JP2016017234A - Synthetic fiber for papermaking having reversible hue change properties and fiber product containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic fiber that is used in the manufacture of a special nonwoven fabric, paper and other fiber products for imparting a forgery prevention effect, exhibits a reversible hue change by visual observation and has physical properties suitable for manufacture of nonwoven fabric and papermaking.SOLUTION: The synthetic fiber includes a lanthanoid rare earth compound and a thermoplastic resin containing polyolefin or polyamide. The content of the lanthanoid rare earth compound is in the range of 7.0 to 45.0 wt% based on the weight of the thermoplastic resin and the primary particle size of the lanthanoid rare earth compound is 0.6 to 9.0 μm.SELECTED DRAWING: None

Description

  The present invention relates to a synthetic fiber containing a lanthanoid rare earth compound whose hue changes reversibly and a textile product containing the same, and prevents the counterfeiting of special paper by changing the hue reversibly according to the light source. The present invention relates to a field related to synthetic fibers suitable for a papermaking process, which can impart effects.

  Conventionally, a photochromic molecule, which is an organic compound, is known as a substance that reversibly changes its color when irradiated with light. The photochromic molecule absorbs light irradiation energy to change its chemical structure and change the color of the compound. As inorganic compounds, oxides of Ho, Nd, and Pr are known. These oxides have a special reflection spectral distribution, and the color of the oxides changes according to the type of light source such as sunlight or a fluorescent lamp. Mixing organic and inorganic substances that cause these reversible changes into printing inks and using them as anti-counterfeit prints, or providing yarns and clothing that change hue by kneading into fibers Are known.

  However, when organic photochromic molecules are used as the dye material, the reversibility of the color change is often incomplete and the time required for the color change is long. In addition, repeated color changes due to light absorption are accompanied by light deterioration such as loss of reversibility of color changes, and reversibility of light changes often disappears by heat and long-term UV irradiation. It is not suitable for preservation. On the other hand, rare earth oxides of inorganic compounds such as Ho, Nd, and Pr have good quality such as weather resistance and heat resistance, but their hue change is small and can be expressed only in a limited range, giving a clear hue change. It was difficult. It has also been proposed to mix an organic or inorganic functional agent having a reversible hue change into printing ink and use it for anti-counterfeit printed matter. Therefore, the anti-counterfeiting technique is limited, and further advanced anti-counterfeiting techniques have been demanded (see, for example, Patent Documents 1 to 4).

Japanese Patent No. 4089114 Japanese Patent No. 4378789 JP 2000-144520 A JP 2000-247077 A

  The subject of this invention is providing the synthetic fiber which shows the big contribution to the improvement of the forgery prevention technique, and can provide the forgery prevention effect. More specifically, it is a synthetic fiber that is used when producing special nonwoven fabrics, paper and other textile products to impart an anti-counterfeit effect, and has a reversible hue change by visual observation. It is to provide a synthetic fiber having physical properties suitable for production, and at the same time, the fiber is also a fiber capable of efficient and continuous production. Yet another object of the present invention is to provide a textile product comprising such synthetic fibers.

  The present invention solves the above-described problem, and is a synthetic fiber including a lanthanoid rare earth compound and a thermoplastic resin containing polyolefin or polyamide, wherein the content of the lanthanoid rare earth compound is the weight of the thermoplastic resin. Is a synthetic fiber characterized in that the primary particle diameter of the lanthanoid rare earth compound is 0.6 to 9.0 μm. Preferably, the lanthanoid rare earth compound is at least one lanthanoid selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The synthetic fiber containing a rare earth element. More preferably, the lanthanoid rare earth compound is a holmium compound, and the primary fiber diameter of the lanthanoid rare earth compound is 0.7 to 8.0 μm.

  According to the present invention, it is possible to provide a synthetic fiber that greatly contributes to the improvement of anti-counterfeit technology and can impart an anti-counterfeit effect. More specifically, it is a synthetic fiber that is used when producing special nonwoven fabrics, paper and other textile products to impart an anti-counterfeit effect, and has a reversible hue change by visual observation. Synthetic fibers having physical properties suitable for production can be provided. When this synthetic fiber is used, counterfeiting is extremely difficult with commercially available color copiers, and genuine and counterfeit products can be clearly distinguished using a simple device, and can be manufactured at low cost. A synthetic fiber suitable for constituting a textile product such as a certain non-counterfeit nonwoven fabric or paper can be provided.

  Furthermore, by containing the fiber in a fiber product such as papermaking in an amount of 0.1 to 100% by weight, mixing in the thickness direction of the fiber product, which has not been achieved with conventional printing inks, is facilitated. It is possible to impart an anti-counterfeit effect. As a result, the present fiber is also preferably used for special paper that is used for bills, securities, official documents, and other uses and that requires a forgery prevention effect.

  In addition, such fibers have good spinning processability during melt spinning and can be mass-produced on an industrial scale. Further, in the production of such special paper, it is necessary to have dispersibility in water suitable for the papermaking process. In order to provide appropriate papermaking processability, existing fiber quality and technology for the same application can be used as they are.

Hereinafter, the present invention will be described in more detail.
(Types of lanthanoid rare earth compounds)
First, a lanthanoid rare earth compound suitable for use in the synthetic fiber of the present invention will be described. In the present invention, examples of the compound having such characteristics include a lanthanoid rare earth compound having a primary particle size of 0.6 to 9.0 μm. The element of the lanthanoid rare earth compound is at least one selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The lanthanoid rare earth element is preferably composed of a simple substance or a material containing a compound of these elements. Here, the compounds of the above elements are oxides, carbides, chlorides, fluorides, sulfides, nitrides, carbonate compounds, hydrogen carbonate compounds, nitrite compounds, nitrate compounds, sulfonate compounds, sulfate compounds, oxalate compounds and At least one compound selected from the group consisting of acetic acid compounds. More specifically, La ₂ O ₃ , LaCl ₃ , La (CO ₃ ) ₃ , LaF ₃ , CeO ₂ , Ce (SO ₄ ) ₂ , Ce ₂ (CO ₃ ) ₃ , Pr ₆ O ₁₁ , PrCl ₃ , Nd ₂ O ₃ , NdCl ₃ , Nd ₂ (CO ₃ ) ₃ , NdF ₃ , Pm ₂ O ₃ , Sm ₂ O ₃ , SmCl ₃ , Eu ₂ O ₃ , EuCl ₃ , Gd ₂ O ₃ , GdF ₃ , Tb ₄ O ₇ , Dy ₂ O ₃ , Dy ₂ (CO ₃ ) ₃ , Dy (NO ₃ ) ₃ , Er ₂ O ₃ , Er ₂ (CO ₃ ) ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ etc. Can be mentioned. Preferably, the lanthanoid rare earth compound is a holmium compound since the change in hue can be confirmed particularly easily by visual observation. Another preferred embodiment is that the primary particle diameter of the lanthanoid rare earth compound is 0.7 to 8.0 μm. Alternatively, the synthetic fiber does not contain particles of the lanthanoid rare earth compound having a primary particle diameter of 10 μm or more. More preferably, the lanthanoid rare earth compound is a holmium compound, the primary particle diameter of the lanthanoid rare earth compound is 0.7 to 8.0 μm, and particles having a particle diameter of 10 μm or more are not included. is there. The most preferred lanthanoid rare earth compound is holmium oxide (diholmium trioxide).

In general, it is known that lanthanoid rare earth elements or compounds thereof have different visual hues under light sources of different types of wavelengths. For example, holmium oxide (Ho ₂ O ₃ ) has major absorption peaks in the wavelength range of 450 to 460 nm, 540 to 550 nm, and 650 to 660 nm, but the holmium oxide powder is visually observed under sunlight. In this case, it looks white as it is. For example, when a three-wavelength fluorescent lamp of 450 nm, 540 nm, and 610 nm is irradiated, the blue wavelength of 450 nm and the green wavelength of 540 nm are largely absorbed. Since only the red wavelength of 610 nm is strongly reflected, it looks dark pink. Similarly, it is not a visual observation under a light source that emits light almost uniformly in the entire wavelength region of the visible light region, but strong light emission at a specific wavelength, that is, a part of the above three types of wavelength regions. Under a light source, it looks like a characteristic hue.

  Next, the relationship between a phenomenon in which the visual hue is different and a characteristic hue appears and a technique for preventing counterfeiting performed using a copying machine such as a copying machine will be described. The principle of a general color digital copying machine is to irradiate a document with light and detect reflected light with a CCD line sensor. In the CCD line sensor, a digital signal corresponding to the intensity of the reflected light is generated and transmitted to a memory in the copying machine. This reading process is performed for three colors of red (R), green (G), and blue (B), and the respective digital signals are stored in the memory. Next, based on the stored digital signal, the surface of the photosensitive drum is irradiated with laser light, and yellow (Y), magenta (M), cyan (C), and black (Bk) toners are applied to the photosensitive drum. The toner is sequentially electrostatically adsorbed, and these toners are sequentially transferred and fixed on a sheet such as paper. Thereby, an elaborate copy on which a color image is formed can be obtained.

  While such color copying is convenient, there is a growing problem that securities such as stock certificates, bonds, promissory notes, checks, and printed materials such as admission tickets and boarding passes are easily forged. For this reason, various proposals have been made to take measures to prevent duplication of printed matter so that it cannot be easily copied.

  A technique has been proposed in which the color of a color copy is different from the color of the original. For example, if a securities that can be used as a manuscript is colored with a very light color, the light color part cannot be accurately reproduced in a copy. Also, if halftone dots of different sizes are formed on the original, the reproducibility of small halftone dots deteriorates even when copied. Furthermore, the color reproducibility of the copy is deteriorated by printing colors such as green, purple, orange, gold, silver, etc., which are not in the toner of the color copying machine. In addition, although the color looks the same by using two types of ink that are characterized by the low visibility of human beings, for example, the wavelength ranges of 380 nm to 450 nm and 650 nm to 780 nm, Reproduced in different colors. As a result, these techniques help prevent counterfeiting.

  Furthermore, a technique has been proposed in which a portion that cannot be identified under visible light is provided in securities. For example, even when a document is printed with a fluorescent material that emits fluorescence when irradiated with ultraviolet rays, such a fluorescent function cannot be reproduced by a commercially available copying machine or printer. Therefore, when the black light is irradiated, the real product emits light, but the counterfeit product does not emit light, and the authenticity can be easily determined. Various other proposals have been made. However, this technique requires a light source with a special wavelength. In some cases, it is necessary to manufacture a verifier so that true / false judgments at that wavelength can be made. For this reason, the hardware cost of the system used for authenticity determination becomes high.

  Therefore, when the non-woven fabric and special paper containing the synthetic fiber of the present invention are used, the hue change can be visually confirmed, and the presence or absence of the hue change can easily determine forgery. It is considered possible. The above-mentioned three-wavelength light-emitting fluorescent lamps are produced and distributed in large quantities over a long period of time, and are installed in various places in Japan. Therefore, it is determined whether or not they are counterfeited without requiring a special verification machine. It is considered possible.

(Thermoplastic resin)
In the present invention, when the above lanthanoid rare earth compound is kneaded into a synthetic fiber and made into a fiber, the melt-spinnable resin is preferably a thermoplastic resin containing polyolefin or polyamide, more preferably a polyolefin. As isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene, high density polyethylene, medium density polyethylene, linear low density polyethylene, low density polyethylene, ethylene / propylene random copolymer polyolefin, vinylon, or third component It is preferable to use polyethylene or polypropylene obtained by block copolymerization or graft copolymerization. The third component in this case is vinyl acetate, vinyl chloride, styrene, methyl acrylate, ethyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, Examples thereof include vinyl chloride, vinylidene chloride, acrylonitrile, and acrylamide. Among these, the above lanthanoid rare earth compounds can be uniformly dispersed, and at the same time, the necessary minimum mechanical properties (breaking strength, breaking elongation, etc.) required for synthetic fibers can be secured, and industrial continuous From the viewpoint that production is possible, in particular, polyethylene, polypropylene, ethylene / propylene random copolymer, polyethylene obtained by block copolymerization or graft copolymerization of maleic anhydride, or block copolymerization or graft copolymerization of maleic anhydride. It is preferable to be a polypropylene. Further, a plurality of the above polyolefins may be selected and mixed for use. Among these polyolefins, polyethylene or polypropylene is preferable, and isotactic polypropylene is more preferable from the viewpoints of minimum required mechanical properties, industrial continuous productivity, and vividness / reversibility of the hue change of fibers. As the polyamide, nylon 6, nylon 11, nylon 12, nylon 4,6, nylon 6,6, nylon 6,10, nylon 6T (polyamide obtained from hexamethylenediamine and terephthalic acid) or nylon 6I (hexamethylene) Polyamide obtained from diamine and isophthalic acid) is preferable. On the other hand, in the case of using a polyester resin, the thermoplastic resin used for the synthetic fiber of the present invention does not have an ester bond because the resin formation is severely deteriorated due to the characteristics of the lanthanoid rare earth compound and the fiber forming property of the polyester resin is remarkably reduced. Resin is good.

  The polyolefin preferably has a melt flow rate of 10 to 30 g / 10 minutes measured by a method based on the method of Table 1 and Condition 4 of JIS standard K7210. More preferably, it is 12 to 28 g / 10 minutes, and still more preferably 15 to 25 g / 10 minutes. The polyamide preferably has a sulfuric acid relative viscosity at 25 ° C. of 1.5 to 3.5 as measured in accordance with JIS standard K6920. Specifically, a 1% concentration solution (a ratio of 1 g of polyamide / 100% sulfuric acid 100 ml) was prepared using 98% sulfuric acid, and the resulting solution was measured for relative viscosity of sulfuric acid measured at 25 ° C. Value.

  The synthetic fiber of the present invention is one kind of a heat stabilizer, an ultraviolet absorber, an antioxidant, a colorant, a lubricant, a release agent, a filler, an antistatic agent, etc., as long as the object of the present invention is not hindered. Or 2 or more types can be contained. In the present invention, when the thermoplastic resin constituting the synthetic fiber is polypropylene, the specific gravity is generally smaller than that of water, and as it is, it floats in water, which may cause inconvenience when producing a wet nonwoven fabric. In the case of the synthetic fiber of the present invention, the apparent specific gravity increases due to the inclusion of the lanthanoid rare earth compound, but for use in a papermaking process factory, if further prevention of floating is required, calcium carbonate, barium sulfate, oxidation By containing titanium, zinc oxide, alumina, silica, potassium methacrylate, or the like in the fiber, the specific gravity can be appropriately adjusted.

(Content and particle size of lanthanoid rare earth compounds)
The content of the lanthanoid rare earth compound in the synthetic fiber is preferably in the range of 7.0 to 45.0% by weight based on the weight of the thermoplastic resin containing polyolefin or polyamide. When the content is less than 7.0% by weight, the change in hue by visual observation as described above, for example, the hue change under a three-wavelength fluorescent lamp is insufficient, and the forgery prevention effect is reduced. On the other hand, if it exceeds 45.0% by weight, the melt spinnability is extremely poor, and the synthetic fiber of the present invention cannot be stably produced. The more preferable content is in the range of 8.0 to 43.0% by weight, the still more preferable content is in the range of 10.0 to 40.0% by weight, and the most preferable content is 16.0 to 35.%. It is in the range of 0% by weight. The content of the lanthanoid rare earth compound in the synthetic fiber referred to here is a calibration curve prepared in advance from the linear relationship between the total absorption amount of the peak absorption band of 650 to 660 nm and the holmium oxide content, which is also a characteristic exhibited by this compound. Measurement evaluation was performed using. In the present invention, in order to achieve a clear hue change in the fiber or fiber product, it is important to incorporate holmium oxide in the above-described content range.

  The primary particle size of the lanthanoid-based rare earth compound to be added is 0.6 to 9.0 μm, preferably 0.7 for the purpose of ensuring the spinning process at the time of melt spinning and reducing the fineness. It is -8.0 micrometers, More preferably, it is 0.9-2.0 micrometers, More preferably, 1.0-1.5 micrometers can ensure processability most. If the primary particle size is too small, the particles tend to re-aggregate during or after the particle production process, and as a result, secondary agglomerated coarse particles are often generated, which may be undesirable. When the amount of coarsely aggregated secondary particles is large, the spinning process at the time of melt spinning may not be good during the production of synthetic fibers, and mass production may be difficult on an industrial scale. Specifically, there may be a problem that the number of yarn breaks during continuous spinning described later is large and the degree of increase in filtration pressure is large. As for the primary particle diameter here, it is general to represent the particle diameters measured in large numbers as the abundance distribution. The primary particle diameter in the present invention is “median diameter (D50)” obtained by SALD-3100 manufactured by Shimadzu Corporation, whose measurement principle is “microtrack (laser diffraction / scattering method)”. Adopted as value. In addition, it is possible to determine whether or not secondary agglomerated particles having a particle diameter of 10 μm or more are contained by using this apparatus depending on the presence / absence of a distribution amount in a region having a particle diameter of 10 μm or more.

(Synthetic fibers containing lanthanoid rare earth compounds)
The single yarn fineness of the synthetic fiber of the present invention is preferably 0.5 to 30.0 dtex. When the fineness is smaller than 0.5 dtex, the ratio of diffused reflection of light and scattered light on the fiber surface increases, and the feeling of blurring may occur, and the change in hue as described above may be difficult to visually recognize. In the case of a thick fineness exceeding 0.0 dtex, the surface of the paper when paper making is carried out due to a large difference in fineness from other fibers or pulp other than the synthetic fiber of the present invention (hereinafter referred to as “matrix fiber”). Smoothness may be impaired and surface printing characteristics may be affected, which may be undesirable. In the synthetic fiber of the present invention, the preferred single yarn fineness is 2.5 to 20.0 dtex, more preferably 2.0 to 19.0 dtex, and still more preferably 5.0 to 17.0 dtex. The synthetic fiber of the present invention can be used either in the form of long fibers or in the form of short fibers having a fiber length of 1.0 to 200 mm, preferably 3.0 to 100 mm, depending on the application. The single yarn fineness can be easily set by those skilled in the art by appropriately setting and adjusting the melt spinning conditions and drawing conditions described later.

  The shape of the synthetic fiber of the present invention (cross-sectional shape, i.e., a cross section perpendicular to the fiber axis) is not particularly limited, and may be a solid circular cross-sectional shape or a hollow shape, Any other cross-sectional shape may be used. Specific examples when the cross-sectional shape of the fiber is an irregular cross-sectional shape include three or more polygons, an elliptical flat shape, a flat shape in which 3 to 8 circles having the same diameter are arranged in a straight line, and a cross shape , C-shape, H-shape, Y-shape, T-shape, V-shape, star shape, multi-leaf shape, and array shape, and these shapes having 1 to 6 cavities may be combined. When the synthetic fiber of the present invention is used as a reinforcing material, if it has an irregular cross-sectional shape with a large surface area, particularly a multi-leaf shape, the adhesive strength with the matrix fiber is increased, and a high-strength fiber reinforced molded article is obtained. be able to. Even when manufacturing non-woven fabrics, paper, etc., if these atypical cross-sectional shapes are used, the number of bonded portions with other synthetic fibers, matrix fibers, etc. of the present invention will increase, so that non-woven fabrics with high strength will be manufactured. Can do.

(Synthesis and production method of lanthanoid rare earth compounds)
Next, a method for synthesizing and producing a lanthanoid rare earth compound suitable for the present invention, particularly holmium oxide, will be described. As a method for producing holmium oxide, an aqueous solution of a holmium compound and an aqueous solution of oxalic acid are used as raw materials, and these are mixed to form a precipitate, which is then washed, dried, fired, and pulverized. The method is known. On the other hand, it has also been proposed to use a holmium nitrate aqueous solution and an ammonium bicarbonate aqueous solution in order to obtain a finer powder with higher purity. However, in recent years, as environmental problems have become more serious, methods using nitrogen compounds are industrially difficult because they require a large amount of capital investment in order to satisfy the nitrogen emission regulations. Therefore, an aqueous solution of a holmium compound, for example, holmium chloride, holmium sulfate, holmium oxalate, and an alkali metal carbonate, for example, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate aqueous solution are mixed to precipitate holmium carbonate. Then, a method has been proposed in which the precipitate is washed with pure water, dried, calcined, and pulverized as desired to produce holmium oxide powder (see, for example, JP-A-2001-335318). In order to obtain holmium oxide having a primary particle size of 0.6 to 9.0 μm necessary for the present invention, it is important to first mix while stirring the raw materials. In this way, the final product can be easily pulverized. Thereafter, the precipitate is dispersed in a slurry in washing water, and the solid and liquid are separated by pressure filtration, atmospheric pressure filtration, vacuum filtration, centrifugal separation, etc., and 600 using a tubular furnace, box furnace, tunnel furnace or the like. Heat in the range of ˜900 ° C. to obtain holmium oxide. Thereafter, holmium oxide is pulverized to a desired particle size, but a wet pulverizer such as a ball mill or an ultrasonic pulverizer is preferable instead of a dry pulverizer such as a pin mill, a hammer mill, or a roll mill. In particular, in order not to generate secondary agglomerated particles, it is important not to make the primary particles too fine, and a nonpolar organic solvent may be used during wet pulverization.

(Synthetic fiber spinning method)
When the synthetic fiber of the present invention and the thermoplastic resin is polypropylene, for example, a method capable of producing a polypropylene fiber having a single yarn fineness of 0.5 to 30.0 dtex using isotactic polypropylene, for example. Any method may be used. As a method for producing polypropylene fiber, a method in which the spinning and drawing steps are continuously performed (direct spinning drawing method), and a method in which an undrawn yarn is once collected and then drawn in another step (hereinafter referred to as “separate drawing method”). However, among them, the synthetic fiber of the present invention employs a general method for producing short fibers that is drawn and cut by a separate elongation method using polypropylene having a melt flow rate of 10 to 30 g / 10 min. By doing so, it can be manufactured smoothly.

That is, after drying the above-mentioned isotactic polypropylene polymer into a chip shape, it is melted and introduced into a known spinneret, extruded as a molten fiber yarn, cooled and solidified at a position of 15 to 100 mm below the spinneret, and a spinning speed of 300 to Winding undrawn yarn is obtained at 2000 m / min. The obtained unstretched yarn is stretched 1.5 to 4.0 times at 60 ° C to 100 ° C, heat-set in a relaxed state at 100 to 130 ° C, and cut into a predetermined length. Synthetic fiber. At this time, in order to reduce the heat shrinkage, there is usually a method of setting the stretching temperature or the heat setting temperature higher.
Moreover, even when a polyamide having a relative viscosity value of sulfuric acid at 25 ° C. of 1.5 to 3.5 is used as the thermoplastic resin, a short fiber is produced by adopting a production method according to the above method using polypropylene. can do.

(Fiber products including synthetic fibers)
Further, a fiber product containing at least a part of the above-described synthetic fiber of the present invention can also be provided. Preferably, the fiber product contains 0.1 to 100% by weight of the synthetic fiber of the present invention, and the specific fiber product is a dry nonwoven fabric using short fibers, a wet nonwoven fabric such as paper. A preferable mixing ratio is 1.0 to 80.0% by weight, and more preferably 5.0 to 60.0% by weight.

For non-woven fabrics, a dry method (card method) in which fibers are spread and mixed using a roller with needles, and a relatively short fiber is dispersed in water, and a wet method (paper making method) is used. After the web is formed by the air laid method (air laid method, dry pulp method) etc., in which a relatively short fiber is sent to a perforated drum by air and dispersed by air and then deposited on the wire to obtain a sheet, entanglement And / or a structure fixed by a heat treatment step. Further, among dry nonwoven fabrics and thermal bond nonwoven fabrics, those having a low density (0.01 to 0.10 g / cm ³ ) have been developed for applications characterized by resilience, cushioning properties, etc. Sometimes referred to as a fiber structure (sometimes simply referred to as a “fiber structure”) or hard cotton. Since the optimum conditions differ depending on the method of manufacturing the nonwoven fabric, each will be described individually below.

<Dry nonwoven fabric>
As a feature of the dry nonwoven fabric, it is possible to produce a wide range from a low basis weight to a high basis weight. If the nonwoven fabric of the present invention to adapt the dry method, the basis weight is preferably in the range of 15~2000g / ^{m 2,} and still more preferably is in the range of from 20~1200g / ^{m 2.} If the basis weight is less than 15 g / m ² , it may be extremely difficult to continuously produce a uniform web. On the other hand, when the basis weight exceeds 2000 g / m ² , productivity may be deteriorated.
Fiber fixing methods include entanglement of fibers by needle (needle punch method), entanglement of fibers by high-pressure water flow (spun lace method), adhesion by binder fiber (air-through method), entanglement by shrinkage, press by hot roll Etc. can be used as appropriate.

  When producing a nonwoven fabric using the synthetic fiber of the present invention, when it is a dry nonwoven fabric, the fiber length is preferably in the range of 30 to 150 mm, more preferably in the range of 50 to 100 mm. . If the fiber length is less than 30 mm, the web connection at the time of fiber opening is weak and there is a possibility that the occurrence of fiber dropout will increase. On the contrary, if the fiber length exceeds 150 mm, entanglement tends to occur and there is a risk that nep and the like are likely to occur. When applying a dry method to a nonwoven fabric using the synthetic fiber of this invention, it is preferable that crimp is provided to the synthetic fiber and matrix fiber of this invention to be used. At that time, as a method for imparting crimp, indentation crimp, gear crimp, three-dimensional crimp using anisotropy at the time of spinning, or the like can be used as appropriate.

<Wet nonwoven fabric>
The characteristics of the wet nonwoven fabric are that the formation is very good, a low-weight nonwoven fabric of several grams / m ² can be made, and the productivity is high. As will be described later, the synthetic fiber of the present invention is preferably used for special paper used for banknotes, securities, official documents, and the like. Is a very suitable fiber.

For synthetic fiber non-woven fabric is wet-laid nonwoven fabric produced using the present invention, the basis weight is preferably in the range of 5 to 200 g / ^{m 2,} and more preferably in a range of 20 to 100 g / ^{m 2.} If the basis weight is less than 5 g / m ² , the production may be extremely difficult. On the contrary, when the basis weight exceeds 200 g / m ² , the productivity of the nonwoven fabric may be deteriorated. When the nonwoven fabric manufactured using the synthetic fiber of the present invention is a wet nonwoven fabric, the fiber length is preferably in the range of 2 to 25 mm, and more preferably in the range of 3 to 20 mm. If the fiber length is less than 2 mm, there is little entanglement between the fibers, and the strength of the nonwoven fabric may be difficult. Conversely, if the fiber length exceeds 25 mm, uniform dispersion may be extremely difficult.

  When the nonwoven fabric produced using the synthetic fiber of the present invention is a wet nonwoven fabric, the binder fiber to be used, the synthetic fiber of the present invention to be used, and the matrix fiber to be used for others are not particularly limited with respect to crimping, In order to increase the bulk, it is preferable to have a zigzag mechanical crimp or a spiral three-dimensional crimp, and when the bulk is unnecessary, a straight fiber having no crimp is preferable.

  When the nonwoven fabric produced using the synthetic fiber of the present invention is a wet nonwoven fabric, the production method is roughly divided into a “paper making process” and a “heat treatment process”. As the paper making process, a short net paper machine, a circular net paper machine or the like can be used, and a multi-layer paper making by a combination of the same method or a combination of other methods may be used. As the heat treatment step, a rotary dryer, a multi-cylinder dryer, a calendar, etc. can be used alone or in combination depending on the use situation. Further, as post-processing, various types of resin processing and fiber entanglement processing by high-pressure water flow may be performed.

<Airlaid nonwoven fabric>
A feature of the airlaid nonwoven fabric is that it has a structure close to that of a wet nonwoven fabric and can have a low density (bulky) structure. For synthetic fiber non-woven fabric is air laid nonwoven fabric produced by using the present invention, the basis weight is preferably in the range of 10 to 400 g / ^{m 2,} and more preferably in a range of 20 to 300 g / ^{m 2.} If the basis weight is less than 10 g / m ² , it may be extremely difficult to produce. Conversely, if the basis weight exceeds 400 g / m ² , the productivity of the nonwoven fabric may be deteriorated.

  When the nonwoven fabric manufactured using the synthetic fiber of the present invention is an air laid nonwoven fabric, the fiber length of the synthetic fiber of the present invention to be used and the matrix fiber to be used for other is preferably in the range of 2 to 15 mm, 3 to 7 mm More preferably within the range. If the fiber length is less than 2 mm, there is little entanglement between the fibers, and the strength of the nonwoven fabric may be difficult. Conversely, if the fiber length exceeds 15 mm, uniform dispersion may be extremely difficult.

  The method for producing an air laid nonwoven fabric is roughly divided into a “web forming step” and a “heat treatment step”. As the web forming step, a method of forming by centrifugal force and suction by the rotation of two perforated drums (sometimes referred to as a head) (dan web method) is preferably used. In addition, the nonwoven fabric which piled up the layer from which a raw cotton structure differs can be manufactured directly by arranging many heads in series. As the heat treatment step, hot air suction type treatment, calendering, embossing and the like can be used alone or in combination depending on the use situation. Further, as post-processing, various types of resin processing and fiber entanglement processing by high-pressure water flow may be performed.

  Furthermore, clothing, sportswear, outdoor wear, lining, raincoat, men's clothing, women's clothing, work clothes, protective clothing, artificial leather, footwear, bags, curtains, tents, which are at least partially composed of these nonwoven fabrics, etc. Sleeping bag, chair upholstery, table cloth, car seat, roller blind, blind, notebook, blanket, bedding lining, bedding cover, bedding mat, chair covering material, partition, altar white cloth, curtain, cushion, carpet, mat, It is a textile product selected from at least one selected from the group represented by separators, special paper, banknotes, securities, official documents and filters. Preferably, the textile product is a special paper used for banknotes, securities, or official documents.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to a following example, unless the summary is exceeded. In addition, the measurement of the various physical properties of the obtained synthetic fiber was implemented with the following method.

(1) Types of thermoplastic resins The types of thermoplastic resins constituting the synthetic fibers obtained by the present invention are commercially available, such as heavy chloroform, heavy DMSO, heavy methanol, heavy toluene, heavy benzene, etc. ¹ H-NMR spectrum or ¹³ C-NMR spectrum at 600 MHz is measured using JEOLA-600 manufactured by JEOL, and dissolved in any appropriate one of the deuterated solvents. It was specified by.

(2) Intrinsic viscosity (IV) and melt flow rate (MFR)
When the thermoplastic resin constituting the synthetic fiber was polyester, IV was measured, and when the thermoplastic resin was polyolefin, MFR was measured. IV calculated the intrinsic viscosity from the solution viscosity which measured the fiber sample in the o-chlorophenol solution at 35 degreeC. The MFR was measured by a method based on the method of Table 1 and Condition 4 of JIS standard K7210. That is, when the obtained synthetic fiber was a polyolefin fiber, MFR was measured from the fiber sample according to JIS K-7210 Condition 4 (190 ° C., 21.18 N). The MFR is a value measured using a pellet before melt spinning as a sample.

(3) Content of lanthanoid rare earth compound Absorption characteristics of fibers with known holmium oxide content and different holmium oxide content are measured with a spectrophotometer U-4000 model manufactured by Hitachi High-Technologies Corporation. did. Focusing on the peak absorption band of 650 to 660 nm that appears when kneading holmium oxide into a thermoplastic resin, a calibration curve is created from the linear relationship between the total absorption amount and the holmium oxide content. As well as the content of holmium oxide in the textiles.

(4) Particle size of lanthanoid rare earth compound The primary particle size of a lanthanoid rare earth compound is generally expressed by a particle size measured in a large number as an abundance distribution. The “median diameter (D50)” obtained by SALD-3100 manufactured by Shimadzu Corporation, which uses “microtrack (laser diffraction / scattering method)” as a measurement principle this time, was adopted as a representative value indicating the particle diameter. In addition, using this apparatus, it was determined whether or not secondary aggregated particles having a particle diameter of 10 μm or more are contained depending on whether or not there is a distribution amount in a region having a particle diameter of 10 μm or more.

(5) Fineness Measured by the method described in JIS L 1015: 2005 8.5.1 Method A.

(6) Spinnability A melt spinning apparatus having a general round discharge hole was used, and a 250 mesh top filter was installed on a spinneret having a hole diameter of 0.15 mm. The spinning temperature was set to an appropriate temperature for each level of matrix resin, and 280 ° C. for polyethylene terephthalate and polybutylene terephthalate, 220 ° C. for polypropylene, and 270 ° C. for nylon 6. Then, when continuous spinning was performed for 6 hours at a discharge rate of 0.06 g / (min · hr) per hole and a spinning speed of 1000 m / min, the average number of yarn breaks per unit time was 10 times or more. ”, 5-10 times as“ × ”, 3-5 times as“ Δ ”, 1-3 times as“ ◯ ”, and 0-1 times as“ 」”.

(7) Filtration pressure rise degree In the above (6) continuous spinning test, the filtration pressure in the spinneret was simultaneously measured. 30 minutes after the start of the continuous spinning test, and when the test was terminated or when the spinning was interrupted due to deterioration of spinning, the filtration pressure immediately before that was read, and the degree of increase was evaluated by magnification. That is, the evaluation was performed using a numerical value represented by the following formula. It can be determined that the greater the degree of increase in the filtration pressure, the higher the risk of deterioration of the spinning condition during industrial production.
(Filtration pressure increase) = (Filtering pressure after 6 hours from the start of continuous spinning or immediately after continuous spinning is impossible) / (Filtering pressure after 30 minutes from the start of continuous spinning)

(8) Hue change under three-wavelength fluorescent lamps Hue changes in fibers and textiles are visible to the human eye because the light reflection characteristics differ depending on the single yarn fineness and the surface condition of the fibers and textiles. Quantitative evaluation of (hue change) is difficult. Therefore, limit samples having different appearances under the three-wavelength fluorescent lamp (day white: natural color) manufactured by Panasonic Corporation were prepared, and the following five-stage evaluation was performed in order of increasing hue change. Further, by comparison with this limit sample, it was possible to determine that the lanthanoid rare earth compound contained in the fiber, the nonwoven fabric, and the mixed paper was holmium oxide.
◎: Extremely significant hue change is recognized ○: Extremely significant hue change is observed □: Significant hue change is recognized Δ: Hue change is slightly observed ×: Hue change is hardly or hardly recognized

(9) Fabric weight, thickness and density of nonwoven fabric The fabric weight of nonwoven fabric is based on JIS P8124 (measuring method of paper and paperboard-basis weight), and the thickness and density of nonwoven fabric is JIS P8118 (paper and paperboard-thickness and density). The measurement was made based on the test method.

[Comparative Example 1]
A polyethylene terephthalate resin having an intrinsic viscosity of 0.64 dL / g contains 30% by weight of holmium oxide having a primary particle diameter (D50) of 0.5 μm, and a melt spinning test aimed at 15 dtex was attempted by a known melt spinning method. . However, after about 10 minutes from the start of discharge, the filtration pressure suddenly increased, discharge spots were generated, and the yarn connection (threading properties) deteriorated, making it impossible to collect the original yarn. Thereafter, when the residue on the filter was analyzed, a large amount of coarse particles (secondary aggregates) were found. The results are shown in Table 1.

[Comparative Example 2]
Using a polybutylene terephthalate resin with an intrinsic viscosity of 0.68 dL / g, a melt spinning test was conducted in the same manner as in Comparative Example 1. Although the rate of increase in filtration pressure was slightly delayed, the results were the same, and it was impossible to collect the yarn. The results are shown in Table 1.

[Comparative Example 3]
No distribution of particles having a particle size of 10 μm or more was observed, and 30 wt% of holmium oxide having a primary particle size (D50) of 1.2 μm was contained, and spinning was carried out in the same manner as in Comparative Example 2. An increase in filtration pressure was suppressed and a raw yarn was obtained, but the spinnability was not good, and it could not be said that the fiber could be continuously produced. Thereafter, it was stretched 2.5 times with a known stretching apparatus to obtain a shortcut cotton. When the obtained product was viewed under a three-wavelength fluorescent lamp, it was confirmed that the hue changed to pink. The results are shown in Table 1.

[Comparative Example 4]
An isotactic polypropylene resin having an MFR of 20 g / 10 minutes contains 50% by weight of holmium oxide having a primary particle size (D50) of 1.2 μm without any distribution of particles having a particle size of 10 μm or more, and is publicly known. A melt spinning test aimed at 15 dtex was attempted by a melt spinning method using a spinneret having a round discharge hole shape. Although fiber formation was possible despite the high content, the spinnability was poor, and it could not be said that the fiber could be produced continuously as in Comparative Example 3. However, the hue change of the obtained product under a three-wavelength fluorescent lamp was remarkable as dark pink. The results are shown in Table 1.

[Examples 1 to 4, Comparative Example 5]
In the same manner as in Comparative Example 4, the melt spinning test was carried out by changing the holmium oxide from 40.0 to 5.0% by weight. As the content of holmium oxide decreases, the degree of filtration pressure rises and the spinnability is improved, but the hue change under a three-wavelength fluorescent lamp is poor. On the other hand, the hue change in Examples 1 to 4 was also reversible, and the hue change speed was sufficiently high. The results are shown in Table 1.

[Example 5]
Under the same conditions as in Example 3, a melt spinning test was conducted with a target fineness of 7 dtex. The process tone was almost the same, but the hue change under the three-wavelength fluorescent lamp was weak as compared with Example 3. However, there was reversibility as well as the hue change in Examples 1 to 4, and the sufficient speed of the hue change remained high. The results are shown in Table 1.

[Examples 6 and 7]
In Example 1 and Example 3, instead of using an isotactic polypropylene resin with MFR = 20 g / 10 min, commercially available nylon 6 was used, and appropriate spinning and stretching conditions were appropriately selected for nylon 6, and holmium oxide was used. Synthetic fibers containing 40 wt% and 20 wt% were obtained. As in Examples 1 to 4, Example 6 with a high content of holmium oxide showed a significant change in hue under a three-wavelength fluorescent lamp, and Example 7 was poor in hue as compared with Example 6. However, in all cases, the hue change was reversible, and the speed of the hue change was sufficiently high. The results are shown in Table 1.

[Comparative Example 6, Examples 8 to 10]
Short cut fibers (single yarn fineness: 1.7 dtex, fiber length: 5 mm) made of ordinary polyester using the holmium oxide-containing fibers (single yarn fineness: 15 dtex, fiber length: 5 mm) produced in Example 1, and these Using shortcut fibers (single yarn fineness: 1.1 dtex, fiber length: 5 mm) made of the same polyester-based polymer that has the binder effect necessary to fix and bond the main fibers, and mix them at the mixing ratios shown in Table 2. Then, by a known paper making method, a 20 cm × 20 cm size mixed paper having a weight per unit area of 50 g / m ² was obtained. The results are shown in Table 2. The mixed paper obtained in Examples 8 to 10 had characteristics necessary as special paper used for banknotes, and was suitable for banknote applications. On the other hand, the mixed paper obtained in Comparative Example 6 was unsuitable for such use.

[Example 11]
Using the holmium oxide-containing fiber produced in Example 3, mixed paper was obtained at the same mixing ratio as Example 9. Regarding the hue change of the obtained mixed paper under a three-wavelength fluorescent lamp, Example 11 having a low content of holmium oxide became light pink. The results are shown in Table 2. The obtained mixed paper had characteristics required as special paper used for banknotes and official documents, and was suitable for them.

[Example 12]
Using the holmium oxide-containing fiber produced in Example 5, a mixed paper was obtained at the same mixing ratio as in Example 9. Regarding the hue change of the obtained mixed paper under a three-wavelength fluorescent lamp, the content of holmium oxide was the same, but Example 12 having a small single yarn fineness became whitish. The results are shown in Table 2. The obtained mixed paper had characteristics necessary as a special paper used for banknotes, and was suitable for banknotes and official documents.

Since this fiber is optimal for special paper with anti-counterfeiting effect used for banknotes, securities, official documents, etc., it is necessary to have dispersibility in water suitable for the papermaking process. In order to provide appropriate papermaking processability, existing fiber quality and technology for the same application can be used as they are.
Furthermore, when the fiber is contained in a part or all of the fiber product such as papermaking in an amount of 0.1 to 100% by weight, it becomes easy to mix the fiber product in the thickness direction, which could not be achieved with conventional printing inks. Further, it becomes possible to impart a further advanced anti-counterfeit effect.

Claims (9)

  A synthetic fiber comprising a lanthanoid rare earth compound and a thermoplastic resin containing polyolefin or polyamide, wherein the content of the lanthanoid rare earth compound is 7.0 to 45.0% by weight based on the weight of the thermoplastic resin. A synthetic fiber, characterized in that the lanthanoid rare earth compound has a primary particle diameter of 0.6 to 9.0 μm.   The lanthanoid rare earth compound is at least one lanthanoid rare earth element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The synthetic fiber according to claim 1, comprising:   3. The synthesis according to claim 1, wherein the lanthanoid rare earth compound is a holmium compound, and the primary particle diameter of the lanthanoid rare earth compound is 0.7 to 8.0 μm. fiber.   The synthetic fiber according to any one of claims 1 to 3, wherein the synthetic fiber does not contain the lanthanoid rare earth compound having a primary particle diameter of 10 µm or more.   The synthetic fiber according to any one of claims 1 to 4, wherein the polyolefin is polyethylene or polypropylene.   The synthetic fiber according to any one of claims 1 to 5, wherein a single yarn fineness of the synthetic fiber is in a range of 0.5 to 30.0 dtex.   The synthetic fiber according to any one of claims 1 to 6, wherein the polyolefin has a melt flow rate of 10 to 30 g / 10 min.   A fiber product comprising 0.1 to 100% by weight of the synthetic fiber according to any one of claims 1 to 7.   The textile product according to claim 8, wherein the textile product is a special paper used for banknotes, securities, or official documents.