JP2726226B2 - Stamp molding method for fiber reinforced thermoplastic resin sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced thermoplastic resin sheet capable of obtaining a molded product suitable for members requiring high mechanical properties and appearance, such as an outer panel of an automobile and a housing of a home electric appliance. And a stamp forming method.

[0002]

2. Description of the Related Art Conventionally, thermoplastic resin (a) has been used as one of molding materials suitable for members requiring high mechanical properties and appearance, such as outer panels of automobiles and housings of home electric appliances. A fiber-reinforced thermoplastic resin sheet made of fibers is used. Such a fiber-reinforced thermoplastic resin sheet is preheated to a temperature equal to or higher than the melting point or softening point of the thermoplastic resin (a), is press-formed under a relatively high pressure between a pair of male and female molds, and has substantially uniform physical properties. It is common to mold into a molded article having However, recently, in order to improve the appearance of molded articles, one or both sides of a fiber-reinforced thermoplastic resin sheet have a higher melting point or softening point than the melting point or softening point of the thermoplastic resin (a) forming the matrix of the sheet. A composite sheet obtained by laminating a thermoplastic resin (b) film or sheet having excellent smoothness and gloss at a temperature not lower than the melting point or softening point of the thermoplastic resin (a) and the melting point of the thermoplastic resin (b) Alternatively, a method in which stamping is performed between male and female molds after preheating to a temperature lower than the softening point has been attempted.

However, in the above-mentioned press molding method, since molding is performed using a high pressure of 100 to 300 kgf / cm ² , not only is the molding apparatus and the molding die large and expensive, but also the reinforcing fiber There is a disadvantage that the appearance of the molded product is poor due to the flow pattern and the like. Further, in the above-mentioned method, since molding can be performed at a relatively low pressure of ^{3 to} 50 kgf / cm ^2, a simple molding apparatus and molding die may be used, which is economically advantageous, and furthermore excellent in appearance. Therefore, among these molding methods, a stamp molding method that requires a low molding pressure is particularly attracting attention.

[0004]

However, one of the drawbacks of stamp molding using the above fiber-reinforced thermoplastic resin sheet is that when the raw sheet is preheated, the melting point or softening of the thermoplastic resin (a) is reduced. The sheet preheated to a temperature exceeding the point expands to a thickness of about 10 times the thickness before the preheating (swelling) due to the recovery of the elastic force of the reinforcing fibers suppressed by the thermoplastic resin (a). ) Then, since a low-density heating sheet with air entrapped inside the sheet is obtained, air remains in a molded article obtained by stamp-molding the sheet at a relatively low pressure, resulting in deterioration of physical properties or remarkable appearance. There was a problem that it would be damaged. Such a problem occurs not only when a layer of a thermoplastic resin (b) having a melting point or softening point higher than the melting point or softening point of the thermoplastic resin (a) is laminated on one surface thereof, but also when the thermoplastic resin ( Even when the film or sheet b) is laminated on both sides, the expansion is not yet completely prevented because about 1.2 to 3 times expansion remains. The present inventor has developed a method of producing a high-performance and excellent-looking molded product by stamping under low pressure, which is economically advantageous, while preventing such air entrapment during preheating as much as possible. Was considered as an issue.

The inventor of the present invention has made intensive studies to solve the above problems, and as a result, in the conventional stamp forming method,
At the time of preheating performed when stamp forming is performed using a composite sheet in which layers of the thermoplastic resin (b) are laminated on both sides of a fiber-reinforced thermoplastic resin sheet, the composite sheet that has been in a molten state is a thermoplastic resin (a Due to the recovery of the elastic force of the reinforcing fibers, which has been suppressed by the above, the composite sheet expands by sucking air from the peripheral side surface of the composite sheet, whereby air is trapped in the molded product. The present invention was completed by examining in detail the method of preventing the expansion of the sheet, that is, the intrusion of air from the side surface of the peripheral edge of the sheet. In particular,
The part of the raw sheet formed by stamping is preheated to a temperature higher than the melting point or softening point of the thermoplastic resin (a) and lower than the melting point or softening point of the thermoplastic resin (b). A practical stamp forming method has been proposed by preventing the peripheral edge portion of the starting sheet from exceeding the melting point or softening point of the thermoplastic resin (a). That is, the stamp molding method for a fiber-reinforced thermoplastic resin sheet of the present invention provides a method for forming a matrix of the fiber-reinforced thermoplastic resin sheet on both sides of the thermoplastic resin (a) having a melting point higher than the melting point or the softening point thereof. Alternatively, a composite sheet obtained by laminating a layer of a thermoplastic resin (b) having a softening point may be formed to have a melting point or softening point of the thermoplastic resin (a) or more and less than a melting point or softening point of the thermoplastic resin (b). In the stamp molding method of forming by stamping after preheating to the temperature of (i), the entire peripheral portion outside the portion of the composite sheet to be formed by stamping is formed of the thermoplastic resin (a). The temperature is maintained at a temperature lower than the melting point or the softening point.

DETAILED DESCRIPTION OF THE INVENTION [I] Composite Sheet (1) Fiber Reinforced Thermoplastic Resin Sheet Layer (i) Fiber for Reinforcement of Raw Material Fiber of composite sheet in stamp forming method of fiber reinforced thermoplastic resin sheet of the present invention As the reinforcing fibers used in the reinforced thermoplastic resin sheet layer, glass fibers,
In addition to carbon fiber and metal fiber, inorganic fiber, organic fiber and the like can be mentioned, and among them, glass fiber is most common. Of course, glass fibers can be mainly used, and reinforcing fibers such as carbon fibers, aramid fibers, metal fibers, and ceramic fibers can be used in combination without departing from the spirit of the present invention. As glass fibers, it is common to use glass chopped strands, and the glass chopped strands may be used according to the application, such as aminosilane coupling agents, epoxy silane coupling agents, and other coupling agents, polyvinyl alcohol, polyvinyl acetate, and polyurethane. What has been subjected to a surface treatment with a sizing agent or the like can be used.

Thermoplastic resin (a) The thermoplastic resin (a) forming the matrix of the fiber reinforced thermoplastic resin sheet layer of the composite sheet in the stamp molding method of the fiber reinforced thermoplastic resin sheet of the present invention is polyethylene or polypropylene. , Polystyrene, polyvinyl chloride, ABS resin, SAN resin, polyamide,
Examples include polycarbonate, polyacetal, polyester (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene oxide, polysulfone, polyphenylene sulfide, and the like. These can be used as a mixture of two or more kinds. Further, additives, fillers, impact modifiers and the like generally used may be mixed and used. Among these thermoplastic resins (a), crystalline resins such as polypropylene, polyamide and polyester (polyethylene terephthalate and polybutylene terephthalate) are considered from the viewpoint of the effect of glass fiber addition (improvement of strength, rigidity and durability). It is preferable to use, and among them, it is particularly preferable to use polypropylene from the balance of moldability, physical properties and economy.

(Ii) Compounding ratio The thermoplastic resin (a) and the reinforcing fibers in the fiber-reinforced thermoplastic resin sheet layer of the composite sheet used as the molding material in the stamp molding method of the fiber-reinforced thermoplastic resin sheet of the present invention. Is blended with the thermoplastic resin (a) 75 to 45
25 to 55% by weight of reinforcing fiber with respect to% by weight, preferably 30 to 50% by weight of reinforcing fiber with respect to 70 to 50% by weight of thermoplastic resin (a), particularly preferably 65 to 65% of thermoplastic resin (a). 55 to 45% by weight of reinforcing fibers 35 to 45
% By weight. When the blending ratio of the thermoplastic resin (a) is 7
If the content is more than 5% by weight, the strength and rigidity of the obtained molded product are insufficient, and the meaning as a fiber reinforced material is reduced. Also, 45
If the amount is smaller than the percentage by weight, the moldability, impact resistance and appearance of the obtained fiber-reinforced material will be poor.

(Iii) Method for producing fiber-reinforced thermoplastic resin sheet As a method for producing a fiber-reinforced thermoplastic resin sheet, a fiber mat for reinforcement is impregnated with a molten thermoplastic resin, and heated and cooled to obtain a fiber-reinforced thermoplastic resin sheet. A method of forming a sheet (lamination method), after mixing and dispersing a thermoplastic resin powder and a certain length of reinforcing fibers, forming the mixture into a web-like form, heating, pressing, and cooling to obtain a fiber-reinforced thermoplastic. A method of forming a resin sheet (dry dispersion method), after mixing and dispersing a thermoplastic resin powder and a certain length of reinforcing fiber in water or water bubbles, forming a web by papermaking, heating, pressing, A method of cooling to obtain a fiber-reinforced thermoplastic resin sheet (wet dispersion method), and the like have been implemented. In the present invention, although not limited to any of them, the dispersion of the reinforcing fibers is basically uniform and stable high physical properties can be obtained, and excellent appearance is easily obtained. It is preferable to use the method.

(2) Thermoplastic resin (b) layer (i) Raw material thermoplastic resin (b) Used in the thermoplastic resin (b) layer of the composite sheet in the stamp molding method of the fiber-reinforced thermoplastic resin sheet of the present invention. The thermoplastic resin (b) is selected from the above-mentioned thermoplastic resins (a), and has a higher melting point or softening point than that of the thermoplastic resin (a), preferably 1
Those which are higher than 0 ° C., particularly preferably higher than 30 ° C. are selected. The thermoplastic resin (b) may be of the same type or a completely different chemical structure from the thermoplastic resin (a), and may be an additive, a filler, or an additive generally used with the thermoplastic resin (b). An impact modifier or the like can be mixed and used.

(Ii) Layer Structure The above thermoplastic resin (b) is used in the form of a film or sheet laminated on both sides of a fiber reinforced thermoplastic resin sheet layer, and one of the layers has a thickness of 10 to 1, 000 μm, preferably 30-500 μm, particularly preferably 50-20
It is formed at 0 μm. If the thickness of the thermoplastic resin (b) layer is less than 10 μm, the molded article is likely to be damaged during stamp molding, or the appearance of the molded article is likely to be impaired due to protrusion of the reinforcing fibers. If it exceeds 1,000 μm, the original performance of the fiber-reinforced thermoplastic resin sheet tends to be impaired.

(3) Lamination (Production of Composite Sheet) A method of producing a composite sheet by laminating a thermoplastic resin (b) film or sheet on a fiber-reinforced thermoplastic resin sheet is as follows. And a method of extruding and coating a thermoplastic resin (b) on the surface of a fiber-reinforced thermoplastic resin sheet (an adhesive resin layer may be interposed if necessary). It is preferable to employ However, in the present invention, as long as there is no air layer between the film or sheet of the thermoplastic resin (b) and the fiber-reinforced thermoplastic resin sheet, both are not necessarily firmly integrated. For example, it may be in a state of being laminated by temporary attachment, coating, or the like.

[II] Stamp molding (1) Preheating In the stamp molding method for a fiber-reinforced thermoplastic resin sheet of the present invention, a composite in which a thermoplastic resin (b) layer is laminated on both sides of the fiber-reinforced thermoplastic resin sheet layer. In stamp forming the sheet, a heat treatment (preheating) is performed in advance. In the present invention, it is essential for the preheating that the temperature of the sheet is maintained below the melting point or softening point of the thermoplastic resin (a) over the entire outer peripheral portion of the portion to be shaped by stamping. The temperature is not particularly limited.

As a method of controlling the temperature of the entire outer peripheral portion of the composite sheet to be lower than the melting point or the softening point of the thermoplastic resin (a), there is a method of controlling the temperature of an area larger than the effective preheating area of the preheating device. A method of using an anti-sheet to prevent the peripheral portion from being preheated. The effective preheating area of the preheating device is larger than the area of the raw sheet, but metal, ceramics, and heat-resistant plastic are provided over the entire periphery of the peripheral portion of the raw sheet. , Heat-resistant tape, masking with a masking material made of heat-resistant material such as paint, etc., and a method of reducing the preheating speed of the peripheral part from the shaping part, etc. are considered, but the present invention is limited to that method. There is no. However, the above method may be more practical in industrial molding methods. Further, the width of the masking portion when preheating by the above method is not particularly limited, but is 3 to
Generally, the width is 50 mm. When forming using a masking material such as metal or ceramics by the above method, it is also effective to provide a cooling mechanism for the masking material as needed and actively cool the masking material.

(2) Clamping of the raw sheet Before forming is performed by stamp molding, the raw sheet flows into the mold during the pressing and forming process, and wrinkles are generated on the product. In many cases, it is preferable to adopt a method in which the peripheral portion of the preheated raw sheet is clamped and then pressed before pressing in order to reduce the commercial value. The clamping is performed by clamping a portion of a margin of a portion outside a portion of the raw sheet formed by stamp molding with edges of the upper and lower molds. The portion of the clamp margin is trimmed in a subsequent step to form a product. Since the portion of the clamp margin usually includes a portion to be masked at the time of preheating of the present invention, the outer size of the portion to be masked is substantially equal to the size of the raw sheet.

(3) Shaping In the stamp forming method of the fiber-reinforced thermoplastic resin sheet of the present invention, a raw sheet having an area larger than a projected area of a final molded product is preheated.
This 3~50kgf / cm ² to between the pair of male and female type, preferably can take a method of molding by pressing under pressure of about 5~30kgf / cm ^2.

The method for stamp forming according to the present invention will be described in more detail below with reference to FIGS. FIG. 1 is a perspective view of a stamp molded product for evaluation manufactured by the stamp molding method for a fiber-reinforced thermoplastic resin sheet of the present invention. The outer dimension of the molded article body 1 is 190
× width 140 mm × maximum depth 40 mm. A portion of a clamp margin 2 for clamping the raw sheet 4 at the time of stamping remains at the peripheral portion of the molded article main body 1,
The size of the portion substantially formed by stamping is 15
It is 0 × 100 mm. The portion of the clamp margin 2 is trimmed in a subsequent step to form a product. The clamp fee 2
The portion 3 includes a portion (shaded portion) 3 subjected to masking at the time of preheating according to the present invention. The size is almost equal to the size.

FIG. 2 is a schematic sectional view of the infrared heater furnace in a state where the raw sheet 4 is preheated in the infrared heater furnace 5. The outer dimensions of the raw sheet 4 are length 230 x width 18
0 mm × thickness of about 3.2 mm, and the entire outer peripheral edge 3 of the raw sheet 4 is masked from the upper and lower surfaces by an iron masking material 6 having a width of 15 mm × a thickness of 5 mm. When the preform is passed through the infrared heater furnace 5 and preheated, the outer peripheral portion 3 of the raw sheet 4 is preheated at a low speed. The melting point or softening point is not devised.

FIG. 3 is a schematic sectional view showing a state in which the preheated raw sheet 4 is set in a molding die (male mold 7, female mold 8). The outer peripheral edge 2 of the raw sheet 4 is completely clamped 9 to enable stamp forming. The mold clamping is performed while the temperature of the raw sheet 4 does not drop below the melting point or softening point of the thermoplastic resin (a). The temperature of the male mold 7 and the female mold 8 is maintained at a temperature sufficiently lower than the thermal deformation temperature of the thermoplastic resin (a). The male mold 7 and the female mold 8 are provided with gas vent holes 10 and 11, respectively, and are present in a mold space (cavity) between the raw sheet 4 and the molds 7 and 8 by the end of mold clamping. The molding is performed while excluding the air generated.

FIG. 4 is a schematic sectional view showing a state immediately after the molding of the molded article 12 is completed and the mold opening is started. In the molded article 12 formed by stamping according to the method of the present invention, air does not enter from the end of the raw sheet 4 at the time of preheating, and expansion of the raw sheet 4 due to elastic recovery of the reinforcing fibers hardly occurs. By molding, 3-50kgf / c
Even when molded at a pressure as low as about m ^2, there is no residual air in the molded product 12, and the product has much better dimensional accuracy and appearance than the conventional method.

FIG. 5 is a partial sectional view of the molded article 12 showing the state of shaping at the deepest corner of the molded article 12 stamped by the method of the present invention.
Is a thermoplastic resin (b) layer, and 14 is a fiber reinforced thermoplastic resin sheet layer.

FIG. 6 is a partial sectional view of the molded article 12 showing the state of shaping at the deepest corner of the molded article 12 stamp-molded by the conventional method, and reference numeral 15 denotes residual air. 5 and 6, the difference occurs at the deepest corner of the molded product 12, and the molded product 12 stamped by the method of the present invention is better than the molded product 12 stamped by the conventional method. It can be understood that it is excellent.

[0023]

【Example】

Example 1 Preparation of Fiber Reinforced Thermoplastic Sheet A surfactant was added to 9 liters of water, and the mixture was stirred well for about 27
MFR is 135 g / 10
Then, 261 g of polypropylene powder having an average particle size of about 350 μm obtained by mechanically pulverizing polypropylene pellets having a melting point of 165 ° C., 112 g of glass chopped strands having a diameter of 10 μm and a length of 13 mm were added, and the mixture was stirred well again, and the web produced by the papermaking method was heated. -By pressurizing and cooling, a 310 x 340 x 3 mmt fiber reinforced thermoplastic resin sheet was produced. Production of a composite sheet A composite sheet obtained by laminating a film obtained by laminating a film of polyamide 6 having a melting point of 215 ° C. (thickness: 100 μm) on both sides of this sheet and a film of maleic anhydride-modified polypropylene (thickness: 20 μm) on one side. It was created.

Preheating A blank obtained by cutting this sheet into 230 × 180 mm was subjected to an outer dimension of 230 × 180 mm and an inner dimension of 200 × 150 m.
m, sandwiched from above and below by an iron frame with a thickness of 5 mm, the surface temperature is 200 ° C with an infrared heater (the temperature of the frame is about 140 ° C)
And placed in a female mold kept at 60 ° C. Stamp Forming Next, the mold was clamped, and the raw sheet was pressed at a pressure of 30 kgf / cm ² to perform the forming. Evaluation The expansion rate of the raw sheet after preheating (value obtained by dividing the thickness of the raw sheet after preheating by the thickness of the raw sheet before preheating), the thickness and density of the bottom of the molded product, and the appearance of the molded product ( The completeness of the molding, the presence or absence of residual air, the unevenness due to the lifting of the reinforcing fibers, and the gloss were visually determined) and the bending characteristics of the test piece cut out from the bottom of the molded product were evaluated. Table 1 shows the results.

Example 2 Except that the thickness of the polyamide 6 film was changed to 30 μm, molding was performed in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Example 3 Except that the thickness of the polyamide 6 film was changed to 200 μm, molding was carried out in exactly the same manner as in Example 1.
The same evaluation was performed. Table 1 shows the results.

Example 4 Except for using a polycarbonate film having a softening point of 230 ° C. instead of the polyamide 6 film, molding was performed in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Was. Table 1 shows the results.

Example 5 When pre-heating a raw sheet, a 1 mm thick sheet was used instead of an iron frame.
The molding was performed in exactly the same manner as in Example 1 except that the frame of the silicone rubber sheet was used, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Comparative Example 1 In the preheating of the raw sheet, molding was carried out in exactly the same manner as in Example 1 except that no iron frame was used, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Comparative Example 2 The molding was performed in exactly the same manner as in Comparative Example 1 except that the thickness of the polyamide 6 film was changed to 200 μm.
The same evaluation was performed. Table 1 shows the results.

Comparative Example 3 The surface temperature of the raw sheet was 220 ° C. (the temperature of the frame was about 18
Molding was performed in exactly the same manner as in Example 1 except that the preheating was performed so as to be 0 ° C.), and the same evaluation as in Example 1 was performed. Table 1 shows the results.

[0032]

[Table 1]

[0033]

The molded article made of the fiber reinforced thermoplastic resin obtained by the method for stamping the fiber reinforced thermoplastic resin sheet of the present invention has a structure in which the entire peripheral portion of the composite sheet is made of thermoplastic resin during preheating before molding. Since the resin (a) is kept sealed at a temperature lower than the melting point or softening point, there is no defect in appearance due to entrainment of air, and it has excellent dimensional accuracy and gloss, so it has high mechanical properties. It is useful for applications such as outer panels of automobiles requiring appearance and housings of home electric appliances.

[Brief description of the drawings]

FIG. 1 is a perspective view of a molded article of a fiber-reinforced thermoplastic resin for evaluation obtained by stamp molding in Examples and Comparative Examples of the present invention.

FIG. 2 is a schematic cross-sectional view of the infrared heater furnace in a state where a raw sheet is preheated in the infrared heater furnace.

FIG. 3 is a schematic cross-sectional view showing a state in which a preheated raw sheet is set in a stamping die.

FIG. 4 is a schematic cross-sectional view of a state immediately after stamp forming is completed and mold opening is started.

FIG. 5 is a partial cross-sectional view of the molded article showing the state of residual air at the deepest corner of the molded article stamp-molded by the method of the present invention.

FIG. 6 is a partial cross-sectional view of a molded article showing a state of residual air at a deepest corner of a molded article stamped by a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Molded product main body 2 Clamping margin for clamping a sheet with a mold at the time of stamp molding 3 Peripheral edge to be masked at the time of preheating 4 Raw sheet 5 Infrared heater 6 Masking material 7 Male 8 Female 9 Clamp 10, 11 Gas Hole 12 Molded article 13 Thermoplastic resin (b) layer having high melting point or softening point 14 Fiber reinforced thermoplastic resin sheet layer 15 Residual air

Claims (4)

(57) [Claims] 1. A thermoplastic resin (b) having a melting point or softening point higher than the melting point or softening point of the thermoplastic resin (a) forming the matrix of the sheet on both surfaces of the fiber reinforced thermoplastic resin sheet. The composite sheet formed by laminating the layers is preheated to a temperature higher than the melting point or softening point of the thermoplastic resin (a) and lower than the melting point or softening point of the thermoplastic resin (b), and then stamped. In the stamp forming method to be shaped, it is preferable that, during the preheating, the entire periphery of a portion of the composite sheet formed by stamp forming be kept at a temperature lower than the melting point or softening point of the thermoplastic resin (a). A method for stamp-forming a fiber-reinforced thermoplastic resin sheet. 2. During preheating, the entire periphery of a portion of the composite sheet to be formed by stamping is sandwiched by a heat-resistant member, so that a temperature lower than the melting point or softening point of the thermoplastic resin (a) is obtained. The stamp molding method for a fiber-reinforced thermoplastic resin sheet according to claim 1, wherein the sheet is held. 3. A fiber-reinforced thermoplastic resin sheet is formed from 75 to 45% by weight of a thermoplastic resin (a) and 25 to 55% by weight of reinforcing fibers, and has a thickness of 10 to 1,000 μm on both surfaces thereof.
The stamp molding method for a fiber-reinforced thermoplastic resin sheet according to claim 1 or 2, wherein the method comprises a composite sheet in which m thermoplastic resin (b) layers are laminated. 4. The fiber-reinforced thermoplastic resin sheet according to claim 1, wherein the sheet is produced by a wet dispersion method using a granular material of the thermoplastic resin (a) and reinforcing fibers. The stamp molding method of the fiber-reinforced thermoplastic resin sheet according to the above.