Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-05-08
2004-05-11
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S159000
Reexamination Certificate
active
06734217
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to flame-resistant high resilience cold-cure moulded foams with reduced smoke intensity and toxicity, processes for their production and use thereof
BACKGROUND OF THE INVENTION
Cold-curing polyurethane flexible moulded foams are used, inter alia, as seats, seat backs or headrests in motor vehicles, rail vehicles and water craft, aircraft and in the furniture sector. In all the above-stated sectors, the flame resistance of the foams is significant. In rail vehicles, aircraft and furniture in particular, flame resistance requirements are very high. In order to meet the appropriate standards, such as for example BS 5852, Part 2, Crib Ignition Source V, CSE RF4/83 or UIC 564/2 or DIN 54341, ASTM E 162, California TB 133, melamine is added to the foam as a flame retardant. A disadvantage of this is that it involves stirring a solid into the polyol formulation, with the attendant dust development. Furthermore, the solid melamine settles out of the polyol formulation, which makes processing difficult. Melamine sedimentation may be prevented by using special stabilised melamine dispersions in polyethers, as described in DE-OS 195 40 809 and EP-A 835 905. Moreover, the incorporation of melamine into the polymer matrix of the foam has a negative effect on the mechanical properties of the foams, in particular their tensile strength, elongation at break and tear propagation resistance. High smoke density and toxicity levels on combustion constitute a further disadvantage.
It is clear from “Polyurethanes World Congress 1991”, Technomic Publishing, Basel, Lancaster 1991, p. 615 ff. that flame-resistant high resilience slabstock foams may be obtained by combining pure toluene diisocyanate with a PHD polyol and liquid phosphorus/halogen compounds. However, a high resilience cold-cure moulded foam made from these components does not fulfil the requirements set by BS 5852, Part 2, Crib V, a fact which may possibly be explained by the differences in polymer synthesis in slabstock foam and moulded foam. Results obtained for slabstock foam cannot thus be applied to moulded foam.
It has now been found that high resilience cold-cure moulded foams with reduced flammability, smoke density and toxicity and improved mechanical properties may be obtained by reacting modified TDI with PHD or PIPA polymer polyols.
SUMMARY OF THE INVENTION
The object of the invention is therefore a high resilience cold-cure moulded foam which may be obtained by reacting
a) modified TDI with
b) dispersions of relatively high-molecular weight polymer-containing hydroxyl compounds, which have been produced by reacting mono- and/or polyisocyanates with polyamines and/or hydrazines and/or hydrazides and/or alkanolamines comprising primary and/or secondary amino groups in a polyether comprising 1 to 8 primary and/or secondary hydroxyl groups and having a number average molecular weight of 400 to 16000,
c) in the presence of chemical and/or physical blowing agents (in particular water), and optionally
d) flame retardants which may be liquid and/or soluble in a) or b) and/or
e) compounds having at least two hydrogen atoms capable of reacting with isocyanates and a molecular weight of 32 to 399, and/or
f) further auxiliary substances.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, modified toluene diisocyanate (TDI) is used as component a). The isomer ratio of 2,4-TDI to 2.6-TDI may be from 100:0 to 65:35. According to the invention, the TDI is modified in a manner known to the person skilled in the art, as described in G. Oertel (Ed.): “
Kunststoff
-
Handbuch
”, Vol. VII, Carl Hanser Verlag, 3
rd
edition, Munich 1993, pp. 91-97, i.e. it is for example allophanatised, biuretised, trimerised, carbodiimidised or prepolymerised with polyethers or some of component b). Commercially available biuretised toluene diisocyanate types may be used to produce the high resilience cold-cure moulded foams according to the invention, for example the High-Performance TDI types made by Bayer AG.
According to the invention, the polyol component b) contains dispersions of relatively high-molecular weight polymer-containing hydroxyl compounds, which have been produced by reacting mono- and/or polyisocyanates with polyamines and/or hydrazines and/or hydrazides and/or alkanolamines comprising primary and/or secondary amino groups in a polyether comprising 1 to 8 primary and/or secondary hydroxyl groups and having a number average molecular weight of 400 to 16000 (“base polyol”). Base polyols with a number average molecular weight of 1500 to 8000 are preferably used. Hydroxyl compounds are preferably used which have been produced by reacting base polyols with hydrazines (PHD polyols). Component b) preferably has an average OH functionality of 2.0 to 3.5. Polyether polyols are preferably used which have a content of primary OH groups of at least 60 mol %, preferably at least 70 mol %. In another preferred embodiment, the component preferably contains, in addition to a base polyol with an ethylene oxide content of at most 40 wt. %, at least one further polyether polyol with an average functionality of 2 to 6, a number average molecular weight of 1500 to 12000 in an amount of 1 to 50 wt. %, relative to the total amount of component b), and an EO content greater than 40 wt. %. This embodiment results in better skinning and an increased proportion of open cells and allows greater latitude in the adjustment of the NCO/OH index and thus better processability of the formulation. A foam is obtained which exhibits higher elasticity and whose hardness, which may be high owing to the polymer dispersion, is reduced to such an extent that it is possible even to produce flexible mouldings.
Chemical and/or physical blowing agents c) are used to produce the foams according to the invention. Water, which produces a blowing gas in the form of carbon dioxide by reacting with isocyanate groups, is preferably used as a chemical blowing agent constituting component c). Water is preferably used in an amount of 2-8 wt. %, particularly preferably 2 to 4 wt. %, relative to the amount of component b). However, it is also possible to add carbon dioxide to the polyol or isocyanate component in gaseous or liquid form continuously or by the batch process by processes known per se. Non-combustible physical blowing agents such as for example dichloromethane, dichloromonofluoromethane, difluoromethane, trifluoromethane, difluoroethane, 1,1,1,2-tetrafluoroethane, tetrafluoroethane (R 134 or R 134a), 1,1,1,3,3,3-hexafluoropropane (R 356), 1,1,1,3,3-pentafluoropropane (R 245fa), chlorodifluoroethane, 1,1-dichloro-2,2,2,-trifluorethane, 2,2-dichloro-2-fluoroethane, heptafluoropropane and sulfur hexafluoride may also be used in component c). Since the blowing agent escapes virtually completely from the foam during the production process, it is also possible to use low-boiling hydrocarbons, e.g. pentane, hexane and isomers thereof. Further suitable blowing agents are carboxylic acids such as formic acid, acetic acid, oxalic acid and chemical blowing agents which release gases in the course of the foaming process, such as carbamates for example. Mixtures of these blowing agents may also be used. These blowing agents are preferably used in combination with water.
Flame retardants d) which arc liquid and/or soluble in one of components a) or b) or in both are optionally used in the production of the foams according to the invention. Commercially available phosphorus-containing flame retardants are preferably used, for example tricresyl phosphate, tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, tris(1,3-dichloropropyl) phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, dimethylmethane phosphonate, diethylethane phosphonate, diethanolaminomethylphosphonic acid diethyl ester. Halogen- and/or phosphorus-containing, flame-retarding polyols or mixtures of the flame retardants mentioned are also suitable. The flame retardants are preferably used in an amount of at most 35 wt. %, preferab
Bohne Franz-Josef
Herrmann Marc
Seifert Peter
Bayer Aktiengesellschaft
Gorr Rachel
Mrozinski, Jr. John E.
Seng Jennifer R.
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