JP2003144868A - Super-water-repellent organic/inorganic composite membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a super-water-repellent organic/inorganic composite membrane. SOLUTION: This super-water-repellent organic/inorganic composite membrane of a new concept and exhibiting excellent separation performance is formed with a skin layer chemically fixed with a functional polymer by using a Grafting-From surface polymerization process on the surface of a porous inorganic base having a flactal surface structure and pores of an nm to μm range.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a superhydrophobic organic / inorganic composite film, and more particularly to a grafting-from surface of a porous inorganic support having a fractal surface structure and pores in the nm to μm range. The present invention relates to a new concept of a superhydrophobic organic / inorganic composite film in which a skin layer in which a functional polymer is chemically fixed is formed by using a (grafting-from) surface polymerization method and which exhibits excellent separation performance.

[0002]

"Membrane separation" refers to the separation of substances in a molecular state from a mixture using the physicochemical properties of the membrane. A membrane is a phase that separates two three-dimensional homogeneous phases, and is a third phase in which the physicochemical properties of the phase influence the rate of material and energy exchange. FIG. 1 of the accompanying drawings is a general overview of membrane separation. In the membrane separation process, the resistance of all migration phenomena is concentrated in the separation membrane, and the resistance is selectively different depending on the substance. Therefore, different substances have different migration rates through the membrane, which causes the substances to separate. The most important factors affecting the separation of a mixture using a separation membrane are the pore size of the separation membrane and the chemistry of the separation membrane surface. That is, the pore size of the separation membrane and the surface material of the separation membrane that comes into contact with the separated substance must be determined in accordance with the size and chemical characteristics of the substance to be separated.

Membranes that are commercially utilized are classified into polymer separation membranes and inorganic material separation membranes. Polymer separation membranes can give various surface characteristics and are therefore excellent in separation efficiency.However, since the polymer material itself has weak thermal and mechanical properties, permeation, which is an important operating condition for membrane separation, is important. There is a limit to changing the pressure and operating temperature to maximize the separation characteristics. On the other hand, in the case of an inorganic membrane, it is very advantageous over the polymer separation membrane in controlling the size of pores and increasing the separation temperature and pressure, which are the main characteristics of the separation membrane,
There is a limitation in increasing the efficiency of separation by diversifying the functionality of the epidermal layer where separation occurs.

In order to improve such a problem, an organic / inorganic composite film having a polymer layer formed on the surface of an inorganic support has been proposed and actively studied. The organic / inorganic composite membrane can accept the severe operating conditions, which are the advantages of the inorganic membrane,
It is a material that is in the spotlight because it can be given various surface functionalities, which are the advantages of organic polymer films.

As a conventional method for producing an organic / inorganic composite film, there is a method of forming a functional organic polymer film on the surface of an inorganic material by using a method of adsorbing a functional polymer solution on an inorganic support. Can be mentioned. The advantages of this method are:
It is that the organic / inorganic composite film can be manufactured most easily. However, the polymer surface layer in the produced organic / inorganic composite film is dispersed on the surface of the inorganic material (dispersion, van de
r Waals) The types of continuous phases that can be used are limited because they are bound only by attractive forces, and the surface layer that is not chemically bound is likely to be easily lost. It has the disadvantage of poor durability.

The disadvantages of the separation membrane manufactured by the solvent immersion method can be solved by the well-known technique of the self-assembly method. That is, by grafting-to polymerization method, a functional polymer film is chemically and firmly bonded by immobilizing the functional polymer film by surface reaction with a polymer having a reactive end group and an inorganic substance. An organic / inorganic composite film having the same can be manufactured. However, when the polymer surface layer is formed by using the grafting-to-polymerization method, the polymer surface formed by the preceding reaction makes it difficult to access the inorganic surface of the subsequent reactive polymer chain. As the functional polymer thin film is covered, the surface concentration gradient of subsequent polymer chains is deepened and a thin film (~ 20 nm) having a limited thickness is formed, so that the thickness of the surface functional thin film can be freely adjusted. However, as a result, there is a limitation in providing various functionalities.

On the other hand, the solid surface having superhydrophobicity is applied not only in daily life but also in various industries. Traditionally, a super water repellent surface has been manufactured by a physical and chemical method to form a fluorine compound layer on the solid surface, but it was very difficult to chemically fix it to the solid surface due to the extremely low surface energy of the fluorine compound. . Further, in order to obtain a very excellent superhydrophobic surface, not only the chemical surface modification but also the geometric structure of the solid surface had to be controlled.

[0008]

Therefore, the present inventors have aimed to produce an organic / inorganic composite film capable of sustaining superhydrophobicity continuously and freely controlling pore size and surface functionality. As a result of years of intensive research, a self-assembled monolayer of init was formed on the surface of the inorganic support having pores having a surface fractal structure and on the surface of the pores.
The present invention has been completed by forming a functional fluorine-containing polymer thin film chemically bonded to the surface of an inorganic support using a continuous surface polymerization technique using iator) and a fluorine-containing monomer. .

Therefore, the present invention has free control of pore size and surface functionality, exhibits extremely excellent water repellency, and has excellent separation characteristics and operating conditions as compared with existing organic / inorganic composite membranes. To provide a separation membrane having.

[0010]

According to one embodiment of the present invention, in the present invention, a skin of a fluoromonomer copolymer is obtained by using an azo chlorosilane initiator as an intermediate layer on the surface of a porous inorganic support. A layer is formed, the initiator is chemically bonded to the surface of the inorganic support, and at the radical site of the initiator, the fluorine-based monomer is chemically bonded to the polymer chain obtained by radical polymerization. A super water-repellent organic / inorganic composite film is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

The present invention has a surface fractal structure, n
After fixing azo chloride silane to the surface of the inorganic support having pores of m to μm size, the functional monomer is radically polymerized on the surface with the fluorine monomer as the main monomer, The present invention relates to an organic / inorganic composite membrane that exhibits excellent performance by easily adjusting the surface characteristics including the super water-repellent effect and the size of the separation membrane pores by forming a fluorine-based polymer thin film on the substrate.

The surface structure of the organic / inorganic composite film according to the present invention is composed of three parts as follows: a porous inorganic support, a self-assembled initiator fixed on the surface of the inorganic support, and a radical of the initiator. A polymer chain that has a water-repellent functional group and is formed by polymerization at a point.

FIG. 2 of the accompanying drawings shows that the present invention is carried out by a surface polymerization method.
m) Shows the progress of polymerization. As shown in FIG. 2A, the grafting-from polymerization is performed by a method in which an initiator is chemically bound to the surface and then the monomer is surface-polymerized by a radical reaction. FIG. 2B shows the XPS analysis results for each step of the grafting-from polymerization method. As a result of XPS analysis on the surface of the untreated support, it was confirmed that a hydroxyl group (—OH) was present. This was because the Si atom peak was 153.6 eV (Si 2s),
O atom peak is 53 at 102.10 eV (Si 2p).
It can be seen from the fact that it appears at 1.40 eV (O 1s). As a result of XPS analysis after fixing the initiator, it was confirmed that an azo bond of the initiator was present, which can be seen from the fact that the N peak appears at 399.3 eV (N 1s).
As a result of XPS analysis after polymerizing the fluorine-based monomer, it was confirmed that the fluorine-based monomer was well polymerized on the surface, but the fluorine (F) peak was 687.8 eV.
It can be understood from the fact that it appears at (F 1s).

The grafting-from polymerization method is different from the grafting-to polymerization method or the usual polymerization method in that the initiator is bonded to the solid surface first, so that the grafting density is increased. Can be increased. Therefore, according to the grafting-from polymerization method, it is easier to control the organic skin layer, the polymer having various functional groups is easily produced, and the skin which is a copolymer of a fluorine-based monomer is used. The layer can maintain the superhydrophobic property continuously, and the difference in the surface energy of the substances can be used to improve the separation efficiency.

The "self-assembling initiator" in the present invention is chemically and firmly bonded to the surface of the inorganic support,
In addition, it is an initiator that causes a monomer having a desired functionality at the radical site of the initiator to chemically bond with a polymer chain produced by radical polymerization. as a result,
One end of the initiator is firmly fixed to the surface of the inorganic support by a chemical bond, and the other end is chemically bonded to a functional polymer chain. In the present invention,
By using azo chloride silane as such a self-assembly type initiator, the concentration adjustment of the functional functional group of the organic / inorganic composite film became easy by this. That is, by adjusting the number of functional groups in the chain by copolymerization of the initiator and other non-reactive monomers, or by adjusting the number of functional groups per unit area, the functionality of the obtained composite membrane Can be adjusted.

The porous inorganic support which can be used in the production of the superhydrophobic organic / inorganic composite film of the present invention has a fractal structure and has a pore size of nm to μm.
Can be used for the porous inorganic material of
It can be applied to inorganic materials having a pore size of ˜200 μm. A "fractal" is a geometric figure that has the property of self-similarity in progressively finer structures. Surfaces with such a structure have the property of being very wettable by water or very well repelled by water. The inorganic support used in the present invention is all inorganic substances having a hydroxyl group (-OH) on the surface in a natural state or artificially, and silica is specifically exemplified by the material of the porous inorganic support. , An inorganic substance containing alumina, titanium oxide, iron oxide, zinc oxide, copper oxide, nickel oxide, cobalt oxide, etc., or a composite of two or more types, and an organic / inorganic complex containing the inorganic substance can be used. .

The fluorine-based monomer used in the production of the superhydrophobic organic / inorganic composite film of the present invention is a monomer generally used for the purpose of water repellency. (1) ~
It is represented by (6), and these fluorine-based monomers can be used alone or in combination of two or more.

[0019]

Embedded image CF ₂ = CF ₂

Embedded image CH ₂ ═CF ₂

Embedded image XC _n F _2n CH ₂ OCOCR ¹ ═CH ₂

Embedded image XC _n F _2n SO ₂ NR ² (CH ₂ ) _m OC
OCR ¹ = CH ₂

Embedded image XC _n F _2n CH ₂ CH (OH) (CH ₂ )
_m OCOCR ¹ = CH ₂

Embedded image XC _n F _2n (CH ₂ ) _m OCOCR ¹ ═CH ₂ (wherein R ¹ is a hydrogen atom or a methyl group; R ² is a methyl group, an ethyl group or a propyl group; X is hydrogen Atom, fluorine atom or chlorine atom; m is an integer of 2 to 6; n is an integer of 3 to 21).

Further, in forming the skin layer of the present invention, a comonomer can be used together with the above-mentioned fluorine-based monomer. Body (VCM), vinylidene chloride (VDC),
(Meth) acrylic acid (AA, MAA), methyl (meth) acrylate (MA, MMA), ethyl (meth) acrylate (EA, EMA), butyl (meth) acrylate (BA, BMA), hexyl (meth) acrylate ( HA, HMA), dodecyl (meth) acrylate (DA, DMA), stearyl (meth) acrylate (SA, SMA), benzyl (meth) acrylate (B
Vinyl monomers such as A, BMA), cyclohexyl (meth) acrylate (CHA, CHMA), acrylonitrile (AN), acrylamide (AAM), vinyl acetate (VA), styrene (St); and N-methylol (meth). ) Acrylamide (MAAM, MMAA)
M), N-methylol acrylamide butyl ether (MAAMBE), N-butoxy (meth) acrylamide (BAAM, BMAAM), 2-hydroxy (meth)
A single or two or more selected from acrylic monomers having a crosslinkable group such as acrylate (HEA, HEMA) and 2-hydroxypropyl (meth) acrylate (HPA, HPMA) can be used together.

The organic / inorganic composite film of the present invention as described above has an extremely low apparent surface energy of about 0.1 dyn / cm. Therefore, it exhibits a very high contact angle of 150 ° or more and exhibits superhydrophobicity. When such a property is used, when a mixture of liquids having different surface tensions is permeated, the difference in the surface tension, which is a physicochemical property of the liquids, causes a difference in substance and energy exchange rates. It can be separated into substances in a molecular state. The fluorine compound used in the present invention is known to have properties such as water repellency, oil repellency, and stain resistance because it has extremely low low energy surface properties. Therefore, it is possible to manufacture an organic / inorganic composite membrane that has a surface functionality that is chemically extremely hydrophobic and that exhibits high mechanical strength, which is an important physical property of a separation membrane.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

EXAMPLE A 500 ml Schlenk glass reactor with an average pore size of 2
0 μm porous silica support (radius 2 cm, thickness 6 m
m), 250 g of dried toluene and 2 g of triethylamine (TEA) were added.

As an azo chlorosilane initiator, 1 g of 4,4-azobis- (4-cyanopentanoic acid- (3-chlorodimethylsilyl) propyl ester was dried to obtain 10 parts of toluene.
After dissolving in ml, the mixture was put into a reactor and sealed. After removing the gas inside the porous silica support, an initiator adhesion reaction was carried out at room temperature for 1 day. The initiator was removed from the reactor after a siloxane bond was formed by a chemical reaction on the surface of the porous silica support. It was washed with toluene, methanol, and acetone to remove the remaining initiator and salts formed. After the washed porous silica support was dried at room temperature, it was placed in a 500 ml Schlenk glass reactor and C ₈ F ₁₇ C ₂ H ₄ OCOC was added as a fluorine-based monomer.
100 g of H = CH ₂ (hereinafter referred to as “FA”) was added. The reaction was carried out for 3 to 8 hours in a constant temperature bath at 50 to 90 ° C. The separation membrane produced after the reaction was washed with 1,1,2-trichloro-1,2,2-trifluoroethane (R-113).

The surface characteristics of the produced separation membrane were investigated for contact angle measurement, and water (H ₂ O) and diiodomethane (CH 2
_The surface apparent energy was calculated using the contact angle measurement results obtained using ₂ I ₂ ) and the geometric mean approximation formula [Formula 1]. The contact angle obtained at this time was 153.8 ° with respect to water and 129 ° with respect to diiodomethane, and the surface energy was 0.19 dyn / cm.

[Formula 1]

Further, the following experiment was conducted in order to investigate the durability and the continuous water repellency of the separation membrane manufactured in Example 1. The separation membrane test piece was dipped in each of toluene, a mixed solution of toluene / methanol (90/10), and a mixed solution of toluene / methanol / paratoluenesulfonic acid (90 / 9.5 / 0.5), and was allowed to stand at room temperature for 48 hours. Left for hours. The result of taking out after standing and measuring the surface energy is shown in FIG. 3 of the accompanying drawings. According to FIG. 3, it can be seen that there is almost no change in the surface energy before or after the reaction. From this, it was confirmed that the separation membrane according to the present invention has strong durability and persistent water repellency against a highly soluble solvent, acid or alkali.

FIG. 4 of the accompanying drawings compares the contact angle formation result (a) of the separation membrane obtained in Example 1 with the contact angle formation result (b) of the separation membrane without surface polymerization. Is the photograph shown. On the porous silica support after the PFA skin layer is formed, the water droplets and the surface are about 150 ° to 1 °.
It exhibits a superhydrophobic contact angle of 60 °.

Further, FIG. 5 of the accompanying drawings shows the first embodiment described above.
The results of a permeation characteristic comparison experiment using water and methanol for investigating the separation characteristics of the composite membrane manufactured by are shown. When water and methanol were allowed to permeate through each of the separation membrane (a) having a PFA skin layer formed on the surface of the porous silica support and the porous silica support separation membrane (b) having no skin layer formed thereon. By comparison, the transmittance of the separation film (a) with the skin layer formed is low due to the super water repellency of the surface. In addition, considering the permeation characteristics of water and methanol, it can be seen that the permeation rate is lower when water is permeated than that of methanol. This is because water has a higher surface tension than methanol. This is because the transmittance changes depending on the difference in tension.

Example 2 In order to obtain various separation membranes having skin layers having various chemical structures by the same reaction apparatus and method as in Example 1, as shown in Table 1 below, a fluorine-based monolayer was used. A monomer or a fluoromonomer and a comonomer were used. When the monomer was in a gaseous state at room temperature, the reactor was cooled with liquid nitrogen using a high pressure reactor, a fixed amount of gas was injected, and the mixture was sealed, and then the surface polymerization reaction was performed in a batch mode. The support and surface characteristics of the produced separation membrane are shown in Table 1 below and FIG. 5 of the accompanying drawings.

[0030]

[Table 1]

The photograph of FIG. 6 is a comparison of the surface characteristics of organic / inorganic composite films having superhydrophobic skin layers formed by using various fluorine-containing monomers on the surfaces of various inorganic supports. .

Also, the silica support / FM prepared above
As shown in FIG. 7 of the accompanying drawings, a comparative experiment was conducted on the separation characteristics of water and methanol for an organic / inorganic composite film composed of an A skin layer, an alumina support / TFE skin layer, and an alumina support / VDF skin layer. The separation characteristics were obtained.

Comparative Example 1 In the case of the separation membrane according to the present invention in which the superhydrophobic skin layer was not formed, the contact angles for water and diiodomethane were all 0 °. These results mean that the apparent surface energy of porous silica, alumina, titanium oxide, etc. is very high.

[0034]

[Table 2]

Comparative Example 2 A water and methanol permeation characteristic comparison experiment was carried out on a porous support having no skin layer formed thereon and an organic / inorganic composite membrane having a superhydrophobic skin layer formed thereon. Figure 8 of the accompanying drawings
Is a silica porous support with no skin layer (thickness 6 m
3 shows the permeation characteristics (a) of water and methanol for m).
In addition, a porous silica support without a skin layer (thickness 9 m
m) and FA on the surface of the porous silica support (thickness 9 mm)
The permeation characteristics of water (b) and methanol (c) with respect to each of the separation membranes formed with a super water repellent skin layer using a fluorine-based monomer were measured at atmospheric pressure and compared.

According to FIG. 8, when the permeabilities (a) of water and methanol are compared only in the porous support having no skin layer, it can be seen that the permeation characteristics are almost the same. However, the difference in water permeability with and without the skin layer is significantly larger than that in methanol. this is,
This is because water has a larger surface energy than methanol.

[0037]

In the separation of the liquid mixture, most of the industrial sites rely on the fractional distillation method using the difference in the boiling points of the liquids, but such a method causes a lot of energy consumption, and the distillation column is used. Not only does it require huge facilities, but it causes environmental problems and occupies a lot of space.

On the other hand, the organic / inorganic composite membrane of the present invention is a separation membrane that uses the difference in the surface tension of liquids, and therefore does not require high energy consumption and does not cause environmental problems. Is. In addition, since it is sufficient to apply only the pressure that allows the liquid to pass through the membrane, a large amount of space is not required when installing the device.

[Brief description of drawings]

FIG. 1 is a general schematic diagram of membrane separation.

FIG. 2 Grafting-from (g) on a porous support.
(a) is a schematic diagram of the progress of the grafting-from polymerization method, and (b) is a XPS for each step of the grafting-from polymerization method. It is an analysis result.

FIG. 3 is a graph showing a result of an experiment for confirming durability and continuous water repellency with respect to a separation membrane having a PFA skin layer formed thereon.

FIG. 4 is a photograph comparing surface characteristics of a separation membrane (a) having a PFA skin layer formed thereon and a separation membrane (b) having no skin layer formed thereon.

FIG. 5 is a graph comparing water and methanol permeation characteristics of a separation membrane (a) having a PFA skin layer formed therein and a separation membrane (b) having no skin layer formed therein.

FIG. 6 is a photograph comparing the surface characteristics of organic / inorganic composite films having skin layers formed using various fluoromonomers and comonomers.

FIG. 7 is a graph comparing the permeation characteristics of water and methanol to organic / inorganic composite membranes in which skin layers using various fluoromonomers are formed on various supports.

FIG. 8 compares the permeation characteristics (a) of a porous support having no skin layer formed therein and the permeation characteristics of water (b) and methanol (c) formed in a separation membrane with and without the formation of a superhydrophobic skin layer. It is a graph.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08F 2/00 C08F 2/00 C 4J100 14/18 14/18 292/00 292/00 // B05D 7 / 24 302 B05D 7/24 302L (72) Inventor Iso Bok Daejeong Souk Wolpyeong-2dong 300 Moosege Apartment 103-203 (72) Inventor Pak In-Jeong Daejeong Daeduk Buk -Don Jorgon Apartment 122-308 (72) Inventor Ik Won-Won South Korea Yousung-Ku Hoon-Don 99 Hanbit Apartment 102-1203 (72) Inventor Kim Dong-Kan South Korea Yousung-Ku Yuh-hun 99 Hanbit Apartment 105- 106 (72) Inventor Jung Hoon South Korea Yousung-ku Yuhoon-don 99 Hanbit Apartment 123-204 (72) Inventor Ha Jung-uk South Korea Mapo Hapyeong-don 390-7 Hyundai Art Villa Be-204 (72) Inventor Park Hyun-Sung, Seoul, Yeongdeungpok, Yeong-Dong, Seven Apartments 11-62 (72) Inventor Jun Tae-Hwan, Taejeong Suk-Wolpyeong-3Don 302 Fansil Apartment 105-307 (72) Inventor Jürgen Rewe Germany 79110 Freiburg Georges-Cola-Alley Albert-Lutowig-University Flive Luku Institute for Microsystem Technology F-term (reference) 4D006 GA03 GA14 MA09 MB10 MC29X MC30X MC79X NA41 NA45 4D075 AE03 CA36 DA25 DB11 EB16 EC37 4F100 AA01A AA05A AA19A AA20A AA21A AA23A AA24A AA25A AB11A AK17B AK17J AK17K AK25B AK25J AL01B BA02 BA07 CA30A DJ00A GB56 JB06B JL11 YY00B 4J011 CA02 CB00 CC07 4J026 AC00 BA02 BA05 BA10 BA11 BA20 BA24 BA26 BA30 BA31 BA32 BB01 BB03 DB12 GA01 4J100 AA02Q AB02Q AC03Q AC04Q AC24P AC26P AG04Q AJ02Q AL03Q AL04Q AL05Q AL08P AL08Q AL09Q AM02Q AM15Q AM21Q BA02Q BA03P BA03Q BA04Q BA59P BB18P BC04Q BC43Q CA01 CA04 DA36 DA37 EA00 FA17 JA24

Claims (7)

[Claims] 1. A skin layer of a fluoromonomer copolymer is formed on the surface of a porous inorganic support by using an azo type chlorosilane initiator as a mediating layer, and the initiator is the surface of the inorganic support. A super water-repellent organic / inorganic composite, which is chemically bonded and is chemically bonded to a polymer chain obtained by radically polymerizing the fluorine-based monomer at a radical site of an initiator. film. 2. The inorganic support is silica, alumina,
A porous support selected from titanium oxide, iron oxide, zinc oxide, copper oxide, nickel oxide and cobalt oxide, which has a fractal structure.
The superhydrophobic organic / inorganic composite film described. 3. The superhydrophobic organic / inorganic composite film according to claim 1, wherein a fluorine compound having a low surface energy is chemically fixed on a porous support. 4. The fluorine-based monomer is represented by the following formula (1):
(6) It is what is represented by (6), The claim 1 characterized by the above-mentioned.
The superhydrophobic organic / inorganic composite film described. ## STR1 ## _CF 2 = CF ₂ ## STR2 ## _CH 2 = CF ₂ ## STR3 ## ^{_{XC n F 2n CH 2 OCOCR 1}} = CH 2 embedded image ^{_{XC n F 2n SO 2 NR 2}} (CH 2) m OCO
CR ¹ = CH ₂ embedded image XC _n F _2n CH ₂ CH (OH) (CH ₂ ) _m
OCOCR ¹ ═CH ₂ embedded image XC _n F _2n (CH ₂ ) _m OCOCR ¹ ═CH ₂ (wherein R ¹ is a hydrogen atom or a methyl group; R ² is a methyl group, an ethyl group or a propyl group. Yes; X is a hydrogen atom, a fluorine atom or a chlorine atom; m is an integer of 2 to 6; n is an integer of 3 to 21). 5. The fluoromonomer further contains a comonomer selected from a vinyl monomer and an acrylic monomer having a crosslinkable group. The superhydrophobic organic / inorganic composite film described. 6. The superhydrophobic organic / inorganic composite film according to claim 1, wherein the polymerization is grafting-from surface polymerization using a fluorine compound monomer on a porous support. 7. The composite film has a contact angle with water of 14 or less.
5 ° -160 °, apparent surface energy 0.1-2d
It is yn / cm, The super water-repellent organic / inorganic composite film of Claim 1 characterized by the above-mentioned.