JP5248158B2 - Pulp processing method - Google Patents

Description

  The present invention relates to a pulp processing method, and a pulp and sheet-like material obtained by the processing method. More specifically, after the pulp is oxidized with an oxidizing agent, the pulp is subjected to a treatment for giving an impact force to the pulp fibers when the cavitation bubbles generated by the liquid jet collapse, and the pulp is treated. The present invention relates to a pulp obtained by the method and a sheet-like substance using the pulp obtained by the method for treating the pulp.

  In recent years, from the viewpoint of saving resources and increasing the added value of paper, paper that is bulkier than conventional paper or paper with less foreign matter has been demanded. As one of the solution methods, improvement of paper quality by modification of pulp fibers has been actively studied. As a method for modifying pulp fibers, for example, a method for cavitation treatment of pulp, a method for oxidation treatment, and the like have been proposed.

  Japanese Patent Application Laid-Open No. 2006-249648 (Patent Document 1) discloses a method for producing bulky pulp by generating cavitation in a pulp suspension and using a shock wave at the time of collapse of microbubbles generated along with the cavitation. Have been described. WO 2005/012632 (Patent Document 2) describes a method for producing a regenerated pulp in which bubbles generated by cavitation are introduced into a pulp suspension so that contaminants adhering to the pulp fibers are peeled off. However, in the method using cavitation, cavitation is generated by a liquid jet using a high-pressure pump, so that power consumption is high.

  On the other hand, in Japanese Patent Application Laid-Open No. 2001-115389 (Patent Document 3), wet strength is obtained by oxidizing a pulp fiber by an oxidation reaction with a nitroxy radical to introduce a specific amount of aldehyde groups and using the aldehyde-modified pulp. It is disclosed that a good paper can be obtained. Japanese Patent Laid-Open No. 2001-336084 (Patent Document 4) discloses a paper containing pulp that has been modified by introducing a carboxyl group into pulp fiber by oxidizing pulp fiber with an N-oxyl compound and an oxidizing agent. In addition, it is disclosed that the yield of the internal additive imparting water resistance and water generation to the paper container is improved. Japanese Patent Laid-Open No. 2006-241601 (Patent Document 5) is characterized in that an aldehyde group is introduced into a beaten pulp by an oxidation reaction with a nitroxy radical, and the pulp fiber is cross-linked with an interfiber binding substance to make paper. A method for producing a high wet paper strength paper is described. However, the above-described method for modifying pulp fibers by oxidation treatment has a drawback that strength properties other than wet paper strength are not improved.

JP 2006-249648 A WO2005 / 012632 JP 2001-115389 A JP 2001-336084 A JP 2006-241601 A

As described above, there has been no method for obtaining paper that is bulky and high in strength and has few foreign matters at low energy and low cost.
In order to solve these problems, the present invention provides a pulp processing method that can easily defibrate pulp fibers or peel off foreign matter, and obtain a paper that is bulky and has high strength. .

  As a result of intensive studies on the above problems, the inventors of the present invention obtained pulp by treating the pulp fibers with an impact force when the cavitation bubbles generated by the liquid jet collapse after the oxidation treatment of the pulp with an oxidizing agent. By using the obtained pulp, it was found that a paper which is bulky and high in strength and has few foreign matters can be obtained, and the present invention has been completed.

  According to the present invention, the swelling and defibration of the target fiber is promoted by oxidizing the pulp, and the defibration of the pulp and the separation of foreign matters are caused by the shock wave generated when the cavitation bubbles collapse in the subsequent cavitation treatment. Paper that easily occurs, is bulky, has high strength, and has few foreign matters can be obtained at lower energy and lower cost.

  The present invention is characterized in that the cavitation treatment is performed after the pulp is oxidized.

  The pulp which is the object of the present invention is made of softwood or hardwood, non-wood fiber, etc. as raw materials. More specifically, chemical pulp such as kraft pulp, mechanical pulp such as crushed wood pulp, thermomechanical pulp, chemithermomechanical pulp, or recycled pulp produced from sheet-like substances made of waste paper or fiber. . As used paper, for example, it can be applied to newspapers, flyers, further magazines, coated magazines, thermal recording paper, pressure-sensitive recording paper, imitation paper, colored fine paper, copy paper, computer output paper, or mixed old paper of these. .

  The place where the pulp is oxidized may be the place where the finished pulp is stored or the production process thereof, or after these raw materials are mixed. The place where the cavitation treatment is performed may be performed continuously after the oxidation treatment, or may be performed after sandwiching other treatments.

  The oxidation treatment of the pulp of the present invention can be performed by a catalytic oxidation reaction with a substance containing an N-oxyl compound. Thereby, the hydroxyl group in the surface of a pulp fiber is oxidized and an aldehyde group or a carboxyl group is introduce | transduced. This oxidation reaction is advantageously performed in the presence of a compound selected from the group consisting of bromides, iodides and mixtures thereof in addition to the N-oxyl compound and the oxidizing agent.

  The pulp solid content concentration during the oxidation treatment is preferably 10% by weight or less, more preferably 5% by weight or less, and still more preferably 0.1 to 4% by weight. It is preferable from the point.

  The N-oxyl compound used in the present invention is a substance represented by the following general formula.

（式中Ｒ１〜Ｒ４は同一又は異なる炭素数１〜４程度のアルキル基を示す。）

(In the formula, R1 to R4 represent the same or different alkyl groups having about 1 to 4 carbon atoms.)

  Among these, 2,2,6,6, -tetramethyl-1-piperidine-oxy radical (hereinafter referred to as TEMPO) and 4-hydroxy TEMPO are preferable, or N represented by any one of the following formulas 2 to 4 An oxyl compound, that is, a hydroxyl group of 4-hydroxy TEMPO is etherified with an alcohol or esterified with a carboxylic acid or a sulfonic acid to give a hydrophobic 4-hydroxy TEMPO derivative, so that an inexpensive and uniform pulp can be obtained. preferable.

（ただし、Ｒは炭素数４以下の直鎖或いは分岐状炭素鎖である。）

(However, R is a linear or branched carbon chain having 4 or less carbon atoms.)

  The amount of the N-oxyl compound used is not particularly limited as long as it is a catalyst amount that exhibits activity against the oxidation reaction, but is preferably 0.01 to 10 parts by weight, more preferably 0 to 100 parts by weight of the pulp dry weight. .1 to 5 parts by weight. When the amount is less than 0.01 part, it takes a long time to obtain a pulp subjected to the necessary oxidation treatment, which is not suitable because a very large storage facility is required. When the amount is more than 10 parts by weight, the cost becomes high and the yellowing of the pulp during heating, which seems to be caused by the by-product of the reaction, is likely to occur.

The oxidizing agent used in the present invention may be any substance that can promote the target oxidation reaction. For example, halogen (chlorine, bromine, iodine, etc.), halogen-containing oxygen acid or salt thereof [hypohalous acid or salt thereof (hypochlorous acid or salt thereof, hypobromous acid or salt thereof, hypoiodous acid or salt thereof) Salt), halogen acid or salt thereof (chlorite or salt thereof, bromite or salt thereof, iodic acid or salt thereof), perhalogen acid or salt thereof (perchloric acid or salt thereof, perbromine) Acid or a salt thereof, periodate, etc.), halogen oxide (eg, halogenated oxygen such as ClO, ClO ₂ , Cl ₂ O ₆ , BrO ₂ , Br ₃ O ₇ ), nitrogen oxide (eg, NO , NO ₂ , N ₂ O _3, etc.), peroxides (hydrogen peroxide, peracetic acid, etc.) and the like. Of these, halogen-containing oxygen acids or salts thereof, particularly hypohalites, are preferred. Of these, sodium hypochlorite, which is currently most widely used in industrial processes and has low environmental impact, is particularly preferred. These oxidizing agents can be used alone or in combination of two or more.

  The amount of the oxidizing agent used can be selected according to the amount of aldehyde group or carboxyl group introduced into the pulp fiber. For example, 0.2 to 500 mmol is preferably added per 1 g of absolutely dry pulp, and 0.2 to 50 mmol is more preferably added. By setting it as this range, the introduction efficiency of an aldehyde group or a carboxyl group can be improved.

  As the bromide or iodide, a compound (particularly an inorganic salt or a metal halide) that is water-soluble and can be dissociated and ionized in water can be used. For example, ammonium salts, bromide or alkali metal iodides, bromide or alkaline earth metal iodides, etc. can be mentioned, and alkali metal bromides or alkali metal iodides are preferred. These bromides and iodides can be used alone or in combination of two or more.

  The amount of bromide, iodide and a mixture thereof used can be selected within a range where the oxidation reaction can be promoted. For example, 0.1 to 100 parts by weight is preferable with respect to 100 parts by weight of dry pulp, and more preferably 1 to 60 parts by weight. Part. When the amount is less than 0.1 part, the oxidation reaction does not proceed efficiently and the effect expected in the present invention cannot be obtained. When the amount exceeds 100 parts by weight, the cost increases and the remaining cargo is colored and / or the fibers are colored by iodide.

  The oxidation reaction of the present invention selectively oxidizes hydroxyl groups on the surface of pulp fibers to introduce aldehyde groups or carboxyl groups. The oxidation reaction is usually carried out in a reaction system using water as a medium, often in a heterogeneous reaction system in which pulp fibers are suspended, and can be carried out with stirring as necessary.

  The oxidation reaction conditions of the present invention are not particularly limited and should be optimized depending on the properties of the cellulose and the equipment used. When the oxidation reaction is carried out in the presence of bromide, iodide and a mixture thereof, it is mild. Even under conditions, the oxidation reaction can proceed smoothly, and the introduction efficiency of aldehyde groups or carboxyl groups can be improved.

  As the oxidation reaction proceeds, an aldehyde group or a carboxyl group is generated in the cellulose, and the pH of the reaction solution is reduced. Therefore, in order to advance an oxidation reaction efficiently, it is preferable to maintain pH in a reaction liquid between 9-12, and it is more preferable to hold | maintain about 10-11.

  The oxidation reaction temperature of the present invention allows the oxidation reaction to proceed smoothly even under mild conditions, and the reaction temperature can be appropriately selected from an appropriate range, but is preferably 0 to 50 ° C. It is more preferable to carry out at 10-30 degreeC.

  If the oxidation reaction is carried out for a long time, carboxyl groups are introduced excessively and the strength of the fiber may be lowered. Therefore, it is preferable to terminate the fiber without making it water-soluble. For example, it is preferably performed for 30 minutes to 4 hours, and more preferably about 2 hours.

  The amount of aldehyde group or carboxyl group introduced into the pulp fiber of the present invention is preferably 0.07 to 1 mmol, more preferably 0.1 to 0.5 mmol, per 1 g of pulp dry weight. That is, when the introduction amount of the aldehyde group or carboxyl group is less than 0.07 mmol, the effect of the present invention is difficult to obtain, and when it exceeds 1 mmol, the strength is lowered and a problem may occur depending on the application.

  In the cavitation treatment of the present invention, the jet liquid is compressed and jetted from the nozzle tip at a high speed, so that the cavitation that occurs simultaneously with the expansion of the liquid itself constituting the suspension due to the extremely high shearing force near the nozzle and sudden pressure reduction The fiber mass is defibrated by the collapse energy of bubbles, and foreign substances such as chemicals adhering to the fiber surface are blown away. Also, since there is no physical contact of the blade with the fiber, it does not cause shortening of the fiber, etc., due to a decrease in dewaterability in the paper machine due to a decrease in freeness, or due to a shortening of the fiber No decrease in strength when sheeted.

  In the method of generating cavitation by the liquid jet in the present invention, tap water, reused water recovered in the papermaking process, pulp squeezed water, white water, and the pulp suspension itself are used as the jet liquid for the pulp suspension. Although it can spray, it is not limited to these. Preferably, by injecting the pulp suspension itself, in addition to the effect of cavitation generated around the jet flow, a hydrodynamic shear force when jetting from a nozzle or orifice tube at high pressure is obtained, so that a larger effect is obtained. Demonstrate the effect. In addition, the fluid in which the liquid jet forms a jet may be any liquid, gas, solid such as powder or pulp, or a mixture thereof as long as it is in a fluid state. Further, if necessary, another fluid can be added as a new fluid to the above fluid. The fluid and the new fluid may be uniformly mixed and ejected, but may be ejected separately.

  As a means for generating cavitation in the present invention, a method using a liquid jet is used. 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.

  The liquid jet is a jet of a fluid or a fluid in which solid particles or gas are dispersed or mixed in the liquid, and refers to a liquid jet containing a slurry or bubbles of pulp or inorganic particles. The gas referred to 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 the following formula 1 (edited by Yoji Kato, new edition of cavitation basics and recent advances, Tsuji Shoten, 1999) ).

  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 cavitation number σ is expressed by the following equation (2) from the nozzle upstream pressure p1, the nozzle downstream pressure p2, and the saturated vapor pressure pv of the sample water. In the cavitation jet, the pressure difference between p1, p2, and pv is large, and p1 >> p2 >> pv. Therefore, the cavitation number σ can be further approximated as in the following Equation 2. (H. Soyama, J. Soc. Mat. Sci. Japan, 47 (4), 381 1998).

  The cavitation condition in the present invention is such that the above-described cavitation number σ is preferably 0.001 or more and 0.5 or less, preferably 0.003 or more and 0.2 or less, and 0.01 or more and 0.1 or less. It is particularly preferred that If 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 if it is greater than 0.5, the flow pressure difference is low and cavitation occurs. It becomes difficult to occur.

  In addition, when the injection liquid is injected through the nozzle or the orifice tube to generate cavitation, the pressure of the injection liquid (upstream pressure) is desirably 0.01 MPa or more and 30 MPa or less, and 0.7 MPa or more and 15 MPa or less. It is preferable that the pressure is 2 MPa or more and 10 MPa or less. When the upstream pressure is less than 0.01 MPa, it is difficult to produce a pressure difference with the downstream pressure, and the effect is small. On the other hand, when the pressure is higher than 30 MPa, a special pump and a pressure vessel are required, and energy consumption increases, which is disadvantageous in terms of cost. On the other hand, the pressure in the container (downstream pressure) is preferably 0.05 MPa to 0.3 MPa in static pressure. Moreover, the pressure ratio between the pressure in the container and the pressure of the spray liquid is preferably in the range of 0.001 to 0.5.

  The jet velocity of the jet liquid is desirably in the range of 1 m / second to 200 m / second, and preferably in the range of 20 m / second to 100 m / second. When the jet velocity is less than 1 m / sec, 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 generation place can be selected from any container such as a tank or inside a pipe, but is not limited thereto. Further, although it is possible to perform processing in 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 liquid injection for generating cavitation may be performed in an open-air container such as a pulper, but is preferably performed in a pressure container in order to control cavitation.

  The solid content concentration of the pulp suspension to be treated when cavitation is generated by liquid jet is preferably 5% by weight or less, more preferably 4% by weight or less, and further preferably 0.1 to 3% by weight. It is preferable from the viewpoint of bubble generation efficiency to perform the treatment within the range. When the solid content concentration of the liquid to be jetted is 5% by weight or more and 20% by weight or less, the effect can be obtained by setting the jet liquid concentration to 4% by weight or less.

  The pH of the pulp suspension is preferably pH 1 to 13, more preferably pH 3 to 12, and still more preferably pH 4 to 11. When 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. It is desirable that the pH is in an alkaline condition because the pulp fiber has better 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 velocity of the jetting liquid is increased, and the pressure is lowered accordingly, and stronger cavitation is generated. Further, by pressurizing the container for storing the liquid to be ejected, the pressure in the region where the cavitation bubbles collapse is increased, and the pressure difference between the bubbles and the surroundings is increased, so that the bubbles collapse violently and the impact force increases. 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, since it is influenced by dissolved gas and vapor pressure, the treatment temperature is preferably 0 ° C. or higher and 70 ° C. or lower, and particularly preferably 10 ° C. or higher and 60 ° C. or lower. In general, since it is considered that the impact force becomes maximum at the midpoint between the melting point and the boiling point, in the case of an aqueous solution, around 50 ° C. is suitable, but even at a temperature lower than that, it is not affected by the vapor pressure. Therefore, a high effect can be obtained within the above range.

  In the present invention, the energy necessary for generating cavitation can be reduced by adding a surfactant. As the surfactant to be used, 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, etc. , Anionic surfactants, cationic surfactants, amphoteric surfactants and the like. These may consist of 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.

  By using the pulp obtained by the above-described treatment, it is possible to produce a paper that is bulky, has high strength, and has few foreign matters.

  When producing paper using the pulp obtained by the present invention, filler, internal sizing agent, dry paper strength enhancer, wet paper strength enhancer, yield improver, drainage improver, colorant, Conventionally used internal chemicals such as dyes and fluorescent dyes, and paper bulking agents for increasing the bulk of paper (lowering the density) can be added as raw materials.

  There is no particular limitation on the paper machine that can be applied when manufacturing paper using the pulp obtained by the present invention, such as long net type, on-top twin wire type, gap former type, circular net type, multilayer type, etc. Is mentioned. A surface treating agent may be applied for the purpose of improving the surface strength and imparting water absorption resistance. When applying the surface treatment agent, there are no particular limitations on the components of the surface treatment agent, and there is no limitation on the size press type, and the size of a liquid film transfer system such as a two-roll size press, a gate roll size press, or a shim sizer. A press or the like can be used as appropriate. Further, for the purpose of smoothing the surface of the paper, the treatment may be performed using a known calendar device such as a machine calendar, a soft nip calender, or a high temperature soft nip calender.

The paper obtained by the present invention is not limited in type and basis weight, and further includes various types of base paper and paperboard. There is no limitation on the ash content in the paper. In addition to single-layer paper, multi-layer paper having two or more layers may be used.
[Action]

  In the present invention, the following reasons can be considered as the reason why a paper that is bulky and high in strength and has few foreign matters can be obtained with low energy and low cost. By subjecting the pulp to an oxidation treatment before the cavitation treatment, swelling and defibration of the target pulp fiber are promoted. Therefore, when performing the cavitation treatment after the oxidation treatment, the fiber is easily defibrated due to the impact force when the fine bubbles generated by the cavitation collapse, and the foreign matter attached to the fiber is easily peeled off. It is considered that paper having high strength and less foreign matter can be obtained. Furthermore, it is considered that less energy is required.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.

[Examples 1 to 3]
<Oxidation treatment>
As raw material pulp, 10 g of finished deinked pulp (DIP) from deinked newspaper is suspended in 750 ml of ion-exchanged water containing 0.025 g of TEMPO and 0.25 g of sodium bromide, and 0.5N aqueous sodium hydroxide solution is used. The pH was adjusted to 10.5. This was subjected to an oxidation reaction at 20 ° C. for 2 hours while maintaining the pH at 10.5 using a 10.5 wt% sodium hypochlorite aqueous solution. Thereafter, ethanol was added to stop the reaction, and the pulp was collected by filtration and washed with ion-exchanged water. This obtained the pulp fiber containing a carboxyl group 0.45 mmol / g.
<Cavitation treatment>
About DIP after oxidation treatment, cavitation treatment was performed for 1 to 5 passes at a pulp concentration of 1.0%, an upstream pressure of 9 MPa, and a downstream pressure of 0.4 MPa using the cavitation jet apparatus described in Japanese Patent Application No. 2005-321231. .
<Measurement of dirt>
Five 60 g / m ² handsheets were prepared based on the Tappi standard method. Dirt on hand-sheets was measured using an image analyzer (Spec Scan 2000: Apogee Technology), and the average value of visible (100 μm or more) contaminants on five different hand-sheets was dirt. It was the number. Moreover, the dart reduction rate was calculated by the following formula. The results are shown in Table 1.
Dirt reduction rate (%) = 100− (number of dirt after treatment / number of dirt before treatment) × 100

[Comparative Examples 1-3]
Dirt was evaluated by performing the same treatment as in Examples 1 to 3 except that the pulp was filtered and washed without performing an oxidation treatment using TEMPO, and the cavitation treatment was conducted. The results are shown in Table 1.

[Examples 4 to 6]
Hardwood kraft pulp (LBKP-A, Canadian standard freeness CSF = 637 ml) was subjected to the same oxidation treatment as in Example 1 to obtain LBKP-B (CSF = 617 ml). About LBKP-B, the same cavitation process (1-5 passes) as Example 1 was performed. At this time, the electric power (beating specific power) required to reduce the freeness of the pulp by 100 ml of CSF was calculated from the power consumption and the freeness reduction range. The results are shown in Table 2.
Measurement of Canadian freeness: according to JIS P 8121: 1995.
Calculation of beating specific power: Cavitation treatment power x 100 ml / Drainage reduction width ml

[Comparative Examples 4 to 6]
Evaluation was performed in the same manner as in Examples 4 to 6 except that only the cavitation treatment was performed without performing the oxidation treatment. The results are shown in Table 2.

[Example 7]
<Paper quality>
About the pulp obtained in Example 3, five handsheets were produced based on JIS P8209. The thickness and basis weight of the handsheet were measured by the following method, and the density was calculated based on this. Furthermore, the fracture length, tensile stiffness, and bending stiffness were measured by the following methods. The results are shown in Table 3.
Thickness: According to JIS P 8118: 1998.
Basis weight: According to JIS P 8124: 1998 (ISO 536: 1995).
Density: Calculated from measured values of hand-sheet thickness and basis weight.
Breaking length and tensile stiffness: JIS P 8113: 1998 was followed.
Flexural stiffness: measured using a Lorenz Stiffness Tester.

[Comparative Example 7]
Evaluation was performed in the same manner as in Example 7 except that neither oxidation treatment nor cavitation treatment was performed. The results are shown in Table 3.

[Comparative Example 8]
Evaluation was performed in the same manner as in Example 7 except that only the cavitation treatment was performed without performing the oxidation treatment. The results are shown in Table 3.

[Comparative Example 9]
Evaluation was performed in the same manner as in Example 7 except that the cavitation treatment was not performed. The results are shown in Table 3.

[Comparative Example 10]
After the oxidation treatment, evaluation was performed in the same manner as in Example 7 except that the treatment was performed up to 3000 counts using a PFI mill instead of the cavitation treatment at a concentration of 10% and a clearance of 0.2 mm. The results are shown in Table 3.

As shown in Table 1, comparing the cases where the number of cavitation treatments is the same, it can be seen that the number of dirt in the example is smaller than that in the comparative example, and the reduction rate of dirt is higher.
As shown in Table 2, comparing the cases where the number of cavitation treatments is the same, it can be seen that the beating ratio power is lower in the example than in the comparative example.
As shown in Table 3, Example 7 in which oxidation treatment and cavitation treatment were performed was stronger than untreated (Comparative Example 7), only cavitation treatment (Comparative Example 8), and oxidation treatment alone (Comparative Example 9). , Tensile stiffness and bending stiffness were high. Further, in Example 7, the density was lower than that in the case of performing the oxidation treatment and the PFI mill treatment which was mechanical treatment (Comparative Example 10).
Therefore, it can be said that the present invention is a method for producing a paper that is bulky, has high strength, and has few foreign matters at low energy and low cost.

Claims (5)

Cavitation bubbles generated by a liquid jet injected through a nozzle or orifice tube collapse after the hydroxyl group on the cellulose fiber surface of the pulp is converted to an aldehyde group or a carboxyl group by an oxidizing agent in the presence of a substance containing an N-oxyl compound. A pulp processing method characterized by imparting the impact force of pulp to a pulp fiber ,
The above method, wherein the upstream pressure of the liquid jet ejected through the nozzle or orifice tube is 0.01 MPa or more and 10 MPa or less, and the ratio of the downstream pressure / upstream pressure is 0.001 to 0.5 . The method according to claim 1 , wherein the N-oxyl compound is 2,2,6,6-tetramethylpiperidine-oxy radical (TEMPO). Catalytic oxidation treatment in which the oxidation treatment is carried out by reacting with pulp in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide and a mixture thereof. The method according to claim 1 or 2 , wherein The pulp obtained by the method in any one of Claims 1-3 . A sheet-like substance obtained using the pulp according to claim 4 .