Nonwoven fabric and its manufacturing method

Abstract

In this non-woven fabric, fibers constituting a web are joined to each other using a binder. A protein hydrolysis product such as fibroin, sericin, or keratin is used as the binder, and the fibers are fixed to each other using the binder. There is obtained a non-woven fabric in which the fibers are joined using a binder derived from a natural product or similar to a natural product.

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric and a method for producing the same. [Background technology]

[0002] The fibers in a nonwoven fabric are bound together by intertwining with each other or by a binder. Most binders are synthetic resins, which are not suitable for nonwoven fabrics made only of natural or similar materials. For this reason, there is a need for nonwoven fabrics that use binders made of natural or similar substances.

[0003] Related prior art: Patent Document 1 (JP Patent Publication 7-236373) discloses that a layer of konjac flour, soy flour, etc. is provided on the surface of a nonwoven fabric to prevent the passage of water and air. However, in Patent Document 1, the konjac flour, etc., is not a binder for the nonwoven fabric, but constitutes the surface layer of the nonwoven fabric. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 7-236373 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a nonwoven fabric in which fibers are bound with a binder made of a substance derived from a natural product or a substance similar to a natural product, and a method for producing the same. [Means for solving the problem]

[0006] The nonwoven fabric of the present invention is characterized in that the fibers constituting the web are bound to each other by a binder, and the binder is a peptide.

[0007] The method for producing a nonwoven fabric of the present invention comprises forming a fiber web and then bonding the fibers constituting the web to each other with a binder. The method for producing a nonwoven fabric of the present invention is characterized in that the binder is a peptide.

[0008] In this invention, a binder made of peptides bridges the fibers at their intersections. This bonds the fibers that make up the web together (Figure 4), resulting in a strong nonwoven fabric. Peptides are substances in which amino groups are bonded together by peptide bonds. In this specification, peptides produced by hydrolysis of proteins are called protein hydrolysis products. It is also possible to synthesize peptides similar to protein hydrolysis products.

[0009] Preferably, the binder is at least one member of the hydrolysis product of fibroin, sericin, or keratin. Both fibroin and sericin are proteins derived from silk, fibroin is fibrous, and sericin binds the fibroins in silk fibers together. Keratin is a hard protein contained in animal hair such as wool, waterfowl feathers, poultry feathers, etc. In addition, waterfowl and poultry feathers are often discarded because they have few uses, so using hydrolyzed keratin derived from feathers as a binder is significant in terms of environmental protection.

[0010] Hydrolysis products of proteins such as fibroin, sericin, and keratin are all derived from natural products and are highly compatible with the human body. Therefore, the nonwoven fabric can be used for artificial skin, membranes to be implanted in the body, etc. In addition, the nonwoven fabric can be used for any purpose such as a sheet to cover an affected area, a bandage, a face mask, a moisturizing mask to be used while sleeping, a hair cover to be used while sleeping, etc. The nonwoven fabric of the present invention is suitable for applications in which it comes into direct contact with the human body.

[0011] The binder preferably has a relatively small molecular weight, for example, a number average molecular weight of 500 to 5000, more preferably 750 to 3000. A binder with a large molecular weight impairs the breathability of the nonwoven fabric and makes the nonwoven fabric hard, impairing the feel.

[0012] Preferably, the fibers constituting the web are at least one member of the group consisting of protein fibers, rayon, and polylactic acid. These fibers are derived from natural products, so there is little risk of allergies even if they come into contact with the human body. In addition, petroleum-derived chemical fibers such as nylon do not mix well with binders derived from keratin, etc., and are therefore not suitable for this invention.

[0013] Particularly preferably, the fibers constituting the web are silk fibers. When the fibers are silk fibers and the binder is silk-derived fibroin or sericin, or keratin derived from waterfowl, poultry, wool, etc., a nonwoven fabric that is compatible with the human body and safe for use in artificial skin, membranes to be worn on the human body, etc. can be obtained. In particular, when genome-edited silkworms are raised in a sterile condition to collect silk fibers that do not contain substances harmful to the human body, such as allergens, and these silk fibers are used as the base material for a nonwoven fabric, a nonwoven fabric that is particularly safe for the human body can be obtained. Furthermore, the strength and size of the nonwoven fabric of this invention do not change significantly even when wet, making it suitable for applications in which it comes into direct contact with the human body. It should be noted that even with protein fibers, animal hair such as wool originally has scales, and friction occurs between the fibers due to contact between the scales. For this reason, nonwoven fabrics can be manufactured without a binder, so they are not very suitable for this invention.

[0014] Preferably, the fibers constituting the web are bound together with a binder made of a hydrolyzed product of protein, and then the web is contacted with a weakly acidic aqueous solution. The aqueous solution has a pH of, for example, 4.5 to 6, preferably 5 to 6. The type of acid is, for example, acetic acid, but when dyeing the nonwoven fabric, an acid dye or an acid wool reactive dye may be used as the acid. The binder is polymerized by the acid treatment as a post-treatment, and the strength of the nonwoven fabric is increased.

[0015] The web is formed, for example, by a spunlace process, which causes the fibers to entangle with one another, and then the fibers are bonded to one another with a binder, which provides the strength of the nonwoven fabric through the entanglement of the fibers by the spunlace and the bonding of the fibers by the binder.

[0016] The method for adding the binder is arbitrary. For example, the binder can be uniformly added to the web by forming a web by the spunlace method and then immersing the web in an aqueous solution of the binder. [Brief description of the drawings]

[0017] [Figure 1] Manufacturing process diagram of nonwoven fabric in the example [Diagram 2] Electron microscope photograph (x250) of nonwoven fabric treated with the spunlace method [Diagram 3] Electron microscope photograph (x550) of the nonwoven fabric of the embodiment [Figure 4] Electron microscope photograph (x2000) of the nonwoven fabric of the embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The best mode for carrying out the invention will be described below. EXAMPLES

[0019] FIG. 1 shows the manufacturing process of nonwoven fabrics. The raw fibers are protein fibers such as silk that do not have scales, rayon such as cupra, polylactic acid, etc., which are natural products such as protein fibers, or processed natural products such as rayon and polylactic acid, or have a composition similar to natural products. The most preferable of these is silk, which is compatible with the human body and safe. In particular, silk from silkworms that have been grown in a sterile environment and have had allergens removed from silk by genome editing is preferable. In the examples, commercially available Benny Silk cotton was used. In Benny Silk, the silk fibers are crimped, making it suitable for producing webs by carding.

[0020] Petroleum-based chemical fibers do not mix well with keratin solutions, so it is not possible to crosslink the intersections of the fibers with keratin. In addition, petroleum-based chemical fibers such as nylon are irritating to the human body. Therefore, petroleum-based chemical fibers are not recommended.

[0021] Protein fibers include animal hair fibers such as wool. However, animal hair fibers originally have scales, and when made into nonwoven fabric, the strength is maintained by the friction between the scales. Therefore, animal hair fibers are not important, although they are not particularly excluded.

[0022] The binder is a hydrolyzed product of protein, and examples thereof include silk fibroin, hydrolyzed fibroin obtained by hydrolyzing sericin, hydrolyzed sericin, and hydrolyzed keratin obtained by hydrolyzing feathers and animal hair of waterfowl and poultry. These binders are derived from natural products and are safe with little irritation to the human body. Furthermore, since feathers of waterfowl and poultry are often discarded due to low demand, keratin obtained by hydrolyzing bird feathers is also excellent in terms of environmental protection. Synthetic peptides may also be used as binders.

[0023] Keratin can be hydrolyzed with alkali or acid, and the upper limit of the molecular weight can be controlled by dialysis. In the examples, feathers were hydrolyzed with alkali, and hydrolyzed keratin with an upper limit of molecular weight of 5000 and a number average molecular weight of 1500 was used. Silk fibroin and sericin can also be hydrolyzed with alkali or acid, and the upper limit of the molecular weight can be controlled by dialysis. The number average molecular weight of hydrolyzed keratin and the like can be measured by gel chromatography. The preferred range of the number average molecular weight is 500 to 5000, particularly 750 to 3000.

[0024] A web is produced from raw fibers, that is, fibers that are in contact with each other and are layered, and the web is sometimes called fleece. In the embodiment, a web is formed from silk cotton using a carding machine, and the fibers are entangled by the spunlace method to give the web strength. In the spunlace method, a water flow is sprayed onto the web, and the fibers are bent and entangled by the water flow. A nonwoven fabric (web) treated by the spunlace method is shown in Figure 2, and the fibers are bent and entangled. A needle punch method (needles are pierced into the web, and the fibers are bent and entangled) may be used instead of the spunlace method, and the method of forming the web and the method of entangling the fibers and whether or not this treatment is performed are optional.

[0025] The spunlaced web was passed through a bath (20°C at 5 mass% concentration) of an aqueous solution of hydrolyzed keratin derived from feathers having a number average molecular weight of 1500 for 5 seconds to add hydrolyzed keratin to the web. The hydrolyzed keratin concentration in the bath is, for example, 1 mass% to 8 mass%, preferably 4 mass% to 6 mass%. The immersion time is, for example, 1 second to 1 minute, preferably 1 second to 10 seconds. The liquid temperature of the bath is, for example, normal temperature of 15°C to 25°C.

[0026] In this treatment, the web is immersed in a relatively concentrated aqueous solution of hydrolyzed keratin for a short period of time. Hydrolyzed keratin is compatible with fibers such as silk, rayon, and polylactic acid, so when the web is dried, the hydrolyzed keratin gathers at the intersections of the fibers and crosslinks between the fibers. The drying method can be any method, such as heating with a heated roll, irradiation with infrared rays, heating in an oven, hot air drying, or natural drying.

[0027] Figure 3 is a photograph of a nonwoven fabric that has been treated with hydrolyzed keratin and then dried, and Figure 4 is an enlarged photograph of the same. In Figure 4, the fibers are bonded together by a film of hydrolyzed keratin. Immersion in an aqueous solution of hydrolyzed keratin bonds the fibers together, increasing the strength of the nonwoven fabric. The aqueous solution of hydrolyzed keratin can also be sprayed onto the web, and the method of adding hydrolyzed keratin itself is optional.

[0028] To further increase the strength of the nonwoven fabric, it is preferable to contact the dried nonwoven fabric with hydrolyzed keratin added with a weakly acidic aqueous solution. For example, the nonwoven fabric is immersed in a bath of an aqueous acetic acid solution with a pH of 5.5 at room temperature, and then the nonwoven fabric is dried. The hydrolyzed keratin polymerizes upon contact with the acid, increasing the strength and shape stability of the nonwoven fabric. The pH is preferably 4.5 to 6, and particularly 5 to 6. For example, silk nonwoven fabric increases in size when immersed in water and subjected to force by a water flow or the like. However, adding hydrolyzed keratin to silk nonwoven fabric can suppress the increase in size when immersed in water. The increase in size of a nonwoven fabric that has not been treated with keratin when immersed in water and subjected to force is set to 100%, and when it is treated with keratin but not with acetic acid, the increase in size is small, about 8%, and when it is treated with acetic acid after adding hydrolyzed keratin, the increase in size is small, about 2%. Furthermore, hydrolyzed keratin is not eluted by the acetic acid treatment, and the content in the nonwoven fabric does not change.

[0029] The content of hydrolyzed keratin was measured from the change in the dry weight of the silk nonwoven fabric. 2 The nonwoven fabric contains 5.3g / m2 of hydrolyzed keratin. 2 The hydrolyzed keratin concentration in the nonwoven fabric was 8.8 mass%. The keratin concentration in the nonwoven fabric is preferably 3.5 mass% or more and 20 mass% or less.

[0030] The obtained nonwoven fabric (width 50 mm × length 200 mm) was held at intervals of 100 mm in the lengthwise direction, and the tensile strength, elongation to break, and stress (modulus) when elongated by 5%, 10%, and 15% were measured. The results are shown in Table 1. For the sample containing hydrolyzed keratin, keratin was polymerized in an aqueous acetic acid solution (pH 5.5) after the addition of keratin.

[0031] Table 1 Nonwoven fabric strength Test items Spunlace only Hydrolyzed keratin added Tensile strength (N) 240 220 Growth rate (%) 40 31 5% Modulus (N) 7 32 10% Modulus (N) 22 60 15% Modulus (N) 43 99

[0032] The addition of hydrolyzed keratin significantly increased the modulus value, which means that the nonwoven fabric became less stretchable and had improved shape stability.

[0033] In the embodiment, the strength of the nonwoven fabric can be increased by bridging between fibers using a binder derived from a natural product. Since the binder is a natural product, it is less irritating to the human body. Furthermore, by binding the silk fibers in the nonwoven fabric with a binder made from fibroin, sericin, or a hydrolysis product of keratin, a nonwoven fabric that is compatible with the human body, has a stable shape even when wet, and is strong, can be obtained, which can be used for medical purposes. The strength of the nonwoven fabric can be further increased by polymerizing the binder added to the nonwoven fabric using a weakly acidic aqueous solution.

Claims

1. A web forming step of forming a web of silk fibers; an immersion step of immersing the formed web in an aqueous solution of a binder comprising hydrolyzed keratin having a number average molecular weight of 500 to 5,000; A method for manufacturing a nonwoven fabric, comprising the steps of: drying a web immersed in an aqueous solution of a binder, thereby collecting the binder at the intersections of fibers in the web and cross-linking the fibers with the binder; and drying the web.

2. The method for producing a nonwoven fabric according to claim 1, wherein in the web forming step, the silk fiber wadding is carded to form the web.

3. 3. The method for producing a nonwoven fabric according to claim 1, wherein in the web forming step, the fibers of the formed web are entangled with each other to impart strength to the web.

4. 4. The method for producing a nonwoven fabric according to claim 3, wherein in the web forming step, the fibers of the formed web are entangled with each other by a spunlace method or a needle punch method.

5. The method for producing a nonwoven fabric according to any one of claims 1 to 4, further comprising the step of contacting the web with a weakly acidic aqueous solution and then drying the web after the drying step.

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