JP2001079930A - Method and apparatus for producing foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a foamed sheet excellent in closed-cell properties and having lightweight properties and high regidity so as to obtain uniform required expansion ratio. SOLUTION: A molten resin is extruded from a T-die and the surface temp. of the resin extrudate is lowered to predetermined temp. from the temp. at the time of the extusion of the molten resin by the temp. control mechanism controlling the temp. of a lip to 80-200 deg.C in the T-die 2. After extrusion, the surface temp. of the obtained foamed sheet 3 is further lowered by small diameter rolls 6a, 6b of which the temps. are controlled to 50-180 deg.C. Since the temp. of the small diameter roll 6a is made higher than that of the small diameter roll 6b and the temps. of both rolls are controlled to two stages, the expansion of the cells of the foamed sheet 3 is not suppressed by the quenching of the foamed sheet 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a foamed sheet capable of producing a lightweight, highly rigid foamed sheet having excellent closed cell properties.

[0002]

2. Description of the Related Art Foamed polyolefin resin sheets have excellent heat resistance and impact resistance, and are widely used for food containers, trays, interior materials for automobiles or building materials. Conventionally, such a foamed sheet is formed by an apparatus as shown in FIG. 4, for example. That is, a raw material in which a chemical blowing agent is previously blended with a polyolefin resin is charged into an extruder (not shown), and the polyolefin resin is heated and melted in a cylinder. The blowing agent is gasified by chemical decomposition or thermal decomposition. Then, the extruder (not shown) connects the conduit 1
The molten resin supplied through the lip portion c passes through the manifold portion a and the land portion b, which are flow paths in the T-die 2.
Extruded from. The sheet-like molten resin flowing out of the lip portion c expands (foams) by being reduced in pressure to become a foamed sheet 3. The foamed sheet 3 is sandwiched by the cooling surface of the metal polishing roll 4, brought into contact, and cooled to room temperature. Thus, a foamed sheet is obtained.

[0003] In particular, in the case of foamed sheet molding using polypropylene, which is an olefin resin, when the expansion ratio is 2 or more, the partial pressure of the foamed gas is high, and it is difficult to retain the foamed gas in the molten resin. Gas diffusion and bubble phenomena (burst of bubbles, open cell formation) are likely to occur. For this reason,
Various methods have been proposed for increasing the melt tension to suppress the diffusion and the bubble breaking phenomenon.

[0004]

Conventionally, a method of manufacturing a foamed sheet by disposing a small-diameter roll immediately after flowing out of the die in order to suppress the escape of the foaming gas from the inside of the foamed sheet after flowing out of the die (see, for example, In Japanese Patent Application Laid-Open No. 63-287873, there is a problem that sufficient cooling cannot be obtained because the area of the foam sheet in contact with the small-diameter roll is small and the cooling time is short. Further, when manufacturing a foam sheet having a wide sheet width, there is a problem that the temperature in the sheet width direction at the time of die outflow becomes non-uniform, and the sheet thickness, the expansion ratio or the bubble shape becomes non-uniform. .

In the method of cooling the foamed sheet after flowing out of the die by bringing the foamed sheet into contact with a small-diameter roll and then placing the foamed sheet in a water tank (for example, JP-A-7-276472), the entire foamed sheet is rapidly cooled, so that the expansion of bubbles is caused. Is suppressed,
There is a problem that it is difficult to obtain a required expansion ratio. In particular, in the production of a polyolefin-based foam sheet having an expansion ratio of 2 or more, it is necessary to lower the temperature of the molten resin, uniformly extrude and cool the resin in order to suppress the foam breaking phenomenon (destruction of bubbles).

The present invention has been made in view of the above circumstances, and provides a method for producing a foamed sheet capable of producing a lightweight, highly rigid foamed sheet which is uniform, has a desired expansion ratio, has excellent closed cell properties, and is excellent in closed cell properties. It is intended to provide the device.

[0007]

SUMMARY OF THE INVENTION A method and an apparatus for producing a foamed sheet according to the present invention have been made in order to solve the above-mentioned problem. In order to perform uniform control in the direction, division control is performed, and further, the foamed sheet is cooled by a small-diameter roll so as not to crush the expanded air bubbles and suppress the expansion,
Then, it is cooled to room temperature by a metal polishing roll.

[0008] That is, in the method for producing a foamed sheet according to the present invention, the lip portion of the T-die is formed by extruding a polyolefin resin containing a foaming agent into a sheet from a T-die. The temperature is set lower than the molten resin in the T-die, and when the molten resin is extruded, the molten resin is cooled by the lip. In this case, it is preferable to maintain a uniform temperature around the lip portion of the T-die in contact with the molten resin, and it is preferable to control the temperature by dividing the lip portion in the width direction.

[0009] The method for producing a foamed sheet according to the present invention is a method for producing a foamed sheet by extruding a polyolefin resin containing a foaming agent into a sheet from a T-die. To
It is characterized in that cooling is performed stepwise by a group of rolls that keep the surface at a lower temperature than the upstream side of the flow path. This group of roles
It can be placed facing the foam sheet flow path from the T die,
Or staggered. In this case, the above T
It is preferable to control the temperature of the foam sheet flowing out of the T die by adjusting the distance between the lip portion of the die and the roll at the most upstream position of the roll group.

In the present invention, the term "blowing agent" refers to a substance which is mixed or dissolved in plastic and foams it, and is a volatile solvent which generates gas by heating or pressure reduction and a liquefiable gas expanding agent. And a chemical blowing agent that generates a gas by being thermally decomposed by heating. The present invention can be applied to the latter. The polyolefin resin in the present invention is, for example, a polyethylene resin having a saturated hydrocarbon chain, a polypropylene resin or a polyisobutylene resin, or a polyisoprene resin or a polybutadiene resin having an unsaturated bond in a main chain. Etc.

The foamed sheet manufacturing apparatus according to the present invention is a foamed sheet manufacturing apparatus for manufacturing a foamed sheet by extruding a polyolefin resin containing a chemical foaming agent into a sheet shape from a T-die. Above T
A temperature control unit (temperature control mechanism) different from the main body of the die is provided to control the temperature at a temperature different from that of the main body of the T-die. That is, when a polyolefin resin containing a chemical foaming agent is extruded into a sheet shape from a T-die to produce a foamed sheet, a temperature control mechanism different from that of the die body is provided near the lip portion so that the temperature is different from that of the T-die body. It has a key controllable feature.

[0012] The temperature control section may include a temperature control tube in contact with the lip portion, and may flow a temperature-controlled medium through the temperature control tube. Further, the temperature control unit may include a temperature control tube embedded in the T-die, and the temperature-controlled medium may flow through the temperature control tube. That is, the above-mentioned lip portion temperature control mechanism makes the temperature control tube ground around the lip or embeds the temperature control tube in the die, and flows the temperature-controlled medium through this to a temperature different from that of the T-die main body. It is configured so that temperature control can be performed.

It is preferable that the temperature adjustment control section performs split temperature adjustment control in the sheet width direction and in the upper and lower portions of the lip, and preferably performs uniform temperature adjustment in the sheet width direction and in the upper and lower portions of the lip. That is, the lip temperature control mechanism is configured so that the temperature in the width direction and the upper and lower lip temperatures can be controlled uniformly by controlling the temperature separately in the sheet width direction and the upper and lower lips.

It is preferable that the temperature control section divides the sheet at predetermined intervals, for example, 50 mm to 300 mm in the sheet width direction, so that the area near the end of the sheet is a half of the sheet center division width. That is, the lip temperature control mechanism can uniformly control the lip temperature in the width direction by dividing the sheet in the width direction by 50 to 300 mm and setting only the vicinity of the end of the sheet to a half area of the center division width of the sheet. The configuration is as follows.

It is preferable that rolls whose temperature can be adjusted are arranged in a zigzag manner downstream of the T-die so that the foam sheet flowing out of the T-die is further cooled by passing between the rolls. This roll is preferably of small diameter and made of metal. That is, small-diameter metal rolls whose temperature can be controlled are arranged in a staggered manner at the tip of the T-die, and the foam sheet flowing out of the T-die is cooled.

It is preferable that the distance from the lip portion (tip portion) of the T die to the first one of the rolls that the foamed sheet comes into contact with can be changed, and that the distance between the rolls through which the foamed sheet passes can be changed. It is preferable that the gap can be changed. That is, in the foam sheet forming machine having the small-diameter roll, the distance between the tip of the T-die and the small-diameter roll where the foam sheet first contacts the ground and the gap between the upper and lower small-diameter rolls can be controlled.

It is preferable that the roll is configured so that the temperature control can be performed in at least two stages, a first stage and a second stage. In this case, a plurality of the rolls, for example, 3 to 10
Arrange in columns. That is, in a foaming sheet molding machine having a small-diameter roll, three to ten rows of small-diameter rolls are arranged so that temperature control can be performed in at least two stages of a front stage and a rear stage.

It is preferable that the foamed sheet passed through the roll is cooled to room temperature by a metal polishing roll. That is, the foamed sheet that has passed through the foamed sheet forming machine having the small-diameter roll is configured to be cooled to room temperature by the metal polishing roll thereafter.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a foam sheet manufacturing apparatus and a manufacturing method using the apparatus according to the present invention will be described with reference to the drawings. Note that, in the embodiment of the present invention, the same components as those in the related art are denoted by the same reference numerals, and those overlapping with the above description will be omitted below.

As shown in FIG. 1, the foam sheet manufacturing apparatus according to one embodiment of the present invention includes a T-die 2, a metal polishing roll 4, a lip temperature control temperature control tube 5, and small metal rolls 6a and 6b. .

The small-diameter rolls 6a and 6b are disposed between the T-die 2 and the metal polishing roll 4, and are staggered above and below the flow path of the foamed sheet 3. The small diameter rolls 6 a and 6 b have a smaller diameter than the metal polishing roll 4.

The small roll 6a is closer to the T-die 2 (front stage).
The small roll 6a which is closest to the T-die 2 is arranged such that its center is separated from the lip c of the T-die 2 by a dimension d (air gap). The air gap d is a distance until the foam sheet 3 flowing out from the tip of the T die 2 first contacts the small-diameter roll 6a. The small rolls 6a are provided with two such pairs, one pair of upper and lower ones adjacent to each other and arranged opposite to each other. The interval between the pair of small rolls 6a is the small-diameter roll gap e.

The small roll 6b is disposed near the metal polishing roll 4 (later stage), and is provided with a pair of adjacent upper and lower pairs, which are arranged opposite to each other. The interval between the pair of small rolls 6b is the gap e between the small diameter rolls similarly to the small roll 6a. In this embodiment, the small rolls 6a and 6b have a total of three pairs (three rows).
Although it is arranged, it is not limited to this, and may have a larger number of rows, for example, 10 rows.

The small rolls 6a and 6b are configured to be able to control the movement, and by adjusting the positions of the small rolls 6a and 6b, the air gap d and the gap e between the small diameter rolls can be appropriately adjusted to predetermined values. Further, the small roll 6a and the small roll 6b are configured to be capable of controlling the temperature independently of each other, so that at least two-stage temperature control can be performed.

As shown in FIG. 1 or FIG. 2A, the lip temperature control temperature control tube 5 is disposed so as to be in contact with the upper and lower portions of the lip portion c, respectively. As shown in (b), each predetermined area divided in the sheet width direction of the lip portion c can be controlled in temperature. That is, the temperature control tube 5 for lip temperature control is divided in the sheet width direction, and the division width is not equal. In particular, the division width g at the end of the sheet is about half of the division width f at the center of the sheet. is there. This division width is, for example, 50 mm to 300 mm.
mm. Note that a temperature-controlled temperature control medium flows through the lip temperature control temperature control pipe 5, and the temperature control is performed by controlling the temperature control medium.

The T die 2 has a lip temperature of 80 degrees Celsius.
A mechanism (lip temperature control mechanism) capable of controlling the temperature so as to maintain the temperature in the range of degrees to 200 degrees is provided. Further, the metal polishing roll 4 has a cooling surface for cooling the foamed sheet 3 to about room temperature.

Next, a manufacturing method using the foamed sheet manufacturing apparatus according to the present embodiment will be described. First, blend the blowing agent and the polyolefin resin in advance,
It is put into an extruder hopper (not shown). In an extruder (not shown), the polyolefin-based resin is melted, and the foaming agent undergoes a chemical reaction to be thermally decomposed to generate cell nuclei. Thereafter, the molten resin containing the bubble nuclei is extruded in a sheet shape through the conduit 1 and the T-die 2. As the resin pressure decreases, the cell nuclei foam and the sheet expands. At this time, the surface temperature of the molten resin is lowered by the lip temperature control mechanism of the T-die 2, and further lowered by being cooled by the small-diameter rolls 6a and 6b. Then, the foamed sheet 3 is cooled by the metal polishing roll 4.
Finally lowers the temperature to room temperature.

The temperature control in producing the foam sheet 3 as described above is performed as follows. As shown in FIG. 1, the temperature of the molten resin flowing out of the T-die 2 is controlled by a temperature control mechanism in the T-die 2 so that the lip temperature becomes 80 to 200 degrees Celsius. The temperature is lowered from the temperature at the time to a predetermined temperature. Further, after the outflow, small-diameter rolls 6a and 6b whose temperature is controlled to 50 to 180 degrees Celsius.
Thereby, the surface temperature of the foamed sheet 3 is further reduced. The small-sized roll 6a is set at a higher temperature than the small-sized roll 6b, and the temperature is controlled in two stages.
Can be prevented from suppressing the expansion of the bubbles due to rapid cooling of the air.

Since the stepwise temperature drop control is performed as described above, the melt tension of the sheet surface layer at the time of outflow and foaming is improved, the expansion of the foaming gas and the formation of open cells due to the foam breaking phenomenon are suppressed, and the required foaming is achieved. Magnification is obtained. Also, by controlling the lip temperature to be lower than the molten resin temperature at the time of outflow,
The effect of adhering the molten resin to the lip c is reduced, and the sheet surface properties can be improved.

In the direction of the flow path of the molten resin after flowing out of the lip c, the temperature of the foamed sheet 3 is controlled by at least two stages, that is, by controlling the temperature with the small roll 6a on the front stage and the small roll 6b on the rear stage. It is possible to prevent the expansion of bubbles due to rapid cooling.

Further, by controlling the movement of the molding machine on the side of the small-diameter roll 3 and appropriately adjusting the air gap d,
The cooling effect of the small-diameter roll 3 can be controlled. The small-diameter rolls 3 are arranged in a staggered arrangement, and the small-diameter roll gap e is set.
By operating, molding without fear of crushing the foamed sheet 3 can be performed.

As shown in FIG. 2, since the temperature control is performed by dividing the sheet in the sheet width direction, the uniformity of the lip temperature in the sheet width direction can be improved. Since the width is half the division width f at the center, uniform accuracy of the lip temperature can be improved. Therefore, by these operations, the lip temperature becomes uniform in the sheet width direction, and the expansion ratio, the sheet thickness, and the cell shape of the obtained foamed sheet 3 become uniform.

In this embodiment, as shown in FIG. 1, the temperature control tube 5 for lip temperature control is provided on the lip portion c. In addition, the temperature control tube 5 for lip temperature control may be embedded in the T-die 2 as shown in FIG. With such a configuration, the air gap d can be shortened, and the cooling effect of the foam sheet 3 after flowing out from the lip portion c can be improved.

[0034]

According to the method for producing a foamed sheet according to the present invention, there is provided a foamed sheet producing method for producing a foamed sheet by extruding a polyolefin resin blended with a foaming agent into a sheet from a T-die. The temperature is set lower than the molten resin in the T-die, and when the molten resin is extruded, the molten resin is cooled by the lip portion, so that the effect of attaching the molten resin to the lip portion can be reduced. Performance can be improved.

The method for producing a foamed sheet according to the present invention is directed to a method for producing a foamed sheet by extruding a polyolefin resin blended with a foaming agent into a sheet from a T-die to produce a foamed sheet. ,
Since the cooling is performed stepwise by a group of rolls that are kept at a lower temperature than the upstream side of the flow channel, the melt tension of the sheet surface layer is improved, the foaming gas is prevented from being diffused and the foaming due to the foam breaking phenomenon is suppressed, and the predetermined foaming ratio is increased. Obtainable.

The foamed sheet manufacturing apparatus according to the present invention is a foamed sheet manufacturing apparatus for manufacturing a foamed sheet by extruding a polyolefin resin blended with a foaming agent into a sheet shape from a T-die. Since a temperature control controller different from the main body of the T-die is provided to control the temperature at a temperature different from that of the main body of the T-die, the effect of adhering the molten resin to the lip can be reduced.
The surface properties of the foam sheet can be improved.

Further, the temperature control control unit includes a temperature control tube in contact with the lip portion, and is configured to flow a temperature-controlled medium through the temperature control tube. Can be diverted by partially improving it, and the installation property of the equipment can be improved.

Further, the temperature control control section includes a temperature control tube buried in the T die, and is configured to flow a temperature controlled medium through the temperature control tube. It is possible to improve the ease of installation and to improve the ease of installation of other components arranged around the T-die.

Further, the temperature adjustment control section performs divided temperature adjustment control in the sheet width direction and the upper and lower lips. If the lip temperature is controlled uniformly in the sheet width direction and the upper and lower lips, the uniformity of the lip temperature is improved. As a result, the expansion ratio, sheet thickness, and cell shape of the obtained foamed sheet can be made uniform.

Further, if the temperature control section is divided at a predetermined interval in the sheet width direction so that the area near the end of the sheet is a half area of the sheet center division width, the uniformity of the lip temperature is improved. Therefore, the expansion ratio, sheet thickness, and cell shape of the obtained foamed sheet can be made more uniform.

Further, if rolls capable of controlling the temperature are arranged in a staggered manner on the downstream side of the T-die and the foamed sheet flowing out of the T-die is further cooled by passing between the rolls, the rolls are arranged in a staggered manner. As a result, there is no risk of the foamed sheet being crushed when passing between the rolls, and since the sheet is cooled during the passage, the melt tension of the surface layer of the sheet is improved, and the foamed gas is diffused and foamed due to foaming phenomenon. Formation is suppressed, and a predetermined expansion ratio can be obtained.

If the distance from the lip of the T die to the first contact of the foam sheet of the roll can be changed, the cooling effect of the foam sheet after flowing out of the lip can be further improved. Can be done.

If the gap between the rolls through which the foam sheet passes can be changed, it can be set according to the manufacturing conditions so that the foam sheet will not be crushed, so that the versatility of the apparatus can be improved. .

Further, if the roll is configured to be able to control the temperature in at least two stages of the former stage and the latter stage, the foam sheet is not rapidly cooled, so that the expansion of bubbles can be prevented from being suppressed, and the predetermined expansion ratio can be reduced. It can be obtained more reliably.

When the foamed sheet that has passed through the above roll is configured to be cooled to room temperature by a metal polishing roll, a foamed sheet having excellent closed cell properties, light weight and high rigidity can be manufactured.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing a foam sheet manufacturing apparatus according to an embodiment of the present invention.

2A is a plan view partially showing the vicinity of a T-die in FIG. 1, and FIG. 2B is a front view of FIG.

FIG. 3 is a front view schematically showing a foam sheet manufacturing apparatus according to another embodiment of the present invention.

FIG. 4 is a front view schematically showing a conventional foam sheet manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conduit 2 T die 3 Foam sheet 4 Metal polishing roll 5a Temperature control tube for lip temperature control (upper side) 5b Temperature control tube for lip temperature control (lower side) 6a Small diameter roll (previous stage) 6b Small diameter roll (rear stage) a Manifold part b Land Part c lip part d air gap e gap between small diameter rolls f division width in sheet width direction (sheet center part) g division width in sheet width direction (sheet end part)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 105: 04 B29L 7:00 C08L 23:00 (72) Inventor Tomomi Nakamura Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi Prefecture No. 1 Takamichi, Mitsubishi Heavy Industries, Ltd. Nagoya Kiki Seisakusho Co., Ltd. (72) Inventor Masahiro Tsuboi No. 1, Iwazuka-cho, Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi F-term inside Nagoya Kiki Mfg. Co., Ltd. 4F074 AA08 AA09 AA17 AA24 AA26 BA00 BA01 CA22 CC05Y CC05Z CC33Y CC64 DA02 DA08 DA12 DA34 DA35 4F207 AA03 AB02 AG01 AG20 AK01 AK02 AP05 AR06 AR07 AR12 KA01 KA11 KF04 KK45 KK64 KK65 KL63 KM05 KM15

Claims (12)

[Claims] 1. A foamed sheet manufacturing method for manufacturing a foamed sheet by extruding a polyolefin resin blended with a foaming agent into a sheet shape from a T-die, wherein the lip portion of the T-die has a lower temperature than the molten resin in the T-die. Wherein the molten resin is extruded and cooled at the lip portion. 2. A foamed sheet manufacturing method for manufacturing a foamed sheet by extruding a polyolefin resin blended with a foaming agent into a sheet from a T-die, wherein the foamed sheet flowing out of the T-die is cooled at a temperature lower than the upstream side of the flow path. A method for producing a foamed sheet, characterized in that the foamed sheet is cooled stepwise by a group of rolls held in the sheet. 3. A foam sheet manufacturing apparatus for producing a foam sheet by extruding a polyolefin resin blended with a foaming agent into a sheet from a T-die, wherein a temperature different from that of the body of the T-die near the lip portion of the T-die. An apparatus for producing a foamed sheet, wherein a temperature control unit is provided so that temperature control can be performed at a temperature different from that of the main body of the T-die. 4. The temperature control unit according to claim 3, wherein the temperature control unit includes a temperature control tube that is in contact with the lip, and the temperature control medium flows through the temperature control tube. The foamed sheet manufacturing apparatus according to the above. 5. The temperature control unit according to claim 3, wherein the temperature control unit includes a temperature control tube buried in the T die, and the temperature control medium flows through the temperature control tube. The foamed sheet manufacturing apparatus according to the above. 6. The temperature control unit according to claim 1, wherein the temperature control unit performs split temperature control in the sheet width direction and in the upper and lower portions of the lip, and uniformly controls the lip temperature in the sheet width direction and in the upper and lower portions of the lip. 6. The foam sheet manufacturing apparatus according to 4 or 5. 7. The foamed sheet according to claim 6, wherein the temperature control section is divided at a predetermined interval in a sheet width direction, and is a region near a sheet end and a half of a sheet central division width. manufacturing device. 8. The temperature controllable rolls are arranged in a zigzag arrangement downstream of the T-die, and the foam sheet flowing out of the T-die is further cooled by passing between the rolls. The foamed sheet manufacturing apparatus according to any one of Claims 7 to 7. 9. The foamed sheet manufacturing apparatus according to claim 8, wherein a distance from a lip portion of the T die to a portion of the roll where the foamed sheet comes into contact first can be changed. 10. The foam sheet manufacturing apparatus according to claim 8, wherein a gap between rolls through which the foam sheet passes can be changed. 11. The foamed sheet manufacturing apparatus according to claim 10, wherein the temperature of the roll is controllable in at least two stages, a first stage and a second stage. 12. The foam sheet passing through the roll,
The foamed sheet manufacturing apparatus according to claim 11, wherein the apparatus is cooled to room temperature by a metal polishing roll.