WASTE TREATMENT

Abstract: A waste liquid including an alcohol and/or a ketone is treated to give a solid reaction product. If alcohol is present, the fluid is contacted with a monomer-free isocyanate under conditions which give a solid polyurethane. If ketone is present, the fluid is contacted with an acid, ammonium compound or bisulphite ion under conditions which give a solid reaction product, if necessary after the addition of acid.

Description: WASTE TREATMENT Field of the Invention This invention relates to the treatment of waste liquid or vapour containing volatile solvents, especially spent inks. Background of the Invention Inks, e.g. those used in ink-jet printing, comprise a mixture of inflammable solvents, primarily methyl ethyl ketone (MEK) and alcohols such as ethanol, propanol and/or butanol. The vapour given off in use is undesirable, and the spent ink is classified as hazardous waste. The disposal of hazardous waste requires specialists, and is expensive; this problem grows as environmental pressures and legislation increase the constraints on disposal. In particular, waste ink should be made inert, as soon as possible. Summary of the Invention According to the present invention, waste liquid or vapour containing an alcohol and/or a ketone is treated in a manner which converts the hazardous component to a harmless, non-inflammable solid which can be disposed of simply and safely. The reactant for the alcohol is a monomer-free isocyanate, which can give a solid polyurethane. The reactant for the ketone is a urea, acid, ammonium compound or bisulphite ion, which gives a solid reaction product, if necessary after the addition of acid (to a ketone-ammonium compound reaction product) . Description of the Invention The waste liquid may be a spent ink, in which case the reactant may simply be mixed with the liquid under suitable conditions. The content of alcohol and/or ketone in an ink is usually from 20 to 90% by weight, and the amount of the appropriate reactant will be chosen in order to provide at least substantially complete removal of the alcohol/ketone. Suitable amounts of reagent with respect to alcohol/ketone are 2 to 4 g/g. The solid product is generally inert and non-inflammable. It can simply be separated from the liquid, and disposed of in, say, a landfill site. The invention can also be used to treat hazardous vapour or reduce odour emission to the atmosphere, e.g. during the operation of an ink jet printer. Thus, for example, vapour comprising MEK and/or other volatile materials may be absorbed and converted to an inert, harmless product by passing them through an on-line filter unit containing the appropriate reagent(s) in solution. A suitable filter unit may be a liquid mixture or a solution absorbed by an absorbent material. For use in the invention, a two-pack kit may be formulated, each pack comprising a reagent for ketone and alcohol, respectively. By way of example, bisulphite ion adds to MEK. The product is a white, crystalline, non-inflammable solid. A suitable reagent is disodium disulphite (sodium etabisulphite, Na 2 S 2 0 5 , as supplied by BDH Chemicals, Dagenham, Essex) . Polyols and alcohols react with polyisocyanates to give polyurethane polymers. The product produced can vary between flexible and tough, to hard and soft, depending upon the selection of precursors and the ratio employed. A catalyst can be added to speed the rate of formation of product . A suitable reagent is l,3,5-tris(6-isocyanatohexyl)biuret (available as Tolonate HDB from Baxenden Chemicals, Baxenden, Lancashire) . A suitable catalyst is dibutyltin dilaurate (available as Lakromark LT173 from Harcros Chemicals, Eccles, Manchester) . The following Examples illustrate the invention. Example 1 An ink is formulated from the following components (amounts in % by weight) : 600 g sodium etabisulphite is dissolved in 1 litre o warm water to give a clear yellow saturated solution. Dibutyltin dilaurate (0.28 g) is mixed with 680 cm 3 of thi solution. Tolonate HDB (620 g) is weighed into anothe container. Both liquids are added to 1 litre of ink in an empt plastic container. The final mixture is vigorously shake for 30 seconds and left to stand. After approximatel another 30 seconds, the ink solution becomes hot. 20-3 mins later the solution starts to solidify. There is a expansion to approximately three times the original volume, as the chemical reaction proceeds. The reaction mixture i left overnight. Next day, a flexible foam is formed. Al inflammable solvents have chemically reacted and thus bee destroyed. Example 2 The procedure of Example 1 is repeated, except tha the reaction is performed in two stages. The bisulphit solution and catalyst are added to the ink and vigorousl stirred. After 1 hour, a thin ink slurry is formed. Th Tolonate is added to this slurry and the reaction left t complete overnight. Example 3 An ink is formulated from the following component (amounts in % by weight) : Methyl ethyl ketone 65.5 Butanol 4.5 Denatured alcohol 9.0 Distilled water 1.5 Isopropyl alcohol 2.7 Other materials 16.8 As for Examples l and 2, the ingredients are adde together or separately. For 1 litre of ink, 1120 cm 3 o bisulphite solution is added together with 500 g o Tolonate and 0.82 g of the catalyst. After 2 days, a soli foam material is formed.

Claims: CLAIMS 1. A process for the treatment of a waste liquid or vapour including an alcohol, which comprises contacting the fluid with a monomer-free isocyanate under conditions which give a solid polyurethane. 2. A process for the treatment of a waste liquid or vapour including a ketone, which comprises contacting the fluid with an acid, ammonium compound or bisulphite ion under conditions which give a solid reaction product, if necessary after the addition of acid. 3. A process for the treatment of a waste liquid or vapour including an alcohol and a ketone, which comprises contacting the fluid simultaneously or sequentially with a monomer-free isocyanate and an acid, ammonium compound or bisulphite ion under conditions which give a solid polyurethane reaction product, if necessary after the addition of acid. 4. A process according to any preceding claim, which additionally comprises separating the solid from the liquid. 5. A process according to any preceding claim, wherein the liquid is a spent ink. 6. A kit suitable for use in a process according to clai 3, which comprises a first pack comprising the acid, ammonium compound or bisulphite ion and a second pac comprising the monomer-free isocyanate and, optionally, catalyst for the polyurethane-forming reaction.

Inventors: HUDD ALAN LIONEL, REZA NASER, HUDD, ALAN, LIONEL, REZA, NASER
Applicants: DOMINO PRINTING SCIENCES PLC
Application year: 1991
Main classification: B01D53
IPC codes: A62D3, A62D101, B01D53, C08G18