CN1435449A - Coated sodium peracrbonate, process for preparing same and use thereof - Google Patents

Abstract

A coated sodium percarbonate, its preparing process and is application as bleaching component in detergent, cleaner, and bleaching agent are disclosed.

Description

Coated sodium percarbonate and its preparing process and application

Technical Field

The invention relates to coated sodium percarbonate, a process for its preparation and its use as a bleaching component in detergent, cleaning agent and bleach formulations. International patent Classification No. belongs to the field of C11D3/39 detergents.

Background

Sodium percarbonate has excellent bleaching, sterilizing and disinfecting functions because of being capable of decomposing and releasing active oxygen, and is widely used in the fields of washing, printing and dyeing, spinning, papermaking, medicine and health and the like, the detergent industry in China is the largest potential market of coated sodium percarbonate, and compared with the traditional chlorine bleaches, phosphorus detergent auxiliaries and sodium perborate, the coated sodium percarbonate is considered as an ideal detergent auxiliary. In recent years, it has found wide use in the foreign detergent industry. Because the use requirements of sodium percarbonate in the aspects of stability and the like in China at present cannot be completely met, the popularization and application of the sodium percarbonate in the detergent industry are greatly limited. With the improvement of the living standard of people in China and the enhancement of environmental protection consciousness, the low-phosphorus and phosphorus-free washing powder gradually replaces phosphorus-containing washing powder. At present, the annual yield of washing powder in China is about 200 ten thousand tons, and the market demand of sodium percarbonate reaches nearly 20 ten thousand tons according to the addition of 8 percent of sodium percarbonate.

The sodium percarbonate can be prepared by a dry method or a wet method. The dry method is to atomize and spray an aqueous solution of sodium carbonate and an aqueous solution of high-concentration hydrogen peroxide on sodium percarbonate seeds in a flowing gas stream, dry and grow crystals, or to add high-concentration hydrogen peroxide to sodium carbonate particles for reaction. Its advantages are no need of filtering, short process, high output rate, high heat release rate, low heat exchange effect, high dust content, and high concentration of hydrogen peroxide. The wet method is that hydrogen peroxide and sodium carbonate aqueous solution react at a certain temperature, crystallize and then dry to obtain the finished product, and because the materials can be fully mixed and easily exchange heat, the process equipment is simple, the investment is low, and the mother liquor can be recycled and reused. At present, wet process is mostly adopted at home and abroad. The industrial production is firstly put into Japan in 1969, the production capacity of the Japanese exceeds 10 ten thousand tons per year, and more than 60.0 percent of the Japanese is used as a washing powder additive. At present, more than 100 million tons of sodium percarbonate are needed globally, and the maximum single set production capacity is 2 million tons. The research and development of China are started in 1983, the national production capacity is still in the research and development stage at present, the domestic annual production capacity is less than 1 ten thousand tons, the material consumption is mainly overhigh, the utilization rate of sodium carbonate is generally only about 80.0%, the utilization rate of hydrogen peroxide is below 90.0%, the storage stability of the product is poor, the storage and transportation of the product are limited, the single set of scale is small, and the scale production is not formed. China is a country with a lot of people, the annual yield of washing powder is more than 200 ten thousand tons, the color bleaching powder is prepared according to 20.0 percent of the annual yield of the washing powder, sodium percarbonate is added according to 8.0 to 10.0 percent of each ton, 3.2 to 4.0 ten thousand tons of sodium percarbonate can be consumed every year, and the usage amount of other industrial fields, breeding industries and other industries is not included. With the development of national economy and the improvement of purchasing power of the national people, a large amount of the bleaching washing powder must enter families within 3 years, and sodium percarbonate has a large development margin in China. The development of sodium percarbonate from China's chemical newspapers and other chemical publications has been called for, because there are dozens of million tons of hydrogen peroxide and nearly million tons of sodium carbonate in China to be added with value, and the production of sodium percarbonate is a good choice.

Sodium percarbonate is a novel and multipurpose fine chemical product, the active oxygen content reaches 15.3 percent, and the sodium percarbonate is called solid hydrogen peroxide. It has strong bleaching, stain removing, sterilizing and other functions. The main application is as an auxiliary agent of a detergent, and the detergent is widely used as a dye finishing agent, a bleaching agent, a color developing agent, a preservative, a bacterium killing agent and an oxygen supply agent in the fields of textile, paper making, food, medical health and the like. The research and the production of sodium percarbonate begin in the early eighties of China, and a large number of documents report the research of the preparation process at present. The major manufacturers in China include Yangzhou pesticide factories, inorganic salt factories in Yu of Zhejiang, Jilin chemical industry, Tianjin chemical industry, Guangzhou Jinzhujiang chemical Co., Ltd and the like, and the wet process is mostly adopted to produce sodium percarbonate.

Sodium percarbonate (2 Na)₂CO₃·3H₂O₂) Can be used as active oxygen component in detergent, cleaning agent and bleaching agent. Since sodium percarbonate is not sufficiently stable in storage in hot and humid environments and in the presence of various detergent and cleaning agent components, the stability of sodium percarbonate must be increased to reduce the loss of active oxygen. One basic principle for the stabilization is to coat the small sodium percarbonate particles with a stabilizing component forming a coating.

GB 174891 discloses a method in which an aqueous sodium water glass solution is sprayed onto an active oxygen-containing compound and subsequently dried in order to increase the storage stability. In the process disclosed in DE-OS2652776, sodium percarbonate is stabilized by coating the sodium percarbonate particles obtained by crystallization with sufficient silicate. Sufficient stability, especially in the presence of detergents and cleaning agents, cannot be achieved by the above-described methods.

From DE-OS 2417572 and DE-PS 2622610, processes are known for stabilizing particulate sodium percarbonate in which a mixture of sodium carbonate and other mineral salts, such as sodium bicarbonate and/or sodium sulfate, is crystallized or a mixture of sodium carbonate, sodium sulfate and sodium silicate is used as coating substance. In these processes, an aqueous solution of the constituents of the coating material is sprayed onto sodium percarbonate particles while maintaining the fluidized bed temperature at 30 to 80 ℃ and the water added is evaporated off to form a firm coating. Despite the greatly increased stability of the sodium percarbonate granules coated in this way, the active oxygen content drops too rapidly on prolonged storage in the presence of detergent powders.

A number of processes are known for effectively stabilizing sodium percarbonate using boron compounds such as boric acid (DE-PS 2800916), borates (DE-OS3321082) and perborates (DE-PS 2651442 and DE-PS 2810379). Despite a somewhat good stabilizing effect, there is an increasing interest in the market for coated sodium percarbonate which does not contain boron compounds.

Another coating composition is known from us patent 4,325,933; stabilization is carried out by treating sodium percarbonate with an aqueous solution of the alkaline earth metal salt magnesium sulfate or magnesium chloride. In the treatment of sodium percarbonate particles, alkaline earth carbonate layers form on the surface, which reduces the water absorption of the sodium percarbonate and increases its stability. However, it has been shown that such stabilized products still do not have sufficient storage stability.

From EP-A0405797 sodium percarbonate compositions with a higher reliability are known; according to this embodiment, the composition comprises a compound of the series of inorganic magnesium compounds and, in addition, an alkali metal carbonate. The composition does not relate to sodium percarbonate particles having a uniform coating layer adhering closely to their core, but to mixtures which are also in the form of particles. It can be determined in the working up of the process described in said document for preparing said compositions that such compositions have an inadequate storage stability in a hot and humid environment in the presence of detergent powders.

Disclosure of Invention

The object of the present invention is to provide a coated sodium percarbonate having a high stability, which has a storage stability exceeding that of the coated sodium percarbonate of the prior art. It is a further object of the present invention to provide a process for the preparation of coated sodium percarbonate which is particularly stable in storage.

The basic principles and key technical contents for implementing the scheme of the invention are as follows.

The synthesis of sodium percarbonate can be represented by the following reaction formula:

sodium percarbonate is an adduct of sodium carbonate and hydrogen peroxide, which is unstable and liberates hydrogen peroxide under the influence of heat and moisture, which resolubilizesWater and oxygen generation:

the decomposition mechanism of hydrogen peroxide is electron transfer and radical reaction, and the heavy metal ions such as iron and copper brought by carelessness in the raw material or synthesis process are used for H₂O₂The decomposition of sodium percarbonate is accelerated by the catalytic action of the catalyst. Therefore, moisture, heat and heavy metal ions are main factors influencing the stability of sodium percarbonate, so the key points for preparing stable sodium percarbonate are as follows:

in the process of preparing sodium percarbonate, the water content of the product is required to be less than 2%. After the synthesis reaction is finished, the wet product is required to be easy to filter, the material which is centrifugally dried has low moisture, is loose and does not agglomerate, the wet material which enters a vibration fluidized drying bed for drying has good fluidization performance, can be dried within the temperature range of 105-plus-material 115 ℃, reduces the loss of the effective oxygen of the product, and can prepare the product with high active oxygen content. The product granularity can not be too small, the granularity is too small, the specific surface area is large, and the product is easy to absorb moisture to cause product decomposition. In order to solve the problem, the crystallization assistant is added at the beginning of the synthesis reaction, and the reaction temperature and the stirring speed are adjusted, so that the wet product is easy to filter, and more than 95.0 percent of the product particles can be controlled within the particle size range of 80-10 meshes.

Adding a stabilizer into the raw materials participating in the reaction, wherein the stabilizer is used for complexing heavy metal ions to remove the heavy metal ions in the raw materials; the organic amine in the stabilizer can not only complex heavy metal ions, but also permeate into the product to play the role of a free radical inhibitor and slow down the decomposition of sodium percarbonate, and the stabilizer added in the reaction raw materials is also called as an internal stabilizer. Internal stabilizer: na (Na)₂SiO₃∶MgSO₄∶EDTA＝8∶3∶2，The solid content of the prepared aqueous solution is 10 to 60 percent (weight), and the dosage of the aqueous solution is 0.02 to 1.0 percent of the weight of the product. In the present invention, all the additives are used in a weight ratio to the product unless otherwise specified.

And thirdly, respectively atomizing and spraying a stabilizing agent liquid and a coating agent liquid at the middle rear part of the small fluidized drying bed, wherein the stabilizingagent sprayed by atomization also comprises a heavy metal ion complexing agent and a free radical inhibitor, and the stabilizing agent is called as an external stabilizing agent. The coating agent is used for forming a thin organic polymer film on the surface of the sodium percarbonate, and blocking the contact with moisture, but not too much, otherwise, the dissolution speed of the sodium percarbonate is influenced, and the bleaching and oxidation performance of a product is limited.

The inventor carries out a film-coated sodium percarbonate pilot test in a 500-liter kettle through a pilot test, adds varieties and proportions of heavy metal ion complexing agents and free radical inhibitors in reaction materials, adds the addition amount, proportion and adding time of a crystallization assistant agent in synthesis, and influences of different stirring speeds and temperatures in different periods on product yield and product granularity in synthesis. The key points are as follows:

respectively adding an internal stabilizer into sodium carbonate slurry and hydrogen peroxide, wherein the main component of the internal stabilizer is Na₂SiO₃、MgSO₄EDTA. The weight ratio of the components is Na₂SiO₃∶MgSO₄The solid content of the prepared aqueous solution is 10 to 60 percent, and the dosage of the aqueous solution is 0.02 to 1.0 percent of the weight of the sodium percarbonate. Equally dividing into two parts, and respectively adding the two parts into a slurry kettle and a hydrogen peroxide kettle. Heavy metal ions are not required to be brought into the used raw materials in the production or storage and transportation processes, and the recrystallization of the raw material sodium carbonate has been proposed, so that the effect is good, but the energy consumption and the material consumption are too high, and the industrial significance is not realized. The stabilizer can be addedinto the reaction raw material liquid to complex heavy metal ions, the organic amine EDTA can complex the heavy metal ions and can also be used as a free radical inhibitor, the added internal stabilizer can enter the interior of product particles to play a role in internal stabilization, the added amount is too small to play a role in stabilization, too much cost is added, even a wet product is agglomerated into blocks, and the filterability is poor. The internal stabilizer is determined by small test and pilot test and is proved by production verification to be reasonable in formula, economical and practical.

(II) adding sodium polyacrylate and/or polyamide as crystallization assistant agent in small flow rate at the beginning of the synthesis reaction, preparing 5-30 wt% water solution of sodium polyacrylate and/or polyamide, and regulating the stirring speed to 10-90 rpm and the reaction temperature to 14-25 deg.c in different reaction stages through frequency varying speed regulation to control the grain size of over 95.0% in the range of 80-10 mesh, and being white ball-shaped, and wet product is easy to filter. Compared with the prior art, if the crystallization assistant is not added at the beginning of the reaction in the pilot plant test, the materials are difficult to filter, the wet product part after the filter is blocked, the moisture of the wet product is as high as 10.0-12.0 percent, and the product yield is only about 85.0 percent based on sodium carbonate. The wet product has poor fluidization condition in the vibration fluidization drying bed, and the temperature of inlet hot air must be increased to 130 ℃, so that the effective oxygen of the product is difficult to ensure to be more than 13.0 percent. When the reaction is started, the moisture of the wet product after the crystallization aid is added and the wet product is subjected to spin filtration is about 6.0%, the temperature of inlet hot air can be reduced to about 105 ℃ during drying, the fluidization condition is good, and the effective oxygen of the product can be ensured to be more than 13.0%. The product yield is more than 90.0 percent calculated by sodium carbonate.

Third, there is a report in literature that the sodium percarbonate product is dissolved in organic solvent with coating agent, and the organic solvent is removed by stirring and soaking for a certain time or the sodium percarbonate, stabilizing agent and coating agent are mixed in a double coneThe mechanical mixing in the rotary mixer has good effect, but has large energy consumption and material consumption, and industrialization is impossible. The latter has poor coating effect and large water content without drying. The process of the invention is that the external stabilizer liquid is atomized and sprayed in the middle section of the first vibration fluidized drying bed by using the pressure of about 0.4Mpa, and the coating agent liquid is atomized and sprayed in the rear section by using the pressure of about 0.4 Mpa. The external stabilizer comprises the following components: na (Na)₂SiO₃、MgSO₄Triethanolamine and an external stabilizer: na (Na)₂SiO₃∶MgSO₄The solid content of the prepared aqueous solution is 25-60 percent (weight), and the dosage of the aqueous solution is 0.5-5.0 percent of the weight of the product sodium percarbonate. The coating agent consists of a high-molecular film forming agent: any one of polyethylene glycol, hydroxyethyl cellulose or acrylic acid-maleic acid copolymer is prepared into aqueous solution with the solid content of 5-30 percent and the dosage of the aqueous solution is 0.02-0.5 percent of the weight of the sodium percarbonate product. The organic amine triethanolamine used isTertiary amines, LD₅₀More than 5000mg/kg, basically has no toxicity, and can inhibit H₂O₂The coating agent and the stabilizing agent have the advantages of unique formula, good coating process effect, product dissolution time of about 80 seconds, no influence on product bleaching effect, and stability and coating treatment in a vibrating fluidized drying bed during drying.

The product (IV) meets the requirement of enterprise standard Q/YT001-2000, the stability is more than 95.0%, the grain diameter after screening is more than 95.0% and 20-50 meshes, the grain diameter distribution range is smaller, the water content of the domestic washing powder is larger and reaches 7.0-8.0%, and the sodium percarbonate is used for the quick decomposition of the active oxygen of the washing powder additive, so the use value is lost. The inventor adds 10.0% of the washing powder into sodium percarbonate which is processed with and without coating according to the formula of Rc007 bleaching washing powder which is listed under the handbook of Chinese chemical products, and the water content of the prepared washing powder is 6.5%, and the stability test shows that the active oxygen of the sodium percarbonate which is processed with the coating by the inventor can reach more than 12.0% even after the sodium percarbonate is stored for half a year, and the active oxygen of the sodium percarbonate which is not processed with the coating is lower than 8.0% after the sodium percarbonate is stored for half a year, so the use value is lost. 1080 kilograms of hydrogen peroxide solution with the consumption of 27.5 percent per ton of products; the usage rate of the hydrogen peroxide reaches 96.0 percent (about 90.0 percent is reported in the literature). 750 kg of sodium carbonate is consumed by each ton of products, the utilization rate of the sodium carbonate is 90.0 percent (the sodium carbonate is reported to be 85.0 percent in the literature), and the material consumption is lowest.

The synthesis of the coated sodium percarbonate adopts 27.5 percent hydrogen peroxide and industrial sodium carbonate as main raw materials, and the coated sodium percarbonate is produced by a wet process and is coated. Adding industrial sodium carbonate and industrial refined salt into a pulping kettle with a fixed amount of mother liquor in a weight ratio of 4: 1 under stirring, adding an internal stabilizer for pulping, adding 27.5% of hydrogen peroxide into a hydrogen peroxide kettle under stirring, adding the internal stabilizer under stirring, cooling the pulp and the hydrogen peroxide to 14-16 ℃ by using a cold salt water jacket, simultaneously adding the pulp and the hydrogen peroxide into a synthesis kettle with the mother liquor under stirring, stirring and cooling to the specified temperature of 14-16 ℃, controlling the adding speed of the two materials, dropwise adding a crystallization assistant agent sodium polyacrylate and/or polyamide into the synthesis kettle when the reaction starts, controlling the reaction temperature to be 16-25 ℃, adjusting the stirring speed to be 10-90 rpm to control the product particles to be in the required range, finishing the feeding, reacting for 5-15 minutes, finishing the reaction, putting the materials into a centrifuge for spin-drying under stirring, the mother liquor enters a mother liquor pool to be recycled and reused, wet materials enter a vibration fluidized drying bed through a vibration feeder, external stabilizer liquid and coating agent liquid are respectively sprayed in the middle and rear parts of the vibration fluidized drying in a pressure atomization mode, the materials are subjected to primary drying, the coated materials are subjected to secondary drying and screening, the materials enter a storage bin, the materials are qualified through inspection, and the finished products are packaged, namely the finished products, see fig. 1.

The main technical indexes of the product are as follows:

item	Index mark
			First-class product	Qualified product
	Appearance of the product	White crystalline or crystalline powder			White crystalline or crystalline powder
The content of active oxygen (O) is not less than			13.0	10.5
	The content of iron (Fe) is less than or equal to	0.002			0.005
Water content is less than or equal to%			2.0
	Bulk density, g/ml	0.40-0.95
pH value (30g/l aqueous solution)				10-11
	Stability,% greater than or equal to	95.0

The main material consumption of ton product is as follows: 1080 kg of 27.5% hydrogen peroxide, 750 kg of industrial sodium carbonate, 200 kg of refined industrial salt sodium chloride, 160 kg of coal and 260 kilowatt-hours of electricity.

Both small and extensive experiments have shown that ① is necessary to add an internal stabilizer, mainly Na, to sodium carbonate solution and hydrogen peroxide simultaneously in the synthesis of coated sodium percarbonate₂SiO₃∶MgSO₄The organic amine EDTA is 8: 3: 2, and the added components are used to eliminate metal ion from the material and raise the stability of the product.

② adding crystal promoter to the reaction liquid, which can be polyacrylic acid and/or polyamide, or sodium polyacrylate and polyamide 2: 1, to prepare 5-30% (wt.) water solution, adding 0.1-1.0% (wt.) crystal promoter to obtain the product with proper granularity, the crystal promoter has flocculation effect to increase yield.

③ the sodium percarbonate obtained by centrifugal drying enters a vibration fluidized drying bed, and the external stabilizer solution and the coating agent solution are respectively sprayed on the middle and back parts of the drying bed by pressure atomization, wherein the external stabilizer is Na₂SiO₃、MgSO₄Organic amine triethanolamine; the coating agent is composed of any one of macromolecule film forming agent polyethylene glycol, hydroxyethyl cellulose or acrylic acid-maleic acid copolymer, the solid content of the prepared aqueous solution is 5% -30%, and the dosage of the aqueous solution is the weight of the sodium percarbonate: 0.02% -0.5%, the total amount is 3% of the product sodium percarbonate. The stability of the sodium percarbonate which is subjected to the stabilizing and coating treatment is obviously improved.

The three measures have good effect when being used for the production of 2000 tons/year coated sodium percarbonate. The main mechanism is that the decomposition of sodium percarbonate is to give out H₂O₂And H is₂O₂The decomposition mechanism of (1) is electron transfer and free radical reaction process, and impurity metal ions such as copper and iron in raw materials are paired with H₂O₂Is decomposedThe catalytic action, the action of adding internal stabilizer in the reaction raw material is to make the metal ion in the raw material be precipitated or complexed by organic amine EDTA, and the organic amine EDTA and organic phenol are the same and are free radical absorbent, and can inhibit H₂O₂The decomposition effect. Silicate and magnesium salt added as external stabilizer can further complex metal ions, and organic amine triethanolamine is a high boiling point substance with boiling point of 360 ℃ and low toxicity, LD₅₀More than 5000mg/kg, can not only complex metal ions, but also inhibit the generation of free radicals, improve the stability of the product, has low price and good intermiscibility with the product, and the external stabilizer can be better attached to the surface of sodium percarbonate particles by the macromolecular film forming agent, but the solubility and the shadow of the sodium percarbonate can be influenced by the overlarge film forming agent dosageBleaching and sterilizing power. Thus, the stabilizer added by the two methods can reduce or complex metal ions in the product or absorb H₂O₂Inhibiting H by the radicals generated by decomposition of₂O₂I.e. to inhibit the decomposition of sodium percarbonate.

The higher the concentration of hydrogen peroxide used in the whole reaction system, the less water is brought into the reaction system, i.e., the less mother liquor is discarded, and the higher the reaction yield calculated by sodium carbonate and hydrogen peroxide (see fig. 2).

Considering the price problem of hydrogen peroxide with different concentrations and the product condition of hydrogen peroxide manufacturers, the inventor selects 27.5 percent hydrogen peroxide which can be supplied by ammonia plants in the west of the Yangtze river.

The higher the reaction temperature is, the higher the decomposition rate of sodium percarbonate synthesized by the reaction is and the lower the relative yield is. The reaction temperature is too low, which affects the product results and leads to a decrease in yield. The process of the invention generally controls the reaction temperature to be 18-25 ℃, and the temperature is too low, so that the energy consumption is too large and uneconomical.

Comparison of temperature with yield

Temperature of	10℃	15℃	20℃	25℃	30℃	35℃
							Yield (%)	93.6	93.4	92.5	92.2	89.5	85

The product is coated by adopting the composite internal stabilizer containing organic amine and the coating agent containing the external stabilizer and the organic polymer film-forming agent, so that the stability of the product is obviously improved, the product is ensured to have moderate dissolution speed and active oxygen release speed while the stability of the product is improved, the product has a washing assisting function, andthe service performance of the product can be improved.

The stability of the product was determined according to the Q/YT001-2000 standard, six samples were taken for stability determination, the average particle size was 35 mesh, and the results are listed in the following table:

numbering	1	2	3	4	5	6
							Original active oxygen (O) (%)	13.42	13.55	13.60	13.22	13.45	13.17
Stability determination of active oxygen (O) (%)	12.83	13.14	13.14	12.84	12.98	12.94
							Stability (%)	95.6	97.0	96.6	97.1	96.5	96.1

The six samples with the stability are sealed in a polyethylene plastic bag by 500 g, the bag is sealed by hot plastic, the six samples are stored for 20 days in 06 months to 21 days in 09 months in 2000, the storage place is a small wooden frame at a shady and ventilated place of a finished product warehouse, and the test results of the six samples in 09 months and 21 days in 2000 are listed in the following table according to the Q/YT001-2000 standard:

numbering	1	2	3	4	5	6
							Original active oxygen (O) (%)	13.42	13.55	13.60	13.22	13.45	13.47
Three months active oxygen (O) (%)	12.91	13.08	13.02	12.73	12.89	12.86
							Decomposition rate%	3.8	3.5	4.3	3.7	4.2	3.5
Stability (%)	96.2	96.5	95.7	96.3	95.8	95.5

The results in the two tables show that the product of the invention has good stability. The Q/YT001-2000 standard stability determination method is matched with the Q/YT001-2000 standard stability determination method compared with the stability of a sample naturally stored for three months.

The coated sodium percarbonate is mainly used as an additive of washing powder to prepare the so-called bleaching powder so as to improve the stain removal function of the washing powder and ensure that the washed fabrics are bright and beautiful. The domestic washing powder has high water content of 7-8%, and is easy to decompose sodium percarbonate and to lose its meaning.

The inventor takes one part of the same batch of sodium percarbonate produced by the inventor without coating treatment, and takes the other part with coating treatment. According to 10 kilograms of domestic general washing powder, the water content is 6.5 percent through detection, 3 kilograms are divided into 6 groups, each group is 500 grams, 10 percent of non-coated sodium percarbonate is added into 3 groups, 10 percent of coated sodium percarbonate is added into the other three groups, a sample is put into a polyethylene bag and sealed, active oxygen is detected after the sample is placed ina natural ventilation place for three months from 08 months to 11 months and 07 days in 2000, and the result is compared with the following table through conversion:

serial number	1	2	3	4*	5*	6*
							Active oxygen value (%)	13.51	13.51	13.51	13.10	13.10	13.10
Active oxygen value after storage (%)	12.92	12.86	12.88	10.52	10.39	10.51
							Stability (%)	95.6	95.2	95.3	80.6	79.3	80.3

^*Is uncoated sodium percarbonate.

It can be seen from the table that the decomposition of the coated sodium percarbonate in the added washing powder is much lower than that of the uncoated sodium percarbonate, i.e. it is much more stable, as deduced from the decomposition rate in the table, the decomposition of the uncoated sodium carbonate is close to40% on average over half a year, the active oxygen content is lower than 8%, the active oxygen content of the sodium percarbonate is more than 8% and the use value is good, while the decomposition rate of the coated sodium percarbonate is less than 10% after half a year, the active oxygen content is still more than 12%, and still is in the range of practical value.

The invention has no waste gas and waste residue, only produces mother liquor containing sodium carbonate and sodium chloride, the mother liquor can be recycled and reused, the mother liquor realizes zero emission, and has no pollution to the environment. This engineering needs to use fan and centrifuge, chooses low noise machine kind for use, arranges in indoor or enclosure and separates the processing of making an uproar.

The invention belongs to the production of inorganic chemicals, and the main equipment is normal pressure production. No combustible gas and liquid exist. The electric equipment can be installed according to the non-explosion requirement. The entrance of the factory building is a main traffic passage in the factory building, and the fire engine can freely enter and exit. The plant is provided with a fire extinguisher, a fire extinguishing cylinder and a fire hydrant.

Production workers are trained to go on duty, each worker has a part-time safety worker, and safety inspection is carried out on the spot. Hydrogen peroxide is a strong oxidant, and necessary labor protection articles such as working clothes, rubber gloves, rubber shoes, masks, protective glasses and the like are prepared in production work. The workshop is provided with a flushing facility and simple health care medicines.

The main technical performance indexes of the product are as follows:

item	Index (I)
		Q/YT001-2000
	Appearance of the product		White powder or granule
Content of active oxygen (O)%		13.0
	Water content%		2.0
pH value (30g/L aqueous solution)		10-11
	Iron (Fe) content%		0.002
Stability degree%		95.0

The stability index reflecting the product stability is provided by our company at first in China.

Unless otherwise specified, all percentages used in the present invention are weight percentages.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

FIG. 2 shows the yield a of sodium percarbonate as a function of H₂O₂Schematic representation of the change in concentration X.

Detailed Description

Example 1

Preparation of raw materials

1. Industrial sodium carbonate: 400 kg

2. Industrial refined salt: 100 kg of

3.27.5% hydrogen peroxide: 700 kg

4. Internal stabilizer: na (Na)₂SiO₃0.8 kg, MgSO₄0.3 kg of EDTA and 0.2 kg of EDTA are mixed with 1.3 kg of water to prepare an aqueous solutionDivided into two equal parts.

5. And (3) a crystallization promoter: 3.25 kg of sodium polyacrylate and 15 kg of water are added.

6. External stabilizer: na (Na)₂SiO₃13 kg, MgSO₄5.0 kg, 1.6 kg triethanolamine and 20 kg water.

7. Coating agent: 1.5 kg of polyethylene glycol and 10 kg of water are added.

Second, the production process

Adding industrial sodium carbonate and industrial refined salt into a slurry kettle in which a certain amount of mother liquor is placed according to a weight ratio of 4: 1 under stirring, adding prepared internal stabilizer after pulping, adding metered hydrogen peroxide into a hydrogen peroxide head tank, adding the prepared internal stabilizer under stirring, cooling the slurry and the hydrogen peroxide to 14-16 ℃ by using a cooling salt water jacket, simultaneously adding the slurry and the hydrogen peroxide into a synthesis kettle in which the metered mother liquor is placed and cooled to 14-16 ℃ under stirring, simultaneously starting to dropwise add a crystallization promoter, controlling the adding speed of the two materials, controlling the reaction temperature to be between 16 ℃ and 25 ℃, gradually increasing the stirring speed along with the gradual increase of reaction materials to control the granularity of the product, controlling the reaction time of the feeding to be 90 minutes, finishing the feeding, reacting for 5-15 minutes, finishing the reaction, placing the materials into a vibration centrifuge under stirring for spin-drying, the mother liquor enters a mother liquor pool to be recycled and reused, wet materials enter a relatively small first vibration fluidized bed through a vibration feeder, the prepared external stabilizer aqueous solution is atomized and sprayed into the middle section of the fluidized bed at the pressure of 0.4Mpa, the prepared coating agent aqueous solution is atomized and sprayed into the rear section of the fluidized bed at the pressure of 0.4Mpa, the product subjected to coating treatment enters a second vibration fluidized drying bed to be dried, the product enters a storage bin after being screened, and the finished product is obtained after the product is qualified and packaged. The obtained product has 14.2% of active oxygen, 1.4% of water and 98.4% of stability.

Example 2

The same effect can be obtained by the production process of example 1 by changing the crystallization aid in example 1 to polyamide 3.25 kg and adding water 15 kg, the coating agent is hydroxyethyl cellulose 1.5 kg and adding water 10 kg, and the other ingredients are not changed.

Claims (10)

1. A coated sodium percarbonate characterized in that:adding industrial sodium carbonate and industrial refined salt into a slurry kettle in which a certain amount of mother liquor is placed according to a weight ratio of 4: 1 under stirring, adding prepared internal stabilizer after pulping, adding metered hydrogen peroxide into a hydrogen peroxide head tank, adding the prepared internal stabilizer under stirring, cooling the slurry and the hydrogen peroxide to 14-16 ℃ by using a cooling salt water jacket, simultaneously adding the slurry and the hydrogen peroxide into a synthesis kettle in which the metered mother liquor is placed and cooled to 14-16 ℃ under stirring, simultaneously starting to dropwise add a crystallization promoter, controlling the adding speed of the two materials, controlling the reaction temperature to be between 16 ℃ and 25 ℃, gradually increasing the stirring speed along with the gradual increase of reaction materials to control the granularity of the product, controlling the reaction time of the feeding to be 90 minutes, finishing the feeding, reacting for 5-15 minutes, finishing the reaction, placing the materials into a vibration centrifuge under stirring for spin-drying, the mother liquor enters a mother liquor pool to be recycled and reused, wet materials enter a relatively small first vibration fluidized bed through a vibration feeder, the prepared external stabilizer aqueous solution is atomized and sprayed into the middle section of the fluidized bed at the pressure of 0.4Mpa, the prepared coating agent aqueous solution is atomized and sprayed into the rear section of the fluidized bed at the pressure of 0.4Mpa, the product subjected to coating treatment enters a second vibration fluidized drying bed to be dried, the product enters a storage bin after being screened, and the finished product is obtained after the product is qualified and packaged.

2. The coated sodium percarbonate of claim 1, characterized in that the industrial grade salt is sodium chloride.

3. The coated sodium percarbonate of claim 1, characterized in that the internal stabilizer is Na₂SiO₃、MgSO₄EDTA which is Na in weight ratio₂SiO₃∶MgSO₄The weight percentage content of the solid of the prepared aqueous solution is 10 to 60 percent, and the dosage of the solid of the aqueous solution is 0.02 to 1.0 percent of the weight of the sodium percarbonate.

4. The coated sodium percarbonate of claim 1, characterized in that the concentration of hydrogen peroxide is 27.5%.

5. The coated sodium percarbonate of claim 1, characterized in that the crystallization aid is sodium polyacrylate and/or polyamide formulated as an aqueous solution in a percentage by weight of 5-30% and in an amount of 0.1-1.0% by weight of the sodium percarbonate product.

6. The coated sodium percarbonate of claim 1, characterized in that the external stabilizer component is Na₂SiO₃、MgSO₄And triethanolamine, wherein the weight ratio of the components is Na₂SiO₃∶MgSO₄The weight percentage content of the prepared aqueous solution solid is 25-60 percent, and the dosage of the aqueous solution solid is 0.5-5.0 percent of the weight of the product sodium percarbonate.

7. The coated sodium percarbonate of claim 1, characterized in that the coating agent is selected from polyethylene glycol, hydroxyethyl cellulose or acrylic acid-maleic acid copolymer, and is formulated into aqueous solution with a solid content of 5% -30% and its amount is 0.02% -0.5% of the weight of the sodium percarbonate product.

8. The coated sodium percarbonate of claim 1, characterized in that the product particle size is 80-10 mesh.

9. The coated sodium percarbonate of claim 1, characterized in that 400 kg of industrial sodium carbonate and 100 kg of industrial refined salt are added to a stock tank containing a fixed amount of mother liquor under stirring in a weight ratio of 4: 1, and then pulped, and then the prepared internal stabilizer is added, wherein the internal stabilizer is Na₂SiO₃0.8 kg, MgSO₄0.3 kg of EDTA, 0.2 kg of EDTA and 1.3 kg of water are added to prepare an aqueous solution which is divided into two parts; 700 kg of hydrogen peroxide with the measured concentration of 27.5 percent is added into a hydrogen peroxide head tank, the prepared internal stabilizer is added under stirring, the slurry and the hydrogen peroxide are cooled to 14-16 ℃ by a cooling salt water jacket, and are added into the hydrogen peroxide tank under stirringAdding 3.25 kg of sodium polyacrylate and 15 kg of water into a synthesis kettle, controlling the adding speed of the two materials, controlling the reaction temperature to be between 16 and 25 ℃, gradually increasing the stirring speed to 10rpm to 90rpm along with the gradual increase of the reaction materials to control the granularity of the product to be within the range of 80 to 10 meshes, controlling the feeding reaction time to be 90 minutes, finishing the feeding, reacting for 5 to 15 minutes, drying the materials in a vibration centrifuge under stirring, recycling the mother liquor into a mother liquor pool, feeding the wet materials into a first relatively small vibration fluidized bed through a vibration feeder, atomizing and spraying the prepared external stabilizer aqueous solution at the middle section of the fluidized bed under the pressure of 0.4MPa, wherein the external stabilizer aqueous solution is Na₂SiO₃13 kg, MgSO₄5.0 kg, 1.6 kg triethanolamine and 20 kg water; atomizing and spraying the prepared aqueous solution of the coating agent at the rear section of the fluidized bed under the pressure of 0.4Mpa, wherein the coating agent is 1.5 kg of aqueous solution polyethylene glycol and 10 kg of water; the product after the coating treatment enters a second vibration fluidized drying bed for drying, the product enters a storage bin after being screened, and the finished product is obtained after the product is inspected to be qualified and packaged, wherein the active oxygen content of the obtained product is 14.2%, the water content is 1.4%, and the stability is 98.4%.

10. Use of the coated sodium percarbonate of claim 1 as bleaching component in detergent, cleaning and bleaching agent formulations.

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