Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
;49
The present invention relates to copolyesters which
are based on poly-1,4-butylene terephthalate and contain
co-condensed branched aiiphatic dicarboxylic acids.
Recently, reinforced and unreinforced poly-1,4-
butylene terephthalate has gained importance as a high-
grade material. This thermoplastic moulding composition is
one of the so-called engineering pla~tics, that is to say
those materials from which mouldings with high mechanical
strength properties can be manufactured by means of suitable
moulding processes~ for example injection moulding or
extrusion. These moulding compositions are also distingui-
shed by advantageous processing properties.
In spite o~ this advantageous spectrum of properties,
this material cannot satis~y the demands made in all the
fields of application. Thus, it has not been possible
hitherto to replace other materials, such as, ~or example,
the polyamides, which are known for the same intended
application but possess certain disadvantages. Inter alia,
the absorption of moisture, and the dependence, associated
therewith, of mechanical properties on the environmental
conditions, is a disadvantage when using polyamides. It is
thus desirable to modify poly-1,4-butylene terephthalate in
such a way that it can fulfil the demands made in various
fields of application where, for example, a higher flexib
ility and a higher toughness of the material is required.
In addition to pure poly-1,4-butylene tereph-thalate,
copolyesters with other diols and dicarboxylic acids have
also been disclosed. In German Offenlegung~schrift
2,051,232 , poly-1,4-butylene terephthalates of higher
molecular weight and copolyesters thereof with aliphatic
dicarbo~ylic acids are proposed ~or the manufacture of
moulded articles. The only branched dicarboxylic acid
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mentioned here is dimethylmalonic,;acid. German Offenlegungs-
schrift 2,049,538 describes cry$~alline sheets of poly-1,4-
butylene terephthalate and copolyesters thereof with
aliphatic dicarboxylic acids, such as adipic acid, azelaic
acid and dimethylmalonic acid. A process ~or the manufacture
of copo]yesters of polyalkylene terephthalates is described
in German Of~enlegungsschrift 2,336,026 ,the co-components
mentioned being some linear aliphatic dicarboxylic acids,
such as, or example, glutarlc acid and sebacic acid.
Finally, German Offenlegungsschrift 2,340,959 discloses
adhesive compositions from a vinyl-aromatic polymer and a
copolyester of poly-1,4-butylene terephthalate and dimer
acid (dicarboxylic acids obtained by dimerisation of
unsaturated fatty acids). These copolyesters can also
contain other aliphatic dicarboxylic acids, such as, for
example, maleic acid, dimethylmalonic acid, adipic acid
or 2-methyladipic acid.
It is the object of the present invention to provide
copolyesters based on poly-1,4~butylene terephthalate (PBT)
which, compared with pure PBT, has increased flexibility
and notched impact strength, without the advantageou-
~processing properties being unduly impaired thereby.
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The present invention relates to linear thermoplas-
tic copolyesters from terephthalic acid, 1,4-butanediol
and a saturated aliphatic dicarboxylic acid, which have a
relative viscosity of at least 1.6, measured at 30 in a
1% strength solutlon of equal parts of phenol and
symmetrical tetrachloroethane, wherein, as the aliphatic
dicarboxylic acid, 2.5-15 mol ~, relative to the polyester,
of one or more branched dicarboxylic acids with 7 to 30
carbon atoms per molecule are co-condensed in the polyester
in statistical distribution.
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Preferably, 3 to 10, especially 4 to 7.5, mol ~ of
dicarboxylic acid are co-condensed, the relative viscosity
is preferably 1.6 to 3.5, the branched dicarboxylic acid
preferably contains 8 to 22 carb'on;atoms and the branched
dicarboxylic acid preferably contains branched alkylene
groups.
The branched dicarboxylic acid can have one or
several branches and the alkyl of the side chain can
preferably contain 1 to 18 carbon atoms. Both long-chain
dicarboxylic acids with short side chains, for example
methyl, and short-chain dicarboxylic acids with longer side
chains, for example ethyl to eicosyl, are suitable. The
short-chain dicarboxylic acids preferably contain 1 to 4
carbon atoms in the alkylene and 4 to 18 carbon atoms in
the alkyl. The shorter the alkylene, the longer preferably
is the alkyl.
Examples o suitable dicarboxylic acids are:
n-butylmalonic acid, decylmalonic acid, n-propylglutaric
acid, 2,3-diethylglutaric acid, 2-methyladipic acid,
2,2,4-trimethyladipic acid, octadecylglutaric acid,
1,3-dodecanedicarboxylic acid, 1,6-tetradecanedicarboxylic
acid, 1,8- or l,9-heptadecanedicarboxylic acid, 1,12-penta-
decanedicarboxylic acid, 1,17-octadecanedicarboxylic acid
and 1,12-eicosanedicar~oxylic acid.
The copolyesters according,to the invention are
manufactured, by means of known processes, by a polycon- ,
densation reaction of terephthalic acid, an aliphatic
branched dicarboxylic acid with 7 to 30 carbon atoms or , ,
polyester-forming derivatives thereof, with 1,4-butanediol.
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Examples of the known processes for the manufacture
of the new polyesters are solution condensation, azeotropic
condensation, interface condensation, melt condensation
or solid phase condensation and also combinations of these
methods, depending on which polyester-forming derivatives
and which reaction catalysts are used. The polyester-
-forming derivatives of terephthalic acid and of the
aliphatic branched dicarboxylic acids are in the main the
low-molecular dialkyl estexs ~ith 1 to 4 carbon atom$ in
the molecule, preferably dimethyl esters or diphenyl esters.
Moreover, the acid dihalides, in particular the acid
dichlorides, and the anhydrides are also suitable.
The new polyesters can be manufactured by ester-
ifying, or transesterifying, terephthalic acid and branched
aliphatic dicarboxylic acids, or low-molecular dialkyl
esters thereof, with 1,4-butanediol in an inert atmosphere,
for example a nitrogen atmosphere, in the presence of
catalysts and with simultaneous removal of the resulting
water or alkanol respectively, at 150-250UC and subse~uent~
ly carrying out the polycondensation at 200 to 270C and
under reduced pressure in the presence of certain catalysts,
until the polycondensed products have the desiredviscosity.
Amines, inorganic or organic acids, for example
hydrochloric acid or p-toluenesulphonic acid, or metals or
metal compounds, which are also suitable as the trans-
esterification catalyst, can be used in a known manneer as
the esterification catalysts.
Since some catalysts preferentially accelerate the
transesterification and other catalysts preferentially
accelerate the polycondensation, it i8 advantageous to use
a combination of several catalysts. Examples of suitable
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transesterlfication catalysts are the oxides, salts or
organic compounds of the metals calcium, magnesium, zinc,
cadmium, manganese, titanium and cobalt. The metals as such
can also be used as catalysts. For example, the polycon-
densation is catalysed by metals such as lead, titanium,
germanium, tin and, in particular, antimony, or bycompounds
thereof. These catalysts can be added to the reaction
mixture together or separately. Thése catalysts are employed
in amounts of about 0.001 to 1.0 per cent by weight,
relative to the acid component.
In the manufacture of the new polyesters, catalysts
which are used with particular advantage are those which
accelerate both the transesterification and the polycon-
densation. Possible catalysts of this type are above all
mixtures of different metals or metal compounds and also
corresponding metal alloys.
The polycondensation reaction is continued until
the polyesters have a relative ~iscosity of at least 1.6,
preferably 1.6 to 3.5. Depending on the type of catalyst
used and on the size of the batch, the reaction times
amount to about 30 minutes up to several hours. After the
resulting polyester melt has been removed from the reaction
vessel and cooled, it is granulated, or cut into chips, in
the customary manner.
In another process for the manufacture of the new
polyesters, dicarboxylic acid dihalides, preferably the
acid dichlorides, are subjected to a polycondensation with
1,4-butanediol in the presence of a basic catalyst in the
temperature range from 0 to 100C, hydrogen halide being
eliminated. The basic catalysts used are preferably amines
or quaternary ammonium salts. The proportion of basic
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catalyst can be from 0.1 to 100 mol %, relative to the
acid halides. It is also possible to carry out this process
without a solvent or in the present of a solvent.
The polycondensation can also be carried out in such
a way that the starting compounds are first subjected to a
condensation in the melt up to a certain viscosity, the pre-
condensate prepared in this way i9 then granulated, ~or
example with the aid of an underwater granulator, and the
granules are drled and then subjected to a solid phase
condensation, a vacuum being applied and a temperature
below the melting point of the granules being employed.
Higher viscosities can be achieved in this way.
Inert additives of any type, such as, for example,
reinforcing fillers, especially 5 to 50% by weight of
sized glass fibres, inorganic or organic pigments, optical
brighteners, delustering agents, agents which promote
crystallisation, mould release agents or flame-retardant
agents, can be added to the reaction composition when the
polyester melt is being worked up or even before the poly-
condensation reaction, or after the reaction in the molten
phase has ended.
If the polycondensation reaction is carried out dis-
continuously, the inert additives can be added already
during the lask stages of the condensation, for example in
the solid phase condensation or at the end of the melt
condensation.
The copolyesters according to the invention are
crystalline and, surprisingly, crystallise somewhat more
readily than, for example, copolyesters with linear dicar-
boxylic acids, such as, for example, adipic acid. This
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behaviour is unexpected since it has been assumed hitherto
that the introduction of branched radicals into the poly-
ester chain more extensively disturbs the symmetry and
hence impairs the crystallisability to a greater extent.
The somewhat improved crystallisabilitymanifests itself in
shorter cycle times, for example particularly in mass
production.
Furthermore, the copolyesters according to the in-
vention have a higher flexibility than pure linear PBT,
the flexibility being approximately similar to that of
polyamide 11 or polyamide 12, and also have better tough-
ness properties, better arc resistance and a lower after-
shrinkage. It has been found here, surprisingly, that the
notched impact strength is increased by aliphatic branched
dicarboxylic acids having a minimum carbon number of about
7, starting from a minimum addition of about 2.5 mol ~.
The copolyesters are valuable thermoplasticmaterials
from which mouldings of various types can be manufactured
by the customary moulding processes, such as casting,
in]ection moulding or extrusion. Examples of these moul-
dings are fuel lines or compressed air lines, conductor
sheathing, components of technical apparatus, profiles or
electrical insulations. They can also be used as a sintered
powder for surface-coatings and for the manufacture of
films, sheets and fibres.
Those copolyesters according to the invention which
contain 3 to 10, in partlcular 4-7.5l mol % of branched
dicarboxylic acids are preferentially employed for
processing by injection moulding and extrusion. Copoly-
esters which contain more than 7.5 up to 15 mol ~ are also
suitable for use as hot-melt adhesives or as bonding
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fibres or fusible fibres for the manufacture of spunbonded
nonwovens.
The polyesters prepared in accordance with theexamples
which follow are characterised in more detail by the
following characteristic data. The polyesters are charac-
terised by those morphological changes which are measured,
by means of differential thermal analysis, on a sample
which has been heattreated fox 3 minutes at a temperature
30C above the melting point or softening point and then
rapidly chilled. The chilled sample is heated, at a heating
rate of 16C/minute, by means of the "DSC-lB" Differential
Scanning Calorimeter from Messrs. Perkin-Elmer. The ther-
mogram of the sample shows the glass transition temperature
ITg) and the melting point (Tm). The point of in~lection
at the discontinuous increase of the speci~lc heat in the
thermogram is quoted as the ~lass transition temperature
and the tip of the endothermic peak is quoted as the mel-
ting point. The relative viscosity of the polycondensed
products is measured, at 30C, on solutlons of l g of
polyester in lO0 ml of a mixture consisting o~ equal parts
of phenol and symmetrical tetrachloroethane.
The crystallisation temperature (Tc) is determined,
after the sample has been heated up, by allowing the sample
to cool at the same rate. The tip of the e~othermic peak
in the thermogram, which is obtained in accordance with the
differential thermal analysis indicated above, is desig-
nated as the crystallisation temperature. In contrast to
customary methods, the Tc is here determined ~rom above
since it is not possible, because of the ready crystal-
lisation of the polyesters, to prepare supercooled m01ts,
that is to say amorphous products. The methods of deter-
mining the mechanicalpropertiesareindicatedin the examples.
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Example_l: 3,492 g (45 mol %) of dimethyl terephthalate
(DMT), 3,605 g of butane-1,4-diol (50 mol %), 376 g
(5 mol %) of dimethyl 2,2,4-trimethyladipate and 2,29 g of
isopropyl titanate are filled into a 10 litre reactor
equipped with a stirrer, nitrogen inlet, condenser and
temperature measurement. Whilst stirring and passing
nitrogen through the reactor, 97% of the amount of methanol
which is theoretically to be expected are distilled off in
the course of 1 hour and 35 minutes, the temperature of
the reaction mixture rising to 214C. After the reaction
mixture has been heated to 240C, a vacuum of 60 mm Hg is
applied in the course of half an hour by means of a water
pump and, at the same time, the reaction temperature is
raised to 250C. The vacuum is increased to 0.90 mm Hg in
the course of 50 minutes by means of a vacuum pump, the ~ -
reaction temperature remaining the same, and the mixture
is left under this vacuum for;210 minutes. The melt is
then discharged and granulated.
The characteristic date of the polyester are in-
dicated in Table 1. The polyester is injection-moulded to
give standard small bars and the mechanical properties
indicated in Table 1 are determined on these bars.
Examples 2-7: The procedure followed is as ln Example
1. ~fter the reaction temperature has been reached, the
vacuum is increased to 0.45 mm Hg in the course of 40
minutes and the mixture is left under this vacuum for 125
minutes. The co-components and the characteristic data of
the polyesters obtained are indicated in Table 1.
For comparison, the properties of P~T are also
indicated in Table 1.
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PBT has a Tc of 177C and a copolyester with 5 mol~
of dimethylmalonic acid has the same T . Copolyesters
with 5 mol % of adipic aeid or 5 mol ~ of azelaic acid
have a Tc of as low as 152C or 151C respectively. By
eomparison with Example No. 1, this shows the better
crystallisability o~ the copolyesters aceording to the
invention as compared with those eontaining linear
eo-eomponents.
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