Hydrophobic coating for material surfaces

Abstract

Hydrophobing agents based on fluorine-free carboxylic acids, phosphoric acid esters and / or phosphonic acids, which are to be applied to a non-textile surface for coating after metal oxide or metal hydroxide particles.

Description

[0001] The present invention relates to an innovative process for the hydrophobization of non-textile surfaces, preferably fiber-based materials such as paper or wood, as well as materials based on ceramics, stone, metal, and plastics. Fiber-based materials such as paper or wood are widely used and versatile materials in numerous applications, from the packaging industry to the construction industry. However, their sensitivity to moisture and water often limits their durability, application possibilities, and resistance to environmental influences.

[0002] Conventional methods for hydrophobizing fiber-based materials such as paper or wood involve the use of waxes and paraffins, resins, or (fluorinated) polymers. Waxes and paraffins must sometimes be applied in significant quantities to achieve a satisfactory water-repellent effect, while the use of synthetic resins or polymers contributes to the generation of microplastics in the environment. The potential for environmental hazards is further increased, particularly through the use of fluorine-containing compounds. Furthermore, the use of the agents described above seals the surface of the materials and alters their tactile and / or optical properties.

[0003] A relatively new possibility for hydrophobizing fiber-based materials is the application of nanoparticles. Patent WO2019102459A1 presents a hydrophobization method for paper in which tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride nanoparticles are applied to the surface to be treated using ultrasound.

[0004] In patent US2018030282A1, 21 nm titanium dioxide particles and fluorine-free polymers based on polyolefins and acrylic acids are used to hydrophobize pulp. The latter compounds form a water-repellent film on the pulp surface, which exhibits increased roughness due to the treatment with titanium dioxide particles. This allows water contact angles of over 150° to be achieved.

[0005] The patent US2015075407A1 mentions the use of chromium complexes, together with metal oxide particles of the metals Al, Si, Ti, Zr, Au, Ag, Ni or Fe (or mixtures thereof) of size 1 to 35 nm and metal carboxylates as well as lecithins as hydrophobic agents.

[0006] Patent US2015330025A1 describes a process for hydrophobizing paper and cardboard using silanized silicon dioxide particles. For this purpose, silicon dioxide nanoparticles are dispersed in an aqueous-alcoholic solution and hydrophobized with (fluorinated) silane compounds. The dispersion is then applied to the paper.

[0007] Substrate onto which the hydrophobized nanoparticles are deposited by evaporation of the solvent.

[0008] Patent CA2739903A1 describes the hydrophobization of paper materials, among others, by applying multiple layers. The first layer consists of hydrophobized metal oxide particles ranging in size from 1 µm to 100 µm and an organic polymer-based binder to increase surface roughness. As a second layer, hydrophobized metal oxide particles ranging in size from 1 nm to 25 µm are applied, using hydrophobizing agents based on (fluorinated) silanes.

[0009] In patent US2014342098A1, the surface to be treated is treated with a sol-gel consisting of organometallic compounds of the metals Si, Al, In, Sn, or Ti, after which corresponding metal oxides or metal hydroxides are deposited on the surface. The treated surface is then brought into contact with (fluorinated) silane compounds dissolved in organic solvents to create the water-repellent effect.

[0010] What all of the patents mentioned have in common is that the coating methods rely on the use of synthetic, petroleum-based polymers, in the form of the particles themselves, the binders, or the hydrophobizing agents, thus representing potential sources for the generation of microplastics. Alternatively, the metal oxide particles used are hydrophobized using organosilicon compounds, which severely impairs the hydrophobization process due to the hydrolysis sensitivity of the latter compounds. Last but not least, silanes are unsuitable for the functionalization of metals such as Al, Ti, or Zr due to their moderate stability. The metal carboxylates used in patent US2015075407A1 are also unsuitable as hydrophobizing agents.

[0011] Patent EP2102406 describes the use of surface-modified metal oxide particles to hydrophobize textiles. These particles are applied to the textile fibers via a (fluorine-containing) dispersant and binder. In addition to silanes, perfluorinated carboxylic acids are also described for the surface treatment of the metal oxides.

[0012] Patent EP2553026, on the other hand, describes the post-treatment of metal oxide particles and / or metal hydroxide particles with organophosphorus compounds, but for use in cosmetic products based on titanium and in a size range of 5 to 100 nm.

[0013] The aim of the present invention is to overcome these challenges and provide an effective, non-toxic, and environmentally friendly method for hydrophobizing non-textile surfaces, preferably fiber-based materials such as paper or wood, without the use of additional dispersing and binding agents. This process creates a hydrophobic layer that significantly reduces or prevents the penetration of moisture and water into the material structure. This increases resistance to moisture damage, extends service life, and expands application possibilities in various environments. Description of the invention

[0014] The present invention encompasses the coating and modification of non-textile surfaces, preferably fiber-based materials such as paper or wood, as well as material surfaces based on ceramics, stone, metal, and plastics, with environmentally friendly compounds free of fluorine and petroleum-based organic polymers to generate a water-repellent effect. For this purpose, particles based on metal oxides and / or metal hydroxides of groups IIA, IVB, VIIB, VIIIB, IB, IIB, IIIA, and IVA, preferably the metals Al, Sn, Mg, Ca, Zn, Fe, Ti, and in particular the metals Al, Mg, Ca, Ti, and Zn, are applied to said material surfaces. Depending on the application process, the particles range in size from 1 nm to 10 µm.If a binder material is additionally used for better particle fixation, this consists of biopolymers based on proteins, polysaccharides, lipids, cutins or suberins, preferably based on polysaccharides, lipids and cutins.

[0015] The surfaces coated with the particles and optionally binders are then treated with hydrophobizing agents based on carboxylic acids and / or organophosphorus compounds, in particular compounds based on phosphoric acid esters or phosphonic acids of the general formula RCOOH, OP(OH)2OR, or OP(OH)2R, where R represents a hydrophobic radical in the form of aliphatic, branched or unbranched, alicyclic, or aromatic hydrocarbon groups with 5-40 carbon atoms, preferably with 8-24 carbon atoms, and in particular with 18 carbon atoms. Furthermore, R can also contain polymerizable functional groups.

[0016] The hydrophobic agents bind by forming bonds between the surface hydroxyl groups of the metal oxide / metal hydroxide particles and the carboxylic acid, phosphoric acid, or phosphonic acid groups of the hydrophobic compounds. Unlike silanes, these compounds offer the advantage of uncomplicated and rapid application with the same, or sometimes even better, stability. Furthermore, these compounds are non-toxic and environmentally friendly. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2019102459A1

[0003] US 2018030282A1

[0004] US 2015075407A1 [0005, 0010] US 2015330025A1

[0006] CA 2739903A1

[0008] US 2014342098A1

[0009] EP 2102406

[0011] EP 2553026

[0012]

Claims

[1] Hydrophobic agents based on fluorine-free carboxylic acids, phosphoric acid esters and / or phosphonic acids, which are to be applied to a non-textile surface for coating after metal oxide or metal hydroxide particles. [2] Hydrophobic agent according to claim 1, characterized by that the carboxylic acids, phosphoric acid esters and / or phosphonic acids are in the general form RCOOH, OP(OH)2OR or OP(OH)2R, where R represents a hydrophobic radical in the form of aliphatic, branched or unbranched, alicyclic or aromatic hydrocarbon groups with 5-40 C atoms, preferably with 8-24 C atoms and in particular with 18 C atoms. [3] Hydrophobic agent according to claim 2, characterized by that R contains polymerizable and / or functional groups. [4] Hydrophobic agent according to one of claims 1 to 3, characterized bythat the non-textile surface comprises substrates of paper, wood and other fiber-based materials, as well as substrates based on ceramic, stone, metal and plastic, preferably paper, wood and other fiber-based materials. [5] Hydrophobic agent according to one of claims 1 to 4, characterized by that the metal oxides and / or metal hydroxides are based on metals of groups IIA, IVB, VIIB, VIIIB, IB, IIB, IIIA and IVA, preferably the metals Al, Sn, Mg, Ca, Zn, Fe, Ti and in particular the metals Al, Mg, Ca, Ti and Zn. [6] Hydrophobic agent according to one of claims 1 to 5, characterized by that the metal oxides and / or metal hydroxides, after application to the substrate, are present as particles with a size of 1 nm to 10 µm, preferably with a size of 30 to 700 nm. [7] Hydrophobic agent according to one of claims 1 to 6, characterized bythat a binder made of non-petroleum-based biopolymers is used to fix the particles. [8] Hydrophobic agent according to one of claims 1 to 7, characterized by that the binder is based on proteins, polysaccharides, lipids, cutins or suberins, preferably on polysaccharides, lipids and cutins.