JP2000343600A - Manufacture of biaxially oriented polyolefin resin pipe and biaxially oriented high density polyethylene pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the high plasticity and the deformability compatible with the peripheral high elasticity and also upgrade the resistance to earthquake by making the degree of orientation of a resin pipe in the peripheral direction higher than that of the resin pipe in the axial direction. SOLUTION: A polyolefin resin is malt-kneaded in an extruder, then is molded in the form of pipe through a mold and the extruded pipe-shaped polyolefin resin is cooled in a water tank or the like while being stretched by a take-up machine, to be cut to the specified length using a cutter. Thus, a billet (a pipe blank) 2 is formed and the pipe blank 2 is made to move forward over the surface of a cone-shaped mandrel 13 whose diameter is enlarged gradually. After this procedure, the pipe blank 2 is forced into the mandrel 13 from behind, while the former is made to closely come into contact with the mandrel 13 by a hydraulic extruder 11. The forcing operation expands the inside dia. of the pipe blank 2 to be oriented in the peripheral and the axial direction simultaneously. Thus the biaxially oriented polyolefin resin pipe is obtained which has polyolefin particles oriented in two directions, i.e., both axial and peripheral. Consequently, it is possible to make the high deformation follow-up properties to an external stress compatible with the high peripheral elasticity and upgrade the resistance to earthquake.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a biaxially oriented polyolefin resin pipe and a biaxially oriented high-density polyethylene pipe, and more particularly, to the ability of a buried pipe to follow the deformation of the pipe as the performance of the pipe. Biaxially oriented high density polyethylene pipe with excellent elasticity in the circumferential direction and high seismic resistance A method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyvinyl chloride synthetic resin pipes (PVC pipes), cast iron pipes, concrete pipes, and the like have been used as water distribution pipes, hot water supply pipes, gas pipes, water supply pipes, sewer pipes, and plant pipes. Have been. In recent years, polyolefin resin pipes made of polyolefin resin have been
Due to its high reliability against earthquake resistance, ground deformation, etc., the demand for underground pipes and the like is increasing and is rapidly spreading. For example, according to a technical report by Sekisui Chemical Co., Ltd., polyethylene pipes have a high ability to follow the deformation (ie, elongation) of the pipes with respect to external stresses inherent in the pipes, so that when the earthquakes or the ground repeatedly fluctuates, However, it is disclosed that a polyethylene pipe buried in the ground does not break due to plastic deformation.

Underground pipes and the like must maintain high durability for a long time against internal pressure, earth pressure and the like. For this reason, in a polyethylene pipe, it is actually performed to increase the thickness of the pipe. In this case, small-diameter polyethylene pipes can be mass-produced industrially, but large-diameter polyethylene pipes are still difficult to mass-produce industrially, and currently, small-diameter polyethylene pipes are mass-produced industrially. However, large-diameter polyethylene pipes have not yet been mass-produced industrially.

[0004] At present, polyolefin-based resin pipes are widely penetrating the market, and there is a demand for improvement in reliability of the polyolefin-based resin pipe such as deformation followability, circumferential elasticity, internal pressure resistance, and long-term strength. Is growing more and more. In order to meet such a demand, an oriented polyolefin-based resin pipe in which a polyolefin-based resin pipe is stretched in an axial direction or a circumferential direction to orient polyolefin molecules in a specific direction has been receiving attention.

When the polyolefin resin tube is stretched in a specific direction to orient the polyolefin molecules, the elasticity in that direction is improved, but the tube tends to be less deformable. Therefore, when the polyolefin-based resin tube is stretched in a specific direction, the elasticity in that direction is improved, so that the tube is not plastically deformed by a small external force from the specific direction, and the function as the tube can be maintained. However, since it becomes difficult to plastically deform, for example, when the buried pipe encounters an earthquake, the pipe may be broken.

When a polyolefin-based resin tube is uniaxially stretched only in the axial direction, the elastic modulus in the axial direction can be greatly improved.
In the event of an earthquake or the like, a polyethylene pipe buried in the ground cannot plastically deform in the axial direction, and the pipe is easily torn in the axial direction. In addition, since it is not stretched in the circumferential direction, not only the resistance to internal pressure and earth pressure is not improved, but also the strength (in particular, elasticity) in the circumferential direction is not improved, and the resulting polyolefin-based resin pipe is not improved. Is inferior in practicality and earthquake resistance.

On the other hand, when the film is uniaxially stretched only in the circumferential direction, the elastic modulus in the circumferential direction can be greatly improved. The resistance to the weight of soil added to the pipe can be improved, but also in this case, since the deformation followability of the pipe is significantly reduced by stretching, it is not possible to plastically deform in the axial direction, and the resulting result is obtained. Polyolefin-based resin tubes have poor earthquake resistance.

For this reason, various studies have been made on biaxially oriented polyolefin-based resin tubes in which a polyolefin-based resin tube is stretched in both the axial direction and the circumferential direction. The polyolefin molecules are larger in the axial direction and smaller in the circumferential direction. Therefore, the conventional biaxially oriented polyolefin-based resin pipe is apt to be torn in the axial direction since the deformation followability (elongation) of the pipe is significantly reduced.

For example, in Japanese Patent Publication No. 4-55379, (1) a hollow work containing a stretchable thermoplastic polymer is supplied from the inlet side of the die, and (2) the hollow work is sent to the outlet side of the die. The workpiece is not solid enough to cause tensile failure of the workpiece, but the solid phase has a cross-section greater than the initial internal cross-section of the workpiece and the interior of the workpiece. (3) A hollow workpiece deformed by being stretched in this manner is given sufficient tensile strength to simultaneously deform and extend the former disposed in the above-mentioned section so that the bulk cross-sectional area of the workpiece is reduced. Is obtained from the exit side of the die to obtain a tube having improved strength as compared with an undeformed material.

According to this method, although the elastic modulus, tensile yield strength, impact strength and internal pressure strength of the obtained pipe are improved, the tensile elongation at break is significantly reduced. Therefore, in the pipe obtained by the method of Japanese Patent Publication No. 4-55379, the ability of the polyolefin-based resin pipe to follow deformation (ie, elongation) of the pipe against external stress is significantly reduced. That is, there is a problem that the tube is not sufficiently deformable to external stress required when the tube is buried, and the tube lacks seismic resistance such as peeling in a layered manner.

Also, Nakamaru et al., Described in Forming Process, Vol. 10, No. 6, p. 394, use a stretching means combining a die and a mandrel to pull a raw pipe called a billet while pulling the original pipe. By passing
A "DIeDrawIng method" for producing a biaxially oriented tube is disclosed. In this report, it is claimed that the DIe DrawIng method has made it possible to control the stretching ratio in the axial direction and the stretching ratio in the circumferential direction, and to freely control the orientation in the resulting tube. However, it has not yet been able to achieve both the internal pressure resistance required when buried and the tube deformation followability with respect to external stress.

Japanese Unexamined Patent Publication No. Hei 5-501993 discloses a uniaxial stretching method in which a billet is stretched only in the circumferential direction by pressing a billet from inside to outside using a pressurized fluid such as compressed air from the inside of a pipe. Although a method is disclosed, no method for increasing the axial strength is disclosed. Therefore, in the uniaxially stretched polyolefin-based resin pipe obtained by this method, the pipe is stretched only in the circumferential direction and not in the axial direction. It has not been possible to achieve both deformability and elasticity in the circumferential direction.

[0013]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a plastic deformability (ie, an external stress to external stress) which is a performance required when used as a buried pipe. To provide a method for producing a biaxially oriented polyolefin-based resin pipe and a biaxially oriented high-density polyethylene pipe that are compatible with high deformation followability of the pipe and high elasticity in the circumferential direction, and have high earthquake resistance. It is in.

[0014]

According to a first aspect of the present invention, there is provided a biaxially oriented polyolefin-based resin tube which is oriented in an axial direction and a circumferential direction, and has a degree of orientation in the circumferential direction. It is characterized by being larger than the degree of orientation in the direction.

The term “degree of orientation” used in the present specification is a numerical value indicating how much the molecular chain of a polyolefin molecule is arranged in that direction, and includes infrared spectroscopy (hereinafter referred to as “IR”). It can be measured by X-ray analysis, polarization microscopy, and microwaves. In the present invention, measurement is performed using a microwave, as described later.

As used herein, the term “biaxially oriented polyolefin resin tube” refers to a refractive index (n
The average value of h) and the average value of the refractive index (na) in the axial direction are respectively 0.002 or more larger than the refractive index (nn) in the non-oriented state, and the outer diameter (D) of the tube and the thickness (t) of the tube. Means a tube made of a polyolefin resin having a ratio (D / t) of 100 or less. When either the average value of the refractive index (nh) in the circumferential direction or the average value of the refractive index (na) in the axial direction is less than 0.002 than the refractive index (nn) in the non-oriented state, the polyolefin molecule The orientation is insufficient and the elastic modulus cannot be improved.

Therefore, resistance to the internal pressure applied to the pipe from the fluid flowing inside the pipe (hereinafter referred to as “internal pressure resistance”)
When polyolefin resin pipes are buried, resistance to pressure applied to the pipes by soil and vehicles traveling on the ground (hereinafter, referred to as
"Earth-pressure resistance" cannot be improved.

The relationship between the refractive index and the degree of orientation is such that the higher the refractive index in a particular direction is higher than the refractive index (nn) in the non-oriented state, the higher the degree of orientation in that direction and is in a substantially proportional relationship. . In order to measure the refractive index, an Abbe refractometer that irradiates a sodium D line (wavelength: 589 nm) is often used because the measuring method is simple, but in the Abbe refractometer, the sodium D line sufficiently penetrates the sample. It is not appropriate to measure the refractive index of an optically opaque polyolefin resin tube using an Abbe refractometer. Therefore, in the present invention, in the microwave region in which dielectric relaxation due to local motion such as twisting of the molecular main chain of a polymer material such as a polyolefin resin is observed, in particular, a microwave around 19 GHz is used for the polyolefin resin. The dielectric constant (ε ′) is measured by irradiating the tube, and the Maxwell's formula ((refractive index (n) =
It is appropriate to determine the refractive index from √ (ε ′)).

The refractive index (nn) in the non-oriented state may be the refractive index (nn) in the non-oriented state as it is before the alignment, but the polyolefin-based resin tube is stretched and oriented. Later, the tube (its melting point + 40
C.) or higher, and then cooled at a rate of about 10 ° C./min, so that the refractive index of the tube whose orientation has been canceled may be set to the non-oriented refractive index (nn).

The thickness of the biaxially oriented polyolefin resin tube is preferably equal to or smaller than that of a normal polyethylene tube or PVC tube. Although the preferred thickness varies depending on the outer diameter of the tube, the ratio (D / t) of the outer diameter (D) of the tube and the thickness (t) of the tube is different.
Is preferably 100 or less as described above. In particular, when creep resistance is required for the biaxially oriented polyolefin-based resin tube, the ratio (D / t) is preferably 30 or less. The shape of the biaxially oriented polyolefin-based resin tube is usually cylindrical, but is not necessarily limited to this. Depending on the use in which the tube is used, an elliptical cross section, an oval shape,
It may have a different shape such as a square tube (for example, a square tube, a triangle tube).

As described above, the higher the refractive index, the higher the degree of orientation. Specifically, as set forth in claim 2, the refractive index (nh) in the circumferential direction is changed to the refractive index (na in the axial direction). )
The refractive index (nh) in the circumferential direction is larger than the refractive index (nn) in the non-aligned state by 0.004 or more, and preferably 0.4 mm or more.
It is preferably larger than 01. That is, when the refractive index (nh) in the circumferential direction is smaller than the refractive index (na) in the axial direction,
Needless to say, the degree of orientation in the axial direction becomes larger than the degree of orientation in the circumferential direction. When the difference between the refractive index (nh) in the circumferential direction and the refractive index (nn) in the non-oriented state is less than 0.004, the orientation of the polyolefin molecules in the circumferential direction by stretching is insufficient. In some cases, the elastic modulus in the circumferential direction cannot be sufficiently improved, and the internal pressure resistance and the earth pressure resistance of the pipe cannot be improved.

Further, as in claim 3, (refractive index in the circumferential direction (nh) -refractive index in the axial direction (na)) / (refractive index in the circumferential direction (nh)) is not less than 0.004 and not more than 0.03. It is preferably not more than 0.006 or more and 0.025 or less, particularly preferably 0.01 or more and 0.02 or less. That is, (the refractive index in the circumferential direction (n
When h) -refractive index in the axial direction (na) / (refractive index in the circumferential direction (nh)) is less than 0.004, the orientation of the polyolefin molecules in the circumferential direction by stretching is insufficient, and In some cases, the elastic modulus cannot be sufficiently improved, and the internal pressure resistance and the earth pressure resistance of the pipe cannot be improved. On the other hand, if (refractive index in the circumferential direction (nh) −refractive index in the axial direction (na)) / (refractive index in the circumferential direction (nh)) exceeds 0.03, the polyolefin molecules are too oriented in the circumferential direction. Since the pipe is stretched too much in this manner, the ability of the pipe to follow the deformation is reduced. Therefore, when an earthquake occurs when the pipe is used as an underground pipe, the pipe tends to be easily broken.

In the present invention, as another means for solving the above-mentioned problems, the tensile elastic modulus (tmh) in the circumferential direction of the biaxially oriented polyolefin-based resin tube is defined as the tensile elastic modulus in the axial direction (tmh). The structure may be larger than tma).
The improvement in the internal pressure resistance is achieved by improving the tensile modulus in the circumferential direction. However, when the pipe is deformed in the axial direction due to an earthquake, a ground crack, or the like, in order to follow the deformation, it is necessary to maintain the deformability of the pipe by lowering the tensile modulus in the axial direction. Therefore, in the biaxially oriented polyolefin resin pipe according to claim 4, the tensile elastic modulus in the circumferential direction (tmh) is changed to the tensile elastic modulus in the axial direction (tm).
By making it larger than a), the internal pressure resistance can be improved, and the deformation followability of the pipe can be maintained.

Specifically, as set forth in claim 5, (tensile elastic modulus in the circumferential direction (tmh)) / (tensile elastic modulus in the axial direction (th)
ma)) is preferably 1 or more and 8 or less, more preferably 1 or more and 5 or less. More preferably, it is 1.2 or more and 5 or less. That is, when (circumferential tensile modulus (tmh)) / (axial tensile modulus (tma)) is less than 1, the axial tensile modulus (tma) increases, while the circumferential tensile modulus increases. Modulus of elasticity (tm
h), the internal pressure resistance tends to be unable to be improved. On the other hand, (the tensile modulus in the circumferential direction (t
mh)) / (tensile modulus of elasticity in the axial direction (tma)) exceeds 8, it is necessary to stretch in the circumferential direction significantly, so that the deformation followability of the pipe is remarkably reduced. If an earthquake occurs when used as a pipe, the pipe tends to break easily.

More specifically, the tensile elastic modulus in the circumferential direction is 0.5 GPa or more and 20 GPa or less, and the tensile elastic modulus in the axial direction is 0.5 GPa or more and 10 GPa.
It is preferably Pa or less. 0.5G tensile modulus
If it is less than Pa (especially, the tensile modulus in the circumferential direction is less than 0.5 GPa), the internal pressure resistance is extremely low, and practicality may be lacking. On the other hand, when the tensile elastic modulus in the circumferential direction exceeds 20 GPa or the tensile elastic modulus in the axial direction exceeds 10 GPa, the deformation followability of the pipe is significantly reduced.
If an earthquake occurs when used as an underground pipe, the pipe cannot be deformed and tends to break.

As used herein, the term “tensile elastic modulus” refers to JISK from the obtained biaxially oriented polyolefin-based resin pipe in the circumferential direction and the axial direction, respectively.
A dumbbell-shaped test piece according to 6774 is cut out, the dumbbell-shaped test piece is subjected to a tensile test according to JISK 7113, a tensile stress-strain curve is drawn, and the following equation ( It is a numerical value calculated by 1).

[0027]

(Equation 1) (In equation (1), Δσ is the difference in stress due to the original average cross-sectional area between two points on the straight line, and Δε is the difference in strain between the same two points).

In the present invention, as another means for solving the above-mentioned problems, the bending elastic modulus (mfh) in the circumferential direction of the biaxially oriented polyolefin-based resin tube is calculated as follows. The structure may be larger than mfa).
In order to improve the earth pressure resistance when the polyolefin-based resin pipe is buried, it is achieved by improving the bending elastic modulus in the circumferential direction. However, when the pipe is deformed in the axial direction due to an earthquake, a ground crack, or the like, in order to follow the deformation, it is necessary to maintain the deformability of the pipe by lowering the bending elastic modulus in the axial direction. Therefore, in the biaxially oriented polyolefin-based resin pipe, the circumferential bending elastic modulus (mfh) is made larger than the axial bending elastic modulus (mfa) to improve the earth pressure resistance. At the same time, the deformation followability of the pipe can be maintained.

Specifically, according to claim 8, (bending elastic modulus in the circumferential direction (mfh)) / (axial bending elastic modulus (mfh))
fa)) is preferably 1 or more and 8 or less, more preferably 1 or more and 5 or less. More preferably, it is 1.2 or more and 5 or less. That is, when (circumferential bending elastic modulus (mfh)) / (axial bending elastic modulus (mfa)) is less than 1, the axial bending elastic modulus (mfa) increases while the circumferential bending elastic modulus increases. Rate (mf
h) tends to be low, so that the earth pressure resistance cannot be improved. On the other hand, (circumferential bending elastic modulus (m
fh)) / (axial flexural modulus (mfa)) of more than 8, it is necessary to extend the pipe in the circumferential direction, so that the ability to follow the deformation of the pipe is significantly reduced. If an earthquake occurs when used as a pipe, the pipe tends to break easily.

More specifically, the flexural modulus in the circumferential direction (mfh) is at least 0.5 GPa and at least 20 GPa.
a, and the flexural modulus in the axial direction (mfa) is preferably 0.5 GPa or more and 10 GPa or less. That is, when the flexural modulus is less than 0.5 GPa (particularly, the flexural modulus (mfh) in the circumferential direction is less than 0.5 GPa), the earth pressure resistance is extremely low, and practicality may be lacking. On the other hand, the bending elastic modulus (mfh) in the circumferential direction is 20 GPa.
Or the flexural modulus (mfa) in the axial direction is 1
When the pressure exceeds 0 GPa, the deformation followability of the pipe is remarkably reduced. Therefore, when an earthquake, a ground crack, or the like occurs, the pipe cannot be deformed, may be broken, and may not be practically usable.

The term "flexural modulus" used in the present specification is obtained from the obtained biaxially oriented polyolefin resin tube as shown in FIG. That is, the bending elastic modulus in the axial direction is determined from the relationship between the load and the deflection when a load is applied to the central portion between the fulcrums from above by supporting a polyolefin-based resin pipe of an appropriate length by two fulcrums. Is a numerical value calculated according to the equation (2). (See FIG. 5B)

[0032]

(Equation 2) (In the equation (2), L is a distance between two fulcrums, and F is a load−
The load at an arbitrarily chosen point on the first straight line portion of the curve in the deflection curve graph, where D is the outside diameter of the tube, d is the inside diameter of the tube, and Y is the deflection at load F).

On the other hand, the bending elastic modulus in the circumferential direction can be calculated from the following equation based on the relationship between the load and the deflection when a load P is applied so as to be crushed from the peripheral side surface of a polyolefin resin pipe having an appropriate length. This is a numerical value calculated according to (3).
(See Fig. 5A)

[0034]

(Equation 3) (In equation (3), P is the applied load, R is the center radius of the wall thickness, I is the quadratic modulus of the section of the tube, ΔD _x is the change in diameter in the horizontal direction, and ΔD _y is the change in diameter in the vertical direction).

In the present invention, as another means for solving the above-mentioned problems, the tensile fracture elongation (tba) in the axial direction of the biaxially oriented polyolefin resin tube is determined in accordance with the tenth aspect. The structure may be larger than the degree (tbh). As described above, when the embedded polyolefin resin pipe is deformed in the axial direction due to an earthquake, ground cracking, etc., the pipe is maintained at a high tensile elongation at break in the axial direction without stretching. Can be maintained, whereby the tube can follow the deformation. However, if the pipe is not stretched, the internal pressure resistance and the earth pressure resistance cannot be improved. In other words, when stretched, the tensile elongation at break decreases, and the deformation followability of the pipe is impaired. Therefore, in the obtained biaxially oriented polyolefin resin tube, the tensile elongation at break (tba) in the axial direction of the obtained biaxially oriented polyolefin-based resin tube is the tensile elongation at break in the circumferential direction (tb).
By stretching to be larger than h), the internal pressure resistance and the earth pressure resistance can be improved, and the deformation followability of the pipe can be maintained.

Specifically, it is preferable that (tensile elongation at break (tba) in the axial direction) / (tensile elongation at break (tbh) in the circumferential direction) is 1 or more and 8 or less. .
That is, when (axial tensile elongation at break (tba)) / (tensile elongation at break in circumferential direction (tbh)) is less than 1, the tensile elongation at break (tba) in the axial direction becomes too low. Deformation followability of the pipe is remarkably lowered, and the pipe tends to be easily broken in the axial direction when an earthquake, a ground crack, or the like occurs. On the other hand, (axial tensile elongation at break (tba)) /
In order for the tensile elongation at break (tbh) in the circumferential direction to exceed 8, it is necessary to stretch the film in the circumferential direction significantly as compared with the axial direction.
Deformation followability of the pipe is impaired, and the pipe tends to break easily when an earthquake, a ground crack, or the like occurs.

More specifically, the tensile elongation at break in the axial direction is preferably 200% or more. In other words, if the tensile elongation at break in the axial direction is less than 200%, the pipe may be broken due to poor deformation followability of the pipe when an earthquake occurs when the polyolefin resin pipe is buried. There is.

Further, the tensile elongation at break in the circumferential direction does not significantly affect the earthquake resistance as compared with the tensile elongation at break in the axial direction, and therefore may be lower than the tensile elongation at break in the axial direction.
It is sufficient if it is within the above range. If the tensile elongation at break in the circumferential direction is less than 20%, the tube is excessively stretched, so that the deformation followability of the pipe may be impaired.

As used herein, the term “tensile elongation at break” refers to the JIS from the obtained biaxially oriented polyolefin resin pipe in the circumferential direction and the axial direction, respectively.
This is a numerical value calculated by the following equation (4) when a dumbbell-shaped test piece in accordance with K6774 is cut out and subjected to a tensile test in accordance with JIS K7113.

[0040]

(Equation 4) (In the formula (4), L is the length of the central portion at the moment when the stress is gradually applied to the dumbbell-shaped test piece having a narrow central portion and the test piece is broken, and L ₀ is the dumbbell-shaped test piece. Length of the central part before applying stress to No. 2 test piece (JISK
3315 ± 2 mm for 7115).

Further, as set forth in claim 10, the biaxially oriented polyolefin resin pipe has a structure in which the tensile elongation at break (tba) in the axial direction is larger than the tensile elongation at break (tbh) in the circumferential direction. In addition to the above, when the structure is such that the tensile yield strength (tyh) in the circumferential direction is larger than the tensile yield strength (tya) in the axial direction, the internal pressure resistance and the soil resistance of the obtained pipe are further increased. The pressure property can be improved.

Specifically, as shown in claim 13,
It is preferable that ((tensile yield strength in the circumferential direction (tyh)) / (tensile yield strength in the axial direction (tya)) is 1 or more and 8 or less.
h)) / (Axial tensile yield strength (tya)) is less than 1, the tensile yield strength (tyh) in the circumferential direction is too low. When this occurs, the pipe tends to break easily in the axial direction. On the other hand, in order for ((tensile yield strength in the circumferential direction (tyh)) / (tensile yield strength in the axial direction (tya)) to exceed 8, it is necessary to remarkably stretch in the circumferential direction as compared with the axial direction. Therefore, this remarkable stretching in the circumferential direction impairs the ability of the pipe to follow the deformation and tends to cause the pipe to be easily broken in the axial direction when an earthquake, a ground crack, or the like occurs.

More specifically, the polyolefin resin is
When it is a high-density polyethylene resin, the tensile yield strength in the axial direction is 25 MPa or more and 200 MPa or less, the tensile yield strength in the circumferential direction is 25 MPa or more and 100 MPa or less, and the tensile elongation at break in the circumferential direction is 20% or more.
The tensile elongation at break in the axial direction is preferably 100% or more. That is, when the range of the tensile yield strength and the tensile elongation at break in the axial direction and the circumferential direction deviates from the range of the above-described conditions, when the high-density polyethylene resin is embedded, the axial direction of the pipe and The balance between the tensile yield strength and the tensile elongation at break in the circumferential direction is deteriorated, and in the case of an earthquake, the pipe may be broken or the internal pressure resistance and the earth pressure resistance may be deteriorated.

As used herein, the term “tensile yield strength” refers to the JIS from the obtained biaxially oriented polyolefin resin pipe in the circumferential direction and the axial direction, respectively.
This is a numerical value calculated by the following equation (5) when a dumbbell-shaped test piece according to K6774 is cut out and subjected to a tensile test according to JIS K7113.

[0045]

(Equation 5) (Here, F is the moment when stress is gradually applied to a dumbbell-shaped test piece having a narrow central portion, and when this test piece is pulled, the increase in elongation is observed without increasing the load. And A is the original minimum cross-sectional area of the specimen).

Examples of the polyolefin resin forming the polyolefin resin tube in the present invention include polyolefin polymers such as polyethylene, polypropylene and polybutene, and polyolefin copolymers such as ethylene-propylene copolymer.

The polyethylene includes high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). Of course, the method for producing polyethylene is not particularly limited, and polyethylene polymerized by using a high-pressure radical polymerization method, a Ziegler-Natta catalyst, a Philip catalyst, a metallocene catalyst, or the like can be used.

Examples of the polypropylene include homopolypropylene, random polypropylene, block polypropylene and the like. Further, resins having different stereoregularities may be used.

Examples of the polyolefin copolymer include, in addition to the above, copolymers obtained by copolymerizing α-olefin, butadiene, vinyl acetate, (meth) acrylic acid, (meth) acrylic acid derivative, styrene, styrene derivative and the like. Copolymers obtained by graft modification of maleic anhydride, itaconic acid, etc., other ionomers, EVAL and the like can be mentioned. The α-olefin has 3 to 12 carbon atoms.
The following are preferred, and specifically, propylene, 1-
Butene, 4-methyl-1-pentene, 1-hexene, 1
-Octene and the like.

Among these, it is preferable to use a polyethylene resin as the polyolefin resin from the viewpoint that it has been conventionally used as a tube and can be oriented at a high magnification. Among the polyethylene resins, high-density polyethylene is preferred from the viewpoint that creep resistance is maintained.

The weight-average molecular weight and molecular weight distribution (= weight-average molecular weight / number-average molecular weight) of the polyolefin resin are not particularly limited, but the weight-average molecular weight is from 30,000 to 1,000.
It is preferably 10,000 or less, more preferably 50,000 or more and 1,000,000 or less. The molecular weight distribution is preferably 2 or more and 80 or less, and 3 or more and 4 or less.
0 or less is more preferable. Polyolefin polymer and polyolefin copolymer may be used alone, but to improve orientation, moldability, durability, etc., the molecular weight,
A polyolefin resin may be obtained by mixing two or more kinds of polyolefin polymers or polyolefin copolymers having different melting points, molecular weight distributions, and composition distributions. Further, the tube may be a laminated tube, and each layer may be formed of a polyolefin polymer or a polyolefin copolymer having different molecular weights, melting points, molecular weight distributions, and composition distributions. For example, the oxygen permeability of the polyolefin-based resin tube can be reduced by forming the polyolefin-based resin tube into a multilayer structure and using a resin having a high oxygen barrier property for the intermediate layer.

Further, as long as the degree of orientation in the present invention is not adversely affected, a part of the polyolefin resin may be crosslinked before or after the stretching, and a resin other than the polyolefin resin may be mixed and used. The crosslinking method is not particularly limited,
For example, physical cross-linking methods such as electron beam cross-linking, photo cross-linking, and plasma cross-linking, and chemical cross-linking using chemical cross-linking agents such as peroxides such as peroxides, silane cross-linking agents, and polyfunctional monomers. Is mentioned. Needless to say, a reaction aid, a catalyst, and a decomposition inhibitor may be used to promote the crosslinking, and these may be mixed with the polyolefin resin as long as they do not adversely affect the orientation of the tube.

The polyolefin resin may contain any additive as long as it does not adversely affect the orientation of the tube. Examples of the additive include an antioxidant, a weathering agent, an ultraviolet absorber, a lubricant, a flame retardant, and an antistatic agent. In addition to these, by adding a crystal nucleating agent to the polyolefin resin, the crystal of the polyolefin resin may be refined to make the properties uniform. Similarly, the polyolefin resin may contain a filler. As fillers that can be used, in addition to fibrous fillers such as glass fiber, carbon fiber, and asbestos, talc, mica, plate-like particles such as acid salts of layered bodies such as smectite, aluminum hydroxide, calcium carbonate, titanium oxide, and the like Spherical particles and ground particles. Further, the polyolefin resin may be colored with a pigment, a dye or the like as needed. Of course, printing or decoration may be performed on the surface of the tube.

Next, a method for producing a polyolefin resin tube according to the present invention will be described. First, a raw tube (a billet) is formed from a polyolefin resin. This means that the polyolefin resin is melt-kneaded inside the extruder, the polyolefin resin is molded into a tube through a tube manufacturing mold attached to the extruder tip, and then the tubular polyolefin resin extruded from the mold is pulled by a take-off machine. While cooling in a water tank or the like, it is achieved by cutting to a predetermined length with a cutting machine.

Next, the method of stretching the billet to orient the polyolefin molecules of the tube in the circumferential direction and the axial direction is not particularly limited, and the simultaneous biaxial stretching method in the circumferential direction and the axial direction, Although any of the sequential stretching methods in which stretching is performed and then stretching in the axial direction may be used, the simultaneous biaxial stretching method is preferred from the viewpoint that the stretching step can be simplified.
The simultaneous biaxial stretching includes (1) a pressure fluid method, (2) a die mandrel method, (3) a mandrel method, and (4) a solid extrusion method.

In the pressure fluid method (1), the billet is pressed from the inside to the outside by using a pressurized fluid such as compressed air from the inside of the pipe to extend in the circumferential direction, and hydraulic pressure is applied to both ends of the pipe. This is a method in which the pipe is stretched in the axial direction by attaching a pulling device.

In the die mandrel method (2), after the pipe is advanced on the surface of the cone-shaped mandrel whose diameter increases, the pipe is pulled from the tip while being in close contact with the mandrel by a tension device using hydraulic pressure or the like. This is a method in which the inner diameter of the tube is expanded to simultaneously extend in the circumferential direction and the axial direction. In this method, it is preferable to combine a die that is fitted onto the mandrel so as to sandwich a space (clearance) corresponding to the thickness of the obtained pipe.

In the mandrel method (3), a pipe is advanced on the surface of a cone-shaped mandrel whose diameter increases, and then pulled from the tip while being in close contact with the mandrel by a tension device using hydraulic pressure or the like. This is a method in which the inner diameter of the tube is increased and the tube is simultaneously stretched in the circumferential direction and the axial direction.
In the solid extrusion method (4), the pipe is advanced on the surface of a cone-shaped mandrel whose diameter is increasing, and then pushed into the mandrel from the rear while the pipe is brought into close contact with the mandrel by an extruder using hydraulic pressure or the like. This is a method in which the inner diameter of the tube is increased and the tube is simultaneously stretched in the circumferential direction and the axial direction. In this method, it is preferable to combine the dies as described above.

In the pressure fluid method (1), it is necessary to pressurize the fluid to a very high pressure when increasing the thickness of the billet and securing the thickness of the drawn tube. Also, (2)
Die mandrel method and (3) mandrel method
Stretching in the axial direction is easier than stretching in the circumferential direction, so that the degree of orientation in the axial direction increases. The solid extrusion method (4) is preferred. In addition, you may extend | stretch by methods other than this, for example, rolling.

Usually, when the tube is drawn, the tube is heated. The heating temperature is equal to or higher than the glass transition temperature (melting point + 50).
It is set below ℃. Specifically, the melting point is preferably from (melting point−50) ° C. to (melting point + 50) ° C. or less. That is, if the temperature is lower than (melting point−50) ° C., the heating is too insufficient, and it is extremely difficult to stretch the polyolefin resin. On the other hand, if it exceeds (melting point + 50) ° C,
It is extremely difficult to express the strength by fixing the orientation. From the viewpoints of the capability of the stretching apparatus, the uniformity of orientation, the improvement of the strength, and the productivity, the melting point is not less than (melting point−40) ° C. (melting point + 4
0) It is preferred to orient the tube at a temperature below 0 ° C.

The outer diameter, inner diameter, and thickness of the obtained biaxially stretched polyolefin resin tube are not particularly limited as long as the outer diameter is 100 times or less the thickness, as described above. The wall thickness t of the polyolefin resin tube is 0.5
mm to 50 mm, preferably 1 mm to 30 mm
The following is more preferable, and the range of 2 mm to 25 mm is particularly preferable.

By stretching as described above, the biaxially oriented polyolefin resin tube according to the present invention, in which the polyolefin molecules are oriented in the axial direction and the circumferential direction, can be obtained. The biaxially oriented polyolefin-based resin tube according to the present invention comprises:
Conventionally, it is used not only as a transport pipe such as water pipe, hot water pipe, gas pipe, water pipe, sewer pipe, plant pipe, agricultural sewage pipe, etc., but also as a protection pipe provided around optical fiber, electric wire, etc., or canned It can be used as a storage tube for storing therein a bottle or the like.

The obtained biaxially oriented polyolefin-based resin tube may be subjected to post-treatments such as annealing and post-crosslinking in order to further improve the quality by improving the dimensional stability and creep resistance. When annealing is performed, it is preferable to perform annealing at a temperature equal to or lower than the melting point of the polyolefin resin.

It is preferable that the obtained biaxially oriented polyolefin resin tube is subjected to a receiving port process, a bending process, a boring process, or the like to improve workability as a tube. Further, a plurality of biaxially oriented polyolefin-based resin tubes may be joined. Examples of the joining method include EF (Electrofusion) fusion, BUTT fusion, rotational joining, socket joining, flange joining (bolt fastening), and the like.

In the present invention, when high-density polyethylene is used as the polyolefin-based resin material, when producing a biaxially oriented high-density polyethylene tube oriented in the axial direction and the circumferential direction, the high-density polyethylene is used. The raw polyethylene resin tube is prepared such that (the stretching ratio of the inner circumference of the raw tube / the stretching ratio of the outer circumference of the raw tube) is in the range of 1 to 10 and the average of the average circumferential stretching ratio is 1 to 20 times. It is preferable to produce a biaxially oriented high-density polyethylene pipe by performing stretching so as to satisfy the conditions within the range of 1 to 3 times. That is, when a biaxially oriented high-density polyethylene pipe is manufactured so as to satisfy the above conditions, a biaxially oriented polyethylene pipe having sufficient seismic resistance and deformation followability as a buried pipe and having sufficient internal pressure strength is obtained. It is preferable because it can be manufactured.

In the above manufacturing method, each draw ratio is as follows: l ₁ : inner circumferential length of the original tube before stretching, l ₂ : inner circumferential length of the original tube after stretching, L ₁ : original length before stretching. Pipe circumference length, L
₂ : Assuming the outer circumferential length of the drawn tube after drawing, inner circumferential draw ratio: l ₂ / l ₁ , outer circumferential draw ratio: L ₂ / L ₁ , average circumferential draw ratio: (l ₂ / l ₁ + L) ₂ / L ₁ ) / 2,
Axial stretch ratio: defining and so ^{_{(L 1 2 -l 1 2)}} / (L 2 2 -l 2 2). For example, when the cross-sectional shapes of the original tube and the drawn tube are circular, d ₁ : the inner diameter of the drawn tube before drawing, d ₂ : the inner diameter of the drawn tube after drawing, and D ₁ : the drawn tube before drawing. Outer diameter, D ₂ : when taken as the outer diameter of the drawn tube after stretching, inner circumference stretching ratio: d ₂ / d ₁ , outer circumference stretching ratio: D ₂
/ D ₁ , average stretching ratio in the circumferential direction: (d ₂ / d ₁ + D ₂ / D
₁₎ / 2, the axial stretch ^{_{ratio: (D 1 2 -d 1 2}} ) / (D 2 2 -
d _{² 2)} is defined as that.

[0067]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) A first embodiment according to the present invention
In the biaxially oriented polyolefin tube A according to the embodiment, the degree of orientation in the circumferential direction is larger than the degree of orientation in the axial direction, and (refractive index in the circumferential direction (nh)> refractive index in the axial direction (na)), ( Circumferential refractive index (nh) −non-oriented refractive index (nn) ≧
0.004), (0.004 ≦ (refractive index (n
h) -axial refractive index (na) / (circumferential refractive index (nh)) ≦ 0.03), (circumferential tensile modulus (tm)
h)> tensile modulus in the axial direction (tma)), (1 ≦ (tensile modulus in the circumferential direction (tmh)) / (tensile modulus in the axial direction (tma)) ≦ 8), (0.5 GPa ≦ perimeter) Tensile elastic modulus in the direction (tmh) ≦ 20 GPa), (0.5 GPa ≦ axial tensile elastic modulus (tma) ≦ 20 GPa), (circumferential bending elastic modulus (mfh)> axial bending elastic modulus (mf)
a)), (1 ≦ (bending elastic modulus in circumferential direction (mfh)) /
(Axial flexural modulus (mfa)) ≦ 8), (0.5G
Pa ≦ bending elastic modulus in the circumferential direction (mfh) ≦ 20 GPa),
(0.5 GPa ≦ axial bending elastic modulus (mfa) ≦ 10
GPa), (tensile rupture elongation in the axial direction (tba)> tensile rupture elongation in the circumferential direction (tbh)), (1 ≦ ((tensile rupture elongation in the axial direction (tba)) / (tensile rupture in the circumferential direction) Elongation (tb
h)) ≦ 8), (200% ≦ axial tensile elongation at break (t
ba)), (20% ≦ tensile elongation at break in circumferential direction (tbh)
≦ 500%), (Axial tensile yield strength (tya)
<(Circumferential tensile yield strength (tyh)), (1 ≦ ((Circumferential tensile yield strength (tyh)) / (Axial tensile yield strength (tya))) ≦ 8) .

The biaxially oriented polyolefin tube A
Can be produced, for example, using a stretching apparatus 1 for stretching by a solid extrusion method as shown in FIG. That is, the stretching device 1 includes a plunger 11 and a die 12
And a mandrel 13.

The die 12 has a cylindrical shape having a billet insertion portion 12a on one side into which the billet 2 serving as a raw material tube is inserted, and a diameter increasing portion 12b on the other side expanding in a trumpet shape. The mandrel 13 faces the inside of the enlarged diameter portion 12b of the die 12, and is located between the outer peripheral surface and the inner peripheral surface of the enlarged diameter portion 12b of the die 12.
An extension passage 14 is formed.

In the stretching passage 14, the distance between the outer peripheral surface of the mandrel 13 and the inner peripheral surface of the enlarged diameter portion 12b of the die 12 gradually narrows from the billet insertion portion 12a toward the outlet of the enlarged diameter portion 12b. ing. In the plunger 11, the plunger body 11a has an outer diameter substantially the same as the inner diameter of the billet insertion portion 12a, and can be moved into and out of the billet insertion portion 12a by a hydraulic device (not shown).

Then, the biaxially oriented polyolefin tube A is
It can be manufactured as follows using this stretching apparatus 1. That is, first, the plunger 11 is retracted to the hydraulic device side to make the inlet of the billet insertion portion 12a open, and the billet 2 is set in the billet insertion portion 12a as shown in FIG.

Next, the plunger 11 is advanced in the direction of the die 2 so that the tip of the plunger body 11a is pressed against the rear end of the billet 2. Further, the plunger body 11a of the plunger 11 is pressed into the billet insertion portion 12a by a hydraulic device, and the billet 2 is stretched in the circumferential direction and the axial direction by the stretching passage to obtain the biaxially oriented polyolefin pipe A as described above. .

Since the biaxially oriented polyolefin tube A obtained as described above has a degree of circumferential orientation larger than that of the axial direction, the polyolefin crystals of the tube are oriented in the circumferential direction and the axial direction, respectively. In addition, the slippage of the crystal plane makes it possible to achieve both improvement in the elastic modulus and securing the deformability of the tube with respect to external stress.

More specifically, the elasticity in the circumferential direction is stronger than the elasticity in the axial direction, whereby the internal pressure applied to the pipe from the fluid flowing inside the pipe, and from the soil around the pipe when the pipe is buried, is applied. Can withstand the earth pressure. That is, the internal pressure resistance and the earth pressure resistance are improved.

Moreover, the ability of the polyolefin pipe to follow the deformation of the pipe against external stress, which is an advantage of the polyolefin pipe, is not significantly impaired, so that even if the buried pipe according to the present invention is subjected to an earthquake, the pipe will not move in the axial direction. Can be plastically deformed,
Does not break.

In particular, the refractive index (nh) in the circumferential direction is larger than the refractive index (na) in the axial direction and the refractive index (n
Since h) is 0.004 or more larger than the refractive index (nn) in the non-aligned state, the elasticity in the circumferential direction can be sufficiently improved, and the deformation followability of the tube can be sufficiently secured without lowering. .

Further, since (refractive index in the circumferential direction (nh) −refractive index in the axial direction (na)) / (refractive index in the circumferential direction (nh)) is 0.004 or more and 0.03 or less, In addition, the elasticity in the circumferential direction can be sufficiently improved, and the deformation followability of the tube can be sufficiently ensured without lowering, so that the balance between the elasticity of the tube and the deformation followability is excellent.

Since the tensile elastic modulus in the circumferential direction is larger than the tensile elastic modulus in the axial direction, the internal pressure resistance can be improved, and the deformability of the polyolefin tube, which is an advantage of the polyolefin tube, can be maintained. be able to. Further, since each tensile modulus is within the above-mentioned predetermined range, it is possible to improve the internal pressure resistance and maintain the deformation followability of the pipe very well.

Similarly, since the bending elastic modulus in the circumferential direction is larger than the bending elastic modulus in the axial direction, the earth pressure resistance can be improved and the deformation followability of the pipe can be maintained. In addition, since each bending elastic modulus is within the above-mentioned predetermined range, it is possible to improve the earth pressure resistance and maintain the deformation followability of the pipe extremely well.

Further, the tensile elongation at break in the axial direction (tba)
Is greater than the tensile elongation at break (tbh) in the circumferential direction,
The internal pressure resistance and the earth pressure resistance can be improved, and the deformation followability of the pipe can be maintained. In addition, since each tensile elongation at break is within the above-mentioned predetermined range, the internal pressure resistance and the earth pressure resistance can be improved and the deformation followability of the pipe can be maintained extremely well.

In addition, the tensile yield strength in the circumferential direction (tyh)
Is greater than the tensile yield strength (tya) in the axial direction,
The balance with the tensile elongation at break in the obtained pipe is improved, and the internal pressure resistance and the earth pressure resistance can be further improved, and the deformation followability of the pipe can be maintained more favorably. Further, since each tensile yield strength is within the above-mentioned predetermined range, it is possible to improve the internal pressure resistance and the earth pressure resistance and maintain the deformability of the pipe extremely well.

When the billet 2 serving as the raw material tube is a high-density polyethylene resin raw tube, the conditions for biaxially orienting the high-density polyethylene resin raw tube are as follows.
(Drawing ratio of inner circumference of raw tube / drawing ratio of outer circumference of raw tube) is 1
When the manufacturing method is performed in which the stretching is performed so that the average stretching ratio in the circumferential direction is in the range of 1 to 3 times, the internal pressure strength and the deformation followability are excellent.
An axially oriented high density polyethylene tube can be manufactured.

(Second Embodiment) A second embodiment according to the present invention
In the biaxially oriented polyolefin tube B of the embodiment, at least a part of the polyolefin resin constituting the tube is crosslinked, the gel fraction is 10% or more and 70% or less, and the density is 0.1% or less.
It is polyethylene of 940 g / cm ³ or more and 0.980 g / cm ³ or less, and the degree of orientation in the circumferential direction is larger than the degree of orientation in the axial direction. (Refractive index in the circumferential direction (nh)> refractive index in the axial direction (na )), (Circumferential refractive index (nh) −non-oriented refractive index (nn) ≧ 0.004), (0.004 ≦
(Refractive index in circumferential direction (nh)-Refractive index in axial direction (na))
/ (Circumferential refractive index (nh)) ≦ 0.03), (circumferential tensile modulus (tmh)> axial tensile modulus (tm)
a)), (1 ≦ (tensile modulus in circumferential direction (tmh)) /
(Axial tensile modulus (tma)) ≦ 8), (0.5G
Pa ≦ tensile elastic modulus in the circumferential direction (tmh) ≦ 20 GPa),
(0.5 GPa ≦ axial tensile modulus (tma) ≦ 20
GPa), (Bending elastic modulus in circumferential direction (mfh)> Bending elastic modulus in axial direction (mfa)), (1 ≦ (Bending elastic modulus in circumferential direction (mfh)) / (Bending elastic modulus in axial direction (mfa)) ) ≤
8), (0.5 GPa ≦ bending elastic modulus in circumferential direction (mfh)
≦ 20 GPa), (0.5 GPa ≦ axial flexural modulus (mfa) ≦ 10 GPa), (axial tensile elongation at break (tba)> tensile elongation at break in peripheral direction (tbh)), (1
≦ ((tensile elongation at break in axial direction (tba)) / (tensile elongation at break in circumferential direction (tbh)) ≦ 8), (200% ≦ tensile elongation at break in axial direction (tba)), (20% ≤ circumferential tensile elongation at break (tbh) ≤ 500% or less, (axial tensile yield strength (tya) <(circumferential tensile yield strength (ty)
h)), (1 ≦ ((tensile yield strength in circumferential direction (tyh)))
/ (Axial tensile yield strength (tya)) ≦ 8.

The biaxially oriented polyolefin tube B
Can be manufactured, for example, using a stretching apparatus 3 using a fluid pressure method as shown in FIG. That is,
The stretching device 3 includes an outer diameter regulating type 31 and pipe chucks 32 and 32.

The outside diameter regulating type 31 regulates the billet 2 to be stretched to have a predetermined outside diameter when the billet 2 to be stretched is expanded outward, and is provided with a heater (not shown). The billet 2 can be heated from the outside by this heater. Pipe chuck 32,
The gripper 32 grips both ends of the billet 2. When the motor 34 is turned on, the billet 2 is pulled from both sides to extend in the axial direction, and the billet 2 is fed from the gas transport pipe 33. The pressurized and heated gas thus obtained is pressed into the billet 2 so that the billet 2 is stretched in the circumferential direction.

The pipe chuck 32 has an air seal structure in the grip portion of the billet 2 so that gas sent from the gas transport pipe 33 to the pipe chuck 32 can be supplied into the billet 2 without leaking. Then, the biaxially oriented polyolefin tube B can be manufactured using the stretching device 3 as follows.

That is, first, both ends of the billet 2 are gripped by the pipe chucks 32 on both sides. Next, the billet 2 is heated from the gas transport pipe 33 to the billet 2 through the pipe chuck 32 while the billet 2 is heated to a temperature not lower than (the melting point of the resin−50 ° C.) and not higher than the melting point + 50 ° C. The heated gas is press-fitted into the billet 2 to expand the diameter of the billet 2, that is, stretched and oriented in the circumferential direction.
Is pulled to both sides and stretched and oriented in the axial direction to obtain a biaxially oriented polyolefin tube B.

The biaxially oriented polyolefin tube B thus obtained has the same effects as the biaxially oriented polyolefin tube A, and has an amorphous polyethylene having a low tensile resistance because the polyethylene resin is crosslinked. The molecular chains in the parts are cross-linked to each other. For this reason, even when the polyolefin resin is pulled, these molecular chains do not extend so as to slip each other, and the deformability of the obtained biaxially oriented polyolefin tube can be further improved. In other words, when stretched and oriented sufficiently, a phenomenon in which the pipe peels in the thickness direction may be observed, which is not very desirable from the viewpoint of earthquake resistance. Can be prevented.

Further, when the density of the resin is 0.940 g / cm
^{Since it is 3} or more and 0.980 g / cm ³ or less, it is possible to more reliably prevent the molecular chains from being excessively crosslinked even in the amorphous portion, and that the deformation followability is rather reduced. The deformability of the obtained biaxially oriented polypropylene tube can be more reliably improved.

The biaxially oriented polyolefin pipe according to the present invention is not limited to the above embodiment. For example, in the above embodiment, the biaxially oriented polypropylene tube A is manufactured by the stretching device 1 using the solid extrusion method, and the biaxially oriented polypropylene tube B is manufactured by the stretching device 3 using the fluid pressure method. The biaxially oriented polypropylene tube B can be produced by the stretching device 1 and the biaxially oriented polypropylene tube A can be produced by the stretching device 3.

[0092]

The present invention will be described in detail below with reference to the following examples, which are used for illustrative purposes only.
It should not be used for limiting purposes.

First, billets I to XII as raw material tubes were prepared as follows. (Billet I) High density polyethylene resin (Asahi Kasei Co., Ltd.,
Product name: "Suntech HD-QB780", density: 0.
953 g / cc, MFR: 0.03 g / 10 min, weight average molecular weight: about 268,000, melting point 132 ° C.) using a no-vent type single screw extruder (cylinder diameter 65 mm, L / D = 3)
0), the mixture is melt-kneaded at 220 ° C. and extruded from a tube-making mold provided at the tip of the extruder to obtain an outer diameter of 8
A billet I having a size of 9.0 mm and an inner diameter of 29.0 mm was produced.

(Billet II) Outer diameter 89.0 mm, inner diameter 1
A billet II was prepared in the same manner as the billet I except that the thickness was 4.0 mm.

(Billet III) Billet III was prepared in the same manner as billet I except that the outer diameter was 89.0 mm and the inner diameter was 66.0 mm. (Billet IV) A billet IV was prepared in the same manner as in the above billet I, except that the outer diameter was 89.0 mm and the inner diameter was 12.0 mm. (Billet V) A billet V was prepared in the same manner as billet I except that the outer diameter was 89.0 mm and the inner diameter was 44.0 mm.

(Billet VI) High-density polyethylene resin (manufactured by Asahi Kasei Corporation, trade name: "Suntech HD-QB78")
0 ", density: 0.953 g / cc, MFR: 0.03 g
/ 10 min, weight average molecular weight: about 268,000, melting point 13
2C), high-density polyethylene resin (manufactured by Nippon Polychem Co., Ltd., trade name: Novatec HD-HR120R),
Density 0.934 g / cc, MFR: 0.19 g / 10
Min, weight average molecular weight: about 216000, melting point 132 ° C)
And an outer diameter of 89.0 mm and an inner diameter of 44.0 m
billet V in the same manner as billet I except that
I was made. (Billette VII) High-density polyethylene resin (manufactured by Asahi Kasei Corporation, trade name: "Suntech HD-QB780", density:
0.953 g / cc, MFR: 0.03 g / 10 min, weight average molecular weight: about 268000, melting point: 132 ° C.) Instead of high-density polyethylene resin (manufactured by Nippon Polychem Co., Ltd., trade name: Novatec HD-HB530), Density 0.964
g / cc, MFR: 0.3 g / 10 min, melting point 136 ° C)
Other than using, billet VII in the same manner as billet I
Was prepared.

(Billet VIII) High-density polyethylene resin (manufactured by Asahi Kasei Corporation, trade name: "Suntech HD-QB78")
0 ", density: 0.953 g / cc, MFR: 0.03 g
/ 10 min, weight average molecular weight: about 268,000, melting point 13
2C), polypropylene resin (manufactured by Nippon Polychem Co., Ltd., trade name: Novatec PP-EC9, density 0.9)
g / cc, MFR: 0.5 g / 10 min), except that billet I was used to produce billet VIII. (Billet IX) A billet IX was prepared in the same manner as in the above billet I, except that the outer diameter was 89.0 mm and the inner diameter was 62.0 mm. (Billet X) High-density polyethylene resin (manufactured by Asahi Kasei Corporation,
Product name: "Suntech HD-QB780", density: 0.
953 g / cc, MFR: 0.03 g / 10 min, weight average molecular weight: about 268,000, melting point: 132 ° C.) 100 parts by weight, 0.5 part by weight of trivinylmethoxysilane and 0.04 part by weight of 2, Billet X was prepared in the same manner as billet I except that 5-dimethyl-2,5-bis-t-butyloxyhexane was added, and the outer diameter was 89.00 mm and the inner diameter was 14.0 mm. (Billet XI) High-density polyethylene resin (manufactured by Asahi Kasei Corporation, trade name: "Suntech HD-QB780", density:
0.953 g / cc, MFR: 0.03 g / 10 min, weight average molecular weight: about 268,000, melting point: 132 ° C.) Instead of high-density polyethylene resin (manufactured by Nippon Polychem Co., Ltd., trade name: Novatec HD-HR120R), Density 0.93
Billet XI was prepared in the same manner as billet I except that 4 g / cc, MFR: 0.19 g / 10 min, weight average molecular weight: about 216,000, melting point: 132 ° C.).

(Billet XII) Polyethylene resin (manufactured by Asahi Kasei Corporation, trade name: "Suntech HD (grade:
QB780) ", density: 0.953 g / cc, MFR:
0.03 g / 10 min, weight average molecular weight: about 26800
0, melting point 132 ° C.) using a no-vent type single screw extruder (cylinder diameter 65 mm, L / D = 30) at 220 ° C. and kneading at 40 ° C./kg from a tube manufacturing mold provided at the tip of the extruder. extruding at an extrusion rate of hr.
A solid cylinder of 0 mm was made and its inner diameter was 8.6 mm
Into a billet.

(Billet XIII) A billet having an outer diameter of 30 mm and an inner diameter of 5.6 mm was prepared in the same manner as in billet XII except that the inner diameter was cut to 5.6 mm. (Billet XIV) A billet having an outer diameter of 30 mm and an inner diameter of 5.4 mm was produced in the same manner as in billet XII except that the inner diameter was cut to 5.4 mm.

(Example 1) A stretching device 4 having the following dimensions as shown in FIG. 3 was prepared. Note that FIG.
Reference numeral 41 denotes a die, 42 denotes a mandrel, and 43 denotes a pressing device. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 156.8 mm D ₃ = 89.0 mm Next, billet I produced as described above was heated to 125 ° C. in a gear oven. After that, mandrel 42
And the temperature of the die 41 were set at 125 ° C. in the billet insertion section 44 of the stretching apparatus 4.

Then, the mandrel 42 and the die 4 were pressed while applying 20 tons of force to the billet I by the pressing device 43.
1 and stretched at a rate of 100 mm / min to orient the polyethylene molecules in the circumferential direction and the axial direction, respectively, to form a non-crosslinking type having an outer diameter of 156.8 mm and an inner diameter of 145.0 mm. A biaxially oriented polyethylene tube was obtained as a sample tube.

(Example 2) Example 1 was repeated except that a stretching device 4 as shown in FIG. 3 having the following dimensions was used.
In the same manner as described above, the outer diameter is 153.0 mm and the inner diameter is 145.0 m
m was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 153.0 mm D ₃ = 89.0 mm

Example 3 An outer diameter of 162.0 mm and an inner diameter of 16 mm were used in the same manner as in Example 1 except that a stretching device 4 and a billet II as shown in FIG. A 145.0 mm non-crosslinked biaxially oriented polyethylene tube was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 162.0 mm D ₃ = 89.0 mm

(Example 4) An outer diameter of 153.0 mm was obtained in the same manner as in Example 1 except that a stretching device 4 as shown in FIG. 3 and a billet III having dimensions as described below were used.
A non-crosslinked biaxially oriented polyethylene tube having an inner diameter of 145.0 mm was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 153.0 mm D ₃ = 89.0 mm

Example 5 An outer diameter of 166.0 mm and an inner diameter of 145 were obtained in the same manner as in Example 1 except that a drawing device as shown in FIG. 1 and a billet IV having the following dimensions were used. A non-crosslinked biaxially oriented polyethylene tube of 0.0 mm was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 166.0 mm D ₃ = 89.0 mm

Example 6 An outer diameter of 154.0 mm and an inner diameter of 15 mm were used in the same manner as in Example 1 except that a drawing device 4 and a billet V as shown in FIG. A 145.0 mm non-crosslinked biaxially oriented polyethylene tube was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 154.0 mm D ₃ = 89.0 mm

(Example 7) A stretching apparatus 4 having the following dimensions and a billet VI as shown in FIG. 3 were used, and the billet VI was heated to 110 ° C. in a gear oven. A non-crosslinked biaxially oriented polyethylene tube having an outer diameter of 156.8 mm and an inner diameter of 145.0 mm was obtained as a sample tube in the same manner as in Example 1 except that the temperature and the temperature of the die 41 were set to 110 ° C. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 156.8 mm D ₃ = 89.0 mm

(Example 8) An outer diameter of 156.8 mm was obtained in the same manner as in Example 1 except that a stretching device 4 as shown in FIG. 3 and a billet VII were used as shown in FIG.
A non-crosslinked biaxially oriented polyethylene pipe having an inner diameter of 145.0 mm was obtained as a sample pipe. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 156.8 mm D ₃ = 89.0 mm

(Embodiment 9) The temperature of the mandrel 42 and the temperature of the die 41 are set to 140 ° C. by using a stretching apparatus 4 as shown in FIG. After heating the produced billet VIII to 140 ° C. in a gear oven, a non-crosslinked biaxially oriented polypropylene tube was obtained as a sample tube in the same manner as in Example 1. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 156.8 mm D ₃ = 89.0 mm

(Embodiment 10) The dimensions of each part shown in FIG.
The following stretching apparatus 10 was prepared. In FIG. 4, 130 is a die, 120 is a mandrel, and 110 is a pressing device. [Dimensions of Each Part of Stretching Apparatus] β = 30 ° d ₁ = 52.8 mm d ₂ = 56.6 mm d ₃ = 30.0 mm Next, the billet XII produced as described above was cooled to 125 ° C. in a gear oven. After heating, mandrel 12
The temperature of the die 130 and the temperature of the die 130 were set in the billet insertion part 140 of the stretching apparatus 10 set to 125 ° C.

Then, while applying 20 tons of force to the billet XII by the pressing device 110, the billet XII is pushed into the stretching passage 150 between the mandrel 120 and the die 130 to be 50 m long.
m / min to orient the polyethylene molecules in the circumferential and axial directions, respectively, so that the outer diameter is 56.6 m.
m, a biaxially oriented polyethylene tube having an inner diameter of 52.8 mm was obtained as a sample tube.

(Example 11) [0112] An outer diameter of 50.000 was obtained in the same manner as in Example 10 except that a stretching apparatus 10 and a billet XIII as shown in Fig. 4 having the following dimensions were used.
A biaxially oriented polyethylene tube having an inner diameter of 0 mm and an inner diameter of 46.0 mm was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] β = 30 ° d ₁ = 46.0 mm d ₂ = 50.0 mm d ₃ = 30.0 mm

(Comparative Example 1) A tension device was connected to the tip of the billet I without using the pressing device of the stretching device of Example 1, and the die mandrel method of pulling from the exit side of the die 41 with this tension device was used. In the same manner as in Example 1, a non-crosslinked biaxially oriented polyethylene tube was obtained as a sample tube.

(Comparative Example 2) An outer diameter of 149.0 mm and an inner diameter of 14 mm were used in the same manner as in Example 1 except that a stretching device 4 and a billet IX as shown in FIG. A 145.0 mm non-crosslinked biaxially oriented polyethylene tube was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] α = 15 ° D ₁ = 145 mm D ₂ = 149.0 mm D ₃ = 89.0 mm

(Comparative Example 3) Billet I itself was used as a sample tube of a non-oriented polyethylene tube. Comparative Example 4 Billet XII itself was used as a sample tube of a non-oriented polyethylene tube.

(Comparative Example 5) An outer diameter of 48.0 m was used in the same manner as in Example 10 except that a stretching apparatus 10 and a billet XIV as shown in FIG.
m, a biaxially oriented polyethylene tube having an inner diameter of 45.3 mm was obtained as a sample tube. [Dimensions of Each Part of Stretching Apparatus] β = 30 ° d ₁ = 45.3 mm d ₂ = 48.0 mm d ₃ = 30.0 mm

With respect to Examples 1 to 9 and Comparative Examples 1 to 3, the refractive index, tensile elastic modulus, flexural elastic modulus, tensile elongation at break, yield strength, and stretch ratio in the circumferential and axial directions were measured. The results are shown as the stretching temperature, the difference between the refractive index in the circumferential direction and the refractive index in the axial direction, the ratio of this difference to the refractive index in the circumferential direction, the outer diameter and inner diameter of the billet used, and the inner diameter and outer diameter of each tube. Are shown in Tables 1 and 2.

[0118]

[Table 1]

[0119]

[Table 2] Further, for Examples 10 and 11 and Comparative Examples 4 and 5,
The stretching ratio of the inner and outer circumferences of the obtained tube, the average stretching ratio in the circumferential and axial directions, the stretching temperature, the tensile yield strength, and the tensile elongation at break were measured.

[0120]

[Table 3] The refractive index was determined by cutting out a test piece (thickness: 0.5 mm) of about 10 mm square from the obtained tube, and using a molecular orientation meter (microwave method, manufactured by Oji Scientific Instruments, model number: MOA30)
By irradiating the test piece with a microwave of about 19 GHz using the
The refractive index in degrees (circumferential direction) was measured.

The yield strength was determined by JIS from the obtained tube.
In accordance with K 7113, when a dumbbell-shaped No. 2 test piece was cut out and pulled while gradually increasing the load at a speed of 50 mm / min, at the first point where an increase in elongation was observed without increasing the load. It means "tensile yield strength" corresponding to tensile stress. In the case where the test piece is broken by cutting or the like before the material yields, the “tensile fracture strength” corresponding to the tensile stress at the moment when the test piece breaks is defined as “yield strength” here.

Tables 1 and 2 show that Comparative Examples 1 to 3
As compared to the sample tube of Example 1, the sample tubes of Examples 1 to 9 each have a higher refractive index in the circumferential direction than the refractive index in the axial direction, and thus the polyethylene molecules are oriented higher in the circumferential direction. It is understood that there is. On the other hand, it is also oriented in the axial direction, but its degree of orientation is lower than that in the circumferential direction, so there is not much decrease in the tube's deformation followability due to the improvement in elasticity in the axial direction, which is seen in ordinary polyethylene tubes It is understood that a sufficient degree of earthquake resistance is maintained.

Examples 1 to 9 and Comparative Examples 1 and 2
In comparison with the sample tubes of Examples 1 to 9,
While the yield strength is higher in the circumferential direction than in the axial direction, the sample tubes of Comparative Examples 1 and 2 are more oriented in the axial direction than in the circumferential direction. Since the flexural modulus is larger than those in the circumferential direction, the ability of the pipe to follow the deformation is impaired, and the pipe cannot withstand a large earthquake.

As described above, since the degree of orientation and the refractive index in the circumferential direction are higher than the degree of orientation and the refractive index in the axial direction, the internal pressure applied to the pipe from the fluid flowing inside the pipe, and the pipe when the pipe is buried, It is understood that the earth pressure applied from the surrounding soil can be sufficiently withstood. On the other hand, for the same reason, the ability to follow deformation, which is the advantage of polyolefin pipes, against external stress is maintained, so that even if the buried pipe is subjected to an earthquake, the pipe may be plastically deformed in the axial direction. It is understood that it can and does not break.

Regarding the tensile modulus, the tensile modulus in the circumferential direction is higher than the tensile modulus in the axial direction. Therefore, it is understood that the biaxially oriented polyethylene pipe obtained thereby has improved internal pressure resistance. Is done. Further, since the bending elastic modulus in the circumferential direction is higher than the bending elastic modulus in the axial direction, it is understood that the biaxially oriented polyolefin pipe obtained thereby has high earth pressure resistance. In addition, since the tensile elongation at break in the axial direction is higher than the tensile elongation at break in the circumferential direction, the obtained pipe can have high internal pressure resistance and earth pressure resistance, while external stress, which is an advantage of polyolefin pipes, can be obtained. It can be understood that the deformation follow-up property to is maintained.

Similarly, since the tensile yield strength in the circumferential direction is higher than the tensile yield strength in the axial direction, in the obtained pipe, it is possible to reliably secure deformation followability with respect to external stress which is an advantage of polyolefin pipe. Is understood. The sample tubes obtained in Examples 1 to 9 not only ensured sufficient seismic performance, but also had excellent pressure resistance and had sufficient performance as a buried tube. In addition, since the thickness of the polyethylene pipe can be reduced, it can be understood that cost reduction can be achieved to obtain a biaxially oriented polyolefin pipe.

Further, according to Table 3, since the tensile yield strength (particularly in the circumferential direction) of Examples 10 and 11 is remarkably improved as compared with the unstretched pipe of Comparative Example 4,
It is understood that the buried pipe has both the necessary internal pressure strength and elongation characteristics. On the other hand, in Comparative Example 5, it is understood that since the values of the tensile yield strength in the circumferential direction and the tensile elongation at break in the axial direction are not good, it is not possible to achieve both the internal pressure strength required for the buried pipe and the elongation characteristics.

[0128]

According to the present invention, it is possible to achieve both high deformation followability and high elasticity in the circumferential direction, which are performances required when used as a buried pipe, and a biaxial orientation with high earthquake resistance. A polyolefin-based resin tube can be provided. In addition, since it is possible to achieve both deformation followability and elasticity in the circumferential direction in this way, compared to cast iron pipes, concrete pipes, etc., it can only maintain high durability for a long time against internal pressure, earth pressure, etc. In addition, by using the method according to the present invention, it is possible to increase the diameter of the pipe while reducing the thickness of the pipe, and to provide a biaxially oriented polyolefin-based resin pipe that is economically excellent.

Needless to say, two or more biaxially oriented polyolefin resin tubes according to the present invention can be used by connecting two or more, similarly to the conventional polyolefin resin tubes. Further, as in the present invention, by orienting the polyolefin molecules in the axial and circumferential directions, gas barrier properties, chemical resistance,
The surface hardness can be improved, and the present invention can be applied to uses other than conventional polyolefin resin pipes (for example, underground pipes).

When high-density polyethylene is used as the polyolefin resin, the ratio of (the stretching ratio of the inner periphery of the original tube / the stretching ratio of the outer periphery of the original tube) is in the range of 1 or more and 10 or less, and Is within the range of 1 to 20 times,
By producing a biaxially oriented high-density polyethylene pipe by stretching so that the stretching ratio in the axial direction satisfies the condition of 1 time or more and 3 times or less, the orientation acts more in the circumferential direction than in the axial direction. This makes it possible to manufacture a biaxially oriented high-density polyethylene pipe suitable as a buried pipe.

[Brief description of the drawings]

FIG. 1 is a view showing a stretching apparatus 1 for producing a biaxially oriented polyolefin tube by a solid extrusion method.

FIG. 2 is a view showing a stretching apparatus 3 for producing a biaxially oriented polyolefin tube by a pressure fluid method.

FIG. 3 is a view showing a stretching device used in Examples.

FIG. 4 is a view showing a stretching apparatus 10 for producing a biaxially oriented polyolefin tube by a solid extrusion method.

FIG. 5A is a cross-sectional view used for explaining a bending elastic modulus in a circumferential direction, and FIG. 5B is a cross-sectional view used for explaining a bending elastic modulus in an axial direction.

[Explanation of symbols]

 1, 3, 10 ... Stretching device 2: Billet 4, 11, 110 ... Hydraulic device 12, 41, 130 ... Die 13, 42, 120 ... Mandrel 31 ... Outer diameter regulation type 32 ... Pipe chuck 33 ... Gas transport tube 34 ... motor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichiro Iwasa 2-2, Kamikaba Kaminokocho, Minami-ku, Kyoto Sekisui Kagaku Kogyo Co., Ltd. (72) Inventor Keisuke Shimazaki 2-4, Nakazaki Nishi, Kita-ku, Osaka-shi −12 Sekisui Engineering Co., Ltd. F term (reference) 4F207 AA03 AA05 AE01 AG08 KA01 KA17 KF01 KW21 KW41 4F210 AA03 AA05 AE01 AG08 QA06 QC07 QG04 QG18

Claims (15)

[Claims] 1. A biaxially oriented polyolefin-based resin tube, wherein the degree of orientation in the circumferential direction is larger than the degree of orientation in the axial direction, in the biaxially oriented polyolefin-based resin tube oriented in the axial direction and the circumferential direction. 2. The refractive index (nh) in the circumferential direction is larger than the refractive index (na) in the axial direction, and the refractive index (nh) in the circumferential direction.
The biaxially oriented polyolefin-based resin tube according to claim 1, wherein is larger than the refractive index (nn) of the non-oriented state by at least 0.004. 3. The ratio of (refractive index in circumferential direction (nh) −refractive index in axial direction (na)) / (refractive index in circumferential direction (nh)) is 0.0.
2. The structure according to claim 1, wherein the value is not less than 04 and not more than 0.03.
Or the biaxially oriented polyolefin-based resin tube according to 2. 4. A biaxially oriented polyolefin resin tube oriented in the axial direction and the circumferential direction, wherein the tensile modulus in the circumferential direction (tmh) is larger than the tensile modulus in the axial direction (tma). Biaxially oriented polyolefin resin tube. 5. (Tensile modulus in circumferential direction (tmh)) /
The biaxially oriented polyolefin-based resin tube according to claim 4, wherein (axial tensile modulus (tma)) is 1 or more and 8 or less. 6. The tensile modulus in the circumferential direction (tmh) is 0.5.
The biaxially oriented polyolefin-based resin pipe according to claim 4 or 5, wherein GPa is 20 GPa or more and 20 GPa or less, and an axial tensile modulus (tma) is 0.5 GPa or more and 10 GPa or less. 7. A biaxially oriented polyolefin-based resin pipe oriented in the axial direction and the circumferential direction, wherein a circumferential flexural modulus (mfh) is larger than an axial flexural modulus (mfa). Biaxially oriented polyolefin resin tube. 8. (Bending elastic modulus in circumferential direction (mfh)) /
The biaxially oriented polyolefin-based resin tube according to claim 7, wherein (axial bending elastic modulus (mfa)) is 1 or more and 8 or less. 9. A flexural modulus in the circumferential direction (mfh) of 0.5
The biaxially oriented polyolefin-based resin tube according to claim 7 or 8, wherein GPa is 20 GPa or more and 20 GPa or less, and an axial bending elastic modulus (mfa) is 0.5 GPa or more and 10 GPa or less. 10. A biaxially oriented polyolefin-based resin tube oriented in the axial direction and the circumferential direction, wherein the tensile elongation at break (tba) in the axial direction is larger than the tensile elongation at break (tbh) in the circumferential direction. Biaxially oriented polyolefin resin tube. 11. ((axial tensile elongation at break (tb)
The biaxially oriented polyolefin resin pipe according to claim 10, wherein a)) / (tensile elongation at break in circumferential direction (tbh)) is 1 or more and 8 or less. 12. The method according to claim 2, wherein the tensile yield strength in the circumferential direction (tyh) is larger than the tensile yield strength in the axial direction (tya). An axially oriented polyolefin resin tube. 13. ((Circumferential tensile yield strength (ty)
h)) / (tensile yield strength (tya) in the axial direction) is 1 or more and 8 or less, the biaxial shaft according to any one of claims 2, 3, 10, and 11. Oriented polyolefin resin tube. 14. The biaxially oriented polyolefin resin tube according to claim 1, wherein the polyolefin resin constituting the tube is polyethylene. 15. A method for producing a biaxially oriented high-density polyethylene pipe oriented in an axial direction and a circumferential direction, wherein a raw pipe made of a high-density polyethylene resin is obtained by:
(The stretching ratio of the outer periphery of the raw tube) is in the range of 1 or more and 10 or less, the average in the circumferential direction is 1 or more and 20 or less, and the stretching ratio in the axial direction is 1 or more and 3 or less. A method for producing a biaxially oriented high-density polyethylene pipe by stretching the pipe so as to satisfy the following conditions.