Note: Descriptions are shown in the official language in which they were submitted.
1910019 E~SS ~AIL : B03100500W
IMPROVED POLYVINYL CHLORIDE BLEND8
Field of the Invention
This invention relates to blends of rigid or semi-
rigid polyvinyl chloride. In particular blends of PVC are
disclosed having improved performance for utilization in
injection molding, in particular, large or intricate
articles such as appliance or office automation (AO)
machine housings.
Background
Thermoplastic vinyl based technology directed to
replacement of metal and higher performance engineering
thermoplastics in AO end-uses for instance, is gaining
momentum. This is a departure from traditional uses
pertaining to extrusion related PVC art. PVC, viewed from
a commodity resin perspective, is known for limited dynamic
thermal stability and high melt viscosity. As a result of
advancements in resin quality and compound formulation,
improved single phase PVC formulations directed to
overcoming these and other limitations are making inroads
in custom injection molding compound (CIM) for a variety of
end-use markets including the aforesaid appliance and
office automation (AO) business machine housing markets.
Specifically, the pertinent art is directed generally
to providing higher melt flow and reduced melt viscosity of
PVC compounds while maintaining or desiredly improving heat
deflection temperature (HDT). These are commercially
valuable property combinations characteristic of higher
valued, more crystalline engineering thermoplastics. U.S.
Pat. Nos. 4,339,554, 4,458,046, and 4,469,845 describe PVC
polyblends containing copolymers of styrene and maleimide.
These disclosures are directed to various copolymers of
styrene and imide derivatives of maleic anhydride blended
- 2 - 2~57~' ~
with PVC resins in order to obtain increased HDT. Impact
modifiers are suggested in U.S. Pat. Nos. 4,469,844 and
4,469,845 which describe improved polyblends of grafted
rubber-modified vinyl chloride resins. The polyblends
optionally contain ABS, MBS, or an ungrafted rubber and
exhibit higher softening temperatures than that of the
vinyl chloride resin.
U.S. Pat. No. 4,595,727 teaches a methacrylate derived
imide blend with rubber modified PVC comprising: 10~ to
90% by weight of a polyglutarimide with 90% to 10% by
weight of rubber modified PVC. The polyglutarimide is
prepared by reacting an acrylic polymer, particularly
polymethyl methacrylate or a copolymer of methyl
methacrylate and a minor amount of an ethylenically
unsaturated comonomer, with an aminating agent such as
ammonia or alkyl amine. The rubber-modified vinyl chloride
resin is prepared by polymerization of vinyl chloride in
the presence of 2 to 50 percent, based on the weight of the
resin, of a rubber to form a graft copolymer.
Kokai application number 56-159243 describes a blend
of glutarimide polymer exhibiting a higher heat deflection
temperature, however it is also demonstrated that melt flow
is reduced. For Ao injection molding PVC based compounds,
higher melt flow rates would be desired. Kokai application
Number 2-142845 provides an improved melt flow component
for a PVC/glutarimide blend comprising a polyolefin or
polystyrene diblock with methacrylate, PVC, ~-caprolactone,
EVA, SMA, and others. Preferred amounts of this diblock
range from 0.5 - 10 weight parts. The glutarimide is
present at 5-50 parts.
An approach aiming at direct modification of
particulate PVC resin can be found in U.S. Pat. No.
4,814,387 pertaining to PVC treated with a low I.V., high
glass transition temperature improving agent. The method
of treatment is overpolymerization on PVC resin of a high
glass transition temperature composition in combination
~ith molecular weight modifying amounts of chain transfer
agent. The overpolymerization component consists of
~ ~ 5 7 ! ' I ~
polymerized monomers selected from styrene and its
derivatives, vinyl nitriles, methacrylates, maleimides,
with the preferred component consisting of a copolymer of
~-methyl styrene and acrylonitrile.
A single phase morphology CPVC composition is
disclosed in U.S. Patent No. 4,847,331 wherein a blend of
CPVC having a chlorine content of between about 60~ and 66%
by weight is combined with a polymethylmethacrylate
comprising not more than 80% by weight of the blend.
Within the specified chlorine content, the composition of
matter displays homogeneous, substantially single phase
behavior with the CPVC and polymethylmethacrylate being
substantially or completely miscible. The resulting
blended material exhibits enhanced temperature and
durability properties and remains homogeneous up to a
temperature of 230C. CPVC generally exhibits
significantly higher melt viscosity than a comparable
molecular weight PVC. This is substantially a result of
appreciably lower melt flow at useful chlorine levels of
63-67 % yet these resins are established for higher
continuous use temperatures.
A ternary blend of PVC/Polycarbonate/ABS is disclosed
in U.S. Pat. no. 3,882,192. Particularly preferred blends
contain from 30-50 parts of each component. The preferred
method of preparation involves a first combination of PVC
and ABS, followed by combination of this blend with
polycarbonate. Impact strength and heat distortion
temperature are notably enhanced.
A single phase PVC modified with a high melt flow
shear modified polypropylene is disclosed in U.S. Patent
No. 4,665,118. This disclosure does not reveal that a
significant limitation in attaining acceptable impact
strength is observed with blends of the disclosed
polyolefin and PVC. It is well established that this is an
incompatible combination. The polypropylene acts generally
as a fusion retardant in an external lubrication function.
~ Q ~
With regard to HDT, such a blend would result in no
appreciable loss in HDT, however not an insignificant
amount of an impact modifier would nonetheless be required.
The presence of this modifier expectedly would decrease
both melt flow and HDT which is an undesired effect.
U.S. Patent No. 4,267,084 discloses a blend of a major
amount of a first higher molecular weight (I.V.~ PVC with a
minor amount of a lower molecular weight PVC. The blend is
disclosed as exhibiting improved thermal stability compared
to a blend wherein the lower I.V. PVC is not modified with
a mercaptan or disulfide compound. The compositions
disclosed contain from 70 weight parts to about 90 weight
parts of a PVC having degree of polymerization (DP) of 1020
and 1320, with 30 to 10 weight parts of a lower molecular
weight PVC having DP of between 130 to about 580. In this
blend it is the higher I.V. PVC which is present in the
major amount and dominates the properties of the continuous
phase.
Owing to the present variety of methods aimed at
enhancing PVC compounds particularly for injection molding
uses, the attendant antagonistic relationships between melt
flow, impact modification and HDT remain as limitations for
enhancements. It would be desirable to arrive at a PVC
blend exhibiting adequate melt flow and inherently better
impact properties thereby requiring less conventional
impact modification. Attaining the desired level of impact
strength with reduced levels of conventional impact
modifiers would be advantageous due to the deleterious
effects of these modifiers on melt flow rate, melt
viscosity, HDT, weatherability and dynamic thermal
stability.
~UMMARY OF THE INVENTION
It is therefore an aspect of the present invention to
provide rigid blends of a first and second PVC (PVC~PVC)
selected according to a relationship between said resins
relative to differences in inherent viscosity (~I.V.)
~b 7~
between the two said resins so as to yield a desired
combination of property improvements.
It is another aspect of the present invention to
provide a blend of said first and second PVC which exhibits
high melt flow achieved by selecting the two said resins
based on this ~I.V. relationship.
In a further aspect of the present invention the
blends can further comprise a Tg enhancing agent and
exhibit elevated annealed heat distortion temperatures in
addition to exhibiting adequate melt flow desired
especially for injection molding processes. These objects
are achieved in a blend comprising a major amount of a PVC
having a lower I.V. relative to a minor amount of a higher
I.V. PVC blended therewith, said difference in I.V. is
specified herein below within preferred ranges.
Specifically, these aspects are achieved in a blend
composition comprising a major proportion of a first
polyvinyl chloride polymer having an inherent viscosity
~I.V.) measured per ASTM-D1243 of between 0.2 and 2.0 and a
minor proportion of a second polyvinyl chloride polymer
having an inherent viscosity between 0.4 and 2.5 wherein
said inherent viscosity for said second polyvinyl chloride
must be at least 0.2 I.V. units higher but preferably not
more than about 1.0 I.V. units higher, provided that the
I.V. can lie between about 1.0 and 2.0 units when the
amount of the higher I.V. PVC does not exceed about 20
weight parts per 100 weight parts of the total PVC.
Surprisingly the beneficial effects occur when the second
PVC is present at between about 0.1 to about 5 weight parts
per 100 weight parts total PVC.
Detailed Deqcription
Polyvinyl chloride resin as referred to in this
specification includes polyvinyl chloride homopolymers,
~inyl chloride copolymers, graft copolymers, vinyl halide
polymers polymerized in the presence of any other polymer
such as a high heat distortion temperature enhancing
polymer, impact toughener, barrier polymer, chain transfer
agent, stabilizer, plasticizer or flow modifier. For
example a combination of modifications may be made with the
PVC polymer by overpolymerizing a low viscosity, high glass
transition temperature (Tg) enhancing agent in the presence
of a chain transfer agent. Such a method is disclosed in
U.S. Pat. No. 4,814,3~37 incorporated herein by reference.
In another alternative vinyl chloride may be polymerized in
the presence of said Tg enhancing agent, the agent having
been formed prior to or during the vinyl chloride
polymerization.
Where the selected PVC is a vinyl chloride copolymer,
any monomer copolymerizable with vinyl chloride and known
in the art may be employed, thus, the practice of the
present invention does not preclude selection of one or
more than one comonomer. Such co-polymerizable monomers
for PVC include olefins, diolefins, acrylate esters,
methacrylate esters, styrene derivatives, acrylonitrile,
vinyl esters, vinylidene chloride, vinyl ethers.
Crosslinking comonomers such as allyl methacrylate, and
diallyl phthalate are preferably absent. Preferred
comonomers include ethylene, propylene, 1-butene, 2-butene,
l-pentene, l-hexene, isobutylene and vinylidene chloride.
The most preferred comonomers are ethylene, propylene, 1-
butene and isobutylene. The amount of comonomer that may
be polymerized with vinyl chloride is a function of the
choice of comonomer, as is well understood by those skilled
in the art. Most preferably, the first polyvinyl chloride
polymer as well as the second polyvinyl chloride blended
therewith are polyvinyl chloride homopolymers or copolymers
with the most preferred comonomer(s).
Of particular importance to the present invention is
the I.V. of the first and second PVC resins. Each must be
selected within a particular range in order to exhibit the
property maxima shown below by way of the examples.
~)a~
Inherent viscosity is defined In ASTM D-1243 as the
ratio of the natural logarithm of the relative viscosity of
a resin and the concentration of the solution used to
measure the viscosity. ASTM D-1243 as measured herein
employs a 0.2 g sample in 100 ~1 of cyclohexanone at 30C.
These values have been related to the polymerization degree
(JIS K 6721) and weight average molecular weight of a
polymer as reported in Plastics, 28 98 (1963). The I.V. of
the preferred first PVC can be chosen within the range of
about 0.2 to about 1.0, more preferably from about 0.3 to
0.7. The I.V. of the preferred second PVC can be chosen
within the range from about 0.6 to 1.9, more preferably
from 0.8 to 1.6 and most preferably from 0.9 to 1.05 I.V.
As introduced above, a trade-off in melt flow versus
I.V. exists for PVC. Conventional PVC flow enhancers such
as ~-methyl styrene polymers or high melt flow
polypropylene generally are brittle. These do not provide
toughening of the compound, and thus require additional
impact modifiers. The approach of the present invention
involves modifying PVC preferably not with an incompatible
flow enhancer which may require further impact modifier and
compatibilizer, but with a minor amount of a higher I.V.
PVC. This approach provides a desired combination of
properties. In particular, a relatively high melt flow PVC
was blended with a minor amount of a second PVC having
higher I.V. than the first PVC . This resulted in a
reduction in the melt flow rate but not so severe as to
limit practical processing of the blend. The reduction in
melt flow rate was accompanied by unexpected improvements
in tensile strength, elongation and impact toughness
achieved without a significant loss in heat deflection
performance. The preferred blends contain a minor
proportion (in relation to total PVC) of a second PVC
having an I.V. at least about 0.2 units higher than the
I.V. of the first PVC and preferably a ~ I.V. of 0.2 to 1.0
r j f,
I.V. with the most preferred ~ I.V. of from 0.35 to 0.65
unitC~ the minor component PVC blended therewith always
having the higher I.V.. With this relationship
acknowledged, a wide range of I.V. can be selected for
both. For example, a preferred first PVC polymer having an
I.V. of from about 0.3 to about 0.7 can be selected in
blends with a minor amount of a PVC polymer having the
higher I.V.. The I.V. of the minor component PVC (PVC2)
which is optimum for a particular first major component PVC
(PVC1) will be preferably from about 0.2 to about 1.0 I.V.
units higher than the I.V. of the first PVC. Where the
first PVC possesses the preferred I.V. relative to the l.V.
for the second PVC employed, the preferred combination of
properties can be achieved. At a point where melt flow
becomes generally inadequate for the intended molding
processes as evidenced by spiral melt flow of less than
about 25 inches (~3 cm), an optional melt flow enhancing
additive can be employed. Preferable flow enhancing
additives are the aforementioned ~-methyl styrene polymers
and low acrylonitrile containing SAN copolymers in addition
to modifications which can be made to the PVC polymer
itself outlined above. Typical usage levels for melt flow
enhancers would be about 0.2 to about 20 parts by weight
based on 100 weight parts of the combined weights of PVC.
Preferredly the levels of such melt flow enhancers are
minimized by selecting the preferred PVC I.V. ranges so as
to give adequate melt flow for the blend.
A conventional PVC resin can be prepared by any known
polymerization process such as, but not limited to
suspension, mass, solution, emulsion, dispersion and
microsuspension techniques. A preferred process for
preparing conventional polyvinyl chloride resin for use in
this invention is the aqueous suspension process. The
suspension process involves an agitated reaction medium
during the entire reaction period. Water is the
polymerization medium
~ ~ ~ 7 3 . .~
and a vinyl monomer to water ratio is selected in the range
of about 1:1 to l:10. Preferably a vinyl monomer : water
ratio in the range of about 1:1 to 1:4 is employed.
Skinless PVC suspension resins may be used in the
blends of the present invention. A preferred embodiment of
the instant invention includes a skinless resin as the
higher I.V. PVC of the blend. A method for preparing
skinless PVC resins is disclosed in U.S. Patent No.
4,711,908, incorporated herein by reference. High I.V.
skinless resin has superior friability.
The particular inherent viscosities for the first and
second PVC resins are generally controlled during the
polymerization of each said resin by controlling
polymerization temperature and/or by the use of chain
transfer agents, both techniques being known in the art.
Within the preferred QI.V. range, further variation of
composition is contemplated by varying the weight ratio of
PVC1 and PVC2. Generally, the higher I.V. PVC is present
in amounts from 0.1 to about 49 weight parts, preferably
from 0.1 to less than 20 weight parts, more preferably from
0.1 weight parts to 10 weight parts and most preferably
from 1.0 to 5 weight parts per lO0 weight parts of combined
PVC in the blend.
The amount employed of the higher I.V. PVC component
is efficient in achieving desired property improvements
with as little as one weight part present, and at the same
time heat distortion temperature is not appreciably
sacrificed. Melt flow is not severely sacrificed and
remains desiredly high for those blends which display an
optimum balance of improved strength, impact resistance,
HDT, and melt viscosity. Moreover it is understood that
conventional impact modifiers generally act as melt flow
suppressants, therefore, with reduced levels of impact
modifier required in the blends of the present invention, a
relative gain in melt flow is achieved.
~J~fi i~
-- 10 --
The PVC1/PVC2 blend can contain effective amounts
generally ranging from 0.5 to about 20 parts by weight per
100 weight parts total PVC (phr) of each of various
lubricants, and stabilizers known in the art. For example,
various primary and/or secondary lubricants such as
oxidized polyethylene, polypropylene, paraffin wax, fatty
acids and the like can be utilized. Thermal and W
stabilizers can be utilized such as various organo tins,
for example dibutyl tin, dibutyltin-S-S'-bis-
(isooctylthioglycolate), dibutyl tin dilaurate, and
dimethyl tin diisooctylthioglycolate. Secondary
stabilizers may be included for example a metal salt of
phosphoric acid or various epoxidized oils. Specific
examples of salts include water- soluble, alkali metal
phosphate salts, disodium hydrogen phosphate,
orthophosphates such as mono-,di-,and tri-orthophosphates
of said alkali metals, alkali metal polyphosphates, -
tetrapolyphosphates and -metaphosphates and the like.
Typical levels of secondary stabilizers range from about
0.1 wt. parts to about 7.0 wt. parts per 100 wt. parts PVC.
In addition, antioxidants such as phenolics, BHT, BHA,
various hindered phenols and various inhibitors like
substituted benzophenones can be utilized.
Inasmuch as good impact strength is often desired,
polymeric impact modifiers can be added, as noted above,
which are known to the art as well as to the literature.
For example, various impact modifiers can be utilized as
set forth in The Encyclopedia of PVC, Volume 2, Chapter 12,
Marcel Dekker, Inc., New York, 1977, which is hereby
incorporated by reference. Examples of various specific
polymeric impact modifiers include various acrylonitrile-
butadiene-styrene (ABS) polymers, the various chlorinated
polyethylenes, the various graft copolymers of acrylic
rubbers, the various poly(ethylene-co-vinyl acetates),
styrene-butadiene-styrene block copolymers, graft
copolymers of methylmethacrylate, butadiene and styrene
(MBS), graft copolymers of acrylonitrile, butadiene and
styrene (ABS) and the like. Polymeric impact modifiers of
these types are commercially available. Preferred impact
modifiers include ABS, MBS, graft copolymers of acrylic
rubbers and chlorinated polyethylene. Regardless of the
particular impact modifier utilized, the amounts thereof
can naturally vary, depending upon the desired impact
strength as typically measured by an Izod impact test (ASTM
D256). The levels of impact modifier present can vary from
about 1 to about 200 parts by weight, preferably from about
5 to about 50 parts by weight, and most preferably vary
from 5 to 20 "parts by weight per 100 weight parts of
PVCl/PVC2" (phr). When employing from about 100 to 400
weight parts of Tg enhancing agent per 100 parts of
PVC1/PVC2, the level of impact modifier preferred is in a
range of from about 30 to 200 phr. Accordingly, the blends
of the present invention have the capacity to be impact-
modified to achieve notched Izod values generally in excess
of 100 N-m/m, desirably in excess of 200 N-m/m and
preferredly in excess of 230 N-m/m.
Various fillers, pigments and reinforcing materials
can also be utilized in amounts up to about 200 or 300
parts by weight for every 100 parts by weight of the PVC
blend. Examples of fillers include calcium carbonate,
clay, silica and various silicates, talc, carbon black and
the like. Reinforcing materials include glass fibers,
polymer fibers and cellulose fibers. Such fillers are
generally added in amounts of from about 3 to about 100
parts by weight for every 100 parts by weight of the
combined PVC resins. Examples of various pigments include
titanium dioxide, carbon black and the like. Fillers,
pigments or reinforcing mater, also can be combined.
Plasticizers may be included in any manner and amount.
Exemplary plasticizers are set forth in The Technology of
Plasticizers, by Sears and Darby, pages 893-1085, John
Wiley and Sons, New York, 1982 , which is incorporated
J ~
- 12 -
herein by reference. Plasticizers typically lower the HDT
and therefore are preferably avoided or present in minor
amounts of no ~ore than about 10 weight parts per 100
weight parts of total PVC.
The compound in a fused, cubed state can be
subsequently extruded, or injection molded or processed by
any suitable melt processing equipment. The vinyl chloride
polymers can also be mixed with the various additives in a
high intensity mixer such as a Henschel mixer and then
processed on an extruder into pellets or directly into a
finished article. In general, any conventional means of
compounding such as a Banbury mixer, two-roll mill,
Henschel mixer, ribbon blender, compounding extruder,
injection molding machine and the like can be used to
produce fused articles of this invention.
The compounds of the present invention are fused under
heat and pressure. The fused compound is then processed by
a variety of steps including injection molding, extrusion,
calendering, thermoforming, compression molding, and blow
molding to form useful articles including molded sheets,
trays, shrouds as for fans, appliance parts and covers,
electrical outlets, business machine parts and housings,
piping, automotive components and numerous others.
The invention will be better understood by reference
to the following examples.
~t~
- 13 -
EXAMP~E8 1-11
The examples in Table 2A employed a first
uncrosslinked PVC (PVCl) having an I.V. of 0.68 and a
second uncrosslinked PV~ (PVC2) having an I.V. of 0.92.
The amount of the second I.V. PVC was varied as was the
level of polymeric impact modifier. All parts are
expressed in parts by weight (pbw). In the examples 1-25,
3 pbw of lubricant, 2 pbw of tin stabilizer and 2 pbw of
acrylic processing aid were also included which are
commonly used in PVC compounding art.
The ingredients were hand mixed and then fluxed in a
Banbury. The fused compounds were milled on a 2 roll mill.
The compound was cubed and injected molded into standard
test specimens. An Instron capillary rheometer was used to
measure low shear viscosity in poise (p) at 149 reciprocal
seconds. Izod impact tests were conducted for notched
copper case (N) and unnotched (UN) specimens, at room
temperature and -40C. Testing of the molded specimens was
performed by the methods of Table 1.
TABLE 1
Method Units
Annealed Heat Dist. Temp. ASTM D648 C
Izod Impact Resistance ASTM D250 J/M of notch
Spiral Mold Flow see below inches
Spiral mold flow is a measure of the length of a
standardized injection shot and is a relative indication of
injection melt flowability under a fixed work input and a
fixed cross-section die. The test can predict limitations
in size and configuration of injection molding dies for a
given resin compound. The test employs a graduated spiral
flow mold with defined cross section used in conjunction
with an injection molding machine. Generally, the mold
temperature is set within a range from 20C to about 75C,
and injection melt pressure is constant. A screw having a
L/D typically greater than 15 is used. For every compound
- 14 - ~J Q~73 J.9
at least three consecutive shots were used for averages of
spiral flow length measurement. The compositions in the
examples were also evaluated for processing stability. A
primary commercial measure of the relative thermal
stability and processability of PVC compounds is the
"dynamic thermal stability time" (DTS) in minutes. This
test is designed to measure the time-torque relationship at
selected temperatures using an instrument such as the
Brabender Plasti-corder. The test value generally
reported, and used for comparison, is the "DTS time". DTS
time is herein defined as the time required for the samples
taken at two minute intervals from the melted mass in the
Brabender bowl to turn to a relatively dark color. The
experienced operator can accurately judge the point which
represents degradation of the polymer. DTS time is
dependent not only on polymer properties, but also on
temperature, sample size, stabilizers, lubricants,
instrument operating conditions, degree of instrument
maintenance, and other conditions which are controlled for
accurate comparison between different compounds.
- 1 5 - ) ~ t~
TABLE2A
-IV. C~ 2- -3 -4 5- C3
68 100 ~ 95 90 80 100
PVC2' 92 0 1 5 10 20
PVC2~ 1.6 _ _ _ _
IMOD. 8 8 8 8 8 13
~wt.pa~s
TABLE2B
r c-l -2 -3 -4 -5 C-6
IzodRTN 18 18.4 18.2 19.2 19.1 18
¦ IzodRTUN 33.9 39.6 40.0 40.0 40.0 40.0
I
¦ Izod-40N 8.07 5.47 11.1 7.2 3.5 3.7
¦ Izod~0UN 36.7 37.5 40.0 31 40 22.7
I HDT66psi 72.5 72 72.5 71.5 70.574.5
I _
VICAT8 84 84 84.5 84 87.5 85
SpiralFlow(in.) 21 21 20 19.5 1B.5 18.8
LoShearVisc.14,56615,607 16,283 15,45119,144 16,283
(mTinS.) 12 12 11 11 :0 10
Table 2B illustrates the properties obtained from an
evaluation of the examples comprising the components listed
in Table 2A. Examples 2-5 represent a series of PVC/PVC
blends having a ~ I.V. (0.92-0.68) equal to 0.24 units
wherein the major component PVC (PVCl) as in all examples
of the present invention has a lower I.V. Examples 2 and 3
illustrate that a preferred balance of properties can be
- 16 - '$~ 6 ~
obtained by incorporation of a minor amount of PVC2 having
an I.V. 0.24 units higher than PVCl. Examples 2 and 3
compare favorably to Examples C1 and C6 absent PVC2.
Examples 2 and 3 achieve comparable impact strength with
impact polymeric modifier alone either at 8 parts or at 13
parts as in Examples C1 or C6. Spiral flow was not
significantly diminished in Examples 2-5 vs. C1. It was
unexpected that Example 3, having 5 parts of PVC2 and the
same level of polymeric impact modifier as in Example 1
would yield the observed, combination of impact strength
HDT, VICAT B, spiral flow and DTS time. Example 5
illustrates loss in some impact properties, HDT, low shear
viscosity, spiral flow and DTS time by the incorporation of
20 parts of PVC2 and is not as desirable.
1 7 ~ tl
TABIE 3~
E~ C--~ 8 -- 10 ~--~ ~--2
WP~/C99 10092 97 95 90 90
10~ wt. parts
TABLE 38
Example C1 _-- 10 11 12
IzorJ RT N 1a 19.5 18.619.4 18.9 18.1
Izod RT UN 39.9 40 39.939.9 39.8 40.0
15l~od 40 N 8.07 9.9 4.0 6.3 7.1 7.0
kod -40 UN 36.7 40.0 29.739.8 39.7 39.7
HDT 66 psi 72.5 72.5 73.5 73 71,5 73.5
VICAT E~ 84 85 85 88.5 89.5 87
Spiral Flow (in.) 21 21 220.7 17.7 19 17.5
20Vlsr,. (poisr~)14,56613,734 14,30615,711 16,075 21,849
DTS 12 = 12 1~ 10 9
Tables 3A and 3B illustrate a series of PVC/PVC blends
wherein the ~ I.V. is equal to 0.92 units (1.60 - 0.68).
The composition of Example 8 comprising 1 weight part of
PVC2 having I.V. of 1.6 yielded a desirable combination of
impact strength, low shear viscosity, spiral flow, Vicat B
and DTS time. Unexpectedly, at 20 weight parts PVC2 as in
Example 12, an undesired combination of properties were
found, in particular, a significant rise in low shear
viscosity renders this composition difficult to process.
1 8 ~J 3 ~ J
TAE~LE 4A
.. .
Exaunp~ I.V. C13 14 15 16 17 18
P~nC1 0.46 100 99 97 95 90 80
. . 11
PVC2' ~6 O _ _ S -
I ~hDd' _ 8 8 8 8 8 8
Wt. pArts
TAE3LE 4B
¦ Example C13 14 15 13 17 18
1 0 ¦Izod RT N 0.3 10.3 6.7 0.9 11.5 10.0
¦~od RT UN 39.8 23.3 39.639.7 39.5
¦~od -40 N 0.8 2.8 0.6 3.8 0.8 3.3
~od ~40 UN 13.6 16.8 33.621.5 27.7 35.3
HDT 66 psi 70.5 69 72 70.5 69.5 68.s
1 5 VICAT 8 80.5 79.5 80.5 82 80.5 83.5
Spiral ~ow (in.)39.5 41.5 38.541.5 38.5 29.5
Low Shesr V~sc.5098 4422 52024994 6087 7803
. _
DTS 12 12 ~ I 12 11 10
Tables 4A and 4B illustrate a series of PVC1/PVC2
blends having a ~ I.V. of 0.46 units. An increase in
notched Izod impact strength both at room temperature and
at -40F occurred for Example 1~ employing just one weight
part of PVC2. Impact properties generally trend upward in
Examples 13-18, spiral flow however is not reduced to a
significant degree up to 10 wt. parts of PVC2. In
addition, low shear viscosity did not rise significantly
nor was DTS time reduced to a significant degree. These
changes in properties are generally favorable compared to
C13, Cl9 and C20.
~ ~ ~ i 3 ~, .~
-- 19 --
TASLE 5A
~ampl- Clg C20 ¦ 21 22 23 24 25
5 L~ ~ ~
PVC2 ' 13 13 3 3 5 10 20
1 0 ~ wt. parts
TABLE 5B
Example C 13 C20 21 22 23 24 35
Izod RT N 8.4 9.6 2.0 2.6 2.3 4.114.4
Izod RT UN 39.7 39.7 39.7 39.739.8 40 40.2
15Izod -40 N 0.6 2.3 0.9 3.7 1.1 2.4 3.1
Izod -40 UN 22.5 39.8 37.1 36.834.3 18 10
HDT 66 psi 70 70 71.5 69.569.5 70.570.5
.
VlCAT B 79.5 81.5 80.5 81 82.5 80.587.5
Spiral Flow fim.) 38.5 31.8 42.5 40 38.5 35 25.8
20Low Shear Visc. 5202 6503 4,5265,6185,9837,439 11,705
(D ~Tn5) 10 8 10 10 1 O 10 3
Tables 5A and 5B represent Examples C19-25, a series
of PVC/PVC blends having a ~ I.V. of 1.14 units wherein the
I.V, of PVCl is 0.46. Examples 21-25 compare favorably
with C13 having no PVC2 component. Generally, impact
properties for Example 21-25 are comparable to C13 and C19.
Spiral flow, VICAT B and HDT are minimally affected.
Examples 21-23 having 1, 3 and 5 weight parts of PVC2
having an I.V. of 1.6 exhibit impact properties comparable
~'J ~ 6 ~ v ~ `t
- 20 -
to C13 with equal level of polymeric impact modifier as
well as Cls having a higher level of polymeric impact
modifier. Spiral flo~, VICAT B and DTS times are not
reduced, and in some cases are improved. Where the ~ I.V.
of the blend ranges from about 1.0 to about 2.0, the amount
of PVC2 preferably will not exceed about 20 weight parts,
and most preferably will not exceed 10 weight parts based
on 100 weight parts of combined PVC.
BLENDS WITH Tg ENHANCING AGENT
The following examples illustrate compositions further
comprising a Tg enhancing agent. Any suitable agent may be
incorporated into the PVC/PVC blend wherein the Tg of the
blend is increased. There may be one higher Tg or two Tg's
exhibited by the combination depending on the miscibility
of the components. The Tg enhancing agent can be
incorporated in an amount ranging from 1 to about 400
weight parts per 100 weight parts of the combined weight of
PVC1/PVC2, and preferably the Tg enhancing agent is present
at from 20 to about 300 weight parts per 100 weight parts
of the combined weight of PV~. Examples of Tg enhancing
agents are polymers containing ~- methyl styrene and it's
derivatives, or imide derivatives, including copolymers,
terpolymers and tetrapolymers. Block or graft versions are
also contemplated. Specific preferred examples include an
~-methyl styrene-acrylonitrile copolymer, a styrene- ~-
methylstyrene-acrylonitrile terpolymer, imidized
polymethylmethacrylate, imidized maleic anhydride
containing polymers an imide polymethylmethacrylate
copolymer, a tetrapolymer of styrene, ~-methyl styrene,
acrylonitrile and N-cyclohexyl maleimide, and a
tetrapolymer of styrene, ~-methyl styrene, acrylonitrile
and N-phenyl maleimide. Any PVC-compatible, preferrably
miscible polymer that raises the heat distortion
temperature of the composition is suitable.
- 21 - ~ J~ i J .`/
EXAMPLE8 26-~7
A first and second PVC, selected according to the ~
I.V. relationship, were blended with a Tg enhancing agent
specified in Tables 6, 7 and 8. The composition further
contained 2 weight parts of tin stablizer and 2 weight
parts of di-butyl phosphite, 17 weight parts of an impact
polymeric modifier, 3.5 parts of lubricants and 1.8 parts
of a methacrylate processing aid. Variable height impact
testing (VHIT) was conducted per ASTM-D2444. Oven sag
testing was conducted at 200F (93C) wherein sag
deflection was recorded in millimeters after 1 hour of heat
soak.
TABLE 6
Examplc I.V. C 6 27 28 29 30
PVCl l.V. ~.5!; 055 50 48 43 40 30
pVC2 IV nc~ 0.92 2 7 10 20
Tg MOD I 50 50 50 50 50
VHIT 2 26(35)24(32)32(43) :10(40) 40(54)
Sag 3 (mm) = 36 30 30 26
~ wt. parts
I Tellalloy A-60 ex. ICanegaruchi Chcmical Industry Co. Ltd.
2 1/2 inch (12.7 mm) conical dan on a 60 mil (1.52 mm) sample.
3 Measurcd in mm. at 200~ (93CC) artcr I hour.
As is shown in Table 6, preferred blends in Examples
28-30 show that drop dart impact was increased compared
with Example C26 absent PVC2. At the same time, owing to
the presence of the Tg enhancing agent (Tg mod) oven sag
was reduced in these examples and is desired.
- 2 2 - ~ 6 7 ~
TABLE 7
_ I v. C31 32 33 3~ 35
PvCI- I.V ~.55 05S 50 48 43 40 30
PVC2~Iv ~ 0.92 O 2 7 10 20
Tg MOD 2 50 50 50 50 50
VIIIT 20(27)32(43)20(27) 36(49
SAG (mm) 16 _ 14 20 15
wt. par~
2~ Elendex 586, ex GE Plastics Inc.
As illustrated in Table 7 using another Tg enhancing
agent, drop dart impact was significantly improved in
Examples 32-34 compared to Example C31 while in some
instances oven sag was reduced as in Examples 33 and 35.
15 Generally, incorporation of the minor amount of a second
PVC having higher I.V. than the first PVC will not reduce
sag resistance in combination with a Tg modifier.
~ 23 ~ i3 ~I"
T~BLE 8
E~mpl~ I.V~ C42 43 44 45 46 47
PVCI ly055 055 50 63 _ 53 4~ ~5 60
PVC2^ 1V t .~2 0.92 O 7 7 7 5 10
5 Tg MOD ~- 50 30 4C 50 30 30
VHIT 4(5)96(130) 22(29)6(8) 88(119) 112(151)
SAG (mm) = 3 58 10 -- 63 170
wl ,oarts
10 3~ Paraloid HT-510, ex Rohm and Haas Inc.
Table 8 illustrates similar effects using a different
Tg enhancing agent. In Examples 43-47 drop dart impact
strength was increased while oven sag evidenced
improvements in proportion to the amount of Tg modifier.
Example 45 represents a particularly preferred embodiment
of a composition containing a Tg enhancing agent wherein
zero sag was obtained.
Various changes and modifications may be made in
carrying out the present invention without departing from
the spirit and scope thereof. While in accordance with the
patent statutes, the best mode and preferred embodiment has
been set forth. The scope of the invention is not limited
thereto, but rather by the scope of the attached claims.
