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Патент USA US2135030

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Paten-ted Nov. `1, 1938`
Ernest R. Boiler, Cleveland Heights, Ohio, as
signer, by mesne assignments, to E. I. du Pont
de Nemours & Company, Wilmington, Del., a
corporation of Delaware
Application July '19,- 1935, serial No. 32,162
,a9 claims.
(c1. :a1-_35)
many commercial applications. It has been im
practical to impregnate finished or semi-finished
v 'I‘his invention >relates to> _processes for deposit
ing preservative compositions, flreprooñng com
positions, and the like, within a porous material, lumber with suitable agents for staining, fire- `
and is particularly directed to such processes' proofing, or .preserving the wood.
It hasbeen proposed to avoid the diiñculties 5
5 wherein such impregnating agents are carried
into the porous materials in dimethyl ether.
It is now the customary practice to preserve
Wood by submerging it in a water solution of a
preserving salt, such as zinc chloride, and then
encountered when wood and the like are im
pregnated by the use of aqueous vehicles, by
using non-aqueous menstruums. It has, for in
injecting the solution into the wood by the use
of pressure. After aidesired degree of penetra
tion of the wood has been effected, the aqueous
solution is ordinarily allowed to drain from _the
pressure receptacle. Water which is retained in
15 the wood» must subsequently be removed by kiln-
hydrocarbons such as gasoline or kerosene `be
used. Such non-aqueous Avehicles display the
same disadvantages as do aqueous- vehicles, to a
greater or lesser extent, and they have the fur
drying or air seasoning.
" '
stance, been suggested. `that alcohol, or liquid
ther disadvantage of being quite‘ expensive.
In - `
addition tothe fact that the non-aqueous solvents
heretofore employed are high in cost for an ini
The injection of Water into the wood causes
tial installation, their expense is rendered even
greater by the fact that it is almost impossible
to recover the solvent from the.p0rous>material.
When wood is to be impregnated-with a pre 20
20 a’certain amount of warping, checking, and rais- '
considerable swelling and, upon drying, the con
sequent shrinkage of the wood is attended by
` ing of the grain. »The extent of this deterioration
servative salt, such as zinc chloride, if a non
of the Wood depends largely, of course,'upon the
characteristics of the wood being treated and, to a
aqueous menstruum is to‘be employed, it has
deterioration is not particularly disadvantageous,
raising of the grain ofthe wood, and, accordingly,
been proposed to use alcoholic solutions rof zinc
lesser degree, upon the care exercised in the treat- » chloride. “Alcohol causes/warping and checking
-25 ing and drying-procedures. When the treated of wood, though toI a' somewhat smallerv extent 25.v
wood is to be employed in certain relations, this than does water. Alcohol, moreover, causes a _ l
but wood which is warped and cheeked cannot -like water, is unsuitable for treating finished
satisfactorily be used for a large number of`
After such a non-aqueous menstruum has been so
injected into wood, “either/î' by pressure processes
Aqueous vehicles are further unsatisfactory be
cause of the relatively long time and the high or by simple immersion, it is impractical to' at
pressures required to effect a satisfactory im
tempt ' recovery of the menstruum. It is, .of '
pregnation of wood. Moreover, ~the large amount course, theoretically possible to recover such non
35 of time required to dry the wood after its impreg
aqueous menstruums, but the cost of such opera 35
nation with an aqueous menstruum results in high tions would be-prohibitive. In a, pressure process
equipment and operating costs if it is kiln dried, of impregnation, there- is, of course, a certain
` and in high carrying charges if it is air seasoned. amount of heat in the Wood, but this heat is in- _
The customary processes of impregnating wood - adequate to distill off the relatively high-boiling
40 by means of an aqueous vehicle have also been menstruum heretofore used. The poor heat con 40
found disadvantageous by reason of the relatively duction of wood, moreover, makes it impractical
large and expensive equipment required for 4the
to distill- o? the vehicles by the application of
ordinary pressure processes. In addition to the heat from an> external source. It isthe ordinary
>`expense attendant upon the installation and practice to recover only the portion ofthe non
45 maintenance of such equipment, there'is the ad- » aqueous vehicle which can be drained from the
ditional disadvantage that the equipment is not
readily adaptable to various types of wood which
require modified _methods of treatment.
wood, and no attempt is made to recover" the fluid
_` retained in the wood.
- Processes employing 'nomaqueous menstruums
Aqueousyehicle's oñ'er vetv another disadvan--ì'> for the pressure impregnation of wood require
tage in that a large number of impregnati‘ng
agents are not water soluble and cannot, vthere
fore, be used in water solution.
equipment comparable in ~size and cost to that 50
used in processes employing- aqueous vehicles.
Processes _employing~ hnon-aqueous menstruums
also require relatively long
of timev for
disadvantages 'have prevented the impregnation j the impregnatlng and `drying operations.
>It is 'an object of my invention to provide proc- .
of wood by the use of an aqueous menstruum in>
Considered together, the.V above enumerated
esses which can be employed for the impregna-tion" of wood and the like without damage there
moved >therefrom by permitting it to boil off.
to. It is a further object of my invention to pro
effect an almost complete evaporation of the di
methyl ether, but, if desired, additional heat may
besupplied. The gas which results from the Cl
Ordinarily, no addition of heat -is necessary to ‘
vide processes whereby wood may be impregnated
-with desired impregnating agents without the
deleterious swelling, shrinking,_warping, check
boiling of the dimethyl ether can- be recovered
ing, and raising of the grain which attends vthe
use of most of the menstruums hitherto known.
A still further object of my invention is to pro
and condensed, whereupon it may be used as a k
solvent for more of the impregnating agent.
It will be `apparentthat the removal of di
AIl() vide processes whereby finished lumber may ~sat
methyl ether is exceedingly easy of accomplish 1o
isfactorily be impregnated with suitable fire
l proofing, staining, and preservative agents.
ment, and it is to be noted that a substantially
A . complete recovery ofl the dimethyl ether is prac- l
still further object of my invention is to provide
processes whereby a deep and uniform penetra
15 tion Aof impregnating agents can- quickly and
economically be achieved. A still further object
of my invention is to provide processes which are
tical. The short time required to effect asepa
`ration of the liquid from the wood is, of course,
~ . low in cost, and which can readily be adapted to
may be better understood, there is illustrated in
highly advantageous.
In order that the preferred sequence of -steps
in a specific process for the impregnation of 'wood
the condition of the Wood. Other objects of my- the accompanying drawing a flow sheet of such a
20 invention will become apparent hereinafter.
typical process.
My objects are accomplished, brieiiy, by impreg
Wood to be impregnated is placed in thetreat
natingwood or the like with suitable impregnat- .
ing cylinder, and a solution of a suitable impreg
ing agents carried in dimethyl ether. -The di
nating agent, for instance Zinc chloride, in di
methyl ether may, of course, be diluted with less methyl ether is admitted to the treating cylin
25 expensive, low boiling materials such as carbon vder from the solution> storage tank. The wood 25
to be impregnated is placed in the treating cyl
Wood and the like may be impregnated accord ' inder and subjected to a vacuum, by means of
ing to the processes of my invention with'impreg
the indicated vacuum pump, toremove most of v «
nating agents such asl pigments, lakes, dyes, the air- from the cylinder and the wood. The
stains, resins, gums, lacs, oils, waxes, parasiti
cides, and fireprooñng compositions. Many water
cylinder is then connected to the solution storage 30
tank, which is at a higher temperature than the
insoluble impregnating agents can be dissolved in ` cylinder, and the solution of impregnating agent
dimethyl ether, and it is thus possible to use such flows intothe cylinder under its own pressure.
waterfinsoluble impregnating agents in an eco
The desired temperatures and the correspond
nomical and practical manner. For instance, ing pressures are maintained in the treating cyl 35
such preservatives as beta-naphthol, tetrachlor
inder by the use of steam coils. The desired tem
perature and pressure are maintained for the
_pheno1, and orthophenyphenol may be used in di
methyl ether. I may also use mixtures of various
time required to effect the desired degree of
impregnating agents.
penetration of the wood.
theimpregnating agent inthe menstruum, butA it
is usually desirable to employ impregnating
than the treating cylinder.
At _the end of this
Dimethyl ether is a solvent- for a wide variety- time, the line between the treating cylinder and 40
of impregnating agents, but there may be found »the solution storage tank is opened, and the solu
an‘impregnatlng agent which is not soluble there
tion is forced from the treating cylinder into the
f in. In such an instance, some of the advantages
solution storage tank which at this time, of
of my invention may be obtained by _dispersing course, is ata lower temperature and pressure
After the solution has been drained from the
Wood and forced into the solution storage tank,
-the-line between the cylinder and the »solution
storage tank is closed, andthe line from the
treating cylinder to' the condenser is opened. 50
The dimethyl ether which has been'retained in
the woodïdistills therefrom and is condensed in
- agents which are soluble in the dimethyl ether.
The impregnation of~ wood or the like may be
accomplished by simply immersing itin the di
50 methyl etlier solution. However, it is usually pre
ferred to inject the non-aqueous vehicle into thel
wood by the use of pressure. Pressures up to the
, critical pressures of the dimethyl ether may be
the condenser from which it is led to a receiving
obtained by heating it. Because of the low boil
55 ing point of dimethyl ether, no large amount of
heat Will be required to obtain relatively high
The temperature of the wood is ordinarily
sufficient to supply the heat required to vaporize 55
substantially all of the menstruum.
pressures, and, under many circumstances, satis- >
The atmosphere of the vaporized dimethyl
factorily high pressures may be obtained without etherwhich remains in the treating cylinder is
the additionof external heat by reason of the
finally swept out with air from a blower, and dis
normal pressure of the dimethyl ether lat ordinary
solved in a suitable solvent, such as 60° Bé. sul
furic acid, in a scrubber. From time to time the
Dimethyl ether is characterized by its relatively " dimethyl ether whichhas been dissolved in the
-low surface tension and its relatively low vis - scrubber is removed from the solvent liquid by
cosity. The impregnation of wood according to >heatingi'and the vaporized dimethyl> ether is
65 the processes of-my invention, accordingly, pro-`> v returned through lthe condenser to the receiving 65
:ceeds very rapidly even at rather moderate pres
- tank and then to the solution storage tank..
f sures, a satisfactory degree of penetration being ' ' The 'condensed liquid in the receiving tank is
obtained in a relatively short period ofv time. ’ heated somewhat and forced, under its own pres
"I'his, of course, is very important from an eco
sure, through the f dissolver where a desired
nomic standpoint because smaller equipment may amount of the impregnating'y agent is put into
be used for handling a given amount of lumber. solution'. - It will be noted that a suitable storage'> 70.
After a desired degree of penetration has been ‘ tank for the ‘liquid is provided,- which storage
` Vobtained, the dimethyl ether is'drained from the tank is equipped with heating and cooling means wood. Afterl the liquid has been drained oil', the whereby the pressure'may'b'e adjusted.
v715 liquid remaining in the wood'can readily be re-_ f
After the dimethyl ether has been evaporated
by the penetration desired, the nature of the
>wood, the >temperature of treatment, and -the
vfrom the wood, and after any remaining gases
have been swept from the cylinder by means of
length of treatment. :When materials which can '
the blower, the wood, which is now entirely dry,
can be removed from the cylinder. The wood is
then ready for use, and no further seasoning or
drying is required.
easily be impregnated are treated, itis, of course, ~
unnecessary to use such high pressures, and the
>processes _of my invention may, under some cir
cumstances, advantageously be practiced at
Considering my invention with more particular>
reference to certain illustrative impregnating atmospheric pressures or at pressures only
agents and certain dimethyl ether solutions, the slightly above atmospheric. ~
It willl also be understood that the scheme
.following examples are given:
of operation illustrated in the accompanying
Example I
drawing may be widely varied without depart
‘ -
_Following the procedure above outlined, a
number of samples of finished wood were sub
15 jected to a 5%- solution of. zincV chloride in
Temperatures of from 40» to 50° ’
ing from the spirit of »my invention. .Instead of
condensing> the vaporized dimethyl ether by
means of refrigeration, >the gas may be con 15
densed by the use of a compressor.- It will be
C. were maintained with corresponding pressures> Vreadily, apparent, moreover, that the processes
from 130 to 150 pounds per square inch. IIfhesel already known for the impregnation of porous
conditions were maintained~_ for 30 minutes.
A’materials by the use of aqueous menstruums ‘
and by the .use of high boiling non-aqueous men 20
fornia white pine, heartand sap, 11/2" x 2" x 4”; . struums may readily be adapted, according vto
the teachings of my invention,`to the' use of
Wisconsin white pine, sap, 3A" x 2" x 4”; 'Doug
20 The woods thus treated were as follows: Cali
lasilr, heart, 11A" x 11A” x'4”‘; red oak, heart,
3A" x 4” x 4".
All of these specimens treated
according `to the procedure of this example were
impregnated with zinc chloride.
_ completely
'I'here was'no discernible swelling, warping, or
raising ofthe grain of these `iinished pieces of
dimethyl ether.
¿While I` have shown certain specific impreg
nating agents, certain'y dimethyl ether solutions
-a'nd certain procedures- and conditions of op
eration, it will be understood that I do not’intend
to be restricted thereby, the scope of my inven
tion being apparent from the following claims:
Example -II
I, claim:
1. In la 'process for the impregnation of a
Av cylinder of seasoned heart white oak, 31/2" in i porous material, the step comprising immers
diameter' and 4" long, was subjected to a 5%
ing the material' in a liquid, non-aqueous men-_
-solution of zinc chloride in dimethyl ether for struum comprising dimethyl ether, the men
three hours at temperaturesof- 40 to 50° C., and ` struum _carrying an impregnatirig agent. _
at corresponding pressures of 130 to-150 pounds
2. «In a .process for the impregnation of Wood,
per square inch. The wood used in this example
is practically impenetrable by aqueous solutions,
‘but under the conditions of this example, approx
imately half of fthe _wood was impregnated with ‘
zinc chloride. There was no apparent swelling,
checking, or distortion of the wood.
the step comprising immersing the `wood in,a
liquid, non-aqueous menstruum comprising dh'
methyl ether,_an impregnating agent being dis
solved in' the menstruum.
3. In a process for the impregnation of wood,
the steps comprising immersing'the material in
Example III
' fa' liquid, non-aqueousk menstruum comprising
Following the procedure of the above examples, `dimethyl ether, the menstruum having an im
pregnating agent dissolved therein, and, after 45
45 a number of.. pieces of Ponderosa pine window
sash were treated with a 5% solution of zinc impregnation of the wood, recovering the 'portionchloride in dimethyl ether. The treatment was of the _menstruum retained therein by volatiliz
ing the menstruum therefrom. '
» '
conducted at 150-pounds per square inch pres
-4. In a process for the impregnation of wood,
sure'for thirty minutes for sapwood and forty-`
the step comprising immersing the wood in a 50
50 live minutes forheartwood. There was no\perceptible swelling, warping, checking, oi' roughen liquid, non-aqueous. menstruum comprising di
ing of the surfaces of thewood. Examination of methyl ether, an impregnating agent being car- ,
typical specimens 'showed complete penetration`
ried by the menstruum.
5. In a process for the impregnation of wood,
the step comprising immersing the wood in a 55
,v liquid,~ non-aqueous menstruum comprising di
.' "
of the wood with zinc chloride, and about one
methyl ether which contains dissolved carbon
.. Example IV
_Following the procedure o_f Example III, but
using dimethyl ether containing dissolved there
.60 in about twenty per cent of carbon dioxide as the
solvent for _zinc chloride, a number of pieces of
i iinished
were" impregnated.
dioxide and a dissolved impregnatingf‘ agent.
l 6. Ina process for the impregnation of Wood.
the steps comprising treating the wood by in 80
jecting thereinto under pressurean impregnat
ing agent dissolved in a liquid non-aqueous men
Excellent . -struum'
results were _. obtained, and it is noted that a
comprising dimethyl ether, and, after
impregnation of- the wood, recovering the por
somewhat more rapid penetration of the wood tion of the menstruum retained therein'by vol
seemed to be obtained than when the dimethyl - atilizing the-menstruum therefrom.
ether was used alone as a solvent.
g _'1. In a process for the impregnation' of wood,
, It will be readily understood that numerous I- ‘the steps comprising immersing -the wood in a
modiñcations may be Amade `in the above illus--> liquid, non-aqueous menstruum comprising di
trative examples without departing from the
spirit of my invention. Theimpregnating agent _ methyl ether >in which is dissolved an impreg 70
'used and its> concentration-will depend, of course, nating agê’nt, sealing the wood and liquid men
upon the characteristics which it is desired to struum ina 'closed receptacle, raising the tem
perature of the menstruum to'obtain a corre
impart to the wood.
` »
' The pressures of treatment may also be widely spending pressure-within the receptacle, with- _
75 varied and they will be‘determined -for each case
drawing the liquid menstruum from the/reeepî
l 2,135,030
tacle, and volatilizing the >portion of the men
struum _retained in the wood to recover it there-‘_
8. In a'process for 4the impregnation of Wood,
the steps comprising withdrawing air from the
wood by preliminary vacuum,.treating the wood
_ under pressure- with an impregnating agent dis
solved in a liquid, non-aqueous menstruum com
prising dimethyl ether, and, after impregnation
10 of the Wood, recovering the portion of the men
. struum retained therein by vclatilizing the men
9'. In a process for the impregnation of wood.
the steps comprising impregnating the Wood with
zinc chloride dissolved in a liquid, non-aqueous
menstruum comprising dimethyl ether, and, after
impregnation of the wood, recovering the por- .
tion of the menstruum retained therein by vola-v __ v
tilizing> the menstruum therefrom.
10 _
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