Preparation method and application of modified polylactic acid

Abstract

The present invention relates to the technical field of polymer material preparation, disclose a kind of preparation method and application of modified polylactic acid, including:α-eleostearic acid is dissolved in dichloromethane, thionyl chloride is added to prepare α-eleostearic acid chloride, ammonia is passed through and reacts and obtains α-eleostearic acid amide;α-eleostearic acid amide is added in dichloromethane, diethyl oxalate, ethanolamine are added, after reacting 12~24h at 30~50 DEG C, compound A is obtained;Compound A and lactide are added in toluene, catalyst A is added, after reacting 6~12h at 120~150 DEG C, modified polylactic acid is obtained;After modified polylactic acid, polylactic acid, triglycidyl isocyanurate are heated to 60~80 DEG C and are dried for 10~20min, antioxidant is added, banburying, obtains polylactic resin.The polylactic resin obtained by the present invention has higher mechanical property, heat resistance, antibacterial property, and its tensile strength, elongation at break, heat deformation temperature, antibacterial rate are all improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material preparation, and in particular to a preparation method and application of modified polylactic acid. Background Art

[0002] Polylactic acid (PLA), a sustainable bio-based polymer, has been widely used in food packaging, medical devices, agricultural films, consumer electronics, and sanitary products due to its biocompatibility, environmental friendliness, high strength (50-70 MPa), and high stiffness (elastic modulus of approximately 3-4 GPa). However, its inherent brittleness and poor ductility limit its widespread application in industrial and medical fields. Improving the toughness of PLA through toughening modification while maintaining its sustainability and biodegradability is a hot topic in current research.

[0003] Patent publication number CN101333332A discloses a polylactic acid resin toughened and modified with an acrylic copolymer and its preparation method. The resin is prepared by drying a polylactic acid resin, a toughening agent, an acrylic copolymer, and an antioxidant, B215, in a 60°C oven and then mixing and blending the mixture on a rubber-plastic mixer at 180°C, 40 rpm, for 5 minutes. The resulting product can be used to make films, plates, sheets, and foamed and injection-molded plastic parts. While the impact strength, tensile strength, and elongation at break of this resin are improved, the toughened and modified polylactic acid resin is still primarily made from petrochemical products, making it environmentally unfriendly. Therefore, the development of environmentally friendly modified polylactic acid materials is crucial. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the disadvantage of poor toughness of the polylactic acid material in the prior art, thereby providing a preparation method and application of modified polylactic acid, using natural products as the main raw materials to obtain modified polylactic acid, and further to obtain polylactic acid resin, and the obtained polylactic acid resin has improved mechanical properties, heat resistance, and antibacterial properties.

[0005] To solve the above technical problems, the present invention provides a method for preparing modified polylactic acid, comprising the following steps:

[0006] (1) Dissolve α-eleostearic acid in dichloromethane, add thionyl chloride to prepare α-eleostearic acid chloride, and introduce ammonia gas to react to obtain α-eleostearic acid amide;

[0007] (2) Add α-eleostearamide to dichloromethane, add diethyl oxalate and ethanolamine, and react at 30-50°C for 12-24 hours to obtain compound A;

[0008] (3) Compound A and lactide are added to toluene, catalyst A is added, and the mixture is reacted at 120-150°C for 6-12 hours to obtain modified polylactic acid;

[0009] The catalyst A is at least one of stannous octoate, tetrabutyl titanate or DMAP;

[0010] The mass ratio of compound A, lactide and catalyst A is 5-10:200:0.05-0.1;

[0011] The structural formula of the compound A is:

[0012] .

[0013] Preferably, the molar ratio of α-eleostearic acid to thionyl chloride is 1:1-1:3, the reaction temperature of α-eleostearic acid and thionyl chloride is 0-20° C., and the reaction time is 4-10 h.

[0014] Preferably, the mass ratio of α-eleostearamide, diethyl oxalate, and ethanolamine is 28:12-18:5-7.

[0015] The present invention also provides a method for preparing modified polylactic acid and use of the modified polylactic acid prepared in preparing polylactic acid resin, comprising the following steps:

[0016] The modified polylactic acid, polylactic acid and triglycidyl isocyanurate are heated to 60-80° C. and dried for 10-20 minutes, and then an antioxidant is added and mixed to obtain polylactic acid resin.

[0017] Preferably, the antioxidant is a composite antioxidant of antioxidant 1010 and antioxidant 168, and the mass ratio of the antioxidant 1010 to the antioxidant 168 is 1:1 to 1:3.

[0018] Preferably, the mass ratio of the modified polylactic acid, polylactic acid, triglycidyl isocyanurate, and antioxidant is 20-40:40-80:5-10:0.1-0.5.

[0019] Preferably, the banburying temperature is 180-200° C., the time is 10-15 min, and the rotation speed is 40-60 rpm.

[0020] The technical solution of the present invention has the following advantages:

[0021] 1. The present invention provides a method for preparing modified polylactic acid, which uses a natural product derivative α-eleostearic acid as a raw material to prepare a modified polylactic acid compound, and further obtains modified polylactic acid and modified polylactic acid resin. The preparation method is simple, the main raw materials are derived from natural products, are biodegradable, are environmentally friendly, and are suitable for industrial production;

[0022] 2. The application of the modified polylactic acid provided by the present invention in the preparation of polylactic acid resin, the obtained polylactic acid resin has high mechanical properties and heat resistance, and its tensile strength, elongation at break, and heat deformation temperature are improved. This is because the addition of modified polylactic acid and triglycidyl isocyanurate further improves the degree of cross-linking in the polylactic acid resin, and the conjugated double bonds of α-eleostearic acid further enhance the network structure of the polymer. The polylactic acid resin of the present invention has a high antibacterial rate against Staphylococcus aureus and Escherichia coli, and has a high mildew resistance grade, and can be used as an antibacterial resin material. This is because the amide groups in the modified polylactic acid and triglycidyl isocyanurate can effectively inhibit bacterial growth. DETAILED DESCRIPTION

[0023] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0024] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0025] The resin was injection molded to obtain a specimen, and the specimen was subjected to a heat deformation temperature test according to the national standard GB / T 1634.2-2004, and the tensile strength and elongation at break tests according to the national standard GB / T 1040.2-2006.

[0026] The antibacterial performance of the resin was tested according to QB / T2591-2003.

[0027] Degradation performance test: For the soil burial degradation performance test in the natural environment, the samples were cut into 4mm×4mm×1mm samples and dried in a vacuum oven at 40℃ to constant weight. The initial mass m0 of the samples was weighed and recorded. The samples were wrapped with a single layer of gauze, marked with numbers, and buried in the soil at a depth of about 30cm in the natural environment. The samples were taken out after 60 days, and the surface of the samples was rinsed with tap water, 75% (volume fraction) ethanol, and distilled water in turn. Then, they were dried in a vacuum oven at 40℃ to constant weight, and the mass m of the sample after degradation was recorded. The sample degradation mass loss rate = [(m0-m) / m0]*100%.

[0028] Example 1

[0029] A method for preparing modified polylactic acid comprises the following steps:

[0030] (1) Dissolve 56g of α-eleostearic acid in 400ml of dichloromethane, add 30g of thionyl chloride at 0℃, react at 10℃ for 4h, and evaporate to obtain α-eleostearic acid chloride; add α-eleostearic acid chloride to 300mL of tetrahydrofuran, introduce ammonia at room temperature until the pH value at the mouth of the reaction bottle is alkaline as measured by pH test paper, and then react at 10℃ for 6h, and evaporate to obtain α-eleostearic acid amide;

[0031] (2) Add 28 g of α-eleostearamide to 200 ml of dichloromethane, add 15 g of diethyl oxalate and 6 g of ethanolamine, and react at 40 °C for 16 h to obtain compound A;

[0032] (3) 8 g of compound A and 200 g of lactide were added to 500 ml of toluene, and 0.1 g of stannous octoate was added. The mixture was reacted at 130 °C for 8 h to obtain modified polylactic acid.

[0033] The structural formula of the compound A is:

[0034] .

[0035] 40 g of modified polylactic acid, 60 g of polylactic acid, and 10 g of triglycidyl isocyanurate were heated to 70°C and dried for 15 min, and then a composite antioxidant of 0.1 g of antioxidant 1010 and 0.2 g of antioxidant 168 was added. The mixture was kneaded at 190°C and 50 rpm for 15 min to obtain polylactic acid resin.

[0036] The tensile strength, elongation at break, and heat deformation temperature of the obtained polylactic acid resin are shown in Table 1. The antibacterial properties and degradation properties of the obtained polylactic acid resin are shown in Table 2 and Table 3, respectively.

[0037] Example 2

[0038] A method for preparing modified polylactic acid comprises the following steps:

[0039] (1) Dissolve 56g of α-eleostearic acid in 400ml of dichloromethane, add 24g of thionyl chloride at 10℃, react at 10℃ for 4h, and evaporate to obtain α-eleostearic acid chloride; add α-eleostearic acid chloride to 300mL of tetrahydrofuran, introduce ammonia at room temperature until the pH value at the mouth of the reaction bottle is alkaline as measured by pH test paper, and then react at 20℃ for 6h, and evaporate to obtain α-eleostearic acid amide;

[0040] (2) Add 28 g of α-eleostearamide to 200 ml of dichloromethane, add 18 g of diethyl oxalate and 7 g of ethanolamine, and react at 50 °C for 24 h to obtain compound A;

[0041] (3) 10 g of compound A and 200 g of lactide were added to 500 ml of toluene, 0.1 g of DMAP was added, and the mixture was reacted at 150 °C for 8 h to obtain modified polylactic acid;

[0042] The structural formula of the compound A is:

[0043] .

[0044] 30 g of modified polylactic acid, 80 g of polylactic acid, and 8 g of triglycidyl isocyanurate were heated to 80°C and dried for 20 min, and then a composite antioxidant of 0.1 g of antioxidant 1010 and 0.1 g of antioxidant 168 was added. The mixture was kneaded at 200°C and 60 rpm for 12 min to obtain a modified polylactic acid resin.

[0045] The tensile strength, elongation at break, and heat deformation temperature of the obtained polylactic acid resin are shown in Table 1. The antibacterial properties and degradation properties of the obtained polylactic acid resin are shown in Table 2 and Table 3, respectively.

[0046] Example 3

[0047] A method for preparing modified polylactic acid comprises the following steps:

[0048] (1) Dissolve 56g of α-eleostearic acid in 400ml of dichloromethane, add 72g of thionyl chloride at 20℃, react at 20℃ for 4h, and evaporate to obtain α-eleostearic acid chloride; add α-eleostearic acid chloride to 300mL of tetrahydrofuran, introduce ammonia gas at room temperature until the pH value at the mouth of the reaction bottle is alkaline as measured by pH test paper, and then react at 25℃ for 6h, and evaporate to obtain α-eleostearic acid amide;

[0049] (2) Add 28 g of α-eleostearamide to 200 ml of dichloromethane, add 12 g of diethyl oxalate and 5 g of ethanolamine, and react at 30 °C for 12 h to obtain compound A;

[0050] (3) Add 5 g of compound A and 200 g of lactide to 500 ml of toluene, add 0.05 g of stannous octoate, and react at 120 °C for 6 h to obtain modified polylactic acid;

[0051] The structural formula of the compound A is:

[0052] .

[0053] 20 g of modified polylactic acid, 40 g of polylactic acid, and 5 g of triglycidyl isocyanurate were heated to 60°C and dried for 10 min, and then a composite antioxidant of 0.1 g of antioxidant 1010 and 0.3 g of antioxidant 168 was added. The mixture was kneaded at 180°C and 40 rpm for 10 min to obtain a modified polylactic acid resin.

[0054] The tensile strength, elongation at break, and heat deformation temperature of the obtained polylactic acid resin are shown in Table 1. The antibacterial properties and degradation properties of the obtained polylactic acid resin are shown in Table 2 and Table 3, respectively.

[0055] Comparative Example 1

[0056] 100 g of polylactic acid and 10 g of triglycidyl isocyanurate were heated to 70° C. and dried for 15 min. Then, a composite antioxidant of 0.1 g of antioxidant 1010 and 0.2 g of antioxidant 168 was added and kneaded at 190° C. and 50 rpm for 15 min to obtain polylactic acid resin.

[0057] The tensile strength, elongation at break, and heat deformation temperature of the obtained polylactic acid resin are shown in Table 1. The antibacterial properties and degradation properties of the obtained polylactic acid resin are shown in Table 2 and Table 3, respectively.

[0058] Comparative Example 2

[0059] 100 g of polylactic acid was heated to 70° C. and dried for 15 min, and then a composite antioxidant of 0.1 g of antioxidant 1010 and 0.2 g of antioxidant 168 was added, followed by banburying at 190° C. and 50 rpm for 15 min to obtain polylactic acid resin.

[0060] The tensile strength, elongation at break, and heat deformation temperature of the obtained polylactic acid resin are shown in Table 1. The antibacterial properties and degradation properties of the obtained polylactic acid resin are shown in Table 2 and Table 3, respectively.

[0061] Table 1 Performance of different embodiments and comparative examples

[0062]

[0063] As can be seen from Table 1, the polylactic acid resins prepared in Examples 1 to 3 of the present application have high mechanical properties and heat resistance, and their tensile strength, elongation at break, and heat deformation temperature are improved. This is because the addition of modified polylactic acid and triglycidyl isocyanurate further increases the degree of crosslinking in the polylactic acid resin, and the conjugated double bonds of α-eleostearic acid further enhance the network structure of the polymer.

[0064] Table 2 Antibacterial properties of different examples and comparative examples

[0065]

[0066] As can be seen from Table 2, the polylactic acid resins prepared in Examples 1 to 3 of the present application have a high antibacterial rate against Staphylococcus aureus and Escherichia coli, and have a high mildew resistance level, and can be used as antibacterial resin materials. This is because the amide groups in the modified polylactic acid and triglycidyl isocyanurate can effectively inhibit the growth of bacteria.

[0067] Table 3 Degradation performance of different examples and comparative examples

[0068]

[0069] As can be seen from Table 3, the degradation rates of the polylactic acid resins prepared in Examples 1 to 3 of the present application are similar to those of the polylactic acid resin, and both are environmentally friendly.

[0070] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. Application of modified polylactic acid in the preparation of polylactic acid resin, characterized in that: The steps include: The modified polylactic acid, polylactic acid and triglycidyl isocyanurate are heated to 60-80°C and dried for 10-20 minutes, and then an antioxidant is added and mixed to obtain polylactic acid resin. The mass ratio of the modified polylactic acid, polylactic acid, triglycidyl isocyanurate, and antioxidant is 20-40:40-80:5-10:0.1-0.5; The preparation method of the modified polylactic acid comprises the following steps: (1) Dissolve α-eleostearic acid in dichloromethane, add thionyl chloride to prepare α-eleostearic acid chloride, and introduce ammonia gas to react to obtain α-eleostearic acid amide; (2) Add α-eleostearamide to dichloromethane, add diethyl oxalate and ethanolamine, and react at 30-50°C for 12-24 hours to obtain compound A; (3) Compound A and lactide are added to toluene, catalyst A is added, and the mixture is reacted at 120-150°C for 6-12 hours to obtain modified polylactic acid; The catalyst A is at least one of stannous octoate, tetrabutyl titanate or DMAP; The mass ratio of compound A, lactide and catalyst A is 5-10:200:0.05-0.1; The structural formula of the compound A is: ； The mass ratio of the α-eleostearic acid amide, diethyl oxalate and ethanolamine is 28:12-18:5-7.

2. The use of the modified polylactic acid according to claim 1 in the preparation of polylactic acid resin, characterized in that: The molar ratio of α-eleostearic acid to thionyl chloride is 1:1-1:3, the reaction temperature of α-eleostearic acid and thionyl chloride is 0-20° C., and the reaction time is 4-10 hours.

3. The use of the modified polylactic acid according to claim 1 in the preparation of polylactic acid resin, characterized in that: The antioxidant is a composite antioxidant of antioxidant 1010 and antioxidant 168, and the mass ratio of the antioxidant 1010 to the antioxidant 168 is 1:1 to 1:

3.

4. The use of the modified polylactic acid according to claim 1 in the preparation of polylactic acid resin, characterized in that: The banburying temperature is 180-200° C., the time is 10-15 minutes, and the rotation speed is 40-60 rpm.

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