JP2015017333A - Method for suppressing slime - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently suppressing slime at a white water circulation system in a papermaking process.SOLUTION: Provided is a method for suppressing slime at a white water circulation system in a papermaking process, including: a step of exposing an oxygen-containing gas to a water system introducing into the white water circulation system; and a step of adding a slime control agent to the water system. Preferably, the slime suppression method further includes a step of measuring at least one kind of item selected from a measurement item group consisting of the oxidation-reduction potential of the white water circulation system, a sulfite ion concentration and a dissolved oxygen content.

Description

  The present invention relates to a slime suppression method in a white water circulation system in a papermaking process.

  At present, paper making is performed by making a paper slurry in which a pulp raw material is dispersed in water. At that time, a large amount of white water containing fine fibers and fillers is discharged from a paper machine or the like. In addition, white water is also circulated and used in the papermaking process from the viewpoint of effective use and reuse of water resources. However, white water contains a large amount of organic substances such as starch, sizing agent, latex, and casein, so it is suitable for the growth of microorganisms such as bacteria and fungi, and slime derived from the microorganisms is in a circulating water system, or in piping and equipment. It tends to occur on the surface. The said slime mixes in a product and reduces product quality and production efficiency. In the white water circulation system, since the fine fibers, starch and the like are concentrated, a part of the white water circulation system is discarded and new water is introduced, but this alone does not solve the above inconvenience.

  An antibacterial method in which a slime control agent such as an organic antibacterial agent is added to the white water circulation system has been developed (see Japanese Patent Application Laid-Open No. 2003-164882). However, when the organic matter decays, a large amount of reducing substances such as hydrogen sulfide and mercaptans are generated with an increase in the number of microorganisms. On the other hand, since many slime control agents are oxidizing agents, they react with sulfite ions derived from reducing substances before reacting with microorganisms, and many of them do not exhibit the desired antibacterial effect. It will be consumed. Therefore, in order to sufficiently suppress the generation of slime, it is necessary to add a large amount of slime control agent to which the amount of slime control agent consumed in the reaction with sulfite ions is added. In addition, slime control agents are relatively expensive, and it has become necessary to provide a more efficient slime control method and to reduce the amount used.

JP 2003-164882 A

  The present invention has been made for the inconveniences described above, and an object thereof is to provide an efficient slime suppression method in a white water circulation system in a papermaking process.

  As a result of intensive studies to solve the above problems, the present inventors aerated an oxygen-containing gas into an aqueous system (hereinafter also simply referred to as an aqueous system) to be introduced into the white water circulation system, and then into the aqueous system a slime control agent. As a result, it was found that generation of slime can be efficiently suppressed, and the present invention has been completed.

The invention made to solve the above problems is
A slime suppression method in a white water circulation system in a papermaking process,
A process of aeration of oxygen-containing gas into the water system introduced into the white water circulation system;
And a step of adding a slime control agent to the aqueous system.

  The slime suppression method reduces the generation of slime in the white water circulation system by aeration of oxygen-containing gas into the water system introduced into the white water circulation system and the addition of a slime control agent compared to the amount of water in the white water circulation system. It can suppress more efficiently and reliably. Moreover, compared with the case where it does not aerate, the usage-amount of a slime control agent can also be reduced and appropriate amount can also be aimed at. The principle is that the sulfurous acid in the whitewater circulation system is reduced by the oxidation of sulfite ions by oxygen in the oxygen-containing gas and the decrease in the solubility of reducing substances such as hydrogen sulfide due to the large amount of oxygen-containing gas dissolved in the whitewater circulation system. It is inferred that the reason is that ions are reduced.

The slime suppression method further comprises a step of measuring at least one item selected from the measurement item group consisting of the redox potential, sulfite ion concentration and dissolved oxygen content of the white water circulation system,
It is preferable to control the aeration amount in the aeration step and / or the slime control agent addition amount in the slime control agent addition step based on the measurement result obtained in this measurement step. By adjusting the aeration amount and / or the addition amount of the slime control agent, the generation of slime can be more stably and reliably suppressed.

The aeration amount in the aeration step and / or the slime control agent addition amount in the slime control agent addition step are the redox potential of the white water circulation system of −150 mV or more, the sulfite ion concentration of 2.0 mgSO ₃ ⁻ / L or less, and the amount of dissolved oxygen Is preferably adjusted to be any one or more of 1 mg / L or more. By adjusting in this way, generation | occurrence | production of slime can be suppressed more effectively.

It is preferable that an aeration tank having an aeration tube at the bottom is used for aeration in the aeration process, and an aeration amount by the aeration tube is 1 m ³ / hour or more and 10 m ³ / hour or less per 1 m ^{2 of the} bottom area of the aeration tank. By adjusting the amount of aeration in this way, it is possible to further promote the reduction of the above slime control agent.

  It is preferable that the said slime suppression method further has the process of aerating oxygen-containing gas to the said white-water circulation system. The generation of slime can be more effectively suppressed by directly aeration of the oxygen-containing gas into the white water circulation system.

  The slime suppression method preferably further includes a step of adding a slime control agent to the white water circulation system. By directly adding a slime control agent to the white water circulation system, generation of slime can be more effectively suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the efficient slime suppression method in the white water circulation system in a papermaking process can be provided. Moreover, the usage-amount of a slime control agent can also be reduced.

FIG. 1 is a diagram showing an embodiment of a papermaking process according to the present invention.

<Slime control method>
The slime suppression method is:
A slime suppression method in a white water circulation system in a papermaking process,
A process of aeration of oxygen-containing gas into the water system introduced into the white water circulation system;
Adding a slime control agent to the aqueous system.

  Preferably, the slime suppression method further includes a step of measuring at least one item selected from a measurement item group consisting of the redox potential, sulfite ion concentration, and dissolved oxygen content of the white water circulation system.

  Similarly, preferably, the slime suppression method further includes a step of aerating an oxygen-containing gas to the white water circulation system and a step of adding a slime control agent to the white water circulation system. Hereinafter, the slime suppression method will be described in detail.

<White water circulation system>
The slime suppression method is used in the white water circulation system in the papermaking process. The oxygen-containing gas is aerated into the water system introduced into the white water circulation system, and a slime control agent is added. Here, “white water” refers to an aqueous solution discharged in large quantities from a paper machine or the like in the paper making process during paper making. White water usually contains fine fibers derived from raw pulp used during papermaking, other papermaking chemicals, and the like. The “white water circulation system” refers to white water that is circulated and used in the paper making process. The “water system to be introduced into the white water circulation system” refers to an aqueous system used for adjusting the concentration of pulp slurry or white water in the white water circulation system. The aqueous system is not particularly limited and includes, for example, soft water for papermaking, hard water, and the like, and may contain a small amount of papermaking chemicals as long as the effects of the present invention are not impaired.

  The raw material pulp used for papermaking is not particularly limited. For example, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP) Chemical pulp such as ground pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP), etc., corrugated wastepaper, liner wastepaper, magazine wastepaper, newspaper wastepaper, ground Examples include used paper pulp recycled from ticket used paper, upper white used paper pulp, deinked pulp, and the like.

  There are no particular limitations on the papermaking chemicals, for example, surfactants, waxes, sizing agents, fillers, rust preventives, conductive agents, antifoaming agents, dispersants, viscosity modifiers, flocculants, coagulants, and paper strength enhancement. Agents, yield improvers, paper powder fall-off preventing agents, bulking agents and the like.

<Aeration process>
In this step, the oxygen-containing gas is aerated into the water system introduced into the white water circulation system. By efficiently aeration of a relatively small amount of the water system as compared with a large amount of white water in the white water circulation system, generation of slime in the entire white water circulation system can be easily suppressed. Specifically, by increasing the amount of oxygen in the white water circulation system or keeping it above a certain level, the amount of slime control agent added in the papermaking process and the generation of slime can be reduced compared to those that do not perform the aeration process. Efficient suppression can be achieved.

  The reason why the above-mentioned effect is achieved by aeration of the aqueous system is not necessarily clear, but it is assumed as follows, for example. In other words, since many slime control agents are oxidizing agents, they react with sulfite ions derived from reducing substances such as hydrogen sulfide and mercaptans from microorganisms before reacting with microorganisms, and thus the desired antibacterial properties. Many of them are consumed before they are effective. However, oxygen in the oxygen-containing gas oxidizes sulfite ions, so that sulfite ions can be oxidized into harmless sulfate ions or the like. In addition, since a large amount of oxygen-containing gas dissolves in the white water circulation system, the partial pressure of a reducing substance such as hydrogen sulfide is reduced, and the solubility of the reducing substance can be reduced. As a result, the amount of the slime control agent added can be reduced while reducing the concentration of sulfite ions in the white water circulation system. Moreover, it is guessed that generation | occurrence | production of slime can be suppressed efficiently, without requiring the amount of excessive slime control agents.

  Moreover, by reducing the addition amount of the slime control agent, it is possible to suppress adverse effects on the paper quality such as a change in the color tone of the paper and a change in the dye due to the use of a large amount of the slime control agent. Furthermore, the entire white water circulation system can be maintained clean during the continuous operation period, and the operation period can be extended.

  Aeration is performed using an oxygen-containing gas. It does not specifically limit as oxygen-containing gas, For example, oxygen gas single-piece | unit, the mixed gas containing oxygen, such as air, etc. are mentioned. Among these, from the viewpoint of availability, a mixed gas is preferable, and air is more preferable. Examples of gases other than oxygen in the mixed gas include known gases such as nitrogen and carbon dioxide. Oxygen containing gas may be used independently and may use 2 or more types together.

  The aeration method is not particularly limited as long as the oxygen-containing gas can be supplied to the aqueous system, and examples thereof include use of an air diffuser and stirring. In these, since aeration can be performed stably and continuously, use of a diffuser tube is preferable. Specifically, aeration can be performed more efficiently by blowing up fine bubbles upward from the bottom and increasing the contact efficiency between water and the oxygen-containing gas. The air diffuser is not particularly limited, and examples thereof include those having a diameter of 1 mm or more and 5 mm or less every 5 to 50 cm. Note that there may be one air diffuser or a plurality of air diffusers.

  The location where aeration is performed in the water system is not particularly limited, and examples thereof include a pipe, a water channel, and an aeration tank. Among these, since aeration can be performed more efficiently and on a large scale, an aeration tank is preferable, and an aeration tank having an aeration tube at the bottom is more preferable. The shape of the aeration tank is not particularly limited, and examples thereof include a box shape, a circle shape, an ellipse shape, and a mortar shape. One aeration tank may be installed in the water system, or a plurality of aeration tanks may be installed.

Aeration amount by diffusion pipe is not particularly limited, the unit bottom area 1 m ² per aeration tank, preferably 0.5 m ³ / time than 10 m ³ / time or less, more preferably 0.5 m ³ / time than ^8m 3 / Below time. If the aeration amount is within the above range, oxygen tends to be sufficiently supplied to the water system. When the amount of aeration exceeds the above upper limit, a larger-scale facility may be required. If the amount of aeration is less than the above lower limit, aeration may be insufficient.

  The aeration time of the oxygen-containing gas is also not particularly limited, and is usually from 3 minutes to 30 days, preferably from 4 minutes to 20 days. When the aeration time is within the above range, oxygen tends to be sufficiently supplied to the water system. If the aeration time exceeds the above upper limit, the production cost may increase. If the amount of aeration is less than the above lower limit, aeration may be insufficient. Moreover, aeration may be continuous and may be performed in several times.

One example of the aeration process, the aeration with aeration tank having a diffusing pipe to the bottom aeration at step the aeration amount of aeration tube unit of the aeration tank bottom area 1 m ² per 0.5 m 3 ^/ time than 10 m ³ / Hour or less.

<Slime control agent addition process>
In this step, a slime control agent is added to the aqueous system. By adding a slime control agent to the aqueous system, the number of bacteria in the white water circulation system can be further reduced as compared with the case where aeration is not performed, and as a result, generation of slime can be further suppressed. The slime control agent can also suppress the generation of slime by suppressing the decomposition of organic substances such as starch contained in the white water.

  The slime control agent is not particularly limited, and examples thereof include organic antibacterial agents and inorganic antibacterial agents.

  The organic antibacterial agent is not particularly limited. For example, methylenebisthiocyanate, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 4,5-dichloro 2-n-octylisothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2-n-octylisothiazolin-3-one, sodium dimethyldithiocarbamate, 2,2-dibromo-3-nitrilopropionamide 2-bromo-2-bromomethylglutaronitrile, 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-2-nitroethanol, 1,1-dibromo-1-nitro-2 -Propanol, 1,1-dibromo-1-nitro-2-acetoxyethane, 1,1-dibromo-1-nitro-2- Cetoxypropane, 2-bromo-2-nitro-1,3-diacetoxypropane, tribromonitromethane, β-bromo-β-nitrostyrene, 5-bromo-5-nitro-1,3-dioxane, 5-bromo -2-methyl-5-nitro-1,3-dioxane, 1,2-bis (bromoacetoxy) ethane, 1,2-bis (bromoacetoxy) propane, 1,4-bis (bromoacetoxy) -2-butene , Methylenebisbromoacetate, benzylbromoacetate, N-bromoacetamide, 2-bromoacetamide, dichloroglyoxime, α-chlorobenzaldoxime, α-chlorobenzaldoxime acetate, 2- (p-hydroxyphenyl) glyoxylohydroxy Moyl chloride, triiodoallyl alcohol, 5-chloro-2,4 , 6-trifluoroisophthalonitrile, 2,4,5,6-tetrachloroisophthalonitrile, 3,3,4,4-tetrachlorotetrahydrothiophene-1,1-dioxide, 4,5-dichloro-1, Examples include 2-dithiol-3-one, hexabromodimethylsulfone, glutaraldehyde, orthophthalaldehyde, dichlorophene, and a quaternary ammonium salt represented by the general formula (1).

In the above formula (1), R ¹ is a linear or branched alkyl group having 1 to 18 carbon atoms. Three R ¹ may be the same or different. R ² is a linear or branched alkyl group having 8 to 18 carbon atoms, a benzyl group, or a hydroxyethyl group.

  Among these, 2,2-dibromo-3-nitrilopropionamide and 2,2-dibromo-2-nitroethanol, which can be expected to have a higher antibacterial effect, are preferable.

  The inorganic antibacterial agent is not particularly limited. For example, hypochlorite such as sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, barium hypochlorite, chlorine dioxide, chlorinated isocyanuric acid. And bonded chlorine type compounds.

  Among these, sodium hypochlorite and bonded chlorine type compounds having a suitable oxidizing power and low reactivity with dissolved organic substances are preferable.

  The combined chlorine type compound is usually produced by reacting a chlorine donor that releases free chlorine with any one of ammonia, an ammonium salt, and an organic nitrogen compound under appropriate conditions. The chlorine donor is not particularly limited, and for example, sodium hypochlorite is used. Examples of the ammonium salt include ammonium halides such as ammonium chloride and ammonium bromide, ammonium sulfate, ammonium nitrate, and the like, and examples of the organic amine include sulfamic acid and urea. In addition, compounds that generate hypochlorous acid and / or hypobromite in water may be used, such as chlorine, chlorine dioxide, highly bleached powder, hypochlorous acid, sodium hypochlorite, potassium hypochlorite, hypochlorous acid. Calcium oxide, ammonium hypochlorite, magnesium hypochlorite, hypobromite, sodium hypobromite, potassium hypobromite, calcium hypobromite, ammonium hypobromite, magnesium hypobromite, Examples include chlorinated and / or brominated hydantoins, chlorinated and / or brominated isocyanuric acid, and sodium and potassium salts thereof.

  The bound chlorine type compound can be produced according to a known method, but is also commercially available as the product name “Fuzzy Side” (manufactured by Kurita Kogyo Co., Ltd.). “Fazicide” is a 1: 1 reaction (molar ratio) of ammonium bromide and sodium hypochlorite.

  A slime control agent may be used independently and may use 2 or more types together. In addition, the slime control agent may be added at once, or may be divided into a plurality of times.

  The method for adding the slime control agent to the aqueous system is not particularly limited, and the slime control agent may be added as it is, or the slime control agent may be dissolved or dispersed in a solvent and used as a solution. It does not specifically limit as said solvent, For example, water, an organic solvent, those mixed solvents, etc. are mentioned.

The organic solvent is not particularly limited, and examples thereof include amides such as dimethylformamide and dimethylacetamide,
Glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol,
Glycol ethers such as methyl cellosolve, phenyl cellosolve, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether,
Glycol esters such as diethylene glycol monoethyl ether acetate, ethylene glycol diacetate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate,
Alcohols having 8 or less carbon atoms,
Methyl acetate, ethyl acetate, butyl acetate, dimethyl maleate, diethyl adipate, ethyl lactate, dimethyl glutarate, dimethyl succinate, dimethyl phthalate, 1,2-dibutoxyethane, 3-methoxybutyl acetate, 2-ethoxy acetate Esters such as ethyl and propylene carbonate,
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone,
Aromatic solvents such as toluene, xylene, 1,2-dimethyl-4-ethylbenzene,
Examples thereof include dimethyl sulfoxide, dioxane, N-methylpyrrolidone and the like.

  Among these, water and diethylene glycol monomethyl ether that can ensure higher dispersibility and solubility are preferable.

  The density | concentration of the slime control agent in a solution is not specifically limited, Usually, 1 mass% or more and 40 mass% or less, Preferably they are 2 mass% or more and 30 mass% or less. When the concentration is within the above range, the slime control agent tends to be sufficiently dispersed or dissolved in the solvent. If the concentration exceeds the above upper limit, the slime control agent may not be sufficiently dispersed or dissolved. If the concentration is less than the lower limit, a large amount of solvent may be required.

  The addition amount of the slime control agent to the aqueous system is not particularly limited, and is usually 0.1 mg / L or more and 1000 mg / L or less, preferably 1 mg / L or more and 100 mg / L or less in terms of solid content. When the concentration is within the above range, generation of slime tends to be sufficiently suppressed. If the concentration exceeds the above upper limit, the production cost may increase. There exists a possibility that generation | occurrence | production of slime cannot be suppressed as a density | concentration is less than the said minimum.

  Further, the time from the aeration treatment to the addition of the slime control agent is not particularly limited, and is preferably 0 minutes or more and 30 minutes or less. If the time from the aeration treatment to the addition of the slime control agent exceeds 30 minutes, the bacteria may be activated and propagated again, and the reducing substances may increase.

  FIG. 1 is a diagram showing an embodiment of a papermaking process according to the present invention. Specifically, the water system 19 introduced into the white water circulation system is aerated with air in an aeration tank 20 having a diffuser tube at the bottom. After the water system 19 and the white water 10 from the white water silo 11 are mixed, they are mixed with the raw material pulp slurry of the machine tank 2. The slime control agent 21 is added to the aeration tank 20 and sent to the inlet 5 via the screen 4 by the fan pump 3. The raw pulp slurry sent to the inlet 5 is supplied to the wire part 6 and dehydrated. The dehydrated wet sheet 7 is sent from the press part 8 to the dryer part 9. The white water 10 separated by the wire part 6 is stored in the white water silo 11, and the white water 8 is circulated (white water circulation system 22).

  Further, it is preferable to aerate the oxygen-containing gas in the aeration tank 17 or the like, or to add a slime control agent 18 or the like.

  That is, it is preferable to further include a step of aeration of the oxygen-containing gas into the white water circulation system (second aeration step). The generation of slime can be suppressed synergistically by aeration of the oxygen-containing gas also in the white water circulation system.

  Moreover, it is preferable to further have the process of adding a slime control agent to the said white-water circulation system (2nd slime control agent addition process). By aeration of the oxygen-containing gas also in the white water circulation system, generation of slime can be further suppressed synergistically.

  The method of aeration and addition in the white water circulation system is not particularly limited, and for example, it can be performed according to the same method as the aeration method and addition method in the aqueous system. Further, the white-water circulation system may or may not have a solid-liquid separation device, and the separated solid content may be discharged or recovered into the raw material system.

<Measurement process>
The slime suppression method preferably further includes a step of measuring at least one item selected from a measurement item group consisting of the oxidation-reduction potential, sulfite ion concentration, and dissolved oxygen content of the white water circulation system. By controlling the amount of aeration in the aeration step and / or the amount of slime control agent added in the slime control agent addition step based on the measurement results obtained in this measurement step, the generation of slime can be more stably and reliably suppressed. it can.

Specifically, aeration of the aeration step and / or slime control agent addition amount of the slime control agent addition step oxidation-reduction potential of the white water circulation system or -150 mV, sulfite ion concentration 2.0mgSO 3 - _/ ^L or less , And the amount of dissolved oxygen is preferably adjusted to be any one or more of 1 mg / L or more. By adjusting in this way, generation | occurrence | production of slime can be suppressed more effectively.

  The oxidation-reduction potential is usually adjusted to −150 mV or more, preferably −100 mV to 500 mV. When microbial contamination progresses and oxygen in the system is consumed, the oxidation-reduction potential tends to decrease. However, if the oxidation-reduction potential is within the above range, the amount of oxygen in the white water circulation system becomes sufficient, and slime is not generated. There is a tendency to be able to suppress effectively. If the oxidation-reduction potential exceeds the above upper limit, the amount of oxygen in the white water circulation system may be excessively larger than necessary. There exists a possibility that generation | occurence | production of slime cannot be suppressed as a redox potential is less than the said minimum.

  The method for measuring the oxidation-reduction potential is not particularly limited, and examples thereof include a potentiometric measurement method and a potentiometric titration method.

The sulfite ion concentration is preferably adjusted to 2.0 mgSO ₃ ⁻ / L or less, more preferably 1.5 mgSO ₃ ⁻ / L or less. When the sulfite ion concentration is within the above range, the sulfite ion concentration in the white water circulation system tends to be sufficiently reduced. If the sulfite ion concentration exceeds the upper limit, the reducing substance may not be sufficiently reduced.

  The sulfite ion concentration can be measured according to JIS K 0102: 2008.

  The amount of dissolved oxygen is preferably adjusted to 1 mg / L or more, more preferably 1 mg / L to 10 mg / L, and even more preferably 3 mg / L to 10 mg / L. When the amount of dissolved oxygen is within the above range, the amount of oxygen in the white water circulation system becomes sufficient, and the generation of slime tends to be effectively suppressed. If the amount of dissolved oxygen exceeds the above upper limit, the amount of oxygen in the white water circulation system may become excessive more than necessary. There exists a possibility that generation | occurrence | production of slime cannot be suppressed as the amount of dissolved oxygen is less than the said minimum. The amount of dissolved oxygen can be measured using a dissolved oxygen meter.

The number of viable bacteria is not particularly limited, and is usually 1 × 10 ⁷ CFU / mL or less, preferably 1 × 10 ⁶ CFU / mL or less. If the number of viable bacteria exceeds the above upper limit, the generation of slime may not be suppressed.

  The number of viable bacteria is measured by a colony counting method, and indicates the number of colonies formed from a certain amount of water of cooling water system which is an object of corrosion prevention and using as a microorganism source. In addition, the number of viable bacteria obtained by an absorbance / turbidity measurement method, a gravimetric method, or the like may be displayed.

  The colony counting method is not particularly limited, and examples thereof include a plate culture method, a capillary method, and a membrane filter method.

  The sterilization rate is not particularly limited, and is usually 99.5% or more, preferably 99.9% or more. There exists a possibility that generation | occurence | production of slime cannot be suppressed as a sterilization rate is less than the said minimum.

  The measurement process can also be performed by measuring other parameters. Other parameters are not particularly limited, and examples include indexes for evaluating microbial activity such as calcium ion content, electrical conductivity, glucose concentration, and pH.

<Others>
Other process conditions such as temperature, pressure, time, and equipment in each process are not particularly limited, and are appropriately set according to the raw materials used. The number of steps in each step is not particularly limited, and may be performed in one step or in multiple steps. The quantification and qualification of raw materials and products can be performed according to known methods such as NMR, IR, elemental analysis, and mass spectrum. Moreover, the raw material to be used may be used independently and may be used combining multiple types of raw material.

  According to the present invention, generation of slime in the white water circulation system in the paper making process can be sufficiently and easily suppressed. Therefore, the said slime suppression method can be used suitably in the papermaking process in the case of paper manufacture. In the papermaking process, it is possible to reuse the slime control agent, reduce the amount of new water used, reduce wastewater treatment, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In Examples and Comparative Examples, measurement was performed by the following method.

<Redox potential (ORP)>
The oxidation-reduction potential (mV) was measured using an oxidation-reduction potentiometer (manufactured by Toko Chemical Co., Ltd.) using a potentiometric method.

<Sulphite ion concentration>
The sulfite ion concentration (mgSO ₃ ⁻ / L) was measured according to JIS K 0102: 2008. Specifically, an appropriate amount of sample was placed in a volumetric flask, and a color was developed by adding a pararose aniline solution, a formaldehyde solution, and a mercury chloride solution. After standing for 20 minutes, a blank solution prepared in the same manner as described above was colorimetrically measured at 572 nm and obtained as a sulfite ion concentration.

<Amount of dissolved oxygen>
The dissolved oxygen amount (mg / L) was measured using a diaphragm electrode type dissolved oxygen meter (manufactured by Orbis Fair).

<Viable count>
The viable cell count (CFU / mL) was obtained by diluting the test water, mixing this fixed amount well with a nutrient-containing agar medium, and culturing the plate for one day, and then counting the number of colonies produced.

<Disinfection rate>
The sterilization rate (%) was calculated using the following formula.
Bactericidal rate (%) = ((viable count before treatment)-(viable count after treatment)) / (viable count before treatment) x 100

<Bactericidal effect>
The bactericidal effect was determined according to the following evaluation criteria.
A: Bactericidal rate is 99.9% or more B: Bactericidal rate is 99.5% or more and less than 99.9% B: Bactericidal rate is 90% or more and less than 99.5% X: Bactericidal rate is less than 90%

<Slime suppression effect>
The slime suppression effect was determined according to the following evaluation criteria.
◎: No slime adhesion ○: Slime thickness is less than 0.1 mm △: Slime thickness is 0.1 mm or more and less than 0.5 mm ×: Slime thickness is 0.5 mm or more

(Formulation A)
12% sodium hypochlorite was prepared as formulation A.

(Formulation B)
Formulation B was prepared by reacting ammonium bromide and sodium hypochlorite in a molar ratio of 1: 1.

(Formulation C)
Formulation C was prepared by blending 20 parts by mass of 2,2-dibromo-3-nitrilopropionamide (DBNPA) and 80 parts by mass of diethylene glycol monomethyl ether.

(Formulation D)
Formulation D was prepared by blending 20 parts by mass of 2,2-dibromo-2-nitroethanol (DBNE) and 80 parts by mass of diethylene glycol monomethyl ether.

(Example 1, Comparative Example 5)
Using white water collected from a paper machine, the oxidation-reduction potential, sulfite ion concentration, dissolved oxygen content and viable cell count were measured (measurement step). The redox potential of white water before the treatment is −387 mV, the sulfite ion concentration is 9.0 mg SO ₃ ⁻ / L, the dissolved oxygen amount is less than 0.1 mg / L, and the viable cell count is 4.1 × 10 6. ⁸ CFU / mL. In the aeration tank having an aeration pipe at the bottom, an aeration pipe having a diameter of 2 mm per 10 cm with an aeration amount of 2 m ³ / hour per 1 m ² of unit area, and the water system introduced into the white water circulation system with air in the aeration tank Aerated (aeration process). After mixing the water system and white water from the white water silo, it was mixed with raw pulp slurry of a machine tank using hardwood bleached kraft pulp and deinked pulp as raw pulp. Formulation A was added to the aeration tank at a rate of 100 mg / L (slime control agent addition step), and sent to the inlet via a screen by a fan pump. The raw pulp slurry sent to the inlet was supplied to the wire part and dehydrated. The dehydrated wet sheet was sent from the press part to the dryer part. White water separated by the wire part was stored in a white water silo, and the white water was circulated (white water circulation system). After 14 days, the redox potential, white sulfite ion concentration, dissolved oxygen content, and viable cell count of white water were measured. Moreover, the amount of slime adhesion in the piping of the white water circulation system was visually confirmed. On the other hand, the oxidation-reduction potential, sulfite ion concentration, dissolved oxygen content, and viable cell count were measured in the same manner as in Example 1 except that the slime control agent (formulation) was not added (Comparative Example 5). The bactericidal rate of Example 1 was calculated from the number of viable bacteria before treatment and the number of viable bacteria of Example 1.

(Examples 2 to 8, Comparative Example 6)
Except that the amount of aeration, the type of slime control agent (formulation), and the addition concentration were as shown in Table 1, redox potential, sulfite ion concentration, dissolved oxygen amount, viable cell count, and bactericidal rate, as in Example 1. Was measured. Moreover, the amount of slime adhesion in the piping of the white water circulation system was visually confirmed.

(Comparative Examples 1-4)
The oxidation-reduction potential, sulfite ion concentration, dissolved oxygen amount, viable bacteria were the same as in Example 1 except that the aeration treatment was not performed and the type and addition concentration of the slime control agent (formulation) were as shown in Table 1. Number was measured. Moreover, the amount of slime adhesion in the piping of the white water circulation system was visually confirmed. Without aeration treatment, the bactericidal rate of Comparative Examples 1 to 4 was calculated from the number of viable bacteria before treatment and the number of viable bacteria of Comparative Examples 1 to 4.

It can be seen from Table 1 that the slime suppression effect of the example is improved as compared with the comparative example. In Tables 1 and 2, aE + b related to the number of viable bacteria means a × 10 ^b .

  According to the present invention, generation of slime in the white water circulation system in the paper making process can be sufficiently and easily suppressed. Therefore, the said slime suppression method can be used suitably in the papermaking process in the case of paper manufacture.

DESCRIPTION OF SYMBOLS 1 Raw material manufacturing process 2 Machine tank 3 Fan pump 4 Screen 5 Inlet 6 Wire part 7 Wet sheet 8 Press part 9 Dryer part 10 White water 11 White water silo 12 Slime control agent 13 Aeration tank 14 Slime control agent 15 Solid-liquid separator 16 Solid content 17 Aeration tank 18 Slime control agent 19 Water system 20 introduced into the white water circulation system Aeration tank 21 Slime control agent 22 White water circulation system 23 Fan pump 24 Fan pump 25 Fan pump 26 Fan pump

Claims (6)

A slime suppression method in a white water circulation system in a papermaking process,
A process of aeration of oxygen-containing gas into the water system introduced into the white water circulation system;
And a step of adding a slime control agent to the aqueous system. Further comprising the step of measuring at least one item selected from the measurement item group consisting of the redox potential, sulfite ion concentration and dissolved oxygen content of the white water circulation system,
The slime suppression method of Claim 1 which controls the aeration amount of an aeration process and / or the slime control agent addition amount of a slime control agent addition process based on the measurement result obtained at this measurement process. The aeration amount in the aeration step and / or the slime control agent addition amount in the slime control agent addition step are the redox potential of the white water circulation system of −150 mV or more, the sulfite ion concentration of 2.0 mgSO ₃ ⁻ / L or less, and the amount of dissolved oxygen The slime-suppressing method according to claim 2, wherein the adjustment is performed so that at least one is 1 mg / L or more. The aeration tank having an aeration tube at the bottom is used for aeration in the aeration process, and the aeration amount by the aeration tube is 0.5 m ³ / hour or more and 10 m ³ / hour or less per 1 m ^{2 of the} bottom area of the aeration tank. The slime suppression method according to any one of claims 1 to 3.   The slime suppression method according to any one of claims 1 to 4, further comprising a step of aeration of an oxygen-containing gas into the white water circulation system.   The slime suppression method according to any one of claims 1 to 5, further comprising a step of adding a slime control agent to the white water circulation system.

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