Process for pigmenting wood

Details Process for pigmenting wood Process for pigmenting wood

2000-09-15

2003-11-11

Gupta, Yogendra N. (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Wood dyeing process

C008S620000, C008S636000, C008S637100, C008S647000

Reexamination Certificate

active

06645257

ABSTRACT:

The background of the invention is constituted by composite wood materials which are to be processed only after colouring. Thin sheets of wood, coloured right through, are bonded together, shaped and then cut at a wide variety of angles to produce artistic effects which depend on the grain. These materials may be used in particular to produce design articles or for decorative purposes. The requirements in terms of light stability and right-through coloration are therefore significantly higher than in the case of customary wood veneers. In particular, it is essential for the individual sheets of wood to be coloured right through with a high degree of homogeneity, even in the case of relatively great thicknesses, since the core of the sheets becomes visible as a result of the artistic cutting.
JP-A-54/113403 discloses a process for the homogeneous colouring of wood veneers, in which the wood is first treated under hot conditions with an alkali, including sodium acetate and sodium bicarbonate, at a pH of 10 and only then is coloured with an appropriate dye, for example with C.I. Acid Blue 171.
JP-A-61/41503 discloses a process for the homogeneous colouring of wood veneers with an anionic direct dye, the optimum being achieved using a moderately soluble salt, including sodium bicarbonate, in saturated concentration.
However, these dyes do not have sufficiently satisfactory fastness properties for the abovementioned applications, especially when used outdoors or when exposed to sunlight, for example as wall boards in a glazed corridor.
WO-98/58027 discloses the colouring of porous materials, including wood, starting from soluble pigment precursors. However, the pigmentation is greater at the surface than in the interior of the material. It has been found, moreover, that the presence of an acid is necessary as a catalyst for regenerating the majority of pigments, to ensure that the pigment is not damaged by overheating to 160° C. or more.
It has now surprisingly been found that pigmentation of wood materials with significantly better penetration is obtained if wood is treated in succession with soluble pigment precursors from WO-98/58027 in the presence of a small amount of a weakly basic salt and subsequently with an organic acid, and only then is the pigment thermally regenerated.
The invention therefore relates to a process for pigmenting wood, which comprises treating wood in succession
a) with a solution comprising
from 0.01 to 80% by weight, based on the solution, of a compound of the formula
A(B)
x
  (I),
in which x is an integer from 1 to 8,
A is the radical of a chromophore of the quinacridone, anthraquinone, perylene, indigo, quinophthalone, indanthrone, isoindolinone, isoindoline, dioxazine, azo, phthalocyanine or diketopyrrolopyrrole series which is attached to x groups B via one or more heteroatoms, these heteroatoms being selected from the group consisting of N, O and S and forming part of the radical A,
B is hydrogen or a group of the formula
 at least one group B not being hydrogen and, if x is a number from 2 to 8, the groups B being identical or different, and
L is any desired group suitable for solubilization; and
from 0.05 to 5% by weight, based on the solution, of a salt of the formula
Kat
+
.An
−
  (II),
Kat
+
.½An
2−
  (III)
or
Kat
+
.⅓An
3−
  (IV),
in which Kat
+
is lithium, sodium, potassium or ammonium, An
−
is formate, acetate, propionate or hydrogen carbonate, An
2−
is oxalate, maleate, fumarate, malonate, carbonate or hydrogen phosphate, and An
3−
is citrate or phosphate,
in water or an organic solvent or in a single-phase mixture thereof,
b) with a solution comprising from 0.01 to 50% by weight, based on the solution, of an organic C
1
-C
6
carboxylic acid in water or an organic solvent or in a single-phase mixture thereof, and
c) converting the compound of the formula (I) thermally to a pigment of the formula A(H)
x
(V).
The wood in question may be any desired hardwood or softwood, such as obeche, ash, birch, poplar, fir, spruce, pine, tulip tree, maple, bird's-eye maple, sycamore maple, oak, beech, mahogany, myrtle, anigre, tay (koto), mappa, elm, zebrano, carbalho, vavona or ogea, for example.
A is the radical of known chromophores having the basic structure A(H)
x
(VI), A preferably having at least one directly adjacent or conjugated carbonyl group on each heteroatom attached to x groups B, such as
for example,
in which Z, for example, is
and x″ is a number from 1 to 16, in particular from 1 to 4; and in each case all known derivatives thereof.
Mention may be made in particular of those soluble chromophores wherein the pigment of the formula A(H)
x
(V) comprises Colour Index Pigment Yellow 13, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 94, Pigment Yellow 95, Pigment Yellow 109, Pigment Yellow 110, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 139, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 175, Pigment Yellow 180, Pigment Yellow 181, Pigment Yellow 185, Pigment Yellow 194, Pigment Orange 31, Pigment Orange 71, Pigment Orange 73, Pigment Red 122, Pigment Red 144, Pigment Red 166, Pigment Red 184, Pigment Red 185, Pigment Red 202, Pigment Red 214, Pigment Red 220, Pigment Red 221, Pigment Red 222, Pigment Red 242, Pigment Red 248, Pigment Red 254, Pigment Red 255, Pigment Red 262, Pigment Red 264, Pigment Brown 23, Pigment Brown 41, Pigment Brown 42, Pigment Blue 25, Pigment Blue 26, Pigment Blue 60, Pigment Blue 64, Pigment Violet 19, Pigment Violet 29, Pigment Violet 32, Pigment Violet 37, 3,6-di(4′-cyanophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-di(3,4-dichloro-phenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione or 3-phenyl-6-(4′-tert-butylphenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione.
Further examples are described by Willy Herbst and Klaus Hunger in “Industrial Organic Pigments” (ISBN 3-527-28161-4, VCH/Weinheim 1993).
In general, these soluble pigment precursors have no deprotonatable carboxylic or sulfonic acid groups.
L is preferably a group of the formula
in which R
1
, R
2
and R
3
independently of one another are C
1
-C
6
alkyl,
R
4
and R
8
independently of one another are C
1
-C
6
alkyl, C
1
-C
6
alkyl interrupted by O, S or N(R
12
)
2
, or unsubstituted or C
1
-C
6
alkyl-, C
1
-C
6
alkoxy-, halogen-, cyano- or nitro-substituted phenyl or biphenylyl,
R
5
, R
6
and R
7
independently of one another are hydrogen or C
1
-C
6
alkyl,
R
9
is hydrogen, C
1
-C
6
alkyl or a group of the formula
R
10
and R
11
independently of one another are hydrogen, C
1
-C
6
alkyl, C
1
-C
6
alkoxy, halogen, cyano, nitro, N(R
12
)
2
or unsubstituted or halogen-, cyano-, nitro-, C
1
-C
6
alkyl- or C
1
-C
6
alkoxy-substituted phenyl,
R
12
and R
13
are C
1
-C
6
alkyl, R
14
is hydrogen or C
1
-C
6
alkyl and R
15
is hydrogen, C
1
-C
6
alkyl, unsubstituted or C
1
-C
6
alkyl-substituted phenyl,
Q is p,q-C
2
-C
6
alkylene which is unsubstituted or substituted one or more times by C
1
-C
6
alkoxy, C
1
-C
6
alkythio or C
2
-C
12
dialkylamino, p and q being different locants,
X is a heteroatom selected from the group consisting of N, O and S, m being 0 if x is O or S and 1 if x is N, and
L
1
and L
2
independently of one another are [-(p′,q′-C
2
-C
6
alkylene)-Z-]
n
—C
1
-C
6
alkyl or C
1
-C
6
alkyl which is unsubstituted or substituted one or more times by C
1
-C
12
alkoxy, C
1
-C
12
alkylthio, C
2
-C
24
dialkylamino, C
6
-C
12
aryloxy, C
6
-C
12
arylthio, C
7
-C
24
alkylarylamino or C
12
-C
24
diarylamino, n being a number from 1 to 1000, p′ and q′ being different locants, each Z independently of the others being a heteroatom O, S or C
1
-C
12
alkyl-substituted N, and C
2
-C
6
alkylene in the repeating units [—C
2
-C
6
alkylene-Z-] being identical or different, and L
1
and L
2
may be saturated or unsaturated 1 to 10 times, uninterrupted or interrupted at

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