GB2095296A

GB2095296A - Process for treatment of wood

Info

Publication number: GB2095296A
Application number: GB8108881A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-03-20
Filing date: 1981-03-20
Publication date: 1982-09-29
Also published as: GB2095296B

Abstract

An oil mixture for the drying- coloring or oil drying of wood products, characterised in that it consists of a mixture of high and lower boiling oil products, so composed that high boiling oil products after the treatment remain in the wood surface and the lower boiling oil products are evaporated from the wood and are recovered, for example by condensation and separation.

Description

SPECIFICATION Process for treatment of wood The applicant has earlier developed some processes for the treatment of wood. One of these British Patent No. 11 81246-covers preservation with aqueous solutions followed by drying/coloring in a hot, high-boiling oil under vacuum (1). In a second treatment British Patent No. 1512549-impregnation takes place with preserving agents in an organic solvent foliowed by drying/coloring in hot oil with the simultaneously recovery of solvent (2). A third-British Patent Application No.

2044311-covers preservation with an emulsion followed by drying/coloring in hot oil (3). A fourth treatment-British Patent No.

1402191concerns drying of wet (green) wood in a special oil (4), and a fifth-British Patent Application No. 8035561-includes drying/coloring of moist or moistened wood (5).

A new way to work with drying-coloring oils in the said treatment processes has been developed.

The new treatment of the wood is carried out in a similar way as in the earlier processes; that is at a temperature preferably around 800C and under ahigh--as a rule at least 80 per cent-vacuum.

The novelty in the present treatment is considered to lie in the fact that the drying-coloring oil is composed of a mixture of high boiling and of lower boiling oils.

During the treatment, part of the oil mixture with its ingredients penetrates the surface layer of the wood. At the same time, part of the lower boiling oils, free of ingredients, evaporates from the oil mixture, together with water (or a solvent in the treatment (2) boiled away from the wood.

After the oil mixture, following the drying period, has been taken out of the treating vessel (and away from the wood) the lower boiling oils which penetrated into the wood surface are evaporated due to the finishing vacuum. Left in the wood surface, there thus remains a portion of the high boiling oils. It gives the wood color, surface protection, etc. The evaporated mixture of lower Iboiling oils and of water boiled away from the wood is condensed by cooling, whereby the lower boiling oils are recovered by separation.

By diluting the high boiling oils in this way, the amount of high boiling oils absorbed by the wood can be regulated. By drying/coloring (1) wood-for instance boards of a thickness of 25 millimeter-an amount of 40-60 kilograms of coloring oil per m3 are often absorbed. This amount is as a rule more than enough. It is several times higher than the amount of oil absorbed by painting. It can be expensive. By diluting the high boiling oils according to the invention with lower boiling oils, which in contrast to ordinary painting are recovered, the amount of coloring oil absorbed by the wood is kept under control. This involves also, due to a lower consumption of high boiling oils and other, related vehicles, better possibilities to use products of a high quality.Another advantage is increased possibilities to use more viscous vehicles such as alkyds, and to use additives, such as waxes and resins.

When it is a question of the drying of wet (green) wood (4), the main advantage is increased possibilities to treat the wood in different ways; it can be given surface preservation or a waterrepel lent surface or color by introducing protecting agents, waxes, vehicles and pigments into the oil mixture.

The mixture properties between high and low boiling oils can vary considerably. In practice, however, they will be limited. By using the present process, the intention is to save a considerable part of the high boiling oils. The content of the high boiling oil in the mixture should thus not be too high. As a rule it may amount to half the oil mixture at the most.

When color pigments are introduced, the amount of high boiling oils must not be too low; as a rule the mixture has to contain at least 1/4 high boiling oils, that is 3/4 low boiling oils have to be present at the most. With a low content of high boiling oils, difficulties occur to keep the pigments dispersed. Stirring faciiitates, however, the dispersion. if the intention is to obtain an oil treatment of the wood surface with no coloring, the content of high boiling oils can be reduced below the given limit: that is the content of low boiling oils can be increased. Even if it in these cases is more difficult to introduce pigments into the oils, the possibility still remains to introduce dissolved substances, such as wax, preservatives against decay, blue strain, mould and insects, etc.

The lower the amount of high boiling oils that is present in the oil mixture, the more the process will be similar to the wood oil vacuum drying treatment (4).

With the treatment (4) the oil is removed from the wood surface by a final vacuum after the drying period. This can be achieved because the oil for the purpose has an adapted boiling point of around 20QOC. In the process according the present invention, the lower boiling oils in the oil mixture are removed in a similar way. Here, however, a somewhat lower boiling point on the lower boiling oils is chosen because the high boiling oils somewhat delay the evaporation of the lower boiling oils.If the content of high boiling oils is comparatively high, then the lower boiling oils ought to boil around 1 750C. The lower the content of high boiling oils, the more ought the boiling point of the lower boiling oils approach the said 2000 C. The high boiling oils should, as with the other treatments referred to, boil around or above 3500 C.

The process can be fulfilled with oil mixtures with less distinct boiling ranges between the high and the low boiling oils. It can even be prosecuted with an oil mixture with no distinct ranges: that is a mixture that successively boils at a higher and higher temperature. With the exception for special cases this does not represent a rational way. Part of the oil remaining in the wood is not sufficient stable against evaporation to give a long time protection. Further difficulties are present to proceed such a treatment under control.

The composition of the high boiling, coloring, protecting oils is described in more detail in the Swedish Patent Application 7908379-6. The lower boiling oils are of the same type as described in British Patent No. 1 402191 covering treatment (4).

Claims

1. An oil mixture for the drying-coloring or oil drying of wood products, characterised in that it consists of a mixture of high and lower boiling oil products, so composed that high boiling oil products after the treatment remain in the wood surface and the lower boiling oil products are evaporated from the wood and are recovered, for example by condensation and separation.

2. An oil mixture as claimed in claim 1, characterised in that it contains lower boiling oils in amounts around half or more of the total oil mixture.

3. An oil mixture as claimed in claim 1 or claim 2, characterised in that it contains low boiling oils in amounts around three quarters or more of the total oil mixture.

4. An oil mixture as claimed in any one of claims 1 to 3, characterised in that the high boiling oils boil around or above 350 , and that the low boiling oils boil around 200 C or below.

5. An oil mixture as claimed in claim 1 substantially as hereinbefore described.

6.A wood product when treated with an oil mixture as claimed in any one of the preseding claims.