Note: Descriptions are shown in the official language in which they were submitted.
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POLYESTERS MODIFIED WITH ABS TE~POLYMERS
Omar M. Boutni
Ping Y. Liu
This invention relates to high-impact mixtures of
polybutylene terephthalate and ABS-graft polymer having
a defined ratio of the A/8/S components therein.
BACR~ROUND OF THE INVENTION
Polybutylene terephthalates have acquired consid-
erable significance as thermoplastic molding
compositions by virtue of their valuable technological
properties, e.g., chemical resistance, rigidity,
hardness, abrasion resistance, stability under dynamic
and thermal stressing, and rapid processibility. A
disadvantage of these molding compositions is that
their notched Izod impact strength is inadequate for
certain specific applications. Proposals have been put
forward for increasing the toughness of thermoplastic
polyesters by the addition of co-condensation of other
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polymers, particularly those based on modified
elastomers and polyolefins (German Offenlegungsschrifts
Nos. 1,694,173 and 1,928,369; German Auslegeschrifts
Nos. 1,961,226 and 1,962,855; German
Offenlegungsschrifts Nos. 2,248,242, 2,310,034,
2,357,406 and 2,364,318 and U.S.Pat. Nos. 3,236,914 and
3,723,574). However, the proposed measures are attended
by the disadvantage that the improvement in toughness
is accompanied by a significant deterioration in other
properties.
DESCRIPTION OF THE INVENTION
It has now been discovered that compositions
comprising of polyester resin and a ABS terpolymer
will have improved impact strength as well as knit
line strength when a terpolymer is used that has a
specific weight ratio of the acrylonitrile-butadine-
-styrene components therein. Specifically, it has been
discovered that the optimum weight ratio of said
components, is (for every one hundred weight parts of
ABS resin) from about 13 to about 18 parts by weight of
- acrylonitrile, from about 45 to about 47 parts by
weight of butadine, and from about 35 to about 42 parts
by weigbt of styrene.
DETAILED DESCRIPTION OF THE INVENTION
The preferred polyesters utilized in the present
invention are higher molecular weight polyesters,
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most preferably linear polymeric glycol esters of
terephthalic acid and isophthalic acids. They can
be prepared by known techniques such as by the
alcoholysis of esters of the phthalic acid with a
glycol and subsequent polymerization, by heating
glycols with the free acids or with halide derivatives
thereof, and similar processes. These are described in
U.S. Pat. Nos. 2,465,319 and 3,047,539, and elsewhere.
In addition to the phthalates, amounts~ e.g., from
about 0.5 to 15% by weight, of other aromatic dicar-
boxylic acids, such as naphthalene dicarboxylic acid,
can be present in the polyester component. Although
the term "linear" is used, the reactants can also
include amounts of tri- or polyfunctional branching
agents, such as trimethylolpropane, pentaerythritol,
and trimethyl trimesate.
Preferred polyesters will be of the family
consisting of high molecular weight, polymeric glycol
terephthalates or isophthalates having repeating units
of the general formula:
O
C
_o-(cH2)n--c ~
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wherein n is a whole number of from 2 to 10, pre-
ferably from 2 to 4, and mixtures of such esters,
including copolyesters of terephthalic and isophthalic
acids of up to about 30 mole % isophthalic units.
Especially preferred polyesters are poly(ethylene
terephthalate and poly(butylene terephthalate). The
most preferred polyesters are poly(butylene
terephthalates), with poly(l,4-butylene terephthalate
being especially preferred.
The preferred polybutyLene terephthalates contain
at least 90 mole percent, based on the dicarboxylic
acid component of terephthalic acid residues and at
least 90 mole percent, based on the diol component, of
1,4-butane diol residues.
In addition to terephthalic acid residues, the
preferred polybutylene terephthalates may contain up
to 10 mole percent of residues of other aromatic,
aliphatic or cycloaliphatic dicarboxylic acids, for
example, succinic acid, adipic acid or isophthalic acid
residues. In addition to butane diol residues, they
may contain up to 10 mole percent of residues of
another diol which may correspond to the following
formula:
HO-CnH2n-OH
in which n is an integer of from 2 to 10. More
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particularly, up to 10 mole percent of
alkyl-substituted diols, such as neopen~yl glycol,
2,2,4-trimethyl-1, 6-hexane diol, 2-ethyl-1.3-propane
diol, 2,2,4-trimethyl-1.3-pentane diol, 2-methyl-
2,4-pentane diol, 3-methyl-2.4-pentane diol or 2-
ethyl-1,3-hexane diol may also be incorporated ~German
Offenlegungsschrifts Nos. 2,407,674; 2,407,776 and
2,715,932).
The preferred polybutylene terephthalates may
aLso be branched by compounds having a branching
effect, such as polycarboxylic acids or polyols
(German Auslegeschrift No. 1,900,270).
The most preferred polybutylene terephthalates
have an intrinsic viscosity of generally from 0.7 to
1.5 dl/g, preferably from 0.8 to 1.3 dl/g and, more
particularly, from 0.8 to 1.05 dl/g, as measured in
phenol/o-dichlorobenzene (1:1 parts by weight).
It has now been discovered that mixtures of a
polyester resin or resins and a ABS terpolymer
will have improved impact strength, over previous
polyester-ABS mixtures, when a terpolymer is used
that has a specific weight ratio of the
acrylonitrile~butadine-styrene components therein.
Specifically, it has been discovered that the optimum
weight ratio of said components, is, for every one
hundred weight parts of ABS resin, from about 13 to
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about 18 parts by weight of acrylonitrile, from about
45 to about 47 parts by weight of butadiene, and from
about 35 to about 42 parts by weight of styrene.
The processes for producing ABS terpolymers are
well known in the art. Suitable ABS terpolymers for
use in the present invention are also available
commercially.
The compositions of the present invention will
preferably contain (a) from about 40 % to about 98 %
by weight, and most preferably from about 60% to about
97% by weight, of at least one polyester preferably
selected from the group consisting of poly(ethylene
terephthalate) and a poly(butylene terephthalate), each
polyester comprising 0-100% of the polyester component,
and, most preferably a poly(butylene terephthalate)
polyester; and (b) from about 2 % to about 60 %
by weight, and most preferably from about 3% to
about 40% by weight, of the specified ABS ter-
polymer, said weight percentages being based on the
total weight of the polyester resins and the ABS
terpolymer.
It should be understood that the compositions
obtained according to this invention may contain one
or more conventional additives such as, for example,
antioxidants, carbon black, reinforcing agents,
plasticizers, lubricity promoters, color stabilizers,
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ultraviolet absorbers, X-ray opacifiers, dyes,
pigments, fillers, mold release agents and the like.
Satisfactory thermal, oxidative and/or ultraviolet
stabilizers comprise phenols and their derivatives,
amines and their derivatives, compounds containing both
hydroxyl and amine groups, hydroxyazines, oximes,
polymeric phenolic esters and salts of multivalent
metals in which the metal is in its lower state.
Representative phenol derivatives useful as
stabilizers include 3,5-di-tert-butyl-hydroxy hydro-
cinnamic triester with 1,3, 5-tris-(2-hydroxyethyl-s-
-triazine-2,4,6-(lH, 3H, 5H) trione; 4,4'-bis-
-(2,6-ditertiary-butylphenol); 1,3,5-trimethyl-2,4,6-
-tris-(3,5-ditertiary-butyl-4-hydroxylbenzyl)benzene
and 4,4'-butylidene-bis (6-tertiary-butyl-m-cresol).
Various inorganic metal salts or hydroxides can be used
as well as organic complexes such as nickel dibutyl
dithiocarbamate, manganous salicylate and copper
3-phenylsalicylate. Typical amine stabilizers include
N,N'-bis(betanaphthyl)-p-phenylenediamine; N,N'-bis-
(l-methylheptyl)-p-phenylenediamine and either phenyl-
-beta-napththyl amine or its reaction products with
aldehydes. Mixtures of hindered phenols with esters or
thiodipropionic, mercaptides and phosphite esters are
particularly useful. Additional stabilization to
ultraviolet light can be obtained by compounding with
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various UV absorbers such as substituted benzophenones
and/or benzotriazoles.
Particularly useful stabilizers are hindered
phenols which include phenols of the formula
R3 OH
~ R
R2
wherein Rl and R3 are hydrocarbon groups having from one
to about 20 carbon atoms, and R2 is a hydrogen atom or a
hydrocarbon group having from one to about 20 carbon
atoms, and bisphenol of the formula
O A ~ (C~2)n ~ A
R5 R6 R6 R5
wherein R4, Rs and R6 are each a hydrogen atom or a
hydrocarbon group having from one to about 20 carbon
atoms, one of the two A's on each ring is a hydroxyl
group and the other A on each ring is a hydrogen atom
or a hydrocarbon group having from one to about 20
carbon atoms; and n is an integer of from 0 to about 20.
Preferred hindered phenols useful in this
invention include 2,6-di-tert-butyl-4-methyl-phenol,
commonly known as BHT (sold under the tradename Ionol
by Shell Chemical Co.); 4,4-methylene bis(2,6-di-tert-
-butylphenol) and 2,6-di-tert-butyl-4-n-butylphenol
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(sold under the tradename Ethyl 702 and Ethyl 744,
respectively, by Ethyl Corp.); and tetrakis[methylene
3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) proprionate]-
methane and stearyl-3-(3',5'-di-tertbutyl-4'-hydroxy-
phenyl) proprionate (sold under the tradenames Irganox1010 and Irganox 1076, respectively, by Ciba-Geigy).
The composition of the present invention will
preferably include reinforcing agents such as
fibrous (filamentous) glass and/or fillers, such as
mineral fillers such as clay, talc and the like,
preferably mica. The fillers can be untreated or
treated with silane or titanate coupling agents, etc.
The preferred reinforcing agent for use in the present
invention is filamentous glass, which is is well known
in the art.
The components of the composition of the present
invention can be intimately blended in a number of
procedures. In one way, the various additives to the
polyester resin(s) are put into an extrusion
compounder with the dry polyester resin(s) and the
blend is heated at an elevated temperature, e.g.,
450-550F., and extruded to produce molding pellets.
In another procedure, the additives are mixed with the
polyester resin(s) by blending at ordinary
temperatures, then the blend is fluxed on a mill,
heated, e.g., at 450-550F., then cooled and
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comminuted; or the blend can be extruded at
450-550F., cooled and chopped. The additives are
mixed with the powdered or granular polyester(s) and
the mixture can be heated and directly formed into blow
molded items using machines which compound and mold.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The following examples are presented to more
fully and clearly illustrate the present invention.
They are presented as illustrative of the invention
and are not to be construed as limiting the invention
thereto. In the examples all parts and percentages
are on a weight basis unless otherwise specified.
In all the examples, the compositions were pre-
pared by melt blending the polyester resins and the
indicated additional components as set forth in the
Tables below using a Prodex single screw extruder at
approximately 470F. The resulting polymeric
composition was formed, by injection molding, into test
specimens, the size of which was consistent which what
is specified in the ASTM methods set forth below.
Certain properties of the composition were tested with
the results of these tests also set forth in the Tables
below.
The following ASTM methods were used in
determining the physical characteristics of the com-
positions:
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Double Gate Unnotched Izod ASTM D256
Notched Izod ASTM D256
DTUL ASTM D648
Example l illustrates an ABS composition having
proportions of the relative components therein which is
outside the scope of the present invention and is
presented for illustrat;ve purposes only. Examples 2 to
7 clearly demonstrate that the claimed composition
range of A/B/S is critical to upgrade the NI properties
as well as the DG,UNI properties of polyester/ABS
blends.
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TABLE I
EX. 1 EX. 2 EX. 2 EX. 4
PBT%91.8 95.8 91.8 91.8
ABS%8.0 4.0 8.0 8.0
A/B/S (16/38/46) (13/46/41) (13/46/41) (15145140)
STAB 0~2 0.2 0.2 0.2
DTUL,F,@264 154 138 145 154
psi
NI 1.55 1.65 1.81 1.55
UNI, DG0.98 1.42 1.82 1.55
TABLE II
EXAMPLE 5 EXAMPLE 6EXAMPLE 7
PBT~/~*~91.8 84.8 79.8
ABS% 8.0 15.0 20.0
A/B/S (18/47/35) (13/46/41) (13/46/41)
STAB 0.2 0.2 0.2
DTUL,F,@264psi 158 162 168
NI 1.87 1.88 2.61
UNI, DG 1.33 1.49 1.71
The stabilizer (STAB) utilized was Irganox 1076.
PBT is poly(l,4-butylene terephthalate), Valox~ 315
from the General Electric Company.
