Stabilization of wood substrates

Details Stabilization of wood substrates Stabilization of wood substrates

2002-02-27

2003-11-25

Pryor, Alton N. (Department: 1616)

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Having -c-, wherein x is chalcogen, bonded directly to...

C514S317000, C514S318000, C514S644000, C514S663000

Reexamination Certificate

active

06653324

ABSTRACT:

This application is a 371 of PCT/EP00/08259 filed Aug. 24, 2000.
The invention relates to a method of stabilizing wood with a water solution or emulsion of a sterically hindered amine N-oxyl or N-hydroxyl against damage by heat and light and to the use of a sterically hindered amine N-oxyl or N-hydroxyl in water for the stabilization of wood.
Surfaces of wood which are exposed to intense sunlight are damaged primarily by the UV component of sunlight. This process is even enhanced by heat due to the absorbed infrared radiation from the sun. The polymeric constituents of the wood are degraded, leading to a roughening and discoloration of the surface. Subsequently, further damage results from infestation by microorganisms, especially by fungi.
The usual method of protecting wood against damage by light without giving up the visual image of the wood surface is to coat it with a colourless varnish containing a light stabilizer, in particular a UV absorber.
Wood protective coatings which contain a UV absorber, an antioxidant and an insecticide are disclosed for example in JP-A-59/115 805.
EP-A-0 479 075 discloses sterically hindered amine stabilizers for wood stains which are substituted at the nitrogen atom by hydrogen, alkyl, allyl, hydroxymethyl, hydroxyethyl, acyl, m benzoyl or benzyl.
EP-A-943 665 discloses a wide range of sterically hindered amine N-oxyls or N-hydroxyls which are applied to the wood substrate as solutions comprising at least one organic solvent. Described are also water miscible systems which contain in addition to the organic solvent a certain amount of water and optionally a polymer binder. The document does not mention impregnating solutions which contain exclusively water.
It has now been found that selected sterically hindered amine N-oxyls or N-hydroxyls have an improved stabilizing activity against light-induced degradation if they are applied from a pure water stain or impregnation to the wood. A top coat of a conventional binder which may contain further light stabilizers may additionally be applied to the wood substrate.
The present invention provides superior weatherability to wood substrates as compared to prior art techniques. In many cases it is for example not necessary to apply an additional coating. If such a coating is applied a very thin or transparent coating is mostly sufficient. This is in many cases desirable for aesthetical reasons.
Wood is a complex polymeric material containing essentially cellulose, hemicellulose and lignin. Lignin itself is a complex mixture of high molecular weight products which are derived from conyferyl alcohol.
Particularly lignin causes discoloration and undergoes degradation upon exposure to actinic radiation. It is therefore also an object of the present invention to prevent the photochemical degradation of the lignin part of wood. In addition, preventing lignin breakdown may remove a source of nutrition for fungi and thus reduce or prevent fungal attack. Therefore reduced amounts or essentially no biocides may be used in some cases.
Accordingly, the invention relates to a method of protecting wood against light-induced degradation by treatment with an impregnation which penetrates the surface of the wood comprising
a) water without an organic solvent and
b) a sterically hindered amine which is selected from the compounds of formulas A to R and a; A* to R*
 wherein
E is oxyl or hydroxyl,
R is hydrogen or methyl,
in formula A and A*,
n is 1 or 2,
when n is 1,
R
1
is hydrogen, alkyl of 1 to 18 carbon atoms, alkenyl of 2-18 carbon atoms, propargyl, glycidyl, alkyl of 2 to 50 carbon atoms interrupted by one to twenty oxygen atoms, said alkyl substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups, or
R
1
is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by —COOZ where Z is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl, or where Z is said alkyl substituted by —(COO
−
)
n
M
n+
where n is 1-3 and M is a metal ion from the 1st, 2nd or 3rd group of the periodic table or is Zn, Cu, Ni or Co, or M is a group N
n+
(R
2
)
4
where R
2
is alkyl of 1 to 8 carbon atoms or benzyl,
when n is 2,
R
1
is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12 carbon atoms, xylylene or alkylene of 1 to 50 carbon atoms interrupted by one to twenty oxygen atoms, substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups,
in formula B and B*,
m is 1 to 4,
when m is 1,
R
2
is alkyl of 1 to 18 carbon atoms, alkyl of 3 to 18 carbon atoms interrupted by —COO—, alkyl of 3 to 18 carbon atoms substituted by COOH or COO—, or R
2
is —CH
2
(OCH
2
CH
2
)
n
OCH
3
where n is 1 to 12, or
R
2
is cycloalkyl of 5 to 12 carbon atoms, aryl of 6 to 12 carbon atoms, or said aryl substituted by one to four alkyl groups of 1 to 4 carbon atoms, or
R
2
is —NHR
3
where R
3
is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aryl of 6 to 12 carbon atoms, or said aryl substituted by one to four alkyl of 1 to 4 carbon atoms, or
R
2
is —N(R
3
)
2
where R
3
is as defined above,
when m is 2,
R
2
is alkylene of I to 12 carbon atoms, alkenylene of 4 to 12 carbon atoms, xylylene, alkylene of 2 to 12 carbon atoms interrupted by —COO—, alkylene of 3 to 18 carbon atoms substituted by COOH or COO—, or R
2
is —CH
2
(OCH
2
CH
2
)
n
OCH
2
— where n is 1 to 12, or
R
2
is cycloalkylene of 5 to 12 carbon atoms, aralkylene of 7 to 15 carbon atoms or arylene of 6 to 12 carbon atoms, or
R
2
is —NHR
4
NH— where R
4
is alkylene of 2 to 18 carbon atoms, cycloalkylene of 5 to 12 carbon atoms, aralkylene of 8 to 15 carbon atoms or arylene of 6 to 12 carbon atoms, or
R
2
is —N(R
3
)R
4
N(R
3
)— where R
3
and R
4
are as defined above, or
R
2
is —CO— or —NH—CO—NH—,
when m is 3,
R
2
is alkanetriyl of 3 to 8 carbon atoms or benzenetriyl, or
when m is 4,
R
2
is alkanetetrayl of 5 to 8 carbon atoms or benzenetetrayl,
in formula C and C*,
R
10
is hydrogen, alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, alkanoyl of 2 to 18 carbon atoms, alkenoyl of 3 to 5 carbon atoms or benzoyl,
x is 1 or 2,
when x is 1,
R
11
is hydrogen, alkyl of 1 to 18 carbon atoms, alkenyl of 2 to 18 carbon atoms, propargyl, glycidyl, alkyl of 2 to 50 carbon atoms interrupted by one to twenty oxygen atoms, said alkyl substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups, or
R
11
is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by —COOZ where Z is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl, or where Z is said alkyl substituted by —(COO
−
)
n
M
n+
where n is 1-3 and M is a metal ion from the 1st, 2nd or 3rd group of the periodic table or is Zn, Cu, Ni or Co, or M is a group N
n+
(R
2
)
4
where R
2
is hydrogen, alkyl of 1 to 8 carbon atoms or benzyl, or
when x is 2,
R
11
is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12 carbon atoms, xylylene or alkylene of 1 to 50 carbon atoms interrupted by one to twenty oxygen atoms, substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups,
in formula D and D*,
R
10
is as defined above,
y is 1 to 4, and
R
12
is defined as R
2
above,
in formula E and E*,
E
1
and E
2
, being different, each are —CO— or —N(E
5
)— where E
5
is hydrogen, alkyl of 1 to 12 carbon atoms or alkoxycarbonylalkyl of 4 to 22 carbon atoms,
E
3
is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl, said phenyl or said naphthyl substituted by chlorine or by alkyl of 1 to 4 carbon atoms, or phenylalkyl of 7 to 12 carbon atoms, or said phenylalkyl substituted by alkyl of 1 to 4 carbon atoms,
E
4
is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl or phenylalkyl of 7 to 12 carbon atoms, or
E
3
and E
4
together are polymethylene of 4 to 17 carbon atoms, or said polymethylene substituted by one to four alkyl of 1 to 4 carbon atoms, preferably methyl,

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