CA1339160C - Maleic anhydride graft copolymers having low yellowness index and films containing the same - Google Patents
Maleic anhydride graft copolymers having low yellowness index and films containing the sameInfo
- Publication number
- CA1339160C CA1339160C CA000574164A CA574164A CA1339160C CA 1339160 C CA1339160 C CA 1339160C CA 000574164 A CA000574164 A CA 000574164A CA 574164 A CA574164 A CA 574164A CA 1339160 C CA1339160 C CA 1339160C
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- Prior art keywords
- polymer
- maleic anhydride
- extruder
- graft copolymer
- ethylene
- Prior art date
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
- B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
- B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F222/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides, or nitriles thereof
- C08F222/04—Anhydrides, e.g. cyclic anhydrides
- C08F222/06—Maleic anhydride
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F255/00—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F255/00—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00
- C08F255/02—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00 on to polymers of olefins having two or three carbon atoms
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
- C08L51/06—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2250/00—Layers arrangement
- B32B2250/24—All layers being polymeric
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2270/00—Resin or rubber layer containing a blend of at least two different polymers
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Graft Or Block Polymers (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
Maleic anhydride can be satisfactorily grafted to polymers at low pressures by feeding the polymer through a multiple screw extruder and injecting the maleic anhydride and a free radical initiator into a polymer filled, pressurized section of the extruder.
The maleic anhydride and initiator can be pre-mixed in a solvent solution. The solvent and unreacted maleic anhydride can be removed by low pressure devolatilization.
The graft copolymer has a yellowness index as measured by ASTM D-1925-70 less than about 10.0 and as measured by ASTM E-313-73 less than about 11Ø
Further, between 0.75 and 2.0 weight percent of the graft copolymer comprises maleic anhydride. The graft copolymer can further be blended with an olefinic polymer to yield adhesive thermoplastics suitable for use as food packaging multilayer coextruded films.
The maleic anhydride and initiator can be pre-mixed in a solvent solution. The solvent and unreacted maleic anhydride can be removed by low pressure devolatilization.
The graft copolymer has a yellowness index as measured by ASTM D-1925-70 less than about 10.0 and as measured by ASTM E-313-73 less than about 11Ø
Further, between 0.75 and 2.0 weight percent of the graft copolymer comprises maleic anhydride. The graft copolymer can further be blended with an olefinic polymer to yield adhesive thermoplastics suitable for use as food packaging multilayer coextruded films.
Description
-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
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~.
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 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.
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 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.
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-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 ~?.;
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~
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-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 ~?.;
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~
Claims (19)
1. A graft copolymer composition comprising the reaction product of maleic anhydride and a backbone polymer characterized by the composition having a yellowness index as measured according to ASTM D-1925 of less than 10.0 and wherein between 0.50 and 2.0 weight percent of said graft copolymer comprises maleic anhydride.
2. The graft copolymer of 1, wherein said backbone polymer is an olefinic polymer selected from the group consisting of high density polyethylene, low density polyethylene, and copolymers of ethylene and a C3 to C10 olefin.
3. The graft copolymer of Claim 1, wherein said backbone polymer is polypropylene or poly(4-methylpentene).
4. The graft copolymer of Claim 1, wherein said backbone polymer is a copolymer of ethylene and a member selected from the group consisting of methacrylic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, methyl acrylate and vinyl acetate.
5. The graft copolymer of Claim 1, wherein said backbone polymer is a copolymer of ethylene and either acrylic acid or carbon monoxide.
6. The graft copolymer of Claim 1, wherein said yellowness index is less than 8.75.
7. The graft copolymer of Claim 1, wherein the whiteness index as measured according to ASTM
E-313-73 is greater than 45Ø
E-313-73 is greater than 45Ø
8. A multilayer film containing at least two layers wherein at least one of said layers comprises a blend of:
(a) the composition of Claim 1; and (b) between 25.0 to 98.5 weight percent polyolefin.
(a) the composition of Claim 1; and (b) between 25.0 to 98.5 weight percent polyolefin.
9. The film of Claim 8, wherein said polyolefin is selected from the group consisting of polyethylene, polypropylene, poly(4-methylpentene), copolymers of ethylene and a C3 to C10 .alpha.-olefin.
copolymers of ethylene and a C4-C8 diolefin and copolymers of ethylene and an ethylenically unsaturated carboxylic acid or derivative and copolymers of ethylene and carbon monoxide.
copolymers of ethylene and a C4-C8 diolefin and copolymers of ethylene and an ethylenically unsaturated carboxylic acid or derivative and copolymers of ethylene and carbon monoxide.
10. The film of Claim 9, wherein said polyethylene is selected from the group consisting of low density polyethylene, high density polyethylene, and linear low density polyethylene,
11. The film of Claim 8, wherein the grain count of diameter size between 5 and 15 mils of said blend is less than 3,000 grains per 1,000 square inches of 1.6 mil film.
12. A method for grafting maleic anhydride to polymers, including the steps of:
(a) feeding the polymer, maleic anhydride and a free radical initiator to a multiple screw extruder;
and (b) melting the polymer by heating and shearing in the extruder; and (c) thereafter mixing the molten polymer and maleic anhydride in the extruder for sufficient time to graft at least part of the maleic anhydride to the molten polymer;
characterized by step (b) preceding addition of maleic anhydride in step (a) and by injecting the maleic anhydride and free radical initiator into a section of the multiple screw extruder that is pressurized and filled with molten polymer.
(a) feeding the polymer, maleic anhydride and a free radical initiator to a multiple screw extruder;
and (b) melting the polymer by heating and shearing in the extruder; and (c) thereafter mixing the molten polymer and maleic anhydride in the extruder for sufficient time to graft at least part of the maleic anhydride to the molten polymer;
characterized by step (b) preceding addition of maleic anhydride in step (a) and by injecting the maleic anhydride and free radical initiator into a section of the multiple screw extruder that is pressurized and filled with molten polymer.
13. The method of Claim 12, wherein the maleic anhydride and the free radical initiator are mixed in a solvent system prior to injection into the extruder, and wherein the extruer is a co-rotating, twin screw, extruder.
14 The method of Claim 12, further comprising the step of devolatilizing the polymer in at least one decompression zone of the extruder.
15. The method of Claim 13, wherein the maleic anhydride and the free radical initiator are mixed within a ketone prior to injection.
16. The method of Claim 12, wherein the polymer is a high density polyethylene resin or a low density copolymer of ethylene/octene.
17. The method of Claim 15, wherein the ketone is selected from methyl ethyl ketone and acetone.
18. The method of Claim 12, wherein the extruder predominantly contains positive conveyance elements, and the polymer filled, pressurized section of the extruder contains a series of mixing type elements that are backed by a negative conveyance element.
19. The method of Claim 12 wherein the product has the composition of Claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000574164A CA1339160C (en) | 1988-08-09 | 1988-08-09 | Maleic anhydride graft copolymers having low yellowness index and films containing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000574164A CA1339160C (en) | 1988-08-09 | 1988-08-09 | Maleic anhydride graft copolymers having low yellowness index and films containing the same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1339160C true CA1339160C (en) | 1997-07-29 |
Family
ID=4138510
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000574164A Expired - Fee Related CA1339160C (en) | 1988-08-09 | 1988-08-09 | Maleic anhydride graft copolymers having low yellowness index and films containing the same |
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| CA (1) | CA1339160C (en) |
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1988
- 1988-08-09 CA CA000574164A patent/CA1339160C/en not_active Expired - Fee Related
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| EP3397665B1 (en) | 2015-12-29 | 2020-12-09 | Dow Global Technologies LLC | Highly grafted ethylene-based polymers, highly grafted ethylene-based polymer compositions, and processes for forming the same |
| US10894852B2 (en) | 2015-12-29 | 2021-01-19 | Dow Global Technologies Llc | Highly grafted ethylene-based polymers, highly grafted ethylene-based polymer compositions, and processes for forming the same |
| CN108431060B (en) * | 2015-12-29 | 2021-10-26 | 陶氏环球技术有限责任公司 | Highly grafted ethylene-based polymers, highly grafted ethylene-based polymer compositions, and methods of forming the same |
| WO2018071507A1 (en) * | 2016-10-12 | 2018-04-19 | Dow Global Technologies Llc | Method to produce functionalized ethylene-based polymers |
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