Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/12—Composite membranes; Ultra-thin membranes
  • B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction

Definitions

• the present invention relates to a method for producing a composite semipermeable membrane useful for selective separation of a liquid mixture, particularly for desalination of brine or seawater.
• Interfacial interface between polyfunctional aromatic amine and polyfunctional acid halide A composite semipermeable membrane consisting of a microporous support membrane coated with an ultra-thin layer of crosslinked polyamide obtained by polycondensation reaction has a high permeability. It is also attracting attention as a reverse osmosis membrane with high selectivity.
• Examples of the production of a composite film by an interfacial polycondensation reaction between a polyfunctional aromatic amine and a polyfunctional acid halide include, for example, U.S. Pat. Nos. 4,277,34 and 4,520, No. 044, No. 4, 529, 646, No. 4, 626, 468, No. 4, 643, 829, No. 4, 661, 25, No. 4, 749, 4 ⁇ and No. 4, 761, ⁇ 4 No. have been known so far.
• a composite semipermeable membrane comprising a microporous support membrane coated with an ultra-thin film made of a polyamide obtained by the interfacial polycondensation reaction of ethylenediamine with a polyfunctional acid halide has excellent oxidation resistance
• a reverse osmosis membrane having high selective separation for example, European Patent Application Publication No. 0,085,111 is known.
• the former polyfunctional aromatic amine and polyfunctional acid
• the composite semipermeable membrane formed by coating a microporous support membrane with an ultrathin film made of a polyamide obtained by interfacial polycondensation reaction with a lipogen compound has excellent permeability and selective separation,
• it did not sufficiently satisfy the oxidation resistance required for a practical reverse osmosis membrane.
• cleaning with an oxidizing agent is usually performed to remove organic substances adhering to the system, and a reverse osmosis membrane having durability against such oxidizing agents, particularly free chlorine. was desired.
• the composite semipermeable membrane obtained by coating the microporous support membrane with the latter ultrathin layer made of polyamide obtained by the interfacial polycondensation reaction between ethylenediamine and polyfunctional acid halide is resistant to oxidation. Although it has excellent properties and selectivity, it did not sufficiently satisfy the permeability required for a practical reverse osmosis membrane. Permeability is one of the very important factors for the economics of a practical reverse osmosis process, and it is desired to develop a reverse osmosis membrane having both high permeability and oxidation resistance. Was.
• An object of the present invention is to provide a method for producing a composite semipermeable membrane having both excellent oxidation resistance and excellent permeability while solving the drawbacks of the prior art.
• the present invention relates to a polyfunctional aromatic amine having two or more amino groups in one molecule and a polyfunctional aromatic amine having two or more halogenated carboxyl groups in one molecule.
• the following structural formula (1) is used as a copolymerization component with the polyfunctional aromatic amine component.
• R 1 and R 2 are each independently an alkyl group having 3 or less carbon atoms or a phenyl group or a hydrogen atom having 6 or less carbon atoms
• R 3 is an alkyl group having 7 or less carbon atoms and has a side chain. Represents a linear or cyclic alkyl group which may be
• separation characteristics such as high permeability and high selective separation, which are characteristics of the crosslinked amide-based composite semipermeable membrane, are hardly changed. Oxidation resistance can be greatly improved. That is, it has a feature that a composite semipermeable membrane having excellent both oxidation resistance, permeability and selective separation can be produced.
• the composite semipermeable membrane of the present invention comprises an ultra-thin film layer having substantially separation performance coated on a microporous support membrane having substantially no separation performance.
• the main component is the crosslinked polyamide obtained by
• polyfunctional aromatic amine a polyfunctional aromatic amine selected from aromatic amines having two or more amino groups in one molecule is used.
• m-phenylenediamine, P-phenylamine Two-diamine, 1,3,5-triaminobenzene can be used.
• the above-mentioned bifunctional or higher-functional aromatic amines can be used by selecting one kind, but may be used in combination of two or more kinds.
• 1,3,5-triamino benzene and m-phenylenediamine When used in combination, a membrane having excellent permeability and selective separation can be obtained.
• the aromatic amine is dissolved in water, and forms an ultrathin film containing a crosslinked polyamide as a main component by interfacial polycondensation by contact with an acid halide compound described later.
• at least one selected from alkyldiamine, 1,3,5-trihydroxybenzene and 1,3-dihydroxybenzene is used in a weight ratio to the multifunctional aromatic amine.
• alkyldiamines 1, 3, 5 — If the amount of cibenzene or 1,3-dihydroxybenzene is less than 1%, the improvement in oxidation resistance is insufficient, and if it exceeds 20%, the permeability becomes poor and is not preferred. A more preferable range is 2 to 15% in terms of oxidation resistance and permeability.
• Alkyldiamine is represented by the following structural formula (1).
• R 1 and R 2 are each independently an alkyl group having 3 or less carbon atoms or a phenyl group or a hydrogen atom having 6 or less carbon atoms
• R 3 is an alkyl group having 7 or less carbon atoms and has a side chain. Represents a linear alkyl group or a cyclic alkyl group which may be possessed.
• alkyldiamines include ethylenediamine, 1,2-propanediamine, 1,3-prono, and the like.
• 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, N-methylethylenediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,4-cyclohexanediamine N, N'-dimethylethylenediamine, N-phenylethylenediamine and the like can be exemplified.
• These alkyl diamines may be used as a mixture of a plurality thereof as long as their total weight is 1% or more and 20% or less with respect to the aromatic amine.
• Ethylene in terms of price and high permeability, high desalination and oxidation resistance of the membrane produced It is most preferred to use ⁇ -diamin.
• 1,3,5-trihydroxybenzene or 1,3-dihydroxybenzene can also be used in place of alkyldiamine.
• 1,3,5-trihydroxybenzene it is preferable to use 1,3,5-trihydroxybenzene in view of the permeability and selective separation of the membrane. Further, it may be used as a mixture with the above-mentioned alkyl dimamine. In this case, the total thereof must be 1% or more and 20% or less with respect to the aromatic amine by weight.
• a polyfunctional acid halide is an acid halide having two or more halogenated carboxyl groups in one molecule, and is obtained by an interfacial polycondensation reaction with the polyfunctional aromatic amine. It gives an amide.
• the polyfunctional acid halide include 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3 Aliphatic or aromatic acid halides such as 1,5-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid can be suitably used.
• the polyfunctional acid halide is preferably a polyfunctional acid chloride, and in consideration of the selective separation property and heat resistance of the membrane, the polyfunctional acid halide is preferred. It is preferably a functional aromatic acid chloride.
• the polyfunctional acid halides are 1,3,5-benzenetricarboxylic acid chloride and 1,3-benzenedicarboxylate It is most preferable to use chlorides and 1,4-benzenedicarboxylic acid chlorides alone or as a mixture.
• the microporous support membrane is a layer having substantially no separation performance and used for imparting strength to an ultrathin film layer having substantially separation performance. It is preferable that the supporting film has a structure in which the fine pores gradually have large fine pores from one surface to the other surface, and the size of the fine pores is such that the surface of one surface is 100 nm or less. .
• Various types of microporous support membranes such as “Millipore Filter VSWP” (trade name) manufactured by Millipore and “Ultra Filter UK 10” (trade name) manufactured by Toyo Roshi Kaisha, Ltd. are available.
• a commercially available material can be selected, but a preferred microporous support membrane is a polymer reinforced with at least one kind of fabric selected from polyester or aromatic polyamide.
• An example is a microsulfur microporous support membrane.
• Such support membranes are described in “Office, Ob Serene Water, Research 'And' Development Report Progress Report” ⁇ 35 9 (1 It can be produced according to the method described in 9 6 8).
• the material used is preferably a homopolymer such as polysulfone, cellulose acetate, cellulose nitrate, polyvinyl chloride, or the like, but is preferably used because it has high chemical, mechanical, and thermal stability. Preference is given to using the sulfone.
• the pore size is easy to control, the dimensional stability is high, and the repeating unit [ ⁇ ]
• a polysulfone consisting of dimethylformamide (DMF) solution of the above polysulfone on a densely woven polyester cloth or nonwoven fabric to a certain thickness, and then to apply it to dodecyl sulfate.
• DMF dimethylformamide
• the ultra-thin film layer having substantial separation performance in the composite semipermeable membrane is composed of the aforementioned polyfunctional aromatic amine, alkyldiamine, 1,3,5-trihydroxybenzene and 1,3-dihydroxy. It is formed by interfacial polycondensation using an aqueous solution containing at least one compound selected from hydroxybenzene and a water-immiscible organic solvent solution containing the above-mentioned polyfunctional acid halide.
• the concentration of the aromatic amine compound in the aqueous polyfunctional aromatic amine solution is preferably 0.1 to 10% by weight, more preferably 0.5 to 5.0% by weight. At least one compound selected from alkyldiamine, 1,3,5-trihydroxybenzene and 1,3-dihydroxybenzene. The concentration is preferably from 0.01 to 0.1% by weight, more preferably from 0.03 to 0.15% by weight, and more than 1% by weight with respect to the aromatic amine. Add 20% or less.
• the aqueous solution may contain a surfactant, an organic solvent, an alkaline compound, an antioxidant, etc. as long as it does not hinder the reaction between the amino compound and the polyfunctional acid halide.
• the pH is preferably from 6 to 13, and in consideration of the reactivity of alkyldiamine and the like, it is more preferable to control the pH to from 0 to 13. Further, a water-soluble polymer compound such as water-soluble polyvinyl alcohol may be contained as long as the performance is not impaired.
• the coating of the aqueous amine solution on the surface of the microporous support membrane may be performed by uniformly and continuously coating the aqueous solution on the surface. It may be performed by a method of coating, a method of immersing the microporous support membrane in the aqueous solution, or the like.
• the excessively applied aqueous solution of the amine is removed by a draining step.
• a draining method for example, there is a method in which the membrane surface is held in a vertical direction and flows naturally, and it is preferable that no liquid droplets remain. After draining, the membrane surface may be dried to remove some of the aqueous solution, but this does not always give good results.
• an organic solvent solution of the above-mentioned polyfunctional acid halide is applied, and an ultra-thin layer mainly containing a crosslinked polyamide is formed by interfacial polycondensation.
• the content of the polyfunctional acid halide in the solution is usually preferably from 0.01 to ⁇ 0% by weight, more preferably from 0.02 to 2% by weight dissolved in an organic solvent.
• an acylation catalyst or the like is contained, interfacial polycondensation is promoted.
• the organic solvent is required to be immiscible with water, dissolve the acid halide and not break the microporous support membrane, and is inactive to the amino compound and the acid halide. Any one may be used. Preferable examples include hydrocarbon compounds and trifluorene trifluorethane. From the viewpoint of the reaction rate and the volatility of the solvent, n-hexane and trifluorene trifluorene are preferred. Considering the safety problem of sex, it is more preferable to use trichloro mouth trifluorethane.
• the method for contacting the polyfunctional acid halide with the aqueous solution of the amino compound may be carried out in the same manner as the method for coating the microporous support membrane with the aqueous solution of the amino compound.
• the composite semipermeable membrane thus obtained exhibits sufficiently good membrane performance by itself, but the composite semipermeable membrane is further immersed in a chlorine-containing aqueous solution having a pH of 6 to 13 to improve the membrane performance.
• a chlorine-containing aqueous solution having a pH of 6 to 13 to improve the membrane performance.
• the desalting rate and the amount of water permeation can be improved.
• Chlorine-generating reagents include chlorine gas, ash powder, sodium hypochlorite, chlorine dioxide, chloramine B, chloramine B, halazones, dichlorodimethylhydantoin, chlorinated isocyanuric acid and And its salts etc.
• the concentration is determined by the strength of the oxidizing power.
• sodium hypochlorite aqueous solution is preferable from the viewpoint of handleability.
• oxidizing power of a chlorine-containing aqueous solution and PH.
• a pH of less than 6 does not show sufficient oxidizing power.
• Above 13 is undesirable because hydrolysis of amide bonds occurs and the ultra-thin film layer is damaged.
• a dechlorination treatment step is then performed.
• desalination can be carried out by contacting with a reducing agent such as bisulfite.
• the exclusion rate was determined by the following equation.
• Rejection rate [ %] (1 ⁇ ⁇ 's ⁇ , concentration) X 1 0 0
• the amount of water permeation was the amount of water per day (cubic meter) per square meter of membrane area.
• the fiber-strengthening polysulfone support membrane used in the present invention was produced by the following method.
• Taffeta made of polyester fiber with a length of 30 cm and a width of 20 cm (Yokote yarn and weft yarn are 150 denier multifilament yarns, 90-density vertical weave Z-inches, Fix 6 7 inch, thickness 16 on the glass plate, A 15% by weight dimethylformamide (DMF) solution of polysulfone (Ude1-P3500, manufactured by Union Power Company) was then placed at a thickness of 20 at room temperature (20 ° C).
• DMF dimethylformamide
• FR-PS support membrane a fiber-reinforced polysulfone support membrane (hereinafter abbreviated as FR-PS support membrane).
• the pure water permeability coefficient of the FR-PS support membrane (thickness 210-215 ⁇ m) obtained as described above was measured at a pressure of lkgZcnf and a temperature of 25 ° C, and was measured at 0,05 ⁇ 0. Olg Zcnf'sec ⁇ atm.
• the FR—PS support film obtained in Reference Example 1 was immersed in an aqueous ami- num solution having the composition shown in Table 1 for 1 minute. After slowly pulling up the support membrane vertically and removing excess aqueous solution from the support membrane surface, it contains polyfunctional acid chloride having the composition shown in Table 1 and 300 ppm of DMF. A solution of trichlorotrifluoroethane was applied so that the surface was completely wetted, and allowed to stand for 1 minute. Next, the membrane was set up vertically and the excess solution was drained off to remove it, and then immersed in a 0.2% by weight aqueous solution of sodium carbonate for 5 minutes.
• the composite semipermeable membrane thus obtained was subjected to reverse osmosis test under the condition of 150 kg Zcnf and 25 ° C using 150 ppm saline solution adjusted to pH 6.5 as raw water.
• the film performances shown in Table 1 were obtained.
• a composite semipermeable membrane was produced in the same manner as in Example 1 except that 0.05% by weight of ethylenediamine was added. As a result, the membrane performance shown in Table 1 was obtained.
• Example 1 after immersing in a 0.2% by weight aqueous solution of sodium carbonate for 5 minutes, the membrane was further subjected to sodium hypochlorite at 600 ppm and phosphoric acid at 1 ppm. After being immersed in an aqueous solution of pH 7 containing 0.2% by weight of lithium for 2 minutes, it was washed with tap water.
• the composite semipermeable membrane thus obtained was subjected to the same reverse osmosis test as in Example 1, and as a result, the membrane performance shown in Table 1 was obtained.
• a composite semipermeable membrane was produced in the same manner as in Example 3 except that the addition amounts of the amine component and the acid halide were changed to the weight percentages shown in Table 1. Comparative Example 1
• Example 1 The membrane obtained in Example 1 was operated for 45 hours at 100 ° ⁇ ⁇ ⁇ , ⁇ 6.5 and 25 ° C. for chlorine for 45 hours, and then purified with citric acid. Changed to In the table, the increase rate of the salt permeability indicates the ratio of the salt permeability before and after the chlorine operation, and the salt permeability () was obtained by (100—desalting rate) (%).
• a composite semipermeable membrane was produced in the same manner as in Example 3 except that ethylenediamine was not added. As a result, the membrane performance shown in Table 1 was obtained. Further, as a result of the chlorine operation in the same manner as in Example 8, the membrane performance was changed as shown in Table 2.
• a composite semipermeable membrane was produced in the same manner as in Example 7 except that ethylenediamine was not added. As a result, the membrane performance shown in Table 1 was obtained. Further, as a result of the chlorine operation in the same manner as in Example 8, the membrane performance was changed as shown in Table 2. Examples 11 to 16
• Example 3 1,3-propanediamine, 1,2-cyclohexadiamine, N-methylethylenediamine, N, ⁇ '-dimethyl instead of ethylenediamine
• Composite semipermeable membrane in the same manner as in Example 3 except that ethylenediamine, ⁇ -phenylethylenediamine, and 1,3,5—trihydroxybenzene were each used at 0.05% by weight.
• the membrane performance shown in Table 3 was obtained.
• the membrane performance was changed as shown in Table 3.
• Desalination rate Increase rate of salt permeability% mVnf
• Example 8 98.81 1.10 1.83
• Example 9 99.51 1.29 2.04
• Example 10 98.90 1, 10 1.57 Comparative Example 2 95.35 1.10 21.1 Comparative Example 3 91. 70 1.56 12, 2

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
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• 1988
  • 1988-01-11 JP JP63004317A patent/JPH01180208A/ja active Granted
• 1989
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