Note: Descriptions are shown in the official language in which they were submitted.
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BLENDS OF POLYESTERS AND POLYOLEFINS
Nan-I Liu
This invention relates to thermoplastic molding
compositions, particularly thermoplastic polyesters,
that can be blended with a polyolefin by incorporating
therein a modified polyolefin and a multifunctional
epoxy compound. More particularly9 the invention
pertains to compositions of (a~ from about 1 % to
about 99 % by weight of at least one polyester
preferably selected from the group consisting
essentially of poly(ethylene terephthalate) and a
poly(l,4-butylene terephthalate), each polyester
comprising 0-100% of the polyester component; (b) from
about 99 % to about l % by weight of a modified
polyolefin; and (c) about 0.01 % to about 2 % by
weight of a multifunctional epoxy compound.
BACKG~OUND OF THE INVENTION
High molecular weight polyesters and particularly
polyesters and copolyesters of glycols and terephthalic
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or isophthalic acid have been available for a number
of years. These are described inter alia in Whinfield
et al, U.S. Pat. No. 2,465,319 and in Pengilly, U.S.
Pat. No. 3,047,539. These patents disclose that the
polyesters are particularly advantageous as film and
fiber-formers.
With the development of molecular weight control,
the use of nucleating agents and two-step molding
cycles, poly(ethylene terephthalate) has become an
important constituent of injection moldable composi-
tions. Further, poly(l,4-butylene terephthalate),
because of its very rapid crystallization from the
melt, is uniquely useful as a component in such
compositions. Work pieces molded from such polyester
resins, in comparison with other thermoplastics, offer
a high degree of surface hardness and abrasion resis-
tance, high gloss, and lower surface friction.
Furthermore, in particular, poly(l,4-butylene
terephthalate) is much simpler to use in injection
molding techniques than poly(ethylene terephthalate).
For example, it is possible to injection mold poly
(1,4-butylene terephthalate) at low mold temperatures
of from about 30C. to 60C. to produce highly
crystalline, dimensionally stable moldings in short
cycle times. On account of the high rate of
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crystallization, even at low mold temperatures, no
difficulty is encountered in removing the moldings from
the molds. Additionally, the dimensional stability of
poly(l,4-butylene terephthalate) injection moldings is
very good even at temperatures near or well above the
glass temperature of poly(l,4-butylene terrephthalate).
It is also known to add polyolefins to thermo-
plastic polyesters to enhance or provide certain
properties. For example, Rein et al, U.S. Pat. No.
3,405,198, disclose the use of polyethylene in
poly(ethylene terepbthalate) as an impact modifier.
Holub et al, U.S. Pat. No. 4,122,061, disclose poly-
ester compositions which comprise a poly(l,4-butylene
terephthalate) resin, a poly(ethylene terephthalate)
resin, a fibrous glass reinforcement, alone or in
combination with a mineral filler and, as an impact
modifier therefor, a polyolefin or olefin based
copolymer resin including polyethylene and propylene-
ethylene copolymer. Cohen et al, U.S. Pat. No.
4,185,047, disclose the use of high pressure low
density polyethylene in thermoplastic polyester compo-
sitions, particularly (poly(ethylene terephthalate) and
poly(l,4-butylene terephthalate) for improved mold
releasability. All of the aforementioned patents are
incorporated herein by reference.
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It has been known, however, that such blends of
polyolefins and polyesters are not extremely compatible
and can pose processing difficulties to the individual
practitioner of the present invention.
It has now been unexpectedly discovered that
polyolefins and polyesters can be compatibly mixed with
an accompanying improvement in physical properties by
mixing a thermoplastic polyester with (1) an epoxy
reactive moiety and (2) a multifunctional epoxy com-
pound.
DETAILED DESCRIPTION OF THE INVENTION
The preferred polyesters utilized in the present
invention are higher molecular weight polyesters,
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
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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
Il
-O-(CH2~n~O~C ~
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 a poly(butylene terephthalate), most
preferably poly(l,4-butylene terephthalate).
Examples of polyolefins which may be utilized
in the present invention include homopolymers as
well as copolymers of polyethylene (high and low
density), polypropylene, polyisobutylene, and random
copolymers of ethylene with propylene, or with poly-
propylene and a nonconjugated diene. Chlorinated
olefin products are also included in the category
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above, as are cross-linked olefins which can be
carboxylated in the manner described herein. The
foregoing categories include copolymers of ethylene
and other polyolefins with nonolefinic groups provided
S they meet the requirements outlined herein.
The linear low density polyethylene useful for
the present invention are well known materials, they
are available commercially, e.g. from Exxon under
the tradename Escorene, from Dow Chemicals under the
tradename DOWLEX or from Union Carbide under the
tradename G. Resins. Alternatively, they may readily
be prepared by state of the art polymerization
processess such as those described in U.S. Pat. No.
4,254,009, U.S. Pat. No. 4,076,698, European Patent
Application 4645 (published Oct. 17, 1979), and U.S.
Pat. No. 4,128,607, all incorporated herein by
reference. These polymers have 8 density between
about 0.89 and about 0.96 gram/cc, preferably between
about 0.915 and 0.945 grams/cc. These linear low
density polyethylene polymers are actually copolymers
of ethylene and a minor amount, less than 20 mole
percent, preferably less than 15 mole %, of an alpha
olefin of 3 to 15 carbon atoms, preferably 3 to 10
carbon atoms, most preferably 4 to 8 carbon atoms.
These linear low density polyethylenes are
distinguishable from polymers such as high pressure
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low density polyethylene and high density polyethylene
made from coordination catalyst systems in that they
are substantially free of side chain branching, having
a controlled concentration of simple side chain
branching as opposed to random branching.
The preferred linear low density polyethylene
copolymers are prepared from ethylene and one or more
alpha olefins selected from the group consisting of
propylene, butene-l, pentene-l, 4 methyl pentene-l,
hexene-l and octene-l, most preferably butene-l and
octene-l. Polymers of desired density may be obtained
by controlling the copolymerization ratio of alpha
olefin and the formation proportion of the polymer
during copolymerization. The addition of increasing
amounts of the comonomers to the copolymers results in
lowering the density of the polymer.
Polymers based on higher olefins are not as
readily available and, therefore, not as preferred.
Examplés of such higher polyolefins are polymers
based on 2-methyl-1-butene, l-pentene, 4-methyl-1-
pentene, and the like. They can be prepared by known
procedures including those described in Encyclopedia
of Polymer Science and Technolo~y, John Wiley & Sons,
Inc., Vol. 9, pp. 440-460, 1965, incorporated herein
by reference.
Olefin-containing copolymers such as olefin
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acrylates and olefin diene terpolymers can also be
used as the olefin component impact modifiers in the
present compositions. An example of an olefin
acrylate copolymer impact modifier is ethylene
ethylacrylate copolymer available from Union Carbide
as DPD-6169. Other higher olefin monomers can be
employed as copolymerrs with alkyl acrylates, for
example, propylene and n-butyl acrylate. The olefin
diene terpolymers are well known in the art and
generally fall into the EPDM (ethylene propylene
diene) family of terpolymers. They are commercially
available such as, for example, EPSYN 704 from
Copolymer Rubber Company. They are more fully
described in U.S. Patent 4,559,388, incorporated
herein by reference.
Various rubber polymers can also be employed
as the olefin component. Examples of such rubbery
polymers are polybutadiene, polyisoprene, styrene-
butadiene, and various other polymers or copolymers
having a rubbery dienic monomer.
Styrene-containing polymers can also be
employed as the olefin component. Examples of such
polymers are acrylonitrile-butadiene-styrene, styrene-
acrylonitrile, acrylonitrîle-butadiene-alpha-
methylstyrene, methacrylate-butadiene-styrene, and
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other high impact styrene-containing polymers such as,
for example, high impact polystyrene.
As indicated above, the polyolefins utilized
in the invention are first modified, by conventional
techniques well known in the art, with epoxy reactive
functional groups. Generally, this is accomplished by
replacing a hydrogen on the polyolefins with the
epoxy reactive functional group which are well known
to those skilled in the art. Exemplary of suitable
functionable groups are anyhydrides, carboxylic acids,
acrylates, amines, etc~
The polyepoxide compounds utilized in the
compositions of the present invention include epoxy
compounds having a functionality (multiple epoxide
functional groups) of more than 2.
Preferred epoxy compounds include epoxies derived
from an orthocresolformaldehyde novolac which is then
reacted with epichlorohydrin to form a polyepoxide.
Such resins are manufactured by Ciba-G~iby under the
name "ECN" (epoxy cresol novolac) resins. One such
preferred epoxy compound is ECN 1299, which has the
following properties:
Molecular weight-approx.- 1270; Weight per Epoxide-235;
Epoxy Value (Eg./100 gm)-0.425; Melting point (C)-99;
Functionality (Epoxide type)-4.
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Additional preferred epoxy compounds are the D.E.N.
400 series epoxy novolac resins manufactured by Dow
Chemical. A particularly preferred novolac epoxy
resin in this series is D.E.N. 485 resin, which is a
solid epoxy novolac having a functionality of 5.5, and
the following structural formula:
O O O
o-CH2-CH-CH2 ~ CH2-CH-CH2 o-cH2-cH-cH2
[~ CH2 ~ CH2--~
n
where the average value of n is 3.5. Another
preferred multifunctional epoxy novolac resins is the
XD series of resins manufactured by the Dow Chemical
Company. One particularly preferred multifunctional
epoxy in this series is XD 9053.01 resin, which
has the formula:
H-C ~ o-CH2-C~H-~CH2)
Other multi-epoxy compounds suitable for use
herein include poly(O- or N-epoxyalkyl-substituted)
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cyclic amide, imide or imidate, which usually con-
taining one and only one non-epoxy cyclic moiety
alehough compounds with linked or fused moieties are
also contemplated. Preferably, these are compounds
in which the epoxyalkyl group is bonded directly to
the oxygen or nitrogen atom; however, compounds con-
taining intervening structures, such as 2-carbo-
glycidyloxyethyl compounds, may also be used.
Illustrative cyclic nuclei which may be present
in such multifunctional epoxy compounds are the
triazine, barbiturate, hydantoin, uracil, pyro-
mellitic diimide, piperazinedione and parabanate ring
systems. As previously noted, the epoxy-containing
functionalities may be present as substituents on
oxygen or nitrogen atoms therein, with nitrogen atoms
frequently being preferred. The most suitable multi-
functional epoxy compounds of this type are triazine
derivatives including triglycidyl cyanurate and
triglycidyl isocyanurate (hereinafter "TGIC"). TGIC
is particularly preferred by reason of its availa-
bility and particular suitability for the formation of
branched polyesters. It has the formula
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fH2CH-CH2
0~ 0
CH2-CHCH2-N ~ ~ N-CH2CH-CH2
o
It should be noted that many polyepoxides of
this type are irritants and/or health hazards. For
example, triglycidyl isocyanurate has mutagenic
properties. Contact with the body and inhalation
should therefore be avoided as much as possible.
According to the present invention, the polyester
resin component of the composition of the present
invention will comprise at least about 1 weight
percent, generally about 10 to about 90 weight percent
and preferably about 15 to about 85 weight percent of
the total composition of polyester resin, polyolefin
resin and epoxy compound. The polyolefin resin
~omponent o~ the present composition will comprise at
least about 1 weight percent, most often about 10 to
about 90 weight percent and preferably about 15 to
about 85 weight percent of the total composition. As
indicated herein, the polyolefin component of the
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composition can be comprised of more than one
polyolefin resin and the polyester component of the
composition can be comprised of more than one polyester
resin.
The amount of the multifunctional epoxy compound
which is present in the instant composition will
generally be dependent upon the particular epoxy
compound used as well as upon the particular polyester
and polyolefin compounds present in the composition.
Generally, however, this amount is at least about 0.01
weight percent, based on the total amount of epoxy
compound, polyolefin compound and polyester resin
present in the composition, preferably at least about
0.1 weight percent, and most preferably at least 0.3
weight percent. An amount of about 2 weight percent of
epoxy compound should not be exceeded, and preferably
an amount of 1 percent of epoxy compound sbould not be
exceeded.
The components of the composition of the present
20 invention can be intimately blended in a number of
procedures. In one way, the polyolefin and epoxy
compound are put into an extrusion compounder with the
dry polyester resin and the blend is heated at an
elevated temperature, e.g., 300-450F., and extruded
25 to produce molding pellets. In another procedure, the
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epoxy compound and polyolefin are mixed with the
polyester resin by blending at ordinary temperatures,
then the blend is fluxed on a mill, heated, e.g., at
450-550F., then cooled and comminuted; or the blend
can be extruded at 450-550F., cooled and chopped.
The epoxy and polyolefin are mixed with the powdered
or granular polyester and the mixture can be heated
and directly formed into blow molded items using
machines which compound and mold..
It should be understood that the composition
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,
ultraviolet absorbers, ~-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-
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-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, mercapides and phosphite esters are
particularly useful. Additional stabilization to
ultraviolet light can be obtained by compounding with
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
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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
A ~ (CH2)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 lonol by
Shell Chemical Co.); 4,4-methylene bis(2,6-di-tert-
-butylphenol) and 2,6-di-tert-butyl-4-n-butylphenol
(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 IrganoxlO10 and Irganox 1076, respectively, by Ciba-Geigy).
The composition of the present invention may also
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include reinforcing fillers such as fibrous
(filamentous) glass and/or mineral fillers, such as
clay, mica, talc and the like. The fillers can be
untreated or treated with silane or titanate coupling
agents, etc. The filamentous glass to be employed
as reinforcement in such embodiments of the present
compositions is well known to those skilled in the art
and is widely available from a number of manufacturers.
DESCRIPTION OF THE PREFERRED EMBODI~NT
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.
The following Example 1 illustrates a compo-
sition following outside the scope of the instant
invention in that it does not contain any multi-
functional epoxy resin compound. This example is
presented for comparative purposes only.
In all the examples, the compositions were pre-
pared by melt blending the polyolefen, polyester and
the indicated additional components using a Prodex
single screw extruder at approximately 470F.
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EXAMPLE 1
A composition was prepared which consisted of
59.8 weight percent of PBT (poly (1,4-butylene
terephthalate) (Valox~ 315 from General Electric
Company); 40 weight percent of Polybond 54-103-14,
a EPDM-acrylic acid terpolymer manufactured by
British Petroleum and 0.2 weight percent of a
stabilizer (Irganox 1010). The resulting polymeric
composition was formed, by injection molding, into
test bars measuring 2.5 inches x 1/2 inches x 1/8
inch. The notched izod of the composition was tested
bearing the results of these tests set forth in the
Table below.
EXAMPLE 2
In Example 2, a polymeric composition containing
59 parts by weight of PBT of a type used in Example 1,
49 parts by weight of the polyolefen of the type used
in Example 1, 0.2 parts by weight of the stabilizer
used in Example 1, and 0.8 parts by weight of TGIC
is injected molded into tests bars of the same
dimensions as in Example 1. These tests bars are
subjected to the notched izod testing procedures as
were the test bars utilized in Example 1, plus
additional physical tests. The results are set forth
in the Table below.
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The following ASTM methods were used in
determining the physical characteristics of the com-
positions:
Flexural Modulus ASTM D790
S Tensile Elongation ASTM D638
Notched Izod ASTM D256
Table
Example No.
1 2
NI 1/8", (ft lb/in)(room temp.) 2.3 10.4
Unnotched Izod 1/8",-30C NB NB
Tensile Strength (psi) _ 3500
Tensile Elongation, % _ 70
Flexural Modulua - 143,000
Sag, 290F - 15
NB = no break
Obviously, other modifications and variations of
the present invention are possible in light of the
above teachings. It is therefore to be understood
that changes may be made in the particular embodi-
ments of the invention described which are within the
full intended scope of the invention as defined by the
appended claims.