JP2010236129A - Paper filled with heavy calcium carbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper compounded with heavy calcium carbonate as an internal filler, having high whiteness and producible in high productivity because wire abrasion can be sufficiently suppressed even by making the paper e.g. at a paper velocity of as high as 1,300 m/min or over. <P>SOLUTION: The paper contains a pulp and the heavy calcium carbonate as the internal filler, wherein ratio of fibers having a fiber length of ≥0.2 μm and <0.5 μm in fibers obtained by defibration according to JIS P 8220 is ≥20% and ≤40%. The paper may further contain regenerated particles, preferably regenerated particle aggregate, and/or talc, and may further contain a coagulant. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to paper made by adding heavy calcium carbonate internally.

  In order to improve the flexibility and feel of the paper, the paper contains a filler that inhibits the binding of pulp fibers, and calcium carbonate, talc, clay, titanium oxide, etc. are used as the filler. Among these, since titanium oxide and calcium carbonate have high whiteness, they are preferably used as internal additives for high-quality paper and coated paper that require high whiteness. Of these, titanium oxide is expensive, and inexpensive calcium carbonate is often used.

  As calcium carbonate, there are heavy calcium carbonate obtained by dry or wet mechanical pulverization of natural limestone, and light calcium carbonate (precipitated calcium carbonate) produced by injecting carbon dioxide into quick lime or slaked lime and neutralizing reaction. is there.

  When paper is made using heavy calcium carbonate or light calcium carbonate as an internal filler, paper with high whiteness can be produced at low cost, while calcium carbonate is harder than talc and clay. There is a problem that the wire of the paper machine is easily worn. In particular, since heavy calcium carbonate is produced by pulverizing natural limestone, the particle surface is formed in a cross-section and is angular, and there is a problem that the wire is more easily worn than light calcium carbonate. When the wire wears out, it is necessary to stop the operation of the paper machine for replacement, leading to a decrease in productivity. In recent years, the speed of paper machines has increased. For example, when heavy calcium carbonate is used as an internal filler in a high speed paper machine with a paper making speed of 1,300 m / min or more, the wear of the wire is particularly easy to progress and the replacement cycle is shortened. The impact on productivity is even greater.

  The following is disclosed as a technique for reducing the wear resistance of heavy calcium carbonate plastic wire. A technique for improving the wire wear and improving the yield of the filler and the whiteness of the paper at the same time by mixing calcium carbonate with, for example, an olivine group first or more silicate mineral (see Patent Document 1). Technology for obtaining neutral paper with extremely low wire wear and excellent quality by using a heavy calcium carbonate added with a special granular composition such as bentonite as a filler (Patent Document 2, 3). A technique of adding silica sand particles having an average particle diameter of 2 to 50 μm to heavy calcium carbonate (see Patent Document 4). Technology to use heavy calcium carbonate or light calcium carbonate filler together with alumina and / or zirconia with a specific average particle size as filler (Patent Document 5), paper making with cationized starch, technology to improve plastic wire wear resistance (See Patent Document 6). However, in any of the above methods, for example, when heavy calcium carbonate is used as an internal filler in high-speed papermaking at a papermaking speed of 1,300 m / min or more, the wire wear cannot be sufficiently reduced.

JP 60-45700 A JP-A-61-194298 JP 62-117899 A Japanese Patent Laid-Open No. 08-144190 Japanese Patent Laid-Open No. 10-298894 JP 2007-100287 A

  The main problem to be solved by the present invention is a paper in which heavy calcium carbonate is blended as an internal filler, and the yield of heavy calcium carbonate, for example, even when paper is made at a high speed of 1,300 m / min or more. Therefore, it is an object of the present invention to provide a highly productive white paper with good productivity that can sufficiently reduce wire wear.

  The present invention contains heavy calcium carbonate as a pulp and filler for internal addition, and among fibers obtained by disaggregation according to JIS P 8220, the proportion of fibers having a fiber length of 0.2 μm or more and less than 0.5 μm is 20 % Or more and 40% or less.

  Preferably, the filler for internal addition further contains regenerated particles and / or talc, and the average particle size of the regenerated particles and / or talc is 5 to 20 times the average particle size of the heavy calcium carbonate. It is.

  Preferably, the average particle diameter of the regenerated particles and / or talc is 12 μm or more and 23 μm or less, and the ratio of the total of the regenerated particles and / or talc to the heavy calcium carbonate is 85:15 to 15% by dry weight. 60:40.

  Preferably, the paper contains a coagulant, and the coagulant is obtained by graft polymerization of at least two different types selected from the group consisting of polyethyleneimine, polyamine, polydadomac and polyacrylamide as a polymer component. It is.

  Preferably, the coagulant has a dendrogram shape.

  Preferably, the coagulant has a molecular weight of 500,000 to 3,000,000 and a charge density of 10 to 25 meq / g.

  According to the present invention, although it is a paper containing heavy calcium carbonate as an internal filler, even when paper is made at a high speed of 1,300 m / min or more, for example, the yield of heavy calcium carbonate is good, so that the wire wear resistance Can be sufficiently reduced, and high whiteness paper with good productivity can be provided.

Partial configuration example of recycled particle manufacturing equipment flow

  Next, an embodiment of the present invention will be described.

(Outline of the present invention)
In the present invention, fine pulp fibers of 0.2 μm or more and less than 0.5 μm are contained in an amount of 20% or more and 40% or less of the whole pulp. By containing a shape-like polymer compound, even when heavy calcium carbonate is used as an internal filler, for example, even when paper making is performed at a high speed of 1,300 m / min or more, the yield of heavy calcium carbonate is increased. Since it is good, the wire wear resistance can be reduced, and a paper with high whiteness can be obtained.

(Specific embodiments of the present invention)
Next, an embodiment of the present invention will be described.

[Formulation process]
After the raw pulp is beaten in the preparation process and the fiber length is adjusted to a predetermined range, various chemicals such as a coagulant and a paper strength improver are added, processed to a predetermined quality, and sent to a paper machine.

〔pulp〕
The pulp used in the present invention preferably has many fine fibers having a fiber length of 0.2 μm or more and less than 0.5 μm obtained by disaggregation according to JIS P 8220. Heavy calcium carbonate used as an internal filler is obtained by pulverizing limestone, so there are many fine particles. To improve the yield of fine particles, pulp fibers also contain a certain amount of fine fibers. It is important to keep fine heavy calcium carbonate on the pulp fibers. Pulp fibers of less than 0.2 μm have a great effect of retaining heavy calcium carbonate in the form of fibers, while the yield of fibers of less than 0.2 μm itself is poor, resulting in a deterioration in the yield of heavy calcium carbonate. On the other hand, pulp fibers of 0.5 μm or more have a long fiber length, so that the effect of retaining heavy calcium carbonate with many fine particles is small, and the yield of heavy calcium carbonate is not improved.

  The content of the pulp fiber of 0.2 μm or more and less than 0.5 μm is required to be 20% or more and 40% or less, preferably 25 to 30% of the whole pulp. By containing fine fibers, the yield of heavy calcium carbonate as a filler can be improved, and the whiteness of the resulting paper is improved. In addition, heavy calcium carbonate contained in white water that passes through the wire without yielding on the paper can be reduced, so the number of contact between the heavy calcium carbonate and the wire can be reduced, and the wire wear resistance is sufficient. Can be improved. Heavy calcium carbonate, in particular, tends to generate many fine particles during the process of pulverizing limestone, and easily damages the wire because of poor yield to pulp. However, when the disaggregated fiber length is 0.2 μm or more and less than 0.5 μm and the fine pulp fibers are contained in an amount of 20% or more and 40% or less of the whole pulp, fine heavy calcium carbonate is easily produced on the fine fibers. When there are many fibers with a long disaggregation fiber length and the pulp fibers with a disaggregation fiber length of 0.2 μm or more and less than 0.5 μm are less than 20% of the whole pulp, the yield of heavy calcium carbonate fine particles decreases and the wire wear resistance Not only worsening, but also whiteness of the resulting paper tends to decrease, which is not preferable. There are many fibers with a short disaggregation fiber length, and when the pulp fiber with a disaggregation fiber length of 0.2 μm or more and less than 0.5 μm exceeds 40% of the whole pulp, the yield of the fine fiber itself of less than 0.2 μm itself is low. The yield of the heavy calcium carbonate is also lowered, the wire wear resistance is deteriorated, and the whiteness of the obtained paper is easily lowered, which is not preferable. In addition, fine fibers are likely to accumulate in the paper machine system, and the spoiled fibers may become foreign matter and enter the paper, which may easily cause foreign matter defects.

<Freeness>
The fiber length can be adjusted by a known technique. For example, the beating condition can be changed with a refiner or the like, and the freeness can be adjusted to be within the above range. The freeness is preferably 500 to 600 ml, more preferably 520 to 580 ml, if it is freeness of softwood bleached pulp (NBKP). When the amount exceeds 600 ml, beating does not proceed and the length of the long fiber increases, and when it is less than 500 ml, the length of the short fiber increases. Similarly, if it is the freeness of hardwood bleached pulp (LBKP), 400-500 ml is preferable, More preferably, it is 420-480 ml. For the same reason, the freeness of mechanical pulp is preferably 100 ml to 150 ml, more preferably 120 ml to 150 ml. If it is a waste paper pulp, 280 ml-380 ml are preferable and 300 ml-340 ml are more preferable.

  The pulp used in the present invention is not particularly limited, and for example, chemical pulp, mechanical pulp, waste paper pulp or other pulp can be used, and one or two or more of these are appropriately selected and used. be able to.

  As the chemical pulp, for example, unbleached softwood pulp (NUKP), unbleached hardwood pulp (LUKP), bleached softwood pulp (NBKP), bleached hardwood pulp (LBKP) and the like can be used.

  Examples of the mechanical pulp include stone grand pulp (SGP), pressurized stone grand pulp (PGW), refiner ground pulp (RGP), chemi-ground pulp (CGP), thermo grand pulp (TGP), ground pulp (GP), Thermo mechanical pulp (TMP), Chemi thermo mechanical pulp (CTMP), refiner mechanical pulp (RMP), etc. are mentioned.

  Examples of the waste paper pulp include disaggregation / deinking waste paper pulp, disaggregation / deinking / bleached waste paper pulp and the like manufactured from magazine waste paper, flyer waste paper, office waste paper, newspaper waste paper, and Kamihaku waste paper.

  In addition, rag pulp, straw pulp, esparto pulp, bagasse pulp, bamboo pulp, kenaf pulp, and other auxiliary pulps such as bast pulp, etc. made from cotton, flax, hemp, jute, manila hemp, ramie, etc. are used. You may do it.

  2-100 mass parts is preferable and, as for the compounding ratio of a conifer bleached pulp among 100 mass parts of all the pulp which comprises a base paper, 5-20 mass parts is still more preferable. If it is less than 2 parts by mass, it is not preferable because a paper having sufficient strength cannot be obtained. If it exceeds 30 parts by mass, fine fibers less than 0.2 μm are beaten to 0.2 μm or more and less than 0.5 μm. This is not preferable because not only the yield of heavy calcium carbonate containing fine particles tends to decrease, but also the whiteness of the resulting paper tends to decrease. The softwood bleached pulp before beating has a fiber length of 2 to 5 mm, which is longer than the fiber length of hardwood bleached pulp (0.5 to 1.5 mm). It is necessary to proceed beating so that fibers of 2 mm to less than 0.5 mm are 20% or more and 40% or less of the whole pulp fiber, fine fibers having a fiber length of less than 0.2 mm are likely to be generated, and the yield of heavy calcium carbonate Is not preferable because the wire wear is not only worsened and the whiteness of the resulting paper is also easily lowered. The blending ratio of the hardwood bleached pulp is preferably 70 to 98 parts by mass, and more preferably 80 to 95 parts by mass so as to complement the softwood bleached pulp. In addition, because waste paper pulp is disaggregated and pulped again, there are many fine fibers of less than 0.2 μm, and when used, the degree of beating is minimized to suppress the generation of fibers of less than 0.2 μm. There is a need to. Sticky beating is effective for such beating.

  As described above, in the present invention, in order to improve the yield of heavy calcium carbonate, 2-30 parts by mass of softwood bleached pulp adjusted to 500-600 ml freeness, and hardwood bleached pulp adjusted to 400-500 ml freeness It is preferable to use 70 to 98 parts by mass and adjust so that fibers having a fiber length of 0.2 mm or more and less than 0.5 mm occupy 20% or more and 40% or less, preferably 25 to 30% of the whole pulp fiber. Furthermore, in order to favorably yield a fiber having a length of 0.2 mm or more and less than 0.5 mm, a longer fiber, a fiber having a fiber length of 0.5 mm or more and less than 1.2 mm, is preferably 55 to 85% of the total pulp fiber, preferably Is adjusted to occupy 60 to 80%, in particular, the yield of fine fibers of 0.2 mm or more and less than 0.5 mm and heavy calcium carbonate can be improved, and only high whiteness paper can be obtained. No wire wear can be improved.

[Filler]
As a filler, it is essential to contain heavy calcium carbonate.

  The particle diameter of heavy calcium carbonate is preferably larger in order to improve the yield and prevent the wire from being worn, but in order to enhance the whiteness enhancement effect, it is preferable that the particle diameter is small and the specific surface area is large. In order to improve both the yield improvement and the whiteness improvement effect of the heavy calcium carbonate particles, it is necessary to have an appropriately fine particle diameter, and preferably the average particle diameter is about 0.5 to 2.0 μm. It is. When the average particle size is less than 0.5 μm, as described above, a pulp having a fiber of 0.2 μm or more and less than 0.5 μm is 20% or more and 40% or less of the whole pulp, and the tree shape is as described above. Yes, even if a predetermined amount of a coagulant having a specific molecular weight and charge density and a predetermined amount of the above-mentioned flocculant having a specific molecular weight and charge density are added, it is difficult to sufficiently retain heavy calcium carbonate. Therefore, it is not preferable. If the average particle diameter exceeds 2.0 μm, the specific surface area of heavy calcium carbonate is small and the whiteness tends to decrease, which is not preferable, and the binding between pulp fibers tends to be locally inhibited, and the surface strength is increased. Is not preferable because there is a possibility of lowering. In addition, the average particle diameter as used in this specification was computed based on the diameter of the minimum circle | round | yen (particle circumscribed circle) which can include particle | grains about the pigment particle | grains image | photographed with the electron microscope.

  The amount of heavy calcium carbonate added is preferably 2 to 10 parts by weight, more preferably 3 to 8 parts by weight, based on 100 parts by weight of pulp. If it is less than 2 parts by mass, sufficient whiteness cannot be obtained, and if it exceeds 10 parts by mass, wire wear and surface strength are likely to deteriorate, such being undesirable.

  In addition to heavy calcium carbonate, fillers generally used for papermaking can be used in combination. For example, light calcium carbonate, titanium oxide, talc, silica, clay, colloidal hydrous silica (commonly called white carbon), inorganic fillers such as aluminum hydroxide, synthetic polymer fine particles such as polystyrene resin and urea formaldehyde resin, paper sludge Known fillers such as regenerated particles or regenerated particle aggregates regenerated from black floss can be used. There is no restriction | limiting in particular about the shape of these inorganic fillers, Various things, such as a granular form, tension form, spindle shape, plate shape, and an amorphous, can be used.

  Among these, the combined use of talc and / or regenerated particles, preferably regenerated particle aggregates, can improve the yield of fine pulp fibers of 0.2 μm or more and less than 0.5 μm, that is, heavy carbon dioxide with many fine particles. Calcium can be effectively retained on paper, and paper with higher whiteness is preferable because it can be manufactured with less wire wear. In particular, among the regenerated particle aggregates, regenerated particle aggregates obtained by setting the primary firing temperature described below to 300 ° C. or higher and lower than 500 ° C. have higher whiteness than regenerated particle aggregates calcined at a temperature of 500 ° C. or higher. The whiteness of the resulting paper is also easy to improve, which is preferable.

  Talc is preferred because it is plate-like and has a strong anionic surface, so it tends to agglomerate with the fine pulp fibers and heavy calcium carbonate particles mixed with the above-mentioned coagulant, and the yield tends to increase. It is done. The reason why the regenerated particle aggregates are preferable is considered to be that the mass shape of the ranchu is easy to improve the yield of heavy calcium carbonate having many fine fibers and fine particles of 0.2 μm or more and less than 0.5 μm.

  As talc and regenerated particles, preferably regenerated particle aggregates, generally known chemicals can be used as they are, but it is preferable to use particles having an average particle size of 12 μm to 23 μm. In the case of particles having an average particle size of less than 12 μm, the particles fall off together with fine fibers as small as 0.2 μm or more and less than 0.5 μm and are difficult to yield, and 0.2 μm or more adhered to talc and / or regenerated particles, preferably regenerated particle aggregates. This is not preferable because the yield of fine fibers less than 0.5 μm and heavy calcium carbonate which is fine particles is also lowered. If the size is larger than 23 μm, there is little possibility that the yield will be lowered. On the other hand, since the particles are large, the binding between pulp fibers is likely to be inhibited, and the surface strength may be locally weakened.

  The ratio of heavy calcium carbonate to talc or regenerated particles, preferably regenerated particle aggregates, is preferably 85:15 to 60:40, more preferably 80:20 to 65:35 in terms of absolute dry weight. If it exceeds 85:15 and the amount of heavy calcium carbonate increases, the yield of heavy calcium carbonate with a large amount of fine fibers and fine particles of 0.2 μm or more and less than 0.5 μm tends to decrease, and not only the whiteness is inferior but also wire wear It is not preferable because the property is likely to deteriorate. If the ratio is less than 60:40 and the amount of talc or regenerated particles, preferably aggregates of regenerated particles is increased, it is not preferable because sufficient whiteness is hardly obtained.

  The amount of filler added is the total of heavy calcium carbonate, talc, regenerated particles, preferably regenerated particle aggregates, preferably 2 to 10 parts by weight, and 3 to 8 parts by weight with respect to 100 parts by weight of pulp. Is more preferable. If the amount is less than 2 parts by mass, a sufficient whiteness improvement effect cannot be obtained, and if it exceeds 10 parts by mass, the wire wear resistance is deteriorated, which is not preferable.

  The regenerated particles and regenerated particle aggregates that can be used in the present invention can be obtained by the following production method.

(Production process of regenerated particles and regenerated particle aggregates)
The recycled particles are obtained by using the deinked floss separated from the pulp fiber in the deinking process of the used paper processing equipment for producing the used paper pulp as a main raw material, and then dehydrating, drying, burning and grinding the main raw material. The combustion process includes at least a two-stage combustion process including a first combustion furnace and a second combustion furnace after which the deinking floss burned in the first combustion furnace is burned again. 1 combustion furnace performs a combustion process at 300 degreeC or more and less than 500 degreeC.

  Next, the production process of regenerated particles will be described in detail.

  FIG. 1 shows a partial configuration example (an example of equipment including a drying / combustion process and a combustion process) of a production facility flow of regenerated particles. This equipment is equipped with various sensors, and controls the state of combustibles, equipment, and processing speed.

  The deinking floss separated from the pulp fiber in the deinking process for producing waste paper pulp (not shown) is dehydrated by a known dehydration equipment (not shown) through various operations. It is desirable that the raw material after dehydration has a high water content of 40% or more, preferably less than 90%, particularly 45% to 70%, more preferably more than 50% to 60%.

  The material 10 after such dehydration is desirably pulverized to a particle size of 40 mm or less by a pulverizer (or pulverizer). The raw material 10 is cut out from the storage tank 12 and charged by a charging machine 15 from one side of the first combustion furnace 14 which is an internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis. An exhaust gas chamber 16 is provided on one side of the first combustion furnace 14, and an exhaust chamber 18 is provided on the other side. Hot air is blown from the other side of the first combustion furnace 14 through the discharge chamber 18, charged from the one side, and sequentially transferred to the other side as the first combustion furnace 14 rotates. It is designed to dry and burn.

  Here, it is desirable that the hot air blown into the first combustion furnace 14 has an oxygen concentration of 0.2% to 20%. The temperature in the furnace is preferably 300 ° C. or more and less than 500 ° C., more preferably 400 ° C. or more and less than 500 ° C., and particularly preferably 400 ° C. or more and less than 450 ° C. Hot air is blown from a hot air generating furnace 20 provided with a burner 20A.

  From the exhaust gas chamber 16, exhaust gas subjected to drying and combustion is sent into the recombustion chamber 22. The fine powder of the combustion material contained in the exhaust gas is discharged from the lower part of the exhaust gas chamber 16 and reused. The exhaust gas is recombusted by the burner in the recombustion chamber 22, precooled by the precooler 24, passed through the heat exchanger 26, and discharged from the chimney 30 by the induction fan 28. Here, after raising the temperature of the outside air, the heat exchanger 26 is sent to the hot air generating furnace 20 and used for the hot air blown from the first combustion furnace 14 to recover the heat of the exhaust gas from the exhaust gas chamber 16. It is like that. The treatment of exhaust gas is effective for removing harmful substances contained in the exhaust gas.

  Combustion products that have undergone drying and combustion treatment in the first combustion furnace 14 are charged into a second combustion furnace 32 that is an external heat kiln furnace in which the main body is placed horizontally and rotates around the central axis. The particle size of the combusted material to be charged is preferably 40 mm or less. As a heat source in the second combustion furnace 32, it is preferable to use an electric adjustment that allows easy temperature control in the second combustion furnace 32 and easy temperature control in the longitudinal direction. Therefore, the first combustion is indirectly performed by an electric heater. It is desirable that the second combustion furnace 32 be of an external heating type in which the combustion product obtained from the furnace 14 is burned again.

  In the second combustion furnace 32, the oxygen concentration is 5% to 20%, preferably 10% to 20%, particularly preferably 10% to 15% by an air or oxygen supply mechanism (not shown) for adjusting the oxygen concentration. It is desirable to burn so that it becomes%. The temperature is preferably 550 ° C. to 780 ° C., more preferably 600 ° C. to 750 ° C. Further, the residence time in the second combustion furnace 32 is 60 minutes or more, more preferably 60 minutes to 240 minutes, particularly 90 minutes to 150 minutes, and optimally 120 minutes to 150 minutes. Desirable to burn.

  The regenerated particles that have been burned are cooled by a cooler 34, and then sorted by a particle size sorter 36 such as a vibration sieve, and the combustion is adjusted to a target particle size in a grinding process using a wet grinding machine or the like. The material is temporarily stored in the combustion product silo 38 and is sent to the application destination of the pigment or filler.

  In addition, although the case where deinking floss was used as a raw material was illustrated, even if it is a combustion thing which used as a raw material what mixed other papermaking sludges, such as papermaking sludge in a papermaking process, with deinking floss as a main raw material Good.

  In the paper of this embodiment, the above regenerated particles can be used as an internal filler. These recycled particles can be recycled and used by firing deinked floss, so there is no need to dispose of landfills as waste, contributing greatly to reducing environmental impact and saving resources. Is. Further, since the raw material is deinked floss generated in the waste paper processing step, there is an advantage that it is inexpensive, the amount of new natural inorganic mineral used can be suppressed, and the manufacturing cost is sufficiently reduced.

  In addition, since the furnace temperature of the first combustion furnace is as low as 300 ° C. or more and less than 500 ° C., particularly when used as an internal filler, paper with high whiteness is easily obtained, which is preferable.

  In the present invention, the regenerated particles obtained by the production process may be used as they are, or those coated with silica by the method described in Japanese Patent No. 3907688 or Japanese Patent No. 3935496 may be used. Specifically, after adding and dispersing the regenerated particles obtained in the above production process in an aqueous alkali silicate solution to prepare a slurry, a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid, etc. at a liquid temperature of 70-100 ° C. while stirring with heating. Is added to form silica sol, and the pH of the final reaction solution is adjusted to the range of 8.0 to 11.0 to obtain silica sol particles having a particle diameter of 10 to 20 nm on the surface of the regenerated particles. White pigments can be used. This silica-coated regenerated particles improve the oil absorption and opacity due to the silica precipitation effect by making calcium, silicon and aluminum into a mass ratio of 30 to 62:29 to 55: 9 to 35 in terms of oxides. Can do.

  The regenerated particles produced by the above method form a regenerated particle aggregate in which several individual particles are aggregated, and have an irregular shape such as a lump-like mass. With this irregularity, it is possible to improve the yield of heavy calcium carbonate with many fine fibers and pulp fibers of 0.2 μm or more and less than 0.5 μm, and to improve whiteness and reduce wire wear. There are advantages.

  As described above, in order to improve the yield of heavy calcium carbonate containing a large amount of fine particles, fibers having a fiber length of 0.2 mm or more and less than 0.5 mm are 20% or more and 40% or less, preferably 25 to 25% of the whole pulp fibers. In addition to occupying 30%, talc and / or regenerated particles having an average particle size of 12 μm or more and 23 μm or less, preferably regenerated particle aggregates are 85:15 to 60:40, preferably 80 to heavy calcium carbonate. When paper is added at a ratio of 20 to 65:35, the yield of heavy calcium carbonate is good, and paper having excellent whiteness can be efficiently obtained. Furthermore, it is preferable to use, as the regenerated particle aggregate, a regenerated particle agglomerate produced at a primary firing temperature described later of 300 ° C. or higher and lower than 500 ° C., because a paper with better whiteness can be obtained.

  In this embodiment, in order to further improve the yield of heavy calcium carbonate and talc and / or regenerated particles, preferably regenerated particle aggregates, it is preferable to combine the coagulants and flocculants described below.

<Coagulant>
In this embodiment, a coagulant is added to effectively adsorb heavy calcium carbonate containing fine fibers and fine particles to pulp fibers. As the kind of the coagulant, a coagulant obtained by graft polymerization of two or more kinds of polymer components is preferable. Examples of the polymer component include polyacrylamide (PAM), polyvinylamine (PVAm), polydiallyldimethylammonium chloride (Polydadomac, PDADMAC), polyamine (PAm), polyethyleneimine (PEI), polyethylene oxide (PEO), and polyacrylic. And acid salts and methacrylates. Among these, a coagulant obtained by graft polymerization of two or more polymer components selected from the group consisting of polyethyleneimine, polyamine, polydadomac and polyacrylamide is preferable. More preferably, polyethyleneimine is used as the main chain, and polyamine or polydadomac is used as the graft chain, and polyamine is preferably used as the graft chain. By using the coagulant having such a structure, the yield of fine fibers of 0.2 μm or more and less than 0.5 μm can be improved as compared with a conventional coagulant composed of one kind of component, and heavy carbon dioxide containing a large amount of fine particles. The yield of calcium can be improved.

  Moreover, it is not preferable that the polymerization state of two or more types of polymer components is a random copolymer in which two or more types of components are mixed alternately or randomly. In the random copolymer, the properties of each component combine to exhibit uniform agglomeration performance, so that the yield of fine fibers and fine filler particles can be sufficiently satisfied, as in the case of a conventional coagulant composed of one kind of component. Hateful. By graft-polymerizing the graft chain having the coagulation ability to the main chain having the cohesion ability, the effect of improving the yield of fine fibers and the yield of heavy calcium carbonate containing many fine particles can be obtained. Paper with excellent whiteness can be made with good wire wear.

  The shape of the coagulant may be a straight chain having only a main chain, a branched form in which a plurality of graft chains are graft-polymerized to the main chain, or a graft chain bonded to the main chain. Further, it may be a dendritic figure (branch and leaf shape) in which a graft chain component or a main chain component is graft-polymerized, or may be a network in which graft chains bonded to the main chain are cross-linked. A micellar shape in which a part of the chain is crystallized may be used. More preferably, it is a net-like or dendrogram that can adsorb fine heavy calcium carbonate efficiently to fine fibers, and fine fibers can be adsorbed to pulp fibers, most preferably a dendrogram.

  The ratio of the graft chain to the main chain varies depending on the structure and molecular weight, but is generally preferably 5 to 70% by mass, more preferably 10 to 50% by mass. If the amount is less than 5% by mass, the yield of fine heavy calcium carbonate and fine fibers tends to be low, and the wire wear is inferior. If the amount exceeds 70% by mass, the graft chain is too large and the agglomeration capacity is excessively increased. Is not preferred because it tends to deteriorate.

  The molecular weight of the coagulant is preferably 500,000 to 3,000,000, more preferably 1,000,000 to 2,000,000. If the molecular weight is less than 500,000, the yield of fine heavy calcium carbonate and fine fibers is likely to be lowered, and not only the whiteness of the resulting paper is likely to be lowered, but also the wire wear is inferior. When the molecular weight exceeds 3 million, fine heavy calcium carbonate tends to concentrate around the fine fiber, and not only the surface strength is lowered but also the formation is easily deteriorated. In addition, the molecular weight said by this invention means the weight average molecular weight measured by the gel permeation chromatography method (GPC method).

  The coagulant is preferably positively charged (cationic). The charge density is preferably 10 to 25 meq / g, and more preferably 15 to 20 meq / g. If it exceeds 25 meq / g, it is not preferable because it collects fine fibers and anion trash and is easily converted into a foreign substance, and it is not preferable because the formation tends to decrease. If it is less than 10 meq / g, the fine fibers and heavy calcium carbonate hardly aggregate. Thus, the surface strength of the obtained paper tends to decrease. In addition, the charge density of the present invention was measured by a colloid titration method using an anionic polymer as a specified solution.

  The addition amount of the coagulant is preferably 0.01 to 0.15 parts by mass, more preferably 0.03 to 0.10 parts by mass with respect to 100 parts by mass of the pulp. Exceeding 0.15 parts by mass is not preferable because the coagulant tends to concentrate around the fine fiber and not only becomes a foreign matter defect but also the formation tends to deteriorate. If the amount is less than 0.01 parts by mass, the yield of fine heavy calcium carbonate and fine fibers is lowered, and not only the whiteness is likely to be lowered, but also the wire wear property is liable to be deteriorated.

  In the present invention, in order to improve the yield of heavy calcium carbonate with a lot of fine particles, two kinds of fine fibers of 0.2 μm or more and less than 0.5 μm are added in addition to 20% or more and 40% or less of the whole pulp. By using a coagulant obtained by graft polymerization of the above polymer components, it is possible to improve the yield of heavy calcium carbonate, to obtain paper with high whiteness, and to suppress wire wear in a paper machine. Furthermore, the ratio of the main chain to the graft chain is 5 to 70% by mass, preferably 10 to 50% by mass, and graft polymerization is carried out in a dendrogram, and the molecular weight is 500,000 to 3 million, preferably 1 million to 2 million. And the charge density is 10 to 25 meq / g, preferably 15 to 20 meq / g, and 0.01 to 0.15 parts by mass, preferably 0.03 to 0.10 with respect to 100 parts by mass of pulp. By adding part by mass, the yield of heavy calcium carbonate, which is the object of the present invention, can be further improved, paper with higher whiteness can be obtained, and paper with sufficiently improved wire wear can be obtained. it can.

<Flocculant>
In this embodiment, after adding the coagulant, a specific flocculant is further added in the pre-stage of the paper making process following the pulp preparation stage, thereby further reducing fine fibers and fine particles of 0.2 μm or more and less than 0.5 μm. Improves the whiteness by improving the yield of heavy calcium carbonate with many particles and the effect of improving wire wear. Components of the flocculant include inorganic flocculants such as bentonite and colloidal silica, organic polymers such as polyacrylamide (PAM), polyvinylamine (PVAm), polyamine (PAm), polyethylene oxide (PEO), and polyethyleneimine (PEI). Any of the system flocculants can be used. However, more preferred are polyvinylamine and polyacrylamide, and particularly preferred is polyacrylamide because of its high aggregation ability. When paper is made after polyacrylamide is added, agglomerates may easily occur. Therefore, the aggregating agent is added before the screen, and the agglomerates generated after the addition are broken once on the screen and appropriately aggregated. It is preferable to weaken the property. As such a screen, a slit type having an opening of 0.33 to 0.37 mm is preferable because it has an excellent effect of suppressing the generation of aggregates.

  The molecular weight of the flocculant is preferably 10 million to 20 million, and more preferably 12 million to 16 million. If it exceeds 20 million, fine fibers and fine heavy calcium carbonate particles will be collected too much, and the formation will be deteriorated. If it is below 10 million, the fibers will not aggregate properly and the surface strength of the resulting paper will be reduced. Therefore, it is not preferable.

  The charge density of the flocculant is preferably 1 to 10 meq / g, more preferably 1 to 5 meq / g. If it exceeds 10 meq / g, it collects fine fibers and fine heavy calcium carbonate particles, and the formation tends to deteriorate. If it is less than 1 meq / g, it is difficult to collect fine fibers and fine heavy calcium carbonate particles. The surface becomes rough and the surface strength tends to decrease.

  The addition amount of the flocculant is preferably 0.05 to 0.30 parts by mass, and more preferably 0.10 to 0.20 parts by mass with respect to 100 parts by mass of the pulp. If the amount exceeds 0.30 parts by mass, fine fibers and fine heavy calcium carbonate particles are collected too much, and the formation tends to deteriorate. If the amount is less than 0.05 parts by mass, the fibers do not aggregate appropriately, and the surface strength is low. It is not preferable because it tends to decrease.

  Moreover, it is preferable to add the flocculant within 20 minutes or more and 40 minutes or less after mixing the pulp fibers containing fine fibers and the coagulant. If it is less than 20 minutes, the fine fibers and fine heavy calcium carbonate particles are difficult to yield, and if it exceeds 40 minutes, aggregates are generated and the formation tends to deteriorate.

  Thus, a flocculant having a molecular weight of 10 million to 20 million, preferably 12 million to 16 million, and a charge density of 1 to 10 meq / g, preferably 1 to 5 meq / g, is added to 100 parts by mass of pulp. 0.05 to 0.30 parts by mass, preferably 0.10 to 0.20 parts by mass, by adding the specific coagulant, particularly a dendritic graft polymer, Since a state in which a lot of fine heavy calcium carbonate particles are agglomerated can be directly formed on paper, an effect of improving the yield of heavy calcium carbonate can be obtained. On the other hand, when the specific flocculant is not used, the fine fibers are difficult to yield, so the fine heavy calcium carbonate particles are difficult to yield, and the fine fibers of 0.2 μm or more and less than 0.5 μm and the fine heavy carbonate It is not preferable because it is difficult to improve the yield of both calcium particles, the whiteness is likely to decrease, and the wire wear resistance is also likely to decrease.

  As described above, in order to improve the yield of heavy calcium carbonate containing a large amount of fine particles, fibers having a fiber length of 0.2 mm or more and less than 0.5 mm are 20% or more and 40% or less, preferably 25 to 25% of the whole pulp fibers. In addition to occupying 30%, talc and / or regenerated particles, preferably regenerated particle aggregates are used in combination, and two or more types of polymer components are graft-polymerized to form a dendritic aggregate having the above molecular weight and charge density The yield of fine heavy calcium carbonate particles can be effectively improved by blending a predetermined amount of the above-mentioned agent and the above-mentioned flocculant having the molecular weight and charge density. It is preferable because of its excellent properties. In addition, by performing these combinations, the conventional ash yield of about 50% can be improved to 70% or more, and the yield of internal fillers such as heavy calcium carbonate can be particularly improved.

<Other chemicals>
In this embodiment, in addition to the above coagulant and flocculant, if necessary, a filler, an internal sizing agent, a fixing agent, a yield improver, a bulking agent, a cationizing agent, a paper strength enhancer, an antifoaming agent, Various paper making aids such as colorants and dyes may be added.

[Paper making process]
The papermaking equipment that can be used in this embodiment is not particularly limited, but in order to improve the yield of fine fibers, a wire part made of a gap former, a press part made of a straight-through type without an open draw, and a pre-made made of a single deck dryer. It is preferable to combine the dryer parts.

<Wire part (head box)>
The prepared pulp slurry is sent to the wire part via the head box. The wire part is not particularly limited, such as a long-form former, a combination of a long-form former and an on-top former, or a twin wire former, but the paper jet ejected from the head box is immediately sandwiched between two wires. Since the gap type gap former is dehydrated from both sides, the movement of the pulp fibers is suppressed and the formation is preferable.

<Press part>
The paper layer in the wire part is transferred to the press part and further dewatered. The press machine can be either a straight-through type, an invar type, or a reverse type, and a combination of these can also be used, but the straight-through type with no open draw is easy to hold the paper, This is preferable because there are few operational troubles such as paper breaks. As a dehydration method, a conventional method such as a suction roll method or a grooved press method can be used. However, if a shoe press with a high dehydration property is used, the linear pressure applied to the paper can be reduced, and the ground pressure can be reduced. It is preferable because the deterioration of the can be reduced.

<Pre-dryer part>
The wet paper that has passed through the press part is transferred to a single-deck pre-dryer part and dried. The pre-dryer part is preferably a no-open draw type single deck dryer which can be dried efficiently with little paper breakage. A drying method using a double deck method is also possible, but it is not preferable because it is inferior to a single deck method in terms of operability such as canvas marks, paper breaks, wrinkles, and paper splicing.

  The paper obtained as described above is a paper containing heavy calcium carbonate containing a lot of fine particles as an internal filler, and pulp fibers of 0.2 μm or more and less than 0.5 μm are contained in 20% or more of the whole pulp. Talc or regenerated particles, preferably regenerated particle aggregates having an average particle size of 40% or less and further having a particle size of 12 μm or more and 23 μm or less and 5 to 20 times larger than the average particle size of heavy calcium carbonate, Since it is contained at a ratio of 85:15 to 60:40, preferably 80:20 to 65:35 with respect to the heavy calcium carbonate, a yield of heavy calcium carbonate is good, and a paper having excellent whiteness is obtained. It can be efficiently manufactured in a state where the wire wear is good.

  Next, although the paper of this invention is demonstrated still in detail based on an Example, this invention is not limited only to these Examples.

  First, NBKP 10% by mass and LBKP 90% by mass as raw material pulp were adjusted to the freeness shown in Table 1 and mixed, and each 100 parts by mass (absolutely dry amount) of the pulp was cationized starch (in solid content). Product No .: Amylofax T-2600, manufactured by Abebe Japan Co., Ltd.) 1 part by mass, the filler described in Table 1, 0.08 parts by mass of a coagulant, and 0.15 parts by mass of a flocculant were added to obtain a pulp slurry. . The chemicals used are as follows.

・ Filler a) Heavy calcium carbonate Product number: Hydrocurve 60, manufactured by Omiya Korea, average particle size: 2.13 μm
b) Talc Product number: Talc NTL, manufactured by Nippon Talc Co., Ltd., average particle size: 12 μm
c) Clay Product number: Contour 1500, manufactured by Imeris, average particle size: 2.5 μm
d) Regenerated particle aggregate Regenerated particle A: manufactured by adjusting the particle diameter according to the production method of Japanese Patent No. 3869455. Specifically, the deinking floss discharged from the waste paper treatment process is dehydrated to a moisture content of 60% (dehydration process), dried at 120 ° C. (drying process), and the moisture content at the firing process inlet becomes 3%. And firing at 550 ° C. so that the unburned portion becomes 7% in the first firing step, and firing so that the unburned portion becomes 12 mass% in the second firing step (baking step), and the particle size A 500 μm regenerated particle agglomerate was produced.

  Regenerated particles B: Regenerated particle aggregates produced in the same manner as the regenerated particles A were used except that they were fired at 400 ° C. in the first firing step.

  The filler was prepared by pulverization using a wet pulverizer (product number: planetary mill, manufactured by Seishin Enterprise Co., Ltd.) and pulverizing until the average particle diameter reached the values shown in Table 1.

  In addition, the average particle diameter of this invention was measured as follows. The obtained paper is cut into A4 size and pasted using a commercially available cellophane tape so as to cover both the front and back surfaces. After pasting, the cellophane tape on one side is peeled off together with the paper, and the paper is peeled from the approximate center in the thickness direction, and the paper is roughly divided into two in the thickness direction. With respect to the two sheets of peeled paper, samples each having a length and width of 5 mm were cut out at a point of Acm from the upper side to the lower side and Acm from the left side, with the short side as the upper side. Here, A is an integer of 1 to 5, and 10 samples were collected face to face. The peeled surface (the surface inside the paper) of the cut sample was photographed at a magnification of 12000 using a scanning electron microscope (model number: S-2150, manufactured by Hitachi, Ltd.). The particle diameter was measured for the filler particles closest to the point Bcm from the upper side to the lower side of the photograph and Bcm from the left side, and the entire particles being photographed. Here, B is an integer of 1 to 5, and after obtaining the particle diameter of 5 particles from one sample and calculating the particle diameter for a total of 50 pigment particles, the average of 50 particle diameters is simply averaged. The particle diameter was taken. Since the pigment particles are not perfect circles, the diameter of the smallest circle that can contain the pigment particles is taken as the particle diameter.

・ Coagulant (all positively charged and cationic)
a) PEI-PAm graft polymer (polyamine grafted polyethyleneimine (product number: SC924, manufactured by Hymo Co., Ltd.), ratio of graft chain to main chain: 30% by mass) In Examples 28 and 29, the shape of the polymer was In Examples 30 to 32, a molecular weight was used, and in Examples 33 to 36, a coagulant having a charge density adjusted as described in the table was used.
b) PDADMAC-PAm graft polymer (polyamine graft polyDADMAC)
c) Polyacrylic acid Na-PAm graft polymer (polyamine grafted sodium polyacrylate)
d) PEI-PDADMAC graft polymer (polyDADMAC grafted polyethyleneimine)

-Flocculant a) Cation PAM (Product No .: ND270, manufactured by Hymo Co., Ltd.) In addition, a flocculant having a molecular weight adjusted in Examples 39 to 42 and a charge density adjusted in Examples 43 to 46 as shown in the table was used. .
b) Colloidal silica (product number: NP442, manufactured by Eka Chemicals Co., Ltd.)
c) Polyethyleneimine (Product No .: Polymin PR8150, manufactured by BASF)
Next, a web was manufactured through a wire part made of a gap former, a straight-through press part without an open draw, and a pre-dryer part made of a single deck dryer. The weight of the paper obtained was 64 g / m ^{2 as} measured according to JIS P 8124. This paper was evaluated as follows. The results are shown in Table 1.

(A) Ash content yield A piece of paper is cut out from a sheet containing no filler (blank) and a sheet containing filler, dried at 105 ° C. for 3 hours, and then measured for dry weight. Next, this absolutely dry paper piece is incinerated according to JIS P 8251: 2003 “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method” to determine the weight of ash content contained in the sheet. Filler yield (%) was calculated from the following formula.
Yield of filler = {(weight of sheet ash with filler / absolute dry weight−weight of blank sheet ash / absolute dry weight)} / filling ratio × 100

(B) Disaggregated fiber length The sheet was disaggregated according to JIS P 8220: 1998 “pulp-disaggregation method”, and the fiber length distribution was obtained with FiberLab manufactured by Metso. The weighted average content ratio was determined for fibers having a fiber length of less than 0.2 μm, 0.2 μm or more and less than 0.5 μm, or less than 0.5 μm.

(C) Degree of wire wear The wire after 24 hours of continuous operation was magnified 10 times with a magnifying glass and visually evaluated as follows.
A: Although the wire has minute scratches, the wire is not worn and can be used.
○: The wire is scratched, but the wire is slightly worn and can be used.
X: The wire has scratches, and defects due to wear of the wire are recognized, so that it cannot be used in practice.

(D) Whiteness Measured according to JISP8148: 2001 “Paper, paperboard and pulp—Method of measuring ISO whiteness (diffuse blue light reflectance)”. If it is 83% or more, the whiteness is particularly excellent. If it is 81% or more, the whiteness is good. If it is 79% or more, the whiteness is inferior, but it can be used. Is inferior in appearance.

(E) Formation The formation of the paper was visually evaluated as follows.
A: The formation is uniform, the image on the printed surface of the following surface strength test is uniform, and the formation is excellent.
○: The texture is uneven, but the image on the printed surface of the following surface strength test is uniform and can be used in practice.
X: The formation is poor, the printed surface image of the following surface strength test is non-uniform, and the appearance is inferior, so it cannot be used.

(F) Surface strength Using an offset printing machine (model number: Lithopia L-BT3-1100, manufactured by Mitsubishi Heavy Industries, Ltd.), color 4 using color ink (product number: ADVAN, manufactured by Dainippon Ink & Chemicals, Inc.) 5000 copies of color printing were performed. With respect to this printed surface, the extent of occurrence of a tray on the paper surface (a trouble in which a part of the paper surface is taken off by a blanket of a printing machine and printing is lost) is visually and magnified (10 times). Evaluation was performed based on the evaluation criteria.
A: No omission, excellent printability, and practical use.
○: Some omission occurs and printability is slightly inferior, but it can be used.
X: Omission occurs, the printability is inferior, and actual use is impossible.

  From Table 1, since the paper of an Example uses heavy calcium carbonate as a filler and contains the fine fiber of 0.2 micrometer or more and less than 0.5 micrometer in 20% or more and 40% or less of the whole pulp, heavy carbonate Paper with good calcium yield, high whiteness, and excellent wire wear.

  On the other hand, even if the paper of the comparative example contains heavy calcium carbonate, the pulp fiber of 0.2 μm or more and less than 0.5 μm does not contain 20% or more and 40% or less of the total pulp. This paper is inferior in wire wear.

  According to the present invention, a paper containing heavy calcium carbonate as an internal filler and having high whiteness can be provided with high productivity.

DESCRIPTION OF SYMBOLS 10 Raw material 12 Storage tank 14 1st combustion furnace 15 Charger 16 Exhaust gas chamber 18 Exhaust chamber 20 Hot air generating furnace 20A Burner 22 Recombustion chamber 24 Precooler 26 Heat exchanger 28 Induction fan 30 Chimney 32 Second combustion furnace 34 Cooler 36 Particle size sorter 38 Combustion product silo

Claims (6)

  Of the fibers containing heavy calcium carbonate as a pulp and filler for internal addition and disaggregated according to JIS P 8220, the proportion of fibers having a fiber length of 0.2 μm or more and less than 0.5 μm is 20% or more and 40%. Paper characterized by:   The filler for internal addition further contains regenerated particles and / or talc, and the average particle size of the regenerated particles and / or talc is 5 to 20 times the average particle size of the heavy calcium carbonate. The paper according to claim 1, wherein:   The average particle diameter of the regenerated particles and / or talc is 12 μm or more and 23 μm or less, and the total ratio of the regenerated particles and / or talc with respect to the heavy calcium carbonate is 85:15 to 60:40 in absolute dry weight. The paper according to claim 2, wherein:   The paper contains a coagulant, and the coagulant is a coagulant obtained by graft polymerization of at least two different types selected from the group consisting of polyethyleneimine, polyamine, polydadomac and polyacrylamide as a polymer component. The paper according to any one of claims 1 to 3, characterized in that:   The paper according to claim 4, wherein the coagulant has a dendrogram shape.   The paper according to claim 4 or 5, wherein the coagulant has a molecular weight of 500,000 to 3,000,000 and a charge density of 10 to 25 meq / g.

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