite sheet according to claim 9, characterized in that, The additives include one or more of the following: chain extenders, hydrolysis stabilizers, compatibilizers, melt reinforcing agents, coupling agents, solubilizers, plasticizers, antioxidants, heat stabilizers, and lubricants.

11. The composite sheet according to any one of claims 1-10, characterized in that, In P(HA-LA), HA is selected from one or more of 3-hydroxypropionic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvalerate, 5-hydroxyvalerate, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, and 3-hydroxydodecanoic acid; LA is 2-hydroxypropionic acid.

12. A method for preparing the composite sheet according to any one of claims 1-11, characterized in that, The preparation method includes mixing the various materials, melting, and shearing to obtain granules.

13. The preparation method according to claim 12, characterized in that, The method for preparing the foamed core layer includes using supercritical carbon dioxide to microfoam granules, and then preparing a three-layer foamed composite sheet by continuous extrusion. The surface preparation method includes feeding granules into a sheet extrusion molding machine, melting and plasticizing them, extruding them through a T-die, and then cooling, shaping, trimming, traction, and winding the extruded melt into a finished product using a three-roll calender.

14. The use of a composite sheet according to any one of claims 1-11 or a composite sheet obtained by any one of the preparation methods according to claims 12-13 in the preparation of products in which the material needs to have biodegradable properties.

15. The application according to claim 14, characterized in that, The products mentioned include food containers, agricultural materials, medical materials, or packaging materials.

Images