Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2001-05-02
2003-05-06
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S083000
Reexamination Certificate
active
06559267
ABSTRACT:
The invention relates to mouldings of thermoplastic polyurethanes (TPU) with reduced fogging behaviour.
Thermoplastic polyurethane elastomers have long been known. They are of industrial importance owing to the combination of high-grade mechanical properties with the known advantages of cost-effective thermoplastic processability. By using different chemical structural components, a wide range of variations in mechanical properties may be achieved. An overview of TPUs, their properties and applications is provided for example in Kunststoffe 68 (1978), pages 819 to 825 and Kautschuk, Gummi, Kunststoffe 35 (1982), pages 568 to 584.
TPUs are built up from linear polyols, generally polyester or polyether polyols, organic diisocyanates and short-chain diols (chain extenders). To accelerate the formation reaction, catalysts may be used. To adjust the properties, the structural components may be varied in relatively wide molar ratios. Molar ratios of polyols to chain extenders of from 1:1 to 1:12 have proven effective and result in products in the hardness range of from 70 Shore A to 75 Shore D.
TPUs may be produced continuously or discontinuously. The best known industrial production processes are the belt process (GB-A 1,057,018) and the extruder process (DE-A 1 964 834 and 2 059 570).
It is known (EP-A 579 988, DE-A 19 611 670) that the polyester polyols, which are used in the polyurethane field, contain low molecular weight cyclic compounds, which, when polyurethanes are used, result in the so-called “fogging effect”. The “fogging effect” is a light-scattering effect which occurs as a result of the condensation of the primarily cyclic compounds which form on the internal faces of panes of glass. This is particularly disturbing in automobile construction, if the windows mist up as a result of fogging generated by the polyurethanes in the internal trim.
Current requirements relating to materials for use in internal motor vehicle trim are very complex. Due to requirements relating to heat or hot air stability, polyester polyols or mixtures of polyester polyols and polyether polyols are preferably used as the polyols for thermoplastic polyurethanes. It is known from flexible polyurethane foam production (EP-A 579 988) that substances also escape from polyester polyurethane foams which result in visible window deposits.
Reduced fogging behaviour is therefore an additional requirement for mouldings for internal automobile trim. Thus, a moulding condensate value (16 hrs at 120° C. to DIN 75201B) of less than 6 mg per 10 g TPU is required by some automobile manufacturers. Other manufacturers demand even lower condensate values for the mouldings.
The path proposed in DE-A 19 757 562 for reducing the condensate value of the TPU by passing hot gas (e.g. air) through the granulate for 5 to 20 hrs at 80° to 110° C. is unsuitable for TPUs containing polyether diols. When subjected to this hot gas treatment, the polyether-containing TPUs tend to change colour (e.g. from white to grey), which is disadvantageous in particular for use inside an automobile.
The object was therefore to provide mouldings of thermoplastic polyurethanes which exhibit low fogging values (measured to DIN 75201B at 120° C. over 16 hours) even after processing (compounding with dyestuffs and additives) and shaping (injection moulding, extrusion, powder-slush processes).
It is known from U.S. Pat. No. 5,545,675 and EP-A 579 988 that polyester diols and cyclic ring esters (main cause of fogging effect apart from additives) are in thermodynamic equilibrium. For this reason, after the distillation of polyester diols for production of ring ester-free polyester diols the cyclic ring esters may re-form again in the distillation residue, in particular at relatively high temperatures. It is known to physically remove the ring esters (EP-A 579 988) from the polyester polyol used by means of vacuum distillation using commercially available apparatus such as thin-film evaporator or short-path evaporator. In U.S. Pat. No. 5,545,675 and EP-A 579 988, reference is made to the fact that the polyester diol has to be cooled rapidly to temperatures of below 120° C. after leaving the distillation apparatus.
It was all the more surprising that the inventive TPU may be extruded at 180° to 240° C. and residence times of 30-90 seconds and yet exhibit low fogging values. No cycles (ring esters) apparently form during production of the inventive TPUs. It was also surprising that, even after compounding and shaping, wherein melt temperatures of 180-230° C. again occur with residence times of 30-120 seconds, TPU mouldings are obtained which likewise exhibit low fogging values.
The present invention provides a moulding containing TPU characterized in that it exhibits condensate values lower than 2 mg/10 g of TPU, determined according to DIN 75 201 at 120° C./16 hours. The inventive TPU is obtained by reacting, optionally in the presence of a catalyst,
A) an organic diisocyanate,
B) a polyester polyol having a number average molecular weight of 600 to 10 000 g/mol, and having a content of 1:1 ring ester of dicarboxylic acid and diol of less than 0.2 percent relative to the weight of said polyester polyol, and
C) a chain extender having an average molecular weight of 60 to 500 g/mol, selected from the group consisting of diol and diamine wherein the equivalent ratio of A) to B) is 1.5:1.0 to 10.0:1.0 and the NCO index (calculated as the quotient of the equivalent ratio of isocyanate groups to the sum of the hydroxyl groups of polyol and chain extender multiplied by 100) is 95 to 105.
The TPU thus obtained may contain conventional auxiliary additives for their art-recognized functions.
Reactant B) may contain up to 80%, preferably up to 70%, relative to its weight, at least one member selected from the group consisting of polyether polyol and polycarbonate polyol, each having a number average molecular weight of 600 to 10 000, preferably 600 to 5 000. In a preferred embodiment, the content of 1:1 ring ester of dicarboxylic acid and diol characterizing reactant B) is less than 0.15 percent relative to the weight of polyester polyol.
The expression “1:1 ring ester of dicarboxylic acid and diol” means a reaction product of 1 mol dicarboxylic acid and 1 mol diol.
Thermoplastic polyurethanes with a condensate value of <2 mg/10 g of thermoplastic polyurethane in a fogging test according to DIN 75201B at 120° C. and 16 hours are preferably used.
Component A) may comprise aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic diisocyanates or any mixtures of these polyisocyanates (c.f. HOUBEN-WEYL “Methoden der organischen Chemie”, Vol. E 20 “Makromolekulare Stoffe”, Georg Thieme Verlag, Stuttgart, New York, 1987, pp. 1587-1593 or Justus Liebigs Annalen der Chemie, 562, pages 75 to 136).
In detail, the following may be mentioned by way of example: aliphatic diisocyanates such as ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cycloaliphatic diisocyanates such as isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate and 1-methyl-2,6-cyclohexane diisocyanate together with the corresponding isomer mixtures, 4,4′-dicyclohexylmethane diisocyanate, 2,4′-dicyclohexylmethane diisocyanate and 2,2′-dicyclohexylmethane diisocyanate together with the corresponding isomer mixtures, also aromatic diisocyanates, such as 2,4-tolylene diisocyanate, mixtures of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate and 2,2′-diphenylmethane diisocyanate, mixtures of 2,4′-diphenylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate, urethane-modified liquid 4,4′-diphenylmethane diisocyanates or 2,4′-diphenylmethane diisocyanates, 4,4′-diisocyanato-1,2-diphenylethane and 1,5-naphthylene diisocyanate. 1,6-hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, dip
Hoppe Hans-Georg
Kaufhold Wolfgang
Röhrig Wolfgang
Bayer Aktiengesellschaft
Franks James R.
Gil Joseph C.
Gorr Rachel
Preis Aron
LandOfFree
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