Controlled release composition and method of manufacturing same

Controlled release compositions are manufactured by subjecting cellulosic pulp rejects to a dewatering operation to remove approximately 25% of the water; flash-drying the obtained partially dewatered rejects, causing the rejects to expand and become porous; adding an additive material to impregnate the expanded and porous cellulosic material, and drying. The cellulosic material holds or retains the additive for delayed release. The compositions have good stability and structural integrity.

FIELD OF INVENTION AND BACKGROUND 
The present invention is directed to controlled release compositions. More 
particularly, the invention is directed to an expanded, porous, cellulosic 
carrier material impregnated with an additive material for subsequent 
release or chemical reaction, and to its process of manufacture. According 
to the present invention, cellulosic pulp rejects from a papermill are 
partially dewatered; flash-dried to cause the rejects to expand and become 
porous; an additive material to be slowly released is applied to the 
expanded porous cellulosic rejects, and then dried. The cellulosic carrier 
material holds or retains the additive for delayed release. 
It is recognized that there are numerous compositions which are necessarily 
or most advantageously applied for slow release over a period of time. 
Such compositions include fertilizers, plant growth stimulants, 
herbicides, pesticides, and fungicides. As a result of this need, various 
time or controlled release compositions have been proposed. U.S. Pat. No. 
4,388,352 discloses a time-released composition wherein a carrier such as 
never-dried cellulosic pulp is immersed in a solution of an impregnant, 
such as a solution of fertilizer; the mixture distilled to exchange the 
fluid in the pores of the carrier with the solution of the impregnant, and 
thereafter the carrier is dried to entrap the impregnant within the pores. 
According to the patent disclosure, during the distillation process the 
solution of impregnant diffuses through the pulp to displace the water 
otherwise in the pores. The pulp is then dried. During the drying, the 
pores of the never-dried pulp irreversibly collapse. The collapse of the 
pores is the manner in which the impregnant is trapped within the pulp. 
Accordingly, the carrier material in the final composition is not porous 
and, therefore, the additive material must pass through the carrier 
material for release. 
U.S. Pat. No. 3,172,752 discloses a controlled release substance having an 
active material such as a herbicide, fungicide or insecticide suspended in 
or on perlite as a carrier material which is then coated. In the 
processing the carrier material is preheated to remove some of the water 
contained therein. Thereafter, the perlite is heated by means of a hot gas 
and caused to expand. The expanded perlite particles, according to the 
patent, provide a relatively inert particulate base for an active 
material. A holding material is added to the composition so that the 
additive material will more readily adhere to the perlite base. The 
holding material can be a material such as lignite, sea kelp, activated 
sewage sludge, or sulfide paper pulp liquor. Perlite, being a hard 
glasslike material, has limitations both from the standpoint of its 
treatment and from its end uses. 
U.S. Pat. No. 3,269,824 discloses a wastepaper soil conditioning and 
fertilizing pellet. According to the patent, wastepaper is repulped and 
water is then added to it, and the mixture cooked under pressure into a 
slurry of finely divided cellulose fibers. Fertilizers and other elements 
are then added to the slurry and thoroughly mixed. The resultant 
composition is drained into a vacuum chamber where excess moisture is 
drawn off until the slurry reaches the consistency of a stiff dough. The 
slurry is then packed into a metal cylinder and extruded into strands 
which are then cut into pellets. Any moisture remaining in the pellets is 
removed by drying under infrared lamps as the pellets move from the 
extrusion step along a conveyor belt. Upon application to soil, the 
moisture in the soil causes the densified pellets to expand gradually to 
double or triple their compressed volume while drying of the soil will 
cause the pellets to contract. The method of manufacture is time-consuming 
and expensive. 
Although the aforesaid methods and compositions are useful and each has 
certain advantages, none is completely acceptable from the standpoint of 
cost of materials and processing, stability and structural integrity of 
the composition, versatility of the carrier material so as to permit the 
use of a single carrier material for a plurality of additive materials, or 
availability of the carrier materials in diverse locations so as to permit 
manufacture of the compositions at or close to the point of use. 
OBJECTS AND GENERAL DESCRIPTION OF THE INVENTION 
Accordingly, it is a primary object of the present invention to provide a 
controlled release composition which is low in cost. 
It is another primary object of the present invention to provide a 
controlled release composition having good stability and structural 
integrity. 
It is another object of the present invention to provide a controlled 
release composition which is versatile permitting the use of a single 
carrier material for the collection and retaining of a plurality of 
additive materials. 
It is another primary object of the present invention to provide an 
improved method of making a controlled release composition which is low in 
cost, has good stability and structural integrity and is versatile in 
permitting the application and retaining of a variety of additive 
materials to a carrier using a single process. 
These and other objects of the invention will become apparent from the 
following general description of the invention, the illustrative drawing, 
and presently preferred detailed embodiment. 
According to the present invention, cellulosic pulp rejects normally 
recovered from a pulpmill in a water slurry are dewatered to remove a part 
of the water. The partly dewatered pulp rejects are then flash-dried, 
which expands and renders the rejects porous. In order to get adequate 
expansion and porosity, it is essential that the cellulosic pulp rejects 
at the time of flash-drying contain from about 40 to 70% water. The 
flash-drying is carried out in a conventional louvered rotary dryer such 
as a Heil or Aeroglide dryer at a temperature of from about 400 to 
700.degree. F. The high temperature causes the water on and in the 
cellulosic rejects to rapidly vaporize, causing the rejects to expand and 
"explode," providing the desired porosity in the cellulosic carrier. After 
the flash-drying, the expanded rejects are transferred to a cyclone 
storage bin from which they are fed to a sizer where they are sized and 
then fed to a blender. In the blender, the sized rejects are impregnated 
with an additive material such as a fertilizer. After the impregnation, 
the impregnated rejects are cooled and subjected to a final drying to the 
extent necessary. The rejects are then fed to a packaging or bagging 
machine, or to a bulk storage bin. 
According to the presently described invention, the carrier material 
comprises the cellulosic rejects of a papermaking plant. These rejects are 
a by-product or waste product of the papermaking operation, and comprise 
cellulosic fibers which are separated from the main body of pulp during 
the treatment of the pulp in the papermaking process. These reject fibers 
are carried in large volumes of water, for example 5% fiber and 95% water. 
The fibers are separated from the water using filtration means. The 
separated cellulosic fibers, commonly referred to as "rejects," still 
contain up to about 85% water. Further, the rejects are in the form of 
lumps or clumps of fibers. In the flash-drying of the rejects, the lumps 
or clumps are broken up into small particles. These particles are then 
impregnated with an additive material without substantial modification of 
the cellulosic particles. Accordingly, there is an abundant, low-cost 
supply of carrier material in the vicinity of every papermaking mill. 
The additive for application to the cellulosic carrier can be virtually any 
additive which is compatible with or which can be made compatible with the 
cellulosic rejects. Cellulosic rejects in water are hydrophilic and, 
therefore, will accept any naturally hydrophilic additive material or 
material which has been treated, for example, with a surfactant to provide 
compatibility. Alternatively, the cellulosic rejects can be treated to 
render them hydrophobic. The surfactants which are useful include the 
nonionic, anionic, and cationic surfactants. The selected surfactant 
depends in part upon the additive material to be utilized. Suitable 
additives include fertilizers such as mixtures of nitrogen, phosphorus and 
potash; as well as insecticides, herbicides, fungicides, and plant growth 
stimulants, particularly those which are to be applied directly to the 
soil. In such applications not only does the cellulosic carrier slowly 
release the additive over a period of time, but it acts as well to 
condition the soil. Over a period of time the carrier is assimilated into 
the soil to provide for aeration without packing and to help protect 
against erosion. Other additives for incorporation into the cellulosic 
rejects include pH-control materials to be used in compositions to be 
applied to the soil for controlling soil pH or for control of pH in a 
pH-sensitive operation. For example, the cellulosic carrier can be 
impregnated with an alkaline material such as sodium hydroxide. The sodium 
hydroxide containing composition can be used as a barrier for an 
acid-containing aqueous slurry. As the slurry, for example from an oil 
well, passes through the barrier, the acid contained in the slurry will be 
neutralized by the sodium hydroxide in the barrier. As will be apparent to 
one skilled in the art, other applications can be realized.

Also in the embodiment shown, pulp sizer and conditioner 12 is utilized to 
treat the dewatered pulp before flash-drying with a nonionic surfactant. A 
suitable nonionic surfactant is an ethylene oxide derivative of 
nonylphenol. The conditioned dewatered pulp is then fed to a flash dryer 
16 where the cellulose is subjected to a temperature of from about 400 to 
700.degree. F., at which temperature the water contained in the reject 
pulp is rapidly volatilized, expanding the pulp reject and rendering the 
pulp porous. The flash dryer utilized in the embodiment illustrated is a 
conventional dryer having a gas burner 17 which permits rapid heating and 
also heat dissipation. 
The flash-dried cellulose rejects are then fed to a cyclone storage bin 18 
for storage until the materials are to be impregnated with an additive 
material. The expanded cellulose is fed from bin 18 through product valve 
20 to a sizer 22 where the cellulosic particles are properly sized. It is 
usually desirable that all of the particles for a particular application 
have the same size within about a 20% range. Thus, depending upon the end 
application, one particle size may be preferable over another. For 
fertilizers it has been found that a preferred size is such that the 
cellulosic carrier will pass through a Tyler Standard Mesh of 8 to 4. This 
mesh corresponds to a 3/32 to 3/16 of an inch particle. After the sizing 
and separation of the different sizes depending upon the application, the 
cellulosic carrier is fed to a blender. In making a fertilizer, particles 
having a size of 3/32 to 3/16 of an inch in diameter are fed to blender 24 
and kept in continuous motion with an auger 25 having baffles 26. While in 
continuous motion, the cellulosic particles are sprayed with a aqueous 
mixture of 20% by weight nitrogen, 20% by weight phosphorus, and 20% by 
weight potash. As illustrated and in the preferred embodiment, a plurality 
of sprayers 28 --such as an air sprayer having adjustable valves to 
control the supply of air entering the mixing chamber within the sprayer 
where air and additive are blended--are arranged along the top or side of 
the blender. After being impregnated and continuously mixed, the 
impregnated cellulosic fibers are fed to a dryer-cooler 30, and from the 
dryer-cooler 30 either to a packaging facility 32, a bagging facility 34, 
or to bulk storage 36. 
The compositions of this invention slowly release the additive material to 
the environment of use, particularly the soil. Further, the compositions 
have structural integrity while being stored. They will, however, when 
applied to the soil become slowly assimilated by the soil, imparting 
aeration to the soil while helping prevent soil erosion. 
As will be apparent to one skilled in the art, various modifications can be 
made within the scope of the aforesaid description. Such modifications 
being within the ability of one skilled in the art form a part of the 
present invention and are embraced by the appended claims.