Process for production of a heat-stabilized acrylate polymer

17 Pages·2014·2.31 MB·English

US008633273B2
(12) Ulllted States Patent (10) Patent N0.: US 8,633,273 B2
Oriani 45 Date of Patent: *Jan. 21 2014
9
(54) PROCESS FOR PRODUCTION OF A 7,015,260 B2 3/2006 Meloni
HEAT-STABILIZED ACRYLATE POLYMER 7,144,938 B1 12/2006 Felnberg er a1~
7,402,631 B2 7/2008 Kubota et al.
. . 7,544,757 B2 6/2009 Wu et al.
(75) Inventor: Steven R Orranr, Landenberg, PA (US) 7,608,216 B2 100009 Park et a1‘
_ 7,960,477 B2 6/2011 Weber et a1.
(73) Assrgnee: E I du Pont de Nemours and 8,142,316 B2 3/2012 Goettsch et a1.
Company, Wilmington, DE (Us) 2002/0019477 A1 2/2002 BartZ et a1.
2004/0242737 A1 12/2004 Topulos
* ~ . ~ ~ ~ ~ 2006/0004147 A1 1/2006 Park et al.
( ) Notrce. Subject‘ to any ((111s(c1la1me5,thet1ermdofth1s mum/0100368 A1 500% Park
Patent 15 exten e or a Juste un er 35 2007/0004854 A1 1/2007 Wu etal.
U.S.C. 154(b) by 0 days. 2007/0004855 A1 1/2007 Wu et al.
. . . . . 2007/0238833 A1 10/2007 Leboeuf et al.
T1115 Patent 15 Sublect to a tenmnal d15- 2007/0265364 A1 11/2007 Oner-Deliomanli etal.
clalmer- 2008/0132370 A1 6/2008 Goettsch et al.
2008/0287600 A1 11/2008 Park et al.
(21) App1_ NO; 13/529,434 2010/0029821 A1 2/2010 Palmer et al.
2011/0028621 A1 2/2011 Martens et a1.
- _ 2012/0328812 A1* 12/2012 Oriani ........................ .. 428/369
(22) Med Jun‘ 21’ 2012 2012/0328813 A1 12/2012 Oriani
_ _ _ 2012/0329914 A1 12/2012 Oriani
(65) Prlor Publlcatloll Data 2012/0329925 A1 12/2012 Oriani
2012/0329926 A1* 12/2012 Oriani ......................... .. 524/255
US 2012/0329928 A1 Dec. 27, 2012 2012/0329927 A1 12/2012 Oriani
2012/0329928 A1 12/2012 Oriani
Related US. Application Data
(60) Provisional application No. 61/499,580, ?led on Jun. FOREIGN PATENT DOCUMENTS
21’ 2011' DE 102008038943 A1 2/2010
EP 0432911 A1 6/1991
(51) Int- Cl- EP 0667367 A2 8/1995
C08G 81/02 (2006.01) JP 7090136 A 4/1995
C08G 59/32 (200601) JP H10251452 9/1998
JP 2001-191387 7/2001
C08J3/22 (200601) JP 2009204097 10/2009
C08L 77/00 (200601) wo 9634048 A1 10/1996
C08F 4/00 (2006.01)
(52) us CL OTHER PUBLICATIONS
USPC """"" " 524/514; 524/257; 525/186; 552255012853 Jha et al. “Thermoplastic Elastomeric Blends of Nylon-6/Acrylate
_ _ _ Rubber: In?uence of Interaction on Mechanical and Dynamic
(58) Field of Classi?cation Search
Mechanical Thermal Properties” Rubber Chemistry and Technology
USPC ................. .. 524/514, 257; 525/186, 183, 255
vol. 70 (1997) p. 798-814.
See application ?le for complete search history.
Zeon Chemicals L.P. HyTemp® Technical Manual, Rev. 2009-1, p.
59-61 (2009).
(56) References Cited
Zeon Chemicals L.P. HyTemp® Technical Manual, Rev. 2009-1, p.
U.S. PATENT DOCUMENTS 46 (2009).
Unimatec Chemicals Germany Noxtite ACM (basic) Jan. 2007, pp.
3,883,472 A 5/1975 Greene et al. 56-57.
3,899,378 A 8/1975 Wragg etal. International Search report for PCT/US2012/043551, Oct. 1, 2012.
3,904,588 A 9/1975 Greene International Search Report for PCT/043561 Oct. 1, 2012.
3,965,055 A 6/1976 Shichmanet al.
4,174,358 A 11/1979 Epstein * cited by examiner
4,275,180 A 6/1981 Clarke
4,310,638 A 1/1982 Coran et al. Primary Examiner * William Cheung
4,410,661 A 10/1983 Epstein et a1.
4,520,183 A 5/1985 Subramanian
(57) ABSTRACT
4,694,042 A 9/1987 McKee et al.
5,070,145 A 12/1991 Guerdoux Polyamide-reinforced polyacrylate polymer compositions
5,112,908 A 5/1992 Epstein
comprising a continuous polyacrylate polymer phase and a
5,166,278 A 11/1992 Rao
5,591,798 A 1/1997 Patel discontinuous polyamide phase are produced by a melt mix
5,688,868 A 11/1997 Fish, Jr. ing process. When crosslinked With peroxide curatives the
5,688,901 A * 11/1997 Fischet al. .................. .. 528/310 polyamide-reinforced polyacrylate polymer compositions
5,777,033 A 7/1998 Venkataswamyet al. exhibit enhanced resistance to heat aging compared to carbon
5,866,658 A 2/1999 Talkowski
black-reinforced polyacrylate polymer compositions.
5,948,503 A 9/1999 Yamamoto et al.
6,133,375 A 10/2000 Betremieux et al.
6,156,849 A 12/2000 Moriyama et al. 20 Claims, N0 Drawings
US 8,633,273 B2
1 2
PROCESS FOR PRODUCTION OF A by El. du Pont de Nemours and Company and HyTemp®
HEAT-STABILIZED ACRYLATE POLYMER elastomers, manufactured by Zeon Chemicals L.P.
In vieW of their excellent oil resistance, polyacrylate elas
CROSS REFERENCE TO RELATED tomers are Widely used in the manufacture of automotive
APPLICATION parts, such as automotive boots, ignition cable jacketing and
hoses.
This application claims priority from Us. Patent Applica Resistance to heat aging is a particularly desirable property
tion Ser. No. 61/499,580, ?led on Jun. 21, 2011, Which is in rubber parts that are used in under the hood automotive
incorporated herein by reference in its entirety. applications, eg hoses, gaskets, and seals. Because such
parts may be exposed to temperatures in excess of 1800 C. for
FIELD OF THE INVENTION periods of several hours on a regular basis, degradation of
physical properties through oxidative embrittlement can
The present invention is directed to peroxide curable amor occur. In polyacrylate rubbers, a reduction in extensibility
phous polyacrylate elastomer compositions, processes for and an increase in hardness and modulus of the polyacrylate
producing these compositions, and cured compositions and rubber article often result. Such effects are disclosed for
articles made from such compositions. example in Zeon Chemicals L.P., HyTemp® Technical
Manual, Rev. 2009-1, p. 59 (2009). Methods to enhance heat
BACKGROUND OF THE INVENTION age resistance of polyacrylate rubbers have involved attempts
to increase the oxidative stability of the polymer by manipu
Polyacrylate elastomers are Well-knoWn synthetic rubbers 20 lation of the monomer types that comprise the copolymeriZed
formed by copolymeriZation of alkyl acrylates. The polyacry units in the polymer backbone including the monomer ratio.
late elastomers may be polyacrylates that contain only copo In theory, such alterations can provide modi?ed polymer
lymeriZed alkyl acrylate units, for example copolymeriZed architectures that exhibit increased stability. More effective
units of methyl acrylate and butyl acrylate. Alternatively, they antioxidants have also been sought. HoWever, there is still a
may be alkyl acrylate copolymers that contain additional 25 need to improve the high temperature resistance of polyacry
copolymeriZed monomers, such as ethylene, and cure site late elastomers.
monomers such as chlorovinyl ether, monomers that contain Although it is knoWn that the presence of ?llers can have an
carboxyl groups, and/or epoxide containing monomers. The adverse effect on high temperature stability of elastomers, the
raW polymers, also knoWn as gums or gum rubbers, may be presence of ?llers in elastomer formulations (also referred to
cured With a Wide variety of curatives, depending on the cure 30 in the art as elastomer compounds) is generally necessary for
site monomers. Some acrylate elastomers may be cured With reinforcement and development of certain physical properties
metal soaps such as sodium or potassium stearate, in combi such as tensile strength and modulus in cured (i.e.
nation With sulfur, a sulfur donor, a tertiary amine or a qua crosslinked) compositions and articles comprising the cured
ternary amine salt. Epoxides, isocyanates, and polyols may compositions. Carbon black is the most Widely used ?ller due
also be used in certain cases. Polyamines, speci?cally 35 to its excellent reinforcement properties and loW cost. Other
diamines, are effective curatives for polyacrylates comprising examples of ?llers that are commonly used in acrylate elas
amine-reactive cure sites. Of these curatives, diamines or tomers include hydrated alumina, calcium carbonate, barium
diamine generators are often preferred because the cured sulfate, titanium dioxide, magnesium silicate, kaolin clay,
polymers produced exhibit enhanced heat aging resistance. and silica. All these ?llers adversely affect heat aging of cured
Diamine curable polyacrylates generally contain at least 0.3 40 acrylate elastomer compositions and articles comprising
mol % of an amine reactive cure site monomer, such as an them.
anhydride, acid-anhydride, half ester anhydride, or epoxide. It has been postulated that ?llers accelerate heat aging of
Some types of polyacrylate elastomers, hoWever, are perox polyacrylate elastomers by facilitating the transport of oxy
ide curable, even When no cure site monomer is present. gen to the polymer-?ller interface. This leads to an increased
Polyacrylate elastomers that have been cured using a diamine 45 rate of formation of free radicals at such locations through
cure system generally exhibit heat aging resistance that is oxidative reactions. The free radicals that are generated in this
superior to that of polyacrylate elastomers that have been manner promote crosslinking reactions, thereby resulting in
cured With other available cure systems. HoWever, diamine eventual embrittlement of the elastomer. Reinforcing grades
cured compounds require a post cure step, for example post of carbon black such as N330 and N550 are particularly
cure for four hours at 1750 C., to develop optimal properties. 50 effective at facilitating transport of oxygen because they con
Peroxide cured compounds advantageously can be used With tain pores that can transport air. HoWever, even non-porous
out a post cure or at most require a short post cure of about 30 ?llers create interfacial regions betWeen the solid ?ller par
minutes at 1750 C. ticles and the elastomer. FeW polymer chains reside in such
Polyacrylate elastomers comprising only polymerized interfacial regions and consequently diffusion of air is
units of acrylate monomers generally exhibit a poor cure 55 enhanced. Thus, exposure of the elastomer to air is generally
response to peroxide. This is because contiguous polymer increased in all ?lled elastomers compared to un?lled elas
iZed units of acrylate monomers may lead to signi?cant chain tomer compositions.
scission in the presence of free radicals, so the net increase in As the reinforcing poWer of the ?ller increases, e.g., the
crosslink density is loW. To enable peroxide curing, the acry ability of the ?ller to increase ShoreA hardness, the tendency
late elastomer must either comprise an unsaturated pendant 60 of that ?ller to loWer resistance of the acrylate elastomer to the
group Which functions as a cure site monomer, or the acrylate deleterious effects of hot air aging also increases. Such effects
elastomer must comprise at least 50 mol % copolymeriZed are disclosed for a range of carbon black types by Unimatec
units of ethylene. CopolymeriZed ethylene monomer units act Chemicals Germany in a publication entitled Noxtite ACM
as spacers betWeen polymeriZed acrylate monomer units to (basic), January 2007, pp. 56-57. It Would be desirable to have
limit R-scission. 65 available an alternative ?ller that permits the attainment of
Examples of commercially available acrylate elastomers good elastic properties such as compression set resistance and
include Vamac® ethylene acrylic elastomers manufactured tensile elongation to break in the cured, ?lled elastomer and
US 8,633,273 B2
3 4
further provides the advantages of ?ller reinforcement (i.e. Us. Pat. No. 4,275,180 discloses blends of thermoplastic
high tensile strength, modulus and Shore A hardness), but polymer With acrylate rubber, the blends being crosslinked or
does not promote oxidative degradation at high temperatures crosslinkable by radiation or peroxide. Fillers may be used in
(i.e. 160° C. or greater). amounts up to 40% by Weight of the composition.
It has noW been found that it is possible to produce cured U.S. Patent Application 2006/0004147 discloses blends of
acrylate elastomer compositions of high hardness, strength, elastomers, for example an acrylate elastomer, With thermo
and elasticity, that exhibit excellent heat aging resistance plastic polymers such as polyamides, in Which both polymers
through use of polyamide as a ?ller. are coupled and crosslinked by free radicals, e.g., by electron
A number of acrylate rubber-polyamide blend composi beam radiation. The compositions may comprise a continu
tions have been disclosed in the prior art. For example, it is ous phase of thermoplastic With dispersed crosslinked elas
knoWn to add uncured acrylate elastomers (i.e. gums) to tomer particles, or a continuous crosslinked elastomer phase
polyamides to form toughened thermoplastic compositions. With dispersed crosslinked particles of What Was initially
U.S. Pat. No. 4,174,358 discloses the use ofvarious uncured thermoplastic.
acrylate elastomers or ethylene based thermoplastics com U.S. Pat. No. 8,142,316 discloses cured blends of elas
prising up to 95 mole percent ethylene, such as ethylene/ tomers and thermoplastics for use in poWer transmission
methyl acrylate/monoethyl maleate/ethylenedimethacrylate belts. The elastomer may be an ethylene acrylic elastomer,
tetrapolymers, or ionomers of ethylene/methyl acrylate/mo and the thermoplastic may be a polyamide. The ethylene
noethyl maleate terpolymers as toughening additives for acrylic elastomer is not noted to be amine curable, and only
polyamides. The polyamide component in such compositions 20 free radical curatives are cited. Free radical curatives are
comprises the continuous matrix and the uncured acrylate disclosed as curing agents.
elastomer is a minor additive. U.S. Pat. No. 5,070,145 dis It is also knoWn to form dynamically cured thermoplastic
closes thermoplastic blends of polyamides With ethylene co compositions having a polyamide matrix continuous phase
polymers comprising units of dicarboxylic acid anhydrides and a cured acrylate rubber phase that is present in the form of
and optionally alkyl (meth)acrylates. U.S. Pat. No. 7,544,757 25 discrete particles. Thermoplastic elastomeric compositions
discloses that blends of ethyleneialkyl acrylate polymers comprising blends of polyamide and ionically crosslinked
may be blended at levels up to 30% by Weight in polyamide to ethylene acrylic rubber are disclosed in Us. Pat. No. 4,310,
produce toughened polyamide compositions.
638. U.S. Pat. Nos. 5,591,798 and 5,777,033 disclose ther
Blends of uncured ethylene acrylic elastomers, polyamides
moplastic elastomer compositions comprising a blend of
and poWdered metals are disclosed in Japanese Patent 2001 - 30 polyamide resins and covalently-crosslinked acrylate rubber.
1 191387.
U.S. Pat. No. 7,608,216 and Us. Patent Application Pub
U.S. Pat. No. 3,965,055 discloses vulcanizates prepared
lication 2006/0100368 disclose compositions prepared by
from a blend of rubber and 2 Wt. % to 10 Wt. % of a crystalline
admixing an uncured thermoset elastomer, for example an
?ber-forming thermoplastic, Wherein the thermoplastic is
acrylate elastomer, With a thermoplastic polymer or another
dispersed in the rubber component in particles not greater 35
uncured (gum) elastomer. Techniques such as fractional cur
than 0.5 micron in cross section With a length to diameter ratio
greater than 2. The high aspect ratio of the thermoplastic ing, partial dynamic vulcaniZation, or the use of high perfor
particles enables pressureless curing Without void formation. mance reinforcing ?llers are disclosed to increase the green
Japanese patent application H10-251452 discloses a dis strength of the uncured or partially cured compound. The
persion of polyamide particles in a hydrogenated nitrile rub 40 admixed compositions may be subsequently crosslinked With
ber (HNBR) matrix Wherein a compatibiliZing polymer that a curing agent for the elastomer component.
may be an ethylene co-polymer or an acrylate elastomer is Polyacrylate rubber-polyamide blend compositions dis
also present. The compatibiliZing polymer is ionically closed in Zeon Chemicals L.P., HyTemp® Technical Manual,
crosslinked by metal oxide during mixing With the HNBR Rev. 2009-1, p. 46 (2009) are said to improve the impact
and polyamide, Which prevents the acrylate elastomer from 45 strength of plastics. They may also be used to produce ther
forming the continuous phase. The HNBR component is then moplastic elastomers.
peroxide or sulfur cured. It has noW been found that When a dispersion of discrete
U.S. Pat. No. 6,133,375 discloses blends of functionaliZed polyamide particles replaces all or a part of the conventional
rubbers With thermoplastics in Which the thermoplastic is particulate reinforcing agent in a continuous polyacrylate
dispersed in the rubber phase. Following addition of a cura 50 elastomer matrix the resultant compositions, When peroxide
tive for the rubber, the composition is crosslinked to produce
cured, exhibit enhanced resistance to embrittlement during
a vulcanized article. Examples of functionaliZed rubbers
heat aging. In addition, such compositions maintain excellent
Which are disclosed include acrylic rubbers such as nitrile
tensile strength, modulus, hardness and elastic properties
butadiene, and hydrogenated nitrile-butadiene, epichlorohy
such as compression set and elongation at break that charac
drin, and rubbers on Which reactive groups have been grafted 55
teriZes compositions containing conventional reinforcing ?ll
such as carboxylated nitrile-butadiene rubber. Thermoplas
tics that are disclosed include polyether-ester block copoly ers.
mers, polyurethanes, polyamides, polyamide ethers or ester
block copolymers, and mixtures of polyamides and polyole SUMMARY OF THE INVENTION
?ns. In the latter case, ethyleneialkyl acrylate copolymers 60
comprising grafted or co-polymeriZed maleic anhydride, gly The present invention is directed to a curable polyamide
?lled acrylate polymer composition, comprising
cidyl methacylate, or (meth)acrylic acid may be used to com
patibiliZe the polyamide-polyole?n blend. A. a polymer blend composition comprising
U.S. Pat. No. 4,694,042 discloses an elastomeric thermo 1. 40-90 Wt. % of one or more amorphous acrylate poly
plastic molding material containing a coherent phase of 65 mers comprising at least 50 Wt. %, based on the total
polyamide and crosslinked elastomeric polyacrylate core Weight of the polymer, of polymerized units of at least
shell polymers. one monomer having the structure
US 8,633,273 B2
6
the steps of providing a polyamide-?lled acrylate polymer
composition prepared by the above-described process and
adding a peroxide curative comprising a peroxide and option
ally a coagent to the polyamide-?lled acrylate polymer com
position at a temperature beloW the crystallization peak tem
peratures of the one or more polyamides to form a curable
polyamide-?lled acrylate polymer composition.
The invention is further directed to a process for preparing
Where R1 is H or Cl-C1O alkyl, and R2 is Cl-Cl2 alkyl,
an acrylate elastomer composition comprising the steps of
Cl-C2O alkoxyalkyl, Cl-Cl2 cyanoalkyl, or Cl-Cl2
?uoroalkyl; and A. providing a polyamide-?lled acrylate polymer compo
sition that has been prepared by a process comprising the
2. 10-60 Wt. % of one or more polyamides having melt
steps
ing peak temperatures of at least 160° C.;
Wherein i) the polymer blend composition has a green 1. providing a polymer blend composition comprising
strength of less than about 2 MPa as determined a. 40-90 Wt. % of one or more amorphous acrylate
according to ASTM D6746-10, ii) the one or more polymers comprising a) at least 50 Wt. %, based on
polyamides are present as a discontinuous phase in the total Weight of the polymer, of polymerized
the polymer blend composition, and iii) the Weight units of at least one monomer having the structure
percentages of the one or more amorphous acrylate
polymers and one or more polyamides are based on 20
the combined Weight of the one or more amorphous
acrylate polymers and one or more polyamides in the
polymer blend composition; and
B. a peroxide curative.
The invention is also directed to a process for preparing a 25
polyimide-?lled acrylate polymer composition comprising
the steps of
Where R1 is H or Cl-Cl0 alkyl, and R2 is Cl-Cl2
A. providing a polymer blend composition comprising
alkyl, Cl-C2O alkoxyalkyl, Cl-Cl2 cyanoalkyl, or
1. 40-90 Wt. % of one or more amorphous acrylate poly
30 C l-C l 2 ?uoroalkyl; and
mers comprising at least 50 Wt. %, based on the total
Weight of the polymer, of polymerized units of a b. 10-60 Wt. % of one or more polyamides having
melting peak temperatures of at least 1600 C.
monomer having the structure
Wherein the Weight percentages of the one or more
amorphous acrylate polymers and one or more
35
polyamides are based on the combined Weight of
the one or more amorphous acrylate polymers and
one or more polyamides in the polymer blend;
2. mixing the polymer blend composition at a tempera
ture above the melting peak temperatures of the one or
40
more polyamides to disperse the one or more polya
Where R1 is H or Cl-Cl0 alkyl and R2 is Cl-Cl2 alkyl, mides Within the one or more acrylate polymers,
Cl-C2O alkoxyalkyl, Cl-Cl2 cyanoalkyl, or Cl-Cl2 thereby forming a polyamide-?lled acrylate polymer
?uoroalkyl, and composition; and
2. 10-60 Wt. % of one or more polyamides having melt 45 3. cooling the polyamide-?lled acrylate polymer com
ing peak temperatures of at least 1600 C.; position to a temperature beloW the crystallization
Wherein the Weight percentages of the one or more amor peak temperatures of the one or more polyamides
phous acrylate polymers and one or more polyamides thereby forming an acrylate polymer composition
are based on the combined Weight of the one or more that i) comprises a continuous amorphous acrylate
amorphous acrylate polymers and the one or more 50 polymer phase and a discontinuous polyamide phase
polyamides in the polymer blend composition; and ii) has a green strength of less than about 2 MPa as
B. mixing the polymer blend composition at a temperature determined according to ASTM D 6746-10; and
above the melting peak temperatures of the one or more
B. adding a curative comprising a peroxide and optionally
polyamides to disperse the one or more polyamides
a coagent to the cooled polyamide-?lled acrylate poly
Within the one or more amorphous acrylate polymers, 55 mer composition to form a curable polyamide-?lled
thereby forming a polyamide-?lled acrylate polymer
acrylate polymer composition; and
composition; and
C. exposing the curable polyamide-?lled acrylate polymer
C. cooling the polyamide-?lled acrylate polymer compo
sition to a temperature beloW the crystallization peak composition to a temperature of at least 1000 C. for a
time su?icient to crosslink the amorphous acrylate poly
temperatures of the one or more polyamides, 60
Wherein i) the polyamide-?lled acrylate polymer compo mer, thereby forming a cured polyamide-?lled acrylate
sition comprises a continuous amorphous acrylate poly elastomer,
mer phase and a discontinuous polyamide phase and ii) Wherein the cured polyamide-?lled acrylate elastomer has
has a green strength of less than about 2 MPa as deter a ShoreA hardness of at least 40, as determined accord
mined according to ASTM D6746-10. 65 ing to ASTM D 2240-06 (1 second reading) and com
The invention is further directed to a process for preparing prises a continuous amorphous acrylate polymer phase
a curable acrylate elastomer composition Which comprises and a discontinuous polyamide phase.
US 8,633,273 B2
7 8
The invention is further directed to a curable acrylate poly is, the curing process, Which is also commonly referred to as
mer composition consisting essentially of crosslinking or vulcanization, converts the polyamide-?lled
A. a polymer blend composition comprising acrylate polymer composition to an acrylate polymer elas
1. 40 to 90 Wt. % of one or more amorphous acrylate tomer composition that exhibits enhanced heat aging resis
polymers comprising at least 50 Wt. %, based on the tance compared to acrylate polymer elastomers that comprise
total Weight of the amorphous acrylate polymer, of carbon black or other reinforcing ?llers.
polymerized units of at least one monomer having the The term “reinforcement” refers to an increase in the hard
ness and tensile strength of the cured (i.e. crosslinked) com
structure
position, relative to the similarly crosslinked but un?lled
acrylate polymer gum rubber. In particular, a crosslinked
acrylate polymer elastomer composition having a Shore A
hardness (ASTM D2240-06, 1 second reading) less than 40 is
too soft for a large majority of acrylate copolymer elastomer
applications, and therefore may be considered insuf?ciently
reinforced. A crosslinked acrylate polymer composition hav
ing a tensile strength of less than 4 MPa (ASTM D4l2-06, die
C) is too Weak for a large majority of acrylate polymer appli
Where R1 is H or Cl-Cl0 alkyl and R2 is Cl-Cl2 alkyl, cations, and therefore may be considered to be insuf?ciently
Cl-C2O alkoxyalkyl, Cl-Cl2 cyanoalkyl, or Cl-Cl2 reinforced.
?uoroalkyl, and 20 One embodiment of the invention is a curable acrylate
2. 5-60 Wt. % of one or more polyamides having melting polymer composition that comprises a polymer blend com
peak temperatures of at least 160° C.; position and a peroxide curative. The polymer blend compo
Wherein i) the one or more polyamides are present as a sition is characterized by having a green strength of less than
discontinuous phase in the polymer blend composi about 2 MPa as determined in accordance With ASTM
tion and ii) the Weight percentages of the one or more 25 D6746- l 0.
amorphous acrylate polymers and one or more polya The polymer blend composition comprises tWo polymers,
mides are based on the combined Weight of the one or an acrylate polymer and a polyamide. The polymer blend is
more amorphous acrylate polymers and one or more referred to herein as a polyamide-?lled acrylate polymer. The
polyamides in the polymer blend composition; acrylate polymer component of the curable polyamide-?lled
B. a peroxide curative; and 30 acrylate polymer compositions of the invention comprises
C. a reinforcing ?ller, the reinforcing ?ller being present in one or more amorphous acrylate polymers.
the curable acrylate polymer composition in an amount The acrylate polymer component of the curable polya
that causes an increase in the Shore A hardness of the mide-?lled acrylate polymer composition that is formed by
cured acrylate polymer composition of no more than the process of the invention comprises one or more amor
phous acrylate polymers.
about 20 points as compared to the ShoreA hardness of 35
a control composition that is of identical composition The term amorphous as used herein With reference to an
but for the absence of the reinforcing ?ller, Wherein i) the acrylate polymer means a polymer Which exhibits little or no
curable acrylate polymer composition and control com crystalline structure at room temperature in the unstressed
position are formed into test specimens of 1 mm to 2.5 state. By amorphous is meant that the acrylate polymer has a
mm thickness, the test specimens are cured by exposure 40 heat of fusion of less than 4 J/g as determined according to
to a temperature of 175° C. for 10 minutes in a closed ASTM D34l8-08.
mold at a pressure of at least 10 MPa, ii) Shore A hard As used herein, the term “copolymer” refers to polymers
ness of the cured acrylate polymer composition and the comprising copolymerized units resulting from copolymer
cured control composition is determined according to ization of tWo or more comonomers. In this connection, a
ASTM D 2240-06 (1 second reading), and iii) the cured 45 copolymer may be described herein With reference to its
acrylate polymer composition has a Shore A hardness constituent comonomers or to the amounts of its constituent
greater than 40. comonomers, for example “a copolymer comprising ethyl
ene, methyl acrylate and 3 Weight % of the monoethyl ester of
DETAILED DESCRIPTION OF THE INVENTION maleic acid”, or a similar description. Such a description may
50 be considered informal in that it does not refer to the comono
The present invention is directed to compositions compris mers as copolymerized units; in that it does not include a
ing blends of acrylate polymers and polyamides that, When conventional nomenclature for the copolymer, for example
cured With a peroxide curative system, exhibit enhanced International Union of Pure and Applied Chemistry (IUPAC)
resistance to physical property loss during heat aging. The nomenclature; in that it does not use product-by-process ter
invention is also directed to a process for preparation of the 55 minology; or for another reason. As used herein, hoWever, a
acrylate polymer/polyamide blend compositions, a process description of a copolymer With reference to its constituent
for preparation of curable acrylate polymer/polyamide blend comonomers or to the amounts of its constituent comonomers
compositions and a process for preparation of elastomers means that the copolymer contains copolymerized units (in
from the curable acrylate polymer/polyamide blend compo the speci?ed amounts When noted) of the stated comonomers.
sitions. 60 It folloWs as a corollary that a copolymer is not the product of
It has been found that When polyamide particles largely a reaction mixture containing given comonomers in speci?c
replace carbon black and conventional reinforcing inorganic amounts, unless expressly stated in limited circumstances to
?llers in curable amorphous acrylate polymers (also knoWn as be such.
acrylate polymer gum rubbers) such that the acrylate polymer The amorphous acrylate polymers useful in the practice of
forms a continuous phase and the polyamide forms a discon 65 the invention described herein comprise polymerized units of
tinuous phase, the resultant compositions, When cured, alkyl esters and/or alkoxyalkyl esters of propenoic acid.
exhibit surprising improvements in physical properties. That Examples of such esters include alkyl acrylates, and alkoxy
US 8,633,273 B2
10
alkyl acrylates as Well as species wherein the propenoic acid as ethylene diminishes compatibility of the acrylate polymer
is substituted With a Cl-Cl0 alkyl group. Examples of such With nylon, and therefore reinforcement Will be decreased.
species include alkyl methacrylates, alkyl ethacrylates, alkyl The polymers may additionally comprise a copolymeriZed
propacrylates, and alkyl hexacrylates, alkoxyalkyl methacry cure site monomer in any amount. For example, the acrylate
lates, alkoxyalkyl ethacryates, alkoxyalkyl propacrylates and polymer may comprise diene cure site monomers such 1,4
alkoxyalkyl hexacrylates. In addition, the alkyl ester groups butadiene, 1,6-hexadiene, ethylidene norbornene, and the
of the propenoic acid esters may be substituted With cyano like. If copolymeriZed diene cure site monomers are not
present, the acrylate polymers must comprise at least 50 mol
groups or one or more ?uorine atoms. That is, the ester group
% ethylene to confer peroxide curability.
Will be a Cl-Cl2 cyanoalkyl group or a Cl-Cl2 ?uoroalkyl
In certain embodiments, Wherein the acrylate polymers are
group. The acrylate polymers may also comprise copolymer
used to form curable compositions comprising a peroxide
iZed units of more than one species of the alkyl esters and/or
curative, the acrylate polymer Will preferably be substantially
alkoxyalkyl esters, for example tWo alkyl acrylates.
free of amine reactive cure site comonomer units selected
The alkyl and alkoxyalkyl esters of propenoic acid and
from the group consisting of unsaturated carboxylic acids,
substituted propenoic acids are preferably C 1 -Cl 2 alkyl esters
anhydrides of unsaturated carboxylic acids, unsaturated
of acrylic or methacrylic acid or C l-C2O alkoxyalkyl esters of
epoxides and mixtures of tWo or more thereof. By substan
acrylic or methacrylic acid. Examples of such esters include
tially free is meant that such polymers Will comprise less than
methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacrylate, butyl acrylate, butyl methacrylate, 2-ethyl 0.3 mol % of the amine reactive cure site comonomer units. In
hexyl acrylate, 2-methoxyethylacrylate, 2-ethoxyethylacry certain embodiments, these comonomers Will be present
Within the range from about 0.03 to 0.3 mol % in the acrylate
late, 2-(n-propoxy)ethylacrylate, 2-(n-butoxy)ethylacylate,
polymers used to form peroxide-curable compositions. When
3-methoxypropylacrylate and 3-ethoxypropylacrylate.
tWo or more amorphous acrylate polymers are present in the
Examples of esters that contain C l-C 1 2 cyanoalkyl and ?uo
curable composition, the range of about 0.03 to 0.3 mol %
roalkyl groups include cyanomethylacrylate, l-cyanoethy
lacrylate, 2-cyanopropylacrylate, 3-cyanopropylacrylate, amine reactive cure sites applies to the Weight average of
mole percent cure site in the individual acrylate polymers.
4-cyanobutylacrylate, l,l-dihydroper?uoroethyl methacry
Although carboxylic acids, anhydrides or epoxide cure sites
late, l,l-dihydroper?uoroethyl acrylate, l,l-dihydroper?uo
ropropyl methacrylate, l,l-dihydroper?uoropropyl acrylate, can inhibit peroxide curing and/ or lead to decreased compres
sion set resistance, these moieties also improve adhesion
and 1,1,5-trihydroper?uorohexyl (meth)acrylate, and 1,1,5
betWeen the polyamide particles and the acrylate elastomer
trihydroper?uorohexyl methacrylate. Preferably, the ester
continuous phase. The improved adhesion betWeen the polya
group Will comprise C l-C8 alkyl groups. More preferably, the
mide and polyacrylate phases leads to improved tensile and
ester group Will comprise Cl-C4 alkyl groups. Particularly
compression set properties in the cured compounds. Conse
useful alkyl acrylate esters are methyl acrylate, ethyl acrylate
quently acrylate polymers comprising such comonomers can
and butyl acrylate. A particularly useful alkyl methacrylate
be preferred in limited amounts for purposes of forming the
ester is methyl methacrylate. Minor amounts of unsaturated
35 peroxide-curable compositions described herein. The
acetates such as ethenyl acetate or 3-butenyl acetate may be
adverse effects of high levels of carboxylic acids, anhydrides,
incorporated into the polymer Without deviating from the
or epoxides (i.e., greater than 0.3 mol %) may be reduced or
scope of this invention. By minor amounts is meant less than
eliminated if these groups are consumed prior to the peroxide
1 Wt. %, based on the Weight of the acrylate polymer.
curing step, e.g., by reaction With amines or epoxides. In
Esters that comprise comonomer units in the acrylate poly
mers may be generally represented by the formula 40 addition, chlorinated cure sites are not generally desirable
because the carbon-chlorine bond is unstable at the melt
processing temperature of the polyamide (greater than 1600
C.), and the decomposition products may be toxic or damag
ing to the polyamide or acrylate polymer. It is preferable that
45 such cure sites are also absent or that the acrylate polymers
comprise less than 0.3 mol % of these cure site monomers.
Although the deleterious effects of these cure sites may be
moderated by various methods, additional complexity and
technical effort is required.
Where R1 is H or Cl-Cl0 alkyl and R2 is Cl-Cl2 alkyl, 50 In some embodiments, the acrylate polymers useful in the
Cl-C2O alkoxyalkyl, Cl-Cl2 cyanoalkyl, or Cl-Cl2 ?uoro practice of the invention Will also comprise copolymeriZed
alkyl. units of additional comonomers, for example ethylene and
In certain embodiments, the acrylate polymers may be other ole?ns such as propylene, l-butene, l -hexene, l -octene,
polymers derived from copolymeriZation of more than one and the like. The ole?n Will be present at a concentration of
acrylate comonomer. Examples of such acrylate polymers 55 less than 50 Wt %, more preferably less than 45 Wt %, and
include copolymers of methyl acrylate and butyl acrylate and most preferably about 40 Wt % or less, based on the Weight of
copolymers of methyl acrylate, butyl acrylate and the mono the acrylate polymer.
ethyl ester of l,4-butenedioic acid. Cure site monomers that permit curing by metallic soap/
The concentration of propenoic acid ester comonomers sulfur donors or metallic soap/amine cure systems may be
that are present in the acrylate polymer Will be at least 50 60 present in the polyacrylate elastomer, but are preferably
Weight percent, based on the Weight of the polymer. Prefer absent because they interfere With peroxide curing.
ably, the concentration Will be at least 55 Weight percent, and Alkyl acrylate dipolymer rubbers are particularly suitable
more preferably at least 60 Weight percent. If the concentra acrylate polymers for use in the process described herein. An
tion of propenoic acid ester is beloW 50 Wt %, the likelihood example of such a rubber is Vamac® DP acrylic elastomer,
that some crystallinity Will be present is high, for example in 65 available from DuPont Performance Elastomers L.L.C.
acrylate polymers that are ethylene acrylate ester copoly The acrylate polymers useful in the practice of the inven
mers. In addition, a high content of non-polar monomer such tion are curable, i.e. crosslinkable, due to the presence in the
US 8,633,273 B2
11 12
polymer chain of polymerized monomer units that can take In general, as the concentration of the polyamide in the
part in free radical reactions. Peroxide curatives function by acrylate polymer blend increases, the use of a polyamide of
forming free radical polymer species under elevated tempera higher inherent viscosity becomes more desirable. In certain
ture conditions, eg at temperatures above 100° C. These embodiments, a polyamide With a high content of amine end
species react to form interchain crosslinks either directly groups, about 60 meq/Kg or greater, can be desirable and
betWeen polymer molecules or indirectly by reaction With permits the use of a loW viscosity polyamide of inherent
viscosity about 0.89 dL/g. Such a high amine end group
multifunctional coagents, such as N,N'-(m-phenylene)dima
content results in a grafting reaction betWeen amine reactive
leimide.
cure sites present in the acrylate rubber and the polyamide
The acrylate polymers that are used to prepare the curable
polyamide-reinforced acrylate polymer compositions amine end groups Which can help to disperse the polyamide in
the acrylate rubber. In some instances, hoWever, use of such
according to a process of the invention are curable gums, i.e.
high amine content polyamide can result in gelling of the
they are substantially uncured rubbers, and retain reactivity
acrylate rubber during melt mixing With the polyamide, mak
toWards crosslinking by peroxide curative systems after
ing subsequent processing more dif?cult. Gelling of the acry
blending With the polyamide. By substantially uncured is
late elastomer becomes more problematic as the concentra
meant that the unblended rubber has a suf?ciently loW vis tion of polyamide in the acrylate copolymer increases.
cosity to be shaped into a ?nished article by molding or The polyamide resin can be produced by condensation
extrusion. Preferably, the Mooney viscosity (ASTM D1646,
polymerization of equimolar amounts of a saturated dicar
ML 1+4 at 100° C.) of the uncured polyacrylate rubber is less boxylic acid containing from 4 to 12 carbon atoms With a
than 120, more preferably less than 80 and most preferably 20 diamine, in Which the diamine contains from 4 to 14 carbon
less than 40. By retaining reactivity toWards crosslinking is atoms. To promote adhesion betWeen the acrylate rubber and
meant that the curable composition intended for production the nylon, preferably the polyamide Will contain some amine
of a molded or extruded article (i.e. the composition that end groups. Polyamide types polymerized from diacids and
includes acrylate polymer, polyamide and curative) exhibits diamines may contain some molecules having tWo amine
an increase in torque When tested in a moving die rheometer 25 groups. In such cases, certain combinations of polyamide and
(MDR 2000 or equivalent from Alpha Technologies, operat acrylate rubber can crosslink or gel slightly so as to produce
ing at an 0.5 degree arc at 190° C. for 15 minutes) of at least compositions With compromised extrusion processability.
2.5 dN-m, more preferably at least 4 dN-m, and most prefer Polyamide types prepared by ring opening polymerization
ably more than 5.5 dN-m. reactions such as nylon 6, or those based solely on aminocar
The acrylate polymers are amorphous polymers, rather 30 boxylic acids such as nylon 7 or 11 are most preferred because
than crystalline thermoplastics. That is, the degree of crystal they avoid the possibility of crosslinking during blending
linity of the acrylate polymer Will generally be less than 4 J/ g With the acrylate rubber. Such polyamide types contain mol
as measured by ASTM D3418, preferably less than 2 J/ g, and ecules With at most one amine group each.
most preferably about 0 J/ g. Examples of polyamides include polyhexamethylene adi
Acrylate polymers of this type may be prepared for 35 pamide (66 nylon), polyhexamethylene azelaamide (69
example according to the procedures described in US. Pat. nylon), polyhexamethylene sebacamide (610 nylon) and
Nos. 3,904,588; 4,520,183; 6,156,849, and 7,402,631. polyhexamethylene dodecanoamide (612 nylon), the polya
The polymer blend composition that comprises one com mide produced by ring opening of lactams, i.e. polycaprolac
ponent of the curable acrylate polymer compositions tam, polylauric lactam, poly-11-aminoundecanoic acid, and
described herein comprises one or more polyamides having a 40 bis(paraminocyclohexyl)methanedodecanoamide. It is also
melting peak temperature of at least about 160° C. as deter possible to use polyamides prepared by the copolymerization
mined in accordance With ASTM D3418-08. Preferably the of tWo of the above polymers or terpolymerization of the
polyamide is solid at the curing temperature of the acrylate above polymers or their components, eg an adipic, isoph
elastomer, meaning that the curing temperature is less than thalic acid hexamethylene diamine copolymer.
the melting peak temperature. While not Wishing to be bound Typically, polyamides are condensation products of one or
by theory, When the polyamide not solid at the curing tem more dicarboxylic acids and one or more diamines, and/or
perature, curative readily diffuses into the polyamide, render one or more aminocarboxylic acids, and/or ring-opening
ing the blend dif?cult to cure. Polyamide resins are Well polymerization products of one or more cyclic lactams.
knoWn in the art and embrace those semi-crystalline resins Polyamides may be fully aliphatic or semi-aromatic.
having a Weight average molecular Weight of at least 5,000 50 Fully aliphatic polyamides useful in practice of the present
and include those compositions commonly referred to as invention are formed from aliphatic and alicyclic monomers
nylons. Thus, the polyamide component useful in the practice such as diamines, dicarboxylic acids, lactams, aminocar
of the invention includes polyamides and polyamide resins boxylic acids, and their reactive equivalents. A suitable ami
such as nylon 6, nylon 7, nylon 6/6, nylon 6/ 10, nylon 6/12, nocarboxylic acid is 11-aminododecanoic acid. Suitable lac
nylon 11, nylon 12, polyamides comprising aromatic mono 55 tams are caprolactam and laurolactam. In the context of this
mers, and poly(amide 6-b-ethylene oxide). The resins may be invention, the term “fully aliphatic polyamide” also refers to
in any physical form, such as pellets and particles of any copolymers derived from tWo or more such monomers and
shape or size, including nanoparticles. blends of tWo or more fully aliphatic polyamides. Linear,
The viscosity of the polyamide resins can vary Widely branched, and cyclic monomers may be used.
While meeting the aims of the present invention. To ensure 60 Carboxylic acid monomers comprised in the fully aliphatic
that the polyamide becomes dispersed Within a continuous polyamides include, but are not limited to aliphatic carboxy
phase of acrylate elastomer, it is desirable that the polyamide lic acids, such as for example adipic acid, pimelic acid,
have an inherent viscosity greater than 0.9 dL/ g, more pref suberic acid, azelaic acid, decanedioic acid, dodecanedioic
erably greater than 1.1 dL/ g, and mo st preferably greater than acid, tridecanedioic acid, tetradecanedioic acid, and pentade
1.3 dL/ g, as measured in accordance With ASTM D2857-95, 65 canedioic acid. Diamines can be chosen from diamines hav
using 96% by Weight sulfuric acid as a solvent at a test ing four or more carbon atoms, including, but not limited to
temperature of 25° C. tetramethylene diamine, hexamethylene diamine, octameth
US 8,633,273 B2
13 14
ylene diamine, decamethylene diamine, dodecamethylene 6 to 20 carbon atoms and said aliphatic diamine having 4 to 20
diamine, 2-methylpentamethylene diamine, 2-ethyltetram carbon atoms; a lactam and/ or aminocarboxylic acid having 4
ethylene diamine, 2-methyloctamethylenediamine; trimeth to 20 carbon atoms; The polyamide may also be a blend of tWo
ylhexamethylenediamine, meta-xylylene diamine, and/or or more polyamides.
mixtures thereof. Preferred polyamides include nylon 6, 6/6, and Group IV
Semi-aromatic polyamides are also suitable for use in the polyamides having a melting point less than about 270° C.
present invention. Such polyamides are homopolymers, These polyamides have a melting point suf?ciently high so as
dipolymers, terpolymers or higher order polymers formed not to limit the scope of applications for the inventive mate
from monomers containing aromatic groups. One or more rials, but not so high that production of the blends causes
aromatic carboxylic acids may be terephthalic acid or a mix signi?cant degradation of the acrylate polymer.
ture of terephthalic acid With one or more other carboxylic Polyamides suitable for use in the invention are Widely
acids, such as isophthalic acid, phthalic acid, 2-methyl commercially available, for example Zytel® resins, available
terephthalic acid and naphthalic acid. In addition, the one or from E.I. du Pont de Nemours and Company, Wilmington,
more aromatic carboxylic acids may be mixed With one or Del., USA, Durethan® resins, available from Lanxess, Ger
more aliphatic dicarboxylic acids. Alternatively, an aromatic many, and Ultramid® resins available from BASF, USA.
diamine such as meta-xylylene diamine can be used to pro The polyamide-?lled acrylate polymer compositions of the
vide a semi-aromatic polyamide, an example of Which is a invention comprise 40-90 Weight percent of the acrylate poly
homopolymer comprising meta-xylylene diamine and adipic mer component described herein and 10-60 Weight percent of
acid. the polyamide component described herein, based on the total
Preferred polyamides are homopolymers or copolymers 20 Weight of the acrylate polymer and polyamide components.
Wherein the term copolymer refers to polyamides that have Preferably, the curable compositions Will comprise 50 to 80
tWo or more amide and/or diamide molecular repeat units. Weight percent acrylate polymer component and 20 to 50
The polyamide component may comprise one or more Weight percent polyamide component, based on the total
polyamides selected from Group I polyamides having a melt Weight of the acrylate polymer and polyamide components.
ing point of greater than 160° C., but less than 210° C., and 25 More preferably, the curable compositions Will comprise 55
comprising an aliphatic or semiaromatic polyamide, for to 70 Weight percent acrylate polymer component and 30 to
example poly(pentamethylene decanediamide), poly(pen 45 Weight percent polyamide component based on the total
tamethylene dodecanediamide), poly(e-caprolactam/hexam Weight of the acrylate polymer and polyamide components.
ethylene hexanediamide), poly(e-caprolactam/hexamethyl These ratios provide a polymer blend composition Wherein a
ene decanediamide), poly(12-aminododecanamide), poly 30 cured article made from the blend exhibits suf?cient Shore A
(12 -amino dodecanamide/tetramethylene terephthalamide), hardness that little or no additional ?ller is needed to further
and poly(dodecamethylene dodecanediamide); Group (II) increase the hardness of the cured composition. In addition,
polyamides having a melting point of at least 2100 C., and the polymer blends exhibit green strengths of less than about
comprising an aliphatic polyamide selected from the group 2 MPa, as determined in accordance With ASTM D6746-10
consisting of poly(tetramethylene hexanediamide), poly(e 35 and have good cure responses When compounded With a
caprolactam), poly(hexamethylene hexanediamide), poly curative to form a curable composition, preferably at least 2.5
(hexamethylene dodecanediamide), and poly(hexamethylene dN-m and more preferably at least 4 dN-m, as determined in
tetradecanediamide); Group (III) polyamides having a melt accordance With ASTM D5289-07a using an MDR 2000
ing point of at least 210° C., and comprising about 20 to about from Alpha Technologies operating at 05° arc and at test
35 mole percent semiaromatic repeat units derived from 40 conditions of 190° C. for 15 minutes, Where ML refers to the
monomers selected from one or more of the group consisting minimum torque value measured and MH refers to the maxi
of (i) aromatic dicarboxylic acids having 8 to 20 carbon atoms mum torque value attained after the measurement of ML. The
and aliphatic diamines having 4 to 20 carbon atoms; and amorphous acrylate polymer component may be made up of
about 65 to about 80 mole percent aliphatic repeat units one or more than one acrylate polymers of the type described
derived from monomers selected from one or more of the 45 herein as being suitable for use in the practice of the invention.
group consisting of an aliphatic dicarboxylic acid having 6 to Similarly, the polyamide component may be made up of one
20 carbon atoms and said aliphatic diamine having 4 to 20 or more than one polyamides of the type described herein as
carbon atoms; and a lactam and/or aminocarboxylic acid being suitable for use in the practice of the invention.
having 4 to 20 carbon atoms; Group (IV) polyamides com The polyamide-?lled acrylate polymer compositions may
prising about 50 to about 95 mole percent semiaromatic 50 be formed by mixing the polyamide component into the acry
repeat units derived from monomers selected from one or late polymer component at temperatures above the melting
more of the group consisting of aromatic dicarboxylic acids peak temperature of the polyamide, under conditions that do
having 8 to 20 carbon atoms and aliphatic diamines having 4 not produce a dynamic cure of the acrylate polymer, folloWed
to 20 carbon atoms; and about 5 to about 50 mole percent by cooling the thus-produced polymer blend to form a polya
aliphatic repeat units derived from monomers selected from 55 mide-?lled acrylate polymer composition. That is, a peroxide
one or more of the group consisting of an aliphatic dicarboxy curative Will not be present When the polyamide component
lic acid having 6 to 20 carbon atoms and said aliphatic and acrylate polymer component are being mixed. This is
diamine having 4 to 20 carbon atoms; and a lactam and/or because the mixing temperature speci?ed is above that at
aminocarboxylic acid having 4 to 20 carbon atoms; Group Which crosslinking and/or gelling of the acrylate polymer Will
(V) polyamides having a melting point of at least 260° C., 60 occur.
comprising greater than 95 mole percent semiaromatic repeat Cooling of the composition formed by mixing the acrylate
units derived from monomers selected from one or more of polymer component and polyamide component serves to
the group consisting of aromatic dicarboxylic acids having 8 crystalliZe the polyamide domains so that the polyamide
to 20 carbon atoms and aliphatic diamines having 4 to 20 becomes solid and therefore cannot coalesce to form a con
carbon atoms; and less than 5 mole percent aliphatic repeat 65 tinuous phase upon subsequent mixing, e. g., When mixed
units derived from monomers selected from one or more of With peroxide curative to form a curable composition. The
the group consisting of an aliphatic dicarboxylic acid having temperature beloW Which the blend must be cooled can be
US 8,633,273 B2
1 5 16
determined by measuring the crystallization peak tempera occurs to an extent that the polyacrylate polymer composition
ture according to ASTM D3418-08. The polyamide-?lled exhibits an elongation at break, or Eb, of less than 100%, as
acrylate polymer compositions may exhibit multiple crystal measured on an ASTM D412-C dumbbell test specimen cut
lization peak temperatures. In such cases, the loWest crystal from a molded (and optionally post cured) plaque, after being
lization peak temperature is taken as the temperature beloW heat aged for 1 Week at 1900 C. in air.
Which the blend must be cooled to fully solidify the polya If additional reinforcing ?llers are used, the ?ller particles
mide component. Generally, the blend Will be cooled to 400 Will generally be present in amounts such that the ?ller con
C. or less, Which is suf?cient to solidify the polyamides useful tributes less than about 20 points Shore A hardness, prefer
in the practice of the present invention. ably less than 10 points, and most preferably less than 5 points
According to one aspect of the process described herein, to the Shore A hardness of the press cured polyamide-?lled
Wherein a polyamide-?lled acrylate polymer composition is acrylate polymer composition.
formed, a blend of the acrylate polymer and polyamide is The compositions of the invention may also comprise addi
mixed at a temperature above the melting peak temperature of tional polymers provided that When addition of such poly
the polyamide to disperse the polyamide Within the acrylate mers occurs at a temperature above the melting peak tempera
polymer, thereby forming a polyamide-?lled acrylate poly ture of the polyamide the presence of such polymers does not
mer composition. The mixing step may be conducted on a increase the green strength of the resulting polyamide-?lled
heated tWo-roll rubber mill but it is generally conducted in acrylate composition to above about 2 MPa. For example, the
internal mixing equipment used to process thermoplastic polyamide-?lled acrylate polymer compositions of the inven
compounds or formulations because of the high temperatures tion may be blended With an acrylate polymer to dilute the
used. Such equipment includes Banbury® internal mixers, 20 polyamide content of the inventive composition by any mix
Haake Rheocord® mixers, Brabender Plastographs®, single ing process, either above or beloW the melting peak tempera
and tWin screW extruders, and Buss® Kneaders. The mixing ture of the polyamide. The acrylate polymer used for the
step provides a polymer blend composition that, When blending process may be the same as or different from that of
cooled, comprises a homogeneous mixture of an amorphous the inventive composition, and may further comprise ?llers,
acrylate polymer continuous phase and a polyamide discrete 25 curatives, or other ingredients. Preferably, such dilution
phase. The particle size of the polyamide phase may range occurs at a temperature beloW that of the melting peak tem
Widely and still provide technical advantages in the ?nished perature of the polyamide, and if a curative is present, beloW
article, but generally better properties are obtained When the the temperature needed to initiate curing.
majority of dispersed polyamide particles present have After the acrylate polymer component and polyamide
dimensions of less than about 2 microns in diameter, and are 30 component of the polymer blend composition have been
approximately spherical. The polyamide-?lled acrylate poly mixed at a temperature of 1600 C. or above for a period
mer composition prepared by this process retains a su?'i suf?cient to form a homogeneous mixture of melted polya
ciently loW viscosity to permit mixing in conventional rubber mide and amorphous acrylate polymer, the mixture is cooled
processing equipment. Preferably, the Mooney viscosity (ML to beloW the crystallization peak temperature of the one or
1+4, 100° C.) of the blend is less than 120, more preferably 35 more polyamides. This provides a composition having dis
less than 100, and most preferably less than 80. crete polyamide particles Within a continuous amorphous
In addition to the acrylate polymer and the polyamide, the acrylate polymer matrix.
polyamide-?lled acrylate polymer composition may also In general, compositions that result from mixing acrylate
comprise processing aids and compounding ingredients that polymer rubbers and polyamides may comprise a Wide range
are chemically stable at the mixing temperature, i.e. above 40 of blend morphologies, ranging from those Wherein discrete,
160° C. Generally, this Will not include crosslinking or curing discontinuous polyamide particles exist Within a continuous
agents, accelerators, or scorch retarders. Such components amorphous acrylate polymer matrix, to compositions
generally react or decompose to some degree at temperatures Wherein high aspect ratio polyamide “threads” are present, to
of 1600 C. or higher. Examples of components that may be compositions that comprise co-continuous structures, to
present include other ingredients normally useful in elas 45 compositions comprising discrete acrylate polymer domains
tomer compounds (i.e. curable formulations), such as colo Within a continuous phase of polyamide. Most of these com
rants, conventional mineral or carbon black reinforcing positions have morphologies that are unsuitable for use in the
agents, antioxidants, processing aids, ?llers and plasticizers. present invention, because the blends have very high Mooney
For optimal heat aging resistance, it is desirable to maintain viscosities, i.e. Mooney viscosity ML 1+4, 1000 C. of greater
the concentration of conventional reinforcing agents to as loW 50 than about 120, and/or poor elastic properties such as a loW
a level as possible, but other properties may be improved by tensile elongation to break, and high compression set. HoW
inclusion of such additives. Mo st commonly, ingredients such ever, if the ratio of components is chosen as described herein,
as conventional reinforcing agents, colorants, antioxidants, polyamide-?lled acrylate copolymer compositions can be
processing aids, plasticizers and the like Will be added during produced that have Mooney viscosities beloW about 120 mL
a loW temperature mixing process, for example during the 55 1+4, 1000 C. and good elastic properties. Such polyamide
step Wherein a curing agent is added. ?lled acrylate polymer compositions of the invention and
Fillers, including carbon black, may be optionally added to those suitable for use in the processes of the invention are
the polyamide-reinforced polyacrylate polymer composition characterized by having green strengths of less than about 2
but they are generally not necessary or desirable. The ?llers MPa, as determined by measurement in accordance With
may be present in forms Well knoWn in the art, including in the 60 ASTM D6746-10. The resultant compositions have good pro
form of so-called nano-materials Where at least one of the cessability and elastic properties. A green strength value less
dimensions of the particles is in the range of 1 to 1000 nm. than about 2 MPa is a basic characteristic of the compositions
Small amounts of such optional ?llers may be added in certain of the invention and is con?rmatory of the presence of a
embodiments so long as the optional ?llers do not adversely continuous acrylate polymer phase and a discontinuous
affect the heat resistance of the cured polyamide-reinforced 65 polyamide phase in the polyamide-?lled acrylate polymer
polyacrylate polymer compositions. By adversely affect is compositions. By “discontinuous polyamide phase” is meant
meant that embrittlement and/ or hardening during heat aging that the polyamide is present in the polymer blend composi
US 8,633,273 B2
17 18
tions of the invention as dispersed particles, or domains sur mineral reinforcing agents, antioxidants, processing aids, ?ll
rounded by a continuous amorphous acrylate polymer matrix. ers and plasticiZers, or it may be an operation separate from
In general, the polyamide domains Will be completely iso addition of other ingredients. The addition may be conducted
lated from each other Within the continuous amorphous acry on a tWo-roll rubber mill or by using internal mixers suitable
late polymer matrix. However, in certain instances a small for compounding gum rubber compositions, including Ban
percentage, less than about 5%, of localiZed sites in the poly bury® internal mixers, Haake Rheocord® mixers, Brabender
mer blend composition may exist Wherein the polyamide Plastograph® mixers, Farrel Continuous Mixers, or single
domains are aggregated or connected to each other. Such and tWin screW extruders.
polymer blend compositions that have green strengths of less Curable polyamide-?lled acrylate polymer compositions
than about 2 MPa are considered to comprise a discontinuous prepared by the above-described process are novel composi
polyamide phase for purposes of the invention. Preferably, tions that are useful for preparing cured (i.e. thermoset) elas
the green strength of the polyamide-?lled acrylate polymers tomeric compositions having excellent physical properties
Will be beloW about 1 MPa. and enhanced heat aging resistance.
A green strength greater than 2 MPa indicates the blend has Curing or crosslinking of the curable polyamide-?lled
high Mooney viscosity, poor extrusion processability, or poor acrylate composition, also referred to as vulcaniZation, typi
elastic properties after curing. These de?ciencies may arise cally involves exposing the compounded composition to
because the polyamide phase of the blend is continuous or elevated temperature and elevated pressure for a time su?i
co-continuous With the acrylate polymer, or because the end cient to crosslink the polymer. Such operations generally are
groups of the polyamide have reacted With the cure site of the conducted by placing the curable composition into a mold
acrylate copolymer to an extent that the acrylate copolymer 20 that is heated in a press (often referred to as press-curing).
has gelled, or any combination of the tWo. Extruded parts are often cured in a pressurized autoclave.
The polyamide-?lled acrylate polymer compositions pre After the press cure or autoclave cycle is completed, this
pared in the above-described process step are polyamide initial cure may be folloWed by an optional post-cure heating
?lled compositions to Which a peroxide curative may then be cycle at ambient pressure to further cure the polyacrylate. For
added to form curable acrylate polymer compositions. Suit 25 example, the vulcaniZate may be formed and cured using
able peroxide curatives, also knoWn as peroxide curing sys conventional press cure procedures at about 1600 C. to about
tems, comprise a peroxide and optionally a coagent. 2000 C. for about 2 to 60 minutes. Post-cure heating may be
Examples of peroxides and coagents include curative systems conducted at about 1600 C. to about 2000 C. for 15 minutes to
as generally knoWn in the art, including those described several hours. Once crosslinked, the compositions described
herein, operative at the temperature employed during vulca 30 herein are not thermoplastic, but thermoset. Suitable cure
niZation. For example, useful organic peroxides are those that conditions Will depend on the particular formulation and are
decompose rapidly Within the temperature range of 150° C. to known to those of skill in the art.
2500 C. These include, for example, dicumyl peroxide, 2,5 The polyamide-?lled acrylate polymer compositions of the
bis(t-butylperoxy)-2,5-dimethylhexane, and a',a'-bis(t-bu invention may contain an antioxidant system. In some
tylperoxy)-diisopropylbenZene (available from GEO Spe 35 embodiments, this may be a phosphorus ester antioxidant, a
cialty Chemicals under the tradename Vul-cup®). In a typical hindered phenolic antioxidant, an amine antioxidant, or a
vulcaniZate composition the peroxide is present in amounts of mixture of tWo or more of these compounds. The proportion
from about 0.5 to 5 parts phr (parts per hundred parts rubber, of the antioxidant compound in the polyimide-reinforced
i.e. parts per hundred parts of the one or more acrylate poly polyacrylate polymer composition is typically 0.1 to 5 phr,
mers present). The peroxide may be adsorbed on an inert 40 preferably about 0.5 to 2.5 phr. The Weight ratio of the phe
carrier such as calcium carbonate, carbon black or kieselguhr; nolic or amine antioxidant to the phosphorus compound in
hoWever, the Weight of the carrier is not included in the above mixtures is about 0.5 to 3, and preferably the ratio is about 1.
range. Generally, an optional coagent Will be present to The phosphorus ester can be for example, tri(mixed mono
increase the state of cure of the ?nished part. The coagent can and dinonylphenyl)phosphite, tris(3,5-di-t-butyl-4-hydrox
be for example, N,N'-(m-phenylene)dimaleamide, trimethy yphenyl phosphate, high molecular Weight poly(phenolic
45
lolpropane trimethylacrylate, tetraallyloxyethane, triallyl phosphonates), and 6-(3,5-di-t-butyl 4-hydroxy)benZyl-6H
cyanurate, tetramethylene diacrylate, or polyethylene oxide dibenZ-[c,c] [1 ,2]oxapho sphorin-6-oxide.
glycol dimethacrylate. A preferred coagent is N,N'-(m-phe Suitable hindered phenolic antioxidants can be, for
nylene)dimaleamide, available from DuPont Performance example 4, 4'-butylidenebis(6-t-butyl-m-cresol), 1,3,5-trim
Elastomers L.L.C. as HVA-2. The amount of the coagent used 50 ethyl-2,4,6-tris-(3,5-di-t butyl-4-hydroxybenZyl)benZene,
is generally about 0 to 5 parts by Weight per 100 parts poly 2,6-di-t-butyl-0t-dimethylamino-p-cresol and 4,4'-thiobis-(3
acrylate (phr), preferably about 1 to 5 parts phr. The coagents methyl-6-t-butylphenol).
usually contain multiple unsaturated groups such as allyl Amine antioxidants include, for example, polymerized 2,2,
groups or acrylic ester groups. While their mode of action is 4-trimethyl- 1 ,2-dehydroquinoline; N-phenyl-N'-(p-toluene
not knoWn With certainty, it is thought that they react With the 55 sulfonyl)-p-phenylenediamine, N,N'-di(naphthyl)-p-phe
initial radical formed on the polymer backbone to form a nylenediamine, loW temperature reaction product of
more stable radical, Which undergoes coupling reactions to phenyl(-naphthyl)amine and acetone, and 4,4'-bis(0t,0t-dim
form crosslinks more readily than chain scission reactions. ethylbenZyl)diphenylamine.
The addition of curative to the polyamide-?lled acrylate Preferred antioxidant compositions contain tri(mixed
polymer composition Will desirably take place at a tempera 60 mono- and dinonylphenyl)phosphite mixed With either 4,4'
ture beloW the decomposition temperature of the curative and butylidenebis(6-t-butyl-m cresol) or 4,4'-bis(0t,0t-dimethyl
beloW the temperature at Which the crosslinking reaction benZyl)diphenylamine. Particularly preferred antioxidant
occurs. Generally, the addition Will take place at a tempera compositions contain 4,4'-bis(0t,ot-dimethylbenzyl)dipheny
ture below 1400 C., preferably at a temperature no greater lamine (available commercially as Naugard® 445 from
than 1200 C. The addition of the curative may take place 65 Chemtura Corp.). Particularly preferred anti-oxidant compo
simultaneously With the addition of optional processing sitions include 4-aminodiphenyl amine, at levels up to about
ingredients, such as colorants, conventional carbon black or 2 phr based on the acrylate polymer component. Antioxidants