JPH04232047A - Method of improving appearance of fiber reinforced thermoplastic resin - Google Patents

Abstract

PURPOSE:To contrive to improve the appearance of porous formed product, which is made of fiber reinforced thermoplastic resin by paper-making technique and in the interior of which voids present. CONSTITUTION:Polypropylene sheets containing 3-30vol.% of inorganic filler are laminated to both sides of sheet-like material made of non-woven material consisting of glass fibers and polypropylene resin powder and, after that, stamped so as to produce fiber reinforced thermoplastic resin formed product having the void of 5-75vol.%.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the appearance of a porous molded article obtained by heating and press-molding a fiber-reinforced thermoplastic resin molding material produced by papermaking technology. The fiber-reinforced thermoplastic resin molded article according to the present invention is widely used for industrial parts.

0002

[Prior Art] Recently, there has been a trend for industrial parts manufactured by metal press processing to be replaced by press-molded products made of fiber-reinforced thermoplastic resin, which are composed of relatively long reinforcing fibers and thermoplastic resin. be. The characteristics of fiber-reinforced thermoplastic resin are that heated fiber-reinforced thermoplastic resin sheet material (
By inserting the molding material (hereinafter referred to as sheet-shaped molding material) into a room temperature or heated mold and compression molding it in a short time, it is possible to manufacture a complex molded product, and the molded product has high mechanical strength. It has the advantage of being lightweight. Furthermore, in order to improve the merit of weight reduction, paper making methods (Japanese Patent Publication No. 52-12283, Japanese Patent Publication No. 55-911
Method for manufacturing porous molded products of sheet-like molded materials (Japanese Patent Application Laid-open No. 179234/1983, Japanese Patent Application Laid-Open No. 62-1989)
-161529) has been proposed.

[0003] The sheet-shaped molding material is produced by applying paper-making technology to produce a non-woven material with a diameter of 3 to 30 μmφ and a length of 3 to 50 mm, in which reinforcing fibers and thermoplastic resin powder are uniformly dispersed.
This nonwoven material is used as a raw material and is manufactured by heating, pressurizing, and cooling. Porous molded products are molded by utilizing the expansion of the sheet that occurs when the sheet-like molding material is heated above the softening point or melting point of the thermoplastic resin that is the matrix before molding.

[0004] Nonwoven materials produced by papermaking technology include
Because the reinforcing fibers are randomly oriented, it is extremely bulky. The thickness of the nonwoven material varies depending on the shape of the reinforcing fibers and the papermaking conditions, but it is 10% thicker than a sheet with voids removed, which is commonly used as a sheet-form forming material.
It is about twice as thick. When the sheet-shaped molding material expands, when it is heated above the softening point or melting point of the thermoplastic resin that is the matrix, the bonding force of the thermoplastic resin to the reinforcing fibers weakens, so the residual stress in the reinforcing fibers is released.
It is caused by springback that tries to return to its original state.

FIG. 1(a) shows an example of a process for forming a porous molded product using the expansion of a sheet-shaped molding material. The sheet-shaped molded material 1 is generally heated in a far-infrared heating furnace 3, and the sheet expands at that time. A porous molded product 5 is manufactured by inserting the expanded heated sheet-like molding material into a mold 4 and stamp-molding it under conditions to obtain a desired expansion ratio.

[0006] Expansion of a sheet-shaped molding material starts from the surface of the sheet, and as heat gradually reaches the center of the sheet thickness, the entire sheet expands, and at the same time, an insulating air layer is formed, resulting in a decrease in thermal conductivity. On the surface of the sheet, the reinforcing fibers 2 are exposed due to expansion, and furthermore, thermal decomposition of the thermoplastic resin occurs due to local heating due to a decrease in the thermal conductivity of the sheet, resulting in a marked deterioration of the appearance. As a result, the appearance of the porous molded product 5 obtained by stamp-molding this expanded heating sheet is deteriorated because it inherits the appearance of the sheet.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for improving the appearance of a porous molded article of fiber-reinforced thermoplastic resin produced by papermaking technology.

[0008]

[Means and effects for solving the problems] The present invention heats a fiber-reinforced thermoplastic resin sheet-like molding material and expands the sheet-like molding material using springback when residual stress of the reinforcing fibers is released. , a method for manufacturing a fiber-reinforced thermoplastic resin molded product having voids by compression molding an expanded sheet-like molding material in a mold,
It is characterized by using a sheet-like molded material in which the ratio of voids is 5 to 75% by volume, and a thermoplastic resin layer containing 3 to 30% by volume of inorganic filler is laminated on the outer surface of a fiber-reinforced thermoplastic resin. This is a method for improving the appearance of fiber-reinforced thermoplastic resin molded products. As the fiber-reinforced thermoplastic resin,
10 reinforcing fibers with a diameter of 3 to 30 μmφ and a length of 3 to 50 mm
A mat-like nonwoven material composed of ~40% by volume and thermoplastic resin powder, or a sheet-like material obtained by heating and press-molding the above-mentioned nonwoven material can be used.

FIG. 1(b) shows an example of the molding process of a porous molded product using the expansion of a sheet-shaped molding material laminated with an inorganic filler-containing thermoplastic resin layer according to the present invention. In the sheet-shaped molded material of the present invention, sheet expansion occurs due to springback of reinforcing fibers when heated in the far-infrared heating furnace 3, similarly to the conventional material shown in FIG. 1(a). however,
The inorganic filler-containing thermoplastic resin layer laminated on the outer surface of the fiber-reinforced thermoplastic resin does not expand, and its melt viscosity increases due to the inorganic filler content of 3 to 30% by volume.
This has the effect of suppressing absorption into the expanded fiber-reinforced thermoplastic resin layer and exposure to the sheet surface due to springback of the reinforcing fibers. Therefore, heating can be performed with the inorganic filler-containing thermoplastic resin layer 6 completely covering the fiber-reinforced thermoplastic resin layer, so that no significant deterioration in the appearance of the sheet surface as seen with conventional materials occurs. As a result, the appearance of the porous molded product 5 obtained by compression molding the sheet-like molding material of the present invention is greatly improved compared to conventional materials.

The porosity of the porous molded product is determined by the expansion ratio during heating of the sheet-like molding material and the stamp molding conditions. The expansion of the sheet-like molding material increases as the reinforcing fiber content increases. This is because residual stress increases with increased fiber content. Further, since an insulating air layer is formed in the expanded sheet-like molding material and the thermal conductivity decreases, the expansion ratio also changes depending on the heating conditions. The expansion ratio is improved by uniformly heating the sheet-shaped molding material for a long time. In order to take advantage of the weight reduction benefits of porous molded products, it is desirable to increase their porosity, but in order to develop strength, it is necessary to sufficiently bond the reinforcing fibers with thermoplastic resin. The porosity of the molded product is 5 to 75% by volume.

In the present invention, as the inorganic filler, a particulate filler such as calcium carbonate or talc, a plate filler such as mica, or a fibrous filler such as chopped glass fiber or rock wool fiber is used. The surface of the inorganic filler is desirably treated with a silane coupling agent or the like in order to improve adhesiveness with the thermoplastic resin for the purpose of developing strength.

[0012] The thermoplastic resin that is the matrix of the inorganic filler-containing thermoplastic resin layer is generally the same as the fiber-reinforced thermoplastic resin layer to be laminated. If improvement in hardness, etc. is required, a thermoplastic resin may be selected depending on the purpose, or a mixture with a different resin may be used. The amount of inorganic filler added to the thermoplastic resin is 3% by volume or more for the purpose of thickening the thermoplastic resin and improving mechanical properties, and 30% by volume or less to enable stable film formation. The inorganic filler and thermoplastic resin are preferably kneaded using an extruder or the like to achieve uniform dispersion, and it is desirable to laminate a film formed using a T-die or the like on the outer surface of the fiber-reinforced thermoplastic resin.

[0013] The selection of the inorganic filler to be added to the thermoplastic resin must be determined depending on the needs for improving the appearance of the molded product. In order to obtain a smoother appearance of the molded product, a diameter of 2~
It is preferable to disperse the inorganic filler in the thermoplastic resin in a dense manner by using fine particles of talc or calcium carbonate having a diameter of 10 μm. In addition, in order to improve the strength of the inorganic filler-containing thermoplastic resin layer to be laminated, a diameter of 3 to 30 μm with a large aspect ratio (fiber length/fiber diameter) is required for the purpose of expressing the reinforcing effect of the filler.
It is desirable to use chopped glass fibers or rock wool fibers having a diameter of 3 to 10 mm. Furthermore, in order to take advantage of the characteristics of both, these inorganic fillers may be used in combination. The thickness of the inorganic filler-containing thermoplastic resin layer to be laminated varies depending on the needs for improving the appearance of the molded product, the environment in which it will be used, and the amount of inorganic filler added, but it is stable when the sheet molding material is heated. In order to maintain the coated layer, it is desirable that the thickness be 0.2 mm or more.

[0014] In the present invention, a sheet-shaped molded material manufactured by papermaking technology is used, and an example of the manufacturing process is shown in Fig. 2.
It was shown to. Reinforcing fibers 2 such as glass fibers having a diameter of 3 to 30 μmφ and a length of 3 to 50 mm and thermoplastic resin powder 7 are continuously introduced into water in a dispersion tank 8. In the dispersion tank, stirring is performed to uniformly disperse the reinforcing fibers and resin powder, and the dispersion liquid is further supplied by a pump 9 to a head box 11 installed above a mesh belt conveyor 10. The inside of the wet box 12 installed under the head box is maintained at a negative pressure, and the dispersion inside the head box is sucked and dehydrated to continuously produce a composite material in which reinforcing fibers and thermoplastic resin powder are uniformly dispersed. A woven material 13 is manufactured. This non-woven material is dried in a ventilation type hot air dryer 14, and at the same time, part or all of the thermoplastic resin is heated to above its softening point or melting point to melt it, and then cooled to convert the reinforcing fibers into thermoplastic resin. It is made into a non-woven material bonded with resin, then heated and pressed in a double belt conveyor type continuous press 15, further cooled and formed into a sheet shape, and finally reeled up 16 or necessary for heating and pressure forming. The sheet-shaped molded material 1 is manufactured by cutting it with a cutter 17 into a shape according to the dimensions. The sheet-shaped molding material may be one in which voids are completely removed when a nonwoven material is molded using a double-belt conveyor type continuous press, or one in which voids are present. Moreover, the nonwoven material can also be provided as a sheet-like molded material in which voids are present, without using a double belt conveyor type continuous press.

The diameter of the reinforcing fibers used in this method is:
From the viewpoint of ease of handling and economy, the diameter is preferably 3 μm or more, and in order to develop sufficient strength, it is preferably 30 μm or less. Further, the fiber length is desirably 3 mm or more from the viewpoint of strength development and 50 mm or less to enable uniform dispersion. Glass fibers, which are commonly used as reinforcing fibers, are manufactured by a melt-spinning method, but a decrease in fiber diameter leads to a decrease in production efficiency and an increase in costs. Furthermore, in order to improve the reinforcing effect, it is necessary to use reinforcing fibers with a large aspect ratio within a range that allows uniform dispersion.

The amount of reinforcing fibers to be added ranges from 10% by volume at which stable expansion occurs due to springback of the reinforcing fibers.
The content is preferably 40% by volume, which allows sufficient adhesion between the reinforcing fibers and the thermoplastic resin. As the reinforcing fibers, in addition to glass fibers, carbon fibers, and metal fibers, inorganic fibers and organic fibers are used. The reinforcing fibers are made of water-soluble polymers and wetting agents to improve hydrophilicity for the purpose of good dispersion in water, and silane coupling agents, etc. to improve adhesion with thermoplastic resins for the purpose of developing strength. It is desirable to perform surface treatment.

Thermoplastic resins include polyethylene, polypropylene, polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer, polyamide, polycarbonate, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, It is a resin such as polyphenylene sulfide, and these two
It also includes mixtures of different types or more, and commonly used plasticizers, heat stabilizers, light stabilizers, fillers, dyes and pigments, impact-resistant agents, extenders, nucleating agents, processing aids, etc. You can also.

[0018] The method of laminating a thermoplastic resin layer containing an inorganic filler on the outer surface of a fiber-reinforced thermoplastic resin in the present invention is to laminate a film formed by a T-die or the like of an extruder on the outer surface of a fiber-reinforced thermoplastic resin. This can be easily done by laminating the layer on the surface, heating and pressurizing it with a press molding machine, and then cooling and molding.

As an example of industrial implementation, the lamination process as outlined in FIG. It is efficient to provide the The thermoplastic resin 18 and the inorganic filler 19 are kneaded in an extruder 20 to achieve uniform dispersion, and further formed into an inorganic filler-containing thermoplastic resin film 22 in a T-die 21 and supplied to the outer surface of the nonwoven material 13. be done. The nonwoven material and the inorganic filler-containing thermoplastic resin film are heated and pressed by a double belt conveyor type continuous press 15, and are further cooled to produce the desired sheet-shaped molded material 23.

In place of the nonwoven material in the lamination process shown in FIG. 3, it is easy to use a nonwoven material as a sheet-shaped material formed by a double belt conveyor type continuous press or the like. In addition, in Figure 3, thermoplastic resin containing inorganic filler is laminated on both sides of the nonwoven material, but if the appearance of only one side is required for the purpose of the molded product, nonwoven material or sheet-like molded material may be used. It is also possible to laminate an inorganic filler-containing thermoplastic resin only on one side. The method for improving the appearance of fiber-reinforced thermoplastic resin molded products of the present invention not only significantly improves the appearance of general hot-press molded products, but also brings about beneficial results in air pressure molding and the like.

[0021]

[Examples] The present invention will be explained in detail with reference to Examples below. Example 1 A glass fiber with a diameter of 10 μmφ and a length of 25 mm as a reinforcing fiber and a spherical pellet with a diameter of 3 mmφ as a thermoplastic resin were crushed, and the crushed product was sieved to a size of 70 mes.
Using polypropylene resin powder divided into spheres ranging from h (opening diameter 0.212 mm) to 10 mesh (opening diameter 1.7 mm), 40% by weight glass fiber (19.
0% by volume) and 60% by weight of polypropylene resin (81.0% by volume)
A non-woven material with a composition of (% by volume) and a basis weight of 2500 g/m2 was manufactured.

A talc-containing polypropylene resin film was produced using fine particle talc with a diameter of 3 μmφ as an inorganic filler and the above-mentioned polypropylene resin as a thermoplastic resin. The film contains 20% by weight of talc (7.4
(% by volume) and 80% by weight (92.6% by volume) of polypropylene resin were kneaded using an extruder, and the mixture was kneaded using a T-die to a thickness of 0.5% by volume.
It was molded to 2 mm.

Using the above-mentioned nonwoven material and talc-containing polypropylene resin film, a sheet-like molding material having the structure shown in Table 1 was molded by hot press molding. A sheet-like molded material A made from only a nonwoven material was manufactured as a comparative example. In sheet-like molded materials B to D, films were laminated on both sides of the outer surface of the nonwoven material. The hot press molding conditions were: preheating at 210°C for 5 minutes with no load, then pressurizing at 20 kgf/cm2 for 5 minutes,
The material was cooled and solidified to form a sheet-like material.

[0024] Using these sheet-shaped molded materials,
By molding a porous molded product as shown in
A porous flat plate of 15 cm and a thickness of 5 mm was stamp-molded.
Its appearance and bending properties were evaluated. A sheet-shaped molding material cut to the same size as the molded product is heated in a far-infrared heating furnace until its surface reaches 220°C, then inserted into a mold whose temperature is adjusted to 60°C, and heated to a pressure of 10 kgf. /cm2
A porous molded product was obtained by stamp molding. The appearance of the molded product was evaluated visually, focusing on the lifting of the glass fibers. Evaluation of bending properties is based on JIS from molded products.
A test piece according to K-7203 was cut out and tested.

[0025]

[Table 1]

As shown in FIG. 1(a), the sheet-shaped molded material A made only of non-woven material expanded when heated, and the glass fibers were raised on its surface. Therefore, the appearance of the molded product was also observed to deteriorate due to the exposure of the glass fibers. Sheet-shaped molded material B in which a talc-containing polypropylene resin film is laminated on the outer surface of a nonwoven material
In ~C, the talc-containing polypropylene resin layer did not expand and was heated while covering the expanded glass fiber-reinforced thermoplastic resin layer inside, so the appearance of the sheet surface like sheet-shaped molding material A did not deteriorate. There wasn't. As a result, the appearance of these molded products was also improved. However, in the case of laminating one talc-containing polypropylene resin film,
Some exposed glass fibers were confirmed. This occurred because a portion of the talc-containing polypropylene resin layer was absorbed into the expanded glass fiber-reinforced thermoplastic resin layer, and the effect of suppressing exposure to the sheet surface due to glass fiber springback was not sufficiently expressed. . When two or more sheets (0.4 mm) of talc-containing polypropylene resin films are laminated, heating can be performed while completely covering the internal glass fiber-reinforced thermoplastic resin layer, so the glass fibers on the sheet surface are not exposed. The appearance of the molded product was also significantly improved.

The thickness of the sheet-shaped molded material was increased by laminating the talc-containing polypropylene resin film. Since the wall thickness of the molded product was kept constant, the expansion ratio and porosity of the molded product decreased, and the apparent density increased. The bending properties (specific bending strength, specific modulus) were slightly reduced by lamination of the talc-containing polypropylene resin film.

Example 2 Using the same talc and polypropylene resin as in Example 1, a composition of 40% by weight (17.6% by volume) of talc and 60% by weight (82.4% by volume) of polypropylene resin was prepared. Knead with an extruder in the same way as in step 1, and use a T-die to give a thickness of 0.2m.
A talc-containing polypropylene resin film of m was molded. Using the same nonwoven material as in Example 1 and the above-described talc-containing polypropylene resin film, a sheet-like molding material having the configuration shown in Table 2 was molded by hot press molding under the same conditions as in Example 1. The film was laminated to both sides of the outer surface of the nonwoven material. Using these sheet-shaped molding materials, the same molding process as in Example 1 was carried out to form a sheet of 15 x 15 cm and a plate thickness of 5.
A porous flat plate with a diameter of mm was stamp-molded, and its appearance and bending properties were evaluated.

Example 3 Chopped glass fibers with a diameter of 10 μmφ and length of 3 mm and the same polypropylene resin as in Example 1 were used as inorganic fillers, and 40% by weight of chopped glass fibers (19.
0% by volume) and 60% by weight of polypropylene resin (81.0% by volume)
Volume %) was kneaded using an extruder in the same manner as in Example 1, and a chopped glass fiber-containing polypropylene resin film having a thickness of 0.4 mm was molded using a T-die.

Using the same nonwoven material as in Example 1 and the above-mentioned chopped glass fiber-containing polypropylene resin film, sheet-shaped molding materials having the configuration shown in Table 2 were molded by hot press molding under the same conditions as in Example 1. . The film was laminated to both sides of the outer surface of the nonwoven material. Using these sheet-shaped molding materials, a porous flat plate of 15×15 cm and 5 mm in thickness was stamp-molded by the same molding process as in Example 1, and its appearance and bending characteristics were evaluated.

[0031]

[Table 2]

In Example 2, the talc content of the talc-containing polypropylene resin to be laminated was increased compared to Example 1. The increase in talc content increased its melt viscosity, suppressed absorption into the expanded glass fiber-reinforced thermoplastic resin layer, and sufficiently exhibited the effect of suppressing exposure of glass fibers to the sheet surface due to springback. Therefore, in Example 2, even when one talc-containing polypropylene resin film (0.2 mm) is laminated, heating can be performed while completely covering the glass fiber-reinforced thermoplastic resin layer, and the glass fibers on the sheet surface are not exposed. The appearance of the molded product was also improved. The bending properties were also slightly improved compared to Example 1 due to the increased talc content. Increasing the filler content of the inorganic filler-containing thermoplastic resin can reduce the laminated thickness and improve the mechanical properties of the molded product, leading to an effective improvement in the appearance of the molded product.

In Example 3, the chopped glass fibers in the chopped glass fiber-containing polypropylene resin layer partially bulge out on the surface, so the appearance characteristics of the molded product are inferior to those in Example 2-B. However, the bending properties of the molded product are
It was confirmed that it was excellent. The chopped glass fibers in the chopped glass fiber-containing polypropylene resin film of Example 3 were damaged to an average fiber length of about 0.3 mm due to the kneading effect of the extruder, but the reinforcing effect was due to the larger aspect ratio compared to talc. is effectively expressed. If the mechanical properties of the molded product are important, it is effective to use a fibrous inorganic filler.

Comparative Example Using the same polypropylene resin as in Example 1, Example 1
Knead with an extruder in the same way as above, and use a T-die to make a 0.2mm thick mixture.
A polypropylene resin film was molded. Example 1 Using the same nonwoven material and the above polypropylene resin film as in Example 1, a sheet-shaped molded material having the configuration shown in Table 3 was prepared.
It was molded by hot press molding under the same conditions as . The film was laminated to both sides of the outer surface of the nonwoven material. Using these sheet-shaped molding materials, a porous flat plate of 15×15 cm and 5 mm in thickness was stamp-molded by the same molding process as in Example 1, and its appearance and bending characteristics were evaluated.

[0035]

[Table 3]

In the comparative example, a good appearance of the molded product could not be obtained unless four or more polypropylene resin films (0.8 mm) were laminated. The reason why the appearance improvement effect of the molded product is inferior to that of the examples is that the melt viscosity of the laminated polypropylene resin is smaller than that of the inorganic filler-containing polypropylene resin of the examples, so that it is absorbed into the expanded fiber-reinforced thermoplastic resin layer. This is because the effect of suppressing exposure of the glass fibers to the sheet surface due to springback was not sufficiently realized. Furthermore, it was confirmed that the polypropylene layer was not reinforced with filler, so its bending properties were also reduced.

[0037]

Effects of the Invention According to the present invention, the appearance of a porous molded product obtained by heat-pressing molding of a sheet-like molded material produced by paper-making technology has been improved. In the present invention, since the inorganic filler-containing thermoplastic resin layer is laminated on the fiber-reinforced thermoplastic resin, the laminated thickness can be reduced, and the strength of the molded product can be suppressed from decreasing due to the reinforcing effect of the inorganic filler. The method for improving the appearance of fiber-reinforced thermoplastic resin molded articles of the present invention also brings about beneficial results in pressure molding and the like.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are schematic diagrams showing an example of molding processing of a porous molded product using expansion of a sheet-shaped molding material.

FIG. 2 is a schematic diagram showing an example of a manufacturing process of a sheet-like molded material using papermaking technology.

FIG. 3 is a schematic diagram showing an example of a process of laminating an inorganic filler-containing thermoplastic resin onto a fiber-reinforced thermoplastic resin.

[Explanation of symbols]

1 Sheet-shaped molding material 2 Reinforcing fiber 3 Far-infrared heating furnace 4 Mold 5 Molded product 6 Inorganic filler-containing thermoplastic resin layer 7
Thermoplastic resin powder 8 Dispersion tank 9 Pump 10 Mesh belt conveyor 11 Head box 12 Wet box 13 Nonwoven material 14 Hot air dryer 15 Double belt conveyor type continuous press 16 Reel up 17 Cutter 18 Thermoplastic resin 19 Inorganic filler 20 Extruder 21 T-die 22 Inorganic filler-containing thermoplastic resin film 23
Thermoplastic resin laminated sheet-shaped molding material containing inorganic filler

Claims (1)

[Claims] 1. Heat a fiber-reinforced thermoplastic resin sheet-like molding material, expand the sheet-like molding material using springback when the residual stress of the reinforcing fibers is released, and insert the expanded sheet-like molding material into a mold. In a method for manufacturing a fiber-reinforced thermoplastic resin molded article having voids by compression molding in a chamber, the percentage of voids is 5 to 75% by volume,
A method for improving the appearance of a fiber-reinforced thermoplastic resin molded product, comprising using a sheet-like molding material in which a thermoplastic resin layer containing 3 to 30 volume % of inorganic filler is laminated on the outer surface of the fiber-reinforced thermoplastic resin. .