Note: Descriptions are shown in the official language in which they were submitted.
Composite Structures and Method of Making Same
Backqround of the Invention
Usually, polypropylene is adhered to polar pol-
ymers, like nylon, ethylene-vinyl alcohol copolymers
(EVOH) and polyvinyl alcohol polymers and to metals like
aluminum, steel, copper, tin, brass, etc., by interposing
a blend of polypropylene grafted with an unsaturated car-
boxylic acid or acid derivative and polypropylene. This
material is used directly as an adhesive layer between
the polypropylene and the polar substrate.
It would sometimes be preEerable to use poly-
ethylene gra~ted with unsaturated carboxylic acid or acid
derivatives because it can be prepared very easily in a
melt reaction system. If one blends the polyethylene
graft copolymers with polypropylene, however, relatively
poor adhesion is obtained to polar polymers and other
; polar substrates. In some instances, no adhesion at all
is obtained between the graft copolymer blend with poly-
~~ ~ propylene and the polar substrate. The methods and re-
sulting structures of this invention avoid these diffi-
culties.
Summary of the Invention
By grafting suitable unsaturated carboxylic
acids or acid derivatives, for example anhydrides, to
2S polyethylene and blending the resulting graft copolymer
with a mixture of polyethylene and an elastomer we have
obtained adllesives with-excellent adhesive strength to
both polypropylene and to various substrates including
polar polymers like nylon, ethylene vinyl alcohol
copolymers, polyvinyl alcohol polymers and copolymers,
metals, glass, paper, wood and the like. The elastomer
aids the blend in adhering to polypropylene since wi-thout
its presence, poor adhesion is obtained to polypropylene.
This result could not have been predicted by those skilled
in the art, and is, therefore, surprising.
IL~
~ la -
The invention in one aspect comprehends the method
of making a composite structure comprising polypropylene,
a polar substrate and an adhesive blend in intimate contact
therebetween comprising applying in contact with the polypropy-
lene a~d the substrate an adhesive blend free of polypropylene,the blend consisting essentially of (a~ a graft copolymer
of about 70-99.999 wt. % of a polyethylene baokbone grafted
with about 30-0.001 wt. % of at least one compound containing
at least one unsaturated carboxylic acid or acid anhydride,
or both blended with both, (b~ at least 30 wt. % of the
blend of at least one elastomer selected from the group
consisting of copolymers of ethylene and an ~-olefi.n, ter-
polymers of ethylene, an a-olefin and a diene, homopolymers
of chloroprene, copolymers of isobutylene, homopolyers
of isobutylene, copolymers of a diene and a vinyl aromatic
compound, copolymers of a hydrogenated diene and a vinyl
aromatic compound, homopolymers of butadiene, copolymers
of an ethylenically unsaturated nitrile and a diene, or
mixtures of these, and (c) at least one non-elastomeric poly-
olefin resin that is either a homopolymer of ethylene, a co-
polymer of ethylene and an ~-olefin, or a mixture of these.
The invention also comprehends the composite
structure of components comprising polypropylene, a solid
substrAte and adhered therebetween the blend as recited
above.
120631Z~
..~ ,~ . .. ....
I
--2
Description of the Preferred Embodiments
The term polyethylene used herein for the
grafting backbone includes homopolymers of ethylene and
copolymers of ethylene with propylene, butene-l and other
unsaturated aliphatic hydrocarbons. Preferably, the eth-
ylene polymer is linear. Also, it is preferable sometimes
to graft blends of two or more of these homopolymers and
copolymers.
The term polyethylene polymers used herein as
a blending resin includes ethylene homopolymers and copol-
ymers of ethylene with other unsaturated hydrocarbons
with higher olefins such as propylene, butene-l andhexene-
1. It is ~ometimes preferable to use blends of two or
more of the above homopolymers or copolymers in the
blending resin.
The polyethylene homopolymers or copolymers may
be prepared by any known process using transition metal
catalysts with low or medium pressure or radical initi-
ators with high pressure. Hence, the polymers may be low
density polyethylenes, linear low density polyethylenes,
medium density polyethylenes or high density polyethyl-
enes.
By elastomer is meant copolymers of ethylene
and an ~-olefin, terpolymers of ethylene, an ~-olefin and
a diene, homopolymers of isobutylene, copolymers of iso-
butylene, homopolymers of chloroprene, copolymers of a
diene and a vinyl aromatic compound~ block copolymers of
a diene and vinyl aromatic compound~ copolymers of hydro-
genated diene and vinyl aromatic compound, hydrogenated
block copolymers of a diene and vinyl aromatic compound,
homopolymers of butadiene, and copolymers of an ethylen-
ically unsaturated nitrile and a diene.
Some examples of these elastomers are copoly-
mers of ethylene and propylene, terpolymers of ethylene,
propylene and a diene, copolymers of isobutylene with
isoprene, chlorinated copolymers of isobutylene and
~:Z(;)63~
isoprene, copolymers of butadiene and styrene, copolymers
of butadiene and vinyl toluene, block copolymers of buta-
diene and styrene, block copolymers of butadiene and vinyl
toluene, block copolymers of isoprene and s~yrene, block
; 5 copolymers of isoprene and vinyl toluene, hydrogenated
copolymers of butadiene and styrene, hydrogenated block
copolymers of butadiene and styrene, hydrogenated block
copolymers o~ isoprene and styrene, styrene-ethylene bu~
tylene styrene block copolymers, copolymers of acrylo-
nitrile and butadiene, copolymers of methacrylonitrile
and butadiene, copolymers of acrylonitrile and isoprene,
and copolymers of methacrylonitrile and isoprene.
It i5 preferred in the invention to use ethylene-
propylene copolymers, ethylene-propylene-diene terpoly-
lS mers, homopolymers of isobutylene, chlorinated copolymersof isobut~lene and isoprene, homopolymers of chloroprene,
hydrogenated block copolymers of styrene and butadiene,
and styrene-ethylene-butylene-styrene block copolymers.
he unsaturated carboxylic acids o~ acia deriva-
tives used as the grafting monomers include compounds
such as acrylic acid, fumaric acid, methacrylic acid,
maleic acid, itaconic acid, citraconic acid, mesaconic
acid, maleic anhydride, citroconic anhydride, itaconic
anhydride, 4-methyl cyclohex-4-ene-1,2-dicarboxylic acid
25 anhydride, bicyclo(2.2.2)oct-S-ene-2,3-dicarboxylic
acid anhydride, l,2,3,4,5,8,9,10-octahydronaphthalene-
2,2-dicarboxylic acid anhydride, 2-oxa-1,3-
diketospiro(4,4)non-7-ene, bicyclo(2.2.1)hept-5-ene-
2,3-dicarboxylic anhydride, maleo-pim~ric acid,
tetrahydrophthalic anhydride,x-methylnorborn~5-ene-2,3-
dicarboxylic acid anhydride, norborn-5-ene-2,3-
dicarboxylic acid anhydride, Nadic anhydride, methyl
Nadic anhydride, Himic anhydride, methyl Himic anhydride
and other fused ring monomers described in U.S. patents
35 3,873,643 and 3,882,194, both assigned to the present
assignee. Cograft copolymers as described in this U.S.
--4--
patent 3,882,194 are also useful in this invention. The
methods of preparation of the graf~ copolymers are
described in the above U.S. patent~.
Since these blends do not contain polypropY1-
ene, the discovery that the blends of this inventionadhere to polypropylene is surprising. Examples of the
Gomposites of this invention are polypropylene/adhesive
blends of this invention/nylon, polypropylene/-
adhesive/ethylene-vinyl alcohol copolymer, polypro-
10 pylene/adhesive/alumlnum, polypropylene/adhesive/steel,polypropylene/adhesive/glass, polypropylene/adhesive/-
wood, polypropylene/adhesive/leather, polypropylene-
/adhesive/nylon/adhesive,~polypropylene r polypropylene/-
adhesive/EVOH/adhesive/polypropylene~ and polypropyl-
eneJadhesive/aluminum/adhesive/polypropylene. Othermetals ~uch as copper, steel, brass, etc., can be used~
Tt is ob~rious that many more combinations can
be made by one skilled in the art using the principles
and blends disclosed~
In preparing the three component blends of this
invention from the above graft copolymers, elastomers and
non~elastomeric ethy~ene homopolymers and copolymers, any
blending equipment or technique may be used. As an example,
only, blends can be prepared in an electrically heated
Brabender PlasticorderTM mixing head using a scroll type
mixer under the following conditions: temp rature - 400~,
rotor speed - 120 rpm and mixing time lO min. after flux.
The resultant blends were comp~ession mo~ded
into films approximately 0.005~0.007 inches thick. The
films were then heat sealed to the substrate under eval-
uation at an appropriate temperature and time. These
conditions are:
3~L~
1. Nylon 6 - 430F, 2 sc.
2. Ethylene-vinyl alcohol copolymer (EVOH)
- ~30C, 5 sec.
3. Polypropylene - 500C, 5 sec.
4. Aluminum - 430F, 2 ~ec.
The resultant composi~es were tested by cut-
ting into strips one inch wide. Adhesion is then tested
by the T-peel test similar to that described in ASTM D
187-72.
Comparative Example 1
X-methyl bicyclot2.2.1)hept-5-ene-2,3-dicar-
boxylic anhydride (XMNA) is ~e~ted with a high density
polyethylene homopolymer resin in a twin screw extruder
to give a graft copolymer resin wi~h 1.5 wt.% XMNA incor-
poration and a melt index of 1.5 g/10 min. The graftcopolymer is blended in varying amounts with a random
polypropyl~ne-ethylene copolymer having a melt 10w rate
(MFR) of 2. These blends were heat sealed to nylon 6 for
2 sec~ at 430F. T-peel adhesion resul~s are summarized
below.
Graft CopolymerAdhesion to
in Blend Nylon 6
(W`t:.Q ~ (lbsJin)
3 0
25 5 0.3
7 0.6
0.
Com~arative Example 2
~sing the same graft copolymer as described in
Example 1, blends were prepared with a propylene-ethylene
bloc~ copolymer having an MFR of 2.
Graft CopolymerAdhesion to
in Blend Nylon 6
twt.%) (lbs/in)
3510 0.0
lS 003
0.0
~9
--6--
Comparative Example 3
The same blends used in comparative Example 2
were heat sealed for 5 sec. at 430F to an ethylene-vinyl
alcohol copolymer (EVOH). All these blends give extremely
poor adhesion to EVOH. The samples could not be tested
because they fell apart.
Comparative Example 4
Ninety percent of a propylene-ethylene block
copolymer containing 7.8% ethylene was blended with 10
wt.% of the same graft copolymers as described in Example
1. This blend was heat sealed to EVOH-and gave a heat
seal adhesion of 0.5 lb/in.
Comparative Example 5
When 90% of a polypropylene homopolymer having
an MFR of 4 blended with 10~ of the same graft copolymer
as described in Example 1, was heat sealed to EVOH, the
resultant heat seal adhesion is 0Ol lb/in. If this same
blend is heat sealed to a random polypropylene copolymer
as described in Comparative Example 1, its adhesion is
greater than 10 lbs/in~
The above examples show that i~ a polyethylene
graft copolymer is blended with a polypropylene homopol-
ymer or a random or a block copolymer containing ethylene,
the adhesion is not satisfactory to polar polymers.
Invention Examples 1-7
Blends were prepared using a low density poly-
ethylene (LDPE) with a melt index of 1.8 gram per 10
minutes, an ethylene-propylene-diene monomer terpolymer
tEPDM) elastomer and the graf~ copolymer described in
Comparative Example 1. These blends were tes-ted for
adhesion to an ethylene-vinyl alcohol copolymer (EVOH),
a random polypropylene copolymer, aluminum and nylon 6.
The results are shown in Table I below:
TABLE I
Composition Adhesion To
LDPEEPDM Gra~t EVOH PP Nylon 6Aluminum ~ - Copolymer Random
- Copolymer
% % lb/inlb/~n lb/in lb/in
Example 1 90 -- 10 ~7.1 0 4.4 54
2 65 25 lO >7.6 0.5
3 60 30 lO ~8.0 2.8 >6.1 4.1
~ 50 40 lO >7~ ~6.3 >5.3 5.9 ~i
>7~7~6.5 ~9.~ 5.3
6 35 55 lO >6.5~6.5 ---
7 25 65 10 7.4>6.8 >8.1
;3~
--8--
These results show that if the blend contains
at least 30% EPDM, adhesion is excellent not only to eth
ylene-vinyl alcohol copolymer, nylon 6 and aluminum, but
also to polypropylene.
s Inven~ion Examples 8-12
Blends were prepared using the same low density
polyethylene as described in Examples 1-7; the same graft
copolymer described in Comparative Example landa styrene-
ethylene-butylene-styrene block copolymer (a styrene-hy-
dxogenated diene-styrene copolymer known as Kraton G 1650
~SEBS)). The results on adhesion are shown below in Table
II.
TABLE II
~omposition Adhesion To
LDPE- SEBS Graft EVOH~ PP Nylon 6Aluminum
Copolymer 'Random
~ Copolymer~
% ~ % lb/inlb/in lb/in lb/in
Example 8 65 25 10 6G 7 1~1 >6.3 ---
9 60 30 10 6.8 5.5 >6.5 7.7
5 . 7 >9 . 9 3 . 7 3 . 7 1 ~,
11 35 SS 10 5.6>lO.Q >5.8
12 25 6~ ~ 0~ 7.~~1 0.0 >6 .2
~.
.
.
, :
; .
~ j .
-10-
Here again, the use of at least 30% of the elas-
tomer enables these blends to adhere to polypropylene in
addition to adhering to ethylene-vinyl alcohol copolymer,
nylon 6 and aluminum.
Invention Examples 13-15
Blends were prepared with a high density poly-
ethylene having an MI of 0.8 and a density o~ 0.96+ with
the same graft modified ~DPE described in Comparative
Example 1 and several elastomers: EPDM as described in
Invention Examples 1-7, a styrene~ethylene-butylene-
styrene block copolymer as described in Examples 8-12 and
a polyisobutylene (PIB) (Vistanex ~80)TM The results in
Table III show that blends containing 45% of the high
density polyethylene, 45% of the elastomer and 10% o the
modified high density graft copolymer give good ~o
excellen~ adhesion to all four substrates.
. , .;
TABLE III
Composition Adhesion to
HDPE EPDM PIBSEBSGraft Aluminum EVOH PP Nylon 6
Copolymer ~, Random
., Copolymer
% % % % % lb/in lb/in lb/in lb/in
~xample 1345 45 10 >6.8 6.2 2.Q >8.7 ~ :-
14 45 -- 45 . 10 3.8 8.3 3.5 >7.3 ~3
-- -- 45 10 3.7 3.4 7.5 4.1
16 90 -- -- -- 10 --- 2.2 0.2 1.9
3~;3:L~
-12-
Since adhesion can be obtained to polypropylene
and to polar polymers, various composites, laminates and
co-extrusions can be prepared using these materials. Com-
posites containing polypropylene, adhesive blend and ny-
lon, aluminum or ethylene-vinyl alcohol can be prepared
both by lamination and by co-extrusion.
In preparing composites one can use any means
for joining two or more layers known to one skilled in
the art. Preferably methods are blown film co-extrusion,
cast film and sheet co-extrusion, blow molding co-extru-
sion, lamination, co-extrusion coatlng. Other methods
are powder coating, rotomolding, profile co-extrusion,
wire coating co-extrusion, etc.
Glossary o~ Terms
EVOH ~ ethylene-vinyl asetate copolymers
;15 XMNA - X-methyl bicyclo(~.2.1)hept-5-ene-
2,3-dicarboxylic acid anhydride
MFR - melt flow rate
HDPE - high density polyethylene
LDPE ~ low density polyethylene
20 EPDM - ethylene-propylene diene monomer terpolymer
SEBS - styrene-ethylene-butylene-styrene copolymer
known as Krato~ G 1650
PIB - polyisobutylene
