JPH0516294A - Ultra-high-molecular-weight polyethylene coated steel pipe - Google Patents

Abstract

PURPOSE:To improve various durabilities such as resistance to stress crack and the like and expand the scope of utilization in the various kinds of pipes used in gas, water, chemicals and the like by disposing a coated layer formed by shrinking an ultra-high-molecular-weight polyethylene shrinkable pipe on the outside of a steel pipe. CONSTITUTION:An ultra-high-molecular-weight coated steel pipe is constituted by a steel pipe 1 and a coated layer 2 formed by shrinking an ultra-high- molecular-weight polyethylene shrinkable pipe disposed on the outside of said steel pipe 1. The ultra-high-molecular-weight polyethylene shrinkable pipe is formed from ultra-high-molecular-weight polyethylene provided with 5.0dl/g intrinsic viscosity [eta] or more, and the outer diameter (D) is set as 10mm or over, and the wall thickness (t) is set as 0.2mm or more and the ratio of outer diameter wall thickness (D/t) is set as 10 or over, and the shrinkage factor in the diameter direction at 140 deg.C is set as 10% or more. Resistance to stress crack, durability, resistance to chemicals, resistance to wear, electric insulation properties and the like of various kinds of pipes used in gas, underwater, chemicals and the like are improved and the scope of use is expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrahigh molecular weight polyethylene-coated steel pipe, and in particular, because it has a coating layer made of ultrahigh molecular weight polyethylene excellent in wear resistance, non-adhesiveness, self-lubricating property and chemical resistance, The present invention relates to an ultrahigh molecular weight polyethylene-coated steel pipe suitable for various applications by making use of these characteristics.

[0002]

2. Description of the Related Art Conventionally, steel pipes used for underground buried pipes, pipes for water, chemicals, water pipes, gas pipes, etc. are exposed to a harsh environment, and in terms of safety, their corrosion resistance and electrical insulation properties. Good chemical resistance and durability are required. Therefore, the steel pipes used for these purposes are covered with a resin or the like to be protected. By the way, ultra-high molecular weight polyethylene is excellent in various properties such as wear resistance, self-lubricating property, chemical resistance, electrical insulation property, corrosion resistance, non-adhesiveness and the like. Therefore, it has been practiced to manufacture a pipe made of this ultrahigh molecular weight polyethylene, insert a steel pipe into this pipe, and coat the steel pipe. This pipe made of ultra-high molecular weight polyethylene has been conventionally manufactured by a method such as compression molding or a method of mechanically grinding a round bar of ultra-high molecular weight polyethylene. As a method for producing a flexible tube made of ultra-high molecular weight polyethylene, the ultra-high molecular weight polyethylene is melted by a screw extruder, and the mandrel is melt-extruded from a tube die having an L / D of 5 which rotates as the screw rotates. Methods have also been proposed. (Japanese Patent Publication No. 2-31270)

[0003]

However, the pipes or tubes made of ultra-high molecular weight polyethylene obtained by the above-mentioned conventional method are not limited to those having an indefinite length, for example, those obtained by mechanical grinding cannot be obtained, and the pipes or tubes can also have a diametrical direction. Is not sufficiently heat-shrinkable. In addition, Japanese Patent Publication No.
In the method described in Japanese Patent Laid-Open Publication No. 2004-242, since the diameter is reduced while being taken at a take-up speed which is 1.1 times or more the extrusion speed, the resulting tube has no heat-shrinkability. Therefore, it has not been possible to economically obtain a long steel pipe in which a long steel pipe is economically covered with a pipe or tube made of ultra-high molecular weight polyethylene.

Therefore, an object of the present invention is to provide a coating layer made of ultra-high molecular weight polyethylene having excellent wear resistance, non-adhesiveness, self-lubricating property, electrical insulating property, corrosion resistance, and chemical resistance. Taking advantage of the above, it is to provide an ultrahigh molecular weight polyethylene-coated steel pipe suitable for various applications.

[0005]

In order to solve the above-mentioned problems, the present invention has a steel pipe and an ultra-high molecular weight polyethylene shrink pipe arranged outside the steel pipe, and a coating layer formed by shrinking the ultra-high-molecular-weight polyethylene shrink pipe. A high molecular weight polyethylene coated steel pipe is provided.

The ultrahigh molecular weight polyethylene shrink pipe is made of ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of 5.0 dl / g or more and an outer diameter (D) of 10 mm or more,
Wall thickness (t) 0.2 mm or more, and outer diameter / wall thickness (D /
It is preferable that the ratio of t) is 10 or more and the shrinkage ratio in the diameter direction at 140 ° C. is 10% or more.

Further, in the ultrahigh molecular weight polyethylene shrink pipe, the ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of 5.0 dl / g or more is supplied to a screw extruder to melt and knead, and the screw of the screw extruder is used. The melt of ultra-high molecular weight polyethylene is continuously extruded from a die having an L / D ratio of at least 10 which is connected to the inner die and which rotates with the rotation of the screw of the screw extruder. After being formed into a cylindrical rough-formed product, the outer diameter of the maximum expanded portion is 1.2 to 3 of the outer diameter of the inner die by the taper core connected to the inner die. While expanding the diameter so that it becomes 0.0 times, it is taken up at a take-up speed of 5 times or less of the extrusion speed of ultra-high molecular weight polyethylene in a screw extruder and taper. In the tapered portion of A when ultra high molecular weight polyethylene is one produced by a process comprising the to start cooling solidification, preferred.

The ultrahigh molecular weight polyethylene-coated steel pipe of the present invention (hereinafter abbreviated as "coated steel pipe") will be described in detail below with reference to the embodiment shown in FIG.

The coated steel pipe of the present invention, as shown in FIG.
It has a steel pipe 1 and a coating layer 2 for coating the outside of the steel pipe 1.

The steel pipe 1 may be made of any material,
There is no particular limitation. Examples thereof include carbon steel, cast steel, special steel such as stainless steel and chrome steel, copper alloy, and light alloy.

The coating layer 2 is formed by shrinking an ultra high molecular weight polyethylene shrink pipe, and usually has a wall thickness of 0.
It is about 2 to 5 mm, preferably about 0.5 to 3.0 mm.

The coated steel pipe of the present invention can be manufactured, for example, by inserting the steel pipe 2 into an ultra-high molecular weight polyethylene shrink pipe and then heating it to heat-shrink the ultra-high molecular weight polyethylene shrink pipe. This can be done by bringing a high molecular weight polyethylene shrink pipe into close contact. The heating temperature for heat shrinkage is usually about 100 to 160 ° C, preferably about 120 to 140 ° C. In the coating with the ultrahigh molecular weight polyethylene shrink pipe, it is preferable to make the outer surface of the steel pipe rough in advance, because the sliding resistance at the contact interface between the shrink pipe and the steel pipe can be improved.

Further, at this time, when the adhesive resin is preliminarily interposed on the outer peripheral surface of the steel pipe and the ultrahigh molecular weight polyethylene shrink pipe is heat-shrinked, the coated steel pipe having good adhesive strength at the interface between the coating layer and the steel pipe. Is preferred, which is preferable. This method can be carried out by previously heat-bonding a powder or film of an adhesive resin to the outer surface of a cylindrical body such as a roll or a steel pipe. Examples of the adhesive resin used include Admer NE060 (trade name, manufactured by Mitsui Petrochemical Industry Co., Ltd.), and modified products thereof.

The heating in the above heat shrinkage can be carried out, for example, according to a method such as heating with an air oven, heating with a liquid heating medium tank, heating with a flame, or the like.

The ultrahigh molecular weight polyethylene shrink pipe used for the coating layer of the coated steel pipe of the present invention is made of ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of 5.0 dl / g or more and an outer diameter (D) of 10 mm or more, The wall thickness (t) is 0.2 mm or more, preferably 0.5 to 3 mm, and the outer diameter / wall thickness (D / t) ratio is 10 or more, preferably 15 to 150.
And the diametrical shrinkage at 140 ° C. is 10% or more, preferably 20% or more, and further 40 to 1
It is preferably 50%. In the present invention, by using this ultra-high molecular weight polyethylene shrink pipe for the coating layer, it is possible to obtain a coated steel pipe having excellent adhesion between the steel pipe and the coating layer, corrosion resistance of the steel pipe, chemical resistance, wear resistance and the like. You can

The production of this ultrahigh molecular weight polyethylene shrinkable pipe is carried out, for example, by supplying ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of 5.0 dl / g or more to a screw extruder to melt and knead the screw extruder. L / D which has an inner die connected to the screw of the screw extruder and which rotates with the rotation of the screw of the screw extruder.
A melt of ultra-high molecular weight polyethylene is continuously extruded from a die having a ratio of at least 10 to form a cylindrical rough molding, and the cylindrical rough molding is then tapered to the inner die. By the core, the outer diameter of the maximum diameter expanded portion is expanded to 1.2 to 3.0 times the outer diameter of the inner die, while the extrusion speed of the ultrahigh molecular weight polyethylene in the screw extruder is 5 times or less. It can be carried out by a method including a step of allowing the ultrahigh molecular weight polyethylene to start cooling and solidification in the taper portion of the taper core while the material is drawn at a take-up speed.

The ultrahigh molecular weight polyethylene, which is the material for the ultrahigh molecular weight polyethylene shrink pipe used in the coated steel pipe of the present invention, contains ethylene as a main component,
For example, a homopolymer of ethylene, a copolymer containing ethylene as a main component and ethylene and a monomer copolymerizable with the ethylene, and the like can be mentioned. Examples of the monomer copolymerizable with ethylene include α-olefins having 3 or more carbon atoms. Specific examples of the α-olefin having 3 or more carbon atoms include propylene, 1-butene, isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl. -1-pentene, 4-methyl-1-pentene, 1-heptene, 1-
Examples include octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like.

Further, the ultra high molecular weight polyethylene includes
You may mix | blend various stabilizers, a pigment, etc. as needed.

Next, this manufacturing method will be described in detail with reference to an embodiment of an apparatus for manufacturing an ultrahigh molecular weight polyethylene shrinkable pipe shown in FIGS.

The ultrahigh molecular weight polyethylene shrink pipe manufacturing apparatus shown in FIG. 2 basically comprises a screw extruder 3 and
It has a die 4 mounted on the screw extruder 3 and a tapered core 5 connected to the die 4.

As shown in FIG. 3, the screw extruder 3 has a grooved cylinder 6 and a screw 7 inserted in the grooved cylinder 6, and further a hopper for supplying an ultra high molecular weight polyethylene as a raw material. It has eight.

The inner diameter of the grooved cylinder 6 is appropriately selected so that a shrink pipe having a desired outer diameter can be obtained. The screw 7 has a compression ratio of 1 to 2.5, preferably a compression ratio of 1.
Those of 3 to 2.0 are used. The effective length (L / D) of this screw is usually about 20 to 28. The length of the compression part of the screw is 25 to 8 of the effective length (L / D).
It is about 0%. Also, the screw flight pitch is
Usually, it is about 0.4 to 0.8. The rotation speed of the screw 7 is usually 10 to 30 rpm. p. m. It is a degree.
In addition, the hopper 8 is preferably a two-stage hopper, because when the raw material is powder, it is possible to prevent the raw material from falling down.

A heating barrel 9 is arranged on the peripheral wall of the screw extruder 3 in order to melt the supplied ultra high molecular weight polyethylene, and a water cooling barrel 10 is arranged in order to adjust the heating temperature. It is set up. The heating temperature in the screw extruder 3 is usually a temperature above the melting point of the ultrahigh molecular weight polyethylene and below 340 ° C., preferably 1
The temperature is adjusted to 60 to 330 ° C.

The die 4 mounted on the screw extruder 3 comprises an inner die 11 and an outer die 12, and the inner die 11 is inserted in the outer die 12. The inner die 11 is connected to the tip 13 of the screw 7 of the screw extruder 3 and rotates with the rotation of the screw 7. The outer die 12 is attached to the tip 14 of the heating barrel 9 of the screw extruder 3.
The die 4 has an L / D ratio of at least 10, preferably 20-50. Also, the inner die 11
Since it rotates together with the screw 7, it is preferable that the surface thereof is coated with a fluororesin in order to improve the sliding property with the ultrahigh molecular weight polyethylene. An electrothermal heater 15 is arranged on the outer peripheral wall of the die 4 in order to adjust the temperature of the ultra high molecular weight polyethylene moving in the die 4. The heating temperature in this die 4 is usually 160 to 2
It is adjusted to about 50 ° C.

In the manufacturing apparatus of the present invention, the inner die 11 of the die 4 has a tapered core 5 whose enlarged view is shown in FIG.
Are lined up. The taper core 5 is the inner die 1.
1 has a shaft 18 connected to the tip 17 and a taper molding member 19 loosely fitted to the shaft 18. The shaft 18 connected to the tip 17 of the inner die 11 rotates together with the inner die 11 connected to the screw 7. The outer diameter of the shaft 18 is usually smaller than the outer diameter of the inner die, and the length is usually about 10 to 50 cm.

The tapered molded member 19 is loosely fitted to the shaft 18 by a bearing 20 and mounted on the shaft 18 so as not to rotate in synchronization with the shaft 18. The taper molding member 19 can effectively expand the diameter of the rough molding extruded from the die 4, and the frictional resistance at the time of the diameter expansion can be kept within a range where molding can be easily performed. Then, with respect to the axial direction of the shaft 18, the taper portion 21 and the taper portion 2 which are formed to be inclined at an angle of usually 5 to 50 degrees, preferably 10 to 30 degrees.
And a cylindrical portion 22 that is connected to 1.

The taper portion 2 of the taper molding member 19
1 and the surface of the cylindrical portion 22 are preferably coated with a fluororesin such as Teflon because the coefficient of friction with the ultra high molecular weight polyethylene molded article is reduced and the molding can be performed smoothly.

In the taper molding member 19, the ratio of the length of the taper portion 21 / the cylindrical portion 22 in the axial direction is usually about 0.2 to 1, preferably 0.3 to 0.7.
Formed to a degree. The outer diameter of the cylindrical portion 22 has a maximum outer diameter of at least 1.2 of the inner die diameter.
To 3.0 times, preferably 1.5 to 3.0 times the diameter of the inner die, and more preferably 1.7 to 2.5.
Double.

According to the method of the present invention, in this manufacturing apparatus,
First, an ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of 5.0 dl / g or more is supplied to a screw extruder 3 to be melted and kneaded, and a melt of the ultrahigh molecular weight polyethylene is continuously extruded from a die 4 to form a cylindrical shape. The inner die 1 having the inner diameter of the maximum expanded diameter portion of the die 4 is formed by the tapered core 5 in that a good contraction pipe having an appropriate wall thickness can be obtained after molding into the rough molding product of
1.2 to 3.0 times the outer diameter of 1, preferably 1.5 to 3.
The diameter is expanded so as to be 0 times, and more preferably 1.7 to 2.5 times. The contracted pipe formed by expanding the diameter is taken by the take-up machine 24 while being cooled in the cooling tank 23. The take-up speed of the take-up machine 24 is 5 times or less, preferably not more than the extrusion speed of the ultra-high molecular weight polyethylene in the screw extruder, in that an ultra-high-molecular-weight polyethylene shrink pipe having a longitudinal shrinkage in an appropriate range can be obtained. 1.
It is 1 to 5 times, more preferably 2 to 3 times. Examples of the take-up machine 24 include a roll type, a caterpillar type, and a belt type.

Further, in view of obtaining an ultrahigh molecular weight polyethylene shrink pipe having a large shrinkage ratio, the ultrahigh molecular weight polyethylene starts to cool and solidify in the tapered portion 21 of the tapered core 5, preferably in a portion thinner than the middle of the tapered portion 21. It is desirable to adjust so that The start of cooling and solidification of the ultra high molecular weight polyethylene shrink pipe can be adjusted by adjusting the extrusion speed of the screw extruder, the position of the tapered core, the position of the cooling air blowing ring, and the like.

The ultrahigh molecular weight polyethylene shrink pipe of the present invention formed by being taken up by the take-up machine 24 is appropriately cut by the cutting machine 25. Examples of the cutting machine 25 include an automatic cutting machine such as a circular saw type machine.

[0032]

EXAMPLES The present invention will be described in detail below with reference to examples of the present invention, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

Example 1 An ultra-high molecular weight polyethylene shrink pipe was manufactured by using a device having the same structure as that of the shrink pipe manufacturing apparatus shown in FIG. 2 and having the following specifications for each part. Extruder: Screw outer diameter 30 mmφ Screw effective length (L / D) 22 Flight pitch 18 mm Screw compression ratio 1.8 Die: Die length 750 mm Outer die outer diameter at die exit 20 mmφ Effective die length (L / D) 37 .5 Inner die outer diameter 15 mmφ Tapered core connected to the tip of the inner die: It has a taper portion and a cylindrical portion integrally formed of aluminum metal, and the surface is coated with Teflon. Tapered portion maximum diameter 30 mmφ length 50 mm Cylindrical portion outer diameter 30 mmφ length 80 mm Furthermore, this device has an air ring for cooling the resin rough molding, a cooling water tank, a roll type take-off machine, and a pipe cutting machine.

In this device, ultra high molecular weight polyethylene
([Η]: 15.1 dl / g, melting point: 136 ° C., bulk ratio
Weight: 0.43 g / cc) of powdered resin, water cooled
Le (C₁), And 3 zones (C₂, C₃, C_Four) Minutes
The temperature in the digitized heating barrel is 20 ° C and 29 ° C, respectively.
Adjusted to 0 ℃, 330 ℃ and 330 ℃, and 3 zones
(D ₁, D₂, D₃) Divided into 2 dies each
30 ℃, 180 ℃ and 170 ℃, screw rotation
A rough molded product at several 12 rpm and an extrusion speed of 18 cm / min
Extruded. Cylindrical extruded at die exit
While cutting the crude molded product with a knife in the extrusion direction, open the cooling water tank.
Equipped with a roll that passes through and rotates at a speed of 30 cm / min
Guide to a roll-type take-up machine, and then stop cutting with a knife.
The taper portion of the tapered core
Diameter, blow cooling air from the air ring, and
Cooling and solidification of the rough molding is tapered by adjusting the air flow rate
Adjusted to start in the middle of the part, outer diameter 31.0mm
Expansion ratio of φ and inner diameter 29.5 mmφ (inner diameter ratio) 1.97
Ultra high with a thermal shrinkage of 45% in the diametrical direction at 140 ° C
A shrink pipe made of high molecular weight polyethylene was produced.

Next, a contraction pipe made of ultra-high molecular weight polyethylene was taken to have a length of 1.7 m, and inside this contraction pipe made of ultra-high molecular weight polyethylene, a carbon steel pipe for pipe having an outer diameter of 27.2 mmφ (length 1. 5 m) was inserted and then heated in an air oven at 140 ° C. for 1 hour. Then, it was taken out from the air oven and cooled at room temperature for 40 minutes to obtain an ultrahigh molecular weight polyethylene-coated steel pipe. The thickness of the ultrahigh molecular weight polyethylene coating layer in the obtained ultrahigh molecular weight polyethylene coated steel pipe was 0.83 mm.

[0036]

The coated steel pipe of the present invention has a coating layer made of ultra-high molecular weight polyethylene excellent in wear resistance, self-lubrication property, corrosion resistance, electrical insulation property, chemical resistance, etc. It has excellent durability, chemical resistance, abrasion resistance, and electrical insulation, and since ultra-high molecular weight polyethylene is non-adhesive, it has excellent workability in handling. Therefore, the coated steel pipe of the present invention can be suitably used for various applications by utilizing these excellent properties. For example, it can be preferably used for underground buried pipes, pipes in water or in chemicals, water pipes, gas pipes and the like.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of a steel pipe covered with an ultrahigh molecular weight polyethylene shrink pipe of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a main part of an apparatus for manufacturing an ultra high molecular weight polyethylene shrink pipe.

FIG. 3 is a diagram illustrating a main part of an apparatus for manufacturing an ultrahigh molecular weight polyethylene shrink pipe.

FIG. 4 is a diagram illustrating a tapered core of an apparatus for producing an ultra-high molecular weight polyethylene irregular pipe.

[Explanation of symbols]

1 steel pipe 2 coating layer 3 screw extruder 4 die 5 taper core 6 grooved cylinder 7 screws 8 hopper 9 heating barrel 10 water-cooled barrel 11 inner die 12 Outer die 13 Tip of screw 6 14 Tip of heating barrel 9 17 Tip of inner die 11 18 shaft 19 Tapered molded member 20 bearings 21 Tapered part 22 Cylindrical part 23 Cooling tank 24 pick-up machine 25 cutting machine

Claims (3)

[Claims] 1. An ultra-high molecular weight polyethylene-coated steel pipe comprising a steel pipe and a coating layer formed by shrinking an ultra-high molecular weight polyethylene shrink pipe disposed outside the steel pipe. 2. The ultra high molecular weight polyethylene shrink pipe is made of ultra high molecular weight polyethylene having an intrinsic viscosity [η] of 5.0 dl / g or more, an outer diameter (D) of 10 mm or more, and a wall thickness (t) of 0.2 mm. The ultrahigh molecular weight polyethylene-coated steel pipe according to claim 1, wherein the ratio of the outer diameter / the wall thickness (D / t) is 10 or more and the diametrical shrinkage ratio at 140 ° C. is 10% or more. . 3. The ultrahigh molecular weight polyethylene shrink pipe, wherein the ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of 5.0 dl / g or more is supplied to a screw extruder and melted and kneaded, and the screw of the screw extruder is used. And an inner die that rotates with the rotation of the screw of the screw extruder is disposed inside, and has an L / D ratio of at least 1
A melt of ultra-high molecular weight polyethylene was continuously extruded from a die of 0 to form a cylindrical rough molding, and then the cylindrical rough molding was formed by a taper core connected to the inner die. While increasing the outer diameter of the maximum diameter expanded portion to 1.2 to 3.0 times the outer diameter of the inner die, at a take-up speed of 5 times or less than the extrusion speed of ultra-high molecular weight polyethylene in a screw extruder. The ultra-high-molecular-weight polyethylene-coated steel pipe according to claim 1 or 2, which is produced by a method including a step of allowing the ultra-high-molecular-weight polyethylene to start cooling and solidification in the taper portion of the tapered core while being taken out.