SK371292A3 - Mixtures of driving agents and blowing agents and their using - Google Patents

Abstract

The invention relates to compositions containing trifluoromethane and a partially halogenated hydrocarbon from the group consisting of dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane and difluoroethane, and to the use thereof as blowing agent compositions.

Description

Technical field

The invention relates to mixtures containing trifluoromethane and to their use as propellants and blowing agents.

BACKGROUND OF THE INVENTION The use of fluorinated and chlorinated hydrocarbons (FCUV) as aerosol propellants as well as blowing agents in the manufacture of foamed plastic clays is no longer desirable for environmental reasons. Many of the alternatives proposed so far, such as e.g. The propane or butane used as aerosol propellants has the drawback that they are readily flammable. Other substitutes which have replaced the conventional FCUV in the production of foamed plastics, in particular in the production of polyethylene, polyurethane or polystyrene foam plastics, have, for example, e.g. carbon dioxide, the drawback that foamed plastics produced using these replacement blowing agents have unsatisfactory thermal insulating properties.

For the production of extruded foam plastics p

the blowing agent used has to satisfy a number of claims in terms of technical use. For example, the blowing agent added to the premix in the manufacture of the foamed plastic should not change its viscosity too much. During expansion, the blowing agent must exhibit a high evaporation rate in order to maintain a small concentration of residual gas. There must also be no penetration of the cells (which may result in the collapse of the cells before the foam plastic solidifies). The blowing agent is also intended to allow the production of low-density fine A-cell foam. Such foam plastics can then be used very well in packaging because of their low weight. In particular, the preparation of a suitable blowing agent, which would replace the hitherto used FCUV in foaming the so-called polyurethane one-component foamed plastics, presents further problems. Polyurethane mono-component foam plastics are obtained when the polyol premix, together with an excess of di- and / or polyisocyanate in the presence of a catalyst and, optionally, other auxiliaries and auxiliaries, is converted to a so-called prepolymer which can be discharged from the pressure reservoir by blowing agent. Most prepolymers for polyurethane mono-component foam compositions have a very high viscosity, so that the blowing agent must have good dissolution properties so that the prepolymer can be foamed without problems from the aerosol container.

SUMMARY OF THE INVENTION It is an object of the present invention to provide novel blends of propellants and blowing agents in which the prior art drawbacks do not occur.

Podstatoivynálezu

Surprisingly, it has now been found that mixtures with trifluoromethane with a partially halogenated hydrocarbon of the group of dichlorotrifluoroethane, difluorofluoroethane, chlorodifluoroethane and difluoroethane are suitable as mixtures of blowing agents and propellants.

The invention therefore relates to mixtures comprising trifluoromethane and a partially halogenated hydrocarbon selected from the group consisting of dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane and difluoroethane.

For the purposes of the invention, dichlorotrifluoroethane means 1,1-dichloro-2,2,2-trifluoroethane (= R123) and its isomeric compounds 1,2-dichloro-1,1,2-trifluoroethane (= R123a) and 1,1 dichloro-1,2,2-trifluoroethane (= R123b), as well as mixtures thereof. The term dichlorofluoroethane, for the purposes of this vanalysis, means 2,3-dichloro-1-fluoroethane (R141),

1,1-dichloro-2-fluoroethane (R141a) and 1,1-dichloro-1-fluoroethane (R141b), as well as mixtures thereof. For the purposes of the invention, chlorodifluoroethane means 1-chloro-2,2-difluoroethane (R142), 1-chloro-1,2-difluoroethane (R142a) and 1-chloro-1,1-difluoroethane (R142b), as well as mixtures thereof. For the purposes of the present invention, difluoroethane means 1,2-difluoroethane (R152) and 1,1-difluoroethane (R152a), as well as mixtures thereof.

Preference is given to propellants and blowing agents which contain trifluoroethane (R23) and from the group of partially halogenated hydrocarbons 1,1-dichloro-1-fluoroethane (R141b), 1-chloro-1,1-difluoroethane (R142b); , 1-dichloro-2,2,2-trifluoroethane (R123) or 1,1-difluoroethane (R52a).

Effective content! propellants and blowing agents according to the invention trifluoromethane (R23) in an amount of from 5 to 35% by weight, preferably 5 to 25% by weight, and a partial halogenated hydrocarbon in an amount of from 65 to 15% by weight. Preference is given to propellants and blowing agents containing them. trifluoromethane (R23) in an amount of from 5 to 25% by weight and 1-chloro-1,1-difluoroethane (R142b) or 1,1-dichloro-1-fluoroethane (R141b) in an amount of from 75 to 95% by weight or 1,1 -dichloro-2,2,2-trifluoroethane (R123) in an amount of from 65 to 80% by weight or 1,1-difluoroethane (R52a) in an amount of from 85 to 95% by weight. Thus, for example, mixtures of R23 and 75 to 85% by weight of R142b are suitable as blowing agents for the production of foamed plastics. Mixtures of R23 and 90 to 95% by weight of R41b are suitable as propellants for the production of aerosols.

It is surprising that trifluoromethane (R23) is useful as a propellant and blowing agent component. Trifluoromethane (R23) has a boiling point of -82 ° C. At 20 ° C pure trifluoromethane (R23) has a very high vapor pressure of about 42 to 43 bar. These physical values of trifluoromethane (R23) therefore lie far beyond the usual limits for propellants and blowing agents. It was not foreseeable that the vapor pressure of the trifluoromethane in the compositions of the present invention was allowed to be compressed so far that trifluoromethane (R23) could be used in mixtures of propellants and blowing agents with the above-mentioned partially halogenated hydrocarbons. The present invention thus enables the preparation of a mixture of propellants and blowing agents with a low ozone depleting potential (ODP) which are equal to the FCUV used so far in terms of propellants and blowing agents. The particular advantage of mixing propellants and blowing agents according to the invention is to be observed in that e.g. When the propellant mixture according to the invention is used in the aerosol spray canisters, the desired propulsion pressure can also be kept practically constant throughout the use.

The propellant / blowing agent compositions of the present invention, composed of trifluoromethane (R23) and dichlorofluoroethane, in particular 1,1-dichloro-1-fluoroethane (R141b), can be used in all applications where FCUV (propellants and blowing agents) has been used ( fluorinated and chlorinated hydrocarbons). The propellant compositions of the present invention, composed of trifluoromethane (R23) and 1,1-dichloro-1-fluoroethane (R141b), can be used to produce an aerosol, for example, in cosmetics, pharmaceuticals, detergents, herbicide, insecticide, pesticides, paints. and paint.

With the propellant compositions of the present invention, composed of trifluoromethane (R23) and 1,1-dichloro-1-fluoroethane (R141b), aerosols can be prepared from the liquid formulations of the active ingredients required for a particular application, e.g. pharmaceuticals, cosmetics, pesticides, insecticides, detergents or paints. These formulations may contain known components, such as dispersants or solvents, such as e.g. water organic solvents, dispersing aids such as surfactants # fillers, for example dispersed silica, excipients for modifying rheological properties such as carboxymethylcellulose or polyvinyl acetate, and binders such as e.g. polyvinylpyrrolidone.

It is a further object of the present invention to use the compositions of the present invention as propellants in a process for producing an aerosol of a liquid to be sprayed from a pressurized container. According to the invention, the process for producing an aerosol of the liquid to be atomized is effected by producing an aerosol from a pressurized container containing the liquid to be sprayed and a propellant mixture according to the invention by relieving the overpressure prevailing in the pressurized container to atmospheric pressure via a suitable aerosol valve. e.g. spray handpiece. When using the composition of the present invention as an aerosol propellant, the composition of the propellant of the invention is combined with a liquid to be sprayed into a pressure die, e.g. aerosol containers.

The amount of propellant is chosen so that a pressure of about 10 bar is established in the pressure reservoir at 50 ° C. Suitable propellants for aerosol containers are, in particular, propellant mixtures consisting of 5 to 10% by weight of trifluoromethane (R23) and 90 to 95% by weight of 1,1-dichloro-1-fluoroethane (R141b). In particular, trifluoromethane (R23) in an amount of 7.5% by weight and 1,1-dichloro-1-fluoroethane (R141b) in an amount of 92.5% by weight are used.

It is a further object of the invention to use the composition of the invention as blowing agents in processes for the production of foamed plastics. Mixtures of blowing agents containing 5 to 25% by weight, in particular 15 to 25% by weight of trifluoromethane (R23) and 75 to 95% by weight, in particular 80% by weight of 1-chloro-1,1-difluoroethane, have proved to be particularly advantageous for this purpose. (R142b) or 5 to 35% by weight, preferably 20 to 35% by weight, of trifluoromethane (R23) and 65 to 95% by weight of 1,1-dichloro-2,2,2-trifluoroethane (R123) or 5 to 15% by weight of trifluoromethan and 85 to 95% by weight of 1,1-difluoroethane (R152a). The process according to the invention is carried out by adding to the melt of starting materials suitable for the production of foamed plastics trifluoromethane (R23) in an amount of from 5 to 35% by weight, based on the total blowing agent, and a partially halogenated hydrocarbon selected from dichlorotrifluoroethane. , dichlorofluoroethane, chlorodifluoroethane and difluoroethane in an amount of from 65 to% by weight, based on the total weight of the blowing agent, singly or admixed, optionally under pressure, and performs a plastic mass, optionally maintaining a slight overpressure or underpressure during the foaming process. The mixing of the blowing agent can be carried out in a manner known per se.

In one preferred variant, the process for producing foamed plastics is carried out using a mixture of propellants according to the invention by an extrusion process. In this case, mixtures suitable for the production of foamed plastics are extruded! directly to foamed boards, foils, moldings, profiles or particles. The extruded products have a very thin outer surface and low density as so-called light foam. Polyethylene or polystyrene foams are particularly preferred in this way. Examples of extruded polystyrene foams that can be manufactured using the blowing agent composition of the present invention include e.g. polystyrene foam sheets, polystyrene foam sheets or polystyrene integral foams. Examples of extruded polyethylene foams are e.g. polyethylene sheets, polyethylene tracks or polyethylene foam pipes as used to insulate pipes.

The extrusion of the foams according to the invention using the blowing agent mixture according to the invention, in particular polystyrene or polyethylene foams, can be carried out in known extrusion loads. In addition, in addition to the polymers and / or the polymerizable components, known additives and / or auxiliaries, for example nucleating agents, pore-regulating agents, preservatives, can be added to the mixtures which are suitable for use in the production of foamed materials. flame retardants, antistatic agents, stabilizers, plasticizers, crosslinkers, fillers or colorants.

The closed-cell foams produced using the blowing agent composition of the invention are characterized by a uniform fine cell structure. The foamed plastics obtained also have a very small space weight with surprisingly high mechanical stability and compressive strength. The closed cell foams thus obtained typically have 3 densities ranging from 25 to about 320 kg / m 2. The polystyrene foam sheets produced with blowing agent compositions according to the invention, in particular mixtures of trifluoromethane (R23) and 1-chloro-1,1-difluoroethane (R142b), have, for example, a density of about 30 kg / m, polystyrene foam sheets having a density of about 35 kg / m. m. The foams obtained using the blowing agent composition according to the invention are characterized by a high thermal insulation capacity.

In a further preferred variant of the invention, blowing agent mixtures according to the invention are used in the manufacture of polyurethane one-component foams, using them from a pressure tank. Polyurethane mono-component foams are formed when a polyol or a polyol mixture is reacted in the presence of a catalyst with an excess of di- and / or polyisocyanate to form a prepolymer. Optionally, the reaction is carried out with the addition of a stabilizer and / or flame retardant. This can take place in a pressure reservoir, e.g. aerosol container, followed by a foamer using a blowing agent. In the process, the prepolymer is expelled from the pressure reservoir by means of a blowing agent, whereby a one-component polyurethane foam is obtained. According to the invention, in the manufacture of a polyurethane one-component foam from a pressurized container comprising a polyurethane foam mixture of one polyol component, one polyisocyanate component, a catalyst and optionally other conventional auxiliaries and the use of a blowing agent mixture according to the invention, the polyurethane one-component foam is obtained by atmospheric pressure reservoir through a suitable valve. The use of a blowing agent composition according to the invention composed of trifluoromethane (R23) in an amount of from 10 to 30% by weight of S and 1-chloro-1,1-difluoroethane (R142b) has proven to be very advantageous in the production of a polyurethane mono-component foam. 1,1-dichloro-2,2,2-trifluoroethane (R123) or 1,1-difluoroethane (R152a) in an amount of up to 70 to 90% by weight. In the foamed mixture of the polyethane mono-component foam, one known polyol component, one polyisocyanate component, a catalyst and, if desired, a flame retardant auxiliary, which are further components of the blowing agent composition according to the invention, can be present in a manner known per se. As the polyol component, e.g. polyether polyols which are obtained as addition products of propylene oxide or ethylene oxide to polyhydric alcohols, water or ethylenediamine, or polyester polyols which are obtained as polycondensation products from polyols with dicarboxylic acids or their anhydrides, or mixtures thereof in polyurethane mono-component foam mixtures. A typical polyol component may be e.g. a mixture of a brominated polyether polyol (e.g., diol or triol) having a hydroxyl number of from 200 to 350 with a polyether polyol (e.g., diol) having a hydroxyl number of 110.

As polyisocyanate component, for example, diphenylmethane-4,4'-diisocyanate, diisocyanato-toluene,

1,5-diisocyanato-naphthalene, triisocyanato-triphenylmethane,

1,6-diisocyanato-hexane, preferably diphenylmethane, or mixtures thereof.

Typical catalysts in polyurethane mono-component foam mixtures which can be foamed in the process of the present invention using a blowing agent composition of the present invention consisting of trifluoromethane (R23) and 1-chloro-1,1-difluoroethane (R142b) are organic amines, aminoalcohols or aminoethers , e.g. 2-dimethylaminoethyl-3-dimethylaminopropyl ether, diethanolamine, dimethylcyclohexylamine, 2-dimethylaminoethyl ether, or morpholine compounds such as e.g. 2,2-dimorpholinodiethyl ether, N, N-dimethylaminoethylmorpholine, N-methylImorpholine.

Morpholine compounds, especially 2,2-dimorpholinodiethyl ether, are preferred.

Tris-chloroisopropyl phosphate, tris-chloroethyl phosphate, trichlopropyl phosphate, dimethylene ethyl phosphate, tris-dichlorisopropyl phosphate, in particular trichloropropyl phosphate can be used as the usual flame retardants.

Siloxane copolymers are suitable as stabilizers.

The blowing agent compositions of the present invention have very good solubility for polyurethane one-component foam

one-component foam mixtures, for example for the filling and foaming process.

The one-component polyurethane foam mixture to be foamed comprises suitably 20 to 30% by weight of a polyol component, 40 to 60% by weight of a polyisocyanate component, 0.1 to 3% by weight of a catalyst or up to 15% by weight of a flame retardant or 1 to 3%. 2% by weight of the foam stabilizer leads up to 25% by weight of the blowing agent mixture according to the invention.

A typical polyurethane one-component foam mixture, which can preferably be foamed with the blowing agent composition of the present invention, is thus comprised, for example, of about 22.5% by weight of a polyol component, e.g. from a mixture of brominated polyether polyol having a hydroxyl number of from 200 to 350 and a polyether polyol having a hydroxyl number of 110 in a 1: 1 mixture ratio, about 42.5% by weight of a polyisocyanate component, e.g. diphenylmethane-4,4'-diisocyanate, about 0.5% by weight of a catalyst such as e.g. 2,2-ditnorfolino diethyl ether, about 1.5% by weight of a silicone foam stabilizer, about 13% by weight of a flame retardant such as e.g. of trichloropropyl phosphate and one portion of about 20% by weight of the blowing agent composition of the invention.

Such a one-component polyurethane foam baton can be used to produce a one-component foam with a uniform fine-cell structure and low raw density, e.g.

, with a crude density of about 25 kg / m. Due to the good thermal insulation properties, one-component polyurethane is suitable

3.0 foams produced according to the process of the invention, particularly well for assembly purposes, e.g. in the construction and housing sector.

The advantages of using a blend of blowing agents and propellants according to the invention are to be seen in that they are e.g. as propellants in aerosol gas packagings, it achieves uniform spraying of the active substance, while the initial pressure is largely maintained by the process of emptying the aerosol can.

The blowing agent mixtures according to the invention can be easily liquefied under pressure and have good solubility in polymerizable bars, which is particularly advantageous for use as blowing agents in the production of foamed plastics / especially in the extrusion of polyethylene or polystyrene foams and also in the use of such blowing agents. polyurethane one-component foams by pressure tank process. Using the blowing agent compositions of the present invention, foamed plastics having a very uniform fine-cellular porous structure and low bulk density, having high compressive strength and good thermal insulation properties, can thus be produced.

The following examples are intended to illustrate the invention in greater detail without limiting its scope.

DETAILED DESCRIPTION OF THE INVENTION

Example 1 A mixture composed of R23 and R141b as an aerosol propellant

A mixture of 300 parts by weight of paint solution and 60 parts by weight of a propellant mixture composed of 7.5% by weight of R23 and 92.5% by weight of R141b is sprayed by means of a conventional aerosol filling device into an aluminum aerosol pressure vessel. The aerosol can is then provided with an aerosol valve. The volume of the aerosol can is 400 cm. At 50 ° C, a pressure of about 10 bar is measured inside the can.

When spraying the mixture, a spray pattern is obtained with 3-color spraying of the paint solution. $ ηί during gradual emptying, no appreciable loss of initial pressure is found at the torus. The container can be emptied completely.

Example 2 Production of polystyrene foam using a blowing agent mixture composed of K23 and R142b

200 kg of polystyrene (melting point 3.0-110) are mixed with 2 kg of talc as nucleating agent. The mixture is metered into a conventional extruder and melt. About 3% by weight of the blowing agent, based on polystyrene, is metered into the polystyrene melt into the melt zone of the extruder. The blowing agent mixture according to the invention, which consists of 20 parts by weight R23 and 30 parts by weight R142b, is used as blowing agent. In the mixing zone, the polystyrene melt is mixed homogeneously with the blowing agent according to the invention, whereupon the mixture obtained is extruded through a nozzle.

A foam with closed cells and an equal, fine-cellular structure is obtained. Polystyrene foam foils or foam plates can be produced in this case according to the extension used on the extruder. The polystyrene foam sheet thus produced has a density of about 35 kg / m < 2 > and good foaming properties. The polystyrene foam sheet 3 thus produced has a density of about 30 kg / t.

EXAMPLE 3 Production of Polyethylene Foam Using a Blasting Agent Composed of R23 and R142b

200 kg of polyethylene (m.p. 3.5-150) are extruded as described in Example 2. The process is carried out with a blowing agent composition according to the invention, consisting of R23 and R42b, from those described in Example 2. The amounts correspond to the figures given in Example 2. A polyethylene foam pipe, as used for pipe insulation, with a density of about 40 is produced. kg / m. A fine-cell polyethylene foam having a shrinkage of about 5% is obtained.

Example 4 Use of a blowing agent mixture consisting of R23 and

R.142b for polyurethane one-component foams

Polyol premix composed of g of polyether polyol (triol), brominated, hydroxyl value 330 50 g polyether polyol (diol), hydroxyl number 110 60 g trichloropropyl phosphate

Hg of silicone foam stabilizer and * 3g of dirnorfolinodiethyl ether are charged into a 1000 cc aluminum aerosol canister. 190 g of diphenylmethane-4,4'-diisocyanate are added and the aerosol canister is sealed with a aerosol discharge valve.

90 g of a blowing agent composition according to the invention, composed of 20% by weight of R23 (corresponding to 18 g) and 80% by weight of R42b (corresponding to 72 g), are then injected into the container by a conventional aerosol filling device. The vessel is shaken briefly and then allowed to stand for 24 hours to form the prepolymer. After this time, the polyurethane one-component foam mixture is ready for use.

The polyurethane one-component foam mixture is expelled from the aerosol container using the blowing agent mixture of the invention.

A 3e polyurethane mono-component foam is obtained with a raw (initial) density of about 25 kg / m < 2 > and a uniform, fine-celled structure. The shrinkage of the polyurethane one-component foam after storage for 7 days at an air humidity of about 90% is about 5% on average.

Example 5 Use of a blowing agent mixture consisting of R23 and

R123 for polyurethane one-component foams

The procedure is as described in Example 4, wherein the blowing agent used is a 90% blowing agent mixture according to the invention which consists of 30% by weight of S23 and 70% by weight of S123.

Example 6 Use of a blowing agent mixture consisting of R23 and

R152a for polyurethane one-component foamed foams

The procedure is as described in Example 4, wherein 90 g of a 3% blowing agent according to the invention is used as the blowing agent, which consists of 10% by weight of R23 and 50% by weight of R152a.

Claims (17)

PATENT CLAIMS 1. Propellants and blowing agents, characterized in that they contain trifluoromethane and a partially halogenated hydrocarbon selected from the group consisting of dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane and difluoroethane. Propellant and blowing agent mixtures according to claim 1, characterized in that they contain trifluoromethane in an amount of 5 to 35% by weight and a partially halogenated hydrocarbon selected from the group comprising dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane and difluoroethane in an amount of 65 to 25% by weight. Propellant-blowing agent mixtures according to claim 2, characterized in that they comprise dichlorofluoroethane as a partially halogenated hydrocarbon, in particular 1,1-dichloro-i-fluoroethane (R 14ib), or chlorodifluoroethane, especially 1-chloro-1,1-difluoroethane (R 142b), in an amount of from 75 to 95% by weight. Propellant and blowing agent mixtures according to claim 2, characterized in that they comprise dichlorotrifluoroethane, in particular 1,1-dichloro-2,2,2-trifluoroethane (R123), in a quantity of from 65 to 80% by weight, as the partially halogenated hydrocarbon. 5. Propellants and blowing agents according to claim 2, characterized in that the halogenated hydrocarbon contains difluoroethane, in particular 1,1-difluoroethane (R152a), in an amount of from 85 to 25% by weight. Use of a propellant mixture according to claim 1 for producing an aerosol of the liquid to be sprayed. Use according to claim 6, characterized in that the propellant mixture used is a mixture composed of 5 to 10% by weight of trifluoromethane (R23) and 90 to 95% by weight of 1,1-dichloro-1-fluoroethane (R41b). 8. A method of making an aerosol of a liquid to be sprayed, comprising: from a pressurized container containing the liquid to be sprayed and a propellant mixture comprised of 5 to 10% by weight trifluoromethane (R23) and 90% by weight 1,1-Dichloro-1-fluoroethane (R141b), produces an aerosol by releasing the excess pressure existing in the pressurized container to atmospheric pressure through a suitable aerosol valve. _e Use of a blowing agent mixture according to claim 1 in the manufacture Foam plastics. * Use according to claim 9, characterized in that a blend 3 consisting of 5 to 25% by weight, preferably 15 to 25% by weight, trifluoromethane (R.23) and 75 to 95% by weight of 1-chloro-1 is used as blowing agent. 1-difluoroethane (R142b ,. Use according to claim 9, characterized in that a mixture of 5 to 35% by weight, preferably 20 to 35% by weight, trifluoromethane (R23) and 65 to 95% by weight 1,1dichior-2 is used as blowing agent. 2,2-trifluoroethane (R123). | Use according to claim 9, characterized in that a mixture of 5 to 15% by weight of trifluoromethane (R23) and 85 to 95% by weight of 1,1-difluoroethane (R152a) is used as the blowing agent. 12. A process for the production of foamed plastics comprising adding to the melt of starting materials suitable for the production of foamed plastics trifluoromethane (R23) in an amount of from 5 to 35% by weight, based on the total a blowing agent and a partially halogenated hydrocarbon selected from the group consisting of dichloro trifluoroethane, dichlorofluoroethane, chlorofluoroethane and difluoroethane in an amount of from 65 to 95% by weight, based on the total blowing agent, singly or in admixture, optionally under by pressure and polymerization of the starting materials for the foamed material produced, optionally, while maintaining a slight overpressure or underpressure during the foaming process. 14. A method according to claim 13, wherein the process is carried out as an extrusion process. Process according to Claim 14, characterized in that the starting materials used for the production of polyethylene or polystyrene foams are used in the process. 16. Production method of polyurethane one-component foam A composition comprising a pressure reservoir comprising a polyurethane mono-constituent foam deer composed of a polyol component, a polyocyanate component, a catalyst and, optionally, other customary auxiliaries as well as a blowing agent consisting of trifluoromethanesulfonate-containing trifluoromethanesulfonate and a portion of trifluoromethanomethane. , dichlorofluoroethane, chlorodifluoroethane, and difluoroethane, produce a polyurethane mono-component foam by releasing the excess pressure exiting in the pressure reservoir to atmospheric pressure through a suitable valve. » 17. A one-component polyurethane foam composition comprising y a polyol component and a polyisocyanate component as a catalyst, a blowing agent and, optionally, other customary auxiliaries, characterized in that it comprises as blowing agent a blowing agent mixture according to claim 1. Polyurethane mono-component foam mixture according to Claim 17, characterized in that it contains, as blowing agent, trifluoromethane (R23) in an amount of from 10 to 30% by weight and 1-chloro-1,1-fluoroethane (R142b) or 1,1-dichloro -2,2,2-trifluoroethane (R123) or 1,1-difluoroethane (R.1.52a) in an amount of from 70 to 90% by weight.