JP3189377B2 - Molding method of foamed synthetic resin molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed synthetic resin molding in which foamable synthetic resin raw material particles are filled in a mold for in-mold foaming molding composed of a pair of molds and foamed and fused. The present invention relates to a method of forming a product.

[0002]

2. Description of the Related Art An ordinary foamed synthetic resin molded article formed by filling foamable synthetic resin raw material particles in a mold for in-mold foaming molding composed of a pair of molds and foaming and fusing is used. Since it is easy to handle and has good buffering performance, it is widely used for various cushioning materials, storage boxes and the like.

[0003] However, such a general foamed synthetic resin molded article is formed by foaming and fusion of raw material particles having a very thin skin, and therefore, the surface thereof has a very thin film of individual raw material particles. Since only a coating in which a squamous skin is formed in a turtle-shape pattern is formed and a continuous thick coating is not provided, it cannot be said that the surface strength is high. For this reason, it is not suitable for use or when repeatedly used or washed with water. Also, there is a problem that when another object rubs or hits the surface, a peeling phenomenon or a depression phenomenon easily occurs. Furthermore, there is also a problem that the surface is not necessarily in a beautiful state because individual raw material particles appear as a turtle-like film on the surface or dents are formed between the foamed and fused raw material particles on the surface. .

[0004] For the purpose of improving the drawbacks of such ordinary foamed synthetic resin molded articles depending on their use and use conditions, conventionally, after molding of molded articles, post-processing has been carried out to synthesize a non-foamed body on this surface. After polymerizing the resin film, apply heat by heating, or apply a non-foamed synthetic resin film by interposing an adhesive on the surface, or heat and melt the surface by post-processing. Thus, an attempt has been made to form a surface coating. Separately, after forming a molded product, a vacuum formed product is attached to form a surface coating.

Further, after inserting a non-foamed synthetic resin sheet between a pair of opened molds, the pair of molds is closed, and the inside thereof is filled with foamable synthetic resin raw material particles. It has also been attempted to form a surface film from a synthetic resin sheet on the surface of a molded product during the in-mold foam molding process.

Further, prior art documents aiming at improving the drawbacks of ordinary foamed synthetic resin molded articles depending on their uses and use conditions, such as French Patent No. 1571274 and Japanese Patent Application Laid-Open No. 58-171924, are disclosed in Japanese Patent Application Laid-Open No. 58-171924. The following method has been proposed. First, French Patent No. 15
No. 71274 discloses that 5 to 10 kg of foamable polystyrene resin material particles filled in a mold for in-mold foam molding is added.
² to 5 kg / cm 2 using steam at a relative pressure of 2 kg / cm 2
A relative pressure of ² (corresponding to a heating state of 140 to 150 ° C.) is applied for 10 seconds, and immediately thereafter, 0 to 1.5 k
A method is disclosed in which the relative stress is reduced to g / cm ² (corresponding to a heating state of 105 to 110 ° C.), and foam molding is performed while maintaining this state. According to this method, it is possible to mold a molded article whose surface side is 10 to 20 times higher in density than the inside side. Next, JP-A-58-1
No. 71924 discloses that foaming polypropylene resin raw material particles are filled in a mold for in-mold foam molding, ordinary foam molding is performed, and subsequently, the surface of the molded product is directly maintained in the mold for molding. A method of forming a surface coating by heating and melting at about 200 ° C. for 30 seconds is disclosed.

[0007]

However, in the case where a non-foamed synthetic resin film is attached by post-processing after the foamed synthetic resin molded article is molded in the mold for in-mold foam molding, the synthetic resin film is not bonded to the synthetic resin film. It is extremely difficult to work without wrinkling. This tendency is particularly remarkable when the shape of the molded product is complicated. Further, when the surface film is formed by heating and melting the surface in post-processing after molding, it is difficult to uniformly melt the raw material particles, and there is a problem that the surface is wavy. In either case, or in the case of attaching a vacuum formed product, the forming process becomes two steps and the work becomes complicated.

Furthermore, when a non-foamed synthetic resin sheet is inserted between a pair of opened molds, the insertion operation itself is troublesome, and the surface is not finished in a beautiful state due to generation of wrinkles and the like. The problem remains. And also in this case,
When the shape of the molded product, that is, the shape of the molding surface of the mold is complicated,
This tendency becomes remarkable.

On the other hand, the method disclosed in French Patent No. 1571274 also has the following problem. Although nothing is described in this publication, the heating temperature of the raw material particles is
Since the melting point of the polystyrene resin is at least 50 ° C. lower than the melting point of about 200 ° C., the melting phenomenon of the raw material particles on the surface side does not occur, and the raw material particles are considered to remain in their original form. For this reason, even if the surface side has a considerably higher density than the inner side, individual raw material particles still appear as a turtle-shaped pattern on the surface, or dents are formed between the foamed and fused raw material particles on the surface. It should be seen that the point has not been improved. In addition, since only the foaming pressure of the mold for in-mold foam molding after closing the mold is used, a portion having a higher density than the inner side is formed on the surface side, so it is not possible to increase the thickness of the high-density portion. There is. Further, raw material particles prefoamed at a high expansion ratio cannot be used, which impairs the light-weight characteristics of a general foamed synthetic resin molded product. Since the high-pressure steam is first brought into direct contact with the raw material particles filled in the molding die, then the low-pressure steam is immediately brought into contact therewith, so that the foam molding operation becomes complicated. In addition, at the initial stage of direct contact with the high-pressure steam, the surface side hardens immediately, and thereafter the steam may not sufficiently pass through the inside side, which requires advanced operations.

In the method disclosed in Japanese Patent Application Laid-Open No. 58-171924, after molding a molded synthetic resin article, the surface of the molded article is heated to the melting point or higher in a mold for in-mold foam molding. Because, due to the air replaced with a part or all of the foaming agent in the foam fusion process that stays in the foam fused raw material particles, a portion where the surface coating is not formed remains,
There are problems that a continuous surface coating is not formed uniformly or that voids are formed between the surface coating and the foamed and fused raw material particles behind. In this case, too, there is a limit in increasing the thickness of the surface coating.

In view of such conventional problems, a method of molding a foamed synthetic resin molded article according to the present invention has been developed.
In particular, it is possible to form a continuous hardened layer uniformly and to a desired thickness on a part or the entire surface of a molded article in an in-mold foam molding process without greatly changing a normal foam molding operation. With the goal.

[0012] In order to achieve the above object, a method for molding a foamed synthetic resin molded product according to claim 1 includes a method for forming a part or the whole of a molding surface of a mold for in-mold foam molding comprising a pair of molds. A step of heating the foamed synthetic resin raw material particles to be filled in the mold closed interior to a melting point or higher, and a step of filling the raw material particles between a pair of closed molds while leaving a gap larger than a general cracking gap. The step of completely closing the pair of molds and the step of forcibly pressing and melting the raw material particles filled between the pair of molds on a portion of the molding surface heated above the melting point of the raw material particles and melting. Forming a molten resin layer in this portion; curing the molten resin layer to form a continuous surface hardened layer in a portion corresponding to the surface of the molded product; and foaming and fusing the raw material particles in the molding space. Process in the in-mold foam molding process Wherein the method forming features and the foamed synthetic resin molded article to form a hardened surface layer from the raw material particles on the molded article surface. Further, the method for molding a foamed synthetic resin molded product according to claim 2 is the method for molding a foamed synthetic resin molded product according to claim 1, wherein a part or the whole of the molding surface is set to a melting point of the foamable synthetic resin raw material particles or higher. The heating step is started prior to the other steps, and the step of contacting the raw material particles with the heated portion of the molding surface to form a molten resin layer is started simultaneously with the step of filling the raw material particles between a pair of molds. It is to let. According to a third aspect of the present invention, there is provided a method for molding a foamed synthetic resin article according to the second aspect, wherein the molten resin layer is formed by bringing the raw material particles into contact with a heated portion of the molding surface. Is continuously performed for a required time after the step of filling the raw material particles between the pair of dies, and after the step of completely closing the pair of dies. The method of molding a foamed synthetic resin molded product according to claim 4 is the method of molding a foamed synthetic resin molded product according to claims 1 to 3, wherein the foamable synthetic resin raw material particles have an expansion ratio of 3 to 150 times. It is a thing to use.
The method of molding a foamed synthetic resin molded product according to claim 5 is the method of molding a foamed synthetic resin molded product according to claims 1 to 4, wherein the thickness of the surface hardened layer formed on the surface of the molded product is 0.1.
５5.0 mm. According to a sixth aspect of the present invention, there is provided a method for molding a foamed synthetic resin molded article, comprising the steps of: It is used by selecting from raw polyolefin resin raw material particles.

[0013]

[0014]

[0015]

Thus, a hardened surface layer for improving the releasability and depressability is formed on the inner surface or the outer surface of the surface of various foamed synthetic resin molded products, or separately at an appropriate place or on the entire surface. Specifically, in a cushioning material, for example, a surface hardened layer is formed on an inner surface that directly contacts a container, and in a storage box, a surface hardened layer is formed on an outer surface that is exposed to the outside, for example. It is.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the method for molding a foamed synthetic resin molded product according to the present invention will be further described with reference to the accompanying drawings.

FIG. 1 shows a cushioning material as an example of a foamed synthetic resin molded product according to the present invention. The molded article 1 is formed by filling expandable synthetic resin raw material particles in a mold for in-mold foam molding composed of a pair of molds, and performing foam fusion. This is a continuous hardened surface layer 2 which is exposed to the outside when housed in another outer box and has an inner surface including an edge which comes into direct contact with the housed material, and which has improved peelability and depression. Is formed by melting the raw material particles in the in-mold foaming process and then curing.

FIGS. 2 and 3 schematically show the structure of the inner surface portion. In FIG. 2, reference numeral 2 denotes a surface hardened layer,
Reference numeral 3 denotes the foamed and fused raw material particles behind it. The continuous surface hardened layer 2 is formed by heating the corresponding portion of the molding surface of the in-mold foam molding die for molding the molded article 1 to a temperature equal to or higher than the melting point of the raw material particles, and forming the molded product 1 in the in-mold foam molding process. The raw material particles are brought into contact with a heated portion of the surface to be melted, a molten resin layer is formed at that portion, and then the molten resin layer is cured. By the way, in order to form such a continuous surface hardened layer 2 uniformly, it is necessary to form a molten resin layer uniformly on a heated portion of a molding surface before this. For this reason, in the process of forming the molten resin layer, by completely closing the pair of molds, not only the outermost material particles in contact with the heated portion of the molding surface, but also at least these material particles That is, the raw material particles behind and behind are forcedly brought into contact with each other and melted. In this way, the surface hardened layer 2 is formed on the surface of the molded article 1 during the in-mold foam molding process. FIG. 2 shows the boundary between the surface hardened layer 2 and the foamed and fused raw material particles 3 behind. A part of the surface hardened layer 2 is formed by melting a part of the raw material particles 3 and the surface hardened layer 2 is adhered to the raw material particles 3 at the back, and FIG. Raw material particles 3 foamed and fused behind hardened layer 2
Indicate fusion-spliced products while maintaining their original shapes.

The raw material particles of the expandable synthetic resin used herein include raw material particles of expandable polystyrene resin, raw material particles of expandable polyethylene resin, and raw material particles of expandable polyolefin resin such as raw material particles of expandable polypropylene resin. In addition, foamable copolymer resin material particles can be used. Among these, the foamable polyolefin-based resin raw material particles are preferable because the surface hardened layer 2 is easily formed. In particular, when the expandable polypropylene resin raw material particles are used, the surface hardened layer 2 to be formed therefrom is formed.
Is excellent in bending resistance, and is effective in forming these hinges when, for example, forming a container having a lid integrally. The raw material particles used here can be any of a crosslinked synthetic resin and a non-crosslinked synthetic resin as a resin material. However, considering that the surface hardened layer 2 is formed favorably, the non-crosslinked synthetic resin can be used. Is preferable.

The raw material particles may not be prefoamed, but the use of prefoamed particles is particularly considered. The expansion ratio of the raw material particles slightly varies depending on the resin material used, but is preferably in the range of 3 to 150 times. The expansion ratio of the expandable polystyrene resin material particles is 3 to 100 times, preferably 3 to 5 times.
0 times, and 3 to 3 times for expandable polyolefin resin raw material particles.
Those in the range of 60 times, preferably 3 to 45 times can be suitably used. Although the particle size slightly varies depending on the resin material used, a particle size in the range of 1 to 10 mm can be suitably used.

Further, the raw material particles forming the surface-hardened layer 2 and the raw material particles to be fused behind the raw material particles do not necessarily use the same type of raw material particles, but may use different types of raw material particles. In addition, the different kind of raw material particles referred to here, even if they are formed from the same kind of resin material, have different expansion ratios, different particle diameters, or colored and uncolored, and further colored. This is a concept that includes things with different colors. In addition, even raw material particles formed from different types of resin materials,
The expandable polystyrene resin material particles and the expandable polypropylene resin material particles are fused.

Further, the thickness of the surface hardened layer 2 is obtained by subtracting the general cracking gap width from the expansion ratio of the raw material particles used and the gap width left when the raw material particles are filled between a pair of dies as described later. It is freely determined according to the relationship of the gap width, but is 0.1 to 5.0 mm, preferably 0.3 to 5.0.
mm.

FIGS. 4 and 5 show the structures of the molded product 1 which is actually molded, 20 times larger than the inner surface portion. Among these, FIG. 4 is the same as FIG.
FIG. 5 corresponds to FIG. still,
In the figure, 4 is the skin of the foamed and fused raw material particles, 5 is the raw material particle 3
The cell is divided by a number of cell films 6 in the cell. By the way, as can be seen from FIGS. 4 and 5, after the raw material particles are melted and cured, the surface hardened layer 2 is formed inside the cells of the raw material particles, and a mold for in-mold foam molding. Bubble 7 which is determined to be formed from a decomposable or active foaming agent or a vaporized substance such as air or a gas serving as a foaming means that stays before being filled therein is present in an independent and dispersed state. or,
This bubble 7 is caused by forcibly pressing the raw material particles filled between the pair of molds on a heated portion of the molding surface of the in-mold foam molding mold at least at one time during the process of forming the bubbles. As can be seen from FIGS. 4 and 5, many are flattened in the thickness direction of the hardened surface layer 2 and, in particular, some of the ends are cut and elongated. For this reason, the surface hardened layer 2 has a large number of air bubbles 7 formed therein, and has a cushioning property and a restoring property as a whole due to the shape of the air bubbles 7.

Next, the method of molding the molded article 1 shown in FIG. 1 will be described in detail based on the outline of the mold for in-mold foam molding. FIG. 6 and FIG. 7 schematically show the molding die 10, which is a pair of a cavity die shown as 11 in the figure.
It is composed of a core mold shown as 12. In the embodiment shown, a pair of cavity mold 11 and core mold 12
And the core mold 12 is retracted to the left side in the figure with respect to the cavity mold 11 so that the pair of cavity molds 11 and the core mold 12 can be opened. Has become. Also, a pair of cavity mold 11 and core mold 12
When the mold is closed, the molding space
13 is formed. In the drawing, reference numeral 14 denotes a molding surface facing the molding space 13 of the cavity mold 11, and reference numeral 15 denotes a molding surface of the core mold 12 facing the same molding space 13. Further, reference numerals 16 and 17 denote heating chambers formed in a closed shape behind the molding surfaces 14 and 15 of the cavity mold 11 and the core mold 12. Reference numeral 18 in the figure denotes a raw material filling feeder for filling expandable synthetic resin raw material particles into a molding space 13 formed between a pair of closed cavity molds 11 and a core mold 12. 19 is the molding surface of the core mold 12
15 shows a heating means provided at the back of the heating device for heating the portion above the melting point of the raw material particles.

Thus, such a mold for in-mold foam molding 10
The molded product 1 shown in FIG. First, by heating the entire molding surface 15 of the core mold 12 by the heating means 19, the material is heated to a melting point of the raw material particles or more, for example, to about 200 ° C. or more when the resin material of the raw material particles is a polystyrene resin or a polyolefin resin. The operation of the first step is performed. Next, a gap between a pair of cavity molds 11 and a core mold 12 closed as shown in FIG. 7 except for a gap of 10 to 150 mm larger than a general cracking gap which is usually 3 to 5 mm. The second step of filling the raw material particles by feeding air into the molding space 13 through the raw material filling feeder 18 is performed. Thereafter, an operation of a third step of completely closing the pair of the cavity mold 11 and the core mold 12 is performed. Here, in parallel with the second step, the raw material particles are brought into contact with the entire molding surface 15 heated above the melting point of the raw material particles of the core mold 12 and melted, and a molten resin layer is formed on the entire molding surface 15. 4th
Operation of the process is performed. Then, after a lapse of a required time, for example, 0 to 150 seconds, after completion of the operation of the third step, for example, cooling water is supplied to the heating chamber 17 behind the core mold 12 to cool it. At the same time, the operation of the fourth step ends. At this stage, the operation of the fifth step of curing the molten resin layer to form the continuous surface hardened layer 2 along the entire molding surface 15 of the core mold 12 is performed. At this time, at the boundary between the surface hardened layer 2 and the raw material particles behind, a part of the surface hardened layer 2 is formed by melting a part of the raw material particles, and the surface hardened layer 2 and the raw material particles behind are bonded. The raw material particles which are not foam-fused or foam-fused behind the surface hardened layer 2 or which are foam-fused remain fused in their original form. Here, the operation of the fourth step of forming the molten resin layer on the entire molding surface 15 of the core mold 12 is performed by filling the raw material particles into the molding space 13 between the pair of cavity molds 11 and the core mold 12. Starting simultaneously with two steps, a pair of cavity molds
After the operation of the third step of completely closing the mold 11 and the core mold 12 is completed, the operation is continued for a required time. This is because in order to form the continuous hardened surface layer 2 uniformly, it is necessary to form the molten resin layer uniformly on the entire molding surface 15 of the core mold 12 heated before this. That is, when the pair of the cavity mold 11 and the core mold 12 are completely closed, the mold closing force and the compression reaction force between the raw material particles are formed on the vertical surface of the molding surface 15 of the core mold 12 in the drawing. The raw material particles filled in the molding space 13 can be forcibly pressed against the middle horizontal plane against the molding surface 15 of the core mold 12 heated by the compression reaction force between the raw material particles. Therefore, not only the outermost material particles in contact with the entire molding surface 15 of the heated core mold 12 but also at least the material particles behind these material particles can be forcibly brought into contact with and melted. It is possible. Also, in the second half when the thickness of the molten resin layer in the fourth step is large, the raw material particles are filled behind it, so that the molten resin layer formed on the vertical surface of the molding surface 15 in the figure does not flow down, Become uniform. Thereafter, steam is supplied to the heating chamber 16 behind the cavity mold 11, and the steam is heated to a normal foaming molding temperature, for example, about 105 to 110 ° C. when the resin material of the raw material particles is a polystyrene resin or a polyolefin resin. Heating and molding space
No. 6 of normal foam molding for foam fusion of the raw material particles in 13
Perform the operation of the process. Finally, the heating chamber 16 behind the cavity mold 11 is cooled by, for example, supplying cooling water. And
With the core mold 12 retracted to the side, a pair of cavity molds
The mold 11 is opened from the core mold 12 and the molded product 1 having the surface hardened layer 2 formed from the raw material particles on the inner surface including the rim corresponding to the entire molding surface 15 of the heated core mold 12 is taken out. .

As described above, the surface hardened layer 2 is formed from the raw material particles on the surface of the molded article 1 during the in-mold foam molding process. The thickness A [mm] of the surface hardened layer 2 is determined by the size of the raw material particles used. The expansion ratio B [times] and the gap width C [mm obtained by removing the general cracking gap width from the gap width left when filling the raw material particles into the molding space 13 between the pair of cavity molds 11 and the core mold 12. ] Is given by the following equation. Thickness of surface hardened layer A [mm] = (expansion ratio B of raw material particles used [times]) / (general cracking based on gap width left when filling raw material particles between a pair of cavity mold and core mold) That is, the gap width C [mm] excluding the gap width) That is, the expansion ratio B of the raw material particles used is 30 times, and the gap width left when the raw material particles are filled between the pair of cavity mold 11 and the core mold 12 is When the gap width C excluding the general cracking gap width is 30 mm, the thickness A of the surface hardened layer 2 formed at a portion corresponding to the surface of the molded article 1 is 1 mm. When the gap width left when filling the material particles into the molding space 13 between the pair of cavity molds 11 and the core mold 12 increases, the thickness A of the surface hardened layer 2 becomes larger than the expansion ratio of the material particles used therewith. It is determined only by B.

Here, after the operation of the third step of completely closing the pair of cavity molds 11 and the core mold 12, an operation of opening a gap between the pair of cavity molds 11 and the core mold 12 again. Can be repeated. In this case, when a gap is provided between the pair of cavity molds 11 and the core mold 12, the raw material particles can be filled again.

Also, a pair of cavity mold 11 and core mold 12
When the raw material particles are filled in the molding space 13 between them, they can be compressed and filled using compressed air.

Further, in addition to performing the above-described operations, a first step of heating the entire molding surface 15 of the core mold 12 and a pair of cavity molds in which the molds are closed while leaving a gap larger than a general cracking gap. The second step of filling the raw material particles into the molding space 13 between the core mold 11 and 11 may be started at the same time, or the first step may be started after the second step, or the second step may be terminated. Thereafter, the first step may be started.
After the operation of the third step is completed, the heating chamber behind the core mold 12 is provided.
Instead of supplying cooling water to the cooling unit 17, for example, steam may be supplied here to lower the temperature to a normal foam molding temperature, and the cooling may be performed after the operation of the sixth step is completed.

The entire molding surface 15 of the core mold 12 is heated to a temperature higher than the melting point of the raw material particles, and in the above-described example, to approximately 200 ° C. or higher. However, the heating temperature varies depending on the resin material of the raw material particles. Therefore, it is considered that the optimum heating temperature is selected after actually performing temporary molding. The lower the heating temperature, the more beautiful the surface hardened layer 2 formed on the surface of the molded article 1.

The core mold 12 is previously formed to be thin so as to increase heat loss, and the raw material particles are melted.
To some extent, the temperature may be naturally lowered. Then, in the case where the core mold 12 is in such an embodiment, the heating temperature is set to be excessively high, and is brought into contact with the raw material particles,
Cooling is also possible.

Next, FIG. 8 schematically shows the structure of the surface portion when the surface hardened layer 2 is formed on the entire surface of the molded article 1. After the surface hardened layer 2 is formed on the entire surface in this way, steam or other heating medium cannot pass through the inside, and the raw material particles 3 inside are in a compressed state without foaming and fusion. Reference numeral 4 denotes the skin of the raw material particles 3 that have not been foam-fused.

FIG. 9 schematically shows a mold 10 for in-mold foam molding for molding the molded article 1 shown in FIG. The molding die 10 is provided with a heating means 19 behind the molding surface 15 of the core mold 12 and a heating means 20 also behind the molding surface 14 of the cavity mold 11. By the way, when the molded article 1 is molded with such a molding die 10, the surface hardened layer 2 is formed.
After the gas is formed, no steam or other heating medium can pass through the inside. Therefore, the inner raw material particles 3 are in a compressed state without foaming and fusion as described above. For this reason, by blowing out the raw material particles inside after molding, a hollow molded article can be molded. Then, in this case, it is also possible to fill different kinds of raw material particles after blowing out the inner raw material particles. At this time, as the different kind of raw material particles, those that do not fuse to the surface hardened layer 2 can be used.

By the way, at the time of such molding, the molding space
It is also possible to project a steam or other heating medium supply pipe having a vent in 13 and blow the steam or other heating medium into the pipe to foam and fuse the internal raw material particles.

In the case where the surface hardened layer 2 is formed on the outer surface of the molded product 1 except for the edge, a molding die (not shown) provided with the heating means 20 only behind the molding surface 14 of the cavity mold 11 is used. Mold with a mold.

Next, FIG. 10 shows a specific example of an in-mold foam molding die 10 for molding the foamed synthetic resin molded article 1 shown in FIG. The molding die 10 includes a pair of cavity dies 11
And the core mold 12 are disposed vertically, and the core mold 12 is retracted to the left side in the figure with respect to the cavity mold 11 to form a pair of the cavity mold 11 and the core mold 12. It can be opened. Reference numeral 13 denotes a molding space for the molded article 1 formed between the pair of cavity mold 11 and core mold 12 when the molds are closed. In the drawing, reference numeral 14 denotes a molding surface facing the molding space 13 of the cavity mold 11, and reference numeral 15 denotes a molding surface of the core mold 12 facing the same molding space 13. Further, reference numerals 16 and 17 denote heating chambers formed in a closed shape behind the molding surfaces 14 and 15 of the cavity mold 11 and the core mold 12. And 18 in the figure is a pair of closed cavity molds
This is a raw material filling feeder for filling expandable synthetic resin raw material particles into a molding space 13 formed between 11 and a core mold 12.
Reference numeral 19 denotes a heating means provided at the rear of the molding surface 15 of the core mold 12 for heating this portion to a temperature equal to or higher than the melting point of the raw material particles.
The heating means 19 includes a core mold 12 as shown in detail in FIG.
A closed heating gap 22 is formed by providing a back wall 21 at an interval behind the molding surface 15 and a heater 23 is provided therein. Further, in the figure, reference numeral 24 denotes a vent for communicating the molding surface 14 of the cavity mold 11 with the heating chamber 16.
By the way, after the molten resin layer is formed on the molding surface 15, the core mold 12 is not provided with such a vent because the steam or other heating medium does not pass therethrough. Further, reference numeral 25 denotes a steam pipe having one end in the heating chamber 16 of the cavity mold 11, and reference numerals 26 and 27 denote heating chambers of the cavity mold 11 and the core mold 12.
Cooling water pipes with one end inserted into 16, 17; 28, 29 are air supply pipes with one end inserted into both heating chambers 16, 17;
31 is a drain tube, and 32 is a release pin provided on the cavity mold 11 side. 33 and 34 are formed on the cooling water pipes 26 and 27 and the molding surfaces 14 and 15 respectively.
Injection nozzles 35, 36 provided toward the back are air supply pipes 28, 29
Also shows an air supply port provided to the rear of the molding surfaces 14 and 15. In the drawings, reference numerals 37 and 38 denote valves provided in the middle of the drain pipes 30 and 31. Further, 39 and 40 are back plates, 41 and 42
Denotes a side plate, 43 denotes an inner plate, and 44 and 45 denote a cavity-side surface member and a core-side surface member forming the molding surfaces 14 and 15 of the cavity mold 11 and the core mold 12, respectively. The back plate 39, 40, the side plates 41, 42, the inner plate 43 and the cavity side surface member
44, from the core side surface member 45, the heating chambers 16, 17 closed behind the molding surfaces 14, 15 of the cavity mold 11, the core mold 12.
Are formed. Also, the molding surface 15 of the core mold 12 described above is used.
As shown in FIG. 11, the heating means 19 on the rear side
It is provided in. Further, between the inner peripheral surface of the cavity mold 11 and the outer peripheral surface of the core mold 12, and in the illustrated embodiment, between the inner peripheral surface of the cavity side surface member 44 and the outer peripheral surface of the core side surface member 45,
A ventilation gap having a gap width through which the raw material particles cannot pass as indicated by 46 in 12 has a pair of cavity mold 11 and core mold 12.
In order to form between the closed state of the mold leaving a gap larger than the general cracking gap when filling the raw material particles between the mold and the state where the pair of cavity molds 11 and the core mold 12 are completely closed. A joining structure 47 is provided. In the molding die 10, when filling the raw material particles into the molding space 13, a pair of the cavity die 11 and the core die 12 are used.
Since a gap larger than a general cracking gap is left therebetween, the joining structure 47 is set longer than a conventional molding die.

In the molding die 10, the cavity die 1
1.When cooling the core mold 12, the cooling water is first sprayed from the injection nozzles 33 and 34 of the cooling water pipes 26 and 27 in the form of mist behind the molding surfaces 14 and 15, and then the air is supplied to the air supply pipes 28 and 29. Compressed air is blown from the ports 35 and 36 to scatter and remove moisture.

The same effect can be expected by using the core side surface member 48 shown in FIG. 13 instead of the core side surface member 45 shown in FIG. The core-side surface member 48 is formed on the molding surface 15 without providing the back wall 21 with an interval behind the molding surface 15.
A pair of opposed walls 49, 49 are provided at intervals on the opposite side to form a closed heating gap 50, and the heating gap 50
23 is decorated. Then, the core side surface member 48
The cooling water pipe 27 and the air supply pipe 29 are provided with the injection nozzle 34 and the air supply port 36 facing the molding surface 15 behind the heating gap 50.

Next, FIG. 14 shows another specific example of the in-mold foam molding die 10 for molding the foamed synthetic resin molded article 1 shown in FIG. This is because mounting means 19 for heating the entire molding surface 15 of the core mold 12 above the melting point of the expandable synthetic resin raw material particles are provided behind the molding surface 15 of the heating chamber 17 of the core mold 12.
One end of a heating cartridge 52 in which a heating medium such as heating oil flows is attached to a large number of insides. In the drawing, 53 is a supply pipe connected to a supply side of a heating medium such as heating oil of the heating cartridge 52, and 54 is a discharge pipe connected to a discharge side thereof. The heating cartridge 52 is disposed in parallel with the supply pipe 53 and the discharge pipe 54. Reference numeral 55 denotes a heating tank provided outside the molding die 10 for heating a heating medium such as a heating oil. An appropriate heating source is provided inside or outside the heating tank 55. The ends of the supply pipe 53 and the discharge pipe 54 on the side opposite to the heating cartridge 52 are exposed to the heating tank 55. still,
Reference numerals 56 and 57 denote valves provided in the supply pipe 53 and the discharge pipe 54, respectively.

By the way, in such a molding die 10, FIG.
The same applies to the molding die 10 shown in FIG. 10, but after the raw material particles are melted and formed on the entire molding surface 15 of the core mold 12 in the in-mold foam molding process, a molten resin layer is formed, which is cured to form a surface. Due to the formation of the hardened layer 2, there is a problem that after the molten resin layer is formed, the raw material particles filled in the molding space 13 cannot be heated from the core mold 12 side. For this reason, in this molding die 10, as shown in FIGS. 15 and 16, the purpose of sufficiently heating the raw material particles filled in the molding space 13 from the cavity die 11 side is to increase the cavity die.
A partition wall 58 that partitions the rear of the molding surface 14 in the heating chamber 16 of 11 into two sections
The heating chamber 16 is divided into a first section heating chamber 16A and a second section heating chamber 16B, and the first and second section heating chambers 16A and 16B are communicated with the steam pipes 25A and 25A, respectively.
25B and drain pipes 30A and 30B are provided independently. In the figure, 59A, 59B, 37A and 37B are the first and second compartment heating chambers 16 respectively.
Valves provided in the middle of each of the steam pipes 25A and 25B and the drain pipes 30A and 30B provided in communication with the pipes A and 16B.
Numeral 24 denotes a vent for communicating the molding surface 14 of the cavity mold 11 with the heating chamber 16.

Next, as shown in FIG. 17, the heating cartridge 52 has a cylindrical body whose both ends are closed by side plates 60, 60.
An inflow pipe 62 is inserted from the outside of the side plate 60 at one end on the left side in the drawing to the inside thereof with a space between the side plate 60 at the other end on the right side in the drawing, leaving the cylindrical main body 61 substantially along the axis of 61. Outflow pipe to the cylindrical body 61 along the side plate 60 at one end through which the inflow pipe 62 of
63 is provided from the outside to the inside, and a spiral partition 64 is formed between the inner surface of the cylindrical main body 61 and the outer surface of the inflow pipe 62 as shown in FIG.
A flow passage 65 communicating the open end of the pipe 63 is provided.
The heating medium such as heating oil flows through the outflow pipe 63 through the flow passage 65. In such a heating cartridge 52, at least the cylindrical main body 61 is formed of copper or aluminum having good heat conductivity.

Here, as the heating oil, silicon oil, alkyldiphenyl and the like can be used.

In the molding die 10, steam is supplied to the heating chamber 16 behind the molding surface 14 of the cavity die 11,
When this is heated to a normal foam molding temperature to foam and fuse the raw material particles in the molding space 13, first, the first compartment heating chamber 16A
The valve 59A of the steam pipe 25A of the second section heating chamber 16B and the valve 59A of the steam pipe 25B of the second section heating chamber 16B and the first section heating chamber are opened.
The valve 37A of the drain pipe 30A of 16A is closed, steam is supplied from the steam pipe 25A of the first section heating chamber 16A, and the second section heating chamber 16 is formed from the first section heating chamber 16A through the molding space 13.
An operation of passing steam through B is performed. Next, open-side valve 59
A and 37B are closed, and the valve 59B on the closing side is closed.
37A is opened, and an operation is performed in which steam is passed from the second compartment heating chamber 16B to the first compartment heating chamber 16A through the molding space 13 in reverse. Lastly, the valves 59A and 59B of the steam pipes 25A and 25B of the first and second compartment heating chambers 16A and 16B are both opened, and the valves 37A and 37B of the drain pipes 30A and 30B are closed together. The operation of supplying steam from one of 28A and 28B to the other of the first and second compartment heating chambers 16A and 16B is repeated once or a plurality of times. In this way, the raw material particles in the molding space 13 are sufficiently foamed and fused by one-side heating from the cavity mold 11 side.

FIG. 18 shows still another specific example of the in-mold foam molding die 10 for molding the foamed synthetic resin molded article 1 shown in FIG. In this configuration, the heating means 19 is configured by providing a radiation heating source 66 in the heating chamber 17 behind the molding surface 15 of the core mold 12. The radiant heating source 66 is provided so as to be able to retreat from behind the molding surface 15 along the retreat means 67 while maintaining the heating state as shown in the figure, or is fixedly provided behind it. The radiant heating source 66 is provided with an oil heater, a gas burner, and the like facing the molding surface 15 behind.

Further, the foamed synthetic resin molded article 1 shown in FIG. 1 is another mold for foam molding in-mold schematically shown in FIG. 19, FIG. 20, and FIG.
It can be molded using 10 as well. First, FIG. 19 shows a configuration in which a heating means 68 for heating the molding surface 15 of the core mold 12 is provided between the pair of cavity molds 11 and the core mold 12 which are opened. Further, the heating means 68 can be retracted from between the pair of cavity molds 11 and the core mold 12 before the molds are closed. As the heating means 68, a radiant heating source is used as shown in FIG. Next, FIGS. 20 and 21 show a heating means 69 for heating the molding surface 15 of the core mold 12, a pair of the cavity mold 11 and the core mold.
FIG. 12 shows an apparatus using a heating tank 71 provided outside the apparatus 12 and containing a heating medium 70 such as heating oil. Shown here is
In each case, after the pair of cavity mold 11 and the core mold 12 are opened, the core mold 12 or the core mold 12 and the heating tank 71 are moved together to heat the molding surface 15 of the core mold 12. Heating is performed by immersion in a heating medium 70 such as heating oil in a tank 71.

[0046]

As described above, the foamed synthetic resin molded article molded by the molding method according to the present invention has a molten resin layer formed by melting the foamable synthetic resin raw material particles on a part or the entire surface thereof. After that, since the continuous surface hardened layer formed by hardening this molten resin layer is formed uniformly, the surface strength increases, and depending on the use and use condition of the general foamed synthetic resin molded article, there are disadvantages. Can be improved. In addition, even if another object rubs or hits the surface, a peeling phenomenon or a depression phenomenon does not easily occur. Further, by forming the surface hardened layer, the surface becomes beautiful. When such a molded product is molded, the conventional foam molding machine can be used as it is and can be dealt with by only slightly changing a part of the mold for in-mold foam molding, which is industrially extremely useful. .

In addition, in such a molding method, the raw material particles are melted in the in-mold foam molding process to form a hardened surface layer. In addition to the above, there is no possibility that the surface hardened layer may be wrinkled. Further, in the process of forming the molten resin layer, the raw material particles are brought into contact with the portion heated to the melting point of the raw material particles or higher on the molding surface for at least one time, while the raw material particles filled here between the pair of molds are forcibly pressed. By doing so, the part where the surface hardened layer is not formed remains, and there is also a problem that a continuous surface hardened layer is not formed uniformly or a void is formed between the surface hardened layer and the foamed and fused raw material particles behind. Can be avoided. The thickness of the surface hardened layer can be freely determined according to the relationship between the expansion ratio of the raw material particles and the gap width obtained by removing the general cracking gap width from the gap width left when filling the raw material particles between the pair of molds. It is possible to decide.

Also, by devising an appropriate pattern on the surface of the molding surface of the molding die where the surface hardened layer is to be formed, or by providing a net-like material or the like, the surface hardened layer can have various shapes. If a design is given or matted, the commercial value can be further increased.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a foamed synthetic resin molded product according to the present invention.

FIG. 2 is an explanatory view schematically showing the structure of this molded article.

FIG. 3 is an explanatory view schematically showing the structure of the molded article.

FIG. 4 is an explanatory diagram showing the structure of a molded article according to the present invention at a magnification of 20 times.

FIG. 5 is an explanatory diagram showing the structure of a molded article according to the present invention at a magnification of 20 times.

FIG. 6 is an explanatory view schematically showing a mold for in-mold foam molding for explaining a molding method according to the present invention.

FIG. 7 is an explanatory view showing an operation state of the molding die.

FIG. 8 is an explanatory view schematically showing the structure of another molded article according to the present invention.

FIG. 9 is an explanatory view schematically showing a mold for in-mold foam molding for explaining another molding method according to the present invention.

FIG. 10 is a sectional view showing a specific example of the mold for in-mold foam molding according to the present invention.

FIG. 11 is a cross-sectional view showing an example of a core-side surface member to be incorporated into the molding die.

FIG. 12 is a cross-sectional view showing a main part of the molding die.

FIG. 13 is a sectional view showing another example of the core-side surface member.

FIG. 14 is a cross-sectional view showing another specific example of the mold for in-mold foam molding according to the present invention.

FIG. 15 is a cross-sectional view showing the back side of the cavity mold of the molding mold.

FIG. 16 is a cross-sectional perspective view showing the back side of the cavity mold of the molding mold.

FIG. 17 is a sectional view showing a heating cartridge.

FIG. 18 is an explanatory view schematically showing still another specific example of the mold for in-mold foam molding according to the present invention.

FIG. 19 is an explanatory view schematically showing another mold for in-mold foam molding used in the molding method according to the present invention.

FIG. 20 is an explanatory view schematically showing another in-mold foam molding die used in the molding method according to the present invention.

FIG. 21 is an explanatory view schematically showing another mold for in-mold foam molding used in the molding method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2 Surface hardened layer 3 Raw material particles 4 Skin 5 Cell 6 Cell membrane 7 Bubbles 10 In-mold foaming mold 11 Cavity mold 12 Core mold 13 Molding space 14 Molding surface 15 Molding surface 16 Heating room 17 Heating room 18 Raw material filling feeder 19 Heating means 20 Heating means 21 Rear wall 22 Heating gap 23 Heater 24 Vent 25 Steam pipe 26 Cooling water pipe 27 Cooling water pipe 28 Air supply pipe 29 Air supply pipe 30 Drain pipe 31 Drain pipe 32 Release pin 33 Injection nozzle 34 Injection nozzle 35 Air supply port 36 Air supply port 39 Back plate 40 Back plate 41 Side plate 42 Side plate 43 Inner plate 44 Cavity side surface member 45 Core side surface member 46 Ventilation gap 47 Joining structure 48 Core side surface member 49 Opposing wall 50 Heating gap 51 Mounting recess 52 Heating cartridge 53 Supply pipe 54 Discharge pipe 55 Heating tank 56 Valve 57 Valve 58 Partition wall 59A, B valve 60 Side plate 61 Cylindrical body 62 Inflow pipe 63 Flow Pipe 64 partition wall 65 flow path 66 radiant heat source 67 retracting means 68 heating means 69 heating means 70 heating medium 71 heating tank

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-57-96831 (JP, A) JP-A-51-109963 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 44/00-44/60 B29C 67/20 B29C 33/02-33/08 C08J 9/22-9/228

Claims (6)

(57) [Claims] 1. A step of heating a part or the whole of a molding surface of a mold for in-mold foam molding composed of a pair of molds to a temperature not lower than a melting point of expandable synthetic resin raw material particles to be filled in a closed mold. And filling the raw material particles between a pair of closed molds while leaving a gap larger than a general cracking gap; completely closing the pair of molds; and melting point of the raw material particles on the molding surface. A step of forcing the raw material particles filled between the pair of molds into contact with the heated portion and forcing the molten material into contact, thereby forming a molten resin layer in this portion, and curing and molding the molten resin layer. The process consists of forming a continuous surface hardened layer on the part corresponding to the product surface, and foaming and fusing the raw material particles in the molding space. Formed synthetic resin characterized by being formed Molding method of molded article. 2. A step of heating a part or the whole of the molding surface to a temperature equal to or higher than the melting point of the expandable synthetic resin raw material particles before the other step is started, and the raw material particles are brought into contact with the heated part of the molding surface. The method for molding a foamed synthetic resin molded article according to claim 1, wherein the step of forming the molten resin layer is started simultaneously with the step of filling the raw material particles between the pair of molds. 3. The step of forming the molten resin layer by bringing the raw material particles into contact with the heated portion of the molding surface, from the step of filling the raw material particles between the pair of dies, completely closing the pair of dies. 3. The method for molding a foamed synthetic resin molded product according to claim 2, wherein the molding is performed continuously for a required time after the completion of the step of performing the molding. 4. The method for molding a foamed synthetic resin molded product according to claim 1, wherein the foamable synthetic resin raw material particles have an expansion ratio of 3 to 150 times. 5. The method for molding a foamed synthetic resin molded article according to claim 1, wherein the thickness of the surface hardened layer formed on the surface of the molded article is 0.1 to 5.0 mm. 6. The foamed synthetic resin molded product according to claim 1, wherein the foamable synthetic resin raw material particles are selected from foamable polystyrene resin raw material particles and foamable polyolefin resin raw material particles. Molding method.