JP2023142260A - composite pipe - Google Patents

Abstract

To provide a composite pipe achieving both the suppression of the occurrence of the tangling of an intermediate layer when exposing an end part of a pipe body by shortening an end part of a coating layer to restore the coating layer to an original state and the suppression of the occurrence of the desertion of the intermediate layer when shortening the end part of the coated layer to expose the end part of the pipe body.SOLUTION: A composite pipe 10 has: a pipe-shaped pipe body 12 made of a resin material; a coating layer 20 which is made of a resin material including an acid denaturation resin, formed into a pipe shape to cover an external periphery of the pipe body 12, formed into a bellows shape with an annular crest part 22 which is protrusive to the outside in a radial direction and an annular trough part 24 which is recessive at the outside in the radial direction alternately formed in an axial direction S of the pipe body 12, and relatively movable with respect to the pipe body 12 by being shortened in the axial direction S while being guided to the external periphery of the pipe body 12; and an intermediate layer 14 which is a porous layer made of a resin material including a resin having a polar group, arranged between the pipe body 12 and the coating layer 20, and bonded to the coating layer 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to composite pipes.

Conventionally, various types of pipes for covering piping have been proposed in order to protect the piping. For example, Patent Document 1 describes a tube body, a coating layer that is expandable and contractible in the axial direction of the tube body, an intermediate layer that is arranged between the tube body and the coating layer and that is expandable and contractible as the coating layer expands and contracts; A composite tube is disclosed that includes an adhesion suppressing layer that is provided between the body and the intermediate layer and suppresses adhesion between the tube body and the intermediate layer.

JP2020-180627A

In a composite pipe having a tubular body, a bellows-shaped coating layer covering the outer periphery of the tube, and an intermediate layer disposed between the tube and the coating layer, for example, the end of the tube during construction. When connecting a joint or the like to the pipe, the covering layer and the intermediate layer are shortened in the axial direction of the pipe to move them relative to the pipe. Then, the end of the tube is exposed by the relative movement, and after the end is connected to a joint or the like, the coating layer is returned to its original state to cover the tube again.
On the other hand, when returning the covering layer to its original state, the intermediate layer may not follow the movement of the covering layer and may become rolled up, causing a phenomenon in which part of the intermediate layer is rolled up (hereinafter also referred to as "rolling"). . Note that if this entanglement occurs, the intermediate layer may not return to its original position.
In addition, when the density of the intermediate layer is high, it is difficult for the intermediate layer to be rolled up, but when the end of the coating layer is shortened to expose the end of the tube, only the coating layer moves in the axial direction, and the intermediate layer A phenomenon in which the coating layer does not follow the movement of the coating layer and is left behind on the tube body (hereinafter also referred to as "leaving behind") may occur.

The present invention provides an embodiment that includes a tubular body, a coating layer that is tubular and covers the outer periphery of the tubular body, and an intermediate layer disposed between the tubular body and the coating layer. Suppressing the occurrence of entanglement of the intermediate layer when shortening the end of the tube to expose the end of the tube and returning the coating layer to its original state, and shortening the end of the coating layer to expose the end of the tube. An object of the present invention is to provide a composite pipe that can suppress the occurrence of the intermediate layer being left behind.

Means for solving the above problems include the following aspects.
<1>
A tubular body made of a resin material, an annular peak portion that is made of a resin material containing an acid-modified resin, and that covers the outer periphery of the tubular body and protrudes outward in the radial direction; Annular troughs with concave outer sides are formed alternately in the axial direction of the tubular body to form a bellows shape, and are shortened in the axial direction while being guided by the outer periphery of the tubular body. A porous layer configured of a resin material including a resin material having a polar group and a coating layer that is movable relative to the tube body, the porous layer being disposed between the tube body and the coating layer, and a composite tube having an intermediate layer glued to the.
<2>
The composite pipe according to <1>, wherein the acid-modified resin includes a maleic anhydride-modified resin.
<3>
The composite pipe according to <1> or <2>, wherein the acid-modified resin is an olefin resin having at least one of a carboxy group and a carboxylic acid anhydride group.
<4>
In the Fourier transform infrared absorption spectrum of the coating layer, when the peak height at 1710 cm ^-1 is Pa and the peak height at 1460 cm ^-1 is Pe, the acid ratio indicating the ratio of Pa to the sum of Pa and Pe is: The composite tube according to <3>, which is 11% or more.
<5>
The composite pipe according to any one of <1> to <4>, wherein the content of the acid-modified resin is 40% by mass or more based on the entire coating layer.
<6>
The composite pipe according to any one of <1> to <5>, wherein the coating layer has a melt flow rate of 0.3 g/10 minutes to 3.0 g/10 minutes.
<7>
The composite pipe according to any one of <1> to <6>, wherein the intermediate layer has a density of more than 20 kg/m ³ .

According to the present invention, in an embodiment including a tubular body, a covering layer that is tubular and covers the outer periphery of the tubular body, and an intermediate layer disposed between the tubular body and the covering layer, the coating layer is Shorten the end to expose the end of the tube to suppress the occurrence of the intermediate layer being rolled up when the coating layer is returned to its original state, and shorten the end of the coating to expose the end of the tube. It is possible to provide a composite pipe that can simultaneously suppress the occurrence of the intermediate layer being left behind during the process.

FIG. 1 is a perspective view showing an example of a composite pipe according to an embodiment of the present invention. FIG. 1 is a longitudinal cross-sectional view showing an example of a composite pipe according to an embodiment of the present invention. FIG. 1 is a partially enlarged longitudinal cross-sectional view of an example of a composite pipe according to an embodiment of the present invention. It is a figure showing an example of a manufacturing process of a compound pipe concerning an embodiment of the present invention. FIG. 2 is a longitudinal cross-sectional view showing an exposed end portion of a tube body in an example of a composite tube according to an embodiment of the present invention. FIG. 4 is a diagram showing a process in which the covering layer and the intermediate layer are shortened and deformed in the longitudinal cross-sectional portion of FIG. 3; FIG. 4 is a diagram showing a state in which the covering layer and the intermediate layer are shortened and deformed in the longitudinal cross-sectional portion of FIG. 3;

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment which is an example of a composite pipe according to the present invention will be described in detail with reference to the drawings as appropriate. Components indicated using the same reference numerals in each drawing mean the same components. Note that redundant descriptions and symbols in the embodiments described below may be omitted.
Note that, in this specification, the term "main component" refers to the component having the highest content on a mass basis in the mixture, unless otherwise specified.
In this specification, the numerical range indicated using "~" includes the numerical values written before and after "~" as the minimum value and maximum value, respectively.
In the numerical ranges described step by step in this specification, the upper limit value or lower limit value described in one numerical range may be replaced with the upper limit value or lower limit value of another numerical range described step by step. In some cases, the values shown in the examples may be substituted.

<Composite pipe>
The composite pipe according to the present invention includes a tubular body, a covering layer that is tubular and covers the outer periphery of the tubular body, and an intermediate layer disposed between the tubular body and the covering layer.
The tube body is made of resin material.
The coating layer is made of a resin material containing an acid-modified resin. In addition, the shape is bellows-shaped, with annular peaks that are convex toward the outside in the radial direction and annular valleys that are concave on the outside in the radial direction alternately formed in the axial direction of the tube. By shortening in the axial direction while being guided by the outer periphery of the body, relative movement with respect to the tube is possible. Hereinafter, the axial direction of the tube will also be simply referred to as the "axial direction."
The intermediate layer is a porous layer made of a resin material containing a resin having a polar group, and is adhered to the covering layer.

By having the above-mentioned structure, the composite tube shortens the end of the coating layer to expose the end of the tube body, suppresses the occurrence of entanglement of the intermediate layer when returning the coating layer, and To simultaneously suppress the occurrence of an intermediate layer being left behind when shortening the end of the layer and exposing the end of the tube body. Specifically, the details are as follows.

As mentioned above, in a composite pipe that has a pipe body, an intermediate layer, and a bellows-shaped covering layer, when connecting a fitting etc. to the end of the internal pipe body, the ends of the covering layer and intermediate layer are The end of the tube is exposed by shortening it and moving it relative to the tube. After the end of the tube is connected to a joint or the like, the shortened covering layer and intermediate layer are stretched and returned to their original positions, and the tube is again covered with the covering layer and intermediate layer.

However, in a composite body in which a tube made of a resin material, an intermediate layer, and a covering layer are laminated in this order, when the intermediate layer is shortened together with the covering layer and then stretched back to its original state, the intermediate layer becomes the covering layer. A phenomenon in which a part of the intermediate layer is not followed by the movement of the intermediate layer and is rolled up between the tube and the coating layer (that is, rolled up) may occur. When the intermediate layer is rolled up, the coating layer is also difficult to return to its original state, resulting in insufficient coverage of the ends of the tube, and the outer peripheral surface of the coating layer swells, which may affect the design. There is.

Although the reason why the intermediate layer becomes entangled is not clear, it is assumed to be as follows.
When moving the covering layer and the intermediate layer in the axial direction, the covering layer and the intermediate layer are usually shifted while grasping from the outside of the covering layer. At this time, since the intermediate layer moves in the axial direction while pressure is applied from the outer circumferential surface of the coating layer toward the radial center of the coating layer, the frictional force generated on the inner circumferential surface of the intermediate layer increases. In particular, the stronger the gripping force from the outside of the coating layer, the greater the frictional force generated on the inner circumferential surface of the intermediate layer. When the frictional force generated on the inner peripheral surface of the intermediate layer becomes larger than the adhesive force between the intermediate layer and the covering layer, it becomes difficult for the intermediate layer to follow the movement of the covering layer.

When the covering layer is stretched and returned to its original state, a force is applied to the outer peripheral surface of the intermediate layer in the direction in which the covering layer returns to its original state, and a force is applied to the inner peripheral surface of the intermediate layer in the axial direction of the covering layer. A force is applied in a direction that tends to keep the object in place relative to the movement. Therefore, if the intermediate layer cannot follow the movement of the coating layer, frictional forces in opposite directions are applied to the intermediate layer from the outer circumferential surface side and the inner circumferential surface side, respectively, and a part of the intermediate layer (the edge of the intermediate layer) portion, axial center portion of the intermediate layer, etc.) may be rolled into lumps. It is presumed that the above-mentioned entanglement occurs in this way.

On the other hand, in the above composite pipe, the coating layer is made of a resin material containing acid-modified resin, and the intermediate layer is a porous layer made of a resin material containing a polar group-containing resin, so it adheres to the coating layer. has been done. Therefore, it is thought that the polar group of the resin contained in the intermediate layer and the acid-modified site of the acid-modified resin contained in the coating layer chemically interact. It is presumed that the chemical interaction increases the adhesive force between the intermediate layer and the coating layer, which becomes greater than the frictional force on the inner circumferential surface of the intermediate layer, thereby suppressing the occurrence of the entrainment. Ru.

In addition, in conventional composite pipes, the higher the density of the intermediate layer, the more suppressed the entrainment, but if the density of the intermediate layer is too high (for example, 27 kg/m ³ or more), the ends of the coating layer When the end of the tube is shortened to expose the end of the tube, only the coating layer moves in the axial direction, and the intermediate layer does not follow the movement of the coating layer and is left behind on the tube (that is, "left behind"). ) may occur.

In contrast, in the above composite pipe, the coating layer is made of a resin material containing an acid-modified resin, the intermediate layer is a porous layer made of a resin material containing a resin having a polar group, and the intermediate layer is a porous layer made of a resin material containing a resin having a polar group. and a covering layer are bonded to each other.
Therefore, even if the density of the intermediate layer is high (for example, 27 kg/m ³ or more), the above-mentioned leaving behind is unlikely to occur.

For the above reasons, in the above-mentioned composite pipe, the ends of the coating layer are shortened to expose the ends of the pipe body, thereby suppressing the occurrence of entanglement of the intermediate layer when returning the coating layer, and It is thought that this achieves both the suppression of the occurrence of the intermediate layer being left behind when the end portion of the tube body is shortened and the end portion of the tube body is exposed.

Here, the state in which the intermediate layer is adhered to the coating layer can be obtained, for example, by bringing the coating layer in a molten state into contact with the outer peripheral surface of the intermediate layer. To confirm that the intermediate layer is adhered to the covering layer, for example, part of the intermediate layer adhered to the covering layer is peeled off, and the adhesive interface between the covering layer and the intermediate layer is observed using an optical microscope. One example of this method is to check whether the coating layer has entered the recesses on the outer circumferential surface of the intermediate layer, which is a porous layer. When the covering layer has entered the recess, the intermediate layer is adhered to the covering layer.

Next, a form for implementing the composite pipe of the present invention will be explained based on the drawings by giving an example.

FIG. 1 is a perspective view of an example of a composite pipe according to this embodiment. Moreover, FIG. 2 is a cross-sectional view along the axial direction of the composite pipe shown in FIG.
A composite pipe 10 according to this embodiment shown in FIGS. 1 and 2 includes a pipe body 12, an intermediate layer 14, and a coating layer 20. Note that the symbol S represents the axis of the tubular body 12 and its axial direction.

(tube)
The tube body 12 is a resin tube that is tubular and made of a resin material. That is, the tube body is made of a resin material containing resin.
Examples of the resin in the resin material include polyolefins such as polybutene, polyethylene, crosslinked polyethylene, and polypropylene, and vinyl chloride, and one type of resin may be used or two or more types may be used in combination. Among these, polybutene is suitably used, preferably containing polybutene as a main component, and more preferably containing 85% by mass or more in the resin material constituting the tube, for example.
Further, the resin material constituting the tube may be a material consisting only of resin, or may contain other additives as long as it contains resin as a main component.

The diameter (outer diameter) of the tubular body 12 is not particularly limited, and can be, for example, in the range of 10 mm or more and 100 mm or less, preferably in the range of 12 mm or more and 35 mm or less.
Further, the thickness of the tubular body 12 is not particularly limited, and may be, for example, 1.0 mm or more and 5.0 mm or less, and preferably 1.5 mm or more and 3.0 mm or less.

(covering layer)
The covering layer 20 has a tubular shape and covers the outer periphery of the tubular body 12 and the intermediate layer 14 . The intermediate layer 14 is arranged between the tube body 12 and the coating layer 20.
The coating layer is made of a resin material containing an acid-modified resin. That is, the coating layer is made of a resin material containing an acid-modified resin.
Here, the term "acid-modified resin" refers to a resin into which at least one type selected from the group consisting of acidic groups and acid anhydride groups has been introduced. Examples include modified resins to which an unsaturated compound having at least one selected from the following is bonded.

Examples of the acidic group include a carboxy group and a carboxylic acid anhydride group.
Examples of unsaturated compounds having at least one selected from the group consisting of acidic groups and acid anhydride groups include unsaturated carboxylic acids such as maleic anhydride, maleic acid, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, and isocrotonic acid. Examples include acids.
Among these, the unsaturated compound having at least one selected from the group consisting of an acidic group and an acid anhydride group is preferably an unsaturated carboxylic acid or its anhydride from the viewpoint of moldability and adhesiveness. Maleic acid is more preferred. That is, the acid-modified resin is preferably an unsaturated carboxylic acid-modified resin or an unsaturated carboxylic anhydride-modified resin, and more preferably a maleic anhydride-modified resin.

Examples of the resin into which at least one selected from the group consisting of acidic groups and acid anhydride groups (hereinafter also referred to as "base resin") include olefin resins. Specific examples of olefin resins include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene, etc. Among them, polyethylene is preferred from the viewpoint of moldability and elasticity of molded products, and low-density polyethylene is more preferred. .

Examples of the acid-modified resin include olefin resins having at least one selected from the group consisting of acidic groups and acid anhydride groups, and olefin resins having at least one of a carboxy group and a carboxylic acid anhydride group are preferred.
Specifically, as the acid-modified resin, an unsaturated bond site in an unsaturated compound having at least one selected from the group consisting of an acidic group and an acid anhydride group is bonded to an olefin resin (for example, by graft polymerization). Examples include acid-modified olefin resins. Among the acid-modified olefin-based resins, unsaturated carboxylic acid-modified polyolefins in which unsaturated bond sites in an unsaturated compound having at least one of a carboxy group and a carboxylic acid anhydride group are bonded to a polyolefin are preferred.
Specific examples of the acid-modified olefin resin include acid-modified polyethylene, acid-modified polypropylene, acid-modified ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and the like.
As the acid-modified resin, acid-modified olefin resins are preferred from the viewpoint of adhesion with the intermediate layer and flexibility of the molded product, among which unsaturated carboxylic acid-modified polyolefins are more preferred, and maleic anhydride-modified polyolefins are even more preferred. , maleic anhydride-modified polyethylene is particularly preferred.
The resin material constituting the coating layer may contain only one kind of acid-modified resin, or may contain two or more kinds of acid-modified resin.

The resin material constituting the coating layer may contain resins other than acid-modified resins. Examples of resins other than acid-modified resins included in the resin material constituting the coating layer include olefin resins such as polybutene, polyethylene, polypropylene, and crosslinked polyethylene; vinyl chloride; and the like. Among these resins other than acid-modified resins, from the viewpoint of moldability and flexibility of molded products, olefin resins are preferred, polyethylene is more preferred, and low-density polyethylene is even more preferred.
The resin material constituting the coating layer may contain only one type of resin other than acid-modified resin, or may contain two or more types of resin.

From the viewpoint of moldability, the resin material constituting the coating layer preferably contains a resin of the same type as the acid-modified resin as a resin other than the acid-modified resin.
Here, "the same kind" means that the skeletons constituting the main chains of both resins have a common skeleton, for example, acid-modified polypropylene is polypropylene, acid-modified polyethylene is polypropylene, and acid-modified polyethylene is This applies to polyethylene.

The content of the acid-modified resin contained in the resin material constituting the coating layer is preferably 30% by mass or more, and 40% by mass, based on the entire resin contained in the resin material, from the viewpoint of improving adhesion with the intermediate layer. The content is more preferably 50% by mass or more, and even more preferably 50% by mass or more. The upper limit of the content of the acid-modified resin is not particularly limited, and may be 100% by mass.

The resin material constituting the coating layer may contain components other than resin. Components other than resin include, for example, pigments, fillers, functional materials (for example, materials that impart weather resistance), and the like.
The content of the resin in the entire resin material constituting the coating layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of improving adhesiveness with the intermediate layer. The upper limit of the content of the resin is not particularly limited, and may be 100% by mass.
The content of the acid-modified resin in the entire resin material constituting the coating layer is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, from the viewpoint of improving adhesiveness with the intermediate layer. , 100% by mass.

When the acid-modified resin contained in the coating layer is an olefin resin having at least one of a carboxy group and a carboxylic acid anhydride group, the peak height at 1710 cm ⁻¹ in the Fourier transform infrared absorption spectrum of the coating layer is Pa, When the peak height at 1460 cm ^-1 is Pe, the acid ratio (hereinafter also simply "acid ratio") indicates the ratio of Pa to the total of Pa and Pe (that is, Pa x 100/(Pa + Pe), unit: %). ) is preferably 10% or more, more preferably 11% or more, and even more preferably 30% or more, from the viewpoint of improving adhesiveness with the intermediate layer.
The acid ratio in the coating layer may be 40% or less, or 35% or less.
The acid ratio in the coating layer may be 10% or more and 40% or less, 10% or more and 35% or less, 11% or more and 35% or less, and 30% or more and 35% or less. There may be.

Here, the acid ratio in the coating layer means the proportion of acidic groups in the resin material contained in the coating layer, and is a value determined as follows.
Specifically, a measurement sample obtained by cutting the coating layer was measured using a transmission method using a Fourier transform infrared spectrophotometer (manufactured by ThermoFisher, product name: NICOLET iN10) in a measurement area of 4000 cm ^-1 to 675 cm. A Fourier transform infrared absorption spectrum (hereinafter also referred to as "FE-IR spectrum") is obtained by measuring under the following conditions: ^-1 , resolution: 8 cm ^-1 , and number of integrations: 16 times.
In the obtained FT-IR spectrum, the peak height at 1710 cm ^-1 is Pa, the peak height at 1460 cm ^-1 is Pe, and the ratio of Pa to the sum of Pa and Pe (that is, Pa × 100/(Pa + Pe), Unit: %) is calculated and used as the "acid ratio".
Note that the peak at 1710 cm ⁻¹ in the FT-IR spectrum is considered to originate from C═O stretching vibration in at least one of the carboxy group and carboxylic acid anhydride group contained in the acid-modified resin as an acidic group. Furthermore, the peak at 1460 cm ⁻¹ in the FT-IR spectrum is considered to be derived from the bending vibration of the C—H bond contained in the base resin of the acid-modified resin.

The melt flow rate (hereinafter also referred to as "MFR") of the coating layer is preferably 0.3 g/10 minutes or more, and 0.6 g/10 minutes or more, from the viewpoint of improving adhesiveness with the intermediate layer. is more preferable, and even more preferably 0.8 g/10 minutes or more. By setting the MFR of the coating layer within the above range, when the molten coating layer contacts the outer circumferential surface of the porous intermediate layer and solidifies, the intermediate layer has a lower MFR than when the MFR is lower than the above range. The coating layer easily enters the recesses on the outer peripheral surface. When the coating layer enters the recess on the outer peripheral surface of the intermediate layer, the contact area between the coating layer and the intermediate layer increases, and the area of the area where chemical interaction occurs between the polar group of the intermediate layer and the acid-modified site of the coating layer increases. It is presumed that the increase in the adhesion between the covering layer and the intermediate layer improves.
In addition, from the viewpoint of moldability of the coating layer, the MFR of the coating layer is preferably 3 g/10 minutes or less, more preferably 2.0 g/10 minutes or less, and 1.6 g/10 minutes or less. It is even more preferable that there be.
The MFR of the coating layer is preferably 0.3 g/10 minutes to 3 g/10 minutes, more preferably 0.6 g/10 minutes to 2.0 g/10 minutes, and 0.8 g/10 minutes to More preferably, it is 1.6 g/10 minutes.

The MFR of the coating layer is a value measured at a temperature of 190° C. and a load of 2.16 kg according to the method specified in JIS K7210-1 (2014).
The method for controlling the MFR of the coating layer within the above range is not particularly limited, and includes, for example, a method of adjusting the molecular structure, molecular weight, etc. of the resin contained as a main component in the coating layer. Examples of the method for adjusting the molecular structure of the resin include a method for adjusting the molecular structure of a monomer serving as a raw material for the resin, a method for adjusting a crosslinked structure, and the like.

As shown in FIGS. 1 and 2, the coating layer 20 has a bellows shape, and includes an annular peak portion 22 that is convex toward the outside in the radial direction, and an annular trough portion 24 that is concave on the outside in the radial direction. are formed alternately and continuously in the axial direction S of the tube body 12. The peak portions 22 are arranged on the outer side of the trough portions 24 in the radial direction R.
FIG. 3 is an enlarged view of a part of the cross-sectional view shown in FIG. 2. FIG. As shown in FIG. 3, if the radially outermost part of the bellows-shaped covering layer 20 is the outer wall 22A, and the radially innermost part is the inner wall 24A, the outer wall 22A and the inner wall 24A in the radial direction are With the intermediate portion M as a boundary, the radially outer side is a peak portion 22, and the radially inner side is a trough portion 24.

The mountain portion 22 has an outer wall 22A extending in the axial direction S, and side walls 22B extending in the radial direction R from both ends of the outer wall 22A. An outer bent portion 22C is formed between the outer wall 22A and the side wall 22B. The trough portion 24 has an inner wall 24A extending in the axial direction S, and side walls 24B extending in the radial direction R from both ends of the inner wall 24A. An internally bent portion 24C is formed between the inner wall 24A and the side wall 24B.

A radially inwardly concave ridge space 23 is formed inside the ridge portion 22 of the coating layer 20 in the radial direction. Note that a convex portion 14B of the intermediate layer 14, which will be described later, may be inserted into the mountain space 23.

Although not particularly limited, it is preferable that the length L1 of the peak portion 22 in the axial direction S is set longer than the length L2 of the valley portion 24 in the axial direction S. The length L1 is preferably at least 1.2 times the length L2 in order to ensure ease of deformation of the outer wall 22A during shortening deformation, which will be described later.

In order to shorten the covering layer 20, the thickness of the covering layer 20 is preferably 0.1 mm or more at the thinnest part and 0.4 mm or less at the thickest part. The thickness H1 of the outer wall 22A is, for example, thinner than the thickness of the inner wall 24A. The thickness H1 is preferably 0.9 times or less of the thickness H2 in order to ensure ease of deformation of the outer wall 22A during shortening deformation, which will be described later.

The radius difference ΔR between the outer surfaces of the peaks 22 and the valleys 24 is preferably 800% or less of the average thickness of the coating layer 20. If the radius difference ΔR is large, even if the portion of the peak portion 22 along the axial direction S is not deformed, the valley portion 24 will not expand radially outward during shortening, and the adjacent peak portions 22 will not come close to each other. It is difficult to get into a distorted deformed state. In order to suppress the above-described deformation when the radius difference ΔR is 800% or less of the average thickness of the coating layer 20, the length in the axial direction S of the peak portion 22 is adjusted to the length of the trough portion 24. It is effective to make the length longer than the length in the axial direction. Note that it is more effective when it is 600% or less.

The diameter of the coating layer 20 (outer diameter of the outermost part) is not particularly limited, but may be, for example, in the range of 12.85 mm or more and 34.25 mm or less.

(middle class)
The intermediate layer 14 is a porous layer that is made of a resin material containing a resin having a polar group and has a porous structure.
Here, the polar group is a group having polarity, and includes, for example, a group having a heteroatom other than a carbon atom and a hydrogen atom. Examples of heteroatoms other than carbon atoms and hydrogen atoms include nitrogen atoms, oxygen atoms, sulfur atoms, and silicon atoms. The polar group is preferably a group containing at least one heteroatom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms; More preferred are groups containing

Specific examples of polar groups include hydroxy group, isocyanate group, urethane bond, amino group, amide group, imido group, cyano group, nitro group, carboxyl group, carbonyl group, thiol group, sulfo group, thionyl group, ester bond, Examples include ether bonds, sulfide bonds, urea bonds, and siloxane bonds.
The polar group is preferably a group that interacts with an acid-modified site (ie, an acidic group or its anhydride) of the acid-modified resin contained in the coating layer. Examples of interactions include hydrogen bonds, ionic bonds, electrostatic interactions, and intermolecular force interactions.
For example, when the coating layer contains at least one selected from the group consisting of an unsaturated carboxylic acid modified resin and an unsaturated carboxylic anhydride modified resin as the acid modified resin, the polar group is at least one of a carboxy group and an anhydride dicarboxy group. A group that forms a hydrogen bond with one of the two is preferable. Examples of the group that forms a hydrogen bond with at least one of a carboxyl group and an anhydride dicarboxy group include a hydroxy group, an isocyanate group, and a urethane bond.
Among these, hydroxy groups, isocyanate groups, and urethane bonds are preferred as the polar groups from the viewpoint of adhesion to the coating layer.

Specific examples of resins having polar groups include polyurethane, acrylic resin, polyamide resin, polyimide resin, polyamideimide resin, polyester resin, polyether resin, epoxy resin, ethylene/vinyl acetate copolymer resin (hereinafter referred to as "EVA resin"). ), etc. Among these, polyurethane and EVA resin are preferable, and polyurethane is more preferable as the resin having a polar group, from the viewpoint of adhesiveness with the coating layer.
The resin material constituting the intermediate layer may contain only one type of resin having a polar group, or may contain two or more types of resin.

The resin material constituting the intermediate layer may include a resin other than the resin having a polar group. Examples of resins other than those having polar groups included in the resin material constituting the intermediate layer include polystyrene, polyethylene, polypropylene, ethylene propylene diene rubber, and the like.
The resin material constituting the intermediate layer may contain only one type of resin other than the resin having a polar group, or may contain two or more types of resin.

The content of the resin having a polar group contained in the resin material constituting the intermediate layer is preferably 80% by mass or more, based on the total resin contained in the resin material, from the viewpoint of improving adhesion with the coating layer, and 90% by mass or more. It is more preferably 95% by mass or more, and even more preferably 95% by mass or more. The upper limit of the content of the polar group-containing resin is not particularly limited, and may be 100% by mass.

The resin material constituting the intermediate layer may contain components other than resin. Examples of components other than resin include catalysts, blowing agents, foam stabilizers, fillers, pigments, and the like.
The content of the resin in the entire resin material constituting the intermediate layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of improving adhesiveness with the coating layer. The upper limit of the content of the resin is not particularly limited, and may be 100% by mass.
The content of the resin having a polar group in the entire resin material constituting the intermediate layer is preferably 80% by mass or more, more preferably 90% by mass or more, and 95% by mass or more from the viewpoint of improving adhesiveness with the coating layer. More preferably, it may be 100% by mass.

The abundance ratio of holes in the intermediate layer 14 (for example, the foaming rate in the case of a foam) is preferably 25 holes/25 mm or more, and more preferably 45 holes/25 mm or less. The abundance ratio of the pores can be measured by the method described in Appendix 1 of JIS K6400-1 (2012).
Moreover, it is preferable that the intermediate layer 14 is a foam.

The density of the intermediate layer 14 is, for example, in the range of 12 g/m ³ or more, and from the viewpoint of suppressing the entanglement of the intermediate layer, it is preferably over 20 kg/m ³ , and preferably over 22 kg/m ³ . More preferably, it is 25 kg/m ³ or more.
As mentioned above, in conventional composite pipes, the higher the density of the intermediate layer, the more suppressed the curling becomes. However, if the density of the intermediate layer is too high, the end of the coating layer is shortened and the end of the pipe body is When exposing the pipe, a phenomenon may occur in which only the covering layer moves in the axial direction, and the intermediate layer does not follow the movement of the covering layer and is left behind on the tube (that is, "left behind").
On the other hand, in the composite pipe according to the present embodiment, the coating layer is made of a resin material containing an acid-modified resin, and the intermediate layer is a porous layer made of a resin material containing a resin having a polar group. In addition, the intermediate layer and the covering layer are bonded to each other. Therefore, even if the density of the intermediate layer is high (for example, 27 kg/m ³ or more), the above-mentioned leaving behind is unlikely to occur.

From the viewpoint of moldability of the material itself, the density of the intermediate layer 14 is preferably 45 kg/m ³ or less, more preferably 35 kg/m ³ or less, and even more preferably 27 kg/m ³ or less. .
The density of the intermediate layer 14 is in the range of 12 kg/m ³ to 45 kg/m ³ , preferably more than 20 kg/m ³ and less than 35 kg/m ³ , more than 22 kg/m ³ and less than 35 kg/m ³ More preferably, it is more than 22 kg/m ³ and not more than 27 kg/m ³ .

Here, the density of the intermediate layer 14 can be measured by the method specified in JIS-K7222 (2005). Note that the measurement environment is an environment with a temperature of 23° C. and a relative humidity of 45%.

The method of controlling the density of the intermediate layer within the above range is not particularly limited, and includes, for example, a method of adjusting the abundance ratio of pores in the intermediate layer (for example, the foaming rate in the case of a foam), a method of controlling the density of the intermediate layer within the above range, Examples include methods of adjusting the molecular structure of (that is, adjusting the molecular structure of monomers used as raw materials for resins and their crosslinked structures).

The intermediate layer 14 is arranged between the tube body 12 and the covering layer 20. The intermediate layer 14 is compressed and sandwiched between the inner wall 24A of the valley portion 24 of the covering layer 20 and the tube body 12, and a compression sandwiching portion 14A is formed.

The inner peripheral surface of the intermediate layer 14 is preferably flat, and more preferably covers the outer periphery of the tube 12 while being in full contact with the outer periphery of the tube 12. Note that "contact on the entire surface" herein does not necessarily mean that all parts are in close contact with each other, but means that substantially the entire surface is in contact. Therefore, for example, when the intermediate layer 14 is formed by wrapping a sheet-shaped porous resin sheet, the seam part may be partially separated, or there may be a wrinkled part between the tube body 12 and the covering layer 20. This includes cases where the two are partially separated.

The intermediate layer 14 can have a sheet-like shape, for example. For example, the intermediate layer 14 is formed by wrapping a sheet-like porous resin sheet around the tubular body 12 so as to have a width approximately equal to the outer circumferential length of the tubular body 12, and then forming the covering layer 20 and the like. It can be constructed by supplying a resin composition to the outer periphery and molding it.

The thickness of the intermediate layer 14 is the same as the outer periphery of the tube body 12 and the radially inner surface of the inner wall 24A in a natural state (no force such as compression or tension is applied, temperature is 23° C., and relative humidity is 45%). It is preferable that the thickness is greater than or equal to the difference, and further thicker than the difference.
In the compression clamping portion 14A, the intermediate layer 14 is thinner than its natural thickness due to compression. A convex portion 14B is formed between adjacent compressed and clamped portions 14A of the intermediate layer 14. The convex portion 14B has a larger diameter than the compression clamping portion 14A, and protrudes into the mountain space 23. In addition, in the mountain space 23, it is preferable that the top part (the most radially outer part) of the convex part 14B and the outer wall 22A are spaced apart. When the intermediate layer 14 is compressed by the inner wall 24A and the tubular body 12, the compression clamping portions 14A and the convex portions 14B are formed alternately and continuously in the axial direction S, and the outer circumferential surface of the intermediate layer 14 becomes wavy. It has become.

Note that the thickness of the intermediate layer 14 in its natural state is in the range of 1.5 mm or more and 4.0 mm or less, from the viewpoint of ease of forming the compression sandwiching part 14A compressed by the inner wall 24A and the tube body 12. is preferable, and more preferably 2.0 mm or more and 3.0 mm or less. The thickness of the intermediate layer 14 in its natural state is the average value obtained by taking the intermediate layer 14 out of the composite pipe 10 and measuring ten arbitrary points.

The length of the intermediate layer 14 in the axial direction S in the natural state when extracted from between the tube body 12 and the coating layer 20 is preferably 90% or more and 100% or less of the length of the coating layer 20 in the axial direction S. This is because if the intermediate layer 14 is held in a stretched state between the tube body 12 and the covering layer 20, relative movement between the intermediate layer 14 and the covering layer 20 is likely to occur when the covering layer 20 is shortened and deformed. This is because the intermediate layer 14 may not be shortened and the outer peripheral end of the tube body 12 may not be exposed. In order to suppress relative movement between the intermediate layer 14 and the covering layer 20, the length of the intermediate layer 14 in the axial direction S in a natural state should be 90% or more and 100% or less of the axial length of the covering layer 20. is preferred.

Next, the operation of the composite pipe 10 of this embodiment will be explained.

When connecting the composite pipe 10 and the joint according to the present embodiment, a force is applied to the coating layer 20 in the state shown in FIG. 2 in a direction that shortens the coating layer 20 in the axial direction S and exposes the tube body 12. to act. As a result, as shown in FIG. 5, the covering layer 20 at one end moves in the direction in which the tube body 12 is exposed.

In addition, in the outer wall 22A of the peak portion 22 and the inner wall 24A of the valley portion 24, it is preferable that the length L1 in the axial direction S is longer than L2, and the thickness H1 is thinner than H2. As a result, the outer wall 22A deforms more easily than the inner wall 24A, and deforms so as to bulge outward in the radial direction, as shown in FIG. Subsequently, as shown in FIG. 7, the outer bent portion 22C of the peak portion 22 and the inner bent portion 24C of the valley portion 24 are deformed so that the adjacent peak portions 22 become closer to each other. In this way, as shown in FIG. 5, the covering layer 20 at one end is more likely to move in the direction in which the tube body 12 is exposed. In this way, when the covering layer 20 is shortened, the outer wall 22A is deformed to bulge, so even if there is some variation in the bending angle or thickness of the covering layer 20, the troughs 24 are It is possible to prevent the ridges from bulging outward or from becoming distorted and deformed because the adjacent peaks 22 do not come close to each other. Thereby, deterioration in the appearance of the shortened covering layer 20 can be suppressed.

Further, it is preferable that the intermediate layer 14 is compressed between the inner wall 24A and the tube body 12, so that the compression clamping portion 14A is brought into close contact with the covering layer 20, and the convex portion 14B is placed on the side wall of the adjacent valley portion 24. 24B, and becomes easier to shorten together with the covering layer 20.

Here, in this embodiment, the covering layer 20 is made of a resin material containing an acid-modified resin, and the intermediate layer 14 is a porous layer made of a resin material containing a resin having a polar group. It is glued. Therefore, when the end portions of the covering layer 20 and the intermediate layer 14 are shortened in the axial direction to expose the end portions of the tube body 12 and then the covering layer 20 and the intermediate layer 14 are stretched and returned to their original state, the intermediate layer 14 can easily follow the movement of the covering layer 20 to extend in the axial direction, and the occurrence of entanglement is suppressed.

In addition, in this embodiment, the thickness H1 of the outer wall 22A is made thinner than the thickness H2 of the inner wall 24A, but the thickness H1 may be the same as the thickness H2.

Further, in the present embodiment, the outer wall 22A has a substantially linear shape along the axial direction S, but it may have an arc shape that bulges outward in the radial direction. Furthermore, the inner wall 24A may have an arc shape that bulges inward in the radial direction.

Further, in this embodiment, another layer may be provided between the intermediate layer 14 and the tube body 12. Examples of other layers include, for example, a low-friction sheet that improves the sliding between the intermediate layer 14 and the tube body 12. By providing a low-friction sheet between the intermediate layer 14 and the tube body 12, when the coating layer 20 is shortened in the axial direction to expose the end of the tube body 12, and when the coating layer 20 is stretched and returned to its original state. At this time, the intermediate layer 14 and the low-friction sheet tend to follow the covering layer 20 and deform.
On the other hand, in this embodiment, the covering layer 20 is made of a resin material containing an acid-modified resin, and the intermediate layer 14 is a porous layer made of a resin material containing a resin having a polar group, and is adhered to the covering layer 20. has been done. Therefore, even if a low-friction sheet is not provided between the intermediate layer 14 and the tube 12 and the intermediate layer 14 is in contact with the tube 12, the occurrence of the intermediate layer 14 being rolled up is suppressed.

(Production method)
Next, a method for manufacturing the composite pipe 10 of this embodiment will be explained.

For manufacturing the composite pipe 10, for example, a manufacturing apparatus 30 shown in FIG. 4 can be used. The manufacturing device 30 includes an extruder 32, a die 34, a corrugating mold 36, a cooling tank 38, and a take-off device 39. In the manufacturing process of the composite pipe 10, the right side in FIG. 4 is the upstream side, and the pipe body 12 is manufactured while moving from the right side to the left side. Hereinafter, this moving direction will be referred to as the manufacturing direction Y. The die 34, the corrugating mold 36, the cooling tank 38, and the take-off device 39 are arranged in this order in the manufacturing direction Y, and the extruder 32 is arranged above the die 34.

Although not shown, upstream of the die 34, a tubular body 12 wound into a coil shape and a sheet-like member 14S formed by winding a porous resin sheet constituting the intermediate layer 14 into a roll shape are arranged. has been done. By being pulled in the manufacturing direction Y by the pulling device 39, the coiled tube 12 and the rolled sheet member 14S are continuously pulled out. A sheet-like member 14S is wrapped around the entire circumference of the continuously drawn out tubular body 12 before the die 34. Note that the sheet-like member 14S is inserted into the die 34 with a slack state before the die 34 so that no tensile force is applied to the sheet-like member 14S.

On the outer periphery of the sheet-like member 14S wrapped around the outer periphery of the tube body 12, a resin material (melted resin composition for forming the coating layer 20) melted from the die 34 is extruded into a cylindrical shape and applied. A resin layer 20A is formed. At this time, for example, the resin material enters the pores (bubbles) of the porous resin sheet, improving the adhesiveness between the sheet-like member 14S and the resin layer 20A.

After the tubular extruded body 21 composed of the tubular body 12, the sheet-like member 14S, and the resin layer 20A is formed, a corrugating process (forming into a bellows shape) is performed using a corrugating mold 36 disposed downstream of the die 34. process) is carried out. The corrugating molds 36 are, for example, two pairs of molds, each of which has a semicircular arc-shaped inner surface, and an annular cavity 36A is formed on the inner periphery of the mold at a portion corresponding to the crest 22 of the coating layer 20. is formed, and an annular inner protrusion 36B is formed in a portion corresponding to the valley portion 24, and has a bellows shape. Each cavity 36A is formed with a ventilation hole 36C, whose one end communicates with the cavity 36A and penetrates the corrugation mold 36. Air is taken into the cavity 36A from the outside of the corrugating mold 36 through the ventilation hole 36C.

On the downstream side of the die 34, the two pairs of corrugating molds 36 approach the resin layer 20A from two directions, bring their inner surfaces into contact with each other, and press the resin layer 20A with their inner protrusions 36B while forming the tubular extruded body 21. It covers the outer periphery and moves in the manufacturing direction Y together with the tube body 12. At this time, air is taken in from the outside of the corrugated mold 36 to create a negative pressure inside the cavity 36A. As a result, the resin layer 20A moves radially outward, and a bellows-shaped covering layer 20 along the corrugation mold 36 is formed.

At this time, the sheet-like member 14S enters into the cavity 36A at the peak space 23 corresponding to the peak part 22 of the coating layer 20, and a convex part 14B is formed. A portion of the valley portion 24 of the covering layer 20 corresponding to the inner wall 24A is compressed between the tube body 12 and the inner wall 24A while maintaining adhesion to the covering layer 20, forming a compressed sandwiching portion 14A. .

After the corrugating process is performed in the corrugating mold 36, the coating layer 20 is cooled in a cooling tank 38. In this way, the composite pipe 10 is manufactured.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to the following examples.

[Preparation of sheet for intermediate layer]
(Preparation of urethane foam sheet A)
The polyisocyanate and polyol as raw materials are mixed together with a catalyst, a blowing agent, and a foam stabilizer, reacted, and then cut into a desired thickness using a cutting machine.The resulting thickness (average thickness in its natural state) is A commercially available urethane foam sheet A having a thickness of 2 to 3 mm was used.
The obtained urethane foam sheet A contains polyurethane as a resin having a polar group, has a pore abundance ratio of 25/25 mm, and a density of 14 kg/m ³ .

(Preparation of urethane foam sheet B)
As raw materials, polyisocyanate and polyol different from urethane foam A are mixed and reacted with the following catalyst, the following blowing agent, and the following foam stabilizer, and cut into the desired thickness with a cutting machine to determine the thickness (in its natural state). Urethane foam sheet B having an average thickness of 2.5 mm was produced.
The obtained urethane foam sheet B contains polyurethane as a resin having a polar group, has a pore abundance ratio of 45/25 mm, and a density of 27 kg/m ³ .

[Preparation of resin composition for coating layer]
(Preparation of resin composition A)
Maleic anhydride-modified polyethylene (acid-modified resin) was used as resin composition A as it was.
Table 1 shows the results of measuring the degree of acid modification and MFR of resin composition A using the methods described above.

(Preparation of resin composition B)
-Maleic anhydride-modified polyethylene (acid-modified resin): 40 parts by mass -Unmodified polyethylene (low-density polyethylene (LDPE)): 60 parts by mass The above components were mixed by dry blending to obtain resin composition B.
Table 1 shows the results of measuring the degree of acid modification and MFR of resin composition B using the methods described above.

(Preparation of resin composition C)
-Maleic anhydride-modified polyethylene (acid-modified resin): 20 parts by mass -Unmodified polyethylene (low-density polyethylene (LDPE)): 80 parts by mass The above components were mixed by dry blending to obtain a resin composition C.
Table 1 shows the results of measuring the degree of acid modification and MFR of resin composition C using the methods described above.

(Preparation of resin composition D)
Unmodified polyethylene (low density polyethylene (LDPE)) was used as resin composition D as it was.
Table 1 shows the results of measuring the degree of acid modification and MFR of resin composition D using the methods described above.

[Example A1]
(Production of composite pipe A1)
A manufacturing apparatus having the configuration shown in FIG. 4 was prepared. A polybutene tube wound into a coil (outer diameter: 17 mm, thickness: 2.10 mm) was attached as the tube body 12, and the urethane foam sheet A obtained above was attached as the sheet-like member 14S. The pulling device 39 was operated to continuously pull out the coiled polybutene pipe and the rolled urethane foam sheet A (sheet-like member 14S), and the urethane foam sheet A was wrapped around the entire circumference of the polybutene pipe. . Note that the urethane foam sheet A was inserted into the die 34 with the sheet being loosened before the die 34.

Next, the molten resin composition A was applied onto the outer periphery of the urethane foam sheet A by extruding it into a cylindrical shape from the die 34 to form a resin layer.

Next, two pairs of corrugated molds 36 placed on the downstream side of the die 34 were brought close to the resin layer from two directions to bring their inner surfaces into contact. Note that the corrugating molds 36 are two pairs of molds with the same inner surface shape, both of which have semicircular arc-shaped inner surfaces, and the inner periphery has a portion corresponding to the peak of the coating layer to be formed. An annular cavity 36A is formed, and an annular inner protrusion 36B is formed in a portion corresponding to the valley, and has a bellows shape. Each cavity 36A is formed with a ventilation hole 36C, whose one end communicates with the cavity 36A and penetrates the corrugation mold 36. While pressing the resin layer 20A with the inner protrusion 36B, it moved together with the polybutene tube in the manufacturing direction Y, and air was taken in from the outside of the corrugated mold 36 to create a negative pressure inside the cavity 36A. In this way, a bellows-shaped coating layer along the corrugation mold 36 was formed.
Next, it was cooled in a cooling tank 38 to obtain a composite pipe A1.

The distance between the inner surface of the trough 24 of the coating layer and the outer surface of the polybutene tube (tube body), that is, the difference between the outer circumference of the tube body and the radially inner surface of the inner wall 24A of the coating layer (compression clamping part clearance) is 2. It was .0 mm.
In the obtained composite tube, the length L1 of the peaks 22 of the coating layer in the axial direction S was 2.1 mm, and the length L2 of the valleys 24 in the axial direction S was 1.5 mm.
The thickness of the coating layer was 0.2 mm at the thinnest part and 0.5 mm at the thickest part.
The radius difference ΔR between the outer surfaces of the peaks 22 and the valleys 24 was 88.9% of the average thickness of the coating layer.
The diameter of the coating layer (the outermost outer diameter) was 23.5 mm.
The inner peripheral surface of the intermediate layer made of urethane foam sheet A was in full contact with the outer surface of the tube.

(Evaluation of composite pipe A1)
<Caught in>
In order to expose the end of the polybutene pipe (pipe body), while applying pressure to the outer peripheral surface of the coating layer, the end of the coating layer was pulled 30 mm to shorten and deform, and then the coating layer was stretched again to return to its original position. I did the action to do so.
At that time, the urethane foam sheet, which is the intermediate layer, did not follow the elongation movement of the covering layer and was rolled up, causing some parts to be rolled up into clumps, or it did not follow the elongation movement of the covering layer. It was visually confirmed that no entanglement occurred and that the urethane foam sheet had returned to its original position.
Specifically, the pressure applied to the outer peripheral surface of the coating layer was varied in steps of 0.005 MPa in the range of 0.030 MPa to 0.070 MPa, and the presence or absence of entrainment at each pressure was checked. Note that the pressure applied to the outer peripheral surface of the coating layer was measured using a pneumatic gripper.
Table 1 shows the lowest pressure at which entrainment occurs (the "entrainment start pressure" in the table). Note that the greater the entrainment start pressure, the more suppressed entrainment is.

<Left behind>
In order to expose the end of the polybutene tube (pipe body), the end of the coating layer was pulled by 50 mm to shorten and deform it while applying a pressure of 0.040 MPa to the outer peripheral surface of the coating layer.
At that time, it was visually confirmed whether the urethane foam sheet serving as the intermediate layer did not follow the stretching motion of the covering layer and was left behind, or whether it followed the stretching motion of the covering layer and did not leave anything behind. . The results are shown in Table 1.

[Example A2]
Composite pipe A2 was manufactured and evaluated in the same manner as composite pipe A1, except that resin composition B was used instead of resin composition A. The results are shown in Table 1.

[Example A3]
Composite pipe A3 was manufactured and evaluated in the same manner as composite pipe A1, except that resin composition C was used instead of resin composition A. The results are shown in Table 1.

[Comparative example A1]
Composite pipe A4 was manufactured and evaluated in the same manner as composite pipe A1, except that resin composition D was used instead of resin composition A. The results are shown in Table 1.

From the results shown in Table 1 above, in Examples A1 to A3 in which the coating layer was made of a resin material containing an acid-modified resin, compared to Comparative Example A1 in which the resin material constituting the coating layer did not contain an acid-modified resin, it was found that The fact that the starting pressure for rolling is high indicates that rolling is suppressed.
In particular, it can be seen that in Examples A2 and A3, the rolling start pressure is higher than 0.040 MPa, which is the general gripping pressure when performing the work of shifting the coating layer in the axial direction.

[Example B1]
(Production of composite pipe B1)
Composite pipe B1 was obtained in the same manner as composite pipe A1 except that urethane foam sheet B was used instead of urethane foam sheet A.

(Evaluation of composite pipe B1)
<Caught in>
Entanglement was evaluated in the same manner as in Example A1. Table 2 shows the lowest pressure at which entrainment occurred ("entrainment start pressure" in the table).

<Left behind>
Evaluation of leaving behind was performed in the same manner as in Example A1. The results are shown in Table 2.

[Comparative example B1]
Composite pipe B2 was manufactured and evaluated in the same manner as composite pipe B1, except that resin composition D was used instead of resin composition A. The results are shown in Table 2.

From the results shown in Table 2 above, in Example B1 in which the intermediate layer has a high density and the coating layer contains an acid-modified resin, compared to Comparative Example B1 in which the intermediate layer has a high density and the coating layer does not contain an acid-modified resin, it is clear that It can be seen that the occurrence is suppressed.

10 composite pipe, 12 pipe body, 14 intermediate layer, 14A compression clamping part, 14B convex part, 14S sheet-like member, 20 covering layer, 22 peak part, 22A outer wall, 23 peak space, 24 valley part, 24A inner wall, S axis direction

Claims (7)

A tubular body made of resin material,
It is made of a resin material containing an acid-modified resin, has a tubular shape, covers the outer periphery of the tube body, and has an annular peak portion that is convex toward the outside in the radial direction and an annular valley portion that is concave on the outside in the radial direction. a covering layer formed alternately in the axial direction of the tubular body to have a bellows shape, and capable of relative movement with respect to the tubular body by being shortened in the axial direction while being guided by the outer periphery of the tubular body;
a porous layer made of a resin material containing a resin having a polar group, and an intermediate layer disposed between the tube and the coating layer and adhered to the coating layer;
Composite tube with. The composite pipe according to claim 1, wherein the acid-modified resin includes a maleic anhydride-modified resin. The composite pipe according to claim 1 or 2, wherein the acid-modified resin is an olefin resin having at least one of a carboxy group and a carboxylic acid anhydride group. In the Fourier transform infrared absorption spectrum of the coating layer, when the peak height at 1710 cm ^-1 is Pa and the peak height at 1460 cm ^-1 is Pe, the acid ratio indicating the ratio of Pa to the sum of Pa and Pe is: 4. The composite tube according to claim 3, wherein the composite tube is 11% or more. The composite pipe according to any one of claims 1 to 4, wherein the content of the acid-modified resin is 40% by mass or more based on the entire coating layer. The composite pipe according to any one of claims 1 to 5, wherein the coating layer has a melt flow rate of 0.3 g/10 minutes to 3.0 g/10 minutes. Composite pipe according to any one of claims 1 to 6, wherein the density of the intermediate layer is greater than 20 kg/m ³ .