Abstrict The present invention relates to a novel desiccant powder and its
use for the drying of solid substrates wetted by an aqueous or oily
liquid such as, in particular, grains or seeds having undergone
a coating or surface film-forming treatment. According to the invention,
this desiccant powder contains at least 50% by weight of absorbents
with respect to the toal weight of the said powder, being preferably
available in the form of particles having a mean diameter less than
about 100.mu., the said absorbents being constituted of at least
one aluminosilicate, in particular mica, to at least 25% by weight
with respect to the total weight of the said absorbents. This powder
makes possible, in particular, the drying of colored grains or seeds.
Claims We claim:
1. A process for drying a germinative substrate of grains or seeds
which have been wetted in a coating or surface film-forming treatment,
said process comprising dusting said substrate with a desiccant
powder comprising absorbents in an amount of at least 50% by weight
with respect to the total weight of the powder, said absorbents
comprising at least one aluminosilicate in an amount of at least
25% by weight with respect to the total weight of the absorbents,
said substrate being dusted with 0.5 to 50 g of dessicant powder
per kilogram of substrate, said powder being substantially free
of components which would interfere with germination of the substrate.
2. A process according to claim 1 wherein the dessicant powder
further comprises a pigment, said pigment being present in said
powder in an amount of up to 50% by weight.
3. A process according to claim 2 wherein said pigment is a micaceous
pigment.
4. A process according to claim 2 wherein said pigment is present
in the form of a pigmentary paste.
5. A process according to claim 2 wherein said powder further
comprises a flow-promoting agent, said flow-promoting agent being
present in said powder in an amount of up to 20% by weight.
6. A process according to claim 5 wherein the flow-promoting agent
is powdered silicas.
7. A process according to claim 1 wherein said absorbents are
in the form of particles having a mean diameter of less than 100
um.
8. A process according to claim 1 wherein said at least one aluminosilicate
is selected from the group consisting of
mica, the illites, the micaceous clays, the micaceous pigments,
kaolin, kaolinite, dickite, nacrite, the montmorillonites, the smectites,
the glauconites, the attapulgites and the vermiculites.
9. A process according to claim 1 wherein said at least one aluminosilicate
comprises mica.
10. A process according to claim 1 wherein said absorbents further
comprise at least one substance selected from the group consisting
of talc, cellulose and its derivatives, and silica.
11. A process according to claim 10 wherein said absorbents consist
essentially of said at least one aluminosilicate and said at least
one substance, said at least one substance being present in said
absorbents in an amount of up to 75% by weight.
12. A process according to claim 10 wherein the powder consists
essentially of said at least one aluminosilicate, said at least
one substance, a pigment, and a flow-promoting agent.
13. A process according to claim 10 wherein the powder consists
essentially of said at least one aluminosilicate, said at least
one substance, a pigment, a film-forming agent and a flow-promoting
agent.
14. A process according to claim 1 wherein the powder further
comprises a pigment and a film-forming agent, and wherein the pigment
and the film-forming agent are present in the powder in an amount
of up to 50% by weight.
15. A process for coating a germinative substrate of grains or
seeds with a dressing to protect or to accelerate the germination
of said substrate, said process comprising
(a) forming a film or coating on the substrate by treating said
substrate with a fluid composition comprising said dressing, a film-forming
agent and water, said composition being sufficiently fluid to ensure
uniform distribution of the dressing on the substrate; and
(b) removing at least some of said water from said substrate by
dusting the substrate with a dessicant powder comprising absorbents
in an amount of at least 50% by weight with respect to the total
weight of the powder, said absorbents comprising at least one aluminosilicate
in an amount of at least 25% by weight with respect to the total
weight of the absorbents, said substrate being dusted with 0.5 to
50 g of dessicant powder per kilogram of substrate, said powder
being substantially free of components which would interfere with
germination of the substrate.
16. A process as claimed in claim 15 wherein the film-forming
agent is glossy, and the substrate after it has been dusted with
said powder has a glossy appearance.
17. A process as claimed in claim 15 wherein the fluid composition
comprises about 50 grams/kilo of substrate treated.
Description Substantially, the object of the present invention is a novel desiccant
powder intended, in particular, for the drying of solid substrates
wetted by an aqueous or oily liquid such as, in particular, grains
or seeds having undergone a coating or surface film-forming treatment.
It is known that the germination capacities of grains or seeds
can be improved by a coating or surface film operation designed
to affix dressing agents for specific additives in predetermined
amounts to these grains or seeds, preferably in a uniform manner.
More precisely, this operation consists of applying to the grains
or seeds, for example, by spraying, blending, churning or any other
known means, a "paste" of surface film or coating containing
essentially plant protection, fungicidal or insecticidal dressings,
additives designed to accelerate germination (micro-organisms, trace
elements) in an aqueous solution of film-forming agents. In addition,
this paste may contain various additional agents, such as binders,
pigments or coloring materials, plasticizers and wetting agents.
The film-forming agents which may be used for the surface film
formation are usually film-forming polymers soluble or dispersible
in water, not exhibiting phytotoxicity and not causing delay or
decline in germination. Such polymers are, for example, acrylic
polymers, polyvinyl alcohols, polylactones and cellulose derivatives.
The document EP-O 133 827 incorporated here for reference, describes
various examples of film-forming compositions for the coating of
solid substrates.
The operation of film formation or coating makes possible a more
rational and more efficient use of the dressing agents and additives
dosed with precision for each seed.
In addition, the application of a surface film to grains or seeds
offers the following three advantages:
it gives to the grain or seed a smooth and attractive appearance,
in particular when the film is colored;
it permits easy identification, for example, as a result of surface
coloration;
finally, it provides better flow in the drills and other mechanical
transfer devices in which the grains slip easily over each other.
Moreover, in order to ensure a good distribution of the dressing
agents and additives on the grains and seeds, the paste from which
the surface film is formed and in particular the film-forming solution
must be sufficiently fluid. For this purpose, the dry material content
rarely exceeds 15 to 20% by weight. Consequently, relatively large
amounts of water (up to about 50 g per kilo of seeds treated) are
to be removed by a drying operation.
This drying operation which, from an industrial point of view,
must be rapid, efficient and inexpensive, usually proves to be difficult.
In fact, some grains, as for example soja, rapidly absorb water
when they are in contact with the surface film paste. The resulting
excess internal humidity may lead to undesirable biochemical reactions,
impair grain storage and modify its germination capacity. Furthermore,
the absorption of water is usually accompanied by swelling of the
grain, which only very slowly resumes its initial form. Now, the
film surrounding the grain is not always sufficiently elastic to
cope with these variations in volume and there is a risk of signs
of disintegration and/or cracking appearing.
Moreover, the formation of agglomerates of film-coated grains is
observed when drying is insufficient or too slow. Such agglomerates
do not lead to uniform seeding and are thus to be avoided.
Finally, in the case of many types of seeds, particularly those
of large-scale crops, the initial cost created by the operation
of surface film formation, and in particular the drying operation,
must be kept to a minimum. This constraint makes it practically
impossible to use sophisticated and expensive machinery.
Among the known drying techniques, hot air blowing is one of the
most commonly used.
In the case of grains with high added value representing small
volumes (kitchen garden and flower seeds, some hybrid species),
equipment of the fluidized air bed type is used. On the other hand,
for less select seeds, simple tunnels or ventilated turbines, operating
at high throughput, are used.
However, air blowing presents a certain number of disadvantages
which limits its value.
In fact, the efficiency of this drying technique remains low on
account of the low temperatures used in order not to damage the
seeds.
In addition, this technique entails heavy expenditure owing to
the depreciation costs of the equipment and the expensive energy
consumption.
Finally, this technique causes certain pollution problems.
The problem of drying has been resolved by the use of desiccant
powders. More precisely, powders are dusted onto the film-coated
grains, by remaining fixed to the film former, by thus avoiding
any correlative risk of dust formation during the subsequent handling
of the grains or seeds.
The use of desiccant powders is a technique which does not require
any expensive investment and which can be implemented easily on
all existing types of film-forming or coating materials.
All of the desiccant powders used hitherto are based on magnesium
silicate, in particular they are based on talc or serpentine.
However, the grains dried with talc possess a dull, lackluster,
whitish appearance. This disadvantage is negligible when the grains
are coated or covered with a surface film by means of a colorless
film-forming agent, but becomes quite flagrant when the surface
film is formed with colored or glossy film-forming agents, one of
the objectives of which is to give to the grain or seed an attractive
appearance.
The aim of the present invention is to resolve the technical problem
consisting in the provision of a novel desiccant powder possessing
the same advantages as the magnesium silicate-based desiccant powders
without having their disadvantages previously mentioned.
It has been discovered, and that constitutes the basis of the present
invention, that the use of aluminosilicate-based, and in particular
mica-based, desiccant powders enables the appearance of the grains
thus dried to be considerably improved. In fact such grains possess
a vivid appearance and their coloration is unaltered.
In addition, it has been quite unexpectedly discovered that the
amounts of such novel desiccant powders required for use are much
lower than the amounts of known desiccant powders based on talc
in order to obtain the same degree of drying.
Thus, according to a first feature, the present invention relates
to a desiccant powder intended in particular for the drying of solid
substrates wetted by an aqueous or oily liquid such as, in particular,
grains or seeds having undergone a coating or surface film-forming
treatment, characterized in that it contains at least 50% by weight,
with respect to the total weight of the said powder, of absorbents
preferably available in the form of particles having a mean diameter
of less than about 100.mu., the said absorbents being constituted
of at least one aluminosilicate to at least 25% by weight with respect
to the total weight of the said absorbents.
According to a particular characteristic of the invention, this
aluminosilicate is selected from the group constituted by mica,
the illites or micaceous clays, the micaceous pigments, kaolin and
its modifications, such as kaolinite, dickite, nacrite, the montmorillonites
or smectites, the glauconites, the attapulgites, the vermiculites.
According to a preferred embodiment, the aforementioned aluminosilicate
is mica.
The absorbents contained in a desiccant powder conforming to the
invention may be constituted exclusively of one or several aluminosilicates,
but may also be constituted of one or several aluminosilicates in
a mixture with one or several traditional absorbents such as talc,
cellulose, silica. The person skilled in the art will easily be
able to define compositions of absorbents according to the intensity
of the glossy effect which it is desired to give to the substrates.
According to another particular characteristic of the invention,
this desiccant powder contains, in addition, up to 50% by weight,
with respect to the total weight of the said powder, of a pigment,
a micaceous pigment, a coloring matter or a pigmentary paste.
According to another particular characteristic, a desiccant powder
conforming to the invention contains, in addition, up to 50% by
weight, with respect to the total weight of the powder of at least
one film-forming agent. The presence of such a film-forming agent
within the powder confers on this latter an improved adherence to
the solid substrate to be dried. It is possible to use any known
type of film-forming agent, and in the particular case of seeds
or grains, film-forming agents of the same type as those used for
the coating operation.
According to another particular characteristic, a desiccant powder
conforming to the invention contains, in addition, up to 20% by
weight, with respect to the total weight of the powder, of at least
one flow-promoting agent such as, in particular, powdered silicas.
The addition of one or several flow-promoting agents to the desiccant
powder improves the uniformity of the dusting of the substrate.
It is possible to use as flow-promoting agent all of those commonly
used in the food or pharmaceutical industries and, in particular,
powdered silicas, in particular Aerosil.RTM. (registered trademark)
or Sipernat.RTM. (registered trademark).
The novel desiccant powders conforming to the present invention
possess the following general characteristics:
they are not toxic towards the substrates; in the case in which
the substrate is a grain, no modification of germination is observed;
they are compatible with plant protection products and do not bring
about any impairment of their activity;
they exhibit a high absorbent capacity (large specific surface),
and stable physical structures.
According to a second feature, the present invention relates to
the use of a desiccant powder such as previously defined for the
drying of solid substrates wetted by an aqueous or oily liquid such
as, for example, grains or seeds having undergone a coating or surface
film-forming treatment.
Finally, according to a last feature, the present invention aims
to cover a process for the drying of solid substrates wetted by
an aqueous or oily liquid such as, in particular, grains or seeds
having undergone a coating or surface film-forming treatment, characterized
in that it comprises the dusting of a desiccant powder such as previously
defined in an amount of 0.5 to 50 g per kilogram of solid substrates.
The following non-limiting examples illustrate the novel desiccant
powders conforming to the invention and their utilization.
In these examples, the aluminosilicate is usually mica, which has
proved to be particularly useful for the manufacture of these novel
desiccant powders. |