DE2457135A1 - Polyether polyols purified by reduction - to prevent scorching in polyurethane foam prodn - Google Patents

Abstract

Polyether polyols are purified by reducing with NaBH4 or LiAlH4. These reducing agents reduce aldehyde, peroxides ketones, acids and esters in the polyether polyol, thus preventing prevulacanisation or scorching during the prodn. of large vols. of polyurethane foam. The redn. is pref. effected with 0.001-1.0 wt. % NaBH4 or LiAlH4, based on the wt. of polyether polyol, at 20-100 degrees C for >=30 mins. The polyether polyol is pref. diluted with 2-20 wt. % H2O and/or the reducing agent is added as a 0.1-5 wt. % aq. soln. esp. also contg. 0.05-10 wt. % of an alkali. e.g. NaOH or KOH.

Description

R e ctio n to the patent application relating to the process for cleaning polyether polyol The invention relates to a method for cleaning of polyether polyol and especially a process in which polyether polyol is obtained, which does not vulcanize in the exothermic reaction in the formation of urethane foams or hardened prematurely (scorch).

It is known that urethane foam is formed by reacting Polyether polyol and organic polyisocyanate compounds and that urethane foam "Vulcanized" by the exothermic reaction of the hydroxyl groups with the isocyanate groups. Scorch occurs inside the foam, especially when large volumes produced by foam as an adiabatic exothermic reaction takes place and the high temperature is maintained for a long time.

To avoid scorching, stabilizers such as phosphites, Hypophosphites and antioxidants from substituted phenols to the polyether polyol added. However, this cannot completely prevent vulcanization.

It is the object of the present invention to produce a polyether polyol, das1 when making large volumes of urethane foam, not for scorching leads.

It has been shown that some special reducing agents scorch on Prevent the polyether polyol by the aldehydes contained in the polyether polyol, Peroxides, ketones, organic acids, alcohols, keto alcohols and organic esters be reduced.

The inventive method is carried out by adding polyether polyol reduced with sodium borohydride or lithium aluminum hydride at 20 to 1000C.

In the method according to the invention, an aqueous solution of Sodium borohydride or lithium aluminum hydride is added to the polyether polyol. That Polyether polyol should be diluted with water. Sodium borohydride or lithium aluminum hydride are usually added dropwise over more than 15 minutes and the mixture is preferred more than 30 minutes after the addition of the sodium borohydride or lithium aluminum hydride touched.

It is very beneficial to take the mixture during the reduction reaction Maintain mild alkaline conditions to allow the reaction to proceed slowly. The amount of water added to the mixture is not limited, but it is customary 2 to 20% by weight, preferably 5 to 10% by weight, are used, especially if that Polyether polyol has a high molecular weight, will have a greater effect of treatment achieved when more water is added4 That added to the polyether polyol However, water should be removed after the reaction. Hence, it shouldn't be too big Amount of water to be applied.

The amount of sodium borohydride or sodium borohydride added to the polyether polyol Lithium aluminum hydride is favorably from 0.001 to 1.0 wt%, preferably 0.01 to 0.1% by weight, based on the polyether polyol. If less than 0.001 wt% Sodium borohydride or lithium aluminum hydride can be used, no significant effect can be achieved.

Even if more than 1.0% by weight of sodium borohydride or lithium aluminum hydride are added, the effect will not correspond to the larger amount of sodium borohydride or lithium aluminum hydride is better, and the larger one makes the treatment more expensive Amount of sodium borohydride or lithium aluminum hydrideO The sodium borohydride or lithium aluminum hydride is preferably used in the form of an alkaline aqueous solution and the concentration of alkali in the aqueous solution is usually from 0.05 to 10% by weight, preferably 0.05 to 0.4% by weight, and various alkaline substances can be applied.

However, sodium hydroxide or potassium hydroxide are considered alkaline substances preferred. The concentration of sodium borohydride or lithium aluminum hydride is favorably 0.1 to 5.0 wt.

preferably 0.5 to 3 wt., -, The reaction is usually at 20 up to 1000 ° C., preferably at 50 to 80 ° C. within 30 minutes to 3 hours. When the reaction mixture is acidic or the reaction is carried out above 1000G violent decomposition of sodium borohydride or lithium aluminum hydride occurs and the hydrogen generated in the reaction mixture cannot be effectively used and the treatment becomes dangerous.

The sodium borohydride or lithium aluminum hydride must be used in the reaction not used up. After the reaction, the polyether polyol is released from the reaction mixture separated in the same way as in the manufacture of polyether polyol Polyol and alkylene oxide. After the reaction mixture with inorganic acids such as. Sulfuric acid, phosphoric acid, hydrochloric acid or organic acids such as acetic acid or Oxalic acid has been brought to a pH of 4 to 7, become adsorbents such as activated charcoal, activated clay and filter aid are added and the + ydratisierung carried out under reduced pressure by distillation and the reaction mixture then filtered to obtain the finished polyether polyol. Usually is the amount of adsorbent or filter aid less as 1 part by weight to 100 parts by weight of polyether polyol. Drainage should be at less than 110 ° C and the concentration of water in the final product should be preferred to less than 0.1% by weight.

With the help of the method according to the invention, various types are treated by polyether polyol and the total lyätherpolyol, which is used for the production of urethane foam used is cleaned. For example, a polyether polyol which has been prepared by adding alkylene oxide to a Starting compound with active hydrogen.

The typical examples are polyether polyols that have been made are by adding ethylene oxide and / or propylene oxide to glycol, ethylene glycol, Glycerine, trimethylolpropane, 1,2,3-hexanetriol, sorbitol, riphenolamine, ethylenediamine, Diethylenediamine, tolylenediamine, aniline or methylenedianiline at 100 to 1800C in the presence of 0.05 to 0.5% by weight alkali catalyst, based on polyether polyol.

The cleaning method according to the invention can also be used on polyether polyols for the production of rigid or flexible foams and it is suitable for preventing scorching of the foam that is formed has been made from polyether polyol, which has been made from sucrose and alkylene oxide.

This polyether polyol normally results in severe scorching.

If necessary, conventional stabilizers and antioxidants can be used are used to increase the effect.

The invention is illustrated by the following non-limiting examples explained in more detail.

Example 1 500 g of water were converted into 10 kg of crude polyether polyol (A) - as stated below - added. The mixture was stirred and brought to about 40 heated to 50 ° C. 100 g of an aqueous solution of sodium borohydride (C) - as below stated - was added to the mixture within 1 hour and the mixture more Stirred for 3 hours. Then the mixture was made with 20 wt% sulfuric acid on brought a pH of 6 to 7 and then 30 g of 2,6-dibutyl-4-methylphenol (bit) dissolved in the mixture.

Then 5 g of magnesium oxide and 10 g of bilter aid were added and that Removed water from the mixture under reduced pressure and filtered the residue.

The obtained polyether polyol (1) had less than 20 ALPHA.

The above treatment was repeated without water and the like an aqueous solution of sodium borohydride (C) was added. The obtained polyether polyol (1 ') had approximately 30 to 40 APHA.

* Raw polyether polyol (A); average molecular weight 3000, hydroxyl number 56, made from glycerine and propylene oxide, * Aqueous solution of sodium borohydride (C); containing 1000 kg of water, 20 g of sodium hydroxide and 60 g of sodium borohydride.

Example 2 500 g of water were converted into 101 (g of crude polyether polyol (B) - as stated otherwise - admitted. The mixture was stirred and further increased to 70 bis Heated to 75 ° C. 100g of an aqueous solution of sodium borohydride were inside added dropwise to the mixture for about 1 hour, and the mixture for another about Stirred for 3 hours. Then the mixture was made up with 15% by weight of phosphoric acid Brought a pH of 6 to 7 and then 10 g activated clay and 10 g bilter aid was added and then the water was removed from the mixture under reduced pressure and the residue is filtered.

The obtained polyether polyol (2) had a value of less than 1 according to the Gardner colorimetric method.

The above treatment was repeated without adding water and the aqueous sodium borohydride solution. The obtained polyether polyol (2t) possessed a value of about 3 by the Gardner colorimetric method.

* Crude polyether polyol (B); average molecular weight 920; Hydroxyl number 460; made from sucrose and propylene oxide.

Experimental Example 1 1. To 4 kg of polyether polyol were added the following Substances added in the order given: Polyether polyol 100 parts by weight Water 4.2 silicone surfactant 1.5 Z inno ctylat 0.35 triethylenediamine 0.1 After mixing well, 52.3 parts by weight of tolylene diisocyanate was added to the mixture intimately mixed and the entire mixture in one. Box with a size of 65 x 65 x 70 cm and caused to foam. After standing for 24 hours it was the foam was cut into 5 cm thick slices and examined for vulcanization.

The results are given in Table 1.

2. The following substances were added to 10 kg of polyether polyol specified amount added: polyether polyol 100 parts by weight trichlorofluoromethane 18.0 I1 silicone surfactant 1.0 tetramethylpropylenediamine 2.0 dibutyltin dilaurate 0.2 1? After mixing well, there was 125.7 parts by weight of prepolymer of tolylene diisocyanate (D) intimately mixed with it and the mixture in a box with a size of 65 x 65 x 70 cm and a foam was generated. After standing for 24 hours, the foam became cut into 5 cm thick slices and observed the vulcanization.

The results are also given in Table 1.

* Prepolymer of tolylene diisocyanate (D) containing 25% by weight —NCO; viscosity at 250C 1200 cps; made from IDI-80 and polyether polyol from sorbitol.

Table 1 Soft foam off Hard foam batch 1 2 3 4 5 Polyether polyol 1 1 '1' 2 2 'Quantity of BHT (parts) 0.3 0 0.3 0.3 0 Color of the APHA APHA APHA Gardner Gardner Polyether Polyols 15 40 40 1 3 Scorch: white brown- yellow white brown color inside yellow yellow of the foam Example 3 The example 1 was repeated except that lithium aluminum hydride and crude polyether polyol (E) was used in place of aluminum borohydride and crude polyether polyol (A).

The obtained polyether polyol (3) had less than 15 ALPHA.

Example 3 was repeated without adding water and the aqueous Lithium aluminum hydride solution.

The obtained polyether polyol (3 ') had about 30 to 40 APHA.

Experimental example 2 Experimental example 1 was repeated with the Exception that polyether polyol (3) and polyether polyol (3 ') were used instead of polyether polyol (1), (1 '), (2) around 5 (2').

The results are given in Table 2.

Table 2 Soft foam formulation 6 7 8 9 Polyether polyol 3 3 '3 3 'Quantity of DHT (parts) 0.3 0.3 0 0 Color of the roly-AFHA ALPHA APHA ALPHA åtherpolyol 10 30 15 40 Scorch color inside the white brown-white brown foam yellow yellow * Raw polyether polyol (E); average molecular weight 1000; Hydroxyl number 174; made from glycerine and propylene oxide.

Claims

Claims (5)

P a t e n t a n s p r ü c h e 1. Method for cleaning PolyCtherpolyol, in that the polyether polyol is mixed with sodium borohydride or lithium aluminum hydride reduced. 2. Method according to claim 1, characterized in that it is not possible to use it that the reduction with 0.001 to 1.0 wt .-% sodium borohydride or lithium aluminum hydride, based on that at 20 to 1000C for more than 30 minutes. Polyäthe rpolyol 3. The method according to claim 1 or 2, characterized g e -k e n n n e i c h n e t that the polyether polyol with 2 to 20 wt .-% water diluted. 4. The method according to claim 1 to 3, characterized in that g e k e n n -z e i c h n e t that the sodium borohydride or lithium aluminum hydride as 0.1 to 5% (Weight) aqueous solution used. 5. The method according to claim 4, characterized in that g e k e n n -z e i c h n e t that the sodium borohydride or lithium aluminum hydride in the form of an aqueous Solution containing 0.1 to 5% by weight of sodium borohydride or lithium aluminum hydride and 0.05 to 10% by weight of an alkaline one. Substance such as sodium hydroxide or potassium hydroside used.