Preparation method of low-temperature-resistant coating for natural gas metal pipeline

Abstract

The invention relates to the technical field of coatings, and discloses a preparation method of a low-temperature-resistant coating for a natural gas metal pipeline, and the low-temperature-resistant coating comprises 85-95 parts by weight of an acrylate monomer, 5-15 parts by weight of 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. Isocyanate-terminated polyurethane is chemically bonded into an acrylic resin matrix, so that a good toughening effect is achieved, and the adhesive force, toughness and impact resistance of a paint film can be improved. And after low-temperature treatment, the acrylic resin molecular chain and the isocyanate-terminated polyurethane still keep a stable cross-linking system, the adhesive force grade and the impact resistance are slightly reduced, and a paint film is not easy to crack and fall off at low temperature and shows good low-temperature resistance.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a method for preparing a low-temperature resistant coating for a natural gas metal pipeline. Background Art

[0002] Acrylic resin is a high-performance resin obtained by polymerization of monomers such as acrylate and styrene. The coating made from it is widely used in metal substrates such as pipelines, instruments and equipment, and transportation vehicles, and can play a role in corrosion resistance and scratch resistance. Improving the water resistance, low temperature resistance, adhesion and other properties of acrylic resin coatings will help expand its practical application in harsh environments such as humidity and severe cold.

[0003] At present, the methods for modifying acrylic resin include monomer modification, cross-linking modification, filling modification, etc. Patent CN113861333B discloses a cross-linked acrylic resin emulsion and its synthesis method and application. The cross-linked acrylic resin prepared from butyl acrylate monomer, cross-linking monomer, fluorine monomer, etc. has good film-forming properties, weather resistance, adhesion, etc., but the cross-linked acrylic resin does not have good anti-corrosion, low temperature resistance, etc. Summary of the invention

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

[0005] (ii) Technical solution: A method for preparing a low-temperature resistant coating for a natural gas metal pipeline: 85-95 parts by weight of an acrylate monomer and 5-15 parts by weight of a methacrylate hydroxyperfluoroalkane are added to a solvent to prepare a monomer solution, 20-30% by volume of the monomer solution is added dropwise to a reactor in a nitrogen atmosphere, heated to 75-85°C, stirred and 0.25-0.32 parts by weight of an initiator are added dropwise, a prepolymerization reaction is carried out for 40-60 minutes, the remaining monomer solution is added dropwise, and 0.85-0.88 parts by weight of an initiator are added dropwise, a polymerization reaction is carried out for 3-4 hours, 0.6-1 parts by weight of a defoamer, 28-40 parts by weight of a filler, and 0.5-0.8 parts by weight of a dispersant are added after cooling, the mixture is ground in a sand mill, and 12-30 parts by weight of an isocyanate-terminated polyurethane prepolymer is added to obtain a low-temperature resistant coating for a natural gas metal pipeline.

[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, methyl styrene, and styrene.

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

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

[0010] Further, the preparation method of methacrylate hydroxyperfluoroalkane is:

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

[0012]

[0013] (2) Add tetrahydrofuran, glycidyl methacrylate and N-methylamino perfluoroalkane ethyl ester in a molar ratio of 1:(1-1.2) to a reaction flask, stir and heat to 40-50°C, react for 6-10 hours, 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 hydroxy perfluoroalkane. The reaction formula is as follows:

[0014]

[0015] Further, the structural formula of perfluoroalkyl acyl chloride is n is 6-8.

[0016] Furthermore, the preparation method of the isocyanate-terminated polyurethane prepolymer is as follows: add polytetramethylene glycol to a reaction bottle, heat to 105°C, vacuum dehydrate, then add diisocyanate and dibutyltin dilaurate, introduce nitrogen, heat to 70-80°C, react for 2.5-3h, 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 effect: The present invention utilizes methacrylate hydroxyperfluoroalkane as a functional monomer to carry out polymerization reaction with monomers such as butyl methacrylate and styrene. The obtained acrylic resin contains a perfluoroalkyl long chain, which is beneficial to improving the water resistance and salt spray resistance of the paint film and exhibits good anti-corrosion performance.

[0019] The methacrylate hydroxy perfluoroalkane of the present invention contains active hydroxyl groups, so that the acrylic resin can undergo a cross-linking reaction with the terminal isocyanate polyurethane, thereby increasing the cross-linking degree of the acrylic resin molecular chain, which is beneficial to improving the hardness and mechanical properties of the paint film. At the same time, increasing the cross-linking degree 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 terminal isocyanate polyurethane of the present invention is chemically bonded to the acrylic resin matrix, which 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 terminal isocyanate polyurethane still maintain a stable cross-linking system, the adhesion level and impact resistance decrease slightly, and the paint film is not easy to crack and fall off at low temperatures, showing good low-temperature resistance. DETAILED DESCRIPTION

[0021] In order to further illustrate the present invention, an epoxy resin composition for copper clad laminate and a method for preparing an epoxy resin copper clad laminate provided by the present invention are described in detail below in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following embodiments.

[0022] Example 1: (1) Add 50 mmol of polytetramethylene glycol 1000 to a reaction bottle, heat to 105°C, vacuum dehydrate, then add 120 mmol of isophorone diisocyanate and 11 mg of dibutyltin dilaurate, introduce nitrogen, heat to 70°C, react for 3 hours, cool, and dry to obtain a terminal isocyanate polyurethane prepolymer.

[0023] (2) In an ice bath, add 70 mL of dichloromethane, 30 mmol of perfluorooctanoyl chloride (CAS registration number 335-64-8), 30 mmol of N-BOC-N-methylaminoethanol (CAS registration number 57561-39-4), and 30 mmol of triethylamine to a reaction bottle, stir and react at 20°C for 18 h, rotary evaporate, wash with water, add the product to 100 mL of dichloromethane, add 80 mL of trifluoroacetic acid, stir and react at 30°C for 3 h, rotary evaporate, wash the product with sodium bicarbonate aqueous solution, and dry 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 490 g of methyl methacrylate, 310 g of butyl acrylate, 150 g of styrene, and 50 g of methacrylate hydroxyperfluoroalkane to 2.5 L of toluene to prepare a monomer solution. In a nitrogen atmosphere, add 30% of the volume of the monomer solution to a reactor, heat to 80° C., stir and add 3 g of initiator dibenzoyl peroxide, and perform a prepolymerization reaction for 60 minutes. Then add the remaining 70% of the volume of the monomer solution and 8.8 g of initiator dibenzoyl peroxide, and perform a polymerization reaction for 4 hours. After cooling, add 6 g of a defoamer, 280 g of filler titanium dioxide, and 6 g of a dispersant. Grind in a sand mill, and then add 120 g of a terminal isocyanate polyurethane prepolymer to obtain a low-temperature resistant coating for a natural gas metal pipeline.

[0026] Example 2: (1) Add 50 mmol of polytetramethylene glycol 1000 to a reaction bottle, heat to 105°C, vacuum dehydrate, then add 130 mmol of toluene-2,4-diisocyanate and 8 mg of dibutyltin dilaurate, introduce nitrogen, heat to 80°C, react for 2.5 hours, cool, and dry to obtain a terminal isocyanate polyurethane prepolymer.

[0027] (2) In an ice bath, add 100 mL of dichloromethane, 30 mmol of perfluorononanoyl chloride (CAS registration number 52447-23-1), 33 mmol of N-BOC-N-methylaminoethanol, and 33 mmol of triethylamine to a reaction flask, stir and react at 15°C for 24 h, rotary evaporate, wash with water, add the product to 100 mL of dichloromethane, add 70 mL of trifluoroacetic acid, stir and react at 20°C for 5 h, rotary evaporate, wash the product with sodium bicarbonate aqueous solution, and dry to obtain N-methylaminoperfluoroalkane ethyl ester.

[0028] (3) Add 20 mL of tetrahydrofuran, 30 mmol of glycidyl methacrylate, and 30 mmol of ethyl N-methylaminoperfluoroalkane into a 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 470 g of methyl acrylate, 300 g of butyl methacrylate, 150 g of styrene, and 80 g of methacrylate hydroxyperfluoroalkane to 2.5 L of butyl acetate to prepare a monomer solution. In a nitrogen atmosphere, add 20% of the volume of the monomer solution to a reactor, heat to 80° C., stir and add 3.2 g of initiator dibenzoyl peroxide, and perform a prepolymerization reaction for 60 minutes. Then add the remaining 80% of the volume of the monomer solution and 8.8 g of initiator dibenzoyl peroxide, and perform a polymerization reaction for 4 hours. After cooling, add 10 g of a defoamer, 400 g of a filler talc, and 8 g of a dispersant. Grind in a sand mill, and then add 180 g of a terminal isocyanate polyurethane prepolymer to obtain a low-temperature resistant coating for a natural gas metal pipeline.

[0030] Example 3: (1) To 3L propylene glycol methyl ether acetate, 470g methyl methacrylate, 280g butyl methacrylate, 130g styrene, and 120g methacrylate hydroxyperfluoroalkane (prepared according to the method of Example 1) were added to form a monomer solution. In a nitrogen atmosphere, 30% volume of the monomer solution was added dropwise to a reactor, heated to 75°C, stirred and 2.5g of initiator azobisisobutyronitrile was added dropwise, and a prepolymerization reaction was carried out for 60min. The remaining 70% volume of the monomer solution was then added dropwise, and 8.5g of initiator azobisisobutyronitrile was added dropwise, and a polymerization reaction was carried out for 4h. After cooling, 9g of a defoamer, 400g of filler talc, and 8g of a dispersant were added, and the mixture was ground in a sand mill. Then 240g of terminal isocyanate polyurethane prepolymer (prepared according to the method of Example 1) was added to obtain a low-temperature resistant coating for a natural gas metal pipeline.

[0031] Example 4: (1) 460 g of methyl acrylate, 270 g of butyl methacrylate, 120 g of styrene, and 150 g of methacrylate hydroxyperfluoroalkane (prepared according to the method of Example 1) were added to 3 L of toluene to form a monomer solution. In a nitrogen atmosphere, 20% volume of the monomer solution was added dropwise to a reactor, heated to 85°C, stirred and 2.8 g of initiator dibenzoyl peroxide was added dropwise, and a prepolymerization reaction was carried out for 40 min. The remaining 80% volume of the monomer solution was then added dropwise, and 8.8 g of initiator dibenzoyl peroxide was added dropwise, and a polymerization reaction was carried out for 3 h. After cooling, 10 g of a defoamer, 280 g of filler titanium dioxide, and 5 g of a dispersant were added, and the mixture was ground in a sand mill. Then 300 g of a terminal isocyanate polyurethane prepolymer (prepared according to the method of Example 1) was added to obtain a low-temperature resistant coating for a natural gas metal pipeline.

[0032] Comparative Example 1: (1) 490 g of methyl methacrylate, 310 g of butyl acrylate and 150 g of styrene were added to 2.5 L of toluene to prepare a monomer solution. In a nitrogen atmosphere, 30% of the volume of the monomer solution was added dropwise to a reactor, heated to 80°C, stirred and 3 g of initiator dibenzoyl peroxide was added dropwise, and a prepolymerization reaction was carried out for 60 min. The remaining 70% of the volume of the monomer solution was added dropwise, and 8.8 g of initiator dibenzoyl peroxide was added dropwise, and a polymerization reaction was carried out for 4 h. After cooling, 6 g of a defoamer, 280 g of filler titanium dioxide and 6 g of a dispersant were added, and the mixture was ground in a sand mill. Then 120 g of a terminal isocyanate polyurethane prepolymer (prepared according to the method of Example 1) was added to obtain a coating.

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

[0034] Comparative Example 3: (1) 490 g of methyl methacrylate, 310 g of butyl acrylate, 150 g of styrene and 50 g of methacrylate hydroxyperfluoroalkane (prepared according to the method of Example 1) were added to 2.5 L of toluene to prepare a monomer solution. 30% volume of the monomer solution was added dropwise to a reactor in a nitrogen atmosphere, heated to 80° C., stirred and 3 g of initiator dibenzoyl peroxide was added dropwise to carry out a prepolymerization reaction for 60 min, and then the remaining 70% volume of the monomer solution was added dropwise, and 8.8 g of initiator dibenzoyl peroxide was added dropwise to carry out a polymerization reaction for 4 h. After cooling, 6 g of a defoamer, 280 g of filler titanium dioxide and 6 g of a dispersant were added, and the mixture was ground in a sand mill to obtain a low-temperature resistant coating for a natural gas metal pipeline.

[0035] The coating was applied to the substrate surface and baked at 120°C for 15 minutes. The paint film was placed at -20°C to 25°C for 120 hours, and then at 25°C for 24 hours. The adhesion grade of the paint film was tested according to GB / T 9286-2021. The impact resistance was tested according to GB / T1732-2020.

[0036] Table 1

[0037]

[0038] Table 2

[0039]

[0040]

[0041] The hardness of the paint film was tested according to GB / T 6739-2022. The water resistance was tested according to GB / T 1733-1993. The salt spray resistance was tested according to GB / T 1771-2007.

[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 Table 1 and Table 2, the coatings prepared by Examples 1 to 4 have higher adhesion grade, hardness, impact resistance, water resistance and salt spray resistance, because the acrylic resin obtained by polymerization contains a perfluoroalkyl long chain by using methacrylate hydroxyl perfluoroalkane as a functional monomer, which is conducive to improving the water resistance and salt spray resistance of the paint film and showing good corrosion resistance.Methacrylate hydroxyl perfluoroalkane contains active hydroxyl groups at the same time, so that acrylic resin can react with terminal isocyanate polyurethane, improves the crosslinking degree of acrylic resin molecular chain, is conducive to improving the hardness and mechanical properties of the paint film, and improves the crosslinking degree of molecular chain at the same time, can inhibit corrosive media such as water and salt from entering the paint film matrix, can further improve the water resistance and salt spray resistance of the paint film.And terminal isocyanate polyurethane is chemically bonded to the acrylic resin matrix, plays a good toughening effect, can improve 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 level and impact resistance decrease very little, the paint film is not easy to crack and fall off at low temperatures, and exhibits good low-temperature resistance.

[0045] In Comparative Example 1, no methacrylate hydroxyperfluoroalkane was added, the acrylic resin did not contain perfluoroalkyl long chains, had poor water resistance and salt spray resistance, did not contain active hydroxyl groups, and 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. Moreover, 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 uses dodecafluoroheptyl methacrylate as the fluorine-containing monomer, and the water resistance and salt spray resistance of the acrylic resin obtained are significantly improved, but it does not contain hydroxyl groups and cannot undergo cross-linking reaction with terminal isocyanate polyurethane. The adhesion grade, hardness, impact resistance, water resistance and salt spray resistance of the paint film are lower than those of Examples 1 to 4.

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

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a low-temperature resistant coating for a natural gas metal pipeline, characterized in that: The preparation method comprises: adding 85-95 parts by weight of acrylic acid ester monomer and 5-15 parts by weight of methacrylate hydroxy perfluoroalkane into a solvent to prepare a monomer solution, dripping 20-30% volume of the monomer solution into a reaction kettle in a nitrogen atmosphere, heating and stirring, dripping 0.25-0.32 parts by weight of an initiator, performing a prepolymerization reaction, dripping the remaining monomer solution, and dripping 0.85-0.88 parts by weight of an initiator, performing a polymerization reaction, adding 0.6-1 parts by weight of a defoamer, 28-40 parts by weight of a filler, and 0.5-0.8 parts by weight of a dispersant after cooling, 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 a natural gas metal pipeline; The structural formula of the methacrylate hydroxyperfluoroalkane is: n is 6-8.

2. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 1, characterized in that: The solvent is toluene, propylene glycol methyl ether acetate or butyl acetate.

3. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 1, characterized in that: The acrylic acid ester monomer is any one or a combination of methyl methacrylate, methyl acrylate, butyl methacrylate, butyl acrylate, methyl styrene and styrene.

4. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 1, characterized in that: The initiator is dibenzoyl peroxide or azobisisobutyronitrile.

5. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 1, characterized in that: The heating temperature is 75-85° C., the prepolymerization time is 40-60 min, and the prepolymerization time is 3-4 h.

6. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 1, characterized in that: The filler is titanium dioxide or talcum powder.

7. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 1, characterized in that: The preparation method of the methacrylate hydroxyperfluoroalkane is: (1) In an ice bath, add dichloromethane, perfluoroalkyl chloride, N-BOC-N-methylaminoethanol, and triethylamine in a molar ratio of 1:(1-1.1):(1-1.1) to a reaction bottle, stir and react at 15-20° C. for 18-24 hours, rotary evaporate, wash, add the product to dichloromethane, add trifluoroacetic acid, stir and react at 20-30° C. for 3-5 hours, rotary evaporate, wash, and dry to obtain N-methylaminoperfluoroalkane ethyl ester; (2) Add tetrahydrofuran, glycidyl methacrylate and N-methylaminoperfluoroalkane ethyl ester in a molar ratio of 1:(1-1.2) to a reaction flask, stir and heat to 40-50° C., react for 6-10 hours, rotary evaporate, and separate by column chromatography to obtain methacrylate hydroxyperfluoroalkane.

8. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 7, characterized in that: The structural formula of the perfluoroalkyl acyl chloride is n is 6-8.

9. The method for preparing the low-temperature resistant coating for natural gas metal pipeline according to claim 1, characterized in that: The preparation method of the isocyanate-terminated polyurethane prepolymer is as follows: add polytetramethylene glycol to a reaction bottle, heat to 105° C., vacuum dehydrate, then add diisocyanate and dibutyltin dilaurate, introduce nitrogen, heat to 70-80° C., react for 2.5-3 hours, cool, and dry to obtain the isocyanate-terminated polyurethane prepolymer.

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

Images