阅读说明：本技术 油水分离过滤器 (Oil-water separation filter ) 是由 白石真也 腰山博史 于 2020-02-20 设计创作，主要内容包括：油水分离过滤器,其包括过滤用无纺布,该过滤用无纺布在纤维间形成多个气孔,该气孔贯穿含有水和油的混合液体流入的一面和与该一面相对的另一面之间。油水分离膜以每1m～(2)过滤用无纺布为0.1g～30g的比例形成于过滤用无纺布的纤维表面,具有硅溶胶水解物,该硅溶胶水解物具有防水性和防油性这两种功能、且包含式(1)所示的含氟官能团成分。含氟官能团成分以0.01质量%～10质量%的比例包含在硅溶胶水解物中,油水分离过滤器的通气度为0.05ml/cm～(2)/秒～10ml/cm～(2)/秒。(An oil-water separation filter includes a nonwoven fabric for filtration having a plurality of pores formed between fibers, the pores penetrating between one surface into which a mixed liquid containing water and oil flows and the other surface opposite to the one surface. The oil-water separation membrane is used for every 1m 2 The non-woven fabric for filtration is0.1 to 30g of a fluorine-containing functional group component represented by the formula (1) is formed on the fiber surface of the nonwoven fabric for filtration, and has a silica sol hydrolysate which has both water-repellent and oil-repellent functions. The fluorine-containing functional group component is contained in the silica sol hydrolysate in a proportion of 0.01 to 10 mass%, and the air permeability of the oil-water separation filter is 0.05ml/cm 2 Second to 10ml/cm 2 In seconds.)

1. Oil-water separation filter, its characterized in that: the oil-water separation filter comprises a nonwoven fabric for filtration having a plurality of pores formed between fibers, the pores penetrating between one surface into which a mixed liquid containing water and oil flows and the other surface from which the mixed liquid flows,

on the surface of the fiber at a ratio of 1m per²The non-woven fabric for filtration is formed into an oil-water separation membrane in a proportion of 0.1g to 30g,

the oil-water separation membrane has a silica sol hydrolysate containing a fluorine-containing functional group component having both water-repellent and oil-repellent functions,

the fluorine-containing functional group component is contained in the silica sol hydrolysate in a proportion of 0.01 to 10% by mass,

the air permeability of the oil-water separation filter is 0.05ml/cm²Second to 10ml/cm²The time per second of the reaction mixture is,

the fluorine-containing functional group component has a perfluoroether structure represented by the following general formula (1) or (2):

[ chemical formula 1]

[ chemical formula 2]

In the formulae (1) and (2), p, q and r are the same or different integers of 1 to 6, and may be straight-chain or branched, X in the formulae (1) and (2) is a hydrocarbon group having 2 to 10 carbon atoms and may contain 1 or more bonds selected from an ether bond, a CO-NH bond, an O-CO-NH bond and a sulfonamide bond, and Y in the formulae (1) and (2) is a main component of a silica sol hydrolysate.

2. The oil-water separator according to claim 1, wherein the silica sol hydrolysate further contains 0.5 to 20 mass% of an alkylene component having 2 to 7 carbon atoms.

3. The oil-water separator filter according to claim 1 or 2, wherein the nonwoven fabric for filtration is composed of a single layer or a multilayer laminate.

4. The oil-water separator according to any one of claims 1 to 3, wherein the fibers constituting the nonwoven fabric for filtration are 1 or 2 or more types of fibers selected from the group consisting of PET (polyethylene terephthalate), PP (polypropylene), glass, alumina, carbon, cellulose, pulp, nylon, and metal.

5. The oil-water separator filter according to claim 4, wherein the fibers constituting the nonwoven fabric for filtration corresponding to the surface into which the mixed liquid containing water and oil flows are glass fibers.

6. The oil-water separator filter according to any one of claims 1 to 5, wherein the filtration nonwoven fabric on the side from which the mixed liquid flows out is supported by being superposed on the other side of the filtration nonwoven fabricA nonwoven fabric for reinforcing a nonwoven fabric for filtration, the nonwoven fabric for reinforcing having an air permeability of 20ml/cm²The nonwoven fabric for reinforcement has a tensile strength of 70N or more per second or more.

7. The oil-water separator according to claim 6, wherein the fibers constituting the reinforcing nonwoven fabric are 1 or 2 or more fibers selected from the group consisting of PET (polyethylene terephthalate), PP (polypropylene), cellulose, pulp, nylon, bamboo, and metals.

Technical Field

The present invention relates to an oil-water separation filter capable of separating emulsified oil or water-soluble oil obtained by emulsifying oil into water and oil with a simple configuration. More specifically, the present invention relates to an oil-water separator filter in which an oil-water separation membrane having water repellency and oil repellency (hereinafter, also referred to as water-and oil repellency) is formed on the fiber surface of a nonwoven fabric for filtration. It should be noted that the international application claims priority from japanese patent application No. 33513 (japanese patent application No. 2019 and 033513) applied on 27/2/2020 and japanese patent application No. 1026 (japanese patent application No. 2020 and 001026) applied on 7/1/2020, and the entire contents of japanese patent application No. 2019 and 033513 and japanese patent application No. 2020 and 001026 are incorporated into the international application.

Background

Generally, a mixed liquid containing water and oil is classified according to its oil-water mixing state into: floating oil floating to the water surface; dispersed oil in which particles of oil are suspended in water; and emulsified oil or water-soluble oil emulsified by mixing oil and water.

The present applicant has proposed a porous oil-water separation body having a porous base material made of a nonwoven fabric having a plurality of pores penetrating between one surface into which a mixed liquid containing water and oil flows and the other surface opposite to the one surface, and an oil-water separation filter having the porous oil-water separation body (see patent document 1 (claim 1, claim 7, paragraph 0020, paragraph 0074)). The pore opening diameter of the oil-water separating porous body was 0.1μm is more than or equal to 180μm or less, forming oil-water separation material on the surface of the pores, oil-waterThe separated product is provided with an oil-water separating material containing a fluorine-based compound having an oil repellency imparting group and a hydrophilicity imparting group.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-;

patent document 2: japanese patent laid-open No. 2000-202247.

Disclosure of Invention

Problems to be solved by the invention

When the mixed liquid containing water and oil is the above-mentioned oil slick or dispersed oil, i.e., the water-insoluble oil, the surface of the oil particles 1a of the water-insoluble oil 1 is covered with CH as shown in fig. 8(a)₃And alkyl groups 1 b. Since the alkyl group 1b has no affinity with water and is not hydrophilic, when the water-insoluble oil 1 is left in place, the specific gravity of the oil particles 1a is smaller than that of the water 1c, and the surface tension thereof is reduced, whereby the oil particles 1a are bonded to each other and float. Therefore, in the oil-water separation filter having an oil-water separator having hydrophilic and oil-repellent properties disclosed in patent document 1, when the mixed liquid is a water-insoluble oil, the mixed liquid can be separated into water and oil and filtered.

On the other hand, when the mixed liquid is emulsified oil or water-soluble oil obtained by mixing and emulsifying oil and water, as shown in fig. 8(b), the surfaces of the oil particles 2a of the water-soluble oil 2 are covered with hydroxyl groups 2 b. The hydroxyl group 2b has high affinity with water 2c, and the oil particle 2a is stably dispersed in water even if the water-soluble oil 2 is left. In the oil-water separator filter shown in patent document 1, since the oil-water separator is a fluorine-based compound having hydrophilicity and oil repellency, there is a problem that the water-soluble oil in which the oil particles are stably dispersed in water, and the oil particles covered with the hydroxyl groups are not chemically blocked by the oil-water separator having a hydrophilicity-imparting group, but pass through a porous base material such as a nonwoven fabric, and the mixed liquid cannot be separated into water and oil. For this reason, a technique of separating emulsified oil or aqueous oil into water and oil by using an oil-water separator using a hollow fiber membrane is known (for example, see patent document 2 (claim 6, paragraph 0028, fig. 5)). However, such an oil-water separator has a problem of complicated structure.

The invention aims to: provided is an oil-water separation filter which can separate emulsified oil or water-soluble oil obtained by emulsifying oil into water and oil with a simple configuration. Another object of the present invention is to: provided is an oil-water separation filter having improved physical strength.

Means for solving the problems

The inventor realizes the invention through the following 3 points: first, an oil-water separation membrane formed on the surface of fibers of a nonwoven fabric for filtration of an oil-water separation filter is made to contain a fluorine-containing functional group component having water-and oil-repellency, so that the surface of the fibers of the nonwoven fabric for filtration chemically repels oil particles of water-soluble oil; secondly, the water permeability of the non-woven fabric for filtration is maintained by using a silica sol hydrolysate having hydroxyl groups as a main component in the oil-water separation membrane; thirdly, the air permeability of the oil-water separation filter is set to a predetermined value, thereby reducing the pores of the nonwoven fabric for filtration and physically blocking the oil particles of the water-soluble oil from passing through.

The invention from 1 st aspect is an oil-water separation filter, characterized in that: the oil-water separation filter comprises: a nonwoven fabric for filtration having a plurality of pores formed between fibers, the pores penetrating between one surface into which a mixed liquid containing water and oil flows and the other surface opposite to the one surface, the pores being formed on the surface of the fibers at a rate of 1m per fiber²An oil-water separation membrane is formed in the non-woven fabric for filtration at a ratio of 0.1 to 30g, the oil-water separation membrane has a silica sol hydrolysate containing a fluorine-containing functional group component having both water repellency and oil repellency, the fluorine-containing functional group component is contained in the silica sol hydrolysate at a ratio of 0.01 to 10 mass%, and the oil-water separation filter has an air permeability of 0.05ml/cm²Second to 10ml/cm²The fluorine-containing functional group component has a perfluoroether structure represented by the following general formula (1) or formula (2):

[ chemical formula 1]

　　　(1)

[ chemical formula 2]

　　　(2)

In the formulae (1) and (2), p, q and r are the same or different integers of 1 to 6, and may be straight-chain or branched, X in the formulae (1) and (2) is a hydrocarbon group having 2 to 10 carbon atoms and may contain 1 or more bonds selected from an ether bond, a CO-NH bond, an O-CO-NH bond and a sulfonamide bond, and Y in the formulae (1) and (2) is a main component of a silica sol hydrolysate.

An aspect 2 of the present invention is the oil-water separation filter according to the aspect 1, wherein the silica sol hydrolysate further contains 0.5 to 20 mass% of an alkylene component having 2 to 7 carbon atoms.

The invention according to claim 3 is the oil-water separator filter according to the invention according to claim 1 or 2, wherein the nonwoven fabric for filtration is composed of a single layer or a multilayer laminate.

The invention according to claim 4 is the oil-water separator according to any one of claims 1 to 3, wherein the fibers constituting the nonwoven fabric for filtration are 1 or 2 or more types of fibers selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), glass, alumina, carbon, cellulose, pulp, nylon, and metal.

In the oil-water separator according to claim 5 of the present invention, which is the invention according to claim 4, the fiber constituting the nonwoven fabric for filtration corresponding to the surface into which the mixed liquid containing water and oil flows is glass fiber.

The invention according to claim 6 is the oil-water separator according to any one of claims 1 to 5, wherein a reinforcing nonwoven fabric supporting the filtration nonwoven fabric is provided on the other side of the filtration nonwoven fabric on the side from which the mixed liquid flows out, and the reinforcing nonwoven fabric has an air permeability of 20ml/cm²Second/secondAs described above, the tensile strength of the reinforcing nonwoven fabric is 70N or more.

The 7 th aspect of the present invention is the oil-water separator filter according to the 6 th aspect of the present invention, wherein the fibers constituting the reinforcing nonwoven fabric are 1 or 2 or more types of fibers selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), cellulose, pulp, nylon, bamboo, and metal.

Effects of the invention

In the oil-water separator filter according to claim 1 of the present invention, the fiber surface is coated with a filler in an amount of 1m²An oil-water separation membrane is formed on the nonwoven fabric for filtration at a ratio of 0.1g to 30g, and the oil-water separation membrane contains a fluorine-containing functional group component having both water repellency and oil repellency represented by the general formula (1) or (2), and the air permeability of the oil-water separation filter is defined to be 0.05ml/cm²Second to 10ml/cm²The pores of the nonwoven fabric for filtration are defined per second, so that when the mixed liquid is immersed in the oil-water separation filter, the oil particles of the mixed liquid are physically blocked from passing therethrough in the case where the oil particles of the mixed liquid are larger than the pore size of the pores. Further, even in the case where the oil particles of the mixed liquid are slightly smaller than the pore diameter of the pores, the fiber surface of the nonwoven fabric for filtration chemically repels the oil particles of the water-soluble oil.

On the other hand, since a material exhibiting water-and oil-repellency, such as polytetrafluoroethylene, does not have a hydroxyl group, it is difficult to impart water permeability to the nonwoven fabric for filtration. As a result, even if the mixed liquid is emulsified oil or water-soluble oil, the oil is accumulated in the oil-water separation filter, and water is separated into water and oil by passing through the oil-water separation filter. Further, since the oil-water separation membrane of the present invention contains a silica sol hydrolysate as a main component, the oil-water separation membrane strongly adheres to the fiber surface of the nonwoven fabric for filtration, and has durability.

In the oil-water separation filter according to claim 2 of the present invention, since the fluorine-containing functional group component contained in the oil-water separation membrane further contains 0.5 to 20 mass% of an alkylene component having 2 to 7 carbon atoms, adhesion to the fibers can be obtained, the thickness of the oil-water separation membrane becomes uniform, and more excellent oil-water separation performance can be imparted to the oil-water separation membrane.

In the oil-water separator according to claim 3 of the present invention, the oil-water separator is simple when the nonwoven fabric for filtration is formed of a single layer, and each layer can be formed according to the oil content of the mixed liquid flowing in, the size of the oil particles, and other properties when the nonwoven fabric for filtration is formed of a multilayer laminate.

In the oil-water separation filter according to claim 4 of the present invention, the material of the fibers constituting the nonwoven fabric for filtration may be selected from polyethylene terephthalate (PET), polypropylene (PP), glass, alumina, carbon, cellulose, pulp, nylon, and metal fibers, depending on the oil content of the mixed liquid flowing in, the properties such as the size of oil particles, or the content of the alkylene component having 2 to 7 carbon atoms formed by hydrolysis of the epoxysilane-containing group in the liquid composition for forming the oil-water separation membrane described later.

In the oil-water separator according to claim 5 of the present invention, the fiber constituting the nonwoven fabric for filtration corresponding to the surface into which the mixed liquid containing water and oil flows is made of glass fiber, and the oil-water separation membrane containing a silica sol hydrolysate as a main component is more strongly adhered to the glass fiber, and is less likely to be peeled off from the fiber of the nonwoven fabric for filtration.

In the oil-water separator according to claim 6 of the present invention, a reinforcing nonwoven fabric supporting the filtration nonwoven fabric is laminated on the other surface of the filtration nonwoven fabric, and the permeability of the reinforcing nonwoven fabric is 20ml/cm²The nonwoven fabric for reinforcement has a tensile strength of 70N or more per second or more, and therefore, the physical strength of the oil-water separator filter can be improved.

In the oil-water separator according to claim 8 of the present invention, the material of the fibers constituting the reinforcing nonwoven fabric may be selected from polyethylene terephthalate (PET), polypropylene (PP), cellulose, pulp, nylon, bamboo, and metal fibers in accordance with the physical strength of the filtering nonwoven fabric, so as to reinforce the oil-water separator.

Drawings

FIG. 1 is a structural view of an oil-water separator including an oil-water separation filter according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a nonwoven fabric for single-layer filtration according to the present embodiment.

FIG. 3 is a cross-sectional view of the nonwoven fabric for double layer filtration of the present embodiment.

Fig. 4 is a cross-sectional view of a single-layer nonwoven fabric for filtration according to the present embodiment on which a nonwoven fabric for reinforcement is superimposed.

Fig. 5 is a cross-sectional view of the double-layer nonwoven fabric for filtration of the present embodiment on which a nonwoven fabric for reinforcement is superimposed.

Fig. 6 is a perspective view of the pleated oil-water separator filter according to the present embodiment in which a reinforcing nonwoven fabric is superimposed on a single-layer filtering nonwoven fabric in a pleated state.

FIG. 7 is a schematic diagram of an apparatus used in a filtration test of each of the oil-water separation filters of examples and comparative examples.

Fig. 8(a) is a schematic view of oil particles in the case where the mixed liquid containing water and oil is water-insoluble oil, and fig. 8(b) is a schematic view of oil particles in the case where the mixed liquid containing water and oil is water-soluble oil.

Detailed Description

Next, a mode for carrying out the present invention will be described with reference to the drawings.

[ oil-water separator ]

As shown in fig. 1, an oil-water separator 10 of the present embodiment includes: a cylindrical mixed liquid inflow portion 12 into which a mixed liquid 11 containing water and oil flows; a sheet-like oil-water separation filter 13 for separating oil of the mixed liquid 11 from water; a funnel-shaped water collecting unit 16 for collecting the water 14 separated by the oil-water separation filter 13; and a cylindrical water storage part 17 with a bottom for storing the water 14 flowing from the water collection part 16. An inflow pipe 18 for the mixed liquid is provided above the mixed liquid inflow portion 12, and a drain pipe 19 is provided at the bottom of the water storage portion 17.

When the oil-water separation filter 13 is composed of only the filter nonwoven fabric described later, although not shown, a metal porous support plate for reinforcing the filter nonwoven fabric is provided over the entire lower surface of the oil-water separation filter 13, so that the filter 13 can withstand the hydraulic pressure of the mixed liquid in the mixed liquid inflow unit 12, and the oil-water separation filter 13 and the support plate are sandwiched between the mixed liquid inflow unit 12 and the water collection unit 16. When the oil-water separation filter 13 is formed of a laminate of a nonwoven fabric for filtration and a nonwoven fabric for reinforcement, a metal porous support plate is not required.

[ oil-water separating filter ]

The oil-water separation filter 13 of the present embodiment includes a nonwoven fabric for filtration and an oil-water separation membrane formed on the fiber surface of the nonwoven fabric. As shown in fig. 2, the filter nonwoven fabric 20, which is a main component of the oil-water separator 13, has one surface 20a into which a mixed liquid containing water and oil flows, and the other surface 20b from which a filtrate (filtrate) opposite to the one surface 20a flows out, and is formed of a single layer. As shown in fig. 3, the oil-water separator filter 23 may be formed by laminating a nonwoven filter fabric 30 as an upper layer and a nonwoven filter fabric 40 as a lower layer. In this case, the upper surface of the upper layer nonwoven filter fabric 30 is a surface 30a into which the liquid mixture containing water and oil flows, and the lower surface of the lower layer nonwoven filter fabric 40 is a surface 40b from which the filtrate flows out, the surface facing the surface 30 a. The lower surface 30b of the nonwoven filter fabric 30 is in close contact with the upper surface 40a of the nonwoven filter fabric 40. The laminate is not limited to a double layer, and may be composed of a plurality of layers such as three layers and four layers.

As shown in the enlarged view of fig. 2, the nonwoven fabric for filtration 20 is formed by winding a plurality of fibers 20c, and pores 20d are formed between the fibers. The pores 20d penetrate between the one surface 20a and the other surface 20b of the nonwoven filter fabric 20. An oil-water separation membrane 21 is formed on the surface of the fiber 20c of the nonwoven fabric for filtration. The oil-water separation membrane 21 is disposed at a rate of 1m²The nonwoven fabric is formed on the fiber surface of the nonwoven fabric for filtration at a ratio of 0.1g to 30 g. The oil-water separation membrane 21 is formed of a silica sol hydrolysate containingA fluorine-containing functional group component having water-and oil-repellency represented by the general formula (1) or (2). The fluorine-containing functional group component is contained in the silica sol hydrolysate in a proportion of 0.01 to 10% by mass. The filtration nonwoven fabric 20 was prepared to have a volume of 0.05ml/cm in a state where the oil-water separation filter 13 having the oil-water separation film 21 formed on the fiber surface was used²Second to 10ml/cm²Air flow/sec. The air permeability was measured according to JIS-L1913: the measurement was carried out by a Frazier type tester described in 2000.

As shown in fig. 4, the oil-water separation filter 33 can be configured by superposing the reinforcing nonwoven fabric 50 on the other surface 20b of the filtering nonwoven fabric 20 so that one surface 50a of the reinforcing nonwoven fabric 50 supporting the filtering nonwoven fabric 20 is in close contact therewith.

In the oil-water separator 33 shown in fig. 4, the mixed liquid containing water and oil flows into one surface 20a of the nonwoven fabric for filtration 20, and the filtrate flows out from the other surface 50b of the nonwoven fabric for reinforcement 50. By doing so, the aforementioned porous support plate made of metal does not need to be provided. As shown in fig. 5, the oil-water separator 43 may be configured by stacking a reinforcing nonwoven fabric 50 to support a two-layer laminate of the filtering nonwoven fabric 30 and the lower filtering nonwoven fabric 40. In the oil-water separator 43, the lower surface 40b of the lower filtration nonwoven fabric 40 is in close contact with the upper surface 50a of the reinforcing nonwoven fabric 50, and the mixed liquid containing water and oil flows into one surface 30a of the filtration nonwoven fabric 30, passes through the filtration nonwoven fabric 40, and the filtrate flows out from the other surface 50b of the reinforcing nonwoven fabric 50.

As shown in fig. 6, in a state where a laminate of the nonwoven fabric for filtration 20 and the nonwoven fabric for reinforcement 50 as shown in fig. 4 is stacked, the laminate may be pleated so as to have valleys to form a pleated oil-water separator filter 33. By doing so, the oil-water separation filter 33 having high physical strength can be produced against the inflow pressure of the mixed liquid. When the mixed liquid containing water and oil flows in, it is preferable that the oil-water separation filter 33 be supported by inserting a plurality of support frames 46, 46 having valleys corresponding to the valleys of the laminate from the reinforcing nonwoven fabric 50 side with a gap therebetween in order to maintain the pleated state. The nonwoven fabric to be reinforced with the reinforcing nonwoven fabric 50 is not limited to the single-layer nonwoven fabric for filtration 20, and although not shown, may be a laminate composed of the nonwoven fabrics for filtration 30 and 40, may not be limited to a two-layer laminate, or may be a laminate composed of a plurality of layers such as three layers or four layers.

If every 1m²When the amount of the oil-water separating film in the nonwoven fabric for filtration is less than 0.1g or the amount of the fluorine-containing functional group component is less than 0.01% by mass, the water-and oil-repellent effect is insufficient, the oil-water separating performance is insufficient, and if the amount is 1m per nonwoven fabric for filtration²When the amount of the oil-water separation membrane in the nonwoven fabric for filtration exceeds 30g, the air permeability becomes less than 0.05ml/cm²In seconds. When the fluorine-containing functional group component exceeds 10 mass%, the adhesion to the nonwoven fabric for filtration is deteriorated. Preferably every 1m²The oil-water separation membrane of the non-woven fabric for filtration is 0.5g to 10 g. The fluorine-containing functional group component is preferably contained in the silica sol hydrolysate in a range of 0.1 to 5% by mass. If the air permeability is less than 0.05ml/cm²The water permeability is poor when the amount of water is measured in seconds, and it is difficult to obtain a filtrate. If it exceeds 10ml/cm²When the oil particles 22 pass through the pores of the nonwoven fabric for filtration, the oil particles 22 fall off from the oil-water separation filter 13 together with water, and water and oil cannot be separated. The air permeability is preferably 0.1ml/cm²Second to 5ml/cm²In seconds.

The operation of the oil-water separator 10 including the oil-water separation filter 13 will be described. As shown in fig. 1, first, the oil-water separation filter 13 is sandwiched between the mixed liquid inflow unit 12 and the water collection unit 16. Then, the mixed liquid 11 containing water and oil is supplied from the inflow pipe 18 to the mixed liquid inflow portion 12. The mixed liquid of this embodiment is a water-soluble oil. The mixed liquid 11 stored in the mixed liquid inflow unit 12 contacts one surface 20a (fig. 2) of the nonwoven filter fabric 20 constituting the oil-water separator 13. Here, since the oil-water separation filter 13 has a predetermined air permeability and the oil-water separation membrane 21 exhibits water-and-oil repellency, water (not shown) of the water-soluble oil is repelled by the oil-water separation membrane 21, but due to the presence of hydroxyl groups of the silica sol hydrolysate, the water passes through the pores 20d formed between the fibers 20c and the fibers 20c as shown in the enlarged view of fig. 2, reaches the other surface 20b, drips therefrom, and is collected in the water collection portion 16. The collected water 14 flows from the water collection unit 16 into the water storage unit 17 and is stored in the water storage unit 17. At the time point when the water storage portion 17 stores a certain amount of water 14, a drain valve, not shown, is opened, and the water 14 separated from the oil is obtained from the drain pipe 19.

On the other hand, as shown in the enlarged view of fig. 2, the oil particles 22 are larger in particle size than the pore size of the pores 20d due to the oil repellency of the oil-water separation membrane 21 formed on the fiber surface of the nonwoven fabric for filtration 20 and due to the predetermined air permeability of the oil-water separation filter, and even if the particle size is slightly smaller than the pore size of the pores 20d, the oil particles cannot pass through the oil-water separation filter 13 and remain between the fibers 20c and the fibers 20c of the nonwoven fabric for filtration 20. The oil-water separation filter 13 is periodically removed from the oil-water separator 10, and the oil accumulated in the nonwoven filter fabric 20 is recovered.

[ preparation method of oil-water separating Filter ]

[ preparation of nonwoven Fabric for filtration ]

First, a sample having a density of 0.3ml/cm was prepared²Second to 10ml/cm²A nonwoven fabric for filtration having an air permeability per second. Specifically, an oil-water separating filter having an oil-water separating film described later formed on the fiber surface of the nonwoven fabric for filtration was prepared, and the oil-water separating film had a thickness of 0.05ml/cm²Second to 10ml/cm²A nonwoven fabric for filtration having an air permeability per second. At every 1m²When the oil-water separation membrane is formed on the nonwoven fabric for filtration in a slightly thick film in the above range, the nonwoven fabric for filtration having a large air permeability is selected and used at a rate of 1m²When the oil-water separation membrane is formed as a slightly thinner membrane on the nonwoven fabric for filtration in the above range, the nonwoven fabric for filtration having a low air permeability is selected.

Examples of the nonwoven fabric for filtration include a cellulose ester-mixed membrane filter, a glass fiber filter, and a nonwoven fabric obtained by mixing polyethylene terephthalate fibers and glass fibers (trade name: 356, manufactured by andel filter paper company). Thus, the nonwoven fabric for filtration is made of a material selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), glass, alumina, carbon, cellulose, pulp, nylon and1 or more than 2 kinds of metal fiber. The fibers may be fibers obtained by mixing 2 or more kinds of fibers. In order to obtain the above air permeability, the thickness (fiber diameter) of the fiber is suitably 0.01μm～10μThe thickness of m. The thickness of the nonwoven fabric is 0.1mm to 5mm in the case of a single-layer oil-water separation filter, and the thickness of the laminate is 0.3mm to 7mm in the case of a multilayer laminate. Since the oil-water separation film-forming material of the present invention contains a silica sol hydrolysate as a main component, a material having a hydroxyl group is preferable in order to obtain adhesion to a fiber. Among them, glass, alumina, cellulose nanofibers, etc. have a small fiber diameter, and the air permeability can be made low in the above range.

As described above, in the case where the nonwoven fabric for filtration is a laminate obtained by laminating a plurality of nonwoven fabrics for filtration 30 and 40 as shown in fig. 3, by using glass fibers as the fibers constituting the nonwoven fabric for filtration 30 corresponding to the surface into which the mixed liquid containing water and oil flows, the oil-water separation membrane containing a silica sol hydrolysate as a main component is more strongly adhered to the glass fibers, and is less likely to be peeled off from the fibers of the nonwoven fabric for filtration.

[ preparation of nonwoven Fabric for Reinforcement ]

An oil-water separation film is formed on the fiber surface of the nonwoven fabric for filtration, while no oil-water separation film is formed on the fiber surface of the nonwoven fabric for reinforcement 50. The nonwoven fabric 50 for reinforcement has an air permeability of 20ml/cm²More than one second. Preferably 25ml/cm²More than one second and 150ml/cm²And less than second. The nonwoven fabric for reinforcement has a tensile strength of 70N or more. Preferably 100N or more and 150N or less. The reason why the nonwoven fabric for reinforcement has lower air permeability than the nonwoven fabric for filtration is that: preventing a decrease in the filtration rate. If the tensile strength is less than 70N, the liquid mixture containing water and oil may not resist the inflow of the liquid mixture, and the nonwoven fabric for filtration may not be reinforced and may be deformed.

The material of the fibers constituting the reinforcing nonwoven fabric 50 is 1 or 2 or more selected from polyethylene terephthalate (PET), polypropylene (PP), cellulose, pulp, nylon, bamboo, and metal. The reinforcing nonwoven fabric 50 may be formed by selecting fibers of an appropriate material from nonwoven fabrics of such fibers, depending on the physical strength of the filter nonwoven fabric. The fibers constituting the nonwoven fabric for reinforcement 50 may be fibers obtained by mixing 2 or more kinds of fibers. The thickness of the nonwoven fabric 50 for reinforcement is preferably 0.2mm to 1mm, and more preferably 0.3mm to 0.8 mm. When a mesh body such as a wire mesh, a porous metal plate, a perforated plate (mesh dish), or the like is selected as the reinforcing material, the nonwoven fabric for filtration may be damaged when a mixed liquid containing water and oil flows into the mesh or the holes when the mesh or the holes are large. In particular, when pressure is applied to the mixed liquid for filtration, the damage becomes significant, and there is a possibility that oil leaks. Further, when the mesh or the hole is small, there is a problem that resistance when the mixed solution is filtered becomes large.

[ method of Forming oil-Water separating film on fiber surface of nonwoven Fabric for filtration ]

In the case of forming the oil-water separation film on the fiber surface of the nonwoven fabric for filtration of the present embodiment, the liquid composition for oil-water separation film formation, which will be described later, is diluted with an alcohol having a boiling point of less than 120 ℃ and a carbon number in the range of 1 to 4, which will be described later, so that the mass ratio to the liquid composition (liquid composition: alcohol) is 1: 1 to 50, immersing the nonwoven fabric for filtration in the diluent, pulling the nonwoven fabric from the diluent, spreading the nonwoven fabric for filtration on a horizontal wire mesh or the like in the air at room temperature, and removing the liquid until a predetermined liquid amount is obtained. As another method, the pulled nonwoven fabric is subjected to liquid removal by passing through a mangle roll (presser). Drying the non-woven fabric for filtration after liquid removal in the air at a temperature of 25 to 140 ℃ for 0.5 to 24 hours. As a result, as shown in the enlarged view of fig. 2, the oil-water separation membrane 21 is formed on the surface of the fiber 20c constituting the nonwoven fabric for filtration 20. At every 1m²The filtering nonwoven fabric is in the range of 0.1 g-30 g oil-water separation membrane, and when the liquid removal amount is small, a thick membrane is formed on the fiber surface of the filtering nonwoven fabric, and when the liquid removal amount is largeIn this case, a film is formed on the fiber surface of the nonwoven fabric for filtration.

[ overlap of nonwoven Fabric for filtration and nonwoven Fabric for Reinforcement ]

As shown in fig. 4 and 5, the filtration nonwoven fabric dried after the liquid removal is superposed on the reinforcement nonwoven fabric 50 to form the oil-water separation filters 33 and 43. The thickness of the oil-water separation filter reinforced with the reinforcing nonwoven fabric of the present embodiment is not particularly limited, but is preferably in the range of 0.2mm to 1 mm. Further, it is not necessary to use a special adhesive for the overlapping, and it is preferable to perform the overlapping by bringing the nonwoven fabric for filtration and the nonwoven fabric for reinforcement into close contact with each other. Further, the air permeability of the oil-water separation filter in the superposed state is preferably 0.05ml/cm²Second to 10ml/cm²The range of/sec.

[ method for producing liquid composition for Forming oil-water separation film ]

The liquid composition for forming an oil-water separation membrane is prepared by the following method.

[ preparation of liquid mixture ]

First, tetramethoxysilane or tetraethoxysilane as a silicon alkoxide, epoxy-containing silane as an alkylene component, fluorine-containing silane as a fluorine-containing functional group component, an alcohol having a boiling point of less than 120 ℃ and a carbon number in the range of 1 to 4, and water are mixed to prepare a mixed solution. Specific examples of the silicon alkoxide include: tetramethoxysilane, oligomers thereof or tetraethoxysilane, oligomers thereof. For example, tetramethoxysilane is preferably used to obtain a highly durable oil-water separation membrane, while tetraethoxysilane is preferably used to avoid methanol generated during hydrolysis.

Specific examples of the epoxy group-containing silane to be the alkylene component include: 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane or multifunctional epoxysilanes. The alkylene component is contained in an amount of 1 to 40 mass%, preferably 2.5 to 20 mass%, based on the total mass of the silicon alkoxide and the alkylene component. When the alkylene component is less than 1% by mass of the lower limit, adhesion to the fiber becomes insufficient when a film is formed on the fiber of the nonwoven fabric containing no hydroxyl group. If the content exceeds 40 mass% of the upper limit, the durability of the formed film is lowered. When the epoxy group-containing silane is contained so that the alkylene component is in the range of 1 to 40% by mass, the epoxy group is also ring-opened during the hydrolytic polymerization to contribute to the polymerization, whereby the leveling (leveling) during the drying process is improved and the film thickness becomes uniform. When the fibers of the nonwoven fabric for filtration contain a hydrophilic group such as glass fibers, the content of the alkylene component may be very small or zero. On the other hand, when the fibers of the nonwoven fabric for filtration do not contain a hydrophilic group, the alkylene component is preferably contained in an amount of 0.5 to 20 mass% in the silica sol hydrolysate (D).

Examples of the alcohol having 1 to 4 carbon atoms include: 1 or 2 or more alcohols within this range. Examples of the alcohol include: methanol (boiling point 64.7 deg.C), ethanol (boiling point about 78.3 deg.C), propanol (n-propanol (boiling point 97-98 deg.C), isopropanol (boiling point 82.4 deg.C)). Methanol or ethanol is particularly preferred. This is because these alcohols are easily mixed with silicon alkoxides. As the water, ion exchange water, pure water, or the like is preferably used to prevent mixing of impurities. An alcohol having 1 to 4 carbon atoms and water are added to a silicon alkoxide and an epoxy-containing silane, and the mixture is preferably stirred at 10 to 30 ℃ for 5 to 20 minutes to prepare a mixed solution.

[ preparation of hydrolysate (silica Sol hydrolysate) ]

The mixed solution thus prepared is mixed with a catalyst comprising an organic acid, an inorganic acid or a titanium compound. In this case, the liquid temperature is preferably maintained at 30 to 80 ℃ and the stirring is preferably carried out for 1 to 24 hours. Thus, a hydrolysate of a silicon alkoxide and an epoxy group-containing silane as an alkylene component and a fluorine-containing silane as a fluorine-containing functional group component (hereinafter, also referred to as a silica sol hydrolysate) can be prepared. The hydrolysate is composed of 2-50 wt% of silicon alkoxide, maximum 30 wt% of epoxy-containing silane, and 0.005-3 wt% of fluorine-containing functional group20% by mass of fluorine-containing silane～98% by mass of an alcohol having 1 to 4 carbon atoms and 0.1% by mass of a solvent～40 mass% of water, 0.01 to 5 mass% of an organic acid as a catalyst, an inorganic acid or a titanium compound, and subjecting the mixture to hydrolysis reaction of a silicon alkoxide, an epoxy-containing silane and a fluorine-containing silane as a fluorine-containing functional group component. If the fluorine-containing silane as the fluorine-containing functional group component is less than 0.005 mass% of the lower limit, the formed film is less likely to be water-and oil-repellent, and if it exceeds 3 mass% of the upper limit, it is less likely to adhere to the fiber surface of the nonwoven filter fabric.

The reason why the ratio of the alcohol having 1 to 4 carbon atoms is limited to the above range is that: if the alcohol ratio is less than the lower limit, the silicon alkoxide is separated without dissolving in the solution, and the reaction solution is liable to gel during the hydrolysis reaction, while if it exceeds the upper limit, the amount of water and catalyst required for the hydrolysis is relatively reduced, so that the reactivity of the hydrolysis is lowered, the polymerization does not proceed, and the adhesion of the film is lowered. The reason why the proportion of water is limited to the above range is that: if the amount is less than the lower limit, the hydrolysis rate is lowered, and therefore, polymerization does not proceed, and the adhesion of the coating film is insufficient, whereas if the amount exceeds the upper limit, the reaction solution is gelled during the hydrolysis reaction and water is excessively increased, so that the silicon alkoxide compound is insoluble in the aqueous alcohol solution, and the separation may be disadvantageously caused.

SiO in the hydrolyzate₂Concentration (SiO)₂Amount) is preferably 1 to 40% by mass. If SiO of the hydrolyzate₂When the concentration is less than the lower limit, polymerization is insufficient, and the adhesion of the film is liable to decrease or cracks are liable to occur, and when the concentration exceeds the upper limit, the proportion of water is relatively increased, and there is a problem that the silicon alkoxide is insoluble and the reaction solution is gelled.

The organic acid, inorganic acid or titanium compound functions as a catalyst for promoting the hydrolysis reaction. As the organic acid, there can be exemplified: formic acid, oxalic acid, as inorganic acids, can be exemplified: hydrochloric acid, nitric acid, phosphoric acid, as titanium compounds, there may be exemplified: titanium tetrapropoxide, titanium tetrabutoxide, titanium tetraisopropoxide, titanium lactate, and the like. The catalyst is not limited to the above. The reason why the ratio of the catalyst is limited to the above range is that: if the amount is less than the lower limit, the reactivity is insufficient and the polymerization becomes insufficient, and no film is formed, while if the amount exceeds the upper limit, the reactivity is not affected, but problems such as corrosion of the nonwoven fabric fibers due to the remaining acid may occur.

The fluorine-containing silane as the fluorine-containing functional group component is represented by the following general formulae (3) and (4). More specifically, the perfluoroether group in the above formulae (3) and (4) includes: a perfluoroether structure represented by the following formulae (5) to (13).

[ chemical formula 3]

a =0 to 3 (3)

[ chemical formula 4]

a =0 to 3 (4)

[ chemical formula 5]

　　　(5)

[ chemical formula 6]

　　　(6)

[ chemical formula 7]

　　　(7)

[ chemical formula 8]

　　　(8)

[ chemical formula 9]

　　　(9)

[ chemical formula 10]

　　　(10)

[ chemical formula 11]

　　　(11)

[ chemical formula 12]

　　　(12)

[ chemical formula 13]

　　　(13)

In addition, as X in the above formulas (3) and (4), there can be mentioned: the following formulae (14) to (18). The following formula (14) represents an example containing an ether bond, the following formula (15) represents an example containing an ester bond, the following formula (16) represents an example containing an amide bond, the following formula (17) represents an example containing a urethane bond, and the following formula (18) represents an example containing a sulfonamide bond.

[ chemical formula 14]

　　　(14)

[ chemical formula 15]

　　　(15)

[ chemical formula 16]

　　　(16)

[ chemical formula 17]

　　　(17)

[ chemical formula 18]

　　　　(18)

Here, in the above formulae (14) to (18), R is²And R³Is a hydrocarbon group having 0 to 10 carbon atoms, R⁴Is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms. As R³Examples of the hydrocarbon group of (3) include: alkylene groups such as methylene and ethylene as R⁴Examples of the hydrocarbon group of (2) include alkyl groups such as methyl and ethyl, and phenyl groups.

In the above formulae (3) and (4), R is¹Examples thereof include: methyl, ethyl, propyl, and the like.

In the above formulae (3) and (4), Z is not particularly limited as long as it is a hydrolyzable group which can be hydrolyzed to form an Si-O-Si bond. Specific examples of such hydrolyzable groups include: alkoxy groups such as methoxy, ethoxy, propoxy and butoxy; aryloxy groups such as phenoxy and naphthoxy; aralkyloxy groups such as benzyloxy and phenethyloxy; acyloxy groups such as acetoxy, propionyloxy, butyryloxy, valeryloxy, pivaloyloxy and benzoyloxy. Among these, methoxy and ethoxy groups are preferably used.

Specific examples of the fluorine-containing silane having a fluorine-containing functional group component having a perfluoroether structure represented by the above formulas (3) and (4) include: the following formulae (19) to (27). In the following formulae (19) to (27), R is a methyl group or an ethyl group.

[ chemical formula 19]

　　　(19)

[ chemical formula 20]

　　　(20)

[ chemical formula 21]

　　　　(21)

[ chemical formula 22]

　　　　(22)

[ chemical formula 23]

　　　(23)

[ chemical formula 24]

　　　(24)

[ chemical formula 25]

　　　(25)

[ chemical formula 26]

　　　(26)

[ chemical formula 27]

　　　(27)

As described above, the fluorine-containing functional group component contained in the liquid composition for forming an oil-water separation membrane of the present embodiment has a structure in which each of 1 or more perfluoroether groups and alkoxysilyl groups is present in the molecule, and a perfluoroether group in which a plurality of short-chain perfluoroalkyl groups having 6 or less carbon atoms and perfluoroalkylene groups are bonded to an oxygen atom is present, and since the fluorine content in the molecule is high, it is possible to impart excellent water-and oil-repellency to the formed membrane.

[ liquid composition for Forming oil-Water separation film ]

The liquid composition for forming an oil-water separation membrane according to the present embodiment is prepared by the above-described preparation method, and includes the above-described silica sol hydrolysate containing a fluorine-containing functional group component and a solvent. The fluorine-containing functional group component has a perfluoroether structure represented by the general formula (1) or (2) and is contained in the silica sol hydrolysate in an amount of 0.01 to 10% by mass.

The solvent is a mixed solvent of water and an alcohol having 1 to 4 carbon atoms, or a mixed solvent of water, an alcohol having 1 to 4 carbon atoms and an organic solvent other than the alcohol. Specific examples of the perfluoroether structure include: the structures represented by the above formulae (5) to (27).

Since the liquid composition for forming an oil-water separation membrane of the present embodiment contains a silica sol hydrolysate as a main component, a high-strength oil-water separation membrane that has excellent adhesion between the membrane and the fibers of the nonwoven fabric for filtration and is less likely to peel off can be obtained. Further, the silica sol hydrolyzate contains a fluorine-containing functional group component having a perfluoroether structure represented by the general formula (1) or (2), and therefore has water-repellent and oil-repellent effects. If the content of the fluorine-containing functional group component is less than 0.01% by mass, the water-and oil-repellency cannot be imparted to the formed film, and if it exceeds 10% by mass, film repulsion or the like occurs, and the film forming property is poor. The content of the fluorine-containing functional group component is preferably 0.1 to 5% by mass.

Examples

Next, examples of the present invention and comparative examples will be described in detail. First, examples 1 to 6 and comparative examples 1 to 6 relating to an oil-water separation filter composed of only a nonwoven fabric for filtration will be described, and next, test examples 1 to 3 and comparative test examples 1 to 3 relating to an oil-water separation filter in which a nonwoven fabric for reinforcement is superimposed on the nonwoven fabric for filtration of example 1 will be described.

< example 1 >

8.52g of a 3-to 5-mer Tetramethoxysilane (TMOS) (trade name: MKC Silicate MS51, manufactured by Mitsubishi chemical Co., Ltd.) as a silicon alkoxide, 0.48g of 3-glycidoxypropyltrimethoxysilane (GPTMS, manufactured by shin-Etsu chemical industries, trade name: KBM-403) containing an epoxysilane as an alkylene component, 0.24g of a fluorine-containing silane (R: ethyl) represented by formula (19) as a fluorine-containing functional group component, 17.34g of ethanol (EtOH) (boiling point 78.3 ℃) as an organic solvent were mixed, and 3.37g of ion exchange water was further added thereto, and the mixture was stirred at 25 ℃ for 5 minutes in a separable flask to prepare a mixed solution. To the mixture was added 0.05g of hydrochloric acid having a concentration of 35% by mass as a catalyst, and the mixture was stirred at 40 ℃ for 2 hours. Thus, a liquid composition for forming an oil-water separation film, which contains a silica sol hydrolysate, was prepared. The contents of the modulation are shown in Table 1.

[ Table 1]

The obtained silica sol hydrolysate of the liquid composition for oil-water separation membrane formation contained 4.5 mass% of the fluorine-containing functional group component and 7.8 mass% of the alkylene component having 7 carbon atoms. Next, 29.0g of industrial ethanol (AP-7, manufactured by Alcohol industries, Japan) was added to and mixed with 1.0g of a silica sol hydrolysate of the liquid composition for oil-water separation membrane formation to prepare a diluted liquid of the liquid composition. The base material of the oil-water separation filter has a volume of 2.5ml/cm²The nonwoven fabric for double filtration having an air permeability per second was immersed in the diluted solution for 30 seconds. The double-layer nonwoven fabric for filtration is a laminate of a nonwoven fabric for filtration composed of glass fibers as an upper layer and a nonwoven fabric for filtration composed of PET fibers as a lower layer. The nonwoven fabric for double filtration was pulled up from the diluted solution, spread on a horizontal wire mesh, and left at room temperature for 30 minutes to remove the solution. Then, the nonwoven fabric for double filtration was dried in a dryer maintained at 120 ℃ for 30 minutesAnd finally obtaining the oil-water separation filter. The oil-water separation filter has an air permeability of 1.2ml/cm²In seconds. The difference between the mass of the double-layer nonwoven fabric for filtration before impregnation and the mass after drying was converted into the mass of the oil-water separation membrane formed on the fiber surface of the nonwoven fabric for filtration. As a result, it was calculated every 1m²The oil-water separation membrane in the nonwoven fabric for filtration (4.0 g). The above results are shown in Table 2.

[ Table 2]

< examples 2 to 6 and comparative examples 2 to 4 >

In examples 2 to 6 and comparative examples 2 to 4, as shown in table 2, the type of the nonwoven fabric for filtration and the type of the fluorine-containing compound of the oil-water separation filter were selected, and the addition amount of TMOS, the addition amount of GPTMS, and the addition amount of the fluorine-containing silane, which were described in example 1, were changed. Except for this, liquid compositions for oil-water separation film formation of examples 2 to 6 and comparative examples 2 to 4 were obtained in the same manner as in example 1. To these liquid compositions, the same industrial ethanol as in example 1 was added, and a diluted solution for impregnating a nonwoven fabric for filtration was prepared in the same manner as in example 1. The nonwoven fabric for filtration shown in table 2 was immersed in these dilutions and dried as in example 1, to obtain oil-water separation filters having the characteristics shown in table 2. In table 2, R in the fluorine-containing silanes represented by formulae (19) to (23) as the fluorine-containing compounds is ethyl.

The nonwoven fabrics for filtration used in examples 5 and 6 and comparative example 4 were different from the nonwoven fabric for filtration used in example 1 in that they were composed of a mixture of PET fibers and glass fibers (PET: glass = 80: 20 in terms of mass ratio), and the air permeabilities (before impregnation with the diluent) thereof were 12.0ml/cm, respectively²Second, 12.0ml/cm²Second and 24.0ml/cm²In seconds. The air permeability of the oil-water separation filter impregnated with the diluent was 9.6ml/cm²Second, 7.7ml/cm²Second and 12.0ml/cm²Second/second. The nonwoven fabrics for filtration used in comparative examples 1 to 3 were composed of two layers of the same nonwoven fabric for filtration of glass fibers and the same nonwoven fabric for filtration of PET fibers as in example 1, and had respective air permeabilities (before impregnation with a diluent) of 2.5ml/cm²Second, 2.5ml/cm²Second and 1.1ml/cm²In seconds. The air permeability of the oil-water separation filter impregnated with the diluent was 2.3ml/cm²Second, 0.02ml/cm²Second and 0.03ml/cm²In seconds.

< comparative example 1 >

In comparative example 1, the same nonwoven fabric for filtration as in example 1 was used, but the silica sol hydrolysate contained no fluorine-containing silane as a fluorine-containing functional group component.

< comparative example 5 >

In comparative example 5, mesh 1 was commercially availableμThe Polytetrafluoroethylene (PTFE) membrane filter m was used as a base material of the oil-water separation filter without treatment, and was used as an oil-water separation filter. The oil-water separation film-forming liquid composition of example 1 was not immersed in a diluted solution thereof.

< comparative example 6 >

As the fluorine-based compound, a fluorine-based compound represented by the following formula (28) shown in synthesis example 1 having an oil repellency imparting group and a hydrophilicity imparting group (oil repellency and hydrophilicity) of patent document 1 was prepared. 0.5g of the fluorine-containing compound was dissolved in 99.5g of the same industrial ethanol as in example 1 to prepare a 0.5 mass% diluted solution.

[ chemical formula 28]

　　　(28)

Will have a volume of 1.1ml/cm²The nonwoven fabric for double layer filtration having the same structure as in example 1 and having an air permeability per second was immersed in the diluted solution for 30 seconds. Except for this, an oil-water separation filter was obtained in the same manner as in example 1. The air permeability of the oil-water separation filter is 1.1ml/cm²Per second, calculate every 1m²The amount of the oil-water separation membrane in the nonwoven fabric for filtration was 1.0 g.

< 1 and evaluation of comparative test >

The 12 types of oil-water separation filters obtained in examples 1 to 6 and comparative examples 1 to 6, which were composed of only nonwoven fabrics for filtration, were each attached to the oil-water separation test apparatus 100 shown in fig. 7. In the test apparatus 100, 100 is added to each reference numeral of the element corresponding to the oil-water separator 10 shown in fig. 1, and each reference numeral of the test apparatus 100 is shown. In the OIL-water separation test apparatus 100, as the emulsified OIL, 0.25g of the screw compressor OIL HISCREW OIL NEXT manufactured by hitachi machine and 5 liters of ion-exchanged water were mixed at 9000rpm for 3 minutes to obtain an emulsified OIL (a mixed liquid containing water and OIL) having an OIL concentration of 50ppm which was white. The emulsified oil is supplied to the mixed liquid inflow unit 112 and filtered by the oil-water separation filter 113. The filtrate 114 which was stored in the water storage part (branched flask) 117 by passing through the oil-water separation filter 113 was collected, and turbidity of the filtrate and oil concentration of the filtrate were evaluated by the following methods. The results are shown in Table 3. The oil-water separation filter 113 is supported by a metal perforated plate 120. In addition, in the filtration of emulsified oil, 12 types of oil-water separation filters obtained in examples 1 to 6 and comparative examples 1 to 6 were adjusted to a predetermined degree of vacuum (-10kPa) by a suction pump, not shown, connected to a branch pipe 121 of a flask 117, and the inside of the flask was depressurized to perform suction filtration on the oil-water separation filter 113. Reference numeral 122 denotes a vacuum gauge.

(a) Turbidity of the filtrate

The turbidity of the filtrate was measured by using a Lacom Tester, TN-100 (manufactured by As One Co.). The filtrate having a low turbidity exhibited good oil-water separation, and the oil-water separation was at a satisfactory level of 1.5 or less.

(b) Oil concentration of the filtrate

The oil concentration of the filtrate was determined by measuring the residual oil content of the filtrate with an oil content meter (OCMA-555, manufactured by horiba, Ltd.). The detection limit of the oil content meter differs depending on the type of oil, and is 1ppm in the emulsified oil used.

[ Table 3]

As is clear from table 3: in comparative example 1, since the silica sol hydrolysate contained no fluorine-containing silane as a fluorine-containing functional group component, the turbidity of the filtrate passed through the oil-water separation filter was 3.0, and 15.0ppm of oil was mixed in the filtrate.

In comparative example 2, since the content of the fluorine-containing functional group component in the silica sol hydrolysate was too large to reach 11.6 mass%, the mixed liquid could not pass through the oil-water separation filter and could not be filtered.

In comparative example 3, the amount of the catalyst was changed to 1m²The mass of the nonwoven fabric oil-water separation membrane was too high and reached as high as 33.0 mass%, and therefore the air permeability of the oil-water separation filter was too low and reached as low as 0.03ml/cm²Second, the mixed liquid cannot pass through the oil-water separation filter and cannot be filtered.

In comparative example 4, although the air permeability of 12.0ml/cm was used²Oil/water separating filter/sec, but for every 1m²The mass of the nonwoven fabric oil-water separation membrane was too small to be as small as 0.05g, and therefore the oil-repellent effect of the oil-water separation filter was insufficient, the turbidity of the filtrate was 2.0, and 8.0ppm of oil was mixed in the filtrate, and the removal of oil was insufficient.

In comparative example 5, a PTFE membrane filter was used as the oil-water separation filter, but the mixed liquid could not pass through the filter and could not be filtered.

In comparative example 6, since the oil-water separation membrane of the oil-water separation filter was imparted with hydrophilic oil repellency and the mixed liquid was emulsified oil, the turbidity of the filtrate was 3.0, and 13.0ppm of oil was mixed in the filtrate, and the removal of oil was insufficient.

On the other hand, the oil-water separation filters of examples 1 to 6 were each 1m in size²The nonwoven fabric is formed into an oil-water separation membrane at a ratio of 0.15g to 28g, the fluorine-containing functional group component having both water repellency and oil repellency is contained in the silica sol hydrolysate at a ratio of 0.02 mass% to 9.8 mass%, and the air permeability of the oil-water separation filter is 0.08ml/cm²Second to 9.6ml/cm²Second, the turbidity of the filtrate was 1.5 or less and the oil concentration of the filtrate was 5ppm of the n-hexane extract content (mineral oil content) as acceptable in the evaluation test, because the turbidity satisfied the range of the invention according to the first aspect 1, and it was confirmed that the oil-water separation filters of examples 1 to 6 had oil-water separation performance.

Next, test examples 1 to 3 and comparative test examples 1 to 3 relating to the oil-water separation filter in which the nonwoven fabric for filtration of example 1 was overlaid with the nonwoven fabric for reinforcement will be described. The tensile strength of the nonwoven fabric used herein was measured according to the general nonwoven fabric test method JIS L19132010 using stragraph VG manufactured by tokyo seiki.

< test example 1 >

In test example 1, the two-layer laminate of example 1, which was composed of a glass fiber layer (upper layer) and a PET fiber layer (lower layer), was used as the nonwoven fabric for filtration. The non-woven fabric for filtration has a thickness of 0.3mm after removing the liquid from the maceration extract and drying, and an air permeability of 1.2ml/cm²In seconds. The nonwoven fabric for filtration had a tensile strength of 70N. As the nonwoven fabric for reinforcement, a two-layer laminate composed of a PET fiber layer (upper layer) and a glass fiber layer (lower layer) was used. The nonwoven fabric for reinforcement has a thickness of 0.4mm and an air permeability of 40ml/cm²In seconds. The nonwoven fabric for reinforcement had a tensile strength of 130N. The results are shown in Table 4.

[ Table 4]

< test examples 2 and 3 and comparative test examples 1 to 3 >

For the oil-water separation filters of test examples 2 and 3 and comparative test examples 1 to 3, the same nonwoven fabric as in test example 1 was used as the nonwoven fabric for filtration. As the oil-water separation filters of test examples 2 and 3 and comparative test examples 2 and 3, nonwoven fabrics having the types, thicknesses, permeabilities, and tensile strengths shown in table 4 were used as the reinforcing nonwoven fabrics. In comparative test example 1, no reinforcing nonwoven fabric was used.

< 2 and evaluation of comparative test >

For each of the 6 types of oil-water separation filters obtained in test examples 1 to 3 and comparative test examples 1 to 3, 2 of the comparative test was performed in the same manner as 1 of the comparative test. In comparative test 2, the perforated plate 120 was removed from the oil-water separation test apparatus 100 shown in fig. 7. Thereafter, the same mixed liquid containing water and oil as in 1 of the comparative test was suction-filtered by a suction pump at different vacuum degrees of-10 kPa and-20 kPa. The time for which the same amount of the mixed liquid as 1 of the comparative test passed through the oil-water separation filter was also measured. The results are shown in Table 5.

[ Table 5]

As is clear from table 5: in comparative test example 1, since no reinforcing nonwoven fabric was used, when filtration and suction were performed in a vacuum degree of-10 kPa in an oil-water separation test apparatus, the oil concentration of the filtrate was less than 1ppm and the turbidity of the filtrate was as low as 0.5, whereas when filtration and suction were performed in a vacuum degree of-20 kPa, the oil concentration of the filtrate was 22ppm and the turbidity of the filtrate was as high as 50, and oil leakage was observed. The nonwoven fabric for filtration was considered to be broken.

In comparative test example 2, the air permeability of the nonwoven fabric for reinforcement was 100ml/cm²Since the tensile strength was 50N/sec, when the filtration suction was performed in a vacuum degree of-10 kPa in an oil-water separation test apparatus, the oil concentration of the filtrate was less than 1ppm and the turbidity of the filtrate was as low as 0.6, which was not problematic, but when the filtration suction was performed in a vacuum degree of-20 kPa, the oil concentration of the filtrate was 5ppm and the turbidity of the filtrate was as high as 10, which resulted in the occurrence of oil leakage. The tensile strength was considered to be insufficient and the nonwoven fabric for filtration was broken.

In comparative test example 3, the nonwoven fabric for reinforcement had an air permeability of 5ml/cm²The oil/second and tensile strength of 170N, so when the oil-water separation test device is used to perform filtration suction under a vacuum degree of-10 kPa, the oil concentration of the filtrate is less than 1ppm, and the turbidity of the filtrate is as low as 0.6, but the filtrate passing time is 350 seconds excessively, which is not acceptable, and the vacuum degree of-20 kPa is not performedThe oil-water separation test was as follows.

In contrast, the oil-water separation filters of test examples 1 to 3 used the nonwoven fabric for filtration of example 1, and the nonwoven fabric for reinforcement had an air permeability of 20ml/cm²Second to 80ml/cm²A tensile strength of 100N to 150N per second. Since these oil-water separating filters satisfy the scope of the invention according to claim 6, the turbidity of the filtrate was 1.5 or less and the filtrate was acceptable when the evaluation test was performed, and the oil concentration of the filtrate was 5ppm of the acceptable content (mineral oil content) of the n-hexane extract, and it was confirmed that the physical strength was improved and the oil-water separating performance was exhibited.

Industrial applicability

The oil-water separation filter of the present invention is useful in the field where it is necessary to recover water by separating oil from emulsified oil or water-soluble oil obtained by emulsifying oil.