JP2004176830A - Flame retardant pipe fittings - Google Patents

Abstract

An object of the present invention is to provide a resin pipe joint which is excellent in flame retardancy without using a flame retardant and is as inexpensive as possible.
In a resin-made flame-retardant pipe joint for connecting and connecting corrugated pipes of the same type, the wall thickness of a wave peak of the pipe joint is greater than the wall thickness of a valley. A flame-retardant pipe joint characterized by the fact that the same type of corrugated pipes are connected to each other and connected with each other, wherein the resin layer of the outer layer of the pipe joint has a wall thickness of a wave crest. Are thicker than the wall thickness of the valley, and the inner layer has a flame-retardant water-absorbing swelling layer which swells when absorbing water.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a pipe joint used for connecting corrugated pipes of the same type, and particularly to a pipe joint excellent in flame retardancy.
[0002]
[Prior art]
Conventionally, when connecting the same type of corrugated pipes to each other, for example, as shown in FIG. 3, the connection has been made by a pipe joint 1 having a shape corresponding to the outer diameter, wave shape, and pitch of the corrugated pipe. Here, the meaning that the corrugated pipes 2 and 3 are of the same type means that the corrugated pipes 2 and 3 have the same size, and means that the corrugated pipes have at least the same outer diameter, wave shape and pitch. The materials 2 and 3 are irrelevant.
Now, the pipe joint 1 and the corrugated pipes 2 and 3 shown in FIG. 3 are both made of a resin such as polyethylene or polypropylene, and the pipe joint 1 is often manufactured by blow molding these resins.
In recent years, these pipe joints 1 and corrugated pipes 2 and 3 are often used as protection pipes for communication cables including power cables and optical fiber cables. It is increasingly required that pipe joints used together with the pipes 2 and 3 have flame retardancy.
[0003]
By the way, the most common method of making a resin-made pipe joint or corrugated pipe flame-retardant is to add a flame retardant to the resin (Patent Document 1).
[0004]
Patent Document 1: JP-A-7-276558
[Problems to be solved by the invention]
However, in the method of adding a flame retardant to a resin, the material cost is increased, and the cost of the pipe joint is inevitably increased.
Further, depending on the flame retardant to be added, when a pipe joint burns due to a fire, a toxic gas such as dioxin is generated. Recently, many companies have been promoting so-called “green procurement” from the viewpoint of environmental protection, and there is an urgent need to develop fittings that solve this problem.
[0006]
As described above, the conventional resin-made pipe joint is often formed by a method generally called blow molding, but when formed by this method, the wall thickness of the pipe joint is shown in FIG. Thus, it becomes uneven depending on the location.
More specifically, when the thickness a of the peak portion, the thickness b of the valley portion, and the thickness of the middle portion between the peak portion and the valley portion are c and d, a <b is inevitable.
Normally, the thickness of the pipe joint 1 is discussed based on the average thickness obtained by (a + b + c + d) / 4. Therefore, such unevenness of the thickness does not cause much problem from the viewpoint of flame retardancy. When the inventors conducted a flame retardancy test in accordance with JIS C 3653, they found that the pipe joint always burned from the peaks and a hole was opened in the pipe joint. Generally speaking, when a hole is formed in a pipe joint, a phenomenon called "chimney effect" by those skilled in the art causes a flow of air in the pipe joint, and the pipe joint burns at once. Therefore, the superiority of the flame retardancy can be easily predicted based on whether or not a hole is formed in the pipe joint in a short time due to the normal test flame.
From such a background, it has been speculated that the thinness of the hills which are initially burnt and have holes may also greatly affect the flame retardancy.
Of course, in such a case, simply increasing the average thickness of the entire pipe joint can improve the flame retardancy, but in that case, more resin material is used, and the cost of the pipe joint is reduced. Will be up.
[0007]
In view of the above problems, an object of the present invention is to provide a resin-made pipe joint which is excellent in flame retardancy without using a flame retardant and is as inexpensive as possible.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present application is directed to a resin-made flame-retardant pipe joint in which corrugated pipes of the same type are connected to each other, and the thickness of a wave crest of the pipe joint is reduced. It is characterized in that it is thicker than the valley wall.
As described above, when the thickness of the wave peak in the pipe joint is made larger than that of the valley, the flame retardancy of the pipe joint can be increased without changing the above-described average thickness and without particularly adding a flame retardant. Can be. Therefore, it is possible to avoid an increase in the cost of the pipe joint due to the addition of the flame retardant and a possibility of generating toxic gas.
[0009]
According to a second aspect of the present invention, there is provided a flame-retardant pipe joint for connecting and connecting corrugated pipes of the same type, wherein the outer layer is made of a resin, and the inner layer has a flame-retardant swelling when absorbing water. Characterized by having a water-absorbing swelling layer.
According to such a pipe joint, the flame retardancy of the pipe joint can be increased without any modification of the outer layer made of resin, that is, without adding a flame retardant. That is, the flame-retardant water-absorbing swelling layer provided inside the pipe joint improves the flame retardancy of the entire pipe joint. Incidentally, it goes without saying that the flame-retardant water-absorbing swollen layer does not contain a flame retardant.
[0010]
Further, the invention according to claim 3 of the present invention relates to a flame-retardant pipe joint for connecting and connecting the same type of corrugated pipes, wherein a resin layer of an outer layer of the pipe joint has a wave valley having a thickness of a valley. Characterized in that it has a flame-retardant water-absorbing swelling layer which swells when absorbing water in its inner layer.
[0011]
According to the pipe joint formed in this manner, since the thickness of the wave peak of the resin pipe constituting the outer layer is larger than the thickness of the valley, it is more difficult to form a hole, and the "chimney effect" acts accordingly. Since it is difficult, the flame resistance of the pipe joint is improved. In addition, since the inner layer has a flame-retardant water-absorbing swelling layer, the flame retardancy is improved from this point as well. In addition, since the inner layer and the outer layer do not contain a flame retardant, the cost can be prevented from increasing, and there is no need to worry about the generation of toxic gas even if the pipe joint burns.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a partial sectional view of an embodiment of the pipe joint of the present invention. The pipe joint 1 is made of polyethylene, and the thickness a of the peak of the wave is larger than the thickness b of the valley. That is, a> b.
In addition, a so-called average thickness e = (a + b + c + d) / averaged by adding the thickness a and the thickness b of the valley to the thickness c and the thickness d of an intermediate portion between the ridge and the valley. The value of 4 is almost unchanged from the conventional one.
Therefore, the material cost of the polyethylene used for the pipe joint 1 is almost the same as the conventional one. The flame retardancy of the pipe joint 1 according to the present invention and the conventional pipe joint in which the relationship between the wall thickness a of the peak portion and the wall thickness b of the valley portion is a <b are compared.
[0013]
(Example)
The outer diameter of the pipe joint is 70 mm, the inner diameter is 60 mm, the thickness of the crest portion made of polyethylene is a = 2.2 mm, the thickness of the valley portion is b = 1.8 mm, the thickness of the middle portion is c = 1.4 mm, and d = 1. 4 mm, average thickness e = 1.7 mm
(Comparative example)
Outer diameter 70 mm, inner diameter 60 mm of pipe joint, thickness a = 1.6 mm of ridge portion made of polyethylene, thickness b = 2.2 mm of valley portion, thickness c = 1.5 mm of middle portion, d = 1. 5 mm, average thickness e = 1.7 mm
[0014]
Five samples of each of the above samples were prepared and subjected to a test in accordance with JIS C 3653 Appendix 1, 5.2 Flame Retardancy Test. The flame contact time is 35 seconds.
As a result, all of the five samples of the example of the present invention passed the test without any problem, but three of the five samples of the comparative example failed.
Thus, it is clear that the example of the present invention has improved flame retardancy compared to the comparative example which is a conventional product.
[0015]
FIG. 2 shows a second embodiment of the present invention. This is provided with a flame-retardant water-absorbent swelling layer 1b, specifically a layer made of a flame-retardant water-absorbent swellable nonwoven fabric, in the inner layer of the pipe joint 1. Reference numeral 1a is a layer made of polyethylene.
In this embodiment, the outer layer made of polyethylene is the same as the conventional one, and the relationship between the thickness a of the hill portion and the thickness b of the valley portion is a <b, but it is in the inner layer. Due to the effect of the layer made of the flame-retardant water-absorbing swelling nonwoven fabric, the flame retardancy is greatly improved. Incidentally, neither the outer layer nor the inner layer of the pipe joint 1 contains any so-called flame retardant.
Specifically, the flame-retardant water-absorbent swelling nonwoven fabric contains sodium polyacrylate as a main component and exhibits flame retardancy due to the action of Na ions in the sodium polyacrylate, and is generally called a flame retardant. It does not include anything to be said.
[0016]
In addition, in addition to the above, the relationship between the thickness a of the peak portion and the thickness b of the valley portion of the polyethylene layer in the outer layer is set to a> b, and the inner layer is formed with a layer made of a flame-retardant water-absorbing swelling nonwoven fabric. The joint also has the flame retardant interaction between the outer layer and the inner layer, and the flame retardancy is further improved.
[0017]
【The invention's effect】
As described above, according to the flame-retardant pipe joint of the first aspect of the present invention, the thickness of the wave peak of the pipe joint is made thicker than that of the valley. Flame retardancy is more improved than that of the part having a smaller thickness. At this time, the average thickness of the corrugated portion is almost the same as that of the conventional product.
[0018]
According to the invention of claim 2 of the present invention, it is possible to enhance the flame retardancy of the pipe joint without any modification to the portion of the pipe joint outer layer made of resin, that is, without adding a flame retardant. Can be. That is, the flame-retardant water-absorbing swelling layer provided inside the pipe joint improves the flame retardancy of the entire pipe joint. Incidentally, it goes without saying that the flame-retardant water-absorbing swollen layer does not contain a flame retardant.
[0019]
Further, according to the pipe joint of the third aspect, since the thickness of the wave peak of the resin layer constituting the outer layer is larger than the thickness of the valley, it is difficult to form a hole, and the "chimney effect" acts accordingly. Since it is difficult, the flame resistance of the pipe joint is improved. In addition, since the inner layer has a flame-retardant water-absorbing swelling layer, the flame retardancy is improved from this point as well. In addition, since the inner layer and the outer layer do not contain a flame retardant, the cost can be prevented from increasing, and there is no need to worry about the generation of toxic gas even if the pipe joint burns.
[Brief description of the drawings]
FIG. 1 is a partial sectional view showing one embodiment of a pipe joint of the present invention.
FIG. 2 is a partial cross-sectional view illustrating a state in which pipes of the same type are connected to each other with a pipe joint according to a second embodiment of the present invention.
FIG. 3 is a partial cross-sectional view showing a state where the same type of corrugated pipes of a conventional pipe joint are connected to each other.
FIG. 4 is a partial sectional view of a conventional pipe joint.
[Explanation of symbols]
1 pipe fitting 2 corrugated pipe 3 corrugated pipe

Claims (3)

A resin-made flame-retardant pipe joint for connecting and connecting pipes of the same type with corrugations, wherein the wall thickness of the wave peak of the pipe joint is larger than the wall thickness of the valley. Flame retardant pipe fittings. In a flame-retardant pipe joint for connecting and connecting the same type of corrugated pipes, the pipe joint has an outer layer made of resin and an inner layer having a flame-retardant water-swelling layer that swells when absorbing water. A flame-retardant pipe fitting characterized by the following. In a flame-retardant pipe joint for connecting and connecting the same type of corrugated pipes, the resin layer of the outer layer of the pipe joint is such that the thickness of the wave peak is greater than the thickness of the valley, and A flame-retardant pipe joint comprising an inner layer having a flame-retardant water-absorbing swelling layer that swells when absorbing water.

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