CA1230453A - After-care of wooden masts, posts and the like, and an agent for this purpose - Google Patents

Abstract

Abstract of the Disclosure: An agent for the after-care or treatment of the heartwood of wooden masts and the like, based on a chemical compound which releases methyl iso-thiocyanate, contains tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione (dazomet) and an essentially anhydrous solvent or dispersant, with the proviso that the mixing ratio and intrinsic viscosity of the solvent or dispersant and, where relevant, the concomitant use of a thickener result in the said agent having a pasty consistency.

Description

~2~ 3 .~ .

O.Z. 0975/00031 A~ter-care of wooden masts, posts and the like, and an agent for_this purpose -Wooden poles and similar wooden structural elements which are to be inserted into the ground are protected from wood-destroying fungi and animals by treatment with fungicides and/or insecticides.
Examples of conventional agents of this type are copper compounds, boron compounds, chromium compounds, arsenic compounds and other heavy metal compounds, organic compounds having a non-specific action, such as tar oils, and a large number of substances whose action is more or less specific.
The conventional treatment of the wooden elements comprises impregnation, usually while alternately reducing and increasing the external pressure (pressure impregnation). The disadvantage of pressure impregnation is that many types of wood are radially permeable to liquid only in the sapwood. Hence, the impregnation does not reach the heartwood, which is preferentially attacked by very special fungi, ie. heartwood-specific fungi, and then exhibits damage typical of heart rot or inner rot.
It has been proposed ~o impregnate the heartwood after perforating the trunk, or to impregnate the freshly felled trunk from the point of cutting. However, these methods have proven unfeasible.
It is therefore usual to make ~he heartwood region accessible through isolated bore holes, ie. a relati~ely small number of appropriate wide bore holes, and to pro-vide the bore holes with a stock of impregnating agent and close them with a plug~ This method is used in parti-cular for after-care; ~hus, after standing for a number of years, the trunk is once again dug out, or the buried foot is bared, holes are drilled in the trunk and the latter is appropriately treated.
Agents convent;onally used for after-care are those which release readily diffusing biocidal substances;

~3~i3 - Z - O.Z. 0975/00031 an agent of this type cons;sts of, for example, an aqueous solution of Na N~methyldithiocarbamate, which decomposes to give the biocidal methyl isothiocyanate.
Since deconposition begins on contact with water, Na N-methyldithiocarbamate decomposes even in aqueous solution.
It is an object of the invention to provide an agent which, in the trunk, is intended to become active only ;n the presence of the moisture that causes inner rot, in dry wood, the agent should remain as a reserve.
We have found an agent which releases diffusable biocidal substances only in the presence of moisture, and which is based on tetrahydro-3,5-d;methyl-2H-1,3,5-thia-diazine-2-thione, whose usual common name is dazomet.
Dazomet is used for decontaminatina soil and for the fungicidal treatment of, for example, paper sizes and the like, and releases methyl isothiocyanate on contact with water.
According to the invention, the agent is used in an essentially anhydrous form; for this purpose, it con-tains, in addition to dazomet, an anhydrous solvent or dispersant and, preferably, also a stabilizer which pre-¦vents the premature decomposition of the dazomet to form methyl isothiocyanate.
~5 The anhydrous solvent or dispersant used is, for example, a polyglycol~ preferably polypropylene glycol.
According to the manufacturers, polyglycols having a suit~
able viscosity have a mean molecular weight ~v (viscos;ty average) of about 600 - 1,000.
A group of dispersants which is also suitable is that comprising the cationic wetting agents and dispers-ants of the benzylammonium salt type. These compounds themselves have a biocidal action, and, in anhydrous form, are more or less viscous liquids.
The amount of dazomet in the dispersion is in gene-ral more than 10, eg. from 25 to 50, % by weight~ based on ~the total weight of the agent.
The stabilizer used can be a heavy metal compoundr ~2~ 53 ~ 3 ~ O.Z. 0975/00031 for example a zinc compound~ the novel agent of which should contain in general an effective amount of less than S % by weight. The term compound is understood as meaning, for example, a salt, an oxide or a hydroxide. Zinc oxide is a very suitable zinc compound.
The action of the heavy metal compound is j~-proved by the addition of a sparingly volatile amine, 'or example an alkanolamine, eg. monoethanolamine. The amount present in the agent is in general from 1 to 5 X by weight~
1û The wettabil;ty of the novel agent can, if required, be improved by adding a conventional ionic or non-ionic wetting agent, for example an alkali metal salt of an alkylarylsulfonate. This is present in general in an amount of less than 10 % by weight, based on the novel agent.
Agents envisaged by the invention generally have a pasty consistency and are applied by apparatuses already availableO An example of such an apparatus is an inoculation gun. A bore hole which has been produced beforehand can be filled using other apparatuses.
Examples of formulations which give agents accord-ing to the invention are described below; the agent is obtained in each case by stirring or kneading the compon~
ents.

50 % of dazomet and 50 % of triethylene glycol (solvent).

50 % of da~omet and 0 50 ~ of phenylglycol (active solvent).

S0 % of dazomet, 49 % of polypropylene glycol and 1 ~ of ~inc oxide.

3~53 ~ 4 ~ O.Z. 0975/00031 50 % of dazomet, 49 X of triethylene ~lycol and 1 X of monoethanolamine.
SEXAI~PLE 5 50 % of dazomet, 47 X of polypropylene glycol and 3 % of salts of dodecylbenzenesulfonic acid.

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. An agent for the after-care or treatment of the heartwood of wooden masts and similar wood articles, based on a chemical compound which releases methyl isothio-cyanate, wherein the said agent contains tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione (dazomet) together with an essentially anhydrous solvent or dispersant, with the proviso that the mixing ratio and intrinsic viscosity of the solvent or dispersant result in the said agent having a pasty consistency.

2. An agent as claimed in claim 1, wherein dazomet is contained in an amount equal to or higher than 10% by weight.

3. An agent as claimed in claim 2, containing from 25 to 50% by weight of dazomet.

4. An agent as claimed in claim 1, 2 or 3, wherein the dispersant is a polyglycol.

5. An agent as claimed in claim 1, 2 or 3, wherein the dispersant is polypropylene glycol.

6. An agent as claimed in claim 1, 2 or 3, further containing a heavy metal compound as a stabilizer.

7. An agent as claimed in claim 1, 2 or 3, further containing a zinc compound as a stabilizer.

8. An agent as claimed in claim 1, 2 or 3, further containing a sparingly volatile amine.

9. An agent as claimed in claim 1, 2 or 3, further containing alkylarylsulfonate as a wetting agent.

10. An agent as claimed in claim 1, 2 or 3, further containing a thickener.

11. A method of preserving wooden masts, compri-sing the steps of drilling bore holes in the masts reaching the heartwood region thereof, and filling said bore holes with an agent as claimed in claim 1.

12. A method as claimed in claim 11, comprising the additional step of closing the bore holes after they are filled.