Method for preparing suede-like microfiber nonwoven fabric

Abstract

To provide a method for preparing a synthetic suede-like microfiber nonwoven fabric having a good touch feeling, elasticity, excellent yellowing-resistant property, and high durability without requiring use of an organic solvent and enabling a soft completed product to be obtained.SOLUTION: A method for preparing a microfiber nonwoven fabric includes: a) a step to prepare a two-component fibers of sea-island type in which a sea component is polymer capable of being removed in hot water or alkali aqueous solution; b) a step to prepare felt by needle-punching the two-component fibers of "sea-island" type; c) a step to impregnate the felt with an aqueous solution of polyvinyl alcohol (PVA) having at least 94% of saponification degree at high temperature; d) a step to obtain a microfiber intermediate product by removing the sea component from the felt; and the like.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a synthetic suede-like microfiber nonwoven fabric, which does not require the use of organic solvents and enables the production of a flexible finished product that has a good feel, is elastic, has excellent resistance to yellowing, high durability, and has the same appearance as products obtained using current solvent methods. [Background of the Invention] In the prior art, a method is known for preparing suede-like microfiber nonwovens obtained from so-called "island-in-the-sea" fibers. According to this technique, a two-component fiber is prepared, consisting of an "island" component completely surrounded by other "sea" components. The fiber is obtained by supplying two polymer components to a spinneret and finished using the methods of the prior art (see, for example, US3,692,423, US3,899,292, and US3,531,368). Generally, the resulting fiber is then used to prepare felt by needle punching, which is subjected to various impregnation steps in aqueous solutions and organic solvents to fix and / or remove various components. To prepare a nonwoven fabric having a suede appearance, the felt obtained by needle punching is generally subjected to initial impregnation with an aqueous solution of polyvinyl alcohol (PVA), followed by dissolution of the "sea" component in, for example, trichloroethylene. The resulting microfiber intermediate is then impregnated again with a polyurethane solution (PU) in an organic solvent (e.g., DMF). Finally, after one or more washes, the PVA is removed, and the resulting product is subjected to finishing processes, including a "splitting" step, followed by buffing and dyeing, respectively.

[0002] Prior art is known for a method of preparing nonwoven fabrics in which both impregnation steps are carried out in PU, both in aqueous solution and in organic solvent (see, for example, EP1353006).

[0003] Methods for preparing nonwoven fabrics are also known, including the formation of sea-island fibers followed by impregnation in PVA and PU without the use of organic solvents (see EP1243691 and EP2780501). While using water instead of conventional organic solvents (e.g., DMF and trichloroethylene) constitutes significant advantages from both a financial and environmental standpoint, and makes it possible to obtain finished products that maintain desirable texture and durability characteristics, there is still a need to find a method that enables the production of nonwoven fabrics that have excellent yellowing resistance, high durability, flexibility, elasticity, a good texture, the same appearance as products obtained using current solvent methods, and are environmentally friendly or have minimal environmental impact, and are achievable using low production costs.

[0004] Furthermore, the method known from EP1243691 involves the use of certain substances that may be harmful to health, such as boric acid. Moreover, variations in the method related to the partial solubility of PVA complexed with boric acid under the dissolution conditions of marine components may lead to a reduction in the overall efficiency of the method.

[0005] While Patent EP2780501 further discloses a method that overcomes the drawback of using boric acid to adjust the solubility of PVA in water, the disclosed method results in a product with a hard, cardboard-like texture due to the excessive adhesion between the polyurethane and microfibers that occurs after the application of polyurethane dispersed in water and subsequent solidification by the disclosed technique.

[0006] This is particularly related to the splitting operation after dyeing, which results in the nonwoven fabric having a hard, and especially unpleasant, texture at the cut edges, because the polyurethane cannot be removed from the cut edges before the dyeing process. Furthermore, the surface appearance of the finished product is not equivalent to that of products obtainable using current solvent methods, because the polyurethane adheres excessively to the microfibers on the surface, causing certain surface fibers to appear as macrofibers.

[0007] The applicant has now devised a method for preparing a microfiber nonwoven fabric that allows the use of water instead of an organic solvent, but unlike known water-based methods, provides a nonwoven fabric with superior resistance and feel, improved resistance to dyeing, and is free from defects caused by excessive adhesion between microfibers and polyurethane, such as noise, low resilience, a stiff, cardboard-like feel, and persistent cracking after rolling. Furthermore, the resulting product is elastic, highly durable, and resistant to yellowing; moreover, the surface appearance is identical to that of products obtained using current solvent methods. [Overview of the prefecture] In the first aspect, the present invention relates to a method for preparing a microfiber nonwoven fabric, a) A step of preparing island-sea type two-component fibers in which the marine component is a polymer that can be removed in warm water or an alkaline aqueous solution; b) A process of preparing felt by needle punching two-component fibers of the "sea island" type; c) A step of impregnating the felt with a high-temperature aqueous solution of polyvinyl alcohol (PVA) having a degree of saponification of at least 94%, which may be supplemented with water-soluble organic or inorganic salts; d) A step to remove marine components from the PVA-impregnated felt obtained in step c) by contacting it with a basic aqueous solution of alkali or alkaline earth hydroxide, thereby obtaining a microfiber intermediate product; e) A step of washing the microfiber intermediate product from step d) with neutral water containing a water-soluble organic or inorganic salt, or with acidic water, or with neutral water if the polyvinyl alcohol (PVA) aqueous solution from step c) has been supplemented with a water-soluble organic or inorganic salt; f) A step of cold impregnating the microfiber intermediate product described in step e) with polyurethane (PU) dispersed in water, which contains additives for adjusting viscosity and optionally water-soluble substances; g) A step of fixing the PU to the microfiber intermediate product by solidification of the PU dispersion and subsequent drying; h) a step of removing the PVA added in step c), the salts optionally added in step c) and / or e), and the additives added in step f); i) The process of cutting the material thus obtained, buffing one or both sides, and dyeing it. This includes methods.

[0008] The dyed nonwoven fabric thus obtained already possesses excellent sensory characteristics in terms of feel and drape, but the increased physical-mechanical resistance allows the nonwoven fabric to be subjected to subsequent processes in cold water (step l)) which, if necessary, involve drying and softening treatments or the addition of silicone agents as needed to give the product a more flexible feel.

[0009] The nonwoven fabric produced by the method of the present invention may be further buffed on the surface in contact with the blade (step m) if necessary, in order to increase or improve the contact surface so that the nonwoven fabric can be subjected to further post-processing, such as bonding to a fabric support, coating with resin and flame retardant treatment, and / or to further reduce the thickness of the dyed nonwoven fabric or to further soften the finished material.

[0010] In a further aspect, the present invention relates to a synthetic suede-like microfiber nonwoven fabric obtained (or obtainable) using the method of the present invention.

[0011] Further features and advantages of the present invention will be described below, also referring to the accompanying drawings.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 shows a cross-section of a microfiber intermediate product impregnated with a polyurethane formulation dispersed in water and then subjected to the removal of PVA (step h)); the polyurethane formulation contains a water-soluble polymer that can improve the adhesion of the polyurethane to the microfibers after being removed in step h) together with the PVA applied in step c). [Figure 2A] FIG. 2A shows the surface of a microfiber intermediate product impregnated with a polyurethane formulation dispersed in water and then with the PVA removed (step h)). [Figure 2B] FIG. 2B shows the surface of a microfiber intermediate product impregnated with a polyurethane formulation dispersed in water and then with the PVA removed (step h)); the surface of FIG. 2B is distinguished from the surface of FIG. 2A by the presence of salts added to the intermediate product in step e) (before the impregnation of the polyurethane) near two outer surfaces, which limits the amount of polyurethane present on the surface and thus makes it possible to promote the separation of the microfibers during the buffing and dyeing processes, resulting in a significantly improved appearance of the surface of the product. [Figure 3] FIG. 3 shows a microfiber intermediate product impregnated with a polyurethane formulation dispersed in water and with the PVA removed (step h)), which is different from the previous microfiber intermediate products by adding an additive that can cause artificial swelling during drying, swelling during preparation, and reducing the density of the polyurethane matrix. In this case, the particles are first swollen and then ruptured to create porosity inside the polyurethane matrix. [Figure 4A]Figure 4A shows a microfiber intermediate product obtained by impregnating a polyurethane compound dispersed in water and removing PVA (step h)), which differs from the preceding microfiber intermediate product due to the use of an additive that can generate gaseous decomposition products during the solidification / drying step (step g)). [Figure 4B] Figure 4B shows a microfiber intermediate product obtained by impregnating a polyurethane formulation dispersed in water, subjecting it to solidification in an aqueous solution of formic acid and subsequent drying (step g)), and then subjecting it to a step of removing PVA (step h)). Note the porous structure resulting from the solidification process in water containing formic acid, and from the limited adhesion between the polyurethane and microfibers, which ensures greater flexibility and elasticity in the final product. [Figure 5A] Figure 5A shows a microfiber intermediate product obtained by impregnating a polyurethane compound dispersed in water and directly subjecting it to solidification / drying (step g). [Figure 5B] Figure 5B shows a microfiber intermediate product impregnated with a polyurethane compound dispersed in water and subjected to a solidification / drying process (step g)) after pretreatment with an IR lamp. After removing PVA from the intermediate product (step h)), a higher polyurethane concentration is observed in the center of intermediate product 5B compared to intermediate product 5A; this results in a more free surface and an overall improvement in the appearance of the final product. [Figure 6] Figure 6 includes Table 1, which shows the impregnation weight ratio and subsequent treatment according to Example 1. [Figure 7] Figure 7 shows Table 2, which includes an evaluation of the prototype obtained by the present invention compared with prototypes prepared by Example 2.2 (Prototype B) and 1.1b (Prototype C) disclosed in Patent EP1323859 (Solvent Method, Prototype A) and Patent EP2780501. [Figure 8]Figure 8 shows a Martindale scale used to evaluate the appearance of a microporous product after an abrasion test using a Martindale abrasion tester. [Detailed Description of the Invention] In the method of the present invention, the preparation of felt in step b) is performed by needle punching of the “sea-island” type two-component fibers obtained in step a). Two-component fibers can be obtained by prior art techniques that allow two pure polymers or a mixture of two polymers, along with additives, to be fed into a spinneret such that one of two polymer components (the “sea”) completely surrounds the other component, which consists of various polymer filaments that form various “islands”.

[0013] The island component can be selected from modified polyester, cationic polyester, nylon or other types of polyamide, polyethylene (PE), polypropylene (PP), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyhydroxyalkanoate (PHA), polyethylene furanoate (PEF), polylactic acid (PLA), and polyethylene terephthalate (PET), the latter being particularly preferred. The aforementioned polymers can be produced from raw materials made from renewable sources (which completely or partially replace current fossil raw materials), or the polymers themselves may be produced by a fermentation process or by the use of microorganisms. Examples of polymers belonging to the first case are PTT, PEF, PET, and PLA, PE. An example of a polymer belonging to the second case is PHA.

[0014] Instead, examples of marine components are spun polymers, preferably selected from polyvinyl alcohol (PVA), polystyrene copolymers containing PVA (co-PVA-PS), styrene copolymers containing maleic anhydride or other organic monomers in the chain (co-PS), copolyesters containing PVA (co-PVA-PES), copolyolefins containing PVA, such as polyethylene or polypropylene (co-PVA-PE, co-PVA-PP, respectively), copolyesters containing a mixture of terephthalic acid + isophthalic acid + 5-sulfoisophthalic acid (HWS), and copolyesters containing both terephthalic acid and 5-sulfoisophthalic acid or their sodium salts (co-PES, which can also be abbreviated with the acronym TLAS), the latter of which is particularly preferred.

[0015] Both the sea component and the island component can be used as mixtures with additives selected from pigments for the island component and incompatible polymers for the sea component. Incompatible polymers (i.e., immiscible with the sea component) create heterogeneous systems with regions dispersed in a matrix of a second polymer where, at a microscopic level, only one of the polymers is present; generally, these systems are brittle and, when used to form the sea component, facilitate shell fracture during the processes of stretching, crimping, and the production of felt intermediates.

[0016] UV stabilizers and carbon black can be cited as pigments inserted into the island components, with carbon black being particularly preferred because it allows for the production of dyed materials in the gray / black and dark color range, reducing the amount of dye used in dyeing to obtain very high lightfastness, thus reducing the cost of the dyeing process. The UV-stabilizing properties of carbon are known to reduce the production cost of dyed materials by suppressing fading after exposure to UV and by reducing the amount of dye used, in conjunction with the reduction in the dye content used in the formulation. If it is not possible to use carbon black (to produce very light colors), using UV stabilizers still allows for increasing the lightfastness of colored materials. Dyes usually have a significant impact on the final cost of the product, especially when selected from materials with high lightfastness.

[0017] PVA added to co-PES and polyethylene glycol (PEG) added to co-PS can be cited as polymers that are incompatible with marine components.

[0018] In one particularly preferred embodiment, the felt of step b) is obtained by needle punching two-component fibers formed of PET and co-PES (with optionally added pigments in the island component and / or incompatible polymers in the sea component), and is cut into flocs about 51 mm in length.

[0019] The ratio of island components to sea components in a two-component fiber is designed to allow the two components to be spun quickly and efficiently by a spinneret. The island / sea ratio is preferably in the range of 20:80 to 80:20, more preferably in the range of 50:50 to 80:20. An island / sea ratio below 50:50 increases the amount of sea component removed, resulting in increased product costs and, in addition to the finished product having a poor appearance due to the lower fiber density on the surface, a clear loss of the physical / mechanical properties of the processed two-component fiber (the sea component is weaker). An island / sea ratio above 80:20 makes the spinning process difficult because the small amount of sea component does not allow for sufficient separation and retention of the microfibers within the two-component fiber.

[0020] Prior to the needle punching process, the two-component fibers are typically treated by methods known in the prior art, which involve adding a lubricant during the drawing process to improve the axial orientation of the polymers and, along with their physical / mechanical properties, reduce the fineness (titre) of the thus obtained fibers, a feature particularly required for producing high-quality products. In a preferred embodiment of the present invention, the fibers have a fineness of 5.5 to 19 dtex, preferably 7.5 to 15 dtex, before being drawn. Furthermore, the drawing is generally carried out at a ratio that varies within the range of 2 to 5, preferably 2.1 to 3.9. At the end of the drawing, the fibers are then cut to produce flocs having a length of 45 to 55 mm. After step b), a thickness of preferably 2 to 4 mm and 0.1 to 0.5 g / cm² are added. 3 It contains, more preferably 0.15 to 0.25 g / cm³ 3A felt having an apparent density is obtained. Advantageously, the density and thickness values ​​are optimal for obtaining a final nonwoven product with good feel, flexibility, elasticity, appearance, and mechanical resistance to process conditions. During the preparation of the felt, it is particularly important to avoid excessive orientation of the fibers following a preferred direction by subjecting the floc to alternating needle penetration on both sides of the felt being formed in the initial steps of the needle punching process, in order to prevent defects arising from cracks (cracks emphasized by rolling) on ​​the s-side obtained by cutting the product in step i).

[0021] Thus, the felt obtained after step b) is impregnated with a high-temperature PVA aqueous solution that is optionally dried and treated at high temperature, and has the characteristic of decreasing solubility under conditions to remove marine components.

[0022] High-temperature impregnation of felt with a PVA solution is carried out at a temperature of at least 50°C, preferably within the range of 60-99°C, to also obtain dimensional stabilization of the intermediate product by releasing the tension accumulated during the spinning, drawing, and felting processes. Dimensional stabilization also generally results in an increase in density, which in turn improves the aesthetic characteristics of the final product.

[0023] In one aspect of the method of the present invention, a water-soluble organic or inorganic salt is added to an aqueous solution of PVA before impregnation (step c)) in a salt / PVA weight ratio, preferably 0.1% to 20% by weight, and more preferably 5% to 12% by weight. Preferred salts are alkali metal salts, such as NaCl and KCl.

[0024] Alternatively, in a subsequent step (step e)), the PVA-impregnated microfiber intermediate product can be washed using a solution containing a water-soluble organic or inorganic salt.

[0025] The pure PVA or PVA with added salt used in step c) is characterized by having solubility in water or aqueous solution that is significantly lower than the solubility of the "sea" component of the two-component fiber under dissolution conditions.

[0026] For this purpose, the method of the present invention provides the use of PVA having a high degree of saponification, i.e., a degree of saponification of at least 94%, and more preferably more than 97%. The degree of saponification allows the PVA to be treated in such a manner that it becomes insoluble in the aquatic environment, so as to withstand the subsequent marine component removal treatment (step d)) without impairing its solubility in water in step h) of the method disclosed below. Advantageously, the use of PVA having the degree of saponification allows step c) to be carried out without the use of crosslinking agents, such as boric acid or vanadium or zirconium compounds, which may be harmful to health, as intended in the prior art.

[0027] The solubility of PVA can be controlled not only by using PVA with a high degree of saponification and the addition of salt, but also by high-temperature heat treatment (also known as thermosetting) or radiation performed at the end of step c) of PVA impregnation and subsequent drying. In particular, the PVA-impregnated felt is treated after drying, for example, by using an air jet oven or infrared radiation, at a temperature of at least 100°C, preferably within the range of about 140°C to about 250°C, for a time that can vary from less than 1 minute to about 15 minutes, depending on the temperature used, the required degree of solubility, the degree of saponification, and the salt content optionally added to the PVA.

[0028] This method makes it possible to stably fix PVA to the felt, and allows subsequent processes to remove the "sea" component to be carried out without substantially altering the PVA content and distribution in the material.

[0029] In this regard, step d) to remove the “sea” component is carried out by contacting the PVA-impregnated felt obtained in the preceding step c) with an alkali or alkaline earth hydroxide, preferably a basic aqueous solution of NaOH or KOH. The contact is preferably carried out by immersion (washing) of the PVA-impregnated felt in a selected basic aqueous solution, followed by repeated washing (step e)) with neutral water, which may or may not contain an organic or inorganic salt solution, or with acidic water to neutralize the solution and form the salt “in situ” in order to ensure the removal of any residue of the alkaline solution that may cause partial hydrolysis of the microfibers during the drying process and / or to precipitate salts near the surface of the microfibers and inside the PVA at concentrations useful for influencing the subsequent polyurethane impregnation process. Among the salts that can be used and obtained by neutralization in the washing process, alkali metals, such as NaCl and KCl, are particularly effective.

[0030] Alternatively, organic or inorganic salt solutions may already be present in the PVA because they are added in step c) of the method; therefore, after the step in a basic aqueous solution to remove marine components, the felt containing the PVA and salts is washed with a neutral aqueous solution.

[0031] The pH of the basic solution used to remove marine components is preferably in the range of 10 to 14. In one embodiment, the concentration of the basic solution is in the range of 0.1% to 48%, preferably 5% to 12%. A low concentration of the basic solution slows down the dissolution process; on the other hand, an excessively high concentration reduces the removal selectivity between marine components and microfibers and further induces precipitation of the marine component removal product in the basic extraction solution.

[0032] The removal of the "sea" component in step d) is carried out at a temperature and time selected to optimize the selective dissolution of this component, dissolving the minimum possible amount of applied PVA while simultaneously avoiding the breakdown of the microfibers of the "island" component. To obtain more effective removal and reduced time, the temperature of the basic solution is preferably at least 40°C, more preferably at least 60°C, and even more preferably in the range of 60°C to 80°C. In the literature, metal cations, such as Na, are used. + or K + and anions, for example, SO4 2- The presence of [unclear element] is known to interfere with the loss of PVA during the removal of marine components (an effect known by the term "salting out"). This also makes it possible to use basic solutions at temperatures above 60°C without significant PVA loss during the marine component removal process. Nevertheless, excessively high temperatures make it difficult to control the marine component removal process and reduce the removal selectivity between marine components and microfibers.

[0033] When co-PES is used as a marine component, the 5-sulfoisophthalic acid (SIPA) content in the polymer significantly affects the solubility of the polymer in the alkaline solution used for its removal. In particular, SIPA content below 8% by weight requires more aggressive co-PES dissolution conditions, such as higher sodium hydroxide concentration and / or higher process temperatures, for the same contact time with the alkaline solution. However, altering these parameters adversely affects the selectivity between the removal of the marine component and the breakdown of the polymer constituting the island, and may also cause the product to precipitate in the basic extraction solution (related to the concentration of sodium hydroxide solution in the solution). On the other hand, SIPA content above 12% reduces the crystallinity of the marine component and may result in the loss of some of the polymer during the production method, adversely affecting the physical / mechanical properties of the resulting two-component fiber. Therefore, the SIPA content present in co-PES should preferably be 8-12%, more preferably 9-11%.

[0034] Furthermore, the amount of SIPA needs to be balanced to allow the use of sodium or potassium hydroxide concentrations below approximately 12%, which is the limit beyond which phthalate oligomers produced after the hydrolysis process will precipitate.

[0035] To avoid excessive overheating of the two-component fibers, heat treatment or radiation processes after drying the PVA at high temperatures cannot be performed (unless minimal PVA loss is acceptable): high temperatures actually increase the crystallinity of the fibers due to the reorganization of the crystalline domains of the microfibers and their marine components. The advantages of less heating are increased flexibility of the microfibers and, consequently, the finished product, as well as increased ease of dissolution of the marine components.

[0036] By preventing an increase in the crystallinity of the marine components, the dissolution temperature of the basic solution is lowered to a value within the 35°C to 50°C range, thereby improving the hydrolysis selectivity.

[0037] The microfiber intermediate obtained by removing the marine components can be washed using cold or medium-temperature water (step e)). Cold water at temperatures below 40°C prevents even partial removal of PVA that occurs during the removal of residues of the basic solution; on the other hand, using medium-temperature water at temperatures between 40°C and 80°C allows for a further increase in the density of the microfiber intermediate, from which the marine components have already been removed, thus enabling the production of materials with particularly high densities and even better appearance, although on the other hand, loss due to PVA may occur.

[0038] A preferred embodiment of the present invention involves using a salt washing solution containing an alkali or alkaline earth metal salt (step e)), which, in addition to preventing the loss of PVA in water, leaves a layer of salt on the intermediate product, which then affects the adhesion and stability of the polyurethane used in the subsequent impregnation step f), particularly near the surface of the material, resulting in a dyed appearance that is particularly fine and similar to that of the current solvent method. These salts can thus be added to the washing solution or obtained by neutralization with a diluted solution of a strong or weak acid of residual sodium hydroxide or potassium, in which case a buffer system is created.

[0039] Water temperatures below 60°C allow for limiting PVA loss to less than 10% of the initial content or close to zero, provided that the PVA is sufficiently fixed in the preceding heat treatment stage.

[0040] The presence of salt near the surface allows for modification of the distribution of polyurethane applied in the subsequent step f), particularly by limiting its amount near the surface of the intermediate product.

[0041] Next, a microfiber intermediate product that does not contain "sea" components and may have salt present around the microfibers and in the PVA is subjected to the PU impregnation process f).

[0042] As is known, PU is a polymer having polymer chains formed by urethane bonds alone (i.e., -NH-(CO)-O-) or by a mixture of urethane and urea bonds (i.e., -NH-(CO)-NH-), and is prepared by the reaction of a polyol or a mixture of polyols with a diisocyanate. To promote the dispersion of the polymer in water, it may be useful to add an ionomer (a molecule containing an ionic group that binds to isocyanate, similar to polyols) to the chain. In the present invention, PU is preferably obtained by the reaction of an aliphatic or aromatic diisocyanate with a polyol having an average molecular weight in the range of 500 to 5000 Da, more preferably selected from polyethers, polyesters, polycarbonates, and polyester-polycarbonates. Polyols obtained from fatty acid dimerization processes or olefin polymerization can also be used, as these allow for the introduction of highly hydrophobic functional groups into the chain to increase the polyurethane's resistance to hydrolysis processes and to increase the total content of renewable source-derived raw materials present in the dyed material (methods for producing simple olefins by fermentation processes and subsequent unsaturation are already known). To increase mechanical and hydrolysis resistance, it is also possible to include polydimethylsiloxane in the reaction to obtain hybrid PUs. During the synthesis process, small amounts of trifunctional monomers of the aminosilane type can be added to the polyurethane chain or chain ends to increase the polymer's resistance to hydrolysis after application and crosslinking.

[0043] The aforementioned raw materials can be obtained by production methods that utilize first-generation renewable sources (food-derived), second-generation renewable resources (agricultural or industrial waste), or third-generation renewable resources (direct synthesis from CO2).

[0044] PU can exist in an aqueous environment, for example, in an emulsion or aqueous dispersion. Two-component polyurethanes are also available, which are reaction systems characterized by the separation of some of the reagents, which are mixed before application and then react in situ or activated by thermal or catalyst addition to produce the finished polymer directly into the microfiber intermediate to which they are applied. These systems usually do not contain solvents, yet still yield good impregnation results because their viscosity is low enough until the end of the reaction that it does not hinder their diffusion into the microfiber intermediate.

[0045] Instead of polyurethane, it is possible to use a mixture of polyurethane and other elastomeric polymers, such as silicone polymers, polyisoprene, polybutadiene and their copolymers, or styrene-butadiene and naturally occurring polymers (for example, natural rubber latex itself or vulcanized rubber latex, etc.).

[0046] Preferably, the concentration of the impregnation solution is 8-40%, more preferably 15-30%. A concentration above 30% can make the impregnation process difficult and limit the polyurethane content in the finished product, while a concentration below 8% can cause poor stability of the PU dispersion over time and significantly alter the structure of the solidified polyurethane and the type of adhesion between the polyurethane and microfibers to the extent that the resistance of the dyed intermediate product is impaired.

[0047] The impregnation of PU by step f) is typically carried out by dosing with immersion and press rollers or by prior art techniques (e.g., pressure waves). Preferably, the microfiber intermediate is impregnated with PU by dosing with immersion and press rollers.

[0048] Impregnation of PU in an aqueous environment can be suitably carried out by using a so-called self-emulsifying polyurethane polymer (containing only ionomers in the chain) and / or by adding a suitable external emulsifier, such as both ionic and nonionic surfactants. Preferably, the emulsifier is used at a concentration of 0.5 to 10% relative to the PU.

[0049] To obtain desirable mechanical properties and solvent resistance, the impregnation in step f) can be carried out in the presence of a crosslinking agent which can be activated during the PU drying process at a temperature of approximately 60°C to 200°C, preferably approximately 70°C to 160°C; the crosslinking time is generally less than 5 minutes at the aforementioned temperatures and generally tends to be completed within 24 hours thereafter.

[0050] The crosslinking agent is preferably used in an amount of 0.5 to 10%, and may be melamine, aziridine, epoxide, zirconium compound, carbodiimide, isocyanate derivative, or preferably a blocked isocyanate or polyisocyanate having a low deblocking temperature (a temperature at which a certain particularly stable group is released from the molecule, thus regenerating isocyanate groups that can react again with the present polyurethane chain). You can choose from the following. Carbodiimides and blocked isocyanates are particularly preferred because they allow for greater control of the process and longer stability times of the dispersion.

[0051] Impregnation with PU is carried out in the presence of viscosity-adjusting additives, which are thickening agents that increase the viscosity of the dispersion, thus allowing control of the migration of polyurethane along the thickness during the drying process. Dispersions with a viscosity below 200 mPa·s at 20°C will result in significant migration to the surface of the polyurethane, resulting in a change in the distribution of the polymer along the thickness; this leads to the presence of excessive polyurethane on the surface as well as defects, such as the appearance of speckling and fluffing (too much polyurethane on the surface makes buffing difficult by excessively adhering microfibers in contact with the abrasive paper, promoting their fatigue failure due to stress, i.e., a phenomenon also known as "nap cutting"), or irregularities (certain microfibers or clusters of microfibers on the surface wrapped in polyurethane withstand the mechanical action of the abrasive paper during the buffing process, producing locally larger and longer fibers, as shown in Figure 2A). Viscous dispersions with a viscosity exceeding 8000 mPa·s at 20°C hinder the migration of polyurethane during the polymer fixation step g), determining the formation of polyurethane residue remaining in the center of the impregnated intermediate. This accumulation of polyurethane on the inner surface (s-surface) that occurs after the splitting step can lead to the formation of a nonwoven fabric that is excessively hard and cardboard-like if the polymer layer is too dense. Thus, the dyed intermediate is particularly hard unless a further buffing step is performed after dyeing the manufactured material to remove some of the polyurethane found on the s-surface (the surface that occurs after splitting); however, this leads to an increase in the cost of the manufactured material due to the increased number of processes. Furthermore, excessively viscous Newtonian dispersions (viscosity exceeding 10000 mPa·s at 20°C) make the impregnation process difficult by hindering the penetration of the polymer throughout the entire thickness of the microfiber intermediate.

[0052] Therefore, viscosity control is a key parameter for obtaining a material that has a suitable distribution of polyurethane along its thickness, and thus a flexible, non-cardboard-like feel and a homogeneous appearance.

[0053] So-called polyurethane-associative thickeners (HEURs) are particularly effective additives for adjusting viscosity. They create polyurethane-thickener-associative structures that are difficult to migrate during the drying or solidification process and, after solidification, result in low-density polymer aggregates.

[0054] Alternatively, additives that increase the viscosity of the dispersion means (water) can also be used, thus making it difficult for the polyurethane to move through the microfiber support during the drying or solidification process. Additives such as acrylic acid derivatives (e.g., polyacrylate or urethane / acrylic resins), synthetic polymers such as PVA, compounds derived from natural polymers such as carboxymethylcellulose (CMC), and certain complex sugars such as xanthan gum belong to this category. Associative thickeners and acrylic thickeners, added as pure substances or mixtures, are particularly preferred.

[0055] Advantageously, when a non-Newtonian thickener is selected, it is also possible to use a PU emulsion or aqueous dispersion with higher viscosity (i.e., viscosity exceeding the set limit). The non-Newtonian thickener actually has the property of temporarily reducing the viscosity of the polyurethane emulsion or aqueous dispersion during the impregnation process carried out by the press roller. This temporary loss of viscosity occurs due to the large stress present in the press roller. At the end of impregnation and the associated stress, the viscosity of the polyurethane emulsion or aqueous dispersion increases again, effectively preventing migration to the surface of the polyurethane.

[0056] Polyurethane can also be colored with carbon black or other pigments to give the finished product a color that limits the perception of the polyurethane after dyeing.

[0057] A further unexpected aspect that makes the present invention particularly interesting is the presence of salts in the PVA on the fibers and in the intermediate product used to impregnate the polyurethane. When the polyurethane is close to areas of the intermediate product that are particularly rich in salts, the aqueous dispersion containing the polyurethane becomes unstable, and the polymer is unable to adhere effectively to the microfibers.

[0058] Furthermore, there is an even more pronounced effect reflected in the near-complete absence of polyurethane in PVA-rich areas (near the surface of the material). This detail allows the microfibers to be effectively freed during the buffing process, resulting in a product with a particularly fine and uniform appearance after dyeing, so that the resulting nonwoven fabric is very similar to nonwoven fabrics produced by current solvent-based methods (comparison between Figures 2A and 2B). The lower adhesion between the fibers and polyurethane is also reflected in increased flexibility of the dyed product compared to materials obtained by solvent-free methods in which no salts are present in the polyurethane or in the intermediate product subjected to polyurethane impregnation. However, if the adhesion is too low, the resulting product will not withstand the final dyeing process (typical dyeing techniques for polyester fibers) which subject the material to a combination of pressure, temperature, and mechanical stress.

[0059] In salt-treated intermediates, the lower adhesion of polyurethane, along with the formation of a more porous PUD structure due to salt loss in the washing process h) after the polyurethane is fixed, makes the intermediates more porous and elastic, resulting in a nonwoven fabric characterized by a superior appearance, a more flexible feel, and significantly improved elasticity and abrasion resistance.

[0060] Furthermore, the impregnation of PU can be carried out in the presence of further additives, preferably in an amount of 0-15%, more preferably 0-8%, relative to the PU, such as surfactants, destabilizers, other alkali metal salts or alkaline earth salts, acid generators that release protons when heated, such as diethylene glycol acetate or diethylene glycol formate, water repellents, plasticizers, wetting agents and dispersants, silicone compounds, and nanoparticles, nanofibers and nanotubes that are dispersible in water. An example of an alkaline earth salt is CaCl2, which is used to promote the destabilization of the polyurethane dispersion as the temperature rises (in the case of thermally solidifying PU).

[0061] In addition to the additives mentioned, water-soluble substances, such as PVA, or polymers similar to the marine components of microfibers but characterized by good solubility in hot water (e.g., hot water-soluble polymers and some co-PES), can also be added to the polyurethane. These are removed in a high-temperature removal step h) after low-temperature impregnation of the microfiber intermediate product by step f) of the method which is the object of the present invention, thus creating artificial porosity that improves the feel and flexibility of the product.

[0062] Another type of additive that can be added to polyurethane to create porosity in the polyurethane structure is expandable microspheres, such as Akzo Nobel products known as ExpanseL®: these are hollow particles of a dispersed polymer containing a low-boiling point liquid inside. During the drying and fixing process of the polyurethane following the impregnation process f), the expansion of the contained liquid causes these particles to swell, creating regions with a low polyurethane content. If heating proceeds until these hollow particles burst, microporosity is created that is related to the size of the hollow particles, the type of liquid contained within them, and the concentration of these particles in the PU dispersion.

[0063] A similar effect can also be obtained by adding a water-soluble substance, such as an unstable salt (e.g., NH4HCO3 or (NH4)2CO3), to the polyurethane compound dispersed in water used in the impregnation step f), which generates a large amount of gas that can create artificial porosity in the structure of the polyurethane to be dried when decomposed by heating at a temperature of 60-70°C, thus promoting the production of more flexible nonwoven fabrics.

[0064] Further types of polymers that can be added to PU to increase the porosity and flexibility of the final nonwoven fabric are polymers that are partially miscible with PU, allowing for the creation of a heterogeneous structure that can make the PU less dense and therefore more flexible. One example is a mixture of polyurethane and silicone polymers.

[0065] After the impregnation step f), the microfiber intermediate product is subjected to the PU fixing step g). Fixation can be carried out by high-temperature air solidification, hot water solidification, solidification in an aqueous solution of electrolyte, high-frequency solidification, microwave solidification, ultrasonic solidification, solidification by IR (infrared) radiation, or vapor solidification. Preferably, air solidification is performed to obtain thermal fixation of the PU, or solidification can be achieved in an aqueous solution containing a salt (e.g., alkali and alkaline earth metal salts, etc.) or an acid that destabilizes the dispersion (e.g., organic acids such as formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, or inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, etc.).

[0066] In the case of high-temperature air solidification, in order to better control the movement of polyurethane during heating, the material obtained after step f) is brought into contact with air at a temperature in the range of about 50°C to about 200°C, preferably in the range of about 50°C to 160°C; the duration of heating can be varied, for example, depending on the type of polyurethane used, for the reason that when using thermally solidifying polyurethane, it is possible to limit the heating of the impregnated intermediate product, avoid complete drying, and thus reduce the amount of energy required to evaporate the present water. Preferably, the PU is solidified on the microfiber intermediate product in an oven, preferably a pin oven, at a rising temperature in the range of 50°C to 160°C. The temperature gradient prevents the water from evaporating so quickly that the solid portion of the dispersion also moves to the surface before it receives enough heat to break down the present surfactant that stabilizes the PU.

[0067] The high-temperature air solidification method disclosed herein advantageously allows for the acquisition of finished products with superior resistance and durability. Furthermore, using high-temperature air solidification, the PU tends to become transparent, thus making the speckling phenomenon less noticeable.

[0068] In the case of solidification in an aqueous solution containing dissolved electrolytes (salts and acids), it is possible to obtain polyurethane solidification at low temperatures (i.e., at temperatures not exceeding 70°C), significantly reducing energy consumption.

[0069] In this case, the impregnated intermediate product obtained after step f) is brought into contact, preferably by immersion, with water at a temperature of about 20°C to 90°C, preferably about 40°C to 80°C, which contains a certain amount of PU dispersion destabilizer (electrolyte) that allows the temperature at which the PU begins to solidify (also defined by the term "cloud point") to be lowered.

[0070] Examples of destabilizing agents include calcium and magnesium halides and sulfates, preferably CaCl2 and MgSO4. The selected agent can be used in amounts of 0.01% to 5% by weight, more preferably 0.1% to 1%. Hot water coagulation is particularly suitable when improvement of the flexibility of the final product is desired.

[0071] Another example of an destabilizer is an acid added to the coagulation solution that causes the protonation of anionic groups present in the polyurethane chain (introduced during synthesis by adding ionomers along with polyols and isocyanates). Such acids can be selected from, for example, organic acids such as formic acid, acetic acid, oxalic acid, maleic acid, or inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid.

[0072] Furthermore, in a preferred embodiment of the present invention, a thickener that can increase the viscosity of the formulation in order to minimize the movement of polyurethane during the solidification process and / or the loss of polyurethane in the solidification tank is also added to the PU-containing formulation. Preferably, the thickener is of the association type, i.e., it associates with PU already present in the form of micelles in the aqueous dispersion, and in this manner can produce a more complex dispersion structure in which the micelles aggregate together. The operation of these association systems is well known to those skilled in the art. Another type of particularly effective thickener is polyacrylate thickener, which not only increases the viscosity of the formulation but also induces a change in the structure of the solidified polyurethane, forming an irregular and partially porous surface. A mixture of these two types of thickeners is also particularly effective in order to act simultaneously on both dispersion steps (water and polyurethane).

[0073] In the case of high-temperature air solidification, it is preferable to use association-type polyurethane thickeners, because acrylic-type thickeners generally impart stiffness to the polyurethane to which they are added.

[0074] The intermediate product is subjected to a crosslinking treatment of the polyurethane after the polyurethane has solidified and before finishing, by activating the crosslinking agent present in the impregnation formulation. The crosslinking treatment generally consists of heating the material to a temperature high enough to induce the crosslinking process and / or release the blocked isocyanate optionally added to the impregnation formulation (step f)) and bond the polyurethane molecules together, thereby increasing its resistance to the subsequent dyeing process (step i)).

[0075] The crosslinking process can also be activated or aided by using ultraviolet light, if the crosslinking agent or other additives absorb UV radiation and can induce the process.

[0076] Prior to the fixing process in step g), the polyurethane dispersion may be rapidly preheated by radiation using an IR lamp or high-frequency or microwave radiation, thereby promoting its fixing in the innermost layer away from the surface. Of these pretreatments, the IR lamp process is particularly preferred because this type of radiation acts from the surface to the entire polyurethane, controlling its movement along the thickness. The effect of using an IR lamp on the impregnation and solidification processes is equivalent to the results obtained by adding salt (step e)) before polyurethane impregnation.

[0077] Selecting a suitable IR wavelength allows for regulating the effect on polyurethane coagulation by acting broadly on the surface or affecting the entire dispersion.

[0078] Subsequently, the intermediate product containing PVA and polyurethane is treated with hot water at a temperature of 80-99°C to remove PVA and other additives that may have been added earlier (step h).

[0079] At the end of the operations of PU impregnation and coagulation and PVA removal disclosed above, the obtained material is subjected to finishing step i) to obtain the suede-like nonwoven fabric of the present invention. In particular, the material is subjected to splitting (cutting), buffing and dyeing operations, which are preferably carried out in the disclosed order.

[0080] The dyed intermediate product thus produced, containing an ionomer polyurethane having ionic groups in its chain, can also be subjected to a second dyeing cycle with specific dyes, such as cationic, anionic, sulfur-based, vat, or reactive dyes, thereby obtaining dyeing of the polyurethane elastomer matrix.

[0081] Polyester microfibers are generally dyed using disperse dyes, as described in the literature and known to those skilled in the art, and dispersing and uniforming agents, to name a few of the main additives present, by subjecting the product to a bath at a temperature of 120°C to 130°C under pressure in an acidic environment where the pH is adjusted by adding a buffer solution, such as acetic acid / sodium acetate.

[0082] The methods disclosed in this invention also allow the dyeing process to be carried out using higher pH values ​​(neutral or alkaline environments) without affecting the physical / mechanical and aesthetic properties of the final product; some polyurethane formulations also allow for improved characteristics of the disclosed properties when the dyeing is carried out in a basic environment. For this reason, in a preferred embodiment, the dyeing process is carried out in a basic environment having a pH of 8-11 (measured at ambient temperature), obtained by adding a sodium salt of a suitable concentration of a weak acid (e.g., acetic acid, citric acid, or carbonic acid) or by using a suitable buffer system for better process control (e.g., an amino acid-based buffer).

[0083] If necessary, especially to produce flexible materials, a further buffing process may be performed on the opposite side (s-side) of the already buffed surface, following the dyeing process, to remove a portion of the polyurethane from the unseen side of the product, resulting in a lighter, more flexible, and thinner finished product. Alternatively, if it is undesirable to alter the appearance and characteristics of the final material by acting on the s-side, the resulting product may be subjected to a softening treatment by a suitable machine, using forced ventilation with bayonet technology to vary the amount of air intake on the product during processing, and subjecting the product to mechanical stress inside a softening chamber; these machines determine the further softening of the material without impairing the dyeing characteristics (color fastness), aesthetic characteristics (surface appearance), or physical-mechanical characteristics obtained using the production method of the present invention. In addition, if required, the softening treatment may be carried out by providing an impregnation process with additives or softeners, such as silicone, which can achieve a plasticizing effect related to polyurethane, for example, to adjust the adhesion between the polyurethane and microfibers or simply to change the feel of the product surface (the slippery effect of the product surface).

[0084] Subsequently, the material produced by the described method can be subjected to further post-processing steps, such as bonding to a fabric support, resin coating and flame retardant treatment, application of a permanent or concealing foam, embossing, inkjet printing, electrowelding and laser engraving, in addition to further cutting operations to further reduce the thickness of the dyed product, with one or the other side being subject to these processes. Using products produced according to the present invention, the softening treatment can be performed even after post-processing steps following dyeing, without adversely affecting the product's physical / mechanical properties and appearance.

[0085] Finally, in further aspects, the present invention relates to synthetic suede-like nonwoven fabrics obtained (or obtainable) using the method of the present invention. Advantageously, nonwoven fabrics obtainable using the method of the present invention exhibit remarkable resistance to yellowing, a good feel, and great durability, and as a result, are particularly suitable for dyeing with light-colored dyes, such as white. Furthermore, the finishing operations carried out as disclosed above enable the method of the present invention to obtain a final nonwoven fabric that may have a thickness of less than 0.7 mm, yet still ensure interesting physical / mechanical properties without the support of a structural fabric, thus making the method highly versatile and usable in a variety of practical applications.

[0086] Furthermore, by using polyurethane having ionic groups in its chains, the nonwoven fabrics obtainable using the method of the present invention can also be dyed in a polyurethane elastomer matrix. Adding salt to the microfiber intermediate before impregnation with polyurethane dispersed in water, as well as pretreatment performed by an IR lamp after the solidification process in aqueous solution or after the polyurethane impregnation process and before subsequent drying in the solidification process with high-temperature air, minimizes the amount of polyurethane bonded to the microfibers near the surface, allowing for better control of adhesion throughout the entire thickness of the material, and enabling the production of particularly flexible nonwoven fabrics with high abrasion resistance, having an appearance identical in all respects and for all purposes to products obtained by today's solvent methods.

[0087] Pretreatment with an IR lamp also provides greater abrasion resistance to the final product, allowing it to have a lower polyurethane content.

[0088] The energy required for drying can be entirely supplied by IR radiation, high frequency, microwaves, or a combination thereof, as is the case with intermediate products of low thickness, where the crosslinking agent can be activated by IR radiation.

[0089] The disclosed final softening treatment also makes it possible to obtain products that are equivalent to the main materials that can be obtained today by conventional solvent manufacturing methods.

[0090] The present invention will now be disclosed in the following experimental section, but this is not intended to limit its scope.

[0091] Example 0 PVA-reinforced felt In the family of Example 0, an intermediate product formed by microfibers and PVA is produced, indicated as "Dn," where n is a sequential number. In some cases, salts may be present.

[0092] Example 0.1 Flocs are prepared from a two-component "sea-island" type fiber, where the island component is made of PET and the sea component is made of co-PES. The ratio of island component to sea component in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0093] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree: approximately 4 cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a volume of 0.212 g / cm³. 3 Density and 599 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0094] This felt is dimensionally shrunk by immersing it in an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, drying it in a first oven, and then treating it in a second oven at 190°C for 3 minutes, which is sufficient time to allow the thermal curing of the PVA, as indicated by the amber coloration of the PVA itself.

[0095] The subsequent process of removing the sea component from the fiber consists of the following two processes, followed by convective drying: alkaline treatment with 8 wt% caustic soda at 65 °C, and low-temperature washing in water sufficient to return the pH to a value below 8. The test specimens thus strengthened contain 28 wt% PVA and are identified as "intermediate product D1".

[0096] Example 0.2 Flock is produced from a "sea-island" type two-component fiber where the island component consists of bio-PET and the sea component consists of bio-coPES.

[0097] Bio-PET was produced by polycondensation of terephthalic acid and ethylene glycol, both obtained from raw materials resulting from a fermentation process and subsequent conversion. In this polymer, the percentage of materials from renewable sources is 100% (measured according to standard ASTM-D6866-08 14 > 95% with respect to the C content).

[0098] Bio-coPES was produced by polycondensation of 5-sulfoisophthalic acid and terephthalic acid synthesized from fossil raw materials and ethylene glycol obtained by fermentation. In this polymer, the percentage of materials from renewable sources is 35% (measured according to standard ASTM-D6866-08 14 equal to 20% with respect to the C content).

[0099] The ratio of the island component to the sea component in the fiber is 57:43. The cross-section of the fiber shows 16 PET microfilaments of circular shape and equal diameter. The flock is obtained by subsequent drawing, crimping and cutting of continuous island-sea fibers.

[0100] The characteristics of the flock are as follows. Denier 4.3 dtex. Length 51 mm Crimp degree about 4 / cm Drawing ratio 2.5:1 The flock thus defined is subjected to mechanical needle punching to 0.202 g / cm3 Density and 603 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0101] This felt is dimensionally shrunk by immersing it in an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, drying it in a first oven, and then treating it in a second oven at 190°C for 3 minutes, which is sufficient time to allow the thermal curing of the PVA, as indicated by the amber coloration of the PVA itself.

[0102] The subsequent process for removing marine components from the fibers consists of two steps followed by convection drying: alkaline treatment with 8% by weight of caustic soda at 65°C, and low-temperature washing in water sufficient to return the pH to below 8. The thus reinforced test specimens contain 27% by weight of PVA and are identified as "Intermediate Product D2".

[0103] Example 0.3 Intermediate product D1 is immersed in a 1% NaCl solution, squeezed with a pair of rollers to douse it with a salt solution, and then dried again in a convection oven. The resulting test specimen contains 23% by weight of PVA and 14% by weight of NaCl and is identified as "Intermediate product D3".

[0104] Example 0.4 Flocs are produced from a two-component fiber of the "sea island" type, where the island component is made of PET and the sea component is made of co-PES.

[0105] In the extrusion process, the PET is supplemented with a masterbatch containing 30% by weight of carbon black (CB) in the PET matrix; thus, the carbon black is dispersed in the PET filament at 1% by weight.

[0106] The ratio of island components to sea components in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0107] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a yield of 0.197 g / cm³. 3 Density and 596 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0108] This felt is dimensionally shrunk by immersing it in an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, then dried in a first oven, and subsequently treated in a second oven at 190°C for 3 minutes.

[0109] The subsequent process for removing marine components from the fibers consists of two steps followed by convection drying: alkaline treatment with 8% by weight of caustic soda at 65°C, and low-temperature washing in water sufficient to return the pH to below 8. The thus reinforced test specimens contain 28% by weight of PVA and are identified as "Intermediate Product D4".

[0110] Example 0.5 Flocs are prepared from a two-component "sea-island" type fiber, where the island component is made of PET and the sea component is made of co-PES. The ratio of island component to sea component in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0111] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a volume of 0.202 g / cm³. 3 Density and 603 g / m³ 2A felt having a unit weight of [weight] is produced.

[0112] This felt is sized up by immersing it in an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, and then dried in an oven.

[0113] The subsequent process for removing marine components from the fibers consists of two steps followed by convection drying: alkaline treatment with 8 wt / wt% caustic soda at 45°C, and low-temperature washing in water sufficient to return the pH to below 8. The thus reinforced test specimens contain 24 wt% PVA and are identified as “Intermediate Product D5”.

[0114] Example 0.6 Flocs are prepared from a two-component "sea-island" type fiber, where the island component is made of PET and the sea component is made of co-PES. The ratio of island component to sea component in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0115] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a volume of 0.202 g / cm³. 3 Density and 603 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0116] This felt is dimensionally shrunk by passing it through an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, drying it in an oven, and then immediately afterward, it is subjected to IR radiation for 1 minute, with the intensity of the IR lamp adjusted so that the surface temperature of the intermediate product is maintained at 200°C. Under these conditions, the browning of the intermediate product is far less than that of the same intermediate product in Example 0.1 and is almost imperceptible.

[0117] The subsequent process for removing marine components from the fibers consists of two steps followed by convection drying: alkaline treatment with 8% by weight of caustic soda at 65°C, and low-temperature washing in water sufficient to return the pH to below 8. The thus reinforced test specimens contain 28% by weight of PVA and are identified as "Intermediate Product D6".

[0118] Example 0.7 Flocs are created from two-component fibers of the "sea island" type, where the island component is made of bio-PET and the sea component is made of fossil-derived co-PES.

[0119] Bio-PET was prepared by polycondensation of fossil-derived terephthalic acid with ethylene glycol obtained by fermentation. In this polymer, the percentage of materials derived from renewable sources was 30% (measured according to standard ASTM-D6866-08). 14 The carbon content is 20%.

[0120] The ratio of island components to sea components in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0121] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a volume of 0.222 g / cm³. 3 Density and 624 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0122] This felt is sized up by immersing it in an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, and then dried in an oven.

[0123] The subsequent process for removing marine components from the fibers consists of the following two steps and subsequent convection drying: alkaline treatment with 8 wt / wt% caustic soda at 45°C, and low-temperature washing in a 1.0% NaCl salt solution.

[0124] The resulting test specimen contains 23% by weight of PVA and 8% by weight of NaCl, and is identified as "Intermediate Product D7".

[0125] Example 0.8 Flocs are produced from a two-component fiber of the "sea island" type, where the island component is made of PET and the sea component is made of co-PES.

[0126] In the extrusion process, a masterbatch containing 30% by weight of carbon black (CB) in the PET matrix is ​​added to the PET; thus, the carbon black is dispersed in the PET filament at a concentration of 1% by weight.

[0127] The ratio of island components to sea components in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0128] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a volume of 0.189 g / cm³. 3 Density and 592 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0129] This felt is sized up by immersing it in an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, and then dried in an oven.

[0130] The subsequent process for removing marine components from the fibers consists of the following two steps and subsequent convection drying: alkaline treatment with 8 wt / wt% caustic soda at 45°C, and cold washing in an acidic pH solution buffered with acetate buffer.

[0131] The resulting test specimen contains 23% by weight of PVA and 12% by weight of sodium acetate, and is identified as "Intermediate Product D8".

[0132] Example 0.9 Flocs are produced from a two-component fiber of the "sea island" type, where the island component is made of PET and the sea component is made of bio-coPES.

[0133] Bio-coPES was prepared by polycondensation of 5-sulfoisophthalic acid and terephthalic acid, synthesized from fossil fuels, with ethylene glycol obtained by fermentation. In this polymer, the percentage of renewable source materials was 35% (measured according to standard ASTM-D6866-08). 14 (The C content is equal to 20%).

[0134] The ratio of island components to sea components in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0135] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching to produce 0.200 g / cm³. 3 Density and 600g / m³ 2 A felt having a unit weight of [weight] is produced.

[0136] This felt is dimensionally shrunk by passing it through an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, drying it in an oven, and then immediately afterward, it is subjected to IR radiation for 1 minute, with the intensity of the IR lamp adjusted so that the surface temperature of the intermediate product is maintained at 190°C. Under these conditions, the browning of the intermediate product is far less than that of the same intermediate product in Example 0.1 and is almost imperceptible.

[0137] The subsequent process for removing marine components from the fibers consists of two steps followed by convection drying: alkaline treatment with 8% by weight of caustic soda at 65°C, and low-temperature washing in water sufficient to return the pH to below 8. The thus reinforced test specimens contain 28% by weight of PVA and are identified as "Intermediate Product D9".

[0138] Example 0.10 Flocs are created from two-component fibers of the "sea island" type, where the island component is made of bio-PET and the sea component is made of fossil-derived co-PES.

[0139] Bio-PET was prepared by polycondensation of fossil-derived terephthalic acid with ethylene glycol obtained by fermentation. In this polymer, the percentage of materials derived from renewable sources was 30% (measured according to standard ASTM-D6866-08). 14 The carbon content is 20%.

[0140] The ratio of island components to sea components in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0141] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a yield of 0.198 g / cm³.3 Density and 609 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0142] This felt is dimensionally shrunk by passing it through an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, dried in a first oven, and then immediately subjected to IR radiation for 1 minute, with the intensity of the IR lamp adjusted so that the surface temperature of the intermediate product is maintained at 200°C. Under these conditions, the browning of the intermediate product is far less than that of the same intermediate product in Example 0.1 and is almost imperceptible.

[0143] The subsequent process for removing marine components from the fibers consists of two steps followed by convection drying: alkaline treatment with 8 wt / wt% caustic soda at 45°C, and low-temperature washing in water sufficient to return the pH to below 8. The thus reinforced test specimens contain 23 wt% PVA and are identified as "Intermediate Product D10".

[0144] Example 0.11 Flocs are created from two-component fibers of the "sea island" type, where the island component is made of bio-PET and the sea component is made of fossil-derived co-PES.

[0145] Bio-PET was prepared by polycondensation of fossil-derived terephthalic acid with ethylene glycol obtained by fermentation. In this polymer, the percentage of materials derived from renewable sources was 30% (measured according to standard ASTM-D6866-08). 14 The carbon content is 20%.

[0146] The ratio of island components to sea components in the fiber is 57:43. The cross-section of the fiber shows 16 circular PET microfilaments of equal diameter. Flocs are obtained by subsequent stretching, crimping, and cutting of continuous island-sea fibers.

[0147] The characteristics of flock are as follows: 4.3 dtex denier. Length: 51mm Curl degree approximately 4cm Stretch ratio 2.5:1 The flocs thus defined are subjected to mechanical needle punching, resulting in a volume of 0.202 g / cm³. 3 Density and 611 g / m³ 2 A felt having a unit weight of [weight] is produced.

[0148] This felt is dimensionally shrunk by immersing it in an 85°C solution containing 11.6% PVA with a high saponification value (98%) for 5 minutes, drying it in a first oven, and then treating it in a second oven at 190°C for 3 minutes, which is sufficient time to allow the thermal curing of the PVA, as indicated by the amber coloration of the PVA itself.

[0149] The subsequent process for removing marine components from the fibers consists of two steps followed by convection drying: alkaline treatment with 8% by weight of caustic soda at 65°C, and low-temperature washing in water sufficient to return the pH to below 8. The thus reinforced test specimens contain 28% by weight of PVA and are identified as "Intermediate Product D11".

[0150] Example 1 impregnation The intermediate product prepared in Example 0 was impregnated with an aqueous dispersion containing a polyurethane emulsion and other additives, such as crosslinking agents, thickeners, salts, and various fillers, in the weight ratios shown in Table 1.

[0151] Specifically, the products used to prepare the aqueous dispersion are as follows: Polyurethane 1: Aliphatic PUD, anionic, polyether / polycarbonate type. Water content 39%. Polyurethane 2: Type 1 bio-PUD (aliphatic PUD, anionic, polyether / polycarbonate type), its polycarbonate fraction is 22% renewable source (measured according to standard ASTM-D6866-08) 14 Contains C content. Moisture content: 41%. Polyurethane 3: Aliphatic PUD, anionic, polyether-based. Water content 40%. Polyurethane 4: Aliphatic bio-PUD, anionic, polyester-based, 45% of its carbon is from renewable sources (measured according to standard ASTM-D6866-08) 14 (Regarding the C content) The moisture content is 56%. Polyurethane 5: Aliphatic PUD, anionic, polycarbonate-based. Water content 40%. A crosslinking agent 1: a blocked aliphatic polyisocyanate dispersed in water, having a deblocking temperature from 120°C and a water content of 55%. A crosslinking agent 2: a polyfunctional polycarbodiimide dispersed in water with a water content of 61%. Thickener 1: Polyurethane-type associative thickener, its active ingredient equals 20% of its weight (33% dry residue). Thickening agent 2: A carboxymethylcellulose-type polymer thickening agent in powder form. Thickening agent 3: Rheological modifier for xanthan gum in powder form. Thickening agent 4: An acrylic thickening agent having 10% by weight of its active ingredient. Filler 1: A polyvinyl alcohol solution with a low shear stress value and a viscosity of <100 cPs at 20°C. Filler 2: co-PES aqueous dispersion solution. Filler 3: Ammonium bicarbonate solution. Filler 4: Hydrophilic emulsion of modified polysiloxane, self-emulsifying type.

[0152] Downstream of the impregnation with the selected formulation, the wet intermediate product is dried and then heated to 150°C using the techniques disclosed in Table 1.

[0153] Next, each test specimen is subjected to washing and drying in hot water, thereby producing the nth intermediate product, identified as "Intermediate Product IEn," where "n" is the number shown in Table 1. The wastewater generated during the washing process contains PVA that can be processed for recovery.

[0154] Example 1.01 To achieve a viscosity of 600 mPa·s at 20°C under the applicable conditions, an aqueous dispersion is prepared containing a mixture of pure polyurethanes of types 2 and 3, a crosslinking agent of type 1, and a thickening agent of type 1 in a 3:1 ratio.

[0155] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0156] Next, the test specimens are washed at atmospheric pressure with soft water (without alkaline earth salts) at a temperature near its boiling point to remove PVA, and then dried again.

[0157] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE1," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0158] Example 1.02 To achieve a viscosity of 450 mPa·s at 20°C under the applicable conditions, an aqueous dispersion is prepared containing a mixture of type 1 and type 3 polyurethanes, a type 1 crosslinking agent, and a type 1 filler in a 3:1 ratio.

[0159] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, subjected to a pretreatment process using infrared radiation in the range of 2 to 10 microns, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0160] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove the PVA, with the help of a PVA dispersant described in the prior art, and then dried again.

[0161] This intermediate product contains 32% polyurethane, is identified as "Intermediate Product IE2," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0162] Example 1.03 To achieve a viscosity of 662 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, a type 3 thickener, and a type 1 filler is prepared.

[0163] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0164] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0165] This intermediate product contains 25% polyurethane, is identified as "Intermediate Product IE3," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0166] Example 1.04 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0167] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, subjected to a pretreatment process using infrared radiation in the range of 2 to 10 microns, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0168] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0169] This intermediate product contains 25% polyurethane, is identified as "Intermediate Product IE4," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0170] Example 1.05 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, a type 1 thickener, and a type 2 filler is prepared.

[0171] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, subjected to a pretreatment process using infrared radiation in the range of 2 to 10 microns, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0172] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0173] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE5," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0174] Example 1.06 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0175] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, subjected to a high-frequency pretreatment process (50 seconds in an oven with a parallel electric field to which a voltage of 0.5KV is applied) until half of the water content is removed, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0176] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0177] This intermediate product contains 34% polyurethane, is identified as "Intermediate Product IE6," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0178] Example 1.07 To achieve a viscosity of 499 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 3 polyurethane, a type 2 crosslinking agent, and a type 1 thickener is prepared.

[0179] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0180] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0181] This intermediate product contains 28% polyurethane, is identified as "Intermediate Product IE7," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0182] Example 1.08 To achieve a viscosity of 790 mPa·s at 20°C under the applicable conditions, an aqueous dispersion is prepared containing a mixture of pure polyurethanes of types 1 and 3 in a 3:1 ratio, a crosslinking agent of type 1, and a thickening agent of type 2.

[0183] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0184] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0185] This intermediate product contains 32% polyurethane, is identified as "Intermediate Product IE8," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0186] Example 1.09 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 2 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0187] The previously defined intermediate product D2 is impregnated with twice its weight of this dispersion by dipping, subjected to a pretreatment process using infrared radiation in the range of 2 to 10 microns, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0188] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0189] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE9," and, after subsequent mechanical splitting and buffing, is subjected to a dyeing process at pH 9.4 with the addition of sodium acetate.

[0190] Example 1.10 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 2 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0191] The previously defined intermediate product D2 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0192] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0193] This intermediate product contains 32% polyurethane, is identified as "Intermediate Product IE10," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0194] Example 1.11 To achieve a viscosity of 600 mPa·s at 20°C under the applicable conditions, an aqueous dispersion is prepared containing a mixture of pure polyurethanes of types 2 and 3, a crosslinking agent of type 1, and a thickening agent of type 1 in a 3:1 ratio.

[0195] The previously defined intermediate product D3 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0196] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0197] This intermediate product contains 32% polyurethane, is identified as "Intermediate Product IE11," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0198] Example 1.12 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0199] The previously defined intermediate product D4 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0200] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0201] This intermediate product contains 32% polyurethane, is identified as "Intermediate Product IE12," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0202] Example 1.13 To achieve a viscosity of 555 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, a type 1 thickener, and a type 3 filler is prepared.

[0203] The previously defined intermediate product D4 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven at a low temperature (60°C to 75°C during oven time) first to thermally break down the ammonium salt, and then at a higher temperature to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0204] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0205] This intermediate product contains 34% polyurethane, is identified as "Intermediate Product IE13," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0206] The addition of Type 3 additives results in a polyurethane structure that is not entirely homogeneous, which leaves the microfibers partially free, as can be seen in the SEM image in Figure 4A.

[0207] Example 1.14 To achieve a viscosity of 450 mPa·s at 20°C under the applicable conditions, an aqueous dispersion is prepared containing a mixture of type 1 and type 3 polyurethanes, a type 1 crosslinking agent, and a type 1 filler in a 4:1 ratio.

[0208] The previously defined intermediate product D5 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0209] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove the PVA, with the help of a PVA dispersant described in the prior art, and then dried again.

[0210] This intermediate product contains 32% polyurethane, is identified as "Intermediate Product IE14," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0211] Example 1.15 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0212] The previously defined intermediate product D5 is impregnated with twice its weight of this dispersion by dipping, subjected to a pretreatment process using infrared radiation in the range of 2 to 10 microns, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0213] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0214] This intermediate product contains 34% polyurethane, is identified as "Intermediate Product IE15," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0215] Example 1.16 To achieve a viscosity of 775 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 4 polyurethane, a type 2 crosslinking agent, and a type 1 thickener is prepared.

[0216] The previously defined intermediate product D5 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0217] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0218] This intermediate product contains 30% polyurethane, is identified as "Intermediate Product IE16," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0219] Example 1.17 To achieve a viscosity of 450 mPa·s at 20°C under the applicable conditions, an aqueous dispersion is prepared containing a mixture of type 1 and type 3 polyurethanes, a type 1 crosslinking agent, and a type 1 filler in a 4:1 ratio.

[0220] The previously defined intermediate product D6 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0221] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove the PVA, with the help of a PVA dispersant described in the prior art, and then dried again.

[0222] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE17," and, after subsequent splitting and buffing, is subjected to a dyeing process at pH 9.4 with the addition of sodium acetate.

[0223] Example 1.18 To achieve a viscosity of 354 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 3 polyurethane, a type 1 crosslinking agent, a type 1 thickener, and a type 4 filler is prepared.

[0224] The previously defined intermediate product D6 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0225] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0226] This intermediate product contains 29% polyurethane, is identified as "Intermediate Product IE18," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0227] Example 1.19 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0228] The previously defined intermediate product D7 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0229] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0230] This intermediate product contains 35% polyurethane, is identified as "Intermediate Product IE19," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0231] Example 1.20 To achieve a viscosity of 450 mPa·s at 20°C under the applicable conditions, an aqueous dispersion is prepared containing a mixture of type 1 and type 3 polyurethanes, a type 1 crosslinking agent, and a type 1 filler in a 4:1 ratio.

[0232] The previously defined intermediate product D8 is impregnated with twice its weight of this dispersion by dipping, subjected to a pretreatment process using infrared radiation in the range of 2 to 10 microns, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0233] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove the PVA, with the help of a PVA dispersant described in the prior art, and then dried again.

[0234] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE20," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0235] Example 1.21 To achieve a viscosity of 560 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0236] The previously defined intermediate product D9 is impregnated with twice its weight of this dispersion by dipping, subjected to a pretreatment process using infrared radiation in the range of 2 to 10 microns, and then heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0237] Next, the test piece is washed at atmospheric pressure with soft water at a temperature near the boiling point to remove PVA, and then dried again.

[0238] This intermediate product contains 33% polyurethane and is identified as "Intermediate Product IE21". After subsequent mechanical splitting and buffing, it is subjected to an acid staining process according to the prior art.

[0239] Example 1.22 To reach a viscosity of 450 mPa·s at 20 °C under the application conditions, an aqueous dispersion containing a mixture of type 1 and 3 polyurethanes, a type 1 crosslinking agent, and a type 1 filler in a ratio of 4:1 is prepared.

[0240] The previously defined intermediate product D9 is impregnated by dipping with twice its weight of this dispersion, subjected to a pretreatment step by infrared radiation in the range of 2 - 10 microns, then the suspended particles are fixed, the remaining water and volatile substances are removed, and heat treatment is carried out in a convection oven to activate the crosslinking agent.

[0241] Next, the test piece is washed at atmospheric pressure with soft water at a temperature near the boiling point to remove PVA with the help of the PVA dispersant described in the prior art, and then dried again.

[0242] This intermediate product contains 33% polyurethane and is identified as "Intermediate Product IE22". After subsequent mechanical splitting and buffing, it is subjected to an acid staining process according to the prior art.

[0243] Example 1.23 To reach a viscosity of 450 mPa·s at 20 °C under the application conditions, an aqueous dispersion containing a mixture of type 1 and 3 polyurethanes, a type 1 crosslinking agent, and a type 1 filler in a ratio of 4:1 is prepared.

[0244] The previously defined intermediate product D9 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0245] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove the PVA, with the help of a PVA dispersant described in the prior art, and then dried again.

[0246] This intermediate product contains 32% polyurethane, is identified as "Intermediate Product IE23," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0247] Example 1.24 To achieve a viscosity of 555 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, a type 1 thickener, and a type 4 filler is prepared.

[0248] The previously defined intermediate product D10 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0249] Next, the test specimens are washed at atmospheric pressure with alkaline earth salt-free water at a temperature near its boiling point to remove PVA, and then dried again.

[0250] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE24," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0251] Example 1.25 To achieve a viscosity of 485 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0252] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove water and volatile substances, and activate the crosslinking agent.

[0253] Next, the test specimens are washed at atmospheric pressure with alkaline earth salt-free water at a temperature near its boiling point to remove PVA, and then dried again.

[0254] This intermediate product contains 35% polyurethane, is identified as "Intermediate Product IE25," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0255] Example 1.26 To achieve a viscosity of 601 mPa·s at 20°C under the applicable conditions, an aqueous dispersion containing a type 1 polyurethane, a type 1 crosslinking agent, and a type 1 thickener is prepared.

[0256] The previously defined intermediate product D11 is impregnated with twice its weight of this dispersion by dipping, and immediately heat-treated in a convection oven to fix the suspended particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0257] Next, the test specimens are washed at atmospheric pressure with alkaline earth salt-free water at a temperature near its boiling point to remove PVA, and then dried again.

[0258] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE26," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0259] Example 1.27 The “intermediate product IE25” is manufactured as disclosed in Example 1.25 and undergoes the same mechanical process.

[0260] In contrast, the dyeing is carried out at pH 9.4 by the addition of sodium acetate.

[0261] This intermediate product contains 35% polyurethane and is identified as "Intermediate Product IE27".

[0262] Example 1.28 To reach a viscosity of 654 mPa·s at 20 °C under the application conditions, an aqueous dispersion containing polyurethane of type 5, crosslinking agent of type 1, and thickening agent of type 1 is prepared.

[0263] The previously defined intermediate product D1 is impregnated by dipping with twice its weight of this dispersion, immersed in a coagulation solution consisting of a 5% acetic acid aqueous solution at 50 °C for 10 minutes, then the coagulated polyurethane particles are fixed, the remaining water and volatile substances are removed, and heat treatment is carried out in a convection oven to activate the crosslinking agent.

[0264] Next, the test piece is washed at atmospheric pressure with soft water at a temperature near the boiling point to remove PVA, and then dried again.

[0265] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE28", and after subsequent mechanical splitting and buffing, is subjected to an acid dyeing process according to the prior art.

[0266] Example 1.29 3.58 s at 20 °C -1 To reach a viscosity of 3433 mPa·s at 20 °C in 3.58 s, an aqueous dispersion containing polyurethane of type 3, crosslinking agent of type 2, and a mixture of thickening agents of type 1 and type 4 in a ratio of 1:1 is prepared.

[0267] The previously defined intermediate product D4 is impregnated by dipping with twice its weight of this dispersion, immersed in a coagulation solution consisting of a 0.25% formic acid aqueous solution in warm water at 60 °C for 15 minutes, then the coagulated polyurethane particles are fixed, the remaining water and volatile substances are removed, and heat treatment is carried out in a convection oven to activate the crosslinking agent.

[0268] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0269] This intermediate product contains 33% polyurethane, is identified as "Intermediate Product IE29," and, after subsequent splitting and buffing, is subjected to the prior art acid staining process.

[0270] Example 1.30 To achieve a viscosity of 768 mPa·s at 20°C with a viscosity of 3.58 s⁻¹, an aqueous dispersion is prepared containing a type 4 polyurethane, a type 1 crosslinking agent, and a mixture of type 1 and type 4 thickeners in a 1:4 ratio.

[0271] The previously defined intermediate product D1 is impregnated with twice its weight of this dispersion by dipping, then immersed for 7 minutes in a solidification solution consisting of a 0.5% formic acid aqueous solution in 60°C hot water, and then heat-treated in a convection oven to fix the solidified polyurethane particles, remove residual water and volatile substances, and activate the crosslinking agent.

[0272] Next, the test specimens are washed at atmospheric pressure with soft water at a temperature near its boiling point to remove PVA, and then dried again.

[0273] This intermediate product contains 29% polyurethane, is identified as "Intermediate Product IE30," and, after subsequent mechanical splitting and buffing, is subjected to the prior art acid staining process.

[0274] The prepared intermediate products were dyed in an industrial jet at an acidic pH or at a basic pH by adding a weak sodium salt, according to prior art for polyester fibers, and then characterized to assess their appearance, feel, abrasion resistance, and durability. Sensory evaluations of feel, appearance, and texture were performed and compared with reference products obtained using solvent methods. Feel was evaluated by determining the parameters of flexibility and gum-up (elasticity and rebound recovery); appearance evaluation was based on the uniformity of the nap and the feel of the surface.

[0275] All sensory evaluations are expressed on a scale of 1 to 5, where 1 is the lowest value, 5 is the highest value, and 3 is still acceptable.

[0276] Wear resistance is assessed by measuring weight loss and / or changes in appearance. In particular, the following are evaluated: - The material was subjected to abrasion testing (EN ISO 12947) using a Martindale abrasion tester at a pressure of 12 kPa for 2,000, 5,000, 10,000, and 20,000 cycles. The resulting pilling was observed by visual comparison with five standard samples. (A surface layer of fibers is formed, which then entangles to form actual fiber balls; this phenomenon is particularly observed in garments made from natural fibers, such as wool.) - Presence of fuzz breakage related to the loss of fuzz from the surface after 2,000, 5,000, 10,000, and 20,000 cycles at a pressure of 12 kPa during abrasion testing using a Martindale abrasion tester (EN ISO 12947); the evaluation is qualitative and based on an estimate of the percentage of abraded surface that is free of fibers. A score of 5 is given when the fiber-free surface accounts for less than 10% of the surface subjected to abrasion, 4 corresponds to when the fuzz-free surface accounts for 10% to 20% of the total surface, 3 is given when the fuzz-free surface accounts for 20% to 30%, 2 is when it accounts for 30% to 40%, and 1 is when the fuzz-free surface accounts for more than 40% of the surface subjected to abrasion.

[0277] These phenomena are generally influenced by the adhesion between the polyurethane and the fibers: when the adhesion is high, pilling does not occur, but fuzzing may occur, which is related to the fibers eventually splitting if they cannot move properly during abrasion testing; on the other hand, if the polyurethane does not bond sufficiently to the fibers, pilling may form, while fuzzing generally does not occur.

[0278] "Durability" is defined as the ability of a dyed material to withstand wear over time, even after prolonged and repeated exposure to light and highly hydrolyzable environments. The degradation tests used to measure "durability" are as follows: 1. The following conditions: relative humidity, 20±10%; black panel temperature, 100±3℃; radiant power, 60W / m 2 UV degradation was performed using a Xenotest BETA apparatus over an exposure time of 190 hours (standard PV1303). 2. Hydrolysis resistance test (commonly known as the "jungle test") performed in an environmental chamber under the following conditions: relative humidity, 90±3%; temperature, 75±1℃; exposure time, 5-7-10 weeks.

[0279] Durability is always evaluated in terms of changes in appearance after degradation testing. In particular, the following are evaluated: - Formation of pilling was determined by visual comparison with five standard samples after subjecting the material to an abrasion test (EN ISO12947) using a Martindale abrasion tester at a pressure of 12 kPa for 20,000 cycles. - The presence of a fuzz-breaking phenomenon.

[0280] The evaluation scale is the one previously disclosed.

[0281] The prototypes prepared according to the previously described examples were subjected to dyeing in an industrial jet and then evaluated, and the results summarized in Table 2 are shown; in the same table, the evaluations of the prototypes prepared according to Examples 2.2 (Prototype B) and 1.1b (Prototype C) disclosed in Patent EP1323859 (Solvent Method, Prototype A) and Patent EP2780501 are shown for comparison.

[0282] The evaluation in Table 2 shows how applying IR technology to pre-treat polyurethane and vary the solubility of PVA results in improvements to both physical / mechanical and aesthetic properties; in addition, the increase in hardness at the same polyurethane content in intermediate products treated using this technology is addressed by a reduction in the required polyurethane percentage, which is significantly advantageous in terms of appearance, manufacturing cost, and associated environmental impact.

[0283] Applying fillers, such as PVA, results in improved flexibility and tactile comfort, but degrades resilience and surface appearance, which is inferior. This deficiency can be partially compensated for by applying IR technology.

[0284] The addition of monovalent salts (in the PVA or in the intermediate product produced in step e of the method) prior to polyurethane impregnation also allows for the modification of the PUD distribution in the specimen, positively affecting the physical / mechanical properties and appearance, but degrading flexibility at the same PUD content. With some polyurethane formulations, the staining pH (acidic or basic) can affect the appearance and physical / mechanical properties of the compound.

[0285] Using a solidification process in an aqueous solution of salt or acid makes it possible to obtain a porous polyurethane structure, which not only gives a flexible product with a feel and appearance similar to that obtained by solvent methods, but also allows for the creation of a porous polyurethane structure similar to that which can be obtained by solvent methods (see Figure 4B).

[0286] The combination of novel technologies disclosed above enables the final properties of the compound to move toward the desired analytical and sensory characteristics.

[0287] In particular, as can be seen from the data shown in Figure 6 and Table 1, prototypes (IE01 to IE30) prepared using the method according to the present invention were compared with prototypes B and C prepared using a similar method disclosed in Patent EP2780501; namely, a method that does not require the use of organic solvents but does not involve a microfiber intermediate cleaning step (step e)). It is possible to confirm how the sensory evaluations of the prototypes of the present invention for tactile feel, flexibility, and appearance are clearly superior to the evaluations obtained for prototypes B and C, and are close to or even equal to the evaluations made for reference prototype A obtained using the current solvent method disclosed in Patent EP1323859.

[0288] Of the 30 prototypes prepared by the method of the present invention, 83% (i.e., 25 prototypes) exhibited a better appearance (sensory evaluation score equal to 4 or 5 out of 5) than the appearance of prototypes B and C (sensory evaluation scores of 2 and 3, respectively), and were close to or even equal to the desirable appearance (5 out of 5) obtainable using the solvent method.

[0289] The tactile and flexibility evaluation scores of prototypes IE01 to IE30 were also better than those of B and C. In particular, 63% (i.e., 19 prototypes) of the tested prototypes of the present invention had greater flexibility, and 53% (i.e., 16 prototypes) had a better tactile feel (sensory evaluation score equal to 4 or 5 out of 5) than prototypes B and C (sensory evaluation score equal to 3), which in this case was also close to or even equal to the flexibility and tactile feel (sensory evaluation score equal to 5 out of 5) of the solvent method.

[0290] Based on the comparative experiments disclosed above, it is clear that the method according to the present invention makes it possible to obtain a finished product that can be achieved using a method with little or no environmental impact, while simultaneously maintaining the desirable tactile, flexible, elastic, and appearance characteristics typical of products obtained using current organic solvent methods.

Claims

1. A method for preparing a microfiber nonwoven fabric, a) A step of preparing an island-sea type two-component fiber in which the marine component is a polymer that can be removed in hot water or an alkaline aqueous solution; b) A step of preparing felt by needle punching the two-component fibers of the "sea island" type; c) Impregnating the felt with an aqueous solution of polyvinyl alcohol (PVA) having a degree of saponification of at least 94%, supplemented with a water-soluble organic or inorganic salt, at a temperature of at least 50°C; d) A step of removing marine components from the felt impregnated with PVA obtained in step c) by contacting the felt with an alkaline or alkaline earth hydroxide basic aqueous solution, thereby obtaining a microfiber intermediate product; e) A step of washing the microfiber intermediate product from step d) with neutral water; f) Impregnating the microfiber intermediate product described in step e) with polyurethane (PU) dispersed in water, which contains an additive for adjusting viscosity and optionally a water-soluble substance; g) A step of fixing the PU to the microfiber intermediate product by solidification of the PU dispersion and subsequent drying; h) a step of removing the PVA added in step c), the salt added in step c), and the additive added in step f); i) The process of cutting the material thus obtained, buffing one or both sides, and dyeing it. Methods that include...

2. The method according to claim 1, wherein the water-soluble organic and inorganic salts present in step c) include a salt-to-PVA weight ratio in the range of 0.1% to 20% by weight.

3. The method according to claim 1 or 2, wherein the solution of the water-soluble organic or inorganic salt in step c) is a solution of NaCl or KCl.

4. The method according to any one of claims 1 to 3, wherein, following step c), the felt impregnated with PVA is subjected to drying, and then subjected to heat or radiation treatment at a temperature of at least 100°C.

5. The method according to any one of claims 1 to 4, wherein in step d), the basic aqueous solution of an alkali or alkaline earth hydroxide is a solution of NaOH or KOH.

6. The method according to any one of claims 1 to 4, wherein the concentration of alkali or alkaline earth hydroxide is in the range of 0.1% to 48%.

7. The method according to any one of claims 1 to 6, wherein the viscosity of the PU dispersion in water in step f) is in the range of 200 to 800 mPa·s at 20°C.

8. The method according to any one of claims 1 to 7, wherein the fixation of the PU in step g) is carried out by high-temperature air coagulation, hot water coagulation, coagulation in an aqueous solution of an acid electrolyte, high-frequency coagulation, microwave coagulation, ultrasonic coagulation, infrared (IR) radiation coagulation, or vapor coagulation.

9. The method according to any one of claims 1 to 7, wherein, prior to the fixing process described in step g), the polyurethane dispersion is rapidly preheated by radiation from an IR lamp or high frequency or microwave, thereby facilitating the fixing process in the innermost layer away from the surface.

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