JPS598614A - Preparation of silica sol using organic solvent as dispersion medium - Google Patents

Abstract

PURPOSE:To obtain high concentrated stable silica sol using an organic solvent as a dispersion medium, by blending silica sol using water as a dispersion medium with the organic solvent, dehydrating it by an ultrafilter. CONSTITUTION:Silica sol having particularly 70-300Angstrom average particle diameter of silica and preferably >=15wt% calculated at SiO2 of silica concentration, using water as a dispersion medium, is prepared. This silica sol is blended with a water-soluble organic solvent (e.g., methanol), the solution wherein both water and the organic solvent exist is filtered with an ultrafilter and concentrated. The concentrate is added to the organic solvent again, diluted, the operation of the filtration through the ultrafilter again is repeated plural times, to give silica sol using the organic solvent as the dispersion medium. In this case, the operation is preferably repeated to make a weight composition ratio of the organic solvent to water of (100:0.1)-(100:7.5). The concentration adjustment of the organosilica sol is carried out by a method to separate and to remove the solvent, and it can be concentrated up to 60wt% when methanol, etc. is used.

Description

[Detailed description of the invention] The present invention is based on silica sol using water as a dispersion medium.

The present invention relates to a method for producing a stable silica sol with a high S degree using an organic solvent as a dispersion medium.

The development of composite materials consisting of inorganic and organic materials.

In addition to the conventional purpose of improving the rather poor heat resistance and weather resistance of organic substances.

Due to the recent depletion of petroleum resources and the resulting rise in prices, the demand for organic materials has increased in recent years for the purpose of saving organic materials. What is especially important when proceeding with the development of composite materials is that
9. Mixing and dispersing technology of inorganic and organic substances. It is no exaggeration to say that this will determine the success or failure of the development of composite materials.

Since the dispersion medium of ordinary silica sol is water, there is a limit to its mixing and dispersion with organic matter. is difficult. In order to widely apply silica sol to the organic industry, it is necessary to replace the dispersion medium water with an organic solvent and to produce diorganosilica sol, and if the organosilica sol is highly concentrated and stable. Includes adhesive and paint.

Widely used for resin processing, etc. It can be used for u.

By the way, as a method for producing an inorganic oxide sol dispersed in an organic solvent, US Pat.
As shown in No. 9, a method of removing water azeotropically by mixing an oxide sol using water as a dispersion medium and a polar organic solvent having an azeotropic composition of '4 with water, Japanese Patent Publication No. 53 As shown in No. 799, siloxine 2-nor is extracted and separated from the neutralized water solution of water glass using a polar organic solvent, and an organosiliconizing agent is added to the resulting bath solution. etc. are conventionally known. However, in the former method, the stability of the sol deteriorates due to the agglomeration effect caused by the collision of silica particles during the heating operation.In addition, when an organic solvent with a low boiling point is used.

During azeotroping, the evaporation rate of the organic solvent is higher than that of water, so there is a drawback that a large amount of organic solvent is consumed. On the other hand, in the latter method, contamination with sodium salt is unavoidable due to the step of neutralizing water glass, and since silica has a low molecular weight, a highly concentrated and stable organosilica sol (4! It is also difficult to do so when extraction is performed using a polar organic solvent with a low boiling point.

Because the yield of silica is low, organosilica sol′ can be produced at low cost.
f: Idiot who can't get it 9 Even if you pay close attention and control to each work, there is still a drawback of poor reproducibility.

The purpose of the present invention is to eliminate the drawbacks of the conventional methods described above, and to provide a method for producing an organosilica sol that has excellent dispersibility in the M@solvent of each building, and is highly concentrated and stable. hand.

The method is characterized by completely mixing silica sol using water as a dispersion medium and an organic solvent, and then dehydrating the mixture using an ultrafiltration membrane.

The silica sol using water as a dispersion medium, which is used as a starting material in the method of the present invention, may be produced by any method such as ion exchange method, peptization method, or dialysis method. It is preferable that the average particle size of 1. is in the range of 40X to 100OX. <, 1 o'clock K 70 X to 300
Those within the range of X are suitable for the present invention. Furthermore, the silica fineness of 15% or more is economical because the use of organic solvents can be reduced.

Organic bath agents include methanol and ethanol.

Aqueous organic solvents such as alcohols, ethers such as dimethyl ether, acetone, ketones such as ethyl methyl ketone, and esters such as ethyl acetate can be used. Two or more of these water-based organic solvents may be used in combination.

Replacing the dispersion medium according to the method of the present invention, the water-soluble organic bath agent described above is mixed with the silica sol using water as the dispersion medium, and the liquid in which water and organic solvent coexist is filtered and concentrated using an ultrafiltration membrane. The concentrated product obtained is diluted by adding a VC-restricted organic solvent, and F) [ultrafiltration membrane treatment is performed by repeating the procedure several times. In this case, ultrafiltration can also be carried out continuously without being carried out batchwise.

The stability of the silica sol substituted with an organic solvent varies depending on the remaining amount of water, so it is preferable to carry out the above steps so that the weight composition ratio of organic solvent to water is in the range of 100:0.1 to 100:5. It is possible to return. The mixing method of silica sol and organic solvent using water as a dispersion medium may be done by adding an organic bath agent to the silica sol, or by adding the silica sol to the organic solvent, but the evaporation of the organic solvent should be minimized and the evaporation should be kept as low as possible. It is important to mix the Also, the equipment used for mixing is a stirrer.

Any mixer or other mixing device can be used.

Any ultrafiltration membrane that has a pore size of several micrometers to several micrometers can be used, but it should be selected while taking into account the silica particle size of the silica sol used as a raw material, the silica preparation, the organic solvent used, etc. Article 6- It is necessary to decide on the conditions. If these conditions are taken into account, any synthetic resin ultrafiltration membrane can be used, and
Various shapes such as a flat diaphragm shape, a seaweed shape, and a hollow fiber shape can be used. Also, the pressure during ultrafiltration6. The operating pressure that matches the membrane usage conditions is sufficient for the purpose'f
However, in order to prevent the silica sol from drying out during operation of the ultrafilter, it is preferable to operate at a low temperature or in a completely closed state.

Note that the concentration of the organosilica sol obtained by the method of the present invention is adjusted by completely separating and removing the solvent, but if a low-boiling point solvent is used for 1%, it can be concentrated in a high yielding tank, and methyl alcohol In such cases, it is possible to concentrate up to 60 times M'. However, the #degree sol should be rolled up so that it dries easily.

Care must be taken when handling the concentrate. Regarding the purity of the reaction mechanism of the present invention, there are some points that are unclear because the structure of silica sol has not been clearly analyzed, but for example, 7'c, the surface of a silica particle is covered with hydroxyl groups, and one or more molecules II'chυ dispersed in an organic solvent with a water-conserving membrane intervening
It is presumed that this helps stabilize the sol.

Next, explanation will be given with reference to comparative examples and examples, but the examples are not intended to limit the scope of the present invention.

Comparative Example 1 This comparative example is provided to facilitate understanding of all the examples carried out by the method of the present invention, which will be described later.

In order to make silica sol using an organic solvent as a dispersion medium without using an ultrafiltration membrane, which is a feature of the present invention, silica sol using water as a dispersion medium (Sin, 20 layers at a time, average particle size 120X, sro , 7N days, 0 heavy lid ratio 500) 1
00d and ethyl alcohol (purity 99% or more) ioom
After mixing thoroughly, pour into a 500d eggplant-shaped flask for an enovolator, and dehydrate while heating with an oil spray. At this time, <9 oorrrl of new fc ethyl alcohol was replenished while keeping the liquid level in the eggplant-shaped flask constant. Afterwards MWIi' 50 ynl in the flask
The evaporated water and ether alcohol were collected by cooling in a condenser.

The organosilica sol thus obtained had a high water content and poor compatibility with other organic solvents.

Comparative Example 2 An organosilica sol was prepared in the same manner as in Comparative Example 1, except that isopropyl alcohol (purity 99% or higher) f: was used as the organic solvent.

The organosilica sol thus obtained had a high viscosity.

Example 1 Silica sol using water as a dispersion medium (8i 0.411 degrees 20%, t%, average particle size 120i, Sin, /NatO
Heavy lid ratio 500) 10100O and ethyl alcohol (
After mixing well for 1000 di (purity: 99 or higher), filtration was performed using an ultrafiltration membrane (fraction molecule lid 50,000).

When the amount of filtration reached 1 oooau, 1000 mg of fresh ethyl alcohol was added to the mother liquor. Thereafter, filtration was carried out in the same manner, and 100,100 O of the filter cap was collected. This operation was performed 6 times in total, and the silica concentration was 20.1.
980 g of silica sol was obtained.

The organosilica sol thus obtained had a low water content and good compatibility with other organic solvents. Further, the above-mentioned organosilica sol was further reduced by ultrafiltration M.

641g of silica sol with a silica concentration of 30.5% by weight was obtained.

The #Pongee organosilica sol thus obtained had low viscosity and good compatibility with other organic solvents.

Example 2 1000 TIL of silica sol (StO, concentration 20% by weight, average particle diameter 120, 8I02/Na, zero-cover ratio 500) using water as a dispersion medium and too much isopropyl alcohol (purity 99% or more) were mixed well.

Using ultrafiltration M (fraction molecule lid 50000) K, filtration was performed a total of 6 times using the same method as in Example 1, and the silica concentration was 30.1.
630 g of organosilica sol with weight t% was obtained.

The organosilica sol thus obtained has low water content and good compatibility with other solvents.

Next, 4! of the organosilica sols obtained in each comparative example and example. In order to evaluate the dispersibility in I8i organic solvent,
The organosilica sol was individually mixed with an organic solvent in a dish ratio of 1:1, and the dispersion mTh of the mixture was observed. In addition, the viscosity of organosilica sol was measured by the Ostwald method at a constant temperature of 25°C. In addition, water content was measured by the Karl Fischer method. The results are shown in Table-1.

(The following is a blank space) It is clear from the above table that: 1. According to the method of the present invention, the dispersibility in various organic solvents is excellent.

At high concentrations, a highly stable organosilica sol can be produced, making it a widely applicable organosilica sol (Ly/E), which can be combined with organic matter to produce composite materials.

%W [Applicant: Catalyst Chemicals]: Gyo Co., Ltd. 13-

Claims (1)

[Claims] 1. A method for producing silica sol using an organic solvent as a dispersion medium, which comprises mixing silica sol using water as a dispersion medium and an organic solvent, and then dehydrating the mixture using an ultrafiltration membrane. 2. The method according to claim 1, which uses water as a dispersion medium and uses a silica sol having an average particle size of silica in the range of 40X to 100OX. 3. Claim 1 in which a water-soluble organic solvent such as alcohol, ether, ketone, or ester is used as the organic solvent
The method described in section. 4. The method according to claim 1, wherein the water is dehydrated using an ultrafiltration membrane having a smaller pore size than the silica particles in the silica sol. 5. By ultrafiltration and dehydration, the silica concentration was reduced to 8i0. as 2
The method according to claim 11, wherein the concentration is 0 to 60% by weight. 6. Is the operation of mixing an organic solvent with silica sol using water as a dispersion medium and dehydrating it with an ultrafiltration membrane a new organic solvent? The method according to claim 1, which is carried out continuously with continuous addition.