Note: Descriptions are shown in the official language in which they were submitted.
2173168
.,
METHODS FOR SUPPRESSING DUST EMISSIONS
FIELD OF THE INVENTION
The present invention relates to methods for suppressing fugitive
dust emissions from dust producing bulk solids by applying a polyvinyl
5 alcohol graft copolymer.
BACKGROUND OF THE INVENTION
Dust dissemination poses safety, health and enviro"",ental prob-
10 lems in many commercial environments. For instance, in many indus-
tries, such as mining, mineral processing, agricultural, power, steel and
paper, the transportation, handling and storage of bulk solids is common.
One major problem associated with bulk solids is dust generation and the
subsequent emission of the dust into the atmosphere.
Industrial sources of fugitive dust include open operations, leaks
and spills, storage, disposal, transit or poor housekeeping of sundry fine-
ly divided solid particulates. The iron and steel industries are replete with
examples of the above enumerated categories. Wind erosion of exposed
20 masses of particulate matter such as coal or mine mill tailings, fertilizers,
- 2173168
etc. c~ ~ses both air pollution and economic waste. Detrimental effects
on health and cleanliness result where these fine particles are carried
aloft by the winds.
A typical ",eti,od for controlling or suppressing dust is to apply a
water spray. However water sprays only control dust for a short period
of time depending upon enviror"nental conditions. The application of the
spray has to be repeated frequently to provide ongoing dust control.
Various lrealments have been utilized to control dust emissions.
U.S. Pat. No. 3 954 662 diecloses aqueous foamable compositions and
their use to suppress coal dust. The co",position contains water an
interpolymer of a pol~",eri able vinyl ester and a partial ester compound
interpolymerizable with the vinyl ester and a detergent wetting agent.
The interpolymer binds coal dust and keeps the dust particles encapsu-
lated after the foam has collarsed
U.S. Pat. No. 4 087 572 discloses a combination of an organic
polymer latex such as a styrene-b~ ~t~diene interpolymer and a silicone
applied to the surface of a coal pile or other mass of finely divided par-
tiu ll~te materials. In addilion a wetting agent may be incor~oraled to
prevent pre,nat.lre coag!J'~tion. The co"l~.nation is applied as an
~queo~ ~s mixture such as by spraying.
2173168
U.S. Pat. No. 4 551 261 discloses the suppression of dust with an
~ueous foam comprising a foaming agent and an elastomeric water in-
soluble polymer. The foam provides immediate dust suppression and
eases application. The polymer coats the material and continues to sup- .
5 press dust generation during handling of the material after the foam has
collapsed.
U.S. Pat. No. 4 594 268 discloses the use of at least one meth-
acrylate polymer for dust suppression. The methacrylate polymer pro-
10 vides dust suppression when applied to a wide variety of materials. Afterapplication the polymer provides a tacky water resistai!t coating which
effectively prevents dusting while additionally acting as an anti-freeze
agent.
U.S. Pat. 4 801 635 discloses a combination of water soluble
anionic acrylic polymers and nonionic glycol polymers and anionic and
nonionic su, ractants useful for the control of dust emissions into the
enviro"" ,enL
20 SUMMARY OF THE INVENTION
The p~sent invention relates to ,nethods for controlling fugitive
dust emissions from bulk granular or powdered solids. Fugitive dust
emissions are controlled by applying an ~ eous solution of a graft
25 copolymer of polyvinyl alcohol and a cationic monomer.
` 2173168
DESCRIPTION OF THE RELATED ART
U.S. Pat. No. 4 080 346 Bedell et al. teaches methods for grafting
cationic and nonionic ",ono",ers onto polyvinyl alcohol using a transition
5 metal ion catalyst. The resulting polymers prove useful às dye mordents.
U.S. 4 308 189 I\~lorilani et al. teaches a method for preparing modified
polyvinyl alcohol polymers via an emulsion process whereby a random
copol~l"e,i~ation of vinyl acetale and calionic ",ono",ers is carried out.
The resulting copolymers are used as a binder in pulp and textiles.
U.S. 4 775 715 Beresniewicz et al. tea~;l,es a process for making
cationic polyvinyl alcohol using ",echanical shear and a non-alkylene
qualer"ary ammonium halide. This process achieved conversions up to
40%. The quaternized polyvinyl alcohol was used as a flocculating
15 agent a stabilizing colloid and in a~l ,esive formulations. U.S. 5 075 401
Zhang teaehes anionic graft copolymers useful in oil recovery. These
copolymers are prepared using a reverse phase emulsion pol~",eri~ation
teehnique. U.S. Pat. No. 5 345 803 Dragner et al. teaches grarling of
predo"linantly non water soluble monoi"ers onto polyvinyl alcohol using
20 p~t~soiurn persulfate or ammonium hydroxide as the initiator. The graft-
ed produet is a latex emulsion useful as t.nders for non-woven products.
French patent 2 214 687 tea~;l,es g(dfling of cationic monomers
onto cellulose polyvinyl alcohol polyamides or polyethylene terephll ,al-
25 ate using electron ir,adiation as the initiator however cerium is conjec-
tured as a potential free radical initiator. The resulting polymers are used
to improve dyeability of polymers. Japanese patent 131 003 teaches a
polyvinyl alcohol grarled with acrylamido-type ",ono,ners using basic
catalysts such as sodium hydroxide having efficaey as sizing agents.
2173168
Japanese Kokoku publication No. 21361 teaches a modified poly-
vinyl alcohol which is prepared by polymerizing vinyl acetate with other
mono,ners such as hydlophobic acrylamides. The vinyl acetale is hydro-
lyzed after polymerization with the comonomers to form the polyvinyl
5 alcohol.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to me~hods for suppressing the dis-
10 semination of fugitive dust pa, ~icl~s into the almosphere from dust pro-
ducing materials comprising applying to the dust producing materials an
aqueous solution of a graft copolymer obtained by graft copolymerizing
cationic monomers onto polyvinyl alcohol.
The resulting polyvinyl alcohol graft copolymer has the general
structure:
FORMULA I
(F)b
I
-(~CH2~CH~)a~
OH
whereby F is H or a cationic monomer having the formula
FORMULA ll
R
--CH2--C--
l =O
R1
.
2173168
wherein R in Formula ll is hydlogen or a C1 to C3 alkyl group and R1 is
the salt of an a~""onium cation.
The ~",i"onium cation R1 has the structure OR2N+R3 4 5M-
5 wherein R2 is a C1 to C4 linear Of branched chain alkylene group R3 R4and R5 are selected from the group consisting of hydrogen C1 to C4
linear or branched chain alkyl C5 to C8 cycloalkyl C5 to C8 aro",dlic or
C5 to C8 alkylaror"dlic group and M is an anion selected from the group
consisting of chloride bromide methyl sulfate and hydrogen sulfate.
The molar per~nlage of a:b in Formula I is from about 95:5 to
about 5:95 with the proviso that the sum of a and b is 100%.
The cationic monomers can be selected from ethylenically unsatu-
15 rated quaternary ~"""onium ions. Pleferably the cationic ",onG",er~ areselected from the group including but not limited to 2-acryloyloxyethyl-
ll ime~l ,yls"""onium chloride (AETAC) 2-",etl ,ac~loyloxyethyltrimethyl-
al"l"onium chloride (METAC) 3-"~ell,acrylamidopropyll,il"etllyl~"~monium
chloride (MAPTAC) dimethyl sulfate salt of diethylaminoethyl acrylate
20 diallyldimethyl ammonium chloride and diallyldiethyl ammonium chloride.
Most preferably the cationic ~onol~er is 2-",etl)acryloyloxyethyl-
trimethyla,r,l"onium chloride.
2173168
The number average molecular weight (Mn) of the resulting co-
polymer is not critical as long as it is water soluble. The number average
molecular weight is preferably in the range of 1 000 to 2 000 000 with a
Mn range of 10 000 to 1 000 000 more preferable. Most preferably the
5 number average molecular weight will range from 50 000 to 500 000.
The preferred means of grafting the cationic ",ono",er onto the
polyvinyl alcohol is by a solution polymer process using cerium IV as a
redox initiator. The methodology for sy,ltl ,esi,ing polyvinyl alcohol graft
10 copolymers has been well documented in the literature and synthesis
procedures similar to those described in U.S. Pat. No. 4 080 346 were
utilized in this invention. The conte"ts of U.S. Pat. No. 4 080 346 are
hereby incor~orated by reference herein.
Ceric a"""onium nitrate is used as the initiator although other
cerium containing molecules which are oxidants such as ceric a" ,r"onium
sulfate and ceric sulfate may also be used. The present inventors antici-
pate that other lantl ,anides such as europium ytterbium and samarium
and transition metals having more than one oxidation state such as vana-
20 dium and manganese may also be employed as initiators.
Conventional initiators such as azo co",pounds persulfates per-
oxides and redox col ~ples may also be employed. It is to be understood
that the aforementioned polymerization methods do not limit the synthesis
25 of the copolymers useful in this invention.
2 1 73 1 68
The reaction temperature is not critical and generally occurs be-
tween 20 and 99C, preferably 35 to 65C. The pH of the reaction mix-
ture is not critical and is generally in the range of 4 to 6. The resulting
copolymer structure has been verified by 13C NMR, IR spectroscopy,
5 and viscosity studies.
The present inventors anticipate that in another embodiment of the
invention that anionic and nonionic ",Gno",er~ can be grarled onto the
polyvinyl alcohol with or without cationic mGno",er present.
The anionic monomer can be selected from the group containing
ethylenically unsaturated c rboxylic acid or sulfonic acid functional groups.
These monomers include but are not limited to acrylic acid, methacrylic
acid, vinyl acetic acid, itaconic acid, maleic acid, allylacetic acid, styrene
15 sulfonic acid, 2-acrylamido-2-methyl propane sulfonic acid (AMPS~) and
3-allyloxy-2-hydroxypropane sulfonic acids and salts thereof.
The nonionic monomer can be selected from the group of ethyleni-
cally unsaturated nonionic monomers which comprise but are not limited
20 to acrylamide, methacrylamide, N-methyloylacrylamide, N,N-dimethyl-
- acrylamide; lower alkyl (C1-C6) esters including vinyl ~cet~te, methyl
acrylate, ethyl acrylate, and methyl ",ethac~late; hydroxylated lower alkyl
(C1-C6) esters including hydroxyethyl acrylate, hydroxypropyl acrylate
and hydroxyethyl metl ,ac~late; allyl glycidyl ether; and ethoxylated allyl
25 ethers of polyethylene glycol, polypropylene glycol and propoxylated
acrylates.
2173168
The copolymers of the present invention may be applied to the
dust producing material (subslrale) by either spraying as a liquid onto the
substrate or by applying as a foam which inco~,uorales an effective sur-
factant-based foaming agent. The liquid spray incorporates a suitable
5 solvent for the copolymers which is preferably aqueous.
For purposes of the present invention, the term "effective amount
for the purpose" is defined as that amount of copolymer which will sup-
press the dissemination of dust. For ex~mple, aqueous solutions of from
10 about 0.1 to about 10.0% polymer can be sprayed or foamed onto the
substrate. The feed rate of sprayed ~queo~ ~s solution ranges from about
0.1 to about 10.0 gallons of solution per ton of subsl~ate. P,eferably, 0.5
to about 5.0 gallons per ton of subslrate are applied by spraying. When
applied as a foam, the copolymers are fed in a range from about 0.1 to
15 about 5.0 gallons of foamed solution per ton of subsl,ate. Pleferred foam
feed rates range from about 0.5 to about 2.5 gallons of foamed solution
per ton of dust producing material. The foam for the dust control treat-
ment may be foamed and applied via conventional techniques such as
those disclosed in U.S. Pat. No. 4,400,220 (Cole), the contents of which
20 are hereby incor~ Graled by reference.
The copolymers of the present invention are suitable for use on
any material prone to create dust, which include but are not limited to
rock, green and calcined petroleum coke, ores (for example, iron ore),
25 grains, li",estone, gypsum, fly ash, ce,nent clinker, steel mill sinter, coal,
bauxite, fertilizers (such as potash and phosphates), metallurgical coke
dust, basic oxygen furnace dust and road dust.
2 1 73 1 68
The copolymers of the present invention may also be used with
other additives for improved dust control. In addition to acting as foaming
agents, anionic, nonionic and/or cationic s~" ra-;tants may also be em-
ployed to improve the wetting properties of the copolymer solutions.
E~tAMPLES
Preparation of polyvinyl alcohol (PVA)/2-methacryloyloxyethyl-
lrin,etl,yl aml''G,'ium chloride (METAC) graft copolymer (1/1 molar ratio).
A suitable flask was equipped with a mechanical stirrer, thermo-
couple and nitrogen line. 57.3 9 of a PVA solution (0.2 moles, 15.3%),
55.3 9 of METAC (0.2 moles, 75%), 70.0 9 of H2O and six drops of 1 M
HNO3 were charged to the flask. 3.29 9 of ceric a"""onium nitrate dis-
15 solved in 9 9 of water was then shot fed to the flask. The nitrogen purgewas continued for the duration of the reaction. After allowing the tem-
perature to equilibrate, the solution was heated to 35C and held for 3
hours.
The copolymer solution had a Brookfield viscosity of 108 cps at
28.0% solids and 25C. The structure of the copolymer was verified by
13C NMR. There was no sign of residu~l monomer in the spectrum.
Similar procedures were used to prepare copolymers of PVA/METAC
with clirrerent mole ratios. Table I s~""",ari es the physical and chemical
prope, lies of these PVA/METAC copolymers.
2l73l68
TABLE I
ExamPle Polvmer ComDosition Ratio % Solids Viscositv (ccs)
1 PVA/METAC 1/1 28.0 108
2 PVA/METAC 1/2.5 17.5 40
3 PVA/METAC 1/5 21.9 99
In order to more clearly illustrate this invention the data set forth
below were dcveloped. The following exa"~pl~s are included as being
illustrations of the invention and should not be construed as limiting the
scope thereof.
15 Perforrnance Testing
The substrate tested was minus 1/4 inch sub-bituminous coal. The
copolymer treal",ents were applied as 0.25% active ~ueous solutions at
a feed rate of 2.5 gal/ton.
The ll edted coal samples were allowed to dry for 48 hours to
dete"nine residual (long-term) dust control effects compared to control
samples (coal treated with water). Relative dustiness measurements
were made using a laboratory dust chamber (modified ASTM dust box).
25 Percent dust suppression (%DS) was cAIculAted based on the relative
dustiness number (RDN) of the control versus treated samples as follows:
%DS = Control RDN - Treated RDN x 100
Control RDN
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All RDN values were measured in triplicate; the average RDN
value was used for the %DS calculation. The results of this testing are
presented in Table Il.
TABLE ll
Treat",ent% Dust SuPPresSiOn
Control o
Example 1 45
Example 2 58
Example 3 50
These results de",onsl(ate that the graft copolymers of the instant
invention in a range of PVA/METAC ratios are effective at suppressing
dust emissions.
While this invention has been desc, ibed with respect to particular
embodiments thereof it is apparent that numerous other forms and modi-
fications of this invention will be obvious to those skilled in the art. The
app~"ded claims and this invention generally should be construed to
cover all such obvious forms and ",odif,calions which are within the true
20 spirit and scope of the present invention.
