DE3405373A1 - METHOD FOR STABILIZING DIMENSIONS AND PROTECTING WOOD AND WOODEN MATERIALS - Google Patents

Description

FEDERAL INSTITUTION FOR MATERIAL TESTING

1 Berlin 45, 02/07/1984 Unter den Eichen 87 Fernruf (030) 8104-1

Patent description

Inventor: Dr. Arno Burmester

Invention: method for dimensional stabilization

and to protect wood and wood containing

materials

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The invention relates to a "method for producing dimensionally stable Wood and wood-containing materials.

Wood changes its dimensions under the influence of changing humidity. This queuing "" and shrinking (moisture deformation) leads to the well-known difficulties in the use of wood, especially in the case of windows, doors, floors and plate surfaces etc. - '^

The problem of reducing moisture deformation is already Has been the subject of numerous experiments in science and practice. An overview of this is contained in the one written by A. Burmester BAM report no. ^ "Dimensional stability of wood against moisture; Basics and remuneration process ", Berlin 1970. J) ie Remuneration procedures that have become known up to now could only be implemented in practice in a few cases because they have disadvantages 'Are related of various kinds that limit their applicability. Given the complexity of the problem, it is not possible to develop a universally applicable remuneration process.

The invention is based on the object of providing a method for improving the dimensional stability of sapwoods such as maple, Birch, beech, poplar, etc. to develop naturally because of their structure and because of the lack of core ingredients a particularly large moisture deformation is inherent, so that they among other things are therefore excluded from many areas of use.

This object is achieved in that a Impregnation is carried out with substances that can be introduced into the cell wall cavities. Only a few are for this Substances suitable. These include the tannins, which occur both as natural substances (tannin) in plants and synthetically getting produced. Tannin is an essential part of the Heartwood of many tree species. It works in the natural Conversion of sapwood into heartwood, however, only little dimensional stabilization, because it is only stored in the lumina of the cells and not in the cell walls. The technical Impregnation of sapwood with tannin solutions caused after

previous .'Jt and de.-. Also know only a moderate dimensional stabilization. Penetration into the cell walls is limited because of the size of the molecules of the tannins and can be caused by soaking ^ _ kung des- wood in the fiber-saturated condition and by extending the Soaking time can only be promoted to a small extent. For practical purposes, however, this dimensional stabilization is not sufficient, when compared with naturally dimensionally stable types of wood. So far it has-rt'icTTt succeeded in tannin in greater To be stored in the cell walls.

It has now been found that a decisive improvement in the " Dimensional stabilization of tanned wood through the action of heat can be achieved at a certain temperature level .. In addition to the lowering of the viscosity of the tannin solution is especially the porosity of the cell walls increased so much that the Impregnant molecules fill the cell wall cavities instead of the moisture deformation the water causing the problem. This largely prevents the wood from shrinking when it dries. For the ability of the impregnation to penetrate the cell walls, its molecular size and the pore size of the cell walls are Meaning. The optimal temperature level when exposed to heat is therefore corresponding to the molecular size of the respective type of tanning agent and the fine structure of the respective wood species. It is generally in the range between 20 ° C and 140 ° C.

Tanning agents can be used alone or in a mixture with other substances, e.g. sugars or salts including wood protection or fire protection salts, be used.

The impregnation of the wood with such solutions is different In the usual way (under pressure or vacuum application as well as in the immersion process) possible. The exposure to heat can be done by soaking with a suitably heated solution, possibly after preheating the wood. It is also possible, heating only after soaking the solution-saturated wood at room temperature or after partial up to complete drying. The degree of dimensional stabilization that can be achieved depends on the moisture content of the Heat treatment as well as its duration and temperature. Further parameters are the type of impregnation agent, the concentration of the solution and Wood moisture before impregnation.

The advantages that can be achieved with the invention are in particular therein ,, that

Y. the dimensional stability of sapwoods is improved to a decisive extent, so that low-quality woods are remunerated to high-quality special woods,

2. Throwing and tearing of the .wood during drying prevented will, _ ^ __—.

3- the loss of volume due to shrinkage and machining essenlixLb_r-e_diLziert is,

k. the impregnation of the wood can take place with any moisture content with the usual equipment,

5. the impregnation substance, especially tannin, is inexpensive and made of can be obtained from the bark of native trees,

.6. with the use of tannin and other extracts' from tree bark an essential contribution to the utilization of this hitherto little used raw material can be provided,

7- the resistance of the tempered wood to attack is increased by fungi and insects, whereby tannin is a non-toxic protective substance for humans, the light Gives sapwood an attractive appearance.

Example 1.

Beechwood canteens 350 mm long, the wood moisture content of which was about 20%, were placed in an autoclave with a tannin solution T.L. flooded by 70 ° C. After half an hour of evacuation, the temperature of the impregnation solution being kept at 70 ° C, was normal air pressure was restored so that the tannin solution penetrated the wood. The scantlings remained in for another 5 hours the 70 ° C warm solution and were then removed. After that, disks were removed from .different length ranges on which the shrinkage was measured. The shrinkage was up to compensation in 20 ° / 86% tangentially 0.81% and radial 0.57%, in 20 ° / 65% 1.80% and 0.97%, respectively. The tangential shrinkage is thus compared to untreated beech wood by 8t> % or 75% reduced.

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The test of the flexural strength and the Ε module showed no change; the compressive strength was increased by 10%.

«^ Example- 2.

Beech wood was made using a vacuum process at room temperature Tannin solution T.L. soaked. After the maximum swelling was reached, it was kept at for 5 hours while preventing dehydration 70 ° C heated. The. Shrinkage measurement showed a reduction in tangential shrinkage by 70%.

Example 3.

Maple wood was made at room temperature in a vacuum process with tannin solution T.L. soaked and dried to fiber saturation. This was followed by a 5 hour period, preventing further drying out Heat treatment at 85 ° C. The measured shrinkage was reduced by 72% compared to untreated wood.

Example * l.

Fresh pine logs with a diameter of 25 cm were soaked with heated mimosa bark extract in the suction tube and then dried in a normal climate. A sample taken from wooden disc ^'l dried without cracking, while occurred in an untreated disk, the typical V-crack.

Example 5.

Beech wood was soaked in a fiber-saturated state with 20% solutions of quebracho extract or synthetic Tanigan LD subsequently heat-treated · The greatest shrinkage reduction was achieved for quebracho extract at 90 ° C and for Tanigan LD at 50 ° C achieved.

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Claims (4)

Process for dimensional stabilization and protection of wood and wood-containing materials Patent claims: 1. Process for dimensional stabilization and protection of wood and wood-containing materials, characterized in that tannins or substances similar in their properties through suitable methods are preferably incorporated into the cell walls. 2. The method according to claim 1, characterized in that wood and wood-containing materials in the highest possible state of swelling with the solutions of the relevant Substances are soaked according to the usual methods. 3. The method according to claims 1 and 2, characterized in that the storage of the relevant » Substances in the cell walls through the action of heat in Temperaturbe- ^ range is carried out, each based on the type of wood, wood moisture- » content and type of material are coordinated. 4. The method according to claims 1 to 3, characterized in that the tanning agents or similar Other substances are added to substances, which e.g. influence the stabilization, fixation and coloring or an additional one Provide protection against fungi, insects and / or fire as well as weathering. COPY