Патент USA US2109676код для вставки
March 1, 1938.v H. R. MINOR 2,109,676 METHOD FOR MAKING SPONGE RUBBER Filed Jan. 17, 1936 5 Sheets-Sheet 1 /6 i OUOOOOUQOOOQOOOOO 0OO00O0OOOOOOOOOOOOOOOOQOOOOOOO00 oooooooooob'oooooo -“ 00000000 0DOQ0000000000000000000000000 00000000 0000000000000000 _. -- 00000000000000 ..-~--.. /2 /8 0 00c ooooooooooooo 000000 oooooo ___________ 00 oooooo 2000000000000 ’ 000 oo oooooo . /5 000000 __ 00000 00000 39 _ 00°00000000000000000000000000 00 000 000000000000000000000000000000000000 - 00000000000 O 00000000000000000 000000000 0000000 /2/ 0 /6 QTMLM m1? ' ‘ATTORNEYS March 1, 1938. H. R. MINOR Q 2,109,676 METHOD FOR MAKING SPONGE RUBBER Filed Jan. 17, 1936 5 Sheets-Sheet 2 /7 /4 /5 /0 /2 25 xm/z-wrol? HENRY IP. MIND/P. ‘ , Arro/Pms'ys March 1, 1938. H R M|N¢R 2,109,676 . METHOD FOR MAKING SPONGE 'RUBBER Filed Jan- 17, 1936 3 Sheets-Sheet s -_F/' 57. 6. TheoFraEtci/ln‘ 20 ‘ . 30 ' 40' gym ‘16% 2,l09,676 ' Patented Mar. 1, .1938 . ’ UNITED STATES ' PATENT ' OFFICE METHOD FOR MAKING SPONGE RUBBER Henry B. Minor, Dayton, Ohio, assignor to -In dustrial Process Corporation, Dayton, Ohio, at _ corporation of New York ' ' ’ Application January l7, 1936, Serial No. 595625 4 Claims. .(CI. 18-53) This invention relates to rubber manuiacture, , p stock attainsea certain degree. oiv plasticity with and in particular, to methods for producing or I out su?icient heat tocause aset-upof the low -. “temperature accelerators during the period that . ,_ treating sponge rubber. 7 ‘One object of_ this invention is tovprovide a - 5 process of manufacturing‘ sponge-rubber by im pregnating the rubber batch with carbon dioxide - the heat ,is applied;Ithas'been- ioundathat' ii su?icient heat'isvapplied?to soiten thiys'stock, but 5 not enougliztojEca'nsefthev included gas to expand iunder' highrpressure prior to vulcanization, this substantially'gii release of thegas pressure is then ' ‘ vulcanization being preferably carried out in an? -' started ?a'uniiorm" ?ne cell structure is obtained. and the expansion or blowing is preferably in a ‘ autoclave, either‘ simultaneously with, the imi, . [vertical direction, which is much to bevdesired. l0 10 pregnation by the carbon dioxide or in successive _ ; ' I ~ '" It the heat is still further maintained in amount - steps. 1 Another object is to providea process oi'man uiacturing sponge'rubberwherein the uncured 'rubber batch is exposed simultaneously to high 15 pressure carbon dioxide‘ gas and to heat, the temperature being caused to rise and the pres sure to subside in a predetermined manner. Another object is to provide a process of man uiacturing sponge rubber wherein the rubber 20 batch is exposed to high pressure‘carbon dioxide gas accompanied by a rise in temperature, after " which the gas pressure is removed and the pres sure around the batch reduced to a subatmos pheric pressure by creating a partial vacuum 25 therearound. ‘ > Another object is to provide ‘a process for man ufacturing sponge rubber wherein a rubber batch containing a “blowing agent" or gas-generating substance, like sodium bicarbonate, is subjected, sumcient to expand the included gas, then the cell structure will be substantially larger and of a reticular nature. It should be noted that if the release of the gas pressure is started prior to the 15 attainment of the‘proper plastic state, then the blowing or expansion tends to be in a horizontal rather than a vertical direction, resulting in iold-- ' ing and poor formation. Another object of this invention is to provide. a process whereby the uncured stock may be ex panded or blown under commercial conditions to from 450 to 600 per cent. expansion, or from 25 to 50 per cent. greater expansion than is possible or customary withchemical sponge. This object is obtained by impregnating with carbon dioxide gas at pressures between the ranges of 50 to 300 pounds, 170 pounds being very satisfactory. It _ under reduced pressure, so as to permit the batch has been discovered that sufficient gas can be in corporated or dissolved in the rubber in an hour 30 and arhalf period, or less, to cause blowing to this degree; ' It should be noted that it is possible to blow by this process, using the pressures here to‘ expand not only under the in?uence of the high pressure gas entrapped in the batch, but also under the in?uence of the gas generated within the batch by the gas generating substance, per cent., but the particular requirements of com mercial conditions are perhaps most easily met when expansion is limited from 450 to 600 per giving as a result a super-expanded sponge rub cent. before curing, ,to the action of a high pressure ~ inert gas, such as carbon dioxide, to impregnate the batch with the gas, and is aiterwardheated, ber. ‘ ' > ‘ Another object is to provide a mold for the manufacture of sponge rubber articles, this mold having perforated walls adapted to permit the entrance of high pressure gases used for impreg nating the rubber batch to enable the batch to be ‘ - 45 subsequently expanded into sponge rubber; this , mold being optionally lined with a ioraminous or inbeiore mentioned to as much as 1000 or more - Another object is to provide a condition during impregnation or ‘carbonation such that penetra 40. tion of the uncured stock is facilitated. This ob :Iect is accomplished by providing that ‘the ?rst hour of the usual hour and a half of impregnation time be at a temperature in the neighborhood‘ oi between 125 and 1'75 degrees F._, "the ‘purpose being to soften or plasticize the rubber so that textileliner to permit the entrance and exit 01 the penetration will be more e?ective. It has been round useful to cool the stock during the ,through. ‘ ' last half-hour‘ oi impregnation to a temperature 50 - Another object is to providesimple means A)! 100 degrees F. or below, better ?lling and bet whereby the formation in the mold and size .0! ter cell structure being obtained ‘when this is ' cell structure are under control. This object is done than when the higher temperature is main the gas, yet retard the passage of rubber there accomplished by application of heat subsequent tained throughout. We have discovered that low to the impregnation period, but prior to the re ' temperature accelerators can be successfully used a lease oi the gas pressure such that the rubber 2_ 2,109,676 _ in conjunction with this process most advanta-' ‘geously, thereby achieving many improvements. Another object of this invention is to provide a process of manufacturing sponge rubber through gas impregnation or carbonation, where in the pressure required to e?ect it is relatively low and requires no unusual commercial equip ment. ' _ ' _ 1 Another object is to provide compounds adapt '10 ed to be vulcanized or cured at- temperatures be lowthose'at which customary chemicals interact to form blowing ingredients. ' Another object is to provide simple means whereby the uniformity of cell formation is under 15 control. I ~ ‘ ' Another object of this invention is to provide a method whereby objects of variable thickness or of relatively great thickness may be impreg inated mold vemployed in the process of this in vention. This ‘mold may be of any suitable shape, according to the shape of the article to be produced. As shown in the drawings, the mold is in the shape of a rectangular block, with inserted portions adapted to provide a sponge rubber cushion-like article, with partitions there in. To this end the mold, generally designated I0, is provided with side walls ll of perforated or foraminated material, such as punched metal 10' plates or meta-l gauze, these side walls ll being provided with outwardly extending ?anges I2. A bottom plate I 3 and a top plate I! are provided for engaging the ?anges l2 to provide a closed container. ' Sheets l5 of lining material are pro vided for the interior of the mold, these being preferably of fabric or of very ?ne gauze. The purpose of this lining material l5 isto permit the passage of gas and impede the passage of rubber. ing required. therethrough. The top and bottom plates 14 20 Another object is to provide a process and and i 3 may be clamped ‘to the ?anges I 2 in. any method whereby objects having portions in a ver "suitable manner, the means shown consisting of tical plane, as well as in a horizontal plane,,may clamps l6 having knurled headed screws I‘! for be made with equal uniformity. applying clamping pressure to the jaws thereof. Another object is to produce a product made In the interior of the mold are arranged core 25 nated or carbonated without additional time be 20 from crude rubber of a kind not hitherto made portions} l8, these also preferably having per from this material. forated walls to permit the passage of gas. rubber portions adjacent these cores are in the interior of the article, the slight tions caused by the extrusion of the In the drawings: . \ ‘ Figure l is a side elevation of a mold suit30 able for carrying out the‘process of this‘ inven tion. ' a ’ Figure 2 is a top plan view, partly broken away, of the mold shown in Figure 1. Figure 3 is a vertical section through the mold .35 of Figures 1 and 2, along the line 3-3 of Figure 2, showing the rubber batch prior to its impreg nation and expansion. » _ Figure 4 is. a view similar to Figure 3, but As the usually projec rubber 30 through .the perforations will not ordinarily be objectionable, hence, a liner is not’ ordinarily used around the cores. It will be understood, how ever, that if‘a comparatively smooth wall is de sired for the interior walls of the-compartments 35 formed by these cores, a suitable liner of fabric or gauze may be provided in a manner similar to the liner ‘l 5 employed in connection'with the outer showing the rubberlbatch after its gas impreg-' walls of the‘ mold. In the embodiment shown in 40 nation and expansion to ?ll the mold with sponge the drawings the side walls II and top and bot 40 ‘ rubber. Figure 5 is a vertical section through an auto clave suitable for carrying out the gas-impreg nation and vulcanization steps, showing the mold 45 of'Figure 1 in position. ‘ _ , Figure 6 is a graph showing the relationship between the pressure of the impregnating gas, ‘the temperature conditions and the percentage of expansion of the rubber product obtained in 50 a modi?cation of the process. ' In general, the process of this invention con sists in preparing a suitable rubber batch of ma terials known ‘to those skilled in the rubber art, and suitable for sponge rubber, an example of 55 such a batch being given later. This batch is’ _ then placed in a perforated or foraminated mold, tom plates l4 and I3 consist of metal sheets hav 'ing small holes is drilled or punched there-_ through. ' For the gas impregnation and/or the vulcaniza tion steps of the process, the apparatus shown in 45 Figure 5 may be employed.‘ This consists of an autoclave, ‘generally designated 20, and having’ outer and inner walls 2| and 22, respectively, with a closed ‘space 23 therebetween. Pipes 24 and 25, controlled by valves 26 and 21, serve for the ad 50 mission or discharge of steam or other suitable heating agent, and also for the introduction of such cooling agents as may be desirable. The front of the autoclave 20 is closed by a door, gen 55 erally designated 28, and having outer and inner the latter being placed within an autoclave and _ walls 29 and 30, separated by the space 3|, which ' subjected to high pressure carbon dioxide gas The gas penetrates the pores f the rubber an is preferably also connected to the source of heat ing or cooling agent, in a manner similarto the pace 23. 60 followed impregnates under pressure, by the thethe application. interior process being‘ with” of heat, ccomplished arbon along dioxide with or the reduction of pressure of the gas. Under these conditions the rubber batch expands to 65 ?ll the mold, due to the reduction in pressure, the application of heat and the presence of the high pressure gas within the cellular structure of the rubber. >~The expanded rubber thus becomes sponge rubber, and this is given apermanent 70 form by the vulcanization which is carried out upon the expanded product. Apparatus Referring to the drawings in detaiLFigures 1 75 to 4 show various views of a perforated or foram ’ . Clamping nuts 32cm the bolts 33, pivoted as at 34, to the outer walls of the autoclave, serve to clamp the door 28 securely to the remainder 60. of the autoclave and to provide a gas-tight junc tion therebetween. The-door 28 is provided with 65 bosses 35 engaging corresponding projections 36 on the walls of the autoclave. These, in connec tion with the hinge pins 31, provide hinges upon which the door may be swung to and fro into its open or closed position. ' Batch I The vbatch of rubber stock from which the sponge rubber is made may be of any suitable composition, the’ following composition having 3. $109,678 ' been found suitable for the production of rubber. tained for a suitable period or time. The exact _ by the apparatus and processdisclosed hereinz: ' depends upon the nature 0! the batch and the time for the exposure of the batch to the gas also ‘ pressure employed, a period of one hour to one 100.00 and one-half hours being irequently used, at the ‘Rubber plastic . Sulphur Zinc oxide _ Mercapto benzothiozole _______________ __ 2.75‘ previously mentioned pressure 01- 170 pounds per 5.00: square inch, Tetramethylthiuramdisul?de. _____ _;..____ .251 Phenylbetanaphthylamine_- ____________ __ 1.00: Stearic acid >_ Petrolahlm Coloring agent 1.00. 15.00 b approximately 200 degrees F. and 235- pounds Rubber Green F. D.) ...._....' ________ "12-..; __________ ..... . The valves 20 and. 21 are now opened and steam is, admitted to the space: 23 between the outer and inner walls 2| and. 22' or the autoclave. 10 Under the influence of this steam the tempera ture and pressure inside the autoclave rise to .50 00' - per square inch, respectively. This particular 7 compound loan“ be: very satisfac The gas is then ?fteen to ' released. slowly over a period of from tory when cured "40 min. at 35 .lbsifand 40 min. at: thirty minutes, the temperature rising as the gas makes its exit with a steam pressure of 30 to 35 45 lbs. in an. autoclave. , , pounds per square inch._ The‘ temperature within . This stock is mixed and calendered, in the man the autoclaveis ‘maintained at a maximum of. ner known to those skilled in the rubber art, the . from 260 to.- 265 degrees F. _When the gas pres‘-v '20, product being obtained in sheets or ‘strips of suit-_ 20 able thickness, according, to the, nature 01.’ the sure drops ‘to a pressure 01.’ .irom 5 to .15» pounds article to be made. These strips are cut to ap-‘ per square inch-‘the gas valve lil'lisiclosed. C'Un-_-_._ '‘ proximate dimensions and a weighed amount of der these conditions the rubber batch-becomes ;] impregnated expands as with the"carbon dioxide gas, and this , this stock is placed in the mold, such as the one .gas external gas pressure is low-’ IO Ol previously described and shown in Figures 1 to 5. ered, thereby forming cells within the rubber...‘ . In the article shown by way oi illustration, the - and expanding the rubber itself to ?ll the mold, stock consists preferably of relatively thin strips as shown by a comparison of Figures 3 and 4. these strips may be, for example,‘ .085 of an inch The lower the residual gas pressure the larger are the cells formed in the sponge rubber.- when '30 for the production of a sponge rubber article one .the rubber has expanded to a suitable amount half an inch thick, and .15 of an inch for sponge within the mold, the article is vulcanized and rubber of'one inch thickness. given its ?nal cure by being treated for ?fty min- ' The pieces or strips are inserted in the mold, utes at a steam pressure of thirty pounds per either ?at or edgewise, cushions having leg por as tions or. partitions being made by inserting strips . square inch, and afterward for another ?fty min utes at a‘ steam pressure of 40 pounds per square of stock on edge engaging the ?at portion of the inch, using a temperature of approximately 240 . cushion. The mold cores l8 serve to occupy the or slabs of the rubber batch. The thickness of > .space between the partitions. In the drawings In Figure 6 is shown a graph giving the rela the cover or top portion 38 and the partition or tionship between the gas pressure and tempera 40 I 40 leg portions 39 are shown in this edge-to-?at rela ‘,ture for a particular procedure. In this proce- I tionship, . . dure the carbon dioxide gas is admitted until it The stock or batch described above is preferably reaches a pressure of 170 pounds per square inch, characterized by the use of low temperature ac and the is steadily raised, beginning celerators, which would be impracticable in the at roomtemperature temperature of approximately '15 de 45 I 45 manufacture of sponge rubber produced by the grees. The pressure and temperature rise con degrees use of gas generating substances in the batch be‘ F. _ . . _ currently, as shown in the graph, over a period oi! cause of the necessity of having to attain relative approximately 12 minutes until the gas reaches a? chemicals react to form the gas for expanding the. pressure oi'about 235 pounds per square inch. The gas pressureisthen released and allowed to so ' 50 rubber into cellular form. _ fall rapidly between the times of 12 and 25 rninqv ly high temperatures before the gas generating Process’ utes, The while gas pressure the temperature subsides ismore increasln‘glyraised; slowly :as the - " With the moldjloaded with the batch or stock in the above-described manner, the top and bot tom plates I4 and It are clamped in position, with 55 the liners I! in proper locations, and the entire assembly is then} placed in the autoclave 20'. The door 28 oi’ the autoclave is then clamped tightly temperature nears its peak of approximately 240 degrees, and decreases to atmospheric pressure 5s after a period oi’ approximately 40 minutes. Meanwhile, the rubber article has expanded to approximately "1200 per cent. of its original vol ume, as shown by the third curve on the chart oi’ against the walls so that the mold occupies a gas ~60 55 tight inclosure. The gas valve 40 in the pipe ll leading into the interior or the autoclave through the passageway 02 is now'opened to permit the entrance of high pressure carbon dioxide. The temperature in the interior oi’ the autoclave is a suitable temperature, which is high enough to soften or plasticise the rubber so that the pene tration will be moree?ective, ‘yet not so high as to vulcanise the stock. Any temperature below Figured , .. - ’ '_ . 60 The point to which the pressure is released I while vulcanization takes place in connection with the thickness of the batch inserted, determines ,, the density of the rubber stock obtained. In re leasing the pressure down to_5 pounds per square inch. for example, a substantial increase inex pansion is obtained over when the f release is only to 15 pounds per'souare inch.‘ _ oi theultimate pressureenables 140 degrees 1'‘. maybe employed. room tempera? .a control rate ‘control of the density- and ?rmness oi the ture being-preferable. The carbon dioxide gas rubber. For ‘example, a su?icient amount oi -> is allowed toenter until its pressure reaches ap - proximately 170 lbs. per square inch, although the upper or lower pressures maybe used, accord ing to the particular-nature oi the batch. The 75, gas valve 40 is then closed and the pressure main batch-to completely ?ll the mold when the pres r square inch, iresure is reduced to'5 poun quently gives'a'stock which is soft and ?imsy. ' thisbeingdesirabletorpurposessuchascushim; ;..; 4 . ‘ 2,109,6 76 but undesirable for other purposes, such as ?llers where a greater density‘ of vstock- or body is re quired. In the ?rst instance‘ the maximum ex pansion would be secured with the minimum amount of stock being used. In the second in stance, however, more stock would be used, or an increase might be made in the thickness . thereof, and by halting the release of the pressure at 15 pounds per square inch the exact ?lling 10 would take place. . ' The temperatures given are approximate and may be varied as they represent thermometer temperatures. For instance, it is possible to have the temperature'range from 205 degrees F. to 270 15 degrees F., depending upon the compound. It will be understood that I. desire to compre ' hend within my invention such modi?cations as come within the scope of the claims and the in vention. ' - while continuing to elevate the temperature, whereby to bring about expansion‘ of the-rubber in sponge form prior to vulcanization; and (c) the step of thereafter releasing substantially all of the pressure prior to vulcanization and con tinuing the heating to complete the vulcaniza~ tion of the rubber in its fully expanded sponge __ condition. . 3. A-process of making- sponge rubber includ ing the following steps: (a) the step of subject‘ ing the rubber to heat at a temperature below a vulcanizing temperature not exceeding ap in proximately 140 degrees F. and simultaneously impregnating the rubber with gas under a pres~ ‘ sure not exceeding 170 pounds per square inch; 15 (b) the step of subsequently increasing the tem perature and pressure to approximately 200 de grees F. and 230 pounds per square inch, respec tively; (c) the step of. thereafter releasing sub Having thus fully described my invention, ' stantially all of the pressure to cause the spong 20 what I claim as new and desire to secure by Let ing of the rubber while continuing to elevate the ters Patent, is: ' temperature, whereby to bring about the maxi l. A process of. making sponge rubber includ- , mum sponging'of the rubber prior to the setting ing the following steps: (a) the step of subject-. 25 ing the rubber toiheat at a sub-vulcanizing tem perature sufficient to soften the rubber yet in sufiicient to vulcanize it and simultaneously im of the rubber’ consequent to vulcanization; and (d) the step of thereafter continuing to elevate the temperature to vulcanize the rubber. 25. 4. A process of making sponge rubber includ ' pregnating the rubber with gas; (b) the step of ing the following steps: (a) the step of subject - subsequently reducing the pressure to cause the ing the rubber ‘to gas pressure to impregnate the 30 sponging of the rubber by expansion of the gas = rubber while applying heat thereto suf?cient to 30 while continuing to elevate the temperature, whereby the gas is substantially released prior to the vulcanization of the rubber; and (c) the step of thereafter heating the rubber to a vul 35 canizing temperature to vulcanize the rubber in its sponged condition. _ _ 2. A process of making sponge rubber includ ing the following steps: (a) the step of subject ing raw rubber stock to heat at a sub-vulcaniz ing temperature sufficient to soften the stock yet insufficient to‘ vulcanize it while impregnating the rubber with substantially dry inert gas; (17) _ - the step of subsequentlylreducing the pressure raise the temperature yet to maintain the tem perature below a vulcanization temperature; (27) the subsequent step of decreasing the pressure to cause the sponging of the rubber while increas ing the temperature whereby to progressively 35 sponge the rubber; and (c) the step of complet ing the sponging of the rubber by continuing to increase the temperature while releasing sub stantially all of the pressure substantially prior to the setting of the rubber by its becoming 40 vulcanized. ' ' _ - HENRY R. MINOR.