A method for synthesizing biodegradable polyester amide

Abstract

The invention discloses a method for synthesizing a bio-based degradable polyester amide, comprising the following steps: 1) weighing a certain mass of butyrolactam and an alkaline catalyst and adding them to a three-necked flask, and continuously stirring, slowly raising the system to a specified temperature and passing nitrogen for dehumidification and deoxygenation, reacting for a period of time under a certain negative pressure, and then dropping to a certain temperature, adding an acyl chloride initiator, and continuously stirring under a negative pressure to cause a polymerization reaction; 2) maintaining an inert atmosphere, adding a certain mass of caprolactone to a three-necked flask, and continuing to stir the reaction for a period of time and then stopping; 3) dissolving the initial reactant obtained in step 2) in an organic solvent, adding an excess of extraction liquid to obtain a precipitate, then washing with water and ethanol for 3-5 times, and drying and collecting the product to obtain polyester amide. The synthetic reaction process is brief, the reaction speed is fast, the yield is high, the cost is low, and the product is easily biodegradable.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a method for synthesizing bio-based degradable polyester amide. Background Art

[0002] As one of the five major engineering plastics, polyamide, especially polyamide materials represented by nylon 6 and nylon 66, play an important role in civil, military, industrial and other fields with their excellent characteristics of high strength, high modulus and high temperature stability. However, its synthetic raw materials are all derived from petroleum refining products. Not only are the raw materials non-renewable, but the polymers are also difficult to degrade naturally, which does not conform to the concept of green environmental protection and sustainable development. In particular, in recent years, research on microplastics has pointed out that there are already a large number of microplastics in the atmosphere / river human living environment. Among them, marine microplastic pollution has been listed as a major global environmental problem on par with global climate change, ozone depletion, and ocean acidification by the Second United Nations Environment Conference (2016). Its potential environmental and health risks have attracted much attention. Among all kinds of plastic products, microplastic pollution caused by synthetic fibers is the most serious. A recent environmental analysis research paper published in Nature Communications pointed out that about 92% of microplastic pollution in the near-surface seawater of the Arctic comes from synthetic fibers. A study from Pennsylvania State University pointed out that 60% of microplastics in freshwater come from laundry fibers. When washing clothes, microfibers will fall off and eventually enter wastewater treatment facilities, and then enter lakes and other large water bodies from there. According to statistics, each person consumes at least 50,000 microplastic particles from their diet every year on average (the survey found that more than 90% of table salt is contaminated by microplastics, and the plastic content of sea salt is higher). These microplastics will also enter the blood and brain, causing Alzheimer's disease, Parkinson's disease, etc. Recent studies have found that microplastics are also present in breast milk and fetuses, which may cause potential harm to infants and young children. Therefore, it is of great significance to find a bio-based degradable polyamide or copolymer material as a fiber-forming polymer to replace the common non-degradable, petroleum-based synthetic polyamide. Bio-based polyamide fiber has similar performance characteristics to petroleum-based polyamide fiber. At the same time, as a green, environmentally friendly, durable and high-performance fiber material, it is also one of the important materials for the upgrading of my country's textile fiber industry. Its excellent biodegradability makes it have broad prospects in alleviating the shortage of petrochemical resources in the world and achieving sustainable development.

[0003] Polydecanediamine sebacate (PA1010) is a typical representative of long-chain polyamides. It is obtained by polycondensation of sebacic acid and decanediamine. Unfortunately, it will partially thermally degrade in the molten state. PA46 is also called polybutylene adipamide. It is formed by polycondensation of adipic acid and butanediamine monomers, but its melting temperature and thermal decomposition temperature are relatively close, which is not conducive to melt processing. The main biomass source of PA56 is corn starch. The glucose extracted from starch is fermented to produce lysine, which is converted into 1,5-pentanediamine under the action of lysine decarboxylase. Bio-based PA56 can be obtained by polymerizing bio-based 1,5-pentanediamine with petroleum-based adipic acid. PA56 has a high thermal decomposition temperature and can be processed by melt extrusion, becoming a competitive new polyamide and fiber material. However, adipic acid is mainly obtained by chemical synthesis, and it is difficult to be called a fully bio-based polyamide. Moreover, PA56 is difficult to biodegrade under natural conditions.

[0004] Polybutyrolactam (commonly known as nylon 4, PA4, PBY) is made of 2-pyrrolidone (also called butyrolactam) as a single monomer through anionic ring-opening polymerization, and 2-pyrrolidone can be synthesized at high temperature from γ-aminobutyric acid extracted from biomass raw materials such as corn and straw. Studies have shown that nylon 4 can be decomposed by microorganisms in organic soil, river water and seawater in nature. However, its thermal decomposition temperature is close to its melting point, which makes it very difficult to process and limits its further industrial application. In order to solve the above problems, researchers have focused on the structural optimization of PA4. The research group of Professor Kawasaki of the National Institute of Advanced Industrial Science and Technology (AIST) of Japan used styrene and vinyl acetate as monomers to copolymerize with butyrolactam to obtain a copolymer with a slightly lower melting point. The above technologies are respectively disclosed in Applied Polymer Science, Vol. 126, No. S2, 2012, pp. E425-E432 and Vol. 132, No. 37, No. 42466, 2015, the article titles are: Synthesis of azo-modified polybutyrolactam / styrene by free radical polymerization, namely KAWASAKI N, YAMANO N, TAKEDA S, et al. Synthesis of an azo macromolecular initiator composed of polyamide 4 and its initiation activity for the radical polymerization of vinyl monomers [J]. Journal of Applied Polymer Science, 2012, 126 (S2): E425-E32 and azo-initiated modified polybutyrolactam-polyvinyl acetate block polymer: thermal, mechanical properties, biodegradation and morphology, namely KAWASAKI N, YAMANO N, NAKAYAMA A. Polyamide4-block-poly(vinylacetate) via a polyamide4 azo macromolecular initiator: Thermal and mechanical behavior, biodegradation, and morphology [J]. Journal of Applied Polymer Science, 2015, 132 (37): 42466. A Chinese patent discloses a polylactic acid-polybutyrolactam biodegradable polymer obtained by click reaction of thiol-terminated polylactic acid and alkynyl-terminated polybutyrolactam, which is copolymerized from all bio-based materials. However, the reaction process is complicated and the cost is high, see "Preparation method of polylactic acid-polybutyrolactam bio-based degradable copolymer", patent number CN202010074336.8.The Chinese patent discloses a new type of polymer formed by block copolymerization of butyrolactam with low molecular weight polypropylene glycol (PPG), polycaprolactone (PCL), polylactide (PLA) and other materials. The viscosity-average molecular weight of the product is greater than 30,000, which is lower than the melting point of polybutyrolactam, and the melting point is above 200°C, but the reaction process is relatively long, see "A preparation process of polybutyrolactam block copolymer", patent number CN202010775937.1. Nakayama et al. used n-butyl lithium as an initiator, added it to a mixed solution of butyrolactam and caprolactone in an ice bath at 0°C, heated it to 50°C and reacted for 3 days to obtain a polybutyrolactam caprolactone copolymer. It was found that the melting point of the copolymer was significantly reduced and the product had good biodegradability. The technology was disclosed in Polymer Degradation and Stability, Vol. 98, No. 9, pp. 1882-1888, 2013, titled Synthesis and biodegradation of poly(2-pyrrolidone-co-ε-caprolactone)s[J]. Polymer Degradation and Stability, 2013, 98(9): 1882-8. However, the initiator is expensive and extremely flammable (used as a rocket propellant), the polymerization conditions are harsh and the reaction time is very long, and industrialization is difficult.

[0005] In summary, it is of great significance and practical value to develop a fully bio-based degradable polyester amide material with low cost, simple synthesis process and melting point suitable for melt processing. Summary of the invention

[0006] In order to solve the problems that the decomposition temperature and melting temperature of the existing all-bio-based PA4 polyamide are close to each other and difficult to be processed industrially, the present invention provides a polyester amide copolymerized by butyrolactam and caprolactone, which can reduce the melting point and cost of PA4 and has biodegradability. The synthesis reaction process is short, the reaction speed is fast, the yield of reactants is high, the synthetic raw materials are simple and easy to obtain, the cost is low, and the product is easily biodegradable.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] 1) Weigh a certain amount of butyrolactam and an alkaline catalyst and add them to a three-necked flask, and continue stirring. The system is slowly raised to a specified temperature and nitrogen is introduced for dehumidification and deoxygenation. After reacting for a period of time under a certain negative pressure, the temperature is lowered to a certain temperature, an acyl chloride initiator is added, and the polymerization reaction is carried out while continuing to stir under negative pressure;

[0009] 2) Maintaining an inert atmosphere, add a certain amount of caprolactone into a three-necked flask, continue stirring the reaction for a period of time and then stop;

[0010] 3) The initial reactant obtained in step 2) is dissolved in an organic solvent, and an excess amount of extraction liquid is added to obtain a precipitate, which is then washed with water and ethanol for 3-5 times, and the product is dried and collected to obtain polyester amide.

[0011] 4) The alkaline catalyst in step 1) includes but is not limited to sodium hydroxide, potassium hydroxide, sodium hydride, potassium hydride, etc. The catalyst feed ratio is 3-10wt%, the process parameter temperature range is 90-130°C, the negative pressure is controlled between 0.01-0.08Mpa, and the reaction time is 2-6h.

[0012] 5) Step 1) Acid chloride initiators include but are not limited to trimethylacetyl chloride, benzoyl chloride, isophthaloyl chloride, preferably benzoyl chloride. The initiator feed ratio is 0.1-5wt%, and the polymerization reaction time is 2-5h.

[0013] 6) Step 2) The caprolactone feed ratio is 1-30 wt%, and the polymerization reaction temperature is controlled in the range of 40-60° C. The organic solvent is formic acid or hexafluoroisopropanol, and the extractant includes but is not limited to water, methanol, ethanol, acetone or a mixed solvent thereof, preferably water or ethanol.

[0014] The technical solution of the present invention has one or more of the following advantages:

[0015] 1) The raw materials and catalysts used in the synthesis method are green and low-toxic, and the obtained polymer is biodegradable.

[0016] 2) The synthesis method has a simple process and low cost.

[0017] 3) It can be used for large-scale industrial production.

[0018] 4) The yield of the synthesized polymer is high.

[0019] 5) The synthesized polymer is easy to process and can be widely used as a meltable polymer in various industries such as engineering plastics molding and fiber forming. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the differential scanning calorimetry DSC curve of the product obtained in Example 5 of the present invention;

[0021] Figure 2 This is the infrared spectrum of the copolymer obtained in Example 5 of the present invention. DETAILED DESCRIPTION

[0022] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0023] Example 1

[0024] Add 50g of 2-pyrrolidone and 2g (4wt%) of sodium hydroxide particles to a three-necked flask, stir continuously, raise the reaction temperature to 90°C, introduce nitrogen, vacuum the reaction at a negative pressure of 0.02Mpa for 1h, cool to 40°C, add 0.8mL of trimethylacetyl chloride, continue stirring at a negative pressure of 0.02Mpa to cause polymerization, add 3g of ε-caprolactone after 1h, cool after 0.5h of reaction, and stop stirring. After cooling to room temperature, add formic acid, after the reactants are completely dissolved, add a mixture of excess acetone and water (9:1) to extract a white precipitate, wash the precipitate with a mixed solution of ethanol and water (1:1), dry to constant weight to obtain a dry solid, 29.04g of polyester amide, a yield of 52.8%, and a degradation rate of 80% within 100 days under compost soil conditions.

[0025] Example 2

[0026] Add 50g of 2-pyrrolidone and 2.5g (5wt%) sodium hydroxide particles to a three-necked flask, stir continuously, raise the reaction temperature to 100°C, introduce nitrogen, vacuum react at a negative pressure of 0.03Mpa for 2h, cool to 45°C, add 0.7mL of benzoyl chloride, continue stirring at a negative pressure of 0.03Mpa to cause polymerization, add 10g of ε-caprolactone after 2h, react for 0.5h, cool, and stop stirring. After cooling to room temperature, add formic acid, after the reactants are completely dissolved, add a mixture of excess acetone and water (9:1) to extract to obtain a white precipitate, wash the precipitate with a mixed solution of ethanol and water (1:1), dry to constant weight to obtain a dry solid, 49.44g of polyester amide, with a yield of 79.1%, and the degradation rate of the product within 100 days under compost soil conditions is more than 75%.

[0027] Example 3

[0028] Add 30g of 2-pyrrolidone and 1.8g (6wt%) sodium hydroxide particles to a three-necked flask, stir continuously, raise the reaction temperature to 100°C, introduce nitrogen, react for 2h at a negative pressure of 0.03Mpa, cool to 40°C, add 0.5mL of benzoyl chloride, continue stirring at a negative pressure of 0.03Mpa to cause polymerization, add 12.85g of ε-caprolactone after 2h, react for 0.5h, cool, and stop stirring. After cooling to room temperature, add formic acid, after all the reactants are dissolved, add a mixture of excess acetone and water (9:1) to extract a white precipitate, wash the precipitate with a mixed solution of ethanol and water (1:1), dry to constant weight to obtain a dry solid, 42.4g of polyester amide, with a yield of 82.6%, and a degradation rate of more than 75% within 100 days under compost soil conditions.

[0029] Example 4

[0030] Add 30g of 2-pyrrolidone and 2.1g (7wt%) sodium hydroxide particles to a three-necked flask, stir continuously, raise the reaction temperature to 120°C, introduce nitrogen, vacuum the reaction at a negative pressure of 0.02Mpa for 2h, cool to 40°C, add 0.7mL of benzoyl chloride, continue stirring at a negative pressure of 0.02Mpa to cause polymerization, add 7.75g of ε-caprolactone after 2h, cool after 0.5h of reaction, and stop stirring. After cooling to room temperature, add formic acid, after all the reactants are dissolved, add a mixture of excess acetone and water (9:1) to extract a white precipitate, wash the precipitate with a mixed solution of ethanol and water (1:1), dry to constant weight to obtain a dry solid, 27g of polyester amide, with a yield of 52.7%, and a degradation rate of 83% within 100 days under compost soil conditions.

[0031] Example 5

[0032] 30g of 2-pyrrolidone and 2.1g (7wt%) sodium hydroxide particles were added to a three-necked flask, and the mixture was stirred continuously. The reaction temperature was raised to 130°C, and nitrogen was introduced. After the reaction was vacuumed at a negative pressure of 0.03Mpa for 2h, the temperature was lowered to 50°C, 0.8mL of benzoyl chloride was added, and the mixture was stirred continuously at a negative pressure of 0.03Mpa for 2h. After 11.5g of ε-caprolactone was added, and the mixture was cooled down after 0.5h of reaction, and the stirring was stopped. After cooling to room temperature, formic acid was added. After the reactants were completely dissolved, a mixture of excess acetone and water (9:1) was added to extract a precipitate. The precipitate was washed with a mixed solution of ethanol and water (1:1), and dried to constant weight to obtain a dry solid, 35.71g of polyester amide, and the yield was 81.9%. The results of differential scanning calorimetry showed that the product had only one melting point, the melting temperature was about 170°C, and the degradation rate exceeded 75% within 100 days under compost soil conditions. (The differential scanning calorimetry (DSC) curve of the obtained product is shown in the attached Figure 1 , infrared spectrum is attached Figure 2 )

[0033] Example 6

[0034] Add 30g of 2-pyrrolidone and 3g (10wt%) sodium hydroxide particles to a three-necked flask, stir continuously, raise the reaction temperature to 130°C, introduce nitrogen, react for 2h at a negative pressure of 0.02Mpa, cool to 60°C, add 0.6mL of benzoyl chloride, continue stirring at a negative pressure of 0.02Mpa to cause polymerization, add 7g of a-caprolactone after 3h, react for 0.5h, cool, and stop stirring. After cooling to room temperature, add formic acid, after all the reactants are dissolved, add a mixture of excess acetone and water (9:1) to extract to obtain a light yellow flocculent precipitate, filter the precipitate, dry to constant weight to obtain a dry solid, 22g of polyester amide, with a yield of 55%, and a degradation rate of 85% within 100 days under compost soil conditions.

Claims

1. A method for synthesizing a biodegradable polyester amide, characterized in that The method comprises the following steps: adding 30 g of 2-pyrrolidone and 2.1 g of sodium hydroxide particles into a three-necked flask, stirring continuously, raising the reaction temperature to 120°C, introducing nitrogen, performing vacuum reaction at a negative pressure of 0.02 Mpa for 2 hours, cooling to 40°C, adding 0.7 mL of benzoyl chloride, continuously stirring at a negative pressure of 0.02 Mpa for polymerization, adding 7.75 g of ε-caprolactone after 2 hours, reacting for 0.5 hours, cooling, and stopping stirring; adding formic acid after cooling to room temperature, and after all reactants are dissolved, adding an excess of a mixed solution of acetone and water in a ratio of 9:1 to extract a white precipitate, washing the precipitate with a mixed solution of ethanol and water in a ratio of 1:1, and drying to constant weight to obtain a dry solid.

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