A method for preparing a low-temperature resistant coating for natural gas metal pipelines

Abstract

The application relates to the technical field of paint, and discloses a preparation method of a low-temperature-resistant paint for natural gas metal pipelines, which comprises 85-95 parts by weight of an acrylate monomer, 5-15 parts by weight of a methyl methacrylate hydroxyl perfluoroalkane, 1.1-1.2 parts by weight of an initiator, 28-40 parts by weight of a filler and 12-30 parts by weight of an isocyanate-terminated polyurethane prepolymer. The isocyanate-terminated polyurethane is chemically bonded to the acrylic resin matrix, plays a good toughening role, and can improve the adhesion, toughness and impact resistance of the paint film. After low-temperature treatment, the acrylic resin molecular chain and the isocyanate-terminated polyurethane still maintain a stable crosslinking system, the adhesion grade and the impact resistance have a very small decline, the paint film is not easy to crack and fall off at low temperature, and good low-temperature resistance is shown.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a method for preparing a low-temperature resistant coating for natural gas metal pipelines. Background Technology

[0002] Acrylic resin is a high-performance resin mainly obtained by the polymerization reaction of monomers such as acrylate and styrene. Coatings made from acrylic resin are widely used on metal substrates such as pipes, instruments, and vehicles, providing corrosion protection and scratch resistance. Improving the water resistance, low-temperature resistance, and adhesion of acrylic resin coatings will facilitate their application in harsh environments such as humid and frigid conditions.

[0003] Currently, methods for modifying acrylic resins include monomer modification, crosslinking modification, and filler modification. Patent CN113861333B discloses a crosslinked acrylic resin emulsion and its synthesis method and application. Using butyl acrylate monomer, crosslinking monomer, fluorinated monomer, etc. as raw materials, the prepared crosslinked acrylic resin has good film-forming properties, weather resistance, and adhesion. However, this crosslinked acrylic resin does not have good anti-corrosion and low-temperature resistance properties. Summary of the Invention

[0004] (I) Technical problem to be solved: The present invention provides a method for preparing an acrylic resin coating for natural gas metal pipelines with good toughness and low temperature resistance.

[0005] (II) Technical Solution: A method for preparing a low-temperature resistant coating for natural gas metal pipelines: 85-95 parts by weight of acrylate monomer and 5-15 parts by weight of methacrylate hydroxyl perfluoroalkane are added to a solvent to prepare a monomer solution. Under a nitrogen atmosphere, 20-30% by volume of the monomer solution is added dropwise to a reaction vessel. The mixture is heated to 75-85°C, stirred, and 0.25-0.32 parts by weight of initiator are added dropwise for a prepolymerization reaction of 40-60 minutes. The remaining monomer solution is then added dropwise, along with 0.85-0.88 parts by weight of initiator, for a polymerization reaction of 3-4 hours. After cooling, 0.6-1 parts by weight of defoamer, 28-40 parts by weight of filler, and 0.5-0.8 parts by weight of dispersant are added. The mixture is then ground in a sand mill. Finally, 12-30 parts by weight of terminal isocyanate polyurethane prepolymer is added to obtain the low-temperature resistant coating for natural gas metal pipelines.

[0006] Furthermore, the solvent is toluene, propylene glycol methyl ether acetate, or butyl acetate.

[0007] Furthermore, the acrylate monomer is any one or a combination of methyl methacrylate, methyl acrylate, butyl methacrylate, butyl acrylate, methylstyrene, and styrene.

[0008] Furthermore, the initiator is benzoyl peroxide or azobisisobutyronitrile.

[0009] Furthermore, the filler is titanium dioxide or talc.

[0010] Furthermore, the preparation method of methacrylate hydroxyperfluoroalkane is as follows:

[0011] (1) In an ice bath, add dichloromethane, perfluoroalkyl acyl chloride, N-BOC-N-methylaminoethanol, and triethylamine to a reaction flask in a molar ratio of 1:(1-1.1):(1-1.1). Stir and react at 15-20℃ for 18-24 h. After rotary evaporation and washing with water, add the product to dichloromethane, add trifluoroacetic acid, stir and react at 20-30℃ for 3-5 h. After rotary evaporation, wash the product with sodium bicarbonate aqueous solution and dry to obtain N-methylaminoperfluoroalkyl ethyl ester. The reaction formula is as follows:

[0012]

[0013] (2) Add tetrahydrofuran, glycidyl methacrylate in a molar ratio of 1:(1-1.2), and N-methylaminoperfluoroalkane ethyl ester to a reaction flask. Stir and heat to 40-50℃, react for 6-10 h, then rotary evaporate and separate by column chromatography. The developing solvent is a mixed solution of propylene glycol methyl ether acetate and dichloromethane to obtain methacrylate hydroxyperfluoroalkane. The reaction formula is as follows:

[0014]

[0015] Furthermore, the structural formula of perfluoroalkyl acyl chloride is as follows: n is 6-8.

[0016] Furthermore, the preparation method of the isocyanate-terminated polyurethane prepolymer is as follows: add polytetrahydrofuran ether diol to a reaction flask, heat to 105°C, dehydrate under vacuum, then add diisocyanate and dibutyltin dilaurate, purge with nitrogen, heat to 70-80°C, react for 2.5-3 hours, cool, and dry to obtain the isocyanate-terminated polyurethane prepolymer.

[0017] Furthermore, the diisocyanate is isophorone diisocyanate or toluene-2,4-diisocyanate.

[0018] (III) Technical effects: This invention utilizes methacrylate hydroxy-perfluoroalkane as a functional monomer, and polymerizes it with monomers such as butyl methacrylate and styrene. The resulting acrylic resin contains long perfluoroalkyl chains, which is beneficial to improving the water resistance and salt spray resistance of the paint film and exhibits excellent anti-corrosion performance.

[0019] In addition, the methacrylate hydroxyl perfluoroalkane of this invention contains active hydroxyl groups, which allows the acrylic resin to undergo a cross-linking reaction with the terminal isocyanate polyurethane, thereby increasing the degree of cross-linking of the acrylic resin molecular chain. This is beneficial for improving the hardness and mechanical properties of the paint film. At the same time, increasing the degree of cross-linking of the molecular chain can inhibit corrosive media such as water and salt from entering the paint film matrix, and can further improve the water resistance and salt spray resistance of the paint film.

[0020] The isocyanate-terminated polyurethane of this invention is chemically bonded to the acrylic resin matrix, providing excellent toughening and improving the adhesion, toughness, and impact resistance of the coating film. Furthermore, even after low-temperature treatment, the acrylic resin molecular chains and the isocyanate-terminated polyurethane maintain a stable cross-linked system, with minimal decrease in adhesion and impact resistance. The coating film is less prone to cracking and peeling at low temperatures, exhibiting excellent low-temperature resistance. Detailed Implementation

[0021] To further illustrate the present invention, the following detailed description of an epoxy resin composition for copper-clad laminates and a method for preparing epoxy resin copper-clad laminates provided by the present invention is provided in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given, only to further illustrate the features and advantages of the present invention, and not to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0022] Example 1: (1) Add 50 mmol of polytetrahydrofuran ether diol 1000 to the reaction flask, heat to 105°C, dehydrate under vacuum, then add 120 mmol of isophorone diisocyanate and 11 mg of dibutyltin dilaurate, purge with nitrogen, heat to 70°C, react for 3 h, cool, and dry to obtain isocyanate-terminated polyurethane prepolymer.

[0023] (2) In an ice bath, 70 mL of dichloromethane, 30 mmol of perfluorooctanoyl chloride (CAS Registry No. 335-64-8), 30 mmol of N-BOC-N-methylaminoethanol (CAS Registry No. 57561-39-4), and 30 mmol of triethylamine were added to a reaction flask. The mixture was stirred and reacted at 20 °C for 18 h. After rotary evaporation and washing with water, the product was added to 100 mL of dichloromethane and 80 mL of trifluoroacetic acid. The mixture was stirred and reacted at 30 °C for 3 h. After rotary evaporation, the product was washed with sodium bicarbonate aqueous solution and dried to obtain N-methylaminoperfluoroalkane ethyl ester.

[0024] (3) Add 30 mL of tetrahydrofuran, 30 mmol of glycidyl methacrylate and 36 mmol of N-methylaminoperfluoroalkane ethyl ester to the reaction flask, stir and heat to 40 °C, react for 10 h, rotary evaporate, and separate by column chromatography. The developing solvent is a mixed solution of propylene glycol methyl ether acetate and dichloromethane to obtain methacrylate hydroxyperfluoroalkane.

[0025] (4) Add 490g of methyl methacrylate, 310g of butyl acrylate, 150g of styrene, and 50g of methyl methacrylate hydroxyl perfluoroalkane to 2.5L of toluene to prepare a monomer solution. Under a nitrogen atmosphere, add 30% of the monomer solution dropwise to the reactor, heat to 80°C, stir and add 3g of initiator benzoyl peroxide, and carry out a prepolymerization reaction for 60min. Then add the remaining 70% of the monomer solution dropwise and add 8.8g of initiator benzoyl peroxide, and carry out a polymerization reaction for 4h. After cooling, add 6g of defoamer, 280g of filler titanium dioxide, and 6g of dispersant, grind in a sand mill, and then add 120g of terminal isocyanate polyurethane prepolymer to obtain a low-temperature resistant coating for natural gas metal pipelines.

[0026] Example 2: (1) Add 50 mmol of polytetrahydrofuran ether diol 1000 to the reaction flask, heat to 105°C, dehydrate under vacuum, then add 130 mmol of toluene-2,4-diisocyanate and 8 mg of dibutyltin dilaurate, purge with nitrogen, heat to 80°C, react for 2.5 h, cool, and dry to obtain isocyanate-terminated polyurethane prepolymer.

[0027] (2) In an ice bath, 100 mL of dichloromethane, 30 mmol of perfluorononanoyl chloride (CAS Registry No. 52447-23-1), 33 mmol of N-BOC-N-methylaminoethanol, and 33 mmol of triethylamine were added to the reaction flask. The mixture was stirred and reacted at 15 °C for 24 h. After rotary evaporation and washing with water, the product was added to 100 mL of dichloromethane and 70 mL of trifluoroacetic acid was added. The mixture was stirred and reacted at 20 °C for 5 h. After rotary evaporation, the product was washed with sodium bicarbonate aqueous solution and dried to obtain N-methylaminoperfluoroalkane ethyl ester.

[0028] (3) Add 20 mL of tetrahydrofuran, 30 mmol of glycidyl methacrylate and 30 mmol of N-methylaminoperfluoroalkane ethyl ester to the reaction flask, stir and heat to 50 °C, react for 6 h, rotary evaporate, and separate by column chromatography. The developing solvent is a mixed solution of propylene glycol methyl ether acetate and dichloromethane to obtain methacrylate hydroxyperfluoroalkane.

[0029] (4) Add 470g of methyl acrylate, 300g of butyl methacrylate, 150g of styrene, and 80g of hydroxyl perfluoroalkane to 2.5L of butyl acetate to prepare a monomer solution. Under a nitrogen atmosphere, add 20% of the monomer solution dropwise to the reactor, heat to 80°C, stir and add 3.2g of initiator benzoyl peroxide, and carry out a prepolymerization reaction for 60min. Then add the remaining 80% of the monomer solution dropwise and add 8.8g of initiator benzoyl peroxide, and carry out a polymerization reaction for 4h. After cooling, add 10g of defoamer, 400g of filler talc powder, and 8g of dispersant, grind in a sand mill, and then add 180g of terminal isocyanate polyurethane prepolymer to obtain a low-temperature resistant coating for natural gas metal pipelines.

[0030] Example 3: (1) Add 470g of methyl methacrylate, 280g of butyl methacrylate, 130g of styrene, and 120g of hydroxyl perfluoroalkane methacrylate (prepared according to the method of Example 1) to 3L of propylene glycol methyl ether acetate to prepare a monomer solution. In a nitrogen atmosphere, add 30% of the monomer solution dropwise to the reactor, heat to 75°C, stir and add 2.5g of initiator azobisisobutyronitrile, and carry out a prepolymerization reaction for 60min. Then add the remaining 70% of the monomer solution dropwise and add 8.5g of initiator azobisisobutyronitrile, and carry out a polymerization reaction for 4h. After cooling, add 9g of defoamer, 400g of filler talc powder, and 8g of dispersant. Grind in a sand mill, and then add 240g of terminal isocyanate polyurethane prepolymer (prepared according to the method of Example 1) to obtain a low-temperature resistant coating for natural gas metal pipelines.

[0031] Example 4: (1) Add 460g of methyl acrylate, 270g of butyl methacrylate, 120g of styrene, and 150g of hydroxyl perfluoroalkane (prepared according to the method of Example 1) to 3L of toluene to prepare a monomer solution. Under a nitrogen atmosphere, add 20% of the monomer solution dropwise to the reactor, heat to 85°C, stir and add 2.8g of initiator benzoyl peroxide, and carry out a prepolymerization reaction for 40min. Then add the remaining 80% of the monomer solution dropwise and add 8.8g of initiator benzoyl peroxide, and carry out a polymerization reaction for 3h. After cooling, add 10g of defoamer, 280g of filler titanium dioxide, and 5g of dispersant. Grind in a sand mill and then add 300g of terminal isocyanate polyurethane prepolymer (prepared according to the method of Example 1) to obtain a low-temperature resistant coating for natural gas metal pipelines.

[0032] Comparative Example 1: (1) Add 490g of methyl methacrylate, 310g of butyl acrylate and 150g of styrene to 2.5L of toluene to prepare a monomer solution. Under a nitrogen atmosphere, add 30% of the monomer solution dropwise to the reactor, heat to 80°C, stir and add 3g of initiator benzoyl peroxide, and carry out a prepolymerization reaction for 60min. Then add the remaining 70% of the monomer solution dropwise and add 8.8g of initiator benzoyl peroxide, and carry out a polymerization reaction for 4h. After cooling, add 6g of defoamer, 280g of filler titanium dioxide and 6g of dispersant, grind in a sand mill, and then add 120g of terminal isocyanate polyurethane prepolymer (prepared according to the method of Example 1) to obtain a coating.

[0033] Comparative Example 2: (1) Add 490g of methyl methacrylate, 310g of butyl acrylate, 150g of styrene, and 50g of dodecafluoroheptyl methacrylate to 2.5L of toluene to prepare a monomer solution. Under a nitrogen atmosphere, add 30% of the monomer solution dropwise to the reactor, heat to 80°C, stir and add 3g of initiator benzoyl peroxide, and carry out a prepolymerization reaction for 60min. Then add the remaining 70% of the monomer solution dropwise and add 8.8g of initiator benzoyl peroxide, and carry out a polymerization reaction for 4h. After cooling, add 6g of defoamer, 280g of filler titanium dioxide, and 6g of dispersant, grind in a sand mill, and then add 120g of terminal isocyanate polyurethane prepolymer (prepared according to the method of Example 1) to obtain a coating.

[0034] Comparative Example 3: (1) Add 490g of methyl methacrylate, 310g of butyl acrylate, 150g of styrene, and 50g of methyl methacrylate hydroxy-perfluoroalkane (prepared according to the method of Example 1) to 2.5L of toluene to prepare a monomer solution. Under a nitrogen atmosphere, add 30% of the monomer solution dropwise to the reactor, heat to 80°C, stir and add 3g of initiator benzoyl peroxide, and carry out a prepolymerization reaction for 60min. Then add the remaining 70% of the monomer solution dropwise and add 8.8g of initiator benzoyl peroxide, and carry out a polymerization reaction for 4h. After cooling, add 6g of defoamer, 280g of filler titanium dioxide, and 6g of dispersant, and grind in a sand mill to obtain a low-temperature resistant coating for natural gas metal pipelines.

[0035] Apply the coating to the substrate surface and bake at 120℃ for 15 minutes. Place the coating film at temperatures ranging from -20℃ to 25℃ for 120 hours, then at 25℃ for 24 hours. Test the adhesion grade of the coating film according to GB / T 9286-2021 standard. Test the impact resistance according to GB / T1732-2020 standard.

[0036] Table 1

[0037]

[0038] Table 2

[0039]

[0040]

[0041] The hardness of the coating film is tested according to GB / T 6739-2022 standard. Water resistance is tested according to GB / T 1733-1993 standard. Salt spray resistance is tested according to GB / T 1771-2007 standard.

[0042] Table 3

[0043] hardness Water resistance (h) Salt spray resistance (h) Example 1 3H 1776 1536 Example 2 4H 1968 1728 Example 3 4H 2112 1896 Example 4 4H 2184 1752 Comparative Example 1 H 1274 984 Comparative Example 2 H 1512 1198 Comparative Example 3 2H 1608 1270

[0044] As shown in Tables 1 and 2, the coatings prepared in Examples 1 to 4 exhibit higher adhesion, hardness, impact resistance, water resistance, and salt spray resistance. This is because the acrylic resin obtained by polymerizing methacrylate hydroxyl perfluoroalkane as a functional monomer contains long perfluoroalkyl chains, which is beneficial for improving the water resistance and salt spray resistance of the paint film, resulting in excellent anti-corrosion performance. Simultaneously, the methacrylate hydroxyl perfluoroalkane contains active hydroxyl groups, allowing the acrylic resin to undergo cross-linking reactions with terminal isocyanate polyurethane, increasing the degree of cross-linking of the acrylic resin molecular chain. This is beneficial for improving the hardness and mechanical properties of the paint film. Furthermore, increasing the degree of cross-linking can inhibit the penetration of corrosive media such as water and salt into the paint film matrix, further enhancing the water resistance and salt spray resistance of the paint film. Moreover, the terminal isocyanate polyurethane chemically bonded to the acrylic resin matrix plays a good toughening role, improving the adhesion, toughness, and impact resistance of the paint film. After low-temperature treatment, the acrylic resin molecular chain and the terminal isocyanate polyurethane still maintain a stable cross-linking system. The adhesion grade and impact resistance decrease only slightly, and the paint film is not easy to crack or peel off at low temperatures, showing good low-temperature resistance.

[0045] Comparative Example 1 did not contain methacrylate hydroxyl perfluoroalkane. The acrylic resin did not contain perfluoroalkyl long chains, resulting in poor water resistance and salt spray resistance. It also did not contain active hydroxyl groups, so it could not undergo cross-linking reaction with terminal isocyanate polyurethane. The hardness, impact resistance, and adhesion of the paint film were low, and the mechanical properties were poor. Furthermore, after low-temperature treatment, the impact resistance and adhesion of the paint film decreased significantly, and the low-temperature resistance was poor.

[0046] Compared with Comparative Example 1, Comparative Example 2 used dodecafluoroheptyl methacrylate as a fluorinated monomer, and the resulting acrylic resin had significantly improved water resistance and salt spray resistance. However, it did not contain hydroxyl groups and could not undergo crosslinking reaction with terminal isocyanate polyurethane. The adhesion grade, hardness, impact resistance, water resistance and salt spray resistance of the coating film were lower than those of Examples 1 to 4.

[0047] Comparative Example 3 did not contain terminal isocyanate polyurethane, so it could not undergo a crosslinking reaction with acrylic resin. The adhesion grade, hardness, impact resistance, water resistance and salt spray resistance of the coating film were lower than those of Examples 1 to 4.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a low-temperature-resistant coating for a natural gas metal pipeline, characterized by, The preparation method is: adding 85-95 parts by weight of monomers, which are any one or combination of methyl methacrylate, methyl acrylate, butyl methacrylate, butyl acrylate, methyl styrene and styrene, and 5-15 parts by weight of methacrylate hydroxyl perfluoroalkane into a solvent to configure a monomer solution, adding 20-30% volume of the monomer solution into a reaction kettle in a nitrogen atmosphere, heating and stirring and adding 0.25-0.32 parts by weight of an initiator to carry out a prepolymerization reaction, then adding the remaining monomer solution and 0.85-0.88 parts by weight of an initiator to carry out a polymerization reaction, adding 0.6-1 parts by weight of a defoaming agent, 28-40 parts by weight of a filler and 0.5-0.8 parts by weight of a dispersant after cooling, and grinding in a sand mill, and then adding 12-30 parts by weight of an isocyanate-terminated polyurethane prepolymer to obtain a low-temperature-resistant coating for natural gas metal pipelines. The structural formula of the methacrylate hydroxyl perfluoroalkane is: n is 6-8.

2. The method for preparing a cryogenic-resistant coating for natural gas metal pipes according to claim 1, characterized by, The solvent is toluene, propylene glycol methyl ether acetate or butyl acetate.

3. The method for preparing a low-temperature resistant coating for natural gas metal pipelines according to claim 1, characterized in that, The initiator is dibenzoyl peroxide or azobisisobutyronitrile.

4. The method for preparing a low-temperature resistant coating for natural gas metal pipelines according to claim 1, characterized in that, The temperature during heating is 75-85℃, the prepolymerization reaction time is 40-60 min, and the prepolymerization reaction time is 3-4 h.

5. The method of claim 1, wherein the low-temperature resistant coating for a natural gas metal pipe is prepared by mixing 100 parts by weight of a base material, 0.1 to 10 parts by weight of a curing agent, and 0.1 to 10 parts by weight of a curing accelerator. The filler is titanium white or talc.

6. The method of claim 1, wherein the low-temperature-resistant coating for a natural gas metal pipe is prepared by mixing 100 parts by weight of a base material, 0.1 to 10 parts by weight of a curing agent, and 0.1 to 10 parts by weight of a curing accelerator. The preparation method of the methacrylate hydroxyl perfluoroalkane is: (1), in an ice bath, add dichloromethane, molar ratio of 1: (1-1.1) : (1-1.1) perfluoroalkyl acid chloride, N-BOC-N-methylaminoethanol, triethylamine to the reaction bottle, stir and react at 15-20℃ for 18-24h, rotary evaporation, after washing, the product is added to dichloromethane, add trifluoroacetic acid, stir and react at 20-30℃ for 3-5h, rotary evaporation, washing, drying, to obtain N-methylamino perfluoroalkane ethyl ester; the structural formula of the N-methylamino perfluoroalkane ethyl ester is ; (2) adding tetrahydrofuran, glycidyl methacrylate with a molar ratio of 1:(1-1.2) and N-methyl amino perfluoroalkane ethyl ester into a reaction bottle, stirring and heating to 40-50℃, reacting for 6-10 h, rotary evaporation, column chromatography separation to obtain the methacrylate hydroxyl perfluoroalkane.

7. The method for preparing a low-temperature resistant coating for natural gas metal pipelines according to claim 6, characterized in that, The perfluoroalkyl acid chloride has a structural formula of n is 6-8.

8. The method for preparing a low-temperature resistant coating for natural gas metal pipelines according to claim 1, characterized in that, The preparation method of the isocyanate-terminated polyurethane prepolymer is: adding polytetrahydrofuran ether diol into a reaction bottle, heating to 105℃, vacuum dewatering, then adding diisocyanate and dibutyl tin dilaurate, passing nitrogen, heating to 70-80℃, reacting for 2.5-3 h, cooling and drying to obtain the isocyanate-terminated polyurethane prepolymer.

9. The method for preparing a low-temperature resistant coating for natural gas metal pipelines according to claim 8, characterized in that, The diisocyanate is isophorone diisocyanate or toluene-2,4-diisocyanate.

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