WO2018124213A1

WO2018124213A1 - Apparatus for manufacturing foamed resin tube and foamed resin tube

Info

Publication number: WO2018124213A1
Application number: PCT/JP2017/047037
Authority: WO
Inventors: 良治菊澤
Original assignee: 株式会社プラ技研
Priority date: 2016-12-27
Filing date: 2017-12-27
Publication date: 2018-07-05
Also published as: WO2018123090A1; JPWO2018124213A1; JP6411700B1; JPWO2018123090A1

Abstract

Provided is an apparatus for manufacturing a foamed resin tube with which a high-foam-content foamed resin tube that has a surface embossed with protrusions and recesses can be manufactured at high yields with few steps with minimal distortion in the cross-sectional shape. A first resin containing a foaming agent is supplied to a first flow channel 35 of a die 2. A second resin having a higher temperature than the first resin is supplied to a second flow channel 36. A thermal insulation layer provided inside dies 31 suppresses heating of the first resin by the second resin, and keeps the temperature of the first resin in the temperature range required to yield a high foam content. A high-foam-content foamed resin tube having an embossed profile is manufactured by performing the following simultaneously within a mold: extrusion of the first resin, which includes the foaming agent; extrusion of the second resin; and molding of the resins.

Description

Foamed resin tube manufacturing apparatus and foamed resin tube

The present invention relates to a foamed resin tube manufacturing apparatus and a foamed resin tube used for a heat insulating material for piping and the like.

Conventionally, a foamed resin tube made of a resin foam obtained by foaming a resin such as cross-linked polyethylene has been widely used as a heat insulating material (insulating cover) for piping. In this foamed resin tube, when it is attached to the outer surface of the bent part of the piping, the generation of wrinkles is suppressed to improve the aesthetic appearance, the bendability is increased to reduce friction during installation, and as a non-slip Some have their surface embossed for functional purposes.

FIG. 6 is a cross-sectional view showing a conventional method for manufacturing an embossed foamed resin tube, and FIG. 7 is a perspective view of a part of the conventional embossed foamed resin tube manufactured by the manufacturing method of FIG.

First, as shown in FIG. 6A, a flat resin foam 81 formed by foaming a resin such as cross-linked polyethylene is prepared, and a film 82 made of a thermoplastic resin is overlaid on the surface. Next, in a state where the surfaces of the film 82 and the resin foam 81 are heated and softened, an embossing roll having irregularities formed on the surface is used to perform an embossing process, as shown in FIG. Then, the uneven layer 83 in which the uneven shape of the embossing roll is transferred to the surface of the resin foam 81 is formed. The embossed resin foam 81 is cut into a strip shape having a width corresponding to the diameter of the foamed resin tube to be formed. Next, as shown in FIG. 6 (c), the cut strip-shaped resin foam 81 is rounded into a cylindrical shape so that the uneven layer 83 is on the outside, and the end faces 84a and 84b of the resin foam 81 are heated and melted. Then, as shown in FIG. 6D, the end faces 84a and 84b are butted and joined. 6A and 7B, the foamed resin tube 80 in which the uneven layer 83 by embossing is formed on the surface of the tubular resin foam 81 is completed.

In addition, in the foamed resin tube manufactured by the manufacturing method shown in FIG. 6, a joint portion 85 in which the end faces of the flat resin foam are joined appears (broken line portions in FIG. 6E and FIG. 7).

Japanese Examined Patent Publication No. 47-46463 JP-A-9-314661

In the conventional manufacturing method described above, a foamed resin tube is manufactured by using a flat resin foam as a material, rounding it into a cylindrical shape, and heat-sealing the end faces. Although there is a difference in circumference between the inner and outer circumferences of the foamed resin tube, the resin foam in the inner circumference side of the foamed resin tube is rounded into a cylindrical shape because the band-shaped resin foam before heat sealing has a certain width. The body will be compressed. For this reason, a stress difference is generated between the inner peripheral side and the outer peripheral side of the foamed resin tube, and the cross-sectional shape of the foamed resin tube becomes a distorted shape instead of a perfect circle due to the stress difference. If the cross-sectional shape of the foamed resin tube is distorted, it is not preferable in terms of aesthetics.

Further, the above-described conventional manufacturing method has a problem that the manufacturing apparatus becomes complicated and the manufacturing cost increases because the number of manufacturing steps is large. In addition, since the flat resin foam is cut into a strip shape in accordance with the pipe diameter of the pipe, if the end material is generated, the yield is lowered and the manufacturing cost is increased.

Also, since the foamed resin tube for heat insulation of water supply pipes and hot water supply pipes is required to have high heat insulation properties, it is necessary to increase the foaming ratio of the resin foam.

Therefore, the present invention provides an apparatus for producing a foamed resin tube, which can produce a high-magnification foamed resin tube having an uneven surface by embossing on the surface while suppressing distortion of the cross-sectional shape and with a small number of processes. The purpose is to do. Another object of the present invention is to provide a high-magnification foamed resin tube with less cross-sectional distortion.

The present invention relates to the production of a foamed resin tube having a tube shape and a resin foam having a foaming ratio of 20 to 30 times, and a film covering the surface of the resin foam and having an embossed pattern formed on the surface. It relates to the device. The foamed resin tube manufacturing apparatus according to the present invention includes an annular first discharge port, a first flow path communicating with the first discharge port, and an annular second discharge port disposed so as to surround the first discharge port. And a die having a second flow path that communicates with the second discharge port and is disposed so as to surround the first flow path, and a thermoplastic first resin is melt-kneaded and a foaming agent is added to the melted first resin. A first resin supply unit that mixes and supplies the first resin supply part to the first flow path of the die, and melts and kneads the thermoplastic second resin, and the molten second resin is heated to a temperature higher than that of the first resin. A plurality of first molds having a recess corresponding to a part of the outer surface shape of the foamed resin tube and a plurality of recesses corresponding to the other part of the outer shape of the foamed resin tube. The first die of the die is formed by performing vacuum molding or pressure molding with air using the second mold. And a molding device for forming an embossed pattern with molding the first resin discharged from the outlet to the tubular. The die includes a mandrel, a tubular first die that surrounds the outside of the mandrel with a predetermined gap, and a tubular second die that surrounds the outside of the first die with a predetermined gap. The first discharge port and the first flow path are configured by the gap between the mandrel and the first die, and the second discharge port and the second flow path are configured by the gap between the first die and the second die. . The first discharge port and the second discharge port of the die are disposed in a molding space sandwiched between the recess of the first mold and the recess of the second mold. A heat insulating layer is provided in the first die to insulate between the first flow path and the second flow path.

The present invention also provides a foamed resin having a tube shape and a foamed resin having an expansion ratio of 20 to 30 times, and a film covering the surface of the resin foam, and having an embossed pattern formed on the surface. It relates to tubes. The foamed resin tube according to the present invention is characterized in that the cross section perpendicular to the longitudinal direction is circular and the cross section has an integral tube shape with no welding marks.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing apparatus of the foaming resin tube which can manufacture the high-expansion foaming foamed resin tube by which the unevenness | corrugation by embossing was provided in the surface can be manufactured with few processes, suppressing a distortion of cross-sectional shape can be provided. . Further, according to the present invention, it is possible to provide a high-magnification foamed resin tube with less cross-sectional distortion.

FIG. 1 is a perspective view of a part of a foamed resin tube manufactured by the foamed resin tube manufacturing apparatus according to the embodiment. FIG. 2 is a schematic view showing the foamed resin tube manufacturing apparatus according to the embodiment. FIG. 3 is a partially enlarged view of the molding apparatus and die shown in FIG. 4 is a cross-sectional view taken along the line IV-IV shown in FIG. FIG. 5A is a diagram showing a detailed configuration of the die shown in FIG. FIG. 5B is a partially enlarged view of the die shown in FIG. 5A. FIG. 6 is a cross-sectional view showing a conventional method for producing an embossed foamed resin tube. FIG. 7 is a perspective view of a part of a conventional embossed foamed resin tube manufactured by the manufacturing method of FIG.

FIG. 1 is a perspective view of a part of a foamed resin tube manufactured by the foamed resin tube manufacturing apparatus according to the embodiment.

A foamed resin tube 10 shown in FIG. 1 is made of a foamed first resin, and has a tube-shaped resin foam 51 and a film 52 that is made of a second resin and covers the surface (outer peripheral surface) of the resin foam 51. Composed. The embossed pattern on the surface is formed on both the film 52 and the outer peripheral portion of the resin foam 51. The foamed resin tube 10 according to the present embodiment has a circular cross section orthogonal to the longitudinal direction, and an integral tube shape having no welding mark (portion corresponding to the joint portion 85 shown in FIG. 6) in the cross section. It is the characteristic to have. Therefore, the foamed resin tube 10 is a foamed resin tube with less distortion of the cross-sectional shape. Here, the expansion ratio of the resin foam 51, that is, the ratio of the volume of the first resin after foaming to the volume of the first resin before foaming is 20 to 30 times, preferably 25 to 30 times. When the expansion ratio of the resin foam 51 is 20 to 30 times, a high heat insulating effect is obtained, and therefore the foamed resin tube 10 is suitable as a heat insulating material for piping for water absorption and hot water supply. In order to obtain such a resin foam 51 having a high expansion ratio of 20 to 30 times, it is necessary to employ gas foaming using a gas as a foaming agent, as will be described later.

FIG. 2 is a schematic view showing the foamed resin tube manufacturing apparatus according to the embodiment.

The foamed resin tube manufacturing apparatus 1 supplies an extrusion molding die 2 for extruding the first resin and the second resin, a first resin extrusion unit 3 for supplying the first resin to the die 2, and supplying the second resin to the die 2. A second resin extruding portion 4 that molds the resin extruded from the die 2 into a tubular shape, and a molding device 5 that transfers the embossed shape to the surface.

The die 2 is a tubular mold having a triple structure, and an annular first discharge port for extruding the first resin to be a resin foam and an annular extruding second resin to be a film for covering the surface of the foam. A second discharge port. Connected to the die 2 are a first resin extruding part 3 for supplying a first resin and a second resin extruding part 4 for supplying a second resin. Details of the structure of the die 2 will be described later.

The 1st resin extrusion part 3 is equipped with

extruder

11a and 11b and the communication path 15 which makes these communicate.

The extruder 11a includes a hopper (not shown) for charging the first resin pellets, a housing 13a having a screw therein and melting the resin therein, and a motor 14a for rotating the screw in the housing 13a. Is provided. The extruder 11a is provided with a heater (not shown) for heating the resin inside the housing 13a. An injection port 18 is provided in an intermediate portion in the longitudinal direction of the housing 13a, and gas is injected as a foaming agent into the housing through the injection port 18. The extruder 11 a mixes the foaming agent injected from the injection port 18 with the melted first resin, and supplies the first resin mixed with the foaming agent into the housing 13 b of the extruder 11 b through the communication path 15.

The extruder 11b includes a housing 13b having a screw for kneading the molten resin therein, and a motor 14b for rotating the screw in the housing 13b. The extruder 11b is provided with a heater (not shown) for heating the resin inside the housing 13b. The temperature in the housing 13b is set lower than the temperature in the housing 13a of the extruder 11a, and the first resin is cooled to a predetermined temperature in the course of being kneaded in the housing 13b. By the cooling and kneading by the extruder 11b, the foaming agent bubbles (called cells) are uniformly dispersed between the molecules of the first resin. The extruder 11 b supplies the cooled first resin to the first flow path communicating with the first discharge port provided in the die 2.

The first resin is not particularly limited as long as it is a foamable thermoplastic resin, but polyurethane, polystyrene, polyethylene (including cross-linked polyethylene), polypropylene, ethylene vinyl acetate copolymer, ethylene-propylene copolymer, Polyethylene terephthalate, polyvinyl chloride, nylon and the like can be used. As the foaming agent, hydrocarbons such as butane and pentane, and inert gases such as carbon dioxide and nitrogen can be used. In the use of a heat insulating material for piping, polyethylene (including cross-linked polyethylene) is preferable as the first resin, and in this case, butane, pentane and the like are preferable as the foaming agent.

The second resin extrusion unit 4 is composed of an extruder 12. The extruder 12 includes a hopper (not shown) for charging the pellets of the second resin, a housing 16 having a screw therein, and a motor 17 for rotating the screw in the housing 16. Further, the extruder 12 is provided with a heater (not shown) for heating the resin inside the housing 16. The extruder 12 melts and kneads the second resin charged from the hopper in the housing 16 and supplies the melted second resin to the second flow path communicating with the second discharge port provided in the die 2. The temperature of the second resin that the second resin extrusion unit 4 supplies to the d die 2 is set higher than the temperature of the first resin that the first resin extrusion unit 3 supplies to the die 2.

The second resin is not particularly limited as long as it is a thermoplastic resin. Polyurethane, polystyrene, polyethylene, crosslinked polyethylene, polypropylene, ethylene vinyl acetate copolymer, ethylene-propylene copolymer, polyethylene terephthalate, polyvinyl chloride, nylon Etc. can be used. Among these, polyolefin resins such as polyethylene, cross-linked polyethylene, polypropylene, and ethylene-propylene copolymer can be suitably used.

The molding apparatus 5 is an apparatus for continuously molding a resin tube (resin pipe) having irregularities on its surface by using a plurality of pairs of

molds

20a and 20b divided into two. Since the molding device 5 is used for continuously molding a long corrugated pipe (corrugated tube), it may be called a corrugator. However, by changing the shape and size of the recesses of the

molds

20a and 20b used in the molding apparatus 5, not only a tube having a corrugated shape on the surface but also a foamed resin tube having various diameters or various embossed patterns is molded. can do. The resin tube is molded by the molding apparatus 5 by vacuum molding in which the pores provided in the mold are vacuum-sucked, and by air being blown into the center of the mold and pressurized. Although there is pressure molding, any method may be adopted. Details of the molding of the resin tube in the molding apparatus 5 will be described later.

A cooling device 6 that cools the molded foamed resin tube 10, a take-up device 7 that takes up the foamed resin tube 10, and a winding device 8 that winds up the foamed resin tube 10 are sequentially provided downstream of the molding device 5. ing.

3 is a partially enlarged view of the molding apparatus and die shown in FIG. 2, and FIG. 4 is a cross-sectional view taken along the line IV-IV shown in FIG.

2, the molding apparatus 5 includes a plurality of pairs of

molds

20a and 20b divided into two. Each mold 20a is transported in the direction of the block arrow in FIG. 2 by the transport mechanism 22a and circulates along the transport path 21a. Similarly, each mold 20b is transported in the direction of the block arrow in FIG. 2 by the transport mechanism 22b and circulates along the transport path 21b. Each of the

molds

20a and 20b is formed with a substantially semi-cylindrical recess for molding a part of a predetermined length in the length direction of the foamed resin tube in the circumferential direction. Further, as shown in FIG. 4 by shading, the surface of the recess formed in the mold 20a is provided with unevenness (an embossed pattern reversal pattern) to be transferred to the surface of the resin tube. Although not shown in the drawings, the concave portion of the mold 20b is similarly provided with unevenness (an embossed pattern reversal pattern) to be transferred to the surface of the resin tube.

3 and 4, the split surfaces 23a and 23b of the pair of

molds

20a and 20b are in surface contact when they are on a straight conveyance path parallel to the central axis of the die 2. Further, on the linear conveyance path, a pair of

molds

20a and 20b in which the split surfaces 23a and 23b are in contact with each other are connected along the linear conveyance path (in a direction parallel to the central axis of the die 2). Inside a plurality of pairs of dies 20a and 20b adjacent in the conveyance path direction, a molding space having a predetermined length having a substantially cylindrical shape corresponding to the outer surface shape of the foamed resin tube is formed.

3 and 4, the die 2 has a pair of molds in which the first discharge port 33 and the second discharge port 34 provided at the tip of the die 2 are in contact with the divided

surfaces

23a and 23b. It arrange | positions so that it may be located in the molding space formed between 20a and 20b.

FIG. 5A is a diagram showing a detailed configuration of the die shown in FIG. 4, and FIG. 5B is a partially enlarged view of the die shown in FIG. 5A.

As shown in FIGS. 5A and 5B, the die 2 includes a rod-shaped mandrel 30, a tubular die 31 that surrounds the outside of the mandrel 30 with a predetermined gap, and a tubular that surrounds the outside of the die 31 with a predetermined gap. And the dice 32.

A first flow path 35 is formed between the outer peripheral surface of the mandrel 30 and the inner peripheral surface of the die 31 by the predetermined gap described above. The first flow path 35 is supplied with a first resin containing a foaming agent extruded from the first resin push-out section 3 through an inlet (not shown). An annular first discharge port 33 for discharging the first resin is formed at the most downstream portion of the first flow path 35, that is, at the tip portion of the die 2. The tip of the mandrel 30 has a cylindrical shape and protrudes from the tip of the die 31. The reason why the tip of the mandrel 30 protrudes from the tip of the die 31 is that the tip of the mandrel 30 is used as a nesting for forming a circular cross section of the hollow portion of the foamed resin tube.

Between the outer peripheral surface of the die 31 and the inner peripheral surface of the die 32, the second flow path 36 including the predetermined gap described above is formed. As shown in FIG. 4, a through hole 37 extending in a direction orthogonal to the central axis is formed in the die 32, and through the through hole 37, the second flow path 36 is connected to the second resin extrusion portion 4. The extruded second resin is supplied. An annular second discharge port 34 for discharging the second resin is formed at the most downstream portion of the second flow path 36, that is, at the tip portion of the die 2.

Furthermore, as shown in FIG. 5B, the die 31 is composed of two coaxial inner divided bodies 38a and outer divided bodies 38b having a tubular shape. The inner divided body 38 a is a member that constitutes the inner peripheral surface of the die 31. On the other hand, the outer divided body 38b is a member constituting the outer peripheral surface of the die 31, and is arranged so as to surround the inner divided body 38a.

In the inside of the die 31, a heat insulating layer 39 that insulates between the first flow path 35 and the second flow path is provided. The heat insulating layer 39 is provided so as to surround the first flow path 35. In the present embodiment, the heat insulating layer 39 is configured by enclosing air in a cylindrical sealed space provided between the inner peripheral surface of the inner divided body 38a and the outer peripheral surface of the outer divided body 38b. Yes. Since air has a low thermal conductivity and air cannot move in the sealed space formed between the outer peripheral surface of the inner divided body 38a and the inner peripheral surface of the outer divided body 38b, the air is enclosed in the sealed space. High heat insulation can be obtained by air. The heat insulating layer 39 is provided to prevent the first resin supplied to the first flow path 35 from being heated by the second resin (higher than the first resin) supplied to the second flow path. This will be described later. In addition, if the thickness of the heat insulation layer 39 in the radial direction is 1 mm or more, it is possible to insulate the first resin that is required when forming the high-expansion foamed resin tube according to the present embodiment. Further, if necessary heat insulating properties can be obtained, a heat insulating material other than air may be sealed or a vacuum heat insulating layer may be provided in the space between the inner divided body 38a and the outer divided body 38b. .

In the present embodiment, a recessed space is formed on the outer peripheral surface of the inner divided body 38a, thereby forming a sealed space between the outer peripheral surface of the inner divided body 38a and the inner peripheral surface of the outer divided body 38b. However, a sealed space may be formed by forming a recess on the inner peripheral surface of the outer divided body 38b, or a recess is formed on both the outer peripheral surface of the inner divided body 38a and the inner peripheral surface of the outer divided body 38b. By doing so, you may comprise a sealed space.

The heat insulating layer 39 is preferably provided at least in a portion where the thickness of the die 31 is constant. The thickness of the die 31 here is the difference between the inner and outer diameters of the die 31 in the radial direction, and is the total thickness of each of the inner divided body 38a, the heat insulating layer 39, and the outer divided body 38b. In the foamed resin tube manufacturing apparatus 1 according to the present embodiment, as shown in FIGS. 2 and 3, an embossed pattern is formed on the surface with the

molds

20 a and 20 b of the molding apparatus 5, and therefore, a predetermined length from the tip of the die 2. Must be inserted into the molding space formed by the

molds

20a and 20b. For this reason, since the outer diameter of the die 2 is limited by the inner diameter of the molding space formed by the

molds

20a and 20b, it is necessary to reduce the thickness of the die 31 constituting the die 2 to some extent. When the thickness of the die 31 is reduced, the heat of the second resin in the second flow path 36 is easily transferred to the first flow path 35 in the portion where the thickness of the die 31 is constant. By providing the heat insulating layer 39 in a portion where the constant is constant, sufficient heat insulating properties can be ensured.

Since the first discharge port 33 provided at the tip of the die 2 is annular, the first resin is discharged from the first discharge port 33 in a tubular shape. The first resin supplied to the first flow path 35 of the die 2 contains a foaming agent (gas). Therefore, when the first resin is discharged from the annular first discharge port 33 at the tip of the die 2, the foaming agent ( Gas) evaporates and the extruded first resin foams. That is, the first resin becomes a tubular foam by being discharged from the first discharge port 33.

Further, since the second discharge port 34 of the die 2 provided at the tip of the die 2 is also annular and is provided so as to surround the first discharge port 33, the second resin is made of the foamed first resin. It is discharged in a tubular shape so as to cover the entire outer surface of the tubular foam.

In the present embodiment, the insides of the

molds

20a and 20b are vacuum-sucked through pores (not shown) provided in the recesses of the

molds

20a and 20b, so that the tubular foam covered with the second resin The first resin foam is pressed against the inner surfaces of the recesses of the

molds

20a and 20b, and the unevenness provided on the inner surfaces of the recesses of the

molds

20a and 20b is transferred to the second resin and the foam of the first resin. As a result, an embossed pattern is formed. Since the plurality of

molds

20a and 20b are conveyed so as to circulate along the

conveyance paths

21a and 21b, the

molds

20a and 20b in which the foamed resin tube 10 is molded are downstream along the central axis of the die 2. The

molds

20a and 20b that have been conveyed and circulated (in the direction away from the die 2) contact the divided

surfaces

23a and 23b to form a new molding space. Therefore, an embossed pattern is formed on the outer surface by discharging the first resin and the second resin from the first discharge port 33 and the second discharge port 34 at a constant discharge speed while circulating and conveying the plurality of

molds

20a and 20b. The foamed resin tube having a long length can be continuously molded. When a foamed resin tube is molded with a crystalline resin such as polyethylene, even if embossing is performed after the resin has once crystallized, if the foamed resin tube is used in a heated environment, the embossed shape is impaired. However, in the foamed resin tube manufacturing apparatus 1 according to the present embodiment, since the embossing is performed almost simultaneously with the extrusion of the molten resin, the resin is cooled and crystallized in a state in which the unevenness is transferred to the molten resin. It will be made. Therefore, the foamed resin tube 10 according to the present embodiment can maintain the transferred embossed shape even in a heated environment as in the case of using it as a heat insulating material for a hot water supply pipe.

Here, the reason why the heat insulating layer 39 surrounding the first flow path 35 is provided inside the die 31 will be described. When a high-magnification resin foam having a foaming ratio of 20 to 30 times is produced by gas foaming using, for example, polyethylene (crosslinked polyethylene) as the first resin, a foaming agent gas (for example, butane gas) is mixed and dispersed. Further, it is necessary to discharge from the first discharge port 33 while maintaining the temperature of the first resin at 100 to 120 ° C., more preferably 100 to 110 ° C. This is because when the temperature of the first resin in which the foaming agent is dispersed exceeds the above-described temperature range, the dispersed gas cell breaks off and escapes from the first resin, and is pushed out from the first discharge port 33. This is because one resin cannot be foamed at a foaming ratio of 20 to 30 times. On the other hand, in order to extrude into a thin film using polyethylene (cross-linked polyethylene) as the second resin, the temperature of the second resin supplied to the second flow path 36 is set to 140 to higher than the temperature of the first resin. It is necessary to make it 160 degreeC. When the first resin and the second resin having a temperature difference are supplied to the same die 2 as described above, the first resin is heated by the second resin in the straight pipe portion where the thickness of the die 31 is constant. The temperature of the first resin in which the foaming agent is dispersed exceeds the above-described temperature range.

In the foamed resin tube manufacturing apparatus 1 according to the present embodiment, the first resin in the first flow path 35 is insulated from the second resin in the second flow path 36 by providing the heat insulating layer 39 inside the die 31. is doing. For this reason, it can suppress that the 1st resin in the 1st flow path 35 is heated by the 2nd resin supplied to the 2nd flow path 36, and the gas disperse | distributed in the 1st resin escapes. Therefore, according to the foamed resin tube manufacturing apparatus 1 according to the present embodiment, the resin foam made of the first resin and the film made of the second resin covering the surface of the first resin are achieved while realizing high-magnification foaming of the first resin. It is possible to form an embossed pattern on the surface while extruding at the same time.

Further, as described above, in the foamed resin tube manufacturing apparatus 1 according to the present embodiment, the first resin containing the foaming agent (gas) is foamed while being extruded into a tubular shape at the same time inside the

molds

20a and 20b. The surface of the first resin is covered with the second resin, and vacuum molding or air pressure molding is further performed. That is, in the foamed resin tube manufacturing apparatus 1 according to the present embodiment, the foaming of the first resin, the coating of the foam of the first resin with the second resin, and the molding into the tube shape having the embossed pattern on the surface are performed simultaneously. Do. Therefore, the number of manufacturing steps can be greatly reduced as compared with the conventional manufacturing method described in FIG.

Further, in the present embodiment, no film is provided inside the resin foam made of the first resin. In other words, the innermost layer of the foamed resin tube 10 is a resin foam made of the first resin. When a film is provided on both the inside and the outside of the resin foam, when the first resin is extruded from the first discharge port 33 and foamed, the gas may not easily escape, and foamability may be reduced. When the film is not provided inside the foam made of the first resin as in the present embodiment, the gas escapes well when the first resin is foamed, and the first resin can be stably foamed at a high magnification. it can.

Moreover, in the foamed resin tube manufacturing apparatus 1 according to the present embodiment, since the resin is directly molded into a tubular shape, a stress difference due to the difference in the circumferential length between the inner circumference and the outer circumference of the foamed resin tube 10 does not occur. Therefore, according to the foamed resin tube manufacturing apparatus 1 according to the present embodiment, it is possible to reduce the distortion of the cross-sectional shape and bring it closer to a perfect circle, and thus it is possible to manufacture the foamed resin tube 10 having an excellent aesthetic appearance. In addition, the foamed resin tube formed by the foamed resin tube manufacturing apparatus 1 according to the present embodiment is a product that is excellent in aesthetics in that there is no joint between end faces as shown in FIG.

Furthermore, although the foamed resin tube 10 as in the present invention is used as a heat insulating material for piping, the foamed resin tube 10 may be cut open by making a slit in the longitudinal direction for attachment to the piping. Since the conventional foamed resin tube shown in FIG. 7 is formed by rounding a flat foam into a cylindrical shape, if the slit is made in the longitudinal direction, the opening of the slit portion may be increased. On the other hand, since the foamed resin tube 10 manufactured by the foamed resin tube manufacturing apparatus 1 according to the present embodiment is directly formed in a tubular shape, it can maintain a tubular shape even when a slit is provided in the longitudinal direction. As a result, the workability at the time of attachment to the piping can be improved.

(Other variations)
In the above embodiment, the outer surface of the foam made of the first resin is covered with the second resin film, but the second resin film may be omitted. In this case, a foamed resin tube without a second resin film can be manufactured by using the die described in the above embodiment (see FIG. 4) and not supplying the second resin to the die. Moreover, when manufacturing the foamed resin tube without a 2nd resin film, it has the 1st supply port and the 1st flow path, the die | dye which does not have a 2nd supply port and a 2nd flow path, and 1st resin mentioned above You may comprise a manufacturing apparatus with an extrusion part and a shaping | molding apparatus. Even in the case where the second resin film is not provided, the first resin foaming and the molding into the tube shape having the embossed pattern on the surface are performed simultaneously, thereby making the manufacturing process as compared with the conventional manufacturing method described in FIG. The number can be greatly reduced. In addition, by directly molding the resin into a tubular shape, it is possible to reduce the distortion of the cross-sectional shape and bring it closer to a perfect circle, so that it is possible to manufacture a foamed resin tube with excellent aesthetics.

In the above embodiment, the foamed resin tube having the lattice-like embossed pattern formed on the outer peripheral surface is described as an example. However, as described above, various outer surface shapes can be obtained by changing the concave shape of the mold of the molding apparatus. Can be produced. For example, a corrugated pipe made of a resin foam can be manufactured using a corrugated mold.

In the above embodiment, an example in which the concave and convex shape of the mold is transferred by vacuum forming has been described. However, a mandrel is provided with a through hole that penetrates the central axis, and air is sealed from the through hole to provide an extruded product. The concavo-convex shape of the mold may be transferred by pressing from the inside of the mold.

The present invention can be used for manufacturing a foamed resin tube used for a heat insulating cover for piping.

DESCRIPTION OF SYMBOLS 1 Foamed resin tube manufacturing apparatus 2 Die 3 1st resin extrusion part 4 2nd resin extrusion part 5 Molding apparatus 10

Foamed resin tube

11a, 11b Extruder 12 Extruder 20 Mold 31 Die 32 Die 33 1st discharge port 34 2nd Discharge port 35 First flow path 36 Second flow path 38a Inner divided body 38b Outer divided body 39 Heat insulation layer 51 Resin foam 52 Film

Claims

An apparatus for producing a foamed resin tube having a tubular shape and having a foaming ratio of 20 to 30 times, a film covering the surface of the resin foam, and having an embossed pattern formed on the surface. And
An annular first discharge port, a first flow path communicating with the first discharge port, an annular second discharge port disposed so as to surround the first discharge port, and a communication with the second discharge port A die having a second flow path disposed so as to surround the first flow path;
A first resin supply unit that melts and kneads a thermoplastic first resin, mixes a foaming agent with the melted first resin, and supplies the first resin to the first flow path of the die;
A second resin supply unit that melt-kneads a thermoplastic second resin and supplies the molten second resin to the second flow path of the die at a temperature higher than that of the first resin;
A plurality of first molds having a recess corresponding to a part of the outer surface shape of the foamed resin tube and a plurality of second molds having a recess corresponding to the other part of the outer surface shape of the foamed resin tube are used. A molding apparatus for forming the first resin discharged from the first discharge port of the die into a tubular shape and forming the embossed pattern by performing vacuum molding or pressure molding with air,
The die is
With mandrels,
A tubular first die that surrounds the outside of the mandrel with a predetermined gap;
A tubular second die surrounding the outside of the first die with a predetermined gap,
The first discharge port and the first flow path are configured by a gap between the mandrel and the first die,
The second discharge port and the second flow path are configured by a gap between the first die and the second die,
The first discharge port and the second discharge port of the die are arranged in a molding space sandwiched between a recess of the first mold and a recess of the second mold,
An apparatus for manufacturing a foamed resin tube, wherein a heat insulating layer is provided in the first die for heat insulation between the first flow path and the second flow path.
The apparatus for producing a foamed resin tube according to claim 1, wherein the heat insulating layer is provided so as to surround the first flow path.
The apparatus for producing a foamed resin tube according to claim 2, wherein the heat insulating layer is provided at least in a portion where the thickness of the first die in the radial direction is constant.
The first die is
A cylindrical inner divided body constituting the inner peripheral surface of the first die;
A cylindrical outer divided body constituting the outer peripheral surface of the first die,
A cylindrical sealed space is configured between the outer peripheral surface of the inner divided body and the inner peripheral surface of the outer divided body, and the heat insulating layer is configured by the sealed space filled with air. The apparatus for producing a foamed resin tube according to any one of claims 1 to 3.
The method for producing a foamed resin tube according to claim 4, wherein the sealed space is constituted by a recess provided on at least one of an outer peripheral surface of the inner divided body and an inner peripheral surface of the outer divided body.
In a foamed resin tube having a tubular shape and having a foaming ratio of 20 to 30 times, a film covering the surface of the resin foam, and having an embossed pattern formed on the surface,
A foamed resin tube characterized by having a circular cross section perpendicular to the longitudinal direction and an integral tube shape with no weld mark on the cross section.