Co-initiated polyether polyol and process for its preparation

Details Co-initiated polyether polyol and process for its preparation Co-initiated polyether polyol and process for its preparation

2001-03-08

2003-03-25

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...

C252S182240, C252S182270, C521S170000

Reexamination Certificate

active

06538043

ABSTRACT:

The present invention relates to a co-initiated polyether polyol, to a process for the preparation of such polyether polyol, to polyol formulations containing such polyether polyol and to polyisocyanurate-modified polyurethane foams obtained from said polyether polyol.
Nowadays polyisocyanurate-modified rigid polyurethane foams (PIR/PUR foams) become more and more accepted in the building insulation market, anyhow in Europe. In this particular market PIR/PUR foams have to compete with the conventional rigid polyurethane foams (PUR foams). In terms of foam properties PIR/PUR foams are very similar to PUR foams. The formulation characteristics of both foams are, however, different. The main difference concerns the amount of isocyanate used to prepare the foam: this amount is higher for PIR/PUR foams. Accordingly, the isocyanate index for PIR/PUR foams is higher than that for PUR foams. The relatively large excess of isocyanate groups in PIR/PUP foaming formulations is reacted by adding trimerisation catalyst(s) to the reaction mixture. In this way the isocyanurate structures are formed. These isocyanurate structures improve the fire retardancy and thermal stability of the final foam and also induce an increased friability.
At present difunctional aromatic polyester polyols are commonly used in the manufacture of PIR/PUR foams. One category of such polyester polyols typically used are the polyester polyols produced from phthalic anhydride and diethylene glycol. Another category uses either the heavy residue of the production of dimethyl terephthalate or scraps of recycled polyethylene terephthalate (PET) as the feedstock.
The present invention aims to provide a dedicated polyether polyol, which can be used for producing PIR/PUR foams without using any polyester polyol. A further purpose of the present invention is to provide a method for producing such dedicated polyether polyol. Still a further object is to provide a PIR/PUK foam, of which the polyol component is entirely polyether polyol based and of which the end-properties are at least comparable to those of the conventional polyester polyol-based PIR/PUR foams.
The term “polyether polyol” as used in this connection refers to polyols comprising poly(alkylene oxide) chains, which polyols are normally obtained by reacting a polyhydroxy initiator compound with at least one alkylene oxide and optionally other compounds. The term “co-initiated polyether polyol” refers to a polyether polyol obtained by the alkoxylation of a blend of at least two different polyhydroxy compounds. The term “molecular weight” as used throughout this specification refers to number average molecular weight. The term “average molecular weight” refers to number average molecular weight per mole of initiator used.
The above objects have been realised by a specific co-initiated polyether polyol based on an aromatic initiator, polyethylene glycol, optionally an aliphatic, initiator and alksylene oxide.
Accordingly, in a first aspect the present invention relates to a process for the preparation of a co-initiated polyether polyol, which process comprises the steps of:
(a) preparing a mixture of:
(a1) at least one aromatic initiator containing at least two active hydrogen atoms per molecule and
(a2) at least one polyethylene glycol having a molecular weight in the range of from 400 to 1000 and
(a3) optionally one or more aliphatic initiators containing from 2 to 6 active hydrogen atoms per molecule in an amount of at most 20 mole % based on total moles of (a1) and (a3),
wherein the molar ratio of (a1) to (a2) is in the range of from 0.5:1 to 5:1, and
(b) reacting the mixture obtained in step (a) in the presence of a suitable alkoxylation catalyst with at least one alkylene oxide having three or more carbon atoms per molecule using such quantity of alkylene oxide that the polyether polyol obtained has a hydroxyl value in the range of from 150 to 400 mg KOH/g, and
(c) recovering the co-initiated polyether polyol.
The aromatic initiator used as component (a1) in step (a) may be any aromatic initiator known in the art to be suitable for acting as a starter molecule in the preparation of polyether polyols. Suitable aromatic initiators should contain at least two active hydrogen atoms per molecule available for reaction with alkylene oxide. Such active hydrogen atoms are typically present in the form of hydroxyl groups, but may also be present in the form of e.g. amine groups. Preferred initiators are those aromatic initiators containing from 2 to 5, more preferably 2 or 3 and most preferably 2 active hydrogen atoms in the form of hydroxyl groups per molecule. Concrete examples of suitable aromatic initiators include 2,2′-bis(4-hydroxylphenyl)propane (bisphenol A), 2,2′-bis(4-hydroxylphenyl)butane (bisphenol B) and 2,2′-bis(4-hydroxylphenyl)methane (bisphenol F). Similar compounds, wherein the hydroxyphenyl moiety contains one or more alkyl substituents, preferably methyl, may also be used. Bisphenol A is a preferred aromatic initiator.
The aromatic initiator component (a1) may consist of one sole aromatic initiator or of a blend of two or more different aromatic initiators provided such blend contains on average at least two active hydrogen atoms per initiator molecule. The aromatic initiator component (a1) may also be used in combination with an aliphatic initiator component (a3) consisting of one or more aliphatic initiators containing from 2 to 6 active hydrogen atoms per molecule. Such aliphatic initiator component, if present, is used in an amount of at most 20 mole % based on total moles of (a1) and (a3), preferably from 0.5 to 10 mole %. The average number of active hydrogen atoms per initiator molecule in such a combination should preferably be in the range of from 2 to 4, more preferably from 2 to 3 and most preferably equals 2. It will be understood that the nominal average functionality of the resulting polyether polyol will correspond with the number of active hydrogen atoms per initiator molecule. Examples of suitable aliphatic initiators are those known in the art including diethylene glycol, glycerol, pentaerythritol tri-methylolpropane, triethanolamine, mannitol and sorbitol. It has, however, been found particularly advantageous to use no aliphatic initiator component, inter alia because it adds to the cost of the formulation while having no recognisably beneficial effect on the end-properties of the PIR/PUR foam eventually obtained.
Suitable polyethylene glycols to be used as component (a2) are those polyethylene glycols having a molecular weight in the range of from 400 to 1000, preferably from 400 to 800, more preferably from 450 to 700. It will be understood that polyethylene glycols contain two hydroxyl groups, which are available to react with alkylene oxide. The polyethylene glycol component (a2) may consist of one or more, preferably one or two, polyethylene glycols. If more than one polyethylene glycol is used, they should all meet the above requirement as to molecular weight. Suitable polyethylene glycols are commercially available from several suppliers or can be prepared by methods known in the art.
In the process of the present invention it is essential that the aromatic initiator component (a1) and the polyethylene glycol component (a2) are admixed before alkylene oxide is allowed to react with the active hydrogen atoms present in both polyethylene glycol and initiator compound(s). The components (a1) and (a2) are mixed in a molar ratio of (a1) to (a2) in the range of from 0.5:1 to 5:1, preferably 1:1 to 4:1, more preferably 1:1 to 3:1. It is preferred that one aromatic initiator is mixed with one polyethylene glycol in step (a) in a molar ratio of aromatic initiator to polyethylene glycol of from 1:1 to 4:1. If any aliphatic initiator component (a3) is present this component should also he admixed with components (a1) and (a2) prior to the reaction with alkylene oxide. By first mixing the initiator(s) and polyethylene glycol(s) before reaction with alkylene oxide, it is ensured that a co-initiated polyether polyol is

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