Note: Descriptions are shown in the official language in which they were submitted.
~' ~) i~:'~ "~'; ~ "3
This inventian relates t:o a pracess for producing
a multi-layered article, and in particular to a process for
producing a multi-layered automotive article and to the article
thus produced.
The production of hollow, mufti-layered articles
using blow molding techniques is by no means new. Examples
of the production of such mufti-layered articles are described
in United States Patents Nos. 3,955,697, which issued to E.I.
Valyi on May 11, 1976; 4,079,850, which issued to T. Suzuki
et al on March 21, 1978; 4,398,642, which issued to T. Okudaira
et al on August 16, 1983; 4,424,834, which issued to T. Sumi
et al on January 10, 1984, and 4,535,901, which issued to T.
Okudaira et al on August 20, 1985. In general, the production
of mufti-layered articles, e.g. articles having two or three
layers of coextruded resins can be quite expensive. Articles
commonly produced using such coextrusion methods include ducts,
hoses, tubes, sealing devices and covers used in automotive
vehicles. Specific articles of this type include shock absorber
boots, rack and pinion boots, steering gear boots, suspension
strut boots, and constant velocity joint boots. Because articles
of this type are exposed to a variety of temperatures and substances
such as grease and oil, it is important that at least one layer
of the articles be formed of a resistant resin. The usual
practice is to form all layers using expensive materials.
The object of the present invention is to reduce
the cost of such articles by forming at least one of the layers
- 1 -
~~(~~~~~'J; );.3
of a less expensive material which can substantially reduce
the overall cost of the article without compromising the chemical
resistant properties thereof.
Accordingly, the present invention relates to a process
for producing multi-layered articles for automotive use camprising
the steps of forming a parison including at least a chemically
resistant inner layer, and a less resistant, relatively in-
expensive outer layer; and blow molding the parison to yield
the article.
When producing a two-layered article such as constant
velocity joint boot, it is important that the inner layer be
formed of a chemically resistant material, since it is the
inner layer which is in constant contact with grease. Table
1 which follows provides examples of articles produced using
a variety of materials, the middle or outer layer of material
being less expensive than the inner layer.
25
_ 2 _
p:: ~~~~~'f :~9; 3
TABLE 1
SAMPLE INNER MIDDLE OUTER
NUMBER LAYER LAYER LAYER
1 SANTOPRENE SALFLEX
103-40 145
2 SALFLEX SANTOPRENE
145 103-40
3 SANTOPRENE SALFLEX SANTOPRENE
103-40 145 103-40
4 HYTREL HYTREL
5612 4275
5 HYTREL HYTREL
4275 5612
6 HYTREL HYTREL HYTREL
4275 5612 4275
7 HYTREL HYTREL HYTREL
5612 4275 5512
8 HYTREL LOMOD HYTREL
5612 BO100 5612
9 BAYER PELPRENE
0148 p55B
10 PELPRENE BAYER PELPRENE
P55B 0148 P55B
11 PELPRENE BASF PELPRENE
P.'i5B C90A P55B
12 H'.tTREL COMPOSITTON 1 HYTREL
5612 5612
13 PELPRENE COMPOSITTON 1 PELPRENE
P55B P55B
14 PELPRENE COMPOSITION 2 PELPRENE
P55B P55B
- 3 -
~:'U~j:~'~:v~3
5antoprene .103-40 is a Monsanto trade mark for a
thermoplastic rubber, which exhibits the elastomer performance
of vulcanized rubbers and the processing simplicty of thermoplastic
polymers. Santoprene rubbers exhibit excellent mechanical
properties over a useful operating range of -40°C to 150°C,
low compression set and tension set, and excellent hot air
aging at temperatures up to 150°C. Santoprene rubbers have
superior abrasion resistance, high tear strength, high dynamic
fatigue resistance and excellent ozone and weathering resistance.
Moreover, Santoprene rubbers are inherently resistance to a
wide variety of oils, solvents and chemicals, and are not readily
soluble in any common solvent. Highly polar fluids such as
alcohols, ketones, glycols, esters and aqueous solutions of
acids, salts and bases have little effect upon the rubber.
Salflex 145 is a trade mark of. Salflex Polymers for
a polypropylene based thermoplastic elastomer.
Hytrel is a DuPont trade mark for a copolyester prepared
by transesterification using readily available starting materials
such as dimethyl terephthalate polytetramethylene ether glycol
and 1,4-butanediol. The polymers are normally synthesized
by conventional equilibrium melt condensation polymerization
in the presence of an ester interchange catalyst. The resulting
products are random block copolymers consisting of crystalline
1,4-butanediol hard segments and amorphous elastomeric poly-
alkylene ether terephthalate soft segments. Hytrel provides
excellent resistance to non-polar materials such as oils and
- 4 -
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hydraulic fluids even at: elevated temperatures, and is resistant
to most polar fluids such as acids, bases, amines and glycols
at room temperature. The resistance of Hytrel to hot moist
environments is also good. In general, Hytrel is resistant
to the same classes of chemicals and fluids as polyurethanes,
both ester and ether based. However, Hytrel has better high
temperature properties than polyurethanes. Hytrel polyester
elastomers do not contain an extractable plasticizer as do
flexible vinyls, certain grades of nylon and many rubber compounds.
Many fluids and chemicals will extract the plasticizer from
these materials, causing a significant increase in stiffness
and volume shrinkage. Hytrel has excellent flexibility at
room temperature and low temperatures, excellent flex crack
resistance, resistance to tear, abrasion and impact, and has
a service temperature of -50°C to 110°C.
Bayer 0148 is a polyester-polyurethane which can
be processed as a thermoplastic.
Pelprene P55B is a polyether ester block copolymer
(elastomer). The polymer provides excellent properties in
terms of rubbery resilience and plastic durability over a wide
range of temperatures, excellent resistance to oils, fuels
and chemicals at high temperatures, and excellent resistance
to any weather condition. Pelprene contains no plasticizers,
so that no extraction of additives by any solvent is possible.
Pelprene has a thermal resistance of -70°C to 150°C.
- 5
Lomod BO100 is a General Electric trade mark for a
polyester.
BASF C90A is a polyester-polyurethane which can be
processed as a thermoplastic, and which can be used in
injection molding, extrusion blow molding and thermoforming.
The plastic also provides excellent resistance to most oils,
gases and engine fluid. The thermal stability of such
materials permits their use in extreme weather conditions.
The polymer is flexible at low and high temperatures and
resistant to abrasian.
Composition 1 is a modified thermoplastic elastomer
containing 46~ Hytrel 5556 (trade mark), 44~ Nordel 5892
(DuPont trade mark) and 10$ Surlyn 1705. Nordel 5892 is
ethylenepropylene dime (EPDM), which is a terpolymer
elastomer produced in several vacations, the principle variant
being the diene mentioned above. Dicyclopentadiene,
ethylidene norbornene and 1,4-hexadiene are the types usually
selected as the nonconjugated dime component. The
unsaturation remaining after the initial synthesis is utilized
in classical sulfur type vulcanization. Nordel hydrocarbon
elastomers are extremely resistant to attack by ozone, oxygen
and weather. Moreover, properly prepared vulcanizates of
Nordel are outstanding in resistance to deterioration by heat,
steam and many chemicals. Surlyn 1705 is an ionomer based on
zinc salts of ethylene/(meth) acrylic acid copolymers. The
zinc ions neutralize from 10 to 90$ of the acid groups, and
- 6 -
~.'(~ i.'~=~r''s'~i:~
the remaining unsaturated carboxylic acids can be either mono
or dica rboxylic acids such as acry:Lic, methacrylic
(preferred), ethacrylic, itaconic, malefic-fumaric acids,
hydrogen maleate and rnethyl hydrogen fumarate. Surlyn
provides thermal stability, excellent abrasion and impact
resistance. Most ionome.rs are insoluble in common organic
solvents at room temperature, and resist attack from most mild
acids and bases. Outstanding low temperature flex and impact
toughness are characteristic. The brittleness temperature for
the polymers is as low as -110°C. Finally, the change in
modulus versus temperature is relatively small.
Composition 2 is a modified thermoplastic elastomer
containing 40~ Hytrel 5556, ~10~ Kraton 61650 and 20$ Surlyn
1705. Kraton 61650 is a Shell trade mark for a styrene-
ethylene-butylene-styrene block copolymer of the A-B-A type,
where A represents polystyrene end blacks and B represents a
polyolefin rubber midblock. Since Kraton G rubbers have a
unique olefin rubber midblock, they are heat and shear stable
at processing temperatures as high as 500~F. Finished
articles formed of Kraton G rubbers are highly resistant to
ozone attack, oxidation and degradation from exposure to
sunlight. The elastomers provide excellent resistance to
water, acids and bases, and axe flexible at low temperatures.
The results of physical tests on the samples listed
in Table 1 are found in Table 2, which follows:
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Lt will be appreciated that the material used in
the inner layers of the coextruded products must be resistant
to a variety of automotive fluids - more so than the middle
and outer layers. The inner layers are directly exposed to
the fluids on a continuous basis, and must resist attack even
under extreme temperature and flex conditions. Table 3 provides
a list of a few examples of oil aged coextruded products, and
a comparison for non-oil aged and single layer samples. The
single layer samples are formed of the same material as the
inner or outer layer. The test is oil aging in ASTM #~3 oil
at 125°C for 168 hours. The samples are tensile bars cut from
fabricated components.
TABLE 3
TENSILE
SINGLE LAYER COEXTRUDED 3-LAYERS
NON-OIL AGED OIL AGED NON-OIL AGED OIL AGED
HYTREL 5612 HYTREL 5612/HYTREL 4275/HYTREL 5612
30.OMPa 24.OMPa 34.2MPa 23.7MPa
HYTREL 4275 HYTREL 4275/HYTREL 5612/HYTREL 4275
28.OMPa 23.OMPa 33.1MPa 22.9MPa
HYTREL 5612 HYTREL 5612/COMP.l/ HYTREL 5612
30.OMPa 24.OMPa 26.7MPa 24.1MPa
It will be noted that the oil aging tensile results
for the coextruded samples are approximately equal to those
obtained for single layer samples, where the single layer is
the inner layer material of a three layer sample. Thus it
is seen that the coextrusion process does not have any deleterious
_ g _
v'~~~j~~~~4.~:_y
effect on the property of the most important layer, namely
the inner Layer of the product.
On the basis of physical and chemical test date,
including stressjstrain tests, it has been found that the
S coextrusion process does not adversely affect the excellent
properties exhibited by thermopi.astic elastomers or polyesters
when used alone. The main advantage of the process described
herein, especially for shock absorber, rack and pinion, steering
gear, suspension strut and constant velocity joint boots or
covers, is reduced cost. At present, the production of such
parts utilizing polyester or thermoplastic elastomers is quite
expensive. Using the coextrusion process of the present in-
vention, a less expensive middle or outer layer can be employed
in combination with chemical, abrasion and flex resistant
materials in the inner or outer and inner layers. The result
is a substantial reduction in the cost of the products.
Table 4 below lists examples of combinations of elastomers
and the characteristics which yield the advantages described
herein.
TABLE 4
SAMPhE N0. LAYER MATERIAL CHARACTERISTICS
1 INNER Santoprene good grease and fluid
103-40 resistance, excellent
high temperature flex
OUTER Salflex 145 less expensive and
lower grease and fluid
resistance than inner
layer
- 10 -
~::6~~3~'~'~,~~~3
3 INNER Santoprene good grease and fluid
103-40 resistance, excellent
high temperature flex
MTDDLE Salflex 145 less expensive, and
lower grease and fluid
resistance than inner
layer
OUTER 5antopr ene good grease and fluid
103-40 resistance, excellent
high temperature flex
4 INNER Hytrel 5612 excellent grease, fluid
and abrasion resistance,
excellent high/low
temperature flex
OUTER Hytrel 4275 excellent grease, fluid
and abrasion resistance,
excellent high/low
temperature flex, and
slightly less expensive
than inner layer
5 INNER Hytrel 4275 see above
OUTER Hytrel 5612 see above
6 INNER Hytrel 4275 see above, slightly
less expensive than
Hytrel 5612
MIDDLE Hytrel 5612 see above
OUTER Hytrel 4275 see above
7 INNER Hytrel 5612 see above
MIDDLE Hytrel 4275 see above
OUTER Hytrel 5612 see above
8 INNER Hytrel 5612 see above
MIDDLE Lomod O100 slightly less expensive
B
than inner layer, with
good chemical and fluid
resistance, and good
temperature flex
OUTER Hytrel 5612 see above
- 11 -
~: ~U ~~=~'-~.v
9 INNER Bayer 0148 less expensive than
Hytrel 5612, with
excellent chemical and
fluid resistance,
excellent strength
(tensile, tear strength)
OUTER Pelprene excellent chemical, fluid
P55B and abrasion resistance,
excellent high and low
temperature flex, and
long flex life
INNER Pelprene
P55B see above
MIDDLE Bayer 0148 see above
10
OUTER Pelprene
P55B see above
11 INNER Pelprene '
P55B see above
MIDDLE BASF 090A less expensive than
inner layer, excellent
resistance to chemicals
and fluids, and excellent
strength (tensile, tear
strength)
OUTER Pelprene
P55B see above
12 INNER Hytrel 5612 excellent grease, fluid
and abrasion resistance,
excellent high and low
temperature flex
MIDDLE composition 1 substantially less
expensive than inner
layer, with good flex
life under hot and
cold temperature
conditions
OUTER Hytrel 5612 see above
- 12 -
l.3 INNER Pelprene
P55B see above
MIDDLE Composition 1 see above
OUTER Pelprene
P55B see above
14 INNER Pelprene
P55B see above
MIDDLE Composition 2 substantially less
expensive than inner
layer, with good flex
life under hot and cold
temperature conditions
It has been found that the middle or outer layer of
the product can be a softer material, which increases the flex
life of the boot or cover under extreme temperature conditions.
For example, in Sample #l, Salflex 145 is less expensive than
Santoprene, and has good high and low temperature flex results.
The Santoprene 103-40 is a softer material for use in the outer
layer to improve the flex life of the product under extreme
temperature conditions. In the case of Sample #5, both of the
Hytrels have excellent chemical, fluid and abrasion resistance,
and excellent high and low temperature flex, but the Hytrel
5612 used in the outer layer is softer than Hytrel 4275 to improve
the flex life under extreme temperatures. For Samples 6 to
12, all of the layers have excellent properties, the softer
material being used in the middle layer to ensure a long flex
life of the product even under extreme temperature conditions.
Although, while most of the examples of 3-layer
- 13 -
p.~~~t'~~'~'~''..D; a
coext.rudr~d articles listed hereinbefore include inner and outer
layers of the same material, it will be appreciated that the
outer layer of material could be changed to a less expensive,
yet still abrasion and .fluid resisted material. In many cases,
the outer layer is not exposed to the same grease and automotive
fluids as the inner layer. Thus, while the outer layer must
be durable, in many cases it is possible to use a polyester
or thermoplastic elastomer which is less expensive than the
outer layer material. Samples 1 and 4 of Table 1 are examples
of inner and outer layer materials, where the outer layer is
less expensive and has a lower resistance 'than the inner layer.
Other examples are Hytrel 5612 as the inner layer, and Saiflex
4275 as the outer layer, Pelprene P55B as the inner layer, and
Lomod BO100 as the outer layer, and Pelprene P55B as the inner
layer, BASF C90A as the middle layer and Lomod B0100 as the
outer layer.
Table 5 which follows provides a list of the fluids
most commonly contacted by the coextruded products. The table
also provides an indication of the changes in physical properties
of the compound contacted by the fluids.
TABLE 5
E'LUID HYTREL PELPRENE SANTOPRENE
PHYSICAL PROPERTIES 5612 & 4275 P55B 103-40
Standard 5612 4275
Tensile (MPa) 32.0 30.0 30.0 19.0
Elongation (o) 700 600 700 560
- 14 -
' F wD
r1 S TM O I L. '~ 1
168hr @ 120C 70 hr
Tensile loss 0 13 11
Elong. loss +9 +14 20
g, Vol. increase2 10 N/A
ASTM OIL #3
168 hr @ 120C 70 hr
Tensile loss +2 19 28
$ Elong. loss +9 5 41
Vol. increase 13 29 N/A
AUTOMATIC
TRANSMISSION
168hr @ 120C
$Tensile loss +10 N/A N/A
Elong. loss +9
$ Vol. increase 6
MOTOR OIL HARMONY #41* TOYOTA 20W-40*
168hr @ 100C 72hr @ 80C N/A
$ Tensile loss +1 +2
$ Elong. loss 2 +20
$ Vol. increase 3 5
HYDRAULIC FLUID:
PYDRAUL 312*
168hr @ 120C
$ Tensile loss 10 N/A 6
$ Elong. loss 9 11
$ Vol. increase 31 N/A
SKYDROL 500B4*
168 hr @ 120C
~ Tensile loss 90 N/A 5
~ Elong. loss 90 7
$ Vol. increase 32 N/A
HYDRAULIC BRAKE NISSAN * SAE J1703f
FLUID 72hr @ 80C 166hr @
80C
$ Tensile loss N/A 8 +.4
$ Elong. loss +21 2
$ Vol. increase 13 N/A
- 15 -
~.'.(:~~~'J~ a
GREr'1SE
168hr @ 120°C TOYOTA MP 2 QUAKER STATE*
~ Tensile loss N/A 0 9
$ Elong. loss +32 13
$ Vol. increase 21 N/A
AS'rM REFERENCE
FUEL C
168hr @ 23°C
~ Tensile loss 7 N/A 6
~ Elong. loss 6 2
$ Vol. increase 24 N/A
* - denotes trade mark
15
25
- 16 -
