Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1998-03-09
2001-06-12
Leary, Louise N. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S580000, C568S583000
Reexamination Certificate
active
06245947
ABSTRACT:
The invention relates to a process for treating polyether polyols prepared in a conventional manner by base-catalyzed reaction of H-functional initiator substances with alkylene oxides and freed from the catalyst and, if appropriate, from salts which are formed, where this treatment is a combination of a thermal-reactive step at a pH of less than 7 and a temperature above 60° C. and a thermal-distillative step in a countercurrent column using a purifying agent.
The preparation of polyether polyols has been known for a long time. Synthesis of polyetherols by anionic polymerization is carried out in particular with the use of alkali metal hydroxides and alkaline-earth metal hydroxides, and at from 60 to 140° C. under increased pressures. After the synthesis, neutralization is carried out using acid, in particular hydrochloric and/or phosphoric acid, in order to remove the catalyst, distillation is carried out, in particular under reduced pressure and at from 80 to 130° C., in order to remove water and other volatile constituents, and finally the salts are removed.
More detail on this topic may be found in Kunststoffhandbuch, Vol. VII, Polyurethane, Carl-Hanser-Verlag, Munich, 1st edition 1966, edited by Dr. R. Vieweg and Dr. A. Höbchtlen, and 2nd edition 1983 and 3rd edition 1993, edited by Dr. G. Oertel.
This preparation process produces, besides the target products, ie. the polyether polyols with various molecular weights, a wide variety of by-products which give various problems in the use of the polyether polyols for preparing polyurethanes (PUR). They may adversely affect the foaming procedure, may give poorer very important physicomechanical values, such as hardness or elasticity, to the foam, and, as a result of lower volatility, may initially remain in the polyurethane and gradually cause disadvantageous odor and fogging.
The odor of PUR foams is problematic in particular for certain applications of flexible PUR foam in the furniture sector and in textile coating. The causes of the odor problem, which derive from the PUR catalysts and the PUR auxiliaries and additives, are removed by changing to higher-boiling, lower-volatility substances with lower vapor pressures and the use of incorporatable catalysts, eg. the spacer amine type of EP-A-0539819. The substances which are derived from the polyols and cause odor may be removed in a manner similar to the removal of cyclic ethers and/or unsaturated polyol constituents, as described in U.S. Pat. No. 4,251,654 and/or EP-A-0576132, by extraction with water or glycols. However, this removes only a very limited proportion of highly volatile substances; other substances transform to give substances having a strong odor only when these conditions are applied (formation and/or cleavage of acetals). The distillation carried out to remove water during the usual purification operation to remove catalyst also eliminates highly volatile constituents, as described, for example, in DD-A-216248. In the case of neutralization and downstream removal of water, continuous changes in pH are caused, giving rise to a wide variety of transformations of the substances causing odor (aldehydes, dioxanes) or, as described and intended in WO-A-9318083, even giving shifts in the molecular weight distribution.
Although important odor-intensive materials are removed in the combined thermal-distillative treatment of polyether polyols described in our U.S. patent application Ser. No. 19629160.7, a large number of by-products is formed continuously in an equilibrium reaction. A purely physical treatment is insufficient to remove them. Distillation processes for preparing low-fogging polyester polyols, as described in EP-A-0579988 for example, operate in a similar manner. Such purely distillative processes are inadequate to remove certain by-products of the polyether polyol preparation, especially since the temperatures which can be used with these polyols are below 150° C. High depletion rates of >95% for by-products affecting quality in polyols have until now been achievable only in complicated apparatus, such as molecular evaporators or extruders, resulting in high investment costs. A better depletion result is also possible with very long residence times in simple apparatus, mixing vessels for example. This, however, gives low yields and unacceptable degradation and discoloration of the product.
It is an object of the present invention to develop a process for post-treatment of polyether polyols from the conventional base-catalyzed reaction of H-functional initiator substances with alkylene oxides and subsequent purification of the raw polyether polyols for catalyst removal, which process permits high depletion rates of the by-products affecting quality and, with less expensive apparatus, permits high yields with complete avoidance of discoloration and degradation of the product. We have found that this object is achieved by subjecting the polyether polyols to a treatment which is a combination of a thermal-reactive step at a pH of less than 7 and a temperature above 60° C. and a thermal-distillative step in a countercurrent column using a purifying agent.
The invention therefore provides a process for treating polyether polyols prepared in a conventional manner by base-catalyzed reaction of H-functional initiator substances with alkylene oxides, wherein the treatment is a combination of a thermal-reactive step at a pH of less than 7 and a temperature above 60° C. and a thermal-distillative step in a countercurrent column using a purifying agent.
The invention also provides the use of the polyether polyols prepared according to the invention for producing low-fogging and low-odor PUR foams.
The novel process may be used for treating any polyether polyol prepared by base-catalyzed addition of alkylene oxide to an H-functional initiator substance.
Such products are prepared by the processes known from the prior art, by mixing the H—, in particular OH— and/or NH— and/or NH
2
-functional initiator substance with the base used as catalyst in an amount of from 0.05 to 1% by weight, removing the resultant water and then metering in and reacting the low-molecular-weight alkylene oxide, in particular ethylene oxide and/or propylene oxide.
The OH-functional initiator substances are usually polyfunctional, in particular bi- and/or trifunctional, compounds, such as glycols, for example ethylene glycol and propylene glycol, glycerol and trimethylolpropane, but also higher-functionality alcohols and sugar alcohols, such as glucose or saccharides. The use of glycerol and/or trimethylolpropane individually or in combination with proportions of glycols is particularly advantageous.
The NH— or NH
2
-functional compounds may be either aliphatic or aromatic mono- or polyfunctional primary or secondary amines. Water may also be used as initiator substance. Mixtures of the abovementioned compounds are frequently used as initiators.
In particular when initiator substances are used which are highly viscous or solid at the reaction temperature, liquid coinitiators are used to permit a homogeneous initiation of the reaction. This applies to sugars, such as sorbitol or sucrose, but also to aromatic amines, such as tolylenediamine or methyldiphenyldiamine and their homologs. Glycols, glycerol and water are in particular used as coinitiators here.
After adding the alkaline catalyst and, if appropriate, after removing the resultant water, the alkylene oxides are metered in. For reasons of safety, inert conditions are created in advance within the reaction vessel using inert gas, in particular nitrogen.
Low-molecular-weight alkylene oxides used are in particular ethylene oxide (EO), propylene oxide (PO) and/or butylene oxide (BO), preferably EO and 1,2-PO.
The catalysts used are basic compounds, in particular alkali metal hydroxides and/or alkaline-earth metal hydroxides and/or amines. The alkylene oxides are added on individually as blocks and/or as random mixture.
The reaction carried out under the conventional reaction conditions, in particular at from 60 to 140° C. and at atmos
Auer Heinz
Bruhn Jens
Dinsch Stefan
Guettes Bernd
Hoeppner Gerd
BASF - Aktiengesellschaft
Borrego Fernando A.
Leary Louise N.
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