JP2015045113A - Sanitary tissue paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sanitary tissue paper having deodorant and antibacterial functions and also having high strength.SOLUTION: The sanitary tissue paper comprises a metal-carrying cellulose fiber in which an oxidized cellulose fiber having a carboxyl group or a carboxylate group on its surface carries one or more metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn and Cu.

Description

  The present invention relates to a sanitary thin paper having deodorant and antibacterial functions.

  Various imparting of deodorizing and antibacterial functions to sanitary thin paper such as tissue paper, toilet paper, and hand towels has been performed. For example, techniques for applying a chemical solution having a deodorizing and antibacterial function to a base paper are disclosed (Patent Documents 1 and 2). In addition, a technique is disclosed in which zeolite is supported inside cellulose fibers, Ag, Cu, etc. are supported in the zeolite, and paper is made from the cellulose fibers to impart deodorant and antibacterial functions to the paper itself ( Trade name Sergaia (registered trademark), Patent Document 3).

JP 2003-325372 A Special table 2010-511806 gazette Japanese Patent No. 4149066

However, when a chemical solution having a deodorizing and antibacterial function is applied to the base paper, the binding between the pulp fibers is weakened, so that paper dust is generated or the hygienic thin paper has the original strength, water absorption, texture, etc. It may be damaged. Furthermore, there is a possibility that the chemical solution released or eluted from the sanitary thin paper may irritate the skin.
On the other hand, in the case of the technique described in Patent Document 3, the fiber is deformed, damaged and shortened by a reaction when zeolite or the like is supported on the cellulose fiber. For this reason, when paper is produced from this cellulose fiber, the bonds between the fibers are weakened, and paper powder is likely to be generated. Also, since the zeolite is physically supported in the cellulose fiber, the zeolite is likely to fall off. .
Accordingly, an object of the present invention is to provide a sanitary thin paper having a deodorizing and antibacterial function and a high strength.

  In order to solve the above-mentioned problems, the sanitary thin paper of the present invention is made of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and oxidized cellulose fibers having a carboxyl group or a carboxylate group on the surface. It includes metal-supporting cellulose fibers that support one or more metal particles selected from the group of Cu.

When the tensile strength in the MD direction and CD direction when drying the sanitary thin paper measured according to JIS P8113 is DMD and DCD, respectively, the GMT value {(DMD × DCD) ^1/2 } is 60 to 420 (N / m ) Is preferable.

  According to the present invention, a sanitary thin paper having a deodorizing and antibacterial function and high strength can be obtained.

The sanitary thin paper according to the embodiment of the present invention is selected from the group of Ag, Au, Pt, Pd, Mn, Fe, Ti, Al, Zn and Cu with respect to the oxidized cellulose fiber having a carboxyl group or a carboxylate group on the surface. Metal-supporting cellulose fibers formed by supporting one or more kinds of metal particles.
This metal-supporting cellulose fiber can be obtained by bringing a metal compound aqueous solution into contact with an oxidized cellulose fiber having a carboxyl group or a carboxylate group introduced on the surface of the cellulose fiber. In addition, as a method for producing sanitary thin paper according to an embodiment of the present invention, in addition to a method of bringing the metal compound aqueous solution into contact with a sheet made of a raw material containing oxidized cellulose fibers, a metal is previously supported on the oxidized cellulose fibers. A method for making a raw material containing metal-supporting cellulose fibers can be exemplified.

The oxidized cellulose fiber can be produced by oxidizing cellulose fiber such as wood pulp using an N-oxyl compound as a catalyst. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and an oxidized cellulose fiber having a carboxyl group or a carboxylate group on the surface is obtained. The raw material cellulose is preferably natural cellulose. The oxidation reaction is preferably performed in water. Although the density | concentration of the cellulose fiber in reaction is not specifically limited, 5 mass% or less is preferable. The amount of the N-oxyl compound may be about 0.1 to 4 mmol / L with respect to the reaction system. A known cooxidant may be used for the reaction. Examples of the co-oxidant include dihalous acid or a salt thereof. The amount of the co-oxidant is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.
The reaction temperature is preferably 4 to 40 ° C., more preferably room temperature. The pH of the reaction system is preferably 8-11. The degree of oxidation can be appropriately adjusted depending on the reaction time, the amount of the N-oxyl compound, and the like.
The oxidized cellulose fiber thus obtained has acid groups on the surface and almost no acid groups inside. This is presumably because the cellulose fiber is crystalline, so that the oxidant hardly diffuses into the fiber.

The carboxyl group refers to a group represented by —COOH, and the carboxylate group refers to a group represented by —COO—. The counter ion of the carboxylate group is not particularly limited. As will be described later, when metal nanoparticles are formed through ionic bonds with carboxylate groups, these metal ions serve as a counter. The carboxyl group or carboxylate group is also referred to as an “acid group”.
The content of acid groups can be measured by the method disclosed in paragraph 0021 of JP2008-001728A. That is, using a precisely weighed dry cellulose sample, 60 mL of a 0.5 to 1 mass% slurry is prepared, and the pH is adjusted to about 2.5 with a 0.1 mol / L hydrochloric acid aqueous solution. Then, 0.05 mol / L sodium hydroxide aqueous solution is dripped and electrical conductivity measurement is performed. The measurement is continued until the pH is about 11. From the amount (V) of sodium hydroxide consumed until the neutralization step of the weak acid, where the change in electrical conductivity shows a gradual change, the acid group amount X1 is determined using the following equation.
X1 (mmol / g) = V (mL) × 0.05 / mass of cellulose (g)

  The amount of acid groups of the cellulose fiber is preferably 0.2 to 2.2 mmol / g. When the amount of acid groups is less than 0.2 mmol / g, the amount of metal particles present on the surface of the cellulose fiber is not sufficient, and the deodorizing and antibacterial functions may be inferior. When the amount of the acid group exceeds 2.2 mmol / g, the metal particles may aggregate, resulting in poor deodorization and antibacterial functions.

Next, an aqueous solution containing the metal compound is brought into contact with the oxidized cellulose fiber to bond the carboxyl group or carboxylate group (acid group) of the oxidized cellulose fiber with the metal compound. The metal compound should just form the coordinate bond and the hydrogen bond with the carboxyl group. Moreover, the metal ion derived from a metal compound may form the ionic bond with the carboxylate group. In this step, since the metal compound is considered to be bonded to the acid group at the molecular level, metal nanoparticles are not formed.
The metal compound aqueous solution is an aqueous solution of a metal salt or an organometallic compound. Examples of metal salts include complexes (complex ions), halides, nitrates, sulfates, and acetates. The metal salt is preferably water-soluble.
With regard to the method of contacting the metal compound, a cellulose fiber dispersion prepared in advance and a metal compound aqueous solution may be mixed, and a dispersion containing cellulose fibers is applied onto a substrate to form a film, and the metal compound is applied to the film. An aqueous solution may be dropped and impregnated. At this time, the film may remain fixed on the substrate or may be peeled from the substrate.
Although the density | concentration of metal compound aqueous solution is not specifically limited, 10-80 mass parts is preferable with respect to 100 mass parts of cellulose fibers, and 30-60 mass parts is more preferable.
You may adjust suitably the time which a metal compound is made to contact. Although the temperature at the time of making it contact is not specifically limited, 20-40 degreeC is preferable. In addition, the pH of the liquid at the time of contact is preferably 2.5 to 13.

Next, metal particles are formed by reducing the metal compound bound to the oxidized cellulose fiber obtained as described above. Although this mechanism is not clear, it is guessed as follows. The metal compound or the ion derived from the metal compound that has been bonded to the acid group by the reduction reaction is reduced to a metal. At this time, the produced metal is supported on the surface of the oxidized cellulose fiber. Similarly, the generated neighboring metals are integrated with each other, so that the particles grow to form nanoparticles. On the other hand, a metal compound or the like that exists in the vicinity of the cellulose fiber but does not bind to the acid group is also reduced to generate a metal. This metal quickly integrates with the metal on the surface of the cellulose fiber to form metal particles.
The reduction reaction may be performed by a known method, but it is preferable to perform the reduction reaction so as not to cleave the bond between the metal compound and the acid group while reducing the metal compound. Examples of such a reduction method include a gas phase reduction method using hydrogen and a liquid phase reduction method using a reducing agent such as an aqueous sodium borohydride solution. Conditions such as time and temperature in the gas phase reduction are appropriately adjusted. For example, the reaction may be performed at 50 to 60 ° C. for about 1 to 3 hours. The gas phase reduction reaction is preferably performed in a state where the oxidized cellulose fiber does not contain water or a solvent. In the reduction reaction, the film may remain fixed on the substrate or may be peeled from the substrate. In the case of liquid phase reduction, a film can be obtained from the above dispersion and subjected to a reduction reaction with or without drying. Further, the dispersion can be subjected to a liquid phase reduction reaction without drying. The reaction temperature in the liquid phase reduction is preferably 4 to 40 ° C., more preferably room temperature.

The metal particles are supported on the surface of the cellulose fiber by using an acid group present on the surface of the cellulose fiber as a contact. That is, the metal particles are fixed to the cellulose fiber surface via acid groups present on the cellulose fiber surface. The chemical bond for immobilization is preferably a coordination bond, a hydrogen bond, or an ionic bond. The bonding state can be analyzed by X-ray photoelectron spectroscopy or infrared spectroscopy.
The average particle diameter of the metal particles is determined from a transmission electron microscope image or X-ray diffraction. In the present invention, the average particle diameter of the metal particles is preferably in the range of 1 to 50 nm when determined from a transmission electron microscope image. Specifically, the average particle diameter is obtained by preparing a transmission electron microscope image of cellulose fibers, obtaining the equivalent circle diameter of primary particles of a plurality of metal particles from the image, and averaging these values.
By using at least one selected from the group consisting of Ag and Cu as the metal particles, an antibacterial function is imparted. On the other hand, the metal particles do not bind to all of the acid groups of the cellulose fiber, and the remaining acid groups neutralize ammonia, which is a odorous component, thereby exhibiting a deodorizing function.

Sanitary thin paper is made from papermaking raw materials containing cellulose fibers. As a papermaking raw material other than the cellulose fiber, for example, virgin pulp such as softwood pulp (NBKP) or hardwood pulp (LBKP), or used paper pulp regenerated from used paper can be used. These pulps are appropriately blended in predetermined types and blending ratios according to the required quality of sanitary paper. Various chemicals may be added (internally added) to the papermaking raw material for the required quality and stable operation. These chemicals include softeners, bulking agents, dyes, dispersants, wet paper strength enhancers, and drying agents. Examples thereof include paper strength agents, drainage improvers, pitch control agents, yield improvers, and the like.
The content ratio of the metal-supporting cellulose fibers in the sanitary thin paper is preferably 5 wt% or more. When the content ratio of the metal-supporting cellulose fiber is less than 10 wt%, the amount of metal particles present on the surface of the cellulose fiber is not sufficient, and the deodorizing and antibacterial functions may be inferior. The sanitary thin paper may consist only of the metal-supporting cellulose fibers.

The basis weight of the obtained sanitary thin paper can be set to, for example, 7 to 40 g / m ² . Further, as the strength of the sanitary thin paper, the GMT value {(DMD × DCD) ^1/2 } can be set to 60 to 420 (N / m).
DMD and DCD are the tensile strengths in the MD direction and CD direction when sanitary thin paper is dried, respectively, and are measured according to JIS P8113. However, the sample width at the time of measurement is 25 mm, and the unit of DMD and DCD is “N / m”.

  The sanitary paper according to the embodiment of the present invention can be manufactured by a known papermaking method. First, a papermaking raw material obtained by appropriately mixing metal-supporting cellulose fibers (or oxidized cellulose fibers before supporting metal) and pulp is supplied from a raw material tank, and further diluted with white water to prepare a paper stock. This debris is degassed for screening and sent to the stock inlet with a fan pump. The stock inlet supplies paper with a proper concentration, speed, and angle over the entire wire width of the paper machine, with a uniform, floc-free (small lump), and well-dispersed fiber so as not to cause flow streaks. To do. As the stock inlet, there are a head box, a pressurization type, a hydraulic type, etc. which are installed in a high place with the atmosphere open, and any of them may be adopted. Then, a stock is jetted from the stock inlet between the wire and the felt to form a sheet (web, wet paper) on the felt.

The web formed between the wire and the felt is closely transferred to the Yankee dryer by a pressure roll. Next, the web is dried by a Yankee dryer and a Yankee dryer hood, peeled off from the Yankee dryer while being creped by a creping doctor, and wound on a reel via a reel drum. The Yankee dryer is a drum made of cast iron or cast steel for drying the web, and the outer diameter is generally 2.4 to 6 m.
Here, creping is a method in which a paper is mechanically compressed in the longitudinal direction (machine traveling direction) to form a wavy wrinkle called crepe, and the bulk (feeling of bulk), softness, water absorption on sanitary paper. Properties, surface smoothness, aesthetics (crepe shape) and the like. Then, a crepe is formed by the creping doctor due to the speed difference between the Yankee dryer and the reel (reel speed ≦ yankee dryer speed). Although the crepe characteristics depend on the speed difference, if the basis weight of the base paper on the Yankee dryer is 7 to 40 g / m ² , the basis weight on the reel is approximately 9 to 50 g / m ² . It becomes larger than the above basis weight.
The crepe rate based on the speed difference between the Yankee dryer and the reel 14 is defined by the following equation.
Crepe rate (%) = 100 x (Yankee dryer speed (m / min)-reel speed (m / min)) ÷ reel speed (m / min)
The quality of the crepe and the operability of the creping are substantially determined by the crepe rate, and in the present invention, the crepe rate is preferably in the range of 10 to 50%.

  It goes without saying that the present invention is not limited to the above-described embodiments, and extends to various modifications and equivalents included in the spirit and scope of the present invention.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these examples of course.

<Experiment A>
16 g of pulp fibers (cellulose) made of NBKP were prepared and dispersed in 1600 g of water. To this dispersion, 0.2 g of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 2 g of sodium hypochlorite as a co-oxidant were added, stirred at room temperature for 2 hours, and oxidized. Reaction was performed and the dispersion liquid of the oxidized cellulose fiber (TEMPO oxidized cellulose fiber) was obtained. This TEMPO oxidized cellulose fiber has a carboxyl group or a carboxylate group on its surface. The acid group amount of the TEMPO oxidized cellulose fiber before supporting the metal particles was 1.6 mmol / g.
The TEMPO oxidized cellulose fiber obtained by the above operation is paper-made with a round hand machine so that the basis weight is 18 g / m 2, dried with a cylinder dryer (105 ° C.), and round with a diameter of about 16 cm. A mold sheet was prepared.
Next, this sheet was impregnated with 200 ppm of an Ag compound aqueous solution, and filter paper was piled up to remove an excess aqueous solution, followed by drying for 15 minutes by a blow dryer at 50 ° C. Thereafter, the sheet impregnated and dried with the Ag compound aqueous solution is impregnated with 200 ppm of the reducing agent solution, the filter paper is overlaid to remove the excess aqueous solution, and dried with an air dryer at 50 ° C. for 15 minutes to form oxidized cellulose fibers in the sheet. Ag nanoparticles were supported. The amount of metal particles supported on the oxidized cellulose fiber was 5.75 mg / g. In Example 3, Cu was used instead of Ag.
Next, a sheet containing this metal-supporting cellulose fiber and pulp were blended at a blending ratio shown in Table 1 to prepare a pulp slurry, and paper making was performed to obtain sanitary thin paper of Examples 1 to 3.
As Comparative Example 1, a commercially available tissue paper was prepared.
As Comparative Example 2, tissue paper was produced by making a paper carrying 10 wt% of Ag particles on zeolite-supported cellulose fibers (trade name Cellgaia (registered trademark)).

<Basis weight>
The basis weight of the obtained sanitary thin paper was measured according to JIS P 8124.
<Paper thickness>
The paper thickness (mm / 10 sheets) when 10 plies (sheets) of the obtained sanitary thin papers were stacked was measured with a peacock type paper thickness gauge (trade name). The measurement pressure was 3.7 kPa.
<Tensile strength>
The tensile strength of MD direction and CD direction at the time of drying of the obtained sanitary thin paper was measured according to JIS P8113. The sample width was 25 mm. In addition, the tensile strength of MD direction and CD direction at the time of drying is represented by DMD and DCD, respectively.
Further, the tensile strength (WMN) in the MD direction when the obtained sanitary thin paper was wet was measured according to JIS P8135. The sample width was 25 mm.
<Water absorption speed>
Measured according to JIS S3104 6.5 (former JIS).
Specifically, the measurement was performed as follows. First, a pipette adjusted so that the drop amount of one drop was 0.1 ml was prepared. The test piece was attached to a holding frame, and 0.1 ml of distilled water having a temperature of 20 ± 1 ° C. was dropped from a height of 10 mm on the test piece with a pipette. The time from when the water droplets reached the test piece until the specular reflection of water completely disappeared was measured with a stopwatch in units of 0.1 second. The test was performed 5 times, and the average value was evaluated as the water absorption rate (seconds).

<Hand feel>
Ten panelists evaluated the hand feel and feel of sanitary thin paper. Evaluation was made according to the following criteria.
◎: Very good ○: Normal ×: Bad <Lint (paper dust)>
According to JIS B9923 (tumbling method), a dust generation test of sanitary thin paper was performed, and measurement was performed with a particle counter (product name “KC-01D1” manufactured by Rion). Evaluation was made according to the following criteria. The better the evaluation, the less paper dust.
◎: Very good ○: Normal △: Somewhat bad ×: Bad

<Deodorizing effect>
A saturated gas of an aqueous ammonia solution (2 mL of ammonia water: 2 mL of water) was inserted into a gas bag with a cock containing four test pieces of 5 cm × 5 cm with a 1.2 mL syringe, and 1.5 L of air was filled with an air pump. The saturated gas was collected from the gas phase in a sealed container containing an aqueous ammonia solution. The ammonia gas concentration in the gas bag after filling with the saturated gas and air was 80 to 90 ppm. Next, the suction tube and the rubber tube were connected to the detection tube, and the rubber tube was connected to the gas bag. And the ammonia gas density | concentration in the gas bag after progress for 15 minutes after filling with air was measured.
◎: Very good Residual concentration is less than 1/3 of the initial value ○: Normal Residual concentration is 1/2 to 3/1 of the initial value
×: Poor residual concentration is 1/2 or more of initial <antibacterial property>
It was evaluated by a halo test. An agar medium containing E. coli was prepared, and a sample of sanitary thin paper was placed on it. After culturing at 37 ° C. for 17 hours, the presence or absence of the “growth inhibition zone” of the test bacteria formed around the sample was confirmed. Evaluation was made according to the following criteria.
○: Growth inhibition zone is recognized and has antibacterial properties.
X: No growth inhibition zone was observed and no antibacterial activity was observed.

  The obtained results are shown in Table 1.

  As is clear from Table 1, in each of the examples, it had a deodorizing and antibacterial function and had high strength and reduced paper dust.

On the other hand, in the case of the comparative example 1 which is a commercial item, the deodorizing and antibacterial functions were not obtained.
In the case of Comparative Example 2 where paper made from zeolite-supported cellulose fibers (trade name Sergaia (registered trademark)) with Ag particles supported, the strength is reduced compared to Example 1 having almost the same basis weight, and there is much paper dust. As it occurred, the hand feel was inferior.

<Experiment B>
NBKP, which is a general pulp (cellulose fiber), the above-mentioned zeolite-supported cellulose fiber (trade name Cellgaia (registered trademark)), and a pulp slurry using the above TEMPO-oxidized cellulose fiber are made into a paper by a square hand machine and have a basis weight of 18 Sheets 1 to 4 of ± 0.5 g / m 2 were prepared. The paper strength enhancer was not added.
For each of the obtained sheets, the basis weight, paper thickness, and tensile strength were measured in the same manner as in Experiment A. The density was calculated from the basis weight and the paper thickness, and the breaking length was calculated from the basis weight and the tensile strength. The tensile strength was measured with a sample width of 25 mm, and the breaking length was determined from the following equation. Further, since the strength of the sheet 1 is low, the tensile strength was measured by stacking three sheets, and the tensile strength per sheet was converted by dividing by 3.
Breaking length (km) = tensile strength (kgf) × 1000 / {weighing (g / m ² ) × sample width (mm)}
The obtained results are shown in Table 2.

As apparent from Table 2, the sheets 2 and 3 have higher strength than the sheet 1. This is thought to be due to the action of beating treatment in the production process of TEMPO-oxidized cellulose fiber. Therefore, the strength of Example 1 in which a papermaking raw material in which general pulp (NBKP or the like) and TEMPO oxidized cellulose fiber are mixed is equivalent to that in Comparative Example 1 in which a general pulp is made.
On the other hand, in the case of the sheet 4 containing 10 wt% of zeolite-supporting cellulose fibers, the strength was reduced by about 20% compared to the sheet 1. This is presumably because the zeolite was crystallized in the cellulose fiber, so that the fiber expanded, obstructing the flattening of the cellulose fiber, and the hydrogen bonds between the fibers decreased. It is also considered that the zeolite-supporting cellulose fibers contain a large amount of short fibers.

Claims (2)

  One or more metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu are supported on the oxidized cellulose fiber having a carboxyl group or a carboxylate group on the surface. Sanitary thin paper containing metal-supported cellulose fibers. When the tensile strength in the MD direction and CD direction when drying the sanitary thin paper measured according to JIS P8113 is DMD and DCD,
The sanitary thin paper according to claim 1, wherein the GMT value {(DMD × DCD) ^1/2 } is 60 to 420 (N / m).