Note: Descriptions are shown in the official language in which they were submitted.
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Docket
Case D 7923 CA
A PROCESS FOR THE PRODUCTION OF ALKYL GLUCOSIDES
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention is a new improved process for the production
of alkyl qlucosides by the transacetalization method using
propylene glycol.
Renewable raw materials are being used to an increasing
extent for the development and production of new surface-active
materials which are suitable as industrial surfactants for the
production of detergents and cleaning preparations. Hitherto,
oleochemical raw materials such as, for example, fatty acid,
fatty acid esters and fatty alcohols, have mainly come into
consideration for this purpose. Recently, surface-active alkyl
glucosides, which are acetals of glucose and fatty alcohols, have
acquired interest in this regard. The term alkyl glucoside is
intended to encompass alkyl monoglucosides and also alkyl
oligoglucosides and alkyl polyglucosides, but especially mixtures
of mono- and oligoglucosides.
The term "alkyl" in alkyl glucoside applies to the residue
of the corresponding primary alcohols of natural and/or synthetic
origin preferably containing C8 to C18 alkyl or alkenyl radicals.
The most important saccharide starting material in practice are
the anhydrous polyglucose compounds widely available in nature,
of which the individual glucose units are present in ~-glucosidic
linkage. The most important natural starting material of this
type is starch which is formed worldwide by useful plants of
various kinds, for example potatoes, corn, tapioca, rice and the
like. Powder-form starches and their partial degradation
products, for example in the form of a corresponding, generally
highly concentrated glucose syrup, are available as comparatively
inexpensiYe starting materials.
The sixties and seventies saw a number of proposals for the
production of alkyl glucosides which were concerned in particular
with two measures. First, it was proposed not to use the
polyanhydroglucose components as such on account of the high
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,ensitivity of polysaccharides to the high temperatures and
pressures hitherto required in the production of alkyl
glucosides, but instead to degrade this starting material of
natural origin to monosaccharide, i.e. to glucose, which could
then be subjected to acetalization as an anhydrous material or
as glucose hydrate.
The second measure adopted makes use of the fact that lower
alcohols and glycols, particularly those having an alkyl chain
length in the C3 5 range, lead comparatively easily to the desired
acetalization of the monosaccharide. However, the resulting
acetals of the monosaccharide show inadequate surfactant
properties. They are converted by transacetalization with the
relatively long-chain (Cg18) monofunctional alcohols into the
desired alkyl glucoside reaction products having surface-active
properties. This apparently comparatively simple method of
production is attended in practice by numerous difficulties, such
as the production of light-colored, color-stable alkyl glucosides
which remain color-stable above all in alkaline medium.
RELATED ART
European patent application 102 558 (corresponding to US
4,704,453) describes the production of long-chain alkyl glucoside
mixtures by transacetalization of C35 alkyl glucosides. This
process starts out from glucose. European patent application 99
133 describes the conversion of saccharides, particularly
2S polysaccharides, such as starch, into glucoside mixtures using
alcohols containing at least 3 carbon atoms. In this case, the
reaction is said to be carried out in the presence of at least
2 mol water per molar saccharide unit and in the presence of, in
particular, acidic catalysts. Preferably, the liquid phase used
to disperse the polysaccharide compound additionally contains an
alcohol-soluble organic auxiliary solvent. Alkanols containing
3 to 6 carbon atoms and, in particular, 3 or 4 carbon atoms
proved to be particularly suitable alcohols for forming the alkyl
glucoside compounds. According to European Patent Application
99~83, the lower alkyl glucosides formed in this way may be used
as intermediate compounds in the production of surface-active
alkyl glucoside compounds, although no particulars of this
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ubsequent reaction step are provided in the disclosure.
US-PS 3,772,269 describes the production of alkyl glucosides
from a saccharide component and relatively long-chain
monofunctional alcohols essentially containing C82s alkyl or
al~enyl chains b}T the transacetalization method using aliphatic
C3 5 glycols, preferably propylene glycol. In a first step,
glycol, higher alcohol containing a primary or secondary OH
group, saccharide, preferably glucose, although oligo- or
polysaccharides may also be used, and an acidic catalyst are
mixed together and the resulting mixture is subsequently heated
to reaction temperature which is between 70 and 160C, depending
on the components used. The reaction mixture is worked up by
methods known E~E se. The products obtained are distinguished
by a high content of glycol glucosides or of fatty alcohol
glucosides, depending on the process conditions. However, to
obtain products having a high content of fatty alcohol glucosides
generally meant that a large excess of fatty alcohol over the
glycol had to be used. The quality of the products in regard to
color and alkali stability is not mentionsd.
The problem addressed by the present invention is to convert
the polysaccharides available as natural starting materials in
the form of starches or their partial degradation products into
surface-active alkyl glucoside compounds in such a way that no
intermediate stages have to be isolated and the reaction products
show the requisite light color, color stability and, in
particular, alkaline color stability.
BRIEF DESCRIPTION OF THE INVENTION
Accordingly, the present invention relates to a process for
the production of alkyl glucosides from a saccharide component
and relatively long-chain monofunctional alcohols containing C8
18 alkyl or alkenyl chains by the transacetalization method using
propylene glycol, characterized in that a saccharide component
(B) containing starch or partial starch degradation products is
added to a reaction medium (A) containing at least propylene
glycol and an acidic catalyst and, optionally, higher fatty
alcohol, which has been heated to 100 to 130C, the alcohol
~ontaining a primary OH group and the molar ratio of higher
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.lcohol to propylene glycol being at most 1.
DETAILED DESC~IPTION OF THE INVENTION
Polysaccharides are particularly useful as the glucose
starting material. The preferred polysaccharide for processing
by the process according to the invention is starch of any origin
and/or partial starch degradation products of the type available
in the form of generally highly concentrated aqueous syrup-like
products as used herein saccharide component refers to starch or
starch partial degradated products.
The useful alcohols comprise monofunctional aliphatic alco-
hols, particularly primary C818 alcohols. Preferred alcohols are
linear alcohols of natural origin (fatty alcohols), although
synthetic primary alcohols, such as for example the so-called oxo
alcohols, which contain a per~entage, generally 20 to 40%, of
branched isomers containing a 2-methyl group are also suitable.
Accordingly, typical suitable alcohols are decanol, dodecanol,
tetradecanol, hexadecanol, octadecanol and 2-methyl undecanol and
also mixtures of C10, C12 and C~4 alcohols.
Paratoluenesulfonic acid is preferably used as the acidic
catalyst by virtue of its less corrosive effect on apparatus and
pipes of steel by comparison with sulfuric acid. However, any
acidic compound, including the acids of phosphorus and Lewis
acids, which catalyze the acetalization reaction between a fatty
alcohol and a sugar molecule, are basically suitable as
catalysts.
In one preferred embodiment of the process, a reaction
medium (A) containing propylene glycol in quantities of 3 to 8
mol per mol saccharide (expressed as anhydroglucose) and an
acidic catalyst in a quantity of 0.01 to 0.03 mol per mol of the
glucose unit present in the saccharide used is heated to a
reaction temperature of 100 to 130C. The saccharide component
(B) containing starch or partial starch degradation products is
then added to this preheated mixture (A) in such a way that the
reaction mixture always remains a clear solution. It has proved
to be preferable in terms of process technology to add a
saccharide component (B) in which the saccharide is suspended in
propylene glycol. Quantities of 2 to 4 mol propylene glycol per
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.ol anhydroglucose units are preferably used. The saccharide
component (B) may be added both in portions and also
continuously, continuous addition of the saccharide component (B)
being the preferred embodiment.
The propylene glycol glucoside obtained as intermediate
product does not have to be isolated because water and excess
propylene glycol are removed under a reduced pressure of the
order of 100 mm Hg with simultaneous introduction of the higher
fatty alcohol preferably preheated to 90 to 100C. The fatty
alcohol is used in quantities of 3 to 8 mol per mol
anhydroglucose units, the molar ratio of fatty alcohol to
propylene glycol being at most 1. In one preferred embodiment,
the fatty alcohol to be added to the reaction mixture formed by
mixing of the (A) and (B) is mixed with 0.5 to 1 mol propylene
glycol per mol fatty alcohol which facilitates a synchronous
propylene glycol/fatty alcohol exchange.
In another preferred embodiment of the process according to
the invention, a mixture containing propylene glycol and the
acidic catalyst in the quantities shown above and, in addition,
higher fatty alcohol in quantities of 3 to 8 mol per mol
anhydroglucose units is used as the reaction medium (A). The
saccharide component (B) is added to the heated reaction medium
(A) as described above. Water and propylene glycol are then
removed by distillation at a temperature of 115 to 120C by
reduction of the pressure in stages from 100 to 15 mm Hg. The
propylene glycol recovered, which may also contain fatty alcohol,
can be recycled.
Accordingly, another preferred embodiment of the process
according to the invention is characterized by the use of a
reaction medium (A) which contains propylene glycol and catalyst
in the quantities shown, but only a portion of the total fatty
alcohol to be used. The remaining fatty alcohol is then
introduced into the intermediate propylene glycol/glucoside
mixture as described above.
The end product obtained by the process according to the
invention is purified and worked up by methods known per se as
described in detail in the literature cited at the beginning and
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n German patent application 37 23 826.
In the process according to the invention, neutralization
of the acid-catalyzed reaction product is preceded by filtration
to remove the unreacted saccharide which may then be reused as
starting material for another batch.
The acidic catalyst may be neutralized with organic or
inorganic basic alkali or, more particularly, alkaline earth
compounds, preferably organomagnesium compounds, such as
magnesium alcoholates, or inorganic magnesium compounds, such as
magnesium oxide or magnesium hydroxide. pH values of at least
8 and preferably of from about 9 to 10 are preferably
established. The establishment of these pH values improves the
color stability of the surfactant in alkaline medium during
storage and in particular during its subsequent processing.
After - another - filtration, the excess fatty alcohol may
be distilled off in known product-friendly vacuum distillation
units. The use of thin-layer evaporators and/or falling-film
evaporators is particularly suitable for this purpose. The fatty
alcohol recovered can be returned to the process.
After cooling, the end product of the reaction is a pale
yellowish wax-like mass which may advantageously be converted
into an aqueous paste having an active-substance content of
approximately 60% in the interests of better handling. Where the
color of the end product has to satisfy particularly stringent
requirements, production of the aqueous paste may be accompanied
by bleaching with hydrogen peroxide or an organic peracid or
corresponding peracid salts to obtain additional color
lightening. A further addition in the form of sodium hydroxide
or a sodium hydroxide/citric acid buffer has proved to be
appropriate.
The color stability of the product is determined by a simple
test. A sample quantity of the product is mixed with water to
form an approximately 50% paste to which concentrated sodium
hydroxide is added at normal temperature to establish a pH value
of about 12 to 13, followed by heating for 60 minutes to lOODC.
In the case of mixtures containing process products, little or
no change in color occurs after this treatment. The color values
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,f the products were determined by the KLETT method (5% solution
in water/isopropanol 70 : 25, l cm cell, blue filter). It is
possible by this method to simulate long-term storage tests of
the product under standard conditions and also methods for
further processing of the stored product, in particular to
detergents and cleaning preparations, and the associated alkaline
conditions. The end products of the process preferably have
Klett values of less than 35.
It has been found that the presence of propylene glycol
glucoside in the end reaction product can be of advantage so
that, in one preferred embodiment, the production process is
displaced in such a way that at most 15% by weight propylene
glycol glucoside remain in the reaction mixture. The residual
content of propylene glycol glucoside may be obtained by
premature termination of the transacetalization or by variations
in the quantity of distillate obtained during removal of the
excess propylene glycol. The presence of the propylene glycol
glucoside not only improves the flow properties of the reaction
mixture, thereby facilitating the removal of fatty alcohol, it
also improves the color and alkaline stability of the end
product, so that bleaching of the end product is not absolutely
essential.
The present invention also relates to certain alkyl
glucoside mixtures as new products obtainable by the process
according to the invention. One preferred embodiment contains
less than 3% by weight residual fatty alcohol. Another preferred
embodiment contains 50 to 65% by weight alkyl monoglucoside, 8
to 15% by weight alkyl diglucoside, 2 to 5~ by weight alkyl
triglucoside, at most 3% by weight residual fatty alcohol, 5 to
15% by weight propylene glycol glucoside and 5 to 20% by weight
polyglucose. In all the products, the free glucose content is
preferably less than 1% by weight.
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E X A M P L E S
Example 1
Potato starch was processed by the single-step process
according to the invention to a reaction product containing
surface-active alkyl glucoside compounds. The following starting
materials were used in the quantities shown:
5.77 kg potato starch (water content 18%), corresponding
to 4.73 kg starch (anhydrous) and 1.04 kg water
13.80 kg propylene glycol, of which 8.13 kg were in-
troduced at the outset and 5.67 kg in admixture
with the starch
kg Cl2 ~4 fatty alcohol (native basis; mixture of
approx. 75% by weight dodecanol and approx. 25%
by weight tetradecanol)
128 g paratoluenesulfonic acid monohydrate
134 g magnesium methylate for neutralization
The propylene glycol and C1214 fatty alcohol were introduced
together with the catalyst and heated to approximately 120~C.
When that temperature had been reached, the slurry consisting of
propylene glycol and potato starch began to be added either
continuously or in 3 portions, the next portion being added as
soon as the reaction mixture was clear. The addition was
terminated after about 50 minutes. To remove the starch
moisture, the pressure was reduced (100 mm Hg) immediately after
the last addition. 1.7 kg liquid (water and propylene glycol)
distilled off.
Another 11 kg liquid (93~ by weight propylene glycol/ 7%
weight C12~4 fatty alcohol) were distilled off at llS to 120-C by
reduction of the pressure in stages (100/7S/S0/ 20/15 mm Hg).
It was found to be appropriate in this regard to heat the
ascending "cooler" to 80C. The reaction mixture was neutralized
with magnesium methylate for 30 minutes at 80~C and adjusted to
a pH value of 9 to 10. Undissolved magnesium methylate (residue
100 g) was then filtered off through an 80 ~m filter bag.
The excess fatty alcohol was distilled off in a thin-film
evaporator in a vacuum of approximately 1 torr and at a sump
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_emperature up to about 160C.
After venting with nitrogen, a sample of the melt was taken
for analytical purposes. The C1214 glucoside thus s~nthesized
consisted essentially of 56% by weight monoglucoside, 12% by
weight diglucoside, 3% by weight triglucoside, 12% by weight
polyglucose, 5~ by weight propylene glycol glucoside and 3% by
weight residual fatty alcohol. The free glucose content was less
than 1% by weight. The OH value was 652. After the melt had
been cooled to 100C, 5 5 kg water preheated to 70 to 80C were
added and, at the same time, the product was bleached with 0.5%
hydrogen peroxide (based on active substance) for 1 hour at pH
10 (addition of sodium hydroxide).
The product obtained in this way had a Klett value of 10
(after the color stability test: 15). A comparable quality
(Klett value 31.7) without subsequent bleaching was shown by only
one product in the production of which only 83% of the propylene
glycol had been distilled off (see Table 1).
Example 2
Potato starch was processed by the multistage process
according to the in~ention to a reaction product containing
surface-active alkyl glucoside compounds. The following starting
materials were used in the quantities shown:
5.77 kg potato starch (water content 18%) corresponding
to 4.73 kg starch (anhydrous) and 1.04 kg water
27.55 kg propylene glycol, of which 8.13 kg were in-
troduced at the outset, 5.67 kg in admixture with
the starch and 13.75 kg together with the fatty
alcohol
kg C1214 fatty alcohol (native basis; mixture of
approx. 75% by weight dodecanol and 25% by weight
tetradecanol)
128 g paratoluenesulfonic acid monohydrate
134 g magnesium methylate for neutralization
35 The propylene glycol and catalyst were initially introduced
together and heated to approximately 120C. The slurry of
propylene glycol and starch was added as in Example 1. After the
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starch moisture (quantity of distillate: 1.7 kg liquid of water
and propylene glycol) had been removed, the mixture of propylene
glycol and fatty alcohol preheated to 90 to 1004C was introduced
in a vacuum of 10~ mm Hg.
The removal of propylene glycol by distillation and the
working up of the product mixture were carried out as in Example
1.
Neither the composition nor the quality of the reaction
product differed significantly from the data of the product
obtained in accordance with Example 1.
In further tests, complete transacetalization was carried
out (0% by weight propylene glycol glucoside in the end reaction
product).
Where MgO was used as the neutralizing agent, a product of
high color quality (Klett value: 15, after the color stability
test: 20) was also obtained with subsequent bleaching (see Table
1). :
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- Table 1
Determination of the Klett values of C1214 glycoside
(5% solutions in H2O: isopropanol = 70 : 25)
.
Neutra- Bleaching % by weight Remarks Klett Color of
lizing yes/no propylene value paste
agent glycol
glucoside
Mg(OEt~2 + 5 ~ 10 Light yellow
Mg(OEt) 2 + 5 pH 12** 15 Light yellow
1 hour,
100 C,
Mg(OEt)2 - lS 83% PG* 31.7 Light yellow
distil-
led off
MgO + - - 15 Light yellow
MgO + _ pH 12**, 20 Light yellow
1 hour,
100 C
NaOH/MgSO4 + - - 27 Light yellow
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NaOH/MgSO4 + - pH 12**, 51.5 Dark yellow
1 hour,
100 C
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NaOH + - - 50 Dark yellow
,45 * PG = propylene glycol
** Color stability test
11
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