Preparation method of coated zinc oxide

Abstract

The invention belongs to the technical field of zinc oxide materials, and particularly relates to a preparation method of coated zinc oxide, clove oil is mixed to obtain clove oil coating liquid, the spray drying effect is good, eugenol cement coated zinc oxide is formed through reaction on the surfaces of zinc oxide particles, and then humic acid is coated to obtain the coated zinc oxide. The zinc oxide coated in the acidic artificial gastric juice stably exists, the humic acid in the slightly alkaline artificial intestinal juice is degraded, dissolved and gradually disintegrated in time, and cement is rapidly disintegrated, so that the internally coated zinc oxide is released. Through gastrointestinal dissolution, intestinal slow release and whole intestine release, the additive amount in the feed is low, the growth performance of pigs is improved, the additive amount of zinc oxide in the feed can be effectively reduced, the utilization rate of the zinc oxide is increased, the surface cement is hard in texture and resistant to friction in the feed processing, storage and transportation processes, the coating layer cannot be damaged even though animals eat and chew, and the coating effect is continuous and stable.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc oxide materials, in particular to a method for preparing coated zinc oxide. Background Art

[0002] The technology of coating zinc oxide has become a hot topic of current research because it can protect zinc oxide from being decomposed by gastric juice and slowly release it in the intestine of piglets, thereby greatly reducing the amount of zinc oxide added. Existing enteric coatings of zinc oxide mostly use pH-sensitive materials such as cellulose acetate phthalate, stearic acid and synthetic polyacrylic resin as acid-resistant enteric materials, dextrin, starch, carboxymethyl cellulose, talc and the like as bonding fillers, and microcrystalline cellulose, cross-linked sodium carboxymethyl cellulose and the like as disintegrants. However, the composition of pH-sensitive materials is complex, and there is a risk of irritating the gastrointestinal environment of piglets. Some coating methods also have the problem of difficulty in disintegration in the intestine of piglets. In addition, lipid-coated lipids mostly use palm oil, hydrogenated vegetable oil and the like. These coating layers are thin and not resistant to friction during feed processing and transportation. Chewing by animals during eating may also cause the coating layer to break, thereby losing the coating effect. In addition, temperature can easily damage it, and the product has a high stomach rate. For example, starch coatings can be decomposed by salivary amylase in the mouth. In summary, currently coated zinc oxide has problems such as unstable coating performance, high production cost, poor product content and particle size uniformity, etc. In order to solve the above problems, those skilled in the art are in urgent need of developing a preparation method of coated zinc oxide to meet the existing market demand and performance requirements. Summary of the invention

[0003] In view of the above problems, the present invention aims to provide a method for preparing coated zinc oxide.

[0004] A method for preparing coated zinc oxide comprises the following steps: a first step, preparing a clove oil coating liquid by using clove oil and fresh fermented glutinous rice distillate in a volume ratio of 1:3-4; a second step, weighing nano zinc oxide powder and adding it into the clove oil coating liquid, stirring and dispersing it evenly by using a high-speed mixer, and then spray drying it to obtain eugenol cement coated zinc oxide; a third step, preparing a black biochemical humic acid solid into a humic acid solution, and coating the humic acid solution on the surface of the eugenol cement coated zinc oxide by using a coating machine to obtain the coated zinc oxide.

[0005] In daily production practice, the production of coated zinc oxide on the production line used to be produced by palm oil lipid coating and sodium carboxymethyl cellulose iron oxide, but it has various defects and can only be maintained barely, like chewing chicken ribs.

[0006] Due to operational errors by the staff on the farm, a small amount of clove oil and humic acid were used by mistake in some batches on the production line. This was discovered in time by quality inspection, but the experimental pigs on the farm had good results. Although the raw materials were misused, they all came from natural plant sources and met the requirements for feed additive raw materials. After expanding the use of the above individual batches of products, it was unexpectedly found that the application effect was good.

[0007] After further in-depth research and pilot tests, it was found that the clove oil coating liquid reacts with the zinc oxide surface to form a chelate, namely cement, which is then coated with humic acid. Although the above coating method does not have related technical disclosure or market product sales, its effect is outstanding and impressive.

[0008] Furthermore, the third step coating machine has a drum inclination angle of 40°, a rotation speed of 50-60 rpm, a steam heating temperature of 50-60°C, 3-4 spray guns, and an air volume of 2600-4500 m 3 / h, exhaust air volume 4000~6000m 3 / h, the coating accounts for 25% to 30% of the mass of the coated zinc oxide.

[0009] Furthermore, the process conditions of the second step spray drying are as follows: an inlet air temperature of 170-180°C, an outlet air temperature of 60-70°C, an atomizing disk speed of 16000-18000 rpm, an atomizing disk diameter of 120-150 mm, and a feed rate of 15-20 mL / min.

[0010] Furthermore, the fresh mash glutinous rice distillate in the first step contains ethanol at a volume concentration of 40% to 50%, and the fresh mash glutinous rice distillate is obtained by distilling fresh mash glutinous rice liquid.

[0011] In order to obtain a better coating effect, an in-depth study of the production process revealed that clove oil is not soluble in water. Fresh glutinous rice distillate contains both ethanol and water, which can disperse clove oil well to obtain clove oil coating liquid. It has a wide source and low cost. Fresh glutinous rice liquid is sweet and refreshing, with a long aftertaste and is attractive.

[0012] The clove oil coating liquid reacts with the zinc oxide surface to form a chelate, namely cement, which has a hard texture. The chelation curing reaction efficiency is high under water conditions, and the fresh fermented glutinous rice distillate contains water, so a good coating effect can be obtained. However, the chelation curing of edible ethanol or pure clove oil under dry conditions is extremely slow or unresponsive. Therefore, the use of fresh fermented glutinous rice distillate will further enhance the coating effect. At the same time, the cement formed on the surface of zinc oxide has a hard texture, is resistant to friction during feed processing and storage and transportation, and has a certain waterproof effect. The chewing of animals during eating will not cause damage to the coating layer, making the coating effect continuous and stable, and also providing conditions for subsequent humic acid coating.

[0013] Furthermore, the mass ratio of the nano zinc oxide powder to the clove oil coating liquid in the second step is 1:11-13.

[0014] The entire coating process is different from the simple mixing of fresh fermented glutinous rice distillate, zinc oxide, eugenol, and humic acid. Simple mixing cannot obtain coated zinc oxide. Fresh fermented glutinous rice distillate assists the dispersion of clove oil and provides conditions for surface chelation and solidification to form a barrier layer with a waterproof effect. The barrier layer is coated with humic acid solution, and humic acid and zinc oxide do not contact or react. Since chelation and solidification provide a solid foundation, humic acid coating is easy and uniform and stable.

[0015] Furthermore, the speed of the high-speed mixer in the second step is 600-800 rpm, and the stirring time is 15-20 min.

[0016] Furthermore, the content of eugenol in the clove oil in the first step is ≥85%.

[0017] Clove oil, as a natural vegetable oil, can be used as a feed raw material. Furthermore, the zinc oxide content in the nano zinc oxide powder of the second step is ≥99.99%.

[0018] Furthermore, the concentration of the humic acid solution in the third step is 30-40 g / L.

[0019] Humic acid is a type of organic substance accumulated through the decomposition and transformation of plant remains by microorganisms and a series of geochemical processes. In the past, it was mainly used in the field of fertilizers.

[0020] Humic acid can be used as a feed additive. It is only soluble in alkali but not in acid, and can resist acid in the stomach and be slowly released in the intestine. In addition, humic acid also has an adsorption effect, which helps the nutrients in the feed to function, enhances the activity of various enzymes, and improves the immunity of animals.

[0021] Beneficial effects of the present invention: A method for preparing coated zinc oxide comprises mixing clove oil with fresh fermented glutinous rice distillate to obtain a clove oil coating liquid, using the coating liquid to disperse clove oil, and having a good spray drying effect and an aroma, reacting eugenol with zinc oxide to form eugenol cement-coated zinc oxide, and then coating humic acid with a coating machine to obtain coated zinc oxide. The coated zinc oxide contains humic acid that is only soluble in alkali but not in acid, and the coated zinc oxide exists stably in acidic artificial gastric juice, while the humic acid is degraded and dissolved in neutral and alkaline artificial intestinal juice, swells in neutral and alkaline artificial intestinal juice, and gradually disintegrates in time, and the cement also disintegrates quickly, thereby releasing the internally coated zinc oxide. The zinc oxide has gastrointestinal dissolution, intestinal sustained release, and whole intestinal release, and the addition amount in feed is low, and the effect is equivalent to that of the original powdered zinc oxide, and the growth performance of pigs can be improved, and the addition amount of zinc oxide in feed can be effectively reduced, the utilization rate of zinc oxide can be increased, and the zinc content in pig manure can be reduced. The clove oil coating liquid reacts with zinc oxide to form a chelate on the surface, namely cement, which has a hard texture. The chelation curing reaction is efficient in the presence of water, and the fresh fermented glutinous rice distillate contains water, so a good coating effect can be obtained. The eugenol zinc oxide cement is resistant to friction during feed processing and storage and transportation, and has a certain waterproof effect. The chewing of animals during eating will not cause damage to the coating layer, making the coating effect sustained and stable, which also provides conditions for subsequent humic acid coating. DETAILED DESCRIPTION

[0022] The present invention is described below with specific examples, but is not intended to be limiting of the present invention. Example 1

[0023] Raw materials and equipment: Anhui Jinhua produces feed-grade nano zinc oxide powder with a zinc oxide content of ≥99.99%; Ang Yida GLZ-200 high-speed centrifugal spray dryer; Wanshen BGB250F coating machine; fresh mash distillate containing 50% ethanol by volume obtained by distilling fresh mash from Hanshan Yuncao Distillery; the content of eugenol in Henan Mugu biological clove oil is ≥85%; Shengda Yifang feed-grade humic acid.

[0024] A method for preparing coated zinc oxide comprises the following steps: a first step, preparing a clove oil coating liquid by using clove oil and fresh fermented glutinous rice distillate in a volume ratio of 1:4; a second step, weighing nano zinc oxide powder and adding it into the clove oil coating liquid, wherein the mass ratio of the nano zinc oxide powder to the clove oil coating liquid is 1:11, using a high-speed mixer to stir and disperse the powder uniformly, and then spray drying, at an inlet air temperature of 180°C, an outlet air temperature of 70°C, an atomizing disk speed of 16000rpm, and an atomizing disk vertical speed of 10000rpm. The diameter is 150mm, the feed speed is 20mL / min, and the spray drying is carried out to obtain the eugenol cement coated zinc oxide. The speed of the high-speed mixer is 800rpm and the stirring time is 20min. The third step is to prepare the black biochemical humic acid solid into a humic acid solution with water, and the humic acid solution is coated on the surface of the eugenol cement coated zinc oxide with a coating machine. The coating machine has a drum inclination angle of 40°, a speed of 60rpm, a steam heating temperature of 60℃, 4 spray guns, and an air intake volume of 4500m 3 / h, exhaust air volume 6000m 3 / h, the coating accounts for 30% of the mass of the coated zinc oxide, that is, the coated zinc oxide is obtained, and the humic acid solution is 30g / L.

[0025] Product: Zinc oxide (as ZnO) 60.0%; Water 3.0%; Release (treated with artificial gastric juice for 2 hours) 5%; Release (treated with artificial intestinal juice for 12 hours) 95.0%; Total arsenic (As) / (mg / kg) ≤5.0; Lead (Pb) / (mg / kg) ≤15.0; Cadmium (Cd) / (mg / kg) ≤2.0; Particle size (pass rate of 840µm test sieve) ≥90.0%. Example 2

[0026] Raw materials and equipment: Feed-grade nano zinc oxide powder with a zinc oxide content of ≥99.99% produced by Anhui Jinhua; Ang Yida GLZ-100 high-speed centrifugal spray dryer; Wanshen BGB150F coating machine; fresh mash distillate containing 40% ethanol by volume concentration is obtained by distilling fresh mash liquid from Hanshan Yuncao Winery; the content of eugenol in Nanjing Jingchen Biological clove oil is ≥85%. Nanjing Bai Nong Biological 009# feed-grade humic acid. A method for preparing coated zinc oxide, comprising the following steps: the first step, using clove oil and fresh mash distillate to prepare clove oil coating liquid in a volume ratio of 1:3; the second step, weighing nano zinc oxide powder and adding it to the clove oil coating liquid, the mass ratio of nano zinc oxide powder to clove oil coating liquid is 1:13, using a high-speed mixer to stir and disperse evenly and then spray drying, at an inlet air temperature of 170°C, an outlet air temperature of 60°C, an atomizing disk speed of 18000rpm, and an atomizing disk vertical speed of 10000rpm. The diameter is 120mm, the feed speed is 15mL / min, and the spray drying is carried out to obtain the eugenol cement coated zinc oxide. The speed of the high-speed mixer is 600rpm and the stirring time is 15min. The third step is to prepare the black biochemical humic acid solid into a humic acid solution with water, and the humic acid solution is coated on the surface of the eugenol cement coated zinc oxide with a coating machine. The coating machine has a drum inclination angle of 40°, a speed of 50rpm, a steam heating temperature of 50℃, 3 spray guns, and an air intake volume of 2600m 3 / h, exhaust air volume 4000m 3 / h, the coating accounts for 25% of the mass of the coated zinc oxide, that is, the coated zinc oxide is obtained, and the concentration of the humic acid solution is 40g / L.

[0027] Product: Zinc oxide (as ZnO) ≥55.0%; Water content 2.0%; Release rate / (artificial gastric juice treatment for 2h) 10.0%; Release rate (artificial intestinal juice treatment for 12h) 90.0%; Total arsenic (As) / (mg / kg) ≤5.0; Lead (Pb) / (mg / kg) ≤15.0; Cadmium (Cd) / (mg / kg) ≤2.0; Particle size (840µm test sieve pass rate) ≥95.%.

[0028] Note: Take 4.0g of sample, accurate to 0.0002g, place in a 250mL beaker, add 10mL of hydrochloric acid solution (1+1), heat to dissolve, cool, and determine according to the provisions of 5.5.2 EDTA titration method in HG / T2792-2011. Water content shall be in accordance with GB / T6435-2014. Release (artificial gastric juice treatment for 2h) Reagents or materials Pepsin: enzyme activity ≥1200U / g, CAS: 9001-75-6. Hydrochloric acid. Dilute hydrochloric acid: Take 234mL of hydrochloric acid, add water to 1000mL, and mix. Artificial gastric juice: Take 16.4mL of dilute hydrochloric acid, add 800mL of water and 10.0g of pepsin, stir well, and then add water to make up to 1000mL. Instruments and equipment Dissolution tester: The temperature adjustment range is 20~45℃; the speed is 25r / min. Electronic balance: sensitivity 0.1mg. Filter paper: qualitative rapid filter paper. Test steps Take 2.0g of sample, accurate to 0.0002g, place in a dissolution cup, use a dissolution tester according to the second method (paddle method) of Part 1, 0931 of the 2020 edition of the Chinese Pharmacopoeia of Veterinary Medicine, add 400mL of artificial gastric juice, set the temperature to 38°C, the speed to 100r / min, rotate for 2h, add 100mL of dilute hydrochloric acid, continue to rotate for 20min, take an appropriate amount of solution, and filter immediately with filter paper. Accurately measure 50mL of filtrate, place in a 250mL conical flask, and measure according to the provisions of 5.5.2.3.2 in HG / T2792-2011. The release degree in the test data processing (treated with artificial gastric juice for 2h) is expressed as mass fraction 𝑤1, expressed as percentage (%), calculated according to formula (1): W1=0.081379VC(400+100) / 50mX0×100%---(1). Where: V——the volume of the standard titration solution of disodium ethylenediaminetetraacetic acid consumed by the sample, in milliliters (mL); C——the concentration of the standard titration solution of disodium ethylenediaminetetraacetic acid, in moles per liter (mol / L); 0.081379——the mass of zinc oxide equivalent to 1mL of the standard titration solution of disodium ethylenediaminetetraacetic acid [c (EDTA) = 1.0mol / L], expressed in grams; m——the mass of the sample, in grams (g); X0——the measured zinc oxide content, in percentage (%). Release (12h treatment with artificial intestinal fluid) Reagents or materials Pancreatic enzyme: Casein conversion power ≥25.0, CAS: 8049-47-6. Pig bile salt: Content (calculated as bile acid) ≥60.0%, CAS: 8008-63-7. Saturated sodium hydroxide solution: Take an appropriate amount of sodium hydroxide and add it to 50mL of purified water, stirring while adding until it cannot be dissolved. Hydrochloric acid. Dilute hydrochloric acid: Take 234mL of hydrochloric acid, add water to 1000mL, and mix well. Ammonia water. Potassium dihydrogen phosphate.Artificial intestinal fluid: Take 6.8g of potassium dihydrogen phosphate, add 500mL of water to dissolve, and adjust the pH value to 6.8-7.4 with saturated sodium hydroxide solution; take 10.0g of pancreatic enzyme and 6.0g of pig bile salt, add appropriate amount of water to dissolve, mix the two liquids, dilute with water to 1000mL, shake well, and you have it. Instruments and equipment Dissolution tester: temperature adjustment range is 20-45℃; speed 25r / min Electronic balance: sensitivity 0.1mg. Filter paper: qualitative rapid filter paper. Test steps Take an appropriate amount of this product (equivalent to 1.0g of zinc oxide), accurate to 0.0002g, and place it in a dissolution cup. Use a dissolution tester according to the second method (paddle method) of Part 1, 0931 of the 2020 edition of the Chinese Pharmacopoeia of Veterinary Medicine, add 400mL of artificial intestinal fluid, set the temperature to 38°C, and the speed to 100r / min. After rotating for 12h, add 100mL of dilute hydrochloric acid, continue to rotate for 20min, take an appropriate amount of solution, and filter it immediately with filter paper. Accurately measure 25mL of the filtrate, place it in a 250mL conical flask, and determine it according to the provisions of 5.5.2.3.2 of HG / T2792-2011. Test data processing: The release rate in the sample (treated with artificial intestinal fluid for 12 hours) is expressed as mass fraction 2, expressed in percentage (%), and calculated according to formula (2): W2=0.081379VC(400+100) / 25mX0×100%---(2) Where: V——the volume of the standard titration solution of disodium ethylenediaminetetraacetic acid consumed by the sample, in milliliters (mL); C——the concentration of the standard titration solution of disodium ethylenediaminetetraacetic acid, in moles per liter (mol / L); 0.081379——the mass of zinc oxide equivalent to 1mL of the standard titration solution of disodium ethylenediaminetetraacetic acid [c(EDTA)=1.0mol / L], expressed in grams; m——the mass of the sample, in grams (g); X0——the measured zinc oxide content, in percentage (%). Total arsenic shall be implemented in accordance with the provisions of GB / T13079-2022. Lead shall comply with GB / T13080-2018. Lead shall comply with GB / T13082-2021. Particle size shall comply with GB / T5917.1-2008.

Claims

1. A method for preparing coated zinc oxide, characterized in that: The following steps are involved: The first step is to prepare a clove oil coating liquid by using clove oil and fresh fermented glutinous rice distillate in a volume ratio of 1:3-4; the second step is to weigh nano zinc oxide powder and add it into the clove oil coating liquid, stir and disperse it evenly by using a high-speed mixer, and then spray dry it to obtain eugenol cement coated zinc oxide; The third step is to prepare the black biochemical humic acid solid into a humic acid solution, and use a coating machine to coat the humic acid solution on the surface of the eugenol cement-coated zinc oxide to obtain coated zinc oxide.

2. The method for preparing coated zinc oxide according to claim 1, characterized in that: The third step coating machine has a drum inclination of 40°, a rotation speed of 50-60 rpm, a steam heating temperature of 50-60°C, 3-4 spray guns, and an air volume of 2600-4500 m 3 / h, exhaust air volume 4000~6000m 3 / h, the coating accounts for 25% to 30% of the mass of the coated zinc oxide.

3. The method for preparing coated zinc oxide according to claim 1, characterized in that: The process conditions of the second step spray drying are as follows: an inlet air temperature of 170-180°C, an outlet air temperature of 60-70°C, an atomizing disk speed of 16000-18000rpm, an atomizing disk diameter of 120-150mm, and a feed rate of 15-20mL / min.

4. The method for preparing coated zinc oxide according to claim 1, characterized in that: The fresh mashed glutinous rice distillate in the first step contains ethanol with a volume concentration of 40% to 50%, and the fresh mashed glutinous rice distillate is obtained by distilling fresh mashed glutinous rice liquid.

5. The method for preparing coated zinc oxide according to claim 1, characterized in that: The mass ratio of the nano zinc oxide powder to the clove oil coating liquid in the second step is 1:11-13.

6. The method for preparing coated zinc oxide according to claim 1, characterized in that: The speed of the high-speed mixer in the second step is 600-800 rpm, and the stirring time is 15-20 min.

7. The method for preparing coated zinc oxide according to claim 1, characterized in that: The content of eugenol in the clove oil in the first step is ≥85%.

8. The method for preparing coated zinc oxide according to claim 1, characterized in that: The zinc oxide content in the nano zinc oxide powder in the second step is ≥99.99%.