Fluorine-free hydrophobic and oleophobic nonwoven fabric

Abstract

The present invention relates to fluorine-free hydrophobic and oleophobic nonwoven fabrics, for use, for example, in automotive engine bays, and methods for making such nonwoven fabrics.

Description

[Technical field]

[0001] The present invention relates to fluorine-free hydrophobic and oleophobic nonwoven fabrics, for use, for example, in automotive engine bays, and methods for making such nonwoven fabrics. [Background technology]

[0002] Nonwoven fabrics contribute to extending the life of automobiles and making them safer, more comfortable, more cost-effective, and more sustainable. The combination of lightweight, fuel-efficient, high-thermal insulation, high-sound absorption, flame retardancy, water resistance, fuel resistance, resistance to extreme temperatures, and abrasion resistance is usually only possible with the combination of fluorine-containing compounds and nonwoven fabrics, i.e., fluorine-based nonwoven fabrics. Fluorine-based nonwoven fabrics protect the engine compartment, prevent liquid absorption, block resin leakage, and promote mold slippage. Examples of the use of fluorine-based nonwoven fabrics in automobiles include motor insulation, battery covers, headliners, and underbodies. The textile industry is under pressure to remove hazardous chemicals from their products and supply chains. Fluorine-containing compounds, which are being banned under the EU REACH regulation, are at the top of the list of chemicals. Per- and polyfluorinated substances are highly attractive in several industrial applications and consumer products such as automobiles because they are resistant to both water and oil. Per- and polyfluorinated substances are highly persistent and highly mobile in the environment. Potential harmful effects on human health and the environment are of concern, and uses that result in releases into the environment should be controlled. Finding alternatives to fluorine-containing compounds while maintaining the same levels of performance and durability is not easy: there are many examples of superhydrophobic coatings, but there has been limited progress in highly oleophobic treatments. The challenge in designing oleophobic coatings stems from fundamental limitations of materials. Typical surface tensions of hydrocarbon oils are in the range of 20-40 mN / m. The surface tension of a smooth oleophobic substrate needs to be around 20 mN / m. The requirement of low surface energy suggests that most commonly used materials are not inherently oleophobic, and only a few fluoro-based materials, such as PTFE, fluorosilanes, and fluoropolymers, can meet this prerequisite for oleophobicity. Essentially, the highly oleophobic treatments developed so far are based on fluoro-based materials with low surface energy. Simple poly(dimethyl)siloxane (PDMS) finishes typically have a surface energy of about 22-24 mN / m, which is not low enough to provide efficient oleophobicity. Furthermore, due to the differing nature of the substrates, PDMS finishes suffer from problems in terms of adhesion, uniformity, and durability. Therefore, there is a need for a fluorine-free finish that has a high degree of oleophobicity and does not suffer from the drawbacks of known solutions. Summary of the Invention

[0003] The solution proposed by the present invention is a method for producing a nonwoven fabric having hydrophobic and oleophobic properties, comprising the steps of providing a nonwoven fabric comprising fibers, and a SiO 2 Nanoscale SiO formed from an aqueous precursor solution containing the product. 2 The method includes the steps of providing an aqueous colloidal solution containing the particles and applying the colloidal solution to a nonwoven fabric to form a hydrophobic and oleophobic finish on the fibers of the fabric, thereby imparting hydrophobic and oleophobic properties. The nonwoven fabric produced by such a method comprises one or two surfaces having hydrophobic and oleophobic properties, where the nonwoven fabric comprises fibers, and a hydrophobic and oleophobic finish is present on the fibers of the fabric, including particularly those exposed at the surfaces, thereby imparting hydrophobic and oleophobic properties to the entire fabric and particularly to the surfaces, and the finish is formed of continuous or discontinuous porous SiO 2 of nanoscale thickness. 2 The containing layer.

[0004] The sol-gel process is a wet chemical process for depositing nanocrystalline coatings. The sol-gel process is characterized by the creation of the coating starting from a liquid sol state, which is converted to a solid state by sol-gel transformation. The sol used is a dispersion of solid nanoparticles, which are dispersed in water, organic solvents, or mixtures thereof. Sol-gel processes are mainly based on organometallic precursors such as siloxanes. The sol-gel process starts from a solution, and a solid network is gradually formed by various polymerization and condensation processes. A typical dense sol-gel coating results in a uniform coating. In the present invention, the colloidal solution is SiO 2 Nanoscale colloidal SiO produced by sol-gel method 2 The structure is preferably SiO 2 The product is silicon alkoxide, which undergoes hydrolysis and subsequent condensation reactions. Specifically, silicon alkoxide molecules in the precursor solution undergo hydrolysis and condensation to form small SiO 2 Forms particles. SiO 2 The particles continue to grow on the fiber surface, come into contact with each other, and may crosslink with each other by further condensation to form a gel structure.

[0005] The finish may have a thickness of 10-300 nm, preferably 50-250 nm, more preferably 80-150 nm. The total surface free energy of the coated fiber and nonwoven surfaces is preferably less than 24 mN / m, preferably less than 22 mN / m, most preferably about 20 mN / m, which is below the typical surface tension value of oil. Porous SiO 2 The containing layer is preferably SiO 2 , RSiO 1.5 , and / or R 2 It comprises structural elements from SiO, where R=H, alkyl, aryl, epoxy-alkyl, or aminoalkyl. The nonwoven fabric is preferably formed from staple fibers, more preferably from staple fibers that include carding. The deposition of the fibers onto the conveyor of the manufacturing line preferably includes cross-depositing a carded web. The staple fibres preferably comprise between 50% and 100% by weight of synthetic fibres, the remaining fibres, if any, may be cellulosic fibres such as viscose, lyocell or hemp.. Examples of suitable synthetic fibres include polypropylene, polyethylene, polyethylene terephthalate, polyacrylate, polyacrylonitrile, polyamide or mixtures thereof.

[0006] Silicon alkoxide can be, for example, tetraalkoxysilane, alkyltrialkoxysilane, dialkyldialkoxysilane, or any mixture. Examples include tetraethoxysilane, trimethoxymethylsilane, dimethoxydimethylsilane, polydimethylsiloxane, vinyltrimethoxysilane, 3-aminopropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and 3-glycidyloxypropyltrimethoxysilane. In general, alkyltriethoxysilane and aminopropyltriethoxysilane can be preferred. The solvent of the aqueous precursor solution is preferably either water or a mixture of water with an alcohol, preferably methanol, ethanol and / or isopropanol.More preferably, the precursor solution contains a hydrolysis condensation catalyst, preferably an acid. The aqueous colloidal solution can typically be formed from the aqueous precursor solution by mixing the precursor solutions and stirring at a temperature below 50° C., preferably between 15-30° C., for a period of 10 minutes to 24 hours, preferably 30 minutes to 12 hours, more preferably 1 to 6 hours.

[0007] In one embodiment, the solid content in the colloidal solution is between 0.1 and 15% by mass, preferably between 1 and 7% by mass. The average particle size of the colloids in the colloidal solution is between 1 and 500 nm, preferably between 5 and 300 nm, more preferably between 20 and 150 nm. In one embodiment, the colloidal solution further comprises a binder, preferably in the form of an acrylic, acrylic-ester, melamine, thermoplastic or self-hardening polymer. Additionally, the colloidal solution may further include a flame retardant in the form of an inorganic component including, for example, phosphorus-based salts and particles. In one embodiment, the colloidal solution is applied to the surface of the nonwoven fabric, preferably in-line, by spray application, coating, or foaming. Application by in-line foaming application may be most preferred. The amount of colloidal solution applied to the nonwoven fabric after drying is preferably between 0.1 grams per square meter and 5 grams per square meter, more preferably between 0.5 grams per square meter and 2 grams per square meter.

[0008] The colloidal solution can be applied to the fabric in a dry state, e.g., after drying if wet-laying or spun-lacing processes are used, or in a semi-dry state, e.g., after partial drying if wet-laying or spun-lacing processes are used. Drying preferably includes passing the fabric through a drying oven. In one embodiment, the colloidal solution is continuously applied to the nonwoven fabric in-line after drying and before winding. Alternatively, the fabric can be formed and dried in-line, then wound to form a fabric roll, and then unwound before applying the colloidal solution offline. In one embodiment, the method further comprises an in-line step of continuously and actively drying the fabric after application of the colloidal solution, again preferably comprising passing the fabric through a drying oven. The speed at which the nonwoven fabric moves through the production line on a conveyor belt can be between 2 meters per minute and 70 meters per minute. More preferably, the line speed is between 5 meters per minute and 25 meters per minute. Preferably, the nonwoven fabrics of the present invention, which have been modified to enhance hydrophobicity and oleophobicity, can be used in automotive applications, such as as motor insulation elements, battery covers, headliners, or underbody liners. Further details and advantages of the invention will become apparent from the following description of the embodiments and figures. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 shows a manufacturing line for carrying out the method of the present invention. [Diagram 2] FIG. 1 illustrates the visual results of a fluorine-free treatment according to the present invention. [Diagram 3] 1 is a photomicrograph of the surface facing fibers of a 30% by weight viscose and 70% by weight polyester nonwoven fabric that has been subjected to a fluorine-free treatment of the present invention. [Figure 4] 1 is a photomicrograph of the face-facing fibers of a 30% by weight viscose and 70% by weight polyester nonwoven fabric before and after the fluorine-free treatment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0010] Example 1 Preparation of colloidal solutions In the first embodiment, the nanoscale SiO 2 Preparation of colloidal aqueous solutions containing particles 100 ml of tetraethoxysilane, 400 ml of water, and 200 ml of 0.01 N hydrochloric acid as a polycondensation catalyst are mixed at ambient temperature (20° C.) and kept stirring (about 5 hours), resulting in an aqueous silica sol-gel with a solid content of about 4.5% and an average particle size of 6 nm. Example 2 Preparation of colloidal solutions In a second embodiment, the nanoscale SiO 2 Preparation of colloidal aqueous solutions containing particles

[0011] 40 ml of tetraethoxysilane, 40 ml of aminopropyltriethoxysilane, 20 ml of 3-methacryloxypropyltrimethoxysilane and 400 ml of water are mixed at ambient temperature (20° C.), where SiO 2The precursors, tetraethoxysilane, aminopropyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, were stirred for 3 hours each, and then dissolved in solvent H in this order. 2 0. Then, while stirring, 200 ml of 0.01N hydrochloric acid carboxylic acid is titrated in as a polycondensation catalyst. As a result, an aqueous silica sol-gel with a solid content of about 6% and an average particle size of 6 nm is obtained. Example 3 manufacturing FIG. 1 illustrates a manufacturing line 100 that can be used to practice the method of the present invention for producing hydrophobic and oleophobic nonwoven fabrics. Production line 100 includes several stations, arranged in sequence. A first station 110 is for fiber preparation and includes means such as a hopper feeder that allows uniform feeding of staple fibers to a carder 120. From the carder 120, a perforated conveyor belt passes through a subsequent spunlacing station 130, followed in-line by a first drying station 140, a foam application station 150, and a second drying station 160, before the finished, dry nonwoven fabric is wound onto a roll.

[0012] The carder 120 and subsequent spunlacing station 130 may be configured as generally known in the art. In station 120, the fibers of the fibrous web formed from the pile may be transported on a conveyor belt at high speeds, for example, between 5 meters per minute and 25 meters per minute, and mechanically bonded by high energy water jets. This is followed by a first drying oven 140 where the wet fabric is dried in a spunlacing process. This is followed by foam application station 150, which represents a critical step in the method of the present invention. The nonwoven textile enters foam application station 150 at a constant moving speed. Foam application station 150 applies a layer of nanoscale SiO 2The foam application system includes a foam application system suitable for uniformly applying the dry content of the colloidal solution containing the particles at a rate high enough to apply between 0.1 and 2 grams per square meter. Foam application station 150 is followed by drying station 160, which includes a drying oven through which the chemical-loaded nonwoven fabric moves at a constant speed under elevated temperatures for drying. In a final in-line step, the dried nonwoven fabric is wound to form large rolls that can be several meters wide and kilometers long. The rolls can be stored in warehouses, transported to various locations, and unwound for further processing. Example 4 Product Testing

[0013] A nonwoven fabric of carded and spunlaced polymeric fibers (100% PET) was prepared. For the samples of the present invention, SiO 2 Based on solids content, 1.03 g / m 2 The colloidal solution of the present invention was spray applied to the fabric, and the fabric was dried in an oven (hot air 190° C.) for 15 minutes. The reference samples consisted of an untreated sample and a sample treated with standard C6 fluorochemicals. During the test, which was carried out according to ISO 14419, five drops of 0.5 ml each of the different liquids were placed on the surface. The results were recorded after 10 seconds. The results are shown in Table 1 below.

[0014] [Table 1]

[0015] The visual results of the fluorine-free treatment of the present invention are shown in Figure 2. As can be seen, liquids 1-7, even those with surface tensions reduced to 20 mN / m, did not penetrate the fabric due to the oleophobic properties imparted by the treatment of the present invention. A photomicrograph of the surface facing fibers of a nonwoven fabric that has been treated with the fluorine-free invention is shown in Figure 3. A comparative photo of the same nonwoven fabric before treatment is shown in Figure 4. The comparison shows the result of nanoscale modified silica surface hierarchy on nonwoven textile fibers produced by the process of the present invention, i.e., the sol-gel method. This structure imparts a surface tension of about 20 mN / m, and thus is both hydrophobic and oleophobic.

Claims

1. 1. A method for producing a nonwoven textile having hydrophobic and oleophobic properties, comprising: Providing a nonwoven fabric comprising fibers; SiO 2 Nanoscale SiO formed from an aqueous precursor solution containing the product. 2 Providing an aqueous colloidal solution containing particles; applying a colloidal solution to the nonwoven fabric to form a hydrophobic and oleophobic finish on the fibers of the fabric, thereby imparting hydrophobic and oleophobic properties; The method comprising:

2. 2. The method of claim 1, wherein the fibers are carded fibers and the step of preparing a nonwoven fabric preferably comprises carding and depositing the carded web on a conveyor of a production line, and most preferably comprises cross-laying the carded web.

3. The method according to claim 1 or 2, wherein the fibres comprise from 50% to 100% by weight of synthetic fibres, preferably formed from polypropylene, polyethylene, polyethylene terephthalate, polyacrylate, polyacrylonitrile, polyamide or mixtures thereof.

4. SiO 2 4. The method according to any of claims 1 to 3, wherein the product is a silicon alkoxide, preferably selected from one or more of tetraalkoxysilanes, alkyltrialkoxysilanes, dialkyldialkoxysilanes, or any mixture thereof, preferably alkyltriethoxysilanes or aminopropyltriethoxysilanes.

5. The method according to any one of claims 1 to 4, wherein the solvent of the aqueous precursor solution is water or a mixture of alcohol and water.

6. The method according to any one of claims 1 to 5, wherein the aqueous precursor solution comprises a hydrolysis and condensation catalyst, preferably an acid.

7. The method according to any of the preceding claims, wherein the solids content in the colloidal solution is between 0.1 and 15% by weight, preferably between 1 and 7% by weight.

8. The method of any of claims 1 to 7, wherein the colloidal solution is applied to the surface of the nonwoven fabric by spraying, coating, or foaming, preferably via in-line foaming application.

9. The amount of colloidal solution applied to the nonwoven fabric is 0.1 g / m 2 ~5g / m 2 between 0.5 g / m 2 ~2g / m 2 The method according to any one of claims 1 to 8, wherein

10. Preferably, a nonwoven textile comprising a surface having hydrophobic and oleophobic properties produced by the method according to any one of claims 1 to 9, wherein the nonwoven textile comprises fibers, and a hydrophobic and oleophobic finish is present on the fibers of the textile, thereby imparting hydrophobic and oleophobic properties to the textile, and the finish is a continuous or discontinuous porous SiO2 layer of nanoscale thickness. 2 A nonwoven fabric comprising a containing layer.

11. The nonwoven textile of claim 10, wherein the layer has a thickness of from 10 to 300 nm, preferably from 50 to 250 nm, more preferably from 80 to 150 nm.

12. 12. The nonwoven textile according to claim 10 or 11, wherein the surface having hydrophobic and oleophobic properties has a surface free energy of 24 mN / m or less, preferably 22 mN / m or less.

13. porous SiO 2 The containing layer is SiO 2 , RSiO 1.5 , and / or R 2 The nonwoven textile of any one of claims 10-12, comprising structural elements from SiO, where R = H, alkyl, aryl, epoxy-alkyl, or aminoalkyl.

14. 14. Use of the nonwoven textile according to any one of claims 10 to 13 in an automotive application, preferably as a motor insulating element, a battery cover, a headliner or an underbody liner.

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