JP6204006B2 - Method for producing inorganic particle aggregate, method for producing inorganic particle aggregate and paper - Google Patents

Description

  The present invention relates to a method for producing an inorganic particle aggregate, an inorganic particle aggregate, and a method for producing paper.

  Various fillers are internally added to the paper in order to improve the whiteness, opacity, printability, etc. of the paper. Such internal addition of the filler to the paper is generally performed by adding the filler slurry to the pulp slurry. At this time, even if the amount of filler added is increased in order to improve the quality of the paper such as opacity, the effect of improving the function in the addition of the filler reaches a peak, and further causes a problem of reducing paper strength such as tensile strength and tear strength. Excess filler is less likely to remain in the paper and the yield of the filler is reduced.

  Accordingly, various methods have been proposed in which the filler remains in the paper during paper making. For example, as a yield improver, there is a method of adding a polymer substance to pulp slurry. Examples of the polymer substance include natural polymer derivatives such as cationized starch, and synthetic polymer substances such as polyethyleneimine. Further, a method has been proposed in which a filler is pre-aggregated with a flocculant such as cationic starch in an aqueous dispersion (slurry) of the filler, the aqueous dispersion is added to the pulp slurry, and paper is made (Japanese Patent Laid-Open No. 2005). -194656).

  However, the filler agglomerated with the cationic starch shown in the above publication tends to have a broad particle size distribution and has low dispersibility in the pulp when added to the pulp slurry. Therefore, the paper quality improvement effect may not be sufficiently obtained.

JP-A-2005-194656

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a method for producing an inorganic particle aggregate that has a high yield when added to paper and exhibits a high paper quality improvement effect.

  As a result of intensive studies to eliminate the above-described disadvantages of the particle size distribution in the filler aggregate, the present inventors sharpened by aggregating inorganic particles using a cationic polymer containing 0.25% by mass or more of nitrogen. The present inventors have found that an inorganic particle aggregate having a proper particle size distribution can be obtained. When conventional flocculants are used, inorganic particles with a large particle size before aggregation tend to aggregate, while inorganic particles with a small particle size are difficult to aggregate. A plurality of diameter distribution peaks may be formed. On the other hand, when agglomeration is performed with a cationic polymer containing a large amount of nitrogen, a certain amount of particles agglomerate to form aggregates regardless of the particle size, and thus an inorganic material having a large average particle size and a sharp particle size distribution. Particle aggregates can be obtained. The reason why a cationic polymer containing a large amount of nitrogen exhibits such agglomeration properties is not clear, but it is constant even for inorganic particles with a small particle size due to the action of nitrogen with a small atomic radius and high coordination binding force. One of the causes is considered to exert an aggregating effect. In particular, when silica composite particles are used as the inorganic particles, it is considered that a stable aggregate can be formed in combination with the anionic property of silica.

The invention made to solve the above problems is
This is a method for producing an inorganic particle aggregate having a step of aggregating inorganic particles with a cationic polymer containing 0.25% by mass or more of nitrogen.

  According to the production method, since the inorganic particles are aggregated by the cationic polymer containing 0.25% by mass or more of nitrogen, an inorganic particle aggregate having a large average particle size and a sharp particle size distribution can be obtained. . Moreover, since the surface of the obtained inorganic particle aggregate is cationized, the fixability to anionic pulp fibers is high. Therefore, according to the production method, it is possible to obtain an inorganic particle aggregate that has high yield and dispersibility when added to paper and can effectively improve paper quality such as whiteness, opacity, and printability.

  Before the aggregating step, it is preferable to further include a step of combining silica with inorganic particles with an alkali silicate salt and a mineral acid. Thus, by combining silica with inorganic particles and aggregating the silica composite particles, inorganic particles having high whiteness, opacity and oil absorption can be obtained, and at the same time, the inorganic particles are stabilized by the anionic nature of silica. Therefore, the production method can produce an inorganic particle aggregate exhibiting higher yield and dispersibility.

  The inorganic particles may be regenerated particles obtained by using paper sludge as a main raw material and undergoing dehydration, heat treatment and pulverization steps. By using such regenerated particles as inorganic particles, an inorganic particle aggregate exhibiting higher opacity, oil absorption and the like can be obtained by the production method. In addition, the environmental load can be reduced by reusing paper sludge.

  The use amount of the cationic polymer is preferably 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the inorganic particles. In the production method, when the amount of the cationic polymer used is within the above range, an inorganic particle aggregate having a large average particle size and a sharper particle size distribution can be obtained.

  The volume average particle diameter D50 of the inorganic particle aggregate is preferably 6 μm or more and 16 μm or less, and the ratio D30 / D70 of the volume 30% particle diameter D30 to the volume 70% particle diameter D70 is preferably 0.4 or more. The ratio of D30 to D70 indicates the degree of sharpness of the particle size distribution, and by making this ratio equal to or higher than the above upper limit, the volume distribution of the inorganic particle aggregate has sharpness suitable for adding to the pulp slurry. Therefore, an inorganic particle aggregate exhibiting higher dispersibility in the paper layer can be obtained by the production method.

  Moreover, the inorganic particle aggregate obtained by the production method of the present invention has a high yield and dispersibility when added to a pulp raw material.

  Moreover, since the inorganic particle aggregate obtained by the said manufacturing method is added to a pulp slurry, the paper manufacturing method of this invention can obtain the paper which improved paper quality, such as whiteness, opacity, and printability. .

  Here, “volume average particle diameter”, “volume 70% particle diameter”, and “volume 30% particle diameter” mean that the particle size distribution measured by the laser diffraction scattering method is 50 accumulated from the smaller diameter side of the cumulative volume distribution. It means the particle diameter corresponding to%, 70% and 30%.

  As described above, according to the method for producing an inorganic particle aggregate of the present invention, it is possible to obtain an inorganic particle aggregate that has a good yield when added to paper and exhibits a high paper quality improvement effect.

It is a typical schematic diagram which shows the apparatus used for the manufacturing method of the inorganic particle aggregate of this invention.

  Hereinafter, the method for producing an inorganic particle aggregate of the present invention will be described in detail with reference to the drawings as appropriate.

<Method for producing inorganic particle aggregate>
The manufacturing method of the said inorganic particle aggregate has the aggregation process which aggregates an inorganic particle with the cationic polymer containing 0.25 mass% or more of nitrogen.

  The inorganic particles used in the method for producing the inorganic particle aggregate are not particularly limited, and for example, calcium carbonate, talc, titanium dioxide, clay, calcined clay, synthetic zeolite, regenerated particles and the like can be used. Among these, regenerated particles that exhibit high whiteness and opacity and contribute to a reduction in environmental burden are preferable. In the manufacturing method, the papermaking sludge is used as a main raw material as the regenerated particles, and the one in which overburning is suppressed by passing through dehydration, heat treatment, and pulverization steps is used to suppress thickening during slurrying. Can do. A preferable method for producing the regenerated particles will be described in detail later.

  It is preferable that the manufacturing method of the said inorganic particle aggregate further has the silica composite process which combines a silica with an inorganic particle with a silicic acid alkali salt and a mineral acid before the said aggregation process. By compounding silica with inorganic particles, particles having a sharp particle size distribution can be obtained while suppressing the generation of coarse particles.

The method for producing the inorganic particle aggregate is, for example,
(1) A slurry preparation step for obtaining a slurry containing inorganic particles and an alkali silicate salt,
(2) a reaction step of adding a mineral acid to the slurry;
(3) A coagulation step of adding a cationic polymer to the slurry.

  The apparatus of FIG. 1 used for the manufacturing method of the said inorganic particle aggregate is equipped with the 1st silica composite reaction tank 1, the 2nd silica composite reaction tank 2, the aggregation reaction tank 3, and the storage tank 4 in this order.

  The inorganic particles X1 were subjected to a slurry adjustment step in the first silica composite reaction tank 1, and then subjected to a reaction step in the first silica composite reaction tank 1 and the second silica composite reaction tank 2, whereby silica was composited. Silica composite particles X2. Thereafter, the silica composite particles X2 are agglomerated in the agglomeration reaction tank 3, and become inorganic particle aggregates X3 and stored in the storage tank 4.

<(1) Slurry preparation process>
(1) In the slurry preparation step, a slurry containing inorganic particles and alkali silicate as raw materials for composite particles is prepared. This slurry may be prepared, for example, by adding and dispersing the inorganic particles X1 in the alkali silicate solution L, or by adding the alkali silicate solution L after dispersing the inorganic particles X1 in water. May be. A preferable method for producing the inorganic particles X1 will be described in detail later.

<Particle size adjustment process>
In the said manufacturing method, it is preferable to perform the particle size adjustment process for making the volume average particle diameter of the inorganic particle X1 into a suitable range for a silica composite etc. In this particle size adjustment step, pulverization, classification, and the like are performed so that the volume average particle size of the inorganic particles X1 falls within a suitable range. As a pulverizer used as a means for pulverizing the inorganic particles X1, 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 can be used.

  The volume average particle diameter of the inorganic particles X1 is not particularly limited, but the lower limit is preferably 0.05 μm, and more preferably 0.1 μm. On the other hand, the upper limit of the volume average particle diameter of the inorganic particles X1 is preferably 3.0 μm, and more preferably 2.8 μm. When the volume average particle size of the inorganic particles X1 is less than the above lower limit, agglomeration becomes necessary because agglomeration with a large number of particles is required to obtain an inorganic particle agglomerate having a sufficient particle size. May collapse and the yield of the inorganic particle aggregate may not be sufficiently obtained. On the contrary, when the volume average particle diameter of the inorganic particles X1 exceeds the above upper limit, the particle size distribution of the inorganic particles X1 becomes broad, and even if aggregation is performed, a sharp particle size distribution cannot be obtained, resulting in a silica composite effect. In addition to being insufficient, there is a possibility that the quality of the paper to which the inorganic particle aggregate obtained by the production method is added is deteriorated due to the presence of particles having a coarse particle size. The volume average particle size of the inorganic particles X1 is measured by measuring the particle size distribution of the sample (inorganic particle particles X1) using a laser diffraction particle size distribution meter (manufactured by Nikkiso Co., Ltd., model number: Microtrack MTII-3000). The particle diameter (D50) when the cumulative volume with respect to the volume of all particles is 50% is determined, and this particle diameter is defined as the volume average particle diameter.

  Although the alkali silicate solution L used in the said manufacturing method is not specifically limited, It is preferable at the point of availability to use a sodium silicate solution (No. 3 water glass).

  As a minimum of silicic acid concentration in silicic acid alkali solution L, 6 g / L is preferred, 8 g / L is still more preferred, and 10 g / L or less is especially preferred. On the other hand, the upper limit of the silicic acid concentration is preferably 18 g / L, more preferably 16 g / L, and particularly preferably 14 g / L. When the silicic acid concentration is less than the above range, the silica sol is not sufficiently formed, and thus inorganic particles X1 in which silica is not combined may be generated. On the contrary, when the silicic acid concentration exceeds the above range, white carbon is generated instead of silica sol, and the inorganic particles X1 are coated with white carbon, so that the porosity of the inorganic particles X1 is lost. The whiteness, opacity, and oil absorption of the resulting inorganic particle aggregate may be reduced.

  In this step, the lower limit of the concentration of the inorganic particles X1 in the slurry containing the inorganic particles X1 and the alkali silicate is preferably 95 g / L, more preferably 100 g / L, and particularly preferably 105 g / L. On the other hand, the upper limit of the concentration of the inorganic particles X1 is preferably 125 g / L, more preferably 120 g / L, and particularly preferably 115 g / L. When the density | concentration of the inorganic particle X1 is less than the said range, a silica production | generation reaction may become dull and there exists a possibility that the productivity of a composite particle may deteriorate. On the other hand, when the concentration of the inorganic particles X1 exceeds the above range, the viscosity of the slurry may increase and the dispersibility of the inorganic particles X1 may decrease.

  Moreover, as silicic acid concentration (SiO2 conversion) in the said slurry, 5 to 15 mass% is preferable. When the silicic acid concentration is less than the above range, the silica composite effect is weakened, and the whiteness, opacity and oil absorption of the resulting composite particles may be reduced. On the contrary, when the silicic acid concentration exceeds the above range, the absorption capacity of the paper coating liquid to which the inorganic particle aggregate obtained by the production method is added becomes large. There is a possibility that the flatness of the surface of the layer is lowered.

  The temperature of the alkali silicate solution L when adding the alkali silicate solution L to the inorganic particle X1-containing slurry or when adding the inorganic particles X1 to the alkali silicate solution L is not particularly limited, but is preferably 50 ° C. or higher. When the alkali silicate solution L is mixed with the inorganic particles X1 while being heated to 50 ° C. or higher, the slurry can be easily homogenized by improving the fluidity.

<(2) Reaction process>
(2) In the reaction step, mineral acid N is added to the slurry, and the pH of the slurry is lowered to obtain silica composite particles X2 in which silica is precipitated on the surfaces of the inorganic particles X1.

  Specifically, in this step, while heating and stirring so that the liquid temperature of the slurry becomes 70 to 100 ° C., the slurry is held at a predetermined pressure in a sealed container, and the alkali silicate solution L contained in the slurry is 20 to 50. % Mineral acid N is added in an amount to be neutralized. As a result, alkali silicate, which is a raw material of silica, reacts with a dilute solution of mineral acid N such as sulfuric acid, hydrochloric acid, nitric acid at high temperature, and silica sol fine particles are generated by hydrolysis reaction and polymerization of silicic acid, and inorganic particles X1 Precipitates on the surface. The particle size of the silica sol fine particles can be adjusted by the stirring conditions during the reaction, the addition conditions of the mineral acid N, and the like.

  The mineral acid N used in the production method is not particularly limited, and for example, sulfuric acid, hydrochloric acid, nitric acid and the like can be used. Among these, sulfuric acid is particularly preferable from the viewpoint of cost and handling.

  As a density | concentration of the mineral acid N used in the said manufacturing method, 0.1 mol / L or more and 5.0 mol / L or less are preferable. When the concentration of the mineral acid N is less than the above range, the generation rate of silica is slow and the silica may not be sufficiently formed. On the other hand, when the concentration of the mineral acid N exceeds the above range, a local reaction occurs, silica is unevenly distributed, and the yield improvement effect of the resulting composite particles may be reduced. The amount of mineral acid N added in this step is preferably such that the alkali silicate neutralization rate is 50% or more and 75% or less.

  The temperature of the slurry during stirring in this step is preferably 70 ° C or higher and 100 ° C or lower. Since the temperature of the slurry affects the generation and growth of the silica sol, if the temperature of the slurry is less than the above range, silica may not be generated, or the generation and growth rate of the silica sol is slowed down, so that the silica has sufficient strength. Since it is not combined with the particles X1, silica may be peeled off during papermaking. On the other hand, when the temperature of the slurry exceeds the above range, production becomes difficult and silica is densely formed on the surfaces of the inorganic particles X1, so that the oil absorption of the obtained composite particles may be reduced.

  The pH of the slurry in this step is preferably 8 or more and 11 or less, and more preferably 8.5 or more and 10.5 or less. When pH is less than the said range, the calcium component contained in an inorganic particle becomes easy to change to calcium hydroxide by excessive addition of a mineral acid, and there exists a possibility that the viscosity of a slurry may increase. Further, white carbon is generated instead of silica sol, and the whiteness, opacity and oil absorption of the inorganic particle aggregate obtained by the production method may be reduced. On the other hand, when the pH exceeds the above range, the reaction between the alkali silicate salt and the mineral acid becomes dull and it is difficult for silica to be precipitated on the surface of the inorganic particles X1, so the opacity of the resulting composite particles may be reduced. .

  In this step, it is preferable to add mineral acid N to the slurry in two stages in order to suppress precipitation of white carbon and precipitate silica more uniformly on the surface of the inorganic particles X1. In this case, mineral acid N is added in such an amount that the alkali silicate solution L contained in the slurry is neutralized by 20 to 50% in the first stage, and then the liquid temperature is raised by 10 ° C. or more than in the first stage. By adding the mineral acid N so that the pH of the reaction solution is 8 or more and 11 or less, homogeneous silica composite particles X2 can be obtained.

  The lower limit of the volume average particle diameter of the silica composite particles X2 obtained by obtaining this step is preferably 3.5 μm, and more preferably 5.5 μm. On the other hand, the upper limit of the volume average particle diameter of the silica composite particles X2 is preferably 9.0 μm, and more preferably 6.5 μm. When the volume average particle diameter of the silica composite particles X2 is less than the lower limit, the yield improvement effect of the inorganic particle aggregate obtained by the production method may not be sufficiently obtained. On the contrary, when the volume average particle diameter of the silica composite particles X2 exceeds the upper limit, the quality of the paper to which the inorganic particle aggregate obtained by the production method is added may be deteriorated due to the presence of coarse particles. .

<(3) Aggregation step>
(3) In the aggregation step, the silica composite particles X2 are aggregated with a cationic polymer containing 0.25% by mass or more of nitrogen to obtain inorganic particle aggregate X3.

  In this aggregation step, the cationic polymer P is added to the composite particle slurry in which the silica composite particles X2 in the aggregation reaction tank 3 are dispersed in water. The solid content concentration of the silica composite particles X2 in the composite particle slurry is preferably 10% by mass or more and 40% by mass or less, and more preferably 12% by mass or more and 35% by mass or less. By making the density | concentration of a composite particle slurry into the said range, coexistence with efficiency improvement of the composite particle and suppression of a raise of slurry viscosity can be aimed at. When the concentration of the composite particle slurry is less than the above range, the composite particles may not aggregate to a suitable size even by the addition of the cationic polymer. On the other hand, when the concentration of the composite particle slurry exceeds the above range, the viscosity may be too high and workability may be reduced, or the particle size distribution of the inorganic particle aggregates may be too wide and the yield may be reduced.

  The cationic polymer P added to the silica composite particle slurry is not particularly limited as long as it contains 0.25% by mass or more of nitrogen and can aggregate a plurality of particles with a sharp particle size distribution. For example, a well-known cationized starch can be used. Specific examples of the cationized starch include starches obtained from corn, potato, tapioca, sweet potato, wheat, rice, etc. and any one of primary, secondary, tertiary amine and quaternary ammonium groups. The cationized starch which has the nitrogen atom which introduce | transduced the above can be used. Among these, a cationized starch having a quaternary ammonium group that exhibits an aggregating effect regardless of pH is preferable.

  The nitrogen content of the cationic polymer P used in this step is 0.25% by mass or more, more preferably 0.28% by mass or more and 1% by mass or less, and 0.30% by mass or more and 1% by mass or less. Is particularly preferred. When the nitrogen content of the cationic polymer is less than the above range, inorganic particle aggregates having a large average particle size and a sharp particle size distribution may not be obtained. Conversely, when the nitrogen content of the cationic polymer exceeds the above range, the production of the cationic polymer may be difficult.

  The anion demand of the cationic polymer P used in this step is preferably 260 μeq / l or more and 500 μeq / l or less, and more preferably 285 μeq / l or more and μeq / 500 l or less. When the anion demand is less than the above range, the agglomeration effect is reduced, and there is a possibility that an inorganic particle aggregate having a large average particle size and a sharp particle size distribution cannot be obtained. On the contrary, when the anion demand exceeds the above range, it is necessary to remarkably increase the nitrogen content, which may make it difficult to produce the cationic polymer. The anion demand is the total amount of charges of the cationic polymer and is measured by a cation demand measuring device.

  The addition amount of the cationic polymer P is preferably 0.5 parts by mass or more and 5 parts by mass or less, and more preferably 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the inorganic particles (composite particles). When the addition amount of the cationic polymer P is less than the above range, a sufficient aggregation effect may not be obtained. On the contrary, when the addition amount of the cationic polymer P exceeds the above range, various properties such as the oil absorption of the inorganic particle aggregate may be lowered.

  In this step, the cationic polymer P may be added while applying fine vibrations to the slurry containing inorganic particles (composite particles). When the inorganic particles are aggregated while applying fine vibration, the inorganic particles are aggregated while being dispersed, so that the homogeneity of the inorganic particle aggregate can be improved. The method for applying the fine vibration is not limited as long as physical vibration can be applied to the inorganic particles, and examples thereof include ultrasonic irradiation and stirring.

  The slurry preparation step, the reaction step, and the aggregation step can be performed in a batch method in which these steps are repeated for each predetermined processing amount, or in a continuous method in which each step is continuously executed, from the viewpoint of production efficiency. It is preferable to adopt a continuous type.

  When performing the said slurry preparation process, reaction process, and aggregation process by a continuous type, an inorganic particle aggregate can be manufactured according to FIG. 1 in the following procedures, for example. In this procedure, mineral acid N is added in two stages in the reaction process. First, the inorganic particle X1, the alkali silicate solution L, and the mineral acid N are continuously supplied to the first silica composite reaction tank 1, and these are stirred under a predetermined temperature and pressure, and part of the slurry adjustment step and the reaction step. At the same time. The slurry obtained in the first silica composite reaction tank 1 is continuously transferred to the second silica composite reaction tank 2. The mineral acid N is further added to the slurry transferred to the second silica composite reaction tank 2 and continuously transferred to the agglomeration reaction tank 3. Since the second silica composite reaction tank 2 has a certain volume, generation and growth of silica proceeds until the slurry is transferred to the agglomeration reaction tank 3, and the inorganic particles X1 become silica composite particles X2. It is continuously supplied to the agglomeration reaction tank 3. The cationic polymer P is added to the slurry containing the silica composite particles X2 in the aggregation reaction tank 3 to form the inorganic particle aggregate X3. Thereafter, the slurry containing the inorganic particle aggregate X3 is transferred and stored in the storage tank 4 and supplied to the papermaking production line as a filler, a pigment and the like.

<Composite particle>
The lower limit of the volume average particle diameter of the inorganic particle aggregate obtained by the production method is preferably 6 μm, more preferably 7 μm, and more preferably 8 μm. On the other hand, the upper limit of the volume average particle diameter of the inorganic particle aggregate is preferably 16 μm, more preferably 13 μm, and more preferably 12 μm. If the volume average particle diameter of the inorganic particle aggregate is less than the above range, the yield improvement effect may not be sufficiently obtained. Conversely, when the volume average particle diameter of the inorganic particle aggregate exceeds the above range, the dispersibility of the inorganic particle aggregate may be reduced.

  The ratio D30 / D70 of the volume 30% particle diameter D30 to the volume 70% particle diameter D70 of the inorganic particle aggregate obtained by the production method is preferably 0.4 or more, more preferably 0.45 or more, and 0.5 The above is more preferable. If D30 / D70 is less than the above lower limit, the particle size distribution of the inorganic particle aggregates will not be sharp, so that the yield improvement effect when added to paper may not be sufficiently obtained, and the dispersibility of the inorganic particle aggregates is reduced. There is a risk.

  The silica ratio in terms of oxide in the inorganic particle aggregate obtained by the production method is preferably 1% by mass or more and 20% by mass or less. When the ratio of silica is less than the above range, the surface of the inorganic particle aggregate is not sufficiently covered, so that the yield improvement effect of the inorganic particle aggregate may be reduced. On the other hand, when the silica ratio exceeds the above range, the amount of precipitated silica becomes excessive, and the whiteness, opacity and oil absorption of the inorganic particle aggregate may be lowered.

  The lower limit of the oil absorption of the inorganic particle aggregate obtained through this step is preferably 50 ml / 100 g, more preferably 70 ml / 100 g. On the other hand, the upper limit of the oil absorption of the inorganic particle aggregate is preferably 150 ml / 100 g, more preferably 100 ml / 100 g. By setting the oil absorption of the inorganic particle aggregate within the above range, it is possible to improve the ink drying property of the paper to which the inorganic particle aggregate is added. When the oil absorption is less than the above range, the effect of improving the ink drying property of the paper to which the inorganic particle aggregate is added may not be obtained. On the contrary, when the oil absorption exceeds the above range, the ink absorbency of the paper to which the inorganic particle aggregate is added becomes too high, and the color developability may be deteriorated due to the sinking of the ink.

  Since the inorganic particle aggregate obtained by the above production method has an appropriate particle size and particle size distribution, it has a high yield when added to paper as a filler. Moreover, since it has high whiteness, opacity, and oil absorption, the whiteness, opacity, ink drying property, etc. of the added paper can be improved.

<Paper manufacturing method>
The paper manufacturing method of the present invention includes an adding step of adding the inorganic particle aggregate obtained by the above manufacturing method to the pulp slurry. As a specific form, the manufacturing method which has the said addition process and the papermaking process of making the pulp slurry to which the said inorganic particle aggregate containing slurry was added can be mentioned, for example.

  In the addition step, an inorganic particle aggregate obtained by aggregating inorganic particles with a cationic polymer in the manufacturing method in advance is added to a pulp slurry containing paper pulp.

  As this raw material pulp, a well-known raw material for producing paper can be used. Moreover, a sizing agent, a paper strength agent, etc. can be suitably mix | blended with the said pulp slurry as an auxiliary agent. Furthermore, you may mix | blend fillers other than the said inorganic particle aggregate with the said pulp slurry. As other fillers, for example, light or heavy calcium carbonate, clay, calcined kaolin, talc, titanium dioxide, white carbon and the like can be used singly or in combination. In light of opacity, whiteness, price, etc., it is preferable to use light calcium carbonate in combination.

  In the paper making step, paper can be obtained by paper making the pulp slurry to which the inorganic particle aggregate has been added in the adding step. The papermaking method is not particularly limited, and papermaking can be performed with a known papermaking machine. Moreover, you may perform the application | coating of the sizing agent to paper front and back, the pressurization by paper passing to a calendar apparatus, a smoothing process, etc. after papermaking as needed.

  The paper obtained by the paper manufacturing method has high paper quality because the inorganic particle aggregate obtained by the inorganic particle aggregate manufacturing method is internally added.

<Method for producing regenerated particles>
Regenerated particles that can be suitably used in the production method of the present invention can be produced by a known production method. Hereinafter, the raw material of regenerated particles and dehydration, heat treatment, and pulverization will be described. In addition, it is preferable to have a mixing | blending and slurry preparation process between a heat treatment process and a grinding | pulverization process, and also other processes can be provided as needed.

(material)
As the raw material for the regenerated particles, papermaking sludge is used as the main raw material, and among the papermaking sludge, deinking floss is preferably used. The deinking floss refers to what is separated from the pulp fiber in the deinking process for removing ink adhering to the used paper in the used paper processing process for producing the used paper pulp.

(Dehydration process)
The dehydration step is a step of removing moisture of a raw material such as deinking floss up to a predetermined ratio. For example, deinking floss separated from pulp fibers in a deinking process for producing waste paper pulp is subjected to various operations and dehydrated by a known dewatering facility.

  The raw material after dehydration (deinking floss) is 40% or more, preferably 40% or more and less than 90%, more preferably 45% or more and 70% or less, and particularly preferably more than 50% and 60% or less. . In addition, the raw material after dehydration is supplied to the heat treatment step by a pulverizer (or pulverizer) or the like, with an average particle size of 40 mm or less, preferably an average particle size of 3 mm to 30 mm, more preferably an average particle size of 5 mm to 20 mm. It is preferable that the particle diameter is uniform, and it is preferable that the particle diameter is uniform so that the ratio of the particle diameter of 50 mm or less is 70% by mass or more. The average particle size in the dehydration step and each heat treatment step described below was measured with a metal plate sieve based on JIS-Z-8801-2 (2000), and the ratio of the particle size was sieved. It is a value calculated by measuring the weight for each particle diameter later.

(Heat treatment process)
The heat treatment step includes a first heat treatment step in which drying for further moisture removal of the dehydrated raw material and a first combustion at a relatively low temperature are performed in series, and the heat treatment product obtained in the first heat treatment step is again used. And a second heat treatment step for heat treatment (combustion) at a higher temperature than the first heat treatment step. By passing through the two-stage heat treatment step in which the temperature is raised in this way, over-combustion of the raw material can be suppressed, and thickening when the obtained regenerated particles are slurried can be suppressed. In addition, by performing the heat treatment at a relatively low temperature, it is possible to similarly suppress over-combustion of the raw material and suppress thickening when the obtained regenerated particles are slurried.

(First heat treatment step)
The raw material that has undergone the dehydration step is heat-treated as a first heat treatment step using, for example, an internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis.

  The heat treatment temperature in the first heat treatment step (for example, the furnace temperature of the internal heat kiln furnace) is 300 ° C. or higher and lower than 500 ° C., preferably 400 ° C. or higher and lower than 500 ° C., more preferably 400 ° C. or higher and 450 ° C. or lower. . When the temperature is excessively low, the organic matter is not sufficiently combusted. On the other hand, when the temperature is excessively high, overcombustion occurs, and calcium oxide is easily generated by decomposition of calcium carbonate.

  In the first heat treatment step, an easily combusted organic substance contained in the raw material is slowly burned, and in order to suppress the formation of residual carbon, the heat treatment is performed for 30 minutes to 90 minutes in the residence (heat treatment) time under the above conditions. Is preferred. If the heat treatment time is less than 30 minutes, sufficient combustion is not performed and the ratio of remaining carbon increases. On the other hand, when the heat treatment time exceeds 90 minutes, thermal decomposition of calcium carbonate occurs due to excessive combustion of the dehydrated product, and the obtained regenerated particles become extremely hard.

(Second heat treatment step)
The raw material which passed through the 1st heat treatment process is heat-processed using the external heat kiln furnace which has the external heat jacket which a main body turns sideways and rotates around a central axis as a 2nd heat treatment process. In this way, through the first and second heat treatment steps, the organic component in the raw material is burned and removed, and the inorganic substance can be discharged as a heat treatment product.

  In the second heat treatment step, in order to burn the residual organic matter that could not be burned in the first heat treatment step, for example, residual carbon, the heat treatment adjusted to a particle size smaller than the particle size of the raw material supplied in the first heat treatment step. It is preferable to use a product. The grain alignment of the heat-treated product after the first heat treatment step is preferably adjusted so as to be an average particle diameter of 10 mm or less, more preferably adjusted so as to be an average particle diameter of 1 to 8 mm, and an average particle diameter of 1 to It is particularly preferable to adjust to 5 mm.

  The heat treatment temperature in the second heat treatment step is preferably 550 ° C to 780 ° C, more preferably 600 ° C to 750 ° C. The residence (heat treatment) time in the external heat kiln furnace as the second heat treatment step is preferably 60 minutes or more, more preferably 60 minutes to 240 minutes, particularly preferably 90 minutes to 150 minutes, and optimally 120 minutes. ~ 150 minutes is desirable for complete combustion of the remaining carbon. In particular, the remaining carbon must be burnt slowly at a high temperature that does not cause the decomposition of calcium carbonate as much as possible. If the residence time is less than 60 minutes, the remaining carbon is burnt in a short time, If the residence time exceeds 240 minutes, the calcium carbonate may be decomposed.

  The average particle diameter of the heat-treated product discharged from the external heat kiln furnace as the second heat treatment step is suitably adjusted to 10 mm or less, preferably 1 mm to 8 mm, more preferably 1 mm to 5 mm. This adjustment can be performed, for example, by passing the heat-treated product between two rotating rolls having a certain clearance.

  The heat-treated product that has undergone the second heat treatment step is preferably an agglomerate, for example, cooled by a cooler, sorted by a particle size sorter such as a vibration sieve, and temporarily stored in a combustion product silo. Thereafter, the particle size is adjusted to the target particle size in the blending / slurry preparation step and the pulverization step, and then is used as a regenerated particle in a destination such as a filler.

  In addition, although the case where the deinking floss was used as a raw material was illustrated above, the deinking floss was used as a raw material, and the raw material was appropriately mixed with other papermaking sludge such as paper sludge in the papermaking process. You can also.

(Formulation and slurry preparation process)
The blending / slurry preparing step is a step of blending an acid and / or salt into the heat treated product discharged from the second heat treating step and suspending the heat treated product in water to make a slurry.

As such an acid and / or salt, those having a solubility in 100 g of water at 20 ° C. in a calcium salt state of 1 g or less are preferable. Specific examples of the acid include sulfuric acid (solubility of calcium sulfate dihydrate 0.21 g / 100 g), hydrofluoric acid (solubility of calcium fluoride 0.0016 g / 100 g), citric acid (calcium citrate , Phosphoric acid (solubility of tricalcium phosphate 0.0025 g / 100 g), carbonic acid (calcium carbonate solubility 0.0014 g / 100 g), phosphonic acid, and the like. Examples of the salt include calcium salts, potassium salts, aluminum salts, and sodium salts of the above acids. Among the acids or salts thereof, calcium sulfate, potassium carbonate, phosphoric acid, sulfuric acid, and sulfuric acid bands (usually used in paper mills from the viewpoint of workability, economy, and homogeneity of the regenerated particles obtained ( Al ₂ (SO ₄ ) ₃ ) and phosphonic acid are preferred, phosphoric acid or dilute sulfuric acid is particularly preferred, and phosphoric acid is even more particularly preferred.

  As a minimum of the compounding quantity of this acid and / or salt, 0.01 mass part is preferred to 100 mass parts of heat-treated materials, and 0.1 mass part is still more preferred. On the other hand, the upper limit of the amount is preferably 10 parts by mass, and more preferably 7 parts by mass. When the compounding amount of the acid and / or salt is less than 0.01 parts by mass, the contact probability with the particles containing calcium oxide or calcium hydroxide and / or calcium ions generated from the particles is low, and the curing reaction inhibiting effect May not be obtained. On the other hand, even if it exceeds 10 parts by mass, the curing reaction suppressing effect may reach its peak.

(Crushing process)
The pulverization step is a step in which regenerated particles are obtained by pulverizing the slurry obtained in the above-described step to obtain fine particles. In this pulverization step, a known pulverizer or the like can be used. Through this pulverization step, the resulting regenerated particles can be suitably used as a pigment for coating, a filler for internal addition, and the like by appropriately granulating the slurry to a necessary particle size.

(Other processes)
In the method for producing regenerated particles, a raw material aggregation process, a granulation process, a classification process between the processes, a carbonation process for carbonizing the slurry, and the like may be provided.

  The obtained slurry of regenerated particles is as alkaline as pH of 12 or more as it is, and may react with other chemicals in the coating liquid adjusting step in the application of coating pigments, for example, and may cause quality deterioration. Therefore, in order to return calcium oxide in the heat-treated product or regenerated particles to calcium carbonate and reduce the pH, carbon dioxide in the exhaust gas discharged in the first heat treatment combustion step or the second heat treatment step is used, for example, pH Is preferably adjusted to 7-9.

  In addition, it is preferable to granulate deinked floss (dehydrated product) that has been subjected to a dehydration treatment in the previous stage of the drying step, and it is more preferable to perform classification to make the particle size of the granulated material uniform. . In granulation, known granulation equipment can be used, but equipment such as a rotary type, a stirring type, and an extrusion type is suitable.

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

  In addition, each measured value in a present Example is the value measured with the following method.

(A) Volume average particle size of inorganic particles and inorganic particle aggregates (unit: μm)
A 10 mg sample of inorganic particles (before aggregation with cationic polymer) or inorganic particle aggregates (after aggregation with cationic polymer) was dispersed for 3 minutes with an ultrasonic disperser (output: 80 W). Using this solution, the volume average particle diameter (D50) of the inorganic particles and the volume average particle diameter of the inorganic particle aggregate (D50) were measured by a laser particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., model number: Microtrack MTII-3000). D50), 30% volume particle diameter (D30) and 70% volume particle diameter (D70) were measured.

(B) Oxide-converted silica ratio and calcium ratio (unit:%)
Using an X-ray microanalyzer (model number: E-MAX · S-2150) manufactured by HORIBA, Ltd., elemental analysis is performed at an acceleration voltage (15 KV), and the content ratio of inorganic particles, titanium dioxide, silica, etc. from the constituent components contained And the oxide-converted silica ratio and calcium ratio were calculated from the content of the silica component after silica coating.

(C) Ash content (regenerated particles) Yield (unit:%)
After adding the inorganic particle aggregate slurry so as to be 30% ash (based on JIS-P8251 (2003)) to the pulp slurry made of LBKP diluted to 1.0% concentration, the pulp concentration becomes 0.75%. Diluted. 700 cc of this pulp slurry was put into a yield tester (manufactured by BTG, model number: DFR-05), stirred for 50 seconds, filtered through a 60 mesh wire, and 100 cc of the filtrate was collected. The ash concentration was measured for each of the pulp slurry and the filtrate, and the ash (filler) yield was calculated by the following formula (1).
Ash content yield = 100 × (A−B) / A (1)
A: Ash content (g / l) of pulp slurry
B: Ash concentration in the filtrate (g / l)

(D) Oil absorption (unit: ml / 100g)
It was measured by the following method in accordance with “Pigment Test Method—Part 13: Oil Absorbance—Section 1: Refined Sesame Oil Method” described in JIS-K5101-13-1. A sample of 2 to 5 g of inorganic particle aggregate dried at 105 to 110 ° C. for 2 hours is placed on a glass plate, and oil (having an acid value of 4 or less) is dripped little by little from the burette onto the center of the inorganic particle aggregate sample. In addition, kneading with a spatula each time, and repeating this work, the amount of oil dripping is obtained when the whole sample is formed into a single rod-shaped body having smooth hardness, and the oil absorption is calculated by the following equation (2). Calculated.
Oil absorption = (Amount of oil dripping (ml) × 100) / Aggregate mass of inorganic particles (g) (2)

(E) Dispersibility (unit: mPa · s)
The measurement was performed using a B-type viscometer (TVM-10M, manufactured by Toki Sangyo Co., Ltd.) under the conditions of an atmospheric temperature of 20 ° C. and a rotor rotation speed of 60 rpm. The lower the viscosity (mPa · s), the better the dispersibility.

(F) Blank paper opacity (unit:%)
Paper (basis weight: paper weight) obtained by making a pulp slurry (pulp blend: LBKP 100%) in which inorganic particles or inorganic particle aggregates are added to the pulp slurry so as to be 30% ash (based on JIS-P8251 (2003)) 40 g / m ² ) and measured according to JIS-P8149 (2000) “Paper and paperboard—Opacity test method (backing of paper) —Diffusion illumination method”.

[Production of regenerated particles]
A deinking floss was used as a raw material, and the dehydration step was performed so that the moisture content was 55% by mass, the average particle size was 10 mm, and the proportion of particles of 50 mm or less was 90% by mass. This dehydrated product was washed with shower water, and the first heat treatment step and then the second heat treatment step were performed under the following conditions to obtain a heat treatment product.

First heat treatment process conditions Combustion type: Internal heat kiln Combustion temperature: 420 ° C
Oxygen concentration: 12%
Residence time: 50 minutes Unburnt rate after the first heat treatment step: 3%
Second heat treatment process conditions Combustion type: Combined use of external and internal heat kilns Average particle diameter at inlet: 5 mm
Combustion temperature: 700 ° C
Oxygen concentration: 8%
Residence time: 140 minutes Average particle diameter at outlet: 5 mm

  To 100 parts by mass of the obtained heat-treated product, 0.3 part by mass of calcium sulfate dihydrate is added as a blending / slurry preparation step, and the additive is suspended in water to obtain a concentration (total slurry). A mass of 35% by mass of a heat-treated product with respect to mass was obtained and pulverized with a pulverizer. The unburned rate is a value obtained by preheating the electric muffle furnace to 600 ° C., putting the sample in a crucible and burning it completely in about 3 hours, and calculating the unburned amount from the mass change before and after combustion. It is.

Example 1
The regenerated particles obtained by the above method were dispersed in water to obtain a regenerated particle slurry having a solid content concentration of 20% by mass. To this regenerated particle slurry, a sodium silicate solution was added so that the concentration of silicic acid in the regenerated particle slurry was 8% by mass (in terms of SiO2) to prepare a slurry. To this slurry, dilute sulfuric acid having a concentration of 0.1 to 5 mol / L and a pH of 9 after the reaction was added in two stages, and the slurry was stirred using a mixer to perform silica composite to obtain composite particles. Obtained. The liquid temperature of the slurry was 60 ° C. in the first stage of dilute sulfuric acid addition and 70 ° C. in the second stage. The composite particles had a volume average particle diameter of 4 μm. To the slurry containing the composite particles, cationized starch (trade name: Amylofax T2600, manufactured by Matsutani Chemical Co., Ltd., nitrogen content 0.33% by mass, anion demand 297 μeq / l, symbol in the table: A) composite particles 100 2.5 parts by mass was added to parts by mass. Thereafter, in order to approach the slurry conditions at the time of actual papermaking, the slurry was irradiated with ultrasonic waves by an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusyo Co., Ltd.) with OUTPUT ADJ as 3 in 10 steps and TUNING as 5 in 10 steps.

  The anion demand of the cationized starch was measured using a cation demand measuring device (model number: PCT15, manufactured by Mutek). This cation demand measuring device introduces a sample into the cell of the test machine and generates a flow of sample liquid between the cell cylinder and the piston by operating the upper and lower pistons, thereby generating distortion in the surface charge of the colloidal particles. The charge requirement of the resulting sample is measured by polyelectrolyte measurement.

(Example 2)
Except that the regenerated particles were not combined with silica, the addition of cationized starch and the conditions of ultrasonic irradiation were the same as in Example 1 to obtain an inorganic particle aggregate.

(Examples 3 and 4)
The type and amount of cationized starch and the conditions for ultrasonic irradiation were the same as in Example 1, except that the conditions of silica composite were adjusted so that the volume average particle diameter of the composite particles would be the values shown in Table 1, respectively. Thus, an inorganic particle aggregate was obtained.

(Example 5)
As a cationic polymer (cationized starch), trade name: Pearl Gum HMS (manufactured by Seiko PMC Co., Ltd., nitrogen content 0.23% by mass, anion demand 207 μeq / l, symbol in table: B) 100 parts by mass of composite particles An inorganic particle aggregate was obtained using the same composite particles and ultrasonic irradiation conditions as in Example 1 except that 2.5 parts by mass was added.

(Example 6)
As a cationic polymer (cationized starch), trade name: Amylofax PW (manufactured by Matsutani Chemical Co., Ltd., nitrogen content 0.35% by weight, anion demand 315 μeq / l, symbol in table: C) 100 mass of composite particles An inorganic particle aggregate was obtained using the same composite particles and ultrasonic irradiation conditions as in Example 1 except that 2.5 parts by mass was added to the part.

(Example 7)
As a cationic polymer (cationized starch), trade name: Amylofax HS (manufactured by Matsutani Chemical Co., Ltd., nitrogen content 0.45% by weight, anion demand 405 μeq / l, symbol in table: D) 100 mass of composite particles An inorganic particle aggregate was obtained using the same composite particles and ultrasonic irradiation conditions as in Example 1 except that 2.5 parts by mass was added to the part.

(Examples 8 to 11)
Inorganic particle aggregates were obtained using the same composite particles and ultrasonic irradiation conditions as in Example 1 except that the same amount of cationized starch (Amylofax T2600) as in Example 1 was added as shown in Table 1. .

Example 12
Inorganic particle aggregates were obtained using the same composite particles as in Example 1 and the type and amount of cationized starch. However, no ultrasonic irradiation was performed.

(Example 13)
Inorganic particle aggregates were obtained in the same manner as in Example 1 except that composite particles composed of silica using calcium carbonate particles instead of regenerated particles were used and the type and amount of cationized starch and the conditions of ultrasonic irradiation were the same as in Example 1. . The calcium carbonate particles were coagulated by adding 200 ppm of a coagulant (trade name: Himax SC100, manufactured by Hymo Co., Ltd.) to the solid content of the calcium carbonate particles before combining the silica.

(Example 14)
Talc was used as the inorganic particles, and inorganic particle aggregates were obtained in the same manner as in Example 1 except for the type and amount of cationized starch and the conditions of ultrasonic irradiation. The talc was coagulated by adding 200 ppm of the same coagulant as in Example 13 to the talc solid content.

(Example 15)
Titanium dioxide was used as inorganic particles, and inorganic particle aggregates were obtained in the same manner as in Example 1 except for the type and amount of cationized starch and the conditions of ultrasonic irradiation. Titanium dioxide was coagulated by adding 200 ppm of the same coagulant as in Example 13 to the solid content of titanium dioxide.

(Comparative Examples 1 and 2)
Using the same composite particles as in Example 1, inorganic particle aggregates were obtained under the same conditions as in Example 1 without adding cationized starch. However, Comparative Example 1 did not perform ultrasonic irradiation, and Comparative Example 2 performed ultrasonic irradiation similar to Example 1.

(Comparative Example 3)
As cationic polymer (cationized starch), trade name: Amylofax T1100 (manufactured by Matsutani Chemical Co., Ltd., nitrogen content 0.12% by weight, anion demand 108 μeq / l, symbol in table: E) 100 mass of composite particles An inorganic particle aggregate was obtained using the same composite particles and ultrasonic irradiation conditions as in Example 1 except that 2.5 parts by mass was added to the part.

For the inorganic particle aggregates of Examples 1 to 15 and Comparative Examples 1 to 3, the volume average particle diameter D50, the volume 30% particle diameter D30, the volume 70% particle diameter D70, the oxide-converted silica ratio, the oxide by the method described above. The converted calcium ratio, ash yield, oil absorption and dispersibility were measured. In addition, the blank opacity of the paper made by adding each inorganic particle aggregate was measured. The measurement results are shown in Table 1.

  As shown in Table 1, according to the production method of the present invention, it is possible to obtain an inorganic particle aggregate having high yield and dispersibility when added to paper and having a high paper quality improving effect.

  According to the method for producing an inorganic particle aggregate of the present invention, it is possible to obtain an inorganic particle aggregate having a good yield when added to paper and exhibiting a high effect of improving paper quality. This inorganic particle aggregate can be suitably used as a filler or pigment for paper.

DESCRIPTION OF SYMBOLS 1 1st silica composite reaction tank 2 2nd silica composite reaction tank 3 Aggregation reaction tank 4 Storage tank X1 Inorganic particle X2 Silica composite particle X3 Inorganic particle aggregate L Silicate alkali solution N Mineral acid P Cationic polymer

Claims (5)

Dispersing inorganic particles in water;
In the slurry after the dispersion step, a step of adding a cationized starch containing 0.25% by mass or more of nitrogen and agglomerating the inorganic particles ;
The manufacturing method of the inorganic particle aggregate for pulp slurry addition which has the process of combining a silica with an inorganic particle with a silicic acid alkali salt and a mineral acid before the said aggregation process . The method for producing an inorganic particle aggregate according to claim 1 , wherein the inorganic particles are regenerated particles obtained from paper sludge as a main raw material and subjected to dehydration, heat treatment and pulverization steps. The manufacturing method of the inorganic particle aggregate of Claim 1 or Claim 2 whose usage-amount of the said cationized starch is 0.5 to 5 mass parts with respect to 100 mass parts of inorganic particles. The inorganic particle aggregates having a volume average particle size D50 is at 6μm than 16μm or less, and claim 1 ratio D30 / D70 is at least 0.4 volume 30% particle diameter D30 with respect to the volume 70% particle diameter D70, wherein The manufacturing method of the inorganic particle aggregate of claim | item 2 or claim 3 . The paper manufacturing method which has the process of adding the inorganic particle aggregate manufactured by the manufacturing method of any one of Claim 1 to 4 to a pulp slurry.

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