Crystalline heat-resistant biodegradable straw material and preparation method thereof

Abstract

The invention discloses a crystalline heat-resistant biodegradable straw material, which is prepared from the following raw materials: 60 to 75 percent of PLA (Polylactic Acid), 0.1 to 0.5 percent of plasticizer, 0.02 to 0.1 percent of compatilizer, 10 to 25 percent of filler and not higher than 20 percent of toughening plastic resin. According to the straw material disclosed by the invention, the dosage of the expensive toughening resin is controlled to be below 20%, and the medium-light pure PLA with lower cost is adopted, so that a biodegradable straw with low cost, high heat resistance, excellent toughness, sanitation and safety can be prepared, the raw material cost is remarkably reduced, and the technical prejudice that high heat resistance must depend on high PBS is broken through.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials, specifically to a crystalline heat-resistant biodegradable straw material and its preparation method. Background Technology

[0002] With the deepening implementation of the "plastic ban," traditional polypropylene (PP) straws have been largely replaced. However, mainstream alternatives such as paper straws have problems such as easy softening and poor taste, while polylactic acid (PLA) biodegradable straws affect the user experience due to their insufficient heat resistance.

[0003] Currently, the mainstream technical approach to improving the heat resistance of PLA straws is to blend them with heat-resistant materials such as polybutylene succinate (PBS). For example, patent CN110804287A discloses a heat-resistant modified polylactic acid composite material, in which the amount of PBS is as high as 25%-40%. Although this approach can effectively improve heat resistance, the high price of PBS (approximately RMB 18,000-25,000 / ton) results in a high cost for the composite material, which seriously hinders the widespread adoption of high-performance biodegradable straws.

[0004] The applicant's in-depth research revealed a deeper technological bias behind the high cost of existing high-PBS content formulations: the industry generally believes that a high PBS ratio (typically greater than 20%) is necessary to provide sufficient crystallization induction and thermal stability to the PLA matrix, thereby ensuring the pipettes achieve the required heat resistance during subsequent processing and use. This bias makes reducing the PBS content a difficult technical approach, as simply decreasing the PBS content leads to a significant decrease in the pipette's heat resistance. Therefore, addressing the shortcomings of the existing technology becomes the problem this invention aims to solve. Summary of the Invention

[0005] The present invention aims to solve the technical problem of how to prepare biodegradable pipette material with excellent heat resistance without relying on a high proportion of high-cost PBS, and provides a crystalline heat-resistant biodegradable pipette material and its preparation method. The present invention is achieved as follows: a crystalline heat-resistant biodegradable straw material, the raw materials of which include: 60-75% PLA, 0.1-0.5% plasticizer, 0.02-0.1% compatibilizer, 10-25% filler, and no more than 20% toughening resin.

[0006] Furthermore, the PLA is a medium-purity lactic acid polymer with a melt index of 2-10 g / 10 min.

[0007] Furthermore, the toughening resin is selected from one or more of polybutylene succinate, polycaprolactone, polypropylene carbonate, and polybutylene terephthalate, and its melt index is 2-10 g / 10 min.

[0008] Furthermore, the plasticizer is one or more of the following: acetylated tributyl citrate, epoxidized soybean oil, diisononyl cyclohexanedicarboxylate, and isononyl cyclohexanedicarboxylate.

[0009] Furthermore, the compatibilizer is selected from one or more of maleic anhydride-grafted PLA and maleic anhydride-grafted PBS.

[0010] Furthermore, the filler is talc powder, and the talc powder has a mesh size greater than 1250 mesh.

[0011] On the other hand, a method for preparing a crystalline heat-resistant biodegradable straw material includes the following steps: S1: Weigh each component material as required and add it to a high-speed mixer for thorough mixing to form a first mixture; S2: Add the first mixture to the main feed of a twin-screw extruder for melt extrusion; the melt extrusion temperature is 150-200℃, and vacuum treatment is performed; S3: After melt extrusion, the material is drawn out from the die outlet, cooled by air, and pelletized to obtain biodegradable straw material particles; S4: Mix the biodegradable straw material particles with color masterbatch as needed to form a second mixture; S5: Extrude the second mixture through a single-screw straw extruder, cool and shape it, and cut it to obtain a preliminary straw; S6: Place the preliminary straw on a crystallization device for crystallization.

[0012] The advantages of this invention are: 1. By controlling the amount of expensive toughening resin (such as PBS) to below 20% and using less expensive pure PLA, the raw material cost of the pipette material has been significantly reduced, breaking the technical prejudice that high heat resistance must rely on high PBS. At the same time, through the synergistic effect of optimized formulation and specific crystallization process, the product's heat resistance temperature can be stably maintained above 82℃, and its toughness, aging resistance and hygiene safety fully meet the usage standards, successfully achieving a balance between low cost and high performance.

[0013] 2. The low-content PBS + medium-purity PLA + high-mesh talc formulation system provided by this invention, combined with a multi-stage baking and crystallization process, provides a stable and uniform thermal environment for the full crystallization of the PLA matrix, perfectly compensating for the heat resistance that may be lost due to the reduction of PBS content. This is a key technical guarantee for achieving low cost and heat resistance.

[0014] 3. The low PBS formulation of the present invention effectively reduces the migration risk of small molecules, especially the total migration in ethanol simulants is significantly reduced and meets national standards, thereby improving the food contact safety of the product.

[0015] 4. The straws produced by this invention not only have good heat resistance, but also excellent low-temperature toughness and aging resistance, with an extremely low breakage rate, making them suitable for a wider range of applications and extending the shelf life and service life of the products. Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0016] This invention provides a crystalline heat-resistant biodegradable straw material, the raw materials of which include: 60-75% PLA, 0.1-0.5% plasticizer, 0.02-0.1% compatibilizer, 10-25% filler, and no more than 20% toughening resin, which significantly reduces material costs. By combining it with a specific crystallization process, it breaks through industry technical biases and achieves high heat resistance at low cost.

[0017] The PLA is a medium-purity lactic acid polymer with a melt index of 2-10 g / 10 min. Using medium-purity PLA not only meets the heat resistance requirements for subsequent crystallization of the straw while ensuring its heat resistance, but also reduces costs. The medium-purity PLA can be any one of the following: FY802 from Fengyuan, PT102 from Pulis, or LX175 from Kebin.

[0018] The toughening resin is selected from one or more of polybutylene succinate (PBS), polycaprolactone (PCL), polypropylene carbonate (PPC), and polybutylene terephthalate adipate (PBAT), with a melt index of 2-10 g / 10 min. Preferably, the toughening resin is polybutylene succinate (PBS), which has a low carboxyl group and good anti-aging properties. The selected biodegradable resin (such as PBS, PBAT, etc.) has good compatibility with PLA, can effectively toughen PLA at low dosages, and ensures the complete biodegradability of the entire system.

[0019] The plasticizer is one or more of the following: acetylated tributyl citrate, epoxidized soybean oil, diisononyl cyclohexanedicarboxylate, and isononyl cyclohexanedicarboxylate.

[0020] The compatibilizer is selected from one or more of maleic anhydride-grafted PLA and maleic anhydride-grafted PBS. Preferably, the compatibilizer is maleic anhydride-grafted PLA, which is a degradable material substrate.

[0021] The filler is talc powder with a mesh size greater than 1250 mesh. Talc powder not only reduces costs as an inexpensive filler, but also acts as a highly efficient nucleating agent. In synergy with the crystallization process, it significantly promotes the crystallization process of PLA, which is one of the keys to improving heat resistance; its effect is superior to organic fillers such as bamboo powder.

[0022] The preparation method of the crystalline heat-resistant biodegradable straw material includes the following steps: S1: Weigh each component material as required and add it to the high-speed mixer for thorough mixing to form the first mixture; S2: Add the first mixture to the main feed of the twin-screw extruder for melt extrusion; the melt extrusion temperature is 150-200℃, and vacuum treatment is performed; S3: After melt extrusion, it is drawn out from the die head outlet, cooled by air, and pelletized to obtain biodegradable straw material particles; S4: Mix the biodegradable straw particles with the color masterbatch as needed to form a second mixture; S5: The second mixture is extruded through a single-screw straw extruder, cooled and shaped, and cut to obtain a preliminary straw; S6: Place the pre-formed straws on the crystallization equipment for crystallization. Place the pre-formed straws, tip upwards, evenly into the crystallization equipment. Then, push the crystallization equipment into the baking chamber for multi-stage baking. The pre-formed straws undergo three stages of baking: Stage 1: 55-65℃, 30-60 minutes; Stage 2: 60-70℃, 30-60 minutes; Stage 3: 70-80℃, 90-120 minutes. Dividing the temperature into three stages ensures that the straws will not deform during the entire baking process.

[0023] The beneficial technical effects of the crystalline heat-resistant biodegradable straw material of the present invention will be illustrated below through several examples and comparative examples. Example 1

[0024] This embodiment provides a crystalline heat-resistant biodegradable straw material, the raw materials of which include: 67.5% PLA, 0.25% plasticizer, 0.05% compatibilizer, 17.2% filler, and 15% toughening resin. The PLA is selected from Fengyuan's FY802 type medium-purity PLA; the toughening resin is polybutylene succinate (PBS); the plasticizer is epoxidized soybean oil; the compatibilizer is maleic anhydride-grafted PLA; and the filler is 1500-mesh talc powder. The preparation method of the crystalline heat-resistant biodegradable straw material includes the following steps: S1: Weigh each component material as required and add it to the high-speed mixer for thorough mixing to form the first mixture; S2: Add the first mixture to the main feed of the twin-screw extruder for melt extrusion; the melt extrusion temperature is 150-200℃, and vacuum treatment is performed; S3: After melt extrusion, it is drawn out from the die head outlet, cooled by air, and pelletized to obtain biodegradable straw material particles; S4: Mix the biodegradable straw particles with the color masterbatch as needed to form a second mixture; S5: The second mixture is extruded through a single-screw straw extruder, cooled and shaped, and cut to obtain a preliminary straw; S6: Place the pre-formed straws on the crystallization equipment for crystallization. Place the pre-formed straws with the tips facing up evenly into the crystallization equipment. Then push the crystallization equipment into the baking chamber for multi-stage baking. The pre-formed straws are baked in three stages: the first stage is 60℃ for 60 minutes; the second stage is 65℃ for 60 minutes; and the third stage is 80℃ for 120 minutes. Example 2

[0025] This embodiment provides a crystalline, heat-resistant, biodegradable straw material, the raw materials of which include: 70% PLA, 0.3% plasticizer, 0.05% compatibilizer, 19.65% filler, and 10% toughening resin. The PLA is selected from Pulliss's PT102 type medium-purity PLA; the toughening resin is polybutylene succinate (PBS); the plasticizer is tributyl acetylacetic acid; the compatibilizer is maleic anhydride-grafted PBS; and the filler is 2000-mesh talc.

[0026] The preparation method of the crystalline heat-resistant biodegradable straw material is the same as in Example 1. Example 3

[0027] This embodiment provides a crystalline, heat-resistant, biodegradable straw material, the raw materials of which include: 63% PLA, 0.4% plasticizer, 0.1% compatibilizer, 18.5% filler, and 18% toughening resin. The PLA is selected from Cobian's LX175 type medium-purity PLA; the toughening resin is polybutylene terephthalate-adipate (PBAT); the plasticizer is isononyl cyclohexanedicarboxylate; the compatibilizer is maleic anhydride-grafted PLA; and the filler is 1250-mesh talc powder.

[0028] The preparation method of the crystalline heat-resistant biodegradable straw material is the same as in Example 1. Example 4

[0029] This embodiment provides a crystalline, heat-resistant, biodegradable straw material, comprising: 73.5% PLA, 0.2% plasticizer, 0.08% compatibilizer, 16.22% filler, and 10% toughening resin. The PLA is selected from Fengyuan's FY802 type medium-purity PLA; the toughening resin is a mixture of PBS and PCL at a mass ratio of 4:1; the plasticizer is epoxidized soybean oil; the compatibilizer is maleic anhydride-grafted PLA; and the filler is 1800-mesh talc powder. The preparation method is the same as in Example 1.

[0030] Comparative Example 1 This example provides a straw material, the raw materials of which include: 50% PLA, 0.25% plasticizer, 0.6% compatibilizer, 16.65% filler, and 32.5% PBS. The PLA is selected as high-purity PLA with a levorotatory optical purity >99%; the toughening resin is polybutylene succinate (PBS); the plasticizer is epoxidized soybean oil; the compatibilizer is maleic anhydride-grafted PLA; and the filler is 1500-mesh talc. The crystallization process in its preparation method is the same as in Example 1.

[0031] Comparative Example 2 This example provides a straw material, the raw materials of which include: 67.5% PLA, 0.25% plasticizer, 0.05% compatibilizer, 17.2% filler, and 15% toughening resin. The PLA is selected from Fengyuan's FY802 type medium-purity PLA; the toughening resin is polybutylene succinate (PBS); the plasticizer is epoxidized soybean oil; the compatibilizer is maleic anhydride-grafted PLA; and the filler is 1500-mesh talc powder. The preparation method of the straw material includes the following steps: S1: Weigh each component material as required and add it to the high-speed mixer for thorough mixing to form the first mixture; S2: Add the first mixture to the main feed of the twin-screw extruder for melt extrusion; the melt extrusion temperature is 150-200℃, and vacuum treatment is performed; S3: After melt extrusion, it is drawn out from the die head outlet, cooled by air, and pelletized to obtain biodegradable straw material particles; S4: Mix the biodegradable straw particles with the color masterbatch as needed to form a second mixture; S5: The second mixture is extruded through a single-screw straw extruder, cooled and shaped, and cut to obtain a preliminary straw; S6: Place the pre-formed straws on the crystallization equipment for crystallization. Place the pre-formed straws with the tips facing up evenly into the crystallization equipment, and then push the crystallization equipment into the hot air circulating oven for constant temperature treatment at 75℃ for 60 minutes.

[0032] Comparative Example 3 This example provides a straw material, the raw materials of which include: 67.5% PLA, 0.25% plasticizer, 0.05% compatibilizer, 17.2% filler, and 15% toughening resin. The PLA is selected from Fengyuan's FY802 type medium-purity PLA; the toughening resin is polybutylene succinate (PBS); the plasticizer is epoxidized soybean oil; the compatibilizer is maleic anhydride-grafted PLA; and the filler is 200-mesh bamboo powder. The preparation method of the straw material includes the following steps: S1: Weigh each component material as required and add it to the high-speed mixer for thorough mixing to form the first mixture; S2: Add the first mixture to the main feed of the twin-screw extruder for melt extrusion; the melt extrusion temperature is 150-200℃, and vacuum treatment is performed; S3: After melt extrusion, it is drawn out from the die head outlet, cooled by air, and pelletized to obtain biodegradable straw material particles; S4: Mix the biodegradable straw particles with the color masterbatch as needed to form a second mixture; S5: The second mixture is extruded through a single-screw straw extruder, cooled and shaped, and cut to obtain a preliminary straw; S6: Place the pre-formed straws on the crystallization equipment for crystallization. Place the pre-formed straws with the tips facing up evenly into the crystallization equipment. Then push the crystallization equipment into the baking chamber for multi-stage baking. The pre-formed straws are baked in three stages: the first stage is 60℃ for 60 minutes; the second stage is 65℃ for 60 minutes; and the third stage is 80℃ for 120 minutes.

[0033] Comparative Example 4 This example provides a straw material, the raw materials of which include: 67.5% PLA, 0.25% plasticizer, 0.05% compatibilizer, 17.2% filler, and 15% toughening resin. The PLA is selected as high-purity PLA (levorotatory optical purity >99%); the toughening resin is polybutylene succinate (PBS); the plasticizer is epoxidized soybean oil; the compatibilizer is maleic anhydride-grafted PLA; and the filler is 1500-mesh talc. The preparation method of the straw material includes the following steps: S1: Weigh each component material as required and add it to the high-speed mixer for thorough mixing to form the first mixture; S2: Add the first mixture to the main feed of the twin-screw extruder for melt extrusion; the melt extrusion temperature is 150-200℃, and vacuum treatment is performed; S3: After melt extrusion, it is drawn out from the die head outlet, cooled by air, and pelletized to obtain biodegradable straw material particles; S4: Mix the biodegradable straw particles with the color masterbatch as needed to form a second mixture; S5: The second mixture is extruded through a single-screw straw extruder, cooled and shaped, and cut to obtain a preliminary straw; S6: Place the pre-formed straws on the crystallization equipment for crystallization. Place the pre-formed straws with the tips facing up evenly into the crystallization equipment. Then push the crystallization equipment into the baking chamber for multi-stage baking. The pre-formed straws are baked in three stages: the first stage is 60℃ for 60 minutes; the second stage is 65℃ for 60 minutes; and the third stage is 80℃ for 120 minutes.

[0034] The straws prepared in each embodiment and comparative example were subjected to performance tests, including temperature resistance tests, aging tests, straw breakage rate statistics, and total migration statistics.

[0035] The detection method for the temperature resistance test is as follows: Place the straw sample in hot water and let it stand for 30 s, then stir it for about 10 s. Observe the maximum temperature the straw can withstand without deformation or bending. Also, gently touch the bottom of the test container with the straw, and the straw should have a certain hardness without bending or obvious deformation. When the straw is lifted out of the water, pinch the soaked part with your hand, and the straw can rebound.

[0036]

[0037] The detection method for the aging test is as follows: Place the straw sample in a thermostatic and humid box. Put your thumb and index finger on the upper and lower sides of the straw mouth respectively, pinch the straw mouth flat into a flat shape, and then release it; then adjust it to a 45-degree angle and perform the same operation again; observe how long it takes for cracking to occur.

[0038]

[0039] The method for counting the straw breakage rate is as follows: Put your thumb and index finger on the upper and lower sides of the straw mouth respectively, pinch the straw mouth flat into a flat shape, and then release it; then adjust it to a 45-degree angle and perform the same operation again; observe whether the straw cracks.

[0040]

[0041] The method for counting the total migration amount is: GB / T4806.7-2023 "National Food Safety Standard - Plastic Materials and Products for Food Contact". A single-sided area less than 10 mg / dm² is qualified.

[0042]

[0043] Based on the test data in Table 1-4, the following conclusions can be drawn: 1. The heat-resistant temperatures of all embodiments (PBS content 10%-18%) of the present invention are all stable above 82°C, and the aging performance, low-temperature toughness (breakage rate), and hygienic safety index (total migration amount) are all qualified. This is comparable to the performance of Comparative Example 1 (high PBS content, 32.5%), but the raw material cost is significantly reduced. In particular, it is worth noting that in Comparative Example 1 with a high PBS dosage, its total migration amount exceeded the standard in ethanol, posing a potential safety hazard, while the low-PBS formulation of the present invention effectively avoided this risk.

[0044] 2. The performance of Comparative Example 2 (without a specific crystallization process) is comprehensively deteriorated, with a heat resistance of only 62°C and a very high breakage rate, fully demonstrating that the three-stage crystallization process adopted by the present invention is a necessary condition and core technical guarantee for achieving high heat resistance with a low-PBS formulation, and it has a strong synergistic effect with the formulation.

[0045] 3. The heat resistance and low-temperature toughness of Comparative Example 3 (using bamboo powder) were significantly lower than those of Example 1 (using talc powder), which shows that the talc powder of a specific mesh size of the present invention has an irreplaceable role in promoting crystallization and improving heat resistance.

[0046] 4. Comparative Example 4 (using high-purity PLA) has comparable performance to Example 1, but at a higher cost. This demonstrates that using medium-purity PLA is entirely feasible under the formulation and process system of this invention, which opens up an effective path for cost reduction.

[0047] 5. Therefore, this invention, through the synergistic combination of an optimized formula of "low-content PBS + medium-purity PLA + high-mesh talc" and a special process of "multi-stage drying oven crystallization", successfully breaks the technical prejudice that "high heat resistance must rely on high PBS", and provides a biodegradable straw solution that combines low cost, high heat resistance, excellent toughness and hygiene safety, with significant commercial value and market competitiveness.

[0048] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A crystalline heat-resistant biodegradable straw material, characterized by: The raw materials include: 60-75% PLA, 0.1-0.5% plasticizer, 0.02-0.1% compatibilizer, 10-25% filler, and no more than 20% toughening plastic.

2. The crystalline heat-resistant biodegradable straw material of claim 1, wherein: The PLA is a medium optical purity lactic acid polymer with a melt index of 2-10 g / 10 min.

3. The crystalline heat-resistant biodegradable straw material of claim 1, wherein: The toughening resin is selected from one or more of polybutylene succinate, polycaprolactone, polypropylene carbonate, polybutylene terephthalate-hexane adipate with a melt index of 2-10 g / 10 min.

4. The crystalline heat-resistant biodegradable straw material of claim 1, wherein: The plasticizer is one or more of acetyl tri-butyl citrate, epoxy soybean oil, diisononyl cyclohexane dicarboxylate, isononyl cyclohexane dicarboxylate.

5. The crystalline heat-resistant biodegradable straw material of claim 1, wherein: The compatibilizer is selected from one or more of maleic anhydride grafted PLA, maleic anhydride grafted PBS.

6. The crystalline heat-resistant biodegradable straw material of claim 1, wherein: The filler is talc powder with a mesh size greater than 1250 mesh.

7. A process for the preparation of the crystalline heat resistant biodegradable straw material according to any one of claims 1 to 6, characterized in that: The method includes the following steps: S1: After weighing the required components, add them to a high-speed mixer for thorough mixing to form a first mixture; S2: Add the first mixture to the main feeding of a twin-screw extruder for melt extrusion; the melt extrusion temperature is 150-200°C, and vacuum treatment is performed; S3: After melt extrusion, draw out from the outlet of the die, pass through air cooling treatment, and cut into particles to obtain biodegradable straw particles; S4: Mix the biodegradable straw particles with color masterbatch as needed to form a second mixture; S5: Extrude the second mixture through a single-screw straw extruder, cool and shape, cut, and obtain a primary molded straw; S6: Place the primary molded straw on a crystallization device for crystallization.

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