Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~365517
This invention relates to thermoplastic moulding compositions, of
which the polymertc component conslsts of organic cellulose esters and copoly-
mers of olefinically unsaturated ni~riles and con~ugated diolefins, the
moulding compositions optionall~ being modified with low molecular weight
plasticisers.
It is known tha~ cellulose can be thermoplasticall~ processed only
after esterification with certain organic acids and, ln some cases, only
after the addition of low molecular weight plasticisers. In principle, the
three hydroxyl groups of the anhydroglucose units of the cellulose may be
lQ esterlfied with a number of organic acids, of which the esters and mixed
esters produced with acetic acid, proplonic acid and butyric acid, namely
cellulose acetate, cellulose acetopropionate and cellulose acetobutyrate,
have acquired particular commercial significance. Moulding compositions for
thermoplastic processing and, for example acetate rayon, block acetate,
film substrates for safety films, electrlcal insulating films and lacquers,
are produced from esters of this kind.
In practice cellulose acetates cannot be processed ~hermoplastically
without ~he addition of low molecular weight plasticisers, because the esters
begin to decompose before soten~ng. In the case of cellulose acetopropionic
and acetobutyrate, too, the softening and decomposition temperatures are
~fairly close to one another, so that in this case, as in the case of cellu-
lose acetate, low molecular weight plasticisers have hitherto had to be
worked in*o the e~ters before thermoplastic processing, reducing the process-
ing temperature and processing viscosity of the cellulose esters. In some
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cases, -the plasticise~s also imp.r~e the me~ anical properties
~or example, -the toughness and ~lexibility o~ articles
produced there:~`rom. By g~adually adapting the additions of
plasticisers to the cellulose esters, it .i.s possible
specifically to adjust certain ~echanical properties for
example, hardness, toughness, flexural and tensi~le streslgth,
dimensional stability under heat and flow.
~he low molecular weight plasticisers used are primarily
aliphatic esters oL phthalic acid, adipic acid, azelaic acid,
sebacic acid and phosphoric acid, for example dimethyl
phthalate, diethyl phthalate, dibutyl adipate, dioctyl
adipate, dibutyl a~elate, trichloroethyl phosphate and
tributyl phosphate. In ma.ny cases, it is also advantageous
to use plast.iciser mixtures.
Although the cellulose ester moulding co~positions
modified with low molecu].ar weight plasticisers show very
good mechanical proparties, it would be desirable further
to improve their dimensional stability under heat and their
mechanical properties for oertain applications.
In addition, the plasticisers gradually migrate to the
: surface of the mouldings, so that ~or example films of modi~ied
cellulose esters cannot be used ~or packagillg certain
foodstuffs.
:~: It has n~ surprisingly been fou~d that moulding
compositions with extremely good thermoplastic processing
properties can be obtained without any of the disadvantages
referred to above by mixing cellulose esters with copolymers
of olefinically unsaturated nitriles and conjugated diolefins.
Accordingly, the invention provides thermoplastic
mouldin~ compositions o~ which the polymer component consists
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of:
1) l to 99% by weight, preferably 50 to 99% by weight of at least one
cellulose ester of an aliphatic carboxylic acid; and
2) 99 to 1% by weight, preferably 50 to 1% by weight of a copolymer of
olefinically unsaturated nitriles and conjungated diolefins with 10 to 60%
by weight, preferably 20 to 40% by weight of incorporated nitrile monomers.
In particular, the present invention provides a thermoplastic moulding
composition comprising A) from 1 to 99% by weigh~ of at least one cellulose
ester chosen from the group consisting of cellulose acetobutyrate and
cellulose acetopropionate; and B) from 99 to 1~ by weigh~ of a copolymer of
acrylonitrile and 1,3-butadiene, wherein the copolymer of component B com-
prises from 10 to 60% by weight of acrylonitrile and 90 to 40% by weight of
1,3-butadiene and has a Mooney viscosity ~ML-4, 100C) in the range of from
20 to 100.
The thermoplastic moulding composition additionally contains 0 to
35% by weigh~ and pre~erably 0 to 20% by weight of a low molecular weight
plasticiser. The sum total of components 1 and 2 together with the plasticiser
amounts to 100% by weight.
The polymer component of the particularly preferred thermoplastic
moulding compositions consists of:
1~ 95 to 70% by weight of a cellulose ester of an aliphatic acid and
2) ~ to 30% by weight of a copolymer of acrylonitrile and 1,3-butadiene
with lO to 60% by weight of incorporated acrylonitrile.
The moulding composition additionally contains from 0 to 20% by
weight of a low molecular weight plasticiser. The sum total of components 1
and 2 toge-ther with the plasticiser amounts to 100 per cent by weight.
Suitable cellulose esters for the production of the moulding com-
positlons according to the invention are cellulose esters of aliphatic
carboxylic acids containing 1 to 5 carbon atoms, preferably cellulose
acetobutyrate and cellulose acetopropionate.
Processes for the production of organic cellulose
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es-ters have been known for some time and are described, for
example, in Ullmanns Enzyklopadie der technischen Chemie (Verlag
Urban ~ Schwar~enberg, Munich-Berlin, 1963), Vol. 5, pages 182
to 201.
Preferred cellulQse acetobutyrates contain from 40 to
500/o of butyric acid, from 15 to 260/o of acetic acid and from
n . 75 to l. 950/o of hydroxyl group.
Cellulose acetobutyrates with the ~ollowing composition
are particularly preferrecl for the moulding compositions
according to the invention: 42 to ~6~o of butyric acid~
18 to 21% of acetic acid and l.0 to l.7~ o-~ hydroxyl group.
Preferred cellulose acetopropionates generally contain
from 50 to 63. 5% of propionic acid, from l to 12% of acetic
acid and from 1.2 to 1.95% oi` hydroxyl group, and particularly
preferred cellulose acetopropionates have the following
composition: 54 to 58% of propionic acid, 5 to 8~/o of acetic
acid and l.5 to l. 8% of hydroxyl group.
Of the cellulose acetates, it is preferred to use
seoondary cellulose acetates.
Both here and in the ~ollowing, percentages represent
per cent by weight and parts are parts by weight.
The cellulose esters used, in the form of 2% solutions
in acetone, have relative viscosities ('~ r0l) at room
temperature of from 3.5 to 4.5 and preferably from 4.0 to 4.5.
Elastomeric components of the moulding compositions
according to the invention are binary copolymers, terpolymers
or quater polymers, hereinafter referred to as copolymers,
of .olefinically unsaturated nitriles and conjugated diolefins,
copolymer mixtures also bsing suitable.
~0 The ~lefinically unsaturated nitrile compounds, preferably
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acrylonitrile or its derivatives, correspond to the general
~ormula
~,CN
R - CH = C
in which R represents hydrogen and/or a hydrocarbon radical
having 1 to 10 carbon atoms. Examples of hydrocarbon radicals
are alkyl, cycloalkyl and aryl, such as methyl, ethyl,
isopropyl, tert butyl, octyl, decyl 9 cyclopentyl, cyclohexyl,
phenyl, tolyl, xylyl, ethylphenyl, ter-t-butylphenyl, etc.
Acrylonitrile and methacrylonitrile are preferably used.
The conjugated diolefins preferably contain from 4 to 8
carbon a-toms for example 1,3-butadiene, piperylene, isoprene~
1,3-hexadiene, 2,4-hexadiene, 1,3-heptadiene, etc. It is
preferred to use 1,3-butadiene because the copolymers produced
therefrom have particularly favourable proper-ties.
~ The copolymers are produced from the monomers in the
; presence of radical-forming initiators by known processes of
the type described, for example, in Houben-Weyl, Methoden
der organischen Chemie, Vol 14/1, ~eorg-Thi~me Verlag,
Stuttgart(1961), and in W Hofmann, Nitrilkautschuk, Verlag
Berliner Union, Stuttgart (1965). Suitable catalysts include
oxides, peroxides, hydroperoxides and azo compounds, etc.
One of the possible polymerisation processes is, for example,
emulsion polymerisation which is carried out in aqueous media
in the presence of emulsifiers and which is described, for
example, on pages 51 et se~ of the above-mentioned book by
W.~ofmann.
In addition, the copolymers may be produced by
polymerisation carried out in the absence of solvents or
precipitants.
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Finally, -the monomers may also be copolymerlsed in solu-
tion in the presence of inert organic solvents.
All the processes referred to above may be carried out
either continuously or in batches.
The copolymers suitable in accordance with the invention
for improving the technological properties of organic cellu-
lose esters may contain a total of from 10 to 60 %, preferably
from 20 to 40 % 9 of nitrile monomers. Accordingly, the suitable
total conten-t of conjugated diolefins amounts to from 9~ to
40 % and preferably from 80 to 60 %.
The Mooney viscosities (ML-4, 100C) determined in
accordance with DIN 53 523 o~ acrylonitrile-bu~adiene copoly-
mers particularly suitable ~or admixture with organic cellulose
esters are in the range from 20 to 100 and pre~erably in the
range from 20 to 65.
The low molecular weight plasticisers used are primarily
aliphatic esters of phthalic acid, adipic acid, azelaic acid,
sebacic aoid and phosphoric acid, for example dlmethyl phtha-
late, diethyl phthalate~ dibutyl adipate, dioctyl adipate,
dibutyl azelate, trichloroethyl phosphate and tributyl phos-
phate. In many cases, it is also ad~antageous to use plasti-
ciser mixtures.
Production of the moulding compositions according to
the invention from organic cellulose esters and copolymers
of olefinioally unsatura-ted nitriles and conjugated diole~ins,
which may optionally be modified with low molecular weight
plasticisers, is carried out by intensively mixing the
components by any known mixing process, for example on
miæing rolls or in sclew e~truders.
The mi~tures may also be prepared from solutions. To
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this end, the components are dissolved ln sui-table solvsnts or
solvent mixtures and the polymer mixtures are precipitated with
suitable non-solvents. The solvents or solvent mixtures may
also be rernoved by e~aporation. Suitable solvents are, for
example 7 methylene chloride or acetone; hexane for example may
be used as common precipitant.
The mixtures according to the invention may be compounded
with certain additives ~or colouring and pigm~nting the polymer
mixtures and for improving their resistance to oxidation,
light or fire and the like. In addition, fillers and strengthe-
ners may be worked into the mixtures.
Given a suitable copolymer content, the mixtures may
be crosslinked in the same way as rubber It is also
possible to use crosslinked rubbers for producing the
mixtures according to the invention.
The moulding compositions according to the invention
of organic cellulose esters and copolymers of olefinically
unsaturated nitriles and conjugated diolefins show a
remarkable increase in notched impact strength as measured
in accordance with DIN 53 453.
In addition, the moulding compositions according to
the invention are distinguished by improved dimensional
stability under heat as measured, for example, in accordance
witll DIN 53 460 (Vicat softening temperature).
The Vica-t softening temperatures are up to 25C above
the softening temperatures of the cellulose esters modified
with corresponding quantities o~ low molecular weight
plasticisers.
By comparison with conventional cellulose ester moulding
compositions containing low molecular weight plasticisers,
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the polymer mix~ures according to the invention additionally
show improved mechanical properties, for example, an i.ncrease
in hardness, tensile strength, flexural strength and elast.i.city
modulus
The known effect of so-called plasticiser migration
does not occur in the polymer mixtures of organic cellulose
esters and copolymers of olefinically ~msa-turated nitriles
and conjugated diolefins, so that moulding compositions of
this kind are also particularly suitable for e~amp].e for
applications involving contact with foodstuffs.
Shaped articles of any kind and also acetate rayon,
block acetate, film substrates for safety films, electrical
insulating films and lacquers, may be produced from the
moulding compositions according to the invention.
.~
,
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EXAMPI.ES 1 to 9
Cellulose acetobutyrate conta:ining 42 to 460/o of butyric
acid, 18 to 21% o~ acetic acid an~ 1.0 to 107% of hydro~yl
groups, was interlsively mixed on m:ixing ro].ls at 180C with
5 5~ 10 and 15%~ respectively, of an acrylonitrile-butadiene
copolymer of the -following composition:
.
Acrylonitrile- Acrylonitrile Mooney-visosity
butadiene content[ ~ ~ ML-4, 100 C
copolymer
.
NBR-2~07 28 + 1 45 ~ 5
NBR-3307 34 + 1 k5 + 5
NBR-3807 39 + 1 45 + 5
The rough sheets were granulated and subsequently
injection-moulded into test specimens at a melt temperature
of 22~C.
~` The moulding compositions of Examples 1, 4 and 7 were
transparent, the rest opaque.
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The abbreviations used in the Table have the following
meanings:
a : impact strength according to DIN 53 453;
n . dimension: [kJ/m2]
unbr: unbroken
~: not~hed impact s~rength according to DIN 53 453;
- dimension: [kJ/m ]
Vicat: Vicat sot~ning temperature according to method B
(Force: 49.05 N) according to DIN 53 460;
dimension: ~C]
bF' bending flow stress according to DIN 53 452;
. dimension: ~Nlmm2]
: B-E-M: bending elasticity modulus measured under three-point
load;
dimension: [N/mm2]
HC30: ball indentation hardness after 30 seconds according
: to DIN 53 456;
dimension: [N/mm
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EXAMPLES 1 to 18
Cellulose acetopropionate containing 54 to 58% of
propionic acid, 5 to 8% of acetic acid and 1.5 to 1.8% of
llyd.roxyl groups was int0nsively mixe~ on a mixing roll at
185C with 5, 10 and 15 /0, respectively~ of an acrylonitrile-
butadiene copolymer of the same composition as in Examples
1 to 9.
The granul.ated rough sheets were injection-moulded in-to
test specimens at a melt temperature of 230C.
`; 10 The mouldlng compositions of Examples 13 and 16 were
transparent, the rest opaque.
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EXA~IPLES 19 to 24
The cellulose acetobutyrate previously ~escribed was used
in Examples 19 to 21. On this occasion, however, i-t contailled
th~ low molecular weight plasticiser (nm-WM) dibu-tyl adipate.
Acrylonitrile-butadien~ rubber of the type described above was
worked into these moulding compositions by int;ensive mixing
on a mixing roll in thc~same way as in Examples 1 to 9, and
further processing was also carried out in the same way as
described above.
The same applies as regards Examples 22 to 247 except
that in their case the cellulose acetopropionate described
above was used as the starting material. The mixtures
were prepared and processed in the same way as in Examples
10 to l~.
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