NO138380B - PROCEDURE FOR SEALING LEAKS USING A GASEFUL SEALER - Google Patents

Description

The invention relates to a new method for sealing

of leaks in containers, pipes and the like by introducing a gaseous sealant, mixed with a carrier gas that is inert to the sealant and does not ignite spontaneously in mixture with this under the conditions used, and creation of an overpressure so that the sealant flows out at the leak points , for a time that is sufficient for a firm seal to form on

the places where the leaks occurred.

The method according to the invention is characterized by the fact that an organic monomer or a mixture of such monomers is used as a sealing agent, the sealing agent being diluted with the carrier gas to a sufficient degree - or used under such conditions - that the mixture does not ignite spontaneously,

and in that the agent is caused to polymerize at the leakage sites by means of a gaseous polymerization catalyst.

The method according to the invention is particularly adapted for sealing very small leaks in underground pipe systems used for the transport of fuel gas, as well as for sealing leaks in telephone cables containing nitrogen and

ler other inert gas under pressure.

The invention not only eliminates gas leakage into the atmosphere, but also into the surrounding ground or through packing materials. The air and the other surrounding materials involved in the sealing operation are referred to below as "the surroundings".

From Norwegian patent document no. 132 907, it is true that a method is known for sealing leaks in containers, pipes and the like using a gaseous sealant. However, what is used here is not an organic monomer which undergoes polymerisation, but certain gaseous or volatile compounds which have in common that they must contain either boron, aluminium, zinc or cadmium. They all react with moisture present on the outside of the leak. According to the patent document, only non-flammable carrier gases are used.

In the patent document, some older proposals are also mentioned

this subject area.

According to a preferred embodiment of the invention, the interior of the vessel is first flushed with a dry, non-reactive gas, e.g. nitrogen, helium, argon or dry natural gas, for to remove the moisture and/or oxygen present. As a sealing agent, a normally gaseous or volatile, plymerisable organic monomer is used.

The monomer may be one capable of polymerization upon contact with air, water, or alkaline or acidic conditions present at the leak site, in which case it is not necessary to add any additional polymerization catalyst. In most cases, however, the sealing agent will comprise both the volatile monomer and a volatile polymerization catalyst for this. When the mixture escapes from a leak into the environment, sealing will occur.

For the purposes of the invention, a volatile organic monomer can be defined as one that has a vapor pressure such that at least approx. 10 ppm sealant is present in the vessel which the bowl is sealed at a certain internal pressure. Under these conditions, the resulting partial pressure of the monomer vapor is too low to be detectable by conventional methods.

The amount of volatile catalyst which is supplied to the leakage sites together with the monomer is at least a catalytic amount, i.e. an amount which is sufficient to induce and maintain the polymerization of the monomer. This amount will vary according to the type of monomer and catalyst, as well as the conditions prevailing in the vessel, but will usually be more than 1% by weight of the monomer. An excess of the catalyst material is not harmful, but may be uneconomical.

The volatile monomer can advantageously be introduced in a mixture with a gaseous solvent or carrier which is inert to the monomer and the catalyst.

As previously mentioned, the concentration of the volatile can.

the sealant used, and the pressure of the carrier gas, are varied over a wide range, depending on the specific components, the type and size of the leaks, and the ambient conditions. The flow time for the sealant can also be varied greatly.

If desired, the consumer can get the sealants in containers or cylinders, mixed in the quantities necessary for the relevant sealing operations. The mixtures can be introduced by suitable means in regulated or measured quantities into the vessel, which has previously been flushed and dried with an inert gas. The inert gas and the added sealant are held at a suitable pressure for a period of time sufficient to plug or seal the leak. If desired, the consumer can also obtain a suitable container containing an inert gas under pressure and with the selected sealants mixed in suitable relationship. If desired, the specific components of the sealant can also be introduced in a volatilized state separately in regulated quantities.

The polymerization of the monomer is activated by it escaping through the leak into the environment, by the influence of moisture, oxygen, the alkalinity or acidity of the soil, or other agents that may be present, or that may be introduced from outside to the location of the leak. The catalyst can also be formed at the leak site before or during the introduction of the monomer by reaction between a suitable volatile additive that reacts with certain components in the soil or atmosphere. thus, activators can be supplied to the leak point by injecting a stream of a suitable agent or a catalyst through a pipe. furthermore, heat and/or moisture can be supplied internally or externally in relation to the leakage site by injecting a stream of steam or hot gas through a piece of pipe at the leakage site. Heat can also be generated at the leak site by reaction between a suitable volatile additive and moisture, oxygen and/or other soil or atmospheric agents, the reaction being exothermic; or by electromagnetic induction from an external fluctuating electric field.

The sealing process according to the invention is particularly useful when sealing leaks in underground pipelines where the leakage can take place at jute-wrapped joints, or in the surrounding ground. In such cases, a matrix of either jute or soil is available to absorb the monomer, providing a site where polymerization can take place and provide the desired solid seal.

Depending on the type of monomer and catalyst used, the monomer and catalyst and other components can be introduced into the vessel one after the other or simultaneously.

The monomer and/or the catalyst are introduced into the vessel under a pressure that is sufficient for the monomer vapors to escape from the leak and into the surroundings, and for a period of time that is sufficient for a polymer to form which forms a solid seal at the location of the leak. The monomers are introduced in a concentration that depends on the size and shape of the vessel and the conditions in the surroundings. The concentration will usually vary from approx. 50 ppm to approx. 10% by weight of the inert carrier gas. If the monomer is not gaseous, but nevertheless volatile, it can be evaporated or dissolved in a suitable volatile organic solvent, e.g. a hydrocarbon, e.g. butane, hexane, heptane, benzene etc., which will volatilize or disperse evenly in the solvent gas.

The organic monomers are preferably gaseous

at normal temperatures and pressures. However, you can use monomers that are volatile liquids with relatively low boiling points, or that have such a vapor pressure that they are easily volatile in the temperature range from approx. 0 to approx. 100°C (which is the range encountered, for example, in underground pipelines), so that they will be present in a concentration of at least approx. 10 ppm in the pipeline. If the upper limit of the relevant temperature range is higher, the range of volatile monomers is naturally expanded. In the case of a gas pipeline for example, the line pressure can be varied from as little as 0.03 and up to as much as 7 kg/cm 2 , or even higher.

The volatile organic monomers that can be used in accordance with the invention include both simple monomer systems, which are capable of forming homopolymers, and comonomer systems, which form copolymers. The general polymerization techniques and catalysts suitable for any given system are well known and do not require detailed discussion, beyond suitable explanation of the manner in which they are used in the practice of the invention.

Although any polymerizable, volatile organic monomer capable of forming a solid seal can be used in the practice of the invention, the sealing systems will advantageously comprise one or more selected monomers that fall within the following categories:

1. Mono-ethylenically unsaturated hydrocarbons

2.Multi-ethylenically unsaturated hydrocarbons

3. Halogen alkenes

4. Alkylene oxides and epoxides

5. Alkylene carbonates

6. Alkenylnitriles

7. Alkenic acids

8. Alkyne hydrocarbons

9. Aldehydes

10. Ketones

11. Alkenyl esters

12. Alkenyl alcohols

13. Alkenyl halides

14. Alkenyl ethers

15. Organo-silanes

16. Compounds with a five-membered ring, containing one hetero-oxygen atom

17. Organometallic compounds

If a suitable volatile polymerization catalyst is used in connection with the volatile monomer, and depending on the type of monomer and type of polymerization, such a catalyst will usually be selected from among the following types:

1. Free radical catalysts

2. Organometallic compounds

3. Metal hydrides

4. Lewis acids

5.Alkaline earth compounds

6. Alkalis

7. Metal halides

8. Metal and metalloid alkoxides.

Aforementioned categories of monomers, the polymerization methods commonly used with them, the types of catalyst used, and exemplification of individual monomers are set forth below, so that the practice of the invention will be better understood.

MONOMERS

Mono-ethylenically unsaturated hydrocarbons

These include gaseous or slightly volatile, liquid hydrocarbons which may be alkenes, with a single double bond, e.g. gaseous or slightly volatile olefins. Examples of such olefins are listed in Table 1:

Of the gaseous olefins, 2-methylpropene (isobutylene) is the one that is easily polymerised catalytically, as it forms butyl rubber. The catalysts are usually acidic substances, e.g. acids or their anhydrides, and metal halides. Examples of acids include sulfuric acid, phosphoric acid, hydrogen fluoride and acid-reactive clay species and silicon dioxide/alumina dioxide composites. The clay species etc. can occur in the soil. The metal halides are e.g. tin(IV) chloride and titanium tetrachloride, both of which are volatile. Halides and hydrides of boron are also good catalysts, including e.g. boron trichloride, b.p. 18°C, and boron trifluoride, a gas, b.p. -101°C, diborane B2H5, b.p. -92.5°C and pentaborane B5H9, 48°C, vapor pressure 66 mm at 0°C. The gaseous nature of the boron catalysts makes them particularly well suited for use in carrying out the invention where streams of polymerizable hydrocarbon and gaseous catalyst are introduced under appropriate conditions of temperature and pressure in a vessel.

Ethylene and propylene can also undergo low pressure polymerization using an organometallic catalyst of the Ziegler type, e.g. aluminum triethyl with titanium tetrachloride, at approximately atmospheric pressure. Other catalysts of this type are tri-isobutyl aluminum and titanium tetrachloride or aluminum alkyl halides with vanadium halides or with titanium esters, e.g. diethyl aluminum chloride with vanadium oxychloride or isopropyl titanate.

Polyethylenically unsaturated hydrocarbons:

This category includes gaseous or slightly volatile hydrocarbons containing polyethylenic unsaturation, e.g. conjugated hydrocarbons such as butadiene or its derivatives, or divinylbenzene, alkenylstyrenes, isoprene and the like. Examples of this class of monomers are given in Table 2:

The styrene is usually polymerized to form a homo-polymer using a free radical catalyst, e.g. benzoyl peroxide. However, both styrene and α-methylstyrene can be polymerized using diborane gas as a catalyst. Likewise, styrene can be copolymerized with butadiene using diborane as a catalyst. Isoprene, which has a low boiling point, namely 34°C, can be polymerized with catalysts of the aluminum or lithium alkyl type with moderate heat. If a small amount of moisture is present, the aluminum alkyl compound reacts with it, thereby creating a source of the necessary heat. Butadiene gas can be polymerized with an "Alfin" type catalyst in the presence of a solid surface. These catalysts are described in chapter 5 of Raish and Schindler, "Polymerization of Organometallic compounds". With "Alfin" catalysis, monomer molecules are adsorbed and oriented before they enter the chain-growth process.

Halogen alkenes:

Examples of polymerizable halogen-alkene monomers and their properties are shown in Table 3:

The aforementioned monomers, e.g. chlorotrifluoroethylene, can be polymerized in gas phase using gaseous borohydride catalysts, e.g. diborane or pentaborane. Vinylidene chloride can be polymerized within 6 hours at 40-50°C with borohydride catalyst.

Alkylene oxides;

This category includes monomers such as e.g. ethylene oxide, b.p. 10.73°C, and propylene oxide, b.p. 33.9°C, vapor pressure 445 mm Hg at 20°C. The polymerization catalyst can be an alkali or alkaline earth metal oxide, e.g. CaO, SrO or a heavy metal oxide, e.g. ZnO, which can be introduced via volatile metal-organic compounds or found in the soil, or also a metal halide such as e.g. SnCl^. Other catalysts are alkaline earth carbonates, e.g. Cacc>3 or Srcc^, which is found in many types of soil, and activated aluminum dioxide or silicon dioxide/aluminium dioxide, again introduced via volatile metal-organic halides etc. Combinations of the acidic oxides, e.g. alumina or silicon dioxide/alumina with a metal alkyl, e.g. boron-tributyl, zinc diethyl and cadmium diethyl can also be used.

Alkylene carbonates:

An example of this type of monomer is vinylene carbonate, which has b.p. 162°C and can be polymerized with a catalyst of the free radical type, e.g. 1-propane-azomethane, during approx. 18 hours at normal temperatures and pressures.

Alkenylnitriles:

Examples of this type of monomer are acrylonitrile, b.p. 77.3, vapor pressure 83 mm Hg at 20°C, 1-fluoroacrylonitrile, b.p. 43-48°C and 1-methylacrylonitrile, b.p. 18°C. Acrylonitrile does not require a polymerization catalyst, but polymerizes spontaneously under certain conditions, especially in the absence of oxygen, or when exposed to visible light, or in the presence of alkalis.

Alkenic acids;

Acrylic acid, b.p..141°C volatilizes easily and polymerizes in the presence of oxygen, without a catalyst. Methacrylic acid, b.p. 163°C also readily volatilizes and polymerizes upon heating or _ presence of traces of HCl.

Alkyne hydrocarbons:

Vinylacetylene monomer is a dimer of acetylene and has a bp of 5°C, is a gas at normal temperature, is polymerizable and forms an elastomer of the neoprene type using HCl as a catalyst.

Aldehydes;

Examples of aldehyde monomers include aliphatic aldehydes, e.g. formaldehyde gas, b.p0 -19.5°c and acetaldehyde, b.p. 21°C. Unsaturated aldehydes include acrolein (acrylic acid aldehyde), b.p. 52.5°C, vapor pressure 214 mm Hg at 20°C. These monomers are easily polymerizable, usually with catalysts of the free radical type. Formaldehyde easily polymerises in contact with a surface at temperatures below approx. 90°C to form a solid polymer. Suitable catalysts are formic acid, HCl, SnCl^, BF3, metal-alkyl compounds, e.g. cadmium dimethyl and also finely divided sulphur.

Ketones:

Acetone, b.p. 56.5°c can be polymerized catalytically to form mesityl oxide which is itself an unsaturated ketone (isopropylideneacetone), b.p. 130°C, vapor pressure 7.9 mm Hg at 20°C. The mesityl oxide polymerizes on contact with air without any specific catalyst to form a solid polymer.

Alkenyl esters:

These monomers are exemplified by such compounds as methyl acrylate, m.p. 80°C, vapor pressure 68.2 mm Hg at 20°C, ethyl acrylate, b.p. 99.6°C, vapor pressure 29.5 mm Hg at 20°C, methyl methacrylate, b.p. 101°C, flash point 29.4°C and ethyl methacrylate, b.p. 119°c, flash point 35.0°C.

These liquids easily polymerize in the presence of light, heat, or catalysts of the free radical type, e.g. methyl ethyl ketone peroxide.

This category also includes vinyl esters, e.g. vinyl acetate monomer, b.p. 7 2.5°c, vapor pressure 88.7 mm Hg at 20°C which polymerizes in light to a phaseless mass, and vinyl formate, b.p. 46.6°C, vapor pressure 270 mm Hg at 20°C.

Alkenyl alcohols;

A monomer of this type is allyl alcohol, b.p. 96-97°C, flash point 21 .1°C which polymerises on standing.

Alkenyl halides:

The main monomers of this category are the vinyl halides, including vinyl bromide, b.p. 15.8°C, vinyl chloride, b.p. -13.37°C, vapor pressure 100 mm Hg at -55.8°C and vinyl fluoride, b.p. -51°c. These monomers generally homopolymerize with catalysts of the free radical type, e.g. methyl ethyl ketone peroxide. They are widely used for the formation of copolymers with vinyl esters, e.g. vinyl acetate, which usually contains from 3 to 30% of the ester, using similar catalysts.

Alkenyl ethers;

Examples of these monomers include vinyl butyl ether,

k.p. 94.3°C, vapor pressure 42 mm Hg at 20°C and vinyl ethyl ether, b.p. 35-36°C and vinyl isobutyl ether, b.p. 80°C. These monomers can be polymerized with catalysts of the boron halide type, e.g. boron trifluoride.

Organosilanes;

Several organosilanes act as monomers and are capable of condensation polymerization either with or without a catalyst. Thus, vinyltriacetoxysilane can form a polymer with moisture

and without catalyst. Dimethyl-diethoxysilane will also polymerize

re to a rubbery, solid substance with moisture and acid or base as a catalyst. Propyltrimethoxysilane will also polymerize to a solid substance with moisture and ammonia as a catalyst.

Compounds with a five-membered ring containing a heterooxygen atom;

An example of this type of monomer is tetrahydrofuran, b.p. 64-66°c, which polymerizes to a solid high molecular weight polymer, m.p. above 100°C, using BF3 or PF3 as catalyst.

Organometallic compounds

There are certain organometallic compounds which have the ability to react with compounds containing ethylenic unsaturation to form solid polymeric adducts. For example, organotin hydrides can react with c-C-unsaturated monomers to form organotin polymers. Thus, a trialkyltin hydride will react with styrene to form a polymer of the structure [ R^Sn (CI^CI^R 1) nl > where R is lower alkyl and R<1> is phenyl. Similar polymers are obtained by reaction with monomeric acrylonitrile or with n-octene.<+>

As explained earlier, the polymerization catalyst to be introduced with the monomer will depend on the monomer itself, the type of polymerization reaction involved, and properties of the catalyst itself. Preferably, the catalyst will be a compound which is either gaseous or easily volatile at room temperatures.

The catalyst can be introduced at the same time as the monomer or before or after this. Furthermore, the catalyst can be used in such a way that it is available for contact with the escaping monomer at the point of leakage, by introducing the catalyst from an external source by means of a "lance" (piece of pipe), or by introducing it into the vessel before the monomer as that the soil or jute at the leak site is pre-sealed. The vessel is then flushed and the monomer is introduced.

Some of the catalysts indicated above cause immediate polymerization when they come into contact with the monomer and therefore cannot be added together with the monomer. They are added in the following way: The vessel is first flushed to remove essentially all oxygen and moisture, and then either the catalyst or the monomer is added to the vessel. The catalyst or monomer is allowed to flow for a predetermined time so that it will escape through the leak and into the surroundings, which + A.J. Leusink et al., "Synthesis of.Group.IV Organometallic Polymers and Related Compounds" (1965) U.S. Dept. Comm.

Clearing House, AD 69554.

in the case of a buried line, will be the surrounding ground. The surrounding soil will preserve the monomer or catalyst at the leak site. An inert gas is then introduced into the vessel to form a barrier between the monomer and the catalyst. then the second compound (whether the monomer or the catalyst) is added to the vessel for a predetermined period of time so that, when it reaches the leak, it will react with the first compound. This sequence is repeated as many times as necessary to seal the leak.

Catalysts

The choice of catalyst for any given monomer has been indicated in the above description of the different types of monomers within the scope of the invention. The different categories of commonly used catalysts have also been discussed above.

These catalyst categories, with examples of individual catalysts, are briefly described with the intention that the implementation of the invention will be better understood.

Free radical catalysts

This category includes various organic peroxides, e.g. acetyl peroxide, methyl ethyl ketone peroxide, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide and also certain nitriles, e.g. α,α-azo-diisobutyronitrile.

Organometallic compounds

Many of these compounds are easily volatile. Examples are: zinc alkyl compounds, e.g. zinc diethyl, b.p. 118°C, vapor pressure 30 mm Hg at 27°C and zinc di-n-propyl, b.p. 160°C, vapor pressure 48 mm Hg at 10°C. Also aluminum alkyl compounds, e.g. aluminum triethyl, b.p. 194°C and aluminum trimethyl, b.p. 130°C; aluminum alkyl hydrides, e.g. diisobutylaluminum hydride and aluminum alkyl halides, e.g. diethylaluminum chloride, b.p. 208°C, vapor pressure 41 mm Hg at 12°C. Also included are metal and metalloidal alkoxides, e.g. silicates, titanates, borates, phosphates, vanadates, i.e. ethyl silicate, isopropyl titanate, methyl borate, ethyl vanadate etc.

Metal hydrides

Examples include borohydrides, e.g. diborane ^ 2^ 6'

a gas, b.p. -92.5°C and pentaborane B2Hg, b.p. 48°C, vapor pressure 66 mm Hg at 0°C.

Lewis acids

These include e.g. boron trifluoride, a gas, b.p. -101°C.

Alkaline earth compounds

These are solid substances that can be found in the soil at the location of the leak, e.g. CaO, Ca (OH)2, CaCO^ and the corresponding strontium compounds.

Alkalis

In some polymerizations, alkalis can be used as catalysts, e.g. ammonia gas, sodium carbonate etc.

Phosphorus halides

Examples include: PCl3, b.p. 76°C, POCl3, b.p. 107°C,PF5(gas) b.p. -84.6°C.

The monomers or catalysts flowing out from the leak may react with oxygen or moisture adsorbed on the surface of mineral particles or with organic materials in the soil or with groundwater or trapped air and thereby initiate polymer growth, or these pre-existing media may activate the catalyst or providing heat to initiate the polymerization.

It is especially when it comes to pipelines that are buried in the ground, that certain components in the ground, e.g. alkaline carbonates, calcium and strontium salts, etc. can act as catalysts. Also trapped oxygen and moisture that is present will activate reactions and form solid reaction products that will seal any leaks, and at the same time bind the soil around the leak and form a solid, reinforcing mass.

The following examples serve to illustrate the practice of the invention.

Example 1

A steel pipe section (2.14 m long, 19.2 mm in diameter) was drilled with a 3.2 mm hole to simulate a leak. The test pipe was buried under 75 cm of moist clay soil with 6.3% moisture content. One end of the tube was connected to a valve-regulated feed line connected to a source of dry nitrogen gas. The nitrogen line was also connected to a heated bubble vessel containing the liquid sealant. Pressure and flow indicators and monitors were also connected to the supply line. The other end of the sample tube was connected to an outlet line, fitted with a valve, which was connected to a manometer and a pressure recorder.<p>The sample tube was first flushed with a stream of dry nitrogen to remove oxygen and moisture. The room temperature varied from 20.0 to 24.4°C. Isoprene monomer and aluminum triethyl in small excess were introduced through separate pipelines into the nitrogen stream bubbler as indicated above, to a concentration of approx. 2000 ppm. At the point of leakage, the aluminum alkyl compound reacted with moisture, whereby hot and simultaneously anhydrous conditions arose. The excess aluminum alkyl then acted as a catalyst for the isoprene polymerization,

and the holes and the area around the opening were sealed with a firm, rubbery plug.

Example 2

Proceeding as in example 1, a stream of ethylene oxide was introduced with a stream of nitrogen, together with zinc diethyl as a catalyst. The concentration of the ethylene oxide was approx. 4000 ppm, while that for zinc diethyl was approx. 500 ppm. When the zinc diethyl reached the leak, it reacted with the moisture in the soil, developing heat, and the excess served to polymerize the ethylene oxide. A firm seal was formed.

Example 3

Proceeding as in Example 1, a stream of tetrahydrofuran, at a concentration of 5000 ppm, and BF^ catalyst at a concentration of 500 ppm, was introduced into a stream of nitrogen and a viscous oil-type polymer was formed, which formed a plug in the pipe openings. Where the pipe is surrounded by soil, the tetrahydrofuran can be introduced into the pipeline first, allowed to pass through the leak opening and saturate the soil, and then the BF^ gas mixed with nitrogen can be passed through the pipe and flow out, so that the tetrahydrofuran polymerizes and saturates the earth. A seal forms in the opening and a reinforcing, solid base mass in the surrounding soil.

Example 4

By proceeding as in example 1, a flow of acrylonitrile and hydrogen peroxide (in the ratio 100 mol:l mol) was established in a concentration of 5000 ppm in nitrogen in the tube. When the gas had become saturated with the monomer, the line pressure was raised to 0.035 kg/cm 2 . Under these conditions, and in contact with the borehole surfaces and moisture, the catalyst was produced by a redox reaction, and the acrylonitrile polymerized to form a solid polymer that sealed the leaks.

Example 5

Proceeding as in example 1, the tube was filled with a flow of nitrogen containing monomeric styrene in a concentration of 5000 ppm and diborane in a concentration of 50 ppm, and the flow was maintained for approx. 15 hours under atmospheric pressure. A seal of solid polystyrene was formed at the leak sites. Excess solid polystyrene was then blown away from the pipe.

Example 6

Proceeding as in example 1, the tube was filled with a nitrogen stream containing a monomer mixture of methyl methacrylate and acrylonitrile in a concentration of 5000 ppm and butyl dibutyl borate in a concentration of 50 ppm. After approx. After 15 hours, the holes were sealed with a solid copolymer of methyl methacrylate and acrylonitrile.

Example 7

By proceeding as in the example, the tube was filled with a nitrogen stream containing equimolar parts of styrene monomer and butadiene monomer, each in a concentration of approx. 5000 ppm;, together with diborane in a concentration of approx. 5% by weight of total monomer used. Within 12 hours, a solid plug of the copolymer formed at the leakage sites.

Claims (9)

1.Procedure for sealing leaks in containers, pipes and the like by introducing a gaseous sealant, mixed with a carrier gas which is inert to the sealant and does not ignite spontaneously in mixture with this under the conditions used, and creating an overpressure such that the sealant flows out at the leak sites, for a time that is sufficient for a firm seal to form in the places where the leaks occurred, characterized by the fact that the sealant used an organic monomer or a mixture of such monomers, the sealing agent being diluted with the carrier gas to a sufficient degree - or used under such conditions - that the mixture does not ignite spontaneously, and by the agent being brought to polymerize at the leakage sites by means of a gaseous polymerization catalyst . 2. Method as stated in claim 1, characterized in that the catalyst is supplied to the leakage points in the carrier gas together with the monomers or the monomer mixture. 3. Method as stated in claim 1, characterized in that only the catalyst is supplied to the leakage points in the carrier gas during a first period, and then the carrier gas with only the monomer or the monomer mixture, this process being repeated until a firm seal is formed. 4. Method as stated in claim 1, characterized in that only the monomer or monomer mixture is supplied to the leakage points in the carrier gas during a first period, and then the carrier gas with only the catalyst. 5. Method as stated in claim 1, characterized in that only the monomer or monomer mixture is supplied to the leakage sites, mixed with the carrier gas, the catalyst being present at the leakage sites in advance or supplied from the outside. 6. Process as stated in claims 1 to 5, characterized in that isoprene is used as monomer, and an aluminum alkyl compound is used as catalyst. 7. Process as stated in claims 1 to 5, characterized in that tetrahydrofuran is used as monomer, and boron trifluoride as catalyst. 8. Process as stated in claims 1 to 5, characterized in that ethylene oxide is used as monomer, and zinc alkyl as catalyst. 9. Method as stated in claims 1 to 5, characterized in that an equimolar mixture of monomeric styrene and butadiene is used to form a copolymer, and that diborane is used as catalyst.