WO2022197270A1

WO2022197270A1 - Capsule technology for providing antifouling feature to the fishing nets

Info

Publication number: WO2022197270A1
Application number: PCT/TR2022/050200
Authority: WO
Inventors: Gülşah EKİN KARTAL; Ayşe MERİH SARIIŞIK; Levent ÇAVAŞ
Original assignee: Dokuz Eylül Üni̇versi̇tesi̇ Rektörlüğü
Priority date: 2021-03-15
Filing date: 2022-03-07
Publication date: 2022-09-22

Abstract

The invention relates to microcapsules providing antifouling properties to the fishing nets and the method of applying these microcapsules to the fishing nets.

Description

CAPSULE TECHNOLOGY FOR PROVIDING ANTIFOULING FEATURE TO THE

FISHING NETS

Technical Field of the Invention

The invention relates to the microcapsule that can be used in the technical textile and fish farming areas and provides an antifouling feature to the fishing nets as well as the method of applying this microcapsule to the fishing nets.

State of the Art of the Invention (Prior Art)

One of the most important problems in aquaculture studies carried out within marine ecosystems is the biofouling event. Biofouling is the attachment of fouling organisms on artificial surfaces immersed in aquatic ecosystems. This event prevents water exchange by closing the mesh opening of the nets used for fish farming and this situation has negative effects on cultural fishing due to the decrease of dissolved oxygen. Meanwhile, the coating of the nets used in fish farming by fouling organisms causes an increase in the weight of the nets.

Tributyltin (TBT) was first used in this field. However, dyes and coatings containing tributyltin (TBT) were banned by the International Maritime Organization (IMO) and the Marine Environmental Protection Committee (MEPC) due to the effects caused by this chemical on the non-target marine organisms. Therefore, self-antifouling coating and dyestuffs have begun to be applied instead of traditional TBT-based coatings. However, its mechanism of action is in the form of biocidal substance release and is the same as TBT. Copper, zinc oxides, and isothiazoles are used in the preparation of tin-free self-antifouling chemicals. Initially, water-insoluble dye matrices (for example, vinyl, epoxy, acrylic or chlorinated rubber polymers) were used for the addition of biocidal substances. However, water-soluble matrix dyes (e.g. rosin) have been developed to maintain the antifouling effect for a long time by adding a binder that dissolves in seawater. Improvement of the antifouling effect is accomplished by using booster biocides or common biocides (e.g. copper and zinc pyrites) and by controlling the degradation rates of the main binder resin. Therefore, factors such as binding systems and common biocides play an important role in complementing the biocidal effect of copper oxide. The environmental toxicity of these compounds is examined while TBT-based antifouling chemicals are replaced with other biocide-releasing coatings.

Marine ecosystems are under serious threat due to the use of existing non-environmentally friendly antifouling dyes. Antifouling dyes are known as toxic dyes in Turkey due to the biocidal agents they contain. The aquaculture industry, which has quite high investment costs and is expected to have a long-term antifouling effect, has a high export potential. Inland aquaculture was reported as 276,502 tons in 2017 according to the report of the Ministry of Agriculture and Forestry dated March 2019 (Ministry of Agriculture and Forestry Statistics on Aquaculture). It is an industry with export potential for Turkey, which is covered with seas on three sides. Fishing nets are also one of the most important elements of this industry. Fishing net production also constitutes an important part of Turkey’s technical textile production.

The prevention of fouling organisms for fishing nets is generally achieved by the selection of the right material and the use of antifouling dye. Today, the coating technology used in fishing nets is based on the use of copper (I) oxide as the basic biocide. Copper (I) oxide provides an effective solution and causes serious damage to the environmental ecosystem. It also creates a negative effect on the flora and fauna in the bottom structure by accumulating in the sediment in addition to the effects of copper ions released from fishing nets on fouling organisms. Therefore, it is absolutely necessary to develop environmentally friendly formulations for sustainable aquaculture studies in aquatic ecosystems.

There are studies on the encapsulation of antifouling agents in the state of the art and the realization of slow and controlled release, thus reducing the harmful effects of these agents.

The patent document WO 2017/095335 A1 relates to heavy metal or copper-free anti-pollution coating compositions for the protection of fishing nets for the control and prevention of biological contamination from algae, fungi, and bacteria on the wetted surface of the net. Microcapsulation takes place here by incorporating the organic biocide (preferably 4,5- dichloro-2-n-octyl-3 (2H)-isothiazolone (DCOIT)) into a polymeric microcapsule. Thus, controlled and long-term biocide release can be achieved from the porous microcapsule. The coating compositions according to the invention are preferably used for coating fishing nets, for coating objects in contact with sea water such as yachts, ships, boats, floating objects, buoys.

In patent document US 2019/0133120 Al, the invention is a biocide-encapsulated microcapsule for use in dyeing, comprising a hydrophobic core formed by polymerization of a hydrophobic monomer comprising an unsaturated bond in the presence of a free radical initiator; a crosslinked hydrophilic shell adapted to surround the hydrophobic core and formed by polymerization of a hydrophilic monomer comprising an unsaturated bond and another crosslinking agent; and a hydrophobic biocide compound. The hydrophobic core and the crosslinked hydrophilic shell surround the scattered biocide. Therefore, the biocide is released from the microcapsule core in the long term, such that a resulting dried dye prevents biological contamination in the long term.

However, there is a need for alternative microcapsule production methods and applications where environmentally friendly chemicals are used with a low amount of active ingredient and can be easily obtained in order to provide an antifouling feature to the fishing nets and to obtain fishing nets with high mesh opening.

Brief Description and Objects of the Invention

The present invention relates to a microcapsule which meets the aforementioned needs, eliminates all the disadvantages and provides some additional advantages, provides antifouling properties to the fishing nets and the method of applying the microcapsule to the fishing nets.

The primary object of the invention is to develop environmentally friendly formulations for sustainable aquaculture studies in aquatic ecosystems. For this purpose, environmentally friendly alternatives have been created with capsulation technology that contains less concentration and releases over a longer period of time instead of applying toxic antifouling agents directly to fishing nets. The object of the invention is to obtain a formulation using environmentally friendly chemicals that can be degraded in a short time by both solar rays and microbial degradation after release, whose release is reduced by encapsulation technology, and which is alternative to the toxic dyes currently in use.

The chemical structure of econea, which is the active ingredient used within the scope of the invention, is 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-lH-pyrrol-3-carbonitrile and it was shown that (Econea chemical substance, which has antifouling properties and is currently used in ship painting, has an effect on fishing nets.

Another object of the invention is to cause less marine ecosystem pollution by using less chemicals and to keep the mesh pores open for a longer time. Microcapsules obtained by microencapsulation technology are known to release using less active ingredient compared to other methods. Thus, a longer-lasting antifouling effect can be achieved with fewer chemicals.

Microcapsulation technology used in the invention has very important advantages in terms of being environmentally friendly, both production and low cost and ease of use compared to alternative methods.

Encapsulation of Econea has been provided within the scope of the invention, but other antifouling agents with antifouling properties can also be encapsulated. These may be tannins and their derivatives, capsaicin and its derivatives, diuron and its derivatives (its ecotoxicity will decrease due to decreased release rate in encapsulation), irgarol and its derivatives (its ecotoxicity will decrease due to decreased release rate in encapsulation), acticide (Thor), chain omadine or tertiary ammonium salts. However, antifouling agents are not limited to these.

Definitions of Figures Describing the Invention

The figures and related descriptions required to better understand the subject of the invention are as follows. Figure 1: FT-IR spectrum of ethyl cellulose

Figure 2: DSC analysis of ethyl cellulose

Figure 3: FT-IR spectrum of Econea active ingredient

Figure 4: DSC analysis of Econea

Figure 5: Absorbance graph of ethyl cellulose

Figure 6: Particle size distribution for capsule sample produced with 2:1 Ethyl Cellulose: Econea (w/w) ratio

Figure 7: Particle size distribution for capsule sample produced with 4:1 Ethyl Cellulose: Econea (w/w) ratio

Figure 8: Particle size distribution for capsule sample produced with 8:1 Ethyl Cellulose: Econea (w/w) ratio

Figure 9: SEM images of microcapsules produced with 2:1 Ethyl Cellulose: Econea (w/w) ratio

Figure 10: SEM images of microcapsules produced with 4:1 Ethyl Cellulose: Econea (w/w) ratio

Figure 11: SEM images of microcapsules produced with 8:1 Ethyl Cellulose: Econea (w/w) ratio

Figure 12: FT-IR spectrum of 2:1 Ethyl Cellulose: Econea microcapsules Figure 13: FT-IR spectrum of 4:1 Ethyl Cellulose: Econea microcapsules Figure 14: FT-IR spectrum of 10:1 Ethyl Cellulose: Econea microcapsules Figure 15: DSC analysis of 2:1 Ethyl Cellulose: Econea capsules

Figure 16: DSC analysis of 4:1 Ethyl Cellulose: Econea capsules Figure 17: DSC analysis of 8:1 Ethyl Cellulose: Econea capsules Figure 18: SEM images after application of microcapsules to fishing nets

Detailed Description of the Invention

The microcapsule providing antifouling properties to the fishing nets and the method of applying this microcapsule to the fishing nets are described only for clarifying the subject matter better and without any limiting effect in this detailed description.

The method of providing antifouling properties to fishing nets according to the invention comprises the following steps; a) Obtaining microcapsules with ethyl cellulose: 4-bromo-2-(4-chlorophenyl)-5- (trifluoromethyl)-lH-pyrrol-3-carbonitrile at a ratio of 2: 1, 4: 1, and 8: 1 by weight, b) Transfer of the obtained microcapsules to the fishing nets by dip coating method with water-based polyurethane or acrylic binder.

Investigation of the Properties of the Active Ingredient and Polymer to be Used in the Preparation of Formulations

Ethyl cellulose was used as the shell material and 4-bromo-2-(4-chlorophenyl)-5- (trifluoromethyl)-lH-pyrrol-3-carbonitrile (Econea) was used as the active ingredient in the production of microcapsules. Ethyl cellulose is a hard, thermoplastic and hydrophobic polymer obtained by reacting alkaline cellulose formed after the cellulose macromolecule is treated with alkalis with ethyl chloride. Diagram 1 shows the chemical structure.

Diagram 1. Chemical structure of ethyl cellulose

It is resistant to alkalis, salts and water and can maintain its strength and flexibility in a wide temperature range. It has wide use in industrial applications since it can be solved in cheap solvents. It is used in adhesives, ceramics, conductors, electronics, food industry, pharmaceuticals, food packaging, and inks. Infrared (IR) spectrum and Differential Scanning Calorimeter (DSC) analyses of ethyl cellulose shell material used in microcapsule production have been carried out within the scope of the invention.

Characteristic stress vibrations of the C-H band at 2870 cm ¹ and 2973 cm ¹ and the -C-O-C- band at 1054 cm ¹ are observed when the FT-IR spectrum of ethyl cellulose is examined (Figure 1). The glass transition temperature (Tg) of ethyl cellulose was found to be around 155°C based on Sigma Aldrich data (Figure 2).

Econea is known as a metal-free antifouling agent for hulls or other marine structures. Econea has a wide spectrum of activity against biofouling organisms. Antifouling dyes containing Econea are comparable to those obtained with copper-based products due to the low water solubility and sealing properties of chemical and physical stability in dyes. It is an ecological chemical because it can be degraded with sea water and sunlight. IUPAC name is 4-bromo-2- (4-chlorophenyl)-5-(trifluoromethyl)-lH-pyrrol-3-carbonitrile. It can be soluble in organic solvents such as acetone (300.5 g/1), ethyl acetate (236.0 g/1) even though its solubility in water is not very high. Diagram 2 shows the chemical structure of the Econea.

Diagram 2. Chemical structure of Econea

There is no known incompatibility between the binder resins, pigments, fillers, solvents, or additives commonly used in Econea and antifouling dyes. Econea is prone to hydrolysis and photolysis in dilute aqueous solutions. However, it has been shown that Econea can be used in water-based antifouling dyes without any stability problems. Photolysis of Econea does not normally occur in pigmented coating systems. Econea shows excellent thermal stability. Only melting (±249 °C) and endothermal decomposition have been observed in dynamic Differential Scanning Calorimetry (DSC) in open atmosphere. Econea has a shelf life of five years in the original sealed container when stored at ambient temperature. Econea is suitable for use in different types of antifouling dyes, including conventional rosin-based Controlled Consumable Polymer (CDP) dye types and Self-Polishing Copolymer (SPC) systems. Infrared (IR) spectrum and Differential Scanning Calorimeter (DSC) analyses of Econea, which is used as an active ingredient in microcapsule production, have been carried out in the invention.

The FT-IR spectra of the Econea active ingredient also coincide with the literature and the structural nitrile (-C º N) functional group of the Econea biocide is seen at 2233 cm ¹. Amines, amides, O-H bonds were detected in the 3357-2852 cm^-1 range. The peaks at 1200- 1000 cm ¹ show the presence of ether in the structure (R-O-R) when the FT-IR graphs of the Econea chemical are examined. Again, CF₃ bands showing double dense bands were detected. The peaks at 1000-750 cm ¹ were observed due to hydrogens (=C-H) bound to carbons. The peaks at 1600-1575 cm ¹ indicate C-N vibrations. In addition, C-Cl (substituted benzene) bonds were detected in a narrow band at a wavelength of approximately 827 cm ¹ (Figure 3).

The melting temperature of the Econea was found to be approximately 249°C as a result of the DSC analysis, in parallel with the literature (Figure 4).

Encapsulation of the Active Ingredient by Spray Drying Method Using Microcapsulation Technology

It is encapsulated according to the spray dryer method with Econea (tralopyryl) ethyl cellulose shell material, which will provide an antifouling effect and is an environmentally friendly substance. The spray drying method selected as the capsule production method is one of the most commonly used methods developed in the 1930s. It is used to produce particles of various sizes, shell thicknesses and permeability as well as adaptability to different types of active ingredients and shell materials. This method can be adapted to a wide range of feeding stocks and product specifications such as solutions, suspensions, melts, and pastes. Many active ingredients such as volatile and fixed oils, drug substances, insecticides are used in capsule production.

Econea active ingredient, which is a substance with known antifouling properties, was mixed with ethyl cellulose shell material in 2:1, 4:1, and 8:1 shell material :active ingredient (g/g) ratios according to the spray drying method and the capsules were produced within the scope of the invention. The solution containing ethyl cellulose and Econea was prepared with a magnetic stirrer and the resulting solution was sent to the hot chamber in the drying device by spraying with the delivery pipe. The temperature reached by the emulsion prepared in the capsule production by the spray drying method at the inlet is the inlet temperature and the temperature reached at the outlet is the outlet temperature and provides the formation of the capsule by the drying process. First, the emulsion is pumped to the feeding area. The pump here is the feeding pump speed of the emulsion. The aspirator provides the circulation of the drying air. The obtained capsules were collected in the collector. Table 1 shows the chemical quantities and test conditions preferably used in the production of capsules by spray drying in the invention.

The method for obtaining microcapsules according to the invention comprises the following steps;

• Dissolving ethyl cellulose: 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-lH- pyrrol-3-carbonitrile at a ratio of 2:1, 4:1, or 8:1 by weight in ethyl acetate and mixing in a magnetic stirrer until a homogeneous emulsion is obtained,

• Setting the inlet temperature of the spray drying device to 135-170°C and the outlet temperature to 85-100°C,

• Setting the pump rate to 2-10 ml/min to ensure the pumping of the prepared emulsion to the device and the aspirator rate to 80-90% to ensure the circulation of the drying air in the device, Feeding the prepared emulsion to the drying device by spraying with the pump.

8 g of ethyl cellulose used as shell material and 4 g of Econea, used as active ingredient, are dissolved in a polymer solution containing 400 ml of ethyl acetate in the spray drying method. The solution is mixed in a magnetic stirrer until a homogeneous emulsion is obtained. The obtained homogeneous solution is pumped into the spray drying device, where the inlet temperature is set to 135°C and the outlet temperature is set to 90°C, and sprayed in the form of an aerosol into a cabinet with hot air. The pump rate is set to 10 ml/min to ensure the pumping of the prepared emulsion to the device and the aspirator rate to 90% to ensure the circulation of the drying air in the device. Polymer solution droplets sprayed into the spray cabinet are dried in cyclone, ethyl acetate used as solvent is removed and accumulated in capsule form in the product collection container of the device. The product is not damaged by the fact that the drying time is short despite the high drying temperatures applied and the product does not theoretically exceed the wet thermometer temperature. The shell material: active ingredient to mass ratio, i.e. the ethyl cellulose:Econea ratio, the viscosity, the concentration and the temperature of the starting solution affect the properties of the microcapsules.

Table 1. Chemical quantities and test conditions used in capsule production by spray drying

Inlet Outlet Pump

Polymer Solution Aspirator (%)

Temperature Temperature (ml/min)

Ethyl

8 g

Cellulose

Econea Variable 135°C 90°C 90 10

Ethyl

400 ml

Acetate

Capsules in different shell material: active ingredient (g/g) ratios were produced with the spray drying device and optimization studies were carried out in this context. Firstly, the capsule yield of the capsules produced at different rates was calculated, and the optimum capsule recipe was created by analyzing SEM images and particle size and distribution. Microcapsule trials produced according to the spray drying method and using Econea as the active ingredient are given in Table 2. Capsule production studies were carried out at 2:1, 4:1, and 8:1 Ethyl cellulose (EC):Econea (w/w) ratios within the scope of this study. The yield calculations of the capsules of the products were carried out. Simple yield calculation was made while calculating the yield and the yield was calculated by using the relationship between the product weights included and the weights of the capsules obtained.

Table 2. EC: Econea capsule studies and yield rates

EC: Econea (w/w) Yield (%)

2:1 65.3±5.4

4:1 25.4±2.8

8:1 15.0±1.7 The production efficiency of the microcapsules produced by the spray drying method varied. The yields of the capsules ranged from 15.0 to 65.3% (w/w). It was concluded that the capsule with the highest yield was microcapsules with a 2: 1 (w/w) ratio when the yield values of the capsules produced at 3 different ratios with Econea active ingredient were examined. As the proportion of the shell material (ethyl cellulose) increases, the microencapsulation yield tends to decrease as the shell material does not have enough active ingredient (Econea) to form a microcapsule.

Analyses were carried out with UV-Vis spectrophotometer in order to determine the amount of active ingredient carried by capsules containing Econea. The absorbance value of ethyl cellulose, which is the shell material, was also determined for this purpose and it was determined whether ethyl cellulose had any effect in the determination of the active ingredient. In this context, the absorbance graph of ethyl cellulose is shown in Figure 5.

It was found that ethyl cellulose made an intervention at approximately 350 nm wavelength when the absorbance graph of ethyl cellulose was examined. Econea has previously been detected to interfere at a wavelength of 296 nm. It was determined in this context that ethyl cellulose did not affect the data obtained at 296 nm in any way. Spectroscopic measurement of the active ingredient released by the complete dissolution of the shell material was provided in the determination of the active ingredient. The absorbance of the Econea amounts in ethyl cellulose capsules and the concentration values calculated based on this result are given in the table (Table 3).

Table 3. EC: Econea capsule active ingredient determination

Capsule Absorbance (296 nm) Concentration (mM)

2L 0.987 122.74±3.47

4:1 0.785 96.53±2.18

8:1 0.514 48.00±1.45

It was determined that the absorbance value given at this wavelength and thus the concentration increased as the concentration of the active ingredient in the capsule increased when the measurements taken at 296 nm were examined. It was observed that the active ingredient in the capsule decreased linearly with the decrease in the rate of active ingredient used in the capsule formation phase. The capsulation of the active ingredient was performed successfully in this case.

The average particle size of the microcapsules was determined by the laser diffraction method and changes in the size of the capsules were observed depending on the changing polymenactive ingredient ratios. It was found that the particle size of the 4:1 (w/w) capsules produced was 3.753 pm and had a high homogeneity when the particle size analysis of the capsules produced at different ratios was evaluated (Figure 7). The particle size of the 2:1 and 8:1 capsules produced was determined to be 6.582 pm and 11.526 pm, respectively. Econea- based capsules with 2:1 and 8:1 ratios were also observed to be homogeneously distributed, but with high standard deviations (48.6% for 2:1 and 110% for 8:1). The high standard deviations may be due to the fact that the microcapsules are agglomerated at a certain rate (Figure 6, Figure 8)

3000 and 5000 times magnified SEM images were taken in order to determine the shapes and surface morphologies of the capsules obtained within the scope of the invention. Images of the capsules produced are shown in Figure 9-11. It was determined that some of the capsules obtained were in spherical form when the SEM images were examined. In particular, it is seen that the capsules obtained in SEM images of 2:1 EC:Econea capsules are in a more spherical form (Figure 9). However, some capsules have been found to be agglomerated in general. It is thought that this is due to the accumulation of the active ingredient around the capsules.

However, it was observed that not all particles appeared morphologically spherical when the micrographs of microcapsules produced especially at the 8:1 (w/w) ratio were examined. It was observed that the center of some microcapsules collapsed when the polymer solution prepared during production entered the hot air cabinet and then due to sudden solvent evaporation (Figure 11). On the other hand, the biggest reason for the Econea-induced collapse in the capsules is thought to be the accumulation of the non-encapsulated active ingredient on the shell material. The optimum Econea content was seen in microcapsules with a 2:1 ratio of ethyl cellulose (EC):Econea (w/w) to obtain homogeneous and spherical capsules according to SEM images of microcapsules.

FT-IR spectra of ethyl cellulose (EC):Econea capsules with different weight ratios are shown in Figure 12-14. Peaks of ethyl cellulose were mainly detected when the FT-IR spectra of the capsules were examined. C-H band at a wavelength of approximately 2870 cm ¹ and 2973 cm ¹ was detected in all capsules. In addition, an increase in the % permeability value of some bands on the same band was observed in ethyl cellulose and Econea chemical. For example, the % permeability in these bands increased at 1200-1000 cm ¹ due to the joint intervention of the presence of ether (R-O-R) and CF₃ bands showing double dense bands. It was found that some peaks of Econea were encapsulated with Econea active ingredient and their permeability decreased or disappeared as they were coated with ethyl cellulose as shell material. For example, it was determined that the band seen at 2233 cm ¹, which is the structural nitrile (-C º N) functional group of the Econea biocide, did not appear in the FT-IR diagrams of the capsules. This shows that the encapsulation is successful. In addition, the FT-IR peaks of ethyl cellulose show a shift and some new peaks are observed due to the Econea active ingredient. It is thought that this situation occurs as a result of the capsule process and the peaks of the Econea shift within the FT-IR bands of ethyl cellulose. Peaks seen to be caused by Econea are thought to be caused by active ingredients that cannot be encapsulated.

The DSC results of the Econea-containing capsules produced within the scope of the invention are shown in Figure 15-17. The DSC analysis was performed to investigate the thermal properties of the capsules produced, qualitatively validating the success of the encapsulation process through noticeable variations in the thermal curves of the active ingredient and charged capsules. The glass transition temperature (Tg) of ethyl cellulose is expected to be around 155°C based on Sigma Aldrich data, and the melting temperature of Econea is expected to be around 249°C in line with the literature. The thermograms of the samples obtained from the combination of shell material and active ingredient were analyzed and it was determined that the diagrams of the encapsulated active ingredient were close to the ethyl cellulose diagram used as shell material. It is concluded that this condition in the peaks of the preparations is almost absent outside the space of the host molecule after the capsulation and thus the formation of the capsule occurs.

Table 4. Complexation amounts of samples containing Econea

Capsule c DH_ί DH₀ Complexation

% J/g J/g %

2:1 EC: Econea 33.33 - - 100.00

4:1 EC: Econea 20.00 0.6118 249.72 98.78

8:1 EC: Econea 11.11 4.821 218.84 80.17

The thermograms of the samples obtained from the combination of shell material and active ingredient were analyzed and no significant thermal change and corresponding peak were observed especially for the capsules in the ratio of 2:1. This loss in the peaks of the active ingredient showed that there was no active ingredient except for the gap of the shell material after the capsulation and that a high rate of complexation occurred. It was found that the active ingredient was successfully encapsulated when the complexation rates of capsules containing Econea were examined. The highest complexation rate was found in capsules containing 2:1 EC:Econea with 100% according to the calculations in Table 4. It was determined that the capsules produced at a 4:1 ratio also complexed at a high rate of 98.78%. It was determined that the capsule formation percentage was the lowest, with 80.17% at the rate of 8: 1 in parallel with the previous studies (SEM, particle size analysis, etc.). According to the results of the characterization studies, microcapsules with a 2:1 EC:Econea (w/w) ratio were preferred as the optimum capsule formulation and applied to fishing nets. The 2:1 capsules with the highest active ingredient ratio were determined as the optimum capsules because the capsules had the best complexation rate and a long-term effect was desired according to SEM images and DSC analyses.

Transfer of Capsules Obtained to Fishing Nets and Undersea Studies

The capsules, whose optimum production parameters were determined by the optimization study, were applied to high-density polyethylene-based fishing nets according to the dip coating method with the help of water-based polyurethane and acrylic binders, dried and fixed.

Table 5. Optimum Capsule Production Parameters

Inlet Outlet Pump

Polymer Solution Aspirator (%)

Temperature Temperature (ml/min)

Ethyl

8 g

Cellulose

Econea 4 g 130°C 90°C 90 10

Ethyl

400 ml

Acetate

The recipe in Table 6 was used to transfer the produced capsules to the fishing nets. Here, the capsule concentration is in the range of 30-50 g/1, preferably 40 g/1. The binder concentration is also in the range of 30-50 g/1, preferably 50 g/1. In the prepared solutions, water-based and APEO (alkylphenol ethoxylate)-free acrylic and polyurethane binders were used to increase viscosity and provide binding efficiency. Polyurethane binders are generally thick, have good elongation ability, good abrasion resistance. They have a very good resistance to cold. Acrylic binders, on the other hand, have a large number of variants and copolymers. They have good UV resistance and optical transparency, usually not expensive. Their washing resistance is very good. In addition, Tween 20 was preferred as a surfactant for the homogeneous distribution of the capsules. Tween 20 is a nonionic surfactant. Its stability and non-toxicity allow it to be used as an emulsifier in many domestic, scientific and pharmacological applications.

Table 6. Process conditions by dip coating method Surfactant

Capsule (g/1) Binder (g/1) Tween 20 Drying+Fixation

(g/i)

Temperature (°C) Duration (min)

40 50 10

110-140 7

After application to fishing nets, SEM imaging analysis was performed on the nets. The obtained capsules were transferred to the fishing nets by dip coating method. The SEM images taken after the 2:1 microcapsules were transferred to the fishing nets are shown in Figure 18.

It is seen that the microcapsules obtained are successfully transferred to the fishing nets when the SEM images are examined. The surfactant used in the transfer of the capsules helped to distribute the capsules homogeneously in the solution. In addition, it was found that the transferred capsules generally spread throughout the net and preserved their spherical form.

Fishing nets with optimum capsule formulation were placed in special frames and kept for 6 months from the end of June to the end of December for undersea studies in a fish farm in the Aegean Region. Images were taken by divers with an underwater camera at certain intervals during this time. Fouling scoring was performed on the net images when the underwater studies were completed. Image analysis was performed on the photos obtained with the image analysis technique (image process analysis) and the mesh opening percentages of the nets were calculated. After the undersea studies, the weight changes were tested with the device defined as a dynamometer and used to determine the strength of the fishing nets.

It was observed that the pores of the fishing nets produced in the ratio of 2:1 (shell material/active ingredient) and transferred to microcapsules with polyurethane binder were more open and their live reproduction on these nets was the least when the images obtained from the field study were examined. This indicates that microcapsules have a long-term effect due to their slow-release properties. It was found that the ratio of mesh openings was better than the chemicals used, but it did not give as good results as the 2: 1 ratio and the fishing nets where polyurethane microcapsules were transferred when the commercial antifouling dye transferred fishing net currently used in the industry was examined. As a result, it was found that the antifouling biocide (Econea), which is generally hydrophobic and has low solubility in water, was successfully encapsulated with the spray drying technique and the desired antifouling properties were obtained at the end of the field studies. In addition, the collection of very small amounts of macroorganisms on the fishing nets transferred to the capsule has also made it easier to clean the fishing nets. This will also allow fishing nets to be used for a longer period of time.

Undersea studies were carried out in order to examine the antifouling activities of the chemicals transferred by dip coating method. The image analysis method was used to calculate the visual evaluations numerically. The fishing nets whose undersea studies were completed were photographed on a white background in order to process the images. The photos obtained were converted into a black and white image (binary image) on the software. White pixels were determined over the images of the fishing nets obtained at the end of 6 months with the image analysis method and the ratio of all of these pixels to the total number of pixels was calculated and the mesh opening (%) was calculated (Table 7).

Table 7. Mesh opening values calculated by the image analysis method of fishing nets

Fishing Net esh Opening (%)

Before Undersea Study 85.93±1.27 Untreated 19.21i3.45

Commercial antifouling dy 55.89i2.14 Capsule Containing 2: 1 Econea + 59.45i2.78 Binder

Capsule Containing 2: 1 Econea + P 72.63i2.42

When the mesh opening values obtained by the image analysis method were examined, it was determined that the percentages obtained gave parallel results with the photos obtained as a result of undersea studies. It was determined that the fishing net with the highest mesh opening percentage was the fishing net produced in the ratio of 2:1 (shell material: active ingredient) with 72.63% and transferred to microcapsules with polyurethane binder. It was found that the mesh opening of the commercial antifouling dye transferred fishing net remained at 55.89%. It was found that microcapsule-transmitted fishing nets showed much better antifouling activity compared to 2:1 microcapsule-transmitted fishing nets (72.63% mesh opening). This indicates that the microencapsulated Econea chemical may be an alternative to commercial antifouling dye.

The strength results of the fishing nets after the field studies are shown in Table 8. Measurements were taken from 30 different parts of the fishing nets and standard deviations were calculated for the strength and elongation values of the nets.

Table 8. Strength and elongation values of fishing nets

Breaking

CV Elongation CV

Fishing Net Strength % (mm) %

(kg)

Fishing Net Before Field Study 90.1±1.5 1.74 31.0±1.0 3.23

Untreated 87.1±1.5 1.72 31.0±1.0 3.23

Commercial antifouling dye 86.6±1.0 1.15 30.0±1.0 3.33

Capsule Containing 2:1 Econea + Acrylic Binder 89.1±1.5 1.68 30.0±1.0 3.33

Capsule Containing 2:1 Econea + PUR Binder 89.9±2.0 2.22 30.0±1.0 3.33 One of the most important parameters in terms of the long-term use of fishing nets is the long term preservation of the strength of fishing nets. For this reason, high strength fibers are used in the nets used in fish farms. Fishing nets that do not lose strength as long as they are undersea are preferred because they provide long-term use. When the load (kg) and elongation (mm) results required for the breaking of the fishing nets where undersea studies were carried out were evaluated, no major changes were observed before and after the field study (Table 8). The strength required for the breaking of the fishing net before the field study has been determined as approximately 90 kg. After the field study, it was determined that the best results were in the samples in which 2:1 EC:Econea capsules with the highest antifouling efficiency were transferred to fishing nets with polyurethane and acrylic binder, even though the strength change was not very large. This is thought to be due to less accumulation of macroorganisms on the fishing nets. Approximately 3-4% strength loss was observed in other nets. The reason for the change in other fishing nets is the presence of dissolved minerals in the marine ecosystem and the corrosive conditions that occur under these conditions. In addition, the accumulation of more macroorganisms in these fishing nets may also be the cause of loss of strength.

It was found that there was no significant change in the elongation rates when the elongation values of the fishing nets were examined. Because the UHMWPE fishing nets used have high strength and bearing capacity, it is believed that the change in elongation percentages is also low.

As is known in fish farming, the coating of the nets used by fouling organisms can cause an increase in the weight of the nets and the breaking of the fishing nets. This situation causes a great disadvantage for farms where cultivation is carried out. The weight changes in the fishing nets before, after and after the cleaning process are given in Table 9.

Table 9. Weight measurements of fishing nets before and after field studies

Before Field After Field

Fishing Net Study (g) Study (g)

Untreated 15.51±0.65 653.11±20.45

Commercial antifouling dye 22.98±0.32 204.62±16.74

Capsule Containing 2: 1 Econea + Acrylic Binder 17.81±0.27 109.87±11.75

Capsule Containing 2: 1 Econea + PUR Binder 18.70±0.29 85.91±10.43

When the weight changes before and after the experiment were examined, the weight change was less in the nets where the Econea capsules with antifouling properties and therefore pores were less closed were transferred to the fishing nets by dip coating method (especially with polyurethane binder). The weight change gave better results than other chemicals in commercial antifouling dye transferred fishing nets, in parallel with the mesh opening percentage, but it was exposed to a greater weight increase than the nets where Econea capsules were transferred at a ratio of 2: 1.

Claims

1. A method of providing antifouling properties to fishing nets, characterized in that it comprises the following steps: a) Obtaining microcapsules with ethyl cellulose: 4-bromo-2-(4-chlorophenyl)-5- (trifluoromethyl)-lH-pyrrol-3-carbonitrile at a ratio of 2:1, 4:1, and 8:1 by weight, b) Transfer of the obtained microcapsules to the fishing nets by dip coating method with water-based polyurethane or acrylic binder.

2. A method according to claim 1, characterized in that in the step b the capsule concentration is in the range of 30-50 g/1 and the binder concentration is in the range of 30-50 g/1.

3. A method according to claim 1, characterized in that obtaining the microcapsules in step a comprises the following steps:

• Dissolving ethyl cellulose: 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)- lH-pyrrol-3-carbonitrile at a ratio of 2:1, 4:1, or 8:1 by weight in ethyl acetate and mixing in a magnetic stirrer until a homogeneous emulsion is obtained,

• Setting the pump rate to 2-10 ml/min to ensure the pumping of the prepared emulsion to the device and the aspirator rate to 80-90% to ensure the circulation of the drying air in the device,

• Feeding the prepared emulsion to the drying device by spraying with the pump.

4. A method according to claim 1 or 2, characterized in that the ambient temperature of the dip coating method in step b is in the range of 110-140°C.

5. A method according to claim 3, characterized in that ethyl cellulose and 4-bromo-2-(4- chlorophenyl)-5-(trifluoromethyl)-lH-pyrrol-3-carbonitrile at a ratio of 2:1 by weight are dissolved in 400 ml of ethyl acetate.

6. A method according to claim 5, characterized in that 8 grams of ethyl cellulose and 4 grams of 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-lH-pynOl-3-carbonitrile are dissolved in 400 ml of ethyl acetate.