Title of Invention	PROCESS FOR COVERING SILICAS WITH WAX
Abstract	The present invention relates to a process for producing a wax covered silica comprising the step coating at least a portion of a surface of at least one silica particle with at least one wax wherein said coating is carried out in a milling chamber with at least one gas at a temperature above the melting point of said wax, while spraying a gas heated to a temperature of from 60 to 160°C into the milling chamber wherein the temperature of the gas at an outlet of the milling chamber is from 40 to 140° C, to obtain at least one wax-coated silica particle.

Title of Invention

PROCESS FOR COVERING SILICAS WITH WAX

Abstract

The present invention relates to a process for producing a wax covered silica comprising the step coating at least a portion of a surface of at least one silica particle with at least one wax wherein said coating is carried out in a milling chamber with at least one gas at a temperature above the melting point of said wax, while spraying a gas heated to a temperature of from 60 to 160°C into the milling chamber wherein the temperature of the gas at an outlet of the milling chamber is from 40 to 140° C, to obtain at least one wax-coated silica particle.

Full Text	The present invention relates to a process for covering silicas with wax and the use of such silicas. Matting agents for coatings based on wax-impregnated silicas are known and described in DE 10 06 100, DE 15 92 865 and EP 0 922 691, for example. In this case, a wax emulsion is converted with a silica suspension, and, if required, a dispersing agent. The impregnated or covered silica thus obtained must then be dried at some expense and also often still contains the dispersing agent. In addition, binding the wax to the silica is inadequate for many applications. Another process for coating silica with wax is described in EP 0 442 325. Here, the silica is first impregnated with a polyol, facilitating binding of the hydrophobic wax to the hydrophilic silica. Coatings containing the impregnated silica according to EP 0 442 325 exhibit an undesirably high viscosity. Comparative examples in EP 0 442 325 indicate that silicas not coated with wax or coated with wax without the addition of polyol considerably reduce the viscosity of a coating. This is presumably due to the excessively hydrophilic surface of the silica particles compared to the hydrophobic coatings. In order to counteract this effect, a polyol must be added, thus constituting an additional process step. A thermal process as disclosed in DE 10 06 100 is known for processing silica gels or silica sols. In this case silica hydrogels are first manufactured, dried and activated in a further step. The dried gel is activated by heating it to around 468 - 538°C and then converted with a molten, microcrystalline wax at 371 °C, wherein 15 - 30% by weight of wax, relative to the hydrosoi, is used. The very fine hydrosol particles exhibit a mesh-type gel structure with a very large water concentration and can therefore only be covered satisfactorily at the above-described high temperatures or high wax concentrations. The high thermal load prohibits the use of many waxes (change in color); furthermore, a rapid cooling of the silica gel thus covered with wax to below the decomposition temperature of the wax must be ensured. Covering of silicas is not described in DE 10 06 100. Silicas and silica gels exhibit different structures on account of the different manufacturing processes. Silicas are manufactured by basic precipitation and exhibit an open particle structure. Water can be removed easily from these open-pored particles. In contrast, silica gels are obtained by acidic precipitation and have a rather closed structure from which water cannot be removed with ease. The aim of the present invention was therefore to provide a process for covering silicas with wax, which makes for easy handling and enables good sedimentation stability and dispersibility of the silicas, in coatings, for example, with minimal use of wax. The object of the present invention is therefore a process for covering silica with wax, wherein such covering is carried out at a temperature above the melting range and below the decomposition temperature of the wax in air. Covering of the silica is preferably performed simultaneously with pulverizing, for instance in an impact mill. In any case, it is appropriate to mix the constituents wax and silica prior to the covering step in a suitable mixing apparatus, such as an Eirich mixer. The melting and decomposition ranges of the waxes employed in the process according to the present invention are between 40 and 250°C, preferably between 60 and 200°C, and particularly preferably between 70 and 130°C. The process according to the present invention is preferably carried out at these temperatures. The process can be carried out with suitably pre-heated air or heated inert gases. Suitable silicas are the precipitated silicas described in the examples. However, corresponding Aerosil grades are also suitable. In the process according to the present invention polyethylene (PE) waxes, Fischer-Tropsch waxes or silicone-based waxes can be used for covering purposes. Covering silica with 2 to 15% by weight of wax, preferably 5 to 10% by weight, relative to the silica, has proved itself in practice. The silicas covered according to the present invention can be utilized as matting agents for coatings such as alkyd resin or other stoving paints. General Process Description Precipitated silica and a coating agent (wax) in a ratio of 3 to 15% by weight are mixed together homogeneously in a mixing apparatus, such as an Eirich mixer. This mixture is milled and classified in a classifier mill (e.g. 50 ZPS or similar) or a jet mill. The milling chamber is heated during milling by spraying in heated air (60 - 160°C), in such a way that at the mill outlet the air still has a temperature of 40 - 140°C. The product is separated off by a filter or cyclone separator. The product covered with the coating agent exhibits a carbon content of 2 to 18% by weight, preferably 3 to 10% by weight, particularly preferably 3 to 6% by weight. The particle fraction can be adjusted by subsequent classification. Embodiments Example 1 Data of the silicas used and of the coating agent used. The precipitated silica from Table 1 is mixed with 6% by weight of PE wax, as in Table 1. In a variation of the process parameters such as classifier speed and milling speed or milling air, the mixture is milled in a Zirkoplex classifier mill 50 ZPS, manufactured by Alpine, at 120°C exit temperature of the milling air, measured at the mill outlet. The test parameters, the physicochemical data and the coating-technical results obtained in a black stoving paint are itemized in Table 2. Example 2 - Varvinq the silica and the coating temperature A precipitated silica, e.g., Sipernat 50, is intimately mixed with a PE wax, e.g., AF 30 (from BASF), in a ratio of 6 parts wax to 94 parts silica. This mixture is fed into an impact classifier mill (ZPS 50). During milling, the impact classifier mill is operated with preheated milling air. The exit temperature of the milling air from the mill is varied. The milling settings (rotary speed of classifier wheel and mill) are not critical for the coating of the silica with wax but are selected so that the product has a distribution suitable for the desired flatting efficiency. Parameters of the silica used BET surface area [m2/g] 450 Mean particle size [\|jm] 27 (instrument: Coulter LS 230) Tapped density [g/1] 180 (unsieved) Loss on drying [%] 6.0 (2h at 105°C) Loss on ignition [%] 5.0 (2h at 1000°C) pH 6.0 (5% in water) DBP absorption [g/100 g] 335.0 Example 3 - Varying the wax and/or its softening temperature The experiment is conducted as described in example 1. Waxes having a softening point lower than that used in example 1 are employed. About 40 g of flatted paint is introduced into glass bottles, which are screwed shut. The samples are stored in a drying cabinet at 50 ± 2°C for 10 d. For assessment, the glass bottles are cooled to room temperature. To test the nature of the sediment, the glass bottles are inverted and the running of the phase containing flatting agent is observed. Subsequently, the glass bottles are shaken twice by hand. Where sediment is not observed, the base of the bottle is scratched with a needle. By this means, even paper-thin unwanted deposits are detected. The nature of the sediment is rated as follows: Rating Assessment 1 no separation of paint and flatting agent 2 fairly loose sediment (The sediment runs completely from the base and can be dispersed by inverting the bottle once or twice.) 3 soft sediment (The sediment does not run completely from the base but can be dispersed by shaking a number of times.) 4 soft sediment, difficult to reagitate (The sediment is still soft but has already agglomerated to such an extent that it can no longer be adequately dispersed by shaking.) 5 solid sediment. Wax detachment 1 g of flatting agent and 35 g of ethoxypropyl acetate are weighed out into a 50 ml wide-necked screw-top flask. The cover is closed and the bottle is shaken by hand. The bottle is conditioned at 50°C overnight. If, under these conditions, wax becomes detached from the flatting agent, it floats on the solvent and the flatting agent settles on the base. Where there is no wax detachment, there is only a sediment of flatting agent on the base. The examples show that the coating of the invention must be carried out at above the melting range of the wax. The terms "melting range" and "softening point" are used synonymously here. WE CLAIM: 1. A process for producing a wax covered silica, comprising the step of coating at least a portion of a surface of at least one silica particle with at least one wax, wherein said coating is carried out in a milling chamber with at least one gas at a temperature above the melting point of said wax, while spraying a gas heated to a temperature of from 60 to 160oC into the milling chamber, wherein the temperature of the gas at an outlet of the milling chamber is from 40 to 140^ C, to obtain at least one wax-coated silica particle. 2. The process as claimed in claim 1, wherein said gas is selected from the group consisting of air, and inert gas. 3. The process as claimed in claim 1, comprising milling said silica particle. 4. The process as claimed in claim 3, wherein the milling is carried out simultaneously with the coating. 5. The process as claimed in claim 3, wherein the milling is carried out prior to the coating. 6. The process as claimed in claim 1, wherein the temperature ranges from 40 to 200' C. 7. The process as claimed in claim 1, wherein said silica particle is coated with 2 to 15% by weight of wax, relative to the weight of the silica particle. 8. The process as claimed in claim 1, wherein said wax, is selected from the group consisting of polyethylene waxes, Fischer-Tropsch Waxes or silicone based waxes. 9. The process as claimed in claim 1, comprises classifying said silica particle. 10. The process as claimed in claim 1, comprises classifying said wax-coated silica particle. 11. The process as claimed in claim 1, wherein said silica is selected from the group consisting of precipitated silica and pyrogenic silica. 12. The process as claimed in claim 1, wherein prior to said coating, said silica particle is dried. f 13. The process as claimed in claim 1, comprises contacting said wax-coated silica particle with a coating composition. 14. A wax-coated silica particle, produced by the process as claimed in claim 1. 15. A matting agent, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1. 16. A coating composition, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1. 17. An alkyl resin, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1. 18. A stoving paint, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1. 19. The process as claimed in claim 1, wherein the wax has a melting point of64°C to ll2°C. 20. The process as claimed in claim 1, wherein the wax has a melting point of from 64°C to 86°C. 21. The wax-coated silica particles as claimed in claim 14, wherein the wax- coated silica particle does not detach the wax when kept at 50°C in ethoxypropylacetate. 22. The process as claimed in claim 19, wherein the coating is carried out at a temperature of from 40° C to 120°C. 23. The process as claimed in claim 19, wherein the coating is carried out at a temperature of from 40° C to 100°C. 24. The process as claimed in claim 19, wherein the coating is carried out at a temperature of from 40 to 80° C. 25. The process as claimed in claim 1, wherein the coating is carried out with a single wax. 26. The process as claimed in claim 1, wherein the wax has a melting point of from 64°C to ll8°C.

Full Text

The present invention relates to a process for covering silicas with wax and the use of such silicas.
Matting agents for coatings based on wax-impregnated silicas are known and described in DE 10 06 100, DE 15 92 865 and EP 0 922 691, for example. In this case, a wax emulsion is converted with a silica suspension, and, if required, a dispersing agent. The impregnated or covered silica thus obtained must then be dried at some expense and also often still contains the dispersing agent. In addition, binding the wax to the silica is inadequate for many applications.
Another process for coating silica with wax is described in EP 0 442 325. Here, the silica is first impregnated with a polyol, facilitating binding of the hydrophobic wax to the hydrophilic silica. Coatings containing the impregnated silica according to EP 0 442 325 exhibit an undesirably high viscosity. Comparative examples in EP 0 442 325 indicate that silicas not coated with wax or coated with wax without the addition of polyol considerably reduce the viscosity of a coating. This is presumably due to the excessively hydrophilic surface of the silica particles compared to the hydrophobic coatings. In order to counteract this effect, a polyol must be added, thus constituting an additional process step.
A thermal process as disclosed in DE 10 06 100 is known for processing silica gels or silica sols. In this case silica hydrogels are first manufactured, dried and activated in a further step. The dried gel is activated by heating it to around 468 - 538°C and then converted with a molten, microcrystalline wax at 371 °C, wherein 15 - 30% by weight of wax, relative to the hydrosoi, is used. The very fine hydrosol particles exhibit a mesh-type gel structure with a very large water concentration and can therefore only be covered satisfactorily at the above-described high temperatures or high wax concentrations. The high thermal load prohibits the use of many waxes (change in color); furthermore, a rapid cooling of the silica gel thus covered with wax to below the decomposition temperature of the wax must be ensured.
Covering of silicas is not described in DE 10 06 100.
Silicas and silica gels exhibit different structures on account of the different manufacturing processes. Silicas are manufactured by basic precipitation and exhibit an open particle structure. Water can be removed easily from these open-pored particles. In contrast, silica

gels are obtained by acidic precipitation and have a rather closed structure from which water cannot be removed with ease.
The aim of the present invention was therefore to provide a process for covering silicas with wax, which makes for easy handling and enables good sedimentation stability and dispersibility of the silicas, in coatings, for example, with minimal use of wax.
The object of the present invention is therefore a process for covering silica with wax, wherein such covering is carried out at a temperature above the melting range and below the decomposition temperature of the wax in air.
Covering of the silica is preferably performed simultaneously with pulverizing, for instance in an impact mill. In any case, it is appropriate to mix the constituents wax and silica prior to the covering step in a suitable mixing apparatus, such as an Eirich mixer.
The melting and decomposition ranges of the waxes employed in the process according to the present invention are between 40 and 250°C, preferably between 60 and 200°C, and particularly preferably between 70 and 130°C. The process according to the present invention is preferably carried out at these temperatures. The process can be carried out with suitably pre-heated air or heated inert gases.
Suitable silicas are the precipitated silicas described in the examples. However, corresponding Aerosil grades are also suitable. In the process according to the present invention polyethylene (PE) waxes, Fischer-Tropsch waxes or silicone-based waxes can be used for covering purposes. Covering silica with 2 to 15% by weight of wax, preferably 5 to 10% by weight, relative to the silica, has proved itself in practice.
The silicas covered according to the present invention can be utilized as matting agents for coatings such as alkyd resin or other stoving paints.
General Process Description
Precipitated silica and a coating agent (wax) in a ratio of 3 to 15% by weight are mixed together homogeneously in a mixing apparatus, such as an Eirich mixer. This mixture is milled and classified in a classifier mill (e.g. 50 ZPS or similar) or a jet mill. The milling chamber is heated during milling by spraying in heated air (60 - 160°C), in such a way that at the mill outlet the air still has a temperature of 40 - 140°C. The product is separated off by a

filter or cyclone separator. The product covered with the coating agent exhibits a carbon content of 2 to 18% by weight, preferably 3 to 10% by weight, particularly preferably 3 to 6% by weight. The particle fraction can be adjusted by subsequent classification.
Embodiments Example 1
Data of the silicas used and of the coating agent used.

The precipitated silica from Table 1 is mixed with 6% by weight of PE wax, as in Table 1. In a variation of the process parameters such as classifier speed and milling speed or milling air, the mixture is milled in a Zirkoplex classifier mill 50 ZPS, manufactured by Alpine, at 120°C exit temperature of the milling air, measured at the mill outlet. The test parameters, the physicochemical data and the coating-technical results obtained in a black stoving paint are itemized in Table 2.

Example 2 - Varvinq the silica and the coating temperature
A precipitated silica, e.g., Sipernat 50, is intimately mixed with a PE wax, e.g., AF 30 (from BASF), in a ratio of 6 parts wax to 94 parts silica. This mixture is fed into an impact classifier mill (ZPS 50). During milling, the impact classifier mill is operated with preheated milling air. The exit temperature of the milling air from the mill is varied. The milling settings (rotary

speed of classifier wheel and mill) are not critical for the coating of the silica with wax but are selected so that the product has a distribution suitable for the desired flatting efficiency. Parameters of the silica used
BET surface area [m2/g] 450
Mean particle size [|jm] 27 (instrument: Coulter LS 230)
Tapped density [g/1] 180 (unsieved)
Loss on drying [%] 6.0 (2h at 105°C)
Loss on ignition [%] 5.0 (2h at 1000°C)
pH 6.0 (5% in water)
DBP absorption [g/100 g] 335.0

Example 3 - Varying the wax and/or its softening temperature
The experiment is conducted as described in example 1. Waxes having a softening point
lower than that used in example 1 are employed.

About 40 g of flatted paint is introduced into glass bottles, which are screwed shut. The
samples are stored in a drying cabinet at 50 ± 2°C for 10 d.
For assessment, the glass bottles are cooled to room temperature.
To test the nature of the sediment, the glass bottles are inverted and the running of the
phase containing flatting agent is observed.
Subsequently, the glass bottles are shaken twice by hand. Where sediment is not observed,
the base of the bottle is scratched with a needle. By this means, even paper-thin unwanted
deposits are detected.
The nature of the sediment is rated as follows:
Rating Assessment
1 no separation of paint and flatting agent
2 fairly loose sediment (The sediment runs completely from the
base and can be dispersed by inverting the bottle once or twice.)
3 soft sediment (The sediment does not run completely from the
base but can be dispersed by shaking a number of times.)
4 soft sediment, difficult to reagitate (The sediment is still soft but
has already agglomerated to such an extent that it can no longer be adequately dispersed by shaking.)
5 solid sediment.
Wax detachment
1 g of flatting agent and 35 g of ethoxypropyl acetate are weighed out into a 50 ml wide-necked screw-top flask. The cover is closed and the bottle is shaken by hand. The bottle is conditioned at 50°C overnight.
If, under these conditions, wax becomes detached from the flatting agent, it floats on the solvent and the flatting agent settles on the base. Where there is no wax detachment, there is only a sediment of flatting agent on the base.
The examples show that the coating of the invention must be carried out at above the melting range of the wax. The terms "melting range" and "softening point" are used synonymously here.

WE CLAIM:
1. A process for producing a wax covered silica, comprising the step of coating at least a portion of a surface of at least one silica particle with at least one wax, wherein said coating is carried out in a milling chamber with at least one gas at a temperature above the melting point of said wax, while spraying a gas heated to a temperature of from 60 to 160oC into the milling chamber, wherein the temperature of the gas at an outlet of the milling chamber is from 40 to 140^ C, to obtain at least one wax-coated silica particle.
2. The process as claimed in claim 1, wherein said gas is selected from the group consisting of air, and inert gas.
3. The process as claimed in claim 1, comprising milling said silica particle.
4. The process as claimed in claim 3, wherein the milling is carried out simultaneously with the coating.
5. The process as claimed in claim 3, wherein the milling is carried out prior to the coating.

6. The process as claimed in claim 1, wherein the temperature ranges from 40 to 200' C.
7. The process as claimed in claim 1, wherein said silica particle is coated with 2 to 15% by weight of wax, relative to the weight of the silica particle.
8. The process as claimed in claim 1, wherein said wax, is selected from the group consisting of polyethylene waxes, Fischer-Tropsch Waxes or silicone based waxes.
9. The process as claimed in claim 1, comprises classifying said silica particle.
10. The process as claimed in claim 1, comprises classifying said wax-coated silica particle.
11. The process as claimed in claim 1, wherein said silica is selected from the group consisting of precipitated silica and pyrogenic silica.
12. The process as claimed in claim 1, wherein prior to said coating, said silica particle is dried.

f
13. The process as claimed in claim 1, comprises contacting said wax-coated silica particle with a coating composition.
14. A wax-coated silica particle, produced by the process as claimed in claim 1.
15. A matting agent, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1.
16. A coating composition, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1.
17. An alkyl resin, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1.
18. A stoving paint, comprising at least one wax-coated silica particle produced by the process as claimed in claim 1.
19. The process as claimed in claim 1, wherein the wax has a melting point of64°C to ll2°C.
20. The process as claimed in claim 1, wherein the wax has a melting point of from 64°C to 86°C.

21. The wax-coated silica particles as claimed in claim 14, wherein the wax-
coated silica particle does not detach the wax when kept at 50°C in
ethoxypropylacetate.
22. The process as claimed in claim 19, wherein the coating is carried out at a temperature of from 40° C to 120°C.
23. The process as claimed in claim 19, wherein the coating is carried out at a temperature of from 40° C to 100°C.
24. The process as claimed in claim 19, wherein the coating is carried out at a temperature of from 40 to 80° C.
25. The process as claimed in claim 1, wherein the coating is carried out
with a single wax.
26. The process as claimed in claim 1, wherein the wax has a melting point
of from 64°C to ll8°C.

Documents:

0689-mas-2001 abstract-duplicate.pdf

0689-mas-2001 claims-duplicate.pdf

0689-mas-2001 description (complete)-duplicate.pdf

689-mas-2001-abstract.pdf

689-mas-2001-claims.pdf

689-mas-2001-correspondnece-others.pdf

689-mas-2001-correspondnece-po.pdf

689-mas-2001-description(complete).pdf

689-mas-2001-form 1.pdf

689-mas-2001-form 26.pdf

689-mas-2001-form 3.pdf

689-mas-2001-form 5.pdf

689-mas-2001-other documents.pdf

« Previous Patent

Next Patent »

Patent Number

222492

Indian Patent Application Number

689/MAS/2001

PG Journal Number

47/2008

Publication Date

21-Nov-2008

Grant Date

14-Aug-2008

Date of Filing

21-Aug-2001

Name of Patentee

DEGUSSA AG

Applicant Address

BENNINGSENPLATZ 1, D-40474 DUSSELDORF,

Inventors:

#	Inventor's Name	Inventor's Address
1	JURGEN SCHUBERT	GARTENSTRASSE 11, 53343 WATCHBERG,
2	KLAUS -DIETER HELLWIG	HUBERSTRASSE 13, 53604 BAD HONNEF,
3	MICHAEL PICKEL	TAUNSSTRASSE 2, 53859 NIEDERKASSEL,
4	HANS-DIETER PUTZ	BRANDENBURGER STRASSE 42, 50129 BERGHEIM,

PCT International Classification Number

C09D191/06

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	101 22 861.9	2001-05-11	Germany
2	100 41 465.6	2000-08-23	Germany