DE10329755B4 - Process for producing a foam from at least two components - Google Patents

Abstract

A method for producing a foam of at least two components from an aerosol can, the interior of which is divided into at least two mutually sealed chambers, and which has a valve plate common to the two chambers, in each of which an outlet valve communicating with its interior is used for each chamber which are actuated together by an axially displaceable trigger member in the sense of opening all valves, wherein the first chamber of the aerosol can is formed by a valve plate mounted on the flexible foil bag and the second chamber is formed by the remaining space of the aerosol can, characterized that in the second chamber one of the two components, mixed with at least two gases, is located, where one gas has a critical temperature tK of ≥ -10 ° C and the other gas has a critical temperature tK of <-10 ° C, and that in the flexible film bag, the other component is taken and that the gas with the critical temperature tK of <-10 ° C causes the discharge of the component from the second chamber and at the same time the application of the component located in the film bag.

Description

The invention relates to a method for producing a foam from at least two components according to the preamble of claim 1.

An aerosol can of the type outlined in the preamble for bicomponent products is off DE 201 18 988 U1 known. In this case, propellant gas, such as R 134a or compressed air is used as propellant. Here, the pressure on the flexible bag is brought by the propellant gas or the compressed air alone in the otherwise empty interior of the can to act to squeeze out the contents of the flexible bag by the gas pressure. For the two-component products no foam is produced.

Out EP 0 111 089 A2 . DE 199 18 957 A1 and WO 96/18556 A1 Two-chamber pressure cans for the production of polymer foams are known. Here, no mixtures of nitrogen and liquid propellant gas are mentioned.

Out DE 39 30 594 A1 and DE 199 26 312 A1 are known one-component polyurethane foams with improved curing. It mentions the mixture of liquid and gaseous propellants in the production of polymer foams.

For a long time 2-component masses (2K masses) z. B. 2K adhesive filled in commercial double cartridges. The two components are pumped through a static mixer with a manual or electric ejection device. This is particularly difficult with viscous masses. However, if thin components are used, the applied mixture immediately dissolves, which is very impractical for the user.

PU topical foam, which can also be referred to as an adhesive, is produced by filling it into aerosol cans. The propellant and possibly a chemical reaction produces foam. The commercially available PU foams from the aerosol can have a density of less than 0.1 g / cm ³ . It does not matter whether it is one-component (1K) or two-component (2K) foam. The advantage of the low density is the large volume and thus the high yield. The disadvantage is the relatively low strength. It is currently not possible to produce a foam with very low density and high strength at the same time.

For many applications, it would be highly desirable to have a foamed adhesive that also has high strength at the same time. It can thus combine the advantages of the adhesive from the double cartridge (high strength) with the advantages of PU foam from the aerosol can (high yield, easy handling).

In view of this prior art, the inventor has set the goal to provide a method for producing a foam of the generic type, which can be used, for example, without the hassle of craft activities. In addition, favorable conditions are to be created for use.

According to the invention for this purpose, a method for producing a foam of at least two components is provided, which is specified in claim 1. Further advantageous embodiments are specified in the dependent claims 2 to 10.

1 shows the schematic structure of an aerosol can that meets the requirements. In a commercially available aerosol can ( 2 ) is a valve plate ( 1 ) with valve bodies ( 3 and 4 ) to EP 0 111 089 and or EP 0 534 308 built-in. On the valve plate a flexible foil bag is mounted ( 7 ). The bag contains one of the two components (eg hardener ( 12 )). In the remaining room ( 8th ) of the aerosol can, which forms a second chamber, is the second component (eg polyurethane or epoxy ( 13 )), liquefied propellant gas (eg R134a) and compressed air and / or nitrogen. The flexible bag ( 7 ) is on a lenticular structure ( 9 ) welded. The lenticular structure ( 9 ) is connected to the nozzle ( 6 ) on the plate ( 1 ) sprayed. In the neck ( 6 ) is a cross-shaped rod ( 10 ). This causes a complete emptying of the bag. At the bottom of the pole ( 10 ) is the ball ( 11 ).

Once the two valve bodies ( 3 and 4 ) are opened, the propellant gas and the compressed air for a simultaneous emptying of the A-component in the can ( 2 ) and the B component in the flexible bag ( 7 ). An advantage of the design is that the mixed components through the propellant gas from the A-chamber immediately foamy and thus the spray tube ( 3 in 2 ) leave as foam and can not run anymore. Another advantage is that there is always the same pressure in the two separate chambers. This ensures that both chambers are always emptied the same.

According to the invention, the chambers - preferably a first chamber formed by the flexible bag and a second in the form of a concentric outer chamber - are assigned, for example, to the following fillings:

Recipe 1:

Filling the flexible bag:

• 61.8 g of polyol with OH number 380
• 2.5 g of amine catalyst
• 0.6 g foam stabilizer
• 0.1 g of dye

Filling the second chamber:

• 130 g of diphenylmethane-4,4'-diisocyanate (hereinafter called isocyanate)
• 10 g LPG R134a
• 0.4 g of nitrogen

The essential feature of the procedure is that in the chamber ( 8th ) a mixture of filling material (eg isocyanate), liquefied propellant gas (eg R134a or dimethyl ether) and a gas which is not liquefied in the can (eg nitrogen). If you want to create a foam with high density, which is physically driven by liquefied propellant gas, you have to work with very little propellant gas. Taking the amounts of propellant as they are filled in the commercial PU foams, the foam is driven much too strong and loses its strength. Practice has shown that the small amount of propellant causes major problems in system reliability. For example, the cans with the filling according to Example 1 only worked well at about 20 ° C. Another disadvantage was the much too slow discharge rate, because of course a small amount of propellant generates only a small pressure. A further disadvantage was that the mixing ratio of the two components did not remain constant during the application time. The strength of the foam adhesive depends very much on the right mixture. All the problems described, which would have made a launch of the product impossible, could be solved by adding a small amount of nitrogen. Nitrogen increases the pressure in the second chamber ( 8th ) from about 3.5 bar to 7 bar at 20 ° C. It is no longer the liquefied propellant gas that causes the components to be discharged from the can, but rather the higher nitrogen pressure. The propellant is dissolved in the isocyanate. It is included in the formula only to cause immediate foaming of the mixed active components as soon as they release the valves ( 3 ) and ( 4 ) and are at normal ambient pressure. This prevents the mixture from bleeding.

Commercially available shaving gels contain gel with liquefied propellant dissolved therein (eg, propane-butane mixture) in a flexible bag in an aerosol can. Around the bag, in the second chamber of the can is compressed air. She squeezes the bag when removing the gel. The main difference of the invention described here is that the gel in one chamber liquefied propellant gas with active ingredient and in the other chamber compressed air, while the foam adhesive in a chamber, a component, liquefied propellant and z. B. compressed air or nitrogen.

In the commercially available PU foams, the aerosol can contains the component (eg PU) and usually two liquefied propellant gases. The essential difference of the invention for this purpose is that the two liquefied propellant gases in PU have a critical temperature t _k of ≥ + 70 ° C (eg R134a and dimethyl ether). However, the foam adhesive contains a gas with a t _k of ≥ + 70 ° C (eg R134a) and a second gas with a t _k of <-10 ° C (eg nitrogen).

In commercial one- or two-component PU foams it is known that in winter the cans do not function properly at low temperatures. With a cold can, the gas pressure decreases drastically. With the invention, this disadvantage can be solved because the non-liquefied nitrogen maintains its pressure even at winter temperatures.

To fill the aerosol can after 1 first the second chamber ( 8th ) is filled with isocyanate. Then the empty flexible bag is inserted as the first chamber. After clinching, the aerosol can is gassed with LPG, charged with nitrogen and shaken. Then the bag through the valve body ( 3 ) through against the pressure in the can filled with a high pressure filler.

To remove the components, an adapter is used 2 , Once pressure on the spray head ( 1 ), the release pins ( 2 ) the valve bodies ( 3 and 4 in 1 ) the can. The two components are replaced by the static mixer ( 4 ) are pumped and mix homogeneously. The nail ( 5 ) prevents the static mixer from the spray tube ( 3 ) is pressed. It can also be mechanically clamped in the spray head or replaced by a weld.

3 shows a more detailed illustration of the cross-shaped rod ( 10 out 1 with molded ball ( 11 out 1 ). It causes a reliable emptying of the bag ( 7 ) in 1 ,

Another advantage of the construction shown here is the arbitrary storage. In contrast to commercial 2K cans, which must be emptied after a single activation in a short time, here the contents can be taken in any portions.

Another feature of the invention is that one after the adapter 2 can use several times. For this purpose, a common aerosol can is filled with cleaning fluid (eg acetone) and propellant gas (eg propane-butane). The can is off with the valve 1 verklinscht. To the valve plate ( 1 ) no bag is welded. By putting the used adapter on the can and pumping the cleaning liquid through, it becomes clean and can be used again.

Particularly suitable is the method for producing Epoxidortsschaum from the aerosol can. In 1934, P. Schlack (IG Farbenindustrie AG) first described the preparation and identification of various phenolic polyglycidyl ethers. The decisive idea to use the great reactivity of the ethylene oxide group of these resins, first with acid anhydrides and later with polyamines, is from P. Castan (De Trey AG, Zurich). In 1938, he patented synthetic resins, which cure without splitting off volatiles and, with surprisingly little shrinkage, yield end products with excellent mechanical properties. The company de Tray was the first to use such resins for dental purposes. These foundations led to the production of epoxy metal adhesives, casting and coating resins at Ciba AG, Basel, in 1946. A few years later, some American companies and factories in the Federal Republic of Germany also began research work in this field.

The epoxy resins (EPH) are compounds which contain one or more very reactive terminal epoxide groups and hydroxyl groups:

• – Warmhärtung durch z. B. Säureanhydride oder aromatische Amine
• – Kalthärtung durch z. B. aliphatische Amine.

EPH are formed by alternating addition and condensation steps of low molecular weight epoxy compounds and phenols (also aliphatic, cycloaliphatic and nitrogen-containing compounds) or alcohols. Depending on the mixing ratio, reaction temperature and starting components, the resulting resins have molecular weights between about 380 and 4000 g / mol and contain reactive groups (epoxide, hydroxy) for crosslinking. The crosslinking reaction can be divided into two groups:

• - Warm hardening by z. For example, acid anhydrides or aromatic amines
• - Cold hardening by z. For example, aliphatic amines.

By adding catalytic tertiary amines, both reactions can be accelerated. For resins which are solid at room temperature, reactive diluents (e.g., low viscosity EP resins) are added which both lower the viscosity and participate in the crosslinking reaction.

The EPH can with powdered or fibrous materials such. B. glass fibers are modified.

• – die Reaktionsformmasse kann in einem großen Viskositätsbereich zwischen fest und flüssig eingestellt werden. Reaktive verdünnte Weichmacher und Füllstoffe ermöglichen die Wahl des jeweils günstigsten Rezeptes;
• – die Wahl der Härtungsmittel ermöglicht das Beschleunigen oder das Verzögern des Härtungsverlaufs bei verschiedenen Temperaturen.

EPH are characterized by the following properties:

• - The reaction molding material can be adjusted in a wide viscosity range between solid and liquid. Reactive diluted plasticizers and fillers allow the choice of the most favorable recipe;
• - The choice of curing agent allows accelerating or retarding the cure at different temperatures.

• – lufttrocknende Härtung,
• – hohe Füllbarkeit
• – geringer Schwund
• – geringe Neigung zur Spannungsrissbildung
• – gute Haftung auf nahezu allen Werkstoffen
• – keine Abspaltung niedermolekularer Reaktionsprodukte
• – hohe Beständigkeit durch den Angriff durch Chemikalien
• – hohe Festigkeit bei zug- und schwingender Beanspruchung
• – gutes Dämpfungsvermögen
• – hohe Formbeständigkeit in der Wärme und Wärmestandfestigkeit
• – günstiges Alterungsverhalten
• – gute elektrische und dielektrische Eigenschaften
• – geringe Brennbarkeit der Standard-Reaktionsharze
• – Geruch- und Geschmackfreiheit
• – Systeme nach Maß einstellbar.

(H. Domininghaus, Die Kunststoffe und ihre Eigenschaften, VDI-Verlag 1986, Seite 752–757).The specific advantages are:

• - air-drying curing,
• - high fillability
• - low shrinkage
• - low tendency to stress cracking
• - good adhesion to almost all materials
• - no cleavage of low molecular weight reaction products
• - high resistance to attack by chemicals
• - high strength under tensile and oscillatory stress
• - good damping capacity
• - high dimensional stability in heat and heat resistance
• - favorable aging behavior
• - good electrical and dielectric properties
• Low flammability of the standard reaction resins
• - Odor and taste freedom
• - Customized systems.

(H. Domininghaus, The plastics and their properties, VDI-Verlag 1986, pages 752-757).

Because of the described good properties, the EPH find a variety of applications, such. As adhesives, castables, matrix material for fiber reinforced components and the like. A certain disadvantage is the relatively high price. Therefore, the desire for foamed epoxy masses was loud, which can be processed as a local foam similar to the known polyurethane local foams from the aerosol can. Foam has a much lower density than the compact material, so that with the same amount of (expensive) base material significantly more volume of foam can be produced. The costs for the processor decrease significantly.

EP foam is known from the literature. Foam is formed when a gas is released during curing of the system. The gas is formed either by the curing reaction as such or by a compound contained in the system. This forms gas either by splitting off gas at elevated temperature or even evaporating at the elevated temperature. In contrast to polyurethane, epoxide does not break down any substances during curing. If water is added to isocyanate in a PU formulation, then CO _{2 is formed} , which serves as a propellant. Polyurethane has therefore already contained the blowing agent in the formulation. Epoxy requires the introduction of a separate blowing agent. As the blowing agent low-boiling fluorine-chlorine hydrocarbons such. B. Frigen be used, which are now prohibited. There are also substances that split off from 70 ° C nitrogen such. B. 2,2'-azobis (isobutyronitrile) (English name of the substance).

In recent developments, a substance is added to the epoxy resin which reacts with the amine hardener to form a gas. A typical system consists of an epoxy resin, a primary amine and a hydrogen-active siloxane. The siloxane reacts with the amine by forming hydrogen as a propellant gas. Instead of amines, other hydrogen-active curing agents such as alcohols, phenols, mercaptans and carboxylic acids can be used. All of these hardeners are able to react with the hydrogen-active siloxane to form molecular hydrogen. (D. Klempner, K.C. Frisch, Handbook of Polymeric Foams and Foam Technology, Hanser Verlag 1991, pages 273-280).

• – Herkömmliche Aerosoldosen können für Epoxid-Systeme (EPS) nicht verwendet werden. EPS ist ein Zweikomponenten-System, das durch eine Polyaddition härtet. Gibt man beide Komponenten in eine Aerosoldose, so werden diese in der Dose hart.
• – FCKW als Schaumbildner ist verboten.
• – Schäumen bei erhöhter Temperatur ist aus praktischen Gründen bei einem Ortsschaum nicht möglich.
• – Schäumen mit wasserstoffaktivem Siloxan ginge theoretisch. Allerdings tritt dann zunächst eine Flüssigkeit aus der Dose aus, die zunächst einmal verläuft bevor sie durch die Schaumbildung thixotrop wird.

The foam systems described are not suitable for a local foam from the aerosol can:

• - Conventional aerosol cans can not be used for epoxy systems (EPS). EPS is a two-component system that hardens through a polyaddition. If you put both components in an aerosol can, they will be hard in the can.
• - CFC as foaming agent is prohibited.
• - Foaming at elevated temperature is not possible for practical reasons in a local foam.
• Foaming with hydrogen-active siloxane would theoretically work. However, then first of all a liquid emerges from the can, which initially runs once before it becomes thixotropic due to the foam formation.

With the described method, an Epoxidortsschaum be provided, which allows a volume increase of at least 1: 3 economically, immediately leads to the final volume of the foam with high stability, so that the Verfüllgrad is immediately apparent and on the other hand when introducing and Ausreagieren the foam The need for formwork is eliminated.

Polyepoxides, namely a mixture of bisphenol A and bisphenol F and epichlorohydrin, are mentioned as an example and preferred group of epoxides.

As foaming low molecular weight z. As C3-C5 hydrocarbons, halogenated hydrocarbons or ethers.

An example recipe shows the recipe 2. Recipe 2: A component: 100 g of epoxy resin with an epoxide equivalent of 175 2 g foam stabilizer 4 g of highly dispersed silicic acid Component B: 100 g of secondary amine 10 g of tertiary amine 1 g of dye 4 g of highly dispersed silicic acid

In the second chamber of the box 1 145 g of epoxy A component, 5 g of propellant R134a and 0.4 g of nitrogen (pressure increase to 7 bar) are filled. In the flexible bag as the first chamber come 22 g of hardener mixture (B component).

Claims (10)

A method for producing a foam of at least two components from an aerosol can, the interior of which is divided into at least two mutually sealed chambers, and which has a valve plate common to the two chambers, in each of which an outlet valve communicating with its interior is used for each chamber which are actuated together by an axially displaceable trigger member in the sense of opening all valves, wherein the first chamber of the aerosol can is formed by a valve plate mounted on the flexible foil bag and the second chamber is formed by the remaining space of the aerosol can, characterized that in the second chamber one of the two components is mixed with at least two gases, one gas having a critical temperature t _K of ≥ -10 ° C and the other gas having a critical temperature t _K of <-10 ° C, and that in the flexible film bag, the other component is taken and that the gas with the critical temperature t _K of <-10 ° C causes the discharge of the component from the second chamber and at the same time the application of the component located in the film bag. A method according to claim 1, characterized in that the foam is an adhesive. A method according to claim 1 or 2, characterized in that a gas has a critical temperature t _k -10 ° C ≤ t _k <+ 70 ° C. A method according to claim 1 or, characterized in that the other gas has a critical temperature t _k ≥ + 70 ° C. A method according to claim 1, characterized in that a gas is nitrogen. A method according to claim 4, characterized in that a gas liquefied gas R is 134a or dimethyl ether. A method according to claim 1, characterized in that a gas is nitrogen and another gas R 134a or dimethyl ether. Method according to one of the preceding claims, characterized in that in the flexible film bag in addition to the component therein is at least one of the gases mentioned in claims 1 to 7. Method according to one of the preceding claims, characterized in that there is a cross-shaped rod in the flexible foil bag. Method according to one of the preceding claims, characterized in that the one component is isocyanate or epoxide.

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