Modified cellulose nanocrystal filled silicone rubber composite separation membrane and preparation method thereof

Abstract

The application discloses a modified cellulose nanocrystal filled silicone rubber composite separation membrane and a preparation method thereof. The composite separation membrane comprises a base film and a separation layer attached to the base film, and the separation layer is composed of a crosslinked product of hydroxyl-terminated methylphenyl silicone oil and octyltrimethoxysilane, and modified cellulose nanocrystal. The hydroxyl-terminated methylphenyl silicone oil, the octyltrimethoxysilane and an organic tin catalyst are dissolved in an organic solvent, and after stirring and reaction, the modified cellulose nanocrystal is added, and after intense stirring, a casting solution is obtained; a layer of the casting solution is coated on the surface of the base film, and after solidification, the modified cellulose nanocrystal filled silicone rubber composite separation membrane is prepared. According to the measurement at 25 DEG C, the O2 and N2 permeation and separation performance of the silicone rubber composite membrane is respectively J N2 > 0.25 m 3 ·m ‑2 ·atm ‑1 ·h ‑1 , and alpha (O2 / N2) > 2.3, and the gas permeability is good.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of composite film preparation, in particular to a modified cellulose nanocrystal filled silicone rubber composite separation film and a preparation method thereof. BACKGROUND

[0002] Membrane gas separation technology refers to a technology for separating or enriching a certain component in a mixed gas under the driving of a pressure difference by using a polymer membrane. The technology has the characteristics of no pollution, low energy consumption, high separation efficiency, small equipment volume, and arbitrary change of scale and processing capacity, and has shown an attractive application prospect in industrial production, environmental protection, biological materials and the like.

[0003] A polymer membrane is the core of the membrane gas separation process, and it is of great significance to develop a high-performance gas separation membrane. A composite membrane refers to an asymmetric membrane with different materials of a base membrane and a separation layer. Generally, the base membrane only plays a mechanical supporting role, and separation is mainly completed by the material compounded on the base membrane. Therefore, the composite membrane is generally prepared by first preparing the base membrane and then preparing the separation layer on the base membrane by a solution coating method or the like. Silicone rubber is a polymer membrane material with the highest permeability since it is applied in industry, and is commonly used as the separation layer of the composite membrane. At present, the silicone rubber composite membrane has been widely applied, and how to further improve the performance of the silicone rubber separation membrane has become a research hotspot in the application field of the silicone rubber. SUMMARY

[0004] The application provides a modified cellulose nanocrystal filled silicone rubber composite separation film and a preparation method thereof to solve the above technical problems.

[0005] In a first aspect, the application provides a modified cellulose nanocrystal filled silicone rubber composite separation film, which is realized by the following technical scheme.

[0006] The modified cellulose nanocrystal filled silicone rubber composite separation film comprises a base membrane and a separation layer attached to the base membrane, and the separation layer is composed of a crosslinked product of hydroxyl-terminated methylphenyl silicone oil and octyltrimethoxysilane and modified cellulose nanocrystals.

[0007] Further, the base membrane is a polymer membrane, and the polymer membrane is selected from one of a polysulfone membrane, a cellulose acetate membrane, a polyimide membrane, a polyetherimide membrane, a polyacrylamide membrane and a polypropylene ultrafiltration membrane.

[0008] Further, the base membrane is a flat membrane.

[0009] Further, the modified cellulose nanocrystals are phenyldimethylchlorosilane modified cellulose nanocrystals, and the size of the modified cellulose nanocrystals is 5-20 nm.

[0010] In a second aspect, the application provides a preparation method of a modified cellulose nanocrystal filled silicone rubber composite separation membrane.

[0011] The preparation method of the modified cellulose nanocrystal filled silicone rubber composite separation membrane comprises the following steps:

[0012] S1. Dissolve hydroxyl-terminated methylphenyl silicone oil, octyltrimethoxysilane and organic tin catalyst in an organic solvent; the mass of the hydroxyl-terminated methylphenyl silicone oil accounts for 3-5% of the total mass of the casting solution, the mass ratio of the octyltrimethoxysilane to the hydroxyl-terminated methylphenyl silicone oil is (1-2):5, and the mass of the organic tin catalyst is 4‰-1% of the mass of the hydroxyl-terminated methylphenyl silicone oil;

[0013] S2. After stirring at room temperature for 3-5 hours, add modified cellulose nanocrystals, which account for 0.2%-1% of the total mass of the casting solution, and then stir vigorously at room temperature for 1-3 hours to obtain the casting solution;

[0014] S3. Coat the casting solution obtained in step S2 on the surface of a base film, and then solidify at 60-90℃ to obtain the modified cellulose nanocrystal filled silicone rubber composite separation membrane.

[0015] By using the above technical scheme, the separation selectivity of the silicone rubber is closely related to the internal free volume, and the selectivity can be improved or the gas flux can be increased to a certain extent by changing the free volume of the silicone rubber. In the application, the cellulose nanocrystals are modified by silanization, which not only improves the solubility of the cellulose nanocrystals in non-polar solvents and the compatibility with the siloxane molecular chain, but also increases the binding force between the cellulose nanocrystals and the siloxane macromolecule due to the π bond conjugated system formed by the aromatic rings carried by the modifier and the aromatic rings contained in the silicone rubber. The silicone rubber forms a network structure by chemical crosslinking, and there are a large number of holes, i.e. free volume, between the molecular chains. After the addition of the cellulose nanocrystals, the nanocrystals are distributed in the silicone rubber and enter the gaps between the chains to occupy the free volume, so that the free volume of the silicone rubber is reduced and the separation selectivity of the silicone rubber separation layer is improved.

[0016] Further, in step S1, the mass ratio of the methyl groups to the phenyl groups in the hydroxyl-terminated methylphenyl silicone oil is 1:1.

[0017] Further, in step S1, the viscosity of the hydroxyl-terminated methylphenyl silicone oil is 1000-3000cst.

[0018] Further, in step S1, the organic tin catalyst is selected from dibutyltin dilaurate or dioctyltin dilaurate.

[0019] Further, in step S1, the organic solvent is selected from one or more of gasoline, n-hexane, cyclohexane, n-heptane, n-octane, iso-octane or petroleum ether.

[0020] Further, in step S2, the hydroxyl-terminated methylphenyl silicone oil, octyl trimethoxysilane and organic tin catalyst are dissolved in the organic solvent and stirred at room temperature, and the stirring speed is 600 r / min.

[0021] Further, in step S2, the stirring speed after adding the modified cellulose nanocrystals is 1000 r / min.

[0022] Further, in step S3, the curing time is 90 min.

[0023] The present application has the following beneficial effects.

[0024] The present application uses hydroxyl-terminated methylphenyl silicone oil as a base polymer, octyl trimethoxysilane as a crosslinking agent, and modified cellulose nanocrystals as a filler to prepare a silicone rubber composite separation membrane. By adjusting the polymer density and structure, the selectivity of the prepared silicone rubber separation layer is improved. The prepared silicone rubber composite membrane can be used in the fields of oxygen and nitrogen separation, recovery of organic vapors such as ethylene, propylene, gasoline, and osmotic gasification. DETAILED DESCRIPTION

[0025] The present application is further described below in conjunction with examples.

[0026] In the following examples, the experimental methods used are conventional methods unless otherwise specified. In the following preparation examples and examples, the materials, reagents, etc. used are commercially available unless otherwise specified.

[0027] The hydroxyl-terminated methylphenyl silicone oil used in the following examples of the present application is purchased from Guangzhou Jiahao Chemical Technology Co., Ltd.

[0028] Preparation Example

[0029] The preparation method of the modified cellulose nanocrystals is as follows:

[0030] 4g of cellulose nanocrystals is dried at 105℃ to a constant weight and then placed in a flask, 96mL of dimethylbenzene is added to obtain a mixed suspension, 0.8g of phenyldimethylchlorosilane is added under the condition of stirring at a speed of 600r / min, and the reaction is carried out at 25℃ for 6h. After the reaction is completed, the reaction liquid is filtered, and the filter cake is vacuum dried at 25℃. The powder obtained after drying is the modified cellulose nanocrystals.

[0031] Example 1

[0032] A preparation method of a modified cellulose nanocrystal-filled silicone rubber composite separation membrane includes the following steps:

[0033] hydroxymethylphenyl silicone oil 1000cst 0.3kg, octyl trimethoxysilane 60g, dibutyltin dilaurate 3g, were dissolved in 9.62kg of gasoline 120# solvent oil; after stirring at 25℃ for 4 hours at 600r / min, 20g of modified cellulose nanocrystals were added, and a casting solution was obtained after stirring at 25℃ for 2 hours at 1000r / min. A layer of the casting solution was coated on the surface of a polysulfone base film (pure water flux 16.5L / (m 2 h), molecular weight cut-off 30000), and dried at 80℃ for 4 hours.

[0034] Example 2

[0035] A preparation method of a modified cellulose nanocrystal-filled silicone rubber composite separation membrane, comprising the following steps:

[0036] hydroxymethylphenyl silicone oil 1500cst 0.4kg, octyl trimethoxysilane 160g, and dibutyltin dilaurate 1.6g, were dissolved in 9.4kg of n-hexane; after stirring at 25℃ for 4 hours at 600r / min, 40g of modified cellulose nanocrystals were added, and a casting solution was obtained after stirring at 25℃ for 2 hours at 1000r / min. A layer of the casting solution was coated on the surface of a polyetherimide base film (pure water flux 14.5L / (m 2 h), molecular weight cut-off 45000), and dried at 90℃ for 2 hours.

[0037] Example 3

[0038] A preparation method of a modified cellulose nanocrystal-filled silicone rubber composite separation membrane, comprising the following steps:

[0039] hydroxymethylphenyl silicone oil 2500cst 0.5kg, octyl trimethoxysilane 150g, and dioctyltin dilaurate 4g, were dissolved in 9.29kg of isooctane; after stirring at 25℃ for 4 hours at 600r / min, 60g of modified cellulose nanocrystals were added, and a casting solution was obtained after stirring at 25℃ for 2 hours at 1000r / min. A layer of the casting solution was coated on the surface of a polyacrylamide base film (pure water flux 20.1L / (m 2 h), molecular weight cut-off 60000), and dried at 80℃ for 2 hours.

[0040] Example 4

[0041] A preparation method of a modified cellulose nanocrystal-filled silicone rubber composite separation membrane, comprising the following steps:

[0042] hydroxymethylphenyl silicone oil 3000cst 0.5kg, octyltrimethoxysilane 100g, and dibutyltin dilaurate 5g were dissolved in 9.32kg of n-heptane; after stirring at 25°C for 4 hours at 600r / min, 80g of modified cellulose nanocrystals were added, and after stirring at 25°C for 2 hours at 1000r / min, a casting solution was obtained. A layer of the casting solution was coated on the surface of a polyimide base film (pure water flux 12.4L / (m 2 h), molecular weight cut-off 25000), and dried at 80°C for 3 hours.

[0043] Example 5

[0044] A method for preparing a modified cellulose nanocrystal-filled silicone rubber composite separation membrane, comprising the following steps:

[0045] hydroxymethylphenyl silicone oil 1500cst 0.3kg, octyltrimethoxysilane 120g, and dibutyltin dilaurate 1.2g were dissolved in 9.48kg of cyclohexane; after stirring at 25°C for 4 hours at 600r / min, 100g of modified cellulose nanocrystals were added, and after stirring at 25°C for 2 hours at 1000r / min, a casting solution was obtained. A layer of the casting solution was coated on the surface of a polypropylene base film (pure water flux 12.4L / (m 2 h), molecular weight cut-off 25000), and dried at 70°C for 4 hours.

[0046] Example 6

[0047] A method for preparing a modified cellulose nanocrystal-filled silicone rubber composite separation membrane, comprising the following steps:

[0048] hydroxymethylphenyl silicone oil 1000cst 0.4kg, octyltrimethoxysilane 80g, and dibutyltin dilaurate 3.2g were dissolved in 9.44kg of n-octane; after stirring at 25°C for 4 hours at 600r / min, 80g of modified cellulose nanocrystals were added, and after stirring at 25°C for 2 hours at 1000r / min, a casting solution was obtained. A layer of the casting solution was coated on the surface of a cellulose acetate base film (pure water flux 30.5L / (m 2 h), molecular weight cut-off 65000), and dried at 90°C for 1 hour.

[0049] Example 7

[0050] A method for preparing a modified cellulose nanocrystal-filled silicone rubber composite separation membrane, comprising the following steps:

[0051] Hydroxyl-terminated methylphenyl silicone oil 3000cst 0.5kg, octyl trimethoxysilane 150g, and dibutyltin dilaurate 2g were dissolved in 9.29kg of petroleum ether; after stirring at 600r / min at 25℃ for 4 hours, 60g of modified cellulose nanocrystals were added, and a casting solution was obtained after stirring at 1000r / min at 25℃ for 2 hours. A layer of the casting solution was coated on the surface of a polyimide base film (pure water flux 35.4L / (m 2 h), molecular weight cut-off 25000), and dried at 60℃ for 4 hours.

[0052] Comparative Example 1

[0053] The commercially available silicone rubber composite separation membrane currently on the market is obtained by polymerization of polyoctylmethylsiloxane and hydrogen-containing silicone oil.

[0054] Performance testing

[0055] The composite separation membranes of Examples 1-7 and Comparative Example 1 were tested for permeation rate and separation factor. The testing process was as follows: a membrane of a fixed size was placed in a steel circular sample cell, nitrogen gas at a certain pressure was introduced into the sample cell, the nitrogen gas volume passing through the membrane per unit time was measured, and the nitrogen gas permeation rate was obtained; oxygen and nitrogen were configured into a mixed gas of a certain molar concentration ratio, the composition of the mixed gas after passing through the membrane was tested, and the separation factor of oxygen and nitrogen for this membrane was obtained by dividing the ratio of the oxygen molar concentration after the membrane to the oxygen molar concentration before the membrane by the ratio of the nitrogen molar concentration after the membrane to the nitrogen molar concentration before the membrane. The experimental results are shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] As can be seen from Table 1, compared with the comparative example, the flux of the silicone rubber composite membrane prepared in each example of the present application is reduced, and the separation factor is improved after filling with modified cellulose nanocrystals.

[0060] The examples of the specific embodiments are preferred embodiments of the present application, and do not limit the protection scope of the present application, so that: equivalent changes made in accordance with the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A modified cellulose nanocrystal filled silicone rubber composite separation membrane, characterized by: The composite separation membrane comprises a base membrane and a separation layer attached to the base membrane, the separation layer being composed of a cross-linking product of a terminal hydroxyl methyl phenyl silicone oil and octyl trimethoxysilane, and modified cellulose nanocrystals; The modified cellulose nanocrystals are phenyl dimethyl chlorosilane modified cellulose nanocrystals, and the size of the modified cellulose nanocrystals is 5-20 nm.

2. The modified cellulose nanocrystal filled silicone rubber composite separation membrane according to claim 1, characterized in that: The base membrane is a polymer membrane, and the polymer membrane is selected from one of polysulfone, cellulose acetate, polyimide, polyetherimide, polyacrylamide and polypropylene ultrafiltration membrane.

3. The modified cellulose nanocrystal filled silicone rubber composite separation membrane according to claim 1, characterized in that: The base membrane is a flat membrane.

4. A method for preparing a modified cellulose nanocrystal filled silicone rubber composite separation membrane according to any one of claims 1-3, characterized in that: The method comprises the following steps: S1. Dissolve the terminal hydroxyl methyl phenyl silicone oil, octyl trimethoxysilane and organic tin catalyst in an organic solvent; the mass of the terminal hydroxyl methyl phenyl silicone oil accounts for 3-5% of the total mass of the casting solution, the mass ratio of the octyl trimethoxysilane to the terminal hydroxyl methyl phenyl silicone oil is (1-2):5, and the mass of the organic tin catalyst is 4‰-1% of the mass of the terminal hydroxyl methyl phenyl silicone oil; S2. After stirring at room temperature for 3-5 hours, add the modified cellulose nanocrystals, which account for 0.2%-1% of the total mass of the casting solution, and then stir vigorously at room temperature for 1-3 hours to obtain the casting solution; S3. Coat a layer of the casting solution obtained in step S2 on the surface of the base membrane, and then solidify at 60-90°C to obtain the modified cellulose nanocrystal-filled silicone rubber composite separation membrane.

5. The method for preparing a modified cellulose nanocrystal filled silicone rubber composite separation membrane according to claim 4, characterized in that: In step S1, the mass ratio of the methyl groups to the phenyl groups in the terminal hydroxyl methyl phenyl silicone oil is 1:

1.

6. The method for preparing a modified cellulose nanocrystal filled silicone rubber composite separation membrane according to claim 4, characterized in that: In step S1, the viscosity of the terminal hydroxyl methyl phenyl silicone oil is 1000-3000 cst.

7. The method of claim 4, wherein the method is characterized by: In step S1, the organic tin catalyst is selected from dibutyltin dilaurate or dioctyltin dilaurate.

8. The method for preparing a modified cellulose nanocrystal filled silicone rubber composite separation membrane according to claim 4, characterized in that: In step S1, the organic solvent is selected from one or more of gasoline, n-hexane, cyclohexane, n-heptane, n-octane, isooctane or petroleum ether.

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