JP2003211489A - Multicolor resin molded product and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a multicolor resin molded product having an excellent connecting strength of a plurality of bases, a light weight and a good appearance and to industrially easily manufacture the multicolor resin molded product. <P>SOLUTION: The method for manufacturing the multicolor resin molded product comprises the steps of supplying, filling molten thermoplastic resin containing foaming agents corresponding to the bases corresponding to base forming parts in cavities of a mold unit having a pair of a male and female molds, primarily cooling the resin, then enlarging the mold cavity, foaming the molten thermoplastic resins, thereafter secondarily cooling to constitute the base by connecting a plurality of the bases formed of the thermoplastic resin, and fusion bonding the connecting parts to the multicolor resin molded product. Then, the method further comprises the steps of manufacturing the multicolor resin molding having a non-famed or finely foamed skin layer and a foamed core layer in each base. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor resin molded article made of a foamed thermoplastic resin substrate and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a base material is divided into two or more base material parts having performances according to respective target parts,
A multicolor resin molded product in which the base material portion is joined at its end is
Due to its economical efficiency and good shaping properties, it is widely used in a wide variety of fields such as automobile interior parts, interior / exterior parts for home appliances.

Such multicolor resin moldings are, for example,
After supplying the molten first thermoplastic resin to a part of the mold cavity between the open molds, mold clamping until the cavity clearance reaches the final product thickness to form the first base material part. While maintaining the cavity clearance, the second thermoplastic resin is injected and supplied to the remaining mold space in the sealed state to form the second base material portion, and both base material portions are heat-sealed at the adjacent ends. (Japanese Patent Application Laid-Open No. 8-25438), and according to this method, the appearance of each of the base material part made of the first thermoplastic resin and the base material part made of the second thermoplastic resin is good, Further, it is possible to manufacture a multicolor resin molded product having no problem in the bonding strength of both base material parts at low cost.

However, since such a multi-colored resin molded article has a non-foamed base material, it has not always been possible to sufficiently meet the recent demand for weight reduction. Therefore, a single molten thermoplastic resin is supplied and filled in the mold cavity to form a solidified layer on the surface, and then the cavity is expanded to foam the thermoplastic resin (Japanese Patent Laid-Open No. 8-3).
00391) A method for producing each of the base materials, and joining the ends of the obtained foamed base materials by a partial heat staking method or a mechanical means such as a screw to form a foamed multicolor resin molded article Is also known. However, such a multicolor resin molded product has a problem that the strength of the joint is insufficient and the appearance is impaired.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
While the present inventors have excellent bonding strength between a plurality of base materials, develop a multicolor resin molded product that is lightweight and has a preferable appearance, and as a result of studying a method for easily manufacturing the product industrially, The present invention has been completed.

[0006]

That is, the first aspect of the present invention is that a plurality of base material portions formed of a thermoplastic resin are joined together to form a base material, and the joined portions are heat-sealed. The present invention provides a multicolor resin molded product, in which each base material part comprises a non-foamed or finely foamed skin layer and a foamed core layer.

The second aspect of the present invention is to form each of the molten thermoplastic resins containing a foaming agent corresponding to each of the base material parts in the respective base material parts in a cavity of a mold composed of a male and female pair. A method for producing a multicolor resin molded product, which comprises supplying and filling corresponding portions, primary cooling, expanding a mold cavity to foam the molten thermoplastic resin, and then secondary cooling. Is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the drawings. Note that this description is an example of the present invention, and the present invention is not limited to this.

FIG. 1 is a plan view showing an example of a multicolor resin molded product of the present invention. A base material portion (1) made of a first thermoplastic resin and a base material made of a second thermoplastic resin are shown. Material part (2)
It consists of and. FIG. 2 shows a cross section of the multicolor resin molded product shown in FIG. 1 taken along line AA, showing a base material portion (1) made of a first thermoplastic resin and a second thermoplastic resin. The base material part (2) made of a resin has a skin layer (1A, 2A) having no voids (non-foaming) or almost no voids (fine foaming) and a foamed core layer (1B) having voids. 2B).

In the multicolor resin molded article of the present invention, the positional relationship between the base material portion (1) made of the first thermoplastic resin and the base material portion (2) made of the second thermoplastic resin is not particularly limited. As shown in a plan view of another example in FIG. 3, a mode in which the base material portion (2) made of the second thermoplastic resin sandwiches the base material portion (1) made of the first thermoplastic resin ( 3 (a)), or a form in which the base material portion (2) made of the second thermoplastic resin surrounds the base material portion (1) made of the first thermoplastic resin (FIG. 3). It may be (b)). Figure 4
Are BB and C of FIG. 3 (a) and FIG. 3 (b), respectively.
It shows a cross section when cut at -C.

Further, as shown in FIGS. 5 (a) to 5 (d), which are cross-sectional examples of the multicolored resin molded product of the present invention, a base material portion (1) made of a first thermoplastic resin and a second thermoplastic resin are used. A skin material (3) is formed on a part or all of the surface of the base material part (2) made of a plastic resin.
It does not matter even if it is formed by pasting.

In order to obtain sufficient weight saving and strength, these multicolor resin molded articles have non-foamed or finely foamed skin layers (1A, 2A, 3A ...) And a foamed core layer in each base material portion. (1
B, 2B, 3B ...) is essential. The density of the foamed core layer is 0.7 g / cm ³ or less, especially 0.60.7 g / c from the viewpoint of weight reduction.
It is preferably m ³ or less. There is no particular lower limit to the density of the foamed core layer, but it is generally about 0.7 g / cm ³ from the viewpoint of reducing the strength of the base material.

Here, the density of the foamed core layer means, as shown in FIG. 6, the skin layer (1A, 2A) and the foamed core layer (1).
When the thickness of the base material portion made of B, 2B) is T, a range of 30% (t = 0.3T) of the thickness of each base material portion is cut out from substantially the center in the thickness direction toward both surface sides. It shows the density in the central layer (2t). When the surface material is laminated and integrated on the surface of the base material, the thickness T of the foamed molded product is the thickness of the part excluding the skin bonding layer such as the surface material or the adhesive layer.

The substrate portion does not have to be flat, and may have a curved surface, a concave portion or a convex portion so as to have a desired shape depending on the purpose of use. The thickness of the base material portion is appropriately determined depending on the purpose of use, but if it is too thin, the strength is poor, so it is generally 2 to 10 mm, preferably 2.5 to
It is about 8 mm. Further, the mass per unit area of the base material portion varies depending on the type of the thermoplastic resin used, the thickness of the foam core layer, the expansion ratio, etc., but is light as long as there is no particular adverse effect on the physical properties such as strength. The better,
Generally less than 2200 g / m ² , preferably 1800 g
/ m ² .

The thermoplastic resin constituting each base material portion of the multicolor resin molded product of the present invention may be the same as the resin type, or may be a resin having a different color or a different expansion ratio. The resins may be different from each other, and the resins are not particularly limited as long as they are heat-sealed to each other, and the resins usually used in compression molding, injection molding, extrusion molding and the like are directly applied.

Examples of such a resin include polypropylene, polyethylene, acrylonitrile-styrene-butadiene block copolymer, polyamide such as polystyrene and nylon, polyvinyl chloride, polycarbonate, acrylic resin, styrene-butadiene block copolymer and the like. Examples include general thermoplastic resins, thermoplastic elastomers such as EPM and EPDM, mixtures thereof, and polymer alloys using these, and the thermoplastic resin in the present invention is a generic term for them.

If desired, these thermoplastic resins may contain commonly used fillers such as glass fibers and various inorganic or organic fillers. Of course, various commonly used pigments are also included. , Lubricant, antistatic agent,
Various additives such as stabilizers may be appropriately mixed.

In the multicolor resin molded product of the present invention, a skin material may be appropriately laminated as described above. Examples of the skin material include woven or knitted fabrics such as moquette and tricot, and non-woven fabrics such as needle punch carpet, Examples thereof include metal foils, thermoplastic resin sheets and thermoplastic elastomer sheets or films. These skin materials may be a laminated skin material having two layers or three or more layers in which a foam layer and a backing layer are appropriately laminated as required, but those capable of being heat-sealed with the first thermoplastic resin. Alternatively, it is necessary that the back surface of the skin material be impregnated with the first thermoplastic resin in a molten state so that it can be bonded to the base resin portion.

In this case, as the foam layer, a polyolefin foam such as polypropylene or polyethylene, a polyvinyl chloride foam, or a soft or semi-rigid polyurethane foam is used.

As the backing layer, a sheet or film made of non-woven fabric, thermoplastic resin or thermoplastic elastomer is used. As the fibers constituting the non-woven fabric, natural fibers such as cotton, wool, silk, linen or polyamide,
Synthetic fibers such as polyester and nylon can be used, and these are used alone or in a blended state to form a nonwoven fabric by various methods. For example, non-woven fabrics such as needle punch type, thermal bond type, spun bond type, melt blow type and spun lace type can be used. Examples of the sheet or film made of a thermoplastic resin or a thermoplastic elastomer include a thermoplastic resin such as polypropylene or polyethylene, or a sheet or a film made of a thermoplastic polyolefin-based elastomer. An adhesive material is used.

The multicolor resin molded product of the present invention can be manufactured, for example, by the method described below. 7 to 11 are schematic cross-sectional views of the mold showing the manufacturing process according to the following method.

FIG. 7 is a schematic cross-sectional view of an example of a mold used for producing the multicolor resin molded product of the present invention. This mold has an outer peripheral portion of a male mold (4) and a female mold (5). The inner peripheral part of the mold consists of a male and female pair that slide against each other, and either mold is usually connected to a mold clamping device such as a press machine and the other is fixed. Both molds can be opened vertically or horizontally. In the figure, the male mold is fixed and the female mold is connected to a pressing device (not shown) so that both molds can be opened and closed in the vertical direction.

Further, a resin stop weir (6) which can project from the surface of the mold cavity is provided in the female mold, and the resin stop weir protrudes into the cavity so that the mold cavity is formed into the respective base portions. And the flow of the molten thermoplastic resin supplied to each side is blocked. This resin stop weir is slidably operated in the opening / 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. Incidentally, this resin stop weir is not always essential,
It is extremely effective in clarifying the joint interface part of both base material parts and forming each base material part independently.

Further, in the female mold, at least one molten resin supply port (8A, 8B) is provided in each of the cavities distinguished by the resin retaining dam described above. The molten resin supply port is connected to a resin injection device (not shown) provided outside through the molten resin supply passages (9A, 9B).

In FIG. 8, the molten thermoplastic resin (10) containing the foaming agent is supplied from the molten resin supply port (8A) into the mold cavity, and the foaming agent is supplied from the molten resin supply passage (8B). The state where the supply of the contained molten second thermoplastic resin (11) is started is shown.

When the molten first thermoplastic resin and second molten resin are supplied, the resin retaining dam (6) is previously projected into the mold cavity to divide the mold cavity into two. However, it is preferable that the flow of the melted first and second thermoplastic resins is stopped so that the two resins supplied to the respective regions do not mix in the cavity.

The cavity clearance at the time of starting the supply of the molten first thermoplastic resin and the second thermoplastic resin is appropriately determined by the molding conditions in the filling and foaming steps after the start of the supply, but it is more stable. In order to obtain an excellent foam molded body, it is preferable to start the supply of the molten resin with both molds closed so that the cavity clearance is smaller than the thickness of the molded body before foaming.

When starting the supply of the first thermoplastic resin and the second thermoplastic resin with both molds closed so that the cavity clearance is smaller than the thickness of the molded product before foaming, The cavity clearance is in a range such that 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 of the required amount of the molten thermoplastic resin before foaming. Is. As the supply of the molten thermoplastic resin progresses, the cavity clearance is expanded, and the supply of the required amount of the molten thermoplastic resin is completed. (Figure 9)

The expansion of the cavity clearance at this time may be positively performed by a pressing device attached to the mold while controlling the expansion amount, or by utilizing the supply pressure of the molten thermoplastic resin to be supplied. Although it may be enlarged, it is desirable to control the enlargement of the cavity clearance so that the pressure applied to the resin at this time is about 2 to 50 MPa.

In the case of the method of expanding the cavity clearance in accordance with the supply of the molten thermoplastic resin, the melt supplied at the time when the supply of the molten first thermoplastic resin and the second thermoplastic resin is completed. The cavity volume may become larger than the volume of the thermoplastic resin. In this case, the molten thermoplastic resin may be filled in the cavity by performing mold clamping so that a predetermined cavity clearance is obtained. However, in some cases, the process may directly proceed to the next foaming step. When the molten thermoplastic resin is supplied for a long time, the temperature of the thermoplastic resin during the supply is lowered. Therefore, it is preferable to supply the molten thermoplastic resin promptly, for 0.5 seconds to 5 seconds. It is desirable to set it to about a second.

In the case where the molten thermoplastic resin is supplied and filled in the cavity in a state where both molds are positioned so that the cavity clearance is the same as the thickness of the molded product before foaming, in ordinary injection molding Similarly to the case, the cavity clearance may be kept to be the same as the thickness of the molded product before foaming from the start of the supply of the thermoplastic resin to the completion of the supply.

Further, when the molten thermoplastic resin is filled in the cavity by the mold clamping operation of both molds, both molds are positioned so that the cavity clearance becomes larger than the thickness of the molded product before foaming. After supplying the required amount of molten thermoplastic resin in this state, and after supplying the thermoplastic resin in this state, or when the supply is completed, mold clamping is performed so that the cavity clearance is the same as the thickness of the molded product before foaming. Method, or start supplying the thermoplastic resin with both molds open so that the cavity clearance is equal to or greater than the thickness of the molded product before foaming, and start clamping the mold while supplying the thermoplastic resin, There is a method of performing mold clamping and filling so that the cavity clearance becomes the same as the thickness of the molded product before foaming at the same time as or after the completion of the supply of the plastic resin.

In any of these methods, the timing of supplying the first thermoplastic resin and the timing of supplying the second thermoplastic resin may be the same or different, for example, the first thermoplastic resin. Although the supply of the second thermoplastic resin may be started after the completion of the supply of No. 2, the supply start timing of both resins is generally the same or almost the same timing from the viewpoint of mold operation.

In any case, when the molten resin is supplied by dividing the mold cavity into two by using the resin stopper weir (6), the resin stopper weir is used to change the mold cavity clearance. It is desirable to synchronize and ensure that the flow of the molten resin is stopped.

It should be noted that the resin stopper weir that has been projected into the mold cavity is not filled with the metal until the first thermoplastic resin and the second thermoplastic resin are completely supplied and the mold cavity is completely filled. The mold cavity may be retracted, and there is no particular restriction on the timing of retreat, but at the same time after the completion of the supply of both the first thermoplastic resin and the second thermoplastic resin,
Alternatively, it is preferable to retract the supply immediately after the completion of supply.

By such a method, the first molten thermoplastic resin and the second thermoplastic resin are filled in the mold cavity (FIG. 10), and primary cooling is performed in this state to contact the mold molding surface. The molten thermoplastic resin is allowed to form a skin layer, but since the mold temperature is generally set to a temperature lower than the melting point or softening point of the thermoplastic resin used,
When this condition is maintained and cooling is performed, the supplied molten thermoplastic resin begins to solidify from the surface portion in contact with the mold molding surface, and eventually a non-foamed skin layer with few voids or a slightly foamed fine foam. A skin layer is formed.

The temperature of the mold is appropriately determined depending on the resin used, but when polypropylene resin is used, it is about 30 to 80 ° C., preferably about 50 to 70 ° C. The primary cooling time at this time is usually 0.01 to 5 seconds, although it varies depending on various conditions such as the mold temperature, the temperature of the molten thermoplastic resin, and the characteristics.

In the process of forming the skin layer, the degree of foaming of the skin layer can be adjusted by adjusting the mold temperature, the cooling time, etc. For example, a non-foaming skin layer having almost no voids is formed. In order to lower the mold temperature to cool the surface portion of the molten resin in contact with the mold molding surface faster, or to lengthen the cooling time to sufficiently solidify the surface layer, which is the next step. It suffices to prevent the surface layer from foaming in the mold expanding process.

After the predetermined skin layers (1A, 2A) are formed, the mold cavity is enlarged in the thickness direction of the molded body (FIG. 1).
1) Then, the foaming gas generated by the decomposition of the foaming agent trapped in the unsolidified portion (core layer portion) of the supplied molten first thermoplastic resin and second thermoplastic resin expands, As a whole, the thickness is increased while forming the foamed layers (1B, 2B) 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. At this time, expand the mold cavity so that the cavity clearance will be slightly larger than the final molded product thickness, and mold until the final molded product thickness is reached while part of the thermoplastic resin foam core layer is still in the molten state. You may tighten it.
In this case, the adhesion between the surface of the foamed molded product and the molding surface of the mold can be improved, the mold shape can be reproduced more faithfully, and the cooling efficiency can be increased. The mold clamping operation at this time may be mechanically controlled, or when both molds are opened in the vertical direction, the cavity may be reduced by the weight of the upper mold.

The secondary cooling time is appropriately determined according to various conditions such as the mold temperature, the temperature of the molten thermoplastic resin, and the characteristics. After the cooling of the first thermoplastic resin and the second thermoplastic resin is completed, The mold is opened and the molded product is taken out.

The final molded body thus obtained is in a heat-sealed state in which the base material portion comprising the first thermoplastic resin and the second thermoplastic resin is in contact with each other in a molten state at the boundary portion in the foaming process. Therefore, after the secondary cooling, both base material parts are firmly joined in a foamed state.

If the skin material (3) is previously supplied to a predetermined position in the mold cavity before the molten first thermoplastic resin and the second thermoplastic resin are supplied, By the method described above, it is possible to obtain a molded product in which the skin material is simultaneously laminated and integrated at a predetermined position as shown in FIG.

The skin material may cover the entire surface of the molded product or may cover only a part of the molded product. When the skin material covers the entire molded article, it may be simply placed on the mold cavity surface, or the skin material may be fixed by using a clamp frame provided on the outer periphery of the mold. Also, when the skin material is laminated and integrated so as to cover a part of the molded product, it may be placed in the mold cavity, but in order to ensure positioning, vacuum suction is applied to the mold cavity surface. Alternatively, it is preferable to fix to the mold cavity surface using a pin or a fixing block provided in the mold. In addition, these skin materials may be preheated before being supplied between the molds, or may be preshaped, depending on the material, product shape, or the like.

As the foaming agent used in such a method, a known chemical foaming agent used in producing a foam of a thermoplastic resin can be used. Specifically, inorganic foaming agents such as sodium bicarbonate, ammonium bicarbonate and ammonium carbonate, nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, azodicarbonamide, azo such as azobisisobutyronitrile and the like. Compounds, sulfonyl hydrazides such as benzene sulfonyl hydrazide, toluene sulfonyl hydrazide, diphenyl sulfone-3,3′-disulfonyl hydrazide, and blowing agents such as p-toluene sulfonyl semicarbazide can be used. It is a preferred embodiment to add salicylic acid, urea and a foaming aid containing these as needed.

The type of the foaming agent is selected in consideration of the melting temperature of the thermoplastic resin used, the target expansion ratio, and the like.
The addition amount is adjusted in consideration of the strength, density, etc. 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. In addition to chemical blowing agents,
Liquid or gaseous carbon dioxide and / or nitrogen may be directly injected into the molten resin.

In the above description, a multicolor resin molded product consisting of two base material parts formed of the first and second thermoplastic resins has been described, but a mold cavity is desired according to the above method. The number of base material parts is divided by resin stop dams and the like, and the molten thermoplastic resin is supplied to each of the cavities corresponding to the respective base material parts. A resin molded product can be easily manufactured, and such embodiments are also included in the present invention.

[0047]

EFFECTS OF THE INVENTION According to the present invention, a multicolored resin molded article comprising a plurality of base material portions, having excellent bonding strength between the plurality of base material portions, having a light weight and having a preferable appearance is provided. A colored resin molded product can be easily manufactured industrially at low cost.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a multicolor resin molded product of the present invention.

FIG. 2 is a sectional view taken along line AA of the multicolor resin molded product shown in FIG.

FIG. 3 is another plan view showing another two examples of the multicolor resin molded product of the present invention.

FIG. 4 is a BB of the multicolor resin molded product (a) shown in FIG.
It is a common cross-sectional view showing the cross section and the CC cross section of the multicolor resin molded product (b).

FIG. 5 is a cross-sectional view showing various examples of multicolor resin molded products to which the skin material of the present invention is attached.

FIG. 6 is a schematic cross-sectional view showing the measurement of the density of the foam core layer in the multicolor resin molded product of the present invention.

FIG. 7 is a schematic sectional view showing an example of a mold used in the method of the present invention.

FIG. 8 is a schematic view of a cross section of a mold showing the manufacturing process of the present invention.

FIG. 9 is a schematic view of a mold cross section showing a manufacturing process of the present invention.

FIG. 10 is a schematic view of a cross section of a mold showing the manufacturing process of the present invention.

FIG. 11 is a schematic view of a cross section of a mold showing the manufacturing process of the present invention.

[Explanation of symbols]

1: First thermoplastic resin 2: Second thermoplastic resin 3: Skin material 4: Male 5: Female 6: Resin stop weir 7: Hydraulic cylinder 8: Molten resin supply port 9: Molten resin supply passage 10: molten first thermoplastic resin 11: Molten second thermoplastic resin 1A: a skin layer made of a first thermoplastic resin 2A: Skin layer made of the second thermoplastic resin 1B: Foam core layer made of the first thermoplastic resin 2B: Foam core layer made of the second thermoplastic resin

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4F202 AD08 AD16 AD17 AD20 AG03                       AG20 AH26 AH42 AR15 CA11                       CB01 CB13 CB21 CB30 CK19                       CK52 CK90 CQ01 CQ05 CQ06                 4F206 AD08 AD16 AD17 AD20 AG03                       AG20 AH26 AH42 AR15 JA03                       JB13 JB21 JB30 JN25 JQ81

Claims (6)

[Claims] 1. A multicolored resin molded article in which a plurality of base material parts formed of a thermoplastic resin are bonded to each other to form a base material, and the bonded parts are heat-sealed together. A multicolor resin molded product, wherein a material portion is composed of a non-foamed or slightly foamed skin layer and a foamed core layer. 2. The multicolor resin molded article according to claim 1, wherein the density of the foam core layer of at least one of the plurality of base material portions is 0.7 or less. 3. The surface material is laminated and integrated on at least a part of the surface of the base material.
The multicolor resin molded product described in. 4. A molten thermoplastic resin containing a foaming agent corresponding to each base material portion is supplied corresponding to each base material portion forming portion in a cavity of a mold consisting of a male and female pair, The method for producing a multicolor resin molded product according to claim 1, wherein after the filling and the primary cooling, the mold cavity is expanded to foam each of the molten thermoplastic resins, and then the secondary cooling is performed. . 5. A resin stopper weir provided in either of the male and female molds is projected to a boundary portion of each base material portion forming portion in the mold cavity, and the resin stopper dam forms the mold cavity as a base material. Divided corresponding to the part forming part, to each of the divided mold cavities, each molten thermoplastic resin containing a foaming agent corresponding to each base material part is supplied and filled, and after primary cooling, The multicolor resin molded product according to claim 4, wherein the resin retaining dam is retracted from the inside of the mold cavity or after being retracted, the mold cavity is expanded to foam each base material portion forming portion. Manufacturing method. 6. The molten thermoplastic resin containing a foaming agent is supplied after one or more skin materials are supplied to a desired position between a pair of male and female molds. 5
The method for producing a multicolor resin molded article according to.