IL138565A - Hydrated polymeric composition and agricultural application thereof - Google Patents

Description

i \y pn OW»I o»itt» e> io amn HYDRATED POLYMERIC COMPOSITION AND AGRICULTURAL ' APPLICATION THEREOF G42106 HYDRATED POLYMERIC COMPOSITION AND AGRICULTURAL APPLICATIONS THEREOF The present invention relates to composite materials of intercoupled collagenic biopolymers and synthetic ternary polymers, to give hydrated polymeric compositions that are compatible with water in liquid or vapor state. More particularly, this invention relates to hydrated polymeric composites useful for soil treatment having high water absorption, thus retaining the humidity required for stimulating and sustaining plant growth.

There are many polymeric materials known that have the capacity of absorbing large quantities of water. These are known as hydrogels. These polymers comprise tridimensional networks, formed with hydrosoluble macromolecular components. The segments between crosslinked bonds belong to different classes of natural and synthetic polymers. Natural polymers can be derived from albumin, gelatin, starch, cellulose and its derivatives and the synthetic polymers are usually polymers and copolymers having basically a carbon chain backbone with optionally other atoms, and polar functional groups such as amines, amides, hydroxy, carboxy and other groups.

The specific properties of these materials determine their different applications. These properties are obtained by generating 3D-structures via specific polymerization reactions such as crosslinking with micromolecular polyfunctional reactants and by intercoupling reactions forming ions or covalent bonds.

The major disadvantages of known polymeric hydrogel materials are their maximum sorption capacity for water, which is about 6,000 % under static conditions, and the narrow pH range 6-8, which limit the number of possible applications. Another problem is the increased G42150 susceptibility to electrolytes in aqueous medium, causing a pronounced decrease in absorption capacity. Hydrogels that have a water uptake of more than lOOg water / g solid are known as superabsorbent hydrogels.

The structural characteristic of superabsorbent hydrogels consists in that the polymeric phase has a three-dimensional configuration, characterized by a reduced number of points of cross-linking which join segments with large ! length carrying hydrophilic functional groups, and the suitable solid has a microporosity which facilitates the water's access and accumulation.

Superabsorbent polymeric materials destined for soil improvement are known. These are generally macromolecular systems, such as acrylamide copolymers, polyacrylates, polyglutamates, formaldehydic resins, polyethers and polyesters, starch derivatives, etc.

These materials have a disadvantage in that they cannot be used in acid soils (pH<4) because of insolubilization of the polymer as a result of the consumption of the ion which is attached to a negative polar charge. Thus, soil with a high content of salt, more than 5%, has drastically diminished water uptake which cancels the principal function of the hydrogel. Polymeric systems with a sorption capacity of water more than 300g water/ g solid have a low elastic modulus (less than 10,000mPa) that prevents their use in plant growth in which the root is at more than 15 cm depth. Owing to their specific chemical structure, these materials are not suited for soil that has a compact or highly aggregated structure which favors porous crust formation which loses accumulated water more easily.

The hydrated polymeric composition, which is the object of this invention, eliminates the disadvantages mentioned above, because it represents a material in the form of granules, with average equivalent diameter of 0.3 - 3mm, of bioartificial polymeric complex.

It is an object of the present invention to provide a hydrated polymeric composition for use in agricultural applications.

G42 I 50 Another object of the invention is to provide a method of soil improvement.

A further object of the invention is to provide a method of treating soils with a superabsorbent polymeric composite.

In accordance with this invention there is provided a superabsorbent polymeric composite comprising a modified collagenic biopolymer, designated component A, and a synthetic ternary copolymer, designated component B. Components A and B will be defined more specifically hereinafter.

In another embodiment of this invention, there is provided a method of soil treatment with a superabsorbent polymeric composite.

A still further embodiment of this invention is to provide a method of soil irrigation with a superabsorbent polymeric composite solution.

Collagen is known to have been modified to form hydrogels. Thus, US 4,164,559 discloses acylated or esterified collagen compounds useful as carriers for ophthalmic medication. US 4,215,200 discloses a quaternary-structured collagen in which the collagen is esterified with alcohol and guanidinated. US 4,883,864 discloses collagen esterified with di- or tri-carboxylic acid halide, trisulfoyl halide or di- or tri-anhydride or di- or tri-active ester coupling agents to form a limited cross-linked chemically modified collagen. US 5,716,633 discloses a collagen-hydrogel for promoting epithelial growth formed by the free radical polymerizations of a hydrophilic monomer solution gelled and crosslinked in the presence of an aqueous solution of collagen. US 5,847,089 discloses a carboxyl-modified superabsorbent protein hydrogel wherein a protein derived from biomass is acylated and then crosslinked with a bifunctional aldehyde.

Eugene Khor, Biomaterials 18 (1997), 95-105 reviewed the methods for the treatment of collagenous tissues for bioprostheses.

Collagen-hydrogel composites with poly (2-hydroxyethylmethyl- G42150 methacrylate) were described by K.P. Rao et al in the Journal of Applied Polymer Science vol. 43, 2333-2336 (1991); and in Biomaterials 15 (1994), 383-389; and by K. Stastny et al in Biomaterials 14 (1993), 1105-1 108.

The modified collagenic biopolymer, component A, has an average molecular weight between 5,000 and 80,000 Da, and 0-30% of the free carboxyl groups of the collagenic material are esterified with a Ci to C6 alcohol and 20 to 30% of the free amino groups are blocked with ionizable hydrophilic groups. Preferably, the carboxylic groups are esterified with ethanol and the amino groups are modified with phthalic or succinic anhydride.

The process for preparing the modified collagenic biopolymer involves the reaction of the collagen extract with HCl acidified alcohol which breaks down the polypeptide chain in the course of esterification. The process is as follows. First, collagen polymer is extracted from mammalian, fish, bird, reptile or mollusk conjunctive tissues, by conventional procedures. The collagen polymer is suspended in an alcohol solution containing 1 to 5% water acidified with HCl to a concentration of about 1 to 3N. The suspension is heated to between 50-100°C and stirred for 4 to 12 hours. It is then cooled to room temperature and gaseous ammonia is bubbled in to neutralize the HCl. The resulting ammonium chloride is filtered off and 0.1 to 0.4% Ν,Ν-dimethylformamide is added to the alcoholic medium. To this is added an organic chloride, acid chloride or acid anhydride having a non-reactive organic part defined by R, and the mixture is heated with stirring to a temperature of 25- 55°C for 1-5 hours. The alcohol is then evaporated under vacuum and the reaction product, an esterified alkylated or acylated collagenic derivative, component A, is recovered by extraction with ethyl ether.

When polymer A is mixed with the synthetic ternary copolymer, polymer B, it forms a highly absorbent and stable bioartificial polymeric composite that can absorb very large quantities of water.

G42150 Polymer B is a synthetic ternary copolymer having an average molecular weight between 20,000 and 200,000 Da, and glass transition temperature Tg = 5-1 10° C. Polymer B is formed by the copolymerization of the monomers C, D and E, as defined hereinafter, in the ratios C:D:E = 55:0:45 to 10:30:60, expressed in weight percent.

C- represents a vinyl or acrylic monomer of the formula: CH2=CR'R2 wherein: R1 = -H, or -CH3; R2 = -H, -C6H5( -CH2C6H5) -CH=CH2) -COOR3 or CN, and R3 = -(CH2)k-H with k = 2-8; D- is a polar monomer having the formula: CHR4=CHR5 wherein: R4 = -H or -COOH; R5 = -COOH, -CN, -0-CO-CH3 -OH, -NH2) -0-(CH2)2-OH, -0-NH2 or -NH-(CH2)2-NH2; and E- is a reactive monomer selected from acryloyl chloride, acrolein, maleic anhydride, itaconic anhydride, glycidylmethacrylate, vinyl oxazole and reactive acrylic ester, having the following formula: CH2=CH(COOR6) wherein R6 = phenyl, benzyl, pentachlorophenyl or p-nitrophenyl. Preferably, the monomer C is selected from styrene and acrylonitrile, the monomer D is selected from acrylic acid and acrylamide, and the monomer E is selected from maleic anhydride and glycidyl methacrylate.

The ratios of components A to B suitable in the present invention range from 10:90 to 75:20.

The ternary polymers B, of this invention are prepared by a two step process. The first step involves a classical solution polymerization process in an aprotic dipolar solvent using free radical catalyst. The second step is a polymer-analogous transformation by adding in polymer solution, chemical agents (water, ethylene glycol, hydroxylamine, hydrazine, diethyl amine, thionyl chloride, CH3-ONa, etc.) and byproduct acceptors (for example, triethyl amine) and monomers that provide new 4 functional groups on the polymer chain, such as carboxyl, acid chlorides, esters and activated esters.

The hydrated polymeric composition of this invention can be applied to soil in a heterogeneous liquid-liquid system at a rate of 75-150kg composite for 1kg of soil having a pH = 2.5-1 1.5, on furrows 5-35 cm deep and having a salt content corresponding to an electrical conductivity of 0.5-2.5 dS/m. The composite may be applied as is or in a mixture with inorganic or organic fertilizers, depending on the germination parameters and plant type.

Example 1 A collagenic biopolymer complex, component A, was formed having 15% of the free carboxyl groups esterified with ethyl alcohol and 25% free amino grbups blocked with phthalic anhydride providing ionizable hydrophilic groups. This complex was mixed with a polymeric component B, comprising a copolymer of styrene (C) - acrylic acid (D) -maleic anhydride E), in a ratio C:D:E = 55:5: 40 , the ratio of A: B being 25:75. This was obtained through direct interface intercoupling polymer -polymer, in heterogeneous system liquid-liquid, in an helicoidally malaxator until a homogeneous mixture is obtained. 10kg of soil was scraped 10 cm deep from the surface of a piece of land lm consisting of soil with a germinative power for wheat. This soil was mixed with 30g of hydrated polymeric composition in the form of granules, with average equivalent diameter of 1.2mm. The granules were spread uniformly on the soil and washed with 5kg of water. After 30 minutes the gel layer which had formed was covered with 1/2 of the scraped soil. Over the loose soil layer is spread uniformly 15g wheat grains. Finally, the wheat layer is mixed with the rest of the scraped soil. The wheat seeds germinated 1.7 times faster than on soil without the hydrated polymeric composition under the same experimental conditions.

G42150 Example 2 A bioartificial polymeric complex, component A, was prepared by modifying a collagenic polymer by esterifying 5 % of the free carboxylic groups with ethanol, and reacting 25% of the free amino groups with succinic anhydride. This component A was blended with a component B consisting of a terpolymer prepared from acrylonitrile (C)-acrylamide (D)- glycidyl methacrylate (E) in a ratio of C:D:E 55:20:25 in the proportion of A:B = 65:35, to form a hydrated polymeric composition. lOg of powdered composition was dissolved in 1000L of natural water (river, lake) and applied to soil as shown in Figure 1.

Figure 1 illustrates an installation for irrigating and wetting agricultural crops by a drip method. Powder and water are mixed and blended in tank 1 where the powder dissolves to form about a 1% solution. This solution is fed via tap 2 to a mixing container 5 which also receives natural water 3 via pump 4 where it is further diluted. From container 4 the diluted composite solution is fed via tubing network 6 to the planted soil 7 at a concentration of about 8g/m . In this manner 1 kg of soil surface can be wetted by the composite solution for 24 hours in a continuous manner.

Use of a hydrated composition has the following advantages: - it help on in reducing irrigation and watering costs; the hydrogel has an absorbency more than 800g water / g dry solids ; - it highly increases water holding capacity of soil during development time of the plants; - the hydrogel controls the biodegradation; - the absorbency capacity does not diminish even after more than 200 cycles of absorption / desorption; - its application improves the soil's structure by controlled biodegradation and enrichment of the ammonium content of the soil; - the hydrogel contributes to reduce the quantity of fertilizers needed by its biopolymer composition; G42150 - the hydrogel contributes to healthy plant life by reducing plant stress; - the hydrogel significantly increases the intervals between watering lawns, gardens, houseplants, trees, and crop fields; - it may be used in horticulture, agriculture and gardening; and - the hydrogel may be used in handicrafts and home decorating.

G42150

Claims (6)

138565/2

1. A hydrated polymeric composition for application to soil comprising: . a mixture of a modified collagen biopolymer, component A, and a synthetic ternary copolymer, component B, in the ratios of A:B = 10:90 to 75:20, wherein: component A comprises a collagen biopolymer having an average molecular weight between 5000 and 80,000 and wherein 0 to 30% of the free carboxyl groups of the collagen material are esterified with a C| to C6 alcohol, preferably ethanol, and 20 to 30% of the free amino groups are blocked with ionizable hydrophilic groups, preferably phthalic or succinic anhydride, and component B comprises a ternary copolymer having an average molecular weight between 20,000 and 200,000 Da, a glass temperature Tg = 5-1 10°C, formed by copolymerization of monomers C, D and E, wherein: C- represents a vinyl or acrylic monomer of the formula: CH2=CR1R2 wherein: R1 = -H, or -CH3; R2 = -H, -C6H5, -CH2C6H5, -CH=CH2, -COOR3 or CN, and R3 = -(CH2)k-H with k = 2-8; D- is a1 polar monomer having the formula: CHR4=CHR5 wherein: R4 = -H or -COOH; R5 = - COOH, -CN, -0-CO-CH3, -OH, -NH2) -0-(CH2)2-OH, -0-NH2 or -NH-(CH2)2-NH2; and E- is a reactive monomer selected from acryloyl chloride, acrolein, maleic anhydride, itaconic anhydride, glycidylmethacrylate, vinyl oxazole and reactive acrylic ester, having the following formula: G42 I 50 9 138565/2 CH2=CH(COOR6) wherein R6 = phenyl, benzyl, pentachlorophenyl or p-nitrophenyl.

2. A hydrated polymeric composition according to Claim 1, wherein the collagenic biopolymer complex, component A, comprises 15% of the free carboxyl groups esterified with ethanol and 25% of the free amino groups reacted with phthalic anhydride, and component B comprises a copolymer of styrene, acrylic acid and maleic anhydride in a ratio of 55:5:40 respectively, and components A:B are in a ratio of 25:75.

3. A hydrated polymeric composition according to Claim 1, wherein the collagenic biopolymer complex, component A, comprises 5% of the free carboxyl groups esterified with ethanol and 25% of the free amino groups reacted with succinic anhydride, and component B comprises a copolymer of acrylonitrile, acrylamide and glycidyl methacrylate in a ratio of 55:20:25 respectively, and components A:B are in a ratio of 65:35.

4. An aqueous irrigating solution comprising a hydrated polymeric composition according to either of Claims 1 or 2.

5. A hydrated polymeric composition according to Claims 1 to 3, in the form of granules with average diameter of 0.3-3mm.

6. A method for applying water and sustained moisture to soil comprising applying to the soil a hydrated polymeric composition according to any one of Claims 1 to 5. Yours very truly, SELIGSOHN GABRIELI & CO. G42150 10