A biodegradable material, its preparation method and application

Abstract

The present invention belongs to the technical field of biodegradable materials, and particularly relates to a biodegradable material, a preparation method thereof and an application. The biodegradable material comprises the following components in parts by weight: 60-90 parts of a flexible biodegradable polyester, 2-10 parts of polylactic acid, 2-30 parts of an inorganic filler, and 0-0.95 parts of an auxiliary agent; the molecular weight distribution coefficient PDI of the flexible biodegradable polyester in the biodegradable material after shearing at 180°C is 1.7-2.3, and the terminal carboxyl group is ≤25 mol / t. The biodegradable material prepared by the present invention has isotropic longitudinal and transverse tearing under high and low temperature conditions and has good aging resistance.

Description

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 PLA and mineral powder (MD) can, on the one hand, produce an inexpensive biodegradable film bag material, and on the other hand, achieve complementary performance. Flexible biodegradable polyester can improve the toughness of PLA, especially its tear resistance at low temperatures. At the same time, PLA can better improve the rigidity of flexible biodegradable polyester, especially its lifting performance at high temperatures. In addition, MD mineral powder helps to improve the bubble stability and opening performance of the flexible biodegradable polyester / PLA alloy. However, due to the poor compatibility between flexible biodegradable polyester and PLA, the processing and mechanical properties of the flexible biodegradable polyester / PLA alloy without the addition of a compatibilizer are poor, especially the anisotropy of longitudinal and transverse tearing, which makes longitudinal tearing more likely to occur in high and low temperature alternating use scenarios. Common toughening methods mainly involve volume expansion. However, after volume expansion using common compatibilizers such as BASF's reactive chain extender (ADR), the stiffness of the blown film decreases, the lifting performance decreases, and there is a sour odor, making it unsuitable for use in the catering bag field. There are also studies using starch to modify flexible biodegradable polyester / PLA. The toughness of the plasticized starch can compensate for the defect of tearing. However, starch materials are easy to absorb water and have poor aging properties. 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] In summer and winter, catering bags, respectively, can experience a sudden shift from high-temperature bags to cold drinks. This can cause the film material to transition from high to low temperatures. In winter, cold bags can also be loaded with hot food, shifting the environment from low to high. Therefore, catering bags must maintain excellent performance at both high and low temperatures, especially tear strength. Aging performance is also crucial for shelf life. After aging under certain conditions, catering bags must avoid significant differences in longitudinal and transverse tear strength, which could lead to failure. Therefore, optimizing the tear strength of degradable materials at both high and low temperatures, as well as after aging, and the ratio of longitudinal and transverse tear strength is crucial.

[0004] Patent document CN 101522797B discloses a starch-based biodegradable multiphase composition comprising a continuous phase of tough polyester, a nanoparticulate starch phase, and a dispersed phase of polyhydroxyalkanoate. The composition exhibits isotropic tearing and elongation 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. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art and provide a biodegradable material, its preparation method and application. The biodegradable material prepared by the present invention is isotropic in longitudinal and transverse tearing under high and low temperature and aging conditions, and has good aging resistance.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A biodegradable material, comprising the following components in parts by weight:

[0007] 60-90 parts of flexible biodegradable polyester, 2-10 parts of polylactic acid, 2-30 parts of inorganic filler, 0-0.95 parts of additive;

[0008] 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. The shearing conditions are as follows: 200 kg is taken and sheared at a temperature of 180°C in a double-screw extruder of model 75A. The shearing speed is 300-400 rpm, the feeding rate is 400-500 kg / h, and the shearing time is 20-25 min.

[0009] In the present invention, the molecular weight distribution coefficient PDI after shearing is obtained by GPC test of molecular weight. The GPC test method is as follows: GPC uses the ACQUITY APC TM equipment of Waters company for testing, the test temperature is 40°C, XT45, XT200 and XT459 chromatographic columns are used, the solvent is tetrahydrofuran, and the flow rate of the mobile phase is 0.5 mL / min. Polystyrene standard is used as the standard sample.

[0010] In the present invention, the terminal carboxyl group of the flexible biodegradable polyester is determined by GB / T 14190-2017 (Method A).

[0011] In the present invention, by screening the molecular weight distribution coefficient and terminal carboxyl group parameters of the flexible biodegradable polyester after shearing, the aging resistance and the tear strength after high and low temperature of the prepared biodegradable material can be effectively improved. At the same time, by controlling the addition amounts of the flexible biodegradable polyester and PLA, the difference in longitudinal and transverse tearing and the adjustment of aging resistance are realized.

[0012] In the biodegradable material of the present invention, the content of the flexible biodegradable polyester is not less than 50%.

[0013] Preferably, the D-lactic acid content of the polylactic acid is 4-20%, the weight-average molecular weight after shearing is 70000-120000, and the molecular weight distribution coefficient PDI is 1.3-2. The shearing conditions are as follows: shearing is carried out at a temperature of 180°C in a double-screw extruder of model 75A. The shearing speed is 300-400 rpm, and the feeding rate is 400-500 kg / h.

[0014] In the present invention, by screening the D-form content of processed PLA, the weight-average molecular weight and the molecular weight distribution coefficient after shearing, the compatibility between the flexible biodegradable polyester and PLA can be significantly improved, thereby effectively enhancing the aging resistance of the obtained biodegradable material and improving the uniformity of transverse and longitudinal tearing.

[0015] More preferably, the molecular weight distribution coefficient PDI of the polylactic acid after shearing is 1.3 - 1.7.

[0016] Preferably, the flexible biodegradable polyester is an aliphatic-aromatic copolyester and / or an aliphatic polyester.

[0017] 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 content of terephthalic acid monomer (PTA) in the PTA unit of the flexible biodegradable polyester in the polymer.

[0018] More preferably, the flexible biodegradable polyester comprises one or a mixture of two of polybutylene adipate terephthalate (PBAT), polybutylene terephthalate sebacate (PBSeT).

[0019] More preferably, the aliphatic polyester comprises at least one of conventional aliphatic polyesters in the art such as polybutylene succinate-adipate resin (PBSA).

[0020] Preferably, the polylactic acid comprises at least one of PLLA, PDLA, and PLLA / PDLA copolymers.

[0021] Preferably, the D50 particle size distribution of the inorganic filler is D50 ≤ 5 μm.

[0022] Preferably, the D50 particle size distribution of the inorganic filler is D50 ≤ 4 μm.

[0023] More preferably, the D50 particle size distribution of the inorganic filler is 1.5 - 3 μm. Selecting an inorganic filler with a suitable D50 particle size can effectively improve the aging resistance of the obtained material.

[0024] Preferably, the inorganic filler is selected from one or a mixture of several of talc powder, 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.

[0025] More preferably, the inorganic filler is selected from at least one of talc powder, calcium carbonate, silicon dioxide, montmorillonite, and kaolin.

[0026] Preferably, the auxiliary agent includes a lubricant and an antiblocking agent.

[0027] More preferably, the weight parts of the lubricant are 0.01 - 0.94 parts; the weight parts of the antiblocking agent are 0.01 - 0.94 parts.

[0028] Preferably, the lubricant includes common components in the art such as erucamide, monoglyceride, ethylene bisstearamide, etc.

[0029] Preferably, the antiblocking agent includes common components in the art such as silicon dioxide, talcum powder, diatomaceous earth, polyethylene wax, etc.

[0030] The present invention also claims protection for a preparation method of the biodegradable material, comprising the following steps:

[0031] Mix a flexible biodegradable polyester, polylactic acid, an inorganic filler, and an auxiliary agent, and then perform melt extrusion granulation to obtain the biodegradable material.

[0032] Preferably, the rotation speed of the mixing is 240 - 380 rpm.

[0033] Preferably, the temperature of the melt extrusion granulation is 150 - 200 °C.

[0034] The present invention also claims protection for a food packaging film / bag prepared from the biodegradable material.

[0035] The present invention also claims protection for an application of the biodegradable material in the field of catering bags.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The biodegradable material prepared by the present invention has excellent longitudinal and transverse tear isotropy under high and low temperature conditions, and has good aging resistance, and can better meet the application scenarios and shelf life requirements of catering bags. Specific Embodiments

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0039] In the following embodiments and comparative examples, the experimental methods used are all conventional methods unless otherwise specified. Unless otherwise specified, the antiblocking agent is obtained commercially, and the same antiblocking agent is used in parallel experiments.

[0040] The raw materials used in the examples and comparative examples are shown in Table 1.

[0041] Table 1

[0042]

[0043]

[0044]

[0045]

[0046] Examples 1-13 and Comparative Examples 1-4

[0047] The biodegradable materials of Examples 1-13 and Comparative Examples 1-4, the components and parts by weight are shown in Tables 2-3.

[0048] The preparation method of the biodegradable materials of Examples 1-13 and Comparative Examples 1-4 includes the following steps:

[0049] The flexible biodegradable polyester, polylactic acid, filler, and auxiliary agent in the formula amount are sequentially added to a high-speed mixer and mixed evenly (rotation speed is 300 rpm), and then added to a twin-screw extruder, melted and extruded into pellets to obtain a biodegradable composite material. The temperature of zone 1 in the twin-screw extruder is 150 °C, the temperature of zone 2 is 170 °C, the temperature of zone 3 is 180 °C, the temperature of zone 4 is 180 °C, the temperature of zone 5 is 180 °C, the temperature of zone 6 is 190 °C, the temperature of zone 7 is 190 °C, the temperature of zone 8 is 190 °C, the temperature of zone 9 is 190 °C, the temperature of zone 10 is 200 °C, and the temperature of the nozzle is 200 °C.

[0050] Table 2 Component dosage (parts by weight) in the examples

[0051]

[0052]

[0053] Table 3 Component dosage (parts by weight) in the comparative examples

[0054]

[0055] Performance test

[0056] The biodegradable materials prepared in the examples and comparative examples are made into vest bags using a bag-making machine, the blown film temperature is 150 °C, and the thickness of the vest bag is 25 μm. And measure the mechanical properties of the vest bags after being treated under different conditions.

[0057] Test method for tear strength:

[0058] Tear strength test: Conducted in accordance with the provisions of GB / T 16578.2-2009. The samples are tested after being placed and conditioned in a standard environment (23±2°C, 50±5% RH) for 24 hours. Data in both the longitudinal and transverse directions of the samples are detected.

[0059] Index requirements at normal temperature state: Longitudinal tear strength ≥ 1000 mN, transverse longitudinal tear strength ≥ 1000 mN, longitudinal-transverse tear ratio 60 - 140%. The calculation formula for the longitudinal-transverse tear ratio is: Longitudinal tear strength / Transverse longitudinal tear strength * 100%.

[0060] Aging conditions: Placed in an environment of 60±3°C and 60±5% RH humidity for 15 days.

[0061] Index requirements: After 15 days of accelerated aging, longitudinal tear strength ≥ 1000 mN, transverse longitudinal tear strength ≥ 1000 mN, longitudinal-transverse tear ratio 60 - 140%. The calculation formula for the longitudinal-transverse tear ratio is: Longitudinal tear strength / Transverse longitudinal tear strength * 100%.

[0062] High and low temperature cycling conditions: Humidity is constant at 60±5 RH%, temperature 60±3°C @ 9 hours → -30±3°C @ 3 hours → 60±3°C @ 9 hours → -30±3°C @ 3 hours.

[0063] Index requirements: After high and low temperature cycling, longitudinal tear strength ≥ 1000 mN, transverse longitudinal tear strength ≥ 1000 mN, longitudinal-transverse tear ratio 60 - 140%. The calculation formula for the longitudinal-transverse tear ratio is: Longitudinal tear strength / Transverse longitudinal tear strength * 100%.

[0064] The aging resistance performance of the biodegradable material is preferably judged from the longitudinal and transverse tear strength values. The higher the longitudinal and transverse tear strengths, the better the aging resistance performance; if the tear strengths are similar, it is judged according to the longitudinal-transverse tear ratio. The closer the longitudinal-transverse tear ratio is to 100% within the range of 60 - 140%, the better.

[0065] The test results are shown in Table 4.

[0066] Table 4

[0067]

[0068] From the data in Table 4, it can be known that the biodegradable material prepared in the embodiments of the present invention can maintain good tear strength and longitudinal-transverse tear ratio under different environmental conditions, so as to better adapt to the application under different environments and the requirements of shelf life.

[0069] Among them, the longitudinal tear strength under normal temperature conditions can be maintained above 1300 mN, the transverse tear strength can be maintained above 1200 mN, and the longitudinal and transverse tear ratio is maintained at 60 - 140%;

[0070] The longitudinal tear strength under aging conditions can be maintained above 1000 mN, the transverse tear strength can be maintained above 1000 mN, and the longitudinal and transverse tear ratio is maintained at 60 - 140%; the longitudinal tear strength under high and low temperature cycling conditions can be maintained above 1000 mN, the transverse tear strength can be maintained above 1000 mN, and the longitudinal and transverse tear ratio is maintained at 60 - 140%.

[0071] In Comparative Examples 1 - 2, the T content of the flexible biodegradable polyester selected, the molecular weight distribution coefficient or the end carboxyl group content after shearing are not appropriate, resulting in a relatively low longitudinal and transverse tear ratio of the finally prepared biodegradable material under aging and high and low temperature environments, which is not conducive to use in the corresponding environments; in Comparative Example 3, the weight part of polylactic acid added is too much, and the longitudinal and transverse tear ratio of the prepared biodegradable material under aging and high and low temperature environments cannot meet the standard requirements and is significantly worse than that of the examples. In Comparative Example 4, the molecular weight distribution coefficient PDI of the flexible biodegradable polyester after shearing is 2.46, which is not within the range of 1.7 - 2.3, and the longitudinal and transverse tear ratio of the prepared biodegradable material under aging and high and low temperature environments cannot be achieved within the range of 60 - 140%.

[0072] The above examples only illustratively explain the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above examples without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still 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 flexible biodegradable polyester has a molecular weight distribution coefficient (PDI) of 1.7 to 2.3 after shearing at 180° C., and a terminal carboxyl group of ≤25 mol / t; The flexible biodegradable polyester is an aliphatic-aromatic copolyester and / or an aliphatic polyester; The aliphatic-aromatic copolyester includes at least one of PBAT and PBAeT; The aliphatic polyester includes PBSA; The T content of the aliphatic-aromatic copolyester is 43-48%.

2. The biodegradable material according to claim 1, wherein The D-lactic acid content of the polylactic acid in the biodegradable material is 4-20%, the weight average molecular weight after shearing is 70,000-120,000, and the molecular weight distribution coefficient PDI is 1.3-2.

3. The biodegradable material according to claim 1, wherein The flexible biodegradable polyester is an aliphatic-aromatic copolyester.

4. The biodegradable material according to claim 1, wherein: At least one of the following (1) to (3): (1) The polylactic acid includes at least one of PLLA, PDLA, and PLLA / PDLA copolymer; (2) The particle size distribution D50 of the inorganic filler is ≤ 5µm; (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.

5. The biodegradable material according to claim 1, wherein: The auxiliary agents include lubricants and opening agents.

6. A method for preparing the biodegradable material according to any one of claims 1 to 5, 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.

7. The preparation method according to claim 6, characterized in that: At least one of the following (1) to (2): (1) The mixing speed is 240-380 rpm; (2) The temperature of the melt extrusion granulation is 150-200°C.

8. A food packaging film / bag, characterized in that: The method is prepared from the biodegradable material according to any one of claims 1 to 5.

9. Use of the biodegradable material according to any one of claims 1 to 5 in the field of catering bags.

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