JP2020090101A - Pre-sheet for manufacturing fiber reinforced thermoplastic and manufacturing method therefor, and fiber reinforced thermoplastic molded article - Google Patents

Abstract

To provide a fiber reinforced thermoplastic excellent in impact resistance, a pre-sheet for manufacturing the fiber reinforced thermoplastic used for manufacturing the same, and a manufacturing method therefor.SOLUTION: There is provided a pre-sheet for manufacturing a fiber reinforced thermoplastic, formed by a heat treatment of a laminate containing an unwoven fabric mat containing a reinforced fiber and a thermoplastic resin, and a reinforced fiber sheet neighboring the unwoven fabric mat and containing a reinforced fiber, in which the reinforced fiber contained in the reinforced fiber sheet has a longer average fiber length than reinforced fiber contained in the unwoven fabric mat, the unwoven fabric mat is an air-laid wave formed by an air-laid method, the reinforced fiber sheet is a carrier sheet used for transportation of the air-laid wave in the air-laid method.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pre-sheet for producing a fiber-reinforced thermoplastic for producing a fiber-reinforced thermoplastic, a method for producing the same, and a produced fiber-reinforced thermoplastic molded article.

Fiber-reinforced materials made of glass fiber, carbon fiber, aramid fiber, and other reinforcing fibers and matrix resin are used in electrical and electronic equipment, office automation equipment, power equipment casings, sports and leisure equipment, aircraft fuselages and parts. It is used for automobile bodies and parts, civil engineering and construction materials, structural parts and housings.

Thermosetting resins and thermoplastic resins are known as matrix resins for fiber-reinforced materials. In recent years, fiber-reinforced thermoplastics, which are fiber-reinforced materials that use a thermoplastic resin as a matrix resin, have been widely used because they can support various shapes.

As a fiber-reinforced thermoplastic, a pre-sheet for producing a fiber-reinforced thermoplastic containing reinforcing fibers and a thermoplastic resin (hereinafter, also simply referred to as "pre-sheet") is manufactured in advance, and a single body or a laminate of this pre-sheet is molded. The resulting fiber reinforced thermoplastics are known.

Patent Document 1 discloses a pre-sheet in which a structure containing reinforcing fibers and a thermoplastic resin and a sheet-like material such as a thermoplastic resin film or a nonwoven fabric are laminated and integrated for the purpose of reinforcing strength. There is.

Patent Document 2 aims to provide a presheet excellent in surface quality while satisfying requirements for strength, and a carbon fiber nonwoven fabric forming an outermost layer, and a carbon fiber as a layer located immediately below the outermost layer is drawn in one direction. Disclosed is a surface layer base material having an aligned unidirectional carbon fiber sheet, and a pre-sheet having a laminated structure formed from the surface layer base material.

JP, 2012-255065, A JP, 2008-132705, A

With the widespread use of fiber-reinforced thermoplastics, there is a demand for fiber-reinforced thermoplastic molded articles that are excellent in impact resistance among physical properties, and pre-sheets for producing fiber-reinforced thermoplastics that can be manufactured. However, Patent Document 1 and Patent Document 2 do not describe the characteristics of the presheet regarding impact resistance.

An object of the present invention is to provide a fiber-reinforced thermoplastic molded article having excellent impact resistance, a pre-sheet for producing a fiber-reinforced thermoplastic, capable of producing the same, and a method for producing the same.

The present invention for solving the above problems has the following aspects.
[1] A sheet formed by heat-treating a laminate including a nonwoven fabric mat containing reinforcing fibers and a thermoplastic resin, and a reinforcing fiber sheet containing reinforcing fibers adjacent to the nonwoven fabric mat. The reinforcing fiber contained in the reinforcing fiber sheet has an average fiber length longer than that of the reinforcing fiber contained in the non-woven mat, and the non-woven mat is an air-laid web formed by an air-laid method. Is a carrier sheet used for transporting the air-laid web in the air-laid method, and is a pre-sheet for producing a fiber-reinforced thermoplastic.
[2] One or more non-woven mats containing reinforcing fibers and a thermoplastic resin, and one or more reinforcing fiber sheets containing reinforcing fibers, at least one of the non-woven mats and at least one of the above-mentioned reinforcing materials. A sheet formed by heat-treating a laminate including a fibrous sheet so as to be adjacent to each other, wherein the reinforcing fibers contained in the reinforcing fiber sheet have an average fiber length longer than that of the reinforcing fibers contained in the nonwoven mat. Long, the non-woven mat is an air-laid web formed by an air-laid method, the reinforcing fiber sheet is a carrier sheet used to convey the air-laid web in the air-laid method, fiber reinforced Presheet for making thermoplastics.
[3] The pre-sheet for producing a fiber-reinforced thermoplastic according to [1] or [2], wherein the non-woven fabric mat further contains a heat-fusible resin.
[4] The pre-sheet for producing a fiber-reinforced thermoplastic according to any one of [1] to [3], wherein the reinforcing fiber sheet is a non-woven fabric.
[5] A fiber-reinforced thermoplastic molded article obtained by molding a single body or a laminate of the presheet for producing a reinforced thermoplastic according to any one of [1] to [4].

The pre-sheet for producing a fiber-reinforced thermoplastic of the present invention and the fiber-reinforced thermoplastic molded article produced therefrom have excellent impact resistance.

It is a table which shows the structure of the pre-sheet which concerns on an Example and a comparative example, and the measurement result of a molded article. It is a schematic diagram which shows the web forming apparatus which can be used in the manufacturing method of the presheet for producing fiber reinforced thermoplastics of the present invention.

<Pre-sheet for producing fiber reinforced thermoplastic>
The pre-sheet for producing a fiber-reinforced thermoplastic of the present invention is a sheet formed by heat-treating a laminate including a nonwoven mat containing reinforcing fibers and a thermoplastic resin, and a reinforcing fiber sheet adjacent to the nonwoven mat. The reinforcing fiber contained in the reinforcing fiber sheet is a sheet having an average fiber length longer than that of the reinforcing fiber contained in the non-woven mat.

Further, the pre-sheet for producing a fiber-reinforced thermoplastic of the present invention comprises at least one nonwoven mat containing one or more non-woven mats containing reinforcing fibers and a thermoplastic resin, and one or more non-woven mats. And a at least one reinforcing fiber sheet adjacent to each other, which is a sheet formed by heat treatment, wherein the reinforcing fiber contained in the reinforcing fiber sheet is more than the reinforcing fiber contained in the nonwoven mat. A sheet with a long average fiber length.

The nonwoven fabric mat is a sheet-like material containing reinforcing fibers and a thermoplastic resin. The non-woven mat can be a non-woven fabric, and can be formed by, for example, an airlaid method, a wet papermaking method, a spunlace method, a needle punch method, or the like.

The nonwoven mat may further contain a heat-fusible resin. For example, when a non-woven mat is formed by the air laid method without using any water, that is, when a non-woven mat is produced by the so-called TDS method (Totally Dry System), the non-woven mat binds its constituent components by heat. For thermal bonding, a heat-fusible resin is contained as an essential component. Since the TDS method does not use water at all, the nonwoven fabric mat can be formed without impairing the functions of the constituent components.

The reinforcing fiber sheet contains reinforcing fibers having an average fiber length longer than that of the reinforcing fibers contained in the nonwoven fabric mat. For example, the reinforcing fiber sheet can be a non-woven fabric, and can be formed by, for example, an airlaid method, a wet papermaking method, a spunlace method, a needle punch method, or the like. Specifically, for example, the reinforcing fiber sheet may be formed by forming the reinforcing fiber into a sheet shape with a card machine and then entwining it with a needle punch.

The reinforcing fiber sheet may be a carrier sheet for an air-laid web when the nonwoven fabric mat is formed by the air-laid method. According to this method, a presheet can be produced in one step (one pass). Further, a pre-sheet having a high interlayer strength between the non-woven mat and the reinforcing fiber sheet can be produced.

The heat treatment can be performed at a temperature equal to or higher than the melting point of the heat-fusible resin to promote interlayer adhesion of each layer in the laminate and binding of constituent components within the layers.

(Pre-sheet layer structure)
The layer structure of the pre-sheet of the present invention includes a structure in which a non-woven mat and a reinforcing fiber sheet are laminated. The layer structure of the pre-sheet of the present invention includes a structure in which a reinforcing fiber sheet is laminated on at least one surface of a laminate of a plurality of nonwoven fabric mats. A reinforcing fiber sheet may be arranged between the layers of the plurality of nonwoven fabric mats. Further, the layer structure of the pre-sheet of the present invention includes a structure in which a nonwoven fabric mat is laminated on at least one surface of a laminated body of a plurality of reinforcing fiber sheets. A non-woven mat may be arranged between the layers of the plurality of reinforcing fiber sheets.

As described above, the pre-sheet of the present invention is a laminated body composed of a plurality of two or more layers. The number of layers included in the pre-sheet and the content of the layers can be variously set depending on the layer thickness of each layer constituting the pre-sheet with respect to the target thickness of the pre-sheet, the desired physical properties of the pre-sheet, and the like. The number of layers included in the pre-sheet of the present invention can be, for example, 2, 3, 4, 5, or more.

For example, the following configurations, which are provided for purposes of illustration and not limitation, are within the scope of the invention.
(1) A structure in which a reinforcing fiber sheet and a nonwoven fabric mat are laminated.
(2) A structure in which a reinforcing fiber sheet, a nonwoven fabric mat, and a reinforcing fiber sheet are laminated in this order.
(3) A structure in which a reinforcing fiber sheet, a non-woven mat and a non-woven mat are laminated in this order.
(4) A configuration in which a reinforcing fiber sheet, a reinforcing fiber sheet, and a non-woven mat are laminated in this order.
(5) A configuration in which a nonwoven fabric mat, a reinforcing fiber sheet, and a nonwoven fabric mat are laminated in this order.
(6) Any combination of the configurations described in (1) to (5) above.
(7) A configuration in which one or more reinforcing fiber sheets or non-woven fabric mats are laminated on the surface or between the configurations in addition to the configurations described in (1) to (6) above.

The possible configuration (6) will be described with an example. For example, when the configuration of (6) is a combination of (1) and (1), as such a configuration, a reinforcing fiber sheet, a nonwoven fabric mat, a reinforcing fiber sheet and a nonwoven fabric mat are laminated in this order. A laminated structure of a reinforced fiber sheet, a non-woven mat, a non-woven mat and a reinforced fiber sheet in this order, and a non-woven mat, a reinforced fiber sheet, a reinforced fiber sheet and a non-woven mat in this order , Can be mentioned. As described above, in the case of combining a plurality of configurations, in addition to stacking the laminates in the same direction (the back and the front are aligned), a configuration in which the front and the back are adjacent to each other is included.

In addition, the possible configuration (7) will be described with an example. For example, when the configuration of (7) is a configuration based on the combination of (2) and (3), such configurations include, for example, a reinforcing fiber sheet, a non-woven mat, a reinforcing fiber sheet, a reinforcing fiber sheet, and a reinforcing fiber sheet. For example, the fiber sheet, the non-woven mat, and the non-woven mat are laminated in this order. This is an example in which a reinforcing fiber sheet is further added between (2) and (3). That is, for example, when one reinforcing fiber sheet is thin, by stacking a plurality of reinforcing fiber sheets in this manner, the thickness and strength of the obtained presheet can be improved.

When a plurality of non-woven mats are contained in one pre-sheet, each non-woven mat may be the same or different. When a plurality of reinforcing fiber sheets are included in one pre-sheet, the reinforcing fiber sheets may be the same or different.

Other layers for the purpose of reinforcing the structure may be arranged between the layers.

(Reinforcing fiber)
Examples of reinforcing fibers applicable to the nonwoven fabric mat and reinforcing fiber sheet of the present invention include carbon fibers (polyacrylonitrile (PAN)-based carbon fibers, pitch-based anisotropic carbon fibers, etc.), inorganic fibers (glass fibers, basalt fibers, titanium). Examples thereof include potassium acid whiskers), organic fibers (aramid fibers, etc.), and the like.

Among the above-mentioned reinforcing fibers, carbon fibers and glass fibers are preferably used because they can further enhance the mechanical properties of the molded product obtained from the presheet.

The reinforcing fibers can be in the form of chopped fibers, for example. Particularly when the nonwoven mat of the present invention is formed by the air laid method, the reinforcing fibers can be in the form of, for example, defibrated chopped fibers.

The average fiber length (Lm) of the reinforcing fibers used in the nonwoven fabric mat of the present invention is preferably 1 mm or more and 100 mm or less, more preferably 2 mm or more and 80 mm or less, and further preferably 2 mm or more and 60 m or less. .. When the average fiber length is within the above range, a web can be easily manufactured and a molded product having high strength can be obtained.

The average fiber length (Ls) of the reinforcing fibers used in the reinforcing fiber sheet of the present invention is preferably 5 mm or more and 100 mm or less, more preferably 5 mm or more and 80 mm or less, and further preferably 5 mm or more and 60 m or less. preferable. When the average fiber length is within the above range, a web can be easily manufactured and a molded product having high strength can be obtained.

Here, in the present invention, the average fiber length (Ls) of the reinforcing fibers mixed in the reinforcing fiber sheet is longer than the average fiber length (Lm) of the reinforcing fibers mixed in the nonwoven fabric mat. That is, in the present invention, it is necessary for the average fiber length to satisfy the relationship of Ls>Lm. When this relationship is satisfied, the non-woven mat contains fibers having a relatively short average fiber length, so that it can be easily deformed and good preformability can be imparted to the obtained presheet. Since the reinforcing fiber sheet contains fibers having a relatively long average fiber length, high strength such as impact resistance can be imparted to the obtained presheet and molded product.

The ratio (Lm)/(Ls) of the average fiber length (Lm) of the reinforcing fibers used in the nonwoven fabric mat of the present invention to the average fiber length (Ls) of the reinforcing fibers used in the reinforcing fiber sheet of the present invention is (Lm)/(Ls)=1/1.5 to 1/20 is preferable, (Lm)/(Ls)=1/2 to 1/17 is preferable, and (Lm)/(Ls )=1/3 to 1/17 is more preferable. When the fiber length ratio (Lm)/(Ls) is within the above range, the average fiber length of the reinforcing fibers contained in each layer constituting the presheet does not extremely differ between adjacent layers. Therefore, it is possible to obtain a molded product having little strength unevenness in the thickness direction and also a molded product having high strength as a whole.

(Chopped fiber)
Here, the chopped fiber is a short fiber obtained by cutting the fiber bundle. The fiber bundle is a bundle of hundreds to thousands of reinforcing fibers bundled with a binding agent such as water or resin. The defibrated chopped fiber is a large number of fibers obtained by defibrating the chopped fiber.

As an example of chopped fibers applicable to the present invention, as chopped carbon fibers, those manufactured by Toho Tenax Co., Ltd. having an average fiber diameter of 4 to 10 μm and an average fiber length of 3 to 13 mm are known. .. Examples of the chopped glass fibers include those manufactured by Owens Corning Co., which have an average fiber diameter of 3 to 18 μm and an average fiber length of 1 to 20 mm. Examples of chopped aramid fibers include those manufactured by Teijin Limited in the form of short-cut fibers (fiber length 0.1 to 5 mm) and short fibers (fiber length 38 to 128 mm) having an average fiber diameter of 10 to 15 μm. Can be mentioned.

(Thermoplastic resin)
The thermoplastic resin has the property of being softened and plasticized when heated to an appropriate temperature and solidified when cooled. In the present invention, the thermoplastic resin is the matrix resin in the fiber reinforced thermoplastic.

The nonwoven fabric mat of the present invention contains a thermoplastic resin as an essential component. The thermoplastic resin applicable to the nonwoven fabric mat of the present invention may be in the form of fibers or particles. From the viewpoint that the strength of the molded product obtained from the pre-sheet becomes higher, the thermoplastic resin is preferably fibrous.

The reinforcing fiber sheet of the present invention may or may not contain a thermoplastic resin. When the reinforcing fiber sheet does not contain a thermoplastic resin, a reinforcing fiber-rich layer is formed in the presheet, and the reinforcing effect in the molded article to be produced is enhanced. Further, when the reinforcing fiber sheet contains a thermoplastic resin, it is possible to adopt a configuration in which the thermoplastic resin is contained in all layers or arbitrary layers of the presheet. By uniformly distributing the thermoplastic resin in each layer of the presheet, it becomes possible to make the strength of the presheet uniform in the thickness direction.

The thermoplastic resin applicable to the reinforcing fiber sheet of the present invention may be in the form of fibers, particles, or pellets. From the viewpoint that the strength of the molded product obtained from the pre-sheet becomes higher, the thermoplastic resin is preferably fibrous.

As the thermoplastic resin, polypropylene (PP), polyethylene terephthalate (PET), nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 612, nylon 6T, nylon 9T, nylon M5T, and other polyamides, polycarbonate, poly Lactic acid, polyetherimide (PEI) and the like can be mentioned. Two or more thermoplastic resins may be used in combination.

The non-woven mat and the thermoplastic resin of the reinforcing fiber sheet forming each layer in one pre-sheet may be the same or different. It is preferable that they are the same from the viewpoint of interlayer adhesiveness of the press-formed product. In addition, by mixing different thermoplastic resins in the reinforcing fiber sheet and the non-woven mat, the physical properties of each layer of the pre-sheet can be arbitrarily changed. This makes it possible to impart a function to the molded product, for example, by making the physical properties of the surface different from that of the interior.

When the thermoplastic resin is fibrous, the fineness of the thermoplastic fiber is preferably 1 dtex to 120 dtex, and more preferably 1 dtex to 85 dtex. The average fiber length of the thermoplastic fibers is preferably 1 to 50 mm, more preferably 1 to 40 mm, and even more preferably 2 to 30 mm. When the fineness and the average fiber length of the thermoplastic fibers are within the above ranges, it is easy to form a nonwoven fabric mat and it is easy to obtain a uniform binding force and a dispersed state.

When the thermoplastic resin is in the form of particles, the average particle diameter of the thermoplastic particles is preferably 1 to 1,000 μm, more preferably 10 to 800 μm.

When the thermoplastic resin is in the form of pellets, one side is preferably 0.1 to 5 mm, more preferably 0.5 to 5 mm.

(Thermal adhesive resin)
The heat-fusible resin in the present invention, which may be blended if necessary, is melted during the preparation of the presheet to bind the reinforcing fiber and the thermoplastic resin depending on the relationship between the melting point and the heat treatment temperature in the presheet preparation process. It is a binder resin that can be applied. The heat-fusible resin can also function as a matrix resin in fiber-reinforced thermoplastics. As described above, in the present invention, both the thermoplastic resin and the heat-fusible resin can be the matrix resin in the fiber-reinforced thermoplastic, but hereinafter, when simply referred to as “matrix resin” in the present specification, Refers to a thermoplastic resin.

The heat-fusible resin may be in the form of fibers or particles. When the presheet is manufactured by a wet method, the heat-fusible resin may have a form in which particles are dispersed in a liquid.

As the heat-fusible resin, polyethylene (PE), polypropylene, low melting point polyethylene terephthalate, low melting point polyamide, low melting point polylactic acid, polybutylene succinate, acrylic, urethane, styrene butadiene copolymer, polyvinyl alcohol (PVA), etc. Is mentioned. Two or more kinds of heat-fusible resins may be used in combination.

When the heat-fusible resin is fibrous, the fineness of the heat-fusible fiber is preferably 1 dtex to 120 dtex, and more preferably 1 dtex to 85 dtex. The average fiber length of the heat-fusible fiber is preferably 1 to 100 mm, more preferably 1 to 60 mm, and even more preferably 2 to 30 mm. When the fineness and the average fiber length of the heat-fusible fiber are within the above ranges, the nonwoven fabric mat can be easily formed, and a uniform binding force and a dispersed state can be easily obtained.

When the heat-fusible resin is in the form of particles, the average particle diameter of the heat-fusible particles is preferably 10 to 1,000 μm, more preferably 20 to 800 μm. When dispersed in an aqueous solution, the average particle diameter of the heat-fusible particles is preferably 10 nm to 100 μm.

(Composite of heat-fusible resin and thermoplastic resin)
The above-mentioned thermoplastic resin and heat-fusible resin may be compounded to form a composite.

As a composite of a thermoplastic resin and a heat-fusible resin, a core-sheath fiber having a core portion made of a thermoplastic resin and a sheath portion made of a heat-fusible resin, half on one side in a cross section perpendicular to the longitudinal direction. Is a heat-fusible resin, and the other half of one side is a side-by-side fiber made of a thermoplastic resin, and core-shell particles having a core made of a thermoplastic resin and a shell made of a heat-fusible resin. Among these, core-sheath fibers are preferably used because different types of resins can be easily compounded.

As the core-sheath fiber, for example, a PP/PE composite core including a core portion made of polypropylene fiber (melting point 160° C.) and a sheath portion made of polyethylene (melting point 130° C.) formed on the outer periphery of the core portion. A sheath fiber is mentioned.

Examples of other core-sheath fibers include PET/low melting point PET composite core-sheath fiber, high density polyethylene/low density polyethylene composite core-sheath fiber, polyethylene/low melting point PET composite core-sheath fiber, polyamide/low melting point polyamide composite. Core/sheath fibers, polylactic acid/low melting point polylactic acid composite core/sheath fibers, polylactic acid/polybutylene succinate composite core/sheath fibers and the like can be mentioned.

Due to the presence of the heat-fusible resin exposed to the outside, these composites can provide the heat-fusibility and can function as a binder. Therefore, these composites can be blended as the heat-fusible resin in the present invention. Further, since these composites contain a thermoplastic resin, strength can be imparted to a molded product obtained from a presheet produced by including the thermoplastic resin.

(Content ratio of each component)
When the presheet does not contain a heat-fusible resin, the ratio A/B of the reinforcing fiber content mass A to the matrix resin content mass B in the presheet is, for example, 10/90 to 90/. It can be 10 and can be 20/80 to 80/20. When the ratio A/B is within the above range, the mechanical properties of the fiber reinforced thermoplastic obtained from the presheet can be sufficiently enhanced.

When the pre-sheet contains the heat-fusible resin, the content mass C of the heat-fusible resin can be 1 to 50 parts, and is 2 to 15 parts, when the total mass of the pre-sheet is 100 parts. You can That is, assuming that the presheet is composed of reinforcing fibers, a thermoplastic resin, and a heat-fusible resin, the content C of the heat-fusible resin is 1 to 50 parts by mass, when the total amount of the presheet is 100 parts by mass. The remaining 99 parts by mass to 50 parts by mass are allocated to the contents of the reinforcing fiber and the thermoplastic resin at the above-mentioned ratio A/B.

When the content ratio of the heat-fusible resin in the entire pre-sheet is high, the strength of the pre-sheet tends to be relatively high when the pre-sheet is produced by a production method including a step of binding constituent components by heating. In addition, when the content ratio of the heat-fusible resin in the entire pre-sheet is low, the strength of the pre-sheet after the hot-pressing step when manufacturing a molded article tends to be high. Although not wishing to be bound by theory, it is considered that when the content ratio of the heat-fusible resin in the whole presheet is low, impurities contained in the molded product are reduced.

(Basis weight)
The basis weight of Pureshito is preferably from 40~4000g / m ^2, more preferably from 100 to 3000 g / m ^2, further preferably 200~3000g / m ^2. When the basis weight of the pre-sheet is equal to or more than the lower limit value, the number of pre-sheets to be laminated can be reduced and the work can be simplified in the hot pressing step when manufacturing a molded product. On the other hand, if the basis weight of the pre-sheet is not more than the upper limit value, the pre-sheet can be easily obtained.

(Effect)
The pre-sheet of the present invention comprises a non-woven mat and a reinforcing fiber sheet arranged adjacent to each other. Both the nonwoven mat and the reinforcing fiber sheet contain reinforcing fibers, and the average fiber length of the reinforcing fibers in the reinforcing fiber sheet is longer than the average fiber length of the nonwoven mat. The pre-sheet of the present invention including a structure in which such a non-woven mat and a reinforcing fiber sheet are composited by heat treatment is given strength and good moldability by the non-woven mat containing the reinforcing fibers having a short average fiber length, Further, the reinforcing fiber sheet containing reinforcing fibers having a long average fiber length imparts higher strength. Therefore, according to the present invention, it is possible to obtain a presheet and a fiber-reinforced thermoplastic molded article having excellent impact resistance, which were not obtained by the nonwoven fabric mat alone.

<Pre-sheet manufacturing method>
The pre-sheet manufacturing method of the present invention includes forming a non-woven mat and forming a reinforcing fiber sheet.

For example, by a known nonwoven fabric manufacturing method such as an airlaid method, a wet papermaking method, a spunlace method, a needle punch method, etc., only a nonwoven fabric mat having no reinforcing fiber sheet is obtained, and the obtained nonwoven fabric mat is separately prepared. A presheet can be produced by laminating and integrating the reinforcing fiber sheet. Further, for example, when a nonwoven fabric mat is produced by the air laid method, the carrier sheet of the air laid method may be the reinforcing fiber sheet according to the present invention.

Examples of methods for forming the reinforcing fiber sheet include an airlaid method, a wet papermaking method, a spunlace method, and a needle punch method. For example, the reinforcing fiber sheet may be formed by forming the reinforcing fiber into a sheet with a card machine and then entwining it with a needle punch.

(Production method of pre-sheet using airlaid method)
Next, a method for manufacturing the pre-sheet of the embodiment using the air laid method will be described in detail. The pre-sheet manufacturing method of the present embodiment includes a defibrating step, a mixing step, a web forming step, and a binding step. Each step will be described below.

(Disentanglement process)
The defibration step is a step of defibrating the chopped fiber with an air flow and/or a mechanical shear to obtain a defibrated chopped fiber.

In the method of defibrating chopped fibers by an air flow, an air flow is formed by a blower or the like, chopped fibers are supplied to the air flow, and the chopped fibers are defibrated by the stirring effect of the air flow. The defibration by the air flow can prevent the reinforcing fibers from breaking and shortening. In particular, carbon fibers and glass fibers are brittle and easily broken by mechanical shearing force, but by breaking with an air flow, breakage can be prevented.

As a defibration method, it is preferable to defibrate with a swirling air flow. According to the defibration method using the swirling airflow, the chopped fiber can be defibrated sufficiently. Therefore, when forming an air-laid web by the air-laid method, the dispersibility of the defibrated chopped fibers can be further enhanced.

Examples of the defibration method using the swirling airflow include a method of introducing chopped fibers into a blower and defibrating with a blower. Further, there is a method in which air is blown into the cylindrical container along a circumferential direction by a blower to form a swirling flow, chopped fibers are supplied into the swirling flow, and the fibers are stirred and defibrated. As a method of using air flow and mechanical shear in combination, there is a method in which a chopped fiber hits the baffle plate by disposing a baffle plate in the blower and the fiber is defibrated by the air flow and mechanical shear. Examples of the method of defibrating with mechanical shear include a method of compressing and spreading a fiber bundle with a roll and a method of carding with a roller having a needle.

The flow velocity of the air flow is appropriately selected according to the amount of chopped fibers, but is usually in the range of 10 to 150 m/sec.

(Mixing process)
The mixing step is a step of mixing the defibrated chopped fiber, the thermoplastic resin, and the heat-fusible resin to obtain a web raw material. An auxiliary agent such as a flame retardant added as necessary can be added in this mixing step.

Upon mixing, in order to improve the dispersibility of the defibrated chopped fiber, it is preferable to stir the defibrated chopped fiber, the thermoplastic resin, and the heat-fusible resin. However, in order to prevent breakage of the defibrated chopped fiber, it is preferable to apply agitation using an air flow instead of agitation using mechanical shearing force.

The mixing step may be performed after the defibration step or simultaneously with the defibration step. When the mixing step is performed simultaneously with the defibrating step, the air flow in the defibrating step is used to mix the defibrated chopped fiber, the thermoplastic resin, and the heat-fusible resin.

(Web forming process)
The web forming step is a step of forming a web from a web material. In this embodiment, the airlaid method is adopted to obtain the airlaid web. Here, the air laid method is a method of forming a web by randomly depositing fibers three-dimensionally using an air flow.

In the web forming step in this embodiment, for example, the web forming apparatus 1 shown in FIG. 2 is used. The web forming apparatus 1 includes a conveyor 10, an air-permeable endless belt 20, a fiber mixture supply unit 30, a first carrier sheet supply unit 40, a second carrier sheet supply unit 50, and a suction box 60.

Here, the conveyor 10 is composed of a plurality of rollers 11. The air permeable endless belt 20 is attached to the conveyor 10 to rotate. The fiber mixture supply means 30 supplies the fiber mixture to the permeable endless belt 20 together with the air flow. The first carrier sheet feeding means 40 feeds the first carrier sheet 41 toward the air-permeable endless belt 20. The second carrier sheet supply means 50 supplies the second carrier sheet 51 toward the first carrier sheet 41 that has passed through the air permeable endless belt 20. The suction box 60 sucks the air permeable endless belt 20 from the inside.

In the web forming apparatus 1, the fiber mixture supply means 30 is installed above the air permeable endless belt 20, the first carrier sheet supply means 40 is installed upstream of the air permeable endless belt 20, and the second carrier sheet. The supply unit 50 is installed downstream of the air permeable endless belt 20.

In the web forming process using the web forming apparatus 1, the rollers 10 are rotated in the same direction to drive the conveyor 10 to rotate the air permeable endless belt 20. Further, the first carrier sheet 41 is fed from the first carrier sheet supply means 40 so as to come into contact with the air permeable endless belt 20.

Next, while suctioning the permeable endless belt 20 by the suction box 60, the fiber mixture is lowered together with the air flow from the fiber mixture supply means 30, and the fiber mixture is dropped onto the first carrier sheet 41 on the permeable endless belt 20. , Deposit. Thereby, the air-laid web A is formed.

Next, the second carrier sheet 51 is supplied onto the air-laid web A by the second carrier sheet supply means 50 to obtain the air-laid web-containing laminated sheet.

The 1st carrier sheet 41 and the 2nd carrier sheet 51 have a function as a conveyance means which conveys an air laid web in an air laid method.

(Binding process)
The binding method is selected from a chemical bond method, a thermal bond method, and a multi-bond method. Either method may be selected, but the thermal bond method is often used from the viewpoint of binding property with the reinforcing fiber. The binding step using the thermal bond method is a step of heating the air-laid web to bind the defibrated chopped fibers to each other with the heat-fusible resin.

Examples of the heat treatment of the air-laid web include hot air treatment and infrared irradiation treatment, and hot air treatment is preferable from the viewpoint of low cost of the apparatus.

As the hot air treatment, a method of heat treating the air-laid web by contacting it with a through-air dryer equipped with a rotating drum having air permeability on the peripheral surface (hot air circulation rotary drum system), or passing the air-laid web through a box type dryer, Examples thereof include a method of heat treatment by passing hot air through the air-laid web (hot air circulating conveyor oven method).

The air-laid web sandwiched between the first carrier sheet and the second carrier sheet to form a laminated sheet, that is, the air-laid web-containing laminated sheet can be treated with hot air as it is. The first carrier sheet and the second carrier sheet can be peeled from the air-laid web after the hot air treatment. In the present embodiment, the first carrier sheet and the second carrier sheet were used as the reinforcing fiber sheet according to the present invention without being separated from the air-laid web.

The heat treatment temperature is preferably a temperature at which the heat-fusible resin melts but the thermoplastic resin does not melt. With such a temperature, it is possible to reliably bind the defibrated chopped fibers to each other and suppress the melting of the thermoplastic resin before forming the presheet.

After the binding step, for the purpose of finely adjusting the thickness and density of the pre-sheet, compression treatment may be performed by passing through a heating roll.

In the method for manufacturing the pre-sheet of the present embodiment, the sheet material to be the reinforcing fiber sheet according to the present invention is used as the carrier sheet that is the conveying means of the air-laid web in the air-laid method. According to the manufacturing method of the present embodiment, the peeling step of peeling the carrier sheet from the nonwoven mat, and the laminating step of laminating the reinforcing fiber sheet on the nonwoven mat obtained by peeling the carrier sheet subsequent to the peeling step are omitted. Therefore, the working efficiency is improved.

In addition, in this embodiment, the web forming apparatus had one fiber mixture supply means. In this web forming apparatus, a presheet having a plurality of nonwoven fabric mats may be obtained by repeating the above steps. Alternatively, the web forming apparatus may be provided with a plurality of fiber mixture supplying means to obtain a presheet having a plurality of nonwoven fabric mats in a single pass process. At this time, a reinforcing fiber sheet or other sheet-like material for the purpose of structural reinforcement or the like may be inserted between the plurality of nonwoven fabric mats.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.

[Example 1]
<Manufacture of pre-sheets>
A chopped PAN-based carbon fiber (fiber diameter 7 μm, fiber length 13 mm) was defibrated using a swirl type jet air flow defibrating device to obtain a defibrated chopped fiber (CF). The processing wind speed in the defibrating machine was 45 m/min, and turbulent flow was made by the baffle provided in the device.

Next, the obtained defibrated chopped fiber (fiber length 13 mm), 6 nylon fiber (fineness 3.3 dtex, fiber length 4 mm, melting point 225° C.), core-sheath type heat-fusible composite fiber (PET/PET composite) A core-sheath fiber, a core melting point of 260° C., a sheath melting point of 130° C., a fineness of 2.2 dtex, and a fiber length of 5 mm) are uniformly mixed by an air flow at a ratio of 35/55/10 (mass ratio) to obtain a fiber mixture. Got

Then, using the web forming apparatus 1 shown in FIG. 2, an air-laid web was formed from the fiber mixture. Specifically, the first carrier sheet feeding means 40 feeds the first carrier sheet 41 onto the permeable endless belt 20 which is mounted on the conveyor 10 and runs. In Example 1, as the first carrier sheet 41, a reinforced fiber sheet manufactured by forming defibrated chopped fibers (fiber length 50 mm) into a sheet by a card machine and then entwining them with a needle punch (basis weight: 100 g/m ² )It was used. The "grammage" was measured according to "Paper and board-Measurement method of grammage" described in JIS P 8124:2011.

While sucking the permeable endless belt 20 by the suction box 60, the fiber mixture was dropped and accumulated from the fiber mixture supply means 30 together with the air flow onto the first carrier sheet 41. At that time, the fiber mixture was supplied so that the basis weight of the air-laid web portion was 500 g/m ² . Here, the air-laid web portion is a portion to be a non-woven mat in the pre-sheet.

Next, the second carrier sheet 51 was laminated on the fiber mixture deposit on the first carrier sheet 41 by the second carrier sheet supply means 50 to obtain an air-laid web-containing laminated sheet. In Example 1, as the second carrier sheet 51, defibrated chopped fibers (fiber length 50 mm) were formed into a sheet by a card machine and then entwined with a needle punch to produce a reinforcing fiber sheet (basis weight 100 g/m ² )It was used. That is, in Example 1, the same reinforcing fiber sheet was used for the first carrier sheet 41 and the second carrier sheet 51.

The obtained laminated sheet was passed through a hot air circulating conveyor oven type box type dryer and subjected to hot air treatment at a temperature of 140° C. to obtain a pre-sheet A having a basis weight of 700 g/m ² . In Example 1, the first carrier sheet 41 and the second carrier sheet 51 are the reinforcing fiber sheets in the pre-sheet.

A presheet B having a basis weight of 600 g/m ² was obtained in the same manner as in the presheet A except that the second carrier sheet was not laminated.

<Production of carbon fiber reinforced thermoplastic moldings>
The presheets A and B were cut into 20 cm×20 cm, and the cut pieces thus obtained were laminated one by one such that the reinforcing fiber sheet and the non-woven mat were alternately arranged, and the length and width were 20 cm×20 cm and the depth was 1 mm. It was placed in a stainless steel mold having an opening. Next, the mold was set in a hot press machine, the temperature was set to the melting point of the matrix resin+30° C., pre-pressed at a pressure of 2 MPa for 3 minutes, further pressurized to 5 MPa and pressed for 10 minutes. Then, it cooled at 5 MPa and obtained the carbon fiber reinforced thermoplastics molded article 1. The obtained molded product had a thickness of 0.96 mm and a density of 1.35 g/cm ³ .

Specifically, in this example, since the pre-sheet contains 6 nylon as a matrix resin, the temperature of the heat press is set to 255° C., which is 30° C. higher than the melting point of 225° C.
Molding was performed. In the present invention, the pre-sheet may contain a plurality of thermoplastic resins as the matrix resin. In that case, the temperature of the heat press machine is such that the main matrix resin with the largest number of parts is melted and decomposed. Set to a temperature that does not occur.

[Example 2]
As the first carrier sheet, except that a reinforced fiber sheet (basis weight 300 g/m ² ) produced by forming defibrated chopped fibers (fiber length 50 mm) into a sheet by a card machine and then entwining them with a needle punch was used. A presheet C having a basis weight of 800 g/m ² was obtained in the same manner as the presheet B of Example 1. That is, the pre-sheet C differs from the pre-sheet B in the basis weight of the reinforcing fiber sheet. Also, a 500 g/m ² presheet D was obtained in the same manner as the presheet B of Example 1 except that the tissue was used as the first carrier sheet to prepare the presheet and then the first carrier sheet was peeled off. That is, the pre-sheet D is different from the pre-sheet B in the presence or absence of the reinforcing fiber sheet, and is made of only the nonwoven fabric mat.

The presheets C and D were cut into 20 cm×20 cm, and the cut pieces thus obtained were laminated one by one so that the nonwoven fabric mat and the reinforcing fiber sheet were alternately arranged. A carbon fiber reinforced thermoplastic molded product 2 was obtained. The obtained molded product had a thickness of 0.96 mm and a density of 1.35 g/cm ³ .

[Comparative Example 1]
Disentangled chopped fiber (fiber length 13 mm), 6 nylon fiber (fineness 3.3 dtex, fiber length 4 mm, melting point 225° C.), core-sheath heat-fusible composite fiber (PET/PET composite core-sheath fiber, core) Part melting point 260°C, sheath part melting point 130°C, fineness 2.2 dtex, fiber length 5 mm) were changed to a ratio (mass ratio) of 45/45/10, and 500 g was carried out in the same manner as in the pre-sheet D of Example 2. A presheet E of /m ² was obtained.

A carbon fiber reinforced thermoplastic molded article 3 was obtained in the same manner as in Example 1 except that the presheet E obtained was cut into a piece of 20 cm×20 cm and three cut pieces thus obtained were laminated. The obtained molded product had a thickness of 0.96 mm and a density of 1.35 g/cm ³ .

[Comparative example 2]
As the first carrier sheet and the second carrier sheet, a reinforced fiber sheet manufactured by forming defibrated chopped fibers (fiber length: 13 mm) into a sheet by a card machine and then entwining them with a needle punch (basis weight: 100 g/m ² A presheet F was obtained in the same manner as the presheet A in Example 1 except for the use of ).

The presheets F and G were cut into 20 cm×20 cm, and the cut pieces thus obtained were laminated one by one such that the reinforcing fiber sheet and the non-woven mat were alternately arranged. A carbon fiber reinforced thermoplastic molded product 4 was obtained. The obtained molded product had a thickness of 0.96 mm and a density of 1.35 g/cm ³ .

<Evaluation>
The flexural modulus, flexural strength, and impact resistance of the obtained molded product were measured by the following methods. The measurement results are shown in the table of FIG.

(Method of measuring flexural modulus and flexural strength of molded products)
The obtained molded product was cut into a width of 15 mm and a length of 100 mm using a diamond cutter to prepare a test piece. After measuring the thickness of the test piece, according to the "bending test method of carbon fiber reinforced plastic" described in JIS K7074, a three-point bending test was performed under the conditions of a speed of 5 mm/min and a fulcrum distance of 80 mm, and bending. The elastic modulus and bending strength were measured. The values of flexural modulus and flexural strength were used as indexes for judging the rigidity of the molded product. The larger the value, the higher the rigidity, and the better the molded product was evaluated.

(Measurement method for impact resistance of molded products)
Using a diamond cutter, the obtained molded product was cut into a width of 10 mm and a length of 100 mm to prepare a test piece. After measuring the thickness of the test piece, the impact resistance was measured by "Charpy impact test of plastic" described in JIS K7111-1. The larger the value, the better the impact resistance and the stronger the impact.

(Measurement result)
The molded articles obtained from the pre-sheets of Examples 1 and 2 are more impact resistant than Comparative Example 1 consisting of a non-woven mat and Comparative Example 2 in which the carbon fibers contained in the reinforcing fiber sheet are relatively short. The flexural modulus and flexural strength were at the same level.

1 Web Forming Device 30 Fiber Mixing Supply Means 41 First Carrier Sheet 51 Second Carrier Sheet A Airlaid Web

Claims (5)

A non-woven mat containing reinforcing fibers and a thermoplastic resin, and a reinforcing fiber sheet containing reinforcing fibers adjacent to the non-woven mat, a sheet formed by heat treatment, the reinforcing The reinforcing fibers contained in the fiber sheet have a longer average fiber length than the reinforcing fibers contained in the non-woven mat,
The non-woven mat is an air-laid web formed by an air-laid method,
A presheet for producing a fiber-reinforced thermoplastic, wherein the reinforcing fiber sheet is a carrier sheet used for conveying the airlaid web in the airlaid method. One or more non-woven mats containing reinforcing fibers and a thermoplastic resin, one or more reinforcing fiber sheets containing reinforcing fibers, at least one said non-woven mat and at least one said reinforcing fiber sheet. Is a sheet formed by heat treatment of a laminate including so as to be adjacent to each other, the reinforcing fibers contained in the reinforcing fiber sheet have a longer average fiber length than the reinforcing fibers contained in the nonwoven mat,
The non-woven mat is an air-laid web formed by an air-laid method,
A presheet for producing a fiber-reinforced thermoplastic, wherein the reinforcing fiber sheet is a carrier sheet used for conveying the airlaid web in the airlaid method. The fiber-reinforced thermoplastics preparation pre-sheet according to claim 1 or 2, wherein the non-woven fabric mat further contains a heat-fusible resin. The said reinforcing fiber sheet is a non-woven fabric, The pre-sheet for fiber reinforced thermoplastics manufacture of any one of Claim 1 to 3 characterized by the above-mentioned. A fiber reinforced thermoplastic molded article obtained by molding and processing a single body or a laminate of the presheet for producing a reinforced thermoplastic according to any one of claims 1 to 4.

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