JP2000328494A - Composite sheet, molded material made from light weight fiber-reinforced plastic and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite sheet capable of molding a composite material made from a fiber-reinforced plastic having a very light weight, a high stiffness and also a good mechanical processing property. SOLUTION: This composite sheet contains a granular matrix resin, 10-450 mass pt. reinforcing fiber having 1-50 mm reinforcing fiber and 2-170 mass pt. heat expansive microcapsules based on 100 mass part above granular matrix resin. The method for producing the same is characterized by passing through the following 2 processes. (1) A process of dispersing and mixing the granular matrix resin with 10-450 mass pt. reinforcing fiber having 1-50 mm reinforcing fiber length and 2-170 mass pt. heat expansive microcapsules based on 100 mass part above granular matrix resin in an aqueous medium to obtain a slurry. (2) A process of obtaining a composite sheet from the slurry obtained in the above process (1) by a wet paper making method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite sheet, and more particularly to a composite sheet having a high thermal expansion property, a lightweight fiber-reinforced plastic molded article, and a method for producing the same.

[0002]

2. Description of the Related Art A so-called foamed resin sheet formed by foaming a synthetic resin is well known in the art, and is widely used as a lightweight material having heat insulation and sound absorption properties in building material panels and packaging materials. Examples of such a foamed resin sheet include foamed polystyrene, foamed polyurethane, foamed polyolefin (polypropylene, polyethylene), and the like.

Although the above-mentioned foamed resin sheet can be obtained with a very low density and a light weight, it has insufficient rigidity and has some difficulty in machinability such as cutting and drilling. Although there is a foamed resin sheet having a relatively high density and a relatively high rigidity, the rigidity is still insufficient, and there has been a problem in machinability.

On the other hand, as a lightweight sheet material having excellent rigidity,
BACKGROUND ART In recent years, fiber-reinforced thermoplastic resin composites in which a thermoplastic synthetic resin is impregnated into mat-like reinforcing fibers, so-called lightweight stampable sheets, have been widely applied as automotive interior materials such as ceiling materials. Conventionally, as such a lightweight stampable sheet, for example, JP-A-7-314442 discloses that a reinforcing glass fiber and a granular thermoplastic resin are dispersed and mixed in water containing a surfactant, dehydrated and dried. The obtained web is hot-pressed to a densified sheet, and then the densified sheet is obtained by heating the thermoplastic resin to a temperature equal to or higher than the melting point of the thermoplastic resin, melting the resin, and expanding the thickness of the densified sheet. A low density lightweight stampable sheet is disclosed.

[0005]

On the other hand, the above-mentioned lightweight stampable sheet is excellent in rigidity due to fiber reinforcement, but has a limit in weight reduction. This is because the expansion force of the sheet depends only on the springback of the glass fiber. The rigidity of the flat plate is (elastic modulus) x
(Thickness) Since it is proportional to ³ , it is very advantageous to increase the thickness to increase the rigidity of the article. However, when manufacturing a plate-like article having a flat surface with a stampable sheet, a large amount of sheets are needed in the thickness direction because the expansion force of the sheet made of the reinforcing fiber and the resin is not sufficient as described above. It was not enough in terms of conversion.

[0006] In view of the above situation, an object of the present invention is to provide a composite sheet which is more heat-expandable than a conventional light-weight stampable sheet, and is capable of obtaining a very lightweight and highly rigid molded article. It is an object of the present invention to provide a fiber-reinforced plastic molded product having good machinability and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, initially, in addition to a granular matrix resin and reinforcing fibers having a fiber length of 1 to 50 mm, In order to obtain foaming properties, various aqueous slurries containing an azodicarbonamide-based or tetrazole-based chemical foaming agent were prepared, and various composite sheets were prepared by a papermaking method. When trying to obtain a molded body having a low bulk density by heating and expanding, the pores formed in the molded body by the springback of the reinforcing fibers become open pores, and therefore, the composite sheet to which the chemical foaming agent as described above is added. Then, when the chemical foaming agent thermally decomposes and foams (when heated to 190 ° C. or more), the foaming gas is released to the outside of the molded body through the previously formed communicating holes. Because it was not possible to greatly improve the heat expansion properties.

Further, the present inventors have searched for various conditions and repeated experimental studies, and as a result, a granular matrix resin,
A composite sheet showing extremely large heat-expandability by a wet papermaking method from a slurry in which a reinforcing fiber having a fiber length of 1 to 50 mm and heat-expandable microcapsules are dispersed and mixed in an aqueous medium at a specific mixing ratio. And found that by thermally expanding this composite sheet under specific temperature conditions, a lightweight and high rigidity can be achieved at a high level, and a molded body with good machinability can be obtained. The present invention has been completed.

That is, the gist of the present invention is that first, a granular matrix resin and a granular matrix resin
The reinforcing fiber 10 having a fiber length of 1 to 50 mm with respect to the mass part
To 450 parts by mass and heat-expandable microcapsules 2-1
And 70 parts by mass.

Secondly, there is provided a method for producing a composite sheet as described above, characterized by passing through the following two steps. (1) Granular matrix resin, 10 to 450 parts by mass of reinforcing fiber having a fiber length of 1 to 50 mm, and 2 to 170 parts by mass of heat-expandable microcapsules, based on 100 parts by mass of granular matrix resin, are mixed with an aqueous medium. (2) a step of obtaining a composite sheet from the slurry obtained in the above (1) by a wet papermaking method.

Third, the matrix resin contains 10 to 450 parts by weight of reinforcing fibers having a fiber length of 1 to 50 mm and 2 to 170 parts by weight of heat-expandable microcapsules with respect to 100 parts by weight of the matrix resin. A lightweight fiber-reinforced plastic molded product characterized by having a bulk density of 0.01 g / cm ³ or more and less than 0.40 g / cm ³ .

Fourth, there is provided a method for producing the above-mentioned lightweight fiber-reinforced plastic molded article, which is characterized by passing through the following three steps. (1) Granular matrix resin, 10 to 450 parts by mass of reinforcing fiber having a fiber length of 1 to 50 mm, and 2 to 170 parts by mass of heat-expandable microcapsules, based on 100 parts by mass of granular matrix resin, are mixed with an aqueous medium. (2) obtaining a composite sheet from the slurry obtained in the above (1) by a wet papermaking method, (3)
A step of heating and expanding the composite sheet obtained in the above (2) at a temperature equal to or higher than the higher of the melting temperature of the matrix resin and the expansion start temperature of the heat-expandable microcapsules.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The composite sheet and molded article of the present invention comprise a matrix resin, reinforcing fibers having a fiber length of 1 to 50 mm, and heat-expandable microcapsules. As the matrix resin used in the present invention, a synthetic resin which is a thermoplastic resin and a thermosetting resin and shows a solid state at normal temperature and normal pressure (1 atm, 20 ° C.) can be used.

Specific examples of such a thermoplastic resin that can be used as the matrix resin in the present invention include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer, polystyrene, polyvinyl chloride, and polyvinylidene chloride. , Methacrylic resin, ABS resin, ethylene-vinyl acetate copolymer, polyamide resin, polyethylene terephthalate, polybutylene terephthalate, polyurethane, polyacetal,
Examples include a homopolymer or copolymer of a known thermoplastic resin such as polyphenylene sulfide and a fluororesin.
Among them, polyolefin resins are preferred because they are lightweight, have excellent chemical resistance, have relatively good strength and heat resistance, and are economical resins. Particularly, polypropylene is preferable. As the thermosetting resin, a phenol resin such as a self-curing modified novolak resin or a solid resol resin is preferable. These matrix resins can be used alone or as a mixture of two or more.

As the granular matrix resin for obtaining the composite sheet of the present invention, the above-mentioned granular material of the matrix resin is used. The average particle size of the granular material is 5 to 2000 μ
m, more preferably 10 to 1000
μm, particularly preferably 20 to 500 μm. If the average particle size is too large, the uniformity of the composite sheet tends to be impaired. If the average particle size is too small, it tends to be scattered at the time of preparing the sheet material, and handling tends to be difficult.

The type of the reinforcing fiber used in the present invention is not particularly limited as long as it is a fiber having a high elastic modulus which has the effect of reinforcing the plastic. Specific examples thereof include meta- or para-aramid fibers, organic fibers such as polyolefin fibers, polyester fibers, and polyvinyl alcohol fibers, glass fibers, and inorganic fibers such as alumina fibers, as well as pitch-based or poly-based fibers. Acrylonitrile-based carbon fibers and the like can be mentioned. Among them, glass fibers and carbon fibers are preferably used. The above reinforcing fibers can be used alone or as a mixture of two or more.

The reinforcing fiber used in the present invention has an average fiber length of 1 to 50 mm, preferably 3 to 25 mm.
It is. If the fiber length is less than 1 mm, no reinforcing effect can be obtained. If the fiber length exceeds 50 mm, dispersion in an aqueous medium becomes difficult, and uniform composite sheets and molded articles cannot be obtained. The average fiber diameter of the reinforcing fibers is 2 to 10
It is preferably in the range of 0 μm, more preferably 5 to 50 μm. If the fiber diameter of the reinforcing fibers is too small, a sufficient expansion effect due to springback during heating cannot be obtained. On the other hand, if the fiber diameter is too large, a reinforcing effect cannot be obtained, and dispersion in an aqueous medium becomes difficult, so that uniform composite sheets and molded articles cannot be obtained.

Particularly preferred examples of the combination of the matrix resin and the reinforcing fiber include a combination of a polypropylene resin and a glass fiber, and a combination of a phenol resin and a carbon fiber. The former is a good combination in terms of recycling because it is excellent in economy and is widely used in conventional stampable sheets, and the latter provides a material having particularly high rigidity and high heat resistance.

Next, the heat-expandable microcapsules used in the present invention will be described. As the heat-expandable microcapsules used in the present invention, known ones can be used. In particular, core-shell heat-expandable microcapsules in which the core is a liquid organic substance and this is encapsulated in a shell made of a thermoplastic resin are preferable. . Examples of the liquid organic substance of the core include hydrocarbons and ethers having a boiling point of 150 ° C. or less at 1 atm and 20 ° C., such as isobutane, pentane, and hexane. Examples of the thermoplastic resin forming the shell include polyethylene, polypropylene, polyolefin resins such as ethylene-propylene copolymer, polystyrene, polyvinyl chloride, polyvinylidene chloride, methacrylic resin, ABS resin, and ethylene / vinyl acetate. Known thermoplastic resins such as copolymers, polyamide resins, polyethylene terephthalate, polybutylene terephthalate, polyurethane, polyacetal, polyphenylene sulfide, and fluororesins are exemplified. A particularly preferred example is a microcapsule in which the core is made of a liquid hydrocarbon such as isobutane, pentane, and hexane, and the shell is made of a thermoplastic resin such as an acrylonitrile copolymer.

The size of the heat-expandable microcapsules in the present invention is such that the average particle size before heat expansion is 5 to 1
000 μm, especially 10 to 30 μm
It is preferred that Further, it is preferable that the outer diameter after the thermal expansion expands to twice or more, preferably about 3 to 10 times the size before expansion. If the particle diameter of the microcapsules is too small, inconvenience tends to occur in handling such as detachment from the fiber-reinforced plastic molded product after thermal expansion. On the other hand, if the particle size is too large, it tends to be difficult to mix uniformly with the matrix resin and the reinforcing fibers.

In the heat-expandable microcapsule of the present invention, the shell softened by heating expands like a balloon by the force of the core to evaporate and expand. The expansion temperature generally has a range of about several tens to one hundred degrees, but the expansion start temperature (lower limit of the expansion temperature) is preferably 80 ° C or higher, more preferably 100 to 230 ° C, and particularly preferably. 110-200 ° C. If the expansion temperature is too low, it tends to be difficult to obtain a fiber-reinforced plastic composite having sufficient strength, and in the wet papermaking method in the process of the production method of the present invention, the temperature at which the formed composite sheet is dried. Is extremely impractical. On the other hand, if the expansion temperature is too high, the synthetic resin tends to deteriorate when heated and expanded.

[0022] Incidentally, the expansion starting temperature, the initial average particle diameter of the thermal expandable microcapsules and T _0, the average particle diameter after leaving for one minute in a hot air dryer set at a constant temperature was set to T ₁ In this case, the lower limit of the temperature is defined such that T ₁ > 1.2T ₀ . The average particle diameter can be measured by a known method such as a laser diffraction method.

In the present invention, the mixing ratio of the matrix resin, the reinforcing fibers and the heat-expandable microcapsules is such that the reinforcing fibers 10 to 4 are added to 100 parts by mass of the matrix resin.
50 parts by mass, heat-expandable microcapsules must be 1 to 170 parts by mass, and the preferable compounding ratio is 25 to 250 parts by mass of reinforcing fibers, heat-expandable microcapsules 5 to 120 based on 100 parts by mass of matrix resin. Parts by weight. If the amount of the reinforcing fibers is too small, the reinforcing effect cannot be obtained. If the amount is too large, it becomes difficult to uniformly impregnate the reinforcing fibers with the matrix resin during thermal expansion molding. When the amount of the heat-expandable microcapsules is too small, the thermal expansion performance is insufficient, and when the amount is excessive, the strength of the molded body is insufficient.

The bulk density of the lightweight fiber-reinforced plastic molded article of the present invention must be 0.01 g / cm ³ or more and less than 0.40 g / cm ³ ,
Is preferably ^{0.04g / cm 3 ~0.30g / cm 3} , it is particularly preferred in view of weight reduction is less than 0.04 g / cm ³ or more 0.20 g / cm ^3. If the bulk density is too small, the strength is insufficient, and if it is too large, the effect of weight reduction cannot be expected.

The composite sheet and the lightweight fiber-reinforced plastic molded article of the present invention can be produced by the production method of the present invention, for example, as follows. First, a granular matrix resin, 10 to 450 parts by mass of reinforcing fiber having a fiber length of 1 to 50 mm and 2 to 170 parts by mass of heat-expandable microcapsules with respect to 100 parts by mass of the granular matrix resin are mixed with an aqueous medium such as water. And disperse and mix in the slurry to prepare a slurry for wet papermaking. In addition to the above-mentioned components, pulp-shaped synthetic fibers (hereinafter abbreviated as synthetic pulp) may be added as needed for the purpose of improving the trapping property of the heat-expandable microcapsules. In this case, the added amount of synthetic pulp
5 to 30 parts by mass of the granular matrix resin
Parts by weight are preferred. Specific examples of the synthetic pulp include polyolefin fiber pulp such as modified polypropylene and modified polyethylene, and aramid fiber pulp. In addition, when dispersing and mixing in an aqueous medium, it is preferable to use a thickener made of a synthetic resin or a natural polysaccharide (such as xanthan gum) in order to improve the dispersibility and obtain a uniform sheet. The amount of such a thickener to be added is preferably less than 2% by mass based on the total mass of the composite sheet. It is also possible to use a small amount of a binder such as an organic polymer latex, that is, less than about 3% by mass, preferably less than 1% by mass, based on the total mass of the composite sheet.

When it is desired to use a matrix resin or a microcapsule having a small particle diameter smaller than the mesh of the papermaking screen, a binder having an ionic charge is used as the above-mentioned binder, and the opposite ion is used. What is necessary is just to coagulate the floc having a size larger than the mesh of the screen by using a coagulant having a charge. As a binder having an ionic charge, a bound sulfonium group,
Acrylic polymer or styrene containing isothiouronium group, pyridinium group, quaternary ammonium group, sulfate group, sulfonate group or carboxylate group
Polymer latexes consisting of substantially water-insoluble organic polymers with bound anionic or cationic charges, such as butadiene polymers, as well as enzymatically or chemically modified ionic starches. Suitable organic coagulants include various organic coagulants such as aluminum polychloride (aluminum hydroxychloride), partially hydrolyzed polyacrylamide, modified cationic polyacrylamide, diallyldiethylammonium chloride, and the like. The amount of the coagulant added is preferably less than about 3% by mass, particularly preferably less than 1% by mass, based on the total mass of the composite sheet.

Thus, a slurry obtained by mixing the particulate matrix resin, the reinforcing fibers, the heat-expandable microcapsules, and the synthetic pulp and chemicals added as necessary, and dispersing and mixing them in an aqueous medium is desirably used. Uses a paper machine or the like to perform solid-liquid separation so that the solid content in the aqueous medium is formed into a sheet in the manner of wet papermaking. Next, the wet sheet is dried to obtain the composite sheet of the present invention. Preferably the basis weight of the composite sheet is 50 to 2000 g / m ^2, and more preferably 100 to 1000 g / m ^2. If the grammage is too small, the sheet strength required for handling cannot be obtained, and if the grammage is too large, it becomes difficult to dry the sheet or to increase the thickness, making it difficult to wind up.

Next, one or a plurality of the composite sheets obtained as described above are laminated and charged into a mold as required, and the melting temperature of the matrix resin and the expansion start temperature of the heat-expandable microcapsules are determined. The composite sheet is heated to a temperature equal to or higher than the higher one and thermally expanded. Here, the mold includes two metal plates or the like that can secure a predetermined clearance with a spacer. Further, a batch-type press or a double-belt press having a predetermined clearance may be used instead of the mold. Since the composite sheet of the present invention has a small thermal expansion in a direction other than the thickness direction, for example, when a board material is formed, a mold for regulating a plane direction is not necessary. When molding by heating and expanding, pressure is applied as necessary so as not to expand beyond a desired thickness. In this heat expansion step, at the same time as the matrix resin, the reinforcing fibers and the synthetic pulp to be added as required are fused firmly, the expansion of the heat expandable microcapsules and the elasticity of the reinforcing fibers effectively act. The sheet thickness expands as a very small bulk density is obtained.

In the heating and expanding step, if the heating temperature is too high, not only does the resin deteriorate, but the expanded composite sheet may contract again. This is because the heat-expandable microcapsules shrink due to excessive heating, and it is desirable to select heating conditions in consideration of this. Even when the matrix resin is a thermosetting resin, it is desirable that re-shrinkage of the microcapsules does not occur at least until the thermosetting resin gels and can maintain a certain shape. Next, while maintaining the thermally expanded shape, the molded product is cooled to obtain the lightweight fiber-reinforced plastic molded product of the present invention. In addition,
As the composite sheet of the present invention, before heating and expanding the microcapsules, the matrix resin is preliminarily melted,
The sheet may be densified while maintaining the heat expansion performance. In that case, a plurality of sheets may be laminated and densified.

The lightweight fiber-reinforced plastic molded article of the present invention obtained as described above has a very low bulk density and can be reduced in mass even with a thick molded article, and has good machinability. Furthermore, since the thermal expansion is greater than the limit due to the springback of the reinforcing fibers, the reinforcing fibers are lying in the sheet plane direction in the molded body. It also has the property that the surface is less irritating to the skin (stinginess). Since the composite sheet of the present invention is particularly excellent in heat expansion property, it can be used as a precursor for obtaining a lightweight fiber-reinforced plastic molded article of the present invention. Is 0.
When used to obtain a molded article made of fiber reinforced plastic having a bulk density of about 40 g / cm ³ or more, which is comparable to that of a conventional lightweight stampable sheet, the surface smoothness can be improved because there is enough room for expansion. it can.

The lightweight fiber-reinforced plastic molded article of the present invention has a continuous pore structure and is not easily deformed even when compressed, and is inserted into, for example, a bag-shaped gas barrier container. By vacuum-evacuating the gas barrier container and sealing the opening, a vacuum heat insulating material can be obtained.

[0032]

Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Table 1 shows the granular matrix resin used in the examples and comparative examples, Table 2 shows the reinforcing fibers, Table 3 shows the heat-expandable microcapsules, and Table 4 shows the synthetic pulp.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

Examples 1 to 9 0.31 g of xanthan gum was added to 12.5 liters of water while stirring, and then heat-expandable microcapsules were added.
Granular matrix resin and, if necessary, synthetic pulp were added according to the composition shown in Table 2, and the mixture was stirred for 5 minutes and well dispersed.
Then, a solid acrylic polymer latex containing 60% water and a reinforcing fiber in this dispersion [Boncoat SFC-55 (trade name) manufactured by Dainippon Ink and Chemicals, Inc.]
After adding 53 g, 0.5% by mass of a cationic coagulant [B
etz Laboratories, product name: Be
tz1260] by adding 17.42 g gradually to obtain a slurry. Next, 12.5 liters of water was spread over a raw material container of a sheet machine [manufactured by Kumagai Riki Kogyo Co., Ltd.], and the above slurry was added.
Dewatering was performed on an 8 mm screen to obtain a wet sheet.
The obtained sheet was lightly compressed and then dried, and the basis weight was 40
A composite sheet of 0 g / m ² was obtained. Each of the obtained composite sheets is laminated two times, and is put together with a spacer having a predetermined thickness between two forming stainless steel plates heated to a predetermined temperature, and heated in a heating press machine for 10 minutes to expand the composite sheet. After that, the entire stainless steel plate was taken out and cooled in a cooling press. In the heating press and the cooling press, a surface pressure of 5 kg / cm ² was applied from above the stainless steel plate with the spacer in between. As described above, a board-shaped lightweight fiber-reinforced plastic molded body having a thickness of 10 to 20 mm corresponding to the thickness of the spacer was obtained.

Example 10 A composite sheet having a basis weight of 400 g / m ² obtained in the same manner as in Example 1 and having a thickness of 10 mm was obtained in the same manner as in Example 1 except that the number of laminated sheets was changed to six. A board-shaped lightweight fiber-reinforced plastic molding was obtained.

Comparative Example 1 A slurry having the composition shown in Table 5 was prepared in the same manner as in Example 1 except that the heat-expandable microcapsules were not used, and a composite sheet having a basis weight of 400 g / m ² was obtained. Two sheets of this composite sheet are laminated, and sandwiched between two stainless steel plates, with a surface pressure of 1
0 kg / cm ² , 190 ° C. and hot press,
Subsequently, a sheet compacted to a thickness of 0.8 mm and a density of 1.0 / cm ³ was obtained by cooling and pressing at the same surface pressure. The densified sheet is placed between two forming stainless steel plates heated to 190 ° C. together with a spacer having a thickness of 1.8 mm, and heated for 10 minutes in a heating press to expand the sheet. Each was taken out and cooled in a cooling press machine. In the heating press and the cooling press, a surface pressure of 5 kg / cm ² was applied from above the stainless steel plate with the spacer in between. As described above, a board-shaped molded article made of fiber-reinforced plastic having a thickness of 1.8 mm was obtained.

Comparative Example 2 A foamable resin powder was prepared by freeze-grinding a mixture obtained by melt-kneading 9 parts by mass of azodicarboxylic acid amide as a chemical foaming agent in 100 parts by mass of a polypropylene resin. Using 109 parts by mass of the expandable resin powder and 73 parts by mass of the reinforcing glass fiber, a slurry having the composition shown in Table 5 was prepared in the same manner as in the example, and a composite sheet having a basis weight of 400 g / m ² was prepared. Obtained. Six composite sheets were laminated, and an attempt was made to form a board-shaped lightweight fiber-reinforced plastic molded article having a thickness of 10 mm in the same manner as in Example 10 except that the heating temperature was set to 230 ° C. However, the thickness of the obtained molded body did not reach 10 mm, and irregularities were observed on the surface. Further, the adhesion between the layers of the laminated sheet was insufficient, and the sheet could be easily peeled off by hand.

Table 5 shows the compositions of the slurries in Examples and Comparative Examples. Table 6 shows the heating temperature and the thickness of the spacer used when molding the fiber-reinforced plastic molded body.

[0043]

[Table 5]

[0044]

[Table 6]

Table 7 shows the physical properties of the fiber-reinforced plastic moldings obtained in the examples and comparative examples. In addition,
The thickness is measured with a micro gauge and the flexural modulus is JIS
It was measured according to K7055.

[0046]

[Table 7]

As is evident from the results of the above Examples and Comparative Examples, the composite sheet of the present invention has a very low bulk density, a high rigidity, and a lightweight fiber reinforcement due to the action of the heat-expandable microcapsules. A plastic molding was obtained. Further, as is clear from Example 10 and Comparative Example 1, the lightweight fiber-reinforced plastic molded article of the present invention can be increased in thickness even if it is lightweight, so that it can be compared with a normal lightweight stampable sheet having the same mass. if you did this,
Rigidity increased due to the effect of thickness. Further, the lightweight fiber-reinforced plastic molded article of the present invention obtained in the examples can be easily and neatly cut with a normal office cutter knife,
It was found that it had good workability.

[0048]

The composite sheet of the present invention is more excellent in thermal expansion property than the conventional lightweight stampable sheet relying only on expansion of the reinforcing fiber by springback due to the sheet expansion effect provided by the heat-expandable microcapsules. I have. Therefore, a molded article having a very low bulk density can be obtained by expansion molding, and a molded article having an improved surface smoothness can be obtained when the bulk density is approximately the same as that of the related art.
The lightweight fiber-reinforced plastic molded article of the present invention has a very low bulk density and a large thickness even when lightweight, so that the rigidity derived from the reinforcing fiber and the synergistic effect of the thickness effect enable the extremely lightweight High rigidity and good workability. Therefore, the lightweight fiber-reinforced plastic molded article of the present invention takes advantage of the above-mentioned features, and is utilized in various industrial applications such as building materials and heat insulating materials, and furthermore, by utilizing the continuous pore structure, is used as a sound absorbing material, or is refrigerated. It can be applied to applications such as core materials of vacuum insulation materials (panels) used for equipment and building materials. According to the production method of the present invention,
The composite sheet and the lightweight fiber-reinforced plastic molded article can be easily manufactured.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuo Inoue 4-1 Hina Kitamachi, Okazaki City, Aichi Prefecture Inside the Unitika Environmental Technology Center Co., Ltd. (72) Inventor Hidenobu Yamazaki 5 Ujidonouchi, Uji City, Kyoto Unitika Ltd. Uji factory

Claims (4)

[Claims] 1. A fiber length of 1 to 50 m with respect to a granular matrix resin and 100 parts by mass of a granular matrix resin.
m. A composite sheet comprising 10 to 450 parts by mass of reinforcing fibers and 2 to 170 parts by mass of heat-expandable microcapsules. 2. The method for producing a composite sheet according to claim 1, wherein the method comprises the following two steps. (1) Granular matrix resin, 10 to 450 parts by mass of reinforcing fiber having a fiber length of 1 to 50 mm, and 2 to 170 parts by mass of heat-expandable microcapsules, based on 100 parts by mass of granular matrix resin, are mixed with an aqueous medium. (2) a step of obtaining a composite sheet from the slurry obtained in the above (1) by a wet papermaking method. 3. A matrix resin comprising 10 to 450 parts by mass of reinforcing fibers having a fiber length of 1 to 50 mm and 2 to 170 parts by mass of heat-expandable microcapsules with respect to 100 parts by mass of the matrix resin. , Bulk density is 0.0
A lightweight fiber-reinforced plastic molded product having a weight of 1 g / cm ³ or more and less than 0.40 g / cm ³ . 4. The method for producing a lightweight fiber-reinforced plastic molded product according to claim 3, wherein the method comprises the following three steps. (1) Granular matrix resin, 10 to 450 parts by mass of reinforcing fiber having a fiber length of 1 to 50 mm, and 2 to 170 parts by mass of heat-expandable microcapsules, based on 100 parts by mass of granular matrix resin, are mixed with an aqueous medium. (2) obtaining a composite sheet from the slurry obtained in the above (1) by a wet papermaking method, (3)
A step of heating and expanding the composite sheet obtained in the above (2) at a temperature equal to or higher than the higher of the melting temperature of the matrix resin and the expansion start temperature of the heat-expandable microcapsules.