High-speed coatable polylactic acid composition and method for preparing the same

Abstract

The application relates to the field of high-molecular synthetic materials, and particularly discloses a polylactic acid composition capable of high-speed film coating and a preparation method thereof. The polylactic acid composition capable of high-speed film coating comprises the following raw materials in mass parts: 80-100 parts of polylactic acid, 10-20 parts of chitosan nano-emulsion and 0.1-0.3 parts of a compatilizer, wherein the chitosan nano-emulsion is chitosan embedded in nano-emulsion; and the preparation method comprises the following steps: S1: polylactic acid is placed into a 115-125 DEG C vacuum drying box and dried for 7-9 hours; and S2: 80-100 parts of polylactic acid, 10-20 parts of chitosan nano-emulsion and 0.1-0.3 parts of a compatilizer are weighed and placed into an extruder at 120-170 DEG C to be melt blended and granulated to obtain the polylactic acid composition. The polylactic acid composition capable of high-speed film coating has the advantages that the antibacterial performance of polylactic acid can be improved.

Description

Technical Field

[0001] This application relates to the field of polymer synthetic materials, and more specifically, to a polylactic acid composition capable of high-speed lamination and a method for its preparation. Background Technology

[0002] Polylactic acid, also known as polylactide, belongs to the polyester family. It is a polymer obtained by polymerizing lactic acid as the main raw material. The raw materials are abundant and renewable, mainly corn, cassava, etc. The production process of polylactic acid is pollution-free, and the product is biodegradable. After use, it can be completely degraded by microorganisms in nature under specific conditions, eventually producing carbon dioxide and water, thus achieving a cycle in nature. Therefore, it is an ideal green polymer material.

[0003] Coated paper is a composite material in which plastic particles are coated onto the surface of paper using a casting machine. Its main characteristics are oil resistance, water resistance (relatively speaking), and heat sealing capability. Currently, coated paper made of polyethylene is used to make disposable paper cups, paper bowls, and other disposable tableware. However, polyethylene is not biodegradable and is detrimental to environmental protection. In contrast, disposable tableware made of polylactic acid coated paper can significantly reduce the burden on natural resources and the environment compared to disposable tableware made of polyethylene coated paper, and is currently favored by consumers.

[0004] Currently, disposable tableware is usually exposed to the air during use, and bacteria can easily grow on its surface. The oligomers produced by the decomposition of polylactic acid are also easily contaminated by various bacteria. Under suitable temperature and humidity conditions, bacteria can multiply very easily, thus affecting human health. Summary of the Invention

[0005] In order to improve the shortcomings of polylactic acid in antibacterial properties, this application provides a polylactic acid composition that can be rapidly coated and a method for preparing the same.

[0006] In a first aspect, this application provides a high-speed lamination-capsulation polylactic acid composition, employing the following technical solution:

[0007] A high-speed lamination-capsulating polylactic acid composition comprises the following raw materials in parts by weight: 80-100 parts polylactic acid, 10-20 parts chitosan nanoemulsion, and 0.1-0.3 parts compatibilizer, wherein the chitosan nanoemulsion is a nanoemulsion in which chitosan is embedded.

[0008] Polylactic acid (PLA) is a bio-based material derived from renewable resources such as corn starch or sugarcane. It is produced by microbial fermentation to produce lactic acid, which is then polymerized to form PLA. It has good biodegradability and can be completely degraded by microorganisms in nature under specific conditions after use, ultimately producing carbon dioxide and water, thus reducing its impact on the environment.

[0009] Chitosan is a natural polymer with advantages such as good antibacterial properties, safety, non-toxicity, and biodegradability. However, chitosan is a natural polysaccharide composed of N-acetylglucosamine and glucosamine units, and is cationic because it can protonate under acidic conditions to form positively charged amino groups. Polylactic acid (PLA), on the other hand, is a synthetic polyester composed of lactic acid units linked by ester bonds and is usually neutral. Therefore, the compatibility between the two is poor. The chitosan nanoemulsion used in this application embeds chitosan within the nanoemulsion. The nanoemulsion can disperse chitosan into nanoscale particles, which have a larger specific surface area and can be more uniformly distributed in the PLA matrix. Furthermore, embedding chitosan in the nanoemulsion improves its stability, promotes the interaction between chitosan and microorganisms, enhances its solubility and absorption, and improves its release properties. This allows chitosan to be well-compatible with PLA and enhances the antibacterial properties of PLA.

[0010] Preferably, the chitosan nanoemulsion comprises the following raw materials: chitosan prepolymer, sodium caseinate solution, and hydroxypropyl-β-cyclodextrin solution.

[0011] Sodium caseinate, as a natural protein, has good biocompatibility and is non-toxic to cells. As an emulsifier, it can help stabilize nanoemulsions, making chitosan prepolymers less prone to aggregation and improving their dispersibility. Hydroxypropyl-β-cyclodextrin, as a stabilizer, is beneficial to improving the stability of nanoemulsions.

[0012] Preferably, the chitosan nanoemulsion comprises the following raw materials in parts by weight: 4.5-5.5 parts chitosan prepolymer, 45-55 parts sodium caseinate solution, and 45-55 parts hydroxypropyl-β-cyclodextrin solution.

[0013] Preferably, the preparation method of the chitosan nanoemulsion is as follows: 45-55 parts of sodium caseinate solution and 45-55 parts of hydroxypropyl-β-cyclodextrin solution are mixed, and 4.5-5.5 parts of chitosan prepolymer are added dropwise while stirring. The mixture is stirred at room temperature for 1-3 hours to obtain a crude chitosan emulsion. The crude chitosan emulsion is placed in a handheld homogenizer and homogenized at a speed of 17000-19000 rpm for 1-3 minutes. Then, the emulsion is ultrasonically treated at a frequency of 10-30 kHz for 7-13 minutes, with the mode on for 1-3 seconds and off for 1-3 seconds to obtain the chitosan nanoemulsion.

[0014] Preferably, the chitosan prepolymer comprises the following raw materials: chitosan, dilute acetic acid solution, ammonium polyphosphate, and sodium phytate solution.

[0015] Preferably, the chitosan is 3-7g, the dilute acetic acid solution is 240-260ml, the ammonium polyphosphate is 0.1-0.2g, and the sodium phytate solution is 8-12g.

[0016] Preferably, the preparation method of the chitosan prepolymer is as follows: Weigh 3-7g of chitosan and dissolve it in a flask containing 240-260ml of dilute acetic acid solution. Stir at 20-30℃ until the chitosan is fully dissolved, then raise the temperature to 50-70℃, add 0.5-1g of ammonium polyphosphate and stir rapidly for 0.5-1.5h, then slowly add 8-12g of sodium phytate solution and continue the reaction for 0.5-1.5h.

[0017] Chitosan can dissolve in dilute acetic acid to form a chitosan-acetic acid solution, which helps improve the water solubility of chitosan. Ammonium polyphosphate composites have highly efficient flame retardant properties for polymers, but they are generally added in large quantities. During use, the flame retardant is prone to precipitation and agglomeration, resulting in uneven dispersion. Therefore, coating the surface of ammonium polyphosphate with chitosan can enhance the flame retardant properties of polylactic acid when the chitosan prepolymer reacts with polylactic acid.

[0018] Secondly, this application provides a method for preparing a polylactic acid composition capable of high-speed lamination, employing the following technical solution:

[0019] A method for preparing a polylactic acid composition capable of high-speed lamination includes the following steps:

[0020] S1: Place polylactic acid in a vacuum drying oven at 115℃-125℃ and dry for 7-9 hours;

[0021] S2: Weigh 80-100 parts of polylactic acid, 10-20 parts of chitosan nanoemulsion and 0.1-0.3 parts of compatibilizer and put them into an extruder at 120-170℃ for melt blending and granulation to obtain a polylactic acid composition.

[0022] In summary, this application has the following beneficial effects:

[0023] 1. Polylactic acid (PLA) is a bio-based material derived from renewable resources such as corn starch or sugarcane. It is produced by microbial fermentation to produce lactic acid, which is then polymerized to form PLA. It has good biodegradability and can be completely degraded by microorganisms in nature under specific conditions after use, ultimately producing carbon dioxide and water, thus reducing the impact on the environment.

[0024] Chitosan is a natural polymer with advantages such as good antibacterial properties, safety, non-toxicity, and biodegradability. However, chitosan is a natural polysaccharide composed of N-acetylglucosamine and glucosamine units, and is cationic because it can protonate under acidic conditions to form positively charged amino groups. Polylactic acid (PLA), on the other hand, is a synthetic polyester composed of lactic acid units linked by ester bonds and is usually neutral. Therefore, the compatibility between the two is poor. The chitosan nanoemulsion used in this application embeds chitosan within the nanoemulsion. The nanoemulsion can disperse chitosan into nanoscale particles, which have a larger specific surface area and can be more uniformly distributed in the PLA matrix. Furthermore, embedding chitosan in the nanoemulsion improves its stability, promotes the interaction between chitosan and microorganisms, enhances its solubility and absorption, and improves its release properties. This allows chitosan to be well-compatible with PLA and enhances the antibacterial properties of PLA.

[0025] 2. Sodium caseinate, as a natural protein, has good biocompatibility and is beneficial to cells.

[0026] It is non-toxic and, as an emulsifier, helps stabilize nanoemulsions, making chitosan prepolymers less prone to aggregation and improving their dispersibility. Hydroxypropyl-β-cyclodextrin, as a stabilizer, is beneficial to improving the stability of nanoemulsions.

[0027] 3. Chitosan can dissolve in dilute acetic acid to form a chitosan-acetic acid solution, which helps improve the water solubility of chitosan. Ammonium polyphosphate composites have highly efficient flame retardant properties for polymers, but they are generally added in large quantities. During use, the flame retardant is prone to precipitation and agglomeration, resulting in uneven dispersion. Therefore, coating the surface of ammonium polyphosphate with chitosan can enhance the flame retardant properties of polylactic acid when the chitosan prepolymer reacts with polylactic acid. Detailed Implementation

[0028] The present application will be further described in detail below with reference to Examples 1-8 and Comparative Examples 1-2.

[0029] raw material

[0030] Polylactic acid (PLA) - Shanghai Yuanye Biotechnology Co., Ltd.; Chitosan CAS: 9012-76-4; Compatibilizer ADR4370S - BASF GmbH, Germany; Sodium caseinate CAS: 9005-46-3; Hydroxypropyl-β-cyclodextrin - Shanghai Aladdin Biochemical Technology Co., Ltd.; Acetic acid CAS: 64-19-7; Ammonium polyphosphate - Jinan Fuming Chemical Co., Ltd.; Sodium phytate - BASF Biotechnology Co., Ltd., Hefei.

[0031] Example

[0032] Example 1

[0033] A high-speed lamination-capsulating polylactic acid composition comprising the following raw materials: 90g polylactic acid, 15g chitosan nanoemulsion, and 0.2g compatibilizer ADR4370S.

[0034] Specifically, the preparation method of the high-speed lamination-capsulated polylactic acid composition includes the following steps:

[0035] S1: Weigh 5g of chitosan and dissolve it in a flask containing 250ml of 1% dilute acetic acid solution (acetic acid to deionized water ratio of 1:99). Stir at 25℃ until the chitosan is fully dissolved, then raise the temperature to 60℃, add 0.75g of ammonium polyphosphate and stir rapidly for 1h. Then slowly add 10g of 10% sodium phytate solution (sodium phytate to deionized water ratio of 1:9) and continue the reaction for 1h to obtain chitosan prepolymer.

[0036] S2: Mix 50g of 2% sodium caseinate solution (sodium caseinate to deionized water ratio of 1:98) and 50g of 1% hydroxypropyl-β-cyclodextrin solution (hydroxypropyl-β-cyclodextrin to deionized water ratio of 1:99) in a 1:1 ratio. While stirring, add 5g of chitosan prepolymer dropwise until the final concentration is 5%. Stir at room temperature for 2 hours to obtain a crude chitosan emulsion. Place the crude chitosan emulsion in a handheld homogenizer and homogenize it at 18000rpm for 2 minutes. Then, treat the emulsion with ultrasound at a frequency of 20kHz for 10 minutes, with the mode on for 2 seconds and off for 2 seconds to obtain a chitosan nanoemulsion.

[0037] S3: Place polylactic acid in a 120°C vacuum drying oven and dry for 8 hours;

[0038] S4: Weigh 90g of dried polylactic acid, 15g of chitosan nanoemulsion and 0.2g of compatibilizer ADR4370S and put them into an extruder at 150℃ for melt blending and granulation to obtain a polylactic acid composition.

[0039] Example 2-3

[0040] The difference from Example 1 is that the amount of each component added in the high-speed lamination-coated polylactic acid composition is different, as shown in Table 1.

[0041] Table 1. Amounts (g) of each component added to the polylactic acid compositions capable of high-speed coating in Examples 1-3.

[0042]

[0043] Example 4

[0044] The difference from Example 1 is that the components of the high-speed coating polylactic acid composition are different, as shown in Table 2.

[0045] Table 2. Amounts (g) of each component added to the polylactic acid composition capable of high-speed coating in Example 4.

[0046]

[0047] Examples 5-6

[0048] The difference from Example 1 is that the amount of each component added in the chitosan nanoemulsion is different, as shown in Table 3.

[0049] Table 3. Amounts (g) of each component added to the chitosan nanoemulsion in Examples 1 and 5-6.

[0050]

[0051] Examples 7-8

[0052] The difference from Example 1 is that the amount of each component added in the chitosan prepolymer is different, as shown in Table 4.

[0053] Table 4. Amounts (g) of each component added to the chitosan prepolymer in Examples 1 and 7-8.

[0054]

[0055] Comparative Example

[0056] Comparative Example 1

[0057] The difference from Example 1 is that chitosan nanoemulsion is no longer added.

[0058] Comparative Example 2

[0059] The difference from Example 1 is that the chitosan prepolymer is replaced with an equal amount of chitosan.

[0060] Performance testing

[0061] Detection methods

[0062] I. Antibacterial Performance Test

[0063] Three samples were taken from Examples 1-8 and Comparative Examples 1-2 respectively, and their antibacterial properties were tested in accordance with the standard QB / T 2591-2003 "Test Methods and Antibacterial Effects of Antibacterial Plastics". The antibacterial rate was then obtained and the average value was taken.

[0064] The test data are shown in Table 5.

[0065] Table 5. Antibacterial performance test results of Examples 1-8 and Comparative Examples 1-2

[0066]

[0067] II. Flame retardant performance test

[0068] Three samples were taken from Examples 1-8 and Comparative Examples 1-2 respectively, and the flame retardancy of the samples was determined using the UL94 method. The flame retardancy rating increased progressively from HB, V-2, V-1 to V-0.

[0069] HB: The lowest flame retardant rating in the UL94 standard, requiring a burning rate of less than 40 mm / min for samples 3-13 mm thick and less than 70 mm / min for samples less than 3 mm thick, or to extinguish before the 100 mm mark.

[0070] V-2: After two 10-second burning tests on the sample, the flame extinguishes within 60 seconds, and burning material may fall off.

[0071] V-1: After two 10-second burning tests on the sample, the flame must extinguish within 60 seconds, and no burning material should fall off.

[0072] V-0: After two 10-second burning tests on the sample, the flame must extinguish within 30 seconds, and no burning material should fall off.

[0073] The test data are shown in Table 6.

[0074] Table 6 Flame retardant performance test table for Examples 1-8 and Comparative Examples 1-2

[0075]

[0076] Combining Example 1 and Comparative Example 1 with Tables 5 and 6, it can be seen that, compared to Example 1, Comparative Example 1 shows a significant decrease in the antibacterial rates against Staphylococcus aureus and Escherichia coli. This indicates that, compared to conventional polylactic acid, the addition of chitosan nanoemulsion can effectively improve the antibacterial rates of the samples against Staphylococcus aureus and Escherichia coli. Furthermore, the flame retardant performance of Example 1 is V-0, while that of Comparative Example 1 is HB, indicating a significant decrease in the flame retardant performance of Comparative Example 1. This further demonstrates that, compared to conventional polylactic acid, the addition of chitosan nanoemulsion can effectively improve the flame retardant performance of the samples.

[0077] The reason for this is that encapsulating chitosan in a nanoemulsion allows the nanoemulsion to disperse chitosan into nanoscale particles. These particles have a larger specific surface area and can be more uniformly distributed within the polylactic acid (PLA) matrix. Encapsulating chitosan in the nanoemulsion improves its stability, promotes the interaction between chitosan and microorganisms, enhances its solubility and absorption, and improves its release properties. This allows chitosan to be well-compatible with PLA and improves PLA's antibacterial properties. Furthermore, the chitosan nanoemulsion contains ammonium polyphosphate, which has highly efficient flame-retardant properties when combined with polymers. However, it is generally added in large quantities, and during use, the flame retardant is prone to precipitation and agglomeration, resulting in uneven dispersion. Therefore, coating the surface of ammonium polyphosphate with chitosan enhances the flame-retardant properties of PLA when the chitosan prepolymer reacts with PLA.

[0078] Combining Example 1 and Comparative Example 2 with Tables 5 and 6, it can be seen that, compared to Example 1, Comparative Example 2 showed a slight decrease in the antibacterial rates against Staphylococcus aureus and Escherichia coli. This indicates that replacing chitosan prepolymer with chitosan affects the antibacterial properties of the samples to some extent. Meanwhile, the flame retardant performance of Example 1 was V-0, while that of Comparative Example 2 was HB, showing a significant decrease in flame retardant performance. This indicates that, compared to adding chitosan, adding chitosan prepolymer can effectively improve the flame retardant properties of polylactic acid.

[0079] Combining Examples 1 and 2-3 with Tables 5 and 6, it can be seen that, compared to Example 1, the antibacterial rates against Staphylococcus aureus and Escherichia coli in Examples 2 and 3 both decreased slightly. This indicates that the amount of each component added to the high-speed lamination-coated polylactic acid composition affects the antibacterial performance of the sample to a certain extent. At the same time, compared to the V-0 flame retardant performance of Example 1, the flame retardant performance of Examples 2 and 3 is also V-0. This indicates that the amount of each component added to the high-speed lamination-coated polylactic acid composition has a relatively small impact on the flame retardant performance of the sample.

[0080] Combining Examples 1 and 4 with Tables 5 and 6, it can be seen that, compared to Example 1, the antibacterial rates against Staphylococcus aureus and Escherichia coli in Example 4 decreased. This indicates that, compared to directly adding chitosan, the addition of chitosan nanoemulsion can effectively improve the antibacterial properties of the samples. Meanwhile, compared to the V-0 flame retardant performance of Example 1, the flame retardant performance of Example 4 is HB. This indicates that, compared to directly adding chitosan, the addition of chitosan nanoemulsion can effectively improve the flame retardant performance of the samples.

[0081] The reason for this is that chitosan is a natural polymer with advantages such as good antibacterial properties, safety, non-toxicity, and biodegradability. However, chitosan is a natural polysaccharide composed of N-acetylglucosamine and glucosamine units, and it is cationic because it can protonate under acidic conditions to form positively charged amino groups. Polylactic acid, on the other hand, is a synthetic polyester composed of lactic acid units linked by ester bonds, and is usually neutral. Therefore, the compatibility between the two is poor.

[0082] Combining Examples 1 and 5-6 with Tables 5 and 6, it can be seen that, compared to Example 1, the antibacterial rates against Staphylococcus aureus and Escherichia coli in Examples 5 and 6 both decreased slightly. This indicates that the amount of each component added to the chitosan nanoemulsion affects the antibacterial properties of the samples to a certain extent. At the same time, compared to the V-0 flame retardant performance of Example 1, the flame retardant performance of Examples 5 and 6 is also V-0. This indicates that the amount of each component added to the chitosan nanoemulsion has a relatively small impact on the flame retardant performance of the samples.

[0083] Combining Examples 1 and 7-8 with Tables 5 and 6, it can be seen that, compared to Example 1, the antibacterial rates against Staphylococcus aureus and Escherichia coli in Examples 7 and 8 both decreased slightly. This indicates that the amount of each component added to the chitosan prepolymer affects the antibacterial properties of the samples to a certain extent. Meanwhile, compared to the V-0 flame retardant performance of Example 1, the flame retardant performance of Examples 7 and 8 is V-1. This indicates that the amount of each component added to the chitosan prepolymer has a certain impact on the flame retardant performance of the samples. The amount of each component added to the chitosan prepolymer in Example 1 can effectively improve the flame retardant performance of the samples.

[0084] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A polylactic acid composition capable of high-speed coating, characterized in that, The raw materials include the following parts by weight: 80-100 parts polylactic acid, 10-20 parts chitosan nanoemulsion, and 0.1-0.3 parts compatibilizer, wherein the chitosan nanoemulsion is chitosan embedded in a nanoemulsion; The chitosan nanoemulsion comprises the following raw materials: chitosan prepolymer, sodium caseinate solution, and hydroxypropyl-β-cyclodextrin solution; The chitosan nanoemulsion comprises the following raw materials in parts by weight: 4.5-5.5 parts chitosan prepolymer, 45-55 parts sodium caseinate solution, and 45-55 parts hydroxypropyl-β-cyclodextrin solution.

2. The polylactic acid composition capable of high-speed coating according to claim 1, characterized in that: The preparation method of the chitosan nanoemulsion is as follows: 45-55 parts of sodium caseinate solution and 45-55 parts of hydroxypropyl-β-cyclodextrin solution are mixed, and 4.5-5.5 parts of chitosan prepolymer are added dropwise while stirring. The mixture is stirred at room temperature for 1-3 hours to obtain a crude chitosan emulsion. The crude chitosan emulsion is placed in a handheld homogenizer and homogenized at a speed of 17000-19000 rpm for 1-3 minutes. Then, the emulsion is ultrasonically treated at a frequency of 10-30 kHz for 7-13 minutes, with the mode on for 1-3 seconds and off for 1-3 seconds to obtain the chitosan nanoemulsion.

3. The polylactic acid composition capable of high-speed coating according to claim 2, characterized in that: The chitosan prepolymer comprises the following raw materials: chitosan, dilute acetic acid solution, ammonium polyphosphate, and sodium phytate solution.

4. The polylactic acid composition capable of high-speed coating according to claim 3, characterized in that: The chitosan is 3-7g, the dilute acetic acid solution is 240-260ml, the ammonium polyphosphate is 0.1-0.2g, and the sodium phytate solution is 8-12g.

5. The polylactic acid composition capable of high-speed coating according to claim 4, characterized in that: The preparation method of the chitosan prepolymer is as follows: Weigh 3-7g of chitosan and dissolve it in a flask containing 240-260ml of dilute acetic acid solution. Stir at 20-30℃ until the chitosan is fully dissolved, then raise the temperature to 50-70℃, add 0.5-1g of ammonium polyphosphate and stir rapidly for 0.5-1.5h. Then slowly add 8-12g of sodium phytate solution and continue the reaction for 0.5-1.5h.

6. A method for preparing a high-speed coated polylactic acid composition according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Place polylactic acid in a vacuum drying oven at 115℃-125℃ and dry for 7-9 hours; S2: Weigh 80-100 parts of polylactic acid, 10-20 parts of chitosan nanoemulsion and 0.1-0.3 parts of compatibilizer and put them into an extruder at 120-170℃ for melt blending and granulation to obtain a polylactic acid composition.

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