JP2013189728A - Web for sanitary paper and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a web for sanitary paper, which has all of strength, bulk (specific volume) and softness, and to provide a method for producing the same.SOLUTION: The web for sanitary paper has a basis weight of 10-25 g/m, a specific volume of 7-25 cm/g, a tensile strength DMDT in a longitudinal direction in a drying state of 1.0 N/25 mm or more, which is based on JIS P8113, and a tensile strength DCDT in a crosswise direction in a drying state of 0.3 N/25 mm or more, which is based on JIS P8113.

Description

  The present invention relates to a base paper (web) for sanitary paper products such as tissue paper, toilet paper, and paper towel, and a method for producing the same.

Sanitary paper products such as tissue paper, toilet paper, and paper towels are made by folding a sheet of paper (web) made by a paper machine into one or two plies and then stacking them into a sheet, or winding them into a roll It is manufactured by processing to a predetermined size as appropriate.
In such sanitary paper products, a high bulk (specific volume) is an important factor in terms of quality in order to ensure the ability to absorb moisture. In addition, strength and softness (a total sensation of suppleness, smoothness, and volume) are also important.

As a method for obtaining a soft web with a high bulk, a chemical called debonder or bulking agent is added to the papermaking raw material in the papermaking process and chemically treated to suppress loosening of the fiber layer of the web by suppressing interfiber bonding of pulp fibers. A method is known (Patent Document 1).
Further, as a mechanical treatment for obtaining a high bulk web, a method TAD (through air drying) method in which the wet paper is air-dried without press dewatering in the dehydration drying process of the paper making process (Patent Document 2). In addition, there is a method of performing unevenness processing on the wet paper web between the wet paper formation and the drying process.
Furthermore, there is a method of mechanically treating the web after paper making by embossing or the like. Further, these methods may be combined.
However, in the case of the above-mentioned chemical treatment method, there is a problem that the cost of medicine is high and the web strength is lowered because the fiber-to-fiber bond of the pulp is lowered. Further, in the case of the above TAD method, the cost of the drying energy becomes enormous. Furthermore, in the method of uneven processing after paper making, the bond between fibers and the paper layer structure are broken, the web strength is reduced, and the apparent bulk of the web is increased, but the paper layer bulk (caliper) of the web itself is increased (softly) There is a problem that it is difficult to express.

On the other hand, in the paper making of the conventional sanitary paper web, the wet paper web is dehydrated by pressing it against the Yankee dryer at one or two roll press nips through the felt, and further dried by being attached to the Yankee dryer (cylinder). Creping (crease) is done when removing the web from the Yankee dryer.
However, there is a problem that the web becomes relatively low bulk due to the pressing to the Yankee dryer. And even if it tries to suppress the bulk fall by creping by adding the above-mentioned bulking agent to a pulp raw material, only the bulkiness effect of about 3 to 5% is obtained at most, On the other hand, intensity | strength falls remarkably.
In addition, the TAD method described above is a technique in which the final drying and creping are performed with a Yankee dryer and dehydrated with a vacuum, and preliminarily dried with a ventilating dryer. High bulk web can be obtained. However, since the TAD method removes moisture equivalent to press nip dehydration by ventilation heat, it is said that about twice as much drying energy is required as compared with the conventional roll press nip method.

Therefore, as a method of performing high bulk processing in the wet paper process without using the TAD method, a method of adjusting pressure dehydration by a wide press nip called a shoe press method has been proposed (Patent Document 3). The shoe press method can obtain a higher bulk and softness than the conventional roll press nip method, but cannot obtain a higher bulk than the TAD method.
Furthermore, as a method for solving these problems, a paper making machine called a fabric press system has been developed (Patent Document 4). The fabric press system follows the conventional press technology, but is provided with an uneven surface on a web by an uneven belt or fabric simultaneously with dehydration. This dewatering and concavo-convex is performed in one or more press nips while the wet web is fed from the felt to the concavo-convex belt, and then the web is transported to a Yankee dryer and dried.
According to the fabric press method, a high bulk equivalent to the TAD method can be obtained while the drying energy is equivalent to that of the conventional roll press nip method.

The web structure by the fabric press method is not a woven fabric, but forms a three-dimensional pattern similar to the woven fabric. This is presumably because the web is roughened as follows. That is, during the pressing process, the fibrous network fills the three-dimensional pattern (pattern) of the concavo-convex belt, but at that time, the three-dimensional pattern of the concavo-convex layer becomes a wet fibrous web. Is granted. Wet fibrous webs are moveable relative to each other, so that the webs take a new position and orientation with each other due to the elastic compression of the press felt. The press felt presses the wet fibrous web against the three-dimensional pattern of the concavo-convex belt so that the web has a structure with increased bulk and softness at the same basis weight.
According to this method, the bulk of the wet fibrous web is kept uncompressed by receiving a fibrous network (network) in the cavities in the belt tissue while dewatering in the press nip. Is done.

Japanese Unexamined Patent Publication No. Hei 7-189171 JP-A-8-3890 JP-A-6-158578 Special table 2001-521999 gazette

However, even if the technique described in Patent Document 4 is used, it is not sufficient to achieve both strength, bulk (specific volume), and softness of the web.
Accordingly, an object of the present invention is to provide a sanitary paper web having both strength, bulk (specific volume) and softness, and a method for producing the same.

In order to solve the above problems, the sanitary paper web of the present invention has a basis weight of 10 to 25 g / m ² , a specific volume of 7 to 25 cm ³ / g, and a tensile strength in the longitudinal direction during drying based on JIS P8113. DMDT is 1.0 N / 25 mm or more, and the transverse tensile strength DCDT at the time of drying based on JIS P8113 is 0.3 N / 25 mm or more.

It is preferable to perform calendar processing with a pair of rolls having a gap of 20 to 80% with respect to the paper thickness after papermaking and drying.
According to the tissue softness measuring apparatus TSA, it is preferable that the maximum value of the power spectrum in the frequency region of 1000 Hz or less is 20 dBV ² rms or less, and the maximum value of the power spectrum in the frequency 6700 Hz region is 20 dBV ² rms or less.
It is preferable that the stiffness (D) measurement value is 3.0 mm / N or more by the tissue softness measuring device TSA.

  The method for producing a sanitary paper web according to the present invention is a method for producing the sanitary paper web, wherein the calendering is performed by a pair of rolls having a gap of 20 to 80% with respect to the paper thickness after the papermaking and drying.

  According to the present invention, a sanitary paper web having improved strength, bulk (specific volume) and softness can be obtained.

It is a figure which shows an example of the manufacturing apparatus of the sanitary paper web which concerns on embodiment of this invention. It is a figure which shows the structure of the calendar part at the time of manufacturing the sanitary paper web which concerns on embodiment of this invention.

Embodiments of the present invention will be described below.
The sanitary paper web according to an embodiment of the present invention has a basis weight of 10 to 25 g / m ² , a specific volume of 7 to 25 cm ³ / g, and a tensile strength DMDT in the vertical direction during drying based on JIS P8113 ( Dry Machine Direction Tensile strength is 1.0N / 25mm or more, and the transverse tensile strength DCDT (Dry Cross Direction Tensile strength is 0.3N / 25mm or more based on JIS P8113. Here, sanitary paper web If it is for toilet paper, it is preferable that the ease of loosening by JIS P4501 method is less than 100 seconds.
If the sanitary paper web is for tissue paper, the wet tensile direction tensile strength (WMDT: Wet Machine Direction Tensile strength) based on JIS P8135 is 0.2 N / 25 mm or more, and if it is for paper towels, DMDT Is preferably 2.0 N / 25 mm or more, and WMDT is preferably 0.4 N / 25 mm or more. The web of the present invention can be 1 PLY or 2 PLY or more.
The flow direction of the web papermaking is defined as “longitudinal direction”, and the direction perpendicular to the flow direction is defined as “lateral direction”.

When the basis weight of the web is 10 g / m ² , the strength decreases, and when it exceeds 50 g / m ² , the softness is inferior.
Further, when the strength of the tissue paper, toilet paper, or paper towel web is less than the above value, it is easily damaged and is not suitable for practical use.
Furthermore, when the specific volume of the sanitary paper web according to the present invention is less than 7 cm ³ / g, the feeling of fluff is poor, the bulk (bulk height) is lowered, and the water absorption capacity is poor. On the other hand, when the specific volume exceeds 25 cm ³ / g, the bulk (bulkiness) increases, but the strength decreases and the smoothness is inferior.
The web according to the embodiment of the present invention can achieve both strength, bulk (specific volume), and softness by defining the basis weight, DMDT and DCDT, and the specific volume within the above ranges.

The sanitary paper web may be composed of 100% wood pulp and may include waste paper pulp and non-wood pulp. For example, wood pulp of NBKP: LBKP = 10: 90 to 70:30 (mass ratio) may be used as a raw material, or waste paper pulp can be contained up to about 50 mass% with respect to wood pulp of this pulp ratio. Waste paper pulp has a large variation in quality, and as the blending ratio increases, the quality of the product, particularly the softness, is greatly affected. Therefore, it is desirable to blend 20% by mass or less with respect to the wood pulp.
In addition, in order to ensure an appropriate strength in accordance with the use of the web, the raw materials can be blended by ordinary means, and the strength can be adjusted by beating the pulp fibers. Moreover, a wet paper strength enhancer can be used according to the use of the web.
Details of the web manufacturing method will be described later.

When the web according to the embodiment of the present invention is measured by a tissue softness analyzer (TSA), the maximum value (TS7) of the power spectrum in the region of frequency 1000 Hz or less is 20 dBV ² rms or less and the frequency 6700 Hz. The power spectrum value (TS750) in the region is preferably ²⁰ dBV ² rms or less.
Moreover, it is preferable that the stiffness (D) measured value by TSA is 2.5 mm / N or more.

Here, the tissue softness measuring device (TSA) analyzes the vibration data detected by various sensors when the paper sample is rotated by the rotor, and parameterizes (TS value) the vibration of the paper. (Hand feeling) is quantitatively evaluated and is a trade name of Emtec Electronic GmbH (Germany, Japan Luft Co., Ltd.) of Germany.
The specific measurement using TSA is as follows: (i) The movable measuring head with the rotating body pushes the sample at the specified pressure against the web sample (10 cm square) placed on the sample stage. The rotating body operates at the speed, and (iii) the resulting vibration is detected by the sensor and the vibration frequency is analyzed. (iv) Next, the sample is deformed at the specified pressure, and elasticity, viscoelasticity, and plastic deformation are calculated from the characteristics at the time of deformation. By the procedures (i) to (iii), the overall hand feel and elements of the hand feel (smoothness, suppleness, volume feeling) of the web can be quantified. The measurement is repeated 5 times per sample and averaged.
The power spectrum is obtained by dividing the power (dB) of a signal into fixed frequency bands and expressing the power of each band as a function of frequency.

The lower the value of TS7, the better the soft feeling, and the lower the value of TS750, the better the smoothness. Moreover, the greater the value of D, the more flexible.
Further, based on the functions of TS7, TS750, and D, a comprehensive hand feel HF can be calculated.
For example, by setting a function of (HF) = A × (TS7) + B × (TS750) + C × (D) + α, the comprehensive hand feel can be objectively (quantitatively) quantified. Here, A, B, C, and α are coefficients, and by appropriately setting these coefficients, smoothness, softness, and stiffness corresponding to the factors constituting HF (that is, TS7, TS750, and D, respectively). ) Can be adjusted to match the actual sensory evaluation of HF.
When A and B are negative values and C is a positive value, the larger the HF value, the better the overall hand feel.

  The sanitary paper web of the present invention can be applied to tissue paper, toilet paper, paper towels, etc. If it is a tissue paper product, for example, the sanitary paper web is 2PLY, folded and laminated with a folding machine, and pop-up type The product should be pulled out continuously. In the case of a toilet paper product, the sanitary paper web can be made 1PLY or 2PLY, wound into a roll with a roll winder machine, and cut into a product. If it is a paper towel product, it can be commercialized in any form described above.

Next, a method for manufacturing a sanitary paper web according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an example of a sanitary paper web manufacturing apparatus 50, and FIG. 2 shows the structure of a calendar part.
The apparatus 50 in FIG. 1 is a fabric press-type paper machine, and can produce a web 103 with unevenness only by pressing means without using a ventilation drying (TAD) facility for preliminary dehydration. The apparatus 50 includes a wet part 1 for forming a continuous web, a press part 2 for dewatering the web to form a pattern or unevenness, and a drying part 3 for finally drying the web.

The wet part 1 forms a wet paper in the form of a crescent former, a head box 5 for supplying a paper material made of fibers and water to the forming region, a forming felt 8 for dehydrating a part of the water of the web, and the forming. It has a wire 7, a plurality of guide rolls 10, and a forming roll 9.
The head box 5 discharges a paper jet in a forming zone 6 between the forming wire 7 and the forming felt 8. The forming wire 7 has an endless loop shape, travels around the plurality of guide rolls 10 and the forming roll 9, and contacts the forming felt 8 with the forming roll 9. Accordingly, the paper material discharged to the zone 6 is dehydrated by the forming wire 7 to form the fibrous web 101, and the fibrous web 101 is conveyed to the press unit 2 by the forming felt 8. The forming felt 8 is also in the form of an endless loop that travels around a plurality of guide rolls 11.
The forming zone 6 may be a suction breast roll former.

The press unit 2 includes a main press (MP) and a textured fabric 15, and the main press includes a # 1 press roll 12 and a # 2 press roll 13. The press rolls 12 and 13 of # 1 and # 2 are pressed together to form a press nip NP1 therebetween. The # 1 press roll 12 is located in the loop of the uneven fabric 15, the # 2 press roll 13 is located in the loop of the forming felt 8, and the forming felt 8 and the uneven fabric 15 are in contact at the press nip NP1. To do. The main press (MP) may be a long nip press or a shoe press (not shown).
The uneven fabric 15 has an endless loop shape, and runs around a plurality of guide rolls 16 and a transfer roll 17 facing the drying unit 3. When the uneven fabric 15 runs around the # 1 press roll 12, it passes through the press nip NP1 of the main press (MP) and comes into contact with the fibrous web 101 conveyed by the forming felt 8. Then, in the press nip NP <b> 1, the uneven fabric 15 performs dehydration and uneven formation of the fibrous web 101 to form the uneven fibrous web 102. The uneven fibrous web 102 is conveyed to the transfer roll 17 by the uneven fabric 15.
The transfer roll 17 faces a drying cylinder 18 of the drying unit 4 described later, and forms a transfer nip NP2 between them. And the uneven | corrugated fibrous web 102 conveyed to transfer nip NP2 is used only for drying, without performing a press and spin-drying | dehydration. The thickness (bulk) of the fibrous web 102 is adjusted by the pattern depth (0.2 to 0.4 mm) of the fabric 15 and the nip pressure of the main press (MP).

  While passing through the press section 2, the dryness of each of the webs 101, 102 can range from a fiber concentration range of 15-30% to a range of 42-52%.

The drying unit 3 includes a drying cylinder 18, a creping doctor 20, and a hood 21 that covers the drying cylinder 18. In the example of FIG. 1, the drying cylinder 18 is a Yankee dryer, but other types of drying units (for example, air-through dryers, metal drying belts) can be applied. Further, the drying unit may be a single drying unit (for example, one cylinder as shown in FIG. 1), or may be constituted by a plurality of drying units.
A coating layer 19 is formed on the surface of the drying cylinder 18 to dry the uneven fibrous web 102 in the vicinity of the transfer nip NP2. Moreover, the creping doctor 20 performs creping on the dried concavo-convex fibrous web 102, thereby obtaining a final web 103 having both concavo-convex and creping. With crepe is a known method in which paper is mechanically compressed in the machine direction (machine running direction) to form a wavy crease called crepe, and the paper is bulky, soft and water-absorbing. , Imparts surface smoothness, aesthetics (crepe shape), etc.
In order to ensure that the web 102 is transferred from the textured fabric 15 to the drying cylinder 18, an adhesive may be applied to the surface of the drying cylinder 18 by the spray device 22. The spray device 22 can be arranged between the creping doctor 21 and the transfer nip NP2.

Next, with reference to FIG. 2, the calendar process which is the characteristic part of the manufacturing method of the sanitary paper web which concerns on embodiment of this invention is demonstrated.
The calendar part 60 is composed of a pair of opposed rolls 61 and 62, and the paper 103 and the web 103 with the unevenness after drying are inserted into the gap between the rolls 61 and 62 and calendered.
Here, the gap distance t ₁ between the rolls 61 and 62 is set to 20 to 80% with respect to the thickness t ₀ of the web 103, and the rotation speed within ± 5% between the top roll and the bottom roll of the calendar. By providing the difference, a bulky web that is smoother and more flexible can be obtained.
When the distance t ₁ is less than 20% of the thickness t ₀ , the web becomes smooth, but valcross is generated, and a bulky web having a specific volume of 7 to 25 cm ³ / g cannot be obtained. If the distance t ₁ exceeds 80% of the thickness t ₀ , it becomes difficult to smooth the web.
The distance _{t 1} is equal 20-80% of the thickness _{t 0,} the roll 61, 62 caliper web (thickness) is restored spontaneously passing through the no decrease in caliper can be seen.
As the rolls 61 and 62, a steel roll, a chilled roll, a metallic roll such as a surface hard plating finish roll, or a cylinder coated with an elastic material can be used. A metal roll is preferable in that the web can be made smoother.

  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.

  A web 103 having unevenness was manufactured by using a fabric press type paper making machine 50 shown in FIG. 1 having a pulp composition (mass%) of NBKP 30% and LBKP 70% and having the characteristics shown in Table 1. Next, using the pull unit calender part 60 shown in FIG. 2, the paper 103 and the web 103 after drying were calendered. Table 1 shows the calendering conditions.

Furthermore, the final web after calendar processing was cut into test pieces of a predetermined size, and the following evaluation was performed.
Tensile strength was measured based on DMDT and DCDT: JIS P8113.
Basis weight: measured based on JIS P8124.
Web thickness: Measured using a thickness gauge (a dial thickness gauge “PEACOCK” manufactured by Ozaki Seisakusho). The measurement conditions were a measurement load of 250 gf, a probe diameter of 30 mm, a sample was placed between the probe and the measurement table, and the gauge when the probe was slowly lowered was read. At this time, only a measuring element was placed. Note that one measurement was performed by stacking five sets of samples (1 ply × 5), and the measurement was repeated 10 times to average the measurement results. Then, the average value obtained per time was divided by the number of sheets to obtain the paper thickness per web (1 ply).
Specific volume: The web thickness is divided by the basis weight and expressed in cm ³ per unit g.
Water absorption: According to the old JIS-S3104 method, 0.1 ml of purified water was dropped in a state of a temperature of 23 ± 1 ° C. and a humidity of 50 ± 2%, and the time (seconds) for the water drop to be absorbed by the web was measured.

TS7, TS750, and D were measured using the TSA apparatus. It is the average value of the values measured on the front and back, and the measurement conditions are also as described above.
The total hand feel HF was calculated based on the formula of (HF) = − 2 × (TS7) −0.5 × (TS750) + 10 × (D) +100. In comparison with the blank material, when HF = 0.5 to 1 point higher, the hand feel (hand) is improved. In comparison with the blank material, when HF = 1 and 3 or less, the hand feel is clearly improved. In comparison with the blank material, when HF is higher than 3, the hand feel is remarkably improved.
Note that the basis weight, tensile strength, web thickness, density, and TSA measurement are performed after maintaining the equilibrium under the temperature and humidity conditions specified in JIS-P8111 (23 ± 1 ° C, 50 ± 2% RH). It was.

  The obtained results are shown in Table 1. T / B in Table 1 represents the rotational speed difference (%) between the top roll and the bottom roll in calendar processing. “Conventional PM” in Table 1 represents a web manufactured by a general paper machine.

As is apparent from Table 1, DMDT is 1.0 N / 25 mm or more, DCDT is 0.3 N / 25 mm or more, and the specific volume is 7 to 25 cm ³ / g. In each of the examples that were calendered with a pair of rolls having a gap of 20 to 80%, a significant hand feel improvement effect was obtained.
In each of the examples, it is understood that the bulk cross (volume reduction rate) is 30% or less compared with the blank material having the same thickness, and the hand feel is improved without greatly reducing the bulk (specific volume). For example, the specific volume ratio between Example 3 and Blank 3 is 8.8 / 12.2 = 0.72.

On the other hand, in the case of Comparative Example 1 calendered with a pair of rolls having a gap of less than 20% with respect to the paper thickness after papermaking and drying, the specific volume is less than 7 cm ³ / g and the valcross exceeds 40% ( The specific volume of Comparative Example 1 and Blank 1 6.8 / 12.4 = 0.54), and the water absorption also decreased.
In the case of Comparative Example 2 calendered with a pair of rolls having a gap exceeding 80% with respect to the paper thickness after papermaking and drying, the valcross is small (the specific volume of Comparative Example 2 and Blank 1 is 12.2 / 12.4). = 0.98), hand feel improvement effect was inferior.

60 Calendar part 61 Top calendar roll (a pair of calendar part rolls)
62 Bottom calendar roll (a pair of calendar part rolls)
103 Papermaking and web after drying (Roughened web)
t ₀ Papermaking and web thickness after drying t ₁ Gap distance between a pair of rolls

Claims (5)

The basis weight is 10 to 25 g / m ² , the specific volume is 7 to 25 cm ³ / g, and the longitudinal tensile strength DMDT during drying based on JIS P8113 is 1.0 N / 25 mm or more, and the drying is based on JIS P8113. A sanitary paper web with a transverse tensile strength DCDT of 0.3 N / 25 mm or more. The sanitary paper web according to claim 1, wherein the sanitary paper web is calendered by a pair of rolls having a gap of 20 to 80% with respect to the paper thickness after papermaking and drying. The maximum value of the power spectrum in a region of a frequency of 1000 Hz or less is 20 dBV ² rms or less by the tissue softness measuring device TSA, and the maximum value of the power spectrum in a region of a frequency of 6700 Hz is 20 dBV ² rms or less. Sanitary paper web. The web according to any one of claims 1 to 3, wherein a stiffness (D) measurement value is 3.0 mm / N or more by a tissue softness measuring device TSA. The method for producing a sanitary paper web according to any one of claims 1 to 4, wherein the sanitary paper is calendered by a pair of rolls having a gap of 20 to 80% with respect to the paper thickness after the papermaking and drying. Web manufacturing method.

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