Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
208~95~ 7
FIELD OF THE INVENTION
This invention relates broadly to improved processing of polar polymers by
addition of relatively low levels of a polyolefin/poly(methacrylate) segmented
copolymer, and to the. resulting blended compositions.
BACKGROUND OF TH~ INVENTION
There are ~wo major classes of polymeric additives useful in plastics
technology. The better-known class are those additives which improve the physical
properties of the matrix resin; of these, best-known are impact modifiers for
toughening the resin, compatibilizing additives which allow blending of two matrix
resins, and additives which add certain key properties, such as gloss-reducing agents
and sag-resistance improvers, additives for increasing modulus, additives for
increasing heat distortion temperature values under various loads, and the like.
A second class of additives are those known as processing aids which aid in
the fabrication of the resin into useful objects. A number of resins, such as
poly(vinyl chloride) (PVC) cannot be processed thermally without some
decomposition prior to "fluxing", which we define here as the conversion of a solid
resin by heat and shear into a molten plastic material capable of being processed by
an extruder, melt calender, and the like. Other resins, having high melting points
and softening temperatures, are aided in their processing by additives which allow
processing at reduced temperatures or pressures. Another category of processing aids
relates to the processing of the resin after "fluxing", such as lubrication to prevent
sticking to hot metal surfaces, improved flow during molding (generally related to
decreased melt viscosity), and improved melt strength during thermoforming
(which may also relate to higher modulus at the processing temperature). The
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processing aid may also aid in the elimination of melt fracture, which produces
undesirable effects on the surface of the processed article, such as lower gloss, or a
"sharkskin" appearance.
Additives for poly(vinyl chloride) which act as processing aids have been
known for over thirty years. Many of these additives are high molecular weight
polymers (>1,000,000) which are predominantly based on methyl methacrylate.
In U.S. Patent 4,957,974, herein incorporated by reference, are described graft
copolymers of a non-polar polyolefin having a weight-average molecular weight
between about 50,000 and 1,000,000 chemically joined to a polymer derived from at
least about 80% of an alkyl, aryl, substituted alkyl, substituted aryl, alkaryl, or
substituted methacrylate ester and less than about 20% of an acrylic or styrenicmonomer copolymerized therewith, having a weight-average molecular weight
between about 20,000 to about 200,000. These graft copolymers are shown to be useful
in adding melt strength to polyolefins during thermoforming of a shaped object and
in compatiblizing polar polymers with polyolefins. The examples of this patent
describe as controls for blending examples blends of low levels (5 and 15 phr, where
phr is parts of additive per 100 parts of resin) of a polypropylene/ poly(methylmethacrylate) graft copolymer with PVC for the purposes of demonstrating little
effect of the physical properties of the blend formed, but does not disclose or suggest
utility in processing.
SU~MARY OF THE INVENTION
We have found that segmented copolymers, such as graft copolymers of
poly(methyl methacrylate) of relatively high molecular weight onto a non-polar,
non-rubbery polyolefin, such as polypropylene, are useful at levels of about 1 to
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a~out 15 weight percent in improving the processing properties of polar polymers,
such as by decreasing the time for PVC to flux, by decreasing the temperature and
pressure requirements for injection molding, and by improving the melt strength of
ABS. More specifically, we have discovered a rnethod for improving the processing
of a polar resin, comprising
a) admixing the polar resin with from about 1 to about 15 phr of a segmented
polymer comprising segments of
1) a non-polar, non-rubbery polyolefin having a weight-average
molecular weight between about 50,000 and 1,000,000;
2) a polymer derived from at least about 80% of an alkyl, aryl, substituted
alkyl, substituted aryl, alkaryl, or substituted methacrylate ester and less
than about 20% of an acrylic or styrenic monomer copolymerized
therewith, having a weight-average molecular weight between about
20,000 to about 200,000;
b) heating with agitation the mixture to a temperature whereby the blend is
fluxed .
We further have discovered a blend comprising an engineering resin
containing aryl groups in the main chain and from about 1 to about 15 phr of a
segmented polymer comprising segments of
1) a non-polar, non-rubbery polyolefin having a weight-aver~ge
molecular weight between about 50,000 and 1,000,000;
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2) a polymer derived from at least about 80% of an alkyl, aryl, substituted
alkyl, substituted aryl, alkaryl, or substituted methacrylate ester and less
than about 20% of an acrylic or styrenic monomer copolymerized
therewith, having a weight-average molecular weight between about
20,000 to about 200,000.
DETAILED DESCRIPTION
By "polar" resins are meant in general polymers containing significant
amounts of atoms other than carbon and hydrogen, such as oxygen (in groups such
as ether, ester, acid, ketone, hydroxyl, and the like), sulfur (in groups such as sulfide,
sulfone, and the like), or nitrogen (in groups such as amide, amine, heterocyclic
groups such as pyridine, and the like). Such polar resins include
acrylonitrile-butadiene-styrene polymer, polyacetals, polyarylates, acrylic-styrene
copolymers, acrylonitrile-styrene-acrylic polymers, acrylonitrile-styrene polymers
modified with ethylene-propylene rubber, cellulosics, polyester-polyether block
copolymers, polyesters such as polybutylene terephthalate and polyethylene
terephthalate, and including liquid-crystal polyesters, polyetheramides,
polyetheretherketones, polyetherimides, polyethersulfones, ethylene-vinyl alcohol
copolymers, polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene
chloride and fluoride, styrene polymers such as styrene-acrylonitrile copolymers,
styrene-butadiene copolymers, styrene-maleic anhydride copolymers copolymerized
with styrene alone or with the additional monomers listed for styrene,
polyphenylene ether, polyphenylene sulfide, polysulfone, polyurethane,
polyamides, i.e., nylons such as nylon 6, nylon 6.6, nylon 6.9, nylon 6.10, nylon 6.12,
nylon 11, nylon 12, and amorphous nylons, polyamideimide, polycaprolactone,
polyglutarimide, poly(methyl methacrylate), other Cl to Cg
poly(alkyl(meth)acrylates) and polycarbonates.
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Particularly of interest are polymers of vinyl chloride, that is, homopolymers
of vinyl chloride and copolymers containing at least 80 weight percent units derived
from vinyl chloride, such as copolymers of vinyl chloride with ethylene, propylene,
vinyl acetate, and the like. Further of interest are polymers of vinyl chloride
containing impact modifiers, such as core/shell polymers with cores of acrylate or
butadiene-based rubbers and with shells of methyl methacrylate, methyl
methacrylate/styrene or styrene/acrylonitrile.
Also of interest are ABS polymers, that is, styrene/acrylonitrile copolymers
containing a rubbery phase of a butadiene, butadiene/styrene, or
butadiene/acrylonitrile rubber, and usually further containing a graft copolymer of
styrene/acrylonitrile onto such a rubbery polymer. Related polymers of interest are
staged polymers of styrene with acrylonitrile formed in the presence of other
elastomeric materials, such as polyacrylate rubbers or ethylene-propylene-based
rubbers.
Also of interest are those polar polymers with aromatic rings (aryl groups)
directly in the polymer chain, that is, with the polymer chain containing an
aromatic group bonded at two sites on the aromatic ring. Such polymers include
polycarbonate, such as bis(phenol A) polycarbonate, polysulfones, such as
polyphenylene sulfone, polyether-sulfones, and the like, polyarylates, which arewholly aromatic polyesters derived formally from bisphenols and aromatic
dicarboxylic acids, poly(ether imides), wherein the chain contains both ether groups
and the imide group which is formally derived from an aromatic dicarboxylic acidand an aromatic amine. Further of interest are poly(phenylene oxide), such as
poly(2,6-dimethylphenylene) oxide, also known as poly(2,6-dimethylphenylene)
e ther.
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Also of interest are polymers containing both aromatic rings and aliphatic
groups directly in the chain, such as polyesters such as poly(ethylene terephthalate),
poly(butylene terephthalate), and the like, and polyamides, such as poly(alkylene
tereph thalamides) .
Liquid crystal polymers, useful for reinforcing plastic matrices and providing
a high modulus, also will process more readily in the presence of small amounts of
the processing aid polymers of the present invention. Such liquid crystal polymers
include those which are polymers containing units derived from p-hydroxybenzoic
acid, 6-hydroxy-2-naphthoic acid, and optionally p-aminobenzoic acid.
As noted, the processing aid polymers of the present invention are segmented
copolymers, which includes block and graft copolymers with segments of defined
molecular weight of a polyolefin and a polymer comprising predominantly units
derived from a methacrylate ester. There are a variety of ways to prepare such
segmented copolymers known to the art, but those methods tend to prepare
copolymers with segments of lower molecular weight. A preferred method to
prepare such polymers is that disclosed in the '974 patent. Control of the
polymerization conditions, such as radical flux, is required to produce a high
molecular weight of the grafted polymer and to avoid degradation of the pre-formed
polyolefin. Alternate methods, such as aqueous dispersion processes, may be
utilized to prepare the segmented polyolefin//polymethacrylate polymer, as long as
control of polymerization conditions is maintained to achieve the desired
molecular weight parameters.
By non-rubbery polyolefin is meant that the polyolefin is either crystalline at
room temperature or, if amorphous, has a glass temperature greater than about 0C.
The non-rubbery polyolefin will exhibit a modulus of at least about 100,000 psi
(6.89 x 10~ kPa).
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As with most methods for making segmented copolymers, free polyolefin or
polymethacrylate may also be present. Removal of such impurities is costly, and the
segmented polymers may generally be used even if ungrafted moieties are present.
The matrix resins are well-known to the art and usually commercially
available. Both they and the additive polymer may contain stabilizers, such as
thermal, ultraviolet, or anti-oxidant stabilizers, fillers, impact modifiers, colorants,
dyes, lubricants, and the like. Such additives will generally not have an adverse
compensating effect on the improved processing imparted by the addition of the
processing aid polymer.
Usually the matrix polymer and the segmented polymer can be dry-blended
prior to processing, but the segmented polymer may be added to the molten matrixpolymer during processing. The blends are compounded and processed by any of
several techniques known to the polymer processing art, such as by milling,
calendering, injection molding, extrusion, such as into profiles, sheet, or film, and
the like.
Demonstration of the processing improvement may be seen in any of several
ways, depending on the matrix polymer. In some cases, the matrix polymer is
conveyed through the processing at lower temperatures, or lower shear rates, or less
extruder work, which imparts less thermal history to the blend. In other case, the
"fluxing" of the polymer is improved, so that the time for thermal degradation prior
to processing the "fluxed " polymer is reduced. In other case, the output from the
processing, such as an extrudate, can be more readily handled during such
processing steps, such as pelletizing, film formation, film stretching, and the like.
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The segmented polymers of the blends of the present invention allow the
matrix polymer to be used more effectively in preparing many articles of commerce,
such as articles from PVC, such as pipe, film, sheet, containers, and the like.
More specifically, these blends are appropriate for injection molded pipe
fittings, plumbing valves and housings, garden tools, automotive parts,
communications devices, business machine parts (housings, enclosures, bases, andconnectors), parts and housings for small and large appliances (motor housings,
handles, covers, bases, doors, ducts, consoles, refrigerator liners, crisper trays, washer
dispenser cups, knobs), car mats, toys, sporting goods, closures for bottles and jars,
footwear, battery cases, and electrical plugs, connectors, housings, receptacles, and
connection boxes.
Processability improvements are also important in extruded profiles, sheet,
and film. Appropriate rigid extruded parts include pipe, tubing, and conduit
(including water pipe, large diameter pipe, drainage pipe, vent pipe, and agricultural
and irrigation pipe), construction profiles (siding, mobile home skirting, gutters,
downspouts, weather stripping, awnings, window shades, and profiles for windows,patio doors, sliding doors, and storm windows). Appropriate extruded flexible parts
include wire coatings, garden hose, film for packaging (blister packaging,
shrink-wrap), and profiles for medical applications and automotive tops, trim and
protective strips.
Calendering operations will also be improved by modifying a vinyl chloride
polymer with the segmented copolymer. Applications include vinyl flooring, rigidsheet for packaging, and sheet or film either laminated or extruded directly onto
fabric (automotive or furniture seating) or board (wall coverings or furniture). Blow
molding processability of bottles and other articles will also be improved by addition
of the segmented graft copolymer to the vinyl chloride resin.
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Articles from the polar engineering resins include housings and containers
for electrical and electronic equipment and the like~
EXAMPLE 1
In Example 1 is listed a series of segmented copolymers, otherwise known as
graft copolymers, of predominantly methyl methacrylate (MMA) polymerized in the
presence of a polypropylene or ethylene-propylene-diene terpolymer (EPDM) by themethods taught in the '974 patent incorporated herein by reference.
The polyolefin content of the graft copolymer was determined by
interpolation of the carbon content between pure acrylic (60.0% carbon) and purepo]yolefin (85.7~ carbon). The per cent of acrylic grafted is the per cent of the acrylic
polymer that is attached to polyolefin (that is, not removed by three THF
dissolution/acetone precipitations for the EPDM graft copolymers and not removedby two hot xylene dissolutions/cold xylene precipitations for the polypropylene graft
copolymers). The molecular weights listed are of the acrylic in the first soluble
fraction.
2 ~
Table I
Polyolefin-Acrylic ~',raft Copolymers
Acrylic Per Cent
Polymer Polyolefin Composition of Acrylic Molec. Wt.
('70) MMA / EA / MAA Grafted wt av no av
Ex. 1-A EPDM (62%) 98 / 2 20 175,00072,100
Ex. 1-B EPDM (57%) 98 / 2 14 244,00094,700
Ex. 1-C EPDM (56%) 98 / 2 12 356,000128,000
Ex. 1-D EPDM (58%) 98 / 2 26 114,00031,900
Ex. 1-E EPDM (58C7O) 93 / 2 / 5 12 127,000 31,700
Ex. l-F PP (66C7O) 98 / 2
Ex. 1-G PP (617O) 93 / 2 / 5
Ex. 1-H PP (57C7O) 98 / 2
Ex. 1-I PP (55C70) 93 / 2 / 5
Ex. 1-J EPDM (65C7O) 93 / 2 / 5
Ex. 1-K PP (47C7c) 95 / 5 11 130,00040,700
Ex. 1-L PP (45qo) 95 / 5
Ex. 1-M PP (45C70) 95 / 5
EXAMPLE 2
This example illustrates the improved processing of poly(vinyl chloride) with
certain of these segmented copolymers. The processability is tested on the mill and
several features of the processing are rated. In all cases the graft copolymer did
promote the fusion of the PVC resin. The polyolefin-acrylic graft copolymers with a
high molecular weight acrylic graft improve the other processability factors,
although they are not fully equivalent to the improvements imparted by a
commercial very high molecular weight methyl methacrylate-based processing aid
(additive 2-C). Additive 2-A is a commercial medium MW metl-yl
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methacrylate//ethyl acrylate 70//30 polymer useful in processing PVC copolymers,and Additive 2-B is a lubricating processing aid copolymer containing a low MW
butyl acrylate/styrene core and a high MW methyl methacrylate shell. Results aresummarized in Table 2. Here, 4 g processing aid are mixed with 204 g. masterbatch,
which is Geon 85, a medium molecular-weight (K=60) PVC homopolymer with 2
phr organotin stabilizer in a blender at 50 to 93C, followed by milling on a two-roll
mill at a temperature of 175C., then sheeting off the blend and determining theprocessing performance by comparison with Examples 2-A, 2-B, and 2-C.
E = excellent, VG = very good, G = good, F = fair,
P = poor, VP = very poor, VVP = very, very poor
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Table 2
Polyolefin-Acrylic Graft Copolymer Processing Aids for PVC
Time to Time to
Band, Flux, Hot Thermo- Rolling
Add. sec. sec. Strength plasticitv Bank Edge Release
Ex. 1-A 90 115 P P P(20) F F
Ex. 1-B 120 155 F P P(20) P G
Ex.1-C 90 105 P P P(20) G G
Ex.1-D 30 50 VP VP P(20) VP P
Ex. 1-E 25 70 VP VP P(20) VP VVP
Ex. 1-F 85 130 VP VP P(20) VP P
Ex.1-G 110 145 VP VP P(20) VP VP
Ex.1-H 65 85 VP VP P(20) VP F
Ex.1-I 265 300 VP VP P(20) VP F
Ex. 1-J 170 195 VP VP VP(25) VP F
Ex. 2-A 40 55 P P P(18) VP G
Ex. 2-B 40 60 P P VP(25) P F
Ex. 2-C 30 45 G G E(<10) VG VG
EXAMPLE 3
In Example 3 are shown additional experiments with a Haake Rheocord,
which shows the time to peak torque and the value of that torque; the earlier the
time to peak torque, the greater the improvement in fusion. In this experiment,
high levels of additives are used to exaggerate the effect. Here, K-58 was used which
contained a thermal stabilizer for PVC. Processing aid effect was measured in a
Haake Rheocord at 80 rpm and 180C.
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Table 3
PVC Processing Aid
time to peak torque at
Processing Aid torque, sec 198C, m-g
NONE 360 1360
8.3 % Ex. 2-C 162 1430
8.3 % Ex. 1-K 90 1960
EXAMPLE 4
Additional experiments were performed with Ex. 1-A graft copolymer at
different levels. The results indicate that it promotes fusion at all levels. The
results also indicate that the effect is greater than that of a polypropylene or of an
acrylic polymer of similar molecular weight. Conditions were those of Example 3.
Table 4
PVC Processing Aid
time to peak torque at
Processing Aid torque, sec 198C, m-g
NONE 240 1450
1 '70 Ex. 2-C 120 1530
3 '70 Ex. 2-C 140 1480
1 % Ex. 1-K 160 1420
3 % Ex. 1-K 110 1560
3 ~/O PMMA (MW 1.1 x 10;) 145 1650
3 '70 PP (MW 3 x 10; ) 195 1450
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EXAMPLE 5:
Injection Molding Additive for High Performance Polymers
This experiment demonstrates that certain high performance polymers with
excellent temperature resistance, but which mold only with difficulty at high
temperatures, are improved in processing by the presence of olefin/methacrylate
segmented copolymers. The results in Table 5 indicate that the graft copolymers
decrease the temperature and pressure requirements for molding. In these
experiments 15 phr of the graft copolymer was used and very dramatic decreases
were observed. Similar results, in that irnproved processing is observed, will be
observed from lower levels of the graft copolymer, levels that will not adversely
affect the performance.
In these Examples, the segmented copolymer is that of Example 1-M. The
polyarylate is Amoco's Ardel DM-100, mfr 4.5 g/ 10 min at 375C, presumed to be a
bisphenol isophthalate fully aromatic polyester. The polysulfone is Amoco's UdelP-1700, mfr 6.5 g/ 10 min. at 343C., presumed to be a condensation product of
2,2-bis(4'-hydroxyphenyl)propane and 4,4'-dichlorodiphenyl sulfone. PPS is the
designation for poly(phenylene sulfide), Phillips Petroleum's Ryton P-4, m.p. 285C,
mfr 60 (5 kg., 316C, 0.21 cm. orifice). PES is ICI's Victrex polyethersulfone,
presumed to be the equivalent of the condensation product of 4,4'-dichlorodiphenyl
sulfone and hydroquinone. I,CP designates a liquid crystal polymer, Celanese Vectra
A 950, m.p. 280C., presumed to be prepared by condensation of p-hydroxybenzoic
acid (737O) and 6-hydroxy-2-naphthoic acid (23%). PEI designates General Electric
Ultem 1000, a polyether imide presumably prepared from pyromellitic dianhydride
and an aromatic diamine.
14
2Q8~ 7
Blends were made in an intermeshing co-rotating twinscrew extruder with a
length~diameter ratio of 10/1. The compounder was run at 200 rpm, and
temperatures were adjusted for each blend and control to achieve a "good"
(uniform, processable) melt, which melt was then directly fed to a 38 mm. singlescrew pelletizing extruder. The pellets were dried and injection molded on a
reciprocating screw injection molding apparatus. The injection molding
temperatures and the pressures in the mold are shown in Table 5.
Table 5
Effect of Segmented Copolymers on Injection Molding
of High Performance Polymers
Injection Molding Set Injection Molding
Ex.1-M Temperatures, C Pressures, kPa
Polvmer phr Rear/Center/Nozzle _ Inject/Hold
Polyarylate 0 299 / 371 / 332 11020 / 4130
Polyarylate 15 260 / 310 / 315 6890 / 2760
Polysulfone 0 299 / 354 / 343 13090 / 4130
Polysulfone 15 274 / 315 / 315 7580 / 2410
PPS 0 260 / 338 / 315 5510 / 2070
PPS 15 274 / 315 / 315 5510 / 2410
PES 0 315 / 371 / 332 13090 / 4130
PES 15 274 / 315 / 315 8270 / 2760
LCP 0 299 / 327 / 321 5510 / 2760
LCP 15 218 / 246 / 260 6890 / 2410
PEI 0 304 / 377 / 343 12400 / 4480
PEI 15 274 / 304 / 310 7580 / 2410
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EXAMPLE 6
This example illustrates the improvement in the melt strength of A8S
imparted by the segmented copolymer. A commercial ABS (Cycolac DFA-R) and a
polypropylene-methacrylate graft copolymer (similar to that designated Example
1-K) were compounded on a 30 mm co-rotating, twinscrew extruder and pellets
extruded. Sheets (24 X 24 X 0.15 cm) were pressed from these pellets on a 100 ton
press. The sheet samples were tested for melt strength by a sag test at 190C.
Unmodified ABS sagged 0.75 inches (1.91 cm.) in 14.5 rninutes. ABS containing
4.76% graft copolymer had sagged less than 0.5 inches in 25 minutes. ABS
containing 12.6% graft copolymer also sagged less than 0.5 inches (1.27 cm.) in 25
minutes. The use of such segmented copolymers as melt strength modifiers in ABS
should permit improved processing (thermoforming, blow molding, foaming) of
grades of ABS that do not process well.
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