A polylactic acid composition, and a method of preparing and using the same

Abstract

The application discloses a polylactic acid composition, a preparation method and application thereof. The polylactic acid composition provided by the application can take into account notch toughness and extrusion stability by limiting the weight fractions of components, and limiting the ratio of melting enthalpy and glass transition temperature, the SiO2 content of talcum powder, the T content of polybutylene terephthalate adipate and the D content of polylactic acid in specific ranges.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a polylactic acid composition, its preparation method, and its application. Background Technology

[0002] Lactic acid is a colorless, transparent liquid produced from starchy corn using modern biotechnology. Through a special polymerization process, lactic acid can be converted into granular polymer materials, namely polylactic acid (PLA). PLA possesses excellent tensile strength and ductility and can be produced using various common processing methods, such as melt extrusion molding, injection molding, blown film molding, foam molding, and vacuum forming. However, the widespread application of PLA as a general-purpose plastic is currently limited, primarily due to its severe brittleness and notched impact strength of less than 3 kJ / m. 2 This severely limits its widespread application. Existing technologies often employ the addition of polybutylene terephthalate (PBAT) to polylactic acid (PLA) to improve its toughness; however, the addition of PBAT easily leads to a decrease in extrusion stability. Therefore, how to improve the toughness of PLA without affecting its extrusion stability is a problem that must be solved to expand the application of PLA in fields such as catering equipment. Summary of the Invention

[0003] To address the technical problem that existing polylactic acid-polybutylene adipate terephthalate-talc compositions cannot simultaneously achieve both toughness and extrusion stability, this invention provides a polylactic acid composition. The polylactic acid composition provided by this invention can achieve both notched toughness and extrusion stability.

[0004] Another object of the present invention is to provide a method for preparing the above-mentioned polylactic acid composition.

[0005] Another object of the present invention is to provide the application of the above-described polylactic acid composition.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A polylactic acid composition, comprising, by weight, the following components: Polylactic acid: 55-90 parts, polybutylene adipate: 3-25 parts, talc: 5-20 parts; The composition satisfies: 0.3 ≤ X / Y ≤ 1. Wherein, X is the enthalpy of melting of the polylactic acid composition, in J / g. Y is the glass transition temperature of the polylactic acid composition, in °C; The SiO2 content of the talc powder is 59~62 wt%; The T content of the polybutylene adipate terephthalate is 45~55 wt%; The D content of the polylactic acid is 0.2~4wt%.

[0008] X / Y is the ratio of the melting enthalpy to the glass transition temperature of the polylactic acid (PLA) composition. This ratio reflects the crystallization characteristics of the PLA composition, which affect its processing stability. If the ratio is too high or too low, the PLA composition will crystallize too quickly or too slowly, resulting in decreased extrusion stability.

[0009] The weight percentages of each component, the SiO2 content of talc, the T content of polybutylene adipate terephthalate, and the D content of polylactic acid affect the ratio of the melting enthalpy to the glass transition temperature of the polylactic acid composition, ultimately affecting the extrusion stability.

[0010] The weight percentages of each component, the SiO2 content of talc, the T content of polybutylene adipate terephthalate, and the D content of polylactic acid also affect notched toughness.

[0011] By controlling the weight percentages of each component in the polylactic acid (PLA) composition, the ratio of the enthalpy of melting to the glass transition temperature of the PLA composition, the SiO2 content of talc, the T content of polybutylene adipate terephthalate (PAT), and the D content of PLA within specific ranges, the PLA composition can simultaneously possess good notched toughness and extrusion stability.

[0012] Specifically, the polylactic acid can be in the following quantities: 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90 parts.

[0013] Specifically, the number of parts of polybutylene adipate terephthalate can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25.

[0014] Specifically, the amount of talc powder can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 parts.

[0015] Specifically, the X / Y can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1.

[0016] Specifically, the SiO2 content of the talc powder can be 59wt%, 60wt%, 61wt%, or 62wt%.

[0017] Specifically, the T content of the polybutylene adipate terephthalate can be 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, or 55wt%.

[0018] Specifically, the D content of the polylactic acid can be 0.2wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, or 4wt%.

[0019] Specifically, the polylactic acid has a melt flow rate of 3~20 g / 10 min at 190°C and 2.16 kg.

[0020] Specifically, the melt flow rate of the polybutylene adipate terephthalate at 190°C and 2.16 kg is 3~10 g / 10 min.

[0021] Preferably, the polylactic acid composition satisfies the following condition: 0.35 ≤ X / Y ≤ 0.7, more preferably 0.4 ≤ X / Y ≤ 0.6. The ratio of the melting enthalpy to the glass transition temperature of the polylactic acid composition within this range exhibits superior extrusion stability.

[0022] Preferably, the D content of the polylactic acid is 0.5~2wt%. Within this range, the D content of the polylactic acid provides both good notched toughness and extrusion stability.

[0023] Preferably, the T content of the polybutylene adipate terephthalate is 47.5~52.5 wt%. Within this range, the T content of the polybutylene adipate terephthalate provides both good notched toughness and extrusion stability.

[0024] The polybutylene adipate terephthalate described in this invention can be derived from commercially available products or can be prepared in-house. Preparation methods include, but are not limited to, the following: Terephthalic acid, adipic acid, butylene glycol and a branching agent are mixed and reacted at 180-200°C for 2-8 hours. A catalyst is added and the mixture is reacted at 230-250°C and 250-350 Pa for 6-18 hours to obtain the polybutylene terephthalate adipate.

[0025] Specifically, the branching agent includes, but is not limited to, glycerol. The amount of the branching agent used is 0.03% to 0.06% of the total mass of terephthalic acid and adipic acid.

[0026] Specifically, the catalyst includes, but is not limited to, tetrabutyl titanate. The amount of the catalyst used is 0.01% to 0.03% of the total molar amount of terephthalic acid, adipic acid, and butanediol.

[0027] Specifically, the total amount of terephthalic acid and adipic acid is in a molar ratio of 1:(1.05~1.2) to butanediol.

[0028] Specifically, the mass ratio of terephthalic acid to adipic acid is 1:(0.5~1.5); specifically, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.90, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5.

[0029] The polylactic acid described in this invention can be derived from commercially available products or can be prepared in-house. Preparation methods include, but are not limited to, the following: Polylactic acid is obtained by using a bulk polymerization method to cause L-lactide and meso-lactide to undergo ring-opening polymerization.

[0030] Preferably, the ring-opening polymerization reaction is carried out in the presence of a catalyst, which includes, but is not limited to, stannous octoate.

[0031] Specifically, the mass ratio of the catalyst to the lactide is 0.0001 to 0.01:100.

[0032] Preferably, the ring-opening polymerization process is as follows: first, react at 130~140℃ and 1100~1300Pa for 3~4 hours, and then react at 160~180℃ and 250~350Pa for 4~6 hours.

[0033] This invention also protects a method for preparing the above-mentioned polylactic acid composition, comprising the following steps: The components were extruded and granulated at 140℃-240℃ to obtain polylactic acid composite material.

[0034] The present invention also protects a biodegradable straw made from the above-mentioned polylactic acid composition.

[0035] This invention also protects the method for preparing the above-mentioned biodegradable straw, comprising the following steps: The polylactic acid composition was extruded into straws on a single screw extruder at an extrusion speed of 30 kg / h to 80 kg / h, a straw weight of 2.0 g to 2.9 g, and a water bath temperature of 20°C to 40°C.

[0036] This invention also protects the use of the above-mentioned polylactic acid composition in the preparation of tableware, straws, and 3D printing consumables.

[0037] The method for determining the enthalpy of fusion and glass transition temperature described in this invention is as follows: The determination is performed on a Netzsch DSC204 thermal analyzer under nitrogen protection. A sample with a mass of 5 ± 1 mg is first heated from 30 °C to 160 °C at a heating rate of 10 °C / min, held at 160 °C for 3 min, then cooled to -110 °C at a rate of 20 °C / min, and then heated to 150 °C at a rate of 10 °C / min. The enthalpy of fusion X of the sample is obtained from the first heating curve, and is obtained by integrating the endothermic peak of the DSC. The glass transition temperature Y of the sample is obtained from the second heating curve, with the intersection of the extrapolated line at the bend and the baseline taken as the value of the glass transition temperature Y.

[0038] The D content mentioned in this invention refers to the mass percentage of polydextrose D-lactic acid (PDLA) in polylactic acid. The D content can be determined using the following method: pure PLLA and pure PDLA are tested by gas chromatography to obtain their spectral peaks; under the same testing conditions, the target polylactic acid is tested, and the PDLA content in the target polylactic acid is calculated using the peak areas δPLLA and δPDLA of the corresponding PLLA and PDLA peaks on the gas chromatogram. The calculation formula is: η = δPDLA / (δPLLA + δPDLA) * 100%.

[0039] The T content mentioned in this invention refers to the ratio of the mass of butylene terephthalate units to the total mass of butylene terephthalate and butylene adipate in polybutylene adipate terephthalate. The T content can be determined by the following method: 1H NMR testing with deuterated chloroform as solvent and TMS as internal standard. The absorption peak area at 8.1 ppm in the 1H NMR spectrum represents the molar ratio of butylene terephthalate units, and the absorption peak area at 2.3 ppm in the 1H NMR spectrum represents the molar ratio of butylene adipate units. Based on the molar ratio of butylene adipate units to butylene terephthalate units and their respective molecular weights, the mass ratio of butylene adipate units to butylene terephthalate units is calculated, and thus the T content is calculated.

[0040] The method for determining the melt flow rate described in this invention is as follows: the test is conducted according to the GB / T 3682-2018 standard, the test temperature is 190℃, and the load is 2.16 kg.

[0041] Compared with the prior art, the present invention has the following beneficial effects: The polylactic acid composition provided by the present invention, by limiting the weight parts of each component and limiting the ratio of melting enthalpy to glass transition temperature, the SiO2 content of talc, the T content of polybutylene adipate terephthalate, and the D content of polylactic acid within a specific range, can take into account both notched toughness and extrusion stability. Detailed Implementation

[0042] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0043] The reagents used in the various embodiments and comparative examples of this invention are described below: 1. Polylactic acid: PLA-1 is a polylactic acid (PLA) with a poly(D-lactic acid) content of 2% by mass and a melt flow rate of 4.5 g / 10 min. It was prepared in-house using the following method: Bulk polymerization was carried out using 96 parts by weight of L-lactide (M1) (99.6% purity) and 4 parts by weight of meso-lactide (M2) (99.6% purity). 0.0015 parts by weight of stannous octoate (m1) were added for ring-opening polymerization. The reaction was first carried out at a temperature of 137℃ (T1) and a pressure of 1100 Pa (P1) for 3.5 hours (t1), and then at a temperature of 160℃ (T2) and a pressure of 310 Pa (P2) for 4 hours (t2). The mixture was then pelletized underwater, crystallized, and dried to obtain PLA-1. PLA-2, a polylactic acid with a polydextrose D-lactic acid content of 0.2% and a melt flow rate of 3.8 g / 10 min; is prepared in-house, and the preparation method differs from PLA-1 only in the following proportions: M1 is 99.6 parts by weight, M2 is 0.4 parts by weight, m1 is 0.005 parts by weight, T1 is 132℃, P1 is 1200 Pa, t1 is 3.8 hours, T2 is 170℃, P2 is 260 Pa, and t2 is 5 hours. PLA-3, polylactic acid with a mass percentage of 4% of polyd-D-lactic acid, melt flow rate of 4 g / 10 min, PLAFY804, Anhui Fengyuan Futailai Polylactic Acid Co., Ltd. PLA-4 is a polylactic acid (PLA) with a polydextrose (D-lactic acid) content of 5% by mass and a melt flow rate of 5 g / 10 min. It is prepared in-house, and the preparation method differs from PLA-1 only in that: M1 is 90 parts by weight, M2 is 10 parts by weight, m1 is 0.01 parts by weight, T1 is 139℃, P1 is 1300 Pa, t1 is 3.2 hours, T2 is 165℃, P2 is 270 Pa, and t2 is 5.5 hours. PLA-5 is a polylactic acid with a polydextrose D-lactic acid content of 0.05% and a melt flow rate of 4.3 g / 10 min. It is prepared in-house, and the preparation method differs from PLA-1 only in the following proportions: M1 is 99.9 parts by weight, M2 is 0.1 parts by weight, m1 is 0.006 parts by weight, T1 is 135℃, P1 is 1250 Pa, t1 is 3.3 hours, T2 is 180℃, P2 is 350 Pa, and t2 is 6 hours.

[0044] The D content of the above-mentioned polylactic acid can be determined by the following method: pure PLLA and pure PDLA are tested by gas chromatography to obtain their spectral peaks; under the same test conditions, the target polylactic acid is tested, and the PDLA content in the target polylactic acid is calculated by the peak areas δPLLA and δPDLA of the corresponding PLLA and PDLA spectral peaks on the gas chromatogram. The calculation formula is: η=δPDLA / (δPLLA+δPDLA)*100%.

[0045] 2. PBAT: PBAT-1, with a T content of 50 wt% and a melt flow rate of 4.1 g / 10 min, was prepared in-house using the following method: terephthalic acid, adipic acid, excess 1,4-butanediol, and glycerol were added to a reaction vessel and stirred at 180°C (T1) for 2 hours (t1). Then, 0.02% of the total amount of acid and alcohol in tetrabutyl titanate was added as a catalyst, and the temperature was raised to 250°C (T2). The reaction was carried out under a vacuum pressure of 310 Pa (P1) for 9 hours (t2) to obtain PBAT-1. By adjusting the mass of terephthalic acid and adipic acid, the butylene terephthalate unit accounted for 50% of the total content of butylene terephthalate and butylene adipic acid units. PBAT-2, T content 45wt%, melt flow rate 3~5 g / 10min, KM801T, KMI; PBAT-3, with a T content of 55 wt% and a melt flow rate of 4.2 g / 10 min; prepared in-house, the only difference between this preparation method and PBAT-1 is that T1 is 190℃ and t1 is 4 hours, T2 is 240℃ and t2 is 6 hours, and the mass of terephthalic acid and adipic acid is adjusted so that the butylene terephthalate unit accounts for 55% of the total content of butylene terephthalate and butylene adipic acid units. PBAT-4, with a T content of 40 wt% and a melt flow rate of 3.6 g / 10 min; prepared in-house, the only difference between this preparation method and PBAT-1 is that T1 is 185℃ and t1 is 7 hours, T2 is 245℃ and t2 is 10 hours, and the mass of terephthalic acid and adipic acid is adjusted so that the butylene terephthalate unit accounts for 40% of the total content of butylene terephthalate and butylene adipic acid units. PBAT-5, with a T content of 60 wt% and a melt flow rate of 4.5 g / 10 min; prepared in-house, the preparation method differs from PBAT-1 only in that: T1 is 200℃, t1 is 8 hours, T2 is 230℃, and t2 is 12 hours. By adjusting the mass of terephthalic acid and adipic acid, the butylene terephthalate unit accounts for 60% of the total content of butylene terephthalate and butylene adipic acid units. The T content of PBAT resin can be determined using the following methods: The T content mentioned in this invention refers to the ratio of the mass of butylene terephthalate units to the total mass of butylene terephthalate and butylene adipate in polybutylene adipate terephthalate. The T content can be determined by the following method: 1H NMR testing with deuterated chloroform as solvent and TMS as internal standard. The absorption peak area at 8.1 ppm in the 1H NMR spectrum represents the molar ratio of butylene terephthalate units, and the absorption peak area at 2.3 ppm in the 1H NMR spectrum represents the molar ratio of butylene adipate units. Based on the molar ratio of butylene adipate units to butylene terephthalate units and their respective molecular weights, the mass ratio of butylene adipate units to butylene terephthalate units is calculated, and thus the T content is calculated.

[0046] 3. Talc powder, sources are shown in the table below. Table 1

[0047] The biodegradable straws of the various embodiments and comparative examples of the present invention are prepared through the following process: The components were extruded and granulated at 190°C to obtain a polylactic acid composition. The polylactic acid composition was extruded into straws on a single screw extruder at an extrusion speed of 55 kg / h, with a straw weight of 2.0 g / straw to 2.9 g / straw and a water bath temperature of 37°C.

[0048] The performance testing methods and standards for the polylactic acid compositions of the various embodiments and comparative examples of the present invention are as follows: Notched impact strength: Notched impact strength is tested according to GB / T 1843-2008 standard.

[0049] Extrusion stability: The extrusion stability of polylactic acid composites was characterized by the range and relative deviation of pipette weight. The sample size for each test group was 200 pipettes. The formulas for calculating the range and relative deviation are as follows: Range = Weight of the heaviest straw - Weight of the lightest straw; Relative deviation = ÷ (average weight of 200 straws) ÷ 200 × 100%.

[0050] Examples and Comparative Examples Table 2

[0051] Continued from Table 2

[0052] As can be seen from Table 2, by limiting the weight parts of each component, the D content of polylactic acid, the T content of PBAT, the SiO2 content of talc, and the ratio of the melting enthalpy to the glass transition temperature of the polylactic acid composition within the range of the present invention, the notched impact toughness of the obtained polylactic acid composition is not less than 3 kJ / m. 2 The extrusion stability of the straw has a basis weight range of ≤0.16g and a relative deviation of <6%, exhibiting both good notch toughness and extrusion stability.

[0053] The D content of polylactic acid used in Comparative Example 1 was too high, which increased the randomness of the polylactic acid molecular chain too much, resulting in an excessive decrease in the melting enthalpy of polylactic acid. The X / Y ratio of the polylactic acid composition was lower than the range of the present invention, which reduced the extrusion stability. The D content of polylactic acid used in Comparative Example 2 was too low. On the one hand, the low D content increased the orderliness of the polylactic acid molecular chain too much, resulting in an excessively high melting enthalpy of polylactic acid. This caused the X / Y ratio of the polylactic acid composition to be higher than the range of the present invention, reducing extrusion stability. On the other hand, it also led to a decrease in toughness. The T content of PBAT used in Comparative Example 3 was too low, resulting in insufficient crystallization promotion effect on polylactic acid, which led to a significant decrease in melting enthalpy and caused the X / Y ratio of the polylactic acid composition to be lower than the range of the present invention, thus reducing extrusion stability. The T content of PBAT used in Comparative Example 4 was too high, which made the rigidity of PBAT too high. On the one hand, this led to an increase in the phase separation between PBAT and polylactic acid, resulting in a significant decrease in the melting enthalpy of the polylactic acid composition. This caused the X / Y ratio of the polylactic acid composition to be lower than the range of the present invention, reducing extrusion stability. On the other hand, it also reduced the toughness. The SiO2 content of the talc used in Comparative Example 5 was too low, resulting in a lower crystallization-promoting effect. On the one hand, this led to a significant decrease in the melting enthalpy of the polylactic acid composition, causing the X / Y ratio of the polylactic acid composition to be lower than the range of the present invention, thus reducing extrusion stability. On the other hand, it also reduced the toughness. The SiO2 content of the talc used in Comparative Example 6 was too high, which reduced the dispersibility of the talc in the polylactic acid composition. On the one hand, this led to a significant decrease in the melting enthalpy of the polylactic acid composition, causing the X / Y ratio of the polylactic acid composition to be lower than the range of the present invention, thus reducing extrusion stability. On the other hand, it also led to a decrease in toughness.

[0054] In Comparative Example 7, the weight percentages of each component, the D content of polylactic acid, the T content of PBAT, and the SiO2 content of talc are all within the range of the present invention. However, due to the different trends and magnitudes of the influence of the above parameters on the melting enthalpy and glass transition temperature, the final ratio of melting enthalpy to glass transition temperature is not within the range, and the extrusion stability of the polylactic acid composition is insufficient.

[0055] 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 polylactic acid composition, characterized in that, By weight, it includes the following components: Polylactic acid: 55-90 parts, polybutylene adipate: 3-25 parts, talc: 5-20 parts; The composition satisfies: 0.3 ≤ X / Y ≤ 1. Wherein, X is the enthalpy of melting of the polylactic acid composition, in J / g. Y is the glass transition temperature of the polylactic acid composition, in °C; The SiO2 content of the talc powder is 59~62 wt%; The T content of the polybutylene adipate terephthalate is 45~55 wt%; The D content of the polylactic acid is 0.2~4wt%.

2. The polylactic acid composition according to claim 1, characterized in that, The T content of the polybutylene adipate terephthalate is 47.5~52.5 wt%.

3. The polylactic acid composition according to claim 1, characterized in that, The D content of the polylactic acid is 0.5~2wt%.

4. The polylactic acid composition according to claim 1, characterized in that, The polylactic acid has a melt flow rate of 3~20 g / 10 min at 190℃ and 2.16 kg.

5. The polylactic acid composition according to claim 1, characterized in that, The melt flow rate of the polybutylene adipate terephthalate at 190°C and 2.16 kg is 3~10 g / 10 min.

6. The polylactic acid composition according to claim 1, characterized in that, The composition satisfies: 0.35≤X / Y≤0.7; more preferably 0.4≤X / Y≤0.

6.

7. A method for preparing the polylactic acid composition according to any one of claims 1 to 6, characterized in that, Includes the following steps: The components are extruded and granulated at 140℃~240℃ to obtain the polylactic acid composition.

8. The use of the polylactic acid composition according to any one of claims 1 to 6 in the preparation of tableware, straws, and 3D printing consumables.

9. A biodegradable straw, characterized in that, The polylactic acid composition according to any one of claims 1 to 6 is used as a raw material.

10. The method for preparing the biodegradable straw according to claim 9, characterized in that, Includes the following steps: The components are extruded and granulated at 140℃-240℃ to obtain the polylactic acid composition. The polylactic acid composition was processed into a suction tube on a single screw extruder at an extrusion speed of 30 kg / h to 80 kg / h and a water bath temperature of 20°C to 40°C.

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