Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ ~ 6~505
l~ood has been used for many years as an important building ànd con-
struction material and its impor~ance as such is increasing Eor a number of
reasons. Typical uses include general construction, residential housing, utili-
ty poles, cross arms, fence posts, railroad ties and pilings. Although wood is
a renewable natural resource, it must be protected from a-ttack by insects and
fungus and marine organisms for many of these applications. Left unprotected
or unpreserved such as by chemical treatment, wood will decay and deteriorate
anywhere from within a few months to a few years, depending upon climate and
soil conditions. Wood objects such as utility poles and timbers deteriorate
rapidly below the ground and at ground level and would require frequent replace-ment if not properly and adequately preserved with a material which is both ef-
fective against attacking organisms and long lasting.
Through the years, a number of different materials have been used for
preservation. ~nong these are included creosote, heavy metal salts, heavy oils
and tars, pitch and various organic materials including chlorinated phenols,
especially pentachlorophenol ~PCP). Each of these materials has its advantages
and disadvantages. Creosote, as well as other heavy oils and tars and pitch
treatments, may have a strong odor and leave the surface greasy and oily to the
; touch.
Chlorinated phenols have found wide use because of their effectiveness,
relative ease of application and durability. Because of its particularly good
fungicidal and insecticidal properties, pentachlorophenol is widely used as a
commercial wood preservative. It is normally dissolved in hydrocarbon solvents
such as medium aromatic oils, volatile petroleum solvents ~propane), light sol-
vents (mineral spirits), or in a chlorinated hydrocarbon solvent-inhibited gradeof methylene chloride. Co-solvents are added in many instanees to achieve propersolubility of pentachlorophenol in the solutions. Because energy conservation
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is becoming increasingly important, many of the traditional treating solvents
are more valuable as feed stocks Eor other chemical products. Therefore, a
low encrgy based solvcnt such as water has been sought as a replacement for these
hydrocarbon solvents. The difficulty has been that pentachlorophenol in a simple
admixture with water has little or no solubility. Prior art shows that penta-
chlorophenol can be reac ed with sodium hydroxide in water to form the water
soluble sodium pentachlorophenate. To date this is the only aqueous soluble
form of pentachlorophenol that has been commonly used in the wood treating in-
dustry. However, sodium pentachlorophenate treating solution has a severe dis-
advantage in its excess leachability during field use and some lack in penetrat-
ing ability. In -the practice of our invention, new water soluble pentachloro-
phe;nol treating solutions are disclosed which overcome these problems even when
using sodium pentachlorophenate.
The closest art known to the applicants is contained in the following
~nited States patents: 1,919,298; 2,322,633, 2,908,607; 3~281,318; and
3,993,752.
In accordance with this invention, novel pentachloro~henol--alcohol--
fatty acid amine oxide systems or tetrachlorophenol-aliphatic alcohol--fatty
acid amine oxide systems are disclosed that are compatible with water and are
soluble therein.
Thùs in broadest aspect this invention provides a water soluble wood
treating and preserving solutions consisting of blends of (~) from about 0.1%
to about 50% by weight of a chlorophenol selected from a group consisting of
pentachlorophenol and tetrachlorophenol and mixtures thereof; (B) from about
1% to about 97% by weight of an alcohol having from 1 to 6 carbon atoms and
mixtures thereof; ~C) from about 0.2% to about 35% by weight of a fatty acid
amine oxide having from 10 to 32 carbon atoms; (D) from about 0.2% to about 35%
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by weight of an am:ine selected from the group consisting o:E ~nonium hydroxide~triethylamine, trimethylamine, methyl amine and methyldiethanolamine and mix-
tures thereof; and ~E) from about 1% to about 97% by weight of water.
In an alternative aspect this invention provides a method of treating
and preserving wooden objects wherein ~C), said fatty acid amine oxide> is an
ami.ne oxide having the following formulation:
1 1
R - N -~ 0
R2
wherein R is a hydrocarbon radical of from about 10 to about 32 carbon atoms andRl and R2 are each aliphatic radicals of from one to two carbon atoms or hydroxysubstituted aliphatic radicals of from one to two carbon atoms, and mixtures
thereof.
In a th:ird alternative aspect this invention provides a water soluble
wood treating and preserving solutions consisting of blends of ~A) from about
0.1% to about 50% by weight of a chlorophenol selected from a group consisting
of pentachlorophenol and tetrachlorophenol and mixtures thereof, ~B) from about
1% to about 97% by weight of an alcohol having from one to six carbon atoms and
mixtures thereof, ~C) from about 0.5% to about 35% by weight of a fat~y acid
amine oxide having from about 10 to about 20 carbon atoms, (D) from about 1% to
about 97% by weight water, (E) from about 0.02% to about 20% by weight sodium
hydroxide, and (F) from about 0.2% to about 35% by weight of an amine selected
from the group consisting of ammonium hydroxide, triethylamine, trimethylamine>
methyl amine, and methyldiethanol amine, and mixtures thereof.
In a fourth alternative aspect this invention provides a method of
treating and preserving wooden objects to penetrate and deposit within the wood
fibers an essentially non~leachable chlorophenol comprising
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I. forming a wood treating and preserving solution by blend;ng ~A) from about
0.1% to about 50% by weight of a chlorophenol selected from ~ group consisting
o:E pentachlorophenol and tetrachlorophenol and mixtures thereof, (B) from about
1% to about 97% by weight of an alcohol having :Erom one to six carbon atoms and
mixtures thereof, ~C) from about 0.5% to about 35% by weight of a fatty acid
amine oxide having from about 10 to about 20 carbon atoms, ~D) :Erom about 1% to
about 97% by weight water~ ~E) from about 0.02% to about 20% by weight sodium
hydroxide, and ~F) from about 0.2% to about 35% by weight of an amine selected
from the group consisting of ammonium hydroxide, triethylamine, trimethylamine,
methyl amine, and methyldiethanol amine, and mixtures thereo:E;
II. impregnating under heat and pressure the wooden objects;
III. separating said wooden objects from said solution; and
IV. drying said treated wooden objects.
In a fifth alternat.ive aspect this invention provides a method of
treating and preserving wooden objects to penetrate and deposit within the wood
fibers an essentially non-leachable chlorophe~ate comprising
I. forming a wood treating and preserving solution by blending ~A) from about
0.1% to about 50% by weight of a chlorophenate selected from a group consisting
of pentachlorophenate and tetrachlorophenate and mixtures thereof, (B) from
about 1% to about 97% by weight of an alcohol having from one to six carbon
atoms and mixtures thereof, (C) from about 0.2% to about 35% by weight of a
fatty acid amine oxide having from about 10 to about 32 carbon atoms, (D) from
: about 1% to about 97% by weight water, and ~E) from about 0.2% to about 35%
by weight of an amine selected from the group consisting of ammonium hydroxide,
triethylamine, trimethylamine, methyl amine and methyldiethanol amine and mix-
tures thereof;
.II. lmpregnating under heat and pressure the wooden objects;
5 ~ 5
III. separating said wooden objects from said solution; and
IV. drying said treated wooden objects.
These systems may contàin ammonia and/or sodium hydroxide. Alcohols,
such as those containing one to six carbon atoms and particula:rly the butyl
alcohols, are essential ingredients in solubili~ing pentachlorophenol in water
even though the butyl alcohols are sparingly water soluble themselves. The
fatty acid amine oxides in the systems are also essential in providing stability
and effective penetration of the systems into the wood fibers being treated.
Upon contact and penetration into cellulosic materials and during the drying
process, the preservative in the wood becomes fixed and essentially non-leach-
able. It has also been found that when soluble metal salts such as copper
sulfate, copper acetate or copper carbonate and chromium salts are included in
these treating systems, additional fixation and preservative properties are ob-
tained. In addition, we have found that additives such as tetrasodium pyro-
phosphate, sodium gluconate, sodium citrate, s~dium N-dihydroxyethylglycinate
and a lignin sulfonate such as ammonium or sodium lignin sulfonate provide in-
creased effectiveness. In the various formulations, water in widely varying
percentages is used as the main solvent to form the tr0ating solution.
The pentachlorophenol employed in the present compositions may be
present in pure form or as a technical mixture. Pentachlorophenol meeting the
requirements of Federal Specification TT-W-570 and American Wood Preservers
Association P~-74 is especially suitable. These specifications require that
pentachlorophenol contain not less than 95% of chlorinated phenols. It shall
contain not more than 1% of matter insoluble in N/l a~ueous sodium hydroxide
solution, and it shall have a freezing point of not less than 174C.
Other chlorinated phenols such as tetrachlorophenol or mixtures of
tetra and pentachlorophenol may also be used in place of the pentachlorophenol
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as well as the sodium salts oE these chlorinated phenols.
Several things must be considered when attempting to prepare water
soluble pentachlorophenol treating solutions. Acceptable aqueous pentachloro-
phenol treating solutions must be capable oE penetrating deep into the wood and
becoming deposited therein in an essentially non-]eachable form. Previous at-
tempts to prepare water soluble pentachlorophenol treating solutions could not
achieve satisfactory results in either of these two requirements.
Therefore, it was unexpected that water soluble pentachlorophenol
treating solutions could be obtained which, in fact, do penetrate deeply into
wood and deposit the pentachlorophenol in an essentially non-leachable form in
the practice of our invention. These solutions generally comprise pentachloro-
phenol, an alcohol, a fatty acid amine oxide, ammonia or sodium hydroxide and
water as the main solvent. When wood is pressure treated with such a solution
and dried, the pentachlorophenol or tetrachlorophenal becomes fixed into the
wood.
The unexpected discovery of the effectiveness of aliphatic alcohols,
especially the butyl alcohols, when used in conjunction with fatty acid amine
oxides in promoting the solubility of pentachlorophenol into aqueous systems is
unique in consideration of the fact that pentachlorophenol itself is very in-
soluble in water and that n~butyl alcohols are only soluble in water at room
temperature to the extent of about 9 parts alcohol to 100 parts water.
It was further discovered that the alcohol--pentachlorophenol--fatty
acid amine oxide water soluble systems could be enhanced by pH control by
ammonia hydroxide or other lower amines and by additions of further such addi-
tives.
Mixtures of various alcohols can be used successfully in the formula-
tions of our invention as well as the specific alcohols alone. Among the alco-
.
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hols used alone or in combination are those having from one to six carbon atoms
including metllyl alcohol! ethyl alcohol, n-butyl alcohol, isopropyl alcohol,
n-propanol, allyl alcollol, secondary butyl alcohol, isobutyl alcohol, tertiary
butyl alcohol, and diacetone alcohol. From about 1% to about 97% of the alcohols
may be used.
An improved wood treating solution that has a high degree of penetra-
tion into the wood fibers as well as reduced time necessary for wood treating
has been formed by the inclusion of a fatty acid amine oxide or oxides. In
addition, the employment of the fatty acid amine oxides greatly increases the
stability of the wood treating and preserving solution, not only cluring the
treating process under increased temperature and pressure but also when the
treating solution is recycled back into the storage and mixing tanks between
treating charges. An additional advantage in employing the fatty acid amine
oxides is that it is easier to reconstitute the recycled solution after it has
been used during the wood treating and preserving operation thus making it more
economical in recovering the spent solution and to bring it back to its proper
quality and effectiveness.
It has also been found that the finished ~reated wood product ex-
hibited improved qualities over other products treated by known wood treating
and preserving solutions iTI that the treated wood was devoid of disagreeable
odor, exhibited no greasy feel, and was substantially free of bleeding of treat-
ing solution from the impregnated wood fibers after drying. It will be appreci-
ated that in the practice of this invention, the non-leachable chlorophenols
are deposited in the wooden object.
Exemplary of the fatty acid amine oxides having from about lO to
about 32 carbon atoms are the aliphatic amines such as dimethylcocoamine oxide
that contains usually from about 12 to about 20 carbon atoms. Also the oxides
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o~ tallowamine, stearyl amine, and the like may be used. Typical of these
amine oxides are the Aromax ~ amine oxides produced by the Armak Company and
includes amines having tlle general chemical structure
1 1
R - N ~ O
R2
where R is an aliphatic radical containing 12 to 20 carbon atoms and Rl and R2
are each aliphatic radicals containing one to two carbon atoms or hydroxy sub-
stituted aliphatic radicals containing one to two carbon atoms or mixtures o~
said amine oxides or hydroxy substituted amine oxides. The preferred amine
oxides of this invention are bis (2-hydroxyethyl) cocoamine oxide, bis (2-
hydroxyethyl) tallowamine oxide, bis ~2-hydroxyethyl) stearylamine oxide, bis-
hydroxyethyldecyloxypropylamine oxide, bishydroxyethyltridecyloxypropylamine
oxide, dimethylcocoamine oxide, dimethyl-hydrogcnated tallowamine oxide~ di-
methylhexadecylamine oxide, and mixtures thereof.
Fatty acid amine oxides also may be used that are produced by the
Sherex Chemical Company having the general chemical structure
R-O-CH2-CH2-CH2N~Rl) O where R is an aliphatic radical containing 9 to 15 ~
carbon atoms and Rl and R2 are two hydroxyethyl and/or two hydroxypropyl radi-
cals.
Other fatty acid amine oxides that may be used are "MAZOX" series by
Mazer ChemicaIs, Inc., the "NINOX" series by Stepan Chemical Co., the
:: * *
; "CHERCAMOX" series by Sher Chemicals, Inc., the AO series by the Tomah
Chemical Co., and include lauryl dimethylamine oxide, myristyl dimethylamine
oxide, myristyl/cetyl dimethylamine oxide, cetyl dimethylamine oxide, stearyl
dimethylamine oxide, cocoamido propyl dimethylamine oxide.
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~ Trademark
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In forming the wood treating and preserving solutlon it has been found
that from about 0.2% ~o about 35% by weight of the fatty acid amine oxide pro-
ciuces a so]ution that cxhibits a high degree oE penetration as well as deposit-
ing an essentially non-leachable chlorophenol within the wood fibers.
It has also been found that the inclusion of up to about 0.5% of a
chelating agent such as ethylenediaminetetraacetic acid ~fiDTA) or the sodium
salts thereof helps to stabilize the wood treating and preserving solution and
ties up metallic radicals in the solution preventing discoloration of the
finished treated wood product. Any suitable chelating agent that is compatible
with the system, such as the ethylenediaminetetraacetic acid ~DTA) or the sodi-
um salts thereof or the like, may be used.
Copper salts which may be used include copper sulfate, copper carbonate,
copper hydroxide, copper oxidc, copper acetate and copper chloride.
In the practice of our invention, wooden objects are treated with com-
positions comprising principally blends from about 0.1% to about 5Q.0% by weight
of pentachlorophenol or tetrachlorophenol, the sodium salts thereof, or mixtures
thereof and from about 1% to about 97% alcohol, i.e., alcohol having from l to 6
carbon atoms, particularly n-butyl alcohol, and from about 0.2% to about 35%
ammonium hydroxide or amines, and from about 0.2% to about 35% of a fatty acid
amine oxide and from 1% to about 97% water.
In addition, these wood treating formulations may include varying
amounts of tetrasodium pyrophosphate ~0-10% by weight), copper salts (0-10% by
weight), sodium citrate ~0-10% by weight), sodium N-dihydroxyethylglycinate
(0-10% by weight~, and a lignin sulfonate such as ammonium or sodium lignin sul-
fonate (0-20% by weight) as added ingredients.
As stated previously, extreme leachability problems have always been
encountered when using water solutions of sodium salts of chlorinated phenols
50~
as wood preservatives. By pract:ice of our inve-ntion lt is now possible to even
prepare water-borne solutions oE sodium pen~achlorophenate zLnd tetrachloro-
phenate which may be deposltecl i-n wood in essentially a non-leachable form.
Either pentachlorophenol or tetrachlorophenol or mixtures thereof may
be used in these particular formulations and formecL into the sodium salt prior
to use by reacting with sodium hydroxide or previously prepared commercially
available sodium pentachlorophenate or tetrachlorophenate may be used.
Pentachlorophenol or tetrachlorophenol are used as the starting materi-
al they can be used as such or mixed with sodium hydroxide and water. Then the
treating solution is prepared from additions of alcohol, amine~s), and water.
In this manner, a treating solution is prepared which, when used to treat the
woo~en objects of this invention, deposits the waterborne penta or tetrachloro-
phenol in the wood in an essentially non-leachable form. Any of the amine,
ammonia or lignin sulfonates previously described may be used. It has been
found that solutions may be prepared using from about 0.1% to about 50% by weight
pentachlorophenol or tetrachlorophenol, from about 0.02% to about 20% by weight
sodium hydroxide ~when additionally used), from about 0.2% to about 35% by weight
amine oxide, from about 0.25% to about 20% by weight lignin sulfonate and from
about 0.1% to about 10% by weight copper sulfate. Water may be used from 1% to
about 97% by weight.
Various formulations of this invention were prepared and tested as to
their effectiveness for wood penetration and wood fixation properties. This
involved wood treatment, leaching tests and analysis. The leaching tests and
analysis generally conform to American Wood Preservers Association specifications
M11-66 Method to Determ;ne Leachability of Wood Preservatives and A5-76 Deter-
mination of Chloride for Calculating Pentachlorophenol in Solution or Wood.
The experimental details of leaching tests may be described as follows:
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Four comparable 3/~" x 3/4" x 3/4" Douglas fir or Southern p:ine sap-
wood blocks treate~ with like solution retentions were split in two groups. The
blocks in Group 1 were directly assayed for pentachlorophenol while the Group 2
blocks were leachcd and then assayed for pentachlorophenol. The blocks were
weighed before and after treatment to dete~mine retention. Retention of con-
trol and leached blocks was considered and corrections made where necessary.
lhe percent pentachlorophenol retained in the leached blocks was reported in the
examples by use of the following equation:
Leached blocks average PCP assay Percent preservative
- - x 100 = retention in leached
Unleached blocks average PCP assay blocks
The retained leaching water was also analyzed for preservative content. The
treating equipment used for the most part (small scale) was that described in
the American Wood Preservers Association specification Mll - 66; however, in
some examples a commercial treating plant operation was used.
Although the examples here contain mostly 1 to 2% pen-tachlorophenol,
they can be readily formulated to contain form 1% to 50% pentachlorophenol.
The 1% to 2% formulas are used because they more closely conform to the amount
generally used in commercially treated wood to meet present military and
American Wood Preservers Asssociations assay retention specifications.
These examples, in general, illustrate the facets and details of this
invention, but are not to be construed as limiting the scope to the same.
EXAMPLE #l
; To formulate a concentrate of tetrachlorophenol (TCP):
Formula:
40 lb. TCP
50 lb. butyl alcohol
10 lb dimethylcocoamine oxide ~Armox DM~IC-W)
Trademark
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The TCP was added with stirring to a mixture of butyl alcohol until the TCP was
completely dissolved and then the cocoamine oxide was slowLy added.
EXAMPLE #2
rO Eormulate a treating solution from the co-ncentrate of Example #1:
Formula:
1026 lb. water
120 lb. NH40H (28%)
9 lb. copper sulfate
45 lb. of concentrate from Example #l
The ingredients of Examples 1 and 2 can be mixed in any order, but it is con-
venient to first dissolve the l'CP in the alcohol and then include the Eatty acid
amine oxide.
The above treating solution was used to impregnate dimensioned lumber
and it was found that a high degree of depth penetration with high retention of
; the tetrachlorophenol was realized.
EXAMPLE #3
To formulate a concentrate of pentachlorophenol (PCP):
Eormula:
42 lb. PCP
32 lb. methyl alcohol
lS lb. 2-hydroxyethyl cocoamine oxide ~Armox C/12W
6 lb. diacetone alcohol
EXAMPLE #4
To formulate a treating solution -from the concentrate of Example #3:
Trademark
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Formula:
~4.9 lb. water
1.5 lb. NH~0ll ~as N~
3.6 lb. concentrate Erom ExampLe #3.
The above treating solution containing the penta conceMtrate of Example 3 was
used to impregnate wooden poles and after testing it was found that the poles
exhibited a high degree of depth penetration and excellent retention of the
pentachlorophenol that had penetrated the poles.
EXAMPL~ #5
Using the treating solution formulated in F.xample ~t4, seven charges
were made and wood products were treated. The treating soLution was 1.5% penta-
chlorophenol solution. A first mix was made totaling approximately 26,400
gallons of 1.5% pentachlorophenol solution. Water was introduced to the stor-
age tanks and then ammonia was added to 1.5%. This solution was pumped into the
retort which is used for pressure treating wood and heated to 140F. After
heating, it was reintroduced to the storage tank and circulated during the addi-
tion of the aqued which is 50% ammonium hydroxide ~28% NH4) and 50% EDTA. Penta
concentrate was then added at 30 psig. pressure. This solution was analy~ed and
found to contain 1.53% penta by weight.
Charge #1 was then treated and contained 733 cubic feet of nominal 4" x 4" x 8'
dry incised Hem-Fir. An initial vacuum of approximately 26 inches of mercury
for 1/2 hour was applied before the introduction of the preservative solution
to the retort. A similar full cell process was used for all subse~uent charges
varying only in maximum temperature and pressure and time at pressure. The
solution temperature during treatment was 120F, and the pressure period lasted
one hour with the maximum pressure at 20 psig. followed by a 15-minute vacuum.
Approximately 25 lb. of solution per cubic foot was pressed into the wood. The
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analysis on cores from twenty pieces of wood showed a 0.48 lb. per cubic foot
of pentachlorophenol retention in the 0 to 0.6" zone. The analysis run in in-
crements of 0.2" to a depth o 0.6" was as follows:
*
Zone Pounds of Penta per Cubic Foot of Wood
.
0.0 - 0.2" 0.78~ )
0.2"' - 0.4" 0.51# ) Average 0.57#
0.4" - 0.6" ~.41# )
Inches of depth of penetration towards core of wooden object.
After the treatment the wood surfaces were clean and dry, and the color of the
treated wood was a light brown similar in appearance to newly cut Western Red
Cedar heartwood.
harge #2 contained 737 cubic feet of nominal 2" x 6" x 14' long unincised in-
land Hemlock from Idaho. This material is considered difficult to treat. It
cannot be satisfactorily impregnated with copper chrome arsenic. Approximately
23 lb. of solution per cubic foot was pressed into this material at 120F and
135 psig. for 8 hours. The solution exhibited the ability to easily penetrate
this wood. Analysis of the cores taken from twenty pieces of wood showed 0.375
of pentachlorophenol per cubic foot retention in the 0.0 - 0.6" zone. This
retention could be increased readily by increasing the solution strength or by
increasing the pressing time. This again was a successful treatment with wood
surfaces having a light brown color and being clean and dry.
Charge #3 contained 466 cùbic feet of 4.5" diameter, 8' long, air seasoned,
.
unincised Lodgepole Pine round stock. A 4 hour pressure period with a maximum
temperature of 120F and pressure of 130 psig. was used. A~lalysis of the cores
taken from twenty posts showed 0.49# of penta per cubic foot retention in the
0.0 - l.0~' zone. The results on this charge were excellent with full sapwood
treatment and clean, dry, light brown wood surfaces.
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Charge #4 contained green and dry Douglas Fir, dry [odgepole Pine, Ponderosa
Pine, Cedar and Cedar shakes, Hem-Fir channel siding and l-umber, and Ponderosa
Pine posts. After ~ hours press time, 18 polmds of solution was retained per
cubic foot of wood. Retention of pentachlorophenol per cubic foot of mate*ial
as analyzed ranged between 0.3# and 0.9~ in the 0.0 to 0.6" zone. Two examples
are Lodgepole Pine ]umber at 0.43# and Ponderosa Pine at 0.49# oE pentachloro~
phenol pe* cubic foot.
A second mix of 2000# of pentachlo*ophenol concentrate contained an
average of 7% additional amine mate*ial. Also included was 126# of aqued. The
addition of the concent*ate, after adding the aqued, increased the solution
strength of approximately 18,000 gallons of 1.53% solution to 1.93%. Enough
ammonia was added to increase its content from 1.5 to 2.0%.
Charge #5 was composed of 888 cubic feet of class 5, 40' long Douglas Fir poles
which we*e air seasoned and incised. This charge after 13 hours subjected to
pressure of I30 psig. and a maximum temperature of 130F was completed.
Approximately 12# of solution per cubic foot was pressed into the poles. The
appearance of the treated poles was excellent--light brown with clean, dry
surfaces. Analysis of samples from poles showed full sapwood penetration of
preservative.
_arge #6 was 1006 cubic feet of Douglas Fi* and Hemlock Poles having a wide
*ange in moistu*e content. Most of the poles we*e unincised class 3, 40' long
Douglas Fir. This charge was steam conditioned at 2~0~F fo* 3 hou*s before
applying an initial 2 hour vacuum. The amount of solution pressed into the
wood was 17-1/2 pounds per cubic foot after 18 hours of pressure at 135 psig.
and a maximum temperature of 140F.
Cha*ge #7 was second growth Western Red Cedar poles. An initial vacuum of 1/2
hour was used and then a maximum pressure of 70 psig. applied Eor 11-1/2 hours.
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The penetration o~ the preservative solution was excellent with 17-1/2 pounds of
solution per cubic Eoot o:E material. The appearance was excellent with clean
dry wood s~lraces.
In all the tests run on the seven charges~ samples of treating solu-
tion were taken Erom the storage tank which was also the wo:rking tank, and the
solution condition remained good. Analysis of the treating solution beEore and
aEter treatments showed that the strength remained constant.
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