Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1998-09-24
2001-08-14
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S130000, C521S131000, C252S182240, C252S182270
Reexamination Certificate
active
06274642
ABSTRACT:
The present invention relates to storage-stable, blowing agent-containing emulsions for producing rigid foams based on isocyanate.
The production of rigid foams based on isocyanate and their use as thermal insulation material has been known for a long time and is widely described in the literature. As chemical structures formed from the isocyanate groups, these foams can comprise polyurethanes, polyureas, polyisocyanurates and also further isocyanate adducts such as allophanates, biurets, carbodiimides and their isocyanate adducts, oxazolidines, polyimides, polyamides, etc. The type of these structures is controlled by the reaction partners of the isocyanates, the catalysis and the reaction conditions. These isocyanate adducts are usually summarized under the term polyurethanes (PUR) since the polyurethanes are the most widespread and most important group of materials among the polyisocyanate adducts. Rigid foams based on isocyanate are therefore frequently referred to as rigid PUR foams or, in the case of a significant proportion of isocyanurate groups, also as rigid polyurethane/polyisocyanurate foams (rigid PUR/PIR foams).
The production of such rigid foams is described, for example, in the Kunststoff-Handbuch, Volume VII, “Polyurethane”, 3rd Edition edited by Gunter Oertl, Carl-Hanser-Verlag, Munich, Vienna, 1993.
In order to obtain very fine-celled rigid polyurethane foams, it is advantageous to emulsify the blowing agent in the polyurethane formative components.
EP-A-351 614 describes a process for producing polyurethane foams in which perfluorinated hydrocarbons which are emulsified in at least one of the polyurethane formative components are used as blowing agent. DE-A-41 43 148 describes blowing agent-containing emulsions of isoalkanes having at least 6 carbon atoms and low-boiling fluorinated or perfluorinated organic compounds. DE-A-42 00 558 describes the combination of fluorine compounds with hydrocarbons having from 4 to 8 carbon atoms, including cyclopentane. DE-A-41 21 161 also describes emulsions comprising fluorinated blowing agents.
The emulsion foams produced using these emulsions have very small cells which lead to low thermal conductivities. An important prerequisite for producing these emulsions is the concomitant use of at least one highly fluorinated and/or perfluorinated compound, if desired together with other blowing agents, for example hydrocarbons.
Further variants of emulsion foams are described, for example, in EP-A-405 439, WO 96/25455, U.S. Pat. No. 5,346,928 or EP-A-662 494, with the object being the provision of open-celled foams for vacuum technology.
WO 95/02620 describes the production of fine- and open-celled foams for vacuum technology by the emulsion method, where the emulsion is prepared with the aid of an inert organic liquid which is insoluble in the polyurethane formative components and is present as disperse phase of a microemulsion. As inert organic liquids, use is again made of highly fluorinated or perfluorinated compounds. All these publications indicate the importance of fluorinated compounds for emulsion formation.
Although the ozone depletion potential (ODP) of these compounds is zero, the fluorine compounds contribute considerably to the global warming potential (GWP). In addition, these compounds decompose in the atmosphere into acidic and environmentally damaging decomposition products, in particular hydrogen fluoride.
A halogen-free emulsion foam is described in EP-A-394 769. It comprises at least one polyester alcohol, an emulsifier and finely divided nitrogen. JP 08/193115 describes a halogen-free emulsion comprising a polyesterol and a prepolymer derived from a polyetherol and isocyanate. DE-A-43 28 383 describes a polyol component comprising an only partially dissolved hydrocarbon blowing agent which is present as an emulsion. The polyol component here comprises at least one polyether alcohol containing oxyethylene groups and at least one polyether alcohol which is free of oxyethylene groups. A disadvantage here is the high intrinsic reactivity of the polyether alcohols comprising oxyethylene groups. This makes it necessary to use less catalyst to set a desired fiber time, as a result of which the reaction proceeds more slowly after reaching the fiber time and the foam cures less well. As a result, demolding times for foaming in molds are undesirably long or working speeds in the double belt process are low. In addition, the emulsions described there have only a very short shelf life.
U.S. Pat. No. 5,488,071, U.S. Pat. No. 5,484,817 and U.S. Pat. No. 5,464,562 propose monofunctional polyoxyalkylene polyetherols with fatty alcohols as initiator substances as emulsifiers and polyester alcohols as polyol components. However, these emulsions too have only insufficient storage stability. In addition, the use of monofunctional emulsifiers greatly reduces the total functionality of the polyol mixture. This results in reduced crosslinking of the foam with all its associated disadvantages such as impaired curing of the reaction mixture and poorer thermal stability of the rigid foam. When non-functional emulsifiers such as benzyl n-butylphthalate are used as described in DE-A-41 09 076, the adhesion of the polyurethane to covering layers and also the thermal stability of the foam are considerably worsened.
It is an object of the present invention to prepare storage-stable halogen-free emulsions for producing rigid foams based on isocyanate comprising hydrocarbons as blowing agents, which emulsions can be processed into rigid foams having improved properties, eg. improved thermal stability, and also with good curing of the reaction mixture.
We have found that this object is achieved by concomitant use of polyether alcohols having a functionality of greater than 1.5 and a hydroxyl number of from 10 to 100 mg KOH/g as reactive emulsion stabilizers in the polyol component.
The present invention accordingly provides a storage-stable, halogen-free emulsions comprising
a) compounds containing hydrogen atoms which are reactive toward isocyanate groups,
b) water,
c) physically acting, halogen-free blowing agents and, if desired,
d) auxiliaries and/or additives which are customary in polyurethane chemistry,
wherein the component a) comprises polyether alcohols having a functionality of greater than 1.5 and a hydroxyl number of from to 100 mg KOH/g in an amount of from 0.2% by mass to 80% by mass, based on the mass of the component a), and the halogen-free, physically acting blowing agents c) used are hydrocarbons having from 3 to 10 carbon atoms.
The invention further provides a process for producing rigid foams based on isocyanate by reacting the emulsions with polyisocyanates and also provides rigid foams based on isocyanate produced by this process.
The polyether alcohols used according to the present invention preferably have a functionality of from 2.5 to 3.5 and a hydroxyl number of from 25 mg KOH/g to 50 mg KOH/g and are used, in particular, in an amount of from 1 to 50% by mass, based on the mass of the component a).
As physically acting blowing agents c), preference is given to using pentanes, in particular cyclopentane. The amount of the physically acting blowing agents is from at least 5% by mass to at most 25% by mass, preferably from 12% by mass to 21% by mass, in each case based on the sum of the components a) to d).
The amount of water b) is from 0.01% by mass to 5% by mass, preferably from 0.35% by mass to 2% by mass and in particular from 0.5% by mass to 1.5% by mass, in each case based on the sum of the components a) to d).
It has been found to be particularly advantageous to use polyether alcohols which are prepared by addition of ethylene oxide and/or propylene oxide onto glycerol or trimethylolpropane (TMP). The distribution of the alkylene oxide in the polyether chain can here be in blocks or be random, with a terminal ethylene oxide block frequently being added on at the end of the chain.
The polyether alcohols used according to the present invention are usually soluble in the reaction mixture, but in exceptiona
Biedermann Anja
Heinz Marion
Hempel Renate
Rotermund Udo
Wiegmann Werner
BASF - Aktiengesellschaft
Borrego Fernando A.
Cooney Jr. John M.
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