JPS59112803A - Gas permselective membrane - Google Patents

Abstract

PURPOSE:To obtain a polyorganosiloxane membrane having a chemical structure effective in obtaining oxygen-enriched air and high mechanical strength. CONSTITUTION:The membrane comprises polyphenylsiloxane with an M.W. of 10<5> or more having a ladder structure or ladder type organosiloxane copolymer in which said polyphenylsiloxane part occupies 60mol% or more shown by a formula (wherein R1 is a phenyl group, R2, R3 and R4 are H, a 1-4C alkyl group, a 1-4C alkoxy group or a phenyl group, m, n, r, and s are an integer of 1 or more and x, y, p and q are zero or larger integer. This polysiloxane is prepared by a method wherein phenyltrichlorosilane is hydrolyzed or substituted trichlorosilane and substituted dichlorosilane are used to be subjected to co- hydrolysis and the resulting hydrolysate is succeedingly subjected to high polymerization reaction. Because this membrane has a ladder type crosslinked structure, it is excellent in heat resistance, oxidation resistance and chlorine resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a selective gas permeable membrane, and an object of the present invention is to provide a gas permeable membrane with excellent gas permeability and gas selectivity, and strong membrane strength. In particular, the present invention relates to an oxygen-enriching membrane comprising a polyorganosiloxane membrane constituted by a specific repeating unit having a chemical structure, ie, a lag structure, which is effective for obtaining oxygen-enriched air from air.

More specifically, the present invention is a high molecular weight lug-type film suitable for producing a novel ultra-thin film that has strong mechanical strength, excellent heat resistance and chemical resistance, and has high performance gas selective permeability and gas permeability. This invention relates to a gas separation membrane made of polysiloxane.

Polymer films, whose main component is polymer, have been generally used mainly for gas barriers, but in recent years, gas separation methods have been proposed that take advantage of the fact that membrane permeability varies depending on the gas. Many polymer membranes have been studied for gas separation, and there are too many to list in the literature.

Normal combustion systems (boilers, for example) use air in addition to fuel, but if oxygen-enriched air, which has an increased oxygen concentration in the air, is supplied to the combustion system instead of this air, combustion efficiency can be improved. It is possible to achieve an improvement in combustion temperature and a reduction in combustion exhaust gas, and a very large effect can be expected in terms of both energy saving and pollution prevention. It is fully predicted that this will make an immeasurable contribution to the fields of internal combustion engines and combustion equipment such as electric power boilers, general industrial boilers, heating boilers, and ship boilers, as well as waste treatment.

Furthermore, research into oxygen selectively permeable membranes has been promoted by the need to develop medical equipment such as artificial lungs, artificial gills, nursery boxes for premature infants, medical equipment for the treatment of respiratory diseases, and medical materials. . Some of these have already been commercialized and are on the market.

Conventionally, there are known methods of separating and concentrating air without using polymer membranes, such as using zeolite or special carbon, but these take advantage of the difference in the adsorption properties of oxygen and nitrogen gas. It has the disadvantage that the desorption process cannot be performed continuously, so it cannot be said to be an efficient separation method.

On the other hand, when using a polymer membrane, separation can be carried out continuously, but all conventionally known membranes have insufficient gas permeability coefficients and permselectivity, and have drawbacks in membrane strength. There are drawbacks such as difficulty in producing extremely thin films, and it can be said that none of them is fully satisfactory in practical terms.

Currently industrialized membranes for gas separation include Chemical Engineering News, May 19, 1980 issue,
There is a Pr15m (trade name of Monsanto Co., USA) membrane, which is made of a polysulfone composite fiber membrane and is introduced on page 57, and is mainly used to separate hydrogen and carbon monoxide.

In addition, as an oxygen enrichment membrane, there is a membrane made of polysiloxane-polycarbonate broth copolymer developed by CF, Inc. in the United States, and Oxygen Enric+ment Co., Ltd.
, Medical Oxygen Enrichment Device” 0ECOMembra
The structure of the film material is said to be as shown in the following formula.

Despite the fact that many other studies have been conducted on polymer membranes for gas separation, the reason why there are so few polymer membranes in practical use is that conventional polymer membranes are This is due to the fact that the amount of gas that permeates is small, and if the film is made extremely thin to increase the amount of gas that permeates, the membrane strength will be weakened, and it is extremely difficult to develop a definitive separation membrane that can satisfy both of these requirements. . For example, JP-A No. 56-26508 discloses a membrane mainly composed of polyorganosiloxane having a ladder structure in part of its molecular structure, but depending on the manufacturing method also disclosed, A membrane with a molecular weight could not be obtained, and therefore this membrane did not have practical strength.

The heart of the oxygen enrichment system is the oxygen enrichment membrane. Many studies have been conducted on the dissolution and diffusion of gases that govern gas permeation through various polymer membranes, and are introduced in detail in Nakayo's review article (Plastics 24tL, No. 12, p. 1..9). There is.

Generally, the amount of gas permeation Q (cn/sec) is expressed by the following formula.

where P; gas permeability coefficient (cJ-am/ctA-
sec ・am Hg) A: Membrane area (cml) Δp: Pressure difference between the primary and secondary sides of the membrane (cmHg) l:
Film thickness (an) In this unit, the largest permeability coefficient among polymer films is on the order of 10-8, and the smallest is on the order of 10-"-
This is the order.

As is clear from this equation, in order to increase the amount of gas permeation, -) use a material with a large gas permeability coefficient P, (2) increase the area A of the membrane, (3) the primary side and increase the pressure difference Δp on the secondary side, (4) reduce the membrane thickness l (
Possible measures include making the size smaller. Regarding the selectivity of gas separation, it is also necessary to select a membrane material that has a large ratio of permeability coefficients for each component gas to be separated. Furthermore, Q can generally be increased by increasing the temperature T of the film.

To summarize the characteristics of polymeric materials preferable as gas permeable membranes from the above points, they have a large permeability coefficient P, sufficient membrane strength to withstand large area or extremely thin membranes, and sufficient heat resistance to withstand high temperatures. It can be said to have excellent durability and king resistance.

For reference, examples of gas permeability coefficients of polymer membranes known so far are as follows.

Table-1 Gas permeability coefficient Material Name Permeability coefficient P (c+A-am/cl ・sec = cm Hg
) Polydimethylsiloxane 3.5 x 10
-8 polydimethylsiloxane- polycarbonate copolymer 2, OX 10-8 natural rubber 2. OX 10-9
Polyethylene 2.9 x 10-
10 polystyrene 2.5 x 1
0-1D polyethylene terephthalate 2.8 x
10-+)-Among the materials listed in Table 1, polydimethylsiloxane and natural rubber have a large permeability coefficient, but have the disadvantage that their membrane strength is weak and it is difficult to form a thin membrane. In particular, polydimethylsiloxane is rubbery and easily deforms even at room temperature, so it must be reinforced with a filler and a film formed on the support. A polydimethylsiloxane-polycarbonate block copolymer was developed to improve film strength, which is a drawback of polydimethylsiloxane.This copolymer has a high permeability coefficient and can be made into a thin film of 1,000 people, but it still has a high permeability coefficient. It has the disadvantage that it does not have sufficient strength and cannot be put to practical use unless it is on a limited porous membrane support. Polyethylene, polystyrene, etc. can be considered excellent materials from the viewpoint of membrane strength, especially if they have a high molecular weight, but when considering practical use as a gas permeable membrane,
The permeability coefficient is too small, requiring a large area, and when used as a gas permeation device, it becomes large and impractical.

The present invention was arrived at as a result of intensive studies in order to eliminate the drawbacks of the membrane materials that have been studied in the past. By using a ladder-type polyorganosiloxane with a crosslinked structure and a high molecular weight of 105 or more as a gas permeable membrane, the permeability coefficient is large (and it is easy to make a thin film).
Furthermore, the present invention provides a gas permeable membrane material with high membrane strength and excellent heat resistance.

The polyorganosiloxane having a ladder structure of the present invention is a polyphenylsiloxane (A) having a ladder structure having a molecular weight of 10!1' or more, or 60 mol% or more of the polyphenylsiloxane (A>) and other single or co-polymerized polyphenylsiloxanes. It is a polymer composition (B) in which less than 40 mol% of the polymer is mixed.Furthermore, the polyorganosiloxane having a ladder structure of the present invention has a molecular weight of 10S or more and a polyphenylsiloxane having a ladder structure It may be a ladder-type organosiloxane copolymer (C) in which the Kira 2 moiety accounts for 60 mol% or more. Siloxane moieties or polyorganosiloxane moieties having a non-ladder structure and having two identical or different substituents per siloxane unit, or fractional moieties thereof, account for less than 40 mol%.

A schematic example of the structure of such a polymer (A>(C)) is considered to be as follows.

(However, in the formula, R1 is a phenyl group, and R2, Ra, and R4 are mutually the same or different groups, and mean hydrogen, a Ct-w4 alkyl group, an alkoxy group, a halogen-substituted alkoxy group, or a substituted or unsubstituted phenyl group. Yes, 171%
n −, r −, S is an integer greater than or equal to 1, x, y, p, q
means an integer greater than or equal to 0. ) The method for producing a high molecular weight polysiloxane having a ladder structure used in the present invention basically consists of hydrolysis of phenyltrichlorosilane followed by a high polymerization reaction. During this hydrolysis, a part of the phenyltrichlorosilane is substituted with substituted trichlorosilane or di-substituted dichlorosilane, and a high molecular weight copolymer ( C
) can also be produced in the same way.

Substituents of substituted trichlorosilane and disubstituted dichlorosilane that can be used in the production of copolymer (C) in the present invention include alkyl groups such as methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, butoxy, 1, Examples include alkoxy groups such as 1°1-to IJ70 loproboxy, substituted moshikuha, unsubstituted phenyl groups, and the like.

The molecular weight and molecular weight distribution (Mw/Mn) of the high molecular weight ladder type polyorganosiloxane used in the present invention were measured using a high performance liquid chromatograph HLC manufactured by Toyo Soda Co., Ltd.
-802UR is a relative value obtained from a calibration curve prepared using polystyrene TSK standard polystyrene also manufactured by Toyo Soda Co., Ltd.

The strength of the membrane according to the present invention was measured by using a Tensilon tensile tester manufactured by Toyo Baldwin Co., Ltd., using a sample film formed on a glass plate by a casting method from a solution of high molecular weight ladder type polyorganosiloxane dissolved in toluene. Shi, ^STM
A tensile test was conducted in accordance with D882-61T, and the values were calculated using a conventional method.

The heat resistance temperature of the membrane according to the present invention indicates the temperature at which thermal decomposition or weight loss starts, as measured using a thermogravimetric measuring device DT-20B or TG-20 manufactured by Shimadzu Corporation.

The high molecular weight ladder type polyorganosiloxane that can be used in the membrane according to the present invention has a molecular weight (Mw) of 10' or more, and if the molecular weight is lower than this, the membrane strength is weak and is not practical. In addition, products with too high molecular weight are not only difficult to manufacture, but also tend to have poor solubility in solvents, contain gel in some parts, and cause fish eyes during film formation. , there will naturally be an upper limit. Ladder type polyorganosiloxanes having a molecular weight in the range of 105 to 106 are preferred.

The molecular weight distribution of the ladder-type polyorganosiloxane used in the membrane of the present invention is not particularly limited, but it is preferably smaller in terms of film formability, film strength, etc., and is preferably 5 or less.

In order to produce such a ladder-type polyorganosiloxane with a high molecular weight and a small molecular weight distribution, a terminal hydroxy type or terminal cage type (silsesquioxane type) siloxane oligomer (intermediate) having a ladder structure is used as a catalyst. The condensation is preferably carried out in the presence of a fluorine compound. In this case, the fluorine compounds include alkali metals,
Fluorides of alkaline earth metals, quaternary ammonium chloride, etc. are effective.

As a method for producing the membrane of the present invention from a ladder type polyorganosiloxane, any known method can be adopted as appropriate. For example, a ladder type polysiloxane is uniformly dissolved in an appropriate solvent,
Methods such as a casting method, a film forming method based on a monomolecular film manufacturing method, and a film forming method of coating on a microporous support can be employed.

Of these methods, the method of coating on a porous support is industrially the simplest. The support used in this method is preferably a microporous support with 100 to 5000 pores on the surface. Such microporous supports can be selected from various commercially available filter materials, and can be prepared according to the manufacturing method of ultrafiltration membranes, reverse osmosis membranes, etc.
It can also be made from various polymers. Furthermore, nonwoven fabric, filter paper, etc. can also be used. When utilizing the high heat resistance of ladder-type polyorganosiloxane, it is preferable to use a support with high heat resistance, and use of heat-resistant engineering plastics, ceramic porous supports, etc. is preferable. As the form of the porous support, a porous flat membrane, a porous hollow fiber membrane, etc. can be used.

In the present invention, the ladder type polyorganosiloxane is generally dissolved in a solvent and used for film formation, but any solvent may be used as long as it does not dissolve the porous support and does not react with the support. In the case of ladder type polyorganosilopenylsiloxane, the types of solvents are benzene, toluene, xylene, tetrahydrofuran, chloroform, 1
, 1.1-) A single solvent such as dichlorethylene, N-methylpyrrolidone, diphenyl ether, dimethyl sulfoxide, or a mixed solvent of two or more thereof can be used. The concentration of the ladder type polysiloxane in these solvents may be 0.5 to 20% by weight, and should be adjusted depending on the type or molecular weight of the raw material. For example, in ladder type polyphenylsiloxane with a molecular weight in the range of 105 to 106, preferably e11 to 1
The concentration is 0% by weight.

When the polyorganosiloxane solution prepared in this manner is applied onto a porous support, it is impregnated into the pores of the support. Thereafter, the entire support is dried with air or hot air to obtain a support coated with a ladder-type polyorganosiloxane film.

In the present invention, by using a uniform and polar BIN mainly composed of a high molecular weight ladder type polyorganosiloxane,
Not only can a high level of oxygen permeability and oxygen selectivity be achieved, but an oxygen-enriched membrane with strong membrane strength, heat resistance, and stability can be obtained, making it possible to manufacture a membrane with the long-awaited performance. Therefore, it can be expected to have great industrial value.

The membrane material of the present invention has a ladder-type crosslinked structure consisting of a 5t-0 skeleton, and therefore has excellent properties such as extremely high heat resistance, oxidation resistance, and chlorine resistance. It is also an effective material for reverse osmosis membranes and ultrafiltration membranes that can be used even under harsh conditions. Furthermore, since it is a cross-linked ladder structure, unlike polymers with a general cross-linked structure, it is easily soluble in solvents and is extremely easy to form into a film.The appropriate solvent and polymer concentration can be selected according to the molecular weight and composition of the polymer. Accordingly, a film of any desired thickness can be easily obtained.

The present invention will be described in more detail below with reference to Examples, but the gist of the present invention is not limited to the Examples.

Example 1 Phenyltrichlorosilane was hydrolyzed in toluene by adding water, the toluene solution was washed to neutrality, the toluene solution was dried, and the toluene was distilled off. a end 10
g was completely dissolved by adding 50 g of toluene. To this, 10+n+r of cesium carbides and 2.5 g of diphenyl ether are added as catalysts, and the reaction is continued while expelling toluene and the produced water as an azeotrope. Gradually raise the temperature to completely expel toluene and reduce to 200-250
Incubate at ℃ for 1 hour. After the reaction was completed, 100 g of toluene was added to dissolve the reactant, which was dropped into a large amount of methanol to precipitate the polymer, which was filtered and dried under vacuum to obtain a ladder type polyphenylsiloxane. The molecule f (Mw) of the polymer obtained in this form was 1.8 x 106, and the molecular weight distribution (Mw/Mn) was 3.2. .

The thermal decomposition temperature was 520°C, and the tensile strength of the film formed by dissolving it in toluene and casting was 3.2 kg/-. In addition, uniform films without pinholes with a film thickness of 5 μm to 100 μm can be easily obtained using the casting method, and when the gas permeability coefficient at 25°C was measured for each film thickness, there was almost no difference in permeability coefficient depending on the film thickness. 2.3X for oxygen
, 10-8-cm/c nitric acid 5ec-c+n fi
g, 8.5 X 10-” cl −>/cs for nitrogen
A・sec・cmHg, and the ratio of permeability coefficients (PO2
/PN2), that is, the separation ratio was 2.7. In addition, using Millibore microporous filter paper as a support, a thin film was formed on the filter paper surface, and the film thickness was calculated from the gas permeability coefficient.
A thin film with a diameter of 0.36 μm and no pinholes could be easily obtained.

Examples 2 to 6 In the method of Example 1, the hydrolysis of phenyltrichlorosilane was carried out by replacing a portion of phenyltrichlorosilane with substituted trichlorosilane.4. A copolymerization intermediate of terminal hydroxy-type polyorganosiloxane and loxane is obtained by cohydrolysis, and a ladder-type polyorganosiloxane copolymer obtained by a high polymerization reaction using this as a raw material is produced by a casting method. The gas permeability of the membrane was measured in the same manner as in Example 1.

Table 2 shows the results.

Examples 7 to 10 A terminal hydroxy ladder type polyorganosilane intermediate obtained by cohydrolyzing phenyltrichlorosilane in the method of Example 1 by replacing a part of phenyltrichlorosilane with di-substituted dichlorosilane. A ladder-type polyorganosiloxane copolymer was synthesized using the polyorganosiloxane copolymer as a raw material, and the gas permeability of the film formed by the casting method was measured in the same manner as in Example 1. Table 3 shows the results.

Claims (1)

[Scope of Claims] Polyphenylsiloxane (A) having a ladder structure with a molecular weight of 105 or more, said polyphenylsiloxane (
Polymer composition (B) in which A) accounts for 60 mol% or more or a polyphenylsiloxane portion having a ladder structure contains 6
A selective gas permeable membrane whose main component is a ladder-type organosiloxane copolymer (C) that accounts for 0 mol% or more and has a molecular weight of 105 or more. 2. Claim 1, wherein the copolymer (C) is obtained by subjecting an intermediate obtained by cohydrolysis of phenyltrichlorosilane and substituted trichlorosilane to a high polymerization reaction.
Selective gas permeable membrane as described in . 3. Claim 1, wherein the copolymer (C) is obtained by subjecting an intermediate obtained by cohydrolysis of phenyltrichlorosilane and di-substituted dichlorosilane to a high polymerization reaction.
Selective gas permeable membrane as described in .