SK200690A3 - Process for producing blown polyurethane insulating foam - Google Patents

Abstract

The foam (I), contg. catalysts, cell stabilisers, and/or flame retardants, has pores free from halogenated hydrocarbons but contg. minor amts. of blowing agent (II) consisting of at least 3-6C alkane with b.pt. at normal pressure (-)10 - (+)70 deg. C. Pref. prepn. of (I) using (II), wherein (1) (II), in conventional amt., is finely distributed either (i) in mixt. of alcohol and isocyanate starting components in conventional ratio for (I), and other finely divided additives such as flame retardants, catalysts, and pore stabilisers, or (ii) in alcohol component, with mixing in of additives, then conventional amt. of isocyanate component for forming (I) is incorporated, finely divided, (2) components are polymerised to form (I) under conventional conditions, partic. of temp.

Description

Process for producing polyurethane insulating foam

Technology area

The present invention relates to a process for the production of a polyurethane insulating foam (PUR) having a particularly uniform cellular structure, wherein the cells are halogenated hydrocarbons such as fluorochlorohydrocarbons (FCKWs) and / or halogenated hydrocarbons (soft hydrocarbons). since they are not used in the process of the invention.

BACKGROUND OF THE INVENTION

Polyurethane foams are used extensively for a variety of purposes, for example, in the manufacture of cushions, carpet backing, furniture upholstery, sponge articles, packaging materials, building insulation materials and refrigeration equipment. So-called polyurethane soft foams, semi-hard foams and hard foams are known. The soft foams are generally foamed by carbon dioxide formed in the reaction of the isocyanates used and water, but also partly by fluorochlorinated hydrocarbons.

In the production of rigid foams, it is used, in particular, and to a large extent, fluorocarbon hydrocarbons as propellant. In production, a significant amount of propellant gas is released into the air or enters the atmosphere from the foam when the cells are disrupted.

Fluorinated chlorinated hydrocarbons appear to be favorable as a propellant from many perspectives because they lend not only good flame retardancy to polyurethane foams, which are required in their use in the furniture industry, but also for the manufacture of cushions and for housing and construction, Due to their physical properties, the polyurethane foams produced, in particular polyurethane hard foams, have very favorable heat conductivity values, the so-called lambda values, so that the polyurethane foams thus produced have very favorable heat conduction characteristics for various applications. By adding further flame retardant products to the mixture of the starting components, the flame retardancy of the obtained polyurethane foams up to the flammability class B2 and B1 can be further increased.

Since the polyurethane foams are foamed from the liquid starting materials, a special cell uniformity with low spatial weight is achievable directly with FCKW or water, and thus a simple foaming in molds or in a belt unit is possible. The belt production, which is used in particular for the production of dampers from polyurethane rigid foams for the construction industry, provides the additional possibility of joining the polyurethane foam to the upper or lower covering layer of a suitable material (flexible or rigid covering layers) during foaming so that a sandwich is obtained. structure.

The disadvantage of this excellent material and its method of manufacture is, from an environmental hygiene point of view, that, to date, almost exclusively fluorocarbon hydrocarbons (FCKW) have been used as the propellant for the foaming of polyurethane foams, especially polyurethane rigid foams, and these fluorochlorinated hydrocarbons have a particularly negative effect. to the Earth's ozone layer. Their use is therefore no longer excusable and is even banned in many countries.

For many years, a variety of gas researches have been used as propellants of fluorochlorinated hydrocarbons for their particular harmfulness, in part or, if possible, with completely different propellants.

For example, attempts have been made to combine the measures known from the production of polyurethane soft compositions based on the addition of water to the diisocyanate-containing starting product so that carbon dioxide is generated as a propellant so that the negative consequences of foam production would be mitigated or eliminated altogether. Such measures, however, lead to a deterioration in the physical properties of the polyurethane foams, since early development of carbon dioxide as a propellant results in polymeric polyurethane products in the form of very open-cell foam. In addition, the material at a slight polymerization stage is still relatively soft and the more or less thin pore walls are easy to tear.

This phenomenon is negligible or even desirable in the case of the polyurethane soft materials themselves, but is undesirable in the case of polyurethane hard materials with the desired high mechanical stability.

However, in connection with water, the thermal insulating ability of the obtained polyurethane foams is also adversely affected by both soft and hard foams. Finally, the use of water also makes polyurethane foam more expensive, since 1 part of water consumes 16 parts of diisocyanate in the chemical reaction, this amount of diisocyanate having to be added in addition to the starting mixture, while using significantly less diisocyanate with chlorofluorocarbons.

Also, other gassing organic liquids cannot be used in the formation of polyurethane, or have proved to be unusable, since halogen-free organic products are much more flammable and even form highly explosive mixtures when gassed and mixed with air oxygen. Especially when using polyurethane foam products in close contact with people using such products, such propellants are forbidden for safety reasons, even when the manufacturer of such polyurethane foam products provides for the removal of the released organic solvent vapors during firming, which is currently technically well possible. However, for many of the above uses, the walls of the closed pores can break and the solvents and vapors contained in the pores can be released, causing a high fire risk when used. On the other hand, a method for producing anti-dyeing by ultraviolet rays of resistant polyurethane foams using halogen-free propellants, but which do not have a sufficiently low foam weight (see JP 57 126 815) is described.

There are also known attempts to replace the fluorocarbon hydrocarbons used as propellant or to reduce the amount of fluorocarbon hydrocarbons used by introducing in a controlled manner air into the polyurethane foam mechanically. Thus, it is known to introduce air into the hydroxyl group containing the components and / or the diisocyanate component mechanically by whipping or mixing before foaming. However, this leads to a dispersing problem (dosing inaccuracies due to different material density). Moreover, we cannot achieve a satisfactory pore structure. However, the fine and uniform pore structure with the low spatial weight of the foam obtained is important for good insulating properties. Also in this case, n low space weights of 30 g / cm < 3 ^> and below are required with air only with difficulty.

Finally, it has been discussed to replace fluorochlorohydrocarbons with not fully halogenated hydrocarbons, for example fluorocarbons called soft FCKW. However, these substances are still very expensive and their long-term effects on the air have not been studied.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide polyurethane foam products which are devoid of halogenated hydrocarbons, having a low specific gravity, low lambda values (i.e. low thermal conductivity, high thermal insulating ability) and high flame retardancy (low flammability class). polyurethane foams in which no halogenated hydrocarbons would be used.

SUMMARY OF THE INVENTION

According to the invention, the process for the production of a polyurethane insulating foam is emulsified as a propellant in relation to a polyol, up to 20% by weight of at least one C 3 -C 6 alkane and at a boiling point at ambient pressure of -10 to + 70 ° C. 5 to 35% based on the total weight of the foam, at least one liquid and / or solid flame retardant and at least one basic catalyst with alcoholic starting materials for the production of polyurethane foams, optionally with admixtures, the isocyanate component and the mixture polymer.

The emulsification is carried out continuously in the premixer prior to admixing the isocyanate, optionally in the presence of at least one emulsifier in an amount of up to 10% by weight, based on the amount of alcoholic components of the polyurethane foam. At least one emulsifier based on fatty acids and derivatives thereof is used. The emulsion of the starting materials with the liquid propellant, the flame retardant and the catalyst can be saturated with at least one noble gas.

As further additives, for example, stabilizers and crosslinking agents are used.

The process according to the invention produces a polyurethane insulating foam with partially or preferably fully closed pores of uniform structure, free from any halogenated hydrocarbons, either FCKW or FCKW, and having a specific gravity of not more than 30 kg / cm 2. It is contained in the pores of the foam

6a at most 30% propellant based on pore volume, depending on the starting materials for the polyurethane. Storage time, reduced pressure and storage temperature and similar conditions promote diffusion of the propellant through the pores of the foam pores.

In a preferred embodiment of the invention, the pores of the foam, when compared to air, contain a greater amount of nitrogen and / or one or more noble gases, while the argon is preferred.

Preferably, the polyurethane foam according to the invention comprises at least one conventional liquid or solid flame retardant, preferably on a phosphorous or boron basis, in particular in an amount of 5 to 35% and in particular in an amount of 7 to 10% to 20% by weight. weight of the polyurethane foam according to the invention as a whole. Most preferably, the polyurethane foam of the invention comprises a solid ammonium salt-based flame retardant, such as a salt of phosphoric acid, metaphosphoric acid, polyphosphoric acid and boric acid alone.

According to another highly preferred embodiment, the polyurethane foam according to the invention comprises a liquid lower flame retardant based on lower alkyl esters of lower alkanephosphonic acid, preferably together with urea, in particular in an amount of 10 to 20% by weight based on the liquid phosphorus-containing flame retardant. as a single flame retardant or together with a solid flame retardant. Particularly preferably, it comprises a liquid phosphorus-containing urea burning agent dissolved therein until saturated.

The catalysts used are preferably basic or strongly basic catalysts in conventional amounts, such as alkali salts of a weak acid, preferably an alkanecarboxylic acid, such as acetic or octanoic acid, and such a catalyst is thus contained in a preferred embodiment of the polyurethane foam according to the invention.

According to another preferred embodiment, the polyurethane foam according to the invention also contains, as a small amount of an organic medium, an anti-combustion agent, preferably an ammonium salt of the abovementioned acids and a preferred anti-combustion agent and urea in said amounts as well as a basic to strongly basic catalyst. According to the starting materials, the polyurethane foam according to the invention optionally contains up to 10% by weight of emulsifier. Preferably, the polyurethane foam according to the invention comprises an emulsifier based on saturated or unsaturated fatty acids or their esters.

The process according to the invention for the production of the polyurethane foam according to the invention is characterized in that a halogen-free organic liquid medium, selected from the group consisting of at least one lower alkane having 3 to 6 carbon atoms, boiling at a min. 70 ° C either finely disperses the mixtures in a mixture consisting of alcoholic starting materials and isocyanate starting materials into a polyurethane foam in the usual ratio of alcohol component and isocyanate component and containing other additives such as catalysts, stabilizers and flame retardants in the usual amount, or preferably, the propellant in the alcoholic starting material is dispersed onto the polyurethane foam with admixture of the other ingredients and then, after finely dispersed, the isocyanate component is admixed in the ratio of alcohol component and isocyanate component common to polyurethane foam and the polymerization of the starting materials to a polyurethane foam is then carried out under otherwise customary conditions, in particular under otherwise customary temperature conditions. In this process, as much organic liquid medium is added as is required to the desired density of the polyurethane foam (i.e. to foam the foam obtained). When attempting to produce more foamed material, i.e., materials with a lower specific density, a greater amount of organic liquid medium must be admixed. A person skilled in the art will readily determine the required amount based on the known volume of gassed organic liquid medium and the desired foam density. Such considerations are known to those skilled in the art from working with propellants known in the art, such as FCKW. If it requires the boiling point of the organic liquid medium used, the polymerization is preferably carried out while maintaining a slight overpressure or underpressure during gasification. Preferably, the obtained polyurethane foam is then stored for two days up to a few months, preferably for 2 to 7 days, at room temperature up to a slightly elevated temperature (about 45 ° C) at ambient pressure to slightly reduced pressure.

The phosphorus-based or boron-based flame-retardant in liquid and / or solid form, preferably in an amount of 5 to 35% by weight, preferably in an amount of 10 to 20% by weight, based on the total weight of reaction mixture used. Particularly preferred is the flame retardant in the form of an ammonium salt based on phosphorus and / or boron and only in solid crystalline form.

According to a further preferred embodiment of the process according to the invention, a lower alkanephosphonic acid ester having 1 to 4 carbon atoms in the alkane moiety, in particular a lower alkanol having 1 to 4 carbon atoms in the ester moiety, such as methylphosphonic acid dimethyl ester, is used. According to another preferred embodiment of the process according to the invention, a liquid phosphorus-containing flame retardant is used in admixture with urea in an amount of 10-20% by weight, based on the weight of the liquid phosphorous-containing flame retardant. against burning with dissolved urea. In this embodiment, good burning values are achieved throughout the time.

Suitable diisocyanates or polyurethane prepolymers having at least two terminal isocyanate groups are known to those skilled in the art. Likewise suitable dialcohols or other compounds having at least two free hydroxyl groups per molecule, such as polyether polyols and / or polyester polyols, are known to those skilled in the art. It is also known to those skilled in the art how the compounds in these groups are used and in what weight ratios these compounds are used to produce polyurethane soft foams, polyurethane semi-rigid foams and polyurethane hard foams to each other.

The German and foreign patent literature of the various authors of the international patent class C 08 G, subclass 18, and the general literature are also recalled in this context. For example, Rompp-Chemielexikon., 7, edition (1975), p. 2774 to 2775 and other references cited therein.

Suitable organic liquid media are those in which the alcoholic components of the polyurethane foams are insoluble or substantially insoluble and which are capable of emulsifying with the alcohol component or alcohol components for the polyurethanes, optionally with emulsifier additives, preferably in an amount of up to 10% by weight, based on starting materials for polyurethane. Examples are lower alkanes, especially having 3 to 6 carbon atoms, such as n-butane, n-pentane, isopentane, n-hexane, dimethylbutane, or mixtures thereof, as obtained in the distillation of petroleum and partially burned to the fact. Particularly good results are obtained with n-pentane or isopentane and therefore these organic solvents are particularly suitable as an organic liquid medium. In this way, very uniform polyurethane foams are obtained with fine and finest pores, which are retained even during storage.

The liquid and solid flame retardants used, in particular phosphorous and boron-based flame retardants, as well as their preferred ammonium salts, are also known to those skilled in the art for the protection of a wide variety of materials. Particular examples are borates, phosphates, metaphosphates and polyphosphates. Among the flame retardants which are added to achieve the firing class B2 in amounts of, for example, about 6000 g / m ³ or more, the solid ammonium salts of this group have proved to be particularly suitable. Other suitable flame retardants for a preferred group of solid products include zinc borate. Solid flame retardants are not introduced through the high-pressure metering pump, since they are abrasive powders resulting in a strong abrasion of the pump. The addition is more efficient by using a kneading screw immediately after the mixed liquid components (polyurethane components + liquid medium) exit from the kneading head.

Suitable emulsifiers are also known to those skilled in the art. Suitable products for a particularly preferred embodiment of the process according to the invention are, for example, fatty acid alkanolamidoethoxylates.

Also suitable products for cross-linking polyurethane foam are known to those skilled in the art as certain Mannich bases. Even very small amounts of water, such as 0.5 to 2% by weight, with respect to the starting mixture, can act as a cross-linking product and can be added to the starting mixture. Optionally, the amount of diisocyanate used must then be increased somewhat in order to maintain the correct ratio between the alcohol components and the isocyanate components. Preferably, both cross-linking means are used.

Advantageously admixing the emulsifier to the starting mixture, the miscibility of the liquid propellant with the polyurethane alcohol component of the present invention substantially improves the necessary emulsion formation, but this is necessary when the finished foamed polyurethane foam is subsequently stored to replace at least one liquid and evaporative foaming process. organic medium to avoid hazardous gases.

The space required for convenient subsequent storage and replacement of the organic liquid medium used for the harmless gases depends on the starting materials, the particular organic liquid medium used, the ambient air temperature, the vacuum used, if any, and the amount of preferred flame retardant used. a basic catalyst and / or an emulsifier.

In part, polyurethane foams according to fire class B2 can be obtained without storage, depending on the choice of the starting materials and the flame retardant used and the quantity thereof, and also on the choice of the catalyst. The storage period is generally 2 to 7 days, but is sometimes longer, for example 6 weeks, and rarely is 4 to 6 months. Usually, the resting is finished in 3 to 4 days. This replacement process can be controlled in a simple way, on the one hand by burning behavior, since after some time it is strongly improved after a certain period of time, on the other hand by a slight increase in the thermal conductivity number from 0.024 W / cm to 0.029 W / (mC). This value of 0.029 W / (m ° C) then remains perfectly constant for some time, and it is concluded that the exchange of hazardous gases has taken place to the desired extent and is essentially complete.

As mentioned above, depending on the choice of ingredients and / or the amount and type of solid flame retardant added, products of fire class B2 are also obtainable without subsequent storage. A subsequent decrease in the heat conductivity number from 0.029 to 0.024 W / (m ° C) was also observed, which was not yet achievable by any method known in the art.

Diametrically with the indicated rise in the thermal conductivity number, the burning behavior changes. Polyurethane foam is often readily flammable and flammable immediately after foaming. In such cases, the burning behavior still improves over several days of storage and the polyurethane foam reaches in about 2 to 7 days, in particular in about 4 days in general the burning behavior corresponding to the burning class B2 or in the case of polyisocyanurate foams and the amount of flame retardant even corresponds to the flame value BI. As mentioned above, the co-use of a phosphorous and urea-containing liquid flame retardant has a beneficial effect on the sustainability of good burning behavior.

In the process of the invention, a small amount of halogenated hydrocarbons can be used as a propellant, for example to comply with DIN 18164, since according to paragraph 3.4 thereof, a suitable polyurethane foam is defined as the halogenated hydrocarbon propellant by chemical reaction with an acidic hydrogen. Certain organic media used according to the invention are readily miscible with halogenated hydrocarbons, so that, for example, 95 or even 99% of the halogenated hydrocarbons needed can be replaced by certain organic media according to the invention. By using small amounts of fluorochlorinated hydrocarbons or methylene chloride boiling in the art (40 ° C), they can be replaced by emulsifiers.

The invention is illustrated in more detail by practical examples, which are not intended to limit the invention.

Example 1

The hard polyurethane foam is produced by emulsifying at 22 ° C a mixture containing (in each case by weight) parts of a polyether alcohol having a hydroxyl number of about 550 (viscosity of about 8000 mPa · s at 25 ° C) from the Shell CARADOL® product range. Chemistry, parts of a saturated polyester with a hydroxyl number crosslinker of about 500 (viscosity 8 - 10000 mPa · s at 25 ^e C), parts of an aromatic polyether alcohol with a hydroxyl number of about 500 (viscosity 5000 at 25 ° C), parts of a liquid dimethyl flame retardant (DMMP) ) with a phosphorus content by weight of 26% of emulsifier EMULGIN ^ 550 ^R of Henkel AG, parts of silicone as pore stabilizer, ammoniumpolyfosfátu parts as the solid flame retardant composition, parts catalyst based on an alkali acetate, and parts of n-pentane.

The emulsion is admixed in a conventional manner for the production of polyurethane foam

172 parts of diisocyanate MDI (diphenylmethane-4,4-diisocyanate) and the obtained mixture are foamed in a conventional shaking unit at normal pressure and room temperature. The obtained polyurethane foam is then stored at room temperature (20 ° C) and under normal pressure for 4 days.

The polyurethane foam obtained has the following characteristics:

o Density immediately after production: 30 to 40 g / cm compressive stress immediately after production: approximately 0.013

MPa, after 4-6 weeks of storage 0.016 to 0.017 MPa, Burning behavior immediately after production: Shortly ignitable, but self-extinguishing, Burning behavior after 4 days of age B2, Conductivity number immediately after production approximately 0.024 W / (m 'C) 20 days after production 0.028 to 0.029 W / (m < 0 > C), after storage for 14 to 16 weeks 0.025, after storage for 4 to 6 months 0.024 W / (m < 0 > C).

Example 2

Polyurethane rigid foam is produced by emulsifying at room temperature a mixture containing (each by weight):

parts of a polyether alcohol having a hydroxyl number of about 550 (viscosity about 8000 mPa.s at 25 ° C), parts of a saturated polyester with a Mannich base crosslinking agent with a total hydroxyl number of about 500 (viscosity about 8 to 10000 mPa.s at 25 ° C) parts of an aromatic polyether alcohol having a hydroxyl number of about 500 (viscosity about 5000 at 25 ° C), parts of a liquid dimethyl flame retardant, parts of Henkel AG EMULGIN ® C 4 emulsifier, parts of a silicone pore stabilizer, parts of a monoammonium phosphate flame retardant, parts of potassium acetate catalyst parts of n-pentane mixed with up to 5% n-propane and n-butane.

The emulsion is admixed to the polyurethane foam in a manner known per se

172 parts of diisocyanate MDI and the mixture obtained is filled in a manner known per se under normal pressure. The obtained polyurethane rigid foam is then stored at room temperature (20 ° C) under normal pressure for four days.

Example 3

At a temperature of 22 ° C, a mixture containing (always by weight) is emulsified:

parts of a polyether alcohol having a hydroxyl number of about 550 (viscosity about 8000 mPa · s at 25 ° C), parts of a saturated polyester with a crosslinking agent having a hydroxyl number of about 500 (viscosity of about 8 to 10000 mPa · s at 25 ^eC ); 500 (viscosity about 5000 mPa · s at 25 ° C), parts as DMF with a phosphorus content of 26% by weight, parts of water, parts of emulsifier EMULGIN ® C 4, parts of silicone as pore stabilizer parts of diammonium phosphate as a solid flame retardant, parts of potassium octoate catalyst, parts of n-pentane.

The emulsion is mixed

172 parts of MDI diisocyanate and the resulting mixture are foamed in a manner known per se under normal pressure. The resulting polyurethane foam is then stored at room temperature (20 ° C) and under normal pressure for 4 days.

Example 4

Polyurethane rigid foam is produced by emulsifying at room temperature a mixture containing (each by weight):

parts of a polyether alcohol having a hydroxyl number of about 550 (viscosity of about 8000 mPa.s at 25 ° C) based on products of the SUCCR 05 ^^ group, parts of a saturated polyester with a hydroxyl number of about 500 (viscosity of about 8 to 1000 mPa.s at 25 ° C) parts of an aromatic polyether alcohol having a hydroxyl number of about 500 (viscosity of about 5000 mPa.s at 25 ° C), parts as a liquid dimethyl flame retardant (DMMP) containing 26% phosphorus, parts of the emulsifier EMULGIN ^ ¹ *) 550 from Henkel AG, parts of silicone as a pore stabilizer, parts of water as a crosslinker, parts of solid ammonium polyphosphate mixed with 5% zinc borate, parts of an alkali acetate catalyst, parts of n-pentane.

It is added to the emulsion

172 parts of MDI diisocyanate and the resulting mixture are foamed in a manner known per se under normal pressure. The resulting polyurethane foam is then stored at room temperature (20 ^Q C) and normal pressure for 4 days.

Example 5

Polyurethane rigid foam is produced by emulsifying at 22 ° C a mixture containing (each by weight):

parts of a polyether alcohol and a hydroxyl number of approximately 550 (viscosity of about 8000 mPa.s at 25 C) from the CARADOLI ^R product group) of Shell Chemie, parts of a saturated polyester with a hydroxyl number crosslinking agent of about 500 (viscosity of about 8 to 10000 mPa.s at 25 Parts of an aromatic polyether alcohol having a hydroxyl number of about 500 at 25 ° C) parts of a saturated dimethylmethylphosphonate (viscosity of about 5000 mPa.s of a urea in liquid (DMMP) solution as a 26% phosphorus-containing liquid flame retardant containing

1.05 parts of urea in 7 parts of DMMP, parts of EMULGIN® ^R ^ 550 from Henkel

AG, parts of silicone as a pore stabilizer, parts of ammonium polyphosphate as a solid flame retardant, parts of an alkali acetate catalyst, parts of n-pentane.

172 diphenylmethane-4,4-diisocyanate is added to the emulsion in a manner known per se for the production of polyurethane foam and stored in a manner known per se in a normal pressure whisker at room temperature (20 ° C) for days.

A class B2 initial flame retardancy is obtained, after further storage for several weeks and maintained at a slightly elevated temperature.

Claims (5)

PATENT CLAIMS cl A process for the production of a polyurethane insulating foam, characterized in that it is emulsified as a propellant in relation to the polyol by weight up to 20% of at least one C 3 -C 6 alkane and boiling point at ambient pressure of -10 to + 70 ° C, 5 to 35% based on the total weight of the foam, at least one liquid and / or solid flame retardant and at least one basic a catalyst with alcoholic starting materials for the production of polyurethane foams, optionally with admixture with other additives, an isocyanate component is added to the emulsion and the mixture is polymerized. Process according to claim 1, characterized in that the emulsification is carried out continuously in the premixer before admixing the isocyanate. Method according to claim 1, characterized in that the emulsification is carried out in the presence of at least one emulsifier. Method according to claim 1, characterized in that at least one emulsifier is added in an amount of up to 10% by weight, based on the amount of alcoholic components of the polyurethane foam. A process according to claim 3 or 4, characterized in that at least one emulsifier based on fatty acids and derivatives thereof is used.