JPS61225024A - Method for heating foamed sheet in molding of sheet - Google Patents

Abstract

PURPOSE:To eliminate the mutual drawing or interference of a foamed sheet and to prevent the shift of a printing position, by forming recessed parts, which demarcate a plurality of molding parts of the foamed sheet, to the contact surface of a heating plate and suppressing the transfer of heat to the foamed sheet at said recessed parts and forming a heating suppressing part to the position demarcating each molding part. CONSTITUTION:A heating plate 10 is perfectly contacted with a foamed sheet S at the parts (a) with which the leading end surface of the heating plate 10 is contacted and strongly pressed not only to soften the parts (a) but also to simultaneously compress the same largely in the thickness direction and a thickness T1 becomes thinner than the thickness T before heating. The parts (b), which are contacted with the shallow circular recessed parts 12 of the heating plate 10, of the foamed sheet S are relatively weakly compressed and the heat softening degree of said parts (b) becomes lower than that of the parts (a) but said parts (b) is softened under heating to a degree necessary for molding. Further, at the parts (c) contacted with the grid shaped recessed parts 13 of the heating plate 10, the foamed sheet S is not contacted with the heating plate 10 and heating is suppressed and, therefore, said parts (c) do not soften under heating or are compressed and the thickness of the foamed sheet S holds the original thickness T as it was.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a method of heating a foamed sheet in sheet molding, in which a foamed sheet of thermoplastic resin that has been softened by heating is bulged and deformed along a mold to form a predetermined shape. It relates to a heating method for heating and softening a foamed sheet as a raw material in so-called sheet molding, which is molded into a product shape.

<Prior art> In the sheet forming process described above, there is a method of heating the foam sheet by bringing a heating plate into contact with both sides of the foam sheet and heating the foam sheet by direct heat transfer from the heating plate. It is disclosed in Japanese Patent Application Laid-Open No. 58-110224 and the like.

This contact heating method using a heating plate is effective in uniformly heating the foam sheet and preventing an increase in thickness due to foam expansion during heating.

In the above-mentioned prior art publication, a heating plate is formed with portions having different heating temperatures, and a foamed sheet that is heated and softened is formed with a high-temperature portion and a low-temperature portion having a partially different heating softening degree. is disclosed.

Among these, the low temperature part is formed by forming a cylindrical recess in the heating plate, and the circular low temperature part is formed at the position corresponding to the molded product in the foam sheet, and the high temperature part is: The foam sheet is formed over the entire portion of the foamed sheet that is ultimately trimmed around the molded product and does not constitute the molded product. And, as an effect of forming such a high temperature part,
During molding, resin is supplied from the high-temperature part with high fluidity to the center of the molded product, stabilizing the wall thickness of the entire molded product,
It is said that it can be molded smoothly. This supply of resin from the outside to the center of the molded product is usually referred to as pulling in the foam sheet, and is extremely important for improving the quality of sheet molding.

On the other hand, when molding multiple molded products at the same time in sheet molding, the adjacent molded product parts of the foam sheets will not be drawn in or interfere with each other in the molding process by crossing their boundaries. It is necessary to do so.

Furthermore, when using a pre-printed foam sheet, the foam sheet must be made so that it does not shift or deform so that the printed pattern and color scheme are placed in the correct position on the molded product. Needs to be shaped.

However, as in the prior art described above, if a high-temperature area is formed around the entire outer periphery of a molded product to increase the retraction toward the center of the molded product, the foam sheets in the peripheral portions of adjacent molded products will be attracted to each other more strongly. , there are problems in that they interfere with each other and cause molding defects, or that the thickness becomes locally uneven. Also,
The high-temperature area formed around the entire periphery of the molded product is very easily deformed and moved, so the position of the printing applied in advance on the foam sheet is likely to shift or shift, resulting in a number of misaligned prints on the molded product. was there. Furthermore, due to the formation of the above-mentioned high-temperature areas, the shape retention of the entire foamed sheet deteriorates, making it easy to warp or loosen, causing the foamed sheet to be transferred from the heating process to the molding process. There also arises a problem that it becomes difficult to hold the image accurately.

<Purpose> Therefore, the purpose of the present invention is to solve the above-mentioned problems of the prior art by improving the contact heating method using a heating plate, and to solve the problem of the drawing of foam sheets into each other when molding a plurality of molded products. We have developed a method that eliminates interference, enables fixed-position molding, eliminates printing position shift, and facilitates handling of the foam sheet after heating.

A further method to achieve the above object is to heat and compress the foam sheet by bringing heating plates into contact with both sides of the foam sheet in order to heat and soften the foam sheet used for sheet forming. A recess shaped to separate the plurality of molded parts from each other is formed on the contact surface of the heating plate,
It is characterized by suppressing heat transfer to the foamed sheet at that location and forming heat-suppressing portions at positions that separate the molded portions of the foamed sheet from each other.

<Example> Next, an example of the present invention will be described below with reference to the drawings.

FIG. 1 shows the entire molding apparatus used for carrying out the present invention, in which (1) is a heating section and (2) is a molding section. A means for transporting the foam sheet (S), such as a chain conveyor equipped with a clamp mechanism, is provided between the heating section (1) and the forming section (2). Then, a long foam sheet (S
) can be continuously fed from the heating section (1) to the forming section (2), and after the foamed sheet (S) is heated and softened one after another, it is subjected to a predetermined forming process. In the illustrated embodiment, a case is illustrated in which a plurality of sealed containers are simultaneously arranged and molded as the molded product (F).

The heating section (1) is made of a material with good thermal conductivity such as aluminum alloy and is placed behind a pair of upper and lower heating plates (10) (10) in order to heat the heating plates (10) (10) to raise their temperature. The heat generating mechanism (11) (11) is equipped with a heating plate (11).
0) and the heat generating mechanism (11) are integrally formed and can be moved up and down by a moving means such as a cylinder mechanism. Then, the heating plates (10) (10) are brought into contact with the upper and lower surfaces of the foam sheet (S) to heat and soften them by direct heat conduction, and at the same time, the heating plates (10) (10) are brought into contact with the upper and lower surfaces of the foam sheet (S). ) to compress it.

The detailed structure of the heating plate (10) is shown in FIGS. 2 and 3. That is, the contact surfaces of the upper and lower heating plates (10) against the foam sheet (S) are entirely formed in the shape of a horizontal plate, and have shallow recesses (12) and deep recesses (
13). And the shallow recess (12)
is formed in a circular shape at a position of the foamed sheet (S) that will come into contact with the central part of the molded product when molded, and is slightly recessed than the tip surface of the heating plate (10). The outer periphery is gently sloped and continues to the tip surface.

The deep recesses (13) are formed in the form of vertical and horizontal lattice grooves at positions of the foamed sheet (S) that are in contact with portions of the foamed sheet (S) that are not used for molding and will be the peripheral portions of the molded product. The depth of this lattice-shaped recess (13) is equal to the depth of the shallow circular recess (13) described above.
The heating plate (1) is placed on the foam sheet (S) much deeper than 2).
0) was heated and compressed in contact with the foam sheet (S
) is formed so deep that even if the foam sheet (S) expands in the thickness direction, the foam sheet (S) does not come into contact with the deep inner part of the lattice-shaped recess (13).

Next, using the heating plate (10) having the above structure,
A method of heating the foam sheet (S) will be explained.

Similar to the conventional heating plate (10), the heating plate (1G) is pressed against both sides of the foamed sheet (S) to soften it by heating and simultaneously compress it in the thickness direction. By appropriately setting the heating time or the pressing force of the heating plate (10), the degree of softening by heating of the entire foamed sheet (S) can be adjusted. However, the foam sheet (S) of the heating plate (10)
The contact surface with the foam sheet (S) is not completely flat as a whole, but has circular recesses (12) and lattice-like recesses (13), so the heating condition differs depending on the part of the foam sheet (S). It's coming.

To explain in detail, in FIG. 2, first, let (T) be the thickness of the foam sheet (S) before heating. Both sides of this foamed sheet (S) are brought into contact with heating plates (10) (10) and heated. Then, among the foam sheets (S), heating plates (1
In the part (a) where the tip surface of the heating plate (10
) are in complete contact and pressing strongly,
The foam sheet (S) is sufficiently heated to raise its temperature.
) is completely softened and at the same time is greatly compressed in the thickness direction. Therefore, the thickness (T1) of this portion is considerably thinner than the thickness (T) before heating.

Next, in the portion (b) of the foam sheet (S) that is in contact with the shallow circular recess (12) of the heating plate (10), the foam sheet (S) is comparatively smaller than the portion (a). It will be compressed to a weaker target, and the degree of heat softening will be lower than that of the part (a). However, it is heated and softened to the extent necessary for expansion deformation in the molding process.

Furthermore, in the portion (C) of the foam sheet (S) that contacts the deep lattice-shaped recesses (13) of the heating plate (10), the heating plate (10) does not come into contact with the foam sheet (S) at all, and the heating plate (10) is not heated. Since the foamed sheet (S) is suppressed, there is almost no heating and softening at that location, and there is no compression, so the thickness of the foamed sheet (S) remains the same as the original thickness (T).

Note that the heating plate (10) shown in FIG. 3 does not have a recess (13) on the entire outer peripheral edge, but in the heated foam sheet (S), the heating plate (10)
Naturally, the outer part does not come into contact with the heating plate (10), and therefore a heating suppressing part (C) similar to the above is formed also at a position corresponding to the outer peripheral edge of the entire heating plate (10). That is, the plurality of molded parts are divided by the heat suppression part (C), and the outer periphery of each molded part is defined by the heat suppression part (C).
It is surrounded by C).

In the above state, there are places where the degree of heat softening is different (
The foamed sheet (S) formed with a) to (C) is placed in the molding section (
The material is sent to a part a and subjected to a predetermined molding process.

To explain the structure of the molding section (2), as shown in Fig. 1, a pair of upper and lower male and female molds (20, 21) are constructed so that they can be clamped and opened using a cylinder mechanism, etc. A heated and softened foam sheet (S) is sandwiched between the molds (20) and (21), and is bulged and deformed along the shape of the molds (20) and (21) to produce a molded product (F). . The structure of the mold (2G) (21) and the molding section (2) as a whole can be implemented using the same conventional molding mechanisms for vacuum forming, pressure forming, and other types of sheet forming.

Then, in the molding process, the portion (b) of the heat-softened foam sheet (S), which has an intermediate degree of heat-softening, is bulge-molded in the same manner as in the conventional molding method, as described above. This will be the center part of the molded product (F). Next, the portion (b) having a high degree of heat softening is largely elongated and deformed around the molded article (F), and becomes a retractable portion that is pulled toward the center. In addition, the part (C), which has the lowest degree of heat softening and is hardly softened by heat, is hardly deformed and becomes a scrap part around the molded product ( ) that is not used at all for molding. Therefore, the molded product (n) is formed by the medium heating portion (b) and the high heating portion (a) of the foamed sheet (S).

Among the foam sheet heating methods described above, as the heating plate (10) for heating the foam sheet (S), the shape and arrangement of a plurality of molded products (F) formed in parallel on the foam sheet (S) are used. According to this, deep recesses (13) may be formed at positions that separate the molded products (F) from each other.
The shape of the recess (13) may be modified as appropriate in addition to the illustrated vertical and horizontal lattice grooves.

The heating plate (10) can be additionally formed with uneven shapes other than the recesses (13) at any position, at any shape, or at any depth, as necessary.
In some cases, it may not be formed.

In the illustrated embodiment, the distal end surface of the heating plate (10) is made substantially flat to form the required recesses (12) and (13), but partial convex portions are formed on the flat distal end surface. It can also be formed.

In addition, the deeper the depth of the recesses (12), (13), etc., the lower the degree of heat softening and the amount of compression for the foam sheet (S). Otherwise, there will be little heat softening and compaction. Therefore, by setting the depth of the recesses (12), (13), etc. or the height of the protrusions, the foam sheet (
The degree of heat softening and compression amount for S) can be freely adjusted.

In the forming process, the highly heated portion (a) of the foamed sheet (S) with a high degree of heat softening is set to correspond to the retracted portion as well as the portion that is particularly greatly bulged and deformed or that is strongly elongated. That's fine.

Further, in practice, the degree of heat softening of each part of the foamed sheet (S) can be set in a plurality of finer stages in accordance with the expansion deformer required in the molding process. For example, for the foamed sheet (S) of the molded product (F), which corresponds to parts with fine shapes or complex uneven shapes, the degree of heat softening is set relatively high, and deformation is required to that extent. In areas where this is not the case, the degree of heat softening may be set low. .

Furthermore, the heat-suppressed part (C
) is effective in preventing displacement and deformation of the foam sheet (S) by forming it on the outer periphery that partitions multiple molded products (F), but it also prevents deformation inside the molded product (F). The heat suppression portion (C) can be formed in a portion where deformation is not required, a portion where deformation must be actively prevented, etc.

Next, regarding the formation of the heating suppressing portion (C), as shown in FIG. The heat-suppressed portion (
C) can be formed.

Next, the uneven shape of the heating plate (10) shown in the figure is formed in exactly the same shape on the upper and lower sides of the foam sheet (S), but the uneven shape of the upper and lower heating plates (10) may be different, or The uneven shape may be formed only on the heating plate (10).

In addition, the heat generation mechanism (11) for heating the heating plate (10) may be a conventional heating structure, such as one equipped with an electric heater or one configured to allow introduction of a heating medium such as steam. Similarly, various structures can be used.

Next, in the above example, for the foam sheet (S),
The heating plate (10) is pressed against both sides to compress the foamed sheet 1-(
It is possible to suppress foaming expansion in the thickness direction and contraction in the plane direction that occur when S) is heated and softened. The thickness of the foam sheet (S) can be arbitrarily adjusted to a certain thickness or less suitable for molding, and the foam sheet (S)
It is possible to control the warping and loosening of the material, and also prevent deformation and movement in the plane direction. It also has the effect of smoothing both sides of the foam sheet (S). It should be noted that the higher the heating softening degree is, the more strongly it is necessary to press the heating plate (10) against the foamed sheet (S), so the amount of compression also increases.

The foamed sheet (S) to be heated by the heating method of this invention may be made of polystyrene, polyethylene, polypropylene, or other various thermoplastic resins.
) can be used, and on one or both sides of the foam sheet (S),
It is also possible to use non-foamed sheets or films made of various thermoplastic resins similar to those described above that have been subjected to W4Mi.

Furthermore, it is preferable to use a printed sheet in which a printed pattern is appropriately formed on the surface of the foamed sheet (S).

Moreover, the molded product (F) to be molded and manufactured can be freely applied to various packaging containers such as the illustrated flaky container, and other molded products.

<Effects> According to the heating method of the present invention configured as described above, the recesses (
By heating and softening the foam sheet (S) while contacting the heating plate (10) formed with The concave part (
A heating suppressing portion (C) having a shape corresponding to 13) is formed.

Then, heat-suppressing portions (C) that are hardly softened by heating and are difficult to deform are formed on the outer periphery of the plurality of molded products (F) at positions that partition each molded product (F). Therefore, deformation and misalignment of the foam sheet (S) can be effectively prevented, position molding can be performed, and printing misalignment can be prevented. In addition, by being able to prevent the entire foam sheet (S) from deforming, it is easy to handle the foam sheet (S) that has been softened by heating.
The arrangement in the molds (20) and (21) for molding can also be performed accurately.

Furthermore, in the molding process in which multiple molded products (F) are simultaneously molded side by side, the foam sheets (S) are prevented from being drawn in or interfering with each other beyond the boundaries of adjacent molded product (F) parts. This can be reliably prevented, and the effect of preventing the above-mentioned position molding and printing misalignment can be more effectively exhibited.

In particular, when trying to increase the retractability during molding by forming a highly heated part (a) around the molded part (F) that has a higher degree of heat softening than the central part, it becomes extremely flexible and deformable. By forming the heat-suppressing portion (C) that is difficult to deform according to the present invention on the outside of the highly heated portion (a) that is easily deformed,
Prevents deformation of the entire foam sheet (S) and prevents adjacent molded products (
F) It is possible to exhibit extremely remarkable effects such as prevention of attraction and interference in the part.

Specific Example> In order to demonstrate the effects of the present invention described above, a heating plate (10) was specifically used to heat and mold a foamed sheet (S).

A foamed polystyrene sheet with a thickness T of 2.5 mm is used as the foamed sheet (S), and a sealed cup container as shown in FIG. 4 is molded as the molded product (F).

As for the structure of the heating plate (10), in FIGS. 2 and 3, the circular recess (12) has a diameter D=160+an+
with a depth of 0.3 mm, and the four lattice parts (13) have a width W.
= 5mm and a depth of 5m111, and the pitch between the plurality of molded products is P = 165u.

Then, by heating and softening the foam sheet (S) at a surface temperature of 150° C. for 2 seconds, the foam sheet (S) has a thickness T2 of the medium heating portion (b) of iu+ and a thickness T1 of the high heating portion (a) of the foam sheet (S). Q, compressed to 7mm, heat suppressed part (C)
In this case, the thickness of the original fabric remained at 2.5111.

As described above, when the foamed sheet (S) having partially different degrees of heat softening was molded in the molding section (21) for sheet molding, the thickness and shape of the molded product (F) were good and the quality was excellent. A molded product (F) was obtained which had no printing deviation and had an extremely good appearance.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a schematic structural diagram of the entire molding device, Fig. 2 is a detailed sectional view of the heating plate portion, Fig. 3 is a plan view of the heating plate, and Fig. 4. 5 is a half sectional view of the molded product, and FIG. 5 is a sectional view of a modified example of the heating plate. (1)... Heating part, (10)... Heating plate, (12) (13)... Concavity, (2)...
... Molding part, (S) ... Foam sheet, (a)
...High heating Is portion, (b), ...Medium heating portion, (C)...Heating suppression portion, (F)...
····Molding.

Claims (1)

[Claims] 1. Processing the foam sheet used for sheet molding on both sides of the foam sheet for heat softening. A method of heating and compressing by bringing a heating plate into contact with the Molding several of the foam sheets A recess with a shape that separates the parts from each other, Formed on the contact surface of the heating plate and Suppresses heat transfer to foam sheet and foams Separate each molded part of the sheet from each other. Forming a heating suppressing part at a position where Foamed silicone for sheet molding featuring How to heat the stove. 2. Of each molded part of the foam sheet, unprocessed Inside the heated part, the molded product is heated during molding. The part that is drawn into the center of the molded product from the periphery minutes, than the contact surface of the heating plate corresponding to Contact surface of the heating plate corresponding to the center side of the molded product Of the foam sheet, The heating softening degree of the above retracted part is The heating softening degree is greater than the above formed The sheet composition according to claim 1 How to heat foam sheets in shape. 3. Forming a heating suppression part on the heating plate Insulating material is buried inside the recess for and suppresses heat transfer to the foam sheet. Sheet according to claim 1 above Method of heating foam sheets during molding.