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...
Patent
1999-05-12
2000-11-14
Gorr, Rachel
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...
525440, G08G 1842
Patent
active
06147181&
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for preparing solid, transparent to translucent polyurethane moulded items which, due to their elastic and optical properties, can be used, for instance, as an alternative material to rubber.
PUR catalysed resins based on polyesterpolyols are generally used to produce semi-rigid PU moulded items. They are particularly suitable for producing moulded items by the casting or injection moulding process because good results with respect to the hardness of the material and the solidification time can be obtained with these over a wide range of system variations. Complex engineering for machines, filling procedures, mould production and mould closures is not normally required, but may be applied in individual cases.
The use of PUR catalysed resins based on polyetherpolyols is also known but is often not chosen because satisfactory and continuously producible high degrees of transparency can only be achieved by using more complicated engineering procedures. Production by the RIM process using catalysed resins which contain both reactive hydroxy and amine terminal groups and requires the use of special moulding and closure equipment, as has been described in accordance with EP 0 299 117 A1, may be mentioned here. Ultimately, however, when using PUR moulding compositions based on polyetherpolyols, the processing window is always very restricted so that, in contrast, PUR systems based on polyesterpolyols have always been used in preference. Astonishingly, this is the case even for applications in exposed areas where hydrolytic/microbial decomposition of the ester components is prevented only by the incorporation of often very costly protective additives.
It has now been found, surprisingly, that PUR moulding compositions based on ether-polyols can be advantageously processed in the same way as those based on esters to give transparent/translucent moulded items if they have been provided with a much higher average molecular weight, and thus an associated increase in viscosity, in a first process stage. A suitable process stage of this type is in particular the reaction described below with difunctional and/or higher functional components with terminal isocyanate groups to give so-called OH-prepolymers. Reaction with difunctional or higher functional carboxylic acids to give comparably extended ether/ester-polyols has also proven to be suitable.
The invention therefore provides a two-stage process for preparing compact, transparent PUR moulded items by the polyisocyanate/polyaddition process with a Shore A hardness of 40 to 90 by reacting reactive hydrogen atoms and optionally presence of containing at least two reactive hydrogen atoms (b), the reaction product of ratio of 15:85 to 40:60, an OH value of 56-28 and a functionality of 2.0, but higher functional, EO/PO-polyetherpolyol started with glycerine, trimethylolpropane, pentaerythritol or sugar (EO/PO ratio 15:85 to 40:60) with an OH value of 60-25, which are composed in the way described under (I) and (II), 500 to 2000 therefrom, obtainable therefrom, functionality of at least 2 (NDI, p-PDI), and the prepolymers obtainable therefrom, a functionality of at least 2 (IPDI, HDI, H-MDI) and the prepolymers obtainable therefrom,
Each of the prepolymers specified in (A) to (G) are obtained, for example, by reacting the isocyanates with an etherpolyol as described under (I) to (V) and are characterised by the presence of terminal, reactive NCO groups.
Reaction of the polyols described under (I) to (V) is also possible with (AA) difunctional and/or higher functional carboxylic acids such as, for example, adipic acid, glutaric acid, succinic acid and other representative of this class of substances and also their mixtures, instead of with isocyanates.
Furthermore, also "short-chain" reaction components such as H.sub.2 O, difunctional and trifunctional OH compounds, OH-amines, diamines and triamines, etc, which have been used in the preliminary reaction and have participated in the reaction and specifically alter the properties of the mater
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Michels Erhard
Pleiss Klaus
Scholtis Franz
Bayer Aktiengesellschaft
Brown N. Denise
Gil Joseph C.
Gorr Rachel
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