WO2000021732A1

WO2000021732A1 - Biaxially oriented polyolefin pipe

Info

Publication number: WO2000021732A1
Application number: PCT/JP1999/005453
Authority: WO
Inventors: Naoki Ueda; Koutarou Tsuboi; Kouichirou Iwasa; Keisuke Shimazaki; Takehisa Sugaya
Original assignee: Sekisui Chemical Co., Ltd.
Priority date: 1998-10-13
Filing date: 1999-10-01
Publication date: 2000-04-20

Abstract

An axially and circumferentially oriented, i.e., biaxially oriented polyolefin pipe, wherein a degree of orientation thereof in the circumferential direction is set higher than that thereof in the axial direction, whereby providing a biaxially oriented pipe having an excellent elastic deformability; i.e. excellent deformation follow-up characteristics with respect to an external stress and an improved circumferential elasticity; and a high earthquake resistance which constitute performances required by this pipe when it is used as a buried pipe.

Description

Specification

Biaxially oriented polyolefin tube

Technical field

The present invention relates to a biaxially oriented polyolefin pipe, and more particularly, to a biaxially oriented polyolefin pipe having excellent deformation followability and circumferential elasticity as pipe performance required for a buried pipe, and high seismic resistance.

Background art

Conventionally, polyvinyl chloride synthetic resin pipes (PVC pipes), steel pipes, concrete pipes, etc. have been used as water distribution pipes, hot water pipes, gas pipes, water supply pipes, sewer pipes, plant pipes, etc. . In recent years, polyolefin pipes made of polyolefin resin have been rapidly spreading due to increased demand for underground pipes and the like because of their high seismic resistance and high reliability against ground deformation. For example, according to a technical report by Sekisui Chemical Co., Ltd., polyethylene pipes have a high ability to follow the deformation of the pipes (ie, elongation) against the external stresses inherent in the pipes, which causes repeated earthquake or ground deformation. It is disclosed that the polyethylene pipe buried in the ground does not break due to plastic deformation even when it is damaged.

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

Now that polyolefin pipes are widely infiltrated into the market, there is an increasing demand for improved reliability of polyolefin pipes such as deformability, circumferential elasticity, internal pressure resistance, and long-term strength. I have. In order to meet such demands, attention has been paid to oriented polyolefin tubes in which polyolefin tubes are stretched in the axial or circumferential direction to orient polyolefin molecules in a specific direction.

When the polyolefin 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 However, when the polyolefin tube is stretched in a specific direction, the elasticity in that direction is improved, so that plastic deformation by a small external force from the specific direction is eliminated, and the function as the tube can be maintained. , or it is plastically deformed: since the flame, if example embodiment, when the buried pipe encounters earthquake, Ru danger tubes resulting in broken ₀

If the polyolefin pipe is uniaxially stretched only in the axial direction, it can significantly improve the elastic modulus in the axial direction. Polyethylene pipes cannot plastically deform in the axial direction, and the pipes tend to tear in the axial direction. In addition, since it is not stretched in the circumferential direction, the strength and strength (especially elasticity) in the circumferential direction are not improved as well as the shochu properties against internal pressure and earth pressure are not improved. Polyolefin pipes are inferior in practicality and earthquake resistance. On the other hand, when stretched uniaxially only in the circumferential direction, the elastic modulus in the circumferential direction can be significantly improved, and the internal pressure applied to the pipe from the fluid flowing through the pipe and the pipe is applied to the pipe when buried underground The resistance to soil weight can be improved, but also in this case, the ability to follow the deformation of the pipe is significantly reduced by extension, and the plastic deformation in the axial direction is not possible. Inferior.

For this reason, various studies have been made on biaxially oriented polyolefin tubes in which the polyolefin tube is stretched in both the axial direction and the circumferential direction.However, the stretching in the axial direction is inevitably greater than the stretching in the circumferential direction. The molecules are large in the axial direction and small in the circumferential direction. Therefore, the conventional biaxially oriented polyolefin pipe is apt to be torn in the axial direction because the deformability (elongation) of the pipe is significantly reduced.

For example, Japanese Patent Publication No. 4-5 539 79 discloses that (1) a hollow workpiece containing stretchable thermoplastic polymer is supplied from the inlet side of the die, and (2) the hollow workpiece is sent to the outlet side of the die. An empty workpiece is insufficient to cause tensile failure of the workpiece, but the workpiece is solid-phase with a die having a cross-sectional area greater than the initial internal cross-sectional area of the workpiece. Apply sufficient tensile strength to simultaneously deform and extend the bulk of the workpiece by passing it through the former disposed inside the workpiece, and (3) deforming by stretching in this way By collecting the hollow workpiece from the exit side of the die. Also, a method is disclosed for obtaining a tube having improved strength compared to an undeformed material. In this method, although the circumferential elastic modulus, tensile yield strength, impact strength, and internal pressure strength of the obtained pipe are improved, the bow [tensile fracture elongation is significantly reduced. For this reason, the pipe obtained by the method disclosed in Japanese Patent Publication No. 4-55379 has a remarkably reduced pipe deformation followability (ie, elongation) with respect to the external stress inherent in the polyolefin pipe. . In other words, there is a problem that the pipe does not have sufficient follow-up ability to respond to the external stress required when the pipe is buried, and that the pipe lacks seismic resistance such as being separated in layers.

Nakamaru et al., Described in Vol.10, No.6, pp.394 of the Forming Process, used a stretching method combining a die and a mandrel to pull a raw tube called a billet while pulling the original tube. The "Die Drawing method" for producing a biaxially oriented tube by passing through a tube is disclosed. In this report, it is argued that the Die Drawing method enabled the control of the stretching ratio in the axial direction and the stretching ratio in the circumferential direction, and the orientation in the resulting tube could be freely controlled. However, it has not been able to achieve both the required internal pressure resistance when buried and the ability to follow the deformation of the pipe to external stress.

Japanese Patent Application Laid-Open No. 5-5101993 discloses that 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. An axial stretching method is disclosed, but no method for improving the strength in the axial direction is disclosed. Therefore, the uniaxially stretched polyolefin pipe obtained by this method stretches only in the circumferential direction and does not stretch in the axial direction. And the elasticity in the circumferential direction cannot be achieved at the same time.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to have high plastic deformability (that is, the ability of a pipe to follow an external stress) which is a performance required when used as a buried pipe. Another object of the present invention is to provide a biaxially oriented polyolefin pipe which has both high elasticity in the circumferential direction and high seismic resistance.

Disclosure of the invention

The biaxially oriented polyolefin tube according to the present invention, which solves the above-mentioned problems, has an axial and And is oriented in the circumferential direction, and the degree of orientation in the circumferential direction is larger than the degree of orientation in the axial direction.

As used herein, the term “degree of orientation” is a numerical value indicating how much the molecular chains of a polyolefin molecule are arranged in that direction, and includes infrared spectroscopy, X-ray diffraction, polarizing microscope (birefringence), And can be measured by microwaves. In the present invention, the measurement is performed using a microwave, as described later.

As used herein, the term “biaxially oriented polyolefin tube” refers to an average value of the refractive index (nh) in the circumferential direction and an average value of the refractive index (na) in the axial direction. ) Means a polyolefin pipe having a diameter (DZ) of not more than 100 and a diameter (DZ) of pipe outer diameter (D) to pipe thickness (t) of not more than 1002. If either the average value of the refractive index (na) in the circumferential direction or the average value of the refractive index (nh) in the axial direction is less than 0.002 than the refractive index (nn) in the non-aligned state, the polyolefin molecule Insufficient orientation to improve elastic modulus

0

Therefore, the resistance to the internal pressure applied to the pipe from the fluid flowing inside the pipe (hereinafter referred to as “r internal pressure resistance”) cannot be improved, and when the polyolefin pipe is buried, it travels on soil and the ground. It is not possible to improve the resistance to pressure applied to pipes from vehicles (hereinafter referred to as “shochu earth pressure resistance”).

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 it is said that the relationship is approximately proportional. In order to measure the refractive index, an Abbe refractometer that irradiates a sodium D line (wavelength 589 nm) is often used because the measurement method is simple, but in the Abbe refractometer, the sodium D line It is not appropriate to measure the refractive index of an optically opaque polyolefin tube using an Abbe refractometer, which requires sufficient transmission. For this reason, in the present invention, a polyolefin tube is used for the microwave region where dielectric relaxation due to local motion such as twisting of the molecular main chain of a polymer material such as polyolefin is observed. It is appropriate to measure the dielectric constant (ε ') by irradiating, and to find the refractive index from Maxwell's formula ((refractive index (n) = ^ (ε')). As the refractive index (nn) in the non-oriented state, the refractive index of polyolefin before orientation may be used as it is as the refractive index (nn) in the non-oriented state. However, if the polyolefin pipe is stretched, the pipe (melting point +40 (° C) or more, and then cooled at a rate of about 10 ° / min., And the refractive index of the tube whose orientation has been canceled may be used as the non-oriented state refractive index (nn).

The thickness of the biaxially oriented polyolefin 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 pipe, the ratio (D / t) of the outer diameter (D) of the pipe to the thickness (t) of the pipe is preferably 100 or less as described above. In particular, when creep resistance is required for the biaxially oriented polyolefin tube, the ratio (DZt) is preferably 30 or less. Also, the shape of the biaxially oriented polyolefin tube is usually cylindrical, but is not necessarily limited to this. Depending on the application in which the tube is used, an elliptical cross section, an oval shape, a rectangular tube shape (for example, square It may have a different shape such as a cylindrical shape or a triangular cylindrical shape.

As described above, the higher the refractive index, the higher the degree of orientation. Specifically, the refractive index in the circumferential direction (nh) is larger than the refractive index in the axial direction (na), and the refractive index in the circumferential direction. (Nh) is preferably 0.004 or more, more preferably 0.01 or more, larger than the refractive index (nn) in the non-aligned state. If the refractive index in the circumferential direction (nh) is smaller than the refractive index in the axial direction (na), it goes without saying that the degree of axial orientation is larger than the degree of circumferential orientation. When the difference between the refractive index (nh) in the circumferential direction and the refractive index (nn) in the non-aligned state is less than 0.004, the orientation of the polyolefin molecules in the circumferential direction by stretching is insufficient. However, the elastic modulus in the circumferential direction cannot be sufficiently improved, and the internal pressure resistance and the earth pressure resistance of the pipe may not be improved.

It is preferable that (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. It is more preferably from 006 to 0.025, particularly preferably from 0.01 to 0.02.

In other words, when (refractive index in the circumferential direction (nh) refractive index in the uniaxial direction (na)) / (refractive index in the circumferential direction (nh)) becomes less than 0.004, the polyolefin molecule by stretching In some cases, the orientation in the circumferential direction is insufficient, 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. 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 should be oriented too circumferentially. Because the pipe is too stretched, its ability to follow the deformation of the pipe is reduced. Therefore, when an earthquake occurs when the pipe is used as an underground pipe, the pipe tends to break easily.

In the present invention, as another means for solving the above problems, a structure in which the tensile elastic modulus (tmh) in the circumferential direction of the biaxially oriented polyolefin pipe is larger than the tensile elastic modulus (tma) in the axial direction may be adopted. The improvement of the internal pressure resistance is achieved by increasing the tensile modulus in the circumferential direction. In order to follow the deformation of the pipe in the axial direction due to the force, force, earthquake, cracks, etc., it is necessary to maintain the ability of the pipe to follow the deformation by lowering the tensile modulus in the axial direction. Becomes Therefore, in a biaxially oriented polyolefin tube, by increasing the tensile modulus in the circumferential direction (tmh) to the tensile modulus in the axial direction (tma), the internal pressure of the shochu is improved, and the tube is deformed. Followability can be maintained.

Specifically, (tensile modulus in the circumferential direction (tmh)) / (tensile modulus in the axial direction (tma)) is preferably 1 or more and 8 or less, more preferably 1 or more and 5 or less. It is more preferably 1.2 or more and 5 or less. That is, if (the tensile elastic modulus in the circumferential direction (tmh)) / (tensile elastic modulus in the axial direction (tma)) is less than 1, the tensile elastic modulus in the axial direction (tma) increases, while the tensile elastic modulus in the circumferential direction increases. Since the tensile modulus (tmh) is low, it tends to be impossible to improve the internal pressure of shochu. On the other hand, if (tensile elastic modulus in the circumferential direction (tmh)) / (tensile elastic modulus in the axial direction (tma)) exceeds 8, it is necessary to remarkably stretch in the circumferential direction, so that the tube will have extremely poor deformation followability. Therefore, when used as an underground pipe, if an earthquake occurs, the pipe tends to break easily.

More specifically, the tensile modulus in the circumferential direction is preferably 0.5 GPa or more and 2 OGPa or less, and the tensile modulus in the axial direction is preferably 0.5 GPa or more and 1 OGPa or less. Tensile modulus is less than 0.5 GPa (especially when the tensile modulus in the circumferential direction is 0.5G (Less than Pa), the internal pressure resistance is remarkably low, and may not be practical. On the other hand, if the tensile elastic modulus in the circumferential direction exceeds 2 OGPa or the tensile elastic modulus in the axial direction exceeds 1 OGPa, the ability of the pipe to follow the deformation is significantly reduced. If an earthquake occurs when used, the pipe cannot be deformed and tends to break.

The term “tensile elastic modulus” used in this specification refers to a dumbbell-shaped test piece in accordance with JISK 6774 cut out from the obtained biaxially oriented polyolefin tube in the circumferential direction and the axial direction, respectively. The specimen is subjected to a tensile test in accordance with JISK7113, a tensile stress-strain curve is drawn, and the value is calculated by the following equation (1) using the first straight line portion of this curve.

Δσ

E _m (Tensile modulus) = (NZ 讓² ) · · · (1)

Δε

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

In the present invention, as another means for solving the above-mentioned problem, the biaxially oriented polyolefin pipe may have a structure in which the bending elastic modulus (mfh) in the circumferential direction is larger than the bending elastic modulus (mfa) in the axial direction. In order to improve the earth pressure resistance when a polyolefin pipe is buried, it is achieved by improving the bending elastic modulus in the circumferential direction. In order to follow the deformation of the pipe in the axial direction due to shear force, earthquake, cracking, etc., it is necessary to maintain the pipe's ability to follow the deformation by lowering the axial bending elastic modulus. Become. Therefore, in biaxially oriented polyolefin pipes, by making the bending elastic modulus in the circumferential direction (mf h) larger than the bending elastic modulus in the axial direction (mfa), the earth pressure resistance is improved and the pipe is improved. O Maintain the deformation followability of

Specifically, (bending elastic modulus in the circumferential direction (mf h)) / (axial bending elastic modulus (mfa)) is preferably larger than 1 and 8 or less, and larger than 1 and 5 or less. Is more preferable, and 1.2 or more and 5 or less are particularly preferable. That is, when (circumferential bending elastic modulus (mfh)) Z (axial bending elastic modulus (mfa)) becomes 1 or less, axial bending elastic modulus (mfa) increases while circumferential elastic modulus (mfa) increases. Flexural modulus (mf h) tends to be lower, so that it becomes difficult to improve the earth pressure resistance. On the other hand, if (bending elastic modulus in the circumferential direction (mίh)) Z (bending elastic modulus in the axial direction (mfa)) exceeds 8, it is necessary to remarkably stretch in the circumferential direction, so that the tube can follow the deformation. Is significantly reduced, and when used as an underground pipe, if an earthquake occurs, the pipe tends to break easily.

More specifically, it is preferable that the bending elastic modulus in the circumferential direction is 0.5 GPa or more and 2 OGPa or less, and the bending elastic modulus in the axial direction is 0.50 or more and 1 OGPa or less. That is, when the flexural modulus is less than 0.5 GPa (particularly, the circumferential flexural modulus is less than 0.5 GPa), the earth pressure resistance is extremely low, and the practicability may be lacking. On the other hand, if the bending elastic modulus in the circumferential direction exceeds 2 OGPa or the bending elastic modulus in the axial direction exceeds 1 OGPa, the deformation followability of the pipe is significantly reduced, causing earthquakes and cracks. In such a case, the pipe may not be deformed and may be broken, and may not be practically used.

The term “flexural modulus” used in the present specification is determined from the obtained biaxially oriented polyolefin tube as shown in FIG. In other words, the bending elastic modulus in the axial direction can be calculated from the relationship between the load and deflection when a load is applied to the center between the fulcrums from above by supporting a polyolefin pipe of an appropriate length by two fulcrums. It is a numerical value calculated according to equation (2).

4L ³ F

Bending elastic modulus in the axial direction (mi a) = ―—————... (2)

37Γ (D ⁴ -d ⁴ ) Y

(In the equation (2), L is the distance between the two fulcrums, F is the load at an arbitrarily selected point on the first straight part of the curve in the load-deflection curve graph, and D is the outside of the pipe. Diameter

, D is the inner diameter of the tube, and Y is the deflection at load F. )

On the other hand, the flexural modulus in the circumferential direction is calculated according to the following equation (3) from the relationship between the load and the deflection when a load P is applied by crushing the appropriate side of a polyolefin pipe from the peripheral side surface. Is the number to be Orientation · · · (3)

(In the equation (3), Ρ is the applied load, R is the thickness center radius, and I is The cross-sectional quadratic coefficient, AD _X is the change in diameter in the horizontal direction, and ΔD _r is the change in diameter in the vertical direction. )

In the present invention, as another means for solving the above-mentioned problems, a structure in which the axial tensile elongation at break (tba) of the axially oriented polyolefin tube is larger than the tensile elongation at break (tbh) in the circumferential direction. Well ,. As described above, when an embedded polyolefin pipe is deformed in the axial direction due to an earthquake, cracks, etc., the pipe is deformed by maintaining a high tensile elongation at break in the axial direction without stretching. The followability can be maintained, so that the pipe can follow the deformation. However, if the pipe is not stretched, the internal pressure of shochu and the earth pressure of shochu cannot be improved. In other words, when stretched, the tensile elongation at break decreases, and the ability of the pipe to follow the deformation is impaired. Therefore, the obtained biaxially oriented polyolefin pipe is stretched so that its tensile elongation at break (tba) in the axial direction is larger than the tensile elongation at break (tbh) in the circumferential direction, so that the shochu internal pressure resistance and It is possible to improve the earth pressure resistance and to maintain the deformability of the pipe.

Specifically, (axial tensile elongation at break (t b a)) (tensile elongation at break in circumferential direction (t b h)) is preferably greater than 1 and 8 or less. That is, when (axial tensile elongation at break (tba)) Z (peripheral tensile elongation at break (tbh)) is 1 or less, axial tensile elongation at break (tba) becomes too low. Deformation of the pipe is extremely low, and the pipe tends to break in the axial direction when an earthquake or ground crack occurs. On the other hand, in order for (axial tensile elongation at break (tba)) Z (circumferential tensile elongation at break (tbh)) to exceed 8, it is necessary to stretch in the circumferential direction markedly in comparison with the axial direction. Because of this significant stretching in the circumferential direction, the ability of the pipe to follow the deformation is impaired, and the pipe tends to break easily in the event of an earthquake or ground cracking.

More specifically, the tensile elongation at break in the axial direction is preferably at least 200%, more preferably at least 250%. That is, 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 pipe is buried. There is.

In addition, the tensile elongation at break in the circumferential direction affects the seismic resistance compared with the tensile elongation at break in the axial direction. The tensile elongation at break may be lower than the tensile elongation at break in the axial direction so as not to give much effect, and it is sufficient if the elongation is in the range of 150% to 500%, preferably 200% to 450%. ,-'

In other words, if the tensile elongation at break in the circumferential direction is less than 150%, the tube may be stretched too much, which may impair the ability of the tube to follow the deformation. On the other hand, if the tensile elongation at break in the circumferential direction exceeds 500%, the internal pressure resistance and the earth pressure resistance cannot be improved because the orientation of the polyolefin molecules in the circumferential direction is not sufficient.

The term “tensile elongation at break” used in the present specification refers to a dumbbell-shaped test piece in accordance with JISK 6774 cut out from the obtained biaxially oriented polyolefin tube in the circumferential direction and in the axial direction, respectively. This is a numerical value calculated by the following formula (4) when a test piece is subjected to a tensile test according to JISK 7113.

L-Lo

(Tensile elongation at break (%)) = X 100 · · · (4)

L 0

(In the equation (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 the narrow central portion and the test piece breaks. The length of the central part before applying stress to the No. 2 test piece (33 ± 2 mm in JISK 7115).

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

Polyethylenes include 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 that has been polymerized by using a high-pressure radical polymerization method, a Ziegler-Natta catalyst, a Phillip's catalyst, a meta-mouth catalyst, or the like can be used.

Homopolypropylene, random polypropylene, polypropylene Rock polypropylene and the like. Further, resins having different stereoregularities may be used.

Examples of the polyolefin copolymers include, in addition to the above, copolymers obtained by copolymerizing, for example, Hi-Ichi-Sai Refin, butadiene, vinyl drunkate, (meth) acrylic acid, (meth) acrylic acid derivatives, styrene, and styrene derivatives. Examples thereof include a copolymer obtained by modifying maleic anhydride, itaconic acid, etc. with a graph, other ionomers, ethylene-vinyl alcohol copolymers, and the like. As the one-year-old olefin, those having 3 to 12 carbon atoms are preferable, and specific examples include propylene, 1-butene, 4-methyl-11-pentene, 11-hexene, and 1-octene.

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 polyethylene resins, high-density polyethylene is preferred from the viewpoint that shochu creep properties are 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 preferably 30,000 or more and 100,000 or less, more preferably 50,000 or more and 100,000 or less. Is more preferred. The molecular weight distribution is preferably from 2 to 80, more preferably from 3 to 40. Polyolefin polymers and polyolefin copolymers may be used alone as the polyolefin constituting the tube.However, in order to improve orientation, moldability, durability, etc., the molecular weight, melting point, molecular weight distribution, and composition distribution are improved. Two or more different polyolefin polymers or polyolefin copolymers may be used as a mixture. Alternatively, the tube may be a laminated tube, and each layer may be formed from 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 tube can be reduced by using a polyolefin tube having a multilayer structure and using a resin having a high oxygen barrier property for the intermediate layer.

As long as the degree of orientation in the present invention is not adversely affected, at least a part of the polyolefin constituting the tube may be crosslinked, and a resin other than the polyolefin resin may be mixed and used. The crosslinking method is not particularly limited. For example, a physical crosslinking method such as an electron beam crosslinking method, a photo crosslinking method, a plasma crosslinking method, or a peroxide method such as a peroxide. A peroxide crosslinking method using an oxide, a chemical crosslinking method using a chemical crosslinking agent such as a silane crosslinking agent or a polyfunctional monomer, etc., can be cited.Of these, the polyolefin resin is sufficiently and reliably used. From the viewpoint that crosslinking is possible, electron beam crosslinking, oxide crosslinking and hot water crosslinking are preferred. Further, 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 thermal crosslinking agent used for thermal crosslinking is not particularly limited, but an organic peroxide can be used, and can be appropriately selected from the viewpoint of the molding temperature and compatibility of the raw material resin used. There are dicumyl peroxide, α'-bis (t-butylperoxy-m-isopropyl) benzene, cyclohexane hydride, 1,1-di (t-butyl butyl) cyclohexane, 1,1 Di (t-butyloxy) 3,3,5-trimethylcyclohexane, 2,2-di (t-butyloxy) octane, n-butyl-4,4di (t-butyloxy) ) Bellelate, g-tert-butyl oxide, benzoyl peroxide, 2,5-dimethyl-2,5-di (t-butylbaroxy) hexane, 2,5-dimethyl-2,5-bis (t-) Butyl vaoxy) Hexin-1, cumyl veroxyneodetate, t-butyl benzooxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butyl butyl isopropyl carbonate, t-Butyloxyarylcarbonate, t-butylperacetate, 2,2-bis (t-butylbutoxy) butane, di-t-butylperoxysophthalate, t-butylperoxymaleic acid, diazo Aminobenzene, N, N'-dichloroazodicarbonamide, trichloride pentagen, trichloromethyl sulfochloride, methylethyl ketone peroxide and the like. Of these, more preferred organic peroxides include dicumyl peroxide,, '-bis (t-butyloxy-1-m-isopropyl) benzene, t-butylcumyl peroxide, and benzoyl peroxide. Oxide, t-butyl peroxide benzoate, methyl ethyl ketone peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (t-butyl Veroxy) hexine-3, more preferred organic peroxidation Products include dicumyl peroxide, α, α'-bis (t-butylvinyloxym-isopropyl) benzene, methylethylketone peroxide, 2,5-dimethyl-12,5-di (t 1-butylperoxy) hexane, 2, -5-dimethyl-

2,5-bis (t-butylperoxy) hexine-3.

When a partially crosslinked polyolefin resin is used, the polyolefin resin preferably has a gel fraction of 10% or more and 70% or less. The higher the gel fraction, the higher the degree of crosslinking.

That is, when the electron beam crosslinking method is used as the crosslinking method, the gel fraction can be increased by increasing the irradiation amount of the electron beam. As described above, when the electron beam cross-linking method is used, the electron beam irradiation amount is not particularly limited. However, in order to keep the gel fraction at 10% or more and 70% or less, the electron beam irradiation amount is generally about 3%. It is preferable to set the value between MR ad and 8 MR ad.

In general, a polyolefin resin is composed of an amorphous portion and a crystalline portion, and when the polyolefin resin is pulled, two molecular chains in the amorphous portion having a low tensile drag are stretched so as to slide on each other. If it is too long, it will eventually break. When the gel fraction of the polyolefin resin is less than 10%, the crosslinking is not so advanced even in the amorphous part, that is, the two molecular chains in the amorphous part having a low tensile force are too small. Since it is not cross-linked, when the polyolefin resin is pulled, it tends to break easily from the amorphous part where the tensile resistance is weak, and the strength of the obtained biaxially oriented polyolefin pipe (especially deformation followability) is sufficient. It may not be possible to increase.

On the other hand, when the gel fraction of the polyolefin resin exceeds 70%, the crosslinking proceeds too much in the amorphous portion, that is, the molecular chains are too crosslinked in the amorphous portion having a low tensile strength. Therefore, when the polyolefin resin is stretched, the two molecular chains cannot slide and extend each other, and the strength of the biaxially oriented polyolefin tube obtained instead (particularly, deformation followability) ), There is a possibility that the performance is reduced.

As used herein, the term “gel fraction” refers to a numerical value determined as “degree of crosslinking” in accordance with JISC305. More specifically, "gel fraction" For the test, cut a lmm-thick annular test piece from the tip of the biaxially oriented polyolefin tube after cross-linking, and then cut this thin, annular test piece into a fan shape to obtain a 0.5 g test piece. The mass of this test piece is accurately measured (this mass is denoted by '), and then the test piece is placed in a test tube containing 50 g of xylene and kept at about 110 ° C for 24 hours. After this, the test piece was removed from the test tube and vacuum desiccated overnight to about 100. (The mass of the test piece after drying for 24 hours at a temperature of 1.3 kPa and a vacuum of 1.3 kPa or less (this mass is referred to as m ₂ ) is accurately measured and calculated based on the following formula (5). It is a numerical value.

Π12

Gel fraction (%) = X 100

In the present invention, it is preferable polyolefin resin is a density 0. 940 gZcm ³ or 0. 980 g / cm ³ or less of polyethylene. Polyethylene resin is composed of a crystalline part and an amorphous part.Generally, crosslinking is more likely to occur in the amorphous part than in the crystalline part, and when a polyolefin resin having a density of less than 0.940 g / cm ³ is crosslinked. In the early stage of the tension, the two molecular chains in the amorphous portion cannot slide and extend with each other, and the polyolefin molecules may be in a restrained state. Therefore, similarly to the case where the gel fraction exceeds 70%, there is a possibility that the deformability of the obtained biaxially oriented polyolefin tube may be reduced. On the other hand, from the above explanation, it seems that if the amount of the amorphous portion is extremely reduced, it becomes impossible to improve the tensile elongation at break by crosslinking, and that the higher the density, the more the amorphous portion Although the amount is small, it is extremely difficult to increase the density of the polyethylene resin to more than 0.980 g / cm ³ . In addition, when the polyethylene resin is pulled, it is a phenomenon specific to the polyethylene resin that the two molecular chains in the amorphous portion having a low tensile drag slip and stretch in the initial stage of the tension.

The biaxially oriented polyolefin tube of the present invention may have a structure in which the tensile yield strength in the circumferential direction (tyh) is larger than the tensile yield strength in the axial direction (tya). That is, the improvement of the internal pressure resistance is achieved by improving the tensile yield strength (tyh) in the circumferential direction. Specifically, it is preferable that (tensile yield strength in the circumferential direction (tyh)) / (tensile yield strength in the axial direction (tya)) is more than 1 and 8 or less, more preferably more than 1 and 5 or less. It is preferably 1.2 or more and 5 or less.

More specifically, the tensile yield strength in the circumferential direction (tyh) is preferably 1 OMPa or more, and the tensile yield strength (tya) in the axial direction is preferably 1 OMPa or more. tyh) is more than 15 MPa and the axial tensile yield strength (tya) is more preferably 15 MPa or more, and the circumferential tensile yield strength (tyh) is more than 2 OMPa and the axial tensile yield More preferably, the strength (tya) force is 15 MPa or more.

The term "tensile yield strength" used in the present specification refers to a dumbbell-shaped test piece in accordance with J IS K 6774 cut out from the obtained biaxially oriented polyolefin tube in the circumferential direction and the axial direction, respectively. This is a numerical value obtained by subjecting a test specimen to a tensile test in accordance with JISK 7113 and drawing a tensile stress-strain curve.

Further, a resin other than the polyolefin resin may be mixed and used as long as it does not affect the degree of orientation in the present invention.

The polyolefin resin may contain optional additives as long as it does not adversely affect the orientation of the tube. Examples of the additives 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 molecule may be finely divided to make the physical properties uniform. Similarly, the polyolefin resin may include a filler. Examples of the filler that can be used include fibrous fillers such as glass fiber, power fiber, bon fiber, and asbestos, plate-like particles such as talc, myriki, smectite, and other plate-like particles, aluminum hydroxide, and the like. Spherical particles and ground particles such as calcium carbonate and titanium oxide are included. Further, the polyolefin resin may be colored with a pigment, a dye or the like as needed. Of course, the surface of the tube may be printed or decorated.

Next, a method for producing a polyolefin tube according to the present invention will be described.

First, a raw tube (billette) is formed from polyolefin resin. This is polio The olefin resin is melt-kneaded inside the extruder, and the polyolefin resin is formed into a tube through a tube manufacturing die attached to the tip of the extruder.Then, the tubular polyolefin resin extruded from the die is pulled by a take-off machine to form a water tank. This is achieved by, for example, cooling after cooling to a predetermined length with a cutter.

Next, the method for stretching the billet to orient the polyolefin molecules of the pipe in two directions, 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, Any of the sequential stretching methods in which the stretching is performed in the axial direction after the stretching may be performed, but 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.

The pressure fluid method of (1) uses a pressurized fluid such as compressed air from the inside of the pipe to press the billet from inside to outside and extend it in the circumferential direction, while using hydraulic pressure at both ends of the pipe. This is a method in which the pipe is stretched in the axial direction by attaching a tension device.

In the die mandrel method (2), the pipe is made to advance on the surface of the cone-shaped mandrel whose diameter increases, and then pulled from the tip while the pipe is brought into 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 pipe is expanded and the pipe is simultaneously stretched in the circumferential and axial directions. In this method, the space corresponding to the thickness of the tube obtained is

It is preferable to combine a die which is fitted onto the mandrel so as to sandwich (clearance).

(3) In the mandrel method, a pipe is advanced on the surface of a cone-shaped mandrel whose diameter increases, and the pipe is pulled from the tip while making 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 pipe is expanded and the pipe is simultaneously stretched in the circumferential and axial directions.

In the solid extrusion method of (4), after the pipe is advanced to the surface of the cone-shaped mandrel whose diameter increases, the pipe is pushed onto the mandrel from behind while the pipe is brought into close contact with the mandrel by an extrusion device using hydraulic pressure or the like. This is a method in which the inner diameter of the pipe is expanded by pushing it in, and the pipe is simultaneously stretched in the circumferential and axial directions. In this method, it is preferable to combine the dies as described above. Further, it may be pulled in the axial direction so as not to impair the orientation in the circumferential direction. In the pressure fluid method of (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 pipe after stretching. In addition, the di-mandrel method of (2) and the mandrel method of (3) are easy to stretch in the axial direction as compared with stretching in the circumferential direction, so that the degree of orientation in the axial direction is increased. The solid extrusion method (4) is preferred. In addition, you may extend | stretch by methods other than this, for example, rolling. Usually, a tube Suruga warming upon stretching the tubing is limited to below the glass transition temperature or higher (melting point + 5 0 ^e C). Specifically, the melting point is preferably (melting point—50 ° C.) or more and (melting point + 50 ° C.) or less. If the melting point is less than (50 ° C.), the heating is too short, 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 fix the orientation and develop the strength. From the viewpoints of the capability of the stretching apparatus, uniformity of orientation, improvement of strength, productivity and the like, it is preferable to orient the pipe at a temperature of (melting point-140 ° C) or more and (melting point + 40.C) or less.

As described above, the outer diameter, the inner diameter, and the thickness of the obtained biaxially expanded polyolefin tube are not particularly limited as long as the outer diameter is 100 times or less the thickness, but the obtained biaxially expanded polyolefin tube is not limited. Is preferably 0.5 mm or more and 5 Omm or less, more preferably 1 mm or more and 3 Omm or less, and particularly preferably 2 mm or more and 25 mm or less. By stretching in this way, a biaxially oriented polyolefin tube according to the present invention in which polyolefin molecules are oriented in the axial direction and the circumferential direction can be obtained. Conventionally, the biaxially oriented polyolefin pipe according to the present invention is used not only as a transport pipe such as a water pipe, a hot water pipe, a gas pipe, a water pipe, a sewer pipe, a plant pipe, or an agricultural sewage pipe, It can be used as a protective tube provided around an optical fiber, an electric wire, or the like, or as a container such as a can or a bottle, or as a flat plate by cutting out.

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

In addition, the obtained biaxially oriented polyolefin pipe was subjected to socket processing, bending, and drilling. It is also possible to improve the workability as a pipe by applying a pipe. Further, a plurality of biaxially oriented polyolefin tubes may be joined. Splicing methods include EF (elect mouth fusion) fusion, BUTT fusion, rotary welding, socket welding, flange welding (bolt fastening), and the like.

BRIEF DESCRIPTION OF THE FIGURES

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

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

FIG. 3 is a diagram illustrating a stretching device used in the examples.

FIG. 4A is a cross-sectional view used to describe the bending elastic modulus in the circumferential direction, and FIG. 4B is a cross-sectional view used to describe the bending elastic modulus in the axial direction.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment)

In the biaxially oriented polyolefin tube A according to the first embodiment of the present invention, the degree of circumferential orientation is greater than the degree of axial orientation. (Refractive index (nh) in the circumferential direction> axial refraction in the axial direction) Index (na)), (refractive index in the circumferential direction (nh) Refractive index in the non-oriented state (nn) ≥ 0.004), (0.004≤ (refractive index in the circumferential direction (nh) — axial refraction) Modulus (na)) (Refractive index in the circumferential direction (nh)) 03), (Tensile modulus in the circumferential direction (tmh)> Tensile modulus in the axial direction (tma)), (1 <(Tensile modulus in the circumferential direction) (t mh)) Z (axial tensile modulus (tma))) ^ 8, (0.5 GPa ≤ circumferential tensile modulus (tmh) ≤ 2 OGPa), (0.5 GP a ≤ axial Tensile modulus (tma) ≤20GPa), (Bending modulus in the circumferential direction (mfh)> Bending modulus in the axial direction (mfa)), (1 <(Bending modulus in the circumferential direction (mfh)) / ( Axial flexural modulus (mf a))) ≤ ≤ 8, (0.50-3 ≤ circumferential flexural modulus (11 ^ 11) ≤ 2 OGPa), (0.5 GPa ≤ axial direction Flexural modulus (mf a) ≤ 1 OGPa), (axial tensile elongation at break (tba)> circumferential tensile elongation at break (tbh)), (1 <((axial tensile elongation at break ( tba)) Z (Circumferential tensile elongation at break (tbh )) ≤ 8), and the condition of (tensile elongation at break in the 300 axis direction (tba)) is satisfied.

The biaxially oriented polyolefin tube A can be produced, for example, by using a stretching apparatus 1 for stretching by a solid extrusion method as shown in FIG.

That is, the stretching device 1 includes the plunger 11, the die 12, and the mandrel 13.

The die 12 has a cylindrical shape having a bill inlet portion 12a into which a billet 2 serving as a raw material tube is inserted, and a diameter-enlarging portion 12b expanding into a trumpet shape on the other side.

The mandrel 13 faces the enlarged diameter portion 12b of the die 12 and forms a stretching passage 14 between its outer peripheral surface and the inner peripheral surface of the enlarged diameter portion 12b of the die 12. ing.

The distance between the outer circumferential surface of the mandrel 13 and the inner circumferential surface of the enlarged diameter portion 12b of the die 12 extends from the billet insertion portion 12a side to the outlet side of the enlarged diameter portion 12b. It gradually becomes narrower.

In the plunger 11, the plunger body 11a has an outer diameter that is substantially the same as the inner diameter of the bill inlet portion 12a, and can be moved into and out of the billet insertion portion 12a by a hydraulic device (not shown). I have.

Then, the biaxially oriented polyolefin tube A can be manufactured as follows using this stretching apparatus 1.

That is, first, the plunger 11 is retracted to the hydraulic device side so as to open the inlet of the pillar insertion portion 12a, and the billet 2 is set into the bill insertion portion 12a as shown in FIG.

Next, the plunger 11 is advanced in the direction of the die 2 such 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 inner portion of 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. Obtain polyolefin tube A.

In the biaxially oriented polyolefin tube A obtained as described above, the degree of orientation in the circumferential direction is greater than the degree of orientation in the axial direction. Sliding of the surface improves the modulus of elasticity and the pipe against external stress. Can be compatible with each other.

More specifically, the elasticity in the circumferential direction is stronger than the elasticity in the axial direction, so that the internal pressure applied to the pipe from the fluid flowing inside the pipe, and the soil applied from the soil around the pipe when the pipe is buried. Can withstand enough pressure. In other words, the internal pressure resistance and the earth pressure resistance of shochu are improved.

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 remains in the axial direction. It can be plastically deformed and does not break.

In particular, the refractive index in the circumferential direction (nh) is larger than the refractive index in the axial direction (na), and the refractive index in the circumferential direction (nh) is 0.04 or more larger than the refractive index in the non-aligned state (nn). Therefore, it is possible to sufficiently improve the elasticity in the circumferential direction, and to sufficiently secure the pipe without following the deformation followability.

Also, since (refractive index in the circumferential direction (nh) refractive index in the uniaxial direction (na)) and (refractive index in the circumferential direction (nh)) are not less than 0.04 and not more than 0.03, Even in this case, the elasticity in the circumferential direction can be sufficiently improved, and it can be sufficiently ensured without deteriorating the deformability of the pipe, and the balance between the elasticity of the pipe and the deformability can be 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 of the shochu can be improved, and at the same time, the deformability of the polyolefin pipe can be maintained with respect to external stress. . Further, since each tensile elastic 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 extremely well.

Similarly, since the flexural modulus in the circumferential direction is greater than the flexural modulus in the axial direction, it is possible to improve the earth pressure resistance and to maintain the deformability of the pipe. Further, 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.

Furthermore, since the tensile elongation at break (tba) in the axial direction is greater than the tensile elongation at break in the circumferential direction (tbh), the internal pressure resistance and the earth pressure resistance should be improved, and the tube should be able to follow the deformation. Can be. Further, each tensile breaking strength is within the above-mentioned predetermined range. Therefore, the internal pressure resistance and the earth pressure resistance can be improved and the deformation followability of the pipe can be maintained extremely well.

(Second embodiment)

In the biaxially oriented polyolefin tube B according to the second embodiment of the present invention, 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% or less. 9408 ^ 111 ³ or more and 0.980 gZcm 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)> (Na)), (refractive index in the circumferential direction (nh)-refractive index in non-oriented state (nn) ≥ 0.004), (0.004≤ (refractive index in the circumferential direction (nh) — refractive index in the axial direction) (na)) / (refractive index in the circumferential direction (nh)) ≤ 0.03), (tensile modulus in the circumferential direction (tmh)〉 tensile modulus in the axial direction (tma)), (1 <( Tensile modulus (tmh)) / (axial tensile modulus (tma))) ≤ 8, (0.5 GPa ≤ circumferential tensile modulus (tmh) ≤ 2 OGPa), (0.5 GP a ≤ Tensile modulus in the axial direction (tma) ≤ 2 OGPa), (Bending modulus in the circumferential direction (mfh)> Flexural modulus in the direction (mfa)), (1 <(flexural modulus in the circumferential direction (mf h)) (flexural modulus in the axial direction (mfa))) ≤ 8, (0.5GPa ≤ Flexural modulus (mf h) ≤ 2 OGPa), (0.5 GP a ≤ axial flexural modulus (mf a) ≤ 1 OGPa), (axial tensile elongation at break (t ba)> circumferential direction Tensile rupture elongation (tbh)), (1 ((Tensile rupture elongation in the axial direction (tba)) Z (Tensile rupture elongation in the circumferential direction (tbh)) ≤ 8), (200 It satisfies the condition of elongation at break (tba)).

The biaxially oriented polyolefin tube B can be produced, for example, by using a stretching apparatus 3 using a fluid pressure method as shown in FIG.

That is, the stretching device 3 includes the outer diameter control type 31 and the pipe chucks 32.

The outer diameter regulating type 31 regulates the billet 2 to be stretched to have a predetermined outer diameter when the billet 2 is expanded outward, and is provided with a heater (not shown). The heater 2 can heat the billet 2 from the outside. The pipe chucks 3 2, 3 2 hold both ends of the billet 2, and when the motor 34 is switched on, the billet 2 is pulled from both sides to extend in the axial direction, The pressurized and heated gas sent from the gas transport pipe 33 is pressed into the inside of the billet 2 to extend the billet 2 in the circumferential direction.

The pipe chuck 32 is provided with an air-sealing structure at 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. I have.

Then, the biaxially oriented polyolefin tube B can be manufactured as follows using this stretching apparatus 3.

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 to a temperature not less than the melting point of the resin—50 ° C. (melting point + 50. The heated gas is pressed into the billet 2 through the pipe chuck 32 to expand the diameter of the billet 2, that is, stretched and oriented in the circumferential direction, and the billet 2 is moved to both sides by the pipe chucks 32 and 32. The biaxially oriented polyolefin tube B is obtained by stretching and orienting in the axial direction.

The biaxially oriented polyolefin tube B thus obtained has the same effects as the above biaxially oriented polyolefin tube A, and since the polyethylene resin is cross-linked, the bow is an amorphous material having a low tensile drag. 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 deformation followability of the obtained biaxially oriented polyolefin tube can be further improved. In other words, when the tube is sufficiently stretched and oriented, a phenomenon in which the pipe separates in the thickness direction may be observed, which is not preferable from the viewpoint of earthquake resistance. Thus, separation can be prevented.

In addition, since the gel fraction of the polyolefin resin is not less than 10% and not more than 70%, as described above, the molecular chains in the amorphous portion having a weak tensile force are simply cross-linked to each other. Not only does it occur, but also in the amorphous part, the molecular chains do not crosslink too much, and the deformation follow-up property is not degraded. Therefore, the deformability of the obtained biaxially oriented polyolefin tube can be more reliably improved.

Furthermore, since the resin density is 0.9408 / 111 ³ or more and 0.g S OgZcm ³ or less, even in the amorphous part, the molecular chains are cross-linked too much and the deformation followability is reduced. Can be more reliably prevented, and 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 produced by the stretching device 1 using the solid extrusion method, and the biaxially oriented polypropylene tube B is produced by the stretching device 3 using the fluid pressure method. Alternatively, 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.

Example

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are used only for illustrative purposes and should not be used for limiting purposes.

First, the billets I to XI to be the raw material tubes were prepared as follows.

(Billet I)

High-density polyethylene resin (Asahi Kasei Co., Ltd., product name: “Suntech HD-QB78 0J, density: 0.953 gZc c, MFR: 0.03 gZ 10 minutes, weight average molecular weight: about 268000, melting point 132 ° C) Melting and kneading at 220 ° C using a non-vent type single screw extruder (cylinder diameter 65 mm, L / D = 30), and extruding from the tube manufacturing die provided at the tip of the extruder to obtain an outer diameter of 89. A billet Omm having an inner diameter of 29.0 mm was prepared.

(Billet)

A billet I was prepared in the same manner as the billet I except that the outer diameter was 89.0 mm and the inner diameter was 14 Omm.

(Billet m)

A billet 作製 was prepared in the same manner as the billet I, except that the outer diameter was 89.0 mm and the inner diameter was 660 mm. (Billet: n

A billet IV was prepared in the same manner as billet I except that the outer diameter was 89. Omm 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. Omm and the inner diameter was 44.0 mm.

(Billet VI)

High-density polyethylene resin (made by Asahi Kasei Corporation, trade name: “Suntech HD—QB78 0J, density: 0.953 g / cc FR: 0.03 10 minutes, weight average molecular weight: about 268,000, melting point 132 ° C) High-density polyethylene resin (Nippon Polychem Co., Ltd., product name: Novatec HD-HR120R, density 0.934 g / cc, MFR: 0.19 g / 10 min, weight average molecular weight: about 216000, melting point 132) was used, and a billet VI was prepared in the same manner as billet I except that the outer diameter was 89.0 mm and the inner diameter was 44. Omm.

(Billette VII)

High-density boroethylene resin (manufactured by Asahi Kasei Corporation, product name: “Suntech HD—QB780”, density: 0.93 g / cc, MFR: 0.03 gZ, 10 minutes, weight average molecular weight: about 268,000, melting point 132 ° C ) Was replaced by a high-density polyethylene resin (product name: Novatec HD-HB530, manufactured by Nippon Polychem Co., Ltd., density: 0.964 gZ cc, MFR: 0.3 gZl 0 min, melting point: 136 ° C) Except for the above, billet W was prepared in the same manner as billet I.

(Billette cor)

High-density boroethylene resin (manufactured by Asahi Kasei Corporation, trade name: "Suntech HD-QB780", density: 0.93 g / cc, MFR: 0.03 g / 10 minutes, weight average molecular weight: about 268000, melting point 132 ° C) was replaced with a polypropylene resin (trade name: Novatec PP-EC9, manufactured by Nippon Polychem Co., Ltd., density: 0.9 gZc c, MFR: 0.5 gZl 0 min). A billet H was prepared in the same manner as described above.

(Billet K) A billet K was prepared in the same manner as billet I except that the outer diameter was 89. Omm and the inner diameter was 62.0 mm.

(Billet X) ,,

High-density polyethylene resin (manufactured by Asahi Kasei Corporation, trade name: “Suntech HD—QB780J, density: 0.953 gZc c, MFR: 0.03 g / 10 min, weight average molecular weight: about 268,000, melting point 1 32 (° C) To 100 parts by weight, add 0.5 parts by weight of trivinylmethoxysilane and 0.04 parts by weight of 2,5-dimethyl-1,2,5-bis-t-butyloxyhexane. A billet X was prepared in the same manner as the above billet I, except that the outer diameter was 89.00 mm and the inner diameter was 14.0 mm.

(Billet XI)

High-density polyethylene resin (Asahi Kasei Co., Ltd., product name: “Suntech HD-QB780J, density: 0.93 g / cc, MFR: 0.03 gZlO content, weight average molecular weight: about 268000, melting point: 1 32 ) Instead of high-density polyethylene resin (Nippon Borichem Co., Ltd., product name: Novatec HD—HR120R, density: 0.934 g Zc c, FR: 0.19 g / 10 min, weight average molecular weight : about 21 6000, except for using the melting point 1 32 ^e C), to prepare a Biretsuto XI in the same manner as described above Biretsuto I

(Example 1)

A stretching device 4 in which the dimensions of each part shown in FIG. 3 are as follows was prepared. In FIG. 3, 41 is a die, 42 is a mandrel, and 43 is a pressing device.

[Dimensions of each part of the stretching device]

α = 15 °

D 1 = 1 45 mm

D ₂ = 1 56.8 mm

D ₃ = 8 9.0 mm

Next, after the billet I produced as described above was heated to 125 ° C in a gear-oven, the stretching device 4 in which the temperature of the mandrel 42 and the temperature of the die 41 were set to 125 ° C was used. It was set in the billet insertion section 44. Then, while adding 20 tons of mosquito to the billet I by the pressing device 43, it is pushed into the stretching passage 45 between the mandrel 42 and the die 41 and stretched at a speed of 10 OmmZ, thereby surrounding the polyethylene molecules. 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 by orienting in each of the direction and the axial direction.

(Example 2)

A non-crosslinked biaxial shaft with an outer diameter of 153.Omm and an inner diameter of 145.Omm in the same manner as in Example 1 except that a stretching device 4 as shown in FIG. An oriented polyethylene tube was obtained as a sample tube.

[Dimensions of each part of the stretching device]

= 15 °

D 1 = 1 45 mm

D ₂ = 1 53. Omm

D ₃ = 89. Omm

(Example 3)

The drawing unit 4 with the dimensions of each part is as follows and the billet]! A non-crosslinked biaxially oriented polyethylene tube having an outer diameter of 162. Omm and an inner diameter of 145. Omm was obtained as a sample tube in the same manner as in Example 1 except that

[Dimensions of each part of the stretching device]

= 15 °

D 1 = 1 45 mm

D ₂ = 1 62. Omm

D ₃ = 89. Omm

(Example 4)

Non-crosslinked with an outer diameter of 153. Omm and an inner diameter of 1 45. Omm in the same manner as in Example 1 except that a drawing device 4 and a billet HI as shown in Fig. 3 were used, each of which had the following dimensions. A biaxially oriented polyethylene tube was obtained as a sample tube.

[Dimensions of each part of the stretching device]

α = 15 °

D ₂ = 1 53. Omm

D ₃ = 89. Omm

(Example 5)

A non-crosslinking type having an outer diameter of 166.Omm and an inner diameter of 145.Omm was performed in the same manner as in Example 1 except that a drawing device and a billet IV as shown in FIG. A biaxially oriented polyethylene tube was obtained as a sample tube.

[Dimensions of each part of the stretching device]

α = 15 °

D 1 = 1 45 mm

D ₂ = 1 66. Omm

D ₃ = 89. Omm

(Example 6)

Non-crosslinked with an outer diameter of 154.Omm and an inner diameter of 145.Omm in the same manner as in Example 1 except that a drawing device 4 and a billet V as shown in FIG. A biaxially oriented polyethylene tube was obtained as a sample tube.

[Dimensions of each part of the stretching device]

= 15 °

D ₂ = 1 54. Omm

D ₃ = 89. Omm

(Example 7)

Using a stretching device 4 and a billet Y [as shown in Fig. 3 with the dimensions of each part as shown below, the billet VI was heated to 110 ° C in a gear oven, and the temperature of the mandrel 42 was increased. A non-crosslinked biaxially oriented polyethylene tube with an outer diameter of 156.8 mm and an inner diameter of 145.0 mm was prepared in the same manner as in Example 1 except that the temperature of the die 41 was set to 110 ° C. Obtained as a sample tube.

[Dimensions of each part of the stretching device]

α = 15 °

D ₂ = 1 56.8 mm

D ₃ = 89.Omm,-

(Example 8)

Non-crosslinked with an outer diameter of 156.8 mm and an inner diameter of 14.5 Omm in the same manner as in Example 1, except that a drawing device 4 and a billet II as shown in Fig. 3 where the dimensions of each part were as follows were used. A biaxially oriented Bolylene tube was obtained as a sample tube.

[Dimensions of each part of the stretching device]

α = 15 °

D 1 = 1 45 mm

D ₂ = 1 56.8 mm

D ₃ = 89. Omm

(Example 9)

Using a drawing device 4 as shown in FIG. 3 in which the dimensions of each part are as follows, the temperature of the mandrel 42 and the temperature of the die 41 were set to 140 ° C., and produced as described above. After heating the cornet 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 the stretching device]

= 15 °

D 1 = 1 45 mm

D ₂ = 1 56.8 mm

D ₃ = 89. Omm

(Comparative Example 1)

Same as Example 1 except that a pulling device was connected to the tip of billet I without using the pressing device of the stretching device of Example 1, and the pulling device used a die mandrel method of pulling from the exit side of die 41. Thus, a non-crosslinked biaxially oriented polyethylene tube was obtained as a sample tube.

(Comparative Example 2)

Using a drawing device 4 and a billet IX as shown in Fig. 3 where the dimensions of each part are as follows. A non-crosslinked biaxially oriented polyethylene pipe having an outer diameter of 149. Omm and an inner diameter of 145. Omm was obtained as a sample tube in the same manner as in Example 1 except for the above.

[Dimensions of each part of the stretching device] ヽ.

Hi = 15 °

D 1 = 1 45 mm

D ₂ = 1 49.0 mm

D ₃ = 8 9. Omm

With respect to the sample tubes obtained in Examples 1 to 9 and Comparative Examples 1 and 2 and billet I as Comparative Example 3, the refractive index in the circumferential direction and the axial direction, the tensile elastic modulus, the elastic modulus in bending, the tensile fracture The elongation, the yield strength, and the draw ratio were measured, and the results were calculated as the draw 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, and the billet used. Tables 1 and 2 show the outer diameter and inner diameter of the pipe and the inner diameter and outer diameter of each pipe.

The refractive index was determined by cutting out a test piece (0.5 mm thick) of about 1 Omm square from the obtained tube, and using a molecular orientation meter (microphone mouth wave method, manufactured by Oji Scientific Instruments, model number: M0A3020A). By irradiating the test piece with microwaves of about 19 GHz using, the refractive indices at 0 degree (axial direction) and 90 degrees (circumferential direction) were measured. The yield strength was determined by cutting a dumbbell-shaped No. 2 test piece from the obtained pipe in accordance with JISK7113 and pulling it while gradually increasing the load at a speed of 5 OmmZ. Means “tensile yield strength”, which corresponds to the tensile stress at the first point where the elongation is increased without increasing the elongation. If 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 referred to as `` yield strength '' here. .

From Tables 1 and 2, the sample tubes of Examples 1 to 9 were compared with the sample tubes of Comparative Examples 1 to 3 in that the refractive index in the circumferential direction was compared with the refractive index in the axial direction. Therefore, it is understood that the polyethylene molecules are highly oriented in the circumferential direction. On the other hand, although it is also oriented in the axial direction, its degree of orientation is lower than that in the circumferential direction, so there is not much deterioration in the ability to follow the deformation of the tube due to the improvement in elasticity in the axial direction, which is seen in ordinary polyethylene pipes It is understood that sufficient earthquake resistance is maintained. O

Also, comparing Examples 1 to 9 with Comparative Examples 1 and 2, the sample tubes of Examples 1 to 9 have higher yield strength 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, and the tensile modulus and the bending modulus in the axial direction are larger than those in the circumferential direction. The ability to follow the deformation of the ship is impaired, making it impossible to respond to a major 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 soil around the pipe when the pipe is buried. It can be understood that it can withstand the earth pressure applied from the sea. On the other hand, for the same reason, the ability of the polyolefin pipe to follow the deformation to external stress, which is an advantage of the polyolefin pipe, is maintained, so that even if the buried pipe is subjected to an earthquake, It is understood that it can be deformed and does not break. As for the tensile modulus, the tensile modulus in the circumferential direction is higher than the tensile modulus in the axial direction, so it is understood that the biaxially oriented polyethylene pipe obtained by this method has improved internal pressure resistance. You. In addition, 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 by this method has high shochu earth pressure.

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 improved internal pressure resistance and earth pressure resistance, while the advantage of a polyolefin pipe is the external strength. It is understood that the deformation followability to stress is maintained.

Similarly, since the tensile yield strength in the circumferential direction is higher than the tensile yield strength in the axial direction, it is understood that, in the obtained pipe, it is possible to reliably ensure deformation followability to external stress, which is an advantage of polyolefin pipe. You.

The sample tubes obtained in Examples 1 to 9 not only had sufficient shochu performance, but also had excellent pressure resistance and had sufficient performance as a buried pipe. In addition, it can be understood that since the thickness of the polyethylene pipe was reduced, the cost can be reduced to obtain a biaxially oriented polyolefin pipe. (Example 10)

Using a billet I, a non-crosslinked type biaxially oriented polyethylene pipe having an outer diameter of 156.8 mm and an inner diameter of 14.5 mm was obtained in the same manner as in Example 1, and the obtained non-crosslinked type was obtained. An electron beam irradiator (Nisshin High Voltage ESP 750 kV) was used to irradiate the biaxially oriented polyethylene tube with an electron beam of 3 MRad at an acceleration voltage of 750 kV. Then, the polyethylene constituting the tube was crosslinked by an electron beam crosslinking method to obtain a crosslinked biaxially oriented polyethylene tube as a sample tube.

(Example 11)

A crosslinked biaxially oriented polystyrene tube was obtained as a sample tube in the same manner as in Example 10 except that the electron beam irradiation amount was changed to 6 MRad.

(Example 12)

A non-cross-linked biaxially oriented polyethylene pipe having an outer diameter of 156.8 mm and an inner diameter of 14.5 O mm was obtained in the same manner as in Example 1 using the billet X. The biaxially oriented polyethylene tube was immersed in hot water at 95 for 48 hours to crosslink the polyethylene constituting the tube to obtain a crosslinked biaxially oriented polyethylene tube as a sample tube.

(Example 13)

Using a billet XI, a non-crosslinked biaxially oriented polyethylene tube having an outer diameter of 156.8 mm and an inner diameter of 14.5 mm was obtained in the same manner as in Example 1, and the obtained non-crosslinked type was obtained. An electron beam irradiator (Nisshin High Voltage ESP 7500 kV) is used to irradiate the biaxially oriented polyethylene tube with an electron beam of 3 MRad at an acceleration voltage of 7500 kV. The polyethylene constituting the tube was crosslinked by an electron beam crosslinking method to obtain a crosslinked biaxially oriented polyethylene tube as a sample tube.

Evaluation of the seismic resistance of the sample tubes (crosslinked biaxially oriented polyethylene tubes) of Examples 10 to 13 and the sample tube (non-crosslinked biaxially oriented polyethylene tubes) of Comparative Example 1 obtained as described above. Table 3 shows the results together with the crosslinking conditions and the gel fraction.

For the evaluation of seismic resistance, cut out a sample in the axial direction of the pipe and use the same method as JISK 757, `` Interlayer Shear Test Method for Glass Fiber Reinforced Plastics '', to determine whether interlayer separation occurs. Was evaluated. And cracks occur, With the increase in stress, the case where the crack propagated was rated X for seismic resistance, and the case where cracks did not occur and the crack did not propagate was rated as Δ for seismic resistance.

Further, from Table 3, it can be understood that if a part of the polyolefin constituting the pipe is crosslinked, no delamination occurs, the degeneration followability can be further improved, and the seismic resistance is excellent.

Further, when Example 12 is compared with other Examples 10, 11, and 13, it can be understood that the crosslinking method may be any of an electron beam crosslinking method and a hot water crosslinking method. .

Industrial applicability

According to the present invention, it is possible to provide a biaxially oriented polyolefin pipe having high seismic resistance, which can achieve both high deformation followability and high elasticity in the circumferential direction, which are performances required when used as a buried pipe. can do. In addition, since it is possible to achieve both deformation followability and elasticity in the circumferential direction in this way, it is possible to maintain high durability for a long time against internal pressure, earth pressure, etc. as compared to steel pipes, concrete pipes, etc. Instead, 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 pipe which is economically excellent.

Further, if at least a part of the polyolefin resin constituting the pipe is cross-linked, higher durability, particularly, earthquake resistance can be obtained.

Of course, two or more biaxially oriented polyolefin tubes according to the present invention can be used by connecting two or more, similarly to the conventional polyolefin tube. Further, as in the present invention, the gas barrier property, chemical resistance, and surface hardness can be improved by orienting the polyolefin molecules in the axial direction and the circumferential direction. It can be expanded to other than the middle buried pipe). (Table 1) Flexural modulus Tensile modulus (GPa) Flexural modulus (GPa) Circumferential direction (nh) 轴 direction (na) Bille, \ (nn) (nh-na) (nh-na) bar nh) Circumferential direction (Tmh) 轴 direction (tma) Circumferential direction (tfh) 轴 direction (tfa)

1 1.490 1.470 1.460 0.02 0.0134 6 2.5 6 2.5

2 1.490 1.480 1.460 0.01 0.0067 6 4 6 4 Actual 3 1.510 1.470 1.460 0.04 0.0265 8 2.5 8 2.5

4 1.475 1.470 1.460 0.005 0.0034 3 2 3 2 Al 51.520 1.470 1.460 0.05 0.0329 9 2.5 9 2.5

6 1.480 1.478 1.460 0.002 0.0014 4 3.8 4 3.8

7 1.485 1.465 1.455 0.02 0.0135 3 1.5 3 1.5 Example

8 1.495 1.475 1.465 0.02 0.0134 7 3 7 3

9 1.480 1.460 1.450 0.02 0.0135 7 3 7 3 Ratio 1 1.470 1.490 1.460-0.02 -0.0136 6 7 6 7 铰 2 1.480 1.485 1.460-0.005 -0.0034 3 4 3 4 Example 3 1.460 1.460 1.460 0 0 1.1 1.1 1.1 1.1

(Table 2) Yield strength (MPa) Tensile elongation at break (%) Stretch ratio (times) Stretching temperature Circumferential direction (tyh) Axial direction (tya) Circumferential direction (tbh) Axial direction (tba) Circumferential direction (° C) )

1 48 40 150 600 3.4 2 125

2 47 43 150 400 3.4 3 125

3 54 30 150 300 6 1.5 125

4 33 30 250 500 2 1.5 125 Application 5 55 31 100 200 7 1.2 125

6 38 37 200 220 2.5 2.2 125

7 27 24 140 500 3.4 2 110 Example

8 52 43 150 600 3.4 2 125

9 51 41 120 250 3.4 2 140 ratio 1 48 60 150 100 3.4 4 125 comparison 2 38 46 400 150 2 3.5 125 Example 3 23.5 23.5 1500 1500

(Table 3) Crosslinking method Gel fraction Seismic evaluation Example 10 Electron beam crosslinking 16% 1 Example 11 Electron beam crosslinking 4 4% 4 Example 12 Hot water crosslinking 25% 〇 Example 13 Electron beam crosslinking 21 % 〇 Comparative Example 1 0 X

Claims

The scope of the claims

1. A biaxially oriented polyolefin tube oriented in the axial and circumferential directions, wherein the degree of orientation in the circumferential direction is greater than the degree of orientation in the axial direction.

2. The refractive index in the circumferential direction (nh) is greater than the refractive index in the axial direction (na), and the refractive index in the circumferential direction (nh) is greater than the refractive index in the unoriented state (nn) by more than 0.004. 2. The biaxially oriented polyolefin tube according to claim 1, wherein the polyolefin tube has a diameter.

3. (Circumferential refractive index (nh)-axial refractive index (na)) No (circumferential refractive index (nh)) is not less than 0.004 and not more than 0.03. Item 3. The biaxially oriented polyolefin tube according to item 1 or 2.

4. In a biaxially oriented polyolefin pipe oriented in the axial direction and the circumferential direction, a tensile modulus in the circumferential direction (tmh) is larger than a tensile modulus in the axial direction (tma). tube.

5. The biaxially oriented polyolefin according to claim 4, wherein (tensile modulus in the circumferential direction (tmh)) / (tensile modulus in the axial direction (tma)) is more than 1 and 8 or less. tube.

6. The tensile modulus in the circumferential direction (tmh) is 0.5 GPa or more and 2 OGPa or less, and the tensile modulus in the axial direction (tma) is 0.5 GPa or more and 1 OGPa or less. Biaxially oriented polyolefin tube.

7. For biaxially oriented polyolefin pipes oriented axially and circumferentially

A biaxially oriented polyolefin tube, wherein the flexural modulus in the circumferential direction (mfh) is larger than the flexural modulus in the axial direction (mfa).

8. The biaxially oriented polyolefin according to claim 7, wherein a force of (circumferential bending elastic modulus (mf h)) / (axial bending elastic modulus (mfa)) is 1 or more and 8 or less. tube.

9. The bending elastic modulus (mf h) in the circumferential direction is 0.5 GPa or more and 2 OGPa or less, and the bending elastic modulus (mf a) in the axial direction is 0.503 or more and 1 OGPa or less. 2. The biaxially oriented polyolefin tube according to 1.

10 0. In biaxially oriented polyolefin tubes oriented axially and circumferentially A biaxially oriented polyolefin tube, wherein the tensile elongation at break (tba) in the axial direction is larger than the tensile elongation at break (t bh) in the circumferential direction.

11. The method according to claim 10, wherein ((axial tensile elongation at break (tba)) Z (circumferential tensile elongation at break (t bh)) is greater than 1 and equal to or less than 8 Biaxially oriented polyolefin tube.

12. The biaxially oriented polyolefin pipe according to any one of claims 1 to 11, wherein at least a part of a polyolefin resin constituting the pipe is crosslinked.

1 3. The biaxially oriented polyolefin tube according to any one of claims 1 to 12, wherein the polyolefin resin constituting the tube has a gel fraction of 10% or more and 70% or less.

14. The biaxially oriented polyolefin pipe according to any one of claims 1 to 13, wherein the polyolefin resin constituting the pipe is polyethylene.

15. The biaxially oriented polyolefin pipe according to claim 14, wherein the density of polyethylene constituting the pipe is 0.940 gZcm ³ or more and 0.980 g / cra ³ or less.