U.S. patent number 3,908,045 [Application Number 05/422,813] was granted by the patent office on 1975-09-23 for encapsulation process for particles.
This patent grant is currently assigned to Lever Brothers Company. Invention is credited to David S. Alterman, Kil Whan Chun.
United States Patent |
3,908,045 |
Alterman , et al. |
September 23, 1975 |
Encapsulation process for particles
Abstract
Particles of a fluidizable substance are coated with a complete
and continuous coating by a process wherein a non-aqueous solution
of a coating substance is sprayed from a nozzle downwardly on a
fluidized bed of the particles to be coated, the nozzle height
being adjusted so that the liquid droplets of coating material
would just cover the cross-sectional area of the upper surface of
the bed, if sprayed on the unexpanded bed. When the aforementioned
coating is a fatty acid having 12-20 carbon atoms applied to
particles of a chlorine-releasing agent, and when a second coating
is applied by treatment with a solution of a fixed alkali
hydroxide, i.e., sodium, potassium, or calcium hydroxide, an
effective, completely encapsulated, non-pinholing bleach product is
obtained.
Inventors: |
Alterman; David S. (Parsippany,
NJ), Chun; Kil Whan (Ridgefield Park, NJ) |
Assignee: |
Lever Brothers Company (New
York, NY)
|
Family
ID: |
27296412 |
Appl.
No.: |
05/422,813 |
Filed: |
December 7, 1973 |
Current U.S.
Class: |
427/213;
252/187.1; 252/187.25; 252/187.26; 252/187.29; 252/187.3;
252/187.33; 252/187.34; 427/214; 427/337; 427/424; 428/403 |
Current CPC
Class: |
B01J
2/006 (20130101); C11D 3/3955 (20130101); C11D
17/0039 (20130101); C01B 15/005 (20130101); Y10T
428/2991 (20150115) |
Current International
Class: |
C01B
15/00 (20060101); C11D 3/395 (20060101); B01J
2/00 (20060101); C11D 17/00 (20060101); B05D
001/02 (); B05D 001/36 () |
Field of
Search: |
;117/1B,62.1,167,87
;252/103,187C ;427/213,214,337,424 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Martin; William D.
Assistant Examiner: Konopacki; Dennis C.
Attorney, Agent or Firm: Dusyn; Kenneth F. Farrell; James J.
Grant; Arnold
Claims
What is claimed is:
1. A process for coating particles of an oxidizing material having
at least one reactive chlorine atom in its molecular structure
comprising the steps of:
i. placing said particles in such a configuration as to define a
layer thereof having a thickness between about 1/2 inch and about 6
inches, on a perforated support,
ii. adjusting the height of a downwardly disposed spraying means
capable of producing a spray of liquid droplets in a downwardly
diverging pattern, to a level such that the outermost droplets of
said spray contact said layer of particles at the perimeter thereof
as defined by said layer in static state,
iii. causing a gas to flow upward through said perforated support,
thereby expanding the thickness of said layer and maintaining said
particles in continuous motion to form a fluidized bed,
iv. spraying a solution of a solidifiable fatty acid on said
fluidized bed until all particles in said bed are completely coated
with said fatty acid, and
v. treating said fatty-acid coated particles with an aqueous
solution of a fixed alkali hydroxide selected from the group
consisting of sodium hydroxide, potassium hydroxide, and calcium
hydroxide, and mixtures thereof, said treatment comprising
a. agitating said fatty acid-coated particles in said aqueous
hydroxide solution for about 10 to about 120 minutes at a
temperature of about 85.degree.F to about 130.degree.F, and not
higher than about 5.degree.F below the melting point of said fatty
acid,
thereby reacting said hydroxide with at least a portion of said
fatty acid, the concentration of said fixed alkali in said solution
being about 3 to about 10 percent when said alkali is sodium
hydroxide, about 10 to about 15 percent when said fixed alkali is
potassium hydroxide, and about 0.1 percent when said fixed alkali
is calcium hydroxide, by weight of said solution.
2. A process in accordance with claim 1 wherein said fatty acid is
a member selected from the group consisting of palmitic and stearic
acids and mixtures thereof, and said aqueous solution of fixed
alkali hydroxide in a solution of about 3 to about 10 percent
sodium hydroxide by weight of said solution.
3. A process in accordance with claim 1 wherein said fatty acid is
substantially lauric acid and said aqueous solution of fixed alkali
hydroxide is a solution of about 10 to about 15 percent sodium
hydroxide by weight of said solution.
4. A process in accordance with claim 1 wherein the concentration
of said sodium hydroxide is about 3 percent NaOH by weight,
solution basis.
5. A process in accordance with claim 1 wherein the concentration
of said sodium hydroxide solution is about 6% NaOH by weight,
solution basis.
6. A process in accordance with claim 1 wherein the concentration
of said sodium hydroxide solution is about 10% NaOH by weight,
solution basis.
7. A process in accordance with claim 1 wherein the concentration
of said potassium hydroxide is about 10 to about 13 percent.
8. A process in accordance with claim 1 wherein said oxidizing
material having at least one reactive chlorine atom in its
molecular structure is potassium dichloroisocyanurate.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The coating or encapsulation of discrete particulate material by a
variety of processes is well known. In particular, the art is aware
of many variations in processes for coating particulate material by
a fluidized bed technique.
The present invention finds utility for applying either a complete
single coating or a double coating of a material to a particulate
substance.
In the case of a single coating, encapsulation methods known
heretofore do not always insure that the particles will have no
adverse side effects during use.
The double coating process of the present invention is especially
applicable to the coating of particles of highly reactive
substances. Most particularly the process finds utility in the
detergent bleach field wherein particulate fabric bleaching agents,
such as potassium dichloroisocyanurate, sodium
dichloroisocyanurate, and the hydrates thereof are employed in home
laundering operations as a dry bleach product to be added
separately to a washing machine or for use in admixture with
particles of a detergent composition to form a commercially
acceptable detergent--dry bleach combination. Because of their
highly reactive nature the particles must not only be thoroughly
and imperviously coated to avoid contact of the bleach particles
with the detergent particles, but the coated particles must not
attack textile materials or the dyes thereon under washing
conditions. Although prior-art processes may provide thorough and
uniform coatings impervious to potassium iodide solution, the
coated particles of chlorine-releasing compounds suffer the defect
that they attack the dye substances at the points of contact with
the fabric and have been known to attack the fabric and make
pinholes therein in a washing process wherein the coated bleach
particles are placed directly on dry clothes.
2. The Prior Art
Art that may be considered in connection with the instant invention
is represented by the patents listed below.
U.s. pat. No. 1,950,956 to Wilhelm: Discloses the coating of
chloramine-T with stearic acid.
U.s. pat. No. 1,480,561 to McNeil: Discloses a process wherein
granules are uniformly coated by dropping granules through a spray
of a solution of a coating substance and spraying the solution
directly upon the granules while they are being agitated in a
tumbling mechanism.
U.s. pat. No. 2,561,392 to Marshall: Relates to process and
apparatus for coating moving particles by spraying a solution of a
coating material thereon. Provision is made to recirculate the
particles to provide a heavier coating. There is also disclosed a
means for removing the solvent from the coating material.
U.s. pat. No. 2,579,944 to Marshall: Discloses a tandem coating
system wherein particles in a turbulent state are coated by
spraying with a solution of a coating substance in a first chamber
and sequentially coated by spraying with a solution of a second
substance in a second chamber. The patentee states in column 6,
lines 18-22 that it is desirable to have the sprayers adjustable
vertically so as to coat the particles properly when the surface of
the bed is changed.
U.s pat. No. 2,594,469 to Mahoney: Relates to a process wherein
particles, such as spraydried detergent particles fall by gravity
within a chamber, and the falling particles are coated by spraying
with a solution of the coating substance.
U.s. pat. No. 2,768,095 to Tadema et al.: Provides a method for
uniformly distributing liquids in finely divided solids without
substantial loss of materials. The liquid may be a solution of one
or more materials in a suitable solvent, and is injected within a
fluidized bed of the finely divided solids either counter to, or
parallel to, the gas stream used for fluidization.
U.s. pat. No. 3,650,961 to Hudson: Discloses a method for
encapsulating chlorocyanurates with hydratable inorganic salts. A
fluidized bed of the inorganic salt is formed, on which is sprayed
droplets of a slurry of a chlorocyanurate, or other detergent
adjunct. By controlling the droplet size, the detergent is made to
form the core material disposed predominantly in the center of the
particle, while the inorganic salt, partially hydrated, surrounds
the core, and the particle size can be controlled to about 10-100
mesh.
U.s. pat. No. 3,671,296 to Funakoshi et al.: Particles are coated
by treatment with a liquid spray while the particles are
circulating in a cyclic pattern. Circulation is accomplished by
moving the particles to the outer edge of a rotating circular,
horizontal dish, the force of this movement carrying the particles
upward along the internal vertical surface of a cylindrical or
inwardly curved barrel, then leaving the barrel surface to move
toward the center of the barrel, thence falling back to the
revolving plate to repeat the circulating process.
SUMMARY OF THE INVENTION
It has now been found that the problem of insuring complete
encapsulation of a particulate material without agglomeration may
be solved by applying a solution of a coating substance to a
fluidized bed of the particulate material, the nozzle from which
the coating substance is sprayed being at a critical height from
the bed when in a static state.
It has moreover been found that the problem of pin-holing,
discussed hereinbefore, can be solved or greatly alleviated by
applying to the particles of the substance which can cause
pinholing, i.e., a substance having at least one reactive chlorine
atom in its molecular structure, a first coating of a solidifiable
saturated fatty acid, and sequentially applying a second coating of
soap by treating the first coating of fatty acid with a solution of
a fixed alkali hydroxide selected from the group consisting of
sodium hydroxide, potassium hydroxide, and calcium hydroxide.
In a first embodiment, the present invention provides a granular,
free-flowing, non-agglomerated, dry chlorinated bleach product for
use during the washing of textiles, wherein the granules are coated
with a substance which prevents reaction of the bleach product
during storage and additionally prevents pinholing of the textiles
and attack on the dyestuffs thereon.
It is therefore an object of the invention to apply a double
coating to particles of a chlorinated bleach substance.
It is another object of the invention to provide a coating system
on particles of a compound having releasable chlorine therein,
whereby bleach damage (pinholing) on colored fabrics is prevented
and good chlorine release during the wash cycle is provided.
It is a further object of the invention to provide a coating
composition for the above-described chlorine-containing bleach
compounds which is relatively slow dissolving to prevent bleach
damage on colored fabrics and to permit good chlorine release
during the wash cycle.
In a second embodiment, the invention provides a process for
depositing a complete and continuous single coating on a
particulate substance in a fluidized state.
The present invention is described herein in terms of potassium
dichloroisocyanurate, a well-known oxidant and household bleach,
which has two reactive chlorine atoms per molecule, and readily
releases the chlorine in an oxidizing action in contact with a
reducible substance, or by hydrolysis in contact with water.
However, the particles which are advantageously coated by the
process of the invention are not limited to the aforesaid potassium
dichloroisocyanurate, but may be any fluidizable substance in
particulate form.
DETAILED DESCRIPTION OF THE INVENTION
In one aspect of the instant invention there is provided a process
wherein particles of a chlorine-releasing agent are coated with a
double layer of coating substances as described hereinafter.
In another aspect the invention provides a process for applying a
single coating substance to any fluidizable particulate
material.
The products obtained by the process of the present invention are
encapsulated, free-flowing, non-agglomerated particles having a
core of the substance to be coated, a first or primary coat of a
solidifiable material, which may be the sole coat, and in the case
of a core substance which is an oxidant having releasable chlorine
in its molecule, the particles have a first coat of a saturated
fatty acid and a second coat of a soap of the fatty acid.
A preferred product made by the process of the present invention is
encapsulated potassium dichloroisocyanurate in particulate form,
said particles having thereon an inner and an outer coating, said
inner coating comprising a fatty acid from 12 to 20 carbon atoms,
or mixtures thereof, and said outer coating comprising a sodium
salt of said acid, or mixtures thereof, said particles of potassium
dichloroisocyanurate having said inner coating being completely
encapsulated by said sodium salt.
Most preferably, the encapsulated particles suitable for bleaching
fabrics in an aqueous medium in accordance with the present
invention comprise:
i. a core of potassium dichloroisocyanurate,
ii. a primary coating contiguous to said core of a fatty acid
comprising about 55% palmitic acid and about 45% stearic acid,
and
iii. an outer coating of the sodium salt of said fatty acid, said
primary coating and said outer coating being substantially
continuous.
The core substance may be any substance in particulate form which
can be fluidized. Suitable non-chlorinated substances are:
sodium perborate
enzymes
optical brighteners
sodium acetyl salicylate
antibacterial agents
polyethylene glycol/terephthalate copolymers.
Among the chlorine-releasing substances suitable as core material,
there may be mentioned those oxidants capable of having their
chlorine liberated in the form of free elemental chlorine under
conditions normally used for detergent bleaching purposes, such as
potassium dichloroisocyanurate, sodium dichloroisocyanurate,
chlorinated trisodium phosphate, calcium hypochlorite, lithium
hypochlorite, monochloramine, dichloramine, nitrogen trichloride,
?(mono-trichloro)-tetra-(mono-potassium
dichloro)!penta-isocyanurate, 1,3-dichloro-5,5-dimethyl hydantoin,
paratoluene sulfondichloroamide, trichloromelamine,
N-chloroammeline, N-chlorosuccinimide,
N,N'-dichloroazodicarbonamide, N-chloro acetyl urea,
N,N'-dichlorobiuret, chlorinated dicyandiamide, trichlorocyanuric
acid, and dichloroglycoluril.
The instant invention is applicable to particulate substances
having a wide range of particle sizes, so long as the particles are
fluidizable. Commonly, particles of 5 to 120 U.S. mesh size are
employed.
When only a single coat is to be deposited by the process described
herein the coating substance may be a fatty acid, or may comprise
such substances as polyvinyl alcohol, polyvinyl pyrrolidone,
polyethylene glycols having a molecular weight from about 6,000 to
about 16,000, copolymers of vinyl methyl ether and maleic
anhydride, etc. The solvent for the coating substance will be
selected with due regard for its volatility and inertness toward
the core material. For example, methanol is a suitable solvent for
depositing a coating of polyethylene glycol (6,000 molecular
weight) on particles of sodium perborate. Preferably the boiling
point of the solvent is about 90.degree.F to about 180.degree.F.
The capacity of the exhaust system will be considered in
determining whether a solvent having a boiling point in the upper
portion of the foregoing range can be used. For example, if
relatively little solvent is required for the coating substance,
the boiling point can be higher than in instances wherein a high
proportion of solvent is needed.
When a dual coating is to be applied, it is essential that the
first coating be a saturated fatty (alkanoic) acid which is
solidifiable and which remains solid at temperatures likely to be
encountered during manufacture or storage, for example, a
temperature of about 85.degree.-130.degree.F. Suitable fatty acids
are the well-known n-alkanoic acids having from about 12 to about
20 carbon atoms. A particularly suitable fatty acid is Emersol 132
(trademark of Emery Industries, Inc.), which is substantially 45%
stearic acid and 55% palmitic acid and which melts at about
131.degree.-132.degree.F. The fatty acid is applied as a solution
in a suitable solvent, methylene chloride being preferred because
of its compatibility, non-reactivity with chlorine-releasing
agents, nonflammability, and low toxicity.
Moreover, the fatty acid will be selected with due regard to its
melting point in relation to the use to which the coated particles
are to be put. For example, in the case of a dual-coated product
intended for use as a bleaching agent in a home laundering
operation, the melting point of the fatty acid may be somewhat
higher than the temperature of the wash solution, but not so high
that it is not removed from the core by the emulsifying action of
the outer soap layer.
The following fatty acids or mixtures thereof are suitable.
______________________________________ Number of Approximate Carbon
Atoms Melting Point, 0.degree.F
______________________________________ Lauric Acid 12 111 Myristic
Acid 14 136 Palmitic Acid 16 147 Stearic Acid 18 157 Arachidic Acid
20 169 ______________________________________
Specific mixtures of saturated fatty acids suitable for use in the
practice of the invention are set forth in the following list.
__________________________________________________________________________
Approximate Melting Technical Typical Chain-Length Distribution
Point Designation Percent .degree.F
__________________________________________________________________________
C.sub.10 C.sub.12 C.sub.14 C.sub.16 C.sub.18 C.sub.20 90% lauric 4
91 4 1 104 95% lauric 1 95 4 109 99% lauric 0.3 99 0.7 111 95%
myristic 2 95 3 127 90% palmitic 1 92 7 140 95% stearic 0.5 97 2.5
154 Triple-pressed 2 52 46 131 stearic Palmitic-stearic 8 75 17 131
Stearic 5 30 65 139
__________________________________________________________________________
Potassium dichloroisocyanurate, typical of the cyanurates suitable
as core substances, is commerically available and may be obtained
from the Monsanto Chemical Company. The chemical structure of this
compound may be represented by the graphic formula: ##EQU1##
Information regarding this and three related compounds may be found
in Monsanto Technical Bulletin I-177.
The second coating is a sodium, potassium, or calcium salt of the
fatty acid which comprises the first coat.
When carrying out the process of the instant invention, the first
coating is conveniently applied by means of the apparatus shown
schematically in FIGS. 1-3.
When the spray nozzle and the spray pattern of droplets issuing
therefrom are conical, the nozzle location is such that the
projection of the nozzle cone surface intersects the tower wall at
the level of the upper surface of the bed of particles when in the
unfluidized state.
The coating solution is contained in vessel 6 and is fed to nozzle
5 by pump 7. The spraying of the coating solution from nozzle 5 is
aided by pressurized air entering tower 1 at 8. Fluidizing gas
passes through duct 9 and is forced through the screen support by
blower 10 and is either cooled by cooling system 13, or heated by
heat exchanger 11, if required, in order to maintain the fluidizing
gas within a critical temperature range. An exhaust blower 12
removes solvent vapors. It will be recognized from the foregoing
description that the height of the spray nozzle relative to the bed
of particles in the static state is critical to obtain the spray
pattern required to deposit a complete and continuous coating on
each particle. It has been found that the particles are not
adequately coated if there is any substantial deviation in the
spray pattern relative to the height of the static bed.
More fully described in terms of a specific embodiment of the
apparatus, equipment suitable for carrying out the process of
applying the first or sole coating on a particulate substance may
comprise a vertical tower 1 having appropriate dimensions, for
example, a diameter of about 1 foot and a height of about 5 feet
comprising a coating chamber. The bottom of the unit contains a
conical shape receptable for entering fluidizing air. The
particulate matter is supported by a screen, grid, or porous plate
having a sufficient number of openings to provide substantially
even distribution of the upward flowing gas over the cross section
of the coating tower. All metal parts are fabricated of stainless
steel.
It is preferred that the support on which the particle bed rests be
substantially a screen, e.g., having about 10 to about 140 U.S.
mesh openings per inch, rather than a perforated plate with
relatively few openings, to aid the circulation of every particle
by the incoming air. Suitably a 60-mesh screen may be used.
Fluidizing air enters the apparatus through a 6 inch diameter
flexible duct 9 below the supporting screen. This air is supplied
from a conventional air blower capable of delivering air at a
superficial air velocity of from about 4-15 feet per second and
preferably from about 7-12 feet per second in the fluidizer.
Provision has been made either to heat or cool the entering air as
required by a steam heat exchanger 11 and a cooling unit 13. In
addition, a small amount of air is supplied through a series of
nine-1/4 inch diameter tubing jets, equally spaced about the inner
perimeter at the support screen level. The function of the air jets
is to help provide uniform particle coating by preventing any
stagnant bed areas from forming at the wall.
Solutions of the coating material are pumped to a two-fluid
atomizing nozzle 5 by a simplex reciprocal constant volume metering
pump. The nozzle head has at least two, and preferably six, holes
so disposed as to spray the coating solution evenly over the entire
cross sectional area of the fluidized bed. This particular spray
pattern provides a maximum available coating zone. The nozzle can
be located at various heights above the support screen depending on
the volume of core material in the bed. However, the most suitable
location of the nozzle is the point at which the coating solution
can be sprayed on the upper perimeter of the unfluidized bed core
material.
The coating solution reservoir and pipe lines leading to the nozzle
are heated in some cases to prevent solidification of the coating
material in solution. Flow meters are used to measure gas flow and
this flow is controlled by conventional valves and gauges.
Air is exhausted through a blower 12 to a wash drum. A cyclone
separator may be used to recycle the smaller particles that have
been elutriated from the bed.
The fluidizer is fitted with two Plexiglas windows and a Plexiglas
door that allow for observation during a run. The door also serves
as a means of filling and emptying the fluidizer of solid
material.
In operation, a known weight of a multiplicity of particles to be
coated is placed on the perforated support, or supporting screen 2,
in coating tower 1. It is convenient to use a starting batch weight
of 10 to 20 pounds of uncoated particles.
Typically the thickness of the layer or bed in the static state is
about 11/2 to about 6 inches. The height of the spray nozzle 5 is
adjusted to a level such that the outermost droplets of the spray
therefrom would contact the layer of particles at the perimeter
thereof as defined by the layer in static state. Air is caused to
flow upwardly by the force created by blower 10 through duct 9,
thereby expanding the thickness of the layer of particles, and
maintaining the particles in continuous motion within the volume
defined by the expanded bed, thus forming a fluidized bed 3.
A solution of a solidifiable coating substance, contained in vessel
6, is sprayed by means of pump 7 through nozzle 5 on the fluidized
bed 3 until all particles in the bed are completely coated. The
time required for a coating run in a 1-foot diameter tower may vary
from about 10 minutes to about 2 hours, depending upon such factors
as type of coating, concentration of coating solution, and the
desired rate of application of the coating solution.
It is critical to control the spray pattern as described
hereinbefore, and to employ supplemental tangential air so as to
insure adequate movement and circulation of all the particles
during fluidization and as a result to achieve a complete and
continuous coating on all the particles. A suitable spray nozzle is
a Sprayco No. 26 nozzle manufactured by the Spraying systems Co.
This nozzle contains six holes in the atomizing head.
the fluidizing air velocity is controlled at an optimum for good
fluidization. Too low a velocity will result in poor particle
circulation and hence a poor coating. Too high a velocity will
promote mechanical breakdown of the particles and excessive
particle carryover from the body of the bed.
The temperature of the fluidizing air, and hence the temperature of
the bed, is controlled within a critical range. Too low a
temperature results in too low a rate of solvent evaporation to
cause the particles to become too wet, circulate poorly, and
agglomerate. Too high a temperature tends to evaporate the solvent
prematurely before the coating solution contacts the particle to be
coated. Normally the temperature of the fluidizing air is such that
the bed temperature is about 80.degree.F to about 130.degree.F.
Particles coated by the above-described procedure are completely
encapsulated with a continuous coating, and are free-flowing and
non-agglomerated.
It is important that each particle be fully covered, particularly
in the case of the bleach compounds having releasable chlorine to
be subjected to treatment with a fixed alkali hydroxide, since
contact thereof with a chlorinated compound may result in a violent
reaction.
When it is desired to apply a second, or outer, coating in
accordance with the invention, for example, when the core substance
is a chlorine-releasing agent to be used as a bleach in
home-laundering operations, the first coating will comprise a
saturated fatty acid as described hereinabove.
After removing the fatty acid coated particles from the fluidizer,
the particles are treated to apply an outer coating of an alkali
metal or alkaline earth soap of the fatty acid which comprises the
first coat. The outer coating is advantageously applied by gently
agitating the fatty acid coated particles in an aqueous solution of
an alkali metal or alkaline earth hydroxide having a concentration
as set forth hereinafter, for about 10 minutes to about 2 hours,
preferably for about 1/2 hour, and until the hydroxide reacts with
at least a portion of the fatty acid, and completely encapsulates
the aparticles with the reaction product of the fatty acid and the
hydroxide
The temperature of the hydroxide solution is suitably between about
35.degree.F and about 200.degree.F and is not higher than the
melting point, and preferably not higher than about 5.degree.F
below the melting point, of the particular fatty acid employed for
the first coat, and in any event not sufficiently high to melt the
fatty acid.
Following the aforementioned treatment the double coated particles
are separated from the treating solution for example by decantation
on a screen, and dried to produce completely encapsulated,
free-flowing, particles coated with a first or inner layer of fatty
acid, and a second or outer layer of the fixed alkali soap of the
fatty acid.
The proportion of the fatty acid coating that is converted to the
corresponding soap is not critical. All that is required is that
the encapsulating coat of the reaction product of the fatty acid
and fixed alkali hydroxide, i.e., soap, completely cover each
particle. The invention contemplates a process wherein some or all
of the primary fatty acid coat is converted to soap in the second
coating step, provided that the conversion to soap proceeds at
least to the extent that the soap covers every particle completely.
In a typical case, each particle will have on the surface thereof a
first coating of a fatty acid and a second, or outer, coating of
the salt of the acid which comprises the first coat.
A critical feature of the second coating is the concentration of
the alkali in the solution employed to react with the fatty acid.
The concentration of sodium hydroxide should be between about 3 to
about 10 percent by weight when the primary coating is stearic acid
or a mixture of stearic and palmitic acids, and should be about 10
to about 15 percent when the primary coating is lauric acid or the
commerical 95 percent material. The concentration of potassium
hydroxide should be between about 10 and about 15 percent. Calcium
hydroxide should be applied as a saturated solution, i.e., about
0.1 percent by weight. Below the critical concentrations the
coating becomes soft and gel-like, and is not protective. At
concentrations above the critical levels, this of course not being
applicable to calcium hydroxide, the particles tend to rise due to
the relatively higher density of the alkali solution and are
difficult to coat properly.
Preferred concentrations are about 3 to about 7 percent sodium
hydroxide when the primary fatty acid coating is in the upper
portion of the soap-making molecular weight range, for example,
palmitic and stearic acids, and about 12 to about 14 percent sodium
hydroxide for the lower portion, for example, when the fatty acid
is lauric acid. The preferred concentration of potassium hydroxide
is about 10 to abut 13 percent, and of calcium hydroxide, about 0.1
percent.
The proportion of primary coating substance relative to the
single-coated particle may be from about 25 to about 75 percent by
weight, preferably about 50 percent. The conversion of fatty acid
to soap to form the outer coating adds very little to the weight of
coating.
The advantages of the dual coating of the present invention (i.e.,
protection without pinholing) appear to be brought about by a
different mechanism by which the bleach particles are made
available to the washing solution. When a fatty acid is the only
coating, the release of the bleach particle depends upon the
melting point of the coating as compared to the temperature of the
washing solution. When the melting point of a fatty acid single
coating material is the same or lower than the washing temperature,
ther is severe color damage on colored fabrics (pinholing); when
the melting point is higher than the washing temperature no
pinholing is discerned but the total available chlorine released
from the coated particles is only about 20 -60 percent of the
theoretical. In contrast, when particles of potassium
dichloroisocyanurate are provided with a dual coating in accordance
with the present invention, the bleach particles are released into
the washing solution by the relatively slow rate of solubility of
the soap coating, to remove as well the undercoating of fatty acid,
possibly by an emulsifying action.
In accordance with the foregoing description, the process for
coating particles of an oxidizing material having at least one
reactive chlorine atom in its molecular structure comprises the
steps of:
i. placing said particles in such a configuration as to define a
layer thereof having a thickness between about 1/2 inch and about 6
inches, on a perforated support,
ii. adjusting the height of a downwardly disposed spraying means
capable of producing a spray of liquid droplets in a downwardly
diverging pattern, to a level such that the outermost droplets of
said spray contact said layer of particles at the perimeter thereof
as defined by said layer in static state,
iii. causing a gas to flow upward through said perforated support,
thereby expanding the thickness of said layer and maintaining said
particles in continuous motion to form a fluidized bed,
iv. spraying a solution of a solidifiable fatty acid on said
fluidized bed until all particles in said bed are completely coated
with said fatty acid,
v. treating said coated particles with an aqueous solution of a
fixed alkali hydroxide selected from the group consisting of sodium
hydroxide, potassium hydroxide, and calcium hydroxide, and mixtures
thereof, thereby reacting said hydroxide with at least a portion of
said fatty acid, and completely encapsulating said particles with
the reaction product of said fatty acid and said hydroxide, the
concentration of said fixed alkali hydroxide in said solution being
about 3 to about 15 percent when said fixed alkali is sodium
hydroxide, about 10 to about 15 percent when said fixed alkali is
potassium hydroxide, and about 0.1 percent when said fixed alkali
is calcium hydroxide, by weight of said solution.
Encapsulated particles of chlorine-releasing agent prepared in
accordance with the instant invention find utility in admixture
with particulate detergent compositions having therein an anionic
or nonionic detergent species that is not adversely affected by
chlorine liberated from the bleaching agent.
The dual-coated particles may be admixed with a particulare
detergent composition. Examples of anionic detergents useful in the
detergent-bleach compositions of the invention are the higher alkyl
mononuclear aromatic alkali-metal sulfonates, such as
alkylbenzenesulfonates having about 9 to about 18 carbon atoms in
the alkyl group wherein the alkyl group is derived from
polypropylene as described by Lewis in U.S. Pat. No. 2,477,382, or
wherein the alkyl group is derived from kerosene, as described by
Flett in U.S. Pat. No. 2,390,295, and Rubinfeld in U.S. Pat. No.
3,320,174, or wherein the alkyl group is a straight chain and the
benzene nucleus is randomly positioned along the alkyl chain, as
described in Baumgartner U.S. Pat. Nos. 2,723,240 and 2,712,530,
and in U.S. Pat. No. 2,972,583, or wherein the alkyl group is a
hexene dimer or trimer as in McEwan U.S. Pat. No. 3,370,100, or
wherein the alkyl group is derived from alphaolefins, as in Swenson
U.S. Pat. No. 3,214,462.
Also there may be employed primary and secondary alkyl sulfates,
i.e., R--O--SO.sub.3 -- compounds wherein R represents an alkyl
group having from 10 to 20 carbon atoms such as sodium, potassium
and magnesium lauryl sulfate, stearyl sulfate, coconut alkyl
sulfate and tallow alkyl sulfate; N-long chain acyl-N-alkyl
taurates and the salts thereof wherein the long chain is from 8 to
20 carbon atoms such as sodium oleoyl methyl taurate, sodium
palmitoyl methyl taurate, sodium lauroyl methyl taurate and the
corresponding acyl ethyl taurates; long chain alkyl-oxyethylene
sulfates wherein the long chain is from 8 to 20 carbon atoms such
as sodium or laurylpolyoxyethylene sulfate, sodium
lauryloxyethylene sulfate and sodium cetylpolyoxyethylene sulfate;
long chain alkyl aryl oxyethylene sulfates wherein the long chain
is from 8 to 20 carbon atoms such as ammonium, sodium or potassium
nonyl- octyl- and tridecylphenoxy mono- and polyoxyethylene
sulfates; long chain acylisethionates wherein the long chain is
from 8 to 20 carbon atoms such as sodium or potassium lauroyl-
stearoyl isethionate; alkane- or alkenesulfonates containing 8 to
20 carbon atoms in the alkane or alkene group such as sodium or
potassium octane-, decane-, tetradecane-, octadecanesulfonate and
octene-, decene-, tetradecene- and octadecenesulfonate;
alkoxyhydroxy- alkanesulfonates wherein the long chain is 8 to 22
carbon atoms such as lauryloxyhydroxypropanesulfonate,
stearyloxyhydroxyethanesulfonate and
tallowoxyhyroxypropanesulfonate; and fatty acid monoglyceride
sulfates wherein the long chain is 8 to 22 carbon atoms such as
lauric-, myristic-, palmitic and stearic monoglyceride sulfates;
alpha-sulfo soap, such as disodium salt of alpha-sulfo fatty acids
wherein the fatty acids are derived from tallow, the
sulfosuccinates, such as dioctyl sulfosuccinate, sodium salt, the
sulfuric acid esters of polyhydric alcohols incompletely esterified
with higher fatty acids, such as the sodium salt of sulfated
coconut oil monoglyceride, and compounds known as "Medialans,"
which are amido carboxylic acids formed by condensing fatty acids
of C.sub.8 -C.sub.22 chain length with sarcosine, CH.sub.3 NH.sub.2
CH.sub.2 COOH. Generally the alkali metal salts are employed.
The soaps are included within the definition of anionic detergents
as used herein. Operable soaps within the present invention are the
sodium and potassium salts of acyclic monocarboxylic acids having
chain lengths of about 8 to about 22 carbon atoms. Particularly
useful are the salts of unsubstituted fatty acids derived from
natural triglycerides, such as tallow, palm oil, cottonseed oil,
olive oil, lard, rapeseed oil, etc., and the so-called "high-lauric
oils," generally exemplified by the tropical nut oils of the
coconut oil class, including in addition to coconut oil, palm
kernel oil, babassu oil, ouri curi oil, tucum oil, cohune nut oil,
and murumuru oil, and for present purposes, ucuhuba butter, a
triglyceride high in myristic acid esters. A particularly useful
soap is one prepared from a mixture of about 80 percent tallow and
about 20 percent coconut oil.
Preferably the detergent composition should be substantially free
of compounds containing amino nitrogen to avoid adverse effects
during the washing operation.
Other suitable anionic synthetic detergents for use in the present
invention can be found in the literature, such as "Surface Active
Agents and Detergents" by Schwartz, Perry and Berch published by
Interscience Publishers, the disclosures of which are incorporated
by reference herein.
The water-soluble polyetheneoxy nonionic organic detergent
compounds suitable for use in the practice of the invention may be
characterized broadly as ethylene oxide condensates of organic
hydrophobic compounds bearing a labile hydrogen atom in a polar
substituent, said organic hydrophobic compounds being within a
molecular weight range such that when serving as a base for a
resulting ethylene oxide condensate, said condensate is capable of
having detergent properties at a sufficiently high ethylene oxide
content.
Suitable hydrophobic bases falling within the foregoing description
are aliphatic alcohols and mixtures thereof having from about 10 to
about 15 carbon atoms, corresponding to an average molecular weight
of about 158 to about 228. The alcohol is preferably straight-chain
but may contain 0 to about 25 percent lower alkyl branching, mainly
methyl, with some 2 -3 carbon alkyl groups, on the 2-position
carbon of the alcohol molecule.
Other suitable hydrophobic compounds include
a. the polyoxypropylene diols which form the hydrophobic base of
the Pluronics. "Pluronic" is a trademark of the Wyandotte Chemical
Corp. the aforementioned hydrophobic base is water-soluble and has
a molecular weight from about 1,500 to about 1,800.
b. Alkylphenols having an alkyl group of about 6 to about 12 carbon
atoms. The alkyl group may be straight or branched and may be
derived from a propylene polymer, diisobutylene, hexene, nonene, or
dodecene, for example, or mixtures of these.
The ethylene oxide content of the detergent molecule may range from
52 to about 80 percent by weight, preferably from about 60 to about
70 percent by weight.
Among the water-soluble polyetheneoxy organic nonionic detergent
compounds useful in the combinations of the instant invention
are
1. condensates of ethylene oxide and a primary or secondary alkanol
having about 8 to about 16 carbon atoms, the proportion of combined
ethylene oxide being from about 52 to about 80 percent by weight,
and mixtures thereof.
2. condensates of ethylene oxide and an alkanol having 14-15 carbon
atoms with about 25 percent 2-methyl branching, the proportion of
combined ethylene oxide in said condensate being from about 52 to
about 80 percent by weight, and mixtures thereof.
3. condensates of ethylene oxide and a hydrophobic base selected
from the group consisting of the reaction product of propylene
oxide and propylene glycol, said reaction product having a
molecular weight of about 1,800.
The water-soluble polyetheneoxy organic nonionic detergent
compounds may include:
1. Poly (ethylene oxide) condesates of primary or secondary
aliphatic alcohols having about 11 to about 15 carbon atoms, said
condensates having an average of about 9 molar proportions of
ethylene oxide per mole of alcohol, and mixtures thereof.
2. Poly (ethylene oxide) condensates of primay aliphatic alcohols
having about 12 to about 15 carbon atoms and having about 25% lower
alkyl branching on the 2-carbon, said condensates having an average
of about 9 to about 20 molar proportions of ethylene oxide per mole
of alcohol, and mixtures thereof.
3. A condensate of 1 mole of octylphenol and about 7 -8 molar
proportions of ethylene oxide.
4. Poly (ethylene oxide) condensates of linear primary alcohols
having about 14-15 carbon atoms, and averaging about 13.5 carbon
atoms, and having about 25 percent lower alkyl branching on the
2-carbons, said condensates having an average of about 13.5 molar
proportions of ethylene oxide per mole of alcohol.
5. The poly (ethylene oxide) condensates of alkylphenols, e.g., the
condensation of products of alkylphenols having an alkyl group
containing from about 6 to 12 carbon atoms in either a straight
chain or branched chain configuration, with ethylene oxide, said
ethylene oxide being present in amounts equal to 6 to 25 moles of
ethylene oxide per mole of alkylphenol. The alkyl substituent in
such compounds may be derived from polymerized propylene,
diisobutylene, octene, dodecene, or nonene, for example.
6. Compounds formed by the simultaneous polymerization of propylene
oxide and ethylene oxide, and containing randomly positioned
propeneoxy and etheneoxy groups.
As examples of specific nonionic detergent compounds finding
utility in accordance with the invention, there may be
mentioned:
A. branched-chain nonyl phenol condensed with about 8-14 molar
proportions of ethylene oxide,
B. a mixed C.sub.11 -C.sub.15 secondary alcohol condensed with 9-14
molar proportions of ethylene oxide, the mixed secondary alcohols
having the following approximate chain-length distribution:
2% C.sub.10 15% C.sub.11 21% C.sub.12 23% C.sub.13 17% C.sub.14 15%
C.sub.15 7% C.sub.16,
C. a mixed C.sub.14 -C.sub.15 alcohol made by the Oxo process
condensed with about 9-15 molar proportions of ethylene oxide,
and
D. a mixture of about 65% C.sub.14 and about 35% C.sub.15 synthetic
straight-chain primary alcohols condensed with about 9-15 molar
proportions of ethylene oxide.
The ternary compositions of the present invention may be formulated
with a detergent builder as a detergency aid, for example, those
mentioned hereinafter, to provide a commercially valuable
detergent-bleach composition.
The term "builder" as used herein refers to any substance
compatible with, and assisting the detergency of the aforementioned
ternary combination.
Suitable builder compounds are tetrasodium and tetrapotassium
pyrophosphate, pentasodium and pentapotassium tripolyphosphate,
sodium or potassium carbonate, sodium or potassium silicates having
an SiO.sub.2 : Na.sub.2 O ratio of about 1:1 to about 3.2:1,
hydrated or anhydrous borax, sodium or potassium sesquicarbonate,
phytates, polyphosphonates such as sodium or potassium
ethane-1-hydroxy-1, 1-diphosphonate, etc.
Also useful are other organic detergent builders such as the sodium
or potassium oxydisuccinates, sodium or potassium oxydiacetates,
carboxymethyloxysuccinates, hydrofuran tetracarboxylates,
ester-linked carboxylate derivatives of polysaccharides, such as
the sodium and potassium starch maleates, cellulose phthalates,
semi-cellulose diglycolates, starch, oxidized heteropolymeric
polysaccharides, etc. The weight percent of the builder present in
the built anionic detergent composition is from an amount of about
6 and up to about 90 percent from about 20 to about 60 percent.
Suitably, a builder may be present in the ratios of about 0.5 to
about 10 parts by weight, preferably about 2 to about 5 parts by
weight, for each part by weight of the detergent component.
Other materials which may be present in the detergent compositions
of the invention are those conventionally employed therein. Typical
examples include the well-known soil suspending agents, corrosion
inhibitors, dyes, perfumes, fillers, optical brighteners, enzymes,
germicides, anti-tarnishing agents, and the like. The balance of
the detergent composition may be water.
The detergent compositions with which the encapsulated bleaching
agents of the invention find utility may have compositions
represented by the following components and ranges of proportions
thereof:
Approximate Percentage ______________________________________
Anionic or nonionic detergent 1-90% Builder 0-90% Encapsulated
bleaching agent 2-25% Optical brightener 0-0.3% Sodium
carboxymethylcellulose 0-1% Water 5-15% Sodium sulfate 0-25%
______________________________________
Detergent compositions formulated for use in the washing of fabrics
in automatic washing machines may contain about 5 to about 30
percent anionic detergent, about 30 to about 60 percent of one or
more of the builders mentioned hereinabove, and sufficient
encapsulated bleaching agent to provide 30-200 parts per million
chlorine in the wash water, or approximately 2 to 25 percent of the
agent in the detergent formulation. Usually included are about 0.1-
0.3 percent optical brightener, and about 0.4 percent sodium
sulfate, and if desired small proportions of other components such
as germicides, anti-caking agents, etc. to confer special
properties on the product.
When the detergent is soap, and comprises the major proportion of
the detergent-bleach product, the soap may be present in amounts
from about 60 to about 90 percent little or no builder being
required, although about 1 to about 10 percent of an alkaline
builder may be advantageous.
When the detergent is nonionic, from about 5 to about 20 percent is
suitable, the balance of the composition being as listed above.
Detergent compositions formulated for mechanical dishwashers and
having the encapsulated bleaching agents of the invention therein
may contain low proportions of nonionic detergent, for example
about 1 to about 4 percent, and may contain a suds depressant and a
high proportion of a builder, for example about 50- 90 percent of a
mixture of sodium tripolyphosphate, sodium carbonate, and sodium
silicate.
The invention may be more fully understood by reference to the
following examples.
EXAMPLE 1
This example describes a dual-coating process within the
invention.
Thirteen pounds of extra coarse grade potassium
dichloroisocyanurate are charged onto the perforated plate of the
cylindrical coating tower 1 (FIG. 1). The perforated plate is a
60-mesh stainless steel screen. The particles are fluidized and
suspended by an upwardly moving air stream supplied by blower 10.
The superficial air velocity of the fluiding air stream is 8.5 feet
per second. The temperature of the air is maintained at 95.degree.
.+-. 2.degree.F, by heat exchanger 11.
The primary coating solution is prepared by dissolving
triple-pressed stearic acid (about 45 percent stearic acid) in
methylene chloride to form a 20 percent solution. A small amount of
ultramarine blue is dissolved in the coating solution for
subsequent use in observing the continuity of the primary
coating.
The primary coating solution is sprayed on the fluidized particles
3, through nozzle 5, appropriately adjusted as to height. Nozzle 5
has six orifices disposed to provide the desired diverging spray
pattern. An auxiliary stream of air is applied to the fluidized bed
through 9 nozzles horizontally disposed at the perforated support
screen level with the tips of the nozzles placed close to the inner
wall of the tower. The air leaves these nozzles in a horizontal
path substantially tangential to the wall of the tower. It is the
function of this tangential air to assist in keeping in motion the
particles at the outer periphery of the plate which do not obtain
the full effect of the fluidizing air.
The coating solution is applied to the fluidized particles for a
period of 2 hours. The weight of the coating is about equal to the
weight of the original particles. The coated particles are of
uniform blue color and size, with substantially no agglomeration,
and are dry and free-flowing. When some of the coated particles are
left immersed for 2 days in an acidified potassium iodide solution,
no color change is observed, indicating complete encapsulation of
the particles.
The second coating is applied in the following manner.
A 5.2% sodium hydroxide solution is prepared by diluting 60 grams
of 50% NaOH solution with 520 grams of distilled water in a
two-liter beaker. The dilute solution is heated to 100.degree.F in
a water bath and 200 grams of the particles coated as described
above are placed in the NaOH solution and gently agitated for 30
minutes, maintaining the temperature of the solution between
105.degree.F and 110.degree.F. The molar ratio of NaOH to fatty
acid is 2:1. After the 30-minute treatment, the solution is
decanted through a 25-mesh stainless steel screen, and the
particles on the screen are dried at room temperature for 24 hours.
The particles are free flowing and white, indicating complete
covering of the blue-colored first coat.
The single- and double-coated particles are tested for east of
chlorine release and for adverse effect on cloth in the following
manner.
Six pounds of white cotton fabric are placed in a top-loading
automatic washing machine. Three swatches of blue denim cloth and
one swatch of black 65/35 Dacron/cotton cloth, each measuring 12
.times. 12 inches are placed on top of the cotton cloth in circular
configuration. Next, there is placed directly on the fabric 3.4
ounces of a detergent-bleach composition containing 8.0percent of
the encapsulated material prepared as above. Water at a temperature
of 132.degree.F .+-. 3.degree.F is run directly on the
detergent-bleach composition for about 150 seconds to a volume of
17.4 gallons. The wash solution is agitated for 10 minutes, and the
fabrics are examined. The results are shown in Table 1.
TABLE 1 ______________________________________ % Pinholing % Bleach
Composition Available (Blue Chlorine KDC Coated With Chlorine
Denim) Released ______________________________________ Single Coat
with Fatty Acid Fatty Acid (A) 35.0 3 97-100 Fatty Acid (B) 37.5 0
20 Fatty Acid (C) 39.0 1 41.5 Dual Coat - First Coat = Fatty Acid
(A) 2.85% NaOH 21.03 2 not 10 min. determined 5.34% NaOH 23.19 1
69.83 30 min. 10.33% NaOH 26.15 1 87.70 30 min. (A) about 45%
stearic acid and 55% palmitic acid; m.p. 131-132.degree.F (B) 95%
palmitic, 4% stearic, 1% myristic acids; m.p. 138-144.degree.F (C)
about 70% stearic acid and 30% palmitic acid; m.p.
138.5-143.degree.F Pinholing Rating 0 = none (excellent) 1 =
minimal pinholing (acceptable) 2 = severe pinholing (unacceptable)
3 = very severe pinholing (unacceptable)
______________________________________
From the foregoing data in Table 1, is may be seen that a single
coating of fatty acid is inadequate to accomplish the dual purpose
of providing a high chlorine release and at the same time avoid
pinholing. It will be noted that fatty acid (A) having a melting
point below the temperature of the wash water, melts to release all
of the chlorine in the encapsulated material, but causes pinholing,
due to contact of the encapsulated material with the fabric upon
the melting of the fatty acid coating. Fatty acids (B) and (C),
having melting points above the temperature of the wash water, are
unsatisfactory, since they do not allow a sufficient release of
chlorine to be of any value as a bleach, although the low level of
chlorine release prevents pinholing.
Again referring to the foregoing data, it will be observed that a
dual coating applied in accordance with the invention prevents
pinholing to a substantial extent, and additionally allows an
adequate release of chlorine.
EXAMPLE 2
This example further illustrates the present process for applying a
first coat of fatty acid to particles of potassium
dichloroioscyanurate.
A coating solution is prepared in vessel 6 by dissolving 10 pounds
of fatty acid (about 70% stearic acid and 30% palmitic acid) in 40
pounds of methylene chloride. Twenty grams of blue pigment is added
and the solution warmed at 95.degree.F.
Ten pounds of extra coarse grade potassium dichloroisocyanurate is
screened to 25 mesh and placed on the 40-mesh supporting screen in
coating tower 1 (FIG. 1). Fluidizing air is forced into the
apparatus through duct 9 at a superficial air velocity of 6.8 feet
per second. Tangential air is supplied as needed. The temperature
of the bed is maintained at 107.degree. .+-. 2.degree.F.
The coating solution is sprayed downward onto the fluidized bed
through a 6-hole atomizing nozzle located 12 inches above the
supporting screen. The coating is applied at the rate of 6.7 pounds
per hour, and the solvent is evaporated at the rate of 23 pounds
per hour.
The coated product is a dry, nonagglomerated, freeflowing
particulate solid of which the particles are substantially uniform
in size. A test in potassium iodide solution indicates that the
particles are completely covered.
After storing for 8 weeks at 80.degree.F and 80 percent relative
humidity admixed with particles of a commercial detergent,
substantially no loss of chlorine occurs. A control wherein the
potassium dichloroisocyanurate is uncoated loses 90 percent of its
chlorine.
EXAMPLE 3
This example illustrates the coating of sodium perborate with
polyethylene glycol, m.w. 6,000.
The process follows that described in Example 1, except that 10
pounds of coarse grade sodium perborate is used as the core
material, and the coating material is polyethylene glycol, m.w.
6,000 applied from a 20% solution in methanol. A small amount of
Congo Red dye is dissolved in the methanol for subsequent use in
judging the continuity of the coating. The weight ratio of coating
to core material is 1:2, that is, the coated particles have
one-third coating material by weight. This requires 25 pounds of
coating solution, or 20 pounds of solvent, i.e., methanol, to be
evaporated. The evaporation is accomplished in 2 hours at a bed
temperature 0f 80.degree.-90.degree.F, and a final fluidizing air
velocity of 6.8 feet per second. The bed of perborate particles is
2 inches thick before fluidizing. The coating solution is applied
from a nozzle located 1 foot from the top of the 2-inch thick
bed.
EXAMPLE 4
The process of this example is the same as that of Example 3,
except that the coating material is polyvinylpyrrolidone having a
molecular weight of 15,000, and the air velocity of the fluidizing
air is 4.3 feet per second.
EXAMPLE 5
A spray-dried detergent composition having the following formula is
prepared by conventional procedures.
______________________________________ % Alkylbenzenesulfonate 10.0
% Sodium tripolyphosphate 33.0 % Sodium silicate solids 6.0
(SiO.sub.2 :Na.sub.2 O = 2.4) % Optical brightener 0.1 %
Carboxymethylcellulose 0.3 % Water 10.0 % Sodium sulfate and
miscellaneous 40.0 matter introduced with the components 100.0
______________________________________
To separate portions of the above-described compositions are mixed
various proportions of the dual-encapsulated product of Example 1,
the proportions being as follows.
Parts By Weight Example No. 5A 5B 5C 5D 5E
______________________________________ Spray-dried composition 80
84 88 92 96 Product of Example 1 20 16 12 8 4
______________________________________
EXAMPLE 6
A composition suitable for use in mechanical dishwashers and having
the following formula is prepared by conventional
% Nonionic detergent.sup.(a) 2.0 % Sodium tripolyphosphate 20.0 %
Trisodium orthophosphate 25.0 % Sodium metasilicate 13.0 % Water
10.0 % Encapsulated bleaching agent 30.0 100.0 .sup.(a) A
condensate of a mixture of primary aliphatic alcohols having about
12-15 carbon atoms with about 25% lower alkyl branching on the
2-carbon, and about 9 molar proportions of ethylene oxide.
EXAMPLE 7
This experiment shows the effect of coating temperature on the
second coat of potassium dichloroisocyanurate when the second
coating solution is a solution of potassium hydroxide. The first
coat is applied as in Example 1. The second coat is applied under a
variety of conditions, namely at several concentrations and at
temperatures of 85.degree.F and 100.degree.F. The results of these
tests show that a satisfactory dual coating is obtained when the
second coating is applied from a 10 percent solution of KOH at a
temperature of 85.degree.F. However, at a temperature of
110.degree.F, the second coating becomes gel-like when the KOH
concentration is less than 10 percent, and cracks upon drying when
the KOH concentration is 15-20 percent.
EXAMPLE 8
This example illustrates the effect of sodium hydroxide
concentration of from 3 to 10 percent in the solution employed for
applying the second coating to particles of potassium
dichloroisocyanurate.
In this experiment the fatty-acid-coated particles are treated with
the alkali solution at a temperature of 110.degree.F and a reaction
time of 30 minutes, other test conditions being as described in
Example 1. The weight of total coating is approximately the same as
the weight of starting core substance.
Eight parts by weight of the double coated potassium
dichloroisocyanurate are admixed with 92 parts by weight of a
spray-dried detergent composition having the formula set forth in
Example 5. The mixture is tested in a washing machine at a
wash-water temperature of 135.degree.F and a 12-minute agitation,
other conditions being as described in Example 1. During the
washing period, the wash solution is analyzed for oxidizing
chlorine, and from this figure is calculated the percentage of
available chlorine in the mixture that is released. Samples are
taken and analyzed 1/2, 2, 5, 8, 10 and 12 minutes after the start
of the agitation of the wash solution. At the end of the test, the
denim swatches are visually observed for pinholing. The results are
provided in Table II, below. It will be noted that the
concentration of the sodium hydroxide in the solution used to apply
the second coat to the particles has no effect on the percentage of
chlorine released during use. Pinholing is virtually absent when
the second coat is applied from a 3-7 percent sodium hydroxide
solution, and is greatly reduced when the concentration is 8-10
percent.
TABLE II.
__________________________________________________________________________
PINHOLE TEST AND AVAILABLE CHLORINE RELEASE Concentration of NaOH
Used Available "Pinholing".sup.1 % Chlorine Released Example to
Apply Second Coat Chlorine (%) Rate 30 sec. 2 min. 5 8 10 12 min.
__________________________________________________________________________
7a 3% NaOH 26.14 0-1 16.88 52.17 80.26 89.13 89.12 89.07 7b 4%
24.79 0-1 0 43.22 50.49 76.47 90.44 89.57 7c 5% 24.50 0-1 4.38
43.35 89.04 89.04 95.6 92.51 7d 6% 26.10 0-1 0 39.73 56.86 77.41
89.32 90.27 7e 7% 27.95 0-1 5.58 56.58 86.32 90.50 91.05 93.23 7f
8% 28.32 1-2 19.23 49.24 78.07 93.26 93.54 90.36 7g 9% 30.29 1-2
20.43 75.08 90.69 87.31 93.10 87.81 7h 10% 27.92 1-2 14.17 63.50
92.23 89.41 94.95 90.0
__________________________________________________________________________
Notes: .sup.1 "Pinholing Rate 0 = No pinholing (excellent) 1 =
Pinholing observed (acceptable) 2 = Severe pinholing
EXAMPLE 9
This example illustrates the substantially complete stability of
potassium dichloroisocyanurate having a double coating in
accordance with the present invention.
To separate portions of the spray-dried detergent composition
having the formula of Example 5 are added double coated particles
of potassium dichloroisocyanurate prepared by the process of
Example 1, the coated particles added to one portion having had the
second coat applied from a 5% NaOH solution, and the coated
particles added to the other portion having had the second coat
applied from a 10% NaOH solution. The proportion of the double
coated potassium dichloroisocyanurate relative to the proportion of
detergent composition is such as to provide about 2 percent
available chlorine, basis total mixture. A control mixture is
prepared wherein uncoated potassium dichloroisocyanurate is mixed
with the detergent composition of Example 5 in a proportion to
provide approximately 2 percent available chlorine.
Six cartons of each of the three aforesaid mixtures are prepared,
each carton containing 400 grams of the total mixture. The base
detergent composition and the bleach component are separately added
to each carton to avoid sampling and segregation errors which might
be possible if the cartons were filled from a larger bulk mixture.
The contents of each carton are blended in a rotating mixer. The
cartons are wax laminated to provide a vapor barrier.
Each sample is stored in the aforementioned cartons in sealed
condition at a temperature of 80.degree.F and 80percent humidity.
Prior to sealing, two weighed samples are removed from two cartons
of each of the three mixtures and analyzed for available chlorine
content. The analysis shows that the available chlorine content
prior to storage ranges from 1.95 to 2.16 percent, with a mean
value of 2.04 percent, basis mixture of detergent composition and
dichloroisocyanurate. The stored mixtures are sampled and analyzed
for available chlorine content after 1, 2, 4 6, 8 and 12 weeks, one
carton of each mixture being removed from storage for a duplicate
analysis at each of these periods. The results, presented in Table
III, show that the uncoated potassium dichloroisocyanurate loses
about 15 percent of its available chlorine under the aforementioned
storage conditions while the double coated dichloroisocyanurate
loses only about 2 percent to about 2.5 percent of its available
chlorine. The protection afforded by the second coating whether
applied from a 5 percent NaOH solution is substantially the
same.
TABLE III.
__________________________________________________________________________
AVERAGE AVAILABLE CHLORINE AND % AV. CHLORINE LOSS Bleach % Av.
Chlorine Storage Time Component and Its Loss 0 Wk. 1 Wk. 2 Wk. 4
Wk. 6 Wk. 8 Wk. 12 Wk.
__________________________________________________________________________
Uncoated % Av. Chlorine 2.04 1.83 1.83 1.81 1.78 1.69 1.74 % Loss
0.00 10.29 10.29 11.27 12.75 17.16 14.71 Coated.sup.(a) % Av.
Chlorine 2.04 2.16 1.99 1.94 2.10 1.98 2.00 % Loss 0.00 -3.43 2.45
4.90 -2.94 2.94 1.96 Coated.sup.(b) % Av. Chlorine 2.04 1.97 1.94
1.93 2.11 2.03 1.99 % Loss 0.00 3.43 4.90 5.39 -3.43 0.49 2.45
__________________________________________________________________________
.sup.(a) Second coating applied from a 5% solution of NaOH .sup.(b)
Second coating applied from a 10% solution of NaOH
EXAMPLE 10
This example shows the effect on stability of coated and uncoated
chlorinated cyanurates admixed with a detergent composition when
stored variously in open wax-laminated barrier cartons and in open
and closed non-barrier cartons, i.e., allowing free or only
partially restricted passage of vapors.
Mixtures are prepared, stored and analyzed as described in Example
8, with the exception that the second coating, when applied, is
applied froma 6% NaOH solution, and other exceptions identified as
follows:
Ex. Core Coating Carton ______________________________________ 9a
Potassium dichloroisocyanurate Double Barrier type Open top 9b
Potassium dichloroisocyanurate " Non-barrier type Open top 9c
Potassium dichloroisocyanurate " Non-barrier type Closed top 9d
Potassium dichloroisocyanurate Not Non-barrier dihydrate Coated
type Open top 9e Potassium dichloroisocyanurate Not Barrier type
Coated Open top 9f Potassium dichloroisocyanurate Not Non-barrier
Coated type Open top 9g Potassium dichloroisocyanurate Not
Non-barrier Coated type Closed top
______________________________________
After 2 weeks' storage at 80.degree.F and 80 percent relative
humidity, the chlorine losses are determined. The protective action
of the double coating as compared with uncoated particles of
chlorine bleaching agent is evident from the data set forth
below:
Storage Time Example 0 Week 2 Weeks
______________________________________ 9a % Chlorine 2.31 2.26 %
Loss -- 2.1 9b % Chlorine 2.28 2.21 % Loss -- 3.1 9c % Chlorine
2.29 2.28 % Loss -- 0.4 9d % Chlorine 2.09 0.96 % Loss -- 54.1 9e %
Chlorine 2.01 1.99 % Loss -- 1.5 9f % Chlorine 2.08 1.75 % Loss --
15.9 9g % Chlorine 1.99 1.86 % Loss -- 6.5
______________________________________
Having described the invention, modifications within the purview
thereof will occur to those skilled in the art, and accordingly the
invention is to be limited only within the scope of the appended
claims.
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