Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-03-27
2003-07-15
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...
C521S108000, C521S130000, C521S131000, C521S169000, C521S170000, C521S174000
Reexamination Certificate
active
06593385
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a halogen-free, pentane-blown, flame-retardant rigid polyurethane foam and to a process for its production, and also to the use of oxalkylated alkylphosphonic acids for producing rigid polyurethane foams of this type.
BACKGROUND OF THE INVENTION
Rigid polyurethane foams are used in many sectors, for example in the refrigeration industry, as insulating materials for construction, for example for heating units or composites, as packaging, and generally as industrial insulation. Rigid polyurethane foams generally have to be provided with flame retardants in order to achieve the high fire-protection requirements desirable in these sectors and sometimes required by legislation. A wide variety of different flame retardants is known and commercially available for this purpose. However, there are often considerable technical problems and toxicological concerns restricting the use of these flame retardants.
For example, when solid flame retardants such as melamine, ammonium polyphosphate or ammonium sulfate are used there are technical problems with metering which frequently necessitate complicated rebuilds or modifications of foaming plants.
Halogen-free flame retardant systems are preferred in principle for reasons of environmental toxicity, and also due to their better performance in terms of the smoke density and smoke toxicity associated with fires.
In the case of pentane-blown rigid polyurethane foams, another factor which has to be taken into account is that the high combustibility of the pentane also requires measures for preventing explosions on the production plants. For flexible polyurethane foam systems, hydroxylated oligomeric phosphoric esters (DE-A-43 42 972) can be used as flame retardants. It is known that these compounds and their properties and effects cannot be similarly used in rigid polyurethane foam systems.
Although in principle flexible and rigid polyurethane foam systems may have approximately the same density and composition, flexible polyurethane foams have only slight crosslinking and exhibit only a low level of resistance to deformation under pressure.
In contrast, the structure of rigid polyurethane foams is composed of highly crosslinked units, and rigid polyurethane foam has very high resistance to deformation under pressure. A typical rigid polyurethane foam is of closed-cell type and has low thermal conductivity.
During the production of polyurethanes, which proceeds via the reaction of polyols with isocyanates, it is primarily the nature and chemistry of the polyol (functionality) which affects the subsequent foam structure and the properties of this material.
It is an object of the present invention to provide a halogen-free, water-blown, flame-retardant rigid polyurethane foam which does not have the abovementioned disadvantages and meets the necessary and prescribed requirements for flame retardancy, ease of production, low smoke density and low smoke toxicity.
SUMMARY OF THE INVENTION
The abovementioned object is achieved by means of a polyurethane foam of the type mentioned at the outset, wherein oxalkylated alkylphosphonic acids are present as flame retardant.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The oxalkylated alkylphosphonic acids preferably have the formula I
where
R
1
is a methyl, ethyl or propyl radical,
R
2
and R
3
are identical or different and are a methyl, ethyl or propyl radical and x is a number from 1.2 to 1.9.
It is preferable for R
1
to be a methyl radical, and x a number from 1.5 to 1.7. The value for x is the average chain length.
The halogen-free, water-blown, flame-retardant rigid polyurethane foam preferably comprises, based on the fully cured rigid polyurethane foam, from 0.1 to 40% by weight of the flame retardant.
The halogen-free, water-blown, flame-retardant rigid polyurethane foam particularly preferably comprises, based on the fully cured rigid polyurethane foam, from 5 to 25% by weight of the flame retardant.
The halogen-free, water-blown, flame-retardant rigid polyurethane foam preferably has a density of from 25 to 80 kg/m
3
.
It particularly preferably has a density of from 30 to 50 kg/m
3
.
The abovementioned object is also achieved by means of a process for producing halogen-free, pentane-blown, flame-retardant rigid polyurethane foams, which comprises using oxalkylated alkylphosphonic acids as flame retardant.
The oxalkylated alkylphosphonic acids preferably have the formula I
where
R
1
is a methyl, ethyl or propyl radical,
R
2
and R
3
are identical or different and are a methyl, ethyl or propyl radical and x is a number from 1.2 to 1.9.
The process is preferably executed by reacting organic polyisocyanates with compounds having at least two hydrogen atoms capable of reaction with isocyanates, with pentane as blowing agent, with stabilizers, with activators and/or with other conventional auxiliaries and additives, in the presence of oxalkylated alkylphosphonic acids of the formula I.
The oxalkylated alkylphosphonic acids of the formula I are preferably compounds liquid at processing temperature. For the purposes of the present invention, processing temperature is the temperature at which the starting components are mixed.
The oxalkylated alkylphosphonic acids of the formula I are preferably compounds reactive toward isocyanates.
The amount of the oxalkylated alkylphosphonic acids used of the formula I is preferably from 0.01 to 50 parts, based on 100 parts of polyol component.
The amount of the oxalkylated alkylphosphonic acids used of the formula I is particularly preferably from 1 to 30 parts, based on 100 parts of polyol component.
The invention also provides the use of oxalkylated alkylphosphonic acids of the formula I as halogen-free flame retardant for producing flame-retardant rigid polyurethane foams.
Regarding the Rigid Polyurethane Foams
These are mainly foams having urethane groups and/or isocyanurate groups and/or allophanate groups and/or uretdione groups and/or urea groups and/or carbodiimide groups. The use according to the invention preferably takes place during the production of polyurethane foams or of polyisocyanurate foams.
The materials used for producing the isocyanate-based foams are: Starting materials: aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic polyisocyanates (see, for example, W. Siefken in Justus Liebigs Annalen der Chemie, 562, pp. 75-136), for example those of the formula Q(NCO)
n
, where n=from 2 to 4, preferably from 2 to 3, and Q is an aliphatic hydrocarbon radical having from 2 to 18 carbon atoms, preferably from 6 to 10 carbon atoms, a cycloaliphatic hydrocarbon radical having from 4 to 15 carbon atoms, preferably from 5 to 10 carbon atoms, an aromatic hydrocarbon radical having from 6 to 15 carbon atoms, preferably from 6 to 13 carbon atoms, or an araliphatic hydrocarbon radical having from 8 to 15 carbon atoms, preferably from 8 to 13 carbon atoms, for example the polyisocyanates described in DE-A-28 32 253, pp. 10-11. Particular preference is generally given to the polyisocyanates readily available industrially and derived from tolylene 2,4- and/or 2,6-diisocayanate or from diphenylmethane 4,4′- and/or 2,4′-diisocyanate.
Other starting materials are compounds having at least two hydrogen atoms capable of reaction with isocyanates, with a molecular weight of from 400 to 10,000 (“polyol component”). For the purposes of the present invention, these are compounds having amino groups, thio groups or carboxyl groups, and preferably compounds having hydroxyl groups, in particular from 2 to 8 hydroxyl groups, and specifically those of molecular weight from 1000 to 6000, preferably from 2000 to 6000, and are generally polyethers or polyesters dihydric to octahydric, preferably dihydric to hexahydric, or else polycarbonates or polyesteramides, as known per se for the production of homogenous or of cellular polyurethanes, and as described in DE-A 28 32 253, for example. The at least dihydric polyethers and polyesters are preferred according to the invention.
Other starting materials
Krieger Wilfried
Witte Anne
Bisulca Anthony A.
Cooney Jr. John M.
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