WO2014181346A2

WO2014181346A2 - A process for manufacturing of boehmite particulate material

Info

Publication number: WO2014181346A2
Application number: PCT/IN2014/000260
Authority: WO
Inventors: Jashvant Ishvarlal SEVAK; Vinayak Mahadeo NATU
Original assignee: Heubach Colour Pvt. Ltd.
Priority date: 2013-04-23
Filing date: 2014-04-22
Publication date: 2014-11-13
Also published as: WO2014181346A4; IN2013MU01494A; WO2014181346A3

Abstract

A process for the preparation of Boehmite particulate material from the waste containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt; said process comprising : a. preparing 2 to 15 wt. % of aqueous slurry of Aluminium hydroxide, said Aluminium hydroxide is recovered from the waste containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt by hydrolyzing the waste with soda ash; b. preparing slurry containing 2 to 10 wt. % of silane and 2 to 10% of silica by making 2 to 10 wt. % of aqueous slurry of silane with stirring followed by adding 2 to 10 wt. % of micro fine precipitated silica powder having average particle size of 3μ and stirring the slurry over night at low speed; c. Mixing slurry obtained in step (a) into step (b) followed by subjecting the reaction mixture to hydrothermal treatment at temperature in the range of 90°C to 250°C for at least 4 hours; and d. collecting Boehmite particulate material by either centrifuging or filter pressing the reaction mixture or any other conventional means followed by drying the product by either spray drying or spin flash drying or any other conventional means and optionally pulverizing to get fine flaky particles with particle size 5 to 8 micron. Boehmite particulate matter having 80 to 84 wt. % of Boehmite along with base material as micro fine precipitated silica powder (8 to 10 wt. %) treated with silane (8 to 10 wt. %) with preferred particles size 5 to 8 microns and a coating comprising thereof.

Description

TITLE OF THE INVENTION

A process for manufacturing of Boehmite particulate material.

This application claims priority from Indian Patent Application No. 1494/MUM/2013 filed on April 23, 2013.

FIELD OF THE INVENTION:

This invention relates to a process for manufacturing of Boehmite particulate material from aluminum hydroxide recovered from waste containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt etc.

Particularly, this invention relates to a process for manufacturing of Boehmite particulate material from aluminum hydroxide recovered from waste containing Aluminium chloride.

This invention also relates to Boehmite particulate material comprising 80 to 84 % of Boehmite, 3 to 10 % silica and 3 to 10 % silane; for use as flatting agent.

BACKGROUND OF THE INVENTION:

Various fillers or additives are used to enhance the properties of Paints, Plastic, Papers, Rubbers, Polymers, or other similar materials. One of such additives is a flatting agent which is also called as matting agent /additive. It is conventionally incorporated into paint systems in order to produce a coating with a reduced gloss level. Depending on the amount of flatting agent used, the. final appearance of the coating can range from satin to matt finish. Low gloss or matt surfaces are sought after for their anti-glare properties, visual appearance or simply to meet fashion requirements. Many of the mineral fillers and pigments used as flatting agents also find utility in plastic film applications as anti-block agents.

Flatting agents includes but not limited to silica, waxes or filler pigments which once added to paint create a micro-rough surface after the coating has dried. It is this rough surface that scatters incoming light to produce the desired matt effect. Boehmite is one such filler pigments used as flatting agent. CA 2,323,289 (Equivalent: US 6,413,308) discloses the use of Boehmite as a flatting agent and the process for the preparation of Boehmite.

Boehmite is an aluminium oxide hydroxide (γ-ΑΙΟ(ΟΗ)) mineral, a component of aluminium ore bauxite. It is dimorphous with diaspore. It crystallizes in the orthorhombic dipyramidal system and is typically massive in habit. It is white with tints of yellow, green, brown or red due to impurities. It has a vitreous to pearly luster, a Mohs hardness of 3 to 3.5 and a specific gravity of 3.00 to 3.07.

Various processes have been disclosed in the existing art which are as follows:

Numerous methods have been advanced for the preparation of oxides of alumina in colloidal or sol form. A number of these methods are summarized in US 2,590,833; US 2,787,522; US 2,915,475; US 3,357,791 and US 3,966,893. These processes have several disadvantages. They require relatively expensive water soluble aluminum salts as raw materials. They generate large volumes of relatively dilute solution of various salts which require much effort and cost to discard and/or reclaim. In addition, the intermediate precipitates require extensive washing to remove various inorganic or organic species. Such washing often leads to loss or alteration of the fine particulate matter.

US 4, 1 17, 105 discloses the method for the preparation of dispersible, colloidal sized particles of Boehmite alumina (alpha-alumina monohydrate). Alumina trihydrate is calcined for the partial dehydration and further mixed with water to form slurry. The slurry is autoclaved to crystallize and rehydrate the alumina followed by spray drying or tray drying for dewatering the aqueous slurry.

US 4,492,682 discloses process for the preparation of homogeneous Boehmites and/or pseudo- Boehmites. Amorphous aluminum hydroxycarbonate is prepared by carbonating an alkali metal aluminate and further admixed with carbon dioxide. The precipitated product is then filtered and washed with a solution of an acid, a base, a salt, or mixture thereof, with the pH of the resulting reaction medium being maintained at a value of less than 1 1. The reaction medium is heated at a temperature of less than 90°C and subsequently the medium is heated at a temperature ranging from 90°C to 250°C.

GB 1 ,328,052 discloses the method for producing Colloidal fibrous Boehmite. The active aluminium oxide, having a residual water content of 2 to 15 % is obtained by the incomplete dehydration of hydrated alumina, by reacting in an aqueous slurry with a monobasic organic acid to give the corresponding basic Al salt which is subsequently subjected to hydrothermal treatment at 120°C to 200°C and 2 to 15 atmospheres in an aqueous suspension have a concentration equivalent to 2 to 20 % by weight of A1₂0₃ until a colloidal fibrous Boehmite solution has been formed. The active aluminium oxide is also obtained by rapid dehydration of the hydrated alumina in a turbulent stream of gas at 400°C to 800°C. Further, it may be converted by heating with the organic acid on the boil until constant viscosity is reached.

EP 1 ,888,463 discloses a method for preparing Boehmite and [gammaj-alumina with high surface area. This method comprised of the steps of hydrolysis of aluminum alkoxides to produce Boehmite which is further calcined to produce [gammaj-alumina. In this method, an alcohol is used as a reaction solvent with a small amount of water.

KR 101 178397 discloses a low soda Boehmite having average particle size of 0.5 to 50 μιη, soda (Na₂G) content of 0.12 wt. % or less, and a specific surface area (BET) of 1 to 5 m²/g. It discloses hydrothermal synthesis in which oxalic acid is added in Aluminium hydroxide aqueous solution to control the pH as 3.0 to 8.0. This solution is processed for hydrothermal synthesis reaction to obtain Boehmite.

US 2007148083 and US 200803 1808 disclose a method of forming Boehmite particulate material. The method comprised of hydrothermal treatment of the aqueous suspension of Boehmite precursor and Boehmite seeds.

EP 0,278,469 discloses a process for preparing Boehmite. The ground aluminium trihydroxide in water is digested at elevated temperatures and pressure in the presence of mineral acid. During the process the Aluminium hydroxide particles are first heated at a temperature of at least 300°C so as to embed Boehmite into a matrix of chi-aluminate. The Boehmite product is then separated by dissolving the chi-aluminate to obtain Boehmite particles of a specific surface area.

CN 101920978 discloses a method for producing Boehmite by using washing liquor from the production of washing red mud by alumina. This method used washing liquor obtained from the production of the washing red mud. The red mud and lime is added to desilicication tank. The desilicication is carried out till desilicication index is more than or equal to 400. The precipitated product is filtered and transferred to a diluting tank for cooling and is subjected to carbonation gelatinizing by using 20 to 60 volume percent C0₂ gas obtained by concentrating and enriching C0₂ waste gas generated in the production of alumina as a precipitator. The gelatinized slurry is heated to 70°C to 100°C and kept aging. The aged slurry is filtered and dried to obtain powdery Boehmite.

US 2010040536 discloses a method for producing Boehmite particles where powder of aluminum hydroxide is subjected to hydrothermal reaction in presence of a nucleation agent, metal salt or sol. of metal oxide, at a pH 8 or lower.

US 5,306,680 discloses a process for preparing fine Boehmite particles. The aluminum hydroxide or hydrated alumina having a particle size of the order of submicron is subjected to hydrothermal treatment in essentially pure water or a solution consisting essentially of an aqueous caustic soda solution or an aqueous sodium carbonate solution at a temperature from 150°C to 350°C and at pressure between 10 to 100 atm.

CN 102139204 discloses a method for the preparation of pseudo-Boehmite containing amorphous silica alumina. Pseudo-Boehmite containing the amorphous silica alumina is obtained according to the conventional ageing, filtering and washing methods after amorphous silica alumina slurry and pseudo-Boehmite slurry are mixed. Pseudo-Boehmite contains 5 to 40 wt. % of silicon oxide, the specific surface area is 250 to 400 m²/g, the pore volume is 0.7 to 1.4 ml/g, the surface acid site mainly comprises weak acid site, and the infrared acidity is 0.28 to 0.55 mmo!/g. Pseudo- Boehmite containing the amorphous silica alumina is mainly applied to hydrogenation treatment, particularly preparation of an intermediate distillate hydrogenation catalyst carrier. This material may not be suitable for Flatting agent. This reported process consumes high energy and thereby makes the process costly. R 20080044307 discloses a method for producing high porosity Boehmite alumina. In this method, an aqueous Boehmite slurry is mixed with an effective amount of a modifier comprising a hydroxide or oxide of an element of group IIIA-VIA on the Periodic Table of Elements and having a p sp of greater than 1 1 to produce a precursor mixture and hydrothermally aging the precursor mixture at an elevated temperature under agitation with an effective consumptive power of greater than 1 kW/m³.

IP 2007223836 discloses a method for producing Boehmite with a new shape suitable for use as filler for a resin or the like without adding elements such as calcium, barium, strontium or cerium, and to provide Boehmite. A reaction stock solution, containing a basic aluminum salt such as basic aluminum chloride or basic aluminum sulfate and a sulfate ion and pH is adjusted to 8 to 13, is subjected to hydrothermal reaction. This Boehmite contains < 100 ppm for each of calcium content, barium content, strontium content and cerium content. Thus, various processes for the preparation of Boehmite particles have been known and examples of such processes as described above include one which comprises conducting pyrolysis of aluminum hydroxide as a starting material in the atmosphere to remove part of the water of crystallization, thereby forming a Boehmite phase, and one which comprises conducting hydrothermal treatment of aluminum hydroxide in a hermetically sealed vessel to form a Boehmite phase.

Although the Boehmite particles prepared by some of above processes can be finely ground mechanically by the use of, e.g., a ball mill, into fine particles having a size of the order of submicron, these processes are problematic in that obtained particles tend to become globular and fine flaky particles are difficult to obtain.

The pyrolysis process has another problem in that when aluminum hydroxide to be used as the starting material is contaminated with fine particles, no Boehmite phase is formed, but chi- alumina (.chi.-Al₂03), which is a transitional alumina, is formed to lower the yield of Boehmite particles. On the other hand, the hydrothermal treatment process has another problem in that the formed Boehmite particles are in the form of a tight aggregate of rhombic prisms and cannot form fine flaky particles, even when they are finely ground.

Heubach Color Pvt. Ltd is the manufacture of Copper Phthalo Cyanine Green and Blue (hereinafter referred to as CPC Green and CPC Blue). The raw materials for CPC Green Plant are Aluminium chloride, cupric chloride, crude CPC Blue, chlorine, caustic soda. During the course of manufacture of CPC green, mother liquor emerges. This mother liquor of the CPC Green mainly contains Aluminium chloride, Copper etc. and is treated with sodium sulphide to get copper as Copper sulphide. The resultant clear mother liquor which is free from copper and other impurities is neutralized with soda ash solution to get Aluminium hydroxide slurry. This slurry is filtered in filer press, washed and dried to get Aluminium hydroxide powder. There is no method existing by which one can utilize Aluminium Hydroxide, as recovered in CPC Green manufacturing, convert into Boehmite particulate material embedded in base material, silica treated with silane and the particulate material has fine flaky particles with particle size in the range of 5 to 8 micron (measured by using laser diffraction method) and industrial utility as flatting agent in Paints, Plastic, Papers, Rubbers, Polymers, or other similar materials.

OBJECTS OF THE INVENTION:

An object of the invention is to provide a process for manufacturing of Boehmite particulate material from aluminum hydroxide; which is recovered from mother liquor of CPC Green; which contains Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt etc; thereby making the process cost-effective.

Another object of the invention is to provide a process for manufacturing of Boehmite particulate material wherein the process eliminates agglomeration thereby eliminating milling process for conversion into fine particles and hence reduces duration as well as cost of the manufacturing process.

Yet another object of the invention is to provide Boehmite particulate material containing 80 to 84 wt. % Boehmite embedded in 3 to 10 wt. % silica treated with 3 to 10 wt. % silane.

Still another object of the invention is to provide Boehmite particulate material having particle size in the range of 5 to 8 micron and may be used as flatting / matting agent.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

Figure 1 illustrates an XRD pattern of Boehmite particulate material prepared according to Example 1. DETAILED DESCRIPTION OF THE INVENTION:

Before the present invention is described, it is to be understood that this invention is not limited to particular methodologies and materials described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention.

Before the present invention is described, it is to be understood that unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it is to be understood that the present invention is not limited to the methodologies and materials; since similar or equivalent to those described herein can be used in the practice or testing of the present invention. The preferred methods and materials are described herein and these may vary within the specification indicated. Unless stated to the contrary, any use of the words such as "including," "containing," "comprising," "having" and the like, means "including without limitation" and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it. Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limiting of the scope of invention. Further the terms disclosed in the embodiments are merely exemplary methods of the invention, which may be embodied in various forms.

It is also understood that the terms "a", "an", "the" and the like are words for the sake of convenience and are not to be construed as limiting terms. Moreover, it will be understood that the illustrations are for the purpose of describing a particular exemplary embodiment of the invention and are not limited to the invention thereto. Further, the present invention is demonstrated by using mother liquor generated during the manufacturing of Copper Phthalocyanine (CPC) pigments namely CPC Green, however, it is possible to recover Aluminium hydroxide from any industrial waste which contains Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt in it, irrespective of source of waste. Thus, the scope of the invention intends to cover the recovery of Aluminium hydroxide from any waste which contains Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt in it but free from other impurities by the process as claimed in the application.

Aecording to the invention, the mother liquor is separated from the plant of manufacturing of CPC Green. This mother liquor of the CPC Green mainly contains Aluminium chloride, Copper etc. and is treated with sodium sulphide to get copper as Copper sulphide, which is separated out. The resultant clear mother liquor, which is free from copper and other impurities; is neutralized with soda ash solution to get Aluminium hydroxide slurry. This slurry is filtered in filer press, washed and dried to get Aluminium hydroxide. Aluminium hydroxide thus obtained is used in the present invention.

According to one of the embodiment of the invention, there is provided a process for the preparation of Boehmite particulate material from the waste containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt;

said process comprising :

a. preparing 2 to 15 wt. % of aqueous slurry of Aluminium hydroxide, said Aluminium hydroxide is recovered from the waste containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt by hydrolyzing the waste with soda ash;

b. preparing slurry containing 2 to 10 wt. % of silane and 2 to 10 wt. % of silica by making 2 to 10 wt. % of aqueous slurry of silane with stirring followed by adding 2 to 10 wt. % of micro fine precipitated silica powder having average particle size of 3μ and stirring the slurry over night at low speed; c. mixing slurry obtained in step (a) into step (b) followed by subjecting the reaction mixture to hydrothermal treatment at temperature in the range of 90°C to 250°C for at least 4 hours; and

d. collecting Boehmite particulate material obtained in step (c) by either centrifuging or filter pressing the reaction mixture or any other conventional means followed by drying the product by either spray drying or spin flash drying or any other conventional means and optionally pulverizing to get fine flaky particles with particle size 5 to 8 micron.

Preferably, step (a) comprises recovering Aluminium hydroxide from the waste, a mother liquor containing Aluminium chloride by hydrolyzing the waste with soda ash followed by filtering the product by filter press followed by spray drying to obtain Aluminium hydroxide.

Preferably, step (a) comprises preparing 4 wt. % of aqueous slurry of Aluminium hydroxide powder by adding Aluminium hydroxide in water with stirring for 30 minutes.

Preferably, in step (b), 3 to 10 wt. % of silane is added in water followed by stirring the slurry for at least 30 minutes followed by adding 3 to 10 % of micro fine precipitated silica powder having average particle size of 3μ and stirring the slurry for at least for 4 to 16 hours, preferably 12 hours at 30 rpm speed.

Preferably, silane used in the step (b) is selected from dimethyl silane, vinyl silane, polyvinyl silane, etc.

More preferably, vinyl silane is used in step (b).

Preferably, step (c) of hydrothermal treatment is carried out at temperature of 130°C for at least 4 hours. Preferably, waste used in the present invention is a mother liquor of CPC Green containing Aluminium chloride.

The resultant Boehmite particulate material has fine flaky particles with preferred particles size of 5 to 8 micron measured by using laser diffraction method.

In another embodiment of the invention, there is provided Boehmite particulate material having 80 to 84 wt. % of Boehmite along with base material as micro fine precipitated silica powder (8 to 10 wt. %) treated with silane (8 to 10 wt. %); said particulate material have particle size in the range of 5 to 8 micron. The polymrophic crystals of Boehmite particulate material are studied by the x-ray diffraction. The XRD pattern of Boehmite particulate material is illustrated in Figure 1, which demonstrates crystalline nature of Boehmite particulate material and having characteristic peaks at 14.475, 14.051 , 49.224, 28.209 and 5.863 Angle, 2-Theta° which confirms the formation of Psuedo-Boehmite

Boehmite particulate matter of the invention having 80 to 84 wt. % of Boehmite along with base material as micro fine precipitated silica powder (8 to 10 wt. %) treated with silane (8 to 10 wt. %) with preferred particles size 5 to 8 micron having characteristic peaks of XRD at 14.475, 14.051 , 49.224, 28.209 and 5.863 Angle, 2-Theta°.

In another embodiment of the invention, the Boehmite particulate material prepared according to the invention was analyzed for their performance as flatting agent in the coating. Acrylic PU resin is selected for study and compared with standard Evonic silica OK 412 as a flatting agent.

3% and 5% of Boehmite particulate material prepared according to the invention is added in Acrylic PU resin with stirring at 1200 RPM. The samples were tested for gloss with Glossometer (BYK Gardner GmBH) vis-a-vis with standard flatting agent Evonic Silica OK 412. The comparative results showed excellent gloss reduction when we have batch containing Boehmite particulate material of the invention as compared to the standard thus very good matting effect is observed vis-a-vis standard.

According to another embodiment of the invention, there is provided a coating composition comprising 3 to 5 % of Boehmite particulate material prepared according to the invention; having matting affect.

Thus, the process for manufacturing of Boehmite particulate material is very cost-effective as starting material, aluminum hydroxide, used in the present invention is recovered from mother liquor of CPC Green or any other liquor containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt. Further, use of silane eliminates agglomeration and hence, eliminating milling process used for conversion of agglomerates into fine particles and hence reduces duration as well as cost of the manufacturing process.

The present invention is described with reference to the following examples illustrating the new process for the preparation of Boehmite particulate material, however, these examples are provided for illustrative purposes only and or not to be construed as limitations on scope of the process of this invention.

EXAMPLES

Reference Example for the preparation of Aluminium hydroxide :

1300 ml of mother liquor containing 3 % Aluminium chloride and Copper (about 1000 ppm) is treated with 3.1 gm of sodium sulphide. The precipitated copper as copper sulphide was removed by filtration. 1300 ml of mother liquor containing 3 % Aluminium chloride free from copper was treated with 180 gm soda ash at room temperature. The Aluminium hydroxide was precipitated at a pH of 6.5 to 7.5 to form slurry. The slurry containing Aluminium hydroxide and sodium chloride was filtered in filter press. The sodium chloride was removed from the pressed cake by washing the same with water. The wet cake of Aluminium hydroxide is used further for production of Boehmite particulate material having varying concentration of silica and silane.

Example 1 (Boehmite comprising 80 wt. % of Boehmite, 10 t. % silane and 10 wt. % silica)

Slurry containing 4 wt. % Aluminium hydroxide :

527.9 gm of press cake of Aluminium hydroxide obtained from Reference Example was charged in 1 L beaker and 500 ml of water was added into it to obtain the homogeneous slurry.

Slurry containing 10 wt. % silica and 10 wt. % vinyl silane :

10 gm of vinyl silane was added in 100 ml of water and the mixture was stirred for 30 minutes. After stirring the slurry, 10 gm of micro fine precipitated silica powder having average particle size 3 μ was added into the slurry. This slurry was stirred further at 30 rpm over night.

Both the slurries were mixed in the autoclave and heated at 130°C for 4 hours. The resultant reaction mixture was filtered by filter press and spray dried to get Boehmite particulate material having particle size of 5 to 8 μιη.

The product was analyzed for its XRD, loss on ignition and loss on drying and results are shown below:

Loss on ignition : 6 to 7 %

The XRD of Boehmite particulate material confirms its crystalline nature i.e.Pseudo Boehmite Loss on drying < 1 %

Example 2 (Boehmite comprising 84 wt. % of Boehmite, 8 wt. % silane and 8 wt. % silica)

Slurry containing 4 wt. % Aluminium hydroxide :

527.9 gm of press cake of Aluminium hydroxide obtained from Reference Example was charged in 1 L beaker and 500 ml of water was added into it to obtain the homogeneous slurry. Slurry containing 8 wt. % silica and 8 wt. % vinyl silane :

8 gm of vinyl silane was added in 8 ml of water and the mixture was stirred for 30 minutes. After stirring the slurry, 8 gm of micro fine precipitated silica powder having average particle size 3 μ was added into the slurry. This slurry was stirred at 30 rpm over night.

Both the slurries were mixed in the autoclave and heated at 130°C for 4 hours. The resultant reaction mixture was filtered by filter press and spray dried to get Boehmite particulate material having particle size of 5 to 8 μ.

Loss on ignition : 6 to 7 %

The XRD of Boehmite particulate material confirms its crystalline nature i.e. Pseudo Boehmite. Loss on drying < 1 %.

Example 3 (Boehmite comprising 90 wt. % of Boehmite, 5 wt.% silane and 5 wt. % silica)

Slurry containing 4 wt. % Aluminium hydroxide :

Slurry containing 5 wt. % silica and 5 wt. % vinyl silane :

5 gm of vinyl silane was added in 100 ml of water and the mixture was stirred for 30 minutes. After stirring the slurry, 5 gm of micro fine precipitated silica powder having average particle size 3 μ was added into the slurry. This slurry was stirred at 30 rpm over night. Both the slurries were mixed in the autoclave and heated at 130°C for 4 hours. The resultant reaction mixture was filtered by filter press and spray dried to get Boehmite particulate material having particle size of 5 to 8 μ.

Loss on ignition : 6 to 7 %

The XRD of Boehmite particulate material confirms its crystalline nature i.e.Pseudo Boehmite. Loss on drying < 1 %.

Example 4 (Boehmite comprising 94 wt. % of Boehmite, 3 wt. % silane and 3 wt. % silica)

Slurry containing 4 wt. % Aluminium hydroxide : ,

Slurry containing 3 wt. % silica and 3 wt. % vinyl silane :

3 gm of vinyl silane was added in 100 ml of water and the mixture was stirred for 30 minutes. After stirring the slurry, 3 gm of micro fine precipitated silica powder having average particle size 3 μ was added into the slurry. This slurry was stirred at 30 rpm over night. ¹

Loss on ignition : 6 to 7 %

Example 5 (Boehmite comprising 96 wt. % of Boehmite, 2 wt. % silane and 2 wt. % silica)

Slurry containing 4 wt. % Aluminium hydroxide :

527.9 gm of press cake of Aluminium hydroxide obtained from Reference Example was charged in I L beaker and 500 ml of water was added into it to obtain the homogeneous slurry.

Slurry containing 3 wt. % silica and 3 wt. % vinyl silane :

3 gm of vinyl silane was added in 100 ml of water and the mixture was stirred for 30 minutes. After stirring the slurry, 3 gm of micro fine precipitated silica powder having average particle size 3 μ was added into the slurry. This slurry was stirred at 30 rpm over night.

Loss on ignition : 6 to 7 %

Example 6

3 % and 5 % of Boehmite particulate material, prepared according to examples 1 to 5, were loaded in 10 gm of two component Acrylic PU resin and apply stirring in disperse mat at 1800 to 2000 rpm for 10 min. 2 gm curing agent was added and centrifuged at 3000 rpm for 1 min and the composition was applied on pre-treated wood surface with 150 micron film thickness and measure gloss on glossometer. The same experiment was repeated with standard Evonic silica OK 412 as a flatting agent. The gloss was measured by using Glossometer for the standard as well as Boehmite particulate material of the invention and comparative results are showed in Table 1. Table l : Comparative Results of Gloss

Sr. Details of Boehmite Gloss of 3 % of Gloss of 5 % of Gloss of Standard

No Boehmite in Boehmite in OK 412 (3 %)

Acrylic PU resin Acrylic PU resin

@ @ @ @ @ @ @ @ @ 20 ° 60 ° 85 ° 20 ° 60 ° 85 ° 20 ° 60 ° 85 °

1 Boehmite comprising 80 wt.

% of Boehmite, 10 wt. %

silane and 10 wt. % silica 1 10 ^• 33 1 8.8 31

(prepared according to

example 1)

2 Boehmite comprising 84 wt.

% of Boehmite, 8 wt. %

silane and 8 wt. % silica 2 13 40 1.3 10 35

(prepared according to

example 2)

1.2 10.7 34.9

3 Boehmite comprising 90 wt.

% of Boehmite, 5 wt. %

silane and 5 wt. % silica 2 1 1 43 1.4 9.9 34.5

(prepared according to

example 3)

4 Boehmite comprising 94 wt.

% of Boehmite, 3 wt. %

silane and 3 wt. % silica 2 10 42 1.3 10.1 33.9

(prepared according to

example 4) Boehmite comprising 96 wt.

% of Boehmite, 2 wt. %

silane and 2 wt. % silica 16 45 1.2 10.5 34.5

(prepared according to

example 5)

According to the results as showed in table 1 , the Boehmite particulate material prepared according to example 1 showed improved results at 3 % and 5% as compared to the Boehmite particulate material prepared according to examples 2 to 5.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

Claims

We claim:

1. A process for the preparation of Boehmite particulate material from the waste containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt;

said process comprising :

a. preparing 2 to 15 wt. % of aqueous slurry of Aluminium hydroxide, said Aluminium hydroxide recovered from the waste containing Aluminium chloride, Aluminium sulfate, Aluminium carbide or any other Aluminium salt by hydrolyzing the waste with soda ash;

b. preparing slurry containing 2 to 10 wt.% of silane and 2 to 10 wt. % of silica by making 2 to 10 wt. % of aqueous slurry of silane with stirring followed by adding 2 to 10 wt. % of micro fine precipitated silica powder having average particle size of 3μ and stirring the slurry over night at low speed;

c. mixing slurry obtained in step (a) into step (b) followed by subjecting the reaction mixture to hydrothermal treatment at temperature in the range of 90°C to 250° C for at least 4 hours; and

d. collecting Boehmite particulate material by either centrifuging or filter pressing the reaction mixture or any other conventional means followed by drying the product by either spray drying or spin flash drying or any other conventional means and optionally pulverizing to get fine flaky particles with particle size 5 to 8 micron.

2. The process as claimed in claim 1 , wherein the step (a) comprises recovering Aluminium hydroxide from the waste, a mother liquor containing Aluminium chloride by hydrolyzing the waste with soda ash followed by filtering the product by filter press followed by spray drying to obtain Aluminium hydroxide.

3. The process as claimed in claim 1 , wherein the step (a) comprises preparing 4 wt. % of aqueous slurry of Aluminium hydroxide powder by adding Aluminium hydroxide in water.

4. The process as claimed in claim 1 , wherein step (b) comprises adding 3 to 5 wt. % in water followed by stirring the slurry for at least 30 minutes followed by adding 10% of micro fine precipitated silica powder having average particle size of 3μ and stirring the slurry for at least for 4 to 16 hours at 30 rpm speed.

5. The process as claimed in claim 1 , wherein the silane used in the step (b) is selected from dimethyl silane, vinyl silane, polyvinyl silane and the like.

6. The process as claimed in claim 1 wherein, the silane used in the step (b) is vinyl silane.

7. The process as claimed in claim 1 , wherein step (c) of hydrothermal treatment is carried out at temperature of 130°C for at least 4 hours.

8. The process as claimed in claim 1 , wherein waste used in the step (a) is a mother liquor of CPC Green containing Aluminium chloride.

9. Boehmite particulate matter having 80 to 84 wt. % of Boehmite along with base material as micro fine precipitated silica powder (8 to 10 wt. %) treated with silane (8 to 10 wt. %) with preferred particles size 5 to 8 micron having characteristic peaks of XRD at 14.475, 14.051 , 49.224, 28.209 and 5.863 Angle, 2-Theta°.

10. A coating composition comprising 3 to 5 % of Boehmite as claimed in claim 9 and prepared according to claims as claimed in claims 1 to 8 having matting affect.