Reverse osmosis membrane cleaning method and reverse osmosis membrane prepared by reverse osmosis membrane cleaning method

Abstract

The invention discloses a cleaning method of a reverse osmosis membrane and the reverse osmosis membrane prepared by the cleaning method. The cleaning method comprises the step of sequentially immersing a nascent state membrane of the reverse osmosis membrane into an aqueous solution containing an imidazole activator, pure water and a glycerol aqueous solution for cleaning, in the aqueous solution containing the imidazole activating agent, the imidazole activating agent is selected from one or more of imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, N-ethylimidazole and N-vinyl imidazole. The membrane performance of the reverse osmosis membrane is remarkably improved while residual polyamine monomers in the membrane are reduced, and compared with an existing residual polyamine removal method, the method has outstanding application advantages.

Description

Technical Field

[0001] The invention relates to a related process of a reverse osmosis membrane, in particular to a method for cleaning a reverse osmosis membrane and a reverse osmosis membrane prepared thereby. Background Art

[0002] Reverse osmosis membranes can be used for separation of a variety of fluids. Currently, the most widely used aromatic polyamide reverse osmosis membrane is prepared by interfacial polymerization of m-phenylenediamine and trimesoyl chloride. After the interfacial polymerization, pure water rinsing or acid washing is usually used to remove excess m-phenylenediamine. Excessive residual m-phenylenediamine not only affects the quality of produced water, but also causes the membrane to oxidize and turn yellow and black during long-term storage, affecting the appearance and performance of the membrane. Therefore, various manufacturers have tried many methods to clean the residual m-phenylenediamine in the membrane, as shown below.

[0003] Patent CN104815561A discloses a rinsing method and cleaning solution for a reverse osmosis membrane. After interfacial polymerization, a mixed aqueous solution of isopropanol, ethyl acetate, and a cationic active agent is used to clean the residual m-phenylenediamine, which can reduce the m-phenylenediamine content in the membrane to 0.05ppm. The cleaning effect is significant, but the cleaning solution uses a large number of solvents, and the flash points of isopropanol and ethyl acetate are low, which poses a great production risk. Patent CN102921305A discloses a cleaning agent and cleaning method for residual aromatic amines in a reverse osmosis membrane. This invention patent uses a water-soluble acid and an active agent to clean m-phenylenediamine, which can reduce the residual amount of m-phenylenediamine from 0.51% to less than 0.2%. However, the water-soluble acids used in the solution, such as sulfuric acid and citric acid, are prone to corrode equipment under long-term use under high temperature conditions, resulting in increased costs. Patent CN209564852U discloses a reverse osmosis cleaning system, which allows the membrane to pass through a first mixed cleaning liquid, which includes a combination of sodium carbonate and / or sodium sulfate and water, and then pass through a second mixed cleaning liquid after rinsing by a second device, which includes a combination of acid and water. After undergoing at least two rinsing systems to prepare a reverse osmosis membrane with low m-phenylenediamine residue, there is also the problem of long-term use of acid causing corrosion to the equipment.

[0004] It can be seen that although some cleaning schemes for reverse osmosis membranes have been formed in the prior art, these cleaning schemes also bring some problems in the actual scale-up production process, such as large production risks and equipment corrosion, when reducing the residual m-phenylenediamine in the membrane, and these schemes do not mention the impact on the performance of the membrane when reducing the residual m-phenylenediamine in the membrane. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for cleaning a reverse osmosis membrane and a reverse osmosis membrane prepared thereby.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for cleaning a reverse osmosis membrane comprises the steps of immersing the nascent membrane of the reverse osmosis membrane in sequence into an aqueous solution containing an imidazole activator, pure water and a glycerol aqueous solution for cleaning.

[0008] In some preferred examples of the present invention, the nascent membrane of the reverse osmosis membrane is a polyamide membrane prepared by interfacial polymerization of polymer monomers including polyamine and polyacyl chloride without post-treatment;

[0009] The preparation of polyamide membrane by interfacial polymerization process using polyamine and polyacyl chloride as polymerization monomers is a relatively mature method for preparing reverse osmosis membrane in the art. On this basis, the polyamide membrane can also be grafted or modified by additives through structural / formula design, etc., see the known technologies CN110756061B, CN114053876B, CN117298880A, etc. for the public introduction of the general preparation method or modification method of the process. In addition, various types of additives that are more common in the industry can be added to the aqueous phase solution including polyamines or the oil phase including polyacyl chlorides to enhance related functions. For example, triethylamine is a compound with camphorsulfonic acid and is often used as a humectant, which plays a role in avoiding the collapse of basement membrane pores during the subsequent membrane drying process.

[0010] In the general preparation process of polyamide reverse osmosis membrane, the main process steps are known to include: first preparing a polymer support membrane; contacting the polymer support membrane with an aqueous solution containing polyamines and an oil solution containing polyacid chlorides in turn, generating a polyamide desalting layer through an interfacial polymerization reaction, that is, obtaining the primary ecological membrane of the reverse osmosis membrane; and finally preparing the polyamide reverse osmosis membrane through post-treatment (heat treatment / washing, etc.).

[0011] In the above preparation process, the optional raw materials and process conditions are as follows:

[0012] Preferably, the polyamine is selected from one or more of m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminoanisole, amphenol, xylene diamine, ethylene diamine, propylene diamine, tris(2-aminoethyl)amine, 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine, preferably m-phenylenediamine;

[0013] Preferably, the mass concentration of the polyamine in the aqueous phase solution containing the polyamine is 0.5-5.0%;

[0014] Preferably, the polybasic acid chloride is selected from one or more of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylic acid chloride, naphthalene dicarboxylic acid dichloride, benzene trisulfonyl chloride, benzene disulfonyl chloride, monochlorosulfonylbenzene dicarboxylic acid chloride, propane tricarboxylic acid chloride, butane tricarboxylic acid chloride, pentane tricarboxylic acid chloride, glutaryl halide, adipic acid halide, cyclopropane tricarboxylic acid chloride, cyclobutane tetracarboxylic acid chloride, cyclopentane tricarboxylic acid chloride, cyclopentane tetracarboxylic acid chloride, cyclohexane tricarboxylic acid chloride, tetrahydrofuran tetracarboxylic acid chloride, cyclopentane dicarboxylic acid chloride, cyclobutane dicarboxylic acid chloride, cyclohexane dicarboxylic acid chloride, and tetrahydrofuran dicarboxylic acid chloride, preferably trimesoyl chloride.

[0015] Preferably, in the oil phase solution containing polyacid chloride, the mass concentration of polyacid chloride is 0.01-0.5%; preferably, the oil phase solution is arbitrarily selected from one or more of isopar G, isopar L, and isopar H isoparaffins.

[0016] Preferably, the polymer support membrane is any one of a polysulfone support membrane, a polyethersulfone support membrane, and a polyacrylonitrile support membrane formed on a non-woven fabric. The general process of the polymer support membrane is: the casting liquid is applied on the non-woven fabric of the base material, immediately immersed in a coagulation bath to form a membrane through phase conversion, and then washed to obtain the support membrane; the effective component of the casting liquid is selected from any one of polysulfone, polyethersulfone, and polyacrylonitrile.

[0017] As a specific method for interfacial polymerization, any known operation mode can be adopted, for example, the polymer support membrane is first immersed in an aqueous solution containing polyamines, maintained for 10-300 seconds, and then the residual aqueous phase on the surface is removed after being taken out, and then an oil phase solution containing polyacyl chlorides is poured / sprayed / coated on the membrane surface or the polymer support membrane is immersed in the oil phase solution containing polyacyl chlorides again to carry out interfacial polymerization reaction. This will not serve as any limitation to the present invention and will not be repeated here.

[0018] Preferably, the temperature of the interfacial polymerization reaction is 15-35°C.

[0019] In some preferred examples of the present invention, the aqueous solution containing an imidazole activator contains an imidazole activator selected from one or more of imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, N-ethylimidazole, and N-vinylimidazole;

[0020] Preferably, the mass concentration of the imidazole activator in the aqueous solution containing the imidazole activator is 10-30%.

[0021] In some preferred examples of the present invention, the treatment condition of the nascent membrane of the reverse osmosis membrane in the aqueous solution containing the imidazole activator is to wash it at 60-90° C. for 1-3 min.

[0022] In some preferred examples of the present invention, the treatment condition of the nascent membrane of the reverse osmosis membrane in pure water is to wash it at 60-90° C. for 1-3 min.

[0023] In some preferred examples of the present invention, the mass concentration of glycerol in the glycerol aqueous solution is 5-10%.

[0024] In some preferred examples of the present invention, the treatment condition of the nascent membrane of the reverse osmosis membrane in the glycerol aqueous solution is to wash it at 20-30° C. for 10-180 s.

[0025] The present invention also provides a reverse osmosis membrane obtained by cleaning through the method described above.

[0026] The present invention uses an imidazole activator to clean the primary ecological membrane of the reverse osmosis membrane. At a higher treatment temperature, the polyamide desalination layer structure in the swelling membrane can be dissolved, so that the polyamide oligomers are dissolved, the water channel is opened, or more pore channels occupied by polymerized polyamines are released, thereby improving the water flux. On the other hand, the polyamines remaining in the membrane are also dissolved, and a significant polyamine cleaning effect is achieved. In addition, imidazole substances can also promote the further reaction of the residual terminal amino groups and terminal acyl chlorides in the polyamide separation layer, improve the desalination rate to a certain extent, and achieve a significant increase in water flux on the basis of maintaining a higher desalination rate, solving the industry problem that the two are difficult to take into account. More importantly, the present invention significantly improves the membrane performance of the reverse osmosis membrane while reducing the residual polyamine monomers in the membrane, and has outstanding application advantages compared to the existing method for removing residual polyamines. DETAILED DESCRIPTION

[0027] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0028] Unless otherwise specified, the raw materials used in the following examples or comparative examples are all commercially available conventional raw materials, wherein the main raw material information is shown in Table 1 below.

[0029] Table 1. Main raw material information

[0030]

[0031]

[0032] The following describes the test methods used or may be used in the embodiments or comparative examples of the present invention:

[0033] 1. Residual amine content test

[0034] The residual m-phenylenediamine content test was carried out on a UV-visible spectrophotometer. First, 20 mL of an ethanol aqueous solution with a mass concentration of 15% was prepared, and then two circular reverse osmosis membrane sheets with a diameter of 7.8 cm were cut and placed in the above mixed solution. The mixture was heated at 80°C for 2 h to dissolve the residual m-phenylenediamine. The absorbance of the mixed solution after heating was measured at a wavelength of 290 nm, and then the content of the residual m-phenylenediamine was calculated by drawing a standard curve.

[0035] 2. Evaluation of salt rejection and permeate flux

[0036] Salt rejection rate and permeation flux are two important parameters for evaluating the separation performance of reverse osmosis membranes. The present invention evaluates the separation performance of reverse osmosis membranes according to GB / T32373-2015 "Test Method for Reverse Osmosis Membrane".

[0037] The desalination rate (R) is defined as: under certain operating conditions, the salt concentration of the feed solution (C f ) and the salt concentration in the permeate (C p ) and then divided by the feed solution salt concentration (C f ), as shown in formula (1).

[0038]

[0039] Permeation flux is defined as the volume of water that passes through a unit membrane area per unit time under certain operating conditions, and its unit is L·m -2 ·h -1 .

[0040] The operating conditions used in the reverse osmosis membrane performance measurement in the present invention are: the feed liquid is a 1500 ppm sodium chloride aqueous solution, the solution pH is 7.5±0.5, the operating pressure is 150 psi, and the operating temperature is 25±1°C.

[0041]

Preparation example

[0042] The reverse osmosis membrane primary ecological membrane used in each embodiment and comparative example was prepared by the following method:

[0043] An aqueous solution containing 2.0% m-phenylenediamine, 2.3% camphorsulfonic acid and 1.1% triethylamine by mass concentration is prepared, and a polysulfone-based membrane is immersed in the aqueous solution for 30 seconds, then taken out and gently squeezed with a roller to remove excess water phase remaining on the surface, and then a n-decane solution with a temperature of 25°C and a mass concentration of 0.12% trimesoyl chloride is applied to the front side of the polysulfone-based membrane after contact with the water phase, and reacted for 30 seconds, and the excess n-decane solution is poured out, and the membrane surface is evenly blown with an air knife until there is no residual solvent on the membrane surface, and then placed in a 70°C oven for drying for 5 minutes to prepare a primary ecological membrane of the reverse osmosis membrane.

[0044] [Example 1]

[0045] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 10% imidazole aqueous solution at a treatment temperature of 90°C for 1 minute; then, it was immersed in a cleaning tank of pure water at a treatment temperature of 80°C for 2 minutes; then, it was immersed in a cleaning tank containing an 8% glycerol aqueous solution at a treatment temperature of 25°C for 30 seconds. After being taken out, the excess glycerol solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0046] [Example 2]

[0047] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 30% imidazole aqueous solution at a treatment temperature of 70°C for 2 minutes; then, it was immersed in a cleaning tank containing pure water at a treatment temperature of 90°C for 2 minutes; then, it was immersed in a cleaning tank containing a 5% glycerol aqueous solution at a treatment temperature of 30°C for 90 seconds. After being taken out, the excess solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0048] [Example 3]

[0049] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 20% imidazole aqueous solution at a treatment temperature of 60°C for 3 minutes; then, it was immersed in a cleaning tank containing pure water at a treatment temperature of 60°C for 3 minutes; then, it was immersed in a cleaning tank containing a 10% glycerol aqueous solution at a treatment temperature of 20°C for 10 seconds. After being taken out, the excess solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0050] [Example 4]

[0051] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 15% N-methylimidazole aqueous solution at a treatment temperature of 80°C for 2 minutes; then, it was immersed in a cleaning tank of pure water at a treatment temperature of 60°C for 3 minutes; then, it was immersed in a cleaning tank containing a 9% glycerol aqueous solution at a treatment temperature of 20°C for 120 seconds. After being taken out, the excess solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0052] [Example 5]

[0053] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 30% N-methylimidazole aqueous solution at a treatment temperature of 90°C for 3 minutes; then, it was immersed in a cleaning tank of pure water at a treatment temperature of 75°C for 2 minutes; then, it was immersed in a cleaning tank containing a 10% glycerol aqueous solution at a treatment temperature of 25°C for 60 seconds. After being taken out, the excess solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0054] [Example 6]

[0055] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 20% 4-methylimidazole aqueous solution at a treatment temperature of 85°C for 3 minutes; then, it was immersed in a cleaning tank containing pure water at a treatment temperature of 80°C for 3 minutes; then, it was immersed in a cleaning tank containing a 10% glycerol aqueous solution at a treatment temperature of 25°C for 20 seconds. After being taken out, the excess solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0056] [Example 7]

[0057] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 25% N-ethylimidazole aqueous solution at a treatment temperature of 70°C for 3 minutes; then, it was immersed in a cleaning tank of pure water at a treatment temperature of 65°C for 3 minutes; then, it was immersed in a cleaning tank containing a 6% glycerol aqueous solution at a treatment temperature of 25°C for 150 seconds. After being taken out, the excess solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0058] [Example 8]

[0059] The nascent membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing an 18% N-vinyl imidazole aqueous solution at a treatment temperature of 75°C for 2 minutes; then, it was immersed in a cleaning tank of pure water at a treatment temperature of 80°C for 2 minutes; then, it was immersed in a cleaning tank containing an 8% glycerol aqueous solution at a treatment temperature of 27°C for 80 seconds. After being taken out, the excess solution on the front and back sides was removed with an air knife, and the membrane was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0060] [Comparative Example 1]

[0061] The nascent membrane of the reverse osmosis membrane was first immersed in a pure water cleaning tank without adding an imidazole activator, with a treatment temperature of 90° C. and a treatment time of 1 minute; the subsequent pure water cleaning, glycerol cleaning and drying processes were consistent with Example 1 to obtain a reverse osmosis membrane.

[0062] [Comparative Example 2]

[0063] The primary green membrane of the reverse osmosis membrane was first immersed in a cleaning tank containing a 10% imidazole aqueous solution, and the treatment temperature was adjusted to 25°C and the treatment time was 1 minute; the subsequent pure water cleaning, glycerol cleaning and drying processes were consistent with Example 1 to obtain a reverse osmosis membrane.

[0064] [Comparative Example 3]

[0065] The primary ecological membrane of the reverse osmosis membrane was first immersed in an aqueous solution containing 10% isopropanol, with a treatment temperature of 90° C. and a treatment time of 1 minute; the subsequent pure water washing, glycerol washing and drying processes were consistent with Example 1 to obtain a reverse osmosis membrane.

[0066] [Comparative Example 4]

[0067] The primary ecological membrane of the reverse osmosis membrane was first immersed in an aqueous solution containing 10% citric acid at a treatment temperature of 90° C. for 1 minute; the subsequent pure water washing, glycerol washing and drying processes were consistent with Example 1 to obtain a reverse osmosis membrane.

[0068] [Comparative Example 5]

[0069] An aqueous solution containing 2.0% m-phenylenediamine, 2.3% camphorsulfonic acid, 1.1% triethylamine and 0.3% imidazole by mass concentration is prepared, and a polysulfone-based membrane is immersed in the aqueous solution for 30 seconds, then taken out and gently squeezed with a roller to remove excess water phase remaining on the surface, and then a n-decane solution with a temperature of 25°C and a mass concentration of 0.12% trimesoyl chloride is applied to the front side of the polysulfone-based membrane after contact with the aqueous phase, and reacted for 30 seconds, and the excess n-decane solution is poured out, and the membrane surface is evenly blown with an air knife until there is no residual solvent, and the membrane is placed in a 70°C oven for drying for 5 minutes to prepare a primary ecological membrane of the reverse osmosis membrane.

[0070] The nascent membrane of the reverse osmosis membrane was first immersed in a pure water cleaning tank without imidazole activator, with a treatment temperature of 90°C and a treatment time of 1 minute; then, it was immersed in a pure water cleaning tank, with a treatment temperature of 80°C and a treatment time of 2 minutes; then, it was immersed in a cleaning tank containing 8% glycerol aqueous solution, with a treatment temperature of 25°C and a treatment time of 30 seconds. After taking it out, the excess solution on the front and back sides was removed with an air knife, and it was placed in a 70°C oven and dried for 6 minutes to obtain a reverse osmosis membrane.

[0071] The residual amine content and basic performance of the reverse osmosis membranes in the examples and comparative examples were tested, and the performance is summarized in Table 2 below.

[0072] Table 2. Performance test results

[0073]

[0074]

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for cleaning a reverse osmosis membrane, characterized in that: The method comprises the steps of immersing the primary ecological membrane of the reverse osmosis membrane in sequence into an aqueous solution containing an imidazole activator, pure water and a glycerol aqueous solution for cleaning.

2. The method for cleaning a reverse osmosis membrane according to claim 1, characterized in that: The nascent membrane of the reverse osmosis membrane is a polyamide membrane prepared by interfacial polymerization of polymerized monomers including polyamine and polyacyl chloride without post-treatment; Preferably, the polyamine is selected from one or more of m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminoanisole, amphenol, xylene diamine, ethylene diamine, propylene diamine, tris(2-aminoethyl)amine, 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine, preferably m-phenylenediamine; Preferably, the polybasic acid chloride is selected from one or more of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylic acid chloride, naphthalene dicarboxylic acid dichloride, benzene trisulfonyl chloride, benzene disulfonyl chloride, monochlorosulfonylbenzene dicarboxylic acid chloride, propane tricarboxylic acid chloride, butane tricarboxylic acid chloride, pentane tricarboxylic acid chloride, glutaryl halide, adipic acid halide, cyclopropane tricarboxylic acid chloride, cyclobutane tetracarboxylic acid chloride, cyclopentane tricarboxylic acid chloride, cyclopentane tetracarboxylic acid chloride, cyclohexane tricarboxylic acid chloride, tetrahydrofuran tetracarboxylic acid chloride, cyclopentane dicarboxylic acid chloride, cyclobutane dicarboxylic acid chloride, cyclohexane dicarboxylic acid chloride, and tetrahydrofuran dicarboxylic acid chloride, preferably trimesoyl chloride.

3. The method for cleaning a reverse osmosis membrane according to claim 1, characterized in that: The aqueous solution containing an imidazole activator is selected from one or more of imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, N-ethylimidazole, and N-vinylimidazole; Preferably, the mass concentration of the imidazole activator in the aqueous solution containing the imidazole activator is 10-30%.

4. The method for cleaning a reverse osmosis membrane according to any one of claims 1 to 3, characterized in that: The treatment condition of the nascent membrane of the reverse osmosis membrane in the aqueous solution containing the imidazole activator is to wash it at 60-90° C. for 1-3 minutes.

5. The method for cleaning a reverse osmosis membrane according to any one of claims 1 to 4, characterized in that: The treatment condition of the primary ecological membrane of the reverse osmosis membrane in pure water is to wash it at 60-90° C. for 1-3 minutes.

6. The method for cleaning a reverse osmosis membrane according to any one of claims 1 to 5, characterized in that: In the glycerol aqueous solution, the mass concentration of glycerol is 5-10%.

7. The method for cleaning a reverse osmosis membrane according to any one of claims 1 to 6, characterized in that: The treatment condition of the nascent membrane of the reverse osmosis membrane in the glycerol aqueous solution is to wash it at 20-30° C. for 10-180 seconds.

8. A reverse osmosis membrane obtained by cleaning by the method according to any one of claims 1 to 7.

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