JP2001079870A - In-mold foam molding method and molded article of polyolefin resin - Google Patents

Abstract

(57) [Abstract] PROBLEM TO BE SOLVED: To improve the aesthetic appearance of a molded article, adjust the fusion rate inside the molded article, and achieve in-mold foam molding of a polyolefin resin capable of achieving both productivity and commercial value. Methods and articles are provided. SOLUTION: A first chamber 13 on the back side of a core mold 2 is provided.
And a second chamber 14 on the back side of the cavity mold 3 and a molding space 4 formed between the core mold 2 and the cavity mold 3. In-mold foam molding device 1 that can individually control working fluid
The pre-expanded beads 5 made of a polyolefin-based resin are filled in the molding space 4 and heated and fused with steam as a working fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an in-mold foam molding method and a molded article using pre-foamed beads made of a polyolefin resin.

[0002]

2. Description of the Related Art As an in-mold foam molding apparatus for producing molded articles using pre-expanded beads made of a thermoplastic synthetic resin,
As shown in FIG. 10, a pair of molding dies 10
0 and 101, and chambers 102 and 103 are formed on the back side of both molds 100 and 101, respectively.
A large number of air holes 105, 106 communicating the chambers 102, 103 and the molding space 104 with both the molds 100, 101.
Are practically used to supply or discharge a working fluid such as heated steam to be described later to the molding space 104 through the ventilation holes 105 and 106. In this case, each chamber 1
02 and 103 are provided with upper ports 107 and 108 for supplying steam for heating and the like, and lower ports 109 and 11 connected to a decompression pump or a drain pipe at the bottom.
0 is provided to supply steam to the molding space 104.

In addition, as shown in FIGS. 11 and 12, a large number of ventilation holes 105 and 106 formed in the molding dies 100 and 101 are actually round holes having a diameter of about 0.5 mm and a width of 0.1 mm. A core vent 111 formed of a cylindrical body having a lid having an outer diameter of 7 to 12 mm, in which a plurality of through holes formed of slits of about 5 mm are formed, is fitted into a core vent mounting hole 112 formed and formed in the molds 100 and 101. And what
0.5mmφ directly formed on the mold 100,101
Core vent holes 113, and these ventilation holes 105, 106
They are provided at a pitch of ５０50 mm.

[0004] Using such an in-mold foam molding apparatus, pre-foamed pre-foamed beads are filled in a molding space 104, heated by heating steam, foamed and fused, cooled, solidified, and cooled. It is taken out as a foamed molded article having a shape. The role of the ventilation holes 105 and 106 in this foamed molding will be further described. JP-A-57-174223
FIG. 13 describes a process chart as shown in FIG. 13, in which (a) to (e) show preheating exhaust for replacing air in a mold and air between pre-expanded beads with steam. The process is displayed, and the following specific contents will be described.
In this figure, the black-filled valve symbol indicates the closed state,
An open valve symbol indicates an open state.

[0005] (a) is an evacuation step, in which after the pre-expanded beads are filled in the molding space 104, steam is supplied to the chambers 102, 103 from the upper ports 107, 108 for a very short time, and the lower ports are filled. The air in the mold, especially in the chambers 102 and 103 is sucked and discharged from the ports 109 and 110 to exhaust the inside. In this case, the chambers 102, 10
The inside of 3 is increased to a positive pressure with steam, and steam is once introduced between the prefoamed beads through the vent holes 105 and 106.
(B) is a two-sided exhaust process, in which the upper utility ports 107 and 108 are closed, and if the inside of the mold is depressurized by continuing the suction decompression operation, the air existing in the space between the pre-expanded beads is also reduced. It is sucked and discharged through ventilation holes 105 and 106 provided in the molds on both sides.

(C) is a one-side preheating step, in which the lower opening 10 is used.
9 and 110 are closed, and steam is supplied for a short time from the upper utility port 108 on the side of one chamber 103 which has been reduced in pressure. In this case, the supplied steam permeates through the vent hole 106 of the mold 101, the pre-expanded beads in the molding space 104, the vent hole 105 of the mold 100 in order, and flows into the opposite chamber 102. Thus, the entire prefoamed beads and each part of the molds 100 and 101 are preheated.
(D) is a one-sided preheating step in which the flow direction of the steam is reversed,
The same operation is performed from the chamber 102 side to form the molding space 10.
4 while completely eliminating the air inside.
Preheating is performed while minimizing the partial temperature difference between 00 and 101 as much as possible.

(E) is a fusion heating step, in which fusion heating steam is supplied to both chambers 102 and 103 to heat the molding dies 100 and 101 and to pass through the respective molding dies 100 and 101. The pre-foamed beads are also heated through the pores 105 and 106 to complete foaming and fuse with each other to form a foam molded article.

[0008]

As described above, the molding die 1
Vent holes 105, 106 formed in 00, 101
Plays an important role as a passage for discharging air between the pre-expanded beads or a passage for supplying heated steam, etc., in order to obtain a homogeneous foamed molded article. Be recognized. (1) In order to compensate for the decrease in strength of the mold due to the provision of a large number of air holes in the mold, it is necessary to set the thickness of the mold made of the aluminum alloy mold material to, for example, 8 to 12 mm. With this configuration, the heat capacity of the mold increases, and the thermal efficiency of heating and cooling decreases,
Since the rate of temperature decrease is slow, there is a problem that control accuracy is lowered.

(2) In a general pair of molds, 20
Since the number of ventilation holes is from 00 to 4000, the drilling work is complicated and the processing cost is high. In addition, since the core vent is manually attached to the mounting hole formed in the molding die, the work is complicated. Yes, and damage to the mold surface is unavoidable, requiring extra rework.

(3) Clogging of scale or the like occurs in the vents such as the core vent and the core vent hole, resulting in poor heating, poor mold release, and poor cooling. Therefore, replacement of the core vent or periodic cleaning with high-pressure cleaning water is performed. Maintenance work such as is required. (4) Since traces of air holes are formed on the surface of the foamed molded product, it becomes a factor of deteriorating the beauty of the appearance of the molded product, and when printing is performed on the outer surface, the trace of the vent hole becomes a hindrance. Cannot be printed neatly. (5) After the molding, the cooling water is sprayed into the chamber to cool the foamed molded product, so that moisture penetrates into the molding space through the air holes and contains about 6 to 10% of the water inside the molded product. A drying step was required. In addition, since the cooling water comes into direct contact with the molded product, it is necessary to manage the cooling water in a clean state in order to obtain a hygienic molded product.

(6) Since the pre-expanded beads are heated under the same heating conditions by passing steam from the chamber into the molding space and foamed and fused, the molded article obtained in this manner (hereinafter, referred to as “below”).
In this case, the surface property changes depending on the fusion ratio of the beads. Specifically, the lower the fusion rate, the worse the surface properties, and the higher the fusion rate, the better the surface properties. On the other hand, the higher the fusion ratio of beads in an isothermally molded product, the higher the physical properties such as the mechanical strength of the molded product are improved, but the heating, foam fusion time and cooling time are longer, and the molding cycle time is longer. There is a problem that the overall length becomes longer and the productivity decreases.

In view of the above, according to the above-mentioned molding technique, the fusion ratio of beads in a molded product is reduced by, for example, 40%.
It is set to ~ 80% to improve the surface properties and secure the beauty of the appearance, and to ensure the mechanical strength by sufficiently securing the fusion rate, but the demand for the mechanical strength is low. Even in a molded product, it is necessary to set the fusion rate to a certain high level in order to secure the beautiful appearance, and there is a problem that the molding cycle time becomes longer and the productivity decreases. In addition, the fusion rate used here is obtained by evaluating the state of the beads at the fractured surface of a molded product by cracking the molded product, and specifically, along the surface of the beads without damaging the beads themselves. What was determined by measuring the percentage of broken beads assuming that the beads themselves were not fused, assuming that the beads themselves were damaged and cracked were fused, and measuring the percentage of those where the beads themselves were broken It is.

As described above, in the foam molding method, a working fluid such as steam or air is supplied into the molding space by utilizing a vent such as a core vent or a core vent hole.
Alternatively, it is configured to obtain a foam molded product by discharging from the molding space. However, since the vent holes are provided, the above-mentioned many problems have actually occurred.

In order to fundamentally solve these problems, the present inventors have earnestly studied the practical use of a foam molding method using a mold having no air holes, and conducted various tests. Although the vent hole is eliminated from the mold, a core vent or a passage instead of the core vent hole for supplying or discharging a working fluid such as steam or air to the molding space is essential. The problem is how and where the fluid is formed, and the problems that need to be solved, such as when to supply the working fluid to such a passage and under what conditions. Are piled up.

SUMMARY OF THE INVENTION It is an object of the present invention to provide in-mold foam molding of a polyolefin-based resin capable of improving the aesthetic appearance of a molded article, adjusting the fusion rate inside the molded article, and achieving both productivity and commercial value. It is to provide a method and a molded article.

[0016]

According to a first aspect of the present invention, there is provided a method for in-mold foam molding of a polyolefin resin, comprising: a vent for forming a core vent and a core vent hole; Using an in-mold foam molding apparatus equipped with a core mold and a cavity mold having no cell, a cell diameter of 100 to 900 μm, an expansion ratio of 5 to 60 times, and DSC
Filling the molding space with pre-expanded beads made of a polyolefin resin having a 2'nd peak ratio of 8 to 60% and a closed cell ratio of 65% or more, and then heating and fusing the filled pre-expanded beads with steam. It is.

In this molding method, an in-mold foam molding apparatus having a core mold and a cavity mold which does not have a vent in a molding portion for molding a conspicuous place on the outer surface of the molded product is used. The traces of the vent holes to be formed are arranged in a place where the surface of the molded product is inconspicuous, and the beauty of the surface of the molded product can be improved. Also, in this molding method, the vent holes are completely or almost completely eliminated, and the working fluid is individually supplied to the rear chamber of the core mold, the rear chamber of the cavity mold, and the molding space. It is also possible to control. In this case, for example, by controlling steam as a working fluid and independently adjusting the heating conditions of each space, the steam supplied to both chambers allows the core mold of the pre-expanded beads filled in the molding space and The surface properties in contact with the cavity mold can be adjusted respectively, and the pre-expanded beads filled in the molding space are heated and foam-fused by the steam supplied to the molding space, and the pre-expanded beads are fused independently of the surface properties. It is possible to adjust the arrival rate. For this reason, it is possible to produce a molded product with a beautiful surface while keeping the fusion rate inside the molded product low, shortening the molding cycle time, and achieving both productivity and commercial value. Become.

Further, since the pre-expanded beads made of the polyolefin resin are used, it is possible to sufficiently ensure the filling of the molding space with the pre-expanded beads.
That is, in the present molding method, in order to accurately control the working fluid in both chambers and the molding space, it is most preferable not to provide a ventilation hole in the molding die. Disturbance is likely to occur in the flow of the filling air, and there is a concern that the filling property of the pre-expanded beads may decrease.However, the pre-expanded beads made of polyolefin resin are soft in material itself and have high gas permeability. Since the particle shape is much more easily deformed than the pre-expanded beads made of a polystyrene resin having the same expansion ratio and contributes to the improvement of the filling property, a decrease in the overall filling property can be effectively prevented.

Further, as pre-expanded beads, the cell diameter is 1
00 to 900 µm, expansion ratio 5 to 60 times, DSC 2 '
Since the one having an nd peak ratio of 8 to 60% and a closed cell ratio of 65% or more is used, the surface property of the molded article can be improved as described below, and the appearance of the molded article can be improved. The restriction on the heating conditions can be relaxed, and the formability and energy saving can be improved. If the cell diameter is less than 100 μm, there is a problem that the surface elongation is poor during molding, the sink is easy to sink, and the appearance of the surface appearance is inferior. If the cell diameter exceeds 900 μm, the cell diameter tends to be non-uniform, Is large, there is a problem that the texture of the surface is rough and the surface appearance is inferior. The expansion ratio is not particularly limited, but is preferably about 5 to 60 times (bulk ratio of expanded beads).

The DSC 2'nd peak ratio is 8% to 60%
It is preferable to set The DSC 2'nd peak ratio is defined as the two DSCs formed on the low-temperature side and the high-temperature side, which are formed due to the crystal melting point of the base resin when the base resin is heated.
(Differential scanning calorimetry) is the ratio of the area of the peak on the high temperature side to the total area of the peaks. When the DSC 2'nd peak ratio is less than 8%, the heating condition width during molding is narrow, and Easy to shrink and sink. On the other hand, if it exceeds 60%, it is necessary to greatly increase the heating conditions, it is necessary to increase the size of the molding machine, and it becomes negative from the viewpoint of energy saving. Therefore, it is preferably set to 8 to 60%.

When the closed cell rate is less than 65%, even if the heating pressure during molding is increased to somehow fuse the beads, shrinkage and sink of the molded body are likely to increase.
Since it becomes difficult to obtain a molded body of the target quality, it is preferable to set the ratio to 65% or more.

The method of filling the pre-expanded beads may be a crack filling method, a pressure filling method, or the like.
Any of the compression filling methods can be employed. In particular, when the filling is performed by the pressure filling method or the compression filling method, it is preferable because the filling density at the bottom of the molded article does not become high unlike the cracking filling method.

The vent may be omitted completely from the core mold and the cavity mold. In this case, the heating conditions for the three chambers of the core mold rear chamber, the cavity mold rear chamber, and the molding space can be set more strictly, and a beautiful surface without traces of vent holes can be set. Is preferable since a molded article of the formula (1) can be obtained. Moreover, since there is no vent hole, it is possible to prevent the cooling water sprayed into both chambers from contacting the molded product during cooling, and to prevent an increase in the moisture content of the molded product due to the contact with the cooling water. In addition, since the cooling water does not directly contact the molded product, it is possible to obtain a sanitary molded product without having to control the cooling water to a clean state.

According to a fourth aspect of the present invention, an inorganic gas of 0.3 to 2.0 kg / cm ² is press-fitted into the pre-expanded beads and filled into the molding space. That is,
Since the polyolefin resin has a lower foaming power than the polystyrene resin and the pre-expanded beads do not sufficiently expand, the foaming power is increased by the inorganic gas press-fitted into the pre-expanded beads by configuring as described in claim 4. It is possible to improve the quality of the molded article by increasing the quality.

The in-mold foam molded product according to claim 5 is made of a polyolefin resin and has a cell diameter of 100 to 900 μm.
m, foaming ratio is 5 to 60 times, DSC 2'nd peak ratio is 8 to 60%, and molded using pre-expanded beads having a closed cell ratio of 65% or more, and has a beautiful surface without traces of core vents and core vent holes. Things.

Such a molded product having a beautiful surface without any trace of the core vent and the core vent hole is preferable because it enables a beautiful printing on the outer surface. Further, as pre-expanded beads, the cell diameter is 100 to 900 μm, and the expansion ratio is 5 to 60.
Since the DSC 2'nd peak ratio is 8 to 60% and the closed cell ratio is 65% or more, the surface property of the molded article is improved and the appearance of the molded article is improved as in claim 1. And the restriction on the heating conditions at the time of molding can be relaxed, so that moldability and energy saving can be improved. Such a molded product can be easily manufactured by the molding method according to any one of claims 1 to 4.

[0027] The molded article according to claim 6 is an isothermally molded article having an internal fusion ratio obtained by heating the surface and the interior under the same heating conditions, and having the same surface property. It is lower than the molded product. Since such a molded article has a lower internal fusion rate than an isothermally molded article having the same surface properties, heating during molding, foam fusion time and cooling time can be reduced, and Cycle time can be shortened and productivity can be improved. Further, the surface property can be sufficiently secured while lowering the internal fusion rate, and the commercial value does not decrease, so that it is possible to achieve both productivity and commercial value.

[0028] The molded article according to claim 7 is an isothermal molded article having an internal fusion ratio obtained by heating the surface and the interior under the same heating conditions, wherein the surface properties are set to be the same. Higher than molded products. Since such a molded product has a higher internal fusion rate than an isothermally molded product having the same surface property set, the mechanical strength of the molded product is increased, and the surface property of the molded product is not required so much. Ideal when only strength is required. In other words, such a molded product has a higher internal fusion rate than an isothermally molded product having the same surface properties, and therefore has a higher mechanical strength. Moreover,
As described above, in the case where the working fluid is individually controlled and molded in the chamber on the back side of the core mold, the chamber on the back side of the cavity mold, and the molding space, the cavity mold is used in the heating step. Since only the heating steam pressure needs to be increased only in the molding space formed by the core mold, the amount of steam used is smaller than in the case of molding an isothermally molded product, and energy saving can be achieved.

As specific examples of the polyolefin resin constituting the pre-expanded beads, polypropylene resin as described in claim 8 and polyethylene resin as described in claim 9 can be obtained at low cost and easily. It can be suitably used.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the in-mold foam molding apparatus 1 is formed by a core mold 2 and a cavity mold 3 as a pair of molding dies opposed to each other, and a core mold 2 and a cavity mold 3. Bead filling means for filling the pre-expanded beads 5 with the flow of air in the molding space 4, pressure reducing means for reducing the pressure in the molding space 4, and compressed air supply means for supplying compressed air into the molding space 4. And steam supply means for heating the pre-expanded beads 5 filled in the molding space 4 with steam to foam and fuse them.

As a material of the pre-expanded beads 5, a polyolefin resin such as a polyethylene resin or a polypropylene resin is used. Specifically, ethylene propylene random polypropylene resin, ethylene propylene block polypropylene resin, homopolypropylene ethylene propylene butene random terpolymer, linear low-density polyethylene (LLDPE), cross-linked low-density polyethylene (cross-linked LDPE), and the like can be suitably used. . The pre-expanded beads of such a polyolefin resin have a soft material itself and high gas permeability,
Since the particle shape is much easier to deform than pre-expanded beads made of a polystyrene resin having the same expansion ratio, it is particularly preferable in that the effect of improving the filling property is exhibited.

If the cell diameter of the pre-expanded beads is less than 100 μm, there is a problem that the surface elongation is poor during molding, the sink is easy to occur, and the appearance of the surface appearance is inferior. There is a problem that the surface is coarse and the surface appearance is inferior because the cell diameter is large and the cell diameter is large. Therefore, it is in the range of 100 to 900 μm, more preferably 150 to 700 μm, and particularly preferably 170 to 5 μm.
It will be set to 50 μm. The expansion ratio is not particularly limited, but is preferably about 5 to 60 times (bulk ratio of expanded beads).

The DSC 2'nd peak ratio is 8% to 60%
It is preferable to set The DSC 2'nd peak ratio is defined as the two DSCs formed on the low-temperature side and the high-temperature side, which are formed due to the crystal melting point of the base resin when the base resin is heated.
(Differential scanning calorimetry) is the ratio of the area of the peak on the high temperature side to the total area of the peaks. When the DSC 2'nd peak ratio is less than 8%, the heating condition width during molding is narrow, and Easy to shrink and sink. On the other hand, if it exceeds 60%, it is necessary to greatly increase the heating conditions, it is necessary to increase the size of the molding machine, and it becomes negative from the viewpoint of energy saving, so it is 8 to 60%, more preferably 10 to 50%. %, Particularly preferably 15 to 40%.

When the closed cell ratio is less than 65%, even if the heating pressure at the time of molding is increased to somehow fuse the beads, shrinkage and sink of the molded body are likely to increase.
Since it becomes difficult to obtain a molded product of the target quality, it is 65% or more, more preferably 75% or more, and particularly preferably 85%.
The above is set.

The core mold 2 and the cavity mold 3 are respectively attached to a housing 12 having a frame-shaped frame 10 and a back plate 11, and a first chamber 13 and a second chamber 13 are provided on the back side of the core mold 2 and the cavity mold 3. 14 are formed respectively. Unlike the conventional molding apparatus, the core mold 2 and the cavity mold 3 do not have a vent such as a core vent or a core vent hole, and the molding space 4 and the chambers 13 and 14 are formed as independent spaces. Have been. However, it is most preferable that the molding space 4 and both chambers 13 and 14 be completely airtightly separated in this manner. However, when a small number of conventional vent holes communicating the molding space 4 and both chambers 13 and 14 are provided. However, those configured to control these spaces independently are within the scope of the present invention.

The first chamber 13 and the second chamber 14 are connected to the steam supply pipe 15 and the air supply pipe 16 via the utility valves SV1 and SV2 and the switching valves SWV1 and SWV2, respectively. The drain valve 17 and the pressure reducing pipe 18 provided with a vacuum pump 19 are connected via switching valves SWV3 and SWV4, respectively. The first and second chambers 13 and 14 are provided with nozzle units 21 each having a plurality of nozzles 20 for spraying cooling water onto the back surface of the core mold 2 and the cavity mold 3, respectively. Cooling water valves CV1, C
The cooling water supply pipe 22 is connected via V2.

The first characteristic configuration of the in-mold foam molding apparatus according to the present invention is that an opening in the molding space 4 is formed in a molding part of the core mold 2 and the cavity mold 3 which molds an inconspicuous part of a molded product. The first opening 30 is formed, and the first opening 30 is provided with a communication passage communicating with the external utility pipes 15 to 18, respectively, and the utility valves SV3 to SV6 and the drain valve DV are provided.
3. By operating the DV4 and the switching valves SWV1 to SWV4, a working fluid such as steam or compressed air can be supplied or discharged from the plurality of first openings 30 to the molding space 4 independently of the chambers 13 and 14. It is in the point configured as follows.

Basically, the first opening 30 is formed at or near the joint between the core mold 2 and the cavity mold 3, and is formed between the filling device 23 and the ejector pin 2.
4 and the like, which are formed in the vicinity of a portion exposed to the molding space 4 of an accessory part, and a combination of the two. First, the first opening 30 formed at or near the joint between the core mold 2 and the cavity mold 3 will be described by exemplifying three types.

(1) In-mold foam molding apparatus 1 of the first type
As shown in FIG. 1 and FIG. 2, slit-shaped first openings 30a and 30b opening to the molding space 4 are arranged along the joint portion between the core mold 2 and the cavity mold 3, and 1 Openings 30a, 30b and external utility pipe 15
, The inter-mold passages 31a, 3
1b and internal pipes 32a and 32b.
The core mold 2 and the cavity mold 3 are not provided with a ventilation hole as in the prior art.
Is airtightly isolated from both chambers 13 and 14,
External utility piping 15 to between core mold 2 and cavity mold 3
The first openings 30a and 30b communicating with the opening 18 are formed.

With this configuration, the pre-expanded beads 5
Can be performed in the following manner using the first openings 30a and 30b instead of the conventional ventilation holes. That is, in the preheating exhaust step, the first opening 30a or the first opening 30
b, the pressure inside the molding space 4 is reduced by evacuation and the pressure is directly reduced.
Similarly, the preheating steam may be directly supplied. In the fusion heating step, the first opening 30a or the first opening 3
It is only necessary to directly supply the vapor at the fusion temperature from 0b to the pre-expanded beads 5 in the molding space 4. In this case, in order to prevent clogging of the pre-expanded beads 5 with respect to the first openings 30a, 30b, the opening width of the first openings 30a, 30b on the molding space 4 side should be adjusted to the outer diameter of the pre-expanded beads 5 to be filled. In order to reduce the occurrence of protrusions and burrs and to improve the finish of the foamed molded product, it is necessary to reduce the opening width as much as possible. Although it is preferable, if the opening width is reduced, the passage resistance of the utility fluid increases, so the opening width is 0.1 to
It is appropriate to set to 1.5 mm.

In the present invention, the first opening 3
It is appropriate that Oa and 30b are provided along the valley portion of the concave portion at the joint between the core mold 2 and the cavity mold 3. In this case, since the slit-shaped first openings 30a and 30b correspond to the convex ridges on the outer periphery of the foamed molded product, the appearance is hardly impaired even if a slight burr remains. Further, as the internal pipes 32a and 32b, 4
It is appropriate to use a copper pipe of 〜15 mmφ. In FIG. 1, a series of communication passages including the first opening 30a, the inter-model passage 31a, and the internal pipe 32a are connected to the first opening 30a.
Although two combinations of b, a series of passages consisting of an inter-mold passage 31b and an internal pipe 32b are shown, the present invention is not limited to this form, and the shape of the obtained foamed molded product, Depending on the size, a combination of three or more is also possible, and it is also possible to carry out a single unit.

When a plurality of the first openings 30 are provided, for example, when a pair of first openings 30a and 30b are provided, as shown in FIG. It is preferable that the molds 2 and 3 are arranged to face each other at the joint between the molding dies 2 and 3 located on opposite sides of the opposite ends. Although the length of the first openings 30a and 30b is not particularly limited,
This makes it possible to employ a utility operation in which utility fluid such as steam can be supplied from one first opening through the molding space 4 toward the other first opening. In particular, it is preferable because advantages such as an operation of replacing air between the pre-expanded beads 5 filled in the molding space 4 with steam and a heating operation of the pre-expanded beads 5 can be obtained quickly. .

The advantages of the first type are summarized as follows. [1] Since the conventional ventilation holes can be removed from the molds 2 and 3, there is no danger of a decrease in strength, and the conventional thickness 8
The thickness of an aluminum alloy mold material of １２12 mm can be reduced to a thickness of 4 to 8 mm. As a result, the heat capacity is reduced, the heat efficiency of heating and cooling is improved, the accuracy of temperature control is improved, and the material cost can be reduced. [2] Drilling of vents and installation of the core vent itself are not required, so that the processing cost can be greatly reduced, and the manufacturing costs of the molds 2 and 3 can be reduced.

[3] In addition, there is no heating failure, mold release failure, or cooling failure due to clogging, and no maintenance work such as replacement of core vents or periodic cleaning with high-pressure cleaning water is required. [4] Since no core vents or traces of core vent holes are left on the surface of the product, the appearance quality is improved, and obstacles to processes such as surface printing and sticking of seal labels are eliminated. [5] Since the cooling water used in the cooling step does not enter the molding space, the moisture of the molded article is reduced from about 6 to 10% of the conventional one to about 0.5 to 4%, so that the drying step is unnecessary. Which greatly contributes to shortening the cycle time.

[6] The greatest advantage of the present invention is that utility operations that could not be realized with a conventional mold can be performed. Conventionally, in order to cause a utility fluid such as steam to act on the pre-expanded beads, the utility fluid supplied from the utility pipe acts on one of the chambers and then passes through the vent hole. In the present invention, the chambers 13 and 14 and the utility passage of the molding space 4 are separated and independent from each other.
Utility fluids such as steam, decompressed air, and cooling water act directly in the molding space 4 through the first openings 30a and 30b, thereby increasing the degree of freedom of utility operations.

For example, when it is desired to reduce the pressure in the molding space 4, in the conventional molding die, it is necessary to reduce the pressure in both chambers. However, in the present invention, the molding volume which is 1/10 of the chamber volume is required. The decompression operation can be performed only on the space 4. Therefore, conventionally, since the response is quickly performed, advantages such as operability are greatly improved.

Further, since the chambers 13 and 14 are formed in a space independent of the molding space 4 and the respective heating conditions can be adjusted independently, a set of molding dies is supplied by steam supplied to the two chambers 13 and 14. The surface temperature of the molded article closely contacting the molds 2 and 3 can be adjusted by independently adjusting the temperatures of the molds 2 and 3, and the preliminary foaming filled in the mold space 4 by the steam supplied to the mold space 4. The beads 5 are heated and foamed and fused, so that the fusion rate of the pre-foamed beads 5 can be adjusted independently of the surface properties. For this reason, the fusion rate inside the molded product is kept low, and the molding cycle time is shortened.
It is possible to produce a molded product with a beautiful surface, and it is possible to achieve both productivity and commercial value.

(2) In-mold foam molding apparatus 1 of the second type
A is a slit-shaped first opening 30 as shown in FIG.
a, 30b are communication passages communicating with the external utility pipes 15-18, and are inter-mold passages formed along the joints of the molding dies 2, 3 from the molding space 4 side to the outside when the dies are closed. 33a, 33b and inter-mold spaces 34a, 34 formed in a state of being surrounded by joints between the frame-shaped frames 10.
b. Other configurations are the same as those of the in-mold foam molding apparatus 1, and therefore the same members are denoted by the same reference numerals and detailed description thereof will be omitted.

In other words, in the in-mold foam molding apparatus 1A, the molds 2 and 3 are not provided with the ventilation holes as in the prior art, and when the mold is closed, the molding space 4 is in the two chambers 13 and 14. The first openings 30a, 30b and the communication passages communicating the first openings 30a, 30b with the utility pipes 15 to 18, that is, the inter-model passages 33a, 33b. And inter-model space 34
a and 34b are the in-mold foam molding apparatuses 1 of the first type.
In the form different from the above, the two molding dies 2, 3 from the molding space 4 side
And it is formed toward the outside along the seam of the frame-shaped frame 10.

In the foam molding apparatus 1A shown in FIG. 3, the working fluid can be operated at the time of foam molding, similarly to the in-mold foam molding apparatus 1, so that all the advantages [1] to [6] described above can be obtained. In addition, since there is no need for the independent internal pipes 32a and 32b which require piping work at the time of production, the production cost of the foam molding apparatus is suppressed, and the advantage that maintenance is not required is obtained.

(3) In-mold foam molding apparatus 1 of the third type
B, as shown in FIGS. 4 and 5, first openings 30 c and 30 d that open into the molding space 4 are formed in the core mold 2 near the joint between the core mold 2 and the cavity mold 3, A communication path formed by a passage forming member 38 fixed inside the core mold 2 so as to surround the first openings 30c, 30d as a communication path communicating the 1 openings 30c, 30d with the external utility pipes 15-18. The spaces 39a and 39b and the communication space 39
a, 39b, and internal piping 40a, 40b that communicates with external utility piping 15-18, and communication spaces 39a, 39b.
And the first opening 30 via the internal pipes 40a and 40b.
It is configured such that utility fluid can be individually supplied or discharged to c and 30d. Other configurations are the same as those of the in-mold foam molding apparatus 1, and therefore the same members are denoted by the same reference numerals and detailed description thereof will be omitted.

That is, in the in-mold foam molding apparatus 1B, the molds 2 and 3 are not provided with vent holes for communicating the molding space 4 with the chambers 12 and 13 as in the prior art.
When the mold is closed, the molding space 4 is
The first openings 30c and 30d and the first openings 3
0c, 30d communicates with utility pipes 15-18,
That is, the communication spaces 39a and 39b and the internal pipes 40a and 4a
0b is formed in a different form from the previous two cases.

The first openings 30c and 30d may be formed with through holes or slits directly in the core mold 2. However, since it is considered that the inner surface is worn by the flow of steam, it is difficult to use the conventional molding method. Like the device, the first openings 30c, 30c
It is preferable to form a core vent attachment hole corresponding to d, and attach the core vent detachably.

In the foam molding apparatus 1B shown in FIGS. 4 and 5, the working fluid can be operated at the time of foam molding, similarly to the in-mold foam molding apparatus 1, so that the advantages of [5] and [6] described above are obtained. You can enjoy. Further, the molding space 4 and the communication spaces 39a, 39b
As described above, a core vent communicating with
Although the advantages of [1] to [4] are somewhat disadvantageous, the number of core vents is significantly reduced because core vents and core vent holes are not formed uniformly over the entire surface of the mold as in the past. It is possible to reduce it. In addition, since the first openings 30c and 30d can be easily abraded by steam, the design becomes more realistic. In this third type of foam molding apparatus 1B, as in the case of the second type of foam molding apparatus 1A, an inter-model space is formed between the joints of the left and right frame-shaped frames 10, and the internal piping 32a, 32b is formed.
May be omitted. In the example shown in FIG. 4, the first openings 30c and 30d are formed on the core mold 2 side. However, when the inner surface side (core mold 2 side) of the molded product is exposed to the outside, the first openings 30c and 30d are formed. It is preferable to form 30c and 30d on the cavity mold 3 side in order to improve the beauty of the molded product.

Next, the case where the first opening 30 is formed in the vicinity of accessory parts such as the filling device 23 and the ejector pin 24 will be described. When the first opening 30 is formed in the vicinity of the accessory, as shown in FIGS. 1, 3, and 4, a substantially cylindrical shape is formed at a position corresponding to the filler 23 and the ejector pin 24 in the cavity mold 3. Is fixed, and the filling device 2 is fixed.
3 and the ejector pins 24 are provided inside the exterior member 41 so as to fit inside the exterior member 41.
A communication passage 42 that individually communicates with the utility pipes 15 to 18 therebetween;
43, and the molding space 4 is formed at the tip of the communication passages 42, 43.
First openings 30e, 30f are formed respectively, and utility pipes 15-18 are connected to the communication passages 42, 43 via utility valves SV5, SV6, respectively, and the first openings 30a-30d are formed.
In the same manner as in the case (1), required steam, pressurized air is supplied, or a pressure reducing operation is performed. In this case, the first openings 30a to 30d are not provided, and the first openings 30e and 3d are not provided.
Although it is possible to achieve the object of the present invention even in a form in which 0f is provided independently, the first openings 30a to 30
It is preferable to use a configuration in which d is provided.

As described above, the first openings 30e and 30f disposed near the tips of the filler 23 and the ejector pins 24 are provided.
And the first openings 30a to 30d described above are shown in FIG.
As shown in FIG. 3 and FIG.
An individual passage communicating from 0 to the external utility pipes 15 to 18 may be provided. In this case, the first openings 30 capable of supplying the utility fluid are provided at at least three places of the opposite end portions of the molding space 4 and the central portion of the molding space 4, and thus the utility openings according to the quality requirements are provided. Fluid can be supplied, and the degree of freedom of control operations, such as supply and stoppage of utility fluid, is increased. Therefore, there is an advantage that the optimal utility operation corresponding to the type and shape of the foam molded article can be performed. .

However, in the examples shown in FIGS. 1, 3 and 4, the first openings 30e and 30f are provided near the tip of the filling device 23 and the ejector pin 24. The invention is not limited thereto, and it is also possible to use other accessories attached to the mold, for example, cooling water pipe fittings. Further, if the structure is such that the steam is uniformly distributed to the entire pre-expanded beads 5 in the molding space 4, it is necessary to form the communication passages 42 and 43 outside all the fillers 23 and the ejector pins 24. Alternatively, one or both of the first openings 30e and 30f can be omitted, and the first openings 30e and 30f are appropriately provided according to the shape of a molded product to be molded.
Also, the first openings 30a to 30d are connected to the first openings 30e,
It may be used as an opening exclusively for discharging steam supplied from 30f to the molding space 4. In FIGS. 1, 3 and 4, the filling device 23 and the ejector pin 24 are formed on the cavity mold 3 side.
When the side) is exposed to the outside, it is preferable to form the filler 23 and the ejector pin 24 on the core mold 2 side in order to improve the beauty of the molded product.

A second feature of the in-mold foam molding apparatus according to the present invention is that a second opening 50 is provided in the molding dies 2 and 3 at a portion where the flow of the utility fluid is uneven in the molding space 4. ,
A communication path for communicating the second opening 50 with the external utility pipes 15 to 18 is provided so that the utility fluid can be supplied or discharged. As shown in FIGS. 6 to 8, for example, as shown in FIGS. 6 to 8, the portion where the flow of the utility fluid becomes uneven is the depth of the bag-shaped recesses 51 and 52 when the bag-shaped recesses 51 and 52 are formed in the molds 2 and 3. A part or a central part of the molds 2 and 3 as shown in FIG. 8 may be considered, but other parts may be used.

The second opening 50 may be in the form of a point similar to a conventional core vent or a slit having a certain length, but in any case, the pre-expanded beads 5 may be used. In order to prevent the opening from being clogged, it is necessary to set the opening width on the molding space 4 side to be equal to or less than the outer diameter of the pre-expanded beads 5 to be filled.

(1) When the second openings 50 are formed in the bag-shaped concave portions 51 and 52, as in the in-mold foam molding apparatus 1C shown in FIG. Second openings 50a and 50b are formed, and the second openings 50a are formed.
Is connected to the internal pipe 32a via the internal pipe 53, and the second opening 50b is connected to the utility pipes 15 to 18 via the independent internal pipe 54 and the utility valve SV7. However, if the second openings 50a and 50b are finally communicated with the utility pipes 15 to 18, the internal pipe 32
a, 32b, or may be communicated with the utility pipes 15-18 without passing through.

As described above, in the molding space 4, the inner ends of the bag-shaped recesses 51 and 52 where the flow of the utility fluid becomes uneven are individually connected to the external utility pipes 15 to 18 respectively. Since the two openings 50a and 50b are formed, the supply of steam, the supply of compressed air, the exhaust for vacuum decompression, or the evacuation for vacuum reduction is performed as necessary in the molding space 4 through the second openings 50a and 50b. Utility operations such as pressure adjustment and drainage in the molding space 4 can be performed individually as in the case of the first openings 30a and 30b, thereby eliminating the unevenness of the utility fluid. It is possible to do.

In such an in-mold foam molding apparatus 1C, as can be easily understood from the configuration, after filling the pre-expanded beads 5 into the molding space 4, the pre-expanded beads 5 are evacuated and then heated with heating steam. Then, in the foam molding method of foaming, fusing, cooling and solidifying, and taking out as a foam molded body made of a predetermined foamed synthetic resin or the like, the first openings 30a, 30b and the second Using the openings 50a and 50b, it is possible to perform the operation as described below.

For example, when depressurizing and evacuating, the inside of the molding space 4 is directly depressurized by depressurizing and evacuating from one or both of the first openings 30a and 30b, and then preheating steam may be directly supplied. At this time, if necessary, the second
Using the openings 50a and 50b, the bag-shaped concave portions 51 and 52 are used.
In this case, the non-uniformity of the utility fluid may be eliminated.

Also, when heating and fusing, the first
The fusion temperature steam may be supplied directly from one or both of the openings 30a, 30b to the pre-expanded beads 5 in the chamber 4, and similarly, the bag is formed using the second openings 50a, 50b. Supplying steam to the concave portions 51 and 52,
This portion where heat is difficult to reach by the steam from the first openings 30a and 30b can be heated. In this case, if necessary, it is needless to say that required steam can be supplied from the chambers 13 and 14 to heat the entire molds 2 and 3 from the back.

When the second openings 50a and 50b are formed in the foam molding apparatus 1A shown in FIG. 3, for example, as in the in-mold foam molding apparatus 1D shown in FIG. An internal pipe 55 that communicates the space 50a with the space 34a is provided. However, at least one of the internal pipes 55 may be individually connected to the utility pipes 15 to 18 via a utility valve (not shown).

In this embodiment, in addition to the above-mentioned advantages, the inter-mold passage 33 which is a part of the molds 2 and 3 having a relatively large heat capacity during heating or cooling during foam molding.
Since the peripheral portions a, 33b and the spaces between the mold spaces 34a, 34b can be efficiently heated or cooled, a remarkable advantage that the molding operation time can be shortened is also obtained.

(2) In order to prevent non-uniform distribution of the working fluid in the center of the molding dies 2, 3, the distribution becomes non-uniform as in the in-mold foam molding apparatus 1E shown in FIG. A second opening 50c is formed in the portion to communicate with the inter-mold spaces 34a and 34b via the internal piping 56,
a, 32b, or a utility valve is interposed to communicate with the utility pipes 15-18.

The uneven distribution of the utility fluid is caused by the gap between the openings 30, 50 for supplying or discharging the utility fluid.
0 mm or more, it is easy to occur.
As shown in FIG. 5, a pair of first openings 30a and 30b is provided at positions of outer peripheral ends opposed to each other with the molding space 4 interposed therebetween, and a facing interval between the first openings 30a and 30b is 100 mm or more. Next, as shown in FIG. 8, the first openings 30a, 30
It is conceivable to form the second opening 50c at an intermediate position of b. Further, it is preferable to form the second opening 50 so that the distance between the first opening 30 and the second opening 50 and the distance between the second openings 50 are 100 mm or less.

According to this embodiment, since the pair of first openings 30a and 30b are opposed to each other with the molding space 4 interposed therebetween, one of the first openings passes through the molding space and the other first opening 30a, 30b. A utility operation capable of supplying a utility fluid such as steam toward the opening can be employed.
This is preferable because advantages such as an operation of replacing the air between the pre-expanded beads 5 filled therein with steam and a heating operation of the pre-expanded beads 5 can be obtained quickly.

Further, since a required number of the second openings 50 are provided at intervals of a maximum of 100 mm, the flow of the utility fluid is prevented so that the flow of the utility fluid in the molding space 4 is not biased or the speed is not uniform. There is an advantage that can be supplemented to be smooth. For this reason, the central flat portion of the molding space 4 has a shape having a long length for the thickness, for example, a length / thickness ratio of 20.
Even in the case described above, unevenness in density and unevenness in foaming at the central flat portion can be suppressed.

Next, a method of molding a molded article using the foam molding apparatus 1 shown in FIG. 1 will be described. The molding method is
A forming step of injecting the inorganic gas into the pre-expanded beads 5, a filling step of filling the pre-expanded beads 5 into which the inorganic gas is injected into the molding space 4, and heating and foaming the pre-expanded beads 5 filled in the forming space 4 It is divided into four steps: a heating step for fusing and a cooling step for cooling the molded article.

First, the pre-expanded beads 5 were filled in a compounding tank (not shown) and heated at 80 ° C. to 3.0 kg / cm ^2.
About 8 hours or 8.0kg under an inorganic gas atmosphere
/ Cm ² for about 3 hours and press-fit the inorganic gas into the pre-expanded beads 5. However, the inorganic gas injection operation may be performed under heating as described above, or may be performed at room temperature for a long time. By the above operation, 0.3 to 2.0 kg / cm ² of inorganic gas is injected into the pre-expanded beads. In other words, the pre-expanded beads used in the present invention are made of a polyolefin-based resin, and generally have a lower foaming power than a polystyrene-based resin. It is conceivable that the quality of the molded product is deteriorated, for example, the adhesion is reduced, the gap between the beads is increased, and the appearance is reduced. For this reason, it is preferable to press-fit an inorganic gas into the pre-foamed beads 5 in advance to increase the foaming power. However, this forming step can be omitted depending on the resin used.

Next, the filling step of the pre-expanded beads 5 will be described. In this step, the core mold 2 and the cavity mold 3
While closing the mold, the drain valves DV3 and DV4 are opened, and the pre-foamed beads 5 are supplied from the filling device 23 to the molding space 4 along with the flow of air, and the air supplied into the molding space 4 is discharged. (1) The pre-expanded beads 5 are discharged out of the molding space 4 through the openings 30a and 30b,
Fill. Note that, as the pre-expanded beads 5, it is possible to use beads to which foaming power is added by injecting air at a pressure higher than the atmospheric pressure into the beads before molding, so-called beads containing beads.

As a specific filling method, a cracking filling method, a pressure filling method, a compression filling method, and the like as described below can be employed. [1] In the cracking filling method, the core mold 2 and the cavity mold 3 are not completely closed at the time of filling (cracking).
For example, the pre-expanded beads 5 are filled while leaving only 10% of the bottom wall thickness of the molded product and discharging the air used for filling from the gap between the core mold 2 and the cavity mold 3. [2] In the pressure filling method, the inside of the raw material tank containing the pre-expanded beads 5 is pressurized to about 0.2 to 1.5 kg / cm ² , and the molding space 4 is opened to the atmospheric pressure. The pre-expanded beads 5 are conveyed and filled in the molding space 4 by utilizing the pressure difference between the preform beads 4 and the molding space 4. [3] In the compression filling method, the pressure p in the raw material tank is increased to about 1.0 to 5.0 kg / cm ^2, which is higher than in the pressure filling method, and the pressure difference (p) from the internal pressure p1 of the molding space 4 is increased. -P1) is changed to transport and fill the pre-expanded beads 5.

Next, the step of heating the pre-expanded beads 5 filled in the molding space 4 with steam will be described. First,
With the drain valves DV1, DV2 open, the utility valve SV1,
By opening the SV2 and flowing steam into the chambers 31 and 32, the air in the chambers 31 and 32 is replaced with steam. However, this step may be performed in the filling step.

Next, while the drain valves DV1 and DV2 are closed and the utility valves SV1 and SV2 are controlled so that the insides of the chambers 31 and 32 have a predetermined vapor pressure, a predetermined heating is performed on the chambers 31 and 32. Steam is supplied only for a certain time, and the core mold 2 and the cavity mold 3 are heated.
In addition, the pre-expanded beads 5 which come into contact with the cavity mold 3 are foam-fused to form the surface of the molded article. On the other hand, a step for heating the pre-expanded beads 5 filled in the molding space 4 is performed in parallel, and this step is largely divided into three steps.

In the first step, the drain valve DV4 is opened and the drain valve DV3 is closed, and the utility valves SV3, SV5,
When the SV 6 is opened and the utility valve SV4 is closed, the steam between the pre-expanded beads 5 is replaced with steam by passing steam into the molding space 4. In the second step, contrary to the first step, the drain valve DV4 is closed, the drain valve DV3 is opened, the utility valve SV3 is closed, and the utility valves SV4, SV5, SV
6 is opened and the air between the pre-expanded beads 5 is replaced with steam by passing steam into the molding space 4. However, this second step may be omitted.

In the third step, while the drain valves DV3 and DV4 are closed and the utility valves SV3 to SV6 are controlled so that the inside of the molding space 4 has a predetermined vapor pressure, a predetermined heating is performed in the molding space 4. Steam is supplied only for a certain time, and the pre-expanded beads 5 are heated and foam-fused to form the inside of the molded article. As described above, the steam supplied to the chambers 31 and 32 and the steam supplied to the molding space 4 can independently heat the surface portion of the molded product and the inside of the molded product. It is possible to individually adjust the fusion rate inside the molded product.

In the next cooling step, the cooling water valves CV1, CV
2 is opened, cooling water is sprayed from the nozzle 24 toward the core mold 2 and the cavity mold 3, and the molded product in the molding space 4 is cooled through the core mold 2 and the cavity mold 3. Since the core mold 2 and the cavity mold 3 are not provided with vents such as a core vent and a core vent hole, the molded article is cooled without coming into contact with cooling water. For this reason, the moisture content of the molded product is only the steam drained in the molding space 4, and its amount is 1/5 to 1/1 as compared with the conventional molding method.
Can be set to 0. After cooling, the molds 2 and 3 are opened while supplying compressed air to the gas holes 45, the molded product is left on the cavity mold 3 side, and the molded product is removed from the mold using the ejector pins 24. Take out.

In this molding method, the heating of the surface of the molded article and the heating of the inside of the molded article can be performed independently in the heating step. For example, in a molded article with a low requirement for mechanical strength, sufficient surface properties can be ensured. At the same time, it is possible to shorten the molding cycle time by lowering the fusion rate inside the molded product, thereby achieving both commercial value and productivity.

The molded article thus formed has a beautiful surface without any trace of core vents and core vent holes on the outer surface. Moreover, regarding the surface properties, while setting the same as that of the isothermally molded article manufactured by the conventional molding technique, the internal fusion rate was set lower or higher than the isothermally molded article of the surface property. It becomes a molded product. In other words, in the conventional molding method, when the pre-expanded beads are heated and foamed and fused, the surface and the interior of the pre-expanded beads are heated under the same heating conditions. As shown in FIG. 9 (a), a gap is formed at the boundary between the beads 5A inside the molded article and the depression 7 is formed on the surface of the molded article. 9A and 9B, the gap 6 is formed at the boundary between the beads 5A inside the molded product as shown in FIG. At the boundary of the beads 5B on the surface of the molded product, almost no depression 7 is formed, and a beautiful molded product with a smooth surface can be realized. In addition, when the internal fusion rate is set to a low value, a molded product that requires high surface properties and does not require much mechanical strength, such as a decorative surface of a concrete surface, a container lid, or a heat insulating material. It can be suitably used as a product, and when the internal fusion rate is increased, surface properties are not so required, but molded products with high demands on mechanical strength and molded products that can withstand repeated use, such as various members for automobiles It can be suitably used as a molded product such as an open box. INDUSTRIAL APPLICABILITY The present invention is more effective and useful for a molded article having a relatively large and complicated shape than a molded article having a small and simple shape such as a cup noodle container. In particular, it is useful for a molded product having both a thick portion and a thin portion.

Next, an evaluation test of the molding method and a quality evaluation test of a molded product manufactured by the method will be described.
Using pre-expanded beads made of polypropylene, molding was performed under the heating conditions shown in Table 1, and the surface properties and the fusion rate inside the molded article were measured. However, the surface property is determined by the depression 7 shown in FIG.
Are evaluated according to five levels in accordance with the degree of appearance. The higher the numerical value, the less the degree of appearance of the dent 7 and the better the surface property. In addition, the fusion rate is obtained by evaluating the state of the beads at the fractured surface by cracking the molded product.Specifically, the one that is broken along the surface of the beads without damaging the beads themselves Assuming that the beads were not fused, the broken and cracked beads were regarded as fused, and the ratio of the broken and cracked beads was measured.

[0083]

[Table 1]

From these results, by controlling the heating condition of the chambers 13 and 14 and the heating condition of the molding space 4 by the steam from the first openings 30a and 30b, the surface properties of the molded product and the degree of fusion inside the molded product are controlled. Can be controlled individually. In the conventional molding method, only molded products having a quality corresponding to cases B and F in Table 1 could be produced. However, in the present invention, cases A to I in which the surface property and the fusion ratio were variously combined were used. A molded product can be manufactured, and the degree of freedom of molding is greatly expanded.

For example, as shown in cases D and G, it is possible to manufacture a molded product having a good surface property while reducing the internal fusion rate. Such a molded product has low mechanical strength due to a low internal fusion rate, but can reduce heating, foam fusion time and cooling time, and can improve productivity while maintaining good surface properties. Therefore, it can be suitably used as a molded product that does not require mechanical strength, such as a decorative surface decorative frame, a container lid, and a heat insulating material. In the case of producing such a molded product by a conventional molding method, if a surface property of evaluation 3 or more is a good product, a molding cycle time of 250 seconds or more is necessary as shown in Case F. However, in the molding method of the present invention, as seen in cases D, E, G, and H, 150 seconds, 220 seconds, 170 seconds, and 230 seconds.
Since each can be molded with a cycle time of seconds, productivity can be improved. In addition, since heating is not performed more than necessary,
Energy costs can also be reduced.

Further, as shown in Case C, a molded product having a slightly lower surface property can be manufactured while the internal fusion ratio is set high. Such a molded product has a high mechanical strength due to a high internal fusion rate, but can shorten the foam fusion time and the cooling time and also have the first openings 30a, 30a.
Since the steam pressure in b can be set low and the mechanical strength can be sufficiently increased, productivity can be improved and energy saving can be achieved. It can be suitably used as a molded product requiring strength. In the case of producing such a molded product by a conventional molding method, if the fusion rate is 80, a molding cycle time of 250 seconds or more is necessary as shown in Case F. According to the molding method of the present invention, as shown in Case C, molding can be performed with a cycle time of 240 seconds, so that productivity can be improved. Regarding the steam pressure in the chambers 13 and 14, Case F was 3.5 kg / cm ² , whereas Case C was 3.0 kg / cm ^2.
Since it can be set to m ² , it can be understood that the steam pressure in the chambers 13 and 14 can be lowered to reduce the energy cost.

[0087]

According to the in-mold foam molding method for a polyolefin resin according to the first aspect of the present invention, no vent hole is formed in a molding portion for molding a conspicuous place on the outer surface of the molded product. The traces of the pores are arranged at inconspicuous places on the surface of the molded product, and the beauty of the surface of the molded product can be improved. Moreover, since the vent holes are completely or almost completely eliminated, the working fluid can be individually controlled for the rear chamber of the core mold, the rear chamber of the cavity mold, and the molding space. By independently adjusting the heating conditions of these three spaces, it is possible to produce a molded product with a beautiful surface while shortening the molding cycle time by, for example, keeping the fusion rate inside the molded product low. Thus, it is possible to achieve both productivity and commercial value.
In addition, since pre-foamed beads made of polyolefin resin are used, the number of air holes formed in the mold is minimized or omitted altogether to improve the control accuracy of the working fluid in both chambers and the molding space. In addition, it is possible to effectively prevent a decrease in the filling property of the pre-expanded beads. Further, as pre-expanded beads, the cell diameter is 100 to 900 μm, the expansion ratio is 5 to 60 times, and the DSC 2′nd peak ratio is 8 to 60.
%, The closed cell rate is 65% or more, so that the surface properties of the molded article can be improved, the appearance of the appearance can be improved, and the restrictions on the heating conditions during molding can be relaxed. Efficiency and energy saving can be improved.

As described in the third aspect, when the ventilation holes are completely omitted from the core mold and the cavity mold, the heating of the three spaces consisting of the molding space and the chambers respectively formed on the back side of the core mold and the cavity mold. It is preferable because the conditions can be set more strictly and a molded product having a beautiful surface without traces of air holes can be obtained. In addition, since there is no vent hole, it is possible to prevent the cooling water sprayed into the chamber during cooling from coming into contact with the molded article, so that the moisture content of the molded article can be reduced and the hygiene management of the molded article can be easily performed.

As described in claim 4, 0.3 to 2.0 kg / cm ^{2 of} an inorganic gas is press-fitted into the pre-expanded beads and filled into the molding space. Even with the pre-expanded beads, the foaming power can be increased by press-fitting the inorganic gas, and the quality of the molded article can be improved.

According to the in-mold foam molded product according to claim 5,
Since the molded product has a beautiful surface without any traces of core vents and core vent holes, it is preferable because it is possible to print beautifully on the outer surface. Further, such a molded product can be easily manufactured by the molding method according to any one of claims 1 to 4. In addition, cell diameter, expansion ratio, DSC2'nd
By appropriately setting the properties of the pre-expanded beads such as the peak ratio and the closed cell ratio, the surface properties of the molded product can be improved, the appearance of the molded product can be improved, and restrictions on the heating conditions during molding can be relaxed. Therefore, moldability and energy saving can be improved.

As described in claim 6, when the internal fusion ratio is lower than that of a thermoformed product having the same surface properties, the heating, foaming fusion time and cooling time during molding can be shortened. Thus, the cycle time for molding can be shortened and the productivity can be improved. In addition, it is possible to sufficiently secure surface properties while lowering the internal fusion rate, and it is possible to achieve both productivity and commercial value without lowering the commercial value.

As described in claim 7, when the internal fusion ratio is higher than that of an isothermally molded product having the same surface property, the mechanical strength of the molded product is increased and the surface property of the molded product is increased. This is optimal when only the strength is required without requiring much. In other words, such a molded product has a higher internal fusion rate than an isothermally molded product having the same surface properties, and therefore has a higher mechanical strength. In addition, as described above, when the working fluid is individually controlled and molded into the chamber on the back side of the core mold, the chamber on the back side of the cavity mold, and the molding space, the cavity is not required in the heating step. Since the heating steam pressure only needs to be increased in the molding space formed by the mold and the core mold, the amount of steam used is smaller than in the case of molding an isothermally molded product, and energy can be saved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an in-mold foam molding apparatus.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an overall configuration diagram of an in-mold foam molding apparatus having another configuration.

FIG. 4 is an overall configuration diagram of an in-mold foam molding apparatus having another configuration.

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 is an overall configuration diagram of an in-mold foam molding apparatus having another configuration.

FIG. 7 is an overall configuration diagram of an in-mold foam molding apparatus having another configuration.

FIG. 8 is an overall configuration diagram of an in-mold foam molding apparatus having another configuration.

FIG. 9 is an explanatory diagram of the surface properties and the internal fusion ratio of a molded product.

FIG. 10 is an overall configuration diagram of an in-mold foam molding apparatus according to a conventional technique.

FIG. 11 is a longitudinal sectional view showing the vicinity of a vent hole according to a conventional technique.

FIG. 12 is a plan view of a core vent according to the related art.

FIG. 13 is an explanatory view of a molding method for a foam molded article according to the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 In-mold foam molding apparatus 2 Core mold 3 Cavity mold 4 Molding space 5 Pre-expanded beads 10 Frame-shaped frame 11 Back plate 12 Housing 13 First chamber 14 Second chamber 15 Steam supply pipe 16 Air supply pipe 17 Drain pipe 18 Pressure reducing pipe 19 Vacuum Pump 20 Nozzle 21 Nozzle Unit 22 Cooling Water Supply Pipe 23 Filler 24 Ejector Pin SV1, SV2 Utility Valve SWV1, SWV2 Switching Valve DV1, DV2 Drain Valve SWV3, SWV4 Switching Valve CV1, CV2 Cooling Water Valve 30 First Opening Part 30a First opening 30b First opening 31a Inter-model passage 31b Inter-model passage 32a Internal piping 32b Internal piping 1A In-mold foam molding device 33a Inter-model passage 33b Inter-model passage 34a Inter-model space 34b Inter-model space 1B In-mold Foam molding device 30c First opening 30d First opening 38 Passage forming member 39a Communication space 39b Communication space 40a Internal piping 40b Internal piping 30e First opening 30f First opening 41 Exterior member 42 Communication passage 43 Communication passage 50 Second opening 50a Second opening 50b Second opening 51 Bag-shaped recess 52 Bag-shaped recess 54 Internal piping 55 Internal piping 1C In-mold foam molding device SV7 Utility valve

Claims (9)

[Claims] 1. An in-mold foam molding apparatus having a core mold and a cavity mold having no vent such as a core vent and a core vent hole in a molding part for molding a conspicuous place on an outer surface of a molded article, and having a cell diameter of 100 Pre-expanded beads made of a polyolefin-based resin having a foaming magnification of 5 to 60 times, a DSC 2'nd peak ratio of 8 to 60%, and a closed cell ratio of 65% or more are filled in the molding space, and then filled. An in-mold foam molding method for a polyolefin resin, wherein the foam beads are heated and fused by steam. 2. The method according to claim 1, wherein any one of a cracking filling method, a pressure filling method, and a compression filling method is used as a method for filling the molding space with the pre-expanded beads. . 3. The in-mold foam molding method for a polyolefin resin according to claim 1, wherein said vent holes are completely omitted from the core mold and the cavity mold. 4. The method according to claim 1, wherein the pre-expanded beads have a particle size of 0.3 to 2.0.
The in-mold foam molding method for a polyolefin resin according to any one of claims 1 to 3, wherein an inorganic gas of kg / cm ² is press-fitted and filled into the molding space. 5. A polyolefin resin having a cell diameter of 100 to 900 μm, an expansion ratio of 5 to 60 times, and a DSC
An in-mold foam molded product having a beautiful surface with no core vents and no traces of core vent holes, molded using pre-expanded beads having a 2'nd peak ratio of 8 to 60% and a closed cell ratio of 65% or more. 6. An isothermally molded product obtained by heating the surface and the interior under the same heating conditions, wherein the fusion ratio inside is lower than that of an isothermally molded product having the same surface property. 6. The in-mold foam molded article according to 5. 7. An isothermally molded product obtained by heating the surface and the interior under the same heating conditions, wherein the internally fused ratio is higher than an isothermally molded product having the same surface property. 6. The in-mold foam molded article according to 5. 8. The in-mold foam molded article according to claim 5, wherein the pre-expanded beads are made of a polypropylene resin. 9. The in-mold foam molded article according to claim 5, wherein the pre-expanded beads are made of a polyethylene resin.