JP2016077944A - Porous laminate, and manufacturing method of porous laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a porous laminate which can obtain a high permeation flow rate while maintaining mechanical strength.SOLUTION: A manufacturing method of a porous laminate, which is formed by laminating a support layer, a collection layer, and a protection layer in this order, includes: a step of laminating a nonporous resin sheet, of which a major component is polytetrafluoroethylene, on the porous support layer; a step of obtaining a primary laminate having the support layer and the collection layer in which the resin sheet is made porous by rolling the laminate of the support layer and the resin sheet; a step of laminating the protection layer through a dry laminate layer on a surface opposite to the support layer of the collection layer of the primary laminate; and a step of pressure-bonding the primary laminate, the dry laminate layer, and the protection layer by heating. Lamination of the dry laminate layer in the lamination step is preferably achieved by coating and drying the dry laminate agent on a surface of the protection layer. The lamination of the dry laminate layer in the lamination step is preferably achieved also by overlapping the dry laminate sheets.SELECTED DRAWING: Figure 2D

Description

  The present invention relates to a porous laminate and a method for producing a porous laminate.

  The porous laminate comprising polytetrafluoroethylene (PTFE) as a main component has the characteristics such as high heat resistance, chemical stability, weather resistance, nonflammability, high strength, non-adhesiveness, and low friction coefficient of PTFE, It has properties such as flexibility due to porosity, liquid permeability, particle trapping property, and low dielectric constant. Therefore, PTFE porous laminates are widely used as liquid and gas microfiltration filters in semiconductor-related fields, liquid crystal-related fields, and food-medicine-related fields.

  In recent years, in the semiconductor manufacturing field, the miniaturization of processing has progressed, and the size of a foreign substance that is desired to be removed from an etching solution, a cleaning solution, and the like has also been miniaturized in accordance with the progress of the microfabrication technology. Therefore, it is required to make the filter pore diameter fine. However, in order to make the filter pore diameter fine while maintaining the processing flow rate, it is necessary to make the PTFE porous laminate thinner. However, when the porous laminate is thinned, there is a disadvantage that the mechanical strength is lowered.

  Also, when using a porous laminate made of PTFE as a filter, in order to obtain a large filtration area, it is often installed in a filter in the form of pleats formed with folds, but porous at the folded part of the folds. Damage is likely to occur in the collection layer corresponding to the outermost surface of the laminate.

  In order to prevent such inconvenience, a filter having a protective layer attached to the collection layer side of a laminate having a porous collection layer and a support layer made of PTFE has been devised as a filter. (See JP 2012-206062 A).

JP 2012-206062 A

  However, when a protective layer is bonded to a laminate having a collection layer and a support layer, the permeate flow rate may be reduced, and desired characteristics of the porous laminate may not be obtained.

  This invention is made | formed based on the above situations, and it aims at providing the manufacturing method of the porous laminated body which can obtain a high permeation | transmission flow volume while maintaining mechanical strength, and a porous laminated body. .

  As a result of intensive studies to solve the above-mentioned problems, the present inventor caused the pore size reduction and pore blockage in the collection layer when the protective layer was bonded to the laminate having the collection layer and the support layer. It has been found that the permeation flow rate is greatly reduced when the protective layer is bonded. In pasting a laminate with a protective layer using an ion exchange resin dispersion as an adhesive, the adhesive is applied to the surface of the PTFE collection layer, and then the protective layer is pasted with the adhesive wet. However, it is presumed that at this time, the adhesive enters the pores of the collection layer and induces a reduction in the diameter of the collection layer and blockage of the holes.

  A method for producing a porous laminate according to an aspect of the present invention devised based on this finding is a method for producing a porous laminate in which a support layer, a collection layer, and a protective layer are laminated in this order, A step of laminating a nonporous resin sheet mainly composed of polytetrafluoroethylene on a porous support layer, and a collection layer in which the resin sheet is made porous by stretching the laminate of the support layer and the resin sheet And a step of obtaining a primary laminate having a support layer, a step of laminating a protective layer via a dry laminate layer on the surface of the collection layer of the primary laminate opposite to the support layer, and the primary by heating And a step of pressure-bonding the laminate, the dry laminate layer, and the protective layer.

  Another object of the present invention is to provide a porous laminate according to another embodiment of the present invention, comprising: a porous support layer; and a polylayer laminated on one surface of the support layer and made porous by stretching. A porous laminate comprising a collection layer mainly composed of tetrafluoroethylene and a porous protective layer laminated on one surface side of the collection layer via a dry laminate layer.

  By the method for producing a porous laminate of the present invention, a porous laminate can be produced in which a high permeation flow rate is obtained while maintaining mechanical strength. Moreover, the porous laminated body of this invention can obtain a high permeation | transmission flow volume, maintaining mechanical strength.

It is a typical sectional view of the porous layered product concerning one embodiment of the present invention. It is typical sectional drawing explaining the manufacturing method of the porous laminated body of FIG. It is typical sectional drawing explaining the process following FIG. 2A of the manufacturing method of the porous laminated body of FIG. It is typical sectional drawing explaining the process following FIG. 2B of the manufacturing method of the porous laminated body of FIG. It is typical sectional drawing explaining the next process of FIG. 2C of the manufacturing method of the porous laminated body of FIG. It is typical sectional drawing explaining the next process of FIG. 2B in the case of using a dry laminate sheet with the manufacturing method of the porous laminated body of FIG. Test No. It is a SEM photograph of the collection layer surface before 1 protective layer bonding. Test No. It is a SEM photograph of the collection layer surface which peeled the protective layer after 1 protective layer bonding. Test No. It is a SEM photograph of the collection layer surface before 2 protective layer bonding. Test No. It is a SEM photograph of the collection layer surface which peeled off the protective layer after 2 protective layer bonding.

[Description of Embodiment of the Present Invention]
A method for producing a porous laminate according to an aspect of the present invention is a method for producing a porous laminate in which a support layer, a collection layer, and a protective layer are laminated in this order, and a polytetra A primary layer having a step of laminating a non-porous resin sheet containing fluoroethylene as a main component, and a trapping layer in which the resin sheet is made porous by stretching the laminate of the support layer and the resin sheet, and a support layer A step of obtaining a laminate, a step of laminating a protective layer via a dry laminate layer on the surface of the collection layer of the primary laminate opposite to the support layer, and heating the primary laminate, the dry laminate layer, and And a step of pressure-bonding the protective layer.

  The method for producing the porous laminate includes a step of laminating a protective layer via a dry laminate layer on the surface opposite to the support layer of the collection layer of the primary laminate having a collection layer and a support layer, and then press-bonding by heating. Thus, since the collection layer and the protective layer are bonded together, the resin of the dry laminate layer is unlikely to enter the pores of the collection layer during thermocompression bonding. For this reason, it is difficult to reduce the pore size and block the hole in the collection layer, and the reduction in the permeation flow rate of the collection layer due to the bonding of the protective layer is suppressed, and the permeation flow rate can be increased. In addition, when a conventional ion exchange resin dispersion is used as an adhesive, it is heated in a wet state when the protective layer is adhered, whereas the method for producing the porous laminate is heated in a dry state in the above-described pressure bonding step. Therefore, the time for heating in the above-described pressure-bonding step is shorter than the heating time for conventional protective layer adhesion. Therefore, according to the method for producing a porous laminate, the time for the entire production process of the porous laminate can be shortened, and the production efficiency can be improved. Here, the “main component” is the most abundant component, for example, a component having a content of 50% by mass or more.

  The lamination of the dry laminating layer in the laminating step may be performed by applying and drying a dry laminating agent on the surface of the protective layer. When the dry laminating agent comes into contact with the collecting layer in a wet state, the resin of the dry laminating layer enters into the pores of the collecting layer. Thus, by applying the dry laminating agent to the surface of the protective layer and drying it, By laminating the dry laminate layer, it is possible to more reliably suppress the resin of the dry laminate layer from entering the pores of the collection layer.

  The lamination of the dry laminate layer in the laminating step may be performed by stacking dry laminate sheets. Thus, it is easy to adhere | attach a collection layer and a protective layer uniformly by using a dry laminate sheet. In addition, since the dry laminate layer can be easily thickened, the anchor effect can be increased and the peel strength between the collection layer and the protective layer can be improved. Moreover, since a commercially available dry laminate sheet can be used, a manufacturing process can be simplified.

  The peel adhesion strength between the trapping layer and the protective layer of the porous laminate obtained after the pressure-bonding step is preferably 0.1 N / 10 mm or more and 10 N / 10 mm or less. Thus, peeling of the protective layer from the primary laminate can be reliably prevented by setting the peel adhesive strength between the collection layer and the protective layer of the porous laminate within the above range. Here, the “peel adhesion strength” is measured according to JIS-K6854-3 (1999).

  As a porosity of the collection layer of the porous laminated body obtained after the said crimping | compression-bonding process, 10% or more is preferable. Thus, the permeation | transmission flow rate can be raised more reliably by making the porosity of the collection layer after a crimping | compression-bonding process 10% or more. Here, the “porosity” means the ratio of the total area of the opening regions in the surface to the area including the opening region of the surface on the dry laminate layer side of the collection layer. The above-mentioned “porosity” can be measured by binarizing and calculating an electron micrograph (5000 times) obtained by photographing the surface of the collection layer, using image processing software such as GNU Image Manipulation Program. Specifically, the electron micrograph is converted into a monochrome image using image processing software and binarized to make the aperture area black, and the porosity is measured by measuring the black ratio from the obtained brightness histogram. Can be calculated.

  The average flow pore size of the porous laminate obtained after the crimping step is preferably 40 nm or less. Thus, by setting the average flow hole diameter after the pressure bonding step to 40 nm or less, the filter can be used as a filter having characteristics that meet recent demands in the field of semiconductor manufacturing. Here, the “average flow pore size” is an index corresponding to the average value of the pore size, and is based on the measurement result by the bubble point method (ASTM F316-86, JIS-K3832 (1990)) using a pore size distribution measuring device or the like. Desired. Specifically, the relationship between the differential pressure applied to the membrane and the air flow rate through the membrane is measured by the bubble point method when the membrane is dry and when the membrane is wet with liquid. The graphs obtained by this measurement are respectively a dry curve and a wet curve, and when the pressure difference at the intersection of the curve and the wet curve with the flow rate of the dry curve being ½ is P (Pa), the formula d = The value of d (μm) represented by cγ / P is “average flow pore size” (c is a constant 2860, and γ is the surface tension (dynes / cm) of the liquid).

  It is preferable that a part of the facing surface between the trapping layer and the dry laminate layer of the porous laminate obtained after the pressure bonding step is not bonded. As described above, by keeping a part of the facing surface of the collection layer and the dry laminate layer from adhering after the pressure bonding step, the separation strength between the collection layer and the protective layer is maintained, and the collection strength is maintained. In the region where the collecting layer and the dry laminate layer are not in contact with each other, it is possible to more surely prevent the trapping layer from being reduced in diameter and blocked.

  The printed porous laminate according to another embodiment of the present invention is mainly composed of a porous support layer and polytetrafluoroethylene laminated on one surface of the support layer and made porous by stretching. A porous laminate comprising a collection layer and a porous protective layer laminated on one surface side of the collection layer via a dry laminate layer.

  In the printed porous laminate, the porous protective layer is laminated on one surface side of the collection layer mainly composed of polytetrafluoroethylene, which is made porous through the dry laminate layer. The penetration of the resin collection layer of the laminate layer into the pores is suppressed. Therefore, it is difficult to reduce the diameter of the pores or block the pores in the collection layer, and the decrease in the permeation flow rate of the collection layer due to the bonding of the protective layer is suppressed, and the permeation flow rate can be increased.

[Details of the embodiment of the present invention]
Hereinafter, a porous laminate and a method for producing a porous laminate according to an embodiment of the present invention will be described with reference to the drawings.

[Porous laminate]
The porous laminate shown in FIG. 1 includes a porous support layer 1 and a collection layer 2 mainly composed of polytetrafluoroethylene laminated on one surface of the support layer 1 and made porous by stretching. And a porous protective layer 4 laminated on one surface side of the collection layer 2 with the dry laminate layer 3 interposed therebetween.

<Support layer>
The support layer 1 is a layer for supporting the collection layer 2 and is a porous body having a larger pore diameter than the collection layer 2. Since the support layer 1 supports the collection layer 2, it is desired to have excellent mechanical strength and the like, and a fluororesin porous body is preferably used. Among the fluororesin porous bodies, a porous body mainly composed of polytetrafluoroethylene is preferably used. The support layer 1 is stretched together with the collection layer 2 after a nonporous resin sheet as the collection layer 2 is laminated on one surface of the support layer 1.

  The average thickness of the support layer 1 is preferably 2 μm or more and 80 μm or less, and more preferably 5 μm or more and 60 μm. When the average thickness of the support layer 1 is less than 2 μm, the strength of the porous laminate may be insufficient. On the contrary, when the average thickness of the support layer 1 exceeds 80 μm, the pressure loss of the porous laminate may increase.

  The average flow hole diameter of the support layer 1 is larger than the average flow hole diameter of the collection layer 2. The average flow pore size of the support layer 1 is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.2 μm or more and 1 μm or less. When the average flow pore size of the support layer 1 is less than 0.1 μm, the permeate flow rate of the porous laminate may be reduced. On the contrary, when the average flow pore size of the support layer 1 exceeds 5 μm, the strength of the porous laminate may be insufficient.

  The porosity of the support layer 1 is preferably 10% or more and 80% or less, and more preferably 15% or more and 70% or less. When the porosity of the support layer 1 is less than 10%, the permeate flow rate of the porous laminate may be reduced. Conversely, when the porosity of the support layer 1 exceeds 80%, the strength of the porous laminate may be insufficient. Here, the “porosity” means the ratio of the total area of the opening regions in the surface to the area including the opening region of the surface of the support layer 1 on the collection layer 2 side.

<Collection layer>
The collection layer 2 is a layer for removing fine foreign matters, and is a porous body having a fine pore diameter that does not allow foreign matters to pass through. The collection layer 2 is a layer mainly composed of polytetrafluoroethylene and made porous by stretching.

  The average thickness of the collection layer 2 is preferably 0.3 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 3 μm or less. When the average thickness of the collection layer 2 is less than 0.3 μm, the collection layer 2 may be easily damaged and the effect of collecting foreign substances may be reduced. Conversely, when the average thickness of the collection layer 2 exceeds 10 μm, the pressure loss of the porous laminate may increase.

  The average flow hole diameter of the collection layer 2 is smaller than the average flow hole diameter of the support layer 1 and the average flow hole diameter of the protective layer 4. The average flow pore size of the collection layer 2 is preferably 1 nm or more and 40 nm or less. When the average flow hole diameter of the collection layer 2 is less than 1 nm, it may be difficult to form the holes of the collection layer 2 uniformly. Conversely, when the average flow pore size of the collection layer 2 exceeds 40 nm, there is a possibility that desired fine foreign matter cannot be removed.

The porosity of the collection layer 2 is preferably 10% or more and 50% or less, and more preferably 15% or more and 40% or less. When the porosity of the collection layer 2 is less than 10%, the permeate flow rate of the porous laminate may be reduced. On the contrary, when the porosity of the collection layer 2 exceeds 50%, there is a possibility that desired fine foreign matter cannot be removed.

<Protective layer>
The protective layer 4 is a layer for increasing the mechanical strength of the porous laminate, and is a porous body having a larger pore diameter than the collection layer 2. Since the porous laminate is required to have heat resistance and chemical resistance, a resin mainly composed of polytetrafluoroethylene is preferably used as the material of the protective layer 4.

  The average thickness of the protective layer 4 is preferably 1 μm to 200 μm, and more preferably 5 μm to 100 μm. When the average thickness of the protective layer 4 is less than 1 μm, the strength of the porous laminate may be insufficient. Conversely, when the average thickness of the protective layer 4 exceeds 200 μm, the pressure loss of the porous laminate may increase.

  The average flow pore size of the protective layer 4 is preferably 0.05 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 5 μm or less. When the average flow pore size of the protective layer 4 is less than 0.05 μm, the permeate flow rate of the porous laminate may be reduced. On the other hand, when the average flow pore size of the protective layer 4 exceeds 10 μm, the strength of the porous laminate may be insufficient.

  The porosity of the protective layer 4 is preferably 10% to 80%, more preferably 15% to 70%. When the porosity of the protective layer 4 is less than 10%, the permeate flow rate of the porous laminate may be reduced. Conversely, when the porosity of the protective layer 4 exceeds 80%, the strength of the porous laminate may be insufficient. Here, the “porosity” means the ratio of the total area of the opening regions in the surface to the area including the opening region of the surface of the protective layer 4 on the collection layer 2 side.

<Dry laminate layer>
The dry laminate layer 3 is laminated between the collection layer 2 and the protective layer 4, and prevents the protective layer 4 from peeling off from the collection layer 2 by firmly adhering to the collection layer 2 and the protective layer 4. To do.

  The dry laminate layer 3 can be formed, for example, by applying and drying a dry laminate agent on the surface of the protective layer 4. The dry laminate layer 3 can also be formed by superposing dry laminate sheets.

  The melting point or glass transition point of the solid content of the dry laminating agent that forms the dry laminating layer 3 is preferably 50 ° C. or higher and 250 ° C. or lower, and more preferably 150 ° C. or higher and 240 ° C. or lower. When the melting point or glass transition point of the solid content of the dry laminating agent is less than 50 ° C., the heating time required for pressure bonding of the collection layer 2 and the protective layer 4 may be long. Furthermore, when used as a filter, the dry laminating agent may fall off and peel off. Moreover, when it heat-processes at the temperature exceeding 260 degreeC, the hole diameter of the collection layer 2 expands notably. Therefore, when the melting point or glass transition point of the solid content of the dry laminating agent exceeds 250 ° C., the pore diameter of the collection layer 2 may be unnecessarily large.

As a solid content of the dry laminating agent for forming the dry laminating layer 3, fluororesin,
What has an ion exchange resin, an amorphous fluororesin, etc. as a main component is preferable, and the thing which has a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) as a main component from the viewpoint of the above-mentioned melting | fusing point or a glass transition point is preferable. The melting point of FEP is about 230 ° C. By forming the dry laminate layer 3 with a dry laminating agent having a solid content mainly composed of FEP, the FEP melts and adheres to the irregularities on the surface of the collection layer 2 when the collection layer 2 and the protective layer 4 are pressed. Excellent peel strength can be obtained by the anchor effect.

  The peel adhesion strength between the collection layer 2 and the protective layer 4 is preferably 0.1 N / 10 mm or more and 10 N / 10 mm or less. When the peel adhesion strength is less than 0.1 N / 10 mm, the protective layer 4 may be easily peeled from the collection layer 2. On the contrary, when the peel adhesion strength exceeds 10 N / 10 mm, it is necessary to increase the pressure at the time of pressure bonding, which may increase the equipment cost.

  When the peel adhesion strength between the collection layer 2 and the protective layer 4 is 0.1 N / 10 mm or more, a part of the facing surface between the collection layer 2 and the dry laminate layer 3 may not be adhered. . As described above, when there is a region that is not bonded to the facing surface of the collection layer 2 and the dry laminate layer 3, it is possible to more reliably suppress the pore diameter reduction and the hole blockage of the collection layer 2 in the region. . In addition, when the part in the surface which the collection layer 2 and the dry laminate layer 3 face is not adhere | attached, the part which the collection layer 2 and the dry laminate layer 3 contact is the collection layer 2 in planar view. And the dry laminate layer 3 are preferably present over the entire overlapping region.

  The ratio of the non-contact total area of the collection layer 2 and the dry laminate layer 3 to the area of the region where the collection layer 2 and the dry laminate layer 3 overlap in plan view is preferably 90% or less, and 80% or less. More preferred. When the ratio of the said non-contact total area exceeds 90%, there exists a possibility that the peeling adhesive strength of the collection layer 2 and the dry laminate layer 3 may fall, and the protective layer 4 may peel from the collection layer 2 easily.

[Method for producing porous laminate]
The method for producing the porous laminate includes a step of laminating a nonporous resin sheet mainly composed of polytetrafluoroethylene on a porous support layer (lamination step), and a laminate of the support layer and the resin sheet. A step of obtaining a primary laminate having a collection layer and a support layer in which the resin sheet is made porous by stretching, and a dry laminate layer on the surface of the collection layer of the primary laminate opposite to the support layer And a step of laminating the protective layer via the step, and a step of crimping the primary laminate, the dry laminate layer and the protective layer by heating (crimping step).

<Lamination process>
As shown in FIG. 2A, a nonporous resin sheet 5 mainly composed of polytetrafluoroethylene is laminated on one surface of a porous support layer 1.

  Specifically, for example, PTFE dispersion is dropped on the surface of an aluminum foil and uniformly stretched, and then dried to produce a nonporous resin sheet 5. Then, PFA dispersion or the like is dropped as an adhesive on the surface opposite to the aluminum foil of the resin sheet 5 and uniformly stretched, and then the expanded PTFE porous body is bonded as the support layer 1. As the expanded PTFE porous body used as the support layer 1, for example, a commercially available expanded PTFE porous body can be used.

<Step of obtaining a primary laminate>
As shown in FIG. 2B, the laminated body of the support layer 1 and the resin sheet 5 laminated in the above-described lamination step is stretched, and the primary laminated body having the collection layer 2 and the support layer 1 in which the resin sheet 5 is made porous. 6 is obtained.

  The above-described stretching of the laminate of the support layer 1 and the resin sheet 5 is performed by a two-step stretching process in which the film is stretched at a low temperature of 80 ° C. or lower and then stretched at a temperature exceeding 80 ° C. The stretching ratio of the low temperature stretching is preferably 1.5 times or more and 10 times or less, and more preferably 2 times or more and 5 times or less. The stretching ratio of the high temperature stretching is preferably 1.5 times or more and 10 times or less, and more preferably 2 times or more and 5 times or less. Low temperature stretching and high temperature stretching can be performed by uniaxial stretching or biaxial stretching, but biaxial stretching is preferred.

  The stretching method of the laminate is not particularly limited. The stretching of the laminate is, for example, a film transport device that grips both side edges of a known long film and transports it in the longitudinal direction, and a long length It can be carried out using a film stretching machine (also referred to as a tenter) that continuously widens (stretches) the film in the width direction while gripping both side edges of the film and transporting it in the longitudinal direction. Specifically, a pair of side edges of the laminate is held by a clip by a film stretching machine, and the laminate is stretched in the width direction while being conveyed in the longitudinal direction by the clip. After stretching the laminate, the other pair of side edges orthogonal to the pair of side edges of the stretched laminate is then gripped with clips of a film stretching machine and similarly stretched, The laminate can be stretched biaxially.

<The process of laminating a protective layer>
In the step of laminating the protective layer, as a method of laminating the dry laminate layer 3, a method of applying a dry laminating agent to the surface of the protective layer 4 and drying, or a method of laminating dry laminate sheets can be used. Below, the process of laminating | stacking a protective layer in the case of using each of these methods is demonstrated.

(Method of applying dry laminating agent to the surface of the protective layer and drying)
First, a case where the dry laminate layer 3 is laminated by applying and drying a dry laminate agent on the surface of the protective layer 4 will be described. First, as shown in FIG. 2C, the dry laminate layer 3 is laminated on the surface of the protective layer 4. Specifically, after applying a dry laminating agent to the surface of the protective layer 4, the dry laminating agent is dried to form the dry laminating layer 3. As the solid content of the dry laminating agent, for example, a material mainly composed of FEP is used.

  Then, as shown in FIG. 2D, the protective layer 4 having the dry laminate layer 3 of FIG. 2C formed on the surface thereof is laminated on the primary laminate 6 obtained in the step of obtaining the primary laminate. Specifically, lamination is performed so that the collection layer 2 of the primary laminate 6 and the dry laminate layer 3 formed on the surface of the protective layer 4 face each other. Therefore, the protective layer 4 is laminated via the dry laminate layer 3 on the surface opposite to the support layer 1 of the collection layer 2 of the primary laminate 6.

  As a heating temperature at the time of drying of the dry laminating agent apply | coated to the surface of the protective layer 4, 100 degreeC or more and 350 degrees C or less are preferable, and 150 degreeC or more and 300 degrees C or less are more preferable. When the said heating temperature is less than 100 degreeC, there exists a possibility that drying time may become long. On the other hand, when the heating temperature exceeds 350, the hole diameter of the pores in the protective layer 4 is excessively increased, and the strength of the protective layer 4 may be reduced.

  The heating time for drying the dry laminating agent applied to the surface of the protective layer 4 is preferably 1 minute to 30 minutes and more preferably 3 minutes to 25 minutes. When the heating time is less than 1 minute, the dry laminate layer 3 is not sufficiently dried, and the trapping layer 2 may be reduced in diameter or closed in the pressure-bonding step described later. On the other hand, when the heating time exceeds 30 minutes, the time for the entire manufacturing process of the porous laminate is prolonged, and the production efficiency may be reduced.

  As solid content concentration of a dry laminating agent, 0.2 to 40 mass% is preferable, and 0.3 to 20 mass% is more preferable. When the solid content concentration is less than 0.2% by mass, a sufficient amount of the dry laminating agent may not be applied to the surface of the protective layer 4. On the contrary, when the solid content concentration exceeds 40% by mass, the dry laminating agent may not be uniformly applied to the surface of the protective layer 4.

  Alternatively, the dry laminating layer 3 may be formed by applying a dry laminating agent to the surface of the collection layer 2 opposite to the support layer 1. After the dry laminate layer 3 is laminated on the primary laminate 6 in this way, the protective layer 4 may be bonded to the primary laminate 6 so that the collection layer 2 and the protective layer 4 face each other. Even in this case, by adjusting the solid content concentration of the dry laminating agent, by adjusting the surface tension so that the dry laminating agent does not enter the pores of the collection layer 2, the porous laminate having a high permeation flow rate The body can be manufactured.

(Method by overlaying dry laminate sheets)
Next, the case where the dry laminate layer 3 is laminated by overlapping the dry laminate sheets will be described. First, a dry laminate sheet 7 is prepared, and the primary laminate 6, the dry laminate sheet 7 and the protective layer 4 obtained in the step of obtaining the primary laminate as shown in FIG. 2E are superposed in this order. Specifically, the collection layer 2 of the primary laminate 6 and the dry laminate sheet 7 are overlapped so as to face each other. Thereby, the protective layer 4 is laminated | stacked through the dry laminate layer 3 on the surface on the opposite side to the support layer 1 of the collection layer 2 of the primary laminated body 6. FIG. As the dry laminate sheet 7, for example, a sheet mainly composed of FEP is used. As the dry laminate sheet 7, for example, a commercially available FEP film can be used.

  A preferable range of the solid content concentration of the dry laminating agent forming the dry laminating sheet 7 is the same as the solid content concentration of the dry laminating agent when the dry laminating layer 3 is laminated by applying and drying the dry laminating agent.

  If the dry laminate sheet 7 is superposed on the surface of the protective layer 4 in the step of laminating the protective layer in this way, the heating step in the case of laminating the dry laminate layer 3 by applying and drying the dry laminating agent becomes unnecessary. The manufacturing process of the porous laminate can be simplified. Moreover, it is easy to adhere | attach the collection layer 2 and the protective layer 4 uniformly by using the dry laminate sheet 7. FIG. Moreover, since the dry laminate layer 3 can be easily thickened, the anchor effect can be increased, and the peel strength between the collection layer 2 and the protective layer 4 can be improved.

<Crimping process>
In the said crimping | compression-bonding process, the primary laminated body 6, the dry laminate layer 3, and the protective layer 4 are crimped | bonded by heating, and the said porous laminated body is obtained.

  As heating temperature in a press-fit process, 70 ° C or more and 260 ° C or less are preferred, and 100 ° C or more and 250 ° C or less are more preferred. When the said heating temperature is less than 70 degreeC, the dry laminating agent which forms the dry laminate layer 3 may not fuse | melt, and there exists a possibility that sufficient peeling strength between the collection layer 2 and the protective layer 4 may not be obtained. On the other hand, when the heating temperature exceeds 260 ° C., the pore diameter of the protective layer 4 is enlarged, and there is a possibility that desired fine foreign matter cannot be removed.

  The heating time in the crimping step is preferably 10 seconds or longer and 30 minutes or shorter, and more preferably 30 seconds or longer and 25 minutes or shorter. When the heating time is less than 10 seconds, the dry laminating agent for forming the dry laminate layer 3 is not sufficiently melted, and the peel strength between the collection layer 2 and the protective layer 4 may be insufficient. On the other hand, when the heating time exceeds 30 minutes, the time for the entire manufacturing process of the porous laminate is prolonged, and the production efficiency may be reduced.

  As a pressure which crimps | bonds the laminated body of the primary laminated body 6, the dry laminate layer 3, and the protective layer 4 in a crimping | compression-bonding process, 0.1 kPa or more and 3 kPa or less are preferable, and 0.3 kPa or more and 1.5 kPa or less are more preferable. When the said pressure is less than 0.1 kPa, the collection layer 2 and the dry laminate layer 3 do not fully adhere | attach, and there exists a possibility that the peeling strength between the collection layer 2 and the protective layer 4 may become inadequate. Conversely, when the pressure exceeds 3 kPa, the equipment cost may increase.

〔advantage〕
In the method for producing the porous laminate, the protective layer 4 is provided on the surface opposite to the support layer 1 of the collection layer 2 of the primary laminate 6 having the collection layer 2 and the support layer 1 via the dry laminate layer 3. After the lamination, the collection layer 2 and the protective layer 4 are bonded together by pressure bonding by heating. Therefore, the resin of the dry laminate layer 3 hardly enters the pores of the collection layer 2 at the time of heat pressure bonding. This makes it difficult for the trapping layer 2 to have a small pore size or blockage of the pores, suppresses a decrease in the permeation flow rate of the collection layer 2 due to the bonding of the protective layer 4, and a porous laminate having a high permeation flow rate. can get.

  Further, in the method for producing the porous laminate, the time for heating in the pressure bonding step is shorter than the heating time for adhering the protective layer in a wet state when using a conventional ion exchange resin dispersion as an adhesive. Therefore, the time for the whole manufacturing process of the porous laminate can be shortened, and the production efficiency can be improved.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example]
PTFE dispersion ("Fluon AD-911" from Asahi Glass Co., Ltd.), PFA latex ("MFA" from Solvay Special Polymers Japan Co., Ltd.) and PFA dispersion with a solid content of 60% by mass ("920HP from Mitsui DuPont Fluoro Chemical Co., Ltd.) )) To prepare a fluororesin dispersion. These were prepared so that the volume ratio of PFA in the PFA latex and PFA in the PFA dispersion to the total volume of the solid content of PTFE dispersion, PFA latex and PFA dispersion was 2%, and then the molecular weight was 200. Ten thousand polyethylene oxide was added to a concentration of 3 mg / ml to prepare the fluororesin dispersion.

  Next, an aluminum foil having an average thickness of 50 μm is spread and fixed on a glass plate so as not to be wrinkled, and after dropping the fluororesin dispersion, a slide shaft made of stainless steel having an outer diameter of 20 mm (Nippon Bearing Co., Ltd.) The company's “Stainless Steel Fine Shaft SNSF Type”) was rolled to stretch the fluororesin dispersion uniformly over the entire surface of the aluminum foil.

  These foils were dried at 80 ° C. for 1 hour, heated at 250 ° C. for 1 hour, and heated at 340 ° C. for 1 hour in this order, and then naturally cooled and fixed on the aluminum foil. A quality fluororesin sheet was formed. The average thickness of the fluororesin sheet calculated from the mass difference per unit area of the aluminum foil before and after the fluororesin sheet was formed and the true specific gravity of the fluororesin (2.25) was about 3 μm.

  Next, PFA dispersion ("920HP" from Mitsui DuPont Fluorochemical Co., Ltd.) is diluted with distilled water to 4 times volume, and further polyethylene oxide with a molecular weight of 2 million is adjusted to a concentration of 3 mg / ml. A 4-fold diluted PFA dispersion was prepared.

  The fluororesin sheet fixed on the aluminum foil was spread and fixed on the glass flat plate so as not to be wrinkled, and the 4-fold diluted PFA dispersion was dropped. Then, while rolling the stainless steel slide shaft and extending the 4-fold diluted PFA dispersion uniformly over the entire surface of the aluminum foil, while the moisture did not dry, the average pore diameter was 0.45 μm and the average thickness was An expanded PTFE porous body having a thickness of 80 μm (“Poreflon FP-045-80” manufactured by Sumitomo Electric Fine Polymer Co., Ltd.) was covered as a support layer.

  Then, each process of drying at 80 ° C. for 1 hour, heating at 250 ° C. for 1 hour, heating at 320 ° C. for 1 hour, and heating at 317.5 ° C. for 8 hours is applied to the foil covered with the support layer on the fluororesin sheet. After carrying out in this order, it cooled naturally. Thus, the said fluororesin sheet | seat was adhere | attached on the said support layer. And the aluminum foil fixed to the fluororesin sheet | seat was melt | dissolved and removed with hydrochloric acid, and the laminated body by which the fluororesin sheet | seat was laminated | stacked on the support layer was obtained.

  Next, this laminate was stretched in the width direction using a tensile tester at a temperature of 15 ° C., a chuck distance of 55 mm, and a stroke of 165 mm (stretch ratio 3 times), and further at the same tensile tester, a temperature of 60 ° C. and a chuck gap of 55 mm. The film was stretched in a direction orthogonal to the width direction at a stroke of 88 mm (stretching ratio: 1.6 times). By these stretching, a primary laminated body in which the fluororesin sheet was used as a collection layer mainly composed of porous polytetrafluoroethylene and the collection layer was laminated on the support layer was obtained.

  On the other hand, low melting point FEP (“Neofluon ND-4R” from Daikin Industries, Ltd.) is diluted to 2 times volume with distilled water to prepare an FEP dispersion having a solid content concentration of 20% by mass, and this FEP dispersion is bar coated. The coating was uniformly applied to the surface of the protective layer ("Poreflon HHP-045-15" from Sumitomo Electric Fine Polymer Co., Ltd.). And after drying at 100 degreeC in the coating furnace, it heated at 250 degreeC for 5 minute (s) in the thermostat, and formed the dry laminate layer of FEP on the surface of the protective layer.

  Next, the primary laminate and the protective layer were bonded so that the collection layer of the primary laminate and the dry laminate layer formed on the surface of the protective layer face each other. And in the state which bonded the primary laminated body and the protective layer, it heat-processed for 20 minutes at 250 degreeC, applying the pressure of 0.48 kPa to a lamination direction in a thermostat, and test No. 1 as an Example. 1 porous laminate was obtained.

[Comparative example]
As an adhesive for adhering the collection layer and the protective layer, an ion exchange resin dispersion having a solid concentration of 20% by mass was prepared. This ion exchange resin dispersion was tested using a bar coat. It apply | coated uniformly on the surface of the collection layer of the primary laminated body produced by the method similar to 1 porous body. And in the state where the ion exchange resin dispersion liquid on the surface of the collection layer is moist, test No. 1 is made so that the collection layer and the protective layer face each other. A protective layer of the same type as 1 was bonded to the primary laminate. Thereafter, heat treatment was performed at 150 ° C. for 2 hours in a thermostatic bath. 2 porous laminates were obtained.

<Peel strength evaluation>
Test No. 1 and test no. The peel strength when the protective layer was peeled from the porous laminate of No. 2 was measured according to JIS-K6854-2 (1999). Table 1 shows the measurement results of the peel strength.

<Air permeability evaluation>
As an evaluation of the permeation flow rate, test No. 1 and test no. About the porous laminated body of 2, the Gurley second before peeling a protective layer and after peeling a protective layer was measured based on JIS-P8117 (2009). Table 1 shows the measurement results of Gurley seconds. In Table 1, “2-layer NM” represents a laminate of a support layer and a collection layer, and “3-layer NM” is a laminate of a support layer, a collection layer, and a protection layer. The porous laminated body before peeling is represented. In addition, “two-layer NM before bonding” refers to Test No. No. 1 is the above-mentioned primary laminated body. In No. 2, it is a thing after apply | coating the ion exchange resin dispersion liquid to the said primary laminated body. Moreover, "the protective layer after bonding" and "two-layer NM after bonding" are the protective layer and the two-layer NM after peeling the protective layer from the porous laminate. The “difference between two layers NM” is a value obtained by subtracting the Gurley seconds of the primary laminate from the Gurley seconds of the two layers NM after the protective layer is peeled from the porous laminate.

<Evaluation of average flow pore size>
Test No. 1 and test no. For the porous laminate of 2, the average flow pore size was measured. The average flow pore size was measured using a pore distribution meter (“Palm Porometer CFP-1500A” manufactured by Porous Materials, Inc.). Specifically, propylene, 1,1,2,3,3,3 oxide hexafluoric acid (GALWICK of Porous Materials, Inc.) is used as a liquid, and the porous laminate is dried and porous. When the porous laminate was wet with the liquid, the relationship between the differential pressure applied to the porous laminate and the flow rate of air passing through the porous laminate was measured with a pore distribution measuring device. Next, the graph obtained from the measurement result was a dry curve and a wet curve, respectively, and the differential pressure at the intersection of the curve and the wet curve with the flow rate of the dry curve being ½ was P (Pa). And the average flow hole diameter d (micrometer) was calculated | required by following formula (1). Here, c is a constant of 2860, and γ is the surface tension (dynes / cm) of the liquid. The measurement results of the average flow pore size are shown in Table 1.
Average flow diameter d (μm) = cγ / P (1)

<Observation layer surface observation>
Test No. 1 and test no. About the porous laminated body of 2, the surface on the opposite side to the support layer of the collection layer before protective layer lamination | stacking and after protective layer peeling was observed. Test No. 3A and 3B show electron micrographs (5,000 times) of the collection layer surface of the primary laminate of the porous laminate 1 and the collection layer surface after peeling of the protective layer, respectively. In addition, Test No. Electron micrographs (5,000 times) of the collection layer surface of the primary laminate of No. 2 porous laminate and the collection layer surface after peeling of the protective layer are shown in FIGS. 3C and 3D, respectively.

[Evaluation results]
From the results in Table 1, the test No. No. 1 porous laminate is test no. It can be seen that the permeate flow rate is higher than that of the porous laminate of No. 2. Thereby, it turns out that the fall of a permeation | transmission flow rate can be suppressed by bonding a collection layer and a protective layer through a dry laminate layer.

  From FIG. 3A and FIG. In the porous laminate of No. 1, the pores after peeling of the protective layer are hardly reduced in diameter on the surface of the collection layer as compared to before the protective layer is laminated. On the other hand, from FIG. In the porous laminate of No. 2, it is remarkably recognized that the pores have become smaller in diameter after the protective layer is peeled off on the surface of the collection layer than before the protective layer is laminated. This is the result of test no. In No. 2, it is considered that the component of the ion exchange resin dispersion as an adhesive entered the pores of the collection layer during pressure bonding with the protective layer. As a result, test no. The porous laminate of No. 1 is the test No. 1. It is considered that a permeate flow rate higher than that of the porous laminate 2 is obtained.

  Further, from the results of Table 1, the test No. No. 1 porous laminate was designated as Test No. It can be seen that the peel strength is remarkably superior to that of No. 2 porous laminate. However, test no. The porous laminate 1 can secure a high permeation flow rate. This is because the FEP of the dry laminate layer melts during pressure bonding with the protective layer and adheres to the irregularities on the surface of the collection layer without entering the pores of the collection layer, thereby obtaining an anchor effect. Conceivable.

  In addition, Test No. The porous laminate of No. 1 has an average flow pore size of 40 nm or less and can be suitably used as a filter that removes fine foreign matters.

  Since the porous laminate produced by the production method of the present invention can obtain a high permeation flow rate while maintaining mechanical strength, it is suitably used as a filter or the like that requires separation of fine particles.

DESCRIPTION OF SYMBOLS 1 Support layer 2 Collection layer 3 Dry laminate layer 4 Protective layer 5 Resin sheet 6 Primary laminated body 7 Dry laminate sheet

Claims (8)

A method for producing a porous laminate in which a support layer, a collection layer and a protective layer are laminated in this order,
A step of laminating a nonporous resin sheet mainly composed of polytetrafluoroethylene on a porous support layer;
A step of obtaining a primary laminate having a collection layer in which the resin sheet is made porous by stretching the laminate of the support layer and the resin sheet, and a support layer;
A step of laminating a protective layer via a dry laminate layer on the surface of the collection layer of the primary laminate opposite to the support layer;
A method for producing a porous laminate comprising the step of pressure-bonding the primary laminate, the dry laminate layer and the protective layer by heating.   The method for producing a porous laminate according to claim 1, wherein the lamination of the dry laminate layer in the lamination step is performed by applying and drying a dry laminate agent on the surface of the protective layer.   The method for producing a porous laminate according to claim 1, wherein the lamination of the dry laminate layer in the lamination step is performed by superposing dry laminate sheets.   The peel adhesion strength between the trapping layer and the protective layer of the porous laminate obtained after the crimping step is 0.1 N / 10 mm or more and 10 N / 10 mm or less. A method for producing a porous laminate.   The manufacturing method of the porous laminated body of any one of Claims 1-4 whose porosity of the collection layer of the porous laminated body obtained after the said crimping | compression-bonding process is 10% or more.   The method for producing a porous laminate according to any one of claims 1 to 5, wherein an average flow pore size of the porous laminate obtained after the crimping step is 40 nm or less.   The porous laminate according to any one of claims 1 to 6, wherein a part of the facing surface of the collection layer and the dry laminate layer of the porous laminate obtained after the crimping step is not bonded. Body manufacturing method. A porous support layer;
A collecting layer mainly composed of polytetrafluoroethylene laminated on one surface of the support layer and made porous by stretching;
A porous laminate comprising a porous protective layer laminated on one side of the collection layer via a dry laminate layer.

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