CN-121975385-A - Long-aging middle-high temperature resistant concentrated nitric acid protective strippable coating and preparation thereof

CN121975385ACN 121975385 ACN121975385 ACN 121975385ACN-121975385-A

Abstract

The invention provides a long-aging middle-high temperature resistant concentrated nitric acid protective strippable coating. The invention takes styrene-ethylene-propylene-styrene segmented copolymer (SEEPS) as a matrix, fluorine-containing chain segments and siloxane chain segments are introduced on a molecular chain through a graft copolymerization technology, and hydrogenated SEEPS provides a saturated hydrocarbon main chain, so that the modified styrene-ethylene-propylene-styrene segmented copolymer has excellent basic flexibility and thermoplastic peelability, the introduction of fluorine atoms endows the chain segments with excellent chemical inertness and low surface energy, can effectively resist oxidation and permeation of concentrated nitric acid, and the siloxane chain segments provide extremely high bond energy, so that the long-term thermal stability of the coating at 100 ℃ is ensured. The three are chemically bonded to form the resin with hardness and softness, so that the acid resistance, heat resistance and strippable performance are unified from the source.

Inventors

LI JINHU
YU JIANLONG
REN JIANGTAO
XU SHENGLIANG
ZHENG XIANGXIANG
LI XUANYU
DING XIAOGANG
YI ZHIHONG

Assignees

中昊北方涂料工业研究设计院有限公司

Dates

Publication Date: 20260505
Application Date: 20260207

Claims (10)

1. The long-aging middle-high temperature resistant concentrated nitric acid protective strippable coating is characterized by comprising the following components in percentage by mass: Name of the name Wt% Fluorine-silicon hybrid modified hydrogenated SEEPS resin 15-25 Auxiliary film-forming resin 2-5 Functional filler 7-10 Corrosion-resistant additive 4-6 Auxiliary agent 2-4 Pigment 1-3 Solvent(s) 55-65
2. The strippable paint of claim 1, wherein the fluorine-silicon hybrid modified hydrogenated SEEPS resin comprises the following components in parts by mass based on 100 parts of SEEPS: Name of the name Parts by mass Fluorine-silicon hybrid modified hydrogenated SEEPS resin 100 Dodecafluoroheptyl methacrylate 15-30 Vinyl triethoxysilane 5-10 Azobisisobutyronitrile 0.5-1.0 Toluene (toluene) 400-600 Tetrahydrofuran (THF) 100-200 Rhodium trichloride 0.05-0.15 Methanol 4L
3. The strippable paint of claim 1, wherein the auxiliary film-forming resin is one or more of a chlorohydrin resin, an ABS resin, a tetrafluoroethylene resin and a polyvinyl chloride resin.
4. The strippable paint of claim 1, wherein the functional filler is one or more of hydrophobically modified silica by precipitation, flaky mica powder, silicon carbide, barium sulfate by precipitation, titanium pigment, glass flake and cerium oxide.
5. The strippable paint of claim 1, wherein the corrosion inhibitor is one or both of zinc phosphate and aluminum tripolyphosphate.
6. The strippable paint of claim 1, wherein the auxiliary agent is one or more of wetting dispersant DISPERBYK-170, DISPERBYK-174, DISPERBYK-183, defoamer BYK-1752, BYK-065, BYK-072.
7. The strippable paint of claim 1, wherein the pigment is one or more of chromium oxide green, carbon black, iron oxide yellow and iron oxide red, and the solvent is one or more of toluene, butanone, tetrachloroethylene, ethyl acetate, tetrahydrofuran, cyclohexanone, butyl acetate and propylene glycol methyl ether acetate.
8. The strippable paint of claim 2, wherein the fluoro-silicon hybridized modified hydrogenated SEEPS resin is synthesized by (1) adding SEEPS and toluene into a three-necked flask under the protection of nitrogen, heating to 80 ℃, mechanically stirring until the resin is completely dissolved, dissolving azodiisobutyronitrile in tetrahydrofuran, adding the three-necked flask, uniformly mixing dodecafluoroheptyl methacrylate and vinyltrimethoxysilane, adding into a dropping funnel, heating to 85+/-2 ℃, slowly and uniformly dropping the mixed monomer into the uniformly stirred reaction solution within 3 hours, and continuing to perform heat preservation reaction for 6 hours after the dropping is completed. Cooling the reaction solution to room temperature, adding the reaction solution into vigorously stirred methanol, filtering, repeatedly washing for 3 times, and drying the product in a 40+/-5 ℃ oven for 12 hours to obtain fluorine-silicon grafted SEEPS; (2) Redissolving the dried SEEPS in a mixed solvent of toluene and tetrahydrofuran, adding a high-pressure reaction kettle, adding rhodium trichloride, sealing the reaction kettle, replacing air in the kettle for 5 times by hydrogen, charging the hydrogen, starting stirring, setting the rotating speed to be 500rpm, heating to 100 ℃, reacting for 8-12 hours, cooling to room temperature, slowly releasing residual hydrogen, pouring the reaction solution into methanol for precipitating, filtering, repeatedly washing for 2-3 times, and drying the product in a 40+/-5 ℃ oven for 24 hours until the quality is unchanged, thus obtaining the final product fluorine-silicon hybrid modified hydrogenated SEEPS resin.
9. The strippable paint of claim 1, wherein the fluorine-silicon hybrid modified hydrogenated SEEPS resin and the auxiliary film-forming resin are added into a high-speed dispersing kettle, a wetting dispersant, a preservative, a functional filler and a pigment are sequentially added at a medium and low rotating speed (700 rpm-900 rpm), the rotating speed is increased to 1000rpm-1500rpm, after the materials are uniformly dispersed, the materials are ground and dispersed by a sand mill until the fineness is less than or equal to 40 mu m, a defoaming agent is added, the viscosity is adjusted by a residual solvent until the materials are coated on a-4 # cup for 80-120 seconds, and the materials are filtered and packaged, so that the strippable paint is obtained.
10. The method of claim 1, wherein the coating is applied to the surface of 304 or 316 stainless steel by brushing or spraying, has a dry film thickness of 0.2-0.4mm, is cured at normal temperature to form a protective coating, is immersed in a nitric acid solution with a concentration of 35% -60% for 2 months at a temperature ranging from 60 ℃ to 100 ℃, and can be peeled off manually or mechanically after the protective period is over.

Description

Long-aging middle-high temperature resistant concentrated nitric acid protective strippable coating and preparation thereof Technical Field The invention relates to the technical field of special protective coating, in particular to a strippable coating which can be used on the surfaces of 304 and 316 stainless steel, can resist the corrosion environment of nitric acid with concentration of 35-60% for a long time within the temperature range of 60-100 ℃ and can be completely stripped as required after service, and a preparation method thereof. Background In the fields of high-end chemical industry and metallurgy such as nitric acid production, concentration, storage and transportation, nitration and the like, related equipment and components such as a concentration tower, a heat exchanger, a pipeline, the inner wall of a reaction kettle and the like are exposed to the extremely corrosive environment of medium-high temperature concentrated nitric acid for a long time. The traditional protection means, such as lining acid-proof bricks or using permanent anti-corrosion coating, have the problems of complex construction, difficult maintenance, high cost and the like. Particularly, when equipment is regularly overhauled, detected or the coating is partially failed, the permanent coating is extremely difficult to remove, the metal matrix can be damaged by forced cleaning, and the maintenance cost and the downtime are greatly increased. The strippable paint is used as a temporary protective material, and can provide effective protection and realize convenient, complete and harmless stripping of the matrix. The prior art has certain technical defects when facing the severe working conditions of superposition of long aging, medium and high temperature resistance and concentrated nitric acid resistance. Most strippable coatings have the core goal of improving universal strippability, and the formulation design is suitable for the purpose, for example, the strippability is guaranteed by using low-adhesion resin, but the protective performance can not meet the index requirement far. Patent CN202410571171.3 provides an aqueous release coating that ensures easy stripping from a wide variety of substrates by adding an organic ester release agent. However, the formula is based on modified acrylic acid copolymer emulsion, and although corrosion resistance is mentioned, the physical shielding layer is extremely easy to lose effectiveness under long-term permeation of high-temperature concentrated nitric acid without long-term aging verification of high-temperature high-concentration strong oxidative nitric acid. Patent CN113527996A discloses a high and low temperature (-20 ℃ to 60 ℃) resistant water-based strippable paint. The technology is an aqueous system, the vaporization heat of water is high, the film forming compactness is poor at high temperature, and molecular chains of the aqueous anionic aliphatic polyether polyurethane dispersoid, acrylic emulsion and other resins are extremely easy to break down and degrade under the oxidation and nitration actions of high-temperature concentrated nitric acid, so that the coating is atomized, and the strength and the peelability are lost. Patent CN119081525B provides a high-low temperature resistant aqueous strippable protective coating, which adopts triple composition of polyurethane, epoxy resin and acrylic emulsion, so that the coating can still maintain stable physical and chemical properties in extremely high temperature or low temperature environment, is not easy to foam and wrinkle and is easy to strip, but the long-time aging protective property of high-temperature and high-concentration nitric acid is not mentioned. The prior art of the strippable coating cannot meet the industrial requirements of stable protection of 35-60% concentrated nitric acid for more than 2 years at the temperature of 60-100 ℃ and convenient and complete stripping during maintenance, along with the technical path (water-based, general parting agent and physical blending modification) and the final performance. Disclosure of Invention The invention aims to overcome the technical defects and provide the single-component coating with integrated protection-stripping performance. Finally, the corrosion environment of nitric acid with the concentration of 35-60% is resisted for a long time on the surfaces of 304 and 316 stainless steel within the temperature range of 60-100 ℃, and the stainless steel can be completely stripped as required after service. Technical proposal The paint comprises the following components in percentage by mass: Name of the name Wt%Fluorine-silicon hybrid modified hydrogenated SEEPS resin15-25Auxiliary film-forming resin2-5Functional filler7-10Corrosion-resistant additive4-6Auxiliary agent2-4Pigment1-3Solvent(s)55-65 The fluorine-silicon hybrid modified hydrogenated SEEPS resin adopts 100 parts of SEEPS as a benchmark and comprises the following components in parts by mass: