JP6923630B2 - Air filter - Google Patents

Description

The present invention relates to an air filter that purifies air containing oil mist and dust. More specifically, the present invention relates to an air filter in which an oil-repellent film having an oil-repellent property is formed on a fiber surface of a non-woven fabric.

Cutting oil is scattered from machine tools such as cutting machines and turning machines that process metal products using cutting oil due to the high-speed operation of the machines, and oil mist is generated, and at the same time, dust is also generated. These oil mists and dust deteriorate the working environment and reduce the working efficiency. For this reason, conventionally, as an air filter for purifying air containing oil mist and dust, an air filter filter medium capable of suppressing clogging due to oil mist as well as dust floating in the air has been proposed (for example,). Patent Document 1 (claim 1, paragraph [0006], paragraph [0021], paragraph [0045], paragraph [0053] to paragraph [0060]).

This air filter filter medium includes a first PTFE (polytetrafluoroethylene) porous membrane and a second PTFE porous membrane, and the air flow is from the first main surface of the air filter filter medium to the first PTFE porous membrane. , The second PTFE porous membrane passes through the second main surface of the air filter filter medium in this order. The thickness of the first PTFE porous membrane is in the range of 4 to 40 μm, the specific surface area of the first PTFE porous membrane is 0.5 m ² / g or less, and the specific surface area of the second PTFE porous membrane. ^{Is in the range of 1.5 to 10 m 2} / g or less, which is larger than that of the first PTFE porous membrane.

The first and second PTFE porous membranes are formed into a sheet-like molded body by adding a mixture of PTFE fine powder and a liquid lubricant, respectively. The first PTFE porous membrane stretches the sheet-shaped molded product while heating it in the longitudinal (MD) direction at a temperature equal to or higher than the melting point of PTFE (327 ° C.) and a magnification of 50 times or higher, and then stretches it in the lateral (TD) direction. It is produced by stretching while heating at a temperature of 130 to 400 ° C. so as to be 5 to 8 times the length before stretching. The second PTFE porous membrane stretches the PTFE sheet-shaped molded product at a temperature below the melting point of PTFE (270 to 290 ° C.) while heating it in the MD direction at a magnification of 15 to 40 times, and then in the TD direction. Further, it is produced by stretching at a temperature of 120 to 130 ° C. so as to be 15 to 40 times the length before stretching while heating at the same magnification as during stretching in the MD direction.

Japanese Unexamined Patent Publication No. 2018-51546

In the air filter filter medium disclosed in Patent Document 1, the first PTFE porous membrane is manufactured by increasing the stretching temperature and the stretching ratio as compared with the second PTFE porous membrane. , The specific surface area of the first PTFE porous membrane ^{is reduced to 0.5 m 2} / g or less, thereby collecting dust and oil mist having a large particle size. On the other hand, the specific surface area of the second PTFE porous membrane ^{is increased to 1.5 to 10 m 2} / g, whereby dust and oil mist having a small particle size are collected.

However, in the air filter filter medium disclosed in Patent Document 1, even if the first and second PTFE porous membranes collect dust and oil mist having different particle sizes, the PTFE porous membranes generate static electricity. It was not easy to process it into a filter shape because it was easy to do and it was difficult to remove the generated static electricity. Further, since the water repellency is higher than the oil repellency, the moisture contained in the atmosphere may block the PTFE porous membrane, and dust easily adheres to the PTFE porous membrane. Therefore, if the air filter filter medium is continuously used, the oil mist continues to remain inside the air filter filter medium, and there is a problem that the air filter filter medium is easily clogged.

An object of the present invention is to provide an air filter capable of purifying air containing oil mist and dust, suppressing clogging, and easily removing collected oil mist and dust.

The first aspect of the present invention is that a large number of pores are formed between the fibers, which penetrate between one surface into which air containing oil mist and dust flows in and the other surface in which the air flows out facing the one surface. a air filter including a nonwoven fabric, the basis weight of the nonwoven fabric is in the range of ^{200g / m 2 ~400g / m 2} , oil-repellent layer is formed on the fiber surface of the nonwoven fabric, the fluorine-containing functional group component, wherein when the silica sol hydrolyzate and 100 wt%, contains a proportion of 0.01% to 10% by weight, air permeability of the air filter is a 1 ml / cm ² / sec -30 mL / cm ² / sec The fluorine-containing functional group component is an air filter characterized by containing a perfluoroether structure represented by the following general formula (1) or formula (2).

（１）

(1)

（２）

(2)

In the above formulas (1) and (2), p, q and r are integers of 1 to 6 which are the same or different from each other, and may be linear or branched. Further, in the above formulas (1) and (2), X is a hydrocarbon group having 2 to 10 carbon atoms and is selected from an ether bond, a CO-NH bond, an O-CO-NH bond and a sulfone amide bond. It may contain one or more bonds. Further, in the above formulas (1) and (2), Y is the main component of the silica sol hydrolyzate.

The second aspect of the present invention is the invention based on the first aspect, and the silica sol hydrolyzate further contains 0.5% by mass to 20% by mass of an alkylene group component having 2 to 7 carbon atoms. Is.

A third aspect of the present invention is an invention based on the first or second aspect, wherein the nonwoven fabric is composed of a single layer or an air filter composed of a laminate of a plurality of layers.

The fourth aspect of the present invention is an invention based on any one of the first to third aspects, wherein the fibers constituting the nonwoven fabric are polyethylene terephthalate (PET), polypropylene (PP), and polytetrafluoro. An air filter which is one or more fibers selected from the group consisting of ethylene (PTFE), glass, alumina, carbon, cellulose, pulp, nylon and metal.

In a first aspect of the air filter of the present invention, the basis weight of the nonwoven fabric is in the range of ^{200g / m 2 ~400g / m 2} , oil-repellent layer is formed on the fiber surface of the nonwoven fabric, oil-repellent coating has been previously described includes a fluorine-containing functional group component having a function of oil repellency represented by the general formula (1) or (2), and at the same time defining the air permeability of the air filter 1 ml / cm ² / sec -30 mL / cm ² / sec To limit the pores of the non-woven fabric. Therefore, when air containing oil mist and dust flows into the air filter from one surface of the air filter, the oil mist and dust are collected by the non-woven fabric, and only air passes through the pores of the non-woven fabric and flows out from the other surface of the air filter. Then the air becomes clean.

At this time, due to the oil-repellent function of the oil-repellent film, the oil mist is not adsorbed on the oil-repellent film on the fiber surface of the non-woven fabric but is repelled and adhered. As the amount of oil mist collected inside the non-woven fabric increases as the air filter continues to be used, when the air filter is placed horizontally, the oil mist liquefies and accompanies the passing air on the other surface of the air filter. When the air filter is arranged vertically, the collected oil mist collects at the lower end of the air filter due to its own weight and does not block the pores of the non-woven fabric. As a result, clogging of the pores due to the oil mist is suppressed.

On the other hand, the dust adheres directly to the oil-repellent film on the fiber surface of the non-woven fabric, or adheres to the oil mist attached to the oil-repellent film. Therefore, when the air filter is used for a long period of time and is clogged with dust or the like, if the air filter is impacted by an air knocker or the like, the dust adhering together with the oil mist can be easily removed, and the air filter can be used. Can be regenerated.

In the air filter according to the second aspect of the present invention, the fluorine-containing functional group component contained in the oil-repellent film further contains 0.5% by mass to 20% by mass of an alkylene group component having 2 to 7 carbon atoms, and thus is oil-repellent. The film adheres well to the fibers of the non-woven fabric, the thickness of the oil-repellent film becomes uniform, and the oil-repellent film can impart even better oil-repellent performance.

The air filter according to the third aspect of the present invention is an air filter having a simple structure when the non-woven fabric is composed of a single layer, and flows in when the non-woven fabric is composed of a laminated body of a plurality of layers. Each layer can be formed according to the properties such as the particle size of dust and the size of oil particles of oil mist.

In the air filter according to the fourth aspect of the present invention, the materials of the fibers constituting the non-woven fabric are polyethylene terephthalate (PET), polypropylene (PP), polytetrafluoroethylene (PTFE), glass, alumina, carbon, cellulose, pulp, and the like. From nylon and metal, the epoxy group-containing silane is hydrolyzed according to the properties such as the particle size of the inflowing dust and the size of the oil particles of the oil mist, or in the liquid composition for forming the oil-repellent film described later. It can be selected according to the content of the alkylene group component having 2 to 7 carbon atoms.

It is a side view of the non-woven fabric of a single layer of this embodiment. It is a side view of the two-layer non-woven fabric of this embodiment.

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

[Air filter]
As shown in FIG. 1, the air filter 10 of the present embodiment includes a non-woven fabric 20 and an oil-repellent film 21 formed on the fiber surface of the non-woven fabric. The non-woven fabric 20, which is the main component of the air filter 10, has one surface 20a into which air containing oil mist and dust flows in, and another surface 20b in which the air flows out facing the one surface 20a, and is composed of a single layer. .. As shown in FIG. 2, the air filter 50 may be composed of a two-layer laminate of the upper non-woven fabric 30 and the lower non-woven fabric 40. In this case, the upper surface of the upper non-woven fabric 30 is one surface 30a into which air containing oil mist and dust flows, and the lower surface of the lower layer non-woven fabric 40 is the other surface 40b facing the one surface 30a. The laminated body is not limited to two layers, and may be composed of a plurality of layers such as three layers and four layers.

As shown in the enlarged view of FIG. 1, the non-woven fabric 20 is formed by entwining a large number of fibers 20c, and pores 20d are formed between the fibers. The pores 20d penetrate between one surface 20a and the other surface 20b of the non-woven fabric 20. An oil-repellent film 21 is formed on the surface of the non-woven fabric fiber 20c. Basis weight of the nonwoven fabric is in the range of ^{200g / m 2 ~400g / m 2} . The oil-repellent film 21 is formed of a silica sol hydrolyzate containing a fluorine-containing functional group component having oil-repellent properties represented by the above-mentioned general formula (1) or formula (2). The fluorine-containing functional group component is contained in a proportion of 0.01% by mass to 10% by mass when the silica sol hydrolyzate is 100% by mass. In the state of the air filter 10 to the oil-repellent film 21 is formed on the fiber surface, the nonwoven fabric 20 is made to have a permeability of 1 ml / cm ² / sec -30 mL / cm ² / sec. The air permeability is measured using the Frazier type tester described in JIS-L1913: 2000.

If the basis weight of the non-woven fabric ^{is less than 200 g / m 2} , the pores between the fibers are too large, and the ability to collect dust is insufficient. If it exceeds 400 g / m ² , the air permeability ^{becomes less than 1 ml / cm 2} / sec, and dust immediately clogs the pores between the fibers, or the air permeability is too low, and the air fill is caused by the resistance of the air sent to the air filter. pressure loss occurs in the data, it is poor efficiency of the blower energy.
If the fluorine-containing functional group component is less than 0.01% by mass when the silica sol gel forming the oil-repellent film is 100% by mass, the oil-repellent effect is poor and the ability to repel oil mist is insufficient. That is, when the oil mist reaches the air filter, the oil mist wets and spreads on the fiber surface, and the pores 20d are easily closed.
If the fluorine-containing functional group component exceeds 10% by mass, the adhesion of the oil-repellent film to the non-woven fabric deteriorates. Basis weight of the nonwoven fabric is preferably in the range of ^{220g / m 2 ~350g / m 2} . Further, the fluorine-containing functional group component is preferably contained in the range of 0.1% by mass to 5% by mass when the silica sol hydrolyzate is 100% by mass.
If the air permeability is ^{less than 1 ml / cm 2} / sec, the air permeability is poor and it becomes difficult for air containing oil mist and dust to pass through. When it exceeds 30 ml / cm ² / sec, the size of the pores 20d of the non-woven fabric becomes much larger than the respective particle sizes of the oil mist oil particles 22 and the dust particles 23 in the air, and the oil particles 22 and The dust particles 23 pass through the pores of the non-woven fabric together with the air from the air filter 10, and the oil mist and the dust cannot be collected. Air permeability is preferably 1.5 ml / cm ² / sec ~25ml / cm ² / sec.

The operation of such an air filter 10 will be described. As shown in FIG. 1, air containing oil mist and dust reaches one surface 20a of the non-woven fabric 20 constituting the air filter 10. Here, since the air filter 10 has a predetermined air permeability and the oil-repellent film 21 exhibits oil repellency, the oil particles 22 of the oil mist have a particle size larger than the pore diameter of the pores 20d, as well as the pores 20d. Even if the particle size is slightly smaller than the pore size of the non-woven fabric 20, it cannot pass through the air filter 13, and while being repelled by the oil-repellent film 21 between the fibers 20c and the fibers 20c of the non-woven fabric 20, it adheres to the oil-repellent film 21 and stops. .. At the same time, the dust particles 23 also adhere to the oil-repellent film 21 and stop. As a result, oil mist and dust are collected on the non-woven fabric 20, and only air passes through the pores 20d formed between the fibers 20c and the fibers 20c shown in the enlarged view of FIG. 1 and reaches the other surface 20b, and the non-woven fabric 20 Pass through.

As the amount of oil mist collected inside the non-woven fabric increases as the air filter continues to be used, when the air filter is placed horizontally, the oil mist liquefies and accompanies the passing air on the other surface of the air filter. When the air filter is arranged vertically, the collected oil mist collects at the lower end of the air filter due to its own weight and does not block the pores of the non-woven fabric. As a result, clogging of the pores due to the oil mist is suppressed. The dust adheres directly to the oil-repellent film on the fiber surface of the non-woven fabric, or adheres to the oil mist attached to the oil-repellent film. The oil mist and dust accumulated in the non-woven fabric 20 can be removed from the air filter 10 by periodically giving an impact to the air filter 10 with an air knocker or the like.

[Manufacturing method of air filter]
[Preparation of non-woven fabric]
First, a 1.1 ml / cm ² / sec ~40ml / cm ² / sec nonwoven having a air permeability of. Specifically, in a state in which oil-repellent film to be described later becomes an air filter formed on the fiber surface of the nonwoven fabric, to prepare a 1 ml / cm ² / sec -30 mL / cm ² / sec nonwoven having a air permeability of. When the oil-repellent film is formed of a thick film, a non-woven fabric having a high air permeability is selected, and when the oil-repellent film is formed of a thin film, a non-woven fabric having a low air permeability is selected. ..

As the nonwoven fabric, for example, cellulose mixed esters of the membrane filter, a glass fiber filter paper, non-woven fabric mix polyethylene terephthalate fiber and glass fiber (Azumi Filter Paper Co., Ltd., trade name: 340) have. As described above, the non-woven fabric is one or two selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), polytetrafluoroethylene (PTFE), glass, alumina, carbon, cellulose, pulp, nylon and metal. Made from the above fibers. The fiber may be a fiber obtained by mixing two or more fibers. The fiber thickness (fiber diameter) is preferably 0.01 μm to 10 μm so that the above-mentioned air permeability can be obtained. The thickness of the non-woven fabric is 0.2 mm to 0.8 mm when the air filter is a single layer, and 0.2 mm to 1.6 mm when the air filter is a multi-layer laminate. The thickness is preferable. Since the main component of the oil-repellent film-forming material of the present invention is a silica sol hydrolyzate, a material having a hydroxyl group is preferable in order to obtain adhesion to fibers. Among them, glass, alumina, cellulose nanofibers and the like have a small fiber diameter, and the air permeability can be set to a low value within the above range.

As described above, when the non-woven fabric is a laminated body in which a plurality of non-woven fabrics 30 and 40 are laminated as shown in FIG. 2, the fibers constituting the non-woven fabric 30 on the side where air containing oil mist and dust flow in are made into glass fibers. As a result, the oil-repellent film containing the silica sol hydrolyzate as a main component adheres to the glass fiber more firmly and is less likely to be peeled off from the fiber of the non-woven fabric.

[Method of forming an oil-repellent film on the fiber surface of non-woven fabric]
In order to form an oil-repellent film on the fiber surface of the non-woven fabric of the present embodiment, a liquid composition for forming an oil-repellent film described later is prepared with an alcohol having a boiling point of less than 120 ° C. and having a carbon number of 1 to 4 described below. Prepare a diluted solution so that the mass ratio (liquid composition: alcohol) to the liquid composition is 1: 1 to 50, dip the non-woven fabric in this diluted solution, pull it up from the diluted solution, and in the air, Spread the non-woven fabric on a horizontal wire net or the like at room temperature and drain until a certain amount of liquid is reached. Alternatively, the non-woven fabric that has been pulled up is passed through a mangle roll (squeezer) to remove the liquid. The deflated non-woven fabric is dried in the air at a temperature of 25 ° C. to 140 ° C. for 0.5 hours to 24 hours. As a result, as shown in the enlarged view of FIG. 1, the oil-repellent film 21 is formed on the surface of the fibers 20c constituting the non-woven fabric 20. When the amount of liquid removed is small, it is formed on the fiber surface of the non-woven fabric on the thick film, and when the amount of liquid removed is large, it is formed on the fiber surface of the non-woven fabric on the thin film.

[Manufacturing method of liquid composition for forming an oil-repellent film]
The liquid composition for forming the oil-repellent film is produced by the following method.
[Preparation of mixture]
First, tetramethoxysilane or tetraethoxysilane as a silicon alkoxide, an epoxy group-containing silane as an alkylene group component, a fluorine-containing silane as a fluorine-containing functional group component, and a boiling point in the range of 1 to 4 carbon atoms having a boiling point of less than 120 ° C. Mix the alcohol in the above with water to prepare a mixed solution. Specific examples of the silicon alkoxide include tetramethoxysilane, an oligomer thereof or tetraethoxysilane, and an oligomer thereof. For example, it is preferable to use tetramethoxysilane for the purpose of obtaining a highly durable oil-repellent film, while it is preferable to use tetraethoxysilane when avoiding methanol generated during hydrolysis.

Specific examples of the epoxy group-containing silane as the alkylene group component include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylmethyl. Examples thereof include diethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane and polyfunctional epoxysilane. The alkylene group component is contained in an amount of 1% by mass to 40% by mass, preferably 2.5% by mass to 20% by mass, based on the total mass of the silicon alkoxide and the alkylene group component. If the alkylene group component is less than 1% by mass of the lower limit value, the adhesion to the fiber becomes insufficient when a film is formed on the fiber of the non-woven fabric containing no hydroxyl group. On the other hand, if it exceeds the upper limit of 40% by mass, the durability of the formed film becomes low. When the epoxy group-containing silane is contained so that the alkylene group component is in the range of 1 to 40% by mass, the epoxy group also opens the ring in the hydrolysis polymerization process and contributes to the polymerization, thereby improving the leveling property in the drying process. The film thickness becomes uniform. When the fibers of the non-woven fabric contain hydrophilic groups such as glass fibers, the content of the alkylene group component may be extremely small or zero. On the other hand, when the fibers of the non-woven fabric do not contain a hydrophilic group, the alkylene group component preferably contains 0.5% by mass to 20% by mass when the silica sol hydrolyzate is 100% by mass.

The alcohol in the range of 1 to 4 carbon atoms includes one kind or two or more kinds of alcohols in this range. Examples of this alcohol include methanol (boiling point 64.7 ° C.), ethanol (boiling point about 78.3 ° C.), propanol (n-propanol (boiling point 97-98 ° C.), isopropanol (boiling point 82.4 ° C.)). Be done. Methanol or ethanol is particularly preferable. This is because these alcohols are easily mixed with silicon alcohol. As the water, it is desirable to use ion-exchanged water, pure water, or the like in order to prevent impurities from being mixed. A mixed solution is prepared by adding alcohol and water having a carbon number in the range of 1 to 4 to the silicon alkoxide and the epoxy group-containing silane, and stirring the mixture at a temperature of preferably 10 to 30 ° C. for 5 to 20 minutes.

[Preparation of hydrolyzate (silica sol hydrolyzate)]
The above-prepared mixed solution is mixed with a catalyst composed of an organic acid, an inorganic acid or a titanium compound. At this time, the liquid temperature is preferably maintained at a temperature of 30 ° C. to 80 ° C., and the mixture is preferably stirred for 1 hour to 24 hours. As a result, a hydrolyzate of silicon alkoxide, an epoxy group-containing silane as an alkylene group component, and a fluorine-containing silane as a fluorine-containing functional group component (hereinafter, also referred to as a silica sol hydrolyzate) is prepared. The hydrolyzate contains 2% by mass to 50% by mass of silicon alkoxide, up to 30% by mass of epoxy group-containing silane, 0.005% by mass to 3% by mass of fluorine-containing silane as a fluorine-containing functional group component, and carbon number. 20% by mass to 98% by mass of alcohol in the range of 1 to 4, 0.1% by mass to 40% by mass of water, 0.01% by mass to 5% by mass using an organic acid, inorganic acid or titanium compound as a catalyst. It is obtained by advancing the hydrolysis reaction of silicon alkoxide, epoxy group-containing silane, and fluorine-containing silane as a fluorine-containing functional group component by mixing at a ratio. If the fluorine-containing silane as a fluorine-containing functional group component is less than the lower limit of 0.005% by mass, the formed film is less likely to have oil repellency, and if it exceeds the upper limit of 3% by mass, it is difficult to adhere to the fiber surface of the non-woven fabric. ..

The reason why the proportion of alcohol in the range of 1 to 4 carbon atoms is limited to the above range is that if the proportion of alcohol is less than the lower limit, the silicon alkoxide does not dissolve in the solution and separates, and during the hydrolysis reaction. On the other hand, when the upper limit is exceeded, the amount of water and catalyst required for hydrolysis is relatively small, so that the reactivity of hydrolysis is reduced and polymerization does not proceed, resulting in a film. This is because the adhesion of the material is reduced. The reason why the ratio of water is limited to the above range is that if the value is less than the lower limit, the hydrolysis rate becomes slower, so that the polymerization does not proceed and the adhesion of the oil-repellent film becomes insufficient. This is because the reaction solution gels during the decomposition reaction, and the amount of water is too large, so that the silicon alkoxide compound does not dissolve in the alcohol aqueous solution, causing a problem of separation.

When the hydrolyzate is 100% by mass, the SiO ₂ concentration (SiO ₂ minutes) is preferably 1 to 40% by mass. If the SiO ₂ concentration of the hydrolyzate is less than the lower limit, the polymerization is insufficient, and the adhesion of the film is likely to decrease and cracks are likely to occur. The alkoxide does not dissolve, causing a problem that the reaction solution gels.

The organic acid, inorganic acid or titanium compound functions as a catalyst for promoting the hydrolysis reaction. Examples of organic acids include formic acid and oxalic acid, examples of inorganic acids include hydrochloric acid, nitric acid, and phosphoric acid, and examples of titanium compounds include tetrapropoxytitanium, tetrabutoxytitanium, tetraisopropoxytitanium, and titanium lactate. .. 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 value is less than the lower limit, the reactivity is poor and the polymerization is insufficient, so that a film is not formed. On the other hand, if the value exceeds the upper limit, the reactivity is not affected. , The residual acid causes problems such as corrosion of the fibers of the non-woven fabric.

The fluorine-containing silane as a fluorine-containing functional group component is represented by the following general formulas (3) and (4). More specifically, examples of the perfluoroether group in the above formulas (3) and (4) include perfluoroether structures represented by the following formulas (5) to (13).

（３）

(3)

（４）

(4)

（５）

(5)

（６）

(6)

（７）

(7)

（８）

(8)

（９）

(9)

（１０）

(10)

（１１）

(11)

（１２）

(12)

（１３）

(13)

Further, examples of X in the above formulas (2) and (3) include structures represented by the following formulas (14) to (18). The following formula (14) is an ether bond, the following formula (15) is an ester bond, the following formula (16) is an amide bond, the following formula (17) is a urethane bond, and the following formula (18) is an example containing a sulfone amide bond. Is shown.

（１４）

(14)

（１５）

(15)

（１６）

(16)

（１７）

(17)

（１８）

(18)

Here, in the above formulas (14) to (18), R ² and R ³ are hydrocarbon groups having 0 to 10 ^{carbon atoms, and R 4} is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group of R ³ include an alkylene group such as a methylene group and an ethylene group, and examples of the hydrocarbon group of R ⁴ include an alkyl group such as a methyl group and an ethyl group, as well as a phenyl group and the like. Can also be mentioned.

Further, in the above formulas (3) and (4), R ¹ includes a methoxy group and an ethoxy group as hydrolyzing groups.

Further, in the above formulas (3) and (4), Z is not particularly limited as long as it is a hydrolyzable group capable of forming a Si—O—Si bond by hydrolysis. Specific examples of such a hydrolyzable group include an alkoxy group such as a methoxy group, an ethoxy group, a propoxy group and a butoxy group, an aryloxy group such as a phenoxy group and a naphthoxy group, a benzyloxy group and a phenethyloxy group. Examples thereof include an aralkyloxy group such as a group, an acetoxy group, a propionyloxy group, a butyryloxy group, a valeryloxy group, a pivaloyloxy group, an acyloxy group such as a benzoyloxy group and the like. Among these, it is preferable to apply a methoxy group or an ethoxy group.

Here, specific examples of the fluorine-containing silane as a fluorine-containing functional group component having a perfluoroether structure represented by the above formulas (3) and (4) are, for example, the following formulas (19) to (27). Examples include the structures represented. In the following formulas (19) to (27), R is a methyl group or an ethyl group.

（１９）

(19)

（２０）

(20)

（２１）

(21)

（２２）

(22)

（２３）

(23)

（２４）

(24)

（２５）

(25)

（２６）

(26)

（２７）

(27)

As described above, the fluorine-containing functional group component contained in the oil-repellent film-forming liquid composition of the present embodiment has a structure having one or more perfluoroether groups and one or more alkoxysilyl groups in the molecule. It has a perfluoroether group in which a plurality of short-chain long perfluoroalkyl groups and perfluoroalkylene groups having 6 or less carbon atoms are bonded to an oxygen atom, and has a high fluorine content in the molecule, so that the formed film has excellent repellency. Water repellent property can be imparted.

[Liquid composition for forming an oil-repellent film]
The liquid composition for forming an oil-repellent film of the present embodiment is produced by the above-mentioned production method, and contains the above-mentioned silica sol hydrolyzate containing a fluorine-containing functional group component and a solvent. This fluorine-containing functional group component has a perfluoroether structure represented by the above general formulas (1) and (2), and when the silica sol hydrolyzate is 100% by mass, 0.01% by mass to 10% by mass. %included.

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-mentioned formulas (5) to (27).

Since the liquid composition for forming an oil-repellent film of the present embodiment contains a silica sol hydrolyzate as a main component, an oil-repellent film having excellent adhesion to fibers of the non-woven fabric of the oil-repellent film and having high strength that is difficult to peel off can be obtained. Be done. Further, since the silica sol hydrolyzate contains a fluorine-containing functional group component having a perfluoroether structure represented by the above general formula (1) or (2), it has an oil-repellent effect. If the content ratio of the fluorine-containing functional group component is less than 0.01% by mass, oil repellency cannot be imparted to the formed film, and if it exceeds 10% by mass, the film is repelled and the film forming property is inferior. The content ratio of the preferable fluorine-containing functional group component is 0.1% by mass to 5% by mass.

Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
8.52 g of tetramethoxysilane (TMS) trimer to pentamer (manufactured by Mitsubishi Chemical Corporation, trade name: MKC silicate MS51) as a silicon alkoxide, and 3-glycidoxy as an epoxy group-containing silane as an alkylene group component. 0.48 g of propyltrimethoxysilane (GPTMS: manufactured by Shinetsu Chemical Industry Co., Ltd., trade name: KBM-403) and 0.24 g of fluorine-containing silane (R: ethyl group) represented by the formula (19) as a fluorine-containing functional group component. And 17.34 g of ethanol (EtOH) (boiling point 78.3 ° C.) as an organic solvent are mixed, and 3.37 g of ion-exchanged water is further added, and the mixture is stirred in a separable flask at a temperature of 25 ° C. for 5 minutes. This prepared a mixed solution. Further, 0.05 g of hydrochloric acid having a concentration of 35% by mass was added to this mixed solution as a catalyst, and the mixture was stirred at 40 ° C. for 2 hours. As a result, an oil-repellent film-forming liquid composition containing a silica sol hydrolyzate was prepared. The contents of this preparation are shown in Table 1.

The silica sol hydrolyzate of the obtained liquid composition for forming an oil-repellent film contained 4.5% by mass of a fluorine-containing functional group component and 7.8% by mass of an alkylene group component having 7 carbon atoms. Next, 7.0 g of an industrial alcohol (manufactured by Japan Alcohol Corporation, AP-7) was added and mixed with 1.0 g of the oil-repellent film-forming liquid composition to prepare a diluted solution of the liquid composition. This diluted solution was dipped with a non-woven fabric having a basis weight of 265 g / m ^{2 as a single layer having an air permeability of 5 ml / cm 2} / sec as a base material for an air filter for 30 seconds. The base material of the air filter was a non-woven fabric made of PET fiber. The non-woven fabric was pulled up from the diluted solution, spread on a horizontal wire mesh, and left at room temperature for 30 minutes to remove the liquid. Then, the single-layer non-woven fabric was put in a dryer maintained at 120 ° C. for 30 minutes and dried to obtain an air filter. The air permeability of this air filter was 3.0 ml / cm ² / sec. The above results are shown in Table 2.

<Examples 2 to 5, Comparative Examples 2 to 4>
For Examples 2 to 5 and Comparative Examples 2 to 4, as shown in Table 2, the type of the base material of the air filter and the type of the fluorine-containing silane as the fluorine-containing functional group component are selected and shown in Example 1. The amount of TMOS added, the amount of GPTMS added, and the amount of fluorine-containing silane added were changed. The liquid compositions for forming an oil-repellent film of Examples 2 to 5 and Comparative Examples 2 to 4 were obtained in the same manner as in Example 1 except for the above. The same industrial alcohol as in Example 1 was added to these liquid compositions to prepare a diluted solution for dipping the air filter base material in the same manner as in Example 1. The air filter base material shown in Table 2 was dipped in these diluted solutions in the same manner as in Example 1 and dried to obtain an air filter having the characteristics shown in Table 2. In Table 2, all Rs in the formulas of the fluorine-containing silanes represented by the formulas (19) to (23) as the fluorine-containing functional group components are ethyl groups.

Unlike the non-woven fabric of Example 1, the non-woven fabric used in Example 3 is composed of two layers of a non-woven fabric of glass fiber and a non-woven fabric of PET fiber, and the air permeability of the air filter obtained from this non-woven fabric is 1.2 ml. It was / cm ² / sec. Further, the non-woven fabric used in Example 5 and Comparative Example 4 is different from the non-woven fabric of Example 1, and is composed of a mixed fiber of PET fiber and glass fiber (PET: glass = 80:20 in terms of mass ratio), and is obtained from these non-woven fabrics. each air permeability of the air filter that is was 28.0 ml / cm ² / sec and 0.5 ml / cm ² / sec. Further, the air filter base material used in Example 6 and Comparative Example 5 is a single-layer non-woven fabric made of PTFE fiber, unlike the non-woven fabric of Example 1, and the ventilation of each of the air filters obtained from these non-woven fabrics. The degree was 3.0 ml / cm ² / sec and 5.0 ml / cm ² / sec.

<Comparative example 1>
In Comparative Example 1, the same non-woven fabric as in Example 1 was used, but the silica sol hydrolyzate did not contain fluorine-containing silane as a fluorine-containing functional group component.

<Comparative example 5>
In Comparative Example 5, as the base material of the air filter, a polytetrafluoroethylene (PTFE) membrane filter of 1μm open eyes that are commercially available with untreated, which was used as an air filter. No dipping was performed on the diluted solution of the oil-repellent film-forming liquid composition as in Example 1.

<Comparative tests and evaluations>
Hexadecane and iron (III) oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) are mixed in a mass ratio of 80:20, imitating oil mist and dust scattered from machine tools that process metal products using cutting oil. It was put into a rotating and revolving stirrer and stirred and mixed to obtain a simulated liquid. After dropping 1 ml of the obtained simulated liquid from above onto the 11 types of horizontally placed air filters obtained in Examples 1 to 6 and Comparative Examples 1 to 5, the air filter was erected vertically to prepare the simulated liquid. The fallability was confirmed. When the simulated liquid soaked into the air filter, the oil repellency of the air filter was "poor", and when the simulated liquid fell from the air filter, the oil repellency of the air filter was "good".

As is clear from Table 2, in Comparative Example 1, since the silica sol hydrolyzate did not contain fluorine-containing silane, which is a fluorine-containing functional group component, the simulated liquid permeated into the air filter and did not fall, and its oil repellency. Was "bad".

In Comparative Example 2, when the silica sol hydrolyzate was 100% by mass, the content of the fluorine-containing functional group component was too high at 11.6% by mass, and the texture of the non-woven fabric was too low at ^{150 g / m 2.} The air permeability of the air filter was too high at 60.0 ml / cm ² / sec, the simulated liquid soaked into the air filter and did not fall, and its oil repellency was "poor".

In Comparative Example 3, the air permeability ^{of the air filter was too high at 35 ml / cm 2} / sec, the simulated liquid soaked into the air filter and did not fall, and its oil repellency was "poor".

In Comparative Example 4, the simulated liquid had fallen from the air filter, but the basis weight of the non-woven fabric was ^{too high at 450 g / m 2} , so the air permeability of the air filter was ^{too low at 0.5 ml / cm 2} / sec and air. The performance as a filter was insufficient.

In Comparative Example 5, a membrane filter made of PTFE was used as the air filter, but the simulated liquid soaked into the air filter and did not fall, and its oil repellency was "poor".

In contrast, in the air filter of Examples 1 to 6, the basis weight of the nonwoven fabric is in the range of ^{210g / m 2 ~380g / m 2} , the fluorine-containing functional group component sol hydro oil-repellent film having a function of oil repellency When the decomposition product is 100% by mass, it is contained in a ratio of 0.02% by mass to 9.8% by mass, and the air permeability of the air filter is 1.2 ml / cm ² / sec to 28.0 ^{ml / cm 2} / sec. Since it satisfied the scope of the invention of the first aspect, it was confirmed that the simulated liquid fell from the air filter and its oil repellency was all "good".

The air filter of the present invention is used in a working environment where there is a machine tool such as a cutting machine or a turning machine that processes a metal product using cutting oil.

10 Air filter 20 Non-woven fabric 20a One side of non-woven fabric 20b Other side of non-woven fabric 20c Non-woven fabric fibers 20d Non-woven fabric pores 21 Oil-repellent film 22 Oil mist oil particles 23 Dust particles

Claims (4)

An air filter containing a non-woven fabric in which a large number of pores are formed between fibers, which are opposed to one surface on which air containing oil mist and dust flows in and the other surface on which the air flows out.
Basis weight of the nonwoven fabric is in the range of ^{200g / m 2 ~400g / m 2} ,
An oil-repellent film is formed on the fiber surface of the non-woven fabric,
The oil-repellent film has a silica sol hydrolyzate containing a fluorine-containing functional group component, and has a silica sol hydrolyzate.
The fluorine-containing functional group component is contained in a proportion of 0.01% by mass to 10% by mass when the silica sol hydrolyzate is 100% by mass.
Air permeability of the air filter is a 1 ml / cm ² / sec -30 mL / cm ² / sec,
The fluorine-containing functional group component is an air filter characterized by containing a perfluoroether structure represented by the following general formula (1) or formula (2).

In the above formulas (1) and (2), p, q and r are integers of 1 to 6 which are the same or different from each other, and may be linear or branched. Further, in the above formulas (1) and (2), X is a hydrocarbon group having 2 to 10 carbon atoms and is selected from an ether bond, a CO-NH bond, an O-CO-NH bond and a sulfone amide bond. It may contain one or more bonds. Further, in the above formulas (1) and (2), Y is the main component of the silica sol hydrolyzate. The air filter according to claim 1, wherein the silica sol hydrolyzate further contains 0.5% by mass to 20% by mass of an alkylene group component having 2 to 7 carbon atoms. The air filter according to claim 1 or 2, wherein the non-woven fabric is composed of a single layer or a laminate of a plurality of layers. One or 2 selected from the group in which the fibers constituting the non-woven fabric consist of polyethylene terephthalate (PET), polypropylene (PP), polytetrafluoroethylene (PTFE), glass, alumina, carbon, cellulose, pulp, nylon and metal. The air filter according to any one of claims 1 to 3, which is a fiber of more than one species.

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