Hydrophobic Surface Modified Aluminas for Polymer Compositions and Method for Making Thereof

Abstract

A method of producing new hydrophobic aluminas by i) providing a slurry comprising an alumina compound, the slurry having a pH of above 5.5; ii) mixing an organic composition comprising carboxylic acids with long hydrocarbon chains with the slurry to form an acid modified slurry; iii) hydrothermally conditioning the acid modified slurry to form a hydrothermally aged slurry; and iv) drying the hydrothermally aged slurry.

The new hydrophobic aluminas have surface modified structures distinguished by a low humidity content and very small nanoparticles. These new hydrophobic aluminas can be uniformly dispersed in a substrate, for example polymers.

Claims

1. A hydrophobic alumina comprising: an alumina compound including an aluminum oxide hydroxide (AlOOH), a boehmite, or a pseudoboehmite, said alumina compound having hydrocarbon chains having a carbon chain length of between 12 and 24 carbon atoms formed on the surface thereof; the hydrophobic alumina having a free water content of less than 2.00%.

2. The hydrophobic alumina of claim 1, wherein the hydrophobic alumina has a final free water content of less than 1.00%.

3. The hydrophobic alumina of claim 1, wherein the hydrophobic alumina has a final free water content of less than 0.5%.

4. The hydrophobic alumina of claim 1, wherein the hydrocarbon chains are covalently bonded to the alumina compound.

5. A composition comprising a hydrophobic alumina as claimed in claim 1 and a substrate, the hydrophobic alumina being dispersed in the substrate.

6. The composition as claimed in claim 5, wherein the substrate is a polymer or a paraffin.

7. The composition as claimed in claim 6, wherein the polymer includes a low molecular weight polymer or a wax.

8. The composition as claimed in claim 1, wherein particles of the hydrophobic alumina are dispersed in the substrate to particle sizes of 3.5 nano meters to 75 nano meters.

9. The composition as claimed in claim 8, wherein particles of the hydrophobic alumina are dispersed in the substrate to particle sizes of 3.5 nano meters to 45 nano meters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In the Figures:

[0071] FIG. 1 is a TGA/DTA analysis of a new hydrophobic alumina as per Example 1;

[0072] FIG. 2 is a DRIFT spectra of the hydrophobic alumina in Example 1 with the characteristic Al-carboxylate signal;

[0073] FIG. 3 is an SEM that shows the structure of HDPE (high density polyethylene) film that contains the hydrophobic alumina of Example 1 dispersed to a dimension comparable to single crystal particles.

[0074] FIG. 4 is a graph showing surface energy of the hydrophobic alumina of Example 1 vs an unmodified powder; and

[0075] FIG. 5 is a graph showing the wettability of the hydrophobic alumina of Example 1 vs an unmodified alumina.

[0076] FIG. 6 is an idealized drawing of a crystal particle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example 1

[0077] This example is a preparation of the hydrophobic alumina of the present invention, specifically a hydrophobic boehmite, using an organic composition including a carboxylic acid having a carbon chain of 18. A hydrothermally treated boehmite slurry from a hydrolysis process of aluminum alkoxide (295 lbs.) at pH value of about 9, was mixed with 4.1 lb. of the organic composition including a carboxylic acid having a carbon chain of 18 (17% wt.) to form an acid modified slurry. The acid modified slurry was hydrothermally treated at 105° C. for 2 hours under low agitation. After 2 hours of mixing a low viscosity hydrothermally treated slurry that contained finely sub-divided particles was obtained. The hydrothermally treated slurry (having a pH of between 7 and 7.5) was cooled and pumped at room temperature to a contact dryer operated under nitrogen, which had an external circulating oil jacket that operated at 240° C. and where the temperature of the gas exiting the dryer was 115° C.

[0078] A hydrophobic alumina was obtained with a bulk density of 0.86 g/cc.

[0079] The hydrophobic alumina included long hydrophobic carboxylate molecules on a surface of alumina crystal particles. This is indicative of the improved compatibility with hydrophobic polymers.

[0080] FIG. 1 is the TGA/DTA analysis of the hydrophobic alumina powder. FIG. 1 shows that there is less than 0.5% of free water on the hydrophobic alumina powder. As per FIG. 2, the crystal particles by X-ray are characterised by a thickness of 35 nm (020) and length of 37 nm (002).

[0081] The particles of the hydrophobic alumina were dispersed in HDPE to a particle size of 45 nano meters. The particle size was detected by SEM and it is essentially consistent with the dimension of a single crystal that was determined by X-ray diffraction. HDPE was compounded with the hydrophobic alumina powder of Example 1 in a Brabender mixer at 150° C., 60 rpm for 15 minutes. FIG. 3 is an SEM that shows the structure of the HDPE film containing the hydrophobic alumina made of boehmite crystal particles which were homogeneously dispersed to a dimension comparable to single crystal particles.

[0082] The Inverse Gas Chromatography technique was then applied to investigate powder surface energies (FIG. 4) and wettability properties of the hydrophobic alumina powder (FIG. 5).

[0083] The examined powder was placed in the chromatographic column. Carefully selected probe molecules with known physicochemical properties were injected into the column. The retention data obtained enabled calculation of values describing surface properties.

[0084] The total surface energy was evaluated through the contribution of two components:

γ.sup.T=γ.sup.D+γ.sup.AB

[0085] γ.sup.D is the dispersive component that is related to the non-polar property of the surface, γ.sup.AB is the polar contribution of the surface.

[0086] The dispersive component of total surface energy was obtained by measuring the adsorption with alkane probe molecules having increasing C-chain length: hexane, heptane, octane and nonane.

[0087] The polar component of the total surface energy was obtained by the use of polar probe molecules: acetonitrile, acetone, ethanol, ethyl acetate and dichloromethane.

[0088] By taking the polar component divided by the total surface energy, γ.sup.AB/γ.sup.T, the wettability profile of the samples was determined. A non-polar nature of the surface is described by a low wettability profile.

[0089] Analysis was carried out by passing different amounts of probe molecules into a column to achieve different surface coverages.

[0090] Comparing the hydrophobic alumina powder to untreated boehmite, it was found that the hydrophobic alumina modified with the organic modifier of Example 1 is significantly lower in surface energy, confirming that the modification has a significant impact. The low surface energy value also corroborates the lower affinity for polar substances. This is also highlighted by the lower wettability profile, thus showing this sample is compatible with non-polar systems. The lipophilic character of the hydrophobic alumina is verified in a typical non polar liquid, an aliphatic mineral oil having a viscosity of 19 cP at 20° C. The powder was mixed at 10 phr with 90 phr of oil. The resulting dispersion was centrifuged and the solid residue on the bottom of the centrifuge tube was weighed after rinsing in hexane and drying at 110° C. The % wt. of particles dispersed calculated by difference with respect to the total amount of powder was 96% wt.

Comparative Example 1

[0091] A comparative example using a fatty acid composition having a carbon chain of equal to 8 was carried out. 2500 grams of boehmite solution from a hydrolysis process of aluminum alkoxide at pH value of about 9, was mixed with 180 grams of water. Subsequently 18 grams of octanoic acid were introduced to obtain a number of moles on boehmite in the range of that applied in the Example 1. Then an ammonia solution at 30-33% wt, in an amount equal to 9.5 grams, was added under stirring. The resulting slurry was kept at constant agitation at 105° C. for 2 hours. The hydrothermally aged slurry was cooled at room temperature, the pH value of the hydrothermally aged slurry was 8.6. The hydrothermally aged slurry was pumped into a spray atomizer that operates with N2 flow to obtain a dry powder. The powder was added to an aliphatic oil under the same conditions of Example 1. During mixing time the viscosity increases considerably until the system exhibited no flow. The test was stopped as the powder was not dispersible in oil.

[0092] Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.