JPH11286557A - Conduit having wear resistance and corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conduit having wear resistance and corrosion resistance, flexibility and high wear resistance, neither deforming a pipe wall nor causing a crack on the pipe wall for a long period of time even in the case of transportation of a fluid at a high speed under high pressure. SOLUTION: This conduit having wear resistance and corrosion resistance comprises a polyethylene having 60-80% crystallinity and 2.5×10<5> to 2.5×10<7> weight-average molecular weight. To be concrete, a high-density polyethylene(HDPE) or a cross-linked high-density polyethylene(XL-HDPE) produced by subjecting the high-density polyethylene(HDPE) to a cross-linking reaction is used as the polyethylene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant and corrosion-resistant conduit suitable for transporting sewage, sludge, slurry, etc., as a conduit for sewage and slurry.

[0002]

2. Description of the Related Art Conventionally, steel pipes and sewage pipes for transporting sewage, sludge, slurry, etc.
Metal tubes such as cast iron tubes have been used. However, since the metal tube does not have flexibility, when an earthquake or the like occurs, the metal tube is directly subjected to a load and is easily cracked. Further, since sewage, sludge, slurry and the like contain solid particles such as stone and sand, the inner wall surface of the metal pipe is rubbed by these and easily worn. further,
The inner and outer wall surfaces of the metal pipe were easily corroded by rainwater, chemical substances, and the like that penetrate into the ground, and chemical substances contained in sewage, sludge, slurry, and the like.

Therefore, recently, polyethylene pipes, especially high-density polyethylene (HDPE) pipes have come to be used as sewage pipes and slurry transport pipes that can solve such problems. Since the high-density polyethylene (HDPE) conduit has flexibility, it is slightly deformed and absorbs the load even in the event of an earthquake or the like. In addition, since the abrasion resistance and the corrosion resistance are high, even when sewage, sludge, slurry or the like is caused to flow, the conduit wall surface is hardly worn or corroded.

[0004]

However, conventional high-density polyethylene (HDPE) conduits are not suitable for long term use when laid on steep slopes or when transporting fluids under high pressure. In some cases, problems occurred in the properties, environmental stress cracking resistance, and the like.

The present invention has been made in order to solve such a problem, and an object of the present invention is to have flexibility, high abrasion resistance and corrosion resistance, and
An object of the present invention is to provide an abrasion-resistant and corrosion-resistant conduit that does not deform the pipe wall and does not crack the pipe wall for a long time even when the fluid is transported under high speed and high pressure.

[0006]

In order to achieve the above object, the present inventors have made various kinds of polyethylene pipes on a trial basis, and have examined their wear resistance, corrosion resistance, creep resistance, and environmental stress crack resistance. We have been conducting intensive studies on the suitability of polyethylene pipes as wear-resistant and corrosion-resistant conduits. As a result, they have found that the crystallinity and weight average molecular weight of polyethylene greatly affect the above properties, and have completed the present invention.

That is, the wear-resistant and corrosion-resistant conduit of the present invention has a crystallinity of 60 to 80% and a weight average molecular weight of 2.5 × 1.
It consists of polyethylene of 0 ^{5 to} 2.5 × 10 ⁷ .

As the polyethylene, first, high-density polyethylene (HDPE) produced by a low-pressure method is exemplified.

[0009] High-density polyethylene (HDPE) is generally produced by a so-called Ziegler process in which alkyl aluminum or alkyl aluminum chloride and titanium tetrachloride are used as catalysts and ion-polymerizing ethylene as a raw material under predetermined conditions. As shown in FIG. 1 (A), the high-density polyethylene (HDPE) is such that the linear part of the polyethylene is crystalline, the side chain part is amorphous, and the tie molecules existing in the amorphous part Are considered to connect the crystalline parts.

In the present invention, as shown in FIG. 1 (B), the number of tie molecules is determined by using a conventional high-density polyethylene (HDP).
E) It is a high-density polyethylene (HDPE) having a degree of crystallinity of 60 to 80% and a weight average molecular weight of 2.5 × 10 ^{5 to} 2.5 × 10 ⁷ , as well as higher.

Second, as the polyethylene, a cross-linked high-density polyethylene (XL-HDP) produced by subjecting a high-density polyethylene (HDPE) to a cross-linking reaction is used.
E).

Crosslinked high density polyethylene (XL-HDP)
E) is generally produced by adding a peroxide to high-density polyethylene (HDPE) or irradiating an electron beam to covalently crosslink polyethylene molecules.

In the present invention, a high-density polyethylene (HDPE) having a crystallinity of 60 to 80% and a weight-average molecular weight of 1.5 × 10 ^{5 to} 3.0 × 10 ⁵ is graft-polymerized with a silanol group, and is subjected to a crosslinking reaction. By doing so, a crystallinity of 60
８０80%, weight average molecular weight 2.5 × 10 ⁵ ２．５2.5 × 1
And 0 ⁷ of crosslinked high density polyethylene (XL-HDPE).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wear-resistant and corrosion-resistant conduit made of polyethylene according to the present invention will be described below in detail.

[0015]

Example 1 Ion polymerization of ethylene as a raw material was conducted using alkylaluminum and titanium tetrachloride as catalysts at a temperature of 80 to 100 ° C. and a pressure of 10 to 20 atm while controlling the weight average molecular weight. Increased the number of tie molecules to give a crystallinity of 64% and a weight average molecular weight of 2.8 × 1
0 ⁵ was produced high density polyethylene (HDPE) particles. Then, the high-density polyethylene (HDPE) particles are supplied to an extruder, melted and kneaded in the extruder,
By extruding from a circular die, the crystallinity of the invention of 64
Abrasion-resistant and corrosion-resistant conduits of high-density polyethylene (HDPE) having a weight-average molecular weight of 2.8 × 10 ⁵ were prepared.

Example 2 Crystallinity 60-80%, weight average molecular weight 1.5 × 10 ⁵
High density polyethylene (HDPE) particles obtained by graft polymerization of silanol groups to high density polyethylene (HDPE) of up to 3.0 × 10 ⁵ are supplied to an extruder together with a catalyst, and are melted and kneaded in the extruder to form a circle. By extruding from a die, a tubular high-density polyethylene (HDP
E) A molded article was manufactured. Then, by placing this high-density polyethylene (HDPE) molded product in warm water or steam, the polyethylene molecules are covalently linked and cross-linked to form a cross-linked polymer having a crystallinity of 72% and a weight average molecular weight of 2.5 × 10 ⁶ or more. An abrasion and corrosion resistant conduit consisting of high density polyethylene (XL-HDPE) was produced.

Next, in order to confirm various characteristics of the wear-resistant and corrosion-resistant conduit of the present invention, various characteristic evaluation tests were carried out while comparing with various conventional conduits.

Abrasion corrosion test test material A material composed of each material shown in Table 1 was cut into 14 × 14
× 5 mm flat test pieces were prepared. Table 2 shows the weight average molecular weight and crystallinity of the polyethylene materials shown in Table 1.

[0019]

[Table 1]

[0020]

[Table 2]

Test Method As shown in FIG. 2A, a test apparatus 1 in which an ejection device 5 is disposed in a flowing section 3 of a liquid tank 4 having a settling section 2 in the upper half and a flowing section 3 in the lower half. used. The slurry stored in the liquid tank 2 is separated into the test liquid and the solid particles in the settling part 2 by the solid particles settling by its own weight, and a part of the test liquid that has become the supernatant is pumped by the pump 6. Flow section 3 through pipe 7
And a part is supplied to the ejection device 3 via a pipe 9 by a pump 8. In the ejection device 3, FIG.
As shown in the figure, the ejection nozzle 10a of the test liquid flow cylinder 10
When the test liquid is ejected from the cylinder, the inside of the slurry flow cylinder 11 becomes a negative pressure.
Slurry flows into 1. Then, the test liquid and the slurry are mixed, ejected from the ejection nozzle 11 a and collide with the set test piece 12, and flow from the flow gap 13 to the flowing portion 3.
Flows out to

As a test solution, ion-exchanged water or a 3% aqueous sodium chloride solution at a temperature of 20 ° C. and a pH of 7.0 is used. As solid particles, silica sand (SiO ₂ ) having a particle size of 200 to 300 μm is used.
And uniformly mixed to prepare a slurry having a particle concentration of 25% by weight.

This slurry is stored in the liquid tank 4 of the test apparatus 1 and the collision speed with the test piece 12 is set to 2 m / s, the collision angle is set to 90 °, and the test is continued for 60 minutes. The change was measured.

Test Results The volume reduction rate (mm ³ / min) was calculated from the weight change of each test piece and the density of each material. FIG. 3 also shows the results when ion-exchanged water or a 3% aqueous sodium chloride solution was used as the test solution.

In the case of ion-exchanged water, the wear resistance is 3%
In the case of a sodium chloride aqueous solution, the wear resistance and the corrosion resistance can be evaluated. As can be seen from FIG. 3, in each case, the volume loss rate was the same as the glass fiber reinforced resin (F
RP), phenolic resin (PF), vinyl chloride resin (P
VC) is the largest resin group, and carbon steel (SG
P), the metal group of cast iron (FC) was the next largest, and the polyethylene (PE) group was the smallest. Therefore,
Regarding wear resistance and corrosion resistance, polyethylene (P
E) The group was found to be the highest, but there was no particular advantage among polyethylene (PE).

Creep Test Test Material Cut a conduit made of high-density polyethylene (HDPE), high-density polyethylene (HDPE-PE100) and cross-linked high-density polyethylene (XL-HDPE) shown in Table 1 with an inner diameter of 32 mm and a wall thickness of 5.5 mm. Thus, a test tube having a length of 500 mm was produced.

Test method A pressure of 0.55 MPa (5.6 kgf / c) was applied to the test tube.
m ² ), fill the test tube at a temperature of 20 ° C.
C., 60.degree. C., and 80.degree. C., and immersed in water.
m ² ) was measured.

Test Results A plot of the breaking strength at each elapsed time on logarithmic graph paper was connected by a straight line, and the result was plotted as a high-density polyethylene (HDP).
FIG. 4 for a conduit made of E) and FIG. 5 for a conduit made of high-density polyethylene (HDPE-PE100).
FIG. 6 shows a conduit made of cross-linked high-density polyethylene (XL-HDPE).

As can be seen from FIG. 4 and FIG.
The creep strength at 50 ° C. for 50 years was 10 MPa or more for the conduit made of high-density polyethylene (HDPE-PE100) and 8 MPa (80 kgf / cm ² ) for the conduit made of high-density polyethylene (HDPE). Further, as can be seen from FIGS.
It has been found that the creep strength at 0 ° C. for a period corresponding to 50 years is highest for a conduit made of crosslinked high density polyethylene (XL-HDPE). Therefore, regarding the creep resistance, high density polyethylene (HDPE-PE10
0), it was confirmed that the conduit made of crosslinked high-density polyethylene (XL-HDPE) was superior to the conduit made of high-density polyethylene (HDPE).

Material for Environmental Stress Cracking Test Test Material A material consisting of high-density polyethylene (HDPE), high-density polyethylene (HDPE-PE100), and cross-linked high-density polyethylene (XL-HDPE) shown in Table 1 was cut.
A flat test piece of 38 × 13 × 2 mm was prepared, and the center of the flat test piece was 19.1 mm long and 0.3 mm deep.
Notch was formed.

Test Method The test piece 13 was placed on the U so that the surface on which the notch was formed was on the outside.
FIG. 7 shows the ten test pieces 13, 13,.
The sample is mounted on the test piece fixture 14 shown in FIG. Thereafter, as shown in FIG. 7B, the test piece fixing device 14 is inserted into the test piece insertion tube 15, and the test pieces 13, 13,... Are immersed in the test solution. As a test solution, a 10% aqueous solution of nonyl-phenyl-polyoxyethylene-ethanol was used, and the temperature was maintained at 50 ° C. Then, the appearance of the test piece 13 was visually observed, and the crack generation time (hr) of each test piece 13, 13,... Was measured.

Test Results Table 3 shows the time during which cracks occurred in five of the ten test pieces (50% crack initiation time: ESCRF ₅₀ ).

[0033]

[Table 3]

As can be seen from Table 3, the 50% crack initiation time was determined for high density polyethylene (HDPE-PE100),
High density polyethylene (HDPE)
000 hr or more, cross-linked high density polyethylene (XL-HD
PE) was 3500 hr or more. Therefore, regarding environmental stress cracking resistance, it was confirmed that crosslinked high-density polyethylene (XL-HDPE) was the best, and both high-density polyethylene (HDPE-PE100) and high-density polyethylene (HDPE) were equally excellent. Was done.

[0035]

The wear-resistant and corrosion-resistant conduit of the present invention has flexibility, and also has excellent wear resistance, corrosion resistance, creep resistance and environmental stress cracking properties, so that it can withstand earthquakes and the like. Even if it is present, cracks are unlikely to occur, and even if sewage, sludge, slurry or the like is made to flow, the pipe wall surface is hardly worn or corroded. Also, when laying on a steep slope or transporting fluid under high pressure, such as when transporting fluid under high pressure, the pipe wall does not deform for a long period of time and cracks on the pipe wall. Also does not occur.

[Brief description of the drawings]

FIG. 1A shows a conventional high-density polyethylene (HDP).
(E) Molecular structure and (B) are explanatory diagrams showing the molecular structure of the high-density polyethylene (HDPE-PE100) of the present invention.

FIG. 2A is a schematic configuration diagram of a test device used in a wear corrosion test, and FIG. 2B is a cross-sectional view of a main part of an ejection device.

FIG. 3 is a diagram showing a volume reduction rate (mm ³ / min) of each material.

FIG. 4 is a diagram showing the creep strength (kgf / cm ² ) of a conventional conduit made of high-density polyethylene (HDPE).

FIG. 5 shows a high-density polyethylene (HDPE-PE) of the present invention.
FIG. 4 shows the creep strength (MPa) of a conduit consisting of 100).

FIG. 6 shows a cross-linked high-density polyethylene (XL-HD) of the present invention.
Creep strength (kgf / cm ² ) of conduit made of PE)
FIG.

FIGS. 7A and 7B are perspective views of a test piece fixture and a test piece insertion tube used in the environmental stress crack test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test apparatus 5 Jetting apparatus 12 Test piece 13 Test piece 14 Test piece fixing fixture 15 Test piece insertion tube

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[Procedure amendment]

[Submission date] April 3, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

FIG. 4

FIG. 5

FIG. 6

FIG. 7

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI F16L 11/08 F16L 11/08 B // B29K 23:00 105: 24 (72) Inventor Masayuki Tsunaga Oita City 843--18 Kasugaura, Oita Plant, Mitsui Kinsei Engineering Co., Ltd. (72) Inventor Shuichi Matsunami 843--18, Kasugaura, Oita City

Claims (3)

[Claims] An abrasion-resistant and corrosion-resistant conduit made of polyethylene having a crystallinity of 60 to 80% and a weight average molecular weight of 2.5 × 10 ^{5 to} 2.5 × 10 ⁷ . 2. The abrasion-resistant and corrosion-resistant conduit according to claim 1, wherein the polyethylene is a high-density polyethylene. 3. The abrasion-resistant and corrosion-resistant conduit according to claim 1, wherein the polyethylene is a cross-linked high-density polyethylene produced by a cross-linking reaction of high-density polyethylene.