JP2008255498A - Method for producing recycled pulp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing recycled pulp, by which sticky foreign matters contained in waste paper of raw material can be reduced to produce the recycled pulp of high quality in a process for producing the recycled pulp. <P>SOLUTION: This method for producing the recycled pulp is characterized by forming bubbles in a pulp suspension by cavitation and contacting the bubbles with skicky foreign matters in the pulp suspension to treat the skicky foreign matters, in a process for producing the recycled pulp. Thereby, impact forces on the collapse of the cavitation bubbles are used to micronize and reduce the skicky foreign matters, and further the stickiness of the sticky foreign matters is lowered with radicals produced on the collapse of the fine bubbles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing recycled pulp. More specifically, a method for producing regenerated pulp with less adhesive foreign matter by positively introducing cavitation bubbles into the pulp suspension and making the adhesive foreign matter present in the pulp suspension finer and harmless. It is about.

  In recent years, due to an increase in the recycling rate of used paper for various papermaking materials, it has become an urgent task to expand the use of not only recycled paper such as newspaper and corrugated cardboard, but also low-grade used paper that has been avoided from recycling. ing. In particular, waste magazine paper currently has a low utilization rate as a papermaking raw material for its generation amount. Due to an increase in the recycling rate of used paper, it is difficult to cover raw paper raw materials with newspaper waste paper and corrugated paper alone, and so-called low-grade waste paper including magazine waste paper must be used as raw paper raw material.

  However, low-grade waste paper including municipal recovered magazine paper contains a lot of sticky foreign matter compared to newspaper waste paper and the like, and as a result, there is a disadvantage that sticky foreign matter is mixed in recycled pulp. If recycled paper containing these sticky foreign substances is used as a raw material for papermaking, paper products may suffer from defects such as dust, and in the papermaking process, they may adhere to the papermaking machine or dryer, causing local peeling or breakage of the paper. Problems such as causing paper and soiling dryers, press rolls, blankets, etc. frequently occur.

  In addition, what is called an adhesive foreign material includes various resin components in wood, various chemicals used in the papermaking process, binders such as latex for paper coating, printing ink binders, adhesives, and the like. The sticky foreign matters that are particularly problematic in the present invention are those that originate from adhesives used in the printing, processing, and packaging stages of paper. For example, pressure-sensitive adhesive paper, adhesive tape, envelopes, glue for paper bags, back glue for forms, and stickers as appendices mixed in magazines, etc. Derived from these.

  Generally, the waste paper pulping method that uses recycled paper as a raw material to obtain recycled pulp is a disaggregation process that disaggregates the waste paper to obtain a pulp suspension, a coarse selection / selection process that separates foreign matter in the suspension in the pulp, and printing ink. Is comprised of a deinking process for separating the color, a bleaching process for whitening the color, and the like. Most of the waste from the raw paper is removed by dust removal equipment such as screens and cleaners in the roughing / selection process, but some of the sticky foreign substances are not removed in the roughing / selection process, Remains.

  That is, impurities in the raw paper other than the sticky foreign material can be removed from the used paper with relative ease using a screen having eye holes and slits having dimensions according to the size and shape thereof. However, since the sticky foreign matter has viscoelasticity, it easily deforms under the influence of a large differential pressure and flow velocity, easily passes through the eye holes and slits, and easily enters the accept pulp side. In addition, since many sticky foreign substances have the same specific gravity as pulp fibers, it is difficult to separate them by a cleaner due to a difference in specific gravity. That is, in the existing dust removal equipment, when a large amount of sticky foreign matter is mixed in the used raw paper, it cannot be removed sufficiently.

  Therefore, various methods have been proposed in order to avoid various troubles caused by sticky foreign substances contained in raw waste paper when producing recycled pulp using waste paper as a raw material.

  Patent Document 1 proposes a waste paper processing method using alkaline lipase and alkaline cellulase. In this method, the adhesive foreign substance decomposition effect by the enzyme is certainly recognized, and it is considered to be an effective means, but the productivity is lowered because a certain reaction time is required to use the enzyme. There are also inconveniences such as requiring capital investment.

  In Patent Documents 2 to 6 and the like, various organic and inorganic flocculants and pitch control agents have been proposed, but none of them has achieved a satisfactory effect of suppressing pitch and adhesive foreign matter.

Japanese Patent Laid-Open No. 9-241985 Japanese Unexamined Patent Publication No. 6-1992988 JP-A-8-325969 JP-A-6-65892 JP-A-5-263385 JP-A-11-93091

  An object of this invention is to provide the method of reducing the adhesive foreign material mixed in raw waste paper and obtaining a high quality recycled pulp in the manufacturing process of a recycled pulp.

  Therefore, as a result of intensive research, the present inventors have generated bubbles by cavitation by liquid jets in the pulp suspension in the production process of recycled pulp, and brought the bubbles into contact with the sticking foreign matter in the pulp suspension. Therefore, the adhesive foreign matter in the regenerated pulp is refined and reduced by the impact force when the cavitation bubbles collapse, and the adhesiveness of the adhesive foreign matter is reduced by the radicals generated when the fine bubbles collapse. I found.

  That is, in the production process of the regenerated pulp, the present invention generates bubbles by cavitation in the pulp suspension and processes the bubbles by bringing them into contact with the sticky foreign matter, thereby removing the sticky foreign matter in the pulp suspension. It is a manufacturing method of the regenerated pulp characterized by reducing.

  As shown in Kato's book (edited by Yoji Kato, new edition of Cavitation Basics and Recent Advances, Tsuji Shoten, 1999), cavitation is a high impact pressure that reaches several GPa in the local region of the order of several μm when the cavitation bubbles collapse. The temperature rises to several thousand degrees Celsius when viewed microscopically by adiabatic compression when the bubbles collapse. As a result, when cavitation occurs, the temperature increases. For these reasons, cavitation has been a technical problem to be solved because it causes damage to the fluid machine, such as damage, vibration, and performance degradation. In recent years, research on cavitation has progressed rapidly, and it has become possible to control the cavitation generation region and impact pressure with high accuracy using the mechanical parameters of the cavitation jet as operating factors. As a result, it is beginning to be 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 effect, and not by cavitation that caused uncontrollable harm that naturally occurs in fluid machinery in the past, but by controlled cavitation. It is a feature of the present invention that the generated bubbles are positively introduced into the process of producing recycled pulp and the energy is effectively used.

  By this invention, it becomes possible to reduce the adhesive foreign material contained in the regenerated pulp suspension, and therefore, operational troubles and machine defects caused by the adhesive foreign material can be reduced.

  The type of used paper targeted by the present invention is not limited. For example, it can be applied to newspapers, flyers, magazines, coat magazines, computer output papers, or a mixture of these, but it is also particularly large when applied to waste paper that contains a lot of sticky foreign matter, such as waste magazine paper. The effect can be expected.

  The present invention can be applied to any process after the disaggregation process of the regenerated pulp manufacturing process, but it is particularly preferable to apply the process to a selective process. Moreover, it is applicable also to the process white water containing the squeezed water etc. which generate | occur | produce in the said process, the rejection after a flotation, the collection | recovery water after washing | cleaning, etc. Furthermore, there is no problem even if a dye, a fluorescent brightening agent, a pH adjuster, an antifoaming agent, a pitch control agent, a slime control agent and the like are added as necessary. There is no restriction | limiting in particular about the ink peeling apparatus to be used, an ink removal apparatus, or those process conditions. Further, if it is necessary to remove foreign matter or increase whiteness, a foreign matter removing step or a bleaching step that is usually used in the ink peeling step can be incorporated.

  The selection process in this invention shows the selection process in the manufacturing process of the regenerated pulp which has a disaggregation process, a rough selection process, an ink peeling process, and a selection process. Specifically, it refers to all the steps after the coarse selection step of removing coarse foreign matters from the pulp after disaggregation by the pulper with a foreign matter removing device represented by a screen or a cleaner. In the fine selection process, a fine foreign matter removal process using a screen or a cleaner having a smaller aperture or slit gap than the coarse selection process and / or a foreign substance refinement / dispersion process using a disperser are performed.

  Examples of the cavitation generating means in the present invention include a method using a liquid jet, a method using an ultrasonic vibrator, a method using an ultrasonic vibrator and a horn-shaped amplifier, and a method using laser irradiation, but are not limited thereto. It is not something. Preferably, the method using the liquid jet has a high effect on the sticky foreign matter 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.

  In this invention, when generating cavitation using a liquid jet, the sticking foreign material in a pulp suspension and the bubble which generate | occur | produces by cavitation can be made to contact by injecting a pulp suspension as a liquid jet. 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.

  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 Equation 1 (edited by Yoji Kato, new edition of cavitation basics and recent advances, Tsuji Shoten, 1999 ).

（p_∞：一般流の圧力、U_∞：一般流の流速、p_v：流体の蒸気圧、ρ：流体の密度）
ここで、キャビテーション数が大きいということは、その流れ場がキャビテーションを発生し難い状態にあるということを示す。特にキャビテーション噴流のようなノズルあるいはオリフィス管を通してキャビテーションを発生させる場合は、ノズル上流側圧力p₁、ノズル下流側圧力p₂、、試料水の飽和蒸気圧p_vから、キャビテーション数σは下記式（２）のように書きかえることができ、キャビテーション噴流では、p₁、p_2、p_v間の圧力差が大きく、p₁≫p₂≫p_vとなることから、キャビテーション数σはさらに以下のように近似することができる（H. Soyama, J. Soc. Mat. Sci. Japan, 47(4)， 381 1998）。

(P _∞: pressure general flow, U _∞: flow rate of the general flow, p _v: fluid vapor pressure, [rho: the density of the fluid)
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 calculated from the following equation (from the nozzle upstream pressure p ₁ , the nozzle downstream pressure p ₂ , and the saturated vapor pressure p _{v of the} sample water: 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 is (H. Soyama, J. Soc. Mat. Sci. Japan, 47 (4), 381 1998).

本発明におけるキャビテーションの条件は、上述したキャビテーション数σが0.001以上0.5以下であることが望ましく、0.003以上0.2以下であることが好ましく、0.01以上0.1以下であることが特に好ましい。キャビテーション数σが0.001未満である場合、キャビテーション気泡が崩壊する時の周囲との圧力差が低いため効果が小さくなり、0.5より大である場合は、流れの圧力差が低くキャビテーションが発生し難くなる。

The cavitation condition in the present invention is preferably such that the cavitation number σ is 0.001 or more and 0.5 or less, preferably 0.003 or more and 0.2 or less, and particularly preferably 0.01 or more and 0.1 or less. 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 is difficult to occur. .

  In addition, when the injection liquid is injected through the nozzle or the Ophiris 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 20 MPa or less. Is preferred. When the upstream pressure is less than 0.01 MPa, it is difficult to produce a pressure difference from 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 1.0 MPa in static pressure. Further, 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.

  Further, the jet velocity of the jet liquid is desirably in the range of 1 m / second to 300 m / second, and preferably in the range of 20 m / second to 200 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, if it is higher than 300 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 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.

  In the method for generating cavitation by a liquid jet in the present invention, tap water, reused water recovered in a papermaking process, pulp squeezed water, white water, and pulp as a jet liquid with respect to a pulp suspension containing sticky foreign matters The suspension itself 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 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 of reducing adhesive foreign matter can be further increased by circulating as many times as necessary.

  The solid 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.

  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, the treatment temperature is preferably 0 ° C. or higher and 70 ° C. or lower, particularly 10 ° C. or higher and 60 ° C. or lower, because it is affected by dissolved gas and vapor pressure. In general, 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, 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 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.

  The adhesive foreign material in the present invention is a hydrophobic substance mainly composed of organic substances such as natural pitch derived from resin components such as triglyceride and abietic acid, additive chemicals used in pulp and paper manufacturing processes, and latex derived from waste paper. This refers to adhesive materials such as white pitch, waste paper-derived adhesive, adhesive tape, magazine back glue, acrylic tapes such as vinyl tape, vinyl acetate, and hot melt.

  The adhesive foreign matter may be considered as being divided into a coarse adhesive foreign matter and a fine adhesive foreign matter depending on the size, but in the present invention, any adhesive foreign matter is a target. Coarse sticky foreign matter is JIS P 8231: 2006 Waste paper pulp-Adhesives and plastics evaluation method-As shown in the image analysis method, it remains on the experimental screen with a slit gap of 100 μm or 150 μm and sticks. It refers to a substance that exhibits sex. On the other hand, a fine adhesive foreign material refers to a substance that passes through the screen and exhibits adhesiveness.

  The measuring method of coarse adhesive foreign materials in the present invention is generally known, (A) a method of extracting a certain amount of pulp using an organic solvent, and estimating by weight of the extracted components and instrumental analysis, (B) A method of hand-pulling sample pulp and determining the melt area of the hot melt by hot pressing. For samples with few foreign substances, first open a flat screen for testing or Pulmac Using a master screen, etc., and then applying the reject to a hand-sheet and determining the melting area of the hot melt by hot pressing. (C) Stirring a certain amount of pulp slurry in a cylindrical container (2) A method for obtaining the weight of a sticky foreign substance on a plastic film or felt fabric attached to the side of the cylinder and determining its weight. Any method may be used, such as a method of counting the sticky foreign matter while separating the cellulose fiber from the cellulose fiber and checking the stickiness of each foreign matter with a stylus by visual observation or under a microscope. The measuring method described in Japanese Patent Application No. 2006-95937 is used, in which the number and area of each can be measured simultaneously.

The measuring method of adhesive foreign matter described in Japanese Patent Application No. 2006-95937 includes the following first to sixth steps, and can measure by distinguishing high-adhesive foreign matter and low-adhesive foreign matter. Here, the low-adhesive foreign material refers to an adhesive foreign material that does not have a strong adhesive force.
(1st process) The mixing foreign material contained in a cellulose fiber slurry is isolate | separated.
(Second step) Prepare two sheet-like materials of different materials, filter and collect the mixed foreign matters on the sheet-like material, and after drying, use a sheet-like material different from the material used for filtration. Cover and sandwich foreign matter between the two sheets.
(Third step) Among the mixed foreign matter sandwiched between two sheet-like materials, the high-adhesive foreign material adheres to the sheet-like material, and the low-adhesive foreign matter adheres to the sheet-like material used for filtration. As above, heat at normal temperature or higher and pressurize.
(4th process) After cooling, a sheet-like material is isolate | separated into two sheets by an adhesion surface.
(5th process) The highly adhesive foreign material adhering to the covered sheet-like material and the low-adhesive foreign material adhering to the sheet-like material used for filtration are dye | stained with a hydrophobic dye. After dyeing, the sheet is washed in a water / ethanol mixed solution to remove the dye from the sheet.
(Sixth step) The number and area of the dyed high-adhesive foreign matter and the dyed low-adhesive foreign matter are measured by image analysis.

  The fine sticky foreign substance in the present invention refers to a substance that passes through a laboratory screen having a specified slit gap (100 μm or 150 μm) and exhibits stickiness. This method for measuring fine sticky foreign substances includes an extraction method using an organic solvent, a method of measuring the amount of adhesion to a hydrophobic film or metal wire, a method of measuring and determining COD and TOC (Mahendra R. Doshi et al. , Comparison of Microstickies Measurement Methods Part I, Progress in Paper Recycling Vol. 12, No. 4, 35-42, 2003, or Mahendra R. Doshi et.al, Comparison of Microstickies Measurement Methods Part II, Progress in Paper Recycling Vol. 13, No. 1, 44-53, 2003) may be used, but in the present invention, the measurement method using a microbalance having a crystal resonator described in Japanese Patent Application No. 2006-99966 was used. A specific method is shown below.

  Q-sence's intermolecular interaction quantitative measurement device (model QCM-D300) is used to measure the degree of foreign matter deposition using a microbalance with a crystal resonator, and the surface of the crystal resonator is used as a measurement sensor. The one coated with stainless steel or polystyrene was used. The measurement was performed at 25 ± 0.5 ° C., and a sample containing 0.5 ml of foreign matter was poured into the reaction cell and then allowed to stand for 15 minutes to monitor the amount of foreign matter adhering to the surface of the crystal unit. After 15 minutes, the operation of pouring distilled water into the reaction cell and washing for 3 minutes was repeated twice, and the amount of adhesion after washing twice was taken as the measured value. FIG. 3 shows an example of measurement. In addition, the measured value with a frequency of 25 MHz was used for the frequency change (Δf) and the dissipation value (ΔD).

  The present invention is characterized in that a fine adhesive foreign matter that passes through a slit of a screen is made fine and harmless. If the adhesive foreign material is made finer by ordinary mechanical means, it is rather easy to pass through the slits of the screen and becomes a problem because it is mixed into the accept pulp side. On the other hand, in the present invention, since the bubbles generated by cavitation collapse in the vicinity of the sticky foreign matter, the adhesiveness of the sticky foreign matter is reduced, so that the sticky foreign matter is refined and accepted. It does not matter if it is mixed into the pulp side.

  Since the regenerated pulp produced through the above steps has significantly reduced sticky foreign matter, paper having no defects can be produced using this pulp.

  When paper is produced from the recycled pulp produced according to the present invention, a known paper machine can be used, but the paper making conditions are not particularly defined. As the paper machine, a long net paper machine, a twin wire paper machine or the like is used. In order to manufacture multilayer paper and paperboard, a circular net type paper machine is used.

  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]
A cavitation jet type device (nozzle diameter: 1.5) shown in Fig. 1 for three raw materials collected from the selection process (dispersing machine inlet) during the deinking pulp manufacturing process using A newspaper waste paper as a raw material. mm), the pressure of the jet liquid (upstream pressure) was set to 7 MPa (jet flow velocity 70 m / s), and the pressure in the jetted container (downstream pressure) was set to 0.1 MPa. The area and average particle size of the sticky foreign matter in the treated sample were measured according to the following method, and the results are shown in Table 1.
<Measurement of area and average particle size of adhesive foreign matter>
A raw material having an absolute dry weight of 1 kg was prepared as a low-concentration slurry, and foreign matters were separated from the papermaking raw material using a test flat screen having a slit width of 0.15 mm. These foreign matters are filtered using a glass fiber filter paper (hereinafter abbreviated as “A”), dried, and then covered with cellulose fiber filter paper (hereinafter abbreviated as “B”) so as to sandwich the foreign matters. The mixture was heated to 105 ° C. and immediately pressurized at 3.5 kg / cm ² for 5 minutes. Next, the upper and the second are peeled off from the foreign material adhesion surface, and the sticking foreign matter (low-adhesive foreign matter) attached to the former and the adhesive foreign matter (high-adhesive foreign matter) attached to the second are dyed with an oil blue N ethanol solution. did. After staining, the sample was washed for 5 minutes in a mixed solution of water / ethanol = 50/50. Washing was repeated twice. After drying the sample, use an image analysis device (Spec Scan 2000, manufactured by Apoge Technologies) to measure the number and area of each of the sticking foreign matter adhering to the former and the second, and then divide the area by the number to determine the average particle size. The diameter was calculated. In addition, the total adhesive foreign material in Table 1 is the total value of the high adhesive foreign material and the low adhesive foreign material.

[Comparative Examples 1-3]
The area and average particle diameter of the sticky foreign matters were determined without subjecting the raw material collected from the factory A selective process (dispersing machine inlet) using newspaper-based waste paper to cavitation jet treatment. The results are shown in Table 1.

[Comparative Example 4]
The area and average particle size of the sticky foreign substances of the raw material collected from the factory A selective process (dispersing machine outlet) using newspaper waste paper were determined. The results are shown in Table 1.

表１に示すとおり、実施例１〜３の総粘着性異物の面積及び平均粒径はキャビテーション処理前のサンプルである比較例１〜３と比べて低下していた（平均粒径についてはそれぞれ12.0％、3.2％、4.7％低下した。）。

As shown in Table 1, the area and average particle diameter of the total adhesive foreign materials of Examples 1 to 3 were lower than those of Comparative Examples 1 to 3 which were samples before the cavitation treatment (the average particle diameter was 12.0 respectively. %, 3.2% and 4.7%).

  Further, when Example 3 and Comparative Example 4 are compared, the average particle size becomes slightly larger after the cavitation treatment as compared with Comparative Example 4 using an existing disperser, but the area of the adhesive foreign material is greatly reduced. Was. This is presumed that, while the existing disperser only refines the sticky foreign matter, the cavitation treatment simultaneously causes the sticky foreign matter to be made fine and non-tacky. Furthermore, the reduction effect was remarkable with the low-adhesive foreign matter.

[Example 4]
Using the cavitation jet type device (nozzle diameter: 1.5 mm) for the raw material collected from the B factory selection process (specific gravity separator outlet) using newspaper newspaper, the pressure of the injection liquid (upstream pressure) is 7 MPa ( The flow rate of the jet was 70 m / s), and the pressure in the container to be ejected (downstream pressure) was 0.1 MPa. Fine adhesive foreign matter in the sample after the treatment was measured according to the following method. The results are shown in Table 2.
<Measurement of fine sticky foreign matter>
The sample was filtered with a 500 mesh sieve, and the filtrate was used for measurement. Q-sence's intermolecular interaction quantitative measurement apparatus (model QCM-D300) was used, and the quartz crystal surface coated with polystyrene was used as the measurement sensor. The measurement was performed at 25 ± 0.5 ° C., and 0.5 ml of the sample was poured into the reaction cell, and then allowed to stand for 15 minutes, and the change in the frequency of the quartz oscillator sensor was monitored. After 15 minutes, the operation of pouring distilled water into the reaction cell and washing for 3 minutes was repeated twice, and the frequency change after the twice washing was taken as the measured value. Here, the frequency change indicates a change in the vibration frequency of the crystal resonator sensor (polystyrene surface), and the change in the frequency depends on the mass of the substance attached to the crystal resonator sensor (polystyrene surface). That is, the frequency change is the mass of the substance attached to the sensor on the polystyrene surface, and indirectly indicates the amount of fine adhesive foreign matter.

[Comparative Example 5]
Fine sticky foreign matters were measured in the same manner as in Example 4 without subjecting the raw material collected from the B factory selection process (specific gravity separator outlet) using newspaper newspaper to the cavitation jet treatment. The results are shown in Table 2.

表２に示されるように、比較例５に対してキャビテーション噴流処理をした実施例４は、周波数変化が小さくなっており、キャビテーション噴流処理により微細な粘着性異物が減少していることが示された。これは、キャビテーション気泡破裂の際に発生するヒドロキシラジカルが微細な粘着性異物表面に作用し、疎水表面を親水表面に改質した結果と考えられる。

As shown in Table 2, in Example 4 in which the cavitation jet treatment was performed with respect to Comparative Example 5, the frequency change was small, and it was shown that the fine sticky foreign matter was reduced by the cavitation jet treatment. It was. This is considered to be a result of the hydroxy radicals generated at the time of cavitation bubble rupture acting on the surface of the fine sticky foreign matter and modifying the hydrophobic surface to a hydrophilic surface.

[Example 5]
Using the cavitation jet type device (nozzle diameter: 2.0 mm), the raw material collected from the C factory selection process (dispersing machine inlet) using newspaper-based used paper containing 5% of used magazine paper, the pressure of the jet liquid (upstream side) The pressure was 7 MPa (jet flow velocity 70 m / s), and the pressure in the container to be ejected (downstream pressure) was 0.3 MPa. About the area and average particle diameter of the adhesive foreign material in the sample after a process, it measured by the method similar to Example 1, and the result was shown in Table 3.

[Comparative Example 6]
The raw material collected from the C factory selection process (dispersing machine inlet) using newspaper-based used paper containing 20% of used magazine paper was subjected to cavitation jet treatment, and the area and average particle size of the sticky foreign matter were determined. The results are shown in Table 3.

[Comparative Example 7]
The area and average particle diameter of the sticky foreign matter were determined without subjecting the raw material collected from the C factory selection process (dispersing machine outlet) using newspaper-based used paper containing 20% of used magazine waste paper to the cavitation jet treatment. The results are shown in Table 3.

表３に示すとおり、雑誌古紙を含んでいてもキャビテーション噴流で処理することで、既存の分散装置と比較しても、粘着性異物の面積が大幅に低減した。

As shown in Table 3, the area of the sticky foreign matter was greatly reduced by treating with a cavitation jet even when containing old magazine paper, even when compared with existing dispersing devices.

It is the schematic of the cavitation jet type washing | cleaning apparatus used in the Example.

Explanation of symbols

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)

A method for producing regenerated pulp, characterized in that, in the process for producing regenerated pulp, bubbles are generated by cavitation in the pulp suspension, and the bubbles are brought into contact with a sticky foreign substance in the pulp suspension. The method for producing regenerated pulp according to claim 1, wherein bubbles are generated by cavitation using a liquid jet in the pulp suspension, and the bubbles are brought into contact with a sticky foreign substance for treatment. In the process of producing recycled pulp from recycled paper containing 3% or more of magazine waste paper, bubbles are generated by cavitation in the pulp suspension, and the bubbles are treated by contacting the sticky foreign matter in the pulp suspension. A method for producing recycled pulp, which is characterized. Paper made from the recycled pulp produced by the method according to claim 1.

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