The present invention concerns a process for the recovery of carboxylic acid from a fraction comprising carboxylic acid and impurities, and a process for the manufacture of treated wood, which comprise the step of submitting a fraction containing carboxylic acid and impurities to a gas stripping operation.

Techniques and products are described for coloring acetylated wood products. An acetylated wood product can be impregnated by a coloring medium within a chamber and the colorant or colorants contained within the coloring medium can be fixed to the acetylated wood product by the application of heat or by application of radio frequency radiation to color any external surface or interior region of the acetylated wood product which has been impregnated by the coloring medium.

Techniques and products are described for coloring acetylated wood products. An acetylated wood product can be impregnated by a coloring medium within a chamber and the colorant or colorants contained within the coloring medium can be fixed to the acetylated wood product by the application of heat or by application of radio frequency radiation to color any external surface or interior region of the acetylated wood product which has been impregnated by the coloring medium.

The present invention relates to a method for continuous acetylation of wood elements. The acetylation is conducted with an acetylation medium at a pressure of at least 1.5 barg in a substantially oxygen free environment. Alternatively, the method according to the invention comprises the steps of: (a) feeding wood elements in a substantially oxygen free environment to a continuous acetylation reactor, and (b) treating the wood elements with an acetylation medium in the continuous acetylation reactor under wood acetylation reaction conditions, at a pressure of at least 1.5 barg.

The process according to the present invention allows to acetylate wood elements to a high acetyl content in a very efficient way, without compromising on the quality of the material. The acetylated wood elements can be used in the production of medium density fibreboards with superior qualities such as dimensional stability and durability.

A method for sulphation and phosphorylation of a wooden body to impart anti-flame properties to the substrate wherein at least one phosphonic acid of the formula (I) is used PO(OH).sub.2RPO(OH).sub.2 as a catalyst for sulphation and phosphorylating agent, and the relative wooden body.

Process for the recovery of carboxylic acid, in particular acetic acid containing carboxylic anhydride in particularacetic anhydride and other impurities, which comprises: (a) treating a fraction, in particular a fraction originating from a wood treatment process, containing carboxylic acid and impurities with a metal salt in the presence of water, (b) treating at least part of the fraction obtained from step (a) to remove metal salt and, (c) treating at least part of the fraction obtained from step (b) by distillation, stripping or membrane separation to recover at least a purified carboxylic acid fraction.

Disclosed is a process for the acetylation of wood, wherein the wood is impregnated with acetylation fluid and heated in stages. It is thereby secured that an acetylation reaction is conducted at a temperature above the boiling temperature of the acetylation fluid, at a stage where the impregnated wood is largely devoid of free acetylation fluid (i.e., acetylation fluid not retained in the wood matrix or in capillaries). Preferably, the process is conducted in a plant having conveyors, such as transportation screws, in the zones in which the separate heating steps are conducted.

Disclosed is the integration of the production of acetic anhydride from ketene, and the acetylation of wood using acetylation fluid comprising acetic acid and acetic anhydride. The invention involves directly using raw acetic anhydride as obtained in the production thereof from ketene, as a wood acetylation fluid.

Disclosed is the integration of the production of acetic anhydride from ketene, and the acetylation of wood using acetylation fluid comprising acetic acid and acetic anhydride. The invention involves combining acetic acid obtained from distillation of acetylation fluid with a residual aqueous acetic acid stream as obtained from ketene production.

Process for the recovery of carboxylic acid, in particular acetic acid containing carboxylic anhydride in particular acetic anhydride and other impurities, which comprises: (a) treating a fraction, in particular a fraction originating from a wood treatment process, containing carboxylic acid and impurities with a metal salt in the presence of water, (b) treating at least part of the fraction obtained from step (a) to remove metal salt and, (c) treating at least part of the fraction obtained from step (b) by distillation, stripping or membrane separation to recover at least a purified carboxylic acid fraction.