WO2011131668A1

WO2011131668A1 - Polyorganosiloxane compounds for protecting wood against termites

Info

Publication number: WO2011131668A1
Application number: PCT/EP2011/056233
Authority: WO
Inventors: Holger Militz; Carsten Mai; Shyamal Ghosh
Original assignee: Georg-August-Universität Göttingen Stiftung Öffentlichen Rechts
Priority date: 2010-04-19
Filing date: 2011-04-19
Publication date: 2011-10-27

Abstract

The invention relates to a method for conferring termite resistance to a lignocellulosic material, to a lignocellulosic material obtained by said method, as well as to specific compositions and their use for conferring termite resistance to a lignocellulosic material, as defined in the claims.

Description

Polyorganosiloxane Compounds for Protecting Wood Against Termites

TECHNICAL FIELD

The invention relates to a method for conferring termite resistance to a lignocellulosic material, to a lignocellulosic material obtained by said method, as well as to specific compositions and their use for conferring termite resistance to a lignocellulosic material.

BACKGROUND OF THE INVENTION

Termites (Order Isoptera) represent one of the most significant insect groups responsible for the destruction of wood. Over 2300 termite species are known and only 10% of them are considered as pests. Termites are typically divided into the higher termites (Termitidae) e.g., Microcerotermes, Microcerotermes and Nasutitermes and the lower termites e.g., Coptotermes, Mastoterm.es, Reticulitermes and Schedorhinoterm.es. The higher termites constitute approximately 80% of all species and the lower termites represent only six families. Termites are generally grouped according to their feeding behaviour. Thus, the commonly used general groupings are subterranean, soil-feeding, drywood, dampwood, and grass-eating. Of these, subterranean and drywoods are primarily responsible for damage to human-made structures, and subterranean termites are considered to be the major contributor to economic loss in wooden constructions. The wide scale global distribution of subterranean termites is observed throughout the tropical, subtropical, and temperate regions with abundance in the temperate areas. The economic loss is attributed to both the destruction of structure as well as protection and/or remedial measures taken against these termites. Their habit of remaining concealed often results in their presence being undetected until the timbers are severly damaged and exhibit surface changes. The characteristic behaviour of most subterranean termites is to feed along the grain of the wood foraging the softest portions and to accumulate soil and dirt within galleries. The Formosan subterranean termites are considered as less discriminating feeders, which often hollow tree trunks or wooden beams. They can cause major structural damage in several - - months and almost complete destruction of unprotected homes built over large colonies in 2 years in some locations. The primitive giant northern termite (Mastotermes da viniensis Froggatt) (Mastotermitidae) and the termite genus Coptotermes Wasmann (Rhinotermitidae), C. acinaciformis (Froggatt), C. frenchi Hill and C. lacteus (Froggatt) are of most economic significance in Australia. Coptotermes spp. are usually very adaptable and may nest in the ground, in mounds (epigeous nests) or in trees. Most species of subterranean termites live deep within the soil, requiring workers to construct elaborate systems of tunnels to forage for food and water.

According to the United States Department of Agriculture, Agricultural Research Service (USD A ARS), termites are causing economic losses of several billion US$ alone in the USA and are considered as pests. The total damage including preventive as well as repair related measures are estimated to 11 billion US$. Among these, the formosan subterranean termite (FST) Coptotermes formosanus shiraki causes an annual total damage of 1 -2 billion US$. Therefore, the FST is considered as "high priority" by the USDA.

Various methods to protect wooden structures from termite damage are the use of naturally durable wood species, preservative treatments, and engineered wood products with enhanced insect and decay resistance. The reduced availability of naturally durable wood species, however, is increasing the dependence on the use of fast grown non-durable wood for construction. The protection of structures made of non-durable wood may require the application of broad spectrum insecticides. The use of various organochlorine insecticides as chemical barriers to termites was a common practice until environmental concerns restricted their widespread applications. Present practices using insecticides as chemical barriers are broadly categorized into three toxic levels, such as repellent, non-repellent causing rapid mortality and non-repellent with a delayed action. New safer treatment procedures in wood and soil are being constantly developed for effective termite control e.g., physical barriers using basaltic particles and stainless steel mesh. These have been developed as substitutes for soil treatment with chemicals. Biological control measures have also been reported using natural parasites or predators to reduce termite population, but show limited field efficacy.

Growing environmental concerns over the use of broad spectrum toxic chemicals for wood protection along with the policy adoption to utilize locally available but less durable wood species has led to several approaches in wood-modification-research in several European countries. The aim of wood modification is to improve wood properties either by using high temperatures or chemical impregnation of the wood matrix so as to improve dimensional stability and durability to insect and fungal damage. Among those processes which have been commercialized, acetylation has been found to impart resistance to termite damage. Furfurylated wood at medium and high level of furfurylation has been shown to resist drywood and subterranean termite damage. Furthermore, wood modified with dimethylol dihydroxy ethylene urea (DMDHEU) has recently been found to be resistant to C. acinaciformis. As a drawback, acetylated Scots pine wood requires 22% weight percent gain (WPG) to show strong resistance (2% mass loss) against termites and furfurylated wood requires moderate (40% to 45%) to high (99% to 160%) WPG.

The development of a wood treatment, which gives protection against staining-, mould- and decay-fungi as well as wood destroying insects in addition to improved material performance, is still a challenge. Silicones were shown to inhibit colonisation by staining- and mould-fungi (Ghosh, S.C., Militz, H., Mai, C. (2008) Decay resistance of treated wood with functionalised commercial silicones, Bioresources 3:1303-1314 2008a) and fungal decay ( Weigenand, O., Humar, M., Daniel, G., Militz, H., Mai, C. (2008) Decay resistance of wood treated with amino-silicone compounds. Holzforschung 62(1): 112-118;) and, to impart moderate dimensional stability and water repellence ( Weigenand, O., Militz, H., Tingaut, P., Sebe, G., de Jeso, B., Mai, C. (2007) Penetration of amino-silicone micro- and macro-emulsions into Scots pine sapwood and the effect on water related properties. Holzforschung 61(1): 51-59; Ghosh et al. 2008a).

Japanese black pine {Pinus thumbergii Pari.) treated with low molecular weight silicic acid exhibited increased termite resistance; the combination with boric acid improved the performance against termites (Yamaguchi 2003). Also, Furuno and Imamura (1998) reported reduced weight loss (2.5%) caused by termites in wood samples treated with water glass in combination with boric acid, borax and potassium borate. However, unlike most other preservatives, borate compounds do not become fixed in the wood and can readily be leached out. Therefore, borate preservatives are used in combination with additional compounds, in order to fix the borate preservative in the wood. For example, Kartal et al. (2007) disclose a combination of commercial silicon emulsion and borate, and US 2007/0042124 Al describes a silicone emulsion composition in which a boron compound is included, in order to impart rot-proof and termite-controlling properties to wood. . .

WO 2006/010667 describes oligomeric silane systems, which are marketed by Degussa Evonik under "Dynasylan^® functional silanes HYDROSIL". These silanes are obtained by hydrolysis and cocondensation of monomelic alcoxy or chlorosilanes by addition of an amount of water. The monomers applied in this condensation are mainly trialkoxy silanes, which bear an additional group directly attached to Si in form of a Si-C bond. The silanes disclosed in formula (I) of WO 2006/010667 comprise at least one unit [- 0(3-i-j)/2Si(Ra{-HX}g)(CH₃)i(OR)j]y. In contrast thereto, the siloxanes according to the invention are mainly linear or branched dialkylsiloxanes.

Thus, there is still a need for wood preservatives conferring resistance against termites, which are multi-functional, avoid the use of potentially toxic biocidal agents and do not require an extensive weight gain to show acceptable activity.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a treatment for the protection of wood, which confers resistance against temiites avoiding the use of potentially toxic biocidal agents. It is a further object of the invention to provide a treatment conferring resistance against termites, which is not readily leached out from the wood, and also confers resistance to staining-, mould- and decay-fungi. It is a further object of the invention to provide an agent to protect wood conferring resistance against termites, which does not require extensive weight gain in order to show acceptable activity as compared to other types of chemical wood modification.

It has been found that these and other objectives can be achieved by impregnating a lignocellulosic material with one or more polyorganosiloxanes, in particular polyorganosiloxanes containing nitrogen, specifically amino or ammonium groups.

Accordingly, in a first aspect, the invention provides a method for conferring termite resistance to a lignocellulosic material, comprising the step of impregnating the lignocellulosic material with a composition which comprises an polyorganosiloxane, and no biocidal termite controlling agent.

In a second aspect, the invention provides the use of the composition as defined in the first aspect for conferring termite resistance to a lignocellulosic material. - -

In a third aspect, the invention provides a lignocellulosic material obtained by the method of the first aspect, wherein said lignocellulosic material may be suitable for use in hazard class 4, as defined in European Standard EN 335-1 2006.

In a fourth aspect the invention provides a composition for conferring termite resistance to a lignocellulosic material as defined in the first aspect.

DETAILED DESCRIPTION OF THE INVENTION

As used herein the term "termite controlling agent" means a termiticide or repellent, i.e. an agent that kills and/or has a warding off/fending off effect on termites.

The term "no termite controlling agent" means no or no essential amount of a termite controlling agent, i.e. an amount, which has no activity against termites.

As used herein the term "polyorganosiloxane" means a polymer consisting of or comprising at least five organosiloxane groups, which are identical or different. If the polyorganosiloxane consists of two or more different organosiloxane groups, the order of these groups is arbitrary, which means two or more groups may be alternating, the order may be statistical or may include blocks of two or more identical organosiloxane groups. Further, the polyorganosiloxanes may be linear, branched or cyclic.

If the polyorganosiloxane comprises but does not consist of organosiloxane groups, then the main chain of the polymer contains groups which are no organosiloxanes, e.g. alkylene, amino, ammonium, amido or urethane groups. In this type of polymer the above said applies in cases of structures containing two or more directly connected organosiloxane groups.

The content of organosiloxane units in the polyorganosiloxane is generally in the range of at least 5, preferably at least 10, more preferred at least 25, even more preferred at least 50 and in particular at least 75, mole percent.

In a preferred embodiment, the polyorganosiloxane used in the method of the invention comprises identical or different organosiloxane units of formula (I),

in which - -

R¹ is identical or different, a substituted or unsubstituted, straight chain, branched or cyclic, saturated, unsaturated or aromatic hydrocarbon radical having up to 20 carbon atoms;

R² is identical or different, a substituted or unsubstituted, straight chain, branched or cyclic, saturated, unsaturated or aromatic hydrocarbon radical having up to 20 carbon atoms, which comprises one or more primary, secondary or tertiary amino groups and/or an acid addition salt thereof;

R³ is identical or different H, R¹ or R²;

a, b, c are 0, 1, 2 or 3, with the proviso that the sum a+b+c < 3.

It goes without saying that the polyorganosiloxane polymer contains organic groups, therefore, a+b+c must not be zero for all organosiloxane groups of formula (I). Preferably a+b+c is > 0 and < 3.

In a further preferred embodiment, the symbols and indices in formula (I) have the following meanings:

R¹ is, identical or different, straight chain or branched Ci-Ci2-alkyl, Cs-Cg-cyclo alkyl, C₆-Ci₂-aryl, Ci-C₁₂-alkyl-C₆-Ci2-aryl, Q-Cn-aryl- CrC^-alkyl, each of said groups being unsubstituted or substituted by one or more substituents selected from the group consisting of OH, SH, halogen, CN, OR', SR', CO-R' and COOR", where R is a straight chain or branched CrCi₂-alkyl or C₆-Ci₂-aryl;

R² is identical or different straight chain or branched C Cio-alkyl, Cs-Cs-cyclo alkyl, C₆-C₁₂-aryl, CrQo-alkyl-Ce-C^-aryl, C6-C₁₂-aryl-(Cj-C₁₀)-alkyl, each of said groups being unsubstituted or substituted by one or more substituents selected from the group consisting of OH, SH, halogen, CN, OR', SR, CO-R' and COOR', where R' is a straight chain or branched Ci-C₁₀-alkyl or C₆-C₁₂-aryl, and each of said groups being substituted with one or more substituents selected from the group consisting of NR"R'" and N⁺R"R'"R"", where R", R^m, R"" are identical or different H, R', a straight chain or branched CrQo-alkyl-NR'2, a straight chain or branched d-do-alkyl-r^R^, C₆-C₁₂-aryl-NR'₂, C₆-C₁ -aryl-N⁺R'₃, OR', COR and COOR';

R³ is H^ or R²;

a, b, c are 0, 1, 2 or 3, with the proviso that the sum of a+b+c < 3.

In a further preferred embodiment the polyorganosiloxane is a polymer which comprises organosiloxane units of formula (II), - -

[R¹. R² _b(OR³)c SiO _w+c) ]_y (II)

2 in which

R¹, R², R³, a, b, c have the meanings or preferred meanings given in formula (I) above, with the proviso that at least one of the symbols or indices is different in the two units;

x, y is, identical or different, an integer from 1 to 300, preferably from 1 to 100, particularly from 1 to 100;

x + y is from 10 to 500, preferably 10 to 400, particularly preferably 10 to

300,

it being possible for the organosiloxane units to be in any order.

If the polyorganosiloxane consists of organosiloxane units the end groups are preferably identical or different groups of formulae -(R¹ _aR² _b(OR³)_c SiO^") and -(SiR¹ _aR² _b(OR³)_c) respectively,

in which R¹, R², R³, a, b, c have the meaning or preferred meanings given above and a + b + c = 3.

In a particularly preferred embodiment R is H and c = 1.

Preferably, the polyorganosiloxane comprises one or more nitrogen atoms, in particular primary, secondary or tertiary amino and/or primary, secondary, tertiary or quartemary ammonium groups,

In one preferred embodiment one or more amino/ammonium groups are located in the organic radicals attached to silicon atoms (R²). In this case b is different from 0 and R² is preferably selected from -CH₂-CH₂-CH₂- H₂, -CH₂-CH₂-CH₂-NH(CH₃), -CH₂-C¾-CH₂- N(CH₃)₂, -CH₂-CH₂-CH₂-NH-CH₂-CH₂-N¾, -CH₂-CH₂-CH₂-NH-CH₂-CH₂-NH(CH₃), -CH₂-CH₂-CH₂-NH-CH₂-CH₂-N(CH₃)₂, -CH₂-CH₂-CH₂-NH-CH₂-CH₂- H(CH₂CH₃) and -CH₂-CH₂-CH₂-NH(cyclo-C₆-Hn). -CH₂-CH₂-CH₂-NH₂ and -CH₂-CH₂-CH₂-NH-CH₂- CH₂-NH₂ are particularly preferred.

In a further preferred embodiment the polyorganosiloxane comprises, preferably consists of -Si(CH₃)₂-0- and Si(CH₃)(CH₂-CH₂-CH₂-NH₂)-0- and/or Si(CH₃)(CH₂-CH₂-CH₂-NH- CH2-CH2-NH2) units and Si(CH₃)₂OH end groups. - -

HO-Si (CH3)2-0-[Si(CH₃)2-0]_x[Si(CH₃)(CH₂-CH₂-CH₂-NH-CH₂-CH2-NH₂)-0]_y - Si(CH₃)₂OH and HO-Si(CH₃)₂-0-[Si(CH₃)₂-0]_x[Si(CH₃) (CH₂-CH₂-CH₂-NH₂)-0]_y-Si(CH₃)₂OH are particularly preferred.

Preferred polyorganosiloxane compounds of this embodiment and their synthesis are further described in DE 10 2004 036 918, more specifically in sections [0021] - [0034]; DE 101 22 626 Al, in particular sections [0012] - [0031]; US 6,294,608, column 2, line 12 to column 5, line 25; DE 199 39 866 Al, specifically page 2, line 67 to page 3, line 8, and page 3, line 25 to page 4, line 27; DE 42 41 727 Al; DE 197 49 380 Al, in particular page 2, line 42 to page 4, line 54

In a further preferred embodiment, one or more nitrogen atoms preferably amino and/or ammonium groups are not part of organosiloxane units and are located in the main chain of the polymer.

In this embodiment the polyorganosiloxane comprises repeating units of formula (III),

-[ U - V ]- (III)

wherein V is selected from the V¹ and V² group, which may be the same or different, in which

V² is selected from divalent and trivalent, straight-chain, cyclic and branched, saturated, unsaturated and aromatic hydrocarbons including at least one Z² group of the formula

wherein groups R may be the same or different and are selected from the group consisting of a straight chain or branched Q-C^alkyl, fluoro(C₁-C₁₀)alkyl, C₆-C₁₀ aryl, and wherein n_!=20 to 1000,

wherein V² includes up to 1000 carbon atoms exclusive of the Z² radical, and

wherein V² may optionally contain one or more groups selected from

-OH, -0-, -NR⁵-, -N⁺R⁵2-, - - in which R is hydrogen, a monovalent, straight-chain, cyclic or branched, saturated, unsaturated or aromatic hydrocarbon radical which has up to 100 carbon atoms and may contain one or more groups selected from -0-, -NH-, -C(O)- and -C(S)-, and which may optionally be substituted by one or more substituents selected from the group consisting of a hydroxyl group, an optionally substituted heterocyclic group preferably containing one or more nitrogen atoms, amino, alkylamino, dialkylamino, polyether radicals and polyether- ester radicals, where, when a plurality of -NR⁵- groups is present, they may be the same or different,

-C(O)-, -C(S)-,

and wherein V¹ is selected from divalent and trivalent, straight-chain, cyclic and branched, saturated, unsaturated and aromatic hydrocarbon radicals which have up to 1000 carbon atoms and may optionally contain one or more groups selected from

-OH, -0-, NR⁵-, -N⁺R⁵2-,

in which R is as defined above, and where the R groups in the V¹ and V² groups may be the same or different,

-C(O)-, -C(S)- and -Z¹, in which -Z¹ is a group of the formula

in which R⁴ is as defined above, where the R⁴ groups in the V¹ and V² groups may the same or different, n₂= 0 to 19,

wherein at least one Z¹ or Z² group is present; U is N⁺R^6R7, NR⁷, or ^N3

^N-— ^N is a 5 or 6 membered saturated, partly saturated or aromatic ring optionally comprising one further hetero atom selected from Ν,Ο and S;

are identical or different, H substituted or unsubstituted, straight chain or branched C₁-C₂₂-alkyl or substituted or unsubstituted C₆-C₁₂-aryl

or the polyorganosiloxane comprises repeating units of formula ( IV), [Y-CO-NH-V-NH-CO-Y-V] ( IV) wherein

V is identical or different and has the same meaning as in formula (III), and

Y is identical or different NR , O or is a substituted or unsubstituted straight chain or branched CrC₂₂-alkylene or substituted or unsubstituted C₆-Ci₂-arylene, and

R⁸ is H or a monovalent organic group.

Preferred polysiloxane compounds and their production of this embodiment are further described in DE 10 2007 012 908 Al, in particular sections [0015] - [0041]; DE 10 2007 027 027 Al, in particular sections [0010] - [0056]; DE 10 2004 062 975, in particular sections [0014] - [0072]; DE 10 2008 014 762 Al, in particular sections [0020] - [0061]; DE 10 2005 036 602 Al, in particular sections [0004] - [0043], and US-A 2006/0235181; which are all incorporated herein by reference, respectively.

Preferred are compounds of formula (III), in particular amino compounds (U = NR⁷)

In a preferred embodiment, the composition comprises a mixture of at least two, such as two, three, four, five, six, seven, eight, nine, ten or even more different polyorganosiloxane polymers as defined above.

In a preferred embodiment said composition further comprises at least one additional additive selected from functional siloxanes, silanes (as disclosed in the cited references) organic polymers, fillers, thickeners, emulsifiers, solubilizers, dispersing agents, buffer substances, flame retardants, pigments, dyes, penetrants, antistatic agents, odor substances, corrosion inhibitors, preservatives, catalysts, and anti-foams.

Suitable catalysts are described in DE 10 2004 036 918, more specifically in sections [0035] - [0038], which is hereby incorporated herein by reference.

Solubilizers and emulsifiers may comprise quaternary fatty amine alcohols, in particular quaternary fatty amine ethanolate, polyalcohols, such as propylene glycol, ethylene glycol or butyl di-glycol, as well as organic solvents such as alcohols, e.g. methanol, ethanol, (iso-)propanol, n-amyl alcohol, i-amyl alcohol; ether, e.g. THF, DMSO, dioxane, diethyl ether, di-isopropyl ether, di-ethylene glycol di-methyl ether; aliphatic and/or chlorinated hydrocarbons, such as dichloromethane,, trichloromethane, tetrachloromethane, 1,2- dichloroethane, trichloroethylene, pentane, hexane, heptane, octane, petroleum ether, benzene, toluene, xylenes; ketones, e.g. acetone, methyl ethyl ketone, di-isopropyle ketone, - - methyl isobutyl ketone; ester, e.g. ethyl acetate, butyl acetate, propyl propionate, ethyl butyrate, ethyl iso-butyrate; and nitrobenzene. Suitabel emulsifiers are further described in DE 101 22 626 Al, more specifically sections [0036] - [0039] and [0041]; DE 197 49 380 Al, more specifically on page 6, lines 4 to 64; which are hereby incorporated by reference. Preferably, the solubilizer and/or emulsifier is non-toxic.

The composition for use in the method of the invention may also contain buffer substances which stabilize the pH in the range of pH 5 to pH 9. In principle, all organic and inorganic acids and bases which are chemically inert with regard to the other components of the composition are suitable. For example, alkali metal, alkaline earth metal and ammonium salts of carboxylic acids, phosphoric acid, carbonic acid and sulphuric acid may be used, of which sodium carbonate, sodium bicarbonate, sodium hydrogen phosphate and a mixture of ammonium acetate are preferred. Further buffer substances are well known to the skilled person. The amount of added buffer substance is generally not more than three percent by weight with regard to the total combined weight of the composition.

In addition, the composition may also comprise a dispersing agent and/or an organic polymer, e.g. fluorinate acrylates or polyurethanes, polyethylene waxes, polyvinyl ether waxes or polyolefin and silicon waxes, or a natural occurring wax from plant origin, e.g. carnauba wax, or candelilla wax. Further organic polymers and waxes are well known in the art. Organic polymers and/or waxes are preferably included into the composition in amounts of 0.01 - 10 % by weight, more preferably 0.01-5 % by weight with regard to the total combined weight of the composition.

Examples for thickeners and fillers are homopolysaccharides, heteropolysaccharides, polyacrylates, carboxy- and hydroxymethylcellulose, which may be added in an amount of 0.05-5 % by weight, more preferably in an amount of 0.1-3 % by weight with regard to the total combined of the composition. However, further thickeners and fillers are well known to the skilled person.

Examples for preservatives are formaldehyde, parabene, benzylalcohol, salicylic acid and salts thereof, benzoic acid and salts thereof, as well as isothiazolinone, whereas non-toxic preservatives are preferred. Further preservatives are also known to the person skilled in the art. Preservatives are preferably added in amounts of 0.01-0.3% by weight, more preferably 0.05-1% by weight with regard to the total combined weight of the composition. - -

Flame retardants, penetrants, antistatic agents, corrosion inhibitors and anti-foams are well known in the art. Other additives, such as pigments, dyes, and odor substances, are also well known in the art and preferably included in an amount of 0.01-1% by weight, more preferably in an amount of 0.05-1% by weight with regard to the total combined weight of the composition.

Preferably, the polyorganosiloxane polymer is used in the form of an emulsion, e.g. an aqueous emulsion. It is well known that emulsion particle size may influence the penetration depth during the impregnation process. Therefore, in a preferred embodiment, the polyorganosiloxane compound is in the form of an emulsion, having an emulsion particle size of less than Ιμιη, preferably less than 900 nm, such as 800 nm, more preferably less than 750 nm, such as less than 700 nm, even more preferably less than 600 nm, such as 500 nm, still more preferably less than 400 nm, such as 300 nm, and most preferably less than 200 nm, such as 150 nm, or even less than 100 nm, such as less than 50 nm, e.g. less than 40 nm. Preferably, the emulsion has a content of the polyorganosiloxane compound of 1 - 50 % w/w, more preferably 5-45 % w/w, even more preferably 10-40 % w/w, and most preferably 15-35 % w/w.

Impregnating of lignocellulosic material can be achieved by various methods and techniques, which are known to the person skilled in the art. In one preferred embodiment, said lignocellulosic material is impregnated by brush coating, roll coating, spray coating, immersion treatment, or vacuum and/or pressure impregnation.

More preferably, said composition is applied by vacuum and pressure impregnation, as e.g. described in the Examples. Particularly, said vacuum and pressure impregnation may comprise 100 mbar vacuum for about lh followed by 12 bar pressure for about lh. Optionally, the impregnation is followed by a drying and/or curing step. In this drying step, the wood may be dried in a high temperature dryer in the presence of high humidity, or may be dried gradually for one day respectively at about 30, 60, 80 and 103°C, in order to prevent the formation of cracks and clefts. Slow drying also conveys that the composition of the invention is not displaced during drying. Further methods for drying wood in a controlled manner are well known in the art.

The term "termite resistance" as used herein is intended to mean the resistance of a lignocellulosic material against destruction caused by an animal of the taxonomic group Termitidiae. Tests for determining termite resistance can be conducted both under - - laboratory and field conditions for the bioassays to compare the susceptibility of materials or the efficacy of protective chemicals under test. Laboratory test methods are usually adopted for termiticide development, while the field tests can simulate the real in-service performance scenario of treated material. A preferred test for determining whether a lignocellulosic material is resistant against degradation by termites is the AWPA test (American Wood-Preservers' Association (2007) E21-06: Standard Test Method for the Evaluation of Preservative Treatments for Lumber and Timbers against Subterranean Termites in Above-Ground, Protected Applications (UC1 and UC2). In: Book of Standards, pp. 365-369. AWPA, Birmingham, Alabama, USA) which is further described in the Examples below. Preferably, a lignocelulosic material is termite resistant, when the material exhibits less than 6 % weight loss, such as less than 5 % weight loss, more preferably less than 4 % weight loss, such as 3 % weight loss, even more preferably less than 2 % weight loss, such as less than 1 % weight loss, and most preferably 0 %, i.e. no weight loss, as determined by one of the above indicated standard tests.

The term "lignocellulosic material" as used herein means any material which substantially consists of lignocellulose. Lignocellulose refers to a plant biomass, mainly found in ligneous plants, which is composed of the carbohydrate polymers cellulose and hemicellulose tightly bound to lignin.

In a preferred embodiment, said lignocellulosic material is wood, plywood, engineered wood, particle boards, oriented strand boards, card board, paper, lignocellulosic insulation board, veneer lumber, fibre board, such as low, medium and high density fibre boards, hard board, high density and low density medium boards, and soft boards, textile fibre, or laminate.

Polyorganosiloxanes are already known to confer resistance to staining-, mould- and decay-fungi. As shown in the Examples, the lignocellulose material impregnated according the invention further exhibits beneficial properties with regard to termite resistance, which allows avoiding the use of potentially toxic biocidal agents. Moreover, in comparison to many other biocidal agents such as boron compounds, polysiloxanes are not readily leached out from the lignocellulosic material.

In another aspect, the invention provides the use of a composition as defined in the first aspect above for conferring termite resistance to a lignocellulosic material without any termite controlling agent or any preferred embodiment thereof. - -

The invention further provides a lignocellulosic material obtained by the method of the first aspect, wherein the lignocellulosic material may be suitable for use in hazard class 4, as defined in European Standard EN 335-1 2006. (European Standard EN 335 (2006). Durability of wood and wood-based products - Definition of use classes.)

This is already achieved with lignocellulosic material having a low weight percent gain resulting from the impregnation.

Thus, in a preferred embodiment after impregnation and drying (optionally curing), the lignocellulosic material has a weight percent gain of 10-50%, preferably 11-45%, such as 12-40%, more preferably 13-35%, and most preferably 14-30% with regard to a corresponding non-treated lignocellulosic material.

Without being limited to a theory, it is currently believed that the effect of water glass mainly resides on its high pH (>12). However, water glass may lead to a loss of strength during drying due to the hydrolysis of polysaccharides in the wood. Moreover, the high pH will decrease by time, since C0₂ is adsorbed, thereby forming carbonic acid, which leads to a loss of its protective function. Further, as long as the pH in wood is alkaline, the water glass will remain water soluble and can be readily leached out. In the acidic region, fixation is significantly improved, but the effect, in particular against fungi (also in the ground, hazard class 4), is lost.

In a further aspect, the invention provides a composition as defined in the first aspect of the invention for conferring termite resistance to a lignocellulosic material.

DESCRIPTION OF THE FIGURES

Figure 1 : Termite foraging in untreated (A, mass loss 42.0%), 5% AlkylSiMaE (C, mass loss 6.3%), 5% water glass (E, mass loss 7.4%) treated Scots pine test specimens exposed to C. acinaciformis, and corresponding test specimens exposed to M. danviniensis (B, mass loss 51.7% ; D, mass loss 8.2%; F, mass loss 1.2%).

The invention is further illustrated by the Examples without limiting it thereby. - -

EXAMPLES

Materials and methods

Chemicals and treatment of wood

Scots pine (Pinus sylvestris L.) sapwood specimens (25 x 75 x 190mm [longitudinal]) were treated with three polyorganosiloxane emulsions (Table 1, Momentive GmbH, Leverkusen, Germany) and aqueous silicate solution ("water glass", Betol^® 39T3, Woellner GmbH, Germany) and the weight percent gain (WPG) was calculated as previously described (Ghosh et al. 2008a). Polyorganosiloxane and silicate concentrations of 5%, 15% and 30% (w/w) were adjusted by diluting the stock solutions with demineralised water. Eight test specimens were treated with each chemical and treatment concentration. Untreated Radiata pine {Pinus radiata D. Don) sapwood (35 x 75 x 190mm [longitudinal]) served as feeder specimens

The treatment was performed using 100 mbar vacuum (lh) followed by 12 bar pressure (lh). The impregnated wood samples were subsequently dried gradually for one day respectively at 30, 60, 80 and 103°C (4 days total drying time). Weight percent gain (WPG) of treated samples was related to the oven dry weight of respective sample. Six replicates (n = 6) were used in this test.

Table 1 : List of chemicals used for wood modification.

Termites

The test specimens and feeder specimens were exposed to C. acinaciformis and M. darwiniensis at two different sites near Townsville, Australia. Coptotermes acinaciformis occurs in mounds on a private property near Black River (19 13'S, 146 47Έ), just north of Townsville. Mastotermes darwiniensis, the most destructive termite in Australia, occurs on a private property at Rowes Bay (19 13'S, 146 47 Έ), Townsville.

Field assay

Termite resistance tests can be conducted both under laboratory and field conditions for the bioassays to compare the susceptibility of materials or the efficacy of protective chemicals under test. Laboratory test methods are usually adopted for the termiticide development research, while the field tests can simulate the real in-service performance scenario of treated material .

Both treated and untreated test specimens (total 104) were exposed to termite feeding according to the Australasian Wood Preservation Committee (AWPC) (2007). The - - specimens were weighed and assigned to 26 test containers (6-litre plastic food containers, 90 x 210 x 310mm long). In each test container there were four test specimens and five feeder specimens. The test specimens in each test container were selected at random from the thirteen treatments (three concentrations of four treatments and untreated control). Two control containers were used with seven feeder specimens in each container. Thirteen test containers and one control container were used for each species of termite.

The test containers with test specimens as well as one container with control specimens were attached to a C. acinaciformis mound, via hollow concrete bricks established adjacent to one another along a section of a trench. Radiata pine feeder stakes were driven into the ground within the gaps of the bricks to facilitate movement of the termites from the ground to the test specimens, according to the method of Peters et al. (2006). Test containers were exposed to M. darwiniensis in the same way as described earlier. Each test container was covered with insulating material secured with soil. The trials were installed on 16^th June 2008 and following exposure for 16 weeks (Australasian Wood Preservation Committee 2007), the specimens were inspected, visually assessed (Table 2) and oven dried to calculate mass losses.

Table 2: The visual rating system used to assess termite damage (adapted from American Wood-Preservers' Association (AWPA) 2007).

Results and discussion

Termite activity was considered strong as evident from the mass loss data for feeder specimens at both sites. The average mass loss of the feeder specimens damaged by C. acinaciformis was 42.5% (Table 3). It is evident from the results that AlkylSiMaE and the water glass treated test specimens sustained minor mass losses (above 5%) due to the damage by C. acinaciformis. This was not observed at higher treatment concentrations i.e., WPG. Furthermore, specimens treated with QuatSiMiE and AminoSiMaE showed strong - - resistance to termite damage at all treatment concentrations, with no visible signs of feeding by termites.

Table 3: Oven dry mass, WPG due to treatment and mass loss due to C. acinaciformis damage.

The average mass loss of the feeder specimens exposed to M. darwiniensis was 45.1% (Table 4). Similar to the results of C. acinaciformis, AlkylSiMaE-treated test specimens showed termite decay and corresponding mass loss at low and moderate WPGs, but no damage was observed at higher WPG (30% treatment concentration). Water glass treated test specimens were also damaged by M. darwiniensis at low WPGs (5% treatment cone.) only. Nevertheless, test specimens treated with QuatSiMiE and AminoSiMaE showed strong resistance to the damage by M. darwiniensis. - -

Oven dry weight, WPG due to treatment and mass loss due to M. darwiniensis

Mass loss results of both test termites were found to be in agreement with the visual rating system for both C. acinaciformis (Table 3) and M. darwiniensis (Table 4) done according to AWPA (2007). Both the QuatSiMiE and AminoSiMaE have been found to be strongly resistant to termite damage even at low WPGs. The occasional "nibble" by M. darwiniensis on test specimens treated with moderate and higher concentrations of AminoSiMaE resulted in mass loss less than 5%. A single termite "nibble" was observed in only one test specimen of AminoSiMaE treatment (both 15% and 30% treatment concentration).

Damage by both termite species in the treated and untreated specimens is shown in Fig. 1. The untreated Scots pine wood specimens were heavily damaged by both termite species (Fig. 1A, IB). However, only surface nibbles were observed in case of 5% AlkylSiMaE treated wood by C. acinaciformis (Fig. 1C) and several holes were created in one test specimen of 5% water glass treatment (Fig. IE). The foraging of M. darwiniensis in 5% - -

AlkylSiMaE (Fig. ID) and water glass test specimens (Fig. IF) were found to be restricted to the surface only. According to the AWPC (2007) protocols both of these treatments could be considered effective in preventing termite damage in the test specimens. Nevertheless, wood treated with AlkylSiMaE and water glass was also resistant to termite damage at 15 and 30% treatment concentration.

Conclusion

Wood treated with quat- and amino-functional silicone emulsions showed resistance against subterranean termites even at less than 15% WPG. AlkylSiMaE and the water glass treatment also reduced the damage by termites to a considerable extent at higher treatment concentrations. Because the silicone emulsions create a new resistant material against decay-and staining- fungi as well as termites they hold good potential to be used for treatment of wood exposed in hazard class 4 (European Standard EN 335-1 2006). LIST OF REFERENCES

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American Wood-Preservers' Association (2007) E21-06: Standard Test Method for the Evaluation of Preservative Treatments for Lumber and Timbers against Subterranean - -

Termites in Above-Ground, Protected Applications (UC1 and UC2). In: Book of Standards, pp. 365-369. AWPA, Birmingham, Alabama, USA.

Australasian Wood Preservation Committee (2007) Protocols for assessment of wood preservatives. AWPC Publication, Melbourne, 30pp. <http://www.tpaa.com.au/files/AWPC%20protocols.pdf> (accessed 09/01/09).

European Standard EN 335 (2006). Durability of wood and wood-based products - Definition of use classes.

Furuno, T., Imamura, Y. (1998) Combinations of wood and silicate. 6. Biological resistance of woodmineral composites using water glass-boron compound system. Wood Sci. Technol. 32:161- 170.

Ghosh, S.C., Militz, H., Mai, C. (2008) Decay resistance of treated wood with functionalised commercial silicones, Bioresources 3:1303-1314.

Ghosh, S.C., Militz, H., Mai, C. (2009) The efficacy of commercial silicones against blue stain and mould fungi in wood. Eur. J. Wood Prod. 67:159-167.

Kartal, S.N., Hwang, W,-J, Yamamoto, A., Tanaka, M., Matsumura, K., Imamura, Y. (2007) Wood modification with a commercial silicon emulsion: Effects on boron release and decay and termite resistance. International Biodeterioration and Biodegradation 60(3): 189-196.

Peters, B.C., Lenz, M., Creffield, J.W. (2006) Re-sealing cut ends of envelope-treated softwood framing timber to protect against damage by the Australian subteiTanean teimite Coptotermes acinaciformis: A revisitation. International Research Group on Wood Preservation, Stockholm, Sweden. IRG Document No. IRG/WP 06-20335. 7pp.

Weigenand, O., Humar, M., Daniel, G., Militz, H., Mai, C. (2008) Decay resistance of wood treated with amino-silicone compounds. Holzforschung 62(1): 112-118.

Weigenand, O., Militz, H., Tingaut, P., Sebe, G., de Jeso, B., Mai, C. (2007) Penetration of amino-silicone micro- and macro-emulsions into Scots pine sapwood and the effect on water related properties. Holzforschung 61(1): 51-59.

Yamaguchi, H. (2003) Silic acid: boric acid complexes as wood preservatives. Wood Sci. Technol. 37: 287-297.

Claims

1. A method for conferring termite resistance to a lignocellulosic material, comprising the step of impregnating the lignocellulosic material with a composition which comprises an polyorganosiloxane and no termite controlling agent,

wherein the polyorganosiloxane comprises identical or different organosiloxane units of formula (I),

R'_a R² _b(OR³)_c SiO _w+c) (I)

2

in which

R 3 is identical or different H, R 1 or R2 ;

a, b, c are 0, 1, 2 or 3, with the proviso that the sum a+b+c < 3.

2. The method as claimed in claim 1, where the symbols and indices in formula (I) have the following meanings:

R¹ is, identical or different, straight chain or branched Cj-Ci₂-alkyl, C₅-Cg- cyclo alkyl, C₆-C₁₂-aryl, Ci-Cn-alkyl-Q-Cn-aryl, C₆-Ci₂-aryl-(Ci-C₁₂)- alkyl, each of said groups being unsubstituted or substituted by one or more substituents selected from the group consisting of OH, SH, halogen, CN, OR', SR', CO-R' and COOR', where R' is a straight chain or branched C Ci₂-alkyl or C₆-C₁₂-aryl;

R² is identical or different straight chain or branched CrQo-alkyl, C₅-Cg-cyclo alkyl, C₆-Ci2-aryl, C-Cio-alkyl-Ce-Cj.-aryl, C₆-Ci₂-aryl-(Ci-Cio)-alkyl, each of said groups being unsubstituted or substituted by one or more substituents selected from the group consisting of OH, SH, halogen, CN, OR', SR', CO-R' and COOR', where R' is a straight chain or branched C Cio-alkyl or C -C₁₂-aryl, and each of said groups being substituted with one or more substituents selected from the group consisting of NR"R^m and N⁺R"R"'R"", where R", R'", R"" are identical or different H, R', a straight chain or branched CrC₁₀-alkyl-NR'₂, a straight chain or branched Ci-Ci₀- alkyl-N⁺R'₃, C₆-C₁₂-aryl-NR'₂, C₆-Ci₂-aryl-N⁺R'₃, OR', COR' and COOR';

R³ is H, R¹ or R²; a, b, c are 0, 1, 2 or 3, with the proviso that the sum of a+b+c < 3.

3. The method as claimed in any one of claims 1 to 2, where the polyorganosiloxane comprises organosiloxane units of formula (II),

[R'a R² _b(OR³)_c SiO ₄__{a+b+c) ]_x [R¹, R² _b(OR³)_c SiO ₄__{a+b+c) ]_y (II) in which

R¹, R², R³, a, b, c have the meanings given in formula (I) in claim 2 or 3, with the proviso that at least one of the symbols or indices is different in the two structures;

is, identical or different, an integer from 1 to 300; the sum x + y is from 10 to 500, it being possible for the organosiloxane units to be in any order.

The method as claimed in any one of claims 1 to 3, where the polyorganosiloxane comprises one or more nitrogen atoms.

The method as claimed in claim 4 where b≠ 0 and R is selected from -CH₂-CH₂- CH₂-NH₂, -CH₂-CH₂-CH₂-NH(CH₃), -CH₂-CH₂-CH₂-N(CH₃)₂, -CH₂-CH₂-CH₂- NH-CH₂-CH₂-NH₂, -CH₂-CH₂-CH₂-NH-CH₂-CH₂-NH(CH₃), -CH₂-CH₂-CH₂-NH- CH₂-CH₂-N(CH₃)₂, -CH₂-CH₂-CH₂-NH-CH₂-CH₂-NH(CH₂CH₃) and -CH₂-CH₂- CH₂-NH(cyclo-C₆-H_n).

The method as claimed in claim 4, where the polyorganosiloxane comprises repeating units of formula (III),

-[ U - V ]- (III) wherein V is selected from the V¹ and V² group, which may be the same or different, in which V² is selected from divalent and trivalent, straight-chain, cyclic and branched, saturated, unsaturated and aromatic hydrocarbons including at least one Z² group of the formula

wherein groups R⁴ may be the same or different and are selected from the group consisting of a straight chain or branched C C₂₂alkyl, fluoro(Ci-C₁o)alkyl, C₆-C₁₀ aryl, and wherein ni=20 to 1000,

wherein V includes up to 1000 carbon atoms exclusive of the Z radical, and wherein V² may optionally contain one or more groups selected from

-OH

-O-

-NR⁵-

in which R⁵ is hydrogen, a monovalent, straight-chain, cyclic or branched, saturated, unsaturated or aromatic hydrocarbon radical which has up to 100 carbon atoms and may contain one or more groups selected from -0-, -NH-, -C(O)- and - C(S)-, and which may optionally be substituted by one or more substituents selected from the group consisting of a hydroxyl group, an optionally substituted heterocyclic group, amino, alkylamino, dialkylamino, polyether radicals and polyether-ester radicals, where, when a plurality of -NR²- groups is present, they may be the same or different,

-C(O)-,

-C(S)-, and wherein V¹ is selected from divalent and trivalent, straight-chain, cyclic and branched, saturated, unsaturated and aromatic hydrocarbon radicals which have up to 1000 carbon atoms and may optionally contain one or more groups selected from

-OH,

-0-,

NR⁵-

-N⁺R⁵ ₂-in which R⁵ is as defined above, and where the R⁵ groups in the V¹ and V² groups may be the same or different,

-C(O)-,

-C(S)- and

-Z¹, in which -Z¹ is a group of the formula

in which

R⁴ is as defined above, where the R⁴ groups in the V¹ and V² groups may the same or different, n₂= 0 to 19,

wherein at least one Z¹ or Z² group is present; U is N⁺R⁶R⁷, NR⁷, or C^N

^N— ^N is a 5 or 6 membered saturated, partly saturated or aromatic ring optionally comprising one further hetero atom selected from N, O and S;

R⁶, R⁷ are identical or different, H substituted or unsubstituted, straight chain or branched Ci-C₂₂-alkyl or substituted or unsubstituted C₆-Ci₂-aryl;

or the polyorganosiloxane comprises repeating units of formula ( IV),

[Y-CO-NH-V-NH-CO-Y-V] ( IV)

wherein V is identical or different and has the same meaning as in formula (III), and

Y is identical or different NR⁸, O or is a substituted or unsubstituted straight chain or branched CrC₂₂-alkylene or substituted or unsubstituted C₆-C₁₂- arylene, and

R⁸ is H or a monovalent organic group and

7. The method as claimed in claim 6, where the polyorganosiloxane comprises repeating units of formula (III).

8. The method as claimed in any one of claims 1 to 7, wherein said polyorganosiloxane is used in the form of an emulsion having an emulsion particle size of less than 1 μηι.

9. The method as claimed in any one of claims 1 to 8, wherein said lignocellulosic material is wood, plywood, engineered wood, particle boards, oriented strand boards, card board, paper, lignocellulosic insulation board, veneer lumber, fibre board, textile fibre, or laminate.

10. The method as claimed in any one of claims 1 to 9, wherein said composition further comprises at least one additional additive selected from organic polymers, fillers, thickeners, emulsifiers, dispersing agents, buffer substances, flame retardants, pigments, dyes, penetrants, antistatic agents, odor substances, corrosion inhibitors, preservatives, catalysts, and anti-foams.

11. The method of any one of claims 1 to 10, wherein said lignocellulosic material is impregnated with said composition by brush coating, roll coating, spray coating, immersion treatment, or vacuum and/or pressure impregnation.

12. The method as claimed in claim 11, wherein said composition is applied by vacuum and pressure impregnation.

13. The method as claimed in claim 11, wherein said vacuum and pressure impregnation comprises 100 mbar vacuum for about lh followed by 12 bar pressure for about lh.

14. The method of claim 13, additionally comprising a drying step, wherein the treated wood is dried gradually for one day at 30, 60, 80 and 103°C respectively.

15. The use of a composition as defined in any one of claims 1-8 or 10 for conferring termite resistance to lignocellulosic material.

16. The use of claim 15, wherein the lignocellulosic material is wood, plywood, engineered wood, particle boards, oriented strand boards, card board, paper, lignocellulosic insulation board, veneer lumber, fibre board, textile fibre, or laminate.

A lignocellulosic material obtainable by the method according to any one of claims 1-14, where the lignocellulosic material is suitable for use in hazard class 4, as defined in European Standard EN 335-1 2006.

The lignocellulosic material of claim 15, having a weight percent gain of 10-50% compared to a corresponding non-treated lignocellulosic material.

A composition for conferring termite resistance to lignocellulosic material as defined in any one of claims 1-8 or 10.