Structure of composite flexible pipe for crude oil and natural gas transportation and laying method of composite flexible pipe

Abstract

[Problem] The present invention relates to a structure of a composite flexible pipe for crude oil and natural gas transportation, a method for laying the same, and a method for transporting crude oil or natural gas. Provided is a method for safely transporting crude oil or natural gas without leaking hydrogen sulfide gas, carbon dioxide, and hydrocarbon gas to the outside environment, by using a pipe having excellent acid resistance and acid gas barrier properties without concern of corrosion. [Solution] A transportation method for transporting crude oil or natural gas through a pipeline comprising a multilayer structure having at least one barrier resin layer containing an ethylene-vinyl alcohol copolymer resin as a main component; a pipe for the delivery method; the invention further discloses a laying method of the pipeline.

Description

[0001] This application is a divisional application of PCT application No. 202080037417.9, filed on May 12, 2020, having a priority date of May 20, 2019, with the title "Structure of a composite flexible pipe for crude oil and natural gas transportation and method for laying the same". TECHNICAL FIELD

[0002] The present application relates to a method for transporting crude oil or natural gas by a pipeline including a multilayer structure having a barrier resin layer (A), and a pipeline used in the transportation method. BACKGROUND

[0003] So far, crude oil, natural gas mining, transportation is mostly used steel pipe. But because the crude oil, natural gas field contains a large amount of acid components represented by hydrogen sulfide gas, steel pipe is very easy to be corroded and lead to crude oil, natural gas leakage. In recent years, with the large-scale exploitation of oil and gas fields, the phenomenon of pipeline corrosion in acid gas field is particularly prominent, and the performance requirements of pipeline corrosion resistance are increasing. In addition, when using nitrogen dioxide, ternary, and alkali driving methods for crude oil mining, the barrier property of the pipe material to carbon dioxide gas also needs to be considered. Moreover, steel pipe is easy to produce sparks when welding, and is extremely dangerous when operating in an environment containing crude oil or natural gas.

[0004] To solve the above problems, so far, a pipeline using a mixture of polyolefin and a polymer that is insoluble in polyolefin has been used (Patent Document 1). In addition, in order to prevent corrosion of steel pipes for transporting natural resources such as crude oil or natural gas, as a corrosion-resistant material for pipelines, a specific ratio of an adhesive resin is also disclosed, i.e., a composite material (Patent Document 2) having a 5-layer structure (composition: polypropylene resin / adhesive resin / EVOH resin / adhesive resin / polypropylene resin) containing a propylene-α-olefin copolymer elastomer, polypropylene, and polypropylene modified with an unsaturated carboxylic acid. In addition, as a flexible pipe for winding a reinforcing layer (glass fiber, etc.) for transporting liquids, gases, etc., it is disclosed that ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) is used as a barrier layer (Patent Document 3).

[0005] Prior art documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 63-252713

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2000-143899

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2013-527814. SUMMARY

[0010] Problems to be Solved by the Invention

[0011] In the pipe described in Patent Literature 1, the insoluble polymer is added to the polyolefin to impart gas barrier properties, but the more the insoluble polymer is added to the polyolefin, the poorer the mechanical strength of the pipe, and thus it is difficult to balance the gas barrier properties and the mechanical strength. On the contrary, too high a content of the polyolefin results in insufficient barrier properties of the hydrogen sulfide gas, and the hydrogen sulfide gas can leak to the outside environment. Further, the barrier material described in Patent Literature 2 is used as a liner for a steel pipe, and the use of the steel pipe requires welding, and thus there is a risk of explosion due to the occurrence of an open flame when the steel pipe is welded. Further, the barrier material is not used as a separate pipe, and even in the case of separate use, the mechanical strength, and the barrier properties against acid gases, hydrogen sulfide gas, are insufficient in the thickness range studied. Further, in the case where the wrapping reinforcing layer (glass fiber, etc.) described in Patent Literature 3 is used on a flexible pipe, the cross section of the barrier resin such as EVOH is easily exposed at the end of the wrapping layer, and the gases such as hydrogen sulfide and carbon dioxide easily leak from the end surface, resulting in insufficient gas barrier properties. Further, the reinforcing layer needs to be fusion-bonded using an open flame, and as described above, there is a risk of explosion during construction.

[0012] The present application is made to solve the above problems, and by using a pipe which is resistant to corrosion and has excellent barrier properties against acid gases, the safety of the transportation of crude oil and natural gas is improved. Further, the gases such as hydrogen sulfide and carbon dioxide are not leaked to the outside environment. Further, the pipe is composed of a thermoplastic resin, and thus can be fusion-bonded by a heater during construction, and thus the safety of the construction work can be significantly improved.

[0013] Means for Solving the Problems

[0014] The present inventors have found that the above problems can be solved by the following means.

[0015] [1] A transportation method in which crude oil or natural gas is transported by using a pipe including a multilayer structure having at least one barrier resin layer (A), the barrier resin layer (A) containing an ethylene-vinyl alcohol copolymer resin as a main component.

[0016] [2] The transportation method according to [1], in which the crude oil or natural gas contains an acid gas.

[0017] [3] The transportation method according to [1] or [2], in which the acid gas is hydrogen sulfide.

[0018] [4] The transportation method according to any one of [1] to [3], in which the content of the hydrogen sulfide is 0.05 mass% or more with respect to the total amount of the crude oil or natural gas.

[0019] [5] The transporting method according to [1] to [4], wherein the barrier resin layer (A) is continuous.

[0020] [6] The transporting method according to [1] to [5], wherein the barrier resin layer (A) contains an antioxidant.

[0021] [7] The transporting method according to [1] to [6], wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 20 to 60 mol%.

[0022] [8] The transporting method according to any one of [1] to [7], wherein the outside of the barrier resin layer (A) and the outside of the adhesive resin layer (B) each has another thermoplastic resin layer (C) via the adhesive resin layer (B) on both sides of the barrier resin layer (A).

[0023] [9] The transporting method according to [8], wherein the another thermoplastic resin layer (C) contains a polyethylene resin as a main component.

[0024]

[10] The transporting method according to [1] to [9], wherein the entire thickness of the pipe is 2 mm to 100 mm, and the thickness of the barrier resin layer (A) is 0.20 mm to 1.00 mm.

[0025]

[11] A pipe for use in the transporting method according to [1] to

[10] .

[0026]

[12] A pipe laying method, which is a pipe laying method for use in the transporting method according to [1] to

[10] , comprising the steps of connecting the cross sections of a plurality of pipes to each other using a pipe fitting, and externally heating the pipe fitting surface by a capacitive heater to connect the pipes to each other.

[0027] At this time, the ethylene content of the EVOH of the barrier resin layer (A) is preferably 20 to 60 mol%.

[0028] The pipe containing the multilayer structure preferably has another thermoplastic resin layer (C) on both sides of the barrier resin layer (A) via the adhesive resin layer (B).

[0029] By transporting crude oil or natural gas using the pipe containing the multilayer structure described above, the above problems can be solved.

[0030] Effects of the Invention

[0031] The method for transporting crude oil or natural gas of the present application uses a multilayer structure including a high gas barrier resin, and thus exhibits high gas barrier properties against hydrogen sulfide gas and carbon dioxide and the like, acidic gases, and thus can safely transport crude oil or natural gas without leaking toxic hydrogen sulfide gas to the outside when transporting crude oil or natural gas from an oil field to a storage tank. In addition, the pipeline used in the method for transporting crude oil or natural gas of the present application is composed of a thermoplastic resin, and can be joined by heating using a belt heater at the time of laying, and thus open flames are avoided, and the safety of the laying work is significantly improved. DETAILED DESCRIPTION

[0032] The method for transporting crude oil or natural gas of the present application is a method for transporting crude oil or natural gas by using a pipeline including a multilayer structure having at least one barrier resin layer (A), and the barrier resin layer (A) includes an EVOH resin as a main component.

[0033] The barrier resin layer (A) used in the present application includes an EVOH resin as a main component.

[0034] (EVOH)

[0035] The EVOH used in the present application is a copolymer having an ethylene unit and a vinyl alcohol unit. The EVOH is generally produced by saponifying an ethylene-vinyl ester copolymer. The production of the ethylene-vinyl ester copolymer and the saponification thereof can be performed by a publicly known method. As the vinyl ester used in the production of the ethylene-vinyl ester copolymer, a fatty acid vinyl ester such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl decanoate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate can be included, and among them, vinyl acetate is preferred.

[0036] The ethylene unit content of the EVOH is preferably 20 mol% or more, and more preferably 25 mol% or more. In the case where the ethylene unit content of the EVOH is less than 20 mol%, the thermal stability of the EVOH decreases, or the flexibility decreases, and thus the barrier properties against crude oil or natural gas can decrease when the pipeline is deformed. On the other hand, the ethylene unit content of the EVOH is preferably 60 mol% or less, and more preferably 35 mol% or less. If the ethylene unit content of the EVOH is greater than 60 mol%, the barrier properties against crude oil or natural gas can decrease.

[0037] The saponification degree of the EVOH is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 99 mol% or more. If the saponification degree of the EVOH is 90 mol% or more, the barrier property of the resulting pipe to crude oil or natural gas, and the thermal stability during melt molding of the pipe are further improved. The saponification degree of the EVOH is usually 99.97 mol% or less, and preferably 99.94 mol% or less. The ethylene unit content and the saponification degree of the EVOH can be determined by a nuclear magnetic resonance (NMR) method.

[0038] Further, the EVOH can also have units derived from other monomers than ethylene units, vinyl ester units, and saponification products thereof, within a range not impeding the object of the present application. The content of the units derived from other monomers in the EVOH is preferably 30 mol% or less, more preferably 20 mol% or less, further preferably 10 mol% or less, and particularly preferably 5 mol% or less, relative to the total monomer units in the EVOH. In the case where the EVOH has units derived from other monomers, the content thereof is preferably 0.05 mol% or more, more preferably 0.10 mol% or more, relative to the total monomer units in the EVOH. As the other monomers, there can be included, for example, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, and the like, or acid anhydrides, salts, or mono- or di-alkyl esters thereof; nitriles such as acrylonitrile, methacrylonitrile, and the like; amides such as acrylamide, methacrylamide, and the like; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and the like, or salts thereof; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxy-ethoxy)silane, γ-methacryloyloxypropylmethoxysilane, and the like; alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, and the like.

[0039] The MFR (melt flow rate) of the EVOH (measured at 210°C under a load of 2160 g) is preferably 0.1 to 100 g / 10 minutes. If the MFR of the EVOH is greater than 100 g / 10 minutes, the strength of the barrier resin layer (A) can possibly be reduced. The MFR of the EVOH is more preferably 50 g / 10 minutes or less, and further preferably 30 g / 10 minutes or less. On the other hand, in the case where the MFR of the EVOH is less than 0.1 g / 10 minutes, melt molding of the barrier resin layer (A) can possibly become difficult. The MFR of the EVOH is more preferably 0.5 g / 10 minutes or more.

[0040] The EVOH can be used singly, or two or more kinds of EVOHs having different ethylene unit contents, saponification degrees, or MFRs, and the like can be used in combination.

[0041] The barrier resin layer (A) contains an EVOH resin as a main component. The content of the EVOH resin in the barrier resin layer (A) is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more. If the content of the EVOH resin is in the above range, high gas barrier properties against hydrocarbon, hydrogen sulfide gas, and carbon dioxide gas can be achieved.

[0042] (antioxidant)

[0043] From the viewpoint of ensuring sufficient mechanical strength when the pipe of the present application is used for a long time, the EVOH resin is preferably a grade containing an antioxidant. The melting point of the antioxidant is preferably 170°C or lower. When the melting point of the antioxidant is higher than 170°C, the antioxidant does not sufficiently melt during the production of the barrier resin by melt mixing, and the antioxidant is localized in the barrier resin, the antioxidant ability is reduced, and thus the mechanical strength is reduced.

[0044] The molecular weight of the antioxidant is preferably 300 or more. When the molecular weight of the antioxidant is less than 300, the antioxidant easily exudes on the surface of the obtained pipe, and the heat stability of the barrier resin is reduced. The molecular weight of the antioxidant is more preferably 400 or more, and further preferably 500 or more. On the other hand, the molecular weight of the antioxidant is preferably 8000 or less, more preferably 6000 or less, and further preferably 4000 or less from the viewpoint of improving dispersibility.

[0045] As the antioxidant, a compound having a hindered phenol group is suitably used. The compound having a hindered phenol group itself has excellent heat stability, and has the ability to capture oxygen radicals that cause oxidative degradation, and thus the effect of preventing oxidative degradation is remarkable when added to the barrier resin as an antioxidant.

[0046] As the compound having a hindered phenol group, a commercially available substance can be used, and products including the following can be used.

[0047] (1) "IRGANOX 1010" manufactured by BASF Co.: melting point 110-125°C, molecular weight 1178, pentaerythritol tetra[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]

[0048] (2) "IRGANOX 1076" manufactured by BASF Co.: melting point 50-55°C, molecular weight 531, octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate

[0049] (3) "IRGANOX 1098" manufactured by BASF Co.: melting point 156-161°C, molecular weight 637, N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide]

[0050] (4) "IRGANOX 245" manufactured by BASF Corporation: melting point 76-79°C, molecular weight 587, triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate]

[0051] (5) "IRGANOX 259" manufactured by BASF Corporation: melting point 104-108°C, molecular weight 639, 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]

[0052] (6) "Sumilizer MDP-s" manufactured by Sumitomo Chemical Co., Ltd.: melting point about 128°C, molecular weight 341, 2,2'-methylene-bis(4-methyl-6-tert-butylphenol)

[0053] (8) "Sumilizer GA-80" manufactured by Sumitomo Chemical Co., Ltd.: melting point about 110°C, molecular weight 741, 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane

[0054] As the antioxidant, it is also preferable to use a compound having a hindered amine group. The compound having a hindered amine group is capable of inhibiting thermal degradation of the EVOH resin, and is capable of capturing aldehydes generated due to thermal decomposition of the EVOH resin. Thereby, generation of decomposition gas is reduced, and thus the voids and bubbles generated in the barrier resin layer (A) at the time of pipe melt molding are inhibited, and the resulting pipe is excellent in gas barrier properties.

[0055] As the compound having a hindered amine group, a piperidine derivative is preferable, and among them, a 2,2,6,6-tetraalkylpiperidine derivative having a substituent at the 4-position is more preferable. As the substituent at the 4-position, a carboxyl group, an alkoxy group, an alkylamino group can be included. Further, the N-position of the hindered amine group of the compound having a hindered amine group can be replaced with an alkyl group.

[0056] As the compound having a hindered amine group, commercially available products can be used, and products including the following can be included.

[0057] (9) "TINUVIN 770" manufactured by BASF Corporation: melting point 81-85°C, molecular weight 481, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate

[0058] (10) "TINUVIN 765" manufactured by BASF Corporation: liquid compound, molecular weight 509, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (mixture)

[0059] (11) "TINUVIN 622LD" manufactured by BASF Corporation: melting point 55-70°C, molecular weight 3100-4000, dimethyl succinate • 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine condensate

[0060] (12) "CHIMASSORB 119FL" manufactured by BASF Corporation: melting point 130-140°C, molecular weight 2000 or more, N,N'-bis(3-aminopropyl)ethylenediamine • 2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate

[0061] (13) "CHIMASSORB 944LD" manufactured by BASF Corporation: melting point 100-135°C, molecular weight 2000-3100, poly[[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl](2,2,6,6-tetramethyl-4-piperidyl)imino] hexamethylene (2,2,6,6-tetramethyl-4-piperidyl)imino]

[0062] (14) "TINUVIN 144" manufactured by BASF Corporation: melting point 146-150°C, molecular weight 685, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate

[0063] (15) "UVINUL 4050H" manufactured by BASF Corporation: melting point 157°C, molecular weight 450, N,N'-1,6-hexanediylbis{N-(2,2,6,6-tetramethyl-4-piperidyl)-formamide}

[0064] These compounds having a hindered phenol group or a hindered amine group can be used alone or in combination of two or more.

[0065] The content of the antioxidant in the barrier resin layer (A) is preferably 0.01 to 5 parts by mass per 100 parts by mass of the EVOH resin. If the content of the antioxidant is less than 0.01 parts by mass, it can be impossible to obtain the above-mentioned effects. The content of the antioxidant is more preferably 0.05 parts by mass or more, and further preferably 0.1 parts by mass or more. On the other hand, if the content of the antioxidant is more than 5 parts by mass, sometimes poor dispersion of the antioxidant occurs. The content of the antioxidant is more preferably 4 parts by mass or less, and further preferably 3 parts by mass, per 100 parts by mass of the EVOH resin.

[0066] (impact resistance modifier)

[0067] From the viewpoint of preventing the pipe of the present application from being damaged by external stress such as vibration of an earthquake, the EVOH resin preferably contains an impact resistance modifier. As the impact resistance modifier, for example, an acrylic elastomer; an olefin elastomer such as an ethylene-butene copolymer, an ethylene-propylene copolymer; a urethane elastomer; a styrene elastomer such as a styrene-ethylene / butylene-styrene block copolymer (SEBS), a styrene-isobutylene-styrene block copolymer (SIBS), a styrene-ethylene / propylene-styrene block copolymer (SEPS), a styrene-butadiene-styrene block copolymer (SBS), a styrene-isoprene-styrene block copolymer (SIS); a conjugated diene elastomer such as a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, an acrylate-butadiene copolymer, a hydrogenated product thereof; a silicone elastomer such as a polyorganosiloxane; an ethylene-based ionomer copolymer; polybutadiene, polyisoprene, a butadiene-isoprene copolymer, polychloroprene, or a multilayer structure polymer particle having the above-mentioned components in the innermost layer, and the like can be included. They can be used alone or in combination with a plurality of kinds. Among them, the impact resistance modifier is preferably at least one selected from the group consisting of an acrylic elastomer, an olefin elastomer, a urethane elastomer, a styrene elastomer, and a conjugated diene elastomer, and more preferably an acrylic elastomer.

[0068] As the impact resistance modifier of the acrylic elastomer, a commercially available substance can be used, and an article including the following can be included.

[0069] (1) "Acrylic impact resistance modifier PARALOID EXL2314" manufactured by Dow Chemical Company

[0070] (2) "Acrylic impact resistance modifier Kanecase FM-21" manufactured by Kaneka Company

[0071] (3) "Acrylic impact resistance modifier Kanecase FM-40" manufactured by Kaneka Company

[0072] (4) "Acrylic Impact Modifier Kaneace FM-50" manufactured by Kaneka Corporation

[0073] (5) "Acrylic Impact Modifier Kaneace M-570" manufactured by Kaneka Corporation

[0074] (6) "Acrylic Impact Modifier Kaneace M-210" manufactured by Kaneka Corporation

[0075] The content of the impact modifier in the barrier resin layer (A) is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of the EVOH resin. If the content of the impact modifier is less than 0.1 parts by mass, the above-mentioned effect may not be obtained. The content of the impact modifier is more preferably 0.5 parts by mass or more, and further preferably 1 part by mass or more. On the other hand, if the content of the impact modifier is more than 20 parts by mass, poor dispersion of the impact modifier may occur. The content of the impact modifier is more preferably 15 parts by mass or less, and further preferably 12 parts by mass or less, relative to 100 parts by mass of EVOH.

[0076] The EVOH resin in the barrier resin layer (A) may contain additives as long as they do not hinder the effects of the present invention. Such additives may include resins other than EVOH resin, metal salts, acids, boron compounds, plasticizers, fillers, antiblocking agents, lubricants, stabilizers, surfactants, colorants, UV absorbers, antistatic agents, desiccants, crosslinking agents, fillers, and reinforcing materials such as various fibers. Of these, metal salts and acids are preferred from the perspectives of thermal stability of the barrier resin and adhesion to other resins.

[0077] (Metal Salt)

[0078] From the perspective of maintaining the gas barrier properties of the pipe of the present invention over a long period of time by improving the interlayer adhesion of the multilayer structure of the pipe of the present invention, the EVOH resin preferably contains a metal salt. The metal salt is preferably an alkali metal salt or an alkaline earth metal salt, and from the perspective of thermal stability, an alkaline earth metal salt is more preferred.

[0079] When the EVOH resin contains a metal salt, its content is preferably 1 to 10,000 ppm in terms of metal element conversion. The metal salt content is more preferably 5 ppm or more, further preferably 10 ppm or more, and particularly preferably 20 ppm or more in terms of metal element conversion. On the other hand, the metal salt content is more preferably 5,000 ppm or less, further preferably 1,000 ppm or less, and particularly preferably 500 ppm or less in terms of metal element conversion. As a method for determining the metal salt content, a method can be used to freeze-grind dried EVOH resin pellets to obtain a sample and quantify the obtained sample using an ICP emission spectrometer.

[0080] (acids)

[0081] From the viewpoint of improving the heat stability of the EVOH resin during pipe melt molding of the present application, the EVOH resin preferably contains an acid. As the acid, a carboxylic acid compound or a phosphoric acid compound is preferred.

[0082] In the case where the EVOH resin contains a carboxylic acid compound, the content thereof is preferably 1 to 10000 ppm. The content of the carboxylic acid compound is more preferably 10 ppm or more, and further preferably 50 ppm or more. On the other hand, the content of the carboxylic acid compound is more preferably 1000 ppm or less, and further preferably 500 ppm or less. As the method for measuring the content of the acid, a neutralization titration method can be included.

[0083] In the case where the EVOH resin contains a phosphoric acid compound, the content thereof is preferably 1 to 10000 ppm or more. The content of the phosphoric acid compound is more preferably 10 ppm or more, and further preferably 30 ppm or more. On the other hand, the content of the phosphoric acid compound is more preferably 1000 ppm or less, and further preferably 300 ppm or less. As the method for measuring the content of the phosphoric acid compound, a method in which dried EVOH resin pellets are frozen and pulverized to obtain a sample, and the obtained sample is quantified by an ICP emission analysis device can be included.

[0084] In the case where the EVOH resin contains a boron compound, the content thereof is preferably 1 to 2000 ppm. The content of the boron compound is more preferably 10 ppm or more, and further preferably 50 ppm or more. On the other hand, the content of the boron compound is more preferably 1000 ppm or less, and further preferably 500 ppm or less. If the content of the boron compound in the EVOH resin is within the above range, the heat stability of the EVOH resin during pipe melt molding is further improved. The content of the boron compound can be measured by the same method as the above phosphoric acid compound.

[0085] As a method of making the EVOH resin contain the above-described phosphoric acid compound, carboxylic acid, or boron compound, a method of adding and kneading these compounds to the EVOH resin, for example, at the time of manufacturing EVOH resin pellets and the like, can be appropriately employed. As a method of adding these compounds to the EVOH resin, a method of adding dry powder, a method of adding a paste impregnated with a solvent, a method of adding a suspension suspended in a liquid, a method of adding a solution dissolved in a solvent, a method of impregnating EVOH resin pellets in a solution can be included. Among these, from the viewpoint of making the phosphoric acid compound, carboxylic acid, or boron compound homogeneously disperse, a method of adding a solution prepared by dissolving in a solvent, or a method of impregnating EVOH resin pellets in a solution is preferable. As the solvent, from the viewpoints of the solubility of the additive, the cost, the ease of handling, the safety of the working environment, and the like, water, for example, is preferable.

[0086] As a method of mixing the above-described additive to the EVOH resin used in the barrier resin layer (A), a publicly known method for mixing EVOH resin can be used. In the case of using a melt kneading method, after adding other resins, antioxidants, impact resistance modifiers, and the like to the EVOH, a screw-type extruder or the like can be used for melt kneading at 200 to 300°C.

[0087] (adhesive resin layer (B))

[0088] The barrier resin layer (A) used in the present application can be directly laminated with another thermoplastic resin layer (C) or other layers, but from the viewpoint of improving long-term durability, it is preferable to be laminated via the adhesive resin layer (B).

[0089] As the resin used in the adhesive resin layer (B), a polyolefin having a carboxyl group, a carboxylic anhydride group, or an epoxy group, for example, is preferable. Among these, from the viewpoints of excellent adhesion to EVOH and excellent adhesion to polyethylene, a polyolefin having a carboxyl group, a carboxylic anhydride group, or an epoxy group is more preferable.

[0090] As the polyolefin containing a carboxyl group, a polyolefin copolymer of acrylic acid, methacrylic acid, and the like is included, and also, all or a part of the carboxyl group contained in the polyolefin can exist in the form of a metal salt, as represented by an ionic resin. As the polyolefin having a carboxylic anhydride group, a polyolefin obtained by graft-modifying maleic anhydride, itaconic anhydride, and the like is included. Further, as the polyolefin-based resin containing an epoxy group, a glycidyl methacrylate copolymer polyolefin is included. Among these polyolefins having a carboxyl group, a carboxylic anhydride group, or an epoxy group, from the viewpoint of excellent adhesion, a polyolefin modified with a carboxylic anhydride such as maleic anhydride, and in particular, polyethylene is preferable. Note that the resin used in the adhesive resin layer (B) is preferably a different resin from the resin used in the other thermoplastic resin layer (C) described later.

[0091] (another thermoplastic resin layer (C))

[0092] The pipe used in the method for transporting crude oil and natural gas of the present application preferably has another thermoplastic resin layer (C) in addition to the barrier resin layer (A) and the adhesive resin layer (B). As the resin used in the another thermoplastic resin layer (C), a polyolefin resin is preferred, and can include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and the like polyethylene; ethylene-based copolymers obtained by copolymerizing ethylene with an α-olefin such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and the like; and the like. The polyethylene can be used alone or in combination of two or more. Among them, as the polyethylene used in the polyolefin layer, high-density polyethylene is preferred.

[0093] The MFR (melt flow rate, 190°C, 2.16 kg load) of the polyethylene used in the another thermoplastic resin layer (C) is preferably 0.01 to 10 g / 10 minutes. In the case where the MFR of the polyethylene is less than 0.01 g / 10 minutes, melt molding becomes difficult. On the other hand, in the case where the MFR of the polyethylene is more than 10 g / 10 minutes, the strength of the polyethylene layer decreases and extrusion molding becomes difficult. The MFR of the polyethylene is more preferably 5 g / 10 minutes or less, further preferably 3 g / 10 minutes or less, and particularly preferably 2 g / 10 minutes or less.

[0094] The another thermoplastic resin layer (C) preferably contains a polyolefin resin as a main component. The content of the polyolefin resin in the another thermoplastic resin layer (C) is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more. If the content of the polyolefin resin is in the above range, the mechanical strength of the pipe of the present application is excellent, and breakage due to external stress can be prevented.

[0095] The another thermoplastic resin layer (C) can contain an additive other than the polyolefin, as long as it does not hinder the effects of the present application. As the additive, the same substances as described above as the additive contained in the barrier resin layer (A) other than EVOH can be included. In particular, in the case where the another thermoplastic resin layer (C) is used in the innermost layer of the pipe that directly contacts crude oil or natural gas, an antistatic agent is preferably added in order to prevent static electricity from occurring.

[0096] As the raw material of the another thermoplastic resin layer (C), a recycled resin composition obtained by recycling a pipe including a multilayer structure of a resin can be used.

[0097] (pipe)

[0098] The pipe used in the method for transporting crude oil or natural gas of the present application is a pipe comprising a multilayer structure having at least one barrier resin layer (A), and the layers constituting the multilayer structure can include the following. In the example, the left side is the inner side, and the right side is the outer side.

[0099] Another thermoplastic resin layer (C) / barrier resin layer (A) / adhesive resin layer (B) / another thermoplastic resin layer (C)

[0100] Another thermoplastic resin layer (C) / barrier resin layer (A) / adhesive resin layer (B) / another thermoplastic resin layer (C)

[0101] Another thermoplastic resin layer (C) / barrier resin layer (A) / adhesive resin layer (B) / another thermoplastic resin layer (C)

[0102] The multilayer structure pipe of the present application does not contain a steel pipe, and thus corrosion of the steel pipe does not occur. In addition, as described above, the pipe has excellent barrier properties against acidic gases and mechanical strength properties.

[0103] The thickness ratio of the barrier resin layer (A) to the entire thickness of the pipe (barrier resin layer (A) / pipe) in the multilayer structure pipe of the present application is preferably 0.02 to 0.5. In the case where the thickness ratio (barrier resin layer (A) / pipe) is less than 0.02, the thickness unevenness of the barrier resin layer (A) becomes large, and the gas barrier properties against crude oil or natural gas can be reduced. On the other hand, from the viewpoint of suppressing a reduction in barrier properties and reducing costs, the thickness ratio (barrier resin layer (A) / pipe) is preferably 0.15 or less.

[0104] The entire thickness of the pipe of the present application is preferably 2 mm or more. In the case where the entire thickness of the pipe is less than 2 mm, the strength and gas barrier properties of the pipe during transportation of crude oil or natural gas are reduced. On the other hand, the entire thickness of the pipe is preferably 100 mm or less, more preferably 10 mm or less. In the case where the entire thickness of the pipe is greater than 100 mm, when the cross sections of the pipes are joined to each other by a pipe fitting in order to lay the pipes, the mode of heat transfer from the outside is not sufficient, and it can be difficult to join the pipes to each other, resulting in defects.

[0105] The thickness of the barrier resin layer (A) in the pipe of the present application is preferably 0.10 mm or more, more preferably 0.20 mm or more, more preferably 0.30 mm or more, further preferably 0.35 mm or more, and particularly preferably 0.40 mm or more. In addition, the thickness of the barrier resin layer (A) is preferably 1.00 mm or less. If the thickness is within the above range, the gas barrier properties of the pipe of the present application against hydrogen sulfide gas contained in crude oil or natural gas are more excellent.

[0106] As the method for producing the pipe of the present application, a method in which the multilayer structure constituting the pipe is melt-formed can be included. As the method for melt-forming the pipe, a method in which the resins constituting the respective layers are co-extruded through a circular die, a co-injection molding method in which the resins constituting the respective layers are melted and continuously injected into a die, and the like can be used.

[0107] In the case of melt-forming the pipe of the present application, a step in which the pipe immediately after melt-forming is cooled with cooling water at 10 to 70°C to solidify is preferably included. If the temperature of the cooling water is within the above range, the resulting pipe does not generate cracks or the like, and the gas barrier property and mechanical strength are excellent. The temperature of the cooling water is more preferably 15°C or higher, and further preferably 20°C or higher. The temperature of the cooling water is more preferably 60°C or lower, and further preferably 50°C or lower.

[0108] The pipe of the present application is continuously produced by extrusion molding as described above, and therefore the barrier resin layer (A) forms a continuous surface over the entire length of the pipe, and thus the barrier property against hydrogen sulfide gas, carbon dioxide, and the like is remarkably excellent.

[0109] The pipe of the present application can be subjected to secondary processing. As the method for secondary processing, a publicly known method can be used, and a method in which the multilayer structure is heated to 80 to 200°C, deformed into a desired shape, and then allowed to stand for 1 minute to 2 hours to be processed and molded can be included.

[0110] As the method for laying the pipe of the present application, a method in which a plurality of pipes are joined can be included. Specifically, a method in which the surfaces of the pipe fittings are externally heated by a heater in a state in which the cross sections of a plurality of pipes suitable for the length of the pipes to be transported are connected to each other by the pipe fittings, and the pipes are joined to each other can be included. As the method for externally heating the surfaces of the pipe fittings by the heater, a method in which the pipe fitting portions are heated by capacitive heating can be included.

[0111] The present application has superior safety in laying work compared to the welding of steel pipes that generate an open flame.

[0112] The pipe of the present application can be wound with a fiber raw material, a wire, or the like for reinforcement around the multilayer structure, and the mechanical strength and the like can be reinforced.

[0113] (crude oil or natural gas)

[0114] The crude oil that can be transported through the pipe of the present application is a high-viscosity liquid containing a mixture of various hydrocarbons and an acidic gas such as hydrogen sulfide gas. As the hydrocarbons contained in the crude oil, there can be included aromatic hydrocarbons such as benzene, ethylbenzene, toluene, xylene, and the like, saturated hydrocarbons such as n-hexane, n-octane, iso-octane, and the like, unsaturated hydrocarbons, saturated cyclic hydrocarbons such as cyclopentane, cyclohexane, and the like. In addition, the crude oil contains hydrogen sulfide gas. The concentration of the hydrogen sulfide gas contained in the crude oil varies depending on the oil-producing region, and generally contains 0.05% by mass or more. The natural gas that can be transported through the pipe of the present application is a gas containing saturated hydrocarbons and hydrogen sulfide, and is transported through the pipe in a state of being pressurized and liquefied. As the saturated hydrocarbons contained in the natural gas, there can be included methane, ethane, propane, butane, and the like. In addition, the natural gas also contains hydrogen sulfide gas. The concentration of the hydrogen sulfide gas contained in the natural gas varies depending on the gas field, and in some gas fields having a high concentration, 15% by mass or more is contained. The pipe of the present application can transport crude oil or natural gas having a high concentration of hydrogen sulfide gas without leaking the hydrogen sulfide gas.

[0115] (Method for transporting crude oil or natural gas)

[0116] When transporting crude oil through the pipe of the present application, a suitable heater is installed on the pipe, and the crude oil is heated to a temperature of 40 to 80°C to be low-viscosity, whereby efficient transportation is possible. In addition, when transporting crude oil or natural gas from an oil field or a gas field, sometimes compressed liquid carbon dioxide is injected into the crude oil or natural gas, and pressurized transportation is performed. The pipe of the present application can transport crude oil or natural gas without leaking carbon dioxide.

[0117] Examples

[0118] Hereinafter, the present application will be further specifically described using examples.

[0119] (1) Crude oil barrier property

[0120] The pipe obtained in each of the examples and comparative examples was cut to a length of 100 mm, and one end was sealed with an aluminum tape ("Aluminum Seal" manufactured by EFP Corporation (crude oil permeation amount: 0 g / m 2 After 500 g of BTEX (benzene 25% by volume, toluene 25% by volume, ethylbenzene 25% by volume, xylene 25% by volume) as a model compound of crude oil was filled into the pipe, the other end was sealed with an aluminum tape, and the tape end was fixed with a metal band. In the same manner, two pipes sealed with the model compound were prepared, and were left to stand in an explosion-proof constant temperature and humidity chamber (40°C, 0% RH or 85°C, 0% RH), and the mass of the pipe was measured every 1 day for 10 days. The maximum value of the mass change per average 1 day was evaluated as the crude oil barrier property of the pipe.

[0121] (2) Hydrogen sulfide gas barrier property

[0122] Each of the pipes obtained in the examples and comparative examples was cut to a length of 100 mm, and one end was sealed with an aluminum tape ("Aluminum Seal" manufactured by Eiwa Chemical Industry Co., Ltd.) and the tape end was fixed with a metal tape. After 500 g of a BTEX solution in which 0.1 mass% of hydrogen sulfide gas was dissolved by bubbling was filled into the pipe, the other end was sealed with an aluminum tape under a nitrogen atmosphere, and the tape end was fixed with a metal tape. Further, the pipe was put into an aluminum pouch, 2 L of nitrogen gas was sealed at 23°C, and the pouch opening was sealed with an aluminum tape. The pouch was left to stand in an explosion-proof constant temperature and humidity tank (40°C, 0% RH or 85°C, 0% RH) for 10 days, and after returning to 23°C, the hydrogen sulfide gas concentration inside the pouch was measured with a hydrogen sulfide detection tube ("Hydrogen Sulfide 4LB" (short-time detection tube, measurement range: 0.5 to 12 ppm) manufactured by Gastec Corporation or "Hydrogen Sulfide 4L" (short-time detection tube, measurement range: 1 to 240 ppm) manufactured by Gastec Corporation), and the hydrogen sulfide gas barrier property of the resin-made pipe was evaluated.

[0123] (3) Carbon dioxide barrier property

[0124] Each of the pipes obtained in the examples and comparative examples was cut to a length of 100 mm, and one end was sealed with an aluminum tape ("Aluminum Seal" manufactured by Eiwa Chemical Industry Co., Ltd.) and the tape end was fixed with a metal tape. After 500 g of a BTEX solution in which 0.1 mass% of carbon dioxide was dissolved by bubbling was filled into the pipe, the other end was sealed with an aluminum tape under a nitrogen atmosphere, and the tape end was fixed with a metal tape. Further, the pipe was put into an aluminum pouch, 2 L of nitrogen gas was sealed at 23°C, and the pouch opening was sealed with an aluminum tape. The pouch was left to stand in an explosion-proof constant temperature and humidity tank (40°C, 0% RH or 85°C, 0% RH) for 10 days, and after returning to 23°C, 1.5 cc of the gas inside the pouch was extracted with a gas-tight syringe, and the gas inside the pouch was measured with a GC-MS ("7890B GC") manufactured by Agilent Technologies, Inc., a detector ("5977B MSD"), and a column ("DB-624" (column length: 60 m, column diameter: 0.25 mm)) at 40°C for 15 minutes, whereby the carbon dioxide concentration inside the pouch was analyzed based on a standard curve prepared separately, and the carbon dioxide barrier property of the pipe was evaluated.

[0125] (4) Acid resistance

[0126] The pipe obtained in each of the examples and comparative examples was cut to a length of 100 mm, and after immersion in a 10 mass% aqueous sulfuric acid solution or a 10 mass% aqueous sodium hydroxide solution at 40°C for 7 days, the surface was washed with pure water and vacuum dried for 12 hours. Using the dried pipe, the same evaluation as described above in (1) was performed to evaluate the acid resistance of the pipe.

[0127] (5) Gas barrier property during crude oil transport

[0128] Using the pipe obtained in each of the examples and comparative examples, which had a length of 5 m and two valves, two crude oil tanks (SUS316-made pressure-resistant vessels, volume 1000 L) were connected with the pipe. Further, the periphery of the pipe was surrounded and sealed with a SUS316-made pipe having a diameter of 20 cm and a thickness of 5 mm with a silicon septum cap. Into one of the crude oil tanks, 500 L of a BTEX solution in which 0.1 mass% of hydrogen sulfide gas was dissolved by bubbling was filled at 23°C, and then the pressure of the crude oil tank was pressurized to 0.1 MPa gauge pressure with carbon dioxide, the valve of the connecting pipe was opened, and the entire solution was pressurized and transported to the other crude oil tank. After the pressurized transport, the two crude oil tanks were depressurized by being emptied, and the solution was again pressurized and transported to one of the crude oil tanks by the same procedure. This operation was repeated 100 times, and with a hydrogen sulfide detector, the gas between the pipe obtained in each of the examples and comparative examples and the SUS316-made pipe was sucked from the septum cap portion and detected, and based on the detected hydrogen sulfide concentration, the gas barrier property during crude oil transport was evaluated according to the following criteria.

[0129] A: hydrogen sulfide concentration less than 0.1 ppm

[0130] B: hydrogen sulfide concentration 0.1 ppm or more.

[0131] Example 1

[0132] The pellets of a high-density polyethylene resin ("Highex 5000H" manufactured by Prime Polymer Co., Ltd., MFR (190°C, 2.16 kg load) = 0.1 g / 10 min) were put into the first extruder, the pellets of a maleic anhydride-modified polyethylene resin ("Admer NF500" manufactured by Mitsui Chemicals, Inc.) were put into the second extruder, and the pellets of an EVOH resin ("Evafur F101B" manufactured by Kuraray Co., Ltd., MFR (210°C, 2.16 kg load) = 3 g / 10 min, ethylene unit content = 32 mol%) were put into the third extruder. A pipe having an outer diameter of 100 mm and a thickness of 5 mm was extrusion-molded using a 3-layer circular mold having a first / second / third / second / first configuration in this order from the outer layer side, and was immediately thereafter cooled and solidified by passing through a cooling water tank adjusted to 5°C, and was cut to a length of 5 m. The layer configuration of the obtained pipe was, in this order from the outer layer side, a high-density polyethylene resin layer (another thermoplastic resin layer (C)) / a maleic anhydride-modified polyethylene resin layer (adhesive resin layer (B)) / an EVOH resin layer (barrier resin layer (A)) / a maleic anhydride-modified polyethylene resin layer (adhesive resin layer (B)) / a high-density polyethylene resin layer (another thermoplastic resin layer (C)) = 2000 μm / 250 μm / 500 μm / 250 μm / 2000 μm. The various evaluation results of the obtained pipe are shown in Table 1.

[0133] Example 2

[0134] After dry blending 99.5 parts by mass of an EVOH resin ("Evafur F101B" manufactured by Kuraray Co., Ltd., MFR (210°C, 2.16 kg load) = 3 g / 10 min, ethylene unit content = 32 mol%) and 0.5 parts by mass of N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide] ("Irgafos 1098" manufactured by BASF Co., Ltd.) as an antioxidant, the barrier resin pellets were obtained by melt-kneading using a twin-screw kneading extruder (screw diameter 25 mmφ, L / D = 30, manufactured by Toyo Precision Machinery and Instrument Co., Ltd.) under the conditions of a cylinder temperature of 230°C and a screw rotation speed of 50 rpm, extruding the melt-kneaded product from a die into a strand shape into a cooling water tank at 5°C, and pelletizing the strand using a strand cutter. The obtained barrier resin pellets were put into the third extruder, and a pipe was produced in the same manner as in Example 1, except for this. The various evaluation results are shown in Table 1.

[0135] Example 3

[0136] After dry blending 89.5 parts by mass of an EVOH resin ("EVAL F101B" manufactured by Kuraray Co., Ltd., MFR (at 210°C under a load of 2.16 kg) of 3 g / 10 min and ethylene content of 32 mol%) having a MFR (at 210°C under a load of 2.16 kg) of 3 g / 10 min and an ethylene content of 32 mol%, an impact modifier containing an acrylic elastomer ("PARALOID EXL2314" manufactured by Dow Chemical), and N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide] ("IRGANOX 1098" manufactured by BASF) as an antioxidant, 0.5 parts by mass, a twin-screw kneading extruder (screw diameter 25 mmφ, L / D = 30, manufactured by Toyo Precision Machinery & Instruments Co., Ltd.) was used to melt-knead at a cylinder temperature of 230°C and a screw rotation speed of 50 rpm, and the melt-kneaded product was extruded into strands from a die into a cooling water tank at 5°C, and the strands were cut by a strand cutter to obtain barrier resin pellets. The obtained barrier resin pellets were fed into the third extruder, and a multilayer pipe was produced in the same manner as in Example 1, except that. The results of various evaluations are shown in Table 1.

[0137] Comparative Example 1

[0138] In the production of the pipe, the thickness of the layer containing the high-density polyethylene resin extruded from the first extruder was set to 5000 μm, and no resin was fed into the second and third extruders, and a single-layer pipe containing the high-density polyethylene resin was produced in the same manner as in Example 1, except that. The results of various evaluations are shown in Table 1.

[0139]

Claims

1. A method for transporting crude oil or natural gas through a pipeline comprising a multilayer structure having at least one barrier resin layer (A), The barrier resin layer (A) contains an ethylene-vinyl alcohol copolymer resin as a main component, The pipe comprising the multilayer structure has another thermoplastic resin layer (C) on both sides of the barrier resin layer (A) via an adhesive resin layer (B), The pipe is continuously manufactured by extrusion, The overall thickness of the pipe is not less than 2 mm and not more than 10 mm. One of the other thermoplastic resin layers (C) is the innermost layer that is in direct contact with crude oil or natural gas. The pipeline for transporting crude oil or natural gas is a plurality of pipelines whose cross sections are connected to each other through pipe fittings, and the pipe fitting surfaces are heated from the outside by a heater so that the pipelines are joined to each other.

2. The conveying method according to claim 1, wherein: Crude oil and natural gas contain acid gases.

3. The conveying method according to claim 2, wherein: Acid gas is hydrogen sulfide.

4. The method for conveying according to claim 1 or 2, wherein: The content of hydrogen sulfide is 0.05% by mass or more based on the total amount of crude oil or natural gas.

5. The conveying method according to claim 1 or 2, wherein: The barrier resin layer (A) is continuous.

6. The method for conveying according to claim 1 or 2, wherein: The barrier resin layer (A) further contains an antioxidant.

7. The conveying method according to claim 1 or 2, wherein: The ethylene unit content of the ethylene-vinyl alcohol copolymer is 20 to 60 mol%.

8. The method for conveying according to claim 1 or 2, wherein: The other thermoplastic resin layer (C) contains a polyethylene resin as a main component.

9. The conveying method according to claim 1 or 2, wherein: The thickness of the barrier resin layer (A) is 0.20 mm to 1.00 mm.

10. A pipeline used in the transportation method according to any one of claims 1 to 9.

11. A pipeline laying method for use in the transportation method according to any one of claims 1 to 9, comprising the following steps: A plurality of pipes are connected to each other by connecting the cross sections of the pipes with pipe fittings, and the pipe fitting surfaces are externally heated by a capacitance heater to join the pipes to each other.

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