¦ ELASTIC S~APED ARTICLE
- BACKGRO~lNn ()F TFTF~ TN~ T
. Field of the Inven=;on-
This invention relates to an elastic shaped article
¦excelling in numerous physical properties including mechanical
~strength, thermal resistance, oil resistance, moldability and i
~flexibility, which elastic shaped article is formed of a laminated
material of at least two layers, i.e. one layer of soft polyvinyl
chloride and one layer of other thermoplastic elastomer.
2. Description of ~the Prior Art:
I Heretofore, those ducts, hoses, tubes, sealing menbers
¦and covering members which are used in transportation machines
,Isuch as automobiles and motor bicycles, construction machines such
as bulldozers, industrial machines such as robots, machine tools,
hydraulic machines and pneumatic machines have been manufactured
¦with vulcanized rubbers such as natural rubber and synthetic
Irubber. These raw materials pose problems due to e~haustibility
of natural resources and involvement of a troublesome wor~ of
l vulcanization. For the sake of the preservation of natural
_ resources and the economization of energy, therefore, development
of a ne~ material capable of taking the place of vulcanized
rubber has been longed for.
. In various industrial fields, therefore, studies are
being continued to e~plore the adoptability of such thermoplastic
. ~ .
2~
elastomers as soft polyvinyl chloride which obv.iate the necessity
,iof vulcanization as the raw materi.al for elastic shaped articles
such as automo.tive boots which have heretofore been preponderantly
Ilmanufactured with vulcanized rubbers.
Generally, elastic shaped articles made of soft polyvinyl
;~chloride exhibit high flexi~ility and enjoy relatively satis-
¦¦factory elasticity and moldability. Unfortunately, they are
inferior to the conventional elastic shaped articles made of
l vulcanized rubbers ln terms of mechanical properties such as
10 ¦ tensile strength and tear strength. They also suffer from a `,
disadvantage that their flexibility is gradually impaired as
their hardness is degraded with elapse of time. They have failed ,
to find utility in applications which.demand these properties.
jWhen these elastic shaped articles are used as boots in the
Isteering units of au-tomobiles, for example, they tend to sustain ,
cracks under impacts frequently exerted by flying pebbles and
¦I the fitting parts serving to retain the boots in position tend
I to come out as the boots are gradually deprived of their fle~-
ibility. The elastic shaped articles of thermoplastic elastomers
are further deficient in thermal resistance and in resistance
to oils such as grease, gasoline and rubricants. They have,
therefore, suffered from a disadvantage that they are not usable
¦ where they are liable to be heated to elevated temperatures or
to be smeared with grease, gasoline and lubricants.
Despite the strong demand for the development of an
ideal substitute for vulcanized rubbers as the raw material for
elastic shaped articles such as boots, ducts, hoses, -tubes and
I
- 2 -
3l;2 03;~6CI
other members for use in various machines, there has not yet
heen perfected any elastic shaped article which excels in
various properties such as flexibility, mechanical strength,
thermal resistance and oil resistance and, moreover, enjoys
high moldability.
SUMMARY OF THE INVENTION
This invention, therefore, has been directed to
development of a raw material for the elastic shaped article
which excels in mechanical strengths such as tensile strenyth,
impact strength and tear strength, thermal resistance, oil
resistance and moldability, retains hardness intact despite
aging, and enjoys ideal flexibility.
An object of an aspect of this invention is to provide
an elastic shaped article which excels in mechanical strengths,
thermal resistance, oil resistance and moldabili-ty, retains
hardness intact despite aging, and enjoys high flexibility.
An object of an aspect of this invention is to provide
an elastic shaped article which particularly excels in oil
resistance at elevated temperatures.
An object of an aspect of this invention is to provide
an elastic shaped article possessed of various outstanding
physical properties, which can be manufactured by the blow
molding method, particularly by the co-extrusion bl~w molding
method.
To accomplish the objects described above and other
objects, according to this invention, there is provided an
elastic shaped article of a laminated construction of at least two
61;1)
' .
i layers, comprising:
' (a) a layer of soft polyvinyl chloride incorporating 30 to 220
parts by weight of a plasticizer per 100 parts by weight
Il of polyvinyl chloride having an average polymerization
,¦ degree of 800 to 12,000, and -~
,, (b) a -layer o at least one thermoplastic elastomer selected
¦, from the group consisting of polyester type elastomers,
i polyurethane type elastomers and polyamide type elastomers.
1, In case the elastic shaped article is required to e~ccel
ll in oil resistance at elevated temperatures, the plasticizer to
I be incorporated in the soft polyvinyl chloride layer is required
¦ to possess an aveFa~e molecular weight of at least 700.
BRIEF DESC~IPTION OF ~rF~ nRAWTN~.s
ll FIG. 1 is a partially cutaway front viet~ of a bellows
I boot of a three-layer laminated construction of the present
I invention.
¦ FIG. 2 is a diagram illustrating the hysteresis curve
to be used for the measurement of modulus of elasti.c recovery
1, of bellows.
ll FIG. 3 (A) through (E) are hysteresis curves obtained
¦¦for the elastic shaped arti.cles prepared in E~camples 7 through 10
and Comparative E~cperiment 4.
DETAILED DESCRIPTION OF THE I~VENTION
According to the present invention, as a result of a
2S I study in search for effective combination OL materials for
-- 4
2~6C~
laminated constructions of soft polyvinyl chloride and other
thermoplastic elastomers, it has noT~l been found that an elastic
shaped article of a laminated construction O.t at least two layers,
¦,-comprising a layer of a soft polyvinyl chloride (hereinafter
5 1i referred to briefly as "soft PVC") and a layer of at least one
¦, thermoplastic elastomer (hereinafter referred to ~riefly as "TE")
~i selected from the group consisting of polyester type elastomers
¦ polyurethane type elastomers, and polyamide type elastomers,
¦i e~cels the conventional elastic shaped articles formed solely of
¦I soft PVC in terms of oil resistance and thermal resistance,
¦l retains intact the desirable properties inherent in soft PVC,
Il exhibits improvements in mechanical strengths such as tensile
¦! strength, impact strength and tear strength, retains its
li original hardness intact despite aging for a long time, and
1~ offers high fle~ibility persistently. The wonderful combination
of outstanding properties thus enjoyed by the elastic shaped
article of the present invention is ascribable to the fact that
oThing to the oil resistance inherently possessed by TE, the TE
I layer functions as a barrier membrane between the soft PVC
! layer and an oil: for preventing the plasticizer contained in
¦ the soft PVC layer from p~ssing into the oil and causing a
¦ change in the attributes of the soft PVC and also protecting
¦ the soft PVC layer against degradation by the action of the
oil and the fact that the high mechanical strengths inherently
2S possessed by TE are conferred upon the laminated constructlon. ; j
By -the lamination of the soft PVC layer and the TE layer,
therefore, there is obtained an elastic shaped article which
.- 5
216~
e:~cels in oil resistance as well as in mechanical strengths,
thermal xesistance, moldability and fle~ibility.
Indeed under the conditions of normal room temperature,
the elastic shaped article comprising a layer of soft PVC and
5 ll a layer of TE as described above e~hibits high resistance to
oils.
Il It has been e~perimentally ascertained that despite the
li high oil resistance inherently possessed by the TE layer, the
I¦ elastic shaped article has its resistance to oils degraded under
I harsh conditions involving an elevated temperature (exceeding
¦ 90C), for example, when the plasticizer contained in the soft
PVC layer has a low molecular weight.
I To be specific,it has been ascertained that when the
¦l elastic shaped article is placed under such harsh conditions
15 ¦l involving an elevated temperature, the oil swells the TE layer,
¦~ the oil now in the swelled TE layer accelerates separation of
the plasticizer of a low molecular weight from the soft PVC layer,
and the plasticizer in the soft PVC layer passes into the swelled
I TE layer, with the result that the physical properties inherently
20 1I possessed by the soft PVC will be degraded and the physical
¦I properties inherently possessed by the TE will be impaired.
~ This defect of -the elastic shaped article manifests conspicuollsly,
¦ particularly ~hen the TE has good compatibility ~ith the soft
! PVC in the laminated construction.
A diligent study devoted to the elimination of this
defect has led to a discovery that when the plasticizer contained ~
in the soft PVC layer has an average molecular ~/eight of at least !
I , 1
- 6 -
700, the otherwise possible passage of -the plasticizer from the
soft PVC layer to the TE is substantially precluded and the oil
resistance and other physical properties of the elastic shaped
article are retained intact when the article is placed under
harsh conditions involving an elevated temperature. For the
purpose of obtaining an elastic shaped article which e~chibits
high oil resistance at an elevated temperature in accordance
with this invention, therefore, it is imperative that the
plasticizer contained in the soft PVC should possess an average
molecular weight of at least 700.
The soft polyvinyl chloride (soft PVC) to be used in
the elastic shaped article of the present invention is obtained
by combining 100 parts by weight of polyvinyl chloride having
an average polymerization degree (P) of 800 to 12,000, preferably
1,300 to 10,000, with 30 to 220 parts by weight, preferably
40 to 200 parts by weight, of a plasticizer. If the average
polymerization degree of the aforementioned polyvinyl chloride
is less than 800, the mechanical strengths such as tensile
strength are less than are desired. If it e~ceeds 12,000,
20 ¦i the parison of the laminate during the blo~ molding has poor
surface condi-tions and the produced article suffers from
e~tremel~y poor moldability. If the amount of the plasticizer
incorporated in the soft PVC is less than 30 parts by weight
based on 100 parts by weight of polyvinyl chloride, the produced
shaped article fails to acquire the desired fle~ibility. If
it e~ceeds 220 parts by weight, the shaped article is notably
deficient in mechanical strengths such as tensile strength.
.
-- 7
In order to ensure the elastic shaped article of this invention
to acquire high fle~i~ility and high elastic recovery, the soft
PVC which forms one of the layers of the elastic shaped article
i of this invention is required to possess hardness in the range
i' of 30 to 93 by the Shore ~ scale~ Generally when the amount of
,' the plasticizer incorporated falls in the range mentioned above,
I' the soft PVC incorporating the plasticizer has its hardness
¦l falling in the range just mentioned. When the arnount of incorpo-
¦! ration of a plasticizer is fixed, the hardness of the soft PVC
is slightly variable from one kind of plasticizer to another to
be incorporated. Thus, the amount of incorporation of a
plasticizer is required to be fixed, depending on the particular
kind of the plasticizer selected, so that the soft PVC incorpo-
Il rating this plasticizer may possess hardness falling in the
15 il aforementioned range. Further, the hardness of the soft PVC
,¦ is desired to be lower than the hardness of TE which forms theother layer of the laminated construction of the elastic shaped
article.
I Optionally, the soft PVC may suitably incorporate
1i therein various additives such as filler, stabilizer,
¦~ sta~ilizing aid and pigment. Although the soft PVC to ~e used
in this invention is desired to be made up of virgin materials,
¦ the virgin materials may adulterated with flashes or fins
I occurring during the production of the shaped article of this
invention to a limited e.~tent in which the effect of the present
invention is retained intact.
For incorporation into the soft PVC, any of all the
known plasticizers usable for polyvinyl chloride can be adopted
ithout any particular limitation by kind. Examples of the
~ plasticizer usable ~or this purpose include, but are not limited
to: phthalic esters such as dimethyl phthalate, diethyl phthalate,
j dibutyl phthalate,;di-n-octyl phthalate, di-n-decyl phthalate,
di-n-lauryl phthalate, diisobuthyl phthalate, dipentyl phthalate,
I di-2-ethylhexyl phthalate, diisooctyl phthalate, dinonyl
I phthalate, diisodecyl phthalate, butylbenzyl phthalate,
¦ butyloctyl phthalate, methyloleyl phthalate, butyllauryl
I phthalate, dicyclohexyl phthalate, diallyl phthalate, allyl
¦ cyclohexyl p'hthalate, dimethoxyethyl phthalate and diethoxyethyl
phthalate; phosphoric esters such as tributyl phosphate,
i tributoxyethyl phosphate, tri-2-ethylhexyl phosphate, triisodecyl
Il phosphate, triphenyl phosphate, diphenyldecyl phosphate and
lS ~ diallyl phosphate; aliphatic dibasic esters such' as di-2-
ethylhexyl adipate, diisodecyl adipate, dicapryl adipate,
¦ di-n-octyl adipate', di-3,5,5-trimethylh~xyl adipate, dimethoxy-
¦ ethyl adipate, dlbutoxyethyl adipate, diisobutyl azelate, di-
!i 2-ethylhexyl azelate, dicyclohexyl azelate, di-n-hexyl azelate,
20 li dibutyl sebacate, di-2-ethylhexyl sebacate and diethyl se3acate;
alicyclic dibasic esters such as di-2-ethylhe:cyl tetrahydro-
phthalate, di-n-octyl tetrahydrophthalate and di-2~ethylhexyl
1~ hexahydrophthalate; epoxy plasticizers such as epoxidized
¦~ soybean oil, epoxidized safflot~er oil, epoxi.dized cottonseed
I oil, allyl epoxystearate, ethyl 'epoxystearate, glycidyl
epoxyoleate, glycidyl epoxystearate and epoxystea~l acrylate;
.. I other aliphatic esters such as oleic esters, s-tearic esters,
_
.
ricinoleic esters and palmitic esters; aromatic carboxylic
esters such as benzoic es~ers, trimellitic es.ers, pyromellitic
il esters and trimesic esters; and polyester type plasticizers
¦ obtained by the reaction of dibasic acids with glycols and
S ¦~ generally further with chain stoppers.
For the purpose of obtaining an elastic shaped artiele
which e.Yhibits hlgh resistance to oils under conditions involving
I an elevated temperature, it is necessary,as alreAady pointed
¦ out,to ineorporate into the soft PVC a plasticizer having an
I average moleeular weight (~) of at leas. 700, preferably at
least 900. For the plasticizer which satisfies this requirement,
the amount of ineorporation into the soft PVC is the same as
descrihed above. If the average molecular weight o the
il plasticizer is less than 700, the plastieizer eontained in the
15 ¦I soft PVC layer is dispersed so mueh as to pass into the TE
, layer and even e~ude out of the laminated construetion. For
I the elastic shaped article to possess high resistanee to oils
¦l under eonditions involving an elevated te.nperature, it is
!l imperative that the average molecular ~leight of the plastieizer
¦i should eceeed at least 700.
I A plasticizer satisfying this require~ment ean be
¦ selee-ted from among polyester type plasticizers and epoc~ type
¦ plastiei2ers.
The polyester type plastieizers have structures ~/herein
rLIonobasic acids or monohydric alcohols seal both ends of ehain
polyesters as indicated by the follotling formulas:
L - G ' D - G t- L
A - D ' G - D ~~n A
11 I
-- 1 IJ --
l .
wherein, I, denotes a monobasic acid (such as caproic acid,
capric acid, pelargonic acid, lauric acid or oleic acid), A
denotes a monohydric alcohol (medium to higher alcohol such
Il as capryl alcohol, lauryl alcohol, oleryl alcohol or stearyl
li alcohol), G denotes a glycol (such as 1,2-propylene glycol,
¦ ethylene glycol, diethylene glycol, triethylene glycol, 1,3-
' butanediol, 1,4-butane diol, neopentyl glycol or 1,6-he~ane
diol), and D denotes a dibasic acid (such as sebacic acid,
~ azelaic acid, adipic acid or phthalic aeid).
I Examples of the epoxy type plasticizer advantageously
usable herein inelude plastieizers obtained by epoxidizing
soybean oil, eottonseed oil, sperrn oil, ete.
The thermoplastie elastomer (TE) which is used in the
~l elastie shaped artiele of the present invention is a high mole-
l~ eular substanee whieh at normal room te.nperature exhibits
¦ elastieity of the kind possessed by ~uleanized rubber and which
i at elevated temperatures is plastieized enough to become moldable.In view of the requireAnents for adhesiveness to the soft PVC layer,
I¦ résistanee to oils such as grease, gasoline and lubrieants, and
,l meehanieal strengths sueh as tensile strength, this thermoplastie
¦ elastomer is seleeted from among polyester type elastomers,
¦¦ polyurethane type elastomers, polyamide type elastomers and
eombinations of such elastomers.
, The polyester type elastomers (hereinafter referred to
briefly as "PEE") are multi-block eopolymers ~Jhich have a soft
segment preponderantly eomposed of an aliphatic polyether, an
aliphatie polyester, or an aliphatic polyether ester and a hard
segment preponderantly composed of a high-melting crystalline
aromatic polyester, for example. Theoretically, numerous types
of polyester type elastomers may be obtained by varying the ~inds
and proportions of dibasic acids, glycols, polyesters, and/or
S ¦i polyethers. For example, polytetramethylene terephthalate and
i polyet~ylene terephthalate are available as aromatic polyesters
and polytetramethylene oxide and polyethylene oxide are available
¦ as aliphatic polyethers.
By selecting a polyester type elastomer as TE, there can
be obtained an elastic shaped article which excels in oil
¦ resistance and elongation and echibits high adhesiveness to
¦ the soft PVC.
l The polyurethane type elastomers (hereinafter referred
¦! to briefly as"PUE") are obtained by the polyaddition of polyethers
I, or polyesters and diols with diisocyanate. They embrace those
~ products which additionally use triol, diamine, or triamine
¦, in the course of the polyaddition. Diisocyanates include 4,4'-
diphenylmethane diisocyanate, 4,4'~dicyclohecylmethane di-
isocyanate, and isophorone diisocyanate; glycols include
i ethylene glycol, 1,4-butylene glycol, 1,4-he~ane diol, bis-
hydrocyethoxy benzene; polyester diols include polyethylene
adipate, poly-1,4-butylene adipate, poly-1,6-he.xane adipate,
¦ polycaprolactone, and polycarbonate; and polyether diols include
¦ polyoxytetramethylene glycol.
The polyamide type elastomers (hereinafter referred to
briefly as "PAE") are multi-bloc~ copolymers which have a;soft
segment preponderantly composed of an aliphatic polyether,
. ' I
- 12 -
aliphatic polyester, or aliphatic polyether ester and a hard
segment preponderantly composed of a poly~nide. Theoretically,
various types of polyamide type elastomers can be o~tained ~y
varying the kinds and proportions of polyamides, polyethers and
polyesters. For e~ample, polyamides include polycapramide,
polyhexamethylene adipoamide, polyhexamethylene sebacamide,
polyundecanamide and polydodecanamide; aliphatic polyethers
include polytetramethylene oxide and polyethylene oYide; and
aliphatic polyesters include polyethylene adipate, polycapro-
lactone and polyethylene sebacate.
The TE to be used in this invention is desired to have
hardness falling in the range of 60 to 99 on the Shore A scale
for the purpose of ~onferring desired mechanical strengths upon
the elastic shaped article.
15 l The elastic shaped article of the present invention is
produced by the blow molding technique. This blow molding
comprises co-e~Ytrudin~ plasticized soft PVC and TE in the form
of a multi-layer parison or multi-layer sheet and thereafter
giving the parison or sheet a three-dimensional shape by use
11 of positive or negative pressure.
The lamination involved in this case is to give a
construction of at least two layers, comprising a layer of soft
PVC and a layer of TE. Optionally, the laminated construction
may involve three layers, comprising an inner and an outer layer
each of l'E and an intermediate layer of soft PVC. The elastic
shaped article of -the present invention is desired to have a
laminated construc-tion such that the inner layer cr outer layer
.
.'
- 13 -
~L ~d~
;
haviny the possibilit~ of being e~posed to contact ~,/ith a highly
permeable oil will be formed of TE. Optionally, the laminate~
construction oE the present invention may be superposed by an
A 1l additional layer of a thermoplastic substance or elastomer
5 1l insof~r as the superposition will not appreciable impair -the
effect of the present invention.
As the means for lamination, the multi-layer blow
I molding method by means of co-extrusion is used In this case,
¦l the overall wall thickness ratio of the TE layer to the soft PVC
¦ layer should fall in the range of 90 : 10 to 0.5 : 99.5, pre-
ferably 50 : 50 to O . S : 99 . 5. When this requirement is
fulfilled, the parison is free from the unwanted phenomenon
of draw down and it can be molded advantageously in the shape
¦, of the metal cavity. Conse~uently, the produced elastic shaped
¦l article can be e~pected to acquire uniform wall thic~ness and
¦ exhibit satisfactory elasticity. Besides, the component layers
of the elastic shaped article of the present invention have
very high interfacial adhesive strength and, therefore, are
~ inseparable from each other. The elastic shaped article having
il-such a laminated construction as described above is desired
¦ to possess hardness in the ranye of 60 to 99 by Shore A scale
; ¦ and elastic recovery of bellows of at least 40~O~ preferably at
least 70%.
FIG. 1 represents a bello~s boo-t as one typical embodi-
ment of the elastic shaped article according to -the present
invention. In the drawing, a bellows boot 1 has a three-la~er
laminated construction, comprising an inner and an outer layer
- 14 -
2, 3 each for~ed or TE and an intermediate layer 4 formed of
i soft PVC. In the boot, "a" denotes the bellows portion and "b"
the connecting end portionsO
1 The bellows boot described a~ove is obtained by
'i' preparing the individual layers each of the material mentioned
above, co-e.~k~dirg the layers -to form a multi layer parison, and
blot~ molding this multi-layer parison.
When the elastic shaped article of the present invention
I is molded in a laminated construction of the three layers,
TE/soft PVC/TE, it can be readily bent and elongated with feeble
force owing to the high fle~ibility of the soft PVC. Since
¦ the inner and outer layers are both formed of TE, these layers
e.~cel in impact resistance, oil resistance, weatherability
¦~ and tensile strength owing to the properties inherent in TE.
15 il Thus, the elastic shaped article very rarely sustains fractures
due to impacts of Elying pebbles and is not degraded by grease
Il and other oils and fats, ozone, water, hot water and detergents
¦! such as are use-i for washing cars. The elastic shaped article
¦l of the three-layer l~ninated construction enjoys higher tensile
il strength than the elastic shaped article forrned solely of the
¦l soft PVC. Further,beca-~se the soft PVC is protected by the
opposed coats (layers) of TE, the elastic shaped article
e.~periences little change of hardness at low temperature and
retains its flexibility at low te.~peratures Exen a-t ele~-ated
-temperatures, lt enjoys an effect of minimizing possible
deforrnation under heat.
When the elastic shaped article is produced in a
I - 15 - -
I 1,
three-layer laminated cons'ruction comprisiny an intermediate
layer of soft PVC and an inner and an outer layer each of T~ wi-t:n
the proportion of the wall thickness of the so'-t PVC layer to the
~ total wall thickness of the laminate fixed to exceed 10% and
Ij not exceed 99.5~, the shaped article excels in fleYibility and
¦ enjoys uniform wall thickness. If the ~iall thic~ness ra-tio
¦~ of the soft PVC layer is less than 10%, the eYtruded parison
i suffers from heav~ draw-down and the production of shaped
Il article entails high defective molding ratio, making it no longer
1l possible to produce elastic shaped articles of uniform wall
¦¦ thic~ness stably. Further the elastic shaped article has its
¦I flexibility i~paried so that the portion thereof to be connected
to other fitting member may be divested of its sealability.
¦l If the wall thickness ratio of the soft PVC layer exceeds 99.5%,
11 the TE layer fails to form a complete layer i~here the blow ratio
!i f the shaped article is higher Consequently the produced
¦¦ elastic shaped article is deprived of the properties of TE and
¦ is liable to sustain pinholes in the course of molding. Thus,
¦j the production of shaped article suffers from high defective
ll molding ratio.
~ hen the elastic shaped article is obtained by the blow
i molding method in a laminated construction of the two layers,
soft PVC~TE, the TE layer side of the article maintains impact
, resistance, oil resistance, and tensile strength at high levels
and the PVC layer side maintains fleYibility and moldabillty.
ThLIs, the operation and effect of this elastic shaped article
are substantially the same as the aforementioned article of
.
, ~2~2~6~
. .
, . .
the three-layer laminated construction.
The elastic shaped article according to the present
invention is useful for -the production of boots, ducts, hoses,
I tubes, other sealing members, covering me~lbers and so on which
5 ¦i are e~pected to possess elasticity and oil resistance so as to be
advantageously used in transportation machines such as automo'ciles
and mo-tor bicycles, construction machines such as bulldozers,
industrial machines such as robots, machine tools, hydraulic
¦ machines and pneumatic machines. Although the elastic shaped
¦ article of this invention is primarily molded by the blow molding
method, it is not necessarily limited to a tubular shape.
I Optionally, the elastic shaped article obtained in the tubular
¦¦ shape may be cut into rings, sheets or small pieces each having
¦¦ the laminated construction comprising a layer of soft PVC and
i a layer of TE and adopted or various uses.
~I Depending on the particular use to which the elastic
;shaped article according to the present invention is put, the
I hardness of the article may be suitably selected without departing
¦' from the spiri-t of the invention. When the elastic shaped article
;!
¦l-is used in automotive boots such as shock absorber boots, rack
I¦ and pinion steering gear boots, suspension strut boots and
constant velocity joint boots, it acquires high mechanical
strengths and high elastic recovery of bellows, the pro~es ide
i for automotive boots, by fi~ing the hardness of the TE above
the level of 60 by the Shore A scale, the hardness of the soft
~VC belo~ the level of 87 by the Shore A scale, and the overall
wall thickness ratio of the TE layer to the soft PVC layer in
the range of 50 : 50 to 0.5 : 99.5. Thus, the boots neither
sustain cracks under impacts e.Yerted by flying pebbles nor
;. .
suffer from separation of joined ends owing to loss of elasticity
I but are permitted to manifest the features of this invention.
!! Now, the present invention will be described more
¦I specifically below with reference to working e~amples of this
¦~ invention and comparative experiments. These examples are
¦~ intended solely for the purpose of illustration and not in the
I least for the limitation thereof in any way.
I Example 1
In an extruder having a screw diameter of 50 mm and
i a screw ratio of length to the diameter (L/D) of 22, soft PVC-(l)
¦ and PEE-(l) indicated in Table 1 were melted and kneaded separate-
i ly. Inside an extrusion die, they were joined as a laminate
15 ¦I comprising an outer layer of PEE and an inner layer of soft PVC
and coe~truded in a cylindrical two-layer parison 40 mm in out-
side diameter and 2 ~ in overall wall thickness (with the wall
thickness ratio of the outer layer to the inner layer fixed at
1~ 20 : 80). The e~truded yarison was tightly enclosed in a split
I type mold and then blow molded therein with compressed air.
Consequently, there was obtained a shaped article comprising a
bellows por-tion and connecting portions formed at the opposite
¦ ends of the bellows portion.
l The shaped article had a length of 200 nm, a diameter
11 of 60 r~m at the ridge and a diameter of 45 mm at the yroove
respec-tively of the bellows portion, a pitch of 11.5 n~.m, and an
average wall thickness of 0.7 ~nm It had a laminated construction
.'. ,". Il I
i comprising an inner layer of soft PVC and an outer layer o~ PE~.
,~ E~ample 2: -
ji In the same e~truder, soft PVC-(2) and PEE-(2) "ere
l, melted and kneaded separately. Within an extrusion die, the~
~, were joined as a laminate comprising an intermediate layer of
so~t PVC and an inner layer and an outer layer each of PEE and
coextruded in a three-layer parison having an outer-intermediate-
inner wall thickness ratio of 10 : 80 10. This extruded
~ perison was blow molded to afford a shaped article. The
I shaped article had a three-layer laminated construciton com-
prising an inner layer and an outer layer each of PEE and an
intermediate layer of soft PVC.
The specification of the extruder, the dimensions of
I the parison, and the shape of the shaped article involved in
lS j, this example were the sæ~e as those of Example 1.
Example 3: ' i
~y fllowing the procedure of Example 2, e~cept that
soft PVC-(3) and PEE-(3) were used as the materials and tne wall
i thickness ratio of outer, intermediate, and inner layers was
20 ¦¦ fixed at lS : 70 : 15, there was obtained a shaped article.
Xn the present example, the speciication of the e~truder, the
dimensions of the parison and the shape of the shaped article
were the same as those of E~ample 1.
Comparative Experiment 1:
A shaped article was obtained by extruding a parison
solely of an polyolef illiC elas-tomer shown in Table 1 and then
blow molding the parison. The specification of the extruder,
- 19 -
l6~
the dimensions of the parison and tne shape of ~le shaped article
were the same as those of Example 1.
Comparative Experiment 2:
I, A shaped article was obtained by extruding a parison
I. solely of soft PVC-(2) and blow molding the parison of soft PVC.
The specification of the extruder, the dimensions of the parison
¦.~ and the shape of the shaped article were the same as those of
Example 1.
I The shaped articles obtained in Examples 1-3 and
Comparative Experiments 1-2 as described above were tested for
! various properties. The results of the test are shown in
Table 2
.,
- 20 -
31LZ~216Q
Il Table 1
I!
! ' ,-- . _
'' Kind (S~ore A) Composition ~ ~ieight
j; Soft PVC-(l) 70 Polyvinyl chloride(polymerization
5 lj degree 3000) 100
Il Polyester type plasticizer ~poly-
I' ~ propylene adipate, molecular
weight 2000) 100
Ii Calcium carbonate 20
10 I Epo~idized soybean oil 3
I . Zinc.-calcium stabilizer. . . 2
j _ . .
Soft PVC-(2) 78 Polyvinyl chloride(polymerization
degree 2500) 100
I DOP (di-2-ethylhe~yl phthalate) 70
15 ! Calcium carbonate 20
¦ Epoxidized soybean oil 3
, Zinc-calc.ium stabilizer 2
l .
j Soft PVC-(3) 79 Polyvinyl chloride(polymerization
j degree 2500) (*1) 100
20j, Rinebole (DL 911P) 70
¦I Calcium carbonate 20
. Epoxidized soybean oil 3
' Zinc_calcium stabilizer 2
: (*2)
j PEE-(l) 96 HYTREL HTG-5612
25PEE-(2) 96 PELPRENE P-70B(
¦I PEE- (3) 97 HYTREL HTG-427S(
I ..
I Polyolefinic (*
I elastomer 78 TPE 1800
!
¦ (*l) Rinebole (DL 911P): trademark of Snell Chemical Co. for
plasticizer,
(~2) HYTREL HTG-5612 and -4275: trademar~s oE DuPont Co. for
polyester type elastomers,
(*3) PEL.PRENE P-70B: trademark of Toyobo Co. for polyesLer t~pe
I elastomer,
35. i (*4) TPE 1800: trademark of Sumitomo Chemical Co. for polyol2finic
elastomer.
I .
- 21 -
Table 2
! Examples Comparative
! ......... ... Experiments
~ Properties
- ,, 1 2 3 1 2
Il .
5 ¦I Tensile strength (kg/'cm2) 244 268 271 96 16S
Elongation (~) 377 432 422 320282
I Tear Strength (kg/cm) 94 115 117 5549
Pierce strength (kg/mm) 2.93.0 3.0 1.51.6
¦~l Oil resistance + 0+ 0 + 0 -30 ~ 6
10 I Thermal resistance (~) 7.2602 6.0 26.5 15.4
Hardness 83 85 87 91 78
Elastic recovery of bellows (~) 88 88 85 - 69
I ~
The data of properties obtained of the shaped articles
¦~ of the working e~amples and the comparative ecperiments shown in
15 ll Table 2 were determined by the following tes.ing me-thods.
Tensile strength: JIS~K-6301 (kg~cm )
Elon~ation: JIS K-6301 (~)
¦ Tear strength: JIS K--6301, type B (kg/cm)
Il Oil resistance: JIS K-6301 (The sample was left standing
20 ll in oil, No. 1, at room temperature for 10
days and the change of hardness was measured
and the value of change was reported.)
¦Pierce strength:
I A part of the wall of each of the shaped articles
~ obtained in the working e~amples and the comparative e:c-
¦, periments was cut off and used as a test piece. The test
- 22 -
L6~
. .
piece ~as fastened in position with its periyher~ attached to
a s-tatiorlary frame con~aining a circular openiny 10 mm in
diameter. A needle 1 mm in diameter having its tip rounded
with a radius of curvature of 0.5 mm was placed on the test
5 , piece and lowered down at a speed of 50 + 5 ~/min. under the
conditions OL 2QC and 65% R~Ho The maxirnum load under which
the needle pierced completely through the tes~ piece was
measured. The pierce strength was calculated by dividing the
I value of the maximum load by the wall thickness of the test
10 I piece. This testing method is practical for the evaluation
of the shaped article where the shaped article is intended
for use under harsh conditions such as involving possible
¦ exposure to collision of pebbles of sharp edges.
~ Thermal resistance:
15 I A given shaped article was secured in position by the
¦ upper end, with a weight of a fixed load hung down from the
lower end thereo~. This shaped article was left stznding
j under conditions of an elevated temperature for a stated
¦ length of time. The length of the shaped article was
20 1 measured beEore and after the standing to find any change in
length during the standing as follows:
~ (%) = x 100
Ii . ..
wherein, ~: change ra-tio of shaped article,
~0: length of the shaped article after one hour's
25 ¦ standing under the load, 100 g, of the weight
at 20C and 65~R.H.
~.
- 23 -
0~
ll
: length of the shaped article after one hour's
standing uncler the load, l00 g, of the weignt
at l20CC.
1l Hardness: AST1~1 D-2240 (Shore A)
5 ll Elastic recovery of be]lows:
A given shaped article was n1pped at one end with a
chuck and mounted at the other end on a load cell and was
compressed at a rate of 200 mm/min under the conditions of
20C and 65~ P~.~Ountil all the ridges and grooves of the
bellows portion of the article were brought into tight
contact. Then the shaped article was drawn out at the same
speed to its original shape. During the return, the load was
measured. The magnitude of the load as the function of the
1~ amount of change in size was plotted as hysteresis curve(FIG.2).
15 l l ~! ( % ~ = A x 10 0
~1 -.
¦I wherein, ~ (%): elastic recovery of bellows,
¦¦ Ao : area enclosed with ~l' a, and X axis, and
Al : area enclosed with ~2' a, and X axis.
1 The value of ~ approaches l00 in proportion as the
20 ¦ shaped article nears perfect elasticity. For the shaped
article to find a wider range of applications, the e~cellence
in elastic recovery of bellows constitutes an important
contribute.
1 The aforementioned method for testing the elastic
recovery ofLeUows is quite practical for the evalua-tion OL
1 the shaped artile.
. I ,
- 2~1 -
il ~2al ~
It is noted from Table 2 which compares the properties
. of the shaped articles obtained in the working examples ~"ith those
obtained in the comparative experiments that the shaped articles
, formed in the working examples of this invention possessed
1, excellent mechanical strensths such as tensilestrength, tear
strength, pierce strength and elastic recovery of bellows never
i attainable by the conventional elastic shaped articles formed
I solely of soft PVC in Comparative Experiment 2 and that they
,I possessed eYcellent thermal resistance and oil resistance never
11 attainable by the elastic shaped article formed solely of an ordi-
¦¦ nary polyolefin type elastomer in Comparative Experiment 1~ ;
¦I E~ample 4:
il In an extruder having a screw diameter OL 50 mm and a
¦I screw rati.o of lengh to the diameter (L/D) of 22, soft PVC-(l)
lS 1¦ and PUE-(1) indicated in Table 3 were melted and kneaded separate-
jj ly. Inside an extrusion die, they were joined as a laminatecomprising an outer layer of PUE and an inner layer of soft PVC
¦ and coextruded in a cylindrical two-layer parison 40 mm in outside
Il dlameter and 2 mm in average ~all thickness (with the wall thick-
¦ ness ratio of the outer layer to the inner layer fi~ed at 20 : 80).
¦I The extruded parison was tightly enclosed in a split type mold
¦ and then blow molded therein with compressed air. Consequentlv,
there was obtained a shaped article comprising a bellows
¦ portion and connecting portions formed at the opposite e~ds o~
the bellows portion.
The shaped article had a length of 200 mm, a diameter
of 60 mm at the ridge and a diameter of 40 mm at the groo~e
I
-- ~3
respecti~ely of the bellows portion, a pitch of ll.S mm, and an
i average wall thickness or 0.7 mm. It had a laminated construction
comprisiny an inner layer of soft PVC and an outer layer o~~ PUE.
Example 5:
5 1, In the same extruder, soft PVC-(2) and PUE-(2) were
melted and kneaded separately. Within an extrusion die, they were
joined as a laminate comprising an intermediate layer of soft
¦ PVC and an inner layer and an outer layer each of PUE and co-
¦ extruded in a three-layer parison having an outer-intermediate-
10 ¦ inner wall thickness ratio of 10 : 80 : 10. This extruded parison
was blow molded to afford a shaped article. This shaped article
was substantially identical in shape wlth the shaped article of
¦ Example 4 and had a three-layer laminated construction comprising
1' an inner layer and an outer layer each of PUE and an intermediate
1, layer of soft PVC. The specification of the extruder, the
dimensions of the parison, and the shape of the shaped article
in this example were the same as those of Example 4.
Example 6:
I By following the procedure of Example 5, except that
,i soft PVC-(3) and PUE-(3) indicated in Table 3 as the materials
i and the wall thickness ratio of outer, intermediate, and inner
il layers ~las fixed at 25 : 50 : 25, there was obtained a shaped
article. The specification of the extruder, the dimensicns
I of the parison, and the shape of the shaped article in this
e:can ple weL e the s me as those o- E:<ample 5 .
2~
, .
Comparative Experiment 3;
. A shaped article was obtained by extrudi~g a parison
,. solely o soft PVC-(2) shown in Table 3 and then blow molding
this parison. The specification of the extruder, the dimensions
. of the parison, and the shape of the shaped article in this
I' example were the same as those of Example 4.
¦I The shaped articles obtainea in.Examples 4-6 and
¦ Comparative Experiment 3 were tested for various properties.
¦ The results of the test are shown in Table 4.
- 27 -
~2~
j Table 3
. . .
. Kind Hardness Composition P~s by
(Shore A) ~;eight
', Soft PVC-(l) 70 Polyvinyl chloride(polymerization
¦ degree 3000) 100
. Polyester type plasticizer (poly-
,1 propylene adipate, molecular
weight 2000) . 100
Calcium carbonate 20
o ! Epoxidized soybean oil 3
i Zinc-calcium stabilizer 2
¦ Soft PVC-(2) 78 Polyvinyl chloride(polymerization
I degree 2500) 100
¦ DOP (di-2-ethylhexyl phthalate) 70
15 ¦ Calcium carbonate 20
¦ Epoxidized soybean oil 3
¦ Zlnc-calcium stabilizer 2
l Soft PVC-(3) 79 Poly~inyl chloride(polymerization
I degree 2500) 100
20 1~ Rinebole (DL 911P) ,70
i Calcium carbona-te 20
Epoxidized Soybean oil 3
. . Zinc-calcium stabilizer 2
' * 1 `
j PUE-(l) 90 ELASTOLLAN E-590`
25 i PUE-(2) 85 ELASTOLLAN E-585(
_ -- i
P~E-(3) 90 ELASTOLLAN E-390(
I
(*1) - (*3) ELASTOLIIAN E-590, E-585, E-390:
trademar~s of Japan Elastollan Co. for
polyurethane type elastomer.
~ ~ _
c~
Table 4
; . . .
. ~ Comparative
. Examples E~periment
Properties
1~l 4 5 6 3
i. Tensile strength (kg/cm2) 251 273 295 165
¦ Elongation (%) 395 460 380 282
Tear strength ~g/cm) 107 98 105 49
Pierce strength (~g~mm)4.7 4.7 5.5 1.6
. Oil resistance + 0 + 1 + 1 + 6
I Thermal resistance (%) 7.4 6.8 6.3 15.4
I Hardness 85 82 84 78
¦ ~lastic recovery of bellows (%) 88 90 87 69
I ......................................... _
E~amples 7-10 and Comparative Experiments 4:
lll In an extruder having a screw diameter of 50 mm and a
lS 1l screw ratio of length to the diameter (L/D) of 22, a varying
l thermoplastic elastomer indicated in Table 5 was melted and
¦ kneaded. Inside an ectrusion die, it was given a layer const-
ruction shown in Table 6 (in the case of a multi-layer construc-
tion, the individual layers were joined within the extrusion die)
¦ and e~truded in a cylindrical parison (in the case of a multi-layer
¦ construction, coe~truted in a cylinderical multi-layer parison)
40 mm in outsicle diameter and 2 mm in overall wall thickness.
This e~truded parison was tightly enclosed in a split type metal
¦ molcl ancl blo~ molded therein with compressed air. Conseqùently,
I there was obtained a shaped ar-ticle comprising a bel.lo~ls
portion and connecting portions formed at the opposite ends oE-
I . ~ ,
11 2~211 Ih~
the bellows portion~
The shaped article had a length of 200 mm, a diameter
i of 60 mm at the ridge and a diameter of 45 mm at the sroove
l,. respectively of the bellows portion, a pitch of 11.5 mm, and an
S ¦. average wall thic!cness of 0.7 mmO In Examples 7 and 10, theshaped articles were each in a two-layer construction comprising
an inner layer and an outer layer. In Examples 8 and 9, the
~¦ shaped articles were each in a three-layer construction comprising
i an inner, an intermediate, and an outer layer. In Comparative
¦; Experiment 4, the shaped article were composed solely of soft
PVC. The layer constructions of the shaped articles of the
working examples of this invention and Comparative Experiment 4
are shown in Table ~.
I The data of the physical properties obtained of the
i shaped articles of the wor.'cing e~amples and Comparative E~periment
1 4 are shown in Table 7 and the hysteresis curves obtained of
, the shaped articles of Examples 7, 8, 9 and 10 are indicated
¦1 in FIGS. 3(A), (B), (C) and (D) respectively and the hysteresis
li curve obtained of the shaped article of Comparative E~periment 4
20 ¦1 is indicated in FIG. 3 (E). In the graphs of FIGS. 3, the con-
¦~ tinuous lines represent the data obtained of the respective
I¦ shaped articles before their immersion in oil and the dotted
lines the data of the sane respective shaped articles after
tneir L~nersion in oil.
l l
~ 'I
I ~ 30 -
Il ~
!l I
~2~2~
Tanle 5
.
.
Kind ... Composition ............... Par-s by
~-e~an~
TE.-.(l) . P.o.lyester type elastomer."P rlpRENE p-70B~
TE-(2) . . . P.o.lvester.type elastomer. "HYT.~EL HTG-4275"
Il TE-(3) Polyurethane type elastomer "E~ASTOLLAN
¦I E-585"
TE-(~) Polyamide type elastomer "DI~ E PAE (
I ~-3798"
10 j Soft PVC-(l) Polyvinyl chloride (P 3,000) l00
Plasticizer (adipic acid-propylene glycol
type, M 2,000) l00
Calcium carbonate 20
¦ Epoxi.d1zed soybean oil 3
15 ¦! Zinc-calcium stabilizer 2
¦ Soft PVC-(2) Polyvinyl chloride (P 2500) . l00
Plasticizer (adipic acid-propylen~ glycol
! type, ~1 l,000) 70
¦ Talc 20
20 ' Epoxidized soybean oil 3
i Zinc-calcium stabilizer 2
:
Soft PVC-(3) Polyvinyl chloride (P 3,000) l00
Plasticizer (sebacic acid-propylene glvcol
¦ type, ~1 2,000) l00
25 I Calcium carbonate . 20
Epocidized soybean oil 3
. . . Zinc-calcium stabilizer .. -. . 2
- 31 ~
~ ~ '- " ' ~
o~
!.
, ' Table 5 - continued
' Kind Composition Parts by
- - ~,~_qht
~ Soft PVC-(a~ Polyvinyl chloride (P 2,500) 100
5 ,' Plasticizer~adipic acid-propylene glycol
type, M 1,200) 70
Calcium carbonate 20
Epoxidized soybean oil 3
1 - - Zinc-calcium,st.abilizer 2
! ~
,I Soft PVC-(5)Polyvinyl chloride (P 2,500) 100
i D~O~Po (di-2-ethylhexyl phthalate, ~1 390) 70
, Calcium carbonate 20
Epoxidized soybean oil 3 -
.I Zinc-calcium stabili~er 2
Il ~
~,~ (*l) DI~IDE PAE X-3798: tradernar~ or Daicel Che~nical Co. for
Il polyamide type elastomer.
I I
¦i Table 6
Il . . . ~
li - - i
E~amples Comparative -
, E.cperlment
j ' , 7 8 9 10
.Construction
Outer la~erTE-(l) TE-(2) TE-(3) TE-(4)
Intermediate layer - PVC-(2) PVC-(3) ~
ll Inner layerPVC-(l) TE-(2) TE-(3) Coft
li Wall thickness ratio
¦ ou-ter layer 20 10 15 30
¦ :[ntermediate layer - 8070 -
; ¦ Inner layer , 80 10 15 70
. . . I
- 32 -
!l
Table 7
. . . . .
Examples ~ Comparati~e
. E~cperiment
Properties
7 8 9 10 4
1, . . .... _
1 Tensile--strength (kg/'cm ) 244 273 281 178 165
i, Elongation (~) 375 425 ~60 340 282
~ Tear strength (kg/crn) 97 119 98 78 43
I
¦ Pierce strength (kg/mm) 2.6 3.0 Sol 2.4 1.5
I Thermal resistance (%) 6.8 5.6 6.9 7.3 17.4
'I Hardness (before immersion) 87 88 82 83 78
j (after immersion) 88 88 84 84 98
Elastic recovery of bellows
~before immersion) 85 83 89 82 80
ll (after immersion) 82 82 83 82 8
15 ¦i The test for hardness and that for elastic recovery of
¦ bellows were determined by the foliowing testing methods.
¦¦ Hardness:
¦' (Before immersion) ASTL~ D-2240 (Shore A)
¦i (After i~nersion) JIS K-6301, with the tes-t piece i~nersed
20 ¦ in oil, ilo. 3, at 120C for 70 hours and
ll tested for hardness after the immersion.
¦¦ Elastic recovery of bellows:
¦l (Before immersion) Same as the testing method described
i , I
previousl~. I
25 ¦(After i~nersion) JIS ~-6301, with the test piece inunersed j
; ¦in oil, No. 3, at 120C for 70 hours and ¦
I I
- 33 -
tested for elastic recovery of bellor~s
after the immersion.
It is noted from Table 7 which compares the data of
physical properties obtained of the shaped articles of the wor~ing
5 i1 examples of this invention with those obtained of the shaped
j article of Comparative Experiment a that the shaped articles
¦ formed in the working e:~amples exhibited e~cellent mechanical
Il strengths such as tensile, tear and pierce strength never
l; attainable by the shaped article formed solely of soft PVC in
, Comparative Experiment 4. Further it is clear from Table 7 and
i FIGS. 3 that the shaped articles obtained in the wor~ing example
¦~, of this invention showed substantially no change in hardness and
elastic recovery of bellows before and after immersion in oil.
Il In contrast, the shaped article obtained in Comparative Experi~ent
lS 11 4 showed notable changes in hardness and elastic recovery of
bellows before and after i~ersion in oil. After the immersion
in oil, this shaped article showed greatly increased hardness and
j notably lowered elastic recovery of bellows. These test results
I indicate that in the shaped articles obtained in accordance with
Il this invention, the plasticizer in the soft PVC layer is preverted
¦, from passing into the TE layer and the fle~ibility and elastici~y
¦11 inherently possessed by soft P~C a~e retained intact and the
¦¦ oil resistance and mechanical strengths inherent in TE are
¦ retained intact even under harsh conditions. Thus, the present
I invention is capable of producing elastic shaped articles of
outstanding properties.
- 34 -
