Note: Descriptions are shown in the official language in which they were submitted.
~ 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
DC-9536 - 1 -
~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 _ ~ _
- 3
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~ ~
s ~
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.
DC-9536 - 6 -
~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.
3Q
DC-953~ - 10
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DC-953S -
12 - ~3~L~ 3, ~
~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 - -
17 57 0 30 A 13
18 57 0 30 B 13
19 52 5 30 A 13
52 5 30 B 13
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
35 DC-9536 - 13 -
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 .
DC-9536 -14 -
. : ~
