JP2016083845A - Thermoplastic resin sheet heating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin sheet heating method including mounting a thermoplastic resin sheet on a conveyance tray formed by providing a plurality of rollers at intervals, conveying the conveyance tray to a heating furnace, heating the thermoplastic resin sheet in the heating furnace and then unloading the conveyance tray from the heating furnace, and capable of preventing a roller indentation from being transferred onto the thermoplastic resin sheet or capable of fading the roller indentation.SOLUTION: Provided is a thermoplastic resin sheet heating method including mounting a thermoplastic resin sheet S on a conveyance tray T formed by providing a plurality of rollers R at intervals, conveying the conveyance tray T mounting thereon the thermoplastic resin sheet S to a heating furnace K, heating the thermoplastic resin sheet S with heat provided from at least below the conveyance tray T and then unloading the conveyance tray T from the heating furnace K, comprising preheating the rollers R constituting the conveyance tray T before heating the thermoplastic resin sheet S in the heating furnace K.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for heating a thermoplastic resin sheet.

  There are a wide variety of molding methods for fiber reinforced resin molded products (FRP) using a thermoplastic resin as a matrix resin. As one of the molding methods, as shown in Patent Document 1, a reinforcing fiber material is contained in the matrix resin. There is a forming method in which a molding material (for example, a thermoplastic resin sheet or the like) is sufficiently heated and softened immediately before it is molded into a desired three-dimensional shape, and then press molding is performed. In some cases, a sheet made of only a thermoplastic resin not containing reinforcing fibers is heated and press-molded.

  In this molding method, from the viewpoint of mass production of molded products, taking the production cycle time into consideration, the thermoplastic resin sheet is transported to the heating furnace and the thermoplastic resin sheet softened in the heating furnace is transported from the heating furnace. In many cases, an automatic conveyance tray is used at the time. More specifically, a thermoplastic resin sheet is placed on a conveyance tray configured with a plurality of rollers at intervals, and conveyed to a heating furnace, and the conveyance tray loaded with a softened thermoplastic resin sheet is unloaded from the heating furnace. To do.

  In this way, when the transport tray on which the thermoplastic resin sheet is placed is transported to the heating furnace and unloaded from the heating furnace, the roller marks constituting the transport tray are transferred to the thermoplastic resin sheet, and the mechanical properties of the thermoplastic resin sheet are improved. It may be a factor that causes a reduction or poor appearance.

  This will be described with reference to FIGS. As shown in FIG. 5, a plurality of rollers R are arranged at intervals, the plurality of rollers R are fixed to the chain C, and the chain C is moved by the drive gear D (X direction). The transport tray T is applied, and the thermoplastic resin sheet S is placed on the transport tray T and transported to the heating furnace K (X direction).

  In the heating furnace K, as shown in FIG. 6, the thermoplastic resin sheet S on the transport tray T is heated and softened by the heat from at least the heater below the transport tray T. Here, the heat provided from the lower side of the thermoplastic resin sheet S is blocked by the roller R in the place where the roller R exists (while the heat supply Y1 is a roller). Heat is directly provided to the back surface of the thermoplastic resin sheet S facing the gap between the roller R and the roller R (heat provision Y2).

  As a result, when the thermoplastic resin sheet S softened in the heating furnace K is unloaded from the heating furnace K and the back surface is viewed, a place where heat supply is inhibited by the roller R as shown in FIG. The roller mark N of the roller R is transferred. More specifically, since a portion of the thermoplastic resin sheet S that is not directly above the roller R does not receive any support from the roller R, the free surface is easily softened by heating in a state where it does not receive pressure. On the other hand, in the portion immediately above the roller R, the sheet weight in that range is supported by the roller R, and the reaction force is received from the roller R. In this way, roller marks are generated due to the heating speed difference and the pressure difference at the boundary between the part freely deformed by heating and the part where the heating is insufficient and the deformation is restricted. Although it depends on the material of the roller, for example, when an iron roller is used, although the thermal conductivity of the roller itself is superior to that of air, the portion where the roller is in contact with the thermoplastic resin sheet is heated in the heating furnace. The heat transfer from the heat source at is delayed, and a heating speed difference is generated, which causes roller marks.

Japanese Patent Laid-Open No. 2014-124834

  The present invention has been made in view of the above-described problems, and places a thermoplastic resin sheet on a conveyance tray in which a plurality of rollers are arranged at intervals, and heats the conveyance tray on which the thermoplastic resin sheet is placed. The present invention relates to a method for heating a thermoplastic resin sheet that is transported to a furnace, heated in the heating furnace with heat provided from at least the lower side of the transport tray, and then unloaded from the heating furnace. It is an object of the present invention to provide a method for heating a thermoplastic resin sheet in which no roller trace is transferred to the roller or the roller trace can be thinned.

  In order to achieve the above object, the method for heating a thermoplastic resin sheet according to the present invention is such that a thermoplastic resin sheet is placed on a transport tray in which a plurality of rollers are arranged at intervals, and the thermoplastic resin sheet is placed thereon. A method for heating a thermoplastic resin sheet in which a transport tray is transported to a heating furnace, the thermoplastic resin sheet is heated in the heating furnace with heat provided from at least below the transport tray, and then the transport tray is unloaded from the heating furnace. Thus, before the thermoplastic resin sheet is heated in the heating furnace, the rollers constituting the transport tray are preheated.

  The method for heating a thermoplastic resin sheet according to the present invention includes preheating the rollers constituting the transport tray before heating the thermoplastic resin sheet in a heating furnace. Even in areas where the heat supply is hindered by the roller, sufficient heat can be provided, and this ensures that the heat supply is as uniform as possible over the entire area of the thermoplastic resin sheet. This is a method that can suppress the transfer of the roller or make the roller marks as thin as possible.

  Here, “preliminarily heat the rollers constituting the conveyance tray” means that each roller is heated by a heater before being conveyed to a heating furnace, or a heating member is brought into contact with each roller to conduct heat. A method of placing the thermoplastic resin sheet on the heated roller in a heated state, a method of heating each roller in a state where the thermoplastic resin sheet is placed on each roller and transporting it to the heating furnace, Furthermore, there are various preheating methods such as a method in which a heating means such as a heater is built in the roller, and the heating means is operated at a predetermined timing before and after conveyance to the heating furnace to heat the roller from the inside. It is included. In addition, “heat provided from at least the lower side of the transport tray” means that a heater or the like is provided only below the transport tray in the heating furnace, and heat is provided only from the lower side. It is meant to include forms in which heat is provided from above, forms in which heat is provided from below, above, and from the side.

  The heat when the roller is preheated is preferably set to an amount of heat that compensates for the amount of heat impeded by the roller when the thermoplastic resin sheet is heated in the heating furnace. The “roller” includes not only a generally cylindrical form but also a flat form or a polygonal form.

  The method for heating a thermoplastic resin sheet according to the present invention is based on an extremely simple process improvement in which the rollers constituting the transport tray on which the thermoplastic resin sheet is placed are only preheated before being heated in a heating furnace. Therefore, it does not increase the manufacturing cost.

  In addition, since the thermoplastic resin sheet can be softened so that no roller marks remain, or roller marks that are thin enough to have no problem in appearance and strength are left, the material yield is improved. This leads to a reduction in material costs and manufacturing costs.

  As can be understood from the above description, according to the method for heating a thermoplastic resin sheet of the present invention, before the thermoplastic resin sheet is heated in a heating furnace, the rollers constituting the transport tray are preheated. Therefore, sufficient heat can be provided even in a portion of the thermoplastic resin sheet in which the heat supply is hindered by the roller in the heating furnace. The mark can be made as thin as possible.

It is the schematic diagram explaining embodiment of the heating method of the thermoplastic resin sheet of this invention. FIG. 2 is a schematic diagram illustrating an embodiment of the heating method of the present invention following FIG. 1. It is the figure which showed the condition of the back surface of the thermoplastic resin sheet heated with the heating method of this invention. It is the photograph figure which showed the observation result, (a) is the figure which showed the thermoplastic resin sheet by a comparative example (conventional heating method), (b) is the heat by an Example (heating method of this invention). It is the figure which showed the plastic resin sheet. It is the schematic diagram explaining embodiment of the heating method of the conventional thermoplastic resin sheet. FIG. 6 is a schematic diagram illustrating an embodiment of a conventional heating method following FIG. 5. It is the figure which showed the condition of the back surface of the thermoplastic resin sheet heated with the conventional heating method.

  Hereinafter, an embodiment of a method for heating a thermoplastic resin sheet of the present invention will be described with reference to the drawings.

(Embodiment of heating method of thermoplastic resin sheet)
1 and 2 are schematic views illustrating, in that order, the embodiment of the method for heating a thermoplastic resin sheet of the present invention, and FIG. 3 shows the back surface of the thermoplastic resin sheet heated by the heating method of the present invention. It is the figure which showed the condition.

  As shown in FIG. 1, the transport tray T has a plurality of rollers R arranged at intervals, the plurality of rollers R being fixed to the chain C, and the chain C being moved by the drive gear D (X direction). ) As a whole. The roller R is a metal roller that can withstand a temperature atmosphere of 200 to 300 ° C. in the heating furnace K.

  A thermoplastic resin sheet S is placed on the transport tray T, transported into the heating furnace K (X direction), and heated under heating conditions according to the matrix resin (the softening point) constituting the sheet in the heating furnace K. Then, the thermoplastic resin sheet S is softened.

  Here, the thermoplastic resin sheet S may be one in which the reinforcing fiber material is not mixed in addition to the one in which the reinforcing fiber material is mixed inside the thermoplastic resin. The material of the matrix resin forming the thermoplastic resin sheet S includes crystals such as polyethylene (PE), polypropylene (PP), polyamide (PA: nylon 6, nylon 66, etc.), polyacetal (POM), polyethylene terephthalate (PET), etc. Amorphous Plastic, Polystyrene (PS), Polyvinyl Chloride (PVC), Polymethyl Methacrylate (PMMA), ABS Resin, Amorphous Plastics such as Thermoplastic Epoxy, etc., or a Mixture of Two or More Can be mentioned. On the other hand, as the material of the reinforcing fiber material, ceramic fibers such as boron, alumina, silicon carbide, silicon nitride, and zirconia, inorganic fibers such as glass fibers and carbon fibers, metal fibers such as copper, steel, aluminum, and stainless steel, polyamide, Any one or a mixture of two or more organic fibers such as polyester can be mentioned.

  In the illustrated heating method, each of the rollers R constituting the transport tray T is preheated before the thermoplastic resin sheet S is heated and softened in the heating furnace K.

  Here, as a pre-heating method for each roller R, before the transport tray T on which the thermoplastic resin sheet S is placed is transported to the heating furnace K, a method for heating each roller R with a heater or conducting heat to the heating member. A method of preheating by a method and the like, placing the thermoplastic resin sheet S on the preheated roller R, and conveying it to the heating furnace K can be mentioned. In addition, after the thermoplastic resin sheet S is placed on the cooled roller R, each roller R is preliminarily heated outside the heating furnace K and conveyed to the heating furnace K or the heating furnace K. The method of performing preheating later can be mentioned.

  Furthermore, a heating means such as a heater is built in the roller R, and the heating means is operated at a predetermined timing before and after the conveyance to the heating furnace K to heat the roller R from the inside.

  After performing the preheating of the roller R by a desired preheating method among various preheating methods, as shown in FIG. 2, at least from the lower side of the transport tray T to the thermoplastic resin sheet S in the heating furnace K. The heat supply is executed.

  At this time, in the portion where the roller R is present, heat supply to the thermoplastic resin sheet S is hindered by the roller R (heat provision Y1 is hindered), and sufficient for the thermoplastic resin sheet S facing the gap between the rollers R. Although heat is provided (heat supply Y2), since the roller R is preheated, sufficient heat is supplied to the entire surface of the thermoplastic resin sheet S.

  Therefore, the surface of the thermoplastic resin sheet S carried out from the heating furnace K after being softened by heating in the heating furnace K is a sheet surface without any transfer of roller marks as shown in FIG. A roller surface is thin, and a sheet surface in a state where there is no problem in appearance and strength is formed.

  In this way, the thermoplastic resin sheet S can be softened in such a way that no roller marks remain, or roller marks that are thin enough to have no problem in appearance and strength, so that the material yield can be reduced. Improvement can be achieved, and this makes it possible to reduce material costs and manufacturing costs.

(Verification experiment and results)
The inventors of the present invention heated a thermoplastic resin sheet in a heating furnace using the heating method of the present invention (Example) and the conventional heating method (a comparative example in which the roller is not preheated). While observing the obtained thermoplastic resin sheet, a three-point bending test of each thermoplastic resin sheet was performed, and an experiment for measuring the bending strength was performed. Here, FIG. 4 is a photograph showing an observation result, FIG. 4 (a) is a view showing a thermoplastic resin sheet according to a comparative example, and FIG. 4 (b) is a thermoplastic resin sheet according to an example. FIG. Table 1 below shows the three-point bending test results.

  From FIG. 4, the roller marks clearly remained in the comparative example, whereas no roller marks could be confirmed in the example.

  In the three-point bending test, in the comparative example, the test was performed when the roller trace was on the top and on the bottom.

  It has been demonstrated that the bending strength of the example increases by about 10% or more with respect to any of the bending strengths of the comparative examples, and the roller marks have a great influence on the strength of the sheet. In the examples, it was confirmed that no roller traces having a great influence on the strength were formed in this way, and therefore no strength reduction was observed.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  T ... transport tray, R ... roller, D ... drive gear, C ... chain, S ... thermoplastic resin sheet, K ... heating furnace

Claims (1)

A thermoplastic resin sheet is placed on a transport tray in which a plurality of rollers are arranged at intervals, and the transport tray on which the thermoplastic resin sheet is placed is transported to a heating furnace, and in the heating furnace, at least from below the transport tray. After heating the thermoplastic resin sheet with the heat provided, it is a method for heating the thermoplastic resin sheet that unloads the transport tray from the heating furnace,
A method for heating a thermoplastic resin sheet, in which a roller constituting a transport tray is preheated before the thermoplastic resin sheet is heated in a heating furnace.

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