CA2174893A1 - Process for dispersing finely divided solids in a liquid - Google Patents
Process for dispersing finely divided solids in a liquidInfo
- Publication number
- CA2174893A1 CA2174893A1 CA002174893A CA2174893A CA2174893A1 CA 2174893 A1 CA2174893 A1 CA 2174893A1 CA 002174893 A CA002174893 A CA 002174893A CA 2174893 A CA2174893 A CA 2174893A CA 2174893 A1 CA2174893 A1 CA 2174893A1
- Authority
- CA
- Canada
- Prior art keywords
- finely divided
- liquid
- dispersing
- divided solids
- particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/50—Mixing liquids with solids
- B01F23/51—Methods thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/50—Mixing liquids with solids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/70—Pre-treatment of the materials to be mixed
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/70—Pre-treatment of the materials to be mixed
- B01F23/703—Degassing or de-aerating materials; Replacing one gas within the materials by another gas
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Dispersion Chemistry (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
Abstract
For the purpose of dispersing finely divided solids in a liquid, the air present between the finely divided particles of solid matter is at least partially replaced by carbon dioxide before the dispersing operation.
Description
Mo4349 LeA 30,962-US/CA/FC
PROCESS FOR DISPERSING FINELY DIVIDED SOLIDS IN A LIQUID
BACKGROUND OF THE INVENTION
In the dispersing of finely divided solids in liquids, the air included between the finely divided particles of solid matter constitutes a problem.
The introduction of particles of solid matter into a liquid takes place either by the batch method or in a continuous manner. When they are introduced by the batch method, the finely divided solids are generally poured onto the liquid, which is present in an agitator vessel, and are stirred in. However the solid matter poured-in contains 30 to 60% by volume of air between the particles of solid matter. In the event of partial fluidization when the solids are placed on the liquid, the portion of air included in the solid matter poured-in may even be up to 80% by volume.
When the solid matter is stirred into the liquid, this air is dispersed in the latter in the form of finely divided air bubbles. After the agitator is switched off, the small gas bubbles emerge, forming a foam on the surface of the liquid. The time necessary for the segregation of the small gas bubbles in the form of foam on the surface of the liquid, and the breaking-down of the foam which is then necessary, depends upon the viscosity of the liquid and its surface tension. It is often not possible to obtain bubble-free dispersions of solid matter within technically practicable periods of time. It has therefore already been proposed to carry out the dispersing of solids in liquids under vacuum. However, this requires considerable outlay in terms of apparatus.
In the continuous mixing of finely divided solids into liquids, adequate periods of time for the segregation of dispersed gas bubbles are generally not available, so in order to guarantee bubble-free dispersions of solid matter it is necessary, according to the prior art, for the dispersing operation to be carried out under vacuum, or at least 21 748~3 -Mo4349 -2-under a pressure which is considerably reduced compared with normal pressure.
DESCRIPTION OF THE INVENTION
For the purpose of manufacturing bubble-free dispersions of solid matter, it is now proposed, according to the present invention, that the air located between the particles of solid matter be at least partially replaced by carbon dioxide before the dispersing of finely divided solids.
Because of the high solubility of carbon dioxide in virtually all organic or inorganic liquids, the carbon dioxide carried into the liquid between the particles of solid matter is dissolved in the said liquid, so that the formation of bubbles or foam does not occur. The solubility of carbon dioxide is generally so high that the dispersing operation according to the invention can be performed, even at elevated pressure, without the formation of gas bubbles in the dispersion occurring after the pressure is relieved and restored to normal. This is particularly important when the dispersing step is to be followed by other process steps, so that there prevails, during the dispersing operation, an excess pressure such as is adequate for overcoming the flow-resistance in downstream lines and units for further processing, without interposed pumps being needed.
The dispersing process according to the invention is particularly suitable for the dispersing of finely divided solids in liquids having a low capacity for dissolving air, that is to say oxygen and/or nitrogen, and a high capacity for dissolving carbon dioxide.
Preferred liquids are liquid precursor compounds for the manufacture of plastics materials. The process is particularly suitable when forming processes for the plastics material are being used in which the plastics material sets at ambient pressure, since in such cases the subsequent dissolution of gas bubbles in the plastics material, such as takes place, for example, in the case of forming using a high internal -~ 1 74893 Mo4349 -3-forming pressure, does not occur. The advantage of the present invention is therefore particularly relevant in the manufacture of plastics materials which contain fillers and in which forming takes place using casting processes, with or without foaming.
The replacement of the air in the solid matter poured-in may be effected in any desired manner. For example, carbon dioxide may be fed in at the bottom of the bin of solid matter. Another possibility is to flush the conveying means, e.g. a worm, by means of which the solid matter is guided into the dispersing vessel, with carbon dioxide.
It has proved possible, by using the dispersing process according to the invention in the manufacture of soft foam materials containing fillers, to effectively prevent the crack-formation that occurs in an irregular manner in the foam material. The crack-formation observed previously was clearly attributable to the fact that, after the dispersing operation, the particles of filler were wetted only inadequately by the polyurethane composition because of air which was still adhering.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.
PROCESS FOR DISPERSING FINELY DIVIDED SOLIDS IN A LIQUID
BACKGROUND OF THE INVENTION
In the dispersing of finely divided solids in liquids, the air included between the finely divided particles of solid matter constitutes a problem.
The introduction of particles of solid matter into a liquid takes place either by the batch method or in a continuous manner. When they are introduced by the batch method, the finely divided solids are generally poured onto the liquid, which is present in an agitator vessel, and are stirred in. However the solid matter poured-in contains 30 to 60% by volume of air between the particles of solid matter. In the event of partial fluidization when the solids are placed on the liquid, the portion of air included in the solid matter poured-in may even be up to 80% by volume.
When the solid matter is stirred into the liquid, this air is dispersed in the latter in the form of finely divided air bubbles. After the agitator is switched off, the small gas bubbles emerge, forming a foam on the surface of the liquid. The time necessary for the segregation of the small gas bubbles in the form of foam on the surface of the liquid, and the breaking-down of the foam which is then necessary, depends upon the viscosity of the liquid and its surface tension. It is often not possible to obtain bubble-free dispersions of solid matter within technically practicable periods of time. It has therefore already been proposed to carry out the dispersing of solids in liquids under vacuum. However, this requires considerable outlay in terms of apparatus.
In the continuous mixing of finely divided solids into liquids, adequate periods of time for the segregation of dispersed gas bubbles are generally not available, so in order to guarantee bubble-free dispersions of solid matter it is necessary, according to the prior art, for the dispersing operation to be carried out under vacuum, or at least 21 748~3 -Mo4349 -2-under a pressure which is considerably reduced compared with normal pressure.
DESCRIPTION OF THE INVENTION
For the purpose of manufacturing bubble-free dispersions of solid matter, it is now proposed, according to the present invention, that the air located between the particles of solid matter be at least partially replaced by carbon dioxide before the dispersing of finely divided solids.
Because of the high solubility of carbon dioxide in virtually all organic or inorganic liquids, the carbon dioxide carried into the liquid between the particles of solid matter is dissolved in the said liquid, so that the formation of bubbles or foam does not occur. The solubility of carbon dioxide is generally so high that the dispersing operation according to the invention can be performed, even at elevated pressure, without the formation of gas bubbles in the dispersion occurring after the pressure is relieved and restored to normal. This is particularly important when the dispersing step is to be followed by other process steps, so that there prevails, during the dispersing operation, an excess pressure such as is adequate for overcoming the flow-resistance in downstream lines and units for further processing, without interposed pumps being needed.
The dispersing process according to the invention is particularly suitable for the dispersing of finely divided solids in liquids having a low capacity for dissolving air, that is to say oxygen and/or nitrogen, and a high capacity for dissolving carbon dioxide.
Preferred liquids are liquid precursor compounds for the manufacture of plastics materials. The process is particularly suitable when forming processes for the plastics material are being used in which the plastics material sets at ambient pressure, since in such cases the subsequent dissolution of gas bubbles in the plastics material, such as takes place, for example, in the case of forming using a high internal -~ 1 74893 Mo4349 -3-forming pressure, does not occur. The advantage of the present invention is therefore particularly relevant in the manufacture of plastics materials which contain fillers and in which forming takes place using casting processes, with or without foaming.
The replacement of the air in the solid matter poured-in may be effected in any desired manner. For example, carbon dioxide may be fed in at the bottom of the bin of solid matter. Another possibility is to flush the conveying means, e.g. a worm, by means of which the solid matter is guided into the dispersing vessel, with carbon dioxide.
It has proved possible, by using the dispersing process according to the invention in the manufacture of soft foam materials containing fillers, to effectively prevent the crack-formation that occurs in an irregular manner in the foam material. The crack-formation observed previously was clearly attributable to the fact that, after the dispersing operation, the particles of filler were wetted only inadequately by the polyurethane composition because of air which was still adhering.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.
Claims (3)
1. A process for dispersing finely divided solid particles in a liquid, comprising at least partially replacing air present between the finely divided particles with carbon dioxide and then dispersing said particles in said liquid.
2. A process for manufacturing plastic material reinforced by finely divided solids, comprising at least partially replacing air present between the finely divided solids with carbon dioxide, dispersing said particles in one or more liquid precursors which are used to prepare said plastic material, mixing all the liquid precursors and recovering said plastic material.
3. A process for manufacturing polyurethane soft foam materials modified by finely divided solids, comprising at least partially replacing air present between the finely divided solids with carbon dioxide, dispersing said particles in at least one of the constituents of the polyurethane reactive mixture, mixing all the constituents and allowing the foam to form.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19515691A DE19515691A1 (en) | 1995-04-28 | 1995-04-28 | Dispersion of finely-divided solids in liquid |
| DE19515691.9 | 1995-04-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2174893A1 true CA2174893A1 (en) | 1996-10-29 |
Family
ID=7760623
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002174893A Abandoned CA2174893A1 (en) | 1995-04-28 | 1996-04-24 | Process for dispersing finely divided solids in a liquid |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPH08302027A (en) |
| KR (1) | KR960037106A (en) |
| CA (1) | CA2174893A1 (en) |
| DE (1) | DE19515691A1 (en) |
| NO (1) | NO961679D0 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001046304A2 (en) * | 1999-12-23 | 2001-06-28 | Mobius Technologies, Inc. | Polymeric foam processing |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3510109A (en) * | 1968-02-08 | 1970-05-05 | Union Carbide Corp | Method and apparatus for incorporating fibrous materials into air-free high solids dispersions |
-
1995
- 1995-04-28 DE DE19515691A patent/DE19515691A1/en not_active Ceased
-
1996
- 1996-04-22 JP JP8122790A patent/JPH08302027A/en active Pending
- 1996-04-24 CA CA002174893A patent/CA2174893A1/en not_active Abandoned
- 1996-04-26 NO NO961679A patent/NO961679D0/en unknown
- 1996-04-26 KR KR1019960013135A patent/KR960037106A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| NO961679D0 (en) | 1996-04-26 |
| JPH08302027A (en) | 1996-11-19 |
| DE19515691A1 (en) | 1996-10-31 |
| KR960037106A (en) | 1996-11-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |