An antibacterial enhanced aqueous polyurethane composite material, its preparation method and application

Abstract

The present invention discloses an antibacterial enhanced waterborne polyurethane composite material, its preparation method and application. The antibacterial enhanced waterborne polyurethane composite material, in terms of parts by mass, comprises the following components: TCNC / Cu NPs composite material: 2 - 5 parts, deionized water: 20 - 25 parts, waterborne polyurethane solution: 20 - 25 parts; wherein, the TCNC / Cu NPs composite material is prepared by the following method: Step 1-1): Dissolve 2 - 4 parts of CNC in 200 - 250 parts of deionized water to obtain a CNC suspension. Add 17 - 19 parts of an oxidant to the CNC suspension and then dropwise add sodium hydroxide to make the pH stable at 10 - 10.5. Centrifuge, wash, and freeze-dry to obtain TCNC; Step 1-2): Dissolve 2 - 3 parts of TCNC in 80 - 100 parts of deionized water to obtain a TCNC suspension. Sequentially add 1 - 4 parts of a copper salt, 1 - 8 parts of a reducing agent, and 0.5 - 4 parts of sodium hydroxide to the TCNC suspension, and then centrifuge, wash, and dry to obtain the TCNC / Cu NPs composite material. The TCNC / CuNP-WPU film material prepared by the method of the present application has good antibacterial properties, tensile strength, and wear resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of waterborne polyurethane composites, and particularly relates to a preparation method of an antibacterial enhanced waterborne polyurethane composite material. Background Art

[0002] Compared with solvent-based polyurethanes, waterborne polyurethanes retain excellent properties inherent in general polyurethanes such as low temperature resistance, abrasion resistance, fatigue resistance, and low volatile organic compound (VOC) content, but the mechanical properties and heat resistance of the coating films are not ideal. A humid environment is more likely to breed bacteria, endangering human health and the sanitary environment. Therefore, it is very necessary to make waterborne polyurethane (WPU) antibacterial. Currently, the antibacterial finishing agents used for waterborne polyurethanes are mainly organic antibacterial agents and inorganic antibacterial agents. Among antibacterial materials, inorganic antibacterial agents have advantages such as low toxicity, good heat resistance, and a long effective antibacterial period compared with organic antibacterial agents, and thus are more widely used.

[0003] Cu NPs have great application potential in antibacterial and other fields due to their good thermal conductivity, antibacterial property, excellent mechanical properties, and low price. However, bare Cu NPs tend to aggregate due to their small size, which will greatly reduce their antibacterial efficiency. Their antibacterial performance can be improved by reducing their agglomeration and organic-inorganic hybridization. Therefore, there is room for improvement in this regard. Summary of the Invention

[0004] This application aims to solve at least one of the problems in the prior art. To this end, this application provides an antibacterial enhanced waterborne polyurethane composite material.

[0005] An antibacterial enhanced waterborne polyurethane composite material, in parts by mass, comprises the following components:

[0006] TCNC / Cu NPs composite material: 2 - 5 parts, deionized water: 20 - 25 parts, waterborne polyurethane solution: 20 - 25 parts;

[0007] Among them, the TCNC / Cu NPs composite material is prepared by the following method:

[0008] Step 1-1): Dissolve 2 - 4 parts of CNC in 200 - 250 parts of deionized water to obtain a CNC suspension. Add 17 - 19 parts of an oxidant to the CNC suspension and then dropwise add sodium hydroxide to make the pH stable at 10 - 10.5. Centrifuge, wash, and freeze-dry to obtain TCNC;

[0009] Step 1-2): Dissolve 2 - 3 parts of TCNC in 80 - 100 parts of deionized water to obtain a TCNC suspension. Sequentially add 1 - 4 parts of a copper salt, 1 - 8 parts of a reducing agent, and 0.5 - 4 parts of sodium hydroxide to the TCNC suspension, and then centrifuge, wash, and dry to obtain the TCNC / Cu NPs composite material.

[0010] Further, in step 1-1): CNC is obtained by hydrolyzing 2-4 parts by mass of MCC in 100-200 parts by mass of 64% sulfuric acid solution; the oxidizing agent is one or a combination of TEMPO, NaBr, and NaClO.

[0011] In step 1-2), the copper salt is one of copper sulfate, copper nitrate, copper acetate, and copper chloride; the reducing agent is ascorbic acid and / or sodium citrate.

[0012] Further, in step 1-1), the total amount of the oxidizing agent is 18 parts by mass, which is a combination of 2 parts of TEMPO, 1 part of NaBr, and 15 parts of NaClO.

[0013] In step 1-2), the reducing agent is 1-4 parts, and sodium hydroxide is 0.5-2 parts.

[0014] Further, the antibacterial enhanced waterborne polyurethane composite material is a film with a thickness of 0.25-0.30 mm; the waterborne polyurethane solution is a waterborne polyurethane solution with a solid content of 35 wt%.

[0015] Furthermore, the antibacterial enhanced waterborne polyurethane composite material, by mass: includes the following components:

[0016] TCNC / Cu NPs composite material: 2 parts, deionized water: 20 parts, waterborne polyurethane solution: 25 parts;

[0017] Among them, the TCNC / Cu NPs composite material is prepared by the following method:

[0018] Step 1-1): Dissolve 2 parts of CNC in 200 parts of deionized water to obtain a CNC suspension. Add 2 parts of TEMPO, 1 part of NaBr, and 15 parts of NaClO to the CNC suspension in sequence. Dropwise add sodium hydroxide to make the pH stable at 10-10.5, and then centrifuge, wash, and freeze-dry to obtain TCNC.

[0019] Step 1-2): Dissolve 2 parts of TCNC in 100 parts of deionized water to obtain a TCNC suspension. Add 2 parts of copper salt, 1 part of sodium citrate, 1 part of ascorbic acid, and 1 part of sodium hydroxide to the TCNC suspension in sequence, and then centrifuge, wash, and dry to obtain the TCNC / Cu NPs composite material.

[0020] In the second aspect, the present invention provides a preparation method of an antibacterial enhanced waterborne polyurethane composite material, including the following steps:

[0021] Step 1): Dissolve CNC in deionized water to obtain a CNC suspension. Add an oxidant to the CNC suspension, and dropwise add sodium hydroxide to keep the pH of the CNC suspension stable at 10 - 10.5. Centrifuge, wash, and freeze-dry to obtain TCNC;

[0022] Step 2) Dissolve the TCNC prepared in Step 1) in deionized water to obtain a TCNC suspension. Sequentially add a copper salt, a reducing agent, and sodium hydroxide to the TCNC suspension, and then centrifuge, wash, and dry to obtain a TCNC / Cu NPs composite material;

[0023] Step 3) Take an aqueous polyurethane solution in a container. After dispersing the TCNC / Cu NPs composite material in deionized water by ultrasonic stirring uniformly, add it to the container;

[0024] Step 4): Place the container in Step 3) in an ultrasonic oscillator for ultrasonic dispersion to obtain an aqueous polyurethane dispersion;

[0025] Step 5): Pour the aqueous polyurethane dispersion prepared in Step 4) into a mold, let it stand, and dry to obtain an aqueous polyurethane composite material.

[0026] Furthermore, in Step 1), the CNC is obtained by hydrolyzing 2 - 4 parts of MCC in 100 - 200 parts of 64% sulfuric acid solution; the oxidant is one or a combination of TEMPO, NaBr, and NaClO.

[0027] Furthermore, in Step 2), the copper salt is copper sulfate, copper nitrate, copper acetate, or copper chloride; the reducing agent is ascorbic acid and / or sodium citrate;

[0028] The aqueous polyurethane solution in Step 3) is an aqueous polyurethane solution with a solid content of 35 wt%;

[0029] The power of the ultrasonic oscillator in Step 4) is 600 - 800 W;

[0030] The temperature of the oven in Step 5) is 80 - 85 °C, and the drying time is 10 - 12 h.

[0031] Furthermore, in Step 1): Take 2 parts of CNC and dissolve it in 200 parts of deionized water to obtain a CNC suspension. Add 2 parts of TEMPO, 1 part of NaBr, and 15 parts of NaClO to the CNC suspension, and dropwise add sodium hydroxide to keep the pH of the CNC suspension stable at 10 - 10.5. Centrifuge, wash, and freeze-dry to obtain TCNC;

[0032] Step 2): Take 2 portions of the TCNC prepared in Step 1) and dissolve them in 100 portions of deionized water to obtain a TCNC suspension. Then, sequentially add 2 portions of CuCl2, 1 portion of sodium citrate, 1 portion of ascorbic acid, and 1 portion of sodium hydroxide to the TCNC suspension. After that, centrifuge, wash, and dry to obtain a TCNC / Cu NPs composite material;

[0033] Step 3): Take 25 portions of an aqueous polyurethane solution in a container. After adding 2 portions of the TCNC / Cu NPs composite material to 20 portions of deionized water and ultrasonically stirring to disperse evenly, add it to the container;

[0034] Step 4): Place the container in Step 3) in an ultrasonic oscillator for ultrasonic dispersion to obtain an aqueous polyurethane dispersion;

[0035] Step 5): Pour the aqueous polyurethane dispersion prepared in Step 4) into a mold, let it stand, and dry to obtain an aqueous polyurethane composite material.

[0036] In a third aspect, the present invention also provides an application of the antibacterial enhanced aqueous polyurethane composite material in antibacterial.

[0037] The following further explains the present application:

[0038] The purpose of the present invention is to provide a preparation of an antibacterial enhanced aqueous polyurethane composite material in view of the deficiencies of the prior art. The nano-hybrid material prepared by this method has a simple preparation process. When applied to an aqueous polyurethane coating, it can endow the aqueous polyurethane with excellent antibacterial properties while also improving its mechanical properties.

[0039] CNCs are used as carriers to directly conjugate metal nanoparticles (NPs) to their surfaces. CNCs are used as carriers and dispersants for Cu NPs to improve the dispersion of Cu NPs. And cellulose nanocrystals have been used to improve the thermal and mechanical properties of WPU films. As nanomaterials with high crystallinity, cellulose nanocrystals have a wide range of applications in polymer reinforcement. Research shows that adding different forms of cellulose nanocrystals to the WPU matrix can improve the physical and mechanical properties of the matrix. Therefore, Cu NPs are loaded on the surface of modified CNCs to obtain TCNC / Cu NPs nano-hybrids, which are added to aqueous polyurethane to improve the dispersion of Cu NPs and prepare an antibacterial enhanced aqueous polyurethane composite material.

[0040] Technical solution:

[0041] An antibacterial enhanced aqueous polyurethane composite material, its preparation method and application, comprising the following steps: (1) By means of acid hydrolysis, microcrystalline cellulose (MCC) is hydrolyzed in a sulfuric acid solution to obtain cellulose nanocrystals (CNC). Then CNC is dissolved in deionized water to form a suspension. After that, 2,2,6,6-tetramethylpiperidine-1-amino radical (TEMPO), sodium bromide (NaBr) and sodium hypochlorite (NaClO) are successively added to the CNC suspension, and sodium hydroxide is added dropwise to stabilize the pH at 10 - 10.5, reacting for 10 h, centrifuging and washing, and freeze-drying to obtain TCNC; (2) Dissolve TCNC in deionized water, and successively add copper chloride (CuCl2), sodium citrate (C6H5Na3O7), ascorbic acid (C6H8O6) and sodium hydroxide (NaOH), and react to obtain TCNC / Cu NPs composite material; (3) Add the hybrid material obtained above to aqueous polyurethane, ultrasonically disperse it, and dry it in a polytetrafluoroethylene mold. The prepared TCNC / Cu NPs antibacterial enhanced aqueous polyurethane composite material of the present invention improves the aggregation of Cu NPs by loading Cu NPs on TCNC, improves the antibacterial property of the aqueous polyurethane material, and due to the addition of carboxylated cellulose nanocrystals, the tensile strength and hardness of the aqueous polyurethane film material are improved to a certain extent.

[0042] An antibacterial enhanced aqueous polyurethane composite material, its preparation method and application, the preparation method comprising the following steps:

[0043] (1) Preparation of carboxylated cellulose nanocrystals: By means of acid hydrolysis, microcrystalline cellulose (MCC) is hydrolyzed in a 64% sulfuric acid solution to obtain cellulose nanocrystals (CNC). Weigh 2 - 4 parts by mass of CNC and dissolve it in 200 - 250 parts by mass of deionized water to obtain a CNC suspension; then successively add oxidants to the CNC suspension, add sodium hydroxide dropwise to make the pH of the suspension stable at 10 - 10.5, stop adding sodium hydroxide until the pH does not change, react for a certain time, centrifuge and wash, and freeze-dry to obtain carboxylated cellulose nanocrystals (TCNC);

[0044] (2) TCNC / nano copper: Take 2 - 4 parts by mass of TCNC prepared in step (1) and dissolve it in 80 - 100 parts by mass of deionized water to obtain a suspension, and successively add 1 - 4 parts by mass of copper salts (copper sulfate, copper nitrate, copper acetate, copper chloride, etc.), 1 - 8 parts by mass of reducing agents and 0.5 - 4 parts by mass of sodium hydroxide (NaOH) to the suspension. After reacting for a certain time, centrifuge, wash and dry to obtain TCNC / Cu NPs composite material;

[0045] (3) Take 20 - 25 parts by mass of an aqueous polyurethane solution with a solid content of 35 wt% in a beaker. After adding 2 - 5 parts by mass of the TCNC / Cu NPs composite material obtained in step (2) to 20 - 25 parts by mass of deionized water and ultrasonically stirring to disperse evenly, add it to the beaker.

[0046] (4) Place the beaker in an ultrasonic oscillator and ultrasonically disperse it under the condition of a power of 600 - 800 W.

[0047] (5) Pour the ultrasonically homogeneous aqueous polyurethane dispersion liquid in step (4) into a polytetrafluoroethylene mold, let it stand for a certain time until there are no obvious bubbles on the surface, and then put it into an oven and dry it at 80 - 85 °C for 10 - 12 h to obtain a circular film with a thickness of 0.25 - 0.30 mm.

[0048] In step (1), 2 parts by mass of CNC is weighed and dissolved in 200 parts by mass of deionized water to obtain a CNC suspension. Then, an oxidant is added to the CNC suspension in turn, and sodium hydroxide is added dropwise to keep the pH of the suspension stable between 10 - 10.5 until the pH does not change, then stop adding sodium hydroxide, centrifuge and wash, and freeze - dry.

[0049] Preferably, in step (1), 2 parts by mass of CNC is weighed and dissolved in 200 parts by mass of deionized water. Then, 3 parts by mass of 2,2,6,6 - tetramethylpiperidine - 1 - amino radical (TEMPO) and sodium bromide (NaBr) (mass ratio 2:1), 15 parts by mass of sodium hypochlorite (NaClO) are added to the CNC suspension in turn. Sodium hydroxide is added dropwise to keep the pH of the suspension stable between 10 - 10.5 until the pH does not change, then stop adding sodium hydroxide, react for 10 h, centrifuge and wash, and freeze - dry.

[0050] In step (2), 2 parts by mass of TCNC obtained in step (1) is dissolved in 100 parts by mass of deionized water to obtain a TCNC suspension. And 2 parts by mass of copper salts (such as copper sulfate, copper nitrate, copper acetate, copper chloride, etc.), 1 part by mass of reducing agent (such as ascorbic acid, sodium citrate, etc.) and 1 part by mass of sodium hydroxide (NaOH) are added to the suspension in turn. After raising the temperature to a certain temperature and reacting for a certain time, centrifuge, wash and dry to obtain the TCNC / Cu NPs composite material.

[0051] Preferably, in step (2), 2 parts by mass of TCNC obtained in step (1) is dissolved in 100 parts by mass of deionized water to obtain a TCNC suspension, and 2 parts by mass of copper chloride (CuCl2), 1 part by mass of sodium citrate (C6H5Na3O7), 1 part by mass of ascorbic acid (C6H8O6) and 1 part by mass of sodium hydroxide (NaOH) are successively added to the suspension. The temperature is raised to 90 °C and the reaction is carried out for 2 h. Then, it is centrifuged, washed and dried to obtain a TCNC / Cu NPs composite material.

[0052] Preferably, in step (3), 25 parts by mass of an aqueous polyurethane solution with a solid content of 35 wt% is taken in a beaker. After 2 parts by mass of the TCNC / Cu NPs composite material obtained in step (2) is added to 20 parts by mass of deionized water and ultrasonically stirred to be uniformly dispersed, it is added to the beaker.

[0053] Preferably, in step (4), the beaker is placed in an ultrasonic oscillator and ultrasonically dispersed for 30 min under the condition of a power of 600 W.

[0054] Preferably, in step (5), the aqueous polyurethane dispersion liquid ultrasonically homogenized in step (4) is poured into a polytetrafluoroethylene mold, allowed to stand for 4 h until there are no obvious bubbles on the surface, and then placed in an oven and dried at 80 °C for 12 h to prepare a circular film with a thickness of 0.30 mm.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] (1) The TCNC / Cu NPs hybrid material prepared by the present invention improves the dispersibility of Cu NPs and makes them not easily agglomerate.

[0057] (2) The TCNC / Cu NPs hybrid material prepared by the present invention loads Cu NPs on TCNC and is compounded with aqueous polyurethane to make Cu NPs uniformly dispersed in the aqueous polyurethane, so that Cu NPs can exert better antibacterial properties.

[0058] (3) The present invention uses TCNC as a carrier and is compounded with aqueous polyurethane, which can greatly improve the tensile strength and wear resistance of the aqueous polyurethane composite material. Description of the Drawings

[0059] Figure 1 Shown are the antibacterial experiments of the films of WPU and the composite materials of TCNC / Cu NPs with different ratios (where a represents Staphylococcus aureus; b is Escherichia coli; 1, 2, 3, 4 represent WPU, TCNC / Cu NP(1:0.5)-WPU, TCNC / CuNP(1:1-WPU) and TCNC / Cu

[0060] NP(1:2)-WPU.)

[0061] In this experiment, the antibacterial test of the samples was carried out using the test method in GB / T 20944.1-2007 "Evaluation of antibacterial properties of textiles - Part 1: Agar diffusion method". The tensile strength test was carried out using the strip method in GB / T 3923.1-1997 "Textiles - Tensile properties of fabrics - Part 1: Determination of breaking force and elongation at break". The hardness of the coating was measured using the pencil hardness test method in GB / T 6739-1996. Specific embodiments

[0062] An antibacterial enhanced waterborne polyurethane composite material, in parts by mass, includes the following components:

[0063] TCNC / Cu NPs composite material: 2 - 5 parts, deionized water: 20 - 25 parts, waterborne polyurethane solution: 20 - 25 parts;

[0064] Among them, the TCNC / Cu NPs composite material is prepared by the following method:

[0065] Step 1-1): Dissolve 2 - 4 parts of CNC in 200 - 250 parts of deionized water to obtain a CNC

[0066] suspension. Add 17 - 19 parts of oxidant to the CNC suspension, then dropwise add sodium hydroxide to make the pH stable at 10 - 10.5, centrifuge and wash, and freeze-dry to obtain TCNC;

[0067] Step 1-2): Dissolve 2 - 3 parts of TCNC in 80 - 100 parts of deionized water to obtain a TCNC

[0068] suspension. Add 1 - 4 parts of copper salt, 1 - 8 parts of reducing agent and 0.5 - 4

[0069] parts of sodium hydroxide to the TCNC suspension in sequence, and then centrifuge, wash and dry to obtain the TCNC / Cu NPs composite material;

[0070] Take the waterborne polyurethane solution in a container. After dispersing the TCNC / Cu NPs composite material in deionized water by ultrasonic stirring evenly, add it to the container;

[0071] Place the container in an ultrasonic oscillator for ultrasonic dispersion to obtain a waterborne polyurethane dispersion;

[0072] Pour the waterborne polyurethane dispersion into a mold, let it stand and dry to obtain the antibacterial enhanced waterborne polyurethane composite material.

[0073] The antibacterial enhanced waterborne polyurethane composite material of this application has good antibacterial properties, tensile strength and wear resistance.

[0074] The present invention will be further described below in conjunction with specific embodiments.

[0075] Example 1

[0076] A method for preparing an antibacterial-enhanced waterborne polyurethane composite material, the preparation method comprising the following steps:

[0077] Step (1): Using the method of acid hydrolysis: Hydrolyze 2 parts by mass of microcrystalline cellulose (MCC) in 100 parts by mass of 64% sulfuric acid solution to obtain cellulose nanocrystals (CNC), and weigh 2 parts by mass of CNC and dissolve it in 200 parts by mass of deionized water to obtain a CNC suspension; then add 2 parts by mass of 2,2,6,6-tetramethylpiperidine-1-amino radical (TEMPO), 1 part by mass of sodium bromide (NaBr) (mass ratio 2:1), and 15 parts by mass of sodium hypochlorite (NaClO) to the CNC suspension in sequence, and dropwise add sodium hydroxide to keep the pH of the CNC suspension stable at 10 - 10.5 until the pH does not change, stop dropping sodium hydroxide, react for 10 h, centrifuge and wash, and freeze-dry to obtain TCNC;

[0078] Step (2): Take 2 parts by mass of the TCNC prepared in step (1) and dissolve it in 100 parts by mass of deionized water to obtain a TCNC suspension, and sequentially add 1 part by mass of copper chloride (CuCl2), 0.5 part by mass of sodium citrate (C6H5Na3O7), 0.5 part by mass of ascorbic acid (C6H8O6), and 0.5 part by mass of sodium hydroxide (NaOH) to the TCNC suspension, heat up to 90 °C, react for 2 h, then centrifuge, wash and dry to obtain the TCNC / Cu NPs composite material;

[0079] Step (3): Take 25 parts by mass of a waterborne polyurethane solution with a solid content of 35 wt% in a beaker, add 2 parts by mass of the TCNC / Cu NPs composite material obtained in step (2) to 20 parts by mass of deionized water, ultrasonically stir to disperse evenly, and then add it to the beaker;

[0080] Step (4): Place the beaker in step (3) in an ultrasonic oscillator, and under the condition of a power of 600 W, ultrasonically disperse for 30 min to obtain a waterborne polyurethane dispersion;

[0081] Step (5): Pour the ultrasonically homogeneous waterborne polyurethane dispersion in step (4) into a polytetrafluoroethylene mold, let it stand for 4 h until there are no obvious bubbles on the surface, and put it in an oven at 80 °C and dry for 12 h to prepare a circular film with a thickness of 0.30 mm. That is, the TCNC / CuNP(1:0.5)-WPU film material is obtained (i.e., the ratio of TCNC:CuCl2 is 2:1).

[0082] Example 2

[0083] A preparation method of an antibacterial enhanced waterborne polyurethane composite material, the preparation method comprising the following steps:

[0084] Step (1): Using the acid hydrolysis method: Hydrolyze 2 parts by mass of microcrystalline cellulose (MCC) in 100 parts by mass of 64% sulfuric acid solution to obtain cellulose nanocrystals (CNC). Weigh 2 parts by mass of CNC and dissolve it in 200 parts by mass of deionized water to obtain a CNC suspension; then sequentially add 2 parts by mass of 2,2,6,6-tetramethylpiperidine-1-amino radical (TEMPO), 1 part by mass of sodium bromide (NaBr) (mass ratio 2:1), and 15 parts by mass of sodium hypochlorite (NaClO) to the CNC suspension. Dropwise add sodium hydroxide to keep the pH of the suspension stable at 10 - 10.5 until the pH does not change, then stop adding sodium hydroxide, react for 10 h, centrifuge and wash, and freeze-dry to obtain TCNC;

[0085] Step (2): Take 2 parts by mass of TCNC obtained in step (1) and dissolve it in 100 parts by mass of deionized water to obtain a TCNC suspension, and sequentially add 2 parts by mass of copper chloride (CuCl2), 1 part by mass of sodium citrate (C6H5Na3O7), 1 part by mass of ascorbic acid (C6H8O6), and 1 part by mass of sodium hydroxide (NaOH) to the TCNC suspension. Heat up to 90 °C and react for 2 h, then centrifuge, wash, and dry to obtain the TCNC / Cu NPs composite material;

[0086] Step (3): Take 25 parts by mass of a waterborne polyurethane solution with a solid content of 35 wt% in a beaker. After adding 2 parts by mass of the TCNC / Cu NPs composite material obtained in step (2) to 20 parts by mass of deionized water and ultrasonically stirring to disperse it evenly, add it to the beaker;

[0087] Step (4): Place the beaker in an ultrasonic oscillator and ultrasonically disperse it for 30 min under the condition of a power of 600 W to obtain a waterborne polyurethane dispersion;

[0088] Step (5): Pour the ultrasonically homogeneous waterborne polyurethane dispersion in step (4) into a polytetrafluoroethylene mold, let it stand for 4 h until there are no obvious bubbles on the surface, and then put it into an oven and dry at 80 °C for 12 h to obtain a circular film with a thickness of 0.30 mm (i.e., obtain the TCNC / CuNP(1:1)-WPU film material (TCNC:CuCl2 is 2:2)).

[0089] Example 3

[0090] A preparation method of an antibacterial enhanced waterborne polyurethane composite material, the preparation method comprising the following steps:

[0091] Step (1): By the method of acid hydrolysis: 4 parts by mass of microcrystalline cellulose (MCC) was hydrolyzed in 200 parts by mass of 64% sulfuric acid solution to obtain cellulose nanocrystals (CNC). 2 parts by mass of CNC was weighed and dissolved in 200 parts by mass of deionized water to obtain a CNC suspension. Then, 2 parts by mass of 2,2,6,6-tetramethylpiperidine-1-amine radical (TEMPO), 1 part by mass of sodium bromide (NaBr) (mass ratio 2:1), and 15 parts by mass of sodium hypochlorite (NaClO) were successively added to the CNC suspension. Sodium hydroxide was added dropwise to keep the pH of the suspension stable at 10 - 10.5 until the pH remained unchanged. Then, the addition of sodium hydroxide was stopped, and the reaction was carried out for 10 h. After centrifugation, washing, and freeze-drying, TCNC was obtained.

[0092] Step (2): 2 parts by mass of TCNC obtained in step (1) was dissolved in 100 parts by mass of deionized water to obtain a TCNC suspension. Then, 4 parts by mass of copper chloride (CuCl2), 2 parts by mass of sodium citrate (C6H5Na3O7), 2 parts by mass of ascorbic acid (C6H8O6), and 2 parts by mass of sodium hydroxide (NaOH) were successively added to the suspension. The temperature was raised to 90 °C, and the reaction was carried out for 2 h. After centrifugation, washing, and drying, a TCNC / Cu NPs composite material was obtained.

[0093] Step (3): 25 parts by mass of an aqueous polyurethane solution with a solid content of 35 wt% was placed in a beaker. After 2 parts by mass of the TCNC / Cu NPs composite material obtained in step (2) was added to 20 parts by mass of deionized water and ultrasonically stirred until evenly dispersed, it was added to the beaker.

[0094] Step (4): The beaker was placed in an ultrasonic oscillator, and under the condition of a power of 600 W, ultrasonic dispersion was carried out for 30 min to obtain an aqueous polyurethane dispersion.

[0095] Step (5): The ultrasonically homogeneous aqueous polyurethane dispersion obtained in step (4) was poured into a polytetrafluoroethylene mold and allowed to stand for 4 h until there were no obvious bubbles on the surface. Then, it was placed in an oven and dried at 80 °C for 12 h to obtain a circular film with a thickness of 0.30 mm (i.e., the TCNC / CuNP(1:2)-WPU film material (the ratio of TCNC:CuCl2 is 2:4) was obtained).

[0096] Comparative Example 1

[0097] The difference lies in pure aqueous polyurethane without adding any antibacterial agent. The specific preparation process is as follows: Step (1): 25 parts by mass of an aqueous polyurethane solution with a solid content of 35 wt% was placed in a beaker, and 20 parts by mass of deionized water was added thereto and stirred.

[0098] Step (2): The beaker was placed in an ultrasonic oscillator, and under the condition of a power of 600 W, ultrasonic dispersion was carried out for 20 min to obtain a dispersion.

[0099] Step (3): Pour the uniformly dispersed dispersion liquid into a polytetrafluoroethylene mold. After standing for 4 hours,

[0100] dry it at 80 °C for 12 hours to obtain a circular film with a thickness of 0.3 mm.

[0101] Comparative Example 2

[0102] The difference is that Cu NPs are not loaded. The specific preparation process is as follows:

[0103] Step (1): Adopt the method of acid hydrolysis: Hydrolyze 2 parts by mass of microcrystalline cellulose (MCC) in 100 parts by mass

[0104] of 64% sulfuric acid solution to obtain cellulose nanocrystals (CNC). Weigh 2 parts by mass of CNC and dissolve it in 200 parts by mass of deionized water to obtain a CNC suspension; then add 2 parts by mass of 2,2,6,6-tetramethylpiperidine-1-amino radical (TEMPO) and 1 part by mass of sodium bromide (NaBr)

[0105] (mass ratio 2:1), 15 parts by mass of sodium hypochlorite (NaClO) into the CNC suspension in sequence. Dropwise add sodium hydroxide to make the pH of the suspension stable at 10 - 10.5 until the pH does not change, then stop

[0106] dropwise adding sodium hydroxide, react for 10 hours, centrifuge and wash, and freeze-dry to obtain TCNC;

[0107] Step (2): Take 25 parts by mass of a WPU solution with a solid content of 35 wt% in a beaker, and then take 2 parts by mass

[0108] of the TCNC obtained in Step (1) and dissolve it in 20 parts by mass of deionized water to form a TCNC suspension, and then add this TCNC suspension to the above 25 parts by mass of the aqueous polyurethane emulsion;

[0109] Step (3): Place the beaker in an ultrasonic oscillator and ultrasonically disperse it for 20 minutes under the condition of a power of 600 W to obtain a dispersion liquid;

[0110] Step (4): Pour the uniformly dispersed dispersion liquid into a polytetrafluoroethylene mold. After standing for a period of time of 4 hours, dry it at 80 °C for 12 hours to obtain a circular film with a thickness of 0.3 mm.

[0111] Performance test

[0112] Table 1 shows the performance test results of Examples 1 - 3 and Comparative Examples 1 - 2

[0113]

[0114] As can be seen from Table 1, when the ratio of modified cellulose nanocrystals to copper salt precursor (i.e., the ratio of TCNC:CuCl2 in Example 1 is 2:1) is 1:0.5, the antibacterial rates of the WPU film against E. coli and S. aureus are 86% and 85% respectively, showing excellent antibacterial effects. When the ratio is 1:1 or 1:2, the antibacterial rate can reach 99.9%. Moreover, when the ratio is 1:1, the mechanical properties of the WPU film are improved to a certain extent. Therefore, the TCNC / CuNP-WPU film material prepared by the method of this application has good antibacterial properties, tensile strength and wear resistance.

Claims

1. An antibacterial enhanced waterborne polyurethane composite material, characterized in that: By mass fraction, it includes the following components: TCNC / Cu NPs composite material: 2 parts, deionized water: 20 parts, aqueous polyurethane solution: 25 parts; wherein, the aqueous polyurethane solution uses an aqueous polyurethane solution with a solid content of 35 wt%. Among them, the TCNC / Cu NPs composite material is prepared by the following method: Step 1-1): Dissolve 2 parts of CNC in 200 parts of deionized water to obtain a CNC suspension. Add an oxidant to the CNC suspension and then dropwise add sodium hydroxide to make the pH stable at 10 - 10.

5. Centrifuge, wash, and freeze-dry to obtain TCNC; among them, in step 1-1), the total amount of the oxidant is 18 parts, which is a combination of 2 parts of TEMPO, 1 part of NaBr, and 15 parts of NaClO. Step 1-2): Dissolve 2 parts of TCNC in 100 parts of deionized water to obtain a TCNC suspension. Sequentially add 2 parts of copper salt, 2 parts of reducing agent, and 1 part of sodium hydroxide to the TCNC suspension, and then centrifuge, wash, and dry to obtain the TCNC / Cu NPs composite material; among them, 2 parts of the reducing agent are 1 part of ascorbic acid and 1 part of sodium citrate.

2. An antibacterial enhanced aqueous polyurethane composite material according to claim 1, characterized in that: In the said step 1-1): CNC is obtained by hydrolyzing 2 - 4 mass parts of MCC in 100 - 200 mass parts of 64% sulfuric acid solution; in the said step 1-2), the copper salt is one of copper sulfate, copper nitrate, copper acetate, and copper chloride.

3. An antibacterial-enhanced aqueous polyurethane composite material according to claim 1, characterized in that: The said antibacterial enhanced aqueous polyurethane composite material is a film with a thickness of 0.25 - 0.30 mm.

4. The preparation method of an antibacterial-enhanced aqueous polyurethane composite material according to any one of claims 1 to 3, characterized in that: It includes the following steps: Step 1): Dissolve CNC in deionized water to obtain a CNC suspension. Add an oxidant to the CNC suspension, dropwise add sodium hydroxide to make the pH of the CNC suspension stable at 10 - 10.5, centrifuge, wash, and freeze-dry to obtain TCNC. Step 2): Dissolve the TCNC prepared in step 1) in deionized water to obtain a TCNC suspension. Sequentially add copper salt, reducing agent, and sodium hydroxide to the TCNC suspension, and then centrifuge, wash, and dry to obtain the TCNC / Cu NPs composite material. Step 3): Take the aqueous polyurethane solution in a container. After dispersing the TCNC / Cu NPs composite material in deionized water by ultrasonic stirring evenly, add it to the said container. Step 4): Place the container in step 3) in an ultrasonic oscillator for ultrasonic dispersion to obtain an aqueous polyurethane dispersion. Step 5): Pour the aqueous polyurethane dispersion prepared in step 4) into a mold, let it stand, and dry to obtain the aqueous polyurethane composite material.

5. The preparation method according to claim 4, characterized in that: In the said step 1), CNC is obtained by hydrolyzing 2 - 4 parts of MCC in 100 - 200 parts of 64% sulfuric acid solution.

6. The preparation method according to claim 4, characterized in that: The copper salt in the said step 2) is copper sulfate, copper nitrate, copper acetate, or copper chloride. The power of the ultrasonic oscillator in the said step 4) is 600 - 800 W. The temperature of the oven in the said step 5) is 80 - 85 °C, and the drying duration is 10 - 12 h.

7. Use of an antibacterial enhanced aqueous polyurethane composite material according to any one of claims 1 - 3 in the preparation of antibacterial materials.

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