Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-07-26
2003-05-13
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S866000, C568S867000, C521S137000, C521S155000, C521S159000, C521S170000, C521S174000, C521S914000
Reexamination Certificate
active
06563007
ABSTRACT:
The present invention relates to a process for the preparation of polyetherols based on solid initiator substances and liquid, hydroxyl-containing coinitiators by a catalyzed addition reaction of alkylene oxides and to the use of these polyetherpolyols for the preparation of polyurethanes (PUR), in particular rigid PUR foams.
The preparation of polyetherols by anionic polymerization has long been known.
Further details in this context appear, for example, in Kunststoffhandbuch, Volume VII, Polyurethane, Carl-Hanser-Verlag, Munich, 1
st
Edition 1966, edited by Dr. R. Vieweg and Dr. A. Höchtlen, and 2
nd
Edition 1983 and 3
rd
Edition 1993, edited by Dr. G. Oertel.
Use of, for example, mono-, di- or polysaccharides and further compounds having a high functionality in the preparation of polyetherols having a high functionality for rigid PUR foams has been widely described. When substances having a high content of hydroxyl groups, for example sucrose, are used, the problem of the reaction of solid substances with alkylene oxides in a pressure autoclave occurs. Moroever, the use of high temperatures during the alkoxylation reaction is limited. Thus, dark products which are undesirable in numerous applications are formed in the reaction of sucrose with alkylene oxides at above 120° C.
A process for the alkoxylation of solid initiator substances, e.g. pentaerythritol, dipentaerythritol, trimethylolpropane, sorbitol or sucrose, is described in U.S. Pat. No. 3,346,557. There, the initiator substance containing from 3 to 8 OH groups per mole is mixed with an amine catalyst and is alkoxylated to give an adduct consisting of a usually solid compound containing from 3 to 8 OH groups per mole, and from 0.5 to 1.5 mol of vicinal alkylene oxide. For example, sucrose, tributylamine and distilled water are mixed and propoxylated. This adduct is stripped, mixed with tributylamine and further propoxylated. The sucrose/propylene oxide adduct serves as a reaction medium for taking up further sucrose during further reaction with alkylene oxides.
However, it has been found that dark products are formed throughout as a result of the long thermal stress in the course of the reaction. The introduction of sucrose into an alkoxylate and further alkoxylation of this mixture furthermore often leads to incomplete conversion of the sucrose added. Free sucrose is present in the polyetherol and is deposited on the bottom. This effect is very highly dependent on the degree of alkoxylation and on the technical equipment of the production plant. As a result of the amine catalysis, these polyetherols have high intrinsic reactivities which adversely affect the curing of the foams and greatly limit their use.
DD-A-211797 describes a process for the stepwise preparation of polyetherols using solid or highly viscous initiator substances in combination with substances which have a combined function as catalyst and coinitiator, for example ammonia and/or its propoxylation products. For example, aqueous ammonia solution, aqueous potassium hydroxide solution and sucrose are mixed and are propoxylated in a first reaction stage. The product is stripped and reacted with further propylene oxide. The incorporation of nitrogen-containing compounds leads to reductions in viscosity with comparable functionality but also to an increase in the intrinsic reactivity of the polyetherol and hence to a deterioration in the curing behavior. The functionality of the polyetherols is also greatly reduced by the high water contents of the solutions of nitrogen-containing compounds. These polyetherols cannot be used for many rigid foam applications. The required distillation step furthermore leads to a poor yield of the raw materials used. Furthermore, the wastewater is polluted necessitating further technical measures.
The process described in DE-A-4209358 for the preparation of polyether alcohols based on solid and highly viscous initiator substances having hydroxyl, imino or amino functional groups comprises adding aliphatic amines in an amount from 0.5 to 5% by weight, based on the weight of the polyol, to the initiator substance or mixture of initiator substances and then carrying out a reaction with alkylene oxides. These polyols have low potassium contents and light colors. In this process, too, the amine content of the polyol results in a higher intrinsic reactivity with respect to isocyanates, which necessitates a decrease in the amount of foaming catalysts and hence adversely affects the curing behavior.
The processes described have not become decisively established to date. When nitrogen-containing compounds are concomitantly used, the intrinsic reactivity of the polyetherols is noticeably increased in a manner undesirable for many applications and thus adversely affects the curing behavior of the rigid foams. The reaction of compounds having a high functionality, such as sucrose, with alkylene oxides in their own alkoxylates leads to polyetherols which have a high functionality and often contain unconverted sucrose.
Numerous processes for the preparation of polyetherols having a high functionality and based on sucrose use glycerol as a coinitiator. This proven procedure leads to polyetherols which meet most property requirements. However, they do not exhaust the possibilities of a higher effective functionality of sucrose polyetherols having improved curing behavior and formation of a highly dense network in the foam. The process presented in U.S. Pat. No. 5,143,941 for the preparation of energy-absorbing PUR foams uses, inter alia, a polyetherol based on sucrose/dipropylene glycol/propylene oxide having a hydroxyl number of about 400 mg KOH/g. In the case of this hydroxyl number, however, it is necessary to reduce the effective functionality to about 3.5, since the viscosity of the polyetherol would otherwise far exceed 10 Pa·s. Consequently the effect of a high network density and of good flow behavior is no longer obtained in the case of such polyols.
CA-A-2135352 describes the preparation of rigid foams having a good insulation effect in combination with good physical properties, good demoldability and K factors. The formulation contains, inter alia, a polyetherol based on sucrose/propylene glycol/water and propylene oxide and a polyetherol based on sucrose/propylene glycol/water and ethylene oxide and propylene oxide. Since excessively high viscosities are generally obtained by the combination of sucrose/propylene glycol and usual hydroxyl numbers for rigid foam applications and the water content reduces the functionality, the useability is subject to limits.
For the use of sucrose polyetherols having a high functionality which possess advantageous processing viscosities, give rise to improved flow behavior or contribute towards sufficiently high network density in the foam and are light in color, novel possibilities are being sought for improving the properties of the foam itself and its processing, such as curing behavior, demolding of the foams, mechanical properties, insulation behavior and heat stability and for ensuring economically advantageous use of the raw materials.
It is an object of the present invention to provide, for rigid PUR foams having high network density and good mechanical properties, polyetherols which, with a large number of functional groups and relatively low viscosity, excellent properties and good thermal stability, can be reacted with polyisocyanates and conventional additives to give PUR foams. It is intended to use economical raw materials and technologies and to achieve a high property level for use in rigid industrial foams for sandwich, refrigerator and district heating applications.
We have found that this object is achieved, according to the invention, if an initiator combination having diols carrying ethoxy structures is used for the preparation of the polyetherols, the ratio of the mean number of hydroxyl groups per mole of initiator combination to the number of ethoxy structures in the polyetherol being from 1:0.2 to 1:1.8 and the ratio of the amounts by weight of the dials carrying e
Dinsch Stefan
Höppner Gerd
Knorr Gottfried
Reichelt Michael
von Malotki Peter
Barts Samuel
BASF Atiengesellschaft
Borrego Fernando A.
Cameron Mary K.
Witherspoon Sikarl A.
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