CA1071076A

CA1071076A - Silane coated silicate minerals and method for preparing same

Info

Publication number: CA1071076A
Application number: CA236,799A
Authority: CA
Inventors: Thomas E. Sample (Jr.); John M. Horn
Original assignee: Dresser Industries Inc
Current assignee: Dresser Industries Inc
Priority date: 1974-10-11
Filing date: 1975-10-01
Publication date: 1980-02-05
Also published as: IT1047816B; FR2287428B3; AU501263B2; BR7506647A; AU8564275A; ZA756203B; GB1533262A; FR2287428A1; JPS5163381A; DE2546061A1; DE2546061C2; NL7511799A

Abstract

Abstract of the Disclosure Phyllosilicate minerals and certain fibrous amphiboles which exhibit in their structure, sequentially, octahedral layers containing magnesium, aluminum and/or iron oxides and tetrahedral layers of silica, are superficially leached with dilute acid to remove the outer octahedral layer under controlled conditions which preserve the basic structural integrity of the mineral sub-strate. The acid leach exposes silanol groups on the outer silicate layer of the mineral so that they become available to form silicon-to-oxygen-to-silicon-to-carbon bonds through con-densation with organo-silanes. The condensation of the organo-silane with the conditioned mineral surface 's accomplished by mixing the acid leached silicate mineral with the organo-silane in a suitable solvent system under mild conditions.
The organo-silane may be chosen from either of two classes; those which impart an oleophilic surface to the mineral or those which enable the mineral surface to form additional chemical bonds with reactive sites within certain polymers and prepolymers. The mineral products of this invention which have been treated to possess oleophilic surfaces are superior additives for rheology control in lubricants, polyolefins, paints and oil well drilling fluids, as well as heat and moisture resistant re-inforcing agents for rubbers; while those mineral products treated to possess surfaces chemically reactive with polymers and per-polymers when incorporated in such systems impart to the finished composites improved mechanical properties and heat and moisture resistance.

1a

Description

~o7~0~6 Related Applications None.
Backgrol1nd of the Invention The field of the invention relates to phyllosilicate minerals such as~ for example, the serpentines and micas, and - certain fibrous amphiboles, such as, for example, amosite, crocidolite, attapulgite and actinolite, which exhibit in their structure, sequentially, octahedral layers containing oxides of magnesium, aluminum and/or iron, and tetrahedral layers of silicon and oxygen, which minerals have been modified for the purpose of rendering them oleophilic or imparting to them certain other desirable properties through having been coated by organo-silanes. The invention further relates to a method for condition-ing said minerals to enable same to react on their surfaces with organo-silanes and to methods for effecting coatings on said minerals with organo-silanes.
In the past, it has been recognized that certain phyllo-silicate and fibrous amphibole minerals possess desirable char-- acteristics for use in plastics and elastomer compounding. In such applications, the most important active functions of these materials are reinforcement, improvement of mechanical properties, ! heat resistance and flow control. In addition to the above uses, certain of these minerals have found applications as additives in oil-based fluid systems, such as, for example, lubricants, paints and oil-well drilling fluids for modification of flow properties~
But in such applications, the unmodified minerals suffer the innate limitation of being wet by water in preference to oil so that composites incorporating them generally show impaired per-formance ln the presence of moisture. Further, the unmodified minerals do not ordinarily interact positively with oils, plastics and elastomers forming at best only simple dispersions therein upon physical mixing without any significant chemical ,' ~

1~'7~

bond being ~ormed between the minerals and the continuous phase.
Such dispersions are usually metastable with the mineral tending to segregate from the continuous phase. It has now been dis-covered that by superficially coating the preconditioned surface of these minerals through chemical reaction with organo-silanes the above-noted deficiencies can be overcome.
The technique of conditioning said minerals, to make therein available free hydroxyl (silanol) groups for reaction with organo-silanes, has been reported in the prior art. See French Patent 2,098,467 issued February 14, 1972. In this prior art, the layered minerals which are made up of alternating sheets of magnesia and silica are subJected to the simultaneous ac~ion of organo-silanes in concentrated mineral acid solution. The effect of this solution on the layered mineral is to leach away through the agency of strong acid the magnesia layers, leaving the alternating silica inter-layers exposed for concomitant chemical reaction with the organo-silanes, the process continuing throughout the entire layered mineral system. The procedure re-sults in the elimination of most, if not all, of the magnesia layers leaving the alternating silica layers separated by layers of chemically reacted organo-silane. The reaction is an in-depth ! reaction controlled by the rate of diffusion of the acid and organo-silane into the body of the mineral as evidenced by the required use of a large excess of concentrated acid, long reaction periods and elevated temperatures.
The overall result of these combined reactions is that instead of a superficial acid leach, i.e., removal of the outer octahedral magnesium layer followed by surface reaction of the exposed surface silanol groups with the organo-silane, the re-action described in the prior art proceeds in depth removing mostof the total magnesia (or isomorphically substituted metal) leav-ing an amorphous silica residue. This silica pseudomorph, which lacks cyrstalline structure, is friable and has, of i~self, lit~le or no mechanical strength. According to the prior art, this material is a distinct organo-mineral polymer in contrast with the superficially coated crystalline minerals of the present invention.
Summary of the Invention This invention relates to organo-silane coated phyllo-silicate and amphibole minerals and to methods for producing sa~e.
The products obtained from the practice of this invention may be categorized as falling within two broad end-use classes: Those which possess thermally and chemically stable oleophilic sur-faces; and those which possess surfaces which are capable of`
forming additional chemical bonds with reactive sites within certain plastics and elastomers.
Those phyllosilicate and amphibole minerals which have been rendered oleophilic according to the teachings of this invention, have been found extremely desirable additives for con-trolling the rheology of oil-based fluids used in oil and gas well drilling, as gelling agents in grease and paint formulating, as reinforcing agents for rubber and elastomer compounding~ and as fillers for polyolefin resins and the like.
. I Those phyllosilicate and amphibole minerals whose sur-faces have been rendered, according to the teachings of this in-vention, capable of forming chemical bonds with reactive sites within plastics and elastomers are particularly useful for the improvement of mechanical properties, dimensional and thermal stability, and moisture resistance of finished composites based on phenolic, epoxy, acrylate and vinyl resins, as well as of both sulfur- and peroxide-cured elastomer systems.
~inerals which have been rendered oleophilic, especially chrysotile, have been found to be particularly effective in high temperature environments. Without an oleophilic character, .
, ~071~76 chrysotile, because of its affinity for water, has found only restricted use in oil-thickening applications. As such systems are exposed to elevated temperatures, in the presence of moisture, chrysotile tends to become water-wet and to agglomerate or s~ttle out of the system. By changing the surface characteristic of chrysotile to oleophilic, this material can be effectively used in oil systems to temperatures in excess of 350F. This invention also relates to a method of preparing such surface altered min~rals through a preliminary superficial acid leach of the mineral and subsequent condensation with an organo-silane.
In accordance with the present invention, the mineral is subjected to a superficial acid leach with dilute acid in order to solubilize and remove the outer octahedral layer o mixed magnesium~ aluminum, or iron oxides which is characteris-tically present on the surface of such minerals. This reactionexposes silanol groups on the outer silicate layer so that they are free to form silicon-to-oxygen-to-silicon-to-carbon bonds through condensation with an organo-silane during a subsequent reaction step. The superficial acid leach is carried out with dilute acid, preferably a mineral acid such as hydrochloric or sulphuric acid~ under conditions which maintain the basic structural integrity of the mineral body. In the case of chrysotile, this acid leach is accomplished with dilute acid and under ambient temperature conditions accompanied by mild agitation for periods up to about three hours.
The conditioned mineral is subsequently coated with the desired organo-silane by mixing these constituents together in the presence of a water miscible coupling agent such as isopropyl alcohol. This coating reaction is carried out after arresting the leaching action of the acid as by adding alkali to the slurry obtained by the aforementioned acid leach or by filtering out and washing the acid leached mineral.

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Detailed Description o~ the Invention Minerals: Phyllosilicate and fibrous amphibole miner-als which are suitable for modification in accordance with this lnvention, are selected from a class of sequentially layered minerals characterized by the presence of octahedral layers con-taining magnesium, alu~ninum and/or iron oxides and tetrahedral layers of silica. The preferred mineral is a phyllosilicate denoted as chrysotile, a common form of asbestos. While chrysotile is the preferred st.arting material, fibrous amphibole such as crocidolite, amosite and attapulgite as well as other phyllosilicate minerals such as biotite can be used in this invention.
Silane Modifying Agent: In accordance with this in-vention, phyllosilicates or fibrous amphiboles are modified through reactlon with organo-silanes. These organo-silanes are characterized by one of the two following structures:

,~ .
Structure G - Si - Y
R' - where G is a hydroxyl group or a group hydroxyzable to hydroxyl such as, for example, alkoxy or halogen, Y is an alkyl group con-taining from 1 to 20 carbon atoms, a phenyl group, or an alkyl substituted phenyl group where the alkyl groups can contain a total of from 1 to 12 carbon atoms; R and R' are selected fr~m the groups described by G and Y or hydrogen; or:

Structure II

R
G- Si - Z
R' . .

107107f~

where G is a hydroxyl group or a group hydroxyzable to a hydroxyl such as, for example, alkoxyl or halogen: Z is an alkyl group containing from..l to 20 carbon atoms bearing a functional group such as, for example, amino, oxirane, mercapto or acryloxy, cap-able of forming chemical bonds with reactive sites within poly-mers and prepolymers or an allyl or vinyl groupj R and R' are selected from the groups described by G and Z, hydrogen, an alkyl group containing from 1 to 20 carbon atoms, phenyl, or alkyl sub-stituted phenyl where the alkyl groups can contain a to~al of from 1 to 12 carbon atoms.
In accordance with one preferred embodiment of this in-vention, it is desired to modify chrysotile by imparting oleo-phillic properties to said mineral. It has been observed that this is accomplished most effectively by the use of organo-silanes selected from the class exemplified in Structure I, where-in Y is an alkyl chain of from 2 to 18 carbon atoms. More 1 specifically, methyloctyl diethoxy silane has been found to be a . preferred material for imparting such oleophilicity to the sur-: face of chrysotile fibers. Methyldodecyldiethoxy silane, decyltriethoxy silane, octyltriethoxy silane and heptyltrimethoxy ~ . silane are also desirable agents for imparting oleophilic :~ ~ characteristics.
: ~ Further, in accordance with another embodiment of this invention, it ls desired to modify chrysotile by imparting to ~ 25 said mineral and reactive sites within the structure of certain types of polymers, copolymers, prepolymers, elastomers and resins; for resins of the phenolic epoxy and urethane types, . this is effectively accomplished by coating the mineral accordlng to the teachings of this invention with.organo-silanes of the class exemplifled by Structure II, wherein Z is the 3-aminopropyl group; for polymers, copolymers and elastomers based on isoprene, .' ~071076 butadiene, butadiene-acrylonitrile or ethylene~propylene-diene, for example, this is effectively accomplished by use of organo-silanes of Structure II wherein Z is the 3-mercaptoethyl group;
and for polyolefins such as, for example, those based on ethylene, propylene, isobutylene and the like or polymers based on vinyl derivatives such as, for example, vinyl acetate, methyl methacrylate, vinyl chloride, vinyl ethers and the like, again according to the teachings of this invention, this may be effected by use of organo-silanes selected from Structure II in which Z is the vinyl or allyl group.
Acid Leaching of Minerals Preparatory to Coating:
According to the technique of this invention, the outer octahedral layer of magne~ium, aluminum and/or iron oxides must be eliminated by acid leaching to have available free hydroxyl groups for reaction with alkoxy groups on the silanes.
As a leaching agent, it has been found that a mineral acid such as hydrochloric or sulfuric are among the most suitable, although other acids which form soluble salts of metallic oxides in the outer octahedral layer such as nitric and acetic acids can also be used.
Further, extreme conditions of reaction time and temperature are to be avoided in order to control the leaching so that only the surface layer of magnesium, iron and/or aluminum compounds are removed. Thus, typically 0.3 to 0.5 ; 25 parts of H2S04 acid by weight in about 10 parts of water reacted with one part of chrysotile at a temperature of 60-800F for a period of up to three hours normally produces a suitable superficial leaching to enable a satisfactory bond to be formed between the organo-silane and the mineral surface without appreciably degrading the . .

basic structural integrity o~ the mineral as evidenced by X-ray diffraction pattern comparison of chrysotile before and after such a typical leaching treatment.
The leaching operation may be carried out in conven-tional mixing equipment under moderate agitation. After the sur-face leaching has been affected it is preferred that sodium or potassium hydroxide be added to raise the pH of the reaction mixture to a value in the range of 2-6.5. This is done to retard undesirable further leaching and adjust the pH of the mixture to within a suitable range for subsequent surface reaction with the selected organo-silane.
Reacting the Conditioned Mineral with Silane: Accord-ing to the preferred method of this invention, organo-silane, preferably dissolved in a suitable water miscible solvent, is added with agitation to the pH adjusted aqueous slurry of the surface acid-leached mineral.
The organo-silanes are utilized in quantities of about 0.5%to about 10% based on the weight of the surface conditioned mineral to be treated. In the specific case where the mineral is chrysotile, 3-10% silane may be used to advantage, the optimum amount being about 5%. If excess organo-silane is employed, a portion of the excess may polymerize if the silane contains two or three of the type groups as G in Structure I and II and dimerize if the silane contains one such group. This polymer or dimer may deposit on the surface of the mineral and have a deleterious effect on subsequent performance.
The organo-silanes may be added to the aqueous mineral slurry without dilution. However, particularly in the case where the organo-silane possesses limited water miscibility, it is advantageously added in the form of a solution in a water misclble coupllng agent. Methyl, ethyl and isopropyl alcohols and acetone have been found to be suitable coupling agents which ' , .

~07:1~76 will disperse the silane in water giving a homogenous mixture upon agitation~ in which the silane is available for reaction with the conditioned mineral surface. Normally, about three to six times by weight of coupling agent to organo-silane is employed.
- - The organo-silane is added to ~he aqueous mineral slurry which is typically agitated for a period of about 4-16 hours at about room temperature. It has been found desirable to keep the temperature of this reaction reasonably low in order to minimize self polymerization of the organo-silanes which tends to take place in the presence of water particularly at higher con-centrations and elevated temperatures.
After reaction has been completed, the mineral is separated from the aqueous phase. Organo-silane which may have been added in excess and self-polymerized may be removed if desired by washing with a suitable solvent (such as water, isopropyl alcohol or benzene). The treated mineral is then dried at about 220-250F and pulverized.
According to an alternate method of this invention, the pH adjusted aqueous slurry of the surface acid-leached mineral is '' t separated from the aqueous phase, dried at about 220-250F and pulver-~zed. The pulverized acid-leached mineral is dispersed in a non-aqueous solvent such as methanol or isopropanol or in a ` hydrocarbon solvent such as, for example, heptane or benzene.
The organo-silane is added to the mineral slurry without dilution.
": The mixture is typically agitated at ternperatures up to reflux for a period of about one to eight hours, after which the mineral ~; is separated from the fluid phase. Organo-silane which may have been added in excess and self-polymerized may be removed if desired by washing with a suitable solvent (such as hexane or acetone). The treated mineral is then dried at about 220-250F
and pulverized.

~071076 Example 1. Chrysotile asbestos was treated to possess o:Leophilic surface properties in accordance with the present in-vention as rOllOws: To a dilute solution of sulfuric acid, com-posed of 300 cc of water and 9 g of 98% sulfurlc acid, 25 g of chrysotile, having an average f~ber aspect ratio (length/dlameter) of between about 200 and 1000, was dispersed and agitated on a Hamilton Beach mixer for about 3 hours at ambient temperature (70-75F). To this mixture 10 cc of 50% aqueous NaOH was added to adjust the pH of the mixture to about 6.5. A solution of

2.5 g of methyloctyldiethoxy silane dissolved in 10 cc of methanol was added to the stirred mixture and stirring continued 16 hours at ambient temperature to complete the reaction. The surface reacted chrysotile was separated by filtration, washed with water, and air dried at about 230F for 2 hours. Finally, the dried product was ground for about 20-30 seconds at about 18000 rpm in a Waring blender.
Example 2. Chrysotile asbestos was treated to possess oleophillic surface properties in accordance with the present invention as follows: To a dilute solution of s~lfuric acid, composed of 3000 cc water and 90 g of 98% sulfuric acid, 300 g of chrysotile, having an average fiber aspect ratio (length/diameter) of between 200 and 1000, was dispersed and agitated on a Hamilton Beach mixer for about 3 hours at ambient temperature (70-75F).
To this mixture, 20 cc of 50% aqueous NaOH was added to ad~ust the pH of the mixture to about 6.5. A solution of 30 g of octyltriethoxysilane dissolved in 90 g of isopropanol was added to the stirred mixture with stirring continued 16 hours at ambie-temperatures (70-75F)to complete ~ereaction. The surface reacted chrysotile was separated by filtration, washed with water and air dried at about 230F for 16 hours and was ground for about 20-30 seconds at about 18000 rpm in a Waring blender.

107107~;

Example 3. Chrysotile asbestos was treated to possess o:Leophilic surface properties in accordance with the present in-vention as follows: To a dilute solution of hydrochloric acid, composed of 1600 cc of water and 400 cc of 37% hydrochloric acid, 2t)0 g of chrysotile, having an average fiber aspect ratio (length/diameter) of between 200 and 1000, was dispersed and agitated on a Hamilton Beach mixer for about one-half hour at ambient temperature (70-75F). The surface washed chrysotile was separated by filtration, washed with water and air dried at about 220F for about 16 hours and crushed in a mortar. To 100 cc of heptane, 20 g of the surface washed crushed chrysotile and 2 g of methyldodecyldiethoxysilane were added. The mixture was dispersed and agitated on a magnetic stirrer for six hours at reflux. The surface reacted chrysotile was separated by filtration, washed wlth heptane and air dried at ambient temperature (70-75F) 16 hours and at about 230F for 2 hours.
Example 4. The oleophilic surfaces produced in accordance with the procedures of Examples 1, 2 and 3 were by this reaction verified by dispersing 10 g of the respective reaction products in 350 cc of a mixture of 95 parts diesel oil to 5 parts water by volume. In each case, the product formed a stable dispersion in this medium whereas untreated chrysotile asbestos fibers sub~ected to the same test prodecure became water wet, flocculated and precipitated from the fluid.
Example 5. The oleophi~c surface properties imparted to chrysotile, according to the teachings of this invention, were evaluated as a gelling agent in an oil mud and compared to another type of conventional gelling agent used in such systems. The base mud used for thls evaluation was a 17.3 #/gal oil mud taken from the Superior Oil Company, D.C. McMann #1, Gonzales County, Texas. To prepare this field mud for a laboratory study, the mud was passed through a 60 mesh screen and then heat aged at 375F

' ' : ' .: . - ,- - .

10~1076 rotating for 16 hours. This process thinned the system drastic-ally making it susceptible for treatment with a gelling additive.
The mud was then split into 1 bbl/eq and treated with the additives by shearing at 60 volts for 10 minutes on a Hamilton Beach mixer. Rheological properties were measured at 150F and then the samples were heat a~ed at 375F for 16 hours rotating.
After cooling to room temperature, the samples were sheared for 10 minutes and 60 volts and the rheology remeasured at 150F.
The following is a summary of this testing:
TABLE

Concentration Aging AV PV YP Gel Additive #/bbl (in cps)(in cps)(in #/ Strength 100 (in #~100 ft2) f~ ) tinltial~
10 min.) Blank 0 Immed. 41 37 7 3/4 16 hrs at 375 41 38 6 4/6 Asbestos 6 Immed. 72 65 14 5/lo 16 hrs at 375 lo 85 29 8/16 Asbestos Coated 6 Immed. 148 110 75 2g/36 per Example 1 16 hrs Methyloctyldiethoxysilaneat 375 121 97 47 17/32 Asbestos Coated 6 Immed. 139 106 65 27/37 per Example 2 16 hrs Octyltriethoxysilane at 375 145 114 59 18/29 Organophilic Clay 6 Irnmed. 70 60 20 9/8 of the Bentone 16 hrs Class at 375 47 44 6 ~/7 These data indicate that the silane coated asbestos materials are very effective in gelling oil muds.
Example 6. Chrysotile asbestos was treated to enable 35 the mineral surface to form additional chemical bonds with re-active sites within resins of the phenolic, epoxy and urethane types in accordance with the present invention as follows: To a dilute solution of hydrochloric acid, composed of 2400 cc of water and 600 cc of 37% hydrochloric acid, 300 g of chrysotile, 40 having an average fiber aspect ratio (length/diameter) of between 200 and 1000, was dispersed and agitated on a Hamilton Beach mixer for about one hour at ambient temperature (70-75F).
The surface washed chrysotile was separated by filtration, washed with water and air dried at about 230F for about 16 hours and ground for about 20-30 seconds in a Waring blender at about 18000 rpm. To 100 cc of heptane, 40 g of the surface washed ground chrysotile and 4 g of 3-aminopropyltriethoxysilane were added. The mixture was dispersed and agitated on a magnetic stirrer for four hours at reflux. The surface reacted chrysotile was separated by filtration, washed with heptane and air dried for one-half hour at about 230F.
The fixed nitrogen content of the washed and dried product was determined by the K~eldahl method to be o.38% by weight. A similar analysis performed on the unreacted chrysotile asbestos showed a 0.0% nitrogen content.
Example 7. Chrysotile asbestos was treated to enable the mlneral surface to form additional chemical bonds with re-active sites wlthin resins of the phenolic and epoxy types, in accordance with the present invention as follows: To a dilute solution of hydrochloric acid composed of 500 cc of water and 50 cc of 37% hydrochloric acid, 50 g of chrysotile having an average ~iber aspect ratio (length/diameter) of between about 200 and 1000 was dispersed and then agitated on a Hamilton Beach mixer for about 3 hours at ambient temperature (70-75F). To this mixture 5 cc of 50% aqueous sodlum hydroxide was added to ad~ust the pH of the mixture to about 6.5. ~ solution of 5 g Ofb~eta-3-4-(epoxycyclohexyl)ethyltrimethoxysilane dissolved in 15 cc of isopropyl alcohol was added to the stirred mixture and stirrlng continued 16 hours at ambient temperature to complete the reaction. The surface reacted chrysotile was separated by filtration, washed with water and air dried at about 230F for 16 hours. Finally the dried product was ground for about 30 seconds at about 18000 rpm in a Waring blender.

.. . ........... .

.

The fixed carbon content of the washcd and drled product was determined by the combustion method to be 4.16% by welght.
A simllar analysls performed on the unreacted chrysotile asbestos showed a 0.21% carbon content.
Example 8. Chrysotile asbestos was treated to enable the mineral surface to form additional chemical bonds with re-active sites within resins of the vinyl acetate, methyl methacrylate, vinyl chloride, vinyl ethers and the like, in . accordance with the present invention as follows: To a dilute solution of sulfuric acid, composed of 1000 cc of water and 30 cc of 98% sulfuric acid, 100 g of chrysotile having an average fiber aspect ratio (length/diameter) of between about 200 and 1000 was dispersed and then agitated on a Hamilton Beach mixer for about three hours at ambient temperature (70-75F). The pH
f this mixture was ad~usted to 6.5 and then a solution of 10 g Or methylvinyldlchlorosilane dissolved in 50 cc of isopropyl al-cohol was added; the pH of that mixture readjusted to 6.5 and stir-ring continued about 16 hours at ambient temperature to complete the reaction. The surface reacted chrysotile was separated by filtration, washed with water, methanol and air dried at about 230F for 16 hours. Finally, the dried product was ground for about 30 seconds at about 18000 rpm in a Waring blender.
The fixed carbon content of the washed and dried product was determined by the combustion method to be 1.1% by weight. A similar analysis performed on the unreacted chrysotile `asbestos showed 0.21% carbon content.
~ .
Example 9. Attapulgite, designated as Attagel 50~
obtained from Engelhard Minerals and Chemical Company, was treated to possess oleophllic surface propertles in accordance with the present lnventlon as follows: To a dilute solution of sulfuric acid composed Or 400 cc Or water and 12 g o~ 98% sul~urlc acld, 40 g Or Attage ~ 50 was added and agltated on a Hamilton Beach ''~;.~ 11~ . ' ~' ' ' ' : . , .. . ............ . - . . -.- .

mixer for about three hours at ambient temperature (70-75F).
To this mixture 4 cc of 50% aqueous sodiu~ hydroxide was added to ad~ust the pH of the mixture to about 6.5. A solution of 4 g of octyltriethoxy silane dissolved in 12 g of isopropyl alcohol was added to the stirred mixture and stirring continued 16 hours at ambient temperature to complete the reaction. The surface reacted attapulgite was separated by filtration and washed with water and air dried at about 220F for 16 hours.
Finally the dried product was ground about 20-30 seconds at about 18000 rpm in a Waring blender.
The reaction was confirmed by measuring the fixed carbon content of the washed and dried product by the combustion method and found to be 4.5% by weight. A similar analysis per-formed on the unreacted attapulgite showed 1.1% carbon content.
The materials were stirred into a mixture of 332 cc of diesel oil and 18 cc of water and rheology measured in a Fann viscosimeter.
TABLE II

Concentration Viscosity Viscosity Gel Strength at 600 at 300 Initial/10 mins.
#/bbl RPM RPM (#/100 ft2) Unreacted Atta-pulgite 30 20 cps 12 cps 1/2 Reacted Atta-pulgite 30 27 cps 17 cps 3/6 Example 10. The oleophillic surface properties imparted to chrysotile asbestos, according to the teachings of this invention, were demonstrated by formulating and evaluating two grease samples employing identical amounts of gelling agents, -one of which was the unmodified chrysotile asbestos used to pre-pare the oleophi~c derivatlve described in Example 2, and the other being the reaction product of the surface acid leached . . .- ~ :
' :1071076 chrysotile asbestos and octyltriethoxysilane described ln Example 2. Elghty-one g of the product obtained in Example 2 were milled for 5 minutes in a Waring blender at about 18Q00 rpm, then added to 369 g of 300 S.u.s. mineral oil, worked to uniformity with a spatula and finally passed through a Morehouse Mill with 0.002 inch clearance. The second grease was then pre-pared utillzing unmodified chrysotile asbestos in an identical manner. The two grease samples were then characterized as ~ollows:
TABLE III

UnworkedWorked Water Penetra- Penetra Drop Resis-tion* tion* Point tance**

Grease formulated with surface re-acted chrysotile 273 275 500+F Passed Grease formulated wlth unreacted chrysotile 301 316 480F Failed *ASTM 217 **MIL-6-3278 Example 11. The oleophilic surface properties imparted to chrysotile asbestos and further the water resistant nature of polymer matrices employing such treated mineral fibers, as taught in this invention, have been demonstrated by formulating and evaluating three nitrile elastomers employing identical amounts of reinforcing agents, one of which was the unmodified chrysotile asbestos used to prepare the oleophilic derivative described in Example 2, another being the reaction product of the surface acid leached chrysotile asbestos and octyltriethoxysilane described in Example ?, and the th~rd being carbon black, designated as type N-326 whlch is commonly used as a nitrile rubber reinforcing agent. Fifty parts of the product obtained in Example ~ were milled, vulcanized and cured under standard conditions with 100 parts of nitrile rubber, and 12 parts of pasticizers, accelerators, and curing agents normally employed in such formulations. The - . , . - . ~ .
.

second and third samples were prepared in a like manner utilizing unmodified chrysotile asbestos in one case and type N-326 carbon black in the other, in lieu of the silane coated asbestos product of E:xample 2.
These three samples were then tested for moisture resistance according to the following procedure. Tensile strips cut from cured slabs were weighed and suspended in an autoclave -steam environment at 400F and 300 psig for 72 hours. The strips were then taken from the autoclave and surface moisture removed. -The slabs were then weighed immediately to determine moisture uptake with the following results:
TABLE IV
Moisture Gain % Based on Weight of Strip Rubber compounded with surface reacted chrysotlle of Example 2 -1.75 Rubber compounded with unreacted chrysotile ~9.2 Rubber compounded with N-326 carbon black +5.6 Example 12. In order to illustrate the application of materials of this invention as reinforcing agents for various resin polymers and the ability of such materials to reduce water absorption of such filled polymers, samples were prepared as follows: 3.3 g of Shell R-15 epoxy resin were mixed with 0.5 g of reinforcing agent andO.67 g of dipropylene triamine curing agent added. This composition was cured for 16 hours at 100F. Water absorption tests were run according to ASTM
D 570-63. The results are set forth in Table Y'below:
TAB~E V
Rein~orclng Agent % Weight gain Unreacted asbestos 1.82 Composition of Example 2 1.15 Composition of Example 6 1.57 Composition o~ Example 7 1.22 .: `

Similar results were obtained with a polymer compound of 8.o g of polyester resin, 2.0 g of reinforcing agent and 0.4 g of methylethyl ketone peroxide which was cured overnight.
Results are shown in Table VI below.
TABLE VI
Relnforcing Agent % Weight gain Unreacted asbestos 0.575 Composition of Example 8 0.369

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composition of matter consisting of chrysotile asbestos mineral having an exposed silica layer chemically bonded to an outer layer of organo-silane with the underlying octahedral oxide layers essentially intact.

2. The composition of matter according to claim 1 wherein said organo-silane is methyloctyldiethxy silane.

3. The composition of matter according to claim 1 wherein said chemically bonded outer layer of organo silane is derived from a compound having the following generalized structural formula:

wherein G is selected from the group consisting of a hydroxyl group and a group hydrolyzable to hydroxyl;
Y is selected from the group consisting of an alkyl group con-taining from 1 to 20 carbon atoms, a phenyl group and an alkyl substituted phenyl group wherein the alkyl groups contain a total of from 1 to 12 carbon atoms; and R and R' are selected from the group consisting of G, Y and hydrogen.

4. The composition of matter according to claim 1 wherein said chemically bonded outer layer of organo-silane is derived from compound having the following generalized structural formula:

wherein G is selected from the group consisting of a hydroxyl group and a group hydrolyzable to hydroxyl;
Z is selected from the group consisting of an alkyl group containing from 1 to 20 carbon atoms and bearing a functional group capable of forming chemical bonds with reactive sites within polymers and prepolymers, an alkyl group and a vinyl group; and R and R' are selected from the group consisting of G, Z, hydrogen, an alkyl group containing from 1 to 20 carbon atoms, a phenyl group and an alkyl substituted phenyl group wherein the alkyl groups contain a total of from 1 to 12 carbon atoms.

5. The composition of matter according to claim 1 wherein said organo-silane is octyltriethoxysilane.

6. The composition of matter according to claim 1 wherein said organo-silane is methyldodecyldiethoxysilane.

7. The composition of matter according to claim 1 wherein said organo-silane is 3-aminopropyltriethoxysilane.

8. The composition of matter according to claim 1 wherein said organo-silane is beta-3-4-(epoxycyclohexyl) ethyl-trimethoxysilane.

9. The composition of matter according to claim 1 wherein said organo-silane is methylvinyldichlorosilane.

10. A method for coating a layered mineral selected from the group consisting of phyllosilicates and fibrous amphi-boles with an organo-silane comprising the steps of:
(a) leaching the mineral with a dilute acid under reaction conditions sufficient only to solubilize a superficial octahedral layer of metal oxide from the mineral and expose silanol groups thereof;
(b) arresting the aforesaid leaching process;
(c) subsequently reacting the leached mineral with organo-silane; and (d) recovering the resultant silane-coated mineral.

11. The method according to claim 10 wherein said layered mineral is chrysotile asbestos.

12. The method according to claim 10 wherein said organo-silane is methyloctyldiethyoxy silane.

13. The method of claim 10 wherein the leaching process is arrested by the addition of alkali to the mixture of acid and mineral to increase the pH thereof.

14. The method of claim 10 wherein the leaching process is arrested by physical separation of the mineral and the acid.