U.S. patent application number 10/058058 was filed with the patent office on 2003-07-31 for process for the preparation of a thermoplastic elastomer comprising a partially vulcanized rubber concentrate.
This patent application is currently assigned to DSM N.V.. Invention is credited to Brzoskowski, Ryszard, Wang, Yundong.
Application Number | 20030144415 10/058058 |
Document ID | / |
Family ID | 27609517 |
Filed Date | 2003-07-31 |
United States Patent
Application |
20030144415 |
Kind Code |
A1 |
Wang, Yundong ; et
al. |
July 31, 2003 |
Process for the preparation of a thermoplastic elastomer comprising
a partially vulcanized rubber concentrate
Abstract
Process for the preparation of a thermoplastic elastomer by melt
mixing a partially vulcanized rubber concentrate, a thermoplastic
polymer and/or additives, optionally oil and a curing agent. The
partially vulcanized rubber concentrate is prepared by melt mixing
at least one elastomer and optionally oil with a thermoplastic
polymer and a curing agent. The elastomer may be EPDM or EPM. The
thermoplastic polymer may be chosen from a thermoplastic
polyolefine. Usefull curing agents are for example sulfur,
sulfurous compounds, metal oxides, maleimides, phenol resins or
peroxides.
Inventors: |
Wang, Yundong; (Leominster,
MA) ; Brzoskowski, Ryszard; (Acton, MA) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
DSM N.V.
|
Family ID: |
27609517 |
Appl. No.: |
10/058058 |
Filed: |
January 29, 2002 |
Current U.S.
Class: |
524/849 |
Current CPC
Class: |
C08L 2312/00 20130101;
C08L 71/123 20130101; C08L 79/08 20130101; C08L 2312/04 20130101;
C08L 71/123 20130101; C08J 2323/16 20130101; C08J 3/005 20130101;
C08L 23/16 20130101; C08L 23/10 20130101; C08L 2666/04 20130101;
C08L 2666/04 20130101; C08L 2666/06 20130101; C08L 2666/06
20130101; C08L 2666/04 20130101; C08L 2666/04 20130101; C08L 81/06
20130101; C08L 79/08 20130101; C08L 91/005 20130101; C08L 23/16
20130101; C08L 81/02 20130101; C08L 23/16 20130101; C08L 81/06
20130101; C08L 81/02 20130101 |
Class at
Publication: |
524/849 |
International
Class: |
C08L 001/00; C08K
003/00 |
Claims
1. Process for the preparation of a thermoplastic elastomer by melt
mixing a. a partially vulcanized rubber concentrate b. a
thermoplastic polymer and/or additives c. optionally oil and d. a
curing agent.
2. Process according to claim 1 characterized in that the melt
mixing is carried out in a twin-screw extruder.
3. Process according to claim 1 characterized in that the melt
mixing is carried out in a single screw extruder.
4. Process according to any one of the claims 1-3 characterized in
that the partially vulcanized rubber concentrate (a) is prepared by
melt mixing: e. at least one elastomer and optionally oil f. at
least one thermoplastic polymer g. a curing agent.
5. Process according to claim 4 characterized in that the partially
vulcanized rubber concentrate is prepared by melt mixing e. 30 to
95 parts by weight of the elastomer(s) and 0-70 parts by weight of
oil f. 5 to 50 parts by weight of the thermoplastic polymer(s) g.
0.1-10 parts by weight of the curing agent whereby the sum of the
parts by weight of the elastomer(s), the thermoplastic polymer(s),
curing agent and oil is 100.
6. Process according to any one of claims 4-5 characterized in that
the elastomer is EPDM or EPM.
7. Process according to claim 1-6 characterized in that the
thermoplastic polymer is chosen from thermoplastic polyolefin homo-
and copolymers, reactor TPO, polyamides, polycarbonate, polyesters,
polysulfones, polylactones, polyacetals,
acrylonitrile-butadiene-styrene (ABS) resins, polyphenylene oxide
(PPO), polyphenylene sulfide (PPS), styrene-acrylonitrile (SAN)
resins, polyimides, styrene maleic anhydride (SMA) and aromatic
polyketones.
8. Process according to claim 7 characterized in that the
thermoplastic polymer is a thermoplastic polyolefin homo- and
copolymer.
9. Process according to claim 8 characterized in that the
thermoplastic polymer is a polypropylene homopolymer.
10. Process according to any one of claims 1-9 characterized in
that the elastomer in the partially vulcanized rubber concentrate
has a gel content higher than 50%.
11. Process according to any one of claims 1-10 characterized in
that the elastomer in the partially vulcanized rubber concentrate
has a gel content higher than 70%.
12. Process for the preparation of a thermoplastic elastomer
according to claims 1-11 by melt mixing: a. 10-90 parts by weight
of the partially vulcanized rubber concentrate b. 90-10 parts by
weight of a the thermoplastic polymer and/or additives c. 0-30
parts by weight of oil d. 0.1-10 parts by weight of the curing
agent whereby the sum of the parts by weight of the partially
vulcanized rubber concentrate, the thermoplastic polymer and/or
additives, the oil and the curing agent is 100.
13. Process according to any one of claims 1-12 characterized in
that the curing agent is chosen from phenol resins, siloxanes or
peroxides.
Description
[0001] The invention relates to a process for the preparation of a
thermoplastic elastomer.
[0002] A process for the preparation of thermoplastic elastomers is
for example known from "Compounding of rubber Concentrate
Thermoplastic Vulcanizates" by Terry M. Finerman, Ph.D., Luc
Vandendriessche, Joseph E. Pfeiffer, presented at the Society of
Plastics Engineers Topical Conference TPEs 2000, Sep. 28-29, 1999.
Described is the preparation of fully vulcanized rubber
concentrates and of thermoplastic elastomers by melt mixing the
fully vulcanized rubber concentrates with ingredients such as oil,
filler, stabilizers, processing aids and thermoplastic polymers for
example polypropylene or polyethylene. The thus obtained
thermoplastic elastomers have the disadvantage that their
mechanical properties are not sufficient for some applications for
example in automotive, building and construction, mechanical rubber
goods or consumer products. For example the tensile strength value
of those thermoplastic elastomers is relatively low and therefore
not meeting the required automotive material specifications.
Another disadvantage of the above process is that the preparation
of fully cured rubber concentrates with consistent properties and
good morphology is difficult because of the high concentration of
elastomeric phase and the minor concentration of thermoplastic
phase.
[0003] The object of the present invention is to completely or
largely eliminate the stated drawbacks.
[0004] This object is achieved in that the thermoplastic elastomer
is prepared by melt mixing:
[0005] a. a partially vulcanized rubber concentrate
[0006] b. a thermoplastic polymer and/or additives
[0007] c. optionally oil and
[0008] d. a curing agent.
[0009] Surprisingly the process of the present invention provides
the preparation of thermoplastic elastomers with improved
mechanical properties which meet the stringent material
specifications needed for some applications in automotive, building
and construction, mechanical rubber goods or consumer products. A
further advantage is that the elastic properties of the
thermoplastic elastomer are improved. Moreover the thermoplastic
elastomers show an improved fluid resistance. Yet another advantage
is that thermoplastic elastomers may be prepared with a better
compression set.
[0010] The partially vulcanized rubber concentrate (a) is prepared
by melt mixing:
[0011] e. at least one elastomer and optionally oil
[0012] f. at least one thermoplastic polymer
[0013] g. a curing agent.
[0014] The elastomer(s) and optionally oil and the thermoplastic
polymer(s) are melt mixed and kneaded above the melting point of
the thermoplastic polymer whereby the elastomer is vulcanized
during mixing and kneading. This process is also known as a dynamic
vulcanization process.
[0015] The elastomer (e) may be any elastomer capable of being
vulcanized by the curing agent. Examples of elastomer(s) are
ethylene-propylene copolymers, hereinafter called EPM,
ethylene-propylene-diene terpolymers, hereinafter called EPDM,
acrylonitrile-butadiene rubber, styrene-butadiene rubber,
isobutene-isoprene rubber, styrene-ethylene/styrene-butadiene block
copolymers, butyl rubber, isobutylene-p-methylstyrene copolymers or
brominated isobutylene-p-methylstyrene copolymers or natural
rubber. Preferably, the elastomer in the partially vulcanized
rubber concentrate according to the invention is an olefinic
elastomer. It is especially preferred to use EPM or EPDM as
elastomer. More preferably, EPDM is used as elastomer. The EPDM
preferably contains 50-70 parts by weight ethylene monomer units,
48-30 parts by weight alpha-olefin monomer units and 1-12 parts by
weight monomer units originating from a non-conjugated diene or
combinations of more than one non-conjugated diene. Preferably the
alpha-olefin is propylene. As non-conjugated diene use is
preferably made of dicyclopentadiene (DCPD), 5-ethylidene-2-
norbornene (ENB) or vinylnorbornene (VNB). The elastomer(s) may be
prepared for example with a Ziegler-Natta catalyst, a metallocene
catalyst or a single site catalyst.
[0016] The elastomer for example comprises between 0-250 parts of
oil per 100 parts of elastomer. Preferably comprises between 20-200
parts per 100 parts of elastomer. It is especially preferred to
comprise between 30-160 parts of oil per 100 parts of elastomer.
Any known oil may be used, examples of oils are processing oils for
example paraffinic, naphtalenic or aromatic oil or isoparaffinic
oil which is also known as polyalfaolefinic oil. Preferably a
highly hydrogenated oil obtained by a hydrocracking and isodewaxing
process is used, for example PennzUltra, 1199, supplied by Pennzoil
in the United States of America. The point in time at which the oil
is metered is not critical. In the process, the oil is for example
added before, during or after the dynamic vulcanisation of the
elastomer. It is also possible that the oil is added partly before
and partly during and/or after the dynamic vulcanisation of the
elastomer. It is also possible that the elastomer has been
pre-mixed with the desired quantity of oil or a proportion thereof.
In fact a person skilled in the art can adjust the ratio of
elastomer(s)/thermoplastic polymer(s)/oil to achieve partially
vulcanized rubber concentrates with a low hardness. The partially
vulcanized rubber concentrate for example has a hardness of 70
shore A or lower measured according to ASTM D-2240. Preferably the
hardness is 60 shore A or lower. Most preferably the hardness is 50
shore A or lower.
[0017] Examples of suitable thermoplastic polymers (f) which may be
used in the preparation of the partially vulcanized rubber
concentrates are thermoplastic polyolefin homo- and copolymers or
blends thereof. For example homopolymers of ethylene or propylene,
copolymers of ethylene and propylene, copolymers of ethylene and an
alpha-olefin comonomer with 4-20 carbon atoms or copolymers of
propylene and an alpha-olefin comonomer with 4-20 carbon atoms. In
case of a copolymer, the content of propylene in said copolymer is
preferably at least 75% by weight. The thermoplastic polyolefin
homo- and copolymers may be prepared with a Ziegler-Natta catalyst,
a metallocene catalyst or with another single site catalyst. Also
suitable thermoplastic polymers are for example reactor
thermoplastic polyolefine elastomers (TPO's), polyamides,
polycarbonate, polyesters, polysulfones, polylactones, polyacetals,
acrylonitrile-butadiene-styrene (ABS) resins, polyphenylene oxide
(PPO), polyphenylene sulfide (PPS), styrene-acrylonitrile (SAN)
resins, polyimides, styrene maleic anhydride (SMA) and aromatic
polyketones. It is possible to use more than one thermoplastic
polymer in the preparation of the partially vulcanized rubber
concentrates.
[0018] Preferably, a polypropylene homopolymer is used as
thermoplastic polymer. The polypropylene may be atactic, isotactic,
syndiotactic or a physical and chemical mixture thereof. The term
chemical mixture means that the polypropylene may have atactic,
isotactic or syndiotactic structures randomly or in blocks along
the molecular chains. The polypropylene homopolymer may be linear
or branched. The Melt flow index (MFI) of the polypropylene
preferably is between 0.3 and 50; more preferably below 20
(according to ISO norm 1133 (230.degree. C.; 2.16 kg load)).
[0019] Examples of suitable curing agents (g) include sulfur,
sulfurous compounds, metal oxides, maleimides, phenol resins and
peroxides. The curing agents may be used with or without
accelerators. Said curing agents are for example described in U.S.
Pat. No. 5,100,947. It is also possible to use siloxane compounds
as curing agent, for example hydrosilane or vinylalkoxysilane. The
elastomer is preferably vulcanized with a phenol resin, a siloxane
or a peroxide. Examples suitable accelerators are sulphur, ethylene
dimethylacrylate, polyethylene glycol dimethylacrylate, trimethylol
propane trimethacrylate, divinyl benzene, diallyl itaconate,
triallyl cyanurate, diallylphtalate, allyl methacrylate, cyclohexyl
methacrylate and m-phenylene bismaleimide.
[0020] The amount of curing agent, the accelerator, the temperature
and the time of vulcanisation are selected in order to obtain the
desired degree of vulcanization. Preferably the amount of curing
agent is between 0.1-10 parts by weight per 100 parts by weight of
elastomer. More preferably the amount of curing agent is between
0.1-5 parts by weight per 100 parts by weight of elastomer.
[0021] The degree of vulcanization of the elastomer can be
expressed in terms of gel content or conversely, extractable
components. The gel content is the ratio of the amount of
non-soluble elastomer and the total amount of elastomer (in weight)
of a specimen soaked in an organic solvent for the elastomer. The
method is described in U.S. Pat. No.4,311,628 and U.S. Pat.
No.5,100,947. In general terms a specimen is soaked for 48 hours in
an organic solvent at temperatures suitable for the thermoplastic
polymer and the elastomer. The solvent should be capable of
dissolving the thermoplastic polymers completely at the temperature
of gel test. After weighing of both the specimen and the residue
the amount of non-soluble elastomer and total elastomer are
calculated, based on knowledge of the relative amounts of all
components in the composition. The elastomer in the rubber
concentrate is partially vulcanized. Partially vulcanized means
that the elastomer may be vulcanized to a relatively low degree as
long as there is no problem with pellet stickiness. Preferably the
elastomer in the partially vulcanized rubber concentrate has a gel
content higher than 50%. More preferably a gel content higher than
70%.
[0022] The partially vulcanized rubber concentrate is preferably
prepared by melt mixing between 30-95 parts by weight of the
elastomer(s), between 0-70 parts by weight of oil, between 5-50
parts by weight of the thermoplastic polymer(s), between 0.1-10
parts by weight of the curing agent per 100 parts by weight of
elastomer, whereby the sum of the parts by weight of the
elastomer(s), thermoplastic polymer(s), curing agent and oil is
100. More preferably the amount of elastomer(s) varies between
35-90 parts by weight, the amount of oil varies between 5-60 parts
by weight, the amount of curing agent varies between 0.1-5 parts by
weight per 100 parts by weight of elastomer and the amount of
thermoplastic polymer(s) varies between 5-40 parts by weight,
whereby the sum of the parts by weight of the elastomer(s),
thermoplastic polymer(s), curing agent and oil is 100. Most
preferably the amount of elastomer(s) varies between 40-85 parts by
weight, the amount of oil varies between 10-50 parts by weight, the
amount of curing agent is between 0.1-5 parts by weight per 100
parts by weight of elastomer and the amount of thermoplastic
polymer(s) varies between 5-30 parts by weight, whereby the sum of
the parts by weight of the elastomer(s), thermoplastic polymer(s),
curing agent and oil is 100.
[0023] The process for the preparation of the thermoplastic
elastomer according to present invention comprises melt mixing
[0024] a. the partially vulcanized rubber concentrate
[0025] b. a thermoplastic polymer and/or additives
[0026] c. optionally oil and
[0027] d. a curing agent.
[0028] The melt mixing may be carried out in conventional mixing
equipment for example roll mills, Banbury mixers, Brabender mixers,
continuous mixers for example a single screw extruder, a Buss
kneader, Ferro continuous mixer (FCM) and a twin screw extruder.
Preferably melt mixing is carried out in a twin screw extruder with
sufficient mixing efficiency, good temperature control and
residence time control. By the use of a twin-screw extruder good
tensile properties are achieved. More preferably the melt mixing is
carried out in a single screw extruder. By the use of a single
screw extruder better compression set values may be achieved. The
use of a single or twin screw extruder depends on the desired
properties the thermoplastic elastomer should have.
[0029] The partially vulcanized rubber concentrate, the
thermoplastic polymer and/or the additives, the oil and the curing
agent may be dry blended prior to the melt mixing. Alternatively
the partially vulcanized rubber concentrate, the thermoplastic
polymer and/or the additives, the oil and the curing agent may be
directly fed by feeders to the continuous mixer.
[0030] Examples of the thermoplastic polymers (b) which may be melt
mixed with the partially vulcanized rubber concentrate (a) are
chosen from the above described thermoplastic polymers (f). The
choice of the thermoplastic polymer in terms of melt flow index or
viscosity depends on the end applications. A person skilled in the
art may select the thermoplastic polymer with proper molecular
weight, molecular weight distribution or molecular structure to
achieve the thermoplastic elastomer with balanced properties.
[0031] Examples of oils (c) which may be used in the process of the
present invention are processing oils for example paraffinic,
naphtalenic or aromatic oil or isoparaffinic oil which is also
known as polyalfaolefinic oil. Preferably a highly hydrogenated oil
obtained by a hydrocracking and isodewaxing process is used, for
example PennzUltra, 1199, supplied by Pennzoil in the United States
of America. The point in time at which the oil is metered is not
critical. In the process, the oil is for example added before,
during or after the dynamic vulcanisation of the thermoplastic
elastomer. It is also possible that the oil is added partly before
and partly during and/or after the dynamic vulcanisation of the
thermoplastic elastomer.
[0032] Examples of the suitable curing agents (d) are described
above as the curing agents (g). The curing agent may be in powder
form, in liquid form or may be soluble in a liquid. If the curing
agent is in powder form the partially vulcanized rubber concentrate
pellets may first be coated with a processing oil and then blended
with the curing agent powder prior to melt mixing with the
thermoplastic polymers. If the curing agent is in liquid form, it
may be dry mixed with the partially vulcanized rubber concentrate
prior to melt mixing with the thermoplastic polymer and/or the
additives. If the curing agent is soluble in a liquid for example
in processing oil or a solvent it may first be dissolved in the
liquid and then coated onto the rubber concentrate pellets prior to
melt mixing with the thermoplastic polymers. Alternatively, liquid
curing agent, curing agent solution in oil or solvent, or curing
agent melt can be dosed or injected directly to the mixer in the
form of a liquid or liquid solution.
[0033] Examples of additives which may be melt mixed are
reinforcing and non-reinforcing fillers, plasticizers,
antioxidants, stabilizers, processing oil, antistatic agents,
waxes, foaming agents, pigments, flame retardants and other known
agents described in for example the Rubber World Magazine Blue
Book. Examples of fillers that may be used are calcium carbonate,
clay, silica, talc, titanium dioxide, and carbon. Another additive
that may optionally be used in the thermoplastic elastomer is a
Lewis base for example a metal oxide, a metal hydroxide, a metal
carbonate or hydrotalcite. The quantity of additive to be added is
known to one skilled in the art.
[0034] In the process of the present invention it is also possible
to prepare the thermoplastic elastomer by melt mixing the partially
vulcanized rubber concentrate, additives and curing agent without
the thermoplastic polymer. In this case suitable additives are
viscosity modifiers, low friction coefficient additives such as
silicon oil and fatty amide lubricants, tackifiers or the additives
as described above. The amount of additives is for example between
0.5-15 parts by weight relative to the total quantity of the
thermoplastic elastomer. Preferably the amount of additives is
between 1-10 parts by weight relative to the total quantity of
thermoplastic elastomer. More preferably the amount of additives is
between 2-8 parts by weight relative to the total quantity of the
thermoplastic elastomer.
[0035] The gel content of the thermoplastic elastomer according to
the present invention may vary between 60 and 100%. Preferably, the
gel content is in excess of 80%. More preferably, the gel content
is in excess of 90%. Most preferable the gel content is in excess
of 97%.
[0036] The process of the present invention comprises the
preparation of the thermoplastic elastomer by melt mixing for
example:
[0037] a. 10-90 parts by weight of the partially vulcanized rubber
concentrate
[0038] b. 90-10 parts by weight of a the thermoplastic polymer
and/or additives
[0039] c. 0-30 parts by weight of oil
[0040] d. 0.1-10 parts by weight of the curing agent
[0041] whereby the sum of the parts by weight of the partially
vulcanized rubber concentrate, the thermoplastic polymer and/or
additives, the oil and the curing agent is 100.
[0042] Preferably the thermoplastic elastomer is prepared by melt
mixing
[0043] a. 15-70 parts by weight of the partially vulcanized rubber
concentrate
[0044] b. 30-85 parts by weight of a the thermoplastic polymer
and/or additives
[0045] c. 0-30 parts by weight of oil
[0046] d. 0.1-5 parts by weight of the curing agent
[0047] whereby the sum of the parts by weight of the partially
vulcanized rubber concentrate, the thermoplastic polymer and/or
additives, the oil and the curing agent is 100.
[0048] The process of the present invention may be carried out in
two stages. In a first stage, the partially vulcanized rubber
concentrate may be prepared whereby at least one elastomer is
partially vulcanized in the presence of at least one thermoplastic
polymer using appropriate curing agents. In a second stage the
partially vulcanized rubber concentrate, the appropriate
thermoplastic polymer and/or additives are melt-mixed in the
presence of the curing agent to iniate a further dynamic
vulcanization. The curing agents used in the first and in the
second stage may be the same or different curing agents. Preferably
the same curing agent is used in the two stages.
[0049] The two stages can be carried out independently in separate
steps or sequentially in the same processing equipment. After
dynamic vulcanization the thermoplastic elastomer may be
pelletized. The thermoplastic elastomer may however also be
directly fed in molten stage to next processing equipment for
example through a die. In such case the continuous mixer is
attached with the die or other necessary downstream equipment and
acts not only as mixer but at the same time as a melting and a
conveying equipment for processes as foaming, film and sheet
extrusion, profile extrusion, film and sheet calendering or
co-extrusion.
[0050] The additives may be added during the preparation of the
partially vulcanized rubber concentrate or during the preparation
of the thermoplastic elastomer or both.
[0051] The thermoplastic elastomer prepared by the process
according to the present invention may be used in automotive,
building and construction, mechanical rubber goods or consumer
products.
[0052] The present invention will be further explained by the
following examples without being limited thereto. The measurements
in the examples were carried out using the following tests:
[0053] Hardness ASTM D-2240, 5 sec delay
[0054] Tensile strength, ASTM D-412, Die C
[0055] Ultimate Elongation, ASTM D-412, Die C
[0056] 100% modulus, ASTM D-412, Die C
[0057] Tear strength, ASTM D-624, Die C
[0058] Compression set, 22 hrs@ 70C % ASTM D-395, method B
[0059] Compression set, 70 hrs@125C % ASTM D-395, Method B
[0060] Oil swell, 70 hrs@125C, ASTM D-471
EXAMPLE 1
[0061] A partially vulcanized rubber concentrate (compound 1) was
prepared in a 92 mm Werner&Pfleiderer intermeshing co-rotating
twin-screw extruder by melt mixing and kneading 67.1 parts by
weight Keltan P597.TM. (50 wt % oil-extended EPDM) with 7.7 parts
by weight polypropylene homopolymer PP 1012.TM. (MFI=1.2) as
thermoplastic polymer, 25.2 parts by weight of Sunpar 150C.TM.
processing oil, 0.3 wt % phenolic resin SP1045.TM. and 0.3 wt %
stannous chloride dihydrate activator. The properties of compound 1
are shown in table 1.
1 TABLE 1 Properties Test value Hardness, Shore A 41 Tensile
strength, Mpa 3,1 Elongation % 424 100% Modulus, Mpa 1 Tear
Strength, kN/m 11,6 Compression set, 22 hrs@70 C., % 25 Compression
set, 70 hrs@125 C., % 35,5 Oil swell in IRM 903, 70 hrs@125 C., %
125
EXAMPLE 2
[0062] A thermoplastic elastomer (compound 2) was prepared of
compound 1 pellets and a polypropylene homopolymer 31S07A (MFI=0.7)
without the addition of phenolic resin SP1045.TM. as curing agent.
Compound 2 was prepared on a 25 mm Berstorff intermeshing
co-rotating twin screw extruder.
EXAMPLE 3
[0063] A thermoplastic elastomer (compound 3) was prepared of
compound 1 pellets and a polypropylene homopolymer 31S07A (MFI=0.7)
with the addition of phenolic resin SP1045.TM. as curing agent.
[0064] To prepare compound 3, the compound 1 pellets were first
coated with a small amount of processing oil Sunpar 150C.TM. and
then blended with SP1045 powder in a cement mixer before the
polypropylene homopolymer 31S07a was introduced. All ingredients
were further dry blended using a cement mixer prior to the melt
mixing.
[0065] Compound 3 was prepared on a on a 25 mm Berstorff
intermeshing co-rotating twin screw extruder.
EXAMPLE 4
[0066] A thermoplastic elastomer (compound 4) was prepared
according to example 3 except that a 1.5 inch Killion single screw
extruder with l/d ratio of 24/1 was used.
[0067] After melt mixing, melt strands were cooled in a cold water
bath before being pelletized. All compounds were dried for at least
three hours to remove any residual moisture prior to injection
molding.
[0068] 4.times.4 cm plaques with a thickness of 3 mm were used for
testing the mechanical properties. The results are shown in table
2
2 TABLE 2 Compound 2 Compound 3 Compound 4 Parts by Parts by Parts
by weight weight weight compound 1 58,6 58 58 PP homopolymer 31S07A
41,4 41,2 41,2 Sunpar 150C.TM. 0,2 0,2 phenolic resin 0,6 0,6
SP1045.TM. Hardness Shore D 39,4 41 39,1 Tensile strength, MPa 14,8
18,2 13,3 Ultimate Elongation, % 728 580 493 100% modulus, MPa 8,8
9,8 8,6 Tear strength, kN/m 73,3 73,6 67 Compression set, 57,5 52,3
45,3 22 hrs@ 70 C., % Compression set, 76,7 69,1 68 22 hrs@ 125 C.,
% Oil swell in IRM 903, 44,4 32 36,7 70 hrs@ 125 C., %
[0069] Table 2 shows that the thermoplastic elastomers prepared by
the process of the present invention have good mechanical
properties.
[0070] Moreover it is clear that the use of a twin-screw extruder
leads to better mechanical properties whereas the use of a single
screw extruder leads to better compression set values. In addition,
the use of the curing agent in the preparation of compounds 3 and 4
shows improved fluid resistance as indicated by the lower oil swell
values in comparison to the control compound 2.
* * * * *