Use of polymers as sticking agents

Details Use of polymers as sticking agents Use of polymers as sticking agents

2001-04-06

2003-03-18

Cain, Edward J. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S027000

Reexamination Certificate

active

06534563

ABSTRACT:

The present invention relates to the use of compounds with particular elongational and flow viscosity characteristics, as an anti-rebound agent included in the composition of formulations used in the presence of an aqueous solution.
More particularly, the present invention relates to the field of plant protection formulations comprising pesticides or agents controlling plant growth.
Further, the present invention relates to plant protection preparations intended for application in the form of a solution, dispersion or emulsion in an aqueous medium to plants to be treated. It should be noted that for simplification, reference will only be made in the description to aqueous solutions, although this term encompasses the variations cited above.
Plant protection formulations used in the presence of an aqueous solution are conventionally sprayed onto the plant to be treated. One of the principal difficulties encountered with this procedure is that it is very difficult to control the quantity of active principle that remains in contact with the plant to be treated. During spraying, a large portion of the active principle is lost as the sprayed droplet rebounds from the hydrophobic surface of the plant and is deposited in an undesirable location (for example the ground). In addition to the economic disadvantage of losing product, depositing an active principle on the earth or indeed on other plants can cause problems with toxicity or phytoxocity.
In order to overcome this problem of undesirable rebound of the droplet of formulation from the surface of the plant to be treated, the introduction of additives has been proposed in order to greatly increase the flow viscosity of the formulation. However, that solution can only be considered to be a partial solution as such formulations are difficult to pump and spray.
There is currently no additive for formulations for use in the presence of an aqueous solution that has both satisfactory flow characteristics as regards the mode of applying that formulation and can avoid the phenomenon of rebound of the droplet of formulation from the surface of the plant to be treated.
The present invention aims to overcome these difficulties.
It consists in the use, as an anti-rebound agent in formulations for use in the presence of an aqueous solution, of at least one compound with an elongational viscosity of twice or more that of water and a flow viscosity less than or equal to six times that of water; these viscosities are measured for compound concentrations in the range 0.05 to 3 g/l.
The compound used as an anti-rebound agent has the dual advantage of eliminating the rebound phenomenon without deleteriously increasing the viscosity of the formulation during its application. In this manner, the formulation is always easy to pump and spray.
Further, said compound endows the solution in which it is used with anti-rebound properties, even when used alone. It is then not necessary to use a surfactant, for example, to obtain good anti-rebound properties.
Further again, the anti-rebound agent of the invention can advantageously be used in a tank-mix, i.e., mixed with the formulation just before its application. The anti-rebound agent of the invention can be present as a biological activator; i.e., it can be formulated with the active principle.
Finally, the anti-rebound agent of the invention can form part of the composition of a number of plant protection formulations that are intended for application in an aqueous medium. Examples that can be cited are solid formulations, in particular wettable powders or dispersible granules; examples of liquid formulations are emulsifiable concentrates, suspensions, suspo-emulsions, and concentrated emulsions.
Further advantages and characteristics will become clear from the following description.
As indicated above, the present invention concerns the use, as an anti-rebound agent in formulations for use in the presence of an aqueous solution, of at least one compound with an elongational viscosity of twice or more that of water and a flow viscosity less than or equal to six times that of water; these viscosities are measured for compound concentrations in the range 0.05 to 3 g/l.
The term “elongational viscosity” means the viscosity measured as a fluid is deformed.
The term “flow viscosity” means the viscosity during simple shear of a fluid.
Further details regarding these viscosities can be obtained from the following work: Rheometry, Chap. VII; K. Walters; Chapman and Hall, 1975, p. 210 ff.
In a particular implementation of the present invention, the compound has an elongational viscosity of ten times or more that of water.
Regarding the flow viscosity of said compound, in a variation of the invention, it is 3 times or less that of water. Preferably, the flow viscosity of the compound is 1.5 times or less that of water.
Advantageously, the compound used as an anti-rebound agent can also have a retraction rate of 200 mm/s or less, preferably 100 mm/s or less.
It should be pointed out that the retraction rate, which corresponds to the phase whereby the diameter of a drop spread on a hydrophobic support reduces, is measured with a formulation comprising 1 g/l of anti-rebound compound, in an aqueous solution. The measurement is carried out by allowing a drop with a diameter of 2 mm to drop from a height of 60 cm onto a hydrophobic surface, i.e., a support for which the contact angle with water is more than 110° (in this case the surface is treated with stearic acid). The variation in diameter of the drop is recorded with a rapid camera capable of taking 1000 photos per second.
The compound used in the invention is selected from hydrosoluble or hydrodispersible surfactant polymers with a molecular weight in the range 5×10
4
to 5×10
6
g/mol. More particularly, the molecular weight of the compound is in the range 5×10
5
to 5×10
6
g/mol, preferably in the range 10
6
to 5×10
6
g/mol.
Preferably, the compound used is such that it comprises at least one polymeric chain the molecular weight of which is included in the ranges defined above. Further, this chain is at least 80%, preferably at least 90% soluble in an aqueous medium; the compound is present in a concentration in the range 0.05 to 3 g/l. In a particularly advantageous implementation, the polymeric chain of said compound, and preferably the compound itself, is completely soluble in aqueous media, under the concentration conditions indicated above.
A first category of compound that can be used as the anti-rebound agent is constituted by a polyhydroxylated polymer or copolymer selected from polysaccharides of animal, vegetable or bacterial origin, or from polyvinyl alcohol, polyphenol alcohols, or derivatives thereof.
The polysaccharides can be used in an ionic or non ionic form.
Xanthan gum, succinoglycanes, gum arabic, carragheens and alginates are representatives of anionic polysaccharides; cationic derivatives of starch can also be cited.
Non ionic polysaccharides that can be cited include galactomannans, such as guar gum or its derivatives such as hydroxypropylguar, carouba gum, soluble starch and its non ionic derivatives, cellulose and its carboxyalkylated or hydroxyalkylated derivatives, wherein the alkyl portion contains 1 to 4 carbon atoms.
Polyvinyl alcohol, polyphenyl alcohols or their derivatives are suitable polyhydroxylated polymers or copolymers, as indicated above.
Possible derivatives include polyetherified (co)polymers such as those wherein the ether portion is a C
1
-C
18
alkyl radical or a C
6
-C
18
aryl radical, or an alkylaryl or arylalkyl radical; the alkyl and aryl portions being as defined above.
Suitable derivatives also include (co) polymers carrying at least one ionic radical (anionic, cationic, zwitterionic, amphoteric). Non limiting examples of anionic radicals are sulphonate type radicals, sulphate, carboxylate, phosphate, phosphonate; examples of cationic radicals that can be cited are quaternary ammonium type radicals such as N(R)
4
+
where R, which may be identical or different, represents a

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