Stainless steel rust removal and gloss retention agent and preparation method thereof

Abstract

The invention provides a stainless steel rust removal and gloss retention agent and a preparation method thereof. The stainless steel rust removal and gloss retention agent comprises the following chemical components in percentage by mass: 2-5% of citric acid-oxalic acid-ultra-low polymerization degree polyvinyl alcohol monoester, 1-10% of a rust remover and the balance of deionized water. According to the stainless steel rust removal and gloss retention agent, the rust remover reacts with rust to form Fe < 2 + >, the Fe < 2 + > can enter a solution under the complexing action of ammonia ions, oxalic acid and citric acid and then leave the surface of stainless steel, and rust removal of the stainless steel is completed; compared with pure use of ultra-low polymerization degree polyvinyl alcohol, acting force with a stainless steel substrate can be enhanced, polycarboxyl is introduced into molecules and can generate a relatively strong chemical adsorption effect with Fe atoms of the stainless steel substrate, so that the combination is firmer, a gloss retention film is formed, and the whole stainless steel surface is completely covered; and the long-time gloss retention effect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel rust removal, and particularly relates to a stainless steel rust removal and light preservation agent; at the same time, the present invention also relates to a preparation method of a stainless steel rust removal and light preservation agent. Background Art

[0002] The principle of stainless steel corrosion protection is mainly based on the chromium element on its surface. Chromium can react with oxygen to form a dense chromium oxide film, namely a passivation film, which can block the erosion of external oxygen, water and other chemical substances, thereby preventing further corrosion of the steel. Although stainless steel is well-known for its corrosion resistance, its surface may still rust after long-term use. This is mainly because the chromium oxide film formed on the surface of stainless steel will be damaged under physical actions (such as mechanical wear, scratches, etc.) or chemical actions (such as salts, acids, alkalis, etc.), resulting in leakage gaps.

[0003] After stainless steel rusts, various methods can be used for rust removal, mainly including mechanical rust removal, chemical rust removal, electrochemical rust removal, and laser rust removal. Among them, the mechanical rust removal method uses tools such as sandpaper and grinding wheels to physically grind the rust layer. This method has obvious rust removal effect and high efficiency. However, after rust removal, if the new surface is not protected in time, it will quickly rust again, and the rusting speed of the new surface will be faster. This is the result of the damage to the original surface oxide layer by mechanical rust removal.

[0004] Chemical rust removal uses various acids to chemically react with rust and dissolve the rust layer, with remarkable effects and wide applications. The surface of the rust-removed stainless steel also needs to be protected, otherwise it is more likely to rust again. This is because most acids can not only dissolve the rust layer, but also damage the protective layer on the normal stainless steel surface. Electrochemical rust removal removes rust spots through electrolysis, which can achieve high-efficiency rust removal, but the equipment is complex and the cost is high, so its application is limited. Laser rust removal uses high-energy laser to evaporate rust, which can achieve high-efficiency rust removal, but the equipment is complex and the cost is high, so its application is limited. Summary of the Invention

[0005] In view of this, the present invention aims to propose a stainless steel rust remover to improve the rust removal effect of stainless steel and have good light preservation performance.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A stainless steel rust removal and light preservation agent, the chemical components of the stainless steel rust removal and light preservation agent include by mass percentage:

[0008] Citric acid - oxalic acid - ultra-low degree of polymerization polyvinyl alcohol monoester 2 - 5%;

[0009] Rust remover 1 - 10%;

[0010] Deionized water for the balance.

[0011] Further, the sum of the amounts of substances of the citric acid and the oxalic acid is greater than the amount of substance of the hydroxyl groups in the polyvinyl alcohol.

[0012] Further, the ratio of the sum of the amounts of substances of the citric acid and the oxalic acid to the amount of substance of the hydroxyl groups in the polyvinyl alcohol is 1.02 - 1.2.

[0013] Further, the rust remover includes ammonium dihydrogen phosphate.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] For the stainless steel rust removal and light preservation agent of the present invention, the rust remover reacts with rust to form Fe 2+ , Fe 2+ Under the complexing action of ammonium ions, oxalic acid, and citric acid, it will enter the solution, thus leaving the stainless steel surface, completing the rust removal of the stainless steel. Citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester, as a light preservation agent, compared with simply using ultra - low - degree - of - polymerization polyvinyl alcohol, can enhance the interaction force with the stainless steel matrix. By introducing multiple carboxyl groups into the molecule, the multiple carboxyl groups can have a strong chemical adsorption effect with the Fe atoms of the stainless steel matrix, making their combination more firm, thus forming a light preservation film, which is equivalent to filling the damaged part of the original stainless steel oxide film, covering the entire stainless steel surface completely, and playing a role in long - term light preservation.

[0016] In addition, making the sum of the amounts of substances of citric acid and oxalic acid greater than the amount of substance of the hydroxyl groups in polyvinyl alcohol can ensure that as many hydroxyl groups in polyvinyl alcohol as possible participate in the reaction, making the reaction proceed in the direction of generating the target product, contributing to the full utilization of polyvinyl alcohol, improving the production efficiency and quality of the light preservation agent. At the same time, the excessive citric acid and oxalic acid can also cooperate with the rust remover to rust the stainless steel surface, thus facilitating the improvement of the rust removal efficiency. The ratio of the sum of the amounts of substances of citric acid and oxalic acid to the amount of substance of the hydroxyl groups in polyvinyl alcohol is 1.02 - 1.2, which is conducive to ensuring that citric acid and oxalic acid have sufficient amounts to fully react with the hydroxyl groups in polyvinyl alcohol, enabling as many hydroxyl groups in polyvinyl alcohol as possible to participate in the reaction, reducing the incomplete reaction caused by insufficient reactants, being beneficial to improving the production efficiency and quality of citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester, and ensuring that the generated citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester has the expected performance. The rust remover includes ammonium dihydrogen phosphate, which has good rust removal performance.

[0017] In addition, another object of the present invention is to propose a preparation method for preparing the above - mentioned stainless steel rust removal and light preservation agent, including:

[0018] Dissolve citric acid and oxalic acid in an ultra - low - degree - of - polymerization polyvinyl alcohol solution, and react at a preset temperature for a preset time to obtain the citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester;

[0019] Add the citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester to deionized water, stir evenly, and then add a rust remover until it is completely dissolved to obtain the stainless - steel rust - removing and light - preserving agent.

[0020] Furthermore, before dissolving citric acid and oxalic acid in an ultra - low - degree - of - polymerization polyvinyl alcohol solution and reacting for a preset time at a preset temperature to obtain the citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester, it further includes:

[0021] Add polyvinyl alcohol to deionized water until it is completely dissolved to obtain a polyvinyl alcohol solution with a mass fraction of 8 - 12%.

[0022] Shear the polyvinyl alcohol solution to reduce the degree of polymerization of polyvinyl alcohol, and then spray - granulate to obtain primary polyvinyl alcohol particles.

[0023] Dissolve the primary polyvinyl alcohol particles in deionized water and filter.

[0024] Spray - granulate the filtered solution again to obtain ultra - low - degree - of - polymerization polyvinyl alcohol particles.

[0025] Dissolve the ultra - low - degree - of - polymerization polyvinyl alcohol particles in deionized water to obtain the ultra - low - degree - of - polymerization polyvinyl alcohol solution.

[0026] Furthermore, the step of dissolving the ultra - low - degree - of - polymerization polyvinyl alcohol particles in deionized water to obtain the ultra - low - degree - of - polymerization polyvinyl alcohol solution includes:

[0027] Slowly add the ultra - low - degree - of - polymerization polyvinyl alcohol particles to deionized water, slowly heat up to 60 - 70 °C until it is completely dissolved to obtain the ultra - low - degree - of - polymerization polyvinyl alcohol solution with a concentration of 4 - 6%.

[0028] Furthermore, the preset temperature is 80 - 85 °C; and / or the preset time is 50 - 70 minutes.

[0029] In the preparation method of the stainless - steel rust - removing and light - preserving agent of the present invention, dissolving citric acid and oxalic acid in an ultra - low - degree - of - polymerization polyvinyl alcohol solution can ensure that citric acid and oxalic acid are fully dissolved and react effectively with the polyvinyl alcohol solution to generate citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester, thereby facilitating the improvement of the use performance of the stainless - steel rust - removing and light - preserving agent.

[0030] In addition, in the preparation of the ultra-low degree of polymerization polyvinyl alcohol solution, the reduction of the degree of polymerization can change the physical and chemical properties of polyvinyl alcohol, such as making it more soluble and having better fluidity, which is more conducive to the subsequent formation of a uniform and stable system to participate in the reaction with citric acid and oxalic acid. Moreover, when applied to the rust removal and light protection agent subsequently, the low-degree-of-polymerization polyvinyl alcohol can spread and form a film better on the stainless steel surface, etc.; spray granulation can convert the liquid polyvinyl alcohol solution into solid particles, which is convenient for storage, transportation and subsequent further treatment, and the granular materials are easier to achieve uniform mixing and impurity separation in subsequent operations such as dissolution and filtration.

[0031] In addition, after adding the ultra-low degree of polymerization polyvinyl alcohol particles into deionized water, slowly heating to 60-70 °C until completely dissolved is beneficial to improving the dissolution effect of the ultra-low degree of polymerization polyvinyl alcohol. The temperature range of 80-85 °C can provide sufficient energy for the reaction of citric acid, oxalic acid and the ultra-low degree of polymerization polyvinyl alcohol solution, making the reactant molecules have higher activity, effectively reducing the activation energy of the reaction, enabling the reaction to proceed quickly and fully, and being conducive to the formation of the expected light protection agent product. Ammonium dihydrogen phosphate in the rust remover has good rust removal performance; 50-70 minutes is beneficial to ensuring the formation efficiency of citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0033] Figure 1 It is a schematic structural diagram of citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester described in Embodiment 1 of the present invention;

[0034] Figure 2 It is a partial enlarged view of the implementation test piece described in Embodiment 1 of the present invention;

[0035] Figure 3 It is a partial enlarged view of the comparative test piece described in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0037] In the description of the present invention, it should be noted that if terms indicating orientation or positional relationship such as "upper", "lower", "inner", "back", etc. appear, they are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present invention. In addition, if terms such as "first", "second", etc. appear, they are also only for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0038] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0039] Embodiment 1

[0040] This embodiment relates to a stainless steel rust remover and light protector. The chemical components of the stainless steel rust remover and light protector include 2-5% of citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester, 1-10% of rust remover, and the balance of deionized water by volume percentage.

[0041] In the stainless steel rust remover and light protector of this embodiment, the rust remover reacts with rust to form Fe 2+ , Fe 2+ Under the complexing action of ammonium ions, oxalic acid, and citric acid, it will enter the solution, thus leaving the stainless steel surface to complete the rust removal of the stainless steel. Citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester, as a light protector, compared with simply using ultra-low degree of polymerization polyvinyl alcohol, can enhance the interaction with the stainless steel substrate. By introducing multiple carboxyl groups into the molecule, the multiple carboxyl groups can have a strong chemical adsorption effect with the Fe atoms of the stainless steel substrate, making their combination more firm, thus forming a light protection film, which is equivalent to filling the damaged part of the original stainless steel oxide film, covering the entire stainless steel surface completely, and playing a role in long-term light protection.

[0042] Among them, citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester plays the role of a light protector. Specifically, it is generated by the reaction of citric acid, oxalic acid, and ultra-low degree of polymerization polyvinyl alcohol monoester. Its structure is as shown in Figure 1 . The specific generation method is described in detail in Embodiment 2 below. Hereinafter, citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester will be simply referred to as the light protector.

[0043] In this embodiment, a special ultra-low polymerization degree polyvinyl alcohol is used as the raw material of the light retaining agent, instead of directly using polyvinyl alcohol (such as polyvinyl alcohol 1788). The specific reason is that the number of chain links of polyvinyl alcohol is about 40, the bond length of carbon-carbon bond is 1.54 angstroms, the length of one chain link is 3-4 angstroms, and the average length of one linear molecule is about 120-160 angstroms. According to the characteristics of the molecular weight distribution of polymer materials, the longest molecule can reach 4-6 times the average number, or even longer. Therefore, the length of some polyvinyl alcohol molecules can reach 500-1000 angstroms (0.5-1 μm).

[0044] In fact, rust corrosion of stainless steel occurs first between crystals. Using a micrometer to measure the minimum distance between crystals is less than 0.5 μm. This means that if polyvinyl alcohol 1788 is used directly as a gloss retaining agent, its molecular length exceeds the length of two crystals. In other words, during use, many polyvinyl alcohol 1788 molecules will be placed between two crystals and cannot be embedded inside, resulting in a weak bond. In this embodiment, ultra-low polymerization degree polyvinyl alcohol is used as the raw material of the gloss retaining agent, which can better embed the entire molecule into the gap between crystals.

[0045] Although ultra-low polymerization degree polyvinyl alcohol can be embedded in the gaps between stainless steel crystals, the force between it and the stainless steel matrix is ​​van der Waals force (intermolecular force), and this bonding force is weak. In order to enhance the force between ultra-low polymerization degree polyvinyl alcohol and the stainless steel matrix, multiple carboxyl groups (COOH) are introduced into the molecule. The carboxyl groups can have a strong chemical adsorption effect with the Fe atoms of the stainless steel matrix, making it more firmly bonded.

[0046] The multiple carboxyl groups (-COOH) on citric acid-oxalic acid-ultra-low polymerization degree polyvinyl alcohol monoester are combined with Fe atoms through "chemical bonds" with strong interaction. Compared with the hydroxyl group (-OH) of polyvinyl alcohol, it has added multiple reaction sites (-COOH) at multiple spatial levels, making it more strongly combined with Fe atoms on the surface of stainless steel, especially more suitable for uneven surfaces and narrow gaps.

[0047] As a preferred embodiment, in this embodiment, the sum of the mass of citric acid and oxalic acid is greater than the mass of hydroxyl groups in polyvinyl alcohol. This ensures that as many hydroxyl groups in polyvinyl alcohol as possible participate in the reaction, so that the reaction proceeds in the direction of generating the target product, which helps to fully utilize polyvinyl alcohol and improve the efficiency and quality of the gloss retaining agent. At the same time, the excess citric acid and oxalic acid can also be used together with the rust remover to remove rust from the stainless steel surface, thereby improving the efficiency of rust removal.

[0048] As a feasible implementation method, the ratio of the sum of the amounts of citric acid and oxalic acid to the amount of hydroxyl groups in polyvinyl alcohol is 1.02 - 1.2. This is conducive to ensuring that there is enough citric acid and oxalic acid to fully react with the hydroxyl groups in polyvinyl alcohol, enabling as many hydroxyl groups in polyvinyl alcohol as possible to participate in the reaction, reducing the incomplete reaction caused by insufficient reactants, being beneficial to improving the production efficiency and quality of citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester, and ensuring that the produced citric acid - oxalic acid - ultra - low - degree - of - polymerization polyvinyl alcohol monoester has the expected performance. During specific implementation, the ratio of the sum of the amounts of citric acid and oxalic acid to the amount of hydroxyl groups in polyvinyl alcohol can be, for example, 1.02, 1.04, 1.08, 1.1, 1.15, 1.18, or 1.2, etc.

[0049] As a preferred implementation method, the rust remover in this embodiment includes ammonium dihydrogen phosphate. This is not only conducive to improving the rust - removing performance on the surface of stainless steel, but also conducive to improving the use performance of the light - preserving agent. Specifically, ammonium dihydrogen phosphate will ionize in an aqueous solution and can release hydrogen ions, thus providing an acidic environment. This acidic environment can chemically react with the rust on the surface of stainless steel (the main component is iron oxide) to dissolve the rust and achieve the purpose of rust removal.

[0050] In addition, the phosphate ion in ammonium dihydrogen phosphate has a certain complexing ability and can form a stable complex with the iron ions in the rust. This complexing effect can make the rust more easily detached from the surface of stainless steel, further improving the rust - removing effect. Moreover, the formed complex usually has good water solubility, which is convenient to be washed off in subsequent treatment, making the surface of stainless steel cleaner.

[0051] Furthermore, the presence of ammonium dihydrogen phosphate can also adjust the performance of the protective film, such as improving the adhesion, flexibility, and corrosion resistance of the film layer. It can cooperate with other film - forming substances to make the protective film more firmly adhere to the surface of stainless steel, not easy to fall off, and at the same time enhance the protection effect of the protective film on stainless steel and extend the light - preserving time.

[0052] During the rust - removing process, as the reaction progresses, the acidity of the solution may change, and the buffering effect of ammonium dihydrogen phosphate can keep the pH value of the solution within a relatively stable range, avoiding the influence on the rust - removing and light - preserving effects due to excessive change in the pH value. This helps to ensure the stability and reliability of the rust - removing and light - preserving agent during use.

[0053] Ammonium dihydrogen phosphate can synergistically interact with other components in the rust-removing and light-preserving agent, such as citric acid, oxalic acid, and polyvinyl alcohol. It jointly regulates the acidity of the solution with acid substances such as citric acid and oxalic acid to achieve better rust-removing effects; it cooperates with film-forming substances such as polyvinyl alcohol to optimize the performance of the protective film and improve the comprehensive performance of the light-preserving agent. The addition of ammonium dihydrogen phosphate is of great significance for enhancing the rust-removing and light-preserving properties of the stainless steel rust-removing and light-preserving agent and is one of the key components for preparing a high-performance stainless steel rust-removing and light-preserving agent.

[0054] In this embodiment, the chemical components of the stainless steel rust-removing and light-preserving agent by mass percentage include 2 - 5% of citric acid - oxalic acid - ultra-low polymerization degree polyvinyl alcohol monoester, 1 - 10% of rust remover, and the balance of deionized water. At this time, of course, the mass percentage of citric acid - oxalic acid - ultra-low polymerization degree polyvinyl alcohol monoester can also be, for example: 2%, 2.5%, 3%, 3.5%, 3.75%, 4%, 4.5% or 5%, etc., and the mass percentage of the rust remover can also be, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

[0055] To verify the performance of the stainless steel rust-removing and light-preserving agent described in this embodiment, after uncovering the protective film, the stainless steel test piece is immersed in the stainless steel rust-removing and light-preserving agent for 1 hour, taken out, drained, and then air-dried naturally. The corrosion resistance test is carried out simultaneously with the untreated stainless steel test piece. For the sake of convenient description, the stainless steel test piece immersed in the stainless steel rust-removing and light-preserving agent is called the test test piece, and the untreated stainless steel test piece is called the comparison test piece.

[0056] The test test piece and the comparison test piece are respectively placed 10 cm above the 5% hydrochloric acid solution (which can not only ensure that the test piece is fully exposed to the corrosive gas volatilized from the hydrochloric acid solution to simulate a certain corrosion environment but also facilitate the subsequent comparison and observation of the corrosion resistance of the test piece under different treatment methods). After being placed at room temperature for 12 h, the test pieces are taken down, rinsed with clean water, air-dried naturally, and then observed under an electron microscope at a magnification of 1000 times. Through such a comparative operation and microscopic observation and analysis, the corrosion resistance of the stainless steel rust-removing and light-preserving agent in actual application can be scientifically and intuitively verified, that is, whether it can truly protect the surface of the stainless steel and make it show better resistance when facing a corrosive environment compared to untreated stainless steel, thus proving its application value.

[0057] Among them, the enlarged picture of the test test piece is as Figure 2 shown, its surface is bright and there is no rust. The enlarged picture of the comparison test piece is as Figure 3As shown, rusting still appears on its surface, indicating that this stainless steel rust-removing and light-preserving agent indeed has good effects of rust removal, light preservation, and improvement of corrosion resistance. It can be understood that the parameters in the test conditions of this embodiment can still be adjusted adaptively according to the usage requirements, or directly place the test piece for implementation and the comparative test piece in the external environment, and then observe the rusting situation after a period of time.

[0058] In addition, the inventor also sprayed the stainless steel rust-removing and light-preserving agent in this embodiment on public areas, such as the stainless steel seats or handrails in the park. Through observations after two months and three months, it was also found that the brightness of the area where the stainless steel rust-removing and light-preserving agent was sprayed was significantly higher than that of the unsprayed area. It also shows that in the actual environment, the stainless steel rust-removing and light-preserving agent can keep stainless steel products bright as new for a long time, which is conducive to reducing the number of rust removal times on the stainless steel surface, and thus conducive to extending the bright time of the stainless steel surface.

[0059] It should be noted that the stainless steel targeted by the stainless steel rust-removing and light-preserving agent in this embodiment is preferably a product that does not need to be frequently cleaned to ensure the service life of the light-preserving film formed by the stainless steel light-preserving agent on the stainless steel product.

[0060] For the stainless steel rust-removing and light-preserving agent described in this embodiment, after the rust removal operation is performed on the stainless steel surface by the rust remover, particularly, citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester formed by the reaction of citric acid, oxalic acid, and ultra-low degree of polymerization polyvinyl alcohol monoester is used as the light-preserving agent, which is conducive to forming a light-preserving film on the surface of the rust-removed stainless steel, and the light-preserving agent can better embed the light-preserving film molecules into the gaps between the crystal grains, thereby fundamentally achieving the effects of rust prevention and light preservation.

[0061] In addition, through the ratio of the sum of the amounts of substances of citric acid and oxalic acid to the amount of substance of hydroxyl groups in polyvinyl alcohol, it is not only conducive to improving the formation effect of the light-preserving agent, but also can cooperate with the rust remover to achieve a better rust removal effect. Further, the stainless steel rust-removing and light-preserving agent in this embodiment is made of common chemical raw materials, thus ensuring its safety and environmental protection during the production and use processes.

[0062] Example Two

[0063] This embodiment relates to a preparation method for preparing the stainless steel rust-removing and light-preserving agent described in Example One. The preparation method includes dissolving citric acid and oxalic acid in an ultra-low degree of polymerization polyvinyl alcohol solution, reacting at a preset temperature for a preset time to obtain citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester; adding the citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester to deionized water, stirring evenly, and then adding a rust remover until completely dissolved to obtain the stainless steel rust-removing and light-preserving agent.

[0064] The preparation method of the stainless steel rust removal and light preservation agent described in this embodiment is to dissolve citric acid and oxalic acid in an ultra-low degree of polymerization polyvinyl alcohol solution, which can ensure the full dissolution of citric acid and oxalic acid and their effective reaction with the polyvinyl alcohol solution to generate citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester, thus facilitating the improvement of the use performance of the stainless steel rust removal and light preservation agent.

[0065] Among them, citric acid and oxalic acid are dissolved in an ultra-low degree of polymerization polyvinyl alcohol solution and react at a preset temperature for a preset time. The carboxyl groups (-COOH) in the citric acid and oxalic acid molecules react with the hydroxyl groups (-OH) in the ultra-low degree of polymerization polyvinyl alcohol molecules to generate citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester. In this process, by controlling the reaction conditions (such as temperature and time, etc.), it is ensured that the esterification reaction proceeds in the direction of generating the target monoester, and the reaction proceeds relatively fully to obtain a monoester product with expected performance.

[0066] Among them, a suitable preset temperature can provide sufficient energy for the esterification reaction, prompting the reactant molecules to overcome the activation energy, accelerating the reaction rate, and enabling the reaction to proceed smoothly. Different temperatures may affect the reaction equilibrium as well as the formation rate and selectivity of the product. If the temperature is too low, the reaction may be extremely slow or even difficult to occur; while too high a temperature may trigger side reactions, affecting the yield and quality of the monoester. Therefore, it needs to be strictly controlled within a specific suitable temperature range.

[0067] The set preset time is the reaction time, which is an important factor ensuring the degree of reaction completion. If the time is too short, the esterification reaction may be incomplete, resulting in insufficient monoester production and affecting the performance of the subsequent light preservation agent; while if the time is too long, continuing the reaction after reaching the reaction equilibrium may cause the decomposition of the product or other side reactions, which is also not conducive to obtaining high-quality citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester. Therefore, the appropriate preset time needs to be determined according to the specific reaction system.

[0068] Specifically, in this embodiment, the preset temperature is preferably 80 - 85 °C, and the preset time is preferably 50 - 70 minutes. Among them, in the reaction of dissolving citric acid and oxalic acid in an ultra-low degree of polymerization polyvinyl alcohol solution to generate citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester, the temperature range of 80 - 85 °C can provide suitable energy conditions for the reaction. The rate of a chemical reaction is usually closely related to temperature. As the temperature increases, the energy obtained by the reactant molecules increases, their movement becomes more intense, the frequency of intermolecular collisions and the probability of effective collisions both increase, thus accelerating the reaction rate. Within this temperature range, the esterification reaction (the reaction between the carboxyl groups of citric acid and oxalic acid and the hydroxyl groups of polyvinyl alcohol) can proceed at an ideal speed, avoiding the situation of low production efficiency caused by too slow a reaction.

[0069] Meanwhile, this temperature range can ensure the selectivity of the reaction and reduce the occurrence of side reactions. Because if the temperature is too high, some unnecessary side reactions may be triggered. For example, polyvinyl alcohol may decompose or undergo excessive polymerization, or the formed monoester may undergo hydrolysis and other reverse reactions, affecting the quality and yield of the monoester. When the temperature is too low, the reaction is difficult to reach the ideal equilibrium state, and the amount of the formed monoester is insufficient to meet the expected requirements for the light stabilizer performance.

[0070] Moreover, the citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester formed at 80-85 °C has a structure and properties that better meet the requirements for the subsequent component of the stainless steel rust removal and light stabilizer. This temperature helps to form a monoester with a stable structure, good film-forming property and chemical activity, enabling it to better play the role of rust removal and light stabilization on the stainless steel surface in the subsequent process. For example, the formed protective film is more uniform and dense, and has a stronger ability to dissolve and complex rust. During specific implementation, the preset temperature can be, for example, 80 °C, 82 °C, 84 °C or 85 °C.

[0071] The preset time of 50-70 minutes is the key to ensuring the full progress of the reaction. From the perspective of chemical reaction kinetics, to convert the reactants into products as much as possible, sufficient reaction time is required. In the reaction of citric acid and oxalic acid with the ultra-low degree of polymerization polyvinyl alcohol solution, as time goes by, the reactants are continuously consumed and the products are gradually formed. Only after a certain reaction duration can it be ensured that there is a sufficient amount of citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester generated to meet the requirements for the subsequent preparation of high-quality stainless steel rust removal and light stabilizer. If the reaction time is too short, the esterification reaction is incomplete, resulting in a low content of the monoester, which in turn affects the overall light stabilization performance of the light stabilizer. During specific implementation, the preset time can be, for example, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 68 minutes or 70 minutes.

[0072] The upper limit of the set time is set to 70 minutes to prevent overreaction. When the reaction reaches a certain degree, it will tend to reach an equilibrium state. If the time is continuously extended, some adverse situations may occur. For example, the formed monoester may undergo decomposition, polymerization and other side reactions in the long-term high-temperature environment, destroying its original structure and properties, which will also have a negative impact on the final light stabilizer performance. Therefore, the time range of 50-70 minutes can better control the reaction degree, enabling the formed monoester to reach the best state in terms of quantity and quality, laying a foundation for the subsequent preparation of a stainless steel rust removal and light stabilizer with excellent performance.

[0073] In this embodiment, before dissolving citric acid and oxalic acid in an ultra-low degree of polymerization polyvinyl alcohol solution and reacting for a preset time at a preset temperature to obtain citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester, the following steps are also included: adding polyvinyl alcohol to deionized water until it is completely dissolved to obtain a polyvinyl alcohol solution with a mass fraction of 8-12%; shearing the polyvinyl alcohol solution to reduce the degree of polymerization of polyvinyl alcohol and then spray granulating to obtain primary polyvinyl alcohol particles; dissolving the primary polyvinyl alcohol particles in deionized water and filtering; spray granulating the filtered solution again to prepare ultra-low degree of polymerization polyvinyl alcohol particles; dissolving the ultra-low degree of polymerization polyvinyl alcohol particles in deionized water to obtain an ultra-low degree of polymerization polyvinyl alcohol solution.

[0074] Among them, in the step of preparing the initial polyvinyl alcohol solution, the setting of the polyvinyl alcohol solution with a mass fraction of 8-12% is for the following reasons. On the one hand, such a concentration facilitates subsequent operation and processing, such as the transportation and stirring of the solution. If the concentration is too high, the polyvinyl alcohol solution will become too viscous, making not only the dissolution process more difficult but also the subsequent operations such as shearing and granulating less likely to achieve uniform mixing and processing. On the other hand, this concentration range can ensure that there is a sufficient amount of polyvinyl alcohol participating in the subsequent reaction, providing an adequate raw material basis for preparing an ultra-low degree of polymerization polyvinyl alcohol solution with good performance, and also helping to reasonably control costs. Specifically in implementation, the mass fraction of the polyvinyl alcohol solution can be 8%, 9%, 10%, 11% or 12%.

[0075] In the step of reducing the degree of polymerization and granulating, the polyvinyl alcohol solution is sheared. The purpose is to reduce the degree of polymerization of polyvinyl alcohol. The degree of polymerization is a key factor affecting many properties of polyvinyl alcohol. Reducing the degree of polymerization can change the physical and chemical properties of polyvinyl alcohol, such as making it more soluble and having better fluidity. After the molecular chain becomes shorter, it can be more evenly dispersed in the system during the subsequent reaction process, which is more conducive to fully and evenly reacting with citric acid and oxalic acid. Moreover, when it is subsequently applied to the rust removal and light protection agent, the polyvinyl alcohol with a low degree of polymerization can better spread and form a film on the stainless steel surface, forming a protective film with better quality.

[0076] After shearing to reduce the degree of polymerization, spray granulation is carried out to obtain primary polyvinyl alcohol particles. This spray granulation process converts the liquid polyvinyl alcohol solution into a solid particle form and has many advantages. First, the particulate material is more convenient for storage and transportation. Compared with the liquid solution, it has higher stability and is less affected by external environmental factors (such as temperature changes and slight shaking). Second, in subsequent operations such as redissolution and filtration, the particles can be more evenly dispersed in water, facilitating better mixing effects and more accurate separation of impurities, preparing for further reducing the degree of polymerization and improving the solution quality.

[0077] In the steps of redissolution and filtration, the primary polyvinyl alcohol particles are dissolved in deionized water. This step is to restore the polyvinyl alcohol particles after spray granulation to a liquid solution state for subsequent further processing. During the dissolution process, some agglomeration phenomena that may originally exist in the particles can be redispersed, restoring and improving the uniformity of the solution, ensuring the uniform distribution of polyvinyl alcohol molecules in the solution, and providing a uniform material basis for subsequent filtration and re-granulation operations.

[0078] Furthermore, after dissolution, a filtration operation is carried out, mainly to remove insoluble impurities that may exist in the solution, such as some tiny solid impurities mixed in during the spray granulation process, and larger degree of polymerization polyvinyl alcohol particles that are not completely dissolved. If these impurities are not removed, they will have an adverse impact on subsequent reactions and the quality of the finally prepared ultra-low degree of polymerization polyvinyl alcohol solution, and may affect the reaction effect with citric acid and oxalic acid, and further affect the performance of the stainless steel rust removal and light protection agent. Therefore, ensuring the purity of the solution through filtration operation is a very crucial step.

[0079] In the steps of secondary granulation and final dissolution, the filtered solution is spray granulated again to obtain ultra-low degree of polymerization polyvinyl alcohol particles. This step further precisely controls the degree of polymerization of polyvinyl alcohol to meet the requirements of ultra-low degree of polymerization. Compared with polyvinyl alcohol with a normal degree of polymerization, ultra-low degree of polymerization polyvinyl alcohol can better cooperate when reacting with citric acid and oxalic acid to form a product with better performance. For example, it can make the formed citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester form a thinner, more uniform and stronger adhesion protective film on the surface of stainless steel, thereby improving the performance of the entire rust removal and light protection agent.

[0080] Finally, the ultra-low degree of polymerization polyvinyl alcohol particles are dissolved in deionized water to obtain an ultra-low degree of polymerization polyvinyl alcohol solution, which can be used for subsequent reactions with citric acid and oxalic acid, laying a foundation for the formation of high-quality citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester, and further ensuring the successful preparation of a stainless steel rust removal and light protection agent with excellent performance that can effectively remove rust and protect light according to the established preparation method.

[0081] Generally speaking, this series of complex and interlocking steps are all centered around the precise preparation of an ultra-low degree of polymerization polyvinyl alcohol solution that meets the requirements. Each step has an indispensable impact on the performance of the final stainless steel rust removal and light protection agent, reflecting the rigor and scientific nature of the preparation process.

[0082] As a preferred embodiment, in this example, ultra-low degree of polymerization polyvinyl alcohol particles are dissolved in deionized water to obtain an ultra-low degree of polymerization polyvinyl alcohol solution, including: slowly adding ultra-low degree of polymerization polyvinyl alcohol particles to deionized water, and slowly heating to 60-70 °C until completely dissolved to obtain an ultra-low degree of polymerization polyvinyl alcohol solution with a concentration of 4-6%.

[0083] Slowly adding ultra-low degree of polymerization polyvinyl alcohol particles to deionized water is a crucial operation. Polyvinyl alcohol particles have a certain hydrophilicity. If added quickly to water, the outer layer of the particles will rapidly absorb water and swell, possibly wrapping the internal particles, making it difficult for the internal particles to contact water, resulting in uneven dissolution or even the formation of lumps. Slowly adding allows the particles to disperse gradually in water, ensuring that each particle can fully contact water, laying a good foundation for the subsequent dissolution process and helping to form a uniform and stable solution.

[0084] After adding the particles, slowly heating to 60-70 °C helps to control the dissolution process. Temperature is one of the key factors affecting the dissolution rate and effect of polyvinyl alcohol. Heating too quickly may cause local overheating, changing the molecular structure of polyvinyl alcohol and affecting its properties. Slowly heating allows the polyvinyl alcohol molecules to gradually adapt to the temperature change, gradually unfold the molecular chains at an appropriate temperature, and disperse evenly in water, thus ensuring the stability of the dissolution process and the quality of the solution.

[0085] The temperature range of 60-70 °C is an appropriate interval for polyvinyl alcohol dissolution verified by practice. At this temperature, the thermal motion of water molecules is relatively active, which can effectively penetrate between the polyvinyl alcohol molecular chains, break the intermolecular interactions, and promote the gradual dissolution of polyvinyl alcohol molecules. At the same time, this temperature is not too high to cause adverse reactions such as decomposition and oxidation of polyvinyl alcohol, thus ensuring that the chemical structure and properties of polyvinyl alcohol are not affected, providing a stable and reliable reactant for the subsequent reaction with citric acid and oxalic acid. Specifically, after adding the particles, slowly heat to 60 °C, 62 °C, 65 °C, 68 °C or 70 °C.

[0086] Obtaining an ultra-low degree of polymerization polyvinyl alcohol solution with a concentration of 4-6% is one of the key links in preparing a high-performance stainless steel rust remover and light protector. Precise control of the solution concentration is crucial for preparing a high-performance stainless steel rust remover and light protector. The appropriate concentration ensures that the ratio of each substance is relatively stable during the subsequent reaction with citric acid and oxalic acid, facilitating the reaction to proceed in the expected direction to produce citric acid-oxalic acid-ultra-low degree of polymerization polyvinyl alcohol monoester with specific properties. If the concentration is too high, the solution viscosity is too large, which may lead to uneven reaction and affect the product quality; if the concentration is too low, it may not provide enough polyvinyl alcohol to participate in the reaction, also affecting the performance of the final light protector. Specifically, the concentration of the ultra-low degree of polymerization polyvinyl alcohol solution can be 4%, 5%, 5.5% or 6%.

[0087] In this embodiment, the detailed regulations regarding the dissolution process of ultra-low degree of polymerization polyvinyl alcohol particles are closely linked from the operating steps to the control of temperature and concentration, jointly ensuring the stable quality of the prepared ultra-low degree of polymerization polyvinyl alcohol solution and providing a solid guarantee for the preparation of a stainless steel rust and light protection agent with excellent performance.

[0088] During specific implementation, in the preparation example of the ultra-low degree of polymerization polyvinyl alcohol solution, 180 g of deionized water was added into a 250 mL flask and immersed in a constant temperature water bath with stirring; 20 g of commercially available polyvinyl alcohol (model 1788) was slowly added to 180 g of deionized water while continuously stirring; the temperature was slowly raised to 90 - 100 °C until completely dissolved, obtaining a polyvinyl alcohol solution with a mass fraction of 10%.

[0089] Shearing was carried out with a high-speed disperser to reduce the degree of polymerization of polyvinyl alcohol under the shearing action. Primary polyvinyl alcohol particles were obtained after spray granulation; the primary polyvinyl alcohol particles were dissolved in hot water at 50 - 55 °C, the undissolved polyvinyl alcohol was filtered off, and the filtered solution was spray granulated to obtain ultra-low degree of polymerization polyvinyl alcohol particles.

[0090] In the preparation example of the light protection agent in this embodiment, 157 g of deionized water was added into a 250 mL flask and immersed in a constant temperature water bath with stirring; 10 g of the above-prepared ultra-low degree of polymerization polyvinyl alcohol was slowly added to 157 g of deionized water, and the temperature was slowly raised to 65 °C until completely dissolved; 22 g (0.1041 mol) of citric acid and 11 g (0.1333 mol) of oxalic acid were taken. The sum of the amounts of substances of citric acid and oxalic acid was greater than the amount of substance of hydroxyl groups (-OH) in polyvinyl alcohol (0.2273 mol), and the ratio of the sum of the amounts of substances of citric acid and oxalic acid to the amount of substance of hydroxyl groups in polyvinyl alcohol was 1.044 and was slowly added while continuously stirring until completely dissolved; the temperature was raised to 85 °C and reacted for 1 h. After natural cooling, 200 g of a solution of the light protection agent "citric acid - oxalic acid - ultra-low degree of polymerization polyvinyl alcohol monoester" (concentration based on ultra-low degree of polymerization polyvinyl alcohol was 5%) was obtained.

[0091] In the preparation example of the stainless steel light protection agent in this embodiment, 150 g of deionized water was added into a 250 mL flask; 40 g of the light protection agent was slowly added to 150 g of water and stirred evenly; 10 g of ammonium dihydrogen phosphate was taken and slowly added to the flask until completely dissolved, obtaining 200 g of a stainless steel rust and light protection agent.

[0092] The preparation method of the stainless steel light protection agent described in this embodiment can prepare the stainless steel light protection agent in Example 1, and through the setting and cooperation of various parameters, it is beneficial to meet the rust removal and light protection performance of the stainless steel light protection agent. Moreover, the whole preparation method is simple and easy to operate, and it is also beneficial to reduce the production cost of the stainless steel light protection agent.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A stainless steel rust removal and gloss retention agent, characterized in that: The chemical components of the stainless steel rust removal and gloss retention agent include, by mass percentage: Citric acid-oxalic acid-ultra-low polymerization degree polyvinyl alcohol monoester 2-5%; Rust remover 1-10%; Deionized water balance.

2. The stainless steel rust removal and gloss retention agent according to claim 1, characterized in that: The sum of the amounts of the citric acid and the oxalic acid is greater than the amount of the hydroxyl groups in the polyvinyl alcohol.

3. The stainless steel rust removal and gloss retention agent according to claim 2, characterized in that: The ratio of the sum of the amounts of the citric acid and the oxalic acid to the amount of the hydroxyl groups in the polyvinyl alcohol is 1.02-1.

2.

4. The stainless steel rust removal and gloss retention agent according to any one of claims 1 to 3, characterized in that: The rust remover includes diammonium phosphate.

5. A method for preparing the stainless steel rust removing and gloss retaining agent according to any one of claims 1 to 4, characterized in that: include: Dissolving citric acid and oxalic acid in a solution of ultra-low polymerization degree polyvinyl alcohol, and reacting at a preset temperature for a preset time to obtain the citric acid-oxalic acid-ultra-low polymerization degree polyvinyl alcohol monoester; The citric acid-oxalic acid-ultra-low polymerization degree polyvinyl alcohol monoester is added into deionized water, stirred evenly, and then a rust remover is added until it is completely dissolved, thereby obtaining the stainless steel rust remover and gloss retainer.

6. The method for preparing the stainless steel rust removing and gloss retaining agent according to claim 5, characterized in that: Before dissolving citric acid and oxalic acid in the ultra-low polymerization degree polyvinyl alcohol solution and reacting at a preset temperature for a preset time to obtain the citric acid-oxalic acid-ultra-low polymerization degree polyvinyl alcohol monoester, the method further comprises: Adding polyvinyl alcohol into deionized water until it is completely dissolved to obtain a polyvinyl alcohol solution with a mass fraction of 8-12%; Shearing the polyvinyl alcohol solution to reduce the degree of polymerization of the polyvinyl alcohol, and then spray granulating to obtain primary polyvinyl alcohol particles; Dissolving the primary polyvinyl alcohol particles in deionized water and filtering; The filtered solution is spray granulated again to obtain ultra-low polymerization degree polyvinyl alcohol particles; The ultra-low polymerization degree polyvinyl alcohol particles are dissolved in deionized water to obtain the ultra-low polymerization degree polyvinyl alcohol solution.

7. The method for preparing the stainless steel rust removing and gloss retaining agent according to claim 6, characterized in that: The step of dissolving the ultra-low polymerization degree polyvinyl alcohol particles in deionized water to obtain the ultra-low polymerization degree polyvinyl alcohol solution comprises: The ultra-low polymerization degree polyvinyl alcohol particles are slowly added into deionized water, and the temperature is slowly raised to 60-70° C. until they are completely dissolved, to obtain the ultra-low polymerization degree polyvinyl alcohol solution with a concentration of 4-6%.

8. The method for preparing the stainless steel rust removing and gloss retaining agent according to claim 6, characterized in that: The preset temperature is 80-85° C.; and / or the preset time is 50-70 minutes.

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