CA1066835A - Process for producing powdery water-soluble polymer - Google Patents

Abstract

Title of the Invention:

PROCESS FOR PRODUCING POWDERY WATER-SOLUBLE POLYMER

Abstract of the Disclosure The aqueous gel of water-soluble acrylic polymer is mixed with a water-unsaturated salt such as anhydrous sodium sulfate, and the water component of aqueous gel is dehydrated as crystal water of said salt, then the polymer is easily powdered.

Description

113 6~:i83~

PROCESS FOR PRODUCING POWDERY I~ATER-SOLUBLE PO~YMER
Background of the Invention:

The present invention relates to a process for producing a powder of a water-soluble polymer from the hydrated water-soluble polymer with a water-unsaturated salt.
Acrylic water-soluble polymers have been widely applied in various industrial fields. The term "acrylic" in the expression "acrylic water-soluble polymers" is used in the sense which includes both the polymerized acryllc radica:L and the polymerized methacrylic radical. Polyacrylamide is an example of an acrylic water-soluble polymer, see Billmeyer, Textbook of Polymer Science, Second Edition, 1971, pages ~09-414.
For example, the acrylic water-soluble polymers have been used for agents for paper manufacture e.g. a paper strength re-inforcing agent, a filler retaining improver, a filtration free-ness improver and the like; flocculants or clarifying agents for industrial drainage or sewage and flotation reayents.
These water-soluble polymers have been commercialized as dry powder or viscous solutions.
The viscous solution of the water-soluble polymer has high viscosity and it is hard to transport it by a pump and is not easily treated in an operation. It is necessary to impart high speed mixing for dissolving the water-soluble polymer whereby a deterioration of the polymer is caused.
When the water-soluble polymer is in a powdery form, the transportation cost is low and the treatment in an operation is easy. Accordingly, various proposals for forming powdery water-soluble polymers have been found. `~
In order to produce powdery water-soluble polymer, it is effective to use a solution of the polymer having a high concen-tration.

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66~335 In order to produce the solu-tion of the polymer having a high concentration, it is usual to consider an aqueous pol~merization in a high concentration; an emulsion polymerization in a hiyh con-centration; a dehydration by a salting-out or a solvent-extraction after a polymerization and the like.
However, it has been hard to produce the powdery water-soluble polymer wi-thout a deterioration of the polymer even by said methods.
In general also, the ~dhesion of particles of the acrylic water-soluble polymer can be prevented by decreasing the water content of the polymer to less than 3Q wt~ %, and the polymer can then be crushed to form non-adhering powder~ ~ `

However, the acrylic water-soluble polymer which is produced by the aqueous polymerization in a high concentration will sub-sequent dehydration by salting out, contains more than 30 wt.~ of watar content.
It is necessary to dry it to form the powder.
The acrylic water-soLuble polymer produced by the emulsion polymerization contains~ large amount of water and is a viscous 20 solution which is not easily dehydrated by a filtration. ~ ~`
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It is quite hard to polymerize the monomer at higher than 70 wt.~ of the monomer content by aqueous polymerization becausc of the need for cooling in view of polymerization heat and the high viscosity of the polymer solution.

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~ It has been known to dri~ the water-soluble polymer by a heat : ~:
drying method, a solvent extraction method, an azeotropic distil- `

lation method etc..
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~ ~ In the heat drying method, the powder is produced by heating : :. :
to evaporate the water component.

~ ~30 The acrylic water-soluble polymer is ~rosslinked by the heat-;~ ing to produce a water-insoluble form, and is deteriorated b~

~ cracking of the polymer:
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~1366~335 In the solvent extraction method, the water conten-t is extracted with methanol.
A large amount of combustible material is used causing various troubles in safety and operation. Moreover, it involves high cost because of expensive solvent.
In this case, it is necessary to remove -the solvent by heating, and accordingly a deterioration of the polymer is caused.
In the azeotropic distillation method, it is necessary to heat it, and to use a solvent and accordingly, there are the troubles of deterioration of the polymer and a safety problem and an economical problem.

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Summary of the Invention It is an object of the present invention to provide a process for producing a powdery acrylic water-soluble polymer by removing the water component of the polymer as a crystal water of the salt hydrate by using a specific water-soluble inorganic salt without a heat-drying step so as to prevent a deterioration of the polymer and accidental combustion and to be economical and to achieve an easily performed operation.
The object of the invention can be attained by the present process for producing from a hydrated water-soluble acrylic polymer containing more than 30% water content a water-soluble acrylic polymer in powdery form.

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~66835 The process comprises mixing the hydrated wa-ter-soluble acrylic polymer with a sufficient amount of water-unsaturated salt capable of tak.ing up at least 5 mole-cules of water of crystallization per molecule of salt and which is selected from the ~roup consi~ting of anhydrous sodium carbonate, sodium carbonate monohydrate,;:-anhydrous sodium sulfate, anhydrous magnesium sulfate, -magnesium sulfate ~onohydrate, anhydrous magnesium carbonate and anhydrous aluminum sulfate in an amount sufficient ;~
to remove a sufficient quantity of the water component of .
the hydrated acrylic water-soluble polymer as water of ;~:.
crystallization of a saturated salt hydrate of the salt.
This decreases the water content of the hydrated polymer :
to less than 30% and produces a crushable mixture without ~.
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heat drying of the acrylic polymer, with the water-unsaturated salt being the sole agent employed for decreasing the water :
content of the hydrated polymer. .-.
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Descri~tion of the Embodi~ents~

The acrylic water-soluble polymers include polymers. :-: .
:20 and co-polymers of sodium:acrylate, acrylamide, methacrylamide, : .:
~ a lower alkylamino methacrylate, a quanternary ammonium salt ~.

: : :~ thereof.

: : The acrylic water-soluble polymers has an...avera~e ;molecular:weight of lQ4 - 10 preferably 105 - 10 . ..

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: ~ : : : ; , : ,, .. ;
~ 4 . ~ . .
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~ ~ ` ; : ' ~: ' Typical polymers are polyacrylamide and polyalkylamino-alkylmethacrylate and copolymers of acrylamide and quaternary ammonium salt of dialkylaminoalkylmethacrylate at desirable ratio.
The other typical polymers are par-tially hydrolyzed poly-acrylamide, copolymers of sodium acrylate and acrylamide, sodium polyacrylate partially hydrolyzed polymethyl acrylate.
It is possible to use modified polymers prepared by modifying said polymer with a modifier by the conventional me-thod disclosed in Industrial and Engineering Chemistry Vol. 48, No. 12, Pages 2132-2137 (December 1956). Examples of the modified polymers include Mannich derivative of polyacrylamide which are reaction products of an amine and formaldehyde with polyacrylamide.
The words 'water-unsaturated salt' as used in the s~ec-ification means a salt having less than the maximum water of crystallization; and the words 'saturated salt hydrate' means a salt having the maximum water of crystallization. Take the ex-ample of sodium sulfate in ordeL to illustrate this more clearly.
Na2S04 and Na2S04 7H20 are water-unsaturated salts and Na2S04 10H20 is a saturated salt hydrate.
The water-unsaturated inorganic salts used in the invention include anhydrous sodium carbonate, sodium carbonate monohydrate, anhydrous sodium sulfatej anyhdrous magnesium sulfate, magnesium sulfate monohydrate, anhydrous aluminum sulfate and the like.
The particle diameter of the salts is usually in a range of 1~ -; ~S~mm preferable 10~ - 1 mm.
.
It is preferable to use a neutral salt such as sodium sul~ate.
When sodium carbonate is used, the polyacrylamide or poly-methacryl amide may be partially hydrolyzed.
When the water-unsaturated salt is contacted with water at room temperature, the state of the crystallization water of the salt is changed~

5 _ ~6t~,835 The water-unsaturated salts usecl in the invention take water or crystalliæation of fi~e or more than Eive molecules of water per 1 molecule of the salt. ~'or example, the crystal water can be taken in to form MgCO3-5M2O; Na2CO3-10~12O; '~
Na SO lOH O; MgSO~-12H2O; AQ2(SO4)3 18~I2O
less than five molecules of water as crystal]ization water per 1 mol,acule of the sal-t is not effective because the ratio oE
the salt to the polymer is too high. r-:
The water content of the acrylic water--soluble polymer is 10decreased to less than 30 wt.~ in accordance with the invention.
The amount of the water-unsaturated sa:Lt added to the polymer is dependent upon the temperature, and ~he contacting ~ ~ ;
time etc., and is usually at least theoretical amount for r decreasing the water content of the polymer to less than 30 wt.%
preferably less than 20 wt.%.
The theoretical amount can be calculated from a difference between the water of crystallization of the salt and the maximum , water of crystallization of the salt. The mixture of the polymer and the. salt can be separated by methods utilizing a difference 20of specific gravity or a difference of particle size or an electrostatic separating method and the like However, it is possible to use the mixture without any separation.
The acrylic water-soluble polymer and the water-unsaturated inorganic salt can be contacted as follows.
,-,- .. .
When the~polymer is a massj the polymer is extxuded rom p -a meat chopper to form granules having a diameter of about 0.5 - ~ mm to 1 cm preferably 1 mm - 3 mm~

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` ~L0~6~335 The water-unsaturated salt is mixed with the granules o~
the polymer in a blender and the resulting mixture is crushed to be the particles having a diameter of 1~ - 1 mm.
~ When the polymer is in a ~orm of a sheet having a thlckness of 1 - 10 cm, it is admixed with the watex-unsaturated salt and the mixture is kneaded in-a kneader and the resulting mixture is crushed.
~ When the polymer is treated by salting out, the polymer is cut to pieces and is mixed with a salt for salting out. The 10 separated polymer is formed to granules havin~ a diameter o~ -1 mm - 5 cm and the granules of the polymer is mixed with the water-unsaturated salt in a blender. The mixture was crushed.
When the polymer is in a orm o~ an emulsion dispersed in a solvent, the solvent is removed and the resulting mass of the polymer and the water-unsaturated salt are kneaded in a kneader and the mixture is crushed.
; The composition of the acrylic water-soluble polymer-and the salt hydrate is crushed to 5 - 200 mesh preferably 10 - 100 mesh.

2~0 ~ ~ In accordance with the invention, the powdery acrylic water-soluble~polymer~ and lts production have the advantages that no deterioration of the polymer is caused because there is no he~at drying; the~production is easy; no~accident is found in the~production; the polymer is easily soluble~because of the remaining saLt no oomplicated process is required~and cost of the~apparatus~for~the production~is low.
The lnvention wil1~be~il1ustrated by certain examples.
In the examp1es, the term of "part" designates "part by , : .

~Q66~335 weight".
EX~MPLI~

~ 3 parLs o~ ~nllydrous sodium sLllîa~c wa~s added lo ~) pal~tx o~ v~.%
of aqueous solution of polyacrylamide. 'I`~le Illixtul~e was kept at ~0C
and was crushed for 2 - 3 minutes under al~out 3, 000 rpm in a Z liter . .
crushing vessel equipped ~Y.it}l a rotary cutter at the bottom.
After` the crushing operation, the polymer was separated from water by a screen. The resulting polymer composition had an average diameter of 1 mm and contained 28 wt.% of polyacrylamide, 56 wt, % of water and 16 wt. % of the salt.
A 3 parts of the polyacrylamide composition conLaining t}le watcr COIIl-ponent ~vas mixed with 1. 3 parts of anhydrous sodium sulfate to form uniform surface, and the mixture was cooled at lower than 30C and was };ept for~24 hours. The polyacrylarnide was separated from the salt .
by USillg a 10 mesh sieve.
~fter the sieve, the compos~ion re~aining on the 10 mesh ~:
sie~e con~ained 45 wt.~ of polyacrylamide, 10 wt.% of water and 45 wt.~ of the salt hydrate. :
The composition was crushed to obtain tlle powder havi~lg an averagc diameter of 0 . 02 mm. The resulting powder had Quiclity retaining the powdery condition. The powdery conditiQn wa,s kept arter 1 month and ~he~solubi~lity in water was observed to have been excellent.
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EXAMPLE 2:
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A 60 g of acrylamide was added to 140 g of water and 1. 2 g of l~o of aqueous solution ammonium persulfate and 0. 5 g oî 1% of aqueous .
solution sodium bisulfite were added in a nitrogen gas atmosphere to ~ -- polymerize it to orm a sheet having a thickness of 1 Cnl.
A Z00 g of anhydrous sodiurn sulfate was added to the resultirlg polymer and the mixture was mixed for 3 hours to obtain powder having no tacki-~ , ~
30 ness. The mixture was separated by an air-flow method by the diffe-rence of specific gravity of the salt hydrate and the polyacrylamide ; to obtain the polyacrylamide COlTlpOSitiOn.
The p~olyacrylamide composition was crus}led to o~tain a powder having an average diameter of O. OS mm which contained 5Z wt. % of polyacryl-amide, lZ wt.% of water and 36 wt.~o of the salt hydrate. -~) - 8-~6~33~;
The powder had fluidity and tlle powdcry condi~ion was Icept after l ~, month and the solul~illty inwater was e.Ycellerlt.

E~ l l'L13 3:

In a 1 liter three n~clced ~lask, :lS g Or acrylami~le ~vas (~issolvccl ill 35 g of ~vater and 400 Int of xylene and 1. 5 g of sc)rl~ilan mono-pallllitate were added and the mixtllre was stirred to expose to nitro~cn gas for 20 minutes.
The polylnerizat;on was conclucled al 3()"C by a(ldi~ r 0.()1~ g of ben%oy~
peroxide .
After 6 hours from the initiation of tlle polymelizatiorl, all elllulsio polymer was obtained.
A 100 g of sodium carbonate was addecl -to the polymer and the mixture was stirred and was kept at room temperature for Z~ minutcs.
Then the xylene was :Eilter~d to obtairl yolyacrylamide. The polyacrylamic~e was crushed to ob tain powder having an average diameter of 0.05-1mn which' contained 10 wt.~ of,polyacryl'amide,

3 wt~ % of water and 87 wt. % of the salt hyd~ate.
The powder had fluidity and the po~vdery con-lition was l~e~ t afLer 1 molltll.
. -EX~MPLE ~

In a 1 liter separable flask, 385 g of a deioni7,ed water as charged and 106 g of acrylamide, 171 g of diethylaminoethylmethacrylate and 38 g of -' sulfuric acid were dissolved. , After removing oxygen from the mixture by bubl~ling nitrogen gas, 4 mQ
of 1% aqueous solution o ammonium persulîate ancl 4 mQ of sodium bi-- ~ sulfite u~ere add~ed to the mixture to polymerize it.
The resulting polymer ~vas extruded from a lneat choppel to obtain granules of the polymer havin~ a diameter of 1. S mm.
The granules of the pol~ner was admixed with 1. 5 times of anhydrous ~ ' .
magnesium sulfate alld tlle mixture was mixecl for 10 llours alld was cruslled. , ' -::
The resulting powder was dried in a vacuulll clesiccaLor to measure tlle water content.
The composition corltained 18 wt.% of the col~olymer, ~ ~vt.% o~ ~valer ~`, ' and 78 ~vt. % of tlle salt hydrate.
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Claims (10)

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

1. A process for producing from a hydrated water-soluble acrylic polymer containing more than 30% water content a water-soluble acrylic polymer in powdery form which comprises mixing the hydrated water-soluble acrylic polymer with a suffic-ient amount of water-unsaturated salt capable of taking up at least 5 molecules of water of crystallization per molecule of salt and which is selected from the group consisting of anhydrous sodium carbonate, sodium carbonate monohydrate, anhydrous sodium sulfate, anhydrous magnesium sulfate, magnesium sulfate monohydrate, anhydrous magnesium carbonate and anhydrous aluminum sulfate in an amount sufficient to remove a sufficient quantity of the water component of the hydrated acrylic water-soluble polymer as water of crystallization of a saturated salt hydrate of the salt so as to decrease the water content of the hydrated polymer to less than 30% and to produce a crushable mixture without heat drying of the acrylic polymer, the said water-unsaturated salt being the sole agent employed for decreasing the water content of the hydrated polymer.

2. A process according to Claim 1, wherein the water-unsaturated salt is anhydrous sodium sulfate.

3. A process according to Claim 1, wherein the water-unsaturated salt is selected from anhydrous sodium carbonate and sodium carbonate monohydrate.

4. A process according to Claim 1, wherein the water-unsaturated salt is selected from anhydrous magnesium sulfate and magnesium sulfate monohydrate.

5. A process according to Claim 1, wherein the water-unsaturated salt is anhydrous aluminum sulfate.

6. A process according to Claim 1, wherein the water-soluble acrylic polymer is selected from polymers and copolymers of sodium acrylate, acrylamide, methacrylamide, dialkylamino-alkylmethacrylate and quaternary ammonium salt thereof, and a Mannich derivative of polyacrylamide obtained by reacting formaldehyde and an amine with polyacrylamide.

7. A process according to Claim 6, wherein water-soluble polymer is polyacrylamide.

8. A process according to Claim 1, wherein water-soluble polymer is partially hydrolyzed polyacrylamide.

9. The process of Claim 7, wherein the water-unsaturated salt is an anhydrous salt and the anhydrous salt is added to crushed hydrated polymer.

10. The process of Claim 7, wherein the water-unsaturated salt is an anhydrous salt and the anhydrous salt is added to the polymer, a powder is produced, polymer is physically separated from at least a portion of the salt hydrate produced from the anhydrous salt, and the separated polymer is crushed.