A selectively permeable membrane composite for chemical protective clothing and a method of making the same

Abstract

The application discloses a kind of selective permeation membrane composite material for chemical protective clothing and its preparation method, belong to chemical protective clothing technical field.Functional monomer is grafted on polyvinylidene fluoride main chain by one-pot method, then it is compounded with fabric outer layer, and composite material is formed.The method is simple in preparation process, low in cost, solves the shortcomings, such as high cost and poor mechanical properties, of traditional Nafion and polystyrene sulfonic acid (PSSA) and other materials used for chemical protective clothing, and the obtained composite material has excellent selective permeability and good mechanical properties, and can be widely used for selective permeation type chemical protective clothing material, which provides guarantee for realizing reliable protection performance and good physiological comfort of chemical protective clothing.

Description

Technical Field

[0001] This invention discloses a selectively permeable membrane composite material that can be used in chemical protective clothing and its preparation method, belonging to the field of chemical protective clothing technology. Background Technology

[0002] Chemical protective clothing (CPC) protects human skin from harmful chemicals. Traditional CPC is typically based on insulating materials such as butyl rubber and halogenated butyl rubber. These materials can completely block all vapor and liquid permeability. However, this type of clothing also blocks vapor transmission, easily causing heat buildup in the wearer, which can lead to dehydration, fainting, or even death in severe cases. On the other hand, absorbent fabrics with activated carbon adsorbents have also been used for chemical protection. While they offer better physiological comfort, they still have drawbacks such as limited adsorbent capacity, high weight, and secondary pollution caused by desorption. Ideally, CPC should block CWA while allowing water vapor to pass through. Currently, an ideal water vapor permeability of 1500-2000 g m³ is generally considered ideal for chemical protective clothing. -2 24h -1 An ideal protective suit should have reliable protective capabilities and an ideal water vapor transmission rate.

[0003] The literature Journal of Membrane Science, 2010, 362(1-2): 137 reported a polystyrene sulfonic acid (PSSA) membrane material with good selective permeability, but with poor mechanical properties.

[0004] The literature Journal of Physical Chemistry B, 2004, 108(26): 8900 studied the selective permeability of commercial perfluorosulfonic acid membrane Nafion, indicating that Nafion has the potential to be used in chemical protective clothing. The disadvantage is that Nafion material is expensive. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as poor mechanical properties and high costs, and to provide a selectively permeable membrane composite material for use in protective clothing and its preparation method. This material consists of an outer fabric layer and an inner selectively permeable membrane layer. Post-treatment of the fabric material improves its hydrophobic, oil-repellent, and abrasion-resistant properties. Polyvinylidene fluoride (PVDF) enhances the material's mechanical strength and ability to block toxic substances. The introduction of functional groups improves the material's water vapor permeability and enhances its physiological comfort. Furthermore, this material is prepared using a one-pot method, which is simple and inexpensive.

[0006] The technical solution adopted by the present invention to solve the above-mentioned shortcomings is: the selective permeable membrane composite material for chemical protective clothing is made of fabric as the outer layer and selective permeable membrane as the inner layer by casting coating;

[0007] The fabric is made of one or more of the following pure or blended fibers: aramid 1313, aramid sulfone, polybenzimidazole, and acrylonitrile chlorofiber, and is finished with perfluorooctyl sulfonyl derivatives, perfluorooctanoic acid compounds, fluorinated polyethers, and organosilicon.

[0008] Selective permeable membranes are composed of a polyvinylidene fluoride backbone and side chains polymerized from grafted functional monomers. The functional monomers include cationic monomers such as sodium styrene sulfonate and acrylic acid, and the counterions include cationic monomers such as hydrogen ions, sodium ions, calcium ions, and iron ions.

[0009] The selected permeable membrane composite material can provide protection against chemical agents, with an aerosol filtration efficiency >99.99%, a protection time of >48 hours against mustard gas / liquid gas, a protection time of >10 hours against soman gas / liquid gas, and a moisture permeability >3000 g / m³. -2 24h -1 .

[0010] The preparation method of the selectively permeable membrane composite material for chemical protective clothing of the present invention comprises the following steps:

[0011] Step 1: Add polyvinylidene fluoride (PVDF) to N,N-dimethylformamide (DMF) and stir to dissolve;

[0012] Step 2: Add tetramethylammonium hydroxide methanol solution (TMAH) to the above PVDF DMF solution and stir for 1.5 h. The concentration of TMAH methanol solution is 1-20 wt%.

[0013] Step 3: Dissolve functional monomers such as sodium polystyrene sulfonate (SSS) or acrylic acid in the above polymer solution;

[0014] Step 4: Add divinylbenzene (DVB) and 2,2-azobis(2-methylpropionitrile) (AIBN) to the polymer solution obtained in Step 3. The amount of DVB is equivalent to 5-20 wt% of the amount of sodium polystyrene sulfonate (SSS), and the amount of AIBN is equivalent to 0.1-5 wt% of the amount of sodium polystyrene sulfonate (SSS).

[0015] Step 5: Heat the polymer solution obtained in Step 4 to 60-90°C under nitrogen protection and maintain it for 6-24 hours. After the reaction is terminated, the inner layer coating solution of the selectively permeable membrane is obtained.

[0016] Step 6: The prepared inner layer coating liquid is evenly coated on the inner surface of the outer layer of the fabric and dried at 50-100℃ to obtain the selective permeable membrane composite material.

[0017] Step 7: Immerse the prepared composite materials in 0.2–2 mol L solutions. -1 Selective permeable membrane composites with cation substitution were obtained in aqueous solutions of HCl, NaCl, CaCl2, and FeCl3.

[0018] The chemical reaction equation for the preparation of the coating solution is shown below:

[0019] (a)

[0020] (b)

[0021] The specific process is as follows:

[0022] 1. Preparation of the outer layer of the fabric

[0023] The flame-retardant fibers are aramid 1313, aramid sulfone, polybenzimidazole or acrylonitrile chlorofiber, and the fibers are pure or blended.

[0024] The finishing process involves impregnating the fabric with a finishing solution containing oil- and water-repellent components and a crosslinking agent, followed by drying and baking. The impregnation rate is 30-90%, the baking temperature is 130-200℃, and the baking time is 0.5-5 minutes. The water- and oil-repellent component is an organic fluorine water- and oil-repellent finishing agent, used at a dosage of 30-150 g / L; the crosslinking agent is one or more of DMDHEU, hexamethylol melamine, epoxy resin, ethylene glycol acetal, and dihydroxyethyl sulfone, used at a dosage of 5-50 g / L.

[0025] 2. Selective synthesis of polymers

[0026] A one-pot reaction of polyvinylidene fluoride (PVDF) modified with sodium styrene sulfonate (SSS), acrylic acid, etc., was used to synthesize a selectively permeable membrane coating solution. First, PVDF was dissolved in a certain amount of dimethylformamide (DMF). Under a nitrogen atmosphere, a methanol solution of tetramethylammonium hydroxide was added, and the reaction was allowed to proceed for 1 hour to complete the PVDF modification. Then, different amounts of functional monomers were dissolved in the above solution to obtain adjustable ion exchange capacity (IEC) values. After all the monomers were dissolved, crosslinking agents such as divinylbenzene (DVB) were added at 10% of the monomer mass, and initiators such as azobisisobutyronitrile (AIBN) were added at 1% of the monomer mass. The temperature was raised to 60–80 °C to carry out a free radical polymerization reaction. The reaction was terminated after 8–24 hours, yielding the selectively permeable membrane coating solution.

[0027] 3. Preparation of Selective Permeable Membrane Composites

[0028] The coating solution is uniformly coated on the inner surface of the outer layer of the fabric. The thickness of the membrane material is controlled by adjusting the distance between the coating roller and the outer layer of the fabric. The preferred thickness is 30-200 μm. The membrane is then dried at 60-90°C to obtain a selectively permeable membrane composite material. This composite material can be soaked in aqueous solutions of different salts such as NaCl, CaCl2, and FeCl3 to obtain membrane materials with different cation exchange rates.

[0029] The beneficial effects of this invention are as follows: 1. The protective material has good protective performance, with an aerosol filtration efficiency of >99.99%, a mustard gas-liquid gas protection time of >48h, and a soman gas-liquid gas protection time of >10h.

[0030] 2. While possessing excellent nuclear, biological, and chemical protective performance, it also exhibits good moisture permeability, with a moisture permeability >3000gm. -2 24h -1 Sweat vapor can pass through well, overcoming the "heat accumulation" phenomenon of existing insulating protective materials and improving thermal and humid physiological comfort.

[0031] 3. This method can be used to prepare selectively permeable membrane composite protective materials. The process is simple and low-cost, with a manufacturing cost of <120 RMB / m². -2 It has significant economic and social benefits. Attached Figure Description

[0032] Figure 1 Selecting permeable membrane composite protective materials using FT-IR spectra

[0033] In the figure: (a) is the FT-IR spectrum of PVDF, (b) is the FT-IR spectrum of modified PVDF, and (c) is the FT-IR spectrum of PVDF-g-SSS;

[0034] The vertical axis represents transmittance in au; the horizontal axis represents wavenumber in cm. -1 .

[0035] Figure 2 Select SEM images through the inner layer of the membrane

[0036] In the figure: (a) is the surface view of the selected transmission layer, and (b) is the cross-sectional view of the selected transmission layer. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0038] Example 1

[0039] PVDF (20g) was dissolved in DMF. The mixture was then stirred at 50°C to obtain a homogeneous, transparent solution. Under a nitrogen atmosphere, 1.0 ml of a methanol solution of tetramethylammonium hydroxide was added, and the PVDF solution was stirred at 50°C for 1.5 h. Subsequently, 16g of sodium styrene sulfonate (SSS) was dissolved in the above solution at 50°C. Then, DVB crosslinking agent (10 wt% relative to SSS) and AIBN initiator (1 wt% relative to SSS) were added. The resulting solution was reacted at 80°C for 8 h to obtain a polymer coating solution. The coating solution was uniformly coated onto a post-finished acrylonitrile chlorofiber outer fabric and dried at 70°C for 8 h to obtain a composite membrane material.

[0040] like Figure 1 FT-IR spectra of PVDF, (b) modified PVDF, and (c) PVDF-g-SSS. Compared with pure PVDF (a), PVDF (b) treated with TMAH showed significantly higher FT-IR spectra at 1610 cm⁻¹. -1 A new band appears at 1007 and 1034 cm⁻¹, representing the stretching vibration of the carbon-carbon double bond, indicating that TMAH eliminates HF and generates active sites for the carbon-carbon double bond. In the FTIR spectrum of the PVDF-g-SSS film, new bands appear at 1007 and 1034 cm⁻¹. -1 The absorption band at the point represents the symmetric stretching vibration of sulfonate, indicating that SSS has been successfully grafted onto the PVDF framework.

[0041] like Figure 2 As shown, a is a SEM image selected through the surface of the inner layer of the membrane, and b is a SEM image selected through the cross section of the inner layer of the membrane. The SEM images clearly show that the membrane has a uniform, dense, and non-porous morphology.

[0042] Selective permeability testing of the composite membrane material was performed as follows: After drying at 60°C for 24 hours, the sample to be tested was placed on top of an open test bottle containing 20 ml of permeate (water, DMMP, or CEPS) and fixed in place to form a permeation cell. The material thickness was measured using digital calipers. The obtained permeation cell was placed in an environmental test chamber at 35°C and 10% RH, and weighed at regular intervals. After the weight loss (W) became constant, it was calculated based on the slope of the weight-time curve obtained by measuring the weight of the permeation cell. The vapor transfer rate (gm³) was then determined. -2 24h -1 (VTR) and vapor permeability (VP, mol m) -1 s -1 The selectivity is calculated using Equations 1 and 2. The ratio of water to DMMP or CEPS vapor is defined as the selectivity and is calculated using Equation 6. Three parallel tests were performed on each membrane to ensure the accuracy of the results.

[0043] VTR=W / (t×A) (1)

[0044] VP=VTR×L (2)

[0045] S = VP water / VP simulants (3)

[0046] At time t, A is the area of ​​the sample to be tested, and L is the thickness of the sample.

[0047] The selectivity and permeability of the composite membrane materials are shown in the table below.

[0048] Table 1. VTR, VP, and membrane selectivity of water and DMMP

[0049]

[0050] The mustard gas-liquid-gas protection time was determined according to GJB535. The composite membrane material and chloramine-Congo red indicator paper were fixed on the test cell. 32 μL of mustard gas-liquid was dropped onto the surface of the composite membrane material and timing was started. Timing was stopped and the time was recorded when the Congo red indicator paper turned blue. The composite membrane material provides mustard gas-liquid-gas protection for >48 hours.

[0051] The water permeability of the composite material was tested using a fabric permeability tester, and the results showed that its hydrostatic pressure was >200 kPa.

[0052] The aerosol protection performance of the composite material was tested using the DOP method, and the results showed that its filtration efficiency was >99.99%.

[0053] An 8-hour hot air aging test was conducted on the composite material at 140℃, and the results showed that the material was neither sticky nor brittle.

[0054] Example 2

[0055] The composite material obtained in Example 1 was immersed in 0.5 mol L... -1 In aqueous solutions of NaCl, CaCl2, FeCl3, etc., cation-substituted composite materials were obtained. The substitution of high-valence ions such as calcium and iron increases the density of the membrane structure, reduces the permeability of the membrane material to water and poisons, and improves the selectivity of the membrane material.

[0056] Ca 2+ The replacement composite material showed approximately 50% improved selectivity for water / DMMP compared to the Na ion-replaced composite material.

Claims

1. A selectively permeable membrane composite for use in chemical protective clothing, characterized in that, The selective permeation membrane composite material for chemical protective clothing is composed of a fabric as an outer layer and a selective permeation membrane as an inner layer by flow coating compounding; The fabric is composed of one or more than one of aramid 1313, polysulfide, polybenzimidazole and cyanochloron, and is finished by perfluorooctyl sulfonate derivative, perfluorooctanoic acid compound, fluorine-containing polyether and silicone; The selective permeation membrane preparation method comprises the following steps: Step one, polyvinylidene fluoride (PVDF) is added to N,N-dimethylformamide (DMF) and stirred to dissolve; Step two, tetramethylammonium hydroxide (TMAH) methanol solution is added to the PVDF DMF solution, and stirred to react for 1.5 hours, the concentration of the TMAH methanol solution is 1-20wt%; Step three, styrene sulfonic acid sodium or acrylic functional monomer is dissolved in the polymer solution, the molar amount of the styrene sulfonic acid sodium or acrylic monomer is 18%-36% of the number of PVDF units; Step four, divinylbenzene (DVB) and 2,2-azobis(2-methylpropionitrile) (AIBN) are added to the polymer solution obtained in step three, the amount of DVB is 5-20wt% of the amount of styrene sulfonic acid sodium, and the amount of AIBN is 0.1-5wt% of the amount of styrene sulfonic acid sodium; Step five, the polymer solution obtained in step four is heated to 60-90℃ under nitrogen protection for 6-24 hours, and the coating solution of the inner layer of the selective permeation membrane is obtained after the reaction is terminated; Step six, the prepared inner layer coating solution is uniformly coated on the inner surface of the outer layer of the fabric, and is dried at 50-100℃ to obtain the selective permeation membrane composite material. Step seven, the prepared composite material is respectively immersed in 0.2-2 mol / L aqueous solution of HCl, NaCl, CaCl2 and FeCl3, and a cation-substituted selective permeation membrane composite material is obtained. -1 Step seven, the prepared composite material is respectively immersed in 0.2-2 mol / L aqueous solution of HCl, NaCl, CaCl2 and FeCl3, and a cation-substituted selective permeation membrane composite material is obtained. The selected permeation membrane composite material can prevent chemical toxicants, the aerosol filtration efficiency is >99.99%, the gas protection time for mustard gas liquid is >48h, the gas protection time for soman liquid is >10h, and the moisture permeation amount is >3000gm -2 24h -1 .

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