Note: Descriptions are shown in the official language in which they were submitted.
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W0 94/18153 PCT/EP94/00345
A process for the production of light-colored
polyol esters
Field of the Invention
This invention relates to a process for the produc-
tion of light-colored polyol esters, in which fatty acids
or fatty acid glycerol esters are esterified or trans-
esterified with polyols in the presence of lithium salts
and the reaction products are subsequently treated with
bleaching agents, to the products obtained by this
process and to their use as auxiliaries for plastics.
Prior Art
Various auxiliaries are used in the production and
processing of plastics. Their functions include, for
example, the reduction of friction during extrusion, the
antistatic finishing of the polymers and the protection
of the polymers against yellowing under the effect of UV
radiation. The most important ingredients of such
auxiliaries besides metal soaps and phosphorus compounds
are polyol esters which are normally prepared by esteri-
fication of fatty acids or by transesterification of
fatty oils with polyols, generally glycerol, in the
presence of catalytic quantities of tin salts.
Basically, tin salts are suitable esterification or
transesterification catalysts. For example, new rapeseed
oil rich in oleic acid can be transesterified with
glycerol in the presence of l to 2% by weight of tin
oxalate, based on the oil, over a period of 8 hours to
form a mixture of mono- and diglycerides in satisfactory
yields. Unfortunately, a disadvantage in this regard is
the high tin content of the products which is undesirable
for applicational reasons. Accordingly, instead of
laboriously removing the tin from the partial glycerides,
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the catalysts are normally used in small quantities of,
typically, 0.02 to 0.04% by weight. Although partial
esters with a tolerably low tin content can be produced
in this way, the advantage of the low catalyst concentra-
tion is offset by the disadvantage of considerably longerreaction times. Another very crucial disadvantage is
that the use of tin catalysts, especially where unsatu-
rated starting materials are used, leads to products of
inadequate color quality which can only be lightened with
hydrogen to a very limited extent, if at all.
Accordingly, the problem addressed by the present
invention was to provide a process for the production of
light-colored polyol esters which would be free from the
disadvantages mentioned above.
` 15
Description of the Invention
The present invention relates to a process for the
production of light-colored polyol esters in which fatty
acids or fatty acid glycerol esters are subjected to
esterification or transesterification with polyols in the
presence of 0.001 to 0.1~ by weight, based on the fatty
compounds, of lithium salts and the resulting polyol
esters are subsequently treated with bleaching agents in
known manner.
It has surprisingly been found that not only are
lithium salts capable of catalyzing the esterification or
transesterification reaction and considerably shortening
the reaction time in - comparatively - very low concen-
trations, they also lead to polyol esters which are very
much easier to bleach, for example with hydrogen perox-
ide, than the known products. Another advantage of the
process according to the invention is that there is no
need for neutralization and/or removal of the lithium
salts in the polyol esters because the small quantities
used do not adversely affect either the properties of the
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WO 94/18153 3 PCT/EP94/00345
products or their further processing behavior.
Raw materials
The fatty acids are aliphatic carboxylic acids
corresponding to formula (I):
RlCO-OH ~I)
in which R1CO is a linear or branched aliphatic, optional-
ly hydroxy-substituted acyl radical containing 6 to 22
carbon atoms and 0 or 1 to 5 double bonds.
Typical examples are caproic acid, caprylic acid,
isononanoic acid, capric acid, undecanoic acid, lauric
acid, myristic acid, palmitic acid, palmitoleic acid,
stearic acid, isostearic acid, oleic acid, elaidic acid,
petroselic acid, linoleic acid, linolenic acid, elaeo-
stearic acid, ricinoleic acid, 12-hydroxystearic acid,
arachic acid, gadoleic acid, behenic acid and erucic acid
and the technical mixtures thereof obtained, for example,
in the pressure hydrolysis of fats and oils or in the
oxidation of aldehydes from Roelen's oxo synthesis.
Fatty acids containing 16 to 18 carbon atoms and 0 or 1
double bond, for example technical tallow fatty acid, are
preferably used.
The fatty acid glycerol esters are triglycerides
corresponding to formula (II):
CH20-CO-R2
I
CH-o-co-R3 (II)
C~2o-Co-R4
in which R2C0, R3Co and R4Co independently of one another
represent linear or branched aliphatic, optionally
hydroxy-substituted acyl radicals containing 6 to 22
carbon atoms and 0 or 1 to 5 double bonds.
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Wo 94/18153 4 PCT/EP94/00345
Typical examples are synthetic, but preferably
natural fatty acid glycerol esters of vegetable or ~n;m~l
origin, for example based on palm oil, palm kernel oil,
coconut oil, rapeseed oil from old and new plants,
sunflower oil from old and new plants, castor oil,
soybean oil, peanut oil, olive oil, linseed oil, beef
tallow or fish oil, and chemically modified triglycerides
of the so-called "soya polyol~ type which are obtained by
epoxidation of soybean oil and subsequent opening of the
oxirane rings with suitable nucleophiles, for example
alcohols. Vegetable triglycerides with a high percentage
content of unsaturated fatty acids, especially those
based on rapeseed oil and sunflower oil from new plants,
are preferably used.
Suitable polyols are compounds containing at least
2 and preferably 3 to 5 hydroxyl groups. Typical exam-
ples are glycerol, oligoglycerols with an average degree
of oligomerization of 1.5 to 10, trimethylol propane and
pentaerythritol. Glycerol is preferably used. Accord-
ingly, the preferred products obtainable by the process
according to the invention are fatty acid glycerides,
more particularly technical mixtures of mono- and digly-
cerides.
Lithium salts
Suitable lithium salts besides lithium hydroxide are
lithium soaps, i.e. salts of lithium with optionally
hydroxy-functionalized fatty acids containing 6 to 22
carbon atoms and 0, 1, 2 or 3 double bonds. Typical
examples are the lithium salts of caproic acid, caprylic
acid, capric acid, lauric acid, myristic acid, palmitic
acid, palmitoleic acid, stearic acid, oleic acid, elaidic
acid, petroselic acid, linoleic acid, linolenic acid, 12-
hydroxystearic acid, ricinoleic acid, arachic acid,
gadoleic acid, behenic acid or erucic acid. The lithium
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salts may be used in the form of aqueous or alcohol
solutions. By virtue of the fact that they are easy to
dose, the lithium salts of unsaturated fatty acids -
which are liquid in any case - are preferably used. The
lithium soaps may be directly added to the reaction
mixture, although they may also be formed in situ, for
example from lithium hydroxide and a fatty acid ester.
The quantity of lithium salts used may be from 0.001
to 0.1% by weight, preferably from 0.002 to 0.05% by
10 weight and more preferably from 0.004 to 0.01% by weight,
based on the starting materials. Since lithium lons can
interchange with the alkali metal ions present in glass,
which can lead to a reduction in the concentration of
lithium ions, it is advisable to carry out the process in
lS apparatus of steel or similarly inert materials. The use
of lithium carbonate together with aluminium oxide for
the autocondensation of glycerol is known from JP Patent
Abstract 13, 372 tC-627)(3270) 17.
Esterification or transesterification and bleaching
The molar ratio of fatty acids or fatty acid glycer-
ol esters to polyols may be from 10:1 to 1:10 and is
preferably from 3:1 to 1:3. The esterification or
transesterification may be carried out in known manner at
25 temperatures of 100 to 250C. The esterification or
transesterification may be complete, i.e. all the avail-
able hydroxyl groups are saturated. However, one prefer-
red embodiment of the invention seeks to achieve only
partial esterification or transesterification. Partial
in this context means a degree of esterification of 10 to
95 and preferably 25 to 75% of the available hydroxyl
groups. It is pointed out that the expert is capable of
controlling the degree of esterification through the
ratio in which the starting materials are used without
having to become involved in inventive activity.
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WO 94/18153 6 PCT/EP94/00345
~ Bleaching may also be carried out in known manner by
adding, for example, 0.3 to 1% by weight and preferably
0.2 to 1% by weight, based on the polyol esters, of
hypochlorite or preferably hydrogen peroxide to the
polyol esters and stirring for 0.5 to 2 h.
The present invention also relates to light-colored
polyol esters which are obtained by subjecting fatty
acids or fatty acid glycerol esters to esterification or
transesterification with polyols in the presence of 0.001
to 0.1% by weight, based on the fatty compounds, of
lithium salts and subsequently treating the resulting
polyol esters with bleaching agents in known manner.
Industrial applications
The light-colored polyol esters obtainable by the
process according to the invention improve slip behavior
in the production of polymers, are suitable for the
antistatic treatment of plastics and have a color-stabil-
izing effect against W radiation.
Accordingly, the present invention also relates to
the use of the light-colored polyol esters obtainable by
the process according to the invention as auxiliaries for
plastics in which they may be present in quantities of
0.1 to 5% by weight and preferably in quantities of 0.5
to 1.5% by weight, based on 100 parts of plastic.
Typical examples of auxiliaries of the type men-
tioned are lubricants, antistatic agents and W stabiliz-
ers. In this connection, the light-colored polyol esters
may be used together with other typical starting materi-
als, for example metal soaps, optionally oxo- or hydroxy-
substituted fatty acids, optionally chemically modified
hydrotalcites, alkyl phosphates, alkyl phosphites,
diketones, epoxidized fatty acid lower alkyl esters or
glycerol esters and the like. Suitable plastics are, in
particular, PVC and polycarbonate.
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WO 94/18153 7 PCT/EP94/00345
~ The following Examples are intended to illustrate
the invention without limiting it in any way.
ExamPles
Example 1:
a) Transesterification. 475.3 g (0.5 mole) of rapeseed
oil from new plants (oleic acid content approximate-
ly 60% by weight) and 27.3 g (0.3 mole) of glycerol
were introduced into a l-liter four-necked-spherical
flask equipped with a stirrer and thermometer and
surmounted by a descending condenser. At the start
of the transesterification reaction, another 4.0 g
(0.04 mole) of glycerol and 12 g (0.04 mole) of
technical oleic acid (Edenor~ TiO5, a product of
Henkel KGaA, Dusseldorf, FRG) and - as catalyst -
0.02 g of lithium hydroxide, corresponding to 0.004%
by weight based on the triglyceride, were added to
the mixture. The reaction mixture was heated with
stirring to 200C and the water of reaction was
continuously removed by application of a light
vacuum. After a reaction time of 4 h, the content
of free glycerol in the mixture was still about 1%
by weight. The crude reaction product was cooled to
90C and filtered after the addition of 0.5% by
weight, based on the reaction product, of bleaching
earth.
The clear light-yellow oil obtained had a
Lovibond color value (1 inch cuvette) of yellow 5.8
and red 1.8.
b) Bleaching. Aqueous hydrogen peroxide (35% by
weight) was added to part of this oil in a quantity
of 0.5% by weight, based on the oil, followed by
stirring for 30 minutes at 90C. A light vacuum was
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WO 94/18153 8 PCT/EP94/00345
~ then applied, the mixture was heated for 90 minutes
to 105C and the water was removed. The resulting
clear and distinctly lightened oil had a Lovibond
color value (1 inch cuvette) of yellow 3.3 and red
0.3.
Comparison Example Cl:
a) Transesterification. Example 1 was repeated using
475.3 g of new rapeseed oil, 31.3 g of glycerol and
12 g of oleic acid. Instead of the lithium salt,
however, 0.1 g of tin oxalate (corresponding to
0.02% by weight, based on the triglyceride) was used
as the catalyst. In this case, however, the limit-
ing value of the residual glycerol content of around
1% by weight was only reached after a reaction time
of 13 h.
b) Bleaching. Part of the oil was bleached with
hydrogen peroxide as in Example 1. The resulting
clear, but not lightened oil had a Lovibond color
value (1 inch cuvette) of yellow 3.4 and red 1Ø
