A method for preparing a polyurethane nanofiber membrane

Abstract

The application provides a preparation method of a polyurethane nanofiber membrane, and belongs to the technical field of superfine fiber membranes. A prepolymer is prepared, a nanofiber membrane is prepared, and halogenation treatment is performed to obtain a finished polyurethane nanofiber membrane. The preparation method solves the defects of existing antibacterial polyurethane nanofiber membranes, and hydroxyl-containing halamine antibacterial monomers are grafted in the structure to endow the polyurethane nanofiber membrane with durable and renewable antibacterial performance.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a polyurethane nanofiber membrane, and belongs to the technical field of superfine fiber membranes. BACKGROUND

[0002] Polyurethane (PU) is a polymer formed by blocks of flexible segments (such as polyether, polyester, and other oligomer polyols) and rigid segments (such as diisocyanate and chain extender). It has excellent properties such as wear resistance, high elasticity, and biocompatibility. In recent years, polyurethane materials have been increasingly applied in the medical field and the field of artificial organs. Polyurethane membranes are one of the main composite membranes currently used in medical supplies. However, polyurethane membranes are prone to bacterial growth under suitable temperature and humidity conditions, which poses a serious threat to human life and health. Therefore, it is of great theoretical value and broad market prospect to develop polyurethane composite membranes with persistent antibacterial properties.

[0003] Polyurethane antibacterial modification can be mainly divided into physical modification and chemical modification. Physical modification is to combine antibacterial agents with polyurethane materials through methods such as blending, soaking, spraying, and coating. This method is simple to operate, but the antibacterial effect is not persistent. Chemical modification is to combine antibacterial agents into polyurethane through chemical bonding. The antibacterial polyurethane materials prepared by this method can be divided into two categories. One category is that the grafted modified polyurethane material itself has antibacterial properties. The other category is that the grafted modified polyurethane material itself does not have antibacterial properties, and the antibacterial agent is released from the material through hydrolysis, enzymatic degradation, or other actions to achieve antibacterial effect. The antibacterial persistence of polyurethane materials prepared by chemical modification is better than that of materials prepared by physical modification, but there will be a certain loss during storage or use, especially for modified polyurethane materials without antibacterial properties.

[0004] Halamine antibacterial agents are antibacterial agents containing one or more N-X structures (X is Cl, Br, or other halogens) in the molecular structure. They are a renewable antibacterial agent prepared by the action of hypohalite on compounds containing amine, amide, or imide groups. The halamine compound molecular structure can introduce active groups such as double bonds (C=C, such as ADMH, VBDMH, etc.), hydroxyl groups (-OH, such as MDMH, DMDMH, etc.), and silicon hydroxyl groups (Si-OH, such as DTH, etc.), which can improve the bonding strength between the antibacterial agent and the substrate, and thus improve the antibacterial persistence of the grafted modified material.

[0005] Therefore, some studies have introduced the above halamine antibacterial agents into polyurethane nanostructures, such as CN 115182070A, ZL 2022108097921, and ZL 2020107965379, to endow the nanofiber material with excellent antibacterial properties. However, the preparation process has many steps and takes a long time. SUMMARY

[0006] Therefore, the application provides a preparation method of a polyurethane nanofiber membrane, which not only endows the polyurethane membrane with good and durable antibacterial property, but also simplifies the processing procedure and makes the application more convenient.

[0007] Specifically, the application is realized by the following scheme:

[0008] A preparation method of a polyurethane nanofiber membrane, comprising the following steps:

[0009] (1) Preparation of a prepolymer:

[0010] 20-30 g of a polymer polyol is added to a reaction device, and dehydration is performed under vacuum for 2-3 h, then 10-20 g of diisocyanate is added, and the temperature is raised to 50-60 ℃, and the reaction time is 50-70 min, then 2-5 drops of dibutyltin dilaurate and 5-10 g of DMF are added, and the temperature is raised to 70 ℃, and the reaction is continued for 60-120 min, then 3-5 g of a chain extender and 10-15 g of DMF are added, and the temperature is raised to 80-90 ℃, and the reaction is continued for 50-70 min, then 50-100 g of DMF is added to control the solid content of the reaction system to 30-40 g, 1-3 g of a halamine antibacterial monomer is added, and the reaction is continued for 50-70 min, to obtain a prepolymer of the halamine antibacterial monomer grafted polyurethane.

[0011] (2) Preparation of a nanofiber membrane:

[0012] The prepolymer obtained in step (1) is used as a raw material, and a nanofiber membrane is spun by electrospinning, and the electrospinning parameters are as follows: the spinning temperature is 25-30 ℃, the spinning humidity is 50-60%, the drum receiving distance is 10 cm, the spinning liquid flow rate is 0.5-1.0 mL / h, the collection rotation speed is 300-500 r / min, the needle head moving back and forth distance is 140 mm, and the spinning voltage is 15 kV.

[0013] (3) Halogenation treatment:

[0014] At room temperature, the nanofiber membrane obtained in step (2) is immersed in a sodium hypochlorite solution with an effective chlorine content of 2000-3000 ppm, and the soaking time is 10-30 min, after the treatment is completed, the nanofiber membrane is taken out, washed with a large amount of deionized water, and dried to obtain a finished polyurethane nanofiber membrane.

[0015] The above scheme not only realizes the antibacterial property of the polyurethane nanofiber membrane, but also endows the polyurethane nanofiber membrane with good mechanical properties: in the preparation process, a halamine antibacterial agent containing hydroxyl groups in the structure is used as a grafting monomer, which is directly grafted with polymer diol, diisocyanate, etc. by one-pot method to obtain a prepolymer, the preparation method is simple, and the polyurethane nanofiber membrane is endowed with durable and renewable antibacterial property and high grafting rate.

[0016] Further, as preferred:

[0017] The diisocyanate is one or a mixture of several of toluene diisocyanate (TDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), preferably a mixture of IPDI and HDI in a mass ratio of 3:1.

[0018] The polymeric polyol is one or a mixture of several of polycaprolactone polyol (PLG), polyether diol (PPG), polyether diol (PTMG), polyester diol (PBA1000), polyester diol (PBA2000) and polyester diol (PBA3000), preferably polyester diol PBA2000.

[0019] The halamine antibacterial monomer is monomethylol dimethyl hydantoin (MDMH), the structure of which is expressed as:

[0020]

[0021] The chain extender is one or a mixture of several of ethylene glycol (EG), 1,4-butanediol (BDO), hydroquinone dihydroxyethyl ether (HQEE) and resorcinol dihydroxyethyl ether (HER), preferably 1,4-butanediol BDO.

[0022] In step (1), the weight average molecular weight of the prepolymer is 80000-100000.

[0023] The preparation method of the renewable antibacterial polyurethane nanofiber membrane obtained by using the present application has the following outstanding advantages and positive effects compared with the prior art:

[0024] (1) The process of the present application is simple and the conditions are controllable: the polymer diol, diisocyanate and halamine antibacterial monomer are grafted in one step to synthesize a prepolymer, and then electrospinning and halogenation treatment are performed to obtain the finished polyurethane nanofiber membrane, the steps are simple, and the reaction is basically carried out at a medium-low temperature below 100℃;

[0025] (2) The polyurethane nanofiber membrane prepared by the present application has excellent antibacterial performance: in the preparation process of the prepolymer, the polymer diol and diisocyanate are first reacted, and then the halamine antibacterial monomer is grafted. This addition timing makes the halamine antibacterial monomer be added after dilution, which gives the prepolymer a grafting rate of more than 90%, and the antibacterial performance is excellent;

[0026] (3) The polyurethane nanofiber membrane prepared by the application has washing resistance and reproducibility: in the preparation of the prepolymer, the chain extender is added before the halamine antibacterial monomer, which avoids the influence of the structure of the halamine antibacterial monomer on the reaction product polyurethane between the polymeric diol and diisocyanate, is conducive to controlling the chain length of the polyurethane, and the corresponding polyurethane has a high molecular weight, and the nanofiber membrane has high tensile breaking strength and good washing resistance. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Figure 1 is a morphological structure diagram of the nanofiber membrane spun by the halamine antibacterial monomer grafted polyurethane prepolymer in Example 1.

[0028] Figure 2 Figure 2 is a morphological structure diagram of the nanofiber membrane without grafting the polyurethane prepolymer.

[0029] Figure 3 Figure 3 is a surface element distribution of the polyurethane nanofiber membrane prepared in Example 1.

[0030] Figure 4 Figure 4 is a single element distribution diagram of the surface of the polyurethane nanofiber membrane prepared in Example 1.

[0031] Figure 5 Figure 5 is an infrared spectrum of the polyurethane and the MDMH modified polyurethane in Example 1.

[0032] Figure 6 Figure 6 is a reproducibility control diagram of the antibacterial effect of the polyurethane nanofiber membrane prepared in Example 1.

[0033] Figure 7 Figure 7 is a diagram of the relationship between the chain extension reaction time and the content of -NCO. DETAILED DESCRIPTION

[0034] Example 1

[0035] The polyurethane nanofiber membrane preparation method of the present application comprises the following steps:

[0036] Step 1: Preparation of halamine antibacterial monomer grafted polyurethane prepolymer

[0037] 30 g of polyester diol PBA2000 was added into the reaction device, and dehydrated under vacuum for 2 h, then 16 g of diisocyanate (a mixture of IPDI and HDI with a mass ratio of 3:1) was added, and the temperature was raised to 55 °C, and the reaction time was 50 min, then 2 drops of dibutyltin dilaurate and 5 g of DMF were added, and the temperature was raised to 70 °C, and the reaction was continued for 80 min, then 4 g of chain extender BDO and 10 g of DMF were added, and the temperature was raised to 80 °C, and the reaction was continued for 60 min, 74 g of DMF was added to control the solid content of the reaction system to 36%, 2 g of halamine antibacterial monomer MDMH was added, and the reaction was continued for 50 min, to obtain a halamine antibacterial monomer grafted polyurethane prepolymer.

[0038] Step two: preparation of polyurethane nanofiber membrane

[0039] The prepolymer prepared in step one was spun into a nanofiber membrane by electrospinning, with a spinning temperature of 25 °C, a spinning humidity of 50%, a drum receiving distance of 10 cm, a spinning solution flow rate of 0.5 mL / h, a collection rotation speed of 300 r / min, a needle moving back and forth distance of 140 mm, and a spinning voltage of 15 kV.

[0040] Step three: chlorination treatment

[0041] The nanofiber membrane obtained in step two was immersed in a sodium hypochlorite solution with an available chlorine content of 2000 ppm at room temperature, and the immersion time was 10 min. After the treatment was completed, the nanofiber membrane was taken out, rinsed with a large amount of deionized water, and dried to obtain the finished polyurethane nanofiber membrane.

[0042] The finished polyurethane nanofiber membrane obtained by the above method was detected, and the results are as follows.

[0043] (1) Surface morphology structure of nanofiber membrane

[0044] The finished polyurethane nanofiber membrane obtained in step three was used as a sample, vacuum gold plating was performed, and the surface morphology structure of the polyurethane nanofiber membrane and the MDMH grafted modified polyurethane nanofiber membrane was observed by using a SU3800 type scanning electron microscope, as shown in Figure 1 The polyurethane prepolymer prepared by the method described in the present case has good spinnability, and the nanofiber membrane (halamine antibacterial monomer grafted polyurethane prepolymer) spun has a high porosity.

[0045] As a comparison, we also prepared an unmodified polyurethane nanofiber membrane by electrospinning and halogenation treatment in the same way, and the results showed that: compared with the nanofiber membrane spun from the halamine antibacterial monomer grafted polyurethane prepolymer, the non-grafted modified polyurethane prepolymer had poor spinnability, and the nanofiber membrane spun had a low porosity, as shown in Figure 2 The fibers were adhered together by a large amount of sheet-shaped polymers.

[0046] (2) Thin film surface element distribution

[0047] The surface element distribution of the polyurethane nanofiber film prepared in Example 1 was analyzed by a JSM-7610F electron spectrometer, as shown in Figure 3 .

[0048] In the polymer element composition prepared from the polymer diol and diisocyanate, the main elements are C, H, N, and O. As can be seen from Figure 3 , Figure 4 , in addition to a large proportion of C, N, and O, there is also a considerable amount of Cl, and the Cl element is uniformly distributed on the surface of the fiber film. This shows that the halamine type antibacterial monomer in the above scheme has achieved effective grafting effect and uniform distribution.

[0049] (3) Infrared spectroscopy experiment

[0050] The finished polyurethane nanofiber film obtained in step three was subjected to an infrared spectroscopy experiment, Figure 5 in which the deformation vibration of -N-H in CO-NH was at about 3367 cm -1 and 1535 cm -1 , the strong stretching vibration peak of -C=O in -CO-NH- was at about 1726 cm -1 , and these three peaks are characteristic vibration peaks of urethane in the polyurethane structure. Both PU and MDMH-PU have strong absorption peaks at these three places. In addition, the modification of MDMH causes a slight shift in the position of some characteristic absorption peaks or changes in absorption intensity through electronic induction effect, such as the enhancement of the C-N bond stretching vibration peak of amide at 1365 cm -1 , the blue shift of the C-N bond stretching vibration peak from 1244 cm -1 to 1253 cm -1 , the weakening of the C-O stretching vibration peak of alcohol at 1076 cm -1 , indicating that MDMH has been successfully grafted into the polyurethane structure.

[0051] (4) Polyurethane molecular weight test

[0052] Using polystyrene as a standard sample for calibration curve, a Waters 1525 / 2414 type gel permeation chromatograph was used to analyze the molecular weight and distribution of polyurethane, the mobile phase was tetrahydrofuran, the flow rate was 1.0 mL / min, the test temperature was 35°C, and the sample collection time was 40 min. After testing, Breeze software was used for data processing.

[0053] The results show that: the number average molecular weight is 84338, the weight average molecular weight is 29716, 2.84.

[0054] (5) Bacteriostatic rate test

[0055] The bacteriostatic rate was tested according to the standard of GB / T 20944.1-2007 Evaluation of Anti-bacterial Property of Textiles Part 1: Agar Plate Diffusion Method.

[0056] The results showed that the inhibition rates of E. coli and S. aureus were both 99.99%.

[0057] (6) Washing resistance test

[0058] A 2g / L washing solution was prepared using a non-phosphorus ECE standard synthetic detergent, the sample was immersed in the washing solution, soaked in a water bath at 25±3°C for 10 min, washed thoroughly with distilled water, and dried, which was recorded as one washing. The results are shown in Table 1. Figure 6

[0059] From Table 1, it can be seen that the bacteriostatic rate of the MDMH modified polyurethane nanofiber membrane after 20 washes was significantly lower than that of the unwashed sample (first chlorinated membrane), and after the fifth chlorination treatment, the bacteriostatic effect of the polyurethane nanofiber membrane was restored to that of the first chlorinated membrane. Figure 6 Table 1: Bacteriostatic rate test results

[0060]

[0061] (7) Tensile strength

[0062] The mechanical properties of the nanofiber membrane were tested using a YM061 electronic single yarn strength tester. The sample width was 5mm, the clamping distance was 50mm, the tensile speed was fixed at 10mm / min, each sample was tested 20 times to take the average value, and the tensile breaking strength (cN) was recorded.

[0063] The results showed that the tensile breaking strength was 520cN.

[0064] Example 2

[0065] The settings of this example and Example 1 were the same, except that MDMH and chain extender were added at the same time, and the results are shown in Table 2.

[0066] Table 2: Effect of MDMH addition method on polyurethane molecular weight

[0067]

[0068]

[0069] ​​As shown in Table 2, the molecular weight of the polyurethane prepared by adding MDMH at the same time as the chain extender is significantly smaller than that of the polyurethane prepared by adding the chain extender for 60 minutes. This is because the structure of MDMH contains a hydroxyl group, which can react with the isocyanate groups in the polyurethane prepolymer to terminate the growth of the molecular chain, so the earlier the MDMH is added, the smaller the molecular weight of the polyurethane and the larger the mass polydispersity coefficient. In addition, the data in Table 2 show that the tensile breaking strength of the polyurethane prepared by adding MDMH at the same time as the chain extender is significantly smaller than that of the polyurethane prepared by adding the chain extender for 60 minutes.

[0070] At the same time, in terms of grafting rate: the grafting rate when MDMH is added before dilution (i.e., added at the same time as the chain extender) is significantly smaller than that when MDMH is added after dilution (i.e., added 60 minutes after the addition of the chain extender). This may be because the polyurethane prepolymer not only has a large system viscosity, but also only the ends of the macromolecular chains contain isocyanate groups. The large viscosity has a blocking effect on the diffusion of MDMH molecules, causing MDMH to be unable to easily diffuse into the system and react with the isocyanate groups at the ends of the prepolymer macromolecular chains. After dilution, the viscosity of the polyurethane prepolymer system is reduced, and MDMH easily diffuses into the system to undergo grafting reaction.

[0071] And combining Figure 7 It can also be seen that within 60 minutes, the content of -NCO groups decreases rapidly as the chain extension reaction time is prolonged, and reaches the theoretical value (the theoretical value is 2.37%) at 60 minutes. After continuing to extend the chain extension time to 90 minutes, the content of -NCO groups no longer changes significantly. This also supports the above-mentioned method of adding MDMH.

[0072] Example 3

[0073] This example has the same settings as Example 1, except that different diisocyanates are used, as shown in Table 3.

[0074] Table 3: Effect of different diisocyanates on nanofiber membranes

[0075] IPDI / g HDI / g TDI / g HMDI / g Tensile breaking strength / cN Tensile breaking elongation / % 16 - - - 535 251 - 16 - - 498 312 - - 16 545 212 - - - 16 556 205 12 4 - - 520 296 8 8 - - 512 306 4 12 - - 501 318 .

[0076] As can be seen from Table 3, under the condition of the same mass of diisocyanate, the tensile breaking strength of the polyurethane nanofiber membrane prepared from HMDI is the largest, but the elongation at break is the smallest, and the tensile breaking strength of the polyurethane nanofiber membrane prepared from HDI is the smallest, but the elongation at break is the largest. It is found in the research that the polyurethane nanofiber membranes prepared from single HMDI and single TDI are easy to break when bending, and the toughness is poor. Table 4 shows that when the mass ratio of IPDI and HDI is 3:1, the tensile breaking strength and elongation at break of the prepared polyurethane nanofiber membrane are moderate, and the toughness when bending is good. This is because IPDI is an alicyclic diisocyanate, and the prepared polyurethane has large rigidity and insufficient toughness. The use of linear diisocyanate with small rigidity improves the tensile elongation and the toughness when bending of the polyurethane nanofiber membrane.

Claims

1. A method for preparing a polyurethane nanofiber membrane, characterized by, Comprising the following steps: (1) Preparation of prepolymer: 20-30 g of polymeric polyol is dehydrated under vacuum for 2-3 h, then 10-20 g of diisocyanate is added, the temperature is raised to 50-60 DEG C, and the reaction is carried out for 50-70 min, then 2-5 drops of dibutyltin dilaurate and 5-10 g of DMF are added, the temperature is raised to 70 DEG C, and the reaction is continued for 60-120 min, then 3-5 g of chain extender and 10-15 g of DMF are added, the temperature is raised to 80-90 DEG C, and the reaction is carried out for 50-70 min, the solid content of the reaction system is controlled to 30-40% by adding DMF, 1-3 g of monomethylol dimethyl hydantoin is added, and the reaction is continued for 50-70 min to obtain a prepolymer of halamine antibacterial monomer grafted polyurethane, and the weight average molecular weight of the prepolymer is 80000-100000, The polymeric polyol is any one of PBA1000, PBA2000 and PBA3000, The diisocyanate is a mixture of isophorone diisocyanate and hexamethylene diisocyanate in a mass ratio of 3:1, The chain extender is one or a mixture of several of ethylene glycol, 1,4-butanediol, hydroquinone dihydroxyethyl ether and resorcinol dihydroxyethyl ether; (2) Preparation of nanofiber membrane: the prepolymer obtained in step (1) is used as raw material to electrospun a nanofiber membrane; (3) Halogenation treatment: at room temperature, the nanofiber membrane obtained in step (2) is immersed in a sodium hypochlorite solution with an effective chlorine content of 2000-3000 ppm for 10-30 min, after the treatment is completed, the nanofiber membrane is taken out, washed with a large amount of deionized water, and dried to obtain a finished polyurethane nanofiber membrane.

2. The method of claim 1, wherein the polyurethane nanofiber membrane is prepared by electrospinning a polyurethane solution. In step (1), 30 g of PBA2000 is added to a reaction device, dehydrated under vacuum for 2 h, then 16 g of diisocyanate is added, the temperature is raised to 55 DEG C, and the reaction is carried out for 50 min, then 2 drops of dibutyltin dilaurate and 5 g of DMF are added, the temperature is raised to 70 DEG C, and the reaction is continued for 80 min, then 4 g of 1,4-butanediol and 10 g of DMF are added, the temperature is raised to 80 DEG C, and the reaction is carried out for 60 min, the solid content of the reaction system is controlled to 36% by adding 74 g of DMF, 2 g of monomethylol dimethyl hydantoin is added, and the reaction is continued for 50 min to obtain a prepolymer of halamine antibacterial monomer grafted polyurethane.

3. The method of claim 1, wherein the polyurethane nanofiber membrane is prepared by electrospinning a polyurethane solution. In step (2), the electrospinning parameters are as follows: spinning temperature 25-30 DEG C, spinning humidity 50-60%, drum receiving distance 10 cm, spinning solution flow rate 0.5-1.0 mL / h, collection rotation speed 300-500 r / min, needle head moving back and forth distance 140 mm, and spinning voltage 15 kV.

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