JPH03166910A - Manufacture of carbon fiber reinforced thermoplastic resin sheet - Google Patents

Abstract

PURPOSE:To improve the mechanical properties and surface qualities and also raise the uniformity by adding binder to a mat-shaped substance made of mixed thermoplastic resin fibers and carbon fibers and then compressing them into a sheet-shaped substance and laminating a thermoplastic resin sheet thereon and heating and pressing them thereafter. CONSTITUTION:First, a blended mat of thermoplastic resin fibers and carbon fibers to be a matrix is made, whereby the handling property of the mat is improved and, since the thermoplastic resin is dispersed previously uniformly in the inner part of a fiber reinforced layer, the sufficient and uniform infiltration of the resin into the fiber reinforced mat can be obtained. Next, after giving a binder in the blended mat, it is made into a sheet-shaped substance with high density through compression. As binders, it is preferred to employ resin such as epoxy resin, unsaturate polyester resin and PVA resin, and it is preferable that the adhesive rate is in the range of 0.1 - 20wt%. In the next place, the blended sheet substance obtained herein is superimposed and laminated with the thermoplastic sheet substance and then they are heated and pressed at the temperature of softening and melting temperature or higher of the thermoplastic resin.

Description

[Detailed description of the invention] Industrial application field> The present invention is a carbon fiber reinforced thermoplastic resin that can be stamped (press molded, punched) using carbon fiber as a reinforcing material and a thermoplastic resin as a base material (matrix). Concerning a method for manufacturing plastic resin sheets. Prior Art> Fiber-reinforced thermoplastic resin sheets using thermoplastic resin as a binder are called stampable sheets, and are used in various fields as intermediate materials for appearance. Its characteristic is that it is heated and softened and then fed into a mold while it is in a fluid state and pressurized to shape it.
Because molded products can be obtained simply by cooling and solidifying, compared to so-called SMC, which uses thermosetting resin as a binder, the molding cycle is shortened because no heat curing time is required, improving production efficiency. The press equipment does not require special capabilities such as SMC, and general-purpose press equipment can be used as is. Furthermore, since it is thermoplastic, it is easy to recycle.
It has advantages such as a high degree of freedom in design. For this reason, it has already been replaced by SMC or steel materials in some areas, and its use as a material for large parts is expected to grow in the automobile and machinery fields in the future. Conventionally, these fibrous (mainly glass fiber) masculinizing thermoplastic resin sheets have been produced by dry process methods and wet process methods. In the former method, for example, as disclosed in Japanese Patent Publication No. 63-4486, at least one reinforced fiber mat and at least one thermoplastic resin sheet are overlapped and supported between double belts. The mat is supplied to the heated and pressurized zone of the ξ lanator to pressurize the resin layer in a molten state, sufficiently impregnating the resin into the mat, and then in the cooling and pressurized zone, solidifying the resin while applying pressure to the resin and the mantle, It is drawn out as a solid sheet of fiber-reinforced resin composed of resin and mat. On the other hand, in the latter wet process, for example, a dispersion of powdered resin and chip-shaped reinforcing fibers (water is usually used as the dispersion medium) is made and shaped into a poultice-like web on a mesh belt. There is a method of taking out the product by drying, heating and pressurizing, and then cooling and solidifying. In the wet process method, the resin particles are uniformly and sufficiently dispersed inside the reinforcing fiber layer in advance, and the reinforcing fibers are distributed evenly. Since the dispersion is good, it has the advantage that a homogeneous sheet can be obtained and the surface is excellent. However, in the process of preparing the dispersion liquid and making the poultice-like web, it is necessary to disperse the fibers evenly. The length has to be shorter compared to the dry process method, which has the disadvantage that the strength and impact resistance of the product are inferior. On the other hand, in the dry process method, in the process of impregnating the mat with resin by heating and pressurizing, there are places where the resin does not fully wrap around the mat, or defects and voids occur, and the surface is also rougher than in the wet process method. Although it has the disadvantage of roughening, it is advantageous in terms of product strength and impact resistance because the usable fiber length is longer than in the wet process method. In dry process methods, to improve the surface quality, long MII! A method has been proposed in which a surface veil of fabric is placed between an inner layer of resin containing i and an outer resin layer.In products produced by this method, the outer resin layer does not contain reinforcing fibers. In that sense, it becomes a heterogeneous material. Also υSP-4,
As disclosed in No. 044,188 and elsewhere, it has been proposed to use a resin layer containing short fibers or a non-material filler on the outside of a resin layer containing long fibers. The structure of the outer and inner layers differs depending on the method, and it is inevitable that the outer layer will be a non-uniform material with poor mechanical properties. Furthermore, when carbon fiber is used as a reinforcing fiber, it is less flexible and easier to handle than glass fiber, and the fibers become short due to damage or breakage, especially during the process of heating and pressurizing, resulting in lower product quality than expected. There is a tendency that it cannot be obtained. The purpose of the present invention is to improve mechanical properties such as bending strength and impact strength and surface The purpose of this paper is to propose a method for manufacturing carbon fiber-reinforced thermoplastic resin sheets that have excellent quality and a highly uniform structure. <Means for Solving the Five Problems> The present invention involves laminating a reinforcing IaI fiber mat and a thermoplastic resin sheet, pressing the resin layer in a softened and molten state while heating, and then applying pressure while cooling and applying pressure. In a method for producing a fiber-reinforced thermoplastic resin sheet in which the resin is solidified, a blended mat of thermoplastic resin fibers and carbon fibers serving as a matrix is prepared in advance, and a binder as a third component is added to this and compressed. Carbon fiber reinforcement characterized by forming a blended sheet-like material, then laminating the sheet-like material with a thermoplastic resin sheet serving as a matrix, and heating and pressurizing the mixture in a temperature range equal to or higher than the softening and melting temperature of the thermoplastic resin. This is a method for manufacturing thermoplastic resin sheets. <Function> According to the present invention, by first making a blended mat of thermoplastic resin fibers and carbon fibers serving as a matrix, the handleability of the mat described above is improved, and the thermoplastic resin is added to the reinforcing fiber layer in advance. Since the resin is uniformly dispersed inside, the resin is sufficiently impregnated into the reinforced woven mat during the heating and pressing process, and a homogeneous material can be obtained. The blending ratio of thermoplastic resin woven fibers and carbon fibers to be blended here is not particularly limited, but if the ratio of thermoplastic resin fibers is too small, the blended mat will not have sufficient handling properties. There is a high possibility that the fibers will be damaged or broken during the pressurizing process. On the other hand, if the ratio of thermoplastic resin fibers is too large, the stacking of thermoplastic resin sheets will have to be extreme in order to achieve the desired carbon fiber content. As a result, the amount of resin on the surface becomes insufficient, resulting in areas where carbon fibers are exposed on the surface and the surface quality deteriorates. Therefore, it is necessary to select an appropriate blending ratio depending on the desired fiber content. Next, a third binder is added to the resulting blended mat, which is then compressed to form a sheet with a high bulk density. The blended mat-like material as it is is not sufficient as a reinforcing mat, as it has a low bulk density and poor morphological stability, and fibers become unevenly distributed during subsequent handling, causing non-uniformity in the thickness direction. Therefore, by applying a binder component to a blended mat-like material and then heating and compressing it, a homogeneous blended sheet with high bulk density and excellent shape stability can be obtained, and it is also easy to handle. The binder component used here has the same meaning as the binder used in general dry-type and wet-type papermaking, and the standard conditions are that it has adhesive ability and does not attack the fiber surface, but in addition, it must have adhesive ability and not attack the fiber surface. Compatibility and continued machining,
Furthermore, considering the heat resistance required during press molding, epoxy type. Resins such as unsaturated polyester and PVA are suitable. Possible application methods include immersion in a binder solution or spraying. The adhesion rate of the binder is not particularly limited, but if it is too low, the binder ability will be insufficient, and if it is too high, it will have a negative effect on the processing properties of the thermoplastic resin that forms the matrix, so it should be 0.1 to 20 wt%. It is preferable to select within the range of (% by weight of fiber). As a compression method, pressure by suction suction or spraying, mechanical compression (roller press plate), etc. can be applied, and conditions must be selected to minimize damage to the TA fiber layer. Thickness of compressed sheet. The bulk density will be appropriately selected depending on the fiber content and product thickness of the final carbon fiber reinforced thermoplastic resin sheet. Next, the obtained blended sheet material is laminated with a thermoplastic sheet material, and heated and pressurized in a temperature range equal to or higher than the softening melting temperature of the thermoplastic resin to bond the thermoplastic resin in the blended sheet with the surface. After fully impregnating the reinforcing fiber layer with resin using a thermoplastic resin sheet, pressure is applied while cooling to solidify the resin and carbon MIIw! Obtain a reinforced thermoplastic resin sheet. In the present invention, since the thermoplastic resin fibers are uniformly dispersed in the carbon fiber layer by blending in advance, the resin can quickly and thoroughly penetrate into the fiber layer during heating and melting. can. In the conventional method, all the thermoplastic resin as a matrix is supplied from the sheet to the inside of the fiber layer, so the temperature and pressure have to be set high to ensure the fluidity of the resin inside. There was a tendency for the resin on the surface to flow too much, resulting in a loss of surface quality. However, according to the present invention, the overlapping thermoplastic resin sheets can be made thinner than in the past, so the above-mentioned difference in fluidity between the surface layer and the inside is eliminated, and the surface quality is also improved. The carbon fiber-reinforced thermoplastic resin sheet obtained in this way allows the use of long fibers, and damage to the SaW during processing can be minimized, so the resulting product has high strength. It has excellent impact resistance and good surface quality. <Example> Polypropylene resin fibers (single diameter 10μ
) are dispersed on average in the blending ratio shown in Table 2, and while the weaving is being opened using a combing roller, which is a general-purpose opening machine, the scattered flocs are passed through a wind tunnel and deposited on a net conveyor by suction suction. A blended mat-like material was obtained. An aqueous dispersion of epoxy resin is sprayed onto the cloak-like material obtained, and fibers (carbon fiber and polypropylene resin fibers) are formed.
! ) The amount of epoxy resin deposited was controlled to be 3% by weight. This was compressed with a roller while being dehydrated and dried at a temperature of 110°C to produce a blended sheet. The obtained compressed sheet and thermoplastic resin sheet (polypropylene) were stacked and laminated under the conditions shown in Table 3, supported between double steel belts, and heated at 210°C.
After being pressurized and knitted with a roller in the F castle, it was cooled while being pressurized to form a carbon fiber-reinforced thermoplastic resin sheet. The evaluation results of the obtained stampable sheets are shown in Table 3, and according to the present invention, compared to those manufactured by the conventional method,
It is clear that it has excellent bending strength 6 WIil resistance and good surface quality. Effects of the Invention> As mentioned above, the carbon fiber reinforced thermoplastic resin sheet produced by the present invention is a blend of thermoplastic resin fibers serving as a matrix and carbon fibers, so that reinforcement is not applied during heating and pressure molding. The resin can be impregnated into the fiber layer uniformly and quickly, preventing uneven distribution of fibers and the occurrence of defects, and the resulting sheet also has uniform dimensions. Physical properties can be obtained. In addition, by blending thermoplastic resin fibers with carbon fiber mats, which have poor flexibility and processability, the handling properties of the mats are improved, and the carbon fibers are less likely to be damaged when pressurized. The shortening of fibers due to breakage is also suppressed, and the benefits of using long fibers (product strength and impact resistance) can be maximized.
Additionally, the laminated thermoplastic resin sheets can be made thinner and have uniform fluidity, resulting in better surface quality. Therefore, it can be used as a material for large parts for automobile outer panels, interior slopes, or for EM that takes advantage of the conductivity of carbon fiber.
It can be used as an I-shield material for housings of OA equipment, etc., and is expected to have more applications than conventional products.

Claims (1)

[Claims] The reinforcing fiber mat and thermoplastic resin sheet are laminated and heated, and the resin layer is pressed to soften and melt.
Next, in a method for manufacturing a fiber-reinforced thermoplastic resin sheet in which the resin is solidified while being cooled and pressurized, a blended mat of thermoplastic resin fibers and carbon fibers serving as a matrix is prepared in advance, and a binder as a third component is added to this. In addition, it is compressed to form a blended sheet-like material, and then the sheet-like material and a thermoplastic resin sheet serving as a matrix are laminated and heated and pressurized in a temperature range equal to or higher than the softening and melting temperature of the thermoplastic resin. A method for producing a characteristic carbon fiber reinforced thermoplastic resin sheet.