Decorated salt brick and method of making same

Abstract

This invention relates to the field of decorative salt brick technology, specifically a decorative salt brick and its preparation method, comprising the following raw materials: Yulin dust salt, modified silica, modified chitosan, titanium dioxide, hydroxypropyl methylcellulose, and anhydrous magnesium chloride. The modified silica stably adsorbs Cl- in a high humidity environment. ‑ It releases Cl under low humidity. ‑ Modified chitosan resists stress damage to decorative salt bricks caused by the intense swelling of poly(N-isopropylacrylamide). Simultaneously, it forms an interpenetrating network with the swollen hydrogel network of poly(N-isopropylacrylamide), significantly improving water absorption and swelling capacity under high humidity. Furthermore, the modified chitosan's -COO... ‑ Can be used as an auxiliary Cl ‑ Adsorption sites. Titanium dioxide can prevent modified chitosan from degrading due to wet-dry cycles. The final decorative salt bricks not only effectively prevent Cl-... ‑ It corrodes metallic materials and greatly extends their service life.

Description

Technical Field

[0001] This invention relates to the field of decorative salt brick technology, specifically a decorative salt brick and its preparation method. Background Technology

[0002] Salt bricks are rich in dozens of minerals such as iron, calcium, magnesium, and potassium. In humid environments, salt bricks release 500 to 700 negative oxygen ions per cubic centimeter through a cycle of moisture absorption and evaporation, neutralizing radiation from electrical appliances and improving air quality. In addition, salt bricks exhibit a natural gradient color from orange-red to pink, and their crystal structure appears translucent under light. Therefore, decorative salt bricks are often placed indoors as diffuser stones, salt lamps, and other decorative items.

[0003] However, the main component of decorative salt bricks is sodium chloride, which has extremely strong hygroscopic properties. It will absorb moisture from the air, causing the salt bricks to dissolve and produce a large number of free ions (Na+). + and Cl - The brine formed by the dissolution of salt bricks is highly corrosive to metallic materials, especially Cl. - It has an extremely strong destructive effect on the protective film of metal. Cl - It has strong penetrating power, easily adsorbs onto metal surfaces, and locally damages the protective film (especially the alumina film), leading to pitting corrosion. Traditional Cl... - Adsorbents, although capable of adsorbing and fixing Cl - This reduces its migration and thus prevents corrosion, but it also prevents decorative salt bricks from recrystallizing, damaging their structure and reducing their lifespan. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide a decorative salt brick and its preparation method, which can significantly avoid the Cl- generation caused by the moisture absorption and dissolution of the decorative salt brick in a high humidity environment. - This prevents corrosion of metal materials and does not affect the crystallization of decorative salt bricks in low humidity environments, thereby improving the service life of decorative salt bricks.

[0006] (2) Technical solution

[0007] To achieve the above objectives, on the one hand, the present invention provides a decorative salt brick, comprising the following raw materials by weight: 100-150 parts of Yulin dust salt, 10-15 parts of modified silica, 5-10 parts of modified chitosan, 1-1.5 parts of titanium dioxide, 1-2 parts of hydroxypropyl methylcellulose, and 2-4 parts of anhydrous magnesium chloride.

[0008] Furthermore, the method for preparing the modified silica includes the following steps:

[0009] S11. Dissolve hexadecyltrimethylammonium bromide in a mixed solvent of water and ethanol, and stir until dissolved;

[0010] S12. After dissolving hexadecyltrimethylammonium bromide, ammonia water was added and stirred. Tetraethyl orthosilicate was added dropwise and stirred continuously until a white precipitate was formed. The solid precipitate was collected by centrifugation, washed with ethanol, and calcined to obtain the first compound.

[0011] S13. The first compound was ultrasonically dispersed in anhydrous toluene, 3-(trimethoxysilyl)propyl acrylate and glacial acetic acid were added, and the mixture was refluxed under nitrogen protection. The solid was collected by centrifugation and washed successively with toluene and ethanol to obtain the second compound.

[0012] S14. The second compound was dispersed in anhydrous N,N-dimethylformamide, and 4-cyano-4-(phenylthiocarbamoylthio)valerate and azobisisobutyronitrile were added. The reaction was carried out under nitrogen bubbling, and the solid was collected by centrifugation and washed with ethanol to obtain the third compound.

[0013] S15. The third compound was mixed with N-isopropylacrylamide, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, and azobisisobutyronitrile. Nitrogen gas was bubbled and stirred to react. The solid was collected by centrifugation, washed with N,N-dimethylformamide, then washed with hot water, and dried under vacuum to obtain modified silica.

[0014] Furthermore, the mass ratio of N-isopropylacrylamide to [2-(methacryloyloxy)ethyl]trimethylammonium chloride is 4~5:1.

[0015] Furthermore, the preparation method of the modified chitosan includes the following steps:

[0016] S21. Crush chitosan, sieve it, and vacuum dry it to remove moisture;

[0017] S22. Mix chitosan, dodecyl glycidyl ether, K2CO3 and glycerol evenly, and grind in a ball mill jar;

[0018] S23. The mixture is loaded into a polytetrafluoroethylene mold, the surface is covered with aluminum foil to prevent sticking, and the reaction is carried out under nitrogen gas at 160~180℃ and 5~15MPa.

[0019] S24. After the reaction is complete, maintain pressure and cool, remove the solid block, crush it, wash it with ethanol using a Soxhlet extractor, and vacuum dry it to constant weight to obtain modified chitosan.

[0020] Furthermore, the mass ratio of chitosan to dodecyl glycidyl ether is 1:1.

[0021] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing decorative salt bricks, applicable to the aforementioned decorative salt bricks, comprising the following steps:

[0022] S31. Crush the Yulin dust salt to 40-80 mesh;

[0023] S32. Weigh the raw materials according to the proportion, place them in a double spiral mixer and mix them evenly. Spray water until the moisture content is 15% to obtain the first mixture.

[0024] S33. Place the first mixture in a fully automatic brick press, press it at 95MPa for 8~12 seconds, and cure it at 60℃ for 24 hours to obtain decorative salt bricks.

[0025] The mechanism of action of the above raw material components is as follows:

[0026] In modified silica, mesoporous silica serves as the base carrier, with moisture-sensitive poly(N-isopropylacrylamide) and quaternary ammonium salt groups with an affinity for chloride ions grafted onto its surface. The quaternary ammonium salt groups (-N... + (CH3)3) acts as an anion exchange group, carrying a permanent positive charge, and can adsorb Cl. - The -CONH- group in the poly(N-isopropylacrylamide) molecular chain is highly polar and can form hydrogen bonds with water molecules in the environment. In high humidity environments, water molecules adsorb onto the polymer surface or penetrate into the internal network, causing the poly(N-isopropylacrylamide) chains to swell, become hydrophilic, and extend, thus forming Cl-. - Provides access and connection channels, -N + (CH3)3 stably adsorbs Cl - In low-humidity environments, the hydrogen bonds formed between -CONH- and water molecules dissociate, causing water molecules to desorb. The poly(N-isopropylacrylamide) chains dehydrate, shrink, and become hydrophobic. The shrunken chains tightly encapsulate the quaternary ammonium salt groups, forming a hydrophobic microenvironment that restricts Cl- concentration. - Approaching -N + The (CH3)3 site, with its hydrophobic environment, significantly weakens the hydration of Cl. - With -N + The electrostatic interaction between (CH3)3 and Cl ultimately affects the material. - The affinity for Cl is significantly reduced, causing previously adsorbed Cl to... - They were released.

[0027] The hydroxyl and amino groups on the modified chitosan molecular chain can form hydrogen bonds or electrostatic interactions with ions on the surface of salt crystals, filling the pores inside the salt bricks and resisting stress damage caused by the intense swelling of poly(N-isopropylacrylamide), thus improving the mechanical strength of the decorative salt bricks. Furthermore, the modified chitosan forms an interpenetrating network with the swollen hydrogel network of poly(N-isopropylacrylamide), significantly enhancing the water absorption capacity and swelling degree of poly(N-isopropylacrylamide) under high humidity conditions. Additionally, the -COO groups on the modified chitosan... - A negative electric field can attract positive charges in a solution (such as Na). + H + This leads to an increase in local positive charge density, which in turn attracts negatively charged Cl- molecules through electrostatic interactions. - .

[0028] Titanium dioxide nanoparticles prevent modified chitosan from degrading in wet-dry cycles and enhance the mechanical strength of decorative salt bricks by forming hydrogen bonds with chitosan molecular chains, resisting stress damage to decorative salt bricks caused by severe swelling of poly(N-isopropylacrylamide). In addition, titanium dioxide nanoparticles can fill the pores of salt bricks and improve their compressive strength.

[0029] Hydroxypropyl methylcellulose and anhydrous magnesium chloride are used as binders, resulting in good molding performance and excellent water retention and crack prevention capabilities. Hydroxypropyl methylcellulose dissolves in water to form a gel, enhancing adhesion, while anhydrous magnesium chloride increases the hardness of decorative salt bricks and reduces the risk of cracking.

[0030] (3) Beneficial effects

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. Modified silica stably adsorbs Cl under high humidity conditions. - To avoid the dissolution of Cl in decorative salt bricks - It corrodes metallic materials and releases Cl at low humidity. - This does not affect the crystallization of decorative salt bricks. This invention achieves Cl... - Dynamic management prevents metal materials from corroding, which not only extends the service life of decorative salt bricks but also preserves their unique recrystallization aesthetic value.

[0033] 2. Modified chitosan and poly(N-isopropylacrylamide) swollen hydrogel networks form an interpenetrating network, significantly improving water absorption and swelling capacity under high humidity conditions. Furthermore, the -COO group of modified chitosan... - Can be used as an auxiliary Cl - Adsorption sites, through electrostatic attraction, assist modified silica in adsorbing Cl. - To prevent Cl - Corrosion of metallic materials.

[0034] 3. Titanium dioxide alleviates the degradation of modified chitosan during wet and dry cycles and works synergistically with modified chitosan to resist stress damage to decorative salt bricks caused by poly(N-isopropylacrylamide) swelling, thereby improving the compressive strength of decorative salt bricks and extending their service life. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment discloses a decorative salt brick, which includes the following raw materials by weight: 100 parts of Yulin dust salt, 10 parts of modified silica, 5 parts of modified chitosan, 1 part of titanium dioxide, 1 part of hydroxypropyl methylcellulose, and 2 parts of anhydrous magnesium chloride.

[0038] It should be noted that decorative salt bricks are mainly composed of sodium chloride, which has extremely strong hygroscopic properties. When the ambient humidity is too high, it will absorb moisture from the air, causing the salt bricks to dissolve and produce a large number of free ions (Cl). - Because of Cl - At weak points on the metal surface (inclusions, scratches, grain boundaries, etc.), the passivation film is damaged, forming tiny anodic points. This allows corrosion to rapidly penetrate deeper, forming small, deep pores that easily damage the metal material. Therefore, modified silica is added to decorative salt bricks. Mesoporous silica provides a large surface area, offering numerous quaternary ammonium salt group sites for poly(N-isopropylacrylamide). When the ambient humidity is high (RH>80%), the poly(N-isopropylacrylamide) chains absorb a large amount of water, swell and stretch significantly, and the swollen hydrogel network allows for the hydration of Cl-. - Free diffusion penetrates into the material's interior and pores, exposing quaternary ammonium salt groups to a hydrophilic environment, where they effectively adsorb and capture hydrated Cl- through strong electrostatic attraction. - Adsorbed Cl - Stabilized by water molecules and polymer networks, it is difficult for it to migrate to metal surfaces and cause corrosion. In low humidity environments (RH < 30%), the poly(N-isopropylacrylamide) chains lose water, undergo a phase transition, and drastically shrink and collapse, becoming hydrophobic. The collapsed hydrophobic polymer tightly encapsulates the quaternary ammonium salt groups and their adsorbed Cl-. - In a hydrophobic microenvironment, hydrated Cl... - The electrostatic attraction between the ion and the quaternary ammonium cation is greatly weakened. Simultaneously, the encapsulation by the polymer chains creates physical barriers, restricting ion movement. This hydrophobic environment and high local concentration allow the trapped Cl- -It is released back into the solution on or near the surface of the salt bricks. As water continues to evaporate, the released Cl-... - with Na + They recrystallize together on the surface of the salt bricks.

[0039] However, the intense swelling process of poly(N-isopropylacrylamide) can lead to stress failure and reduced mechanical strength in decorative salt bricks. Therefore, modified chitosan and titanium dioxide are added to fill the pores of the salt bricks, enhancing their hardness and compressive strength. Simultaneously, the modified chitosan and the swollen hydrogel network of poly(N-isopropylacrylamide) form an interpenetrating network, significantly improving the water absorption capacity and swelling degree of poly(N-isopropylacrylamide) under high humidity. Furthermore, the -COO groups on the modified chitosan... - A negative electric field can attract positive charges in a solution (such as Na). + H + This leads to an increase in local positive charge density, which in turn attracts negatively charged Cl- molecules through electrostatic interactions. - .

[0040] Furthermore, because modified chitosan is easily soluble in wet-dry cycles, titanium dioxide nanoparticles can be uniformly dispersed in the chitosan matrix to form a dense physical barrier that hinders water molecule penetration. In wet-dry cycles, this barrier can reduce the chance of chitosan chains coming into contact with water and lower the hydrolysis rate of modified chitosan. In addition, titanium dioxide can be used as a nanofiller to enhance the mechanical strength of decorative salt bricks by forming hydrogen bonds with chitosan molecular chains and resisting stress damage caused by the severe swelling of poly(N-isopropylacrylamide).

[0041] The preparation method of modified silica includes the following steps:

[0042] S11. Dissolve hexadecyltrimethylammonium bromide in a mixed solvent of water and ethanol, and stir until dissolved;

[0043] S12. After dissolving hexadecyltrimethylammonium bromide, ammonia water was added and stirred. Tetraethyl orthosilicate was added dropwise and stirred continuously until a white precipitate was formed. The solid precipitate was collected by centrifugation, washed with ethanol, and calcined to obtain the first compound.

[0044] S13. The first compound was ultrasonically dispersed in anhydrous toluene, 3-(trimethoxysilyl)propyl acrylate and glacial acetic acid were added, and the mixture was refluxed under nitrogen protection. The solid was collected by centrifugation and washed successively with toluene and ethanol to obtain the second compound.

[0045] S14. The second compound was dispersed in anhydrous N,N-dimethylformamide, and 4-cyano-4-(phenylthiocarbamoylthio)valerate and azobisisobutyronitrile were added. The reaction was carried out under nitrogen bubbling, and the solid was collected by centrifugation and washed with ethanol to obtain the third compound.

[0046] S15. The third compound was mixed with N-isopropylacrylamide, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, and azobisisobutyronitrile. Nitrogen gas was bubbled and stirred to react. The solid was collected by centrifugation, washed with N,N-dimethylformamide, then washed with hot water, and dried under vacuum to obtain modified silica.

[0047] It should be noted that the modified silica was prepared from tetraethyl orthosilicate using hexadecyltrimethylammonium bromide as a template via a sol-gel method. Mesoporous silica prepared by this method has a large surface area and controllable pore size, making it easy to perform surface functionalization modification. Subsequently, polymerizable acrylate double bonds were introduced onto the silica surface using 3-(trimethoxysilyl)propyl acrylate. Finally, N-isopropylacrylamide and [2-(methacryloyloxy)ethyl]trimethylammonium chloride were grafted onto the silica surface via reversible addition-fragmentation chain transfer polymerization (RAFT) using 4-cyano-4-(phenylthiocarbamoylthio)valerate as the RAFT reagent and azobisisobutyronitrile as the initiator, thus preparing the modified silica.

[0048] The mass ratio of N-isopropylacrylamide to [2-(methacryloyloxy)ethyl]trimethylammonium chloride is 4:1.

[0049] The preparation method of the modified chitosan includes the following steps:

[0050] S21. Crush chitosan, sieve it, and vacuum dry it to remove moisture;

[0051] S22. Mix chitosan, dodecyl glycidyl ether, K2CO3 and glycerol evenly, and grind in a ball mill jar;

[0052] S23. The mixture is loaded into a polytetrafluoroethylene mold, the surface is covered with aluminum foil to prevent sticking, and the reaction is carried out under nitrogen gas at 160~180℃ and 5~15MPa.

[0053] S24. After the reaction is complete, maintain pressure and cool, remove the solid block, crush it, wash it with ethanol using a Soxhlet extractor, and vacuum dry it to constant weight to obtain modified chitosan.

[0054] It should be noted that chitosan is composed of glucosamine units and N-acetylglucosamine units. The C2 position of the glucosamine unit carries a primary amino group (-NH2), which is the main reaction site for hydrophobic modification. The -NH2 density on the chitosan molecular chain is extremely high, much greater than the concentration of dodecyl glycidyl ether. Based on kinetic advantages, -NH2 preferentially captures epoxy groups. The chitosan amino group undergoes SN2 nucleophilic substitution with the dodecyl glycidyl ether epoxy group. The high temperature of 160–180°C provides the activation energy, promoting the attack of the chitosan amino group on the epoxy group. The reaction process is exothermic, driving the reaction to completion. Since the side reaction of dodecyl glycidyl ether self-polymerization requires a strong base or a high concentration of weak base catalysis, the K2CO3 used in this invention is a weak base, which is preferred over a strong base. By limiting the amount of weak base used, the OH- catalysis is slowed down. - The rate of attack on epoxy groups is increased, thereby limiting side reactions. Furthermore, this invention employs a hot-pressing process, where dodecyl glycidyl ether is bound between chitosan chains, preferentially contacting -NH2 rather than free OH groups. - The hot-pressing process also eliminates the risk of solvent molecules (such as water) participating in side reactions and limits the hot-pressing time, shortening the self-polymerization time window. Self-polymerization requires multiple chain growth steps and is relatively slow, while chitosan-NH2 ring opening is a single-step fast reaction. By implementing the above conditions, the side reaction of dodecyl glycidyl ether self-polymerization is suppressed, making the main reaction of chitosan modification the dominant process.

[0055] It should be noted that chitosan must be thoroughly dried during raw material pretreatment to prevent side effects. Chitosan is prone to yellowing and caramelization at high temperatures, requiring a temperature gradient and protection with an inert gas. This method achieves the grafting of chitosan with the hydrophobic reagent dodecyl glycidyl ether under solvent-free conditions through a solid-state reaction under high temperature and pressure, generating hydrophobically modified chitosan ether. This method avoids the use of organic solvents, making it more environmentally friendly.

[0056] The mass ratio of chitosan to dodecyl glycidyl ether is 1:1.

[0057] A method for preparing decorative salt bricks includes the following steps:

[0058] S31. Crush the Yulin dust salt to 40-80 mesh;

[0059] S32. Weigh the raw materials according to the proportion, place them in a double spiral mixer and mix them evenly. Spray water until the moisture content is 15% to obtain the first mixture.

[0060] S33. Place the first mixture in a fully automatic brick press, press it at 95MPa for 8~12 seconds, and cure it at 60℃ for 24 hours to obtain decorative salt bricks.

[0061] It should be noted that decorative salt bricks of different colors can be prepared by adding different pigments (such as iron oxide red).

[0062] Example 2

[0063] This embodiment discloses a decorative salt brick, which includes the following raw materials by weight: 120 parts of Yulin dust salt, 12 parts of modified silica, 7 parts of modified chitosan, 1.25 parts of titanium dioxide, 1.5 parts of hydroxypropyl methylcellulose, and 3 parts of anhydrous magnesium chloride.

[0064] The preparation methods of the modified silica and modified chitosan in this embodiment are the same as those in Example 1. The preparation method of the decorative salt brick in this embodiment is also the same as that in Example 1.

[0065] Example 3

[0066] This embodiment discloses a decorative salt brick, which includes the following raw materials by weight: 140 parts of Yulin dust salt, 14 parts of modified silica, 9 parts of modified chitosan, 1.25 parts of titanium dioxide, 1.5 parts of hydroxypropyl methylcellulose, and 3 parts of anhydrous magnesium chloride.

[0067] The preparation methods of the modified silica and modified chitosan in this embodiment are the same as those in Example 1. The preparation method of the decorative salt brick in this embodiment is also the same as that in Example 1.

[0068] Example 4

[0069] This embodiment discloses a decorative salt brick, which includes the following raw materials by weight: 150 parts of Yulin dust salt, 15 parts of modified silica, 10 parts of modified chitosan, 1.5 parts of titanium dioxide, 2 parts of hydroxypropyl methylcellulose, and 4 parts of anhydrous magnesium chloride.

[0070] The preparation methods of the modified silica and modified chitosan in this embodiment are the same as those in Example 1. The preparation method of the decorative salt brick in this embodiment is also the same as that in Example 1.

[0071] Example 5

[0072] The difference between this embodiment and Example 1 is that the mass ratio of N-isopropylacrylamide and [2-(methacryloyloxy)ethyl]trimethylammonium chloride is different.

[0073] This embodiment discloses a decorative salt brick, which includes the following raw materials by weight: 100 parts of Yulin dust salt, 10 parts of modified silica, 5 parts of modified chitosan, 1 part of titanium dioxide, 1 part of hydroxypropyl methylcellulose, and 2 parts of anhydrous magnesium chloride.

[0074] The mass ratio of N-isopropylacrylamide to [2-(methacryloyloxy)ethyl]trimethylammonium chloride is 5:1.

[0075] The preparation methods of the modified silica and modified chitosan in this embodiment are the same as those in Example 1. The preparation method of the decorative salt brick in this embodiment is also the same as that in Example 1.

[0076] Example 6

[0077] The difference between this embodiment and Embodiment 1 is that the modified silica is not grafted with N-isopropylacrylamide.

[0078] This embodiment discloses a decorative salt brick, which includes the following raw materials by weight: 100 parts of Yulin dust salt, 10 parts of modified silica, 5 parts of modified chitosan, 1 part of titanium dioxide, 1 part of hydroxypropyl methylcellulose, and 2 parts of anhydrous magnesium chloride.

[0079] The method for preparing the modified silica includes the following steps:

[0080] S11. Dissolve hexadecyltrimethylammonium bromide in a mixed solvent of water and ethanol, and stir until dissolved;

[0081] S12. After dissolving hexadecyltrimethylammonium bromide, ammonia water was added and stirred. Tetraethyl orthosilicate was added dropwise and stirred continuously until a white precipitate was formed. The solid was collected by centrifugation, washed with ethanol, and calcined to obtain the first compound.

[0082] S13. The first compound was ultrasonically dispersed in anhydrous toluene, 3-(trimethoxysilyl)propyl acrylate and glacial acetic acid were added, and the mixture was refluxed under nitrogen protection. The solid was collected by centrifugation and washed three times with toluene and ethanol to obtain the second compound.

[0083] S14. The second compound was dispersed in anhydrous N,N-dimethylformamide, and 4-cyano-4-(phenylthiocarbamoylthio)valerate and azobisisobutyronitrile were added. The reaction was carried out under nitrogen bubbling, and the solid was collected by centrifugation and washed with ethanol to obtain the third compound.

[0084] S15. The third compound was mixed with [2-(methacryloyloxy)ethyl]trimethylammonium chloride and azobisisobutyronitrile, and the mixture was stirred under nitrogen bubbling. The solid was collected by centrifugation, washed with N,N-dimethylformamide, washed with hot water, and dried under vacuum to obtain modified silica.

[0085] The preparation method of the modified chitosan in this embodiment is the same as that in Example 1. The preparation method of the decorative salt brick in this embodiment is the same as that in Example 1.

[0086] Example 7

[0087] The difference between this embodiment and Example 1 is that the modified silica is not grafted with [2-(methacryloyloxy)ethyl]trimethylammonium chloride.

[0088] This embodiment discloses a decorative salt brick, which includes the following raw materials by weight: 100 parts of Yulin dust salt, 10 parts of modified silica, 5 parts of modified chitosan, 1 part of titanium dioxide, 1 part of hydroxypropyl methylcellulose, and 2 parts of anhydrous magnesium chloride.

[0089] The method for preparing the modified silica includes the following steps:

[0090] S11. Dissolve hexadecyltrimethylammonium bromide in a mixed solvent of water and ethanol, and stir until dissolved;

[0091] S12. After dissolving hexadecyltrimethylammonium bromide, ammonia water was added and stirred. Tetraethyl orthosilicate was added dropwise and stirred continuously until a white precipitate was formed. The solid was collected by centrifugation, washed with ethanol, and calcined to obtain the first compound.

[0092] S13. The first compound was ultrasonically dispersed in anhydrous toluene, 3-(trimethoxysilyl)propyl acrylate and glacial acetic acid were added, and the mixture was refluxed under nitrogen protection. The solid was collected by centrifugation and washed three times with toluene and ethanol to obtain the second compound.

[0093] S14. The second compound was dispersed in anhydrous N,N-dimethylformamide, and 4-cyano-4-(phenylthiocarbamoylthio)valerate and azobisisobutyronitrile were added. The reaction was carried out under nitrogen bubbling, and the solid was collected by centrifugation and washed with ethanol to obtain the third compound.

[0094] S15. The third compound was mixed with N-isopropylacrylamide and azobisisobutyronitrile, and the mixture was bubbled with nitrogen and stirred to react. The solid was collected by centrifugation, washed with N,N-dimethylformamide, washed with hot water, and dried under vacuum to obtain modified silica.

[0095] The preparation method of the modified chitosan in this embodiment is the same as that in Example 1. The preparation method of the decorative salt brick in this embodiment is the same as that in Example 1.

[0096] Control group 1

[0097] The difference between this control group and Example 1 is that no modified silica is added.

[0098] This control group discloses a decorative salt brick, which includes the following raw materials by weight: 100 parts of Yulin dust salt, 10 parts of modified silica, 5 parts of modified chitosan, 1 part of titanium dioxide, 1 part of hydroxypropyl methylcellulose, and 2 parts of anhydrous magnesium chloride.

[0099] The preparation method of the modified chitosan in this control group is the same as that in Example 1. The preparation method of the decorative salt brick in this control group is also the same as that in Example 1.

[0100] Control group 2

[0101] The difference between this control group and Example 1 is that no modified chitosan was added.

[0102] This control group discloses a decorative salt brick, which includes the following raw materials by weight: 100 parts of Yulin dust salt, 10 parts of modified silica, 5 parts of modified chitosan, 1 part of titanium dioxide, 1 part of hydroxypropyl methylcellulose, and 2 parts of anhydrous magnesium chloride.

[0103] The preparation method of the modified silica in this control group is the same as that in Example 1. The preparation method of a decorative salt brick in this control group is also the same as that in Example 1.

[0104] Control group 3

[0105] The difference between this control group and Example 1 is that titanium dioxide is not added.

[0106] This control group discloses a decorative salt brick, which includes the following raw materials by weight: 100 parts of Yulin dust salt, 10 parts of modified silica, 5 parts of modified chitosan, 1 part of titanium dioxide, 1 part of hydroxypropyl methylcellulose, and 2 parts of anhydrous magnesium chloride.

[0107] The preparation methods for the modified silica and modified chitosan in this control group are the same as in Example 1. The preparation method for a decorative salt brick in this control group is also the same as in Example 1.

[0108] Experimental verification:

[0109] 1.Cl - Adsorption / Release Test

[0110] S1. Prepare decorative salt bricks according to the example, embed 304 stainless steel sheets into the bottom of the decorative salt bricks to a depth of 1 mm, and vacuum dry at 60°C for 24 hours.

[0111] S2. Place the decorative salt bricks in an 80%RH, 25℃ humidity chamber for 24 hours to allow the salt bricks to absorb moisture and dissolve, and adsorb Cl. - After completion, remove the salt brick and stainless steel sheet, rinse with 10 mL of ultrapure water, and detect the Cl- in the metal-adhered solution using IC detection. - Concentration, calculated from multiple tests, averaged and denoted as C. 金属Cl - .

[0112] S3. Set the humidity chamber to 30% RH, and place the decorative salt brick in the 25℃ humidity chamber for 24 hours. After the 24 hours, scrape off 0.1 mm of the newly crystallized layer from the surface, dissolve it in 10 mL of ultrapure water, and detect the Cl- using IC. - Concentration, calculated from multiple tests, averaged and denoted as C. 结晶Cl - .

[0113] 2. Cyclic durability test

[0114] Repeat S2 and S3 5 times, weigh the initial salt brick and the salt brick after 5 cycles using an electronic balance, calculate the mass loss rate of the decorative salt brick, and take the average value of multiple tests, which is recorded as Q loss.

[0115] 3. Compressive strength test

[0116] The decorative salt bricks were placed in a constant humidity chamber at 60%RH and 25℃ for 4 hours. The compressive strength of the decorative salt bricks was tested using a universal testing machine in accordance with the standard GB / T3810.4 / ISO10545-4. The average value of multiple tests was taken.

[0117] Table 1 Performance Tests of Decorative Salt Bricks in Examples and Control Groups

[0118]

[0119] The performance tests of decorative salt bricks in the example group and the control group are shown in Table 1. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) - In terms of Example 4, C 金属Cl - Lowest, best effect. Comparison of Example 1 with Examples 6 and 7 C 金属Cl - The lower humidity indicates that when the ambient humidity is high, the -CONH- groups in the poly(N-isopropylacrylamide) molecular chain form hydrogen bonds with water molecules in the environment. The poly(N-isopropylacrylamide) chain absorbs a large amount of water, swells and stretches significantly, allowing hydrated Cl- to form. - Free diffusion into the material's interior and pores, quaternary ammonium salt groups effectively adsorb and capture hydrated Cl- through strong electrostatic attraction. - Adsorbed Cl - Stabilized by water molecules and polymer networks, it is difficult for it to migrate to the metal surface and cause corrosion. Example 1 vs. Control Group 2 (C) 金属Cl - The lower value indicates that the modified chitosan has a lower -COO content. - For Cl - Adsorption has a certain effect.

[0120] During the release of Cl - In terms of Example 4, C 结晶Cl - The highest and best results were achieved. Comparison of Example 1 with Examples 6 and 7 (C) 结晶Cl - The higher humidity indicates that the hydrogen bonds formed between the -CONH- group of poly(N-isopropylacrylamide) and water molecules dissociate under low humidity, leading to dehydration of the poly(N-isopropylacrylamide). The collapsed hydrophobic polymer tightly encapsulates the quaternary ammonium salt group and its adsorbed Cl-. - In a hydrophobic microenvironment, hydrated Cl... -The electrostatic attraction between the ion and the quaternary ammonium cation is greatly weakened. Simultaneously, the encapsulation by the polymer chains creates physical barriers, restricting ion movement. This hydrophobic environment and high local concentration allow the trapped Cl- - It is released back into the solution on or near the surface of the salt bricks. As water continues to evaporate, the released Cl-... - with Na + They recrystallize together on the surface of the salt bricks.

[0121] Regarding the loss rate, Example 4 had the lowest loss rate. Example 1 had an even lower loss rate compared to Control Group 1, indicating that the modified silica can adsorb Cl generated from the dissolution of decorative salt bricks under high humidity conditions. - It releases Cl in low humidity environments. - This causes the decorative salt bricks to recrystallize, reducing the Cl- content. - The loss rate is reduced, extending the service life of decorative salt bricks. Regarding compressive strength, Example 6, with modified silica without N-isopropylacrylamide grafting, exhibited the highest compressive strength, indicating that N-isopropylacrylamide swells violently in high humidity environments, causing stress damage to the decorative salt bricks and reducing their compressive strength. In contrast, Example 1 showed higher compressive strength compared to Control Groups 2 and 3, demonstrating that modified chitosan and titanium dioxide can resist stress damage caused by the violent swelling of poly(N-isopropylacrylamide), enhancing the compressive strength of the decorative salt bricks.

[0122] Finally, it should be noted that although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A decorative salt brick, characterized in that, The raw materials include the following by weight: 100-150 parts of Yulin dust salt, 10-15 parts of modified silica, 5-10 parts of modified chitosan, 1-1.5 parts of titanium dioxide, 1-2 parts of hydroxypropyl methylcellulose, and 2-4 parts of anhydrous magnesium chloride. The method for preparing the modified silica includes the following steps: S11. Dissolve hexadecyltrimethylammonium bromide in a mixed solvent of water and ethanol, and stir until dissolved; S12. After dissolving hexadecyltrimethylammonium bromide, ammonia water was added and stirred. Tetraethyl orthosilicate was added dropwise and stirred continuously until a white precipitate was formed. The solid precipitate was collected by centrifugation, washed with ethanol, and calcined to obtain the first compound. S13. The first compound was ultrasonically dispersed in anhydrous toluene, 3-(trimethoxysilyl)propyl acrylate and glacial acetic acid were added, and the mixture was refluxed under nitrogen protection. The solid was collected by centrifugation and washed successively with toluene and ethanol to obtain the second compound. S14. The second compound was dispersed in anhydrous N,N-dimethylformamide, and 4-cyano-4-(phenylthiocarbamoylthio)valerate and azobisisobutyronitrile were added. The reaction was carried out under nitrogen bubbling, and the solid was collected by centrifugation and washed with ethanol to obtain the third compound. S15. The third compound was mixed with N-isopropylacrylamide, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, and azobisisobutyronitrile. Nitrogen gas was bubbled and stirred to react. The solid was collected by centrifugation, washed with N,N-dimethylformamide, washed with hot water, and dried under vacuum to obtain modified silica. The preparation method of the modified chitosan includes the following steps: S21. Crush chitosan, sieve it, and vacuum dry it to remove moisture; S22. Mix chitosan, dodecyl glycidyl ether, K2CO3 and glycerol evenly, and grind in a ball mill jar; S23. The mixture is loaded into a polytetrafluoroethylene mold, the surface is covered with aluminum foil to prevent sticking, and the reaction is carried out under nitrogen gas at 160~180℃ and 5~15MPa. S24. After the reaction is complete, maintain pressure and cool, remove the solid block, crush it, wash it with ethanol using a Soxhlet extractor, and vacuum dry it to constant weight to obtain modified chitosan.

2. A decorative salt brick according to claim 1, characterized in that, The mass ratio of N-isopropylacrylamide to [2-(methacryloyloxy)ethyl]trimethylammonium chloride is 4~5:

1.

3. A decorative salt brick according to claim 1, characterized in that, The mass ratio of chitosan to dodecyl glycidyl ether is 1:

1.

4. A method for preparing decorative salt bricks, applied to the preparation of decorative salt bricks as described in any one of claims 1 to 3, characterized in that, The method includes the following steps: S31. Crush the Yulin dust salt to 40-80 mesh; S32. Weigh the raw materials according to the proportion, place them in a double spiral mixer and mix them evenly. Spray water until the moisture content is 15% to obtain the first mixture. S33. Place the first mixture in a fully automatic brick press, press it at 95MPa for 8~12 seconds, and cure it at 60℃ for 24 hours to obtain decorative salt bricks.

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