JP2015089986A - Method of producing vulcanized fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vulcanized fiber improved in flexibility.SOLUTION: A method of producing a vulcanized fiber includes a step of immersing base paper based on natural fiber in an aqueous solution of a reaction chemical having properties of swelling and gelatinizing pulp to swell and gelatinize the surface of the base paper, a deliquoring step of removing the aqueous solution swelling and gelatinizing pulp from the base paper with a cleaning solution to obtain a base material and a drying and finishing step of drying and finishing the base material, and the base material after the deliquoring step is impregnated or applied with a nitrogen-containing sulfur-containing water-soluble compound.

Description

  The present invention relates to a method for producing a vulcanized fiber. More specifically, by improving hardness and brittleness, it has excellent flexibility in opening and closing use that requires bending and bending, bending processing, etc., suitable for applications that require flexibility such as bags, wallets, hinges, etc. The present invention relates to a method for producing a vulcanized fiber that can be used in the manufacturing process.

  Vulcanized fiber swells and gelatinizes the base paper surface by immersing a base paper mainly composed of natural fiber such as wood pulp and cotton pulp into a reaction chemical that swells and glues pulp such as an aqueous solution of zinc chloride. It is a tough organic industrial material produced by removing the reaction chemicals with a cleaning solution to stop the swelling / gliding reaction, followed by drying and finishing. Excellent mechanical strength such as impact resistance and wear resistance, and good workability such as punching and pressing. Furthermore, it is a material excellent in oil resistance and electrical insulation. Conventionally, lighting, television, audio, spacers, washers (see Patent Document 1), motor core ends, slot wedges, spacers, arc-extinguishing plates for circuit breakers, due to this excellent mechanical strength, electrical insulation, and post-processing suitability・ Fuse cylinders, electronic parts containers / partition plates, dry cell peripheral parts, electrical equipment parts for electrical insulation bonded to Nomex and PET film, or impact resistance, wear resistance, heat resistance, resin adhesion Utilizing abrasive discs (see Patent Document 2) and various packings as base materials for abrasive belts, machine parts, or decorative board substrates and plywood surface materials depending on impact resistance, resin processability, printability, aging resistance, etc. As a building material, or as a mask for welding, welding holder, helmet by impact resistance, durability, non-melting property, electrical insulation, drawing workability, etc. Safety equipment, or large transport boxes, delivery boxes, suitcases, paperback boxes, trays, tape cases, musical instrument cases, waste paper collection boxes, bag cores, shoe cores, depending on impact resistance, abrasion resistance, aging resistance, drawing workability, etc. , Various tags, armor equipment (refer to Patent Document 3), cosmetic box (refer to Patent Document 4), various containers and miscellaneous goods as various structural members for bowling alleys, or a school utilizing the warm taste and processability of natural materials Work materials, paper clips, toys (see Patent Document 5), environmentally friendly fiber hooks as teaching materials, stationery, clothing, wrap film and aluminum foil cutting blades (see Utility Model Document 6) that are easy to separate and collect There are uses such as food packaging materials. Since vulcanized fibers are composed of natural cellulose fibers, vulcanized fibers are environmentally friendly industrial materials that have biodegradability when discarded and clean incineration suitability.

  In addition, this vulcanized fiber is blended with carbon fiber (see Patent Document 7) in the base paper to give a conductive function, or polyester (see Patent Documents 8 and 9) to give a dimensional stability function. In addition, various inorganic fibers, organic chemical synthetic fibers, and fillers can be blended, for example, by adding powder of aluminum hydroxide (see Patent Document 10) to the base paper to impart a flame-retardant function.

  There has also been a proposal of impregnating a vulcanized fiber with a humectant typified by glycerin to impart moisture retention and moisture absorption for the purpose of improving flexibility (see Patent Document 11).

  Since the vulcanized fiber swells and glues the surface of the base paper and expresses its strong mechanical strength, it is generally hard, weak against bending and stretching, and has a problem that wrinkles and cracks are likely to occur. There is also a method for improving flexibility by impregnating with a moisturizing agent as in Patent Document 11 described above, but in this case, depending on the amount of moisturizing agent impregnated, the moisture content of the vulcanized fiber becomes too high, such as bags and wallets. When applied to products, there were problems such as the contents getting wet and the hands getting dirty when touched.

JP 2007-159415 A JP2011-148058A JP 58-203781 A JP 2003-125828 A JP 2009-291433 A Utility Model Registration No. 2571103 JP-A-2-000505 JP-A-2005-240253 JP 2006-200044 A JP-A-2-33398 Utility model registration No. 3099092

  The present invention improves the hardness and brittleness of vulcanized fibers, has excellent flexibility in opening and closing use and bending processing that requires bending and stretching, and uses that require flexibility such as bags, wallets, hinges, etc. Another object of the present invention is to provide a vulcanized fiber with improved flexibility that can be suitably used for the above.

  In order to achieve the above object, the method for producing vulcanized fiber of the present invention is characterized by impregnating or applying a nitrogen-containing / sulfur-containing water-soluble compound after the liquid removal step in order to improve flexibility.

  The present invention includes the following means. In the method for producing vulcanized fiber of the present invention, a base paper mainly composed of one or more natural fibers is immersed in an aqueous solution of a reactive chemical having a property of swelling and gelatinizing pulp, for example, an aqueous solution of zinc chloride. The process of swelling and gluing the surface of the base paper, the step of laminating those base papers when two or more base papers are used, and the removal of reactive chemicals that have the property of swelling and gluing the pulp from the base paper with the cleaning liquid In the method of producing a vulcanized fiber by sequentially applying a liquid removal step for obtaining a base material and drying and finishing steps of the base material, a nitrogen-containing / sulfur-containing water-soluble compound is added to the base material after the liquid removal step. Is impregnated or coated.

  Moreover, in this invention, content in the vulcanized fiber of the said nitrogen-containing and sulfur-containing water-soluble compound is good also as 10-45 mass% in conversion of solid content with respect to the dry weight of the said base material. With such a configuration, sufficient flexibility can be obtained, and an increase in humidity control moisture due to excessive addition and an increase in cost and an economical disadvantage can be suppressed.

  In the present invention, the thickness of the vulcanized fiber may be 2 mm or less. By setting it as such a structure, sufficient softness | flexibility can be provided to a vulcanized fiber even if the impregnation time to the base material of a nitrogen-containing and sulfur-containing water-soluble compound is comparatively short.

  In the present invention, moisture may be adjusted to 5 to 11% when the vulcanized fiber is conditioned in an environment of 23 ° C. × 50% RH. By adopting such a configuration, the brittleness and easy cracking due to the moisture being too low are prevented, and when making a product such as a bag or a wallet, the moisture is too high and the contents become wet. Problems such as contamination can be prevented.

  According to the present invention, by improving the hardness and brittleness of a vulcanized fiber, it is possible to provide a vulcanized fiber having improved flexibility while maintaining an appropriate amount of water. The vulcanized fiber of the present invention has excellent flexibility in opening and closing use and bending work that requires bending and stretching, and can be suitably used for applications requiring flexibility such as bags, wallets, and hinges. it can.

  Hereinafter, the present invention will be described, but the present invention is not construed as being limited to these embodiments.

  In the method for producing vulcanized fiber of the present invention, a base paper whose main fiber is composed of natural fiber such as wood pulp and cotton pulp is used. Wood pulp chemicals such as softwood dissolved sulfate pulp (NDSP), softwood bleached kraft pulp (NBKP), softwood unbleached kraft pulp (NUKP), hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP) Examples thereof include mechanical pulp such as pulp, groundwood pulp (GP) and thermomechanical pulp (TMP), and waste paper pulp such as deinked pulp. One or more selected from these raw material pulps can be used. Among these, it is particularly preferable to use singly or in combination. For example, 15 to 55 parts by mass of NDSP, 25 to 75 parts by mass of NUKP, and 5 to 25 parts by mass of NBKP with respect to 100 parts by mass of total pulp slurry, or NDSP with respect to 100 parts by mass of total pulp slurry. A pulp slurry containing 25 to 45 parts by mass, 35 to 65 parts by mass of NUKP, and 10 to 20 parts by mass of NBKP is used. The pulp slurry is preferably adjusted to an appropriate freeness. For example, it is preferable to make it 450 to 750 ml CSF and 550 to 650 ml CSF by beating with Canadian standard freeness (freeness) (JIS P 8121: 1995 “Pulp Freeness Test Method”). Further, this base paper is preferably made of cotton fibers such as cotton boro pulp and linter, paper pulp for wood fibers, non-wood fibers such as kenaf and bamboo pulp, and regenerated cellulose fibers such as rayon by wet papermaking. Can be used. Further, organic chemical synthetic fibers and inorganic fibers can be blended within the range in which the intended effect of the present invention is not impaired. The base paper has appropriate water absorption, air permeability, and uniformity so that the zinc chloride aqueous solution can uniformly penetrate into the base paper when immersed in a certain reactive chemical, such as zinc chloride aqueous solution, which swells and glues pulp. It is preferable to have a good formation.

  This base paper is immersed in an aqueous solution of a reaction chemical such as zinc chloride by a conventional method to swell and gelatinize the surface of the base paper. In this case, the zinc chloride concentration is preferably 65 to 74 Baume (° Be). Further, the temperature of the immersion treatment is preferably 33 to 55 ° C. At this time, when two or more base papers are used, these base papers are laminated. The vulcanized fiber made of one sheet of paper does not require a lamination process. The reactive chemical is not particularly limited as long as it swells and gelatinizes the cellulose fiber. In addition to the aqueous solution of zinc chloride, N-methylmorpholine-N-oxide, N-methylmorpholine-N- A mixed solution of oxide and polar liquid, sulfuric acid, or the like can be used, but a method using an aqueous solution of zinc chloride is most industrialized and is most desirable for mass production.

  After the surface of the base paper is swollen and glued, and laminated as necessary, the base material is obtained by removing the reactive chemicals having the property of swelling and gelatinizing the pulp in the dewatering step with a washing liquid. For example, a zinc chloride solution with a concentration lower than 65-74 Baume, such as a 15-33 Baume zinc chloride aqueous solution to a solution containing almost no zinc chloride or water containing no zinc chloride step by step. Prepare the solution as a cleaning solution. It may be drained stepwise by placing it in a plurality of washing tubs. Furthermore, in the liquid removal process, as disclosed in JP 09-302594 A, a single-stage or multi-stage vibrating blade is rotated around a vibrating shaft that vibrates in the axial direction in order to advance the removal of reactive chemicals such as zinc chloride. An apparatus that is impossiblely fixed may be put into a cleaning liquid in a dechlorination zinc tank, and the liquid removal treatment may be performed while applying vibration with a vibration frequency of 10 to 60 Hz and a vibration width of 2 to 30 mm to the vibration blade plate.

  After removing the reactive chemical from the base paper in the liquid removal step to obtain a base material, the base material is impregnated or coated with a nitrogen-containing / sulfur-containing water-soluble compound. As a method of impregnating or applying the nitrogen-containing / sulfur-containing water-soluble compound, a method of impregnating the substrate after the liquid removal step through the impregnation tank while wet, a part of the substrate after the liquid removal step in the drying step or A method of allowing all moisture to evaporate and then impregnating it through an impregnation tank. Substrate after the liquid removal process is sufficiently evaporated in the drying process and then dipped in water, letting it wet and then passing through the impregnation tank. The impregnation may be performed by any method of impregnation. In any of the above methods, impregnation by a size press, application by shower spraying, application by a coating machine such as a roll coater is possible instead of impregnation in an impregnation tank. Regardless of which method is used for impregnation or application, drying is performed after impregnation or application of the nitrogen-containing / sulfur-containing water-soluble compound.

  As the nitrogen-containing / sulfur-containing water-soluble compound to be impregnated or applied to the substrate, a nitrogen-containing / sulfur-containing water-soluble compound commercially available as an aqueous solution is preferable. A solid nitrogen-containing / sulfur-containing water-soluble compound may be used as long as it can be dissolved in water at a concentration at which the content of the base material sufficient to impart flexibility can be obtained. Here, the nitrogen-containing / sulfur-containing water-soluble compound is not particularly limited. For example, guanidine sulfamate compound, guanidine methylolsulfamate compound, ammonium sulfamate compound, guanidine sulfate compound, ammonium sulfate compound, sulfoamide. Compounds, ammonium persulfate compounds, and the like. These compounds can be used alone or in combination of two or more. Specific examples include ammonium sulfamate, ammonium phosphate, guanidine sulfamate, and the like.

  The content of the nitrogen-containing / sulfur-containing water-soluble compound in the vulcanized fiber is not particularly limited, but is preferably 10 to 45% by mass with respect to the dry weight of the substrate. More preferably, it is 15-40 mass%, More preferably, it is 18-38 mass%, Furthermore, it is 20-35 mass%. By setting the content of the nitrogen-containing / sulfur-containing water-soluble compound in the vulcanized fiber within this range, sufficient flexibility can be given to the vulcanized fiber, and adjustment by excessive addition of the nitrogen-containing / sulfur-containing water-soluble compound is possible. An increase in wet moisture and an increase in cost can be suppressed. If the amount is less than 10% by mass, sufficient flexibility may not be imparted to the vulcanized fiber. If the amount exceeds 45% by mass, excessive addition will not be disadvantageous in terms of cost, but also increase the moisture content. Invite. As a result, when applied to a product such as a bag or a wallet, there is a risk that the contents become damp or the hand gets dirty when touched. The content of nitrogen-containing / sulfur-containing water-soluble compounds in vulcanized fibers can be adjusted by the concentration of impregnation solution and impregnation treatment time when impregnating the base material, and the amount of application if applied. Can be adjusted. The flexibility of the vulcanized fiber does not completely correlate with the evaluation of the bending brittleness described later, but Gurley stiffness can be used as one index. By including the nitrogen-containing / sulfur-containing water-soluble compound, the Gurley stiffness can be lowered compared with the case where the nitrogen-containing / sulfur-containing water-soluble compound is not contained, and the reduction rate can be 20% or more. .

  The thickness of the vulcanized fiber of the present invention can be set to a desired thickness in the application. For example, it can be set to 0.1 mm to 2.5 mm. Furthermore, the thickness of the vulcanized fiber of the present invention is preferably 2 mm or less. In order to reduce the thickness of the vulcanized fiber to 2 mm or less, it is necessary to make the thickness of the substrate 2 mm or less. By making the thickness of the substrate relatively thin, the substrate of nitrogen-containing / sulfur-containing water-soluble compound can be obtained. Even if the impregnation time is relatively short, sufficient flexibility can be imparted to the vulcanized fiber. In order to give the vulcanized fiber sufficient flexibility, it is necessary to contain a sufficient amount of nitrogen-containing / sulfur-containing water-soluble compound up to the inside of the base material. Impregnation may not be possible. However, if the thickness of the vulcanized fiber is 2 mm or less, the thickness of the base material can be made relatively thin, and sufficient flexibility can be obtained even with relatively short impregnation. Nitrogen / sulfur-containing water-soluble compounds can be impregnated inside the substrate.

  After impregnating or coating the substrate with a nitrogen-containing / sulfur-containing water-soluble compound, a vulcanized fiber is obtained through a drying and finishing process. The drying method is not particularly limited, and hot air drying, microwave drying, infrared drying, roll dryer drying, and the like can be used, and the vulcanized fiber is dried to a desired moisture. In the finishing process, cutting is performed to a predetermined dimension such as roll winding or flat plate cutting. Moreover, in a finishing process, you may give a smoothness by giving a calendar process. Furthermore, embossing with an embosser may be performed.

  In the present invention, the moisture when the vulcanized fiber is conditioned in an environment of 23 ° C. × 50% RH may be 5 to 11%. More preferably, it may be 5 to 10.5%. If the water content is less than 5%, the vulcanized fiber may become brittle or easily broken. If the water content exceeds 11%, there is a risk that when the product is made into a bag, a wallet or the like, the water content is too high and the contents become wet, and when touched, the hand becomes dirty. The method for adjusting the moisture is not particularly limited, and a known method used in the paper industry can be used, and it can be adjusted mainly by the aforementioned drying step. The drying temperature is preferably set appropriately in the range of 80 to 180 ° C. In addition, many of the nitrogen-containing and sulfur-containing water-soluble compounds used in the present invention have relatively high moisture retention, and the moisture content of the vulcanized fiber varies depending on the amount of impregnation, so the conditions such as the drying temperature should be taken into consideration. It is preferable to set appropriately. In many cases, the moisture content tends to increase as the amount of impregnation of the nitrogen-containing / sulfur-containing water-soluble compound increases.

  Hereinafter, although the manufacturing method of the vulcanized fiber which concerns on this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. In the examples, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified. The number of added parts is a value in terms of solid content.

Example 1
<Production of base material>
A pulp slurry comprising 35 parts of NDSP, 50 parts of NUKP and 15 parts of NBKP is C.I. S. The papermaking raw material was obtained after adjusting to F600 ml. Five base papers made using this paper raw material were immersed in an aqueous solution of zinc chloride (69 ° Be, 44 ° C.) to swell and glue the surface of the base paper, and then the five base papers were laminated. Thereafter, each tank is immersed stepwise in a plurality of baths containing a cleaning solution whose concentration is gradually reduced from a 23 ° Be zinc aqueous solution to water containing no zinc chloride, thereby removing the aqueous zinc chloride solution from the base paper. Liquid removal treatment was performed to obtain a substrate.
<Preparation of impregnation liquid>
Sulfur-containing, high-molecular guanidine phosphate (trade name: Nikkafinon S-200, stock concentration 42%, manufactured by Nikka Chemical Co., Ltd.) is added to water as a nitrogen-containing / sulfur-containing water-soluble compound and stirred. An impregnating liquid having a solid content concentration of 30% was obtained.
<Production of vulcanized fiber>
By impregnating the impregnating solution on an impregnating bat and immersing the substrate therein, the content of the nitrogen-containing and sulfur-containing water-soluble compound is 37% by mass in terms of solid content with respect to the dry weight of the substrate. So that the desired vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 10 minutes. The thickness of the vulcanized fiber was 0.5 mm.

(Example 2)
A vulcanized fiber was obtained in the same manner as in Example 1 except that impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 22% by mass in terms of solid content with respect to the dry weight of the substrate. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Example 3)
Nitrogen- and sulfur-containing water-soluble compounds are changed to sulfoamide compounds (trade name: Bigor H-31-2, stock solution concentration 48%, manufactured by Daikyo Chemical Co., Ltd.) A vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so that the solid content was 23% by mass in terms of solid content. The immersion time of the base material in the impregnating liquid was 5 minutes.

Example 4
Nitrogen- and sulfur-containing water-soluble compounds are changed to phosphorus / sulfoamide compounds (trade name: Bigor PN-12, stock solution concentration 44%, manufactured by Daikyo Chemical Co., Ltd.) A vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so as to be 22% by mass in terms of solid content with respect to the weight. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Example 5)
Nitrogen- and sulfur-containing water-soluble compounds were changed to sulfoamide compounds (trade name: Bigor R-501, stock solution concentration 50%, manufactured by Daikyo Chemical Co., Ltd.), and the content of water-soluble compounds was changed to the dry weight of the substrate. On the other hand, a vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so that the solid content was 24% by mass. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Example 6)
Nitrogen- and sulfur-containing water-soluble compounds are changed to sulfamate derivatives (trade name: Sun Flame NF-6, stock solution concentration 60%, manufactured by San Nopco Co., Ltd.), and the content of water-soluble compounds is reduced to the dry weight of the substrate. On the other hand, a vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so that the solid content was 22% by mass. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Example 7)
Nitrogen- and sulfur-containing water-soluble compound was changed to guanidine sulfamate aqueous solution (trade name: EFNICA FK187-20, stock concentration 37%, manufactured by Nanjo EFNICA Co., Ltd.). A vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so as to be 27% by mass in terms of solid content with respect to the weight. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Example 8)
Nitrogen- and sulfur-containing water-soluble compounds were changed to guanidine sulfamate (trade name: Apinone-145, stock solution concentration 45%, manufactured by Sanwa Chemical Co., Ltd.), and the content of water-soluble compounds is based on the dry weight of the substrate. A vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so that the solid content was 25% by mass. The immersion time of the base material in the impregnating liquid was 5 minutes.

Example 9
Nitrogen- and sulfur-containing water-soluble compound was changed to a mixture of ammonium phosphate and ammonium sulfamate (trade name: Nikkafinon 900, stock solution concentration 47%, manufactured by Nikka Chemical Co., Ltd.). Was obtained in the same manner as in Example 1 except that it was impregnated so as to be 20% by mass in terms of solid content with respect to the dry weight of the base material. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Example 10)
Example 1 except that the thickness of the vulcanized fiber was 0.2 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 17% by mass in terms of solid content with respect to the dry weight of the substrate. Similarly, vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 3 minutes.

(Example 11)
Example 1 except that the thickness of the vulcanized fiber was 0.3 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 22% by mass in terms of solid content with respect to the dry weight of the substrate. Similarly, vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 1 minute.

(Example 12)
Example 1 except that the thickness of the vulcanized fiber was 0.3 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 12% by mass in terms of solid content with respect to the dry weight of the substrate. Similarly, vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 0.6 minutes.

(Example 13)
Example 1 except that the thickness of the vulcanized fiber was 0.3 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 42% by mass in terms of solid content with respect to the dry weight of the substrate. In the same manner, a flexible treated vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Example 14)
Example 1 except that the thickness of the vulcanized fiber was 1.0 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 31% by mass in terms of solid content with respect to the dry weight of the substrate. Similarly, vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 10 minutes.

(Example 15)
Example 1 except that the thickness of the vulcanized fiber was 1.4 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 19% by mass in terms of solid content with respect to the dry weight of the substrate. In the same manner, a flexible treated vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 15 minutes.

(Example 16)
Example 1 except that the thickness of the vulcanized fiber was 2.0 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 15% by mass in terms of solid content with respect to the dry weight of the substrate. Similarly, vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 20 minutes.

(Example 17)
Example 1 except that the thickness of the vulcanized fiber was 0.3 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 8% by mass in terms of solid content with respect to the dry weight of the substrate. Similarly, vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 0.3 minutes.

(Example 18)
Example 1 except that the thickness of the vulcanized fiber was 2.4 mm and impregnation was performed so that the content of the nitrogen-containing / sulfur-containing water-soluble compound was 10% by mass in terms of solid content with respect to the dry weight of the substrate. Similarly, vulcanized fiber was obtained. The immersion time of the base material in the impregnating liquid was 25 minutes.

(Comparative Example 1)
A vulcanized fiber was obtained in the same manner as in Example 1 except that the thickness of the vulcanized fiber was 0.5 mm, and it was dried without impregnating the nitrogen-containing / sulfur-containing water-soluble compound.

(Comparative Example 2)
A vulcanized fiber was obtained in the same manner as in Example 1 except that the thickness of the vulcanized fiber was 0.3 mm, and it was dried without impregnating the nitrogen-containing / sulfur-containing water-soluble compound.

(Comparative Example 3)
The thickness of the vulcanized fiber is 0.3 mm, and polyethylene glycol (trade name: PEG-200, stock concentration 100%, manufactured by Meisei Chemical Industry Co., Ltd.) is used instead of the nitrogen-containing / sulfur-containing water-soluble compound. A vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so that the content was 22% by mass in terms of solid content with respect to the dry weight of the substrate. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 4)
Instead of the nitrogen-containing or sulfur-containing water-soluble compound to be impregnated into the base material, guanidine phosphate (trade name: Bigor No415, stock solution concentration 47%, manufactured by Daikyo Chemical Co., Ltd.) is used, and the content of guanidine phosphate is the base material. A vulcanized fiber was obtained in the same manner as in Example 1 except that it was impregnated so as to be 24% by mass in terms of solid content with respect to the dry weight. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 5)
Carbamine phosphate (trade name: Bigol TP, stock solution concentration 40%, manufactured by Daikyo Chemical Co., Ltd.) is used instead of the nitrogen-containing / sulfur-containing water-soluble compound impregnated into the substrate, and the content of carbamine phosphate is the substrate. A vulcanized fiber was obtained in the same manner as in Example 1 except that it was impregnated so as to be 22% by mass in terms of solid content with respect to the dry weight. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 6)
Polyphosphate carbamate (trade name: Nikkafinon P-3, stock solution concentration 31%, manufactured by Nikka Chemical Co., Ltd.) was used instead of the nitrogen-containing / sulfur-containing water-soluble compound impregnated into the base material, and the inclusion of polyphosphate carbamate A vulcanized fiber was obtained in the same manner as in Example 1, except that the amount was 17% by mass in terms of solid content with respect to the dry weight of the substrate. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 7)
A condensed phosphoric acid carbamate-based mixture (trade name: Pyroguard F-400N, stock solution concentration 50%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is used instead of the nitrogen-containing / sulfur-containing water-soluble compound impregnated into the base material. A vulcanized fiber was obtained in the same manner as in Example 1, except that the content of the carbamate mixture was impregnated so as to be 24% by mass in terms of solid content with respect to the dry weight of the substrate. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 8)
Instead of the nitrogen-containing or sulfur-containing water-soluble compound impregnated into the base material, ammonium polyphosphate salt (trade name: KD-240M, stock solution concentration 40%, manufactured by Takamatsu Yushi Co., Ltd.) is used. A vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so as to be 24% by mass in terms of solid content with respect to the dry weight of the substrate. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 9)
A guanidine phosphate aqueous solution (trade name: EFNICA FK781, stock solution concentration 15%, manufactured by Nanjo EFNICA Co., Ltd.) is used instead of the nitrogen-containing / sulfur-containing water-soluble compound impregnated in the base material, and the content of guanidine phosphate is A vulcanized fiber was obtained in the same manner as in Example 1 except that the impregnation was performed so as to be 12% by mass in terms of solid content with respect to the dry weight of the substrate. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 10)
Instead of nitrogen-containing and sulfur-containing water-soluble compounds to be impregnated into the base material, guanidine phosphate (trade name: Apinon-307, stock concentration 50%, manufactured by Sanwa Chemical Co., Ltd.) is used, and the content of guanidine phosphate is based on A vulcanized fiber was obtained in the same manner as in Example 1 except that the material was impregnated so as to be 23% by mass in terms of solid content with respect to the dry weight of the material. The immersion time of the base material in the impregnating liquid was 5 minutes.

(Comparative Example 11)
A vulcanized fiber was obtained in the same manner as in Example 1 except that the thickness of the vulcanized fiber was 0.2 mm and the vulcanized fiber was dried without impregnation with the nitrogen-containing / sulfur-containing water-soluble compound.

(Comparative Example 12)
A vulcanized fiber was obtained in the same manner as in Example 1 except that the thickness of the vulcanized fiber was 1.0 mm and the vulcanized fiber was dried without impregnation with the nitrogen-containing / sulfur-containing water-soluble compound.

(Comparative Example 13)
A vulcanized fiber was obtained in the same manner as in Example 1 except that the thickness of the vulcanized fiber was 1.4 mm and the vulcanized fiber was dried without impregnation with the nitrogen-containing / sulfur-containing water-soluble compound.

(Comparative Example 14)
A vulcanized fiber was obtained in the same manner as in Example 1 except that the thickness of the vulcanized fiber was 2.0 mm and the vulcanized fiber was dried without impregnation with the nitrogen-containing / sulfur-containing water-soluble compound.

  Table 1 shows the compositions and evaluation results for the vulcanized fibers obtained in each Example and Comparative Example. The evaluation results shown in Table 1 were performed by the following method.

<Thickness>
JIS P 8118: 1998 Paper and paperboard-The thickness of vulcanized fiber was measured according to the thickness and density test method.

<Measurement of humidity control moisture>
In accordance with JIS C2315-2: 2010 electrical vulcanized fiber test method, vulcanized fiber was conditioned. With respect to the conditioned sample, moisture was measured according to a method using a JIS P8127: 2010 paper and paperboard (lot moisture test method) dryer.

<Measurement of Gurley stiffness>
JAPAN TAPPI Paper Pulp Test Method No. 40: 2000 Paper and Paperboard-Stiffness Test Method by Load Bending-Measurements were made in the longitudinal direction (MD direction) and lateral direction (CD direction) of the vulcanized fiber according to the Gurley method.

<Evaluation of fragility>
When the corners of the vulcanized fiber pieces obtained in each of the examples and comparative examples are folded by 180 degrees so as to form a triangle at a location about 1 cm from the corner, the folded portion is returned to a flat state again, and the outer side of the fold portion is restored. Were visually observed and evaluated as follows.
◎ No wrinkles when folded back. Pass.
○ When folded back, the surface will wrinkle but will not crack. Pass.
△ When folded back, the middle layer cracks from the surface that does not break. failure.
× When folded back, all layers crack and break. failure.

  As is clear from the results shown in Table 1, the vulcanized fibers obtained in Examples 1 to 18 have good fragility and good ◎ and ○, and are bent with improved hardness and brittleness. It was possible to have excellent flexibility in opening / closing use and bending work that required stretching.

  On the other hand, the vulcanized fibers obtained in Comparative Examples 1, 2, 4 to 14 were in a brittle state with a low evaluation of bending brittleness.

  Further, the vulcanized fiber obtained in Comparative Example 3 has good Gurley stiffness and breakage brittleness, but has very high moisture. This is probably because the moisture retention of the polyethylene glycol used in the impregnation liquid is very high, and the moisture of the impregnated vulcanized fiber is increased and the flexibility is improved, but the moisture is very high. For this reason, when the vulcanized fiber is touched with a hand, there is a sticky feeling, and when processed into a product such as a bag or a wallet, the contents become wet, and when touched, the hand becomes dirty.

  The vulcanized fiber obtained in Example 13 had a relatively high moisture content of 10.9%. Therefore, when the vulcanized fiber was touched by hand, there was a slight stickiness although it was an acceptable level. If the moisture is higher than this, there is a possibility that the contents become damp when processed into a product such as a bag or wallet, and that the hand may become dirty when touched. Therefore, it is preferable that the suitable more preferable water | moisture content of a vulcanized fiber is 10.5% or less.

Claims (5)

  The base paper mainly composed of natural fibers is immersed in an aqueous solution of reactive chemicals that can swell and gelatinize pulp, and the surface of the base paper is swelled and gelatinized. In the method for producing a vulcanized fiber by sequentially applying a liquid removal step for removing the aqueous solution to obtain a base material and drying and finishing steps of the base material, the base material after the liquid removal step contains nitrogen A method for producing a vulcanized fiber, which comprises impregnating or applying a sulfur water-soluble compound.   The method for producing vulcanized fiber according to claim 1, wherein the reactive chemical having the property of swelling and gelatinizing the pulp is zinc chloride.   The method for producing a vulcanized fiber according to claim 1, wherein the nitrogen-containing / sulfur-containing water-soluble compound is 10 to 45% by mass in terms of solid content with respect to the dry weight of the substrate.   The thickness of the said vulcanized fiber shall be 2 mm or less, The manufacturing method of the vulcanized fiber in any one of Claims 1-3 characterized by the above-mentioned.   The method for producing a vulcanized fiber according to any one of claims 1 to 4, wherein the moisture when adjusted in an environment of 23 ° C x 50% RH is 5 to 11%.