CA1071841A - Process for modifying the appearance of crystalline sodium chloride - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process is provided for preparing substantially non-cajubg crystalline sodium chloride wherein the sodium chloride is treated with an effective amount of N-2-acetamide iminodi-acetic acid or N,N-bis(2,2'-acetamido)glycine. The product crystalline sodium chloride is found to have a modified appearance as well as being substantially non-caking.

Description

10'71841 BACXGROUND OF T~ VE~TION
This invention is~in the field of sodium-chloride.
M~re particularly it is in thQ field of modifying the appearance by creating it o~ sodium chloride/wlth ~N-2-acetamide)iminodiacetic acid ~hereinaf~er MA) or N,~-b~s~2,2'-acetamido)glycine (hereinafter ~A). ~he treated crystalline sodi~m chloride is substantially non-caking.
M~ has the formula ~C~2coNH2 2CC3~
~2COO~.
DA has the formula - ~ H CONH
: N r~2CONH2 CH2C0~7H . . - - . --` Prior art metho ~ for modifying the appearance or ~he crystal habit of sodium chloride~or for decreasing the ten~ency of sodium chloride to c.ke are well known. Such methods are ta~ght by the following US Patents: . -Patent No. In~entor~s~ Class No.

2,539,012 Diamond et al 99/143 . 2,642,335. May et al 23/89 2,990,246 Scott et al 23/89

3,000,708 Rapsenberg et Al - 23/303 ~-3,09S,281 Schinkel et al 23/300 3,148,023 Ploss- 23/89 3,174,825 Birch~.ll e,t al 23/89 3,281,206 Yan ~eele et al 23!65 3,556,718 Bachmann et al 23/89 . 3,558j512 Jacoby et al 252/383 3,567,371 B_rchall 23/89 .~ ~ff - ' . .
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`~ 1071841 British Patent Specification No. 1,003,216 teaches that sodium chloride crystals obtained by crystallizing sodium chloride from a brine in the presence of nitrilotri-acetamide, N--~C ~ CONH2)3, are three-dimensional dendrites.
I do not obtain dendrites where crystallizing sodium chloride from brine in the presence of M~ or DA.
Neither do I obtain dendrites where treating cubic sodium chloride crystals-(conv~ntional crystalline sodium - chloride) with aqueous solutions of MA or DA.
Methods for inhibiting the caking of inorganic salts are taught by L. Phoenix, Rritish Chemical Engineering, Vol. 11, No. 1 (Ja~. 1966), pp. 34-38.
The crystal habit of sodium chloride and the modification thereof is taught by Rir~-Othmer, "Encyclopedia of Chemical Technology", Vol 18, pp. 478-480 ~1969).

S~HM~RY OF THE INVENTION

In Summary, this invention is directed to a process for preparing substantially non-caking crystalline sodium chloride from a sodium chloride brine containing an amount of MA or DA effective for causing the product crystalline sodium cXloride o have a modified appearance and to be substantially non-caXing.

DESCRIPTION OF PREFERP~D EMBODIMENTS
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The following procedures and compositions represent preferred em~odim~nts of the instant invention:
1. A process for changing the appearar.ce of crystalline so2ium chloride comprising admlxing ; cor.ventional sodium chlorided crystals with a solution consisting essentially of water and an amo~nt or ~

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^~ 1071~41 or DA effective for modifying the app~ara~ce of the sodium chloride crystals, the solution and the ~odium chloride crystals being admixed in amounts to provide 10-1000 parts of MA or DA per million parts of sodium chloride.
2. A free-flowing non-caking sodium chloride composition consisting essentially of crystalline sodium chloride and ~A or DA, the MA or DA being present in an amount effective for rendering the composition non-caking.
3. Transparent non-caking sodium chloride -crystals containing an amount MA effective for rendering the sodium chloride crystals non-caking.

4. A free flowing mixture consisting essentially of an intimate mixture of particulate sodium chloride and MA or DA, the MA or DA being present in an amount effective for rendering the particulate sodium chloride free flowing ~e.g., 10-1000 parts of ~A or DA per million parts of sodium chloride).

5. A process for reducing the tendency of -crystalliners~dium chloride to cake characterized in that to the solid crystalline sodium chloride is added an amount of MA or DA effective for reducing the --caking tendency of the crystalline sodium chloride te.g., 10-1000 parts of MA or DA per million parts of sodium chloride).

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~ , DET~ILED DESCRIPTION OF THE INVENTION
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Where treating particulate sodium chloride with a solution o~ ~A or MA (i.e., where admixing particulare chloride sodium/with an aqueous solution o~ DA or MA) to render the particulate sodium chloride substantially non-caking and/or to change the appearance of crystalline sodium chloride generally prefer to use a solution of DA or ~A which contains about 2-5% (more preferably about 3-4%~ DA or MA, but I have obtained excellent results with more dilute and more concentrated solutions of DA or MA.
MA can be prepared by a process comprising reacting nitilotriaceto~itrile (NTAN) with aquecus sodium hydroxide . .
usi~g 2 moles of sodium hydroxide per mole of NTAN at about 65C. The product is disodium ~N-2-acetamide)-; m; nodiacetat_. This reaction is represented by the following equation:

f H2CON}i2 ~(CH2CN)3 + 2NaOH + 3~2 -- -) N~ C~2CNa + 2N~3 (NT~N) ~ H2COONa ~ANa2) Disodium (N-2-acetamide)iminodiacetate (MANa2) can be converted to ~N-2-acetamide)iminodiacetic acid hydrochloride (~ HCl) by reacting it with hydrochloric acid according to the reaction represented by the following equation:

f H2CONH2 f H2CONH2 N \ H2COON2 3XC;~ HCl .~----CH2CGOH + 2NaCl ~CH2COONa CH2COOH

( ~ia2) (M~ XCl~

" ` '` 10~71~41 (N-2-acetamide)iminodiacetic acid hydrochloride can be converted to free ~N-2-acetamide)iminodiacetic acid ~MA) by reacting it with a stoichiometric amount of sodium bicarbonate (sodium hydrogen carbonate) according to the following equation: --2 H2 f H2CONH2 HCl~N---C~2COOH + NaHC03 ~N--CH2COOH + NaCl + H20 + C02 \C~2COOH \~ H2CH
(M~-~Cl) ~A) MA, which is also known as N-(acetamide)-iminodiacetic acid (AIA) can also be prepared by a process comprising preparing a solution of NTAN by dissolving 67 g (0.5 ~ole) of NTAN i~ 200 g of water at 95C and adding thereto one mole (40 g) of sodium hydroxide dissolved in 200 ml of water while maintaining the resulting mixture at about 95C. It is desirable that the sodium hydroxide be added slowly --while stirring the solution to which it (the sodium hydroxide solution) is added. After all of the sodium hydroxide - has been added the resulting mixture should be maintained at about 95C until evolution of ammonia has been completed;
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this requires about 2-3 hours. The resulting ammonia free solution is cooled to about 20C and its p~ is adjusted to 2 by adding 18 molar sulfuric acid thereto to precipitate the product ~A as the free acid - i.e., as CH CONH
N ~ H2COOH

.: ` CH2COOH .

~ 6 ,'. ~ ' .

~071841 -~ DANa is known to those skilled in the art. It can ~e converted to DA HCl by treating with hydrochloric acid, and DA~HCl can be converted to DA by treating with NaHC03. The following e~uations represent the reactions involved:

~CH2CON~12 N CH2CONH2 ~ 2~Cl ~ HCl- \ H2CONH2 + NaCl -\ C~2COONa t CH2COOH

(DANa) - (DA HCl) 2CON$2 ~C~I2CON~12 HCl-N ~ C~2CONH2 + NaHC03~N - C~2CON~2 + NaCl + ~2 ~ C2 CH2COOH . H2COOH
(DA-~Cl) (DA) Sodium chloride is well-known article of commerce.
Unfortunately, sodium chloride, which is usually sold and shipped in particulate form, has a decided tendency to cake-especially where exposed to a humid atmosphere such as that prevailing in California in the wintar time and in the - , ~
eastern part of the United States in the summer.
This invention relates to a procedure which I have developed for substantially eliminating the caking tendency of sodium chloride including the tendency of sodium chloride to cake when it (the sodium chloride) is exposed to a humid atmosphere.
The method comprises admixing the sodium chloride with an amount of ."~ or DA effective for e7iminating (or 107~841 s~b`stantially eli~unating) the ~endency of the particulate sodium chloride to cake.
Preferred methods for admiv.ing particulate sodium chloride with MA or DA include; ~a) crystalizing sodium chloride ~rom a brine containing the MA or DA; and (b) treating the particula.e sodium chloride with an aqueous solution of MA or D~.
In either method the sodium chloride is admixed with an amDunt of MA or DA effective for reducing the caking tendency af the sodium chloride. The amount of MA or DA
used is not critical and a finite amount produces a finite reduction in the caking tendency of sodium chloride. However, I have found that the best results are obtained where using about 10-1000 parls of .NA or DA per million parts of sodium chloride. Quantities gre_ter than 1000 parts of MA or DA per million parts of s-dium chloride do not produce any greater improvement i the caking tendency of the sodium chlori~e than do 1000 par s. Hence, while much greater quantity than 1000 parts of .~A or DA per million parts or sodium chloride can be used no advantages can be obtained in so d~ing. Also, it was found that when the quantity of MA or DA used is less than about S parts per million parts of sod~um chloride the effect (improvement in caking tendency to particulate so~ium chloride) is somewhat diminisned.
The M~ or DA can be added as; (a) the free amide;
(b) as an acid salt (e.g., as the hydrochlorlde of DA or MA, as the acetat~ of DA or 1~, as a sulfate o~ DA or ~, as a phosphate of DA o_ MA, or the like); or (c) as an al~ali metal (preferably sodi~m) or a~..onium salt (e.g., as a sodium ;

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' salt of DA or MA, as an ammonium salt of DA or MA or as a .
potassium salt o~ DA or ~
It has been ~ound that MA, ~ hydrochloride (MA-HCl) and the sodium salt of MA (~u~a2) are equivalent for ,, rendering particulate sodium chloride substantially non-caXing and for modifying the appearance of crystalline sodium chloride. Thus MA-~C1 or MANa~ can be substituted for MA
on a le f,or mole basis in my process and in my composition.
It ~as also been found that DA, DA hydrochloride (DA-~Cl), and the sodium salt of DA (D~a) are equivalent for rende~ing sodium chloride substantially non-caking.
T~us DA-~Cl or DANa can be substituted for L~A on a mole for mole basi,s in my process and in my composition.
Accordingly, it is understood that where I state ~A
herein equivalent results can be obtained by replacing all -or part o~ the MA with MA ~Cl or MANa2. It is also understood that where I state D~ herein equivalent results can be obtained ~y replacing all or part of the DA with DA-~Cl or DANa.
The instant invention will be better understood by referring to the,f~ollowing specific but non-limiting examples. It is understood that said invention is not limited to these examples which are offered merely illustrations; it is also understood that mod'ifications can be made without departing from the spirit and scope of the invention.

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`` 1071841 EXA~LE 1 , . , A 0.2 g portion of MP was dissolved in 6 ml of water.
- Said solution was admixed with a 200 gram portion of particulate reagent grade sodium chloride having a particle size substantially the sa~e as that of ordinary table salt.
This provided lO0 parts per million of ~ based on ; ' the weight of the sodium chlori'de. The thus moistened sodium chloride was well mixed, formed into a cake having diameter of about 2 3/4 inches, pressed with a pressure of about 2-3 psig and allowed to dry for 24 hours at room temperature (ca 25~).' ' A blanX or control was run using the identical -; techni~ue except that 6 ml of water rather than 6 ml of,the solution of MA in w ter was used to moisten the sodium chloride.
' The relative hardness of the resulting cakes was ;' compared by dropping the cakes from a height of about 18 inches onto a stone tabl~ top. The c-~ke made from the, . , sodium chlori,de treated with the ~A broke into small particles while the cake made b~I treau~Rnt with water (without the MA~ remained intact when dropped onto the , same table top fro~ the same height.
: In the above run the MA used was the hydrochloride of ~, MA. Identical results were obtained when the hydrochloride was replaced with the free MA, and with the sodium salt of MA, using in each instance 100 ppm of the ~ moiety ~f H2CONEI~

~N'~CX2COO

- ~ C~ COt~

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O

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.~ -base~ on tha weight cf the sodium chloride.
Identical results were obtained in the runs ~here using 10, 50, 500, 1000, and 10000, ppm o.f MA. Identical results were also obtained where the MA was added as MANa2 and as MA-HCl-rather than as MA per se.

The general procedure of ~-xa~ple 1 was repeated; however, in this instance the procedure was modified by replacing the MA with DA (added as the hydrochloride).. In this instance the caXe of sodium chloride which was treated with DA at the rate.of 100 parts of DA moiety ' / C~2C

~ N~C~I2CONH2 J
CX2COO~
per million parts of sodium chloride broke into small f-agments when dropped from 18 inches onto a stone table top.
The sodium chloride particles which were prepared by treating par'ticulate sodium chloride with aqueous DA
were observed to be opa~ue cubes rather.than clear cu~es ~-while sodium chloride particles treated with water were ;. clear cubes.
: Identical results were obtained where using 10, 50, SOO, and 1000, ppm of the DA moiety.
Identical results were also obtained where the DA was added as the sodium salt and as free DA applied at the rate of 50, 500; and 1000 ppm of DA moiety.

-DA, added as hydrochloride, was admixed with a saturated sodium chloride brine in an amount to provide 100 parts of "
~he DA moiety per million parts of sodium chloride present in the saturated sodium chloride brine.
A small portion of the brine was allowed to evaporate slowly in a watch glass. Incipiient crystallization was obser~ed under a 40 power microscope. The resulting crystals were opaque cubes while crystals fro~ a blan~
~or control run) in which the DA was omitted were perfectly clear cubes.
Similar results were obtained when the DA was added as the sodium salt and as free DA.
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The general procedure of Example 3 was repeated.
~owever, in this instance the DA was replaced with MA
(added as the hydrochloride). Crystals obtained rom the brine treated with MA were perfectly clear ~ut, the corners of the cubes were ~lopped off" to produce 14 sided particles.
Crystals obtained in Example 1 from sodium chloride which had been treated with ~A were found, on examination under the microscope to be cubes with the corners lopped off (i.e., 14 sided particles). On the other hand, sodi~m chloride particles which had been crystallized from water without an additive present (the control run of Exam?le 1) were perfectly clear cubes.

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107184~

' E~AMPLE 5 Sodium chloride wa crystallized from a 100 gallon batch of brine (drawn from a lot of nearly saturated sodium chloride brine) by evaporating water therefrom. Before starting the evaporation ~ was added thereto (as the hydrochloride salt) in an amount to provide 100 parts of the MA moiety per million parts of sodium chIoride present in the brine (i.e., the NA moiety was provided at a rate of 100 ppm).
The recovered sodium chloride crystals were clear, but the corners of the cubes were ~lopped o~f" to produce 14 , sided particles.
; A 200 g portion of said recovered sodium chloride was admixed with 6 ml of wat~r, formed into a cake having a diameter of about 2 3/-i inches, pressed under a pressure of about 2-3 psig, and dried for 24 hours at room temperature.
The dried cube of said r~covered sodium chloride broke into small particles whe.l dropped onto a stone _able top from a height of 18 inches while a similar cake made from sodium chloride crystals ~clear cubes) recovered from the same lot of brine but without the .~A additive remained intact where dropped onto the same table top from tne same height.
Identical results were obtained where using 10, 50, 500, and 1000 ppm of the MA moie~y added 25 the hydrochloride.
Identical results were also obtained where the ~A hydrochloride was replaced with MA per se (free MA) and with the sodium salt of ~ hNa2).

~ In each instance where testing sodium chloride particles recovered from-brine in which the MA moiety was present in amounts greater than about 5 ppm based on the sodium chloride content of the brine a cake fo~med by admixing 6 ml of water with 200 g of the sodium chloride crystals pressing the cake under a pressure of about 2-3 psig, and drying the cake for 24 hours at room temperature broke into small pihces when dropped onto a stone table top from a height of 18 inches thereby establishing that the MA moiety rendered the particulate sodium chloride non-caking. Such sodium chloride (that recovered from the MA-containing brine) was a free flowing particulate solid.

Sodium chloride was crystallized from a 100 gallon batch of brine (taken from a lot of nearly saturated sodium chloride brine) by evaporating water therefrom.
Before starting the evaporation DA was added thereto (as the hydrochloride salt) in an amount to provide 100 ppm of the DA moiety per million parts of sodium chloride present in the brine.
The recovered sodium chloride crystals were opaque cubes while sodium chloride crystals recovered from the same lot of brine but without an additive (3A or ~A) were clear cubes.
A 200 g portion of said recovered sodium chloride was admixed with 6 ml of water, formed into a cake having a diameter of about 2 3/4 inches, pressed under a pressure ; ~071841 of about 2-3 psig, and dried for 24 hours at room temperature. The dried ~ake of recovered sodi~m chloride broke ~nto small particles ~hen dropped onto a stone table top from a ~eight of 18 inches while a similar cake made form sodium c~loride recovered from the same lot of brine but without ~he DA remained intact where dropped onto the same table top ,from the same height.
Identical results were obt~air.ed where using 10, 50, 500, and 1000 ppm of the DA moiety added as the hydroch}oride.
Identical results were also obtained where the DA hydrochlori~e was replaced with DA per se and with the sodium salt (DANa).
In each instance where the DA moiety was present in amounts g,reater than about 5 ppm based on the sodium chloride content of the brine a cake formed by admixirg

6 ml of w~ter with 200 g of the sodium chloride crystals pressing the cake under a pressure of about 2-3 psig, and drying the cake for 24 hours at room'temperature broke into pieces when dropped onto a stone table top from a -~
height of i8 inches thereby establishing that the DA
moiety rendered th~ particulate sodium chloride non-caking.
Such sodium chloride (that recovered from the DA-containing brin~ was a free flowing particulate solid.

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~07~84~
In no instance were the crystals obtained in any of the above runs dendritic.
~ s used herein, the ~erm "mole" has its generaily accepted meaning, that is a mole of a substance is that quantity of the substance which contains the same number o molecules of the substance as there are atoms in 12 g of pure 12C.

As used herein,.the term "percent (%)" means parts per hundred.

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As used herein, the term ~parts n means parts by weight.

As used herein, the term n g~ means gram or grams.

: As used herein, the term "ppm" means parts per million.
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As applied to MA the term ppm means parts of the MA moiet y 2cONH2 ~ \CX2C
~ C~2COO ~ per million parts of Na l;
and as applied to DA the term ppm means p~ ts of the : DA moiety I ,~CH2CONH2 ' ~N~CH2C~NH2 J
~ CH2COO ~ per million parts of NaCl.

As used herein, the term "psig" means pounds per square inch, gauge pressure.

As used herein, the term "MA" means (N-2-acetamide)-.. i~inodiacetic; its formula is ~ H CONH
N ~ CH2COOH
`CH2COOH -As used herein, the term "DA" ~.eans N,N-bis(2,2'-acetamldo)glycine; its fo~ula is H2CON~i2 N;~cH2coNH2 : `CH2COOH .

As used herein the term "room temperature" means about 2Q-28C.
As used herei~, the ter~ "~ hydrochloride (or MA-~Cl)-n means HCl-N \ CX2COOH

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As used herein, the term "DA hydrochloride (or DA ~C13 n ~ means ~CE2CONH2 ~ECl N ~ H2CONH2 ~2COOH

As used herein, the term "sodium salt of MA (or NE~Ja2) n means /CH2CO~H2 \ 2 - CH2COONa ~:

., , As uaed herein the term "sodium salt of DA (or DA~a) n - - -means f H2CONH2 N ~ CH2CNH2 ~CH2COONa :' .

Claims

The embodimetns of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for preparing crystalline sodium chloride having a modified appearance comprising crystallizing the sodium chloride from a sodium chloride brine containing an amount (N-2-acetamide)iminodiacetic acid or N,N-bis (2,2'-acetamido)glycine effective for causing the product crystalline sodium chloride to have a modified appearance, said product crystalline sodium chloride being substantially non-caking.