CA1061659A - Process for protecting wood with a preservative containing o-boric acid/propylene oxide adduct - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A process for protecting wood against ligniperdous insects, termites, ligniperdous fungi, soft rot and mold fungi, which comprises bringing into contact with the wood an effective amount of wood preservative compounds effective against ligni-perdous insects, termites, ligniperdous fungi, soft rot and mold fungi, said compounds being o-boric acid/propylene oxide adducts having a molar ratio of said acid to said propylene oxide in the range of 1:1 to 1:5, respectively, said adducts being formed by reacting said o-boric acid and propylene oxide either in an aprotic solvent at 100°C to 160°C in the absence of a catalyst or at 70°C to 120°C in a closed vessel in an aprotic solvent and in the presence of a catalytic amount of a base or a Lewis acid at a pressure of said propylene oxide of 4 to 9 bars, and thereafter distilling off said solvent.

Description

~L~6~659 The pxesent invention relates to a process for protecting `~
wood against fungi and insects with a wood preservative containing o-boric acid/prop~lene oxide adduct.
i, ~ t is known (Chemical Week, 3uly 26, 1972, p. 43) to use boric acid for protecting wood against insects and fungi.
We have now found that o-boric acid/propylene oxide adducts have a strongly destructive actîon on wood-destroying insects and fungi, and are therefore eminently suitable as wood preservatives. By "wood" is meant not only solid wood but also `
wood-base materials prepared from wood particles, e.g., wood chips. ;~
The adducts exhibit not only a good fungicidal action but also an action on ligniperdous insects such as Hylotrupes bajalus, `~

,~
Anobium punctatum and Lyctus ~runneus, and on termites. The following .
ligniperdous fungi and soft rot and mold fungl may be controlled with the active ingredients of the invention:

,;
Coniophora cerebellaj Merulius lacrimans, Lentinus lepideus, Lenzites trabea, Porio vaporaria, Polystictus (Coriolus) versicolor, Paxillus panuoides, Stereum purpureum, Fomes annosus, Bispora effusa, Stachybotrys atra, Chaetomium globosum, Trichoderma viride, 2Q Aspergillus niger, Hormiscium spec., and Stemphylium spec.
By contract to boric acid and borax, which are unsuitable as active ingredients for oil-type wood preservatives on account -.
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~V~659 of their poor solubility in or~anic solvents, the o-boric acid/ ~-p~pylene oxide adducts are very readily soluble in the aromatic and aliphatic solvents usually employed; these active ingredients _ -in solvent formulations also mix well with other fungicides and insecticides used for protecting wood~ Compounds with which the adducts of the invention are miscible are for example the `
aluminum salt Or N-cyclohexyl-N~nitrosohydroxylamine, pentachloro-phenol, chloronaphthalene, N-dichlorofluoromethylthio-N',N'-di-methyl-N-phenylsulfonyl diamide, and N-phenyl-N,N~-dimethyl-N~
10 dichlorofluoromethylthiosulfonyl diamideO The active ingredients .
may not only be used in solvent wood preservative formulations ~-which are applied to the wood by painting, dipping or spraying, but also added, in aqueous solution, to glues for the manufacture of wood-base materials. Sultable binders for the manufacture of wood-base materials are urea/formaldehyde, melamine/formaldehyde, urea/formaldehyde/melamine and isocyanate resins. As the active ingredient solutions can be added to the glue direct, there is no danger, as is the case with o-boxic acid, of the formation of lumps which result in poor distribution of the active ingredient.
It is also known that, when o-boric acid is mixed with wood chips before gluing, difficulties occur with regard to homogeneous distribution~ Furthermore, aqueous active ingredient solutions may also be used for impregnating wood by the pressure process. ~ ~
The wood to be protected against insect and fungus attack ~~ -is treated with the preservative in such a manner that the active ingredient is uniformly distributed over the surface of the wood and penetrates into the wood as far as possible. When the surface is treated, the applioation rate i8 approximately 5 to 100 g of

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~6~<~ i active ingredient per m . For impregnation, or for the treatment of wood ch~ps in the manufacture of wood-base -'materials, the application rate is about 5 to 25% of active ingred~ent, ~ased on dry wood substance. Examples of suitable solvents fcr the active ingredient are benzene -~
fractions conta~ning up to 30wt% of aromatics, drying oils such as are used in paintaing, alcohols, esters, ketones and ~lycol ethers. The active ingredient may also be mixed with solid carriers such as clay, silica gel, lima dust and lQ diatomaceous earth.
The present invention is concerned with a process `~
for protecting wood against ligniperdous insects, termites, ligniperdous fungi, soft rot and mold fungi, which comprises ~ -bringing into contact with the wood an effective amount of -~
wood preservative compounds effective against ligniperdous insects, termites, ligniperdous fungi, soft rot and mold fungi, said compounds being o-boric acid/propylene oxide adducts having a molar ratio of said acid to said propylene oxide in the range ' of 1:1 to 1:5, respectively, said adducts being formed by 2Q reacting said o-bor;c acid and propylene oxide either in an '~
aprotic solvent at 100C to 160C in the absence of a catalyst -' or at 70C to 120C in a closed vessel in an aprotic solvent -' and in the presence of a catalytic amount of a base or a Lewis acid at a pressure of said propylene oxide of 4 to 9 bars, and thereafter distilling off said solvent.
The wood preservatives contain ~rom about 1 to 30wt% of the o-boric acid/propylene oxide adduct. "
In accordance with the invention, "aprotic organic ;' solvents" are those which do not possess a mobile hydrogen

3~ atom in the molecule. They may be polar or non-polar. ,~
Examples of polar solvents are acetone, dioxane, dimethyl~
formamide, formamide, and dimethyl acetamide; carbon tetrachloride is an example of a non-polar solvent.
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The reaction may be carried out preferably at temperatures of from 12a to 150C without the addition of catalysts. It is however preferred to carry out the reaction in the presence of bases or Lewis acids because these reagents have a catalytic action. Examples of bases are terkiary amines such as dimethyldodecylamine, catalytic amounts of an alkali such as sodium hydroxide, and alkoxides such as sodium methylate and potassium tert-butylate; examples of Lewis acids are boron trifluoride etherate, aluminum chloride and zinc chloride. When catalysts are used, the temperatures employed are preferably from 80 to 110 C.
In th;s case the reaction is expediently carried out in a closed system, for instance an autoclave, in which is placed the aprotic solvent a~d to which is added from 20 to 200wt%, based on solvent, of o-boric acid and, if desired, from 0.1 to 5wt% of base or Lewis acid, based on o-boric acid.
The system is then pressured, in accordance with the molar ratios given, with from 1 to 5 times, preferably from 3 to 4 times, the molar amount of propylene oxide, based on o-boric acid, and the contents heated to from 70 to 120C and as stated above pre~erably from 80 to 110C. By definition the pressure should rise preferably to from 5 to 7 bars. The total -~
. . .
duration of the reaction is about 3 to 8, preferably 5 to 6,hours.
Upon completion of the reaction and after the pressure in the ~,' , ~,.: :''.
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reaction vessel has been let down, the solvent and water of reaction are removed by distillation~ -Depending on the amount and type Or alkylene oxide used, there remain water-soluble to water-insoluble, liquid to viscous products which can be characterized by viscosity, infrared spec-troscopy~ and mass spectroscopy.
Visco~ity measurements carried out on propoxylation products give for~instance - at 20C - viscosities of 1,600 to 1,700 cSt;

butoxylation products approx. 100 cSt. -Inrrared spectra have B-0 bands at 1,310 to 1,350 cm 1.
In mass spectroscopy, characteristic fragments are obtained from which it is possible to conclude that the reaction products are, depending on the molar ratios of o-boric acid to propylene :i oxide, cyclic esters, the most frequent of which are compounds having the following structure:

2nCn ~ ~ E-0-CnEl2n-0-E \ / enH2n 0C H2n0\ -.

n = 2 to 0CnH2n0 ;c . , , ~
Some Or the products obtained by the process Or the invention - can be puri~ied by distillation and fractionatedO They may be used a5 a mixture or as individual fractions.

The following examples, in which the parts are by weight, illustrate the invention ~ 5 -', ~ ~ :' '. ' :, ': ~ ''~
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';'~; ' .' O.Z 31,996 ~ -o-boric acid/1 2-butylene oxide In a V2A stirred autoclave are placed 93 parts (1.5 moles) ,`
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of o-boric acid, 93 parts oP dioxane and 2.79 parts ~3wt%, based on o-boric acid) of dimethyldodecylamine; subsequently, 432 parts r~ .
(6 moles) of 1,2-butylene oxide is pressured in in portions at 130 to 140Co Pressuring time: 3 hours Pressure: 7 atmospheres gauge Temperature: 138C ~ -Stirring time: 3 hours A clear brown liquid is obtained. The rate of conversion, based on oxide consumption, is 1:3.60 After removal of residual epoxide and the mixture of dioxane and water of reaction, 3 Practions are obtained: j~
Fraction I: b.p. (0.7 mm) 57C, 37 g; n20: 1.4390 -Fraction II: b.p. (0.5 mm) 120-130C, 75 g; n20: 1.4400-1.4404 ;~
D20: 0.995 Fraction III: b~p. (0.5 mm) 145-160C, 17 g; n20: 1.4411-1.4444 ~20 ~ 9~ cP (98.6 cSt) (290 g of resinous residue) EXAMPLE 2 ~- `
o-boric acid/ethylene oxide In a V2A stirred autoclave are placed 248 parts (4 moIes) of o-boric acid, 248 parts of dioxane and 3.72 parts (1.5wt%, based on o-boric acid) oP BF3 etherate; subsequently, 528 parts (12 moles) of ethylene oxide is pressured in in portions at :`. , ' '' ;'''''' "
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, O.Z. 31,996 110 to 120C, and unreacted ethylene oxide and the mixture of dioxane and water of reaction are removed in vacuo at 90 to 100C/15 mm Hgo There is obtained 775 parts of a pasty wax-like (Vaseline-like) compound. The rate of conversion, based on oxide consumption, is 1:3, .
Pressuring time: 6 hours Pressure: 7 atmospheres gauge ..

Temperature: 110-115C `
Stirring time: 3 hours o-boric acid/1,2-butylene oxide :
~ In a V2A stirred autoclave are placed 93 parts (1.5 moles) 1~ -¦ of o-boric acid, 18~ parts of dioxane and 2.79 parts (3wt%, based ;~
on o-boric acid) of sodium methylate; subsequently, 378 parts (5.25 moles) of 1,2-butylene oxide is pressured in in portions ~
at 135 to 140C. ;
Pressuring time: 6 hour~
Pressure: 7 atmospheres gauge ,- ; ~ :
: Temperature: 138C .
¦~ Stirring time: 3 hours 11 parts of unreacted o-boric acid is separated by suction ~ .:

filtration from the dioxane solution containing water of reaction. ::
The rate of conversion, based on oxide consumption, is 1:2.5.
l After removal of the dioxane-water mixture, the unreacted ~:
., epoxide and high vacuum distillation, 3 fractions are obtained: :
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OOZ. 31,996 Fraction I: bop~ (Ool mm) 53-55C/23 parts of a pale yellow oil f' Fraction II: b~p (002 mm) 95C/14 parts of a pale brown oil Fraction III: b,p~ (003 mm) 160C/ 42 parts of a pale brown oil 90 g of a resinous residue EXAMPLE 4 -~

o boric acid/propylene oxide ,, .
In a V2A stirred autoclave are placed 248 parts (4 moles) ~`
of o-boric acid, 7.44 parts (3wt%, based on o-boric acid) of dimethyldodecylamine and 248 parts of dioxane; subsequently, `r 928 parts (16 moles) of propylene oxide is pressured in in '~

portions at from 100 to 110Co Pre suring time: 8 hours Pressure: 8 atmospheres gauge f~,' ' Temperature: 108C ;~
Stirring timeo 3 hours -After removal of the excess propylene oxide and the mixture "f'~ ~ . ' `, '`
of dioxane and water of reaction, 1,013 parts of a pale yellow oil is obtained.
d20: 1.070-10065 ;`;f'''~''""

n20: 10444 ~ `

~20 1,695 cP
b.p. (760 mm): 270C

Rate o~ conversion, based on oxide consumption: 1:303 ~`
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o-boric aic/2,3-butylene oxide In a V2A stirred autoclave are placed 93 parts (1.5 moles) of o-boric acid, 93 parts of dioxane and 2.79 parts (3wt%, based -'f," ' ' ' ' ' ' ',~

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~6~ OoZO 31,996 on o~boric acidj of dimethyldodecylamine; subsequently, 432 parts (6 moles) Or 2,3-butylene oxide is pressured in in portions at from 120 to 140Co `~
Pressuring time: 8 hours Pressure: 8 atmospheres gauge Temperature: 138C
Stirring tîme: 3 hours ~ ~
Rate o~ conversion, based on oxide consumption: 1:2,35,~3~ "
After removal of residual epoxide and the mixture of dioxane ,;
and water of reaction, and after high vacuum distillation, 3 frac- ~ -tions are obtained as pale yellow to colorless liquids:
Fraction I: bop~ (0~4 mm) 70C (37 g~; nD: 1.4324; ~20 = 135 cP
(133.5 cSt) Fraction II: bop~ (004 mm) 90C (22 g); n20: 1.4330, ~20 = 140 cP `~
(139.5 cSt) ~,`
Fraction III: b.p. (o.ll mm) 146C (95 g); n20: 1.4330; ~20 = 145 cP ;~
(143.5 cSt) 89 g o~ a resinous residue EXAMPLE 6 ;i ~
o-boric acid/isobutylene oxide ~ -~, , .
In a V2A stirred autoclave are placed 124 parts (2 moles) of o-boric acid, 62 parts of dioxane, and 3.72 parts (3wt%, based on o-boric acid) of sodium methylate; subsequently, 504 parts ~-(7 moles) of isobutylene oxide is pressured in in portions at ; from 140 to 150Co Pressuring time: 9 hours -Pressure: 8 atmospheres gauge `
Stirring time: 3 hours _ g~

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9 0,Z~ 31,996 ~ After removal of the residual epoxide and the mixture of '~ dioxane and water of reaction at subatmospheric pressure, there is obtained 290 parts of a yellow oil Rate of conversion, based on oxide consumption: 1:1015 ;~
Boiling point(003 mm): 105C
~20 = 5204 cP (= 51 cSk) r D20 : 1.028 pH : 4.5 EXAMPLE 7 ;~
o-boric acid/styrene oxide In a 2 liter V2A stirred autoclave are introduced 62 parts ~10 (1 mole) of o-boric acid, 62 parts of dioxane, 1086 parts (3wt%, `~` based on o-boric acid) of dimethyldodecylamine, and 360 parts :, :
(3 moles) of styrene oxide; the contents are slowly heated, and ~`! stirred for 6 hours at 150C under a nitrogen blanket.
After removal of the dioxane in vacuo, there is obtained `1 350 parts of a red-brown, viscous, water~insoluble product.
~j Rate of conversion~ based on oxide consumption: 1:2.4 ;~
EXAMPLE 8 ~
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~- To prepare an oil-type wood preservative containing 7.5% `
of boric acid/propylene oxide product, 7.5 parts of the latter product (Example 4) is mixed with 13.7 parts of an alkyd resin ` `
~20 of medium oil content r20% solid resin3. There is then added ~ -. 1 ,. ~ . .
,l 47~3 parts of an aromatics-containing benzene fraction, the ~;
mixture i3 if desired filtered to remove impurities, and is then made up to 100 parts with a benzene fraction containing aliphatic '~
compounds. ~`
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;~l "` ' ".. ' . . ' ' O~Z. 31,996 EXAMPLE 9 .
An oil-type wood preservative containing 15.1% of active ~` -ingredient is prepared in similar manner, except that only ~:
3917 parts of the aromatics-containing benzene fraction is used ` : ~ .
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instead of 47.3 parts EXAMPLE 10 `: :
To determine the effectiveness of the preservatives of the invention on wood-destroying fungi, pine sapwood and beechwood 2 ` !
blocks 50x25x15 mm in size were coated with 200 g/m of wood sur- : :
face Or the oil-type wood preservative formulations of Examples 8 and 9. After 4 weeks' storage the treated blocks were placed, i.;~ .:
together with untreated controls, in glass dishes containing3 .:. ~ .in a nutrient medium, the test fungi Coniophora cerebella and Polystictus (Coriolus) versicolorO The dishes were then incubated under controlled conditions (22C; 70% relative humidity). ::
, . . .
After four months the mycelium adhering to the blocks ~ : :
was removed and the blocks were dried. The weight loss and :
degree of wood destruction wère then ascertainedD ~;
, Amount of Coniophora cerebella Polystictus versicolor boric acid/ (pinewood) (beechwood) propylene oxide weight degree of weight degree of :~
product in ~or- loss in destruction loss in destruction . ~.:
mulation in % % %
7.5 0 1 2 2a ~:
15.1 0 1 0 Control . ~
(untreated) 21 3b/4a 18 3b ~;, . ' ' :. :~
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~ 9 O.Z. ~1,996 Scale ~ , .
1 = undamaged -~
2a - slight attack in parts 2b = slight attack overall ~, 3a = marked attack in parts 3b = marked attack overall 4a = completely destroyed ln parts 4b = completely destroyed overall The boric acid/propylene oxide product was added as preserv- ~`
ative to an aqueous wood glue mixture based on a urea/formaldehyde polycondensate. Beech and spruce chips were glued with these binder ;
mixtures, 9 parts of resin (dry weight) being used for 100 parts of chips~ The chips coated with binder were pressed for 6 minutes at a temperature of 165C to give 18 mm thick chipboard. The amount of preservative was such that the finished boards contained 7.5%
of the boric acid/propylene oxide product, based on dry chips.
For comparison purposes, chipboard was produced to which boric ~
I0 acid in powder form had been admixed in amounts of 2%, based on ~ ' ::~
dry chips, after the chips had been glued. The amount of 2% boric ,~ -acid corresponds to the boric acid content of the 705% boric acid propylene oxide product obtained in accordance with Example 4. .,~
Specimens 50x25x18 mm in size were cut from the chipboard and examined as to their resistance to attack by the wood-de~
stroying fungi Coniophora cerebella and Polystictus versi_ol_r and by the mold fungi A~pergillus niger and Trichoderma viride. The specimens were placed on biomalt nutrient agar glass plates covered `~.''' ~3~
oOzO 31~996 with the wood-destroying fungi, and incubated at 22C. After 16 weeks the extent oP fungus spread on the specimens was ..~,,, assessedO The experiments with the mold fungi were carried out ~ :
analogously, however, the duration was only 14 days here, as :
the untreated specimens were completely covered with fungus `~
after this length o~ time.

Specimen; Extent of fungus spread on wood after 16 weeks fungicide added Coniophora cerebella Polystictus versicolor `~:
7.5% boric acid/ : - `
propylene oxide 0 0 2% boric acid ::
(comparative agent) 2 none (untreated) 3 3 Specimen; Extent of fungus spread after 14 days . :
fungicide added Aspergillus niger Trichoderma viride .
.. . - . ........ _ . : : .
7.5% boric acid/
propylene oxide 0 0 ~` :
2% boric acid .
(comparative agent) 1 2 ..
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none (untreated) 3 3 ~ - .
` ! . ' 0 no fungus on specimen .;~
1 sides of specimen covered with fungus 2 specimen covered to a considerable extent with fungus ~ .
3 specimen completely covered with fungus - 13 - ~ .

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Claims (5)

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

1. A process for protecting wood against ligniperdous insects, termites, ligniperdous fungi, soft rot and mold fungi, which comprises bringing into contact with the wood an effective amount of wood preservative compounds effective against ligni-perdous insects, termites, ligniperdous fungi, soft rot and mold fungi, said compounds being o-boric acid/propylene oxide adducts having a molar ratio of said acid to said propylene oxide in the range of 1:1 to 1:5, respectively, said adducts being formed by reacting said o-boric acid and propylene oxide either in an aprotic solvent at 100°C to 160°C in the absence of a catalyst or at 70 C to 120°C in a closed vessel in an aprotic solvent and in the presence of a catalytic amount of a base or a Lewis acid at a pressure of said propylene oxide of 4 to 9 bars, and thereafter distilling of said solvent.

2. A process as claimed in claim 1, wherein said adducts embody compounds having the formulae and wherein n denotes 3.

3. A process as claimed in claim 1, wherein said molar ratio is in the range of 1:3 to 1:4.

4. A process as claimed in claim 1, wherein the wood is coated with a liquid containing a fungicidally effective amount of said adducts.

5. A process as claimed in claim 1, wherein the wood is wood chips, and said adduets are brought into contaet with said wood chlps by bonding said chips with a wood glue containing an effective amount of said adducts.