The invention relates to the use of liquid dyestuff preparations for dyeing wood.
Liquid dyestuff preparations for dyeing wood are usually called woodstains. Woodstains are intended not to mask but to emphasize the grain of the wood and its veneers, giving them colour, and therefore comprise only truly dissolved dyestuffs. Solutions of basic or acidic dyestuffs in water or of solvent dyestuffs in organic solvents are known in practice. In addition to these so-called water-based and solvent-based stains, a combination of these two stains became established at the start of the '80s as a further type. These are water-dilutable solutions of organic dyestuffs in mixtures of water and solvent.
Woodstains are chiefly employed indoors and serve chiefly for decorative purposes. On application with a sponge, brush or a spray gun, they should penetrate as uniformly as possible and as deeply as possible into the wood material and give a uniform dyeing which is fast to light, water and abrasion after drying. It should furthermore also be possible to protect and preserve the stained wood with clear furniture varnishes without the dyestuffs bleeding out into the clear varnish.
Woodstains chiefly comprise metal complex dyestuffs.
It has been found that water-dilutable woodstains which meet the requirements in practice in an outstanding manner are provided with the liquid dyestuff preparations described in the following.
The invention relates to the use of liquid dyestuff preparations for dyeing wood, characterized in that the liquid dyestuff preparations comprising
5 to 30% by weight, in particular 12 to 23% by weight, of a dyestuff of the formula I
n1 and n2 denote the number 1 or 0,
X represents N or CH, Ct+ represents a cation
and the polyvalent radicals A, B, G and D independently of one another represent heterocyclic or aromatic radicals, in particular optionally substituted phenylene and naphthylene radicals, the particular complexing —COO— or —O— group being in the ortho-position relative to the azo and azomethine group (X═CH) respectively,
15 to 90% by weight, in particular 15 to 60% by weight, preferably 20 to 90% by weight, more preferred 25 to 60% by weight, of an alkoxy-alcohol of the formula (II)
R denotes a straight-chain or branched C1-C4-alkyl,
Z denotes a straight-chain or branched C2-C3-alkylene and
n3 represents 1, 2 or 3, and
5 to 75% by weight of water are employed.
In general, “liquid” is understood as meaning a liquid state at room temperature under normal pressure.
In a particular embodiment of the process according to the invention, dyestuff preparations which comprise dyestuffs of the formula (I) which are preferably built up from azo or azomethine compounds which, in the form of their free acid, correspond to the compounds (III) and (IV)
wherein a, B, G, D, n1 and n2 have the abovementioned meanings, are employed.
Preferred dyestuffs of the formula (I) are derived from the following radicals:
Possible radicals of the formula
Possible radicals of the formula —B—OH are, preferably:
Possible radicals of the formula -G-(CO)n2
OH are, preferably:
Possible radicals of the formula -D-OH are, preferably:
Dyestuffs which are employed as further preferred dyestuffs of the formula (I) are those of the formula (V):
A, B, G, D, n1, n2 and Ct+ have the abovementioned meanings, and
m represents 0 or 1 and
R represents 4-nitro or 5-chloro, and in the case where m=1, the o-chlorophenylazo group is in the para-position relative to the complexing —O— group.
Preferred substituents of the polyvalent radicals A, B, G and D are, for example, those chosen from the group consisting of: NO2, halogen, in particular chlorine, sulphonamide and C1-C4-alkyl.
The dyestuffs of the formula (I) which can be used according to the invention are known in most cases and can be prepared by known methods, such as are described, for example, in EP-A 066 230, EP-A 072 501 or EP-A 532 994.
The cation represented by Ca+ is preferably an alkali metal cation, in particular a lithium, sodium or potassium cation, an ammonium ion, the cation of an organic amine, such as, for example, that of mono-, di- or triethylamine, mono-, di- or tri-ethanolamine, N-methyldiethanolamine, N-butyldiethanolamine or N,N-diethylethanolamine, or a tetraalkylammonium, such as, for example, tetramethylammonium. A particularly preferred cation is the lithium cation.
Preferred dyestuffs of the formula I correspond to a dyestuff of the formula (Ia) (yellow)
a dyestuff of the formula (Ib) (orange)
a dyestuff of the formula (Ic) (red)
a dyestuff of the formula (Id) or (Ie) (each brown)
a dyestuff of the formula (If) (blue)
and/or the black dyestuff of the formula (Ig)
The dyestuffs of the formulae (Ia) to (Ig) wherein Ct+=Li+ are particularly preferred.
Preferred alkoxy-alcohols of the formula (II) which are mentioned are, for example, the following representatives: C1-C4-monoalkyl ethers of mono- and polyglycols, such as methyl glycol, ethyl glycol, propyl glycol, butyl glycol, methyldiethylene glycol, butyldiethylene glycol, methyltriethylene glycol, 1-methoxy-2-propanol, 2-methoxy-1-propanol, 1-ethoxy-2-propanol, 2-ethoxy-1-propanol, dipropylene glycol monomethyl ether means (3-(3-methoxy-propoxy)-1-propanol) and dipropylene glycol monoethyl ether means (3-(3-ethoxy-1-propoxy)-1-propanol).
Particularly suitable alkoxy-alcohols of the formula (II) are the C1-C4-monoalkyl ethers of glycols and diglycols and the monoalkyl ethers of 1,2-propylene glycol and of ethylene glycol, in particular monoalkyl ethers of 1,2-propylene glycol. 1-Ethoxy-2-propanol is especially preferred.
The dyestuff preparations used according to the invention can furthermore comprise
0 to 40% by weight, in particular 20 to 35% by weight, of a cyclic ester or amide and
0 to 5% by weight of auxiliaries customary in woodstains, such as fungicides, UV stabilizers, binders and/or surfactants.
Possible preferred cyclic esters or amides are, for example, lactones, such as 4-butyrolactone, and lactams, such as pyrrolidone, N-methylpyrrolidone, ε-caprolactam, N-methyl-ε-caprolactam and N-ethyl-ε-caprolactam.
Further water-miscible organic solvents which are customary in woodstains can also be used. There may be mentioned here in particular: lower alcohols, such as ethanol, ketones, such as methyl ethyl ketone, mono- and polyglycols, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol and dipropylene glycol, and carboxamides, such as formamide and dimethylformamide, as well as cyclic ureas, such as 1,3-dimethyl-2-imidazolidinone.
The dyestuffs of the formula (I) are readily water-soluble. The concentration and stability of the aqueous solutions can also be increased considerably, for example, by addition of a water-miscible organic solvent.
It has been found that concentrated aqueous solutions of these dyestuffs of the formula (I), in particular those of the formulae (II) to (VIII), preferably in a mixture of water and at least one water-miscible organic solvent, are valuable woodstains with which weatherfast and lightfast wood dyeings can be achieved by various methods of application.
Possible materials for dyeing are shaped wood in the most diverse forms, including in finely divided form, such as wood shavings and sawdust, but above all wood veneers. The veneers are as a rule large-area wooden sheets of various timbers of a thickness of, in general, 0.5 to 10 mm. Possible types of wood are pine, spruce, fir, larch, Scots pine, oak, beech, ash, maple, walnut, pear, teak, mahogany, chestnut, birch, hazelnut, linden, willow, poplar or plane.
The dyestuffs of the formula (I) which can be used according to the invention can be on the surface or inside the wood material to a greater or lesser depth, depending on the nature and type of wood and depending on the dyeing conditions. Veneers are usually dyed as far as possible through the entire cross section.
The use according to the invention takes place in the customary manner, and the dyestuff preparations are preferably applied to the wood, for example, by brushing, rolling, spraying or impregnation. In the case of brushing, rolling or spraying, the dyestuff preparations are preferably used in undiluted form, while in the case of impregnation or immersion dyeing, the dyestuff preparations can be diluted with up to 300 times the amount of water.
A deeper penetration of the dyestuff into the wood material or through-dyeing of a wood veneer is as a rule achieved by immersion dyeing in closed containers. The depth of penetration is determined by the treatment time, the temperature of the dyebath and the pressure applied to the container. The treatment time can be up to 10 hours, the temperature is as a rule 20 to 120° C. and the pressure is preferably 1 to 2 bar.
The dyestuffs of the formula (I) are distinguished by a good penetration and as a rule give wood dyeings with an adequate depth of penetration or a complete penetration after just 3 hours at temperatures of up to 100° C.
In the case of immersion dyeing in a closed container, the goods to be dyed should be moistened beforehand in order to avoid deformations during the dyeing process. So that the dyestuff is fixed better in the wood, the pH of the dyebath is lowered to 5 to 4.5. After the treatment, the dyed material is generally dried in air, either at room temperature or in a circulating air cabinet at higher temperatures, preferably at 40 to 80° C. Weather-resistant dyeings which have wet-fastness properties and have a good fastness to light and overpainting are obtained in this manner using the dyestuffs of the formula (I).