Environmentally friendly plastic with antibacterial function and preparation method

Abstract

The invention relates to the technical field of antibacterial plastics, and discloses an environmentally friendly plastic with antibacterial function and a preparation method thereof. The plastic comprises, by weight, 0.5-10 parts of benzimidazole salt modified starch, 0.2-0.6 parts of an antioxidant, and 89-99 parts of polyethylene: the benzimidazole salt modified starch is used as a macromolecular biological antibacterial agent, has better heat resistance and thermal processing stability, is not easy to be thermally decomposed, and will not migrate and fall off from a polyethylene matrix during long-term use; the long-chain alkylbenzimidazole salt structure and the alkyl cation thereof can interact with anions in a bacterial cell membrane, change the permeability of the bacterial cell membrane, and destroy the integrity of the cell membrane; the plastic has the advantages of being non-toxic, environmentally friendly, and having a fast sterilization speed, and has excellent broad-spectrum and long-acting antibacterial performance.

Description

Technical Field

[0001] The invention relates to the technical field of antibacterial plastics, in particular to an environmentally friendly plastic with antibacterial function. Background Art

[0002] In daily life, since bacteria and microorganisms will breed on plastics, fibers and other products, people will inevitably come into contact with bacteria and microorganisms, which will spread diseases and affect health and safety. It is of great significance to explore and develop antibacterial plastics, fibers and other products. Currently, the commonly used antibacterial agents mainly include benzimidazoles, imidazole salts, quaternary ammonium salts, guanidines, etc., which are widely used in plastics and other polymer materials.

[0003] Polyethylene is one of the most widely produced general-purpose plastics. It has good chemical stability, high solvent resistance and excellent electrical insulation. It is mainly used to manufacture film materials, packaging materials, containers and pipes, wires and cables, etc. However, traditional polyethylene plastics do not have antibacterial properties, and the development of polyethylene plastics with antibacterial effects is a research difficulty.

[0004] Adding antimicrobial agents, such as quaternary ammonium salts and halamine antimicrobial agents, to polyethylene plastics can achieve antimicrobial modification of polyethylene plastics. However, small molecule antimicrobial agents have poor heat resistance. During the mixing process with plastics, small molecule antimicrobial agents are not resistant to high temperatures, and there is a problem of easy migration of antimicrobial agents during use.

[0005] Starch is widely present in plants and crops. It is a cheap, readily available, green and environmentally friendly biomaterial. It can also be used as an antibacterial agent carrier and is widely used in polymer materials, such as quaternary ammonium starch antibacterial agents, quaternary phosphonium starch antibacterial agents, etc. Summary of the invention

[0006] The invention solves the problems that the antibacterial agent is easy to migrate in the material matrix, the processing thermal stability is poor, and the antibacterial property of polyethylene plastic is not good.

[0007] The technical solution of the present invention is: a method for preparing an environmentally friendly plastic with antibacterial function, comprising the following raw materials, in parts by weight, 0.5-10 parts of benzimidazole salt modified starch, 0.2-0.6 parts of antioxidant, and 89-99 parts of polyethylene; the preparation method of the environmentally friendly plastic is as follows:

[0008] Step (1): Add acetonitrile, hydroxyethylbenzimidazole-s-triazine compound, chlorinated alkane (C n H 2n+1 Cl, n is any one of 10-16), heating to 80-90° C. and reflux for 36-72 hours, concentrating to remove acetonitrile, and recrystallizing with ethanol to obtain a hydroxyethylbenzimidazole salt triazine compound.

[0009] Step (2): Add starch to dimethyl sulfoxide in a flask, heat to 70-80° C. and stir for 1-2 hours, then introduce nitrogen into the flask, add hexamethylene diisocyanate, hydroxyethylbenzimidazole salt triazine compound and dibutyltin dilaurate, continue to react for 2-3 hours, cool, add methanol to the solution to precipitate solid precipitates, filter, and wash with water to obtain benzimidazole salt modified starch.

[0010] Step (3): extruding the benzimidazole salt modified starch, antioxidant and polyethylene into master batches in a twin-screw extruder, and then performing injection molding by an injection molding machine to obtain an environmentally friendly plastic with antibacterial function.

[0011] Furthermore, in the step (1), the ratio of acetonitrile, hydroxyethylbenzimidazole-s-triazine compound, and chlorinated alkane is 1L:(20-120)g:(28-180)g.

[0012] Furthermore, in step (2), the ratio of dimethyl sulfoxide, starch, hexamethylene diisocyanate, hydroxyethylbenzimidazole salt triazine compound and dibutyltin dilaurate is 1L:(10-80)g:(5-42)g:(6-50)g:(0.02-0.16)g.

[0013] Furthermore, in step (3), the temperature of zones 1-4 of the extruder is 175-200° C., and the screw speed is 150-300 r / min.

[0014] Furthermore, the preparation method of the hydroxyethylbenzimidazole-triazine compound is as follows:

[0015] Step (4): Add ethanol, 4,4',4"-s-triazine-2,4,6-triyl-tribenzoic acid, o-phenylenediamine and phosphoric acid aqueous solution in a ratio of 1L:(40-200)g:(30-160)g:(1.5-3)L into a flask equipped with a condenser reflux tube, heat to 115-130°C and reflux for 4-8h, cool, add sodium hydroxide to neutralize, concentrate, wash with deionized water, and dry to obtain benzimidazole-s-triazine.

[0016] Step (5): add ethanol, benzimidazole-s-triazine, 2-bromoethanol, sodium hydroxide aqueous solution and tetrabutylammonium bromide into a flask, react at room temperature for 4-10 hours, concentrate to remove ethanol, add ethyl acetate for extraction, separate and collect the organic layer, concentrate, wash with petroleum ether, and dry to obtain a hydroxyethylbenzimidazole-s-triazine compound.

[0017] Furthermore, the mass fraction of the phosphoric acid aqueous solution in (4) is 75-85%.

[0018] Furthermore, in (5), the ratio of ethanol, benzimidazole-s-triazine, 2-bromoethanol, sodium hydroxide aqueous solution and tetrabutylammonium bromide is 1L:(50-200)g:(35-160)g(1-2)L:(5-25)g.

[0019] Furthermore, the mass fraction of the (5) sodium hydroxide aqueous solution is 20-35%.

[0020] The technical effect of the present invention is as follows: the present invention uses a hydroxyethyl benzimidazole salt s-triazine compound as a small molecule antibacterial agent, which contains three hydroxyethyl groups, and uses hexamethylene diisocyanate as a cross-linking agent to carry out a cross-linking reaction with starch to obtain a benzimidazole salt modified starch, thereby grafting the benzimidazole salt s-triazine antibacterial agent into the starch to form a macromolecular biological antibacterial agent, which is then compounded with polyethylene to obtain an environmentally friendly plastic with antibacterial function.

[0021] Compared with small molecule antimicrobial agents, benzimidazole salt modified starch, as a macromolecular biological antimicrobial agent, has better heat resistance and thermal processing stability, is not easy to thermally decompose, and will not migrate and fall off from the polyethylene matrix during long-term use. Its long-chain alkylbenzimidazole salt structure and its alkyl cation can interact with the anions in the bacterial cell membrane, change the permeability of the bacterial cell membrane, and destroy the integrity of the cell membrane. It has the advantages of being non-toxic, environmentally friendly, and having a fast sterilization speed, and has excellent broad-spectrum and long-lasting antimicrobial properties. In addition, benzimidazole salt modified starch contains heat-resistant triazine rings and starch cross-linking structures, which are beneficial to improving the carbonization of the polyethylene matrix and have better heat resistance. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1: 100 mL of ethanol and 10 g of 4,4',4"-s-triazine-2,4,6-triyl-tribenzoic acid (structural formula) were added to a flask equipped with a condenser reflux tube. ), 9g o-phenylenediamine, 200mL of 80% by mass phosphoric acid aqueous solution, heated to 130°C and refluxed for 6h, cooled, added with sodium hydroxide for neutralization, concentrated, washed with deionized water, and dried to obtain benzimidazole-s-triazine.

[0024] Add 100 mL of ethanol, 20 g of benzimidazole-s-triazine, 16 g of 2-bromoethanol, 150 mL of 30% sodium hydroxide aqueous solution, and 2.5 g of tetrabutylammonium bromide into a flask, react at room temperature for 8 hours, concentrate to remove ethanol, add ethyl acetate to extract, separate and collect the organic layer, concentrate, wash with petroleum ether, and dry to obtain a hydroxyethylbenzimidazole-s-triazine compound.

[0025] Add 250 mL of acetonitrile, 5 g of hydroxyethylbenzimidazole s-triazine compound, and 7 g of chlorodecane to a flask equipped with a condenser reflux tube, heat to 90°C and reflux for 36 hours, concentrate to remove acetonitrile, and recrystallize from ethanol to obtain a hydroxyethylbenzimidazole salt s-triazine compound. Reaction route:

[0026]

[0027] Add 5 g of starch to 500 mL of dimethyl sulfoxide in a flask, heat to 75 ° C and stir for 1 hour, then introduce nitrogen into the flask, add 2.5 g of hexamethylene diisocyanate, 3 g of hydroxyethylbenzimidazole salt triazine compound and 0.01 g of dibutyltin dilaurate, continue to react for 3 hours, cool, add methanol to the solution to precipitate a solid precipitate, filter, and wash with water to obtain benzimidazole salt modified starch.

[0028] By weight, 0.5 parts of benzimidazole salt modified starch, 0.6 parts of antioxidant, and 98.9 parts of polyethylene are extruded into masterbatch in a twin-screw extruder. The temperatures of zones 1-4 of the extruder are 175, 185, 190°C, and 200°C, respectively. The screw speed is 150r / min, and the injection molding machine is used for injection molding to obtain an environmentally friendly plastic with antibacterial function.

[0029] Example 2: Into a flask equipped with a condenser reflux tube, 100 mL of ethanol, 4 g of 4,4',4"-s-triazine-2,4,6-triyl-tribenzoic acid, 3 g of o-phenylenediamine, and 150 mL of 85% phosphoric acid aqueous solution were added, the temperature was raised to 115°C and refluxed for 8 h, cooled, sodium hydroxide was added for neutralization, concentrated, washed with deionized water, and dried to obtain benzimidazole-s-triazine.

[0030] Add 100 mL of ethanol, 12 g of benzimidazole-s-triazine, 10 g of 2-bromoethanol, 100 mL of 35% sodium hydroxide aqueous solution, and 1.8 g of tetrabutylammonium bromide into a flask, react at room temperature for 10 h, concentrate to remove ethanol, add ethyl acetate to extract, separate and collect the organic layer, concentrate, wash with petroleum ether, and dry to obtain a hydroxyethylbenzimidazole-s-triazine compound.

[0031] To a flask equipped with a condenser reflux tube, 250 mL of acetonitrile, 16 g of a hydroxyethylbenzimidazole s-triazine compound, and 24 g of chlorododecane were added, the temperature was raised to 80° C. and refluxed for 48 h, the acetonitrile was removed by concentration, and the hydroxyethylbenzimidazole salt s-triazine compound was obtained by recrystallization with ethanol.

[0032] Add 40 g of starch to 500 mL of dimethyl sulfoxide in a flask, heat to 75 ° C and stir for 2 hours, then introduce nitrogen into the flask, add 21 g of hexamethylene diisocyanate, 25 g of hydroxyethylbenzimidazole salt triazine compound and 0.08 g of dibutyltin dilaurate, continue to react for 3 hours, cool, add methanol to the solution to precipitate a solid precipitate, filter, and wash with water to obtain benzimidazole salt modified starch.

[0033] According to the weight proportions, 2 parts of benzimidazole salt modified starch, 0.5 parts of antioxidant and 97.5 parts of polyethylene are extruded into masterbatch in a twin-screw extruder. The temperatures of zones 1-4 of the extruder are respectively 175, 185, 190°C and 200°C. The screw speed is 200r / min. The injection molding machine is used for injection molding to obtain an environmentally friendly plastic with antibacterial function.

[0034] Example 3: Into a flask equipped with a condenser reflux tube, 100 mL of ethanol, 20 g of 4,4',4"-s-triazine-2,4,6-triyl-tribenzoic acid, 16 g of o-phenylenediamine, and 300 mL of a 75% by mass aqueous phosphoric acid solution were added, the temperature was raised to 130°C and refluxed for 4 h, cooled, sodium hydroxide was added for neutralization, concentrated, washed with deionized water, and dried to obtain benzimidazole-s-triazine.

[0035] Add 100 mL of ethanol, 5 g of benzimidazole-s-triazine, 3.5 g of 2-bromoethanol, 200 mL of 20% sodium hydroxide aqueous solution, and 0.5 g of tetrabutylammonium bromide into a flask, react at room temperature for 8 hours, concentrate to remove ethanol, add ethyl acetate to extract, separate and collect the organic layer, concentrate, wash with petroleum ether, and dry to obtain a hydroxyethylbenzimidazole-s-triazine compound.

[0036] To a flask equipped with a condenser reflux tube, 250 mL of acetonitrile, 30 g of a hydroxyethylbenzimidazole s-triazine compound, and 45 g of chlorohexadecane were added, the temperature was raised to 90° C. and refluxed for 36 h, the acetonitrile was removed by concentration, and the hydroxyethylbenzimidazole salt s-triazine compound was obtained by recrystallization with ethanol.

[0037] Add 25 g of starch to 500 mL of dimethyl sulfoxide in a flask, heat to 75 ° C and stir for 2 hours, then introduce nitrogen into the flask, add 15 g of hexamethylene diisocyanate, 12 g of hydroxyethylbenzimidazole salt triazine compound and 0.04 g of dibutyltin dilaurate, continue to react for 3 hours, cool, add methanol to the solution to precipitate a solid precipitate, filter, and wash with water to obtain benzimidazole salt modified starch.

[0038] By weight, 5 parts of benzimidazole salt modified starch, 0.2 parts of antioxidant, and 94.8 parts of polyethylene are extruded into masterbatch in a twin-screw extruder. The temperatures of zones 1-4 of the extruder are 175, 185, 190°C, and 200°C, respectively. The screw speed is 300r / min, and the injection molding machine is used for injection molding to obtain an environmentally friendly plastic with antibacterial function.

[0039] Example 4: The difference from Example 1 is that, by weight, the benzimidazole salt-modified starch is 8 parts and the polyethylene is 91.4 parts.

[0040] Example 5: The difference from Example 1 is that, by weight, the benzimidazole salt modified starch is 10 parts and the polyethylene is 89.6 parts.

[0041] Comparative Example 1: The difference from Example 1 is that, based on weight percentage, 0.5 parts of benzimidazole salt-modified starch is not added, but only 0.5 parts of starch is added.

[0042] Comparative Example 2 is different from Example 1 in that, by weight, 0.5 parts of benzimidazole salt modified starch is not added, and only 0.5 parts of hydroxyethylbenzimidazole salt s-triazine compound is added.

[0043] Comparative Example 3: The difference from Example 1 is that, based on weight percentage, instead of adding 0.5 parts of benzimidazole salt modified starch, only 0.5 parts of starch and 0.3 parts of hydroxyethylbenzimidazole salt triazine compound are added, and the amount of polyethylene is 98.6 parts.

[0044] Escherichia coli was used as the test bacteria, and the antibacterial performance test was carried out according to the standard of QB / T 2591-2003. The film sticking method was used for testing. The contact time between the plastic and the test bacteria was 24 hours. The environmentally friendly plastic with antibacterial function was used as the experimental sample group, and the pure polyethylene plastic was used as the control group. The total colony count was determined according to the standard of GB / T4789.2-2003.

[0045] Antibacterial rate W = (BC) / B × 100, B is the average number of recovered bacteria in the control group (CFU / mL), and C is the average number of recovered bacteria in the experimental sample group (CFU / mL).

[0046]

[0047] In each embodiment, as the amount of benzimidazole salt modified starch gradually increases, the antibacterial rate of the polyethylene environmentally friendly plastic also gradually increases, reaching a maximum of 99.9%.

[0048] In Comparative Example 1, only starch was added, and the polyethylene obtained did not have antibacterial properties.

[0049] In Comparative Example 2, only hydroxyethyl benzimidazole salt triazine compound is added. Although benzimidazole salt triazine has excellent antibacterial properties, the temperature is high during the processing, the hydroxyethyl benzimidazole salt triazine compound is not resistant to high temperatures, and the processing thermal stability is poor, and the compound may decompose. Therefore, the antibacterial rate of the polyethylene plastic prepared in Comparative Example 2 is 89.0%, which is lower than that in Example 1.

[0050] In Comparative Example 2, only starch and hydroxyethylbenzimidazole salt triazine compound were added, and the antibacterial agent was not loaded into the starch. The hydroxyethylbenzimidazole salt triazine compound was also not resistant to high temperatures and had poor processing thermal stability. The antibacterial agent may be thermally decomposed. In Comparative Example 3, the amount of hydroxyethylbenzimidazole salt triazine compound used was 0.3 parts, so the antibacterial rate was slightly lower than that of Comparative Example 2.

[0051] Long-term antibacterial experiment: Immerse the environmentally friendly plastic with antibacterial function in water, stir it at a temperature of 55°C, change the water every 12 hours, stir it for 15 days, and then test the long-term antibacterial rate W1.

[0052] Antibacterial rate W1 = (BC) / B × 100, B is the average number of recovered bacteria in the control group (CFU / mL), and C is the average number of recovered bacteria in the experimental sample group (CFU / mL).

[0053]

[0054] After the long-term antibacterial experiment, the antibacterial rate of the polyethylene environmentally friendly plastic prepared in each embodiment still reaches 94.7-99.9%, and the long-term antibacterial performance can be maintained.

[0055] Comparative Examples 2 and 3 did not load the hydroxyethylbenzimidazole salt triazine compound into starch, which may cause the antibacterial agent to fall off, resulting in a significant decrease in the antibacterial rate.

[0056] Thermogravimetric analysis: In a thermogravimetric analyzer, the temperature was raised from room temperature to 700°C at a heating rate of 20°C / min under a nitrogen atmosphere.

[0057]

[0058]

[0059] In each embodiment, as the amount of benzimidazole salt modified starch gradually increases, the mass residual rate of polyethylene environmentally friendly plastic also becomes larger and larger. This is because the benzimidazole salt modified starch contains triazine rings and starch cross-linking structures, which can promote carbonization of the matrix at high temperatures, which is beneficial to improving the heat resistance of the plastic.

[0060] Comparative Example 1 only added starch, and Comparative Example 2 only added hydroxyethylbenzimidazole salt triazine compound, which could not effectively improve the charring property of polyethylene plastic. Comparative Example 3 added starch and hydroxyethylbenzimidazole salt triazine compound, and the charring property of polyethylene was improved to a certain extent, but it did not have a heat-resistant cross-linked structure, and its charring property and mass residual rate were slightly lower than those of Example 1.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an environmentally friendly plastic with antibacterial function, characterized in that: The environmentally friendly plastic comprises the following raw materials, in parts by weight: 0.5-10 parts of benzimidazole salt modified starch, 0.2-0.6 parts of antioxidant, and 89-99 parts of polyethylene; the preparation method of the environmentally friendly plastic is as follows: Step (1): adding acetonitrile, hydroxyethylbenzimidazole s-triazine compound and chlorinated alkane to a flask equipped with a condenser reflux tube, heating to 80-90° C. and reflux for 36-72 hours, concentrating to remove acetonitrile, and recrystallizing with ethanol to obtain a hydroxyethylbenzimidazole salt s-triazine compound; the chlorinated alkane is any one of chlorodecane, chlorododecane and chlorohexadecane; Step (2): add dimethyl sulfoxide and starch into a flask, heat to 70-80° C. and stir for 1-2 hours, then introduce nitrogen into the flask, add hexamethylene diisocyanate, hydroxyethyl benzimidazole salt triazine compound and dibutyltin dilaurate, and continue to react for 2-3 hours to obtain benzimidazole salt modified starch; Step (3): extruding the benzimidazole salt modified starch, antioxidant and polyethylene into masterbatch in a twin-screw extruder, and then injection molding by an injection molding machine to obtain an environmentally friendly plastic with antibacterial function; In the step (1), the ratio of acetonitrile, hydroxyethylbenzimidazole-s-triazine compound, and chlorinated alkane is 1L:(20-120)g:(28-180)g; In step (2), the ratio of dimethyl sulfoxide, starch, hexamethylene diisocyanate, hydroxyethylbenzimidazole salt triazine compound and dibutyltin dilaurate is 1L: (10-80) g: (5-42) g: (6-50) g: (0.02-0.16) g; The preparation method of the hydroxyethylbenzimidazole-s-triazine compound is as follows: Step (4): Add ethanol, 4,4',4"-s-triazine-2,4,6-triyl-tribenzoic acid, o-phenylenediamine and phosphoric acid aqueous solution in a ratio of 1 L: (40-200) g: (30-160) g: (1.5-3) L into a flask equipped with a condenser reflux tube, raise the temperature to 115-130 ° C and reflux for 4-8 hours to obtain benzimidazole-s-triazine; Step (5): adding ethanol, benzimidazole-s-triazine, 2-bromoethanol, sodium hydroxide aqueous solution and tetrabutylammonium bromide into a flask, and reacting at room temperature for 4-10 hours to obtain a hydroxyethylbenzimidazole-s-triazine compound; The ratio of ethanol, benzimidazole-s-triazine, 2-bromoethanol, sodium hydroxide aqueous solution and tetrabutylammonium bromide in (5) is 1L:(50-200)g:(35-160)g(1-2)L:(5-25)g.

2. The method for preparing environmentally friendly plastic with antibacterial function according to claim 1, characterized in that: In the step (3), the temperature of zones 1-4 of the extruder is 175-200° C., and the screw speed is 150-300 r / min.

3. The method for preparing the environmentally friendly plastic with antibacterial function according to claim 1, characterized in that: The mass fraction of the phosphoric acid aqueous solution in (4) is 75-85%.

4. The method for preparing environmentally friendly plastic with antibacterial function according to claim 1, characterized in that: The mass fraction of the (5) sodium hydroxide aqueous solution is 20-35%.

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