Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to solid phosphorous
acid ester preparations stable to hydrolysis and having an
improved stabilizing effect in plastics materials.
Phosphorous acid esters gain in importance as anti-
oxidants in stabilizing systems for plastic materials, inparticular for the mass products polyethylene, polypropy-
lene and polyvinyl chloride. Solid products in the form of
powders or scales are preferred to liquid products, owing
to the fact that they can be easier dosed and that they
are easier misciblenot only with the plastic material, but
also with the other components of the total stabilizing
composition. However, a weighty disadvantage of these pro-
ducts resides in the fact that they h-ydrolyze rapidly in
humid air, partially even in the package, during the tran-
sport to the consumer and in particular during storageor when the package is opened thereby losing their action
as stabilizer. Then the hydrolysis products react with
other components of the stabilizing system, such as metal
soaps to give insoluble compounds which render the plastic
turbid and can even notably disturb or interrupt the
production course.
The present invention searchs to surmount these dis-
advantages of the solid phosphorous acid esters and to
- hinder a hydrolysis thereof or to reduce it considerably,
without impairing their efficiency.
Attempts have been made in the past to improve the
stability to hydrolysis of phosphorous acid ester stabi-
lizers. For example, German Offenlegungsschrift No.
2,626,225 points to the possibility of adding small quan-
tities of an amine, proposed at an earlier date. This
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procedure has the disadvantages that the stabilizing ac-
tion is very brief and that rather inconvenient discolo-
rations occur, when using the phosphite treated according
to this process, for example in polyvinyl chloride.
The same Offenlegungsschrift recommends the addi-
tion of metal salts of organic acids as a more convenient
method. However, hydrolysis cannot be prevented by such a
procedure. Only following reactions thereof, which become
evident in a pH reduction, can be combated. Hence, this
method does not exclude the above mentioned sieve obstruc-
tion during the plastic processing and a turbidity of the
latter.
It has now been found that the hydrolysis of solid
phosphorous acid esters can be substantially avoided and
in addition that the stabilizing action of these esters in
plastic materials can be considerably increased when com-
bining them with highly hydrophobic waxes.
The invention, consequently, relates to solid, phos-
phorous acid ester preparations stable to hydrolysis and
having an improved stabilizing effect in plastic materials,
which preparations consist from 20 to 97 ~ by weight of a
phosphorous acid ester known per se as stabilizer for
plastics and from 80 to 3 % by weight of a wax.
The preparations according to the invention are di-
stinguished by an excellent stability to hydrolysis and bythe surprising fact that their stabilizing effect is
higher than that of the pure phosphite. This was not to
be expected, since the waxes to be added do not have a
29 stabilizing effect in plastics. On the contrary, the con-
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tent of phosphite groups acting as stabilizers is reduced
by the addition of waxes. It is astonishing that the sta-
bilizing action is not reduced as a consequene of this di-
lution effect, but that on the contrary an enormous impro-
vement of this effect can be observed. Apparently the phos-
phorous acid ester and the wax exert a synergistic action.
The improvement of the efficiency of the phosphites
of the lnvention combined with waxes applies not only to
the processing stability of the plastic but also to its
long-duration stability. For example, the reduction of
the viscosity occuring when submitting the plastic to a
multiple extrusion is retarded considerably when adding
to the plastic instead of the pure phosphite an identical
quantity by weight of a mixture of wax and phosphite.
The long-duration stability of the plastic is in-
fluenced in similar advantageous manner. For example, in
this case, the resistance to ageing under heat is improv-
ed considerably when adding instead of pure phosphite an
identical quantity by weight of the combination of phos-
phite and wax.
Hence,,the use of the phosphorous acid ester prepa-
rations'according to the invention makes it possible to
replace a part of the expensive phosphite by the far less
expensive wax, thus even increasing the stabilizing ef-
fect.
A further advantage Or the phosphorous acid esterpreparations resides in the fact that their distribution
in the plastic material during processing is accelerated.
29 It is quite natural that this effect is ,especially di-
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stinct with high melting phosphite compounds. However,
the influence on rather low melting phosphites is advan-
tageous as well. It was not to be expected at all that
the combination of a wax and a phosphite stabilizer re-
sults in a more rapid and more thorough distribution there-
of in the plastic.
Finally in some cases a distinct rise of the melting
point can be observed when adding a few weight ~ of wax
to the phosphite. This effect is surprising, since the
melting point of a substance drops generally, as a conse-
quence of impurification. The increase of the melting
point is especially advantageous when it is intended to
use the phosphite for the so-called Bunker stabilization
of polyolefin powder. In this process the plastic powder
obtained after polymerization has a temperature of from
about 60 to 80C. Stabilizer mixtures that contain a low-
er melting phosphite, agglomerate at this temperature.
Thus, their homogeneous distribution in the plastic
powder is rendered rather difficult. This advantage can
be avoided when using phosphites, whose solidification
point is increased by adding waxes. A further advantage
of these phosphites resides in the fact that they can be
easier confectionned by spraying or flaking and that their
tendancy to agglomerate under the action of heat and pres-
sure is less pronounced than that of untreated phosphites.
Finally, it is surprising that the volatility of thephosphites at elevated temperature is enormously reduced
by the addition of waxes or is even completely suppressed
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in the case of a rather high portion of wax. This effect
is of great importance since it makes sure that in the
course of the plastic processing present persons are not
exposed to vapors that might be injurious to health.
Known phosphorous acid esters that are suitalbe for
the stabilization of plastics include solid, organic phos-
phites, for example di-stearylphosphite, tri-stearylphos-
phite, preferalby pentaerythritylphosphites as disclosed,
for example, in German Offenlegungsschriften Nos.
2,219,695; 2,347,977; 2,621,323; 2,630,257; 2,431,623 and
German Patents 1,237,312 and 2,505,152; sugar alcohol
phosphites as disclosed in German Offenlegungsschriften
Nos. 2,633,392, 2,633,393 and solid triarylphosphites as
disclosed in German Offenlegungsschrift 2,606,358. In
the case of the latter compounds, the occasional undesir-
ed high melting point may be lowered by the addition of
waxes and the particularly high tendancy to sublimate at
elevated temperature may be reduced as well by this me-
thod.
By waxes there are understood products that contain
of from 20 to about 500, preferably of from 30 to 250 car-
bon atoms in the molecule and that are covered by the ge-
neral definition of the term "wax" according to the DGF
standard methods M I1 (75) . ( DGF means the German
Society for Fat Investigation). Examples thereof are paraf-
fins, for example refined cake paraffins having a melting
point in the range from about 40 to about 80C, micropa-
raffins, synthetic paraffins having a melting point in the
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range from 80 to 130C, long chain plant and insect waxes
such as carnauba wax, cadelilla wax, partially synthetic
ester waxes such as montan wax derivatives, synthetic waxes
such as amide waxes, for example distearylethylene-diamide,
polyolefin waxes such as polyethylene and polypropylene
waxes having a molecular weight in the range of from about
2,000 to 10,000; polyethylene wax oxidates and esters
thereof which may be obtained by addition of dialkylphos-
phites to long chain ~olefins in the presence of free
radical-forming catalysts. Mixtures of said waxes like-
wise be used. Preference is given to ethylene polymeriz-
ed waxes and amide waxes, in particular to the latter.
The proportion of wax in the wax-phosphorous acid ester
preparations according to the invention should be between
3 and 80 ~, preferably between 5 and 40 %, by weight.
The preparations according to the invention are ob-
tained preferably in the following manner: The wax and
the solid phosphorous acid ester are melted together. Then
the molten product is confectioned in known manner, for ex-
ample by flaking, spraying, centrifugation or, after,standing, by grinding. It is possible, to addd to the
wax-phosphite melt also some components or all components
of a total stabilization system such as phenolic antioxi-
dants, for example substituted tertiary butylphenols, or-
ganic sulfides such as thioglycolic acid esters or di-
stearylsulfide; metal sslts of fstty acids, such as stea-
rates, laurates, or montanates of calcium, a barium, mag-
nesium, cadmium, zinc and lead; light stabilizers such as
29 benzophenones, triazoles or hindered amides. These stabi-
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lizers often have a wax-like character and are thus capa-
ble of intensifying the hydrolysis-avoiding action of the
wax. In the case of a total stabilization system there
is chosen that individual compound of the series of wax
types that guarantees the homogeneity of the melt of the
total mixture. This mode of operation has the additional
advantage that in a later step all stabilizers may be ad-
mixed to the plastic in one operation.
A further possibility of manufacturing the prepara-
tions according to the invention consists in coating dis-
crete particles of the phosphorous acid ester to be pro-
tected with a wax film, for example by applying the wax
as melt or dissolved in a solvent onto the phosphite par-
ticles prior to or after spraying or flaking the phosphite.
The preparations according to the invention are em- ~ -
ployed for the stabilization of plastic compositions bas-
ed on polyolefins or chlorine-containing polymers against
the detrimental influence of light and heat in an amount
of from 0.01 to 5, preferably 0.05 to 2 % by weight, cal-
culated on the plastic composition and on the proportion
Or phosphorous acid ester in the preparation. Examples
of such compositions are those made from polyethylene,
preferably polypropylene, copolymers of ethylene and C3-
C5 ~ olefins, polyvinylchloride, copolymers thereof with
vinylidene chloride and other olefins, chlorinated polyole-
fins, and mixtures of polymers.
The following examples illustrate the invention:
E X A M P L E 1: tPreparation Example)
29 a) 2 g Paraffin, melting point from 58 to 60C, are
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dissolved in 100 ml heptane by boiling. Then after
cooling to 80C, 18 g finely ground isophthalic acid
di-pentaerythritol phosphite ester, which has been pre-
pared according to German Offenlegungsschrift 2,506,207,
Example 6, are added while stirring, whereupon the sol-
vent is removed at the rotation evaporator at 30C.
b) Analogously to the procedure sub 2), 18 g isophthalic
acid pentaerythritol ester are coated with 2 g of a
- synthesis paraffin having a melting point of 102C.
c) Analogously to a) 18 g isophthalic acid pentaerythritol
ester are coated with 2 g of a cracked-polyethylene wax .
having a chain length of about 200 carbon atoms.
d) Analogously to a) 18 g of acetoacetic acid pentaerythri-
tol phosphite ester prepared according to German Aus-
legeschrift 2,505,152 are added to a heptane solution
containing 2 g of a cracked-polyethylene wax which has
a chain length of about 200 carbon atoms, at 60C and
the resulting mixture is cooled. The cooled solution
is filtered under pressure and concentrated.
e) 20 g Acetoacetic acid pentaerythritol phosphite ester
are added while stirring to a melt containing 20 g of a
synthesis paraffin having a melting point of 102C.
Then the resulting mixture is cooled.
f) 10 g Di-stearyl-pentaerythrityl diphosphite are added
while stirring to a solution of 2 g of triacontylphos-
phonic acid methyl ester in heptane which has a tem-
perature of about 50C. The solvent is evaporated in
- the rotation evaporator at 30C.
29 g) 20 g Di-stearyl-pentaerythrityl diphosphite are added
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while stirring to a melt of 20 g of triacontylphospho-
nic acid dimethyl ester. The melt is flaked.
Then each time 18 g di-stearyl-pentaerythritol di-
phosphite are melted with
h) 2 g synthesis paraffin, melting point 102C or
i) 2 g polyethylene wax, having a molar weight of about
2,000 or
j) 2 g microparaffin or
k) 2 g paraffin having a melting point from 58 to 60C.
The molten products are flaked.
j) 18 g Distearyl-~-hydroxytriacontyl-sorbityl-triphosphite
which have been prepared according to German Offenle-
gungsschrift 2,633,392, Example 6, are melted with 2 g
of a synthesis paraffin having a melting point of 102C.
The melt is sprayed.
m) 18 g Di-stearyl-~-hydroxytriacontyl-sorbityl-triphos-
phite are melted with 2 g of a polyolefin wax having a
chain length of about 200 carbon atoms. The mixture is
flaked.
E X A M P L E 2:
This example is intended to show the improved stabi-
lity to hydrolysis of the phosphite preparations according
to the invention.
a) 5 g each of the respective samples prepared according
to Example 1 are refluxed in 100 ml of demineralized
water fcr 20 minutes. The resulting product is filter-
ed off while still hot through a folded filter. 40 ml
each of the respective samples are withdrawn from the
; 29 aqueous phase and titrated with 0.1 M KOH against bromo-
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phenol blue.
The following table indicates the degree of hydro-
lysis determined under these conditions, as quotient of
the actual consumption of KOH and the theoretically
possible consumption of KOH with a complete hydrolysis.
For comparative purposes, the stability to hydrolysis
of the basic phosphites of the individual preparations
are determined.
Preparation degree of
accord. hydrolysis
to Ex. consisting of the components (% of the
theory)
la) 90 % isophthalic acid pentaerythritol phosphite 3.9
10 % paraffin 58/60
lb) 90 % isophthalic acid pentaerythritol phosphite 5.0
10 % synthesis paraffin
1c) 90 % isophtalic acid pentaerythritol phosphite 5.0
lO % polyethylene wax
Comp. 100 % isophthalic acid pentaerythritol phosphite 16.0
1g) 50 % di-stearyl-pentaerythrityl-diphosphite 7.0
50 % microparaffin
1h) 90 % di-stearyl-pentaerythrityl-diphosphite 19.0
10 ~ synthesis paraffin
li) 90 % di-stearyl-pentaerythrityl-diphosphite 19.0
10 % polyethylene wax
1j) 90 % di stearyl-pentaerythrityl-diphosphite 23.0
10 % microparaffin
lk) 90 % di-stearyl-pentaerythrityl-diphosphite 24.0
10 ~ paraffin 58/60
Comp. 100 % di-stearyl-pentaerythrityl-diphosphite 51.0
ll) 90 % di-stearyl-R-hydroxytriacontyl-sorbityl- 4.1
triphosphite
10 % synthesis paraffin
1m) 90 % di-stearyl-~-hydroxytriacontyl-sorbityl- 4.0
triphosphite
10 % polyolefin wax -
Comp. 100 % di-stearyl-R-hydroxytriacontyl-sorbityl- 9.0
triphosphite
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b) Water absorption of a phosphorous acid ester prepara-
tion according to the invention in comparison with that
of the basic phosphorous acid esters when stored in an
atmosphere saturated with steam.
Phosphite: Di-stearyl-pentaerythritol di-
phosphite
Test specimen: circular platelets having a dia-
meter of 60 mm and a height of
5 mm
10 Temperature of the air: 20C
Humidity of the air: lOO %
Duration: 24 hours
Test Composition of the water absorption
No. test specimen in % of the weight of
the test specimens __
2b l lOO % phosphite 10.15
2b 2 70 % phosphite 0.3
30 % cake paraffin 50/60
2b 3 50 % phosphite 0.1
50 % cake paraffin 50/60
2b 4 70 % phosphite *) 1.0
30 % amide wax
2b 5 50 % phosphite 1.0
50 % amide wax
2b 6 70 % phosphite 0.5
30 ~ polyethylene wax
MW 2 000 - 3 000
2b 7 50 % phosphite 0,3
50 % polyethylene wax
MW 2 000 - 3 000
distearoylethylene diamide.
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E X A M P 1, E 3: .
.
This example is intended to show the advantageous
rise of the solidification point of the organic phosphi-
tes treated according to the invention.
a) Tristearyl-sorbityl-triphosphite prepared according
to German Offenlegungsschrift 2,633,393, Example
1 which has a flow point/drop point of 52/53C is
mixed in the molten state with 3.5 weight % of a
polyethylene oxidate having a drop point of 117C
and an acid number of 19. The cooled product has
a flow point/drop point of 86/91C.
b) When melting together tristearyl-sorbityl-triphosphite
and 4.5 weight % of a polyethylene oxidate having an
acid number of 9 and a drop point of 115C, t,here is ob-
tained a preparation having a flow point/drop point of
76/80C.
c) The flow points/drop points of the preparations sub 1h)
to 1k) which consist of 90 weight % of di-stearyl-penta-
erythritol-diphosphite and 10 weight % of various waxes
are determined and compared with that of the pure phos-
phite.
Preparation consisting of Flow point / Drop point .:
90 % phosphite 94 / 95
10 ~ synthesis paraffin
90 % phosphite 103 / 104
10 ~ polyethylene wax
90 % phosphite 76.5 / 77
10 % microparaffin
90 % phosphite 62 / 62.5
10 % paraffin 58/60
100 % phosphite 58 / 60
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E X A M P L E 4:
This example is intended to show the improved effi-
ciency of the phosphite preparations according to the in-
vention as compared to that of the basic phosphites. It
can be seen from the measured values that with the prepa-
rations according to the invention both the ageing stabi-
lity under heat and the processing stability are consi-
derably improved and that the phosphite content is in all
cases lower than that in the comparative tests.
a) Examination of the ageing stability under heat
A mixture of
100 parts by weight of unstabilized polypropylene
powder having a density of 0.90 (melt
index about 6 g/10 minutes determined
according to ASTM D t238-62 T) and
0.15 part by weight of 3',5'-di-tertiary butyl-4'-
hydroxy-phenyl-propionic acid octadecyl
ester and
; 0.1 part by weight each of the respective phosphite
or of the phosphite preparation is homoge-
nized for five minutes at 200C on a two
roll mill. The plastic melt is molded at
200C into a rough sheet of 1 mm thickness.
Strip specimens of 60 x 10 x 1 mm are
punched out from the sheet and are then
suspended in a heating cabinet with air
circulation on a moter driven stand with
rotating trays. The samples are submitted
29 to a uniformous temperature treatment of
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140C in a controlled atmosphere while
supplying a definite quantity of fresh air.
The time is measured after which a begin-
ning local embrittlement can be observed
at several positions. This phenomenon is
characterized according to the German in-
dustrial standard DIN 53,383 by the forma-
tion of discolored, turbid, partially flak-
ing-off zones. This period, expressed in
days, is indicated in the following table.
b) Examination of the processing stability
The mixture described sub a) is used to determine
its melt index (i2/300) prior to and after a thermal
stress at 300C for a period of 60 minutes. The de-
; 15 termined melt indices are listed in the following
table as the quotiert i prior. The smaller this quo-
i after
tient, the higher the thermal decomposition of the
plastic melt and the lower its processing stability.
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phosphite according Ageing resistance Processing stability
to Example under heat i prior to
1a) (da56ys) 0.173
1b) 62 0.195
1c) 65 0.184
isophthalic acid dipentaerythri- 48 0.160
tol phosphite ester (Comp.)
1d) 63 0.234
le) 61 0.185
acetoacetic acid pentaerythritol 44 0.147
phosphite ester (Comp.)
1f) 57 0.227
1g) 51 0.218
di-stearylpentaerythrityl-di- 43 0.144
phosphite (Comp.)
E X A M P L E 5:
This example is intended to show that the volatility
of phosphites is reduced with the addition of waxes accord-
ing to the present invention.
- For this purpose 1 g each of the respective phosphite
is melted together with 2 g polyethylene wax having a molar
weight of from 2,000 to 3,000. Then a precisely weighed
quantity of th~is mixture is stored in a heating cabinet for
two hours at 200C at the air and then the mixture is
weighed again.
The following table summarizes the determined volati-
lities and the flow points/drop points compared to that of
the starting phosphites.
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phosphite or phosphite Flow / Drop Volatility
wax mixture point point (weight %)
tris-(2,4-di-tert.-butyl- 180 29.8
phenyl)-phosphite
dto. with 2 parts poly-152/156 1.23
ethylene wax
di-stearyl-pentaerythri-55/ 60 6.85
tyl diphosphite
dto. with 2 parts poly-114/115 0.92
ethylene wax
di-stearyl-~-hydroxytri-75/ 78 10.9
acontylsorbityl-triphos-
phite
dto. with 2 parts poly- 114/115 0.24
ethylene wax
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