A preparation method of degradable nitrile latex and its application in disposable medical gloves

Abstract

The invention relates to the technical field of degradable nitrile gloves and discloses a preparation method of degradable nitrile latex and application of the degradable nitrile latex in disposable medical gloves. The preparation method comprises the following steps: uniformly mixing 100 parts by weight of carboxyl nitrile latex, 3-15 parts of modified starch grafted polylactic acid emulsion, 2-3 parts of zinc oxide, 1-2 parts of potassium hydroxide, 0.9-1.3 parts of sulfur S, 0.4-0.6 parts of accelerator BZ, 0.1-0.3 parts of antioxidant, 3-5 parts of titanium dioxide and deionized water, followed by vulcanization to obtain the obtained product. The modified starch grafted polylactic acid emulsion is obtained by grafting starch onto acrylonitrile and methacrylic-modified star-shaped polylactic acid. The nitrile latex gloves prepared by the present application can maintain good mechanical stability in the early stage of use, and have excellent degradation rates under different conditions in the later stage of use. The degradation rate after being buried in soil for 8 weeks reaches 96.5%, thereby substantially achieving complete degradation of the nitrile latex gloves.

Description

Technical Field

[0001] The present invention relates to the technical field of degradable nitrile gloves, in particular to a preparation method of degradable nitrile latex and application of the same in disposable medical gloves. Background Art

[0002] In the medical industry, disposable medical gloves are important protective equipment to ensure the safety of medical staff and patients. Nitrile latex, as an important synthetic rubber emulsion, is made from butadiene and acrylonitrile through polymerization. It has excellent oil resistance, chemical corrosion resistance, good physical and mechanical properties, and does not contain natural latex protein, and will not cause allergic reactions. Therefore, it has been widely used in the field of disposable medical gloves; however, traditional disposable nitrile medical gloves contain a large amount of plastic components, which are difficult to degrade in the natural environment. Long-term accumulation will cause serious pollution to the ecosystem. After a large number of discarded gloves are discarded, they not only take up a lot of space, but also cause serious pollution to the environment. Therefore, the research and development of biodegradable nitrile gloves has very important practical significance and market prospects.

[0003] As an important synthetic rubber material, nitrile latex occupies a key position in the field of glove manufacturing. However, the products produced by the existing nitrile latex preparation methods often find it difficult to strike a balance between mechanical properties and biodegradability: some methods use high-temperature polymerization, which leads to excessive branching and cross-linking of the products and increased gel content, thereby affecting the mechanical properties of the gloves; some methods have complex feeding processes, which increases the difficulty of industrial implementation; at the same time, most of the existing biodegradable materials cannot meet the performance requirements of disposable medical gloves, such as strength, elasticity, and chemical resistance; for example, starch materials are biodegradable and cost-effective. Although starch has the advantages of being cheap and widely available, its native particle size is generally between several and tens of microns, which is too coarse for rubber reinforcement. This results in a small specific surface area, weak binding ability with rubber and latex particles, and easy to fall off in the latex, thus forming voids and depressions, causing material defects and further stress concentration. Its mechanical properties and water resistance are poor, and direct use is difficult to meet the performance requirements of gloves. Although polylactic acid is a bio-based degradable polymer material, it has problems such as poor toughness, slow and difficult to control degradation, and poor hydrophilicity, which limit its application in the field of disposable medical gloves.

[0004] Patent No. CN116333388A discloses a disposable, biodegradable, and environmentally friendly nitrile latex glove and its processing technology. The glove comprises carboxylated nitrile latex, modified starch, and hydroxypropyl methylcellulose ether. The modified starch is obtained by reacting starch with bis(3-triethoxysilylpropyl) tetrasulfide. However, starch has poor compatibility with polymers such as nitrile latex, and delamination and agglomeration are prone to occur during processing, affecting the quality and performance of the gloves and making it difficult to meet the requirements for use of disposable medical gloves. The present invention aims to utilize the complementary properties of starch and polylactic acid. Starch can improve the hydrophobicity of polylactic acid and enhance its compatibility with nitrile latex, while polylactic acid enhances the mechanical properties and degradation properties of starch. By modifying starch and polylactic acid, the non-degradability and poor mechanical properties of nitrile latex can be improved. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for preparing degradable nitrile latex and its application in disposable medical gloves, thereby solving the problem that traditional nitrile gloves are difficult to degrade and cause pollution to the environment, and at the same time greatly improving the mechanical properties of the gloves.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a degradable nitrile latex is carried out according to the following steps:

[0008] Step (1): under a nitrogen atmosphere, 100 parts by weight of starch and deionized water are added to a reaction flask, gelatinized at 75-90° C. for 20-40 min, 2-4 parts of emulsifier OP-10 are added, stirring is continued for 5-10 min, 0.8-1.5 parts of initiator ammonium persulfate are added, and the mixture is reacted for 10-20 min, 80-90 parts of acrylonitrile and 20-35 parts of methacrylic modified star-shaped polylactic acid are added, the mixture is reacted at 80-100° C. for 3-8 h, cooled to room temperature, and the pH is adjusted to 6-7 to obtain a modified starch grafted polylactic acid emulsion.

[0009] Step (2), according to the dry ratio formula (weight parts), 100 parts of carboxyl nitrile latex, 3-15 parts of modified starch grafted polylactic acid emulsion, 2-3 parts of zinc oxide, 1-2 parts of potassium hydroxide, 0.9-1.3 parts of sulfur S, 0.4-0.6 parts of accelerator BZ, 0.1-0.3 parts of antioxidant, 3-5 parts of titanium dioxide and deionized water are added to a reaction bottle, stirred and matured at 20-35°C until uniformly dispersed, filtered and debubbled to obtain a degradable nitrile latex.

[0010] Furthermore, the starch in step (1) is any one of corn starch, potato starch or sweet potato starch.

[0011] Furthermore, the antioxidant in step (2) is any one of 4-methyl-6-tert-butylphenol, 2-mercaptobenzimidazole or nickel dibutylthiocarbamate.

[0012] Furthermore, the preparation method of the methacrylic modified star-shaped polylactic acid in step (1) is:

[0013] Step S1: Under a nitrogen atmosphere, add lactide and polyol to a reaction flask, stir evenly, add stannous octoate, react at 180-200° C. for 1-3 hours, then cool to 120-140° C. for 24-48 hours, cool to room temperature, recrystallize with methanol, filter and dry to obtain a multi-arm star-shaped polylactic acid.

[0014] Step S2: Under a nitrogen atmosphere, add multi-arm star-shaped polylactic acid and tetrahydrofuran to a reaction flask, stir evenly, add triethylamine and methacryloyl chloride, stir and react, after the reaction is completed, filter to remove the white precipitate, concentrate the filtrate, recrystallize with methanol, and dry to obtain methacrylic-modified star-shaped polylactic acid.

[0015] Furthermore, in step S1, the polyol is any one of glycerol, trimethylolethane or pentaerythritol.

[0016] Furthermore, in step S1, the weight ratio of lactide, polyol, and stannous octoate is 100:2-5:0.5-1.

[0017] Furthermore, in step S2, the weight ratio of the multi-arm star-shaped polylactic acid, triethylamine, and methacryloyl chloride is 100:10-15:12-20.

[0018] Furthermore, in step S2, the reaction temperature is 0-10° C., and the reaction time is 5-12 h.

[0019] Furthermore, the preparation method of medical gloves is: preheating the hand mold to 90-100°C, dipping it into a biodegradable nitrile latex mixture, adopting a segmented heating vulcanization process, dipping it in a release agent, curling it, cooling and demoulding it, to obtain disposable medical gloves.

[0020] Furthermore, the process of the segmented heating vulcanization process is: first vulcanize at 100-110° C. for 20-30 minutes, and then vulcanize at 120-130° C. for 15-25 minutes.

[0021] By adopting the above technical solution, the beneficial effects of the present invention are:

[0022] (1) Excellent mechanical properties: After starch is copolymerized with star-shaped polylactic acid and acrylonitrile, it contains a structure similar to that of carboxyl nitrile latex, and is similarly compatible, which improves the interfacial compatibility. After the modified starch is added to the film, the hydroxyl groups on the surface of its particles and the carboxyl groups of carboxyl nitrile latex can form hydrogen bonds, thereby enhancing the interaction between the starch particles and the rubber matrix. At the same time, due to the decrease in crystallinity of star-shaped polylactic acid, the intermolecular force is reduced, and the branched chain shows flexibility. Star-shaped polylactic acid is grafted onto the starch molecular chain, and several polymer chains are combined to form a cross-linked structure, which overlaps and entangles with each other and can disperse the stress to other molecular chains through the cross-linking points. When there is an external force, the network-like structure can bear more external force; in addition, grafting polylactic acid on starch can also significantly improve its cold water solubility and hydrophilicity, and then disperse it evenly and stably in the rubber matrix during the process of compounding with latex and vulcanization. Polylactic acid grafted on the surface of starch particles also improves the reaction and binding ability of starch with other substances, reduces the agglomeration of starch itself, and ultimately significantly improves the mechanical properties of the film; the cross-linked network structure formed by chemical cross-linking of starch and polylactic acid can form complementary advantages, so that the glove material has both sufficient strength and good toughness, thereby improving the durability and service life of the gloves.

[0023] (2) Excellent degradability: Polylactic acid and starch are both renewable resources. Their blending can reduce dependence on non-renewable resources such as petroleum. Since nitrile gloves provide molecular chain movement energy after being given heat from the outside world, cross-linking bonds and fragile hydrogen bonds will break. At the same time, there is oxygen in the heating process, which can accelerate the thermal degradation of starch. Starch dehydrates at high temperature and then undergoes thermal cracking and other degradation processes to produce small molecular substances. Polylactic acid can be degraded into non-polluting substances such as carbon dioxide and water. The cross-linked structure produced by the synergistic effect of the two helps to reduce the production of microplastics during the degradation process, reduces the risk of microplastics produced by incomplete degradation of a single material, and is more conducive to environmental protection. At the same time, under natural and buried conditions, under the influence of natural environments such as light oxygen, ultraviolet rays, and humidity, the moisture inside the gloves also evaporates, forming a larger number and size of crystalline areas in the gloves, increasing the stress concentration effect, reducing the film's ability to withstand further elongation, and thus accelerating the degradation rate. In this way, the gloves can maintain good stability in the early stage of use, and in the later stage of use, the synergistic degradation characteristics of starch and polylactic acid can accelerate the overall degradation of the gloves. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] Unless otherwise stated, the raw materials and reagents used in this application are commercially available or can be prepared by known methods.

[0026] Carboxylated nitrile latex: total solid mass fraction 48%, product of Shanghai Xintema Chemical Co., Ltd.

[0027] Starch: commercially available, Jiangsu Baobao Suqian National Biotechnology Co., Ltd.

[0028] Example 1

[0029] (1) Under nitrogen atmosphere, add 100 g of lactide and 3 g of propylene glycol into a reaction flask, stir evenly, then add 0.8 g of stannous octoate, react at 190 °C for 2 h, then cool to 130 °C for 32 h, cool to room temperature, recrystallize with methanol, filter and dry to obtain multi-arm star-shaped polylactic acid.

[0030] (2) Under nitrogen atmosphere, 100 g of multi-arm star-shaped polylactic acid and 1000 mL of tetrahydrofuran were added to a reaction flask. After stirring evenly, 12 g of triethylamine and 15 g of methacryloyl chloride were added. The mixture was reacted at 5 °C for 8 h. The white precipitate was removed by filtration. The filtrate was concentrated, recrystallized with methanol, and dried to obtain methacrylic-modified star-shaped polylactic acid.

[0031] (3) Under nitrogen atmosphere, 100 g corn starch and 2300 mL deionized water were added to the reaction flask, gelatinized at 85 °C for 30 min, 34 g emulsifier OP-10 was added, and stirring was continued for 7 min. Then 1.2 g initiator ammonium persulfate was added, and the mixture was reacted for 15 min. 85 g acrylonitrile and 30 g methacrylic modified star-shaped polylactic acid were added, and the mixture was reacted at 90 °C for 6 h. The mixture was cooled to room temperature and the pH was adjusted to 7 to obtain a modified starch grafted polylactic acid emulsion.

[0032] (4) According to the dry ratio formula, 100 g of carboxyl nitrile latex, 3 g of modified starch grafted polylactic acid emulsion, 2.5 g of zinc oxide, 1.6 g of potassium hydroxide, 1.1 g of sulfur S, 0.5 g of accelerator BZ, 0.2 g of 4-methyl-6-tert-butylphenol, 4 g of titanium dioxide and deionized water were added to the reaction bottle, stirred and matured at 25 ° C until uniformly dispersed, filtered and debubbled to obtain biodegradable nitrile latex.

[0033] (5) Preheat the hand mold to 95°C, immerse it in a mixture of biodegradable nitrile latex, and use a segmented heating vulcanization process. First, vulcanize it at 105°C for 28 minutes, then vulcanize it at 125°C for 20 minutes. Then, immerse it in a release agent, curl the edges, cool and demould, and obtain disposable medical gloves.

[0034] Example 2

[0035] (1) Under nitrogen atmosphere, add 100 g of lactide and 2 g of trimethylolethane into a reaction flask, stir evenly, then add 0.5 g of stannous octoate, react at 200 °C for 3 h, then cool to 120 °C for 48 h, cool to room temperature, recrystallize with methanol, filter and dry to obtain multi-arm star-shaped polylactic acid.

[0036] (2) Under nitrogen atmosphere, 100 g of multi-arm star-shaped polylactic acid and 800 mL of tetrahydrofuran were added to a reaction flask. After stirring evenly, 10 g of triethylamine and 12 g of methacryloyl chloride were added. The mixture was reacted at 10 °C for 5 h. The white precipitate was removed by filtration. The filtrate was concentrated, recrystallized from methanol, and dried to obtain methacrylic-modified star-shaped polylactic acid.

[0037] (3) Under nitrogen atmosphere, 100 g of potato starch and 2000 mL of deionized water were added to the reaction flask, gelatinized at 90 °C for 20 min, 2 g of emulsifier OP-10 was added, and stirring was continued for 10 min. Then, 0.8 g of initiator ammonium persulfate was added, and the mixture was reacted for 20 min. 80 g of acrylonitrile and 20 g of methacrylic-modified star-shaped polylactic acid were added, and the mixture was reacted at 100 °C for 3 h. The mixture was cooled to room temperature and the pH was adjusted to 6 to obtain a modified starch grafted polylactic acid emulsion.

[0038] (4) According to the dry ratio formula, 100g of carboxyl nitrile latex, 6g of modified starch grafted polylactic acid emulsion, 2g of zinc oxide, 1g of potassium hydroxide, 0.9g of sulfur S, 0.6g of accelerator BZ, 0.1g of 2-mercaptobenzimidazole, 3g of titanium dioxide and deionized water were added to the reaction bottle, stirred and matured at 35°C until uniformly dispersed, filtered and debubbled to obtain biodegradable nitrile latex.

[0039] (5) Preheat the hand mold to 100 °C, immerse it in a mixture of biodegradable nitrile latex, and use a segmented heating vulcanization process. First, vulcanize it at 110 °C for 20 minutes, then vulcanize it at 130 °C for 15 minutes. Then, immerse it in a release agent, curl it, cool it and demould it to obtain a disposable medical glove.

[0040] Example 3

[0041] (1) Under nitrogen atmosphere, add 100 g of lactide and 5 g of pentaerythritol to a reaction flask, stir evenly, then add 1 g of stannous octoate, react at 180 °C for 3 h, then cool to 120 °C for 48 h, cool to room temperature, recrystallize with methanol, filter and dry to obtain multi-arm star-shaped polylactic acid.

[0042] (2) Under nitrogen atmosphere, 100 g of multi-arm star-shaped polylactic acid and 1200 mL of tetrahydrofuran were added to a reaction flask. After stirring evenly, 15 g of triethylamine and 20 g of methacryloyl chloride were added. The mixture was reacted at 0°C for 12 h. The white precipitate was removed by filtration. The filtrate was concentrated, recrystallized from methanol, and dried to obtain methacrylic-modified star-shaped polylactic acid.

[0043] (3) Under nitrogen atmosphere, 100 g of sweet potato starch and 2500 mL of deionized water were added to the reaction flask, gelatinized at 75 °C for 40 min, 4 g of emulsifier OP-10 was added, and stirring was continued for 10 min. Then, 1.5 g of initiator ammonium persulfate was added, and the mixture was reacted for 20 min. 90 g of acrylonitrile and 35 g of methacrylic-modified star-shaped polylactic acid were added, and the mixture was reacted at 80 °C for 8 h. The mixture was cooled to room temperature and the pH was adjusted to 6 to obtain a modified starch grafted polylactic acid emulsion.

[0044] (4) According to the dry ratio formula, 100 g of carboxyl nitrile latex, 9 g of modified starch grafted polylactic acid emulsion, 3 g of zinc oxide, 2 g of potassium hydroxide, 1.3 g of sulfur S, 0.4 g of accelerator BZ, 0.3 g of nickel dibutylthiocarbamate, 5 g of titanium dioxide and deionized water were added to a reaction bottle, stirred and matured at 20 ° C until uniformly dispersed, filtered and debubbled to obtain biodegradable nitrile latex.

[0045] (5) Preheat the hand mold to 90 °C, immerse it in a biodegradable nitrile latex mixture, and use a segmented heating vulcanization process. First, vulcanize it at 100 °C for 30 minutes, then vulcanize it at 120 °C for 25 minutes. Then, immerse it in a release agent, curl it, cool it and demould it to obtain a disposable medical glove.

[0046] Example 4

[0047] (1) Under nitrogen atmosphere, add 100 g of lactide and 4 g of propylene glycol into a reaction flask, stir evenly, then add 0.9 g of stannous octoate, react at 185 °C for 3 h, then cool to 135 °C for 40 h, cool to room temperature, recrystallize with methanol, filter and dry to obtain multi-arm star-shaped polylactic acid.

[0048] (2) Under nitrogen atmosphere, 100 g of multi-arm star-shaped polylactic acid and 1100 mL of tetrahydrofuran were added to a reaction flask. After stirring evenly, 11 g of triethylamine and 16 g of methacryloyl chloride were added. The mixture was reacted at 8 °C for 12 h. The white precipitate was removed by filtration. The filtrate was concentrated, recrystallized from methanol, and dried to obtain methacrylic-modified star-shaped polylactic acid.

[0049] (3) Under nitrogen atmosphere, 100 g corn starch and 2400 mL deionized water were added to the reaction flask, gelatinized at 85 °C for 25 min, 3.5 g emulsifier OP-10 was added, and stirring was continued for 6 min. Then 1.3 g initiator ammonium persulfate was added, and the mixture was reacted for 18 min. 88 g acrylonitrile and 32 g methacrylic-modified star-shaped polylactic acid were added, and the mixture was reacted at 95 °C for 5 h. The mixture was cooled to room temperature and the pH was adjusted to 7 to obtain a modified starch grafted polylactic acid emulsion.

[0050] (4) According to the dry ratio formula, 100 g of carboxyl nitrile latex, 12 g of modified starch grafted polylactic acid emulsion, 3 g of zinc oxide, 1.6 g of potassium hydroxide, 1.2 g of sulfur S, 0.5 g of accelerator BZ, 0.3 g of 4-methyl-6-tert-butylphenol, 4.2 g of titanium dioxide and deionized water were added to a reaction bottle, stirred and matured at 30 ° C until uniformly dispersed, filtered and debubbled to obtain biodegradable nitrile latex.

[0051] (5) Preheat the hand mold to 100 °C, immerse it in a biodegradable nitrile latex mixture, and use a segmented heating vulcanization process. First, vulcanize it at 110 °C for 30 minutes, then vulcanize it at 120 °C for 20 minutes. Then, immerse it in a release agent, curl it, cool it and demould it to obtain a disposable medical glove.

[0052] Example 5

[0053] (1) Under nitrogen atmosphere, add 100 g of lactide and 3 g of trimethylolethane into the reaction flask, stir evenly, then add 0.7 g of stannous octoate, react at 195 °C for 3 h, then cool to 120 °C for 24 h, cool to room temperature, recrystallize with methanol, filter and dry to obtain multi-arm star-shaped polylactic acid.

[0054] (2) Under nitrogen atmosphere, 100 g of multi-arm star-shaped polylactic acid and 1050 mL of tetrahydrofuran were added to a reaction flask. After stirring evenly, 14 g of triethylamine and 16 g of methacryloyl chloride were added. The mixture was reacted at 0°C for 9 h. The white precipitate was removed by filtration. The filtrate was concentrated, recrystallized with methanol, and dried to obtain methacrylic-modified star-shaped polylactic acid.

[0055] (3) Under nitrogen atmosphere, 100 g of potato starch and 2250 mL of deionized water were added to the reaction flask, gelatinized at 80 °C for 35 min, 3 g of emulsifier OP-10 was added, and stirring was continued for 8 min. Then 1.3 g of initiator ammonium persulfate was added, and the mixture was reacted for 15 min. 82 g of acrylonitrile and 25 g of methacrylic-modified star-shaped polylactic acid were added, and the mixture was reacted at 90 °C for 6 h. The mixture was cooled to room temperature and the pH was adjusted to 6 to obtain a modified starch grafted polylactic acid emulsion.

[0056] (4) According to the dry ratio formula, 100 g of carboxyl nitrile latex, 15 g of modified starch grafted polylactic acid emulsion, 2.2 g of zinc oxide, 1.8 g of potassium hydroxide, 1.1 g of sulfur S, 0.45 g of accelerator BZ, 0.25 g of 2-mercaptobenzimidazole, 5 g of titanium dioxide and deionized water were added to the reaction bottle, stirred and matured at 35 ° C until uniformly dispersed, filtered and debubbled to obtain biodegradable nitrile latex.

[0057] (5) Preheat the hand mold to 90 °C, immerse it in a mixture of biodegradable nitrile latex, and use a segmented heating vulcanization process. First, vulcanize it at 105 °C for 28 minutes, then vulcanize it at 125 °C for 25 minutes. Then, immerse it in a release agent, curl the edges, cool and demould, and obtain disposable medical gloves.

[0058] Comparative Example 1

[0059] (1) According to the dry ratio formula, 100 g of carboxyl nitrile latex, 3 g of methacrylic modified star-shaped polylactic acid (prepared in Example 1), 2.5 g of zinc oxide, 1.6 g of potassium hydroxide, 1.1 g of sulfur S, 0.5 g of accelerator BZ, 0.2 g of 4-methyl-6-tert-butylphenol, 4 g of titanium dioxide and deionized water were added to a reaction bottle, stirred and aged at 25°C until uniformly dispersed, and then filtered and debubbled to obtain nitrile latex.

[0060] (2) Preheat the hand mold to 95°C, immerse it in the nitrile latex mixture, and use a segmented heating vulcanization process. First, vulcanize it at 105°C for 28 minutes, then vulcanize it at 125°C for 20 minutes. Then, impregnate it with a release agent, curl it, cool it and demould it to obtain a disposable medical glove.

[0061] Comparative Example 2

[0062] (1) Under nitrogen atmosphere, 100 g corn starch and 2300 mL deionized water were added to a reaction flask and gelatinized at 85 °C for 30 min. 34 g emulsifier OP-10 was added and stirred for 7 min. 1.2 g initiator ammonium persulfate was then added and reacted for 15 min. 85 g acrylonitrile was added and reacted at 90 °C for 6 h. The mixture was cooled to room temperature and the pH was adjusted to 7 to obtain starch grafted acrylonitrile.

[0063] (2) According to the dry ratio formula, 100 g of carboxyl nitrile latex, 3 g of starch grafted acrylonitrile, 2.5 g of zinc oxide, 1.6 g of potassium hydroxide, 1.1 g of sulfur S, 0.5 g of accelerator BZ, 0.2 g of 4-methyl-6-tert-butylphenol, 4 g of titanium dioxide and deionized water were added to a reaction bottle, stirred and matured at 25 ° C until uniformly dispersed, and then filtered and debubbled to obtain nitrile latex.

[0064] (3) Preheat the hand mold to 95°C, immerse it in the nitrile latex mixture, and use a segmented heating vulcanization process. First, vulcanize it at 105°C for 28 minutes, then vulcanize it at 125°C for 20 minutes. Then, impregnate it with a release agent, curl it, cool it and demould it to obtain a disposable medical glove.

[0065] Comparative Example 3

[0066] (1) According to the dry ratio formula, 100 g of carboxyl nitrile latex, 3 g of corn starch, 2.5 g of zinc oxide, 1.6 g of potassium hydroxide, 1.1 g of sulfur S, 0.5 g of accelerator BZ, 0.2 g of 4-methyl-6-tert-butylphenol, 4 g of titanium dioxide and deionized water were added to a reaction bottle, stirred and matured at 25°C until uniformly dispersed, and then filtered and debubbled to obtain nitrile latex.

[0067] (2) Preheat the hand mold to 95°C, immerse it in the nitrile latex mixture, and use a segmented heating vulcanization process. First, vulcanize it at 105°C for 28 minutes, then vulcanize it at 125°C for 20 minutes. Then, impregnate it with a release agent, curl it, cool it and demould it to obtain a disposable medical glove.

[0068] Mechanical properties test: Disposable medical gloves were cut into dumbbell-shaped specimens according to GB / T528-2009 "Vulcanized rubber or thermoplastic rubber - Determination of tensile stress-strain properties". The tensile strength, elongation at break, and 100% modulus of tensile stress were tested at a rate of 500 mm / min.

[0069] Table 1 Mechanical properties test

[0070]

[0071] It can be seen from the test results in the above table that with the increase of the content of modified starch grafted polylactic acid emulsion, the mechanical properties of nitrile gloves are gradually enhanced, wherein the tensile strength in Example 4 reaches 45.7MPa, the elongation at break is 542.5%, and the 100% tensile stress reaches 2.8MPa. This is because after the starch is copolymerized with star-shaped polylactic acid and acrylonitrile, it contains a structure similar to that of carboxyl nitrile latex, and similar compatibility improves the interfacial compatibility. After the modified starch is added to the film, on the one hand, the hydroxyl groups on the surface of its particles and the carboxyl groups of the carboxyl nitrile latex can form hydrogen bonds, thereby enhancing the interaction between the starch particles and the rubber matrix. At the same time, due to the decrease in crystallinity of the star-shaped polylactic acid, the intermolecular force is reduced, and the side chains show flexibility. The star-shaped polylactic acid is grafted onto the starch molecular chain, and several polymers The chains combine to form a cross-linked structure, overlapping and entangled with each other, which can disperse and transfer stress to other molecular chains through the cross-linking points. When there is an external force, the network-like structure can bear more external force; on the other hand, the grafting of polylactic acid on starch can also significantly improve its cold water solubility and hydrophilicity, and then it can be evenly and stably dispersed in the rubber matrix during the process of compounding with latex and vulcanization. The grafting of polylactic acid on the surface of starch particles also improves the reaction and bonding ability of starch with other substances, reduces the agglomeration of starch itself, and ultimately significantly improves the mechanical properties of the film; the cross-linked network structure formed by starch and polylactic acid after chemical cross-linking can form a complementary advantage, so that the glove material has both sufficient strength and good toughness, thereby improving the durability and service life of the gloves.

[0072] In Comparative Example 1, methacrylic-modified star-shaped polylactic acid is added, which has a structural similarity with carboxylated nitrile latex and has good toughness, but does not contain starch and has a low tensile strength; in Comparative Example 2, starch-grafted acrylonitrile is added, which has a similar structure to nitrile latex, but the starch has poor water resistance and low toughness; in Comparative Example 3, unmodified starch is added, and direct blending causes phase separation in the system, and it does not contain polylactic acid, so its toughness is insufficient and its mechanical properties are the worst.

[0073] Thermal oxidation degradation test: The cut dumbbell-shaped specimens were placed in an oven at 120°C for thermal oxidation for 72 hours. The specimens were then taken out for tensile strength testing and the rate of change in tensile strength was calculated.

[0074] Natural degradation test: The prepared gloves were hung on an iron rack exposed outdoors. After hanging for 4 weeks, they were removed and subjected to a tensile strength test and the rate of change in tensile strength was calculated.

[0075] Soil degradation performance test: The prepared gloves were buried in the soil to a depth of 5 cm, ensuring that the soil humidity was 70%. After 8 weeks of burial, the gloves were taken out, cleaned and naturally dried. The tensile strength of the samples was taken out and the tensile strength change rate was calculated.

[0076] The change rate of tensile strength = (initial tensile strength - tensile strength after degradation) / initial tensile strength × 100%. The greater the change rate of tensile strength, the higher the degree of degradation, that is, the better the degradation performance.

[0077] Table 2 Degradation performance test

[0078]

[0079] From the test results in the above table, it can be seen that with the increase of the content of modified starch grafted polylactic acid emulsion, the thermal oxidation degradation, natural degradation and soil burial degradation performance of nitrile gloves gradually improve. This is because polylactic acid and starch are renewable resources. Their blending can reduce the dependence on non-renewable resources such as petroleum. Since nitrile gloves provide molecular chain movement energy after being given heat from the outside world, cross-linking bonds and fragile hydrogen bonds will break. At the same time, there is oxygen in the heating process, which can accelerate the thermal degradation of starch. Starch dehydrates at high temperature, and then undergoes thermal cracking and other degradation processes to generate small molecular substances. Polylactic acid can be degraded into carbon dioxide and water. There are no pollutants, and the cross-linked structure produced by the synergistic effect of the two helps to reduce the generation of microplastics during the degradation process, reduces the risk of microplastics produced by incomplete degradation of a single material, and is more conducive to environmental protection; at the same time, under natural and buried conditions, affected by natural environments such as photooxidation, ultraviolet rays, and humidity, the moisture inside the gloves also evaporates, forming a larger number and size of crystalline areas in the gloves, increasing the stress concentration effect, reducing the film's ability to withstand further elongation, and thus accelerating the degradation rate; in this way, the gloves can maintain good stability in the early stage of use, and in the later stage of use, the synergistic degradation characteristics of starch and polylactic acid can accelerate the overall degradation of the gloves.

[0080] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple variations can be made to the technical solution of the present invention, and these simple variations all fall within the scope of protection of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner when there is no contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for preparing a degradable nitrile latex, characterized in that: The preparation method is carried out according to the following steps: Step (1), under a nitrogen atmosphere, add 100 parts by weight of starch and deionized water to a reaction flask, gelatinize at 75-90°C for 20-40 minutes, add 2-4 parts of emulsifier OP-10, continue stirring for 5-10 minutes, then add 0.8-1.5 parts of initiator ammonium persulfate, then react for 10-20 minutes, add 80-90 parts of acrylonitrile and 20-35 parts of methacrylic modified star-shaped polylactic acid, react at 80-100°C for 3-8 hours, cool to room temperature, adjust the pH to 6-7, and obtain a modified starch grafted polylactic acid emulsion; Step (2), according to the dry ratio formula, in parts by weight, 100 parts of carboxyl nitrile latex, 3-15 parts of modified starch grafted polylactic acid emulsion, 2-3 parts of zinc oxide, 1-2 parts of potassium hydroxide, 0.9-1.3 parts of sulfur S, 0.4-0.6 parts of accelerator BZ, 0.1-0.3 parts of antioxidant, 3-5 parts of titanium dioxide and deionized water are added to a reaction bottle, stirred and matured at 20-35°C until uniformly dispersed, filtered and debubbled to obtain a degradable nitrile latex; The preparation method of the methacrylic modified star-shaped polylactic acid in step (1) is as follows: Step S1: Add lactide and polyol to a reaction flask under a nitrogen atmosphere, stir evenly, add stannous octoate, react at 180-200° C. for 1-3 hours, then cool to 120-140° C. for 24-48 hours, cool to room temperature, recrystallize with methanol, filter and dry to obtain a multi-arm star-shaped polylactic acid; Step S2: Under a nitrogen atmosphere, add multi-arm star-shaped polylactic acid and tetrahydrofuran to a reaction flask, stir evenly, add triethylamine and methacryloyl chloride, stir and react, after the reaction is completed, filter to remove the white precipitate, concentrate the filtrate, recrystallize with methanol, and dry to obtain methacrylic-modified star-shaped polylactic acid.

2. The method for preparing the degradable nitrile latex according to claim 1, wherein The starch in step (1) is any one of corn starch, potato starch or sweet potato starch.

3. The method for preparing the degradable nitrile latex according to claim 1, wherein The antioxidant in step (2) is any one of 4-methyl-6-tert-butylphenol, 2-mercaptobenzimidazole or nickel dibutylthiocarbamate.

4. The method for preparing the degradable nitrile latex according to claim 1, wherein In step S1, the polyol is any one of glycerol, trimethylolethane or pentaerythritol.

5. The method for preparing the degradable nitrile latex according to claim 1, wherein In step S1, the weight ratio of lactide, polyol, and stannous octoate is 100:2-5:0.5-1.

6. The method for preparing the degradable nitrile latex according to claim 1, wherein In step S2, the weight ratio of the multi-arm star-shaped polylactic acid, triethylamine, and methacryloyl chloride is 100:10-15:12-20.

7. The method for preparing the degradable nitrile latex according to claim 1, wherein In step S2, the reaction temperature is 0-10° C., and the reaction time is 5-12 h.

8. Use of the degradable nitrile latex obtained by the preparation method according to any one of claims 1 to 7 in disposable medical gloves, characterized in that: The preparation method of the medical gloves comprises the following steps: preheating a hand mold to 90-100° C., dipping the hand mold into a degradable nitrile latex mixture, adopting a segmented heating and vulcanization process, dipping the hand mold into a release agent, curling the hand mold, cooling the hand mold, and demoulding the hand mold to obtain a disposable medical glove.

9. The use of the degradable nitrile latex in disposable medical gloves according to claim 8, characterized in that: The process of the segmented heating vulcanization process is: first vulcanize at 100-110° C. for 20-30 minutes, then vulcanize at 120-130° C. for 15-25 minutes.

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