U.S. patent number RE35,398 [Application Number 08/533,278] was granted by the patent office on 1996-12-10 for thermoplastic olefin compositions of epdm rubber and ethylene copolymer resin.
This patent grant is currently assigned to Advanced Elastomer Systems, L.P.. Invention is credited to Donald R. Hazelton, Robert C. Puydak.
United States Patent |
RE35,398 |
Hazelton , et al. |
December 10, 1996 |
Thermoplastic olefin compositions of EPDM rubber and ethylene
copolymer resin
Abstract
Heat shrinkable thermoplastic compositions are prepared by
blending an ethylene copolymer resin with an EPDM rubber and
dynamically vulcanizing the rubber. The ethylene copolymer resin is
a copolymer of ethylene with an alkyl ester of an alpha, beta
monoethylenically unsaturanated monocarboxylic acid as well as
copolymers of ethylene with the acid per se. The preferred
copolymer is ethylene-vinylacetate copolymer. Uncured rubber can be
included in the composition.
Inventors: |
Hazelton; Donald R. (Hudson,
OH), Puydak; Robert C. (Bath Township, OH) |
Assignee: |
Advanced Elastomer Systems,
L.P. (Akron, OH)
|
Family
ID: |
22887188 |
Appl.
No.: |
08/533,278 |
Filed: |
September 25, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
235858 |
Aug 23, 1988 |
04894408 |
Jan 16, 1990 |
|
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Current U.S.
Class: |
524/425; 524/445;
524/522; 524/523; 524/524; 525/133; 525/192; 525/193; 525/194;
525/195; 525/196; 525/197; 525/211; 525/221; 525/222; 525/227;
525/93 |
Current CPC
Class: |
C08L
23/0853 (20130101); C08L 23/0869 (20130101); C08L
23/16 (20130101); C08L 23/28 (20130101); C08L
23/16 (20130101); C08L 23/0853 (20130101); C08L
23/0869 (20130101); C08L 23/16 (20130101); C08L
23/28 (20130101); C08L 23/0815 (20130101); C08L
91/00 (20130101); C08L 2205/02 (20130101); C08L
2205/03 (20130101); C08L 2666/06 (20130101); C08L
2666/02 (20130101); C08L 2666/02 (20130101); C08L
2666/02 (20130101); C08L 2666/02 (20130101) |
Current International
Class: |
C08L
23/04 (20060101); C08L 23/00 (20060101); C08L
23/08 (20060101); C08L 23/16 (20060101); C08L
23/20 (20060101); C08L 023/28 (); C08L 023/32 ();
C08L 023/08 (); C08L 033/00 () |
Field of
Search: |
;525/194,222,227,211,93,221,133 ;524/425 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Seccuro; Carman J.
Attorney, Agent or Firm: Banner & Allegretti, Ltd.
Claims
What is claimed is:
1. A thermoplastic olefin composition comprising an EPDM rubber
fully cured by dynamic vulcanization .Iadd.with a phenolic resin
cure system .Iaddend.in a thermoplastic resin consisting of (A)
from 25 to 100 wt% of an ethylene copolymer resin selected from the
group consisting of copolymers of ethylene with vinylacetate,
copolymers of ethylene with alpha, beta monoethylenically
unsaturated monocarboxylic acids and copolymers of ethylene with
alkyl esters of said acids and (B) from 0 to 75 wt% of at least one
additional polyolefin resin selected from the group consisting of
polybutylene, low density polyethylene, very low density
polyethylene, and linear low density polyethylene.
2. The composition of claim 1 wherein the ethylene copolymer resin
comprises from about 20 to about 90 wt.% of the resin/rubber
component of the composition.
3. The composition of claim 1 wherein the vulcanized EPDM rubber
comprises about 10 to about 80 wt.% of the resin/rubber component
of the composition.
4. The composition according to claim 1 wherein the vulcanized EPDM
rubber comprises from about 20 to about 75 wt.% of the resin/rubber
component of the composition.
5. The composition according to claim 4 wherein the vulcanized EPDM
rubber comprises from about 40 to about 60 wt.% of the resin/rubber
component.
6. The composition according to claim 1 wherein an inorganic filler
is incorporated therein.
7. The composition according to claim 6 wherein the inorganic
filler is calcium carbonate or clay.
8. The composition according to claim 1 wherein the ethylene
copolymer resin is an ethylene-vinylacetate copolymer resin.
9. The composition according to claim 8 wherein the vinylacetate
content of the copolymer is from about 2 to about 30 wt.%.
10. The composition according to claim 8 wherein the vinylacetate
content of the copolymer is from about 9 to about 29 wt.%.
11. The composition according to claim 1 wherein the ethylene
copolymer resin is an ethylene-methylacrylate copolymer resin.
12. The composition according to claim 1 having incorporated
therein from 0 to about 50 wt.%, based on total rubber, of an
uncured rubber.
13. The composition according to claim 12 wherein the uncured
rubber comprises from about 5 to about 20 wt.% of the total rubber
in the composition.
14. The composition according to claim 12 wherein the uncured
rubber is selected from EP copolymer rubber and polyisobutylene
rubber.
15. The composition according to claim 12 wherein the uncured
rubber is styrene ethylene-butene block copolymer.
16. A process for preparing a DVA composition comprising the steps
of
(a) blending a thermoplastic resin consisting of (A) from 25 to 100
wt% of an ethylene copolymer resin selected from the group
consisting of copolymers of ethylene with vinylacetate, copolymers
of ethylene with alpha, beta monoethylenically unsaturated
monocarboxylic acids and copolymers of ethylene with alkyl esters
of said acids and (B) from 0 to 75 wt% of at least one additional
polyolefin resin selected from the group consisting of
polybutylene, low density polyethylene, very low density
polyethylene, and linear low density polyethylene and an EPDM
rubber at a temperature above the melting point of the resin;
(b) adding a .[.non-peroxide.]. .Iadd.phenolic resin .Iaddend.cure
system for the rubber to the resin/rubber blend; and
(c) vulcanizing the rubber under dynamic vulcanization conditions
for a time sufficient to fully vulcanize the rubber.
17. The process according to claim 16 wherein an additional rubber
not vulcanizable by the .[.vulcanizing agent.]. .Iadd.phenolic
resin cure system .Iaddend.is incorporated.
18. The process according to claim 17 wherein the additional rubber
is introduced during the blending of the resin and rubber and prior
to dynamic vulcanization.
19. The process according to claim 17 wherein the additional rubber
is added after the rubber to be vulcanized is fully vulcanized,
blending being continued until the additional rubber is uniformly
dispersed in the resin/vulcanized rubber blend.
20. The process according to claim 16 wherein an additional rubber
is added to the composition after the rubber to be vulcanized is
fully vulcanized; said additional rubber being vulcanizable by the
.[.vulcanization agent.]. .Iadd.phenolic resin cure
system.Iaddend.; provided, however, that the .[.vulcanizing
agent.]. .Iadd.phenolic resin cure system .Iaddend.is fully
consumed during the dynamic vulcanization step and is unavailable
to vulcanize any part of the additional rubber.
21. The process according to claim 16 wherein an additional rubber
which is vulcanizable by the .[.vulcanizing agent.]. .Iadd.phenolic
resin cure system .Iaddend.is added to the rubber/resin blend after
the rubber to be vulcanized is fully vulcanized; said
.[.vulcanizing agent.]. .Iadd.phenolic resin cure system
.Iaddend.being present in an amount sufficient to at least
partially cure the additional rubber, but insufficient to fully
vulcanize the additional rubber.
22. The process according to claim 17 wherein the additional rubber
is selected from EP copolymer rubber and polyisobutylene
rubber.
23. The process according to claim 20 wherein the additional rubber
is a styrene ethylene-butene block copolymer.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polymer blends which have a
combination of both elastic and thermoplastic properties and, more
particularly, relates to dynamically vulcanized alloys (DVAs)
wherein an EPDM rubber is dispersed into a thermoplastic ethylene
copolymer resin and subsequently vulcanized by dynamic
vulcanization techniques utilizing a non-peroxide curing system.
Compositions of the present invention when fully cured manifest
unexpected resiliency characteristics as well as improved heat
shrinkability.
2. Prior Art
Dynamic vulcanization techniques for producing polymer compositions
having both elastic and thermoplastic properties are described by
Gessler and Haslett in U.S. Pat. No. 3,037,954 wherein a
vulcanizable elastomer is dispersed into a resinous thermoplastic
polymer and subsequently cured while continuously mixing and
shearing the polymer blend. The result is a micro-gel dispersion of
cured rubber in an uncured matrix of resinous thermoplastic
polymer.
Dynamically cured thermoplastic olefin ("TPO") compositions wherein
the elastomeric material is an EPDM rubber are well known. For
example, U.S. Pat. No. 4,130,535 discloses fully cured TPO
compositions wherein the rubber component is an ethylene-propylene
terpolymer (EPDM) and the thermoplastic polyolefin resin is
polypropylene. Ethylene copolymer resins are not disclosed. The
curative system may include a peroxide, azide or accelerated sulfur
curative system.
U.S. Pat. No. 4,311,628 discloses fully cured TPO compositions
wherein the rubber component is an EPDM rubber and the demonstrated
thermoplastic polyolefin resin is polypropylene. Improved
compression set is reportedly achieved utilizing a phenolic
curative which includes a phenolic curing resin and a cure
activator such as zinc oxide. Ethylene copolymer thermoplastic
resins are not disclosed.
Other patents which disclose a least partially cured
EPDM-containing compositions include U.S. Pat. Nos. 4,409,365;
4,350,795; 4,212,787; 4,202,801; 4,087,485; 3,904,470; 3,862,106;
3,806,558; and 3,758,643; and JP 8145741.
TPO compositions wherein the thermoplastic polymer resin is an
ethylene copolymer resin utilized in the present invention are also
well known. For example, U.S. Pat. No. 4,639,487 discloses fully
cured TPO compositions wherein the thermoplastic polyolefin resin
is an ethylene-vinyl ester copolymer or an ethylene-alkyl acrylate
copolymer and a rubber component selected from a group of rubber
materials which includes butyl, halogenated butyl, EPDM,
polyisoprene, polychloroprene, SBR, nitrile and chlorosulfonated
polyethylene rubbers. The curative system can be any non-peroxide
curing system.
Other patents which disclose at least partially cured TPOs
containing the ethylene copolymer resins utilized in the present
invention include U.S. Pat. Nos. 4,350,795 and 4,212,787; and JP
8145741.
SUMMARY OF THE INVENTION
The present invention resides in the discovery that unexpected
superior resiliency characteristics as well as improved heat shrink
properties are obtained from DVAs wherein an EPDM rubber is
dispersed into an ethylene-alkyl acrylate copolymer resin or an
ethylene-vinyl ester copolymer resin and subsequently vulcanized by
dynamic vulcanization techniques utilizing a non-peroxide curing
system. DVAs comprising this particular EPDM rubber in combination
with one of these particular ethylene copolymer resins are
particularly suited for utilization in window-seal and weatherstrip
applications which require retention of sealing capability under
dynamic conditions.
DETAILED DESCRIPTION
This invention relates to DVA compositions having unexpected
resiliency properties and improved heat shrink properties. In
particular it relates to thermoplastic elastomeric compositions
which, while having the reprocessibility of thermoplastic resins,
are heat shrinkable and elastomeric in nature and, most
importantly. manifest unexpected resiliency characteristics. The
DVA compositions of this invention are obtained by blending a
particular thermoplastic ethylene copolymer resin with a particular
rubber, namely, an EPDM rubber, and fully curing the rubber by
dynamic vulcanization techniques.
As used in the specification and claims, the term "dynamic
vulcanization" means a vulcanization process for a
rubber-containing TPO composition wherein the rubber is vulcanized
under conditions of high shear. As a result, the rubber is
simultaneously cross-linked and dispersed as fine particles of a
"micro-gel" within a polyolefin matrix. Dynamic vulcanization is
effected by mixing the TPO ingredients at a temperature which is at
or above the curing temperature of the rubber in equipment such as
roll mills, Banbury mixers, continuous mixers, kneaders or mixing
extruders, e.g., twin screw extruders. The unique characteristic of
the dynamically cured compositions is that, notwithstanding the
fact that the rubber component is fully cured, the compositions can
be processed and reprocessed by conventional rubber processing
techniques such as extrusion, injection molding, compression
molding, etc. Scrap or flashing can be salvaged and
reprocessed.
The term "dynamically vulcanized alloy" (DVA) as used in the
specification and claims means a composition comprising a
thermoplastic copolymer resin and a rubber wherein at least a part
of the rubber has been dynamically vulcanized to a fully cured
state. The compositions are prepared by blending together the
polyolefin resin and the rubber with a curative system under
conditions of dynamic vulcanization.
In preparing the DVA compositions of this invention, at least one
ethylene copolymer resin is blended with at least one EPDM rubber
and the EPDM rubber is vulcanized by dynamic vulcanization
utilizing a non-peroxide cure system. While blends of polyolefin
resins may be utilized in the practice of this invention, the
preferred polyolefin resin is a copolymer of ethylene with
unsaturated esters of lower carboxylic acids and the DVA
composition of this invention must include a polyolefin resin of
the preferred class. Polyolefin resins which can optionally be
incorporated in the compositions of the invention include
polybutylene, LDPE, VLDPE and LLDPE. The term "low density
polyethylene" or "LDPE" as used in the specification and claims
means both low and medium density polyethylene having densities of
about 0.910 to about 0.940 g/cc. The terms include linear
polyethylene as well as copolymers of ethylene which are
thermoplastic resins.
The term "very low density polyethylene" or "VLDPE" as used in the
specification and claims means polyethylene having a density of
below about 0.910 g/cc and include linear polyethylene as well as
copolymers of ethylene which are thermoplastic resins.
Linear low density polyethylene (LLDPE) as used in the
specification and claims means low and very low density
polyethylene characterized by little, if any, long chain branching.
The processes for producing LLDPE are well known in the art and
commercial grades of this polyolefin resin are available.
Generally, it is produced in gas-phase fluidized bed reactors or
liquid-phase solution process reactors, the former process can be
carried out at pressures of about 100 to 300 psi and temperatures
as low as 100.degree. C.
The term "polybutylene" as used in the specification and claims
means thermoplastic resins of both poly (1-butene) homopolymer and
the copolymer with, for example, ethylene, propylene, pentene-1,
etc. Polybutylene is manufactured via stereospecific Ziegler-Natta
polymerization of monomer(s). Commercially useful products are of
high molecular weight and isotacticity. A variety of commercial
grades of both homopolymer and ethylene-butene-1 copolymer are
available with melt indices that range from about 0.3 to about
20g/10 min.
The term "ethylene copolymer resin" as used in the specification
and claims means copolymers of ethylene with an alkyl ester of an
alpha, beta monoethylenically unsaturated monocarboxylic acid as
well as copolymers with the acid per se. In particular, copolymers
of ethylene with vinylacetate or alkyl acrylates, for example
methyl acrylate, ethyl acrylate and butyl acrylate, can be
employed. These ethylene copolymers typically comprise from about
70 to about 98 wt% ethylene, preferably from about 70 to 95 wt%
ethylene, more preferably from about 73 to about 91 wt% ethylene,
the balance of the copolymer being the alkyl ester. The expression
"EVA" means, specifically, ethylene-vinylacetate copolymers. The
ethylene-copolymer resins suitable for use in the practice of this
invention have a melt index of from about 0.2 to about 50 (ASTM D
1238 Condition E).
The term EPDM is used in the sense of its ASTM designation. EPDM is
a terpolymer of ethylene, propylene and a non-conjugated diene.
Illustrative non-limiting examples of suitable non-conjugated
dienes are 5-ethylidene-2-norbornene (ENB); 1,4-hexadiene;
5-methylene-2-norbornene (MNB), 1,6-octadiene;
5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene;
1,3-cyclopentadiene; 1,4-cyclohexadiene, tehahydroindene,
methyltetrahydroindene, dicyclopentadiene,
5-iso-propylidene-2-norbornene; 5-vinyl-norbornene, and the like.
The preferred EPDM rubber is a terpolymer of ethylene, propylene
and ENB.
The ethylene copolymer resin component of the polyolefin resins
used in the practice of this invention comprises from about 25 to
about 100 wt% of the polyolefin resin component of the blend,
preferably from about 35 to about 100 wt% ethylene copolymer resin;
more preferably from about 45 to about 100 wt%.
When one or more of the optionally included LDPE, VLDPE, LLDPE or
polybutylene materials are utilized, the amount utilized will be
from 0 to about 75 wt% of the polyolefin resin component;
preferably from about 10 to about 55 wt%, more preferably from
about 15 to about 35 wt%.
In its most preferred embodiment, the polyolefin resin component of
the DVA composition of this invention consists of EVA. The EVA
polyolefin resin is blended with at least one EPDM rubber and the
EPDM rubber component of the blend is vulcanized using dynamic
vulcanization techniques. The EVA polyolefin ream comprises from
about 20 to about 90 wt% of the polyolefin resin plus EPDM rubber
in the DVA; preferably from about 30 to about 80 wt% resin; more
preferably from about 40 to about 60 wt% resin. The EPDM rubber
component of the DVA composition comprises from about 80 to about
10 wt% of the composition based on the polyolefin resin plus EPDM
rubber: preferably from about 75 to about 20 wt% EDPM rubber; more
preferably from about 60 to about 40 wt% EPDM rubber.
Where it is desired to prepare a DVA composition of this invention
to produce blown film having improved heat shrink properties, the
curable EPDM rubber preferably comprises from about 10 to about 40
wt% of the polyolefin resin plus EPDM rubber component of the
DVA.
Where it is desired to prepare a DVA composition of this invention
to produce a molded article having unexpected superior resiliency
properties, the curable EPDM rubber comprises from about 15 to
about 50 wt.% of the polyolefin resin plus EPDM rubber component of
the DVA.
The ethylene copolymer resin must comprise at least about 10 wt% of
the total composition, i.e., ethylene copolymer resin, plus EPDM
rubber and additives; preferably at least about 12 wt%; more
preferably at least about 15 wt%.
In addition to its polymer components, the DVA composition of this
invention can include reinforcing and non-reinforcing fillers,
antioxidants, stabilizers. rubber processing oils, lubricants
(e.g., oleamide), antiblocking agents, antistatic agents, waxes,
coupling agents for the fillers, foaming agents, pigments, flame
retardant additives and other processing aids known to the rubber
compounding art. The pigments and fillers can comprise up to 50 wt%
of the total DVA composition based on polymer components plus
additives; preferably pigments and fillers comprise from 0 to about
30 wt% of the total composition.
Fillers can be inorganic fillers such as calcium carbonate, clays,
silica or carbon black. Any type of carbon black can be used, such
as channel blacks, furnace blacks, thermal blacks, acetylene black,
lamp black and the like.
Rubber process oils have particular ASTM designations depending on
whether they fall into the class of paraffinic, naphthenic or
aromatic process oils. They are derived from petroleum fractions.
The type of process oil utilized will be that customarily used in
conjunction with the EPDM rubber component. The skilled rubber
chemist will recognize which type of oil should be utilized with a
particular rubber. The quantity of EPDM rubber process oil utilized
is based on the total rubber content, both cured and uncured, and
can be defined as the ratio, by weight, of process oil to the total
EPDM rubber in the DVA. This ratio can vary, from 0 to about 1.5/1;
preferably from about 0.1/1 to about 0.75/1; more preferably from
about 0.2/1 to about 0.5/1. Larger mounts of process oil can be
used, the deficit being reduced physical strength of the
composition. Oils other than petroleum based oils such as oils
derived from coal tar and pine tar can also be utilized. In
addition to the petroleum derived EPDM rubber process oils, organic
esters and other synthetic plasticizers can be used.
Antioxidants can be utilized in the composition of this invention.
The particular antioxidant utilized will depend on the EPDM rubber
utilized and more than one type may be required. Their proper
selection is well within the skill of the rubber processing
chemist. Antioxidants will generally fall into the class of
chemical protectors or physical protectants. Physical protectants
are used where there is to be little movement in the part to be
manufactured from the composition. These are generally waxy
materials which impart a "bloom" to the surface of the rubber part
and form a protective coating or shield the part from oxygen,
ozone, etc.
The chemical protectors generally fall into three chemical groups:
secondary mines, phenolics and phosphites. Illustrative,
non-limiting examples of types of antioxidants useful in the
practice of this invention are hindered phenols, amino phenols,
hydroquinones, alkyldiamines, amine condensation products, etc.
Nonlimiting examples of these and other types of antioxidants are
styrenated phenol; 2,2'-methylene-bis-(4-methyl-6-1, butylphenol);
2,6'-di-t-butyl-o-dimethyl-amino-p-cresol; hydroquinone monobenzyl
ether, octylated diphenyl amine, phenyl-beta-naphthylamine,
N,N'-diphenyl-ethylene diamine; aldol-alpha-naphthylamine;
N,N'-diphenyl-p-phenylene diamine, etc. The physical antioxidants
include mixed petroleum waxes and microcrystalline waxes.
Any conventional cure system for the EPDM rubber to be dynamically
vulcanized can be used except that peroxide cures are specifically
excluded from the practice of this invention. Under conditions
which would result in a fully cured EPDM rubber using peroxide, the
ethylene copolymer resin of the present invention would vulcanize,
thereby resulting in a fully cured nonthermoplastic composition.
Otherwise, any particular curatives known in the art for the
vulcanization of EPDM rubbers are suitable. These include sulfur
cures as well as non-sulfur cures. Of course, accelerators such as
dithiocarbamates or thiurams and thioureas can be included in these
sulfur cures which also normally include zinc oxide.
Resin cures can be used for the EPDM rubbers. The resins useful as
curatives are phenolic resins, brominated phenolic resins, urethane
resins, and the like. The halogenated resin cure systems are
generally metal activated for EPDM rubbers.
While phenolic resin cures are preferred, they impart a yellowish
or orangish tinge to the rubber part. For EPDM rubbers, a sulfur
cure system may be employed to permit the use of pigments such as
TiO.sub.2 to give bright white compositions.
It is within the scope of this invention to incorporate an uncured
rubber in the composition. This can be accomplished by selecting as
the uncured rubber a rubber which cannot be vulcanized by the
vulcanizing agent used to cure the EPDM rubber which is to be
dynamically vulcanized. For the EPDM rubbers of the present
invention, where the cure system comprises sulfur or phenolic
resins, any other rubber not vulcanizable can be included. Such
rubbers include completely saturated EP rubber, polyisobutylene
rubber and the like. In another embodiment the DVA can be prepared
from the resin and the EPDM rubber to be dynamically vulcanized.
After vulcanization a second uncured rubber can be blended into the
DVA at a temperature above the melting point of the resin.
In another embodiment of this invention, two rubbers, at least one
of which is an EPDM rubber, are blended together and the EPDM
rubber is dynamically vulcanized using a curative which is not a
vulcanizing agent for the other rubber, thereby forming a
composition comprising a fully vulcanized rubber dispersed within
the unvulcanized rubber. This composition can then be let down into
an ethylene copolymer to form the composition of this
invention.
In a variant of this invention, an EPDM rubber is dynamically
vulcanized while in intimate contact with an ethylene copolymer
utilizing an excess of vulcanizing agent to form the DVA of this
invention. Thereafter, additional rubber is added and dynamically
vulcanized, the quantity of curative having been preselected to
ensure that it is inadequate to fully vulcanize the additional
rubber.
In another variant, the DVA of this invention is prepared using an
ethylene copolymer and EPDM rubber. Subsequently, under conditions
of dynamic vulcanization a second rubber is added to the DVA with
only sufficient curative to partially cure the second rubber. For
example, EVA and an EPDM are blended and a sulfur curative added.
The EPDM is dynamically vulcanized to form the DVA of this
invention. Subsequently, chlorobutyl rubber is added with just
sufficient ZnO to only partially cure the chlorinated butyl
rubber.
Where an uncured rubber is included in the DVA composition of this
invention, it comprises from 0 to about 50 wt% of the total rubber
in the composition, preferably from about 5 to about 20 wt%.
In a preferred embodiment, the rubber to be vulcanized is EPDM
rubbers which are preferably vulcanized with resin cures.
In the practice of this invention the polyolefin resin and EPDM
rubber are mixed together at a temperature sufficient to soften the
resin or, more commonly, at a temperature above its melting point
where the resin is at least partially crystalline at room
temperature, e.g., EVA. After the resin and rubbers are intimately
mixed, the curative is added. Heating and masticating at
vulcanization temperatures are generally adequate to complete
vulcanization in about 0.5 to about 10 minutes. The vulcanization
time can be reduced by elevating the temperature of vulcanization.
A suitabIe range of vulcanization temperatures is from about the
melting point of the resin (about 90-110.degree. C. in the case of
EVA) to about 250.degree. C.; more typically, the temperature range
is from about 150.degree. C. to about 225.degree. C. Preferably the
vulcanization is carried out at a temperature of from about
160.degree. C. to about 200.degree. C.
It is preferred that the mixing process be continued until
vulcanization is complete. If vulcanization is permmitted to
continue after mixing has stopped, the composition may not be
reprocessible as a themoplastic. However, the dynamic vulcanization
can be carried out in stages. For example, vulcanization can be
commenced at high temperatures in a twin screw extruder and before
vulcanization is complete pellets can be formed of the partially
prepared DVA using an underwater pelletizer, thereby quenching the
curing step. At a later time vulcanization can be completed under
dynamic vulcanization conditions. Those skilled in the art will
appreciate the appropriate quantities, types of curatives and
extent of mixing time required to carry out the vulcanization of
the rubber. Where necessary the rubber can be vulcanized using
varying amounts of curative to determine the optimum cure system to
be utilized and the appropriate cure conditions to achieve a full
cure.
While it is preferred that all components are present in the mix
prior to carrying out the dynamic vulcanization process of this
invention, this is not a necessary condition. For example, if a
rubber is present which does not cure utilizing the selected curing
agents, only the rubbers need be mixed thoroughly, followed by
dynamic vulcanization in the absence of polyolefin resin. After
vulcanization is complete, the dynamically vulcanized blend of
rubbers can be let down into an ethylene copolymer resin to prepare
the compositions of this invention.
The term "fully vulcanized" as used in the specification and claims
with respect to the dynamically vulcanized rubber component of this
invention means that the rubber component to be vulcanized has been
cured to a state in which the physical properties of the rubber are
developed to impart elastomeric properties to the rubber generally
associated with the rubber in its conventionally vulcanized state.
The degree of cure of the vulcanized rubber can be described in
terms of gel content or conversely extractable components.
Alternatively, the degree of cure can be expressed in terms of
cross-link density.
Where the determination of extractables is an appropriate measure
of the state of cure, the improved thermoplastic elastomeric
compositions are produced by vulcanizing the curable rubber
component blends to the extent that the composition contains no
more than about four percent by weight of the cured rubber
component extractable at room temperature by a solvent which
dissolves the rubber which is intended to be vulcanized, and
preferably to the extent that the composition contains less than
two percent by weight extractable. In general, the less
extractables of the cured rubber component, the better are the
properties and still more preferable are compositions comprising
essentially no extractable rubber from the cured rubber phase (less
than 0.5 weight percent). Gel content reported as percent gel is
determined by a procedure which comprises determining the amount of
insoluble polymer by soaking the specimen for 48 hours in organic
solvent at room temperature and weighing the dried residue and
making suitable corrections based upon knowledge of the
composition. Thus, corrected initial and final weights are obtained
by subtracting from the initial weight, the weight of soluble
components, other than the rubber to be vulcanized, such as
extender oils, plasticizers and components of the composition
soluble in organic solvent, as well as that rubber component of the
DVA which it is not intended to cure. Any insoluble pigments,
fillers, etc., are subtracted from both the initial and final
weights.
To employ cross-link density as the measure of the state of cure
which characterizes the improved thermoplastic elastomeric
compositions, the blends are vulcanized to the extent which
corresponds to vulcanizing the same rubber as in the blend
statically cured under pressure in a mold with such amounts of the
same curatives as in the blend and under such conditions of time
and temperature to give an effective cross-link density greater
than about 3.times.10.sup.-5 moles per milliliter of rubber and
preferably greater than about 5.times.10.sup.-5 or even more
preferably 1.times.10.sup.-4 moles per milliliter of rubber. The
blend is then dynamically vulcanized under similar conditions with
the same amount of curative based on the rubber content of the
blend as was required for the rubber alone. The cross-link density
so determined may be regarded as a measure of the amount of
vulcanization which gives the improved thermoplastics. However, it
should not be assumed, from the fact that the amount of curative is
based on the rubber content of the blend and is that amount which
gives the rubber alone the aforesaid cross-link density, that the
curative does not react with the resin or that there is no reaction
between the resin and the rubber. There may be highly significant
reactions involved but of limited extent. However, the assumption
that the cross-link density determined as described provides a
useful approximation of the cross-link density of the thermoplastic
elastomeric compositions is consistent with the thermoplastic
properties and with the fact that a large proportion of the resin
can be removed from the composition by high temperature solvent
extraction, for example, by boiling decalin extraction.
The cross-link density of the rubber is determined by equilibrium
solvent swelling using the Flory-Rehner equation. J. Rubber Chem
and Tech, 30, p. 929. The appropriate Huggins solubility parameters
for rubber-solvent pairs used in the calculation were obtained from
the review article by Sheehan and Bisio, J. Rubber Chem. &
Tech., 39, 149. If the extracted gel content of the vulcanized
rubber is low, it is necessary to use the correction of Bueche
wherein the term y is multiplied by the gel fraction (%gel/100).
The cross-link density is half the effective network chain density
y determined tn the absence of resin. The cross-link density of the
vulcanized blends will, therefore, be hereinafter understood to
refer to the value determined on the same rubber as in the blend in
the manner described. Still more preferred compositions meet both
of the aforedescribed measures of state of cure, namely, by
estimation of cross-link density and percent of rubber
extractable.
In the practice of this invention, resins such as LDPE, VLDPE,
LLDPE and polybutylene can be utilized in conjunction with the
ethylene copolymer resin. Generally, any resin with a crystalline
melting point of less than 126.degree. C. can be used in
conjunction with the subject ethylene copolymer resin.
In order to produce a heat shrink article from the DVA composition
of this invention, the DVA compositions are prepared, oriented at a
temperature slightly below the softening point of the polyolefin
resin and "frozen" into the oriented configuration, i.e., film,
tubing, tape, etc. The forming of a product and its orientation can
be continuous, e.g., blown film, or can be accomplished in a
separate operation. Upon subsequent heating to a temperature above
the softening point of the resin, the composition will shrink.
In order to produce an article for use in window-sealing or
weatherstrip applications, the DVA compositions are prepared, and
then extruded utilizing traditional thermoplastic resin processes
well known in the art. The profile is quenched by air or water upon
exiting the die of the extruder and typically, is transported by a
conveyor belt take-away system. Alternatively, the DVA compositions
can be utilized in molding processes.
The advantages of the instant invention will be more readily
appreciated by reference to the following examples. Ingredients are
described in Table II.
EXAMPLES I-VII
The compositions in Table I were Banbury mixed and underwater
pelletized. The blends were dynamically vulcanized in the mixer by
prolonging the mix (for about 4 minutes) at an elevated temperature
(from about 170.degree. to about 190.degree. C.) after the addition
of the cure system.
TABLE I
__________________________________________________________________________
Example I Example II Example III A B C D E F G H
__________________________________________________________________________
EPDM (VISTALON 3777)1 -- 47.3 -- 47.3 47.3 38.3 29.3 20.3 EPDM
(VISTALON 6505)2 -- -- -- -- -- -- -- -- EPDM (VISTALON 3708)3 --
-- -- -- -- -- -- -- Chlorobutyl 1066 4 27 -- 27 -- -- -- -- -- EVA
(20% VA) 27 27 -- -- -- -- -- -- EVA (18% VA) -- -- -- -- -- -- --
-- EVA (12% VA) -- -- 20 20 27 36 45 54 EVA (9% VA) -- -- -- -- --
-- -- -- EMA (17% MA) -- -- -- -- -- -- -- -- Dowlex 4001 5 -- --
-- -- -- -- -- -- EY 904-25 (52% VA) -- -- 7 7 -- -- -- -- Circosol
4240 (oil) 20 -- 20 -- -- -- -- -- Atomite 17.1 17.3 17.1 17.3 16.6
17.5 18.5 19.3 Titanox 2071 3 3 3 3 3 3 3 3 SRF Black N774 -- -- --
-- -- -- -- -- Stearic Acid 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Weston
626 -- -- -- -- 0.1 0.1 0.1 0.1 Irganox 1010 0.1 0.1 0.1 0.1 -- --
-- -- Cyanox 1790 -- -- -- -- 0.1 0.1 0.1 0.1 Maglite D 1.2 -- 1.2
-- -- -- -- -- Tinuvin 770/327 -- -- -- -- .4/.2 .4/.2 .4/.2 .4/.2
Zinc Oxide 3.3 0.8 3.3 0.8 0.8 0.6 0.5 0.4 SP-1055 Resin -- 3.7 --
3.7 3.7 3.0 2.3 1.6 Stannous Chloride -- 0.3 -- 0.3 0.3 0.3 0.2 0.2
Permalux 0.8 -- 0.8 -- -- -- -- -- Hardness, Shore A 78/77 71/71
68/67 67/66 71/71 77/77 78/78 81/81 (Instantaneous/5 sec.) Tension
Set.sup.(6). % 19 10 -- -- 10.3 15.6 17.6 26 Compression Set B.
Plied, % 22 hrs. @ 50/70.degree. C. 65.9/79.1 64.9/65.6 -- -- -- --
-- -- 22 hrs. @ RT/70.degree. C. -- -- 22/60 23/54 20/54 19/66
25/69 27/78 Tensile Strength (psi) 855 1020 617 650 839 935 1123
1330 Elongation, % 400 459 214 189 248 242 390 409 Modulus
100%/300% 310/601 317/621 383/-- 423/-- 486/-- 626/-- 742/-- 831/--
Flexural Modulus, psi 2286.3 2615.4 -- -- 1405 2924 4253 6239 Vicat
Softening Point 71 79 85 90 89 91 92 95 (200 gm: .degree.C.) Set at
Break, % -- -- 33 24 50 63 154 255 Heat Shrink Recovery, % -- -- --
-- -- -- -- -- Tear Strength, ppi -- -- -- -- -- -- -- --
__________________________________________________________________________
Example IV Example V Example VI I J K L M N O
__________________________________________________________________________
EPDM (VISTALON 3777)1 29.3 29.3 47.3 47.3 47.3 -- 47.3 EPDM
(VISTALON 6505)2 -- -- -- -- -- -- -- EPDM (VISTALON 3708)3 -- --
-- -- -- -- -- Chlorobutyl 1066 4 -- -- -- -- -- 27 -- EVA (20% VA)
-- 9 -- -- -- -- EVA (18% VA) -- -- -- 27 18 -- -- EVA (12% VA) 45
36 -- -- -- -- -- EVA (9% VA) -- -- 9 -- -- -- -- EMA (17% MA) --
-- -- -- -- -- -- Dowlex 4001 5 -- 9 9 -- 9 27 27 EY 904-25 (52%
VA) -- -- -- -- -- -- -- Circosol 4240 (oil) -- -- -- -- -- 20 --
Atomite 18.5 18.5 16.6 16.6 16.6 17.1 17.3 Titanox 2071 3 3 -- --
-- 3 3 SRF Black N774 -- -- 3 3 3 -- -- Stearic Acid 0.5 0.5 0.5
0.5 0.5 0.5 0.5 Weston 626 0.1 0.1 -- -- -- -- -- Irganox 1010 --
-- 0.1 0.1 0.1 0.1 0.1 Cyanox 1790 0.1 0.1 0.1 0.1 0.1 -- --
Maglite D -- -- -- -- -- 1.2 -- Tinuvin 770/327 .4/.2 .4/.2 .4/.2
.4/.2 .4/.2 -- -- Zinc Oxide 0.5 0.5 0.8 0.8 0.8 3.3 0.8 SP-1055
Resin 2.3 2.3 3.7 3.7 3.7 -- 3.7 Stannous Chloride 0.2 0.2 0.3 0.3
0.3 -- 0.3 Permalux -- -- -- -- -- 0.8 -- Hardness, Shore A 78/78
81/81 75/74 74/74 75/75 77/76 79/78 (Instantaneous/5 sec.) Tension
Set.sup.(1). % 17.6 19.7 -- -- -- 18 19 Compression Set B. Plied, %
22 hrs. @ 50/70.degree. C. -- -- -- -- -- -- -- 22 hrs. @
RT/70.degree. C. 25/69 27/66 28/59 28/75 28/62 16/42 24/39 Tensile
Strength (psi) 1123 1264 725 909 915 999 963 Elongation, % 390 337
284 373 332 354 275 Modulus 100%/300% 742/-- 812/-- 390/-- 362/712
391/822 449/869 492/-- Flexural Modulus, psi 4253 4870 -- -- --
4272 4984 Vicat Softening Point 92 99 103 82 89 107 120 (200 gm:
.degree.C.) Set at Break, % 154 251 55 100 80 -- -- Heat Shrink
Recovery, % -- -- -- -- -- -- -- Tear Strength, ppi -- -- -- -- --
-- --
__________________________________________________________________________
Example VII P Q R S T U V W
__________________________________________________________________________
EPDM (VISTALON 3777)1 -- 47 47 -- -- -- -- 47.3 EPDM (VISTALON
6505)2 -- -- -- 27 -- -- -- -- EPDM (VISTALON 3708)3 -- -- -- -- 27
27 27 -- Chlorobutyl 1066 4 27 -- -- -- -- -- -- -- EVA (VA 27%) --
-- -- -- -- 27 -- -- EVA (20% VA) 27 27 27 27 27 -- -- 27 EVA (18%
VA) -- -- -- -- -- -- -- -- EVA (12% VA) -- -- -- -- -- -- -- --
EVA (9% VA) -- -- -- -- -- -- -- -- EMA (17% MA) -- -- -- -- -- --
27 -- Dowlex 4001 5 -- -- -- -- -- -- -- -- EY 904-25 (52% VA) --
-- -- -- -- -- -- -- Circosol 4240 (oil) 20 -- -- 20 20 20 20 --
Atomite 17.1 17.3 19 17.6 17.6 17.6 17.6 22.1 Titanox 2071 3 3 3 3
3 3 3 3 SRF Black N774 -- -- -- -- -- -- -- -- Stearic Acid 0.5 0.5
0.5 0.5 0.5 0.5 0.5 0.5 Weston 626 -- -- -- -- -- -- -- -- Irganox
1010 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Cyanox 1790 -- -- -- -- -- --
-- -- Maglite D 1.2 -- -- -- -- -- -- -- Tinuvin 770/327 -- -- 0.5
-- -- -- -- -- Zinc Oxide 3.3 0.8 1.5 0.8 0.8 0.8 0.8 -- SP-1055
Resin -- 3.7 -- 3.7 3.7 3.7 3.7 -- Stannous Chloride -- 0.3 -- 0.3
0.3 0.3 0.3 -- Permalux 0.8 -- -- -- -- -- -- -- Hardness, Shore A
58/57 61/59 62/60 59/57 64/60 55/55 73/70 57/53 (Instantaneous/10
sec.) Tension Set.sup.(1). % 19 16 16 13 13 16 13 13 Compression
Set B. Plied, % 22 hrs. @ 50/70.degree. C. 52/-- 52/-- 52/--
45/--
52/-- 66/-- 49/-- 69/-- 22 hrs. @ RT/70.degree. C. 32/-- 33/--
30/-- 25/-- 32/-- 34/-- 27/-- 52/-- Tensile Strength (psi) 765 980
850 820 915 900 755 900 Elongation, % 370 475 480 270 285 400 120
830 Modulus 100%/300% 345/630 380/625 360/550 390/-- 465/-- 340/665
665/-- 265/350F Flexural Modulus, psi -- -- -- -- -- -- -- -- Vicat
Softening Point -- -- -- -- -- -- -- -- (200 gm; .degree.C.) Set at
Break, % 69 94 88 31 44 56 5 300 Heat Shrink Recovery, % 38 41 44
50 50 47 -- 35 Tear Strength, ppi 80 125 110 80 115 100 120 100
__________________________________________________________________________
1 EPDM. 53 ML 1 + 8(127.degree. C.), 75 phr oil. 66% ethylene 2
EPDM. 46 ML 1 + 8(127.degree. C.), 53% ethylene 3 EPDM. 50 ML 1 +
8(127.degree. C.), 65% ethylene 4 Chlorinated isobutyleneisoprene
Copolymer, 55 ML 1 + 8(100.degree. C.), 1.2 wt. % Cl.sub.2 5 VLDPE,
.912 density, 1 ML 6 Extended 100% at RT for 10 min., relaxed at RT
for 10 min. under no tension. 7 Dumbbells from Tension Set test
reexposed to 50.degree. C. for 10 min. under no tension.
TABLE II ______________________________________ INGREDIENT LIST
Designation Description Supplier
______________________________________ Vistalon 3777 EPDM. 75 phr
oil extender Exxon Chemical Americas (ECA) Vistalon 6505 EPDM ECA
Vistalon 3708 EPDM ECA Chlorobutyl Chlorinated Isoprene- ECA 1066
Isobutylene copolymer, 51-60 ML(1 + 8) 100.degree. C. EVA -- ECA
EMA -- Gulf Oil Chemical Co. Dowlex 4001 VLDPE, 0.912 density, 1 MI
Dow Chemical Co. EY 904-25 VAE resin (52% vinyl acetate) USI
Chemicals Circosol Naphthenic oil Sun Oil Co. 4240 (oil) ASTM
D2226, Type 103 Atomite Natural ground calcium Thompson, carbonate,
mean particle Weinman & Co. size - 3 microns Titanox 2071
Titanium Dioxide NL Industries, Inc. SRF Black Large particle size
furnace Several N774 black Stearic Acid Long Chain Fatty Acid
Several Weston 626 Anti-oxidant Borg-Warner Irganox 1010
Anti-oxidant, thermal stabilizer Ciba Greigy Cyanox 1790
Anti-oxidant, phosphite type American Cyanamid Maglite D Magnesium
oxide C. P. Hall Tinuvin Stablizers Ciba Geigy 770/327 Zinc Oxide
-- New Jersey Zinc SP-1055 Brominated alkyl phenol resin
Schenectady Resin Chemical Stannous -- Several Chloride Permalux
Di-ortho guanidine salt DuPont of dicatechol borate Elastomers
Chemicals Dept. ______________________________________
These examples demonstrate the unexpected improvement in resiliency
of the EPDM-containing DVAs, particularly over the
chlorobutyl-containing DVAs, as measured by tension set and by
completeness of recovery from deformation. For example, the
compositions of Example VII, Q-V, utilizing EPDM rubber show about
twenty percent (Q, R & U) to over forty percent improvement in
resiliency (tension set) as compared to Example VII, P utilizing
chlorobutyl rubber. Furthermore, the tensile strength and tear
strength of articles produced from the EPDM compositions are also
significantly improved, particularly over articles produced from
the chlorobutyl compositions. Similar results are achieved in
Examples I, III, IV and VI. Higher service temperature, as
indicated by higher Vicat temperatures, and unexpected improvement
in shrink recovery are also obtained with the EPDM-containing DVA
compositions of this invention. For example, the compositions of
Example VII, Q-U, utilizing EPDM rubber show from about eight to
about twenty-five percent improvement in heat shrink recovery as
compared to P which utilizes chlorobutyl rubber.
Thus, the subject EPDM compositions are suitable for utilization in
shrink applications such as film, tape and tubing used for
automotive, electrical and packaging applications. Most
importantly, such compositions are particularly suitable where high
Vicat and/or improved resilience are required or desired, such as,
for example, in window-sealing and weatherstrip applications which
require retention of sealing capability in dynamic situations,
particularly at elevated temperatures.
While the illustrative embodiments of the invention have been
described with particularity, it will be understood that various
other modifications will be apparent to and can be readily made by
those skilled in the art without departing from the spirit and
scope of the invention. Accordingly, it is not intended that the
scope of the claims appended hereto be limited to the examples and
descriptions set forth herein but rather that the claims be
construed as encompassing all the features of patentable novelty
which reside in the present invention, including all features which
would be treated as equivalents thereof by those skilled in the art
to which the invention pertains.
* * * * *