JPH0839597A - Manufacture of light-weight stampable sheet - Google Patents

Abstract

PURPOSE:To manufacture a light-weight stampable sheet in which a bending strength is improved by laminating two webs to match the inside with the surfaces in contact with a porous support at the time of making the web, and reheating it at the melting point or higher of the resin to expand it in its thickness direction. CONSTITUTION:Dispersion in which glass fiber and thermoplastic resin particles are dispersed in a surfactant-containing medium containing air bubbles is continuously made on a moving porous support to make a web. In this case, the fiber content in the dispersion is set to 0.2-4.0, the velocity of the separated aqueous solution through the support is set to 4cm per sec or more, and the moving speed of the support is set to 4cm/sec or more. At the time of making the web, the surface in contact with the support is disposed inside, two webs are laminated, reheated, expanded to form a high expanded layer 3 and a low expanded layer 4. Thus, a stampable sheet can be reduced in weight, and its bending strength can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a member that is required to be lightweight and highly rigid, especially a lightweight stampable sheet that is most suitable as an interior material for automobiles.

[0002]

2. Description of the Related Art A fiber-reinforced thermoplastic resin composite material in which a thermoplastic resin is impregnated in a mat-like reinforcing fiber, that is, a so-called stampable sheet has been rapidly spread in recent years. Its features are that it has a specific gravity as low as 1.5 or less, and that it can be easily pressed into various molded products within a cycle time of several minutes if a temperature of about 200 ° C is applied.

In particular, a stampable material obtained by applying heat and pressure to a web composed of glass fibers and a granular thermoplastic resin prepared by the papermaking method disclosed in JP-A-60-158227, and then cooling the web. Since the glass fibers of the sheet are opened to almost monofilament state, if the glass fibers are heated again to the melting point of the thermoplastic resin or higher, the glass fibers restrained by the resin cause springback and the thickness direction is increased. It is possible to obtain a porous stampable sheet that is uniformly expanded, that is, a lightweight stampable sheet.

The characteristic features of this lightweight stampable sheet are that it is lighter than a normal stampable sheet before being inflated, and has a large load bearing capacity per unit weight and a small deflection. Such lightness and excellent rigidity make it possible to use a small amount of material and greatly contribute to cost reduction. However, depending on the application, the lightweight stampable sheet may be required to have further increased tensile strength or bending strength. To improve the bending properties of a material, as shown in Fig. 2 (a), a method of introducing a component (layer) 2 having a low hardness inside the material and a component (layer) 1 having a high hardness due to the surface layer of the material is adopted. Is generally known. vice versa,
As for the improvement of tensile properties, as shown in Fig. 2 (b), the component (layer) with higher hardness is added to the center layer in the plate thickness direction
The method of introducing 1 is effective. In forming a light-weight stampable sheet, a method of suppressing the amount of expansion, introducing a layer having few voids and high toughness as a surface layer for improving bending strength and a central layer for improving tensile strength is used. It is valid.

In Japanese Patent Publication No. 2-48423, three or more sheets are laminated to form a lightweight fiber reinforced resin sheet,
Moreover, there is a technique for improving bending rigidity by disposing a sheet having a small expansion amount on both outer sides and a sheet having a large expansion amount on the inner side. However, in this method, since at least three sheets are used for molding, a web having a basis weight of 300 g / m ² or less must be manufactured in order to obtain a molded product having a basis weight of 1000 g / m ² . Such a low basis weight web produced by the papermaking method does not have sufficient strength for handling and is not suitable for actual forming.

On the other hand, for the purpose of increasing the tensile strength of the lightweight fiber reinforced resin sheet, both sides of the sheet are uniformly heated, and the heating is controlled so that the central portion of the sheet does not reach the softening point or more. JP-A-61-501398 discloses a technique for obtaining a sheet in which the hardness of the sheet is expanded and the hardness of the sheet is maintained while the central portion is compressed. However, with this method, it is difficult to control the heating temperature during molding, and thus the thickness of the central portion that does not expand.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lightweight stampable sheet which can easily obtain a lightweight stampable sheet excellent in bending strength or tensile strength, in which an appropriate weight per unit area of the web can be obtained for handling. Is to propose a manufacturing method of.

[0008]

Means for Solving the Problems As a result of earnest studies, the inventors of the present invention have realized that a papermaking method can realize a structure in which the amount of expansion differs in the thickness direction of a single web, as desired. As a result, it was found that a lightweight stampable sheet with improved bending properties or tensile properties can be easily obtained.

The present invention was made on the basis of the above-mentioned findings, and is a porous liquid that moves a dispersion liquid in which glass fibers and granular thermoplastic resin are dispersed in a surfactant-containing aqueous medium containing air microbubbles. A sheet-shaped web is prepared by continuously making paper on a support, and after this web is heated and pressed to solidify, it is reheated to a temperature equal to or higher than the melting point of the resin and expanded in the thickness direction to obtain a density of 0.4 to in 1.0g / cm ^3, glass fiber 20
In the method for producing a porous lightweight stampable sheet composed of 70% by weight and a thermoplastic resin of 30 to 80% by weight, the web-making process comprises (a) a glass fiber content in the dispersion liquid of 0.2 to 4.0% by weight, and (b) when the dispersion is made on the porous support, the rate at which the separated aqueous surfactant solution passes through the porous support is 4 cm / sec or more,
And (c) a method for producing a lightweight stampable sheet, characterized in that the moving speed of the porous support is 1 to 10 m / min, and the present invention provides a web prepared by the above method, Manufacture of a lightweight stampable sheet with improved flexural strength by stacking two sheets, with the surfaces that were in contact with the porous support during the papermaking process, aligned inside and reheated above the melting point of the resin to expand in the thickness direction. The present invention also provides a method
Two webs prepared by the above method were laminated with the surface that was in contact with the porous support during the paper making process being on the outside.
Reheat above the melting point of the resin to expand in the thickness direction,
A method for manufacturing a lightweight stampable sheet having improved tensile strength.

[0010]

The present invention will be described below in more detail. In the present invention, a structure in which the amount of expansion at the same heating temperature differs in the thickness direction in one web has a sectional structure in the thickness t direction as shown in FIG. That is, the lower layer portion 3 of the web has a structure in which the glass fibers 5 are bent in a loop shape and are three-dimensionally entangled,
The upper layer portion 4 has a structure in which the glass fibers 5 are straight and are arranged only in a two-dimensional direction. In the structure such as the lower layer portion 3 (hereinafter referred to as a high expansion layer), the amount of springback of the glass fiber 5 is extremely large, and the expansion amount is larger than that in the upper layer portion 4 (referred to as a low expansion layer).

If a sheet obtained by heating and pressing such a web to be solidified is used, two high expansion layers 3 are faced to each other and laminated, and reheated to a temperature equal to or higher than the melting point of the resin to expand in the thickness t direction. As a result, a lightweight stampable sheet with improved bending characteristics can be obtained. Further, by stacking two low-expansion layers 4 facing each other and expanding them, a lightweight stampable sheet with improved tensile properties can be obtained.

Usually, the web of the stampable sheet produced by the papermaking method is, as disclosed in JP-A-60-158227, a glass fiber and a granular thermoplastic resin, and an aqueous solution of a surfactant containing fine air bubbles. It is prepared by continuously paper-making the dispersion liquid dispersed in 1. on a moving porous support. Here, in order to prepare a web having a structure as shown in FIG. 1, it is important to realize the following papermaking conditions.

(A) The content of the glass fiber in the above dispersion liquid satisfies the range of 0.2 to 4.0% by weight. When the glass fiber content is less than 0.2%, the number of glass fibers intersecting each other in the dispersion is reduced, and the three-dimensional entanglement of glass fibers in the web does not occur. If it exceeds 4.0%, the concentration of the dispersion becomes high, and it becomes difficult to produce a web having a uniform basis weight.

(B) When the dispersion is prepared on the porous support, the aqueous surfactant solution must be passed through the porous support at a rate of 4 cm / sec or more. Below this speed, no looping of the glass fibers in the web occurs. (c) In continuous papermaking, the moving speed of the porous support should be 1 to 10 m / min. Above 10 m / min, the glass fibers are aligned along the porous support and no loop bending occurs. A moving speed of less than 1 m / min is not practical in terms of productivity.

The web prepared under the above papermaking conditions is
30 to 50% by weight of the porous support side of the web is the high expansion layer 3,
Furthermore, the layer above it forms the low expansion layer 4. This structure is not lost even in the sheet obtained by heating and pressing the web to solidify it. This solidified sheet alone,
Or you can stack multiple sheets according to your purpose
A light-weight stampable sheet can be obtained by expanding it to an arbitrary ratio by the method disclosed in Japanese Patent Publication No.

The density of the lightweight stampable sheet of the present invention is
It should be in the range of 0.4 to 1.0 g / cm ³ . If it is less than 0.4 g / cm ³ , the effect of the internal voids as a strength defect appears more strongly, and sufficient rigidity is not exhibited. If it exceeds 1.0g / cm ³ ,
There is no difference from normal stampable seats, and no weight reduction effect can be expected. The length of the glass fiber used in the present invention is preferably 6 to 50 mm in order to obtain its reinforcing effect and ensure dispersion in the surfactant-containing aqueous medium. If the glass fiber length is too small, a sufficient reinforcing effect cannot be obtained.
If the glass fiber length is too large, aggregation of the glass fibers occurs in the step of dispersing the glass fibers in the aqueous medium,
This causes a decrease in expandability.

The glass fiber has a weight ratio of glass fiber to thermoplastic resin (fiber / resin) of 20 / in webs and sheets.
Used to be 80 to 70/30. Excessive blending of glass fibers is a process of heating and pressing the web to solidify,
It becomes difficult to uniformly impregnate the glass fiber with the thermoplastic resin. In addition, if the amount is too small, the reinforcing effect is naturally small. Thermoplastic resins that can be used in the present invention include, for example, polyethylene,
Polypropylene, polystyrene, polyethylene terephthalate, polycarbonate, polyamide, polyacetal, polyvinyl chloride, etc., and copolymers or graft compounds and blends containing these resins as main components, for example, ethylene-propylene copolymer, ethylene-vinyl chloride. Examples thereof include a copolymer and a styrene-butadiene-acrylonitrile copolymer.

An adhesive resin may be used for the purpose of improving the adhesion between the glass fiber and the thermoplastic resin. For example, when the matrix resin is polypropylene, examples of the adhesive resin include polyolefin modified with maleic anhydride, acrylic acid, etc., and resin modified with epoxy such as bisphenol A type.

[0019]

EXAMPLES The present invention will be specifically described below based on examples. (Example 1) Sodium dodecylbenzenesulfonate 0.
08% by weight aqueous solution, glass fiber (average length 13mm, diameter 11μ
m) and granular polypropylene were added to the aqueous solution in an amount of 0.4% by weight and 0.6% by weight, respectively, and the mixture was stirred and foamed to prepare a dispersion liquid. This dispersion was continuously poured on a porous support (polyester plain weave cloth, trade name Planet, manufactured by Nippon Filcon) that moves horizontally at 4 m / min,
A paper having a basis weight of 500 g / m ² was prepared by making a paper so that the speed at which the above aqueous solution was separated by the porous support and passed through was 4 cm / sec. After drying this web, it was cut into a size of 25 × 25 cm, preheated at 210 ° C., placed between cooling plates and pressed at a pressure of 5 kg / cm ² to obtain a solidified dense sheet. It was Two sheets of this sheet were laminated together, with the surfaces that were in contact with the porous support during the papermaking process, placed on the lower mold of a flat plate mold (clearance 2.0 mm) heated to 210 ° C, and after 5 minutes, The mold was cooled to obtain an expanded porous lightweight stampable sheet A (Basis weight: 1000 g / m ² ). The results of bending test and tensile test of this sheet are shown in Table 1. The density was 0.50 g / cm ³ . (Example 2) Two solidified and dense sheets prepared in the same manner as in Example 1 were laminated so that the surface which was in contact with the porous support during the papermaking process was facing outward, and the same procedure as in Example 1 was performed. It was expanded in the mold to obtain a lightweight stampable sheet B. The results of bending test and tensile test of this sheet are shown in Table 1. The density was 0.50 g / cm ³ . (Comparative Example 1) Two solidified and dense sheets prepared in the same manner as in Example 1 were laminated so that the surfaces in contact with the porous support in the papermaking step faced in the same direction, and the same procedure as in Example 1 was performed. Then, it was expanded in a mold to obtain a lightweight stampable sheet C.
The results of bending test and tensile test of this sheet are shown in Table 1. The density was 0.50 g / cm ³ . (Comparative Example 2) Sodium dodecylbenzenesulfonate 0.
08% by weight aqueous solution, glass fiber (average length 13mm, diameter 11μ
m) and 0.1% by weight of granular polypropylene were added, and the mixture was stirred and foamed to prepare a dispersion liquid. A paper having a basis weight of 500 g / m ² was prepared by making a paper from this dispersion in the same manner as in Example 1, and was heated and pressed in the same manner as in Example 1 to obtain a solidified and dense sheet. Two sheets of this sheet were laminated, with the surface that was in contact with the porous support during the papermaking process, with the inside facing in, and heated to 210 ° C (clearance 3.7 mm)
Placed on the lower mold for 5 minutes and then the mold was cooled to obtain an expanded porous lightweight stampable sheet A ′. The results of bending test and tensile test of this sheet are shown in Table 1.
The density was 0.50 g / cm ³ . (Comparative Example 3) Two solidified and dense sheets prepared in the same manner as in Comparative Example 2 were laminated so that the surface which was in contact with the porous support during the papermaking process was facing outward, and the same procedure as in Example 1 was performed. It was expanded in the mold to obtain a lightweight stampable sheet B '. The results of bending test and tensile test of this sheet are shown in Table 1. The density was 0.50 g / cm ³ .

[0020]

[Table 1]

[0021]

According to the present invention, a lightweight stampable sheet excellent in bending strength or tensile properties can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross-sectional structure in the thickness direction of a web of the present invention.

FIG. 2 (a) is a schematic view showing a cross-sectional structure in the thickness direction of a sheet material which is strong against bending load and (b) tensile load.

[Explanation of symbols]

 1 layer with high hardness 2 layer with low hardness 3 high expansion layer (lower layer portion) 4 low expansion layer (upper layer portion) 5 glass fiber t thickness

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication B29K 105: 04 105: 12 309: 08 B29L 31:58 (72) Inventor Seiji Hanatani Chiyoda-ku, Tokyo 2-3-2 Uchisaiwaicho Hibiya International Building Kawasaki Steel Works Tokyo Head Office

Claims (3)

[Claims] 1. A continuous dispersion of a glass fiber and a granular thermoplastic resin dispersed in a surfactant-containing aqueous medium containing air microbubbles on a moving porous support. Prepare a sheet-shaped web, heat and pressurize this web to solidify, reheat to above the melting point of the resin, expand in the thickness direction to a density of 0.4 to 1.0 g / cm ³ , and a glass fiber 20 to In the method for producing a porous lightweight stampable sheet consisting of 70% by weight and a thermoplastic resin of 30 to 80% by weight, the web-making process comprises (a) a glass fiber content of 0.2 to 4.0 in the dispersion. %, And (b) when the dispersion is made on the porous support, the rate at which the separated aqueous surfactant solution passes through the porous support is 4 cm / sec or more, and ( c) The moving speed of the porous support is 1 to 10 per minute.
A method for manufacturing a light-weight stampable sheet, characterized in that it is m. 2. A web is laminated by stacking two webs so that the surface which is in contact with the porous support during the papermaking process is aligned with the inside, and is reheated to a temperature not lower than the melting point of the resin to expand in the thickness direction thereof, thereby increasing the bending strength. The method for manufacturing a lightweight stampable sheet according to claim 1, wherein the method is improved. 3. A web is laminated by stacking two webs with the surface that was in contact with the porous support during the papermaking process being the outside, and reheated to a temperature above the melting point of the resin to expand in the thickness direction to improve the tensile strength. The method for manufacturing a lightweight stampable sheet according to claim 1, wherein