Note: Descriptions are shown in the official language in which they were submitted.
--1--
-13~glfiO
MALEIC ANHYD~IDE ~RA~T ~OPOLYMER P~ODUCT5
HAVI~ LOW YELLOWNESS INDEX AN~ PREPARATION
~ hi~ invention rel~tes to a novel proces~ of
gra~t~ng monomer~, ln partlcular maleic anhy~ride, to
polymer~ using novel polymer extruding equipment and
novel product~ produ~ed therefrom. Such product~ when
blended with a ~ynthetic re~in can be coextruded into
multilaye~ film~ ~uitable for the packaging of food
produçt~.
~lend~ of maleic anhydride g~aft copolymer~ ~nd
p~lyolefin~ h~ve a broa~ range of application~,
including u~e a~ a component ln food packagin~ fllms
and plpe çoatln~s.
Proces~e~ for grafting an ethylenically
~n~aturated mon~mer suçh as maleic an~ydride onto
olefinic polymer~ are well doeumented in the art.
Typlc~lly, the processe~ in~ol~e reaçtin~ maleic
anhydride with molten ole~lnie polymer under condition~
of hlgh ~hear. A wlde ran~e o~ mlxin~ de~içe3 are
g~ner~lly described a-~ being ~uitable. However, the
only actual worklng example includln~ the u~e of a
multiple ~crew extruder l~ found ln Ex~mple 1 of
commonly a~.qigned U.S. Patent No. 4.6~4,57~, relatin~
33,064A-F
-2- l 3~5 1 60
to the preparation of precur~or 8rafted polymer that ig
t~ereafter b~ended with other polyolefin~ to ~ive a
blended product that l~ adhesive~ That ex~mple does
not inherently make, di~close or suggest the critical
condltion~ now found to be nece3sary to produce a
grafted product ~uitable for food packaging film~ which
requ~re ab~ence oP odor, 14W gra~n con~ent and non-
yellow color
Products obtain~d from prior art extruder
proce3~e3 are not ~uitable for u~e in foo~ packaging
fll~ for t~ree ma~or reason~:
1) Odor. Incorporatlon o~ monom~r in the
graft copoly~er in the prior art proce~e~ i~ extremely
low~ Generally the ~raft copolymer conta~ns le~s than
0.50 weight percent maleic anhydride. Such graPt
copolymers contain a signi~icant amount of ~eYidual
monomer an~ other ~purit~e~ which in turn impart to
resulting P~lms an extremely unplea~ant odor. Such
film~ arc unacceptable therefore for use as food
packa~ing materlal.
2) Hi~h Grain Content. ~rain, de~ined a3
globular mas~c~ diqcrete from the polymer per ~e hav~n~
a diameter between 5 and 15 mil~ has long been
recognized as ad~ersely aPPeetlng clarlty and ~lo~ of
extruded films. Howells and Ren~ow, ~Flow Defects in
Polymer Melt~", Tran~. J. Plast. Inst. 30 (1962) 240-
253, conclude that graln Pormation i~ attributed tointermolecular ~hain entan~ement durin~ t~e extru~ion
proc~s~ and that quch en~an~lement can be reduced but
not eliminate~ by shea~ing. In general t the higher the
degree o~ suoh chain entangling, the greater the
quantity of g~ain in the extruded fllm and thus the
33,06~A-F -2-
~3~ i339160
haz~er ~he film. Fllms comprising the graft copolymer3
of the prior art have high lev~l~ of graln and thua are
no~ desirable in ~ood packagi~ application~.
3) Yellowne~. Films produced from the graft
S copoly~er~ of the prior art further h~ve the
undesir~ble feature of yellow dlscoloratlon,
ae~t~etically unaccepta~le to consumer~ ~nd thus
lmpra~tlcal for food packa~n~ appllcation~.
It would be advantageous to devise a p~ocedure
for producing a maleic anhydride graft çopolymer w~lch,
when blended with a polyolefin, would ~ende~ a film
~uitable for u~e as a food packa~ln~ materlal. In
particul~r, it would be desirable to produc~ a gr~ft
copolymer contalnln~ greater than 0.50 wei~ht percent
incorporated maleic anhydride with a low yellowne~
index which, when blended with a polyolefinJ render~
fll~ ~ith low grain content.
In accordance with à fir~t broad a~pect of the
present inventlon, a method for ~ra~tln~ maleic
anhydride to polymer~, including the ~teps o~;
(a) feedln~ the polymer, maleic anhydride and
a free radical initiator to a multiple ~crew extruder
and
(b) melting the polymer by heatin~ and
~hearlng in the extrude~; and
(c) therea~ter mix~ng the molten polymer and
maleic anhydrlde in the extruder for sufflc~ent time to
~raft at leas~ part of the ~aleic anhydride to the
molten polymer~
characterized by ~tep (b) pr~ceding addltion of malelc
anhydrlde ~n 3~ep (a) and by injecti~g the m~leic
anhydride ~nd free r~dlcal lnltlator into a 3ection of
33,064A-F -3-
13.~gl60
the multiple ~crew extrud~r ~hat i~ pres~urized and
fllled wlth moltcn polymer. The mal~c anhydride and
the free radical initiator are prefera~ly mixed in a
solvent sy~tem prior to injection into the extr~der.
Devolatilization of the ~raft copolymer preferably
occur~ in one or more dscompre~-~ion ~ctions of the
extruder.
In a ~econd broad a~peet o~ thi~ inven~ion
there is di~clo~ed a graft copolymer compo~itlon
0 comprising the rea~tion product of maleic anhydride and
a backbone poly~er characterlzed by the compo~ition
havln~ a yellowne3~ index a~ mea~ured accordlng to AST~
D-1925 of leQ.~ than 10.0 and wher~in between 0.50 and
2.0 weight percent o~ ~aid ~raft copoly~er compri~e~
maleic anhydride.
In ~ thlrd broad a~pect of thi~ inventlon,
there is di~cl~ed a multilayer coextruded film u~d
for packaging food~ contain~ng at lea~t two layer~
wherein ~t lea~t one layer ~ompri~e~ a blend of (a)
between about ~.5 to 75.0 weight percent graft
copolymer havin~ a ye~l4wnes~ lndex a~ mça~ured
according to ASTM-~-1925 of le~ than 10.0 wherein the
graft copolymer compri~e~ the reaction product of
maleic anhydride and backbone polymer and further
whereln the ~raft copolymer comprises between 0. 5 and
.0 wei~ht percent of maleic anhydride and, (b) between
2~.0 to 98.5 weight perc~nt polyolefin.
Figure 1 is a -~chematic drawing of a preferred
apparatu~ for grafting maleic anhydride to polymers.
~ he pre~ent invention i~ directed toward~ an
extru~ion proce~s of ~rafting maleio anhydri~e onto a
33,064A-F -4-
-5- l 3~91 60
polymer backbone. The re~ultlng no~el graft copolymer
ha~ a yellowne~s index as mea~u~ed in accordance with
ASTM ~-19~S-70 and ASTM E-313-73 le~ than 10 ~d 11,
re~pectiv~ly, and hag particular applicabillty a~ a
component in a ~ultllayer extruded film; the latter
being particularly u-~eful a~ a food packagin~ material,
The ~raft copol~mer of thl3 inven~lon i~
manufactured in a multiple ~crew extruder co~pri~ing
posit~ve ~nd ne~ative conveyance ~crew elements, and
10 lobed knead~n~/mixing plates, paddl~s or blook~. In
general, po~itive conveyance ~crew element~ convey the
polymer-maleic anhyd~ide ~tream ~way Prom the ~irst
zone of the extruder (wherein-the poly~er, maleic
anhydride and initia~or ar~ initlally recelved and
mixe~) and tow~rd~ the latter zone~ of the extruder
(wherein the polymer 1~ devolatllized and di~charged
from the extruder). Negative conveyanc~ ~crew element~
attempt to force the ~tream away from the last zone and
toward~ the fi~t z~ne. It ls the negatlve conveyance
~crew elements which act to backup polymer or flll the
extruder reglon lo~ated upstream of them. In es~ence,
any mult~ple ~crew extruder containing ~orew elements
w1th qimilar mean~ a~ tho~e de-~cribed herein may be
~5 employed. Such ~crew~ could conceivably counter-rotate
to each other.
A representative example of a ~uitable multiple
~crew extruder for use ln this inventiOn i~ the fully
3~ interme~hlng co-rotating twin screw extruder,
~chematically 1llustrated ~n Fig. 1. The term "oo
rotating~' mean~ that a~l of the ~crew elements rotat~
ln the ~ame directlon at the ~me rate of revolution.
~he invention will be ~e~cribed with refere~ce to this
figure although it 1~ under3to~d that any multiple
33,064A-F _5_
-6- 13~91fiO
~crew extruder contaln~n~ ~imilar means as those
di~cus~ed above m~y be employed.
Drive unit 4 rotat~ po~itlve conveyance
elements 6, negative convey~nce element~ 8, and
mlxing/kneading paddle~ or block3 1~ within the
extru~er barr~l 2. The po~itive conveyance elements 6
generally con~ey mat~rial withln the extruder barrel 2
from left to right on Figur~ 1. The ne~ative
conveyance elements 8 momentarlly retard the movement
of the materia1 cau~ln~ th~ m~terial to backup ~n~
a portion of the extruder barrel 2 up~t~e~m of that
negative conveyance ~lement 8. The negatiYe conveyance
element~ 8 divide the extruder barrel 2 into four
~ep~rate zone~ 10, 12, 141 16. A fir~t zone 10
includes po~itive conveyance element~ 6 and mixing type
element~ 18 for recelvlng and mixing ~ polymer1 maleic
anhydride, and a fre~ ra~ical lnitiator. A ~econd zone
1Z eontain~ po~itive con~eyance ~lement~ 6 and further
zo mlxe~ the polymer by ~hearing ac~lon while grafting
occurs. If add~tional mixing or re~idence time i~
de~ired, ne~ative conveyance 8, or mixing/k~eadin~
paddles 18 may be ~ubstltuted for ~ome of ~he positive
~onveyance element~ 6 in zone 1~ o~ the extruder. A
third zone 14 and a fourth zone 16 contain po~itive
conveyance element~ 6 and are provided to dcvolatilizc
the polymer a~ de~cri~ed more fully ~elow.
A ba~e or ~ackbone polyme~ is fed in pellet
form from a feed hopper 20 to a fee~ metering conveyer
2Z and then to a feed inlet 24 in the extru~er barrel
2. The feed inlet 24 i~ poYitioned near ~he beginning
of th~ ~ir~t ~one 10 within the extruder barrel ~. The
backbone polyme~ can incl~de, but i~ not limited to,
(l) a poly~lefin ~uch a~ polypropylene, poly (4-
33,064A-F -6-
~ _7_ 1339160
64693-4265
methylpentene), hlgh den~ity polyethylene, "HDPE"
(den~itle~ from 0.940 ~ram/cm3 to 0.965 grams/cm3), low
denslty polyethylene, "LDPE". The prlncipal
distinction~ of ~uch polymera are well known to tho.Ye
~killed in the art and are fully de~crlbed in U.S.
Patent No. 4,327,009;
(ii) llnear low d~n~ity polyethylene, "LLDPE"
(den~ltieq from 0.870 gr~ms/c~.3 to 0.9~ gr~ma/cm3),
or linear copolymers of ethylene and ~-olefln~ having
between about 3 to about 10 carbon atoms such a.~ 1-
octene; (iil) copolymer~ o~ ethylenR an(l carbon
monoxide; and ( iY ) copoly~ers o~ ethylene and an
ethylenically un~aturated carboxylic acid or ~erlYative
includlng, but not being limited to, tho~e ~elected
15 from the gr~oup con.slstitlg of acryllc aeid, methacryllc
acid, alkylacrylate~ (such a3 ethylacrylate, butyl
acrylate, etc.) and vinyl acetate.
The extruder barrel 2 i~ heal~d, prefcrably by
Z0 clamped-on electric elerrlent~, or' cooled, preferably by
eirculating water, to control the temperature of the
polymer. The temperature wlthin each of the four zone~
10, 12, 14, 16 is independently controlled to obtain
the desired temperature proflle, even when processlng
polymer~ having ~lfferent melt characterl~ticY.
Maleic anhydrlde an~ a free radlcal initiator
are in~ected into the polymer fllled, pres~urized
sectlon of the extruder barrel Z, preferably at th~
3~ mixing element3 1~ at th~ cnd of the fIr~t z~n~ 10. A.q
u~ed herein, the phrase "polymer filled" when u~ed in
reference to the extruder refers to that ~ectlon
wherein the fllght~ of the ~crew and ~ub~antially all
void~ ln the region are es3entially filled with
polymer. ~urther the term "pres~urlze~ ~ection" when
3 3, o6 4~-F _7_
,~
,.
~339160
8 74~69-40
used in reference to the extruder refers to that area under
pressure from polymer flow and filled with polymer such that
substantlally no gaseous voids exist and further is sealed to such
an extent that any solvent pumped into the area is substantially
maintained belo~J i-ts vaporization point. The negative conveyance
element 8 at the end of the first zone 10 keeps the mixing
elements 18 filled with polymer and lmproves mixing.
~ uitable free radical initiators include, but are not
lirnited to, alkyl and dialkyl peroxides such as tertiary-butyl
peroctoate (2-ethyl hexanoate~ or 2,5-dimethyl-2,5-di(t-
~utylpero~y)he~yne-3. Initiators having higher stabilities are
preferred.
The maleic anhydride is preferably mixed in a non-
reactive solvent such as ketones, benzene, alkyl acetates, or
chlorinated benzenes and stored in a maleic anhydride feed tank
3G. The ketones are preferably selected from methyl ethyl ketone
and acetone. The maleic anhydride can be dissolved in ~he solvent
up to its saturation level. Further, the free radical initiator
can be mixed with the maleic anhydride during storage or injected
into the e~truder barrel 2 separately. The maleic anhydride and
solvent solution is pumped from the storaye tank 30 ~y a metering
pump 32 and is injected into the first zone 10 through an
injection nozzle 34. If the free radical initiator is added
separately or if additional initiator is required, the free
radical initiator can ~e stored in a solvent solution in a second
storage tank 40 and pumped by a second metering pump 42 for
injection into the first zone 10 through a second injection nozzle
44. The amount of initiator used does not appear to be critical
and ratios of maleic anhydride to initiator of from
,~
9 13~9160
about 1/.015 to about 1~.1 by ~el~ht have been fo~nd to
be sa~lsfactory, w~th ratio~ f~om 1/.025 to 1/.035
being preferred
The temperature oP the poly~er ln the fir~t
zone 10 will normally be below its melting point, and
the polym~r temperature ~n the ~econd zone 12 must
high enough ~o keep the polymer ln ~ts molten ~tate.
Independent temperature oontrol for each zone ~9
de~ired because the polymer~ generally experience an
increa~e in vi~co~ity as maleic anhy~ride i9 grarted to
ths polymer~. High m~lt temperatures, e.g. great~r
than ~50~C, may ~equire a more stabl~ initiator than the
ones mentioned above. Polymers having melt
temperature~ of 85~C to 1gO~C p~ior to feed injection
have worked w~ll when Luper~ol 130 wa-~ u~ed a~ the
ini tiato~.
The pre~ure in the fir~t zone 10 i~ not
critical. ~owever, th~ area where ~he maleic ~nhydride
i~ in~ected 34 into the extruder should ~e maintained
at a pre~ure above the vaporization pre~ure of maleic
a~hydride, preferably at about 50 to 100 p~ig. The
pressure in the third zone 1~ and the fourth zone 16
must be ~u~ficiently low to allow remo~al oP solvent
and unreacted maleio anhydride. Vacuum ~ource3 50 are
provided to reduce th~ pre-~ure in t~e third and fourth
zone~ 14 and 16, and a vacuum between 28 and 29.g
lnches of mercury ha~ proven ~ufficient to remove most
3~ of the unreacted maleic anhydride.
The t~mperature of the graf~ cop~lymer during
devolatilization i3 prePerably kept between a~out 160~C
and 300~C to a~si~t in devolatilization. Higher
temperatures give lower volatile levels, but may lead
33,0~4A-F _9_
~ ~O~
133gl60
to highe~ grain levels. Lower temperature~ lead ~o
higher vola~ile levels or more work input to remove the
volatile~, but may re~ult in lower ~raln level~.
Temperature~ of from about 180~C to 260~C are preferred
to give the bç~t balance of devolatilization and grain
level-
The graft copolymer exit~ the extruder ~arrel 2through a die face 60 ~hich produce~ ~trand~ of thu
~raft copolymer. ~he polymer ~trand~ can th~n be 3ent
to ~ strand choppe~ ro to prepare po~ymer pellet~ for
u~e 1n other proce~3e~. As an alternatlve, an
underwate~ pelletizer may optionally be employed in
place ~P strand chopper 70. Either of the~e technique~
are commonly known to those well ver~ed in the art.
A multlple Ycrew ~xtruder parti~ularly ~uited
for thi~ invention i~ a commercially available Werner-
Pfleiderer ZSK-53/5L co-rotating, twin-~rew extruder.
Thi~ extruder oan ~ra~t maleic anhydr~de ~o the polymer
backbone at rates from 40 pound~ per hour to 160 pounds
per hour wlth no ~igniPicant change in percent
conver~ion. Production rate~ of up to the maximum for
this equipment (about 300 pound~ per hour) can even be
obtainable. The backbone is prefera~ly metered into
the polymer feed inlet at a low enough rate to ~tarve
the extruder at the operating speed prior to the
addition oP male1c anhydride and the free radical
initlator. The average re~idence time~ within ~he
3~ extruder range~ Prom about 140 se~ond~ at 40 pound~ per
hour down to about ~5 3econd~ at 160 pound~ per hour
polymer rate~. A ~imilarly equipped extruder of larger
diameter al~o give~ an equi~alen~ product at higher
rates .
33,064A-F -10-
i3391 60
The abo~e de~crlbed method and appa~atu~ ha~
been usRd to ~raft malelc anhydride to polymers to
produce graft copolymer~ havin~ up to about 2 percent
by welght of maleic anhydride. The percent of
incorporation of maleic anhydride is generally related
to the ratio of m~leic anhy~ride to polymer feed untll
about the level of maximum incorpor~tion, ~enerally
about two percent. Preferred products generally
l~corporate from about 0.3 percent to about 1.5 percent
malelc anhydride by weight, moat prePerably ~reater
than 0.5n percent by wel~ht, and mo3t preferred greater
~han 0.75 percent by weight.
A conver~ion of 75 percent o~ the feed maleic
anhy~r1de to ~rafted maleic ~nhydride has bcen achieved
for linear low den~ity polyethylene~, and lower pe~cent
conver~ions are generally ~btained for high den~ity
polyethylene~,
The 8raft copolymer produced from the proce~
of thi~ invention has improved color prope~tie3 and
when manufactured into a Pilm i~proved grain
propertie~. In partlcular, the yellownes~ index of a
polymer according to the present invention as mea~ured
~5 according to ~STM D-1~25-7~ is le~ than about 10.0,
and usually less than about 8.75, and a~ mea~ured in
accord~nce with ASTM E-313-73 is generally le~ than
abouS 11.0, usually le~ than about 8.15. Further, the
whlten~s index ~s me~-~ured ac~ordin~ to ASTM E-313-73
is greater than ~5Ø In addition, when proce~se~ into
films the blend3 of thi~ inVention compri3ing a
polyolefin an~ graft oopolymer are cha~acterized by a
grain count of partiele diameter ~ize between 5 mils
and 1~ m$1s of le3~ than about 3,000 grain~ per 1,000
~quarc inche~ of 1.6 mil film. Such film~ have a
33,0~4A-F
-12- ~3~160
hlghly glo~y appearance and are suitable ~o~ u~e as a
food packagin~ material in multilayer coextruded or
lamlnated ~tructures.
The polyolefin with which the graf~ copolymer
of thls invention i~ ~lende~ can be an ethylene
homopolymer including LDPE and HDPE. In addition,
~uitabl~ polyolefin~ ~or the production o~ film~
in~lude polypropylene, poly (4-methyl pe~tene) and
copolymer~ of ethylene and a ~3 to C10 a-olefin, ~uch
a~ LLDPE, propylene and l-butene, copolymer~ of
ethylene an~ C4-C8 diolefins ~uch a~ butadiene and
copolymers of ethylene and an ethylenically un~aturated
c~rboxylic acid or derivative ~uch as vinyl acetate,
ac~ylic acid, methac~yllc acid, ethyl acrylate, butyl
acrylate, methyl metha~rylate, and me~hyl acrylate and
copolymer3 of ethylene and carbon monoxide. The ~atio
of graft copolymer to polyolefin employed ln the blend
i~ gener~lly between about 1.5: 98.5 to about 75:25 by
weigh~, pre~erably abou~ 2.~;97.5 to about 35;65 by
wei~ht, and most pre~erably abou~ 5.0:95 to about ~5;75
by wei~ht.
The graPt copolymer and poly~lefin may bc
~5 blended by methods known to one skilled In the art ~uch
a~ by u~e of a blende~, m~xer, kne~der, roller,
extruder, etc. Likewl~e, the production of multilayer
films from ~uch ~lend~ can be accompli~hed by
technique-~ ~uch as ca~t fllm, blown film, coext~uded
3~ blow moldin~, coextruded -Yheetln~, la~inatlon or other
techn~que~ availa~le to a ~killa~ practitioner. The
layer~ o~ ~uch multilayer film~ (oth~ than th~ layer
comprising the blend of ~raft copolymer and polyo~efln)
may con~l3t of ~uch 3ynthetlc r~sin~ as polyamide (~.g.
nylon, etc~)~ ethylene - vinyl alcohol copolymer~.
33,064A-~ -12-
-13- i3 ~l 60
polyolefin~ (e.g. polypropylene, polyethylene, e~c.
polye~ter, polycarbonate, and poly(vinylindene
chloride), ~ellulo~ç and derivative~ thereof, and
met~
The following Example~ 1-3 snd part of E~ample~
8-12 provide detail~ of making and u~lng preferred
~raft copolymer~ by the method of the pre~ent
invention. The followin~ Comp~r~tiv~ Example3 4-7, 13,
and part o~ 8-12 are not prior art. They illustrate
the Yurprl~ing nature of the lnvention. In the
exampleY and comparati~e example~, "melt flowability"
repre~ent~ the ~elt flow index a3 mea~ur~d u~n~ ASTM
D-1~38, Standard De~ign~tion 1gO/10.0 (condition N).
Yellowne~ index (A) wa~ determine~ u~ing ASTM D-1925-
7D. Whltene~ Index and Yellowne~ Index (B) wer~
determined u~ing ASTM E-313-73.
Example 1
A line~r lo~ dcn~ity polyethylene ~old under
the trademark DOWLEX1 LLDP~ 203~, having a ~elt index of
6 dg~min and a den~ity of 0.919 gram~/cc, wa~ fed into
a Werner-Pfleiderer ZSK-53/5L co-rotating, twin-~crew
extruder operating at the followin~ condition9-
1 A trad~m~rk of Ths Dow Chemical Company. DOWLEX
LLDP~ 2035 i~ a copolymer of oc~ne/ethylene.
3o
33,064A-F -13-
i339160
Zone 1 2 ~ 4
Barrel Temp., ~C 215 2~8 233 235
~elt Temp., ~C 135 200 210 ~40
Screw Speed 2~0 rpm
Polymer Rate 150 lb/hr
A mixture of maleic anhydri~e/methyl ethyl
l~ ketone/LUPERSOL2 130 at a weight ra~io of 1/1/0.03 was
fed lnto the extruder through a Werner-Pfl~iderer
injectlon nozzle by a po3tt~ve diqplacement ~etering
pump at a rate of Z.24 pound~ per hour, The inject~on
nozzle wa~ located ~u~t up~tream of a ~erie~ of
kneading block~ ~r mixing type ele~ents backed by a
negative conveyance element whlch kept the portion of
the extruder from ~ome point up~tream of the ln~ection
nozzle to the negative eonveyance screw element polymer
filled and preq~urized. A vacuum of 29 inche~ of
mercury wa~ m~intained on zone~ 3 and ~ to devolatilize
the grafted polymer. The graft copolymer exhibited a
maleic anhydride ~ncorporation of 0.55 percent by
weight of the grafted polymer.
2 A trademark of Pen~alt for 2,5-dimethyl-2,5-
dl(tertiary butylperoxy)hexyne-3.
3o
33,064A-F _14
-15~ 39160
Example
A high den~ity polyethylene homopolymer ~old a~
DOW HDPE 10062 havlng a melt index o~ 10 dg/min ~nd a
den~ity of 0.962 ~/cc was fed into the extruder of
Example 1 under ths followin~ condltions:
Zone No 1 2 3 4
~arr~l Temp., ~C 170 230 220 220
Sorew Spe~d ~00 rpm
Polymer Rate 150 lb/hr
A 45/55/0.032 (methyl ethyl ketone/maleic
anhydride/LUPERSOL 130) ~ol~tlon w~ fed throu~h the
injection nozzle at a rate of 5.9 lb/hr. The vacuum
leYel at zone~ 3 and 4 wa~ 2g inche~ mercury. The
pro~uct contained 1.15% Bra~ted maleic anhydrlde.
Thi~product wa~ then blended with DoWLEX3 LLDPE 2035,
linear low den~ity polyethylene (LLDPE) having a melt
lndex of 6 dg~min and a density of 0.919 ~Jçc, at a
ratio of 11.5/88.5 (88.5% LL~PE), melt blended in an
extruder, and then co-extruded as the adhe~ive (middle)
layer in a three layer film including high den~ity
polyethylene and nylon. The re~ulting film, when
converted into bagsl has excellent ~tru~tural integrity
an~ ultable for heat~ng contalned food~ in a
mlcrowave oven.
3o
3 A tradema~k of Th~ Dow Chemlcal Company. DOWLEX
LL~PE 2035 1~ a copolyme~ of ocetenç/ethylene.
33,064A-F -15-
-16- 1~391~U
Example 3
A high den~ity ethylene homopolyme~ ~ld aQ DOW
~DPE 10062 having a melt index of lO dg/min. was fe~
into the extruder of Example 1 under the f~llowing
cond~tion~:
Zone No. 1 2 3 4
Barrel Temp, ~C 102201 201 221
Screw Speed - 300 rpm
~olymer Feed Rate - 200 lb/h~
Methyl ethyl ketone, maleic anhydr~de and
LUPERSO~ 130 were fed through the injection nozzle at
3,~, 3.4 and 0.10 lb/hr., reYpectively, T~e ~n~ection
nozzle wa~ located ju~t up~tream of a series of
kneading ~loek~ or mixing type elements backed by a
negative conveyance element which kept the entire
injec~ion area polymer filled and pre~urized. The
~acuum level at zone~ 3 and 4 wa~ 29 inche~ mercury.
The re~ultin~ product contained l.O~ incorporated
maleie anhydride repré~entln~ a conver~ion of 63.0% of
the feed malei~ anhydrlde to inoorporated maleic
anhydri~e.
The re3ultlng graft copolymer~ exhlbited the
followin~ properties;
33,06~A-F -16-
_17_ 13-39160
Melt Flowability 9.8
Whltene~ Index 49.94
Yellowne~s In~ex (A~ 8.53
Yellownes~ Indçx (B) 8.69
~Comparat~e) ExamDles 4-6
Th~se example~ demon~trate that hlgher
yellowne~ and lower Wh~ tene~ indices are obtained
when the maleic ~nhydride an~ ~nitiator are not
in~ect~d into a polymer f1lled sec~ion of the extruder.
Into the polymer feed aection o~ the extruder
of Example 1 were added Dow HDPE 10062, ~alel~
anhydr~de tMAH) and LUPERSOL 130. The extruder w~
~perated at the followln~ conditions:
E X A M P L E N O S.
g ~ 6
Barrel Temp. t ~ 181 1~1 184
Zone 1 1g9 200 203
Zone 2 20~ 203 201
Zone 3 200 194 232
Zone 4 ~00 250
Screw Speed, rpm
Polymer Fee~ 100 100 200
Rate,lb~hour
3~ MAH Feed Ra~e. 1.9 1.9 3.8
lb/hour
~UP~RSQL Feed Rate,0.1 0.25 0.1
lb/hour
33,064A-F -17-
~339160
The vacuum level at zone~ 3 and 4 wa~ ~9,~ inche~
mercury. The in ject 10n nozzle wa3 arranged a~ ~n
Ex~mpl~ 3 above.
. The re~ulting graft eopolymer~ exhibi~ed the
p~opertle~ 3ummarized in Table I.
TABLE I
E X A M P L E N O S.
4 5 6
M~lt Flowability ~.~ 0.9 8.2
MAH Incorporatlon ~ 0.98 1.20 1.11
by wt)
MAH Conver~on (~ by 51.5 53.7 58.
wt)
Whitene~ Index 37.12 -9.56 42.36
Yellowne~s Index (A) 12.78 28.22 1.13
Yellownes~ Index (B) 13.34 30~31 11.59
(Comoarative) Example 7
~0
Thi~ example lllu~trates the importance in the
de~ign of the ~crew ~lement~ of the extruder.
A twin ~crew extruder sim~lar to that of
Example 1 wa~ u~ed except that the negat1~e conveyance
element wa~ repla~ed by a po~itive conYeyance element.
(A~ a result, the extruder ~ not polymer filled or
pre~urized at the injectlon point.) A ~acuum level of
~9 inches of mercury waq maintained on zones 3 and ~ to
3~ devolatilize the graft oopolymer.
Into zone 2 of the extruder w~e a~ed M~H,
LUPERSOL 130 an~ methyl ethyl ketone (MEK). The
operating eondition~ of the extru~er were;
33,o64A-F
-19- ~33gl60
Zone ~o 1 Z 3 4
Barrel 'remp., ~C 85 119 19~ 1~2
Screw Speed 200 rpm 300
MAH Feed Rate 3.7 lb/hr~
MEK Fe~d Rate 3.7 lb/hr.
L~PERSOL Feed Rate 0.11 lb/h~.
DOW HDPE 10062 was fed into the extruder at a rate of
1 200 pound~ per hour.
Propertie~ of the re~ulting ~raft copolymer~
were;
Ta~le I
Melt Flowability 15.4
MAH Conver~lon (% by wt) 17.3
MAH Incorporatlon (~ by wt~ 0.32
Whltene~ Index 56.84
Yellowne~ Index (A) 6.Z8
Yellowne~ Index (B) 7,10
Additionally, thl~ graft copolymer had an unacceptably
~trong, unplea~ant odor due to re-~idual monomer.
33~064~-F _19_
-20- ~339160
Example~ 8-12
158 gram~ of the produots obtained ln Example 3
and ~ompa~ative Examples 4-7 above were melt hlended
w1th 1~2 gram~ of DoWLEX4 LLDPE 4035 u~ing a three
zone, one-inch ~ingle ~crew extruder wlth a
length/diameter ratlo of ~:1, barrel te~perature o~
32~CF in Zone l and 3~5~F in zone~ 2 and 3. The
re~ult~ng pellet~ were th~n fed to a three-quarter inch
Klllion ~ln~le screw blown ~llm extrude~ ha~ing a
barrel temperature in zone~ 1 and 2 of 300~F and 375~F
respectively, an~ 375~F in dle zone~ ~ and 2. A
frostline of three in~he~ wa~ malntained ln each ca~e.
The extruded monolayer film had a final maleic
anhydri~e comonomer content of 0.13% by weight.
An ~ inch wide film having a thickne~s oP 1.fi
mil~ of each o~ Example 3 and ~omparative Example~ 4-7
(C. 4-7) was placed on a li~ht box. A 1.5 inch x 0.5
inch template wa~ place~ ov~r the film. The number of
grains havin~ a diameter ~etween 5 ~nd 15 mil~ wlthin
the template area unde~ a ~0 fold ma~nificatlon lamp
(Art Specialty Co., Chicago, Ill~nois) were then
determined. The re~ult~, tabulated below, are
expre~sed in unit3 of number of grain~ per l,000 ~qu~re
inche~ of 1.6 mil fllm.
4 A trademark o~ The Dow Che~ieal Company- DOWLEX
LLDPE 4035 i~ a linear low den~ity polyethylene
(LLDP~) ~aving a melt index of 5.~ ~g/min and a
den~i~y of 0.919 ~/cc.
33,o64~-F -20-
-21- 133916~
EXAMP~E N0
~ C C.~ C.6 C-7
2,773 8,10715,~19 4tO53
*~ould not be made into fil~ u~ing blend level~
~hich give a maleic anhydride content ~uitable for
adhe~ive performanee.
(Comparatire) Example 1~
Thi~ ex~mple demon~trate~ that les~ conver3ion
i~ obtained when the m~leic anhydrlde (MAH) ~raftlng
~onomer i~ fed to the extruder premixed (Sample A) t
conc~rrently (Sample B) or in the conven~lonal fee~
port~ (Samplç C) than the embodiment~ of this in~ention
(~n partic~lar a~ illu~trated in Examples 1-3).
Sample A
Into the extruder of Example 1 wa-~ fed a
~ixture of malelc anhydride an~ dicumyl peroxide (10:1
weight ratio, re~peetively). ~he mixture was dis~olved
in acetone and sprayed on pellet~ of hlgh den~ity
polyethylene ~HDPE). The a~etone wa~ evaporated, ~nd
t~e coated pellets were fed a~ a concentrate lnto the
~uetlon of the extr~der, along with ~irgin pellet-~ to
~eed a 97.8~ polymer/2% malei~ anhydride/0.~% dic~myl
psroxide mixture. Devolat~lization was performed in
Zon~ 3. Data i~ provided in Table II.
33,064A-F -21-
22 1339160
Sample B
A malelc anhydride concentrate in a 25 melt index
linear low density polyethylene (LLDPE) was made on a Banbury
mlxer, and subsequently granulated. The concentrate contalned
10% malelc anhydrlde. A dry blend of thls concentrate wlth
dlcumyl peroxlde powder was made, and the concentrate fed to
the extruder of Example 1 along wlth vlrgln polyethylene to
glve a feed ratlo of 97.91 polymer/1.9% malelc anhydrlde/0.19
dicumyl peroxlde. Data ls provlded ln Table II. Addltlon-
ally, these copolymers had an unacceptable odour for use as afood packaglng component.
TA~LE II
PHR PHR %MAH %
MAHPeroxlde GraftedConverslon Polymer Sample
2.2 0.2 0.60 27.3 HDPE A
1.9 0.2 0.52 27.4 LDPE B
PHR = Pounds per one hundred rate (of polymer~
Sample C
The extruder of Example 1 was employed except that
malelc anhydrlde (MAH) and peroxide dlssolved ln methyl ethyl
ketone (MEK) at a welght ratlo of 59/3/38, (MAH/peroxlde/MEK)
was ln~ected lnto Zone 2 vla a tube fltted into a plate from
whlch was attached a metal plug, normally used to contour the
shape of the twln screws to ellminate some of the air in the
extruder and act as part of the barrel. Polymer was fed into
the suction of the extruder. At the point where the solutlon
was lntroduced, the polymer was molten. The solvent and
k~ 74069-40
~?.;
1339160
23
unreacted monomer was vacuum devolatillzed in Zone 3 and 4.
Pertlnent data is provided ln Table III. Note that these
copolymers had an unacceptable odour for use in a food
packaging component.
TABLE III
GRAFTING MALEIC ANHYDRIDE BY SAMPLE C METHOD
PHR PHR %MAH %
MAH Peroxide Grafted ConversionPolYmer
2 0.12 0.16 8 HDPE
2 0.13 0.11 5.5 HDPE
2 0.12 0.58 29 LLDPE
2 0.12 0.44 2Z LLDPE
2 0.12 0.37 18.5 LLDPE
2 0.1Z 0.82 41 LLDPE
2 0.1 0.48 24 LLDPE
PHR = Pounds per one hundred rate (of polymer)
Dicumyl Peroxide
3 t-Butylhydroperoxide
4 Lupersol 130
7406g-40
~r~
