JP4534360B2 - Thermoplastic resin foam molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermoplastic resin foam molded article.
[0002]
[Prior art]
In addition to home appliance parts and building materials, various trims such as door trims and side trims, various pillars, and interior parts of automobiles such as instrument panels are strongly desired to have heat insulation and weight reduction. As a technique, for example, Japanese Patent Application Laid-Open No. 11-179752 discloses an automobile interior part made of an olefin-based resin foam molded body composed of a skin layer and a foam layer.
Such a foam-molded body is used for attaching the foam base material portion to a vehicle body or other member on a foam base material portion comprising a foam layer and a dense skin layer formed on the surface thereof and having no voids. Ribs and boss-like protrusions are integrally provided on the foam base material.
[0003]
However, when such ribs or boss-like protrusions are attached to the foam base material part, the skin layer of the foam base material part and the outer peripheral surface in the height direction of the protrusion part are perpendicular or depending on the attachment angle. For this reason, when an external force is applied, there is a problem that stress is concentrated on the corner and the protrusion is easily detached.
[0004]
[Problems to be solved by the invention]
For this reason, the present inventor has provided a foamed thermoplastic resin molded article in which a foamed base material portion is provided with a foamed rib or boss-like projection that is integrated with the foamed base material portion. Thus, as a result of studies to develop a thermoplastic resin foamed molded article in which the protrusions are not easily detached from the foamed base material and are firmly bonded, the present invention has been achieved.
[0005]
[Means for Solving the Problems]
That is, the present invention relates to a thermoplastic resin foam molded article in which a foam base material portion is provided with an optionally foamed rib or boss-like projection that is integrated with the foam base material portion. The material part has a skin layer having no voids, and the ratio (R / L) of the curvature R of the joint part between the protruding part and the foamed base material part to the thickness L of the skin layer is 3-50. A thermoplastic resin foam molded article characterized by the above is provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below.
The thermoplastic resin foam molded article of the present invention has a foamed rib or boss that is integrated with the foamed base material portion (1), as shown in FIG. It has a structure provided with a protrusion (hereinafter also referred to simply as a protrusion) (2).
The protruding portion may be integrally formed of the same material as the foam base material portion, or a protrusion portion manufactured in advance as a separate member is integrally attached to the foam base material portion by heat fusion or the like. However, it is more preferable that it is integrally formed of the same material as the foam base material portion.
[0007]
The foam base material portion (1) has a skin layer (3) having almost no voids or almost no voids on the surface in most of the main components, and the inside thereof is formed inside. It has a multilayer structure in which a foamed layer (4) having voids is formed.
The skin layer formed on the surface on the design surface side may be provided with various patterns and grain patterns, and if necessary, various sheets such as sheets or films made of thermoplastic resin, woven fabrics, nonwoven fabrics, knitted fabrics, etc. A skin material may be laminated.
The protrusions are usually provided on the non-design surface side, but various non-design surfaces such as sheets and films made of a thermoplastic resin, or various skin materials and backing materials such as woven fabrics, unwoven fabrics, and knitted fabrics. May be laminated. In this case, the skin material and the backing material are generally laminated except for the joined projections, but in some cases, they are laminated on the foam base material part so as to wrap the projections. Also good.
Moreover, the opening hole (5) for providing a speaker grill, various switch panels, etc. may be suitably provided in a part of foam base material part, The structure is arbitrary.
[0008]
In such a foamed base material portion, the density of the foamed layer is 0.7 g / cm3 or less, preferably 0.6 g / cm3 or less in order to obtain sufficient lightness, and the lower limit is not particularly limited. From the viewpoint of reducing the strength of the layer, it is about 0.2 g / cm @ 3.
[0009]
Here, as shown in FIG. 2, the density of the foam layer of the foam base material portion (1) is as shown in FIG. 2, where T is the thickness of the foam molded body including the skin layer (3). The density of the center layer (2t) which cut out the range of 30% (t = 0.3T) of a molded object thickness toward the side is shown, respectively.
When the skin material is bonded to the surface of the foam base material portion, the thickness of the portion excluding the skin material bonding layer (15) such as the skin material (13) and the adhesive layer is set to the thickness of the foam molded body. The thickness is T.
[0010]
The foam base material portion (1) does not need to be a flat surface, and may have a curved surface, a concave portion, or a convex portion so as to have a desired shape depending on each purpose of use.
The thickness of the foamed substrate portion (1) is appropriately determined depending on the purpose of use, but if it is too thin, it is inferior in strength, and is generally about 2 to 10 mm, preferably about 2.5 to 8 mm.
The mass per unit area of the foam base portion varies depending on the type of thermoplastic resin used and the thickness of the foam base portion, but the lighter is preferable as long as there is no particular adverse effect on the physical properties such as strength, Generally, it is 2200 g / m 2 or less, preferably 1800 g / m 2 or less.
[0011]
In the present invention, the ribs and boss-like protrusions (2) that are integrally provided on the foam substrate (1) are ribs, bosses, pins, clip seats, etc. as shown in FIG. This means a protrusion provided for the purpose of fitting or mounting with a vehicle body (structural member) or other parts.
[0012]
The present invention is a thermoplastic resin foam molded article in which such a protrusion (2) is joined to the foamed base part (1), and in this case, the protrusion (2) and the foamed base part (1) is bonded so that the surface skin layer of the foamed base material portion and the outer peripheral surface in the height direction of the protrusion are curved at the joint portion, and the curvature R of the joint portion and the skin in the foamed base material portion It is characterized by being bonded so that the ratio (R / L) of the thickness L of the layers is 3-50.
Here, the joining part (6) is a boundary where the foamed base material part and the curvature part of the projecting part are joined in the region where the foam base material part (1) and the projecting part (2) are joined. (14) It refers to the inside, and the curvature R takes a value on the outermost surface of the foamed base material portion and the protruding portion.
[0013]
The thickness of these protrusions is appropriately set according to the purpose. For example, in the case of a clip seat, the thickness is generally about 1 to 5 mm, and in the case of a rib or boss, it is about 1 to 3 mm. is there.
[0014]
The protrusion (2) joined to the foam base (1) is preferably non-foamed or foamed and has a low foaming ratio of 1.3 times or less even when the average foaming ratio is 1.3 times or less.
When the protruding portion (2) is foamed, the foamed portion may be the entire protruding portion, or may be partially expanded, for example, only the central portion.
The average foaming ratio indicates the average foaming ratio in the entire protrusion, and when the non-foaming part is provided, the average foaming ratio is obtained by combining both the non-foaming part and the foaming part.
[0015]
Here, in calculating the average expansion ratio of the protrusion (2), the protrusion means a portion protruding outside from the boundary (14) of the joint, and the specific gravity of the non-foamed portion in the protrusion is It can be represented by the ratio of the specific gravity of the entire protrusion (specific gravity of the non-foamed portion / specific gravity of the entire protrusion).
If there is no non-foamed portion in the protrusion, a part of the protrusion is once melted at a temperature suitable for the material, and a non-foamed body is created by a cooling press or the like, and the specific gravity is set to the non-foamed portion. May be used as the specific gravity. The pressure at the time of pressing is in the range of 0.1 to 5 MPa.
Each specific gravity is measured by a known method such as a general underwater substitution method.
[0016]
These protrusions (2) and the foam base material part (1) are joined together by a joining part (6) having a certain curvature R. In this case, the dimension of the curvature R and the side where the projecting part is joined are joined. It is necessary that the ratio (R / L) of the thickness L of the skin layer of the foamed substrate portion is in the range of 3 to 50, preferably 10 to 30.
If this ratio is too small, the stress concentrated on the joint becomes high when an external force is applied, the skin layer of the joint easily breaks, and the protrusion is easily detached. A sink-like appearance defect is generated on the surface of the foamed base material portion on the side opposite to the protruding portion.
[0017]
Here, the thickness L of the skin layer of the foamed base material portion on the side to which the protrusions are joined is measured from the cross sections in the thickness direction at any three points in the vicinity of the protrusions excluding the joint (6). It is set as the average value of thickness.
Specifically, after cutting in the thickness direction at any three points in the vicinity of the protrusion except for the joint (6), and taking a scanning electron micrograph of each cross section, as shown in FIG. A vertical line is drawn at any five positions from the foam molded body surface (16) on the photograph toward the foam core layer (4), and the first bubbles (17) from the molded body surface (16) on each straight line. Measure the length up to. This is performed for each cross section, and the average value of the measured values of at least 15 points in total measured in each cross section is defined as the skin layer thickness L.
[0018]
In the present invention, the thickness of the skin layer in the vicinity of the protrusion is not particularly limited, and is appropriately determined depending on the shape of the molded body and the material used, but is generally about 0.1 to 1 mm. Is desirable.
[0019]
The thermoplastic resins used in such foamed molded products include polypropylene, polyethylene, polyethylene terephthalate (PET), acrylonitrile styrene copolymer (AS resin), acrylonitrile butadiene styrene terpolymer (ABS resin), polystyrene (PS resin). Further, thermoplastic resins such as polycarbonate (PC resin) and polyamide, polymer alloys made of these, or a mixture thereof are used, and the thermoplastic resin in the present invention includes all of them.
Such thermoplastic resins may contain reinforcing fillers such as various fillers and fibers, coloring pigments and various colorants for non-uniform patterns, polyester fibers, etc., or elastomers for imparting flexibility. Good. Moreover, various additives, such as an antistatic agent, a weathering agent, and a lubricant, may be included.
[0020]
Among such thermoplastic resins, a propylene-based resin alone or a mixture thereof with other thermoplastic resins and elastomers is preferably used in terms of excellent moldability and lightness. Here, the propylene-based resin may be a polypropylene homopolymer, or a copolymer obtained by copolymerizing propylene as a main component and other olefin components such as ethylene.
[0021]
When a propylene resin is used, it is desirable to add various compounding materials so that the Izod impact value at 23 ° C. is 10 kJ / m 2, preferably 15 to 60 kJ / m 2 (with JIS K6758 notch).
In the present invention, a mixture obtained by mixing an elastomer for imparting flexibility to the propylene-based resin is more preferably used.
[0022]
Elastomers used for this purpose include natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, olefin rubbers such as ethylene-propylene rubber, ethylene-butene rubber, ethylene-octene rubber, and fluorine rubber. Among them, DSC has a PEAK value of about 40 to 100 ° C. (temperature increase rate of 10 ° C./min), Shore A hardness of 70 to 90 (JIS-K6301, 23 ° C.), and tensile. An olefin rubber having an elongation of 600% (JIS-K6301, 23 ° C.) or more is desirable.
[0023]
When such elastomers are mixed and used, the amount added is appropriately selected depending on the type of thermoplastic resin used and the properties required of the desired molded article. Addition of olefin rubber to propylene resin In this case, the ratio is about 7: 3 to 9: 1 by weight.
[0024]
As a method for producing the thermoplastic resin foam molded article of the present invention, for example, as described above, the protrusion may be integrally molded with the same material as the foam base material part, or may be molded in advance as a separate member. The protruding portion may be attached to the foamed base material portion by heat fusion or the like, but it is more preferable that the foamed base material portion and the protruding portion are integrally formed of the same material.
In the case of the former method, in the mold cavity of a mold comprising a pair of males and females having a cavity designed so that the projection mounting part to the foamed base material part satisfies the conditions specified in the present invention. A method is applied in which a molten thermoplastic resin containing a foaming component is supplied and filled, and then a part or all of the mold cavity of the mold is expanded to foam the molten thermoplastic resin.
[0025]
As the foaming component to be blended in the thermoplastic resin, a conventionally known chemical foaming agent may be used, or a gas body such as carbon dioxide gas or nitrogen gas or these gases are liquefied in the molten thermoplastic resin. You may press-fit directly.
When the chemical foaming agent is used, the type thereof is not particularly limited, but an inorganic foaming agent mainly containing sodium bicarbonate is preferably used because it is difficult to corrode the mold.
Such chemical foaming agents may be added and blended as they are at the time of melt-kneading with the thermoplastic resin. Generally, these foaming agents are added to the thermoplastic resin so that the content thereof is 20 to 80% by weight. Used as a master batch.
[0026]
The typical method will be described below.
FIG. 5 is a schematic sectional view showing an example of a mold used in such a method. This mold consists of a male and female pair of male mold (7) and female mold (8), and both molds are usually connected to a mold clamping device such as a press device, and the other is fixed in the vertical direction. Alternatively, both molds can be opened and closed laterally.
In the figure, the male mold (7) is fixed and the female mold (8) is connected to a press device (not shown) so that both molds open and close in the vertical direction.
At a predetermined position of such a mold, a carving for forming a protrusion, a slide core for forming a clip seat, and the like are provided.
In the figure, the engraving is provided in the lower mold, but it may be provided in the upper mold, or both, and the intended use or use of the molded body It is determined appropriately according to the form. Here, the molded body finally obtained forms a predetermined curvature R at the joint portion such as the engraved surface that forms the projection surface and the mold surface that forms the foam base material portion.
[0027]
The method for supplying the molten thermoplastic resin (9) into the mold cavity is arbitrary, but in general, a resin supply apparatus (such as an injection machine) via a resin supply path (10) provided in the mold. It is preferable to provide a resin supply port (12) connected to 11) on the molding surface of either or both dies, and supply the molten thermoplastic resin (9) into the cavity from the resin supply port.
In this case, an arbitrarily controllable on-off valve is provided in the resin supply passage (10) in the vicinity of the resin supply port (12), and supply and stop of the molten thermoplastic resin stored in the resin supply device (11) are optional. It is preferable that the control can be performed.
[0028]
Filling the mold cavity with the molten thermoplastic resin (9) may be performed by injection filling with both molds closed, or the melted heat between the two molds in the open state. After supplying the plastic resin, it may be filled by the clamping operation of both molds, and the method is appropriately selected depending on the desired product form and the like.
[0029]
In any method, the temperature of the molten thermoplastic resin to be supplied varies depending on the type of the thermoplastic resin to be used, and an optimum temperature is set depending on each resin. For example, an olefin rubber is added to a polypropylene resin. When using the thermoplastic resin material, it is about 170-260 degreeC, Preferably it is about 190-230 degreeC.
[0030]
As the former injection filling method, the supply of the molten thermoplastic resin (9) is started with both molds positioned so that the cavity clearance is smaller than the thickness of the molded body before foaming (FIG. 6). ) Open the mold while supplying the molten thermoplastic resin (FIG. 7), and at the same time the supply of the molten thermoplastic resin is completed, the cavity clearance matches the thickness of the molded body before foaming. A method of filling (FIG. 8) and a method of supplying the molten thermoplastic resin into the cavity with both molds positioned so as to have the same cavity clearance as the thickness of the molded body before foaming can be mentioned.
[0031]
When the supply of the molten thermoplastic resin (9) is started in a state where both molds are positioned 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 The cavity volume at that time is usually in the range of 5% by volume or more and less than 100% by volume, desirably 30% by volume to 70% by volume, with respect to the volume of the molded body before foaming.
[0032]
When the supply of the molten thermoplastic resin (9) is started in such a state, the movable mold is retracted and the cavity clearance is expanded as the supply of the molten thermoplastic resin proceeds, and the required amount of the molten thermoplastic resin is increased. When the supply is completed, the volume of the supplied molten thermoplastic resin becomes substantially equal to the volume of the cavity, and the cavity is filled with the molten thermoplastic resin.
[0033]
At this time, the cavity clearance may be enlarged by a press device attached to the mold while controlling the amount of enlargement, or by using the supply pressure of the molten thermoplastic resin to be supplied. However, 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.
Further, in the process of expanding the cavity clearance, the cavity volume may become larger than the capacity of the supplied molten thermoplastic resin (9). In this case, the supply of the molten thermoplastic resin is almost completed or not completed. At the same time, the mold may be clamped so as to have a predetermined cavity clearance, which is not a problem. At this time, it is desirable that the pressure applied to the resin does not deviate from the above range.
[0034]
In the latter case, when the molten thermoplastic resin (9) is supplied and filled in the cavity with both molds positioned so that the cavity clearance is the same as the thickness of the molded body before foaming, normal injection is performed. As in the case of 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.
[0035]
As a method of filling the molten thermoplastic resin into the cavity by the mold clamping operation of both molds, melt the required amount with both molds opened in advance so that the cavity clearance is equal to or greater than the thickness of the molded body before foaming. After the molten thermoplastic resin is supplied (FIG. 11), and after the molten thermoplastic resin is supplied or simultaneously with the completion of the supply, the mold is clamped and filled so that the cavity clearance becomes the same as the thickness of the molded body before foaming (FIG. 12). ) Start the supply of molten thermoplastic resin with both molds opened in advance so that the cavity clearance is equal to or greater than the thickness of the molded body before foaming, and clamp the mold while supplying the molten thermoplastic resin. The cavity clearance starts before the foaming, almost simultaneously with the completion of the supply of the molten thermoplastic resin, or after the supply is completed, while supplying the molten thermoplastic resin and clamping the mold in parallel. It may be the same as the body thickness.
[0036]
The mold cavity filled with the molten thermoplastic resin (9) is almost free of voids.
In this state, the skin layer (3) is formed on the surface of the molten thermoplastic resin in contact with the mold forming surface. Generally, the mold temperature is set to a temperature lower than the melting point or softening point of the thermoplastic resin to be used. Therefore, when cooling is carried out while maintaining this state, the supplied molten thermoplastic resin starts to solidify from the surface portion in contact with the molding surface, and eventually the skin layer (3) having almost no voids is formed on the surface. It is formed.
The temperature of the mold is appropriately determined depending on the type of thermoplastic resin to be used. For example, when a resin material obtained by adding an olefin elastomer to a polypropylene resin is used, it is about 40 ° C. to 80 ° C., preferably 50 ° C. to 70 ° C. Degree.
[0037]
The cooling time at this time, that is, the time from when the molten thermoplastic resin is filled in the cavity until the next process mold is opened greatly affects the formation of the skin layer. When the time is too long, the skin layer becomes too thick. Therefore, the cooling time is appropriately set so that the desired skin layer thickness L is obtained.
The cooling time at this time varies depending on various conditions such as the mold temperature, the temperature of the molten thermoplastic resin, the type of the resin, etc., but is usually about 0.1 to 20 seconds.
[0038]
After the predetermined skin layer is formed, when the mold cavity is opened in the thickness direction of the molded body, the foaming component confined in the unsolidified portion of the supplied molten thermoplastic resin expands and becomes a foamed state. As a whole, the thickness is increased in the mold opening direction, that is, in the thickness direction (FIG. 9).
[0039]
When the cavity clearance reaches the final molded body thickness after foaming, the mold opening operation is stopped, and the molded body is cooled while maintaining the cavity clearance at this thickness.
[0040]
At this time, the mold is opened so that the cavity clearance is slightly larger than the final molded body thickness, and the mold is clamped until the final molded body thickness is reached while a part of the foam layer of the thermoplastic resin is still in a molten state. May be.
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 controlled mechanically, and when both molds are opened in the vertical direction, the cavity may be reduced by the weight of the upper mold.
[0041]
Furthermore, by using a mold provided with a vacuum suction port having a fine hole diameter at least on the mold cavity surface on the design surface side, a suction device connected to the vacuum suction port before or after the supply of molten thermoplastic resin is started. By vacuum suction and adsorbing the formed skin layer to the cavity surface, it is possible to improve the adhesion between the surface of the foam molded body and the mold molding surface, reproducing the mold shape more faithfully, Cooling efficiency can be increased.
[0042]
After the cooling is completed, the mold is completely opened, and the foamed molded body as the final molded body is taken out from the mold (FIG. 10), and a dense skin layer (3) on the surface as illustrated in FIG. It is possible to obtain a thermoplastic resin foam molded body having a foam layer (4) in the inside and having a predetermined shaped protrusion integrally formed.
[0043]
Further, after a skin material (16) such as a sheet or a film is supplied in advance to a desired position in the mold and then molded by the method described above, a molded body whose cross section is illustrated in FIG. It is possible to produce a thermoplastic resin foam molded article having a skin material bonded to which a surface material such as a sheet or a film is bonded to part or all of the surface.
[0044]
【The invention's effect】
The thermoplastic resin foam molded article of the present invention is lightweight and highly rigid, and also has excellent bonding strength between the foamed base material portion and the rib or boss-like projection, so that it can be used for automobile interior parts, home appliance parts, and building materials. In particular, it is useful as an automobile interior part.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a molded body example of the present invention.
FIG. 2 is a schematic cross-sectional view for illustrating density measurement of a foam base material portion in the molded article of the present invention.
FIG. 3 is a schematic cross-sectional view showing a joint portion between a foam base material portion and a protrusion in the molded body of the present invention, and each drawing shows a difference in shape of the protrusion.
FIG. 4 is a schematic cross-sectional view showing a method for measuring the thickness of the skin layer of the foamed base material portion in the molded article of the present invention.
FIG. 5 is a schematic sectional view showing an example of a mold used in the method of the present invention.
FIG. 6 is a schematic sectional view of a mold showing a process for producing a thermoplastic resin foam molded article of the present invention.
FIG. 7 is a schematic sectional view of a mold showing a process for producing a thermoplastic resin foam molded article of the present invention.
FIG. 8 is a schematic sectional view of a mold showing a process for producing a thermoplastic resin foam molded article of the present invention.
FIG. 9 is a schematic sectional view of a mold showing a process for producing a thermoplastic resin foam molded article of the present invention.
FIG. 10 is a schematic sectional view of a mold showing a process for producing a thermoplastic resin foam molded article of the present invention.
FIG. 11 is a schematic sectional view of a mold showing a process for producing a thermoplastic resin foam molded article of the present invention.
FIG. 12 is a schematic sectional view of a mold showing a process for producing a thermoplastic resin foam molded article of the present invention.
FIG. 13 shows an example of a foamed molded product in which a skin material is bonded in the thermoplastic resin foamed molded product of the present invention.
[Explanation of symbols]
1: foam base material part 2: projection part 3: skin layer 4: foam layer 5: opening hole 6: joint 7: male mold 8: female mold 9: molten thermoplastic resin 10: resin supply path 11: resin supply Device 12: Resin supply port 13: Skin material 14: Boundary portion 15 between foamed base material and projection 15: Skin material bonding layer 16: Molded body surface 17: Air bubbles

Claims (4)

In the foamed thermoplastic resin molded article in which the foamed base material portion is provided with a rib or boss-like protrusion that may be foamed integrated with the foamed base material portion, at least the foamed base material portion has a gap. A heat having a skin layer that does not have, and a ratio (R / L) of a curvature R of a joint portion between the protrusion and the foam base material portion to a thickness L of the skin layer is 3 to 50 Plastic resin foam molding. The thermoplastic foam-molded article according to claim 1, wherein the average foaming ratio of the protrusions is 1 to 1.3 times. The thermoplastic resin foam molded article according to claim 1 or 2, wherein the thermoplastic resin is made of a propylene-based resin having an Izod impact value at 23 ° C of 10 KJ / m 2 or more. The thermoplastic resin foam molded article according to any one of claims 1 to 3, wherein the thermoplastic resin foam molded article is for an automobile interior.

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