JP2016079553A - Nonwoven fabric, production method therefor, and fiber-reinforced plastic formed article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a nonwoven fabric that can, when used as a forming material for a fiber-reinforced plastic (FRP) molded article, produce an FRP molded article having a high flexural modulus; a production method for said nonwoven fabric; and an FRP molded article produced by heat pressure forming said nonwoven fabric.SOLUTION: Provided is a nonwoven fabric comprising a flat-shape glass fiber having a cross section perpendicular to the longitudinal direction of flat shape and having a ratio of the major axis to minor axis of said cross section (major axis/minor axis) of 1.5 to 8, and a thermoplastic resin fiber; said nonwoven fabric preferably is a wet type nonwoven fabric, and can be produced by a process comprising a papermaking step for papermaking a fluid dispersion containing said flat shape glass fibers and said thermoplastic resin fibers; and the FRP formed article produced by heat pressure forming the obtained nonwoven fabric, has an excellent flexural modulus.SELECTED DRAWING: None

Description

  The present invention relates to a nonwoven fabric suitably used as a molding material for a fiber-reinforced plastic molded body, a method for producing the nonwoven fabric, and a fiber-reinforced plastic molded body obtained by heating and pressing the nonwoven fabric.

  A fiber reinforced plastic (FRP) molded body in which glass fiber, carbon fiber, or the like is blended with a resin as a reinforcing material is used in a wide range of fields because of its excellent mechanical properties such as strength. Further, it is known that the mechanical properties of the FRP molded body are improved by using flat glass fibers having a flat cross section perpendicular to the longitudinal direction as glass fibers. As a method for producing such an FRP molded body, a method is known in which a thermoplastic resin and glass fiber are melt-kneaded into pellets, and the pellets are injection-molded (see, for example, Patent Documents 1 and 2).

JP 2013-221072 A JP 2013-166840 A

  However, recently, higher mechanical properties have been required for FRP molded products, and it has not been said that FRP injection molded products manufactured by the above method have a sufficient flexural modulus.

  The present invention relates to a nonwoven fabric that can produce an FRP molded body having a high flexural modulus when used as a molding material for an FRP molded body, a method for producing the nonwoven fabric, and an FRP molded body in which the nonwoven fabric is heated and pressed. For the purpose of provision.

The present invention has the following configuration.
[1] A flat glass fiber having a flat cross section perpendicular to the longitudinal direction and a ratio of a major axis to a minor axis (major axis / minor axis) of the cross section of 1.5 to 8, and a thermoplastic resin fiber And a non-woven fabric.
[2] The nonwoven fabric of [1], which is a wet nonwoven fabric.
[3] The average value of the major axis of the flat glass fiber is 10 to 50 μm, the average value of the major axis of the thermoplastic resin fiber is 9 to 40 μm,
The total content of the flat glass fiber and the thermoplastic resin fiber is 100% by mass, the content of the flat glass fiber is 30 to 90% by mass, and the content of the thermoplastic resin fiber is 10 to 70% by mass. The nonwoven fabric of [1] or [2].
[4] The nonwoven fabric of [1] to [3], wherein the thermoplastic resin fiber is made of a thermoplastic resin having a melting point of 150 ° C. or higher or a glass transition temperature of 120 ° C. or higher.
[5] The nonwoven fabric of [1] to [4], wherein the flat glass fibers are dispersed in a single fiber shape.
[6] A fiber-reinforced plastic molded article obtained by heating and pressing the nonwoven fabric of [1] to [5].
[7] A flat glass fiber having a flat cross section perpendicular to the longitudinal direction and a ratio of the major axis to the minor axis (major axis / minor axis) of the cross section of 1.5 to 8, and a thermoplastic resin fiber A method for producing a non-woven fabric, which comprises a paper making step of making a paper dispersion.
[8] The viscosity of the dispersion medium of the dispersion at 25 ° C. (however, according to the measurement method specified in JIS Z 8803 “Method for measuring viscosity of liquid”) exceeds 1.00 mPa · s and is 4.00 mPa · s. The method for producing a nonwoven fabric according to [7], which is as follows.
[9] The method for producing a nonwoven fabric according to [7] or [8], wherein the dispersion has a solid content concentration of 0.1% by mass or less.
[10] The method for producing a nonwoven fabric according to [7] to [9], wherein the thermoplastic resin fibers have a length-weighted average fiber length of 3 to 100 mm.
[11] The method for producing a nonwoven fabric according to [7] to [10], wherein the flat glass fiber has a length-weighted average fiber length of 3 to 100 mm.

  According to the present invention, when used as a molding material for an FRP molded body, a nonwoven fabric capable of producing an FRP molded body having a high flexural modulus, a method for producing the nonwoven fabric, and FRP molding in which the nonwoven fabric is heat-press molded. Can provide the body.

It is explanatory drawing explaining the method of determining the major axis and minor axis of the cross section of a fiber. It is sectional drawing which shows the cross-sectional shape of a flat glass fiber.

Hereinafter, the present invention will be described in detail.
<Nonwoven fabric>
The nonwoven fabric of the present invention contains flat glass fibers and thermoplastic resin fibers, and is suitably used as a molding material for FRP moldings (substrate for fiber-reinforced plastic moldings) and the like. As will be described in detail later, the nonwoven fabric of the present invention is formed into an FRP molded body by one sheet or two or more sheets being stacked and heated and pressed.

[Flat glass fiber]
The flat glass fiber acts as a reinforcing material in the FRP molded body formed using the nonwoven fabric of the present invention.
In this specification, the flat glass fiber refers to a glass fiber having a flat cross section and a ratio of a major axis to a minor axis (major axis / minor axis) in the range of 1.5 to 8.

In this specification, the cross section of the fiber means a cross section perpendicular to the longitudinal direction of the fiber.
In the present specification, the major axis of the cross section of the fiber is the length L ¹ of the long side of the rectangle R when the rectangle R circumscribing the cross section of the fiber 10 is assumed as shown in FIG. the minor axis of the cross section, the short side is the length L ^2.

In a nonwoven fabric, the flat glass fiber whose ratio (major axis / minor axis) is in the above range is easily oriented so that the major axis direction is along the surface direction of the nonwoven fabric. And also in the FRP molded object shape | molded using such a nonwoven fabric, a flat glass fiber is easy to orientate so that the major axis direction may follow the surface direction of a FRP molded object. Therefore, the obtained FRP molded object is excellent in a bending elastic modulus.
Further, as will be described later, when the nonwoven fabric is a wet nonwoven fabric produced through a papermaking process of making a dispersion containing flat glass fibers and thermoplastic resin fibers, in the wet nonwoven fabric, the flat glass fibers are: It is easy to orient so that the major axis direction is along the surface direction of the nonwoven fabric. Therefore, the FRP molded body in which the wet nonwoven fabric is heat-pressed is superior in bending elastic modulus.

  On the other hand, in the FRP injection molded product produced by a method of melt-kneading flat glass fibers and thermoplastic resin into pellets and injection-molding the pellets, the flat glass fibers have undergone melt-kneading. Folded and shortened. Moreover, it does not orientate so that the major axis direction follows a specific direction, and it exists at random. Therefore, such an FRP injection molded product has a low flexural modulus. In addition, in the injection molding, if it is attempted to increase the flat glass fiber content in the injection molded body, the molding itself becomes difficult and a sufficient amount of flat glass fiber cannot be contained.

  2-7 are preferable and, as for the said ratio (major axis / minor axis) of the cross section of a flat glass fiber, 2.5-6 are more preferable. When the ratio (major axis / minor axis) is less than the lower limit of the above range, the flexural modulus of the obtained FRP molded product becomes insufficient. If the ratio (major axis / minor axis) exceeds the upper limit of the above range, the fiber becomes too thin and may be destroyed during molding or the like, and the desired effect may not be obtained.

  The cross-section of the flat glass fiber is not limited in shape as long as the ratio (major axis / minor axis) is within the above range, and the shape of the ellipse as shown in FIG. 2 (a) or the constricted portion 20 as shown in FIG. A certain ellipse, a rectangular shape in which a pair of opposing short sides 21 and 21 are convex outwardly as shown in FIG. When the cross-sectional shape is an ellipse with the constricted portion 20 as shown in FIG. 2B, the constricted portion 20 of the flat glass fiber is fitted with a portion other than the constricted portion 20 of the other flat glass fiber, and the flat shape in the nonwoven fabric is obtained. Glass fiber filling efficiency is likely to increase. Therefore, the flexural modulus of the obtained FRP molded body is more excellent. Moreover, since the rectangular shape as shown in FIG. 2C has straight long sides, it is easy to laminate the long sides in contact with each other, the contact area between the flat glass fibers is increased, and the filling efficiency is increased. Also gets higher. Therefore, the flexural modulus of the obtained FRP molded body is more excellent.

The fiber length (longitudinal direction) of the flat glass fiber is preferably 3 to 100 mm, more preferably 3 to 75 mm, and particularly preferably 3 to 50 mm as a length-weighted average fiber length. If the fiber length of the flat glass fiber is not less than the lower limit of the above range, the flexural modulus of the obtained FRP molded product is more excellent. Moreover, when the nonwoven fabric is a wet nonwoven fabric, it is manufactured through a papermaking process described later. In the papermaking process, flat glass fibers are not easily dropped from a wire (papermaking net), and the flat glass fiber yield is excellent. If the fiber length of the flat glass fiber is equal to or less than the upper limit of the above range, the flat glass fiber is easily oriented as described above, and the FRP molded product obtained has a better bending elastic modulus, and the flat glass fibers in the papermaking process Is difficult to get involved.
In the present specification, the length weighted average fiber length is an average value of fiber lengths measured for 100 fibers.

  The flat glass fibers are dispersed in a single fiber form in the nonwoven fabric. By being dispersed in the form of a single fiber, the obtained FRP molded product tends to be homogeneous in properties such as bending elastic modulus and has an excellent appearance. In the present specification, “dispersed in the form of single fibers” means that they are not in the form of strands in the nonwoven fabric, and some overlap of single fibers is allowed.

  Even if the flat glass fiber contained in the nonwoven fabric is only one type, it is two or more types that differ in one or more of the major axis, minor axis, ratio (major axis / minor axis), fiber length, cross-sectional shape, etc. Also good.

[Thermoplastic resin fiber]
The thermoplastic resin fiber acts as a matrix resin in the FRP molded body formed using the nonwoven fabric of the present invention. The thermoplastic resin fiber maintains a fibrous form in the nonwoven fabric, but does not maintain the fibrous form in the FRP molded body obtained by heating and pressing the nonwoven fabric.

  There is no restriction | limiting in particular in the shape of the cross section of a thermoplastic resin fiber, What kind of shape may be sufficient. For example, it may be a so-called round cross section (circular cross section) in which the major axis and minor axis of the cross section are the same, or may be various shapes such as a flat having a different major axis and minor axis of the cross section. Thermoplastic resin fibers are preferred.

  The thermoplastic resin constituting the thermoplastic resin fiber is not particularly limited, but a resin satisfying a melting point of 150 ° C. or higher or a glass transition temperature of 120 ° C. or higher is preferable from the viewpoint of heat resistance of the FRP molded product. . The melting point of the thermoplastic resin constituting the thermoplastic resin fiber is more preferably 155 ° C. or higher, and the glass transition temperature is more preferably 140 ° C. or higher.

In the present specification, the melting point is determined by differential scanning calorimetry. Specifically, in accordance with JISK 7121, the temperature is raised at a rate of 5 ° C./min from a temperature 50 ° C. or more lower than the melting temperature to a temperature 30 ° C. higher than the melting temperature, and a temperature 30 ° C. higher than the melting temperature. Of the endothermic peak when the temperature is raised to 5 to 10 ° C./min to a temperature lower than the melting temperature by 50 ° C. or more and then heated again to a temperature 30 ° C. higher than the melting temperature at 5 ° C./min. Temperature.
In this specification, the glass transition temperature is a midpoint glass transition temperature obtained by differential scanning calorimetry.

Examples of the thermoplastic resin include polycarbonates, polypropylenes, polyamides, polyetherimides, polyesters such as polyethylene terephthalate (PET), and the like, and one or more types can be selected depending on the use of the FRP molded product. Polycarbonate and polyetherimide are non-crystalline thermoplastic resins and correspond to resins having a glass transition temperature of 120 ° C. or higher. Polyesters such as polypropylene, polyamide, and PET are crystalline thermoplastic resins and correspond to resins having a melting point of 150 ° C. or higher.
For example, when the FRP molded body is a housing of an electrical appliance such as a personal computer (including a tablet personal computer), a mobile phone, a smartphone, etc., polycarbonate or the like is preferably used. When the FRP molded body is an automobile exterior material (bumper, etc.), interior material (ceiling material, etc.), polypropylene, polyamide, etc. are preferably used, and the FRP molded body is a member used for railway vehicles and aircraft. In particular, polyether imide or the like is preferably used in a case where it is preferable to have low smoke generation in a fire or the like.

  Even if the thermoplastic resin fiber contained in the nonwoven fabric is only one type, it may be two or more types that differ in one or more of melting point, glass transition temperature, major axis, minor axis, fiber length, cross-sectional shape, etc. Good.

  The thermoplastic resin fiber is derived from a fiber having a core-sheath structure in which a sheath made of a thermoplastic resin having a low melting point or glass transition temperature is formed on the outer periphery of a core made of a thermoplastic resin having a high melting point or glass transition temperature. Things may be included. The sheath portion of the fiber having such a core-sheath structure acts as a binder that is melted by heat applied during the manufacturing process of the nonwoven fabric (for example, heating in a drying process described later) to bond the fibers together. In the nonwoven fabric, the fibrous form is hardly maintained. Therefore, the portion derived from the sheath of the core-sheath type fiber is not included in the thermoplastic resin fiber constituting the nonwoven fabric and is handled as a binder component described later. On the other hand, the core of the fiber having such a core-sheath structure is not melted by heat applied during the manufacturing process of the nonwoven fabric, and maintains a fibrous form. Therefore, about the core part, it handles as the thermoplastic resin fiber which comprises a nonwoven fabric.

As the thermoplastic resin fiber having a core-sheath structure, the core part is a resin having a melting point of 150 ° C. or higher, preferably 155 ° C. or higher, or a glass transition temperature of 120 ° C. or higher, preferably 140 ° C. or higher. Preferably, the material is at least one selected from the above-described polycarbonate, polypropylene, polyamide, polyetherimide, polyester such as PET, and the like.
The sheath part handled as the binder component is (meth) acrylic resin, modified PET (so-called low melting point PET), polyolefin (polyethylene, polypropylene, etc.).
1) or more selected from among others.
Examples of the combination of the core and the sheath of the core-sheath type thermoplastic resin fiber include “PET / modified PET”, “PET / EVA”, “PP / PE” and the like. Here, the material described before “/” means the core, and the material described behind means the sheath. EVA means an ethylene-vinyl acetate copolymer, PP means polypropylene, and PE means polyethylene.

In 100% by mass of the thermoplastic resin fibers constituting the nonwoven fabric, thermoplastic resin fibers derived from such core-sheath structure fibers (that is, the core portion of the core-sheath structure fibers remain in the form of fibers). There is no restriction | limiting in particular in the ratio of what is, and may be the range of 0-100 mass%. However, when the ratio of the thermoplastic resin fibers derived from the fibers of the core-sheath type structure contained in the nonwoven fabric is high, the ratio of the resin derived from the sheath treated as a binder component is increased along with it, and in that case, it is obtained. The heat resistance, mechanical properties, etc. of the FRP molded product may be reduced. From such a viewpoint, the ratio of the thermoplastic resin fiber derived from the fiber having the core-sheath structure in 100% by mass of the thermoplastic resin fiber constituting the nonwoven fabric is determined by the amount of the resin derived from the sheath handled as the binder component. It is preferable to adjust so that it may become in the preferable range mentioned later with respect to a total of 100 mass parts of a flat glass fiber and a thermoplastic resin fiber.
As a ratio in 100% by mass of the thermoplastic resin fibers constituting the nonwoven fabric, the ratio of the thermoplastic resin fibers derived from the fibers of the core-sheath structure (ratio of the core part) is preferably 30% by mass or less, 20 mass% or less is more preferable.

  The fiber length of the thermoplastic resin fiber is preferably 3 to 100 mm, more preferably 3 to 50 mm, and particularly preferably 3 to 25 mm as a length-weighted average fiber length. If the fiber length of the thermoplastic resin fiber is equal to or greater than the lower limit of the above range, when the nonwoven fabric is a wet nonwoven fabric, the thermoplastic resin fiber is unlikely to fall from the wire in the paper making process of the manufacturing process, and the thermoplastic resin Excellent fiber yield. If the fiber length of the thermoplastic resin fiber is not more than the upper limit of the above range, the thermoplastic resin fibers are hardly entangled in the paper making process.

  The thermoplastic resin fibers are dispersed in a single fiber form in the nonwoven fabric. By being dispersed in the form of a single fiber, the obtained FRP molded product tends to have uniform properties such as a flexural modulus.

[Diameter and blending ratio of flat glass fiber and thermoplastic resin fiber]
In the nonwoven fabric, the flat glass fiber is easily oriented so that the major axis direction thereof is along the surface direction of the nonwoven fabric, so the average value of the major axis of the cross section of the flat glass fiber is 10 to 50 μm, the major axis of the cross section of the thermoplastic resin fiber The average value is 9 to 40 μm, and the total content of flat glass fibers and thermoplastic resin fibers is 100% by mass, the content of flat glass fibers is 30 to 90% by mass, and the content of thermoplastic resin fibers is It is preferable that it is 10-70 mass%.
When the average value of the major axis of the cross section of the flat glass fiber is 10 to 50 μm as described above, if the average value of the major axis of the cross section of the thermoplastic resin fiber is not more than the upper limit of the above range, the thermoplastic resin fiber is Since it is not so thick, even if thermoplastic resin fibers are interposed between the flat glass fibers, it is difficult to prevent the flat glass fibers from being oriented as described above.
On the other hand, if the average value of the major axis of the cross section of the thermoplastic resin fiber is not less than the lower limit of the above range when the content of the thermoplastic resin fiber is within the above range, the thermoplastic resin fiber is thick and in the nonwoven fabric. The number of thermoplastic resin fibers present will be reduced. As described above, when the number of thermoplastic resin fibers present in the nonwoven fabric is small, many flat glass fibers are easily oriented as described above without being disturbed by the thermoplastic resin fibers.

The average value of the major axis of the cross section of the flat glass fiber is more preferably 15 to 40 μm, and particularly preferably 20 to 35 μm. The average value of the major axis of the cross section of the thermoplastic resin fiber is more preferably 10 to 35 μm, and particularly preferably 13 to 32 μm. It is more preferable that the content of the flat glass fiber is 60 to 90% by mass and the content of the thermoplastic resin fiber is 10 to 40% by mass with respect to the total 100% by mass of the flat glass fiber and the thermoplastic resin fiber.
When each is within such a range, the flat glass fibers are more easily oriented so that the major axis direction is along the surface direction of the nonwoven fabric.
Further, the ratio of the average value of the minor axis of the cross section of the flat glass fiber to the average value of the minor axis of the thermoplastic resin fiber (average value of the minor axis of the cross section of the flat glass fiber / average value of the minor axis of the thermoplastic resin fiber ) Is preferably 0.125 to 2.0. Thereby, flat glass fiber and thermoplastic resin fiber tend to exist uniformly in the nonwoven fabric.

  In addition, in this specification, the average value of the long diameter of the cross section of flat glass fiber, the average value of a short diameter, the average value of the long diameter of the cross section of a thermoplastic resin fiber, and the average value of a short diameter are the average about 100 fibers, respectively. Each major axis and minor axis can be measured by microscopic observation.

[Other ingredients]
(Binder component)
The nonwoven fabric of this invention may contain the binder component for couple | bonding a flat glass fiber and a thermoplastic resin fiber mutually and maintaining the shape retention property of a nonwoven fabric.
As described above, by using a thermoplastic resin fiber having a core-sheath type structure as the material of the nonwoven fabric, the sheath portion may be melted and become a binder component and included in the nonwoven fabric. In the production process of the nonwoven fabric, the binder component can be applied in the form of powder, fiber, liquid (solution, emulsion, etc.) and the like.
In addition, if necessary, a core-sheath structure thermoplastic resin fiber is used as the material of the nonwoven fabric, and the binder component can be applied in the form of powder, fiber, liquid, etc. in the nonwoven fabric manufacturing process. .

  In addition, in the manufacturing process of a nonwoven fabric, when a fiber is entangled by the hydroentanglement method mentioned later, a nonwoven fabric does not contain a binder component normally.

Examples of the binder component include thermoplastic resins such as polyvinyl alcohol, (meth) acrylic resin, modified PET, and polyolefin (polyethylene, polypropylene, etc.). The binder component is melted by heat applied during the manufacturing process of the nonwoven fabric (for example, heating in the drying process described later) and acts as a binder. The drying step is performed at a temperature at which the thermoplastic resin fiber does not melt.
The nonwoven fabric may contain one type of binder component or two or more types of binder components.

  The content of the binder component is preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass in total of the flat glass fiber and the thermoplastic resin fiber. If the amount of the binder component is not less than the lower limit of the above range, the fibers can be sufficiently bonded. If the amount of the binder component is not more than the upper limit of the above range, the heat resistance, mechanical properties and the like of the FRP molded product are hardly lowered.

(Other ingredients)
The nonwoven fabric of this invention may also contain the glass fiber which does not correspond to the above-mentioned flat glass fiber in the range which does not prevent the effect. When the glass fiber is contained, the amount thereof is preferably 20 parts by mass or less, more preferably 15 parts by mass or less with respect to 100 parts by mass of the flat glass fiber.
Moreover, the nonwoven fabric of this invention may also contain 1 or more types among fillers, such as glass powder and flat glass powder, another reinforcing fiber, a thermosetting resin, a pigment, etc. in the range which does not inhibit the effect.

[Basis weight, thickness]
The basis weight of the nonwoven fabric of the present invention is preferably 20~600g / ^{m 2,} more preferably from 25~550g / ^{m 2,} more preferably from 25~500g / ^{m 2,} 50~150g / M ² is particularly preferred. If the basis weight is not less than the lower limit of the above range, the nonwoven fabric can be produced with high production efficiency. Moreover, if it is below the upper limit of the said range, in a nonwoven fabric, a flat glass fiber will be easy to orientate so that the major axis direction may follow the surface direction of a nonwoven fabric, and a nonwoven fabric with high basic weight and the uniformity of fiber orientation is high. Can be obtained.
The density of the nonwoven fabric of this invention is about 0.1-0.5 g / cm < ³ > normally in the state which passed through the papermaking process and drying process which are mentioned later, for example. The nonwoven fabric of the present invention can be used as it is, but from the viewpoints of transportation cost, handling properties, etc., for the purpose of reducing its volume, this is performed by a heat-pressing press or the like under conditions that do not affect the nonwoven fabric. May be compressed to increase the density.
The thickness of the nonwoven fabric of the present invention is not particularly limited, and is determined by basis weight and density.

<Nonwoven Fabric Manufacturing Method>
The method for producing a nonwoven fabric according to the present invention is based on a so-called wet papermaking method, and has a papermaking process for papermaking a dispersion containing the above-described flat glass fibers and thermoplastic resin fibers. A dispersion means a liquid in a stock inlet of a paper machine, which is supplied to a paper machine wire in a paper making process, and a dispersion medium of the dispersion liquid is usually water. Examples of the paper machine include a circular net paper machine, a long net paper machine, and an inclined paper machine.

The dispersion may include a binder component for binding the flat glass fiber and the thermoplastic resin fiber. Examples of the binder component include, as described above, thermoplastic resins such as polyvinyl alcohol, (meth) acrylic resin, modified PET, polyolefin (polyethylene, polypropylene, etc.), and powder, fiber, liquid (solution, emulsion, etc.) Etc.) can be added to the dispersion.
The dispersion may contain a dispersing agent such as a surfactant (which improves the dispersibility of the flat glass fiber and the thermoplastic resin fiber), and a glass fiber that does not correspond to the flat glass fiber used as necessary. .

  The viscosity of the dispersion medium of the dispersion at 25 ° C. (however, according to the measurement method specified in JIS Z 8803 “Method for measuring viscosity of liquid”) is more than 1.00 mPa · s and not more than 4.00 mPa · s. Is preferable, and 1.05-2.00 mPa · s is more preferable. When the viscosity of the dispersion medium is equal to or higher than the lower limit of the above range, the flow of the dispersion near the wire becomes a laminar flow without being disturbed, and even when flat glass fibers are mixed with thermoplastic resin fibers, the long diameter direction of the flat glass fibers It is easy to orient along the surface direction of the non-woven fabric. Further, when performing dewatering with a dewatering box or the like of a paper machine, a wide adjustment range of the suction force can be taken, and the amount of dewatering can be easily adjusted. When the viscosity of the dispersion medium is not more than the upper limit of the above range, the papermaking process can be performed with good productivity and excellent productivity.

  In order to adjust the viscosity of the dispersion medium to the above range, it is preferable to add a viscous agent. As the sticking agent, for example, polyacrylamide, polyethylene oxide and the like are preferable. If the viscous agent is powder, dissolve it in water to a concentration of 0.3% by mass or less in advance so that it does not become lumpy in the liquid or undissolved matter remains. It is preferable to add.

The viscosity of the dispersion medium may be measured by collecting the filtrate obtained by filtering the dispersion with an 80 mesh filter, or the same viscosity as that used for the dispersion may be the same concentration. A sample for viscosity measurement added to may be separately prepared and measured.
In the present specification, the viscosity is measured at 25 ° C. according to a measuring method defined in JIS Z 8803 “Method for Measuring Viscosity of Liquid”.

The solid content concentration (inlet concentration) of the dispersion is preferably 0.1% by mass or less, and more preferably 0.001 to 0.07% by mass. When the solid content concentration of the dispersion medium is low as described above, the degree of freedom of movement of fibers in the dispersion increases. Therefore, it is easy to orient along the surface direction of the nonwoven fabric which can obtain the major axis direction of flat glass fiber.
In addition, solid content is a flat glass fiber and the other glass fiber used arbitrarily, a thermoplastic resin fiber, and a binder component.

The jet wire ratio in the paper making process is preferably 1 or less, more preferably 0.9 or less, and particularly preferably 0.8 or less. The jet wire ratio is preferably 0.7 or more in that the fibers are oriented in the same direction.
The jet wire ratio is a ratio of the flow velocity (J) of the dispersion to the traveling speed (W) of the wire in the paper machine, and is represented by J / W. By adjusting J / W to the said range, the flow of the dispersion liquid in the vicinity of the wire can be controlled in a laminar flow region, and this makes it easy to orient the flat glass fibers so that the major axis direction is along the surface direction of the nonwoven fabric. Further, as described above, when the solid content concentration of the dispersion medium is low and the degree of freedom of movement of the fibers in the dispersion is high, the jet wire ratio is 1 or less, preferably 0.9 or less. By doing so, it becomes easier to orient the flat glass fiber along the surface direction of the nonwoven fabric in which the major axis direction is obtained by the synergistic effect of the solid content concentration and the jet wire ratio.

As the paper machine, as described above, a known paper machine such as a circular paper machine, a long paper machine, and an inclined type paper machine can be used, but it is easy to adjust the paper machine conditions such as the jet wire ratio, Even when mixed with plastic resin fibers, it is preferable to use an inclined paper machine because flat glass fibers can be easily oriented along the surface direction of the nonwoven fabric in which the major axis direction is obtained.
Adjustment of the jet wire ratio in the inclined paper machine can be performed by a conventional method for controlling the supply speed of the dispersion liquid to the wire and the speed at which the dispersion medium in the supplied dispersion liquid is sucked by the dehydration box through the wire. .

  The traveling speed (W) of the wire is preferably 5 to 200 m / min. If the running speed (W) of the wire is equal to or higher than the lower limit value of the above range, the uniformity of the resulting nonwoven fabric is enhanced. If the wire traveling speed (W) is equal to or lower than the upper limit value of the above range, the flow of liquid in the inlet is not disturbed. It is easy to orient the fibers along the surface direction of the nonwoven fabric in which the major axis direction is obtained. The traveling speed (W) of the wire corresponds to “paper making speed”.

The paper making process is performed as follows, for example.
First, a dispersion is prepared in a tank with an agitator. Specifically, flat glass fibers, thermoplastic resin fibers, water (dispersion medium), a dispersing agent, and a sticking agent are mixed and stirred with an agitator. At this time, the dispersant may be added after being dissolved or diluted with water. Further, a binder component may be added. Thus, a raw material liquid in which flat glass fibers and thermoplastic fibers are converted into monofilaments (single fibers) is prepared.
As the flat glass fiber and the thermoplastic resin fiber, those described above for the nonwoven fabric are used.
The solid content concentration of the raw material liquid is preferably adjusted to about 0.5 to 2.0% by mass.
As for the addition amount (net amount) of a dispersing agent, about 0.01-3.0 mass parts is preferable with respect to 100 mass parts of flat glass fiber.

  Subsequently, water (for example, white water) is added to the raw material liquid thus prepared to obtain a dispersion having a solid content concentration in the above range. It is preferable to add a viscosity agent to the water added here in advance so that the viscosity of the dispersion falls within a preferable range.

And a dispersion liquid is supplied to the wire of a paper machine from the stock inlet of a paper machine, and a fiber layer is formed. At this time, the jet wire ratio is preferably controlled within the above range.
Thereafter, the fiber layer is dehydrated to obtain a wet web. Dehydration is performed by passing the fiber layer through, for example, a suction box.

After such a papermaking process, a binder supply process or a hydroentanglement process is performed as necessary. Then, the drying process which evaporates and dries the water | moisture content of a wet web with a Yankee dryer etc. is performed.
The binder supply step and the hydroentanglement step may be performed when the wet web obtained in the papermaking step includes a binder component, but is usually performed when the wet web does not include the binder component.
The binder supplying step is performed by, for example, a method of spraying, applying, or impregnating a wet web after dehydration with a liquid containing a binder component. The binder component thus imparted is dissolved by the heat in the subsequent drying step to bond the fibers together. When the binder component is a (meth) acrylic resin, an emulsion is preferably used as the liquid containing the binder component.
The hydroentanglement step is a step of partially entwining the fibers by injecting high-pressure water onto the wet web, and can be performed by a known method. According to the hydroentanglement method, a nonwoven fabric having appropriate strength can be obtained.

When the wet web supplied to the drying step contains a binder component, the binder component is melted and the fibers are bonded together in addition to evaporating and drying the moisture by the heat applied in the drying step.
When the wet web supplied to the drying process does not contain a binder component and has undergone a hydroentanglement process, moisture is evaporated and dried in this drying process.
As described above, a wet nonwoven fabric containing flat glass fibers and thermoplastic resin fibers can be produced.

<Fiber-reinforced plastic molding>
The FRP molded product of the present invention can be obtained by heat-pressing the above-mentioned nonwoven fabric. The nonwoven fabric may be formed by heating and pressing only one sheet, or two or more sheets may be stacked by heating and pressing, and can be determined according to the use of the FRP molded body.
The temperature of the heating and pressing is preferably determined according to the melting point or glass transition temperature of the thermoplastic resin fiber, and in the case of a thermoplastic resin fiber made of a crystalline thermoplastic resin, it is higher than the melting point of the thermoplastic resin fiber. In the case of a thermoplastic resin fiber made of an amorphous thermoplastic resin at a temperature 5 to 100 ° C. higher, the temperature is 50 to 200 ° C. higher than the glass transition temperature of the thermoplastic resin fiber (for example, a temperature higher by 100 ° C.). Is preferred. When the thermoplastic resin fiber is made of a crystalline thermoplastic resin, the temperature for heat and pressure molding is determined based on the melting point. When the thermoplastic resin fiber is made of an amorphous thermoplastic resin, since the resin does not show a melting point, the temperature of the heat and pressure molding is determined based on the glass transition temperature.

  Below, an example of melting | fusing point and glass transition temperature of a thermoplastic resin fiber is shown, and an example of the temperature of the suitable heat press molding at the time of using this thermoplastic resin fiber is shown.

(Amorphous thermoplastic resin)
Polycarbonate: Glass transition temperature is 140 to 160 ° C., and heat and pressure molding temperature is 200 to 280 ° C.
Polyetherimide: Glass transition temperature is 210 to 220 ° C., and temperature of heat and pressure molding is 280 to 400 ° C.

(Crystalline thermoplastic resin)
Polypropylene: Melting point is 160 to 170 ° C., and temperature for heat and pressure molding is 180 to 230 ° C.
Polyamide: Melting point is 210 to 230 ° C., and temperature of heat and pressure molding is 200 to 280 ° C.

  The pressure of the heating and pressing is about 3 to 50 MPa, and the heating and pressing time is about 5 to 1200 seconds.

  The FRP molded body thus obtained is excellent in bending elastic modulus because the nonwoven fabric of the present invention is formed by heating and pressing. Therefore, for example, it is suitably used for casings of electrical appliances such as personal computers (including tablet personal computers), mobile phones, smartphones, exterior materials (bumpers, etc.) and interior materials (ceiling materials, etc.) of automobiles.

Hereinafter, the present invention will be specifically described with reference to examples.
Example 1
The nonwoven fabric (wet nonwoven fabric) containing each fiber in the ratio shown in Table 1 was manufactured through a papermaking process using an inclined type paper machine (inclined wire type paper machine) as follows.
As the flat glass fiber, a flat glass fiber manufactured by Nittobo Co., Ltd. having a length-weighted average fiber length of 13 mm, a major axis of 28 μm, a minor axis of 7 μm, and a ratio (major axis / minor axis) of 4 was used. This flat glass fiber had a cross-sectional shape as shown in FIG.
As the polycarbonate fiber (thermoplastic resin fiber), a polycarbonate fiber (round cross-section fiber) manufactured by Daiwabo Polytech Co., Ltd. having a length-weighted average fiber length of 15 mm and a major axis and a minor axis both of 30 μm was used. The polycarbonate fiber had a glass transition temperature of 150 ° C.

First, flat glass fibers and water were introduced into a tank with a propeller-type agitator so that the concentration of the flat glass fibers was 0.5% by mass. Furthermore, a 0.5% by mass aqueous solution of “Emanon (registered trademark) 3199V” (manufactured by Kao Corporation, polyethylene stearate) as a dispersant has a solid content of 0.5% relative to 100 parts by mass of flat glass fiber. It added so that it might become a mass part, and it stirred at the rotation speed of 250 rpm using the propeller-type agitator.
Next, polycarbonate fiber and polyvinyl alcohol fiber (“VPB105-2” (manufactured by Kuraray Co., Ltd.)) as a binder component were added so as to have a blending ratio (mass ratio) shown in Table 1, and stirring was continued at a rotational speed of 250 rpm. . Since the polyvinyl alcohol fiber is water-soluble, the form of the fiber is not maintained in the obtained nonwoven fabric.

Subsequently, a 0.2% by mass aqueous solution of a polyacrylamide-based viscosity agent (“FA-40MT” (manufactured by Aqua Polymer Co., Ltd.), mass average molecular weight: 17 million) was used, and the solid content of polyacrylamide was 9 ppm with respect to the obtained raw material liquid. The mixture was stirred at a rotational speed of 250 rpm to obtain a raw material liquid in which each fiber was monofilamentized.
Thereafter, water was added thereto, and the solid content concentration (total concentration of flat glass fiber, polycarbonate fiber, and polyvinyl alcohol fiber) was adjusted to 0.5% by mass.

  Thereafter, water (white water) was added to the raw material liquid to obtain a dispersion having a solid content concentration of 0.05% by mass. The viscosity of the dispersion medium of this dispersion at 25 ° C. (however, according to the measurement method specified in JIS Z 8803 “Method for measuring viscosity of liquid”) was 1.05 mPa · s.

This dispersion was continuously supplied to the wire of the inclined type paper machine, and the paper making process was performed by adjusting the paper making speed to 10 m / min and the jet wire ratio to 0.8. After passing through a suction box and dewatering, it was dried at 140 ° C. with a Yankee dryer to obtain a nonwoven fabric having a width of 50 cm and a basis weight of 100 g / m ² .

20 sheets of the obtained non-woven fabrics were laminated, placed in a hot press preheated to 245 ° C., and subjected to heat and pressure molding under the conditions of temperature: 245 ° C., pressure: 10 MPa, time: 60 seconds.
Then, it cooled to 70 degreeC and obtained the FRP molded object of thickness 1.2mm.

About the obtained FRP molded object, according to JISK7074 (bending test method of a carbon fiber plastic molded object), the orientation direction (machine direction, hereafter referred to as "MD direction") and the direction orthogonal to the MD direction ( The flexural modulus of cross direction (hereinafter referred to as “CD direction”) was measured.
And the geometric mean value of the value of MD direction and CD direction was calculated | required with the following formula.
Geometric mean value = √ (bending elastic modulus in MD direction × flexural elastic modulus in CD direction)
Table 1 shows the values of the respective flexural moduli.

(Examples 2 to 10, Comparative Examples 1 to 3)
In the same manner as in Example 1, nonwoven fabrics containing each fiber were produced at the ratios shown in Tables 1 and 2, and FRP molded bodies were obtained. And about the FRP molded object, it carried out similarly to Example 1, and measured the bending elastic modulus.
In addition, the same flat glass fiber and polycarbonate fiber as Example 1 were used.

  However, in Examples 2 to 10 and Comparative Examples 1 to 3, the polyvinyl alcohol fiber used in Example 1 was not used. Instead, the core was PET (melting point: 260 ° C.) and the sheath (melting point: 110 ° C.) A core-sheath type thermoplastic resin fiber having a modified PET (length-weighted average fiber length of 5 mm, major axis and minor axis of 12.5 μm, core major axis and minor axis of 4.4 μm, core and sheath) The mass ratio of core: sheath = 1: 1 was used. In this fiber, the core exists as a thermoplastic resin fiber in the obtained nonwoven fabric, and the sheath exists as a binder component.

Examples 7 to 9 are examples in which polyetherimide fibers (Example 7), acid-modified polypropylene fibers (Example 8), and polyamide fibers (Example 9) were used in place of the polycarbonate fibers of Example 6. is there.
In Example 7, a polyetherimide fiber (round cross-section fiber) having a length-weighted average fiber length of 15 mm and a major axis and a minor axis of 15 μm was used. Since the glass transition temperature of this fiber was 217 ° C., the heat and pressure molding was performed under the conditions of temperature: 317 ° C. (temperature during preheating and molding), pressure: 10 MPa, and time: 60 seconds.
In Example 8, an acid-modified polypropylene fiber (manufactured by Daiwabo) having a length-weighted average fiber length of 15 mm and 2.2 dtex was used. Since the melting point of this fiber was 160 ° C., the heat and pressure molding was performed under the conditions of temperature: 180 ° C. (temperature during preheating and molding), pressure: 10 MPa, and time: 60 seconds.
In Example 9, a nylon 6 (registered trademark) fiber (manufactured by Toray Industries, Inc.) having a length-weighted average fiber length of 15 mm and 3.3 dtex was used as the polyamide fiber. Since the melting point of this fiber was 225 ° C., the heat and pressure molding was performed under the conditions of temperature: 250 ° C. (temperature during preheating and molding), pressure: 10 MPa, and time: 60 seconds.
Further, in Example 10 and Comparative Examples 1 to 3, a round-section glass fiber having a length-weighted average fiber length of 18 mm, a major axis and a minor axis of 9 μm and not flat was used as the glass fiber.

(Comparative Example 4)
Using a twin-screw extruder (Technobel "TZW15-TW"), flat glass fibers and pellet-like polycarbonate resin were melt-kneaded at the ratio shown in Table 2 to produce pellets. The pellets were molded with “Nissei Resin“ FNX110III ”” to obtain a plate-like injection-molded body having a thickness of 1.0 mm (cylinder temperature: 310 ° C., mold temperature: 110 ° C.). About the obtained injection molded object, it carried out similarly to Example 1, and measured the bending elastic modulus.
The flat glass fiber used was the same as that used in Example 1, and the polycarbonate resin used was the same resin used to produce the polycarbonate resin fiber used in Example 1.

(Comparative Example 5)
In the same manner as in Comparative Example 4, the flat glass fibers and the polycarbonate resin were melt-kneaded at the ratio shown in Table 2 to produce pellets and injection-molded. The uniformity was lowered and cracked, and a plate-shaped molded body could not be produced.

As shown in Table 1, the FRP molded body obtained by heating and pressing the nonwoven fabric of each example was excellent in the flexural modulus. Further, from the comparison between Example 5 and Example 10, even if the total amount of glass fibers contained in the non-woven fabric is the same, the FRP molded body having an excellent flexural modulus when the proportion of flat glass fibers is larger It was found that can be manufactured.
On the other hand, as shown in Table 2, in Comparative Examples 1 to 3, flat glass fibers were not used as glass fibers, and round cross-section glass fibers were used, so an FRP molded body excellent in bending elastic modulus was not obtained.
Further, from the results of Comparative Examples 4 and 5, the FRP injection-molded article containing flat glass fibers has a low bending elastic modulus, and the injection-molded article with a high content of flat glass fibers is difficult to manufacture itself. I understood.

Claims (11)

  A cross section perpendicular to the longitudinal direction is a flat shape, and includes a flat glass fiber having a major axis / minor axis ratio (major axis / minor axis) of 1.5 to 8 and a thermoplastic resin fiber. , Non-woven fabric.   The nonwoven fabric according to claim 1, which is a wet nonwoven fabric. The average value of the major axis of the flat glass fiber is 10 to 50 μm, the average value of the major axis of the thermoplastic resin fiber is 9 to 40 μm,
The total content of the flat glass fiber and the thermoplastic resin fiber is 100% by mass, the content of the flat glass fiber is 30 to 90% by mass, and the content of the thermoplastic resin fiber is 10 to 70% by mass. The nonwoven fabric according to claim 1 or 2.   The said thermoplastic resin fiber is a nonwoven fabric as described in any one of Claims 1-3 which consists of a thermoplastic resin whose melting | fusing point is 150 degreeC or more or whose glass transition temperature is 120 degreeC or more.   The nonwoven fabric according to any one of claims 1 to 4, wherein the flat glass fibers are dispersed in a single fiber shape.   A fiber-reinforced plastic molded article obtained by heating and press-molding the nonwoven fabric according to any one of claims 1 to 5.   A cross section perpendicular to the longitudinal direction is a flat shape, and includes a flat glass fiber having a major axis / minor axis ratio (major axis / minor axis) of 1.5 to 8 and a thermoplastic resin fiber. A method for producing a non-woven fabric, comprising a paper making step of making a dispersion.   The viscosity of the dispersion medium of the dispersion at 25 ° C. (however, according to the measurement method defined in JIS Z 8803 “Method for measuring viscosity of liquid”) is more than 1.00 mPa · s and not more than 4.00 mPa · s. The manufacturing method of the nonwoven fabric of Claim 7.   The manufacturing method of the nonwoven fabric of Claim 7 or 8 whose solid content concentration of the said dispersion liquid is 0.1 mass% or less.   The manufacturing method of the nonwoven fabric as described in any one of Claims 7-9 whose length weighted average fiber length of the said thermoplastic resin fiber is 3-100 mm.   The manufacturing method of the nonwoven fabric as described in any one of Claims 7-10 whose length weighted average fiber length of the said flat glass fiber is 3-100 mm.

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