Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to glass
reinfoxced molding composltions which have improved heat
distortion resistance and warp resistance in the molded
article~ More partiaularly, it pertains to compositions
comprising a polyblend of poly(l,4-butylene terephthalate)
resin and poly(ethylene terepthalate) resin, and as a
reinforcement therefor, glass fibers combined with finely
ground mica.
High molecular weight linear polyesters and
copolyesters of glycols and terephthalic or isophthalic
acid have been available for a number of years. These are
described inter` alia in Whinfield et al., U.S. 2,465,319
dated September 2, 1969 and in Pengilly, U.S. 3,047,539
dated July 31, 1962. 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 compositions. Poly~1,4-butylene tere-
phthalate~, because of its very rapid crystallization from
the melt, is uniquely useful as a component in such compositions.
Workpieces molded from such polyester resins, in comparison
~ith other thermoplastics, offer a high degree of surface
hardness and abrasion resistance, high gloss, and lower surface
friction~
It is known that glass reinforced thermoplastic
compositions of poly(l,4-butylene terephthalate) and poly(
ethylene terephthalate can be molded to articles having
greater resistance to warpage or heat distortion if a small,
effective amount of talc is included and the amount of glass
is maintained below about 10 parts by weight per 100 parts by
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weight of the composition~
It has now been discovered that superior
polyblends of poly(l,4-butylene terephthalate) resin and
poly(ethylene terephthalate~ resin are obtained upon
reinforcement with ~ibrous glass, in combination with finely
divided mica. The new compositions possess less inherent
~arpage in the molded article and good moldability when
compared with compositions of glass fiber reinforced polyblends
of polyester resins. The improved resistance to heat
distortion and decrease in warpage is achieved without any
appreciable decrease in other mechanical properties, such
as notched Izod impact strength, tensile strength and mod-
ulus. The flexural strength is improved.
According to this invention, there are provided
reinforced thermoplastic compositions, useful for molding,
e.g., injection molding, compression molding, transfer molding,
and the like, the composition comprising:
(a) a poly(l,4-butylene terephthalate) resin;
(b) a poly(ethylene terephthalate) resin; and
(c) a reinforcing agent combination in an amount
at least sufficient to provide reinforcement comprising (i)
glass fibers and (ii) fine particle size ground mica.
The mica suitable for this invention as component
(c) (ii) can be obtained from a number of commercial sources.
By "finely ground" it is meant that nearly all will pass
through a 325 mesh U.S. standard sieve. Water ground mica is
suitable. A source for this is English Mica Co., Stamford,
Connecticut 06905, U.S.A.
The polyester resins of the compositions of this
invention are available commercially or can be prepared
by known techniques such as by the alcoholysis of esters of
terephthalic acid with ethylene glycol or 1,4-butanediol and
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subsequent polymerization, by heating the glycols with the
free acids or with halide derivatives thereof, and similar
processes. These are described in U.S. 2,465,319 dated
September 2, 1969 and U.S. 3,0~7,539 dated July 31, 1962,
and elsewhere.
Illustratively, these high molecular weight
polyesters will have an intrinsic viscosity of at least about
0.4 deciliters/gram and preferably, at least 0.8 deciliters/
gram as measured in a 60:40 phenol/tetrachloroethane mixture
at 30 C.
In preferred embodiments component (a) comprises
from 1 to 99 parts by weight, and component (b) comprises
from 99 to 1 parts by weight per 100 parts by weight of the
total resinous components in the composition.
The filamentous glass to be employed as component
(~) (i) of the reinforcement in the present compositions is
well known to those skilled in the art and is widely
available from a number of manufacturers. For compositions
ultimately to be employed for electrical uses, it is preferred
to use fibrous glass filaments comprised of lime-aluminum
borosilicate glass that is relatively soda free. This is known
as "E" glass. However, other glasses are useful where
electrical properties are not so important, e.g., the low soda
glass known as "C'1 glass. The filaments are made by standard
processes, e.g., by steam or air blowing, flame blowing and
mechanical pulling. The preferred filaments for plastics
reinforcement are made by mechanical pulling. The filament
diameters range from about 0.00012 to 0.00075 inch, but this
is not critical to the present invention.
The length of the glass filaments and whether or
not they are bundled into fibers and the fibers bundled in
turn to yarns, ropes or rovings, or woven into mats, and the `
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like, are also not critical to the invention. However, in
preparing the molding compositions, it is convenient to use
the filamentous glass in the form of chopped strands of from
about one-eighth to about 2 inches long. In articles molded
from the compositions, on the other hand, even shorter lengths
will be encountered because, dur:ing compounding, considerable
fragmentation will occur. This :is desirable, however, because
the best properties are exhibited by thermoplastic injection
molded articles in which the filament lengths lie between
about 0.00005 and 0.125 (one-eighth) inch.
In general, best properties will be obtained if
the reinforcing agent combination comprises from at least
about 1 part by weight and, preferably, from about 1 to about
60 parts by weight, based on 100 parts of the combined weights
of components (a), (b) and (c).
In the most preferred compositions, the glass
fibers (c) (i) comprise from about 1 to about 10 parts by
weight, and the mica component (c) (ii) comprises from about
15 to about 30 parts by weight per 100 parts by weight of
components (a), (b) and (c).
The compositions of this invention can include, in
addition to the reinforcement combination, other ingredients,
such as dyes, pigments, stabilizers, plasticizers, flame
retardants, drip retardants, and the like, added for their
conventionally employed purposes. Illustrative flame retardant
additives are disclosed in U.S. 3,833,685 dated September
3, 1974; U.S. 3,341,154 dated August 1, 1967; U.S. 3,915,926
dated October 28, 1975 and U.S. 3,671,487 dated June 20, 1972.
Other flame retardants are disclosed in U.S. 3,681,281 dated
August 1, 1972 and U.S. 3,557,053 dated January 19, 1971;
U.S. 3,830,771 dated August 20, 1974 and U.K. 1,358,080.
The compositions of this invention can be prepared
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by a number of procedures. In one way, the reinforcement,
e.g., glass fibers and mica, is put into an extrusion
compounder with the resinous components to produce molding
pellets. The reinforcement is dispersed in a matrix of the
resin in the process. In another procedure, the reinforcement
combination (c) is mixed with the resins (a) and (b) by dry
blending, then either fluxed on a mill and comminuted, or they
are extruded and chopped. The reinforcing agent combination
can also be mixed with the resins and directly molded, e.g.,
by injection or transfer molding techniques.
It is always important that all of the ingredients;
resin, reinforcement and any optional, conventional additives
be as free from water as possible.
In addition, compounding should be carried out to
ensure that the residence time in the machine is short; the
temperature is carefully controlled; the friction heat is
utilized; and an intimate blend between the resin and the
reinforcement is obtained.
Although it is not essential, best results are
obtained if the ingredients are pre-compounded, pelletized
and then molded. Pre-compounding can be carried out in
conventional equipment. For example, after carefully pre-drying
the polyester and the reinforcing agent combination, e.g.,
under vacuum at 100C. for 12 hours, a single screw extruder
is fed with a dry blend of the ingredients, the screw employed
having a long transition section to ensure proper melt~ng.
On the other hand, a twin screw extrusion machine e.g., a
Werner & Pfleiderer machine can be fed with resins and
additives at the feed port and reinforcement down stream.
In either case, a generally suitable machine temperature will
be about 450 to 460F.
The pre-compounded composition can be extruded
and cut up into molding compounds such as conventional granules,
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pellets, etc., by standard techniques.
The composition can be molded in any equipment
conventionally used for glass-filled thermoplastic compositions,
e.g., a Newbury type injection molding machine with conventional
cylinder temperatures, e.g., 525F. and conventional mold tem-
peratures, e.g., 150 F.
The following example illustrates the invention.
It is set forth as a further description but is not to be
construed as limiting the invention thereto.
A dry blend of poly(l,4-butylene terephthalate),
intrinsic viscosity 0.8 dl/g., melt viscosity 1700 poise, poly
(ethylene terephthalate), intrinsic viscosity 0.62 dl/g.,
1/8" glass fibers (Owens Corning 419), finely divided mica,
Ferro 904 antioxidant are compounded and extruded at 5~5F. in
an extruder. The extrudate is pelletized and injection
m~lded at 525F. (mold temperature 130F). The formulations
and physical properties obtained are shown in the following
table:
TABLE. Physical Properties
Ingredients (parts by weight) 1 lA
poly(l,4-butylene terephthalate) 45.5 45.5
poly(ethylene terephthalate) 30.5 30.5
fibrous glass reinforcement
1/8 inch 4 4
mica, 325 mesh 20
talc - 20
antioxidant 0.05 0-05
Properties
Heat Deflection Temp., F.
264 psi 321 287
Warp: As moldedl mm. 0 0
After 30 min. at 350 F., mm. 1.5 7
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Notched Izod impact,
ft.lbs./in. 0.540.56
Unnotched Izod impact,
ft.lbs./in. 6.9 6.7
Tensile strength, psi 11,000 10,000
Flexural modulus, psi 886,000 775,000
Flexural strength, psi 20,000 17,000
* control - talc product designated EMTAL 500.
The composition of this invention (Example 1) is
injection molded into a large part with only slight warpage.
In contrast thereto, an identical part molded from the control
sample (lA*) would have a significantly increased warpage.
Only by such expensive expedients as treating the talc with a
coupling agent is it possible to approach the superior
resistance to heat deflection, warp resistance, flexural
strength and modulus shown by the composition of this
invention.
Obviously, other modifications and variations of
the present invention are possible in the light of the above
teachings. It is therefore to be understood that changes may
be made in the particular embodiments described above which
are within the full intended scope of the invention as defined
in the appended claims.
.
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Supplementary Disclosure
In the principal disclosure we have shown that
articles molded from compositions comprising an admixture of
poly(l,4-butylene terephthalate) and poly(ethylene terephthalate)
reinforced with glass fibers have significantly improved heat
deflection properties when particulate mica is incorporated
therein. The mica under consideration was described as being
fine particle size ground mica, this being defined as being
generally less than 325 U.S. Standard Sieve size.
~e have now found that other grades of particulate
mica may be employed for the same purpose. Suitable grades
range in size from about 10 mesh, U.S. Standard Sieve, to
less than 325 mesh. Commercial mica grades in addition to
those earlier mentioned which are suitable for the present
purposes are available e.g. from Martin-Marietta under the
trade mark "Suzorite" (20H, 10-20 mesh; 200 ~, less than
100 mesh; 00 S, less than 100 mesh; 80 S, 99~ less than 100 mesh).
The best combination of properties, including warp, impact, over-
all strength and paintability, appear to be conferred by a
mica typically represented by Suzorite 200 S.
The following Examples are further illustrating of
our invention.
EXA~IPLES 2-4
The procedure of Example 1 is repeated, omitting
talc and making substitutions in amounts including the mica and
other additives. The ~ormulations and results are set forth
in Table 2.
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Table 2. - Composition of Polyester Resins,
Glass and Mica
_ . . _ .
Example ~ 3 4
Ingredients (parts by weight)
poly(l,4-butylene terephthalate) 46.7 41.7 31.7
poly(ethylene terephthalate) 5 10 15
fibrous glass reinforcement, 1/8" 11 11 11
mica, 10-20 mesha 25 25 25
antioxidant~ .05/1.5 .05/1.5 .05/1.5
impact modifierC 10 10 10
polyethylened 2 2 2
mold releasee 0.1 0.1 0.1
Properties
Deflection Temperature under
load at 264 psi, F. 356 351 321
Warp: as molded, mm. 0 0 ~1
after 30 min at 350F., mm. 1 1 <1
Notched Izod impact, ft.lbs./in. 1.3 1.3 1.1
Unnotched Izod impact, ft.lbs./in. 4.4 4.4 4.4
Tensile strength, psi 8,100 8,400 7,900
a Suzorite 20 H
b Ferro 904/Irganox 1093
c Copel 3320 - Silicone - polycarbonate block copolymer (GE)
d Microthene FN 510 (U.S.I. Chemicals)
e Mold Wiz (Int. EQ-6)
The resistance to warpage is remarkable.
EXAMPLES 5 - 9
Following the general procedure of Example 1 a series
of formulations according to this invention are prepared, molded
and tested. The antioxidant, polyethylene and mold release are
identified in Table 2. The results are set forth in Table 3:
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Table 3. - Composition of Polyester Resins,
Glass and_Mica
Example 5 6 7 8 9
Composition (parts by weight)
poly(l,4-butylene terephthalate) 41.7 36.7 31.7 31.7 28.7
poly(ethylene terephthalate) 10 15 20 20 20
fibrous glass, 1/8" 11 11 11 11 11
mica, 10-20 mesha 25 25 25 -- 25
mica, 99% <100 meshb -- -- -- 25 --
antioxidant .05/.15 .05/.15 .05/.15 .05/.15 .05/.15
impact modifierC 10 10 10 10 --
impact modifierd -- -- -- -- 15
polyethylene 2 2 2 2 --
mold release 0.1 0.1 0.1 0.1 0.1
Properties
Deflection Temperature
under load at 264 psi, F. 352 360 350 371 310
Warp: as molded, mm. 0 0 0 2 0
after 30 min. at 350F., mm. 0 ~1 ~1 2.8 <1
Notched Izod Impact,ft.lbs./in. 1.2 1.1 1.2 .9 1.4
Unnotched Izod impact,ft.lbs./in. 3.9 3.8 4.3 6.2 4.4
a Suzorite 20 H
b Suzorite 80 S
c Copel 3320 (see Table 2)
d Hytrel 4056, Dupont, segmented copolyester.
The compositions have excellent resistance to warpage.
EXAMPLES 10 - 13
The general procedure of Example 1 is repeated and
a series oE formulations according to this invention is prepared,
molded and tested. The results are set forth in Table 4:
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Table 4. - Compositions of Polyester Resins
Glass and Mica
Example 10 11 12 13
Composition (parts by wei~ht)
poly(l,4-butylene tere-
phthalate) 31.7 28.7 31.7 28.7
poly(ethylene tere-
phthalate) 20 20 20 20
fibrous glass, 1/8" 11 11 11 11
mica, 10-20 mesha -- 25 25 --
mica, ~100 meshb 25 -- -- --
mica, 99% ~100 meshC -- -- -- 25
antioxidant* .05/.15 .05/.15 .05/.15 .05/.15
impact modifierd -- 15 10 15
impact modifiere 10 -- -- --
polyethylene* 2 __ 2 __
mold release* 0.1 0.1 0.1 0.1
Properties
Deflection Temperature under
load at 264 psi, F. 360 306 329 321
Warp: as molded, mm. 1.5 0 0 1.5
after 30 min. at 350F., mm. 7 2.5 1 8
~otched Izod impact, ft.lbs./
in. 1.0 1.4 1.2 1.0
~nnotched Izod impact,
ft.lbs./in. 6.9 4.7 4.8 7.2
Flexural strength, psi 15,800 -- -- -
Flexural, modulus, psi 840,000 -- -- --
Tensile strength, psi 9,400 -- -- --
a Suzorite 20 H *See Table 2
b Suzorite 200 S
c Suzorite 80 S
d Hytrel 4056, Dupont
e Rohm & Haas, XP7709
EXAMPLES 14 - 15
Because the mica designated Suzorite 200 S appears to
confer the best balance of overall properties, e.g., warp, impact,
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strength and paintability, two additional formulations are
prepared, molded and tested following the general procedure of
Example 1. The results are set forth in Table 5:
Table 5. - Compositions Comprising Polyester
Resins, Glass Fibers and Mica
Example 14 15
Compositions (parts by weight)
Poly(1,4-butylene terephthalate) 31.7 31.7
Poly(ethylene terephthalate) 20 20
Fibrous glass, 1/8" 11 11
Mica, ~100 mesh 25 25
antioxidant* .05/.15 .05/.15
impact modifierb 13 --
impact modifierC -- 10
polyethylene* 2 2
mold release* 0.1 0.1
Properties
neflection Temperature under
load at 264 psi, F 345 335
Warp, as molded, mm. 0 0
a~ter 30 min. at 350F., mm. 9 9
Notched Izod impact,
ft. lbs./in. 1.1 1.0
Unnotched Izod impact,
~t.lbs./in. 7.0 6.8
Flexural strength, psi 17,100 16,000
Flexural modulus, psi 868,000 826,000
Tensile strength 10,200 9,900
a Suzorite 200S
b Hytrel 4056
c LR 3320
* See Table 2
Obviously, other modifications and variations of the
present invention are possible in tne light of the above teachings.
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It is therefore to be understood that changes may be made
in the particular embodiments described above which are within
the full intended scope of the invention as deined in the
appending claims.
The following trademarks are referenced in the
foregoing disclosure:
"Capel"-- A General Electric trademark for silicone-
polycarbonate block copolymers.
"Emtal" - An Emery Industries Inc. trademark for
talc products.
"Ferro" - A trademark for a series of antioxidants/
stabilizers.
"Hytrel" - An E.I. duPont de Nomours and Company
trademark for segmented copolyesters.
"Irganox" - A Geigy Chemical Corporation trademark
for a series of complex high molecular weight stabilizers that
inhibit oxidation and thermal degredation of ~any organic
materials.
"Suzorite" - A Marietta Resources Internation, Ltd.,
2Q trademark for a series of commercial grades of mica.
A copending Canadian Application Serial No. 293,154
discloses, but does not claim, subject matter disclosed and
claimed in the present application.
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