Corrosion-resistant thin film, pipe and preparation method and application of corrosion-resistant thin film and pipe

Abstract

The invention provides a corrosion-resistant film, a pipe and a preparation method and application of the corrosion-resistant film, the corrosion-resistant film at least contains modified LCP, the modified LCP comprises p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 3, 4-dihydroxythiophene methyl diformate, the p-hydroxybenzoic acid, the 6-hydroxy-2-naphthoic acid and the 3, 4-dihydroxythiophene methyl diformate are used as raw materials, and the 6-hydroxy-2-naphthoic acid and the 3, 4-dihydroxythiophene methyl diformate are used as raw materials. And the molar ratio of the 2, 4-dihydroxy thiophene methyl dicarboxylate is (60-80): (5-40): (0.5-3). The corrosion-resistant thin film provided by the invention is excellent in mechanical property and corrosion resistance, and the corrosion-resistant pipe provided by the invention is high in combining capacity with the thin film and good in corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the field of material science, and in particular to a corrosion-resistant film, a pipe, and a preparation method and application thereof. Background Art

[0002] Metal pipes are widely used in various industries due to their high strength and excellent performance, such as the oil and gas industry, aerospace industry, shipbuilding industry, and power industry. However, when metal pipes are exposed to harsh environments, they are easily corroded by chemical media, causing the pipes to become thinner or even damaged, resulting in serious economic losses. For example, when metal pipes are used to transport crude oil, the crude oil contains corrosive chemicals such as sulfides, acids, and dissolved gases, which can corrode the interior of the pipes.

[0003] The traditional solution to pipeline corrosion is to apply anti-corrosion coatings inside and outside metal pipes. However, during the coating application process, the coating thickness is difficult to control. Improper application or uneven coating can easily lead to uneven coatings, which in turn can easily cause localized corrosion spots. Furthermore, using traditional lamination methods such as bonding or welding to bond anti-corrosion coatings to metal pipes can lead to problems such as weak interface bonding, insufficient adhesion, and low production efficiency. These issues are even more pronounced when applying corrosion protection to the interior of metal pipes.

[0004] Therefore, in view of the problems existing in the prior art, it is very necessary to provide a new corrosion-resistant pipe with good corrosion resistance, a corrosion-resistant coating that is tightly combined with the pipe, a long service life, and a simple preparation process. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a corrosion-resistant film, a pipe, and a preparation method and application thereof, so as to solve the problems in the prior art.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention is achieved through the following technical solutions.

[0007] A first aspect of the present invention provides a corrosion-resistant film, wherein the raw material components of the corrosion-resistant film contain at least modified LCP, wherein the raw material components of the modified LCP include p-hydroxybenzoic acid (p-HBA), 6-hydroxy-2-naphthoic acid (HNA) and 3,4-dihydroxythiophenedicarboxylic acid methyl ester (DHTD), and the molar ratio of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 3,4-dihydroxythiophenedicarboxylic acid methyl ester is 60-80:5-40:0.5-3. For example, it can be 60-75:20-40:0.5-3, or it can be 62.5-75:22-37:0.5-3.

[0008] Specifically, the structural formula of the p-hydroxybenzoic acid, the structural formula of the 6-hydroxy-2-naphthoic acid, and the structural formula of the 3,4-dihydroxythiophenedicarboxylic acid methyl ester are shown in the following formulas I, II, and III, respectively:

[0009]

[0010] Preferably, the number average molecular weight of the modified LCP is 2.5w to 5w.

[0011] Preferably, the water absorption rate of the corrosion-resistant film is less than or equal to 0.5‰, such as 0.4‰ to 0.45‰, 0.1‰, 0.2‰, 0.3‰, 0.4‰, or 0.45‰.

[0012] Preferably, the tensile strength of the corrosion-resistant film is 110-140 MPa, for example, the tensile strength may be 125-133 MPa, 110-133 MPa, or 125-140 MPa.

[0013] Preferably, the elongation at break of the corrosion-resistant film is 3-5.5%, such as 4.5-5.2%, 3-5.2%, or 4.5-5.5%.

[0014] A second aspect of the present invention provides a method for preparing a corrosion-resistant film, comprising the following steps:

[0015] Providing modified LCP, granulating the modified LCP and then casting it into a film at high temperature to obtain the corrosion-resistant film;

[0016] The preparation method of the modified LCP is as follows: after the above-mentioned p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and methyl 3,4-dihydroxythiophenedicarboxylate are mixed in proportion, an acetylation reaction is carried out with acetic anhydride under the condition of a catalyst, and after the acetylation reaction is completed, a melt polymerization reaction and a solid phase polymerization reaction are carried out to obtain the modified LCP.

[0017] Preferably, the temperature of the acetylation reaction is 130-150°C, such as 130-145°C, 130-140°C, or 140-150°C.

[0018] Preferably, the acetylation reaction time is 1 to 3 hours, for example, 1 to 2 hours, or 2 to 3 hours.

[0019] Preferably, the acetylation reaction is carried out in an inert gas environment. More preferably, the inert gas comprises nitrogen.

[0020] Preferably, the catalyst is one or more of potassium acetate, sodium acetate, magnesium acetate, zinc acetate and calcium acetate.

[0021] Preferably, based on the total mass of the modified LCP raw material, the content of the catalyst is 0.01 wt% to 0.05 wt%, such as 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, or 0.05 wt%.

[0022] Preferably, the molar ratio of acetic anhydride to the total components of the modified LCP raw materials is acetic anhydride: the sum of the molar numbers of the total components of the modified LCP raw materials = 1.01-1.10:1. For example, it can be 1.02-1.08:1, 1.02-1.05:1, or 1.05-1.08:1.

[0023] Preferably, the melt polymerization reaction includes a first-stage reaction and a second-stage reaction; the first-stage reaction temperature is 210-240°C; the second-stage reaction temperature is 260-320°C. For example, the first-stage reaction temperature may be 210-230°C, 210-220°C, or 220-230°C; and the second-stage reaction temperature may be 260-300°C, 260-280°C, or 280-300°C.

[0024] Preferably, the second stage reaction time is 1 to 3 hours, such as 1 to 2 hours or 2 to 3 hours.

[0025] Preferably, the acetic acid and acetic anhydride by-products are discharged by condensation reflux during the melt polymerization reaction.

[0026] Preferably, the second stage reaction further includes vacuuming; when the second stage reaction continues until no liquid flows out of the condenser, vacuuming is performed, the vacuum degree is 0.01-1 kPa, and the vacuuming time is 1-2 hours. For example, the vacuum degree can be 0.01-0.1 kPa, 0.1-1 kPa.

[0027] Preferably, the melt polymerization reaction is carried out in an inert gas environment. More preferably, the inert gas comprises nitrogen.

[0028] Preferably, the solid phase polymerization reaction temperature is (T m -35)℃~(T m -25)℃,T m is the melting temperature of the modified LCP; the solid phase polymerization reaction time is 6 to 12 hours. For example, the solid phase polymerization reaction temperature can be 235 to 255°C, 245 to 255°C, 250 to 255°C, or 245 to 250°C; and the solid phase polymerization reaction time can be 6 to 8 hours or 8 to 12 hours.

[0029] Preferably, the melting temperature of the modified LCP is 270-280°C.

[0030] Preferably, the temperature of the high-temperature casting film is 300-340°C. For example, the temperature may be 310-340°C, 310-320°C, or 300-320°C.

[0031] A third aspect of the present invention provides a corrosion-resistant pipe, the inner wall of which is completely laminated with the corrosion-resistant film described above.

[0032] Preferably, the pipe is one or more of a stainless steel pipe, a titanium alloy pipe and an aluminum alloy pipe.

[0033] Preferably, the thickness of the corrosion-resistant film is 30-80 μm, such as 50-60 μm, 50-55 μm, or 55-60 μm.

[0034] A fourth aspect of the present invention provides a method for preparing the corrosion-resistant pipe as described above, comprising providing a pipe and pretreating the inner surface of the pipe; providing the corrosion-resistant film as described above and completely and tightly fitting the corrosion-resistant film to the inner surface of the pipe; performing high-temperature compounding and cooling to obtain the corrosion-resistant pipe.

[0035] Preferably, the pretreatment includes one or more of sandblasting, grinding, cleaning and pickling.

[0036] Preferably, the cleaning process comprises ultrasonic cleaning using one or more of anhydrous ethanol or deionized water.

[0037] Preferably, the pickling treatment is performed using one or more of hydrochloric acid, sulfuric acid, dilute nitric acid or hydrofluoric acid.

[0038] Preferably, during pickling, the acid concentration used is 2-7%, the temperature is 40-60° C., and the pickling time is 5-10 minutes.

[0039] Preferably, the temperature of the high-temperature compounding is 270-300°C, such as 270-280°C, such as 280-300°C.

[0040] Preferably, during high-temperature compounding, the tube is further vacuumed to maintain a vacuum degree of 50-100 kPa, such as 50-80 kPa or 80-100 kPa.

[0041] Preferably, the tube is kept in a sealed state during vacuuming.

[0042] More preferably, detachable sealing heads are provided at both ends of the pipe opening to ensure that the inside of the pipe is in a sealed state.

[0043] Preferably, a medium frequency induction heating coil is used to provide the temperature required for high temperature compounding. More preferably, the frequency of the medium frequency induction heating coil is 500-2000 Hz.

[0044] A fifth aspect of the present invention provides an application of the corrosion-resistant pipe material as described above in the oil and gas industry as a crude oil transportation pipeline.

[0045] Beneficial effects of the present invention:

[0046] 1. The corrosion-resistant film provided by the present invention has excellent corrosion resistance and metal adhesion properties, and can effectively protect metal pipes from corrosion and fall-off in harsh environments, effectively extending the life of the pipes;

[0047] 2. The method for preparing corrosion-resistant pipes provided by the present invention avoids coating the inner wall of the pipe with paint. Instead, the formed film is directly attached to the inner wall of the pipe and heated by a specific medium-frequency induction heating coil. This effectively avoids uneven coating caused by processes such as spraying or spin coating, and prevents the formation of localized corrosion spots.

[0048] The preparation method has a simple process and is easy to operate. At the same time, it allows the inner wall of the pipe to be tightly bonded to the film, resulting in strong adhesion, effectively avoiding blistering or shedding of the coating in a short period of time. It is also low-cost and very suitable for large-scale promotion and use.

[0049] 3. The corrosion-resistant pipe provided by the present invention has excellent corrosion resistance, the internal film layer has strong adhesion to the pipe and is not easy to fall off, can transport corrosive liquids for a long time, and has a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Shown is a schematic diagram of heating of the pipes in Examples 4 and 5 of the present invention when laminating the thin film.

[0051] Figure 1 Component number description

[0052] 1. Pipes;

[0053] 2. Medium frequency induction heating coil;

[0054] 3. Head sealing. DETAILED DESCRIPTION

[0055] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0056] Before further describing the specific embodiments of the present invention, it should be understood that the scope of the present invention is not limited to the specific embodiments described below. It should also be understood that the terminology used in the examples is intended to describe specific embodiments and is not intended to limit the scope of the present invention. The experimental procedures in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0057] When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the understanding of the prior art by those skilled in the art and the description of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention may also be used to implement the present invention.

[0058] The technical solution of the present application provides a corrosion-resistant film and a preparation method thereof. The corrosion-resistant composite film introduces 3,4-dihydroxythiophenedicarboxylic acid methyl ester into the raw material components, and utilizes the introduction of the planar conjugated structure in the thiophene ring to enable the modified LCP copolymer to form a denser molecular arrangement. This structural property significantly enhances the corrosion resistance of the modified LCP material after the film is formed. At the same time, due to the introduction of sulfur atoms in the thiophene ring, it provides the possibility for subsequent strong bonding with metal pipes.

[0059] The present application also provides a corrosion-resistant pipe with excellent corrosion resistance and strong film coating adhesion and its preparation method, wherein the preparation method of the present application is to combine the modified LCP film containing sulfur provided in the present application with a metal pipe at high temperature, which can not only greatly improve the corrosion resistance of the metal pipe, but also utilize the coordination effect of the lone pair electrons of the sulfur element in the film with the metal surface, and can significantly enhance the adhesion of the corrosion-resistant film to the metal surface. This preparation method avoids the problem of uneven coating in the prior art, and effectively solves the problems of weak interface bonding, insufficient adhesion, and low production efficiency when traditional composite methods such as bonding or welding are used to composite anti-corrosion films with metal pipes. In addition, the high-temperature composite method used in the present application is simple to operate, low cost, and is conducive to large-scale promotion and application.

[0060] Example 1

[0061] This embodiment provides a specific corrosion-resistant film and its preparation method, which specifically includes the following steps:

[0062] 1) Preparation of modified LCP

[0063] 1-1) Acetylation reaction

[0064] 0.68 mol of p-hydroxybenzoic acid, 0.3 mol of 6-hydroxy-2-naphthoic acid and 0.02 mol of methyl 3,4-dihydroxythiophenedicarboxylate were mixed and poured into a reactor, and 1.05 mol of acetic anhydride and 3.1 g of magnesium acetate as a catalyst were added. The reactor was evacuated and nitrogen was introduced to protect the reaction raw materials. The temperature was then raised to 145° C. and refluxed for acetylation reaction for 2 hours.

[0065] 1-2) Melt polymerization

[0066] After the acetylation reaction was completed, the reactor temperature was raised to 210° C., and the condensation system was opened at the same time. The first stage reaction was carried out under a nitrogen atmosphere for 1 hour, and the by-products acetic acid and acetic anhydride were separated by the condensation system. The reactor temperature was further raised to 260° C., and the second stage reaction was carried out under a nitrogen atmosphere for 3 hours until no liquid flowed out of the condensation system, and then vacuum was applied to a vacuum degree of 0.1 kPa, which was maintained for 1 hour to complete the melt polymerization.

[0067] 1-3) Solid-phase polymerization

[0068] After melt polymerization, the product was transferred to a solid phase polymerization device, heated to 255° C., and solid phase polymerization was carried out for 8 hours under a nitrogen atmosphere to obtain the modified LCP.

[0069] 2) Preparation of corrosion-resistant film

[0070] The modified LCP obtained in step 1) was granulated and then subjected to film casting at 310° C. to obtain the corrosion-resistant film having a thickness of 50 μm.

[0071] Example 2

[0072] This embodiment provides a specific corrosion-resistant film and its preparation method, which specifically includes the following steps:

[0073] 1) Preparation of modified LCP

[0074] 1-1) Acetylation reaction

[0075] 0.75 mol of p-hydroxybenzoic acid, 0.22 mol of 6-hydroxy-2-naphthoic acid and 0.03 mol of methyl 3,4-dihydroxythiophenedicarboxylate were mixed and poured into a reactor, and 1.02 mol of acetic anhydride and 3.04 g of magnesium acetate as a catalyst were added. The reactor was evacuated and nitrogen was introduced to protect the reaction raw materials. The temperature was then raised to 140° C. and refluxed for acetylation reaction for 2 hours.

[0076] 1-2) Melt polymerization

[0077] After the acetylation reaction was completed, the reactor temperature was raised to 230° C., and the condensation system was opened at the same time. The first stage reaction was carried out under a nitrogen atmosphere for 1 hour, and the by-products acetic acid and acetic anhydride were separated by the condensation system. The reactor temperature was further raised to 280° C., and the second stage reaction was carried out under a nitrogen atmosphere for 3 hours until no liquid flowed out of the condensation system. The reaction was then evacuated to a vacuum degree of 0.1 kPa and maintained for 1 hour to complete the melt polymerization.

[0078] 1-3) Solid-phase polymerization

[0079] After melt polymerization, the product was transferred to a solid phase polymerization device, heated to 250° C., and solid phase polymerization was carried out for 8 hours under a nitrogen atmosphere to obtain the modified LCP.

[0080] 2) Preparation of corrosion-resistant film

[0081] The modified LCP obtained in step 1) was granulated and then subjected to film casting at 320° C. to obtain the corrosion-resistant film with a thickness of 60 μm.

[0082] Example 3

[0083] This embodiment provides a specific corrosion-resistant film and its preparation method, which specifically includes the following steps:

[0084] 1) Preparation of modified LCP

[0085] 1-1) Acetylation reaction

[0086] 0.625 mol of p-hydroxybenzoic acid, 0.37 mol of 6-hydroxy-2-naphthoic acid and 0.005 mol of methyl 3,4-dihydroxythiophenedicarboxylate were mixed and poured into a reactor, and 1.08 mol of acetic anhydride and 4.7 g of magnesium acetate as a catalyst were added. The reactor was evacuated and nitrogen was introduced to protect the reaction raw materials. The temperature was then raised to 130° C. and refluxed for acetylation reaction for 3 hours.

[0087] 1-2) Melt polymerization

[0088] After the acetylation reaction is completed, the reactor temperature is increased to 220° C., and the condensation system is opened at the same time. The first stage reaction is carried out under a nitrogen atmosphere for 1 hour, and the by-products acetic acid and acetic anhydride are separated by the condensation system; the reactor temperature is further increased to 300° C., and the second stage reaction is carried out under a nitrogen atmosphere for 2 hours until no liquid flows out of the condensation system, and then vacuum is applied to a vacuum degree of 0.1 kPa, which is maintained for 1 hour to complete the melt polymerization;

[0089] 1-3) Solid-phase polymerization

[0090] After melt polymerization, the product was transferred to a solid phase polymerization device, heated to 245° C., and solid phase polymerization was carried out for 12 hours under a nitrogen atmosphere to obtain the modified LCP.

[0091] 2) Preparation of corrosion-resistant film

[0092] The modified LCP obtained in step 1) was granulated and then subjected to film casting at 320° C. to obtain the corrosion-resistant film with a thickness of 55 μm.

[0093] Comparative Example 1

[0094] This comparative example provides a specific film and its preparation method, which specifically includes the following steps:

[0095] 1) Preparation of LCP in the prior art

[0096] 1-1) Acetylation reaction

[0097] The raw materials were replaced with 0.68 mol of p-hydroxybenzoic acid and 0.3 mol of 6-hydroxy-2-naphthoic acid, methyl 3,4-dihydroxythiophenedicarboxylate was not added, and the ratio of acetic anhydride to the catalyst and other reaction conditions were the same as in Example 1.

[0098] 1-2) Melt polymerization

[0099] Same as in Example 1.

[0100] 1-3) Solid-phase polymerization

[0101] The same procedure as in Example 1 was followed to obtain LCP.

[0102] 2) Preparation of corrosion-resistant composite films

[0103] The LCP obtained in step 1) was granulated and then cast at 310° C. to obtain a film with a thickness of 50 μm.

[0104] Comparative Example 2

[0105] This comparative example provides a specific film and its preparation method, which specifically includes the following steps:

[0106] 1) Preparation of LCP in the prior art

[0107] 1-1) Acetylation reaction

[0108] The raw materials were replaced with 0.68 mol of p-hydroxybenzoic acid, 0.3 mol of 6-hydroxy-2-naphthoic acid, and 0.003 mol of methyl 3,4-dihydroxythiophenedicarboxylate. The ratio of acetic anhydride to the catalyst and other reaction conditions were the same as those in Example 1.

[0109] 1-2) Melt polymerization

[0110] Same as in Example 1.

[0111] 1-3) Solid-phase polymerization

[0112] The same procedure as in Example 1 was followed to obtain LCP.

[0113] 2) Preparation of corrosion-resistant composite films

[0114] The LCP obtained in step 1) was granulated and then cast at 310° C. to obtain a film with a thickness of 50 μm.

[0115] Comparative Example 3

[0116] This comparative example provides a specific film and its preparation method, which specifically includes the following steps:

[0117] 1) Preparation of modified LCP

[0118] 1-1) Acetylation reaction

[0119] The raw materials were replaced with 0.68 mol of p-hydroxybenzoic acid, 0.3 mol of 6-hydroxy-2-naphthoic acid and 0.05 mol of methyl 3,4-dihydroxythiophenedicarboxylate. The ratio of acetic anhydride to the catalyst and other reaction conditions were the same as those in Example 1.

[0120] 1-2) Melt polymerization

[0121] Same as in Example 1.

[0122] 1-3) Solid-phase polymerization

[0123] Same as in Example 1.

[0124] 2) Preparation of corrosion-resistant film

[0125] After the modified LCP obtained in step 1) was granulated, it was found that a large number of fine wrinkles appeared on the surface of the LCP particles, which seriously affected the surface smoothness of the product and did not meet the film-forming conditions.

[0126] Comparative Example 4

[0127] This comparative example provides a specific film and its preparation method, which specifically includes the following steps:

[0128] 1) Preparation of modified LCP

[0129] 1-1) Acetylation reaction

[0130] The raw materials were replaced with 0.68 mol of p-hydroxybenzoic acid, 0.3 mol of 6-hydroxy-2-naphthoic acid and 0.1 mol of methyl 3,4-dihydroxythiophenedicarboxylate. The ratio of acetic anhydride to the catalyst and other reaction conditions were the same as those in Example 1.

[0131] 1-2) Melt polymerization

[0132] Same as in Example 1.

[0133] 1-3) Solid-phase polymerization

[0134] Same as in Example 1.

[0135] 2) Preparation of corrosion-resistant film

[0136] After pelletizing the modified LCP obtained in step 1), film casting was performed at 310°C. The polymer in step 1) was found to be crosslinked and agglomerated, failing to meet film-forming conditions. This was likely due to the addition of excessive methyl 3,4-dihydroxythiophenedicarboxylate as the raw material.

[0137]

[0138] This comparative example provides a specific film and its preparation method, which specifically includes the following steps:

[0139] 1) Preparation of modified LCP

[0140] 1-1) Acetylation reaction

[0141] Same as in Example 1.

[0142] 1-2) Melt polymerization

[0143] Except that the temperature was increased to 330° C. during the second stage reaction, the remaining steps were the same as those in Example 1.

[0144] 1-3) Solid-phase polymerization

[0145] Same as in Example 1.

[0146] 2) Preparation of corrosion-resistant film

[0147] The modified LCP obtained in step 1) was pelletized and then cast into a film at 310° C. It was found that the polymer melt strength in step 1) was low, resulting in failure to form a film.

[0148] This may be because during the melt polymerization reaction, the excessively high reaction temperature causes excessive degradation of the polymer and a decrease in molecular weight, which seriously affects the melt strength of the polymer and leads to the inability to form a film.

[0149] The applicant conducted performance tests on the films prepared in Examples 1 to 3 and Comparative Examples 1 to 4, including tensile strength test, elongation at break test, water absorption test and salt spray test.

[0150] The specific test method is:

[0151] The test method for tensile strength is carried out in accordance with GB / T 1040.3-2006.

[0152] The test method for elongation at break is carried out in accordance with GB / T 1040.3-2006.

[0153] The test method for water absorption is carried out in accordance with GB / T 1034-2008.

[0154] The salt spray test method is carried out in accordance with GB / T 10125-2021, using the acetic acid salt spray test (AASS): a 5% sodium chloride acid solution with glacial acetic acid is atomized for testing, using a circulating spray method until corrosion occurs on the test material. The time in Table 1 below is the time when corrosion occurs in the salt spray test.

[0155] The specific results are shown in Table 1 below.

[0156] Table 1

[0157]

[0158]

[0159] As shown in Table 1, during the acetic acid salt spray test, the films of Examples 1-3 showed no corrosion for at least 1500 hours. However, the films of Comparative Examples 1 and 2 showed spotty or cloudy discoloration and localized bubbles, indicating corrosion, after 1000 and 1200 hours, respectively. This demonstrates that the films of Examples 1-3 exhibit excellent corrosion resistance. Table 1 also shows that the films of Examples 1-3 exhibited tensile strengths of 125-133 MPa, elongations at break of 4.5%-5.2%, and water absorption of 0.4-0.45‰, demonstrating excellent mechanical properties and low water absorption.

[0160] As shown in Example 1 and Comparative Example 1, the LCP films modified with methyl 3,4-dihydroxythiophenedicarboxylate in Examples 1 to 3 significantly improved their corrosion resistance compared to the film in Comparative Example 1, with no corrosion observed for at least 1500 hours. This demonstrates that the addition of methyl 3,4-dihydroxythiophenedicarboxylate enhances the corrosion resistance of the films and also improves their mechanical properties, such as tensile strength and elongation at break.

[0161] As shown in Example 1 and Comparative Example 2, compared to the film in Comparative Example 2, the LCP films modified with a specific amount of 3,4-dihydroxythiophenedicarboxylic acid methyl ester in Examples 1 to 3 significantly improved the corrosion resistance of the films, exhibiting no corrosion for at least 1500 hours. This demonstrates that the content of 3,4-dihydroxythiophenedicarboxylic acid methyl ester is a critical parameter. Only within the specific range specified in this application can the corrosion-free effect of at least 1500 hours as described in this application be achieved. If the content is too low, such excellent corrosion resistance cannot be achieved.

[0162] In summary, the corrosion-resistant film provided by the present invention has good mechanical properties, excellent flexibility and mechanical stability. At the same time, the corrosion-resistant film provided by the present invention has low water absorption, which means that it has good stability in complex application environments and excellent corrosion resistance.

[0163] Example 4

[0164] This embodiment provides a specific corrosion-resistant pipe and its preparation method, which specifically includes the following steps:

[0165] 1) Pretreatment of pipes

[0166] 1-1) Immerse the aluminum alloy pipe completely in anhydrous ethanol and ultrasonically clean it for 10 minutes. Then, rinse it with deionized water until the inner surface of the aluminum alloy pipe is clean and free of oil and other impurities, and then dry it.

[0167] 1-2) The aluminum alloy tube obtained in 1-1) was completely immersed in hydrochloric acid (concentration of 5%, temperature of 50° C.) for 5 minutes, then washed with deionized water until the aluminum alloy tube became neutral, and dried.

[0168] 2) Composite corrosion-resistant film

[0169] The corrosion-resistant composite film prepared in Example 1 is completely and tightly attached to the inner surface of the pretreated aluminum alloy pipe, and a movable medium-frequency induction heating coil (frequency 500-2000 Hz) is set around the outer surface of the aluminum alloy pipe and heated to 280°C. The medium-frequency induction heating coil is moved so that all pipes are in an environment of 280°C.

[0170] At the same time, a detachable head is used to seal the pipe so that the inside of the pipe is in a sealed state. A detachable head is connected to a section of the vacuum pump to evacuate the inside of the pipe until the vacuum degree reaches 80kPa. After keeping warm and pressurized for 30 minutes, the pipe is naturally cooled to obtain the corrosion-resistant pipe.

[0171] Example 5

[0172] This embodiment provides a specific corrosion-resistant pipe and its preparation method, which specifically includes the following steps:

[0173] 1) Pretreatment of pipes

[0174] 1-1) Same as Example 4.

[0175] 1-2) No pickling treatment is performed.

[0176] 2) Composite corrosion-resistant film

[0177] The corrosion-resistant pipe is obtained in the same manner as in Example 4.

[0178] Comparative Example 5

[0179] This comparative example provides a specific corrosion-resistant pipe and its preparation method. Specifically comprising the following steps:

[0180] 1) Pretreatment of pipes

[0181] Exactly the same as Example 4

[0182] 2) Composite corrosion-resistant film

[0183] The corrosion-resistant film used in Example 4 was replaced by the corrosion-resistant film prepared in Comparative Example 1, and the rest was the same as in Example 4.

[0184] Comparative Example 6

[0185] This comparative example provides a specific corrosion-resistant pipe and its preparation method, which specifically includes the following steps:

[0186] 1) Pretreatment of pipes

[0187] Exactly the same as Example 4

[0188] 2) Composite corrosion-resistant film

[0189] The corrosion-resistant film used in Example 4 was replaced by the corrosion-resistant film prepared in Comparative Example 2, and the rest was the same as in Example 4.

[0190] The applicant also conducted performance tests on the pipes prepared in Examples 4-5 and Comparative Examples 5 and 6, including salt spray tests and adhesion tests.

[0191] The specific test method is:

[0192] The salt spray test method is carried out in accordance with GB / T 10125-2021, using the acetic acid salt spray test (AASS): a 5% sodium chloride acid solution with glacial acetic acid is atomized for testing, using a circulating spray method until corrosion occurs on the test material. The time in Table 2 below is the time when corrosion occurs in the salt spray test.

[0193] The test method of adhesion test is carried out in accordance with GB / T 5210-2006.

[0194] The specific results are shown in Table 2 below.

[0195] Table 2

[0196]

[0197] When the same salt spray test was conducted only on aluminum alloy pipes, it was found that the aluminum alloy pipes showed slight white rust or pitting after 72 hours.

[0198] As can be seen from Examples 4 to 5 in Table 2, the corrosion-resistant pipe provided by the invention has excellent corrosion resistance and can maintain no corrosion for at least 1500 hours during the acetic acid salt spray test. In addition, the film has strong adhesion to the surface of the pipe and can achieve a tensile strength of 6.4 to 7.2.

[0199] It can be seen from Example 4 and Comparative Example 5 in Table 2 that the pipe in Comparative Example 5 had local bubbles and local shedding of the film after 500 hours, which shows that the use of the LCP film modified with methyl 3,4-dihydroxythiophenedicarboxylate in this application is a very important technical means. If the unmodified LCP film in the prior art is used, the film has weak adhesion to the surface of the pipe and is easy to fall off, which leads to poor corrosion resistance of the pipe.

[0200] As can be seen from Example 4 and Comparative Example 6 in Table 2, local bubbles and local shedding of the film appeared in the pipe in Comparative Example 6 after 800 hours, which shows that the use of the LCP film modified with 3,4-dihydroxythiophene dicarboxylic acid methyl ester in this application is a very important technical means, and the amount of 3,4-dihydroxythiophene dicarboxylic acid methyl ester added is very specific. Only within the range provided in this application (the molar ratio of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 3,4-dihydroxythiophene dicarboxylic acid methyl ester is 60-80:5-40:0.5-3) can the stronger adhesion when combined with the metal in this application be achieved, thereby further achieving the technical effect of maintaining no corrosion for at least 1500 hours in the acetic acid salt spray test.

[0201] In summary, the thin film coating in the corrosion-resistant pipe provided by the present invention has a strong bonding ability with the metal pipe, the film has good adhesion ability, and the pipe has excellent corrosion resistance.

[0202] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A corrosion-resistant film, characterized in that: The raw material components of the corrosion-resistant film contain at least modified LCP, and the raw material components of the modified LCP include p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 3,4-dihydroxythiophenedicarboxylic acid methyl ester, and the molar ratio of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 3,4-dihydroxythiophenedicarboxylic acid methyl ester is 60-80:5-40:0.5-3.

2. The corrosion-resistant film according to claim 1, characterized in that The number average molecular weight of the modified LCP is 2.5w to 5w; And / or, the water absorption rate of the corrosion-resistant film is less than or equal to 0.5‰; and / or, the corrosion-resistant film has a tensile strength of 110 to 140 MPa; And / or, the elongation at break of the corrosion-resistant film is 3 to 5.5%.

3. A method for preparing a corrosion-resistant film, characterized in that: The specific steps are: providing a modified LCP, granulating the modified LCP and then casting it into a film at high temperature to obtain the corrosion-resistant film; The preparation method of the modified LCP is as follows: after the above-mentioned p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and methyl 3,4-dihydroxythiophenedicarboxylate are mixed in proportion, an acetylation reaction is carried out with acetic anhydride under the condition of a catalyst, and after the acetylation reaction is completed, a melt polymerization reaction and a solid phase polymerization reaction are carried out to obtain the modified LCP.

4. The preparation method according to claim 3, characterized in that The temperature of the high-temperature casting film is 300-340°C; and / or, the temperature of the acetylation reaction is 130-150° C.; and / or, the acetylation reaction is carried out in an inert gas environment; and / or, the catalyst is one or more of potassium acetate, sodium acetate, magnesium acetate, zinc acetate and calcium acetate; And / or, the melt polymerization reaction includes a first stage reaction and a second stage reaction; the first stage reaction temperature is 210-240° C.; the second stage reaction temperature is 260-320° C.; and / or, discharging acetic acid and acetic anhydride by-products by condensation reflux during the melt polymerization reaction; and / or, the melt polymerization reaction is carried out in an inert gas environment; And / or, the solid phase polymerization reaction temperature is (T m -35)℃~(T m -25)℃,T m is the melting temperature of the modified LCP; And / or, the melting temperature of the modified LCP is 270-280°C.

5. The preparation method according to claim 3, characterized in that Based on the total mass of the modified LCP raw material, the content of the catalyst is 0.01wt% to 0.05wt%; and / or, the molar ratio of the acetic anhydride to the total components of the modified LCP raw materials is acetic anhydride: the sum of the molar numbers of the total components of the modified LCP raw materials = 1.01 to 1.10:1; And / or, the second stage reaction further includes vacuuming; when the second stage reaction is completed until no liquid flows out of the condenser, vacuuming is performed, and the vacuum degree is 0.01-1 kPa.

6. A corrosion-resistant pipe, characterized in that: The inner wall of the pipe is completely compounded with the corrosion-resistant film according to any one of claims 1 to 2.

7. The corrosion-resistant pipe according to claim 6, characterized in that: The pipe is one or more of a stainless steel pipe, a titanium alloy pipe and an aluminum alloy pipe; And / or, the thickness of the corrosion-resistant film is 30 to 80 μm.

8. A method for preparing a corrosion-resistant pipe according to any one of claims 6 to 7, characterized in that: Providing a pipe and pretreating the inner surface of the pipe; providing the corrosion-resistant film according to any one of claims 1 to 2, and completely and tightly fitting the corrosion-resistant film to the inner surface of the pipe; performing high-temperature compounding and cooling to obtain the corrosion-resistant pipe.

9. The preparation method according to claim 8, characterized in that The pretreatment includes one or more of sandblasting, grinding, cleaning and pickling; and / or, the temperature of the high-temperature compounding is 270-300°C; And / or, during high temperature compounding, the tube needs to be evacuated to maintain a vacuum degree of 50-100 kPa; And / or, a medium frequency induction heating coil is used to provide the temperature required for high temperature compounding.

10. Use of the corrosion-resistant pipe according to any one of claims 6 to 7 as a crude oil transportation pipeline in the oil and gas industry.

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