A, hydrophobic silica:
Hydrophobic silica is also called silane-treated silica or surface-treated silica. White amorphous fine powder.
It is hydrophobic. Soluble in caustic potash (sodium). Insoluble in water and acid. Non-toxic and tasteless No corrosiveness. No combustion, no oxidation. Will not decompose at high temperature. Sodium ions were removed from diluted water glass by ion exchange, hydrochloric acid was added for acid-thermal reflux concentration, dimethyldichlorosilane monomer solvent was added for hydrophobic treatment, and the product was obtained after solvent removal and drying. Mainly used as silicone rubber reinforcing agent, plastic filler, coating and thickener of ink.
2. Hydrophobic silica and its production method
Silicon dioxide has a wide range of uses, and is often added to paints, inks, plastics, rubber and cosmetics to improve properties, such as oil absorption, matting and mechanical properties. And the cost can be reduced. Its surface properties must conform to the characteristics of additives in order to be evenly dispersed. General industrial silica can be divided into two types due to different preparation processes, one is dry and calcined, and the other is wet and precipitation. The surface areas of the two types are different, and the hydroxyl groups (-OH) on their surfaces are the same. Generally speaking, the former is less and the latter is more, and both surfaces are hydrophilic, for example, when applied to lipophilic polymers.
Generally, the simplest method, as mentioned in Professor Zhao's book Fundamentals of Interface Science, Dispersion Principles and Applications, uses the adsorption of surfactants on solid surfaces to change the polarity of solid surfaces. If zinc stearate is dissolved in a polar solvent, silicon dioxide is added, and the solvent is removed, the zinc ion part faces the silicon dioxide, and the alkyl part of the stearate part faces the outside, thus forming the hydrophobicity of the particle surface, or when the silicone compound is added to the silicon dioxide, the methoxy or ethoxy group on the silicon atom will react with the hydroxyl group (-OH) on the surface of the silicon dioxide, while the organic part (vinyl, epoxy and acryl).
The silicon dioxide changes from hydrophilicity to hydrophobicity in the following ways: the surface of silicon dioxide is covered with organic fatty alkyl; German patent number 1 163784, which was directly synthesized by dimethyldichlorosilane under high pressure; Japan's Sho 6 1-50882 is an improved method to overcome the shortcomings of the West German patent 1 163784 in producing by-products and hydrogen chloride. And silica treated with dimethylpolysiloxane oligomer having three Si-OH groups at the terminal group. All the above methods make the surface of silica hydrophobic, but they have no good defoaming effect.
The invention aim to provide silicon dioxide with polysiloxane grafted on that surface. The specific surface area is 100 ~ 400 m2/g, the surface is hydrophobic and has defoaming function, the preparation process is simple, and it can be operated at normal pressure below 100℃ without producing by-products (such as hydrogen chloride).
The invention provides a hydrophobic silica solid powder with siloxane grafted on the surface. No matter whether the silica is sintered by dry method or precipitated by wet method, its surface contains silanol, and the polysiloxane terminal group that can react with silanol group must have alkoxy group or silanol group, and react in the presence of Lewis Ac-Id or Lewis base catalyst. In order to make the surface of silica fully contact with polysiloxane molecules, dispersant and molecular weight regulator must be added to make the molecular weight of polysiloxane grafted on the surface of silica appropriate.
There are two ways to make hydrophobic silica. One method is to add (1) dispersant into the glass container, such as mineral oil, organic solvent (xylene), octamethyl tetracyclosiloxane or silicone oil. (2) hydrophilic silica solid powder (silica) with a surface area of 100 ~ 400 m2/g and a contact angle of less than 70; (3) silicone oil; (4) Catalysts, such as sodium hydroxide solution, potassium hydroxide solution, ammonium carbonate solution or sulfuric acid. (5) A molecular weight regulator is usually used, the purpose of which is to make the molecular weight of silicon compounds grafted on silica particles suitable, such as tetramethyldisiloxane, hexamethyldisiloxane or pentamethylmethoxysilane. Mix and homogenize with a homogenizer for 5-20 minutes, then raise the temperature to 60℃-80℃, continue to stir and homogenize for 30 minutes to 120 minutes, filter the hydrophobic silica solid powder obtained by the extraction reaction with an organic solvent (such as xylene), and dry it in an oven at 120℃ for about 6 hours. In another method, the reactants are the same as those in the first method except that silicone oil is replaced by silicon compound monomer. Commonly used silicon compound monomers, such as tetramethyldimethoxysilane, do not need to add other dispersants because of their own dispersion. As for the reaction method, in addition to mixing and homogenizing with a homogenizer, reflux is used to promote the reaction after heating, and the reflux time is about 10 ~ 30 minutes. After the reaction is completed, the residual silicon compound is removed by vacuumizing, and then extracted with an organic solvent (such as xylene), and the reacted silica solid powder is filtered, and the solid powder is placed at 65438. The hydrophobic silica solid powder was used for contact angle measurement, FTIR spectrometer measurement and defoaming test, and the results are listed in the table below.
In order to make the above and other objects, features and advantages of the present invention more obvious and easy to understand, a preferred embodiment is listed below, which is explained in detail in the following table: Example 1: 80g xylene is put into a 200ml glass container, and 10g silicone oil (Dow corning, DC-350) is added. 0. 1g hexamethyldisiloxane, 2 drops10wt% sodium hydroxide, 20g hydrophilic silica solid powder (PPG, No.20), with a particle size of 30nm and a surface area of 200m2/g. Mix and homogenize with a homogenizer for 65,438 00 minutes, and then raise the temperature to 80℃. Example 2 Take 80g of tetramethyldimethoxysilane, put it in a 200ml glass container, add 0.8g of pentamethylmethoxysilane, 2g of 20wt% ammonium carbonate and 20g of hydrophilic silica (PPG, No.20), mix and homogenize with a homogenizer for 65438 00 minutes, continue to mix and homogenize after heating, reflux for 20min, vacuumize to remove silicon compound monomer, and extract and wash with xylene. After the reaction, silicone grafted silica solid powder was filtered, put in an oven at 65,430℃ for defoaming test and preparation of defoaming emulsion: hydrophilic silica particles (PPG, No.20) and silica particles prepared in Example 1 and 2 were 65438±0.5g each, and appropriate amount of silicone oil, emulsifier and dispersant were added, mixed and homogenized by a homogenizer to form solid content. Experimental steps: Put the prepared foaming agent (Tween 800. 1%) into four glass containers 1 liter, and reserve the foaming height of more than 8 cm. Put the glass containers filled with Tween 80 aqueous solution into a thermostat at 25℃, connect the circulating pump in each container, start the circulating pump, measure the foaming time of 8 cm, and drop them into 65438 respectively.
Table 1. Comparison of silicon dioxide contact angle before and after reaction Item contact angle Lsbel 20 (before reaction) 0 cases 1 145 cases 2 1 12 Table 2. The wave number (Cm- 1) of FTIR absorption spectrum of silica before and after the reaction was compared. Before and after the functional group reaction, 1260 Si-C, 296 1 Si, organic alkyl, 3500 -OH, Table 3. Comparison of defoaming performance of silica before and after reaction Tween 80 plus defoaming emulsion, foam emulsion before high defoaming time, bubble height label 208cm5min 30seconds 6.5cm (before reaction). Example 1: 8cm 2 minutes 30 seconds1cm Example 2: 8cm 2 minutes 30 seconds 2.5cm is used to define the present invention. Any person familiar with the field can make some changes and modifications without departing from the spirit and scope of the invention, so the protection scope of the invention should be as defined in the appended claims.
claim of right
1. A method for preparing hydrophobic silica comprises mixing reactants, hydrophilic silica solid powder, silicone oil, dispersant, catalyst and molecular weight regulator for about 5 to 20 minutes at room temperature; Heating to 60-80 DEG C, continuously stirring for about 30 minutes to 65438+/-0.20 minutes, and reacting to form hydrophobic silicon dioxide; Extracting, washing and filtering hydrophobic silica with solvent; Remove the solvent and residual reactants.
2. The manufacturing method according to claim 1, wherein the contact angle of the hydrophilic silica solid powder is less than 70 degrees.
3. The manufacturing method according to claim 1, wherein the surface area of the hydrophilic silica solid powder is 100 to 400 m2/g..
4. The manufacturing method according to claim 1, wherein the dispersant is mineral oil, octamethyl tetracyclosiloxane or xylene.
5. The manufacturing method according to claim 1, wherein the catalyst is sodium hydroxide, potassium hydroxide, ammonium carbonate or sulfuric acid.
6. The manufacturing method according to claim 1, wherein the molecular weight regulator is hexamethyldisiloxane, pentamethyldisiloxane or tetramethyldisiloxane.
7. The manufacturing method according to claim 1, characterized in that the mixing is completed by a homogenizer.
8. The manufacturing method according to claim 1, wherein the solvent is xylene.
9. The manufacturing method according to claim 1, wherein the method of removing solvent and residual reactant is drying in an oven at 120℃ for 6 hours.
10. The manufacturing method according to claim 1, wherein the hydrophilic silica is 2 to 3 times the weight of the silicone oil.
1 1. The manufacturing method according to claim 1, wherein the dosage of the catalyst is 0. 1 to 1 wt%.
12. The hydrophobic silica prepared by the manufacturing method of claim 1 has a hydrophobic contact angle of 70 to 150 degrees.
13. A method for producing hydrophobic silica, which comprises mixing reactants, hydrophilic silica solid powder, silicon compound monomer, catalyst and molecular weight regulator for about 5 to 20 minutes at room temperature; Heating to the boiling point of reactants, continuously stirring, refluxing10-30 minutes, and reacting to generate hydrophobic silicon dioxide; Extracting, washing and filtering hydrophobic silica with solvent; Remove the solvent and residual reactants.
14. The manufacturing method according to claim 13, wherein the contact angle of the hydrophilic silica solid powder is less than 70 degrees.
15. The manufacturing method according to claim 13, wherein the surface area of the hydrophilic silica solid powder is 100 to 400 m2/g..
16. The manufacturing method according to claim 13, wherein the silicon compound monomer is tetramethyldimethoxysilane.
17. The manufacturing method according to claim 13, wherein the catalyst is sodium hydroxide, potassium hydroxide, ammonium carbonate or sulfuric acid.
18. The manufacturing method according to claim 13, wherein the molecular weight regulator is hexamethyldisiloxane, pentamethyldisiloxane or tetramethyldisiloxane.
19. The manufacturing method according to claim 13, characterized in that the mixing is completed by a homogenizer.
20. The manufacturing method according to claim 13, wherein the solvent is xylene.
2 1. The manufacturing method according to claim 13, wherein the method of removing solvent and residual reactants is drying in a coal box at 120℃ for 6 hours.
22. The manufacturing method according to claim 13, wherein the amount of the catalyst is 0. 1 to 1 wt%.
23. The hydrophobic silica prepared by the manufacturing method of claim 13 has a hydrophobic contact angle of 70 to 150 degrees.