Note: Descriptions are shown in the official language in which they were submitted.
CA 02339021 2001-01-30
PRODUCT FOR THE DE-ACIDIFICATION OF CELLULOSE MATERIAL,
AND PRODUCTION AND USE THEREOF
FIELD OF THE INVENTION
This invention relates to the preservation of
objects that contain cellulose-type materials, in
particular, to a product, in the form of a solution, for
de-acidification of cellulose-type materials composed of
carbonated magnesium di-n-propylate, n-propanol and a
hydrofluorocarbon diluent.
BACKGROUND OF THE INVENTION
There is a lot of concern for the deterioration
undergone by cellulose-type materials (books, documents,
maps, press, magazines and tissues) held in libraries,
newspaper archives, museums and archives. This
deterioration endangers the physical integrity of many
documents, books and tissues and thus forces a
restriction in access and handling thereof. The most
significant cause of deterioration in cellulose-type
materials is hydrolysis catalyzed by acids in the
cellulose, giving rise to a shortening of the polymeric
chains of the cellulose, which, in turn, leads to a
weakening of the cellulose fibers and they become more
fragile. Many factors contribute to the acidification
of cellulose-type materials. For example, acidic gases
present in contaminated air, the use of alum and
colophony (abietic acid) in paper production, products
for oxidative degradation of cellulose, inks and other
substances that oxidize cellulose which are present in
paper and books.
A great deal of effort has been put in to the
development of processes to achieve de-acidification of
cellulose-type materials and thus to prolong their
useful life by stopping acidic hydrolysis degradation
processes. Specific compositions and products have been
CA 02339021 2001-01-30
2
studied for de-acidification, capable of neutralizing
the acid present in cellulose-type materials and
introducing an alkaline reserve, which inhibits re-
acidification. Technology has moved on from expensive
craft methods using aqueous medium to the development of
methods for applying alkaline reagents, dissolved in
non-aqueous vehicles, either in liquid or solid state,
to prevent books from falling apart.
The North American patent US 3.676.182 (R.D. Smith,
llth July 1972) relates to a procedure for non-aqueous
de-acidification of paper using magnesium methoxide,
dissolved in methanol to a concentration lying between 5
% and 11 0, as the de-acidifying agent. The resulting
solution can be diluted with a chlorofluorocarbon (CFC)
diluent, such as trichlorofluoromethane or dichloro-
difluoromethane, until a liquid is formed, under
pressure, that contains between 1 % and 2 % of the de-
acidifying agent. The CFC compound quickly evaporates
from paper impregnated with the de-acidifying solution
containing methanol, thus minimizing the solvent effect
of methanol on certain inks. The books and papers can
be treated by immersion in the de-acidifying solution,
or the solution can be applied with a brush or using a
spray. Nevertheless, this method is not free from
drawbacks as the magnesium methoxide is extremely
sensitive to water. So much so that even traces of
moisture lead to immediate hydrolysis forming a
gelatinous precipitate of magnesium hydroxide. This is
insoluble in water and many organic solvents. Unless the
paper has been sufficiently desiccated before treatment
premature hydrolysis of the magnesium methoxide may
occur, leading to the formation of unwanted white marks
of powdered magnesium hydroxide on the surface of the
paper, giving the paper a rough feel. On the other
hand, the spray nozzles frequently become blocked and
the brush bristles become caked, making it necessary to
CA 02339021 2001-01-30
3
clean them and then dry them thoroughly before using
them again.
The North American Patent US 3.939.091 (Kelly,
G.B., 7th February 1976) discloses and claims a product
for the de-acidification of paper that overcomes the
problems of previous de-acidification solutions based on
magnesium methoxide dissolved in CFC. The magnesium
methoxide dissolved in methanol or in a methanol and
trichlorotrifluoroethane (Freon~ F7) mixture is reacted
with gaseous carbon dioxide to obtained a colourless 20
% solution of methoxymagnesium methylcarbonate. The
resulting solution is more tolerant of water than the
magnesium methoxide solutions, and obstructions are not
produced in the spray nozzles as often as before.
The Canadian patent CA 1.147.510 (Smith, R.D., 7th
of June 1983) discloses a method for the production of
methoxymagnesium methylcarbonate. Metallic magnesium is
allowed to completely react with methanol to form
magnesium methoxide. This is then re-dissolved in
methanol saturated with carbon dioxide forming a
methoxymagnesium methycarbonate solution. This solution
is diluted with trichlorotrifluoro-ethane or with
dichlorodifluoromethane. The diluted solution is
sprayed onto the paper to be de-acidified. As an
alternative, the paper can be submerged in the same
solution, with the liquid state being maintained under
pressure.
The North American patent US 4.860.685 (Smith,
R.D., 29th of August 1989) and the corresponding
Canadian patent CA 1.272.018 (31st of July 1990)
describe a flexible spraying system for the de-
acidification of cellulose-type materials. A de-
acidifying agent, preferable an alkoxide of magnesium
carbonate, is combined with a CFC diluent, preferably
CA 02339021 2001-01-30
4
trichlorotrifluoroethane, and with a propellant gas,
preferably dichlorodifluoromethane. Additional
pressurization and propulsion can be achieved using an
inert gas such as nitrogen. The carbonated magnesium
alkoxide, such as methoxymagnesium methylcarbonate or
ethoxymagnesium ethylcarbonate, is produced by
dissolving the corresponding magnesium alkoxide in
alcohol in the presence of carbon dioxide.
The procedures described above use CFCs as these
are essentially non-reactive and so do not imply a
direct toxic risk for living beings. However, these
same properties of chemical inertness that the CFCs
possess make them problematic in the stratosphere. It
has been demonstrated that the CFCs are the main factor
responsible for the destruction of the stratospheric
ozone layer and that they contribute to the greenhouse
effect in the troposphere. The problem revolves around
the chlorine that is liberated when the CFCs are exposed
to ultraviolet radiation and other more penetrating
radiations in the stratosphere. The chlorine destroys
ozone by catalysing its transformation into molecular
oxygen. The production of CFCs has been banned since
the lst of January 1996 (Copenhagen Agreement which
amends the Montreal Protocol of the 23-25'h of November
1992), and use thereof should be totally eliminated
before the year 2030.
The Canadian patent CA 2.142.195 (Worsford, D.
James, 8th of February 1995) discloses and claims a
product for de-acidification of cellulose-type materials
which consists of a de-acidifying reagent, such as
methoxymagnesium methylcarbonate or ethoxymagnesium
ethylcarbonate, a solvent such as methanol or ethanol,
and a hydrochlorofluorocarbon diluent (HCFC) or
hydrofluorocarbon (HFC). The product patented can be
applied to the cellulose-type material by spray or with
CA 02339021 2001-01-30
a brush, or by immersing the cellulose-type material in
the product. As a novelty with respect to the patents
cited earlier this patent describes the use of diluents
that are not prohibited by the Montreal Protocol [HCFCs
5 and HFCs].
The use of HCFCs and HFCs as a substitute for CFCs
substantially reduces the number of chlorine radicals
that can be liberated in the stratosphere on exposure to
cosmic radiation, thus reducing the potential for ozone
destruction. On the other hand, the presence of
hydrogen means that the compound is more reactive, such
that it tends to decompose more easily before reaching
the stratosphere. The rate of decomposition of HCFCs
and HFCs is higher than that of the CFCs, whose lifetime
is quoted at being between 60 and 100 years.
The object of the present invention is to find a
riew product for the non-aqueous de-acidification of
cellulose-type materials, thus providing an addition to
the arsenal of means available for combating
acidification of cellulose-type materials.
Therefore, an object of this invention consists of
a product, in the form of a solution, for the non-
aqueous de-acidification of cellulose-type materials
which comprises carbonated magnesium di-n-propylate, n-
propanol and an HFC diluent.
An additional object of this invention consists of
a procedure for production of said product for the de-
acidification of cellulose-type material.
Another additional object of this invention
consists of a method for de-acidification of cellulose-
type material which comprises use of the aforementioned
product.
4
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6
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a product for de-
acidification of cellulose-type material, hereinafter
denominated the product of the invention, characterized
because it is presented in the form of a solution and is
comprised of:
- carbonated magnesium di-n-propylate,
- n-propanol, and
- an HFC diluent selected from 1,1,1,2-tetrafluoro-
ethane (HFC 134a) y 1,1,1,2,3,3,3-heptafluoropropane
(HFC 227).
Carbonated magnesium di-n-propylate is a white
solid, with the formula (CH3CH2CH2O) 2 MgOCO, soluble in
anhydrous n-propanol and in medium-polarity solvents,
such as HFC 227 and HFC 134a, whose polarities are 0.8
Debyes (D). The meaning of the term " organic solvents
of medium polarity" in this description includes
solvents with a dipole moment ( ) less than water [:
1.8 D] , for example, toluene [: 0.40 D] and n-propanol
[: 1.5 D]. carbonated magnesium di-n-propylate has a
dipole moment of 0.8 D and so, in general, it is soluble
in any proportion in the HFC diluent used for producing
the product of the invention. The dipole moment of this
diluent is approximately 0.9 D. Carbonated magnesium
di-n-propylate, on coming into contact with moist air,
reacts to give magnesium carbonate and magnesium
hydroxide, and slowly releases n-propanol according to
the reaction [1]
2(CH3CH2CH2O) zMgOCO + 3H20 Mg (OH) z+ MgCOj + 4CH3CH2CHZOH
[1]
Carbonated magnesium di-n-propylate reacts
vigorously with mineral acids releasing carbon dioxide
and n-propanol, forming soluble magnesium salts as
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7
indicated by reaction [2]:
(CH,CH,CH-0),MgOCO + 2 HC1 MgC12 + C02 + 2 CH,CH2CH2OH
[2l
As a result of the high solubility of carbonated
magnesium di-n-propylate in polar solvents,
characterized by low surface tension and viscosity
values, it can be dispersed deeply through the pores in
the paper, reaching all points of cellulose-type
material, and neutralizing the acids present. The
excess reagent slowly decomposes into magnesium
carbonate hydroxide, a stable compound of the formula
(MgCO, )~. Mg (OH) z. 5HZ0, which it deposited among the paper
fibres to act as a alkaline reservoir protecting against
acidic atmospheric contaminants and acids released in
the paper during ageing. The trials carried out on
papers treated and submitted to accelerated ageing have
shown that treatment with the product of the invention
[see Example 31 stabilizes the properties of the
mechanical resistance of the paper, manifesting itself
as a stabilization in the degree of whiteness.
Carbonated magnesium di-n-propylate can be obtained
from magnesium di-n-propylate by a procedure that
comprises the stages of:
- reacting a suspension of magnesium di-n-propylate
in n-propanol with gaseous anhydrous carbon dioxide,
until a solution of carbonated magnesium di-n-propylate
is obtained; and
- separating said solution of carbonated magnesium
di-n-propylate in n-propanol from the residual products,
for example by decantation.
Reaction of magnesium di-n-propylate with anhydrous
carbon dioxide is an exothermic reaction, reaching
CA 02339021 2001-01-30
g
temperatures of up to 45 C and the initial solid
compound insoluble in n-propanol [magnesium di-n-
propylate] is transformed into a soluble form consisting
of carbonated magnesium di-n-propylate. The reaction is
taken to have reached its conclusion when the
temperature drops to room temperature. Next, the dark
solid insoluble particles are allowed to sediment out on
the bottom of the recipient and to give a clear and
transparent solution. The resulting solution is
collected by conventional techniques, for example, by
decantation or, preferably, by suction under vacuum, and
transferred to recipients suitable for loading, dilution
or dosing. The carbonated magnesium di-n-propylate
obtained is purified, for example, by evaporation of
part of the solvent (typically 20-30 %) under vacuum.
The concentration of carbonated magnesium di-n-
propylate in the alcoholic solution lies between 30 and
70 %(P/P), preferably between 45 and 50 % (P/P) of
carbonated magnesium di-n-propylate, the rest consisting
of n-propanol. It can be adjusted to the desired
concentration by conventional methods, for example, by
dilution with n-propanol or by elimination of excess
solvent.
Magnesium alkoxides can be obtained using known
methods, for example, Metal Alkoxides, by Bradley, D.C.,
Mehrotra, R.C. and Gaur, D.P., Academic Press, London
(1978), and the work of Thoms, H., Epple, M., Viebrock,
H. and Reller, A., J. Mater. Chem. 5(4)589, (1995),
where the synthesis of different magnesium alkoxides
from alcohols of up to four carbon atoms is described.
Although various magnesium alkoxides are known, the
literature only describes carbonated magnesium alkoxides
derived from methanol (methoxymagnesium methylcarbonate)
and ethanol (ethoxymagnesium ethylcarbonate) and the
carbonate of methoxy and butoxy polyethylene glycol [WO
CA 02339021 2001-01-30
9
90/03466).
The suspension of magnesium di-n-propylate in n-
propanol can be prepared by different procedures. One
of them (Procedure A) comprises reacting magnesium metal
with anhvdrous n-propanol, in the presence of iodine, at
the temperature corresponding to the boiling point of
the mixture. Another procedure (Procedure B) comprises
reacting magnesium metal with anhydrous n-propanol in
the presence of iodine at reflux temperature and the
addition of toluene to form an azeotrope with n-
propanol. The magnesium metal used in either Procedure
A or B may in the form of a strip, in which case, it
requires a suitable preparation (see Example 1.2).
Alternatively, the suspension of magnesium di-n-
propylate in n-propanol can be prepared by a procedure
(Procedure C) which does not require the use of a strip
of magnesium but rather magnesium in powder form, with a
granulometric distribution between 50 and 150 M. This
procedure C therefore comprises of; (i) reacting
magnesium in powder form, with a granulometric
distribution between 50 and 150 m, with anhydrous n-
propanol in the presence of iodine, which acts as a
catalyst. The mixture is gently heated until hydrogen
begins to be released. From this moment on, as the
reaction is strongly exothermic, the next step (ii)
consists of cooling the reaction mixture to the
temperature corresponding to the boiling point, with a
view to controlling the reaction rate with gentle
boiling until hydrogen is no longer given off and the
last remaining particles of magnesium have disappeared.
In this fashion a suspension of magnesium di-n-
propylate in n-propanol is obtained.
The use of magnesium in the form of powder with the
indicated granulometric distribution (50-150 m) means
CA 02339021 2001-01-30
that the reaction of magnesium with n-propanol in the
presence of iodine is exothermic, and so the reaction
medium should be cooled instead of additional energy
being provided. This also allows the reaction time to
5 be reduced [typically, the total reaction time for
production of magnesium di-n-propylate is 4-5 hours].
Carbonated magnesium di-n-propylate can be used in
the production of a product, in the form of a solution,
10 suitable for de-acidification of cellulose-type material
along with n-propanol, and a diluent selected from HFC
134a and HFC 227.
The meaning of " cellulose-type material" as used
in this description refers to a material totally or
partially composed of cellulose fibres, including paper
of all classes, tissues and fabrics which contain
cellulose fibres of vegetal origin, for example, those
produced from wood, cotton, flax, jute, hemp and other
plants. Examples of such cellulose-type materials
include books, documents, maps, works of art, articles
elaborated with said materials, clothing, flags, etc.
For use as a reagent for de-acidification of
cellulose-type material a solution of carbonated
magnesium di-n-propylate and n-propanol is produced, in
HFC diluent, at a concentration lying between 30 % and
70 % (W/V) for application by machine and of 3.5 o to
4.5 0(W/V) in said HFC diluent for application by
sprays. In general, said solution is of light chestnut
colour and viscous. To reduce as much as possible the
unwanted effects of the alcohol on the components of the
paper, it is useful to concentrate the resulting
solution as much as possible while maintaining a
suitable fluidity for dosing.
The concentrated solution of carbonated magnesium
CA 02339021 2001-01-30
11
di-n-propylate is diluted to the desired concentration
with a chemically inert and non-toxic diluent which
allows the de-acidifying reagent to be carried inside
the cellulose-type material. An HFC selected from HFC
134a and HFC 227 can be used as diluent. HFC 227 is
preferable. HFC 227 has a boiling point of -17.3 C at
normal pressure (101.3 kPa), a liquid density of 1.417
g/cm' at 20 C (399.3 kPa) . The surface tensions are 9.31
mN/m (at 0 C), 6.96 mN/m (at 20 C) and 4.8 mN/m (at
40 C) and its dipole moment is 0.2 0.14 D. HFC 227 has
been marketed since 1991 as a substitute for R12 and
R114 in sectors where these chemicals have been used as
coolants. The company SOLVAY brought this product onto
the market at the beginning of 1996 as, in September
1995, the European Commission for Pharmaceutical
Products in Brussels (CPMP) established that HFC 227 was
suitable for pharmaceutical inhalers.
Dilution of the concentrated solution of carbonated
magnesium di-n-propylate is carried out with the chosen
HFC, preferably HFC 227, in pressurized containers, up
to de-acidification reagent concentrations [carbonated
magnesium di-n-propylate] lying between 1 % and 10 0
(W/V) , preferably between 1 % and 10 s (W/V) and up to
concentrations of n-propanol less than 10 o(V/V). In a
particular and preferred embodiment of the invention,
the product of the invention contains between 3.8 and
4.5 % (W/V) of carbonated magnesium di-n-propylate,
between 2 and 3 % (V/V) of n-propanol, the rest of the
mixture consisting of the HFC diluent chosen from HFC
227 and HFC 134a, and the product of the invention of
said formulation is especially suitable for use with
spray systems.
Additionally and optionally, the product of the
invention may contain an inert gas, for example,
nitrogen, with a view to achieving additional pressure
CA 02339021 2001-01-30
12
and propulsion.
The resulting diluted solutions of carbonated
magnesium di-n-propylate may be applied by conventional
methods, for example, by direct spray onto the
cellulose-type material. This method of applying the
de-acidification product does not require prior
desiccation, under vacuum, of the cellulose-type
material, as the distribution and impregnation attained
using the spray is very uniform and does not lead to the
accumulation of any type of deposit or residue on the
cellulose-type material to be treated. In general, it
is advisable to work in a fume cupboard and use means of
personal protection to avoid inhaling the spray.
The product of de-acidification product of the
cellulose-type material can also be carried out by means
of dissolving in HFC to a known concentration, for the
bulk de-acidification of books and documents, using the
equipment and method described in the Spanish patent
application P9600016 filed by the same applicant. The
apparatus described is formed of a treatment chamber,
which serves for the drying stages under vacuum prior to
impregnation and recovery of solvent by evaporation-
condensation.
Therefore, the invention also provides a method for
de-acidification of cellulose-type material, which
comprises the application, of a quantity sufficient of
the product of the invention for de-acidifying the
cellulose-type material to be treated. The product of
the invention may be applied to the cellulose-type
material to be treated by means of a bulk de-
acidification system or by spray.
The product of the invention can be obtained
through a procedure that comprises:
CA 02339021 2001-01-30
13
preparing a solution of carbonated magnesium di-
n-propylate in n-propanol; and
- diluting said solution by addition of an HFC
diluent selected from among HFC 134a and HFC 227.
In a particular embodiment, the concentration of
carbonated magnesium di-n-propylate in said alcoholic
solution lies between 30% and 70% (W/V).
Additionally and optionally, the product of the
invention may contain an inert gas, for example,
nitrogen.
The following examples serve as an illustration of
the present invention and should not be considered as
limiting the scope thereof.
EXAMPLE 1
Preparation of carbonated magnesium di-n-propylate
1.1 Dehydration of n-propanol
To dehydrate n-propanol a procedure such as the one
described by A.I. Vogel, in " Practical Organic
Chemistry" , 3a Ed. Longmans, London, 1961, pag. 168, is
used, duly modified for the case of n-propanol.
N-propanol (Panreac quality PS) is used with a
water content of less than 0.1%. The residual water is
almost completely eliminated following the procedure now
described.
In a 2-litre round-bottomed flask 1.25 1 of 1-
propanol are placed and 7 g of clean metallic shiny
sodium added. Once the sodium has completely reacted,
27 g of di-n-ethyl phthalate are added and the mixture
boiled for 2 hours. Next, n-propanol is distilled over
the temperature range 97-98 C, collecting it in a dry
flask protected from external moisture with a tube
containing anhydrous calcium chloride. This treatment
allows almost complete elimination of water, given that
CA 02339021 2001-01-30
14
the sodium hydroxide formed is consumed by hydrolysis of
the phthalic ester, according to the following
reactions:
n-PrOH + Na ---> n-PrONa + 1/2 H2
H2 + Na ---> NaOH + 1/2 H2
NaOH + di-n-propylate phthalate ---> Na phthalate + 2 n
-PrOH
1.2 Preparation of the magnesium strip
To assure that the magnesium metal reacts well the
surface layer of oxides, carbonates, etc., which has
formed on coming into contact with the atmosphere,
should be removed. To achieve this, about 200 g of
magnesium strip are treated with 0.5 1 of dilute
hydrochloric acid (approximately 5 % concentration) for
a short time, normally 5 minutes, shaking in an open
Erlenmeyer flask so that the hydrogen is eliminated.
Then it is quickly washed with distilled water several
times until the acid is completely eliminated. This
elimination can be verified by means of conventional
methods for quantifying the presence of chloride ions.
The next step is to eliminate the water with successive
washes, usually 2 or 3 washes, with absolute ethanol,
before drying between filter papers and storing in a
topaz flask under a nitrogen atmosphere. The strip is
then dried in an oven at 1000 C for 15 minutes, allowed
to cool, always under dry nitrogen atmosphere, and the
container hermetically sealed.
1.3 Preparation of magnesium di-n-pror)vlate
(Procedure A)
In a 5-litre round-bottomed flask 3.750 ml of
anhydrous n-propanol are placed (3 kg, 50 mols) prepared
according to the procedure described in Example 1.1.
CA 02339021 2001-01-30
ti
Next, 146 g(6 mols) of magnesium metal are added in the
form of a strip prepared according to the procedure
described in Example 1.2 along with 3 g of iodine as
catalyst. Next, the reaction mixture is heated to
5 boiling for 6 hours, thus obtaining a suspension of
magnesium di-n-propylate, a grey-coloured grey-white
coloured crystalline solid in n-propanol. The resulting
suspension is allowed to cool before proceeding to the
next step in the reaction. A quantity of product of
10 between 770 and 800 g is obtained, with yields of
between 90 and 92 %. The concentration of magnesium di-
n-propylate in said suspension lies between 34 and 35 0
by weight.
15 1.4 Preparation of magnesium di-n-propylate
(Procedure B)
To 1,250 ml of anhydrous n-propanol (1 kg, 50 mols)
prepared according to the procedure described in Example
1.1, 48.8 g (2 moles) of magnesium metal in the form of
a strip prepared according to the procedure described in
Example 1.2 are added, along with 1 g of iodine as a
catalyst. Next, the reaction mixture is boiled under
reflux for 16 hours, and 350-390 ml of toluene are added
to the product thus obtained to eliminate part of the n-
propanol and to suitably concentrate the solution to
achieve product concentrations of between 45 and 50 % by
weight. The toluene is used to provide an azeotropic
mixture with a lower boiling point to eliminate the n-
propanol. The composition of the azeotrope is 48 %
propanol and 52 % toluene and the boiling point (b.p.)
of the azeotrope is 92 C [b.p. of propanol: 97.2 C,
and b.p. of toluene: 110.6 C].
Operating in this way, adding 390 ml of toluene
leads to the elimination of 350 ml of n-propanol by the
composition of the azeotrope. Thus a solid impregnated
with n-propanol is obtained, with a small amount of
toluene (less than 1~), which for yields of the order
CA 02339021 2001-01-30
16
of 90 % gives a concentration of the order of 50 % of
magnesium di-n-propylate.
1.5 Preparation of carbonated magnesium di-n- ro ylate
A current of carbon dioxide, completely anhydrous
after passing through drying towers filled with
anhydrite, is passed through a suspension of magnesium
di-n-propylate in n-propanol obtained in Example 1.3 or
in Example 1.4. Prior to this, said suspension of
magnesium di-n-propylate in n-propanol has been cooled
as the reaction with carbon dioxide is exothermic and
goes more slowly and with slight decomposition of the
products if carried out at temperatures greater than 500
C. The solid starting product [magnesium di-n-
propylate] is transformed into a soluble form consisting
of carbonated magnesium di-n-propylate, by raising the
temperature to 45-50 C. The reaction is over after 5-6
hours, and this is manifest by a drop in the temperature
of the reaction mixture to room temperature. Next, the
dark insoluble solid particles are allowed to sediment
out until they deposit on the bottom of the flask
leaving a clear and transparent solution, over a time
period of 48.72 hours and the solution of carbonated
magnesium di-n-propylate is collected and transferred by
suction under vacuum to the recipient for loading and
dosing.
The amount of carbonated magnesium di-n-propylate
obtained from 6 mols of magnesium is 912 g in
approximately 1,700 g of n-propanol, giving rise to a
concentration in the carbonated product of the order of
54 % by weight.
The carbonated magnesium di-n-propylate is purified
by total evaporation of n-propanol under vacuum, and;
(i) its magnesium content is analysed by complexometric
titration, and (ii) its bound carbon dioxide content
analysed through decomposition of a sample with
concentrated phosphoric acid, and collection of COZ in a
CA 02339021 2001-01-30
17
series of towers containing a known excess of barium
hydroxide. The following results were obtained:
Theoretical CO2: 23.62% CO, found: 23.43%
Theoretical Mg: 13.04% Mg found: 12.92%
The infrared spectrum of the product [carbonated
magnesium di-n-propylatel shows a medium-narrow band at
536 cm1 corresponding to the Mg-O bond, and an intense
band at 1,652 cm corresponding to the C=O bond of the
carbonate.
The molar ratio Mg/CO, is close to 1:1, thus the
formula of carbonated magnesium di-n-propylate is
CH,CH,CHZOMgOCOOCH CHzCH, [MgC7H14O9, molecular weight :
1861.
The solubility of carbonated magnesium di-n-
propylate in HFC 227 reaches values lying between 1 g%
up to 200 go. Thus it can be affirmed that the product
is soluble at any proportion. The carbonated magnesium
di-n-propylate is soluble in HFC 134a in analogue
proportions.
EXAMPLE 2
Preparation of carbonated magnesium di-n-propylate
2.1 Preparation of magnesium di-n-proipvlate
(Procedure C)
In a 5-litre round-bottomed flask, 3.750 ml of
anhydrous n-propanol are placed (3 kg, 50 mols),
prepared according to the procedure described in Example
1.1. Next, 146 g (6 mols) of magnesium metal are added
in the form of a powder with a granulometric
distribution lying between 50 and 100 m, along with 7.5
g of iodine as a catalyst. Next the mixture is heated
gently until hydrogen begins to be given off, and from
then on, as the reaction is strongly exothermic, the
reaction medium is cooled with a view to controlling the
CA 02339021 2001-01-30
18
rate of reaction at a gentle boiling for six hours until
hydrogen is not longer released and the last particles
of magnesium have disappeared. A suspension of
magnesium di-n-propylate, a light grey-coloured solid,
is obtained in n-propanol. The mixture is allowed to
cool before proceeding to the next step in the reaction.
770-800 g of product are obtained, with yields between
90-92%.
2.2 Preparation of carbonated magnesium di-n-prol2ylate
A current of carbon dioxide, completely anhydrous
after passing through two drying towers full of
anhydrite, is passed through the suspension of magnesium
di-n-propylate in n-propanol. The reaction is
exorthermic, reaching temperatures of 450 C. The solid
starting product [magnesium di-n-propylate] is
transformed into a soluble form consisting of carbonated
magnesium di-n-propylate. The reaction is over after 4-
6 hours. When the temperature drops to room temperature
the product is allowed to sediment out for 24-48 hours
until the solid dark insoluble particles are lying at
the bottom of the flask, and the solution appears clear
and transparent. This solution may be collected by
decantation or even better transferred by suction under
vacuum, to recipients appropriate for loading, dilution
or dosing. The magnesium content in this solution,
measured by complexometric titration, is greater than 5
%, which represents 40 o as carbonated magnesium di-n-
propylate.
The product is purified by total evaporation of n-
propanol under vacuum, and the Mg content analysed by
complexometric titration, and the CO2 content is
determined by decomposition of a sample with
concentrated phosphoric acid and collection of COz in a
series of towers containing a known excess of barium
hydroxide. The results obtained coincide with these
mentioned in Example 1.5.
CA 02339021 2001-01-30
19
EXAMPLE 3
Efficacy assays
In order to check the efficacy of a product for the
de-acidification of the cellulose-type material provided
by the invention some assays have been carried out to
determine the absorption of said product on a cellulose-
type material to assay, along with some assays to
determine the mechanical characteristics of the
cellulose-type material treated.
Parallel to this, by way of comparison, a
commercial paper de-acidification product [Bookkeeper]
of high efficiency has been assayed and the results
compared in each case.
3.1 Absorption assays
The absorption of the product for de-acidification
constitutes an indication of the alkaline reserve
created in the cellulose-type material. This reservoir
may piay an important role in combating the degradation
of cellulose by acid hydrolysis and, therefore, is going
to contribute to the better preservation of the
cellulose material.
In the assays carried out to check the efficacy of
the product provided by the invention the cellulose-type
material used was paper in different stages of ageing
(without ageing and submitted to accelerated ageing).
Briefly, the assay carried out consisted of
applying the product for de-acidifying the paper to the
sheets of paper, either to one side or to both sides,
and then determining the alkaline reserve created in the
paper. Assays have been affected in different
conditions of ageing of the paper. The results obtained
are shown in Tables 1-3.
3.1.A. Without ageing
The results obtained at zero time, in other words,
CA 02339021 2001-01-30
without submitting the paper to an accelerated ageing
process are shown in Table 1.
Table 1
5 Efficacy assay (Without ageing of the paper)
Initial Dry Humidity HC1 NaOH Alkaline
Sample weight weight (~) reserve
(g) (g) (mol/kg)
Bookkeeper 1.017 0.948 6.78 2.565 2.39 0.184
1 side
Bookkeeper 1.006 0.923 8.18 2.565 2.25 0.341
2 sides
Invention 1 1.012 0.910 10.9 2.565 2.01 0.609
side
Invention 2 1.006 0.905 10.1 2.565 1.5 1.176
sides
Bookkeeper: Commercial product comprising micronised magnesium
oxide, a humectant and a freon.
10 Invention: Solution of carbonated magnesium di-n-propylate and n-
propanol in an HFC diluent selected from HFC 134a and HFC 227, at 4
HC1: No. of HC1 equivalents.
NaOH: No. of NaOH equivalents.
As can be seen, the alkaline reserve created by the
product of the invention is very much better (a little
greater than three times better) than that created using
Bookkeeper.
3.1.B. Accelerated ageing (5 years)
Additional assays were carried out submitting the
paper to an accelerated ageing process, consisting of
keeping the paper in a chamber at a temperature of 90 C
and a relative humidity of 50 %. Under these
conditions, 1 hour of treatment of the paper is
equivalent to an ageing of 7.5 days. Next, the product
CA 02339021 2001-01-30
21
is applied to the aged paper with the cellulose-type
material to be de-acidified. In Table 2 the results
obtained after submitting the paper to a 10-day
treatment are shown. This period corresponds to an
ageing of the paper of 5 years.
Table 2
Efficacy assay (Accelerated ageing of the paper: 5 years)
Initial Dry Humidity HC1 NaOH Alkaline
Sample weight weight (~) reserve
(g) (g) (mol/kg)
Bookkeeper 1.015 0.962 5.57 2.565 2.40 0.171
1 side
Bookkeeper 1.011 0.964 4.27 2.565 2.23 0.347
2 sides
Invention 1 1.017 0.961 5.54 2.565 1.98 0.608
side
Invention 2 1.021 0.964 5.56 2.565 1.73 0.866
sides
Bookkeeper: Commercial product comprising micronised magnesium
oxide, a humectant and a freon.
Invention: Solution of carbonated magnesium di-n-propylate and n-
propanol in an HFC diluent selected from HFC 134a and HFC 227, at 4
%.
HC1: No. of HC1 equivalents.
NaOH: No. of NaOH equivalents.
Just as with the previous case, the alkaline
reserve created by the product of the invention is very
much better (between 2.5 and 3.5 times better) than that
created using Bookkeeper.
3.1.C. Accelerated ageing (10 years)
Other assays were carried out submitting the paper
to the treatment for accelerated ageing as mentioned
above [keeping the chamber at a temperature of 90 C and
CA 02339021 2001-01-30
22
the relative humidity at 50 %] for a period of 20 days,
which represents an ageing of the paper of 10 years.
Next, the product is applied to the aged paper with the
cellulose-type material to be de-acidified. The results
obtained are shown in Table 3.
Table 3
Efficacy assay (Accelerated ageing of the paper: 10 years)
Initial Dry Humidity HC1 NaOH Alkaline
Sample weight weight ($) reserve
(g) (g) (mol/kg)
Bookkeeper 1.023 0.984 3.75 2.565 2.39 0.177
1 side
Bookkeeper 1.028 0.977 4.95 2.565 2.32 0.250
2 sides
Invention 1.022 0.972 4.84 2.565 1.83 0.756
1 side
Invention 1.032 0.987 4.33 2.565 1.64 0.925
2 sides
Bookkeeper: Commercial product comprising micronised magnesium
oxide, a humectant and a freon.
Invention: Solution of carbonated magnesium di-n-propylate and n-
propanol in an HFC diluent selected from HFC 134a and HFC 227, at 4
%.
HC1: No. of HC1 equivalents.
NaOH: No. of NaOH equivalents.
Just as with the previous cases, but in an even
more noticeable fashion, the alkaline reserve created by
the product of the invention is very much better
(between 3.7 and 4.2 times approximately) than that
created using Bookkeeper.
3.2 Assay of mechanical prolperries
Through use of conventional methods (based on the
corresponding ASTM, ISO and TAPPI technical guidelines)
CA 02339021 2001-01-30
23
the tearing load, the stretching, the elastic limit, the
length of tear and the pH of the sheets of paper
treated, in one case with the product for de-
acidification of cellulose-type materials provided by
this invention [Invention], and in the other case with
Bookkeeper. The results obtained are shown in Table 4
where each value indicated represents the mean from 7
measurements. The pH is calculated with a mean of 5
values taken from different areas of the sheet of paper.
CA 02339021 2001-01-30
24
Table 4
Mechanical properties
[11 [21 [3] [41 [51 [61 [71 [81 191
Bookkeeper 0.184 55.8 3.64 16.8 0.84 4802 54.3 8.3
1 side, (4.2) (0.26) (3.5) (0.08) (360) (6.9)
0 days
Bookkeeper 0.171 55.4 2.30 17.4 0.81 4738 30.6 7.4
1 side (5.3) (0.28) (3.6) (0.09) (456) (7.8)
days
Bookkeeper 0.177 46.8 1.98 16.1 0.74 4070 19.9 8.2
1 side (5.3) 10.28) (8.2) (0.32) (462) (5.9)
days
Bookkeeper 0.341 54.5 3.69 14.3 0.80 4627 53.9 8.5
2 sides (3.2) (0.23) (4.1) (0.12) (272) (5.9)
0 days
Bookkeeper 0.347 49.4 2.17 16.8 0.80 4268 24.0 7.8
2 sides (3.8) (0.25) (2.9) (0.06) (329) (6.2)
10 days
Bookkeeper 0.250 52.1 2.22 17.4 0.82 4417 26.1 8.0
2 sides (3.0) (0.24) (6.2) (0.12) (225) (5.3)
20 days
Invention 0.609 56.3 3.54 15.9 0.81 4791 53.6 9.3
1 side (4.7) (0.25) (4.7) (0.12) (396) (8.8)
0 day
Invention 0.608 56.5 2.22 19.4 0.84 4736 29.3 8.0
1 side (8.8) (0.45) (5.3) (0.11) (742) (13)
10 days
Invention 0.756 60.3 2.58 20.1 0.85 5020 37.4 8.7
1 side (2.9) (0.18) (4.7) (0.08) (242) (6.0)
20 days
Invention 1.176 65.1 3.42 18.0 0.81 5316 58.6 10.2
2 sides (2.1) (0.08) (3.6) (0.13) (171) (3.0)
0 days
Invention 0.866 59.6 2.23 16.2 0.75 4879 30.1 8.4
2 sides (4.1) (0.29) (4.5) (0.08) (333) (7.3)
10 days
Invention 0.925 54.5 2.38 21.4 0.89 4596 30.7 9.1
2 sides (4.4) (0.36) (2.5) (0.06) (373) (8.6)
20 days
5 Key:
[1] : Sample
[2]: Alkaline reserve (mol/kg)
[3]: Tearing load (N)
[41: Stretching (mm)
CA 02339021 2001-01-30
[5]: Elastic limit (N)
[6]: Extension of elastic limit (mm)
[7]: Length of tear (m)
[8]: Traction energy absorption [T.E.A.] (J)
J [9] : pH
Invention: Solution of carbonated magnesium di-n-propylate and n-
propanol in an HFC diluent selected from HFC 134a and HFC 227, at 4
Bookkeeper: Commercial product comprising micronised magnesium
10 oxide, a humectant and a freon.
The values in brackets indicate standard deviations.
The results highlight the better behaviour of the
product of the invention compared to Bookkeeper.
