JPH08216172A - Production of fiber reinforced thermoplastic resin foam - Google Patents

Abstract

PURPOSE: To produce a fiber reinforced thermoplastic resin foam excellent in bending strength and enhanced in specific strength and specific elasticity by laminating a foamable resin compsn. to the inside of a cylindrical body shaped from a fiber reinforced thermoplastic resin composite sheet so that the staple fiber-containing surface of the sheet becomes inside and pressing the cylindrical body to the inner surface of a mold by the foaming pressure of the resin compsn. to shape the same so as to have a desired cross-sectional shape. CONSTITUTION: At first, a composite sheet 15 wherein staple fibers are applied to one surface of a fiber reinforced thermoplastic resin sheet is inserted in a mold 24 from the gap thereof so that the staple fiber-containing surface thereof becomes inside and continuously shaped into a cylindrical body from a U-shape while both end parts of the sheet are abutted without being overlapped with each other. A foamable resin compsn. is extruded from a single-screw extruder 23 at about 200 deg.C to be laminated to the inside of the cylindrical body and, at the same time, foaming is started and the temp. of the resin compsn. is held to about 200 deg.C by a heating mold 27 to complete foaming. Thereafter, the foamed one is cooled by a cooling mold 29 until the temp. of the outer layer thereof becomes about 60 deg.C to obtain a fiber reinforced thermoplastic resin foam 32 with a foaming magnification of about 3, 2 times having, for example, a square cross section.

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 foam mainly having a modified cross-sectional shape in which a core layer made of a thermoplastic resin foam is provided with a skin layer made of a fiber-reinforced thermoplastic resin. The present invention relates to a method for manufacturing a body.

[0002]

2. Description of the Related Art A molded article having a long and irregular cross-sectional shape and having a foamed layer inside thereof is used as a material excellent in specific strength and specific elasticity in building materials and other fields.
It is used as well as natural wood or as a substitute.
In such applications, in order to increase the specific strength and the specific elasticity, the core material layer is made of a thermoplastic resin foam and the skin layer is made of a fiber reinforced thermoplastic resin.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 4-339635, in order to continuously manufacture a composite having excellent mechanical strength and lightness, a synthetic resin foam is continuously transferred in one direction. A method has been proposed in which continuous fibers impregnated with a thermosetting resin are supplied to the outer surface, and the fibers are heated and pultruded.

[0004]

However, in this method, in order to form a molded product having an irregular cross-sectional shape, it is necessary to prepare a synthetic resin foam having an irregular cross-sectional shape in advance, so the process is complicated. In addition, since it is necessary to use a low-viscosity resin for pultrusion, uneven thickness of the skin layer and non-uniform mechanical strength are likely to occur, and deformation and treatment inside the mold are likely to occur. There is a problem that the shape is difficult.

In view of this point, a fiber-reinforced thermoplastic resin shaped into a cylindrical body is supplied into a mold, and the foamed resin is extruded into the mold, and the foaming pressure causes the cylindrical body to move to the inner surface of the mold. While pressing to shape the tubular body to the desired cross-sectional shape,
A method for producing a fiber-reinforced thermoplastic resin foam, in which a core material layer made of foamed resin is formed, is also conceivable.

However, the fiber-reinforced thermoplastic resin foam obtained by this method has a problem that the fusion property at the interface between the skin layer and the core material layer is weak, and that the skin layer and the core material layer are In order to improve the fusion property at the interface, it is necessary to increase the foaming ratio of the foamed resin to increase the foaming pressure, so that the foaming ratio of the core layer becomes high, and the obtained fiber-reinforced thermoplastic resin foam There is a problem that the specific strength and the specific elasticity of are reduced.

The present invention has been made for the purpose of solving the above-mentioned conventional problems and providing a method for producing a fiber-reinforced thermoplastic resin foam having excellent bending strength, high specific strength and high specific elasticity. It is a thing.

[0008]

The invention according to claim 1 of the present application (hereinafter referred to as the present invention 1) is a composite sheet having short fibers on one surface of a fiber reinforced thermoplastic resin sheet, and a surface having short fibers. To form a tubular body by shaping the tubular body so that the inside is inside, the tubular body is supplied into a mold, and the inside of the tubular body contains a thermoplastic resin and a foaming agent. The foamable resin composition to be supplied is heated to a temperature not lower than the foaming agent and supplied while foaming, or after being supplied, it is heated to a temperature not lower than the foaming agent to cause the outer layer of the foamed resin to bite into the short fibers. A method for producing a fiber-reinforced thermoplastic resin foam, which comprises a step of shaping the tubular body into a desired cross-sectional shape by pressing the tubular body against the inner surface of the mold by the foaming pressure while breaking the bubbles.

The invention according to claim 2 of the present application (hereinafter referred to as the present invention 2) is a composite sheet having a short fiber on one surface of a fiber reinforced thermoplastic resin sheet, a thermoplastic resin and a foam on a surface having a short fiber. A step of forming a laminated cylindrical body by laminating a core material forming layer made of a foamable resin composition containing an agent to form a laminated sheet into a tubular shape with the core material forming layer being on the inside, After supplying the laminated cylindrical body into the mold, it is heated to a temperature not lower than the foaming temperature of the foaming agent to foam the core material forming layer, and the outer layer of the foamed resin bites into the short fibers to break the foam, and the foaming pressure A method for producing a fiber-reinforced thermoplastic resin foam, comprising the step of pressing the skin forming layer of the laminated tubular body against the inner surface of the mold to shape the tubular body into a desired cross-sectional shape.

In the present invention 1 and the present invention 2 (hereinafter collectively referred to as the present invention), as the thermoplastic resin constituting the fiber-reinforced thermoplastic resin sheet, for example, a Koka type flow tester can be used for heat fusion. Outside diameter 1m at various temperatures
m, the apparent viscosity when extruded from a 100 mm long nozzle under the condition of 150 kg / cm ² is 1 × 10 ⁵ to
It is particularly limited as long as it is a resin that does not easily flow due to its own weight in a melting temperature range (a temperature range in which heat fusion can be performed) such as 1 × 10 ⁷ poise, and further that the fluidity can be suppressed by being combined with fibers or the like. It can be appropriately selected according to the purpose of use without being performed.

Examples of such a thermoplastic resin include polyvinyl chloride, chlorinated polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyamide, polycarbonate, polyphenylene sulfide, polysulfone and polyether ether ketone. In the step, when the fiber reinforced thermoplastic resin sheet is stretched, it is preferable to use a thermoplastic resin rich in extensibility, and a processing treatment may be performed to improve the extensibility. These thermoplastic resins may be used alone or in combination.

In the thermoplastic resin, if necessary, additives such as heat stabilizers, plasticizers, lubricants, antioxidants, ultraviolet absorbers, pigments, inorganic fillers, reinforcing short fibers, and processing aids, A modifier or the like may be added.

The reinforcing fibers constituting the fiber-reinforced thermoplastic resin sheet include, for example, all the glass fibers, carbon fibers, metal fibers, synthetic fibers such as aramid fiber and vinylon fiber, and reinforcing fibers such as natural fibers. Fiber is used.

In the present invention, the fiber-reinforced thermoplastic resin sheet is not particularly limited, but is manufactured as follows, for example. When obtaining a fiber reinforced thermoplastic resin sheet in which reinforcing fibers are aligned in one direction, a powdered thermoplastic resin is put in the impregnation tank and compressed from a perforated plate provided at the bottom of the tank. It is made to float by blowing out air, and guided by guide rolls through it to allow a plurality of fiber bundles to pass through in a widened state to form a thermoplastic resin-impregnated fiber bundle, which is placed between heating rolls. It is passed to form a sheet, and then passed through a cooling roll.

When the fiber-reinforced thermoplastic resin sheet, in which the reinforcing fibers are arranged in one direction as described above, is used, the core material is continuously passed through the mold and taken out. It is preferable because cutting due to frictional force generated by sliding between the layer and the inner surface of the mold can be prevented.

When it is desired to obtain a fiber-reinforced thermoplastic resin sheet in which fibers are randomly arranged, the thermoplastic resin-adhered fiber bundle obtained as described above is cut by a rotary cutter and The endless belt is dropped and accumulated, and is sandwiched between the upper and lower endless belts and pressed to pass through the heating furnace to form a sheet, and then passed through a cooling roll.

The fiber-reinforced thermoplastic resin sheet may be a single layer or a plurality of laminated layers. The thickness of the fiber-reinforced thermoplastic resin sheet is not particularly limited,
If it is too thin, the reinforcing effect is not sufficient, and if it is too thick, it becomes difficult to shape it into a tubular body.
m is preferred. The fiber amount of the fiber-reinforced thermoplastic resin sheet does not have a sufficient reinforcing effect when it is too small, and conversely, when it is too large, the fusibility of fibers to each other due to the thermoplastic resin decreases,
On the contrary, the reinforcing effect decreases, so 5 to 70% by volume is preferable.

The composite sheet has short fibers on at least one surface of the fiber-reinforced thermoplastic resin sheet. As the short fibers, for example, fibers such as glass fibers, carbon fibers, metal fibers, synthetic fibers such as aramid fibers and vinylon fibers, and natural fibers are used. If the diameter of the short fibers is too large, the foamed resin will not easily bite, resulting in a decrease in the fusion property at the interface between the core layer and the surface layer. Conversely, if it is too small, the diameter of the foamed resin and the fibers will decrease. At the interface of the reinforced thermoplastic resin sheet, it becomes difficult to form a skin due to foam breakage of the foamed resin, the bending strength of the resulting fiber-reinforced thermoplastic resin foam is reduced, and melting at the interface between the core layer and the surface layer occurs. Since the adherence decreases, 1 μm to 1 mm is preferable.

As for the length of the short fiber, whether the length is too long or too short, the effect of improving the interfacial fusion property by the short fiber biting into the foamed resin and the fiber obtained by the skin formation by the foam breaking of the foamed resin are obtained. Since the effect of improving the bending strength of the reinforced thermoplastic resin foam is not recognized so much, 100 μm to 10 μm
mm is preferred. As the amount of short fibers, if it is too large, it becomes difficult to contain it in the fiber-reinforced thermoplastic resin sheet, conversely, if it is too small, the fusion property of the core material layer and the surface layer deteriorates, or the fiber-reinforced thermoplastic resin foam obtained. Since the flexural strength and the like of (3) are reduced, it is preferably 5 to 50% by volume in the composite sheet.

As the short fibers, in addition to the above short fibers,
For the purpose of recycling and cost reduction, wood materials, wood powder, crushed SMC, etc. can also be used.

The method of incorporating the short fibers is not particularly limited, but, for example, when the fiber-reinforced thermoplastic resin sheet as described above is prepared, the short fibers are added immediately before passing the thermoplastic resin-adhered fiber bundle through a heating roll. Examples include a method of spraying and then passing through a heating roll, and a method of forming a fiber-reinforced thermoplastic resin sheet, then spraying short fibers thereon and passing through a heating roll again.

In the present invention, the expandable thermoplastic resin is
It contains a thermoplastic resin and a foaming agent. As the thermoplastic resin, all foamable thermoplastic resins are used, for example, polyvinyl chloride, chlorinated polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyimide,
Polycarbonate, polyphenylene sulfide, polysulfone, polyether ether ketone, and the like can be mentioned. However, in the molding temperature range, when a resin having a low fluidity and a relatively low viscosity with respect to the thermoplastic resin used for the composite sheet is used, it is obtained. It is preferable since the uniformity of the thickness of the skin layer of the foam to be obtained can be improved. These thermoplastic resins may be used alone or in combination.

The thermoplastic resin forming the expandable thermoplastic resin does not have to be the same as the thermoplastic resin forming the fiber reinforced thermoplastic resin sheet, and the skin layer of the resulting fiber reinforced thermoplastic resin foam is obtained. It suffices if the interface between the core material layer and the core material layer is in a fused state in which it is not easily broken.

Further, the thermoplastic resin constituting the expandable resin composition may be subjected to a crosslinking treatment in order to improve the expandability. The crosslinking treatment method is not particularly limited,
For example, a method of crosslinking by irradiation with an active energy ray such as visible light, ultraviolet rays, α rays, β rays, γ rays, X rays or electron rays, a method of adding an organic peroxide to decompose and crosslink, a crosslinkable silane modification A method in which a thermoplastic resin is added and water treatment is performed to crosslink, and the like can be mentioned.

Examples of the thermoplastic resin which is crosslinked by electron beams include thermoplastic resins having α-hydrogen such as polyethylene, polypropylene and polystyrene.
Further, in the case of crosslinking with visible light or ultraviolet rays, a photopolymerization initiator (photosensitizer) is optionally contained. Examples of the photopolymerization initiator include benzoin alkyl ether type, acetophenone type, benzophenone type and thioxanthone type.

The organic peroxide is not particularly limited, but for example, isobutyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexene, 1,3- Bis (t-butyl-
Those having a relatively high decomposition temperature such as (oxyisopropyl) benzene, t-butylcumyl peroxide and di-t-butylperoxide are used.

At this time, the addition of the organic peroxide generally facilitates the cleavage of the thermoplastic resin itself, but if the crosslinking does not proceed to a desired degree, the crosslinking of triallyl cyanurate, diallyl phthalate, etc. is appropriately carried out. Auxiliary agents may be added.

Although the fiber diameter and the fiber length are not particularly limited in the thermoplastic resin, reinforcing fibers can be contained in order to further increase the specific strength and specific elasticity of the fiber-reinforced thermoplastic resin foam obtained. . As the reinforcing fiber, in addition to the reinforcing fiber forming the fiber-reinforced thermoplastic resin sheet, wood material, wood powder, crushed S, etc. for recycling and cost reduction.
MC or the like is used. The content of the reinforcing fiber is preferably 60% by volume or less in the composite sheet. If the content exceeds 60% by volume, it becomes impossible to uniformly foam,
On the contrary, the reinforcing effect is reduced.

In addition, in the thermoplastic resin, if necessary, a heat stabilizer, a plasticizer, a lubricant, an antioxidant, an ultraviolet absorber, a pigment, an inorganic filler, an additive such as a reinforcing short fiber, and a processing aid. Agents, modifiers and the like may be added.

The foaming agent is not particularly limited, and may be either a decomposing type foaming agent or a physical type foaming agent, and may be appropriately used depending on whether the foaming resin composition is being foamed while being supplied or after being foamed. As the decomposition type foaming agent, for example, azodicarbonamide, azobisisobutyronitrile, N, N'-dinitropentamethylenetetramine-
p, p′-oxybisbenzenesulfonyl hydrazide,
Examples thereof include barium azodicarboxylate, trihydrazinotriazine, and 5-phenyltetrazole.

Examples of the physical type foaming agent include aliphatic hydrocarbons such as isopentane, heptane and cyclohexane,
Examples thereof include fluorinated aliphatic hydrocarbons such as trichlorotrifluoroethane and dichlorotetrafluoroethane.

The amount of the foaming agent added can be appropriately selected depending on the desired expansion ratio of the foamable resin composition, and is usually 1 to 15 parts by weight with respect to 100 parts by weight of the thermoplastic resin.

In the first step of the first aspect of the present invention, the method of shaping the composite sheet into a tubular shape to form a tubular body is not particularly limited, but, for example, a method using a mold described later in Examples and , A method of gradually bending it with a synthetic resin shoe or roll. At this time, in order to prevent cracks and tears, it is preferable to perform shaping while heating the far-infrared heater or a hot air blower to soften the thermoplastic resin.

The term "cylindrical" includes not only those in which the side edges are butted against each other or overlapped with each other, but also those in which the side edges have a slight gap.

In the second step of the present invention 1, the foamable resin composition may be supplied to the inside of the cylindrical body while foaming, or may be supplied in an unfoamed state. As a method for supplying the foamable resin composition to the inside of the tubular body while foaming, for example, a foaming agent obtained by melt-kneading or impregnating a thermoplastic resin with a foaming agent at a temperature lower than the foaming temperature is obtained. A method in which the resin composition is supplied to an extruder and heated to a temperature equal to or higher than the foaming temperature of a foaming agent and supplied while foaming, or a thermoplastic resin is supplied to an extruder and melt-kneaded to obtain a heat in a molten state. Examples include a method in which a physical-type foaming agent is supplied into the plastic resin from the middle of the extruder and is supplied while foaming. The foaming temperature means the decomposition temperature in the case of a decomposition type foaming agent, and the boiling point in the case of a physical foaming agent.

As a method for supplying the foamable resin composition to the inside of the cylindrical body in an unfoamed state, for example, it is obtained by melt-kneading or impregnating a thermoplastic resin with a foaming agent at a temperature lower than the foaming temperature. Examples of the method include supplying the foamable resin composition in a desired shape such as a pellet shape, a sheet shape, a rod shape, or a pipe shape.

In the second step of the present invention 1, the tubular body is pressed against the inner surface of the mold by the foaming pressure due to the foaming of the expandable resin composition to form a desired cross-sectional shape along the inner surface shape of the mold. . Then, it cools and a fiber reinforced thermoplastic resin foam is obtained.

The expansion ratio at the center of the core layer is 30.
If it exceeds 2 times, the core material layer itself cannot hold the stress and the bending strength, specific strength and specific elasticity become low. Therefore, it is limited to 30 times or less, but in that range, it is optimal depending on the combination with the reinforcing fiber. The magnification can be appropriately selected, and it is preferably about 2 to 5 times from the viewpoint of the balance between mechanical strength such as bending strength and lightness.

In the outer layer of the core material layer, a low-magnification skin layer is formed during foaming by biting into and breaking the short fibers on the inner peripheral surface of the tubular body. The expansion ratio of the skin layer varies depending on the factors of the short fibers to be broken, but considering the specific strength and the specific elasticity, it is preferably about 1 to 3 times.

The core material layer does not need to be formed in a state in which the inside of the skin layer is filled so long as the above-mentioned problems during foam molding do not occur, and a layer having a constant thickness is formed inside the skin layer. None, a void may be formed in a part of the central portion. As a method of generating a void in a part of the central portion, for example, a method of periodically changing the extrusion rate or the take-up speed of the expandable resin composition, a core is provided in a mold, and the core is cooled by the mold. Examples thereof include a method of extending to a portion and a method of providing an air pipe in the core and injecting compressed air from the air pipe.

In the second aspect of the present invention, a method for forming a laminated sheet by laminating a core material forming layer made of a foamable resin composition containing a thermoplastic resin and a foaming agent on the surface of the composite sheet having short fibers, Although not particularly limited, for example, a core material forming layer is formed by extruding a foamable resin composition containing a thermoplastic resin and a foaming agent at a temperature lower than the foaming temperature of the foaming agent on the surface of the composite sheet having short fibers. And the like. Thereby, it is possible to prevent voids from remaining at the laminated interface between the surface of the composite sheet having the short fibers and the core material forming layer, and it is possible to suppress the occurrence of locally weak portions.

In the first step of the second aspect of the present invention, the laminated sheet is formed into a cylindrical shape with the core material forming layer facing inside,
The method for forming the laminated tubular body is not particularly limited, and examples thereof include the same method as the method for forming the tubular body in the first step of the first invention.

In the second step of the second aspect of the present invention, the core forming layer of the laminated cylindrical body is heated and foamed, and the foaming pressure presses the skin forming layer against the inner surface of the mold to shape it into a desired cross-sectional shape.
Then, it cools and a fiber reinforced thermoplastic resin foam is obtained.

[0044]

According to the method for producing a fiber-reinforced thermoplastic resin foam of the present invention 1, a composite sheet having short fibers on one surface of a fiber-reinforced thermoplastic resin sheet is formed into a tubular shape with the surface having the short fibers facing inward. Forming into a tubular body, the tubular body is fed into a mold, and a foaming resin composition containing a thermoplastic resin and a foaming agent is foamed inside the tubular body. Supply it while heating above the foaming temperature of the agent to foam it,
Or, after supplying, heating above the foaming temperature of the foaming agent, while biting the outer layer of the foamed resin into the short fibers to break the foam, the foaming pressure presses the cylindrical body against the inner surface of the mold to obtain the cylindrical body. By having a step of shaping into a cross-sectional shape, the core material layer can be a skin layer with a high expansion ratio in the center and a low expansion ratio with the outer layer ruptured, and short fibers are added to the outer layer of the core material layer. Since it can be bitten, a fiber-reinforced thermoplastic resin foam having high bending strength, specific strength and specific elasticity can be obtained.

In the method for producing a fiber-reinforced thermoplastic resin foam of the present invention 2, a thermoplastic resin and a foaming agent are contained on the surface having short fibers of a composite sheet having short fibers on one surface of a fiber-reinforced thermoplastic resin sheet. A step of forming a laminated tubular body by laminating a core material forming layer made of a foamable resin composition to form a laminated sheet into a tubular shape with the core material forming layer facing inside, and the laminated cylinder. The core material forming layer is foamed by heating above the foaming temperature of the foaming agent after supplying the shaped body into the mold, and the outer layer of the foamed resin bites into the short fibers to break the foam, and the foaming pressure causes the laminated tubular shape. By having a step of pressing the skin forming layer of the body against the inner surface of the mold to shape the tubular body into a desired cross-sectional shape, the core material forming layer is laminated on the surface having the short fibers of the composite sheet in advance. Laminated interface between the surface of the composite sheet having short fibers and the core forming layer Weak portions of locally intensity can be possible to prevent the voids from remaining can be suppressed from occurring.

[0046]

The present invention will be described below with reference to examples. Example 1 (1) Production of composite sheet The following A and B were used as the thermoplastic resin composition. Thermoplastic resin composition A: 100 parts by weight of polyvinyl chloride (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "TK-800"), tin-based heat stabilizer [manufactured by Sankyo Machine Gosei Co., Ltd., trade name "STANNNM"
(N)] A resin composition comprising 1 part by weight of polyethylene WAX (manufactured by Mitsui Yuka Co., Ltd., trade name "HIWAX 4202E").

Foaming resin composition B: 100 parts by weight of polyvinyl chloride (trade name "TK-600" manufactured by Shin-Etsu Chemical Co., Ltd.),
Tin-based heat stabilizer [Sanko Machine Gosei Co., Ltd., trade name "STANN
ONZ142F] 2.5 parts by weight, polyethylene WAX
(Mitsui Yuka Co., Ltd., trade name "HIWAX 220RTK")
0.2 parts by weight, acrylic processing aid (manufactured by Mitsubishi Rayon Co.,
Trade name "Metablene P-570") 8 parts by weight, calcium carbonate 35 parts by weight, dioctyl phthalate 2 parts by weight, sodium carbonate as a foaming agent (manufactured by Eiwa Chemical Co., Ltd., product name "S
C-D ") 3.5 parts by weight of a resin composition.

As shown in FIG. 1, 14 roving-like glass fiber aggregate bundles (4400 tex) 11 composed of filaments having a diameter of 23 μm were arrayed, and the powdery thermoplastic resin composition A (particle diameter: 80 μm) 12 is passed through the impregnation tank 13 in a floating state by the air fed in the direction of the arrow, and the glass fiber aggregate bundle 11
Was impregnated with the powdery thermoplastic resin composition A12.

16 chopped strand-shaped short fibers composed of filaments having a diameter of 13 μm and a length of 3 mm were sprinkled on one surface of the filaments 16 and heated by passing through a heating furnace 14 heated to about 200 ° C. Press, width 92
A composite sheet 15 having a thickness of 0.7 mm and a thickness of 0.7 mm was obtained. The resin: glass fiber: short fiber volume ratio of the obtained composite sheet 15 was 70:20:10.

(2) Production of Fiber Reinforced Thermoplastic Resin Foam The production apparatus shown in FIG. 2 has an unwinding roll 22 around which the composite sheet 15 obtained in (1) is wound, and a foamable resin composition. Extruder 23 of the object, a mold 24 having a tip bent at a right angle to the traveling direction, and having a through hole in the center thereof, which can shape the composite sheet into a circle, and the mold 24. The heat insulating material 26, the heating die 27, the heat insulating material 28, and the cooling die 29 are arranged on the traveling direction side, and the take-up machine 30 is provided on the traveling direction side.

The heating die 27 has a resin flow passage having a cross-sectional shape of 2
A 9 mm circular mold 27a has a resin flow path with a cross-sectional shape of 2
A 7 mm × 27 mm square mold 27b is connected, and the connected portion is processed so as to smoothly deform from a circular shape. Heat insulating material 28 and cooling die 29
Also has a square resin channel having a cross section of 27 mm × 27 mm inside. The mold 24 has a composite sheet 1
There is a U-shaped gap into which 5 can be inserted.

First, the composite sheet 15 is removed from the gap of the mold 24.
Inserted so that the short fiber-containing side is the inner side, the composite sheet 15 is abutted from the U-shape inside the mold 24 without overlapping the both ends, and the outer diameter is 29 mm and the thickness is 0.7 mm.
It was continuously shaped into a cylindrical body.

The expandable resin composition B31 was placed in the cylindrical body.
(Used after kneading and pelletizing with a twin-screw extruder having a diameter of 30 mm at a temperature of 170 ° C. or less in advance)
0 mm single screw extruder (L / D = 30, compression ratio 2.5) 2
3. At the same time, the resin was extruded at a resin temperature of 200 ° C. and laminated, and at the same time foaming was started.
After maintaining the temperature at 0 ° C. to complete the foaming, the cooling mold 29
The outer layer temperature was cooled to 60 ° C. to obtain a fiber-reinforced thermoplastic resin foam 32 having a square cross section with a side length of 27 mm and a foaming ratio of about 3.2 times. The molding speed was 1.5 m / min.

Example 2 A fiber reinforced thermoplastic resin foam 32 was obtained through the same steps as in Example 1 except for the following differences from Example 1.
Instead of the thermoplastic resin composition A, as the thermoplastic resin composition C, high density polyethylene [trade name “S561” manufactured by Mitsubishi Yuka Co., Ltd., melt index (hereinafter referred to as MI) = 0.75) is foamed. Instead of the resin composition B,
As the foamable resin composition D, 100 parts by weight of high-density polyethylene (manufactured by Mitsubishi Petrochemical Co., Ltd., trade name “ZH-52”, MI = 3), homopropylene (manufactured by Mitsubishi Petrochemical Co., Ltd., trade name “PY2”)
40B ", MI = 5) 100 parts by weight, silane crosslinked polypropylene (manufactured by Mitsubishi Petrochemical Co., Ltd., trade name" XPM800 "
H ”, MI = 11) 30 parts by weight, and a resin composition comprising 5 parts by weight of dicarbonamide was used.

The foamable resin composition D has a caliber of 3
Using a 0 mm twin-screw extruder, pelletizing at a resin temperature of 175 ° C., immersing the pellets in hot water of 100 ° C. under 1 atmosphere for 1 hour, and then drying the foamable resin composition D for the inner layer. I was there. In FIG.
0 mm single screw extruder (L / D = 30, compression ratio 2.5) 2
After extrusion lamination was performed while controlling the resin temperature to 165 ° C. in 3, the heating mold 27 heated to 205 ° C. was used to start foaming. Immediately before or immediately after the foamed resin layer fills the composite sheet, it is introduced into the cooling mold 29, cooled to the outer layer resin temperature of 60 ° C., and is reinforced with a square cross section having a side length of 27 mm and a foaming ratio of 6.1 times. Thermoplastic resin foam 3
2 was obtained.

Although not shown, a ventilation hole is provided inside the mold core 25 from the rear of the mold core 25, and the air pressure in the space formed near the tip of the mold core 25 is 0.3 kg / cm ^2.
Was adjusted so that Heating die 27 and cooling die 29
As the inner surface, a fluororesin-treated tetrafluoroethylene was used. These series of steps were performed at 1.8 m / min.

Example 3 The following E and F were used as the thermoplastic resin composition. Thermoplastic resin composition E: polypropylene (manufactured by Mitsubishi Petrochemical Co., Ltd., trade name "MA4", MI = 5). Expandable resin composition F: 100 parts by weight of high-density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd., trade name "EY-40H", MI = 1.5), silane crosslinkable polypropylene (manufactured by Mitsubishi Yuka Co., Ltd., trade name "XPM800HM" , MI = 11) 15 parts by weight,
A resin composition containing 5 parts by weight of tetradicarbonamide.

A composite sheet was produced in the same manner as in Example 1 except that the thermoplastic resin composition E was used instead of the thermoplastic resin composition A. The expandable resin composition F was maintained at a resin temperature of 170 ° C. or lower by a twin-screw extruder having a diameter of 30 mm, and thus a sheet having a thickness of 1 mm was prepared.
Laminated and fused to the short fiber-containing surface of the composite sheet at 20 ° C., and apply 20 m to the portions where the expandable resin composition layer is not laminated at both ends.
m, the thickness of the foamable resin composition layer is 1 mm, the thickness of the composite sheet layer is 0.7 mm, and the width is 240 mm.
A laminated sheet of was obtained.

Instead of the composite sheet 15 in FIG.
Unwinding the laminated sheet obtained by the above method,
Foaming was started by heating with a heating die 27 whose temperature was controlled to 5 ° C. Immediately before or immediately after the foamed resin fills the inner surface of the laminated sheet, it is introduced into the cooling mold 29 to adjust the outer layer resin temperature to 6
Cooled to 0 ° C, one side 27 mm, foaming ratio 7.3
A fiber-reinforced thermoplastic resin foam 32 having a double section square was obtained.

Although not shown, a ventilation hole is provided inside the mold core 25 from the rear of the mold core 25, and the air pressure in the space formed near the tip of the mold core 25 is 0.3 kg / cm ^2.
Was adjusted so that Heating die 27 and cooling die 29
As the inner surface, a fluororesin-treated tetrafluoroethylene was used. These series of steps were performed at 1.2 m / min.

Comparative Example 1 A fiber-reinforced thermoplastic resin foam was obtained in the same manner as in Example 1 except that a fiber-reinforced thermoplastic resin sheet containing no short fibers was used. Comparative Example 2 A fiber-reinforced thermoplastic resin foam was obtained in the same manner as in Example 2 except that a fiber-reinforced thermoplastic resin sheet containing no short fibers was used.

Comparative Example 3 A fiber-reinforced thermoplastic resin foam was obtained in the same manner as in Example 3 except that a fiber-reinforced thermoplastic resin sheet containing no short fibers was used.

With respect to the fiber-reinforced thermoplastic resin foam obtained by the above method, cross-section observation, bending strength, specific strength, specific elasticity, and fusion property between the core material layer and the surface layer were evaluated. The results are shown in Table 1. Regarding the cross-section observation, the cross section of the obtained fiber-reinforced thermoplastic resin foam was observed with an optical microscope.

Regarding bending strength, JIS K7203
It measured according to. The specific strength was calculated by measuring the volume and weight per unit length to determine the specific gravity, and dividing the bending strength by the specific gravity. Regarding specific elasticity, JIS
The flexural modulus was measured according to K7203, and the specific gravity was obtained by measuring the volume and weight per unit length, and the flexural modulus was divided by the specific gravity.

Regarding the fusing property between the core material layer and the surface layer, a cross section including the fused portion of the core material layer and the skin layer was cut into a small piece having a width of 20 mm and a length of 150 mm, and about 90 mm from one end.
Then, a cut was made with a knife, the core material layer was grasped and fixed by the chuck A, the skin layer was grasped by the chuck B, and the load when pulled in the 90 ° direction with respect to the chuck A was measured.

[0066]

[Table 1]

[0067]

EFFECTS OF THE INVENTION Since the method for producing a fiber-reinforced thermoplastic resin foam of the present invention 1 is configured as described above, a fiber-reinforced thermoplastic resin foam having high bending strength, specific strength and specific elasticity can be obtained. be able to.

Since the method for producing a fiber-reinforced thermoplastic resin foam according to the second aspect of the present invention is configured as described above, the mechanical strength such as bending strength can be further locally increased as compared with the first aspect. It is possible to obtain a fiber-reinforced thermoplastic resin foam having no weak portion.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating a manufacturing process of a composite sheet in an example of a method for manufacturing a fiber-reinforced thermoplastic resin foam of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a step of producing a fiber-reinforced thermoplastic resin foam in an example of the method for producing a fiber-reinforced thermoplastic resin foam of the present invention.

[Explanation of reference symbols] 15 composite sheet 16 short fiber 24 mold 27 heating mold 32 fiber reinforced thermoplastic resin foam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29K 105: 12 B29L 9:00

Claims (2)

[Claims] 1. A process for forming a tubular body by shaping a composite sheet having short fibers on one surface of a fiber-reinforced thermoplastic resin sheet into a tubular shape with the surface having the short fibers facing inward.
The tubular body is supplied into a mold, and inside the tubular body, a foamable resin composition containing a thermoplastic resin and a foaming agent,
The foaming agent is heated to a temperature higher than the foaming temperature and supplied while foaming, or after being supplied, it is heated to a temperature not lower than the foaming temperature of the foaming agent to bite the outer layer of the foaming resin into the short fibers to break the foam, and the foaming pressure The method for producing a fiber-reinforced thermoplastic resin foam, which comprises the step of pressing the tubular body against the inner surface of the mold to shape the tubular body into a desired cross-sectional shape. 2. A core material forming layer made of a foamable resin composition containing a thermoplastic resin and a foaming agent is laminated on the surface of a composite sheet having short fibers on one surface of a fiber-reinforced thermoplastic resin sheet. Then, the step of forming the laminated sheet into a cylindrical shape with the core material forming layer facing inward to form a laminated cylindrical body, foaming the foaming agent after supplying the laminated cylindrical body into the mold. While heating above the temperature to foam the core forming layer, the outer layer of the foamed resin bites into the short fibers to break the foam, and the foaming pressure pushes the skin forming layer of the laminated tubular body against the inner surface of the mold to form a cylinder. A method for producing a fiber-reinforced thermoplastic resin foam, which comprises the step of shaping the shaped body into a desired cross-sectional shape.