Note: Descriptions are shown in the official language in which they were submitted.
6~
Title: "Process For The Aqueous Impregnation 0~ Green Wood With Oil
Soluble MetAl Salts"
BACKGROUND OF THE INVENTION
The present invention relates to an inexpensive method for
impregnating wood with metal salts, and more particularly, to a method for
impregnating wood with preservative and fungicidal treatments.
In order to prevent decay of wood and timbers, and thereby
increase their life, it is common practice to impregnate the wood or timbers
with a preservative such as creosote dissolved in liquid aromatic hydr~
carbons, mixtures of organic compounds which are dissolved or dispersed in
water, or certain compounds which are d;ssolved in petroleum distillates.
The protection afforded by the application of these materials is dependent
up~n deep and reasonably ur~iform penetration into the wood or timber by
the preservative materi~l. It also is desirable that the treatment be
effected without a significant change in the original dimensions and surface
texture of the wood or timbers.
The subject of wood treatment and wood preservation is dis-
cussed in some detail in the two volume treatise entiSled "Wood Deteriora-
tion and its Prevention by Preservative Treatmentsn, Darrel DD Nicholas~
Editor, Syracuse Wood Science Series 5, Syracuse University Press,
Syracusey N.Y., 19730 Among the examples of wood preservatives described
therein are various creosote compositions, pentachloro-phenol, copper nap~
then~te, copper-8~uinolinolate, organotin compounds, vrganomercury com-
pounds) zinc naphthenate, chlorinated hydrocarbons, ammoniacal copper
arsenite (ACA), acid copper chromate (AGC), zinc salts such as zin~
c}~oride, zinc oxide and zinc sulfate, chromated copper arsenate (CCA~, etc.
In Volume II, Chapter 3, pages 279-298y processes and equipment for
treating wood are discussed. The pressure treatment is described as the
most effective method of protecting wood against attack of decay, ir~ects,
fire, etc. Non-pressure treatments also are discussed in this chapter.
Dipping is suggested primarily as a satisfactory surface treatment although
some penetration is observed. Another non-pressure technique is the
7~
difiusion process with unseasoned wood. The author indicates the process
requires long treating periods because of slow diffusion rates.
While the literature on the subject of such wood treatments is
extensive and covers a period of at least lû0 years, most of the procedures
which have been ~escribed for treating wood with preservatives and resin
components, including pressure treatments, do not result in extensive
uniform impregnation of the material into the heart of the wood and/or the
procedures require a long period to effect the penetration. The problem is
particularly acute when treating some types of green or incompletely
seasoned wood such as soft pine.
The use of liquid aromatic hydrocarbons for preparing impreg-
nating solutions imparts to the wood strong odors and leaves the wood with a
surface which is oily and difficult to paint. Moreover, liquid aromatic
hydrocarbons are ~lammable materials requiring special handling and safety
prec~utions which add to the cost of the wood treatment~
Wocd treated with organic preservatives dissolved in petroleum
distillates have the same disadv ntages as wood treated with the aromatic
hydrocarbons. Using lower boiling petroleum distillates, such as mineral
spirits, as the solvent, fails to eliminate the disadvantages completely.
Prolonged air seasoning after treatment is frequently required to permit
sufficient evaporation of the solvent if the wood is to be painted. During
this period of air seasoning, a portion of the preservative can migrate to the
sur~ace of the wood with the solvent, and thus, the retention of the
preservative into wood is reduced below that contemplated iby the treat-
ment.
One technique for utilizing a~ueous systems of polyhPlophenols is
described in U.S. Patent 4,090,000. Briefly, the method involves the use of
an aqueous solution containing a water-soluble salt o~ the polyhalophenol
and an acid forming material which can undergo a reaction in the solution to
liberate an acid which displaces the polyhalophenol from said salt after the
solution is impregnated into the wood.
Regardless o~ which impregnating solution is ernployed, the most
common commercial procedure or impregnating wood involves subjecting
7~96~
wood to the preservative under relatively high pressures such as 15U to 200
pounds to the square inch for a substantial period of time such ~s from one
hour to 24 hours. The process also may require relatively high temperatures
such as from about 75C to about 90 to 95C. Although increases in pressure
tend to increase the amount of preservat,ve absorbed by the wood, it may
cause the penetration to be erratic or uneven. Moreover, the application of
pressure can cause compression of the outer layers of the wood9 particularly
after wood is weakened and softened by steaming. The collapse of the wood
cells is likely to occur especially when relatively soft, unseasoned wood of
low specific gravity is being treated. On collapse OI the wood cells in an
area, there is formed a relatively impenetrable layer which restricts or even
completely blocks the flow of preservatives into the interior of the wood.
It also has been suggested to improve the method of pressure
treatment by first subjecting the wood to a vacuum treatment. Examples of
prior art patents describing methods of impregnating wood utilizing a
vacuum followed by pressure include U.S. Patents 2,668,779; 3,2û0~003 and
3,968,276.
U.S. Patent 3,677,805 describes a modification of the pressure
treatment. ln this procedure, the wood is immersed in a treatment liquid
inside a pressure vessel, and the pressure is increased to operating pressure
whereupon the contents of the vessel then are subJected to the action of a
pulsating pump which provides sinusoidal pressure pulses within the vessel.
In other words, pressure pulses are applied repetitively in modulated
amplitude to provide variable pressure peaks above and below the ambient
pressure maintained in the pressure vessel. This procedure req-~ires equip-
ment which includes a pulsating pump operating into a pressure vehicle
equipped with a pressure release means.
The above described prior art represents a small sampling of the
suggestions which have been made for treating wood with preservative
materials to prevent decay. In spite of these many suggestions made in the
prior ~rt, there continues to be a need for an inexpensive, safe, non-toxic
treatment which is effective and which results in the uniform penetration of
the preservatives and other chemicals to the core of the wood.
.i
SUMMARY OF THE INVENTION
An improvement in the preservation of wood utilizing a pro-
cedure which does not require speci~l and expensive equipment, and which
res~ts in good penetration of the treating chemic ls into the wood is
described. More particularly, in accordance with the present invention, a
method of impregnating unseasoned and green wood with metal salts is
described. This method comprises
(a) contacting the green wood with an aqueous system com-
prising
~i~ water,
(ii) at least one oil-soluble metal salt, and
(iii) at least one surfactant,
for a period of time sufficient to enable the metal salt to penetrate into th
wood, and
(b) removing the wood frorn contact with the aqueous system.
Preferred metal salts ~re acid, neutral or basic metal salts of organic
carboxylic acids. Generally, the aqueous mixture will contain less than 20%
of hydrocarbon solvent and may contain optional and desirable ingredients
such as flame retardants, coloring agents ~nd insecticides. The method can
be conducted under vacuum, at atmospheric or at elevated pressures.
DESCRIPTION O~ THE PREFERRED EM130DIMENTS
It now has been found that good penetration of desirable treating
chemicals into green or unseasoned wood is obtained by the procedure of the
invention which does not require unusual or expensive equipment.
In accordance with the present invention, unseasoned or green
wood can be impregnate~ with metal salts which9 preferably, act as
f~mgicides when incor~orated into the wood. The procedure of the present
invention involves an aqueous system thereby reducing, if not eliminating9
the problems of many prior art processes based on organic solvents which
are 1ammable and often toxic. Moreover~ as mentioned above~ the process
of the present invention is applicable to unseasoned and green wood.
Accordingly, the method of the invention eliminates the requirement for
costly and time-consuming drying and/or seasoning procedures.
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The aqueous systems utilized in the method of the invention
comprise
(i) lNater~
(ii) at least one oil-soluble metal salt, and
(iii) at least one surfactant.
The aqueous systems will comprise from about 5096 to about 98% OI water
and more specifically, from about 6~% to about 83% of water.
The second essential component of the aqueous systems utilized
in the present invention is at least one oil-soluble metal salt. The oil-
solubility of the metal salts of the invention is believed to contribute
greatly to the advantageous and desirable results which are obtained. Since
the organic compound is oil-soluble and essentially hydrophobic, it ther~
fore, does not have a tendency to be ex$racted or leached from the treated
wood even over an extended period of time.
Particularly preferred types of oil-soluble metal salts which are
usef~l in the aqueous systems of the present invention are the acid, neutral
and basic salts of organic carboxylic acids. These salts also are known in
the art as "soaps".
The choice of metal contained in the s~lts will depend upon the
properties which are desired to be imparted to the wood being treated,
availability, cost and èffectiveness. Certain metals are more commonly
used in the method of the invention, and these include, copper, zinc,
chromium, iron, ant;mony, lead and mercury. Salts containing a mixture of
the ions of two or more OI these metals also can be used.
As mentioned, the salts can be acid, neutral or basie. The acid
salts contain insufficient metal cation to neutralize the acid. The neutral
salts contain ~n amount of metal cation just sufficient to neutralize the
acidic groups present in the salt anion. The basic salts contain an excess of
metal cation and are often referred to as overbased, hyperbased or
superbased salts. These acid, basic and neutral salts preferably are OI oil-
soluble organic carboxylic acids and mixtures of such acids.
The carboxylic acids from which suitable acid, neutral and basic
s~lts can be prepared include aliphatic, cycloaliph~tic and aromatic mon~
i6CI
--6
and polybasic carboxylic acids~ The organic carboxylic acids can be either
natursl or synthetic or mixtures thereof. The examples of natur~l acids9
although usually refined, include straight and branched chain carboxylic
acids and mixtures such as t~ll oil ac;ds and cyclic carboxylic acids such as
naphthenic acids. A variety of synthetic carboxylic acids, and particularly
aliphatic carboxylic acids or mixtures thereof is useful, and these generally
contain six or more carbon atoms.
The metal salts or soaps can be prepared by fusion or precipita-
tion methods. The soaps normally are prepared in an inert liquid medium
such as a hydrocarbon oil or solvent. The organic carboxylic acids generally
wi~l have at least six carbon atoms and as many as 30 carbon atoms, but
when more than one carboxylic acid is employed, carboxylic acids containing
as little as two carbon atoms may be employed as one of the aci~s of the
mixture. Examples of useful organic carboxylic acids include acetic acid,
propionic acid, butyric acid, isopentanoic acid, hexoic acid, 2-ethyl butyric
acid, nonylic acid9 decanoic acid, ~-ethylhexoic acid, isooctanoic acid,
isononanoic acid, neodecanoic acidg lauric acid, palmitic acid, stearic acid~
oleic acid, linoleic acid, naphthenic acid, and commercially available
mixtures of two or more carboxylic acids such as naphtheni~, tall oil acids,
rosin acids, etc.
Examples o acid salts are acid copper salts containing less than
a stoichiometric equivalent of copper per acid equivalent ~or meta3s other
than copper, the basic salt~ or soaps are preferred since these contain higher
amounts of metal. For example, solutions of norm~l zinc salts of mon~
carboxylic acids such as neodecanoic acid contain about 6% zinc whereas a
solution of a basic zinc neodecanoate can contain up to about 16% or more
of zinc.
Basic metal salts or soaps of carboxylic acids also can be
prepared by methods well known in the art. Examples of neutral and basic
s~lts and of metal salt complexes as ~Nell as their preparation can be found
in, for example, U.S. Patents 29251,798; 2,955,949; 3,723,152 and 3,9d~1,606.
Some of the basic salts have been referred to as complexes because they
are not simple salts.
For example, the basic compositions described in U.S. 3,941,606 are referred
to as "metal carboxylate-alkoxy alcoholatef' complexes. For the purpose of
this invention such basic complexes me to be included in the term metal
salts or soaps as used in this specification and claims.
Specific examples of the salts or soaps which are useîul in the
method of the invention include those described below in Table 1 and the
following specific examples.
TABLE I
Carboxylate Metal Salts
10Component Metal Metal Conten$ (%) Acid
B-l Cu 16 neodecanoic
B-2 Cu 11 neodecanoic
B-3 Cu 6 naphthenic
B-4 Zn 18 2-ethyl hexoic
15 B-5 Zn 8 naphthenic
B-6 Zn 10 mixture of C8~13
The preparation of the above-described metal s~lts is illustrated
by the following examples.
EXAMPLE B-l
A mixture of 250 parts of crude neodecannic acid, 103 parts of
propionic acid, 400 parts of mineral spirits, 172 parts of copper powder, 91
parts of Methyl Cellosolve, 14 parts of dipropylene glyeol, 7D parts of water,
10 parts of oetyl-phenoxy polyethoxy ethanol (Triton X-l~ from Rohm 5c
Haas Company~ and 3 parts of Santoflex-77*is prepared and sparged with air
while heating to a temperature of about 80C. Reaction under these
conditions continues for about 6 hours. A sma~l amount of boric acid (7
parts) is added and the heating is continued at 80C with air sparging. The
reaction is continued at this temperature until 180% acid neutralization is
achieved (total, 14 hours). The mixture is heated for an addi$ional 2 hours at
a temperature of about 150C to 190% acid neutralization. The air blowing is
terminated, and an inert nitrogen atmosphere is employed while the mixture
is slowly heated to about 150C over a period of 8 hours while excess water
is removed~
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Four approximately equal proportions of amyl phosphate
totalling 176 parts are added at 3-hour intervals while maintaining a
temperature of about 145C and a nitrogen atmosphere. The mixture then is
cooled to about 125C, settled to remove excess copper and filtered.
The filtered product can be heated under vaeuum to a tempera-
ture of about 150C in order to remove the mineral spirits to yield the
desired concentration of metaL
The remaining component examples B-2 through B-6 in Table I
can be prepared by methods similar to those described above for B-l or by
alternative procedures known in the art.
EXAMPLE B-7
A mixture of 840 parts of distilled naphthenic acid, 176 parts of
2-ethyl hexoic acid, 512 parts of mineral spirits, 48 parts of Carbit~ (a
diethylene glycol ether available commercially from Union Carbide Corp.),
4~8 parts of ~cetic acid, 1.6 parts of water and 10~9 parts of an anti-foam
agent is charged to a reactor, and the mixture is heated with agitation to a
temperature of about 65nC. The mixture is sparged with carbon dioxide and
214.4 parts of zinc oxide are added to the mixture which is then heated to a
temperature of about 105C. The reaction is continued at this ternperature
while periodic checks are made for percent zinc, the acid value and percent
water. If necessaryJ the acid value is adjusted to minus 33 to minus 3B for
10% zinc. If the water content is over 0.4%, the mixture is dehydrated.
About 100 parts of filter aid are added with stirring to the
mixture which is then filtered. The filtrate is a clear liquid which is
adjusted to a zinc content of 10% using mineral spiritsO
Carboxylate metal salts of the type described above are avail-
able commerci~lly such as from Mooney Chemicals, Inc., Cleveland, Ohio,
44113 under the general trade designations TEN-CEM9 CEM-ALL9 NAP-ALL,
HEX-CEM, LIN-ALL9 and NEO-NAP. These mineral spirit solutions can be
adapted for use in preparing the aqueous systems of the present invention by
adjusting the mineral spirits content (generaLly reducing the amount of
mineral spirits) and mixing said mineral spirit solutions with water and
surfactants as described below~
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,.:,,~,j
7~6~
Water dispersable solutions/dispersions of metal s~1ts also are
available from Mooney Chemicals, IncO under the general trade designation
HYDRO-NAP(TM~. The metal content of these salts also ranges from about
4% to about 10%, but these solutions/dispersions already contain the desired
surfactants and can be readily mixed with water to form the desired aqueous
systems. Mixtures of the carboxylic acid salts such as those described in
Table I are easily prepared and utilized in accordance with the invention.
For exampleJ a mixture in accordance with the invention is prepared from
equal parts of components B-l and B-6 resulting in a mixture containing 8%
copper and 596 zinc. A mixtllre of two parts of component B-l with one part
of component B-6 will eontain lO.7% copper and 3.3% of zinc~
Examples of other neutral and basic salts include lead naphthen-
ate, lead neodecanoate, lead 2-ethyl hexoate, lead tallate, zinc tallate,
chromium 2~thyl hexoate, chromium tallate, chromium oleate9 antimony
octoate~ antimony oleate, iron naphthenate, iron tsllate7 phenyl mercury
oleate, mercury dioleate, etc.
In addition to the metal s~1ts and soaps described abovet the
aqueous systems utilized in the methcd of the invention also contain at least
one surfact~nt. Preferably, the surfactants are anionic or nonionic
factants. Many such surfactants are known in the art. See, for exampley
McCutcheon's "Detergents and Emulsifiers", 1979~ North American Edition,
published by McCutcheon's Division7 MC Publishing Corporation7 Glen Rock,
New Jersey, U.S.A.9 particularly pages 15-2U.
In gener~l, the nonionic surfactants such as those containing
ether linkages are particularly useful. Examples of such ethe~containing
surfactants are those having the general formula
Rl~ [(CE~2)nO] XH
wherein Rl is an aryl or alkyl group containing from about t; to 20 carbon
atoms, n is two or three, and x is an integer bctween 2 and lO0. Such
surfactants are produced generally by treating fatty alcohols or alkyl-
substituted phenols with excess ethylene oxide or propylene oxide. The alkyl
carbon chain may contain from about 14 to 24 carbon atoms and may be
., .
~'7~6~
derived from a long chain fatty alcohol such as oleyl a~cohol or stearyl
alcohol.
Nonionic polyoxyethylene compounds of this type are described
in U.S. Patent No. 3,855,08$. Such polyoxyethylene compounds are available
commercia~y under the general trade mark "Surfynol" by Air
Products and Chemicals, IncO of Allentown, Pennsylvania, and under the
trade mark l'Pluronic" or "Tetronic" by BASF Wyandotte Gorp. of
Wyandotte, Michigarl. Examples of specific polyoxyethylene condensation
products include "Surfynol 465n which is a product obtained by reacting
about 10 moles of ethylene oxide with 1 mole of tetramethyldecynediolO
'Surfynol 4~5" is the product obtained by reacting 30 moles of ethylene
oxide with tetramethyldecynedio~ "Pluronic L 35" is a product obtained by
reacting 22 moles of ethylene oxide with polypropylene glycol obtained by
the condensation of 16 moles of propylene oxide. Also useful is Atlo~1045A
from ICI America, Inc. which is a polyoxynlkylene sorbitol oleate-laurate
mixture.
Amine, long ch~in fatty amine, long chain fatty acid7 alkanol
amines, di~mines, amides, alkanol amides and polyglycol-type surfact~ts
known in the art are also use~ul. C)ne type found particularly useful is the
group obtained by the addition of a mixture of propylene oxide and ethylene
oxide to diamines. More specifically, compounds ~ormed by the addition of
propylene oxide to ethylene diamine followed by the addition of ethylene
oxide are useful and are available commercially from BASF Wyandotte Inc.
Chemical Group under the general trade mark "T~tronic~.
Carbowax-type wetting agents which are polyethylene glycols
having different molecular weights have been found to give good results.
For example Carbowax No. 100û has a molecular weight range of from about
950 to 1,05û and contains from 20 to 24 ethoxy units per molecule.
Carbowax*No. 4000 has a molecular weight range of from about 3000 to
370û and contains from 68 to 85 ethoxy units per moleculeO Other known
nonionic glycol derivatiYes such as polyalkylene glycol ethers and methoxy
polyethylene glycols which are available commercially c~ be utilized as
surfactants in the compositions of the invention.
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1~7~60
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Anionic surfactants also are useful in the aqueous systems of the
invention. Among the useful anionic surfactants are the widely-known
metal carboxylate soaps, organo sulfates, sulfonates, sulfocarboxylic acids
and their salts, and phosphates. '~arious anionic surfactants are readily
available commercially, and further information about anionic surfactants
can be found in the text "Anionic Surfactants" Parts Il and m, edited by W.
1\1. Linfield, published by Marcel Dekker, Inc., New York, 1976. Examples of
anionic surfactants available from ICI America, Inc. include Atlas G-2205
which is an aromatic phosphate and Atlas G-3300 which is an allcyl aryl
sulfonate. Examples of anionic surfactants available from Rohm and Haas
Comp~ny include Triton 7~0 which is a sodium sslt o~ an all~l aryl polyether
sulfate, Triton BR-5M which is n dioctyl sodium sulfosuccinate, Triton H-55
which is a phosphate surfactant, potassium salt, Triton W-30 and Triton X-
200 which are sodium salts of aL~cyl aryl polyether sulfonates, et~.
Mixtures of the nonionic and anionic surfactants can and are
generally utilized in the aqueous systems of the present lnvention. The
amount OI surfactant conta;ned in the aqueous mixture ean vary over a wide
range, but is generally from 0.25% to about 7.5% and more preferably
between 1% and 5S~.
2G The aqueous systems of the present invention generally contain
at least about 67% of water and less than about 20% of hydrocarbon
solvents. Preferably, the amount of hydrocarbon solvenll contained in the
aqueous mixture is maintained at a minimum and will generaLly be less than
about 15% of the aqueous system. The metal content of the aqueous systems
may vary from about 0.2 to about 10% by weight.
The aqueous systems of the present invention can be prepared by
mixing the metal salt and the surfactants with sufficient water to provide
the desired levels of ingredients. Alternatively, and more preferably, the
aqueous systems are prepared from water-dispersable additive concentrates
which contain the desired metal salt, one or more surfactants and a
hydrocarbon so'lvent As mentioned above, such additive concPntrates are
available commercially such as from Mooney Chemic~ls, Inc. under the
general trade designation HYDRO-NAP. Moreover, such water~ispersable
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additive concentrates can be prepared from commercially available solu-
tions OI metal salts and mineral spirits and by blending the mineral spirit
solutions with the desired surfactants with or without additional hydro-
carbon solvents such as mineral oils~ For example, a water-dispersable
5 additive concentrate can be prepared from the metal salt solutions in
mineral spirits illustrated above as Examples B-l to B-7 by thoroughly
mixing the mineral spirit solutions with mineral oil and surfactants~ A
specific example of such a procedure is the blending of 800 parts of the
product of Example B-7 with 100 parts o mineral oil~ 75 parts of Atlas G-
3300 and 25 parts of Atlox-1045A. Similar water-dispersable additive
concentrates can be prepared from compositions identified as B-l to B-7
utilizing the same or other surfactants.
The water~ispersable additive concentrates of the types d~
scribed above can be converted to the aqueous systems utilized in the
15 invention by dilution with water. This dilution usually is accomplished by
standard mixing techniques. This offers a convenient procedure since the
additive concentrate can be shipped to the point of use before the water is
added, thereby reducing the cost of shipping.
The aqueous systems of the present invention also may contain
20 other additives which impart desirable properties to the treated wood. For
exampleg the aqueous systems of the invention may zontain (~) flame
retardant compositions, ~vi~ coloring agents, (vii) insecticides and ~viii)
odorants. Gener~lly, these additives can be included in the aqueous systems
of the invention in the disperse phase or dissolved in the water. The amount
25 of such additives included in the aqueous systems of the invention may vary
over a rather wide range although amounts of from about 0.5 to about 5% of
these compositions generally is satisfactory.
Inorganic fire retardant compositions are particularly useful in
the aqueous systems of the invention. Examples of inorganic materials
30 include diammonium phosphate~ monoammonium phosphate, ammonium
chloride, ammonium sulfate, borax and zinc chloride. Examples o organic
fire retard~nts include 2 number of halogenated and organophosphorus
compounds which either may be dispersed in the aqueous systems as
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~9~7~6~
-13--
mentioned above or rendered soluble by forming water-soluble salts or
solutions of the fire retardants which can then be mixed with the water-
dispersible additive concentrates or the aqueous systems of the invention
For example, ammonium salts of organophosphorus compounds may be
employed in the aqueous systems of the invention. In particular, examples
include ammonium salts of bis-dibromo propyl phosphate, diethyl phosphate9
bis(beta-chloroethyl) phosphate, bis(l,3~ichloropropyl) phosphate, etc.
Other water-soluble organic fire retardants inelude aliphatic carboxylic
acids containing over 50% organically bound bromine, alkyl sulfamates,
ammonium alkyl phosphates, antimony trichloride with tertiary amines such
as ethanol amines, urea with ammonium phosphate and urea with sulfamic
acid.
Although the various types of green wood which can be treated
in accordance with the method of the invention genera~ly have a satisfac-
tory appearanee for most purposes, the appearance can be modified if
desired by imparting different color effects. The present invention contem-
plates the inclusion in the aqueous systems of coloring agents which either
are soluble or dispersable in the aqueous systems of the invention. Any OI
the known oil~oluble9 water-soluble or water dispersable coloring agents
can be used. These agents are mixed either with the water dispersable
additive concentrates of metal salts described above~ or the aqueous
systems, and when the wood is immersed in the aqueous systems of the
invention cont~ining coloring agents, the coloring agents penetrate the wood
with the metal salts give desirable coloring effects which in many instances
emphasize the grain of the wood. Examples o~ coloring agents which may be
used depending on the desired results include: Bruco Creosote Brown RGY
available from Bruce Chemical Co., Iron Cem~All available from Mooney
Chemical Inc., and Pylaklor Red Brown LX-6249 available from Pylam Dye
Co.
Insecticides also can be included in the aqueous systems of the
invention, and it is preferable that the insecticide either be soluble in oil,
water or readily dispersable in water. Examples of such insecticides include
Dursban TC ~vailable frorn Dow Chemical and Ficam 76WP available from
BFC Chemicals Inc.
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Odorants can be included in the aqueous systems of the inven-
tion; and one preferred odorant is pine oil. Other water-soluble or
dispersable compounds having desired odors can be included in the aqueous
systems.
5The process of this invention involves contacting the green wood
with the aqueous systems a period of time sufficient to enaMe the desired
amount of metal salt to penetrate into the wood. Contact between the
wood and the aqueous system can be effected by brushing, spraying,
painting, immersing, etc. One of the surprising features and advantages o~
10the present invention is that exceLlent results have been obtained when the
green wood is immersed in aqueous systems containing as little as 2% of
metal for periods of as little as 5 to l0 minutes. Moreover, subsequent
analysis of the green wood treated in accordance with this procedure reveals
an excellent met~1 salt pick-up with exceedingly g~od penetration of the
l5metal salt into the wood~
In one method of the present invention, the agueous system in
which the green wood is immersed can be maintained at a temperature of
from about 5 to about g5C at atmospheric pressure. However, the method
of the invention can be, and is preferably carried out at ambient tempera-
20ture thereby eliminating the need for any equipment or materials for
heating or cooling $he aqueous systems. In some instances, it may be
advantageous to heat the aqueous systems to elevated temperatures to
increase the rate of penetration.
As mentioned above, after the green wood has been contacted
25with the aqueous systems of the present invention for the desired period of
time, the wood is removed from contact with the aqueous system. The thus
treated green wood is ready for shipping, although it may be desirable in
some instances to allow the wood to at least partially dry before shipping.
It is surprising that desirable results can be obtained with such
30short contact times of the wood and aqueous systemsO It is believed that the
aqueous systems used in this invention deposit the desired amount of
material on and in the outer layers of the wood during the brief contact to
provide the desired results even though the metal salts and other additives
` ~ !,
L9'7~
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have not completed the penetration process into the wood. After the
treated logs are removed from the aqueous system, the sal ts and other
additives continue to penetrate into the wood while the wood is in storage or
in shipment. Accordingly this invention provides a method for treating wood
5 which not only uses inexpensive equipment (such as a large open tank), but a
method by which the wood to be treated is in the equipment for short
periods of time.
The method of the invention also can be conducted on wood
conta;ned in an enclosed vessel under vacuum or pressure conditions or a
10 combination thereof. The use OI pressure for improving the penetration of
various chemicals into all types of wood is well known in the art. In this
technique, the green wood is placed in a chamber which is sealed and
evacuated in a regulated cycle which is related to and determined from a
consideration of the species of wood. Generally, the period of evacu~tion
15 will vary from about 15 minutes to one hour and the pressure within the
sealed chamber is brought to a level of about two inches of mercury or less.
The purpose of this step is to remove air and wood volatiles from the wood.
The diluted aqueous systems of the invention then are introduced into the
enclosed container, and the amount of composition should be sufficient to
20 immerse the wood completely. Pressurization of the vessel is then initiated
and the pressure maintained at a desired level for a given period of time.
Initially, the pressure within the vessel will decrease as the aqueous system
within the container penetrates into the wood. The pressure can be raised
to maintain a desirable level throughout the penetration period of treat-
25 ment. Stabilization of the pressure with;n the vessel is an indication thatthere is no longer any penetration of the liquid into the woodO At this point,
the pressure can be released, the vessel drained, and the wood removed.
The details of the pressure process, including pressure ranges,
concentratlon of aqueous composition and the cycling of vacuum and
pressure with respect to a particular species of wood can be readily
30 determined by one skilled in the art from $he examples which follow and
also hy following the procedure of this invention on the particular wood
while varying process parameters to provide optimum results. For example,
7~6~
the pressures utilized in the above-described pressure method can be as high
flS 300 pSig., and are generally from about 50 to 250 psig.
The method of the invention can be carried out on a wide variety
of wood types. The actual time OI contact of the green wood with the
5 aqueous systems of the invention wiU vary depending on the amount of
metal salt to be introduced into the wood and the difficulty of penetration
into the various types. Examples of wood species which can be treated in
accordance with the method of the invention include Western Red Cedar,
Douglas Fir9 Spruce, Sugar Maplea Ash, Walnut, Cherry, White Pine, Red
10 Pine, Birch, Red Oak, Elm, Hickory and Linden. Green wood gener lly iæ
defined in the industry as wood containing 30% or rnore by weight of water
based on bone dry wood~
The following is a specific example of the method of the
invention conducted at atmospheric pressure in an open tank.
15 Example A
Logs (debarked) are immersed in an aqueous system prepared hy
diluting zinc Elydr~Nap (TM) available from Mooney Chemicals, Inc. and
containing 8% ~:inc as zinc naphthenate with water and stirring to provide an
aqueous system containing about 2.67% ~inc. The aqueous system is
20 maintained at ambient temperature, and the wood logs are immersed in the
aqueous system for about 6 minutes. The logs then are removed from the
aqueous system and allowed to drip dry. Examination of the log specimens
treated in accordance with this procedure shows good zinc pick-up and
retention. Moreover, subseguent examination of the log specimens treated
25 in accordance with this procedure shows excellent penetration of the zinc
salt into the logs, and there is no significant change in the original
dimensions and surface texture of the wood. The metal salts which have
penetrated into the wood logs exhibit resistance to leaching by water.
The following are specific examples of the method of the
30 invention conducted at elevated pressures in an enclosed vessel.
Fxam~e R
Green Norway pine logs are pressure treated with an aqueous
system prepared by diluting Zinc Hydro-Nap (Mooney Chemicals) containing
~97~
--17--
8% zinc as zinc naphthenate with sufficient water to provide an aqueous
system containing about 0.57% of zinc. The logs are immersed in the
system in an enclosed pressure vesselO The pressure treatment ;s conducted
at a maximum pressure of 2~û psig for a total pressure time of about one
5 hour. The logs are then removed from the vessel and allowed to drip dry.
The logs treated in this manner contain zinc which exhibits good retention
properties.
Example C
The procedure of Example B is repeated except that the diluted
10 aqueous system contains 0.39% of zinc as zinc slaphthenate and the
maximum pressure is 300 psig during a treating period of about 2 hours. The
weight increase of the logs after treatment is about 38%.
