Note: Descriptions are shown in the official language in which they were submitted.
A. FIELD OF T~E INVENTION
The present invention rel~es to a process f~r trea-ti~g
aqueou solutions or mixtures of acrylic polymers by
` adjusting the pH of the mixture or solution so that the
.~ acrylic polymers are precipitated from the mixture or
solution.
,
~s : B. BACNROUND OF THE INVENTION
:
~ isp~sal of the aqueous acrylic polymer solutions or
mixtures has historically ~een performed in two ways. 1) It
has been diluted and sewered. With increased environmental
1~ c~ncerns this option is no longer acceptable in many areas~
2):Waste treatment firms have degraded the solutions or
mixtures either chemically or bioligically. The ~acilities
: required for such treatment of the wa~te is expensive and is
reflected in the disposal cosit.
Rothman et al. in Canadlan patent 1 238 146 describes
method for separating polyacrylic acids from aqueous
,t,~:,." :''`"':`'`: ''ii; ~ ' ; i
2 ~
solu-tions by modifyinc~-the p~ of the so:lu-tion and
~ubsequ~ntly ~dsorbing the acid. This pro~ess dj.ffers
undamentally from the process ob-tained from -this in~en-tion,
The object of modi~ying the pEI in the pro~ess des~ribed by
Rothman et al. is to charlge the lonisat.ion of the aeid so
that it can be adsorbed~ Precipitation of the polymer is
not taught and would i~telfere with the adsorption of the
acid.
The proces~ of precipita-ting the acrylic polymers rom
the solution or mixture by modifying the p~l of th~ solution
or mixture is new and has not been suggested in the
techni~al literature.
.
C. SUMMARY OF THE INVENTION
. . _
The present invention provides a process for separa-ting
the acrylic polymers from the aqueous solution or mixture in
which they are contained. The process comprises: 1~ adding
an acid in the range from 0~01 to 100 weight perc~nt basPd
on the w~ight oE the acrylic polyme~/ 2~ adding a
.1 flocculating agent, surfac-tant or other chemical to modi~y
the n~ture of the precipitated mass; and 3) separ~ting the
~, precipitated ma~ by filtration, decantation, centrifu~ation
;.1 or similar proce~s~
1 Aqueou~ solutions or mixtures of acrylic polymers are
;~3~ frequently used to make acrylic ~ilms~ For example, in the
~i~ printing indu~try a layer of an acrylic polymer solution or
mixture is applied over the printed matter. The printed
matter with wet acrylic overcoating is dried so that a
glosæ-iike film i~ produced over the printed matter.
! Howe~er, wa~te water streams containin~ acryli~ polymer
solu~ion.~ or mixtures is a hazardous waste. Disposal of
uch waste stream is expensive. Thi~ invention change~ ~he
~1
. ~ :
'! :
(, ~ : ~ :
. ' ~ .
~ ~ 7 ~
physi~al state of the acrylic w~ste fr~m a solution o~
mixture to an insoluble 501icl. ~nder current regulations,
as an i.n~oluble solid, it i~ a non-hazarclouici waste.
Probably the most com~on a~rylic polym~r is the
polym~rized ester o~ methyl methacrylate. The present
invention is not limited to solutions o.r mixtures o:E methyl
methaicrylate polymers, but applies to any acrylic polymer~
Naturally, if such acryli~ poly~er solu~ions or
mixtures contain in~redients ~hich are to~ic or hazardous,
the waste stream which contain~i tho~io toxic or hazardous
ingredients i.s toxic or hazardousO
D. _ETAILED DESCRIPTION
To the aqu ous solution or rnixture of acryli~ polymers
the flocculating agent, sur~actan-t or other chemical ~any
chemical desired which influence~ the precipitation of the
acryli.c polymer3~ is added in the quantity required to
achei~e the desired effects. Flocculating ag~nts and
surfactants are usually ad~ed in quanti$i~s ranging ~rom
0.001 to 20 weight percent bacied on the weight o~ acrylic
polymer in the s~lution or mixture, and preferably in
quantities ranging from 0.01 to 10%, and even more
prePerably in quantities ranging ~rom 0.01 to 3%. The
soluti.on or mixture is well ~itirred to ensure proper
distribution of the chemicals added ~
i
I ~ After addition of on~ or more of the chemicals liited
~:~ above, an acid i~ added to precipitate the acrylic polym~r.
~: ~ The acid used can be from the category of either mineral cr
organic acid~. Preferably an organic acid is used and of
the organic acidi~ acetic acidi is preferred. The amount of
~7~
acid to be ~dded depenclis on -~he c~Jmposltion oE -the isolu-~ion
or mixture, on the type of ac~ylic polymer p~esen-t and on
the acid chosen. Typically, when using acetic acid, between
.01 and 100 weicJh-t percent basecl on the weight of acrylic
polymer is added, and preferably less -than 50~, and even
more preferably between 0.1 and 10%o
After addition of the acicl a white precipitate is
observed. The precipita-te can be removed from the solu-tion
or mixture by filtering with a fast filter paper.
Al-ternately the solution or mixture can be decantecl leaving
the precipitate in the reaction container. The precipitate
is of a nature that it can easily be separated from the
solution or mixture using solid/liq~icl separating methods
well known in the ~rt.
Accepta~le re~ults were obtained when proce~sing
according to the examples tabllla-ted below:
E~Ie 1
i
i A~ aqueous mixture containing short to meclium chainecl
acrylic polymers was obtained from a printing plantc The
mixture is used by the printing plant as a water based
overcoat. The mixture was analyised and containecl 54%
acrylic by weightO The mixture was opaque, white and had a
vi~cosity of approximatly 500cps.
About ~50 mls of the solution was treatecl with 250 mls
o 5% acetic acid. A separation occured i~mediatly
i following the addition of the acid. The precipitate was
gravity filterecl and driecl~ Once dry it was in the ~orm of
a single white and solid mass. Analysis of the liquid and
of the precipit~te showed that 100~ of the acrylic polymer
~ wa~ recovered.
1 ~;
~ E~a~le 2
_ _
To the sarne aqu~ouZ3 mixture aZ3 in example 1~ 041% hasecl
on the weight of the acrylic polymer of sodium lauryl
sulphate was added. The same amount of the same acid was
subsequently added. The yield was the sa~e, and a loo~er
product was obtained after drying than in example 1.
Example 3
A polyacrylate known under the trade name C~lsize VR
and manufactured by Allied Colloids WciS diZ~Zsolved at 10%
:` sZolids in water. The viscosity was about aocps. To 250 mls
of the polyacrylate Z~olution 25d mls ~f 5% acetic acid waZ~
added. The precipitate was reco~ered in the same fashion as
~l in example l-
Example 4
Using the Zs7lame aqueous mixture as in example 1, 0.5~,
based on the weight of acrylate, of sodium stearate was
J adAed, The Zsame amount of the Z3ame aZicid as in example 1
were added~ The results were the same as for e~ample 2.
le S
,~ ; : Following the ~Zame proceaure as in example l, the
Z~ : acetic acid was replaced with 100 mis of 2% ~Cl. The
resultZs obtained were the same as in sample 1.
~Z~
