EP3065924A1

EP3065924A1 - Means and method for preventing a tannin migration from wood

Info

Publication number: EP3065924A1
Application number: EP13789190.9A
Authority: EP
Inventors: Thomas Staffel; Marina Fleischhauer; Siegbert Weber
Original assignee: BK Giulini GmbH
Current assignee: BK Giulini GmbH
Priority date: 2013-11-08
Filing date: 2013-11-08
Publication date: 2016-09-14
Also published as: WO2015067291A1; EA201690950A1; IL244963A0; JP2016535691A; JP6161815B2; CA2923099A1; US20160279823A1

Abstract

The invention relates to the treatment of wood or wood products, in particular for preventing the leakage or migration of tannin from the wood. Said leakage can be effectively prevented by treating the wood with a gelatin solution and/or with a wood treating agent which contains gelatin and gelatin derivatives.

Description

Means and methods for preventing tannin migration from wood

The present invention relates to the treatment of wood or

Wood products, in particular for preventing the escape or migration of tannin from the wood. This leakage can be effectively prevented by treating the wood with a gelatin solution and / or with a wood treatment agent containing gelatin and derivatives.

It is well known that in the processing or use of wood and wood products, the tannins contained in the wood, despite being treated with

Paints, pigments, leak and make themselves noticeable by disturbing stains, also known as staining or "bleading-out" phenomena ".

Chemically, tannins are polyhydroxyphenols which are soluble in both water, ethanol and acetone. The vegetable tannins vary significantly in their chemical structure and biological activity. They are found in the wood bark of oaks, birch and chestnuts, in tropical hardwoods, in the pericarp of walnut, in grapes and in plant galls. Monomeric groups of tannins are also found in hops as well as in black and green tea.

Wood is widely used in the area of home, yard and garden as a building material.

It is subject to weather conditions, direct earth contact or and is thereby destroyed by bacteria, fungi or insects. Therefore, wood is generally treated to protect it permanently from these harmful influences. In the

Wood treatment has recently become more and more important for so-called low-emission agents, especially when the treatment is required for wood indoors. When using wood as a building material e.g. As wooden ceilings or doors and windows, it is therefore often treated with water-soluble paints. A common problem is the bleeding of water-soluble

Wood ingredients, especially the tannins from the wood body, despite one

superficial painting with paints and varnishes. The exiting tannins form colored, often ugly, but in any case unwanted stains and discoloration. Such an intensified discoloration is particularly common in the area of the so-called knotholes of the wood, because there the concentration of tannins is often higher.

However, the trend or the legislation demands more and more water-based

Paints in contrast to solvent-containing agents for reasons of environmental protection. This is one of the main reasons why water-based paints are very common in wood.

The problem of so-called tannin migration has been solved differently in the prior art:

In US 4,104,228 and in 4,075,394 it has been proposed to avoid

Tannin migration to use a wood paint containing a linear, partially deacylated poly (N-acyl) alkylenimine in the formulation. This polymer can be previously applied directly to the wood or together with the wood paint in the formulation on the wood.

In US 6,485,786, a water-based tannin-blocking paint or coating has been proposed, consisting of an emulsion copolymer which is polymerized from ethylenically unsaturated monomers.

Another method has been disclosed in US 6,113,989. There were not acidic inorganic compounds such as ammonium, sodium or potassium

Zirconium carbonates incorporated in the polymeric wood paints. It has been coated with these means the wood and after

corresponding drying formed a vapor-impermeable, semi-permeable film on the surface of the wood, which has prevented the escape of tannin from the wood.

In US 6,533,856, to prevent tannin migration from the wood

Aluminum and tin compounds formulated in the wood paints.

In US 6,245,141, organo-inorganic compounds, e.g. one

Neoalkoxy titanate incorporated into the coating compositions is disclosed as a tannin blocker. These titanium compounds preferably have one or more amino functional groups. Also relevant in this connection is the US Pat. No. 6,531,223 in which a coating without a primer, ie a primer coat, is proposed. These

Coating essentially contains two components, namely one

water-soluble latex emulsion and so-called microspheres, which absorb little water. These include e.g. Sodium, or potassium aluminum silicate particles, glass beads, hollow glass beads, or also expanded acrylonitrile / vinylidene chloride copolymers u.a. It was essential here that the diameter of these particles, if possible not more than 210 [im should be.

In US 5,529,811, zinc cyanamide was proposed as a tannin blocker and US 5,27,619 used organosilane-containing latex copolymers as additives to prevent tannin migration.

Although the abovementioned proposed solutions for preventing tannin migration have already been made in the prior art, there has hitherto been no solution approach which makes use of a natural, naturally occurring compound.

A simple and effective solution to the problem of tannin migration from wood has surprisingly been found in the use of gelatin.

Gelatin is a mixture of polypeptides, depending on the extraction with molecular weights of about 13500 to 500000 (determined by SDS gel electrophoresis or

Gel chromatography), which is mainly obtained by a more or less extensive hydrolysis of the collagen contained in pig swine, split bovine calf, and their bones. Gelatine is available as granules in commerce, and as leaf gelatine and as a solution. The

Amino acid composition largely matches that of the collagen from which it is derived. It is odorless and practically colorless, insoluble in ethanol, ethers and ketones, soluble in ethylene glycol, glycerol, formamide and acetic acid.

In the context of the present invention, essentially a gelatin solution which no longer exhibits the ability to gel, which is obtainable from a gelatin powder by dissolution in water, can be used. In analogy to leather tanning, where tannin is used as a tanning agent, especially for cross-linking the collagen present in the skins, the inventors have found that the use of gelatin, as a collagen degradation product, in the prevention of tannin migration can be used successfully and very good results. In tanning, tannins or tannins obtained from oak or spruce bark, mimosa and sumac and other wood species are used as bark tannins ("Gerberlohe"), in which process the collagen molecules apparently become tannins with the aid of tannins are, respectively contain, networked and thus permanently bound.

When using gelatin as an additive in the corresponding

Wood paints, the tannin is converted into an insoluble gelatin (collagen) -Tannin complex, it forms a water-insoluble, colorless precipitate. In this way, tannin is virtually bound and prevents staining and bleeding.

According to the invention, gelatine can be spread or sprayed directly onto the wood surface as an aqueous solution. After this treatment, the wood can be aftertreated with any paint - the desired

blocking effect can be achieved in this way optimally. It is essential that the concentration of the aqueous gelatin solution is between 2 and 8 wt .-% moves.

Such a solution can be easily prepared by dissolving a gelatin powder in cold or warm water.

Gelatin powders are commercially available, in particular the types from Gelita, for example Collagen A or Biogel, for example Vitagel PLPR. The amount of gelatin, which is applied per cm ^{2 of} wood surface, is 5 to 10 mg / m ² based on the wood surface.

According to the invention there are 2 essential ways to apply the gelatin or derivatives on the wood surface. 1. You can apply to the wood surface, the aqueous gelatin solution, z. B. by brushing or spraying, and continue to process the wood surface after drying with other common wood paints.

2. You can the gelatin powder or the gelatin solution in the usual

Wood paints incorporate, which is possible without problems, because the gelatin has no adverse interactions with the wood paints or their components. In this approach, but the

Prerequisite for the manufacturer of these wood coatings to incorporate the gelatin directly into the formulations.

In accordance with the present invention, examples were developed for both ways to prove the effect of preventing tannin migration.

Example 1 separate order

In this test, a 5% aqueous gelatin solution was prepared by dissolving gelatin powders (gelatin 2 and 3) in water. It was also a liquid gelatine with 20% concentration used (Gelatinel)

Gelatine 1 = liquid gelatine with 20% active ingredient

Gelatine 2 = gelatine in powder form with 100% active ingredient / sourced from Switzerland

Gelatine 3 = powdered gelatin containing 100% active ingredient / based on

Germany

All gelatin types are commercially available products.

The gelatin solutions were each thinly applied to an oak board (30 × 11 cm) with a brush and dried for 24 hours at room temperature. Here, the total order amount was always 2 g.

After drying, a white wood finish with a layer of 150 μm layer thickness is applied to each pretreated piece of wood. The boards were at 25 ° C and 50% rel. Humidity stored for 1 week and then carried out with a photometer of the brand "Minolta CR 200" a whiteness measurement. Table 1 Results for Ex. 1:

Example 2 separate order

For this example, each of the two gelatin powders prepared a 10% aqueous solution, in all cases with distilled water.

In the blank sample, only tap water was applied to the wood before applying the wood paint.

The gelatin solutions prepared were, as in Example 1, on a

Oak board (30 xx11 cm) applied thinly with a brush and dried for 24 hours at room temperature. Here, the total order amount was always 2 g. After drying, a white wood finish with a layer of 150 μιη layer thickness was applied to each pretreated piece of wood. The boards were at 25 ° C and 50% rel. Humidity stored for 1 week and then with a

Photometer of the brand "Minolta CR 200" carried out a whiteness measurement.

Table 2 Results for Ex. 2

In this example, the product gelatin 2 showed the best results. Therefore, gelatin 2 was selected for Example 3.

Example 3: Gelatin was incorporated into the wood treatment agent (white wood finish)

100 g of white wood varnish were prepared / according to the formulation of Celanese, weighed and a gelatin solution 2 with three different

Concentrations, 3, 5 and 8%, corresponding to 40% solids content

made, then added to the wood finish.

The finished samples were stored for 24 hours at room temperature in a sealed box. Thereafter, they were applied with a doctor in amounts of 150 and 250 μιη layer thickness on an untreated oak board and at 25 ° C and 50% rel. Humidity stored for 1 week.

The whiteness measurement was carried out with the photometer "Minolta CR 200" / predecessor model of CR 400 /.

As a comparative experiment, a wood varnish without gelatine additive was also tested.

Table 3 with 150 gm layer thickness

Lb +

Comparison paint 92.6 5.4

without addition

3% additive 93.7 4.7

5% addition 94.7 4.4

8% additive 94.6 4.5 Table 4 with 250 μm layer thickness

The sample with 5% gelatin 2 additive, shows the best results.

The wood varnish used in the tests has the frame formula below:

Water 160 g

Dispersant 20 g

Brightener 50 g

Biocide 4 g

Defoamer 4 g

Thickener 45 g

Ti0 ₂ 460 g / pigment /

Solvent 80 g

Binder 1100 g

Water 73 g The measurement of the whiteness was performed according to L ^* , a ^* , b * in the CIE 1976 color order system (DIN 6174). Thus, the higher the L ^* value, the higher the whiteness level, and the higher the b * value, the higher the yellowness level in a sample.

Claims

patent claims

1. A method for preventing tannin migration from wood, thereby

characterized in that the wood before treatment with a

Wood treatment agent, namely, coated with an aqueous gelatin solution, wherein concentration of this gelatin solution 2 to 10%, and the application amount per cm ² 0.5 to 5 grams.

2. The method according to claim 1, characterized in that as

Gelatin solution, powdered gelatin dissolved in water, is used.

3. The method according to claim 1, characterized in that the water-soluble gelatin is incorporated in a wood treatment agent formulation.

4. Use of gelatin solution to prevent tannin migration from wood.

5. Use of gelatin-containing wood treatment agents for

Prevention of tannin migration from wood.