JP2002307524A - Method for manufacturing thermoplastic resin foam and molding apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing thermoplastic resin foam capable of obtaining plate-shaped thermoplastic resin foam having good surface properties, good right angle properties in its cross section and large thickness. SOLUTION: In the method for manufacturing the thermoplastic resin foam by extruding a thermoplastic resin containing a foaming agent through a cap equipped with an arcuate orifice and passing the extruded foam through the gaps between a plurality of upper and lower arcuate roll sets arranged in the foam extrusion direction while pressing the upper and lower surfaces thereof, a plurality of the roll sets are rotationally driven at independently controlled speeds and the foam extruded from the arcuate orifice is passed through an arcuate mold and subsequently passed while pressed by the upper and lower arcuate roll sets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermoplastic resin foam and a molding apparatus for producing the same. More particularly, the present invention relates to a method for producing a plate-like thermoplastic resin foam having a desired cross section by extrusion foaming, and a molding apparatus used for the production.

[0002]

2. Description of the Related Art Thermoplastic foams are widely used as industrial products having excellent heat insulation and cushioning properties. As a method for producing the same, an extrusion foaming method in which a thermoplastic resin containing a foaming agent is extruded from an extruder to form a foam is widely used.

[0003] In such a conventional extrusion foaming method, when an attempt is made to obtain a plate-like foam having a large thickness by extrusion foaming, a corrugated foam is likely to undulate in the width direction, and the thickness of the foam is uniform. Difficult to get a perfect foam. In order to prevent this, Japanese Patent Publication No. 53328/1987 discloses, for example, a molding apparatus and a method for obtaining a plate-like foam by passing a foam extruded from an arc-shaped orifice while pressing it with an arc-shaped roll set. Has been described. However, according to the method described in Japanese Patent Publication No. 53328/1987, it was found that the foaming of the desired shape could not be obtained because the waving of the foam could not be suppressed depending on the extrusion conditions. Further, there is a problem that the thickness of the side portion is reduced even under the condition that a substantially plate-shaped foam can be obtained, which leads to an increase in the cost of a post-processing step.

Japanese Patent Publication No. 2-7820 discloses that a foam extruded from an arc-shaped orifice is passed while being pressed by an arc-shaped roll set, and then the width of the foam is controlled by an edge forming roll. A method is described. However, even according to the method described in Japanese Patent Publication No. 2-7820, a foam having a desired shape cannot be obtained because the waving of the foam cannot be suppressed depending on the extrusion conditions. Further, even under the condition that a substantially plate-shaped foam can be obtained, the problem that the thickness of the side portion of the foam becomes thin, which leads to an increase in the cost of the post-processing step remains.

[0005] In addition, a molding apparatus combining an arc-shaped orifice and a molding die has been proposed. For example, Japanese Patent Publication No. 63-16250 discloses a molding apparatus and method for obtaining a plate-like foam through a molding die having an arc-shaped inlet corresponding to the arc of the orifice. Have been. However, according to the method described in Japanese Patent Publication No. 63-16250, the foam has a thickness distribution in which the center portion is thicker and the side portions are thinner under the condition that the resistance when passing through the molding die is small. Further, there is a problem that the side portion is wavy, and under the condition of high resistance, the surface of the foam is cracked or peeled and the surface property is deteriorated.

As described above, there is known a method of extruding a foamed sheet having a large thickness by using a molding apparatus in which a foam extruded from an arc-shaped orifice is combined with an arc-shaped roll set or a molding die having an arc-shaped inlet. However, the conventional molding apparatus and method have a problem that the uniformity of the thickness of the cross section of the foam is insufficient and the surface property is deteriorated.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a large thickness plate-like thermoplastic resin foam having good surface properties and good cross-section perpendicularity. It is an object of the present invention to provide a method for producing a thermoplastic resin foam and a molding apparatus for producing the same.

[0008]

According to the method for producing a thermoplastic resin foam of the present invention, a thermoplastic resin containing a foaming agent is extruded through a base provided with an arc-shaped orifice, and the upper and lower surfaces of the extruded foam are formed. A method for producing a thermoplastic resin foam in which a plurality of sets of rolls arranged in an arc shape are arranged along the direction in which the foam is extruded and passed while being pressed by an arc-shaped upper and lower set of rolls. After being driven to rotate at a controlled speed, the foam extruded from the arc-shaped orifice is passed through an arc-shaped molding die, and then passed while being pressed by the arc-shaped upper and lower roll sets. And

In the method for producing a thermoplastic resin foam of the present invention, it is preferable that the rotational speed of each of the roll sets is set to gradually increase in the direction of the extrudate.

The method for producing a thermoplastic resin foam according to the present invention is further characterized in that the gap between the arc-shaped forming die and the upper and lower roll sets closest to the forming die is closest to the forming die. It is preferable to set the rotational speed of the upper and lower rolls in an arc shape sufficiently low as long as the foam does not undulate in the extrusion direction.

In the method for producing a thermoplastic resin foam of the present invention, it is preferable that the foam is a plate-like foam whose width is 5 to 500 times the thickness.

Further, the molding apparatus for producing a thermoplastic resin foam of the present invention comprises: a die having an arc-shaped orifice connected to an extruder; and a direction in which the foam is extruded, which presses the upper and lower surfaces of the foam. Upper and lower roll sets having a plurality of donut-shaped flakes arranged in plural sets along the arc, an arc-shaped forming die arranged between the die and the upper and lower roll sets, and the upper and lower roll sets And a rotary drive mechanism for the flakes connected to one of the flakes at the side ends of the alternate roll sets to rotate adjacent flakes together, and the upper and lower roll sets are independently pressed against the extrudate with a constant force. A pressing mechanism and rotation control means for rotating and driving each of the plurality of roll sets independently at a controlled speed are provided, and the foam extruded from the arc-shaped orifice is passed through an arc-shaped molding die. Was The Chi, characterized in that the passage while nipped by said arcuate roll sets.

In the molding apparatus for producing a thermoplastic resin foam according to the present invention, the drive control means may include a speed adjusting circuit for setting the rotational speed of each roll set to gradually increase in the direction of the extrudate. It is preferred to include.

In the apparatus for producing a thermoplastic resin foam of the present invention, it is preferable that both the inlet and the outlet of the molding die are arc-shaped.

In the apparatus for producing a thermoplastic resin foam according to the present invention, it is preferable that the cross section of the resin passage of the arc-shaped molding die is widened in the width direction in the direction of travel of the extrudate. Further, it is preferable that the thickness of the resin passage of the molding die is increased at least in the vicinity of the orifice in the direction of travel of the extrudate.

Further, in the molding apparatus for producing a thermoplastic resin foam of the present invention, it is preferable that a coating portion of polytetrafluoroethylene is formed on at least a part of an inner surface of the arc-shaped molding die.

[0017]

DETAILED DESCRIPTION OF THE INVENTION The inventors of the present invention have conducted intensive studies on a method and a forming apparatus for improving the above-mentioned conventional problems, and as a result, have found that a plurality of sets of arc-shaped orifices and arc-shaped upper and lower roll sets are arranged. In the meantime, an arc-shaped molding die is provided, and the foam extruded from the arc-shaped orifice is molded in the arc-shaped molding die so that the cross section becomes substantially plate-shaped, and then independently controlled at a controlled speed. If the foam is stretched in the width direction with the thickness regulated, if it is passed while being pressed by the arc-shaped roll set driven by rotation,
It has been found that a large plate-like thermoplastic resin foam having good surface properties and good cross-section perpendicularity and a large thickness can be easily obtained.

Embodiments of the present invention will be described below, but any method is not limited to the following.

One embodiment of the manufacturing method of the present invention will be described with reference to the drawings. 1 is a side view of a molding apparatus according to the manufacturing method of the present invention, FIG. 2 is a front view of the molding apparatus of FIG. 1, FIG. 3 is a diagram schematically showing a cross section of the molding apparatus of FIG. FIG. 5 is a cross-sectional view showing an example of a thin section, FIG. 6 is a side view of the thin section in FIG. 5, and FIG.
FIG.

As shown in FIGS. 1 to 4, the forming apparatus used in the manufacturing method of the present invention includes upper and lower roll sets 1 and 2 having a plurality of donut-shaped thin pieces P, and the roll sets 1 and 2.
And a roll driving mechanism A connected to one of the flakes P at the side ends of the alternate roll sets 1 and 2 to rotate the adjacent flakes P together, and a constant force independently of the roll sets 1 and 2 And pressing mechanisms B and C for pressing against the extrudate. The upper and lower roll sets 1 and 2 each include a stationary roll shaft 3 and a plurality of donut-shaped thin pieces P rotatably mounted on the roll shaft 3 in a juxtaposed relationship. As shown in FIGS. 5 and 6, for example, the thin piece P has an annular projection 4 formed on the inner periphery and a tapered surface 5 toward the tip.
Are formed, and five engaging protrusions 6 are formed at equally spaced positions on the side surface, and fifteen engaging holes 7 are formed at equally spaced positions between the engaging protrusions 6. . Roll set 1, 2
Are inserted into the engaging holes 7 of the adjacent thin pieces P by displacing the engaging projections 6 of the thin pieces P by one pitch.
The engaging projection 6 of the adjacent thin piece P and the engaging hole 7 of the other adjacent thin piece P are engaged with each other by shifting the engaging projection 6 by one pitch.
At this time, the height of the engagement protrusion 6 is, for example, three pieces P
Of the same thickness. In order to smooth the rotation of the thin piece P with respect to the roll shaft 3, it is preferable to arrange a ball bearing or a slide bearing on the inner circumferential surface of the thin piece P or on the inner circumferential surface between the thin pieces P.

The rotary drive mechanism A includes a connector 11 connected to a thin piece P disposed at a side end, and a drive motor 1
2 and a sprocket 13 connected to the drive motor 12
And a chain 14 wound around a sprocket portion formed on the connecting tool 11 can be used. The rotation drive mechanism A is connected to the pressing mechanisms B and C, respectively.

The pressing mechanism B of the roll set 1 is connected to an air cylinder 17 provided vertically on a side portion of a main body frame 15 via a joint portion 16 and to a tip of the air cylinder 17 via a ring ball 18. And the elevating member 19 can be used. The elevating member 19 is composed of a slide shaft 20 erected on the upper and lower portions of the main body frame 15 and an elevating table 21 inserted through the slide shaft 20. The roll shaft 3 and the drive motor 12 of the upper roll set 1 are connected to the lift 21 by a flange or the like.

A pressing mechanism C for the lower roll set 2
A rotating portion 24 in which left and right pinion shafts 22 supported by a shaft are connected by a universal joint 23 meshes with a pinion 25 of the rotating portion 24, and is supported by an elevating table 26 inserted through the slide shaft 20. Rack 27
An elevating speed reducer 28 that rotates one of the pinion shafts 22 supported by bearings 27 and driven to rotate can be used. The roll shaft 3 of the lower roll set 2
The drive motor 12 is connected to the lift 26 by a flange or the like.

In the molding apparatus according to the present embodiment, FIG.
As shown in FIGS. 4 to 4, the base 31 is tightly connected to the tip of the extruder 32, and the base of the base 31 is provided with an arcuate orifice 33. A molding die 34 whose inlet and outlet are both arc-shaped is connected. In the molding die 34, a resin passage 35 connected to the orifice 33 is formed.
A coating portion 36 coated with polytetrafluoroethylene is formed on a surface in contact with the resin passage 35. An arc-shaped upper roll set 1a, 1b, 1c through which the extruded foam 36 is passed while being pressed at the tip of the molding die 34.
1d, 1e and an arcuate lower roll set 2a, 2b, 2
Five sets of upper and lower rolls consisting of c, 2d, and 2e are arranged.

In this embodiment, after the thermoplastic resin containing the heat-plasticized foaming agent is supplied from the extruder 32 to the base 31, it is foamed through the arc-shaped orifice 33 and both the inlet and the outlet are formed. It is extruded into the resin passage 35 of the arc-shaped molding die 34. In the resin passage 35, the extruded material is foamed, but is extruded while being regulated so as to have a substantially plate-shaped cross section by being regulated in both the thickness direction and the width direction. The foam 36 having a substantially plate-shaped cross section further includes an arc-shaped upper roll set 1a, 1b, 1c, 1d, 1e and an arc-shaped lower roll set 2a, 2b, 2c, 2d, 2d.
e and passes while being pinched by the arc-shaped roll sets 1 and 2. At this time, since the foam 36 is stretched in the width direction in a state where the thickness is regulated, a large plate-like thermoplastic resin foam having a good surface property and a good cross-section perpendicularity is used. Obtainable. As the thermoplastic resin, a resin having a low expansion ratio of less than 10 times or a resin having a high expansion ratio of 10 times or more can be used.

In the present embodiment, the foam 36
A first arc-shaped roll set composed of an upper roll set 1a and a lower roll set 2a, a second arc-shaped roll set composed of an upper roll set 1b and a lower roll set 2b, Roll set 1c and lower roll set 2c
, A fourth arc-shaped roll set including an upper roll set 1d and a lower roll set 2d, and a fifth arc-shaped roll including an upper roll set 1e and a lower roll set 2e. Although the roll sets are arranged in the order of the sets, in the present invention, the number of roll sets is not particularly limited to five, and at least two sets are sufficient. The molding apparatus of the present embodiment is connected to the drive motor 12 by rotation control means which is a control panel 37 for controlling the speed of a plurality of roll sets. Here, when the thermoplastic resin having a low expansion ratio is extruded by two or more sets of upper and lower arc-shaped rollers, as the foamed resin is extruded from a molding die, the second roll with respect to the speed of the first roll set is increased. If the speed after the roll set is too high, extrusion molding is performed before foaming proceeds. Therefore, the speed ratio of the second roll set to the first roll set is 1.0 times, preferably 1. 0 to 1.1 times. On the other hand, when the thermoplastic resin having a high expansion ratio is extruded by two or more sets of upper and lower arc-shaped rollers, the control panel 37 increases the rotation speed of each set of rolls in the traveling direction of the extrudate. It is preferable to include a speed adjusting circuit for setting the speed gradually higher. By adjusting the rotation speed of each of the arc-shaped roll sets 1 and 2, it is possible to appropriately control a situation in which the foam 36 passes while being pressed by the arc-shaped roll sets 1 and 2. For example, the second arc-shaped roll set 1b, 2b is replaced with the first arc-shaped roll set 1a, 2b.
a is rotated at a speed ratio of 1.01 to 1.2 times, preferably 1.015 to 1.15 times faster than a, and the third arc-shaped roll set 1c, 2c is rotated by the first arc-shaped roll set 1a, 2a
Than the first arc-shaped roll set 1a, 2a by rotating the fourth arc-shaped roll set 1d, 2d at a speed ratio of 1.02 to 1.4 times, preferably 1.025 to 1.35 times. And the fifth arc-shaped roll set 1e, 2e is rotated at a speed ratio of 1.045-1.55 times faster than the first arc-shaped roll set 1a, 2a.
By rotating 1.75 times faster, the foam 36 is gradually stretched in the width direction while the thickness is regulated,
A large plate-like thermoplastic resin foam having good surface properties and good cross-section perpendicularity and a large thickness can be obtained.

When the extrudate foams in the resin passage 35, the gap between the molding die 34 and the arc-shaped first roll set 1a, 2a closest to the molding die 34 (see FIG. 7
As shown in FIG.
a, 2a), the rotational speed of the first roll set 1a, 2a is set sufficiently low within a range where the foam 36 does not undulate in the extrusion direction. By doing so, the foam 36 can be extruded while being formed in the molding die 34 so as to be regulated in both the thickness direction and the width direction and to have a substantially plate-shaped cross section. This makes it possible to eliminate waviness on the side of the thermoplastic resin foam. For example, the first roll set 1a,
When the gap 40 is twice or more the thickness of the foam 36, the rotation speed of 2a is 0.3 to 3 times the value derived from the following equation (1), preferably 0.5 to 2 times. It is twice.

V × p / S (1) Here, V: volumetric flow rate of resin (cm ³ / min) p: expansion ratio S: outlet cross-sectional area of molding die (cm ² ).

The resins used in the present invention include:
Thermoplastic resins such as polyolefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene, polyester resins such as polyethylene terephthalate, and polyvinyl halide resins such as polyvinyl chloride, alone or as a mixture of two or more. Can be used.

The blowing agents used in the present invention include, as physical blowing agents, propane, butane, isobutane,
Hydrocarbons such as pentane, HFC134a, HFC1
Alternative fluorocarbons such as 52a, chlorinated hydrocarbons such as methyl chloride and ethyl chloride, lower alcohols such as methanol, ethanol and propanol, ethers such as diethyl ether, dimethyl ether, methyl and ethyl ether, nitrogen, carbon dioxide, air And inorganic gases such as argon, water and the like, and sodium bicarbonate, azodicarbonamide, dinitrosopentamethylenetetramine and the like as a chemical foaming agent can be used alone or as a mixed gas thereof. These blowing agents are mixed in an amount of 0.01 to 50% by weight based on the thermoplastic resin.

When a foam is produced by the production method of the present invention, in addition to the resin and the foaming agent, a bubble-forming nucleating agent, a flame retardant, a stabilizer, a lubricant, a plasticizer, a pigment, a dye, an antistatic agent, and the like. May be appropriately used.

The dimensions of the plate-like foam produced by the present invention are, for example, a width of about 1000 mm and a thickness of 5 to 5 mm.
There are various sizes such as 100 mm, and the ratio of the width of the plate-like foam to the thickness is in the range of 5 to 500 times.

The shape of the inlet of the molding die needs to be formed immediately after being extruded from a die having an arcuate orifice. Therefore, an arcuate shape matching the shape of the arcuate orifice is preferable. As the shape of the exit of the mold, it is necessary to allow the mold to pass while being pressed by an arc-shaped roll set before being cooled and solidified. Therefore, an arc-shaped one that matches the shape of the arc-shaped roll set is preferable.

Regarding the cross-sectional shape of the resin passage of the arc-shaped molding die, if either the thickness or the width is constant or reduced in the direction of travel of the extrudate, the shape during extrusion is reduced. Since the resistance increases and the surface property of the obtained foam becomes poor, it is preferable that the foam also expands in the thickness direction and the width direction.

Further, as for the resin passage surface of the molding die, it is preferable that at least a part of the inner surface is coated with polytetrafluoroethylene in order to reduce the resistance at the time of extrusion.

As the extruder used in the present invention, a known extruder used as an extruder for a thermoplastic resin can be used, but the extruder is mixed with a resin and a foaming agent to reach a temperature suitable for foaming. It needs to be able to cool, single-screw extruder,
A kneading and cooling device such as a twin-screw extruder, a cooling mixer or a static mixer, or a polymer material such as those obtained by connecting a plurality of them can be heated to an appropriate temperature and kneaded while applying an appropriate shear stress under pressure. Devices, but are not limited to these.

[0037]

EXAMPLES The contents of the present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A molding apparatus shown in FIGS. 1 to 4 was prepared, and a resin passage surface of a molding die was coated with polytetrafluoroethylene.

Then, low-density polyethylene was used as a thermoplastic resin, and 100 parts by weight of the low-density polyethylene was mixed with 2 parts by weight of azodicarbonamide as a foaming agent, and the mixture was supplied to an extruder having a diameter of 30 mm. After mixing and melting with an extruder, the thickness is 1 mm and the length is 100
mm and an orifice having an arc radius of 50 mm was extruded so that the extrusion amount per hour was 5 kg.

The entrance of the molding die has a thickness of 3 mm,
The arc length is 100 mm, the arc radius is 50 mm,
The exit of the molding die has a thickness of 10 mm and an arc length of 2 mm.
It was 00 mm and the radius of the arc was 100 mm. The foam was passed while being pressed by five rolls. At this time, all the outermost velocities of the flakes in the five roll sets were set to 0.15 meters per minute (V =
From 92 cm ^{3 /} min, p = 4.0, S = ²⁰ cm ² ,
Since the value of the above equation (1) is V × p / S = 0.18,
If the ratio at this time is 0.83, 0.18 × 0.8
3 = 0.15).

The obtained foam has a density of 225 kg / m
^{3. The} width is 185mm, the average thickness is 10mm, the difference between the maximum and minimum thickness is 0.3mm, the cross-section is perpendicular, and the surface is free from cracks, pock and shark skin. A plate-like foam was obtained.

Example 2 Polystyrene was used as a thermoplastic resin, and 2 parts by weight of sodium bicarbonate was used as a foaming agent, and extruded in the same manner as in Example 1 so that the extrusion amount per hour was 6 kg. At this time, all the outermost velocities of the flakes in the five sets of rolls were set to 0.3 m / min.
V = 100 cm ^{3 /} min, p = 4.8, S = 20 cm ²
Therefore, the value of the above equation (1) is V × p / S = 0.24. If the ratio at this time is 1.25, then 0.24 ×
1.25 = 0.3).

The density of the obtained foam was 258 kg / m.
^{3. The} width is 188mm, the average thickness is 10mm, the difference between the maximum and minimum thickness is 0.3mm, the cross-section is perpendicular, and the surface is free from cracks, pock and shark skin. A plate-like foam was obtained.

Comparative Example 1 The same procedure as in Example 1 was carried out except that no molding die was used.

The resulting foam has a density of 208 kg / m
^{3. The} width was as thin as 202 mm and the average thickness was 8 mm, and the difference between the maximum and minimum thicknesses was as large as 5.1 mm. A corrugated wavy parallel to the extrusion direction remained in the foam, and the side portions were particularly thin, so that it could not be said that the foam plate had good cross-section perpendicularity.

Comparative Example 2 The same operation as in Example 1 was carried out except that the roll was not pressed and passed using an arcuate roll set.

The obtained foam had a width of about 30
In the direction of thickness, it undulated in the extrusion direction with a swing width of about 1 cm in the thickness direction in the thickness direction. The thickness distribution of the cross section was also thin on the side, and it could not be said that the foam plate had good cross-section perpendicularity.

Comparative Example 3 In Example 1, the thickness of the resin passage surface of the molding die was 1
The operation was performed in exactly the same manner as in Example 1 except that the distance was fixed at 0 mm.

On the surface of the obtained foam, there are many fine undulations in the direction perpendicular to the extrusion direction, and cracks and cracks are observed in some places, so that it cannot be said that the foam plate has good surface properties. Was something.

Example 3 Next, the same forming apparatus as in Example 1 was prepared except that the number of arc-shaped roll sets was changed to three. Then, polystyrene is used as the thermoplastic resin, 0.1 part by weight of talc, 4 parts by weight of isobutane and 2 parts by weight of dimethyl ether are injected as the foaming agent, and the extrusion amount per hour is the same as in Example 1 so that the extrusion amount becomes 6 kg. And the foamed body was passed through while pressing the foam with three sets of rolls. At this time, in the first roll set closest to the molding die among the three roll sets, the speed of the outermost periphery of the flake (the speed of the surface where the flake comes into contact with the foam) is set to 1.05 m / min ( Note that V = 100
From cm ^{3 /} min, p = 25.6 and S = ²⁰ cm ² , the value of the above equation (1) is V × p / S = 1.28. Therefore, if the ratio at this time is 0.82, 1 .28 × 0.82
= 1.05), and in the gap (30 mm) between the molding die and the roll set closest to the molding die, the speed was sufficiently slowed down within a range where the foam did not undulate in the extrusion direction. In the second set of rolls, the speed of the outermost periphery of the flake was set to 1.1 per minute.
In the third roll set farthest from the molding die among the three roll sets, the speed of the outermost periphery of the flake is 1.25 meters per minute (speed ratio 1.1).
9), and each roll set was set so as to rotate gradually and rapidly in the direction of travel of the extrudate.

The obtained foam had a density of 39 kg / m ³ ,
The width was 229 mm, the thickness was 11 mm on average, and the difference between the maximum and minimum thickness was 0.6 mm. Further, the obtained foam had a good cross-section perpendicularity, no side waving, and a good surface without cracks, pock or shark skin on the surface.

Example 4 Polystyrene was used as the thermoplastic resin, and talc 0.1 was used.
Parts by weight, 4 parts by weight of isobutane and 2 parts by weight of dimethyl ether as a foaming agent were pressed in to extrude 6 parts per hour.
Extruded in the same manner as in Example 3 so as to obtain kg. An arc-shaped forming die and an arc-shaped roll set similar to those used in Example 3 were used. In the roll set closest to the molding die, the outermost peripheral speed of the flake was set to 1.1 m / min, and in the second roll set, the outermost peripheral speed of the flake was set to 1.2 m / min (speed ratio 1 .09) (V = 100 cm)
^{From 3 /} min, p = 27.0 and S = 20 cm ² , the value of the above equation (1) is V × p / S = 1.35. Therefore, if the ratio at this time is 0.89, then 1. 38 × 0.89 =
1.2), and the speed of the outermost periphery of the flake in the third roll set furthest from the molding die was set to 1.3 m / min (speed ratio 1.18).

The obtained foam had a density of 37 kg /
m ³ , width 219 mm, thickness 10 mm on average, and the difference between the maximum and minimum thickness was 0.4 mm. The obtained foam had a good cross-section perpendicularity, no wavy side portions, and had good surface properties without cracks, pock and shark skin on the surface.

Comparative Example 4 Example 3 was carried out in exactly the same manner as in Example 3 except that the outermost peripheral speeds of the flakes in the three roll sets were all set to 1.05 meters per minute.

The obtained foam has a density of 41 kg /
m ³ , the width was 242 mm, the thickness was 12 mm on average, and the difference between the maximum and minimum thickness was 0.8 mm. In the foam, fine streaky cracks are generated parallel to the extrusion direction,
The sides were wavy.

Comparative Example 5 In Example 3, the speed of the outermost periphery of the flakes in the first roll set closest to the molding die among the three roll sets was 1.2 m / min, The speed of the outermost periphery of the flakes in the roll set is 1.5 meters per minute, and 3
In the set of rolls, the speed of the outermost periphery of the flakes in the roll set farthest from the forming die is set to 1.8 m / min.
The operation was carried out in exactly the same manner as in Example 3 except that each set of rolls was set so as to gradually rotate in the direction of the extrudate.

The obtained foam had a density of 35 kg / m ^3.
And the width is 195 mm. The average thickness is 9m
m, which was smaller than the thickness of the foam of Example 3.
The difference between the maximum and the minimum of the thickness is 1.1 mm,
It was larger than the difference of Example 3. The side portion of the foam had a small thickness and was wavy, and could not be said to be a foam having good perpendicularity in cross section.

Comparative Example 6 Example 3 was carried out in the same manner as in Example 3 except that all the outermost velocities of the flakes in the three roll sets were changed to 1.2 m / min.

[0059] The obtained foam has fine cracks in the form of stripes parallel to the extrusion direction, and the side of the foam has a small thickness and has undulations. Neither the perpendicularity nor the surface properties were good foams.

[0060]

As described above, according to the present invention, an arc-shaped molding die is provided between an arc-shaped orifice and an arc-shaped roll set, and the foam extruded from the arc-shaped orifice is formed into an arc-shaped orifice. After being formed into a substantially plate-shaped cross section in a forming die, the sheet is passed while being pressed by the arc-shaped roll set, so that the surface property is good, and the thickness of the cross section is perpendicularity and the thickness is good. A plate-like thermoplastic resin foam can be obtained.

Further, by arranging a plurality of roll sets along the direction in which the foam is extruded, and by rotating and driving the roll sets at independently controlled speeds, the surface properties are good and the perpendicularity of the cross section is good. At the same time, it is possible to obtain a plate-like thermoplastic resin foam having a large thickness and having no wavy side portions.

[Brief description of the drawings]

FIG. 1 is a side view of a molding apparatus according to a manufacturing method of the present invention.

FIG. 2 is a front view of the molding apparatus of FIG.

FIG. 3 is a view schematically showing a cross section of the molding apparatus of FIG. 1;

FIG. 4 is a sectional view taken along line II of FIG. 3;

FIG. 5 is a cross-sectional view showing an example of a thin piece.

FIG. 6 is a side view of the slice of FIG. 5;

FIG. 7 is an enlarged view of a main part of FIG.

[Explanation of symbols]

 1, 2 Roll set 1a, 1b, 1c, 1d, 1e Upper roll set 2a, 2b, 2c, 2d, 2e Lower roll set 3 Roll shaft 4 Annular protrusion 5 Tapered surface 6 Engagement protrusion 7 Engagement hole 31 Base Reference Signs List 32 extruder 33 orifice 34 molding die 35 resin passage 36 coating part of polytetrafluoroethylene 36 foam 37 control panel A rotation drive mechanism B, C pressing mechanism P slice

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 B29L 7:00 (72) Inventor Mamoru Ishida 3-15-3 Hibarigaoka, Takarazuka-shi, Hyogo F-term (Reference) 4F207 AB02 AG20 AP08 AR09 KA01 KA11 KL74 KL75 KL76 KM06 KM16 KM21

Claims (9)

[Claims] 1. A thermoplastic resin containing a foaming agent is extruded through a base provided with an arc-shaped orifice, and a plurality of sets of upper and lower surfaces of the extruded foam are arranged along the direction in which the foam is extruded. A method for producing a thermoplastic resin foam in which a plurality of sets of rolls are independently rotated and driven at a controlled speed, and are extruded from the arc-shaped orifice. A method for producing a thermoplastic resin foam, characterized in that, after passing the foamed body through an arc-shaped molding die, the foamed body is passed while being pressed by the upper and lower rolled arc sets. 2. The method for producing a thermoplastic resin foam according to claim 1, wherein the rotational speed of each of the roll sets is set to gradually increase in the direction in which the extrudate advances. 3. In the gap between the arc-shaped forming die and the upper and lower arc-shaped roll set closest to the forming die, the rotational speed of the arc-shaped upper and lower roll set closest to the forming die is set to the foam. 3. The method for producing a thermoplastic resin foam according to claim 2, wherein the temperature is set sufficiently slow as long as the resin does not undulate in the extrusion direction. 4. The width of the foam is 5 to 50 with respect to the thickness.
The method for producing a thermoplastic resin foam according to claim 1, wherein the foam is a 0-fold plate-like foam. 5. A base provided with an arc-shaped orifice connected to an extruder, and a plurality of donut-shaped flakes arranged in a plurality of sets along a direction in which the foam is extruded, for clamping the upper and lower surfaces of the foam. An upper and lower roll set having an arc shape, an arc-shaped forming die arranged between the die and the upper and lower roll sets, and one of the side end flakes in the alternate roll set of the upper and lower roll sets A thin section rotation drive mechanism that is connected to and rotates adjacent thin sections together, a pressing mechanism that independently presses the upper and lower roll sets against the extrudate with a constant force, and independently sets the plurality of roll sets. Rotation control means for rotating and driving at a controlled speed.After passing the foam extruded from the arc-shaped orifice through an arc-shaped molding die, the foam is passed while being pressed by the arc-shaped roll set. Sa A molding apparatus for producing a thermoplastic resin foam. 6. The production of a thermoplastic resin foam according to claim 5, wherein said drive control means includes a speed adjusting circuit for setting the rotation speed of each roll set gradually faster in the direction of travel of the extrudate. Method. 7. The apparatus for producing a thermoplastic resin foam according to claim 5, wherein an inlet and an outlet of the molding die are both arc-shaped. 8. The cross section of the resin passage of the arc-shaped molding die expands in the width direction toward the direction in which the extruded material advances, and at least the vicinity of the orifice also expands in the thickness direction. Or an apparatus for producing a thermoplastic resin foam according to 7. 9. The molding apparatus for producing a thermoplastic resin foam according to claim 5, wherein a coating portion of polytetrafluoroethylene is formed on at least a part of an inner surface of the arc-shaped molding die. .