JP7082928B2 - Laminated tube - Google Patents

Description

The present invention relates to a laminated tube having a structure in which a plurality of resin layers are laminated.

Conventionally, a laminated tube having a two-layer or three-layer structure has been used for a tube for transporting fuel of an automobile or the like (see Patent Documents 1 to 3). For example, Patent Document 1 describes a laminated tube in which at least two layers, an inner layer made of a polyamide resin or a fluororesin and an outer layer made of a soft thermoplastic resin having a hardness of 90 or less, are laminated, and each layer is heat-sealed. ing.

On the other hand, Patent Document 2 describes a laminated tube in which an innermost layer and an outermost layer are formed of a resin containing 40% by mass or more of a semi-aromatic polyamide, and an intermediate layer is formed of a material having a flexural modulus of 800 MPa or less. .. Further, Patent Document 3 describes a laminated structure in which an outer layer is a polyolefin-based thermoplastic elastomer layer and an inner layer is a semi-aromatic polyamide layer, and an adhesive layer containing a modified propylene-based polymer is provided between them.

Japanese Unexamined Patent Publication No. 11-151768 International Publication No. 2016/152537 JP-A-2017-177548

However, since the laminated tube described in Patent Documents 2 and 3 described above has an inner layer formed of a semi-aromatic polyamide resin having high rigidity, it has a large repulsion at the time of bending and is not suitable for applications such as assembling while bending. be. On the other hand, in the laminated tube described in Patent Document 1, since the inner layer is formed of a polyamide resin or a fluororesin, the flexibility is improved as compared with the case where a semi-aromatic polyamide resin is used, but the flexibility is sufficient. However, when a fluororesin is used for the inner layer, there is a problem that the manufacturing cost increases. If the laminated tube lacks flexibility, buckling may occur, and in addition, there are problems that it is difficult to save space and secondary processing is required.

Therefore, an object of the present invention is to provide a laminated tube which is easy to bend and hardly buckles.

The laminated tube according to the present invention is formed of an inner layer made of a thermoplastic resin having a flexural modulus of 0.4 GPa or less, and a thermoplastic resin provided outside the inner layer and having a hardness lower than that of the inner layer. It has an outer layer and an intermediate layer provided between the inner layer and the outer layer, and the thickness ratio of each layer is as follows: inner layer: intermediate layer: outer layer = 1: 0.06 to 0.49: 0.1 to 8. .4 .
In the present invention, the inner layer can be formed of, for example, a polyamide 12 elastomer, and the outer layer can be formed of, for example, a polyolefin-based elastomer.
The intermediate layer can be formed of, for example, a polyolefin-based adhesive resin having a polar group.

According to the present invention, it is possible to realize a laminated tube which is excellent in flexibility and hardly causes buckling even when it is bent when it is incorporated into a product or when it is used.

It is sectional drawing which shows typically the structure of the laminated tube of embodiment of this invention. A and B are conceptual diagrams of the flexibility evaluation method in the embodiment of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments described below. FIG. 1 is a cross-sectional view schematically showing the structure of the laminated tube of the present embodiment. As shown in FIG. 1, the laminated tube 10 of the present embodiment has a three-layer structure in which an inner layer 1, an intermediate layer 2, and an outer layer 3 are laminated.

[Inner layer 1]
The inner layer 1 is formed of a thermoplastic resin having a flexural modulus of 0.4 GPa or less. When the inner layer 1 is formed of a material having a high flexural modulus, the rigidity of the laminated tube 10 becomes high and it becomes difficult to bend. Specifically, when the flexural modulus of the resin forming the inner layer 1 exceeds 0.4 GPa, the flexibility of the laminated tube 10 is lowered. Therefore, in the laminated tube 10 of the present embodiment, the inner layer 1 is formed of a thermoplastic resin having a flexural modulus of 0.4 GPa or less, thereby suppressing the rigidity of the entire tube and improving the flexibility.

As the thermoplastic resin forming the inner layer 1, for example, various elastomers such as polyolefin-based elastomers, polystyrene-based elastomers, polyester-based elastomers, polyamide 12 elastomers, and polyurethane elastomers can be used. Among these thermoplastic resins, polyamide 12 elastomer is preferable because it is excellent in flexibility, flexibility, transparency and moldability. By forming the inner layer 1 with the polyamide 12 elastomer, the flexibility can be improved and buckling can be less likely to occur as compared with the conventional laminated tube using a general polyamide resin.

Further, various additives can be added to the thermoplastic resin forming the inner layer 1 as needed. Examples of the additive contained in the inner layer 1 include antioxidants, plasticizers, heat stabilizers, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers and flame retardants.

[Middle layer 2]
The intermediate layer 2 is a layer for adhering the inner layer 1 and the outer layer 3, and is formed of a resin having excellent adhesiveness to both the inner layer 1 and the outer layer 3. The resin forming the intermediate layer 2 can be appropriately selected depending on the resin forming the inner layer 1 and the outer layer 3, but the adhesive strength to the inner layer 1 and the outer layer 3 measured by a method according to JIS K6854-3 is 10 N. It is preferable to use a resin having a value of / cm or more. As a result, delamination is unlikely to occur, and even if delamination occurs, it is difficult to proceed.

Since the intermediate layer 2 needs to be chemically bonded to various resins constituting the inner layer 1 and the outer layer 3, it is preferably formed of an adhesive resin having a polar group, and has specific gravity, cost and moldability. From the viewpoint of the above, a polyolefin-based adhesive resin is particularly preferable.

[Outer layer 3]
When the laminated tube 10 is bent, the radius of curvature becomes large outside the bending radius, so that tensile stress acts on the outer layer 3 located on the outside. At this time, if the hardness of the material constituting the outer layer 3 is high, the outer layer 3 cannot follow the deformation at the time of bending, and the flexibility is impaired. In particular, when the outer layer 3 is made of a material having a hardness higher than that of the inner layer 1, the flexibility of the outer layer 3 affects the flexibility of the entire tube, so that the flexibility of the laminated tube 10 is lowered and sufficient flexibility is obtained. Cannot be obtained.

Therefore, in the laminated tube 10 of the present embodiment, the outer layer 3 is formed of a thermoplastic resin having a hardness lower than that of the resin forming the inner layer 1. As a result, the outer layer 3 easily follows the bending deformation and the repulsive force at the time of bending becomes small, so that the laminated tube 10 having excellent flexibility and less buckling can be obtained.

As the thermoplastic resin forming the outer layer 3, for example, various elastomers such as polyolefin-based elastomers, polystyrene-based elastomers, polyester-based elastomers, polyamide 12 elastomers, and polyurethane elastomers can be used. As a general rule, the outer layer 3 uses a different type of resin from the inner layer 1. Further, among the above-mentioned thermoplastic resins, polyolefin-based elastomers are preferable because they are excellent in flexibility and moldability.

Various additives can be added to the thermoplastic resin forming the outer layer 3 as needed. Examples of the additive contained in the outer layer 3 include antioxidants, plasticizers, heat stabilizers, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers and flame retardants.

[Thickness of each layer]
The thicknesses of the inner layer 1, the intermediate layer 2 and the outer layer 3 described above are not particularly limited, but for example, when the thickness of the inner layer 1 is 1, the thickness of the outer layer 3 is 0.1 to 8.4. Is preferable, and more preferably 0.8 to 1.3. The thickness of the intermediate layer 2 is preferably 0.06 to 0.49, more preferably 0.13 to 0.17. By setting the thickness of the inner layer 1, the intermediate layer 2 and the outer layer 3 within the above-mentioned range, the flexibility and flexibility of the laminated tube 10 can be improved in a well-balanced manner.

Further, for example, when the diameter of the laminated tube 10 is 20 mm or less, the ratio of the inner layer 1: the intermediate layer 2: the outer layer 3 = 0.2 to 0.8: 0.001 to 0.2: 0 in terms of the ratio to the thickness of the entire tube. It is preferably 2 to 0.8. As a result, the flexibility and flexibility of the laminated tube 10 can be improved in a well-balanced manner.

[Production method]
The laminated tube 10 of the present embodiment can be formed, for example, by melting and co-extruding each resin forming the inner layer 1, the intermediate layer 2, and the outer layer 3, or by sequentially laminating each layer.

As described in detail above, the laminated tube of the present embodiment has excellent flexibility because the inner layer is formed of a thermoplastic resin having a flexural modulus of 0.4 GPa or less. Further, in the laminated tube of the present embodiment, since the hardness of the outer layer is low, the repulsive force at the time of bending can be suppressed, and since the inner layer has a higher hardness than the outer layer, the occurrence of buckling can be prevented. As a result, the laminated tube of the present embodiment has excellent flexibility, and buckling is unlikely to occur even if it is bent when it is incorporated into a product or when it is used.

The laminated tube of the present embodiment is suitable for piping of an industrial robot because it can be expected to have an effect of convenience of arrangement and space saving. Further, when it is used, secondary bending processing is not required, so that the processing cost can be reduced.

In the present embodiment, a laminated tube having a three-layer structure has been described as an example, but the present invention is not limited to the structure shown in FIG. 1, and may include at least an inner layer, an intermediate layer, and an outer layer. , Other resin layers, fiber reinforcing layers, etc. may be provided as long as the effects of the present invention are not impaired.

Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples. In this example, a laminated tube having the structure shown in FIG. 1 was produced and its performance was evaluated. Specifically, each resin forming the inner layer, the intermediate layer and the outer layer is melted by a separate molding machine, and each resin is discharged by a coextrusion method to form a tube having an outer diameter of 5.9 mm and an inner diameter of 4.3 mm. After molding into a shape, it was cooled to obtain laminated tubes of Examples and Comparative Examples. As a reference example, a tube having a single-layer structure with an outer diameter of 5.9 mm and an inner diameter of 4.3 mm was produced, and the performance was evaluated by the same method.

The performance of each laminated tube of Examples and Comparative Examples and the single-layer tube of Reference Example was evaluated by the method shown below.

<Peeling strength>
For the laminated tubes of Examples and Comparative Examples, the peel strength between the resins of the inner layer and the outer layer and the intermediate layer was measured. At the time of measurement, a sheet having a length of 17 cm, a width of 17 cm, and a thickness of 0.5 mm is formed from each resin forming the inner layer, the outer layer, and the intermediate layer, and the inner layer and the intermediate layer, and the outer layer and the intermediate layer are laminated and heated by a heating press. The resin laminated sheets were prepared by laminating them. A mini test press machine manufactured by Toyo Seiki Seisakusho Co., Ltd. was used to prepare the resin laminated sheet, and 5 cm from the end of the sheet was chucked at the time of measurement, so that it was not adhered in advance.

This laminated resin sheet was cut into a width of 25 cm and a length of 17 cm to prepare a sample for evaluation. The measurement was carried out by a method according to JIS K6854 with a peeling speed of 20 mm / min. As a result, those having a peel strength of 10 N / cm or more were regarded as acceptable (◯), and those having a peel strength of less than 10 N / cm were regarded as rejected (×).

<Bending load test>
The flexibility of the laminated tubes of Examples and Comparative Examples and the single-layer tubes of Reference Examples was evaluated by cutting out evaluation samples having a length of 20 cm from each tube and performing a bending load test. The test was carried out in an environment of a temperature of 23 ° C. and a humidity of 50% using three types of straight pipes made of polyvinyl chloride (diameters 125 mm, 83 mm, 54 mm) having different diameters. 2A and 2B are conceptual diagrams of a bending load test, FIG. 2A shows a state without a load, and FIG. 2B shows a state with a load.

First, as shown in FIG. 2A, one end of the evaluation sample 20 was fixed to a jig (polyvinyl chloride straight tube) 21. Then, as shown in FIG. 2B, a load was applied to the evaluation sample 20, and the load required to run the sample 20 up to 1/4 of the circumference was measured by a digital spring scale. The measurement was performed three times, and the average value was calculated. As a result, the bending load of the jig having a diameter of 125 mm was 0.8 N or less, the bending load of the jig having a diameter of 83 mm was 1.2 N or less, and the bending load of the jig having a diameter of 54 mm was 1.5 N or less. Those that exceeded the specified value were evaluated as acceptable (○), and those that exceeded the specified value were evaluated as rejected (×).

<Buckling>
Place the laminated tube of Examples and Comparative Examples and the single-layer tube of Reference Example on a circular jig (straight tube made of polyvinyl chloride) with a diameter of 44 mm up to 1/4 of the circumference, and use a pipe gauge to shorten the deformed part. The diameter (minimum outer diameter dimension) was measured. When the minor axis of the deformed portion was 70% or less of the outer diameter of the tube, it was designated as "with buckling (x)", and when it exceeded 70%, it was designated as "without buckling (◯)".

The above results are summarized in Tables 1 and 2 below. The polyolefin (PO) -based elastomer shown in Tables 1 and 2 below is Esporex WSB080A manufactured by Sumitomo Chemical Co., Ltd., and the polyolefin (PO) -based adhesive resin is Modic M512 manufactured by Mitsubishi Chemical Co., Ltd. The PA) 12 elastomer is UBESTA XPA9048HV manufactured by Ube Kosan Co., Ltd., the polyamide (PA) is UBESTA3030U manufactured by Ube Kosan Co., Ltd., and the polystyrene (PS) -based elastomer is Tuftec H1221 manufactured by Asahi Kasei Corporation. The "layer thickness ratio" shown in Tables 1 and 2 below is the thickness of the outer layer and the intermediate layer when the thickness of the inner layer is 1.

As shown in Table 2 above, No. 1 which is a reference example. The single-layer tube of No. 10 did not buckle, but had a high bending load. On the other hand, No. In the laminated tubes of 7 to 9, there was no problem in the peel strength between the intermediate layer and the inner layer and the outer layer, but in the laminated tube of No. 7, the flexural modulus of the resin used for the inner layer was 1.4 GPa, which is within the range of the present invention. Since it was significantly exceeded, the flexibility was impaired, the bending load increased, and buckling also occurred.

In the No. 8 laminated tube, the hardness (40A) of the resin used for the inner layer was lower than the hardness (78A) of the resin used for the outer layer, so that buckling occurred. No. The laminated tube of No. 9 had a low bending load and improved flexibility, but buckling occurred because the flexural modulus of the resin used for the inner layer was 0.5 GPa, which was beyond the range of the present invention.

On the other hand, as shown in Table 1 above, the inner layer has a three-layer structure of an inner layer, an intermediate layer, and an outer layer, and the inner layer is formed of a thermoplastic resin having a flexural modulus of 0.4 GPa or less, and the outer layer has a hardness higher than that of the inner layer. The No. 1 to 6 laminated tubes made of a low thermoplastic resin did not cause buckling and were excellent in flexibility. From the above results, it was confirmed that according to the present invention, a laminated tube that is easy to bend and does not easily buckle can be obtained.

1 Inner layer 2 Intermediate layer 3 Outer layer 10 Laminated tube 20 Evaluation sample (tube)
21 Jig (polyvinyl chloride straight pipe)

Claims (3)

An inner layer made of a thermoplastic resin having a flexural modulus of 0.4 GPa or less,
An outer layer provided outside the inner layer and formed of a thermoplastic resin having a hardness lower than that of the inner layer,
It has an intermediate layer provided between the inner layer and the outer layer, and has an intermediate layer.
A laminated tube in which the ratio of the thickness of each layer is inner layer: intermediate layer: outer layer = 1: 0.06 to 0.49: 0.1 to 8.4 . The inner layer is made of a polyamide 12 elastomer and is made of
The laminated tube according to claim 1, wherein the outer layer is made of a polyolefin-based elastomer. The laminated tube according to claim 1 or 2, wherein the intermediate layer is made of a polyolefin-based adhesive resin having a polar group.

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