JP5882029B2 - Paper manufacturing method - Google Patents

Description

  The present invention relates to a paper manufacturing method using regenerated particles as a filler and paper obtained by this manufacturing method.

  In order to improve the opacity, whiteness, printability, etc. of the paper, various fillers are internally added to 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, if the amount of filler added is increased to improve the paper quality such as opacity, the effect of improving the function of filler addition will reach its peak, and it will cause problems of reducing paper strength such as tensile strength and tear strength. The filler becomes difficult to remain in the paper, and the yield of the filler decreases.

  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. In addition, a method has been proposed in which a filler is pre-aggregated with a flocculant in an aqueous dispersion (slurry) of the filler, the aqueous dispersion is added to the pulp slurry, and paper is made. As a specific method for pre-aggregating the filler, for example, a cationic polymer compound using diallyldimethylammonium chloride as a monomer is used, and the average particle size of the paper-made filler after mixing is set to 1.0-2. The method of making it 0 times is proposed (refer patent 4324073 gazette).

  On the other hand, the reuse of inorganic substances in paper sludge discharged from various processes in a paper mill as so-called recycled particles for paper making fillers has become an important issue related to environmental problems in the paper manufacturing industry. As a method for producing such regenerated particles, paper sludge is used as a main raw material, and dehydration, heat treatment and pulverization steps are generally performed in this order. In the method for producing regenerated particles through such a process, calcium carbonate decomposes and changes to calcium oxide due to the influence of overcombustion in the heat treatment process, and this calcium oxide further changes to calcium hydroxide in water. Therefore, a large amount of calcium ions and hydroxide ions are present in the slurry. Alternatively, calcium carbonate and aluminum silicate in paper sludge react to produce a hydration curable material such as calcium aluminate. Therefore, due to these factors, when the regenerated particles are used as a filler, the viscosity of the pulp slurry is increased and the workability is lowered.

  In particular, when the filler is pre-aggregated with a flocculant as described above, when regenerated particles are used as the filler, the viscosity of the aqueous dispersion (slurry) increases in combination with the aggregation of the regenerated particles, so that the workability decreases. And inconveniences such as aggregation of regenerated particles more than desired occur. On the other hand, if the amount of the flocculant added to suppress thickening is reduced, there is a disadvantage that appropriately aggregated regenerated particles (filler) cannot be obtained and the yield of the filler is lowered.

Japanese Patent No. 4324073

  The present invention has been made in view of the above-described circumstances, and in the case where regenerated particles are used as a filler, the thickening of the slurry is suppressed and the workability is improved, and the paper having high opacity due to the high filler yield. It is an object of the present invention to provide a manufacturing method and paper obtained by this manufacturing method.

The invention made to solve the above problems is
A regenerated particle agglomeration step in which papermaking sludge is used as a main raw material, and agglomerated regenerated particle-containing slurry is obtained by aggregating regenerated particles obtained through dehydration, heat treatment and pulverization steps with a coagulant,
An addition step of adding the agglomerated regenerated particle-containing slurry to the pulp slurry, and a paper making step of papermaking the pulp slurry to which the agglomerated regenerated particle-containing slurry is added,
In the method for producing paper, the aggregated regenerated particles have a volume average particle diameter of 2.5 μm or more and 10 μm or less.

  According to the production method, by setting the volume average particle diameter of the aggregated regenerated particles in the above range, the viscosity of the slurry is suppressed and the workability is improved, and the yield of the regenerated particles in the paper is improved. And highly opaque paper can be obtained.

The coagulant is cationic,
The charge density of the coagulant is preferably 5 meq / g or more and 25 meq / g or less.

  By using a cationic coagulant having a charge density in the above range, the cationic charge density can be easily adjusted to a desired range, etc., thereby suppressing slurry thickening and agglomeration of regenerated particles to an appropriate particle size. It can be achieved more efficiently.

The coagulant contains a polyethyleneimine derivative as a main component,
The mass average molecular weight of the coagulant is preferably 100,000 or more and 1.5 million or less.

  By using a coagulant containing a polyethyleneimine derivative as the main component and having a mass average molecular weight in the above range, the thickening of the slurry is more effectively suppressed, workability is improved, and a desired secondary particle size is provided. The paper can be aggregated into aggregates, and the yield of regenerated particles in the paper can be improved to obtain paper having high opacity.

  Therefore, the paper obtained by the production method of the present invention has a high yield of regenerated particles as a filler, and as a result, has a high ash content and high opacity.

  Here, the volume average particle diameter refers to the volume median particle diameter (D50) in the particle size distribution measured by the laser diffraction scattering method.

  As described above, according to the paper manufacturing method of the present invention, it is possible to manufacture a paper that suppresses thickening of the slurry and has an excellent filler yield despite using the regenerated particles as a filler. Therefore, it is possible to improve the productivity of paper, and to obtain a high-quality paper having a large amount of ash and high opacity.

  Hereinafter, the paper manufacturing method of the present invention and the paper obtained by this manufacturing method will be described in detail.

<Paper manufacturing method>
The paper manufacturing method is:
(1) A regenerated particle agglomeration step using a paper sludge as a main raw material, and aggregating regenerated particles obtained through dehydration, heat treatment and crushing steps with a coagulant to obtain an agglomerated regenerated particle-containing slurry;
(2) An addition step of adding the agglomerated regenerated particle-containing slurry to the pulp slurry, and (3) a paper making step of papermaking the pulp slurry to which the agglomerated regenerated particle-containing slurry is added.

<(1) Regenerated particle aggregation step>
(1) In the regenerated particle aggregating step, regenerated particles as a filler are aggregated in advance with a coagulant before adding to the pulp slurry to obtain an agglomerated regenerated particle-containing slurry containing agglomerated regenerated particles. In this production method, paper sludge is used as a main raw material as the regenerated particles, and by using what is obtained through dehydration, heat treatment and pulverization steps, overcombustion is suppressed, and thickening at the time of slurrying is increased. Can be suppressed. A preferable method for producing the regenerated particles will be described in detail later.

  This regenerated particle aggregation step can be performed, for example, by adding a coagulant to a regenerated particle slurry in which regenerated particles are dispersed in water. The solid content concentration of the regenerated particles in the regenerated particle slurry is preferably 10% by mass to 40% by mass, more preferably 12% by mass to 35% by mass, and particularly preferably 15% by mass to 25% by mass. By making the density | concentration of a reproduction | regeneration particle slurry into the said range, coexistence with efficiency improvement of the reproduction | regeneration particle | grain and suppression of a raise of slurry viscosity can be aimed at. When the concentration of the regenerated particle slurry is less than the lower limit, the regenerated particles may not aggregate to a suitable size even by the addition of a coagulant. On the other hand, when the concentration of the regenerated particle slurry exceeds the above upper limit, the viscosity becomes too high and the workability may be lowered, or the particle size distribution of the aggregated regenerated particles may be too wide and the yield may be decreased.

  The volume average particle diameter of the regenerated particles before adding the coagulant (before this step) is not particularly limited, but is preferably 1.5 μm or more and 3.5 μm or less, and more preferably 2 μm or more and 3 μm or less.

  The coagulant added to the regenerated particle slurry is not particularly limited as long as it can agglomerate a plurality of particles by the action of the electric charge, and a polymer compound such as a cationic polymer or an anionic polymer is used. However, it is preferable to use a cationic polymer that can suitably aggregate the negatively charged regenerated particles.

  The lower limit of the mass average molecular weight of the coagulant is preferably 100,000, more preferably 300,000, and particularly preferably 400,000. On the other hand, the upper limit of the mass average molecular weight is preferably 1.5 million, more preferably 1.3 million, and particularly preferably 1,200,000. By setting the molecular weight of the coagulant within the above range, suitable cohesiveness with respect to the regenerated particles can be exhibited. In particular, for regenerated particles having a volume average particle size as described above, an agglomerate having a desired particle size can be efficiently obtained by using a coagulant having a molecular weight in such a range. . The mass average molecular weight is a numerical value measured using a gel permeation chromatography method (GPC method).

  When the mass average molecular weight of the coagulant is less than the above lower limit, sufficient aggregating ability cannot be exhibited and the regenerated particles do not agglomerate, so that the yield may not be improved. Conversely, if this average molecular weight exceeds the above upper limit, the agglomeration ability is too strong, the occurrence of partial agglomeration, the viscosity of the slurry is increased, the paper workability is reduced, the paper strength of the resulting paper is It may decrease.

  Further, the lower limit of the cationic charge density of the coagulant is preferably 5 meq / g, more preferably 8 meq / g, and particularly preferably 10 meq / g. On the other hand, the upper limit of the cation charge density is preferably 25 meq / g, more preferably 22 meq / g, and particularly preferably 20 meq / g. By setting the cationic charge density of the coagulant within the above range, suitable cohesiveness with respect to the regenerated particles can be exhibited. In addition, this cation charge density says the cation charge density as the whole coagulant, when using a some component as a coagulant.

In the present invention, the cationic charge density is a value measured by the following method. First, after adjusting the sample to an aqueous solution of pH 4.0, the amount of anion required by titration using a 1/1000 normal aqueous potassium potassium sulfate solution with a particle charge measuring device (Muteck PCD-03) based on the streaming potential method. Measure. The cation charge density per 1 g of sample is calculated by the following formula (1) using the obtained anion demand.
Cationic charge density = A / B (1)
A: Anion requirement of the aqueous coagulant solution adjusted to pH 4.0 (μeq / l)
B: Solid content concentration of coagulant aqueous solution (g / l)

  When the cationic charge density of the coagulant exceeds the above upper limit, the entire surface of the regenerated particles may have a cationic charge, and aggregation may not easily occur due to repulsion due to the charge. On the contrary, when the cationic charge density of the coagulant is less than the above lower limit, the effect of being able to electrically aggregate the negatively charged regenerated particles cannot be sufficiently exhibited, and the broad particle size distribution and There is a case.

  In this way, in the aggregation of the regenerated particles, the use of the coagulant having the above-mentioned preferable ranges in both the mass average molecular weight and the cation charge density can reduce both the cohesiveness of the regenerated particles and the suppression of the thickening of the slurry. This is preferable because it can be suitably achieved. The reason for this is not clear, but for example, the reason for agglomeration is that the regenerated particles, which are a mixture of various inorganic substances and inorganic oxides, vary in the surface charge distribution. This is probably because the use of a cationic synthetic polymer having a density can exert an electrical aggregation (coagulation) action.

  In addition, in the thickening of the regenerated particle slurry due to the presence of a hydration curable substance such as calcium oxide due to the influence of overburning, a coagulant having an appropriate molecular weight effectively coats the regenerated particle surface, It is considered that reaction to calcium hydroxide can be suppressed. At this time, it is considered that the coagulant having an appropriate cationic charge density suppresses the reactivity of calcium oxide contained in the regenerated particles, and as a result, it is possible to suppress the thickening of the slurry.

  Examples of the cationic polymer that can be suitably used as the coagulant include organic polymers such as polyacrylamide, polyvinylamine, polyamine, polyethyleneimine, and derivatives thereof.

  Among these, a polyethyleneimine derivative is particularly preferable from the viewpoints of agglomeration property with respect to regenerated particles and suppression of thickening of the slurry.

  The coagulant is preferably added to the regenerated particle slurry as an aqueous solution. The addition amount of the coagulant is preferably 200 ppm or more and 3,500 ppm or less, more preferably 1,000 ppm or more and 3,000 ppm or less, and more preferably 1,500 ppm or more and 2,500 ppm in terms of solid content with respect to the solid content of regenerated particles. The following are particularly preferred:

  When the addition amount of the coagulant is less than the above lower limit, the regenerated particles cannot be sufficiently aggregated, and the yield improvement effect may not be exhibited. On the other hand, when the addition amount of the coagulant exceeds the above upper limit, the thickening of the slurry may occur remarkably, or tertiary and quaternary aggregation may occur, and the paper strength of the resulting paper may be reduced.

  The upper limit of the volume average particle diameter of the aggregated regenerated particles obtained through this step is 10 μm, preferably 8 μm, particularly preferably 7 μm. On the other hand, the lower limit of the volume average particle diameter of the aggregated regenerated particles is 2.5 μm, preferably 4 μm, and more preferably 5 μm. By making the volume average particle diameter of the aggregated regenerated particles in the above range, the yield of the regenerated particles in the paper making process can be improved efficiently.

  When the volume average particle diameter of the aggregated regenerated particles exceeds the above upper limit, the viscosity of the aggregated regenerated particles-containing slurry becomes too high, and the workability is decreased, or the paper strength of the obtained paper is decreased. Conversely, when the volume average particle diameter is less than the lower limit, the yield of recycled papermaking paper is not sufficiently improved.

  According to the knowledge of the inventors, the viscosity of a suitable agglomerated regenerated particle-containing slurry greatly changes at a boundary of 500 cps. When the viscosity exceeds 500 cps, workability deteriorates and contamination in the papermaking system becomes obvious. Occurs. Particularly preferably, by adjusting to 300 cps or less, and further to 200 cps or less, the workability can be improved and the particle size distribution of the resulting aggregated regenerated particles can be made sharper, which is the subject of the present invention, due to the yield of the filler. It is possible to more effectively realize a method for producing paper having high opacity and provision of paper obtained by this production method.

<(2) Addition process>
(2) In the addition step, the aggregated regenerated particle-containing slurry obtained in the above step is added to the pulp slurry.

  As the raw material pulp to be blended in this pulp slurry, known paper manufacturing raw materials are used. For example, chemical pulp such as LBKP and NBKP, various mechanical pulps, DIP, and the like can be used. Among these pulps, chemical pulp and DIP are preferred in consideration of cost and environmental impact.

  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 a regenerated particle 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., light calcium carbonate is preferably used in combination.

  The amount of the aggregated regenerated particle-containing slurry added to the pulp slurry is preferably 10 kg or more and 200 kg or less, more preferably 50 kg or more and 150 kg or less as regenerated particles with respect to 1 t of pulp. When the amount of (aggregated) regenerated particles is less than the above lower limit, there is a possibility that a paper excellent in opacity or the like having a preferable ash content cannot be obtained. On the other hand, when the addition amount exceeds the above upper limit, the ratio of regenerated particles that do not remain in the paper increases, yield may decrease, and productivity may decrease.

<(3) Papermaking process>
(3) In the papermaking process, paper can be obtained by papermaking the pulp slurry to which the aggregated regenerated particle-containing slurry is added in the above process. The papermaking method is not particularly limited, and papermaking can be performed with a known papermaking machine. In addition, if necessary, a sizing agent may be applied to the front and back surfaces of the paper after papermaking, or may be passed through a calendar device to perform pressurization, smoothing treatment, and the like.

  As the sizing agent used in the paper making process, a commonly used sizing agent may be appropriately used. Examples of such a sizing agent include oxidized starch, etherified starch, esterified starch, enzyme-modified starch, and cationization. Starch, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyvinyl alcohol (PVA), styrene / acrylic acid copolymer, styrene / (meth) acrylic acid copolymer, styrene / (meth) acrylic acid / (meth) acrylic acid ester Polymers, styrene / maleic acid copolymers, styrene / maleic acid half ester copolymers, styrene / maleic acid ester copolymers, water-soluble polymers such as polyacrylamide, alkyds such as rosin, tall oil and phthalic acid Anio such as saponified resin, saponified petroleum resin and rosin Sex low molecular compounds, such as cationic polymers, such as Isojianeto based polymers. Among these, water-soluble polymers are preferable, starch is more preferable, and processed starch in which a carboxyl group, an aldehyde group, a carbonyl group or the like is further introduced into the molecule after being reduced in molecular weight by an oxidation reaction with sodium hypochlorite or the like is further added. preferable. The above sizing agents may be used alone or in combination of two or more. By adding these sizing agents, the vehicle content of cold-set offset ink is quickly absorbed, and even if the amount of printing ink increases due to the use of a high-speed rotary press or the use of a tower press for double-sided color, sufficient absorption is achieved. Since the drying property is expressed and the filler is securely fixed to the fiber, it is possible to prevent the filler from falling off and to ensure excellent printing opacity, printability, and the like.

<Paper>
The paper obtained by the above production method has a high yield of regenerated particles as a filler and has a high ash content. The lower limit of the ash content of the paper obtained by the production method is preferably 1%, more preferably 3%, and more preferably 5%. On the other hand, the upper limit of the ash content is preferably 20%, more preferably 15%, and more preferably 10%. The obtained paper can exhibit excellent characteristics such as opacity when the ash content is in such a range.

  Although it does not specifically limit as a use of the paper obtained by the said manufacturing method, It can use suitably as a newsprint paper. Since the above manufacturing method has a high yield of filler, newsprint paper having excellent printing characteristics such as printing opacity can be obtained. As a result, the newsprint obtained by the manufacturing method can be suitably used for high-speed offset rotary printing.

<Method for producing regenerated particles>
Here, a method for producing regenerated particles suitable for the production method of the present invention will be described in detail in the order of raw materials and steps of dehydration, heat treatment and pulverization. In addition, it is preferable to have a mixing | blending / slurry 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. In the used paper pulp manufacturing process in papermaking, for the purpose of continuously producing used paper pulp of stable quality, the used paper is selected and selected, and used paper of a certain quality is used. For this reason, the types, ratios, and amounts of inorganic substances brought into the used paper pulp manufacturing process are basically constant. Moreover, even if the waste paper contains plastics such as vinyl and film that cause fluctuations in unburned materials, these foreign matters are removed at the stage before the deinking process for obtaining the deinking floss. Accordingly, the deinking floss is a raw material for producing regenerated particles having extremely stable quality as compared with papermaking sludge generated in other processes such as a factory drainage process and a papermaking raw material preparation process.

(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.

  Examples of the dehydration step include the following steps. First, water is separated from the deinking floss by a screen as one dehydrating means and dehydrated. The deinking floss dehydrated to 90% to 97% in this screen is sent to another dehydrating means such as a screw press, and further dehydrated to a predetermined moisture content.

  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. .

  If the moisture content of the raw material after dehydration exceeds 70%, the processing temperature in the heat treatment process is lowered, energy loss for heating becomes large, and uneven combustion of the raw material is likely to occur and it is difficult to promote uniform combustion. Become. Further, the exhaust gas discharged has a large amount of moisture, which has the disadvantage that the efficiency of the recombustion treatment in the dioxin countermeasures is reduced and the load of the exhaust gas treatment equipment is increased. On the other hand, if the moisture content of the raw material after dehydration is as low as less than 40%, it causes excessive combustion of the deinking floss. It also goes against the reduction of dehydration energy.

  As described above, if the raw material (deinking floss) is dehydrated in a multi-stage process and abrupt dehydration is avoided, the outflow of inorganic substances can be suppressed and the deinking floss flocs do not become too hard. In the dehydration treatment, an auxiliary agent for improving the dehydration efficiency such as an aggregating agent for aggregating the deinking floss may be added, but it is preferable to use an aggregating agent that does not contain iron. When iron is contained, the whiteness of the regenerated particles may be reduced due to oxidation of iron.

  It is preferable in terms of production efficiency that the equipment for the dehydration process is adjacent to the equipment of other processes of the regenerated particles, but the equipment is provided in advance adjacent to the waste paper pulp manufacturing process to transport the dehydrated material. It is also possible to transport to a metering feeder by a transport means such as a truck or a belt conveyor, and to supply the heat treatment process from this metering feeder.

  The raw material after dehydration is a particle having an average particle diameter of 40 mm or less, preferably an average particle diameter of 3 mm to 30 mm, more preferably an average particle diameter of 5 mm to 20 mm by a pulverizer (or pulverizer) before being supplied to the heat treatment step. It is preferable to arrange the diameters, and it is preferable to arrange the particle diameters so that the ratio of the particle diameters of 50 mm or less is 70% by mass or more. If the average particle size is less than 3 mm, overcombustion tends to occur. Conversely, when the average particle diameter exceeds 40 mm, it becomes difficult to uniformly burn the raw material core.

  The average particle diameter and the ratio of the particle diameter in the dehydration step are values measured using a sample solution sufficiently dispersed by a stirring type disperser. In addition, the particle diameter in each heat processing process mentioned later is the value measured with the metal plate sieve based on JIS-Z8801-2: 2000.

(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. Specifically, the upper limit of the heat treatment temperature is preferably 780 ° C, more preferably 750 ° C.

(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.

  In this internal heat kiln furnace, hot air generated in the hot air generation furnace is sent from the outlet side so as to counter-flow with the raw material flow. An exhaust gas chamber is provided on one side of the internal heat kiln furnace, and an exhaust chamber is provided on the other side. Hot air is blown from the other side of the internal heat kiln furnace through the discharge chamber, and is charged from the other side to dry and burn the raw material sequentially transferred to the other side as the internal heat kiln furnace rotates. To do.

  In this way, in the first heat treatment step, the raw material is dried and burned gently from the supply port to the discharge port by drying and burning in the internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis. Can control the degree of combustion of raw materials with various properties such as agglomeration, hard and soft, and stable grain alignment. Can do. In addition, drying can be divided into separate steps and dried by, for example, a blow-up type dryer.

  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. . In the first heat treatment step, it is preferable to heat-treat at a temperature in the above range for the purpose of slowly burning the combustible organic matter and suppressing the formation of residual carbon that is difficult to burn. 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 addition, when the temperature is 500 ° C. or higher, drying / combustion proceeds locally faster than the grain alignment of dehydrated materials having various properties such as hard and soft, so that the particle surface and the interior of the particle are not. It becomes difficult to reduce the difference in the flammability and make it uniform.

  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. In terms of organic combustion and production efficiency, heat treatment is preferably performed with a residence time of 40 minutes to 80 minutes. In order to ensure constant quality, it is preferable to perform heat treatment combustion with a residence time of 50 minutes to 70 minutes.

(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. If the average particle diameter at the inlet of the external heat kiln in the second heat treatment step is less than 1 mm, there is a risk of overcombustion. If the average particle diameter exceeds 10 mm, the remaining carbon is difficult to burn, and combustion may not proceed to the core. There is a possibility that the whiteness of the regenerated particles may decrease.

  As the external heat source of the external heat kiln furnace, an electric heating type heat source that is easy to control the temperature in the external heat kiln furnace and easy to control the longitudinal temperature is suitable. Is preferred. By using electricity as an external heat source, the temperature in the furnace can be finely and uniformly controlled, and the degree of combustion of the heat-treated product having various properties such as formation of aggregates, hard and soft, Grain alignment can be performed stably. In addition, by providing a plurality of electric heaters in the flow direction of the furnace, the electric furnace can arbitrarily provide a temperature gradient, and the temperature of the heat-treated product can be maintained at a constant temperature for a certain period of time. Residual organic content in the heat-treated product after one heat treatment step, especially residual carbon, can be brought to zero as much as possible without causing decomposition of calcium carbonate in the second heat treatment step, for example, low wire wear compared to heavy calcium carbonate However, regenerated particles with high whiteness can be obtained.

  The heat treatment temperature in the second heat treatment step is preferably 550 ° C to 780 ° C, more preferably 600 ° C to 750 ° C. In the second heat treatment step, as described above, since it is necessary to burn the residual organic matter that has not been burned in the first heat treatment step, particularly the residual carbon, it is preferable to perform the heat treatment at a higher temperature than the first heat treatment step. If the heat treatment temperature is less than 550 ° C., there is a possibility that the residual organic matter cannot be burned sufficiently. If the heat treatment temperature exceeds 780 ° C., decarboxylation of calcium carbonate in the heat treatment proceeds and the particles become hard. There is a fear.

  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 most preferably 120 minutes to 150 minutes. Minutes are 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. In addition, in the stable production of the heat-treated product, it is preferable that the residence time is 60 minutes or more, and in order to prevent overcombustion and secure productivity, the residence time is 240 minutes or less.

  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. Then, after adjusting to the target particle diameter in the blending / slurry step and the pulverization step, the particles are used as reclaimed particles for application destinations such as fillers.

  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 / slurry process)
The blending / slurrying step is a step of blending an acid and / or salt into the heat-treated product discharged from the second heat treatment step and suspending the heat-treated product in water to make a slurry.

  This heat-treated product is preferably pulverized after being suspended in water by using a mixer or the like in order to achieve effective pulverization in the subsequent pulverization step. In this case, the lower limit of the slurry concentration (mass ratio of the heat-treated product added to the whole slurry) is preferably 15%, and more preferably 20%. Further, the upper limit of the slurry concentration is preferably 50%, and more preferably 40%. When the slurry concentration is less than the above lower limit, when the finally obtained particles are made into a solid state, production efficiency decreases, for example, enormous energy is generated. On the other hand, if the slurry concentration exceeds the above upper limit, effective pulverization may be difficult in the subsequent pulverization step, and solidification and solidification may easily occur.

  The acid and / or salt can precipitate a calcium salt in the presence of calcium ions. According to the acid and / or salt, it reacts with calcium ions dissolved in the slurry due to calcium oxide and metakaolin generated by overcombustion, and precipitates calcium salt, so that it coexists in the slurry with calcium ions. The reaction with silicate ions and aluminate ions can be suppressed, and the generation of a cured substance can be suppressed. As a result, by using this acid and / or salt, solidification and solidification of the slurry can be suppressed. The reason will be described below.

  Calcium oxide, metakaolin, and the like are generated from calcium carbonate and kaolin, which are constituents of papermaking sludge, by overcombustion in a heat treatment step or the like. When this calcium oxide is mixed with water (in the slurry), it becomes calcium hydroxide, and is attracted to calcium ions resulting from this calcium hydroxide, causing silicate ions and aluminate ions to solidify and solidify the slurry. . The reason for this is not clear, but this calcium ion reacts with silicate ions and aluminate ions that coexist in the slurry, and the hydration hardening reaction of these silicate ions and aluminate ions (formation of hydrates such as ettringite) ). In addition, this silicate ion and aluminate ion originate in the metakaolin etc. which arise by overcombustion.

  Here, when the acid and the salt thereof are added to the slurry, it reacts with calcium ions in the slurry to form a calcium salt. If the solubility of this calcium salt in water is low, it precipitates as a solid, reduces the calcium ions in the slurry, and suppresses the formation of silicate ions and alumina ions due to metakaolin and the like. As a result, it is considered that solidification and solidification of the slurry can be prevented because no hydration curable substance is generated in the 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. According to the acid and / or salt having such low solubility in water, the calcium salt produced by the reaction reacts with calcium ions in the slurry during the blending / slurry process in the normal production process of regenerated particles. Precipitating on the surface of particles containing calcium oxide or calcium hydroxide can effectively prevent the slurry from solidifying and solidifying.

  Moreover, according to this acid and / or salt, the whiteness of the obtained regenerated particles can be increased. Many calcium salts obtained from acids or salts thereof have high whiteness. Therefore, the whiteness of the regenerated particles obtained by coating these calcium salts with particles containing calcium oxide can be increased.

  As the acid and / or salt, a calcium salt can be precipitated in the presence of calcium ions, and preferably, the solubility in 100 g of water at 20 ° C. in the calcium salt state is 1 g or less. Alternatively, it may be a salt thereof, an inorganic acid or a salt thereof. The precipitation of calcium salt in the presence of calcium ions means that the calcium salt can be precipitated in a slurry in a general process for producing regenerated particles.

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.

  In addition, the acid and / or salt is preferably an acid or a salt that exhibits acidity when hydrolyzed from the viewpoint of reducing the pH of the slurry. Since regenerated particles having a high pH may react with other chemicals and cause a reduction in quality, it is effective to reduce the pH by adding an acid.

  It is preferable that the mixing (mixing step) of the acid and / or salt with the heat-treated product is performed before or simultaneously with the slurrying (slurrying step) of the heat-treated product. When acid and / or salt is added after slurrying the heat-treated product, the calcium oxide in the heat-treated product is already changed to calcium hydroxide, and the hydration hardening reaction due to the generated calcium ions has already started. Therefore, the effect of suppressing solidification and solidification cannot be obtained, or the effect may be reduced.

  As a method of blending the acid and / or salt into the heat-treated product before slurrying the heat-treated product, the solid acid salt (calcium sulfate, tricalcium phosphate, etc.) is added to the heat-treated product in powder form. The method of mixing etc. can be mentioned. As a method of adding acid and / or salt to the heat-treated product at the same time as slurrying of the heat-treated product, (1) a method of dissolving the acid and / or salt in water and suspending the heat-treated product in the aqueous solution ( 2) A method in which an acid and / or salt and a heat-treated product are mixed in water at the same time. According to the method of adding the acid and / or salt to the heat-treated product at the same time as the slurry of the heat-treated product, the acid and / or salt is present only in the aqueous solution (carbonic acid etc.) Even in difficult cases (such as sulfuric acid), it can be blended without any inconvenience.

  The lower limit of the amount of the acid and / or salt is preferably 0.01 parts by weight, more preferably 0.1 parts by weight, and particularly preferably 0.3 parts by weight with respect to 100 parts by weight of the heat-treated product. 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 step, a granulation step, a classification step between each step, a silica precipitation (coating) step, a carbonation step for carbonating the slurry, and the like may be provided.

(Silica precipitation (coating) process)
The regenerated particles can be used as a filler as they are after undergoing the above pulverization step, but by further precipitating (fixing) silica on the regenerated particles, the function as regenerated particles can be further enhanced. it can. The method for depositing silica on the regenerated particles is described below.

  A suitable method for precipitating silica is to add and disperse the regenerated particles in an alkali silicate aqueous solution to prepare a slurry, and then heat and stir the solution while maintaining the liquid temperature at 70 to 100 ° C., more preferably at a predetermined pressure in a sealed container. By retaining and adding an acid to form a silica sol and adjusting the pH of the final reaction solution to a range of 8.0 to 11.0, silica can be deposited on the surface of the regenerated particles. Silica deposited on the surface of regenerated particles is obtained by reacting sodium silicate (water glass) as a raw material with a dilute solution of mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid at high temperature, and by hydrolysis and polymerization of silicic acid. Silica sol particles having a particle diameter of 10 to 20 nm.

  Silica sol crystals grow by attaching silica sol fine particles of about several nanometers generated by adding acid such as dilute sulfuric acid to sodium silicate solution so as to cover the entire porous surface of the regenerated particles. Bonding occurs between the silica sol fine particles on the surface and silicon, calcium, and aluminum included in the regenerated particles, and silica can be deposited on the surface of the regenerated particles.

At this time, the pH of the reaction solution is preferably in a neutral to weakly alkaline range, and more preferably in a range of 8 to 11. If sulfuric acid is added until the pH reaches an acidic condition of less than 7, white carbon is generated instead of silica sol. The alkali silicate solution used here is not particularly limited, but a sodium silicate solution (No. 3 water glass) is desirable in terms of availability. The concentration of the alkali silicate solution is preferably 3 to 10% by mass in terms of the silicic acid content in the aqueous solution (in terms of SiO ₂ ). If it exceeds 10% by mass, the silica deposited on the regenerated particles becomes white carbon from the form of the silica sol, impairing the porosity of the regenerated particles, and the effect of improving the opacity and oil absorption becomes low. On the other hand, if the amount is less than 3% by mass, the silica component in the regenerated particles is lowered, so that silica deposition on the surface of the regenerated particles is difficult to occur. Silica is precipitated on the surface of the regenerated particles, and calcium, silicon and aluminum are made into a mass ratio of 30 to 62:29 to 55: 9 to 35 in terms of oxides, thereby improving oil absorption and opacity due to the silica precipitation effect. Can be made.

(Carbonation process)
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.

  The carbonation step may be performed between the blending / slurry step and the pulverization step, simultaneously with the pulverization step, or after the pulverization step. The carbon dioxide blowing may be a blending / slurrying step as a blending of carbonic acid instead of or in addition to blending with other acids and / or salts.

  During carbonation, a gas blowing port is provided at the bottom of the reaction tank, and a pH meter for measuring the pH in the tank is provided, and batch processing is performed on the slurry in the tank until the pH of the slurry falls below a predetermined value. This can be done by blowing gas. Further, a gas blowing port is provided in a portion where the gears such as a VF pump mesh with each other, and pulverization and gas blowing can be simultaneously performed on the slurry.

As carbon dioxide for carbonation, carbon dioxide can be separated from exhaust gas using a carbon dioxide separator such as a PSA separator in the CO ₂ separation step. Moreover, exhaust gas can be used directly, or commercially available carbon dioxide gas can be used and used together.

  The blowing rate of carbon dioxide can be constant or variable, and in the case of being variable, it can be appropriately adjusted according to the transition of pH.

  The slurry whose pH adjustment has been completed is sent to a dehydrator or the like to increase the concentration to 50 to 70%. The regenerated particles having a concentration of 50 to 70% are solid (cake). As the dehydrator, for example, a filter press, a centrifugal dehydrator, a belt press, or the like can be appropriately selected and used.

  The regenerated particles that have become solid are sent to a dispersion step to form a high-concentration slurry. As the dispersing device, for example, a mixer, a coreless disperser, a ball mill and the like can be appropriately selected and used. The concentration of the regenerated particles at this time is 50 to 70% by mass, preferably 55 to 70% by mass, and more preferably 60 to 65% by mass. When the slurry concentration is less than 50% by mass, for example, the concentration of the coating liquid in the application of the coating pigment is reduced, the effect of the aggregation inhibitor is reduced, the precipitation of the particles in the regenerated particle slurry, and the like. There is a risk that the quality stability of the product will deteriorate. On the other hand, if the slurry concentration exceeds 70% by mass, the slurry may be thickened and solidified, and an increase in energy required for dehydration becomes a problem.

  In this embodiment, in order to further stabilize the quality of the regenerated particles, it is preferable to classify the particle diameter of the object to be processed uniformly in each step, and coarse particles and fine particles are fed back to the previous step. As a result, the quality can be further stabilized.

  In addition, it is preferable to granulate the deinked floss (dehydrated product) that has been subjected to dehydration in the previous stage of the drying process, and it is more preferable to classify the granulated product to make the particle size uniform. The quality can be further stabilized by feeding back coarse and fine granulated particles to the previous process. 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 diameter of aggregated regenerated particles (unit: μm)
10 mg of the aggregated regenerated particle sample was dispersed with an ultrasonic disperser (output: 80 W) for 3 minutes. The average particle diameter of this solution was measured with a laser particle size distribution measuring device (measured with a laser diffraction particle size distribution measuring device SALD-2200, manufactured by Shimadzu Corporation, standard refractive index (1)).

(A) Particle size distribution of aggregated regenerated particles From the particle size distribution waveform of the aggregated regenerated particle sample measured using the laser particle size distribution measuring device, it was determined whether the particle size distribution was sharp or broad.

(C) Viscosity of regenerated particle slurry (unit: cps)
A digital B-type viscometer (manufactured by Toki Sangyo Co., Ltd., model number: TVB-10M) was used. Measurement was performed at 60 rpm and 25 ° C. using a No. 2 rotor.

(D) Ash content (regenerated particles) Yield (Unit:%)
The flocculant regenerated particle slurry was added to a pulp slurry made of LBKP diluted to a concentration of 1.0% so as to have an ash content of 30%, and then diluted to a pulp concentration of 0.75%. 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 (2).
Ash content yield = 100 × (A−B) / A (2)
A: Ash content (g / l) of pulp slurry
B: Ash concentration in the filtrate (g / l)

(E) Printing opacity (unit:%)
The ratio of the backside reflectance after printing to the backside reflectance before printing when the offset rotary printing press is used to change the ink amount of the ink for offset rotary printing (black) and the printed surface reflectance is 9% ( %). The reflectance is a value measured with a spectral whiteness colorimeter (manufactured by Suga Test Instruments Co., Ltd.).

[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 parts by mass of calcium sulfate dihydrate is added as a blending / slurry 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.

[Agglomeration of regenerated particles]
The regenerated particles obtained by the above method were dispersed in water to obtain a regenerated particle slurry. The coagulant or flocculant shown in Table 1 as Examples 1 to 9 and Comparative Examples 1 to 3 was added to the regenerated particle slurry, and the volume average particle diameter and slurry viscosity of the obtained agglomerated regenerated particles were measured. The results are shown in Table 1. The coagulant or flocculant was diluted to a solid content concentration of 0.1% by mass and added. The coagulant and flocculant used in each example and comparative example are as follows.

Coagulant A: “Himax SC-100” manufactured by Hymo Co., Ltd.
Diallyldimethylammonium chloride polymer Mass average molecular weight: 300,000 Cationic charge density: 6.0 meq / g
・ Coagulant B: “Himax SC-924” manufactured by Hymo Co., Ltd.
Modified polyethyleneimine Mass average molecular weight: 500,000 Cationic charge density: 18.0 meq / g
・ Coagulant C: “Cassiofast SF” manufactured by BASF
Polyethyleneimine Mass average molecular weight: 1,000 to 1,200,000 Cationic charge density: 11.0 meq / g
-Flocculant A: "Himolock ND270" manufactured by Himo Corporation
Cationic polyacrylamide Mass average molecular weight: 15 million Cationic charge density: 2.0 meq / g

Next, 100 g (solid content) of the agglomerated regenerated particle-containing slurry obtained above for each example and comparison was blended with 100 kg (solid content) of pulp in 1 kg (solid content) in a pulp slurry composed of 100% LBKP. Paper) (hand-made sheet) having a basis weight of 40 g / m ² was obtained.

About Examples 1-9 and Comparative Examples 1-3, while measuring the ash content yield in the procedure mentioned above, the printing opacity of the obtained paper was measured. In calculating the printing opacity, paper with a basis weight of 40 g / m ² and paper with a basis weight of 50 g / m ² were prepared, and after calculating the printing opacity, the paper was converted to a basis weight of 45 g / m ² . It is the value. The measurement results are shown in Table 1.

  As shown in Table 1, according to the production method of the present invention, paper with a high yield of ash (regenerated particles) and excellent printing opacity can be obtained. Further, by using a coagulant having a mass average molecular weight and a cation charge density in a specific range, even when regenerated particles are used as a filler, the slurry can be appropriately aggregated while suppressing the viscosity increase of the slurry.

  According to the paper manufacturing method of the present invention, recycled particles can be used efficiently as a filler, and therefore can be suitably used in a paper mill or the like.

Claims (3)

A regenerated particle agglomeration step for obtaining a slurry containing agglomerated regenerated particles by aggregating the regenerated particles obtained through papermaking sludge as a main raw material, through a heat treatment and a pulverization step for dehydration and combustion with a coagulant
An addition step of adding the agglomerated regenerated particle-containing slurry to the pulp slurry, and a paper making step of papermaking the pulp slurry to which the agglomerated regenerated particle-containing slurry is added,
A method for producing paper, wherein the aggregated regenerated particles have a volume average particle diameter of 2.5 μm or more and 10 μm or less. The coagulant is cationic,
The method for producing paper according to claim 1, wherein the coagulant has a charge density of 5 meq / g or more and 25 meq / g or less. The coagulant contains a polyethyleneimine derivative as a main component,
The method for producing paper according to claim 2, wherein the coagulant has a mass average molecular weight of 100,000 to 1,500,000.