JP5882679B2 - Manufacturing method of filler - Google Patents

Description

  The present invention relates to a method for producing a filler.

  Currently, in the paper industry, fillers are added (internally added) to pulp materials to improve paper quality such as opacity, whiteness, and printability. However, since the yield is poor even if the filler is simply added, for example, Patent Document 1 proposes that the recycled filler is aggregated in advance with a cationized polymer and added internally. Further, Patent Document 2 proposes that the filler is pretreated on the assumption that, when the filler is aggregated, the yield is improved, but improvement in paper quality such as opacity and whiteness is not sufficient. This proposal suggests that a predetermined cationic polymer compound is mixed in the filler, and the average particle size is preferably 1.0 to 2.0 times that before mixing. However, the present inventors have found that the yield is not sufficiently improved only by increasing the average particle diameter.

  On the other hand, the present applicant has proposed a method for producing regenerated particles that can be suitably used as a filler (see Patent Document 3). In this proposal, deinked floss is dehydrated and heat-treated, and the regenerated particles that have become aggregates in the heat treatment process are suspended in an aqueous alkali silicate solution, and mineral acid is added to produce silica composite regenerated particles. It is. This silica composite recycled particle has an extremely high paper quality improvement effect such as opacity and whiteness, and also solves the problem of paper sludge disposal because it uses deinked floss as a raw material. However, the silica composite regenerated particles have room for improvement in terms of yield. Further, the method for producing the silica composite regenerated particles is a so-called “batch type” in which the production of a predetermined amount of silica composite regenerated particles is repeated, and not the “continuous type” in which the silica composite regenerated particles are continuously produced. In this regard, continuous production of silica composite regenerated particles improves production efficiency. However, for example, problems such as scale precipitation occur, and a specific method for solving this problem has not been established.

Japanese Patent Laid-Open No. 2003-119692 JP 2006-118092 A JP 2008-81390 A

  The main problem to be solved by the present invention is to provide a method for producing a filler that has a good yield when added to a pulp raw material and can improve paper quality such as whiteness. More preferably, it is to provide a method for producing a filler capable of improving paper quality such as opacity. More preferably, it is to provide a method capable of continuously producing a filler.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
A previous step of mixing the inorganic particles, alkali silicate and mineral acid;
The mixed slurry obtained in this preceding step possess a step after mixing the aluminum salt, and
Mixing in the previous step is performed in a preceding tank, mixing in the subsequent step is performed in a subsequent tank different from the preceding tank, and the mixed slurry in the preceding tank is directly from the preceding tank or via another tank It shall flow to the following tank,
At least a dispersant mainly composed of polyacrylic acid soda is added to the mixed slurry in the preceding tank, and the filler is continuously produced .

(Main effects)
In the previous step of mixing the inorganic particles, alkali silicate and mineral acid, silica is combined with the inorganic particles. Therefore, according to this method, a filler capable of improving paper quality such as whiteness is produced. In the step after mixing the aluminum salt, aluminum ions are bonded to the silica surface (cationization), and the anionic silica surface can be modified to be cationic. Therefore, a filler with a good yield when added to the pulp raw material is produced. This is an effect obtained because the aluminum ion is cationic and ionically bonds to pulp fibers that are anionic. Therefore, according to the present method, the filler has a self-fixing property to pulp fibers. Is manufactured. In this respect, this self-fixing property contributes to improving the yield, and also contributes to, for example, uniformly distributing the filler throughout the wet paper.
In contrast, when an aluminum salt is mixed when silica is combined with inorganic particles, silica is condensed with aluminum ions as a nucleus, and white carbon is generated. Therefore, according to the method, a mixture of inorganic particles and white carbon may be produced. The present inventors have made the above invention through this knowledge and the like.
Mixing in the previous process is performed in the preceding tank, mixing in the subsequent process is performed in the succeeding tank different from the preceding tank, and the mixed slurry in the preceding tank flows from the preceding tank directly or through the other tank to the succeeding tank. If this is the case, the filler is temporarily produced continuously, but there is a problem of scale precipitation, which cannot be carried out continuously. However, when a dispersant containing polyacrylic acid soda as a main agent is added to at least the mixed slurry in the preceding tank, the problem of scale precipitation can be solved and continuous implementation can be achieved.

[Invention of Claim 2]
Using a sulfate band as the aluminum salt,
The manufacturing method of the filler of Claim 1.

(Main effects)
When a sulfuric acid band is used as the aluminum salt, the silica composite particles are cationized by aluminum ions, and the alkali silicate is neutralized by the sulfate ions, and the silica composite is advanced. In addition, since the sulfuric acid band is a chemical that is generally used in the paper industry, it is easy to manage chemicals and comply with safety standards, and to suppress an increase in cost.

  According to the present invention, it is a method for producing a filler that has a good yield when added to a pulp raw material and can improve paper quality such as whiteness.

It is a manufacturing flow figure of a filler.

Next, the form for implementing this invention is demonstrated.
The method for producing a filler according to this embodiment uses inorganic particles, alkali silicate (preferably an aqueous solution), mineral acid and aluminum salt as main raw materials, composites silica with inorganic particles, and further cationizes the silica.

  The kind of inorganic particles that can be used as a raw material is not particularly limited. For example, known inorganic particles such as light calcium carbonate, heavy calcium carbonate, clay, talc, kaolin, calcined kaolin, titanium dioxide, aluminum hydroxide are used. Preferably, calcium carbonate, clay, talc, and regenerated particles that are preferably used as a filler or pigment for papermaking can be used.

  On the other hand, since the problem of papermaking sludge disposal and the like can be solved at the same time, it is preferable to use a heat-treated product obtained by heat-treating an object to be treated using papermaking sludge as a main raw material as inorganic particles. Below, the case where the heat processing thing obtained by heat-processing the to-be-processed object which uses papermaking sludge as a main raw material (especially the ground material which grind | pulverized the heat processing thing in this form) is used as an inorganic particle.

(Heat treatment process)
In the manufacturing method of the present embodiment, as shown in FIG. 1, first, an object to be processed X1 using papermaking sludge as a main raw material (50% by mass or more) is heat-treated in a heat treatment step 10 to obtain a heat-treated product X2. Paper sludge that is the main raw material of the object to be treated X1, for example, those that have been transferred to wastewater without using fiber components such as pulp, organic substances such as starch and synthetic resin adhesive, inorganic substances such as fillers and pigments, etc. In addition, lignin and fine fibers generated in the pulping process, fillers and printing ink derived from waste paper, surplus sludge generated from the biological wastewater treatment process, and the like can be used.

  However, in the used paper pulp manufacturing process, in order to continuously produce a used paper pulp having a stable quality, a used paper of a certain quality that has been selected and selected is used. Therefore, the types, ratios, amounts, etc. of inorganic substances brought into the waste paper pulp manufacturing process are basically constant. Moreover, even if plastics such as vinyl and film that cause a change in the ratio of the unburned portion remaining in the heat-treated product X2 are contained in the waste paper, these lead to a deinking process in which deinking floss is generated. For example, it is removed by a pulper, a screen, a cleaner or the like in the previous stage. Therefore, compared to papermaking sludge generated in other processes such as factory drainage process and papermaking raw material preparation process, deinking floss becomes a raw material for producing extremely stable quality inorganic particles and can be used suitably. it can.

  In the manufacturing method of the present embodiment, the process through which the workpiece X1 is converted into the heat-treated product X2 is not particularly limited. For example, a purchased heat-treated product (product) can be used. In addition, when the heat-treated product is also produced by itself, the material to be treated X1 that has been dehydrated and pulverized as necessary can be heat-treated and further pulverized and classified as necessary.

  Here, the heat treatment of the workpiece X1 means performing drying, thermal decomposition, combustion, and the like of the workpiece. This heat treatment may be performed continuously in one apparatus, but at least drying and other heat treatments are preferably performed in separate apparatuses. The drying temperature at this time may be controlled to be 200 to 600 ° C., for example. On the other hand, the preferred range of the temperature of the other heat treatment varies depending on the number of steps of the heat treatment. For example, when the heat treatment is performed in one stage, the temperature may be controlled to be 550 to 780 ° C. When the heat treatment temperature is lower than 550 ° C., the organic component in the workpiece X1 is not sufficiently heat treated, and the whiteness may be lowered. On the other hand, when the heat treatment temperature exceeds 780 ° C., the inorganic content in the workpiece X1 may be melted, resulting in a decrease in whiteness and generation of a hard substance. Next, when the heat treatment is performed in two stages, the temperature may be controlled so that the first stage has a relatively low temperature of 300 to 600 ° C. and the second stage has a relatively high temperature of 550 to 780 ° C. Thus, when the first stage is relatively low in temperature, excessive combustion in the first stage is prevented, and the workpiece X1 that has passed through the first stage is easily whitened in the second stage. As a result, whitening can be reliably advanced at a relatively high temperature second stage, and a heat-treated product X2 having high whiteness can be obtained. Further, when heat treatment is performed in three stages, the temperature may be controlled so that the temperature is increased in order so that the first stage is 250 to 370 ° C., the second stage is 360 to 560 ° C., and the third stage is 550 to 780 ° C. . According to this heat treatment method, high calorific value components such as acrylic organic substances and cellulose are removed by heat treatment from the object to be treated X1 in the first stage, and styrene organic substances are heat treated and removed from the object to be treated X1 in the second stage. In the third stage, the organic matter such as residual carbon contained in the workpiece X1 is removed by heat treatment. The above drying and other heat treatments can be performed using a known apparatus such as a stalker furnace, fluidized bed furnace, cyclone furnace, kiln furnace, etc., but other heat treatments are performed using a horizontal rotary kiln furnace. It is preferable to use.

(Particle size adjustment process)
The obtained heat-treated product X2 is, for example, a particle size adjusting step such that the median diameter (D50) of the volume average particle diameter is 0.2 to 5.0 μm, preferably 1.0 to 4.0 μm. It is preferable to perform pulverization or classification at 20. If the volume average particle size of the pulverized product X3 obtained by pulverization or the like is less than 0.2 μm, the yield may not be sufficiently improved. On the other hand, since the particle size distribution of the heat-treated product X2 is broad, the particle size distribution is not sharp even if the pulverized product X3 is pulverized so that the volume average particle diameter exceeds 5.0 μm, causing problems such as deterioration of the paper surface. There is a fear.

  The volume average particle size of the pulverized product X3 was determined by measuring the particle size distribution of the sample (crushed product X3) using a laser diffraction particle size distribution meter (model number: SA-LD-2200, manufactured by Shimadzu Corporation). The particle diameter (D50) when the cumulative volume with respect to the volume of the particles is 50% is determined, and this particle diameter is defined as the volume average particle diameter. When measuring the particle size distribution, the pulverized product X3 is added to a 0.1% sodium hexametaphosphate aqueous solution and dispersed by ultrasonic waves for 1 minute. The heat-treated product X2 can be pulverized using, for example, a dry pulverizer such as a jet mill or a high-speed rotary mill, or a wet pulverizer such as an attritor, a sand grinder, or a ball mill.

The obtained pulverized product X3 may be crystallized by CO ₃ ions, SO ₄ ions, or the like in the presence of calcium oxide, and the volume average particle size may vary. Therefore, it is preferable that the obtained pulverized product X3 is reacted with phosphoric acid or carbon dioxide to crystallize calcium ions in advance. By carrying out this reaction, it is possible to prevent fluctuations in the volume average particle diameter and to prevent solidification and thickening when the pulverized product X3 is slurried.

  The pulverized product (regenerated particles) X3 obtained as described above has a high whiteness of 75 to 85%, preferably 80 to 85%, and little variation in whiteness.

(Previous process)
The inorganic particles (ground product) X3 obtained as described above are mixed with alkali silicate and mineral acid to obtain a silica composite in which silica is combined with the inorganic particles X3. Since the fine particles contained in the inorganic particles X3 form aggregates due to the composite of silica, the particle diameter becomes large, so that the yield when internally added to the pulp raw material is improved. Moreover, there is an advantage that the degree of wire wear is reduced by the composite of silica.

  The specific method of combining silica with the inorganic particles X3 is not particularly limited. For example, the inorganic particles X3 are dispersed in an alkali silicate aqueous solution to form an inorganic particle slurry, and a mineral acid is added to the inorganic particle slurry and appropriately stirred. The method can be adopted.

(Later process)
An aluminum salt is further mixed into the silica composite slurry thus obtained. By this mixing, aluminum ions are bonded to the silanol groups of silica compounded with the inorganic particles X3, and the silica surface is cationized. Therefore, the yield when added to the pulp raw material is improved. This is an effect obtained because aluminum ions are cationic and ionically bond to anionic pulp fibers. Therefore, the filler manufactured through this step has self-fixing property with respect to the pulp fiber. In this respect, this self-fixing property contributes to improving the yield, and also contributes to, for example, uniformly distributing the filler throughout the wet paper.

  On the other hand, if there is no distinction between the previous step and the subsequent step, that is, when an aluminum salt is mixed when silica is combined with the inorganic particles X3, the silica aggregates with aluminum ions as a nucleus, and white Carbon is produced. Therefore, according to the method that does not provide this distinction, a mixture of inorganic particles X3 and white carbon is produced.

  In this embodiment, as the aluminum salt, aluminum sulfate (sulfuric acid band), basic aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum chloride, aluminum nitrate, basic aluminum nitrate, or the like can be used. However, as the aluminum salt, it is preferable to use a sulfuric acid band as described later.

  The amount of aluminum salt mixed with the silica composite is preferably such that the reaction completion pH is preferably 6.0 to 9.5, more preferably 7.5 to 9.3. The mixing amount with respect to 100 parts by mass is preferably 18 parts by mass to 48 parts by mass, more preferably 23 parts by mass to 43 parts by mass, and particularly preferably 28 parts by mass to 38 parts by mass. When the mixing amount is less than 18 parts by mass, there is a possibility that the binding with the pulp fiber when the final product (filler) is added to the pulp raw material becomes insufficient. On the other hand, even if the mixing amount exceeds 48 parts by mass, the effect of mixing may reach its peak.

  The mixing of the silica composite and the aluminum salt can be performed, for example, by adding the aluminum salt to a slurry in which the silica composite is dispersed in water and appropriately stirring the mixture. The silica composite slurry may be produced by dispersing the silica composite in a dry state in water. For example, the slurry of the previous step can be used as it is. The density | concentration of the silica composite in the slurry in this case can be 5-25%, for example. The cationized product thus obtained can be, for example, filtered, washed with water, dehydrated, etc. to obtain a wet cake, and dried appropriately to obtain filler X5.

(Continuous)
The above-mentioned previous process and the subsequent process can be performed in a batch system in which the processing is repeated for each predetermined amount, but it is preferable to perform the process in a continuous system in terms of production efficiency. Hereinafter, this continuous type will be described in detail.

  In the case where the composite and cationization of silica are continuously performed, a plurality of reaction vessels, in this embodiment, four reaction vessels 41 to 44 are prepared as shown in FIG. And an aqueous solution L of an alkali silicate such as water glass.

The concentration of silicic acid (SiO ₂ ) in the alkali silicate aqueous solution L is preferably 6 to 18 g / L, more preferably 8 to 16 g / L, and particularly preferably 10 to 14 g / L. When the silicic acid concentration is less than 6 g / L, the silica sol is not sufficiently generated, and silica may not be combined with some of the inorganic particles X3. On the other hand, when the silicic acid concentration exceeds 18 g / L, white carbon is generated instead of silica sol, and a part of the inorganic particles X3 may be covered with white carbon. If the inorganic particles X3 are covered with white carbon, the advantage that the inorganic particles X3 of this embodiment are porous may be lost, and for example, the opacity of the internally added paper may not be sufficiently improved. .

  Further, the concentration of the inorganic particles X3 in the first reaction tank 41 is preferably 95 to 125 g / L, more preferably 100 to 120 g / L, and particularly preferably 105 to 115 g in the state before adding the mineral acid N. / L. When the concentration is less than 95 g / L, productivity is poor, and the purpose of improving productivity as a continuous type may be reduced. On the other hand, when the concentration exceeds 125 g / L, the viscosity increases and the dispersibility of the porous inorganic particles X3 may be reduced.

  In the first reaction tank 41, the slurry S of the reaction layer 41 preferably has a pH of 10.0 to 11.0 so that the pH is preferably more than 9.5 and not more than 11.5. Further, a mineral acid N such as sulfuric acid, hydrochloric acid or nitric acid is added. The concentration of the mineral acid N is preferably 0.5 to 4.0 mol / L (1 to 8 N (normality)), more preferably 1.0 to 3.0 mol / L (2 to 6 N), particularly preferably. 1.75 to 2.25 mol / L (3.5 to 4.5). If the concentration of the mineral acid N is less than 0.5 mol / L, the silica sol may not be generated sufficiently. On the other hand, when the concentration of the mineral acid N exceeds 4.0 mol / L, the dispersibility of the mineral acid N is deteriorated, so that the generated silica sol may be inhomogeneous.

  The amount of mineral acid N added to the slurry in the fourth reaction tank 44 is preferably pH 6.5 to 8.5, more preferably pH 7.0 to 8.5, and particularly preferably pH 7.2 to 8 .. This is a range that becomes zero. When the pH is less than 6.5, when the sulfuric acid band A is added as the aluminum salt in the third reaction tank 43 or when the mineral acid N is separately added, white carbon is generated instead of silica sol. In the reaction tank 44, the mixture of inorganic particles X3 and white carbon becomes a mixture, and the target silica composite particles may not be obtained. Moreover, when the pH is less than 6.5, calcium, which is a constituent component of the inorganic particles X3 of the present embodiment, is changed to calcium sulfate or the like, for example, the volume average particle diameter of the filler X5 to be produced is excessively reduced, There is a risk that the shape becomes uneven. On the other hand, when the pH exceeds 8.5, even if the sulfuric acid band A or a separate mineral acid N is added in the third reaction tank 43, the silica sol is not sufficiently generated, and the fourth reaction tank 44 is free from the inorganic particles X3. There is a possibility that the composite of silica cannot be sufficiently advanced.

  In this embodiment, the mineral acid N can be added also in the third reaction tank 43 as described later. The addition of the mineral acid N in the third reaction layer 43 is preferably such that the slurry S of the fourth reaction layer 44 has a pH of 6.5 to 8.5, more preferably a pH of 7.0 to 8.5, and particularly preferably a pH of 7. It is preferably used as a means for fine adjustment so as to be 2 to 8.0.

Silica is generally roughly classified into silicic anhydride (SiO ₂ ) and hydrated (hydrous) silicic acid (SiO ₂ .nH ₂ O), and the silica sol produced in this embodiment is mainly hydrous silicic acid sol. It is. However, this is not to deny that other silicate sols are produced. Silica sol is generally considered to be in the form of particles having a particle diameter of 10 to 20 nm, but these particles exist in a chained state.

  Hot water is separately supplied to the first reaction tank 41 as necessary, and the concentration of the inorganic particles X3 and the temperature of the slurry composed of the inorganic particles X3 and the alkali silicate aqueous solution L can be adjusted. The temperature of the slurry is preferably 60 to 100 ° C, more preferably 70 to 100 ° C, and particularly preferably 90 to 100 ° C. If the temperature of the slurry is less than 50 ° C., the silica sol may not be sufficiently generated. On the other hand, if the temperature of the slurry exceeds 100 ° C., it becomes necessary to use an autoclave or the like, which complicates the equipment. Further, if the temperature of the slurry exceeds 100 ° C., the heat energy is wasted and the liquid level fluctuates due to the boiling of the slurry, so that the scale may adhere to the inner wall surface of the first reaction tank 41. In addition, since the concentration of the slurry is increased by evaporation of moisture, the viscosity is increased, and there is a possibility that poor stirring due to the increased viscosity may occur. Note that the temperature of the slurry can also be adjusted by providing a heating facility in the first reaction tank 41. Further, the temperature of the slurry is the temperature of the slurry existing at the center of the bottom surface of the first reaction tank 41.

The slurry in the first reaction tank 41 can be stirred as necessary. This stirring is performed so that the Reynolds number (Re) of the slurry is preferably 4000 to 16000, more preferably 6000 to 14000, and particularly preferably 8000 to 12000. If the Reynolds number is less than 400, the inorganic particles X3 may not be sufficiently dispersed, and silica may be non-uniformly formed. On the other hand, if the Reynolds number exceeds 16000, the inorganic particles X3 may be miniaturized. The Reynolds number (Re) is a dimensionless number indicating the nature of the slurry flow in the first reaction tank 41 and is represented by the following equation (1).
Re = ρvd / μ (1)
In the equation (1), “ρ” is the slurry density (g / cm ³ ), “v” is the slurry flow velocity (cm / s), and “d” is the diameter (cm) of the first reaction tank 41. , “Μ” is the viscosity coefficient (Ns / cm ³ ) of the slurry.

  The passage time of the slurry in the first reaction tank 41 is preferably 2 to 20 minutes, more preferably 4 to 18 minutes, and particularly preferably 8 to 12 minutes. If the passage time is less than 2 minutes, the silica sol may not be sufficiently generated. On the other hand, even if the passage time exceeds 20 minutes, the treatment efficiency is lowered and it is not useful for the production of silica sol. Note that this passage time is a calculated time from when the mineral acid N is added to the slurry until it flows out of the first reaction tank 41, and does not include the time before the mineral acid N is added.

  Here, it is more preferable to add a dispersant mainly composed of polyacrylic acid soda together with the mineral acid N to the first reaction tank 41. By adding this dispersing agent, generation of scale due to the addition of mineral acid N is prevented. In this embodiment, mineral acid N is also added in the third reaction tank 43 as will be described later, but since this addition is auxiliary, the dispersant is added at least in the first reaction tank 41. It is preferable to add it in the third reaction tank 43, and it becomes more preferable.

  However, the dispersant can be added to the second reaction tank 42 and the fourth reaction tank 44, for example. In addition, in this form, a main ingredient means the component which occupies 50 mass% or more.

  The type of dispersant mainly composed of polyacrylic acid soda is not particularly limited, and examples thereof include Aron T540 (manufactured by Toa Gosei), Poise 520 (manufactured by Kao), SN Dispersant 5040 (manufactured by San Nopco) and the like. . However, it is preferable to use a dispersant mainly composed of polycarboxylic acid soda, and it is more preferable to use a dispersant mainly composed of polycarboxylic acid soda having a strong anionic property and many carboxylic acid groups. Examples of the dispersant mainly composed of polycarboxylic acid soda having many carboxylic acid groups include Poise 520 (manufactured by Kao), SN Dispersant 5040 (manufactured by San Nopco), and the like.

  The addition amount of the dispersant is preferably 0.013 to 0.66 parts by mass, and 0.04 to 0.40 parts by mass with respect to 100 parts by mass of the inorganic particles (X3) in terms of solid content. Is more preferable, and 0.07 to 0.20 parts by mass is particularly preferable. If the added amount of the dispersant is less than 0.013 parts by mass, the cationic groups contained in the inorganic particles X3 and acrylic acid groups such as carboxylic acid groups are condensed to increase the viscosity of the slurry, and scale may be generated. There is sex. Further, due to the condensation of the inorganic particles X3 and the dispersant, there is a possibility that the particle size distribution of the filler finally obtained becomes broad on the large diameter side.

  On the other hand, when the added amount of the dispersant exceeds 0.66 parts by mass, the electrolyte concentration in the slurry increases, and the slurry is thickened, and scale may be generated. In addition, when the obtained filler is used as a filler for papermaking, the yield may be reduced due to the electrolyte present in excess.

  The slurry S in the first reaction tank 41 continues to flow to the second reaction tank 42 through piping or the like. In the second reaction tank 42, addition of new inorganic particles X3, addition of alkali silicate aqueous solution L, mineral acid N or the like is not performed. In the second reaction tank 42, when silica is combined with the inorganic particles X3 by the silica sol produced in the first reaction tank 41, the small-sized inorganic particles X3 are converted into other inorganic particles X3 by the silica sol. Aggregation makes the particle size distribution of the inorganic particles X3 sharp.

  The temperature of the slurry S in the second reaction tank 42 can be the same as that in the first reaction tank 41. However, in adjusting the temperature of the slurry S, for example, a method of providing a heating facility in the second reaction tank 42 can be adopted, but each reaction tank 41, 42 is formed of a heat insulating material, Installation of heating equipment can be omitted. The temperature of the slurry S is the temperature of the slurry existing at the center of the bottom surface of the second reaction tank 42.

  The slurry S in the second reaction vessel 42 can be stirred as necessary in the same manner as in the first reaction vessel 41. However, the passage time of the slurry S in the second reaction tank 42 is preferably 20 to 50 minutes, more preferably 25 to 45 minutes, and particularly preferably 30 to 40 minutes. If the passage time is less than 20 minutes, the composite of silica with the inorganic particles X3 and the aggregation of the small-diameter inorganic particles X3 may not sufficiently proceed. On the other hand, even if the passage time exceeds 50 minutes, the composite of silica with respect to the inorganic particles X3 and the condensation of the small-diameter inorganic particles X3 do not proceed, and the processing efficiency may be reduced. This passage time is a calculated time from when the slurry S flows into the second reaction tank 42 to when it flows out to the third reaction tank 43.

  The above reactions in the first reaction tank 41 and the second reaction tank 42 are mainly for the composite of silica with the inorganic particles X3, and correspond to the above-mentioned “previous step”. These reactions can also be performed in one reaction tank (preceding tank) without providing separate reaction tanks. However, from the viewpoint of proceeding the reaction uniformly and reliably, it is preferable to carry out the reaction in two or more reaction vessels as in this embodiment.

  The slurry S in the second reaction tank 42 continues to flow into the third reaction tank 43 through piping or the like. In the third reaction tank 43, the sulfuric acid band A is added to the slurry S as the aluminum salt, and more preferably, the mineral acid N or a dispersant is added.

  When sulfate band A is used as the aluminum salt added to the third reaction tank 43, the silica composite is cationized by aluminum ions, and the composite of silica with the inorganic particles X3 is advanced by the sulfate ions. Further, since the sulfuric acid band A is a chemical that is generally used in the paper industry, it is easy to manage chemicals and comply with safety standards, and to suppress an increase in cost.

  On the other hand, the mineral acid N may be the same type as the mineral acid N used in the first reaction tank 41 or a different type. However, the same type is preferable from the viewpoint of the stability of the treatment, and dilute sulfuric acid is preferably used from the viewpoints of price, handling property and the like.

  The concentration of the mineral acid N is preferably 0.50 to 4.00 mol / L (1 to 8N (normality)), more preferably 1.00 to 3.00 mol / L (2 to 6N), and particularly preferably 1 .75 to 2.25 mol / L (3.5 to 4.5 N). When the concentration of the mineral acid N is less than 0.50 mol / L, the generation of silica sol becomes insufficient, and there is a possibility that the composite of silica with the inorganic particles X3 in the fourth reaction tank 44 cannot be sufficiently advanced. . On the other hand, when the concentration of the mineral acid N exceeds 4.00 mol / L, the dispersibility of the mineral acid N is deteriorated, so that the generation of the silica sol becomes uneven and the homogeneity of the produced filler X5 may be lowered. is there.

  The amount of the mineral acid N added to the slurry S in the fourth reaction tank 44 is preferably pH 6.5 to 8.5, more preferably pH 7.0 to 8.5, and particularly preferably pH 7.2 to 8 .. Adjust within the range of 0. The reason is as described above.

  In addition, since the sulfuric acid band A is also added in the third reaction tank 43, it is necessary to avoid the condensation of silica with aluminum ions as a nucleus when adding the mineral acid N. Therefore, the mineral acid N added in the third reaction tank 43 is auxiliary to the mineral acid N added in the first reaction tank 41 described above, and the addition of the mineral acid N in the third reaction tank 43 is performed. The amount is such that the reaction completion pH is preferably 6.0 to 9.5, more preferably 7.5 to 9.3, preferably 0 to 12% by volume, more preferably the total mineral acid addition amount. 0 to 10% by volume, particularly preferably 0 to 8% by volume. Therefore, if the pH is already 6.0 to 9.5, the addition of the mineral acid N is unnecessary. Excessive addition of mineral acid N may reduce the yield. Further, when the addition ratio of the mineral acid N exceeds 12% by volume, the addition ratio of the mineral acid N in the first reaction tank 41 decreases, and silica sol is not sufficiently generated in the first reaction tank 41, and the second There is a possibility that the silica composite and small-diameter inorganic particles X3 in the reaction tank 42 are not sufficiently aggregated.

  In the present embodiment, the form in which the sulfuric acid band A and the mineral acid N are added to the third reaction tank 43 is shown. However, from the viewpoint of avoiding the agglomeration of silica having aluminum ions as a nucleus, separate reaction tanks are used. It is preferable to provide them separately. When the sulfuric acid band A and the mineral acid N are added separately, the sulfuric acid band A and the mineral acid N can be added in this order, or the mineral acid N and the sulfuric acid band A can be added in this order. It is preferable to add them in the order of band A.

  The slurry S in the third reaction tank 43 can be stirred as necessary in the same manner as in the first and second reaction tanks 41 and 42 described above. However, the passage time of the slurry S in the third reaction tank 43 is preferably 2 to 20 minutes, more preferably 4 to 18 minutes, and particularly preferably 8 to 12 minutes. If the passage time is less than 2 minutes, the silica sol may not be sufficiently generated. On the other hand, even if the passage time exceeds 20 minutes, the generation of silica sol does not proceed and the processing efficiency may be reduced. The passage time is a calculated time from the addition of the mineral acid N to the slurry S until the mineral acid N flows out of the third reaction tank 43. The inflow of the slurry S and the addition of the mineral acid N are continuous. Therefore, the passage time is the same as the calculation time from when the slurry S flows in until it flows out.

  The temperature of the slurry S in the third reaction tank 43 can be the same as that in the first and second reaction tanks 41 and 42. Moreover, in adjusting the temperature of the slurry S, for example, a method of providing heating equipment in the third reaction tank 43 can be adopted, but each reaction tank 41 to 43 is formed of a heat insulating material, Installation of heating equipment can be omitted. The temperature of the slurry S is the temperature of the slurry S present at the bottom center of the third reaction tank 43.

  The slurry S in the third reaction tank 43 continues to flow to the fourth reaction tank 44 through piping or the like. In the fourth reaction tank 44, addition of new inorganic particles X3, addition of alkali silicate aqueous solution L, mineral acid N or the like is not performed. In the fourth reaction tank 44, the silica combined with the inorganic particles X3 is cationized by aluminum ions, and the silica sol generated in the third reaction tank 43 advances the composite of silica with the inorganic particles X3.

  The slurry S in the fourth reaction tank 44 can be stirred as necessary in the same manner as in the first to third reaction tanks 41 to 43. However, the passage time of the slurry S in the fourth reaction tank 44 is preferably 20 to 50 minutes, more preferably 25 to 45 minutes, and particularly preferably 30 to 40 minutes. If the passage time is less than 20 minutes, the cationization and the composite of silica may not sufficiently proceed. On the other hand, even if the passage time exceeds 50 minutes, the cationization and the composite of silica do not proceed, causing the treatment efficiency to decrease. The passage time is a calculated time from when the slurry S flows into the fourth reaction tank 44 to when it flows out.

  The temperature of the slurry S in the fourth reaction tank 44 can be the same as that in the first to third reaction tanks 41 to 43. Moreover, in adjusting the temperature of the slurry S, for example, a method of providing heating equipment in the fourth reaction tank 44 can be adopted, but each reaction tank 41 to 44 is formed of a heat insulating material, Installation of heating equipment can be omitted. The temperature of the slurry S is the temperature of the slurry S present at the center of the bottom surface of the fourth reaction tank 44.

  The reaction in the third reaction tank 43 and the fourth reaction tank 44 described above mainly aims at cationization of silica combined with the inorganic particles X3, and corresponds to the above-mentioned “subsequent process”. These reactions can also be performed in one reaction tank (following tank) without providing separate reaction tanks. However, from the viewpoint of proceeding the reaction uniformly and reliably, it is preferable to carry out the reaction in two or more reaction vessels as in this embodiment.

  In the post-treatment step 50, the silica composite slurry S obtained through the above steps is, for example, filtered, washed with water, dehydrated, etc. to obtain a wet cake, and is appropriately dried to obtain a filler X5.

The physical properties of the filler X5 are measured using, for example, a median diameter (D50) of 1.6 to 13.0 μm and a plastic wire abrasion meter (manufactured by Nippon Filcon, 3 hours, slurry concentration 2% by mass). The degree of wire wear is 15 to 100 g / m ² and the oil absorption calculated by the kneading method described in JIS K 5101-13-2 is 50 to 180 ml / 100 g.

  When the volume average particle size of the filler X5 is less than 1.6 μm, the yield may be insufficient when used as a filler, and the opacity may not be sufficiently improved. On the other hand, when the volume average particle diameter exceeds 13.0 μm, when used as a filler, the strength between pulp fibers is reduced, and the paper strength may be reduced. On the other hand, when the volume average particle diameter exceeds 13.0 μm, the uniform dispersibility in the slurry or the coating liquid is lowered, and the opacity and the opacity after printing may not be sufficiently improved.

Specifically, this oil absorption amount is obtained by taking 2 to 5 g of a sample (filler X5) dried at 105 to 110 ° C. for 2 hours on a glass plate and removing purified linseed oil (oxidized 4 or less) from the buret in small amounts. Repeat the operation of dripping in the center and kneading with a spatula each time, and obtain the amount (ml) of refined linseed oil dripping at the time when the whole was first assembled into a single rod (end point), calculated by the following formula It is.
Oil absorption (ml / 100) = (linseed oil amount (ml) × 100) / sample (g)

  Moreover, the ratio (silica composite rate) of the silica component of the filler X5 is preferably 2 to 30% by mass, more preferably 5 to 20% by mass, and particularly preferably 5 to 15% by mass. If the ratio of the silica component is less than 2% by mass, there is a possibility that the effects of silica composite such as whiteness improvement and yield improvement may not be sufficiently achieved. On the other hand, when the proportion of the silica component exceeds 30% by mass, the pores of the porous inorganic particles X3 are blocked, and the opacity may be reduced or the oil absorption may be reduced. In addition, the component structure of the filler X5 becomes a mass ratio of calcium: silicon: aluminum = 30-80: 10-50: 7-30, for example in oxide conversion. This component structure is a value obtained by performing elemental analysis at an acceleration voltage (15 KV) using an X-ray microanalyzer manufactured by Hitachi High-Technologies Corporation and converting the component components into oxides.

(Application example)
The filler X5 obtained by the above production method can be added (internally added) to the pulp raw material in the paper making process to obtain a filler-added paper. This filler-added paper is a paper with improved paper quality such as opacity, whiteness, and printability due to the properties of the filler X5. Further, since the filler X5 has a high yield, the above paper quality improving effect can be surely achieved, and the amount of the filler X5 added can be reduced, so that the paper is excellent in economic efficiency. Furthermore, if the amount of filler added is increased, the filler will accumulate in the filtered water (white water), and this filler may combine with fine fibers, organic papermaking chemicals, pitch, etc., leading to the occurrence of defects on the paper surface. When the filler X5 is used, this problem does not occur.

  For example, chemical pulp, mechanical pulp, semi-chemical pulp, etc. can be used as a pulp raw material for the filler-added paper. In addition to virgin pulp, used paper pulp, synthetic pulp, etc. can also be used. it can. In addition to filler X5, various chemicals such as a dry paper strength improver, a wet paper strength improver, a drainage improver, a dye, and a neutral sizing agent may be added to the pulp raw material as necessary. You can also. Furthermore, as the filler, in addition to the filler X5 obtained by the production method of the present embodiment, known fillers such as calcium carbonate, clay, talc, silica, titanium dioxide, and satin white can be used as long as the effects of the present invention are not inhibited. Can be used together.

  The pulp raw material to which the filler X5 and various chemicals are added is made into a filler-added paper through a wire process, a press process, a drying process, a coating process, a calendar process, and the like as necessary.

Next, examples of the present invention will be described.
The present inventors conducted a test to confirm whether the yield is improved when the silica composite particles are cationized. This test is an example of adding dilute sulfuric acid to the inorganic particle slurry in the previous step and adding a sulfuric acid band in the subsequent step (Examples 1 to 4), and adding sodium aluminate in the subsequent step. Comparison between (Example 5) and an example in which dilute sulfuric acid is added in both the previous step and the subsequent step (Comparative Example 1), a silica composite, and an example in which cationization is not performed (Comparative Example 2) It was. The results are shown in Table 1. Other conditions were as follows.

[Inorganic particles]
As the inorganic particles, regenerated particles (heat-treated products) having a volume average particle size (D50) of 2.0 μm obtained by heat-treating an object to be treated using paper sludge as the main raw material (50 mass%) in a horizontal combustion kiln are used. did. In the production of the regenerated particles, the method disclosed in Japanese Patent Application No. 2006-31396 was followed.

[Particle size distribution / largest coarse particle]
Using a laser diffraction particle size distribution measuring apparatus [Microtrack / Nikkiso Co., Ltd.] (model number: MT-3300), particle diameter (μm) at a ratio of 10% (D10), 50% (D50), 90% (D90), The particle diameter of the largest coarse particle (particle diameter indicating the maximum measurement frequency value) was measured. In preparation of the measurement sample, a filler was added to a 0.1% sodium hexametaphosphate aqueous solution and dispersed with an ultrasonic wave for 1 minute.

[Oil absorption]
It measured according to the kneading method described in JIS K 5101. That is, 2 g to 5 g of a filler sample dried at 105 ° C. to 110 ° C. for 2 hours is taken on a glass plate, and refined linseed oil (having an acid value of 4 or less) is dropped from the buret to the center of the filler sample in small amounts each time with a spatula. The operations of kneading and dripping kneading were repeated, and the amount of refined linseed oil dropped was determined with the end when the whole was first assembled into a single rod shape, and the oil absorption was calculated according to the following equation.
Oil absorption = [linseed oil amount (mL) × 100] / paper (g)

[Aluminum content]
It measured by the X-ray diffraction method (the Rigaku Electric make, RAD2X). Measurement conditions are: Cu-Kα-curved monochromator: 40 KV-40 mA, divergence slit: 1 mm, SS: 1 mm, RS: 0.3 mm, scanning speed: 0.8 degrees / minute, scanning range: 2 theta = 7 to 85 Degree, sampling: 0.02 degree.

[(Filler) yield]
Add the filler to be tested to 85% waste paper pulp and 15% thermomechanical pulp, and add 1% cationized starch, 0.5% sulfuric acid band, neutral sizing agent (trade name: KW) -504, manufactured by Arakawa Chemical Industry Co., Ltd.) 0.1% was added, and JIS P 8222: 1998 was used using an experimental square handsheet sheet machine (25 cm × 25 cm, wire: 80 mesh, Kumagai Riki Kogyo Co., Ltd.). Based on the above, five handsheets were prepared, moisture was adjusted with a press, and then dried with a drum dryer to prepare a handsheet sheet sample (filler-added paper) having a basis weight of 45 g / m2. The amount of filler in the paper was calculated from the basis weight and ash content (measured in accordance with JIS P 8251) of the filler-added paper thus obtained, and the yield was calculated from the ratio to the amount of charged filler.

  As shown in Table 1, when the silica composite particles were cationized, the yield was improved. From this, it can be seen that the particle size of the filler can be reduced if the yield is made comparable. If the particle size of the filler is reduced, the dispersibility at the time of internal addition increases, and for example, improvement in opacity can be expected.

  The present invention is applicable as a method for producing a filler internally added to a pulp raw material.

  DESCRIPTION OF SYMBOLS 10 ... Heat processing process, 20 ... Particle size adjustment process, 41-44 ... Reaction tank, 50 ... Post-processing process, A ... Aluminum salt, L ... Alkali silicate aqueous solution, N ... Mineral acid, S ... Slurry, X1 ... To-be-processed object , X2 ... heat-treated product, X3 ... ground product, X5 ... filler.

Claims (2)

A previous step of mixing the inorganic particles, alkali silicate and mineral acid;
The mixed slurry obtained in this preceding step possess a step after mixing the aluminum salt, and
Mixing in the previous step is performed in a preceding tank, mixing in the subsequent step is performed in a subsequent tank different from the preceding tank, and the mixed slurry in the preceding tank is directly from the preceding tank or via another tank It shall flow to the following tank,
At least a dispersant mainly composed of polyacrylic acid soda is added to the mixed slurry in the preceding tank, and the filler is continuously produced .
A method for producing a filler characterized by the above. Using a sulfate band as the aluminum salt,
The manufacturing method of the filler of Claim 1.

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