JP5186883B2 - Method for manufacturing molded structure - Google Patents

Description

The present invention relates to a method for producing a formed shape structure.

A molded structure used for a door trim or the like has a base material in which fibers are closely packed, and a molded body such as a bracket is formed by injection-molding a thermoplastic resin on the base material (for example, the following patent documents) 1). The base material has a structure in which fibers are bonded using a thermoplastic resin as a binder. When injection molding is performed, the thermoplastic resin on the surface of the base material is softened by the heat of the molten resin and is pushed into the base material. Thereby, although the fiber is exposed on the surface of the base material, the formed body is bonded to the base material by bonding the exposed fiber as an anchor portion to the injected molten resin.
Japanese Patent Laid-Open No. 2006-212824

However, when the fiber density is increased for the purpose of improving the quality such as reducing the unevenness of the substrate surface, the molten resin cannot easily enter the voids between the fibers, so the anchor effect is reduced and the bonding strength is reduced. . Further, although the thermoplastic resin on the surface of the base material is softened by the molten resin, it is not completely melted, so that the effect of welding the resins cannot be expected. However, when the bonding area between the base and the molded body is increased in order to increase the bonding strength of the molded body, when the injected molten resin is cooled and contracted, the opposite side of the base to the bonded portion is raised Therefore, it becomes defective in appearance evaluation.
This invention is completed based on the above situations, Comprising: It aims at raising the joining strength, without increasing the joining area of a base material and a molded object.

  The present invention is a molded structure comprising a base material formed by entanglement of fibers with each other, and a molded body formed by injecting molten resin to the base material set in a mold. The bonding portion of the base material with the molded body is characterized in that it is configured to be a low density portion in which the density of the fibers is lower than that of the periphery of the bonding portion.

  First, the base material is set in a mold and the molten resin is injected. At this time, since the joint portion of the base material with the molded body is set to a low density portion where the density of the fibers is low, the molten resin penetrates deeper into the base material than usual. Thereby, joining strength resulting from an anchor effect can be raised because a molten resin gets entangled with more fibers. Therefore, even if the bonding area is small, the bonding strength between the base material and the molded body can be increased.

The following configuration is preferable as an embodiment of the present invention.
The base material is formed by forming a preboard by primary molding of fibers together with a thermoplastic resin, and then setting the preboard on a molding die and performing secondary molding. It is also possible to adopt a configuration in which the molten resin is injected onto the pre-board that has been heated again to be simultaneously molded with the base material.

  According to such a configuration, the preboard is heated, the thermoplastic resin is in a softened state, and the base material is formed by molding with a molding die, and the low density portion of the fiber is formed in a part of the base material, The thermoplastic resin is pushed into the inside of the base material by the injection pressure of the molten resin into the low density portion, and the molten resin is entangled with the fiber, so that the bonding strength due to the anchor effect can be increased. Furthermore, since the injected molten resin is mixed with the thermoplastic resin of the base material and becomes a unitary body, the bonding strength due to the welding effect between the resins can be increased.

  The base material is compressed when the mold is closed to reduce the plate thickness, and the low density portion is formed in the molding space for molding the molded body as the mold is closed. It is good also as a structure.

  According to such a structure, the part shape | molded with a shaping | molding die among base materials will be compressed when a shaping | molding die is closed, and plate | board thickness will become small. On the other hand, since the portion corresponding to the molding space in the base material is not compressed, the low-density portion is formed in a raised state than the portion to be compressed. And a molded object is formed in a low density part by inject | pouring molten resin to molding space. That is, since the low density portion is formed in the process of forming the molded body, a step of forming the low density portion may not be provided separately.

The temperature of the preboard heated in the secondary molding may be 180 ° C. or higher and 200 ° C. or lower.
If it does in this way, since the thermoplastic resin of a preboard can be made into the molten state, the welding effect with the injected molten resin can be improved reliably.

The density of the fiber in the low density part may be 0.5 g / cm ³ or more and less than 0.8 g / cm ³ .
For example, when the fiber density of the base material is set to 0.8 g / cm ³ , the fiber density of the low density part is set to 0.5 g / cm ³ or more and less than 0.8 g / cm ³ , It is possible to increase the bonding strength. On the other hand, if the fiber density of the low density portion is set to be smaller than 0.5 g / cm ³ , the fiber becomes fuzzy on the surface of the base material, which tends to be defective in appearance evaluation.

  Further, the molded structure of the present invention is a method for producing a molded structure in which a molded body is injection-molded on a base material formed by entanglement of fibers with each other, and the fibers are heated together with a thermoplastic resin. Primary forming process to form pre-board by forming, and secondary forming to form low density part with low fiber density in part of base material while heating preboard again and secondary forming to form base material You may manufacture by the manufacturing method of the shaping | molding structure provided with the process and the simultaneous shaping | molding process which inject | pours molten resin to a low density part and co-molds a molded object in the state of secondary shaping | molding.

  According to the present invention, a compact can be firmly joined to a substrate with a small joint area.

<Embodiment>
An embodiment of the present invention will be described with reference to the drawings of FIGS.
As shown in FIG. 1, a door trim (an example of the “molded structure” of the present invention) 1 according to the present embodiment has a bracket (an example of the “molded body” of the present invention) 3 such as a clip seat on the trim board 2. It is formed by being fixed. Although a plurality of brackets 3 are originally attached to one surface of the trim board 2, in FIG. 1, the trim board 2 is broken and only the joint portion of one bracket 3 is shown.

  The flat trim board 2 has a base material 21 in which a wood fiber obtained by weaving wood or the like, or a bast plant fiber such as kenaf or the like is impregnated with polypropylene which is a thermoplastic resin. It is constituted by covering a skin 22 made of synthetic leather, natural leather or fiber. The skin 22 is formed by bonding the bracket 3 to the base material 21, applying an adhesive to the surface of the base material 21, and press-bonding it by vacuum forming or the like.

  The base material 21 in the present embodiment is formed by primary molding a mat-like (board thickness of about 5 mm) preboard P in which kenaf fibers are entangled with each other and impregnated with polypropylene, and this preboard P is formed by secondary molding to a thickness of 3 mm. It is formed by compressing to a degree so that the fiber density is higher than that of the preboard P. Although polypropylene plays a role as a binder for connecting fibers, the base material 21 is made of only polypropylene or other thermoplastic resin, or a mixture of a thermoplastic resin other than polypropylene, such as polyethylene terephthalate, and a fiber. You may form in.

  As shown in FIG. 1, the bracket 3 is integrally formed of polypropylene, and has a shape that divides a cylindrical body whose outer peripheral surface is inclined, and its large diameter side is joined to the base material 21 of the trim board 2. Has been. Further, a substantially semicircular flat standing wall 31 is provided at the tip of the bracket 3, and a perfect circular cutout 32 is formed at the end.

  On the other hand, the low density part 23 in which the fiber density of the base material 21 is lower than the periphery of the joint part is provided in the joint part of the base material 21 with the bracket 3. As will be described later, the low density portion 23 is a portion that remains in a state close to the preboard P because it was not compressed by the molding apparatus 4 when the preboard P was closed. The low density portion 23 in the present embodiment is formed from the front surface to the back surface of the base material 21. Therefore, the molten resin 5 in which the polypropylene is in a molten state is more easily penetrated into the low density portion 23 than the surroundings. In addition, as the molten resin 5, you may use other thermoplastic resins, such as a polyethylene terephthalate.

  Next, a molding apparatus 4 that molds the bracket 3 on the trim board 2 will be described with reference to FIGS. 2 to 5. The molding apparatus 4 in this embodiment is an injection molding apparatus that includes an injection unit 40, an upper mold 41, a lower mold 42, and a slide mold 43. The skin 22 may be molded and pasted by the molding device 4 simultaneously with the molding of the bracket 3.

  The injection unit 40 is a screw type unit, and is disposed above the upper mold 41 in this embodiment. A hot runner H that allows the molten resin 5 to pass therethrough is routed inside the upper mold 41. The hot runner H communicates with the bracket molding space S2 for molding each bracket 3, and the molten resin 5 is supplied from the injection unit 40 into the bracket molding space S2 through the hot runner H. That is, since the common injection unit 40 is used for each bracket molding space S2, variations in the injection pressure of the molten resin 5 injected into each bracket molding space S2 can be eliminated.

  The upper die 41 is fixed to the molding device 4 by appropriate means such as welding, press-fitting, and fastening such as bolts. The upper die 41 has a shape protruding downward, and a concave portion 41A that can accommodate the slide die 43 is formed on the lower surface thereof. On the other hand, the lower mold 42 is fixed to the drive device 44 via a shaft, and can be moved in the vertical direction between an open mold position shown in FIG. 2 and a molding position shown in FIG. As shown in FIG. 3, the lower mold 42 has a shape recessed downward so that the upper mold 41 can be received when the mold is closed, and is separated from the upper mold 41 by the plate thickness of the base material 22 at the molding position. Are opposed to each other.

  That is, a base material forming space S1 is formed between the upper die 41 and the lower die 42, and the base board 21 is formed by the preboard P being compressed and sandwiched between the base material forming spaces S1. The base material 21 formed in this manner has a configuration including a flat portion 21A and an outer wall 21B that rises from the flat portion 21A by bending the outer peripheral portion of the flat portion 21A upward. Since both end portions of the preboard P are cut by shearing as the upper die 41 and the lower die 42 are closed, the base material 21 can be formed into a regular length.

  The slide mold 43 is fixed to the drive device 45 via a shaft, and is inclined along the inclined surface 46 in the recess 41A between the molding position shown in FIG. 3 and the open mold position shown in FIG. It is movable. When the slide mold 43 is in the molding position, the lower surface of the slide mold 43 and the lower surface of the upper mold 41 are flush with each other. Further, a bracket molding space S2 is formed between the upper mold 41 and the slide mold 43 at the molding position inside the recess 41A. The size of the bracket forming space S2 is minimized when the slide die 43 reaches the forming position, and the shape thereof matches the shape of the bracket 3 to be formed.

  As each of the drive devices 44 and 45, any device such as an actuator using an electric motor, an air cylinder, a hydraulic cylinder, and an electromagnetic solenoid actuator can be used. Each of the drive devices 44 and 45 is controlled by a controller (not shown). The controller detects the rotational position by, for example, a pulse encoder attached to the electric motor, and based on this, the lower mold 42 and the slide mold 43 are opened. And can be moved to the molding position.

  Next, the manufacturing method which manufactures the base material 21 is demonstrated based on drawing of FIG. 2 thru | or FIG. The manufacturing method of the base material 21 includes a primary molding process for forming the preboard P and a secondary molding process for forming the base material 21 from the preboard P (an example of the “secondary molding process” and the “simultaneous molding process” of the present invention). It consists of and.

  In the primary molding step, a mat material in which kenaf fibers and polypropylene are mixed (for example, 50% of kenaf fibers and 50% of polypropylene is heated) is press-molded, and this is pressed to a predetermined length (after molding). The plate-like pre-board P is formed by cutting with a length longer than the length of the substrate 21. Since the preboard P is heated immediately after the primary molding, the internal polypropylene is in a softened state.

In the secondary molding step, as shown in FIG. 2, the slide mold 43 is moved to the molding position, and the preboard P molded by the primary molding is heated again to the extent that the polypropylene melts and softens, and is in the mold opening position. After being set on the lower mold 42, the lower mold 42 is moved to the molding position while the slide mold 43 is held at the molding position, as shown in FIG. Then, both ends of the preboard P are cut off by shearing, and the preboard P is molded into the base material 21 by being compressed by the molding surface of the base material molding space S1. At this time, the portion of the preboard P located in the bracket forming space S2 is not compressed, and thus is relatively raised from the surroundings. The density of the kenaf fiber in the raised portion is lower than the kenaf fiber density (0.8 g / cm ³ ) of the base material 21, and the range from the raised portion to the molding surface of the lower die 42 in the base material 21 is low density. Formed as portion 23. The density of the fibers of the low density portion 23 is set to be 0.5 g / cm ³ or more and less than 0.8 g / cm ³ .

  Next, the molten resin 5 is injected into each bracket forming space S <b> 2 via the hot runner H by the injection unit 40. At this time, the temperature of the preboard P is set to 180 ° C. or higher and 200 ° C. or lower. The injected molten resin 5 penetrates into the inside of the kenaf fiber in place of the softened polypropylene while pushing the softened polypropylene inside the base material 21 downward in the low density portion 23. At the same time, the molten resin 5 that has penetrated into the inside of the kenaf fiber is mixed with the softened polypropylene inside the base material 21 and becomes a unitary. Thus, when the molten resin 5 is filled in the bracket molding space S2 and cooled, the bracket 3 is molded as shown in FIG. After that, as shown in FIG. 5, the trim board 2 in which the bracket 3 is fixed to the base material 21 is obtained by moving both the lower mold 42 and the slide mold 43 to the open mold position.

  As described above, in the present embodiment, the molten resin 5 injected into the bracket molding space S2 penetrates deep inside the kenaf fiber at the low density portion 23, so that the bonding strength due to the anchor effect can be increased. Moreover, since the injected molten resin 5 is mixed with the softened polypropylene in the base material 21, the bonding strength due to the welding effect can be increased. Further, in the process of manufacturing the trim board 2, the low density portion 23 is formed by compressing the preboard P and secondary-molding the base material 21. Since the bracket 3 is molded simultaneously with the molding of the base material 21 (secondary molding), an injection molding process may not be provided separately.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In this embodiment, by closing the molding device 4 while the preboard P is heated, the portion located in the bracket molding space S2 is relatively raised to form the low density portion 23. However, according to the present invention, the low density portion 23 may be formed by applying hot air to the joint portion of the bracket 3 in a state where the substrate 21 is finished (that is, in a cooled state). If it does in this way, the molten resin 5 inside the base material 21 will melt | dissolve partially with a hot air, and the kenaf fiber will be released from the entangled state by the spring back, and will be in the state which rose, and the low density part 23 will be formed. Such a device for sending hot air may be provided in the upper mold 41 for forming the bracket 3 or may send hot air through a blower passage communicating with the bracket forming space S2. Furthermore, after the hot air is sent in, lowering the density of the low density portion 23 may be promoted by evacuating the bracket forming space S2.

  (2) In this embodiment, although the formation of the low density portion 23 and the formation of the base material 21 are performed simultaneously, according to the present invention, these formations may be performed separately.

  (3) Although the formation of the base material 21 and the formation of the bracket 3 are performed simultaneously in this embodiment, according to the present invention, these formations may be performed separately.

  (4) Although the present embodiment is applied to a vehicle door trim as a molded structure, according to the present invention, the present invention may be applied to building materials and the like in addition to vehicle parts such as quarter trims and pillar garnishes other than vehicle door trims. .

  (5) In this embodiment, although the low density part 23 is formed with a kenaf fiber and a thermoplastic resin, according to the present invention, a material such as a foam may be used as the low density part 23.

A perspective view of a door trim with the trim board broken and showing only one bracket joint Sectional view showing the preboard set in the molding machine Sectional view showing the state before the molten resin is injected after the mold is closed Sectional view showing the state after injecting molten resin after closing the molding device Sectional view showing the state where the molding device is opened after molding the bracket

Explanation of symbols

1 ... Door trim (molded structure)
2 ... Trim board 3 ... Bracket (molded body)
4 ... Molding device (mold)
5 ... Molten resin 21 ... Base material 23 ... Low density part P ... Pre-board

Claims (4)

  A method for producing a molded structure in which a molded body is injection-molded on a base material formed by interlacing fibers with each other and impregnated with a thermoplastic resin,
  A primary molding step of heating the fibers together with the thermoplastic resin, and primary molding to form a preboard;
  The preboard is heated to a temperature at which the thermoplastic resin melts and softens, and the mold is closed and compressed to form the base material by secondary molding, and the thermoplastic resin is melted and softened. A secondary molding step of forming a low density portion having a low fiber density in a part of the base material in a molding space for molding the molded body as the mold is closed;
  Simultaneous molding step of injecting molten resin into the low density portion and simultaneously molding the molded body with the base material in the mold closing state and the thermoplastic resin being melted and softened in the secondary molding step The manufacturing method of the shaping | molding structure provided with these.   2. The method for producing a molded structure according to claim 1, wherein the temperature of the preboard in a heated state in the secondary molding step is 180 ° C. or higher and 200 ° C. or lower.   The density of the fibers in the low density part is 0.5 g / cm. ³ 0.8 g / cm or more ³ The method for producing a molded structure according to claim 1 or 2, wherein the molding structure is less than 3.   A plurality of the molded bodies are bonded to the base material,
  The plurality of molded bodies are such that the molding space for molding each molded body communicates with a hot runner that allows the molten resin to pass through.
  4. The molten resin is supplied to the plurality of molding spaces from a common injection unit through the hot runner in the simultaneous molding step. A method for producing a molded structure.

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