METAL CLAD LAMINATE MANUFACTURING METHOD

Abstract

To provide a nonwoven fabric allowing a molding excellent in surface smoothness and dielectric characteristics to be obtained.SOLUTION: A nonwoven fabric includes glass fibers, thermoplastic resin fibers having at least either melting point or glass transition point of 200°C or more, and a binder exhibiting binding property at 180°C or less. Relative dielectric constant of the glass fibers at 1 GHz is 7.0 or less. Dielectric loss tangent of the glass fibers at 1 GHz is 0.004 or less. Relative dielectric constant of the thermoplastic resin fibers at 1 MHz is 3.5 or less. Dielectric loss tangent of the thermoplastic resin fibers at 1 MHz is 0.002 or less. The binder is hydrophobic resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a nonwoven fabric, a molded article, and a metal clad laminate. [Background technology]

[0002] Glass fibers have high bending strength and bending modulus, and are therefore excellent in strength, and are therefore used as reinforcing fibers for printed wiring boards for electronic devices, fiber-reinforced plastics, etc. Meanwhile, in recent years, electronic devices and the like have become increasingly high-frequency. Therefore, glass fibers used in electronic devices are required to have low dielectric constants and dielectric loss tangents, and excellent dielectric properties (Patent Document 1). Patent Document 1 describes a glass fiber reinforced resin molded product containing specific glass fibers. In the examples of Patent Document 1, a glass fiber reinforced resin molded product is obtained by injection molding resin pellets containing specific glass fibers and polybutylene terephthalate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-81909 Summary of the Invention [Problem to be solved by the invention]

[0004] As in the examples described in Patent Document 1, when resin pellets containing glass fibers are injection molded into a sheet, the glass fibers may protrude from the surface of the molded product. Therefore, in the glass fiber reinforced resin molded product described in Patent Document 1, the surface smoothness of the molded product may be insufficient. If the surface smoothness is insufficient, the adhesion of the metal layer in a laminate provided on the surface of the molded product will be reduced. The present inventors therefore thought that if a nonwoven fabric containing glass fibers were heated and cooled while being pressed using a heat press technique, a molded article with excellent surface smoothness could be obtained.

[0005] However, when the present inventors prototyped a nonwoven fabric containing glass fibers and heat-pressed the nonwoven fabric to form a molded body, they found that the molded body had a high dielectric constant and dielectric dissipation factor, and in some cases it was not possible to achieve excellent dielectric properties. The present invention provides a nonwoven fabric from which a molded article having excellent surface smoothness and dielectric properties can be obtained; a molded article having excellent surface smoothness and dielectric properties; and a metal clad laminate having the heat-press molded article. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have found that hydrophilic resins such as polyvinyl alcohol, which have traditionally been used as binders to bind fibers together during the production of nonwoven fabrics, are the cause of the deterioration of dielectric properties when the fabric is molded. Therefore, the inventors discovered that by using a hydrophobic resin as a binder for the nonwoven fabric and by using specific thermoplastic resin fibers in addition to glass fibers in the nonwoven fabric, it is possible to achieve excellent dielectric properties when molded into a molded product, and to obtain a molded product with excellent surface smoothness, which led to the completion of the present invention.

[0007] The present invention has the following aspects. [1] A nonwoven fabric comprising glass fibers, thermoplastic resin fibers having at least one of a melting point and a glass transition point of 200°C or higher, and a binder exhibiting binding properties at 180°C or lower, wherein the glass fibers have a relative dielectric constant of 7.0 or lower at 1 GHz, a dielectric loss tangent of 0.004 or lower at 1 GHz, a relative dielectric constant of 3.5 or lower at 1 MHz, and a dielectric loss tangent of 0.002 or lower at 1 MHz, and the binder is a hydrophobic resin. [2] The nonwoven fabric according to [1], wherein the thermoplastic resin fiber is at least one fiber selected from the group consisting of crystalline polystyrene fiber, crystalline polyphenylene sulfide fiber, and polyphenylene ether fiber. [3] The nonwoven fabric according to [1] or [2], wherein the binder is at least one selected from the group consisting of polyester resin, acrylic resin, polyethylene resin, polypropylene resin, and polyamide resin. [4] The nonwoven fabric according to any one of [1] to [3], wherein the content of the binder is 0.1 to 15 parts by mass per 100 parts by mass of the total of the glass fibers and the thermoplastic resin fibers. [5] A molded product which is a heat-press molded product of any one of the nonwoven fabrics [1] to [4]. [6] The molded body of [5], having a relative dielectric constant of 3.5 or less at 10 GHz. [7] The molded article of [5] or [6], having a dielectric loss tangent of 0.007 or less at 10 GHz. [8] A molded product according to any one of [5] to [7], having a thickness of 0.5 mm or less. [9] A metal clad laminate comprising the molded article according to any one of [5] to [8] and a metal layer provided on the surface of the molded article. [Effects of the Invention]

[0008] According to the nonwoven fabric of the present invention, a molded article having excellent surface smoothness and dielectric properties can be obtained. The molded article of the present invention has excellent surface smoothness and dielectric properties. The metal clad laminate of the present invention has excellent adhesiveness of the metal layer. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following terms have the following meanings: The "relative permittivity at 1 GHz" is a value measured using a split post dielectric resonator under the conditions of a temperature of 23°C, humidity of 50%, and 1 GHz. The "relative permittivity at 1 MHz" is a value measured using an LCR meter (automatic balancing bridge method) under conditions of a temperature of 23°C, humidity of 50%, and 1 MHz. The "dielectric loss tangent at 1 GHz" is a value measured using a split post dielectric resonator under the conditions of a temperature of 23°C, humidity of 50%, and 1 GHz. The "dielectric loss tangent at 1 MHz" is a value measured using an LCR meter (automatic balancing bridge method) under conditions of a temperature of 23°C, humidity of 50%, and 1 MHz. "(Meth)acrylate" is meant to include both "acrylate" and "methacrylate", and "(meth)acrylic acid" is meant to include both "acrylic acid" and "methacrylic acid". The "water absorption rate" of the molded body is determined by the method described in the examples below. The symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] <Nonwoven fabric> The nonwoven fabric of the present invention contains glass fibers, thermoplastic resin fibers, and a binder. The nonwoven fabric of the present invention may further contain components other than the glass fibers, thermoplastic resin fibers, and binder, as long as the effects of the present invention are not impaired.

[0011] (glass fiber) The dielectric constant of the glass fiber at 1 GHz is 7.0 or less, preferably 6.9 or less, more preferably 6.0 or less, and even more preferably 5.0 or less. When the dielectric constant of the glass fiber at 1 GHz is the above-mentioned upper limit or less, the dielectric constant of the molded article is low, and the dielectric properties of the molded article are improved. The lower limit of the dielectric constant of the glass fiber at 1 GHz is preferably as small as possible, and is not particularly limited. It may be set depending on the availability of the glass fiber and the desired performance. The dielectric dissipation factor of the glass fiber at 1 GHz is 0.004 or less, preferably 0.003 or less, more preferably 0.0025 or less, and even more preferably 0.002 or less. When the dielectric dissipation factor of the glass fiber at 1 GHz is the above-mentioned upper limit or less, the dielectric dissipation factor of the molded article is low, and the dielectric properties of the molded article are improved. The lower limit of the dielectric dissipation factor of the glass fiber at 1 GHz is preferably as small as possible, and is not particularly limited. It may be set depending on the availability of the glass fiber and the desired performance.

[0012] The composition of the glass fiber is not particularly limited as long as the relative permittivity and dielectric loss tangent of the glass fiber at 1 GHz are within the above-mentioned ranges. The glass fiber preferably contains boric acid (BO), and preferably has a relatively low content of alkaline earth metals such as MgO and CaO and a relatively high content of BO. As an example of such a glass fiber composition, the glass fiber composition disclosed in JP 2019-81909 A may be used. A preferred example of the composition of the glass fiber is composition A shown below. Composition A: With respect to 100% by mass of glass fiber, the SiO2 content is within the range of 52.0 to 59.5% by mass, the B2O3 content is within the range of 17.5 to 25.5% by mass, the Al2O3 content is within the range of 9.0 to 14.0% by mass, the SrO content is within the range of 0.5 to 6.0% by mass, the MgO content is within the range of 1.0 to 5.0% by mass, the CaO content is within the range of 1.0 to 5.0% by mass, and the total content of F2 and Cl2 is within the range of 0.1 to 2.5% by mass.

[0013] The fiber length of the glass fiber is not particularly limited and is generally within the range of 1 to 50 mm, preferably 3 to 30 mm, and more preferably 5 to 25 mm. When the fiber length of the glass fibers is equal to or greater than the lower limit, the glass fibers are less likely to come off the mesh of the papermaking wire during the production of the nonwoven fabric, and are less likely to be unevenly distributed on the side where the glass fibers have come off the papermaking wire, resulting in a less decrease in yield. In addition, the number of contact points between the glass fibers increases, resulting in higher tensile strength, tear strength, and elongation of the nonwoven fabric. When the fiber length of the glass fibers is equal to or less than the upper limit, the glass fibers are less likely to clog pipes and pumps during the production of the nonwoven fabric, and are less likely to become entangled in the mixer, making the nonwoven fabric easier to produce. In addition, the amount of undispersed glass fibers and agglomerates is reduced, improving the uniformity and texture of the nonwoven fabric.

[0014] The diameter of the glass fiber is not particularly limited and is generally within the range of 3 to 18 μm, preferably 4 to 15 μm, and more preferably 6 to 13 μm. When the diameter of the glass fiber is equal to or greater than the lower limit, the strength of the nonwoven fabric or molded article tends to be high and the glass fiber is easy to obtain and handle.When the diameter of the glass fiber is equal to or less than the upper limit, the dispersibility of the glass fiber during the production of the nonwoven fabric tends to be good and the glass fiber is easy to obtain and handle.

[0015] The aspect ratio (fiber length / diameter) of the glass fiber is not particularly limited and is generally within the range of 100 to 20,000, preferably 160 to 18,000, and more preferably 200 to 15,000. When the aspect ratio of the glass fiber is equal to or greater than the lower limit, the strength of the nonwoven fabric or molded article tends to be high. When the aspect ratio of the glass fiber is equal to or less than the upper limit, the dispersibility of the glass fiber during production of the nonwoven fabric tends to be good.

[0016] (thermoplastic resin fiber) The thermoplastic resin fiber is a component that functions as a matrix resin that melts when heated in the hot press of the nonwoven fabric and then solidifies when cooled. At least one of the melting point and the glass transition point of the thermoplastic resin fiber is 200° C. or higher, preferably 230° C. or higher, and more preferably 250° C. or higher. Since at least one of the melting point and the glass transition point of the thermoplastic resin fiber is equal to or higher than the lower limit, at least one of the melting point and the glass transition point of the thermoplastic resin fiber is higher than the drying temperature in the nonwoven fabric production process. Therefore, during drying, the thermoplastic resin fiber does not melt and can maintain its fibrous form. The upper limit of at least one of the melting point and the glass transition point of the thermoplastic resin fiber is not particularly limited. However, since hot press molding can be performed at a lower temperature, the lower the upper limit of at least one of the melting point and the glass transition point of the thermoplastic resin fiber, the more preferable. The lower limit of at least one of the melting point and the glass transition point of the thermoplastic resin fiber is preferably 400°C or less, and more preferably 350°C or less.

[0017] The dielectric constant of the thermoplastic resin fiber at 1 MHz is 3.5 or less, preferably 3.4 or less, more preferably 3.2 or less, and even more preferably 3.0 or less. When the dielectric constant of the thermoplastic resin fiber at 1 MHz is the above upper limit or less, the dielectric constant of the molded article becomes low and the dielectric properties of the molded article become good. The lower limit of the dielectric constant of the thermoplastic resin fiber at 1 MHz is preferably as small as possible, and is not particularly limited. It may be set depending on the availability of the thermoplastic resin fiber and the required performance. The dielectric loss tangent of the thermoplastic resin fiber at 1 MHz is 0.002 or less, preferably 0.0019 or less, more preferably 0.0018 or less, and even more preferably 0.0017 or less. When the dielectric loss tangent of the thermoplastic resin fiber at 1 MHz is equal to or less than the upper limit, the dielectric loss tangent of the molded article is low, and the dielectric properties of the molded article are improved. The lower limit of the dielectric loss tangent of the thermoplastic resin fiber at 1 MHz is preferably as small as possible, and is not particularly limited. It may be set depending on the availability of the thermoplastic resin fiber and the desired performance.

[0018] The content of the thermoplastic resin fiber is preferably 50 to 1,000 parts by mass, more preferably 75 to 750 parts by mass, per 100 parts by mass of the glass fiber. When the content of the thermoplastic resin fiber is equal to or greater than the lower limit, the moldability of the nonwoven fabric during hot pressing tends to be sufficient. When the content of the thermoplastic resin fiber is equal to or less than the upper limit, the strength and elastic modulus of the molded product tend to be high. In addition, the linear thermal expansion coefficient tends to be low, and the heat resistance (heat distortion temperature) also tends to be improved.

[0019] The fiber length of the thermoplastic resin fiber is not particularly limited and is generally within the range of 1 to 50 mm, preferably 3 to 30 mm, and more preferably 5 to 25 mm. When the fiber length of the thermoplastic resin fiber is equal to or greater than the lower limit, the fiber is less likely to come off the mesh of the papermaking wire during the production of the nonwoven fabric, and is less likely to be unevenly distributed on the side where the fiber has come off the papermaking wire, resulting in less reduction in yield. In addition, the number of contact points between the thermoplastic resin fibers increases, resulting in higher tensile strength, tear strength, and elongation of the nonwoven fabric. When the fiber length of the thermoplastic resin fiber is equal to or less than the upper limit, the fiber is less likely to clog pipes and pumps during the production of the nonwoven fabric, and is less likely to become entangled in the mixer, making the production of the nonwoven fabric easier. In addition, the amount of undispersed and aggregated thermoplastic resin fibers is reduced, resulting in improved uniformity and texture of the nonwoven fabric.

[0020] The diameter of the thermoplastic resin fiber is not particularly limited and is generally within the range of 1 to 120 μm, preferably 3 to 100 μm, and more preferably 4 to 70 μm. When the diameter of the thermoplastic resin fiber is equal to or greater than the lower limit, the dispersibility in water tends to be improved. When the diameter of the thermoplastic resin fiber is equal to or less than the upper limit, the dispersibility of the thermoplastic resin fiber during production of a nonwoven fabric tends to be improved.

[0021] The aspect ratio (fiber length / diameter) of the thermoplastic resin fiber is not particularly limited and is generally within the range of 10 to 20,000, preferably 50 to 18,000, and more preferably 100 to 15,000. When the aspect ratio of the thermoplastic resin fiber is equal to or greater than the lower limit, the strength of the nonwoven fabric tends to be high. When the aspect ratio of the thermoplastic resin fiber is equal to or less than the upper limit, the dispersibility of the thermoplastic resin fiber during production of the nonwoven fabric tends to be good.

[0022] The constant length count of the thermoplastic resin fiber is not particularly limited. The constant length count of the thermoplastic resin fiber is generally within the range of 0.1 to 150 dtex, preferably 0.2 to 100 dtex, and more preferably 0.2 to 50 dtex. When the constant length count of the thermoplastic resin fiber is equal to or greater than the lower limit, the dispersibility in water tends to be improved. When the constant length count of the thermoplastic resin fiber is equal to or less than the upper limit, the dispersibility of the thermoplastic resin fiber during the production of a nonwoven fabric tends to be improved.

[0023] The thermoplastic resin in the thermoplastic resin fiber is not particularly limited as long as the relative dielectric constant and dielectric loss tangent at 1 MHz of the thermoplastic resin fiber are within the above-mentioned specified ranges and at least one of the melting point and the glass transition point is 200°C or higher. The thermoplastic resin fiber is preferably at least one selected from the group consisting of crystalline polystyrene fiber, crystalline polyphenylene sulfide fiber, and polyphenylene ether fiber. The crystalline polystyrene fiber is a fiber whose main component is crystalline polystyrene resin. The crystalline polyphenylene sulfide fiber is a fiber whose main component is crystalline polyphenylene sulfide. The polyphenylene ether fiber is a fiber whose main component is polyphenylene ether resin (glass transition point: 214°C, relative dielectric constant at 1 MHz: 2.45, dielectric loss tangent at 1 MHz: 0.0007).

[0024] The crystalline polystyrene resin in the crystalline polystyrene fibers may be a syndiotactic polystyrene resin (SPS) or an isostatic polystyrene resin (APS). As the crystalline polystyrene resin, SPS and APS may be used alone or in combination. It is preferable to use SPS alone, as this tends to further reduce the relative permittivity and further improve the dielectric properties when molded into a molded article. When SPS and APS are used in combination, it is preferable to use less than 10% by mass of APS relative to 100% by mass of the total of SPS and APS. Here, polyphenylene ether resin has high compatibility with polystyrene, so it can be mixed and used in combination with SPS and APS.

[0025] (binder) The binder is a component that binds the fibers in the nonwoven fabric together. The binder is a hydrophobic resin that exhibits binding properties at temperatures below 180°C. "Exhibiting binding properties at temperatures below 180°C" means that the resin that functions as the binder has a melting point, softening point, or glass transition point of 180°C or lower. When the binder has a melting point, the melting point is 180°C or lower, which is lower than the melting point and glass transition point of the thermoplastic resin fiber. When the binder does not have a melting point but has a softening point or glass transition point, the softening point or glass transition point of the binder is 180°C or lower. 180°C is the same as or lower than the drying temperature in the nonwoven fabric manufacturing process. Therefore, the binder exhibits binding properties when the nonwoven fabric is dried in the manufacturing process. The temperature at which the binder exhibits binding properties is preferably 70 to 180°C, more preferably 80 to 180°C, even more preferably 90 to 170°C, and particularly preferably 100 to 160°C. When the temperature at which the binder exhibits binding properties is equal to or higher than the lower limit, unintended binding of the binder during production is less likely to occur, and handling properties tend to be sufficient. When the temperature at which the binder exhibits binding properties is equal to or lower than the upper limit, binding properties are obtained at low temperatures, allowing the drying temperature to be set low, and facilitating production of nonwoven fabrics.

[0026] The binder content is preferably 0.1 to 15 parts by mass, more preferably 0.4 to 12 parts by mass, and even more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the total of the glass fibers and thermoplastic resin fibers. When the binder content is equal to or greater than the lower limit, the strength of the nonwoven fabric or molded article is sufficient, the nonwoven fabric is less likely to break during production, and handling tends to be satisfactory. When the binder content is equal to or less than the upper limit, the molded article tends to have a lower relative permittivity and dielectric loss tangent, further improving the dielectric properties and heat resistance. In addition, the binder is less likely to fuse to rolls, etc., when heated during production of the nonwoven fabric.

[0027] The binder is not particularly limited as long as it is a hydrophobic resin that exhibits binding properties at 180°C or less, but a hydrophobic thermoplastic resin that exhibits binding properties at 180°C or less is preferred. Examples of thermoplastic resins that function as binders include polyester resins, acrylic resins, polyolefin resins (polyethylene, polypropylene, etc.), styrene-acrylic resins, ethylene-vinyl acetate resins, and urethane resins. Among these, at least one selected from the group consisting of polyester resins, acrylic resins, polyethylene, polypropylene, and polyamide resins is preferred. Among these thermoplastic resins, those that exhibit binding properties at 180°C or less can be selected as binders.

[0028] The polyester resin is preferably polyethylene terephthalate (PET). The polyester resin may be a modified polyester resin obtained by modifying a polyester resin to lower its melting point. The modified polyester resin is preferably modified polyethylene terephthalate. The modified polyethylene terephthalate is preferably copolymerized polyethylene terephthalate (CoPET). A specific example of copolymerized polyethylene terephthalate is urethane-modified copolymerized polyethylene terephthalate. The melting point of the copolymerized polyethylene terephthalate is preferably not more than 140° C., more preferably not more than 120° C. As the copolymerized polyethylene terephthalate, the copolymerized polyester described in JP-B 1-30926 may be used since it can provide binding properties at low temperatures. An example of a commercially available modified polyester resin fiber is "Melty (registered trademark) 4000" (a binder fiber in which all the fibers are CoPET) manufactured by Unitika Ltd.

[0029] Examples of acrylic resins include copolymers obtained by polymerizing a monomer mixture containing at least one acrylic monomer selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate. The copolymers have at least one of a structural unit derived from methyl (meth)acrylate and a structural unit derived from ethyl (meth)acrylate. Preferred acrylic resins are copolymers having at least one of a structural unit derived from methyl methacrylate and a structural unit derived from ethyl methacrylate.

[0030] The binder may be used alone or in combination of two or more. However, since the relative permittivity and dielectric dissipation factor of the molded article are further reduced and the dielectric properties are further improved, it is preferable to use a combination of acrylic resin and polyester resin as the binder. In this case, the content of the acrylic resin is preferably 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, relative to 100% by mass of the nonwoven fabric. The total content of the acrylic resin and polyester resin is preferably 1 to 15% by mass, more preferably 2 to 12% by mass, relative to 100% by mass of the nonwoven fabric.

[0031] The form and shape of the binder are not particularly limited and may be fibrous or powdery. In the production of nonwoven fabrics, the binder may be used in the form of an emulsion such as an aqueous dispersion. When a slurry containing a binder mixed with glass fibers and thermoplastic resin fibers is made into a papermaking slurry during the production of nonwoven fabrics, the binder is less likely to slip through the mesh of the papermaking wire. Therefore, the binder is preferably in the form of a fiber or a powder with an average particle diameter of 10 μm or more. On the other hand, when a binder emulsion is applied to a fiber layer such as a wet sheet during the production of nonwoven fabrics, the binder is preferably in the form of an emulsion, emulsified product, or dispersion with an average particle diameter of 10 μm or less, as this facilitates spray application. Thus, the form and shape of the binder may be selected depending on the production method of the nonwoven fabric.

[0032] When the binder is fibrous, the fiber length of the binder is preferably 1 to 50 mm, more preferably 2 to 40 mm, and particularly preferably 3 to 30 mm. When the fiber length of the binder is equal to or greater than the lower limit, the binder is less likely to come off the mesh of the papermaking wire and is less likely to be unevenly distributed on the side where the papermaking wire has come off, and the yield is less likely to decrease. When the fiber length of the binder is equal to or less than the upper limit, the binder is less likely to clog pipes and pumps and to become tangled in a mixer, making it easier to produce nonwoven fabrics.

[0033] When the binder is fibrous, the diameter of the binder is in the range of 1 to 120 μm, preferably 3 to 100 μm, and more preferably 4 to 70 μm. When the diameter of the binder is equal to or greater than the lower limit, dispersibility in water tends to improve. When the diameter of the binder is equal to or less than the upper limit, dispersibility during production of a nonwoven fabric tends to improve.

[0034] When the binder is fibrous, the constant length count of the binder is preferably 0.1 to 100 dtex, more preferably 0.2 to 50 dtex. When the constant length count of the binder is equal to or greater than the lower limit, the dispersibility in water tends to be improved. When the constant length count of the binder is equal to or less than the upper limit, the dispersibility during production of a nonwoven fabric tends to be improved.

[0035] When the binder is fibrous, the binder may be a sheath-core fiber having a core and a sheath. As the fiber having a core-sheath structure, a polypropylene / polyethylene sheath-core fiber containing polypropylene in the core and polyethylene in the sheath is preferred because it has excellent binding properties at low temperatures. In the case of a fiber having a core-sheath structure, the ratio of the volume of the sheath to the volume of the core is preferably 80 / 20 to 20 / 80. An example of a commercially available polypropylene / polyethylene sheath-core fiber is "NBF" manufactured by Daiwabo Polytech Co., Ltd. Other binder fibers with a sheath-core structure that can be suitably used include "Melty 4080" manufactured by Unitika Ltd. and "N-720" manufactured by Kuraray Co., Ltd. Here, when the binder is a sheath-core fiber, the binder content is calculated as the total amount of resin in the core and resin in the sheath.

[0036] When the binder is in powder form, the average particle size of the binder is preferably 10 to 1000 μm, more preferably 20 to 500 μm. When the average particle size of the binder is equal to or greater than the lower limit, the binder is less likely to come off the mesh of the papermaking wire during the production of the nonwoven fabric, and is less likely to be unevenly distributed on the side where the papermaking wire has come off, resulting in less reduction in yield. When the average particle size of the binder is equal to or less than the upper limit, the binder tends to be more dispersible during the production of the nonwoven fabric. Here, the average particle size of the powdery binder can be measured by a laser diffraction particle size distribution measuring device.

[0037] The nonwoven fabric of the present invention preferably does not contain a hydrophilic thermoplastic resin such as polyvinyl alcohol resin as a binder. Conventionally, polyvinyl alcohol resin has been widely used in the production of nonwoven fabrics. However, when polyvinyl alcohol resin is used as a binder, the water absorption and equilibrium moisture content increase when the nonwoven fabric is molded into a body, regardless of the binder form (fibrous, powder, emulsion). As a result, the relative permittivity and dielectric loss tangent of the molded body increase, impairing the dielectric properties. Therefore, the nonwoven fabric of the present invention preferably does not contain a polyvinyl alcohol resin as a binder.

[0038] (Other ingredients) Other components of the nonwoven fabric include silica fine particles, a dispersant and a thickener, which will be described later, etc. However, the other components are not limited to these examples. When the nonwoven fabric of the present invention further contains silica fine particles within a range that does not impair the effects of the present invention, it is expected that the thermal expansion in the thickness direction of the nonwoven fabric can be reduced and dimensional stability can be improved. The average primary particle diameter of the silica fine particles may be within a range of 1 to 100 nm. The silica fine particles may form aggregated particles or may be bonded to the glass fiber via a binder. The thickness and density of the nonwoven fabric may be appropriately determined depending on the intended use and the desired performance.

[0039] (Nonwoven fabric manufacturing method) The nonwoven fabric of the present invention can be produced, for example, by the following methods (1), (2), and (3). Method (1): A method in which a slurry of glass fibers, thermoplastic resin fibers, and a binder dispersed in water is made into paper and the resulting fiber layer is dried. Method (2): A method in which a slurry of glass fibers and thermoplastic resin fibers dispersed in water is made into a papermaking slurry to obtain a fiber layer, and then an emulsion of a binder dispersed in a liquid medium is applied to the fiber layer, and the fiber layer is then dried. Method (3): A method in which a slurry of glass fibers, thermoplastic resin fibers, and a binder dispersed in water is made into a papermaking slurry to obtain a fiber layer, and then an emulsion of the binder dispersed in a liquid medium is applied to the fiber layer, and the fiber layer is then dried.

[0040] [Method (1)] In method (1), first, a slurry in which glass fibers, thermoplastic resin fibers, and a binder are dispersed in water is made into paper. The slurry used in papermaking can be said to be an aqueous dispersion of glass fibers, thermoplastic resin fibers, and a binder dispersed in water. In method (1), the binder is preferably in a fibrous form because it is less likely to slip through the mesh of the papermaking wire when the slurry is used in papermaking.

[0041] The slurry can be prepared by mixing glass fibers, thermoplastic resin fibers, a binder, and water and stirring. The order in which the glass fibers, thermoplastic resin fibers, binder, and water are mixed is not particularly limited. For example, the thermoplastic resin fibers and binder may be added after mixing the water and glass fibers; the glass fibers may be added after mixing the water, thermoplastic resin fibers, and binder; or the water, glass fibers, thermoplastic resin fibers, and binder may be mixed simultaneously. The method for preparing the slurry is not limited to these examples. The amounts of the glass fibers, thermoplastic resin fibers, and binder may be appropriately set depending on the desired composition of the nonwoven fabric. For example, the composition of the nonwoven fabric can be adjusted by adjusting the amounts of these fibers according to the above-mentioned preferred numerical ranges and adjusting the composition of the slurry. The slurry may further contain a dispersant to suppress aggregation of fibers, etc. The slurry may further contain a thickener to adjust the viscosity.

[0042] The viscosity of the slurry at 23°C is preferably 0.9 to 3.0 mPa·s, more preferably 1 to 2.5 mPa·s. When the viscosity of the slurry is within this range, even if the Reynolds number is the same, the dispersibility of the glass fibers is excellent and a nonwoven fabric with less breakage or breakage of the glass fibers tends to be produced with high productivity. Specifically, when the viscosity of the slurry is equal to or greater than the lower limit, the glass fibers and thermoplastic resin fibers are less likely to aggregate, and the dispersibility of the glass fibers and thermoplastic resin fibers tends to be improved. When the viscosity of the slurry is equal to or less than the upper limit, the dewatering resistance is reduced and productivity can be improved. Therefore, it is preferable to set the viscosity in consideration of productivity and suppression of aggregation of the glass fibers and thermoplastic resin fibers. Here, the viscosity of the slurry at 23°C is the viscosity at 23°C measured by filtering the slurry through an 80-mesh filter to remove glass fibers and thermoplastic resin fibers, and then collecting the filtrate using a Cannon-Fenske viscometer in accordance with the measurement method specified in JIS Z 8803 "Method for measuring viscosity of liquids."

[0043] The slurry can be made into paper using a paper machine that is commonly used in the production of wetlaid nonwoven fabrics. As the paper machine, either a batch type paper machine or a continuous type paper machine can be used. As the filter medium for the paper machine, for example, one with an opening size of 30 to 150 mesh can be used.

[0044] A batch-type papermaking machine is a papermaking machine that repeats each of the steps of supplying a slurry to a raw material container, forming a fiber layer by papermaking (dewatering), and recovering the fiber layer as one cycle. When using a batch-type papermaking machine, the solids concentration of the slurry in the raw material container (total amount of glass fiber, thermoplastic resin fiber, and binder) is preferably in the range of 0.001 to 1.00 mass%, more preferably in the range of 0.002 to 0.7 mass%. When the solids concentration of the slurry is within this range, the degree of freedom of fiber movement in the slurry is increased, and sufficient dewatering speed can be obtained during dewatering. As mentioned above, the viscosity of the slurry in the raw material container at 23°C is preferably in the range of 0.9 to 3.0 mPa·s.

[0045] A continuous paper machine is a paper machine that continuously performs the steps of supplying a slurry to an inlet, forming a fiber layer by papermaking (dewatering), and recovering the fiber layer. Examples of continuous paper machines include an inclined paper machine, a cylinder paper machine, and a Fourdrinier paper machine. Among these paper machines, it is preferable to use an inclined paper machine, which can dilute the solids concentration of the polymer dispersion in the inlet and rapidly dewater it. This is because rapid dewatering makes it easier for the water flow to orient short thermoplastic resin fibers in the thickness direction. When using an inclined papermaking machine, the solids concentration of the slurry in the inlet is preferably in the range of 0.001 to 0.5% by mass, more preferably in the range of 0.002 to 0.3% by mass, and even more preferably in the range of 0.008 to 0.1% by mass. When the solids concentration of the slurry in the inlet is within the above numerical range, a sufficient dehydration rate can be obtained, allowing the thermoplastic resin fibers to be sufficiently oriented in the thickness direction. Furthermore, since the dehydration load is not too high, nonwoven fabrics can be produced with energy efficiency. As mentioned above, the viscosity of the slurry in the inlet at 23°C is preferably in the range of 0.9 to 3.0 mPa·s.

[0046] The slurry is then made into a paper-like fiber layer, which is then dried to obtain a nonwoven fabric. A heating dryer such as a hot air dryer can be used to dry the fiber layer. The drying temperature may be appropriately set depending on the melting point, softening point, and glass transition point of the binder. For example, the drying temperature may be 70 to 180°C, 80 to 180°C, 90 to 170°C, or 100 to 160°C. When drying the fiber layer, the wet sheet immediately after papermaking may be dried as the fiber layer.

[0047] [Method (2)] In method (2), a slurry in which glass fibers and thermoplastic resin fibers are dispersed is first made into paper. When preparing the slurry in method (2), the glass fibers, thermoplastic resin fibers, and water are mixed and stirred without using a binder. The order in which the glass fibers, thermoplastic resin fibers, and water are mixed is not particularly limited, as described in method (1). In method (2), the slurry may further contain a thickener and a dispersant, as in method (1). The details and preferred range of the viscosity of the slurry are the same as those in method (1). However, method (2) differs from method (1) in that the viscosity of the slurry is measured in the absence of a binder. In addition, the details and preferred aspects of papermaking from the slurry can be the same as those described for method (1).

[0048] Next, in method (2), an emulsion in which a binder is dispersed in a liquid medium is applied to the fiber layer obtained by papermaking from the slurry, and then the fiber layer is dried. The emulsion is not particularly limited as long as the binder is dispersed in a liquid medium. The liquid medium may be an aqueous medium or an oil-based medium and can be selected depending on the binder, but water is preferred. In addition, in method (2), the binder is used in the form of an emulsion, so the emulsion can be easily applied by spray coating. The solid content of the emulsion is preferably 1 to 30% by mass, more preferably 2 to 20% by mass. When the solid content is equal to or higher than the lower limit, it becomes easier to adjust the binder content when the nonwoven fabric is made, and it tends to be possible to apply a sufficient amount of binder. When the solid content is equal to or higher than the lower limit, it becomes easier to suppress the occurrence of coating unevenness during application.

[0049] The emulsion can be applied by spray coating, curtain coating, or other methods. The amount of emulsion to be applied may be adjusted so that the binder content of the resulting nonwoven fabric falls within the preferred range described above. The fiber layer to which the emulsion is applied may be a wet sheet or a dry sheet. A dry sheet is a wet sheet pre-dried at 40 to 160°C. In method (2), the nonwoven fabric is obtained by drying the fiber layer after applying the emulsion. The details and preferred aspects of the drying can be the same as those described for method (1).

[0050] [Method (3)] In method (3), a slurry in which glass fibers, thermoplastic resin fibers, and a binder are dispersed in water is first made into paper. The details and preferred aspects of the slurry in method (3) can be the same as those described for method (1). The details and preferred aspects of making the slurry into paper can also be the same as those described for method (1).

[0051] Next, an emulsion in which a binder is dispersed in a liquid medium is applied to the fiber layer obtained by papermaking the slurry, and the fiber layer is then dried. Details and preferred aspects of the emulsion can be the same as those described for Method (2). Details and preferred aspects of applying the emulsion can also be the same as those described for Method (2). The emulsion-coated fiber layer is dried to obtain a nonwoven fabric. The details and preferred modes of drying can be the same as those described for Method (1).

[0052] (Action and effect) In the nonwoven fabric of the present invention described above, the binder is a hydrophobic resin. Therefore, the molded article obtained by hot-press molding of the nonwoven fabric is less likely to absorb moisture. As a result, increases in the relative dielectric constant and dielectric loss tangent due to absorbed moisture are suppressed, and the molded article has low relative dielectric constant and dielectric loss tangent, resulting in improved dielectric properties. Furthermore, when the nonwoven fabric of the present invention is molded by hot-press molding, a molded article with excellent surface smoothness can be obtained.

[0053] <Molded body> The molded article of the present invention is a hot-press molded product of the nonwoven fabric of the present invention. The molded article of the present invention can be obtained by molding the nonwoven fabric of the present invention by hot pressing. Therefore, the molded article of the present invention is in the form of a sheet. The heating temperature during the heat pressing is not particularly limited as long as it is equal to or higher than the melting point and glass transition point of the thermoplastic resin fiber contained in the nonwoven fabric. The optimum temperature range for the heating temperature varies depending on conditions such as the type and content of the thermoplastic resin fiber, so it cannot be determined uniformly, but it is within the range of 210 to 400°C, preferably 230 to 350°C, and more preferably 250 to 300°C.

[0054] The pressure during the heat pressing can be appropriately set depending on conditions such as the thickness of the nonwoven fabric, the thickness of the desired molded product, etc. The pressure is in the range of 1 to 50 MPa, preferably 2 to 20 MPa. The heating time is not particularly limited. The heating time is within a range of 1 to 100 minutes, and preferably within a range of 1 to 30 minutes. In order to obtain a molded product with even better smoothness, it is preferable to cool the heated nonwoven fabric while maintaining the pressurized state after heating until the temperature reaches 200°C or less, preferably 160°C or less, and more preferably 120°C or less.

[0055] The dielectric constant of the molded article at 10 GHz is preferably 3.5 or less, more preferably 3.3 or less, and even more preferably 3.1 or less. The dielectric loss tangent of the molded article at 10 GHz is preferably 0.007 or less, more preferably 0.005 or less, and even more preferably 0.004 or less. When the dielectric constant and dielectric loss tangent of the molded article at 10 GHz are not more than the upper limit values, the dielectric properties of the molded article are even more excellent. The lower limit values ​​of the dielectric constant and dielectric loss tangent of the molded article are not particularly limited, and the lower the value, the better.

[0056] The thickness of the molded article is preferably 0.5 mm or less, more preferably 0.3 mm or less, and even more preferably 0.2 mm or less. When the thickness of the molded article is equal to or less than the upper limit, it is easily applicable to parts that require thinning and miniaturization. There is no particular limit to the lower limit of the thickness of the molded article. It can be set depending on the application of the molded article and the required performance.

[0057] The density of the molded body can be determined depending on the density and content of the glass fiber, thermoplastic resin fiber, and binder, as well as the molding conditions. The density of the molded body is 1.0 to 1.7 g / cm3 is preferred, and 1.1 to 1.6 g / cm 3 More preferably, 1.2 to 1.5 g / cm 3 When the density of the molded article is equal to or greater than the lower limit, the strength of the molded article is further improved. When the density of the molded article is equal to or less than the upper limit, the molded article is easily applicable to parts that require weight reduction. However, even if the density of the molded body is within the above-mentioned range, if there are voids in the molded body, the moisture absorption will be high and the dielectric properties (particularly the dielectric loss tangent) may be high. Therefore, in order to reduce the moisture absorption and obtain excellent dielectric properties, it is preferable to increase the blending amount of thermoplastic resin fibers as much as possible and produce a molded body with a relatively low glass fiber density so that voids are not formed (i.e., a molded body with a density equal to or less than the above-mentioned upper limit). Furthermore, in order to increase the strength, modulus of elasticity, and heat resistance (heat distortion temperature) of the molded body and to decrease the linear expansion coefficient, it is preferable to increase the glass fiber content and produce a molded body with a relatively high glass fiber density (i.e., a molded body with a density equal to or higher than the above-mentioned lower limit) so that voids are not formed.

[0058] The water absorption rate of the molded body is preferably 0.5% or less, more preferably 0.4% or less, and even more preferably 0.3% or less. When the water absorption rate of the molded body is the above upper limit or less, the relative dielectric constant and dielectric loss tangent of the molded body become low, and the dielectric properties become further improved. The lower the lower limit of the water absorption rate of the molded body, the better, and it may be set depending on the application and required performance of the molded body.

[0059] The molded article of the present invention is a hot-press molded product of the nonwoven fabric of the present invention, and therefore has excellent surface smoothness and dielectric properties, and is excellent in adhesion when a metal layer is provided on the surface of the molded article. The molded article of the present invention can be suitably applied to electronic devices that use electromagnetic waves in the high frequency range of 3 to 100 GHz, for example.

[0060] <Metal-clad laminate> The metal clad laminate has the molded article of the present invention and a metal layer provided on the surface of the molded article of the present invention. The metal clad laminate may have a metal layer on one side of the molded article of the present invention, or may have a metal layer on both sides of the sheet of the molded article of the present invention. Examples of materials for the metal layer include copper, aluminum, silver, and gold. Among these, copper is preferred in terms of conductivity, corrosion resistance, and processability. Rolled copper foil is preferably used for thick molded articles having a thickness of 100 to 300 μm. Electrodeposited copper foil is preferably used for thin molded articles having a thickness of several μm to 100 μm. When used in a high-frequency range, electrolytic copper foil with low roughness is preferably used.

[0061] The metal clad laminate can be produced by, for example, bonding the metal layer and the laminate with an adhesive, or by providing a metal layer on the surface of a molded body by a method such as vapor deposition. The metal clad laminate can be used as a material for, for example, a wiring board, and for example, a wiring board can be obtained by patterning the metal layer of the metal clad laminate by a technique such as etching.

[0062] The metal clad laminate of the present invention has excellent dielectric properties because it has a molded article that is a hot-press molded product of the nonwoven fabric of the present invention. In addition, the metal clad laminate of the present invention has a molded article with excellent surface smoothness, so it has excellent adhesion between the molded article and the metal layer. [Example]

[0063] [Example 1] (1) Preparation of slurry 40 g of glass fiber (manufactured by Taiwan Glass Co., Ltd., E-glass, fiber length: 10 mm, diameter: 9 μm) with a relative permittivity of 6.8 at 1 GHz and a dielectric dissipation factor of 0.0035 at 1 GHz was weighed out and added to 20 L of water containing 0.15 g of dispersant (0.3% by mass based on the glass fiber). The mixture was stirred and dispersed using a laboratory stirrer to obtain an aqueous glass fiber dispersion. The dispersant used was LACCOL AL manufactured by Meisei Chemical Industry Co., Ltd. The laboratory stirrer used was an Ultra Stirrer DC-CHRM25 manufactured by AS ONE Corporation.

[0064] To the aqueous glass fiber dispersion containing the E-glass dispersed therein, 60 g of polyphenyl sulfide (PPS) drawn fibers (manufactured by Toyobo Co., Ltd., melting point: 278°C, fiber length: 5 mm, diameter: 15 μm, constant-length count: 2.2 dtex) having a dielectric constant of 3.4 at 1 MHz and a dielectric dissipation factor of 0.001 at 1 MHz, and 5 g of core-sheath polyethylene terephthalate (PET) fibers (manufactured by Kuraray Co., Ltd., core melting point: 270°C, sheath bonding temperature: 110°C, fiber length: 5 mm, diameter: 14 μm, constant-length count: 2.2 dtex) were added as a binder, and the mixture was stirred using the laboratory stirrer. The ratio of the volume of the sheath to the volume of the core of the sheath-core PET fiber was 5:5.

[0065] Next, 500 mL of a thickener solution with a thickener concentration of 0.1% by mass was added to the glass fiber aqueous dispersion after the addition of the PPS oriented fiber and the core-sheath PET fiber, and the mixture was stirred with the laboratory stirrer. An anionic polymer polyacrylamide thickener (Sumifloc (registered trademark), manufactured by MT Aquapolymer Co., Ltd.) was used as the thickener. Water was then added to bring the total weight to 28 kg, and the mixture was stirred with the laboratory stirrer. In this way, a slurry with a solids concentration of 0.5% by mass was prepared, in which the glass fiber, PPS fiber, and core-sheath PET fiber were uniformly dispersed.

[0066] (2) Preparation of nonwoven fabric 1250 g (solid content: 6.25 g) of the slurry prepared in (1) above was taken out. The taken out slurry was placed in a stock container of a 25 cm square handsheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd.), and papermaking was carried out in accordance with a method conforming to JIS P8222. That is, water was added to the stock container to dilute it to 16 L, and the contents of the stock container were stirred and then dehydrated to obtain a wet sheet. Then, an aqueous emulsion in which an acrylic resin was dispersed in water (solid content concentration of acrylic resin: 5% by mass) was spray-coated onto the obtained wet sheet, and the coating amount was 2 g / m2 in terms of solid content. 2 After the wet sheet was suction-dehydrated to a temperature of 160°C, it was dried in a hot air dryer and then reconstituted into a nonwoven fabric (25cm length x 25cm width, basis weight: 102g / m 2Here, Acryset EMN-188E (methacrylic resin, glass transition temperature: 60° C.) manufactured by Nippon Shokubai Co., Ltd. was used as the aqueous emulsion of acrylic resin.

[0067] [Example 2] A nonwoven fabric was produced in the same manner as in Example 1, except that syndiotactic polystyrene fiber (SPS fiber, manufactured by Idemitsu Kosan Co., Ltd., melting point: 270°C, fiber length: 15 mm, diameter: 110 μm, constant length count: 100 dtex) having a relative dielectric constant of 2.6 at 1 MHz and a dielectric dissipation factor of 0.001 at 1 MHz was used as the thermoplastic resin fiber.

[0068] [Example 3] A nonwoven fabric was produced in the same manner as in Example 1, except that the glass fiber used was a glass fiber (manufactured by Taiwan Glass Co., Ltd., LDK-CS, fiber length: 3 mm, fiber diameter: 9 μm) having a relative dielectric constant of 4.9 at 1 GHz and a dielectric dissipation factor of 0.0015 at 1 GHz.

[0069] [Example 4] A nonwoven fabric was produced in the same manner as in Example 2, except that the glass fiber used was a glass fiber (manufactured by Taiwan Glass Co., Ltd., LDK-CS, fiber length: 3 mm, fiber diameter: 9 μm) having a relative dielectric constant of 4.9 at 1 GHz and a dielectric dissipation factor of 0.0015 at 1 GHz.

[0070] [Comparative Example 1] A nonwoven fabric was produced in the same manner as in Example 1, except that granular polyvinyl alcohol (PVA, average particle size: 150 μm, manufactured by Denka Co., Ltd., K-177) was used as the binder instead of the core-sheath PET fiber when preparing the slurry, and no aqueous emulsion of acrylic resin was used. Here, the average particle size of the granular PVA is a value measured using a laser diffraction particle size distribution analyzer.

[0071] Comparative Example 2 A nonwoven fabric was produced in the same manner as in Example 1, except that, instead of 60 g of PPS drawn fibers, core-sheath polyethylene terephthalate (PET) fibers (manufactured by Kuraray Co., Ltd., melting point: 270°C, fiber length: 5 mm, diameter: 9 μm, constant length count: 0.84 dtex) having a relative dielectric constant of 3.2 at 1 MHz and a dielectric dissipation factor of 0.005 at 1 MHz were used as the thermoplastic resin fibers.

[0072] Table 1 shows the glass fibers, thermoplastic resin fibers, binders, and their contents used in preparing the slurries and fabricating the nonwoven fabrics in Examples 1 to 4 and Comparative Examples 1 and 2. The relative permittivity and dielectric loss tangent at 1 GHz of the glass fibers used in the above-mentioned Examples were measured using a split post dielectric resonator (manufactured by Agilent Technologies) in an environment of 23°C and 50% humidity. The relative permittivity and dielectric loss tangent at 1 MHz of the thermoplastic resin fibers used in the Examples were measured using an LCR meter (auto-balancing bridge method) at DJK. For the measurements, the glass fibers and thermoplastic resin fibers were heated to or above their melting points, melted, and molded into plates.

[0073] [Table 1]

[0074] A laminate of three sheets of the nonwoven fabric obtained in Examples 1 to 4 and Comparative Examples 1 and 2 was heat-press molded by heating and pressing for 3 minutes at 280°C and 5 MPa using a hot and pressure press, and then cooled to 70°C while maintaining the pressurized state, and then removed from the hot and pressure press. The obtained molded articles of each example were measured for relative permittivity and dielectric loss tangent at a temperature of 23° C., a humidity of 50%, and a frequency of 10 GHz using the split post dielectric resonator. For each molded article, the mass W1 was measured after drying for 24 hours in a hot air dryer at 50°C, and then the molded article was immersed in water at 23°C for 24 hours. After wiping off the surface water, the mass W2 of the molded article was measured. The increase in mass before and after immersion (W2 - W1) was used as the amount of water absorbed, and the water absorption rate was calculated using the following formula. (Water absorption rate [%])=[(W2-W1) / W2]×100

[0075] Table 2 shows the thickness, density, relative dielectric constant, dielectric loss tangent, and water absorption of the molded bodies obtained in Examples 1 to 4 and Comparative Examples 1 and 2.

[0076] [Table 2]

[0077] In Examples 1 to 4, in which glass fibers and thermoplastic resin fibers within the ranges specified in the present invention were used and a hydrophobic resin was used as a binder, the molded articles had low relative permittivity and dielectric loss tangent, and the dielectric properties were good. In addition, the water absorption rate was low, which is thought to have suppressed the deterioration of the dielectric properties of the molded articles due to moisture. The molded body of Comparative Example 1 uses PVA, a hydrophilic resin, as a binder, which is thought to have resulted in a high water absorption rate, a high dielectric constant and a high dielectric loss tangent, and poor dielectric properties. The molded article of Comparative Example 2 uses core-sheath PET fibers, the dielectric loss tangent of which is outside the range specified in the present invention, as the thermoplastic resin fiber, and therefore, compared with Examples 1 to 4, the molded article has a higher dielectric loss tangent and deteriorated dielectric properties.

Claims

1. A method for producing a metal clad laminate, comprising the steps of: heat-pressing a nonwoven fabric, cooling the fabric to obtain a molded body, and providing a metal layer on the surface of the molded body; the nonwoven fabric contains glass fibers, thermoplastic resin fibers that serve as a matrix resin for the molded body, and a binder that exhibits binding properties at 180°C or less; The glass fiber has a relative dielectric constant of 7.0 or less at 1 GHz, The dielectric loss tangent of the glass fiber at 1 GHz is 0.004 or less, The thermoplastic resin fiber has at least one of a melting point and a glass transition point of 200°C or higher, The thermoplastic resin fiber has a relative dielectric constant of 3.5 or less at 1 MHz, The thermoplastic resin fiber has a dielectric loss tangent of 0.002 or less at 1 MHz, The method for producing a metal clad laminate, wherein the binder is a core-sheath fiber made of a combination of polyethylene terephthalate and an acrylic resin.

2. The method for producing a metal clad laminate according to claim 1, wherein the nonwoven fabric is heat-pressed at 2 to 20 MPa and then cooled to obtain the formed body.

3. The method for producing a metal clad laminate according to claim 1 or 2, wherein the nonwoven fabric is heat-pressed for 1 to 30 minutes and then cooled to obtain the formed body.

4. The density of the molded body is 1.0 to 1.7 g / cm ３ The method for producing a metal clad laminate according to any one of claims 1 to 3, wherein the metal clad laminate is hot-pressed so that the temperature is 100°C.

5. The method for producing a metal clad laminate according to any one of claims 1 to 4, wherein the content of the binder in the nonwoven fabric is 0.1 to 15 parts by mass per 100 parts by mass of the total of the glass fiber and the thermoplastic resin fiber.

6. The method for manufacturing a metal clad laminate according to any one of claims 1 to 5, wherein the content of the thermoplastic resin fiber in the nonwoven fabric is 75 to 750 parts by mass per 100 parts by mass of the glass fiber.

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