CN100463851C - A kind of preparation method of superfine hydrophobic silicon dioxide - Google Patents

Abstract

The invention relates to a preparation method of superfine hydrophobic silicon dioxide, which uses the chemical substance ethyl orthosilicate as the raw material, uses ammonium chloride as the catalyst, deionized water as the reactant, and absolute ethanol as the Solvent, with hydrochloric acid and ammonia water as the pH controller, γ-aminopropyltriethoxysilane as the modification additive, and ethylene glycol as the modification solvent, after reasonable chemical substance ratio, selection, and purity control , Catalysts, solvents, modified additives, optimized use of modified solvents, sol, gel, pH value control and adjustment, after drying, grinding, sieving, roasting at 250 ° C, cooling, hydrophobic modification treatment, compound reaction , suction filtration, secondary drying, detection analysis and comparison, and finally obtain high-purity ultrafine hydrophobic silica white powder, the product powder particles are evenly distributed, the shape is close to spherical, the particle size is 60-70nm, and the product has good hydrophobicity , can be matched with a variety of similar materials and polymer materials. This preparation method uses less equipment, short process flow, less environmental pollution, high yield, up to 97%, and good purity, up to 98%, which is very The ideal method for preparing ultra-fine hydrophobic silica white powder.

Description

A kind of preparation method of superfine hydrophobic silicon dioxide

Technical field:

The invention relates to a method for preparing ultrafine hydrophobic silicon dioxide, which belongs to the technical field of methods for preparing inorganic compounds of non-metallic composite materials.

Background technique:

Inorganic compound silica is an inorganic additive with excellent performance and wide application. It is commonly known as white carbon black. Thermal, wear-resistant and welding properties, are widely used in rubber, plastics, coatings, adhesives, sealants, optical fiber materials, polymer materials, modern medicine, bioengineering, optics and other fields.

At present, there are many methods for preparing modified silica, such as gas phase method, precipitation method, gravity sedimentation method, etc., and the modified form is modified by adding thiol silane coupling agent, such as 3-thiol group Methoxypropyl silane method, adding titanate method, dry method, wet method, heat treatment method, chemical treatment method, etc., for surface coverage modification, mechanochemical modification, outer film modification, local active modification, these Each method has its advantages, but there are also many shortcomings.

For example: the gas phase method uses silicon halide as the raw material to produce silicon tetrachloride by hydrolysis in an oxyhydrogen flame. It hydrolyzes silicon dioxide gas at a high temperature of 1200°C and then condenses it. The gas phase method has a small concentration of substances and produces The particle aggregation is less, the preparation and roasting temperature is high, the production process consumes a lot of energy, the cost is high, and the pollution is large.

For example: the precipitation method uses basic silicate as the raw material and uses water or organic solvent as the reaction medium. The precipitation method also has various forms: preparing silica with high dispersion performance in organic solvent, acidifying agent and silicate Reaction, precipitation, separation, drying to prepare silica, alkali metal silicate and inorganic acid mixed preparation, water glass carbonation preparation, spray granulation preparation, due to the difference in reaction medium, reaction ratio and process conditions, the properties of the obtained product Very different, not easy to control.

For example: the gravity sedimentation method is to make the particles in the suspension settle, diffuse, crystallize and obtain silica particles under the gravitational field, but it is difficult to control the orderly arrangement of the crystal particles of silica, and the preparation time is long .

There are also many forms of silica modification, but in the modification process, there are also many shortcomings, some do not meet the product requirements, some have a long modification period, and some have unstable chemical properties after modification.

Invention content:

Purpose of the invention:

The purpose of the present invention is exactly for the deficiency of background technology, adopts a kind of brand-new sol, gel technology, adopts new production technological process, makes raw material with orthosilicate ethyl ester, makes catalyst with ammonium chloride, uses deionized water As a reaction agent, use absolute ethanol as a solvent, use hydrochloric acid and ammonia water as a pH regulator, use γ-aminopropyltriethoxysilane as a modification additive, and use ethylene glycol as a modification solvent. Gel, drying, sieving, roasting, modification reaction, suction filtration, and secondary drying to finally obtain high-purity, high-dispersion ultrafine hydrophobic silica white powder.

Technical solutions:

The chemical substance used in the present invention is: tetraethyl orthosilicate, absolute ethanol, deionized water, ammonium chloride, ammoniacal liquor, hydrochloric acid, γ-aminopropyltriethoxysilane, ethylene glycol, and its combination ratio is : Units of measurement are grams and milliliters

Tetraethyl silicate: C ₈ H ₂₀ O ₄ Si 5ml ± 0.2ml

Absolute ethanol: C ₂ H ₅ OH 50ml±1ml

Deionized water: H ₂ O 50ml±0.2ml

Ammonium chloride: NH ₄ Cl 0.5ml±0.02ml

Ammonia water: NH ₃ ·H ₂ O 0.20ml±0.02ml

Hydrochloric acid: HCl 0.30ml±0.02ml

γ—Aminopropyltriethoxysilane NH ₂ C ₃ H ₆ Si(OC ₂ H ₅ ) ₃

0.5ml±0.02ml

Ethylene glycol _{C4H6O2 50ml ±} 1ml

The preparation method of the present invention is as follows:

(1) Selected chemical substances

The chemical substances required for the ratio should be selected and controlled for purity:

Tetraethyl silicate: 99.9%

Absolute ethanol: 99.7%

Deionized water: 99.9%

Ammonium chloride (concentration): 28.0%

Ammonia (concentration): 40.0%

Hydrochloric acid (concentration): 38.0%

γ-Aminopropyltriethoxysilane: 99.8%

Ethylene glycol: 99.9%

(2) Configure the solution and mix

Select the chemical substances required for the ratio and prepare the solution:

Tetraethyl silicate: 5ml ± 0.2ml

Absolute ethanol: 50ml ± 1ml

Deionized water: 50ml±0.2ml

Put 5 ml ± 0.2 ml of tetraethyl orthosilicate in a three-necked flask, then add 50 ml ± 1 ml of absolute ethanol, insert a stirrer and stir for 5 minutes, then insert a dropping funnel, add 50 ml ± 0.2 ml of deionized water Slowly drop it into a three-necked flask, and stir it for 10 minutes while adding it, to make it clear and form a clear mixed solution;

(3) Adjust pH value

Slightly acidic adjustment: place the three-neck flask on an electric heating mantle at a heating temperature of 60°C±1°C, drop in successively 0.5ml±0.02ml of ammonium chloride and 0.3ml±0.02ml of hydrochloric acid into the dropping funnel, and use a stirrer to Stir vigorously, the stirring time is 3 minutes ± 0.3 minutes, keep warm at constant temperature for 12 minutes ± 1 minute, hydrolyze ethyl orthosilicate, pH value = 3-4, slightly acidic;

Alkaline adjustment: the temperature of the mixed solution in the three-necked bottle is 60°C ± 1°C, drop 0.20ml ± 0.02ml of ammonia water into the dropping funnel, add it, heat it, stir vigorously, keep warm at constant temperature, and stir vigorously for 15 Minute ± 1 minute, the pH value of the mixed solution is 8-9, slightly alkaline;

The mixed solution is polycondensed, and the mixed solution becomes a wet gel state, then the electric heating mantle is turned off, heating and stirring are stopped, and a wet gel product is generated;

A compound reaction will occur during sol and gel, and the reaction formula is as follows:

In the formula: SiO ₂ ·2H ₂ O—hydrated silicon dioxide

(4) drying

Take out the wet gel product and place it in a corundum product boat, and dry the wet gel product together with the product boat in an oven at a temperature of 60°C±1°C for 90 minutes±1 minute. The product becomes a dry gel product after drying;

(5) Grinding and sieving

Place the dry gel product in an agate mortar, grind it with a grinding rod, sieve it through a 180-mesh sieve after grinding, grind and sieve it repeatedly, and leave a fine powder, which is a fine powder of the silica product;

(6) Roasting

Put the product white fine powder of silica in a corundum product boat, put the product and the product boat in a high-temperature furnace for roasting, the roasting temperature is 250 ° C ± 3 ° C, the roasting constant temperature holding time is 30 minutes ± 1 minute, the roasted The powder is superfine silicon dioxide white powder;

(7) cooling

The calcined ultrafine silicon dioxide powder is placed in a cooling container and cooled in natural air at a cooling rate of 2.5°C/min for 90 minutes until it reaches a normal temperature of 20°C±3°C, then taken out and placed in a special container save;

(8) Hydrophobic modification treatment of ultrafine silica powder

Hydrophobic modifier: γ-aminopropyltriethoxysilane 0.5ml±0.02ml

Hydrophobic modification solvent: ethylene glycol 50ml ± 1ml

Step 1: Dissolve the solvent, put the cooled white silicon dioxide powder in a four-necked flask, insert a stirrer, dropping funnel, thermometer, and condensing reflux tube, and place the four-necked flask on an electric heating mantle, when heated When the temperature is 198°C±0.5°C, add 50ml±1ml of modified solvent ethylene glycol according to the ratio, and stir at the same time to dissolve the silica powder, and the time is 1 minute±0.2 minutes;

The second step: add modifier, modifying reaction, after the modified solvent ethylene glycol is added, drop in the modified additive γ-aminopropyltriethoxysilane 0.5 ml ± 0.02 ml, drop and use Stir with a stirrer, and heat the solution at 198°C ± 0.5°C to mix and react the solution for 120 minutes ± 1 minute to form a mixed solution. The reaction formula is as follows:

Ethylene glycol is used as a solvent, which will change the surface characteristics of silica and produce hydroxyl center accumulation. The hydroxyl groups on the surface of _SiO2 can be hydrogen bonded with the hydroxyl groups of ethylene glycol to undergo condensation reaction. The reaction is as follows:

Where: Si——silicon H——hydrogen C——carbon

O——oxygen OH——hydroxide HO——hydroxide

After the modifier γ-aminopropyltriethoxysilane is added, the modification reaction will be carried out, and the reaction formula is as follows:

In the formula: NH ₂ C ₃ H ₆ Si ₂ ·H ₂ O——Aminopropyl hydrate

The third step: suction filtration, place the mixed solution after the modification reaction in a circulating water vacuum pump for suction filtration, and extract the liquid to form a viscous white product;

The fourth step: drying, put the viscous white product in an oven for drying, the oven temperature is 200°C ± 1°C, and the drying time is 60 minutes ± 1 minute to obtain superfine hydrophobic silicon dioxide white powder .

(9) Collecting products

Put the modified product—white superfine hydrophobic silicon dioxide powder—in a brown transparent glass container, and store it in airtight and dark place;

(10) Detection analysis comparison

The purity, color, shape, shape, phase structure, particle size, hydrophobicity, hydroxyl ultraviolet absorption degree, physical and chemical properties of ultrafine hydrophobic silica white powder are detected, analyzed, compared, and particle size analyzers are used Carry out particle size and particle size distribution test, and use transmission electron microscope and X-ray diffraction analyzer to conduct comparative analysis of particle shape and size;

(11) storage

The prepared superfine hydrophobic silicon dioxide white powder is placed in a brown transparent glass container and stored in a dry, cool and clean environment away from light. The storage temperature is 20°C ± 3°C. It must be strictly waterproof, Moisture-proof, fire-proof, sun-proof, anti-acid and alkali erosion.

The preparation of the ultra-fine hydrophobic silicon dioxide uses ethyl orthosilicate as a raw material, ammonium chloride as a catalyst, deionized water as a reactant, absolute ethanol as a solvent, and hydrochloric acid and ammonia as a pH The regulator of the pH value uses γ-aminopropyltriethoxysilane as the modifying agent and ethylene glycol as the modifying solvent.

In the process of sol and gel, under the heating state of 60°C±1°C, the mixed solution of ethyl orthosilicate, deionized water and absolute ethanol was dripped into 0.5ml±0.02ml of ammonium chloride, 0.3ml of hydrochloric acid mL ± 0.02 mL, and vigorously stirred with a stirrer, the stirring time is 3 minutes ± 0.3 minutes, kept at a constant temperature for 12 minutes ± 1 minute, hydrolyzed tetraethyl orthosilicate, pH value = 3-4, slightly acidic; at 60 ° C ± Under heating at 1°C, add 0.2ml ± 0.02ml of ammonia water dropwise, stir vigorously for 15 minutes ± 1 minute, the pH value of the mixed solution is 8-9, slightly alkaline.

The calcination of the superfine hydrophobic silica powder is carried out in a high-temperature furnace, the heating rate of the high-temperature furnace is 5°C/min, and the heating time is 45 minutes, until the calcination temperature is 250°C ± 3°C, and the calcination is kept at a constant temperature. The time is 30 minutes ± 1 minute. After calcination, it is naturally cooled to 20°C ± 3°C in the air, the cooling rate is 2.5°C/min, and the cooling time is 90 minutes.

The dissolution of the modified solvent ethylene glycol and the addition of the modifier γ-aminopropyltriethoxysilane are carried out under heating, the heating temperature is 198°C±0.5°C, and the ethylene glycol dissolution time is 1 minute ±0.2 minutes, γ-aminopropyltriethoxysilane was added and the mixing time was 120 minutes±1 minute.

The shape of the ultrafine hydrophobic silicon dioxide is highly dispersed amorphous white powder, and its particle size is 60-70nm.

Effect:

Compared with the background technology, the present invention has obvious advances, adopts reasonable chemical substance ratio, selected purity control, optimized use of catalyst, solvent, modified additive, modified solvent, sol, gel, pH value The control and adjustment of drying, grinding, sieving, roasting, cooling, hydrophobic modification treatment, compound reaction, suction filtration, drying, detection and analysis comparison, using ethyl orthosilicate as raw material and ammonium chloride as catalyst, Deionized water is used as a reactant, absolute ethanol is used as a solvent, hydrochloric acid and ammonia water are used as pH regulators, γ-aminopropyltriethoxysilane is used as a hydrophobic modifier, and ethylene glycol is used as a modifying solvent Finally, high-purity ultra-fine hydrophobic silica white powder is obtained. The product particles are evenly distributed, the shape is close to spherical, and the particle size is 60-70 nm. The product has good hydrophobicity and can be matched with a variety of similar materials and polymer materials. , the preparation method uses less equipment, short process flow, low roasting temperature, low environmental pollution, high yield, up to 97%, good purity, up to 98%, and is an ideal superfine hydrophobic carbon dioxide Preparation method of silicon white powder.

Description of drawings

Figure 1 is a process flow chart for the preparation of superfine hydrophobic silica white powder

Fig. 2 is the coordinate diagram of roasting temperature and time

Figure 3 is the condensation reflux diagram during the modification process

Figure 4 is the pH value of the sol and the gel time coordinate diagram

Fig. 5 is the pH value of sol and product particle size coordinate diagram

Fig. 6 is the ratio n of the amount of deionized water and tetraethyl orthosilicate and the gel time coordinate diagram

Fig. 7 is the ratio n of the amount of deionized water and tetraethyl orthosilicate and the coordinate relationship diagram of product particle size

Figure 8 is a graph of solution temperature and gel time coordinates

Fig. 9 is a coordinate relationship diagram between solution temperature and product particle size

Figure 10 is a 1×10 ^4x image of ultrafine hydrophobic silica powder transmission electron microscope

Figure 11 is a particle size distribution diagram of ultrafine hydrophobic silica powder

Figure 12 is an X-ray diffraction intensity diagram of ultrafine hydrophobic silicon dioxide powder

Figure 13 is a comparison chart of modification time and hydroxyl UV absorption rate

As shown in the figure, the part number list is as follows:

1. Electric heating mantle 2. Four-neck flask 3. Stirrer 4. Condensation return pipe

5. Water outlet pipe 6. Air port 7. Water inlet pipe 8. Dropping funnel

9. Thermometer

Implementation method:

The present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1, the production of ultrafine hydrophobic silica powder must be carried out strictly according to the process flow chart, and each production parameter must be strictly controlled and operated in sequence.

The chemical materials required for the production of tetraethyl orthosilicate, absolute ethanol, deionized water, ammonium chloride, ammonia water, hydrochloric acid, ethylene glycol, γ-aminopropyltriethoxysilane must be strictly selected, And the purity control is carried out, no impurities can intervene, and by-products are prevented from being generated.

The required chemical substances must be strictly controlled according to the proportioning and weighing, and must not exceed the maximum and minimum ranges.

The sol-gel is carried out continuously, and the acidity and alkalinity of the pH value has a great influence on the sol-gel, so strict operation control is required, and a strong stirrer must be used to stir vigorously during the sol-gel, and the number of revolutions of the stirrer The speed is 500 rpm, no intermittent, to prevent precipitation, each chemical substance will produce a compound reaction to form a silica product.

The calcination of the silica product is carried out in a high-temperature furnace, the calcination temperature is 250°C ± 3°C, and the temperature is kept at a constant temperature for 30 minutes ± 1 minute, and then it is taken out and cooled naturally in the air. The calcination process is very important and must be strictly carried out. operate.

The modification of silica is based on γ-aminopropyltriethoxysilane as the modifier and ethylene glycol as the modifying solvent. After heating, suction filtration and drying, the final product - ultrafine hydrophobic Silica white powder, modification process is the key to determine the hydrophobicity of silica, in order to change the physical and chemical properties of its surface.

Equipment required for preparation: mixing container, agate mortar, product boat, booster stirrer, beaker, grinding rod, oven, high temperature roasting furnace, screen, circulating water vacuum filter pump, testing instrument, product container Keep it clean and free from contamination.

In the process of preparing superfine hydrophobic silica white powder, due to sol, gel, pH adjustment, suction filtration, vigorous stirring, high temperature roasting, compound reaction, modification treatment, grinding, sieving, drying, Cooling will also slightly change the morphology of the prepared ultrafine hydrophobic white powder, but it will not affect its chemical and physical properties, nor will it affect the matching effect with other similar chemical substances.

The ratio of chemical substances for preparing superfine hydrophobic silica white powder is determined within a preset value range, with grams and milliliters as measurement units, and for industrial production, kilograms and liters as measurement units unit.

As shown in Figure 2, it is a coordinate diagram of the high-temperature furnace roasting temperature rise, constant temperature, heat preservation, and cooling. When the temperature of the high-temperature furnace rises from the normal temperature of point A at 20°C±3°C to 250°C±3°C, the heating rate is 5°C/min. It takes 45 minutes, intersects at point B, and keeps warm for 30 minutes ± 1 minute. The holding period is B-C section. After constant temperature holding, it is the cooling period, that is, from point C to point D, to normal temperature 20°C ± 3°C, Cool naturally in the air at a rate of 2.5°C/min and a cooling time of 90 minutes.

As shown in Fig. 3, it is the condensation reflux diagram in the modification process, the four-necked flask 2 is placed on the electric heating mantle 1, the upper left part of the four-necked flask 2 is a thermometer 9, the middle and upper part is a dropping funnel 8, agitator 3, The upper right part is the condensate return pipe 4, the upper part of the condensate return pipe 4 is the air port 6, the upper part is the water inlet pipe 7, and the lower part is the water outlet pipe 5. During the modification process, the condensate return pipe 4 is opened, and the water inlet pipe 7 enters Water, the outlet pipe 5 discharges water to form a flowing water stream to condense.

As shown in Figure 4, the pH value of the sol and gel is inversely proportional to the gelation time. When the pH value is 9, the gelation time is shortened. When the pH value is 3, the reaction is slow and the gelation time is prolonged.

As shown in Figure 5, when the pH value of sol and gel is 3, the particle size of the product is small, 23nm, and when the pH is 9, the particle size of the product is large, 96nm..

Shown in Fig. 6, 7, the ratio of the amount of deionized water and tetraethyl orthosilicate is n, i.e. n=50 milliliters: 5 milliliters, the size of n value will affect the particle diameter of gel time and product, when n When it is greater than 10, the larger the n value, the more deionized water, the lower the concentration of the polycondensate, the lower the viscosity of the sol, and the longer the gel time. The n value is proportional to the particle size of the product. The larger the n value, the larger the particle size; At 10, the larger the n value, the more water, the shorter the gel time, and the n value is inversely proportional to the particle size of the product, the larger the n value, the smaller the particle size; the gel time is the shortest when n=10, and the gel time is After 30 minutes, the average particle size of the product is the smallest, which is 63.5nm., and n=10 is the best.

As shown in Figure 8, when the solution temperature is 60°C, the gel time is 50 minutes, and the higher the temperature, the shorter the gel time, which is inversely proportional.

As shown in Figure 9, when the solution temperature is 60°C, the average particle size of the product is 63.5nm. When the temperature rises, the particle size of the product increases, which is proportional.

As shown in Figure 10, it is the 1×10 ⁴ times appearance of the hydrophobic silicon dioxide white powder transmission electron microscope, and the product is a hydrophobic amorphous powder with a particle size of 60-70nm.

As shown in Figure 11, it is the particle size distribution state of the product, and the particle size is mainly concentrated at 60-70nm.

As shown in Figure 12, it is a product X-ray diffraction peak intensity state diagram, the ordinate is the relative intensity index, and the abscissa is the 2θ angle of the X-ray diffraction peak intensity, there is a steamed bun peak at 2θ=21°, and the intensity number is 35.

As shown in Figure 13, it is a comparison table of modification time and hydroxyl ultraviolet absorption rate. The modification treatment has a curvilinear relationship with the product absorption rate. The modification time is 2 hours, and the ultraviolet absorption rate can be at least 4.1%, and its value is 0.0058. The physical and chemical properties are the best.

Example 1:

All production equipment is in ready working condition;

Select and weigh 5 milliliters of tetraethyl orthosilicate, 50 milliliters of absolute ethanol, 50 milliliters of deionized water, 0.5 milliliters of ammonium chloride, 0.20 milliliters of ammonia water, 0.3 milliliters of hydrochloric acid, 50 milliliters of ethylene glycol, γ-aminopropyl 0.5 ml of triethoxysilane;

Sol, put 5 milliliters of the chemical substance ethyl orthosilicate in a three-necked flask, add 50 milliliters of absolute ethanol, after 5 minutes, drop in 50 milliliters of deionized water, stir evenly, and make it clear;

Adjust pH value: heating temperature 60℃±1℃

Add 0.5 ml of ammonium chloride, 0.3 ml of hydrochloric acid, stir vigorously for 3 minutes ± 0.3 minutes, keep warm at constant temperature for 12 minutes ± 1 minute, pH value = 3-4, slightly acidic;

Add 0.20 ml of ammonia water, stir vigorously with a stirrer for 15 minutes, pH = 8-9, slightly alkaline;

Gel, forming a wet gel product;

Drying is carried out in an oven, the drying temperature is 60°C ± 1°C, and the drying time is 90 minutes ± 1 minute to form a dry gel product;

Grinding, sieving, 180 mesh screen, repeated;

Roasting, put the silica powder in the product boat, and put them together in a high-temperature furnace for roasting: the roasting temperature is 250°C ± 3°C, and the temperature is kept at a constant temperature for 30 minutes ± 1 minute to form a dry gel product;

Cooling, cooling in air after taking out the dry gel product;

modified:

Add modified solvent: silicon dioxide powder + modified solvent ethylene glycol 50 ml, dissolve;

Add modification additive: γ-aminopropyltriethoxysilane, 0.5 ml;

Modification and compounding reaction: carried out under heating, the heating temperature is 198°C ± 0.5°C, and the time is 120 minutes ± 1 minute;

Suction filtration: The modified mixed solution is suction-filtered in a circulating water-type vacuum pump, and a viscous white product is formed after suction filtration.

Drying in an oven: put the viscous white product in an oven at a temperature of 200°C ± 1°C, and dry for 60 minutes ± 1 minute. After drying, it will become an ultrafine hydrophobic silicon dioxide white powder;

Collecting the product: Put the superfine hydrophobic silicon dioxide white powder in the product container, thus completing the whole process of preparation.

Claims (1)

1. the preparation method of a super fine hydrophobic silicon dioxide, it is characterized in that: the chemical substance of use is: tetraethoxy, dehydrated alcohol, deionized water, ammonium chloride, ammoniacal liquor, hydrochloric acid, γ-aminopropyl triethoxysilane, ethylene glycol, its combination matching is: be measure unit with the milliliter

Tetraethoxy: C ₈H ₂₀O ₄5 milliliters ± 0.2 milliliter of Si

Dehydrated alcohol: C ₂H ₅50 milliliters ± 1 milliliter of OH

Deionized water: H ₂50 milliliters ± 0.2 milliliter of O

Ammonium chloride: NH ₄0.5 milliliter ± 0.02 milliliter of Cl

Ammoniacal liquor: NH ₃H ₂0.20 milliliter ± 0.02 milliliter of O

0.30 milliliter ± 0.02 milliliter of hydrochloric acid: HCl

γ-aminopropyl triethoxysilane: NH ₂C ₃H ₆Si (OC ₂H ₅) ₃

0.5 milliliter ± 0.02 milliliter

Ethylene glycol: C ₄H ₆O ₂50 milliliters ± 1 milliliter

Preparation method is as follows:

(1) selected chemical substance

To carry out selectedly to the required chemical substance of proportioning, and carry out control of purity:

Tetraethoxy: 99.9%

Dehydrated alcohol: 99.7%

Deionized water: 99.9%

γ-aminopropyl triethoxysilane: 99.8%

Ethylene glycol: 99.9%

Required following chemical substance is carried out concentration control:

Ammonium chloride: 28.0%

Ammoniacal liquor: 40.0%

Hydrochloric acid: 38.0%

(2) configuration solution and mixing

Choose the required chemical substance of proportioning, carry out the solution preparation:

Tetraethoxy: 5 milliliters ± 0.2 milliliter

Dehydrated alcohol: 50 milliliters ± 1 milliliter

Deionized water: 50 milliliters ± 0.2 milliliter

Tetraethoxy is placed there-necked flask for 5 milliliters ± 0.2 milliliter, add 50 milliliters ± 1 milliliter of dehydrated alcohol then, inserting agitator stirred 5 minutes, insert dropping funnel then, slowly splash in the there-necked flask deionized water for 50 milliliters ± 0.2 milliliter, the limit splashes into, stirred 10 minutes on the limit, makes its clarification, becomes the clarification mixing solutions;

(3) regulate the acidity-basicity ph value

Slant acidity is regulated: place electrically heated to put there-necked flask, 60 ℃ ± 1 ℃ of Heating temperature, in dropping funnel, splash into successively 0.5 milliliter ± 0.02 milliliter of ammonium chloride,, 0.3 milliliter ± 0.02 milliliter of hydrochloric acid, and to use agitator vigorous stirring, churning time be 3 minutes ± 0.3 minute, constant temperature insulation 12 minutes ± 1 minute, teos hydrolysis, acidity-basicity ph value=3-4, slant acidity;

Meta-alkalescence is regulated: the mixing solutions temperature in the there-necked flask is 60 ℃ ± 1 ℃, splash into 0.20 milliliter ± 0.02 milliliter of ammoniacal liquor in dropping funnel, the limit splashes into, heat on the limit, the limit vigorous stirring, constant temperature insulation, vigorous stirring 15 minutes ± 1 minute, acidity-basicity ph value=8-9 of mixing solutions, meta-alkalescence;

Mixing solutions polycondensation, mixing solutions become the wet gel state, close the electrically heated cover then, stop heating, stir, and generate moist jel product;

When colloidal sol, gel combination reaction will take place, reaction formula is as follows:

In the formula: SiO ₂2H ₂O---hydrated SiO 2

(4) oven dry

Moist jel product taking-up is placed corundum product boat, place baking oven to dry together with the product boat moist jel product, bake out temperature is 60 ℃ ± 1 ℃, and the time is 90 minutes ± 1 minute, and moist jel product oven dry back becomes the dryness jel product;

(5) grind, sieve

The dryness jel product is placed agate mortar, grind, grind the back and sieve, grind, sieve and carry out repeatedly, stay fine powder, be the silica product fine powder with 180 eye mesh screens with grinding rod;

(6) roasting

Product silicon-dioxide white fine powder is placed corundum product boat, product and product boat are placed the high temperature kiln roasting, maturing temperature is 250 ℃ ± 3 ℃, and roasting constant temperature soaking time is 30 minutes ± 1 minute, and the powder after the roasting is the superfine silicon dioxide white powder;

(7) cooling

Superfine silicon dioxide white powder after the roasting places cooling vessel to cool off at natural air, and speed of cooling is 2.5 ℃/minute, and be 90 minutes cooling time, and to 20 ℃ ± 3 ℃ of normal temperature, taking-up places special container to preserve then;

(8) hydrophobically modified of micro-size silica powder is handled

Hydrophobically modified agent: 0.5 milliliter ± 0.02 milliliter of γ-aminopropyl triethoxysilane

Hydrophobically modified solvent: 50 milliliters ± 1 milliliter of ethylene glycol

The first step: dissolution with solvents, cooled silicon-dioxide white powder is placed four-hole boiling flask, insert agitator, dropping funnel, thermometer, condensing reflux pipe, place electrically heated to put four-hole boiling flask, when Heating temperature is 198 ℃ ± 0.5 ℃, press proportional quantity and add 50 milliliters ± 1 milliliter of modification solvent ethylene glycol, stir simultaneously, make the silicon-dioxide powdery dissolving, the time is 1 minute ± 0.2 minute;

Second step: add properties-correcting agent, modified-reaction, after the modification solvent ethylene glycol adds, splash into 0.5 milliliter ± 0.02 milliliter of property-modifying additive γ-aminopropyl triethoxysilane, the limit splashes into, stir with agitator on the limit, under 198 ℃ ± 0.5 ℃ state of heating, solution is mixed and reaction, 120 minutes ± 1 minute time became mixing solutions, and reaction formula is as follows:

Ethylene glycol solvent will change the silica sphere characteristic, produce the hydroxyl center and will pile up, at SiO ₂The hydroxyl on surface can be connect by hydrogen bond with the oh group of ethylene glycol, carries out condensation reaction, and reaction formula is as follows:

---silicon H---hydrogen C---carbon in the formula: Si

O---oxygen OH---hydroxide radical HO---hydroxide radical

The properties-correcting agent γ-An Bingjisanyiyangjiguiwan will carry out modified-reaction after adding, and reaction formula is as follows:

NH ₂C ₃H ₆Si(OC ₂H ₅) ₃+SiO ₂·2H ₂O→NH ₂C ₃H ₆Si ₂·H ₂O+H ₂O

In the formula: NH ₂C ₃H ₆Si ₂H ₂O---hydration aminopropyl

The 3rd step: suction filtration, place circulation ability of swimming vacuum filtration pump to carry out suction filtration the mixing solutions behind the modified-reaction, liquid is extracted out, become thick white product;

The 4th step: oven dry, place baking oven to dry thick white product, oven temperature is 200 ℃ ± 1 ℃, drying time 60 minutes ± 1 minute promptly obtains the super fine hydrophobic silicon dioxide white powder, grain size 60-70nm;

(9) collect product

With the product after the modification---the super fine hydrophobic silicon dioxide white powder places brown transparent Glass Containers, airtight keeping in Dark Place;

(10) check and analysis contrast

The super fine hydrophobic silicon dioxide white powder is carried out purity, color and luster, form, pattern, phase structure, particle size, hydrophobic performance, hydroxyl ultraviolet radiation absorption degree, physical and chemical performance detect, analyze, contrast, carry out granularity and size distribution test, carry out granule-morphology, size comparative analysis with transmission electron microscope, X-x ray diffraction analysis x instrument with particle size analyzer;

(11) store

To the super fine hydrophobic silicon dioxide white powder of producing, place brown transparent Glass Containers, lucifuge is airtight to be stored in drying, cool place, the clean environment, and storing temp is 20 ℃ ± 3 ℃, strict waterproof, protection against the tide, fire prevention, sun-proof, anti-soda acid to corrode.

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