GB1601787A

GB1601787A - Hydrolytic decomposition method and apparatus

Info

Publication number: GB1601787A
Application number: GB21431/78A
Authority: GB
Original assignee: Ford Motor Co Ltd; Ford Motor Co
Current assignee: Ford Motor Co Ltd; Ford Motor Co
Priority date: 1977-08-22
Filing date: 1978-05-23
Publication date: 1981-11-04
Also published as: DE2834325C2; FR2400933A1; FR2400933B1; CA1101890A; DE2834325A1; JPS5443277A; BE869868A

Description

(54) HYDROLYTIC DECOMPOSITION METHOD AND APPARATUS (71) We. FORD MOTOR COMPANY LIMITED. of Eagle Way. Brentwood, Essex CMl3 3BW. a British Company. do herebv declare the invention for which we pray that a patent may be granted to us. and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to hydrolytic decomposition methods and apparatus.

The recovery of polyurethane scrap material. such as polyurethane foam. has been the subject of considerable inventive effort.

Despite this effort. polyurethane foam is still commercially disposed often in land fill.

It is apparent that a need exists for expedient methods and apparatus for recovery of such materials.

Among the approaches proposed for re covert hydrolysis is known to offer certain advantages pa;ticularly if it can eliminate or reduce a need for large scale use of organic solvents. The low thermal conductivity of materials such as polyurethanes. however.

normally is a limitation in gaseous hvdrolysis methods due to extended warm-up periods required before conditions satisfactory for hydrolysis are obtained. Such warm-up periods are troublesome even though catalysts may speed the decomposition reaction after hydrolytic decomposition conditions are attained.

Another difficulty presented with hvdro lytic decomposition methods is that of water content as well as amine content in the recovered polyol. Seemingly low levels of water and amine can markedly reduce the value of the recovered polyol and such value. understandably, is integral factor for determining competitiveness of the hydrolytic process.

According to the present invention. a solid material preferably a porous material such as open-pore polyurethane foam.

which is susceptible to hydrolytic decom- position, is heated and separated into liquid and gaseous decomposition products by (A) admitting saturated steam into an evacuated chamber containing the solid; (B) maintaining hydrolytic decomposition conditions for a period sufficient to effect the decomposition; (C) releasing gaseous effluent comprising the gaseous decomposition product; and preferably (D) evacuating the chamber to remove residual water.

An embodiment of the invention will now be described, by way of example only with reference to the drawing, which shows in schematic relationship the various components of apparatus suitable to carry out this invention.

Referring to the drawing, the preferred general steps of this invention comprise introducing porous solid into the vacuum chamber, evacuating the vacuum chamber having the porous solid therein to remove residual air (e.g., to pressure well below 10.1 atmospheres, more preferably below about 3 x 10.2 atmospheres), admitting high pressure saturated water vapour into the vacuum chamber to provide a pressure therein of about 30 atmospheres or greater while heating the walls of the vacuum chamber to a temperature in a range that prevents substantial condensation of water vapor thereon (e.g.. 200"C or higher). releasing the gaseous effluent comprising decomposition product from the vacuum chamber through a vacuum chamber exhaust valve, cooling the gaseous effluent from the exhaust valve in the condenser whereby water and decomposition product such as diamine may be obtained, preferably continuing evacuation to pressures below about 10- atmosphere (more preferably 2 x 10.2 or below) in the vacuum chamber to dry and purify the liquid residue (e.g. polyol) in the bottom of the vacuum chamber, and finally releasing the vacuum in the cooled vacuum chamber and collecting the liquid compo nent.

Heating of the porous solid to hydrolytic decomposition conditions occurs rapidly (i.e., within about 10 minutes or less desirably as little as about 1-3 minutes) because it reaches a temperature corresponding to the vapor pressure of steam admitted to the vacuum chamber nearly instantaneously.

This is so even though porous solid such as open-pore flexible polyurethane foam is initially compressed to volumes of one fifth or less its original volume in the vacuum chamber. (Other porous solids include solid closed pore polyurethane which has been comminuted into small pieces (preferably about 1 mm or less) and desirably placed into perforated containers suitable for con finding them in the vacuum during hydrolvsis).

The boiler used may be any standard type boiler that provides saturated steam at least 30 atmospheres, more preferably 35 atmospheres or more up to pressures which the system may conveniently handle. Normally, pressures between about 35-60 atmospheres can be employed in the vacuum chamber to give advantageous results without resort to more costly high pressure equipment.

Upon hydrolytic decomposition of the porous solid. e.g.. open cell polyurethane flexible foam. gaseous effluent is released from the vacuum chamber and cooled in a condenser wherein water and liquid or solid diamines are collected. Release of carbon dioxide also occurs and such gas can be vented from the condenser. Advanta,eeous- lv. the cool condenser may comprise a pluralitv of small metallic pieces to insure maximum surface area for collection of diamine component.

Usually. a period of up to about 30 minutes is required for complete hydrolytic decomposition of polyurethane foam at saturated vapor pressures of about 3()-4() atmospheres, although action of catalysts as well as high pressures may reduce the time required. Continuance of admission of the saturated steam to maintan such pressures permits the endothermic reaction to proceed expeditiously.

Advantageously. the evacuation of the vacuum chamber can be continued after hydrolytic decomposition. In this way, the liquid decomposition component (e.g.

polyol) is conveniently freed of excess water and and diamines thereby increasing the value of this component. Thereafter, the vacuum chamber can be drained of polyol and the process begun again, or. for example continued by introducing porous solid from a standbv chamber.

As previously mentioned. although porous solids such as open cell polurethane foam. particularly flexible polyurethane foam. are preferred, other material of low thermal conductivity may also be rapidly heated in accordance with this invention when it is finely divided to permit its exposure over a large surface area to the saturated water vapor. However, rapid heating of porous solids such as open cell polyurethane foam takes full advantage of the method and apparatus herein.

The following examples illustrate this invention and are not intended as limiting the scope thereof as many modifications will be apparent according to the hereinbefore and hereinafter descriptions of this invention.

Example 1 Using an apparatus as illustrated in the drawing, urethane foam, at a density of 48 kglm3 is stuffed into the reactor (i.e., vacuum chamber) and compressed to about 240 kg/m3. The reactor is sealed and the vacuum pump started. The reactor with its exhaust system, including condensers, is evacuated to an absolute pressure of approximately 2 kPa (15 mm Hg or 0.3 psia). The high pressure boiler is energized and brought up to pressure, about 10.300 kPa at 315"C. The reactor exhaust valve is closed vacuum pump operation continues - and the electric heaters on the reactor sidewalls and in the reactor base and top flange are energized, with the heater controllers set at the desired wall temperature (200 to 750"C). Steam is immediately admitted to the reactor until a reactor pressure of 3.8 MPa to 4.1 MPa (550 psig to 600 psig) is attained. As soon as this pressure is reached. a 2500 to 255"C temperature is immediately established within the reactor.

Steam flow rate is then reduced until reactor pressure is just maintained for a period of not more than 30 minutes, when the reactions will have been well completed. The steam valve is then closed and the reactor exhaust valve is partially opened. The exhaust valve is modulated so as not to exceed a pressure of 6.5 kPa absolute (t).9 psia) in the vacuum svstem. This prevents an excessive flow of vapor into the vacuum pump.

When the reactor pressure has again been reduced to 2 kPa absolute (0.3 psia) at a reactor temperature of about 250"C. the reactor heaters are de-energized and the reactor is cooled to room temperature. The polyol is then drained from the reactor for use. (The polvol has less than 1/4eXc by weight amine and less than 1/4CC by weight water). The toluene diamine is removed from the condenser system by heating and draining. re-evaporating. or with a solvent flush. The residue. composed of fillers such as crushed dolomite. poly propylene, etc. is removed from the reactor and the equipment is then readv for re-use.

Exalple 2 Urethane foam. at a densitv of 36.8 Kg m- is stuffed or packed into a basket constructed from perforated stainless steel sheet and compressed to a densitv of 500 k?,m'. The basket with its contents is then placed in the reactor. The reactor is sealed and the procedure of Example 1 is followed leading to similar diamine and polyol separation rx ple 3 Non-porous urethane is reduced to small chips of less than 1 mm in any dimension which are placed in a perforated metal or metal mesh basket. The basket, loaded with urethane chips is placed in the reactor. The reactor is sealed, whereupon the procedure of Example I is followed leading to desired polyol and diamine components.

It is to be understood that the apparatus as shown in the drawing may be advan tageously modified such that the boiler surrounds the vacuum chamber thereby eliminating the need for separate heating element to heat the vacuum chamber. On the other hand. the apparatus as shown permits ready construction and has the advantage that the exterior of the vacuum chamber may be heated to some extent by the enterimg saturated steam condensing on the inner walls thereof thereby preventing undesinibly high temperature walls contacting porous solid in the absence of saturated water vapor. Still further, the apparatus as illustrated in the drawing advantageously allows for precise control of reaction conditions so that high quality decomposition products mav be consistently obtained.

WHAT WE CLAIM IS: l. A hvdrolvsis method for solid mate- rial suscepiible to hvdrolvtic decomposition that separates liquid and gaseous decomposition products thereof. which comprises: (A) admitting saturated steam into an evacuated chamber that contains the solid: (B) maintaining hydrolytic decomposition conditions within the chamber for a period sufficient to decompose the solid: and (C) releasing gaseous effluent from the vacuum chamher.

2. A method according to Claim 1 further comprising: (D) evacuating the chamber to remove water therefrom.

3. A method according to Claim 1 or Claim ' wherein the solid material is porous.

4. A method according to Claim 3.

wherein the solid material comprises open cell polyurethane foam.

5. A method according to any one of Claims l to 4. wherein the steam is admitted while maintaining the walls of the vacuum chamber at a temperature of at least 200"C.

6. A method according to any one of Claims 1 to 5, wherein the hydrolytic decomposition conditions comprise saturated steam in the vacuum chamber at a pressure of at least 30 atmospheres.

7. A method according to any one of Claims 1 to 6, which comprises compacting the solid material to below one-fifth its original volumn prior to admitting the saturated steam.

8. A hydrolysis method substantially as described herein in any one of the Examples.

9. An apparatus for rapid heating with saturated water vapor of solids of low thermal conductivity and simultaneous separation of liquid and gaseous decomposition thereof, which comprises: (A) a vacuum chamber having opening means for introducing the solid: (B) evacuation means for evacuating the vacuum chamber; (C) steam inlet control means for controllably introducing saturated water vapor into the evacuated vacuum chamber; (D) temperature control means for heating the exterior of said vacuum chamber having said saturated water vapor and the solids therein; (E) gaseous outlet control means positioned between the vacuum chamber and the evacuation means for controllably releasing gaseous effluent from the upper portion of the vacuum chamber; (F) condensing means positioned between the gaseous outlet control means and the evacuation means for cooling said gaseous effluent: and (G) liquid outlet means positioned to drain liquid from the lower portion of the vacuum chamber.

10. Apparatus according to Claim 9, wherein the temperature control means comprises a water boiler surrounding the vacuum chamber that is adapted to release steam into the vacuum chamber through the steam inlet means.

11. A hydrolysis method for open cell polyurethane foam that separates liquid polyol and gaseous diamine components simultaneously, which comprises: (A) admitting saturated steam into an evacuated chamber that contains the open cell foam to provide a pressure thereof in a range above 30 atmospheres; (B) continuing admittance of the saturated steam to maintain a pressure in a range above about 30 atmospheres to complete the hydrolysis reaction; (C) releasing gaseous effluent from the upper portion of the chamber; (D) cooling the gaseous effluent to collect the diamine component; and (E) collecting the liquid polyol compo

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Exalple 2 Urethane foam. at a densitv of 36.8 Kg m- is stuffed or packed into a basket constructed from perforated stainless steel sheet and compressed to a densitv of 500 k?,m'. The basket with its contents is then placed in the reactor. The reactor is sealed and the procedure of Example 1 is followed leading to similar diamine and polyol separation rx ple 3 Non-porous urethane is reduced to small chips of less than 1 mm in any dimension which are placed in a perforated metal or metal mesh basket. The basket, loaded with urethane chips is placed in the reactor. The reactor is sealed, whereupon the procedure of Example I is followed leading to desired polyol and diamine components.

It is to be understood that the apparatus as shown in the drawing may be advan tageously modified such that the boiler surrounds the vacuum chamber thereby eliminating the need for separate heating element to heat the vacuum chamber. On the other hand. the apparatus as shown permits ready construction and has the advantage that the exterior of the vacuum chamber may be heated to some extent by the enterimg saturated steam condensing on the inner walls thereof thereby preventing undesinibly high temperature walls contacting porous solid in the absence of saturated water vapor. Still further, the apparatus as illustrated in the drawing advantageously allows for precise control of reaction conditions so that high quality decomposition products mav be consistently obtained.

WHAT WE CLAIM IS: l. A hvdrolvsis method for solid mate- rial suscepiible to hvdrolvtic decomposition that separates liquid and gaseous decomposition products thereof. which comprises: (A) admitting saturated steam into an evacuated chamber that contains the solid: (B) maintaining hydrolytic decomposition conditions within the chamber for a period sufficient to decompose the solid: and (C) releasing gaseous effluent from the vacuum chamher.
2. A method according to Claim 1 further comprising: (D) evacuating the chamber to remove water therefrom.
3. A method according to Claim 1 or Claim ' wherein the solid material is porous.
4. A method according to Claim 3.

wherein the solid material comprises open cell polyurethane foam.
5. A method according to any one of Claims l to 4. wherein the steam is admitted while maintaining the walls of the vacuum chamber at a temperature of at least 200"C.
6. A method according to any one of Claims 1 to 5, wherein the hydrolytic decomposition conditions comprise saturated steam in the vacuum chamber at a pressure of at least 30 atmospheres.
7. A method according to any one of Claims 1 to 6, which comprises compacting the solid material to below one-fifth its original volumn prior to admitting the saturated steam.
8. A hydrolysis method substantially as described herein in any one of the Examples.
9. An apparatus for rapid heating with saturated water vapor of solids of low thermal conductivity and simultaneous separation of liquid and gaseous decomposition thereof, which comprises: (A) a vacuum chamber having opening means for introducing the solid: (B) evacuation means for evacuating the vacuum chamber; (C) steam inlet control means for controllably introducing saturated water vapor into the evacuated vacuum chamber; (D) temperature control means for heating the exterior of said vacuum chamber having said saturated water vapor and the solids therein; (E) gaseous outlet control means positioned between the vacuum chamber and the evacuation means for controllably releasing gaseous effluent from the upper portion of the vacuum chamber; (F) condensing means positioned between the gaseous outlet control means and the evacuation means for cooling said gaseous effluent: and (G) liquid outlet means positioned to drain liquid from the lower portion of the vacuum chamber.
10. Apparatus according to Claim 9, wherein the temperature control means comprises a water boiler surrounding the vacuum chamber that is adapted to release steam into the vacuum chamber through the steam inlet means.
11. A hydrolysis method for open cell polyurethane foam that separates liquid polyol and gaseous diamine components simultaneously, which comprises: (A) admitting saturated steam into an evacuated chamber that contains the open cell foam to provide a pressure thereof in a range above 30 atmospheres; (B) continuing admittance of the saturated steam to maintain a pressure in a range above about 30 atmospheres to complete the hydrolysis reaction; (C) releasing gaseous effluent from the upper portion of the chamber; (D) cooling the gaseous effluent to collect the diamine component; and (E) collecting the liquid polyol compo

nent from the lower portion of the chamber.
12. Apparatus substantially as hereinbefore described with reference to the drawing.