JPS6181442A - Bulk density increase for filler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides densification (
density increase) or compaction method.

More particularly, the present invention relates to a method of increasing the bulk density of a low bulk density material by contacting the low bulk density material with a suitable liquid and then evaporating the liquid to obtain a more dense material. .

Fumed silica is well known as a reinforcing agent or filler commonly used to improve the physical properties of silicone rubber. Basically, fumed silica consists of silicon dioxide particles in a very finely divided form. Its specific surface area typically ranges from about 100 to about 400 m2/g.

Similarly, the density is correspondingly about 2-31'b/ft3
It is.

Other materials with lower densities are obvious to those skilled in the silicone industry and many other industries, such as organic rubbers, e.g. fumed alumina, carbon black and ], -r:I gels, e.g. There is silica aerogel.

The main disadvantage of such low bulk density materials (3L) is that they are relatively expensive to transport and store; Containers such as freight cars cannot carry large amounts of filler by weight, forcing them to pay a premium for shipping.Furthermore, once such fillers are received, compounders and compounders must storage area,
For example, payments must also be made for eight warehouses, silos, etc., and these costs are of course ultimately passed on to the consumer or end user.

Therefore, it is highly desirable to establish a means of increasing the density of fillers and other low bulk density materials to reduce transportation and storage costs.

There are many mechanical means of increasing the bulk density of powder materials, such as fumed silica. An example of this type of equipment for densifying and granulating powdered materials is the Oldham
et al., US Pat. No. 3,114.930@. The Oldham et al. patent uses a vacuum to remove air from an air-containing powder material, thereby increasing its density.

In Carter, US Pat. No. 3,664,385, a rotary screw feeder is used to compress finely divided particulate material. On the other hand, Leon (le.

O) et al. solve the densification problem by arranging a pair of mutually opposing gas permeable belts on opposite sides of a common axis and defining converging densification regions between adjacent surfaces of the belts. has been resolved.

Other examples of Akebono mechanical densification devices include Lo 77 (L o
U.S. Pat.
US Pat. No. 4,326,852 (tel).

Although the density of many materials can be increased by mechanical means, some drawbacks and disadvantages still remain. For example, in the case of fumed silica, its density can be measured using mechanical equipment to approximately 6I! When it increases to more than b/ft3, agglomerates and coarse particles exceeding the measurement range are formed. moreover,
2 Such a l-Umed silicone force will cause the silicone polymer to
It was also found that it does not disperse as well as low bulk density fumed silica.

It is also known that carbon black can be densified with water to create materials with high bulk densities, but such materials contain excessive ω coarse particles and can be reinforced when incorporated into silicone sealants or rubber compounds. It is extremely ineffective as a drug.

Fitzgerald (-itzg) assigned to the applicant.
U.S. Patent Application No. 539.5p7 of Erald et al.
(filed October 6, 1983), the above-mentioned process is accomplished by blending 1-foamed silica or other powder materials with silicone polymers to obtain free-flowing powders with higher densities than those produced by mechanical means. We have developed an excellent non-mechanical solution to this problem.

Lucas U.S. Patent No. 2.938°0
No. 09 discloses that certain materials, such as fumed silica, can be treated with cyclic furkylpolysiloxanes to reduce structuring in curable organopolysiloxane compositions. When carrying out the treatment step, the cyclic alkyl polysiloxane used is sufficiently volatile in order to diffuse the polysiloxane throughout the silica particles, so that at a suitable temperature, e.g. It is desirable that volatilization occurs easily. One method of obtaining a treated filler includes placing the filler in intimate contact with a cyclic alkylpolysiloxane in a matrix of 5-50 weight percent cyclic polysiloxane, based on the weight of the filler being treated. It is said to include the process of

According to the teachings of Lucas, treatment of filler by this method results in a bulk density of the treated filler that is lignically unchanged from the high density of the initial untreated filler. Moreover, according to Lucas, this is not a problem in the prior art, e.g., U.S. Pat.
．． This is in stark contrast to the results normally achieved by treating fillers with organosilicon compounds as described in No. 264. That is, with this prior art, depending on the jp combination.

The bulk density will be less than half that of the original untreated filler.

As will be readily understood by those skilled in the art, the Lucas method is based on heating the filler/cyclopolysiloxane mixture to diffuse the cyclopolysiloxane throughout the filler. That is, filler processing relies on the interaction of gaseous and solid reactants.

The inventors should cover the interaction of powder materials such as fumed silica with organic or organosiloxane liquids such as cyclopolysiloxane and a number of other materials that are preferably non-polar or slightly polar. It has been found that by subsequently evaporating the liquid, the bulk density of the powdered material can be significantly increased without producing unacceptably large agglomerates or grit.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a method for increasing the bulk density of low density materials.

Another object of the present invention is to provide a method for increasing the bulk density of low 7:S density materials without forming unacceptably large agglomerates or grit.

Yet another object of the present invention is to provide a method for increasing the bulk density of a low bulk density +A first, thus allowing the material to be more easily incorporated into base compounds such as polymers. It's about doing.

According to the present invention, (A) a suitable mixing vessel contains (1) a low bulk density material and (2) an organic or organopolysiloxane liquid effective to densify the low bulk density material. in addition, (B) mixing the low bulk density material and the organic or organopolysiloxane liquid for a time effective to reduce the volume of the low bulk density material; and (C) mixing the organic or organopolysiloxane liquid with the low bulk density material; A method is provided for increasing the bulk density of a low bulk density material, characterized in that substantially all of the bulk density is removed to obtain a material with increased bulk density.

In a particularly preferred example, the low bulk density material is fumed silica and the liquid is octamethylsiloxane.

In a somewhat less preferred example, the liquid is 1°1.1-
1-lichloroethane, toluene, hegisan, xylene,
It is a non-polar or low polar liquid selected from mineral spirit, dibutyl ether, isopropanol, 2-ethylhexylnol, methyl ethyl ketone, nitrobenzene and chlorobenzene.

DETAILED DESCRIPTION The method of increasing the density of a low density material of the present invention includes: (A) densifying (1) a low density material and (2) this low density 44i1 in a suitable mixing container; (B) adding an organic liquid or organopolysiloxane liquid effective for warming the low bulk density material and an organic or organopolysiloxane liquid to reduce the volume of the low bulk density material; mixing for an effective period of time, and (C) removing substantially all of the organic or organopolysiloxane liquid to obtain a material with increased bulk density.

In general, the low bulk density material can be any composition that can normally be classified as a "powder". For the purposes of the present invention, a powder is defined as any solid that is produced by comminution of relatively large units, mechanical comminution, combustion (e.g. fumed silica) or precipitation from a chemical reaction and has a very small particle size down to colloidal dimensions. Defined as a dry material (“Abridged Chemistry Dictionary (T
scd Chemical [)ic onary)
J, 10th edition, edited by G. G. Howley, edited by van Nostrand Rei.
nhold Company), 1981, see
.

Powders used in the practice of this invention include fumed silica, carbon black, fucombed aluminum, aluminum, and aerogel.

Of particular interest is fumed silica, which is the most preferred low density material for practicing the invention. For convenience of explanation, fumed silica should be understood to include any material within the definition of powder set forth above.

Liquids that can be mixed with the low bulk density materials mentioned above to achieve the superior effects of the present invention may be polar or non-polar. Suitable liquids are nonpolar or low polarity liquids, and most preferred liquids are nonpolar liquids, such as octamethylcyclotetrasiloxane.

The definition of organopolysiloxane generally includes 7
Contains furkylborisiloxanes. Orka! Although a methyl group is preferable as a base, it is not necessary that the ortoga first base be a methyl group.

Examples of suitable liquids for use in the practice of this invention are listed below.

Nonpolar octamethylsiloxane cyclobentasiloxane octamethyl trisiloxane decamethyl tetrasiloxane toluene xylene hexanes octanes decane mineral spirits low polarity 1.1.1-trichloroethane chlorobenzene nitrobenzene dibutyl ether methyl ethyl ketone polar Isopropanol Butanol 2-Ethylhexanol It will be apparent to those skilled in the art that numerous powders and liquids not specifically mentioned herein can be used in the practice of the present invention without departing from the spirit of the invention. .

In the practice of the present invention, a low density material is placed in a suitable mixing vessel along with a mouth liquid effective to densify the low bulk density material. Preferably, the liquid is added by spraying the liquid onto the filler while stirring the filler in turbulent conditions.

Here, by liquid J is meant sufficient liquid to reduce the volume of the initially low bulk density material. Of course, the factors determining the effective amount of liquid will vary depending on the low density material, the liquid used and the strength of the filler and liquid combination. However, one skilled in the art would be able to make such determinations without undue experimentation.

General guidelines: The minimum rA of the liquid that can be used "wets" or contacts substantially all of the particles of the powder material, and the volume of the powder material The maximum amount of liquid desired is sufficient to indicate that there is excess liquid after mixing. However, the mixing of powder and liquid must be After completion,
There is no upper limit since the liquid is removed, for example by evaporation. Taking a mixture of fumed silica and octamethylcyclotetrasiloxane as an example in particular, there should be at least about 15% by weight of octamethylcyclotetrasiloxane, more preferably at least about 60% by weight based on the weight of the fumed silica. There is. As can be seen from the examples shown below,
It is preferable that the amount of the liquid used in the Migashiyama be as large as three times the amount of fumed silica based on heavy FFI standards.

Mixing of the low density material with the organic or organosiloxane liquid is preferably carried out in a mixing vessel with vigorous agitation, such as a mixer or blender, to ensure that substantially all of the particulate material is wetted with the liquid. However, for the purposes of the present invention, the term [mixing vessel J or "mixing in a suitable vessel" and other similar terms is intended to encompass any means of achieving wetting of the powder by a liquid. For example, methods such as rolling, spraying, fluidizing, and stirring are equivalent means that can be used to carry out the present invention. It will be understood by those skilled in the art that the process of the present invention can be carried out either in a quarter (batch) mode or in a continuous mode.

The time required to perform the mixing must be sufficient to reduce the volume of the initially low density material. Mixing times can therefore range from as short as 5-10 seconds to an hour or more. The mixing time will, of course, depend on the particular low bulk density materials and liquids used to practice the invention, the intensity of mixing and the use of the liquids. A person of ordinary skill in the art should be able to determine effective mixing times without undue experimentation.

If, after mixing, the volume of the original low bulk density material remains substantially unchanged, additional volumes of liquid may be added and mixing continued for a further appropriate period of time. This procedure can be continued until the initial low density material (4 vJ) is reduced as desired.

Furthermore, in some cases it may be advantageous to proceed in stages, rather than later removing the liquid by evaporation. As can be easily understood, the less velocity a liquid has, the less energy it takes to evaporate it.

It should be understood that the present invention is not limited to increasing the density of materials that have not undergone another density increasing treatment. for example,
It is also within the scope of the present invention to further densify fumed silica that has previously been partially densified by mechanical or other means.

After mixing the low bulk density material with the liquid for a period of time effective to reduce the volume of the low bulk density material, the liquid is removed from the mixture. Typically, removal of liquid from the mixture is accomplished simply by evaporation. However, depending on the type of powder and liquid, it may be desirable to evaporate the liquid under reduced pressure or to first remove most of the liquid by passing through.

Although other methods of removing liquid from the powder will be apparent to those skilled in the art, evaporation is the preferred means of removing liquid.

The time required to remove all of the liquid from the powder depends primarily on the type of liquid used and the size of the batch prepared. Completion of the drying process can be determined by inspecting the drying powder every few minutes. Alternatively, and more conveniently, the drying time may be continued for a longer period of time, for example 1 hour for small batches or overnight for medium batches. Of course, liquid removal is much faster if the boiling point of the liquid is low and the liquid/filler mixture is turbulently stirred under a purge gas, such as 14 M of nitrogen. On the other hand, the process of the present invention is slower when the boiling point of the liquid is high, the process temperature is relatively low, no purge gas is used, and the agitation of the -C filler/liquid mixture is weak.

Materials, in particular filling vB agents, e.g. fumed silica, which are prepared according to the invention by densification of materials with low high densities, have significantly higher densities and k
The agglomerates and coarse particles can be easily incorporated into pond materials, such as silicone polymers used in making room temperature curable (RTV) compositions.

Those skilled in the art will understand the present invention more fully! For the sake of clarity, the following examples are given by way of illustration, but they are not intended to limit the invention in any way.

Unless otherwise specified, all parts are by weight.

Example Example 1 Density 2.2j! 1329 octamethylcyclotetrasiloxane fluid was sprayed into a 1 gallon Waring [F] blender containing 449 b/ft3 of fumed silica. The two components were mixed vigorously for about 1 minute. The volume occupied by the wet fumed silica is approximately one third of the volume of the initial wet filler.

The samples were then placed in an oven for 2 hours at 200'C, with occasional agitation, to allow all of the liquid to evaporate.

The bulk density of the fumed silica filler was measured and found to be 8.
5ρb, I finished with '['.

This filler was then added to Lucas U.S. Pat.
Octamethyl Schiff 1l- at 270°C according to No. 009
) 1~Rashi 111: I) 1'' treated and then added to (room temperature curable silicone) Sealan 1 composition.

The dispersion of this filler in the 1'<rV cushion composition was as good as the same sealant obtained from the same fumed silica without the compaction according to the invention.

waiting list applicant

Claims (1)

Claims: 1. (A) In a suitable mixing vessel, (1) a low bulk density material and (2) an amount of an organic liquid or organopolysiloxane effective to densify the low bulk density material. (B) mixing the low bulk density material and the organic or organopolysiloxane liquid for a period of time effective to reduce the volume of the low bulk density material; A method for increasing the bulk density of a material, characterized in that substantially all of the organic or organopolysiloxane liquid described above is removed from the material to obtain a material with increased bulk density. 2. The method of claim 1, wherein said low density material is selected from fumed silica, carbon black, fumed alumina and aerogel. 3. The method of claim 1, wherein said low bulk density material is fumed silica. 4. The method according to claim 1, wherein the organic or organopolysiloxane liquid is a nonpolar or low polarity liquid. 5. The method according to claim 1, wherein the organic or organopolysiloxane liquid is a nonpolar liquid. 6. The above organic or organopolysiloxane liquid is octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, toluene, xylenes, hexanes, octanes, decanes, mineral spirits,
1,1,1-trichloroethane, chlorobenzene, nitrobenzene, dibutyl ether, methyl ethyl ketone,
2. A method according to claim 1, wherein the alcohol is selected from isopropanol, butanol and 2-ethylhexanol. 7. The above organic or organopolysiloxane liquid is octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, toluene, xylenes, hexanes, octanes, decanes, mineral spirits,
2. A method according to claim 1, wherein the compound is selected from 1,1,1-trichloroethane, chlorobenzene, nitrobenzene, dibutyl ether and methyl ethyl ketone. 8. The above organic or organopolysiloxane liquids include octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, toluene, xylenes, hexanes, octanes, decanes, and mineral spirits. A method according to claim 1 selected from: 9. The method of claim 1, wherein said organic or organopolysiloxane liquid is selected from octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, octamethyltrisiloxane and decamethyltetrasiloxane. 10. The method of claim 1, wherein said low bulk density material is fumed silica and said organic or organopolysiloxane liquid is octamethylcyclotetrasiloxane. 11. The method of claim 10, wherein said octamethylcyclotetrasiloxane is present in an amount of 15% by weight or more based on the weight of the fumed silica. 12. The method of claim 10, wherein the octamethylcyclotetrasiloxane is present in an amount of 60% by weight or more based on the weight of the fumed silica. 13. In step (A), the organic or organopolysiloxane liquid is added to the mixing vessel by spraying while stirring the low bulk density material in a turbulent state.
The method described in section. 14. The method according to claim 1, wherein the low bulk density material is partially densified beforehand. 15. The method according to claim 14, wherein the partial densification is carried out by mechanical means. 16. Claim 1 wherein substantially all of the above organic or organopolysiloxane liquid is removed by evaporation.
The method described in section. 17. (A) Add (1) 100 parts by weight of fumed silica and (2) 15 parts by weight or more of octamethylcyclotetrasiloxane to a suitable mixing container, (B) Add the above fumed silica and octamethylcyclotetrasiloxane. (C) substantially all of the octamethylcyclotetrasiloxane is evaporated to obtain fumed silica with increased bulk density. 18. The method according to claim 17, further comprising, after step (C), treating the fumed silica with octamethylcyclotetrasiloxane by heating it to a temperature of 250° C. or higher.