Wood-blended resin pipe

Abstract

To provide a wood-blended resin pipe that can suppress generation of thermal expansion or flexure due to temperature variation.SOLUTION: A wood-blended resin pipe includes: an outer layer including a resin composite including a polyolefin resin or a polyolefin resin and a woody material; and an inner layer including a resin composite including a polyolefin resin and a woody material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wood-blended resin pipe. [Background technology]

[0002] Corrugated pipes are used as protective tubes for communication cables and electrical wiring inside buildings, on exterior walls, and on rooftops. Corrugated pipes are generally flexible, allowing for the wiring direction to be freely changed. However, flexible corrugated pipes are sometimes shipped in a wound state, which can leave a tendency to curl. Therefore, when flexible corrugated pipes are installed in long, straight sections, in particular, they can bend into an S-shape due to the tendency to curl, detracting from the aesthetic appearance. Furthermore, friction can occur between the inside of the corrugated pipe and the communication cables when they are routed, resulting in misalignment of the corrugated pipe. This problem can be solved by using non-flexible (rigid) corrugated pipes for long straight sections and flexible corrugated pipes for curved sections. By using corrugated pipes for the rigid protective pipes used in long straight sections, the entire straight and curved sections have a corrugated structure, creating a unified overall appearance and resulting in a protective pipe with excellent aesthetics.

[0003] As an example of such a non-flexible corrugated pipe, Patent Document 1 discloses a corrugated pipe having an inner diameter of 14.34 to 35.72 mm and an outer diameter of 22.83 to 45.30 mm, whose main component is a flame-retardant polyolefin resin, and in which valleys and solid peaks wider than the valleys are alternately formed on the outer periphery, the inner diameter of the pipe at the center of the valleys is smaller than the inner diameter of the pipe at the center of the peaks, and the pipe rises slightly in an arc shape toward the inside of the pipe, and the inner diameter of the solid peaks is smaller than the outer diameter of the valleys, the average wall thickness of the valleys is 1.40 mm to 2.06 mm, and the average wall thickness of the peaks is 3.3 mm to 3.76 mm, and the pipe has a bending rigidity of 2.50 N·m 2 More than 5.00N m 2The present invention discloses a non-flexible protective tube for cables, etc., having excellent bending rigidity and compression recovery properties, characterized in that the compression loss rate in a compression load test based on JIS C 8411 when a compression load of 1,250 N or more is 10% or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-23954 Summary of the Invention [Problem to be solved by the invention]

[0005] Regardless of whether they are flexible or not, corrugated pipes use thermoplastic resin as the base resin. Therefore, corrugated pipes are prone to thermal expansion and contraction due to temperature changes after installation, and to bending. The expansion and contraction of corrugated pipes can cause deformation of the support parts that secure the corrugated pipes, or can cause problems such as the corrugated pipes coming off the support parts.

[0006] An object of the present invention is to provide a wood-blended resin pipe that can suppress thermal expansion and contraction and bending due to temperature changes. [Means for solving the problem]

[0007] As a result of investigations aimed at solving the above problems, the inventors have found that by making the corrugated pipe have at least a two-layer structure consisting of an outer layer and an inner layer, and by making the inner layer a layer of a resin composite containing a wood material, the resulting corrugated pipe can be prevented from thermal expansion and contraction or warping due to temperature changes. Based on these findings, the present invention has been completed through further investigations.

[0008] That is, the above problems were solved by the following means. [1] A wood-blended resin pipe having an outer layer containing a polyolefin resin or a resin composite containing a polyolefin resin and a wood material, and an inner layer containing a resin composite containing a polyolefin resin and a wood material. [2] The wood-blended resin pipe according to [1] above, wherein the ratio of the polyolefin resin to the wood material in the resin composite is polyolefin resin:wood material=20:80 to 99:1 (mass ratio). [3] The wood-blended resin pipe according to [1] or [2], wherein the inner surface of the inner layer is smooth. [4] The wood-blended resin pipe according to any one of [1] to [3], wherein the wood-blended resin pipe contains a flame retardant. [5] The wood-blended resin pipe according to any one of [1] to [4], wherein the wood-blended resin pipe is a corrugated pipe. [Effects of the Invention]

[0009] The wood-blended resin pipe of the present invention can suppress thermal expansion and contraction and bending due to temperature changes. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a partial cross-sectional view schematically showing one embodiment of a wood-blended resin pipe of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Wood compound resin pipe] The structure of the wood-mixed resin pipe of the present invention is not particularly limited except as specified in the present invention. As a preferred embodiment of the wood-mixed resin pipe of the present invention, a corrugated pipe (hereinafter also referred to as the "corrugated pipe of the present invention") will be described as an example, but the following explanation other than the corrugated structure of the corrugated pipe also applies to wood-mixed resin pipes with structures other than the corrugated pipe.

[0012] The corrugated pipe of the present invention has an outer layer containing a polyolefin resin or a resin composite containing a polyolefin resin and a wood material, and an inner layer containing a resin composite containing a polyolefin resin and a wood material. By forming at least the inner layer of the corrugated pipe from a resin composite containing a wood material, rigidity is imparted. Therefore, this corrugated pipe is a non-flexible corrugated pipe that does not have the flexibility (flexibility that allows it to bend without cracking) imparted by the corrugated structure. FIG. 1 schematically illustrates one embodiment of a corrugated tube 1 according to the present invention. In FIG. 1, the view to the right of the dashed-dotted line illustrates the appearance of the corrugated tube 1 according to the present invention, and the view to the left of the dashed-dotted line illustrates a longitudinal cross-sectional view of the corrugated tube 1 according to the present invention. The corrugated tube 1 according to the present invention illustrated in FIG. 1 has a repeating structure (accordion-like structure) on its outer periphery, in which valley portions 2 and solid peak portions 3 wider than the valley portions 2 are alternately formed. The corrugated tube 1 according to the present invention illustrated in FIG. 1 has an outer layer 4 containing a polyolefin resin and an inner layer 5 containing a resin composite containing a wood material. The inner surface of the inner layer 5 (the inner surface of the corrugated tube 1 according to the present invention) is linear and smooth.

[0013] In the manufacture of corrugated pipes, a resin tube (cylinder) formed by extrusion molding is placed against a mold (a mold with a corrugated shape) and vacuum is applied from the mold contact surface, resulting in a corrugated outer surface similar to that of the mold. During this process, the inside of the resin tube is also pulled outward, resulting in a corrugated inner surface. The resulting corrugated tube has a corrugated structure on both its inner and outer surfaces (a tube with corrugated inner and outer surfaces), providing the desired flexibility. In contrast, a preferred embodiment of the corrugated pipe of the present invention is non-flexible. Therefore, by forming the resin composite constituting the inner layer thick, the inner surface of the inner layer can be made smooth (without any irregularities due to the outer surface) even when the outer surface is corrugated by vacuuming. The smooth inner surface further improves the rigidity of the resulting corrugated pipe of the present invention. In other words, by forming the inner layer containing the resin composite to a certain thickness, the inner surface of the inner layer becomes smooth, resulting in superior rigidity and better suppressing thermal expansion / contraction and deflection due to temperature changes. Furthermore, due to the shape of the wood material contained in the resin composite that constitutes the inner layer, minute gaps are generated within the layer. Therefore, compared to when the same amount of resin (resin without wood material) is used to manufacture the inner layer, when the resin composite is used, the thickness of the entire inner layer can be increased by the amount of the minute gaps, and it is presumed that even with a small amount of resin, it is easier to make the inner surface of the inner layer smooth. In this specification, "suppressing the occurrence of thermal expansion / contraction or deflection due to temperature change" includes reducing the degree of thermal expansion / contraction or deflection due to temperature change.

[0014] Furthermore, when a communication cable or the like is passed through a corrugated pipe having a corrugated structure on both the inner and outer surfaces, the cable or the like may get caught on the unevenness of the inner surface, preventing smooth passing through or damaging the cable. In the corrugated pipe of the present invention, by making the inner surface smooth, the cable or the like passed through the corrugated pipe of the present invention does not get caught on the inner surface, and damage caused by contact with the inner surface of the corrugated pipe can be reduced. Furthermore, since there are no irregularities on the inner surface due to the corrugated shape, the strength against external pressure and internal pressure is improved, and the heat insulation properties can also be improved.

[0015] The corrugated tube of the present invention is a non-flexible corrugated tube having a shape in which valleys and peaks are alternately formed on its outer surface along the pipe axis, and therefore can be used in combination with a flexible corrugated tube of similar shape and size and connected using a corrugated pipe coupling. Therefore, by using the corrugated tube of the present invention with improved rigidity, even when used in combination with a conventional corrugated tube, it is possible to create a unified aesthetic appearance as a whole, achieving both excellent rigidity and aesthetics. The corrugated shape of the corrugated pipe of the present invention is not particularly limited, and may be a shape in which valleys and solid peaks wider than the valleys are alternately formed. For example, the dimensions of the corrugated pipe of the present invention may be an outer diameter of 10 to 105 mm and an inner diameter of 3 to 85 mm, or may be an outer diameter of 15 to 100 mm and an inner diameter of 8 to 80 mm, or may be an outer diameter of 20 to 95 mm and an inner diameter of 13 to 75 mm. Note that the "inner diameter" refers to the minimum inner diameter. Furthermore, the inner cross-section of the corrugated pipe of the present invention when cut perpendicular to the pipe axis is circular. Furthermore, the average wall thickness of the valleys may be 1.7 to 2.7 mm and the average wall thickness of the peaks may be 2.8 to 3.8 mm, or may be 1.8 to 2.6 mm and 2.9 to 3.7 mm, or may be 1.9 to 2.5 mm and 3.0 to 3.6 mm. The widths of the valleys and peaks can be determined appropriately depending on the size and use of the corrugated tube of the present invention. For example, the width of the peaks can be 1.1 to 4 times the width of the valleys, or 1.3 to 3 times, or 1.5 to 2 times. The above-mentioned numerical values ​​of dimensions, etc. are merely examples, and the shape, etc. of the corrugated tube of the present invention are not limited to these.

[0016] The configuration of the corrugated tube of the present invention will be described in more detail below.

[0017] <Outer layer> In the corrugated pipe of the present invention, the outer layer contains a polyolefin resin or a resin composite containing a polyolefin resin and a wood material.

[0018] (Polyolefin resin) In the present invention, the term "polyolefin resin" means not only polyolefin itself (polyolefin component) but also mixtures (compositions) of polyolefin with various additives. The polyolefin constituting the polyolefin resin is not particularly limited, and may be an olefin homopolymer or an olefin copolymer. An olefin homopolymer is a polymer of one type of olefin. An olefin copolymer is a copolymer of a certain olefin with another olefin (for example, an ethylene-propylene copolymer (random copolymer or block copolymer)), or a copolymer of an olefin with a compound having a carbon-carbon double bond other than an olefin (for example, a vinyl compound or a styrene compound). In other words, any polymer containing an olefin component as a constituent is included in the category of "polyolefin." The olefin resin is preferably a polypropylene resin, a polyethylene resin, or an ethylene-vinyl acetate copolymer. The polyethylene resin is preferably a high-density polyethylene (density: 0.942 to 0.970 g / cm 3 The polyolefin resin may be one kind of polyolefin resin or two or more kinds of polyolefin resins. The olefin resin can be synthesized by a conventional method, or a commercially available product can also be used.

[0019] The polyolefin resin preferably has a melt flow rate (MFR) of 1 to 100 g / 10 min, more preferably 10 to 50 g / 10 min, at a temperature of 230° C. and a load of 2.16 kg. The MFR can be measured in accordance with JIS K7210-1:2014.

[0020] The polyolefin resin may contain, in addition to polyolefin, additives such as flame retardants, colorants (dyes, organic pigments, inorganic pigments), antioxidants, ultraviolet absorbers, antistatic agents, lubricants, and anti-drip agents, as long as the effects of the present invention are not impaired. In particular, the inclusion of a flame retardant can impart self-extinguishing properties to the corrugated pipe of the present invention. Examples of such flame retardants include halogen-based flame retardants and phosphorus-based flame retardants. Furthermore, a polyolefin resin modified with, for example, an unsaturated carboxylic acid or a derivative thereof may also be blended.

[0021] The content of the polyolefin component in the polyolefin resin is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and can be 90% by mass or more, or even 95% by mass or more, or even 99% by mass or more.

[0022] (resin composite) The resin composite contains a polyolefin resin and a wood material. By blending the wood material, which has a smaller thermal expansion coefficient than the polyolefin resin, the thermal expansion and contraction and deflection of the resulting resin composite can be reduced and the rigidity can be improved. Furthermore, the wood material is inexpensive, and by blending the wood material, the corrugated pipe of the present invention can be made lighter than conventional corrugated pipes, improving workability. From the viewpoint of more effectively reducing thermal expansion / contraction and warping, the content ratio of the polyolefin resin to the wood material in the resin composite is preferably 20:80 to 99:1 by mass, more preferably 40:60 to 90:10, or may be, for example, 60:40 to 90:10, or 70:30 to 90:10. In order to impart self-extinguishing properties to the resin composite, it is preferable that a flame retardant is blended in. The flame retardant may be blended together with the polyolefin resin and the wood material, or may be blended in the polyolefin resin itself.

[0023] -Polyolefin resin- The polyolefin resin to be blended in the resin composite may be any of the polyolefin resins described above. The preferred embodiments are also the same as those described above.

[0024] -Wood material- Examples of wood materials that can be incorporated into resin composites include wood chips. The size of the wood material is not particularly limited; for example, wood chips with an average thickness of 0.01 to 0.5 mm (preferably 0.1 to 0.3 mm) and an average width and length of 1 to 5 mm (preferably 1 to 3 mm) can be used. Examples of such wood materials include planer chips. The corrugated pipe of the present invention utilizes wood materials, such as planer chips, that have traditionally been discarded as industrial waste, contributing to the effective utilization of resources and promoting initiatives such as carbon recycling, which reuses carbon resources. The size (width, length, and thickness) of the wood material can be the minor axis, major axis, and thickness (triaxial diameters) of a rectangular parallelepiped circumscribing the wood material. The average thickness is calculated by measuring the thickness of 20 randomly selected wood pieces from the wood material and averaging the measured values. Similarly, the average width and average length are the average values ​​of the widths and lengths of the 20 wood pieces. The species of wood material is not particularly limited, but examples include conifers such as cedar, cypress, spruce, fir, and radiata pine, and broad-leaved trees such as birch, apitong, cameller, sengonlaut, and aspen.

[0025] The resin composite can be obtained by melt-kneading the polyolefin resin and the wood material. For example, except for the above-mentioned requirements, it can also be obtained by a method based on the method described in JP 2012-56297 A.

[0026] <Inner layer> In the corrugated pipe of the present invention, the inner layer contains a resin composite containing a polyolefin resin and a wood material. The resin composite is the same as the resin composite described above for the outer layer. When the outer layer contains a resin composite, the resin composite of the inner layer may be the same as or a different type of resin composite from that of the outer layer. From the viewpoint of improving the adhesion between the outer layer and the inner layer, when the outer layer contains a resin composite, it is preferable that the inner layer contains the same resin composite as that of the outer layer. In order to impart self-extinguishing properties, the resin composite contained in the inner layer preferably contains a flame retardant. The flame retardant may be blended together with the polyolefin resin and the wood material, or may be blended in the polyolefin resin itself. In the corrugated tube of the present invention, the inner surface of the inner layer is smooth.

[0027] When the corrugated pipe of the present invention has at least a two-layer structure consisting of a layer containing a polyolefin resin and a layer containing a resin composite, the content ratio of the polyolefin resin constituting the outer layer to the resin composite constituting the inner layer is not particularly limited and can be appropriately adjusted so as to obtain a smooth inner surface. For example, the content ratio of the polyolefin resin constituting the outer layer to the resin composite constituting the inner layer, by mass, of polyolefin resin:resin composite may be 10:90 to 99:1, 15:85 to 90:10, 30:70 to 85:15, or 60:40 to 80:20.

[0028] <Coating layer> The corrugated pipe of the present invention may also have a coating layer further inside (the innermost layer) the inner layer. The coating layer is not particularly limited and may be a layer containing a thermosetting resin or a layer containing a thermoplastic resin. When the coating layer contains a thermoplastic resin, it can be produced by co-extrusion together with the outer and inner layers. The coating layer may also contain, for example, a flame retardant. Examples of such flame retardants include brominated flame retardants. In the present invention, since the inner surface of the inner layer is smooth, the surface of the coating layer provided further inside the inner layer is also smooth. By having the coating layer, friction with cables or the like passed through the corrugated pipe of the present invention can be further reduced.

[0029] [Method of manufacturing the corrugated tube of the present invention] The corrugated tube of the present invention can be manufactured by a method for manufacturing a normal corrugated tube, except that at least the inner layer contains a resin composite. For example, the corrugated tube of the present invention can be manufactured to have the dimensions specified in JIS C8411:2019 "Synthetic resin flexible electrical conduit." For example, the components constituting the outer and inner layers are melt-kneaded in a batch kneader such as a roll, kneader, or Banbury mixer, or a commonly used kneading device such as a twin-screw extruder, to obtain a resin composition. The resulting resin tube is then inserted into a mold and vacuumed to obtain a corrugated tube of the present invention, with the outer surface corrugated. The screw configuration of the extruder is not particularly limited, and a conventional full-flight screw, double-flight screw, tip double-flight screw, Maddock screw, or the like can be used. The conditions for extruding the resin composition are not particularly limited, but from the viewpoint of reducing the load on the extruder (extrusion molding machine), an extrusion temperature (head) of 100 to 230°C is preferred, and 120 to 200°C is more preferred. The conditions for vacuuming are not particularly limited, and for example, a vacuum of 800±50 mbar (hPa) can be used. Other conditions can be appropriately set depending on the purpose. [Example]

[0030] The present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to these.

[0031] The corrugated pipes of Example 1 and Comparative Example 1 were manufactured by the following method. -Materials used- (1) Polyolefin resin High-density polyethylene (2) Wooden materials Average thickness: approx. 0.2 mm, average width: approx. 1 mm, average length: approx. 2 mm (3) Flame retardant MB (masterbatch compound) Brominated flame retardant masterbatch compounds

[0032] Examples 1 to 4 High density polyethylene (pellets) was used as the resin for the outer layer. Furthermore, as a resin composite for the inner layer, high-density polyethylene (80 parts by mass) and wood material (20 parts by mass) were mixed and melt-kneaded at a temperature of 130 to 200°C using a 1-liter kneader. The kneaded material was then formed into a sheet using an open roll, cooled, and then cut and granulated using a pelletizer to form pellets. Moreover, high density polyethylene (pellets) was used as the resin for the coating layer. The above-mentioned resin for the outer layer (60 parts by mass), a mixture of the resin composite for the inner layer (25 parts by mass) and flame retardant MB (6 parts by mass), and the above-mentioned resin for the coating layer (8 parts by mass) were supplied to an extruder set at a temperature of 200 to 230°C, and the three-layer resin pipe formed by simultaneous extrusion was used in a mold for molding flexible protective pipes (corrugated pipes) with nominal diameters of φ16, 22, 28, and 36 according to JIS C8411:2019.A negative pressure of 0.08 MPa was applied to give the outer surface a corrugated shape, and each of the corrugated pipes of Examples 1 to 4 was produced.

[0033] (Comparative Examples 1 to 4) High density polyethylene (pellets) was used as the resin for the outer layer. Moreover, high density polyethylene (pellets) was used as the resin for the coating layer. A mixture of the resin for the outer layer (86 parts by mass) and flame retardant MB (6 parts by mass), and the resin for the coating layer (8 parts by mass) were supplied to an extruder set at a temperature of 190 to 230°C, and the resin pipe (resin pipe having an outer layer and a coating layer) molded into a two-layer structure by simultaneous extrusion was subjected to a negative pressure of 0.08 MPa in a mold for molding flexible protective pipes (corrugated pipes) with nominal diameters of φ16, 22, 28, and 36 according to JIS C8411, to give the outer surface a corrugated shape, thereby producing each of the corrugated pipes of Comparative Examples 1 to 4.

[0034] <Evaluation method and results> (deflection displacement) In a temperature-controlled room, the corrugated tubes of Examples 1 to 4 (hereinafter collectively referred to as "Examples") and Comparative Examples 1 to 4 (hereinafter collectively referred to as "Comparative Examples") were each cut into a 2.5-m length and fixed to a vertically installed panel so that each corrugated tube was horizontal. Each corrugated tube was fixed at three points: the tip and the center of each corrugated tube, using supports. Two communication cables were run through each corrugated tube, and the temperature in the temperature-controlled room was raised from -5°C to 60°C (heating rate: 65°C / hour, heating time: 1 hour). The amount of deflection of the corrugated tube caused by the temperature change was measured. The amount of deflection was defined as the maximum vertical length between each support (two sections) from the horizontal position before the test to the deflected portion.

[0035] For each of the corrugated pipes of the Examples and Comparative Examples molded using the same mold, the ratio of the deflection displacement of the Example to the deflection displacement of the Comparative Example ([Deflection displacement of the Example] / [Deflection displacement of the Comparative Example]) was calculated. As a result, the ratio of the deflection displacement of the Example to the deflection displacement of the Comparative Example was approximately 0.4 to 0.6 in all of the Examples.

[0036] (length change) The corrugated tubes of Example 1 and Comparative Example 1 were each cut into 2.5 m lengths and left to stand in a temperature-controlled room. The temperature in the temperature-controlled room was then raised from -5°C to 60°C (heating rate: 65°C / hour, heating time: 1 hour), and the change in length of each corrugated tube ([length after test] - [length before test]) was measured.

[0037] For each of the length changes measured above, the ratio of the length change of the Example to the length change of the Comparative Example ([length change of the Example] / [length change of the Comparative Example]) was calculated for each of the corrugated pipes of the Example and Comparative Example molded using the same mold. As a result, the ratio of the length changes of the Example was approximately 0.25 to 0.4 in all of the Examples.

[0038] From the above, it was shown that the corrugated tubes of the present invention (Examples 1 to 4) can effectively suppress deflection and elongation due to temperature changes compared to the conventional corrugated tubes (Comparative Examples 1 to 4). [Explanation of symbols]

[0039] 1 Corrugated tube 2 Valley 3 Yamabe 4 Outer layer 5 Inner layer

Claims

1. A wood-blended resin pipe having an outer layer containing a polyolefin resin or a resin composite containing a polyolefin resin and a wood material, and an inner layer containing a resin composite containing a polyolefin resin and a wood material.

2. The wood-blended resin pipe according to claim 1, wherein the mass ratio of the polyolefin resin to the wood material in the resin composite is polyolefin resin:wood material = 20:80 to 99:

1.

3. 3. The wood-blended resin pipe according to claim 1, wherein the inner surface of the inner layer is smooth.

4. The wood-blended resin pipe according to claim 1 or 2, wherein the wood-blended resin pipe contains a flame retardant.

5. The wood-blended resin pipe according to claim 3, wherein the wood-blended resin pipe is a corrugated pipe.

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