Use of a preparation for insulation/sealing and coating purposes and method for sealing manhole covers

The invention relates to the use of a preparation for insulation/sealing and coating purposes, comprising an apolar, non-setting fluid polymer having a glass transition temperature lower than -60.degree. C., wherein the polymer has a surface tension of less than 40 mN/m above the glass transition temperature. Preferably, the preparation contains one or more fillers having a different particle size and a different particle size distribution.

The invention relates to the use of a preparation for insulation/sealing 
and coating purposes, comprising an apolar, non-setting, fluid polymer 
having a glass transition temperature lower than -60.degree. C., and a 
method for sealing manhole covers. The invention relates in particular to 
the use of a preparation for insulating and sealing underground objects 
which are in contact with moisture or water, for example underground steel 
manhole covers, underground tanks, lines, pipes and cable sleeves. 
U.S. Pat. No. 4,094,911 discloses that linear poly(perfluoroalkylene oxide) 
with functional end groups, which has a glass transition temperature lower 
than -78.degree. C. and a number average molecular weight of 500 to 20 
000, can be used as insulating material. 
European patent Application 0 359 273 relates to polyurethanes comprising 
rubber-like polyoxyperfluoroalkylene blocks and rigid elements, which are 
derived from compounds having a low molecular weight and from 
(cyclo)aliphatic or aromatic diisocyanates. Said polyurethanes have a 
glass transition temperature lower than -80.degree. C. Said polymers can 
be used, for example, as insulating material and sealing means. 
Manhole covers are covers for manholes, which are openings in, for example, 
above- or below-ground steel or concrete storage chambers for liquids and 
gases, such as LPG tanks, boilers, cesspits and rainwater tanks. Said 
openings are of a size such that a person is able to pass through them. 
Manhole covers, underground tanks, lines and the like are made of metal and 
therefore show a tendency to corrode. This corrosion is undesirable since 
it weakens the metal. That is why attempts are made to counteract or to 
prevent this formation of corrosion. 
Various techniques and preparations are known for counteracting or 
preventing corrosion formation. For instance, lines and pipes of 
underground tanks, for example LPG tanks, are protected with the aid of 
so-called cathodic protection. This technique comprises the application of 
a low voltage to the tank or to the lines which are connected to the tank, 
as a result of which electrochemical reactions which lead to the formation 
of corrosion are not able to occur. However, this technique has a number 
of disadvantages. In addition to the continuous consumption of power, 
which is economically unattractive, there is a risk that the system will 
fall as a result of, for example, power disruptions. Moreover, formation 
of vesicles under the coating of the tank or lines may occur which is 
caused by decomposition of water into hydrogen and oxygen gas. It is for 
this reason that preparations are preferably used to seal or insulate such 
lines and tanks, although the preparations according to the prior art 
frequently also give rise to problems. 
For sealing, for example, manhole covers, use is made not only of bitumen 
but also, for example, of preparations which contain synthetic, 
thermosetting resins, for example epoxy or polyurethane resins. These 
preparations have the disadvantage that a hard coating or seal is 
produced. This hard seal can easily split or tear under the influence of, 
for example, mechanical stresses. Another disadvantage of these 
preparations is that solvents are needed for their application. Following 
the application of the preparation, these solvents will evaporate, as a 
result of which a microporous seal or coating is produced, which is 
partially permeable to water. Water is therefore able to penetrate through 
this coating, with the result that corrosion formation occurs. The 
situation also arises that once the water has penetrated through the 
protective layer, the protective layer crumbles away as a result of the 
osmotic pressure (polar substances such as salts are not able to penetrate 
through the protective layer), with the consequence that the manhole cover 
is no longer adequately protected. Yet a further disadvantage of these 
preparations is that they are difficult to remove, which, for example, can 
be necessary in the case of repairs. It is therefore difficult to clean 
the surface of the manhole cover to be sealed, as a result of which the 
application of a fresh layer leads to mediocre sealing of the manhole 
cover. 
Bitumen-containing materials are also partially permeable to water and in 
general do not meet the requirements laid down by the KIWA 
(Keuringsinstituut voor Waterleidingartikelen; Dutch Inspection Institute 
for Water Supply Articles). As bitumen are characterised by having a glass 
transition temperature more than about 10.degree. C., removal of bitumen 
is difficult during the summer and formation of cracks in the bitumen 
layer may occur during the winter. 
Preparations which contain synthetic, thermosetting resins are also used 
for sealing cable sleeves. In these sleeves as well splitting and tearing 
can occur, for example as a result of mechanical stresses, for example 
road traffic, earth movements and the like, with the consequence that 
water is able to penetrate into the cable sleeve and that the cables 
contained therein are no longer adequately protected. Another problem 
which arises when sealing cable sleeves with preparations of this type is 
that once cable sleeves have been sealed said sleeves have to be replaced 
or additional cable sleeves have to be applied to make new branches. 
It is clear from the above that many problems can arise when the techniques 
and preparations according to the prior art are used. The present 
invention provides a solution to these problems by using a fluid material 
instead of setting materials. Said fluid materials have a better seating 
on the article to be sealed or to be insulated, as well as better 
deformability and very good adhesion, that is to say a good adhesive power 
to the surface. The preparation according to the invention is therefore 
also kneadable and simple to apply and to remove using a trowel. A clean 
surface is left behind on removal. The preparation according to the 
invention does not set and therefore remains soft and is also not 
permeable to water and is pore-tight. No additional adhesive means are 
required for the application of the preparation according to the invention 
to the surface to be sealed or to be protected. The invention therefore 
also relates to the use of a preparation as described in the preamble, 
characterised in that the polymer has a surface tension of less than 40 
mN/m above the glass transition temperature. 
Polymers having a glass transition temperature lower than -20.degree. C. 
have the advantage that when these are used in the preparations according 
to the invention they have good deformability and remain soft within the 
temperature range in which the preparations are used, because the polymers 
are in the rubber-like state. Polymers which have a surface tension of 
less than 40 mN/m at 20.degree. C. have the advantage that when they are 
used in the preparation according to the invention good adhesion to the 
surface to be sealed, to be insulated or to be protected is obtained. Such 
polymers, which are suitable for use in the preparations according to the 
invention, comprise apolar, non-setting fluid polymers. Such polymers are 
known in the prior art, for example polyalkanedienes, polyalkenes and 
polysiloxanes. 
It is advantageous to use preparations which comprise apolar, non-setting, 
fluid polymers which have a glass transition temperature lower than 
-60.degree. C. and a surface tension of less than 40 mN/m at 20.degree. C. 
Polymers of this type are likewise known in the prior art and comprise, 
for example, polyalkanedienes, polyalkenes and polysiloxanes. Examples of 
suitable polyalkanedienes are polyisoprene, poly(1-butylene), 
poly(1-pentylene), poly(1-ethyl-1-butylene), poly(1-butyl-1-butylene) and 
poly(1-heptyl-1-butylene). An example of a suitable polyalkene is 
polyisobutene. Examples of suitable polysiloxane are 
poly(oxydimethylsilylene)(=polydimethylsiloxane) and 
poly(oxymethylphenylsilylene). Polyisobutene and poly(oxydimethylsilylene) 
are preferably used. Therefore, according to the invention a preparation 
is preferably used which comprises apolar, non-setting, fluid polymers, 
wherein the polymers have a glass transition temperature lower than 
-60.degree. C. 
The molecular weight of suitable polymers can vary over a wide range. The 
molecular weight of, for example, suitable polyalkenes can be, for 
example, 500 to 100 000. Suitable polyalkenes have a viscosity at 
100.degree. C. of approximately 10 to 50 000 cSt. The density of suitable 
polyakenes lies approximately between 0.75 and 1.10, preferably 
approximately between 0.85 and 0.95, the bromine number (g Br.sub.2 /100 
g) approximately between 0.1 and 50, the acid number (mg KOH/g) 
approximately between 0.01 and 0.05 and the specific electric resistance 
at 100.degree. C. is preferably greater than 10.sup.12 .OMEGA..cm. 
Suitable polysiloxanes (polyoxysilylenes) are, for example, those which at 
25.degree. C. have a density of approximately 0.75 to 1.10, preferably of 
0.90 to 1.00, a surface tension of less than 35, preferably less than 25 
mN/m, an acid number of approximately 0.01 mg KOH/g and a specific 
electric resistance according to the standard DIN 53482 of greater than 
10.sup.12 .OMEGA..cm. 
According to the present invention, polymers comprising polyisobutene 
and/or poly(oxydimenthylsilylene) which have a viscosity of between 60 000 
and 1 200 000 cSt (60 to 1200 Pa.s) at 20.degree. C. are advantageously 
used. 
The preparation according to the invention is able to withstand many 
chemical substances. For instance, the preparation is able to withstand 
water-containing solutions of inorganic and organic substances such as 
salts, acids and bases, for example solutions of hydrochloric acid, 
sulphuric acid, phosphoric acid, chlorosulphonic acid, potassium 
hydroxide, sodium hydroxide, potassium bichromate, acetic acid, organic 
solvents, for example benzene, and corrosive gases, such as ammonia. 
The preparation according to the invention can also contain stabilising 
agents, for example agents against oxidation under the influence of heat, 
such as 2,6-di-t-butyl-4-methylphenol, and agents against the action of 
ultraviolet light. 
The preparation according to the invention can contain one or more fillers. 
Said fillers can be of organic or inorganic nature. Examples of inorganic 
fillers are polyvinyl chloride, polyethene, polypropene, polyisoprene and 
rubber. Examples of inorganic fillers are inorganic minerals, salts and 
oxides, for example chalk, boron sulphate, aluminium oxide, silicon 
dioxide, ground quartz, glass, talc, slate, bentonite and the like. 
Preferably, a mixture of coarse and fine particles, in a specific mixing 
ratio, of one or more fillers is used. The rheological characteristics of 
the preparation according to the invention can be controlled by means of 
the amount of filler. According to the invention, it is therefore 
preferable that the fillers comprise one or more fractions, each fraction 
having a different particle size and a different particle size 
distribution. In particular, the fillers comprise at least one fraction 
having a particle size of 0.1 .mu.m to 1500 .mu.m. 
The fillers can be swellable or non-swellable, that is to say they increase 
substantially or slightly in volume as a result of the absorption of 
water. One example of a swellable filler is bentonite. The preparation 
according to the invention can therefore contain one or more polymers 
having a low molecular weight and/or a high molecular weight and one or 
more non-swellable and/or swellable fillers. 
The fillers can have a low or a high density. The density of the fillers 
can be between approximately 0.1 and 5 kg/dm.sup.3. Examples of a filler 
having a low density, for example between approximately 0.3 and 0.1 
kg/dm.sup.3, are so-called "hollow spheres", which, for example, are 
produced from glass, polyvinylidene chloride or syndiotactic foams, and 
cork. Examples of fillers having a high density, for example a density of 
between 2 and 4 kg/dm.sup.3, are inorganic fillers such as talc and chalk. 
The preparation according to the invention can also contain one or more 
products which optionally have been obtained directly from petroleum. 
Examples of such products are bituminous products and paraffin-like 
products, for example petroleum gel and wax. 
The preparation according to the invention is very suitable for sealing 
manhole covers, which may or may not be underground. Materials which are 
used for sealing manhole covers must meet a number of conditions. For 
instance, the specific electric resistance must be high and, according to 
Netherlands Guideline NPR 6912, the current density of such materials must 
be less than 100 .mu.A/m.sup.2, preferably less than 10 .mu.A/m.sup.2. 
Therefore, according to the invention a preparation is preferably used 
which has an infinitely high electric resistance and a current density of 
less than 10 .mu.A/m.sup.3, in particular of less than 1 .mu.A/m.sup.3. 
When a preparation is used for the application as described above, for 
example the sealing of manhole covers, the preparation must not be porous. 
If pores are present, these can fill with water in the course of time, as 
a result of which the sealing and insulating properties of the preparation 
become poorer, which is reflected in an increased current density. This 
effect will be more pronounced when the water contains an electrolyte, for 
example an inorganic salt, such as sodium chloride. It is therefore 
preferable that a material is used which is pore-tight, that is to say 
that the material contains relatively few to no pores. Therefore, 
according to the invention a preparation is preferably used which has a 
current density of less than 10 .mu.A/m.sup.2 when the preparation is in 
contact with a water-containing containing electrolyte which has a 
specific resistance of 100 .OMEGA..m. 
Materials which are used to seal manhole covers must comply with the 
standard NEN 6910. For assessment of the pore density, these materials are 
spark-tested. According to the standard NEN 6910, the spark length must be 
at least 1.5 times the thickness of the layer of the material applied. 
Therefore, according to the invention a preparation is preferably used 
which has a pore density such that a spark having a length of 45 mm is not 
able to bridge a layer of the preparation which has a thickness of 30 mm, 
in particular of 16.5 mm. 
The preparation according to the invention is deformable, even long after 
it has been applied. Because the preparation is and remains deformable and 
it has a paste-like to rubber-like appearance, it is therefore capable of 
absorbing vibration and shocks. Thus, in addition to the sealing effect, 
it also provides protection against mechanical effects, such as 
vibrations, with the result that damage to the article to be sealed will 
occur less rapidly. The preparation is not sensitive to low temperatures 
such as can occur during the winter months. In contrast to bitumen, the 
preparation does not change shape under the influence of temperature. 
Moreover, the preparation is not hazardous to the user, that is to say it 
is not toxic and does not release toxic substances and it is not 
irritating to the skin and the eyes. The preparation contains no 
substances which are harmful to the environment. The preparation adheres 
to every type of surface, for example surfaces comprising concrete, stone, 
glass, synthetic materials, such as plastics, and the like. These surfaces 
can be dry or damp. 
For sealing manhole covers the preparation is preferably used at a 
temperature of no higher than 50.degree. C. and no lower than -10.degree. 
C. For other uses, however, these temperatures may be as low as -30 
.degree. C. and a high as 150.degree. C. the preparation can be filled 
into cartridges or tubes or into larger containers such as buckets. The 
preparation can therefore be applied easily using a so-called mastic gun, 
a plunger pump, a trowel, a spatula or a knife. The tools which are used 
can be cleaned easily using natural or synthetic soap and water. 
The preparation according to the invention is therefore suitable for 
sealing cable sleeves, underground lines and pipes and also tanks and 
manhole covers according to the standard NEN 2768. The preparation 
according to the invention is, in particular, suitable for sealing manhole 
covers. For this purpose, a layer of at most 30 mm of the preparation is 
applied around the manhole cover. 
The preparation according to the invention is also suitable for providing 
protection against mechanical effects from the outside, such as vibrations 
and shocks. In particular, the preparation according to the invention can 
be used to damp sound vibrations which have a frequency of 25 to 25 000 
Hz. The preparation according to the invention can therefore 
advantageously be used for insulating, for example, machines, building, 
loud-speaker cabinets and the like. 
The preparation according to the invention is also suitable as an 
anti-corrosion agent for welding joints and connectors for both 
underground and above-ground pipelines and gas lines, for flanges, crane 
hooks, thermit weldings in divisible shafts below the ground level and in 
T-joints. 
The preparation can also advantageously be used to protect sensitive 
electronic apparatus, for example electronic measurement and control 
apparatus and electronic apparatus for sound recording and reproduction, 
against moisture, dust and gases, for example corrosive gases. 
The preparation according to the invention can also be used for the 
insulation of above-ground and/or underground components which are used in 
the electricity generating and consuming industries, for example low- and 
high-voltage cables and connectors, and for the protection thereof against 
moisture and gases, for example corrosive gases. 
The preparation according to the invention can furthermore be used in 
combination with specific types of tape or in combination with mats. The 
tape or the mats can be made of a butyl rubber, polyurethane, 
polysulphide, polyvinyl chloride, polyethene and the like. The width of 
the mat or tape can be 2 cm to 2 m. For an application of this type, an 
approximately 0.1 to approximately 2 cm layer of the preparation according 
to he invention is applied to the mat or tape. Mats or tapes of this type 
are, in particular, suitable for the provision of mechanical strength 
and/or for improving the chemical resistance of the article to which the 
mat or tape is applied. The combination mat/preparation is also suitable 
to be sued as roofing material and as a substitute for textile materials, 
e.g. those which are used in the automobile industry. 
The preparation according to the invention may also be sued in combination 
with means such as shrink sleeves, tapes and belts, geofabrics, mats and 
mats and tapes having an open cel structure. These means may be used to 
impart mechanical strength to the preparation. These combination can be 
wrapped around welded joins of two joined tubes and flanges or other 
objects to be sealed for prohibiting corrosion. The combination shrink 
sleeve/preparation may be used as follows. A shrink sleeve is mounted 
around one of the tubes and the tubes are welded together. The preparation 
is applied to the welded joint after the welded joint has cooled to e.g. 
room temperature. The shrink sleeve is then moved over the welded joint so 
as that between the joint and the sleeve a layer of the preparation is 
present, said layer having a thickness of about 0.1 to 2 cm. After heating 
the shrink sleeve a completely sealed seal is obtained and the welded 
joint is completely protected from moisture, dust and gases. 
The mats described above can also be used in shipbuilding for covering very 
large surfaces. For an application of this type the mats can be up to 4 m 
wide. Such mats are, in particular, suitable for covering metal objects on 
the inside of ships. 
The preparation according to the invention can furthermore be used as such 
as ship-building and in the offshore industry, for example for protecting 
the legs of drilling platforms, and steel components and pipes located 
under seawater. 
The suitability of the preparation according to the invention for sealing, 
in particular, underground steel manhole covers has been determined in a 
number of tests. It has also been demonstrated in these tests that better 
and more durable sealing of manhole covers is obtained with the use of the 
preparation according to the invention than with the use of the materials 
according to the prior art. The following experiments were carried out on 
the preparation that had been applied two years previously to manhole 
covers in a petrol station. The preparation according to the invention 
also complies with the standard NEN 2768.

The invention will now be further illustrated by the following examples 
which are not considered as limiting or restrictive. 
EXAMPLE I 
In order to determine the environment around the manhole cover that had 
been sealed using the preparation according to the invention, soil samples 
of the packing sand alongside the manhole cover were taken. The specific 
electric resistance of the packing sand in the dry state is about 1000 
.OMEGA..m and in the wet state about 500 .OMEGA..m. This means that the 
packing sand complies with the CPR 8.1 guideline and is thus of high 
quality. The specific electric resistance of this packing sand has a 
preventive action against corrosion. 
The metal-electrolyte potential V.sub.in and the associated current density 
of a tank body which had not been dug free were determined (Experiment 1, 
Table 1). The metal-electrolyte potential is the voltage difference 
between a metal object (this is the tank in this experiment) in an 
electrolyte and a measurement electrode which is in contact with the 
electrolyte. The measurement electrode comprises a galvanic half-cell, 
consisting of a copper rod in a saturated solution of copper sulphate. The 
metal-electrolyte potential was measured as such and immediately after 
switching off the protective current. The protective current is a current 
supplied to the metal object by a galvanic sacrificial anode, which is 
made of a metal which is less noble than the metal from which the object 
is made, or by an external current source, and which neutralises the 
potential differences at the metal's surface. The measurement in the 
absence of the protective current provides the true potential of the metal 
object V.sub.out, which is lower than the metal-electrolyte potential in 
the presence of a protective current. This reduction is caused by the 
current which flows through the electric circuit. 
The metal-electrolyte potential was also determined after the risers of the 
tank had been dug free (Experiment 2) and after the manhole cover had been 
dug free (Experiment 3). 
TABLE 1 
______________________________________ 
Experiment 
V.sub.in (mV) V.sub.out (mV) 
I (.mu.A) 
______________________________________ 
1 1520 820 45.0 
2 1520 820 40.0 
3 1520 820 40.0 
______________________________________ 
These experiments show that the specific electric resistant of the 
preparation is infinitely high. 
EXAMPLE II 
The current density of the preparation was also determined in the above 
experiment. It was found that in a high-ohm environment the current 
density was approximately 0 .mu.A/m.sup.2. 
EXAMPLE III 
The pore density of the preparation was determined with the aid of DC 
sparking equipment in accordance with the standard NEN 6910. The 
specification for a bitumen coating on the manhole cover is that no 
arc-over may occur when the spark length is 1.5 times the thickness of the 
layer applied (this approximately corresponds to a voltage of 4.5 kV per 
mm layer thickness). It was found that with a spark length of 45 mm no 
arc-over occurred with layer thicknesses of 30 mm and did not occur even 
with layer thicknesses of 16.5 mm. 
EXAMPLE IV 
The pore density of the preparation was also determined in another 
experiment. The manhole cover from Example I was steeped with an 
electrolyte-containing solution which had a specific electric resistance 
of 100 .OMEGA..m. That is to say the cavity dug out, in which the manhole 
cover is located, is filled with the electrolyte-containing water. The 
metal-electrolyte potential was then determined in the presence and the 
absence of the protective current, in accordance with the method of 
EXAMPLE I, it being found that V.sub.in was 1520 mV, V.sub.out 800 mV and 
I 50 .mu.A. This means that even in a damp and aggressive environment the 
specific electric resistance of the preparation is infinitely high. 
EXAMPLE V 
In this experiment the adhesion of the preparation to metal was tested. A 
V-shaped cut was made in the preparation which had been applied to a 
manhole cover without an additional adhesive and the preparation was 
removed using a trowel. Traces of the preparation were visible on the 
metal, which demonstrates that the adhesion was satisfactory. It was also 
found that the metal surface was not corroded and that no accumulation of 
water had occurred beneath the preparation. 
EXAMPLE VI 
The specific resistance of the preparation was also determined in the 
following experiment. 
The preparation was placed in a so-called CIGRE cell and the cell was then 
heated to 100.degree. C. A direct voltage of 500 V was then applied over 
the cell and the specific resistance was determined after 5 minutes. The 
specific resistance was found to be 19*10.sup.12 .OMEGA..m.