EP0655394B1 - Pressurized container - Google Patents

Description

The invention relates to a pressure can, the frame of which has a cylinder, a preferably indented base, a dome-like upper part with a valve for dispensing a can filling consisting of product component and propellant and which contains a piston which is guided and overhung on the inner wall of the cylinder and which contains the propellant gas space separates from the product component and has a recess in a piston roof. The pressure cell is particularly suitable for dispensing assembly foams, for example one-component polyurethane foams, such as are often used for construction and sealing purposes.

Such pressure cans are used to dispense various products. These include rubber-oil, butyl, silicone and acrylate-based sealants, but especially foaming agents based on polyisocyanate prepolymers. After application, such polyisocyanate prepolymers are converted into polyurethane foams upon contact with water (atmospheric moisture), which are used for sealing, filling, insulating, gluing and fastening, in particular in the building industry. The pressure cans for dispensing such polyisocyanate-based foaming agents generally consist, also because of the considerable internal pressure, of sheet steel using special valves which facilitate the processing of the contents of the can.

Pressure cans of this type are known, for example, from US Pat. No. 3,362,589. When used for the production of polyurethane foams, such pressure cans contain a filling which consists, for example, of 60% by weight of polyurethane prepolymer and about 40% by weight of propellant gas. The majority of the propellant gas is used as a means of transport to bring the prepolymer out of the pressure cell. Only a small part of the propellant, about 10%, passes into the foaming agent and supports the expansion.

If the can is stored for a long time, the recipe components usually separate, with the specifically heavier propellant settling on the bottom of the pressure can. Before processing, it is advisable to bring about an intensive mixing of foaming agent and blowing agent by vigorous and long shaking. As far as the gas acts as a blowing agent and escapes from the pressure can with the foaming agent, it evaporates in the atmosphere under expansion.

EP-A 0 078 936 describes a pressure can for dispensing assembly foams, the frame of which has a cylinder, a preferably indented base and a dome-like upper part with a closure, into which a valve for dispensing the can filling consisting of a blowing agent and foaming agent is inserted the inside of the wall of the cylinder of the frame leads the shirt of an overhung piston which is overhung between the propellant or foaming agent filling housed in separate can spaces and separates the lower propellant gas space from the space above which receives the foaming agent. When the filling is being discharged, the piston moves with increasing degree of emptying into the upper region of the pressure cell in order to hit the dome-like upper part of the pressure cell after it has been finally emptied. In order to enable extensive emptying, the piston head is adapted to the contours of the can dome and has a recess in the area in which the valve disk extends into the interior of the can. According to EP-A 0 078 936, the piston is fitted into the can cylinder in such a way that propellant between the can wall and the piston can pass from the propellant space into the foaming agent space, but the foaming agent essentially remains in the upper space provided for this.

Pressure cans of the type described in EP-A 0 078 936 have proven extremely well in practice. They allow extensive use of the foaming agent filling, so that only small amounts of foaming agent remain after the can has been completely emptied. These small amounts are in the range of about 5% of the original can filling. However, it is disadvantageous that the polyisocyanate prepolymers used as foaming agents are highly reactive and toxic. For this reason, pressure cans that have already been emptied cannot easily be disposed of, but require special treatment within the framework of the regulations issued for such residues. This leads to considerable impairments and costs. The same applies to a number of other products that are sold in pressure cans and are highly reactive and / or toxic.

The aim of the invention is therefore to provide a pressure can in which the product components remaining therein after use and extensive emptying, that is to say in particular polyisocyanate prepolymers, can be converted into ecologically and / or toxicologically harmless or justifiable secondary products. This implementation should inevitably start when the pressure cell has released the part of its filling that can be brought out from it.

This goal is achieved with a pressure can of the type described in the introduction, in which a component present in the recess which is reactive with the product component is closed off by a seal against the product component and in which an explosive device is provided in the interior of the dome-like upper part which opens the seal, when the piston takes up a position directly under the dome-like upper part.

According to the invention it is thus achieved that when the piston guided in the pressure can flies against the underside of the dome-like upper part, the blasting device arranged there blows up the closure, as a result of which the reactive component contained in the recess and hermetically sealed up to the time of the blasting against the product component is released and enabled to react with the product component. As a result of this reaction, the product component is converted into harmless secondary products that can be disposed of easily. It is particularly advantageous here that the conversion occurs automatically when the pressure cell has released the part of its filling which can be dispensed and thus only contains residues which have remained and can no longer be dispensed. The reactive component is released automatically without the influence of the person using the can.

The blasting device is expediently a mandrel which is provided, for example, on the underside of the valve plate. The arrangement of the recess on the top of the piston roof is such that it is able to interact with the explosive device, in particular the mandrel. If the mandrel is arranged on the underside of the valve plate, a central recess on the piston roof is expedient.

The closure with which the recess against the product component is closed can be made of any material and can have any shape, provided that the interaction with the blasting device leads to the opening or blasting. The closure expediently consists of a film, for example a polyethylene, polypropylene or aluminum film. Other suitable materials can be used for such films. It should be noted that if the reactive component is a low-molecular substance, for example water, polyethylene and polypropylene, it cannot guarantee complete closure, since water diffuses through these substances. In this case it is Appropriately use an aluminum foil. If the piston is not made of metal, but consists of polyethylene or polypropylene, it is also expedient to line the recess with an aluminum foil if water is to be used as a reactive component, the end foil made of aluminum with the side lining to form a kind of bag or Can is connected.

The reactive component present in the recess on the piston roof is expediently present in an amount which is certainly sufficient to completely convert the amount of product components remaining in the pressure can after the piston has stopped at the dome-like upper part into ecologically and / or toxicologically harmless secondary products. The amounts required for this are extremely small and are about 0.5 to 1 g water for a pressure can for the production of polyurethane foam from polyisocyanates with a filling volume of 750 ml and a degree of application of 95%.

In the case of moisture-curing product components, in particular OH-reactive substances come into consideration as reactive components, for example the water already mentioned, monohydric, lower alcohols, for example ethanol, polyhydric alcohols, such as, for example, ethylene or propylene glycol or glycerol, or lower carboxylic acids, for example acetic acid or propionic acid, and their mixtures with water and / or with one another. NH-reactive substances, preferably mono- or polyvalent primary or secondary amines, can also be used. With these substances, it is necessary to add stoichiometric or slightly excess amounts to the remaining amount of product component in order to achieve the most complete possible implementation of the product component.

Alternatively, catalytically active substances can also be added as the reactive component, for example the polymerization of the reactive component initiate. Examples of such agents are metal alkanoates, such as sodium or potassium octoate. However, catalytically active substances can also be added to increase the reactivity of OH-reactive substances, for example in the form of tertiary amines.

It is particularly expedient to add water and / or a polyhydric alcohol as the reactive component when using a commercially available prepolymer based on isocyanate, it being possible to add a catalytically active substance, for example triethylenediamine, to accelerate the reaction. Other known reaction accelerators can be used. As a reactive component, however, a Pirk catalyst can also be used, which causes the radical polymerization of the remaining isocyanate to give tolerable secondary products.

The pressure cans according to the invention are filled with customary product components and blowing agents. The reactive components are capable and adapted to react with these product components, which are also known per se. The pressure cans used according to the invention also correspond to conventional pressure cans in terms of their shape and application technology, if one disregards the arrangement of the explosive device and the special design of the piston with the reactive component arranged thereon and closure against the interior of the can.

• Fig. 1 schematisch und unter Fortlassung aller für das Verständnis der Erfindung nicht erforderlichen Einzelheiten eine Druckdose gemäß der Erfindung, teilweise im Schnitt,
• Fig. 2 in vergrößerter Darstellung das obere Ende der Druckdose im Schnitt und
• Fig. 3 einzelne Darstellungen a bis c eines erfindungsgemäß zum Einsatz kommenden Kolbens im Schnitt.

Details of the invention emerge from the following description of an embodiment with reference to the attached figures; show it

• 1 schematically and omitting all details not necessary for understanding the invention, a pressure can according to the invention, partly in section,
• Fig. 2 in an enlarged view the upper end of the pressure cell in section and
• Fig. 3 individual representations a to c of a piston used according to the invention in section.

The pressure cell shown in FIGS. 1 and 2 has a frame designated 1, which according to the illustrated embodiment consists of sheet steel. The middle part consists of a cylinder 2, the lower end edge of which is flanged at 3 together with the edge 4 of a base 6 turned at 5. The upper edge 7 of the cylinder 2 goes into a dome-like, i.e. truncated cone-shaped upper part 8, in the edge 9 of which surrounds a central opening has a closure designated by 11. The closure has a plate 10, the edge 13 of which is crimped around the edge 9. The plate 10 has a central opening 40, in which a plug-shaped rubber seal 41 of a valve 12 is housed. The valve body denoted by 42 is tubular and closed at its inner end 43 with a plate which lies on the rubber seal under the influence of the internal pressure of the can. There are one or more openings 44 under the plate 10 and inside the tube part which is sealed off from the outside, through which the contents of the can can pass outwards as soon as the valve body 42 is tilted and the valve plate 43 is thereby lifted off. On the underside of the valve plate 43 there is a mandrel 45 which extends vertically in the middle into the interior of the pressure cell.

In the cylinder 2, a piston designated 14 is overhung. The piston skirt 15 runs on the cylinder wall, but the piston in the can has enough play to be able to move in the direction of the can axis A without jamming. The arrangement of the piston in the cylinder is such that propellant between the piston skirt 15 and the inner wall of the cylinder 2 in from the lower can area can cross the upper can area. However, it is also possible to provide a seal between the piston skirt 15 and the inner wall of the can cylinder 2 or to design the distance between the piston skirt and the cylinder wall in such a way that a film seal is produced by product components which have entered this space.

In the idle state, the piston floats on the propellant gas filling while the product component is above it. When the valve is actuated, liquid propellant gas evaporates from the filling and drives the piston and product component upwards towards the valve.

The piston 14, which is thus between the propellant gas filling and product component filling, thus defines a variable lower length 19 of the cylinder 2. The section 19 of the cylinder 2 thus surrounds a space 20 which is filled with propellant and from the can bottom 6 down and from the Bottom 17 of the piston 14 is shot upwards. The propellant is filled with the aid of a filling needle, not shown, via a radial opening 21 of a valve neck in the can bottom and a valve rubber ring 22 which is placed around the valve neck.

The piston 14 floats on the propellant filling of the propellant gas space 20; the liquid product component is located in the space 23 above the piston roof 26. This space is enclosed by the remaining length 24 of the cylinder 2, the dome 8 and the closure 11.

According to the exemplary embodiment shown, the piston roof 26 is provided with a recess 25 on its side facing the space 23 and has a frustoconical edge surface which is curved outwards, ie convexly. Parts of the curved surface 26 can strike the inside of the dome-like upper part or the closure as soon as the piston 14 has reached its upper end position.

The mandrel 45 protrudes into the recess 25 on the underside of the valve plate 43. The mandrel may be in the form of a tapering needle, but may also be any other shape suitable for bursting open the end 16.

The recess 25 in the piston roof 26 has a glued-on or welded-on closure film 16, which can be supported both on the top of the piston roof 26 and on a projection 28 encircling the recess 25 (shown here for the former case). In the space 18 defined by the recess 25 and the film 26, there is the reactive component which, because after the filling has been applied by the valve, the piston 14 projects into the dome 8 when the upper end position is reached and the film 16 against the mandrel 45 leads, which tears them apart, is released.

The reactive component in space 18 is integrated into the piston when it is manufactured and introduced into the pressure cell with the piston.

To fill the can, the product component is introduced into the can, which is initially still open at the top, with a certain amount of propellant being added if it is a foaming agent. After flanging the edge of the plate 10 around the edge 9, the can is closed. After the foaming agent has been filled in, the blowing agent is introduced into the lower can region via the opening 21 and the valve rubber ring 22 using a hollow needle. After reaching the required pressure in the propellant gas space 20, the filling needle is withdrawn, whereby the one-way valve closes automatically under the pressure of the propellant gas. The can is now ready for use.

In the design of the pressure can according to the invention for the application of assembly foam, it is expedient that between the piston skirt 15 and the cylinder wall 2 propellant can pass into the filling 23 in order to provide a part of the to provide the gas necessary for the expansion. If the piston skirt is correctly adjusted to the inner cylinder diameter, the liquid filling from 23 cannot pass into the propellant gas space 20, without prejudice to the respective position of the can.

Such a pressure can for assembly foams is actuated by tilting the valve 12 with the plate 43. If the valve is opened by tilting the plate 43, foaming agent emerges and the piston 14 moves upward. In Fig. 1, the position of the piston is indicated after approximately half emptying of the can. As soon as the valve 12 is closed, the piston 14 remains in its respective position in order to start moving again when the valve is opened again.

Finally, the piston reaches its upper end position, in which it strikes the dome 8 or the film 16 on the mandrel 45. The reactive component emerges from room 18. Now flowing propellant gas, which discharges the remaining foaming agent, simultaneously distributes the reactive component in the greatly reduced or largely closed space 23, so that a reaction of the remaining foaming agent with the reactive component can take place to produce harmless secondary products. These secondary products remain in the pressure can and are disposed of with the intended disposal. Disposal can take place in conventional landfill or incineration plants if the amount of propellant is dimensioned so that no or only a small amount remains in the pressure can.

3 shows expedient embodiments of pistons used in the pressure cell according to the invention in section. The piston according to FIG. 3a shows a film 16 which is glued or welded onto the piston roof 26 via the circular recess 25. The reactive component is located in space 18 of piston 14 defined by film 16 and recess 25.

3b shows a further embodiment, according to which the recess 25 has an inner circumferential projection or edge 28 to which the film 16 is glued. This embodiment has the advantage that a larger part of the product component can be discharged before activation of the reactive component, which at the same time also reduces the need for reactive component. Depending on the design of the pressure can dome and the required amount of reactive component, the protrusion 28 encircling the recess 25 can extend further or lower in the recess 25.

3c shows a third variant, in which the end foil 16 is connected to a lining 29 of the recess 25 to form a bag. The bag is expediently fixed in the recess 25, for example mechanically - by means of projections - or by gluing. This variant allows the reactive component to be introduced individually into the flask 14. It also enables the use of water as a reactive component in a flask made of polyethylene and propylene if the bag is made of aluminum foil which is impermeable to water.

Claims (11)

1. Pressurized can, in particular for the expulsion of building foams such as single-component polyurethane foames, the body (1) of which comprises a cylinder (2), a preferably pushed-in bottom (5), a dome-like top section (8) with a valve (12) to expel the can contents consisting of product component and propellant, and which has a floating plunger guided on the interior wall of the cylinder (2), which separates the propellant gas chamber from the product component and which has a cavity (25) in its upper side (26), characterized in that in the cavity (25) a component reactive with the product component is sealed off from the product component by a seal (16), and that a trigger device (45) is provided in the dome-like top section (8), which opens the seal (16) when the plunger (14) reaches a position immediately below the dome-like top section (8).
2. Pressurized can according to claim 1, characterized in that the trigger device (45) is a spike.
3. Pressurized can according to claim 1 or 2, characterized in that the trigger device (45) is placed on the underside of the valve disk (43).
4. Pressurized can according to anyone of claims 1 to 3, charcterized in that the seal (16) is a foil.
5. Pressurized can according to anyone of claims 1 to 4, characterized in that the seal (16) is made of polyethylene, polypropylene or aluminum.
6. Pressurized can according to anyone of claims 1 to 5, characterized in that the seal (16) is made of aluminum, and the cavity (25) is lined with aluminum foil, such that the seal (16) and the lining are connected to each other in a sealed manner.
7. Pressurized can according to anyone of claims 1 to 6, characterized in that the reactive component in the cavity (25) is available in a quantity sufficient to convert the product component remaining in the pressurized can after the plunger (14) strikes up against the dome-like top section (8) into enviromentally and/or toxicologically harmless byproducts.
8. Pressurized can according to anyone of the claims 1 to 7, characterized in that the reactive component is an OH-reactive substance, preferably water, a monovalent or polyvalent alcohol, a carbonic acid or a mixture of these, or a NH-reactive substance, preferably a monovalent or polyvalent primary or secondary amine.
9. Pressurized can according to anyone of claims 1 to 8, characterized in that the reactive component is or contains a catalytically active substance, preferably a monovalent or polyvalent tertiary amine or a metal alkanoate.
10. Pressurized can according to anyone of claims 1 to 9, characterized in that the product component is a commonly sold prepolymer on isocyanate basis.
11. Pressurized can according to anyone of claims 1 to 10, characterized in that the reactive component consists of water and/or a polyvalent alcohol, optionally in conjunction with a catalytically active substance to enhance the reaction, or a Pirk catalyst.

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