A biodegradable polyester composite material and its preparation method, and a biodegradable membrane bag.

Abstract

This invention relates to a biodegradable polyester composite material and its preparation method, as well as a biodegradable film bag, belonging to the technical field of polymer compound compositions. The biodegradable polyester composite material of this invention comprises the following components in parts by weight: 60-90 parts of PBAT resin (including PBAT resins A and B with melt flow rates ≤6 g / 10 min and ≥22 g / 10 min respectively), 6-10 parts of PLA resin with a D-lactic acid molar content ≥8%, and particle size D... 50 The composition includes 10-20 parts of calcium carbonate with a particle size of ≤1.5 μm and 0.5-1 parts of organic opening aid. Based on the total molar amount of structural units derived from terephthalic acid and adipic acid in PBAT resin, the molar percentage of structural units derived from terephthalic acid in PBAT resins A and B is 39%-41%. This biodegradable polyester composite material exhibits both good blown film stability and excellent heat-sealing strength.

Description

Technical Field

[0001] This invention relates to the field of polymer compound composition technology, and more particularly to a biodegradable polyester composite material and its preparation method, as well as a biodegradable film bag. Background Technology

[0002] Butylene-adipate (PBAT) is a flexible, biodegradable polyester with properties similar to PE. It can be blown into film and is widely used in shopping bags, milk tea bags, and express delivery bags. However, in practical use, the heat-sealing strength of the bottom or side seals of biodegradable PBAT film bags is relatively low, easily leading to problems such as bottom seal bursting or side seal failure, seriously affecting the consumer experience. Modified PBAT film products mainly include mineral powder-filled modified PBAT and starch-filled modified PBAT. Currently, applications with high heat-sealing requirements typically choose starch-filled modified PBAT, mainly because starch is an organic material that provides a certain degree of adhesion when heated. However, dispersing starch as a filler is difficult, and starch modification is costly. Compared to starch, mineral powder is easier to disperse when used as a filler. However, since mineral powder is an inorganic substance, it cannot provide a certain degree of adhesion after being heated like starch. Generally, it is necessary to add other biodegradable resins with good heat-sealing properties to form an alloy to improve the heat-sealing performance of mineral powder-filled modified PBAT. However, the heat-sealing strength of this type of PBAT product is still relatively low. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a biodegradable polyester composite material, its preparation method, and a biodegradable film bag.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a biodegradable polyester composite material, comprising the following components by weight: 60-90 parts of PBAT resin, 6-10 parts of PLA resin, 10-20 parts of calcium carbonate, and 0.5-1 part of organic opening aid.

[0006] The PBAT resin includes PBAT resin A and PBAT resin B;

[0007] For the PBAT resin A, based on the total molar amount of structural units derived from terephthalic acid and adipic acid in the PBAT resin, the molar percentage of the structural units derived from terephthalic acid is 39% to 41% (for example, it can be any one or any two of 39%, 39.5%, 40%, 40.5%, 41%).

[0008] For the PBAT resin B, based on the total molar amount of structural units derived from terephthalic acid and adipic acid in the PBAT resin, the molar percentage of the structural units derived from terephthalic acid is 39% to 41% (for example, it can be any one or any two of 39%, 39.5%, 40%, 40.5%, 41%).

[0009] The PBAT resin A has a melt flow rate ≤ 6 g / 10 min under conditions of 190°C and 2.16 kg (test standard is ISO 1133-2011) (for example, it can be any one or any two of 6 g / 10 min, 5 g / 10 min, 4 g / 10 min, 3 g / 10 min, 2 g / 10 min), and the PBAT resin B has a melt flow rate ≥ 22 g / 10 min under conditions of 190°C and 2.16 kg (test standard is ISO 1133-2011) (for example, it can be any one or any two of 22 g / 10 min, 23 g / 10 min, 24 g / 10 min, 25 g / 10 min, 26 g / 10 min, 27 g / 10 min, 28 g / 10 min, 29 g / 10 min, 30 g / 10 min, 31 g / 10 min, 32 g / 10 min).

[0010] The molar content of D-lactic acid in the PLA resin is ≥8% (for example, it can be any one or any two of 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%; the molar content of D-lactic acid can be obtained by dividing the peak area of ​​D-lactic acid methyl ester by (the peak area of ​​L-lactic acid methyl ester + the peak area of ​​D-lactic acid methyl ester), and the specific test method can be found in CN115403902A).

[0011] The particle size D of the calcium carbonate 50 ≤1.5μm (for example, it can be a range of any one or both of 1.5μm, 1.4μm, 1.3μm, 1.2μm, 1.1μm, 1.0μm, 0.9μm, 0.8μm, 0.7μm, 0.6μm, and 0.5μm).

[0012] This invention combines PBAT resin A with low melt flow rate and PBAT resin B with high melt flow rate, and controls the molar ratio of terephthalic acid-derived structural units in the PBAT resin. At the same time, it is combined with PLA resin with a specific D-lactic acid content and calcium carbonate with a specific particle size to improve the heat-sealing strength of biodegradable polyester composite materials and make them have good blown film stability.

[0013] By controlling the molar percentage (T content) of terephthalic acid-derived structural units in PBAT resins A and B within the range of 39% to 41%, the melt heat-sealing of biodegradable polyester composites can be effectively promoted, ensuring high heat-sealing strength after heat sealing. By blending PBAT resin A with a melt flow rate ≤6 g / 10 min with PBAT resin B with a melt flow rate ≥22 g / 10 min, not only can the blown film stability of the biodegradable polyester composite be maintained, but its resin adhesion can also be improved, thereby increasing the heat-sealing strength. Using PLA resin with a D-lactic acid molar content ≥8% can improve the melt heat-sealing of biodegradable polyester composites, thus enhancing their heat-sealing strength. By selecting a particle size D... 50 Calcium carbonate with a thickness of ≤1.5μm can reduce the surface roughness of biodegradable polyester composites (films), thereby promoting resin contact heat sealing and improving the heat sealing strength of biodegradable polyester composites.

[0014] Based on the total mass of the biodegradable polyester composite material, the PBAT resin has a mass percentage content of ≥65%. Optionally, the specific weight parts of PBAT resin in the biodegradable polyester composite material can be any one or both of the following: 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, and 90 parts; the specific weight parts of PLA resin can be any one or both of the following: 6 parts, 7 parts, 8 parts, 9 parts, and 10 parts; the specific weight parts of calcium carbonate can be any one or both of the following: 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, and 20 parts; and the specific weight parts of the organic opening aid can be any one or both of the following: 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, and 1 part.

[0015] In a preferred embodiment of the biodegradable polyester composite material of the present invention, the components of the biodegradable polyester composite material include 70-80 parts by weight of PBAT resin and 12-17 parts by weight of calcium carbonate.

[0016] As a preferred embodiment of the biodegradable polyester composite material of the present invention, the melt mass flow rate of the PBAT resin A is 3~5 g / 10 min, preferably 4 g / 10 min.

[0017] As a preferred embodiment of the biodegradable polyester composite material of the present invention, the melt mass flow rate of the PBAT resin B is 24~30 g / 10 min, preferably 28 g / 10 min.

[0018] In a preferred embodiment of the biodegradable polyester composite material of the present invention, the mass ratio of PBAT resin A to PBAT resin B is (50~70):(10~20). For example, by weight parts, PBAT resin A can specifically be any one or both of 50 parts, 53 parts, 55 parts, 58 parts, 60 parts, 62 parts, 65 parts, 67 parts, and 70 parts; and PBAT resin B can specifically be any one or both of 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, and 20 parts. By controlling the mass ratio of PBAT resin A to PBAT resin B within the above range, while maintaining good blown film stability of the biodegradable polyester composite material, its resin adhesion can be better improved to enhance heat-sealing strength.

[0019] In a preferred embodiment of the biodegradable polyester composite material of the present invention, the molar content of D-lactic acid in the PLA resin is 10% to 12%. Studies have found that a higher molar content of D-lactic acid in the PLA resin is more beneficial to improving the performance of the biodegradable polyester composite material. However, increasing the molar content of D-lactic acid also significantly increases the difficulty of synthesizing the PLA resin. Therefore, based on a comprehensive consideration of performance and cost, the molar content of D-lactic acid in the PLA resin is preferably 10% to 12%.

[0020] As a preferred embodiment of the biodegradable polyester composite material of the present invention, the calcium carbonate has a particle size D 50 The particle size ranges from 0.5 to 1.2 μm. Studies have found that as the particle size D of calcium carbonate increases... 50 The reduction in calcium carbonate particle size makes it more difficult to achieve uniform dispersion in the resin (PBAT resin + PLA resin). Partially aggregated calcium carbonate is detrimental to reducing the surface roughness of the biodegradable polyester composite material (film), thus affecting the heat-sealing strength of the biodegradable polyester composite material. Therefore, the particle size D of calcium carbonate is important. 50 The preferred size is 0.5~1.2μm.

[0021] In a preferred embodiment of the biodegradable polyester composite material of the present invention, the organic opening aid includes at least one of oleamide and erucamide; preferably oleamide.

[0022] Secondly, the present invention provides a method for preparing the above-mentioned biodegradable polyester composite material, comprising the following steps: mixing each component evenly and then melt-extruding to obtain the biodegradable polyester composite material.

[0023] Optionally, the above preparation method can be carried out by melt extrusion using a twin-screw extruder, with a melt extrusion temperature of 160~200℃ and a screw speed of 250~350 rpm.

[0024] Thirdly, the present invention provides a biodegradable film bag made of the aforementioned biodegradable polyester composite material. For example, biodegradable film bags include, but are not limited to, fruit and vegetable bags, bread / pastry bags, meat tray films, lunchbox sealing films, disposable tableware packaging bags, tea / coffee capsule packaging bags, beverage cup sealing films, garbage bags, shopping bags, express delivery bags, document bags, flower packaging, etc.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention combines PBAT resin A with low melt flow rate and PBAT resin B with high melt flow rate, and controls the molar ratio of terephthalic acid-derived structural units in the PBAT resin. It also combines PLA resin with a specific D-lactic acid content and calcium carbonate with a specific particle size to improve the heat-sealing strength and blown film stability of biodegradable polyester composite materials. Detailed Implementation

[0027] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0028] Unless otherwise specified, all other materials, reagents, etc. used in the examples and comparative examples are commercially available.

[0029] 1. Raw materials and reagents

[0030] 1) PBAT resin

[0031] PBAT resin is prepared by the following method: terephthalic acid, adipic acid, 1,4-butanediol (excess), and branching agent (glycerol, 500 ppm) are added to a reaction vessel, stirred at 190°C for 1-8 hours (T1), then tetrabutyl titanate is added as a catalyst, and the temperature is raised to 240°C for 3-20 hours (T2) to obtain different PBAT resins; wherein the molar ratio of the total amount of terephthalic acid and adipic acid to 1,4-butanediol is 1:1.4.

[0032] The T content (based on the total molar amount of structural units derived from terephthalic acid and adipic acid in PBAT resin, wherein the molar percentage of structural units derived from terephthalic acid) is achieved by adjusting the molar percentage of terephthalic acid while keeping the total amount of terephthalic acid and adipic acid constant.

[0033] The melt flow rate of PBAT resin was controlled by adjusting T1 and T2. The melt flow rate of PBAT resin was measured according to ISO 1133-2011 standard at 190℃ and 2.16kg, as shown in Table 1.

[0034] Table 1. PBAT Resins A, B, and C

[0035]

[0036] 2) PLA resin

[0037] PLA-1, with a D-lactic acid molar content of 10%, is manufactured by Kingfa Biotechnology, and its brand name is KB600 NF50.

[0038] PLA-2, with a D-lactic acid molar content of 12%, manufactured by Natureworks, brand name PLA 4060D;

[0039] PLA-3, with a D-lactic acid molar content of 4%, is manufactured by Kingfa Biotechnology, and its brand name is KB600 NF30.

[0040] 3) Calcium carbonate and talc

[0041] Calcium carbonate 1, particle size D 50 The particle size is 0.9μm, the manufacturer is Guangdong Dongyuan, and the grade is DY-66999.

[0042] Calcium carbonate 2, particle size D 50 It is 1.2μm, manufactured by Guangdong Xinrong, and its grade is ACC-812;

[0043] Calcium carbonate 3, particle size D 50 It is 1.5μm, manufactured by Guangdong Xinrong, and its grade is ACC-815;

[0044] Talc, particle size D 50 It has a particle size of 0.7μm, is manufactured by Liaoning Aihaiyimi, and has the brand name HTPultra5 L.

[0045] 5) Organic opening aids

[0046] Oleamide, manufactured by Crodamida (UK), brand name Crodamida VRX;

[0047] Erucamide, manufactured by Crodamide (UK), brand name Crodamide ER-CH-BE-(SI).

[0048] 2. Preparation method of the biodegradable polyester composite material of the present invention

[0049] According to the formula, the components are mixed evenly and then added to a twin-screw extruder. The mixture is melt-extruded and granulated at 160~200℃ to obtain a biodegradable polyester composite material. The screw speed of the twin-screw extruder is 300 rpm.

[0050] 3. Performance Testing

[0051] 1) Heat sealing strength

[0052] The biodegradable polyester composite materials used in the various examples and comparative examples were dried, with the moisture content controlled below 500 ppm, and then subjected to blown film processing to obtain biodegradable films. The blown film processing temperature was 130–160°C, the blown film die diameter was 70 mm, the blow-up ratio was 3.0, and the resulting biodegradable film had a perimeter of 660 mm and a thickness of 20 μm. The heat-sealing strength of the biodegradable films prepared above was tested according to the QB / T 2358-1998 standard.

[0053] 2) Blown film stability

[0054] The biodegradable polyester composite materials in each example and comparative example were dried and the moisture content was controlled to be less than 500 ppm. Then, they were subjected to blown film treatment (the blown film treatment temperature was 130~160℃, the blown film die diameter was 70 mm, the blow-up ratio was 3.0, and the resulting biodegradable film had a perimeter of 660 mm and a thickness of 20 μm) to obtain a biodegradable film. At the same time, the stability of the blown film was observed during the blown film process and evaluated according to the following levels.

[0055] Level 1: No abnormalities found in blown film;

[0056] Grade 2: Slight shaking of the membrane vesicle;

[0057] Grade 3: The membrane bubble vibrates severely, and occasional membrane breakage occurs;

[0058] Level 4: Severe film bubble breakage, making rewinding difficult.

[0059] Table 2. Parts by weight of each component in the biodegradable polyester composite material in each embodiment.

[0060]

[0061] Table 3. Weight parts of each component in the biodegradable polyester composite materials of each comparative example.

[0062]

[0063] In Tables 2 and 3, " / " indicates that there are no relevant parameters.

[0064] According to the data in Table 2, the heat-sealing strength of the biodegradable polyester composite materials in Examples 1 to 15 is ≥10.2 MPa, and the blown film stability assessment level is 1 or 2, indicating that the biodegradable polyester composite material of the present invention has both good blown film stability and excellent heat-sealing strength. Meanwhile, according to Comparative Examples 1 and 2 in Table 3, both excessively low and excessively high molar proportions of terephthalic acid-derived structural units in PBAT resin will reduce the heat-sealing strength of the biodegradable polyester composite material. According to Comparative Examples 3 and 4, excessively high melt flow rates of PBAT resin A will significantly reduce the blown film stability of the biodegradable polyester composite material; while excessively low melt flow rates of PBAT resin B will significantly reduce the heat-sealing strength of the biodegradable polyester composite material. According to Comparative Example 7, excessively low molar content of D-lactic acid in PLA resin will also reduce the heat-sealing strength of the biodegradable polyester composite material. According to Comparative Example 8, using talc as a filler will reduce the heat-sealing strength of the biodegradable polyester composite material.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A biodegradable polyester composite material, characterized by, The components include, by weight fraction, 60-90 parts of PBAT resin, 6-10 parts of PLA resin, 10-20 parts of calcium carbonate, and 0.5-1 part of organic opening agent. The PBAT resin includes PBAT resin A and PBAT resin B. For the PBAT resin A, the mole fraction of structural units derived from terephthalic acid is 39-41% based on the total mole amount of structural units derived from terephthalic acid and adipic acid in the PBAT resin. For the PBAT resin B, the mole fraction of structural units derived from terephthalic acid is 39-41% based on the total mole amount of structural units derived from terephthalic acid and adipic acid in the PBAT resin. The PBAT resin A has a melt mass flow rate of 2-6 g / 10 min at 190℃ under a load of 2.16 kg, and the PBAT resin B has a melt mass flow rate of 22-32 g / 10 min at 190℃ under a load of 2.16 kg. The mole content of D-lactic acid in the PLA resin is 8-15%, and the calcium carbonate has a particle size D50 of 0.5-1.5 μm.

2. The biodegradable polyester composite of claim 1, wherein, The PBAT resin is 70-80 parts by weight, and the calcium carbonate is 12-17 parts by weight in the components of the biodegradable polyester composite material.

3. The biodegradable polyester composite of claim 1, wherein, The PBAT resin A has a melt mass flow rate of 3-5 g / 10 min.

4. The biodegradable polyester composite of claim 1, wherein, The PBAT resin B has a melt mass flow rate of 24-30 g / 10 min.

5. The biodegradable polyester composite of claim 1, wherein, The mass ratio of the PBAT resin A to the PBAT resin B is (50-70):(10-20).

6. The biodegradable polyester composite of claim 1, wherein, The mole content of D-lactic acid in the PLA resin is 10-12%.

7. The biodegradable polyester composite of claim 1, wherein, The calcium carbonate has a particle size D50 of 0.5-1.2 μm.

8. The biodegradable polyester composite of claim 1, wherein, The organic opening agent includes at least one of oleic acid amide and erucic acid amide.

9. Process for the production of a biodegradable polyester composite material according to any one of claims 1 to 8, characterized in that, The method includes the step of melt extruding the components after being uniformly mixed to obtain the biodegradable polyester composite material.

10. A biodegradable film pouch characterized by, The biodegradable polyester composite material is made of any one of claims 1-8.

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