Safe and stable sodium hydrosulfite composition and preparation method thereof

Abstract

The invention relates to a safe and stable sodium hydrosulfite composition and a preparation method thereof, and belongs to the technical field of sodium hydrosulfite. The preparation method comprises the following steps: reacting epoxy-terminated polydimethylsiloxane with 4-amino-2, 6-di-tert-butylphenol to prepare a functional modifier containing a phenol structure and a siloxane chain segment, and preparing the microcapsule type sodium hydrosulfite from methacrylic acid and sodium hydrosulfite through a water-in-oil type microcapsule preparation method. And finally, combining the functional modifier with the microcapsule type sodium hydrosulfite through esterification reaction to obtain the safe and stable sodium hydrosulfite composition. The functional modifier disclosed by the invention has antioxidant phenol groups and siloxane chain segments, so that the contact between oxygen and moisture and the sodium hydrosulfite is more effectively blocked, the sodium hydrosulfite is prevented from being oxidized or decomposed, and the safety in storage and transportation is improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium hydrosulfite technology, specifically, it relates to a safe and stable sodium hydrosulfite composition and its preparation method. Background Technology

[0002] Sodium dithionite, also known as sodium hydrosulfite, is an inorganic compound with strong reducing properties. It is widely used in textile printing and dyeing, papermaking, food processing, pharmaceutical intermediate synthesis, and wastewater treatment. Its core value lies in its high-efficiency reducing performance. However, it is chemically unstable, easily oxidized, and decomposes to release toxic gases, and may even cause explosions, posing a great risk to storage and transportation. This characteristic has become a key bottleneck restricting its production, storage, transportation, and application.

[0003] Ordinary sodium dithionite compositions typically employ a double coating of sodium dithionite with both inorganic salt and polymer coating agents, forming a relatively simple coating structure that can improve the stability of sodium dithionite to some extent. However, during storage and transportation, it may still slowly decompose due to external environmental influences, failing to continue its protective function. Furthermore, the decomposition rate is relatively fast during use, and to ensure it possesses the reducing power required for industrial production, the amount of sodium dithionite used often exceeds the theoretical dosage.

[0004] Therefore, developing a safe and stable sodium hydrosulfite composition is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a safe and stable sodium hydrosulfite composition and its preparation method, in order to solve the problems mentioned in the background art.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a safe and stable sodium hydrosulfite composition includes the following steps: Step 1: Under a nitrogen atmosphere, add terminal epoxy polydimethylsiloxane and 4-amino-2,6-di-tert-butylphenol to toluene, stir evenly, and then heat to 80-100℃ for 2-4 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain the functional modifier.

[0007] Step 2: Under nitrogen protection, methacrylic acid and azobisisobutyronitrile are dissolved in tetrahydrofuran to obtain an oil phase; sodium hydrosulfite and stabilizer are then dissolved in deionized water to obtain an aqueous phase; the aqueous phase is added to the oil phase, followed by the addition of sorbitol monooleate, and the mixture is stirred for 30-45 minutes to obtain a water-in-oil emulsion. The mixture is then heated to 50-70°C and stirred for 4-6 hours. After cooling to room temperature, the microcapsules are collected by vacuum filtration, washed with ethanol, and dried to obtain microcapsule-type sodium hydrosulfite.

[0008] Step 3: Add microcapsule-type sodium hydrosulfite, functional modifier, and 4-dimethylaminopyridine to N,N-dimethylformamide, stir evenly, heat to 50-60℃, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 4-6 hours, after the reaction is completed, cool to room temperature, filter to separate the modified microcapsules, wash with deionized water, and dry to obtain a safe and stable sodium hydrosulfite composition.

[0009] Furthermore, the degree of polymerization of the terminal epoxy polydimethylsiloxane in the first step is 20-50.

[0010] Furthermore, in the first step, the mass ratio of terminal epoxy polydimethylsiloxane to 4-amino-2,6-di-tert-butylphenol is 94-125:85-90.

[0011] Furthermore, in the second step, the mass ratio of methacrylic acid, sodium hydrosulfite, stabilizer, sorbitan monooleate, and azobisisobutyronitrile is 75-100:35-55:0.2-0.3:48-64:1.3-1.8.

[0012] Furthermore, the stabilizer is strong sodium oxide or soda ash.

[0013] Furthermore, in the third step, the mass ratio of microencapsulated sodium hydrosulfite, functional modifier, 4-dimethylaminopyridine, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 60-80:50-60:1.5-1.8:20-35.

[0014] The beneficial effects of this invention are: 1) In this invention, a functional modifier containing both phenolic structure and siloxane segment is first prepared by reacting terminal epoxy polydimethylsiloxane with 4-amino-2,6-di-tert-butylphenol. Then, methacrylic acid and sodium hydrosulfite are prepared by water-in-oil microcapsule preparation method to prepare microcapsule sodium hydrosulfite. Finally, the microcapsule sodium hydrosulfite and the functional modifier are subjected to esterification reaction to obtain a safe and stable sodium hydrosulfite composition.

[0015] 2) Polydimethylsiloxane has good hydrophobic properties, and loading it onto the surface of microcapsules can effectively improve the moisture resistance of the sodium hydrosulfite composition encapsulated in the microcapsules. However, polydimethylsiloxane has poor affinity with polymethacrylic acid wall material and is usually difficult to react. This invention improves the loading efficiency of polydimethylsiloxane on the surface of microcapsules by modifying it by grafting lipophilic 4-amino-2,6-di-tert-butylphenol onto the end groups of polydimethylsiloxane.

[0016] 3) The functional modifier in this invention has a phenol structure and polysiloxane segments. Phenol provides antioxidant properties; the polysiloxane segments provide waterproof properties and can also lubricate the surface of the wall material, reducing collision and wear during transportation and feeding, and preventing leakage of internal sodium hydrosulfite.

[0017] 4) The main body of the wall material in this invention is polymethyl methacrylate wall material, which is in a rigid glassy state with small molecular gaps. It can effectively block oxygen and moisture, so that the SO2 release rate of the sodium hydrosulfite is low and the effective content retention rate is high during storage. This plays a protective role for the core material of the sodium hydrosulfite, improves the problem that traditional sodium hydrosulfite is easy to absorb moisture and decompose when exposed to oxygen, and makes the sodium hydrosulfite safer and more stable. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] The room temperature was 25±5℃.

[0020] Example 1 A method for preparing a safe and stable sodium hydrosulfite composition includes the following steps: Step 1: By mass, under a nitrogen atmosphere, add 125 parts of terminal epoxy polydimethylsiloxane with a degree of polymerization of 50 and 85 parts of 4-amino-2,6-di-tert-butylphenol to toluene. After stirring evenly, heat to 80°C and react for 4 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain the functional modifier.

[0021] Step 2: Under nitrogen protection, 100 parts by mass of methacrylic acid and 1.3 parts by mass of azobisisobutyronitrile were dissolved in tetrahydrofuran to obtain an oil phase; then 35 parts by mass of sodium hydrosulfite and 0.2 parts by mass of sodium hydroxide were dissolved in deionized water to obtain an aqueous phase; the aqueous phase was added to the oil phase, and then 48 parts by mass of dehydrated sorbitan monooleate were added. The mixture was stirred for 45 min to obtain a water-in-oil emulsion. The emulsion was heated to 50 °C and stirred for 6 h. Then it was cooled to room temperature, and the microcapsules were collected by vacuum filtration. The microcapsules were washed with ethanol and dried to obtain microcapsule-type sodium hydrosulfite.

[0022] Step 3: By weight, add 80 parts of microcapsule-type sodium hydrosulfite, 50 parts of functional modifier, and 1.8 parts of 4-dimethylaminopyridine to N,N-dimethylformamide, stir evenly, heat to 50°C, then add 35 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 4 hours, after the reaction is completed, cool to room temperature, filter to separate the modified microcapsules, wash with deionized water, and dry to obtain a safe and stable sodium hydrosulfite composition.

[0023] Example 2 A method for preparing a safe and stable sodium hydrosulfite composition includes the following steps: Step 1: By mass, under a nitrogen atmosphere, add 94 parts of terminal epoxy polydimethylsiloxane with a degree of polymerization of 20 and 90 parts of 4-amino-2,6-di-tert-butylphenol to toluene. After stirring evenly, heat to 100℃ and react for 2 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain the functional modifier.

[0024] Step 2: Under nitrogen protection, 75 parts by mass of methacrylic acid and 1.8 parts by mass of azobisisobutyronitrile were dissolved in tetrahydrofuran to obtain an oil phase; then 55 parts by mass of sodium hydrosulfite and 0.3 parts by mass of soda ash were dissolved in deionized water to obtain an aqueous phase; the aqueous phase was added to the oil phase, and then 64 parts by mass of dehydrated sorbitan monooleate were added. The mixture was stirred for 30 min to obtain a water-in-oil emulsion. The emulsion was heated to 70 °C and stirred for 4 h. Then it was cooled to room temperature, and the microcapsules were collected by vacuum filtration. The microcapsules were washed with ethanol and dried to obtain microcapsule-type sodium hydrosulfite.

[0025] Step 3: By weight, add 60 parts of microcapsule-type sodium hydrosulfite, 60 parts of functional modifier, and 1.5 parts of 4-dimethylaminopyridine to N,N-dimethylformamide, stir evenly, heat to 60°C, then add 20 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 6 hours, after the reaction is completed, cool to room temperature, filter to separate the modified microcapsules, wash with deionized water, and dry to obtain a safe and stable sodium hydrosulfite composition.

[0026] Example 3 A method for preparing a safe and stable sodium hydrosulfite composition includes the following steps: Step 1: By mass, under a nitrogen atmosphere, add 110 parts of terminal epoxy polydimethylsiloxane with a degree of polymerization of 30 and 88 parts of 4-amino-2,6-di-tert-butylphenol to toluene. After stirring evenly, heat to 95°C and react for 3 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain the functional modifier.

[0027] Step 2: Under nitrogen protection, 93 parts by mass of methacrylic acid and 1.5 parts by mass of azobisisobutyronitrile were dissolved in tetrahydrofuran to obtain an oil phase; then 48 parts by mass of sodium hydrosulfite and 0.25 parts by mass of sodium hydroxide were dissolved in deionized water to obtain an aqueous phase; the aqueous phase was added to the oil phase, and then 52 parts by mass of dehydrated sorbitan monooleate were added. The mixture was stirred for 40 min to obtain a water-in-oil emulsion. The emulsion was heated to 65 °C and stirred for 5 h. Then it was cooled to room temperature, and the microcapsules were collected by vacuum filtration. The microcapsules were washed with ethanol and dried to obtain microcapsule-type sodium hydrosulfite.

[0028] Step 3: By mass, add 72 parts of microcapsule-type sodium hydrosulfite, 54 parts of functional modifier, and 1.6 parts of 4-dimethylaminopyridine to N,N-dimethylformamide, stir evenly, heat to 55°C, then add 28 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 5 hours, after the reaction is completed, cool to room temperature, filter to separate the modified microcapsules, wash with deionized water, and dry to obtain a safe and stable sodium hydrosulfite composition.

[0029] Example 4 A method for preparing a safe and stable sodium hydrosulfite composition includes the following steps: Step 1: By mass, under a nitrogen atmosphere, add 96 parts of terminal epoxy polydimethylsiloxane with a degree of polymerization of 25 and 86 parts of 4-amino-2,6-di-tert-butylphenol to toluene. After stirring evenly, heat to 85°C and react for 2.5 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain the functional modifier.

[0030] Step 2: Under nitrogen protection, 78 parts by mass of methacrylic acid and 1.4 parts by mass of azobisisobutyronitrile were dissolved in tetrahydrofuran to obtain an oil phase; then 39 parts by mass of sodium hydrosulfite and 0.26 parts by mass of sodium hydroxide were dissolved in deionized water to obtain an aqueous phase; the aqueous phase was added to the oil phase, and then 52 parts by mass of dehydrated sorbitan monooleate were added. The mixture was stirred for 35 min to obtain a water-in-oil emulsion. The emulsion was heated to 55 °C and stirred for 4.5 h. Then it was cooled to room temperature, and the microcapsules were collected by vacuum filtration. The microcapsules were washed with ethanol and dried to obtain microcapsule-type sodium hydrosulfite.

[0031] Step 3: By weight, add 65 parts of microcapsule-type sodium hydrosulfite, 53 parts of functional modifier, and 1.56 parts of 4-dimethylaminopyridine to N,N-dimethylformamide, stir evenly, heat to 53°C, then add 25 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, react for 4.5 hours, after the reaction is completed, cool to room temperature, filter to separate the modified microcapsules, wash with deionized water, and dry to obtain a safe and stable sodium hydrosulfite composition.

[0032] Example 5 A method for preparing a safe and stable sodium hydrosulfite composition includes the following steps: Step 1: By mass, under a nitrogen atmosphere, add 120 parts of terminal epoxy polydimethylsiloxane with a degree of polymerization of 45 and 89 parts of 4-amino-2,6-di-tert-butylphenol to toluene. After stirring evenly, heat to 90°C and react for 3.5 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain the functional modifier.

[0033] Step 2: Under nitrogen protection, 86 parts by mass of methacrylic acid and 1.7 parts by mass of azobisisobutyronitrile were dissolved in tetrahydrofuran to obtain an oil phase; then 53 parts by mass of sodium hydrosulfite and 0.28 parts by mass of sodium hydroxide were dissolved in deionized water to obtain an aqueous phase; the aqueous phase was added to the oil phase, and then 61 parts by mass of dehydrated sorbitan monooleate were added. The mixture was stirred for 38 min to obtain a water-in-oil emulsion. The emulsion was heated to 60 °C and stirred for 5.5 h. Then it was cooled to room temperature, and the microcapsules were collected by vacuum filtration. The microcapsules were washed with ethanol and dried to obtain microcapsule-type sodium hydrosulfite.

[0034] Step 3: According to the mass fraction, add 73 parts of microcapsule-type sodium hydrosulfite, 58 parts of functional modifier, and 1.75 parts of 4-dimethylaminopyridine to N,N-dimethylformamide, stir evenly, heat to 57°C, and then add 33 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide. React for 5.5 hours. After the reaction is completed, cool to room temperature, filter to separate the modified microcapsules, wash with deionized water, and dry to obtain a safe and stable sodium hydrosulfite composition.

[0035] Comparative Example 1 Compared with Example 1, Comparative Example 1 did not modify the microcapsules, but the other preparation steps remained unchanged, resulting in a sodium hydrosulfite composition.

[0036] Comparative Example 2 Compared with Example 1, Comparative Example 2 only used polydimethylsiloxane to graft microcapsules without modifying them, and the other preparation steps remained unchanged to obtain a sodium hydrosulfite composition.

[0037] Experimental Example 1 The sodium hydrosulfite compositions in Examples 1-3 and Comparative Example 1 were subjected to the following performance tests, and the test results are shown in Table 1.

[0038] 1. Waterproofing test: Take 50g of each sample and place it in a 1m³ sealed chamber at 45℃ and 75% relative humidity for 15 days. Then, measure the concentration of SO2 in the air inside the chamber according to GB / T37186-2018 "Determination of sulfur dioxide and nitrogen oxides by ultraviolet differential absorption spectrometry".

[0039] 2. Antioxidant test: Take 50g of freshly prepared sodium hydrosulfite composition sample from each group, break the coating of the sodium hydrosulfite composition under high-speed stirring to release sodium hydrosulfite, and titrate with iodine standard solution. Calculate the effective content of sodium hydrosulfite by the amount of iodine consumed. Then, take another 50g sample from each group and place it in an environment of 20℃ and 50% oxygen concentration for 15 days. Measure the results and compare the two values ​​to calculate the effective content retention rate of sodium hydrosulfite.

[0040] Table 1 <![CDATA[SO2 concentration (%)]]> Retention rate of effective sodium hydrosulfite content (%) Example 1 2.2 94 Example 2 2.3 93 Example 3 2.5 92 Comparative Example 1 3.8 85 Comparative Example 2 3.1 86 According to Table 1, compared with Comparative Examples 1-2, Examples 1-3 have lower sulfur dioxide release and higher retention rate of effective sodium hydrosulfite content, indicating that the water resistance and antioxidant properties of Examples 1-3 are higher than those of Comparative Examples 1 and 2. It can be seen that the present invention can effectively improve the safety and stability of the sodium hydrosulfite composition. Compared with Comparative Example 2, Examples 1-3 have significantly better water resistance, indicating that the modification effectively improves the loading rate of functional modifier and microcapsule.

[0041] The present invention provides a detailed description of a safe and stable sodium hydrosulfite composition and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combination method. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles. In particular, as long as there is no structural conflict, the features in the embodiments disclosed in this invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a safe and stable sodium hydrosulfite composition, characterized in that, The preparation method is as follows: Step 1: Terminal epoxy-terminated polydimethylsiloxane undergoes a ring-opening reaction with 4-amino-2,6-di-tert-butylphenol to obtain a functional modifier; The second step is to prepare microcapsule sodium hydrosulfite with polymethacrylic acid as the wall material and sodium hydrosulfite as the core material. The third step involves esterifying microcapsule sodium hydrosulfite and functional modifiers to obtain a safe and stable sodium hydrosulfite composition.

2. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 1, characterized in that, The degree of polymerization of the terminal epoxy polydimethylsiloxane in the first step is 20-50.

3. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 1, characterized in that, In the first step, the mass ratio of terminal epoxy polydimethylsiloxane to 4-amino-2,6-di-tert-butylphenol is 94-125:85-90.

4. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 1, characterized in that, The reaction temperature in the first step is 80-100℃, and the reaction time is 2-4 hours.

5. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 1, characterized in that, The preparation method of the microcapsule-type sodium hydrosulfite in the second step is as follows: Under nitrogen protection, methacrylic acid and azobisisobutyronitrile were dissolved in tetrahydrofuran to obtain an oil phase; sodium hydrosulfite and a stabilizer were then dissolved in deionized water to obtain an aqueous phase; the aqueous phase was added to the oil phase, followed by the addition of sorbitol monooleate, and the mixture was stirred to obtain a water-in-oil emulsion. The mixture was then heated to 50-70°C and stirred continuously to obtain microencapsulated sodium hydrosulfite.

6. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 1, characterized in that, In the third step, the mass ratio of microcapsule sodium hydrosulfite to functional modifier is 60-80:50-60.

7. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 1, characterized in that, The reaction temperature in the third step is 50-60℃, and the reaction time is 4-6 hours.

8. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 5, characterized in that, In the preparation method of the microcapsule-type sodium hydrosulfite, the mass ratio of methacrylic acid, sodium hydrosulfite, stabilizer, sorbitan monooleate, and azobisisobutyronitrile is 75-100:35-55:0.2-0.3:48-64:1.3-1.

8.

9. The method for preparing a safe and stable sodium hydrosulfite composition according to claim 8, characterized in that, The stabilizer is sodium hydroxide or soda ash.

10. A safe and stable sodium hydrosulfite composition obtained by the preparation method according to any one of claims 1-9.