JP2009263844A - Tissue paper for domestic use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide soft tissue paper for domestic use having a good hand touch feeling, and excellent strength. <P>SOLUTION: The tissue paper for domestic use comprises pulp obtained by applying impact force produced during collapse of bubbles generated by cavitation to pulp fibers. Furthermore, the tissue paper for domestic use composed of two or more paper layers comprises pulp obtained by applying impact force produced during collapse of bubbles generated by cavitation to at least one paper layer in tissue paper for domestic use. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to tissue paper such as toilet paper facial tissue, and household thin paper such as paper towels, and more particularly relates to household thin paper that is soft and excellent in touch feeling and strong.

  Conventionally, as pulp used for so-called household thin paper such as tissue paper such as toilet paper and facial tissue, paper towels, etc., it is in a slurry state produced from chemical pulp obtained by digesting wood chips from hardwood and conifers. Slushed pulp, dry pulp obtained by dehydrating and drying this slush pulp, or deinked wastepaper pulp obtained by deinking wastepaper, and these pulps are used. Is used in the state of unbleached pulp and bleached pulp, or in the state of unbeaten and beaten pulp, either alone or in combination depending on the quality design.

  Research has been conducted on techniques for improving the softness and touch feeling, which are important quality of tissue paper, for example, laminated tissue paper in which the type of pulp to be laminated and papermaking and its use ratio are adjusted, and a method for producing the same (Patent Document 1, Patent Document 2), by appropriately selecting a paper machine such as a long net, a short net, a twin wire, a circular net Yankee machine, or a paper softener such as a fatty acid ester softener (Patent Document) 3), quaternary ammonium salt type cationic surfactant (Patent Document 4), urethane alcohol or a salt thereof, or cationized product (Patent Document 5), non-cationic surfactant (Patent Document 6, Patent Document 7) , Polyphosphate (Patent Document 8), polysiloxane (Patent Document 9, Patent Document 10) and other additive chemicals are added to slush pulp. Various methods have been proposed, such as a method of improving the slip of the loop itself to make it softer and softer, and a method of bending the fiber by adding a mechanical kneading treatment after concentrating the pulp (Patent Documents 11 and 12). ing.

  The method using the additive chemicals may provide a good softening effect, but because of its high foaming property, there is a risk of hindering the paper making operation itself. In some cases, the paper strength and water absorption are reduced. There was a problem of inviting. In addition, when the fiber is bent by mechanical treatment, there is a problem that it is disadvantageous in terms of energy because the raw material concentration step is excessively increased.

  In order to improve the wet strength of tissue paper, wet paper strength improvers such as polyamide, polyamine, and epoxy resin are mainly used, but the tissue paper itself becomes stiff and soft and has a feeling of touch. There was a problem of becoming negative.

Conventionally, in order to improve the smoothness of the surface, one or two calendars made of a pair of fully polished chilled rolls and metal rolls are used after the tissue paper machine. However, when the linear pressure is increased in order to improve smoothness with this calendar, there is a problem that the thickness becomes thin and rigid, and the touch feeling becomes stiff.
JP 54-46914 A Japanese Utility Model Publication No. 4-66992 US Patent 3,296,065 JP 48-22701 Japanese Unexamined Patent Publication No. 60-139897 JP-A-2-99690 JP-A-2-99691 JP-A-2-36288 JP-A-2-224626 Japanese Unexamined Patent Publication No. 3-900 Japanese Patent Laid-Open No. 5-23262 JP-A-6-14848

  An object of the present invention is to provide a household thin paper that is soft and has a good touch feeling and excellent strength.

  As a result of intensive research, the present inventors have included a pulp obtained by giving an impact force generated when bubbles generated by cavitation collapse to a pulp fiber, so that it is soft and has a good touch feeling and excellent strength. The present inventors have found that a thin paper for household use can be obtained and have completed the present invention.

  According to the present invention, it is possible to obtain a household thin paper which is soft, excellent in touch feeling and excellent in strength.

  The household thin paper of the present invention is characterized by containing pulp obtained by giving an impact force to the pulp fiber generated when bubbles generated by cavitation collapse. Hereinafter, giving an impact force generated when bubbles generated by cavitation collapse to a pulp fiber is referred to as cavitation treatment.

  The pulp to be subjected to the cavitation treatment of the present invention is not particularly limited, and chemical pulp obtained by digesting lignocellulosic material with an alkaline cooking chemical (conifer bleached kraft pulp (NBKP) or unbleached kraft pulp). (NUKP), hardwood bleached kraft pulp (LBKP)), mechanical pulp (groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), etc.), deinking Pulp (DIP) or the like can be used. As the chemical pulp, kraft pulp, polysulfide pulp, soda pulp, alkaline sulfite pulp, carbonated soda pulp, oxygen-soda pulp and the like can be used.

  The chemical pulp may be cooked by adding a cyclic keto compound (for example, anthraquinone, 1,4-dihydro-9,10-diketoanthracene) as a cooking aid to the cooking chemical solution described above. The above-mentioned chemical pulp suitable for the present invention is kraft pulp. This kraft pulp is a so-called modified alkaline cooking method comprising split addition of cooking liquor, co-current cooking and countercurrent cooking inside the digester. The pulp obtained by the above may be used. These chemical pulps can be used alone or in combination as appropriate in the state of unbleached pulp and bleached pulp, or in the state of unbeaten and beaten pulp.

  The cavitation treatment will be described in more detail. The impact force generated when bubbles generated by cavitation collapse is given to the pulp fiber to promote the external fibrillation of the pulp, while the internal fibrillation is suppressed and the freeness is reduced. Is to adjust. As the cavitation treatment, a cavitation jet treatment as described in WO2005 / 012632 is suitable.

  The pulp fiber may be externally fibrillated by combining cavitation treatment and mechanical beating treatment. The pulp suspension may contain inorganic fine particles derived from fillers and pigments contained in waste paper and broke in addition to pulp fibers. The cavitation treatment promotes external fibrillation of the pulp fiber, while suppressing internal fibrillation. Therefore, compared with the pulp subjected to beating treatment by mechanical force using a conventional method such as a refiner, the same drainage In terms of degree, a bulky pulp having excellent strength can be obtained. Household thin paper containing pulp having external fibrils obtained by the cavitation treatment is more flexible and is superior in strength.

  The Canadian standard freeness of pulp prepared by cavitation treatment is preferably 50 to 650 ml in the case of chemical pulp, and preferably 50 to 400 ml in the case of mechanical pulp or waste paper (deinked) pulp. When the above pulp is mixed, the total Canadian standard freeness is preferably in the range of 100 to 550 ml.

  Next, the cavitation process will be described in detail. As described in Kato's book (edited by Yoji Kato, new edition of Cavitation Basics and Recent Advances, Tsuji Shoten, 1999), cavitation is reduced to several GPa in a local region of several μm order when the cavitation bubbles collapse. High impact force is generated, and the temperature rises to several thousand degrees Celsius when viewed microscopically by adiabatic compression during bubble collapse. As a result, when cavitation occurs, the temperature increases. For these reasons, cavitation has a problem that causes damage such as damage, vibration, and performance degradation in the fluid machine, and has been regarded as a technical problem that needs to be controlled so as not to occur. In recent years, research on cavitation has progressed rapidly, and it has become possible to control the cavitation generation region and impact force with high precision using the hydrodynamic parameters of the cavitation jet as operating factors. As a result, it is expected to effectively utilize the powerful energy by controlling the bubble collapse impact force. Therefore, it has become possible to control cavitation with high accuracy by performing operations and adjustments based on hydrodynamic parameters. This shows that it is possible to maintain the stability of the technical effects, and not by cavitation that causes uncontrollable harm that naturally occurs in fluid machinery, but by controlled cavitation. It is a feature of the present invention that the generated bubbles are positively introduced into the pulp suspension to effectively use the energy.

  Examples of the cavitation generating means in the present invention include, but are not limited to, a method using a liquid jet, a method using an ultrasonic transducer, a method using an ultrasonic transducer and a horn-shaped amplifier, and a method using laser irradiation. It is not a thing. Preferably, the method using the liquid jet has a high effect on the pulp fiber because the cavitation bubble generation efficiency is high and a cavitation bubble cloud having a stronger collapse impact force is formed. The cavitation generated by the above method is clearly different from cavitation that causes uncontrollable harm that naturally occurs in conventional fluid machines.

  As described above, as the cavitation treatment, a cavitation jet treatment using a liquid jet as described in WO2005 / 012632 is suitable and will be described in detail below.

  The liquid jet is a jet of fluid in which solid particles or gas are dispersed or mixed in the liquid or liquid, and refers to a liquid jet containing slurry or bubbles of pulp or inorganic particles. The gas here may include bubbles due to cavitation.

  Since cavitation occurs when a liquid is accelerated and the local pressure is lower than the vapor pressure of the liquid, flow rate and pressure are particularly important. From this, the basic dimensionless number representing the cavitation state, the cavitation number σ, is defined as follows (edited by Yoji Kato, new edition of cavitation basics and recent advances, Tsuji Shoten, 1999).

(P _∞ : general flow pressure (absolute pressure), U _∞ : general flow velocity, p _v : fluid vapor pressure (absolute pressure), ρ: density)
Here, a large number of cavitations indicates that the flow field is in a state where cavitation is difficult to occur. In particular, when cavitation is generated through a nozzle or orifice tube such as a cavitation jet, the nozzle upstream pressure p ₁ (absolute pressure), the nozzle downstream pressure p ₂ (absolute pressure), and the sample water saturation vapor pressure p _v (absolute ), The cavitation number σ can be rewritten as the following equation (2). In the cavitation jet, the pressure difference between p ₁ , p ₂ , and p _v is large, and p ₁ >> p ₂ >> p _v Therefore, the cavitation number σ can be further approximated as follows (H. Soyama, J. Soc. Mat. Sci. Japan, 47 (4), 381 1998).

  Thus, the cavitation number σ is expressed by two values of the upstream pressure and the downstream pressure of the nozzle. In addition, all the pressures measured in the Example of this invention are gauge pressures, and the cavitation number (sigma) in this invention is represented like following formula (3).

(However, p3: Nozzle upstream pressure (gauge pressure), p4: Nozzle downstream pressure (gauge pressure))
The cavitation condition in the present invention is such that the above-mentioned cavitation number σ is preferably 0.001 or more and 0.5 or less, more preferably 0.003 or more and 0.2 or less, and particularly preferably 0.01 or more and 0.1 or less. When the cavitation number σ is less than 0.001, the effect is small because the pressure difference with the surroundings when the cavitation bubbles collapse is low, and when it is greater than 0.5, the flow pressure difference is low and cavitation is difficult to occur. .

  Further, when the cavitation is generated by injecting the injection liquid through the nozzle or the Ophiris tube, the pressure of the injection liquid (nozzle upstream pressure) is desirably 0.01 MPa (gauge pressure) or more and 60 MPa (gauge pressure) or less. 0.7 MPa (gauge pressure) or more and 30 MPa (gauge pressure) or less is preferable, and 2 MPa (gauge pressure) or more and 15 MPa (gauge pressure) or less is particularly preferable. When the pressure on the upstream side of the nozzle is less than 0.01 MPa (gauge pressure), it is difficult to produce a pressure difference from the pressure on the downstream side of the nozzle, and the effect is small. In addition, when the pressure on the upstream side of the nozzle is higher than 60 MPa (gauge pressure), a special pump and pressure vessel are required, which increases the energy consumption, and is disadvantageous in terms of cost, and the pulp fiber is excessively damaged. It is not suitable for use as a papermaking raw material. On the other hand, the pressure in the vessel (nozzle downstream pressure) is preferably 0.05 MPa (gauge pressure) or more and 2.6 MPa (gauge pressure) or less in static pressure. The reason for applying pressure to the downstream side is that the pressure in the area where the cavitation bubbles collapse is increased by pressurizing the container containing the liquid to be injected (pulp suspension), and the pressure difference between the bubbles and the surroundings increases. This is because the impact force increases as the bubbles collapse more violently. Note that if the pressure in the container becomes too high, cavitation itself is difficult to occur. Moreover, the pressure ratio ((gauge pressure) / (gauge pressure)) between the pressure in the container and the pressure of the propellant is preferably in the range of 0.001 to 0.5.

  Further, the jet velocity of the jet liquid is preferably in the range of 1 m / second to 200 m / second, and more preferably in the range of 20 m / second to 100 m / second. When the jet velocity is less than 1 m / second, the effect is weak because the pressure drop is low and cavitation hardly occurs. On the other hand, when it is higher than 200 m / sec, a high pressure is required and a special device is required, which is disadvantageous in terms of cost.

  In the present invention, the cavitation treatment can be performed in any container such as a tank or in a pipe, but is not limited thereto. Further, although it is possible to perform processing by one pass, the effect can be further increased by circulating the required number of times. Furthermore, it can be processed in parallel or in permutation using a plurality of generating means.

  The jet for generating cavitation may be made in a container open to the atmosphere such as a pulper, but is preferably made in a pressure vessel in order to control cavitation.

  In the present invention, for example, in a method for generating cavitation by a liquid jet, as a jet liquid, for example, distilled water, tap water, industrial water, reused water recovered in a papermaking process, pulp squeezing, White water, pulp suspension, alcohol or the like can be sprayed, but is not limited thereto. Preferably, by injecting the pulp suspension itself, in addition to the effect of cavitation generated around the jet, the hydrodynamic shear force when jetting from the orifice at high pressure can be obtained, so that a greater effect is exhibited. To do. In addition, when using a pulp suspension as an injection liquid, it is also possible to circulate and process the whole quantity made into a process target.

  When processing by generating cavitation with a liquid jet, the solid content concentration of the pulp suspension to be processed is preferably 5% by weight or less, more preferably 3% by weight or less, and still more preferably 0.1 to 1.5% by weight. % Is preferable from the viewpoint of bubble generation efficiency.

  The pH of the pulp suspension during the treatment is preferably pH 1 to 13, more preferably pH 3 to 12, and further preferably pH 4 to 11. If the pH is less than 1, corrosion of the apparatus becomes a problem, which is disadvantageous from the viewpoint of material and maintenance. On the other hand, if the pH exceeds 13, an alkali burn of the pulp fiber occurs and the whiteness decreases, which is not preferable. Alkaline conditions are desirable because the pulp fibers have good swelling properties and the amount of OH active radicals generated is increased.

  In the present invention, by increasing the jetting pressure of the liquid, the flow rate of the jetting liquid is increased and more powerful cavitation is generated. Further, by pressurizing the container for storing the liquid to be injected, the pressure in the region where the cavitation bubbles collapse is increased, and the pressure difference between the bubbles and the surroundings increases, so that the bubbles collapse violently and the impact force increases. Here, the jet liquid refers to a liquid ejected from an orifice at a high pressure, and the liquid to be ejected refers to a liquid ejected in a container or piping. Cavitation is influenced by the amount of gas in the liquid, and when there is too much gas, collision and coalescence of bubbles occur, so that a collapse impact force is absorbed by other bubbles, and the impact force is weakened. Therefore, the treatment temperature must be not lower than the melting point and not higher than the boiling point because it is affected by dissolved gas and vapor pressure. When the liquid uses water as a medium, a high effect can be obtained by setting the temperature preferably in the range of 0 to 80 ° C., more preferably 10 to 60 ° C. Generally, the impact force is considered to be maximum at the midpoint between the melting point and the boiling point, so in the case of an aqueous solution, the optimum temperature is around 50 ° C, but it is not affected by the vapor pressure even at lower temperatures. Therefore, a high effect can be obtained within the above range. A temperature higher than 80 ° C. is not suitable because the pressure resistance of the pressure vessel for generating cavitation is remarkably lowered and the vessel is easily damaged.

  In the present invention, the energy required to generate cavitation can be reduced by adding a substance such as a surfactant that lowers the surface tension of the liquid. Substances to be added include known or novel surfactants, for example, nonionic surfactants such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, higher alcohols, alkylphenols, alkylene oxide adducts such as fatty acids, and the like. Examples include, but are not limited to, ionic surfactants, cationic surfactants, amphoteric surfactants, and organic solvents. These may be a single component or a mixture of two or more components. The addition amount may be an amount necessary for reducing the surface tension of the jet liquid and / or the liquid to be jetted. Further, the addition place may be any place in the process before the place where cavitation is generated, and when the liquid is circulated, it may be after the place where cavitation is generated.

  In the present invention, the blending ratio of the cavitation-treated pulp with respect to the total pulp content is not particularly limited, but the higher the blending ratio, the stronger and more flexible household thin paper can be obtained. In that respect, 5% by weight or more is preferable, 30 to 100% by weight is more preferable, and 60 to 100% by weight is more preferable with respect to the absolute dry weight of the whole pulp. If the blending ratio is less than 5% by weight, there is no change in softness and touch feeling, and the strength cannot be improved.

  Household thin paper is composed of one or more layers, but one or more layers may be made of cavitation-treated pulp alone, or two or more types of cavitation-treated pulp may be mixed to make paper. In addition, paper made by mixing slush pulp, dry pulp, and deinked pulp (DIP) with cavitation-treated pulp may be used.

  When laminating two layers of household thin paper consisting of multiple layers, if the layers containing the cavitation treated pulp are placed on the outside, the layer touching the hand becomes the layer containing the cavitation treated pulp. Is further improved. In addition, when the layer containing the cavitation-treated pulp is pressed against a Yankee dryer and dried so that the surface is placed outside the thin paper for household use, the feeling of touch is further improved.

  In addition, as pulp other than cavitation-treated pulp, chemical pulp (coniferous bleached kraft pulp (NBKP) or unbleached kraft pulp (NUKP), hardwood bleached kraft pulp (LBKP)) or unbleached kraft pulp (LUKP), etc. , Pulp (groundwood pulp (GP), refiner mechanical pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), etc.), deinked pulp (DIP), etc. May be used.

  The cavitation-treated pulp is a pulp whose external fibrillation has been promoted, and a pulp having scale-like external fibrils may be obtained, which will be described below.

  According to the book by Ogai et al. (Akira Ogai, “Materials Chemistry of Cellulose”, The University of Tokyo Press, p68, 2001), beating of pulp gives mechanical shear stress to wet pulp fibers and It is to create voids between the microfibrils (internal fibrillation), fluff the outer fibrils of the pulp fibers (external fibrillation), increase the specific surface area and improve the swelling properties of the pulp fibers with water, A fine fiber in which the fiber is partially cut and the outer peripheral surface of the fiber is peeled off is generated.

  The pulp beating process increases the bonding area between fibers formed when paper is produced, and various mechanical properties, optical properties, and liquid absorption properties are changed. However, when the pulp fiber is viewed at the molecular level, the molecular weight of the cellulose is slightly decreased and the crystallinity is hardly changed during the beating process. This is considered because the amorphous and hydrophilic hemicellulose portion absorbs mechanical energy like a cushion.

  According to Shimaji et al.'S book (Co-authored by Ken Shimajima, “Wood Organization”, Morikita Publishing, p55, 1976), external fibrils found in wood pulp beaten by conventional methods can be seen with an optical microscope. This refers to a thread-like structure having a width of about 0.4 to 1 μm. A microfibril is an assembly of cellulose molecules having an elemental structural unit existing in a cell wall and having a width of about 9 to 37 nm. In the pulp having scale-like external fibrils used in the present invention, the characteristic scale-like external fibrils have a width of 3 μm or more, preferably about the same size as the pulp fiber width. This refers to flaking or fluffing on the fiber surface. The above-mentioned microfibrils are arranged side by side to form an aggregate and form a wide layer. The microfibrils on the fiber wall surface peel in a state of maintaining a layer structure. It is what. Further, the thickness is in the range of 9 nm to 2 μm. In addition, when observing the fiber with an electron microscope, it is desirable to measure in a dry state in which hydrogen bonding is inhibited, but this is because when the fiber is simply dried, external fibrils are formed on the fiber surface by capillary action. Therefore, it is difficult to accurately observe such fibrils.

  The scaly external fibrils in the present invention are characterized by being dyed with a high molecular weight dye having a molecular weight of 10,000 or more. That is, the external fibril refers to a microfibril aggregate capable of adsorbing a high molecular weight dye having a molecular weight of 10,000 or more. As dyes having a molecular weight of 10,000 or more, Simon et al. (FL Simons, Tappi, 33 (7), 312 (1950)) and Xiaochun et al. (Y. Xiaochun et al., Tappi Journal, 78 (6) , 175 (1995).) Orange dyes such as CI Constitution no. 40000-40006 including Direct Orange 15 (old Color Index (CI) no, 621, or CI Constitution no. 40002/3) However, there is no particular limitation as long as it is a substance that can dye fibers mainly composed of cellulose.

  According to Xiaochun et al., The above-mentioned dye having a molecular weight of 10,000 or more is a molecule having a hydrodynamic size of 5 nm or more from light scattering measurement, and cannot penetrate into pores of less than 5 nm existing on the surface of pulp fiber. . On the other hand, fibrils composed of aggregates of microfibrils on the surface of pulp fibers are exposed to the outside of the pulp fibers, so that the dye molecules having the molecular weight of 10,000 or more can be easily approached. The part can be selectively stained.

  In order to optically emphasize and observe the fibril part, Direct Blue 1 (old Color Index (CI) no.518 or CI Constitution no.24410), Direct Blue 4, By dyeing the entire fiber with a low molecular weight dye such as Direct Blue 15, Direct Blue 22, or Direct Blue 151, you can observe with more contrast. Although low molecular weight dyes are adsorbed to the entire fiber, high molecular weight dyes have stronger adsorption power, and therefore, low molecular weight dyes are substituted. As a result, it is possible to dye fibril parts that can adsorb high molecular dyes (orange dyes) in orange and dye fiber pores that cannot adsorb high molecular dyes with low molecular dyes (blue dyes). Therefore, the fibril portion can be emphasized. The low molecular weight dye contains 51% or more of molecules having a molecular weight of less than 10,000, preferably less than 2000, and more preferably 300 to 1500.

In the pulp having scale-like external fibrils of the present invention, the area ratio of the external fibril part represented by the following formula 4 is 20% or more in the unit of one fiber, and the external fibril part represented by the following formula 5 It is preferable that the perimeter length ratio is 1.5 or more. Since the scale-like external fibrils of the pulp of the present invention have a larger surface area than ordinary fibrils, these values are increased.
Area ratio (%) of external fibril portion = [(area of external fibril portion) / (area of external fibril portion + total surface area of pulp fiber)] × 100 (Formula 4)
Perimeter length ratio of external fibril portion = (perimeter length of external fibril portion + total perimeter length of pulp fiber) / (total perimeter length of pulp fiber) (Formula 5)
[Action]
The reason why the texture and strength of tissue paper containing cavitation-treated pulp are both excellent is considered as follows.

  Generally, when the bulk is high (the density is low) and the surface is smooth, the texture of the tissue paper is improved. By the way, as described above, the cavitation-treated pulp is a pulp whose external fibrillation has been specifically promoted. That is, as described in WO2006 / 085598, the external fibrillation is promoted while maintaining the rigidity of the fiber, so that it is bulkier than conventional mechanical processing such as a double disc refiner. In the equivalent case, the strength becomes high, and if the pulp is prepared so that the strength is equivalent, the bulk becomes high.

  Further, when a cavitation-treated pulp is used, a smooth surface such as a metal roll is easily transferred, so that the paper is likely to be smooth.

  For these reasons, it is considered that tissue paper containing cavitation-treated pulp tends to be excellent in feel and strength.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is of course not limited thereto. In the examples and comparative examples, “%” represents “% by weight” unless otherwise specified. Pulp prepared in the following examples and comparative examples was paper-made with a twin-wire type three-layer Yankee paper machine. The crepe was applied by measuring the speed difference between the dryer and the take-up reel. Unless otherwise noted, stack the two sheets so that the surface (YD surface) of the tissue paper base sheet in contact with the Yankee dryer is on the outside (the side that touches the user's hand), and this surface is on the outside. The dried surface in contact with the Yankee dryer was soft calendered. In both the examples and the comparative examples, the pulp was produced from domestic hardwood chips using the kraft pulp method, and bleached hardwood bleached pulp having a whiteness of 84% was used.

The evaluation methods used in Examples and Comparative Examples are as follows.
<Hand feeling>
Ten panelists evaluated the hand touch and feel. Displayed in the following categories.
Very good; ◎, good; 〇, normal; △, bad; ×
<Measuring method of tensile strength (longitudinal)>
Tensile strength: The sample was cut into a width of 15 mm in the MD direction and the CD direction, the tensile strength in each direction was measured with one ply, and the tensile strength was calculated by the following formula.
Tensile strength (g) = (MD tensile strength x CD tensile strength) ^1/2
<Measurement method of bulk>
The paper thickness (mm) when 10 plies of the sample were stacked was taken as bulk.
<Measurement of basis weight>
JIS P 8124: 1998 (ISO 536: 1995) was followed.
<Adjustment of cavitation treated pulp>
The cavitation treatment was performed with a cavitation jet treatment apparatus shown in FIG. In FIG. 1, a pulp suspension (concentration 1.1%) (not shown) is accommodated in a sample tank 1, and a temperature sensor 12 and a mixer 13 are inserted into the sample tank 1. The pulp suspension in the sample tank 1 is introduced as a jet liquid into the cavitation jet cell 3 through a predetermined pipe via the plunger pump 4. A nozzle 2 is provided below the cavitation jet cell 3, and more specifically, a pulp suspension in the sample tank 1 is jetted from the nozzle 2 into the jet cell 3. Further, a water supply valve 9 and a circulation valve 10 are provided in a pipe from the side of the sample tank 1 toward the jet cell 3, and the pulp suspension in the sample tank 1 is supplied into the jet cell 3 as an injection liquid. An upstream pressure control valve 5 is interposed in another pipe from the side of the sample tank 1 toward the nozzle 2. On the other hand, a downstream pressure control valve 6 is interposed in another pipe from the upper part of the jet cell 3 to the sample tank 1, and the pulp suspension is injected into the nozzle 2 by adjusting the valves 5 and 6. The pressure can be adjusted. An upstream pressure gauge 7 is provided on the inlet side of the nozzle 2, and a downstream pressure gauge 8 is provided on the upper part of the jet cell 3. A drain valve 11 is provided at the bottom of the jet cell 3.
[Example 1]
About the raw material of the upper layer and lower layer among three layers, it prepared as follows. After the pulp sheet of hardwood bleached kraft pulp is disaggregated with a low-concentration pulper and adjusted to an arbitrary concentration, the pressure of the jet liquid (on the upstream side of the nozzle) is adjusted using the cavitation jet processing device (nozzle diameter 1.5 mm) shown in FIG. The pressure was set to 8 MPa (gauge pressure, jet flow velocity 80 m / sec), and the pressure in the container to be ejected (nozzle downstream pressure) was set to 0.4 MPa (gauge pressure). In addition, a 3% by weight pulp suspension was used as the propellant, and the pulp suspension (concentration 3% by weight) in the container was subjected to cavitation treatment to obtain a raw material A with a Canadian standard freeness of 435 mL. . Tissue paper was produced from raw material A and middle-layer raw material B (hardwood bleached kraft pulp pulp sheet with low-concentration pulper, Canadian standard freeness of 500 mL). The basis weight of the tissue paper made was adjusted to 16.6 g / m ² .
[Comparative Example 1]
The upper layer and lower layer raw materials were beaten with a double disc refiner instead of the cavitation treatment, and a Canadian standard freeness was set to 470 mL to obtain a raw material C. Tissue paper was produced from the raw material C and the middle layer raw material B. The basis weight of the tissue paper made was adjusted to 16.6 g / m ² .

As shown in Table 1, Example 1 and Comparative Example 1 have the same hand feeling, but Example 1 had a tensile strength about 20% higher than Comparative Example 1. Although the strength of Example 1 was significantly higher than that of Comparative Example 1, the decrease in bulk was slight.
[Example 2]
The raw material of the upper layer and the lower layer was processed in the same manner as in Example 1, and the raw material D was obtained with a Canadian standard freeness of 420 mL. A wet paper strength enhancer 0.1% (per weight of completely dry pulp) was added to raw material D and middle layer raw material B to produce tissue paper. The basis weight of the tissue paper made was adjusted to 13.0 g / m ² .
[Comparative Example 2]
The raw material of the upper layer and the lower layer was processed in the same manner as in Comparative Example 1 to obtain a raw material E with a Canadian standard freeness of 410 mL. A wet paper strength enhancer 0.1% (per weight of completely dry pulp) was added to raw material E and middle layer raw material B to produce tissue paper. The basis weight of the tissue paper made was adjusted to 13.0 g / m ² .

As shown in Table 2, Example 2 had a better feel than Comparative Example 2, and the tensile strength was almost the same. Furthermore, the bulk of Example 2 was about 7% higher than that of Comparative Example 2.
[Example 3]
Using the cavitation jet processing equipment (nozzle diameter 1.5mm), the upper layer and lower layer raw materials are 8MPa in pressure (nozzle upstream pressure) and the inside of the container to be jetted. The raw material F was obtained in the same manner as in Example 1 except that the two-pass treatment was carried out with the pressure (nozzle downstream pressure) of 0.4 MPa (gauge pressure), and the Canadian standard freeness was 390 mL. A wet paper strength enhancer 0.1% (per weight of completely dry pulp) was added to the raw material F and the middle layer raw material B to produce tissue paper. The basis weight of the tissue paper made was adjusted to 15.1 g / m ² .
[Comparative Example 3]
The raw material of the upper layer and the lower layer was processed in the same manner as in Comparative Example 1 to obtain a raw material G with a Canadian standard freeness of 470 mL. A wet paper strength enhancer 0.1% (per weight of completely dry pulp) was added to the raw material G and the middle layer raw material B to produce tissue paper. The basis weight of the tissue paper made was adjusted to 15.1 g / m ² .

As shown in Table 3, Example 3 had a better feel than Comparative Example 3, and the tensile strength was about 20% higher. Although the tensile strength of Example 3 was significantly higher than that of Comparative Example 3, the decrease in bulk was slight.
[Example 4]
Except using hardwood bleached kraft pulp sheet (the moisture content of the pulp sheet is about 50% by weight (per dry weight of pulp)) that is easy to get strength but tends to be inferior in touch as the raw material for the upper and lower layers The raw material H was obtained by performing the same treatment as in Example 1 and setting the Canadian standard freeness to 440 mL. A wet paper strength enhancer 0.1% (per weight of completely dry pulp) was added to the raw material H and the middle layer raw material B to produce tissue paper. The basis weight of the tissue paper made was adjusted to 15.1 g / m ² .
[Comparative Example 4]
The same material as Comparative Example 1 except that hardwood bleached kraft pulp sheet (the moisture content of the sheet sheet is about 10% by weight (per dry weight)) is usually used as the raw material for the upper and lower layers. The raw material I was obtained by carrying out the treatment and setting the Canadian standard freeness to 480 mL. A wet paper strength enhancer 0.1% (per weight of completely dry pulp) was added to raw material I and middle layer raw material B to produce tissue paper. The basis weight of the tissue paper made was adjusted to 15.1 g / m ² .

As shown in Table 4, Example 4 using hardwood bleached kraft pulp, which tends to be inferior in hand feeling, has almost the same hand feeling even when compared with hardwood bleached kraft pulp sheet comparative example 4 in which the hand feeling tends to be good. It was equivalent. In addition, the tensile strength of Example 4 was improved by about 40% compared with Comparative Example 4.

It is the schematic of the cavitation jet type processing apparatus used in the Example. 1: Sample tank 2: Nozzle 3: Cavitation jet cell 4: Plunger pump 5: Upstream pressure control valve 6: Downstream pressure control valve 7: Upstream pressure gauge 8: Downstream pressure gauge 9: Water supply valve 10: Circulation valve 11: Drain valve 12: Temperature sensor 13: Mixer

Claims (4)

Household thin paper characterized by containing pulp obtained by giving an impact force generated when bubbles generated by cavitation collapse to pulp fibers. Household thin paper consisting of two or more paper layers, comprising at least one paper layer containing pulp obtained by applying impact force to pulp fibers generated when bubbles generated by cavitation collapse Tissue paper. The household thin paper according to claim 1 or 2, wherein the pulp obtained by applying impact force generated when bubbles generated by cavitation collapse to the pulp fiber has scale-like external fibrils. The pulp content obtained by giving impact force generated when bubbles generated by cavitation collapse to pulp fibers is 30 to 100% by weight based on the absolute dry weight of all pulps. Household tissue paper described in 1.

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