Freeze-dried supported aerogel particles with biocidal properties

Abstract

The present invention relates to silica aerogels with encapsulated biocidal and / or biorepellent compounds at high to very high loadings (55-90% w / w), high porosity and low thermal conductivity, and to methods of making and using such aerogels in antifouling compositions, which are especially suitable for onshore and offshore coatings (marine paints, coatings, sealants, varnishes, wood protection or similar controlled leaching systems) that are naturally exposed to humid conditions and / or water (including seawater) and thus are prone to fouling.

Description

Technical Field

[0001] This invention relates to encapsulated biocide and / or biorepellent compounds with high to very high loadings (55-90% w / w), silica aerogels with high porosity and low thermal conductivity, and to methods for preparing and using such aerogels in antifouling compositions, which are particularly suitable for onshore and marine coatings (marine paints, coatings, sealants, varnishes, wood protectants or similar controlled leaching systems) that are naturally exposed to humid conditions and / or water (including seawater) and are therefore prone to fouling. Background Technology

[0002] Biocides and biorepellents are substances used to prevent the growth of harmful biological organisms in buildings, installations, or other areas. Biocides and biorepellents are typically added to products such as protective coatings (including paints and varnishes) that can be applied to areas susceptible to such harmful growth, and also to elastic sealants such as silicone sealants.

[0003] Protective coatings applied for external or internal use typically serve two basic functions: protection and decoration. Elastic sealants are typically used to seal joints and cracks between non-elastic surfaces such as tiles, where the sealant functions to conceal the joints or cracks, absorb deposits on the non-elastic surface, and prevent moisture ingress.

[0004] Attacks by biological organisms (such as fungi and algae on wet or painted surfaces) can impair the protective properties of paint films and their decorative effects. This biological process is called staining. Mold (mildew) is a common type of fungus that can attack indoor and outdoor surfaces that frequently become damp. Mold spores can become a serious allergy problem, and over time, mold and other fungi can damage wood-based structural materials, so effectively preventing mold and other types of staining is important.

[0005] Ship surfaces exposed to seawater present unique problems because they tend to harbor microorganisms, plants, algae, and animals, increasing propulsive drag and consequently reducing speed or increasing fuel consumption. This bioprocess is known as fouling and can be divided into two main groups: Microbial fouling It includes colonies of single-celled algae and bacteria, often referred to as "slime," and Large biofouling This includes both plant (weed) and animal fouling. Large biofouling, in particular, causes problems related to propulsion drag.

[0006] Paints, coatings, and sealants (which release active biocidal compounds onto surfaces) are commonly used to prevent the aforementioned types of contamination. Biocides are chemical compounds that are toxic to microbial cells and thus prevent the growth of harmful microorganisms and large organisms (i.e., dirt), while less frequently used biorepellents typically have relatively low toxicity and work by repelling or preventing harmful organisms from entering areas that would otherwise attract dirt.

[0007] Most antifouling compounds are not effective against all types of dirt, which is why combinations of active compounds are used. In traditional antifouling coatings and sealants, the leaching of active compounds rarely follows the same decay curve. Therefore, a coating or sealant may only be partially successful in preventing dirt buildup before the end of its service life.

[0008] The release of biocides and / or biorepellents from antifouling coatings can be controlled by encapsulating active compounds. This extends their effective lifespan in various matrices by protecting them from leaching and harmful degradation reactions and by allowing for slow release. Therefore, ideally, the encapsulation method should allow for high loadings of biocides / biorepellents in the encapsulating material, ensuring continuous release of active compounds throughout the coating's lifespan. This combination of features ensures durable antifouling performance, maximizes the use of added active compounds, and thus reduces both cost of goods sold (CoG) and negative environmental impact.

[0009] The inventors of this invention have previously developed a method for encapsulating solid active compounds in silica aerogel particles, as described in International Patent Application WO 2009 / 062975. Such “loaded” aerogels having an encapsulated solid active compound content of about 50% w / w can be produced on a small scale according to the described procedure involving drying the initial wet gel using supercritical CO2 extraction. This encapsulation scheme was later elaborated by the inventors in International Patent Application WO 2020 / 002659, which describes aerogels having an encapsulated solid active compound content of 60%–90%.

[0010] The loading limit of solid active compounds in silica aerogels is important for their final use as antifouling components in coating or sealant compositions. When adding biocides encapsulated in silica aerogels to antifouling compositions, the silica must also be added at a ratio determined by the specific aerogel loading percentage. The inventors have found, empirically, that antifouling compositions should not contain more than about 1.5% w / w SiO2 (silica), otherwise the composition becomes too thick / viscous and difficult to apply uniformly. Therefore, due to the silica limit of 1.5%, simply adding a larger amount of loaded aerogel to the coating composition cannot increase the amount of biocide in an antifouling coating or sealant composition.

[0011] For example:

[0012] An aerogel containing 40% biocide contains 60% silica. To maintain a silica content below the 1.5% limit, this aerogel can therefore be added at a maximum of 2.5% w / w to the coating composition. Therefore, a coating or sealant composition made with this aerogel will contain 1.25% w / w of biocide. It is impossible to add more biocide through this route without exceeding the 1.5% silica limit.

[0013] An aerogel containing 50% biocide contains 50% silica. Therefore, this aerogel can be added at a maximum of 3% w / w of the composition to maintain a silica limit below 1.5%. This means the final composition will contain 1.5% w / w biocide. It is impossible to add more biocide via this route without exceeding the 1.5% silica limit.

[0014] • An aerogel containing 80% w / w biocide contains 20% silica, therefore up to 7.5% w / w of this aerogel can be added to the composition. The final composition prepared with this aerogel will contain 80% × 7.5% = 6% w / w biocide, and still not more than 1.5% silica.

[0015] • If an aerogel with a biocide loading of 90% is used, 15% w / w of aerogel can be added to bring the biocide level in the composition to 13.5% w / w, but not exceeding the 1.5% "silica limit".

[0016] Figure 2 The content of biocide (in w-%) in the coating composition varies with the biocide loading in the aerogel when up to 1.5% silica can be added to the composition.

[0017] The loaded aerogel particles of WO 2009 / 062975 and WO 2020 / 002659 are both produced by sol-gel encapsulation of biocompounds in a silica-containing wet gel, followed by drying via supercritical (SC) CO2 extraction. This production method has proven versatile and well-suited for providing many different types of loaded gels for research and development (R&D) purposes. However, for larger-scale production, the supercritical extraction step is considered undesirable because the process consumes large amounts of solvent and requires a considerable amount of time to exchange the solvent, thus increasing the overall cost.

[0018] Furthermore, the required production equipment is not only expensive, but also poses certain operational risks due to the need for high pressure. Muhammad 2021 ).

[0019] Furthermore, due to solubility issues, certain types of biocides are not easily encapsulated in aerogels using supercritical drying. Finally, the SC-dried aerogel particles prepared according to WO 2009 / 062975 or WO 2020 / 002659 are generally too hard to be directly mixed with other paint components, requiring a separate grinding step before formulation into antifouling paints.

[0020] The inventors of this invention further improved the sol-gel process in the co-pending international application PCT / EP 2020 / 087730, but could not overcome the problem of drying the initial wet gel in a scalable, industrially applicable, and economically viable manner. Therefore, initial attempts to use freeze-drying instead of supercritical (SC) CO2 extraction only yielded gels with relatively poor total porosity and high packing density.

[0021] Therefore, a scalable encapsulation method is still needed that can provide a wide selection of encapsulated biocides and biorepellents in the following forms:

[0022] • High loading of active compounds,

[0023] • Satisfactory pore structure to ensure sufficient water absorption in the resulting coatings or sealants incorporating encapsulated biocides, and

[0024] • A constant biocide concentration on the surface of the antifouling composition throughout its entire lifespan, and

[0025] • A competitive CoG. Attached Figure Description

[0026] Figure 1 The surface of an antifouling coating or sealant composition is shown, the composition comprising solid biocide particles ( Figure 1(Black circles) These particles continuously appear on the film surface as the coating or sealant degrades over time, for example, through exposure to water, high humidity, and / or temperature fluctuations. Soon after, some of the abraded particles are washed out of the coating. Figure 1 (white semicircle).

[0027] Figure 2 The content of biocide (in w-%) in a paint composition varying with the biocide loading in the aerogel is shown when up to 1.5% silica can be added to the coating. The composition contains biocide encapsulated in silica aerogel particles.

[0028] Figure 3 A cross-section of an antifouling composition layer containing aerogel particles uniformly distributed in the layer is shown. The paint layer in this case is approximately 300 μm thick. Each aerogel particle may contain several discrete active compound particles, and the size of each aerogel particle is approximately 10 μm depending on the fineness of the grinding.

[0029] Figure 4 It shows that it contains Figure 3 A close-up of the antifouling composition layer of the aerogel particles shown. When the composition is exposed to moisture, it begins to absorb water, thus producing what is known as... Leaching layer The upper layer. Due to the porosity and hygroscopicity of the silica-based aerogel, the aerogel particles embedded in the leaching layer absorb water, and soon after, a saturated solution of active compounds (e.g., biocides) is generated within the aerogel particles. An active biocidal film is formed on the surface of the antifouling composition layer through diffusion via the leaching layer.

[0030] The leaching layer can be renewed, for example, by eroding the upper portion of the layer and allowing water to penetrate deeper into the intact antifouling composition layer. If erosion is negligible or slow, the leaching layer will increase over time and the biocidal effect will be solely due to diffusion.

[0031] Figure 5 Table 1 presents the porosity determination results of freeze-dried aerogels FD1-FD4, originally disclosed in the co-pending international application PCT / EP 2020 / 087730. Table 1 compares two empty gels and two loaded gels frozen at two different temperatures (-18°C and -80°C). All gels in Table 1 were prepared using pre-condensed TEOS+MTMS. As can be seen, all gels have a total porosity of <40% and close to 1 g / cm³. 3The bulk density. Total porosity is significantly affected by the presence of the loaded biocide (compare FD1 / FD2 and FD3 / FD4), while freezing temperature does not appear to have a significant effect on either total porosity or density (FD1 / FD3 and FD2 / FD4).

[0032] Figure 6 Table 2 shows the porosity determination results of six freeze-dried supported aerogels FD5-FD10 prepared according to the present invention. Reference number FD5 contains 66% Econea, FD6 contains 56% DCOIT, FD7 contains 75% zineb, FD8 contains 75% copper pyridinethione (CuPt, reference sample), FD9 contains 75% zinc pyridinethione (ZnPt), and FD10 contains 75% Econea. All gels except FD5 were prepared using TEOS and MTMS, except for FD5 which was prepared without MTMS. For all samples, the total porosity was at least 50%, and the mesopore diameter (i.e., the inner diameter of the particles) was at least 10 nm. Table 2 also contains the porosity determination results of sample FD11, which is a supercritically dried (CO2) gel containing 75% Econea and is otherwise similar to sample FD10.

[0033] Figure 7 Table 3 shows the thermal conductivity of various supported aerogels prepared under freeze-drying or supercritical (for comparative purposes) conditions. References SC7 and FD7 are supported gels containing 75% zineb, dried under supercritical or freeze-drying conditions, respectively. Similarly, references SC8 and FD8 are supported gels containing 75% CuPt and dried under supercritical or freeze-drying conditions, respectively. FD5 is a supported gel containing 66% icosyl and was freeze-dried. References TC1 and TC2 are two freeze-dried supported gels containing 75% CuPt and 75% ZnPt, respectively, whose thermal conductivity was originally disclosed in the co-pending international application PCT / EP 2020 / 087730.

[0034] Figure 8 This is a table showing the chemical structures of some of the biocides used to produce the supported aerogels according to the invention, along with their densities and water solubilities. As can be seen, there are considerable differences in chemical structure, density, and solubility among the biocidal compounds. Summary of the Invention

[0035] The inventors of this invention have now discovered that aerogels (hereinafter referred to as “loaded aerogels”) with high to very high loadings (55-90% w / w) of encapsulated biocide and / or biorepellent compounds can be prepared by modifying the manufacturing method of WO 2020 / 002659, in which the supercritical (SC) extraction step is replaced by freeze drying.

[0036] Further findings using mercury porosimetry have revealed that the freeze-dried loaded aerogel has a total porosity of at least 50% and an intraparticle pore diameter (or “mesopore” diameter) of at least 10 nm. The inventors believe that a total porosity of at least 40% is sufficient to achieve satisfactory water absorption in the final antifouling composition, provided that the mesopore diameter is at least 10 nm.

[0037] Ultimately, it was discovered that the freeze-dried loaded aerogels had low thermal conductivity (30-75 mW / m*K), which was unexpected, as their high-loaded compounds had thermal conductivity on the order of 200-300 mW / m*K.

[0038] Therefore, in a first aspect, the present invention provides an antifouling additive comprising...

[0039] a. An inorganic silica-containing aerogel, wherein the inorganic silica-containing aerogel comprises

[0040] b. A porous gel lattice, which has

[0041] i. at least 40% total porosity, and

[0042] ii. Mesopore diameter of at least 10 nm,

[0043] c. Optionally, an alkyl oxy metal, including Sc, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Ru, Hf, Ta, W, Re, Al, Ge, In, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and

[0044] d. At least 55% by weight of a biocide or biorepellent compound selected from one or more of the following embedded in the aerogel: 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethylpyrrole (Iconi), zinc ethylidene dithiocarbamate (Zinc), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (Diuron), 3-iodo-2-propynyl butylcarbamate (IPBC), 2-tert-butylamino-4-ethylamino-6-methyl-thio-1,3,5-trimethylamino-4-ethylamino-6-methyl ... Azamine (terbufenozide), 1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pent-3-ol (tebuconazole), zinc pyrithione, toluenesulfonamide, pyrimiphos, N,N-didecyl-N,N-dimethylammonium carbonate, N,N-didecyl-N,N-dimethylammonium bicarbonate, 2-thiazolyl-4-yl-1H-benzimidazole (thiabendazole), 4-[1-(2,3-dimethyl-phenyl)ethyl]-3H-imidazole (medetomidine), and mixtures thereof.

[0045] The encapsulation of one or more biocidal or biorepellent compounds occurs during the sol-gel formation of the gel, and the sol-gel precursor is one or more alkoxysilanes selected from tetraethoxysilane, tetrapropoxysilane, and alkyltrialkoxysilane.

[0046] As mentioned, the antifouling additive of the first aspect can be provided by a newly developed manufacturing process, which is a further development of the method described in PCT application WO 2020 / 002659.

[0047] Therefore, in a second aspect, the present invention further provides a method for providing the antifouling additive of the first aspect, the method comprising the following steps:

[0048] a. Preparation of sol-gel precursor solution 1:

[0049] i. Dissolve 100-450 parts of one or more biocidal or biorepellent compounds in 100-500 parts of a lower alcohol (e.g., ethanol). Optionally, a dispersant may be added. Optionally, HCl (or another aqueous inorganic acid) may also be added. Optionally, a hydroxyl metal may be added at this time, including Sc, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Ru, Hf, Ta, W, Re, Al, Ge, In, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.

[0050] ii. Mix 100 parts of tetraalkoxysilane with 0-50 parts of alkyltrialkoxysilane.

[0051] iii. Mix the alkoxysilane mixture with a solution of one or more biocidal or biorepellent compounds.

[0052] b. Preparation of catalyst solution 2:

[0053] Mix 100 parts of a lower alcohol (such as ethanol), approximately 50 parts of water, and 0.25-15 parts of a gelling catalyst.

[0054] c. Gradually add solution 2 to solution 1 while stirring vigorously. Continue stirring at a reduced speed until signs of gelation are observed. The resulting solution can be transferred to one or more separate containers for gelation.

[0055] d. Age the gel in a suitable container for 2–5 days, then freeze it, typically at -18°C or lower, such as -80°C, depending on the solvent used. Before freezing the wet gel, the solvent can be replaced with another solvent with a higher melting point and preferably a lower coefficient of thermal expansion, such as tert-butanol.

[0056] e. The frozen gel is then freeze-dried under a suitable vacuum, keeping the shelf temperature below the gel's collapse temperature T. C This continues until the frozen solvent is removed by sublimation. The freeze-dried solid can then undergo a secondary drying stage at an elevated temperature.

[0057] The one or more biocidal or biorepellent compounds are embedded in the gel during sol-gel formation.

[0058] To prepare solutions 1 and 2, ethanol or another C1-C4 alcohol can be conveniently used as a solvent. The gelling catalyst can be basic or acidic, depending on the specific biocide.

[0059] Collapse temperature T C It is defined as the temperature at which a material softens to the point that it can no longer support its own structure. T C This is typically close to the glass transition temperature Tg', which is defined as the temperature at which a frozen material changes from a brittle to a flexible structure. Freeze-drying microscopy (FDM) can be used to confirm the temperature at which a specific frozen gel undergoes a visible change (see Methods section).

[0060] In a third aspect, an antifouling additive is provided that is obtainable by the method according to the second aspect.

[0061] In the fourth aspect, the use of antifouling additives according to the first or third aspect is provided in marine coatings or coatings intended for use in wood protection, facades, terraces or fronts, and other damp environments or for use in damp indoor environments.

[0062] In a fifth aspect, a stain-resistant paint or sealant composition is provided, comprising a stain-resistant additive according to the first or third aspect of the invention. Detailed Implementation

[0063] As described in the invention summary, the inventors have developed a novel manufacturing process well-suited for the commercial / industrial production of aerogel particles containing encapsulated biocide and / or biorepellent. This is an objective because the inventors of this invention recognized that the antifouling effectiveness of antifouling coatings and sealants containing biocide and / or biorepellent active compounds encapsulated in aerogel particles largely depends on the proper management of the composition's water absorption rate. Specifically, it has been found that excessively low water absorption rates (<1 wt%) can lead to fouling (because the biocide cannot function under excessively dry conditions), while excessively high water absorption rates can lead to overly rapid dissolution and potentially the ultimate loss of the biocide.

[0064] Therefore, it has been found important that the antifouling composition absorbs sufficient water to maintain a saturated solution of the active compound in the surface layer of the coating or sealant composition. A water absorption rate in the range of approximately 1.5%–6% is considered optimal.

[0065] Furthermore, the inventors have discovered that, in order to adjust the performance of antifouling coating and sealant compositions, the water absorption rate of the embedded aerogel particles themselves must be controlled. For this purpose, the two most important influencing parameters are 1) the loading of the active compound in the encapsulated aerogel particles and 2) the porosity of the aerogel particles. High content uniformity, i.e., a highly uniform distribution of the encapsulated biocide or biorepellent within the aerogel particles, is also important for the performance of antifouling coating and sealant compositions.

[0066] Therefore, an object of the present invention is to provide silica aerogel particles (“loaded aerogel particles”) having a uniform distribution of biocide and / or biorepellent with high to very high loadings (55-95% w / w), resulting in a satisfactory water absorption rate of the dry coating when these particles are formulated into antifouling coatings, for example, in the range of 1.5-6% w / w. Coatings prepared for use onshore timber structures can have even higher ranges, for example, up to 11% w / w. A further object is that the manufacturing process of the loaded aerogel particles should be scalable and verifiable in industrial implementation. Even a further object is that the loaded aerogel particles should be easily formulated into antifouling coatings, sealants, etc.

[0067] The inventors have continued to develop the encapsulation procedure disclosed in WO 2020 / 002659, with the aim of allowing for a wider selection of biocides and biorepellents that have so far been limited by solubility issues during the supercritical drying stage (e.g., DCOIT and other biocides that are highly soluble in ethanol) or incompatible with the chosen gelling catalyst or conditions.

[0068] These objectives have now been achieved against a wide range of different biocides and / or biorepellents.

[0069] Similar to the method used in WO 2020 / 002659, the production method of the present invention begins with the gelation of a mixture of one or more sol-gel precursors in the presence of a gelling catalyst. The sol-gel precursor used is an alkoxysilane selected from tetraalkoxysilanes and alkyltrialkoxysilanes.

[0070] When alkoxysilanes (typically methoxy and ethoxy, R = Me or Et) react with water (typically in the presence of a catalyst), three reactions together lead to the formation of silica nanoparticles (which eventually interconnect to form a gel). The first of these reactions is hydrolysis, where the alkoxysilane reacts with water to form silanol (Si-OH) groups. These silanol groups can then react with each other or with alkoxide groups (Si-OR) to form siloxane bridges (Si-O-Si), resulting in two molecules combining into a larger molecule. Each silicon atom can form up to four siloxane bridges (because silicon is tetravalent), allowing many small molecules to link into giant molecules containing thousands of siloxane bridges. However, in the formation of silica nanoparticles, not every silicon atom ultimately forms four siloxane bridges, but rather attaches to one or more of its hydroxyl (-OH) or original alkoxy (-OR) groups. These are called "terminal groups" and cover the surface of the nanoparticles.

[0071] At a certain point, the silica nanoparticles reach a critical size, at which point they cease growth and instead aggregate with other nanoparticles. The terminal hydroxyl and alkoxy groups on the surface of the nanoparticles allow them to connect with each other, somewhat like atomic Velcro spheres. When enough of these nanoparticles bind together, a continuous network spans the liquid solution, forming an "alcohol gel."

[0072] The difference between methods for preparing "ordinary" (i.e., unloaded) aerogels and methods for preparing loaded aerogels (such as those described in WO 2020 / 002659 and / or herein) lies in the addition of a biocide (or biorepellent) to a solution of one or more alkoxysilanes before gelation begins, i.e. before the formation of the "alcohol gel." This ensures that the biocide (or biorepellent) is ultimately encapsulated within the gel.

[0073] When the sol reaches its gel point, the silica backbone of the gel still contains a large number of unreacted alkoxide groups, and therefore must be given sufficient time to strengthen the silica network, a process commonly referred to as "aging". The gel is best left to stand for up to 48 hours.

[0074] It is well known that (see also) K Sinco 2010 Variations in synthesis conditions (e.g., types of precursors, catalysts, and surfactants; water-to-precursor ratio; concentration; medium pH; solvent; drying method) alter the structure and properties of aerogels. Synthesis parameters affect both hydrolysis and condensation rates, and thus modulate the kinetics and mechanism of the sol-gel process.

[0075] Numerous studies have reported on the influence of precursors. The most common silicon precursors are alkoxysilanes, Si(OR)4. The reaction rates of these compounds decrease in the following order:

[0076] Si(OMe)4>Si(OEt)4>Si(O n Pr)4>Si(O i Pr)4

[0077] This "alkoxy effect" on reaction rate can influence the characteristics of the final product. Therefore, compared with aerogels obtained from various silanols, tetramethoxysilane [Si(OMe)4] was found to produce narrower and more uniform pores and a higher surface area than tetraethoxysilane [Si(OEt)4]. Zhang (2011) Similarly, it was found that when these gel precursors were used to prepare “ordinary” (i.e., unloaded) aerogels, the resulting gels exhibited different physical properties. Therefore, Zhang (2011) mentions on page 40: “It has been found that the precursors TEOS, TMOS, and PEDS (polyethoxydisiloxane) strongly influence physical properties such as packing density, porosity percentage, pore size distribution, light transmission, surface area, thermal conductivity, and the microstructure of silica aerogels.”

[0078] Li et al. (2020)Another study indicates that different precursors can lead not only to differences in aerogel density, porosity, etc., but also to molecular differences in the terminal groups located on the surface of the resulting aerogel particles. Therefore, unless the aerogel surface has been explicitly modified / derivatively modified (e.g., through a chemical reaction with trimethylchlorosilane (Me3SiCl), "...silica aerogels have silanol and / or alkoxy groups on their inner surfaces derived from silica precursors (water glass, silanols) and gelling, aging, and washing solutions (alcohols, water)...unmodified aerogels have a surface covering of silanol and alkoxy groups and are hydrophilic." (Li 2020).

[0079] It is evident that the chemically unmodified gel particles produced using these three different precursors, TMOS, TEOS, and TPOS, will have silanol groups and surface coatings with methoxy, ethoxy, and propoxy groups, respectively.

[0080] In the manufacture of silica aerogels, the final and most important process is the step in which the liquid inside the gel is removed, leaving only the interconnected silica network.

[0081] If a wet gel is dried where capillary forces cause partial collapse of the porous silica structure, the dried and then typically wrinkled gel is called a dry gel or crystal gel. Therefore, to maintain the porous structure of the gel, it can be dried using a supercritical drying method where capillary forces do not occur. First, the organic solvent is extracted from the gel using compressed CO2 under operating conditions above the critical point of the mixture of pore liquid and CO2. This ensures that extraction takes place in a single-phase mixing process where there is no liquid-gas interface and therefore no possibility of capillary forces. After the organic solvent has been completely replaced with CO2, CO2 can also be released during the single-phase process under operating conditions above the CO2 critical temperature during slow decompression. What remains is a dry gel whose pores are directly filled with CO2 after the drying process. When the dry gel is exposed to air, the CO2 is exchanged with the air, and the gel is called an aerogel. This method is by far the most common way to produce aerogels and has also been widely used by the applicant to produce supported aerogels, such as those disclosed in WO 2020 / 002659.

[0082] It has been found (for example, Dorcheh 2008Chemically unmodified aerogel particles prepared from tetraalkoxysilanes and dried with supercritical CO2 will have only hydroxyl (Si-OH) terminal groups on their surface. The original alkoxy (Si-OR) groups are hydrolyzed under the process conditions (in a fluid phase system, at approximately 40 °C and 110 bar for several hours). This differs from the freeze-drying process, in which very low temperatures (-80 °C) and / or the solid phase system essentially prevent the reaction of the terminal groups. Therefore, the difference between chemically unmodified aerogels dried with CO2 under supercritical conditions and freeze-dried aerogels will not only lie in their different bulk densities, porosities, etc., as discussed above, but also in the different terminal groups on the surfaces of the two types of aerogels. Aerogels dried with CO2 under supercritical conditions will typically have a surface covered with silanol (Si-OH) terminal groups, while aerogels prepared by freeze-drying will typically have a mixture of silanol (Si-OH) and alkoxysilane (Si-OR) terminal groups.

[0083] The most significant difference between this invention and the disclosure in WO 2020 / 002659 involves drying the initially formed alcohol gel (“wet gel”) by using freeze-drying (lyophilization) instead of supercritical carbon dioxide extraction.

[0084] The use of freeze-drying for the preparation of supported aerogels was initiated by the inventors in their co-pending international application PCT / EP 2020 / 087730, which relates to a process improvement over the method in WO 2020 / 002659, primarily in the sol-gel formation of the wet gel (increased water content in the gelling mixture + reverse addition of reactants). Inspired by higher water content, the inventors made some initial attempts with the freeze-dried supported wet gels of PCT / EP 2020 / 087730, which resulted in a relatively low porosity (<40%) and close to 1 g / cm³. 3 The bulk density of the gel (Table 1) Figure 5 (Ref. FD1-FD4 in the table). Table 1 compares two empty gels and two loaded gels frozen at two different temperatures (-18°C and -80°C). All gels in Table 1 were prepared using pre-condensed TEOS+MTMS.

[0085] As can be seen, porosity is significantly affected by the presence of the loaded biocide (compare FD1 / FD2 with FD3 / FD4), while freezing temperature does not appear to have a significant effect on total porosity or density (FD1 / FD3 with FD2 / FD4).

[0086] Another difference from the method in WO 2020 / 002659 involves the use of the gel precursor, specifically the tetraalkoxysilane employed. In the applicant's earlier work, such as those disclosed in WO 2020 / 002659 and WO 2009 / 062975, tetramethoxysilane (TMOS) was preferably or even specifically used as a gel precursor due to its short gelation time. In conjunction with the applicant's work leading to WO 2020 / 002659, TMOS is therefore used as the gel precursor in all disclosed practical embodiments. WO 2020 / 002659 mentions the production of a single supercritically dried gel using TEOS, but does not provide any further experimental details.

[0087] Since the filing of this application, the applicant has recognized that, for safety reasons, TMOS should no longer be considered as a relevant gel precursor due to its high toxicity, and therefore TMOS has not been included as a potential precursor herein. Tetraethoxysilanes (TEOS) and tetrapropoxysilanes (TPOS) are safer alternatives (see, for example, the NIOSH Pocket Guide to Chemical Hazards). Pocket Guide to Chemical Hazards|NIOSH|CDC Therefore, the most preferred tetraalkoxysilanes are tetraethoxysilane (TEOS) and tetrapropoxysilane (TPOS).

[0088] Based on the applicant’s work on the freeze-dried loaded gel of the present invention, no particular behavioral differences were observed compared with previously prepared loaded gels using TMOS and supercritical CO2 extraction as disclosed in WO 2020 / 002659.

[0089] Therefore, using TEOS as a gel precursor combined with freeze-drying as a drying method provides a supported aerogel with similar technical characteristics (bulk density, porosity, etc.) to the supported aerogel obtained using TMOS as a gel precursor combined with supercritical drying. This similarity must be considered to be of arbitrary origin, since it is known, for example, from Sinco (2010) and Zhang (2011), that TEOS and TMOS provide gels with different physical properties (such as bulk density, porosity percentage, etc.).

[0090] As discussed above, it is important that the antifouling composition can absorb enough water to maintain a saturated solution of the active compound in the surface layer of the coating or sealant composition, and this requires the antifouling additive to have sufficient porosity to allow water to penetrate the silica gel lattice and dissolve the encapsulated biocide or biorepellent compound.

[0091] Total porosity is defined as the fraction of the bulk volume of the loaded aerogel that is not occupied by solid material. Another way to analyze the porosity of loaded aerogels is by analyzing the inter-particle and intra-particle pore structure of the material. This is done using mercury porosimetry (see the Methods section of this paper). interparticle porosity Measurements were performed at relatively low pressures (LP) and the median distance between aerogel particles is given in μm. Intragranular Porosity The study was conducted at much higher pressures (HP), and the median diameter of the pores within the aerogel particles is given, in nm. The pore size within the particles is most relevant to the water absorption rate of the loaded gel. When this diameter is <2 nm, the pore size within the particles is considered... micropores And when the diameter is >2nm, it is Mesoporous .

[0092] Due to the disclosure of early freeze-dried aerogel samples (FD1-FD4, Table 1) in the co-pending international application PCT / EP 2020 / 087730, Figure 5 The high packing density of the gel implies partial collapse during the freeze-drying process of the corresponding wet gel, thus the development of freeze-drying methods has been ongoing, leading to this invention. Although, as stated above, freezing temperature does not significantly affect porosity, it has been found, on the other hand, to be beneficial for maintaining the temperature below the collapse temperature T of the freeze-drying step while sublimating the cryo-liquid. C It is of utmost importance.

[0093] Therefore, by keeping the temperature below T during the sublimation phase C This yields much better porosity results. Table 2 ( Figure 6 Table 2 shows the analysis of six freeze-dried loaded gels (reference numbers FD5-FD10) initially frozen at -80°C. All gels were again prepared using pre-condensed TEOS + MTMS (except for FD5 (Iconi), which was prepared from pure TEOS) and freeze-dried. Table 2 also lists the supercritically dried gel (FD11) containing 75% Iconi, which can be compared with the freeze-dried gel FD10.

[0094] As from Figure 6As shown in Table 2, the total porosity values ​​of gels FD5-FD10 are consistently >50%, and the average bulk density is 0.5 g / ml, approximately half the values ​​observed in earlier freeze-dried samples FD1-FD4. This indicates that the conditions of the present invention have substantially prevented gel collapse. FD10 and FD11 are both gels with an icosene content of 75% w / w, but for comparison, they were dried under freeze-dried or supercritical conditions, respectively. As can be seen from Table 2, the total porosity of the two samples is very similar (58.7% vs. 54.6%), but the intraparticle (mesopore) diameters differ considerably.

[0095] Further observation revealed that the bulk density of the freeze-dried gel varied considerably (FD5-FD10) and depended on both the loading percentage and the density of the pure (unencapsulated) biocide.

[0096] from Figure 6 As can also be seen from Table 2, (FD5-FD10) Intraparticle porosity (Mesopore) diameter variation ratio Total porosity The significantly larger diameters (range: 10.0–62.70 nm, vs. range: 52.9%–70.7%) strongly suggest that both characteristics are crucial for characterizing the freeze-dried supported aerogels of this invention. The difference in variability also indicates that the mesopore diameter of the freeze-dried supported aerogels according to the invention cannot be definitively predicted from a given value of their total porosity.

[0097] Further observation revealed that the intraparticle (mesoporous) pore diameter and total porosity were significantly higher than those of the mesoporous pores. Figure 5 The bulk density values ​​observed in the early freeze-dried samples in Table 1 are lower than those observed in the early freeze-dried samples.

[0098] Therefore, in a first aspect, the present invention provides an antifouling additive comprising...

[0099] a. An inorganic silica-containing aerogel, wherein the inorganic silica-containing aerogel comprises

[0100] b. A porous gel lattice, which has

[0101] i. at least 40% total porosity, and

[0102] ii. Mesopore diameter of at least 10 nm,

[0103] c. Optionally, an alkyl oxy metal, including Sc, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Ru, Hf, Ta, W, Re, Al, Ge, In, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and

[0104] d. At least 55% by weight of a biocide or biorepellent compound selected from one or more of the following embedded in the aerogel: 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), 2-(p-chloro-phenyl)-3-cyano-4-bromo-5-trifluoromethylpyrrole (Iconi), zinc ethylidene dithiocarbamate (Zinc), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (Diuron), 3-iodo-2-propynyl butylcarbamate (IPBC), 2-tert-butylamino-4-ethylamino- 6-Methyl-thio-1,3,5-triazine (terbutaline), 1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pent-3-ol (tebuconazole), zinc pyrithione, toluenesulfonamide, pyrimiphos, N,N-decyl-N,N-dimethylammonium carbonate, N,N-decyl-N,N-dimethylammonium bicarbonate, 2-thiazolyl-4-yl-1H-benzimidazole (thiabendazole), 4-[1-(2,3-dimethylphenyl)ethyl]-3H-imidazole (metopril), and mixtures thereof.

[0105] The encapsulation of one or more biocidal or biorepellent compounds occurs during the sol-gel formation of the gel, and the sol-gel precursor is one or more alkoxysilanes selected from tetraethoxysilane, tetra-n-propoxysilane, and alkyltrialkoxysilane.

[0106] As stated above, the inventors believe that a total porosity of at least 40% is sufficient to achieve desired water absorption in the final antifouling composition, provided that the mesopore diameter is at least 10 nm. Nevertheless, in some embodiments, the method of the present invention also provides an antifouling additive according to the first aspect having a total porosity of at least 50%, such as at least 60%, such as at least 65%, such as at least 70%. In other embodiments of the invention, the antifouling additive according to the first aspect has a mesopore (i.e., intraparticle) diameter of at least 11 nm, such as at least 12 nm, or such as at least 13 nm.

[0107] Furthermore, freeze-dried supported aerogels have been found to have considerably low thermal conductivity (λ values ​​of 30-75 mW / m*K), as seen in the examples in Table 3 (reference numbers FD7-FD8). This is unexpected, given that high loadings of the pure form (i.e., unencapsulated form) of the compound are known to have thermal conductivity on the order of 200-300 mW / m*K (see, for example...). Kim2018 , Holberg2017 ).

[0108] Against this backdrop, the inventors also analyzed whether the drying method (supercritical or freeze-drying) affected the thermal conductivity of the supported aerogel. It appears that essentially identical prepared supported wet gel samples dried under supercritical or freeze-drying conditions were found to have significantly different λ values ​​(compare SC7 with FD7, and compare SC8 with FD8). This is consistent with... Czlonka et al. In contrast to their findings, they reported that the thermal conductivity of freeze-dried aerogels was only slightly higher than that of their corresponding supercritically dried aerogels.

[0109] Table 3 ( Figure 7 The study also included λ values ​​for two loaded aerogel samples (TC1 and TC2) prepared by supercritical extraction, originally disclosed in the co-pending international application PCT / EP 2020 / 087730. The λ values ​​for these two samples were found to be between 30 and 40 mW / m*K, which is highly consistent with the λ values ​​measured for SC7 and SC8.

[0110] Interesting is Table 3 ( Figure 7 It was noted that the λ value (36.6 mW / m*K) of the freeze-dried Iconi-gel (FD5) was significantly lower than that of the other two freeze-dried loaded gels (approximately 70 mW / m*K), and the porosity of the FD5 gel was also noted to be considerably higher (>70%). This particular gel was prepared using pure TEOS, i.e., without the addition of MTMS, which clearly affected the gel structure (the addition of MTMS resulted in a more hydrophobic gel). Furthermore, the loading of this gel (66%) was lower than that of the other two samples (75%). These factors are very likely to affect the thermal conductivity of the final loaded gel, but have not yet been further investigated in conjunction with this application.

[0111] According to reports, the thermal conductivity of native ("empty") aerogels is typically between 15 and 20 mW / m*K, while that of "hybrid" (i.e., polymer-crosslinked) aerogels with a polymer content of <20% by weight is approximately 30 mW / m*K, and that of hybrid aerogels with a polymer content of >50% by weight is approximately 50 mW / m*K. Bertino 2019 It was also reported that, for this type of hybrid aerogel material, the thermal conductivity is in the range of 38-66 mW / m*K. White 2016 This is very similar to the discovery of the loaded aerogel for the present invention.

[0112] The porous structure of the loaded aerogel still isolates the biocide from the surrounding environment so effectively that the loaded aerogel has only 15%–40%, typically up to 30%, of the thermal conductivity of the pure encapsulated biocide.

[0113] In a preferred embodiment of the invention, the antifouling additive according to the first aspect has a thermal conductivity between <100mW / m*K, for example <90mW / m*K, for example <80mW / m*K, for example <75mW / m*K, for example 30-75mW / m*K.

[0114] In a preferred embodiment, the antifouling additive according to the first aspect comprises one or more biocidal or biorepellent compounds selected from: toluenesulfonamide, sulfadiazine, N,N-decyl-N,N-dimethylammonium carbonate, N,N-decyl-N,N-dimethylammonium bicarbonate, zinc ethyl dithiocarbamate (zine), zinc pyrithione, copper thiocyanate, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), 3-iodo-2-propynylbutylaminomethyl esters (IPBC), 2-thiazolyl-4-yl-1H-benzimidazole (thiazolidazole), 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethylpyrrole (Iconi), 2-tert-butylamino-4-ethylamino-6-methylthio-1,3,5-triazine (tert-butylamine), 1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pent-3-ol (tebuconazole), 4-[1-(2,3-dimethylphenyl)ethyl]-3H-imidazole (metopril), or mixtures thereof, see the Examples section.

[0115] In a preferred embodiment, the antifouling additive of the first aspect comprises aerogel particles containing at least 55% by weight of encapsulated biocide and / or biorepellent (“active compound”), such as at least 60% by weight, such as at least 65% by weight, such as at least 70% by weight, at least 75% by weight, at least 80% by weight, at least 85% by weight, at least 90% by weight, or about 95% by weight.

[0116] To the knowledge of the inventors, silica-containing aerogels with a combination of the following mandatory features have not been previously disclosed, and in particular not disclosed as freeze-dried solids:

[0117] • At least 40% total porosity

[0118] • Mesopore diameter of at least 10 nm, and

[0119] • At least 55% by weight of encapsulated material.

[0120] Measurements based on porosity determination (in this paper) Figures 5 to 7 These two drying methods (supercritical drying and freeze-drying) result in different aerogel particle morphologies, which is also supported by the literature, such as Li 2020, Zhang 2011, and Dorcheh 2008 discussed above. However, from a technical point of view, both types of drying are suitable for producing loaded aerogels with a suitable combination of characteristics for introduction into antifouling coatings and sealants. However, freeze-drying allows for more commercially attractive scalability and can be adapted to an even wider range of biocides / biorepellents while still maintaining the original purpose of providing loaded aerogel particles that result in a satisfactory water absorption rate when formulated into antifouling coatings.

[0121] The loaded gel particles of the present invention thus allow for the addition of large amounts of biocides and / or biorepellents (“active compounds”) to antifouling coatings and sealants, while keeping the accompanying addition of silica below the 1.5% w / w limit discussed above.

[0122] The present invention also provides a method for producing loaded aerogels according to the first aspect.

[0123] Therefore, in a second aspect, the present invention further provides a method for providing the antifouling additive of the first aspect, the method comprising the following steps:

[0124] a. Preparation of sol-gel precursor solution 1:

[0125] i. Dissolve 100-450 parts of one or more biocidal or biorepellent compounds in 100-500 parts of a lower alcohol (e.g., ethanol). Optionally, a dispersant may be added. Optionally, HCl (or another aqueous inorganic acid) may also be added. Optionally, a hydroxyl metal may be added at this time, including Sc, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Ru, Hf, Ta, W, Re, Al, Ge, In, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.

[0126] ii. Mix 100 parts of tetraalkoxysilane with 0-50 parts of alkyltrialkoxysilane.

[0127] iii. Mix the alkoxysilane mixture with a solution of one or more biocidal or biorepellent compounds.

[0128] b. Preparation of catalyst solution 2:

[0129] Mix 100 parts of a lower alcohol (such as ethanol), approximately 50 parts of water, and 0.25-15 parts of a gelling catalyst.

[0130] c. Gradually add solution 2 to solution 1 while stirring vigorously. Continue stirring at a reduced speed until signs of gelation are observed. The resulting solution can be transferred to one or more separate containers for gelation.

[0131] d. Age the gel in a suitable container for 2–5 days, then freeze it, typically at -18°C or lower, such as -80°C, depending on the solvent used. Before freezing the wet gel, the solvent can be replaced with another solvent with a higher melting point and preferably a lower coefficient of thermal expansion, such as tert-butanol.

[0132] e. The frozen gel is then freeze-dried under a suitable vacuum, keeping the shelf temperature below the gel's collapse temperature T. C This continues until the frozen solvent is removed by sublimation. The freeze-dried solid can then undergo a secondary drying stage at an elevated temperature.

[0133] The one or more biocidal or biorepellent compounds are embedded in the gel during sol-gel formation, and the sol-gel precursor is one or more alkoxysilanes selected from tetraethoxysilane, tetra-n-propoxysilane, and alkyltrialkoxysilane.

[0134] To prepare solutions 1 and 2, ethanol or another C1-C4 alcohol can be conveniently used as a solvent. The gelling catalyst can be basic or acidic, depending on the specific biocide.

[0135] Collapse temperature T C It is defined as the temperature at which a material softens to the point that it can no longer support its own structure. T C This is typically close to the glass transition temperature (Tg'), which is defined as the temperature at which a frozen material changes from a brittle to a flexible structure. Freeze-drying microscopy (FDM) can be used to confirm the temperature at which a specific freeze gel undergoes a visible change. Therefore, FDM measurements can be used to optimize specific freeze-drying cycles, keeping the product temperature below a minimum critical temperature with a reasonable safety margin. In the absence of Tg'... C In the case of measurements, the freezing point of the solvent used can be used as the target temperature.

[0136] Therefore, embodiments of the present invention provide a method for producing freeze-dried loaded aerogels having a total porosity of >40%, a mesopore diameter of at least 10 nm, and a loading of at least 55% by weight of a biocide or biorepellent compound.

[0137] According to an embodiment of the method of the invention, after the sol-gel gelation process is completed, optionally after the solvent of the wet gel is replaced with a suitable solvent having a low coefficient of expansion and a high sublimation pressure, the solvent within the wet gel is frozen. The frozen gel is then placed in a vacuum chamber within a freeze dryer, wherein the solvent is subjected to a process below the collapse temperature (T0). C The substance is removed by sublimation at a temperature of [temperature missing]. Both steps can be performed in a commercial freeze dryer.

[0138] Maintain a sufficiently low temperature during the sublimation phase to avoid melting of the frozen solvent, preferably below the collapse temperature T of the frozen wet gel. C For example, this can be assessed using freeze-drying microscopy (FDM). It has been found that the collapse temperature T is important. C The following sublimation process is performed to provide a loaded aerogel having the desired combination of total porosity, mesopore diameter, and achievable high loading capacity described in the first aspect of the invention. Collapse temperature T C This is a parameter that must be evaluated for a single gel, using standard methods familiar to technicians, such as freeze-drying microscopy. If this is unavailable, the freezing point of the solvent used can be used instead. C As the target temperature.

[0139] The described procedure offers numerous advantages over supercritical drying, including reduced harmful risks associated with drying under supercritical conditions and the ability to scale the method for commercial purposes without introducing risks. A second advantage of this invention is the significant reduction in capital expenditure. Autoclaves used for supercritical drying require thick walls and introduce liability issues due to the high pressures (on the order of 70 atmospheres) used in supercritical drying. Freeze-drying, instead, uses a vacuum chamber, which is much less expensive to produce and introduces minimal liability issues. Typically, a supercritical drying autoclave costs ten times more than a freeze-drying vacuum chamber of the same capacity.

[0140] Finally, freeze-drying allows for the preparation of loaded aerogels containing biocide and / or biorepellent compounds, which are partially or substantially removed from the wet gel under supercritical drying conditions due to the leaching of the encapsulated biocide during solvent exchange with supercritical CO2. Therefore, for some biocides, freeze-drying can allow for higher yields of loaded aerogels.

[0141] Therefore, the manufacturing method of the present invention satisfactorily solves the limitations of the known prior art in the production of loaded aerogels.

[0142] In one embodiment of the manufacturing process, solution 1 contains 20-50 parts of alkyltrialkoxysilane. In another embodiment, particularly if a hydrophilic loaded aerogel is envisioned or a very high loading of biocide is required, solution 1 contains less than 20 parts of alkyltrialkoxysilane, such as 15 parts, or 10 parts, or 5 parts or less. In yet another embodiment, solution 1 is free of alkyltrialkoxysilane.

[0143] For this application, tetramethoxysilane (TMOS) was included at the time of filing as an optional tetraalkoxysilane gel precursor, although no actual examples using TMOS were included. The applicant has recognized that, for safety reasons, TMOS should no longer be used as a relevant gel precursor due to its high toxicity. Tetraethoxysilane (TEOS) and tetrapropoxysilane (TPOS) are safer alternatives (see, for example, the NIOSH Pocket Guide to Chemical Hazards). Pocket Guide to Chemical Hazards |NIOSH|CDC Therefore, the most preferred tetraalkoxysilanes are tetraethoxysilane (TEOS) and tetrapropoxysilane (TPOS).

[0144] In another preferred embodiment, the pre-hydrolyzed / pre-condensed tetraalkoxysilane is selected from pre-hydrolyzed tetraethyl orthosilicate (e.g., A) or pre-hydrolyzed tetra-n-propyl orthosilicate (e.g. P).

[0145] In a preferred embodiment, the alkyltrialkoxysilane is selected from MTMS (methyltrimethoxysilane) and MTES (methyltriethoxysilane), but other lower alkyltrialkoxysilanes such as TMES (trimethylethoxysilane) and ETES (ethyltriethoxysilane) may also be used.

[0146] The gelling catalyst can be any readily available catalyst for aerogel formation, such as ammonia (a conveniently concentrated aqueous solution of NH3 or 25% in water). Other suitable gelling catalysts include ammonium fluoride, sodium fluoride, and sodium carbonate. Such alternative catalysts are preferred where the biocide can react with ammonia. Acidic catalysis, such as with hydrochloric acid, can also be used, especially where the biocide to be encapsulated is sensitive to ammonia or generally alkaline conditions.

[0147] Implementation examples of using different versions of the general method can be found in the experimental section.

[0148] It is known that (for example, from) Dorcheh 2008Chemically unmodified aerogel particles prepared from tetraalkoxysilanes and dried with supercritical CO2 will have a surface containing only hydroxyl (Si-OH) terminal groups. The original alkoxy (Si-OR) groups undergo significant hydrolysis under the process conditions (in a supercritical fluid phase system, at approximately 40 °C and 110 bar for several hours). This differs from freeze-drying, where the very low temperature (-80 °C) and solid phase (freeze-gel) effectively prevent any reaction of the terminal groups. Therefore, the difference between chemically unmodified aerogels dried with CO2 under supercritical conditions and freeze-dried aerogels will not only lie in their different bulk density, porosity, etc., as discussed above, but also in the different terminal groups on the surfaces of the two types of aerogels. Supercritically dried aerogels with CO2 will typically have a surface primarily covered by silanol (Si-OH) terminal groups, while freeze-dried aerogels will typically exhibit a mixture of silanol (Si-OH) and alkoxysilane (Si-OR) terminal groups.

[0149] Therefore, when both the gel precursor and drying steps are considered, the manufacturing process directly affects important product parameters, such as the porosity, bulk density, and surface structure of the final product. Thus, it is reasonable to define the product of this invention based on its manufacturing method.

[0150] Therefore, in a third aspect, an antifouling additive that is obtainable by the method according to the second aspect is provided.

[0151] In a preferred embodiment, the present invention provides an antifouling additive according to a first or third aspect of the invention, the antifouling additive comprising one or more biocidal or biorepellent compounds selected from the group consisting of: pyridinethione compounds, basic copper carbonate, isothiazolinone compounds, substituted triazines, carbamates, chlorinated aromatic ureas, triazoles, and combinations thereof. Examples of pyridinethione compounds include metal pyridinethione compounds, such as zinc pyridinethione, zirconium pyridinethione, sodium pyridinethione, etc. Examples of isothiazolinone compounds include, for example: 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), 1,2-benzisisothiazolin-3-one (BIT), n-butylisothiazolinone (BBIT), n-octylisothiazolinone (OIT), and mixtures thereof. Substituted triazines include, for example, tert-butylamine (2-tert-butylamino-4-ethylamino-6-methylthio-1,3,5-triazine). Carbamates include, for example, iodopropynyl butylcarbamate (IPBC). Chlorinated aromatic ureas include, for example, diuron (dichlorophenyl dimethylurea). From a cost and effectiveness perspective, zinc pyrithione is generally used in pyrithione compounds. Those skilled in the art will be able to determine which active ingredients can be used in this invention based on the intended use of the encapsulated biocide or biorepellent compound.

[0152] As used herein, the term "biocidal or biorepellent compound" is intended to refer to an ingredient having biocidal or biorepellent properties, including but not limited to active ingredients with antimicrobial, spore-killing, or fungicidal properties.

[0153] The intended use of the antifouling additive of the present invention is to be added to antifouling coatings or sealant compositions for use in wood protection (fences, buildings, etc.), marine applications (ships, yachts, commercial vessels, static structures submerged in water such as oil drilling platforms and other offshore structures, etc.), and humid indoor environments such as bathrooms, toilets, saunas, gyms, indoor swimming pool areas, etc., which are naturally / frequently exposed to humid conditions and / or water.

[0154] When the prepared aerogel particles are incorporated into antifouling coatings or sealants, the encapsulated active compounds are uniformly distributed in the resulting layer. Each aerogel particle may contain several discrete active compound particles ( Figure 3 ).

[0155] Furthermore, as demonstrated by the non-limiting examples herein, the disclosed procedures for producing freeze-dried loaded aerogels have been found to be well-suited to a wide variety of structurally quite different biocidal and / or biorepellent compounds.

[0156] Using the manufacturing process of this invention, the inventors have produced loaded aerogels containing various biocides, such as 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethylpyrrole (Iconi), zinc ethylidene dithiocarbamate (Zinc), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (Diuron), 3-iodo-2-propynyl butylcarbamate (IPBC), 2-tert-... Butylamino-4-ethylamino-6-methylthio-1,3,5-triazine (terbutaline), 1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pent-3-ol (tebuconazole), zinc pyrithione, toluenesulfonamide, thiamethoxam, N,N-decyl-N,N-dimethylammonium carbonate, N,N-decyl-N,N-dimethylammonium bicarbonate, 2-thiazolyl-4-yl-1H-benzimidazole (thiabendazole), and mixtures thereof, see the Examples section.

[0157] In a preferred embodiment, the antifouling additive of the first aspect comprises aerogel particles containing at least 55% by weight of encapsulated biocide and / or biorepellent (“active compound”), such as at least 65% by weight, such as at least 70% by weight, at least 75% by weight, at least 80% by weight, at least 85% by weight, at least 90% by weight, or about 95% by weight.

[0158] After formulation in antifouling coatings and sealants, the freeze-dried loaded aerogel particles of the present invention exhibit satisfactory water absorption rates. Therefore, these particles are found to be valuable as antifouling additives for use in both marine and onshore antifouling coatings and sealants.

[0159] Therefore, in the fourth aspect, the use of antifouling additives according to the first or third aspect in marine coatings or coatings intended for wood protection or for use in humid environments is provided.

[0160] Therefore, the antifouling additive of the present invention is ideally suited for formulation into coatings to be applied to marine surfaces that are frequently or continuously submerged in water. Examples of surfaces that are frequently or continuously submerged in water include the hulls of ships, vessels, and other vessels (including commercial tankers, cruise ships, and yachts), as well as static structures such as swimming pools, stormwater basins, port structures, oil drilling platforms, and fish farming structures (such as aquaculture nets) that include structural portions that are continuously submerged. Biofouling of aquaculture nets can cause serious maintenance and operational problems, see, for example... Swain 2014 The direct economic cost of controlling biofouling in aquaculture is estimated at 5%-10% of production costs. Reports indicate that biofouling can increase net weight by up to two hundred times and drag five times after just a few months of soaking. Historically, this additional weight and drag has led to the collapse or failure of several large commercial mariculture structures. Fouling also reduces mesh openings and water circulation through the cages. This results in a significant reduction in carrying capacity and can lead to increased fish mortality. Biofouling can also act as a reservoir for parasites and diseases, and some fouling species, such as hydroids and sea anemones, can cause harm through nematocysts that can sting and irritate the skin. Currently, net fouling is typically controlled by replacing and cleaning the nets or by using chemical antifouling agents containing biocides such as cuprous oxide, copper isothiocyanate, copper pyrithione, zinc pyrithione, zinc oxide, and icoplanin. While using untreated nets is environmentally safe, frequent cleaning and replacement can stress animals, damage the nets, increase maintenance costs, and reduce profit margins. The antifouling additive of this invention, when formulated as a coating, is ideally suited for application to aquaculture nets, ensuring durable biocide protection and minimizing the need for biocides due to the controlled release of biocides from the loaded aerogel particles of this invention.

[0161] Examples of surfaces that are frequently submerged in water include static marine structures, such as offshore wind turbine towers and other offshore structures, and the lower parts of dock and port structures, which experience frequent submersion cycles during high tide or by being submerged by waves.

[0162] The antifouling additive of the present invention has also been found to be useful in paints and sealants applied to shore surfaces that are frequently exposed to humid air and rainfall. Such surfaces are typically found on houses and other buildings located in tropical regions or near the ocean and experiencing frequent rainfall or fog. Other examples include interior surfaces in rooms frequently exposed to high humidity, such as bathrooms, shower rooms, saunas, and indoor swimming pools. For such humid indoor environments, the antifouling additive of the present invention has been found to have particular use in sealants, for example, for filling cracks between tiles that are frequently susceptible to mold.

[0163] In a fifth aspect, an antifouling coating or sealant composition is provided, comprising an antifouling additive according to the first or third aspect of the invention.

[0164] Antifouling coatings on ship hulls or other "marine surfaces" are typically about 100 μm thick, while sealants are applied at a much higher thickness. However, in both cases, as discussed above, when the antifouling composition is exposed to wet conditions, a layer of about 20-40 μm thickness gradually forms, having absorbed water from the surrounding environment (Bressy C. et al., "Tin-free self-polishing marine antifouling coatings," Woodshead Publishing, 2009), and it becomes porous due to the dissolution of copper oxide particles in the coating. The thickness of this layer depends on the type of antifouling coating or sealant composition: solvent-based compositions are generally less prone to absorbing water than water-based compositions. This "wetting" layer is referred to as... Leaching layer This is because one or more biocidal compounds are dissolved from the cured composition layer and transported to the surface via diffusion.

[0165] Due to the porosity and hygroscopicity of silica-based aerogels, aerogel particles embedded in the leachate layer of coatings or sealants begin to absorb water. This creates a localized aqueous environment within the exposed aerogel particles, surrounding the slowly dissolving particles of the embedded active compound. Shortly thereafter, a saturated solution of the active compound is formed within the aerogel particles. Figure 4 ).

[0166] The saturated solution then acts as a reservoir for the active compounds, and is released onto the surface of the antifouling coating or sealant as the active compounds penetrate the porous structure of the aerogel particles and efflux onto the surface. The leaching layer is constantly renewed due to the erosion of the upper portion of the coated surface as it is exposed to water or (for static outdoor applications) rain, sunlight, and temperature fluctuations. For indoor applications, erosion will be caused by frequent exposure to water, such as in a shower, and physical cleaning (using detergents) of the surface to which the antifouling composition has been applied. While the thickness of the leaching layer decreases due to erosion from the top, it is simultaneously renewed by the inclusion of deeper regions of the antifouling composition layer.

[0167] For onshore coatings, porous layers similar to the aforementioned "leaching layer" have gradually been developed. The mechanism for developing this layer differs from that of coatings on marine surfaces and depends particularly on the well-known ability of silica to swell and contract when absorbing / desorbing water, which occurs with variations in ambient humidity, temperature fluctuations, and incident sunlight during the day. This dynamic behavior leads to surface erosion (initially at the microscopic level) of the onshore antifouling coating (containing the aerogel particles of this invention), allowing ambient moisture, dew, rainfall, snowmelt, etc., to penetrate the coating and approach the aerogel particles. Over time, this results in the formation of a saturated solution of biocide that diffuses from the aerogel particles and onto the surface of the coating (similar to coatings on marine surfaces).

[0168] Therefore, in the following text, the concept and term "leaching layer" will be used for both "marine conditions" and onshore coatings.

[0169] The erosion and renewal of the leaching layer ensures that a sufficient amount of biocide is always present throughout the entire service life of the dry antifouling composition to maintain the desired antifouling effect on the surface of the dry antifouling composition.

[0170] As the leachate layer is eroded, the embedded aerogel particles become gradually exposed to the environment.

[0171] However, even when partially exposed, the aerogel particles remain in the antifouling composition (along with their remaining biocide content) until they are eventually removed by the erosion of the coating or sealant as discussed above.

[0172] This is with Figure 1The key difference compared to the situation shown is that the graph illustrates how the non-encapsulated biocide particles are lost from the coating long before they can fully exert their antifouling effect. As long as undissolved active compounds remain within the aerogel particles, thus ensuring a saturated reservoir of dissolved active compounds, these compounds are released to the surface with essentially zero-order kinetics. In other words, the release curve is essentially linear over time.

[0173] Therefore, during the expected service life of the coating or sealant, as long as the surface is frequently exposed to moisture such as humid air, especially air with a relative humidity >65%, rainwater, or contact with water, the concentration of biocides / biorepellents on the surface of the antifouling coating remains almost constant.

[0174] If more than one biocide / biorepellent is required, each active compound can be individually encapsulated and included in the antifouling composition at an appropriate ratio, thus ensuring that the various active compounds do not interact with each other during storage and that a constant ratio between the compounds released from the final coating or sealant is maintained during its expected service life.

[0175] In a preferred embodiment, the present invention provides antifouling coating compositions comprising an amount of antifouling additives according to the present invention, corresponding to at least 0.1%, such as at least 0.5%, such as at least 1% w / w, such as at least 1.25% w / w, such as at least 1.5% w / w, such as at least 2% w / w of a biocide, such as at least 3% w / w of a biocide, such as at least 4% w / w of a biocide, such as at least 5% w / w of a biocide, such as at least 6% w / w of a biocide, such as at least 7% w / w of a biocide.

[0176] In another embodiment of the invention, an antifouling coating is provided comprising two or more different biocides and / or biorepellents, which are individually encapsulated in different aerogels and then added to the antifouling composition in a desired ratio.

[0177] The procedures described herein have been found to be applicable to many distinctly different chemical structures, such as pyridinethiones, isothiazoles and isothiazolones, triazoles, imidazoles and benzimidazoles, halopyrroles, ureas, carbamates, sulfonamides, and zinc and copper salts, such as zinc thiocarbamate, copper thiocyanate, copper(II) hydroxide and copper(II) carbonate-copper(II) hydroxide (1:1), and metallic copper.

[0178] In one embodiment, the encapsulated biocide or biorepellent compound is selected from pyrithione of the following formula:

[0179]

[0180] Met is a metal selected from copper, zinc, zirconium, or sodium.

[0181] In a preferred embodiment, the encapsulated biocide or biorepellent compound is selected from zinc pyrithione or sodium pyrithione.

[0182] In another embodiment, the encapsulated biocide or biorepellent compound is selected from isothiazoles of the following formula:

[0183]

[0184] R1 and R2 can be halogens or hydrogen, or R1 and R2 can be fused to form an optionally further substituted aromatic ring, and R3 = C3-C 12 alkyl.

[0185] In a specific implementation, the biocidal or biorepellent compound is selected from 2-butyl-benzo[d]isothiazolidin-3-one (BBIT), 2-octyl-2H-isothiazolidin-3-one (OIT), or 4,5-dichloro-2-octylisothiazolidin-3(2H)-one (DCOIT).

[0186] In another embodiment, the encapsulated biocide or biorepellent compound is selected from triazoles of the following formula:

[0187]

[0188] Wherein, R4 = hydrogen, C1-C6 alkyl, R5 = C1-C6 alkyl, C1-C6 alkoxy, R6 = aryl, C1-C6 arylalkyl, and wherein R4 and R5 can be fused to form a 5-6 membered ring containing at least one oxygen atom.

[0189] In a specific implementation, the biocidal or biorepellent compound is selected from 1-(4-chlorophenyl)-4,4-dimethyl-3-(1,2,4-triazol-1-yl-methyl)pentan-3-ol (tebuconazole), 1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolanecyclo-2-yl]methyl]-1H-1,2,4-triazole (propiconazole), or (2RS,3RS; 2RS,3SR)-2-(4-chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol (cycloconazole).

[0190] In another embodiment, the encapsulated biocide or biorepellent compound is selected from triazine of the following general formula:

[0191]

[0192] Wherein, R7 = C1-C6 alkylthio, R8 = C1-C6 alkylamino, and R9 = C1-C6 alkylamino.

[0193] In a preferred embodiment, the biocide or biorepellent compound is 2-ethylamino-6-methylthio-4-tert-butylamino-1,3,5-triazine (tert-butylamine).

[0194] In another embodiment, the encapsulated biocide or biorepellent compound is selected from imidazoles of the following general formula:

[0195]

[0196] Among them, R 10 and R 11 It can be hydrogen, C1-C6 alkyl, or C1-C3 arylalkyl, or fused to form a benzimidazole ring, and R 12 = Hydrogen, heteroaryl or carbamoyl.

[0197] In specific implementation schemes, the biocidal or biorepellent compound is selected from 2-thiazol-4-yl-1H-benzimidazole (thiabendazole), (RS)-4-[1-(2,3-dimethylphenyl)ethyl]-3H-imidazole (metopril) and 1H-benzimidazole-2-ylcarbamate (carbendazim).

[0198] In another embodiment, the encapsulated biocide or biorepellent compound is selected from halogenated pyrroles of the following general formula:

[0199]

[0200] Among them, R 13 =Aryl, R 14 = Halogen, cyano, trifluoromethylsulfonyl, R 15 = Halogen, trifluoromethylthio, R 16 = Cyano, trifluoromethyl, halogen, R 17 = Hydrogen, C2-C6 alkoxymethyl

[0201] Among them, R 14 R 15 and R 16 At least one of them is a halogen.

[0202] In a specific implementation, the biocidal or biorepellent compound is selected from 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrolo-3-onitrile (Tralopyril) and 4-bromo-2-(4-chlorophenyl)-1-ethoxymethyl-5-trifluoromethylpyrrolo-3-onitrile (Chlorfenapyr).

[0203] In another embodiment, the encapsulated biocide or biorepellent compound is selected from urethanes, ureas, or sulfonamides of the following general formulas:

[0204]

[0205] Where Q = carbonyl (C = O) or sulfonyl (O = S = O), R 18 =Aryl, C1-C8 alkyl, hydrogen and R 19 =C1-C6 alkyl, hydrogen, G=OR 20 or N(R) 21 R 22 ), where R 20 =C3-C6 alkynyl, C1-C6 alkyl, R 21 =C1-C8 alkyl, trihalomethylthio, hydrogen and R 22 =C1-C8 alkyl, aryl, hydrogen.

[0206] In another embodiment, the biocidal or biorepellent compound is selected from the following three general formulas: carbamate, urea, or sulfonamide.

[0207]

[0208] Among them, R 18 =Aryl, C1-C8 alkyl, hydrogen and R 19 =C1-C6 alkyl, hydrogen, R 20 =C3-C6 alkynyl, C1-C6 alkyl, R 21 =C1-C8 alkyl, trihalomethylthio, hydrogen and R 22 =C1-C8 alkyl, aryl, hydrogen.

[0209] In specific implementation schemes, the biocidal or biorepellent compound is selected from 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), dichloro-N-[(dimethylamino)-sulfonyl]-fluoro-N-(p-tolyl)-methanesulfonamide (toluenesulfonamide), N-(dichlorofluoromethylthio)-N',N'-dimethyl-N-benzenesulfonamide (Iprodione), and 3-iodo-2-propynyl butylcarbamate (Iodocarb).

[0210] In yet another embodiment, the encapsulated biocide or biorepellent compound is selected from zinc and copper salts, such as zinc thiocarbamate, copper thiocyanate, copper(II) hydroxide, and copper(II) carbonate-copper(II) hydroxide (1:1), as well as metallic copper.

[0211] In a particularly preferred embodiment, the encapsulated biocide or biorepellent compound is selected from tolyolfluanid, N,N-decyl-N,N-dimethylammonium carbonate, N,N-decyl-N,N-dimethylammonium bicarbonate, zinc pyrithione, diuron, 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), 3-iodo-2-propynyl butylcarbamate (IPBC), 2-thiazolyl-4-yl-1H-benzimidazole (thiabendazole), 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethylpyrrole (= icoconil or tralopyril) or mixtures thereof.

[0212] experiment

[0213] Materials used in aerogel synthesis.

[0214] The gel-forming material is selected from metal oxides based on Si, Ti, Fe, and Al, such as tetraethyl orthosilicate (TEOS, tetraethoxysilane) or tetrapropyl orthosilicate (TPOS, tetrapropoxysilane). For the preparation of more hydrophobic materials, methyltrimethoxysilane (MTMS or similar) may be included. Prepolymerized (pre-hydrolyzed, pre-condensed) tetraalkoxysilanes are commercially available or can be produced by hydrolyzing the relevant tetraalkoxysilane under weakly acidic conditions followed by polymerization at low temperature overnight.

[0215] A general method for preparing aerogels containing encapsulated biocide / biorepellent.

[0216] To accommodate a wide selection of biocides / biorepellents with different solubilities and tolerances to acidic or alkaline conditions, and to allow for the use of different combinations of tetraalkoxysilanes and alkyltrialkoxysilanes, the following method was developed to produce the encapsulated biocides / biorepellents of the present invention.

[0217] • Original formulation (WO 2020 / 002659) Dynasylan M / TMOS gel (for encapsulating compounds with low solubility in ethanol / alcohol, such as CPT, ZPT, zineb, and diuron)

[0218] 1. Combine Dynasylan M, MTMS (with or without), and EtOH on a magnetic stirrer for 10 minutes. Add the biocidal agent and mix vigorously for about 5 minutes or until a homogeneous mixture is achieved.

[0219] 3. Mix NH4OH with EtOH + water and add it to the biocide mixture while stirring.

[0220] 4. Reduce the stirring speed until the reaction mixture becomes as large as pudding, which takes about 15-25 minutes.

[0221] 5. Seal the container and add a small amount of ethanol on top of the gel to prevent it from drying out. Let the material mature for about 3 days (this can be done in the refrigerator).

[0222] 6. This formulation is typically used in conjunction with supercritical fluid extraction. To enable freeze drying, the ethanol in the wet gel is replaced with an alcohol with a higher melting point, such as tert-butanol.

[0223] 6. Subsequently, the wet gel was frozen and freeze-dried according to the general procedure described herein.

[0224] • Gel preparation - Ammonium fluoride - Gels with TEOS / Dynasylan A (e.g., CPT, ZPT, zineb, diuron, icoplanin)

[0225] Preparation of stock solutions

[0226] Weigh 1.852 g of NH4F and add it to 100 mL of water. Add 20.50 g (22.78 mL) of ammonium hydroxide solution. This is referred to as the "ammonium fluoride / ammonium hydroxide stock solution" ("catalyst base").

[0227] Gel preparation

[0228] 1. Mix Dynasylan A / TEOS and ethanol in a container. Allow it to mix for 10 minutes. This is called an "alkoxide solution".

[0229] 2. Add the biocidal agent to the alkoxide solution. Stir for 5-15 minutes or until homogeneous.

[0230] 3. In another container, mix water and ethanol. Add ammonium fluoride / ammonium hydroxide stock solution. This is called the "catalyst solution".

[0231] 4. Pour the catalyst solution into the alkoxide solution and stir. This is the "sol".

[0232] 5. Stir vigorously until gelation begins. When the sol-gel thickens, reduce the mixing speed. The gelation time is approximately 8-40 minutes. The gelation time depends on the alcohol / water ratio and the ratio of (DynA + MTMS) to (water + ethanol). Transfer the wet gel to a mold or container for storage and aging.

[0233] 6. Seal the container and let the ingredients mature for about 3 days (this can be done in the refrigerator).

[0234] • Gel preparation - the reverse order in cases of high water ratios (for example, Iodocarb, terbutaline, toluenesulfonamide, due to ethanol solubility / miscibility).

[0235] 1. Combine water, ethanol, dispersant (and defoamer) in a container. Allow to mix on a magnetic stirrer for 10 minutes.

[0236] 2. Add biocides. Stir for 10 minutes.

[0237] 3. Mix TMOS and MTMS in another container.

[0238] 4. Pour the TMOS / MTMS mixture into the EtOH / water-based biocidal solution and stir for 5-15 minutes or until homogeneous.

[0239] 5. Add NH4OH- as an alkaline catalyst.

[0240] 6. Stir vigorously until gelation begins. When the sol-gel thickens, reduce the mixing speed. Transfer the wet gel to a mold or container for storage.

[0241] 7. Seal the container and let the ingredients mature for about 3 days (this can be done in the refrigerator).

[0242] 8. Subsequently, the wet gel was frozen and freeze-dried according to the general procedure described herein.

[0243] • Gel preparation - acidic catalysis (e.g., required for DCOIT, which is sensitive to alkaline conditions)

[0244] 1. Mix water, ethanol, and dispersant in a tank for about 10 minutes with mechanical stirring.

[0245] 2. Add HCl and mix for 10 minutes.

[0246] 3. Add biocides. Stir for 10 minutes.

[0247] 4. Mix Dynasylan A and MTMS in another container.

[0248] 5. Pour DynA / MTMS into EtOH / aqueous solution / biocid and stir for 5-15 minutes or until homogeneous.

[0249] 6. Add NH4OH- as an alkaline catalyst.

[0250] 7. Stir vigorously until gelation begins. When the sol-gel thickens, reduce the mixing speed. Transfer the wet gel to a mold or container for storage.

[0251] 8. Seal the container and let the ingredients mature for about 3 days (this can be done in the refrigerator).

[0252] 9. Subsequently, the wet gel was frozen and freeze-dried according to the general procedure described herein.

[0253] • General drying methods including solvent exchange

[0254] Depending on the composition of the sol phase, the solvent in the wet gel can be exchanged with tert-butanol (4 × gel volume, 3 times every 4 hours) before freeze-drying. For wet gels containing a high proportion of water, solvent exchange before freezing is not required. For wet gels containing a high proportion of ethanol, solvent exchange with tert-butanol before freezing allows for subsequent freeze-drying at higher temperatures, which is preferred for larger-scale operations.

[0255] Freeze-drying can be performed in commercial freeze dryers (such as VirTis), as described below:

[0256] The wet gel was frozen in a commercial freezer at, for example, -18°C or -80°C, and at a temperature T higher than the collapse temperature of that particular frozen gel. C (T C Evaluation can be performed, for example, by freeze-drying microscopy (FDM), see Methods section, at a shelf temperature approximately 5 degrees lower and a pressure of <3 Torr. The collapse temperature T of the gel is determined before starting freeze-drying of the freeze-dried wet gel of the present invention. C It is advantageous because we understand T. C This enables the development of the most cost-effective freeze-drying method. However, if the T of a specific gel... C If the location is unknown, the portion of the sample placed in the chamber should be kept at a temperature approximately 5 degrees Celsius lower than the freezing point of the solvent / solvent mixture in the wet gel; this may make identification easier. The frozen gel should then be freeze-dried, maintaining a temperature below the collapse temperature T. C Alternatively, the temperature can be lower than the freezing point of the solvent used. During the drying process, the temperature can be gradually increased.

[0257] Non-limiting embodiments

[0258] The following provides some non-limiting examples of how to produce the supported aerogel of the present invention.

[0259] Gel Example 1 (Reference Example). An aerogel with approximately 75% encapsulated CuPT was prepared from pre-condensed TEOS (or pure TEOS).

[0260] Step 1. Solution 1: In a glass container, mix 28.16 g of pre-condensed TEOS (or pure TEOS), 13.35 g of MTMS, and 115.2 g of ethanol (96.6%) with a mechanical stirrer for approximately 15 minutes. Add 48.64 g of copper pyrithione while mixing. Mix the solution for another 15 minutes.

[0261] Step 2. Solution 2: 1.28 g ethanol (96.6%), 76.8 g water (demineralized), and 3.71 g catalyst base (weigh 1.852 g NH4F and add it to 100 mL of water. Add 20.50 g (22.78 mL) ammonium hydroxide solution. This is the "catalyst base").

[0262] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for approximately 30 minutes, gelation occurs. Allow the resulting gel to age for approximately 3-5 days, then dry.

[0263] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: Approximately 63 grams.

[0264] For the purpose of comparing porosity measurements, identical wet gels were prepared and dried under supercritical conditions. Therefore, the wet gel from step 3) was cut into smaller pieces and transferred to a 1 / 2 L pressure vessel (a 1 / 2 L flow reactor equipped with heating jackets and molten metal at both ends) under ethanol. The temperature in the heating jackets was increased to 37°C–40°C, and the pressure was increased to 100 bar at a rate of 3 bar / min. This was maintained at 40°C and 100 bar for approximately 4 hours. 1 2 kg of CO2 was flowed through the container at a rate of approximately 6 mL / min. After flow, the pressure was slowly released over a 2-hour period. The weight of the supercritically dried aerogel was approximately 50 g.

[0265] Gel Example 2. An aerogel with approximately 75% encapsulated zineb was prepared from pre-condensed TEOS (or pure TEOS).

[0266] Step 1. Solution 1: In a glass container, mix 28.16 g of pre-condensed TEOS (or pure TEOS), 13.35 g of MTMS, and 115.20 g of ethanol (96.6%) with a mechanical stirrer for approximately 15 minutes. Add 48.64 g of zineb while mixing. Mix the solution for another 15 minutes.

[0267] Step 2. Solution 2: 1.28 g ethanol (96.6%), 76.8 g water (demineralized) and 3.71 g catalyst base (see Reference Example 1).

[0268] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for another 30 minutes, gelation occurs. Allow the resulting gel to age for approximately 3-5 days, then dry.

[0269] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: Approximately 70 grams.

[0270] For the purpose of comparing porosity measurements, identical wet gels were prepared and dried under supercritical conditions. Therefore, the wet gel from step 3) was cut into smaller pieces and transferred to a 1 / 2 L pressure vessel (a 1 / 2 L flow reactor equipped with heating jackets and molten metal at both ends) under ethanol. The temperature in the heating jackets was increased to 37°C–40°C, and the pressure was increased to 100 bar at a rate of 3 bar / min. This was maintained at 40°C and 100 bar for approximately 4 hours. 1 2 kg of CO2 was flowed through the container at a rate of approximately 6 mL / min. After flow, the pressure was slowly released over a 2-hour period. The weight of the supercritically dried aerogel was approximately 65 g.

[0271] Gel Example 3. An aerogel with approximately 66% encapsulated trelopelli (Iconi) was prepared from pre-condensed TEOS (or pure TEOS).

[0272] Step 1. Solution 1: In a glass container, mix 31.24 g of pre-condensed TEOS (or pure TEOS) and 56.9 g of ethanol (95%) with a mechanical stirrer for approximately 10 minutes. Add 24 g of Icotin while mixing. Mix the solution for another 10 minutes.

[0273] Step 2. Solution 2: 20 g ethanol (95%), 45.98 g water (demineralized) and 1.2 g catalyst base (see Reference Example 1).

[0274] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for another 20 minutes, gelation occurs. Transfer the wet gel to a container with a lid. Allow the resulting gel to age for approximately 3-5 days, then dry.

[0275] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: 33.4 g.

[0276] For the purpose of comparing porosity measurements, identical wet gels were prepared and dried under supercritical conditions. Therefore, the wet gel from step 3) was cut into smaller pieces and transferred to a 1 / 2 L pressure vessel (a 1 / 2 L flow reactor equipped with heating jackets and molten metal at both ends) under ethanol. The temperature in the heating jackets was increased to 37°C–40°C, and the pressure was increased to 100 bar at a rate of 3 bar / min. This was maintained at 40°C and 100 bar for approximately 4 hours.1 2 kg of CO2 was flowed through the container at a rate of approximately 6 mL / min. After flow, the pressure was slowly released over a 2-hour period. The weight of the supercritically dried aerogel was approximately 36 g.

[0277] Gel Example 4. Preparation of an aerogel with approximately 56% encapsulated DCOIT

[0278] Step 1. In a container, mix 112 g of demineralized water, 6.5 g of ethanol (96.6%), and 1.1 g of dispersant (e.g., Tegodispers 740W) with a mechanical stirrer. Add 3.26 g of 0.2 M HCl and stir for about 10 minutes.

[0279] Step 2. Add 22.74g of DCOIT. Continue stirring for 10 minutes. This is the DCOIT solution.

[0280] Step 3. Mix 28g Dynasylan A (or TEOS) and 10.25g MTMS in a separate container and pour into the DCOIT solution. Stir the reaction mixture for 5-15 minutes or until homogeneous.

[0281] Step 4. Add 0.2 g of NH4OH- base catalyst (see above) to the reaction mixture. After 30 minutes, add another 0.25 g to the tank (monitor the pH; it should not exceed 8.5).

[0282] Step 5. Stir the reaction mixture until it begins to gel. When the sol-gel thickens, reduce the mixing speed and then transfer the wet gel to a mold or container for aging.

[0283] Step 6. Seal the container and let the ingredients mature for about 3 days (this can be done in the refrigerator).

[0284] Step 7. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: 40.4 g.

[0285] Gel Example 5. An aerogel with approximately 75% encapsulated icosene was prepared from pre-condensed TEOS (or pure TEOS).

[0286] Step 1. Solution 1: In a glass container, mix 22.0 g of pre-condensed TEOS (or pure TEOS), 10.43 g of MTMS, and 90.0 g of ethanol (96.6%) with a mechanical stirrer for approximately 10 minutes. Add 38.0 g of Iconium while mixing. Mix the solution for another 10 minutes.

[0287] Step 2. Solution 2: 1.0 g ethanol (96.6%), 60.0 g water (demineralized) and 6.0 g catalyst base (see Reference Example 1).

[0288] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for another 50 minutes, gelation occurs. Transfer the wet gel to a container with a lid. Allow the resulting gel to age for approximately 3–5 days, then dry.

[0289] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: Approximately 50 g.

[0290] For the purpose of comparing porosity measurements, similar wet gels with the same final icosene concentration were prepared and dried under supercritical conditions. The wet gel from step 3) was cut into smaller pieces and transferred to a 1 / 2 L pressure vessel (1 / 2 L flow reactor, equipped with heating jackets and molten metal at both ends). The temperature in the heating jackets was increased to 37°C–40°C, and the pressure was increased to 100 bar at a rate of 3 bar / min. This was maintained at 40°C and 100 bar for approximately 4 hours. 1 2 kg of CO2 was flowed through the container at a rate of approximately 6 mL / min. After flow, the pressure was slowly released over a 2-hour period. The weight of the supercritically dried aerogel was approximately 50 g.

[0291] Gel Example 6. An aerogel with approximately 75% encapsulated ZnPT was prepared from pre-condensed TEOS (or pure TEOS).

[0292] Step 1. Solution 1: In a glass container, mix 28.16 g of pre-condensed TEOS (or pure TEOS), 13.35 g of MTMS, and 115.2 g of ethanol (96.6%) with a mechanical stirrer for approximately 15 minutes. Add 48.64 g of zinc pyrithione while mixing. Mix the solution for another 15 minutes.

[0293] Step 2. Solution 2: 1.28 g ethanol (96.6%), 76.8 g water (demineralized) and 3.71 g catalyst base (see Reference Example 1).

[0294] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for approximately 48 minutes, gelation occurs. Allow the resulting gel to age for approximately 3-5 days, then dry.

[0295] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: Approximately 65 grams.

[0296] Gel Example 7. An aerogel containing approximately 66.4% encapsulated metopridine was prepared from pre-condensed TEOS.

[0297] Step 1. Solution 1: In a glass container, mix 4.4 g of pre-condensed TEOS (or pure TEOS), 2.09 g of MTMS, and 18.0 g of ethanol (96.6%) with a mechanical stirrer for approximately 15 minutes. Add 5.0 g of metoprimidine while mixing. Mix the solution for another 15 minutes.

[0298] Step 2. Solution 2: 0.2 g ethanol (96.6%), 12.0 g water (demineralized) and 1.2 g catalyst base (see Reference Example 1).

[0299] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for approximately 57 minutes, gelation occurs. Allow the resulting gel to age for approximately 3-5 days, then dry.

[0300] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: Approximately 7.5 grams.

[0301] Gel Example 8. An aerogel containing approximately 75% encapsulated 2-(4-thiazolyl)benzimidazole was prepared from pre-condensed TEOS.

[0302] Step 1. Solution 1: In a glass container, mix 11.0 g of pre-condensed TEOS (or pure TEOS), 5.22 g of MTMS, and 45.0 g of ethanol (96.6%) with a mechanical stirrer for approximately 15 minutes. Add 19.0 g of thiabendazole while mixing. Mix the solution for another 15 minutes.

[0303] Step 2. Solution 2: 0.5 g ethanol (96.6%), 30.0 g water (demineralized) and 3.0 g catalyst base (see Reference Example 1).

[0304] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for approximately 22 minutes, gelation occurs. Allow the resulting gel to age for approximately 3-5 days, then dry.

[0305] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: Approximately 25 grams.

[0306] Gel Example 9. An aerogel containing approximately 75% encapsulated tebuconazole was prepared from pre-condensed TEOS.

[0307] Step 1. Solution 1: In a glass container, mix 11.0 g of pre-condensed TEOS (or pure TEOS), 5.22 g of MTMS, and 45.0 g of ethanol (96.6%) with a mechanical stirrer for approximately 15 minutes. Add 19.0 g of tebuconazole while mixing. Mix the solution for another 15 minutes.

[0308] Step 2. Solution 2: 0.5 g ethanol (96.6%), 30.0 g water (demineralized) and 3.0 g catalyst base (see Reference Example 1).

[0309] Step 3. While mixing at full speed on a mechanical stirrer, add solution 2 to solution 1. After mixing for approximately 22 minutes, gelation occurs. Allow the resulting gel to age for approximately 3-5 days, then dry.

[0310] Step 4. Freeze the aged gel overnight at -80°C in an industrial freezer, and then freeze-dry it at a pressure of <10 mbar and a condenser temperature of -110°C. Yield: Approximately 25 grams.

[0311] Methods for characterizing aerogels

[0312] Mercury porosimetry

[0313] High-pressure mercury (Hg) infiltration analysis was performed in an Autopore V instrument from Micromeritics (early measurements: Autopore IV model 9520 or similar). Samples were measured at pressures ranging from 0.5 psia to 30,000 psia, equivalent to pore size scans from 338 μm to 6.6 nm.

[0314] 1. Load all samples into a transilluminator specifically designed for analyzing powder samples (i.e., 5 ml volume, 1.13 ml capillary stem volume). The amount of sample poured into the transilluminator is sufficient to achieve a 20% volume stem utilization, which ensures better data resolution.

[0315] 2. Prior to analysis, the transilluminator with the sample was degassed under vacuum to bring it below the setpoint limit of 50 μmHg. The sample was then analyzed in two different operating modes: low pressure (up to 40 psia, 17 points) and high pressure (up to 30,000 psia, 32 points).

[0316] 3. Once the low-pressure analysis is complete, weigh the permeameter containing Hg and the packed bed again. This value will be used as software input to determine the bulk density (i.e., interparticle porosity).

[0317] 4. Then, the permeameter is placed in the high-pressure port, and the intraparticle porosity is determined in relation to the apparent density when a higher pressure is reached.

[0318] 5. Using Washburn's equation, assuming a contact angle (θ) of 130 degrees and a mercury surface tension (γ) of 0.48 J / m. 2 The aperture is then calculated. Finally, the data summary is displayed by the device software.

[0319] Water absorption rate

[0320] Weigh approximately 0.2 grams of the sample into a small petri dish and place it in a desiccator with blue silica gel at the bottom, and then place it in a climate chamber.

[0321] 1. Record the weight loss of the sample until a stable weight is obtained normally after 4 to 6 days, and record the dry weight.

[0322] 2. Place the dried sample in a desiccator with tap water (approximately 86% RH) at the bottom. Record any increase in sample weight until a stable weight is achieved after 4 to 6 days.

[0323] Calculate the added weight. This can be expressed as pore volume = (weight of saturated sample - weight of dry sample) / density of water.

[0324] The test was conducted in a duplo at 23±2℃.

[0325] BET Analysis

[0326] Specific surface area, including pore size distribution, of samples is measured using BET (Brunauer, Emmett, and Teller) analysis. The specific surface area of ​​a powder is determined by the physical adsorption of gas on a solid surface and by calculating the amount of adsorbed gas corresponding to a monolayer on the surface. Physical adsorption is caused by relatively weak forces (van der Waals forces) between the adsorbed gas molecules and the adsorption surface area of ​​the test powder. Measurements are typically performed at liquid nitrogen temperatures. The amount of adsorbed gas can be measured by volume or a continuous flow procedure. Note that this method assumes that the gas is connected between the pores and the surrounding volume. In practice, this means that the pores must not be closed cavities. The BET device used in this study was the Micromeritics Gemini series with a Micromeritics VacPrep or equivalent drying station. It can measure pore volumes >4. * 10 -6 cm 3 / g.

[0327] Thermogravimetric (TGA) measurement

[0328] The samples were analyzed in a Mettler Toledo TGA 40. Typically, 10–25 mg of sample was placed in a crucible and weighed. The temperature was increased from room temperature to 800 °C at a rate of 10 °C / min. Weight loss was recorded. Solvents typically disappear before 250 °C, and solvents relevant to gel production typically disappear before 150 °C. Other organic materials (including polymers) disappear before 450 °C. At 800 °C, typically only inorganic materials remain. Indium was used for instrument functional control to ensure the temperature profiles were within the instrument calibration range. Weight loss was evaluated using the STARER software program version 7.01.

[0329] The collapse temperature T of the frozen wet gel was measured by FDM. C

[0330] Before considering freeze-drying, freeze-drying microscopy (FDM) can be used to evaluate the collapse temperature T of the freeze-wet gel of the present invention. C This allows for the determination of optimal freeze-drying conditions by identifying the minimum temperature required to prevent sample collapse. For FDM, the sample is frozen in a small microscope chamber using liquid nitrogen. While a vacuum is applied, the temperature is gradually increased and the sample dries. During this temperature ramp, the sublimation front is observed and recorded under a microscope. Changes in the dried layer can be used to determine the state of the system (amorphous or crystalline) and the sample's collapse temperature.

[0331] Thermal conductivity measurement

[0332] Test methods

[0333] According to ISO 22007-1(2008): General principles—Line source method

[0334] According to ASTM D 5930-0: Method for testing the thermal conductivity of plastics by means of a transient line source technique. The measurement is based on the hot-wire method (needle probe method), which is a transient technique for measuring the temperature change at a known distance from a linear heat source embedded in the test sample.

[0335] equipment

[0336] ISOMET 2114 heat transfer analyzer - equipped with a needle probe (0.015-0.050 [W / m K]).

[0337] ISOMET 2114 is a portable, handheld measuring instrument for directly measuring the heat transfer properties of a wide range of isotropic materials, including porous insulations, plastics, liquids, powders, and soil.

[0338] Test conditions

[0339] The average measured temperature is approximately 25°C.

[0340] The measurements were performed six times consecutively, with a 10-minute pause between each measurement. The test results were... Figure 7 As shown in the image.

[0341] Antifouling paint composition

[0342] The water absorption rate of a paint film is a key parameter related to the leaching layer, the leaching of active compounds, the erosion rate, and therefore, antifouling properties. Water absorption rate is affected by pigment selection, the chosen gel, and the amount of gel. Aerogels are highly porous and must reach equilibrium between the different components before effective measurement is possible. It has been shown that in paint compositions, the binder system permeates the aerogel, which reduces the water absorption rate until equilibrium is reached between the components and also ensures that the aerogel particles are firmly fixed in the dry paint layer and are not washed out over time due to exposure to water. A similar mechanism is conceivable to operate in sealant compositions. It is assumed that gels with high-pressure infiltration volume values ​​(e.g., measured by mercury porosimetry) can be more easily permeated by the binder system.

[0343] References

[0344] 1.S et al., Freeze-drying method as a new approach to the synthesis of polyurea aerogels from isocyanate and water. Journal of Sol-Gel Science and Technology (2018) 87:685-695.

[0345] 2. A. Muhammad et al., Recent Progress in Polysaccharide Aerogels: Their Synthesis, Application, and Future Outlook. Polymers, 2021, 13, 1347.

[0346] 3. K Onwukamike et al., Sustainable Approach for Aerogel Preparation from the DBU-CO2 Switchable Solvent. ACSS Sustainable Chemistry & Engineering, American Chemical Society, 2019, 7(3), pp. 3329-3338.

[0347] 4. Bertino et al., “METHODS FOR FABRICATION OF SILICA AEROGELS WITH CUSTOMSHAPES USING FREEZE DRYING”. US2019 / 0143290 A1 (May 2019)

[0348] 5. LS White et al., Fabrication of native silica, cross-linked, and hybrid aerogel monoliths. Transl. Mater. Res. 3 015002 (2016).

[0349] 6. S. Holberg et al., Fouling-Release Coatings for Steam Condensers. Heat Exchanger Fouling and Cleaning - 2017, p. 177

[0350] 7. KJ Kim et al., THERMAL INSULATING COATING WITH LOW THERMAL CONDUCTIVITY. WO 2018 / 200488 A1 (2018)

[0351] 8. Zhang et al., Synthesis, Structural and Thermal Properties of Nanoporous SiO2-based Aerogels, Advances in Nanocomposites-Synthesis, Characterization and Industrial Applications (2011). Edited by Dr. Boreddy Reddy, ISBN: 978-953-307-165-7 (Chapter 3, pp. 39-60)

[0352] 9. Li et al., Silica aerogels with tailored chemical functionality. Materials and Design, 193(2020): 108833

[0353] 10. K. Sinco, Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels. Materials, 2010, 3, 704-740.

[0354] 11. G.S. Wain et al., Comparing Biofouling Control Treatments for Use on Aquaculture Nets. Int J Mol Sci. Dec 2014; 15(12):22142-22154.

[0355] 12. Dorcheh et al., Silica aerogel; synthesis, properties and characterization. Journal of Materials Processing Technology, Vol. 199, No. 1-3, April 1, 2008, pp. 10-26.

Claims

1. An antifouling additive comprising an inorganic silica-containing aerogel, the inorganic silica-containing aerogel comprising: 1) A porous gel lattice, which has i. At least 40% total porosity, and ii. Mesopore diameter of at least 10 nm, 2) Optionally, the alkyl oxymetal may be Sc, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Ru, Hf, Ta, W, Re, Al, Ge, In, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and 3) At least 55% by weight of a biocide or biorepellent compound selected from the following embedded in the aerogel: 4,5-dichloro-2-octyl-4-isothiazolin-3-one, 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethylpyrrole, zinc ethylidene dithiocarbamate, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-iodo-2-propynyl butylcarbamate, 2-tert-butylamino-4-ethylamino-6-methyl -Thio-1,3,5-triazine, 1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol, zinc pyrithione, toluenesulfonamide, thiophanate-methyl, N,N-decyl-N,N-dimethylammonium carbonate, N,N-decyl-N,N-dimethylammonium bicarbonate, 2-thiazolyl-4-yl-1H-benzimidazole, 4-[1-(2,3-dimethylphenyl)ethyl]-3H-imidazole, and mixtures thereof. The encapsulation of one or more biocidal or biorepellent compounds occurs during the sol-gel formation of the aerogel, and the sol-gel precursor is one or more alkoxysilanes selected from tetraethoxysilane, tetra-n-propoxysilane, and alkyltrialkoxysilane, and the inorganic silica-containing aerogel contains alkoxysilane terminal groups selected from ethoxysilane or n-propoxysilyl groups.

2. The antifouling additive according to claim 1, wherein the sol-gel alkoxysilane precursor is tetraethoxysilane and wherein the inorganic silica-containing aerogel contains ethoxysilane terminal groups.

3. The antifouling additive according to any one of claims 1 to 2, comprising at least 60% by weight of the one or more biocidal or biorepellent compounds.

4. The antifouling additive according to claim 3, comprising at least 75% by weight of the one or more biocidal or biorepellent compounds.

5. The antifouling additive according to claim 3, comprising at least 80% by weight of the one or more biocidal or biorepellent compounds.

6. The antifouling additive according to claim 3, comprising at least 85% by weight of the one or more biocidal or biorepellent compounds.

7. The antifouling additive according to claim 1, wherein it has a mesopore diameter of at least 11 nm.

8. The antifouling additive according to claim 7, wherein it has a mesopore diameter of at least 12 nm.

9. The antifouling additive according to claim 7, wherein it has a mesopore diameter of at least 13 nm.

10. The antifouling additive according to claim 1, wherein it has a total porosity of at least 50%.

11. The antifouling additive according to claim 1, having a concentration of < 100 mW / m * The thermal conductivity λ value of K.

12. The antifouling additive according to claim 11, having a concentration of 30-75 mW / m * The thermal conductivity λ value between K.

13. The antifouling additive according to claim 1, wherein, The alkyltrialkoxysilane is selected from methyltrimethoxysilane and methyltriethoxysilane.

14. The antifouling additive according to claim 1, wherein, The biocidal or biorepellent compound is selected from zinc pyrithione, 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethylpyrrole, 4,5-dichloro-2-octyl-4-isothiazolin-3-one, and zinc ethylidene dithiocarbamate.

15. An antifouling coating composition comprising the antifouling additive according to any one of claims 1 to 14, for use on marine surfaces that are frequently or continuously immersed in water.

16. The antifouling coating composition according to claim 15, wherein, The sea surface includes ship hulls and marine structures, ports, oil drilling platforms, aquaculture nets, and wharves.

17. An antifouling coating composition for onshore use, the antifouling coating composition comprising an antifouling additive according to any one of claims 1 to 14.

18. The antifouling coating composition according to claim 17, wherein, The antifouling coating composition is used as a protective coating for wood-based structural materials or humid indoor environments.

19. A stain-resistant sealant composition comprising the stain-resistant additive according to any one of claims 1 to 14.

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