TWI819269B - A kind of super slippery anti-stick surface in water and its use - Google Patents

Abstract

The invention relates to a super-smooth anti-fouling surface imitating an eel structure, which is made by injecting highly hydrophilic water glue into microstructure materials to achieve super-hydrophilic, smooth, low-friction, anti-sticking characteristics, and at the same time has excellent Mechanical strength and stability, the super-smooth anti-fouling surface of the eel-like structure of the present invention can be especially used in water or wet conditions.

Description

A kind of super slippery anti-stick surface in water and its use

The present invention relates to the technical field of bionic materials, and in particular provides an ultra-smooth and anti-fouling surface imitating an eel structure, which includes microstructure materials and highly hydrophilic water glue.

In nature, many organisms have developed various adhesion systems (adhesion and anti-adhesion) in order to adapt to the environment and survive, which are worth learning and imitating. Many bionic adhesive systems have been developed in the past. For example, the dry tape imitating gecko feet is based on the clinging patterns on gecko feet. These tiny patterns are made up of billions of filamentous bristles tightly arranged. The Gecko can easily climb on the wall through the van der Waals force between the fine bristles and the wall; the dry tape imitating the octopus suction cup imitates the structure of the suction cup on the octopus tentacles. When grabbing something, the inside of the suction cup will A vacuum-like phenomenon occurs, which can produce suction in both air and water. This type of bionic dry tape uses nano-patterns to provide physical structure adsorption, rather than using glue or adhesive layers to generate adhesion. Therefore, it has no glue residue, can be re-attached, and has anisotropic adhesion. In addition, the all-purpose non-toxic adhesive modified coating imitating the mussels in the sea is inspired by the mussel mucin secreted by the mussel byssal glands, forming strong protein filaments that allow the mussels to be fixed on any surface under the sea and resistant to The wind and waves hit.

On the other hand, the development of anti-sticking systems, for example: artificial hydrophobic materials imitating lotus leaves, the concept comes from the special nanostructure on the surface of lotus leaves that will form an air cushion, allowing water droplets to gather and slide off, forming a super-hydrophobic interface. However, this material is not resistant to oil and other complex liquids. is insufficient, and has problems such as inability to operate under high pressure, easy damage, high price, and difficulty in production; the super-slippery coating material of bionic Nepenthes "slippery liquid-infused porous surfaces" (SLIPS), A "solid-liquid" interface is used to achieve the superhydrophobic effect. This surface is mainly composed of two parts: (1) a solid matrix covered with micron or nanopores; (2) a lubricant injected into the porous matrix, thereby making the surface Forming a lubricating layer only a few nanometers thick, it has the characteristics of super hydrophobicity, super slippery, and extremely low friction coefficient. However, the lubricant used in SLIPS contains fluorocarbons, which causes doubts about the safety of this material on the human body and is difficult to be used in biological applications. Related materials (see Patent Document 1).

The invention is inspired by eels, eels and other creatures with slippery body surfaces. The mucus on their body surfaces has a gel supramolecular structure and will flow and deform (shear thinning) under external stimulation, which can effectively reduce the impact of foreign matter on organs and organs. The friction of the skin has excellent lubrication function, which not only reduces the resistance to swimming, but also prevents skin damage and sticking when drilling sand and digging soil. In recent years, studies have pointed out that the dermis of eels can store mucus, and the epidermis has micron or nanometer pores, which can quickly eject mucus when exposed to external forces, and while moving rapidly in the water, the colloids on the surface will not scatter around. In the water, the smooth surface of the eel can be maintained.

[Previous technical literature]

【Patent Document】

[Patent Document 1] US 20150152270A1

Water glue has good hydrophilicity and can form a layer of water on the surface, making the surface super slippery. However, water glue can easily cause its structure to collapse due to the impact of external forces. Difficulty of application in practice. The general hydrophilic modification layer is only applied to the surface of the material for adsorption, chemical reaction, or surface polymerization to make the surface have a hydrophilic layer. Based on the requirement that the hydrophilic layer must be strong and durable, when the hydrophilic colloid is made through bridging When fixed and the bridging degree is low, it can provide the maximum movement of colloidal molecules, and the surface is relatively soft and easy to slide. However, the structure of this modified surface is extremely fragile and easily damaged by external forces. If the bridging degree is increased, the movement of colloidal molecules will be difficult, and the hydrophilicity will be greatly increased. Reduced, although the structure of this modified surface is relatively hard, it will lose the required smooth and low friction characteristics.

In view of the above problems, the purpose of the present invention is to provide an ultra-slippery and anti-fouling surface with an eel-like structure, which exhibits smooth, low friction, and anti-stick characteristics, and at the same time has good mechanical strength and stability, improving the traditional hydrophilic modification layer. The problem of vulnerability. In addition, the ultra-smooth anti-fouling surface of the eel-like structure provided by the present invention can overcome the problem that bionic Nepenthes SLIPS cannot be applied to biologically related materials, making the present invention more widely applicable.

In order to achieve the above object, the present invention provides the following technical means.

In one aspect, the present invention provides an ultra-slippery and anti-fouling surface imitating an eel structure, which is characterized in that it contains microstructure materials and highly hydrophilic water glue.

In some embodiments, the aforementioned microstructure material is a bulk material with high-density holes. Preferably, the aforementioned microstructure material is a bulk material with a porous structure, fiber structure, foam structure, etc.; in some embodiments, In the state, the aforementioned microstructure material is a surface coating with high-density holes. Preferably, the aforementioned surface coating is formed by means of self-assembly, micro-nano imprinting, surface foaming, surface etching, particle deposition, etc. Density hole structure. The aforementioned microstructure material serves as a carrier for the aforementioned highly hydrophilic water glue to enhance its mechanical strength.

In some embodiments, the polymer side chain of the highly hydrophilic hydrogel contains at least one polar group that captures water molecules, and the polar group is a non-ionic polar group or an ionic polar group; in some cases In an embodiment, the nonionic polar group is selected from at least one of -OH, -NH ₂ , -NRH, -CONH ₂ , -CONR ₂ , -CONRH, and -COOH; in some embodiments, , the aforementioned ionic polar group is selected from -COO-, -SO ₃ ^- , -PO ₃ ^- , -N ⁺ H ₂ (CH ₂ ) _n SO ₃ ^- , -P(=O)(O ^- )OCH ₂ At least one of the group consisting of CH ₂ N ⁺ H ₃ and -P(=O)(O ^- )OCH ₂ CH ₂ N ⁺ (CH ₃ ) ₃ .

In some embodiments, the highly hydrophilic hydrocolloid is selected from natural colloids or artificial glue materials; in some embodiments, the aforementioned natural colloids are specifically selected from the group consisting of collagen, hyaluronic acid, sodium hyaluronate, pectin, and gum arabic. , alginic acid, chitin, chitin, cyclodextrin (Cyclodextrin), poly-L-lysine, poly-L-glutamic acid, agar Agar, gelatin, fibrin, dextran, hydroxymethyl fiber Glue, starch, Guanhua bean gum, mucopolysaccharide and other water-absorbing loose viscose; in some embodiments, the aforementioned artificial glue material is specifically selected from PVA, PEG, PMPC, PSBMA, POEGMA, Pluronic, poly(amido-amine), Polyvinylpyrrolidone, polyNipaam, polyDMAEMA, polyHPMA, polyHEMA, polyHEA, polyHEEMA, polyHDEEMA, polyMEEMA, polyMDEEMA, polyPEG, polyAN, polyAM, polyAA, polyMAA and other hydrocolloids. The aforementioned hydrophilic hydrocolloid can be any hydrocolloid commonly used in the field of the present invention, prepared by copolymerization or mixing.

In some embodiments, the aforesaid highly hydrophilic hydrocolloid is a lightly bridging hydrocolloid material, which further fixes the colloid and the microstructure material through bridging, thereby improving the mechanical strength and stability, so that the aforesaid highly hydrophilic hydrocolloid will not be affected by Lost by washing with water.

In some embodiments, a small amount of bridging agent is added and mixed with the above-mentioned highly hydrophilic water glue for coating, and cross-linking is generated by irradiation or polymerization to maintain the stability in the above-mentioned microstructure material.

In another aspect, the present invention provides a super-slip anti-skid structure with the above-mentioned eel-like structure. The purpose of staining surfaces is characterized by its ability to be applied in water or in a wet state.

In another aspect, the present invention provides a use of the above-mentioned eel-like structure of an ultra-slippery and anti-fouling surface, which is characterized in that it can be applied to bio-related materials.

The super-smooth and anti-fouling surface of the eel-like structure of the present invention is made by injecting highly hydrophilic water glue into microstructure materials to achieve a super-lubricating structure that penetrates into glue, so that the water glue can form a moist water layer on the surface after absorbing water and swelling. , while maintaining the movement and rotation of local water molecules and colloid molecules to consume friction energy, thereby achieving ultra-slippery, low friction, anti-sticking characteristics, and excellent mechanical strength and stability, improving the fragility of the traditional hydrophilic modified layer Mechanical properties and increased service life.

The microstructure material of the present invention does not expand and shrink due to water absorption, so it can provide a good skeleton to grasp loose water glue and serve as a carrier of water glue; in addition, the highly hydrophilic water glue has molecular chains that are wrapped around and filled In the microstructured material, the part of the super-slippery anti-fouling surface of the eel-like structure of the present invention that contacts the object exhibits the shear thinning characteristics of non-Newtonian fluids, providing super-slippery, difficult to fix and adsorb, and anti-stick effects.

The super-slippery and anti-fouling surface of the eel-like structure of the present invention also has excellent super-slippery, low friction, anti-stick properties, and excellent mechanical strength and stability. Due to the use of water glue materials, the present invention has wider applicability. , preferably applied in water or in a wet state, and can even be applied to biologically related materials.

10: Super smooth and anti-fouling surface imitating eel structure

101:Building bridges

102:Porous structure

103: Water glue embedded in porous structure

104: Water glue for loose distribution in aqueous environment

105:Water layer

106:Dirty

[Figure 1] Schematic diagram of the ultra-slippery anti-fouling surface based on the eel-like structure of the present invention

[Figure 2] Comparison of the oily dirt adsorption test results of the ultra-slippery anti-fouling surface based on the eel-like structure of the present invention and the comparative example

[Figure 3] Comparison of the water-based dirt adsorption test results of the ultra-slippery anti-fouling surface based on the eel-like structure of the present invention and the comparative example

The following discloses the embodiments of the present invention, which does not limit the present invention to be implemented in the following manner, but is intended to illustrate the details and implementation effects of the present invention.

The super-smooth anti-fouling surface of the eel-like structure of the present invention includes microstructure materials and lightly bridging highly hydrophilic water glue; among them, the microstructure material serves as a skeleton for grasping the water glue and can be any material in the technical field to which the present invention belongs. A material with holes and roughness as understood by those with ordinary knowledge is ideally a material with high density of holes. For example, a bulk material, such as a microstructured material with a porous structure, fiber structure, foam structure, etc., can be used, and the material can be immersed in a water glue solution to prepare the ultra-slippery anti-fouling surface of the eel-like structure of the present invention. For example, a surface coating with high-density holes can also be prepared on the surface of the substrate through experimental steps. The aforementioned experimental steps can be any preparation method for forming a high-density hole structure that is understood by those of ordinary skill in the art. , such as self-assembly, micro-nano imprinting, surface foaming, surface etching, particle deposition, etc., the present invention is not limited to this.

The highly hydrophilic hydrocolloid of the present invention can be a lightly bridged highly hydrophilic hydrocolloid material, and means that the polymer side chain contains at least one polar group that captures water molecules. The polar group can be ionic or non-ionic. Ionic, but the polymer side chain can also contain both ionic and non-ionic polar groups. Exemplarily, the nonionic polar group can be at least one of the group consisting of -OH, -NH ₂ , -NRH, -CONH ₂ , -CONR ₂ , -CONRH, and -COOH, and the ionic polar group can be Can be -COO ^- , -SO ₃ ^- , -PO ₃ ^- , -N ⁺ H ₂ (CH ₂ ) _n SO ₃ ^- , -P(=O)(O ^- )OCH ₂ CH ₂ N ⁺ H ₃ , - At least one of the groups P(=O)(O ^- )OCH ₂ CH ₂ N ⁺ (CH ₃ ) ₃ .

Furthermore, the hydrophilic hydrocolloid of the present invention can be a natural colloid or an artificial glue material, as long as its polymer side chain contains a polar group for grabbing water molecules, and the present invention is not limited to this. For example, the hydrophilic colloid of the present invention may be collagen, hyaluronic acid, sodium hyaluronate, pectin, gum arabic, alginic acid, chitin, chitosan, cyclodextrin, poly-L-ion. Natural colloids such as amino acid, poly-L-glutamic acid, agar, gelatin, fibrin, dextran, hydroxymethyl cellulose, starch, Guanhua gum, mucopolysaccharide, etc. can also be used, such as PVA, PEG, PMPC , PSBMA, POEGMA, Pluronic, poly(amido-amine), polyvinylpyrrolidone, polyNipaam, polyDMAEMA, polyHPMA, polyHEMA, polyHEA, polyHEEMA, polyHDEEMA, polyMEEMA, polyMDEEMA, polyPEG, polyAN, polyAM, polyAA, polyMAA and other artificial adhesive materials. The aforementioned hydrophilic hydrocolloid can be any hydrocolloid commonly used in the field of the present invention, prepared by copolymerization or mixing.

The present invention reacts with the preparation of microstructured materials and lightly bridging hydrophilic colloids to form an ultra-smooth and anti-fouling surface imitating an eel structure. In addition, a small amount of bridging agent can also be added during the preparation process. The aforementioned bridging agent can be any bridging agent commonly used in the field of the present invention, mixed and coated with highly hydrophilic water glue, and cross-linked by illumination or polymerization. , to maintain the stability of the hydrogel in the microstructure material.

The schematic diagram of the specifically prepared and synthesized eel-like structure of the ultra-slippery and anti-fouling surface is shown in Figure 1. As shown in Figure 1, the eel-like super-slippery anti-fouling surface 10 may include bridges 101, porous structures 102, hydrocolloids 103 embedded in the porous structures, and hydrocolloids 104 loosely distributed in a water-containing environment. In Figure 1, the bridge 101 is represented by a curved black line, which helps the water glue to be fixed on the porous structure 102 to form a water glue 103 embedded in the porous structure; for the convenience of understanding, the porous structure 102 is shown in yellow in Figure 1 and is embedded in the porous structure. The water glue 103 is shown in gray, but those with ordinary knowledge in the technical field to which the present invention belongs can understand that this is only a schematic diagram for illustrating the embedding of the water glue into the porous structure of the present invention, and is not a limitation of the structure of the present invention. In fact, The distribution of water glue embedded in the porous structure will change due to the preparation process.

In addition, when the ultra-slippery anti-fouling surface of the eel-like structure of the present invention comes into contact with water, As shown in Figure 1, the interface between the porous structure and the water layer 105 will further have hydrocolloid 104 loosely distributed in the aqueous environment; and when the dirt 106 contacts the super-slippery anti-fouling surface 10 of the eel-like structure, it will It slides off immediately without sticking to the ultra-slippery and anti-fouling surface 10 of the eel-like structure, thereby achieving the effect of being ultra-slippery and anti-fouling.

Accordingly, the present invention can prepare eel-like structure materials with ultra-smooth, anti-fouling, and anti-stick surfaces; in addition, the friction coefficient, friction coefficient, and friction coefficient can also be measured by any method known to those with ordinary knowledge in the technical field to which the present invention belongs. The physical properties of the super-slippery anti-fouling surface of the eel-like structure of the present invention are measured by means of physical properties such as stickiness and surface slippery, and the actual anti-fouling effect of the material surface is tested at the same time, so as to evaluate the composition and preparation method of the material. Evaluation.

[Example]

Next, specific embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

<Example 1>

Configure water glue solution:

Add 3.85g hydroxyethyl methacrylate, 0.5g acrylamide, 0.15g N,N'-methylenebisacrylamide, 0.005g hyaluronic acid, 0.225g photoinitiator (irgacure 2959) and 5.5g water, stir for 30 minutes under nitrogen atmosphere.

Preparation of surface patterned hydrogel modification layer:

Take a light-curing primer (Model: ETERCURE 6148J-75), apply it on the surface of the substrate to be modified, cover the pattern mold on the surface, illuminate it with light for photo-curing, and prepare a The surface has a rough and porous pattern. Next, the above-mentioned hydrocolloid solution is coated on the patterned surface, illuminated for photocuring, and solidified to form a hydrocolloid, thereby preparing a patterned hydrocolloid modification with an eel-like structure and a super-smooth and anti-fouling surface. quality layer.

<Example 2>

Configure reaction solution:

Dissolve 12.5g polyvinyl alcohol and 0.2g alumina powder in 87.5g water to prepare polyvinyl alcohol mixed solution with alumina powder; then, dissolve 5g of borax in 95g of water to prepare a borax aqueous solution.

Preparation of surface patterned hydrogel modification layer:

Take a grooved mold, add 10g of the above-mentioned mixed solution of polyvinyl alcohol and alumina powder, then add 2ml of the above-mentioned borax aqueous solution, stir it and let it stand for 10 minutes; according to this, the alumina powder will be fixed on the polyvinyl alcohol. The hydrocolloid generated by the reaction of vinyl alcohol and borax aqueous solution forms a skeleton that grasps the hydrocolloid and generates a rough surface, thereby preparing a patterned hydrocolloid modified layer with an eel-like structure and an ultra-slippery and anti-fouling surface.

<Example 3>

Configure water glue solution:

Add 3g hydroxyethyl methacrylate, 0.9g N-isopropylacrylamide, 0.5g acrylamide, 0.1g N,N'-methylenebisacrylamide, and 0.12g potassium persulfate into the reactor. and 5.5g of water, and stirred for 30 minutes in a nitrogen atmosphere to prepare a monomer solution. In addition, dissolve 1g of silver nitrate in 10ml of water to prepare a silver nitrate solution.

Preparation of hydrogel composites:

First, take 5g of the above-mentioned monomer solution, add 0.5ml of the above-mentioned silver nitrate solution, and stir it evenly. Then, take a porous material, such as fiber, sponge and other porous base materials, and immerse it in the above-mentioned uniformly stirred solution, so that the solution fills the pores, and at the same time, the redox polymerization reaction is carried out, and the reaction is completed after about 2 minutes. Glue to prepare a hydrogel composite material with an eel-like structure and an ultra-smooth and anti-fouling surface.

<Comparative example 1>

That is, the porous material of Example 3 was taken as Comparative Example 1, but without surface modification and without being immersed in the hydrocolloid solution.

<evaluation>

First, the material with the super-slippery anti-fouling surface of the eel-like structure obtained in the above-mentioned Examples 1-3 was subjected to an evaluation test for anti-fouling and anti-sticking of oil stains, water stains and high-viscosity fluids. In this example, Use olive oil and red pigment as oil stains, diluted ink as water stains, and Ketchup acts as a highly viscous fluid. First, the material with the super-slippery anti-stick surface obtained in Examples 1-3 was tilted at an angle, and the above-mentioned oil stains, water stains or high-viscosity fluid stains were respectively dropped on the surface, and the sliding was observed. Adhesion to the surface. If the dirt does not stick to the surface of the material but can slide off, the evaluation is ◎; if it can slide but is partially sticky, the evaluation is O; if it is slightly slidable but can stick, the evaluation is △. Furthermore, if the dirt is sticky, further use the method of soaking in water to clean and observe whether the dirt can be removed. If it can be removed, the evaluation will be ◎; if not, the evaluation will be X. The evaluation results are shown in Table 1.

[Table I]

According to this, it is shown that through the ultra-slippery and anti-fouling surface of the eel-like structure including microstructure materials and highly hydrophilic hydrocolloids of the present invention, even if it is contaminated with dirt, it can be easily removed, showing that it is ultra-slippery and difficult to fix and adsorb. , anti-sticking effect.

Further, the material with the super-smooth anti-fouling surface of the eel-like structure of the present invention and Comparative Example 1 were respectively subjected to staining and anti-sticking evaluation tests, that is, the two were immersed in water stains and oil stains respectively, and then Soak it in clean water to observe the stickiness and dirt slipping off.

The evaluation results are shown in Figures 2 and 3. The results show that the material with an eel-like structure and a super-slippery anti-fouling surface of the present invention has an excellent effect of sliding off dirt after being immersed in oil and water stains, and after being immersed in clean water, there is almost no dirt on the surface of the material. Residues; in contrast, Comparative Example 1 has a significantly poorer effect on oil and water stains, and even if it is immersed in clean water for cleaning, the material still maintains serious dirt sticking, especially when water stains stick. Clean water is more effective for comparison. The material in Example 1 has almost no cleaning effect.

Based on this, it is apparent that the ultra-slippery and anti-fouling surface of the eel-like structure of the present invention can indeed achieve ultra-slippery, low friction and anti-stick properties, as well as excellent mechanical strength and stability, especially when used in water or wet conditions. , and can further be applied to biologically related materials.

[Possibility of industrial utilization]

Illustratively, the super-smooth anti-fouling surface of the eel-like structure of the present invention can be applied to:

(1) Anti-scaling of water pipe systems: It can be used in sewers or air-conditioning water pipe systems to avoid mineralization and scaling, which affects transportation and cooling efficiency;

(2) Anti-adhesion of artificial organs: It can be used for surface coatings such as artificial blood vessels and artificial organs to avoid protein adhesion and thrombus; it can also be used for artificial hip joints, knee joints and cartilage surfaces to avoid wear and inflammation;

(3) Easy-to-clean wiping tool: It can be designed to be used on general water-absorbing or oil-removing materials. It utilizes the super-smooth anti-fouling surface of the eel-like structure of the present invention to make highly viscous dirt easy to detach, achieving easy cleaning and extending service life. Effect;

(4) Mechanical wear resistance in water: Mechanical devices that wear in water can use the super-slippery anti-fouling surface of the eel-like structure of the present invention to reduce friction and increase service life.

The terms and descriptions used above are used to describe the embodiments of the present invention, but the present invention is not limited thereto. Modifications and changes that have the technical characteristics of the present invention are also included as long as they do not deviate from the patent scope of the present invention. Within the scope of protection of this patent.

10: Super smooth and anti-fouling surface imitating eel structure

101:Building bridges

102:Porous structure

103: Water glue embedded in porous structure

104: Water glue for loose distribution in aqueous environment

105:Water layer

106:Dirty

Claims (8)

An anti-fouling surface with an eel-like structure. The characteristic of the eel-like structure is that the eel-like dermis can store mucus, the epidermis has micron or nanometer pores, and the mucus on the body surface has a gel molecular structure. , will flow and deform under the stimulation of external force, and has a lubrication function; the aforementioned anti-fouling surface includes a microstructure material and a hydrocolloid embedded in the aforementioned microstructure material; the aforementioned microstructure material has micron or nanometer holes; the aforementioned microstructure material is embedded in the The polymer side chain of the hydrogel contains at least one polar group that captures water molecules. The aforementioned polar group is a non-ionic polar group or an ionic polar group; the aforementioned hydrogel embedded in the aforementioned microstructure material is a bridging hydrogel. Material; when the anti-fouling surface of the eel-like structure is in contact with water, the interface between the microstructure material and the water layer further has hydrocolloids that are loosely distributed in the aqueous environment. The hydrocolloids that are loosely distributed in the aqueous environment are not It will disperse in the water and maintain the smooth surface properties of eels. The anti-fouling surface as claimed in claim 1, wherein the microstructure material is a bulk material with micrometer or nanometer holes. The antifouling surface as claimed in claim 1, wherein the microstructure material is a surface coating with micrometer or nanometer holes. The antifouling surface imitating eel structure as described in claim 1, wherein the aforementioned non-ionic polar group is selected from -OH, -NH ₂ , -NRH, -CONH ₂ , -CONR ₂ , -CONRH, -COOH. At least one of the groups. The antifouling surface imitating eel structure as described in claim 1, wherein the aforementioned ionic polar group is selected from -COO ^- , -SO ₃ ^- , -PO ₃ ^- , -N ⁺ H ₂ (CH ₂ ) _n At least one of the ₃ groups SO ₃ ^- , -P(=O)(O ^- )OCH ₂ CH ₂ N ⁺ H ₃ , -P(=O)(O ^- )OCH ₂ CH ₂ N ⁺ (CH ₃ ) One kind. The anti-fouling surface with an eel-like structure as described in any one of claims 1 to 3, wherein, The hydrocolloid embedded in the microstructure material is selected from natural colloid or artificial glue. The anti-fouling surface with an eel-like structure as described in any one of claims 1 to 3, wherein a bridging agent is additionally added and mixed and coated with the aforementioned water glue embedded in the aforementioned microstructure material, and cross-linking is generated by irradiation or polymerization. , maintaining stability in the aforementioned microstructured materials. The use of the anti-fouling surface with an eel-like structure as described in any one of claims 1 to 7, characterized in that it can be used in water or in a wet state.