Note: Descriptions are shown in the official language in which they were submitted.
20~~~8~
- 1 -
'l W0-I~AYI~_R I'tll;$L~2~8.~'i_'-!C I,Lp~;I;.QMG1~_.allldl:~:l
FIEhD OF THE II1V :N'~~
The present invention relates to a two-:Layer
thermoplastic elastomer sheet. More particularly, t:he
invention relates to a two-layer therrnop.last::i.c: e.l<x:~tomer
sheet which is excellent in vacuum forming properLie:~ and
can provide molded products of excelaent in the s<.~fl.
touch..
SACK ~ROU~p OI' TI1L1..~~LQI9.
Polyvinyl chloride (PVC) resins have been hermt:ofore
widely used as materials for interior automot.:i ve t_ r i.rn.
However, the automotive trim made of the pol.yv:i.nyl c:lrloride
resins have problems in various properties such a::> h<:at
resistance, low-temperature resistance, heat aca.i.ncy
characteristics, light resistance, anti-fogg:Lng prui>c:rties,
odor development, lack of the soft touch anti c:hcat:w-:lookinc~
appearance. For this reason, polyole:Ein the.rnu>plu:~t:i.c:
elastomers excellent in those properties are pa:i.d rrnnc:h
attention as replacements of the polyvinyl. c:h:loriclc: .resins.
In the case of using the pol.yolefin the.r°mopl.a:>tic
elastomer for a vacuum forming sheet, a rubber content in
the polyolefin thermoplastic elast:omer needs t.o b~ :ro:duced
from the viewpoint of vacuum forming propert:i.e::>. 1(caw~ver,
if a sheet made of the polyolefin the:rmoplast:Lc: a l.ust:omer
- 2 -
having a low content of rubber is subjected to vacnunr
forming, the resulting molded product is rig:i.<~ and :lacking
in soft touch (softness).
~g,-rr. ~m of TEtF IlY~l=L7:QI~
The present invention is to solve the ai~ove-mmr~t_ionect
problems existing in the prior arts, and it:. :i> an <W-ject oL
the invention is to provide a two-layer t-hermopla:;l:ic
elastomer sheet which is excellent in vacuum form:i.rpl
.LO properties and can produce molded products exce:l.icW: .in the:
soft touch.
~L~I&$.Y OF TtIE INVEN'PTOI9.
There is provided by the present invention a two-layer
thermoplastic elastomer sheet comprising a sk:i.n .layer [I]
and a reverse surface layer [II], wherein:
the skin layer i.s composed of a thermop:l.a.rst:i<:
elastomer containing a polyolefin resin (A) i.n an amount o.f:
1 to 85 parts by weight and an Cc-olefin <:oF.~c>:tymc.r ~wWber
(B) in an amount of 99 to 15 parts by we:iglrt, t:ot<r 1. amount
of (A) and (B) being 100 parts by we:i.ght;
the reverse surface layer [II] is composed oi: a
thermoplastic elastomer containing a polyo:lc:Fin rea:in (A)
in an amount of 6 to 90 parts by weight and an cx-o l.c:fi.n
copolymer rubber (B) in an amount of 94 to :10 part::, by
weight, total amount of (A) and (t3) bein<~ 700 i>arL::c ly
weight; and
a dif.Eerence [ (I~) - (III) ] between the auumoil. (I~i) o.f
the cx-olefin copolymer rubber (i3) contained :i.n tLm
thermoplastic elastomer of the skin layer (T) and t.hc;
amount (Tlir) of the oc-olefin copo:l.ymer rubber (i3) contained
in the thermoplastic elastomer of the reverse: surf<~cc: layer
(II) is in the range of 5 to X35 parts by we.iglU..
If a light stabilizer i.s added to the t:hc:rmop:lustic
elastomer constituting the skin layer [T] arn<i a E:1<.~me-
retardant is added to the thermoplastic elastomer
constituting the reverse surface layer [II], t.h<:r~ can be
obtained a two-layer thermoplastic elastomur sheet: capable
of producing a molded product which is excellent :i.n .l.i.ght
resistance and flame retardance and is :free from occurrence
of bleedout.
At the same time the two-layer thermop.l.a:~t::i.c c.:i.astomer
sheet can provide molded products having exce:l:l.ent. vacuum
forming properties and the soft touch.
DFTAThED D>SGRIPTTON Of Til>a -.tjyyJ_~~S2il
The two-layer thermoplastic elastomer :>heet of the
present invention is concretely described below.
The two-layer thermoplastic elastomer ;sheet of: the
invention comprises a skin layer [I] and a reverse, surface
layer [II], and these layers are <~omposed <>it:hermcy.>lasti.c
- ~ - 20~~~~~
elastomers (TPE) of different kinds which d:i.f.'fe.r i.n the
amounts of a polyolefin resin (A) and an Oc-ol.ef:in copolymer
rubber (B) contained therein.
Examples of the polyolefin resins (A) :incl.ude;
homopolymers of ethylene or propy:l.ene, and copol.yrrrc:rs of
ethylene or propylene with a small amount o.f: ot:he.r
polymerizable monomer (e. g., propylene-ethya.ene: copolymer,
propylene-1-butene copolymer, propylene-:L-hexe:rre c:of.rol.ymer,
propylene-4-methyl-1-pentene copolymer) . A:> the a:rt>cwe-
mentioned other polymerizable monomers of a snral.l. amount,
there can be mentioned vinyl acetate, ethyl ac:ryl.aate and
methacrylic acid. In the invention, the me:l.t :i.ndex (ASTM-
D-1238-65T, 230 °C) of the polyolefin resin is preferably
within the range of 0.1 to 100, more prefer<rbl.y 5 k:o 50.
As the polyolefin resin, a mixture of polyethylene
(particularly, low-density polyethylene) and pc>:l.ypropylene
having a mixing ratio of 10/90 to 70/30
(palyethylene/polypropylene) can be used for the pu~~pose of
enhancing forming properties (fornrab:ility) and .ue;~ i.utance
of damage of the resulting sheet.
The cx-olefin copolymer rubber. (B) empl.oy<xh:Lc. .i.rr the
invention is an amorphous elastomeric copol.yme:r. containing w
olefin as a host component, such as ethyleno-~>:ropy:l.c:ne
copolymer rubber, propylene-ethylene copo:lymex- :ru1>k~c:r.,
ethylene-propylene non-conjugated dime copo:Lymer rubber,
propylene-ethylene non-conjugated dime copolymer robber,
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ethylene-butadiene copolymer rubber and propy:l.ene-t>ictadiene
copolymer rubber. Further, 'the cx-olefin co~ao:l.ycner .rwbber
is a rubber which is reduced in flowabili.ty o:r :Lo~~~~>
flowability by the crosslinking when it i.s mixed w:it.h
organic peroxide and kneaded therewith under hE:at.i.rcg . The
non-conjugated diene is a generic name to
dicyclopentadiene, 1,4-hexadiene, dicycloctadie;ne,
methylene norbornene, ethylidene norbornene, etc.
Of these copolymer rubbers, ethylene-propylene non-~~
conjugated diene copolymer. rubber, particular:Ly et:hylene-
propylene-ethylidenenorbornene copolymer rubber., i.:~
preferably used in the invention, because <v l.he:rmol>:lastic
elastomer molded product excellent in heat res:i.stan<.:e,
tensile characteristics and impact resilience c:an be
obtained. The Mooney viscosity [MLI~n (100 °C) ] of t:he
copolymer rubber is preferably in the range of 10 t:o 120,
more preferably 40 to 80. In 'the case of using a copolymer
rubber having Mooney viscosity of the above range, a
thermoplastic elastomer product having h:i.gh t:ensi 1. c:
characteristics can be obtained. The iodine va:l.ue (degree
of unsaturation) of the copolymer rubber is prc::terab:Ly not
more than 16. In the thermoplastic elastomer c:onst:i.tuting
the skin layer [I] of the two-layer thermop:l.ast.ic e:lastomer
,:
sheet of the invention, the po:Lyol.ef.in r.esira (A) i.~ used :in
an amount of 1 to 85 parts by weight, pre:Eer-ab:l.y 20 to 80
parts by weight, more preferably 30 to 50 parts by weight,
6
and the Oc-olefin copolymer rubber (B) is used .in an amount
of 99 to 15 parts by weight, preferably 80 to 20 parts by
weight, more preferably 70 to 50 parts by we:i.ght, per 100
parts by weight of 'the sum of the po:Lyolef:i.n resin (A) and
the Ot-olefin copolymer rubber (B).
In the thermoplastic elastomer constituti.nd Lhe
reverse surface layer [II] of the two-layer t:hermop:Lastic
elastomer sheet of the invention, the polyolel::i.n re:~:i.n (A)
is used in an amount of 6 to 90 parts by we:i.ght:, f:>.rc:a:erabl.y
20 to 80 parts by weight, more prefe.rabl.y 30 t.o 50 parts by
weight, and the cx-olefin copolymer rubber (k3) is used in an
amount of 9A to 10 parts by weight, preferably 80 to 20
parts by weight, more preferably 70 to 50 parts by weight,
per 100 parts by weight of the sum of the po:Lyolet:i.n resin
, (A) and the oc-olefin copolymer rubber (B) . 'Phe total
amount of the polyolefin resin (A) and the cx-o:l.efin
copolymer rubber (B) is 100 parts by weight. 11 dif.Eerenc~
[ (In) - (III) ] between the amount (Irs) of the cx-ol.e.Gin
copolymer rubber (B) contained in the thermopl.ast:i.c
elastomer of the skin layer (I) and the amo~:mt (I:fis) of the
cx-olefin copolymer rubber (B) contained in the
thermoplastic elastomer of the reverse surface layer (II)
is in the range of 5 to 85 parts by weight, preFerab:Ly 10
to 70 parts by weight, more preferably 15 l0 50 parts by
weight.
- 7
When two kinds of the thermoplastic elast:omers having
a difference of the above range in the content o.t' k:tre (x-
olefin copolymer rubber (B) are used, a two-:layer sheet
having high vacuum forming properties and capab:l.e o:l
producing a molded product especially soft in k.he touch
In the invention, the thermoplastic el.asi:omer~ of the
skin layer [T] and the reverse surface layer [:II]
constituting a two-layer sheet may contain a peroxi.cte non-
crossl.inkable hydrocarbon gum rubber (C) and/or a mineral
oil softening agent (D) in addition to the po:l.yo.lc:fin resin
(A) and the oc-olefin copolymer rubber (B).
The peroxide non-crosslinkable hydrocarbon gi.rm rubber
(C) employable in the invention is a gum rubber: of
hydrocarbon type which is not crosslinked and is not
reduced in flowability even when it is mixed with peroxide
and kneaded therewith under heating. Examples of the gum
rubber include pol.yisobutylene, butyl rubber (:k:l:R) ,
propylene-ethylene copolymer rubber having propylene
content of not less than 70 o by mole, and atact:ic
polypropylene. Of these, polyisobutylene and k~utyl. rubber
are most preferred because of good performance and easy
handling.
The peroxide non-crosslinkab:le hydroctrrbon guru :rubber
(C) shows an effect to improve flowability of <:r
thermoplastic elastomer composition. Tn the invent::ion, ,.
suitably employed is a peroxide non-crosslinkab.le
hydrocarbon gum rubber having Mooney viscosity [ML,.~,~ (100
°C)] of not more than 60.
The peroxide non-crosslinkable hydrocarbon gum rubber
(C) is used in the invention in an amount o:f 5 to _1.00 parts
by weight, preferably 10 to 50 parts by weight, tTlUre
preferably 15 to 40 parts by weight, per 100 parts by
weight of the sum of the polyolefin resin (A) and the Cc-
olefin copolymer rubber (B).
The mineral oil softening agent (D) emp:Loyable in the
invention is a high-boiling petroleum cut which is
generally used for mitigating intermolecular force of
rubber to facilitate processing of rubber in the roll.-
processing procedure, assisting di.spersibili.ty of carbon
black, white carbon, etc. added as a filler, o.r reducing
rigidness of vulcanized rubber to increase fl.exib:ili.ty and
elasticity thereof. The mineral oil softening agent is
classified into paraffin type, naphthene type, aromatic
type, etc.
A molded product obtained from a thermopl.ast:i.c
elastomer composition containing the naphthene type mineral
oil softening agent shows less surface tackiness as
compared with a molded product obtained from a
thermoplastic elastomer composition containing paraffin
type mineral oil softening agent, so that t:he naphthene
type mineral oil softening agent is more pre:Eerab:l.y used in
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the invention than the paraffin type mineral. oil softening
agent.
In the invention, the mineral ail soften:i.ng agent (D)
is used in an amount of 5 to 100 parts by wei<jht,
preferably 10 to 80 parts by weight, more preferab7.y 20 to
70 parts by weight, per 100 parts by weight. of the sum of
the polyolefin resin (A) and the oc-olefin copolymer rubber
(B) .
The two-layer thermoplastic elastomer sheet ol: the
invention may contain other additives, provided float the
addition of the additives does not mar the object of the
invention. Examples of the additives include po:lyalefin
plastics such as high-density polyethylene, :intermediate
density polyethylene, low-density polyethylene, isotactic
polypropylene and propylene-a-olefin copolymer; inorganic
fillers such as calcium carbonate, calcium silicate, clay,
kaolin, talc, silica, diatomaceous earth, mica powder,
asbestos, alumina, barium sulfate, aluminum su:l:Eate,
calcium sulfate, basic magnesium carbonate, molybdenum
disulfide, graphite, glass bulb and shirasu bal._Loon; and
colorants such as carbon black, titanium oxide, zinc white,
blood red, ultramarine blue, Milori blue, azo pigment,
nitroso pigment, lake pigment and phthalocyanine pigment.
Further, the two-layer thermoplastic el.astomer sheet
of the invention there may be used known heat stab:i:Lizers
such as heat stabilizers of phenol type, su:l.fi.te type,
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~~~8~~~
phenylalkane type, phosphite type and amine type, ag:ing-
inhibiting agent, weathering stabilizer, ant:i_staL.i.c agent,
metallic soap, and lubricant such as wax. 'they can be
added in such an amount as generally used for conventional
polyolefin resins or oc-olefin copolymer rubbers.
If a light stabilizer such as ul.traviol.et absorl>:ing
agent, light absorbing agent and hindered amin<:s is added
to the thermoplastic elastomer constituting the skin :Layer
[I] of the two-layer thermoplastic elastomer sheet: of the
invention and a flame-retardant is added to the
thermoplastic elastomer constituting the reverse surface
layer [IT] thereof, there can be obtained a two-la°ryer
thermoplastic elastomer sheet capable of provicLinc~ a molded
product which is excellent in light resistance and flame
retardance and free from occurrence of bleedout that causes
marked deterioration in merchandise value.
However, if the light stabilizer and ttie .P7.amc:-
retardant are together added to and allowed to present in
the same thermoplastic elastomer according t:o L:he prior
art, occurrence of bleedout could not be preverstecl.
There is no specific limitation on the :Li<~ht
stabilizer and the flame-retardant employab:l.e a.n the;
invention, provided that they are generally used for
conventional polyolefin thermoplastic elastomex~s.
Concrete examples of the light stabili.zer.s prefor~ably
used in the invention include antioxidants of hindered
- 1:1 -
phenol type represented by pentaerythritol-tetrak:is[3-(3,5-
di-t-butyl-4-hydroxyphenyl)propionate] and oc:tadecy:l.-3-
(3,5-di-t-butyl-~1-hydroxyphenyl)propionate; and l.i.ght
stabilizers of hindered amine type represented by
bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate.
In the case of using the above-mentioned l.i.ght
stabilizers of hindered amine type, light stabilizers of
benzotriazole type represented by 2-(3-t-butyl.-5-methyl-2-
hydroxyphenyl)-5-chlorobenzotri.azole. can be employed .in
combination. The antioxidants of hindered phenol type and
the light stabilizers of hindered amine type uay be used
singly or in combination.
The amount of the light stabilizer used i.n the
invention is generally in the range of 0.07. to 0.3 phr,
preferably 0.05 to 0.2 phr.
Concrete examples of the flame-retardants preferably
used in the invention include inorganic flame-retarciants
represented by antimony oxide and aluminum hydroxide; and
halogen type flame-retardants represented by
decabromodiphenyl ether and chlorinated polyethy:lene:.
The organic flame-retardant and the ha7.ogen type
flame-retardant can be employed singly or :i.n comb:i.nal,ion.
When the inorganic flame-retanddnt i.s used, the amount
of the flame-retardant used in the i.yvention i.:~ gene.>:ally
in the range of 10 to 200 phr, preferab~.y 5 to 150 plr.
When the halogen type flame-retardant was used, the amount
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~~~~28~
of the flame-retardant used is generally :in the range of 10
to 100 phr, preferably 25 to 55 ph r.
The thermoplastic elastomer as ment:i.oned above can be
obtained, for example, by dynamically heat-treat:i.n<~ a blend
of the above-mentioned components in the presence o.L
organic peroxide to be partially crosslinked.
The expression "dynamically heat-treat:i.ng a blend"
means that a blend is kneaded in the molten state of
dissolution.
Concrete examples of organic peroxides employable for
preparing the thermoplastic elastomer in the invention
include dicumyl peroxide, di-tart-butylperoxi.de, 2,5-
dimethyl-2,5-di-(tart-butylperoxy)hexane, 2,5-dirnethyl-2,5-
di(tert-butylperoxy)hexine-3, 1,3-bis(tert-
butylperoxyisopropyl)benzene, l,1-bis(tert-butylpe.roxy)-
3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-
butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl
peroxide, 2,9-dichlorobenzoyl peroxide, tent-
butylperoxybenzoate, tart-butylperbenzoate, ter:t-
butylperoxyisopropyl carbonate, d:i.acetyl. peroxide, l.auroyl
peroxide and tart-butylcumyl peroxide.
Of these, from the viewpoints of odor development and
scorching stability, preferred are 2,5-dimethyl.-2,5-
di (tart-butylperoxy) hexane, 2, 5-dimethyl-2, 5-d:i. (temt-
butylperoxy)hexine-3, 1,3-bis(tert-
butylperoxyisopropyl) benzene, :l, 1-bis (tart-butylper~oxy) -
- 13 -
2~~~2~~
3,3,5-trimethylcyclohexane and n-butyl-9,9-bis(tert:--
butylperoxy)valerate, and most preferred is 1,3-bis(t:ert-
butylperoxyisopropyl)benzene.
The amount of the organic peroxide used a.n the
invention generally is in the range of 0.05 to 3 '~ by
cveight, preferably 0.1 to 1 o by weight, more preferably
0.1 to 0,5 ~ by weight, based on the total amount of the
above-mentioned components (A), (B) and (C). When the
amount of the organic peroxide is within the above range,
the obtained thermoplastic elastomer becomes excellent in
properties required for rubbers such as heat resistance,
tensile characteristics, elastic recovery and :i.mpact
resilience as well as excellent in strength and
formability.
As the kneading apparatus, an extruder is used in the
invention. Particularly, an unopened extruder is
preferably used. Kneading is preferably carried out in an
atmosphere of inert gas such as nitrogen or carbonic acid
gas. In the invention, kneading is carried out: at such a
temperature that the half-life of 'the used organic peroxide
becomes shorter than 1 minute (generally at a temperature
of 150 to 230 °C, preferably 170 to 290 °C), far 1 to 20
minutes, preferably 1 to 10 minutes. 'The shearing force
applied in the kneading procedure is in the range of. 10 to
10~ sec-1, preferably 102 to 103 sec-1, in terms of a shear
rate.
- 14 -
In the aforementioned partially crossli.nk:ing
processing using the organic peroxide in the invention,
there can be added crosslinking assistants such as sulfur,
p-quinonedioxime, p,p'-dibenzoylquinonedioxime, N-methyl-
N,4-dinitrosoaniline, nitrobenzene, diphenyl guanidine and
trimethylolpropane-N, N'-m-phenylenedimaleimide;
polyfunctional methacrylate monomers such as divinyl.
benzene, triallyl cyanurate, ethylene glycol
dimethacrylate, diethylene glycol dimethacrylate,
polyethylene glycol dimethacrylate, trimethylolpropane
trimethacrylate and allyl methacrylate; and polyfunctional
vinyl monomers such as vinyl butyrate and vinyl stearate.
By the use of these compounds, homogeneous and moderate
erosslinking reaction can be expected. Of these compounds,
divinyl benzene is most preferably used .in the invention,
because it can be easily handled and is compatible with the
Oc-olefin copolymer rubber and'the polyolefin resin which
are main components of the blend to be treated. further,
divinyl benzene has solvency action for the orc~ariic
peroxide and serves as a dispersing assistant of the
peroxide, so that a composition having homogeneous
crosslinking effect and good balance between f:l.owabil:ity
and physical properties can be, obtained., In the invention,
the crosslinking assistant or the polyfunctional vinyl
monomer is used in an amount of O.l to 2 ~ by weigtrt,
preferably 0.3 to 1 ~ by weight, based on the totaa: amount
- 15 -
of the blend to be treated. When they are used in such
amount, obtainable is a composition which shows high
flowability and brings about no change in physical
properties caused by heating history in the molding .
procedure.
Decomposition accelerators such as tertiary am:i.nes
(e.g,, triethylamine, tributylamine and 2,9,6-
tris(dimethylamino)phenol) and naphthenic acid salts (e. g.,
aluminum, cobalt, vanadium, copper, calcium, z:ircon:ium,
manganese, magnesium, lead and mercury) can be used to
accelerate decomposition of the organic peroxide.
As described above, the thermoplastic elastomer is
partially crosslinked when it is dynamically heat-treated
in the presence of the organic peroxide.
In the invention, the expression "the thermoplastic
elastomer is partially crosslinked" means that the gel
content measured by the following method is not less than
~, preferably in the range of 20 to 99.5 0, morn
preferably ~5 to 98 0.
20 Mt''~s.~~. -m n' of ate 1 .On _ .n
100 mg of a specimen of the thermoplastic elastomer is
weighed out, and it is cut unto pieces having a size of 0.5
mm x 0.5 mm x 0.5 mm. The pieces of the specimen are
immersed in 30 ml of cyclohexane at 23 °C for 48 hours in a
sealed container, then the residue is taken out o:E the
container onto a filter paper, and dried at: roam
- 16 -
temperature for 72 hours until the weight of the specimen
becomes constant.
From the weight of the dried .residue are subt.r~acted
the total weight of the cyclohexane-insoluble components
(fibrous filler, filler, pigment, etc.) other than the
polymer component and the weight of the polyolefin resin
component contained in the specimen before immersing in
cyclohexane, and the obtained value .is "compensated final
weight (Y)".
On the other hand, the weight of the cx-olefin
copolymer rubber contained in the specimen, namely, the
value obtained by subtracting the weight of the
cyclohexane-soluble component l (e.g., mineral. oil and
plasticizer) other than the Oc.-olefin copolymer rubber, the
weight of the polyolefin resin component 2 and the weight
of the cyclohexane-insoluble component 3 (e. g., fibrous
filler, filler and pigment) other than the polymer
component from the weight of the specimen, is "compensated
initial weight (X)".
The gel content is determined by the following
formula:
Compensated final weight (Y)
Gel content (wt.~) _ x 100
Compensated initial weigtxt (X)
17 -
In the present invention, the light stabilizers and
the flame-retardants are added at any steps, constituting
the process for producing the thermoplastic elastomer
composition. FIowever, it is preferred that the flame-
s retardant is added to the thermoplastic elastomer by using
an extruder or Banbury mixer intermediately or with an
elapse of time after the dynamically heat-treatment in the
presence of the organic peroxide.
In the invention, the skin layer [I] composed of the
thermoplastic elastomer constitutes a skin layer of a
vacuum forming molded product. The thickness of the skin
layer [I] constituting a skin layer of the vacuum Forming
molded product is generally in the range of 0.01 to 50 mm,
preferably 0.10 to 20 mm, while the thickness of the other
layer [II] constituting the inner layer of the vacuum
forming molded product is generally in the range of 0.01 to
100 mm, preferably 0.10 to 50 mm.
The two-layer thermoplastic elastomer sheet of the
invention can be obtained by fusing the above-mentioned two
kinds of the thermoplastic elastomers to each other
utilizing, for example, conventionally known extrusion
laminating method or injection molding method.
Otherwise, the two-layer thermoplastic el.astomer sheet
of the invention can be also obtained by fusing two kinds
of sheets having been beforehand molded, which constitutes
the skin layer [I] and the reverse surface layer [:LI] of
- 18 -
the two-layer sheet, at a temperature not lower than the
temperature at which at least one of the two sheets is
melted using a calender roll molding machine, a compression
molding machine, etc.
Further, the two-layer thermoplastic el.astomer sheet
of the invention can be also obtained by fusing a
beforehand molded sheet which constitutes the skin layer
[I] or the reverse surface layer [II] of the two-~.ayer
sheet to a sheet which constitutes the reverse surface
layer [IT] or the skin layer [I] of the two-layer sheet at
the time when the latter sheet is prepared by extrusion
molding or calendering.
The two-layer thermoplastic elastomer sheet of the
invention is generally subjected to vacuum forming with
other core materials to produce a molded product being
particularly soft in the touch.
.F~F ~.r~.T OF THE IN~NTTON
The two-layer thermoplastic elastomer sheet of the
invention is excellent in yaculm forming properties and can
provide a molded product excellent in the soft touch.
Further, the two-layer thermoplastic elastomer sheet
of the invention also shows softness, flexibility and
warmth in its appearance.
The two-layer thermoplastic elastomer sheet of the
invention having the above-mentioned effects can be widely
- 19 -
employed for various interior automotive trim such as
instrument panel.
The present invention is further described by the fol-
lowing examples, but the examples are given by no means to
restrict the invention.
At first, methods for evaluating vacuum forming
properties (formability) and the soft: touch of two-Layer
thermoplastic elastomer sheets obtained by an example and
comparative examples and single-layer sheets produced using
the components of the two-Layer sheets are described below.
[Evaluation Method]
(1) Evaluation on vacuum forming properties (formability)
The sheet is subjected to vacuum forming using a drape
forming mold until the extensibility of the sheet becomes
250 ~ and 900 ~, and then occurrence of sheet break is
observed.
Condition of drape forming: upper and lower heaters
are operated so that the surface temperature of the sheet
is 150 °C.
(2) Evaluation on the soft touch
The surface of the vacuum forming molded product is
touched with fingers, and the touch is classified in o 5
levels.
5: very soft
9: soft
- 20 -
3: normal
2: hard
1: very hard
$KAMPT.~ 1
In -the first place, pellets of two kinds of
thermoplastic elastomers (referred to hereinafter as TPE
(I) and TPE (II)) were prepared as follows.
[Preparation of pellet of TPE (I)]
37 parts by weight of a isotactic polypropylene resin
(i) [melt flaw rate: 13 g/10 min (230 °C)], 63 parts by
weight of an ethylene-propylene-ethylidenenorbornene
terpolymer rubber (ii) [ethylene unit / propylene unit
(molar ratio): 78/22, iodine value: 15, Mooney viscosity
ML1+q (121 °C): 61], and 30 parts by weight of a naphthene
type process oil (iii.) were kneaded at 180 °C for 5 minutes
in a nitrogen atmosphere using Banbury mixer . Than, the
obtained kneadate was cut into angular pellets a sing a
sheet cutter.
Thereafter, with 100 parts by weight of the angular
pellets was kneaded 1 part by weight of a mixture (iv) of
20 wt.$ of 1,3-bis(tert-butylperoxyisopropyl)benzene ,-30
wt.~ of divinyl benzene and 50 wt.o of a parafFin mineral
oil in Henschel mixer. Then, the obtained kneadate was
extruded at 220 °C in a nitrogen atmosphere using an
21
extruder, to prepare pellets of a thermoplastic elastomer
[TPE (1) ] .
[Preparation of pellet of TPE (II)]
The above procedure for preparing the pellets of TPE
(I) was repeated except for using the isotactic
polypropylene resin (i) in an amount of 50 parts by weight
and the ethylene-propylene-ethylidenenorbornene terpolymer
rubber (ii) in an amount of 50 parts by weight, to prepare
pellets of a thermoplastic elastomer [TPE (II)].
Then, a skin layer sheet of a two-layer sheet was
prepared from the above pellets of TPE (I) in the following
manner.
[Preparation of TPE (I) sheet]
The pellets of TPE (I) were melted at 220 °C and
subjected to calendering using a calendering molding
machine (produced by NIPPON Roll, Co., Ltd.), to obtain a
thermoplastic elastomer [TPE (I)] sheet having a thickness
of 0,3 mm.
[Preparation of two-layer sheet]
The pellets of TPE (II).were melted at 220 °C, and the.,
obtained molten TPE (II) was coated on the reverse surface
of the above TPE (I) sheet using a calender:ing molding
22
machine (produced by NIPPON Roll, Co., Ltd.), to obtain a
two-layer thermoplastic elastomer sheet having a thickness
of 0.9 mm.
The obtained two-layer thermoplastic elastomer sheet
was evaluated on the vacuum forming properties and the soft
touch according to the aforementioned evaluation methods.
The results are set forth in Table 1.
.~OM~3Am_rVE EXAMPr_,E 1
A thermoplastic elastomer [TPE (T)] sheet having a
thickness of 9 mm was prepared in the same manner as that
for preparing the TPE (T) sheet in Example 1.
Thus prepared sheet was evaluated on the vacuum
forming properties and softness according to the
aforementioned evaluation methods.
The results are set forth in Table 1.
~,OMPARATTVE EXAM T~ .
The procedure for preparing the TPE (:I) sheet in
Example 1 was repeated except that pellets of TPE (TI) was
used instead of the pellets of TPE (I), to prepare a
thermoplastic elastomer [TPE (II)] sheet having a thickness
of 0.9 mm.
Thus prepared sheet was evaluated on the vacuzum
forming properties and softness according to the
aforementioned evaluation methods.
- 23 -
The results are set forth in Table 1.
~OMPARATTVE EXAMP~~
[Preparation of pellet of TPE (III)]
'Phe procedure for preparing the pellets of TPE (I) in
Example 1 was repeated except for using the isotactic
polypropylene resin (i) in an amount of 10 parts by weight
and the ethylene-propylene-ethylidenenorbornene terpolymer
rubber (ii) in an amount of 90 parts by weight, to prepare
pellets of a thermoplastic elastomer [TPE (III)].
[Preparation of pellet of TPE (IV)]
The procedure for preparing the pellets of TPE (I) in
Example 1 was repeated except far using the isotac is
polypropylene resin (i) in an amount of 97 parts by weight
and the ethylene-propylene-ethylidenenorbornene terpolymer
rubber (ii) in an amount of 3 parts by we9.ght, to prepare
pellets of a thermoplastic elastomer [TPE (IV)].
Then, a skin layer sheet of a two-layer sheet was
prepared from the above pellets of TPE (III) in the
Following manner.
[Preparation of TPE (III) sheet]
The pellets of TPE (III) were melted at 220 °C and
subjected to calendering using a calendering molding
- 24 -
machine (produced by NIPPON Roll, Co., Ltd.), to obtain a
thermoplastic elastomer [TPE (III)] sheet having a
thickness of 0.3 mm.
[Preparation of two-layer sheet)
The pellets of TPE (IV) were melted at 220 °C, and the..,
obtained molten TPE (IV) was coated on the reverse surface
of the above TPE (IIT) sheet using a calendering molding
machine (produced by NTPPON Roll, Co., Ltd.), to obtain a
two-layer thermoplastic elastomer sheet having a thickness
of 0.9 mm.
The obtained two-layer thermoplastic elastomer sheet
was evaluated on the vacuum forming properties and the soft
touch according to the aforementioned evaluation methods.
The results are set forth in Table d.
[Preparation of pellet of TPE (V))
The procedure for preparing the pellets of TPE (I) in
Example 1 was repeated except for using the isotactic
polypropylene resin (i) in an amount of 40 parts by weight
and the ethylene-propylene-ethylidenenorbornene terpolymer
rubber (ii) in an amount of 60 parts by weight, to prepare
pellets of a thermoplastic elastome.r [TPE (V)).
-- 25 -
[Preparation of two-layer sheet]
The pellets of TPE (V) were melted at 220 °C, and the
obtained molten TPE (V) was coated on the reverse surface
of the TPE (T) sheet of Example 1 using a calendering
molding machine (produced by NIPPON Roll, Co., Ltd.), to
obtain a two-layer thermoplastic elastomer sheet having a
thickness of 0.9 mm.
The obtained two-layer thermoplastic elastomer sheet
was evaluated on the vacuum forming properties and softness
according 'to the aforementioned evaluation methods.
The results are set forth in Table 1.
- 26 -
Table 1
Ex. 1 Com. Ex. Com. Com. Ex. Com.
1 Ex. 3 Ex.
2 4
Structureskin single single skin layerskin
layer layer
of vacuumof layer layer of of
of of
forming TPE (I),TPE (I) TPE (II)TPE (III),TPE (I),
molded reverse reverse reverse
product surface surface surface
layer layer layer
of of of
TPE (II) TPE (IV) TPE (V)
Difference
of rubber
content 13 - - 87 3
[part
by
wei ht)
Vacuum
forming
properties
Exterisi-break break break break break
is not is not is not iS is not
bility observedobserved observedobserved observed
of
250 ~
Extensi- break break break break break
is not is is not is is
bility observedobserved observedobserved observed
of
400 $
Softness
Extensi-
bility 5 5 3 5 5
of
250 $ .. .
Extensi-
bility 5 5 3 5 5
of
400 $
Note: Difference of rubber content in Table 1 is obtained
by the formula of [(rubbe.r content of skin layer) - (rubber
content of reverse surface laver)1.
