US20040241056A1 - Method and apparatus for producing hydrophobic silica fine powder - Google Patents
Method and apparatus for producing hydrophobic silica fine powder Download PDFInfo
- Publication number
- US20040241056A1 US20040241056A1 US10/797,037 US79703704A US2004241056A1 US 20040241056 A1 US20040241056 A1 US 20040241056A1 US 79703704 A US79703704 A US 79703704A US 2004241056 A1 US2004241056 A1 US 2004241056A1
- Authority
- US
- United States
- Prior art keywords
- silica
- fine powder
- silica fine
- bag filter
- hydrophobizing
- 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
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 198
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 99
- 239000000843 powder Substances 0.000 title claims abstract description 31
- 230000002209 hydrophobic effect Effects 0.000 title claims abstract description 12
- 238000000034 method Methods 0.000 title abstract description 13
- 238000005243 fluidization Methods 0.000 claims abstract description 44
- 229910000077 silane Inorganic materials 0.000 claims abstract description 10
- -1 silane compound Chemical class 0.000 claims abstract description 5
- 239000002912 waste gas Substances 0.000 abstract description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 19
- 239000007789 gas Substances 0.000 description 18
- 239000003795 chemical substances by application Substances 0.000 description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 11
- 229910021485 fumed silica Inorganic materials 0.000 description 9
- 239000000499 gel Substances 0.000 description 8
- 239000003921 oil Substances 0.000 description 8
- 238000011084 recovery Methods 0.000 description 8
- 239000004744 fabric Substances 0.000 description 7
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 239000005055 methyl trichlorosilane Substances 0.000 description 6
- JLUFWMXJHAVVNN-UHFFFAOYSA-N methyltrichlorosilane Chemical compound C[Si](Cl)(Cl)Cl JLUFWMXJHAVVNN-UHFFFAOYSA-N 0.000 description 6
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 5
- 229910052801 chlorine Inorganic materials 0.000 description 5
- 239000000460 chlorine Substances 0.000 description 5
- 238000009833 condensation Methods 0.000 description 5
- 230000005494 condensation Effects 0.000 description 5
- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 229910052736 halogen Inorganic materials 0.000 description 4
- 150000002367 halogens Chemical class 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 150000003377 silicon compounds Chemical class 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 239000012212 insulator Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000009969 flowable effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000000700 radioactive tracer Substances 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 239000000565 sealant Substances 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 239000006200 vaporizer Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/28—Compounds of silicon
- C09C1/30—Silicic acid
- C09C1/3081—Treatment with organo-silicon compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/50—Agglomerated particles
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/90—Other properties not specified above
Definitions
- the present invention relates to a method and apparatus for producing hydrophobic silica fine powder which can be used as a thickener for coatings, adhesives and synthetic resins, as a reinforcement for plastics, and to improve flowability in toners for copiers.
- Pyrogenic silica (silicon dioxide) is very fine, having a particle size of about 5 to 50 nm. Because it is difficult to collect in this form, it is agglomerated, then collected. The agglomerated silica contains a high concentration of chlorine, and must therefore be deacidified. Deacidification is generally carried out in a fluidization vessel. When agglomerated silica is deacidified, only a small amount of silica flies out of the fluidization vessel together with waste gases.
- silica when the silica is treated with a hydrophobizing agent, due to breakup of the agglomerate by such treatment, at least several times more treated silica flies out of the fluidization vessel together with waste gases than when agglomerated silica is directly deacidified.
- the presence of such fugitive treated silica in the waste gases leads to a number of practical obstacles when the waste gases are treated with a scrubber, such as the formation of foam, which cannot be easily removed with filters.
- fly-out ratio 0.3 to 0.5% when conventional pyrogenic silica is deacidified in a fluidization vessel, and 4 to 15% when such silica is first treated with a hydrophobizing agent then deacidified. While the shape of the equipment and the fluidizing conditions also have an effect on the fly-out ratio, this large difference appears to be attributable to the breakup of agglomerates in hydrophobizing treatment, which leads to easier fly-out than when the silica is subjected only to deacidification. Recovery of the fugitive silica is thus necessary to improve product yield and alleviate the burden on waste gas treatment.
- silane hydrophobizing agent present in the waste gases forms a gel or oil due to the condensation of moisture in the waste gases, which can lead to the clogging and obstruction of equipment and lines.
- silane unreacted organohalosilane hydrophobizing agent present in the waste gases
- the temperature of the equipment and waste gases is maintained at 100° C. or higher, the moisture present in the waste gases does not condense and undesirable products such as gels or oils due to moisture and unreacted silane do not form.
- the absence of gel or oil formation on the filter fabric in a bag filter keeps the filter fabric free of clogging, making it possible to carry out continuous operation.
- the degree of fly-out also varies with the flow conditions.
- hydrophobizing treatment a high concentration of chlorine is generally present in the gas, creating a need for subsequent deacidification.
- it is more effective to carry out hydrophobizing treatment and deacidification separately, in which case the presence or absence of moisture comes to have an effect on flow of the material during deacidification.
- An investigation on the level of water showed us that material fluidization is poor in the absence of moisture, but that the addition of even a very small amount of water to the fluidizing gas improves the flow state and reduces fly-out. Less fly-out makes it possible to lower the burden on cyclones and especially bag filters.
- the invention provides a method for producing hydrophobic silica fine powder.
- a silane compound is pyrolyzed to form a silica fine powder.
- the silica fine powder is then hydrophobized with an organohalosilane in a fluidization vessel, giving hydrophobized silica fine powder which is collected.
- the hydrophobized silica fine powder which flies out of the fluidization vessel is collected with a cyclone and bag filter which are held at a temperature of 100 to 500° C.
- the fluidization vessel includes a hydrophobizing section where the silica fine powder is hydrophobized and a deacidifying section where deacidification is carried out following hydrophobization.
- Deacidification is preferably carried out in the deacidifying section by adding 0.1 to 1 vol % of water to a fluidizing gas.
- the invention also provides an apparatus for producing hydrophobic silica fine powder, which apparatus includes a means for pyrolyzing a silane compound to form silica fine powder, a means for agglomerating the silica fine powder, a first cyclone and a first bag filter for collecting the agglomerated silica fine powder, a fluidization vessel having a hydrophobizing section for hydrophobizing the collected silica fine powder, and a second cyclone and a second bag filter for collecting the hydrophobic silica fine powder which flies out of the fluidization vessel.
- the second cyclone and the second filter can each be held at a temperature of 100 to 500° C.
- the advantages of the invention are as follows.
- silane is flame-hydrolyzed to form silica fine powder, and the silica is then hydrophobized in a fluidization vessel using a hydrophobizing agent such as an organohalosilane
- the amount of silica that flies out of the vessel into the waste gases is greater than when hydrophobizing treatment is not carried out.
- the condensation of moisture in the waste gases converts unreacted organohalosilane hydrophobizing agent which emerges together with the waste gases into an undesirable gel or oil.
- the inventive method and apparatus enable essentially 100% recovery of fugitive silica, resulting in a higher product yield.
- An additional advantage is that, even when the waste gases are treated with a scrubber, there is little if any fugitive silica-induced formation of foam, which cannot be easily removed with filters. This greatly alleviates the burden on waste gas and wastewater treatment.
- FIG. 1 is a flow diagram illustrating an embodiment of the invention.
- FIG. 2 is a flow diagram illustrating Comparative Example 1 described below.
- the inventive process for producing hydrophobic silica fine powder involves pyrolyzing a silane compound (a halogenated silicon compound) to form a silicon dioxide fine powder (pyrogenic silica), then treating the pyrogenic silica in a fluidization vessel with a hydrophobizing agent, more specifically an organohalosilane.
- a silane compound a halogenated silicon compound
- pyrogenic silica silicon dioxide fine powder
- the pyrogenic silica may be prepared by a known process using a halogenated silicon compound such as methyl-trichlorosilane.
- a silica powder having a BET specific surface area of 50 to 400 m 2 /g is desirable in terms of flowability and other characteristics.
- pyrogenic silica is prepared by a known method from a halogenated silicon compound, it is preferably agglomerated and halogen gases such as chlorine are separated off and removed. Thereafter, the agglomerated silica is hydrophobized in a fluidization vessel using an organohalosilane as the hydrophobizing agent and using also steam and an inert gas.
- the fluidization vessel is divided into a hydrophobizing section and a deacidifying section. Hydrophobization of the pyrogenic silica is carried out in the hydrophobizing section, followed by deacidification in the deacidifying section.
- a part of the hydrophobized silica fine powder which flies out of the fluidization vessel (including both the hydrophobizing section and the deacidifying section) is collected with a cyclone and bag filter held at temperatures within a range of 100 to 500° C.
- the collected powder is returned to the fluidization vessel, and in particular the deacidifying section.
- adding 0.1 to 1 vol % of water to the fluidizing gas is preferable for promoting fluidization and deacidification.
- production and recovery of hydrophobized silica fine powder is carried out as a continuous process within an apparatus that includes a pyrogenic silica-producing operation.
- this is not an essential feature of the invention.
- Pyrogenic silica is produced according to a conventional process by burning a halogenated silicon compound together with hydrogen and air in a combustion chamber (pyrolyzing means) 1 and agglomerated by an agglomerator (agglomerating means) 2 for subsequent collection by cyclones 3 and a bag filter 4 .
- Use of the cyclones 3 and bag filter 4 also serves to separate off chlorine and other halogen-containing gases that form as by-products in the combustion chamber 1 .
- the separated halogen-containing gases are sent to a scrubber.
- the agglomerated silica then passes through rotary valves 5 and is collected in a hopper 6 .
- Agglomerated silica that has been retrieved by the bag filter 4 also is recovered in the hopper 6 .
- the agglomerated silica passes through a double damper 7 , and is delivered by a diaphragm pump 8 to a fluidization vessel 9 for hydrophobization.
- the fluidization vessel 9 is divided into a hydrophobizing section A and a deacidifying section B.
- the hydrophobizing section A and the deacidifying section B communicate in the lower portion of the fluidization vessel 9 .
- Silica hydrophobization is carried out in hydrophobizing section A, and the halogen gas such as chlorine which accompanies the silica from the hydrophobizing section A is removed in the deacidifying section B.
- hydrophobization and deacidification may be carried out in separate devices.
- the silica is fluidized with an inert gas, generally nitrogen (N 2 ), and is treated with a hydrophobizing agent.
- an inert gas generally nitrogen (N 2 )
- the hydrophobizing agent 10 is sent by a pump 11 through a vaporizer 12 and to the fluidization vessel 9 .
- the hydrophobizing agent 10 may be mixed with the silica before the silica enters the fluidization vessel 9 .
- An alternative is to heat fluidizing nitrogen having water entrained thereon, then mix the hydrophobizing agent into the gas stream and introduce the resulting mixture into the fluidization vessel 9 .
- the silica is hydrophobized at a temperature of preferably 400 to 600° C., and most preferably 450 to 550° C.
- the flow velocity is preferably from 1 to 6 cm/s, although a velocity within a range of 1.4 to 3 cm/s is especially preferred for achieving a stable fluidized state and holding down the fly-out of silica. Water is used at this point because it has a beneficial effect on hydrophobizing treatment.
- the water 14 is fed with a pump 15 to the fluidizing inert gas, following which the gas is heated with a heater 13 and introduced to the hydrophobizing section A of the fluidization vessel 9 .
- the amount of water used for hydrophobization is preferably 0.1 to 5 parts by weight, and most preferably 0.5 to 3 parts by weight, per 100 parts by weight of silica.
- the hydrophobizing agent is an organohalosilane, and most preferably dimethyldichlorosilane.
- the silica is fluidized with an inert gas, typically nitrogen, and subjected to deacidification.
- Water is typically added to the fluidizing gas so that deacidification can be carried out in a water-containing atmosphere.
- the water 16 is added to the fluidizing gas with a pump 17 , following which the gas is heated with a heater 13 and introduced to the deacidifying section B.
- the amount of water added to the fluidizing gas for this purpose is preferably at least 0.1 vol %, and most preferably 0.1 to 1 vol %.
- the silica may become less flowable, making it necessary to use more fluidizing gas, which in turn results in increased fly-out. This is particularly undesirable from the standpoint of the burden on the bag filter.
- too much moisture may give rise to such undesirable effects as condensation when the deacidified silica is recovered in a recovery vessel 24 from the deacidifying section B.
- the deacidification temperature is preferably 400 to 500° C., and the flow velocity is preferably 1 to 6 cm/s.
- Waste gases from the fluidization vessel 9 (including both hydrophobizing section A and deacidifying section B) are sent to a scrubber via a cyclone 18 and a bag filter 19 .
- Silica accompanying the waste gases passes from the cyclone 18 to a rotary valve 20 or is trapped by the bag filter 19 , then is collected in a hopper 21 , following which it is returned to the deacidifying section B via a rotary valve 22 and a diaphragm pump 23 .
- the deacidified silica is collected in the recovery vessel 24 .
- T 1 and T 2 are each thermometers which measure the temperature of the waste gases.
- the temperature readings at T 1 and T 2 must be at least 100° C., although a higher temperature, such as 130° C. or more, is preferred at the bag filter, both for the gases themselves and also for areas of the bag filter that come into direct contact with the gases. Accordingly, the interior of the exhaust system must be held at a temperature within a range of 100 to 500° C.
- the production apparatus shown in FIG. 1 is also provided with a heat insulator 28 and a steam tracer 29 to keep the temperature from falling.
- hydrophobic silica produced by the treatment method and apparatus of the invention are not subject to any particular limitation, although a specific surface area of about 110 m 2 /g, a carbon content of at least about 0.9 wt %, and a pH of at least 4.5 are preferred. Hydrophobic silica having such properties is highly suitable for use in sealants and related applications.
- the apparatus shown in FIG. 1 was operated continuously for a total of 500 hours. During operation, 50.3 kg/h of methyltrichlorosilane was burned together with hydrogen and air, producing 20.1 kg/h of silica. The resulting silica was subjected to hydrophobizing treatment at a nitrogen feed rate of 30 Nm 3 /h, a dimethyldichlorosilane feed rate of 2.0 kg/h, and a water feed rate of 0.5 kg/h into section A of the fluidization vessel 9 , and a temperature of 490° C. The flow velocity of silica into section A was 2.0 cm/s.
- the hydrophobized silica was then deacidified at a nitrogen feed rate of 35 Nm 3 /h and a water feed rate of 0.2 kg/h to section B of the fluidization vessel 9 , a temperature of 480° C., and a flow velocity of about 2.2 cm/s.
- the treated silica had, on average, a specific surface area of 114 m 2 /g, a carbon content of 0.97 wt %, and a pH of 4.7.
- the temperatures of the cyclone 18 and the bag filter 19 were, on average, 150° C. (T 1 ) and 135° C. (T 2 ).
- the pressure difference P 1 at the bag filter was 0.8 kPa at the start of operation, and 1.4 kPa at the end of operation.
- the combined amount of silica collected by the cyclone 18 and the bag filter 19 on the discharge side of the diaphragm pump 23 during operation was 0.8 kg/h, representing a fly-out ratio of about 4%.
- the scrubber fluid was almost entirely free of suspended silica. Nor was there any gel or oil deposited on the filter fabric of the bag filter.
- the apparatus shown in FIG. 1 was operated for a period of 7 hours by burning 49.6 kg/h of methyltrichlorosilane together with hydrogen and air, thereby producing 19.8 kg/h of silica.
- Hydrophobization of the silica was carried out in section A of the fluidization vessel 9 in the same manner as in Example 1.
- Deacidification was carried out in section B of the fluidization vessel B without feeding water and at a nitrogen feed rate of 45 Nm 3 /h, a temperature of 480° C., and a flow velocity of about 2.8 cm/s.
- the treated silica had a specific surface area of 114 m 2 /g, a carbon content of 0.95 wt %, and a pH of 4.6.
- the amount of silica collected on the discharge side of the diaphragm pump 23 was 2.4 kg/h. Hence, the fly-out ratio was about 12%.
- the apparatus shown in FIG. 1 was operated for a period of 7 hours by burning 50.4 kg/h of methyltrichlorosilane with hydrogen and air, thereby producing 20.1 kg/h of silica.
- Treatment in section A was the same as in Example 1.
- the treated silica had a specific surface area of 108 m 2 /g, a carbon content of 0.95 wt %, and a pH of 4.8.
- the amount of silica collected on the discharge side of the diaphragm pump 23 was 1.2 kg/h, indicating a fly-out ratio of about 6%. Condensation was observed in the silica recovery vessel 24 on the outlet side of the fluidization vessel 9 .
- FIG. 2 The apparatus shown in FIG. 2 was used.
- the apparatus included fluidization vessels 31 and 32 , a hydrophobizing agent container 33 , a constant-temperature vessel 34 , water tanks 35 and 37 , pumps 36 and 38 , a bag filter 39 , a heater 40 and a heat insulator 42 .
- Other parts serving the same purposes as parts in FIG. 1 are designated by the same reference numerals.
- the apparatus also includes thermometers T 51 , T 52 and T 53 , and a differential pressure gauge P 51 .
- the inventive method and apparatus use a cyclone and a bag filter to recover silica that flies out of the fluidization vessel. Under simple controlled conditions that involve holding these devices at temperatures of at least 100° C., essentially 100% of the fugitive silica can be recovered, resulting in increased yield of the product and reducing the burden on waste gas treatment.
Abstract
Hydrophobic silica fine powder is produced by pyrolyzing a silane compound to form a silica fine powder and hydrophobizing the silica fine powder with an organohalosilane in a fluidization vessel. Hydrophobized silica fine powder which flies out of the fluidization vessel is collected with a cyclone and bag filter which are held at a temperature of 100-500° C. An apparatus for carrying out the process is also provided. Under simple controlled conditions that involve holding the cyclone and bag filter for recovering fugitive silica from the fluidization vessel to temperatures of 100-500° C., the method and apparatus are able to recover essentially 100% of fugitive silica, thus increasing yield of the product and alleviating the burden on waste gas treatment.
Description
- 1. Field of the Invention
- The present invention relates to a method and apparatus for producing hydrophobic silica fine powder which can be used as a thickener for coatings, adhesives and synthetic resins, as a reinforcement for plastics, and to improve flowability in toners for copiers.
- 2. Prior Art
- Pyrogenic silica (silicon dioxide) is very fine, having a particle size of about 5 to 50 nm. Because it is difficult to collect in this form, it is agglomerated, then collected. The agglomerated silica contains a high concentration of chlorine, and must therefore be deacidified. Deacidification is generally carried out in a fluidization vessel. When agglomerated silica is deacidified, only a small amount of silica flies out of the fluidization vessel together with waste gases. However, when the silica is treated with a hydrophobizing agent, due to breakup of the agglomerate by such treatment, at least several times more treated silica flies out of the fluidization vessel together with waste gases than when agglomerated silica is directly deacidified. The presence of such fugitive treated silica in the waste gases leads to a number of practical obstacles when the waste gases are treated with a scrubber, such as the formation of foam, which cannot be easily removed with filters.
- It is therefore an object of the invention to provide a method and apparatus for producing hydrophobic silica fine powder by hydrophobizing agglomerated silica with an organohalosilane in a fluidization vessel, which are designed such that a part of the treated silica which flies out of the vessel together with waste gases can be reliably recovered without complicating the apparatus or process control.
- In studies where we installed cyclones and bag filters to recover silica that had flown out from fluidization vessels and examined the degree of fly-out based on the amount of silica recovered, we found the fly-out ratio to be 0.3 to 0.5% when conventional pyrogenic silica is deacidified in a fluidization vessel, and 4 to 15% when such silica is first treated with a hydrophobizing agent then deacidified. While the shape of the equipment and the fluidizing conditions also have an effect on the fly-out ratio, this large difference appears to be attributable to the breakup of agglomerates in hydrophobizing treatment, which leads to easier fly-out than when the silica is subjected only to deacidification. Recovery of the fugitive silica is thus necessary to improve product yield and alleviate the burden on waste gas treatment.
- However, unreacted organohalosilane (referred to hereinafter as “silane”) hydrophobizing agent present in the waste gases forms a gel or oil due to the condensation of moisture in the waste gases, which can lead to the clogging and obstruction of equipment and lines. On measuring and studying the temperature at various places in the exhaust system, we have found that, if the temperature of the equipment and waste gases is maintained at 100° C. or higher, the moisture present in the waste gases does not condense and undesirable products such as gels or oils due to moisture and unreacted silane do not form. In particular, the absence of gel or oil formation on the filter fabric in a bag filter keeps the filter fabric free of clogging, making it possible to carry out continuous operation.
- The degree of fly-out also varies with the flow conditions. In hydrophobizing treatment, a high concentration of chlorine is generally present in the gas, creating a need for subsequent deacidification. However, it is more effective to carry out hydrophobizing treatment and deacidification separately, in which case the presence or absence of moisture comes to have an effect on flow of the material during deacidification. An investigation on the level of water showed us that material fluidization is poor in the absence of moisture, but that the addition of even a very small amount of water to the fluidizing gas improves the flow state and reduces fly-out. Less fly-out makes it possible to lower the burden on cyclones and especially bag filters.
- We thus discovered that by holding down fly-out and maintaining the temperature of the cyclone and bag filter at 100° C. or higher, essentially 100% of fugitive silica can be recovered.
- Accordingly, the invention provides a method for producing hydrophobic silica fine powder. A silane compound is pyrolyzed to form a silica fine powder. The silica fine powder is then hydrophobized with an organohalosilane in a fluidization vessel, giving hydrophobized silica fine powder which is collected. The hydrophobized silica fine powder which flies out of the fluidization vessel is collected with a cyclone and bag filter which are held at a temperature of 100 to 500° C.
- In a preferred embodiment, the fluidization vessel includes a hydrophobizing section where the silica fine powder is hydrophobized and a deacidifying section where deacidification is carried out following hydrophobization. Deacidification is preferably carried out in the deacidifying section by adding 0.1 to 1 vol % of water to a fluidizing gas.
- The invention also provides an apparatus for producing hydrophobic silica fine powder, which apparatus includes a means for pyrolyzing a silane compound to form silica fine powder, a means for agglomerating the silica fine powder, a first cyclone and a first bag filter for collecting the agglomerated silica fine powder, a fluidization vessel having a hydrophobizing section for hydrophobizing the collected silica fine powder, and a second cyclone and a second bag filter for collecting the hydrophobic silica fine powder which flies out of the fluidization vessel. The second cyclone and the second filter can each be held at a temperature of 100 to 500° C.
- The advantages of the invention are as follows. When silane is flame-hydrolyzed to form silica fine powder, and the silica is then hydrophobized in a fluidization vessel using a hydrophobizing agent such as an organohalosilane, the amount of silica that flies out of the vessel into the waste gases is greater than when hydrophobizing treatment is not carried out. During recovery of the silica in the waste gases, the condensation of moisture in the waste gases converts unreacted organohalosilane hydrophobizing agent which emerges together with the waste gases into an undesirable gel or oil. In the method and apparatus of the invention, by maintaining the cyclone and bag filter used as the recovery devices at a temperature of at least 100° C., no organohalosilane gel or oil forms and thus no clogging of lines or bag filter pores occurs, making continuous operation possible. Moreover, the inventive method and apparatus enable essentially 100% recovery of fugitive silica, resulting in a higher product yield. An additional advantage is that, even when the waste gases are treated with a scrubber, there is little if any fugitive silica-induced formation of foam, which cannot be easily removed with filters. This greatly alleviates the burden on waste gas and wastewater treatment.
- The objects, features and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings.
- FIG. 1 is a flow diagram illustrating an embodiment of the invention.
- FIG. 2 is a flow diagram illustrating Comparative Example 1 described below.
- The inventive process for producing hydrophobic silica fine powder involves pyrolyzing a silane compound (a halogenated silicon compound) to form a silicon dioxide fine powder (pyrogenic silica), then treating the pyrogenic silica in a fluidization vessel with a hydrophobizing agent, more specifically an organohalosilane.
- The pyrogenic silica may be prepared by a known process using a halogenated silicon compound such as methyl-trichlorosilane. A silica powder having a BET specific surface area of 50 to 400 m2/g is desirable in terms of flowability and other characteristics.
- After pyrogenic silica is prepared by a known method from a halogenated silicon compound, it is preferably agglomerated and halogen gases such as chlorine are separated off and removed. Thereafter, the agglomerated silica is hydrophobized in a fluidization vessel using an organohalosilane as the hydrophobizing agent and using also steam and an inert gas. In a preferred embodiment, the fluidization vessel is divided into a hydrophobizing section and a deacidifying section. Hydrophobization of the pyrogenic silica is carried out in the hydrophobizing section, followed by deacidification in the deacidifying section.
- In the practice of the invention, a part of the hydrophobized silica fine powder which flies out of the fluidization vessel (including both the hydrophobizing section and the deacidifying section) is collected with a cyclone and bag filter held at temperatures within a range of 100 to 500° C. The collected powder is returned to the fluidization vessel, and in particular the deacidifying section. In the deacidifying section, adding 0.1 to 1 vol % of water to the fluidizing gas is preferable for promoting fluidization and deacidification.
- In one preferred embodiment, production and recovery of hydrophobized silica fine powder is carried out as a continuous process within an apparatus that includes a pyrogenic silica-producing operation. However, this is not an essential feature of the invention.
- Referring to FIG. 1, a preferred embodiment of the invention is described below. Pyrogenic silica is produced according to a conventional process by burning a halogenated silicon compound together with hydrogen and air in a combustion chamber (pyrolyzing means)1 and agglomerated by an agglomerator (agglomerating means) 2 for subsequent collection by
cyclones 3 and abag filter 4. Use of thecyclones 3 andbag filter 4 also serves to separate off chlorine and other halogen-containing gases that form as by-products in thecombustion chamber 1. The separated halogen-containing gases are sent to a scrubber. The agglomerated silica then passes throughrotary valves 5 and is collected in ahopper 6. Agglomerated silica that has been retrieved by thebag filter 4 also is recovered in thehopper 6. - Next, the agglomerated silica passes through a
double damper 7, and is delivered by adiaphragm pump 8 to afluidization vessel 9 for hydrophobization. - The
fluidization vessel 9 is divided into a hydrophobizing section A and a deacidifying section B. In the apparatus depicted in FIG. 1, the hydrophobizing section A and the deacidifying section B communicate in the lower portion of thefluidization vessel 9. Silica hydrophobization is carried out in hydrophobizing section A, and the halogen gas such as chlorine which accompanies the silica from the hydrophobizing section A is removed in the deacidifying section B. Alternatively, hydrophobization and deacidification may be carried out in separate devices. - In the hydrophobizing section A, the silica is fluidized with an inert gas, generally nitrogen (N2), and is treated with a hydrophobizing agent. In the apparatus shown in FIG. 1, the
hydrophobizing agent 10 is sent by apump 11 through avaporizer 12 and to thefluidization vessel 9. Thehydrophobizing agent 10 may be mixed with the silica before the silica enters thefluidization vessel 9. An alternative is to heat fluidizing nitrogen having water entrained thereon, then mix the hydrophobizing agent into the gas stream and introduce the resulting mixture into thefluidization vessel 9. - The silica is hydrophobized at a temperature of preferably 400 to 600° C., and most preferably 450 to 550° C. The flow velocity is preferably from 1 to 6 cm/s, although a velocity within a range of 1.4 to 3 cm/s is especially preferred for achieving a stable fluidized state and holding down the fly-out of silica. Water is used at this point because it has a beneficial effect on hydrophobizing treatment. The
water 14 is fed with apump 15 to the fluidizing inert gas, following which the gas is heated with aheater 13 and introduced to the hydrophobizing section A of thefluidization vessel 9. The amount of water used for hydrophobization is preferably 0.1 to 5 parts by weight, and most preferably 0.5 to 3 parts by weight, per 100 parts by weight of silica. The hydrophobizing agent is an organohalosilane, and most preferably dimethyldichlorosilane. - In the deacidifying section B, the silica is fluidized with an inert gas, typically nitrogen, and subjected to deacidification. Water is typically added to the fluidizing gas so that deacidification can be carried out in a water-containing atmosphere. Preferably, as shown in FIG. 1, the
water 16 is added to the fluidizing gas with apump 17, following which the gas is heated with aheater 13 and introduced to the deacidifying section B. The amount of water added to the fluidizing gas for this purpose is preferably at least 0.1 vol %, and most preferably 0.1 to 1 vol %. In the absence of moisture, the silica may become less flowable, making it necessary to use more fluidizing gas, which in turn results in increased fly-out. This is particularly undesirable from the standpoint of the burden on the bag filter. On the other hand, too much moisture may give rise to such undesirable effects as condensation when the deacidified silica is recovered in arecovery vessel 24 from the deacidifying section B. - The deacidification temperature is preferably 400 to 500° C., and the flow velocity is preferably 1 to 6 cm/s.
- Waste gases from the fluidization vessel9 (including both hydrophobizing section A and deacidifying section B) are sent to a scrubber via a
cyclone 18 and abag filter 19. Silica accompanying the waste gases passes from thecyclone 18 to arotary valve 20 or is trapped by thebag filter 19, then is collected in ahopper 21, following which it is returned to the deacidifying section B via arotary valve 22 and adiaphragm pump 23. The deacidified silica is collected in therecovery vessel 24. - The silica that flew out of the
fluidization vessel 9 together with the waste gases was collected and the physical properties examined. Treatment appeared sufficient in terms of the carbon content, but the pH was 3.7 to 4.1, indicating a need to again deacidify the collected silica. Hence, the silica collected by thecyclone 18 andbag filter 19 are fed by adiaphragm pump 23 to the center of the deacidifying section B of thefluidization vessel 9. Unreacted silane accompanies the waste gases. The condensation of moisture accompanying the waste gases on the walls of the apparatus at temperatures below 100° C. converts the silane into a gel or oil, which obstructs pipelines and in particular clogs the pores of the filter fabric used in thebag filter 19. Accordingly, it is necessary to maintain the interior of the system at a temperature of at least 100° C. In FIG. 1, T1 and T2 are each thermometers which measure the temperature of the waste gases. The temperature readings at T1 and T2 must be at least 100° C., although a higher temperature, such as 130° C. or more, is preferred at the bag filter, both for the gases themselves and also for areas of the bag filter that come into direct contact with the gases. Accordingly, the interior of the exhaust system must be held at a temperature within a range of 100 to 500° C. and, for reasons associated in part with the choice of filter fabric and bag filter, preferably in a range of 130 to 200° C. The formation of gummy or oily deposits on the filter fabric of thebag filter 19 causes the pressure difference to rise, making normal operation difficult. It is thus desirable to install a differential pressure gauge P1 on thebag filter 19 to monitor changes in the pressure difference. The production apparatus shown in FIG. 1 is also provided with aheat insulator 28 and asteam tracer 29 to keep the temperature from falling. - The properties of the hydrophobic silica produced by the treatment method and apparatus of the invention are not subject to any particular limitation, although a specific surface area of about 110 m2/g, a carbon content of at least about 0.9 wt %, and a pH of at least 4.5 are preferred. Hydrophobic silica having such properties is highly suitable for use in sealants and related applications.
- The following examples are provided to illustrate the invention, and are not intended to limit the scope thereof.
- The apparatus shown in FIG. 1 was operated continuously for a total of 500 hours. During operation, 50.3 kg/h of methyltrichlorosilane was burned together with hydrogen and air, producing 20.1 kg/h of silica. The resulting silica was subjected to hydrophobizing treatment at a nitrogen feed rate of 30 Nm3/h, a dimethyldichlorosilane feed rate of 2.0 kg/h, and a water feed rate of 0.5 kg/h into section A of the
fluidization vessel 9, and a temperature of 490° C. The flow velocity of silica into section A was 2.0 cm/s. The hydrophobized silica was then deacidified at a nitrogen feed rate of 35 Nm3/h and a water feed rate of 0.2 kg/h to section B of thefluidization vessel 9, a temperature of 480° C., and a flow velocity of about 2.2 cm/s. The treated silica had, on average, a specific surface area of 114 m2/g, a carbon content of 0.97 wt %, and a pH of 4.7. The temperatures of thecyclone 18 and thebag filter 19 were, on average, 150° C. (T1) and 135° C. (T2). The pressure difference P1 at the bag filter was 0.8 kPa at the start of operation, and 1.4 kPa at the end of operation. The combined amount of silica collected by thecyclone 18 and thebag filter 19 on the discharge side of thediaphragm pump 23 during operation was 0.8 kg/h, representing a fly-out ratio of about 4%. Following the end of operation, the scrubber fluid was almost entirely free of suspended silica. Nor was there any gel or oil deposited on the filter fabric of the bag filter. - In another run, using the apparatus shown in FIG. 1, methyltrichlorosilane was burned to form 20 kg/h of silica, and the silica was treated for 6 hours with dimethyldichlorosilane, whereupon an average of 1.4 kg/h of fugitive silica was recovered at the
diaphragm pump 23 outlet. In a further run wherein dimethyldichlorosilane was not supplied and only deacidification was carried out, the amount of fugitive silica recovered was 0.07 kg/h. Each of the above runs was carried out several times, whereupon the fly-out ratio was 0.3 to 0.5% without hydrophobization, and increased considerably to 4 to 15% with hydrophobization. - The apparatus shown in FIG. 1 was operated for a period of 7 hours by burning 49.6 kg/h of methyltrichlorosilane together with hydrogen and air, thereby producing 19.8 kg/h of silica. Hydrophobization of the silica was carried out in section A of the
fluidization vessel 9 in the same manner as in Example 1. Deacidification was carried out in section B of the fluidization vessel B without feeding water and at a nitrogen feed rate of 45 Nm3/h, a temperature of 480° C., and a flow velocity of about 2.8 cm/s. The treated silica had a specific surface area of 114 m2/g, a carbon content of 0.95 wt %, and a pH of 4.6. The amount of silica collected on the discharge side of thediaphragm pump 23 was 2.4 kg/h. Hence, the fly-out ratio was about 12%. - The apparatus shown in FIG. 1 was operated for a period of 7 hours by burning 50.4 kg/h of methyltrichlorosilane with hydrogen and air, thereby producing 20.1 kg/h of silica. Treatment in section A was the same as in Example 1. Aside from feeding 2.0 kg/h of water to section B, treatment in section B was also carried out as in Example 1. The treated silica had a specific surface area of 108 m2/g, a carbon content of 0.95 wt %, and a pH of 4.8. The amount of silica collected on the discharge side of the
diaphragm pump 23 was 1.2 kg/h, indicating a fly-out ratio of about 6%. Condensation was observed in thesilica recovery vessel 24 on the outlet side of thefluidization vessel 9. - The apparatus shown in FIG. 2 was used. Referring to FIG. 2, the apparatus included
fluidization vessels hydrophobizing agent container 33, a constant-temperature vessel 34,water tanks bag filter 39, aheater 40 and aheat insulator 42. Other parts serving the same purposes as parts in FIG. 1 are designated by the same reference numerals. The apparatus also includes thermometers T51, T52 and T53, and a differential pressure gauge P51. - About 3 kg/h of methyltrichlorosilane was burned with hydrogen and air, yielding about 1.2 kg/h of silica. Hydrophobization was carried out at a temperature of 500° C. in
fluidization vessels fluidization vessel 31 of 0.03 kg/h, and a water feed rate to thefluidization vessel 32 of 1 part by volume per 100 parts by volume of the fluidizing gas. The flow velocity was about 2.7 cm/s. The treated silica had a specific surface area of 115 m2/g, a carbon content of 0.92 wt %, and a pH of 4.5. The average temperatures were 110° C. at T51, 90° C. at T52, and 75° C. at T53. The reading on the differential pressure gauge P51 at the bag filter was 0.7 kPa at the start of operation. However, this rose to 2.8 kPa, and so operation was stopped after a total of 40 hours. After the end of operation, the filter fabric at the bag filter had an oily and tacky feel. No oil or gel deposits were found on the walls of the pipeline at T51, but considerable deposits were noted at T52. - As demonstrated in the foregoing examples, the inventive method and apparatus use a cyclone and a bag filter to recover silica that flies out of the fluidization vessel. Under simple controlled conditions that involve holding these devices at temperatures of at least 100° C., essentially 100% of the fugitive silica can be recovered, resulting in increased yield of the product and reducing the burden on waste gas treatment.
- Japanese Patent Application No. 2000-262219 is incorporated herein by reference.
- Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.
Claims (1)
1. An apparatus for producing hydrophobic silica fine powder, comprising:
a means for pyrolyzing a silane compound to form silica fine powder,
a means for agglomerating the silica fine powder,
a first cyclone and a first filter for collecting the agglomerated silica fine powder,
a fluidization vessel having a hydrophobizing section for hydrophobizing the collected silica fine power, and
a second cyclone and a second filter for collecting hydrophobic silica fine powder which flies out of the fluidization vessel, which second cyclone and second filter can each be held at a temperature of 100 to 500° C.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/797,037 US20040241056A1 (en) | 2000-08-31 | 2004-03-11 | Method and apparatus for producing hydrophobic silica fine powder |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2000262219A JP3685250B2 (en) | 2000-08-31 | 2000-08-31 | Method and apparatus for producing hydrophobic silicon dioxide fine powder |
JP2000-262219 | 2000-08-31 | ||
US09/941,742 US6749823B2 (en) | 2000-08-31 | 2001-08-30 | Method for producing hydrophobic silica fine powder |
US10/797,037 US20040241056A1 (en) | 2000-08-31 | 2004-03-11 | Method and apparatus for producing hydrophobic silica fine powder |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/941,742 Division US6749823B2 (en) | 2000-08-31 | 2001-08-30 | Method for producing hydrophobic silica fine powder |
Publications (1)
Publication Number | Publication Date |
---|---|
US20040241056A1 true US20040241056A1 (en) | 2004-12-02 |
Family
ID=18749935
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/941,742 Expired - Fee Related US6749823B2 (en) | 2000-08-31 | 2001-08-30 | Method for producing hydrophobic silica fine powder |
US10/797,037 Abandoned US20040241056A1 (en) | 2000-08-31 | 2004-03-11 | Method and apparatus for producing hydrophobic silica fine powder |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/941,742 Expired - Fee Related US6749823B2 (en) | 2000-08-31 | 2001-08-30 | Method for producing hydrophobic silica fine powder |
Country Status (4)
Country | Link |
---|---|
US (2) | US6749823B2 (en) |
EP (1) | EP1184424B1 (en) |
JP (1) | JP3685250B2 (en) |
DE (1) | DE60100977T2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060067868A1 (en) * | 2004-09-30 | 2006-03-30 | Kutsovsky Yakov E | Metal and oxides thereof and methods to make same |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7052541B2 (en) * | 2002-06-19 | 2006-05-30 | Board Of Regents, The University Of Texas System | Color compositions |
JP4968569B2 (en) * | 2002-12-27 | 2012-07-04 | 日本アエロジル株式会社 | Highly dispersible hydrophobic silica fine powder and production method thereof |
US7425235B2 (en) * | 2005-02-11 | 2008-09-16 | The Board Of Regents Of The University Of Texas System | Color compositions and methods of manufacture |
US20070033747A1 (en) * | 2005-06-17 | 2007-02-15 | The Board Of Regents Of The University Of Texas System | Organic/Inorganic Lewis Acid Composite Materials |
JP5003310B2 (en) * | 2006-06-30 | 2012-08-15 | 住友化学株式会社 | Surface hydrophobized metal oxide powder and method for producing the same |
CN100431955C (en) * | 2006-09-04 | 2008-11-12 | 上海氯碱化工股份有限公司 | Apparatus and method of synthesizing acidic material on SiO2 surface by eliminating gas phase method |
CN102530962B (en) * | 2010-12-10 | 2015-06-03 | 中国科学院过程工程研究所 | Method for synthesizing hydrophobic nanometer silicon dioxide particle through combustion method |
DE102012203826A1 (en) * | 2012-03-12 | 2013-09-12 | Wacker Chemie Ag | Process for the surface modification of particulate solids |
CN103466636B (en) * | 2013-08-27 | 2016-08-17 | 合盛硅业股份有限公司 | A kind of system utilizing methyl trichlorosilane to produce fume colloidal silica |
CN108394910B (en) * | 2018-05-15 | 2020-02-14 | 湖北兴瑞硅材料有限公司 | Method for mixing raw materials for producing fumed silica |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3924029A (en) * | 1962-03-30 | 1975-12-02 | Degussa | Method of modifying the surface properties of finely divided metal oxides |
US4503092A (en) * | 1982-03-27 | 1985-03-05 | Degussa Aktiengesellschaft | Process for the hydrophobization of pyrogenically produced silica |
US5372795A (en) * | 1992-12-03 | 1994-12-13 | Wacker-Chemie Gmbh | Process for hydrophobicizing of pyrogenic silica |
US5458916A (en) * | 1992-07-02 | 1995-10-17 | Wacker-Chemie Gmbh | Hydrophobicization of pyrogenic silica |
US6103004A (en) * | 1995-04-26 | 2000-08-15 | Grace Gmbh | Matting agent based on aggregated silica |
US20020155256A1 (en) * | 1998-10-14 | 2002-10-24 | Tetsuji Ohta | Ink jet recording materials |
-
2000
- 2000-08-31 JP JP2000262219A patent/JP3685250B2/en not_active Expired - Fee Related
-
2001
- 2001-08-30 US US09/941,742 patent/US6749823B2/en not_active Expired - Fee Related
- 2001-08-31 EP EP01307400A patent/EP1184424B1/en not_active Expired - Lifetime
- 2001-08-31 DE DE60100977T patent/DE60100977T2/en not_active Expired - Lifetime
-
2004
- 2004-03-11 US US10/797,037 patent/US20040241056A1/en not_active Abandoned
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3924029A (en) * | 1962-03-30 | 1975-12-02 | Degussa | Method of modifying the surface properties of finely divided metal oxides |
US4503092A (en) * | 1982-03-27 | 1985-03-05 | Degussa Aktiengesellschaft | Process for the hydrophobization of pyrogenically produced silica |
US5458916A (en) * | 1992-07-02 | 1995-10-17 | Wacker-Chemie Gmbh | Hydrophobicization of pyrogenic silica |
US5372795A (en) * | 1992-12-03 | 1994-12-13 | Wacker-Chemie Gmbh | Process for hydrophobicizing of pyrogenic silica |
US6103004A (en) * | 1995-04-26 | 2000-08-15 | Grace Gmbh | Matting agent based on aggregated silica |
US20020155256A1 (en) * | 1998-10-14 | 2002-10-24 | Tetsuji Ohta | Ink jet recording materials |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060067868A1 (en) * | 2004-09-30 | 2006-03-30 | Kutsovsky Yakov E | Metal and oxides thereof and methods to make same |
US7892643B2 (en) | 2004-09-30 | 2011-02-22 | Cabot Corporation | Metal and oxides thereof and methods to make same |
Also Published As
Publication number | Publication date |
---|---|
US6749823B2 (en) | 2004-06-15 |
US20020025289A1 (en) | 2002-02-28 |
EP1184424B1 (en) | 2003-10-15 |
EP1184424A1 (en) | 2002-03-06 |
JP2002068726A (en) | 2002-03-08 |
JP3685250B2 (en) | 2005-08-17 |
DE60100977T2 (en) | 2004-08-12 |
DE60100977D1 (en) | 2003-11-20 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6696034B2 (en) | Method for producing hydrophobic silica fine powder | |
US6749823B2 (en) | Method for producing hydrophobic silica fine powder | |
KR101302646B1 (en) | Process for Producing Hydrophobic Silica Powder | |
JPH0624729A (en) | Method of making pyrolysis silica hydrophobic | |
US4503092A (en) | Process for the hydrophobization of pyrogenically produced silica | |
WO2001081480A3 (en) | Process for making durable titanium dioxide pigment by vapor phase deposition | |
US3924029A (en) | Method of modifying the surface properties of finely divided metal oxides | |
US5855860A (en) | Method for porifying fine particulate silica | |
CA2363701A1 (en) | High-structure precipitated silicas | |
JP2003165718A (en) | Non-porous spherical silica and method for producing the same | |
US4022152A (en) | Apparatus for making particulate materials, particularly oxides, hydrophobic | |
NL7908270A (en) | PROCESS FOR THE CONTROLLED PREPARATION OF DOMICLIC ACID USING FLAME HYDROLYSIS. | |
JPH06206720A (en) | Method of producing hydrophobic silica by thermal decomposition process | |
JPH01230421A (en) | Porous spherical silica fine particle | |
US4007050A (en) | Hydrophobic oxides of metals and for metalloids | |
US4036933A (en) | Highly-active, finely divided super-dry silicon dioxide | |
EP0727389B1 (en) | Method of recovering particulate silicon from a by-product stream | |
CN101100300A (en) | Precipitated silicas with special surface properties | |
JP3841143B2 (en) | Method for producing hydrophobic silica fine powder | |
US4147760A (en) | Thickening agent for liquid media consisting of highly dispersed silicon dioxide and process for making the same | |
JP3767672B2 (en) | Method for producing hydrophobic silicon dioxide fine powder | |
CN103482573B (en) | Method and device for drying hydrogen chloride gas in polysilicon production | |
JP2000191317A (en) | Production of fused spherical silica | |
JP2004250247A (en) | Alkali-resistant chemically modified silica gel | |
US4524189A (en) | Preparation of chlorinated polyolefins |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |