HYDROLYSIS OF POLYURETHANES

Abstract: Vapour phase hydrolysis of scrap polyurethanes, espe­ cially 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 hydrolysis.

Description: SP@CIFICATION TITLE HYOROLYSIS OF POLYURETHAN@S DESCRIPTION This invention relates to the hydrolysis of polyurethanes. Convertion of scrap polyurethane materials, especially polyurethane foams, by chemical metilods into useful decomposition products has received considerable recent attention. Of the various approaches proposed for decomposition of polyurethane scrap, high temperature hydrolysis has the merit of minimizing the need for large amounts of organic solvents, as i.' required in accordance with other approaches. High teznprature hydroiysis, however, necessitates a choice between the desirable high reaction rates obtainable at high pressures, e.g., 30-60 atmosphGre, where relatively expensive pressure vessels are required for the reaction, and the undesirable slow reaction rates obtainable at low pressures where more conventional, but larger and cheaper equipment can be used. One attempt at upgrading low pressure processes is exemplified by U.S. Serial No. 816,636, (German Patent Application P2831S832) wherein ammonia is introduced into a low pressure hydrolysis system. The reaction rates are however still relatively slow. According to the present invention, there is provided a method of hydrolysing polyurethane which comprises treating the polyurethane with superheated steam characterised in that the hydrolysis is effected in the presence of a basic alkali metal or alkaline earth metal compound. The basically reacting alkali metal or alkaline earth metal compounds provide a catalytic effect in the super heated hydrolysis of polyurethanea, especially polyurethane foams. 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 made by reacting a mixture comprising aromatic diisocyanate (e.g., toluene diisocyalete), high molecular weight polyol (e.g., polyether triol with number average molecular weight in excess of 1000 up to about 9000), and water in the presence of a small amount of amine or other catalysts, e,g., dimethylaminomorpholine triethylenediamine. Other ingredients typically included in the form@l- ations are aurfactants, fillers, pigments and so forth most ofteTl in minor amounts. Other foams suitable include those jirepared from diisocyanates and polyestera such as esters of 1,4 butane diol and adipic aoid. Still other foams as rigid and semi-flexible foams are typically made with similar ingredients but with the active hydrogen compound, e.g., polyol, being of lover molecular weight. Decompoa- ition of any such foams that include ester type (e.g., urethane) linkages and amide type (e.g., urea) linkages predominantly constitute the preferred type of jiolyurethane scrap material that may be recover ea by hydrolysis according to the invention herein, Polyurethane foam technology is described, for instance, in Polyurethane, Chemistry and Technology, by J. H. Saunders and K. C, Friach, Part II Technology, Interscience Publishers, New York (1967). In a currently preferred method of carrying out this invention an aqueous dilute solution, e.g., less than lO%I active, of the basically reacting compound is used to apply such compound uniformly on the polyurethane prior to its decomposition, One method of application is prior to introduction of a polyurethane foam material into a zone wherein the hydrolysis reaction takes place am this method utilizes immeraion of the foam material into the dilute solution and thereafter drying the foam material to leave a uniform deposit of the solid basically reacting compound. Placing foam wetted with aqueous solution as above into a reaction zone comprising dry steam can perfect drying of at least a po@- tion of the foam to provide a concentrated layer of basically reacting compound on the foam. Alternatively, the foam may be oried in a separat stage prior to its inclusion in th zone of hydrolysis. Still other methods for applying the basically reacting compound on polyurethane f@a@ include application prior to its decomposition during hydrolysis as by injection or spraying on its surface as the foam is being decomposed during hydrolysis. The basically reacting alkali metal or alkaline earth metal com- pound preferably comprises alkali metal as, for example, alkali metal hydroxides, particularly sodium hydroxide in view of its solubility. Other basically reacting compounds, such as alkaline earth oxides as calcium oxide may be applied, for example, from aqueous or alcohol j utions or dispersions. Still other basically reacting compounds inclu@@ alkoxides, especially lower alkoxide, e.g., sodium or potassium ethoxide. Normally, because of convenience and cost, hydroxide, particularly sodium hydroxide alone will be preferred as the basically reacting compound there aqueous solution are employed for application prior to decomposition of the foam. The basically reacting compound such as sodium hydroxide is used in a catalytic amount and normally below 5, and preferably no more than 3, parts by weight per 100 parts by weight of the scrap polyurethane and, in the case of flexible foam, advantageously as little as 1 part or less by weight of basic reacting compound per 100 parts by weight foam. Remarkably, amounts in a range between about 0.1-30 parts by weight per 1000 parts of flexible foam are seen to provide particularly desirable reaction rates, providing uniform application at least on the surface of the foam is obtained. The conditions under which the polyurethane is hydrolyzed include elevated temperatures up to about 300 C, more preferably superheated steam in a range between about 150 C-275 C at up to ten or more atmospheres, advantageously super heated steam at between 0.5-5.0 atmospheres within the latter temperatures. Inert gas may be included as diluent, if desired. In one preferred way of carrying out the hydrolysis, dry steam is admitted into an evacuated reaction chamber containing the foam having the basically reacting compound deposited thereon whereby hydrolysis begins with gaseous effluent containing diamine reaction product allowed to be discharged from the chamber while liquid polyol product is collec tedaat the bottom of the chamber. An apparatus suitable to carry out this invention is described in U,S. Patent Application Serial No. 816,636, filed July 18, 1977 (German Patent Application P2831483.7). Of course, in such apparatus, there need be only one inlet tube for admitting the water vapour rather than one for ammonia and one for water vapour. Moreover, the apparatus described in U.S. Patent 4,025,559 can also be used to advantage with this invention. Still other apparatus include extrusion type apparatus wherein the basically reacting com- pound is applies during extrusion of the polyurethane foam as bere super heated steam is formed from the evaporation of water applied to the foam during extrusion which contains the basically reacting compound. The time required to carry out the hydrolytic decomposition varies in accordance with such conditions as temperature, pressure, foai type and amount of catalyst present. Theoretical yields are achievable, however, as measured by diamine prodnction, in less than two hours and even within one hour at higher temperature within the above noted ranees. Even at lower temperatures within tile above ranges the rate of hydroysis can exceed twice that of water alone, especially in the early stages of the decomposition. This invention is illustrated by the following specific resulta that are achieve(t by utilizing preferred procedures as hereinbefore described. The scope of this invention, however, is not to be limited to the particular details shown below as those skilled in the are wil) appreciate that many procedures can be designed to exploit the discovery of this invention. All parts are arts by weight in the examples. Example l (a) An analytical flexible polyurethane foam is made from the ingredients of Table I below by rapid mixing of ingredients 1-8 with ingredient 9 (Polyisocyanates) for about 15 secords and pouring the foaming product into a mould whereby a light cream coloured flexible urethane foam (density about 2.1) is obtaine@ after a cure of 5-10 minutes at 12O0C. table l FORMULATION OF FL@XIBL@ POLYUKETHANE FOAM Material - Source Parts Description 1. Pluracol 535 (Polyol) (BASF) 100 1640 eq.wt. mostly tr@@l 2. Amine (Union Carbide) 2 Diethanolamine 3. Water 2.8 Distilled 4. Amine (Air Prod.) 0.14 5. Amine (Air Pred.) 0.20 Dimeathylaminoethyl morpnoline 6. Glyccl (Union Carbide) 0.10 70C; bis(2-Dimethylam@) ethyl) other, 3 dip@ pylene glycol 7. Surfactant (Dow Corning) 1.4 Sil@con glycol cop@@y@ 8. Catalyst (M & ) 0.015 Dibutyltindilaura@ 9. Diisocyanate (Mobay) 3@.4 Toluem diisocyana@ (b) Certain test an control samples each being 100 pals; weight are taken from foam prepared as in (a) above and treated a follows. The samples are zipped into 0.1, 1.0 and 5.0 percent by wei@@ @@ueous solutions of sodium hydroxide, blotted dry and then dried under @@@um. A first series of control samples are then titrated with an @@@eous solution of hyurochloric acid. It is determined by titration @@at approximately 0.1, 0.3 and 2.9 parts by wieght for each 100 part by @@ght sample of sodium hydroxide are deposited by this dipping and drying @@ocedure by the above solutions of C .1, 1.0 and 5.0 percent by weight @@dium hydroxide, respectively. The test sampl@s and other control samples (untreated by the @@@ium hydroxi@e solutions) are then individually introduced into a @@ated hydrolysis chamb@r having inlet and outlet tubes and filled with perheated steam at a pressure approximately one atmosphere passing @herethrough. Prior to introduction into the heated hydrolysis chamber @@b @ample is placed in a heating zone wherein it is heated to 175 C by Iatrogen gas so that it is introduced into the heated hydrolysis chamber the the temperature of the super heated steam therein. In Table II below ar: the results of hydrolysis of the foam at varying temperatures and at slightly above one; atmospheric pressure of super heated steam with and without use of sodium hvdroxide. The results in Table 11 are obtaine-d by ultraviolet analysis of the condensed gaseous effluent to measure the amount of toluene diamine as a function of time. This is accomplished by comparing the ultra violet light absorption results with a set of calibration curves obtained from passing standard toluene diamine samples through the ultraviolet absorption analyzer. The values shown in Table II are weight percent foam hydrolyzed at the end of the indicated periods, Table IT Sodium hy@roxide Catalyzed Foam Hycrolysis Percent Hydrolysis" 0.1 part Naoll 0.8 part NaOll 2.9 part NaOll Steam Only 100 part foam 100 part foam 100 part foam 190 C Time, Min 5 4.0 10.0 @3.5 22.4 10 7.2 18,5 36.2 36.0 15 10.5 24.6 @5.0 44.8 20 12.9 29.5 51.9 51.5 25 15.0 33.6 57.0 57.1 35 17.8 - 64.8 63.3 @ 210 C Time, Min 2 5.7 - 14.4 4 12.7 - 28.8 6 17.7 - 38.8 8 20.4 - 46.1 10 23.1 - 52.0 15 27.G - 62.4 20 30.8 - - 25 32.7 - 74.9 35 36.2 - 81.5 250 C Time, Min 2 21.9 47.7 57.0 4 33.6 75.@ 80.5 6 39.8 86.2 8@.3 8 44.6 90.8 89,3 10 48.6 92.2 90.2 15 57.5 93.6 - 25 64.9 94.3 "Based upon the theoretical yield of 19.4 parts by weighu toluene diamine per 100 parts of foam, Example 2 The procedures of A ample 1 are followed using potassium hydroxide rather than so@ium hydroxide, Catalytic inerease in the hydrolysis rate is also seen. Example 3 A straw coloured liquid polyol product. obtained from hydrolysis in accordance with the procedure of Example 1 using a foam with 0.1 part by weight sodium hydroxide deposited per 100 parts by weight foam and hydrolized at 1.1 atmospheres of super heated steam at 220 C is used to replace 20% by weight of the polyols described in Table 1. Excellent quality foam is achieved following standard foaming techniques.

Claims: CLAIMS 1. A method of hydrolysing polyurethane which comprises treating the polyurethane with super heated stearn characterised in that the hydrolysis is effected in the presence of a basic alkali metal or alkaline earth metal compound, 2. A method in accordance with Claim ), characterised in that the polyurethane comprises flexible polyuretl3ane foam. 3. A method in accordance withClaim 1 or Claim 2, characterised in that the basic compound comprises an alkali metal hydroxide, 4. A method in accordance with any one of Claims 1 to 3 characterised in that the hydrolysis is effected in the presence of no more than 3 parts by eight of alkali meta] compound per 100 parts by weight of polyurethane. 5. A method in accordance with any one of Claims 1 to 4 wherein the alkali metal or alkaline earth metal compound is incorporated vith the foam prior to hydrolysis by applying to the polyurethane an aqueous solution containing the said compound. 6. A method in accordance with any one of Claims 1 to 5 characterised in that the basic compound is applied to the polyurethane prior to hydrolysis to form a uniform solid layer thereon. 7. A method in accordance with any one of Claims 1 to 6 characterised in that the super heated steam is at a pressure of from 0.4 to 10 atmospheres. 8. A method in accordance with Claim 7 characterised in that the super heated steam is at a pressure of from 0.9 to 5.0 atmospheres. 9. A method according to any one of Claims 1 to 8 characterised in that the hydrolysis is effected at a temperature of up to 300 C, 10. A method according to Claim 9 characterised in that the hydrolysis is effected at a temperature of from 1500 to 275 C.

Inventors: GERLOCK, JOHN LAWRENCE
Applicants: FORD FRANCE SOCIETE ANONYME, FORD MOTOR COMPANY, FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1978
Main classification: C08J11
IPC codes: C08J11