A polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane and preparation method thereof

Abstract

The present invention belongs to the technical field of separation membrane materials, and particularly relates to a polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane and a preparation method thereof, wherein chloride, nonionic polyurethane and LDH are prepared into a polyurethane / cation-LDHs hybrid by a chemical precipitation method and a solution intercalation method; the polyurethane / cation-LDHs hybrid is then added to a polyolefin polymer material and mixed evenly, and then a pore-forming agent and a plasticizer are added, and a mixture melt A is obtained by heating; finally, at a certain temperature, the mixture melt A is coated and cast on a glass plate, and a film scraper is used to spread evenly, and finally a polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane is obtained. The membrane has the characteristics of high moisture permeability, high porosity, etc., and does not fall off after washing with water. The application of separation membranes in the field of air exchange membranes is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of separation membrane materials, and in particular relates to a polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane and a preparation method thereof. Background Art

[0002] At present, with the popularity of air conditioning, people spend most of their time indoors, so the indoor air quality, especially the increase in carbon dioxide, has an increasing impact on human health and life. As an air conditioning auxiliary device, the total heat exchanger exchanges air and humidity between the incoming fresh air and the exhausted dirty air on the gas-barrier and moisture-permeable membrane, thereby ensuring the oxygen content of the indoor circulating air and increasing the humidity of the indoor air. Among them, the gas-barrier and moisture-permeable membrane is a key component of the total heat exchanger. Many mature products on the market use paper film as the gas-barrier and moisture-permeable membrane, but this membrane has defects such as easy breeding of bacteria and mold, non-flame retardant, poor gas barrier performance and heat exchange performance.

[0003] Currently, the materials used for total heat exchange are mainly paper membrane and polymer membrane. Paper membrane generally has problems such as low gas barrier, easy to mildew during use, and limited lifespan, and is gradually being replaced by polymer membrane in the current market. Compared with paper membrane, polymer membrane has the advantages of being resistant to water washing, not easy to mildew, good gas barrier and long service life, but the moisture permeability of existing polymer membranes is generally poor. Summary of the invention

[0004] The purpose of the present invention is to provide a polyurethane / cation-LDHs hybrid gas barrier and moisture permeable polyolefin film and a preparation method thereof, wherein the gas barrier and moisture permeable film prepared by the method can obtain good water vapor permeability, gas barrier property and water washability. The hybrid film is suitable for fields such as air exchange and food cling film.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane comprises the following steps:

[0007] S1. Add polyurethane, chloride, and LDH to an aqueous solution and stir thoroughly, heat in a water bath at 60-80°C and stir for 1-2h, then add alkaline hydroxide solution dropwise for hydrothermal reaction, filter the precipitate and dry to obtain a polyurethane / cation-LDHs hybrid;

[0008] S2. The polyurethane / cationic-LDHs hybrid obtained in step S1 is added to the polyolefin, and then a pore-forming agent and a plasticizer are added, stirred at 220-250° C. for 1-2 h, and then allowed to stand for 20-40 min to defoam to obtain a solution;

[0009] S3. Cast the melt into a film on the surface of a glass plate at 80-100° C., and spread it evenly using a film scraper to obtain a polyolefin gas-barrier and moisture-permeable film.

[0010] Furthermore, the LDH is a two-dimensional layered double metal hydroxide with a powdery flake diameter of 1-2 μm, and the manufacturer is Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.; the polyurethane is one of anionic polyurethane, cationic polyurethane and non-ionic polyurethane; the chloride is at least one of calcium chloride, lithium chloride, copper chloride, ferric chloride and nickel chloride; the mass ratio of polyurethane: chloride: LDH is 1.2-3:0.5-1.5:5-10, and the total mass concentration of the three substances in the solution is 20-30%.

[0011] Furthermore, in step S1, the alkaline hydroxide is sodium hydroxide or magnesium hydroxide, the mass concentration of the alkaline hydroxide solution is 20-50%, and the mass ratio of chloride:alkaline hydroxide solution is 1:2-5.

[0012] Furthermore, in step S2, the polyolefin is polypropylene or polyethylene; the mass ratio of polyurethane / cationic-LDHs hybrid: polyolefin is 0.5-0.8:1; the pore-forming agent is polyvinyl pyrrolidone (PVP) K30, analytical grade, produced by Shanghai Gongbi Ke; the plasticizer is dibutyl phthalate, analytical grade, produced by Zhejiang Sunrise Fine Chemical Co., Ltd.; wherein the mass ratio of polyvinyl pyrrolidone: dibutyl phthalate: polyolefin is 0.1:0.1:1.

[0013] Another object of the present invention is to provide a polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane prepared by the above method.

[0014] The advantages of the present invention are:

[0015] 1. The LDHs used in the present invention are two-dimensional layered double metal hydroxides, which have a strong adsorption effect. The polyurethane and chloride are adsorbed in the middle of the two-dimensional layer by water bath heating to form a stable complex. The complex runs through the polyolefin membrane and plays a role in pore formation in the process of preparing the polyolefin membrane.

[0016] 2. The polyurethane aqueous binder used in the present invention is in the form of an emulsion in the solution state. After drying, the polyurethane undergoes a cross-linking reaction to form a film and becomes insoluble in water. It will not be carried away by the passage of water vapor during use, and the polyurethane binder penetrates the hybrid body to play a role in plugging holes;

[0017] 3. The chloride in the present invention contains monovalent and divalent metal ions. Such metal ions exist in the diaphragm and have the function of adsorbing water vapor, which greatly improves the water vapor permeability performance of the diaphragm itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a magnified electron microscope image of the polyolefin gas barrier and moisture permeable film prepared in Example 3 of the present invention.

[0019] Figure 2 It is a local magnified electron microscope image of the polyolefin gas barrier and moisture permeable film prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0020] Example 1

[0021] A method for preparing a polyurethane / cation-LDHs hybrid polyolefin gas barrier and moisture permeable film:

[0022] (1) Preparation of polyurethane / cationic-LDHs hybrid: 1.5 g nonionic polyurethane, 0.5 g CaCl2, and 6 g LDH were weighed in sequence and dissolved in 20 g water. The mixture was heated and stirred in a water bath at 60 °C for 1.5 h. Then, 2 g of 30% NaOH solution was added dropwise until the reaction was fully completed. The solid was filtered using filter paper and dried at 100 °C to obtain a polyurethane / Ca-LDHs hybrid.

[0023] (2) Preparation of polyolefin modified membrane: Weigh 80g polyurethane / Ca-LDHs hybrid and 100g polypropylene particles, add 10g PVPK30 and 10g DBP and mix well, heat to 230℃ for dissolution and stirring, let stand for 30min for defoaming, and obtain polyolefin modified solution. After cooling, cast on a glass plate at 80℃ with a scraper to obtain a polyolefin gas barrier and moisture permeable membrane. The prepared polyolefin gas barrier and moisture permeable membrane has a porosity of 82.3%, and the test membrane has an air permeability of 2265 S / 100ml and a water vapor permeability of 3624.6g / m 2 ·day.

[0024] Example 2

[0025] (1) Preparation of polyurethane / cationic-LDHs hybrid: 1.5 g nonionic polyurethane, 0.5 g CaCl2, and 6 g LDH were weighed in sequence and dissolved in 20 g water. The mixture was heated and stirred in a water bath at 60 °C for 1.5 h. Then, 2 g of 30% NaOH solution was added dropwise until the reaction was fully completed. The solid was filtered using filter paper and dried at 100 °C to obtain a polyurethane / Ca-LDHs hybrid.

[0026] (2) Preparation of polyolefin modified membrane: Weigh 60g polyurethane / Ca-LDHs hybrid and 100g polypropylene particles, add 10g PVPK30 and 10g DBP and mix well, heat to 230℃ for dissolution and stirring, let stand for 30min for defoaming, and obtain polyolefin modified solution. After cooling, cast on a glass plate at 80℃ with a scraper to obtain a polyolefin gas barrier and moisture permeable membrane. The prepared polyolefin gas barrier and moisture permeable membrane has a porosity of 61.3%, and the test membrane has an air permeability of 2882.4 S / 100ml and a water vapor permeability of 3416.7 g / m 2 ·day.

[0027] Example 3

[0028] (1) Preparation of polyurethane / cationic-LDHs hybrid: 1.5 g nonionic polyurethane, 1.0 g CaCl2, and 6 g LDH were weighed in sequence and dissolved in 20 g water. The mixture was heated and stirred in a 60°C water bath for 1.5 h. Then, 2 g of 30% NaOH solution was added dropwise until the reaction was fully completed. The solid was filtered using filter paper and dried at 100°C to obtain a polyurethane / Ca-LDHs hybrid.

[0029] (2) Preparation of polyolefin modified membrane: Weigh 80g polyurethane / Ca-LDHs hybrid and 100g polypropylene particles, add 10g PVPK30 and 10g DBP and mix well, heat to 230℃ for dissolution and stirring, let stand for 30min for defoaming, and obtain polyolefin modified solution. After cooling, cast on a glass plate at 80℃ with a scraper to obtain a polyolefin gas barrier and moisture permeable membrane. The prepared polyolefin gas barrier and moisture permeable membrane has a porosity of 83.0%, and the test membrane has an air permeability of 2388.95 S / 100ml and a water vapor permeability of 4203.5g / m 2 ·day.

[0030] Example 4

[0031] (1) Preparation of polyurethane / cationic-LDHs hybrid: 3 g of nonionic polyurethane, 0.5 g of CaCl2, and 6 g of LDH were weighed in sequence and dissolved in 20 g of water. The mixture was heated and stirred in a water bath at 60 °C for 1.5 h. Then, 2 g of 30% NaOH solution was added dropwise until the reaction was fully completed. The solid was filtered using filter paper and dried at 100 °C to obtain a polyurethane / Ca-LDHs hybrid.

[0032] (2) Preparation of polyolefin modified membrane: Weigh 60g polyurethane / Ca-LDHs hybrid and 100g polypropylene particles, add 10g PVPK30 and 10g DBP and mix well, heat to 230℃ for dissolution and stirring, stand for 30min for defoaming, and obtain polyolefin modified solution. After cooling, cast on a glass plate at 80℃ with a scraper to obtain a polyolefin gas barrier and moisture permeable membrane. The prepared polyolefin gas barrier and moisture permeable membrane has a porosity of 60.4%, and the test membrane has an air permeability of 4436.65 S / 100ml and a water vapor permeability of 3367.2 g / m 2 ·day.

[0033] Comparative Example 1

[0034] The polyolefin gas barrier and moisture permeable membrane prepared by removing CaCl2 on the basis of Example 1 has a porosity of 82.2%, a test membrane air permeability of 2200.55 S / 100ml and a water vapor permeability of 2505.4 g / m 2 ·day.

[0035] Comparative Example 2

[0036] The porosity of the prepared polyolefin gas barrier and moisture permeable film was 63.4% by removing the nonionic polyurethane on the basis of Example 2. The air permeability of the tested film was 374.6 S / 100ml and the water vapor transmission rate was 3216 g / m 2 ·day; Verify the pore-blocking effect of polyurethane glue and its water-resistant effect. After the polyurethane is dried and formed into a film, water vapor cannot take it away.

[0037] Comparative Example 3

[0038] Based on Example 3, the LDH two-dimensional layered double metal hydroxide was removed, and the porosity of the prepared polyolefin gas barrier and moisture permeable membrane was 43.9%. The tested membrane air permeability was 766.8 S / 100ml and the water vapor transmission rate was 1631 g / m 2 ·day.

[0039] Comparative Example 4

[0040] The preparation steps of the hybrid were removed from Example 4, and polypropylene was directly prepared into a film. The porosity of the prepared polyolefin gas barrier and moisture permeable film was 45.2%, and the air permeability and water vapor transmission rate of the tested film were 544.3 S / 100ml and 1462 g / m 2 ·day.

[0041] Comparative Example 5

[0042] On the basis of Example 4, calcium chloride and polyurethane were removed, and only LDH was added, and then a film was prepared with polypropylene. The porosity of the prepared polyolefin gas barrier and moisture permeable film was 64.9%, and the air permeability of the tested film was 340.05S / 100ml and the water vapor permeability was 2256g / m 2 ·day.

[0043] Performance Analysis

[0044] The porosity test process was carried out according to GB / T 24218.1-2009, and the data results are shown in Table 1.

[0045] The water vapor transmission rate test was carried out according to GB / T 1037-1988. The test temperature was 38°C and the humidity of the permeable surface was 29%. The water vapor transmission rate (g / m 2 ·day), the data results are shown in Table 2.

[0046] The gas barrier performance test was carried out according to GB / T 458-2008. The time required for 100 ml of the same gas to pass through the same area of ​​the tested film was measured, and the air permeability was obtained as S / 100 ml. The data results are shown in Table 2.

[0047]

[0048] Conclusion Analysis: Porosity table shows: The content of the hybrid directly affects the porosity of the diaphragm.

[0049] Compared with Example 1 and Example 3, the variable is the increase of calcium chloride, and calcium chloride has little effect on porosity, so the porosity of the two is not much different. Compared with Examples 1 and 3, Examples 2 and 4 reduce the content of the hybrid, and the hybrid plays a pore-forming role, so reducing the content will reduce the porosity. The porosity of Example 4 is reduced relative to Example 2. The variable is that the polyurethane content in Example 4 increases, and polyurethane has a pore-blocking effect, so the porosity of Example 4 is reduced relative to Example 2. Calcium chloride is not added in Comparative Example 1, and calcium chloride does not work on pore formation, so the porosity of Comparative Example 1 does not change much relative to Example 1. Comparative Example 2 does not add polyurethane relative to Example 2, and polyurethane has a pore-blocking effect, so the porosity of Comparative Example 2 is improved relative to Example 2.

[0050] Comparative Example 3 does not add LDH relative to Example 3, and LDH mainly plays a role in pore formation, so the porosity in Comparative Example 3 is greatly reduced; Comparative Example 4 does not add a hybrid relative to Example 4, but Comparative Example 4 adds less polyurethane relative to Comparative Example 3, so the porosity of Comparative Example 4 is increased relative to Comparative Example 3. Comparative Example 5 only adds LDH relative to Example 4, and does not have polyurethane, so Comparative Example 5 has a higher porosity than Examples 2 and 4.

[0051]

[0052] The data in Table 2 are as follows: High air permeability indicates serious pore blocking, because the time required for the same volume of gas to pass through the same area of ​​the membrane represents the characterization of air permeability. Example 1 and Example 3 compare the increased amount of calcium chloride content. Calcium chloride has super hygroscopicity, so Example 3 has a larger water vapor permeability than Example 1, the calcium chloride content is increased, and the pores are slightly blocked. Example 3 has an increased air permeability than Example 1. Example 4 increases the amount of polyurethane content relative to Example 2, and polyurethane has a pore blocking effect, so Example 4 has a much higher air permeability than Example 2. Examples 1 and 3 have a higher content of hybrids relative to Examples 2 and 4, and a larger porosity, so Examples 1 and 3 have a larger overall water vapor permeability relative to Examples 2 and 4. Comparative Example 1 does not add calcium chloride relative to Example 1, and calcium chloride has super hygroscopicity, so the water vapor permeability of Comparative Example 1 decreases significantly relative to Example 1. Comparative Example 2 does not add polyurethane relative to Example 2, and polyurethane has a pore blocking effect, so the air permeability in Comparative Example 2 is reduced more. Comparative Example 3 does not add LDHs relative to Example 3. LDHs mainly play a pore-forming role. The porosity of Comparative Example 3 is lower than that of Comparative Example 2, so the air permeability of Comparative Example 3 is greater than that of Comparative Example 2. The porosity of Comparative Example 2 is greater than that of Comparative Example 3, so the water vapor permeability of Comparative Example 2 is greater. Comparative Example 4 does not add a hybrid relative to Example 4, and the hybrid has a pore-forming effect, so Comparative Example 4 has better air permeability and reduced moisture permeability relative to Example 4. Comparative Example 4 does not have calcium chloride and polyurethane relative to Comparative Example 3, so Comparative Example 4 has lower air permeability and reduced moisture permeability. Comparative Example 5 only adds LDHs relative to Example 4, and does not have polyurethane and calcium chloride, so Comparative Example 5 has a higher porosity than Comparative Examples 2 and 4. Therefore, the air permeability of Comparative Example 5 is smaller than that of Comparative Examples 2 and 4, and the porosity of Comparative Example 5 is smaller than that of Comparative Example 1, and the moisture permeability of Comparative Example 5 is smaller than that of Comparative Example 1.

Claims

1. A method for preparing a polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane, characterized in that: The following steps are involved: S1. Add polyurethane, chloride and LDH to aqueous solution and stir thoroughly, heat in a water bath at 60-80°C and stir for 1-2h, then add alkaline hydroxide solution dropwise for hydrothermal reaction, filter the precipitate and dry to obtain polyurethane / cation-LDHs hybrid; the LDH is a two-dimensional layered double metal hydroxide with a powdery flake diameter of 1-2μm; the polyurethane is one of anionic polyurethane, cationic polyurethane and non-ionic polyurethane; the chloride is at least one of calcium chloride, lithium chloride, copper chloride, ferric chloride and nickel chloride; the mass ratio of polyurethane: chloride: LDH is 1.2-3:0.5-1.5:5-10, and the total mass concentration of the three substances in the solution is 20-30%; S2. The polyurethane / cationic-LDHs hybrid obtained in step S1 is added to the polyolefin, and then a pore-forming agent and a plasticizer are added, stirred at 220-250° C. for 1-2 h, and then allowed to stand for 20-40 min to defoam to obtain a solution; S3. Cast the melt into a film on the surface of a glass plate at 80-100° C., and spread it evenly using a film scraper to obtain a polyolefin gas-barrier and moisture-permeable film.

2. The method for preparing the polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane according to claim 1, characterized in that: In step S1, the alkaline hydroxide is sodium hydroxide or magnesium hydroxide, the mass concentration of the alkaline hydroxide solution is 20-50%, and the mass ratio of chloride:alkaline hydroxide solution is 1:2-5.

3. The method for preparing the polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane according to claim 1, characterized in that: In step S2, the polyolefin is polypropylene or polyethylene; the mass ratio of polyurethane / cationic-LDHs hybrid: polyolefin is 0.5-0.8:1; the pore-forming agent is polyvinyl pyrrolidone, the plasticizer is dibutyl phthalate, and the mass ratio of polyvinyl pyrrolidone: dibutyl phthalate: polyolefin is 0.1:0.1:

1.

4. A polyurethane / cation-LDHs hybrid gas-barrier and moisture-permeable polyolefin membrane prepared according to any one of claims 1 to 3.

Images