CA2042893A1 - Filled polyethylene compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A mouldable filled polyethylene composition is disclosed. The composition consists essentially of a polyethylene component, 10-60% by weight of a particulate cellulosic component and 4-20% by weight of a toughening component. The polyethylene component is 85.99%, by weight of the composition, of a homopolymer of ethylene or copolymer of ethylene and at least one C4-C10 hydrocarbon alpha-olefin, or a mixture thereof, having a density in the range of 0.89 to 0.97 g/cm3 and a melt index in the range of 0.30 to 120 dg/min., and 0.01-86%, by weight of the composition, of a grafted polyethylene obtained by the grafting of a homopolymer of ethylene or copolymer of ethylene and at least one C4-C10 hydrocarbon alpha-olefin with a grafting monomer that is at least one of an ethylenically unsaturated aliphatic carboxylic acid or anhydride. The grafted polyethylene contains at least 0.01% of the grafting monomer. The toughening component is selected from (i) ethylene/propylene/diene copolymers, (ii) ethylene/hydrocarbon alpha-olefin copolymers having a density of less than 0.910 g/cm3, (iii) copolymers of ethylene and vinyl acetate having a vinyl acetate content of at least 5%, (iv) copolymers of ethylene and at least one alpha,beta ethylenically unsaturated aliphatic carboxylic acid having from 3 to 8 carbon atoms, (v) ionomers of the copolymers of (iv), and (vi) copolymers of (c) (i)-(v) that have been grafted with at least one of an ethylenically unsaturated aliphatic carboxylic acid or ethylenically unsaturated aliphatic acid anhydride. The compositions may be used to form a variety of moulded articles e.g. containers, trays, boxes and other shaped articles.

Description

~ 1 --FILLED POLYETHYLENE COMPOSITIQNS
The present invention re.lates to mouldable filled polyethylene composi ions, and especi~lly to such compo5.itions in which th~ filler is a particulate cellulosic material.
The forest industry uses substantial quantities of cellulosic materials in processes ~or the preparation of cellulosic product~, Example~s o~ the latter include pulp for the manufacture of pape.r and related products and lumber for the construction industry. Whlle such processes may produce a high proportion of cellulosic products of acceptable quality, no~etheless second grade, scrap or other waste mat~rial is formed. Such ~a~erial may include waste paper, sawdust, chips, shavings and the like.
Plastics, for example polyethylene~ are used in a wide variety of end-uses. Filled polyet~ylene compositions are useful in some end-uses, esp~cially as moulded ~r other formed products. The filler may be used to impart particular properties to the polyethylene e.g.
stiffness, or merely be used to reduce the effective cost of the polymer.
The use o~ cellulosic fillers is kno~n. For example U.S. 3 485 777 of M.G. t;;aylord, which issued 1969 December 23, relates to the ~ompatibilization of normally incompatible polymers, one of which is highly hydrogen bonded polyhydric polymer e.g. a cellulosic material, and the other being a thermoplastic polymer ~.g.
polyethylene. The two polymers are mixed with a compatibilizer e.g. a graft copolymer, under shear conditions. U.S. 3 649 939, also of N.G. Gaylord, which issued 1972 February 29~ relates to compatibili7ati~n of hydroxyl containing materials e.g. cellulose, with thermoplastic materials containing labile ato~s, such as 3~ polyethylene, by reacting the materials with a coupling ~3 agent e.g. maleic anhydride, ~n the presence of a free radical initiator.
Cellulosic fillars that have been heat treated with glyoxal and which are intended for use in thermoplastiC polymers are disclosed in U . S O ~1 7~3 493 of T. Motegi et al ., which issued :L988 November 08 . U. S .
4 717 742 of A.D. Beshay~ which issued 1988 January 05, discloses reinforced thermoplasl:ic cvmposites in which th~ filler is obtained by the gr~aftiJlg o~ ~:ilanes onto cellulosic materials in the presence oP fre~ radical initiators. U.S. 4 791 020 o~ B.V. Kokta, which issued 1988 December ~3, discloses composites made from cellulosi~ fibres dispersed in a matrix o~ polyethylene and an isocyanate.
U.S. 4 746 688 of L. Bistak et al, which issued 1988 May 24, relates to sound ~eadening materials formed from celllllosic filled polyol~fins containing lO0 parts of polyolefin, 20-150 parts of cellulose particulates and 20-l20 part~ of cross-linked elas~o~eric particles. U.S.
20 4 323 625 of C. Aubert et al, which issued 1982 April 06, relates to composites of grafted polyolefins and cellulosic fibres in which th~ polyole~in has been modified by grafting with methylol phenolic groups in the presence of ~n activator.
Compositions of ethylene copolymers5 plasticizers and cellulo5ic fill~rs, op ionally containing elastomers or ethylene and propylene homo- and copolymers are disclosed in U.S. 4 472 545 and 4 480 061, both of M.C, Coughlin et ~l, which issued 19~4 Septe~ber 30 18 and 1984 October 30, respectively. The ethylene copolymers are, for example, ethylene/vinyl ester copolymers or copolymer~ of ethylene and unsaturated mono- and dicarboxylic acids or their esters or salts.
Mouldable ~illed polyethylene compositions o~
improved toughness properties, as measured by impact strength and elongation, and formed from polyethylene and DC-9536 _ ~ _ cellulosic ~aterials have now been ~ound~
Accordingly, th~ present invention provides a mouldable filled composition con~isting ~ssentially of:
(a) a polyethylene component comprising (i~
0-85.99%, by weight o the composition, of a homopolymer of ethylene or a copolymer o~
ethylene and at least on~ C~-CI~
~ydrocarbon alpha~olefin, or a ~ixture th~reo~, said homopolym~r or copolym~r having a dens;ty in the range oE 0.89 to 0.97 g~cm3 and a melt index in the range of 0.30 to 120 dg/min., and ~ 0.01-86~, by weight of the composition~ of a grafted poiy~thylene obtained by the grafting o a homopolymer o~ ethylene or copolymex of ethylene and at least one C~-C10 hydrocarbo~
alpha-olePin with a grafting monomer that is at least one of an ethylenically unsaturated aliphatic carbsxylic acid or e~hylenically unsaturated aliphatic carboxylic acid anhydride, ~aid graPted polyethylene containing at lea~t 0.01~ o~
the grating monomer;
(b) 10-60~, by weight of the compositlon, o a particulate cellulosic material: and (c) 4-20~, by weight of the composition, of a toughening component sel~cted fro~ (i~
ethyleneJpropylene/diene copolymers, (ii~
ethylene~hydrocarbon alpha-olefin copolymers having a density of less than 0.910 g/cm3, (iii~ c~polymers of ethylene and vinyl acetate having a vinyl acetate content o~ at least 5%, ( iY~ cop~lymers of ethylene and 2t least one alpha,beta ethylenically unsaturated aliphatic DC-9536 _ 3 _ carboxylic acid having from 3 to 8 oarbon atoms, (v) ionomers of the copolymers of (iv), and (vi~ copolymers of (c)(i)-(v~ that have been grafted with at least one of an ethylenically unsaturated aliphatlc carboxylic acid or ethylenically unsaturated aliphatic acid anhydride.
In a preferred embodiment of the composition of the present invention, the gra~ting monomer i~ maleic acid or mal~ic anhydrid~.
The present inven~ion rela~es to a composition having a.po~yethylene component, a cellulosic matarial and a toughening component. The polyethylene component is a blend formed ~rom polyethylene i.e. un-qrafted polyethylene, and grafted polyethylene; the un-gra~ted polyethylene is 0-8S.99% by weight of the composi~ion, preferably 25-75%, and the grafted polyethylene is 0.01-~6~ by weight of the composition, preferably 1-20~.
The un-grafted polyethylene m~y be a homopolymer of ethylene or a copolymer of ethylene with at lea~t one C4-~10 hydrocarbon alpha-olefin, or mixtures ~hereo~. Ihe preferred copolymers are copolym~rs ~f ethylene with butene-l, hexene-l and/or octen~ he density of the polymers may be varied over a wide range e.q. in the ran~e of from abou~ 0.890 g~cm3 ~o about G.970 g/cm3, and especially in the range of 0.92 to 0.96 y/cm3. The melt index of the polymer, as measured by the procedure of AS~M D-123~ (Condition E, also ~nown as 190~2.16) is preferably in the range of 0.30 to 1~0 dg/min, and especi~lly in the range o~ 0.75 to 100 dg/min.
The polyethylene of the grafted polyethylene may be a homopolymer of ethylene or a copolymer of ethylene with at least one C~-C10 hydrocarbon alpha-ole~in, or mixtures thereof. The preferred copolymers are ~opolymers of ethylene with ~utene-l, hexene-l and/or octene-l. The density of the polymers may be varied over a wide range e.g. in the ran~e of from about 0.89 g~cm3 ~C-9536 - 4 ~

1~ ~

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to about 0.970 g/cm3) and especially in the range of 0.91 So O.96 g/c~3. The melt index of t~e polymer i5 prefera~ly in the range of 0.30 to 1~0 dg/min, and especially in the range of 0.75 to 100 dg/min. The polyethylene of the un grafted polyethylene and o~ th~
graPted polyethylene may be the same or di~ferent.
The monomer that is grafted onto the polyethylene is an *thylenically unsaturated aliphatic carboxylic acid or derivative thereo~. The grafting monomer is selected ~ro~ the group consisting of ethylenically unsaturated aliph,atic carboxylic acids and ethylenically unsaturated aliph,atic carboxylic acid anhydrides, including derivatives o~ such acids.
Examples of the ~cids and anhydrides, which may be mono-, di- or polycarboxylic acids, are acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, itaconic anhydride, maleic anhydride and substituted maleic anhydride e.g. dimethyl mal~ic anhydride, nadic anhydride, nadic methyl anhydride and tetrahydro phthalic anhydride. Exa~ples of derivatives of the unsaturated acids are salt~, amides, i~ides and esters e.g. mono- and disodium maleate, acrylamide, maleimide, glycidyl methacrylate and diethyl fumarate.
The preferred ~onomer i5 ~aleic acid or ~aleic anhydride.
The amount of grafted monomer of the grafted polyethylene may ~e varied over a wide range, but should be at lea5t 9 ppm by weight of the polyethylene. In embodi~ents, the a~ount of grafted monomer may be as high as 5% by weight, especiallr 0.01-0.2% by weight and in 30 particular in the ran~ of 0. 02-0.15~ by weightO Gxafted polyolefins are available commercially e.g. under the trademark Fusabond from Du Pont Canada Inc. In addition, methods for the grafting of monomers onto polyolefins are disclosed in U.S. Patent 4 612 155 of R.A. Zelonka and 3~ C.S. WGng, issued 1986 September 16. The amount of graft monomer in the polyethylene used accordinq to the present DC-9536 5 _ invention may b~ obtained by grafting the requir~d amount onto the polyethylene or by blending a polymer having a higher level o~ graft monomer w:ith un-grated polyethylene or polyethylene wil:h a lower level o~ graft monomer~ In alternative embodiments, the grated polyethylene may be replaced with an acid copolymer e.g.
a copolymer of ethylene and an unsaturated carboxylic acid, examples of which are ethylene/acrylic acid and ethylene/methaCryliC acid copol~rmer~, or with ionomers of such copolymers. Examples of both the acid copolymers and ionomers are commercially available.
The cellulosic material may be obtained from a variety of sources~ For instance~ the cellulosic substrate may have been derived from particles, chip~, flakes, sawdu~t, paper (including recycled paper) and/or other fragment5 of wood. Moreover, the fra~ments of wood may be derived from a variety of tree5, including both hardwood and softwood trees. Examples o~ such trees include, but are not limited to, aspen, beech, birch, cedar, Douglas and other firs, hemlock7 pine ~nd spruce in Canada, but in other countries could be ex~mplified by other types o~ trees. In addition, the cellulosic material may be recycled material e.g. recycled paper i.e. paper in the form of newspapers, maga~ines and other communicatiOns or scrap paper or the like that has been recovered for re-uset The cellulosic material is in a comminuted form, and it may be necessary to 5ubject potentially useful material to a COmminUtlon process so as to obtain the cellulosic material in an accepta~le particulate siæe for the proposed end-use. In ~referred embodiments, the particulate size of the cellulosic material is less than 2 . O mm, and especially less $han 1. O mm. The ams:unt o~
cellulosic material may be 10-60~ by weiqht of th~
composition, especially 15-40% by weight of the composition.

~3~ 7,J
The touqhe~ing component i~ salected fr3m ~i) ethylene/propylene/dlene copolymer~ L) ethylene/-hydrocarbon alpha-olefin copolymers hav:Lng a den~ity of less than 0.910 g/cm3, sometimes referred to in ~h~
trade as flexomers, (iii) copolymers of ethylene and vinyl acetate having a vinyl acetate content o~ at least 5~, especially at least 9% by weight, (iv) copolymers oP
ethylene and at least one ~thyl~nlcally unsa~ura~ed aliphatic carboxylic acid, (v) iLonomers o~ ~he copolymers of ~iv), and (vi) copolymers of (G) (i)-(V) that ha~e been grafted with at least one ~f an e~hylenically unsa~urated aliphatiC carboxylic acid or et~lylenically unsaturated aliphatic acid anhydride. The ~onomers that may be grafted on are described above with respect to the grafting sf polyethylene. The ethylene~propylene/diene copolymers are polymers that are frequently referred to as elastomers, many examples of which are available commercially. The ethylene/hydrocarbon alpha-olefin copolymers are copolymers of e~hylene wi~h at least one C3-C10 hydrocarbon alpha-olefin e.~. copolymer of ethylene with propylene, butene-l, hexene-l and/or octene~l, that have densities of less than 0.910 g/om3, especially less than 0.900 9/cm3, and preferably have melt indic~5 of 0.60 to 270~ e5pecially 0.9 to 1.1 dgJmin. The ~thylene/vinyl acetate copolymers have vinyl acetate contents o~ at least 5~ by weight and e~pecially at least 9% by weight, and preferably have melt indices of 2 to 500, especially 5 to 200 dg/min.
The copolymers of ethylene and at least on~
alpha, beta ethylenically unsaturated carboxylic acid having from 3 to 8 carbon atoms may be ~ormed usinq a variety of such acids e.q. acrylic acid~ methacrylic acid and the like. The acid moieties may be randomly or non-randomly distributed i~ the polymer chain, and b8 ~or example 0.5-50~ by wei~ht of the polymer. The ionomers may be ionomers having for example sodium, zinc or DC-9536 _ 7 _ aluminum ions. Examples of the copoly~ler~ and ionomers are available commercially e.g. as Nucrel0 acid copolymer5 and Surlyn~ ionomer~ from E.I. du Pont de Nemour9 and Company of Wilmington, ~elaware, U.S.A.
The compositions of the present inventlon may be prepared by feeding the compone~nts of the composition to an internal ~ixer e.g. in a batch process, or extrud~r e.g. in a continuous process, especially an ~xtruder adapted for the co~pounding of polymer compositions. All of the components may be fed in the ~orm of a physical blend to the hopper of an internal mixer e.g. a Banbury mixer, or an extruder or some o~ the polymeric components may be fed by other means into the mixer or extruder. It may be advantageous to feed the particulate cellulosic material directly into molten polymeric components, instead of making a physical blend of cellulosic and polymeric components and feeding the blend ~o the extruder or mixer. The mixer or extruder should be operaSed at temperatures above th~ melting point of all of the polymeric components of the composition. The compo5ition obtained from the mixer or extruder would normally be in the form o pellets, granules or other comminuted shapes, but the composition may be fed to other proc~ssing apparatus or otherwise directly formed 2~ into a sh~p~d articl2.
The compositions of the invention m~y be used in a variety of processes, especially moulding or ther~oforming processes. For example, the composltions may be injection moulded into containers, trays, boxes and other shaped articles, or thermoformed into trays and the like, as will be a~preciated by those skilled i~ the art.
The ]present invention is illustrated by the following exalmples 3S ExamPle I
A series of compositions were formed frsm a DC-9~36 linear ethylene homopolymer haviny a density of 0.96 g/cm3 and a ~elt index o 5~0 dy/m.in. The composition contalned 5% by weight of a hlgh densi~y polyethylene that had been grafted with malei.c anhydride, such that the grafted polym~r contained OOg% by weight of grafted maleic anhydride. The cellulosic ~iller was a sand~rdust formed from spruce, pine and ~ir wood.
The blends were m01t compounded using a 2 c~
co-rotating twin screw extruder. Samples ~or testing were prepared usin~ a 90 tonne Engel~ inject1on moulding machine. Testing of the moulded samplas was carried out according to the follow.ing procedures:
Tensile Strength ... ASTM D 638 Elongation at Break 0.. ASTM D 638 Flexural Modulus ... ASTM D 790 Notcned Izod Impact Strength ... AST~ D 256A
Further details oP th2 composition~ and results obtained are shown in TAB~E I as Runs 1-10, o~ which Runs 1, 2, 6 and 10 are comparative runs.
The results show that addition o~ ~ither o~ th~
grafted ethyl~neJpropylene~diene copolymer or grafted very low densi y polyethylene resulted in an increase in elongation and notched I70d impact strength of the composit~, compared to t~e control sample ~Run 2~ that did not contain either of such grafted copolymers: the increase in elongation and impact strength are a measure of the improvement in the toughness o~ ~h~ romposite~
Tensile strength and flexural modulus were decreased co~pared to that of the control but were significantly higher than the polyethylene that did not contain sanderdust. At a 15~ loading level, the ethylene~propylene~diene copolymer resulted in a 2-4 fold increase in impact strength.
Dart impact test were carried out on a 2.54 mm thick plaque at room temperature using a 3.75 cm tip dart, following the procedure o AST~ D302~, Method F.

DC-9536 _ 9 _ ~ 10 ~ 2 The results indicate that the presence of the 'lelastomer"
improved the dart impact strength.
E~l~I
The procedure o Example I was repeated using recycled high density polye~hylene that had been obtained from used ~ilk jugs and comminuted recycled paper ins~ead of the sanderdust. The results obtained are also shown in Table I, as Runs 11-13 of which only Run 13 is a run of the invention.
The compositions o~ the invention showed properties similar to those of Exampl~ I. The addition of 5~ by weight of graftPd ethylene~- propylene~diene copolymer resulted in a small increase in elongation and notched Izod strength i~e. a small increase in toughne~, compared with the control sample (Run 12~ that did not contain grafteA copolymer. Tensile strength and flexural modulus were decreased compared with the control~ but were significantly higher than the sample that did not contain recycleA paper.

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~xample III
The procedure o~ Example I was repeated, using the following compositions:
(a~ 65% ~y weight o~ Sçlair'U 2111 polyethylene, 5 by weight of the grafted polyeth~ylen~ oP Example I and 30~ by weight of t~ sanderdust ~Df Exampl I; and ~b) 60% by weighg o~ Sclair 2111 polyethylene, 5% by weight of the graPted polyethylene o~ Example I, 30~ by weight of the sanderdust o~ Exam~ple I and 5~ by weight of the grafted ethylene/propylene/d:iene elastomer of Exa~ple I.
The compositions were compounded on a 2.0 cm Welding Engineers twin-screw extruder. Plaques for testing were compression moulded at 170-C.
The results obtained were as follows:

Run No. Tensile Elongation Flex. Mod. Notched Izod Strength (%) (MPa) Impa~t Strength (MPa) (3/m~
~ .1 16 820 63.3 17.2 15 960 80.6 Note:
(1) Run 14 is composition ~a) and Run 15 is compo~it;on (b)o (~) Sclair ~111 polyethylene is an ethylene/~utenP l copolymer having a density of 0.924 g/cm and a melt index o 20 dg/min.
The results show that addition of the grafted elastomer improved the Izod impact strength and flexural modulus of the compositions.
~m~
A series of compositions were formed in a Brab nder Plasticorder. The compositions were compression moulded and test specimens were cut ~r~m the moulded articl~s. Details of the compositions prepared and the resultc; obtained are given in Table IY.
DC-953~ 12 -,. .

- 13 - ~J~ 3 TABLE IV
Run Polymer* Grafted Filler~ ~ough~nex No. (~) Polymer* (%) Type* (~) (~) 16 7~ 0 30 - -21 58.5 5 3~ ~ ~.5 22 45.5 5 30 ~ 19.5 23 ~2 5 30 C 13 24 65 5 3~ _ _ * "Polymer" was an ethylene homopolymer having a density o~ 0.96 g/cm3 and a melt index o~ 5.0 dg/~in "Grafted Polymer" was an e~hylene/butene-l copolymer having a density o~ 0.95 g/cm3 and a melt index of 2.0 dg/min, that had been grafted with 0. 9% of maleic anhydride.
"Filler" was sanderdust "Toughener A" was an ethylene/vinyl acetate copoly~er having a vinyl acetate content vf 28% and a mel~ index of 1.7 dg/mi~, that had been grafted with 104~ of maleic anhydride; density was O.g5 g/~3 .
"Toug~ener B" was Elv~x~ 260, an ethylene/vinyl acetate copolymer having a vinyl acetat~ content of 28% and a melt index of 6.0 dg/min; density was 0.955 g/cm3.
"Toughener C" was Elvax 265, an ethylen~/vinyl acetate copolymer having a vinyl acetate content o~
28% and a melt index o~ 3.0 dy/min; density was 0.~55 g~cm3.
i Table X~
R~n Tensile Elongation Flex. Mod. Notched Izod No. Strength (%) (MPa) Impaot Strength ~MPa) (J/m) 16 25.6 <3 2~60 32 17 25.1 7 1160 53 1~ 18.1 5 1260 35 19 3~.2 11 1330 7~
31.6 11 1770 77 21 3~.2 9 19~0 6 22 2~.1 9 1450 80 23 31.6 8 1~10 70 24 3~.5 ~ 2~0 ~7 The results ~how an improvement in impact strength and elongation evident in the samples containiny the ethylenetvinyl acetate copolymer~ . The resul ts also 1~ show the importance o~ having grafted polyethylene, even if grafted ethylene/vinyl acetate copolymer was also present .

. : ~

Claims (6)

1. A mouldable filled composition consisting essentially of:
(a) a polyethylene component comprising (i) 0-85.99%, by weight of the composition, of a homopolymer of ethylene or a copolymer of ethylene and at least one C4-C10 hydrocarbon alpha-olefin, or a mixture thereof, said homopolymer or copolymer having a density in the range of 0.89 to 0.97 g/cm3 and a melt index in the range of 0.30 to 120 dg/min., and (ii) 0.01-86%, by weight of the composition, of a grafted polyethylene obtained by the grafting of a homopolymer of ethylene or copolymer of ethylene and at least one C4-C10 hydrocarbon alpha-olefin with a grafting monomer that is at least one of an ethylenically unsaturated aliphatic carboxylic acid or ethylenically unsaturated aliphatic carboxylic acid anhydride, said grafted polyethylene containing at least 0.01% of the grafting monomer;
(b) 10-60%, by weight of the composition, of a particulate cellulosic material; and (c) 4-20%, by weight of the composition, of a toughening component selected from (i) ethylene/propylene/diene copolymers, (ii) ethylene/hydrocarbon alpha-olefin copolymers having a density of less than 0.910 g/cm3, (iii) copolymers of ethylene and vinyl acetate having a vinyl acetate content of at least 5%, (iv) copolymers of ethylene and at least one alpha,beta ethylenically unsaturated aliphatic carboxylic acid having from 3 to 8 carbon atoms, (v) ionomers of the copolymers of (iv), and (vi) copolymers of (c)(i)-(v) that have been grafted with at least one of an ethylenically unsaturated aliphatic carboxylic acid or ethylenically unsaturated aliphatic acid anhydride.

2. The composition of Claim 1 in which the toughening component is an ethylene/propylene/diene copolymer.

3. The composition of Claim 1 in which the toughening component is an ethylene/hydrocarbon alpha-olefin copolymer having a density of less than 0.910 g/cm3.

4. The composition of Claim 1 in which the toughening component is a copolymer of ethylene and vinyl acetate having a vinyl acetate content of at least 5%.

5. The composition of Claim 1 in which the toughening component is at least one of an ethylene/propylene/diene copolymer, ethylene/hydrocarbon alpha-olefin copolymer having a density of less than 0.910 g/cm3 and a copolymer of ethylene and vinyl acetate having a vinyl acetate content of at least 5%, that has been grafted with at least one of an ethylenically unsaturated aliphatic carboxylic acid or ethylenically unsaturated aliphatic acid anhydride.

6. The composition of any one of Claims 1-5 in which the grafting monomer is maleic acid or maleic anhydride.