Background of the Invention:
Field of the Invention
The present invention relates to composite articles of a hard and
a soft component having improved adhesion to each other and a method for improving
the adhesion. In detail, the hard component is selected from cellulose esters and
the soft component is selected from thermoplastic elastomers.
Cellulose esters are polymers made from renewable energy sources which
become more and more popular because of their natural origin. Cellulose esters are
transparent which makes them a candidate of choice for applications where transparency
and clarity is needed. Furthermore, cellulose esters can be plastisized which increases
their toughness at low temperatures. One representative cellulose ester is cellulose
There are many applications, for instance, in the automobile industry
or for mechanical rubber goods, in which a combination of flexible and rigid materials
is required. In most cases, a soft component is adhered onto the rigid cellulose
propionate. Actually, this can be achieved by putting an adhesive system between
the surface and the hard component of the article. These methods, however, are inherently
expensive since they require extensive laboratory time. For details it is referred
to A. Van Meesche and C. Radar, Adhesion of Elastomeric Alloy Thermoplastic Vulcanizates,
in 'Elastomerics', September 1987, pages 21 to 24 and J.P. Vander Kooi and L.A.
Goettler, Bonding Olefinic Thermoplastic Elastomers, in 'Rubber World', May 1985.
EP-A-0 718 347 discloses a method to adhere thermoplastic elastomer
blends to polyester substrates by treating the surface of the substrate with a blocked
diisocyanate and optionally an epoxy resin.
One way to reduce the cost of the manufacture of the article is, for
instance, to use sequential injection molding, a process during which the soft part
is over-molded onto the rigid or hard material, and vice-versa. This technology
gives outstanding adhesion between the soft and the hard polymers if they are miscible
or at least compatible. If the two polymers are incompatible, they do not adhere
Cellulose esters and, as an example, cellulose propionate, are known
to be incompatible with any other polymer (see Paul, Polymer Blends, Vol. 1 and
2, Academic Press, New York, 1977).
Therefore it was an object of the present invention to provide a method
for adhering polymers, and in detail non-polar thermoplastic elastomers to cellulose
esters providing an outstanding adhesion when over-molded, co-molded, co-blow molded
Description of the Invention
According to the present invention there is provided a method for
adhering a soft polymeric material to the surface of a hard polymeric material which
polymeric materials would normally be incompatible with each other. According to
the present invention compatibility, i.e., adhesion is achieved by a modifying component
which can be added to either or both of the two normally incompatible polymers to
In detail the present invention relates to a method to adhere a cellulose
ester component to a surface of a thermoplastic elastomer component in the absence
of any additional adhesive wherein at least one of said components comprises in
a blend a block-copolymer obtainable from
- (a) 5 to 95% by weight, based on the amount of (a)+(b), of a chemically modified
- (b) 95 to 5% by weight, based on the amount of (a)+(b), of a thermoplastic polyurethane
(TPU), copolyester or copolyamide, and
- (c) 0.05 to 5.0 parts by weight, based on 100 parts by weight of (a)+(b), of
one or more coupling agent(s).
Of course, either of the two polymeric materials mentioned above,
i.e., the cellulose ester or the thermoplastic elastomer compound may form the substrate
onto which the respective other component is adhered. Furthermore, the modifying
block-copolymer can be added to the cellulose ester and/or the thermoplastic elastomer
component. Adding the modifying block-copolymer to the cellulose ester may reduce
the transparency thereof. Of course, this aspect is of no relevance in case of applications
where transparency is not needed.
According to the present invention no adhesive is used at the surface
between the two above-mentioned components which are adhered to each other.
The preparation of the thermoplastic elastomer/modifying block-copolymer-blend
or the cellulose ester/modifying block-copolymer blend can be carried out by conventional
methods which are known in the art.
The amount of the modifying block-copolymer in the respective blend
is between 5 to 70% by weight, preferably 10 to 50% by weight, more preferably 10
to 30% by weight, based on the total amount of the respective blend comprising the
modifying block-copolymer. If the block-copolymer is added to both components, the
thermoplastic elastomer and the cellulose ester, the amounts for the block-copolymer
mentioned above relate to each of the components.
In a further embodiment the present invention relates to a shaped
composite article comprising, in adhesion to each other, the cellulose ester component
and the thermoplastic elastomer component, wherein at least one of said components
comprises in a blend the modifying block-copolymer of the kind and in the amount
as defined above. According to the present invention excellent adhesion is achieved
without using any adhesive on the surfaces of the components to be adhered.
Further embodiments of the present invention will become apparent
from the present description and the claims.
1. Cellulose Ester Component:
The cellulose ester component which is used as the transparent and
hard component of the present invention is selected from fully or partially acylated
cellulose in which the acyl-groups may contain up to 8, preferably up to 6 carbon
atoms. Specific examples of cellulose esters are cellulose acetate, cellulose propionate,
cellulose acetate propionate, cellulose acetate phthalate and cellulose acetate
butyrate, with cellulose propionate being preferred. The invention is not restricted
to commercially available materials but further synthetic esters can be used. Of
course, blends of the cellulose esters can be used as well. The cellulose esters,
their manufacture and their properties are well known in the art.
2. Thermoplastic Elastomer Component:
The term thermoplastic elastomer" (TPE) in general defines blends
of polyolefins and rubbers in which blends the rubber phase is not cured, i.e.,
so called thermoplastic olefins (TPO), blends of polyolefins and rubbers in which
blends the rubber phase has been partially or fully cured by a vulcanization process
to form thermoplastic vulcanizates (TPV), or unvulcanized styrene/conjugated diene/styrene
block-copolymers or blends thereof.
The thermoplastic elastomers according to the present invention are
selected from blends of rubbers and polyolefins in which the rubber has been partially
or fully ured or in which the rubber is not cured, styrene/conjugated diene/styrene
block-copolymers or their hydrogenated derivatives and blends thereof. Preferably,
the thermoplastic elastomers are non-polar.
2.1 Rubber/ Polyolefin Blend:
The polyolefins include thermoplastic, crystalline polyolefin homopolymers
and copolymers. They are desirably prepared from monoolefin monomers having 2 to
7 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene, 1-pentene, 1-hexene,
1-octene, 3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, mixtures thereof
and copolymers thereof with (meth)acrylates and/or vinyl acetates. Preferred, however,
are monomers having 3 to 6 carbon atoms, with propylene being most preferred. As
used in the specification and claims the term polypropylene includes homopolymers
of propylene as well as reactor and/or random copolymers of polypropylene which
can contain 1 to 20 wt% of ethylene and/or an α-olefin comonomer of 4 to 16
carbon atoms, and mixtures thereof. The polypropylene can be highly crystalline
isotactic or syndiotactic polypropylene. Commercially available polyolefins may
be used in the practice of this invention. Further polyolefins which can be used
in terms of the invention are high, low, linear-low, very low-density polyethylenes
and copolymers of ethylene with (meth)acrylates and/or vinyl acetates.
The polyolefins mentioned above can be made by conventional Ziegler/Natta
catalyst-systems or by metallocene-based catalyst-systems.
The curable rubber suitable for use in the manufacture of the thermoplastic
elastomer may be monoolefinic copolymer rubbers (elastomers) comprise non-polar,
rubbery copolymers of two or more α-monoolefins, preferably copolymerized
with at least one polymer, usually a diene. Saturated monoolefin copolymer rubber,
for example ethylene-propylene copolymer rubber (EPM) can be used.
However, unsaturated monoolefin rubber such as EPDM rubber is more
suitable. EPDM is a terpolymer of ethylene, propylene and a non-conjugated diene.
Satisfactory non-conjugated dienes include 5-ethylidene-2-norbornene (ENB); 1,4-hexadiene;
5-methylene-2-norbornene (MNB); 5-vinyl norbornene (VNB); 1,6-octadiene; 5-methyl-1,4-hexadiene;
3,7-dimethyl-1,6-octadiene; 1,3-cyclopentadiene; 1,4-cyclohexadiene and dicyclopentadiene
Butyl rubbers are also useful in the compositions of the invention.
As used in the specification and claims, the term "butyl rubber" includes copolymers
of an isoolefin and a conjugated monoolefin, terpolymers of an isoolefin and a conjugated
monoolefin, terpolymers of an isoolefin with or without a conjugated monoolefin,
divinyl aromatic monomers and the halogenated derivatives (halogenated butyl rubber)
of such copolymers and terpolymers.
The useful butyl rubber copolymers comprise a major portion of isoolefin
and a minor amount, usually less than about 30 wt%, of a conjugated multiolefin.
The preferred copolymers comprise 85-99.5 wt% of a C4-7 isoolefin such
as isobutylene and 15-0.5 wt% of a multiolefin of 4 to 14 carbon atoms, such as
isoprene, butadiene, dimethyl butadiene and piperylene. Commercial butyl rubber,
chlorobutyl rubber, bromobutyl rubber, useful in the invention, are copolymers of
isobutylene and minor amounts of isoprene with less than 3% halogen for the halobutyl-derivatives.
Other butyl co- and terpolymer rubbers are illustrated by the description in US-A-5,916,180
which is incorporated herein by reference.
Another suitable copolymer within the scope of the olefinic rubber
of the present invention is a copolymer of a C4-7 isomonoolefin and a
para-C1-8-alkylstyrene, and preferably a halogenated derivative thereof.
The amount of halogen in the copolymer, predominantly in the para-alkylstyrene,
is from 0.1 to 10 wt%. A preferred example is the brominated copolymer of isobutylene
and para-methylstyrene. These copolymers are more fully described in US-A-5,162,445
which is incorporated herein by reference.
A further olefinic rubber suitable in the invention is natural rubber.
The main constituent of natural rubber is the linear polymer cis-1,4-polyisoprene.
It is normally commercially available in the form of smoked sheets and crepe. Synthetic
polyisoprene can also be used. Furthermore, polybutadiene rubber and styrene-butadiene-copolymer
rubbers can also be used.
Blends of any of the above olefinic rubbers can be employed, rather
than a single olefinic rubber.
Further suitable rubbers are nitrile rubbers. Examples of the nitrile
group-containing rubber include a copolymer rubber comprising an ethylenically unsaturated
nitrile compound and a conjugated diene. Further, the copolymer rubber may be one
in which the conjugated diene units of the copolymer rubber are hydrogenated.
Specific examples of the ethylenically unsaturated nitrile compound
includes acrylonitrile, α-chloroacrylonitrile, α-fluoroacrylonitrile,
methacrylonitrile. Among them, acrylonitrile is particularly preferable.
Examples of the conjugated diene include 1,3-butadiene, 2-chlorobutadiene
and 2-methyl-1,3-butadiene (isoprene). Among them, butadiene is particularly preferred.
Especially preferred nitrile rubbers comprise copolymers of 1,3-butadiene and 10
to 50 percent of acrylonitrile.
Another suitable rubber in terms of the present invention are based
on polychloroprene rubber. These rubbers are commercially available under the trade
names Neoprene® and Bayprene®.
The elastomer (rubber) component of the rubber/polyolefin blend may
be used uncured to form TPO's or it can be partially or fully vulcanized (crosslinked)
to form TPV's. Those ordinary skilled in the art will appreciate the appropriate
quantities, types of cure systems and vulcanization conditions required to carry
out the vulcanization of the rubber. The elastomer can be vulcanized using varying
amounts of curative, varying temperatures and varying time of cure in order to obtain
the optimum crosslinking desired. Any known cure system can be used, so long as
it is suitable under the vulcanization conditions for the elastomer or combination
of elastomers being used and is compatible with the thermoplastic polyolefin component
of the TPV. These curatives include sulfur, sulfur donors, metal oxides, phenolic
resin systems, maleimides, peroxide-based systems, high energy radiation, both with
and without accelerators and co-agents.
Another curing system which can be used is the hydrosilylation system
which consists of the use of a silicon hydride curative catalyzed with a platinum
or rhodium derivative. Such systems are disclosea, for instance, in EP-A-0776937.
Phenolic resin curatives are preferred for the preparation of the TPV composition
of the invention, and such cure systems are well known in the art and literature
of vulcanization of elastomers. Their use in TPV compositions is more fully described
in US-A-4,311,628, the disclosure of which is fully incorporated herein by this
reference. Usually 5 to 20 weight parts of the curative or curative system are used
per 100 weight parts of the rubber to be cured.
The process of dynamically curing the rubber in a polyolefin matrix
is well known in the art. Early work found in US-A-3,037,954 discloses the technique
of dynamic vulcanization wherein a vulcanizable elastomer is dispersed into a resinous
thermoplastic polymer and the elastomer is cured in the presence of a curative while
continuously mixing and shearing the polymer blend. The resulting composition [dynamically
vulcanized alloy, or thermoplastic vulcanizate (TPV)] is a microgel dispersion of
cured elastomer in an uncured matrix of thermoplastic polymer. Since then the technology
has advanced significantly. For further general background information it is referred
to EP-A-0 473 703, EP-A-0 657 504, WO-A-95/26380 and other patent applications of
2.2 Styrene/Conjugated Diene/Styrene Block-Copolymers:
In the block-copolymers of styrene/conjugated diene/styrene, which
are traditionally made by anionic polymerization and in which the conjugated diene
may be hydrogenated, non-hydrogenated or partially hydrogenated, the conjugated
diene is selected from butadiene, isoprene or a mixture of both. Specific block-copolymers
of the styrene/conjugated diene/styrene-type are SBS, SIS, SIBS, SEBS and SEPS block-copolymers.
Exemplary styrene/conjugated diene/styrene block-copolymers are styrene-butadiene-isoprene-styrene
block-copolymer or its hydrogenated derivative, styrene-ethylene-butene-styrene
block-copolymer and blends thereof.
3. Modifying Block-Copolymer:
The block-copolymer which can be used to modify the components is
obtainable from a blend of a (a) chemically modified polyolefin, (b) a thermoplastic
polyurethane (TPU), copolyester or copolyamide, and (c) one or more coupling agent(s)
3.1 Modified Polyolefin
The term "modified polyolefin" means a random, block, or graft olefin
copolymer having in a main or side chain thereof a functional group such as carboxylic
acid; C1 to C8 carboxylate ester such as carbomethoxy, carboethoxy,
carbopropoxy, carbobutoxy, carbopentoxy, carbohexoxy, carboheptoxy, carboctoxy,
and isomeric forms thereof; carboxylic acid anhydride; carboxylate salts formed
from the neutralization of carboxylic acid group(s) with metal ions from Groups
I, II, III, IV-A and VIII of the periodic table, illustratively including sodium,
potassium, lithium, magnesium, calcium, iron, nickel, zinc, and aluminum, and mixtures
thereof; amide; epoxy; hydroxy; amino; C2 to C6 acyloxy such
as acetoxy, propionyloxy, butyryloxy; wherein said functional group is part of an
unsaturated monomer precursor which is either copolymerized with an olefin monomer
or grafted onto a polyolefin to form said modified polyolefin.
The modified polyolefin component defined above is represented by
a large number of polyolefin random, block, and graft copolymers which have long
been known in the art and, for the most part, are commercially available. Otherwise
they are readily prepared using the conventional techniques for polymerizing olefin
monomers; see Preparative Methods of Polymer Chemistry, W.R. Sorenson and T.W. Campbell,
1961, Interscience Publishers, New York, N.Y. Illustrative but non-limiting of the
basic olefin monomers for copolymerization with the functional group containing
unsaturated monomers are ethylene, propylene, butylene, mixtures of ethylene/propylene,
mixtures of ethylene/butylene, mixtures of propylene/ butylene, mixtures of ethylene/C3
to C12 α,β-unsaturated alkenes. Alternatively, the above illustrative
monomers or mixtures are first polymerized to their corresponding polyolefins prior
to grafting with said functional group containing monomers. A preferred class of
modified polyolefin comprises a modified polyethylene, that is to say a polyethylene
copolymer wherein the major molar proportion (at least 50 percent) of the copolymer
consists of ethylene units copolymerized with at least one unsaturated monomer having
a functional group substituent defined above, or a polyethylene (HDPE, LDPE or LLDPE)
having grafted thereon a minor molar proportion (0.005 to 5 percent) of said at
least one unsaturated monomer having the functional group substituent.
As illustrative embodiments of modified polyolefins in copolymer form
are those derived from the copolymerization of any one of the olefin monomers set
forth above but preferably ethylene in the minimum molar proportions of at least
50 percent with a vinyl functional group containing monomer such as acrylic acid,
methacrylic acid, maleic acid, maleic anhydride, acrylamide, methacrylamide, glycidyl
acrylate, glycidyl methacrylate, vinyl acetate, vinyl butyrate, methyl acrylate,
ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, sodium acrylate, zinc acrylate,
the ionic hydrocarbon polymers from the polymerization of α-olefins with α,β-ethylenically
unsaturated carboxylic acids as described in US-A-3,264,272 the disclosure of which
is incorporated herein by reference. It will be understood that in the case of the
olefin/vinyl acid copolymers that the carboxylic acid groups can be wholly or partially
converted to metal salts (i.e., sodium, potassium, zinc) after formation of the
copolymer. Such ionic copolymers are collectively recognized by the term "ionomers".
The vinyl functional monomers can be used in combination. Furthermore, mixtures
of any of these modified polyolefins can be used.
As illustrative embodiments of modified polyolefins in grafted form
are those derived from the graft polymerization of any one of the vinyl functional
group containing monomers set forth above (preferably maleic anhydride) onto any
one of the olefin polymers set forth above but preferably polyethylene (HDPE, LDPE,
LLDPE). The proportions of said graft monomers are preferably within the molar range
of 0.005 to 5 percent set forth above. As with the copolymers above, mixtures or
combinations can be employed. Further, the vinyl functional group containing monomers
can be grafted onto the modified polyolefin copolymers discussed above. A preferred
embodiment of such a polymer type includes the product obtained by grafting maleic
acid or anhydride onto an ethylene/vinyl carboxylate copolymer or the saponified
copolymer derived from ethylene/vinyl acetate. The graft-copolymerization of the
unsaturated carboxylic acid or its functional derivative or another functional group-containing
vinyl monomer onto the olefin polymer can be conducted using various methods. For
example, the olefin polymer, the graft monomer and a free-radical initiator are
incorporated in a solution or suspension of the olefin polymer in a suitable solvent.
It is also possible to conduct the graft copolymerization in the presence of the
thermoplastic polyurethane elastomer, i.e., after being blended with the thermoplastic
It will be understood by those skilled in the art that the modified
polyolefins can be prepared using any combination of monomer reactants in either
a copolymer, grafted copolymer, or copolymer-grafted copolymer configuration. However,
a most preferred class of modified polyolefin comprises a copolymer or graft copolymer
of ethylene or polyethylene (particularly LDPE or LLDPE) with at least one vinyl
monomer having a functional group selected from carboxylic acid, carboxylate salts,
dicarboxylic acid or anhydride thereof, carboxylate ester, and acyloxy, and mixtures
of said modified polyolefins. Particularly, preferred species of modified polyethylene
in this class are ethylene/vinyl acetate copolymer, ethylene/methylacrylate copolymer,
ethylene/methacrylic acid copolymer, ethylene/acrylic acid copolymer, ethylene/maleic
anhydride graft copolymer, maleic anhydride grafted ethylene/ vinyl acetate copolymer,
and mixtures thereof in any combination and proportions.
Another group of modified polyolefins which can be used in terms of
the present invention either alone or in combination with the modified polyolefins
mentioned above are styrene/ butadiene/styrene-block copolymer (SBS) and its hydrogenated
form, i.e., SEBS block-copolymer grafted with the functional grafting group mentioned
Specific examples of said grafted modified polyolefin are polypropylene
or ethylene propylene rubber grafted with anhydride, acid or primary or secondary
amine, ethylene acrylic acid copolymers.
The modified polyolefin is present in the block copolymer according
to the invention preferably in amounts from 20 to 80 percent by weight, most preferably
from 30 to 70 percent by weight, based on the total amount of the modified polyolefin
(a) and the thermoplastic polyurethane, copolyester or copolyamide.
Best block copolymers are formed when the reactive group of the polyolefin,
the coupling agent and the reactive group of the thermoplastic polyurethanes are
the same, i.e., when the stoichiometric ratio is used.
3.2 Thermoplastic Polyurethane/Copolyester/Copolyamide
3.2.1 Thermoplastic Polyurethane:
The polyurethane component has no limitation in respect of its formulation
other than the requirement that it be thermoplastic in nature which means that it
is prepared from substantially difunctional ingredients, i.e., organic diisocyanates
and components being substantially difunctional in active hydrogen containing groups.
However, often times minor proportions of ingredients with functionalities higher
than 2 may be employed. This is particularly true when using extenders such as glycerol,
trimethylol propane. Such thermoplastic polyurethane compositions are generally
referred to TPU materials. Accordingly, any of the TPU materials known in the art
can be employed within the scope of the present invention. For representative teaching
on the preparation of TPU materials see Polyurethanes: Chemistry and Technology,
Part II, Saunders and Frisch, 1964, pp 767 to 769, Interscience Publishers, New
York, N.Y. and Polyurethane Handbook, Edited by G. Oertel 1985, pp 405 to 417, Hanser
Publications, distributed in U.S.A. by Macmillan Publishing Co., Inc., New York,
N.Y. For particular teaching on various TPU materials and their preparation see
U.S. patent publications US-A-2,929,800; 2,948,691; 3,493,634; 3,620,905; 3,642,964;
3,963,679; 4,131,604; 4,169,196; Re 31,671; 4,245,081; 4,371,684; 4,379,904; 4,447,590;
4,523, 005; 4,621,113; 4,631,329; 4,883,837; 3,394,164; 3,644,457; 3,883,571; 4,031,026;
4,115,429; 4,118,411; 4,299,347; 3,384,653; 4,057,595 and 4,631,329 all of which
are incorporated herein by reference.
The preferred TPU is a polymer prepared from a mixture comprising
at least one organic diisocyanate, at least one polymeric diol and at least one
difunctional extender. The TPU may be prepared by the prepolymer, quasi-prepolymer,
or one-shot methods in accordance with the methods described in the references cited
Any of the organic diisocyanates previously employed in TPU preparation
can be employed including blocked or unblocked aromatic, aliphatic, and cycloaliphatic
diisocyanates, and mixtures thereof.
The TPU's can be prepared by conventional methods which are known
to the artisan, for instance from US-A-4,883,837 and the further references cited
3.2.2 Thermoplastic Copolyesters:
Instead of the thermoplastic polyurethane thermoplastic copolyester
elastomers can be employed.
The thermoplastic polyester elastomer (A) is a polyester block copolymer
and has, in the polymer chain, (A-1) a high-melting crystalline segment composed
mainly of an aromatic polyester unit and (A-2) a low-melting polymer segment composed
mainly of an aliphatic polyether unit and/or an aliphatic polyester unit.
The aromatic polyester unit in the high-melting crystalline segment
(A-1) (which is a hard segment) is derived from an acid component and a glycol component.
The acid component is substantially terephthalic acid and/or 2,6-naphthalene dicarboxylic
acid. As the acid component, there may be used, in combination with terephthalic
acid and/or 2,6-naphthalene-dicarboxylic acid, a small amount of other aromatic
dicarboxylic acid (e.g., isophthalic acid) or an aliphatic dicarboxylic acid (e.g.,
adipic acid, sebacic acid, cyclohexane-1,4-dicarboxylic acid, dimer acid).
The glycol component constituting the aromatic polyester unit is a
glycol of 2-12 carbon atoms, such as ethylene glycol, propylene glycol, tetramethylene
glycol, neopentyl glycol, hexanediol, decanediol or mixtures thereof.
The aliphatic polyether unit in the low-melting polymer segment (A-2)
(which is a soft segment) is derived from a polyalkylene glycol. The polyalkylene
glycol is, for example, polyethylene glycol, polypropylene glycol, polytetramethylene
glycol or polyethylene glycol-polypropylene glycol block copolymer.
The aliphatic polyester unit, which is another unit in the low-melting
polymer segment (A-2), is derived from an aliphatic dicarboxylic acid as a main
acid component and a glycol. The aliphatic dicarboxylic acid as a main acid component
is, for example, succinic acid, adipic acid, sebacic acid or decane dicarboxylic
acid. The aliphatic dicarboxylic acid may be used in combination with a small amount
of an aromatic dicarboxylic acid (e.g., isophthalic acid).
The glycol component constituting the aliphatic polyester unit is
a glycol of 2-12 carbon atoms. Its specific examples are the same as those mentioned
for the glycol component constituting the aromatic polyester unit of the high-melting
crystalline segment (A-1).
The aliphatic polyester unit is obtained by polycondensing the above
aliphatic dicarboxylic acid and the above glycol by ordinary processes which are
known in the art. It may be a homopolyester, a copolyester, or a polylactone (e.g.,
a poly-ε-caprolactone) obtained by subjecting a cyclic lactone to ring-opening
polymerization. The upper limit of the melting point of the aliphatic polyester
unit is not critical, though it is preferably 130 °C or less, particularly preferably
100 °C or less.
As the thermoplastic polyester elastomer (A), an elastomer having
a softening point of 100 °C or more is particularly appropriate.
The thermoplastic polyester elastomer (A) can be produced by ordinary
polymerization processes which are known in the art.
Another alternative for the thermoplastic elastomers are thermoplastic
copolyamides, and in detail polyether block amides obtained by the molten state
polycondensation reaction of polyetherdiol blocks and dicarboxylic polyamide blocks.
Thermoplastic copolyamides and the method of their manufacture are known in the
art and it is referred to a comprehensive review in Chapter 9B in "Thermoplastic
Elastomers", edited N.R. Legge, G. Holden, H.E. Schroeder, Hanser publishers, 1987
and the references cited therein.
The polyetherdiol blocks are derived from dihydroxypolyoxyethylene,
dihydroxypolyoxypropylene and dihydroxypolyoxytetramethylene. The polyamide precursors
can be selected from C4 to C18, preferably from C6
to C18 amino acids or lactams, C4 to C18, preferably
C6 to C18 dicarboxylic acids and diamines. The melting point
of the thermoplastic copolyamides which can be used according to the present invention
ranges from 120 to 210 °C, preferably from 140 to 210 °C. The respective copolyamides
are commercially available under the designation PEBAX®.
Preferably the amount of the thermoplastic polyurethane, copolyester
or copolyamide in the block copolymer is from 80 to 20 percent by weight, most preferably
from 70 to 30 percent by weight, based on the amount of the chemically modified
polyolefin (a) + thermoplastic polyurethane, copolyester or copolyamide.
3.3 The Coupling Agent
The coupling agent (c) is represented by blocked or unblocked aromatic,
aliphatic and cycloaliphatic diisocyanates and mixtures thereof. Illustrative isocyanates
which can be used as coupling agent are those mentioned above in context with the
preparation of the thermoplastic polyurethane. Also included in this definition
are polyurethane prepolymers containing isocyanate groups at both ends of the polymer
A combination of the isocyanate coupling agents with another coupling
agent may be required in case that the functional group on the modified polyolefin
does not react with the isocyanate group of the isocyanate coupling agent. Such
co-coupling agents are selected from the group of primary or secondary diamines,
diols, diepoxides, amino/hydroxy and amino/epoxy compounds. Said co-coupling compounds
may be linear or branched aliphatic or aromatic in structure comprising up to 18,
preferably up to 12 carbon atoms.
It is evident that in cases in which said co-coupling agent is used
it has to be used in an approximately equimolar amount relative to the coupling
According to the invention one or more coupling agent(s) can be used.
Preferably the amount of the coupling agent(s) is from 0.05 to 5 parts by weight,
most preferably from 0.1 to 4 parts by weight based on 100 parts by weight of (a)
chemically modified polyolefin and (b) thermoplastic polyurethane, copolyester or
3.4 Preparation of the Modifying Block-Copolymer
The modifying block-copolymer is obtainable by reactive processing
of a mixture comprising (a) the chemically modified polyolefin, (b) the thermoplastic
polyurethane, the copolyester or copolyamide and (c) the coupling agent(s) in the
amounts indicated above.
In detail the block-copolymers according to the present invention
are prepared by melt-mixing, i.e., reactive processing the polymers together in
the presence of the coupling agent(s) in an internal mixer, a single screw extruder,
a co- or counter rotating twin-screw extruder, an open mill or any other type of
equipment suitable and known in the art. The coupling agent(s) can also be added
after the polymers have been molten and blended. The reaction temperature depends
on the melting-point of the polar polymer and is between 150 °C to 250 °C, preferably
between 180 °C and 230 °C.
I an in-situ process the modifying block-copolymer can also be prepared
in the presence of the thermoplastic elastomer under the conditions mentioned above.
Additives known in the art, such as reinforcing and non-reinforcing
fillers, oil, antioxidants, plasticizers, stabilizers, lubricants, antistatic agents,
pigments, flame retardants, UV-stabilizers, waxes, process aids, such as lubricants
can be added while making the modifying block-copolymers and/or the blends. The
amount of said additives, if present, is between 0.05 and 50% by weight, based on
the total amount of the blends, depending on the nature of the additives themselves.
The invention is further explained by the following examples.
- Cellulose propionate:
Tenite® 371-12, cellulose acetate propionate available from Eastman, U.S.
- Thermoplastic polyurethane TPU:
Texin® DP7-1089 Mobay - Bayer
DM 7015 is the pure modifying block copolymer. It is a blend of a hydroxyl containing
polypropylene (Exxon) and the TPU (Texin®) in a 20/80 weight ratio. The coupling
agent is Grilbond® IL-6, a blocked diisocyanate (EMS-Chemie) at a level of 0.38
The following modified thermoplastic elastomers were used:
- DM 7018 is a blend of Santoprene®8211-35 with DM 7015 at a weight ratio
- DM 7019 is a blend of Santoprene®8211-35, DM 7015 and Texin®1089 at
a weight ratio 70/20/10.
- DM 7020 is a blend of Santoprene®8211-35, DM 7015 and Texin®1089 at
a weigh ratio 60/20/20.
blend of polypropylene with crosslinked EPDM with a Shore A hardness of 35 (ASTM
D 2240), available from AES, Advanced Elastomer Systems, Akron, U.S.
An 80 ton Engel injection molding machine was used to two shot mold
development materials DM7019 and DM7020 onto Tenite® Propionate in the form
of a T-bar. Processing conditions for the development materials were as follows:
Machine heat settings were approximately 204°C in the rear of the barrel increasing
to about 232°C at the nozzle. An average melt temperature was 229°C. Tooling temperatures
of the stationary and moveable halves ranged from 38-66°C. Initial injection pressure
ranged from 2.40-3.10 MPa. Holding pressure was about 0.52 MPa.
Processing conditions for the Tenite® Propionate were as follows:
Machine heat settings of approximately 204°C in the rear of the barrel and increasing
to about 232°C in the nozzle. An average melt-temperature was 238°C. Tooling temperatures
of the stationary and moveable halves ranged from 38-66°C. Initial injection pressure
ranged from 3.80-4.48 MPa. Holding pressure was about 0.69 MPa.
The T-bars specimens measure 13.33 cm long by 2.54 cm wide having
approximately 2.54 cm long tabs. A Tensometer T-10 was used to test the peel strength
of the T-bars according to ASTM D 429-81. The rate of pull on the T-10 was 5.08
cm/min. Peel strength adhesion properties are found in the Table 1 below:
Peel Strength in N/m
An 80 ton Engel injection molding machine was used to two shot mold
a blend of 60% Santoprene®8211-35 and 40% DM7015 (Blend A) onto Tenite®
Propionate and a blend of 50% Santoprene®8211-35 and 50% DM7015 (Blend B) onto
Tenite® Propionate. Processing conditions for Blend A, Blend B, and Tenite Propionate
were similar to Example 1. Peel strength adhesion properties are found in the Table
Peel Strength in N/m
The type of failure using Blend A and Blend B onto Tenite® Propionate
varied between cohesive and non-cohesive. Cohesive means that tear occurs in the
TPE component, non-cohesive means that tear occurs at the interface between the
two components. If the modifying block-copolymer is absent from either component
in the above examples no adhesion was observed at all.