JP4144949B2 - SMC manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an SMC sheet for use in a sheet molding compound (SMC) that can be applied to automobile exterior products and the like.
[0002]
[Prior art]
The SMC can be obtained by sandwiching a resin liquid mixed with roving between the SMC sheet and the release sheet, and applying pressure and heating. An SMC molded product can be obtained by molding the SMC. Since such SMC molded products are used for large automobile exterior parts such as automobile body panels, spoilers, bumper guards, etc., the SMC sheet has resistance to light resistance, surface strength, etc., and suitability for three-dimensional processing. Is required.
[0003]
Suitable materials for SMC sheets that have resistance and suitability for three-dimensional processing include thermoplastic resin sheets made of acrylic resins, vinyl chloride resins, light-resistant olefin resins, nylon resins, fluorine resins, and the like. is there.
[0004]
[Problems to be solved by the invention]
However, when these sheets are used as SMC sheets, there is a problem that gas generated from the resin liquid remains when the SMC size is large and the thickness of the SMC is thick. Further, since the SMC sheet does not have gas permeability, there is a problem that air is easily interposed between the SMC sheet and the adhesion of the SMC sheet is not good.
[0005]
Accordingly, an object of the present invention is to provide a sheet for SMC that has no adhesion of gas generated from a resin liquid and has high adhesion.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0007]
That is, the SMC manufacturing method of the present invention is a nonwoven fabric composed of any one of spandex, acrylic fiber, polyethylene fiber, and polyamide fiber, and can release gas generated from the resin liquid to the outside when manufacturing SMC. A gas permeable sheet and a thermoplastic resin sheet were laminated to form an SMC sheet, and the resin liquid was finally poured onto the gas permeable sheet of the SMC sheet.
[0012]
In the above invention, the thermoplastic resin sheet or the gas permeable sheet may have a design layer.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a cross-sectional view showing an embodiment of the SMC sheet of the present invention. FIG. 2 is a cross-sectional view showing a process of manufacturing SMC using the SMC sheet of the present invention. FIG. 3 is a cross-sectional view showing a deep drawing mold used for examining the characteristics of the SMC sheet. FIG. 4 is a perspective view showing an apparatus for measuring the tensile elongation at break of the SMC sheet. FIG. 5 is a plan view showing a portion for fixing a test piece of an apparatus for measuring tensile elongation at break. FIG. 6 is a cross-sectional view showing a portion for fixing a test piece of an apparatus for measuring tensile elongation at break. In the figure, 1 is a sheet for SMC, 2 is a gas permeable sheet, 3 is a thermoplastic resin sheet, 4 is a pattern layer, 5 is a resin liquid, 6 is roving, 9 is SMC, 20 is a test piece, 21 is a screw, 22 is a chuck, 23 is a chuck, and 24 is a movable member.
[0015]
In the SMC sheet 1 of the present invention, the SMC sheet 1 is composed of a laminate of two types of sheets, the sheet in contact with the resin liquid 5 is the gas permeable sheet 2, and the other sheet is the thermoplastic resin sheet 3. (See FIG. 1).
[0016]
The gas permeable sheet 2 allows the gas generated from the resin liquid 5 when the SMC 9 is manufactured to be released to the outside without accumulating due to the presence of the SMC sheet 1. Further, the gas permeable sheet 2 also has a function of physically improving the adhesiveness when the resin liquid 5 finally enters the gas permeable sheet 2.
[0017]
As the gas permeable sheet 2, a nonwoven fabric, a flocked fiber sheet, a foamed sheet, a normal woven fabric, or the like may be used. In particular, in consideration of the uniformity of physical properties in the vertical and horizontal directions in the SMC sheet 1 and the defoaming effect when manufacturing the SMC 9, a nonwoven fabric is suitable.
[0018]
Moreover, as for the thickness of the gas-permeable sheet 2, 30-2500 micrometers is preferable. If it is less than 30 μm, it is difficult to manufacture the gas permeable sheet 2 because each fiber must be formed very thin and thin. If it exceeds 2500 μm, the strength of the gas permeable sheet 2 becomes too high, and it becomes difficult to punch or cut the SMC 9 into an arbitrary shape.
[0019]
As the thermoplastic resin sheet 3, acrylic resin, vinyl chloride resin, light-resistant olefin resin, nylon resin, fluorine resin, polyethylene terephthalate resin, polyurethane resin having resistance and three-dimensional processability, A thermoplastic resin sheet 3 made of polycarbonate resin, ethylene vinyl alcohol resin, polystyrene resin, polybutylene terephthalate resin, or the like may be used. In particular, automotive exterior parts require severe resistance such as heat resistance, moisture resistance, light resistance, and water resistance. In such applications, as the thermoplastic resin sheet 3, acrylic resin, polyvinyl chloride type A resin, a light-resistant olefin resin, a fluorine resin, a polycarbonate resin, or the like may be used.
[0020]
The thickness of the thermoplastic resin sheet 3 is preferably 5 to 700 μm. If it is less than 5 μm, wrinkles are likely to occur in the thermoplastic resin sheet 3, and when the pattern layer 4 is formed, it is difficult to print. When it exceeds 700 μm, it is difficult to wind the thermoplastic resin sheet 3, and it becomes difficult to continuously produce the SMC sheet 1. More preferably, it is 5 to 200 μm. When the thermoplastic resin sheet 3 is thin as in this range, the length of the thermoplastic resin sheet 3 that can be wound on one roll is increased, and thus the production efficiency is increased.
[0021]
In order to laminate the gas permeable sheet 2 and the thermoplastic resin sheet 3 into the SMC sheet 1, there are a method such as a thermal lamination method and a dry lamination method using an adhesive. That is, as a method by thermal lamination, it is preferable that the thermoplastic resin sheet 3 is coated with a gas permeable sheet 2 and a thermoplastic resin having good adhesiveness, and the gas permeable sheet 2 is overlapped and thermally laminated. Further, when the thermoplastic resin sheet 3 itself has adhesiveness to the gas permeable sheet 2, it is not necessary to coat the thermoplastic resin. Also, as a method by dry lamination, it is preferable to coat the thermoplastic resin sheet 3 with a dry laminate adhesive with a thick film of at least 10 μm or more and laminate the gas permeable sheet 2 by pressing. This is because the surface of the gas permeable sheet 2 often has irregularities, and there is a possibility that a portion that does not come into contact with the surface of the gas permeable sheet 2 unless the thickness is 10 μm or more. As an adhesive for dry laminating, a urethane-based adhesive or a polyester-based adhesive is suitable because it can be applied to a wide range of gas-permeable sheets 2 and has excellent resistance.
[0022]
The thickness of the entire SMC sheet 1 is preferably 50 to 3000 μm. If it is thinner than 50 μm, the mechanical strength is insufficient, and there is a risk of breaking during SMC9 processing. When it exceeds 3000 μm, it becomes difficult to obtain a wound SMC sheet 1. In particular, 50-1500 micrometers is preferable. When the thickness of the SMC sheet 1 is within this range, it becomes easy to form a three-dimensional shape with a deep drawing. Furthermore, when trimming and removing unnecessary portions of the SMC sheet 1 after SMC molding, a slightly thinner 50 to 300 μm is preferable because it is easy to cut.
[0023]
Separation between the thermoplastic sheet of the SMC sheet 1 and the gas permeable sheet 2 when the SMC 9 is locally stretched during molding of the SMC molded product or when processing such as vacuum forming is required in advance. Or peel off inside the gas permeable sheet 2 or break the gas permeable sheet 2. In order to prevent such a problem from occurring, it is preferable that the difference in elongation during SMC molding between the gas permeable sheet 2 and the thermoplastic resin sheet 3 does not become large. In particular, since the thermoplastic resin sheet 3 exhibits considerable elongation at the SMC processing temperature that is equal to or higher than the softening temperature of the thermoplastic resin sheet 3, the gas permeable sheet 2 is also selected to extend in accordance with the thermoplastic resin sheet 3. Good.
[0024]
For this reason, in this invention, it is preferable to select so that the mechanical characteristic of the gas-permeable sheet 2 may be as similar as possible to the thermoplastic resin sheet 3. The temperature suitable for three-dimensional processing of the thermoplastic resin sheet 3 is approximately 110 to 150 ° C. As a result of examining a tensile test at the lowest processing temperature of 110 ° C., the mechanical properties that at least the elongation is 90% or more are obtained. It was found that the SMC sheet 1 possessed can be processed into a very deep three-dimensional shape even in a single sheet state. Therefore, even if it is the sheet | seat 1 for SMC which laminated | stacked two sheets, if a material is selected so that this property may be satisfied, what can be easily three-dimensionally processed can be obtained.
[0025]
That is, the test piece 20 of the SMC sheet 1 having a width of 20 mm is sandwiched between a pair of chucks at an environmental temperature of 110 ° C., and fixed at a distance of 100 mm between the opposite edges of the chuck. It is preferable that the tensile elongation at break is 90% or more when a tensile test is performed by applying a load at a constant speed of 3 mm / sec. By configuring in this way, when the shape is changed while heating, peeling between the laminated sheets does not occur, or only one sheet is not broken, and the shape can be changed without difficulty to a three-dimensional shape. SMC9 can be obtained. 4 to 6, the upper pair of chucks 22 are fixed by screws 21 with the upper end of the test piece 20 sandwiched therebetween. Further, the lower pair of chucks 23 are fixed by screws 21 with the lower end of the test piece 20 sandwiched therebetween. As shown in FIG. 4, the upper pair of chucks 22 are fixed to the test apparatus, while the lower pair of chucks 23 are lowered downward at a speed of 3 mm / second by the movable member 24 and pulled to the test piece 20. Apply force.
[0026]
Here, the environmental temperature is the temperature of the atmosphere in which the test piece 20 is actually tested. The test piece 20 is obtained by cutting the SMC sheet 1 into a size that can be used for a tensile test with a width of 20 mm and a distance between a pair of chucks of 100 mm. Actually, the dimensions of SMC9 manufactured to obtain SMC molded products were 300mm x 1300mm for body panels that are automotive exterior parts, 250mm x 1200mm for spoilers, and 350mm x 1800mm for bumper guards. The ratio between the width and the length of these SMCs 9 is approximately 2:10. Based on this ratio, the test piece 20 is set to have a width of 20 mm and a distance between a pair of chucks of 100 mm.
[0027]
In the present invention, a material having good extensibility such that the mechanical properties of the gas permeable sheet 2 are as similar as possible to those of the thermoplastic resin sheet 3 is selected, and Nihon Kogyo is a measurement method for confirming that the mechanical properties are similar. A tensile test method based on the standard (JIS) C5318 was selected, and how to set the environmental temperature and the appropriate range was examined.
[0028]
The environmental temperature of 110 ° C. is obtained by adopting 110 ° C. which is the lower value of 110 to 150 ° C. which is a temperature suitable for three-dimensional processing of the thermoplastic resin sheet 3. Molding at the lowest possible processing temperature can prevent thermal deterioration of the ink of the pattern layer 4 and the SMC sheet 1. The speed at which the test piece 20 is pulled is set to 3 mm / second, which is the minimum value of the speed at which the SMC sheet 1 is stretched during three-dimensional processing.
[0029]
Specifically, when the thermoplastic resin sheet 3 is vacuum formed, the temperature applied to the various sheets is 110 ° C. for a vinyl chloride sheet, 120 ° C. for an acrylic sheet, 120 ° C. for a polystyrene sheet, 140 ° C for the polycarbonate sheet, 150 ° C for the light-proof polypropylene sheet, 140 ° C for the polybutylene terephthalate sheet, and 110 ° C for the polyurethane sheet. A certain 110 ° C. was selected as the environmental temperature.
[0030]
The tensile elongation at break referred to in the present invention means that the test piece 20 of the SMC sheet 1 having a width of 20 mm is fixed at a distance of 100 mm between a pair of chucks at an environmental temperature of 110 ° C., and one end of the test piece 20 is 3 mm / second. The breaking elongation obtained when carrying out a tensile test in which a load is applied at a constant speed, that is, the elongation when the test piece 20 is broken. When the maximum elongation of the SMC sheet 1 used for some SMC molded products was measured, it was 120 to 300% for the body panel, 90 to 180% for the spoiler, and 100 to 280 for the bumper guard. In the present invention, 90% or more, which is the minimum of these values, is regarded as the tensile elongation at break.
[0031]
As the gas permeable sheet 2 satisfying the above conditions, there is a nonwoven fabric composed of any of spandex, acrylic fiber, polyethylene fiber, and polyamide fiber. All of these nonwoven fabrics exhibit a large elongation behavior at a low load.
[0032]
In selecting the gas permeable sheet 2, it is ideal to select a sheet in which the thermoplastic resin sheet 3 and the tensile elongation load curve substantially coincide. However, even if the tensile elongation load curves do not match, the load difference in the elongation value of each sheet constituting the SMC sheet 1 is 5.0 kg at maximum within the range until reaching the upper limit of tensile elongation at break. If a value within the range is selected, favorable results can be obtained.
[0033]
The tensile elongation load curve is a material machine when a load is applied to a specimen 20 of a material (width 20 mm in the present invention, distance between a pair of chucks 100 mm) and pulled at a constant speed (3 mm / second in the present invention). The vertical axis is the load, the horizontal axis is the elongation of the material (the increased length of the test piece 20 in the tensile direction is the length of the original test piece 20 in the tensile direction (100 mm in the present invention)). It is a curve depicting the relationship until the test piece 20 breaks.
[0034]
In the present invention, the moldability of the SMC sheet 1 composed of various gas-permeable sheets 2 and thermoplastic resin sheets 3 was tested using a deep drawing mold having a shape as shown in FIG. As a result of performing a tensile test on the gas permeable sheet 2 and the thermoplastic resin sheet 3 constituting the SMC sheet 1, the elongation of each sheet constituting the SMC sheet 1 is within the range until reaching the upper limit of tensile elongation at break. In the case of the SMC sheet 1 in which the load difference in the degree value is within 5.0 kg at maximum, the SMC sheet 1 was laminated, and this value was set because it was in a range where no trouble occurred.
[0035]
The SMC sheet 1 may be provided with a design layer 4. The design layer 4 may be provided on either the thermoplastic resin sheet 3 or the gas permeable sheet 2. The design layer 4 is used to represent characters, figures, symbols, etc. on the surface of the SMC molded product, or to represent a colored surface. Further, the design layer 4 may be a solid color with no pattern such as black or silver metallic color, or it may be a single color or multicolor with a pattern such as a wood grain pattern or a stone pattern. There may be. Alternatively, the pattern layer 4 may be formed by laminating a transparent yellow full-color solid or pattern layer and a silver metallic color full-color solid or pattern layer to express a golden full-color solid or pattern layer. The pattern layer 4 is composed of at least one layer selected from the group consisting of a pigment ink layer composed of a pigment and a resin binder, a glitter pigment layer composed of a pearl pigment and a resin binder, and a dye ink layer composed of a dye and a resin binder. Composed. Such a pattern layer 4 may be formed by a normal printing method such as an offset printing method, a gravure printing method, or a screen printing method, or a coating method such as a roll coating method or a spray coating method. The thickness of the pattern layer 4 is preferably 0.1 to 20 μm. According to the normal printing method, it is in this range.
[0036]
The design layer 4 may be composed of a metal thin film layer, or may be composed of a combination of a metal thin film layer and a printing layer. The metal thin film layer is formed by a vacuum deposition method, a sputtering method, an ion plating method, a plating method, or the like. Depending on the metallic luster color to be expressed, a metal such as aluminum, nickel, gold, platinum, chromium, iron, copper, tin, indium, silver, titanium, lead, or zinc, or an alloy or compound thereof is used.
[0037]
Moreover, it is good also as the sheet | seat 1 for SMC decorated with the color of the thermoplastic resin sheet 3 or the gas-permeable sheet 2 itself, without providing the pattern layer 4.
[0038]
Next, a method for manufacturing the SMC 9 using the SMC sheet 1 having such a configuration will be described.
[0039]
Usually, instead of the polyethylene release sheet used for the production of SMC 9, a roll-shaped SMC sheet 1 is installed on one side or both sides. As shown in FIG. 2, the chopped strand obtained by cutting the roving 6 into a certain length is dropped onto the SMC sheet 1, and at the same time, the slurry-like resin liquid 5 is poured, and the release sheet or the SMC sheet 1 is covered. The resin liquid 5 contains a gelling agent, a low shrinkage agent, a pigment, and the like. Next, defoaming is performed by applying pressure with a pressure roll, and the resin liquid 5 is gelled by appropriate heating and wound. In this way, the SMC 9 in which the SMC sheet 1 and the resin layer are in close contact with each other can be obtained.
[0040]
The SMC molded product can be obtained by cutting the SMC 9 obtained as described above into a suitable shape and three-dimensionally processing it by a compression molding method or the like.
[0041]
Note that the SMC sheet 1 of the present invention is not limited to the SMC 9 for automotive exterior parts, but for other uses such as building material panels such as unit bath panels, containers such as bottles and cases, toys, sundries, etc. Is also applicable.
[0042]
【Example】
An SMC molded product for a unit bus panel was manufactured under the following conditions.
[0043]
A polyethylene terephthalate sheet having a thickness of 100 μm was used as the thermoplastic resin sheet, and a pattern layer having a stone-tone pattern was formed thereon by a gravure printing method using white and cream vinyl resin-based ink.
[0044]
Next, a non-woven fabric having a thickness of 1.5 mm made of spandex was used as the gas permeable sheet, and was laminated on the thermoplastic resin sheet with a urethane resin dry laminate adhesive to obtain an SMC sheet.
[0045]
Next, as shown in FIG. 2, the SMC sheet was placed on an SMC production line and sent out, and an SMC was obtained using a polyester resin compound as a resin liquid.
[0046]
The SMC thus obtained was free from gas accumulation of the resin liquid, and the SMC sheet and the resin layer were firmly adhered.
[0047]
Next, the SMC was placed in a compression mold and processed into a three-dimensional shape by a compression molding method to obtain an SMC molded product for a unit bus panel.
[0048]
【The invention's effect】
Since the present invention adopts the configuration as described above, the following effects can be obtained.
[0049]
That is, the SMC sheet of the present invention is generated from the resin liquid because the SMC sheet is a laminate of two types of sheets, and the sheet on the surface that is bonded to the resin liquid of the SMC sheet is a gas permeable sheet. Gas does not remain in the resin, and the adhesion of the SMC sheet to the resin is high.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of an SMC sheet according to the present invention.
FIG. 2 is a cross-sectional view showing a process of manufacturing SMC using the SMC sheet of the present invention.
FIG. 3 is a cross-sectional view showing a deep drawing mold used for examining the characteristics of an SMC sheet.
FIG. 4 is a perspective view showing an apparatus for measuring the tensile elongation at break of an SMC sheet.
FIG. 5 is a plan view showing a portion for fixing a test piece of an apparatus for measuring tensile elongation at break.
FIG. 6 is a cross-sectional view showing a portion for fixing a test piece of an apparatus for measuring tensile elongation at break.
[Explanation of symbols]
1 SMC sheet 2 Gas permeable sheet 3 Thermoplastic resin sheet 4 Pattern layer 5 Resin liquid 6 Roving 9 SMC
20 Test piece 21 Screw 22 Chuck 23 Chuck 24 Movable member

Claims (2)

A non-woven fabric composed of spandex, acrylic fiber, polyethylene fiber, or polyamide fiber, and a gas-permeable sheet that can release gas generated from the resin liquid when SMC is produced; and a thermoplastic resin sheet; A method for producing SMC, characterized in that an SMC sheet is formed by laminating and a resin liquid is finally poured onto a gas-permeable sheet of the SMC sheet . The method for producing SMC according to claim 1 , wherein the thermoplastic resin sheet or the gas permeable sheet has a design layer .

Images