Biodegradable material and manufacturing method therefor and use thereof

Abstract

The present invention relates to the technical field of biodegradable materials, and in particular to a biodegradable material and a manufacturing method therefor and a use thereof. The biodegradable material comprises the following components in parts by weight: 60-90 parts of flexible biodegradable polyester, 2-10 parts of polylactic acid, 2-30 parts of an inorganic filler, and 0-0.95 part of an auxiliary agent. The flexible biodegradable polyester of the biodegradable material has a molecular weight distribution coefficient PDI of 1.7 to 2.3 and a carboxyl end group content of less than 25 mol / t after shearing at 180°C. The biodegradable material manufactured in the present invention has the isotropy of longitudinal and transverse tearing under high and low temperature conditions, and has good aging resistance.

Description

A biodegradable material and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of biodegradable materials, and in particular relates to a biodegradable material and a preparation method and application thereof. Background Art

[0002] Blending flexible biodegradable polyester with polylactic acid (PLA) and mineral powder (MD) can produce an inexpensive biodegradable film bag material while also achieving complementary performance. The flexible biodegradable polyester improves the toughness of PLA, particularly its tear resistance at low temperatures. Meanwhile, PLA improves the rigidity of the flexible biodegradable polyester, particularly its lifting performance at high temperatures. Furthermore, the MD mineral powder helps improve the bubble stability and opening performance of the flexible biodegradable polyester / PLA blend. However, due to the poor compatibility between the flexible biodegradable polyester and PLA, the processing and mechanical properties of the flexible biodegradable polyester / PLA blend are poor without the addition of a compatibilizer, particularly the anisotropy of longitudinal and transverse tearing, making longitudinal tearing more likely in high- and low-temperature alternating applications. Common toughening methods involve increasing the volume, but using common compatibilizers such as BASF's reactive chain extender (ADR) results in decreased stiffness and lifting performance of the blown film, along with a sour odor, making it unsuitable for use in foodservice bags. There are also studies using starch to modify flexible biodegradable polyester / PLA, using the toughness of starch after plasticization to compensate for the defect of tearing. However, starch materials are easy to absorb water and have poor aging performance. Their performance will be worse in high and low temperature usage scenarios. In addition, the smell of starch itself will mask the smell of food and beverages, causing trouble to consumers.

[0003] When used in summer or winter, catering bags may be used to hold iced drinks at high temperatures, causing the film material to transition from a high-temperature to a low-temperature environment. In winter, catering bags are used to hold hot food at very low temperatures, causing the environment to transition from a low-temperature to a high-temperature environment. Therefore, catering bags must maintain excellent performance at both high and low temperatures, especially tear strength. Furthermore, aging performance is crucial for shelf life. After aging under certain conditions, catering bags must not exhibit significant differences in longitudinal and transverse tear strength, otherwise they will fail. Therefore, optimizing the tear strength of degradable materials at both high and low temperatures and after aging, as well as the ratio of longitudinal and transverse tear strength, is particularly important.

[0004] Patent document CN101522797B discloses a starch-based biodegradable multiphase composition comprising a continuous phase of tough polyester, a nanoparticulate starch phase, and a dispersed phase of polyhydroxyalkanoate. This composition exhibits isotropic tear extension in both the longitudinal and transverse directions. However, this system's aging resistance and other properties do not meet the application requirements of catering bags.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a biodegradable material and its preparation method and application. The biodegradable material prepared by the present invention has isotropic longitudinal and transverse tearing under high and low temperature and aging conditions and has good aging resistance.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: a biodegradable material comprising the following components in parts by weight:

[0008] 60-90 parts of flexible biodegradable polyester, 2-10 parts of polylactic acid, 2-30 parts of inorganic filler, 0-0.95 parts of additives;

[0009] The flexible biodegradable polyester has a molecular weight distribution index (PDI) of 1.7 to 2.3 after shearing at 180° C., and a terminal carboxyl group content of ≤25 mol / t. The shearing conditions are as follows: 200 kg of the polyester is extruded in a 75A twin-screw extruder at 180° C., a rotation speed of 300 to 400 rpm, a feed rate of 400 to 500 kg / h, and a shearing time of 20 to 25 minutes.

[0010] The molecular weight distribution index PDI after shearing in the present invention is obtained by molecular weight GPC test. The GPC test method is: using Waters' ACQUITY APC TM GPC tests were performed at 40°C using XT45, XT200, and XT459 columns, tetrahydrofuran solvent, and a mobile phase flow rate of 0.5 mL / min. Polystyrene standards were used as standards.

[0011] The terminal carboxyl groups of the flexible biodegradable polyester in the present invention are determined by GB / T14190-2017 (Method A).

[0012] The present invention effectively improves the aging resistance and tear strength of the resulting biodegradable material at high and low temperatures by screening the molecular weight distribution coefficient and terminal carboxyl group parameters of the flexible biodegradable polyester after shearing. Furthermore, by controlling the amounts of flexible biodegradable polyester and PLA added, the longitudinal and transverse tear properties can be differentiated, and the aging resistance can be adjusted.

[0013] In the biodegradable material of the present invention, the content of the flexible biodegradable polyester is not less than 50%.

[0014] Preferably, the polylactic acid has a D-lactic acid content of 4-20 wt %, a weight-average molecular weight after shearing of 70,000-120,000, and a molecular weight distribution index (PDI) of 1.3-2. The shearing conditions are as follows: shearing in a 75A twin-screw extruder at a temperature of 180° C., a shearing speed of 300-400 rpm, and a feeding rate of 400-500 kg / h.

[0015] In the present invention, by screening the D-lactic acid content of the processed PLA, the weight-average molecular weight after shearing, and the molecular weight distribution coefficient, the compatibility of the flexible biodegradable polyester and PLA can be significantly improved, thereby effectively enhancing the aging resistance of the prepared biodegradable material and improving the uniformity of the transverse and longitudinal tearing.

[0016] More preferably, the molecular weight distribution coefficient PDI of the polylactic acid after shearing is 1.3-1.7.

[0017] Preferably, the flexible biodegradable polyester is an aliphatic-aromatic copolyester and / or an aliphatic polyester.

[0018] Preferably, the flexible biodegradable polyester is an aliphatic-aromatic copolyester, and the T content of the flexible biodegradable polyester is 43-48%. The T content of the flexible biodegradable polyester is the molar ratio of the terephthalic acid monomer (PTA) units in the flexible biodegradable polyester to the total polyacid monomer units in the flexible biodegradable polyester.

[0019] More preferably, the flexible biodegradable polyester includes one or a mixture of polybutylene adipate terephthalate (PBAT) and polybutylene sebacate terephthalate (PBSeT).

[0020] More preferably, the aliphatic polyester includes at least one of conventional aliphatic polyesters in the art, such as polybutylene succinate-adipate resin (PBSA).

[0021] Preferably, the polylactic acid includes at least one of levorotatory polylactic acid (PLLA), dextrorotatory polylactic acid (PDLA), and a PLLA / PDLA copolymer.

[0022] Preferably, the D50 particle size distribution of the inorganic filler is D50≤5 μm.

[0023] Preferably, the D50 particle size distribution of the inorganic filler is D50≤4 μm.

[0024] More preferably, the D50 particle size distribution of the inorganic filler is 1.5 to 3 μm. Selecting an inorganic filler with a suitable D50 particle size can effectively improve the aging resistance of the obtained material.

[0025] Preferably, the inorganic filler is selected from one or a mixture of talc, calcium carbonate, silicon dioxide, montmorillonite, kaolin, chalk, graphite, gypsum, conductive carbon black, calcium chloride, iron oxide, dolomite, wollastonite, titanium dioxide, silicate, mica, glass fiber or mineral fiber.

[0026] More preferably, the inorganic filler is at least one selected from talc, calcium carbonate, silicon dioxide, montmorillonite and kaolin.

[0027] Preferably, the auxiliary agent includes a lubricant and an opening agent.

[0028] More preferably, the weight portion of the lubricant is 0.01-0.94 parts; the weight portion of the opening agent is 0.01-0.94 parts.

[0029] Preferably, the lubricant includes erucamide, monoglyceride, ethylene bisstearamide and other common components in the art.

[0030] Preferably, the opening agent includes common components in this field such as silicon dioxide, talc, diatomaceous earth, polyethylene wax, etc.

[0031] The present invention also claims a method for preparing the biodegradable material, comprising the following steps:

[0032] The flexible biodegradable polyester, polylactic acid, inorganic filler and additives are mixed, and then melt-extruded and granulated to obtain the biodegradable material.

[0033] Preferably, the mixing rotation speed is 240-380 rpm.

[0034] Preferably, the temperature of the melt extrusion granulation is 150-200°C.

[0035] The present invention also claims protection for a food packaging film / bag made from the biodegradable material.

[0036] The present invention also claims protection for a use of the biodegradable material in the field of catering bags.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The biodegradable material prepared by the present invention has excellent longitudinal and transverse tearing isotropy under high and low temperature conditions, and has good aging resistance, and can better adapt to the application scenarios and shelf life requirements of catering bags. DETAILED DESCRIPTION

[0039] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] In the following examples and comparative examples, the experimental methods used are conventional methods unless otherwise specified. Unless otherwise specified, the opener is commercially available, and the same opener is used in parallel experiments.

[0041] The raw materials used in the examples and comparative examples are shown in Table 1.

[0042] Table 1

[0043] Examples 1 to 13 and Comparative Examples 1 to 4

[0044] The components and weight proportions of the biodegradable materials of Examples 1 to 13 and Comparative Examples 1 to 4 are shown in Tables 2 to 3.

[0045] The preparation method of the biodegradable materials of Examples 1 to 13 and Comparative Examples 1 to 4 comprises the following steps:

[0046] The formulated amount of flexible biodegradable polyester, polylactic acid, filler, and additives were sequentially added to a high-speed mixer and mixed evenly (rotating speed was 300 rpm), and then added to a twin-screw extruder for melt extrusion and granulation to obtain a biodegradable composite material. In the twin-screw extruder, the temperature of zone 1 was 150° C., the temperature of zone 2 was 170° C., the temperature of zone 3 was 180° C., the temperature of zone 4 was 180° C., the temperature of zone 5 was 180° C., the temperature of zone 6 was 190° C., the temperature of zone 7 was 190° C., the temperature of zone 8 was 190° C., the temperature of zone 9 was 190° C., the temperature of zone 10 was 200° C., and the temperature of the nozzle was 200° C.

[0047] Table 2 Component dosage (parts by weight)

[0048] Table 3 Component dosage in comparative example (parts by weight)

[0049] Performance Testing

[0050] The biodegradable materials prepared in the examples and comparative examples were used to make vest bags using a bag making machine. The film blowing temperature was 150° C. and the thickness of the vest bags was 25 μm. The mechanical properties of the vest bags after being treated under different conditions were measured.

[0051] Tear strength test method:

[0052] Tear strength test: Conducted in accordance with GB / T 16578.2-2009, samples were conditioned in a standard environment (23±2°C, 50±5% RH) for 24 hours before testing. Tests were performed in both the longitudinal and transverse directions.

[0053] Normal temperature state index requirements: longitudinal tear strength ≥ 1000mN, transverse longitudinal tear strength ≥ 1000mN, longitudinal and transverse tear ratio 60-140%, the calculation formula of the longitudinal and transverse tear ratio is: longitudinal tear strength / transverse longitudinal tear strength*100%.

[0054] Aging conditions: Place in an environment of 60±3℃, 60±5%RH for 15 days.

[0055] The index requirements are that after 15 days of accelerated aging, the longitudinal tear strength is ≥1000mN, the transverse tear strength is ≥1000mN, the longitudinal and transverse tear ratio is 60-140%, and the calculation formula of the longitudinal and transverse tear ratio is: longitudinal tear strength / transverse tear strength*100%.

[0056] High and low temperature cycle conditions: constant humidity 60±5RH%, temperature 60±3℃@9 hours → -30±3℃@3 hours → 60±3℃@9 hours → -30±3℃@3 hours.

[0057] The index requirements are that after high and low temperature cycles, the longitudinal tear strength is ≥1000mN, the transverse longitudinal tear strength is ≥1000mN, the longitudinal and transverse tear ratio is 60~140%, and the calculation formula of the longitudinal and transverse tear ratio is: longitudinal tear strength / transverse longitudinal tear strength*100%.

[0058] The aging resistance of biodegradable materials is first judged by the longitudinal and transverse tear strength values. The higher the longitudinal and transverse tear strengths, the better the aging resistance. If the tear strengths are similar, they are judged based on the longitudinal and transverse tear ratio. The closer the longitudinal and transverse tear ratio is to 100% in the range of 60-140%, the better.

[0059] The test results are shown in Table 4.

[0060] Table 4

[0061] From the data in Table 4, it can be seen that the biodegradable material prepared in the embodiment of the present invention can maintain good tear strength and longitudinal and transverse tear ratio under different environmental conditions, thereby better adapting to the application and shelf life requirements in different environments.

[0062] The longitudinal tear strength at room temperature can be maintained above 1300mN, the transverse tear strength can be maintained above 1200mN, and the longitudinal to transverse tear ratio can be maintained at 60-140%.

[0063] The longitudinal tear strength under aging conditions can be maintained above 1000mN, the transverse tear strength can be maintained above 1000mN, and the longitudinal and transverse tear ratio can be maintained at 60-140%; the longitudinal tear strength under high and low temperature cycling conditions can be maintained above 1000mN, the transverse tear strength can be maintained above 1000mN, and the longitudinal and transverse tear ratio can be maintained at 60-140%.

[0064] The flexible biodegradable polyester used in Comparative Examples 1 and 2 had inappropriate T content, molecular weight distribution coefficient after shearing, or terminal carboxyl group content, resulting in low longitudinal and transverse tear ratios of the resulting biodegradable material under aging and high and low temperature environments, making it unsuitable for use in these environments. In Comparative Example 3, excessive amounts of polylactic acid were added, resulting in longitudinal and transverse tear ratios of the resulting biodegradable material under aging and high and low temperature environments failing to meet standard requirements and significantly worse than those of the examples. In Comparative Example 4, the molecular weight distribution coefficient (PDI) of the flexible biodegradable polyester after shearing was 2.46, outside the range of 1.7-2.3. Consequently, the resulting biodegradable material failed to achieve a longitudinal and transverse tear ratio within the range of 60-140% under aging and high and low temperature environments.

[0065] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A biodegradable material, characterized in that: The composition comprises the following components in parts by weight: 60-90 parts of flexible biodegradable polyester, 2-10 parts of polylactic acid, 2-30 parts of inorganic filler, 0-0.95 parts of additives; The molecular weight distribution coefficient PDI of the flexible biodegradable polyester after shearing at 180° C. is 1.7-2.3, and the terminal carboxyl group is ≤25 mol / t.

2. The biodegradable material according to claim 1, characterized in that: The D-lactic acid content in the polylactic acid is 4-20wt%, the weight average molecular weight after shearing is 70000-120000, and the molecular weight distribution coefficient PDI is 1.3-2.

3. The biodegradable material according to claim 1, characterized in that: The flexible biodegradable polyester is an aliphatic-aromatic copolyester and / or an aliphatic polyester.

4. The biodegradable material according to claim 3, characterized in that: At least one of the following (1) to (3) is satisfied: (1) the flexible biodegradable polyester is an aliphatic-aromatic copolyester, and the T content of the flexible biodegradable polyester is 43-48%; (2) the aliphatic-aromatic copolyester comprises at least one of PBAT and PBSeT; (3) The aliphatic polyester includes PBSA.

5. The biodegradable material according to claim 1, characterized in that: At least one of the following (1) to (3) is met: (1) The polylactic acid comprises at least one of PLLA, PDLA, and PLLA / PDLA copolymer; (2) The particle size distribution D50 of the inorganic filler is ≤5 μm; (3) The inorganic filler is selected from one or a mixture of talc, calcium carbonate, silicon dioxide, montmorillonite, kaolin, chalk, graphite, gypsum, conductive carbon black, calcium chloride, iron oxide, dolomite, wollastonite, titanium dioxide, silicate, mica, glass fiber or mineral fiber.

6. The biodegradable material according to claim 1, characterized in that: The auxiliary agents include lubricants and opening agents.

7. A method for preparing a biodegradable material according to any one of claims 1 to 6, characterized in that: The following steps are involved: The flexible biodegradable polyester, polylactic acid, inorganic filler and additives are mixed, and then melt-extruded and granulated to obtain the biodegradable material.

8. The preparation method according to claim 7, characterized in that: At least one of the following (1) to (2) is met: (1) The mixing speed is 240-380 rpm; (2) The temperature of the melt extrusion granulation is 150-200°C.

9. A food packaging film / bag, characterized in that: The method is prepared from the biodegradable material as claimed in any one of claims 1 to 6.

10. Use of the biodegradable material according to any one of claims 1 to 6 in the field of catering bags.

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