JP5309517B2 - Foam sheet manufacturing equipment - Google Patents

Description

The present invention relates to a foam sheet manufacturing apparatus .

Conventionally, a T-die is usually widely used as a die for forming and forming a sheet or film using a thermoplastic material, and a thermoplastic resin containing a foaming gas is extruded and foamed using this T-die. It is difficult to form a sheet.
One of the causes is that when the thermoplastic resin containing the foaming gas comes out of the T die, it foams not only in the thickness direction but also in the width direction. For this reason, a curtain-like undulation phenomenon occurs, and it becomes very difficult to obtain flatness. Further, there is a problem that the foaming gas becomes a continuous bubble and the gas escapes.

  As a method to increase the smoothness of the surface of the foam sheet and increase the strength, a skin layer that contains almost no bubbles due to foaming gas is provided on the surface by using a method such as coextrusion. There is a problem in terms of sex and cost.

In order to solve this problem, a die lip having a through-hole through which a coolant passes and a through-hole through which a heat medium passes is connected via a flexible portion, and the constricted portion of the resin passage is covered with a heat medium. In order to suppress heating and foaming of the resin surface, a T die has been proposed that cools the channel wall surface temperature at the tip of the die lip so as to be kept at a low temperature by a refrigerant (for example, see Patent Document 1).
Japanese Patent No. 3354730

  In the T die described in Patent Document 1, since the foaming process is performed inside, the molded product is restrained from being foamed by the wall surface of the T die even when the expansion of the foaming gas is still in progress. However, when the resin flows from the constricted portion of the resin passage into the foamed portion where foaming occurs, the timing of the molten resin contacting the wall of the T die is delayed because the gap between the thickness dimensions of both is large, and the molten resin Large variations in foaming may occur.

  Specifically, the expansion ratio is high at a portion where the distance from the constricted portion to the wall surface of the foam portion is long, and unevenness of the foam distribution is generated where the expansion ratio is suppressed at a portion where the distance is short. Therefore, as the distance from the constricted part where the foaming ratio increases to the part where the gap is large, the outflow of the foaming gas due to the tearing of the resin film increases, and this is between the skin layer made earlier. When sandwiched, there is a problem that a large void is formed and the strength of the molded product is significantly inhibited. This phenomenon becomes more prominent as the thickness of the sheet to be molded is larger and as the expansion ratio is higher.

  For this reason, in the T-die described in Patent Document 1, a good foam can be made if the foamability of the thermoplastic resin is sufficient, but a resin that is usually difficult to foam, such as a resin having a low melt tension, Resins containing a large amount of fillers are difficult to form with a large thickness or a high expansion ratio.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a foamed sheet manufacturing apparatus that can form a foamed sheet having a large thickness and a high foaming ratio with little variation in internal foaming ratio. To do.

A foamed sheet manufacturing apparatus according to a first aspect of the present invention is a T-die for manufacturing a foamed sheet by molding a thermoplastic resin, and includes a manifold portion in which the thermoplastic resin is supplied, A heating section having a resin flow path through which the thermoplastic resin flows and attached to a downstream side of the manifold section, and having a heat medium flow path for heating the resin flow path on a wall surface around the resin flow path; A plate-shaped resin flow path dividing member fixed in the resin flow path of the heating unit so as to be orthogonal to the thickness direction of the foamed sheet; and a molding space for the thermoplastic resin therein. A cooling molding unit which is attached to the downstream side of the heating unit and has a coolant channel for cooling the molding space on a wall surface around the molding space, and is disposed between the heating unit and the cooling molding unit. and the heat insulating member, and the T die Ru wherein the cooling formed Disposed downstream of the parts, and a traction unit for pulling the foam sheet to the downstream side, the pulling portion is characterized by being configured to have a roller for winding the foam sheet.
According to the foamed sheet manufacturing apparatus of the present invention, since the resin flow path in the heating section is divided into a plurality in the thickness direction of the sheet formed by the resin flow path dividing member, the resin flowing through each divided flow path Is maintained in a suitable state.

  The resin flow path dividing member may enter the inside of the manifold portion. In this case, since the flow of the resin is adjusted before the resin moves to the heating unit, the occurrence of the turbulent flow of the resin is suppressed.

  The T-die of the present invention further includes a reinforcing member that is disposed and fixed in the heating portion in parallel with the thickness direction of the foam sheet, and the resin flow path dividing member is fixed to reinforce the resin flow path dividing member. May be. In this case, the resin flow path dividing member can be fixed more reliably. Inconveniences such as the resin flow path dividing member dropping off due to the pressure of the resin can be prevented.

  The heating unit, the heat insulating member, and the cooling molding unit may be integrally formed, and may be detachable from the manifold unit. In this case, according to the thickness etc. of the foam sheet to be molded, a set of a plurality of heating parts, heat insulating members, and cooling molding parts can be used by being replaced with a manifold part.

According to the foamed sheet manufacturing apparatus of the present invention, it is possible to form a foamed sheet having a large thickness and a high foaming ratio with little variation in the internal foaming ratio.

Hereinafter, a T die according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a plan view showing a T die 1 of the present embodiment. As shown in FIG. 1, the T die 1 includes a manifold portion 2 to which a thermoplastic resin (hereinafter simply referred to as “resin”) is supplied, a heating portion 3 attached to the downstream side of the manifold portion 2, A cooling molding unit 4 attached to the downstream side of the heating unit 3 and a heat insulating member 5 disposed between the heating unit 3 and the cooling molding unit 4 are configured.

  2 is a cross-sectional view taken along line AA in FIG. The manifold portion 2 is connected to a supply pipe P that supplies resin. As shown in FIG. 2, the internal space through which the resin flows is formed as a substantially circular cross section so that the pressure applied to the resin is uniform.

  The heating unit 3 has a first resin channel (resin channel) 6 through which resin flows, and is connected to the manifold unit 2 so that the first resin channel 6 communicates with the internal space of the manifold unit 2. Yes. On the upper wall 3A and the lower wall 3B surrounding the first resin flow path 6, a heat medium flow path 3C through which a heat medium for heating the first resin flow path 6 and the resin flowing therethrough is formed. .

Further, in the first resin flow path 6, three plate-like torpedos (resin flow path dividing members) 7A, 7B, 7C are provided in the thickness direction of the sheet to be molded (that is, the first resin flow path in FIG. 2). 6 in the vertical direction). As for each torpedo 7A, 7B, 7C, the both ends of the width direction of the T die 1 are being fixed to the heating part 3 by means, such as welding. By these torpedoes 7A to 7C, the first resin flow path 6 is divided into four divided flow paths 6A to 6D in the sheet thickness direction.
The resin flow direction dimension of each torpedo 7 </ b> A to 7 </ b> C is set longer than the surrounding wall surface, and is attached so that the protruding end portion enters the internal space of the manifold portion 2.

The number and thickness of the torpedoes may be appropriately changed according to the thickness of the foam sheet to be molded and the foaming suitability of the resin to be used.
For example, when molding is performed using a resin having such a characteristic that the resin film is broken and gas escapes when the expansion ratio exceeds 2 times (the reciprocal of the specific gravity change rate after foaming), By setting the thickness to be approximately the same as the dimension in the thickness direction of the divided flow path, the foamed sheet can be favorably molded.

  Also, a resin filled with a large amount of filler or a resin with a low melt tension is difficult to foam because the film is easily torn, but up to a certain amount of foaming, gas can be embraced inside, so that the amount of foaming It is possible to form a foam sheet by setting the dimension in the thickness direction of the divided flow path and the thickness of the torpedo so that it flows out of the other flow path and comes into contact with the foamed resin at the time of foaming Become.

  The cooling molding section 4 has a second resin flow path (molding space) 8 through which resin flows, and the heating section 3 so that the second resin flow path 8 communicates with the first resin flow path 6 of the heating section. It is attached to the downstream side. The upper wall 4A and the lower wall 4B surrounding the second resin flow path 8 are formed with a refrigerant flow path 4C through which the second resin flow path resin 8 and a refrigerant for cooling the resin flowing therethrough flow.

The heat insulating member 5 is interposed and fixed between the heating unit 3 and the cooling molding unit 4 and has a function of maintaining a temperature difference generated between the two.
The heating unit 3, the cooling molding unit 4, and the heat insulating member 5 are integrally configured as a foam sheet molding unit 9 and are detachable from the manifold unit 2.

A procedure for forming a foam sheet using the T die 1 configured as described above will be described below.
First, as shown in FIG. 3, a resin R mixed with a foaming agent is pushed from the supply pipe P into the internal space of the manifold portion 2 to be filled (first step). As the resin R, various thermoplastic resins such as polystyrene, polyolefin, polypropylene (PP), and polylactic acid can be used. In the manifold part 2, since the pressure is kept high, foaming is not yet started.

  Next, as shown in FIG. 4, when the resin R is further pushed out from the supply pipe P, the resin R is divided by the torpedo 7A to 7C and moves to the heating unit 3 while flowing into the divided flow paths 6A to 6D. (Second step).

  The resin R flowing in each flow path of the heating unit 3 is heated by the heat medium flowing in the heat medium flow path 3C, and is extruded toward the cooling molding unit 4 in a molten state as shown in FIG. At this time, when the resin R is extruded from each of the divided flow paths 6A to 6D, the resin R starts to foam while spreading upward and downward by the thickness of the torpedo 7A to 7C.

  As shown in FIG. 6, the resin R is united again in the cooling molding portion 4 and proceeds in the second resin flow path 8. At this time, the resins R1 and R4 that have flowed through the divided flow paths 6A and 6D that are close to the wall surface immediately contact the upper wall 4A and the lower wall 4B, respectively, as they enter the cooling molding section 4, and flow through the refrigerant flow path 4C. Cooled by. And it hardens | cures before foaming and 10 A of skin layers which hardly accompany foaming are formed.

  On the other hand, as shown in FIG. 7, the resins R2 and R3 that have flowed through the divided flow paths 6B and 6C away from the wall surface are gradually cooled while foaming as they proceed through the second resin flow path 8 of the cooling molding portion 4. Then, the foaming is stopped in the cooling molding portion 4 to complete the foamed sheet 10 (third step).

  At this time, the resins R2 and R3 are well foamed in a state in which the pressure is maintained by the skin layer 10A and gas escape caused by the foaming agent is suppressed. The completed foam sheet 10 is sequentially pushed out of the T-die 1 from the cooling molding unit 4. Since the foam sheet 10 has already been cured at this point, the foam sheet 10 does not swell in the thickness direction or the width direction outside the T-die 1 and does not cause a phenomenon such as undulation.

  FIG. 8 is a cross-sectional view of the foam sheet 10 formed using the T-die 1. Skin layers 10A that are hardly foamed are formed at both ends in the thickness direction of the foamed sheet 10, and the diameter of bubbles formed by foaming gradually increases toward the inside. This is because the pressure of the first bubble layer 10B close to the skin layer 10A is strongly held by the skin layer 10A, so that the bubble diameter is small. In the second bubble layer 10C inside, the skin layer is formed by the first bubble layer 10B. This is because the pressure is held weaker than 10A, and the bubble diameter increases.

The foam sheet 10 formed using the T-die 1 will be further described below with reference to examples.
(Example)
First, as a resin for forming a foam sheet, resin 1: homo PP (melt flow rate (MFR) = 7), resin 2: L polylactic acid (MFR = 7), resin 3: 40% by weight of talc as an inorganic filler Three types of PP (MFR = 1) were prepared and mixed with a baking soda foaming agent (trade name: Fine Cell Master, manufactured by Dainichi Seika Kogyo Co., Ltd.) at a weight ratio of 100: 3.

These three kinds of resins were formed into foamed sheets having a thickness of 10 millimeters using the T-die of the present invention in which torpedo was arranged in the heating section, which were designated as Examples 1 to 3, respectively.
Three torpedoes with a thickness of 0.5 mm were arranged, and the dimension in the thickness direction of the divided flow path was set to 0.5 mm.

(Comparative example)
About the above-mentioned resin 1 thru | or 3, it shape | molded using the conventional T die without a torpedo, and it was set as the comparative examples 1 thru | or 3, respectively.
The results of each example and comparative example are shown in Table 1.

  In each comparative example, foaming failure due to gas escaping from the surface of the foamed sheet, wavy phenomenon accompanying expansion after being injected from the T-die, etc. occur, and a flat foamed sheet can not be molded. There was no (cannot be formed).

  On the other hand, in each Example, it was possible to form a flat foamed sheet having a foaming ratio of 2.5 and foaming well and having no waviness. Looking at the cross section of the molded foam sheet, the skin layer was formed above and below in the thickness direction as described above, and the bubble diameter gradually increased toward the inside.

  According to the T-die 1 of the present invention, a plurality of divided flow paths 6A to 6D having desired dimensions can be formed in the thickness direction of the sheet to be formed by the torpedo 7A to 7C. Variations in the expansion ratio are less likely to occur in the injected resins R1 to R4. Therefore, even a resin that has been difficult to form a conventional foamed sheet, such as a low foaming ratio that can be molded, can be molded satisfactorily.

  In addition, since a foamed sheet can be formed even with a resin mixed with a filler at a high mixing ratio, a foamed sheet that can be applied to building materials that require flame retardancy and a low coefficient of linear expansion. Can be molded.

  In addition, since the end of the torpedo 7A to 7C on the manifold part 2 side penetrates into the internal space of the manifold part 2, the resin flow is adjusted before the resin R moves to the heating part 3. Therefore, the turbulent flow of the resin R does not easily occur in the manifold portion 2, and the foamed sheet can be molded well.

  Further, since the resins R1 and R4 that have flowed through the divided flow paths 6A and 6D near the both ends in the thickness direction of the sheet are cooled by the refrigerant that flows through the refrigerant passage 4C immediately after moving to the cooling molding unit 4, they hardly foam. And a smooth skin layer 10 </ b> A is formed on the surface of the foamed sheet 10. Therefore, in the portion on the inner side in the thickness direction from the skin layer 10A, the skin layer 10A can maintain a good pressure, and thus foaming can be performed and a foam sheet having no problem in strength can be formed. .

  In addition, since the foaming process of the foam sheet 10 is completely completed in the cooling molding part 4 of the T-die 1, when the foam sheet 10 is extruded from the cooling molding part 4, it further expands in the thickness direction or the width direction. There is no. Therefore, it is possible to form a flat foam sheet that does not generate undulations or irregularities.

In addition, since the foamed sheet molding part 9 is detachable from the manifold part 2, a plurality of dimensions in the thickness direction of the resin flow path, the number of torpedo installations, or dimensions in the thickness direction of the divided flow paths are different. By preparing the foamed sheet molding part in advance and sequentially changing it in accordance with the foamed sheet to be molded, it is possible to mold foamed sheets of various types of resins and various thicknesses with one T die.
In particular, thick foam sheets and foam sheets with a high foaming ratio have been extremely difficult to form conventionally, but the T-die of the present invention can form any number of divided flow paths using torpedo. Therefore, it is possible to easily form a thick foam sheet with good physical properties.

  Then, the foam sheet manufacturing apparatus which concerns on 2nd Embodiment of this invention is demonstrated with reference to FIGS. 9-11. In addition, about the component similar to the above-mentioned embodiment, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  FIG. 9 is a side view showing the foam sheet manufacturing apparatus 20 of the present embodiment. The foam sheet manufacturing apparatus 20 includes a T-die 21 of the present invention and a roller (traction section) 22 that pulls the molded foam sheet.

  FIG. 10 is a front view of the heating unit 23 of the T die 21. Three torpedes 24 </ b> A, 24 </ b> B, and 24 </ b> C are fixed to the heating unit 23. In addition, reinforcing members 25A, 25B, and 25C are arranged and fixed at substantially equal intervals in the heating unit 23 substantially in parallel with the thickness direction of the sheet to be formed.

The reinforcing members 25A to 25C are rod-shaped or plate-shaped members, and upper and lower ends thereof are fixed to the upper wall 23A and the lower wall 23B of the heating unit 23 by means such as welding, respectively. Each torpedo 24A to 24C is fixed to the side wall of the heating unit 23 at both ends in the width direction by means of welding or the like, similarly to the T-die 1 of the first embodiment, and further intersects with the reinforcing members 25A to 25C. Are fixed to each reinforcing member.
The fixing of the torpedo and the reinforcing member may be performed by welding or the like, or may be performed by providing a cut in the reinforcing member and engaging with the torpedo. In addition, the number of installation and the installation interval of the reinforcing members may be arbitrarily set.

  The roller 22 includes a first roller 22A disposed on the upper side of the molded foam sheet and a second roller 22B disposed on the lower side, and holds the foam sheet extruded from the T-die 21 by a frictional force or the like. While pulling downstream. The surface of the roller 22 that contacts the foam sheet is preferably formed of a material such as silicone rubber that generates a large frictional force and does not damage the surface of the foam sheet.

The operation at the time of use of the foamed sheet manufacturing apparatus 20 configured as described above will be described.
As shown in FIG. 11, as in the first embodiment, the resin R mixed with the foaming agent is supplied from the supply pipe P to the manifold portion 2 and is divided by the torpedes 24 </ b> A to 24 </ b> C toward the heating portion 23. Moving.

At this time, the first resin flow path 26 in the heating unit 23 is not only divided in the thickness direction like the first resin flow path 6 of the first embodiment, but also has a thickness as shown in FIG. It is also divided in the width direction by reinforcing members 25A to 25C arranged and fixed substantially parallel to the direction. That is, the resin R moves to the heating unit 23 through a plurality of divided flow paths divided in a lattice shape.
Although a large pressure is applied to each torpedo by the resin R, each torpedo is fixed to each reinforcing member 25A to 25C in addition to both ends in the width direction. Is suppressed.

  The foam sheet 27 that has finished foaming in the T-die 21 and is pushed out is sandwiched between the first roller 22A and the second roller 22B and pulled in the direction of arrow F in FIG. By adjusting the pulling by the roller 22 and the extrusion of the resin R from the supply pipe P, the expansion ratio of the resin R is more suitably controlled. For example, if the take-up speed by the roller is increased for the same resin discharge amount, the amount of resin per unit length of the foam sheet decreases, so if the thickness of the sheet can be maintained by foaming, the specific gravity of the foam sheet to be produced can be increased. Can be lightened.

  According to the foam sheet manufacturing apparatus 20 of the present embodiment, the torpedoes 24A to 24C arranged in the first resin flow path 26 are fixed not only through both ends in the width direction but also through the reinforcing members 25A to 25C. . Therefore, the resin R does not fall off due to a large pressure for extruding the resin R, the dimension in the thickness direction of each divided flow path is stably maintained, and the expansion ratio is suitably controlled.

  Further, since the resin R and the foamed sheet 27 are also subjected to the pulling force by the roller 22 in addition to the pressure of the resin extrusion from the supply pipe P, the foaming ratio of the resin R is more suitably controlled, and a high-quality foamed sheet is obtained. Can be molded.

  Although the embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

It is a top view which shows T-die of 1st Embodiment of this invention. It is sectional drawing in the AA of FIG. It is sectional drawing which shows the T die at the time of foaming sheet shaping | molding. It is sectional drawing which shows the T die at the time of foaming sheet shaping | molding. It is sectional drawing which shows the T die at the time of foaming sheet shaping | molding. It is sectional drawing which shows the T die at the time of foaming sheet shaping | molding. It is sectional drawing which shows the T die at the time of foaming sheet shaping | molding. It is sectional drawing of the foam sheet shape | molded using the same T die. It is a figure which shows the structure of the sheet manufacturing apparatus of 2nd Embodiment of this invention. It is a front view which shows the heating part of the sheet manufacturing apparatus. It is a figure which shows the sheet manufacturing apparatus at the time of foaming sheet shaping | molding.

Explanation of symbols

1, 21 T-die 2 Manifold part 3, 23 Heating part 3C Heat medium flow path 4 Cooling molding part 4C Refrigerant flow path 5 Heat insulation member 6, 26 First resin flow path (resin flow path)
7A, 7B, 7C, 24A, 24B, 24C Torpedo (resin channel dividing member)
8 Second resin flow path (molding space)
10, 27 Foam sheet 20 Foam sheet manufacturing apparatus 22 Roller (traction section)
25A, 25B, 25C Reinforcing member

Claims (4)

A T-die for forming a foamed sheet by molding a thermoplastic resin,
A manifold part to which the thermoplastic resin is supplied;
Heating having a resin flow path through which the thermoplastic resin flows and attached to the downstream side of the manifold portion, and having a heat medium flow path for heating the resin flow path on a wall surface around the resin flow path And
A plate-like resin flow path dividing member fixed so as to be orthogonal to the thickness direction of the foam sheet in the resin flow path of the heating unit;
A cooling molding section having a molding space for the thermoplastic resin therein and attached to the downstream side of the heating section, and having a coolant channel for cooling the molding space on a wall surface around the molding space;
A heat insulating member disposed between the heating unit and the cooling molding unit;
And a T-die Ru with a,
A traction unit disposed on the downstream side of the cooling molding unit and pulling the foam sheet to the downstream side;
With
The said pulling part has a roller which winds up the said foam sheet, and is comprised, The foam sheet manufacturing apparatus characterized by the above-mentioned. The foamed sheet manufacturing apparatus according to claim 1 , wherein the resin flow path dividing member enters the inside of the manifold portion. Said heating portion, wherein the foam sheet is parallel to fixed in the thickness direction of the, claims and further comprising a reinforcing member the resin flow path dividing member is fixed reinforce the resin flow path dividing member The foamed sheet manufacturing apparatus according to 1 or 2 . The foam according to any one of claims 1 to 3 , wherein the heating unit, the heat insulating member, and the cooling molding unit are integrally formed and are detachable from the manifold unit. Sheet manufacturing equipment .

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