DD257607A1 - METHOD FOR THE CHEMICAL FAIRING OF VENEERS - Google Patents

Abstract

The invention relates to the refinement of veneers from indigenous deciduous trees by a pickling process. The veneers are treated with an aqueous solution of sodium carbonate. It will receive through veneered veneers.

Description

Field of application of the invention

The invention relates to a process for the refinement of veneers from native deciduous trees by uniform staining while preserving the natural wood texture.

Characteristic of the known state of the art

It is known to physically stain veneer by suitable dye solutions. Due to the greater absorbency of the porous, naturally bright Frühholzpartien here a negative image of the wood texture is obtained. The "artificial" impression created by this circumstance is usually undesirable in the design of furniture surfaces and in the interior design and partly also covers the wood texture.

On the other hand, there is the technique of pickling, which consists in a color development by chemical reaction of wood-containing inactive substances with the mordant. As such are mainly used heavy metal salts. There are also proposals to use for the pickling alkaline media. According to DE-PS 206997, the wood is embedded in wet, humus-rich soil and, with the addition of alkalis (lime milk, ammonia-containing alkalis, eg horse dung), left to act for 2 to 3 months. The disadvantages of the method, in addition to its exclusively manual implementation especially in the extremely long treatment times. It should be noted that this method - like essentially all pickling methods - is primarily applicable to conifers, preferably for American redwood (Sequoia sempervirens).

In DE-OS 3347151 a Laugenbeizverfahren is described, is treated in the wood with about 25% caustic soda or Ätzkalilauge. After immersion for 5 minutes, the caustic is allowed to act on the wood for 16 to 24 hours, after which the dried caustic residue is removed by further immersion in a dilute acid bath. The disadvantages of the method consist in the long exposure times still required here, on the other hand in the required for the neutralization of the strong liquor acid bath precisely matched concentration. The method will be primarily applicable to lumber, as the adverse effects of veneer lumbering on the wood, known to be caused by leaching, lead to processing problems such as veneer cutting and sticking.

Apart from the einbebenbei the advantage of preserving the positive image of the wood texture but also in the latter method there is a defect that a uniform coloration of the wood is not achieved, so that in necessary surface treatments (loops) or even minor damage the unpickled Wood comes to light.

Object of the invention

The aim of the invention is to give veneers of deciduous trees a brown shade over the entire cross section, with the greatest uniformity and durability of the dyeing in times acceptable for industrial implementation.

Explanation of the essence of the invention

The invention has for its object under suitable conditions to achieve a running in the shortest possible time, uniform and permanent staining of veneer by utilizing reactions of the natural ingredients of the wood. According to the invention, a veneer is treated for a period of 2 to 4 hours at a temperature of 20 to 60 ° C with an aqueous solution of 3 to 6 g / l of sodium carbonate at a pH of 9.5 to 12. The veneer is placed in a suitable container in the prepared soda solution and the solution circulated during treatment at least temporarily. To improve wetting, a wetting agent may be added to the solution. It is expedient to use the softest possible water with a water hardness of less than 5 degrees dH. Preferably veneers up to 1.0 mm thick are used.

The sodium carbonate causes an oxidative change in the lignin contained in the wood and / or other wood ingredients, with a pleasant brown color (cherry or pear tree color) is achieved over the entire veneer cross-section with complete preservation or highlighting of the texture. Surprisingly, particularly good results can be achieved in particular hardwoods, preferably veneers of birch, lime, willow and black poplar wood. Softwood veneers are not suitable for this treatment.

embodiment

A total of 100 square meters birch veneer of 0.7 mm thickness and a wood moisture content of 12% are placed in a dyeing basket according to DD-PS 229645 and lowered herein into a container with the prepared treatment bath. To prepare the bath, 30 kg of soda and 100 g of fit (as wetting agent) are dissolved in 6000 l of boiler feed water, the bath being circulated by means of a pump for 30 min.

The veneers are left in the bath for 2 hours at a pH of 10.8 and a temperature of 35 ° C, then removed and rinsed with water for 15 minutes. Subsequently, the veneers are dried in a conventional manner. There are thus colored veneers in a brownish, pear-like shade obtained.

Claims (3)

T. A process for the chemical dyeing of veneers from hardwoods, characterized in that the veneer for 2 to 4 hours at a temperature of 20 to 60 ° C with an aqueous solution of 3 to 6g / l sodium carbonate at a pH of 9.5 treated to 12.0. 2. The method according to claim 1, characterized in that a veneer is used to 1.0mm thickness. 3. The method according to claim 1, characterized in that the dyebath with water of a water hardness of less than 5 degrees dH recognized and the dyeing liquid wetting agent is added.