RU2118610C1 - Composition for extraction of diamond and/or cubic boron nitride - Google Patents

Abstract

FIELD: superhard materials. SUBSTANCE: tool waste containing diamond and/or cubic boron nitride are treated with composition consisting of the following components, wt.-%: addition forming chelate compound with aluminium 5-25; antioxidant addition 1-5; eutectic melt of alkaline metal hydroxides - up to 100 in muffle oven at 200-250 C. Product is cooled, leached, washed out with water, separated and dried. Extraction degree of diamond and/or cubic boron nitride is 96%. Washings have alkaline metal aluminates and can be used as coagulants. Invention can be used for recuperation of superhard materials. EFFECT: improved quality of composition. 4 cl, 3 ex

Description

The invention relates to the extraction (recovery) of superhard materials (SM) - diamond and cubic boron nitride (CBN) from a used abrasive tool containing electrocorundum (α-Al ₂ O ₃ ) as a filler, and can be used in enterprises manufacturing and using abrasive tool based on superhard materials.

A known process for the extraction of diamond from sludges (wastes) containing alumina and silicate compounds formed during the processing of ceramic materials on diamond grinding wheels by heating the sludges with brown or with brown and potassium fluoride at 700 - 1000 ^o C in a non-oxidizing atmosphere (US Patent N 3644094, NCI: 23-209.9, 1970).

 One of the objectives of the invention is the extraction of diamond from sludges containing corundum, by dissolving the latter.

A known composition for the extraction of Elbor (brand name CBN) from a concentrate containing electrocorundum, which is a mixture of borax and soda in a ratio of 3: 1 (USSR Author's Certificate N 420555, C 01 B 21/064, 1974). The extraction process is carried out at 800 - 900 ^o C.

 The objective of the invention is to extract CBN from a spent tool on a ceramic bond containing electrocorundum.

A known composition for the separation of cubic boron nitride from a mixture of hexagonal boron nitride containing a eutectic melt of alkali metal hydroxides or mixtures thereof with water (US Patent N 3661521, NKI: 423-290, 1972). The process is carried out at a temperature of about 300 ^o C.

 The objective of the invention is to remove impurities of hexagonal boron nitride and the extraction of cubic boron nitride from the products of its synthesis.

 The known composition is the closest analogue to the claimed composition in terms of features, however, using it to extract SM from a used abrasive tool on a bunch of fused alumina is ineffective.

 The objective of the invention is to develop a new composition that allows you to effectively use it to extract the grinding grain and especially grinding powders of diamond and cubic boron nitride in the grain range from 28 to 200 microns from the used and defective abrasive tools on a ceramic bond containing electrocorundum as a filler.

 Another objective of the invention is to increase the degree of extraction of SM from sludges containing aluminosilicate wastes generated by grinding ceramic materials in circles of diamond and cubic boron nitride. Another task is to reduce the temperature of the SM extraction process with almost complete absence of losses of diamond and cubic boron nitride of small fractions (28-60 μm).

The problem is achieved in that the composition for the extraction of diamond and cubic boron nitride contains a eutectic melt of alkali metal hydroxides, an additive forming a complex compound with aluminum and selected from the series: oxalic acid, tartaric acid, citric acid, one of the salts of ammonium, potassium, sodium lithium of these acids, an antioxidant additive, which is used as at least one of the chlorides of an alkali or alkaline earth metal selected from the series: potassium, sodium, lithium or calcium chloride I in the following ratio of components, wt.%:
The additive forming a complex compound with aluminum - 5 - 25
Antioxidant Supplement - 1 - 5
Eutectic melt of alkali metal hydroxides - Up to 100
the composition mainly contains a eutectic melt of sodium and lithium hydroxides, as an additive forming a complex compound with aluminum, mainly contains oxalic acid or its salts, as an antioxidant additive, the composition mainly contains sodium or calcium chloride.

Extraction of SM is based on the inertness of diamond and cubic boron nitride to the proposed composition and dissolution of electrocorundum, while oxalic acid, tartaric acid, citric acid and their salts accelerate the dissolution process, i.e., the transition of α-Al ₂ O ₃ to aluminates, due to formation of complex compounds of the type: [Al (C ₂ O ₄ )] Cl, Na ₃ [Al (C ₂ O ₄ ) ₃ ], Na [Al (C ₂ O ₄ ) ₂ ], [Al ( ₄ O ₆ H ₄ ) ] Cl and others.

 Chlorides of sodium, potassium, lithium or calcium prevent the oxidation of SM and allow the process to be carried out in an oxidizing environment.

 Example 1

Take 100 g of industrial concentrate intended for the manufacture of a diamond abrasive tool containing 40 g of 100/80 μm diamond grinding powder and 60 g of 60/40 μm electrocorundum, place the concentrate in a Teflon bath, fill in 300 g of the composition in the following ratio, wt.%: eutectic melt of potassium hydroxide and lithium - 70, oxalate sodium - 25 and sodium chloride - 5. Content bath placed in a muffle furnace and kept at a temperature of 230 ^o C for 1.5 hours, then cooled and leached and washed with water, separating the residue m and dried. The selected residue in an amount of 40 g is, according to x-ray phase analysis, a diamond that does not contain corundum impurities.

 With this treatment, corundum powder turned into a soluble state in the form of alkali metal aluminates.

 After the diamond is isolated, the washings are evaporated and sent for disposal, either to neutralize acidic effluents, or as coagulants for wastewater treatment.

 Example 2

The working layer of the used APP 200 × 3 × 10 × 75 circle, containing in the initial concentrate grinding powder of ACP diamond 100/80 μm in the amount of 25% and 37.5% of electrocorundum powder 80/63 μm, is separated from the base and crushed to particles 1 - 2 mm. Take 100 g of powdered powder, remove the metal binder by treatment in mineral acid, the residue in an amount of 65 g is placed in a Teflon bath, 300 g of the composition containing in wt.% Are filled in: eutectic mixture of sodium and lithium hydroxides - 94, potassium tartrate - 5 and chloride lithium - 1. The contents of the bath are kept in a muffle furnace at 250 ^o C for 1 hour, cooled, leached and washed with water, the residue is separated and dried. The selected residue in an amount of 24 g (96%) is a diamond without an admixture of corundum. The degree of diamond extraction is 96%, the losses in the amount of 4% are apparent and are explained by a change in the concentration of diamond during the work of the circle. The fractional composition of the selected diamond powder has not changed and its main fraction, more than 70%, is 100/80 microns, which allows the diamond to be reused for the manufacture of an abrasive wheel.

 Example 3

An artificial mixture is prepared from powders of cubic boron nitride grade KO 50/40 μm and electrocorundum 28/20 μm in a ratio of 1: 1 by weight. Take 100 g of the prepared mixture and treat it at 200 ^o C for 2 hours with a composition containing in wt.%: A eutectic mixture of potassium and sodium hydroxides - 88, potassium citrate - 10 and calcium chloride - 2. After leaching and washing with water, the residue separated and dried. According to x-ray analysis, this is cubic boron nitride without an admixture of aluminum oxide. The particle size of cubic boron nitride has not changed, so it can be reused.

 The number of examples presented in the description does not limit the possibility of using other components of the proposed composition.

 The use of other compositions containing additives such as oxalic, tartaric, citric acid or ammonium salts of these acids also show the complete dissolution of fused alumina and the complete removal of SM from the used tool, sludge and waste.

 It is also possible to use, as complexing additives, crystalline hydrates of salts, acid salts and double salts of potassium and sodium of these acids.

 The proposed composition can be used to extract diamond and cubic boron nitride when they are together, as well as to extract SM from the products of their synthesis, in the case of using aluminum or aluminum oxide as additives in the initial charge for the synthesis of superhard materials.

 The process of using the composition is waste-free, because after the extraction of superhard materials, washing water containing alkali metal aluminates can be used as coagulants in wastewater treatment.

Claims (3)

1. The composition for the extraction of diamond and / or cubic boron nitride, containing a eutectic melt of alkali metal hydroxides, an additive forming a complex compound with aluminum and selected from the series: oxalic acid, tartaric acid, citric acid, one of the salts of ammonium, potassium, sodium, lithium of these acids and an antioxidant additive, which is used as at least one of the chlorides of an alkali or alkaline earth metal selected from the series: potassium, sodium, lithium or calcium chloride in the following ratio com onentov, wt.%:
The additive forming a complex compound with aluminum - 5 - 25
Antioxidant Supplement - 1 - 5
Eutectic melt of alkali metal hydroxides - Up to 100
2. The composition according to claim 1, characterized in that it mainly contains a eutectic melt of sodium and lithium hydroxides.  3. The composition according to claims 1 and 2, characterized in that it contains oxalic acid or its salts as an additive forming a complex compound with aluminum.  4. The composition according to paragraphs. 1 to 3, characterized in that it mainly contains sodium or calcium chloride as an antioxidant additive.