Note: Descriptions are shown in the official language in which they were submitted.
107~90
The inventlon relates to a floating fender from rubber
or an elastic plastic, especially meant for use on behalf of
ships or drilling platforms, which should also be provisioned,
loaded and unloaded in the open sea at a high wind-force, or for
use in locks. Another application possibility is formed by
heavy-draught tanker-vessels, which pump a portion of their
load over into smaller tanker-vessels Stable floating fenders,
which absorb the possible shocks and which separate both ships,
are indispensable for this difficult nautical manoeuvre.
Especially for tanker-vessels of large dimensions the
pressure exerted from the outside on the ship's wall may not
exceed an amount of about 50 tonsJm2. This leads to the use
of fenders of a very large volume, with which it is possible to
reduce large occurring forces to limited pressures (per m2).
Moreover, the presence of a limited amount of man-power on board
of large vessels leads to endeavours towards large units with
a minimum total number of fenders needed.
Starting from the large dimension of the fenders to
be used for the above purpose the embodiments known in this
respect appear to give large problems in the practice.
For example, use is made of an air-filled, balloon-
s~aped fender, connected to the ship by one or more cables and
floating on the water surface. Bésides a high vulnerability
(chance of damage), whereby the fender may sink and get lost,
this construction has the disadvantage that this fender is
easily thrown back on board of the ship from its floating condi-
tion in case of rough weather, which may be lead to damage of
ship-parts and to personal accidents.
~ urthermore, fenders of massive rubber are known having
a density of more than 1.0 which are usually attached at their
extremities to the ship by means of cables, for which purpose
a shaft or frame may have been incorporated in the rubber mate-
.
- B
990
rial An advantage of this construction is present tha-t in
comparison with the pneumatic fender, which exactly follows each
undulatory motion, this massive fender can be suspended complete-
ly or partially under the water, whereby it stays better where
it is with respect to the ship A disadvantage, h~wever, is
that on contrary movements of the ships the fender may be pushed
down, the cables may break and the fender may sink and yet lost,
and furthermore that on rolling movements the ships may get in
touch above or beneath the fender
One tried to remove this last-mentioned disadvan'tage
by manufacturing fenders which partly consist of massive rubber
and have been built up for the remaining part of sponge- or foam
rubber, whereby the overall density of the fender is less'~than
1 0 and a floating construction originates Thus, such fenders
cannot sink. Irrespective of the problems originating while
. manufacturing such large rubber articles of various composition
and especially while vulcanizing them, it should be pointed out
that such fenders are less suitable for the heavy conditions of
use to which they are subjected. Thus, the use of foam or
sponge rubber components always leads to a decrease of the ri-
gidity and the tear resistance of the rubber article, which
properties are of great importance for fenders It is also
possible on a lasting use and the repeating compression and
expansion of the fender occurring thereby, that water enters
whereby the gas-bubbles cannot perform their function and the
density exceeds the value 1.0 again
Now the inventive idea is present in the fact that
these disadvantages are removed by using a rubber quality, which
also in massive vulcanized form (so without gas- or air-filled
closed pores being present therein) has a density of less than
1 0 preferably at most 0 97
It is clear that with such a density of the technical
1074990
(vulcanized) rubber quality a floatiny body can be manufactured,
which also in Lresh water still rises partially above the water
surface, whereby it is not necessary to hang up the fender on
cables Also in that case it is excluded that the fender
sinks or gets lost
For some time already saturated synthetic rubbers are
commercially available, the density of which is smaller than
that of natural rubber (natural rubber and the type of synthetic
rubber that is used most often have a density of 0 92)
The so-called EPDM rubbers (vide the Elastomers Manual,
edited 1974, page 7) have for instance a density of about 0 86.
However, reinforcing fillers have to be added to such
elastomers to give the articles prepared therefrom the desired
application properties.
In order to be usable in practice fenders should be
manufactured from a rubber mixture having a rigidity at 25% of
elongation of at least 3.5 kg/cm2 and a tear resistance in order
to prevent tearing of at least 10 kg/cm2 (determined according
to the so-called Delft method, ~EN 5603).
To realize these minimum requirements a dosage of a
carbon black usual for such purposes of about 40 parts per 100
parts of polymer is in general necessary for the use of synthetic
rubber polymers, such as ethylene-propylene-diene rubber.
~owever, as the density of active carbon black is always about
1.8 it is clear that without other additions decreasing the
density the carbon black dosage has been limited in order to
prevent that the density becomes more than 0.97.
Now it has surprisingly been found that if an active
carbon black, which distinguishes itself by a small particle size
and a high structure and was developed for a completely different
purpose, namely for making rubber electrically conductive, is
used, also with low dosages a reinforcement is obtained, which
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re~ults in properties on an acceptable level, viz. above the
limits indicated above as minimum value. These carbon blacks
are generally indicated as CF carbon black (vide Kirk-Othmer,
Encyclopedia of Chemical Technology, 2nd Edition 1964, Vol. 4,
page 265).
If the substantially synthetic rubber per se has a
density of at most 0.91, one obtains with these active carbon
blacks in an active amount a rubber article of which has a
density after vulcanization of at most 0.97
So the invention relates to a floating rubber fender
to be used for ships or drilling platforms or locks etc. con-
sisting of a rubber body manufactured from massive rubber, cha-
racterized in that the rubber body has been manufactured from a
substantially synthetic ~ubber having a density below about 0.91
and in that therein as reinforcing filler a carbon black promo-
ting the electrical conductivity and having a small particle
size and a high structure, is added in such an amount that the
density of the rubber after vulcanization amounts to at most
0.97.
With "a rubber body manufactured from massive rubber"
is meant that in the rubber as such no closed pores are present.
The body may indeed have cavities, it may for instance have the
form of a thick-walled hollow cylinder. Each type of carbon
black, which promotes the electrical conductivity and has a
small particle size and a high structure, for example of the CF
type, may be used for the manufacture of the fenders according
to the invention. Very suitable are the extra-conducting carbon
blacks, e.g. the carbon black put on the market by AKZO N.~. !
under the trade mark Ketjenblack EC.
Preferably an amount of carbon black of the CF type
is used of 5-35 parts by weight per 100 parts by weight of
synthetic rubber, especially 5-20 parts by weight. Besides a
.
1~)7~90
carbon blacX of the CF type the usual softeners (oils), activa-
tors (zinc oxide), resins and accelerators are incorporated in
the rubber mixture.
The invention is elucidated by the following example~.
In these examples the following basis recipe was lsed.
EPDM-rubber
Zinc-oxide (active)
Conductive carbon black
Stearic acid
Resin
Softener
Accelerator sy~tem.
The amounts of the various components in this mixture
are chosen such that the,following conditions are met:
1. A density of at most 0.97
2. A tear resistance of at least 10 kg/cm
3. A rigidity of at least 3.5 kg/cm2 at 25% of elonga-
`~ tion.
Example I
,:
- 20 1) ~ordel 1070 E* 90Parts by weight
2) Nordel 2744 * 40
Zincoxide/active , 2 "
6) Vulcan XXX carbon black* 10 "
4) Escorez 5300* 6
7) Mexphalt* 5
Stearic acid 1 "
5) BP50 oil* 5
Zincdibutyldithiocarbamate (ZDBC) 2 "
Tetramethylthiurardisulfide (TMTD) 0.5 "
Telluriumdiethyldithiocarbamate
(Tellurac)* 0.4
* Trade mark
B - 5 _
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Mercaptobenzodiazole (MBT)1.0 Parts by weight
Sulphur (S) 2.0 "
164.9 Parts by weight
Example II
8) Keltan 520 x 50* 90 Parts by weight
9) Keltan 578* 40 "
Zincoxide 2 "
3) Ketjenblack EC 10 "
4) Escorez 5300 6 "
7) Mexphalt 5
Stearic acid ~ 1 "
5) BP50 oil 5
ZDBC 2 "
TMTD . 0-5
Tellurac 0.4
MBT 1.0 "
2.0 "
164.9 Parts by weight
Exam~le III
1) Nordel 1070 E
Paxts by weight
2) ~ordel 2744 40 i'
Zincoxide active . 2
3) Ketjen carbon black EC 14 '~
Stearic acid 1 "
4) Resin: Escorez 5300~ 6 " ~:
Softener:.
5) BP process oil P50 10 "
ZDBC 2 l :
TMTD 0-5
Tellurac 0-4
MBT 1 " ~ --
Sulphur 2 "
* Trade mark - 6 - 16e.9 Parts by weight
3~ .
:
~v~ 9o
1) An EPDM rubber exterlded with 50 parts of naphtenic oil such
as provided by Dupont (vide The Elastomers Manual, '74 Edition
Table VIII, page 34)
2) An extended EPDM rubber as provided by Dupont (The Elastomers
Manual, '74 Edition, Table VIII, page 34).
3~ Provided by ~Z0 Chernie Nederland
4) Hydrocarbon resin, obtained by cracking olefins and diole-
fins, average molecular weight 800, provided by Esso Chemical
5) Low viscous paraffin oil provided by British Petroleum
6) Provided by Cabot Carbon Ltd
7) Mineral rubber, provided by Shell, softening point 135C
8) An EPDM rubber extended with 50 parts o-f naphtenic oil as
provided by DSM (Dutch States Mines) (The Elastomer Manual, '74
~, Edition, Table VIII, page 36)
9) An unextended EPDM rubber as provided by DSM (Dutch States
Mines) (The Elastomers Manual, '74 Edition, Table VIII, page .
36).
The mechanical properties of a vulcanized rubber plate
(vulcanized during 20 minutes at 150C) from these mixtures were
determined, with the following results
,:
Example I
Density = 0.95
Tear resistance (method NEN 5603) = 13 kg/cm
Rigidity at 25% of elongation = 3.6 kg/cm
Example II
Density = 0.95
Tear resistance (method NEN 5603) = 20 kg/cm
Rigidity at 25% of elongation = 5 3 kg/cm ,
Example III
Density = 0 96
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Tear resistance (Inethod NEN 5603) = 15 kg/cm
Riyidity at 25% of elonyation = 5,0 ky/cm .
The invention is not limited to the embodiments espe-
cially explained in the examples and small changes in the dis-
pensiny which are obvious for the expert can be applied without
more.
