Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 This invention relates to a watex~swellable
elastomer composition consisting essentia.lly of an elas-
tomer, a water absorbent resin and a water-soluble resinO
Heretofore, there has been proposed the use of
a water-swellable rubber which is produced by mixing a
rubber with a water-absorbent material such as crossli~ked
polyvinyl alcohol, crosslinked polyacrylate, crosslinked
starch-acryla~e copolymer, crosslinked carboxyme~hyl-
cellulose or the like; a water-swellable urethane resin;
a hydrophilic group-containing rubber; or the like for the
purpose of the caulking or sealing of gaps or the stopping
of water in civil engineering and construction works or
the like, or the preservation of airtightness in machinery
and apparatus [Japanese Patent Application Kokai (Laid-
Open) Nos. 33,032/81 and 190,065/82~.
However, if watex-swellability is imparted to a
rubber by mixing a water-absorbent material therewith, the
swelling rate and degree of swelling of the rubber are
low, and in addition, the rubber has also such problems
that the water-absorbent material is separated off upon
contacting with water for a long period of timel so that
the swellability is ultimately lost, the strength is
remarkably decreased, and water is polluted.
When a water-swellable urethane resin or hydro-
philic gxoup-containing rubber is mixed with a rubber,
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1 ~he water-swellability of the rubber thus obtained is
inferior because these have a low degree ~f swelling and
a low swelling rate, and therefore, no satisfactoxy efect
can be expected.
The present inventors have conducted exten~ive
research for the purpose of overcoming the above-men~ioned
problems. As a result thereof, they have found that when
a water-absorbent resin and a water-soluble resin are homo-
geneously dispersed in an elas~omer, the water-absorbent
resin can be prevented from being separated off, and a water-
swelling elastomer cQmposition having an extremely high
swelling rate and an extremely high degree of swelling, is obtained.
An object of this invention is to provide an
elastomer which can be swollen with water.
1~ Another objec~ of this invention is to provide
a water-swellable elastomer composition having an extremely
high swelling rate and a high degree of swelling.
Other objects and advantages of this invention
will be apparent from the following description.
~0 According to this invention, there is provided
a water-swellable elastomer composition having a high
swelling rate a~d a high degree of swelling, said com-
position consisting essentially of a homogeneous mixture of an
elastomer, 5~300 parts by weight of a water-absorbent resin
per 100 parts by weight of the elastomer and wherein said
water-absorbent resin absorbs water in an amount of at least
20 times the weight of the resin and has a particle size of
400 ~m or less, and 1-50 parts by weight of a water-soluble
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resin per 100 parts by weight of the elastomer.
The elastomer used in this invention includes a
natural rubber and a synthetic rubber. The synthe~ic rubber
includes many known rubbers such as chloroprene
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1 rubbex, butadiene rubber, styrene~butadienerubber,
acrylonitrile-bu~adiene xubber, isobutylene isoprene
rubber, fluororubber, ~thylene-propylene rubber, chloro-
sulfonated polyethylene, silicone rubber, urethane rubber,
S polyaulfide rubber, acrylic rubber and thf~ like, and it is
preferable to use chloroprene rubber or st:yrene-butadiene
rubber from ~he standpoint of processability and economy.
These rub~ers can be properly selected depencling
upon the application fields of water-swellable rubbers.
For instance, chloroprene rubber or chlorosulfonated
polyethylene are suitable for the requirement of weathçr
resistance, and silicone rubber or fluororubber are pre-
ferred when heat resistance is required.
The water-absorbent resin used in this invention
includes crosslinked products of polyacrylates, crosslinked
products of starch-acrylate graft copolymers, crosslinked
products of a hydrolyzate of starch-acry~onitrile graft
copolymer, crosslinked products of carboxymethylcellulose,
crosslinked products of polyvinyl alcohol, crosslinked
products of a hydrolyzate of methyl (meth)acrylate-vinyl
acetate copol~mer, crosslinked products of cellulose-sodiu~
acrylate graft copol~mer, and the like, and in particular,
crosslinked products of polyacrylates have an excellent
effect.
Although any of the above water-absorbent resins
can be used in this invention, it i5 necessary to use a
water-absorbent resin which absorbs water in an amount of
at least 20 times the weight of the resin.
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1 The water soluble ~esin used in this invention
includes polyethylene oxide, polyvinyl pyrrolidone, hydroxy-
ethylcellulOse, hydroxypropylcellulose or ~he like. Poly
ethylene oxide and polyvinyl pyrrolidone are preferably used
from the standpoint of rubber-compatibility and processabi-
lity because they are ~hermoplastic, and a water swellable
elastomer containing polyethylene oxide or polyvinyl
pyrrolidone is preferred in view of the appearance and
pexformance.
The amount of the water-absorbent resin added is
5-300 parts by weight, preferably 10 200 parts by weight,
per 100 parts by weight of the elastomer. If the content of
the water-absorbent resin is too small, neither a sa-tisfactory
swelling rate nora satisfactor~ degree of swelling are
obtained. On the other hand, if the content is too large,
the water~absorbent resin is separated off from the
elastomer, and th composition becomes in some cases un-
suitable for water stopping ox water retention.
A water-swellahle elastomer obtained by mixing an
elastomer only wi~h a water-absorbent resin as i~ usual in
the conventional method exhibits only a slow swelling
rate and a low degree of swelling. Moreover, the water-
absorbent resin is separated off from the water-swellable
elastomer in some cases, and.hence, the purpose is not
achieved.
However, by adding a water-soluble resin
together with a water-absorbent resin to an elastomer
according to this invention, a homogeneous water-swelling
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1 elastomer composition is obtained, and when it contacts
with water a swollen product which has a high degree of
swelling/ is homogeneous and has a smooth surface, is
obtained from the water-swelling elastomer composition.
~he amount of the water-soluble resin added is
0.5-100 parts by weight, pre~erably 1-50 parts by weight,
per 100 parts of the elastomer. If the amount of the
water-soluble resin is too small, the intended effect of
the addition cannot be obtained and the degree of swelling
of the elastomer is low. If the amount of the water-
soluble resin is too large, the degree of swelling is not
so much increased, and adverse effects such as elution or
the like tend to take place.
The particle diameter of a wa-ter-absorbent resin
used in this invention is 400 ~m or less, preferably 100 um
or less. If the particle becomes finer, a more homogeneous
composition is obtained, and a swollen product obtained
therefrom becomes homogeneous.
When 10-100 parts by weight of water per 100 parts
by weight of the water-absorbent resin is previously contain-
ed in an elastomer prior to mixing the elastomer with the
water-absorbent resin, a water-s~elling elastomer composi-
tion having an extremely high swelling rate is obtained.
If the amount of water is too smalll the effect is not suf-
ficient. Qn the other hand, if the amount of water is toolarge, mixing operation becomes difficult. As for the
stage of enabling wate~ to be contained it is not always
necessary to previously contain the water in the water-
absorbent resin, and an equivalent effect is obtained by
1 adding water at the time of mixing
The water-swellable elastomer of this invention
is produced by uniformly dispersing a water-absorbent resin
and a water-soluble resin in an elastomer by a mechanical
procedure. For example, roll mixing~ mixing with a
Banbury mixer, mixing with an extruder~ or the like are
mechanical dispersing methods which are applicable to
this invention. A vulcanizing agent and a vulcanization
accelerator are mixed during the mixing procedure in this
invention, and if necessary, a coloring agent, a filler,
a plasticizer, an antioxidant and the like are incorporat-
ed. The compound obtained by mixing is heat-vulcanized
and molded according to a conventional method to form a
water-swellable elastomer composition in the form of a
plate, rod or the like depending on intended uses.
The water-swellable elastomer of this invention
can be applied to various uses as water-stopping material,
water-retaining material, medical supplies and the like,
and suitable compounding recipes are selected depending
upon uses to form compositions.
This invention is further explained in detail
below referring to Examples and Comparative Examples.
However, it should not be interpreted ~hat this inven-
tion be limited to the Examples.
Degree of swelling in the Examples and Compara-
tive Examples is defined as follows:
Degree of swelling = -a a_ x 100 (%)
a: weight before swelling
b: weiyht after swelling
1 The size of a s~mple is 2 x 4 cm with a thick-
ness of 1 mm.
In the Examples and Comparative Examples all
parts are hy weight unless o~herwise specified.
Example 1
A compound obtained ~y roll-mixing a chloroprene
rubber (Toyo Soda Mfg. Co., I,td.: "Sk~prene B-30)" as an
elastomer, a crosslinked product of polysodium acrylate
tSeitetu Kagaku Co., Ltd.: ~quakePp 4S, average particle
diameter, 70 ~ as a water-absorbent resin and a poly-
***
ethylene oxide (Seitetsu Kagaku Co., Ltd.: PEO-3~ as
a water-soluble resin in the amounts shown in Table 1
was vulcanlzed at 150C at a pressure of 150 kg~m2 G
for 30 minutes to prepare a water-swellable elastomer
composition. A sheet of 29 x 40 x 1 mm was formed from
this elastomer composition, and soaked in ion-~xchanged
water to swell the sheet.
The degrees of swelling are shown in Table 2.
* Trademark
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*** Trademark
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Table 1
~ ... ~ __ _ _
Component Part
__ _ _ _ __ ~ _~
Chloroprene 100
Carbon black 30
Zinc white S
~Sagnesium oxide
Stearic acid
Ethyl~ne thiourea 0.5
Aquakeep 4S" (trademark) 100
Polyethylene oxlde 10
__ _ _ .
Table 2
__.
Soaking Time 10 min 1 hr 24 hrs
~j _ _ _
Degree of 40 98 830
swelllng ( % )
_ _ _ _ _ _
1 Example 2
A compound obtained by roll mixing a styrene
butadiene rubber ISumitomo Chemical Co., Ltd.: Sumitomo
SBR 1778S) as an elastomer, a crosslinked product of
polysodium acrylate ~Seitetsu Kagaku Co., Ltd.~ "Aquakeep
4S, average particle diameter, 70 ~m) as a water-absorbent
resin and a polyethylene oxide iSeitetsu Xagaku Co., Ltd.:
**
"PEO-3) as a water-soluble resin in the amounts shown
in Table 3 was vulcanized at ~50~C at a pressure of
* Trademark
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1 150 kg/cm2 G for 30 minukes to produce a water-swellable
ela~tomer composition. The degree of swelling deter
mined in the same manner as in Example 1 are shown in
Table 4.
~able 3
_~ .
Component Part
~ ____
Styrene-butadiene rubber 100
Carbon black 30
Sulfur 4
2-Benzothiazyl disulfide
Tetramethylthiuram disulfide
Aquakeep 4S 100
Polyethylene oxide 10
Water 30
_ _ . . _ _
Table 4
~ . .
¦ Soaking Time 10 min1 hr 24 hrs
~ _
¦ Degree sf 75 240 1~570
I swelling (~)
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Comparative Example 1
A water swellable elastomer composition was
prepared in the same manner as in Example 1, excep~ that
the polyethylene oxide was omitted. Because of the
absence of polyethylene oxide, the components were
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1 unable to be hsmogeneously mixed, and the water aksorbent
resin was remarkably separated off from th~e elastomer
2 hours after the soaking in water.
Comparative Ex~mple 2
A water-swelling elastomer composition was
prepared in the 6ame manner as in Example 2, ~xcept
that the polyethylene oxide was omitted. The degxees of
swelling determined in the same manner as in ~xample 1
are shown in Table 5.
Table 5
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Soaking Time 10 min 1 hr 24 hxs
_ __ _ e ~ _ .
swelling (%) 18 _ _ 315
Example 3
A water-swellable elastomer composition was
prepared in the same manner as in Example 2, except that
a crosslinked product of starch acrylate graft copolymer
(Sanyo Chemical Industry, ~td.: Sanwet IM-300t was used
~5 as a water~absorbent resin ins~ead of ~he crosslinked
product of polysodium acrylate. The degrees o swelling
determined in the same manner a in Example 1 are shown
in Table 6.
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Table 6
Soaking Time 10 min 1 hr24 hrs
~ _ . _ ~
Degree of 50 1701,150
swelling (%) ~
_ _ _ ~ ~
1 Example 4
A water-swellable elastomer composition was
prepared in the same manner as in Example 2~ except
that a hydroxyethylcellu}ose ~FU3I C~EMICAL CO., LTD.:
Fujihec AH-15) was substituted for the polyethylene
oxide. The degrees of swelling determined in the same
manner as in Example 1 are shown in Table 7.
Table 7
_ _ _ ~ _
Soaking Time 10 min 1 hr 24 hr~
_ _ _ _ ~ _ .
Degree of 40 150 1,050
swelling (%)
_ _ _ _ ~ _ _
Example 5
A water-swellable elasto~er composition was
prepared in the ~ame manner as in Example 2, except
that a polyvinylpyrrolidone lKISHIDA KAGAKU: K-15
was substituted fox the polyethylene oxide.
Soaking the sheet obtained in water for a
predetermined time and observing the surface state, the
swollen product was fou~d to be smooth and slimeless.
* Trademark
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1 The degrees of swelling determined in the same manner
as in Example 1 are shown in Table 8.
Table 8
Soaking Time 10 min 1 hr 24 hrs
~ _ ~ _
swelling (~) 60 210 1,250 .
Examples 6 - 10
A water-swellable elastomer composition was
prepared by vulcaniæing at a pressure of 150 kg/cm2 G
at 150C for 30 minutes a compound obtained by roll-
mixing the components shown in Table ~ in the same
manner as in Example 1. The degrees of swelling
determined in ~he same manner as in Example 1 are shown
in Table 10. The swollen sheets had favorable surfaces
which were smooth and slimeless.
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Table ~
~Parts)
__ _ __ _ _
Example No. 6 7 8 9 10
. . ___ _ _ _ _ _
EPT 100
NR 100
CSM 100
NBR 100
IIR 100
Carbon black 30 30 30 30 30
Zinc white (ZnO) 3 3 5 5
Magnesium oxide ~gO) 5
Sulur (S) 1.5 2 1.5
Stearic aci.d 1 1 1 1
Vulcanization
accelerator M 0.5
" TT 1~0 0.5
It BZ
" TRA 2
" DM 0.5
,i P2
Antioxidant (Antigen NBC~ 1
Process oil 10 10 10 10 10
A~-4S' (trademark) 70 70 70
Waterlock ~-100" (trademark) 70
Sumikagel S-50" (trademark) 70
Water 35 35 35 35 35
PVP 15 15 15 ~5 15
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Nste:
~ Com~ound Trade Mark ~
EPT- Ethylene-propylene Esprene 505" Sumitomo Chem.
terpolymer rubber
NR- Natural rubber ~ -
CSM: Chlorosulfonated ~ypalone 40" Dupont
polyethylene rubber
NBR: Nitrile rubber "Nipole 1042" ~ippon Zeon
obutylene-isoprene ~SSOBUTY~ 268 Esso. Chem.
rubber
M: 2-Mercaptoben20-
thiazole
TT: Tetramethylthiuram
disulfide
BZ: Zinc dibutyl-
dithiocarbamate
TRA: Dipentamethylene-
thiuram tetrasulfide
DM: Dibenzothiazyl
disulfide
PZ: Zinc dimethyl-
dithiocarbamate
Anti- Nickel dibutyl- "~nt,lgen
oxidant dithiocarbamate NBC Sumitomo Chem.
AK-4S: Crosslinked product "Aquakeep 4S" Seitetgu
of polysodium Ragaku
acrylate
"Water Crosslinked saponi Grain-
lock * fication product proce~sing
-A100:" of starch-acrylo- Corp.
nitrile copolymer
"Sumikagel Crcsslinked saponi- Sumitomo Chem.
5~50:"** fication product o
methyl acrylate-vinyl
acetate copolymex
PVP: Polyvinylpyrrolidone ~ 15 KISHIDA K~GAKU
* Trademark - 14 --
** Trademark
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Table 10
Soaking Tlme 10 min 1 hr 24 hrs
_ _._ __ _ _ _ ._
Example 6 30 70 580
,- 7 25 65 520
" 8 30 70 600
,. 9 20 60 500
" 10 30 75 530
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