Laminate

Abstract

To provide a laminate that prevents peeling off of a nonwoven fabric layer, and falling off of a structure fiber of the nonwoven fabric from the laminate, and whose physical properties are difficult to change unintentionally.SOLUTION: In a laminate, both of a structure resin of a matrix layer and a resin making structure fiber of a nonwoven fabric layer have a combination of resin which can melt in the same solvent, so that the surface of the matrix layer and the surface of the structure fiber of the nonwoven fabric layer can be melted to adhere. Because the laminated layers are united, peeling off of the nonwoven fabric layer from the laminate can be prevented. Falling off of the structure fiber of the nonwoven fabric layer from the laminate can be prevented because the resin making the structure fiber of the nonwoven fabric layer contains polyvinylidene fluoride-based resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate comprising a base layer and a nonwoven fabric layer. [Background technology]

[0002] Nonwoven fabrics have traditionally been used or are being considered for various industrial applications, including filters for masks, filters for air conditioning equipment or liquid filtration systems, separators and electrolyte membrane supports for electrochemical elements, supports for catalyst particles, and supports for thin films such as gas separation membranes and liquid separation membranes. Nonwoven fabrics composed of small-diameter fibers, in particular, offer improved filter performance and electrolyte membrane reinforcement capabilities, making them suitable for even more diverse industrial applications. However, nonwoven fabrics (especially those composed of small-diameter fibers) tend to have low strength and poor dimensional stability, so their use as laminates reinforced with a base material is being considered.

[0003] As an example of a laminate comprising such a substrate layer (hereinafter referred to as the substrate layer) and a nonwoven fabric layer (hereinafter referred to as the nonwoven fabric layer), the example in Japanese Patent Application Publication No. 2011-132634 (Patent Document 1) discloses a multilayer nanofiber sheet in which a water-insoluble layer (corresponding to the nonwoven fabric layer) containing polylactic acid nanofibers is deposited on the surface of a polyethylene terephthalate mesh (corresponding to the substrate layer) by subjecting a spinning solution obtained by dissolving polylactic acid in a mixed solvent of chloroform and dimethylformamide to an electrospinning method. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-132634 (Claims, 0052, etc.) [Overview of the project] [Problems that the invention aims to solve]

[0005] The applicant has found that when a laminate comprising a base material layer and a nonwoven fabric layer according to the prior art is used for industrial applications, a problem is likely to occur in which the nonwoven fabric layer peels off from the laminate, unintentionally changing the physical properties of the laminate.

[0006] In addition, when laminates equipped with a nonwoven fabric layer, particularly one composed of small-diameter fibers, are used in industrial applications, the constituent fibers of the nonwoven fabric layer tend to break easily, causing them to detach from the laminate and unintentionally altering the physical properties of the laminate. [Means for solving the problem]

[0007] The present invention "(Claim 1) A laminate comprising a base material layer and a nonwoven fabric layer, The nonwoven fabric layer consists only of continuous fibers. The base layer is a fiber layer derived from a fiber web or nonwoven fabric, in which the constituent fibers consist only of continuous fibers. The resin forming the constituent fibers of the base layer and the resin forming the constituent fibers of the nonwoven fabric layer are soluble in the same solvent. The resin constituting the constituent fibers of the base layer is polyethylene terephthalate only, and the resin constituting the constituent fibers of the nonwoven fabric layer is polyvinylidene fluoride resin only. The surface of the constituent fibers of the base material layer and the surface of the constituent fibers of the nonwoven fabric layer are welded together in a portion thereof. Lamination body. " That is the case. [Effects of the Invention]

[0008] The laminate according to the present invention has a combination of resins in which the constituent resin of the base layer and the resin forming the constituent fibers of the nonwoven fabric layer are both soluble in the same solvent. Furthermore, it is characterized in that the surface of the base layer and the surface of the constituent fibers of the nonwoven fabric layer are welded together to form a laminated, integrated structure. Since both resins constituting the layers are soluble in the same solvent, for example, by using a spinning solution prepared by dissolving the resin constituting the nonwoven fabric layer's constituent fibers in a solvent to deposit the fibers constituting the nonwoven fabric layer onto a substrate to form a nonwoven fabric layer, the portion in contact between the surface of the substrate layer and the surface of the constituent fibers of the nonwoven fabric layer can be dissolved together by the solvent remaining in the nonwoven fabric layer. Then, by removing the remaining solvent, the surface of the substrate layer and the surface of the constituent fibers of the nonwoven fabric layer are welded together, thereby providing a laminate in which the substrate layer and the nonwoven fabric layer are laminated and integrated.

[0009] In the laminate according to the present invention, the surface of the base material layer and the surface of the constituent fibers of the nonwoven fabric layer are welded together at microscopic contact points, and these welded areas are uniformly distributed throughout the entire area between the two layers. Therefore, in the laminate according to the present invention, the physical properties of the base material layer, the nonwoven fabric layer, and the area between the two layers are not unintentionally altered, such as when voids that occur when a binder is used for lamination are blocked by the binder. As a result, the two layers are firmly laminated and integrated, making it difficult for the nonwoven fabric layer to peel off from the base material layer.

[0010] Furthermore, when the resin constituting the nonwoven fabric layer contains polyvinylidene fluoride resin, the constituent fibers are less likely to detach from the nonwoven fabric layer, even in laminates with a nonwoven fabric layer composed of small-diameter fibers, possibly due to the high strength and extensibility of the resin.

[0011] Based on the above, the present invention provides a laminate whose physical properties are less likely to change unintentionally, even when used in industrial applications. [Modes for carrying out the invention]

[0012] In the present invention, various configurations can be appropriately selected, such as the following configurations. In addition, unless otherwise specified or defined, various measurements described in the present invention were performed under atmospheric pressure at a temperature of 25°C. And, unless otherwise specified or defined, various measurement results described in the present invention were obtained by measuring up to a value one digit smaller than the required value, and the required value was calculated by rounding off the value one digit smaller. As a specific example, when the value up to the first decimal place is the required value, the value up to the second decimal place was obtained by measurement, and the value up to the first decimal place was calculated by rounding off the obtained value of the second decimal place, and this value was used as the required value. Also, the upper limit values and lower limit values exemplified in the present invention can be arbitrarily combined.

[0013] The laminate according to the present invention includes a base material layer and a nonwoven fabric layer, and is characterized in that the constituent resin of the base material layer and the resin constituting the constituent fibers of the nonwoven fabric layer are soluble in the same solvent. Whether the resin here is soluble in the solvent can be determined by the following method.

[0014] (Method for determining whether a resin is soluble in a solvent) (1) Prepare 1.00 g of a sample composed of the resin to be determined. The shape of the sample may be a film shape, a fabric shape such as a nonwoven fabric, in addition to a pellet shape. (2) Prepare 200 ml of the solvent to be determined. Then, immerse the prepared sample in the solvent heated to the boiling point of the solvent. (3) After immersing for 3 hours, take out the sample from the solvent and remove the solvent from the taken-out sample. If the sample is completely dissolved and the sample cannot be taken out of the solvent, it is determined that the resin is soluble in the solvent. (4) Weigh the mass (unit: g) of the sample after removing the solvent to the value of the third decimal place, and substitute the value Y rounded to the second decimal place into the following formula. And the calculated value is taken as the "mass change percentage (unit: mass%)" of the measurement object. Mass change percentage = (Y / 1.00) × 100 (5) When the calculated value of the mass change percentage is less than 90% by mass, it is determined that the resin is soluble in the solvent. When the calculated value of the mass change percentage is 90% by mass or more, it is determined that the resin is not soluble in the solvent.

[0015] Also, the solubility parameters (SP values) of the resin according to the present invention and the solvent according to the present invention are preferably close values. The closer the combination of the resin and the solvent is in terms of SP value, the more likely the resin is to be efficiently dissolved in the solvent, and the substrate layer and the non-woven fabric layer can be firmly laminated and integrated.

[0016] The combination of the constituent resin (A) of the substrate layer, the resin (B) forming the constituent fibers of the non-woven fabric layer, and the solvent (C) capable of dissolving both the above-mentioned resins A and B according to the present invention can be appropriately selected. A: polyethylene terephthalate (hereinafter, may be abbreviated as PET), B: polyvinylidene fluoride resin (hereinafter, may be abbreviated as PVDF), C: N,N-dimethylformamide (hereinafter, may be abbreviated as DMF). A: PET, B: PVDF, C: dimethylacetamide. A: PET, B: polyethersulfone, C: dimethylacetamide. Combinations such as these can be exemplified.

[0017] In the laminate according to the present invention, the surface of the substrate layer and the surface of the constituent fibers of the non-woven fabric layer are welded. The welding here means that at the contact portion between the surface of the substrate layer and the surface of the constituent fibers of the non-woven fabric layer, the boundary of the contact portion is not clear and the boundary cannot be confirmed, and they are melted and integrated.

[0018] In this embodiment, a laminate formed by laminating and integrating the surface of a base material layer and the surface of the constituent fibers of a nonwoven fabric layer can be prepared, for example, by directly spinning a nonwoven fabric layer onto a base material using a spinning solution prepared by dissolving the resin constituting the constituent fibers of the nonwoven fabric layer in the solvent according to the present invention. In other words, it can be prepared by dissolving the portion in contact between the surface of the base material layer and the surface of the constituent fibers of the nonwoven fabric layer with the solvent remaining in the nonwoven fabric layer, and then removing the remaining solvent.

[0019] If a nonwoven fabric layer is formed by directly spinning molten resin onto the surface of a base layer, such as by using a melt-blown method, the boundary of the contact area between the surface of the base layer and the constituent fibers of the nonwoven fabric layer can be confirmed. In a laminate formed in this manner of lamination and integration, the base layer and the nonwoven fabric layer are not sufficiently laminated and integrated, and the nonwoven fabric layer is prone to peeling off from the base layer. Whether or not the surface of the base material layer and the surface of the constituent fibers of the nonwoven fabric layer are welded together can be determined by the following method.

[0020] (How to determine whether or not it is welded) 1. Take a sample (shape: square or rectangle) from the laminate to be measured. To facilitate the verification process described later, the constituent resin of the sample may be stained using a staining solution (for example, Kayastain Q (manufactured by Nippon Kayaku Co., Ltd.)). 2. Take an optical microscope photograph or electron microscope photograph (hereinafter collectively referred to as a microscope photograph) of the cross-section of the sample (photographing area: a square shape of 3 mm x 3 mm). 3. Visually confirm the area where the surface of a resin structure (A, e.g., fiber) that constitutes one of the main surfaces of the object being measured, as seen in the microscope image, is in contact with the surface of a fiber (B) of the same type as the fiber that constitutes the other main surface of the object being measured. 4. If the boundary between the structure (A) and the fibers (B) in the area confirmed in item 3 is not clear and the boundary could not be confirmed (for example, if the surface portion of the structure (A) and the surface portion of the fibers (B) are mixed and integrated in the area of ​​contact), the laminate being measured will be judged to have a portion where the surface of the base layer and the surface of the constituent fibers of the nonwoven fabric layer are welded together.

[0021] The laminate of the present invention comprises a nonwoven fabric layer, which is a layer derived from a fiber web or nonwoven fabric. Because the nonwoven fabric layer is formed by random entanglement of fibers, the shape and size of the voids between the fibers can be uniform, and therefore the laminate comprising the nonwoven fabric layer can be used in a variety of industrial applications.

[0022] The type of resin that makes up the constituent fibers of the nonwoven fabric layer can be appropriately selected as long as it satisfies the configuration of the present invention. For example, polyether resins (polyethylene glycol, polypropylene glycol, etc.), phenolic resins, epoxy resins, polyimide resins, polyamide-imide resins, polyamide resins (for example, aromatic polyamide resins such as aramid resin, aromatic polyetheramide resin, nylon resin, etc.), urethane resins, epoxy resins, polysulfone resins (polysulfone, etc.), polyethersulfone resins (polyethersulfone, sulfonated polyethersulfone, etc.), fluorine resins (polytetrafluoroethylene, polyvinyl fluoride, etc.) The resin can be any known resin, such as redene resins (hereinafter referred to as polyvinylidene fluoride homopolymers, polyvinylidene fluoride copolymers, perfluorosulfonic acid resins, etc.), vinyl alcohol resins (polyvinyl alcohol, polyvinyl acetate, etc.), polycaprolactone, polyglycolic acid, polyvinylpyrrolidone, polybenzimidazole resins, acrylic resins (for example, polyacrylonitrile resins copolymerized with acrylic acid esters or methacrylic acid esters, modacrylic resins copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride, etc.), and may be just one type of resin or a mixture of multiple types of resins.

[0023] These resins may consist of either linear or branched polymers, and may be block copolymers or random copolymers. Furthermore, the three-dimensional structure and crystalline nature of the resins may vary.

[0024] In particular, it is preferable that the resin forming the constituent fibers of the nonwoven fabric layer contains a polyvinylidene fluoride resin, so that the laminate can be provided in which the constituent fibers are less likely to fall off the nonwoven fabric layer even if the nonwoven fabric layer is composed of fibers with a small fiber diameter, by having a nonwoven fabric layer composed of fibers with high strength. Furthermore, since polyvinylidene fluoride resin is a resin with high extensibility, it is preferable that it can follow the deformation of the base layer and provide a laminate in which the nonwoven fabric layer is less likely to peel off from the base layer. Here, polyvinylidene fluoride resin refers to a resin having a -(CH2CF2)- structure in the molecular structure of the main chain. Examples of PVDF include polyvinylidene fluoride homopolymers and polyvinylidene fluoride copolymers such as PVDF-HFP.

[0025] The mass percentage of PVDF in the resin constituting the nonwoven fabric layer can be adjusted as appropriate. However, a higher mass percentage makes it easier to provide a laminate in which the constituent fibers are less likely to fall off the nonwoven fabric layer, so it is preferable that the constituent fibers of the nonwoven fabric layer consist only of PVDF. Similarly, the proportion of PVDF-containing fibers in the nonwoven fabric can be adjusted as appropriate, but a higher proportion makes it easier to provide a laminate in which the constituent fibers are less likely to fall off the nonwoven fabric layer, so it is preferable that the constituent fibers of the nonwoven fabric layer consist only of PVDF-containing fibers.

[0026] By providing a laminate with a fine average fiber diameter of the constituent fibers of the nonwoven fabric layer, it is possible to provide a filter with excellent filtration performance (especially for masks) and a laminate that can be used for various industrial applications. From this viewpoint, the average fiber diameter of the constituent fibers is preferably 1 μm or less, preferably less than 450 nm, and preferably 400 nm or less. On the other hand, by not having an average fiber diameter that is too fine, it is possible to provide a laminate that can be used for various industrial applications, such as a filter (especially for masks) in which the shape of the nonwoven fabric layer is maintained even during washing and the constituent fibers are less likely to be cut by washing. From this viewpoint, it is practical for the average fiber diameter of the constituent fibers to be 10 nm or more, preferably greater than 100 nm, preferably greater than 130 nm, and preferably 150 nm or more. In this invention, "average fiber diameter" refers to the arithmetic mean of the individual fiber diameters of 50 fibers measured based on 5000x electron microscope images of the cross-section or surface of the object to be measured. Furthermore, if the fiber diameter is too small to measure, it can be measured using electron microscope images at a magnification higher than 5000x. If the cross-sectional shape of the fiber is non-circular, the diameter of a circle with the same area as the cross-sectional area can be considered as the fiber diameter.

[0027] The fiber length of the constituent fibers can be selected as appropriate, but they can be short or long fibers of a specific length, or continuous fibers with a length that is practically impossible to measure. A small number of fiber ends in the nonwoven layer results in a smooth surface, uniform thickness, and excellent physical properties such as mechanical strength. This allows for the creation of filters (especially mask filters) that maintain their shape during washing and are less prone to cutting during cleaning, making them suitable for a variety of industrial applications. Therefore, it is preferable to include continuous fibers with a continuous length as constituent fibers, and more preferably to consist solely of continuous fibers. In this invention, "fiber length" can be measured based on 5000x electron microscope images of the cross-section or surface of the object being measured. If the fiber length is too long to measure, it can be measured based on electron microscope images at a lower magnification than 5000x.

[0028] The constituent fibers may be single fibers, fibril fibers, or composite fibers. Examples of composite fibers include core-sheath type, sea-island type, side-by-side type, orange type, and bimetal type fibers. The constituent fibers may have a cross-sectional shape other than a roughly circular or elliptical shape. Examples of fibers with irregular cross-sectional shapes include hollow shapes, polygonal shapes such as triangular shapes, alphabetic shapes such as Y shapes, irregular shapes, multi-lobed shapes, symbolic shapes such as asterisk shapes, or shapes in which multiple of these shapes are combined.

[0029] The method for preparing the constituent fibers can be appropriately selected, but for example, methods such as electrospinning, which involves applying an electric field to a spinning solution obtained by dissolving a resin in a solvent and spinning it; a method of using centrifugal force to spin a spinning solution obtained by dissolving a resin in a solvent and spinning it; a method of using an entrained airflow to spin a spinning solution obtained by dissolving a resin in a solvent and spinning it, as described in Japanese Patent Publication No. 2011-012372; and neutralization spinning, which is a type of electrospinning method described in Japanese Patent Publication No. 2005-264374.

[0030] Furthermore, by collecting the fibers spun using the method described above, fiber webs and nonwoven fabrics composed solely of continuous fibers can be prepared. In addition, depending on the spinning conditions, the fiber webs and nonwoven fabrics prepared using the method described above may have film-like or granular non-fibrous material called "shots" attached to their main surface. Whether or not non-fibrous material is present on the main surface of the nonwoven fabric layer can be adjusted as appropriate, and a laminate may be prepared with a nonwoven fabric layer having non-fibrous material on its main surface, or a laminate may be prepared with a nonwoven fabric layer not having non-fibrous material on its main surface.

[0031] The various physical properties of the nonwoven fabric layer, such as basis weight and thickness, can be selected as appropriate. For example, the thickness can be 0.1 to 200 μm, 0.2 to 150 μm, 0.2 to 100 μm, or 0.2 to 50 μm. In this invention, "thickness" refers to the average value of 10 randomly selected points measured using an outside micrometer (0 to 25 mm) as specified in JIS B7502:1994, according to the measurement method of JIS C2111 5.1(1).

[0032] For example, the basis weight is 0.05 to 10 g / m². 2 It can be 0.1~5g / m 2 It can be 0.3~3g / m 2 It can be 0.5~2g / m 2 It can be. Note that the "basis weight" in this invention refers to the value measured as 10cm x 10cm in accordance with JIS L1085.

[0033] The laminate of the present invention comprises a base layer, which serves to reinforce the nonwoven fabric layer. The type of base layer can be appropriately selected from fabrics (fiber webs, nonwoven fabrics, woven or knitted fabrics), films (porous or non-porous films), or foams, depending on the industrial material application in which the laminate will be used. In particular, it is preferable that the base layer is derived from fabrics (fiber webs, nonwoven fabrics, woven or knitted fabrics), and it is preferable that the base layer is a fiber layer derived from fiber webs or nonwoven fabrics, similar to the nonwoven fabric layer. Because the physical properties are similar to those of the nonwoven fabric layer, and because welding can be performed at the microscopic areas where the constituent fiber surfaces of the nonwoven fabric layer and the constituent fiber surfaces of the base layer are in contact, it is possible to prevent unintended changes in the physical properties of the base layer, the nonwoven fabric layer, and the area between the two layers, thereby firmly laminating and integrating the two layers. As a result, the base layer and the nonwoven fabric layer become less likely to peel off, making it easier to provide a laminate that can be used in a variety of industrial applications. A preferred combination of such a base material layer and nonwoven fabric layer is a combination of spunbond nonwoven fabric and electrospun nonwoven fabric layer.

[0034] When the base layer is derived from woven fabric, the fiber diameter and fiber length of the fibers constituting the base layer can be appropriately selected. The average fiber diameter of the base layer can be 1 to 1000 μm, 2 to 500 μm, or 5 to 100 μm. In addition, the constituent fibers of the base layer may be single fibers, composite fibers, or yarns composed of multiple fibers.

[0035] The fiber length of the fibers constituting the base layer is selected as appropriate, but like the constituent fibers of the nonwoven fabric layer, they can be short fibers, long fibers, or continuous fibers. Because a small number of fiber ends in the base layer results in a smooth surface, uniform thickness, and excellent physical properties such as mechanical strength, the base layer and the nonwoven fabric layer can be firmly laminated and integrated. Therefore, it is preferable that the base layer contains continuous fibers with a continuous length as constituent fibers, and it is even more preferable that the constituent fibers of the base layer consist only of continuous fibers.

[0036] The type of resin constituting the base layer can be appropriately selected as long as it satisfies the configuration of the present invention, and can be appropriately selected from the resins or combinations of resins listed as usable as resins for forming the constituent fibers of the nonwoven fabric layer. In particular, in order to provide a laminate in which the surface of the base layer (especially the surface of the constituent fibers of the fabric constituting the base layer) and the surface of the constituent fibers of the nonwoven fabric layer are sufficiently welded together, it is preferable that the constituent resin of the base layer contains PET, and it is preferable that the constituent resin of the base layer is PET only.

[0037] Various physical properties of the base layer, such as basis weight and thickness, can be selected as appropriate. For example, the thickness can be 10 μm to 2 mm, 12 μm to 1 mm, 15 μm to 0.5 mm, or 20 μm to 0.2 mm. For example, the basis weight can be 2 to 500 g / m². 2 It can be 3-200g / m 2 It can be 4-100g / m 2 It can be 5-50g / m 2 It can be.

[0038] Next, the method for manufacturing the laminate according to the present invention will be explained with specific manufacturing examples. Note that explanations of points that are the same as those described above will be omitted. (1) A process of preparing a fabric made of PET fibers, (2) A step of preparing a spinning solution by dissolving PVDF in DMF, (3) A step of spinning PVDF by supplying the spinning solution to an electrospinning apparatus and reducing its diameter, (4) A step of forming a laminated web in which a fiber web made of PVDF fibers is laminated on one main surface of the fabric by collecting the DMF remaining in the spun PVDF fibers on the main surface of the fabric, (5) A step of preparing a laminate by removing the DMF remaining in the laminated web, One method for manufacturing a laminate comprising a base layer made of PET fibers and a nonwoven fabric layer made of PVDF fibers is provided. This method for manufacturing a laminate allows for the welding of the surface of the fabric (the surface of the PET fibers) and the surface of the constituent fibers of the nonwoven fabric layer (the surface of the PVDF fibers) to produce a laminate in which the base layer and the nonwoven fabric layer are laminated together.

[0039] First, let's explain step (2). The type of solvent is appropriately selected so as to be able to dissolve both the constituent resin of the base layer and the resin that makes up the constituent fibers of the nonwoven fabric layer. Examples include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, acetonitrile, dimethyl sulfoxide, 1,4-dioxane, pyridine, formic acid, water, and alcohol. A spinning solution prepared using a mixed solvent consisting of multiple types of solvents may also be used, but it is preferable to prepare a spinning solution using a single type of solvent because it allows for the preparation of a laminate in which the two layers are more firmly laminated and integrated.

[0040] The resin concentration in the spinning solution is adjusted as appropriate, as described later, so that the fibers spun with residual solvent can be collected on the main surface of the base layer.

[0041] The temperature and viscosity of the spinning solution are appropriately selected so that the desired non-woven fabric layer can be prepared. The temperature of the spinning solution can be 5 to 40 °C, can be 10 to 35 °C, and can be 15 to 30 °C. Also, the viscosity of the spinning solution can be 0.05 to 8 Pa·s, can be 0.1 to 6 Pa·s, and can be 0.2 to 5 Pa·s. Note that this "viscosity" is the value at a shear rate of 100 s -1 when measured at a temperature of 25 °C using a viscosity measuring device.

[0042] Next, steps (3) and (4) will be described. The method of spinning by thinning the diameter of the spinning solution is appropriately selected so that the desired non-woven fabric layer can be prepared. For example, a direct spinning method can be adopted. When the electrospinning method is adopted, a voltage is applied to the spinning solution, and a voltage opposite to this voltage is applied to a counter electrode such as a metal plate provided separated from the discharge portion of the spinning solution, so that the spinning solution flies toward the counter electrode and is thinned. Then, the thinned spinning solution is collected on the main surface of the base material layer provided between the discharge portion and the counter electrode, thereby forming a fiber web on the base material layer.

[0043] When the electrospinning method is adopted, the spinning conditions are appropriately adjusted so that the fibers spun in a state where the solvent remains can be collected on the main surface of the base material layer. Specifically, by using a spinning solution with a large proportion of the solvent in the spinning solution, shortening the spinning distance, increasing the spinning amount, keeping the concentration of the volatilized solvent in the spinning space in a high state, and adjusting the temperature and humidity of the spinning space so that the solvent is difficult to volatilize, etc., it is possible to easily collect the spun fibers on the main surface of the base material layer in a state where the solvent is contained.

[0044] Then, step (5) will be described. The method for removing residual solvent from the laminated web can be selected as appropriate, but one example is to subject it to a heating device. The type of heating device can be selected as appropriate, for example, a device that heats or pressurizes with a roll, an oven dryer, a far-infrared heater, a dry heat dryer, a hot air dryer, or a device that can heat by irradiating with infrared rays can be used. The heating temperature of the heating device should be selected as appropriate, but it should be adjusted so that the residual solvent can be volatilized and removed, while the constituent components such as the constituent fibers do not unintentionally decompose or denature.

[0045] Furthermore, if adhesive components or crosslinkable resins are present in the constituent fibers of the base layer or nonwoven fabric layer, the fibers may be bonded by the adhesive components or the crosslinkable resins may be crosslinked by subjecting the heating device to the heat.

[0046] The laminate manufactured as described above may be subjected to processes such as calendering to adjust its thickness, sulfonation, plasma treatment, or fluorine gas treatment to make it hydrophilic, or punched out or molded into shape, depending on its intended use and application.

[0047] Furthermore, while the laminate can be used on its own, if necessary, it may be laminated with separately prepared fabrics (fiber webs, nonwoven fabrics, woven or knitted fabrics), films (porous or non-porous films), or foams. The lamination method can be selected as appropriate, and methods such as simply overlapping, partially melting and bonding the components, laminating and integrating with a binder, integrating by ultrasonic welding, or sewing can be employed. [Examples]

[0048] Examples of the present invention are described below, but the present invention is not limited to these examples.

[0049] (Preparation of base material) The following substrates were prepared. • A PE wet-type nonwoven fabric (basis weight: 10g / m²) made by wet-processing polyethylene short fibers (fineness: 0.8 dtex, fiber length: 5 mm, hereafter polyethylene will be abbreviated as PE) 2 (Thickness: 35 μm) • A PET wet-type nonwoven fabric (basis weight: 9g / m²) made by wet-processing PET short fibers (fineness: 0.8 dtex, fiber length: 5 mm). 2 (Thickness: 30 μm) • PET spunbond nonwoven fabric (basis weight: 15g / m²) composed of continuous PET fibers (average fiber diameter: 20μm). 2 (Thickness: 80μm)

[0050] (Preparing the spinning solution) Polyvinylidene fluoride homopolymer was dissolved in DMF (boiling point: 153°C) to prepare a spinning solution with a solid content of 16% by mass. Note that DMF is a solvent that can dissolve both polyvinylidene fluoride homopolymer and PET, but it is not a solvent that can dissolve polyethylene.

[0051] (Comparative Example 1) Electrospinning was performed by applying the spinning solution under the following spinning conditions. The spun fibers, while still containing the solvent, were collected on one main surface of a PE wet nonwoven fabric, and a laminated web was prepared in which a fiber web made of continuous fibers was laminated on a substrate. • Shape of the spinning fluid discharge portion in the metal nozzle (spinning fluid discharge portion): circular • Distance between the tip of the metal nozzle and the collecting body (metal plate on which a substrate capable of forming a substrate layer is placed): 10 cm Voltage applied to the spinning solution: 15kV • Spinning solution dispensed from a metal nozzle: 1g / hour • Electrospinning environment conditions: Temperature 25°C, Humidity 30%RH Then, the prepared laminated web is brought into contact with a heated roll whose surface temperature has been adjusted to 130°C to remove any remaining solvent from the laminated web, resulting in a laminate (nonwoven fabric layer basis weight: 1.00 g / m²). 2 A nonwoven fabric layer with a thickness of 3 μm and an average fiber diameter of 200 nm was prepared. In the laminate prepared in Comparative Example 1, the surface of the PE wet nonwoven fabric, which is the base layer, and the surface of the polyvinylidene fluoride homopolymer fibers, which are the constituent fibers of the nonwoven fabric layer, were not welded together.

[0052] (Example 1) The laminate was manufactured in the same manner as in Comparative Example 1, except that PET wet-spun nonwoven fabric was used instead of PE wet-spun nonwoven fabric. Specifically, electrospinning was performed by applying the spinning solution under the same spinning conditions as in Comparative Example 1, and the spun fibers, while still containing the solvent, were collected on one main surface of the PET wet-spun nonwoven fabric. A laminated web was then prepared by laminating a fiber web made of continuous fibers onto the substrate. Then, the prepared laminated web is brought into contact with a heated roll whose surface temperature has been adjusted to 130°C to remove any remaining solvent from the laminated web, resulting in a laminate (nonwoven fabric layer basis weight: 1.00 g / m²). 2 A nonwoven fabric layer with a thickness of 3 μm and an average fiber diameter of 200 nm was prepared. In the laminate prepared in Example 1, the surface of the PET wet nonwoven fabric, which is the base layer, and the surface of the polyvinylidene fluoride homopolymer fibers, which are the constituent fibers of the nonwoven fabric layer, were welded together.

[0053] (Example 2) The laminate was manufactured in the same manner as in Comparative Example 1, except that PET spunbond nonwoven fabric was used instead of PE wet nonwoven fabric. Specifically, electrospinning was performed by applying the spinning solution to the same spinning conditions as in Comparative Example 1, and the spun fibers, while still containing the solvent, were collected on one main surface of the PET spunbond nonwoven fabric. A laminated web was then prepared by laminating a fiber web made of continuous fibers onto the substrate. Then, the prepared laminated web is brought into contact with a heated roll whose surface temperature has been adjusted to 130°C to remove any remaining solvent from the laminated web, resulting in a laminate (nonwoven fabric layer basis weight: 1.00 g / m²). 2 A nonwoven fabric layer with a thickness of 3 μm and an average fiber diameter of 200 nm was prepared. In the laminate prepared in Example 2, the surface of the PET spunbond nonwoven fabric, which is the base layer, and the surface of the polyvinylidene fluoride homopolymer fibers, which are the constituent fibers of the nonwoven fabric layer, were welded together.

[0054] We attempted to peel off the nonwoven fabric layer from the laminates prepared as described above using our bare hands. The nonwoven fabric layer could be easily peeled off from the laminate prepared in Comparative Example 1, whereas it could not be easily peeled off from the laminates prepared in Examples 1 and 2.

[0055] In particular, the laminate prepared in Example 2 was even more resistant to peeling of the nonwoven fabric layer than the laminate prepared in Example 1. This was thought to be because both layers were fiber layers composed solely of continuous fibers, resulting in a stronger lamination and integration of the base layer and the nonwoven fabric layer.

[0056] Furthermore, in the laminates prepared in Examples 1 and 2, the constituent fibers were less likely to detach from the nonwoven fabric layer. [Industrial applicability]

[0057] The present invention relates to a laminate comprising a base layer and a nonwoven fabric layer. This laminate can be used in a variety of industrial applications. Specifically, it can provide washable and reusable masks (e.g., two-dimensional sheet-shaped masks, three-dimensional corrugated or pleated masks, folded masks, cup-shaped masks), washable and reusable air filters for air purification and air conditioners (e.g., two-dimensional sheet-shaped filters, three-dimensional corrugated or pleated filters, depth filters), and supports for thin films such as gas separation membranes and liquid separation membranes.

Claims

[Claim 1] A laminate comprising a base layer and a nonwoven fabric layer, The nonwoven fabric layer consists only of continuous fibers. The base layer is a fiber layer derived from a fiber web or nonwoven fabric, in which the constituent fibers consist only of continuous fibers. The resin forming the constituent fibers of the base layer and the resin forming the constituent fibers of the nonwoven fabric layer are soluble in the same solvent. The resin constituting the constituent fibers of the base layer is polyethylene terephthalate only, and the resin constituting the constituent fibers of the nonwoven fabric layer is polyvinylidene fluoride resin only. The surface of the constituent fibers of the base material layer and the surface of the constituent fibers of the nonwoven fabric layer are welded together in a portion thereof. Laminated structure.