JP4201638B2 - Corrugated pipe manufacturing method and corrugated pipe manufactured by the manufacturing method - Google Patents

Description

【００４０】
中間層（発泡層）に添加する発泡剤には、クエン酸および重炭酸ナトリウム（合計で４０ｗｔ％程度）を含むポリエチレン系発泡剤を使用した。ポリエチレン系発泡剤の添加率は、中間層（発泡層）の成形材料に対し重量比で３．０ｗｔ％とした。
前述した構成の押出金型および波付け機を用いて、それぞれ同一の製造条件の下、ほぼ同一の外径および内径をもつコルゲート管を製造した。
【００４１】
コルゲート管の評価方法は、平滑性、屈曲性および融着性の各項目について行った。
平滑性の評価は、管内面がほぼ平滑であるものを「◎」、管内面がやや波状であるものを「○」、管内面に皺が発生したもの「△」とした。屈曲性の評価は、折り曲げやすさが極めて良好なもの「◎」、やや良好なものを「○」、良好なものを「△」とした。融着性の評価は、各層が手で剥がれない程度に融着しているものを「◎」、いずれかの層が手で剥がれるものを「○」、成形の段階でいずれかの層が分離するものを「△」とした。評価の結果を表１に示す。
【００４２】
表１に示すように、試験例１〜５によるサンプルは、平滑性、屈曲性または融着性のいずれかの評価で他のサンプルよりも劣るものがあるのに対し、試験例６では、全ての評価項目で優れた結果を示した。このような結果から、本発明によるコルゲート管を製造する場合の成形材料としては、外側層に低密度ポリエチレン、中間層（発泡層）にオレフィン系エラストマー、内側層にオレフィン系エラストマーのを組み合わせると、高品質のコルゲート管が得られることが判る。
【００４３】
次に、中間層（発泡層）の発泡剤添加率を変化させた場合の各種コルゲート管について品質を評価した。
表２に示すように、試験例７〜１１は、外側層に低密度ポリエチレン（ＬＤＰＥ）、中間層（発泡層）にオレフィン系エラストマー、内側層にオレフィン系エラストマーを使用した。
【００４４】
【表２】

【００４５】
中間層（発泡層）に添加する発泡剤には、クエン酸および重炭酸ナトリウム（合計で４０ｗｔ％程度）を含むポリエチレン系発泡剤を使用した。
発泡剤添加率は、中間層（発泡層）の成形材料に対し重量比で１．０〜５．０ｗｔ％まで順に増加するように設定した。
前述した構成の押出金型および波付け機を用いて、それぞれ同一の製造条件の下、同一の外径および内径をもつコルゲート管を製造した。
【００４６】
なお、試験例７〜１１で使用したオレフィン系エラストマーの比重は０．９７であり、ポリエチレン系発泡剤のオレフィン系エラストマーへの添加時の比重変化は、２ｗｔ％添加時では重量比４３％、３ｗｔ％添加時では重量比４８．５％、４ｗｔ％添加時では重量比５４％の軽量化となるものであった。
【００４７】
コルゲート管の評価は、平滑性、屈曲性および融着性について、前述した評価方法と同様な方法で行った。
表２に示すように、発泡剤添加率が２．０ｗｔ％よりも少ないと、管内面に皺が発生しやすくなり、一方、発泡剤添加率が４．０ｗｔ％を超えると、各層の融着性が不十分になる。この結果、発泡剤の添加量２．０〜４．０ｗｔ％程度であるとき、すなわち、発泡剤添加時のオレフィン系エラストマーの比重変化が４５％〜５４％程度（試験例８〜１０）、望ましくは４８〜４９％程度（試験例９）の範囲になるとき、より品質の高いコルゲート管が得られることが判る。
【００４８】
前記実施形態では、三層構造のコルゲート管の製造方法を説明したが、その他の実施形態としては、成形材料の層数や層厚を変更することにより、多彩な構造のコルゲート管を製造することができる。
【００４９】
例えば図８に示す他の実施形態では、内側層を二層構造にしている。コルゲート管３０は、外側層１２、中間層１３および内側層３１、３２が順に積層されている。コルゲート管３０の製造方法としては、押出工程において、外側層１２、中間層１３および内側層３１、３２の成形材料をそれぞれ専用の導入口から押出金型に導入し、原料通路で各成形材料を重ねて押し出す。次いで、前述したような波付け用の金型で管状押出品に波付けを行う。
【００５０】
このような実施形態によれば、内側層３１および３２が二層構造であるため、成形材料の節約を図ることができる。例えば、内側層３２に耐水性、耐蝕性等に優れた成形材料を用い、内側層３１には再生材料を用いると、低コストで高品質のコルゲート管を製造することが可能になる。
また、内側層３１および３２を二層構造にすることで、波付け溝の吸引力が管内面に及びにくくなり、より平滑な内面をもったコルゲート管を製造することができる。
【００５１】
また、図９に示す他の実施形態は、外側層を二層構造としている。コルゲート管４０は、波形の外側層４１および４２の内側に発泡層１３および内側層１４が積層される。外側層４１は、内側層４２よりも層厚が厚い。コルゲート管４０を製造方法としては、例えば、押出工程において、外側層４１、４２、中間層１３および内側層１４の成形材料をそれぞれ専用の導入口から押出金型に導入し、原料通路で各層を積層して押し出す。次いで、前述したような波付け用の金型で管状品押出品に波付けを行う。外側層４１、４２の成形材料については、各成形材料の押出量を調節することにより、それぞれ層厚の異なる外側層４１および４２を形成することができる。
【００５２】
このような実施形態によれば、外側層４１および４２が二層構造になっているため、管壁の耐圧力および偏平化強度を向上させることができる。また、外側層４１に透明な材料を使用し、外側層４２に色付き材料等を用いることで、低コストで美観の優れたコルゲート管を製造することができる。
【００５３】
その他の実施形態としては、例えば、中間層を省略した二層構造のコルゲート管とすることもできる。この場合、内側層を発泡層とし、この内側層の発泡力が波付け溝の吸引力と釣り合うようにする。また、管壁の層数は、前記実施形態に示したものに限られることなく、五層以上の多層構造にしてもよい。
前記実施形態で説明した押出金型および波付け機の構成についても、これらの構成に限定されることなく、本発明を適用することができるものであれば、種々の型式ものを用いることができる。
【００５４】
【発明の効果】
以上説明したように、本発明のコルゲート管の製造方法によれば、次のような優れた効果を奏する。
(a) 屈曲性が良好で、かつ、平滑な内面をもつ多層構造のコルゲート管を簡単に製造することができる。
(b) 複雑な構成の装置を用いることなく、細径のコルゲート管を低コストで製造することができる。
(c) 管壁に発泡層を介在させるため、コルゲート管の断熱化および軽量化を図りやすくなる。
【図面の簡単な説明】
【図１】本発明の実施形態によるコルゲート管を示す部分切欠き側面図である。
【図２】本発明の実施形態によるコルゲート管を示す縦断面図である。
【図３】図２に示すIII−III線横断面である。
【図４】本発明の実施形態による押出金型の構成例を示す断面図である。
【図５】本発明の実施形態による波付け機の構成例を示す全体構成図である。
【図６】本発明の実施形態による波付け機の金型を示す部分拡大断面図である。
【図７】本発明の実施形態によるコルゲート管の成形時の作用を説明するための部分拡大断面図である。
【図８】本発明の他の実施形態によるコルゲート管を示す縦断面図である。
【図９】本発明の他の実施形態によるコルゲート管を示す縦断面図である。
【図１０】従来の実施形態によるコルゲート管を示す縦断面図である。
【図１１】従来の他の実施形態によるコルゲート管を示す縦断面図である。
【符号の説明】
１０ コルゲート管
１０ａ 凸部
１０ｂ 凹部
１１ 管壁
１２ 外側層
１３ 中間層（発泡層）
１４ 内側層
２０ 押出金型
２３ 環状ノズル
２５ 波付け機
２６Ａ、２６Ｂ 金型
２８ 管状押出品
Ｒ 減圧室
Ｓ 空洞
Ｔ 通気孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a corrugated tube and a corrugated tube manufactured by the manufacturing method. The corrugated pipe | tube by this invention is used as flexible hoses, such as household appliances (an air conditioner, a washing machine, etc.), a vending machine, a water purifier, a medical device, for example.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, corrugated pipes having a wave-like continuous pipe wall are known. As shown in FIG. 10, the conventional corrugated tube 1 has a wave-like convex portion 2 a and a concave portion 2 b formed on the tube wall 2. The convex portions 2a and the concave portions 2b are connected in a ring shape in the circumferential direction of the tube wall 2, and are alternately arranged in the length direction.
As a manufacturing method of such a corrugated pipe 1, a corrugated mold is arranged in front of a nozzle of an extrusion mold in advance, and the outer layer 3 and the inner layer 4 are placed between these molds. The molding material is stacked and extruded into a tubular shape. Next, the tube wall 2 is formed into a wave shape by pressing the peripheral surface of the tubular extrudate against the wave groove (corrugation groove) of the mold or by vacuum suction.
[0003]
[Problems to be solved by the invention]
However, in such a conventional corrugated tube manufacturing method, when corrugating the tube wall 2, the outer layer 3 and the inner layer 4 are simultaneously adsorbed in the corrugated groove, so A dent H is easily formed. For this reason, such dents H have caused problems such as dust easily clogging the pipe, and the flow of fluid through the pipe worsening.
[0004]
On the other hand, the manufacturing method of the corrugated pipe which solved such a malfunction is also known. According to this type of manufacturing method, the molding material of the outer layer and the inner layer is extruded from different annular nozzles, and only the molding material of the outer layer is corrugated by vacuum suction into the corrugated groove. Thereafter, before the molding material hardens, the outer layer and the inner layer are fused in the mold (see Patent Document 1).
[0005]
In the corrugated tube 5 manufactured by such a manufacturing method, as shown in FIG. 11, a corrugated tube wall is formed only on the outer layer 6, and is not formed on the inner layer 7. Since the inner surface of the inner layer 7 is formed smoothly, the fluid resistance in the pipe is reduced, and the fluid flows smoothly.
[0006]
[Patent Document 1]
Japanese Patent Publication No. 51-20548
[Patent Document 2]
JP 10-95051 A
[Patent Document 3]
Japanese National Patent Publication No. 11-503217
[Patent Document 4]
JP-A-8-170761
[0007]
[Problems to be solved by the invention]
However, the manufacturing method of such a corrugated tube also has the following problems in its manufacturing method. That is, since an annular nozzle for extruding the outer layer and the inner layer is separately required, the configuration of the tip die portion of the extrusion die tends to be complicated. In particular, when trying to manufacture a corrugated pipe having a small diameter, it becomes difficult to process an annular nozzle or the like, and the manufacturing cost increases.
[0008]
Further, since it is difficult to reduce the size of the annular nozzle, as shown in FIG. 11, the thickness of the inner layer 7 tends to be larger than that of the outer layer 6, and the corrugated tube 5 is thick and has poor flexibility. Cheap.
For these reasons, the conventional corrugated tube manufacturing method has a problem that it is difficult to provide a small-diameter flexible hose whose demand has been increasing in recent years.
[0009]
The present invention has been made in view of such a current situation. Even if the diameter of the pipe is reduced, the inner surface of the pipe is smoothly finished, and a corrugated pipe capable of producing a pipe wall having a multilayer structure with good flexibility is provided. It aims at providing the manufacturing method of.
[0010]
[Means for Solving the Problems]
[First invention]
The method for manufacturing a corrugated tube of the present invention (first invention) for solving the above-mentioned problems is as follows.
A process of stacking molding materials in multiple layers and extruding from an annular nozzle;
Sending the multi-layered tubular extrudate extruded from the annular nozzle to a corrugating channel for corrugation;
A method of manufacturing a corrugated pipe, comprising: suctioning the periphery of the tubular extrudate with a corrugated groove of the corrugated mold and corrugating the pipe wall of the tubular extrudate;
Any layer inside the outer layer of the tubular extrudate is a foamed layer, and the foaming force of the foamed layer is controlled so as to cancel out the suction force of the corrugated groove.
[0011]
According to the present invention (first invention), when the tubular extrudate is sucked into the corrugated groove, the outer layer of the tubular extrudate is formed into a wave shape. At this time, foaming gas is generated inside the foaming layer, and the foaming force (positive pressure) by the foaming gas cancels out the suction force (negative pressure) of the corrugated groove, so the foamed layer is sucked into the corrugated groove. Avoided. As a result, the suction force from the corrugated groove hardly acts on the layer inside the foam layer, and the inner surface of the corrugated tube becomes smooth.
[0012]
In the present invention (first invention), the foam layer can be formed by foaming a molding material by a chemical or physical method. As a chemical method, for example, a foaming layer can be obtained by mixing an appropriate amount of a foaming agent into a molding material, and as a physical method, a gas such as carbon dioxide gas is mixed into the molding material at an appropriate ratio. By doing so, a foamed layer can be obtained.
Preferably by chemical methods. This is because it is easy to obtain a uniform foamed state, and handling of the foaming agent is easy and it is easy to ensure safety.
[0013]
The method for controlling the foaming force of the foamed layer is preferably performed by adjusting the amount of foaming agent added to the molding material. Specifically, taking into account the molding temperature, extrusion speed, suction pressure of the corrugated groove, etc., the suction force acting on the foam layer from the corrugated groove and the foam force generated in the foam layer during co-extrusion of the molding material Adjust the expansion ratio so that the balance is balanced. It is advisable to conduct an appropriate test or the like according to the conditions of use of the extruder or corrugating machine, and to set the optimum amount of foaming agent.
[0014]
As the molding material, a thermoplastic resin generally used for producing a flexible hose can be used. For example, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, nylon (polyamide), polyester, polycarbonate, Examples include polyacetal and cellulose acetate.
It should be noted that the molding materials for each layer may be all different types, or may be the same type of molding material.
[0015]
In the present invention (the first invention), “the extent to which the foaming force of the foam layer cancels the suction force of the corrugated groove” means that foaming does not cause wrinkles on the inner surface of the corrugated tube by the suction force of the corrugated groove. It means that the foaming power of the layer is increased. When the suction force of the corrugated groove and the foaming force of the foamed layer are almost evenly balanced, the inner surface of the corrugated pipe becomes a smooth surface without irregularities. When the foaming force of the foamed layer is too small to sufficiently cancel out the suction force of the corrugated groove, a bowl-shaped recess H is formed on the inner surface of the corrugated tube as shown in FIG. The range of foaming force control according to the present invention (first invention) includes foaming of the foamed layer to such an extent that the inner surface of the corrugated tube becomes a uniform smooth surface, and such ridge-shaped dents are eliminated. Includes those with controlled force.
[0016]
Note that Patent Documents 2 and 4 are cited as prior arts in which a foam layer is used in a corrugated pipe having a multilayer structure. The inventions described in these documents do not corrugate by sucking the outer layer of the tubular extrudate, but in order to increase the accuracy of the outer diameter of the corrugated tube, the outer layer is pushed outward by foaming force to corrugate. It is a thing to do. In such a manufacturing method, when the foaming force of the foamed layer is controlled so that the inner surface of the inner layer is smooth, the accuracy of the outer diameter is deteriorated, and it is difficult to manufacture a high-quality corrugated pipe.
On the other hand, in the present invention (first invention), the outer layer is corrugated by the suction force of the corrugated groove, and the inner layer is smoothed by the foaming force of the foam layer. In other words, by controlling the foaming force of the foamed layer to such an extent that the suction force of the corrugated groove is offset, it is possible to achieve highly accurate corrugation of the outer layer and smoothing of the inner layer at the same time. It is possible to manufacture a high quality corrugated tube with an inner surface.
[0017]
[Second invention]
The corrugated tube manufacturing method of the present invention (second invention) is the same as the corrugated tube manufacturing method of the present invention (first invention), in which the molding material is shared in a multilayer state in the corrugated passage of the corrugated mold. It is characterized by being extruded.
[0018]
In general, in a manufacturing method for smoothing the inner surface of a multilayer corrugated tube, the outer layer molding material is first extruded, the corrugated groove is corrugated, and immediately thereafter, the inner layer molding material is extruded, and the outer layer is extruded. Fused to the inner surface. That is, the molding material of each layer is extruded into the corrugated passage with a time difference by using different tubular nozzles (caps). Further, in this type of manufacturing method, in order to securely bond the outer layer and the inner layer, the inner surface of the inner layer is pressure-formed outwardly by a mandrel extending in the tube axis direction (patent) References 1, 3 and 4).
[0019]
According to the present invention (second invention), since the molding material in a multilayer state is simultaneously extruded into the corrugated passage, the molding material of each layer can be extruded from a single tubular nozzle without considering the time difference. . As a result, the configuration of the tip cap portion is simplified and it is easy to reduce the size. Further, the co-extrusion of the molding material improves the adhesion between the layers, so that it is not necessary to perform pressure molding of the corrugated tube with a mandrel. Furthermore, by simultaneously extruding a multi-layer molding material containing a foam layer into the corrugated passage, the outer layer is adsorbed into the corrugated groove and the inner layer is repelled by the foaming force at almost the same time, and the suction force It becomes easy to control the foaming force with respect to.
[0020]
[Third invention]
The corrugated pipe of the present invention (third invention) is manufactured by the method for manufacturing a corrugated pipe according to the first invention.
According to the corrugated tube of the present invention (third invention), as described above, the inner surface thereof is formed into a smooth surface. This makes it easier for the fluid to flow smoothly through the tube and makes it difficult for dust and the like to adhere to the inner wall of the tube.
Further, in the corrugated pipe according to the present invention (third invention), a cavity due to the foaming gas is easily formed around the foam layer (particularly the outer portion of the foam layer). Such a cavity can also improve the heat insulation and flexibility of the tube wall.
[0021]
[Fourth Invention]
The corrugated tube of the present invention (fourth invention) is characterized in that the foamed layer is a thermoplastic elastomer.
In general, as a molding material for a flexible hose, low density polyethylene excellent in water resistance, corrosion resistance and the like is often used. When a corrugated tube is manufactured by the manufacturing method of the present invention (first invention), low density polyethylene may be used as a molding material for each layer, but if low density polyethylene is used for a foam layer, the tube wall becomes hard. , Flexibility tends to be insufficient.
According to the corrugated pipe of the present invention (fourth invention), since the foam layer is formed of a thermoplastic elastomer, the flexibility is improved by the elastic force of the foam layer. In addition, the foaming force can be easily controlled due to the flexible nature of the elastomer.
[0022]
As the thermoplastic elastomer, olefin elastomer, styrene elastomer, polyester elastomer, polyurethane elastomer, polyamide elastomer, and the like can be used.
Examples of the olefin elastomer include those obtained by copolymerization of propylene and ethylene, those obtained by copolymerization of propylene and butene-1, those obtained by copolymerization of ethylene and butene-1, propylene, ethylene and butene-1. Examples of the copolymer include propylene, ethylene copolymerized with hexadiene, norbornene, cyclopentadiene, and other olefins.
Examples of the styrene elastomer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, and styrene-butadiene random copolymer.
A blend of these different types of thermoplastic elastomers may be used.
[0023]
[Fifth Invention]
The corrugated pipe of the present invention (the fifth invention) is characterized in that the foam layer is provided in an intermediate layer between the outer layer and the inner layer of the tubular extrudate.
Normally, fine irregularities due to bubbles are likely to occur on the surface of the foam layer, so that if the foam layer is exposed on the inner surface of the corrugated tube, the fluid resistance and other performance of the tube inner surface tends to deteriorate, and the fluid penetrates into the bubbles. There is a risk.
According to the present invention (fifth invention), since the foam layer is provided between the outer layer and the inner layer, the surface of the foam layer is not exposed to the inner surface of the corrugated tube. Thereby, the inner surface of the corrugated pipe can be made smoother, and a corrugated pipe excellent in performance such as fluid resistance can be manufactured.
[0024]
[Sixth Invention]
In the corrugated tube of the present invention (sixth invention), the molding material of the outer layer, the intermediate layer and the inner layer is an outer layer: low-density polyethylene, an intermediate layer: an olefin-based elastomer, and an inner layer: an olefin-based elastomer, A foaming agent is added to the olefin-based elastomer of the intermediate layer.
[0025]
According to the corrugated pipe of the present invention (sixth invention), since the low density polyethylene is used for the outer layer, the water resistance, corrosion resistance, weather resistance and the like of the pipe surface are improved.
Moreover, the flexibility of a corrugated pipe | tube becomes favorable by using an olefin type elastomer for an intermediate | middle layer and an inner layer.
Furthermore, since the outer layer, the intermediate layer, and the inner layer are olefin-based molding materials, the compatibility of the molding materials is improved, and a strong corrugated tube that is difficult to separate for each layer can be manufactured.
[0026]
As the foaming agent added to the olefin elastomer of the intermediate layer, it is desirable to use an olefin foaming agent containing citric acid and sodium bicarbonate. The addition rate of the olefinic foaming agent may be adjusted so that, for example, the change in specific gravity of the olefinic elastomer is about 45% to 54%, preferably about 48% to 49% by weight, at atmospheric pressure. . In addition, the range of the weight ratio by the specific gravity change of this olefin elastomer can be applied also when foaming an intermediate | middle layer by physical gas foaming, without using a foaming agent.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
An example of a corrugated tube according to an embodiment of the present invention is shown in FIG.
The corrugated tube 10 has a tube wall 11 having a three-layer structure. On the outer periphery of the tube wall 11, wavy convex portions 10 a and concave portions 10 b are alternately formed. The tube wall 11 is freely deformed by the protrusions 10a and the protrusions 10a extending and contracting in the length direction. That is, the wave-like convex part 10a and the convex part 10a play the role which makes the flexibility of the corrugated pipe | tube 10 favorable and raises flattening intensity | strength.
[0028]
As shown in FIGS. 2 and 3, the tube wall 11 has an outer layer 12, an intermediate layer 13, and an inner layer 14 laminated in order. Of these layers, the intermediate layer 13 is a foamed layer.
[0029]
A cavity S is formed between the outer layer 12 and the intermediate layer 13. A portion of the outer layer 12 that forms the concave portion 10 b is in contact with the intermediate layer 13, and a portion that forms the convex portion 10 a is at a position away from the intermediate layer 13. The wall surface 13a of the intermediate layer 13 exposed in the cavity S is slightly expanded toward the convex portion 10a.
Inside the intermediate layer 13, an inner layer 14 extends in the length direction with a constant layer thickness. The inner layer 14 extends in a cylindrical shape in the length direction of the corrugated tube 10, and the inner surface thereof is a substantially uniform smooth surface.
[0030]
Next, the manufacturing method of the corrugated pipe | tube 10 is demonstrated.
[Preparation of molding material]
As the molding material of the corrugated tube 10, for example, low density polyethylene can be used for the outer layer 12, and an olefin-based elastomer can be used for the intermediate layer 13 and the inner layer 14. An appropriate amount of a foaming agent is added to the molding material of the intermediate layer 13 in advance so that the foaming force of the intermediate layer 13 and the suction force acting on the outer layer 12 from the corrugated groove are balanced.
[0031]
[Extrusion process]
The extrusion step of the molding material can be performed by an extrusion die for producing a multilayer tube that is generally used conventionally. An example of the configuration of the extrusion mold is shown in FIG.
As shown in FIG. 4, the extrusion mold 20 includes a transfer unit 21 and a nozzle unit 22. The transfer unit 21 is provided with an inlet for feeding the molding material. The molding material thrown into the introduction port of the transfer part 21 is sent to the nozzle part 22 side while maintaining a predetermined temperature. The nozzle portion 22 is provided with an annular nozzle 23 for extruding a molding material into a tubular shape.
[0032]
The transfer section 21 is provided with passages r1, r2, and r3 for supplying the molding material. Molding materials are fed into the passages r1, r2, and r3 from different inlets. The passages r1, r2, and r3 merge at a position advanced by a predetermined distance to form a single passage R1, and continue to the passage R2 of the annular nozzle 23.
When the molding materials of the outer layer 12, the intermediate layer 13, and the inner layer 14 are introduced into the inlets of the passages r1, r2, and r3, the molding materials pass through the passages r1, r2, and r3, and overlap each other in the passage R1. Become a structure. Then, it passes through the passage R2 while maintaining the multilayer structure and is pushed out from the annular nozzle 23.
[0033]
[Wavy process]
In the corrugation process, the tubular extrudate extruded from the extrusion mold is vacuum-formed with a corrugation mold while being conveyed at a constant speed. For example, a caterpillar type corrugating machine as shown in FIGS. 5 and 6 can be used.
[0034]
As shown in FIG. 5, the corrugating machine 25 is configured such that a pair of corrugating dies 26 </ b> A and 26 </ b> B face each other on the extension of the annular nozzle 23 and can move. Corrugated grooves (cavities) are formed on the surfaces of the molds 26A and 26B facing each other. As shown by the arrows in FIG. 5, the molds 26 </ b> A and 26 </ b> B are moved by a predetermined distance, then once separated, moved in the reverse direction, and returned to the annular nozzle 23 side. That is, the operation of corrugating while conveying the tubular extrudate is repeated.
[0035]
FIG. 6 shows an enlarged view of the molds 26A and 26B. The molds 26 </ b> A and 26 </ b> B are provided with a vent hole T in each groove of the corrugated groove. The vent hole T extends through the molds 26A and 26B. One end of the vent hole T is opened inside the molds 26A and 26B, and the other end of the vent hole T is opened outside.
A decompression chamber R is provided around the molds 26A and 26B (see FIG. 5). By reducing the pressure in the decompression chamber R, a suction force acts on the mold via the vent hole T.
When the tubular extrudate 28 is introduced between the molds 26A and 26B to lower the pressure in the decompression chamber R, the outer peripheral surface of the tubular extrudate 28 is sucked into the corrugated groove and formed into a wave shape. By sequentially moving the dies 26A and 26B along the conveying direction of the tubular extrudate 28, a continuous wave shape is formed on the tube surface.
[0036]
[Action]
As shown in FIG. 7, the molding material is simultaneously extruded from the annular nozzle 23 to the corrugation passage between the molds 26A and 26B in a multilayer state. At this time, when the periphery of the tubular extrudate is sucked by the molds 26A and 26B, only the outer layer 12 is adsorbed to the corrugated groove, and the intermediate layer 13 and the inner layer 14 are hardly adsorbed and keep the original laminated state.
This is due to the following actions. That is, when the corrugated groove is depressurized through the vent hole T, the outer layer 12 of the tubular product is sucked into the corrugated groove and is brought into close contact with the wavy groove surface by the suction force. At this time, the intermediate layer 13 foams with a rapid pressure drop, and releases a part of the foamed gas toward the outer layer 12. The foaming force of the foaming gas exhibits an effect of canceling out the suction force of the corrugated groove, and the intermediate layer 13 is pulled away from the outer layer 12.
Due to the action of the foaming gas, the outer layer 12 and the intermediate layer 13 are separated from each other in the corrugated groove, and a cavity S is generated between them. In addition, a bulge that slightly protrudes toward the cavity S is formed on the outer surface of the intermediate layer 13. And since the attraction | suction force from a corrugation groove hardly acts on the inner surface of the inner layer 14, it becomes a smooth surface.
[0037]
Thus, according to the manufacturing method of the corrugated tube according to the present embodiment, a corrugated tube having a multilayer structure having a smooth inner surface can be easily manufactured.
Further, since the molding material having a multilayer structure is extruded from a single annular nozzle, the thickness of the tube wall can be easily suppressed, and the bendability of the corrugated tube can be improved.
Furthermore, since the structure of the nozzle part (die part) of the extrusion mold is simplified and it is not necessary to provide an auxiliary member such as a mandrel, a multilayer structure having a smooth inner surface even when a small corrugated pipe is manufactured. The corrugated tube can be manufactured with high accuracy. According to the prototypes of the inventors, the inner surface of the corrugated tube having an inner diameter of about 8 mm to 30 mm could be finished to a substantially uniform inner surface.
[0038]
Next, the corrugated tube evaluation test will be described.
The quality of the corrugated tube was evaluated by combining various molding materials with the outer layer, the intermediate layer (foamed layer) and the inner layer.
As shown in Table 1, in Test Examples 1 to 6, low density polyethylene (LDPE) was used for the outer layer, and low density polyethylene (LDPE) or an olefin-based elastomer was used for the intermediate layer (foamed layer). For the inner layer, any one of low density polyethylene (LDPE), very low density polyethylene (LLDPE), high density polyethylene (HDPE), polypropylene (PP), and olefin elastomer was selectively used.
[0039]
[Table 1]

[0040]
The foaming agent added to the intermediate layer (foaming layer) was a polyethylene foaming agent containing citric acid and sodium bicarbonate (about 40 wt% in total). The addition rate of the polyethylene-based foaming agent was set to 3.0 wt% with respect to the molding material of the intermediate layer (foamed layer).
A corrugated tube having substantially the same outer diameter and inner diameter was manufactured under the same manufacturing conditions using the extrusion mold and corrugating machine having the above-described configuration.
[0041]
The corrugated tube was evaluated for each of the items of smoothness, flexibility and fusion.
In the evaluation of smoothness, “◎” indicates that the inner surface of the tube is substantially smooth, “◯” indicates that the inner surface of the tube is slightly wavy, and “Δ” indicates that wrinkles are generated on the inner surface of the tube. In the evaluation of the flexibility, “」 ”indicates that the bendability is extremely good,“ ◯ ”indicates that it is slightly good, and“ △ ”indicates that it is good. For the evaluation of fusing properties, “◎” indicates that each layer is fused to the extent that it cannot be peeled by hand, “○” indicates that any layer is peeled by hand, and any layer is separated at the molding stage. The thing to do was set as “△”. The evaluation results are shown in Table 1.
[0042]
As shown in Table 1, the samples according to Test Examples 1 to 5 are inferior to other samples in any of the evaluations of smoothness, flexibility or fusion, whereas in Test Example 6, all Excellent results were shown in the evaluation items. From such a result, as a molding material in the case of producing a corrugated tube according to the present invention, when combining an outer layer with a low density polyethylene, an intermediate layer (foamed layer) with an olefin elastomer, and an inner layer with an olefin elastomer It can be seen that a high quality corrugated tube is obtained.
[0043]
Next, the quality was evaluated about various corrugated pipe | tubes at the time of changing the foaming agent addition rate of an intermediate | middle layer (foaming layer).
As shown in Table 2, in Test Examples 7 to 11, low density polyethylene (LDPE) was used for the outer layer, olefin elastomer was used for the intermediate layer (foamed layer), and olefin elastomer was used for the inner layer.
[0044]
[Table 2]

[0045]
The foaming agent added to the intermediate layer (foaming layer) was a polyethylene foaming agent containing citric acid and sodium bicarbonate (about 40 wt% in total).
The foaming agent addition rate was set so as to increase in order from 1.0 to 5.0 wt% by weight with respect to the molding material of the intermediate layer (foamed layer).
Corrugated tubes having the same outer diameter and inner diameter were manufactured under the same manufacturing conditions using the extrusion mold and corrugating machine having the above-described configuration.
[0046]
The specific gravity of the olefin elastomer used in Test Examples 7 to 11 is 0.97, and the specific gravity change when the polyethylene foaming agent is added to the olefin elastomer is 43% by weight, 3 wt% when 2 wt% is added. When added to 4% by weight, the weight was reduced to 48.5% and when added at 4 wt%, the weight was reduced to 54%.
[0047]
The corrugated tube was evaluated in the same manner as the evaluation method described above with respect to smoothness, flexibility and fusing property.
As shown in Table 2, when the foaming agent addition rate is less than 2.0 wt%, wrinkles are likely to occur on the inner surface of the tube, whereas when the foaming agent addition rate exceeds 4.0 wt%, the layers are fused. Sexuality becomes insufficient. As a result, when the addition amount of the foaming agent is about 2.0 to 4.0 wt%, that is, the specific gravity change of the olefin elastomer at the time of adding the foaming agent is about 45% to 54% (Test Examples 8 to 10), desirably It can be seen that a higher quality corrugated tube can be obtained when it is in the range of about 48 to 49% (Test Example 9).
[0048]
In the above embodiment, the method of manufacturing the corrugated pipe having the three-layer structure has been described. However, as another embodiment, the corrugated pipe having various structures can be manufactured by changing the number of layers and the layer thickness of the molding material. Can do.
[0049]
For example, in another embodiment shown in FIG. 8, the inner layer has a two-layer structure. In the corrugated tube 30, the outer layer 12, the intermediate layer 13, and the inner layers 31 and 32 are laminated in order. As a manufacturing method of the corrugated tube 30, in the extrusion process, the molding materials of the outer layer 12, the intermediate layer 13, and the inner layers 31, 32 are introduced into the extrusion mold from the dedicated inlets, and each molding material is introduced into the raw material passage. Extrude repeatedly. Next, the tubular extrudate is corrugated using the corrugating mold as described above.
[0050]
According to such an embodiment, since the inner layers 31 and 32 have a two-layer structure, it is possible to save the molding material. For example, when a molding material having excellent water resistance and corrosion resistance is used for the inner layer 32 and a recycled material is used for the inner layer 31, a high-quality corrugated tube can be manufactured at a low cost.
Further, by making the inner layers 31 and 32 have a two-layer structure, the corrugated tube having a smoother inner surface can be manufactured because the suction force of the corrugated groove hardly reaches the inner surface of the tube.
[0051]
In another embodiment shown in FIG. 9, the outer layer has a two-layer structure. In the corrugated tube 40, the foam layer 13 and the inner layer 14 are laminated inside the corrugated outer layers 41 and 42. The outer layer 41 is thicker than the inner layer 42. As a manufacturing method of the corrugated pipe 40, for example, in the extrusion process, the molding materials of the outer layers 41 and 42, the intermediate layer 13 and the inner layer 14 are respectively introduced into the extrusion mold from the dedicated inlets, and each layer is put in the raw material passage. Stack and extrude. Next, the tubular product extrudate is corrugated with the corrugating mold as described above. Regarding the molding materials of the outer layers 41 and 42, the outer layers 41 and 42 having different layer thicknesses can be formed by adjusting the extrusion amount of each molding material.
[0052]
According to such an embodiment, since the outer layers 41 and 42 have a two-layer structure, the pressure resistance and flattening strength of the tube wall can be improved. Further, by using a transparent material for the outer layer 41 and using a colored material or the like for the outer layer 42, it is possible to manufacture a corrugated tube having excellent aesthetics at low cost.
[0053]
As other embodiment, it can also be set as the corrugated pipe of the two-layer structure which abbreviate | omitted the intermediate | middle layer, for example. In this case, the inner layer is a foam layer, and the foaming force of the inner layer is balanced with the suction force of the corrugated groove. The number of tube wall layers is not limited to that shown in the above embodiment, but may be a multilayer structure of five or more layers.
The configurations of the extrusion mold and the corrugating machine described in the embodiment are not limited to these configurations, and various types can be used as long as the present invention can be applied. .
[0054]
【The invention's effect】
As described above, according to the corrugated tube manufacturing method of the present invention, the following excellent effects can be obtained.
(a) A corrugated pipe having a multilayer structure having good flexibility and a smooth inner surface can be easily produced.
(b) A thin corrugated tube can be manufactured at a low cost without using an apparatus having a complicated configuration.
(c) Since the foam layer is interposed on the pipe wall, the corrugated pipe can be easily insulated and lightened.
[Brief description of the drawings]
FIG. 1 is a partially cutaway side view showing a corrugated tube according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing a corrugated tube according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view taken along line III-III shown in FIG.
FIG. 4 is a cross-sectional view showing a configuration example of an extrusion mold according to an embodiment of the present invention.
FIG. 5 is an overall configuration diagram showing a configuration example of a corrugating machine according to an embodiment of the present invention.
FIG. 6 is a partially enlarged cross-sectional view showing a mold of a corrugating machine according to an embodiment of the present invention.
FIG. 7 is a partially enlarged cross-sectional view for explaining an operation at the time of forming a corrugated pipe according to an embodiment of the present invention.
FIG. 8 is a longitudinal sectional view showing a corrugated tube according to another embodiment of the present invention.
FIG. 9 is a longitudinal sectional view showing a corrugated tube according to another embodiment of the present invention.
FIG. 10 is a longitudinal sectional view showing a corrugated tube according to a conventional embodiment.
FIG. 11 is a longitudinal sectional view showing a corrugated tube according to another conventional embodiment.
[Explanation of symbols]
10 Corrugated tube
10a Convex part
10b recess
11 pipe wall
12 Outer layer
13 Intermediate layer (foamed layer)
14 Inner layer
20 Extrusion mold
23 Annular nozzle
25 Corrugating machine
26A, 26B Mold
28 Tubular extrudate
R decompression chamber
S cavity
T Vent

Claims (1)

A process of stacking molding materials in multiple layers and extruding from an annular nozzle;
Sending the multi-layered tubular extrudate extruded from the annular nozzle to a corrugating channel for corrugation;
A method of manufacturing a corrugated pipe, comprising: suctioning the periphery of the tubular extrudate with a corrugated groove of the corrugated mold and corrugating the pipe wall of the tubular extrudate;
The corrugated tube is obtained by performing the molding material preparation step and the molding material extrusion step.
The extrusion molding process of the molding material,
A. A step of feeding the molding material of the outer layer, the intermediate layer and the inner layer of the corrugated pipe into an extrusion mold from a predetermined inlet;
B. A step of simultaneously extruding the outer layer, the intermediate layer and the inner layer in a multilayer state from the annular nozzle of the extrusion mold, and foaming the intermediate layer;
C. A step of separating only the outer layer from the intermediate layer and adsorbing it to the corrugation groove at the time of extrusion in the step B, and forming a void by the foaming gas of the intermediate layer between the outer layer and the intermediate layer; Including
In the step of preparing the molding material, wrinkles due to the suction force of the corrugated mold are formed on the inner surface of the corrugated pipe obtained by the steps A to C by adjusting the amount of the foaming agent added to the molding material of the intermediate layer. A method of manufacturing a corrugated pipe, comprising the step of controlling the foaming force of the intermediate layer to such an extent that it does not occur.

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