|Publication number||US2235531 A|
|Publication date||Mar 18, 1941|
|Filing date||Sep 4, 1931|
|Priority date||Sep 4, 1931|
|Publication number||US 2235531 A, US 2235531A, US-A-2235531, US2235531 A, US2235531A|
|Inventors||Plumstead Joseph E|
|Original Assignee||West Virginia Pulp & Paper Com|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (3), Classifications (12)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Patented Mar. 18,
` Joseph E. rlumsma, wumi nml, Del., assignor,
by mesne assignments, to West Virginia Pulpv & Paper Company, New York, N. VY., a corporation of Delaware Application september 4, 1931, semi No. 561,241
. I4 Claims.
My present invention relates to an improved process of producing a sulte or sulfate product particularly for useas a paper iiller, although adapted for use as a pigment, disinfectant or reducing agent or other uses.-
More particularly, the invention relates to va filler for use in paper making and to the method of producing the ller.
An object of the invention is to produce economically an effective paper illler for deterring aging or deterioration of the paper. y
Another object is to provide a illler particularly valuable for paper made from mechanical or ground wood pulp, which ller has a whiteoolor and a reducing action which tends to produce a whiter paper from mechanical wood pulp and also tends to prevent the yellowing of such paper due to age and exposure to air and sunlight.
A further object is to produce an eliective age deterrent paper i'lller by utilizing the materials available at the pulp and paper mills, thus effecting substantial savings.
Another object is the production' of solid or liquid carbon dioxide as a part of the process of producing the paper filler, or substantially con-l currently with the 'processof producing the paper filler. l
Another object is to provide a process whereby a sulfate ller'may be produced from bi-sulte without requiring the use of hydroxide.
The drawings shown flow sheets or charts diagrammatically explanatory of the process. Figs. 1 and 2 show the simultaneous production of pig-A ment and solid carbon dioxide. Figs. 3 and 4 show the filler production.
The invention consists in the process and product hereinafter described and particularly pointed out in the claims.
In carrying out my invention I have taken the calcium carbonate refuse remaining after the causticizing operation in a soda pulp mill and have treated this with sulfur dioxide until a solution of calcium bi-suliite has been formed. This solution of bi-sulflte was iiltered and claried and then treated with enough milk of lime,
may be exemplified, as
(ci. '2s-122) This ller is particularly valuable for pape' Y made from mechanical or ground wood pulp due to the fact that the reducing action of the calcium suliite, together with its naturally white color tends to produce a whiter paper from mechanical wood pulp and also tends to prevent the yellowing of such paper due to age and exposure to vair and sunlight.
If itis desired to convert the calcium sulte iiller into a calcium sulfate filler, the addition of calcium hypochlorite solution will accomplish the desired result and if thereactions are properly handled the calcium hydroxide in the hypochlorite solution will b e utilized.
The oxidizing action of the hypochlorite on the calcium sulflte may be indicated as follows:
Thereaction including the function of the calcium hydroxide may be indicated as follows:v
It is necessary'in making up calcium hypochlorite solutions to have an excess of calcium hydroxide present to stabilize the hypochlorite. It is this calcium hydroxide which is used to `form additional filler, either sulte or sulfate, depending upon the amount of hypochlorite solution used. The calcium which is combined as calcium hypochlorite is not used as it goes to form calcium chloride which is soluble.
All of these steps in the process described are particularly apropos for pulp and paper mills inasmuch as the equipment for making the various chemicals is usually at hand. The sulfur dioxide would be available in a suliite mill as also would be the limestone in case no soda mill calcium carbonate refuse or sludge were available. Calcium hypochlorite is usually manufactured and used by pulp mills.
The products resulting from my process and which are particularly adapted for use as age deterring paper iillers, are calcium suliite, magnesium sulfite, and calcium sulfate. Magnesium sulfate is soluble in water and so would not be a pigment. Therefore, with this exception magl nesium may be read into the specification and 4claims where calcium is specied, it being understood that calcium or an equivalent substance is intended, and that the claims are not to be restricted to calcium.
This pigment which among other uses may be used for a paper filler, may be produced by the use of a by-prcduct lime, either carbonate as hereinbefore indicated or hydroxide, to form a soluble bi-sullte which may be filtered and clarifled to free the lime from gritty and insoluble undesirable substances. The soluble bi-sulflte is formed from the by-product lime carbonate or hydroxide by treatment withsulfur dioxide gas.
The reaction of the sulfur dioxide onvthe carbonate of lime has been indicated hereinbefore. The. reaction of the sulfur dioxide on the hydroxide is indicated as follows:
This shows how an excess of sulfur dioxide will react with the excess of calcium hydroxide in the hypochlorite solution to form calcium bisulfite.
Or the soluble bi-sulte resulting from the treatment of the by-product lime carbonate or hydroxide with sulfur dioxide, may be i'lltered and clarified and then treated according to my present invention with a pure milk of lime suspension in such quantity or amount that a neutral or slightly acid or slightly alkaline, normal sulfite is formed.
The sulfite product which may as readily be produced with magnesium as with calcium may be used as a pigment, paper ller, disinfectant or reducing agent.
Also according to my process, calcium hypochlorite solution is used to react upon the bisulfite as produced in the first treating step with sulfur dioxide, as well as upon the sullte as produced in the second treating step with milk of lime as hereinbefore indicated, in such a way as to react with the hypochlorite and to produce a sulfate product. 'I'he oxidizing power of the hypochlorite produces a quantity of calcium sulfate from the bi-sulfite or sulflte product, which quantity of calcium sulfate would-be greater in weight, by reason of the calcium hydroxide in the hypochlorite solution, than the Weight of calcium sulfate produced by the oxidization of the sulfite compound so acted upon. Equations indicating the reactions of the hypochlorite solution upon the sulfite have been hereinbefore set forth. 'I'he reaction of the hypochlorite and the bi-suliite may be indicated as follows:
In regard to the reaction of calcium hypochlorite upon bi-sulfite, this is a modification which might be used to produce calcium sulfate without the use of calcium hydroxide. If calcium hypochlorite solution were added to the calcium bi-sulte solution the result would be a calcium sulfate suspension in an acid calcium bisulflte solution, which acid calcium bi-sulfite solution can be ltered from the calcium sulfate and be used again to react on additional calcium carbonate to form more calcium bi-sulte, thereby entirely or partially obviating the necessity for the use of calcium hydroxide in the productionof the calcium sulfate.
If additional sulfur dioxide is required, this of course, will be made up from the gas burner supply. 'I'he point intended to be conveyed is that the filtrate from the calcium sulfate ltering operation, after the addition of hypochlorite solution, will contain bi-sulilte of lime, not necessarily with an excess of sulfurous acid but this would probably be the case. In any case however this ltrate would be used for making up the next batch rather than to use fresh water for the purpose. The exact amounts of sulfurolls acid" and calcium bi-sulte remaining in the ltrate would be determined by test and upon this test would rest the determination of the calcium carbonate or hydroxide addition.
The sulfate product may be used as a pigment, in paper making as a illler. either separately or mixed with some other pigment.
An important feature of the process lies in the complete dissolving of the lime so that it may be clarified and filtered, thus ridding the product of all gritty matters and insoluble substances which would be harmful in the use of the product as a paper filler or pigment. 'I'he use of a pure milk oi lime or calcium hydroxide suspension for precipitation, a milk of lime which has been elutriated after slaking, is necessary in order to further assure and insure the purity and utility of the finished product.
I also contemplate the use of limestone in the first step as a substitute for the'by-product lime.
The by-product lime may be the oial from the causticizing process, from the sugar industry, from the production of acetylene gas from calcium carbide and from various other industries where lime is used in process work and later discarded. 'I'he oifal from soda pulp mill black ash operation contains carbon.
The reaction between sulfurous acid or calcium bi-sulfite and milk of lime is a rapid one for the greater part of the reaction. However, some of the milk of lime particles and some of the calcium sulflte particles may occlude sulfurous acid or calcium hydroxide, as the case may be, and cause a slowing up of the reaction toward the end. If the reaction is not properly balanced an inferior product will be obtained. Allowing the suspension to stand permits completion of the reaction.
My process further involves the production of a superior quality material by allowing the neutralized calcium suliite water suspension to stand for sufilcient time to insure completion of the reaction, and then throwing it back to a slightly acid reaction with the addition of any of the following: sulfur dioxide, iron free aluminum sulfate, or sulfuric acid or other suitable materials. I have also found that a material of superior quality may be produced by allowing the neutralized calcium suliite water suspension to stand for suiilcient time for completion of the reaction, and then throwing it to the alkaline side with a suitable material such as sodium aluminate. Usually much less than 1% of acid or alkali weight figured on total weight of chemical is used to throw the suspension slightly on the acid side or slightly on the alkaline side.
By' shortening the mixing time of reacting the acid calcium bi-sulfite and calcium hydrate suspension, a white product has resulted according to the present process. In order to -shorten the mixing time, the reacting chemicals are put together in the proper proportions as quickly as possible and after being put together are agitated and kept in contact with one another with suicient time for completion of the reaction as explained above.
In regard to the term proper proportion these are strictly chemical reactions and proper proportions can mean only one thing, which is, that the raw materials must be tested for purity and combined, taking into consideration molecular weights and the determined raw material purity.
In regard to the statement "sufficient time to complete the reaction the completion of the reaction is determined by tests and to run for one, two or three hours could not be specified except by tests showing completion oi' the reaction. Ii.' the reaction is tc be completed, the reacting chemicals must be in contact until the desired result is obtained. The physical state of the operation has a great deal to do with this speed oi?4 reaction completion. Temperatures, pressures and speeds of mixing and agitation iniluence the time required to complete the reaction.
Acid calcium bi-sulilte means that an excess of sulfur dioxide or sulfurous acid is absorbed in the calcium bi-sulfite solution. This may be a large excess or not as desired.I Ordinarily there is about three times as much uncombined sulfur, dioxide as combined.
A whiter product is also producedl by reacting approximately lproper chemical proportions of acid calcium bi-sulfite and calcium Ahydrate suspensioxr without allowing any part of the final product of normal calcium sulte to stand for any substantial time in a calcium hydrate suspension, nor in an acid calcium bi-suliite solution, nor in a calcium bi-suliite solution. In other words, a whiter product is produced by proportioning the reacting chemicals to complete the reaction properly and without permitting ex,- cess of either reacting chemical to act on the normal suliite product.
By the action of the sulfur dioxide or sulfurous acid gas upon the water slurry of calcium carbonate, in addition to the calcium bi-sulfite product there is the product of carbon dioxide gas. This carbon dioxide product, according to my process is conilned in a closed high pressure vessel and this carbon dioxide in the high pressure vessel builds up its own pressure to a point such that the discharge or release of the carbon dioxide gas into a vessel at a lesser pressure will result in solidiiication or liquefaction ci the gas so discharged. v
I may produce the solid carbon dioxide by pumping into a closed high pressure vessel a solution of calcium acid bi-sulfite and a suspension of calcium carbonate, and building up the pressure of the carbon dioxide gas to a point such that discharge of the gas into a vessel at a lesser pressure solidies or liquefles the carbon diox ide.
Also by the use of sulfuric acid and calcium carbonate I may produce substantially simili-` taneously a calcium sulfate pigment product and solid or liquid carbon dioxide product. according to the following equation:
H2SO4 +CaCOa=CaSO4 +CO2+H2O The solid or liquid carbon dioxide is produced as above suggested by building up pressure of the gas in ahigh pressure vessel and discharging it into a low pressure vessel.
A liquid pump is required for vforcing in the chemicals but no gas pump is required for the carbon dioxide. Much smaller equipment will be required for handling a certain amount of It will therefore not be necessary to form the bi-sulfite 'except wherev raw material is used which needs to be puried. It it is desired to convert a pure calcium carbonate into calcium sulilte or suli'ate it will not be necessary to' go through the steps of bi-suliite formation and filtration. But in the case of heavy limestone, it
will be necessary to go to the bi-sulfite in order to remove a coat of calcium suliite from the'surface of the limestone to be reacted upon, in order to physically permit the reaction to continue. Also, although the suite may be formed in the high pressure vessel, it must go to the iiltrablev bi-sulfite in order to separate it from impurities in the waste lime carbonate used.
I am producing filler and carbon dioxide as two products. The iiller maybe used for its physical or for its chemical properties or for both purposes. In considering its physical properties, ilneness; color and cleanliness are important. Chemically,A calcium carbonate does not require going through the bi-sulte stage for the forma'- tion of sulfite. If the calcium carbonate vused in the reaction is suiiiciently iine .and suiciently pure, a pure calcium calcium bi-sulfite solution and a pure calcium carbonate suspension may be ,mixed in the proper chemical proportions and produce thereby a pure calcium s uliite of a white color and iine texture, with the liberation of carbon dioxide. This reaction would be used:
-.(l) In -the high pressure vessel in order to coniine the carbon dioxide and build up its pressure. 4
(2) 'I'he reaction might also be used in case it would be desired to use a Waste lime for absorbing all of the sulfur dioxide required for producing a certain amount of calcium sulflte and for furnishing one-half the calcium supply to produce this given amount of calcium sulfite and to use pure, finely divided calcium carbonate instead of calcium hydroxide for the other half of the calcium supply for the calcium suli-lte production.
In a mixture ofv calcium carbonate and calcium bi-sulilte the acid radical in the calcium bisulfite is more loosely combined and has more afiinity for the calcium inthe carbonate than it has for the calcium suliite, consequently the calcium bi-sullte .gives up its loosely combined acid radical which goes over to the calcium which is combined with carbon dioxide as calcium carbonate, with a liberation of carbonidioxide and the formation of calcium sulte as follows:
Referring to Fig. l, the excess of sulfurous acid in the acid calcium `bisulte solution will have to be large when pumped into the large closed high pressure vessel, ii any great amount of carbon dioxide is to be generated. Some of the carbon dioxide gas generated at atmospheric pressure during the iirststages of the acid calciurn bi-sulflte reaction, may be forced into the l reacting mass which forms carbon dioxide in of the reaction.
Thisvstep would not be necessary however in .thc formation of calcium sulfate from sulfuric acid and calcium carbonate in the closed high pressure vessel, as represented in Fig. 2. Y
Fig.v 1 isa flow chart indicating diagrammatically the simultaneous production of suli'lte pigment and solid carbon dioxide. As indicated in this chart, the sulfurous acid and calcium carbonate suspension are passed into reaction in the absorption tower, to produce calcium bivsuliite and low pressure carbon dioxide which are drawn off as indicated. To this calcium bi-sulflte is supplied additional sulfurous acid, by-passed as` shown from the source of supply or from any` other source, and this mixture is delivered to the .pump as shown. To the pump is also delivered calcium carbonate and Water and the pump forces these materials into the high pressure vessel as indicated to produce the calcium bi-sulte product which may be ltered oi as shown, and the carbon dioxide product. The carbon dioxide gas builds upa high pressure in the vessel, and may be augmented by the low pressure carbon dioxide gas pumped at high pressure into the reacting mass in the high pressure vessel as indicated. The combined carbon dioxide gas under high pressure is then released from the high pressure vessel to solidify. The calcium bi-sulfite ltered off from the high pressure vessel is delivered to the reaction tank to which is also supplied calcium hydroxide, the reaction producing the desired calcium sulfate pigment.
` In. the formation of the calcium bl-suliite in the absorption tower and in the high pressure vessel, this goes through thegstages of calcium carbonate, then calcium suliite, then calcium bisulfite, then acid calcium bi-suliite. In other words, the sulfurous acid comes into the absorption tower in which there is calcium carbonate and water, thereby first forming calcium sulfite, then as more sulfurous acid comes in the bi-sulnte is formed and as still more acid comes in the acid calcium bi-sulte is formed. The greater the excess sulfurous acid which maybe present, the greater the amount of calcium carbonate which may be charged into the high pressure vessel separately, as indicated.
Fig. 2 is a flow chart showing the direct production of the sulte pigment from pure calcium carbonate and sulfurous acid without the necessity of the intermediate formation of the bi-sulfite. This chart also shows the simultaneous production of the pigment and solid carbon dioxide. This chart also shows the production of calcium sulfate pigment bythe action of sulfuric acid on the lime carbonate.
In regard to the pressure required for liquefying carbon dioxide, it will be understood that any gas which has been liquefied hasa certain boiling point temperature under given pressure conditions just as water does and in order to give pressures for liquefaction would require a set of tables just as is shown in any mechanical engineers hand book on steam. However, it may be stated in general that carbon dioxide sublimes passing directly from the solid to gas or from the gas to liquid at minus 78.2 C. under atmospheric pressure. It will depend upon the temperature of the cooling water used and the eiiiciency of the coolers as to what pressure, and consequently what temperature, will be required in any-given case. Each case would require separate study in order to determine the extremes of summer and winter or seasonal cooling media temperature conditions.
Fig. a is a now chart showing the production of the sulfate pigment by treatment of the acid calcium bi-sulflte-produced as shown in Figs. 1
, or 1 -,with calcium hypochlorite and calcium hycium hydroxide and the calcium chloride Washed out of the precipitated calcium sulite which is returned to the process.
In the production of soda pulp there is carbon charcoal Waste amounting to approximately 10% of the weight of the pulp produced. This charcoal contains about 10% of mineral substances, mostly calcium, which if treated by an acid would result in an activated char. I propose the mixing of this waste char With the Waste lime sludge and the simultaneous acid treatment and activation of this char with the formation of illterable calcium bi-suliite and an activated, adsorbent or absorbent carbon or char, which may be used as a decolorizing agent or for other Well known purposes for which activated carbons are used.
Fig. 4 shows by Way of flow chart, the production of the sulflte pigment or filler together with activated char. The sulfurous acid is delivered to the absorption tower and the calcium carbonate with waste char are also delivered theretto. The carbon dioxide gas produced by the reaction is passed off, and the bi-suliite and char are filtered off and the activated char is passed out as a product. The bi-sulfite is treated in the reaction tank with calcium hydroxide and other whitening agents, to produce the calcium sulflte pigment product.
'I'he invention also contemplates producing the calcium sulfite from the bi-sulfite by boiling the bi-sulte which will give oi SO2 gas and will deposit the sulflte. In other words, instead oi forming the bi-sulte, filtering and then forming the suliite by treating the bi-sulte with calcium hydroxide as indicated in Fig, 1, the bi-sulflte may be formed, ltered, and then the suliite thrown out from solution by boiling, and reclaiming the, SO2 gas.
That phase of the invention disclosed herein which relates to the product resulting from the addition of the improved pigment or filler material to pulp, and more particularly mechanical or ground wood pulp, has been divided from -thisv application and will be made the subject ma-tter of a separate, divisional application.
1. The herein described method of producing a substance of improved qualities for use as a paper malclng ller or for other uses, comprising treating a suitable lime material with sulfur dioxide gas in the presence of Water to produce'calcium bi-suliite solution, filtering and clarifying the calcium bi-sulfite solution to remove impurities, and treating the same with calcium hypochlorite solution so as to neutralize the lime in the hypochlorite solution and to oxidize the bi-suliite to produce a calcium sulfate product.
2. The herein described method'of producing calcium sulfate without requiring the use of calcium hydroxide,.comprising adding calcium hypochlorite solution to a calcium bi-sulfite solution, to produce a calcium sulfate suspension in an acid calcium bi-sulte solution, and iiltering 3. The method of producing a calcium sulfate' pigment comprising treating calcium sulfite with calcium hypochlorite solution so as to neutralize the lime in the hypochlorite solution and to oxidize the sullte .to produce a calcium sulfate product. y
4. The herein described method of producing a calcium sulfate pigment comprising treating acid calcium bl-sulte solution with calcium hypochlorite and calcium hydroxide solution, producing a calcium sulfate pigment, filtering off from said sulfate pigment the excess bi-sulilte or sulte and calcium chloride solution, and returning said excess filtrate to the initial reaction at the beginning of the process.
5. The method of claim 4 including by-passing a portion of the illtrate before returning it to the beginning of the process, and removing excess calcium chloride by treating the by-passed portion off the ltrate with calcium hydroxide and washing out the calcium chloride, and returning the precipitated calcium suliite to the process.
6. The herein described process of producing a pigment comprising passing sulfurous acid and a mixture of waste lime sludge and char into reaction in an absorption Itower or the like, producing carbon dioxide gas and calcium bi-suliite, passing oil the carbon dioxide gas, iiltering out the calcium bi-suliite and char, withdrawing the activated char from said bi-suliite, passing the bi-sulilte into reaction with calcium hydroxide to produce the sulilte pigment which is withdrawn.
7. The herein described method of producing a substance of improved qualities for use as a paper mahng illler or for other uses, comprising treating a suitable lime material with sulfur dioxide gas in/the presence of water to produce calcium bi-suliite solution, filtering and clarifying the calcium bi-sulte solution to remove insoluble impurities, reacting the ltered clear solution with a pure milk oi lime suspension to precipitate a calcium sulte product and allowing the calcium sulfltesuspension thus formed to stand for sumcient time for completion of the reaction and then making vit slightly acid with additional materlal.
8. The herein described method of producing a substance of improved qualities for use as a paper making ller or for other uses, comprising treating a suitable lime material with sulfur dioxide gas in the presence of water to produce calcium bi-sulte solution. filtering and clarifying the calcium bi-suliite solution to remove insoluble impurities, reacting the iltered clear solution with a pure milk of lime suspension to precipitate a calcium sulilte product and allowing the calcium sulfite suspension thus formed to stand for suillcient time for completion of the reaction, and then making it alkaline with addi- /1 tional lime material.
' 9. The herein described method of producing a substance ot improved qualities for use as a paper making ller or for other uses, comprising treating a suitable lime material with sulfur dioxide gas in the presence of water to produce calcium bi-sulilte solution, ltering and clarifying the calcium bi-sulte solution to remove insoluble impurities, reacting the ltered clear solution with a pure milk of lime suspension to precipitate a calcium sulflte product and allowing the calcium sumte suspension thus formed to stand for a suiiicient period to complete the reaction. and then making it alkaline with sodium aluminate.
10. The herein described method oi producing a substance of improved qualities for use as a paper making filler or tor'cther uses, comprising treating a suitable lime material with sulfur dioxide gas in the presence of water to produce calcium bi-suliite'solution, filtering and clarifying the calcium bi-suliite solution to remove insoluble impurities, reacting the' irltered clear solution with a pure milk of lime suspension to precipitate a calcium sulfite product. the proportions of calcium bil-sulite and lime material being in approximately definite proportions whereby no part of the final product of normal calcium sulte will be allowed to stand 4for any substantial time in any one of a group consisting of calcium hydrate suspension, acid calcium bi-sulilte solution, and calcium bi-sulfite solution to thereby increase the whiteness of the calcium sulte product.
11. 'Ille herein described method of producing a pigment for use as a filler for paper making or other uses, comprising mixing waste carbon char with waste lime sludge and simultaneously treating the mixture with acid to activate the char and to form lterable calcium bisulilte, filtering and clarifying the calcium bi-sulfite solution and precipitating calcium sulfite by reacting said solution with pure lime milk suspension.
12. The herein described method o! producing a substance of improved qualities for use as a paper making iller or for other uses. comprising treating a suitable lime material with sulfur dioxide gas in the. presence of water to produce calcium bi-sulnte solution. ltering and clarifying the calcium bi-sulte solution to remove insoluble impurities, reacting the filtered clear solution with a pure milk of lime suspension to pre-r` cipitate a calcium sulite product. and allowing the neutralized calcium sulfite water suspension thus formed to stand for suiclent time for completing the reaction, and then making it slightly acid with a material selected from the group consisting of sulfur dioxide, iron free aluminum sulfate and sulflu'ic acid.
13. The herein described method of producing a substance of improved qualities for use as a paper making liervor for other uses, comprising treating a lime carbonate material in the presence of water with sulfur dioxide gas producing carbon dioxide gas and calcium bi-suliite solution, passing oi the carbon dioxide gas,4 illtering and clarifying the calcium bi-suliite solution to remove impurities. and treating the same with calcium hypochlorite solution so as to neutralize the lime in the hypochlorite solution and to oxidize the bi-sulte to produce a calcium sulfate product.
14. The herein described method of producing a substance of improved qualities for use as a paper making ller or for other uses, comprising treating a lime carbonate material with sulfur dioxide gas in the presence of water, producing calcium bi-sulte solution and carbon dioxide. passing ofi the carbon dioxide gas, illtering and clarifying the calcium bi-sulte solution to remove insoluble impurities, treating the ltered clear solution with a pure milk ot lime suspension to precipitate a calcium sulite product and allowing the calcium sulte suspension thus formed to stand for sulcient time for completion of the reaction and then making it slightly acid to slightly alkaline.
JOSEPH E. PLUMSTEAD,
4 l Y CERTIFICATE oF COREGTION.
No n 2, 553-; l .JOSEPH E. PLUMSTEAD. A
is hereby certified that errer appears in the printed specification Y of the above Anumbered patent requiring correction as follows: 'Page l, first coli'nnn, line 51,1for the wordshovn" reed --shoN-; page `5, second co1- rf'mn, line 67, plaimlh., for *"treating" read reaotingand that the said Letters'Petent lould'be read withthis correction therein that the same mey conform to the `record o f the cese in the Patent. Office.
signed and sealed 'this 17th day of June A. D. '19141.
Henry Van Arsdale (Seal) vloting Commissioner of Patents.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US2520850 *||Feb 12, 1944||Aug 29, 1950||John Minnick Leonard||Process of whitening alkaline earth carbonates|
|US4124563 *||Feb 14, 1977||Nov 7, 1978||Kureha Kagaku Kogyo Kubushiki Kaisha||Stretched molding composed of calcium sulfite-containing polyethylene composition and a process for the preparation thereof|
|US4801355 *||Jan 16, 1987||Jan 31, 1989||United States Gypsum Company||Tabular acicular gypsum and method of filling paper|
|U.S. Classification||423/166, 162/181.3, 423/159, 423/160|
|Cooperative Classification||C01F11/48, C09C1/02, C01P2006/60, C01F11/464|
|European Classification||C09C1/02, C01F11/46D, C01F11/48|