Note: Descriptions are shown in the official language in which they were submitted.
CA 02293005 1999-12-21
AD-69 94w~r
POLYOXYMETHYLENE RESIN COMPOSITIONS HAVING
IMPROVED MOLDING CHARACTERISTICS
Background of the Invention
The present invention relates to polyoxymethylene (also referred to herein
as polyacetal) resin compositions having improved moldability and improved
physical properties of the molded article.
Polyacetal resin is manufactured by polymerizing a mostly formaldehyde
monomer or a formaldehyde trimer (trioxane). Acetal homopolymer is a
homopolymer of formaldehyde (for example, Delrin~ acetal resin, manufactured
by E.I. du Pont de Nemours and Company). Acetal copolymer is obtained, for
example, by copolymerizing alkylene oxide with for example; trioxane.
Polyoxymethylene resin, because of its high mechanical strength,
excellent abrasion resistance, fatigue resistance, moldability, and the like,
is
extensively used, for example, in electrical and electronic applications,
automotive applications, and precision machine applications.
Polyoxymethylene resins are the most crystalline of the engineering
polymers and as a consequence, freeze quickly in a mold. However, these resins
also exhibit high shrinkage, which often leads to dimensional imbalance
problems
for precise part molding. Recently, nucleated polyoxymethylene resins have
been
2 0 introduced to improve set-up time and reduce shrinkage. But, it is still
desirable
to provide a polyoxymethylene resin having reduced post mold shrinkage
character, a lower thermal expansion coefficient, and improved gear
preciseness
if the application is a gear application.
Summary of the Invention
2 5 Our invention includes a composition comprising polyoxymethylene;
polyalkylene/unsaturated carboxylic acid lower alkyl ester polymeric
nucleating
material, in an amount between about 0.1 and about 20 weight percent of the
composition; waxy material, in an amount between about 0.05 and 5 weight
percent of the composition; and nucleant, in an amount between about 0.001 and
30 about 6 weight percent of the composition. In one aspect, the polymeric
nucleating material comprises ethylene/methyl acrylate copolymer, the vyaxy
material comprises aliphatic amide wax, and the nucleant comprises branched or
cross-linked acetal copolymer or terpolymer in an amount between about 0.1 and
1
CA 02293005 1999-12-21
about 5 weight percent of the composition. In another aspect, the nucleant
comprises talc, silane coated talc or boron nitride, in an amount between
about
0.001 and about 1 weight percent of the composition. The aliphatic amide wax
may comprise ethylene bis stearamide.
Our invention also includes articles molded from our compositions. In
one aspect, the molded article is a gear. In another aspect, the molded
article is a
printer gear.
Detailed Description of the Preferred Embodiments
Preferred compositions in accordance with this invention comprise
polyoxymethylene, polymeric nucleating material, waxy material, and nucleant.
These compositions may also include other ingredients, modifiers, and
additives.
Our compositions exhibit advantageous properties, such as reduced post
mold shrinkage character, lower thermal expansion coefficients, and improved
preciseness in molding applications.
Polyoxymethytene
The polyoxymethylene component preferably comprises the balance of the
composition after all other components and additives are accounted for. The
polyoxymethylene component may also comprise preferably between about 70
and about 99 weight percent of the composition, more preferably between about
2 0 75 and about 99 weight percent of the composition, and even more
preferably
between about 90 and about 98 weight percent of the composition. These ranges,
however, are not meant to be limiting in any way.
The polyoxymethylene preferably includes a wide variety of
homopolymers and copolymers which are known in the art. These polymers are
2 5 generally polymers of formaldehyde in which the polymer chain, exclusive
of the
terminal portions of the chain, is a series of methylene to oxygen linkages.
The
polymer chain can also include moieties of the general formula:
Ri
30 I
- (CO)m
I
Rz
wherein m is an integer of 1 to 5 and R, and RZ are inert substituents which
will
not cause undesirable reactions in the polymer. Such additional components of
3 5 the polymer chain are present as a minor proportion of the repeating
units.
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CA 02293005 1999-12-21
More specifically, the polyoxymethylene resin component as used herein
includes homopolymers of formaldehyde or a cyclic oligomer of formaldehyde,
the terminal groups of which are end capped by esterification or
etherification,
and copolymers of formaldehyde or of a cyclic oligomer of formaldehyde and
other monomers that yield oxyalkylene groups with at least two adjacent carbon
atoms in the main chain, the terminal groups of which copolymers can be
hydroxyl terminated or can be end capped by esterification or etherification.
The polyoxymethylene resin used in this invention can be linear or
substantially linear with only minor amounts of branching and will generally
have
a weight average molecular weight in the range of 5,000 to 200,000, preferably
30,000 to 85,000, more preferably 30,000 to 75,000. The molecular weight can
conveniently be measured by gel permeation chromatography in m-cresol at
160°C or alternatively, hexafluoroisopropanol at room temperature.
Although
polyoxymethylene resins of higher or lower weight average molecular weights
can be used, depending on the physical and processing properties desired, the
polyoxymethylene resins with the above mentioned weight average molecular
weight are preferred to provide optimum balance of good mixing of various
ingredients to be melt blended into the composition with the desired
combination
of physical properties in the components made from such compositions.
2 0 As indicated above, the polyoxymethylene resin can be either
homopolymer with different weight average molecular weights, copolymers of
different weight average molecular weights or mixtures thereof. Copolymers can
contain one or more comonomers, such as those generally used in preparing
polyoxymethylene compositions. Comonomers more commonly used include
2 5 alkylene oxides of 2-12 carbon atoms and their cyclic addition products
with
fonmaldehyde. The quantity of comonomer will preferably not be more than 20
weight percent, more preferably not more than 15 percent, and most preferably
about 2 weight percent. The commonly used comonomers include ethylene
oxide, dioxalane, and butylene oxide. Generally, polyoxymethylene
3 0 homopolymer is preferred over copolymer, because homopolymer has greater
tensile strength and stiffness as well as a lower thermal expansion
coefficient than
copolymer. Preferred polyoxymethylene homopolymers include those whose
terminal hydroxyl groups have been end capped by a chemical reaction to form
ester or ether groups, preferably acetate or methoxy groups, respectively.
35 Polymeric Nucleating Material
The polymeric nucleating material comprises preferably between about
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CA 02293005 1999-12-21
0.1 and about 20 weight percent of the composition, more preferably between
about 0.2 and about 10 weight percent of the composition, and even more
preferably between about 0.5 and about 5 weight percent of the composition.
More than one of the below described compounds may comprise the polymeric
nucleating material component of our compositions.
Preferred polymeric nucleating materials include polyalkylene/unsaturated
carboxylic acid lower alkyl ester polymeric nucleating materials.
Polyalkylene/unsaturated carboxylic acid lower alkyl ester polymeric
nucleating
materials in general are copolymers or terpolymers of a lower alkene (CZ-C4)
and
a lower alkyl ester of an unsaturated acid. An example of polymeric nucleating
materials useful in this invention are ethylene-based polymers of the formula
E/X/Y, preferably E/X, where E is ethylene and X, Y is an unsaturated
carboxylic
acid ester.
The unsaturated carboxylic acid esters include alkyl (C, to Cg, preferably
C, to C4) esters of unsaturated carboxylic acids having 3 to 8 carbon atoms.
Illustrative unsaturated acids include acrylic and methacrylic acids.
Particular
examples of esters are methyl acrylate, ethyl acrylate, propyl acrylate,
isopropyl
acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl
methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl
methacrylate,
2 0 isobutyl methacrylate, glycidyl methacrylate and glycidyl acrylate, among
which
ethyl acrylate and methyl methacrylate are preferred.
Ethylene methyl acrylate copolymer ("EMA") component is particularly
preferred as the polymeric nucleating material and is, in general, a
commercially
available material and can be prepared by known means. The amount of methyl
2 5 acrylate in the EMA is generally about 3-40 weight percent, preferably
about 1 S-
weight percent, of the EMA.
The polyalkylene/unsaturated carboxylic lower alkyl ester nucleating
additive can also be an ethylene-based random polymer of the formula E/X/Y
wherein E is ethylene, X is selected from methylmethacrylate, ethyl acrylate,
and
3 0 butyl acrylate, and Y is selected from glycidyl methacrylate and glycidyl
acrylate,
and glycidyl methacrylate is preferred for Y. E/X/Y consists essentially of
about
5-99% E, about 0-35% X, and about 0.5-10% Y.
An example of the ethylene-based random polymer consists essentially of
about 90%-99% by weight ethylene and about 1%-10% by weight
glycidylmethacrylate. Preferably, this ethylene/glycidyl methacrylate ("EGMA")
random polymer consists essentially of about 90%-97% by weight ethylene and
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CA 02293005 1999-12-21
about 3%-10% by weight glycidyl methacrylate ("GMA").
Another preferred ethylene-based random polymer consists essentially of
about 55%-98.5% by weight ethylene, about 0.5-35% by weight butyl acrylate
("BA"), and about 1%-10% by weight glycidyl methacrylate ("GMA").
Preferably, this ethylene/butyl acrylate/glycidyl methacrylate ("EBAGMA")
random polymer consists essentially of about 55%-84% by weight ethylene, about
15%-35% by weight BA, and about 1%-10% by weight GMA. Most preferably,
this EBAGMA random polymer consists essentially of about 57.5%-74% by
weight ethylene, about 25%-35% by weight BA, and about 1%-7.5% GMA.
The ethylene-based random polymer component can be prepared by
techniques readily available to those in the art. An-example of the EBAGMA
random polymer is provided in U.S. Pat. No. 4,753,980.
Waxy Material
The waxy material component comprises preferably between about 0.05
and about 5 weight percent of the composition, more preferably between about
0. l and about 2 weight percent of the composition, and even more preferably
between about 0.3 and about 1 weight percent of the composition. More than one
of the below described compounds may comprise the waxy material component
of our compositions.
2 0 The waxy material is preferably a material that is capable of being
dispersed in the polyacetal resin and may be a liquid at normal room
temperatures. Alternatively, if this material is a solid at normal room
temperatures, it must become f<uidized at a temperature lower than the
temperature at which the polyacetal is being processed or molded.
2 5 A highly preferred waxy material is an aliphatic amide wax. Aliphatic
amide wax is a chemical compound that is obtained preferably by the
dehydration
of aliphatic carboxylic acid and aliphatic amine, and it has at least one
(preferably
two) amide bond segments) in a molecule. The melting point of the above
compounds is preferably greater than about 60 deg C, more preferably greater
3 0 than about 80 deg C, and most preferably greater than about 100 deg C. A
preferred aliphatic amide wax is ethylene bis stearamide wax, such as Kaowax
EB-FF (available from Kao Corporation, Tokyo, Japan) or Acrawax C (available
from Lonza, Fairlawn, NJ, U.S.A.). Other aliphatic amide waxes include without
limitation stearamide;12-hydroxystearamide; N, N'-Ethylene bis lauramide; N,
35 N'-Ethylene behenamide; and N, N'-Distearyl adipic amide.
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CA 02293005 1999-12-21
Other examples of useful wax materials are natural or synthetic waxes, for
example hydrocarbon and polymeric waxes. Hydrocarbon waxes include mineral,
petroleum, paraffin or microcrystalline waxes and synthetic waxes, such as,
for
example ethylenic polymers. The polymeric waxes include polyethylenes,
polypropylenes and ethylene/propylene copolymers. Good blending is obtained if
the components are mixed together in a twin-screw extruder, which is the
preferred mixing device.
Nucleant
The nucleant component comprises any finely divided solid and preferably
includes at least one of boron nitride, talc, silane coated talc, silica,
polyimides,
branched or cross-linked acetal copolymer or terpolymer, a melamine-
formaldehyde resin, calcium carbonate, diatomite, dolomite, or other commonly
known nucleants for polyoxymethylene. The nucleant component comprises
preferably between about 0.001 and about 6 weight percent of the composition,
and more preferably between about 0.01 and about 4 weight percent of the
composition.
If present in the nucleant component, branched or cross-linked acetal
copolymer or terpolymer comprises preferably between about 0.1 and about 5
weight percent of the composition, and more preferably between about 0.5 and
2 0 about 2 weight percent of the composition. All other nucleants, if present
in the
nucleant component, each comprises preferably between about 0.001 and about 1
weight percent of the composition, more preferably between about 0.01 and
about
0.5 weight percent of the composition, and even more preferably between about
0.02 and about 0.2 weight percent of the composition.
2 5 Branched or cross-linked polyoxymethylene copolymers, talc or silane
coated talc and boron nitride are particularly preferred. Preferred branched
or
cross-linked polyoxymethylene copolymers include Duracon U-10 (available
from Polyplastics K.K., Osaka, Japan) and Celcon CFX 0288 (available from
Ticona, Summit, NJ, U.S.A.). Preferred talc sources include Mistron CB talc
30 (available from Luzenac America, Engelwood, CO, U.S.A.) and Ultratalc 609
(available from Barretts Minerals, Inc., Dillon, MT, U.S.A.).
In a preferred embodiment, the nucleant component comprises branched
or cross-linked acetal copolymer or terpolymer in an amount preferably between
about 0. I and about 5 weight percent of the composition, and more preferably
3 5 between about 0.5 and about 2 weight percent of the composition.
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CA 02293005 1999-12-21
In a another preferred embodiment, the nucleant component comprises
talc, silane coated talc or boron nitride in an amount preferably between
about
0.001 and about 1 weight percent of the composition, more preferably between
about 0.01 and about 0.5 weight percent of the composition, and even more
preferably between about 0.02 and about 0.2 weight percent of the composition.
Also, especially preferred is the use of branched or cross-linked
polyoxymethylene copolymers, talc or silane coated talc, when the waxy
material
component is an aliphatic amide wax, such as ethylene bis stearamide. The
nucleant can optionally be surface treated by standard processes.
The branched or cross-linked polyoxymethylenes useful as nucleants in
the invention may be obtained:
a. by copolymerization of trioxane with at least one compound reacting
multifunctionally and being copolymerizable with trioxane and, optionally,
with
at least one compound monofunctionally reacting and copolymerizable with
trioxane, or
b. by branching or cross-linking reactions performed subsequently with a
linear poly(oxymethylene) having lateral or chainlinked functional groups, or
c. by copolymerization of trioxane with at least one compound reacting
monofunctionally and being copolymerizable with trioxane and a branched or
2 0 cross-linked polyether or by reaction of a linear poly(oxymethylene) with
a
branched or cross-linked polyether.
Small average particle size is preferred for the nucleant. The average
particle size of the nucleant should be less than 20 microns, preferably less
than
10 microns, and more preferably less than 5 microns.
2 5 The nucleant may be an encapsulated nucleant. As used herein,
"encapsulated nucleant" consists essentially of an encapsulant polymer and a
nucleant, and includes within its meaning a "predispersed nucleant," that is,
a
nucleant that is predispersed in, rather than encapsulated by, the encapsulant
polymer.
3 0 The encapsulant polymer can be any moderate melting polymer, i.e., any
polymer which melts at the processing temperatures of the polyoxymethylene
resin of the encapsulated nucleant. Illustrative encapsulant polymers include
linear low density polyethylene ("LLDPE"), high density polyethylene ("HDPE"),
and polypropylene, each of which have a solid density of less than or equal to
1
3 5 gram per cubic centimeter, as measured by ASTM D 1 SOS. Preferably, the
7
CA 02293005 1999-12-21
encapsulant polymer is either LLDPE or HDPE. The encapsulant polymer either
lacks long chain polymer branching in its molecular structure or it is
predominantly linear. The lack of long chain branching is due to the method by
which the encapsulant polymer is produced.
The encapsulant polymer is selected from a group of polymers well known
in the art. The encapsulant polymers are commercially available or,
alternatively,
can be prepared by techniques readily available to those skilled in the art.
Generally, the encapsulant polymers are prepared by polymerizing ethylene or
ethylene and alpha-olefin comonomers in solution phase or gas phase reactors
using coordination catalysts, particularly Zieglar or Phillips type catalysts.
It is preferred that the LLDPE encapsulant polymer have a melt index, as
measured by ASTM D1238 method, condition E, in the range of 5 to SS grams
per 10 min. It is preferred that the HDPE encapsulant polymer have a melt
index,
as measured by ASTM D1238 method, condition E, of about 0.5-7 grams per 10
min. Compositions containing LLDPE or HDPE having melt indices outside the
range given above may yield stock shapes with good porosity values, but can
give
rise to compounded resin and extruded stock shapes having other undesirable
characteristics, such as decreased stability or separation of the
polyoxymethylene
and LLDPE or HDPE (i.e., de-lamination).
2 0 Other optional components
Compositions in accordance with our invention may optionally include, in
addition to the components described above, other ingredients, modifiers, and
additives, including without limitation lubricants, thermal stabilizers and co-
stabilizers, antioxidants, colorants (including pigments), toughening agents
(such
2 5 as thermoplastic polyurethanes), reinforcing agents, ultraviolet
stabilizers (such as
benzotriazoles or benzophenones), including hindered amine light stabilizers
(especially those wherein the hindered nitrogen is of tertiary amine
functionality
or wherein the hindered amine light stabilizer contains both a piperidine, or
piperazinone ring, and a triazine ring), polytetrafluoroethyIene powder or
fiber,
30 glass, and fillers. Suitable thermal stabilizers include polyamides
(including a
nylon terpolymer of nylon 66, nylon 6/10, and nylon 6 and the polyamide
stabilizer of U.S. Pat. No. 3,960,984); meltable hydroxy-containing polymers
and
copolymers, including ethylene vinyl alcohol copolymer and the stabilizers
described in U.S. Pat. No. 4,814,397 and U.S. Pat. No. 4,766,168; non-meltable
3 S hydroxy-containing or nitrogen-containing polymers as described in U.S.
Pat. No.
5,011,890 and in particular, polyacrylamide; and microcrystalline cellulose;
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CA 02293005 1999-12-21
polybeta-alanine (as described in German published application 3715117);
polyacrylamide; or stabilizers disclosed in U.S. Pat. Nos. 4,814,397,
4,766,168,
4,640,949, and 4,098,984; and mixtures of any of the above. Typical
antioxidants include hindered phenols such as triethyleneglycolbis(3-(3'-
tertbutyl-
4'hydroxy-5'methylphenyl)proprionate, N,N'-hexamethylenebis(3,5-di-tert-butyl-
4-hydroxy-hydrocinnamide), and mixtures thereof as well as antioxidants,
including those described in U.S. Pat. No. 4,972,014.
Additives or ingredients that can have an adverse effect on the oxidative or
thermal stability of polyoxymethylene should be avoided.
The compositions described herein may be prepared by mixing all
components with the acetal polymer at a temperature above the melting point of
the acetal polymer by methods known in the art. It is known to use intensive
mixing devices, such as rubber mills, internal mixers such as "Banbury" and
"Brabender" mixers, single or multiblade internal mixers with a cavity heated
externally or by friction, "Ko-kneaders", multibarrel mixers such as "Farrel
Continuous Mixers", injection molding machines, and extruders, both single
screw and twin screw, both co-rotating and counter rotating, in preparing
thermoplastic polyacetal compositions. These devices may be used alone or in
combination with static mixers, mixing torpedoes and/or various devices to
2 0 increase internal pressure and/or the intensity of mixing, such as valves,
gates, or
screw designed for this purpose. Extruders are preferred, with twin screw
extruders being most preferred. Of course, such mixing should be conducted at
a
temperature below which significant degradation of the polyacetal component
will occur. Generally, polyacetal compositions are melt processed at between
170
2 5 °C and 290 °C, preferably between 185 °C and 240
°C and most preferably 195 °C
and 225 °C.
Shaped articles may be made from the compositions of the present
invention using methods known in the art, including compression molding,
injection molding, extrusion, blow molding, rotational molding, melt spinning,
3 0 and thermoforming. Injection molding is preferred.
Examples of shaped articles include gears, sheet, profiles, rod stock, film,
filaments, fibers, strapping, tape, tubing, conveyor links or chains and pipe.
In
particular, gears can be molded with high preciseness and low post mold
reduced
shrinkage. To make a relatively precise gear, it is desirable to control
3 5 dimensional changes (e.g. shrinkage, post mold shrinkage, and thermal
expansion) caused by environmental changes. With our resin composition, it is
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CA 02293005 1999-12-21
possible to mold a gear having reduced thermal expansion as well as high
preciseness and low post mold reduced shrinkage. Particularly preferred are
printer gears molded from our compositions. Also, conveyor links or chains can
be formed by injection molding. Such shaped articles can be post treated by
orientation, stretching, coating, annealing, painting, laminating, and
plating. Such
shaped articles and scrap therefrom can be ground and remolded.
Examples
The following examples illustrate embodiments of our invention. Our
invention, however, is not limited to these examples.
The following abbreviations used in the examples are explained as
follows:
POM: polyoxymethylene
EMA: ethylene/methyl acrylate copolymer
EBSA: ethylene bis stearamide
Example 1
Sample Nos. 1-7 are embodiments of our invention. The compositions of
Sample Nos. 1-3 are displayed below in Table lA, and the compositions of
Sample Nos. 4-7 are displayed below in Table 1B.
In Samples 1 and 3, the POM is a capped POM with a flow grade of 900,
2 0 whereas in Sample 2, the POM is a capped POM with a flow grade of 1700.
In Sample 6, the branched POM copolymer is Duracon U-10, whereas in
Sample 7, the branched POM copolymer is Celcon CFX 0288.
TABLE lA
Sample No.
POM 95.475 96.45 96.45
EMA 2.000 2.00 2.00
EBSA 0.800 0.80 0.80
Branched POM 1.000 _ _
Copolymer
Talc - 0.15 0.15
Polyacrylamide 0.625 0.50 0.50
(thermal stabilizer)
Irganox 245 (antioxidant)0.100 0.10 0. l0
TOTAL 100.00 100.00 100.00
CA 02293005 1999-12-21
TABLE 1 B
Sample No. 4 5 6
POM 96.375 96.375 95.475 ~ 95.475
EMA 2 2 2
2
EBSA 0.8 0.8 0.8 0.8
Branched POM - - 1.0 i.0
Copolymer
Fine Talc 0.1 _
Silane Coated - 0.1 _
Talc
Polyacrylamide 0.625 0.625 0.625 0.625
(thermal stabilizer)
Irganox 245 (antioxidant)0.1 0.1 0.1 0.1
TOTAL 100.00 100.00 100.00 100.00
~
Example 2
Sample Nos. 1-3 were evaluated for shrinkage, post mold shrinkage,
roundness, gate seal time, and crystallization half time.
All dimensional measurements were conducted on a molded pulley having
a 100 mm outer diameter, a 10 mm inner diameter, and a 10 mm height.
Shrinkage and post mold shrinkage for evaluated resins were measured by
the calculation of the following formulae.
S = ~D"~ D° ~ x 100 (I)
where S is Shrinkage, Dm is Dimension of Mold tool, and Dp is Dimension of
Parts; and
PMS = S;";,;~, - SaureaIrJ
where PMS is Post Mold Shrinkage, S initial is Shrinkage as mold, and S
a""ealed is
Shrinkage after annealed for 4 hours in 70 deg C air oven.
1 S With respect to roundness, we measured roundness of the pulley using a
roundness tester. We employed a Mitutoyo Roundtest RA-2A (available from
Mitutoyo Corporation, Kanagawa, Japan).
Regarding gate sealing time, we defined gate sealing time as the time the
weight of the pulley remained unchanged as the hold pressure time increased
2 0 gradually.
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CA 02293005 1999-12-21
We measured crystallization half time using isothermal DSC. The test
conditions were as follows.
Starting temperature: 200 deg C
End temperature: 150 deg C
Cooling rate: 200 deg C / min.
The results are displayed below in Table 2.
TABLE 2
Property Sample No. Sample No. Sample No.
1 2 3
Shrinkage (%) 2.13 1.90 1.97
Post mold shrinkage0.062 0.065 0.075
(%)
Roundness (gym) 29 21 26
Gate seal time 12 15 16
(secs)
Crystallization 0.31 0.39 0.39
half time
(min.)
Example 3
Sample Nos. 1-3 were evaluated for warpage. Warpage evaluations were
conducted using a three dimensional coordinate measurement machine on a round
molded article having a 100 mm diameter and 1.6 mm thickness. We used a
Mitutoyo Coordinate Measuring Machine LJ704 (available from Mitutoyo
Corporation). Before measurement, the molded article remained in the
temperature/humidity-controlled room for three days after being molded.
Warpage value should be as low as possible for precise part application.
The results are set forth in Table 3 below.
TABLE 3
Sample No. Z 2 3
Warpage (mm)0.135 0.072 0.055-
I
2 0 Example 4
Sample Nos. 1-3 were evaluated for tensile strength, elongation, flexural
modulus, and N Izod impact. Each test was conducted in accordance with ASTM
methods widely used for the evaluation of engineering plastics.
The results are set forth in Table 4 below.
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CA 02293005 1999-12-21
TABLE 4
Property ' Sample No. Sample No. Sample No.
1 2 3
Tensile strength63.5 64.2 66.4
(MPa)
Elongation (%) 50.3 20.4 32.3
Flexural modules3077 3106 3200
(MPa)
N lzod impact 62. I 48 61.1
(J/m)
Example 5
Sample Nos. 4-7 were evaluated for post mold shrinkage, roundness, and
gate seal time in accordance with the same procedures employed in Example 2.
The results are set forth in Table 5 below.
TABLE 5
Property Sample Sample Sample Sample No.
No. 4 No. 5 No. 6 7
Post mold shrinkage0.06 0.04 0.04 0.05
(%)
Roundness (pm) 30 32 34 30
Gate seal time 11 11 11 11
(secs)
While this invention has been described with respect to what is at
present considered to be the preferred embodiments, it is to be understood
that the
invention is not limited to the disclosed embodiments. To the contrary, the
invention is intended to cover various modifications and equivalent
arrangements
included within the spirit and scope of the appended claims. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass
all such modifications and equivalent formulations and functions.
13
