JP4207431B2 - Manufacturing method of multicolor resin molded products - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a multicolored resin molded article in which a base material is composed of a foamed base material portion and a non-foamed base material portion.
[0002]
[Prior art]
Molded products based on thermoplastic resins are widely used in a wide range of fields such as automobile interior parts, interior / exterior parts of household electrical appliances, etc. due to their economy, light weight, and good formability. When lightness is required, a molded product made of a foamed base material obtained by foaming the base material is also well known.
[0003]
However, foamed molded products in which all of the base material is foamed have a problem that it is weak in mechanical strength as a molded product even though the lightness can be satisfied. There has been proposed a molded article made of a base material in which a foamed part and a non-foamed part are combined.
[0004]
Conventionally, a non-foamed thermoplastic resin base material part and a foamed thermoplastic resin base material part are combined to form a base material to produce a multicolor resin molded product. Produced by forming the foam base material part and the foam base material part separately, assembling the edges of both base material parts together in the subsequent process, and mechanically joining them using means such as heat staking How to do is known.
As another method, the present inventors first supply a foam sheet made of a thermoplastic resin corresponding to the foam base material portion into the mold cavity in advance, and then supply a molten thermoplastic resin. A method of filling and integrating a thermoplastic resin corresponding to an end portion of a foamed sheet made of a thermoplastic resin and a non-foamed base material by heat fusion is proposed (Japanese Patent Application No. 2001-092323).
[0005]
However, in the former method, there are problems that the process is complicated, and that a positional shift occurs when the two are joined, and that heat is applied to the surface during caulking, resulting in a defective appearance of the product.
In the latter method, a product having no problem in appearance and bonding strength can be produced, but it is necessary to produce a foamed sheet in advance, which is not necessarily sufficient in terms of cost.
[0006]
[Problems to be solved by the invention]
For these reasons, the inventors of the present invention in a multicolored resin molded product in which a base material is formed by combining a base material portion made of a non-foamed thermoplastic resin and a base material portion made of a foamed thermoplastic resin. As a result of studying a low-cost method for producing a multicolored resin molded article having no problem in the bonding strength between the base material parts and being light and having a good appearance, the present invention has been achieved.
[0007]
[Means for Solving the Problems]
That is, the present invention is based on the fact that a thermoplastic resin foam base part and a thermoplastic resin non-foam base part are adjacent to each other, and a joint part between the adjacent foam base part and the non-foam base part is thermally fused. A method for producing a multicolor resin molded article comprising a material, wherein a molten state containing a foaming agent in a mold cavity portion corresponding to a forming portion of a foam base material portion, between both molds consisting of a male and female pair After the thermoplastic resin is supplied, filled, and primary cooled, the mold cavity is expanded to foam the molten thermoplastic resin, followed by secondary cooling, and then corresponds to the formation part of the non-foamed substrate part The present invention provides a method for producing the above-mentioned multicolor resin molded product, characterized in that a molten thermoplastic resin is supplied to and filled in a mold cavity portion to be cooled and subjected to tertiary cooling.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
This description is an example of the present invention, and the present invention is not limited to this.
[0009]
FIG. 1 is a plan view showing an example of a multicolor resin molded product obtained by the production method of the present invention. The base material of the multicolor resin molded product is a foamed base material portion (1 ) And a non-foamed substrate portion (2) made of a thermoplastic resin.
FIG. 2 shows a cross-section when the multicolor resin molded product shown in FIG. 1 is cut by AA, and the foamed substrate portion (1) has no or almost no voids. It consists of a non-performing skin layer (1A) and a foamed core layer (1B) having voids.
[0010]
3 (a) and 3 (b) are plan views showing examples of other multicolor resin molded products, and FIG. 4 is a multicolor resin molded product shown in FIGS. 3 (a) and 3 (b). It is sectional drawing when cut | disconnecting by BB and CC respectively.
As illustrated in the figure, in the multicolor resin molded product that is the subject of the present invention, if the base material portions of the foam base material portion (1) and the non-foam base material portion (2) are adjacent to each other. The positional relationship is arbitrary, and the non-foamable substrate portion (2) may be in a form in which the foamable substrate portion (1) is sandwiched (FIG. 3 (a)), or the non-foamable substrate portion (2 ) May surround the foamed base material portion (1) (FIG. 3B), and although not shown, both base material portions may be appropriately combined depending on the purpose. Good.
[0011]
In addition, the multicolor resin molded product may have a skin material (3) bonded to the surface thereof, and the skin material in that case is a foamed base material portion as shown in FIGS. It may be bonded to part or all of the surface of (1) or the non-foamed substrate part (2), or to the entire surface of the substrate.
[0012]
Below, the manufacturing method of such a multicolor resin molded product is demonstrated.
In the following description, for the sake of clarity, an example of producing a multicolor resin molded product in which one foamed base material part and a non-foamed base material part are adjacent to each other and the joint part is heat-sealed is shown. Even if either or both of the foamed base material part and the non-foamed base material part are composed of a combination of two or more, they can be produced in the same manner according to this method.
[0013]
FIG. 6 is a schematic cross-sectional view of an example of a mold used in the method of the present invention. In this mold, the outer periphery of the male mold (4) and the inner periphery of the female mold (5) are slidable to each other. It consists of a pair of sliding males and females, and both molds are usually connected to a clamping device such as a press device, and the other is fixed so that both molds can be flattened vertically or horizontally. Yes.
In the figure, the male mold is fixed, the female mold is connected to a press device (not shown), and both molds open and close in the vertical direction.
[0014]
Further, a resin stop weir (6) that can protrude into the cavity is provided at a position corresponding to the boundary between the foamed base material portion and the non-foamed base material portion on the mold cavity surface in the male mold. By protruding the resin stop weir, the mold cavity is separated into each of the foam base part and the non-foam base part, and the flow of the molten thermoplastic resin supplied to one base part side is the resin stop weir. It has a structure that is prevented from flowing to another adjacent substrate portion side.
[0015]
Although this resin stop weir is not always essential, the base material is clearly separated into a foamed part and a non-foamed part, and the thermoplastic resin supplied to each base part is prevented from intermingling more than necessary. It is extremely effective in doing so.
[0016]
This resin stop weir is slidable in the opening and closing direction of the mold by a hydraulic cylinder or the like (7), and its operation timing can be controlled by a timer or the like.
[0017]
Furthermore, at least one molten resin supply port (8A, 8B) is provided on the male mold surface of the cavity corresponding to each base material section divided by the above-mentioned resin stop weir. The resin supply port is connected to a resin injection device (not shown) provided outside via a molten resin supply passage (9A, 9B).
[0018]
FIG. 7 shows a state in which the supply of the molten first thermoplastic resin (10) containing the foaming agent into the mold cavity corresponding to the foam base material portion is started from the molten resin supply port (8A). Yes.
When supplying the molten first thermoplastic resin, as described above, the resin stop weir (6) protrudes into the mold cavity in advance and the mold cavity corresponds to the foam base material portion. It is divided into cavities corresponding to the non-foamed base material part, and the flow of the molten thermoplastic resin containing the blowing agent supplied is blocked so that it does not flow into the cavity corresponding to the non-foamed base material part. preferable.
[0019]
The cavity clearance when the first molten thermoplastic resin containing the foaming agent is supplied and filled into the mold cavity corresponding to the foam base material may be injection filled with both the male and female molds closed. However, after the molten thermoplastic resin is supplied into the mold cavity in an open state, it may be filled by clamping the two molds. It is preferable to perform injection filling with the molds closed. Furthermore, supply of the molten thermoplastic resin is started with both molds closed so that the cavity clearance is smaller than the thickness of the molded body before foaming. Is more preferable.
[0020]
When the supply of the molten first thermoplastic resin containing the foaming agent is started with both molds closed so that the cavity clearance is smaller than the thickness of the molded body before foaming, the cavity clearance at the start of supply is A range in which the cavity volume at that time is usually 5% by volume or more and less than 100% by volume, more preferably 30% by volume or more and less than 70% by volume, relative to the volume before foaming of the required amount of the molten thermoplastic resin. It is.
As the supply of the molten thermoplastic resin proceeds, the cavity clearance is expanded and the supply of the required amount of the molten thermoplastic resin is completed. At this time, the volume of the molten thermoplastic resin supplied and the volume of the cavity become substantially equal, and the molten thermoplastic resin is filled into the cavity corresponding to the foamed base material portion in an unfoamed state. (Fig. 8)
[0021]
At this time, the cavity volume may be larger than the volume of the molten thermoplastic resin supplied when the supply of the molten first thermoplastic resin containing the foaming agent is completed. The mold is clamped so that the cavity clearance is obtained, so that the molten thermoplastic resin is filled into the cavity.
If the molten thermoplastic resin is supplied over a long period of time, the temperature of the thermoplastic resin being supplied is lowered. Therefore, it is preferable to supply the molten thermoplastic resin promptly, and the supply time is 0.5 seconds. It is desirable to set it to about 5 seconds.
[0022]
The expansion of the cavity clearance associated with the supply of the foamed thermoplastic resin containing the foaming agent may be positively performed by a press device attached to the mold while controlling the amount of expansion, or the supplied molten heat Although the expansion may be performed using the supply pressure of the plastic resin, it is desirable to control the expansion of the cavity clearance so that the pressure applied to the resin is about 2 to 50 MPa.
[0023]
When supplying molten thermoplastic resin with both molds positioned so that the cavity clearance is the same as the thickness of the molded body before foaming and filling the cavity, the same as in normal injection molding The cavity clearance may be kept the same as the thickness of the molded body before foaming from the start of supply of the molten thermoplastic resin to the completion of supply.
[0024]
The method of filling the cavity with molten thermoplastic resin containing a foaming agent by clamping the molds of both molds is necessary with both molds open so that the cavity clearance is larger than the thickness of the molded body before foaming. After supplying a sufficient amount of molten thermoplastic resin, or at the same time as the supply is completed, mold filling is performed so that the cavity clearance becomes the same as the thickness of the molded body before foaming, and the thickness of the molded body before foaming is expanded. As described above, the supply of the molten thermoplastic resin is started with both molds open, and the mold clamping is started while supplying the molten thermoplastic resin, and simultaneously with the completion of the supply of the molten thermoplastic resin. Alternatively, there is a method of performing mold clamping so that the cavity clearance becomes the same as the thickness of the molded body before foaming after completion of the supply.
[0025]
In any of these cases, the resin stopper weir (6) is used to separate the mold cavities into cavities corresponding to the respective base portions and supply the molten thermoplastic resin. The movement of the resin stop weir is synchronized with the change of the mold cavity clearance so that the tip of the inner surface is always inscribed in the female mold surface, so that it does not flow into the cavity corresponding to the other adjacent base part. It is desirable to reliably stop the flow of the molten thermoplastic resin.
[0026]
By such a method, the foamed first thermoplastic resin containing the foaming agent is filled into the mold cavity corresponding to the foam base material portion (FIG. 8), and in this state, the primary cooling is performed, Although the skin layer is formed on the molten thermoplastic resin in contact with the resin, the mold temperature is generally set to a temperature lower than the melting point or softening point of the thermoplastic resin to be used. Then, the supplied molten thermoplastic resin starts to solidify from the surface portion in contact with the mold forming surface, and eventually a skin layer having almost no void is formed.
[0027]
The temperature of the mold is appropriately determined depending on the resin to be used. For example, when a polypropylene resin is used, it is about 30 to 80 ° C, preferably about 50 to 70 ° C. The primary cooling time at this time varies depending on various conditions such as the mold temperature and the temperature and characteristics of the molten thermoplastic resin, but is usually about 0.01 to 5 seconds.
[0028]
After the predetermined skin layer (1A) is formed, when the mold cavity is expanded in the thickness direction of the molded body, the foam trapped in the molten first thermoplastic resin containing the foaming agent is filled. The foaming gas generated by the decomposition of the agent expands, and the thickness is increased as a whole while forming the foamed layer (1B) in the expansion direction of the mold, that is, in the thickness direction. When the cavity clearance reaches the final molded product thickness after foaming, the expansion operation of the mold is stopped, and the molded body is secondarily cooled while maintaining the cavity clearance at this thickness. (Fig. 9)
[0029]
At this time, the mold cavity may be enlarged so that the cavity clearance becomes larger than the final molded product thickness, and the mold may be clamped until the final molded product thickness is reached while a part of the foam core layer is still in a molten state. . In this case, it is possible to improve the adhesion between the surface of the foam molded body and the molding surface of the mold, to reproduce the mold shape more faithfully and to increase the cooling efficiency.
The mold clamping operation at this time may be mechanically controlled, and when both molds are opened in the vertical direction, the cavity clearance may be reduced by the weight of the upper mold.
[0030]
The secondary cooling time is appropriately determined depending on various conditions such as the mold temperature, the temperature of the molten thermoplastic resin, and characteristics, but if it is too short, the first thermoplastic resin is not sufficiently solidified. There is a possibility that the molten second thermoplastic resin for forming the non-foamed base material portion may enter the foam core layer or shift the position of the edge portion, resulting in poor appearance. Further, if the secondary cooling time is too long, the temperature drop of the foam core layer becomes large, so that the molten second thermoplastic resin supplied thereafter is not sufficiently heat-sealed, resulting in insufficient adhesive strength. There is a fear. Therefore, the secondary cooling time is usually about 3 to 30 seconds, preferably about 5 to 20 seconds.
[0031]
After the secondary cooling is completed, the cavity that corresponds to the adjacent non-foamed base material part is retracted from the mold cavity surface while the cavity clearance is maintained in this state, and the resin stop weir that has been projected into the mold cavity is retracted. A molten second thermoplastic resin (11) is supplied from the molten resin supply port (8B) provided in the inside (FIG. 10) and filled.
[0032]
When supplying and filling the molten second thermoplastic resin, it is necessary to hold the cavity clearance to the final product thickness, so that the cavity clearance does not expand due to the supply pressure of the molten resin. It is preferable to keep the cavity clearance by pressing both the male and female dies, such as by applying a pressing pressure.
[0033]
After supplying and filling the melted second thermoplastic resin into the cavity corresponding to the non-foamed base material, the third cooling is performed while maintaining this state, and the molten second thermoplastic resin is cooled. After solidification is completed, the mold is opened and the multicolor resin molded product is taken out.
[0034]
Thus, the end of the previously formed foam base material portion that was in contact with the resin stop weir and the non-foam base material portion formed thereafter are in the molten state supplied for the non-foam base material formation. By contacting the second thermoplastic resin, heat fusion can be performed, and a multicolor resin molded product in which both base material portions are firmly bonded can be obtained.
[0035]
Further, in this method, if the skin material (3) is supplied in advance to a predetermined position in the mold cavity before supplying the molten first thermoplastic resin containing the foaming agent, the above-described method. Thus, a molded product in which the skin material is simultaneously bonded and integrated at a predetermined position as shown in FIG. 5 can be obtained.
When the skin material covers the entire molded product, it may be simply placed on the mold cavity surface, or the skin material may be fixed using a clamp frame provided on the outer periphery of the mold. In addition, when the skin material is bonded and integrated so as to cover a part of the molded product, it may be simply placed at a predetermined position in the mold cavity, but in order to ensure positioning, the mold cavity surface It is preferable that the mold is fixed to the mold cavity surface by vacuum suction or using a pin or a fixing block provided in the mold. Further, these skin materials may be preheated in advance or preliminarily shaped according to the product shape.
[0036]
In the method of the present invention, the thermoplastic resins used for the formation of the foamed base material portion and the non-foamed base material portion may be the same or different, particularly if the respective resins are heat-sealed to each other. The resin that is usually used in compression molding, injection molding, extrusion molding and the like is applied as it is without limitation.
[0037]
Examples of such resins include polypropylene, polyethylene, acrylonitrile-styrene-butadiene block copolymers, polyamides such as polystyrene and nylon, polyvinyl chloride, polycarbonate, acrylic resins, and styrene-butadiene block copolymers. Examples thereof include thermoplastic resins, thermoplastic elastomers such as EPM and EPDM, mixtures thereof, polymer alloys using these, and the like, and these are collectively referred to as thermoplastic resins in the present invention.
[0038]
Moreover, these thermoplastic resins may contain fillers such as reinforcing fibers such as normally used glass fibers and various inorganic or organic fillers such as talc, if necessary. Various additives such as various pigments, lubricants, antistatic agents and stabilizers may be blended.
[0039]
In addition, as a foaming agent used by blending with a thermoplastic resin to form a foam base material portion, a known chemical foaming agent used when producing a foamed thermoplastic resin is used. be able to. Specifically, inorganic foaming agents such as sodium bicarbonate, ammonium bicarbonate and ammonium carbonate, nitroso compounds such as N, N′-dinitrosopentamethylenetetramine, azodicarbonamide and azo such as azobisisobutyronitrile. Compounds, benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, sulfonyl hydrazides such as diphenylsulfone-3,3′-disulfonyl hydrazide, and blowing agents such as p-toluenesulfonyl semicarbazide are exemplified, and if necessary, salicylic acid, urea and It is a preferred embodiment to add a foaming aid containing these.
[0040]
The type of foaming agent is selected in consideration of the melting temperature of the thermoplastic resin to be used, the target foaming ratio, and the like. The amount added is adjusted in consideration of the strength, density and the like of the target molded product, but is generally 0.1 to 5 parts by weight with respect to 100 parts by weight of the resin. As the foaming agent, in addition to such a chemical foaming agent, liquid or gaseous carbon dioxide and / or nitrogen or the like may be used by directly dissolving or injecting into a molten resin.
[0041]
When the skin material is bonded in the method of the present invention, the skin material used is a woven or knitted fabric such as a moquette or tricot, a nonwoven fabric such as a needle punch carpet, a metal foil, a sheet or a film of a thermoplastic resin or a thermoplastic elastomer. can give.
These skin materials may be a single layer or a laminated skin material having two or more layers in which a foam layer or a backing layer is appropriately laminated as necessary. It is necessary that the back surface of the material can be heat-sealed with a thermoplastic resin for forming the base material portion, or that the back surface of the skin material is impregnated with a molten thermoplastic resin and can be bonded to the base material portion. It is.
[0042]
Examples of the foam layer laminated on the skin material include polyolefin foam such as polypropylene and polyethylene, polyvinyl chloride foam, and soft or semi-rigid polyurethane foam, and the backing layer is nonwoven fabric or synthetic resin. Sheets and films are used.
As the fibers constituting the nonwoven fabric, natural fibers such as cotton, wool, silk, hemp and the like, or synthetic fibers such as polyamide, polyester, nylon, etc. can be used. Used. For example, non-woven fabrics such as a needle punch type, a thermal bond type, a spun bond type, a melt blow type, and a spun lace type are listed.
Examples of sheets and films made of synthetic resin used as the backing layer include thermoplastic resins such as polypropylene and polyethylene, and polyolefin thermoplastic elastomer sheets and films, and are fused with the thermoplastic resin used as the base resin. Something that is characteristic is used.
[0043]
【The invention's effect】
In a multicolor resin molded product in which a base material is formed by combining a base material part made of a non-foamed thermoplastic resin and a base material part made of a foamed thermoplastic resin, there is a problem in the bonding strength between the base material parts. In addition, it is possible to efficiently produce a multi-colored resin molded product that is lightweight and has a good appearance at low cost.
[Brief description of the drawings]
FIG. 1 is a plan view showing an example of a multicolor resin molded product obtained by the present invention.
FIG. 2 is a cross-sectional view of the multicolor resin molded product shown in FIG. 1 cut along AA.
FIG. 3 is a plan view showing another example of the multicolor resin molded product obtained by the present invention.
4 is a cross-sectional view of the multicolor resin molded product shown in FIGS. 3 (a) and 3 (b) cut along BB and CC, respectively. FIG.
FIG. 5 is a cross-sectional view showing an example of a multicolor resin molded product to which a skin material obtained according to the present invention is bonded.
FIG. 6 is a schematic sectional view showing an example of a mold used in the present invention.
FIG. 7 is a schematic diagram showing a cross section of a mold according to the manufacturing process of the present invention.
FIG. 8 is a schematic diagram showing a cross section of a mold according to the manufacturing process of the present invention.
FIG. 9 is a schematic diagram of a mold cross section showing the manufacturing process of the present invention.
FIG. 10 is a schematic diagram showing a cross section of a mold according to the manufacturing process of the present invention.
FIG. 11 is a schematic view of a mold cross section showing the manufacturing process of the present invention.
[Explanation of symbols]
1: Foam base material part 1A: Skin layer 1B: Foam core layer 2: Non-foam base material part 3: Skin material 4: Male mold 5: Female mold 6: Resin stop weir 7: Hydraulic cylinder 8A, 8B: Molten resin supply Mouth 9: Molten resin supply passage 10: Molten first thermoplastic resin 11: Molten second thermoplastic resin

Claims (3)

The foamed base material portion made of thermoplastic resin and the non-foamed base material portion made of thermoplastic resin are adjacent to each other, and the joint portion between the adjacent foam base material portion and the non-foamed base material portion is heat-sealed to form the base material A molten thermoplastic resin containing a foaming agent in a mold cavity portion corresponding to a forming portion of a foam base material portion between both molds of a male and female pair. Supply, fill, and primary cooling from 0.01 seconds to 5 seconds , then expand the mold cavity to foam the molten thermoplastic resin, perform secondary cooling for 3 seconds to 30 seconds , and then non-foamed group The method for producing a multicolored resin molded product according to the above, characterized in that a molten thermoplastic resin is supplied and filled in a mold cavity corresponding to a forming part of the material part and subjected to tertiary cooling.   After the resin stop weir protrudes from either the male or female mold at the boundary between the foamed base material part and the non-foamed base material part in the mold cavity, the foam base material part is formed. After supplying and filling a molten thermoplastic resin containing a foaming agent into the mold cavity corresponding to the part and performing primary cooling, the mold cavity is expanded to foam the molten thermoplastic resin, and the secondary Cooling, retreating the resin stop weir from inside the mold cavity, and then supplying and filling molten thermoplastic resin into the mold cavity corresponding to the formation part of the non-foamed substrate part, and tertiary cooling The method for producing a multicolor resin molded article according to claim 1.   The method for producing a multicolor resin molded product according to claim 1 or 2, wherein the skin material is supplied in advance to a desired position between the pair of male and female dies.

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