Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-06-20
2003-07-08
Cooney, Jr., John M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S128000, C521S134000, C521S170000, C521S174000
Reexamination Certificate
active
06590007
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to flame-resistant HR cold-cure moulded foams with reduced smoke intensity and toxicity, a process for the preparation thereof and the use thereof.
Cold-curing polyurethane flexible moulded foams are used, inter alia, as seats, back and arm rests or head rests in automobiles, track vehicles and water-craft, aeroplanes and in the furniture sector. In all the above-mentioned sectors, the flame resistance of the foams is an important factor. The requirements in respect of flame resistance are very stringent in the case of track vehicles, aeroplanes and furniture in particular. In order to meet the relevant standards, such as, e.g., BS 5852, Part 2, Crib Ignition Source V, CSE RF4/83 or UIC 564/2 or and DIN 54341, ASTM E 162; California TB 133, melamine is added to the foam as a flame retardant. A disadvantage of this is that a solid has to be stirred into the polyol formulation with the development of dust. Moreover, the melamine solid settles out of the polyol formulation, making processing difficult. The sedimentation of melamine may be prevented by the use of specially stabilised melamine dispersions in polyethers, as described in DE-OS 195 40 809 and EP-A 835 905. Moreover, the mechanical properties of the foams, particularly the tensile strength, elongation at break and tear propagation resistance are adversely affected by the incorporation of melamine in the polymer matrix of the foam. A further disadvantage is that high smoke intensities and toxicities occur during combustion.
It follows from “Polyurethanes World Congress 1991”, Technomic Publishing, Basel, Lancaster 1991, p. 615 ff that flame-resistant HR slabstock foams can be obtained by the combination of pure toluene diisocyanate with a PHD polyol and liquid phosphorus halogen compounds. An HR cold-cure moulded foam produced with these components does not, however, meet the requirements laid down in BS 5852 Part 2, Crib V, this possibly being attributable to the different polymer structure in slabstock foam and moulded foam. The results obtained on slabstock foam cannot, therefore, be transferred to moulded foam.
It has now been found that by reacting mixtures of TDI and MDI with PHD or PIPA polymer polyols, it is possible to obtain HR cold-cure moulded foams with reduced flammability, smoke density and toxicity.
SUMMARY OF THE INVENTION
The invention provides, therefore, an HR cold-cure moulded foam which may be obtained by reacting
a) mixtures of TDI and MDI in the weight ratio 95:5 to 60:40 with
b) dispersions of polymers containing relatively high molecular weight hydroxyl compounds which were prepared by reacting mono- and/or polyisocyanates with polyamines and/or hydrazines and/or hydrazides and/or alkanolamines having primary and/or secondary amino groups in a polyether having 1 to 8 primary and/or secondary hydroxyl groups with a number-average molecular weight from 400 to 16000,
c) in the presence of chemical and/or physical blowing agents (specially water), and
d) optionally flame retardants which are liquid and/or soluble in a), b) or c), and/or
e) optionally compounds with at least two hydrogen atoms which are reactive towards isocyanates and with a molecular weight from 32 to 399, and/or
f) optionally further auxiliaries.
According to the invention, mixtures of toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MD) are used as component a). The weight ratio between TDI and MDI is 95:5 to 60:40, preferably 95:5 to 70:30, particularly preferably 95:5 to 80:20. The isomer ratio of 2,4-TDI to 2,6-TDI may be from 100:0 to 65:35. In the MDI used, the content of binuclear diisocyanates, i.e. 2,2′-MDI, 2,4′-MDI and 4,4′-MDI is preferably between 35 and 100 wt. %, wherein 2,4′-MDI accounts for a proportion from 0 to 60 wt. % of the total amount of MDI. Higher homologues of the mixtures containing the MDI series (“polymeric MDI”, “crude MDI”) may also be used. According to the invention, both TDI and MDI may be modified in a manner known to the expert, as described in G. Oertel (ed.): “Kunststoff-Handbuch”, Vol, VII, Carl Hanser Verlag, 3rd edition, Munich 1993, p. 91-97, i.e., for example, to form an allophanate, biuret, trimer, carbodiimide, or prepolymerised with polyethers or parts of component b). If mixtures are used in which an isocyanate component is modified with polyethers or parts of component b), then the weight ratio of TDI to MDI is calculated on the basis of the unmodified isocyanates.
According to the invention, the polyol component b) contains dispersions of polymers containing relatively high molecular weight hydroxyl compounds which were prepared by reacting mono- and/or polyisocyanates with polyamines and/or hydrazines and/or hydrazides and/or alkanolamines having primary and/or secondary amino groups in a polyether having 1 to 8 primary and/or secondary hydroxyl groups with a number-average molecular weight from 400 to 16000 (“base polyol”). Base polyols with a number-average molecular weight from 1500 to 8000 are used in preference. Hydroxyl compounds used in preference are those which were prepared by reacting polyether polyols with hydrazines (PHD polyols). The component b) preferably has an average OH functionality from 2.0 to 3.5. Polyether polyols used in preference are those which have a primary OH group content of at least 60 mole %, preferably at least 70 mole %. In a further 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 other polyether polyol with an average functionality from 2 to 6, a number-average molecular weight from 1500 to 12000 in an amount from 1 to 50 wt. %, based on the total amount of compound b) with an EO content of more than 40 wt. %. This embodiment leads to better skin formation, a greater open-cell character and allows more scope for adjusting the NCO/OH index and hence better processability of the formulation. The foam obtained has increased elasticity and its hardness, which may be high due to the polymer dispersion, is reduced to such an extent that even flexible moulded parts may be produced.
Chemical and/or physical blowing agents c) are used for the preparation of the foams according to the invention. The chemical blowing agent used as component c) is preferably water which yields carbon dioxide as blowing gas by reaction with isocyanate groups. Water is used preferably in an amount from 2 to 8 wt. %, particularly preferably 2 to 4 wt. %, based on the amount of component b). Carbon dioxide may, however, also be added to the polyol or isocyanate component as a gas or in the liquid form, online or in the batch process according to inherently known methods. In component c) it is also possible to use non-flammable physical blowing agents such as, e.g., 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-trifluoroethane, 2,2-dichloro-2-fluoroethane, heptafluoropropane and sulfur hexafluoride. Mixtures of said blowing agents may also be used. As the blowing agent escapes almost completely from the foam during the production process, low-boiling hydrocarbons, e.g., pentane, hexane and isomers thereof may also be used. Other suitable blowing agents are carboxylic acids such as formic acid, acetic acid, oxalic acid and chemical blowing agents which liberate gases during the foaming process, such as, e.g., carbamates. These blowing agents are used preferably in combination with water.
Optionally, liquid flame retardants d) which are liquid and/or soluble in one or more of components a), b) or c) are used for the preparation of the foams according to the invention. Commercial flame retardants containing phosphorus are used in preference, for example, tricresyl phosphate, tris-(2-chloroethyl) phosphate, tris-(2-chloropropyl) phosphate, tris-(2,3-dibromopropyl) ph
Bohne Franz-Josef
Herrmann Marc
Seifert Peter
Bayer Aktiengesellschaft
Brown N. Denise
Cooney Jr. John M.
Gil Joseph C.
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