Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
21~219~
D~'TnTT~ICATION OF ~T~T~T~T~n~3Ic M~TT~DTaT.
FIBI,D OF T~ lnv~
The present invention relates to the field of
5 ~ese1v~tion of cellulosic materials, such as books,
documents, works of art, clothing and flags, and in
particular, to a process for deacidification of cellulosic
materials .
10 R~ OF Ti~S lh ~
There is much concern about the deterioration of aging
cellulosic materials, particularly those of library, museum
and archive collections . The most signif icant cause of
deterioration of cellulosic materials ls acid-catalyzed
15 hydrolysis of c~ ]lose which results in shortened
c~ loc~ molecules, and weak and brittle fibres. There
are a number of factors which cause an acidic condition in
cellulosic materials including air pollutants, the use of
alum in the paper k~n~ process and the degradation
20 products of cellulose and ink.
In an effort to reduce the deterioration of cellulosic
materials by acid-catalyzed hydrolysis, researchers have
turned their attention to processes for deacidification of
c~ lo~ic materials. Attention has been specifically
25 directed to non-aqueous deacidification compositions to
neutralize the acidity of the cellulosic materials and to
introduce an A 1 kA l; nr~ reserve to inhibit re-acidif ication .
United States Patent Number 3,676,182 (R.D. Smith,
July 11, 1972) relates to a process for non-agueous
30 deacidifica~ion of paper using magnesium r ' h~.Y;~ as a
deacidif ication agent . The deacidif ication agent is
dissolved in methanol to a concentration of about 5 to 11%.
The resultant solution may be diluted with a
chlorofluorocarbon, such as trichlorofluoromethane or
35 dichlorodifluu~ n~ to produce a solution of about 1
to 2% magnesium methoxide. The chlorofluorocarbon
contributes to rapid evaporation of the solution and
21~2195
imparts hydrophobic properties to ~ ac~ ication solutions
conta ining methano 1, thereby m i n i m i ~ i n~ attack on certain
inks by methanol. Books and papers may be dipped in the
solution or the solution may be applied by brushing or
5 spraying.
However, m-gnP~ m h~Yi~ is t!X~L~ -ly sensitive to
water such that even traces of moisture cause immediate
hydrolysis and a gelatinous precipitate of magnesium
hydroxide which is insoluble in water and inorganic
10 solvents . Unless the paper is suf f iciently dried prior to
LL~a~ -nt, pL. ~U' r! hydrolysis of the magnesium methoxide
may occur, causing an undesirable glaze of magnesium
hydroxide to be formed on the surface of the paper.
Furthermore, the nozzles of spray guns are subject to
15 frequent plugging. The bristles of brushes also become
clogged and must be cleaned and dried prior to reuse.
United States Patent Number 3,939,091 (Kelly, G.B.,
February 17, 1976~ discloses a composition for use in the
deacidification of paper which c~v~:~r - the problem of the
20 prior art ~c-a~ ication solutions comprised of magnesium
methoxide dissolved in a chlorof luorocarbon . M;l~n~ lm
r ~ hnYi~ i8 dissolved in methanol or in a mixture of
methanol and trichlorotrifluoroethane (FREONTM TF). Carbon
dioxide is then introduced into the solution to produce a
25 colourless 20% methoxymagnesium methylcarbonate solution.
The resultant solution is very tolerant of water compared
to solutions of magnesium ~Yi de and does not cause
plugging of spray nozzles or gumming of brushes.
~ n;~ n Patent Number 1,147,510 (Smith, R.D., June 7,
30 1983) describes another method for production of
methoxymagnesium methylcarbonate. Nagnesium metal is
reacted with absolute methanol to produce dried magnesium
methoxide. The magnesium ~ is then re-dissolved in
methanol containing carbon dioxide to produce a solution of
35 metho,~y~ llm methylcarbonate. The solution is diluted
with trichlorotrif luoroethane or dichlorodif luoromethane .
The diluted solution is sprayed or brushed onto papers to
21421g5
deacidify the paper. Alternatively, the paper can be
dipped into the solution. This method for preparation of
methuxy.l,ayllesium methylcarbonate allows the dry material,
namely magnesium ~ , to be prepared prior to
5 delivery to a work site and then re-dissolved in methanol
and reacted with carbon dioxide on site.
United States Patent Number 4,860,685 (Smith, R.D.,
August 29, 1989) and ccLL~ ing ~AnA~iAn Patent Number
1, 272, 018 (July 31, 1990) describe a soft spray system for
10 ~l~A~ if ication of cellulosic materials. A 19~A~ if ication
agent, preferably a carbonated magnesium Alkr~Yi~l~, is
combined with a chlorofluorocarbon diluent, preferably
trichlorotrifluoroethane, and a chlorofluorocarbon gas
propellant, preferably dichlorodifluoromethane. Additional
15 ~L~S~-uLizing and propelling may be provided by an inert gas
suc~ as nitrogen . The carbonated magnesium A 1 kf~Yi ~1~, such
as methoxymagnesium methyl~aLI,u..ate or ethoxymagnesium
ethylcarbonate, is produced by dissolving the corr~ p~n~lin ~
magnesium Alk~Y~ in a lower alcohol in the presence of
carbon dioxide.
The prior art processes described herein use
chlorofluorocarbons since they are substantially unreactive
and, as such, pose no direct toxic threat to living
organisms. However, these very same characteristics that
render chlorofluorocarbons inert pose significant problems
in the stratosphere . Chlorof luorocarbons have been
recognized as being a major factor responsible for
stratospheric ozone depletion and for contributing to the
greenhouse effect. Of particular concern is the chlorine
which is liberated when the chlorofluorocarbons are e_posed
to strong W radiation in the stratosphere. Chlorine
depletes ozone by catalyzing its conversion to molecular
oYygen. Production and cu._ ~ion of chlorofluuLuuaLbol~s
has been substantially reduced and must be eliminated by
January 1, 1996 (~op~nhAgen Agreement to amend Montreal
Protocol, November 23-25, 1992). Accordingly, a substitute
must be found for the chlorofluorocarbon diluent of the
21~2195
prior art compositions.
It i8 an object of the present invention to provide a
compo6ition for deacidification of aging cellulosic
material comprising a diluent to replace the
5 chlorofluur uuaLbu~l diluents Or the prior art.
8UM~Y OF THE 1~ v b.. I _
According to one aspect of the present invention,
there is provided a composition for deacidification of a
cellulosic material, comprising a carbonated magnesium
~lk~Y;~.-, a solvent, and a hydrochlorofluorocarbon and/or
a hydrof luorocarbon di luent .
According to another aspect of the present invention,
there is provided a method for preparing a composition for
deacidification of a CPlllllosic material, comprising the
steps of r~fl-lY;n~ r-~nps;llm metal in methanol to produce
a suspension of magnesium methoxide in methanol; cooling
the 6uspension of magnesium methoxide in methanol;
saturating the cooled suspension of magnesium methoxide in
methanol with carbon dioxide to produce a solution of
methu,~y~ yllesium methylcarbonate in methanol; and diluting
the solution of methu~yl,lc.y.lesium methylcarbonate with a
hydrochlorofluorocarbon or hydrofluorocarbon diluent.
DT~T~TTT~n DE8CRIPTION OF TIIE: L.~bCI~ JIM~
In accordance with the present invention, the
chlorofluorocarbons of the prior art deacidification
compositions are replaced with a hydrochlorofluuLuLc~Lbu
and/or a hydrofluorocarbon.
3 0 The present inventor has discovered that carbonated
magnesium llko~ le de~ ication agents are soluble in
hydrochlorofluuLuui~Ll,ulls and/or hydrofluorocarbons and that
the resultant compositions are effective in deacidification
of cellulosic materials. Moreover,
hydrochlorofluorocarbons and hydrofluorocarbons are
subctantially inert and are not toxic.
The use of hydrochlorofluorocarbons and
2142195
hydrofluorocarbons to replace the chlorofluorocarbons of
the prior art compositions substantially reduces the
available number of chlorine ions which may be liberated
upon ~.L~O;jw~ e to strong W radiation in the stratosphere,
5 as compared with the prior art chlorof luorocarbons .
Fur~hl ~, the ~L~sen~e of IIYdLOY~II renders the ~ _ '
more reactive so that it is more likely to be ~1P~ - sed
before it reaches the stratosphere. Noreover, the rate of
de -~ition is higher than that of chloroflu<,lo~LI,ul,s
which have a lifetime of about 60 ~o 100 years. nhile
regulations will eventually prohibit the use of
hydrochlorofluorocarbon6, the phase-out 5rhp~ e for
c.-._ Lion only begins on January 1, 1996 with elimination
!:~hP,l.ll P~ for 2030 (Copenhagen A~L~ L to amend Montreal
Pro~ocol, N~ 23-25, 1992). There are no such
regulations in place with respect to hydrof luorocarbons .
The hydrochlorofluorocarbon and/or hydrofluorocarbon
act as a diluent for delivery of a dP~r~ ication agent
and a solvent to aging c~ l osic materials. Elereinafter,
20 the term "cellulosic material" will be understood to
include paper, books, documents, archival records, maps,
worlcs of art and articles made from cotton and/or linen
including clothing and f lags .
A suitable deacidif ication agent is a carbonated
25 magnesium AlkoY;dP, such as methoxymagnesium
methylcarbonate or etho.~y."ay.lesium ethylcarl:~onate.
One method for pro~ tirln of methoxymagnesium
methylcarbonate is described in United States Patent Number
3,939,091. Ml~nPsium metal is refluxed in methanol to give
30 a suspension of magnesium methoxide in methanol. After
cooling, the s~ pPn~ of magnesium methoxide in methanol
is saturated with carbon dioxide to form a solution of
methc~y",~y~lesium methylcarbonate in methanol.
Nethoxymagnesium methylcarbonate and ethoxymagnesium
35 ethylcarbonate may also be produced as described in
~ ln;~ n Patent Number 1,147,510 wherein magnesium metal is
reacted with methanol or ethanol to produce r-~nPsillm
214219~
methoxide or magnesium eth~)yi~lo~ respectively. The
resultant solution is dried, by a method known to those
skilled in the art, to form a dried powder of magnesium
~lknY;~le. The dried magnesium r '' 'rlo or r-gnoclllm
5 ethoxide is subsequently added to methanol or ethanol in
the presence of carbon dioxide to form methoxymagnesium
methylcarbonate or ethu,,y.l~a~..esium ethylcarbonate,
respectively .
Preferably, the ~;aLl,u..ated magnesium :Rlkr Yl~e i8
methoxymagnesium methylcarbonate or ethoxymagnesium
ethyl~aLbol~ate~ with methoxy --~rlosillm methylcarbonate being
the most preferable. ~owever, it will be appreciated by
those skilled in the art that other suitable carbonated
magnesium ~lk~lYirlos can be prepared by either of the above-
mentioned methods using other solvents to produce the
r~ur ~ nrJ homologs of methoxy~magnesium methylcarbonate.
The solvent must however be evaluated for the potential for
damage to the h~n-1inqs, inks, etc. of the material being
treated.
The concentration of carbonated magnesium alk~lYirlo in
the solvent is suitably in the range of from about 5 to 20%
(w/v). Preferably, the cu-.c~ ation is about 20% (w/v).
The resultant solution of carbonated magnesium
alkoxide in solvent is diluted with a
hydrochlorofluorocarbon and/or a hydrofluorocarbon to yield
a concentratior: of carbonated magnesium ~lkoYido in the
range of from about 0.1 to 2% (w/v). Preferably, the
cu..ct~-L atiOn of carbonated magnesium ~lkoyir~o in the
diluted solution is in the range of from about O . 5 to 1. 5%
30 (w/v). The hydrochlorofluorocarbon and/or
hydrofluorocarbon diluent contributes to rapid evaporation
of the solution and minimi70~; attack on certain inks by the
solvent. It is desirable that the r_o~.c~l.LLation of solvent
in the rloA~ir~lfication composition of the present invention
35 is as low as possible. Preferably, the curlcr:llLr ation of
solvent in the diluted solution is less than about 59
(v/v).
214219~
.--
Suitable hydrochlorofluolouclL},ol~ diluents are
di~luorochloroethane, trif luorochloroethane,
tetrafluorochloroethane, hydrochlorofluo~o},Lu~anes and
hydrochlorof luorobutanes . A particularly suitable
5 hydrochlorofluorocarbon diluent is 1,1-dichloro-1-
fluoroethane. ChlorodifluuLl AnP may be added as a co-
diluent to increase the vapour ~l~5~UL~ of the mixture,
thereby increasing evaporation of the solution.
Preferably, the c.,l.c~ Lc.tion of chlorodifluul~ ~AnP
10 added as a co-diluent is not greater than about 10% (v/v),
in view of the high vapour ~L~:lSr~ULt: of
chlorodif luoromethane .
Suitable hydrofluuLù~lLbulls are fluorinated methanes,
ethanes, propane~ and butanes.
The deacidification composition of the present
invention may also include additives, such as a
plasticizer, to reduce the brittleness of the cellulosic
material .
The ~l~Ari-lification composition of the present
invention may be applied to CPll-]lofiic materials in a
manner known to those skilled in the art, for example by
spraying with a spray gun or an aerosol can, by brushing or
by dipping the cPllllloc~r materials into the
deacidification composition.
Preferably, the method for ~P~A~rill~fication of
cPlllllogic materials is as follows.
The cellulosic materials are placed in a vessel
capable of withstanding a vacuum. The vessel is sealed and
evacuated with a vacuum pump. Preferably, the water
content of the cPl l-llo~:ic materials is reduced from a
normal eguilibrium moisture content of from about 5 to 6~
to a residual moisture content of from about 1 to 2~6 under
vacuum. The (lP~A~ri(li fication composition of the present
invention is then introduced to the vessel and the
cellulosic materials are i ~ed in the composition for a
time sufficient to allow penetration of the composition
into the cellulosic materials.
2142195
If desired, a positive ~res~7uL~, for example by
introduction of carbon dioxide or another gas, may be
applied to the vessel to increase the penetration of the
composition .
The treatment may be cqn~ tPd at room temperature or
greater. It will be appreciated by those skilled in the
art that the t: a LUL 3 must not be 80 great as to damage
the cellulosic material being treated.
At the end of the LL~i L, the vessel is drained and
a vacuum is applied to the vessel to recover âny 1l ;n;n~
solvent and diluent. The cellulosic material is then
removed from the vessel and is allowed to air dry in a
fumehood. This method is particularly advantageous in that
it permits simultaneous ~L~at L of a large number of
books, for example. Furth ~, the solution can be
readily ~cuv~L.d from the vessel.
Alternatively, the ~lPat~ ;fication composition of the
present invention may be applied by the soft spray system
described in United States Patent Number 4,860,685,
discussed hereinabove. It will be appreciated by those
skilled in the art that other methods of contacting the
~-Pl ~ osic materials with the deacidification composition
of ~he present invention are also suitable. For example,
it is not nPcP~SAry that the cellulosic material be dried
under a vacuum prior to contacting with the clPar~ ;fication
composition of the present invention. The cellulosic
material may also be contacted with the deacidification
composition of the present invention by brushing or
spraying .
The deacidification composition of the present
invention may also be used in the method and apparatus
described in ~AnA~iAn Patent Application Number 2,009,621
(Eggersdorfer, R. et al, pllhl;~hPd August 11, 1990).
~An?l~l;An Pa~ent Application Number 2,009,621 relates to a
method and apparatus for ~lPa~ ; fication of cellulosic
materials by pre-drying the paper by high frequency
radiation in a vacuum, neutrali~ing with a deacidification
21~2195
.
solution and evaporating the solvent in a vacuum with high
fre~uency radiztion. The ~ aLclLu6 described i8 a single
treatment chamber ~or the pre-drying, neutralizing and
~:v~lpuL~ting steps in an enclosure for total solvent
5 recovery.
