"BIODEGRADABLE ARTIFICIAL BAITS"

DESCRIPTION

The present invention relates to biodegradable artificial baits obtained from biodegradable compositions substantially insoluble in an aqueous environment, and capable of releasing attractive substances that are able to attract aquatic organisms of interest in the same aqueous environment.

In the fishing sector, in particular the industrial one, there exists a need for a replacement of natural baits with baits of different origin. In fact, since natural baits are constituted by organisms that must in turn be bred or caught, they represent an important element of cost. Moreover, if they do not come from a breeding centre, their use represent a contribution to the impoverishment of the stock of fish, which is currently being significantly eroded on account of intensive fishing on an industrial scale.

The problem above is now solved according to the present invention by biodegradable artificial baits, obtained by biodegradable compositions substantially insoluble in an aqueous environment and capable of releasing attractive substances that are able to attract aquatic organisms in such aqueous environment.

The biodegradable artificial bait according to the present invention comprises a composition comprising at least one biodegradable substance of renewable origin, at least one biodegradable (co)polymer of synthetic origin, and at least one attractive biodegradable substance that is able to attract aquatic organisms.

In the composition according to the present invention the biodegradable substance of renewable origin is present in an amount of from 10 to 90 wt%, preferably from 20 to 80 wt%, and still more preferably from 30 to 70 wt%. The substance of renewable origin comprises natural polymers that are able to become thermoplastic in suitable conditions of temperature and in the presence of plastifϊers. Said natural polymers comprise, for example, starches, modified starches, alginates, lignins, celluloses, modified celluloses, etc.

In a particularly preferred embodiment, the substance of renewable origin is starch. In particular, the starch can derive from potato, rice, tapioca, maize, peas, wheat, and the like. Potato starch or maize starch is preferred. The starch can be also modified either chemically or physically.

The composition moreover contains at least one biodegradable thermoplastic (co)polymer of synthetic origin.

The biodegradable thermoplastic (co)polymers that can be used as components of the artificial

baits according to the invention are chosen among the following classes: a) biodegradable polymers of synthetic origin or obtained by fermentation, in particular polyesters such as homopolymers or copolymers of aliphatic hydroxyacids having from 2 to 24 carbon atoms, or of the corresponding lactones or lactides, such as, for example: - poly(epsilon) caprolactone, its grafted or block copolymers, the products of reaction of caprolactone oligomers or polymers with aromatic or aliphatic isocyanates, copolymers with lactic acid, with glycolic acid, with poly-hydroxybutyrate and poly- hydroxybutyrate-valerate; polymers of lactic acid or of lactide, polymers of glycolic acid or of polyglycolide, copolymers of lactic acid or of glycolic acid; long-chain, medium-chain, and short-chain polyhydroxyalkanoates such as, for example, poly-hydroxybutyrates (e.g. poly-hydroxybutyrate-valerateP), polyhydroxyhexanoates, polyhydroxyoctanoates, polyhydroxydecanoates, and copolymers with other polyesters; b) polyesters derived from bifunctional acids and aliphatic diols, such as, for example: aliphatic or aliphatic-aromatic polyesters such as polyalkylene adipates, polyalkylene succinates, polyalkylene azelates, polyalkylene sebacates, and polyalkylene brassilates, possibly copolymerized with aliphatic or aromatic isocyanates possibly increased in weight by means of chain extenders; such as, for example, polyethylene adipate, polybutylene adipate, polyethylene adipate-co-terephthalate, polybutylene adipate-co-terephthalate, polyethylene succinate, polybutylene succinate, polybutylene succinate-co-adipate, polyethylene azelate, polybutylene azelate, polyethylene sebacate, polybutylene sebacate, polyethylene sebacate-co- terephthalate, polybutylene sebacate-co-terephthalate, polyethylene brassilate, and polybutylene brassilate; c) polymers that are able to interact with starch by complexing it, i.e., polymers containing hydrophilic groups interspersed in hydrophobic sequences such as: ethylene-vinyl alcohol copolymers containing up to 50 wt%, preferably 10-44 wt%, of ethylene units, ethylene-vinyl alcohol copolymers oxidized or terminated with fatty acids or grafted with polycaprolactone or modified with acrylic or methacrylic monomers and/or pyridinium; ethylene-vinyl acetate copolymers, even partially hydrolized; ethylene-acrylic ester copolymers;

ethylene-acrylic ester-maleic anhydride terpolymers or ethylene-vinyl acetate- glycidyl methacrylate terpolymers; ethylene copolymers with unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic anhydride, etc., in particular ethylene-acrylic acid copolymers containing 5-50 mol%, and preferably 10-30 mol%, of units deriving from acrylic acid; terpolymers of ethylene and vinyl acetate hydrolized totally or partially with acrylic acid or methacrylic acid or crotonic acid or itaconic acid;

6-6, 6-9 or 12 aliphatic polyamides, aliphatic polyurethanes, random or block polyurethane-polyamide, polyurethane-polyether, polyurethane-polyester, polyamide-polyester, polyamide-polyether, polyester-polyether copolymers; polycaprolactone-urethane, where the size block of polycaprolactone is between 300 and 3000 units of molecular weight and where the isocyanates used are MDI

(methylen-diphenyl diisocyanate), toluene diisocyanate, hexamethylene diisocyanate. d) polymers selected from the group consisting of polyvinyl alcohol in the various degrees of hydrolysis, optionally modified with acrylates or methacrylates, polyvinyl alcohol previously plastified or modified in order to lower the melting point, optionally containing gelling agents such as boric acid, borates or phosphates, copolymers of vinyl acetate in the various degrees of hydrolysis with vinyl pyrrolidone or styrene, polyethyloxazoline, polyvinyl pyridine; or polymers capable to form hydrogen bonds with starch.

Particularly preferred is an alkenolic homopolymer and/or alkenolic copolymer in an amount of from 10 to 90 wt% with respect to the composition, preferably from 10 to 40 wt%. The preferred alkenolic homopolymer is polyvinyl alcohol, in particular with a degree of hydrolysis of between 80 and 99 mol%, preferably between 90 and 99 mol%, and still more preferably between 96 and 99 mol%.

The composition moreover contains attractive biodegradable substances of natural or synthetic origin that are able to attract aquatic organisms of interest in an amount of from 1 to 30 wt%, advantageously from 1 to 15 wt%. Amongst the attractive substances of natural origin, particularly preferred are extracts of yeast, oligopeptides, mixtures of oligopeptides, amino acids, mixtures of amino acids or combinations thereof. Extracts of yeasts are particularly preferred. The preferred yeast is Saccharomyces Cerevisiae. The attractive substances of natural origin mentioned above may be used as such to attract

aquatic organisms, even if not in the form of baits. Also in this case extracts of yeasts are particularly preferred. The preferred yeast is Saccharomyces Cerevisiae.

The composition can moreover contain additional elements such as plastifiers, colouring agents, fillers, lubricating agents, nucleating agents, animal and vegetable fats, inorganic salts, detaching agents, vegetable gelatins, additives in general.

Advantageously, the composition contains at least one plastifier, i.e., a substance that can be incorporated in the material in order to increase the flexibility and processability thereof or to reduce the viscosity of the melt or reduce the elasticity modulus of the product. The term "plastifier" includes all known types of plastifiers, whether solvent ones or non-solvent ones. The composition can contain at least one plastifier in an amount of from 5 to 50 wt%, preferably from 5 to 30 wt%. The preferred plastifier for starch-based compositions is water. The artificial bait according to the present invention is insoluble in an aqueous environment, i.e., it looses less than 20 wt%, preferably less than 10 wt% and still more preferably less than 5 wt% when it is left for 24 h in an aqueous environment at a temperature lower than 10 ⁰ C. The artificial bait according to the present invention can be present in the form of extrudate, in the injection-moulded form, in the form of sheet, film, mesh, fibre and combinations thereof. The bait can be used in different shapes according to the different fishing techniques, particularly in the form of complex structures that are able to optimize the volume/surface ratio for controlling the kinetics of release. In a particularly preferred embodiment, the artificial bait according to the present invention has the form of a meshlike container containing extruded granules. Said embodiment is particularly advantageous in fishing techniques where traps are used where the aim is to catch the fish alive without the use of hooks. In the case of multibait systems, particularly advantageous are instead injection-moulded articles with shapes suitable for controlling release.

The compositions described above can be processed in conditions known to the person skilled of the sector. In a particularly preferred process the compositions are mixed and brought up to the melting point in an extruder to yield an extrudate that can be used as such (in the form of "spaghetti", flat strips, sectional strips, fine tubes, pellets) or in turn reprocessed, for example by injection moulding. Example 1

A composition containing: - maize starch 57%

- PVOH Lamovil CI 179

(degree of hydrolysis 98.5-99.2%) 21%

- Water 15%

- Yeast extract in powder form (aroma) (Gistex Standard Powder, Chimab) 7% was fed into a two-screw extruder L/D 35 + XLT working at 170 r.p.m. and with the following temperature profile (degrees centigrade) 30-90-130-140-150x2-160x2-140-110x6.

The processing capacity was 10.1 kg/h.

The granules obtained were then tested as regards their solubility in water and release of aroma in an aqueous environment.

Solubility in water

A specimen of approximately 12 g of granules, containing 10 wt% of water, was put into 1.5 1 of water and kept stirred for 24h. At the end of the treatment the specimen was collected, dried in a ventilated stove at a temperature of 50 ⁰ C to eliminate the surface water, and weighed, and the water content thereof was determined. The loss in weight between the start and the end of the treatment was approximately 4.1 wt%. Such value was obtained by applying the following formula:

(dry weight of specimen at start of treatment) - (dry weight of specimen at the end of treatment)

(dry weight of specimen at start of treatment)

Test for release of aroma

A specimen of approximately 50 g of granules was put into 1.5 1 of water containing 3.5% of NaCl, thermostated at 4-6°C and kept under stirring for 24 h. In the course of the 24 h various specimens of the aqueous solution were taken and analysed with a UV-VIS spectrophotometer (Cary IE Varian model) to determine the absorbance thereof at 280 nm. The values of absorbance, correlated via the Lambert-Beer law to the concentration of the aroma in the solution, are given in the table below.