JP2002267054A - Resin tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin tube which is low in permeability not only for regular gasoline but also for the fuel containing alcohol, sufficiently high in adhesiveness of a barrier layer (a fuel shut-off layer) to a covered layer (a layer for protecting the fuel shut-off layer), and is capable of easily recycling ends and formed of inexpensive material. SOLUTION: In this resin tube, at least two resin layers are laminated in a tubular manner, at least one layer is the resin layer mainly consisting of PPS, and the other layer is the resin layer mainly consisting of PBT copolymer. At least one set of the resin layer mainly consisting of PPS and the resin layer mainly consisting of PBT are provided, and the other layers are formed of PBT copolymer. At least naphthalene di-carboxylic acid unit is substituted for a part of terephthalic acid unit constituting the PBT copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin tube, and more particularly, to a resin tube formed by laminating resin layers.
The present invention relates to a resin tube which has rust resistance, excellent delamination resistance in a high-temperature atmosphere, high fuel barrier properties (fuel impermeability), and is easy to reuse.
Further, the resin tube of the present invention can be suitably used typically as a tube for fuel system piping of an automobile.

[0002]

2. Description of the Related Art Conventionally, fuel pipes for automobiles such as feed tubes, return tubes, evaporative hoses and filler hoses are made of metal, rubber, resin, or two or more of these. A piping structure that mixes three or three types is used. In recent years, in place of metal, which has been the mainstream until now, it has been cut to resin.Because there is no rust, weight can be reduced, and cost is more advantageous. It is changing. However, in general, resin-made ones have a disadvantage that they are inferior in fuel permeation resistance as compared with metal-made ones.
It is strongly demanded that fuel permeation regulations, which are expected to become more stringent in the future, be further suppressed.

[0003] Although various developments aimed at improving the resistance to fuel permeation of resin piping and the like have been reported, the permeability to alcohol-containing fuel is low, and further, in terms of materials and production. No inexpensive configurations have been reported to be practical. For example, JP-A-5-164273 discloses that an inner layer (barrier layer) is made of a fluorine resin (ethylene / tetrafluoroethylene copolymer), an intermediate layer is provided with an adhesive layer, and an outer layer is made of polyamide 12. A configuration has been proposed. However, in this case, the fluororesin itself is expensive, and furthermore, the fluororesin and the polyamide 12 as the outer layer are expensive.
However, there is a problem that an adhesive layer for bonding is expensive.

On the other hand, in order to reduce material costs,
Although a reduction in the thickness of the layer containing a fluororesin is considered, sufficient pressure resistance cannot be ensured, so that it is difficult to achieve a sufficient reduction in thickness and cost reduction cannot be achieved. Further, in order to obtain a stronger adhesiveness, when extruding the inner layer fluororesin, applying a chemical treatment solution containing a sodium-ammonia complex to the surface thereof, and performing a surface treatment for introducing an active group, etc. The manufacturing process becomes extremely complicated and further increases the cost.

On the other hand, Japanese Patent Application Laid-Open No. H11-156970 discloses that a polyphenylene sulfide (PPS) is used as a barrier layer.
Has been proposed. However, also in this case, it is necessary to provide an adhesive layer, and the PPS layer and the adhesive layer are expensive, which is a combination having a practical cost level like the above-mentioned fluororesin. hard.

[0006] These problems are caused in each case by using different materials for the barrier layer and the protective layer (outer layer). That is, when different materials are combined,
Since a strong adhesiveness cannot be obtained as it is, an adhesive layer is required, and at least a three-layer structure is required. Further, since the adhesive layer itself is expensive, piping (laminated tube) is necessarily expensive. There are challenges.

Further, JP-A-10-30764 and JP-A-2000-55248 disclose a method of bonding a barrier layer (inner layer) and a protective layer (outer layer) by surface treatment such as plasma without providing an adhesive layer. Proposed. However, the manufacturing process becomes complicated, and it is difficult to provide a fundamental solution to the above problem. Also, in such a combination of different materials, it is extremely difficult to reuse the offcuts in the process, and this point is also a major problem.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to have a low permeability to alcohol-containing fuel in addition to ordinary gasoline. To provide a resin tube having a sufficiently high adhesiveness between a barrier layer (fuel blocking layer) and a coating layer (layer protecting the fuel blocking layer), and having a low-cost material configuration in which recycle of scrap materials and the like is easy. It is in.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved by forming a laminated structure using a predetermined resin. The invention has been completed.

That is, the resin tube of the present invention is a resin tube in which two or more resin layers are laminated in a tubular shape, and at least one layer is a resin layer mainly composed of polyphenylene sulfide. The other layers are resin layers containing a polybutylene terephthalate copolymer as a main component.

A preferred embodiment of the resin tube of the present invention is a resin tube formed by laminating three or more resin layers in a tubular shape, wherein at least one set of non-contacting polyphenylene sulfide is a main component. It has a resin layer and a resin layer containing polybutylene terephthalate as a main component, and the other layers are made of a polybutylene terephthalate copolymer.

Further, in another preferred embodiment of the resin tube of the present invention, the resin layer mainly composed of the above-mentioned polybutylene terephthalate copolymer has a layer in contact with the above-mentioned resin layer mainly composed of polyphenylene sulfide. , And further comprising polyphenylene sulfide.

Still another preferred embodiment of the resin tube of the present invention is characterized in that the resin layer containing polyphenylene sulfide as a main component further contains a polybutylene terephthalate copolymer.

In another preferred embodiment of the resin tube of the present invention, the above-mentioned polybutylene terephthalate copolymer is
Polybutylene terephthalate as a hard segment,
It is a polyester / ether block copolymer elastomer comprising a polyether as a soft segment.

Still another preferred embodiment of the resin tube of the present invention is a polyester-ester block copolymer elastomer, wherein the polybutylene terephthalate copolymer has a hard segment of polybutylene terephthalate and a soft segment of polyester. It is characterized by being.

Further, in another preferred embodiment of the resin tube of the present invention, the above-mentioned polybutylene terephthalate copolymer is characterized in that terephthalic acid or its ester-forming derivative and hydrogenated dimer acid or its ester-forming derivative as an acid component. And a copolymerized polyester containing 1,4-butanediol as a glycol component as a main component.

In still another preferred embodiment of the resin tube according to the present invention, at least a part of the terephthalic acid unit constituting the polybutylene terephthalate copolymer includes:
It is characterized by being substituted by a naphthalenedicarboxylic acid unit.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a resin tube of the present invention will be described in detail. In this specification, “%” indicates mass percentage unless otherwise specified. As described above, the resin tube of the present invention is formed by laminating two or more resin layers into a tubular shape, at least one layer being a resin layer containing polyphenylene sulfide (PPS) as a main component, and the other layers being made of polyphenylene sulfide (PPS). Butylene terephthalate copolymer (PB
(T copolymer) as a main component.

Here, the resin layer containing PPS as a main component has low permeability to fuel and the like and has a function as a layer for blocking permeation (hereinafter, this layer is referred to as a "fuel blocking layer"). Further, the layer containing the above PBT copolymer as a main component,
It has a function as a coating layer for coating and protecting the fuel cutoff layer (hereinafter, this layer is referred to as a “coating layer”). In particular,
As shown in FIG. 1, a resin tube 10 in which a coating layer 3a is coated on the outer periphery of a fuel cut-off layer 2a having a hollow portion through which fuel or the like can flow at the center, or as shown in FIG. A resin tube 20 in which a coating layer 3b is further coated on the inner periphery of a tube having the same configuration as 10 or a tube having the same configuration as the resin tube 20 as shown in FIG. A resin tube 30 and the like in which the fuel cutoff layer 2b and the coating layer 3c are coated in this order can be exemplified. In addition, the resin tube of the present invention is shown in FIGS.
It is needless to say that the present invention is not limited to the two- to five-layer structure shown in FIG. Further, the term "mainly containing" means that the resin layer contains 50% or more of the material, depending on the material.

Further, since the fuel cutoff layer contains PPS as a main component, it is excellent even when a mixed fuel containing alcohol such as ethanol or methanol flows in a resin tube in addition to a normal gasoline fuel. Has permeation resistance. Further, in both the case where the fuel cut-off layer 2a comes into contact with the fuel as shown in FIG. 1 and the case where the coating layer comes into contact with the fuel as shown in FIGS. 2 and 3, the amine-based detergent contained in the fuel is used. Deterioration is extremely small, and it has extremely excellent resistance to sour gasoline (degraded gasoline). Furthermore, any of the above-mentioned fuel cut-off layer and the coating layer may be the innermost layer, and the sealing property with metal or the like can be remarkably improved. It is hard to slip even if you insert it.

In addition, a resin layer mainly composed of PBT can be laminated as the fuel cutoff layer in addition to a resin layer mainly composed of PPS. In this case, it is possible to obtain a high fuel cutoff at a low cost, which is effective. However, PBT and P
Since PS and PS have extremely low adhesiveness, and these laminates may cause problems in practical use, the resin tube is formed by laminating three or more resin layers in a tubular shape and forming at least one set of non-contact PPS. Resin layer mainly composed of PBT and PBT
And a layer other than the above is made of PB
It is preferable to be composed of a T copolymer. In this case, the layers can be laminated with a high adhesive force via a resin layer containing a PBT copolymer as a main component.

Further, the above-mentioned fuel barrier layer is more excellent in the fuel barrier property as the PPS content is higher. However, when a small amount of the PBT copolymer is contained, the fuel barrier layer may be laminated or laminated with a coating layer (PBT copolymer). This is preferable because the adhesion with the main component can be improved. Accordingly, when excellent adhesion between layers is required, it is desirable to appropriately adjust the content of the PBT copolymer. Since PPS has a solubility coefficient close to that of polyamides and is excellent in miscibility, polyamide resins such as polyamide 6 and polyamide 66 can be mixed in the fuel barrier layer. In this case, the material configuration can be made inexpensive.

Further, since the coating layer contains a PBT copolymer as a main component, it exhibits high miscibility with the above-mentioned fuel barrier layer (PPS or PBT), and has sufficient adhesiveness only by co-extrusion. And ensures excellent delamination even in a high-temperature atmosphere. In other words, sufficient adhesive strength can be imparted without providing an adhesive layer between the above-mentioned coating layer and fuel blocking layer.
In addition, since high adhesive strength is developed, extrusion or the like during molding can be performed quickly, and tact can be shortened. Further, it is preferable that PPS is contained in the coating layer for the same reason as the above-mentioned fuel cut-off layer, whereby the interlayer adhesion can be improved, and an adhesive layer is provided between the fuel cut-off layer and the cover layer. There is no need to obtain a resin tube at extremely low cost.

The PBT copolymer has excellent flexibility and can effectively function as a coating layer for protecting the fuel barrier layer (for example, preventing the fuel barrier layer from decreasing its strength and preventing damage). For example, when the present resin tube is attached to a vehicle or the like as a fuel tube, the tube can be bent and easily arranged. At this time, since the coating layer may come into contact with the fuel although the amount is small, it is preferable that the coating layer has resistance to the fuel. Since the PBT copolymer has PBT in the basic skeleton, it has the flexibility required for the coating layer and also has fuel resistance.
Since PBT has a low glass transition point (about 20 ° C.), the PBT copolymer can easily obtain a low glass transition point, and is excellent even at a low temperature of −40 ° C. required for vehicles and the like. It can have flexibility. Further, the flexibility of the coating layer is desirably 1.5 GPa or less, and particularly 1.0 GPa or less in bending elastic modulus at room temperature for a resin tube having an outer diameter of φ8 mm and a wall thickness of about 1 mm. desirable.

Further, the segment in the PBT copolymer may be composed of either a block type (block type PBT copolymer) or a random type (random type PBT copolymer).

That is, when the PBT copolymer is a block type, the hard segment is PBT and the soft segment is polytetramethylene glycol or polyhexamethylene from the viewpoint of availability in the market and flexibility at low temperatures. Examples thereof include polyethers such as glycol, adipates such as ethylene adipate and butylene adipate, and polyesters such as polycaprolactone, polyvalerolactone, and aliphatic polycarbonate. Typically, it is preferable to use a polyester / ether block copolymer elastomer comprising PBT as a hard segment and polyether as a soft segment from the viewpoint of stability of physical properties from low to high temperatures, workability and flexibility. . At this time, the polyether is more preferably polytetramethylene glycol. Also,
For the same reason, a polyester comprising PBT as a hard segment and polyester as a soft segment
It is preferable to use an ester copolymer elastomer. At this time, the polyester is more preferably polycaprolactone.

On the other hand, when the PBT copolymer is of a random type, it is preferable to include a dicarboxylic acid component and a glycol component as main components from the viewpoint that one of the polymerization steps can be omitted as compared with the block type. Typically,
The dicarboxylic acid component includes terephthalic acid or an ester-forming derivative thereof and a hydrogenated dimer acid or an ester-forming derivative thereof, and the glycol component includes 1,
It is preferable that the PBT copolymer contains 4-butanediol. Further, the copolymer composition of the hydrogenated dimer acid is preferably at a ratio of 3 to 30 mol% with respect to all the acid components, whereby flexibility at a low temperature is obtained and processability can be improved. If the ratio is out of this range, sufficient flexibility may not be obtained after the tube is formed, or sufficient "hip" may not be obtained. Further, the 1,4-butanediol is desirably used in an amount of 70 mol% or more from the viewpoint of improving the molecular weight.

Examples of the ester-forming derivative include dimethyl terephthalate. Further, the hydrogenated dimer acid is obtained after separating and hydrogenating unsaturated fatty acid from a low polymer using a viscosity catalyst to remove by-products such as trimer acid and monomer acid. At this time, the purity of the hydrogenated dimer acid is desirably 99% or more. Other examples of the acid component include isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, sebacic acid and adipic acid. Examples thereof include aromatic and aliphatic compounds, which can be used in combination as appropriate.

As described above, regardless of whether the PBT copolymer is of a block type or a random type, the melting temperature of the fuel barrier layer material and the coating layer material are close to each other. It is easy to extrude the tube. Further, since there is miscibility between the fuel cutoff layer and the coating layer, high adhesiveness between the layers can be provided.

The constituent materials of the above-mentioned fuel cutoff layer and coating layer need not be special ones, but may be those easily available on the market. Also, as required,
Heat resistance and hydrolysis resistance can be imparted, conductivity can be imparted by mixing a filler or the like, and reinforcement can be achieved by mixing an inorganic material and the like.

The thickness ratio of each layer is not particularly limited.
A resin tube can be appropriately manufactured at a desired thickness ratio. In particular, from the stability when manufactured by extrusion molding,
It is desirable that the thickness of each layer is 10% or more of the total thickness (thickness of the resin tube), and also from the viewpoint of protection of the fuel cutoff layer and from the viewpoint of maintaining appropriate flexibility. The thickness ratio of the coating layer is 40 to 90 with respect to the total thickness.
% Is desirable. For example, in a three-layer tube as shown in FIG. 2, 0.1 mm from the inner layer side,
Layer structures such as 0.3 mm and 0.6 mm can be taken. The outer diameter of the resin tube varies depending on the type of the distribution medium, but is typically about 3 to 20 mm.

Further, since a material having a high miscibility is used in combination, an adhesive is not required at the time of forming the tube, and the tube can be reused very easily.
For example, offcuts generated during the manufacturing process and unnecessary fuel tubes can be simultaneously pulverized and re-melted without separating the respective layers, and can be reused for desired resin parts.

Further, in the resin tube of the present invention, at least a part of the terephthalic acid unit constituting the PBT copolymer can be replaced with a naphthalenedicarboxylic acid unit. In this case, the solubility coefficient of the copolymer increases, and the resin layer containing PPS as a main component or PB
The adhesiveness with the resin layer containing T as a main component can be further improved, and the fuel barrier property can be improved. Further, since the solubility coefficient of the copolymer can be made closer to PPS or the fuel barrier property can be improved in accordance with the amount of the naphthalenedicarboxylic acid unit mixed, the amount of mixing may be appropriately adjusted according to the desired characteristics. When all of the terephthalic acid units are replaced with naphthalenedicarboxylic acid, a PBN copolymer is obtained. At this time, the adhesiveness and fuel barrier properties are particularly excellent. Further, as the naphthalenedicarboxylic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,5-dicarboxylic acid, or the like can be used.

[0034]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Performance Evaluation Method] A laminated tube (single layer only in Comparative Example 2) was molded with the layer structure shown in Examples 1 to 7 and Comparative Examples 1 to 3, and a 1-inch wide test piece was formed from the molded product. Was collected and subjected to a 180 ° peel test according to JIS-K6301. Further, a material having the same constitution as the laminated tube was extruded into a flat plate shape, and a permeation resistance test was performed using the extruded material.
Here, the permeation resistance is such that gasoline or an alcohol-containing fuel is used at 60 ° C.
It was measured by the amount permeated under an atmosphere and after a specified time.
Tables 1 and 2 show these results. The gasoline used was a commercially available regular gasoline, and the alcohol-containing fuel used was a mixture of 90 parts by volume of this regular gasoline and 10 parts by volume of ethanol. In Table 1, ◎, ○,
Δ and X are relative evaluations when the result of Comparative Example 1 was evaluated as ○, ◎ indicates that the result was better than this, は indicates that it was equivalent, △ indicates that it was slightly inferior, and × indicates that it was significantly inferior. .

(Example 1) PPS resin (manufactured by Toray Industries, Inc .; A670X01) was used for the inner layer, and PBT copolymer (polyester / ether block copolymer elastomer) was used for the outer layer.
Toray DuPont; Hytrel 5577) was extruded at a volume ratio of 3: 7 to obtain a resin tube (extruded outer diameter 8 mm, inner diameter 6 mm) and a flat plate (1 mm thick) of this example.

(Example 2) The outer layer PBT copolymer was replaced with another PBT copolymer (polyester / ester block copolymer elastomer, manufactured by Toyobo Co., Ltd .;
A resin tube and a flat plate of this example were obtained by repeating the same operation as in Example 1 except for changing to 3001).

Example 3 The same operation as in Example 1 except that the outer layer PBT copolymer was changed to another PBT copolymer (random polyester copolymer, manufactured by Kanebo Gosen Co., Ltd .; Perprene P02121). Was repeated to obtain a resin tube and a flat plate of this example.

(Embodiment 4) The PPS of the inner layer is PPS and P
The same operation as in Example 1 was repeated except that the mixture was a mixture of BT copolymer (weight ratio 90:10) to obtain a resin tube and a flat plate of this example.

(Example 5) PBT copolymer (polyester ether block copolymer elastomer, manufactured by Du Pont-Toray Co., Ltd.)
Hytrel 7277) was laminated, and the same operation as in Example 1 was repeated except that the inner layer: intermediate layer: outer layer was changed to a volume ratio of 1: 3: 6 to obtain a resin tube and a flat plate of this example.

Example 6 A PBT copolymer (prototype in-house) was laminated as an inner layer on the inner periphery of the PPS of the intermediate layer.
The same operation as in Example 1 was repeated, except that the volume ratio of the intermediate layer: the outer layer was 1: 3: 6, to obtain a resin tube and a flat plate of this example.

(Embodiment 7) From the inner layer side, P
BT copolymer (polyester / ether block copolymer elastomer, manufactured by Toray DuPont; Hytrel 5577), PPS as an inner layer (manufactured by Toray, Inc .; A
670X01), a PBT copolymer (polyester ether block copolymer elastomer, manufactured by Toray DuPont; Hytrel 5577) as an intermediate layer, and a PBT (manufactured by Kanebo Gosen Co., Ltd .: PBT71) as an outer layer.
9), as the outermost layer, a PBT copolymer (polyester ether block copolymer elastomer, manufactured by Du Pont-Toray Co., Ltd .: Hytrel 5577) is laminated, and the innermost layer:
Inner layer: middle layer: outer layer: outermost layer in volume ratio of 1: 1: 1:
The same operation as in Example 1 was repeated except that the ratio was set to 3: 4, to obtain a resin tube and a flat plate of this example.

Comparative Example 1 Ethylenetetrafluoroethylene copolymer (ETFE) was used for the inner layer, a mixture of ETFE and polyamide 12 (PA12) was used for the intermediate layer, and PA12 was used for the outer layer.
And the volume ratio of inner layer: intermediate layer: outer layer = 1.5: 1.
5: 7, and extruded the resin tube (extruded outer diameter 8
mm, inner diameter 6 mm) and a flat plate (1 mm thickness).
The peel strength is a measurement result at the interface between the inner layer and the intermediate layer.

Comparative Example 2 Polyamide 11 (PA11)
A resin tube of this example, that is, a single-layer tube (extruded outer diameter 8 mm, inner diameter 6 mm) and a flat plate (1 mm thick) were obtained only by the above method.

Comparative Example 3 The PBT copolymer of the outer layer was PB
The same operation as in Example 1 was repeated, except that T (5201-X10) was used, to obtain a resin tube and a flat plate of this example.

[0046]

[Table 1]

As is clear from the results shown in Table 1, the resin tubes obtained in Examples 1 to 7 were all superior to Comparative Examples 1 to 3 in terms of characteristics (permeation resistance and peel strength).
Was measured. In particular, the peel strength is sometimes very difficult to measure, and it can be understood that the material for the resin tube obtained in the examples has excellent adhesiveness without requiring a special adhesive step.

Although the present invention has been described in detail with reference to the embodiments, the present invention is not limited thereto, and various modifications can be made within the gist of the present invention. For example,
The material resin of each layer used in the present invention includes an antioxidant and a heat stabilizer (hindered phenol, hydroquinone, thioether and phosphite, or an arbitrary mixture or a substituted product thereof), an ultraviolet absorber (Resorcinol, salicylate, benzotriazole, benzophenone, etc.), lubricants and release agents (silicone resin, montanic acid and their salts, stearic acid and their salts, stearyl alcohol, stearyl amide, etc.), dyes (nitrosine, etc.) and pigments A coloring agent containing (such as cadmium sulfide or phthalocyanine), an additive impregnating liquid (such as silicon oil), and a nucleating agent (such as talc or kaolin) can be added alone or in an appropriate combination. The cross-sectional shape of the resin tube is typically circular or elliptical, but may be a cross-sectional shape other than these. Furthermore, even when a laminate using the material of each layer is used in a shape other than a tube, for example, a shape like a gutter or a sheet, permeation resistance and the like can be obtained. Further, the resin tube may be applied to blow molding, which can be easily manufactured by extrusion molding, or to impart a corrugated shape (to make bellows).

[0049]

As described above, according to the present invention, since a laminated structure using a predetermined resin is employed, it has a low permeability to alcohol-containing fuel in addition to ordinary gasoline. In addition, the present invention provides a resin tube which has a sufficiently high adhesiveness between a barrier layer (fuel blocking layer) and a coating layer (layer protecting the fuel blocking layer), is easy to recycle offcuts and the like, and is inexpensive. be able to.

[0050]

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example (two-layer structure) of a resin tube.

FIG. 2 is a schematic view showing an example of a resin tube (three-layer structure).

FIG. 3 is a schematic view showing an example (five-layer structure) of a resin tube.

[Explanation of symbols]

 10, 20, 30 Resin tube 2a, 2b Fuel cutoff layer 3a, 3b, 3c Coating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 67/04 C08L 67/04 81/02 81/02 (72) Inventor Tetsuya Enomoto Kanagawa-ku, Yokohama, Kanagawa No. 2 Takaracho Nissan Motor Co., Ltd. F-term (reference) 3H111 BA15 CA53 CB03 CB04 CB06 CB21 DA09 DB08 EA04 EA06 4F100 AK42B AK57A AL01B AL02B AL05A AL05B AL09B BA02 BA07 BA10B DA02 EH20 GB32 JB01 JD05 CF100 CN

Claims (11)

[Claims] 1. A resin tube formed by laminating two or more resin layers in a tubular form, wherein at least one layer is a resin layer containing polyphenylene sulfide as a main component, and the other layers are made of polybutylene terephthalate. A resin tube comprising a resin layer mainly composed of a polymer. 2. A resin tube in which three or more resin layers are laminated in a tubular form, wherein at least one pair of resin layers mainly composed of polyphenylene sulfide not in contact with each other and mainly composed of polybutylene terephthalate. The resin tube according to claim 1, further comprising a resin layer, wherein the other layer is made of a polybutylene terephthalate copolymer. 3. A resin layer comprising the polybutylene terephthalate copolymer as a main component, wherein a layer in contact with the resin layer comprising a polyphenylene sulfide as a main component further comprises polyphenylene sulfide. The resin tube according to claim 1. 4. The resin tube according to claim 1, wherein the resin layer containing polyphenylene sulfide as a main component further comprises a polybutylene terephthalate copolymer. 5. The polyester-ether block copolymer elastomer according to claim 1, wherein said polybutylene terephthalate copolymer is a polyester-ether block copolymer elastomer comprising polybutylene terephthalate as a hard segment and polyether as a soft segment. The resin tube according to any one of the above items. 6. The resin tube according to claim 5, wherein said polyether is polytetramethylene glycol. 7. The polybutylene terephthalate copolymer is a polyester / ester block copolymer elastomer comprising polybutylene terephthalate as a hard segment and polyester as a soft segment. A resin tube according to any one of the above items. 8. The resin tube according to claim 7, wherein the polyester is polycaprolactone. 9. The polybutylene terephthalate copolymer contains terephthalic acid or an ester-forming derivative thereof as an acid component and hydrogenated dimer acid or an ester-forming derivative thereof as an acid component, and comprises 1,4-butanediol as a glycol component. The resin tube according to any one of claims 1 to 4, wherein the resin tube comprises a copolymerized polyester as a main component. 10. The resin tube according to claim 9, wherein the copolymer composition of the hydrogenated dimer acid is 3 to 30 mol% based on the total acid components. 11. The method according to claim 1, wherein at least a part of the terephthalic acid unit constituting the polybutylene terephthalate copolymer is replaced by a naphthalenedicarboxylic acid unit. The resin tube as described.