FR3107427A1 - Coating composition for seeds of natural origin based on dextrins and polyols - Google Patents

Abstract

The present application relates to a seed coating composition, in particular seeds, which can be used as a film-coating or coating composition. The coating composition comprises at least one binding agent chosen from native or modified dextrins, preferably native dextrins, and at least one plasticizer chosen from polyols, and in that the mass ratio of the dry masses of total dextrins / total polyols is included in a range from 0.1 to 9. This composition has the advantage of being of natural origin, and easily biodegradable. It partially or totally replaces the coating compositions formulated from polymers of petrochemical origin. It reduces the dust generated during the flow of seeds, while maintaining the ability to germinate.

Description

Seed coating composition of natural origin based on dextrins and polyols

The present application is in the field of seed treatments, called coating or coating. In particular, the seeds concerned are seeds, preferably dry seeds.

State of the art

Plant seeds are often covered before sowing, for example to protect them from damage during handling and/or to improve their handling properties. Seeds, especially seeds and seedlings, are often coated to also provide substances useful to the seed and seedlings during germination, for example plant nutrients, growth promoting agents and plant protection products. Typical seed coating methods include film-coating, granulation and potting.

The introduction of compounds of natural origin in the film coating or coating compositions of seeds or seeds dates back to the first half of the 20th century. Then the advent of petrochemical polymers brought about a shift towards state-of-the-art solutions still widely used, which use synthetic polymers or shaped plastic materials, to form film-coating or seed or grain coating. These synthetic or petrochemical polymers used hitherto are polyalkylene glycols, in particular polyethylene glycols, polyvinyl alcohols, polyacrylic derivatives, or water-soluble polyesters, or even water-insoluble polymers, in the form of latex, such as as polystyrenes, polystyrene butadienes, polyvinyl or polyacrylic derivatives.

Patent EP0334258 proposes a film-forming liquid composition for coating seeds, based on hydrolyzed acrylic polymers, such as hydrolyzed polyacrylonitrile. Application WO85/01736 describes a coating composition made of polyacrylamide plastic particles and finely divided and mixed polyacrylate particles, to form a hygroscopic coating.

Today however, a will of the agricultural world, transcribed in regulatory texts, pushes the actors of the field to seek new solutions free of any petrochemical material or of petrochemical origin. There is a real and proven need for seed coating compositions, in particular film-coating or coating compositions, consisting of natural ingredients or ingredients of natural origin.

Among the solutions that already exist, mention will be made of film-forming compositions of chitosan or polysaccharides derived from chitosan, as described in patent EP0652707. Cellulose derivatives, in particular cellulose esters or ethers, or hydroxy cellulose, are film-forming polymers of natural origin used as a substitute for synthetic polymers. But these polymers of natural origin still have the disadvantage of comprising parts totally of petrochemical or even synthetic origin.

Seed producers and users are currently still waiting for a technical solution to obtain seed coatings, which have coating performance equivalent or equal to petrochemical products, and which are as natural as possible. The coating compositions that are the subject of the present application meet this hitherto unmet need.

A subject of the present application is a composition for coating seeds, in particular for film-coating or coating seeds, comprising at least one binding agent chosen from native or modified dextrins, and at least one plasticizer chosen from polyols, and having a mass ratio of total dextrins/total polyol dry masses is within a range extending from 0.1 to 2.

A second object is the seed covered with at least one layer of coating, in particular film coating or coating, comprising the coating composition which is the subject of the present application, or consisting of the coating composition which is the subject of the present application.

A third object is a seed treatment method comprising a step of coating, in particular film-coating or coating, with the coating composition which is the subject of the present application, in an apparatus chosen from granulators, fluidized beds, rotary film-coating machines “Rotary Coater” type from the manufacturer Satec.

A fourth object is the use of the previous method in order to facilitate the flow of seeds or seeds, and/or in order to reduce the dust generated during the transport of these seeds or seeds, and this while maintaining the ability to germinate. of these seeds or seeds.

seeds :

By "seed" is meant any plant organ that can lead to the regeneration of a plant and obtained, either by sexual means, in which case we will speak of seed, or by vegetative multiplication, in which case we will speak of plant or explant.

The seed qualifies for species with sexual multiplication the organ which allows the reproduction of the plant species, for example a wheat seed. It is very generally a dry, dormant organ. Water and air will allow it to germinate and give birth to a plant. We speak of “dry” seed. There are also organs that allow sexual reproduction but do not go through a dry and dormant way. Example, the wet seed of the cocoa tree, which does not keep, once extracted from its fruit, the "pod". This is called a “wet” seed.

The organs that allow vegetative multiplication such as the plant, the bulb... which are rooted or called to root quickly, are also seeds. In practice, by shortcut, those skilled in the art can speak of seeds to designate the seeds, and of plants to designate the rooted organs. In our application, the term seed is used in its most general sense, and therefore covers everything that can be sown in agriculture to produce plants, which includes seeds, seedlings and explants, rootstocks, regenerative and plant-forming tissues, as well as tubers and bulbs.

In addition, "semen" within the meaning of the invention also essentially denotes naked semen before any treatment. However, the coating composition that is the subject of the present application can also be applied to seeds that have already been covered, either by at least one prior coating, or by at least one prior coating.

The seeds which can be used according to the process of the invention have very varied dimensions. In the case of seeds, they are generally between 0.1 and 25 millimeters. In the case of seedlings, they are generally between 0.5 cm and 10 cm.

According to one embodiment, the coating composition is a seed coating composition.

Seed:

The term "seed", as used in the present application, designates in particular the matured ovum of gymnosperms and angiosperms, which contains an embryo surrounded by a protective envelope. In particular, the term covers cereal grains. The protective coating may include the seed coat (testa). Some seeds include a pericarp or fruit coat around the seed coat. In particular, when this layer adheres tightly to the seed, as in cereal seeds, it is sometimes called caryopsis or achene. As used in this application, the term "seed coat" is intended to include caryopsis or achene.

Seed is a plant seed, which can be a seed of an agricultural crop such as cereals, fruits and vegetables, a grass seed, a wildflower seed, an ornamental seed, a lawn seed, a tree seed or a bush seed.

According to one embodiment, the plant seed is an agricultural crop. The seed may be of the order Monocotyledoneae or of the order Dicotyledoneae. Suitable seeds include soybeans, cottonseed, maize, peanuts, maize, wheat, barley, oats, triticale rye, mustard, oilseed rape (or canola), sunflower, sugar beet, safflower, millet, chicory, flax, rapeseed, mountain ash, tobacco, hemp seeds, alfalfa, fireweed, clover, sorghum, chickpeas, beans, peas, vetch, rice, sugar cane and flax seeds . Examples of suitable vegetable seeds include asparagus, chives, celery, leeks, garlic, beets, spinach, beets, kale, cauliflower, sprouting broccoli, white cabbage , red cabbage, kohlrabi, cauliflower, cauliflower, watermelon cauliflower, melon, cucumber, pickle, marrow, parsley, fennel, peas, beans, radishes, black salsify, eggplant, sweet corn, popcorn, carrot, onion, tomato, bell pepper, lettuce, snap bean, cucurbits, shallot, shallot, broccoli, Brassica and Brussels sprouts.

Coating:

The term "coating" as used in this application means a material applied to the surface of a seed, for example as a layer of material covering the surface of a seed. The coating may be a film coating, a so-called "dressing" coating, a granulation coating, or an encapsulating coating, or a combination of these types of coatings. The coating is preferably applied over substantially the entire surface of the seed, such as over 90% or more of the surface of the seed, to form a layer. However, the coating can be complete or partial, for example more than 20% or more of the surface of the seed, or 50% or more.

According to one embodiment, the seed coating is a film coating, called “film coating”. According to a second embodiment, the seed coating is a coating coating, called “coating”.

Lamination:

By "filming" is generally meant the deposition, on the surface of a seed, of a very thin film, of regular thickness, of a non-phytotoxic film-forming product. This film, which does not substantially modify the shape of the seed, may contain additives such as in particular presentation additives, fillers, adhesives, dyes or products promoting the growth of plants, in particular products for defense against diseases and parasites. Film-coating therefore makes it possible to confer on the seed, in addition to an improvement in its appearance and its presentation increasing its suitability for sowing, a reduction in dust, a more regular phytosanitary protection using a minimum of protective active ingredient, and more durable, due to good adhesion of the film to the seed.

Coating composition:

A coating composition is generally in the form of an aqueous solution or suspension comprising a mineral filler, a binding agent, and additives such as, for example, surfactants, dyes, phytopharmaceuticals and biostimulants.

"Open" embodiments

According to one embodiment, the coating composition that is the subject of the present application comprises at least one binding agent chosen from native dextrins and modified dextrins, and at least one plasticizer chosen from polyols.

According to an alternative of this embodiment of the coating composition, the mass ratio of the total mass of “total dextrins” to the total mass of “total polyols” is included in a range ranging from 0.1 to 9, preferentially from 0.25 to 4, more preferably from 0.45 to 3, most preferably from 1 to 2.5.

According to another alternative of this embodiment of the coating composition, the binding agent is chosen from native dextrins. According to another embodiment, the plasticizer is chosen from polyols having a number of carbon atoms ranging from 1 to 10, or ranging from 2 to 8, or ranging from 5 to 6, said polyols being linear or branched. or cyclical. According to a variant of this alternative, the plasticizer is chosen from sorbitol, mannitol, maltitol, xylitol, isosorbide, or from sorbitol, mannitol, isosorbide, or is sorbitol. According to another embodiment, combining the two previous embodiments, the coating composition comprises at least a binder chosen from native dextrins, and at least one plasticizer chosen from polyols having a number of carbon atoms ranging from 1 to 10, or ranging from 2 to 8, or ranging from 5 to 6, said polyols being linear or branched or cyclic. According to another variant of this alternative, the plasticizer is chosen from sorbitol, mannitol, maltitol, xylitol, isosorbide, or from sorbitol, mannitol, isosorbide, or is sorbitol.

“Closed” embodiments

According to another embodiment, the coating composition that is the subject of the present application comprises, as sole binding agent, a dextrin or a mixture of dextrins, chosen from native dextrins and modified dextrins, and at least one plasticizer chosen from polyols. According to an alternative embodiment, the mass ratio of the total mass of total dextrins to the total mass of total polyols is within a range ranging from 0.1 to 9, preferably from 0.25 to 4, more preferably from 0 .45 to 3, most preferably from 1 to 2.5.

According to another embodiment, the seed coating composition comprises at least one binding agent chosen from native and/or modified dextrins, and as sole plasticizer a polyol or a mixture of polyols. According to an alternative of this embodiment, the polyol is chosen from polyols having a number of carbon atoms ranging from 1 to 10, or ranging from 2 to 8, or ranging from 5 to 6, said polyols being linear or branched. or cyclical. According to an alternative of this embodiment, the plasticizer is chosen from sorbitol, mannitol, maltitol, xylitol, isosorbide, or from sorbitol, mannitol, isosorbide, or is sorbitol. According to another alternative of this embodiment, the mass ratio of the total mass of total dextrins to the total mass of total polyols is within a range ranging from 0.1 to 9, preferably from 0.25 to 4, more preferably from 0.45 to 3, most preferably from 1 to 2.5.

Finally, according to another embodiment combining the two previous embodiments, the seed coating composition comprises, as sole binding agent, a dextrin or a mixture of dextrins, chosen from native dextrins and/or modified dextrins, and as sole binding agent plasticizing a polyol or a mixture of polyols. According to an alternative of this embodiment, the polyol is chosen from polyols having a number of carbon atoms ranging from 1 to 10, or ranging from 2 to 8, or ranging from 5 to 6, said polyols being linear or branched. or cyclical. According to an alternative of this embodiment, the plasticizer is chosen from sorbitol, mannitol, maltitol, xylitol, isosorbide, or from sorbitol, mannitol, isosorbide, or is sorbitol. According to another alternative of this embodiment, the mass ratio of the total mass of total dextrins to the total mass of total polyols is within a range ranging from 0.1 to 9, preferably from 0.25 to 4, more preferably from 0.45 to 3, most preferably from 1 to 2.5.

By being according to one of the preceding embodiments or one of the alternative embodiments, the coating composition can also advantageously contain a mass content of “total dextrins”, and a mass content of “total polyols”, such that the sum of these mass contents, expressed as a percentage by mass of the coating composition, is within a range going from 2.5% to 35%, preferentially from 4% to 20%, very preferentially from 5% to 10% . This allows the seed coating composition to exhibit a Brookfield viscosity at 25°C of less than 4000 mPa.s, or less than 3000 mPa.s, or less than 2000 mPa.s, or less than 1000 mPa.s.

Dextrin native :

By "dextrinenative" is meant polysaccharides resulting from the chemical or enzymatic hydrolysis of starch, and whose free hydroxyl groups carried by the anhydroglucose rings are intact, that is to say not having undergone chemical functionalization. by substitution of the hydroxyl groups carried the anhydroglucose rings.

The origin of the starch used to prepare the dextrin is chosen from corn, potato, sweet potato, wheat, rice, sago, tapioca, corn, rice, pea, quinoa , sorghum, beans. The starch can also be corn or potato starch, rich in amylopectin, that is to say generally containing at least 80% amylopectin, or at least 90% amylopectin, or at least 95 % amylopectin, or at least 99% amylopectin. The starch can also be a corn or potato starch, rich in amylose, that is to say generally containing at least 50% amylose, or at least 60% amylose, or at least 70 % amyloidosis.

The dextrins useful for the composition that is the subject of the present application are characterized by a weight-average molecular weight ranging from 20 kDa to 5000 kDa. The mass average molecular weight can be determined by a method of size exclusion liquid chromatography coupled with multi-angle light scattering detection, generally referred to as HPSEC-MALLS. The dextrins can also be characterized by a molecular weight distribution measured by HPSEC-MALLS exhibiting a polydispersity index greater than or equal to 2, or greater than or equal to 5, or greater than or equal to 10, or greater than or equal to 15.

Among the native dextrins useful for the coating composition that is the subject of the present application, three families of dextrins can be found which have distinctive structural characteristics. A first family of dextrin is made up of dextrins obtained by acid hydrolysis of starch in the dry phase, of which two sub-families are white dextrins and “chemically transglycosidated” dextrins. A second family consists of dextrins obtained by hydrolysis of starch in the milk phase by acid hydrolysis and/or by enzymatic hydrolysis by one or more enzymes chosen from among amylases, isoamylases or glucanosyltransferases. A third family consists of dextrins obtained by hydrolysis in the milk phase by the direct action of a branching enzyme, or by the action of a branching enzyme on a dextrin of the first or second family.

First e dextrin family s natives

The native dextrins of the first family are generally classified into three categories grouping together:

- white dextrins, generally obtained by transformation of starch at temperatures often between 120 and 170°C, in the presence of chemical agent(s), in particular acid, in relatively high quantities,

- yellow dextrins, often produced by transformation of starch at higher temperatures, generally between 170 and 230°C, in the presence of chemical agent(s), in particular acid,

- so-called “British GUM” dextrins obtained by the sole action of heat, at high temperature, often above 230°C.

Dextrinification processes generate different reactions. The importance of each of these reactions varies according to the process conditions such as the nature and quantity of chemical agent used, the water content during the reaction, the temperature profile and the reaction time. A person skilled in the art generally considers that various mechanisms may occur during the dextrinification reaction of starch. The hydrolysis reaction is significant at the beginning of the transformation and this from 50°C. Linked to the presence of acid and a still sufficient quantity of water, it decreases the molecular mass. The condensation or reversion reaction forms an alpha-(1,6) bond from a primary alcohol of one chain and the reducing end of another chain. It is favored by temperatures below or close to 150°C. The "transglucosydation" reaction, forming an alpha-(1,6) bond by cutting an alpha-(1,4) bond without releasing water, is predominant at temperatures above 150°C. Allowing the production of more branched molecules, it is essential for the expression of the properties of dextrins, in particular, yellow dextrins. Other reactions also take place, such as internal “anhydrization” between carbons 1 and 6, or recombination resulting from the reaction between a reducing end and a hydroxyl group at C2, C3 or C4. The relative importance of these phenomena gives dextrins specific properties. In the transformation of white dextrins, the predominant mechanism is hydrolysis. It follows that these white dextrins have either a high molecular weight with low water solubility, or the opposite. In the case of yellow dextrins, hydrolysis is important and all of the mechanisms described above are equally important, resulting in low molecular weight, usually branched, products with high water solubility.

First embodiment of s dextrins of the first family

According to a first embodiment of the native dextrins of the first family, said dextrins have a weight-average molecular mass, measured by HPSEC-MALLS, ranging from 20 kDa to 5000 kDa. In addition, said dextrins may advantageously have a polydispersity index greater than 5, preferably greater than 10, and more preferably still greater than 15.

According to an alternative of this embodiment, said dextrins can also have a solubility, measured according to a T test, ranging from 2% to 95%. According to another alternative of this embodiment, said dextrins are obtained by dextrinification of a starch rich in amylopectin. According to another alternative of this embodiment, said dextrins have also undergone at least one chemical functionalization chosen from hydroxypropylation, carboxymethylation, crosslinking by at least one organic phosphate salt, preferentially have undergone crosslinking by a trimetaphosphate of sodium.

Second embodiment of s dextrins of the first family

According to a second embodiment of the native dextrins of the first family, said dextrins have a weight-average molecular mass, measured by HPSEC-MALLS, ranging from 100 kDa to 500 kDa. In addition, said dextrins may advantageously have a polydispersity index greater than or equal to 2, or greater than or equal to 5, or greater than or equal to 10, or greater than or equal to 15.

According to an alternative of this second embodiment, the dextrin is characterized by a distribution of molecular weights, measured by HPSEC-MALLS, having, relative to the total weight of dextrin:
- a mass fraction of between 0.5 and 10%, between 1 and 7%, of dextrin molecules with a molecular mass greater than 1,000,000 Da,
- a mass fraction of between 25 and 50%, between 26 and 45%, of dextrin molecules with a molecular mass greater than 100,000 Da and less than or equal to 1,000,000 Da,
- a mass fraction between 30 and 50%, between 35 and 47%, between molecules of dextrins with a molecular mass greater than 10,000 Da and less than or equal to 100,000 Da,
- a mass fraction of between 10 and 25%, between 15 and 20%, of dextrin molecules with a molecular mass greater than 1000 Da and less than or equal to 10,000 Da,
- a mass fraction of less than 10% of molecules of dextrins of molecular mass less than or equal to 1000 Da.

According to an alternative of this second embodiment, said dextrins may have a solubility, measured according to a T test, ranging from 45% to 85%, preferably ranging from 55% to 65%.

According to an alternative of this second embodiment, said dextrins may have an alpha-(1,6) glucosidic bond content greater than or equal to 4%, or 5%, or 6%, or 7%, as measured by NMR of the proton.

According to an alternative of this second embodiment, said dextrins may have an alpha-(1,4) glucosidic bond content measured by proton NMR greater than or equal to 81%, measured by proton NMR.

Examples of commercially available dextrins according to this embodiment are “Stabilys® CWS” from the company Roquette, “C*Icoat” from the company Cargill.

Third embodiment of s dextrins of the first family

According to a third embodiment of the native dextrins of the first family, said dextrins have a weight-average molecular mass ranging from 500 kDa to 2000 kDa. In addition, said dextrins may advantageously have a polydispersity index greater than or equal to 2, or greater than or equal to 5, or greater than or equal to 10, or greater than or equal to 15.

According to an alternative of this embodiment, said dextrins also have a solubility, measured according to a T test, ranging from 2% to 45%. Examples of dextrins according to this embodiment are “Stabilys® EVO” from the company Roquette.

Fourth Embodiment of s dextrins of the first family

According to a fourth embodiment of the dextrins of the first family, said dextrins have been prepared from a legume starch, having an amylose content of between 28% and 60%, preferably between 30% and 50%, plus preferably between 32.5% and 40%. By “legume” within the meaning of the present invention, is meant more particularly the Papilionaceae family, the most important of which are beans, peas, lentils, broad beans, alfalfa, clover, lupine. An example of such a dextrin is that marketed under the name TACKIDEX® C760 by Roquette.

Second th family of native dextrins

The native dextrins of the first family are the dextrins generally called “maltodextrins”. Examples of commercial products are the Glucidex® marketed by Roquette.

Third family of native dextrins trendy

A third family of dextrins useful for the coating composition which is the subject of the present application is that of the "branched" and "hyper-branched" dextrins, that is to say with an alpha-1,6 glucosidic bond content greater than or equal to 6%, or 8%, or 10%, or 12%, as measured by proton NMR. Examples of commercial products are “Nutriose®”, such as “Nutriose® 06” or “Nutriose® 10” from Roquette, or “Promitor®” from Tate & Lyle, or “Oligo-fiber®” from Cargill.

Modified dextrin:

By "modified dextrin" is meant the native dextrins according to all the embodiments described above, having undergone one or more chemical functionalizations by chemical substitution of the hydroxyls carried by the anhydroglucose rings of the starch. Examples of modified dextrins are hydroxypropyl dextrins, carboxymethylated dextrins, octenylsuccinilated dextrins, cross-linked dextrins. According to one embodiment, the modified dextrin is a dextrin crosslinked with at least one organic phosphate salt, preferably with sodium trimetaphosphate. According to another embodiment, the modified dextrin is a dextrin obtained by dextrinification of a starch rich in amylopectin which has then been cross-linked with sodium trimetaphosphate.

Polyol:

By “polyol”, we mean polyhydric alcohols, i.e. carrying at least two alcohol functions, and no other chemical function apart from the carbon chain.

According to one embodiment, the polyol is chosen from polyols having a number of carbon atoms ranging from 1 to 10, or ranging from 2 to 8, or ranging from 5 to 6, said polyols being linear or branched or cyclic. According to another embodiment, the polyol is chosen from sorbitol, mannitol, maltitol, xylitol, isosorbide, or from sorbitol, mannitol, isosorbide, or is sorbitol.

Complementary additives:

Additionally, the seed coating composition that is the subject of the present application may optionally contain additives, such as presentation additives, fillers, colorants, formulations of plant protection products, formulations of phytopharmaceuticals, diluents such as water, nutrients and/or inoculants such as beneficial fungi or bacteria, plant growth supporting substances such as agrochemical active ingredients e.g. fungicides, insecticides, phytotoxicity inhibitors, herbicides, regulators of growth, corvifuges, inoculums of microorganisms...etc.

Process for coating seeds with the coating composition subject of the application:

Another object of the present application is the seed coating process comprising a step of applying a coating composition according to the present application, such that the quantity of coating composition relative to the quantity of seed is less than 100 g of coating composition per kg of seed, or less than or equal to 75 g/kg, or less than 50 g/kg.

Effects of the composition subject of the application:

The coating composition that is the subject of the present application may be in the form of a liquid capable of forming a highly adhesive, biodegradable film on the surface of the seed. This composition forms a non-toxic film for the seed, for plants, animals and humans, and the environment in general. The coating composition that is the subject of the present application has a solubility adapted to its disappearance in order to allow germination.

For example, the effects of the mass ratio of the total mass of total dextrins on the total mass of total polyols, in the case of a dextrin being Stabilys® CWS and the polyol being sorbitol, on the coating formed on the surface of the seeds are the following:

When the “Stabilys CWS / Sorbitol” mass ratio is greater than 2.67: the coating is friable, not flexible; however, it does not confer a dust-reducing effect, and in fact contributes to increased dust due to the formation of film debris following impact between seeds.

When the "Stabilys CWS / Sorbitol" mass ratio is greater than 2.10 and less than or equal to 2.67: the coating is flexible, non-sticky, smooth; dust formation during pouring is reduced; wet and dry flows are correct; however, the coating becomes dry after storage for less than 15 days, and becomes friable. This range of ratios therefore makes it necessary to use the seeds before the coating dries too much, which prohibits long-term storage.

When the “Stabilys CWS / Sorbitol” mass ratio is greater than 1.33 and less than or equal to 2.10: the coating is flexible, non-sticky, and smooth; dust formation during dry flow is reduced; wet and dry flows are correct; the coating remains flexible, non-friable during storage for a period of up to 15 days, or 2 months, or 6 months, or 1 year, or 2 years, or 3 years. This range of ratios makes it possible to keep the coating flexible and smooth for storage times long enough to keep the seeds for a long time, i.e. one year, or two years, or three years.

When the "Stabilys CWS / Sorbitol" mass ratio is less than or equal to 1.33: the coating is flexible, but adhesive so that the seeds stick together and form agglomerates; the formation of dust in dry flow is still much reduced, but wet and dry flow are largely degraded.

The coating composition object of the present application can be used in order to reduce the dust generated from the transfer of seeds, while maintaining the flow rate and the ability to germinate at nominal values, or at values greater than or equal to 90 % of nominal values, or at values equal to greater than or equal to 80% of nominal values

Measurement method molecular mass distribution and mass average values d are dextrins:

As regards the molecular mass (M) of a dextrin, it is expressed in kDa and can be determined by the person skilled in the art using steric exclusion chromatography of the HPSEC-MALLS type (High Performance Size Exclusion Chromatography coupled on-line with Multiple Angle Laser Light Scattering).

This mass can be measured by steric exclusion chromatography, according to the following protocol:

1- Preparation of a sample by solubilization of the dextrin, by heating at 100°C for 30 min in a dilution solvent consisting of a DMSO/NaNO3 mixture (0.1M of NaNO3 in DMSO), said sample possibly presenting a concentration ranging from 2 to 10 mg of starch per mL of dilution solvent;

2- Use of a high-performance liquid chromatography (HPLC) device equipped with a pump, operating in isocratic mode, circulating an eluting solvent at 0.3 mL/min, a refractometer, a detector multiple angle light scattering laser with 18 angles heated to 35°C, for example a DAWN DSP detector from Wyatt, and a column thermostating oven heated to 35°C, for example equipped with SUPREMA type polyhydroxymethacrylate columns and whose eluting solvent is for example an aqueous solution of sodium nitrate at 0.1M, containing 0.02% by mass of sodium azide;

3- Injection into the device of an injected sample volume of approximately 100µL.

4- The weight- and number-average molecular masses can be determined from the spectra obtained, for example by reprocessing the 1st order exponential spectra, using ASTRA v.4 type analysis software.

Method for measuring the solubility of dextrins:

Solubility is measured using the T test, which consists of the following method:
1- take a test sample mass (m test sample) of about 5.0 g of dextrin, this mass being expressed as dry mass;
2- dispersion in 200 mL of water at 22° C. in an Erlen, which is then placed at 22° C. in a water bath for 4 hours under magnetic stirring with stirring for 5 minutes every 30 minutes;
3—Filtering the contents of the flask on a filter with a porosity of 8 μm, for example of the Whattamn 2 V type;
4- pipetting 50 mL of filtrate and introducing this quantity into a dry, calibrated crystallizer;
5- evaporate the water from the crystallizer by heating at 60° C. for 45 minutes, then at 130° C. for 90 minutes;
6- after cooling in a desiccator, weigh the mass of dextrin obtained after drying (m dry extract).

The solubility is calculated as follows:
Solubility = [m dry extract × 200 × 100] / [50 × m test sample]

The dry mass of the test portion is calculated according to ISO 1666:1996.

Examples

Example 1 : selection n of the composition coating

In order to roughen the products that can be used to produce a viscoelastic and film-forming lamination film, equipment called “LabCoat®” sold by TQC is used to produce films on a flexible cardboard plate. The tests are carried out on the sheets "Black Scrub Test Panels" (P121-10N) from LENETA.

Preparation of the coating composition :

Dissolution of the binding agent and the plasticizing agent in the necessary volume of water at 25°C with stirring for 30 minutes until a homogeneous solution is obtained. The solution obtained may not be clear, and cloudiness is possible due to the presence of the binder in colloidal form or not completely dissolved.

Coating of a sheet by the composition coating:

The coating composition is spread by Le Labcoat® automatically through the threaded rod to a film thickness of 200µm. The spreading criterion is observed during this film coating phase:
- Good spreading: the coating solution maintains its position on the sheet following the passage of the spreading rod. There is no shrinkage of the film at the ends or even inside the surface of the film.
- Bad spreading: behind the spreading rod, a contraction of the film can be observed, which can take place on the edges and/or in the inner surface.

The film is dried for about twenty minutes at 50° C. in an oven at atmospheric pressure and ambient humidity. The coated plate is left to return to room temperature for 1 hour.

We then appreciate the stickiness of the film by passing our finger over the film. If the finger sticks to the film, then the film is said to be sticky. If the finger slides without resistance on the film, then the film is smooth and not sticky.

The flexibility of the film is then evaluated. To do this, the plate is folded in half widthwise by manual action on the ends. The state of the film is observed at the torsion line. If no cracks are observed with the naked eye, then the film is flexible. If one or more cracks are observed with the naked eye, the film is brittle.

Paragraph on stability: 1 weeks, 2 weeks, 2 months. Plate kept at 22°C, ambient humidity.

Effect of and the agent plasticizer

We study the effect of the plasticizer, by its nature and its dose, on the characteristics of the films formed by coating with LabCoat® according to the protocol described above.

[Table 1]: characteristics of the films obtained from a composition coating assholes you itute a binder of a fixed nature, a Stabilys dextrin ® CWS , to the height of 20 %m , and a polyol plasticizer by nature variable to the height of 15 %m

Nature of the plasticizer Spreading Sticky Flexibility (related to friability) Sorbitol Good Weak Good Isosorbide Good AVERAGE Good Mannitol Bad Weak Bad Isosorbide dioctanoate Bad AVERAGE Bad

The results in Table 1 show that at 6.6% w/w of Stabilys CWS dextrin, the polyols giving a film with good spreading, good flexibility and medium or low tackiness are sorbitol and isosorbide.

[Painting 2 ]: characteristics of the films obtained from a composition coating consisting of a binder of a fixed nature, a dextrin Stabilys® CWS, up to 20 %m , and a polyol-type plasticizer of variable nature at 15% DM

Nature of the plasticizer Spreading Sticky Flexibility (related to friability) Sorbitol Good AVERAGE Good Mannitol Good Weak Bad

Effect of and the agent binder

The effect of the binding agent, by its nature and its dose, on the characteristics of the films formed by coating with LabCoat® according to the protocol described above is studied.

[Painting 3 ]: characteristics of the films obtained from a composition coating assholes you ituated from a binder of variable nature to 20%MS height and a plasticizer fixed, sorbitol, up to 10% DM

Nature of the binder Spreading Sticky Flexibility Stabilys CWS (Corn Dextrin) Good Weak Good Tackidex C760 (cross-linked pea dextrin) AVERAGE Weak Good Tackidex I231 (cross-linked corn dextrin) Good Weak Good Clearam LI4000 (pregelatinized and cross-linked pea starch) Bad Nil (powdery touch) Good

[Painting 4 ]: effect sorbitol content on the viscoelasticity of a film

Sorbitol content Viscoelasticity 6 to 7% Film very brittle after one day 8 to 9% Brittle film after 15 days Greater than or equal to 10% Viscoelastic film (at least up to 2 months)

The results in Table 3 show that a minimum sorbitol content is required to obtain a viscoelastic film with stable viscoelasticity over time.

Example 2: seed coating wheat

Coating solutions were prepared according to the compositions in the following table, in order to use them for carrying out the coating of wheat seeds. Each solution is prepared by dispersing the desired quantities of ingredients in the quantity of water and keeping under stirring at 22°C for 1 hour.

[Painting 5 ]: composition of coating lamination according to the invention

Ingredient Lamination A Lamination B Lamination C Lamination D Binding agent / binding agent content Stabilys CWS /
6.6%m Tackidex C760 /
6.6%m Lycoat RS780 /
6.6%m Tackidex I231 /
6.6%m Plasticizer / plasticizer content Sorbitol / 3.4%m Mineral load / mass content Calcium carbonate / 3.4% m Pigment / mass content Red pigment / 5%m Water 81.6 %m

For each film-coating solution, a batch of wheat seeds coated with said film-coating solution is prepared. To do this, a given quantity of seeds is added to the Rotary Coater (equipment with a rotating plate in the bottom) and the rotating plate is put into operation at speed 3.

The desired dose of coating solution is added using a syringe on the rotating central disc (as close as possible, with a pipe) on the seeds in 5-10 seconds. The rotation speed is increased again so as to maintain the height of the seed bed at the periphery at the initial level, that is to say before addition of the coating solution.

Following the addition of the product, the seeds are still left for 20s in the equipment under agitation for a short drying. Unload and make three aliquots. On an aliquot, a flow measurement is made afterwards (called wet flow), then the coated seeds are left in storage at 23°C 50% humidity for 24 hours, then the flow is measured again (so-called dry flow) . The results of these measurements are presented in Example 3. On the second aliquot, stored for 48 hours at 23° C. 50% humidity, the dust measurement is made, the results of which are presented in Example 4. Then on the third aliquot, a germination test is carried out, the results of which are presented in Example 5.

Example 3 : measurement of seed flow wheat

The flow test is carried out at 2 different points in time:
- the first is carried out just after the lamination has been carried out with the Rotary Coater.
- the second is carried out after 24 hours (in the meantime the seeds are stored at 23°C and 50% relative humidity).

To carry out the test, 300g of seeds are added to a closed funnel having a passage diameter of 2 cm, and the cone of which makes an angle of 30° with respect to the vertical. The stopwatch is started by opening the funnel to determine the time for the entire volume of seeds to flow out, and the speed of seed flow in g/s is then calculated. The measurement is repeated 10 times with the same sample of coated seeds, to obtain an average value.

[Painting 6 ]: flow velocity measurements

Wet flow just after lamination (g/s) Wet flow after 1 hour (g/s) Dry flow (g/s) Unshelled seeds n.d. n.d. n.d. Reference Lamination 1 n.d. n.d. 35.8 Film coating with solution A 12.2 29.6 34.6 Lamination with solution B 11.5 26.7 31.3 Film coating with solution C 15.8 32.5 35.5 Film coating with solution D 14.6 30.3 35.5

The wheat seeds coated with the solutions that are the subject of the present application have dry flow speeds equivalent to that obtained with the reference solution 1. The wet flow speed after one hour of drying is almost equivalent to the speed of flow dry.

Example 4 : Measurement of dust generated

The dust measurement is carried out on the seeds coated and dried in an oven for 48 hours at 23° C. and 50% humidity. This measurement is made according to the so-called “ESTA” method using the Dustmeter Heubach type 1 equipment, from the manufacturer Heubach.

About 100g of seeds are placed in the rotating drum of the Dustmeter (which has wedges in order to agitate the seeds) at a rotation speed of 30 rpm, under a flow of air drawn in at a rate of 40 L in 2 min. Under the action of the movement induced by the drum, the seeds collide, which generates dust, which is suspended and drawn off by the suction of air on a filter.

With the counter-weighing of the filter before and after treatment, the dust level of the seeds tested is determined in mg/100g of seeds.

[Painting 7 ]: measurements of dust generated in Dustmeter Heubach

Dust (mg/100g) Variation compared to uncoated Unshelled seeds 6.94 n / A. Reference Lamination 1 2.11 -70% Film coating with solution A 4.54 -35% Lamination with solution B 4.12 -41% Film coating with solution C 3.21 -54% Film coating with solution D 2.61 -62%

In terms of dust reduction, the film-coating solutions that are the subject of the application allow a reduction in dust of 35 to 62% compared to uncoated seeds.

Example 5 : measurement of germination

Germination tests are carried out on seeds coated and dried in an oven for 48 hours at 23° C. and 50% humidity. In a Petri dish containing absorbent paper, add 4 mL of water to create a humid atmosphere inside the box, then place 10 seeds on top of the damp cotton. For each coating solution, five Petri dishes are prepared.

The boxes are closed, then placed at 23° C. and exposed to daylight for 6 days. At the end of the 6 days of exposure, the number of germinated seeds is counted, then the percentage germination rate is calculated.

[Painting 8 ]: germination rate measurements

Germination Unshelled seeds 98% Reference Lamination 1 95% Film coating with solution A 100% Lamination with solution B 98% Film coating with solution C 97% Film coating with solution D 96%

The use of the film-coating solutions that are the subject of the present application make it possible to achieve a completely acceptable germination rate, equivalent to reference 1 of a petrochemical nature. Coating solutions A and B even achieve a germination rate equivalent to uncoated seeds.

Claims (14)

Seed coating composition, characterized in that it comprises at least one binding agent chosen from native dextrins and modified dextrins, and at least one plasticizer chosen from polyols. Seed coating composition according to Claim 1, characterized in that it comprises at least one binding agent chosen from native or modified dextrins, preferably native dextrins, and at least one plasticizer chosen from polyols, and in that the mass ratio of the total mass of total dextrins to the total mass of total polyols is within a range ranging from 0.1 to 9, preferably from 0.25 to 4, more preferably from 0.45 to 3, most preferably from 1 to 2.5. Seed coating composition according to one of the preceding claims, characterized in that the binding agent has a weight-average molecular mass ranging from 20 kDa to 5000 kDa. Seed coating composition according to one of the preceding claims, characterized in that the binding agent has a molecular weight distribution having, with respect to the total weight of binding agent:
- a mass fraction of between 0.5 and 10%, between 1 and 7%, of dextrin molecules with a molecular mass greater than 1,000,000 Da,
- a mass fraction of between 25 and 50%, between 26 and 45%, of dextrin molecules with a molecular mass greater than 100,000 Da and less than or equal to 1,000,000 Da,
- a mass fraction between 30 and 50%, between 35 and 47%, between molecules of dextrins with a molecular mass greater than 10,000 Da and less than or equal to 100,000 Da,
- a mass fraction of between 10 and 25%, between 15 and 20%, of dextrin molecules with a molecular mass greater than 1000 Da and less than or equal to 10,000 Da,
- a mass fraction of less than 10% of molecules of dextrins of molecular mass less than or equal to 1000 Da. Seed coating composition according to one of the preceding claims, characterized in that the binding agent has a solubility, measured according to a T test, ranging from 2% to 95%. Seed coating composition according to one of the preceding claims, characterized in that the binding agent has an alpha-(1,6) glucosidic bond content measured by proton NMR greater than or equal to 4%, or greater than or equal 5%, or greater than or equal to 6%, or greater than or equal to 7%. Seed coating composition according to one of the preceding claims, characterized in that the binding agent has an alpha-(1,4) glucosidic bond content measured by proton NMR of greater than or equal to 81%, measured by proton NMR proton. Seed coating composition according to one of the preceding claims, characterized in that the binding agent has undergone at least one chemical functionalization chosen from hydroxypropylation, carboxymethylation, crosslinking by at least one organic phosphate salt, preferably in that the binding agent has undergone crosslinking with sodium trimetaphosphate. Seed coating composition according to one of the preceding claims, characterized in that the binding agent is a dextrin obtained by dextrinification of a starch rich in amylopectin which has then been cross-linked with sodium trimetaphosphate. Seed coating composition according to one of the preceding claims, characterized in that the polyol is chosen from polyols having a number of carbon atoms ranging from 1 to 10, or ranging from 2 to 8, or ranging from 5 to 6, said polyols being linear or branched or cyclic, preferably from sorbitol, mannitol, maltitol, xylitol, isosorbide, or from sorbitol, mannitol, isosorbide, or is sorbitol. Seed coating composition according to one of the preceding claims, characterized in that the sum of the mass contents of "total dextrins" and of "total polyols", expressed as a percentage by mass of the coating composition, is included in a range ranging from 2.5% to 35%, preferably from 4% to 20%, most preferably from 5% to 10%. Seed coating composition according to one of the preceding claims, characterized in that the Brookfield viscosity at 25°C is less than 4000 mPa.s, or less than 3000 mPa.s, or less than 2000 mPa.s, or less at 1000 mPa.s Seed coating process comprising a step of applying a coating composition according to one of the preceding claims, characterized in that the quantity of coating composition relative to the quantity of seed is less than 100 g of coating composition per kg of seed, or less than or equal to 75 g/kg, or less than 50 g/kg. Use of a coating composition according to one of Claims 1 to 12 for reducing the dust generated from the transfer of seeds, while maintaining the flow rate and the ability to germinate at nominal values, or at values higher or equal to 90% of the nominal values, or to values equal to or greater than 80% of the nominal values.