US2012975A - Method of impregnating wood - Google Patents

Description

Sept. 3, 1935. c. SCHMITTUTZ METHOD OF IMPREGNATING WOOD Filed Sept. 28, 1954 I I INVENTOR. gar/ 56/)(174072 A ORNEY.

J55 the Patented Sept. 3, 1935 UNITED STATES PATENT oFFicE METHOD OF IMPREGNATING WOOD Carl Schmittutz,

Bad Kissingen, Germany, as-

signor to Osmose Holzimpraegnierungs G. in.

b- He, Leip many Germany, a corporation of Ger- Application September 28, 1934, Serial No.

13 Claims.

substance into the wood, it has hithertobeen.

considered necessary to cut the trees while the sap content is at the minimum, that is, during the winter. The cut treesare dried for a long period of time during which the wood frequently becomes impregnated with spores of fungi, molds and other organisms. The impregnation is then carried out with the aid of vacuum, pressure and elevated temperature necessitating the use of "complicated and expensive apparatus including vacuum chambers or immersion tanks and means fcr heating the same. However, even with the expenditure of much time and expensive equipment, it has not been possible heretofore to extend the impregnation intothe heart wood of the tree.

It is a general object of the invention to effect the impregnation of green wood by a simple and economical process which makes use of the natural phenomenon of osmosis to bring about the substantially complete impregnation of the wood without the use of vacuum, pressure or elevated temperature. 3

It is another object of the invention to preserve green wood by impregnating wood substantially completely with a preservative and fixing the preservative so as to prevent its escape when the wood is subjected to leaching soil.. It is a further object of the invention to preserve green wood by applying to the surface of the wood a preservative carried in a medium which enables the preservative to difiuse into the wood by osmosis and retarding the drying out of the treated wood until the preservative has so diffused into the wood.

It is a specific object of the invention to provide a novel process for the preservation of green wood characterized by the use of a'preservative adapted to penetrate the wood by osmosis, a pro tective agent adapted to penetrate the wood by capillary diffusion and to prevent the escape of the preservative'from the-wood, and a carrier adapted to bring the preservative and" protective agents into intimate contact with. the surface of wood.

by rain or damp' of treatment.

In Germany January 19, 1931 Other objects of the invention will in part be obvious and will in part appearhereinafter.

The invention accordingly comprises a process having the steps and the relation of steps, one toanother, and a composition having the ingredientsarfi" the proportion of ingredients all as set forth in the following detailed description and the-scope of the application of which will be given in the claims.

For a more complete understanding of the nature and objects of the invention, reference should be had to the follbtving detailed description taken in connection with the accompanying drawing, in which;

Fig. 1 illustrates a method of debarking felled the timber in accordance with the process of invention;

' Fig. 2 illustrates a method of applying the impregnating substance to the debarked trees;

Fig. 3 illustrates one 0d of stacking the treated trees in accordance with the invention;

Fig. 4 illustrates one embodiment of the method of protecting the treated and stacked trees from atmospheric conditions; and

' Fig. 5 is a view in section pregnated in invention.

According to the invention, the preservation of green wood is carried out by stripping the bark 0 from green trees immediately after they have been cut down, coating the debarked surface with a paste comprising a preservative adapted to impregnate the wood by osmosis, a pasteforming colloidal substance, water, and preferably a protective agent adapted to impregnate the wood by capillary diffusion and to prevent tli'e..1escape of the preservative, and protecting the coated wood from excessive drying out until the preservative has diffused substantially into 40 wood.

, The process of the invention is carried out preferably in the forest where the trees are felled, but it may be carried out at a concentration camp or treating place, in which case the trees are not debarked until they reach the place As shown in Fig. 1, a freshly cut I green tree I is cut down and trimmed as desired. The bark 2 is removed from the tree by a suitable means and then, without barked surface to dry out to a substantial degree, a coating 3 of the .paste is applied by suitable means such, for example, as a brush 4 as shown I in Fig. 2 or a spraying device. The amount of paste applied is varied in accordance with the I embodiment of the meth- 20-" 25 4 of a tree trunk imaccordance with the process of the permitting the de- :For the most efiective .from the wind,

.The coated wood is then stacked and the drying out retarded at atmospheric temperatures until the impregnation is substantially complete.

It has been found that the degree of impregnation is a function of the manner in which the treated wood is stored during the drying period.

stacked as close together as possible. For example, as shown in Fig. 3, the treetrunks I are arranged parallel in a three-cornered stack 4 with their arcuate surfaces contacting each other as they lie side by side, as illustrated in Fig. 4. When the tree trunks vary in length, the trunks of the same length are stacked together with the longer trimks forming the bottom layers and 4 upper layers. The stack isv then enclosed in a waterproof and windproof covering 5. This covering may comprise a layer of straw 6r, as shownbe fashioned of strips cloth positioned in Fig. 4. the covering may 6 of tar-impregnated paper or lengthwise of the stack with the lower edges of.

each strip overlapping the upper edge of the next strip, as in laying shingles. The strips may be fastened together and held against the wood by known means such, for example. as tacks I driven through the overlaps directly into the underlying. wood. The covered in order that a wind blowing lengthwise of the stack may not pass through the interstices between the tree trunks and'dry out the surface of the wood. The bottom of the stack may be protected by a covering in a like manner. The entire stack may be supported abovethe ground by suitable sleepers positioned transverse of the stack as shown in Fig. 4.

changes but-seldom, so that the drying out of the wood is retarded and the natural moisture of the wood remains until the impregnation is substantially complete. Enclosing the coated wood in a protective covering as described has been found to inhibit materially the checking" of the wood, that is, the development of cracks in the wood.

As an alternative to the above .described covering, each of the individual tree trunks may be enclosed in a protective bandage or covering. For example, the paste may be applied to a strip of paper having a width of from 10 to 15 cm. and the strip wound spirally about the debarked tree trunk, the turns of the strip overlapping so as to completely cover the surface.

As long as moisture remains in the wood, the impregnation proceeds. Therefore, the protective covering is left on the wood to retard the drying for'a period suificient to effect the desired impregnation, which period is usually from two to four months. Obviously, when. the impregnation is completed, the covering 'may be removed and the wood permitted to dry as desired.

The composition utilized in the process of the invention consists of any preferably one comprising a preservative agent adapted to penetrate the wood by osmosis, a paste-forming colloidal substance and water, and preferably also a protective agent adapted to penetrate the wood by capillary diffusion.

For the preservative agent, there is employed impregnation, the wood is the shorter trunksiorming the end of the stack'also. is

the air within the intersticessuitable aqueous paste copper sulphate,'potassium sulphide, mercuric chloride,'zinc fiuorosilicate. If desired, the preservative may comprise one or more insecticides such, for example, as a soluble arsenic salt such as sodium or potassiumarsenite, sodium or potassium arsenate. The water-soluble substances may be employed either singly or in admixture. The inorganic substance should be preferably one with high solubility in water and high mobility, that is, high osmotic pressure and rate of diffusion. 1

Further, the invention contemplates the use of pastes comprising two or more soluble inorganic substances capable of reacting to form within the wood an insoluble or difficultly soluble product.

For example, with a fluoride or an arsenate, there may be used a water-soluble, inorganic dichromate such as sodium or potassium dichromate. It would appear that the dichromate salt is reduced, within the wood, to a chromate salt which reacts with the fluoride or' arsenate to form a diflicultly soluble product having the general structure of a cryolite compound.

For the protective agent, there is employed an organic substance such, for example, as dinitrophenol, dinitrocresol, tar oils, liquid petroleum. The protective agent is preferably one'which is substantially insoluble in water or incompletely miscible therewith, and which has a low viscosity and a high toxicity toward fungi, insects. The expression water-insoluble organic .substance shall include organic substances having a relatively slight solubility in water'when compared to the-water-soluble preservative agentsherein disclosed. v I

' The paste-forming ingredientcomprises preferahly a gultinous substance capable of forming a water-swelling colloid such,- for example, as

starch, disintegrated casein, glue, gelatine, agar agar, gum arabic; This ingredient is prefer-- ably one adapted to give a tacky paste with water. In general, the preservative agent comprises from. about 50% to the protective agent from about 10%. to 35% and the glutinous substance from about 5% to 20% by weight.

By way of illustration, but not by way of limit-- ing the scope of the invention, the following examples are given, the ingredients being in parts by weight.

Examples I n m IV v v1 Sodium fluoride 000 900 900 Sodium "senate 50 .150

Dinitrophenol 170 170 170 50 36 70 Gum arabic. 30

Disintegr ted casein 10 firm-oh 80 40 -The several ingredients are ground and mixed thoroughly with water in an amount sufilcient to'give a paste of the required viscosity.

If desired, the paste may comprise'a wetting agent such, for example, as glycerine, to assist in bringing the preservative and the protective agent into more intimate contact with the wood. -There may be added also, if desired, substances adapted to color the wood or to render the same fireproof, mothproof, etc.

If desired, the protective agent may be applied to the wood by incorporating it in the paste water-soluble, inorganic and/or by applying it alone as a coating subsequent to the application of the paste to the wood. For example, the debarked wood may be coated first with an aqueous paste comprising a preservative, a paste-forming glutinous substance and water, and a protective agent of the class described is subsequently applied to the wood, by

coating or otherwise, after the paste has dried and before and/or after the wood has become air dry.

There is illustrated in Fig. 5 the cross section' of a tree trunk treated according to the process of the invention. The preservative agent being a salt, diffuses by osmosis through the cell walls into the wood cells; it also diffuses through the capillaries and interstices between the cells. The penetration of the salt is rapid. and to a substantial depth as indicated by the area designated A.-- In time the salt may difattack. It the green protective agent ,preservative when the in damp soil or exposed to rain.

tinuously decreases as in the wood which fuse completely throughout the heart wood I as well as throughout the sap wood 9.

The protective agent, being an organic substance and insoluble in water, diffuses chiefly through the capillaries and the interstices be tween the cells. The depth of penetration is slight compared to that of the water-soluble preservative, the ratio of the depths of penetra-- tion being about 1: 4, and the penetration of the is confined to the outermost. layers as shown by the area designated B. This area B, impregnated by the water-insoluble organic substance, forms a waterproof zone which prevents the leaching out of the water-soluble treated timber is placed The paste-forming substance dries on the surface of the wood to form a hornycoating'designated C which prevents the paste from being washed'o'fi or falling off during the storing period. If there are cracks In in the tree trunk, the paste fills the same and at these points the inwardly diffusion is more or less increased, depending upon the depth of the crack.

Since the area of wood to be impregnated conthe salt difluses inwardly toward the center of the tree. the fall in the concentration of the salt is very gradual. The outer layers contain the impregnating agents in the highest concentration, which is highly desirable since these" layers are most subjectto tree is cut down whenthe Sap is at the maximum, and the freshly cut tree treated with the composition of the present invention, it frequently happens that the osmotic diffusion of the water-solublesalt proceeds to completion even after the outer layers of the tree have become air dry.

The process of the present invention is applicable for the preservation of various types of woods such, for example, as pine, fir, spruce, larch, beech, oak and ash. The process may be carried out on the entire tree trunk or upon finished or partly finished lumber or timbers cut from trees The process is especially applicable. for the treatment 01' telegraph poles, fence poles, structural timbers and other woods used in the open. Trees intended for'use as mine timber, cross ties and marine piles are preferably treated with the compositions containing fluoride another pair of inorganic salts an insoluble compound withis resistant to leaching when the wood is immersed in water or damp soil.

, By the present invention there has been proand dichromate-or capable of forming trate the wood by treated before the vided a novel pree'ss for preserving green wood having many new and unusual advantages. The process permits the tree to be cut down while the sap is at the maximum, i. e. in the spring and summer when the cutting operations are. unencumbered by snow and ice. The tree may be wood has been attacked by insects and plant organisms. Any cracks existing in the surface of the wood are filled with the paste, in consequence of which the impregnation is deeper at these points and the protection at a maximum. The coating of aqueous paste and the action of the impregnating salt on the sap slows up the rying of the wood and retards the development of injurious cracks in the wood.

Further, the present process is characterized by its simplicity and economy of operation and equipment, despite which the depth of penetration is greater than that obtained by the use of vacuum, high pressure and elevated temperatures.

The presentinvention shortens the useless life of cut timber because the impregnation and drying out proceed simultaneously instead of successively as in the usual practice.

Since certain changes in carryingv out the above process, and certain modifications in the composition which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not -in a limiting sense.

In the appended claims, the expression green woodfis intended 'to designate both green wood containing live sap and wood which is relatively preservative has diffused substantially into the wood.

2. In a process for preserving green wood, the steps comprising coating debarked wood on its outer surface with an aqueous tacky paste comprising a water-soluble preservative, a pasteforming colloidal substance and water, and retarding the drying out the preservative has diffused substantially into the wood.

3. In a process for preserving green wood, the

steps comprising debarking freshly cut trees, coatingthe debarked surface with an aqueous paste comprising a preservative adapted topenetrate the wood by osmosis, a protective agent adapted to penetrate the wood by capillary diffusion, a paste-forming colloidal substance and water, and retarding the wood until the preservative has diffused substantially into the wood.

4. In a process for preserving green wood, the steps comprising debarking freshly cut trees, coating the debarked surface with an aqueous paste comprising a preservative adapted to peneosmosis, a protective agent adapted to penetrate the wood by capillary difdrying out of the coatedof the coated wood until 1 outer surface whereby drying out fusion, 9. paste-forming colloidal substance and water, arranging the coated wood in a closely packed stack, enclosing the stack in a waterproof and windproof covering and maintaining the stack in a covered condition until the preservative has diifused substantially into the wood.

5. In a process for preserving green wood, the

steps comprisingdebarking freshly cut trees and coating the debarked surface with an aqueous paste comprising a water-soluble inorganic substance, a paste-forming colloidal substance and water, and thereafter applying to the debarked surface a water-insoluble organic substance after the paste has dried.

6. In a process for-preserving green wood, the steps comprising debarking freshly cut trees, coating the debarked surface with an aqueous paste comprising a water-soluble inorganic substance, a water-insoluble organic substance, 9. paste-forming colloidal substance and water, the inorganic substance penetrat'ng the woodby osmosis to a substantial. depth and'the organic substance forming in the outermost layers of the wood a waterproof zone substantially preventing the leaching out of the inorganic substance, and enclosing the coated wood in a protective covering.

7. In a process for preserving green wood, the steps comprising debarking coating the debarked surface with an aqueous paste comprising a water-soluble inorganic fluoride, a water-soluble inorganic dichromate, dinitrophenol, a paste-forming colloidal substance and water, the fluoride and the dichromate A reacting within the wood to produce a waterinsoiuble product.

8. In a process green wood, the wood on its outer surface with an aqueous tacky paste comprising a water-soluble preservative, a pasteforming colloidal substance and water, and enclosing the coated wood in a protective covering of the coated wood is retarded untilithe preservative has diffused subfor preserving stantially into the wood.

9. In a process for preserving green wood, the

steps comprising coating debarked' wood on its prising a preservative adapted to penetrate the wood by osmosis, a paste-forming colloidal sum tive has diffused substantially freshly cut trees,

with an aqueous tacky paste comstance and water, arranging the coated wood in a. closely packed stack, andenclosing the stack in a protective covering whereby the drying out of the coated wood is retarded until the preservainto the wood. 10. In a process for preserving green wood, the steps comprising coating debarked wood on its outer surface with an aqueous tacky paste com-, prising a preservative adapted to penetrate thel wood by osmosis, a paste-forming colloidal substance and water, retarding the drying out of the coated wood until the preservative has diffused substantially into the wood and thereafter applying to the surface of the wood a. water-insoluble organic substance, said organic substance 15 forming in the outermost layers of the wood a waterproof zone substantially preventing the leaching out of the preservative.

1-1. In a process for preserving green wood, the steps comprising coating debarked wood onits outer surface with an aqueous tacky paste comprising a water-soluble preservative in an amount of from 50% to 80%, a water-insoluble protective agent in an amount of from about 10% to 35%, a paste-forming glutinous substance in an amount of from about 5% to 20% by weight, and water, and retarding the drying out of the coated wood until the preservative has diffused substantially into the wood.

12. In a process for preserving green wood, the steps comprising coating debarked wood on its outer surface with an aqueous tacky paste comprising a water-soluble inorganic dichromate, a water-soluble inorganic fluoride, a paste forming colloidal substance and water, the dichromate and the fluoride forming within the wood a waterinsoluble product, and retarding the drying out of the coated wood until the preservative has dlfiused substantially intothe wood.

13. Inga process for preserving green wood, the steps comprising coating debarked wood on its outer; surface with an aqueous tacky paste comprising a water-soluble inorganic dichromate, a water-soluble inorganic arsenate, a paste forming colloidal substance and water, the dichromate and the arsenate forming within the wood a water-insoluble product, and retarding the drying out of the coated wood until the preservative has diffused substantally into the wood.

CARL SC

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