JPS6247457B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hydrophilic film obtained by introducing sulfone groups into a thin film containing a vinyl chloride resin,
More specifically, the present invention relates to a hydrophilic membrane with improved acid deterioration resistance of a hydrophilic membrane containing a vinyl chloride resin and having cation exchange properties. Ion exchange membranes with cation exchange properties are already widely used industrially for desalination of seawater, electrodialysis for concentrating common salt, electrolysis of alkali metal salts, etc., but new applications, such as separators for primary and secondary batteries,
Various applications have been proposed, such as diaphragms for diffusion dialysis and diaphragms for fuel cells that utilize the functions of polymer electrolyte membranes. However, despite these wishes,
There have been very few cation exchange membranes that satisfactorily satisfy the functions necessary for ion exchange membranes, such as good selectivity, sufficient mechanical strength, low oil swelling, and low electrical resistance, as well as economic efficiency. Conventionally, the method for manufacturing a cation exchange membrane by reacting a vinyl chloride resin thin film with a sulfonating agent is as follows:
It is known from Japanese Patent Publication No. 36-2193 and Japanese Patent Publication No. 36-2695. However, in the cation exchange membranes obtained by these methods, it is necessary to react with the sulfonating agent for an extremely long period of time in order to introduce sulfone groups into the interior of the vinyl chloride resin thin film, so the surface layer of the thin film is mainly sulfonated. Furthermore, due to the long sulfonation time, side reactions other than sulfonation increase, resulting in weak mechanical strength, and the disadvantage that a film with low electrical resistance in the electrolyte cannot be obtained, and furthermore, it is uneconomical. Therefore, there were practical problems. In Japanese Patent Application No. 56-116152 (Japanese Unexamined Patent Publication No. 58-17122), the present inventors proposed a hydrophilic membrane that solved the drawbacks of the hydrophilic membrane made of the above-mentioned vinyl chloride resin thin film, and a method for manufacturing the same. did. The method for producing a hydrophilic membrane in the above-mentioned patent application No. 56-116152 significantly shortens the sulfonation time compared to the conventional method, resulting in high strength in a short time and low electrical resistance in the electrolyte. Moreover, it is an epoch-making product that makes it possible to economically produce a hydrophilic membrane with excellent selectivity. However, even in the hydrophilic membrane of Japanese Patent Application No. 56-116152, the hydrophilic membrane made of a single film without reinforcing material, such as woven fabric, non-woven fabric, knitted fabric, or microporous membrane, has particularly high oxidation resistance. In applications requiring this, it was necessary to improve its oxidative deterioration resistance. The inventors of the present invention have conducted extensive studies aimed at improving the above-mentioned oxidative deterioration resistance, and as a result, they have arrived at the present invention. To explain the present invention, the hydrophilic membrane of the present invention is made of vinyl chloride resin (A) and chlorinated polyethylene (B).
and a hydrophilic film in which sulfone groups are introduced into a thin film formed from a resin composition containing a plasticizer, (A)/
It is characterized in that the weight ratio of (A)+(B) is 0.2 to 0.95. Such a hydrophilic film has significantly improved oxidative deterioration resistance compared to a hydrophilic film obtained by introducing sulfone groups into a thin film containing a vinyl chloride resin obtained by a conventional method. In the present invention, vinyl chloride resin (A)
The content of is determined by the weight ratio [(A)/(A)+(B)
] A suitable value is 0.2 to 0.95; if it is less than 0.2, the reaction time with the sulfonating agent becomes long, making it difficult to obtain the desired hydrophilic membrane. Moreover, if it exceeds 0.95, the effect of adding chlorinated polyethylene will be small, and as mentioned above,
A value of 0.2 to 0.95, preferably 0.4 to 0.85, results in a hydrophilic film that has excellent oxidative deterioration resistance, short reaction time with the sulfonating agent, and excellent productivity. In the present invention, the content of sulfonic groups is preferably from 0.1 to 3 milliequivalents/gram,
In a hydrophilic membrane of 0.2-2 meq/g,
In particular, the result is a hydrophilic film in which the effect of adding chlorinated polyethylene is significantly exhibited. If the content of sulfonic groups is less than 0.1 meq/g, the electrical resistance in the electrolyte is relatively high, so there are few applications that require particularly high oxidation resistance, and the hydrophilicity obtained by conventional methods is low. Even the film has sufficiently high oxidation deterioration resistance, so the above-mentioned
In a hydrophilic membrane of 0.1 meq/g or more,
The effect of adding chlorinated polyethylene is expressed. In addition, in order to maintain significantly high oxidative deterioration resistance in a hydrophilic film with a high content of sulfonic groups, it is necessary to increase the proportion of chlorinated polyethylene added, and as a result, the reaction time with the sulfonating agent increases. In the end, the content of the above-mentioned sulfone group is 0.1 to 3 meq/g, more preferably 0.2 to 2 meq/g, and the hydrophilic acid with excellent oxidative deterioration resistance can be produced continuously in a single time period. It is possible to produce a sexual membrane. The above-mentioned hydrophilic membrane of the present invention retains various characteristics of the hydrophilic membrane obtained by introducing sulfone groups into a vinyl chloride resin thin film, and has extremely excellent oxidative deterioration resistance even in an alkaline electrolyte. It becomes something. For example, the electrical resistance of the hydrophilic membrane of the present invention described above in dilute sulfuric acid is 5Ω·cm ² or less, preferably 1
A hydrophilic membrane having a resistance of Ω·cm ² or less, more preferably 0.5 Ω·cm ² or less can be provided. Furthermore, even in an alkali, a hydrophilic membrane with a high sulfonic group content has a low electrical resistance, preferably 5 Ω·cm ² or less, more preferably 1 Ω·cm ² or less. be able to. In addition, the electrical resistance in alkali is 0.5Ω・^cm2 , and even for a hydrophilic membrane, the area swelling rate in alkali is
It is characterized by an extremely small area swelling rate of 5% or less in an electrolytic solution, so it can be used in a variety of applications by taking advantage of its high selectivity and low electrical resistance characteristics in acidic, neutral, and alkaline electrolytes. Furthermore, the hydrophilic membrane of the present invention has the property of selectively permeating water from aqueous solutions typified by water-organic compounds. In the advanced pervaporation method, it selectively permeates water even from deep inside.
Separation coefficient αA/B (A=water, B=ethanol)
However, it also becomes a hydrophilic film of 5 or more, preferably 10 or more. In addition, the hydrophilic membrane of the present invention has excellent barrier properties even against compounds that are relatively similar to water, such as methanol. 10 ^-3 cm/
min or less, preferably 1×10 ^-3 cm/min or less,
More preferably, it also becomes a hydrophilic membrane having a characteristic of 5×10 ⁻⁴ cm/min or less. As described above, the hydrophilic membrane of the present invention has various excellent properties, and improves the deterioration resistance of the hydrophilic membrane obtained by introducing sulfone groups into a thin membrane containing a vinyl chloride resin. Various uses as a hydrophilic membrane,
For example, diaphragms for electrodialysis, electrolytic separation membranes, dialysis membranes for diffusion dialysis, alkaline solutions that take advantage of the low electrical resistance properties in alkaline or dilute sulfuric acid, separators for various batteries that use dilute sulfuric acid as an electrolyte, and polymer electrolytes. Various types of diaphragms for fuel cells that take advantage of the characteristics of
It can also be used in a wide range of applications, such as concentrated membranes, lipophilic compounds, barrier films that take advantage of their impermeability to oxygen, and antistatic films that take advantage of their low surface resistivity, especially in applications that require resistance to oxidative deterioration. It becomes suitable. Furthermore, the hydrophilic membrane of the present invention has superior mechanical toughness compared to conventional membranes, and therefore has excellent workability. The hydrophilic membrane of the present invention can be applied to woven fabrics, nonwoven fabrics,
It can be applied to the various uses described above in the form of a composite with a reinforcing material such as a knitted fabric or a microporous membrane, or in various shapes depending on the purpose, such as a film, a tube, a hollow fiber, and a bag. Next, an example of the method for producing the hydrophilic membrane of the present invention will be described.
A thin film made of a mixture containing 10 to 200 parts by weight of a plasticizer that is compatible with the resin component and extractable based on the weight part, while containing the plasticizer,
Alternatively, by extracting the plasticizer and then reacting it with fuming sulfuric acid, the exchange capacity can be increased to produce a hydrophilic membrane with excellent oxidative deterioration resistance and having sulfonic groups of 0.1 to 3 milliequivalents/gram in a short time. can. And, the vinyl chloride resin referred to in the present invention is
Polymers of vinyl chloride monomers or copolymers of vinyl chloride with monomers copolymerizable with vinyl chloride, such as vinyl acetate, acrylonitrile, vinylidene chloride, acrylic esters, ethylene, propylene, etc., or from the above polymers and copolymers Chosen 2
It is a mixture consisting of more than one species. In addition, the vinyl chloride copolymer in the present invention refers to a vinyl chloride content of 50% by weight or more, a comonomer
It is a copolymer with a vinyl chloride content of less than 50% by weight, preferably a vinyl chloride content of 80% by weight or more, and more preferably a vinyl chloride content of 90% by weight or more. In addition, the chlorinated polyethylene referred to in the present invention is
An amorphous or low-crystalline resin with high rubber elasticity obtained by reacting polyethylene with chlorine, with a chlorine content in the range of 20 to 50%, which is compatible with vinyl chloride resin and has good hydrophilic properties. Desirable from the viewpoint of film flexibility and oxidative deterioration resistance. In addition, the above-mentioned plasticizer that is compatible with the above-mentioned resin component and can be extracted is defined as a plasticizer that can be uniformly dispersed in at least 10 parts by weight with respect to 100 parts by weight of the above-mentioned resin component, and that can be used by melt molding or solution casting. A thin film can be formed by a method, etc., and it can be extracted from the film or hydrophilic membrane immediately before, during, or after the reaction with a solvent that hardly dissolves the resin component or with fuming sulfuric acid, etc. Good. Examples of plasticizers include phthalic acid esters such as dibutyl phthalate, diethyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, butyl lauryl phthalate, dilauryl phthalate, butyl benzyl phthalate; dioctyl adipate, dioctyl aze; Linear dibasic acid esters such as esters, dioctyl sebacate; phosphoric acids such as tricresyl phosphate, tricylenyl phosphate, monooctyl diphenyl phosphate, monobutyl-dixylenyl phosphate, trioctyl phosphate, etc. Esters; Epoxy plasticizers such as epoxidized vegetable oils; Polyester plasticizers; Chlorinated substances such as chlorinated paraffin and pentachlorinated butyl stearate; Chlorinated fatty acid esters; Paraffins and other commonly used plasticizers for plastics. or at least one other various additives that meet the above requirements, and can be appropriately selected from those that can be dispersed in the resin component in a nearly molecular state and can plasticize the resin component. There are no particular restrictions on the method of mixing the vinyl chloride resin, chlorinated polyethylene, and plasticizer.
Methods used in normal plastic processing, such as impregnating vinyl chloride resin and chlorinated polyethylene with a plasticizer and mixing them in a Henschel mixer, or methods that can dissolve vinyl chloride resin, chlorinated polyethylene, and plasticizers There is a method of dissolving it in a suitable solvent and dispersing it uniformly. In the case of a mixture that does not contain a solvent, the above resin composition is processed by a compression molding method, an extrusion method, etc., and in the case of a product containing a solvent, a single film without reinforcing material is formed by a solvent casting method, etc., to a thickness of about 5 to 100 μm. It is suitable to form a film of the original fabric. In order to introduce the sulfone group into the film, for example, the above-mentioned plasticizer is extracted from the film with a solvent that can dissolve the plasticizer without dissolving the resin component, or without extracting the plasticizer. It can be obtained by reacting the containing state with fuming sulfuric acid. Preferable reaction conditions are appropriately determined depending on the concentration of fuming sulfuric acid, the amount of chlorinated polyethylene added, the amount of plasticizer added, the thickness of the film, the shape of the film, the presence or absence of reinforcing material, etc., but it is generally preferred to be 60°C or lower. The reaction time is 3 hours or less, more preferably 150 minutes or less, and still more preferably 1 to 100 minutes at a temperature of 45°C to 20°C. Generally, it is desirable to obtain the hydrophilic membrane of the present invention under these conditions because side reactions other than sulfonation can be reduced. After the sulfonation treatment, the reaction solution adhering to the membrane is diluted with sulfuric acid, etc., thoroughly washed with water, and treated with an alkaline reagent such as potassium carbonate or potassium hydroxide, or a salt such as sodium chloride or potassium chloride. After converting the -SO ₃ H group into a metal salt of sulfonic acid, it is convenient to wash it thoroughly with water and dry it before handling it. In the hydrophilic film produced by the above manufacturing method, the plasticizer dispersed within the film is replaced with fuming sulfuric acid during sulfonation or becomes a sulfonated product.
It is removed by the fuming sulfuric acid or the washing and/or neutralization step carried out after the sulfonation reaction, and almost no residue remains in the final hydrophilic membrane. The reason why the hydrophilic membrane obtained from the above production example has excellent oxidative deterioration resistance is not clear at present, but it is compatible with vinyl chloride resin.
Inherently excellent in oxidation and deterioration resistance, rich in rubber elasticity,
It is mixed with chlorinated polyethylene vinyl chloride resin, which has characteristics such as being easily plasticized by a plasticizer and relatively difficult to be sulfonated, and then being plasticized and/or swollen with a plasticizer, to make it predominantly chlorinated in a short time. By sulfonating the vinyl resin, we were able to retain the excellent properties of chlorinated polyethylene such as oxidative deterioration resistance and rubber elasticity, and as a result, we were able to obtain a hydrophilic film with excellent oxidative deterioration resistance. I am guessing that it is. Further, for the above reasons, it is presumed that the hydrophilic membrane of the present invention can maintain various properties of a hydrophilic membrane obtained by introducing sulfone groups into a thin membrane made of a vinyl chloride resin. In addition to additives such as stabilizers, lubricants, and colorants that are usually added during plastic processing, the hydrophilic film of the present invention is mixed with a small amount of other fillers or polymers within a range that does not contradict the purpose of the present invention. It is self-evident that it includes what is obtained from what is done.
In addition, crosslinking can be achieved by crosslinking, for example, by irradiating ionizing radiation, or by adding an organic peroxide or hexamethylene diamine to the mixture of the resin component and plasticizer, forming a film, and then crosslinking. It goes without saying that it also includes hydrophilic membranes made from films. Furthermore, in the hydrophilic membrane of the present invention, patent application No. 56
Needless to say, treatment with a suitable bleaching agent or oxidizing agent after sulfonation as proposed in No. 15798 can be applied. In addition, various characteristics described in the present invention,
Exchange capacity, electrical resistance in alkali, oxidative deterioration resistance, area swelling rate in alkali, electrical resistance in dilute sulfuric acid, cation transference number, ethanol-water separation coefficient α
The permeability coefficients of A/B (A=water, B=ethanol) and methanol were measured by the following methods. (1) Exchange capacity (milliequivalent/gram) A sulfonic acid (-SO ₃ H) type membrane is placed in a certain amount of calcium chloride (1N) aqueous solution to achieve equilibrium, and the hydrogen chloride generated in the solution is 0.1N. Titrate with an aqueous solution of caustic soda (potency = f) using phenolphthalein as an indicator, and divide the value X (cc) by the dry weight W (g) in the potassium salt state Exchange capacity = 1 / ¹⁰ f x Set the current density between the electrodes (nickel plate) at 23℃.
When a constant DC current of 5 mA/cm ² is applied, the voltage drop due to the sample is measured using a mercury oxide electrode, and the value calculated from the following formula is used as the electrical resistance. (Before measurement, add the sample to a 31% by weight potassium hydroxide aqueous solution.)
Immersed for over 24 hours) R ₁ = (V ₂ - V ₁ )/0.005 (Ω・cm ² ) R ₁ = Electrical resistance of the sample (Ω・cm ² ) V ₁ = Voltage drop when the sample is not set ( V) V ₂ = Voltage drop when the sample is set (V) (3) Oxidation resistance Two nickel plate electrodes, 3.8 cm x 3.8 cm in the center
The sample was sandwiched between two polyethylene spacers with a 7.6 cm opening, and 31 wt%
immersed in potassium hydroxide aqueous solution (80℃),
A constant DC current of 100 mA is applied for a predetermined period of time to cause the electrolytic oxygen to react with the sample. According to the above accelerated deterioration test, a hydrophilic film with excellent oxidative deterioration resistance has a small change in electrical resistance. (4) Area swelling rate in alkali (%) Drying area S _d of area S _w of hydrophilic membrane in 31% by weight potassium hydroxide aqueous solution at 23°C (A sample thoroughly washed with water was heated with warm air at 60°C Area swelling rate in alkali = S _w - S _d / S _d × 100
%) (5) Electrical resistance in dilute sulfuric acid (Ω・cm ² ) A sample was set in a measuring device (based on JIS C2313) filled with dilute sulfuric acid with a specific gravity of 1.2 (at 23°C), and a voltage of 25 mA/cm was applied between the electrodes. Measure the voltage drop across the sample when a constant DC current of ² is applied, and use the value calculated from the following formula as the electrical resistance in sulfuric acid. [Before measurement, prepare the sample with a specific gravity of 1.2 (at 23℃)
24 hours or more in dilute sulfuric acid] R ₂ = (V ₄ - V ₃ )/0.025 (Ω・cm ² ) R ₂ = Electrical resistance of the sample in dilute sulfuric acid (Ω・cm ² ) V ₃ = Sample Voltage drop when the sample is not set (V) V ₄ = Voltage drop when the sample is set (V) (6) Cation transfer number Potassium chloride is used as the electrolyte, and the concentrations on both sides of the sample are 0.2M/0.1M, The membrane potential was measured according to a conventional method under the condition that the liquid temperature was maintained at 23°C, and calculated using the Nernst equation. (7) Ethanol water separation coefficient αA/B (A=water,
B = ethanol) 50% by weight on the feed liquid side by pervaporation method *1
The value was calculated from the following formula by charging ethanol water, keeping the permeate side under vacuum, and separating water at 30°C. αA/B = (weight fraction of water on the permeate side) / (weight fraction of ethanol on the permeate side) / (weight fraction of water on the feed liquid side) / (weight fraction of ethanol on the feed liquid side) ) A membrane with a larger value of αA/B has a higher separation ability and is a membrane suitable for a separation membrane. *1 Kagaku Special Issue, 69 ('76), P.109 (8) Methanol permeability coefficient Dilute sulfuric acid (A) with a specific gravity of 1.2 (at 23℃) and
A solution (B) of 4 vol% methanol mixed with 1.2 (at 23°C) diluted sulfuric acid was brought into contact with the sample through the sample.
This is the value obtained by measuring the amount of methanol permeation from liquid (B) to liquid (A) under the temperature condition of °C, and calculating the permeation coefficient of methanol according to a conventional method. Hereinafter, the present invention will be explained in detail using Examples, Comparative Examples, and Experimental Examples. Example 1 60 parts by weight of vinyl chloride-vinyl acetate copolymer resin (vinyl chloride content >95% by weight, degree of polymerization = 1500, manufactured by Chitsuso Corporation, Nipolitsu MH) and chlorinated polyethylene (chlorine content = 30% by weight, Showa 40 parts by weight of Elasuren 301A (manufactured by Denko Co., Ltd.) was dry blended at room temperature [(A)/(A)+(B)=0.6], and the above mixture 10
0 parts by weight, 100 parts by weight of dioctyl phthalate and an organic tin malate stabilizer (TVSN2000E4 manufactured by Nitto Kasei Co., Ltd.) at a ratio of 5.5 parts by weight to 100 parts by weight of vinyl chloride-vinyl acetate copolymer resin. Add to the above resin mixture and use a kneader to
The mixture was melt-kneaded at 160° C. for 30 minutes to obtain a resin composition containing vinyl chloride resin/chlorinated polyethylene/plasticizer/stabilizer. Next, the resin composition was extruded using an extruder to form a film with a thickness of 40 μm. The above film was reacted with fuming sulfuric acid containing about 12% by weight of free sulfur trioxide at 40°C for 25 minutes, washed in the order of concentrated sulfuric acid, diluted sulfuric acid, and water.
It was neutralized with a 31% by weight aqueous potassium hydroxide solution, washed with water and dried to obtain a hydrophilic membrane having sulfone groups. As shown in Table 1, the result was a hydrophilic film with low electrical resistance in alkali and excellent resistance to oxidative deterioration.

[Table] Example 2 Using the vinyl chloride resin, chlorinated polyethylene, plasticizer and stabilizer used in Example 1, 40 parts by weight of vinyl chloride resin and 60 parts by weight of chlorinated polyethylene
Mix parts by weight at room temperature [(A)/(A)+(B)=0.4], and add 100 parts by weight of the plasticizer and 100 parts by weight of the vinyl chloride resin to 100 parts by weight of the above mixture. It was added to the resin mixture in an amount of 5.5 parts by weight, and a thin film with a thickness of 45 μm was obtained by compression molding. Hereinafter, a hydrophilic membrane was created in substantially the same manner as in Example 1. As shown in Table 1, the results were significantly superior in oxidative deterioration resistance compared to Comparative Example 1. Comparative Example 1 Contains vinyl chloride resin/plasticizer/stabilizer = 67.5/29.0/3.5 in weight ratio using almost the same method as Example 1 except that chlorinated polyethylene was not added.
A film with a thickness of 40 μm was obtained. From the above film, the method was almost the same as in Example 1 except that the reaction time with fuming sulfuric acid was slightly shortened.
A hydrophilic membrane with an electrical resistance of 1.5Ω·cm ² in alkali was obtained. When the oxidative deterioration resistance was measured, the hydrophilic film became brittle within 72 hours of the accelerated deterioration test, and the electrical resistance could not be measured. Examples 3 to 4 Vinyl chloride-based resin was converted from vinyl chloride-vinyl acetate copolymer resin to vinyl chloride straight resin (degree of polymerization = 1450, Chitsuso Corporation, Nipolitsu SH)
A hydrophilic membrane was created in almost the same manner as in Example 1, except that the content of vinyl chloride resin was changed to 0.8 in weight ratio [(A) / (A) + (B)]. did. The results are in Table 2
As shown in Figure 2, it was a hydrophilic film with excellent resistance to oxidative deterioration.

[Table] Comparative Example 2 Electrical resistance in alkali was 1.0 using a method similar to Example 3 except that chlorinated polyethylene was not added.
A hydrophilic membrane of Ω·cm ² was obtained. This hydrophilic membrane can be tested within 72 hours for accelerated degradation.
It became brittle and electrical resistance could not be measured. Example 1 Regarding the hydrophilic membranes of Example 1 and Comparative Example 1, the area swelling ratio in alkali, electrical resistance in dilute sulfuric acid, methanol permeability coefficient, and cation transfer number were measured, and the results are shown in Table 3. As shown, the hydrophilic membranes of Example 1 and Comparative Example 1 have almost the same values, and Example 1
The hydrophilic membrane retained the excellent properties of the vinyl chloride resin sulfonated membrane.

[Table] Examples 5 to 6 The type of chlorinated polyethylene was changed to crystalline chlorinated polyethylene (chlorine content = 30% by weight, Elastrene 301B manufactured by Showa Denko K.K.) and chlorine content.
40% chlorinated polyethylene (Elastrene 401A)
Hydrophilic films were prepared in the same manner as in Example 3, except that the plasticizer was changed to dibutyl phthalate, and the oxidative deterioration resistance was measured. It was something I had. Experimental Example 2 When the ethanol-water separation coefficient αA/B of the hydrophilic membranes of Examples 5 and 6 was measured, both had good values of 10 or more.

Claims (1)

[Claims] 1. Vinyl chloride resin (A) and chlorinated polyethylene (B)
and a hydrophilic film in which sulfone groups are introduced into a thin film formed from a resin composition containing a plasticizer, (A)/
A hydrophilic membrane characterized in that the weight ratio of (A) + (B) is 0.2 to 0.95. 2. The hydrophilic membrane according to claim 1, wherein the weight ratio is from 0.4 to 0.85. 3. The hydrophilic membrane according to claim 1 or 2, wherein the content of sulfone groups is 0.1 to 3 milliequivalents/gram. 4 The content of sulfonic groups is 0.2 to 2 milliequivalents/
The hydrophilic membrane according to claim 3, which is gram.