A biodegradable polyester composition, and a method for preparing and using the same

Abstract

The present application relates to a kind of biodegradable polyester composition and its preparation method and application, belong to the technical field of polymer compound composition.The biodegradable polyester composition of the present application, by weight parts, includes the following components: biodegradable polyester 52~76 parts, crosslinking starch 20~35 parts, plasticizing agent 5~10 parts;The biodegradable polyester includes PBAT resin;Based on the total molar amount of structural unit derived from terephthalic acid and adipic acid in the PBAT resin, the mole percentage of the structural unit derived from terephthalic acid is ≤53%;The plasticizing agent is composed of glycerol, water and ester compound, and the ester compound includes at least one of saturated glyceride, citric acid ester.The biodegradable polyester composition has good mechanical properties and low potassium permanganate consumption.

Description

Technical Field

[0001] This invention relates to the field of polymer composition technology, and more particularly to a biodegradable polyester composition, its preparation method, and its application. Background Technology

[0002] Plastic films are widely used in food packaging, electronic product packaging, supermarket shopping bags, garbage bags, and express delivery bags. However, traditional plastic films are difficult to decompose in the natural environment, easily leading to the accumulation of large amounts of solid waste and impacting the ecological environment. Compared to traditional plastic films, biodegradable plastic films can be decomposed into water, carbon dioxide, and biomass by microorganisms under suitable conditions, effectively reducing environmental pollution. Polybutylene terephthalate-co-butylene adipate (PBAT) is currently the most widely used thermoplastic biodegradable material, often combined with starch to reduce production costs; however, the current market consumption of potassium permanganate in this type of biodegradable material is relatively high, making it difficult to meet the application requirements for its use as a food-grade contact plastic material and product. Summary of the Invention

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

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a biodegradable polyester composition comprising, by weight parts: 52-76 parts of biodegradable polyester, 20-35 parts of crosslinked starch, and 5-10 parts of plasticizer. The biodegradable polyester includes PBAT resin; 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 ≤53%; The plasticizer is composed of glycerol, water, and ester compounds, wherein the ester compounds include at least one of saturated glycerides and citrate esters.

[0005] In some embodiments, the saturated glyceride includes, but is not limited to, at least one of triacetylglycerol, caprylic glycerol, and nonanoic glycerol.

[0006] In some embodiments, the citrate ester includes, but is not limited to, at least one of triethyl citrate, tributyl citrate, and acetylated tributyl citrate.

[0007] Based on the total mass of the biodegradable polyester composition, wherein the mass percentage of biodegradable polyester is greater than or equal to 50%.

[0008] In some embodiments, the weight parts of biodegradable polyester in the biodegradable polyester composition may be, but are not limited to, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, or 76 parts, or fall within the range of any two of the above values.

[0009] In some embodiments, the weight parts of crosslinked starch in the biodegradable polyester composition may be, but are not limited to, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35 parts, or fall within the range of any two of the above values.

[0010] In some embodiments, the weight parts of the plasticizer in the biodegradable polyester composition may be, but are not limited to, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, 6 parts, 6.2 parts, 6.4 parts, 6.6 parts, 6.8 parts, 7 parts, 7.2 parts, 7.4 parts, 7.6 parts, 7.8 parts, 8 parts, 8.2 parts, 8.4 parts, 8.6 parts, 8.8 parts, 9 parts, 9.2 parts, 9.4 parts, 9.6 parts, 9.8 parts, or 10 parts, or fall within the range of any two of the above values.

[0011] As a preferred embodiment of the biodegradable polyester composition of the present invention, 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 43% to 52%, for example, but not limited to 43%, 43.5%, 44%, 44.5%, 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, 50.5%, 51%, 51.5%, or 52%, or within the range of any two of the above values.

[0012] As a preferred embodiment of the biodegradable polyester composition of the present invention, the gelatinization temperature of the crosslinked starch is 80°C to 95°C. And / or, the mass ratio of the glycerol, water and ester compound is (1~2):(2~3):(0.5~1).

[0013] In some embodiments, the gelatinization temperature of the cross-linked starch may be, but is not limited to, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, or 95°C, or fall within the range of any two of the above values.

[0014] By controlling the gelatinization temperature of cross-linked starch within the above range, the hydrophilicity and solubility of cross-linked starch can be better reduced, thereby reducing the small molecule reducing substances produced by starch hydrolysis and further reducing the consumption of potassium permanganate.

[0015] Cross-linked starch can be prepared by the following method: starch is mixed with water to form an emulsion, and the pH value of the emulsion is controlled between 11.0 and 11.5. Then, a cross-linking agent is added, and the cross-linking reaction is carried out at 40°C to 55°C for 2 to 4 hours. After the reaction is completed, the pH value of the system is adjusted to neutral, and the cross-linked starch is obtained by dehydration, washing, drying, pulverizing and sieving.

[0016] In some embodiments, the crosslinking agent includes, but is not limited to, at least one of sodium trimetaphosphate, phosphorus oxychloride, and epichlorohydrin.

[0017] In some embodiments, the crosslinking agent has a mass fraction of 0.03% to 0.1% relative to starch, preferably 0.05% to 0.08%.

[0018] In some embodiments, the starch includes, but is not limited to, at least one of corn starch, potato starch, rice starch, and tapioca starch.

[0019] In some embodiments, the weight parts of glycerol in the plasticizer may be, but are not limited to, at least one or at least two of the following ranges: 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, and 2 parts; the weight parts of water in the plasticizer may be, but are not limited to, at least one or at least two of the following ranges: 2 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, and 3 parts; and the weight parts of ester compounds in the plasticizer may be, but are not limited to, at least one or at least two of the following ranges: 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, and 1 part.

[0020] As a preferred embodiment of the biodegradable polyester composition of the present invention, the PBAT resin has a melt mass flow rate of 1.5 g / 10 min to 10 g / 10 min at 190°C and 2.16 kg (ISO 1133-2011 standard), for example, but not limited to 1.5 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 g / 10 min, 5.5 g / 10 min, 6 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, 8.5 g / 10 min, 9 g / 10 min, 9.5 g / 10 min, or 10 g / 10 min, or within any two of the above values.

[0021] As a preferred embodiment of the biodegradable polyester composition of the present invention, the biodegradable polyester further includes at least one of PLA resin and PBST resin.

[0022] As a preferred embodiment of the biodegradable polyester composition of the present invention, at least one of the following conditions is met: (1) The PLA resin includes at least one of PLLA, PDLA, and PLLA / PDLA copolymer, preferably PLLA / PDLA copolymer.

[0023] (2) The melt mass flow rate of the PBST resin at 190°C and 2.16 kg (ISO 1133-2011 standard) is 1.5 g / 10 min to 10 g / 10 min, for example, but not limited to 1.5 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 g / 10 min, 5.5 g / 10 min, 6 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, 8.5 g / 10 min, 9 g / 10 min, 9.5 g / 10 min or 10 g / 10 min, or within the range of any two of the above values.

[0024] (3) Based on the total molar amount of structural units derived from terephthalic acid and succinic acid in the PBST resin, the molar percentage of the structural units derived from terephthalic acid is 44% to 50%, for example, but not limited to 44%, 44.5%, 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5% or 50%, or within the range of any two of the above values.

[0025] As a preferred embodiment of the biodegradable polyester composition of the present invention, the biodegradable polyester composition further includes 0.1 to 2 parts of processing aids; the processing aids include at least one of opening agents, slip agents, antioxidants, weathering agents, and antistatic agents.

[0026] In some embodiments, the weight parts of the processing aid in the biodegradable polyester composition may be, but are not limited to, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 2 parts, or fall within the range of any two of the above values.

[0027] In some embodiments, the opening agent includes, but is not limited to, at least one of talc, calcium carbonate, and silicon dioxide.

[0028] In some embodiments, the slip agent includes, but is not limited to, at least one of erucamide, oleamide, and stearamide.

[0029] In some embodiments, the antioxidant includes, but is not limited to, at least one of hindered phenolic antioxidants, phosphite antioxidants, and thioether antioxidants.

[0030] In some embodiments, the weathering agent includes, but is not limited to, at least one of hindered amine light stabilizers and ultraviolet absorbers.

[0031] In some embodiments, the antistatic agent includes, but is not limited to, at least one of monoglyceride antistatic agents and alkyl ethoxyamine antistatic agents.

[0032] Secondly, the present invention provides a method for preparing the above-mentioned biodegradable polyester composition, comprising the following steps: mixing each component evenly and then melt-extruding to obtain the biodegradable polyester composition.

[0033] Optionally, the above preparation method can be carried out by melt extrusion using a twin-screw extruder, with a melt extrusion temperature of 120°C to 150°C and a screw speed of 200 rpm to 400 rpm.

[0034] Thirdly, the present invention provides an application of the above-mentioned biodegradable polyester composition in the preparation of biodegradable membranes.

[0035] Fourthly, the present invention provides a film made of the above-described biodegradable polyester composition.

[0036] For example, the above-mentioned film can be used for fruit and vegetable bags, bread / pastry bags, meat tray films, lunch box sealing films, disposable tableware packaging bags, tea bag / coffee capsule packaging bags, beverage cup sealing films, garbage bags, shopping bags, express delivery bags, document bags, flower packaging, etc.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: The biodegradable polyester composition of the present invention has both good mechanical properties and low potassium permanganate consumption. Detailed Implementation

[0038] 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.

[0039] Unless otherwise specified, all other materials, reagents, etc. used in the examples and comparative examples are commercially available.

[0040] 1. Raw materials and reagents 1) PBAT resin PBAT resin is prepared by the following method: terephthalic acid, adipic acid, and 1,4-butanediol (in excess) are reacted at 230-235°C and 75-80 kPa to obtain a first product (T1). The first product is then reacted at 240-245°C and 1200-1400 Pa to obtain a pre-condensation product (T2). Finally, the product is reacted at 244-249°C and 150-200 Pa to obtain different PBAT resins (T3). The total molar ratio of terephthalic acid and adipic acid to 1,4-butanediol is 1:1.4. The melt flow rate of PBAT resin was controlled by adjusting T1, T2, and T3. 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.

[0041] Table 1 PBAT Resin The “T content” in Table 1 represents the total molar amount of structural units derived from terephthalic acid and adipic acid in PBAT resin, where the molar percentage of structural units derived from terephthalic acid is; this can be achieved by keeping the total amount of terephthalic acid and adipic acid constant and adjusting the molar percentage of terephthalic acid.

[0042] 2) Cross-linked starch Cross-linked starch 1, gelatinization temperature 95℃; Cross-linked starch 1 was prepared by the following method: starch (corn starch, purchased from Shandong Jinyumi) was prepared into an emulsion with a mass concentration of 35%, and an appropriate amount of sodium chloride was added to inhibit starch swelling. The pH value of the system was controlled between 11.0 and 11.5 using sodium hydroxide solution. The cross-linking reaction was carried out at 50°C using sodium trimetaphosphate (STMP) as a cross-linking agent for 4 hours, wherein the amount of cross-linking agent added was 0.08% of the starch mass. Then, the pH value of the system was adjusted to neutral using dilute hydrochloric acid solution. After dehydration, washing, drying, pulverizing and sieving, cross-linked starch 1 was obtained.

[0043] Cross-linked starch 2, gelatinization temperature 84℃; Cross-linked starch 2 was prepared by the following method: starch (potato starch, purchased from Heilongjiang Shufeng Potato Industry Co., Ltd.) was prepared into an emulsion with a mass concentration of 40%, and an appropriate amount of sodium chloride was added to inhibit starch swelling. The pH value of the system was controlled between 11.0 and 11.5 using sodium hydroxide solution. The cross-linking reaction was carried out at 45°C using sodium trimetaphosphate (STMP) as a cross-linking agent for 2 hours, wherein the amount of cross-linking agent added was 0.05% of the starch mass. Then, the pH value of the system was adjusted to neutral using dilute hydrochloric acid solution. After dehydration, washing, drying, pulverizing and sieving, cross-linked starch 2 was obtained.

[0044] The gelatinization temperature of cross-linked starch was determined by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min under a nitrogen atmosphere. For sample preparation, 3-5 mg of starch sample was accurately weighed, and then three times its mass of deionized water was added. The mixture was stirred evenly at the bottom of the crucible using a fine needle to form a slurry. The aluminum crucible was quickly sealed, and the mixture was allowed to equilibrate at room temperature for 1 hour before DSC testing.

[0045] 3) Plasticizers Plasticizer 1 is composed of glycerol (commercially available), water, and triacetin (commercially available) in a mass ratio of 1.5:2.5:0.7; Plasticizer 2 is composed of glycerin (commercially available), water, and tributyl citrate (commercially available) in a mass ratio of 2:2:0.5; Plasticizer 3 is composed of glycerin (commercially available), water and tributyl acetylacetonate (commercially available) in a mass ratio of 1:3:1.

[0046] Plasticizer 4 is composed of glycerin (commercially available) and water in a mass ratio of 1.5:2.5.

[0047] Plasticizer 5 is composed of glycerol (commercially available) and triacetin (commercially available) in a mass ratio of 1.5:0.7; Plasticizer 6 is composed of water and triacetin (commercially available) in a mass ratio of 2.5:0.7.

[0048] 4) Processing aids Processing aid 1 is an opening agent (talc), brand name TYT-777A, manufactured by Haicheng Tianyuan Chemical. Processing aid 2 is a slip agent (erucamide), brand name ER-CH-MB-(SI), manufacturer: Croda.

[0049] 2. Preparation method of the biodegradable polyester composition of the present invention 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 120°C to 150°C to obtain a biodegradable polyester composition. The screw speed of the twin-screw extruder is 300 rpm.

[0050] Table 2 shows the weight parts of each component in the biodegradable polyester compositions of Examples 1 to 10. Table 3 shows the weight parts of each component in the biodegradable polyester compositions of Comparative Examples 1 to 7. In Tables 2 and 3, " / " indicates that there are no relevant parameters. In Table 3, "glycerol / sorbitol" refers to a compound composed of commercially available glycerol and commercially available sorbitol in a mass ratio of 1:1.

[0051] 3. Performance Testing 1) Mechanical property testing: The biodegradable polyester composition was dried and the moisture content was controlled below 500 ppm, then subjected to blown film processing to obtain a biodegradable film. The blown film processing temperature was 130℃ to 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. The biodegradable film was tested for longitudinal tensile strength and transverse tensile strength according to GB / T 1040.3-2006 standard, with a tensile rate of 500 mm / min.

[0052] 2) Potassium permanganate consumption test: The potassium permanganate consumption of the biodegradable polyester composition was tested according to the standard GB 4806.7-2023 "National Food Safety Standard for Plastic Materials and Products for Food Contact".

[0053] Table 4. Performance of the biodegradable polyester compositions in each example and comparative example. As shown in Table 4, the longitudinal tensile strength of the biodegradable polyester compositions in Examples 1 to 10 is ≥21 MPa and the transverse tensile strength is ≥10 MPa, while the potassium permanganate consumption is below 9 mg / kg, indicating that the biodegradable polyester compositions of the present invention have both good mechanical properties and low potassium permanganate consumption. Comparative Example 1 shows that, based on the total molar amount of structural units derived from terephthalic acid and adipic acid in PBAT resin, an excessively high molar proportion of structural units derived from terephthalic acid will severely degrade the degradation performance of the biodegradable polyester composition. Comparative Examples 2 and 3 show that, while replacing cross-linked starch with a physical mixture of corn starch and sodium trimetaphosphate, or using conventional plasticizers such as glycerol / sorbitol mixtures, has a relatively small impact on the mechanical properties of the biodegradable polyester composition, it cannot effectively reduce potassium permanganate consumption. Comparative Examples 5 to 7 also show that using any two of glycerol, water, and ester compounds as plasticizers cannot simultaneously achieve both good mechanical properties and low potassium permanganate consumption in the biodegradable polyester composition.

[0054] 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 composition, characterized in that, By weight, it includes the following components: 52-76 parts of biodegradable polyester, 20-35 parts of cross-linked starch, and 5-10 parts of plasticizer; The biodegradable polyester includes PBAT resin; 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 ≤53%; The plasticizer is composed of glycerol, water, and ester compounds, wherein the ester compounds include at least one of saturated glycerides and citrate esters.

2. The biodegradable polyester composition according to claim 1, characterized in that, 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 43% to 52%.

3. The biodegradable polyester composition according to claim 1, characterized in that, The gelatinization temperature of the cross-linked starch is 80°C to 95°C; And / or, the mass ratio of the glycerol, water and ester compound is (1~2):(2~3):(0.5~1).

4. The biodegradable polyester composition according to claim 1, characterized in that, The PBAT resin has a melt flow rate of 1.5 g / 10 min to 10 g / 10 min at 190 °C and 2.16 kg.

5. The biodegradable polyester composition according to claim 1, characterized in that, The biodegradable polyester also includes at least one of PLA resin and PBST resin.

6. The biodegradable polyester composition according to claim 5, characterized in that, At least one of the following conditions must be met: (1) The PLA resin includes at least one of PLLA, PDLA, and PLLA / PDLA copolymer; (2) The melt flow rate of the PBST resin at 190°C and 2.16 kg is 1.5 g / 10 min to 10 g / 10 min; (3) Based on the total molar amount of structural units derived from terephthalic acid and succinic acid in the PBST resin, the molar percentage of the structural units derived from terephthalic acid is 44% to 50%.

7. The biodegradable polyester composition according to any one of claims 1 to 6, wherein the biodegradable polyester composition further comprises 0.1 to 2 parts of processing aids; the processing aids include at least one of opening agents, slip agents, antioxidants, weathering agents, and antistatic agents.

8. A method for preparing the biodegradable polyester composition according to any one of claims 1 to 7, characterized in that, The process includes the following steps: mixing the components evenly and then melt-extruding to obtain a biodegradable polyester composition.

9. The use of the biodegradable polyester composition according to any one of claims 1 to 7 in the preparation of biodegradable membranes.

10. A thin film, characterized in that, Made from the biodegradable polyester composition according to any one of claims 1 to 7.

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