CA1144569A

CA1144569A - Vapor phase hydrolysis of polyurethanes

Info

Publication number: CA1144569A
Application number: CA000310616A
Authority: CA
Inventors: John L. Gerlock
Original assignee: Ford Motor Company of Canada Ltd
Current assignee: Ford Motor Company of Canada Ltd
Priority date: 1977-10-20
Filing date: 1978-09-05
Publication date: 1983-04-12
Also published as: JPS5470377A

Abstract

ABSTRACT OF THE DISCLOSURE
Vapor phase hydrolysis of scrap polyurethanes, especially flexible polyurethane foams, is improved through the use of catalytic amounts of basically reacting alkali metal or alkaline earth metal compounds applied to the foam prior to hydrolosis.

Description

11~4~69 The present invention relates to hydrolysis of scrap polyurethane.
Converting scrap polyurethane materials including foams by chemical methods into useful decomposition products has received considerable recent attention. Of approaches proposed for decomposition of polyurethane scrap, high temperature hydrolysis has the merit of minimizing the need for large amount of added organic solvents as is ~-required in accordance with other approaches.
High temperature hydrolysis, however, necessitates a choice between the desirable high reaction rates obtainable at high pressures, e.g., 3a-60 atmosphere where pressure vessels are required for the reaction and the undesirable 810W reaction rates obtainable at low pressures where more conventional, but larger equipment can be used.
One attempt at upgrading low pressure processes is exemplified by U.S. Patent No. 4,196,148 in the name of L.R. Mahoney and assigned to Ford Motor Company, wherein ammonia is introduced into a low pressure hydrolysis system.
The reaction rates herein, according to analytical test data, are in considerable excess of such ammonia hydrolysis.
The present invention involves an improvement in a method of super-heated steam decomposition of polyurethanes, especially polyurethane foams, at elevated temperatures in a range up to about 300C in the presence o super-heated steam at about 0.4 to 10 atmospheres whereby liquid polyol product and gaseous diamine are recovered.
The impro~ement comprises incorporating with the polyurethane prior to its decomposition one or more basically reacting alkali metal or alkaline earth metal compounds in an amount sufficient to increase the rate of hydrolysis of the polyurethane. Remarkably in such reactions, basically reacting compounds (at low levels as compared to the amount of foam present) can increase hydrolysis rate by a factor of two or more in super-heated steam where one would not expect liquid water to be present at any appreciable level.
This invention is advantageously suitable for recovery of flexible polyurethane foams ~lade by reacting a mixture comprising aromatic diisocyanate ~e.g., toluene diisocyanate), high molecular weight polyol (e.g , polyether triol with number average molecular weight in excess of lQOQ up to about 9000~, and water in the presence of a small amount of amine or other catalysts, e.g., dimethylaminomorpholine triethylene-d~m~ne. Other ingredients typically included in the formulations are surfactants, fillers, pigments and so forth most often in minor amounts. Other foams suitable include those prepared from diisocyanates and polyesters such as esters of 1,4 butane diol and adipic acid. Still other foams as rigid and semi-fle~ible foams are typically made with s$milar ingredients but with the active hydrogen compound, e.g., polyol, being of lower molecular weight. Decomposition of any such ~oams that include ester type (e.g., urethane) linka~es and amide type ~e.g. urea~ linkages predominantly constitute the preferred type of polyurethane scrap material that may be reco~ered by hydrolysis according to the invention herein.

11~4S69 1 Polyurethane foam technology is described, for

2 instance, in Polyurethane, Chemistry and Technology, ~y

3 J. ~ aunders and K. C. Frisch, Part II Technology,

4 Interscience Publishers, liew York (1967).
ln a currently preferred method of carrying out this 6 invention an aqueous dilute solution, e.g., less than 10%
7 active, of a basically reacting compound is used to apply 8 such compound uniformly on the polyurethane prior to its 9 decomposition. One method of application is prior to intro-duction of a polyurethane foam material into a zone wherein 11 the hydrolysis reaction takes place and this method utilizes 12 immersion of the foam material into the dilute solution and 13 thereafter drying the foam material to leave a uniform deposit 14 of the solid basically reacting compound.
~lacing foam wetted with aqueous solution as above 16 into a reaction zone comprising dry steam can effect drying 17 of at least a portion of the foam to provide a concentrated 18 layer of basically reacting compound on the foam. Alternatively, 19 the foam may be dried in a separate stage prior to its inclusion in the zone of hydrolysis. Still other methods for applying 21 the basicaily reacting compound on polyurethane foam include 22 application prior to its decomposition during hydrolysis as 23 by injection or spraying on its surface as the foam is being 24 decomposed during hydrolysis.
The basically reacting alkali metal or alkaline earth 26 metal compound preferably comprises alkali metal as, for 27 example, alkali metal hydroxides, particularly sodium hydroxide 23 in view of its solu~ilit~. Other basically reacting comlo~nds 29 as alkaline earth oxldes as calcium oxi~e may be applied, lor example, from a~uecus or ~lcohol solutions or d spersions.

11~4569 1 Still other basically reacting compounds include alkoxides, 2 especially lower alkoxide, e.g., sodium or potassium ethoxide.
3 i~ormally, because of convenience and cost, hydroxide, particularly 4 sodium hydroxide alone will be preferred as the basically reacting compound where aqueous solution are employed for 6 application prior to decomposition of the foam.
7 The amount of basically reacting compound as sodium 8 hydroxide used is a catalytic amount and normally below 5 9 parts by weight per 100 parts by weight of the scrap poly-urethane and in the case of flexible foam advantageously as 11 little as 1 part or less by weight basic reacting compound 12 per 100 parts by weight foam. Remarkably, amounts in a range 13 between about 0.1-30 parts by weight per 1000 parts of flexible 14 foam are seen to provide particularly desirable reaction rates, providing uniform application at least on the surface of the 16 foam is obtained.
17 The conditions under which the polyurethane is 18 hydrolyzed include elevated temperatures up to about 300C, 19 more preferably superheated steam in a range between ahout 150C-275C at up to ten or more atmospheres, advantageously 21 super heated steam at between 0.5-5.0 atmospheres within the 22 latter temperatures. Inert gas may be included as diluent, 23 if desired.
24 In one preferred way of carrying out the hydrolysis, dry steam is admitted into an evacuated reaction chamber con-26 taining the foam having the basically reacting compound 27 deposited thereon whereby hydrolysis begins with gaseous 28 effluent containing diamine reaction product allowed to be dis-29 charged from the chamber while li~uid polyol product is collected at the bottom of the chamber. An apparatus suitable to carry out this invention is described in U.S. Patent No. 4,169,148.
Of course, in such apparatus, there need be only one inlet tube for admitting the water vapor rather than one for ammonia and one for water vapor. Moreover~ the apparatus described in U.S. Patent 4,025,55~ which is herein incorpor-ated by reference for its disclosure can also be used to advantage with this invention. Still other apparatus include extrusion type apparatus wherein the basically reacting compound is applied during extrusion of the poly-urethane foam as where superheated steam is formed from the evaporation of water applied to the foam during extrusio~
which contains the basically reacting compound.
The time required to carry out the hydrolytic decom-position varies in accordance with such parameters aR
temperature, pressure, foam type and a unt of catalyst present. ~heoretical yields are achievable, however~ as measured by diamine production, in less than two hours and even within one hour at higher temperature within the above noted ranges. Even at lower temperat~res within the above ranges the rate of hydrolysis can exceed twice that of water alone, especially in the early stages of the decomposition.
This invention is illustrated ~y the following specific results that are achieved by utilizing preferred procedures as hereinbefore described. The scope of this invention, however, is not to be limited to the particular details shown ~elow as those skilled in the art will appreciate that many procedures can be designed to exploit the discovery of this invention. All parts are parts by weight in the examples.

_ 5 ~

Example 1 1(a) An analytical flexible polyurethane foam is made 2 from the ingredients of Table I below by rapid mixing of 3 ingredients 1-8 with ingredient 9 (polyisocyanates) for about 4 15 seconds and pouring the foaming product into a mold whereby a light cream colored flexible urethane foam (density about 62.1) is obtained after a cure of 5-10 minutes at 120C.

9 Material - 5ourceParts DescriPtion A lo 1. Pluracol1 535 (Polyol) (BASF) 100 1640 eq. wt. mostly triol 11 2. Amine (Union Carbide)2 Diethanolamine 12 3. Water 2.8 Distilled 13 4. Amine (Air Prod.) 0.14 Triethylenediamine 14 5. Amine (Air Prod.) 0.20 Dimethylaminoethyl-r,orpholine 16 6. Glycol (Union Carbide) 0.10 70% bis(2-Dimethylamino-17 ethyl) ether, 30% dipro-18 pylene glycol 19 7. Surfactant (Dow Corning) 1.4 Silicon glycol copolymer 8. Catalyst (M~T) 0.015 Dibutyltindilaurate 21 9. ~iisocyanate (Mobay) 38.4 Toluene diisocyanate 22 (b) Certain test and control samples each being 100 23 parts by weight are taken from foam prepared as in (a) above 24 and treated as follows.
The samples are dipped into 0.1, 1.0 and 5.0 percent 26 by weight aqueous solutions of sodium hydroxide, blotted dry 27 and then dried under vacuum. A first series of control samples 28 are then titrated with an aqueous solution of hydrochloric acid.
29 It is determined by titration that approximately 0.1, 0.8 and 2.9 parts by weig~t for each 100 part by weight sample of sodium ~ rraG~2~k 1 hydroxide are deposited by this dipping and drying procedure 2 by the above solutions of 0.1, 1.0 and 5.0 percent by weight 3 sodium hydroxide, respectively.
4 The test samples and other control samples (untreated by the sodium hydroxide solutions) are then individually 6 introduced into a heated hydrolysis chamber having inlet and 7 outlet tubes and filled with superheated steam at a pressure 8 approximately one atmosphere passing therethrough. Prior to intro-9 duction into the heated hydrolysis chamber each sample is placed in a heating zone wherein it is heated to 175C by 11 nitrogen gas so tnat it is introduced into the heated 12 nydrolysis cham~er at near ~ne temEeralur~ or ~ne superneatea 13 steam therein.
14 In Table II below are the results of hydrolysis of the foam at varying temperatures and at slightly above one 16 atmospheric pressure of superheated steam with and without use 17 of sodium hydroxide.
18 The results in Table II are obtained by ultra-19 violet analysis of the condensed gaseous effluent to measure the amount of toluene diamine as a function of time. This 21 is accomplished by comparing the ultraviolet light absorption 22 results with a set of calibration curves obtained from 23 passing standard toluene diamine samples through the ultra-24 violet absorption analyzer. The values shown in Table II are weight percent foam hydrolyzed at the end of the indicated 26 periods.

TABLE II
Sodium Hydroxide Catalyzed Foam Hydrolysis Percent Hydrolysis*
- 0 1 part NaOH 0.8 part NaO~ 2.9 part NaOH
Steam Only 1 0 part foam 100 pa~r~F~ 100 part foam 190C Time, Min 4.0 10.0 23.5 22.4 7.2 18.5 36.2 36.0 10.5 24.6 45.5 44.8 12.9 2g.5 51.9 51 5 15.0 33.6 57.0 57 1 17.8 - 64.8 63.3 210C Time, Min 2 5.7 - 14.4 4 12.7 - 28.8 6 17.7 - 38.8 8 20.4 - 46.1 23~1 - 5~.0 27.6 - 62.4 30.8 - - -32.7 - 74.9 36.2 - 81.5 250C Time, Min 2 2i.9 47.7 57.0 4 33.6 75.8 80.5 6 39.8 86.2 87.3 8 44.6 90.8 89.3 48.6 92.2 90.2 57.5 93.6 64.9 94.3 *Based upon the theoretical yield of 19.4 parts by weight toluene diamine per 100 parts of foam.

Example 2 The procedures of Example 1 are followed using potassium hydroxide rather than sodium hydroxide. Catalytic increase in the hydrolysis rate is also seen.

Example 3 1 A straw colored liquid polyol product obtained from 2 hydrolysis in accordance with the procedure of Example 1 using 3 a foam with 0.1 part by weight sodium hydroxide deposited per 4 100 parts by weight foam and hydrolized at 1.1 atmospheres of super heated steam at 220C is used to replace 20% by weight 6 of the polyols described in Table I. Excellent quality foam 7 is achieved following standard foaming techniques.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a method of superheated steam decomposition of polyurethanes at elevated temperatures in a range up to about 300°C in the presence of superheated steam at between about 0.4-10 atmospheres whereby liquid polyol product and gaseous diamine are recovered, the improvement which comprises incorporating with the polyurethane prior to its decomposition one or more basically reacting alkali metal or alkaline earth metal compounds in an amount sufficient to increase the rate of hydrolysis of the polyurethane.

2. The method in accordance with Claim 1, wherein the polyurethane comprises flexible polyurethane foam.

3. The method in accordance with Claim 2, wherein the basically reacting compound comprises alkali metal hydroxide.

4. The method in accordance with Claim 3, wherein there is less than 3 parts by weight alkali metal hydroxide per 100 parts by weight foam.

5. The method in accordance with Claim 2, wherein the basically reacting alkali metal or alkaline earth metal compound is incorporated with the foam by applying thereto an aqueous solution containing the basically reacting compound.

6. The method in accordance with claim 5, wherein the hydrolysis temperature is in a range between about 150-275°C.

7. The method in accordance with claim 1, wherein the basically reacting compound comprises alkali metal hydroxide and is applied to the foam to form a uniform solid layer thereon.

8. The method in accordance with claim 1, wherein the super-heated pressure is between about 0.9 and 5.0 atmos-pheres.

9. The method in accordance with claim 5, wherein the super-heated steam pressure is between 0.9 and 5.0 atmos-pheres.

10, The method in accordance with claim 8, wherein the basically reacting alkali metal or alkaline earth metal comprises a basically reacting sodium compound.

11. The method in accordance with claim 8, wherein the basically reacting sodium compound comprises sodium hydroxide.

12. The method in accordance with claim 1, wherein the basically reacting alkali metal or alkaline earth metal comprises a basically reacting sodium compound.

13. Decomposition of polyurethane foams at elevated temperatures up to about 300°C in the presence of super-heated steam at between about 0.4-10 atmospheres by incorporating therewith one or more basically reacting alkali metal or alkaline earth metal compounds in an amount sufficient to increase the rate of decomposition.