JP7795564B2 - Resin pipe for microducts - Google Patents

Description

The present invention relates to a resin pipe for a microduct into which an optical fiber cable is inserted and laid.

The so-called microduct system method, in which optical fiber cables are inserted and installed in small-diameter microducts installed inside a large-diameter main duct, has been widely adopted in Europe and the United States because once the conduit (microduct) is installed, optical fiber cables can be added, changed, or updated without large-scale construction work. Microduct system methods generally employ methods that use high-pressure compressed air to force the optical fiber cable through the microduct, or methods that combine air-forced insertion and solid-state insertion (see, for example, Patent Document 1).

In either method, the tube that constitutes the microduct must have low friction, be resistant to cable buckling, and have good air pumping characteristics. Conventionally, pipes and tubes for pneumatic optical cables have been made of synthetic resins such as polyethylene (see, for example, Patent Documents 2 and 3). Patent Document 2 proposes a pipe for pneumatic optical cables that consists of a synthetic resin pipe body and a spiral wire partially embedded in the inner wall surface of the pipe body. Patent Document 3 also proposes a plastic pipe made of polyethylene with a Vicat softening point of 120 to 140°C, a density of 0.950 to 0.970 g/cm ³ , and an Olsen stiffness of 7500 to 13000 kg/cm ² .

Japanese Patent Application Laid-Open No. 2001-309519 Japanese Patent Application Publication No. 5-323128 Japanese Patent Application Publication No. 10-62665

In recent years, the distances over which optical fiber cables are inserted and installed have become longer, and there is a demand for resin pipes for microducts that have lower friction and are easier to insert using air pressure or solid-state methods. However, the conventional resin pipes mentioned above have poor sliding properties with the cable, making them unsuitable for long-distance installation.

The present invention aims to provide a resin pipe for microducts that has excellent optical fiber cable insertion and installation performance.

The resin pipe for a microduct according to the present invention is a resin pipe for a microduct into which an optical fiber cable is inserted and laid, and has an outer diameter of 4 to 40 mm, an inner diameter of 2 to 38 mm, and a thickness of 1 to 3 mm, and is composed of two or more layers, with at least the innermost layer having a substantially circular cross section and formed from a polyethylene resin containing 0.05 to 10 mass % of a non-reactive silicone gum or non-reactive silicone rubber , and the outermost layer being formed in close contact with the entire surface of the layer directly below, and the thickness of the innermost layer being 5 to 30% of the overall thickness, and having a dynamic friction coefficient of 0.2 or less against high-density polyethylene, as measured using a friction coefficient measuring device in accordance with the method specified in JIS K7125, with contact surface dimensions of 63 mm x 63 mm, a load during measurement of 50 g, and a table moving speed of 100 mm/min.
The polyethylene resin may contain two or more types of polyethylene having different densities, and at least polyethylene having a density of 0.91 to 0.97 g/cm ³ and polyethylene having a density of 0.91 to 0.93 g/cm ³ can be used. In this case, the polyethylene resin may contain high-density polyethylene (HDPE), low-density polyethylene (LDPE) and/or linear low-density polyethylene (LLDPE), and the content of the low-density polyethylene (LDPE) and the linear low-density polyethylene (LLDPE) may be 0.01 to 20% by mass.
The outermost layer of the resin pipe for a microduct of the present invention may be formed, for example, from a polyethylene resin that does not contain non-reactive silicone. In this case, one or more intermediate layers may be provided between the innermost and outermost layers, and these intermediate layers may be formed from a polyethylene resin that does not contain non-reactive silicone.
Alternatively, one or more intermediate layers may be provided between the innermost layer and the outermost layer, and the intermediate layers may be formed from a polyethylene resin that does not contain non-reactive silicone, while the outermost layer may be formed from a polyethylene resin that contains 0.01 to 20% by mass of any one selected from the group consisting of non-reactive silicone gum, silicone rubber, and silicone oil.
The resin pipe for a microduct of the present invention can have an oblateness of 10% or less, calculated by measuring the maximum and minimum values of the outer diameter at any position with a vernier caliper and taking the arithmetic mean.

This invention reduces friction on the inner surface that comes into contact with the optical fiber cable, thereby improving the insertion and installation performance of the optical fiber cable.

1 is a cross-sectional view showing an example of the structure of a resin pipe according to an embodiment of the present invention. 10A and 10B are cross-sectional views showing other structural examples of the resin pipe according to the embodiment of the present invention.

The following describes in detail the embodiments of the present invention, with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

The resin pipe according to an embodiment of the present invention is a resin pipe for a microduct into which an optical fiber cable is inserted and laid, and at least the inner surface is formed from a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone. The "inner surface" here refers to the hollow surface that comes into contact with the optical fiber cable. The optical fiber cable may be inserted by air pressure pushing, solid pushing, or a combination of these.

[structure]
1 and 2A and 2B are cross-sectional views showing examples of the structure of a resin pipe according to an embodiment of the present invention. The resin pipe according to this embodiment may have a single-layer structure composed of only a single resin layer 11, such as resin pipe 1 shown in Fig. 1; a two-layer structure composed of an inner layer 21 and an outer layer 22, such as resin pipe 2 shown in Fig. 2A; or a three-layer structure having an inner layer 31, an outer layer 32, and an intermediate layer 33, such as resin pipe 3 shown in Fig. 2B. The intermediate layer 33 shown in Fig. 2B may be composed of multiple layers, and may include a layer formed of a resin or material other than polyethylene.

In the case of the single-layer resin pipe 1 shown in Figure 1, the entire resin layer 11 is formed from a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone. In the case of the two-layer resin pipe 2 shown in Figure 2A, both the inner layer 21 and the outer layer 22 may be formed from a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone. However, from the perspective of suppressing increases in manufacturing costs, it is preferable to form the outer layer 22 from a polyethylene resin that does not contain non-reactive silicone. This makes it possible to impart slidability to the inner surface 20 while reducing manufacturing costs.

Furthermore, in the case of the three-layer resin pipe 3 shown in Figure 2B, it is sufficient that at least the inner layer 31 is formed from a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone. The middle layer 33 and outer layer 32 may also be formed from a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone, but from the perspective of suppressing increases in manufacturing costs, it is preferable that the middle layer 33 be formed from a polyethylene resin that does not contain non-reactive silicone. On the other hand, from the perspective of suppressing increases in manufacturing costs, it is preferable that the outer layer 32 be formed from a polyethylene resin that does not contain non-reactive silicone, but by forming it from a polyethylene resin that contains 0.01 to 20% by mass of non-reactive silicone, it is possible to impart slidability to the outer surface as well.

The sizes of the resin pipes 1, 2, and 3 can be selected appropriately depending on the specifications of the microduct, but can be, for example, an outer diameter of 4 to 40 mm, an inner diameter of 2 to 38 mm, and a thickness of 1 to 3 mm. In the case of the two-layer resin pipe 2 shown in Figure 2A, the thickness of the inner layer 21 is preferably 1 to 50% of the total thickness (total thickness of the inner layer 21 and outer layer 22), and more preferably 5 to 30%. In the case of the three-layer resin pipe 3 shown in Figure 2B, the thicknesses of the inner layer 31 and outer layer 32 are each preferably 1 to 45% of the total thickness (total thickness of the inner layer 31, outer layer 32, and intermediate layer 33), and more preferably 5 to 30%.

The length of the resin pipes 1, 2, and 3 is not particularly limited and can be selected appropriately depending on the specifications of the microduct, production equipment, etc. Furthermore, the inner and/or outer surfaces of the resin pipes 1, 2, and 3 may be subjected to surface treatments such as unevenness and spirals.

[Non-reactive silicone]
In the resin pipes 1, 2, and 3 of this embodiment, the polyethylene resin constituting the inner surfaces 10, 20, and 30 contains non-reactive silicone in an amount ranging from 0.01 to 20% by mass. If the non-reactive silicone content is less than 0.01% by mass, the effect of improving the sliding properties of the inner surfaces 10, 20, and 30 is not obtained. Furthermore, adding more than 20% by mass of the non-reactive silicone does not further improve sliding properties, resulting in increased manufacturing costs and reduced moldability (shapeability). From the perspective of balancing the sliding properties of the inner surfaces 10, 20, and 30 and manufacturing costs, the amount of non-reactive silicone in the polyethylene resin is preferably 0.05 to 10% by mass.

The non-reactive silicone used in the resin pipes 1, 2, and 3 of this embodiment may be any silicone that does not have reactive functional groups, such as non-reactive silicone gum, silicone rubber, silicone oil, and silicone powder.

[Polyethylene resin]
The polyethylene resin constituting the inner surfaces 10, 20, and 30 of the resin pipes 1, 2, and 3 is not particularly limited as long as it is a resin whose main component is polyethylene, but from the viewpoint of improving sliding properties, an HDPE resin whose main component is high-density polyethylene (HDPE) is preferred. Furthermore, in the case of the single-layer resin pipe 1 shown in Fig. 1, from the viewpoint of ease of insertion of an optical fiber cable, the flexural modulus of the polyethylene resin is preferably 600 to 1800 MPa when the main component is high-density polyethylene (HDPE), 100 to 400 MPa when the main component is low-density polyethylene (LDPE), and 150 to 600 MPa when the main component is linear low-density polyethylene (LLDPE).

On the other hand, from the viewpoint of improving the dispersibility of the non-reactive silicone and imparting flexibility, it is preferable to form the inner surfaces 10, 20, 30 from a polyethylene resin containing two or more types of polyethylene with different densities. When the polyethylene resin contains two types of polyethylene, for example, polyethylene with a density of 0.91 to 0.97 g/cm3 ^and polyethylene with a density of 0.91 to 0.93 g/ ^cm3 can be used.

More preferably, the polyethylene resin constituting the inner surfaces 10, 20, and 30 contains high-density polyethylene (HDPE), low-density polyethylene (LDPE), and/or linear low-density polyethylene (LLDPE). In this case, the content of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) in the polyethylene resin can be selected appropriately depending on the amount of non-reactive silicone blended and the physical properties required of the resin pipes 1, 2, and 3, such as flexibility, but can be, for example, 0.01 to 20% by mass.

In the case of the two-layer resin pipe 2 shown in Figure 2A, the polyethylene resin forming the inner layer 21 and the polyethylene resin forming the outer layer 22 may be the same or different. In the case of the three-layer resin pipe 3 shown in Figure 2B, the polyethylene resin forming the inner layer 31, the polyethylene resin forming the outer layer 32, and the polyethylene resin forming the middle layer 33 may be the same or different.

In addition, the resin pipes 1, 2, and 3 of this embodiment may be appropriately colored by adding pigments or dyes to the polyethylene resin described above. Weathering agents, heat resistance agents, and the like may also be added to the polyethylene resin. Furthermore, other additives may be added to the polyethylene resin as needed, as long as they do not impair the effects of the present invention. Examples of other additives that may be added to the polyethylene resin include processing heat stabilizers, light stabilizers, ultraviolet absorbers, antioxidants, lubricants, colorants, antistatic agents, flame retardants, water repellents, waterproofing agents, hydrophilic agents, electrical conductivity agents, thermal conductivity agents, electromagnetic wave shielding agents, translucency adjusters, fluorescent agents, lubricity agents, transparency agents, antiblocking agents, metal deactivators, and antibacterial agents.

As described above in detail, at least the inner surface of the resin pipe of this embodiment is formed from polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone, thereby reducing friction on the surface that comes into contact with the optical fiber cable and improving sliding properties. As a result, a microduct can be realized that has excellent optical fiber cable insertion and installation performance and allows for long-distance installation.

The effects of the present invention will be specifically explained below using examples and comparative examples. In these examples, resin tubes were produced using the method described below, and their formability and sliding properties were evaluated.

<Preparation of evaluation samples>
(1) Raw Materials Polyethylene Resin A: High-density polyethylene resin Polyethylene Resin B: Low-density polyethylene resin Non-reactive silicone: Silicone gum

(2) Method for Producing Resin Pipes The raw materials described above were blended and kneaded in the proportions shown in Table 1 below, and the resulting mixture was molded using an extruder equipped with a pipe die to obtain resin pipes of the Examples and Comparative Examples. The molding conditions were a rotation speed of 26.7 rpm, pipe die nozzle dimensions of 18 mm outer diameter and 12 mm inner diameter, and molding speed of 3 m/min. The dimensions of the resin pipes were 12 mm outer diameter, 8 mm inner diameter, and 2 mm wall thickness.

<Evaluation>
(1) Shapeability The shapeability of the resin pipes of the examples and comparative examples was evaluated by the roundness calculated from the flattening ratio. Specifically, for each resin pipe prepared by the above-mentioned method, the maximum and minimum values of the outer diameter at any position were measured with a vernier caliper, and the flattening ratio was calculated by the arithmetic mean. As a result, those with a flattening ratio of 10% or less were evaluated as acceptable (○), and those with a flattening ratio of more than 10% were evaluated as unacceptable (×).

(2) Sliding property The kneaded material was placed in a mold of 150 mm x 150 mm x 2 mm, and a load of 10 MPa was applied for 3 minutes using a hot press at 220 ° C. to form a sheet. The sheet was cut into a width of 63 mm to obtain an evaluation test piece (length 150 mm, thickness 2 mm). Then, in accordance with the method specified in JIS K7125, the dynamic friction coefficient of the surface of each test piece was measured. For the measurement, a friction coefficient measuring device was used, which included a table movable in a direction parallel to the installation surface, a reinforcing plate for fixing the test piece to the table, a mating material placed on the test piece, a weight for pressing the mating material against the test piece with a constant load, and a load cell connected to the mating material.

The opposing material used was polyethylene resin A, which was also used for the test specimen. The dimensions of the contact surface of the opposing material with the test specimen were 63 mm x 63 mm, the weight of the weight (load during measurement) was 50 g, and the table movement speed was 100 mm/min. Results showing a dynamic friction coefficient of 0.2 or less were rated as acceptable (○), and results showing a dynamic friction coefficient of more than 0.2 were rated as unacceptable (×).

(3) Overall Evaluation A sample that was evaluated as acceptable (○) for both the shapeability and the sliding property was evaluated as passed (○), and a sample that was evaluated as unacceptable (×) for even one of the items was evaluated as unacceptable (×). The results are shown in Table 1 below.

As shown in Table 1 above, Comparative Example 1, which was formed from a polyethylene resin containing no non-reactive silicone, had poor sliding properties. Furthermore, Comparative Example 2, which used a polyethylene resin containing more than 20% by mass of non-reactive silicone, had poor formability. In contrast, Reference Examples 1 and 2 and Examples 3 and 4 , in which the inner surface was formed from a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone, had good formability and sliding properties.

These results confirm that the present invention makes it possible to create a resin pipe for microducts that has excellent optical fiber cable insertion and installation performance.

The present invention can also take the following forms.
[1]
A resin pipe for a microduct into which an optical fiber cable is inserted and laid,
A resin pipe for a microduct, at least the inner surface of which is formed from a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone.
[2]
The resin pipe for a microduct according to [1], wherein the polyethylene resin contains two or more types of polyethylene having different densities.
[3]
The resin pipe for microducts according to [1] or [2], wherein the polyethylene resin contains high-density polyethylene (HDPE) and low-density polyethylene (LDPE).
[4]
The resin pipe for a microduct according to any one of [1] to [3], wherein the non-reactive silicone is silicone gum, silicone rubber, silicone oil, or silicone powder.
[5]
It consists of two layers, an inner layer and an outer layer,
the inner layer is formed of a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone,
The resin pipe for a microduct according to any one of [1] to [4], wherein the outer layer is formed of a polyethylene resin that does not contain non-reactive silicone.
[6]
It has an inner layer, a middle layer, and an outer layer,
the inner layer is formed of a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone,
the intermediate layer is formed of a polyethylene resin that does not contain non-reactive silicone;
The resin pipe for microducts according to any one of [1] to [4], wherein the outer layer is formed of a polyethylene resin containing 0.01 to 20% by mass of non-reactive silicone or a polyethylene resin that does not contain non-reactive silicone.

1 to 3: Resin pipe 10, 20, 30: Inner surface 11: Resin layer 21, 31: Inner layer 22, 32: Outer layer 33: Intermediate layer

Claims (7)

A resin pipe for a microduct into which an optical fiber cable is inserted and laid,
The outer diameter is 4 to 40 mm, the inner diameter is 2 to 38 mm, and the thickness is 1 to 3 mm;
It consists of two or more layers,
At least the innermost layer has a substantially circular cross section and is formed from a polyethylene resin containing 0.05 to 10 % by mass of a non-reactive silicone gum or a non-reactive silicone rubber ;
The outermost layer is formed in close contact with the entire surface of the layer directly below.
The innermost layer is
The thickness is 5 to 30% of the total thickness,
The dynamic friction coefficient against high density polyethylene measured using a friction coefficient measuring device in accordance with the method specified in JIS K7125, with the contact surface dimensions of 63 mm x 63 mm, a load of 50 g during measurement, and a table movement speed of 100 mm/min, is 0.2 or less.
Resin pipe for microducts. The polyethylene resin contains two or more types of polyethylene having different densities,
2. The resin pipe for microducts according to claim 1, which contains at least polyethylene having a density of 0.91 to 0.97 g/cm ³ and polyethylene having a density of 0.91 to 0.93 g/cm ³ . The resin pipe for microducts described in claim 2, wherein the polyethylene resin contains high-density polyethylene (HDPE), low-density polyethylene (LDPE), and/or linear low-density polyethylene (LLDPE), and the content of the low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) is 0.01 to 20% by mass. The resin pipe for a microduct according to any one of claims 1 to 3, wherein the outermost layer is formed of a polyethylene resin that does not contain non-reactive silicone. one or more intermediate layers are provided between the innermost layer and the outermost layer,
5. The resin pipe for a microduct according to claim 4, wherein the intermediate layer is formed of a polyethylene resin that does not contain non-reactive silicone. one or more intermediate layers are provided between the innermost layer and the outermost layer,
the intermediate layer is formed of a polyethylene resin that does not contain non-reactive silicone;
The resin pipe for microducts according to any one of claims 1 to 3, wherein the outermost layer is formed of a polyethylene resin containing 0.01 to 20 mass% of any one selected from non-reactive silicone gum, silicone rubber, and silicone oil. The resin pipe for microducts according to any one of claims 1 to 3, wherein the maximum and minimum values of the outer diameter at any position are measured with a vernier caliper and the flattening ratio calculated as the arithmetic mean is 10% or less.