JP6641918B2 - Housing using fiber-reinforced plastic molded body and method of manufacturing the same - Google Patents

Description

  The present invention relates to a fiber-reinforced plastic molding. Specifically, the present invention relates to a fiber-reinforced plastic molded article containing a reinforcing fiber and a thermoplastic resin. INDUSTRIAL APPLICABILITY The fiber-reinforced plastic molded article of the present invention has excellent bending rigidity and bending strength, and is suitable for use in a thin-shaped housing or the like.

BACKGROUND ART Fiber-reinforced resin molded articles obtained by heating and pressing a non-woven fabric containing a reinforcing fiber such as a carbon fiber or a glass fiber and molded are already used in various fields such as sports, leisure goods, and aircraft materials. In particular, in recent years, the development of fiber-reinforced plastic molding sheets using a thermoplastic resin as the matrix resin and containing reinforced fibers has been promoted because of the advantage that the molding sheets can be stored for a long period of time in a nonwoven fabric state and the molding process is easy. Have been. As such a molding sheet, for example, a fiber-reinforced plastic molding sheet obtained by dispersing and mixing reinforcing fibers such as glass fibers and carbon fibers in the air or a dispersion medium with a fibrous thermoplastic resin. Is disclosed. As the thermoplastic resin used for the fiber-reinforced plastic molding sheet, a polyester resin such as a polycarbonate resin, a polypropylene resin, a polyamide resin, a polyetherimide (PEI) resin, and the like are often used. In particular, polyetherimide (PEI) resin is preferably used depending on the application because it is said that the flame retardancy and heat resistance of the paper substrate (nonwoven fabric) can be improved.
Fiber-reinforced plastic molded articles using the above-mentioned fiber-reinforced plastic molding sheet include, for example, flame-retardant and heat-resistant electromagnetic wave shielding boxes, lighting equipment housings, home appliance housings for personal computers and televisions, and reinforcing materials for housings. , LED board, carrier plate, fuel cell material, battery case, flame-retardant / sound absorbing floor material, aircraft furniture, aircraft interior material, in-flight entertainment machine parts, railway furniture, in-car bulletin board system members, electrical component cases, wiring members, etc. Used for various applications.

  The product stiffness of these compacts increases in proportion to the cube of the wall thickness when compared at the same density. However, as the wall thickness increases, the weight of the product increases and the cooling time increases, resulting in poor productivity. There was a problem that On the other hand, if the molded body is made thinner for weight reduction, the rigidity is insufficient, and when the product is obtained, the unevenness of the internal component structure can be felt and the quality of the product is impaired. . For this reason, it has been adopted to improve the rigidity of the product while suppressing the weight of the molded product by using an injection molded product in which a rib is provided on the back side of the molded product. The provided fiber reinforced resin molded product has been proposed. However, in the case of an injection molded product using a thermoplastic resin containing reinforcing fibers, the fiber length of the reinforcing fibers dispersed in the thermoplastic resin cannot be increased, and it is difficult to improve the mechanical strength of the molded product. there were. Further, in the first place, since the resin containing the reinforcing fiber has low fluidity, it is difficult to produce a thin injection molded body itself. In order to solve this problem, a method has been proposed in which a nonwoven fabric made of reinforcing fibers is previously placed in a mold and a thermoplastic resin is injection-molded, as in Patent Document 2. However, it is extremely difficult to completely impregnate a nonwoven fabric with a thermoplastic resin having a high melt viscosity. Therefore, molding cannot be said to be as easy as a molded article using a fiber-reinforced plastic molding sheet containing a reinforcing fiber using a thermoplastic resin as a matrix resin. Therefore, there is a demand for a fiber-reinforced plastic molded body capable of easily and mass-producing a thin molded article having excellent rigidity and strength. Furthermore, there is a demand for a multi-thick fiber-reinforced plastic molded article having a thin portion and receiving a difference in height of internal components.

JP-A-11-229684 Re-published WO2011 / 118226

In view of the above circumstances, the present inventors have manufactured a thin-shaped molded product that uses a thermoplastic resin as a matrix resin, contains reinforcing fibers, can be easily molded, and has excellent rigidity and strength. The possible fiber-reinforced plastic moldings were studied diligently. As a result, a fiber-reinforced plastic molded body having a high-density region and a low-density region can be easily molded, and is a lightweight and thin shape, yet has high rigidity and bending strength. Was obtained, and the present invention was completed.
According to the present invention, the high-density region and the low-density region are made to have a difference in wall thickness, and the respective regions are arranged according to the height difference of the device internal components, so that the difference in height of the device internal components can be felt. It is possible to manufacture a housing that can be hidden from the user.
Specifically, the present invention has the following configuration.

[1] A fiber-reinforced plastic molded article containing a reinforcing fiber and a thermoplastic resin and having a thin high-density region and a thick low-density region on its surface, wherein the porosity of the low-density region is 78% or less, A fiber-reinforced plastic molding characterized by having a porosity greater than that of a high-density region.
[2] The fiber-reinforced plastic molded article according to [1], wherein the porosity of the high-density region is 10% or less, and the porosity of the low-density region is larger than that of the high-density region.
[3] The fiber-reinforced plastic molding according to [1] or [2], wherein the porosity of the low-density region is 60% or more, and the porosity of the high-density region is smaller than that of the low-density region. body.
[4] The above-mentioned [1] to [3], wherein the mass ratio of the reinforcing fiber to the thermoplastic resin contained in the fiber-reinforced plastic molded product is 35:65 to 65:35 (% by mass). The fiber-reinforced plastic molded article according to any one of the above.
[5] The fiber-reinforced plastic molded article according to any one of [1] to [4], wherein the outer edge of the fiber-reinforced plastic molded article is a high-density region.
[6] The ratio according to any one of [1] to [5], wherein the high-density region accounts for 5 to 70% of the entire area of the fiber-reinforced plastic molded body. Fiber-reinforced plastic moldings.
[7] The fiber-reinforced plastic molding according to any one of [1] to [6], wherein the fiber-reinforced plastic molding has a high-density region substantially surrounded by a low-density region. body.
[8] The reinforcing fibers described above, wherein the reinforcing fibers have an average fiber length of 55 mm or less, an average fiber diameter of 20 µm or less, and have no glass transition point at 210 ° C or less. The fiber-reinforced plastic molded article according to any one of [7].
[9] The fiber-reinforced plastic molded article according to any one of [1] to [8], wherein the reinforcing fiber component is an inorganic fiber.
[10] The fiber-reinforced plastic molded article according to [9], wherein the inorganic fibers include glass fibers having a flat cross-sectional shape.

[11] The fiber-reinforced plastic molded article according to any one of [1] to [10], wherein the thermoplastic resin has an LOI value (limit oxygen index) of 25 or more.
[12] The thermoplastic resin is one or more thermoplastic resins selected from the group consisting of a polycarbonate resin, a polyetherimide resin, a polyphenylene sulfide resin, and a polyether sulfone resin [1] to [1]. The fiber-reinforced plastic molded article according to any one of [11].
[13] The fiber-reinforced plastic molded article according to any one of [1] to [12], which has flame retardancy of UL-94 standard HB level or higher.
[14] The fiber-reinforced plastic molded article according to any one of [1] to [13], having a thermoplastic resin layer on a surface.

[15] A fiber-reinforced plastic molded article including (A) a step of obtaining a sheet for forming a fiber-reinforced plastic containing a reinforcing fiber and a thermoplastic resin, and (B) a forming step of forming and processing the sheet for forming a fiber-reinforced plastic. (B) in the forming step, the fiber-reinforced plastic molding sheet is heated to a temperature at which at least a portion of the thermoplastic resin is melted, and at the same time, pressurized at different pressures to reduce the temperature. A method for producing a fiber-reinforced plastic molded body, comprising a heating and pressurizing step of providing a high-density region and a high-density region.

[16] In the heating and pressurizing step, the area of 5 to 70% of the area of the fiber-reinforced plastic molded body is pressurized at a pressure higher than the pressure applied to the entire fiber-reinforced plastic molded body. The method for producing a fiber-reinforced plastic molded product according to [15].
[17] The heating and pressurizing step includes a step of pressing a mold having an uneven shape against the fiber-reinforced plastic molding sheet to perform molding processing [15] or [16]. The method for producing a fiber-reinforced plastic molded article according to the above.
[18] The method according to any one of [15] to [17], wherein the heating and pressurizing step includes a step of heating the sheet for molding a fiber-reinforced plastic containing a reinforcing fiber and a thermoplastic resin to Tg to Tg + 200 ° C. A method for producing a fiber-reinforced plastic molded product according to the above item. (However, Tg represents the glass transition temperature of the thermoplastic resin.)
[19] The fiber reinforcement according to any one of [15] to [18], wherein two or more fiber-reinforced plastic molding sheets are laminated and molded in the heating and pressurizing step. Manufacturing method of plastic molded body.
[20] A lightweight keyboard housing for a personal computer, which is the fiber-reinforced plastic molded article according to any one of [1] to [14].

ADVANTAGE OF THE INVENTION According to this invention, the fiber reinforced plastic molded object which can manufacture a thin molded article excellent in rigidity and strength easily and in large quantities can be obtained. That is, a fiber-reinforced plastic molded article having high rigidity and bending strength, which is easily formed, is lightweight and thin, and is advantageous in flame retardancy, is a flame-resistant and heat-resistant electromagnetic shielding box. , Lighting equipment housings, home appliance housings for PCs and televisions, and reinforcing materials for housings, LED boards, carrier plates, fuel cell members, battery cases, flame-retardant and sound-absorbing flooring materials, aircraft furniture, aircraft interior materials, It is suitably used for various applications such as in-flight entertainment mechanical parts, railway furniture, in-vehicle bulletin board system members, electrical component cases, wiring members, and the like.
Further, according to the present invention, the high-density region and the low-density region are made to have a difference in thickness, and the respective regions are arranged in accordance with the height difference of the internal components of the device. It is possible to manufacture a housing that can be hidden from the tactile sensation. Therefore, various lightweight mobile devices, for example, mobile phones, electronic paper terminals, lightweight personal computers, commercial POS terminals, portable televisions, portable navigation systems, and their accompanying devices, such as keyboards, pointing devices, covers, protectors, thin speakers, It is suitable for use as an image input device.

FIG. 1 is a bird's-eye view showing an example of the shape of the fiber-reinforced plastic molding of the present invention. FIG. 2 is a deflection-bending load curve (SS curve) showing the behavior of the bending stiffness and the bending strength of each region having a different porosity of the fiber-reinforced plastic molded article of the present invention.

  Hereinafter, the present invention will be described in detail. The description of the components described below may be made based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In addition, in this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

(Fiber reinforced plastic molding)
The present invention relates to a fiber-reinforced plastic molding containing a fiber component (reinforced fiber) and a thermoplastic resin. In the fiber-reinforced plastic molded article of the present invention, a thin-walled high-density region and a thick-walled low-density region are arranged in the plane direction, and the porosity of the thin-walled high-density region is increased by the porosity of the thick-walled low-density region. It is a larger fiber-reinforced plastic molding. Note that the density is a value obtained by dividing the mass of a certain region by the apparent volume of the region.
In the high-density region of the fiber-reinforced plastic molded article of the present invention, the voids between the reinforcing fibers are filled with the molten thermoplastic resin, and the porosity is low. In the low-density region, the reinforcing fibers are bonded by a thermoplastic resin with a space between the fibers, and the porosity and the thickness are large. The porosity is a ratio of a void volume obtained by subtracting an actual volume of a material constituting the region from an apparent volume of the region to an apparent volume of the region, and is a molded body having the same mass per area. In this case, the flexural rigidity increases as the porosity increases and the thickness increases, but if the porosity exceeds 78%, the adhesion between the reinforcing fibers becomes insufficient, and the reinforcing fibers are liable to come off. Are adjusted to a porosity of 78% or less.
The bending strength of a certain region of the molded body is the magnitude of the load at the yield point due to the bending load applied to the region. Up to a porosity of about 60%, the bending strength increases as the porosity decreases, but the bending strength decreases as the porosity is further reduced to make the region thinner.

The fiber-reinforced plastic molded article of the present invention is a fiber-reinforced plastic molded article having a thin high-density region and a thick low-density region disposed on a surface. In order to use a molded shape using the difference in thickness between the thick portion and the thin portion, it is preferable that the high-density region be thin and the porosity be 10% or less. On the other hand, the porosity of the low-density region is preferably 60% or more and 78% or less in order to ensure that the low-density region is sufficiently thick and the bending rigidity of the fiber-reinforced plastic molded body is secured.
The flexural rigidity and flexural strength of the fiber-reinforced plastic molded article of the present invention can be measured according to JIS K7171-1994 Plastics-Bending property test method.

The mass ratio of the reinforcing fiber to the thermoplastic resin contained in the fiber-reinforced plastic molded article of the present invention is preferably 20:80 to 80:20, more preferably 30:70 to 70:30, respectively. The ratio is more preferably from 40:60 to 60:40. By setting the content mass ratio of the reinforcing fiber and the thermoplastic resin within the above range, it is possible to effectively increase the bending strength of the fiber-reinforced plastic molded article and achieve high bending rigidity.
In the present invention, the content ratio by mass of the reinforcing fibers to the thermoplastic resin is preferably substantially constant in the entire region of the fiber-reinforced plastic molded product. The fact that the content ratio between the fiber component and the thermoplastic resin is substantially constant indicates that the content ratio may vary by ± 5%.

In the high-density region of the fiber-reinforced plastic molded article of the present invention, at least a part of the thermoplastic resin is dissolved and solidified. Thereby, the amount of air contained between the fibers is reduced, and the fibers are firmly bonded. As described above, the strength of the fiber-reinforced plastic molded body is increased at a portion having strongly bonded fibers. It is preferable that the density of the high-density region is higher because the strength of the fiber-reinforced plastic molded body can be increased, and the density can be increased to be equal to the density of the material used. The outer edge of the fiber-reinforced plastic molding is preferably a high-density region. Here, the outer edge of the fiber-reinforced plastic molded body is a region including the outer peripheral edge of the fiber-reinforced plastic molded body, and refers to a portion formed to have a substantially constant width along the outer peripheral edge. In the case where the fiber-reinforced plastic molded article is rectangular, the constant width is preferably 1 to 20% of the total length of one side of the square including the width, and is preferably 2 to 10%. Is preferred. When the fiber-reinforced plastic molded article is not square but circular or the like, it has a high density of a substantially constant width so as to occupy 1 to 30%, preferably 2 to 20% of the area of the fiber reinforced plastic molded article. Preferably, a region is formed. By making the outer edge portion a high-density region in this way, it is possible to prevent the reinforcing fibers from scattering or falling off from the fiber-reinforced plastic molded body. In addition, by making the outer edge of the molded body a high-density region, the corners and edges have a strong structure, so that the strength of the fiber-reinforced plastic molded body can be effectively increased.

On the other hand, when the density of the low-density region is extremely low, the fiber components and the fibrous thermoplastic resin contained in the low-density region are not preferable because they scatter or fall off from the fiber-reinforced plastic molded body. In particular, when a fiber-reinforced plastic molded article is used for precision equipment such as electronic equipment, such scattering or dropping of fiber components is not preferable because it causes serious problems in electronic equipment. The porosity of the low density region is preferably adjusted in the range of 20 to 78%.

The fiber-reinforced plastic molded product of the present invention has a high-density region and a low-density region as described above, and is formed into a housing-shaped molded product with a difference in the thickness of each region, while being lightweight and thin. Thus, it is possible to obtain a fiber-reinforced plastic molding having high rigidity and bending strength. The ratio of the high-density region to the entire area of the fiber-reinforced plastic molded article of the present invention is 5 to 70%, more preferably 10 to 65%, and still more preferably 15 to 60%. . The ratio occupied by the low-density region is preferably from 30 to 95%, more preferably from 35 to 90%, even more preferably from 40 to 85%. In addition, in order to obtain a fiber-reinforced plastic molded body that is hard to bend and has high strength while having a thin shape, it is necessary that a high-density region to be thin is substantially surrounded by a low-density region having large thickness and rigidity. preferable. Here, “substantially surrounded” means that the low-density region is provided in 70% or more around the high-density region, more preferably 80% or more, and more preferably 90% or more. More preferred. In addition, a region having an intermediate density may be provided in part or all between the high-density region and the low-density region. For example, when the fiber-reinforced plastic molded article of the present invention is used for a housing of an electric appliance such as various lightweight mobile devices, for a wiring or the like, a low-density region within a range that does not impair the effects of the present invention. An unenclosed part can be provided.

  FIG. 1 is a diagram showing an example of the fiber-reinforced plastic molded article of the present invention. A high-density region (region 1) having a porosity of 0% and a rectangular region 2 having a porosity of 50% and having a porosity of 50% adjacent to the region 1 are provided in a central portion. It is a sketch of the molded object provided so that the low-density area | region (area | region 4) shifted | deviated and surrounded it. In the low density region, a slightly smaller rectangular region 3 having a porosity of 66% is provided alongside the high density region, and a high density region having a porosity of 0% is provided at the outer edge. .

FIG. 2 shows a deflection-bending load curve (SS curve) of the fiber-reinforced plastic molded product of Example 1 measured for each region having a different porosity. The mass around the area of each region of the molded body is the same, and the comparison is made in a state where the region with a higher porosity has a larger thickness of the sample.
The rising slope of the bending-bending load curve indicates the stiffness of each porosity region, and shows the behavior of yielding when a certain load is reached. When the porosity decreases from 75% to 66%, the stiffness slightly decreases, but the yield point (the magnitude of the bending stress when yielding) increases. Further, when the porosity is reduced to 50%, the rigidity is considerably reduced, and the yield point is also reduced. When the porosity decreases to 0% (high-density region), the rigidity further decreases, and the yield point also decreases.

  The average film thickness in the high-density region of the fiber-reinforced plastic molded body is not particularly limited, but is preferably 0.3 to 50 mm in order to have general mechanical strength and to be a lightweight structural material. It is more preferably 5 to 30 mm, and further preferably 0.5 to 10 mm. The average film thickness of the low-density region is preferably from 1.5 to 150 mm, more preferably from 2.0 to 90 mm, and even more preferably from 2.0 to 30 mm. By setting the average film thickness of the high-density region and the average film thickness of the low-density region of the fiber-reinforced plastic molded body within the above ranges, it is suitable for use as a housing and at the same time, obtains sufficient strength and rigidity. be able to. Further, as a fiber-reinforced plastic molded body, a plurality of sheets for a fiber-reinforced plastic molded body may be laminated to adjust the porosity and thickness of a target region.

(Reinforced fiber)
The reinforcing fiber used in the present invention functions to increase the strength and rigidity of the fiber-reinforced plastic molded body. The average fiber length of the reinforcing fibers is preferably 55 mm or less, more preferably 5 to 50 mm, and even more preferably 10 to 45 mm. If the average fiber length of the reinforcing fibers is longer than the upper limit, the fibers are not uniformly dispersed, and the uniformity in the fiber-reinforced plastic molded article and the uniformity of the mixing ratio with the reinforcing fibers tend to decrease. If it is shorter than the lower limit, the strength and rigidity of the fiber-reinforced plastic molded article tend to decrease.
Further, the average fiber diameter is preferably 20 μm or less. If the average fiber diameter of the reinforcing fibers is larger than the above upper limit, the flexibility of the nonwoven fabric may be inferior, or the skin or the eyeball may be damaged.
The reinforcing fiber used may have a single fiber diameter and a single fiber length, or may have different fiber diameters and fiber lengths.
At a temperature at which the thermoplastic resin melts or softens, the reinforcing fibers preferably do not soften, deform, or flow, and preferably do not have a glass transition temperature at a temperature of 210 ° C. or less. As such a reinforcing fiber, for example, a reinforcing fiber using a high heat-resistant resin having a glass transition temperature of 210 ° C. or more, an intangible fiber having no glass transition temperature, or the like can be used. In the present invention, a reinforcing fiber having a glass transition temperature of 210 ° C. or lower and a glass fiber having a glass transition temperature of 210 ° C. or higher as described above and a non-reinforced fiber having no glass transition temperature 1 shows a reinforcing fiber exemplified as a fiber. Such a reinforcing fiber preferably has no glass transition temperature at 220 ° C. or lower, and more preferably has no glass transition temperature at 230 ° C. or lower.

The reinforcing fiber used is not particularly limited as long as it satisfies the above conditions and does not hinder the strength and rigidity of the fiber-reinforced plastic molded article. Examples of the reinforcing fibers that can be used in the present invention include, for example, aramid fibers, inorganic fibers such as glass fibers, ceramic fibers, and rock wool fibers. Among them, it is particularly preferable to use glass fiber in view of the balance between price, heat resistance, and availability. Glass fibers include types such as E glass and S glass, but are not particularly limited. Generally, it is efficient to use E glass which is easily available. The average fiber diameter of the glass fibers is preferably 3 μm or more because glass fibers having a diameter of less than 3 μm are feared to affect the human body. As the reinforcing fibers, other fibers may be used in combination with the glass fibers, and for example, fibers such as carbon fibers, metal fibers, and ceramic fibers may be mixed. However, the glass fiber content is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more of the whole reinforcing fibers.
Further, flat glass fibers are also preferably used as the inorganic fibers. By using a glass fiber having a flat fiber cross section as the reinforcing fiber, the bending strength of the molded body can be improved.

(Thermoplastic resin)
As the thermoplastic resin used for the fiber-reinforced plastic molded article of the present invention, it is preferable to use a highly heat-resistant and flame-retardant thermoplastic resin called a so-called engineering plastic. There is also a super-engineering plastic having higher heat resistance.
The thermoplastic resin used in the fiber-reinforced plastic molded article of the present invention has an LOI value (limit oxygen index) of 25 or more in a fibrous state. Here, the “LOI value (limit oxygen index)” indicates the oxygen concentration necessary for continuing combustion, and refers to a numerical value measured by a method described in JIS K7201. That is, when the limiting oxygen index is 20 or less, it indicates that combustion takes place in normal air. The LOI value (critical oxygen index) may be 25 or more, preferably 27 or more, and more preferably 30 or more. By setting the LOI value (critical oxygen index) within the above range, the fiber-reinforced plastic molded article can exhibit high flame retardancy.

  The glass transition temperature of the thermoplastic resin is preferably 140 ° C. or higher. Even if the glass transition temperature is lower than this, it is preferable that the resin has a deflection temperature under load of 190 ° C. or higher. Note that the glass transition temperature of the thermoplastic resin is preferably lower than the glass transition temperature of the above-described fiber component. Thus, when the molded sheet is subjected to the heat and pressure treatment, only the thermoplastic resin can be melted.

As the thermoplastic resin, polycarbonate resin (PC), polyetherimide resin (PEI), polyphenylene sulfide resin (PPS), polyethersulfone resin (PES), polyetheretherketone resin (PEEK), polyamideimide resin (PAI) And polyether ketone ketone resin (PEKK), but are not limited thereto.
Among these, one or more thermoplastic resins selected from the group consisting of polycarbonate resins, polyetherimide resins, polyphenylene sulfide resins, and polyether sulfone resins are particularly preferably used. Before the heat treatment, the thermoplastic resin may be present as a powder or a fibrous form. However, when the thermoplastic resin is in a fibrous form, uniform mixing with a fiber component and sheet strength during production are not sufficient. Is particularly preferred. As the thermoplastic resin fiber, it is preferable to use PEI fiber obtained by fiberizing polyetherimide. Since the PEI resin has an extremely small smoke emission amount, the LOI value in a molten and molded state is 40 or more, and the smoke emission amount during 20 minutes combustion measured by the method described in ASTM E-662 is around 30 ds. It is preferably used. Polycarbonate resins are also preferably used because they have excellent adhesiveness to reinforcing fibers, have heat insulating properties and self-extinguishing properties, and are used as thermoplastic resin fibers.

  The thermoplastic resin used for the fiber-reinforced plastic molded article of the present invention is required to be sufficiently fluid under a temperature condition of 220 to 400 ° C. when the fiber-reinforced plastic molded article is subjected to heat and pressure treatment. Can be In addition, it is preferable that the fibrous state can be sufficiently maintained under the heating conditions in the production stage of the nonwoven fabric sheet before the heat and pressure treatment. Therefore, the glass transition temperature of the fiberized engineering plastic fiber is preferably 140 ° C. or higher. Even if the glass transition temperature is lower than this, it is preferable that the resin has a deflection temperature under load of 190 ° C. or higher. In general, engineering plastics have a high melt viscosity, so if a large amount of reinforcing fibers are blended by a method such as injection molding, it is difficult to uniformly disperse the reinforcing fibers, so there is a limit to the compounding ratio of the reinforcing fibers. . However, in the fiber-reinforced plastic molded article of the present invention, the ratio between the reinforcing fiber and the matrix resin fiber can be set relatively freely according to the required strength.

  The thermoplastic resin forms binding points at the intersections of the matrix or the reinforcing fibers during the heating and pressurizing treatment. Such a sheet for a non-woven fiber reinforced plastic molded article using a reinforcing fiber and a thermoplastic resin does not require an autoclave treatment as compared with a fiber reinforced plastic molded article using a thermosetting resin, and is not required for processing. Heat and pressure molding time is short, and productivity can be increased. However, in order to heat-press the fiber-reinforced plastic molded body in a short period of time, it is necessary that the thermoplastic resin used is rapidly melted under high temperature conditions. The fiber diameter is preferably small. This is because when the fiber diameter is small, the number of contact points between the fibers increases, so that the contact area between the fibers increases, and the heat conduction becomes good. In addition, since the heat capacity of the fiber is reduced, the amount of heat required for melting is reduced.

  The average fiber length of the thermoplastic resin fibers is not particularly limited, but is preferably 55 mm or less, more preferably 5 to 50 mm, and further preferably 10 to 45 mm. By setting the average fiber length of the thermoplastic resin fibers within the above range, the strength of the molded sheet can be effectively increased. If the average fiber length is longer than the above upper limit, the fibers are not uniformly dispersed, and the uniformity of the sheet and the uniformity of the mixing ratio with the fiber component are reduced. On the other hand, if the length is shorter than this, the strength of the molded sheet is reduced, and breakage or the like is likely to occur in the manufacturing process. The thermoplastic resin fibers used may have a single fiber diameter and a single fiber length, or may have different fiber diameters and fiber lengths.

  The average fiber diameter of the thermoplastic resin fibers is preferably 4 times or less, more preferably 3 times or less, the average fiber diameter of the reinforcing fibers, and the average fiber diameter of the thermoplastic resin fibers and the average fiber diameter of the reinforcing fibers. Is more preferably about the same. According to the study of the present inventors, the average fiber diameter of the thermoplastic resin fiber and the reinforcing fiber is preferably 30 μm or less, more preferably 20 μm or less. Thereby, the reinforcing fibers and the thermoplastic resin fibers are easily mixed uniformly, and a fiber-reinforced plastic molded article having high strength can be obtained.

(Other components)
The fiber-reinforced plastic molding of the present invention may further contain a binder component. The binder component functions to fill the gaps between the layers and increase the strength, suppress the fluffing of the surface, and exert the effect of improving the sheet strength in the sheet manufacturing process. As the binder component, when the thermoplastic resin is a PEI resin or a polycarbonate resin, a binder compatible with the PEI resin or the polycarbonate resin (fiber) is preferable in order to maintain a binder force (binding force) and heat resistance. Examples thereof include a polyester resin and a modified polyester resin. Further, an acrylic resin, an epoxy resin, an SBR resin, a polyvinyl alcohol resin, or the like can be used. However, since the LOI value of the binder component is generally lower than that of engineering plastics used for a thermoplastic resin, a high binder content impairs flame retardancy. For this reason, the content of the binder is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less, based on the total mass of the fiber-reinforced plastic molded body. preferable.
Each region of the fiber-reinforced plastic molded article of the present invention has a flame retardancy higher than the HB level in UL-94 standard.

  The method of adding the binder component is not particularly limited, and powder or fibrous materials may be added or sprayed. Further, a liquid or resin emulsion may be added at the time of papermaking, or may be added by spraying (shower or the like), coating, impregnating, or the like. Alternatively, it may be added and coated in advance to other sheet components such as reinforcing fibers.

  The surface of the fiber-reinforced plastic molding of the present invention can have a thermoplastic resin layer. As the thermoplastic resin forming the thermoplastic resin layer, an engineering plastic or a super engineering plastic as used in the above-mentioned fiber-reinforced plastic molded article containing the reinforcing fiber and the thermoplastic resin can be used. The thickness of the thermoplastic resin layer provided on the surface of the molded body is not necessarily limited, but is preferably in the range of 10 to 100 μm. By providing a thermoplastic resin layer on the surface of the low-density region, the strength and flame retardancy of the region can be improved. The method of providing the thermoplastic resin layer is not particularly limited, and a method of laminating a thermoplastic resin film on the surface side to form a fiber-reinforced plastic molded product, or a method of forming a thermoplastic resin film on the surface of the fiber-reinforced plastic molded product Can be used as appropriate, such as a method of laminating or bonding and a method of coating the surface of a fiber-reinforced plastic molded article.

(Method of manufacturing fiber-reinforced plastic molded body)
The method for producing a fiber-reinforced plastic molded article according to the present invention comprises: (A) a step of obtaining a sheet for a fiber-reinforced plastic molded article containing reinforcing fibers and a thermoplastic resin; and (B) molding the sheet for a fiber-reinforced plastic molded article. It includes a forming step for processing.
(A) In the step of obtaining a sheet for a fiber-reinforced plastic molded article, a general method of obtaining a nonwoven fabric sheet by a dry method or a wet method can be used. The dry method, particularly the air laid method, is suitable in that a nonwoven sheet having a bulky and high basis weight can be obtained. On the other hand, a nonwoven fabric manufacturing method by a wet method is preferable in that a uniform and wide nonwoven fabric sheet can be obtained relatively easily.

  (B) The forming step includes heating the sheet for a fiber-reinforced plastic molded body to a temperature at which at least a part of the thermoplastic resin is melted, and simultaneously applying different pressures to the low-density region and the high-density region. And a heating and pressurizing step. In the heating and pressurizing step, the pressure applied to the sheet for a fiber-reinforced plastic molded article differs between the low-density region and the high-density region arranged in the plane direction.

  In the heating and pressurizing step, a pressure higher than the average pressure is preferably applied to a region of 5 to 70% of the sheet for a fiber-reinforced plastic molded product. The area subjected to pressure treatment at a pressure higher than the average pressure is a high-density area, and the other areas are low-density areas. In addition, pressure may not be applied to the low-density region, and pressure treatment may be performed so that a pressure lower than the average pressure is applied.

  In the heating and pressurizing step, it is preferable that a mold having an uneven shape is pressed against a sheet for a fiber-reinforced plastic molded body to perform a molding process. Specifically, the heating and pressurizing treatment can be performed by pressing a pre-heated concave-convex mold against a sheet for a fiber-reinforced plastic molded product. When the mold is brought into contact with the sheet for the fiber-reinforced plastic molded article, a low-density region is formed in a place where a space can be formed between the mold and the sheet for the fiber-reinforced plastic molded article, and the mold and the fiber A high-density region is formed at a place where little space is formed between the sheets for a reinforced plastic molded product. In the present invention, the shape of the low-density region can be freely changed by changing the concave-convex shape of the mold into various shapes, and the area of the low-density region can be appropriately changed. Therefore, according to the present invention, the difference in thickness between the high-density region and the low-density region is determined, and the respective regions are arranged according to the difference in height between the internal components of the device. It is possible to manufacture a housing that can be hidden from the user.

  In the heating and pressurizing step, it is preferable to heat the fiber reinforced plastic molded body sheet so that the surface temperature of the sheet becomes Tg to Tg + 200 ° C. Here, Tg represents the glass transition temperature of the thermoplastic resin. That is, by heating to a temperature at which the thermoplastic resin fibers flow, a high-density region is formed. The heating temperature is preferably a temperature at which the thermoplastic resin fibers flow, and a temperature range in which the reinforcing fibers do not melt. By setting such a temperature zone, the strength of the fiber-reinforced plastic molded body can be increased.

  In the step of obtaining a nonwoven sheet, for example, a mixed weaving method in which reinforcing fibers and thermoplastic resin fibers are alternately knitted, or a chopped strand in which reinforcing fibers and thermoplastic resin fibers are cut to a certain length is dispersed in the air. A method of forming a web by trapping in a net (a dry nonwoven method), a method of dispersing both chopped strands in a solvent, and then removing the solvent to form a web (a wet nonwoven method) can be used.

  In the nonwoven fabric sheet before the heating and pressurizing treatment, voids are present in the sheet because the thermoplastic resin and the reinforcing fibers cross each other. Therefore, unlike the nonwoven fabric in which the resin is completely filled between the fibers, such as the melting method (hot melt method), the solvent method, the dry powder coating method, the powder suspension method, the resin film impregnation method (film stacking method), thermoforming Before, the sheet itself is flexible and drapable, and it can be stored and transported in a rolled form, and it can be heated and pressed after it is arranged along a curved mold, and it is easy to handle The feature is that it is excellent. Further, when processed into a molded sheet, a low density region and a high density region can be formed.

  When the binder is contained in the nonwoven fabric sheet, the binder is mixed in the process of forming the nonwoven fabric sheet, or after the nonwoven fabric sheet is formed, the liquid or emulsion-like binder is sprayed, coated or impregnated into the sheet. Can be granted. The binder is preferably contained so as to concentrate on both surface layers of the nonwoven fabric sheet. Thereby, scattering, fluffing, and falling off of the surface fibers can be suppressed, and a molded sheet excellent in handleability can be obtained. Further, it is preferable that a binder is also contained in the inside (middle layer) of the nonwoven fabric of the sheet in order to maintain the interlayer strength of the sheet.

  In the present invention, a single nonwoven fabric sheet may be subjected to a heat and pressure treatment, or a plurality of laminated nonwoven sheets may be subjected to a heat and pressure treatment so as to have a desired thickness. By processing a laminate of a plurality of nonwoven sheets, it is possible to obtain a molded sheet having better sound absorbing properties. Further, by processing a laminate of a plurality of nonwoven fabric sheets, a heat insulating effect can be exhibited, and it is preferably used as an electronic device or a building material.

  The molded sheet manufactured by the above steps can exhibit an excellent sound absorbing effect and has sufficient strength. In addition, since it has excellent heat insulating properties, it can be applied to all uses.

(Housing for lightweight keyboard for personal computer)
INDUSTRIAL APPLICABILITY The fiber-reinforced plastic molded article of the present invention can be suitably used for a keyboard housing for a personal computer since a fiber-reinforced plastic molded article having high bending rigidity and bending strength can be obtained while being lightweight and thin. According to the present invention, the high-density region and the low-density region are made to have a difference in wall thickness, and the respective regions are arranged according to the difference in height of the device internal components. A housing that can be hidden can be manufactured.

  Hereinafter, features of the present invention will be described more specifically with reference to examples and comparative examples. Materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples described below.

(Example 1)
45 parts by mass of a polycarbonate fiber chop (fiber diameter 30 μm, fiber length 15 mm) made from a polycarbonate resin having a fiber diameter of 9 μm, a fiber length of 18 mm and a LOI value of 27 by a melt spinning method, and a sheath portion And 5 parts by mass of a core-sheath binder fiber (N-720 manufactured by Kuraray Co., Ltd.) using PET fiber in the core. The amount of water was set to be 200 times the weight of the input fiber (0.5% as the fiber slurry concentration).
To this slurry, as a dispersant, "Emanon 3199" (Kao Corporation, trade name) was added in an amount of 1 part by mass with respect to 100 parts by mass of the fiber, and the mixture was stirred to obtain a fiber slurry in which the fiber was uniformly dispersed in water. Prepared.

A wet web was formed from the fiber slurry by a wet papermaking method and dried by heating at 180 ° C. to produce a glass fiber-polycarbonate fiber mixed nonwoven fabric having a basis weight of 410 g / m ² .

  This nonwoven fabric was cut into A4 size (210 x 297 mm), two of which were laminated, placed on a wire net, heated in an infrared oven (280 ° C) for one and a half minutes, softened, and kept at 60 ° C. A press die having a non-equal thickness cavity shape conforming to the shape of the molded body shown in FIG. 1, which is press-formed with a load of 100 t, and a porosity region as shown in FIG. 1 is arranged on the surface. A fiber-reinforced plastic molded product was obtained.

(Example 2)
In the same manner as in Example 1 except that flat glass fibers having a flat cross section with an aspect ratio of 4: 1 (manufactured by Nitto Boshoku; 28 μm in major axis, 7 μm in minor axis, 13 mm in cut length) were used instead of the glass fibers in Example 1 Then, a flat glass fiber-polycarbonate fiber mixed papermaking nonwoven fabric was produced. Using this flat glass fiber-polycarbonate fiber mixed papermaking nonwoven fabric, a non-equal thickness fiber-reinforced plastic molded product was obtained in the same manner as in Example 1.

(Comparative Example 1)
Instead of the mold of Example 1, pressing was performed with a parallel flat plate at 60 ° C. containing a spacer having a thickness of 2.5 mm to obtain a fiber-reinforced plastic molded body having a thickness of 2.5 mm.

(Comparative Example 2)
Polyethylene terephthalate fiber (EP203 made by Kuraray, diameter: 14 μm, cut length: 10 mm, LOI value: 20) was used instead of the polycarbonate fiber of Example 1, and a glass fiber / polyester fiber mixed paper nonwoven fabric having a basis weight of 470 g / m ² was used. Was prepared, and a non-equal-thickness fiber-reinforced plastic molded product was obtained in the same manner as in Example 1.

(Comparative Example 3)
Similarly, the glass fiber-polycarbonate fiber mixed nonwoven fabric (360 g / m2 basis weight) was replaced with 30 parts by weight of glass fiber of Example 1 and 65 parts by weight of 45 parts by weight of polycarbonate fiber chop. ² ) was prepared. Using this glass fiber-polycarbonate fiber mixed papermaking nonwoven fabric, a non-equal thickness fiber-reinforced plastic molded body was obtained in the same manner as in Example 1.

(Comparative Example 4)
A glass fiber-polycarbonate fiber mixed nonwoven fabric (basic weight 480 g / m2) was similarly prepared except that the glass fiber of Example 1 was replaced with 70 parts by mass and the polycarbonate fiber chop was replaced by 45 parts by mass with 25 parts by mass. ² ) was prepared. Using this glass fiber / polycarbonate fiber mixed papermaking nonwoven fabric, molding was attempted under the same molding conditions as in Example 1. However, even after the heat-press treatment, the molded product did not have the shape shown in FIG. It was still.

(Example 3)
Thickness obtained by cutting two sheets of A4 size (210 × 297 mm) of a glass fiber-polycarbonate fiber mixed paper nonwoven fabric having a basis weight of 410 g / m ² in Example 1 and laminating the upper and lower outer layers to A4 size. A 50 μm thick flame-retardant black polycarbonate film (manufactured by Sun Delta: Sun Morphy V) is stacked one by one, placed on a wire mesh, and heated and softened in an infrared oven (280 ° C.) for one and a half minutes. Pressing was performed under the same conditions as in Example 1 except that a spacer having a thickness of 0.1 mm was inserted between the upper mold and the lower mold of the mold, and a 50 μm-thick polycarbonate film was formed on each of the surface layers (front and back). Was pressed to obtain a fiber-reinforced plastic molded article having a maximum thickness of 2.1 mm.

(Evaluation method)
[Void ratio, bending strength, bending rigidity of each area]
[Preparation of sample]
The non-equal-thickness fiber-reinforced plastic molded articles of Examples 1 to 3 and Comparative Examples 2 and 3 each consisted of four regions having different thicknesses. Regions 1 to 4 were set in order of the thickness, and a rectangular section of 1.5 × 6 cm was cut out from each region to obtain a sample. Comparative Example 1 was a molded body having a constant thickness of 2.5 mm, and was formed of a single region. Similarly, a 1.5 × 6 cm rectangular section was cut out from this region to obtain a sample.

[Calculation of porosity]
The thickness and mass of each sample were measured.
The density of each region is calculated from the thickness and mass of the sample, and using the theoretical density (1.64 g / cm ³ ) in a completely consolidated state (porosity = 0) calculated from the density and the material composition, The porosity (%) was calculated according to Equation 1.
Porosity (%) = {1- (density / theoretical density in perfect consolidation state)} × 100 (Equation 1)

[Measurement of bending strength and bending rigidity]
For these samples, a bending-bending load curve (SS curve) was measured using a three-point bending test apparatus according to JIS K7171-1994 at a distance between fulcrums of 4 cm and a test speed of 5 mm / min. FIG. 2 shows SS curves measured for each region having a different porosity in Example 1.
The maximum load (yield point) of the SS curve was defined as the bending strength (N) of the sample, and the maximum slope of the tangent to the SS curve was defined as the bending rigidity (N / mm).

[Strength evaluation]
The strength at the time of manually handling the fiber-reinforced plastic molded articles produced in the examples and comparative examples was sensory evaluated according to the following criteria.
3: Normally, when a force is applied with a fingertip with the force of holding a housing of a notebook personal computer or the like, bending, deformation, and detachment of the reinforcing fiber do not occur.
2: When a force is applied with a fingertip with a force such as to hold a housing of a notebook computer or the like with some care, bending, shape loss, and detachment of the reinforcing fiber do not occur.
1: If it is not handled carefully, it bends or loses its shape, and detachment of the reinforcing fibers easily occurs.

[UL94-HB standard flame retardant]
The flame-retardant properties of the fiber-reinforced plastic molded articles produced in the examples and comparative examples were evaluated according to UL94-HB standard.
〇: Conforms to standard ×: Does not conform to standard-: Not measured

The fiber-reinforced plastic molded products of Examples 1 to 3 and Comparative Examples 1 to 3 were measured for porosity, bending strength and bending rigidity in each region by the above-described evaluation method, and the strength of the fiber-reinforced plastic molded product was measured. UL94-HB standard flame retardancy was evaluated. The results are shown in Tables 1 to 3.

  From Table 1, the non-equal thickness fiber-reinforced plastic molded article of Example 1 can be used in any region from the thin portion (high-density region: porosity 0%) to the thick portion (low-density region: porosity 75%). , The bending strength and the bending rigidity are maintained at high levels, and the fiber-reinforced plastic molded article having the high-density region and the low-density region of Example 1 or 2 has excellent strength characteristics. On the other hand, in Comparative Example 1 (low density: porosity 80%), the flexural strength and flexural rigidity were inferior, and it was found that those having this region could not be obtained as a fiber-reinforced plastic molded product.

  The non-equal-thickness fiber-reinforced plastic molded article of Example 1 maintained flame retardancy conforming to the UL94HB standard at any portion from the thin portion (high density) to the thick portion (low density). Further, as shown in Table 2, Comparative Example 2 was inferior in flame retardancy, and a fiber-reinforced plastic molded article conforming to the UL94-HB standard could not be obtained. In the non-equal-thickness fiber-reinforced plastic molded article of Comparative Example 3, a thick portion having a low density was inferior in flame retardancy and did not conform to the UL94HB standard. In Comparative Example 3, the strength in comparison with Example 1 was inferior to any portion from the thin portion (high density) to the thick portion (low density).

  Comparative Example 4, in which the reinforcing fibers were 70% by mass, was not suitable as a material for forming a molded article.

  According to Table 3, the strength of the fiber-reinforced plastic molded article having the film pressed on the surface was significantly improved as compared with the fiber-reinforced plastic molded article having the same thickness.

Claims (17)

A housing using a fiber-reinforced plastic molded body that includes a reinforcing fiber and a thermoplastic resin, and is divided into a low-density region and a high-density region in a plane direction,
The low-density region is a region having a porosity of 60 to 78%, and the high-density region is a region having a porosity of less than 60% and thinner than the low-density region.
Wherein among the high-density region, at least in part, a housing with a fiber-reinforced plastic molding, characterized in that are enclosed rare to the low-density regions. The low among the density regions of the enclosed rare and have high-density regions, at least in part, a housing with a fiber-reinforced plastic molded article according to claim 1 porosity of 10% or less. The housing using the fiber-reinforced plastic molded product according to claim 1 or 2, wherein a part of the high-density region is formed at an outer edge. The case using the fiber-reinforced plastic molded body according to claim 3, wherein the high-density region formed on the outer edge has a porosity of 10% or less. Housing with fiber-reinforced plastic molded article according to claim 1 in which the basis weight is one Jode Te plane direction odor. A housing using the fiber-reinforced plastic molded product according to any one of claims 1 to 5, wherein a mass ratio of the reinforcing fiber to the thermoplastic resin is 35:65 to 65:35 (% by mass). The fiber-reinforced plastic according to any one of claims 1 to 6, wherein the reinforcing fiber has an average fiber length of 55 mm or less, an average fiber diameter of 20 µm or less, and does not have a glass transition temperature of 210 ° C or less. A housing using a molded body. The housing using the fiber-reinforced plastic molding according to any one of claims 1 to 7, wherein the reinforcing fiber is an inorganic fiber. The housing using the fiber-reinforced plastic molding according to any one of claims 1 to 8, wherein the reinforcing fiber contains a glass fiber having a flat cross-sectional shape. The housing using the fiber-reinforced plastic molded product according to any one of claims 1 to 9, wherein the thermoplastic resin has an LOI value (limit oxygen index) of 25 or more. The fiber-reinforced plastic molding according to any one of claims 1 to 10, wherein the thermoplastic resin is at least one selected from the group consisting of a polycarbonate resin, a polyetherimide resin, a polyphenylene sulfide resin, and a polyether sulfone resin. Housing using body. A housing using the fiber-reinforced plastic molded product according to any one of claims 1 to 11, which has a flame retardancy of UL-94 standard HB level or higher. A housing using the fiber-reinforced plastic molded product according to any one of claims 1 to 12, which has a thermoplastic resin layer on a surface. A housing using the fiber-reinforced plastic molded product according to any one of claims 1 to 12, which is a keyboard housing of a personal computer. (A) a step of obtaining a nonwoven fabric sheet containing reinforcing fibers and a thermoplastic resin, and (B) a mold having a concave surface and a convex surface at the same time as heating the nonwoven fabric sheet to a temperature at which at least a part of the thermoplastic resin is melted. A method of manufacturing a housing using a fiber-reinforced plastic molded body including a heating and pressing step of pressing and pressing,
Among the convex surface of the mold, at least in part, cage circumference Marete the concave,
In the heating and pressing step, heating and pressing are performed under the condition that the porosity of the nonwoven fabric sheet corresponding to the concave surface is 60 to 78% and the porosity of the nonwoven fabric sheet corresponding to the convex surface is less than 60%. A method for manufacturing a housing using a fiber-reinforced plastic molded body, characterized by comprising: The method for manufacturing a housing using a fiber-reinforced plastic molded product according to claim 15 , wherein a part of the convex surface is formed in a portion of the mold corresponding to an outer edge of the nonwoven fabric sheet. The method for manufacturing a housing using a fiber-reinforced plastic molded product according to claim 15 or 16 , wherein in the heating and pressurizing step, two or more laminated nonwoven fabric sheets are heated and pressed.

Images