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CRR020191 0072G ~ .... PATZh'T 90A401 CELLULAR MATERIALS BACKGROUND OF THE Z~N'V'~q'TZO~ AC 10335 Field of ~he Invention This invention relates to 8 process and apparatus for expanding cellular material b~, impregnating ~he cellular material with a liquefied gas at an elevated pressure, removing excess liquefied gas from the cellular material and causing the impregnated gas to vaporize, thereby expanding the cellular material. More particularly, the invention relates to a ~ethod of reducing the ~aE~stlon of the temperature of the liquefied gas in its storage ssel throughout the impregnation process. 8fief Descrimtlon o£ the Prior Art In the processing of cellular materials there is f¢equently a need or a desire to reduce the density of the material. For instance, when cellular products such as tobacco or other smoking products, fruits, vegetables, meats, cereals, and other food products are dried, they generally undergo shrinkage. It is often desirable to expand these products to modify their properties, such as burning characteristics, water absorbability, and appearance. Similarly, it is often desirable to expand other cellular materials such as cellulosic materials, for example sawdust, crushed fibre materials, etc. to inc¢ease their liquid absorbability or insulating properties. 0 0

-/ AC 10335 CRR0201gl ~. PATENT 0092G ~1~ , Dkt. He. 90k401 - 2 - A number of method• ire known for expanding cellular materials. In ~eneral, these methods involve lntzoducing an expending agent, i.e. a substance capable of undergoing ezpansiono 88 bl~ a phase change from • liquid to • gas, into the cells of the material, and causing the agent to expand. A particularly suitable method o£ expanding one o~ the above-described cellular materials comprise• introducing s liquefied gas which is inert to the cellular material into s sealed vessel containing the material; soaking the cellular material in the liquefied gas sufficiently long to enable the liquefied g88 to penetrate the cells o£ the meter181; removing excess liquefie~ g88 from the cellular material; and expanding the cellular meteri|l by heating it, thereby vaporizing the liquefied g•8 within the cells of the material. The increased pressure of the vaporised liquefied gas in the cells cause• the cellular material to expand. It is also known to expand cellular material impregnating it with a liquefied gas c~panding agent, such as liquefied carbon dioxide, at an elevated pressure; removing excess expanding agent from the cellular material; reducing the pressure in the vessel in which the cellular material is contained, thereby causing the expanding agent to solidi~y; and heating the cellular material, such as by exposure to a hot gas stream, e.g. steam, air, etc, o to cause the solidified expanding agent to evaporate or sublime. The solidified expanding agent vaporizes at a rate greater than the rate at which the agent in gaseous form can escape from the cellulaz mate~ial. As a result of this treatment, the cellular material is forced to expand. US Patent 4,340,073 discloses a process and apparatus for expanding tobacco by impregnating the tobacco with carbon dioxide under conditions such that the carbon dioxide in contact with the tobacco is in liquid form, removing excess ~0 0 0

AC !0335 0072G ~'" ;. Dkt. ,0. ,0A401 -3- liquefied carbon dioxide from the tobacco, reducing the pressure of the impregnated tobacco to solidify carbon dioxide within the tobacco structure and rapidly hestinq the tobacco st atmospheric pressure to vaporize the csrbon dioxide and expand the ~obscco. UK Patent Specification 1,484,536 discloses • particularly useful process for expanding 8n organic substance using liquid carbon dioxide. The process of this patent compzlses the steps of pressurizing a vessel containing the substance to be expanded to & pressure in the range of about 200-1070 psi with carbon dioxide, im~ersing the substance in liquid carbon dioxide while maintaining the pressure within the vessel, thereby impregnating the substance vith the liquid carbon dioxide, removing excess ligui~ carbon dioxide from the impre~n~t~on veasel~-depresauria~n~ the vessel to substantially atmospheric ;resaure, thereby causing l~quefied carbon dioxide on and ~n the substance to solidify, removing the impregnated substance from the vessel, and heatin~ ~he substance to cause expansion of ~ho substance b~r at least 10~. ~n the process of this patent specification, the carbon dioxide used to pressurize the impregnation vessel is taken from the vapor space of the p~ocess vessel that is used to provide liquid carbon dioxide to the impreqnation chamber. It is further stated in th~s patent specification that after removal of the liqui~ carbon dioxide from the i=preqnation chamber, the impregnation cha~be~ may be vented to the atmosphere or to a carbon dioxide recover~ system. US Patent 4,165,618 discloses a process and system similar to that disclosed in UK patent specification 1,484,536 using a liquid cryoqen, such as liquefied carbon dioxide. In the process of this patent, the vessel in which the tobacco is Impregnated is purged and pressurized by t~snsferring gls from the vapor space of a liquid cr3"ogen storage vessel to the impreqnating vessel. Subsequent to pressurization, liquid 0 0 -I~

// AC 10335 C1~R020191 o. PATENT 0072G C ~.. Dkt. No. 90A401 - 4 - cryogen is transferred to the impregnation vessel from the liquid storage vessel. The tobacco is permitted to soak in the liquid cryogen for a predetermined time period, after which it is returned to the liquid storage vessel. The glleOUl cryogen remaining in the impregnation vessel after removal of the liquid cryogen is then transferred to s aeries of accumulators from which the gas is compressed and eventually returned to the main reservoir for the liguid cryogen. The processes ~iscloaed in these patent! have the disadvantage tha~ the gas used to purge snd pressurize the impregnation vessel COmes from the vapor space of the liquefied gas storage vessel. Unfortunately, removal of gas from the vapor space of this vessel reduces the pressure in the vessel, thereby disrupting the equilibrium balance in the vessel and "-causing liquid in the vessel to boil. This in turn cools th~ ......... liquid. In order to restor~ the pressure and temperature in the vessel ~o the desired equilbrium value, it is necessary to frequently heat the liquid in the storage vessel. Heating contents o~ the storage vessel to maintain temperature and pressure equilibrium of the liquid and vapor in the vessel significantly increases the cost ~£ the impregnation process. In ~rocesses such as the one disclosed in U.$. Patent 4,165,615, discussed above, in which the vented gas is recovered and, after being compressed, is returned to the storage vessel, some of the heat lost from the liquid crTogen may be replaced by the return of ~he hot compressed gas to the storage vessel. The gas is hot because its temperature is raised u~on compression. However, the additional heat returned to the storage vessel from the compressed gas is inadegua~e to maintain the desired pressure and temperature equilibrium in the storage vessel. Consequently, it ~$ st~ll necessary to hea~ the liquid in the storage vessel to re-es~ablish temperature and pressure equilibrium. O0 0 0 -I~

C~020191 o. Dk~. ~0. ~0A401 - 5- US Paten~ 3,771,533 discloses impregnation of tobacco with a mizturs of an~nia and carbon diozide, which react to form an~onlum carbonate. ~he ~s~.~nlum carbonate is theres~te~ decomposed by heat to release gases which expand the impregnated ~obscco. US Patent 4,1E5,618 discloses the use of a variet~ of lique£ied inert c~ogens, inclu~in~ o~gen, a:9on, hydrogen, helium, ~thane, the ~:eons, ~nozide an~ ca:~n dioxide as i:p:e~nen~s in ~he ezpansion ~obacco and AiMs Fzoduc~s. Zn order to improve the economics of liquefied 9as impregnation process, improvements that will lower the cost of processing, are continuously sought. The present invention provides an improvement that reduces the costa of impregnation processes. AC 10335 Xt is an object of the invention to provide an impro~e~ method ,nd apparatus for the e=p,nsion o~ cellular materials. Z~ As another object of ~he invention be provide a more efficient and economic process and improved apparatus £or the expansion o~ cellular materials b~ means o~ s 1A~ue~ed gas. Xt is another object o~ the invention to provide an improved method Cot purging and e~ualizing the pressure ia a cha~er used ~o i~re~na~e a cellular material with a liquefied ~as. Xt is another object of the invention to provide an improve~ ~thoO for reducing the variation of the tem1~ratute of a liquefied gas contained in the storage vessel of a cellular material impregnation sT~tem throughout the course of the impregnation p~ocess. 0 0 C0

will become apparent from the follo~ing description of the AC 10335 In mccordance with the invention, an improvement in a process for ezpar~ing a cellular mater|el is provide~. In its broadest embodiment, the process comp;'=ea the steps: a cellular material is charge~ So an impregnation 9easel which can be sealed from tL~ environment. The impregnation vessel has an openin~ locatc~ in its upper region, near the tOp of the vessel, and an opening located near the bottom of the vessel. The upper opening o£ the impregnation vessel is ~ositioned such that it will always remain above the top level o~ cellular material that is charged into the impregnation vessel ~or treatment. Upon charging the impregnation ~esael wi~h the cellular material, the sealed and purged with a low pressure inert gas. The pressure of the low pressure gas is not critical, but it is ~enerally in the range of about 15 to 300 pain. During the purging step. air and other non-condensables are £orced out o~ the impregnation vessel through the upper opening, and these substances are discharged to the atmosphere through an atmospheric vent. Upon completion of the purging step, the impregnation chamber is pressurized with the same inert gas but at a pressure substantially greater than the pressure of the inert gee used for purging the impregnation vessel. The pressure Of the pressurization gas is at lea~t as high as the pressure in the liqcefied inert gas process vessel described bale,. Following the pressurization step, the same inert gas in liquefied form is transferred from a process vessel in which it 0 oJ

AC 10335 00720 ~° ~ , Dkt. No. 90A401 -7 - l| |retaKe to the impregnation vessel in a volume sufficient to Completely autx~erge the cellular material in the liquefie~ inert gas. The liquefied inert gas in the process vessel i8 maintained at a pressure in the r~nge of about 300 to about 1200 pain, the selected pressure being dependent upon the liquetied gas being used, the cellular material beinq treated and other variables, such as the degree ox~anlion des/red. The temperature of the liquefied gas will be the temperature at which the liquefied inert gas and the inert gas in the vapor |pert above the liquefied inert gem ~re in equilibrium. This will, of course, depend upon the particular inert qss employed and the pressure existing in the process vessel. During the transfer of liquefle~ inert gas from the process vessel into the impregnation vessel, inert gas is permitted to circulate through the top opening of the impregnation vessel and back to the vapor space in the top of the process vessel. This enables the transfer to take place with little or no change of pressure in the process tank. The liquefied inert gas is permitted to remain in the impregnation chsm~r for a sufficient per~od of t~me to permit it to penetrate to the desired extent into the cells of the cellular material. The liquefied inert gas is then transferred back to the process vessel by drainage or pumping. Durlnq this step, inert gas is permitted to transfer from the vapor space of the process vessel back to the impregnation vessel via the upper opening Of the impregnation vessel, thus again ensuring that little or no change of pressure takes place in the process vessel. After the excess liquefied inert ga=. is removed from the impregnation vessel, the inert gas re~sin~ng in this vessel is permitted to vent to the atmosphere. ~ter the venting step is completed, the impregnation vessel can be opened and the cellular material removed therefrom. Upon reduction of the pressure ~n the impreqnaCion vessel, some e~pansion of the

00720 C (" Dkt. ,o. ,0,.401 . $- AC10335 cellular material may occur due to evaporation and expsnston of the liquefied inert gas contained within the cells of the cellular ma~eri81. While some of the inert gas evaporates, the remainder of it ~ill remain in the liquid state or, ~epending on which inert gas is used, will solidify. The expansion process is co~pleted t,j' heating the cellular material, which causes the liquified or solidified inert gas to vapoLize or sublime, which, in turn, causes the pressure in the cells to greatly increase, and results in the exp~nsion of the cellular material. The inventive feature of the process of the invention is that the purging and pressurization steps are conducted with a source of inert gas which is completely independent of the inert gas contained within the process chamber. Thua, during the purging and pressurization steps, no inert gas will be withdcn~rn f~om the process vessel. Consequently, the pressure and temperature within the process vessel will not be affected by the purging and pressurization steps of the process. The variation 0£ pressure and tempersturo o~ the liquefied 9as in the process vessel is kept to a miuimum since substsntisll~ the onl~ inert gas or liquefied inert gas that is lost from thi~ vessel is that which re=sins on or in the cellular matec~al. In a preferred embodiment of the invention, the inert gas that is vented from the impregna~ion vessel following the soaking step is recovered. This is accomplished by permitting the inert gas to vent from the impregnation chamber into • low pressure inert gas storage vessel. Thi: vessel may be the same vessel that is used as the source o~ ine~t gas for the purging step. In another preferred embodiment of the invention, the high pressure inert gas that is used to pressurize the lm~regnstion vessel i~ provided by taking inert gas from the low pressure inert gas storage vessel, compressing i~ to the desJre~5 0 0 .!~ .1~

AC10335 C~R020191 °. P~TEI~' O072G ~ Dk~. leo. 90~401 o 9 "° pressure and transferring it to the hl~h pressure inert gas In other preferred e~o~Imnts of the Invention, the cellular msterial may b~ tobacco or other a~o~lng mterial or a dried food product, such a~ d~led fruits, drleo vegetables, ~rled meats, or dried cereals; and the inert gas may be sir, carbon dioxide, nitrogen, oxygen, argon, helogenated h~lrocerbons0 ammonia, l~er ol:~anes or mixtures o~ ~hese. In the ~ost preferred en~<~ln~nt of the invention, the cellular material is tobacco and ~he inert gee is carbon dioxide. The apparatus of the invention comprises an impregnation vessel that can be eeel~d from the environment after it is charged ~tth cellular meterisl, a liquefied ine~t ~as process vessel, conduit and pu~p~n~ ~eens for transferring the liquefied inert gas from the process vessel into the impregnation vessel and hack, conduit and relying ~eans to permit inert gas to transfer hack and forth between the impregnation vessel and the upper part of the process vessel end storage, conduit and valve ~eans, independent of the process vessel, for providing and tran=fer~ing purging gas and pressurization gas to the impregnation vessel. In a preferred m~bodiment o~ the apparatus aspect o~ the invention, ~ans provid~ to vsn~ the impregnation vessel to a storage vessel for the low prossure inert gas used for p~rgin~ the impregnation vessel. In another preferred ~t~nt o~ apparatus asp~t of the invention, ~ans is provid~ compressin~ inert gas ~aken from the low p~essure inert storage vessel end transferring the compressed inert ~s ~o storage vessel ~o= the high p~essure gas us~ fo~ the i~re;na~ion vessel. 0 0

C~R0~0191 oo 0072G 4n- Dkt. ~o. 90A401 - 10 - ~RIE~ DESRIPTIO~ OF THE DRAMI~G$ Yhe Inventlon is illustrated in the drawings, in which: • i~. 1 depicts a preferred em~x~i~ent of a syste~ for Impre~natlng a cellular materlal with a liquefied ~as in accordance with the principle of the invention; and Fi~. 2 illustrates a variation of the apparatus illustrated in Fig. 1. Like characters designate like or corresponding parts throughout the several vie~a. The present invention provides a ~ethod of impregnating a cellular material with a lique£ied g88 and expendin~ the cellular material to the deaired denait7 b~ vaporizing the impregnated liquefied gas. The invention may be applied to the expansion of any cellular material that is capable of expansion. The invention is particularly suitable for the expansion o£ tobacco and other smoking materials and food products, including dried fruits, meat and cereals. The invention is particularly suitable for the expansion of tobacco. The agent used in the expansion of the cellular material may be any inert, normally ~aseous ~luid, i.e. any ~luid that will not react with or otherwise adversely a~fect the cellular material and thereby interfere with its intended use. Preferred inert ~ases are those that can be liquefied and solidified at temperatures and pressures contemplated in the process of the invention. T~pical of inert gas fluids useful in the invention are air, carbon dioxide, chloronate~ hydrocarbons, such as the fluorochlorohydrocarbons use~ as AC 10335