JP2009242981A - Paper highly compounded with waste paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide paper suppressed in developing foreign matter defects due to fine fiber yield drop, developing aggregates due to fine fiber yield rise, and developing foreign matter defects due to residual ink aggregation, even if used pulp rich in such fine fibers, such as waste paper. <P>SOLUTION: In the paper, a coagulant is internally added in pulp, wherein the coagulant is obtained by graft copolymerization of two or more different polymer components. Preferably, the polymer components is selected from the group consisting of polyethyleneimine, polyamine, polyDADMAC, and polyacrylamide. In the pulp, 70 mass% or more of the whole pulp is preferably deinked pulp (MDIP) regenerated from magazine waste paper or handbill waste paper. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to paper made using a pulp containing a large amount of fine fibers such as deinked pulp and a method for producing the same.

  From the viewpoints of environmental conservation, resource saving, and recycling, the use of waste paper has increased dramatically, and the production of recycled paper using waste paper pulp has also increased. On the other hand, for the recycling of waste paper pulp, it is necessary to disaggregate, deink, and bleach the recovered waste paper. In the disaggregation and deinking processes, mechanical pressure is applied to the fibers, and in the bleaching process, the pulp fibers are damaged by bleaching chemicals. For example, recycled paper pulp has lower fiber strength and more fine fibers than chemical pulp produced from wood. When the fiber strength is weak, the strength and rigidity of the resulting paper is inferior, and when there are many fine fibers, not only the pulp fibers are retained on the paper, but the recovered resources cannot be used effectively, but the yield is also reduced. There is a problem in that the fine fibers that have not accumulated accumulate inside the paper machine, resulting in foreign matter defects and a deterioration in paper quality. Further, it is difficult to completely remove the ink component from the deinked pulp even after the above process, and there is a problem that the ink component that cannot be completely removed is aggregated to form a foreign matter defect.

  In order to improve the yield of fine fibers, it is necessary to adsorb the fine fibers to the pulp fibers. Since both fine fibers and pulp fibers are anionic, generally a cationic polymer compound or a cationic inorganic chemical such as a sulfuric acid band is added as a coagulant. However, if the yield of the fine fibers is too good, there is a problem that, on the contrary, the fine fibers are gathered in one place and agglomerates are formed.

  Patent Document 1 discloses a paper production method in which a cationic acrylamide polymer is added in advance to a slurry of recycled pulp made from waste paper, but the acrylamide polymer has a strong aggregating action and yields fine fibers. Even though the occurrence of foreign matter defects due to the reduction can be prevented, the occurrence of foreign matter defects due to the aggregation of aggregates and ink components (residual ink) that could not be removed cannot be prevented.

  In addition, Patent Document 2 includes a water-soluble cationic polymer subpolymer, a water-soluble cationic polymer main polymer, and anionic organic polymer fine particles, and even a paper material having a lot of fine fibers has no foreign matter defects. Although a method for producing a small amount of paper is disclosed, it is necessary to use three types of polymers in this method, and there are many fluctuation factors as compared with a method for producing two types of a normal flocculant and a coagulant, Not only is stable operation difficult, but cost increases due to an increase in purchased chemicals are inevitable. Further, the disclosed water-soluble cationic polymer main polymer is based on acrylamide, and the water-soluble cationic polymer sub-polymer is a dimethyldiallylammonium polymer or a copolymer with acrylamide, (Meth) acryloyloxyethyltrimethylammonium chloride polymer or copolymer with acrylamide, both of which have a strong agglomeration effect, so the effect of suppressing the occurrence of foreign matter defects due to improved yield of fine fibers is Although it is high, there is a problem that agglomerates are generated due to excessive aggregation, and a foreign matter defect due to agglomeration of residual ink occurs.

In this way, while improving the yield of fine fibers and preventing the occurrence of foreign matter defects, it is possible to produce paper that prevents the formation of aggregates without excessively agglomerating fine fibers and prevents the aggregation of residual ink. The method has not yet been obtained.
JP-A-5-9892 JP 2005-54311 A

  The main problem to be solved by the present invention is that, even when pulp containing a large amount of fine fibers such as waste paper is used, the occurrence of foreign matter defects due to the decrease in the yield of fine fibers, the generation of agglomerates due to the increase in yield, and the residual ink An object of the present invention is to provide a paper in which the occurrence of foreign matter defects due to aggregation is suppressed.

The present invention that has solved this problem is as follows.
(1) Paper in which a coagulant is internally added to pulp, wherein the coagulant is a coagulant obtained by graft polymerization of two or more different polymer components.
(2) The paper according to (1), wherein the polymer component is selected from the group consisting of polyethyleneimine, polyamine, polydadomac and polyacrylamide.
(3) The paper according to (1) or (2) above, wherein the coagulant has a tree-like shape.
(4) The paper according to any one of claims (1) to (3), wherein the coagulant has a molecular weight of 500,000 to 3,000,000 and a charge density of 10 to 25 meq / g.
(5) In the pulp, 70% by mass or more of the total pulp is deinked pulp (MDIP) regenerated from waste magazine paper or leaflet waste paper, according to any one of (1) to (4), Paper.
(6) In addition to the coagulant, the coagulant further contains polyacrylamide having a molecular weight of 12 to 16 million and a charge density of 1 to 10 meq / g, (1) -Paper in any one of (5).

  According to the present invention, even when a pulp containing a large amount of fine fibers such as waste paper is used, the occurrence of foreign matter defects due to a decrease in the yield of fine fibers, the occurrence of agglomerates due to the improvement in yield, and the foreign matter defects due to the aggregation of residual ink Therefore, the printed material can be printed with a good appearance.

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

(Outline of the present invention)
In the present invention, by using a polymer having a specific component as a coagulant, even if used paper pulp containing a large amount of fine fibers is used, the generation of foreign matter defects due to the decrease in the yield of fine fibers, and the improvement in the yield of fine fibers It is possible to suppress the generation of agglomerates and the occurrence of foreign matter defects due to the aggregation of residual ink. Furthermore, by making paper in the presence of a specific flocculant, the generation of foreign matter defects and agglomerates is further suppressed.

(Specific embodiments of the present invention)
Next, an embodiment of the present invention will be described by taking a coated paper as an example.

〔pulp〕
Waste paper pulp used in the present invention includes, for example, disaggregation / deinking waste paper pulp, disaggregation / deinking / bleached waste paper pulp, etc. produced from magazine waste paper, flyer waste paper, office waste paper, newspaper waste paper, Kamihiro waste paper, etc. From the viewpoint of environmental protection, it is preferable to blend a large amount of these waste paper pulps.

  Among these, when pulp (MDIP) obtained by disaggregating and deinking waste magazine paper or leaflet waste paper is used, it is easy to prevent the cohesive action of the coagulant and flocculant described later, and a printed material with good appearance can be obtained. It is preferable because it becomes a paper to be used. When the present invention is used, the same effect can be obtained by using not only MDIP but also deinked pulp (NDIP) made of newspaper wastepaper, but the ink used for magazines and flyers has a lower concentration than newspapers. Since the viscosity is high, foreign matter defects tend to increase due to the cohesive action of the residual ink. For this reason, in particular, when pulp (MDIP) obtained by disaggregating and deinking used magazine paper or used leaflet paper is used, the effect of suppressing the occurrence of foreign matter defects becomes higher than that of the conventional method.

  The blending ratio of waste paper pulp is preferably 70% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass in the total amount of pulp. When making paper with a high content of waste paper, problems with foreign matter defects due to reduced yield of fine fibers, agglomerates due to improved yield, and foreign matter defects due to residual ink aggregation are problems. However, since a specific coagulant is used in the present invention, these problems are unlikely to occur. On the contrary, when pulp other than waste paper pulp (chemical pulp, mechanical pulp, etc.) is used, since the ratio of fine fibers is low, the inside of the system is easy to rotate and the effects of various papermaking aids described later are difficult to obtain. Therefore, it is necessary to reduce the addition amount of the coagulant, which is not preferable because aggregates are easily generated.

  The type of pulp used for other than the used paper is not particularly limited. For example, chemical pulp, mechanical pulp, or other types of pulp can be used, and one or two or more of these can be 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.

  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.

[Formulation process]
In the preparation process, various chemicals such as a coagulant and a paper strength improver are added to the pulp, processed to a predetermined quality, and sent to a paper machine.

<Freeness>
The freeness of waste paper pulp is preferably 280 cc to 380 cc, more preferably 300 cc to 340 cc. If it is less than 280 cc, the beating progresses too much and the fine fibers increase, and the yield of fine fibers deteriorates. Even if it exceeds 380 cc, since the drainage is fast, the fine fibers are difficult to yield, and the inside of the paper machine is soiled. Defects are likely to occur.

  For the same reason, the freeness of chemical pulp is preferably 380 cc to 480 cc, more preferably 400 cc to 440 cc. For the same reason, the freeness of mechanical pulp is preferably 100 cc to 150 cc, more preferably 120 cc to 150 cc.

<Coagulant>
In this embodiment, a coagulant is added to effectively adsorb fine fibers to pulp fibers. The kind of the coagulant needs to be a coagulant obtained by graft polymerization of two or more kinds of polymer components. 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 a coagulant having such a structure, the yield of fine fibers can be improved, the generation of agglomerates can be effectively suppressed, and the occurrence of foreign matter defects derived from residual ink can be effectively prevented.

  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 characteristics of each component combine to show uniform agglomeration performance. Therefore, as with a conventional coagulant composed of one kind of component, the yield of fine fibers is improved, the generation of agglomerates is suppressed, and the residual ink It is not possible to satisfy all of the aggregation prevention. A grafting agent that satisfies all of the improvement in the yield of fine fibers, the suppression of the generation of aggregates, and the suppression of aggregation of the remaining ink by graft polymerization of the graft chain having the aggregation ability to the main chain having the aggregation ability. can get.

  The shape of the coagulant may be a straight chain in which a plurality of graft chains are graft-polymerized to the main chain, and the graft chain component and the main chain component are further graft-polymerized to the graft chain bonded to the main chain. It may be a dendritic figure (branch and leaf), a network in which graft chains bonded to the main chain are cross-linked, or a micellar shape in which a part of the main chain or graft chain is crystallized. May be. More preferably, it is a mesh or dendrogram, which can efficiently adsorb fine fibers to pulp fibers, has less foreign matter defects, less aggregates, and less cohesive action of residual ink, most preferably It is 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 effect of suppressing the occurrence of foreign matter defects is reduced. If the amount exceeds 70% by mass, the graft chain is too large and the aggregating capacity is increased so that aggregation of aggregates and residual ink is likely to occur. Therefore, it is not preferable.

  The molecular weight of the coagulant is preferably 500,000 to 3,000,000, and preferably 1,000,000 to 2,000,000. When the molecular weight is less than 500,000, the yield of fine fibers is lowered, and the density of the obtained paper is lowered, so that the rigidity of the paper is lowered. When the molecular weight exceeds 3 million, the coagulant concentrates around the fine fiber, and foreign matter defects derived from agglomerates and residual ink tend to occur. 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 easy to collect fine fibers and anion trash, and if it is less than 10 meq / g, it is difficult to collect fine fibers and anion trash, the paper surface becomes rough, and the printability of the resulting paper decreases. . 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% by mass, and more preferably 0.03 to 0.10% by mass with respect to the total amount of pulp. If it exceeds 0.15% by mass, the coagulant tends to concentrate around the fine fibers and foreign matter defects increase, which is not preferable. If it is less than 0.01% by mass, the yield of the fine fibers decreases and the resulting paper is obtained. The density of the resin decreases and the rigidity decreases.

  In the present invention, by using a coagulant obtained by graft polymerization of two or more kinds of polymer components, the occurrence of foreign matter defects and agglomerates can be suppressed even when a pulp having a lot of fine fibers is used. By regulating the ratio of graft chains and the molecular structure, molecular weight, and charge density of the resulting graft polymer and optimizing the amount added, it is possible to effectively generate foreign matter defects and agglomerates, which is the object of the present invention. Can be suppressed.

<Flocculant>
In this embodiment, after adding the coagulant, further adding a specific flocculant in the pre-stage of the paper making process following the pulp preparation stage, further excellent generation of foreign matter defects due to improved yield of fine fibers It is possible to achieve the effect of preventing, the effect of suppressing the generation of aggregates, and the effect of preventing aggregation of residual ink. 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 be generated easily. Therefore, a flocculant is added before the screen, and the generated agglomerates are broken once on the screen, so that the agglomerates are moderately agglomerated. It is preferable to weaken. For 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 formation 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, it becomes easy to collect fine fibers and anion trash, and if it is less than 10 million, the fibers do not agglomerate appropriately, and the strength of the resulting paper decreases, so that the rigidity decreases.

  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, fine fibers and anion trash are collected and easily converted into foreign matters. If it is less than 1 meq / g, it is difficult to collect fine fibers and anion trash, the paper surface becomes rough, and the coating performance decreases.

  The amount of the flocculant added is preferably 0.05 to 0.30 mass%, more preferably 0.10 to 0.20 mass%, based on the total amount of pulp. If it exceeds 0.30% by mass, fine fibers and anion trash are easily collected and become foreign matters. If it is less than 0.05% by mass, the fibers are not properly aggregated and unevenness in strength occurs, resulting in a decrease in rigidity.

  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 yield of fine fibers decreases, and if it exceeds 40 minutes, a problem that aggregates are easily formed occurs.

  In this way, the reason why the generation of foreign matter defects and agglomerates can be suppressed by adjusting the molecular weight, charge density, and addition amount of the flocculant is the fine fiber formed by the specific coagulant (graft polymer). This is considered to be because the state in which the particles are finely dispersed and agglomerates are not formed can be directly made on paper. That is, when the specific flocculant is not used, the flocculant does not yield the fine fibers, and it becomes a foreign substance defect, or conversely, it tends to gather in one place, and agglomerates are easily generated.

<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.

<Filler>
As the filler, a filler generally used for papermaking can be used. For example, heavy calcium carbonate, 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 A known filler such as can be used.

  There are no particular restrictions on the shape of these inorganic fillers, and various types such as granular, tension, spindle, plate, and amorphous can be used. Regarding the particle size, gloss, paper flexibility, paper surface, etc. Therefore, generally, talc is preferably 15 μm or less, and calcium carbonate is preferably 3 μm or less.

[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. A gap-type gap former is preferable because it dehydrates from both sides, so that the movement of pulp fibers is suppressed and aggregates are hardly generated.

[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.

[Coated base paper]
Since the coated base paper obtained as described above contains a specific coagulant, the yield of fine fibers is high, the generation of agglomerates is reduced, the surface property of the coated base paper is improved, and it is uniform and stable. Coating can be performed.

  In addition, since the fine fiber has a larger specific surface area than the pulp fiber that has not been refined, the hydrogen bond inside the paper is increased and the rigidity is improved. The effect of improving the rigidity depends on the coating and flattening conditions to be described later, but the paper of the present invention is a paper having higher rigidity even after the application compared to the conventional general paper.

[Undercoating]
For the purpose of improving rigidity, a water-soluble polymer can be undercoated on the coating base paper using a roll coater. Examples of water-soluble polymers include starches such as oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch and raw starch or derivatives thereof, synthetic polymers such as polyacrylamide and polyvinyl alcohol, and water resistance and surface strength improvement. The paper strength enhancing agent described above, the externally added sizing agent for the purpose of imparting sizing properties, or those commonly used as surface treatment agents can be used alone or in combination. Of these, oxidized starch is preferred because it can improve the workability while minimizing the decrease in whiteness while improving the rigidity.

Coating amount in the case of using the oxidized starch as a water-soluble polymer is not particularly limited, preferably 0.1~1.5g per side / m ^2, more preferably 0.2~1.3g / m ^2, most preferably from 0.3 to 1.0 g / m ^2. If it is less than 0.1 g / m ² , the coverage is poor and the effect of improving the rigidity of the base paper is small. When it exceeds 1.5 g / m ² , the rigidity is improved, but the original color of starch tends to appear on the coated paper, and not only the whiteness is decreased, but also the coating liquid is applied by increasing the coating liquid. Since the liquid is scattered, coating mist is generated, and defects and foreign matters are easily generated, and workability is deteriorated.

  Such a water-soluble polymer is applied to, for example, a two-roll size press coater, a gate roll coater, a blade metering size press coater, a rod metering size press coater, or a film transfer type roll coater such as a shim sizer or a JF sizer. Can be applied by machine tool. A film transfer type roll coater is preferable because it has high surface coverage and can effectively improve printability. Coating machines other than those described above, such as blade coaters and air knife coaters, are unfavorable because the coatability is poor at low coating amounts and non-coated parts are likely to occur, and uniform coating is required for spray coaters and curtain coaters. Is not obtained and printability is deteriorated, which is not preferable.

[Flatening treatment (pre-calendar)]
The base paper after the undercoating is preferably subjected to a flattening process using a precalender before the topcoating (pigment coating). As the pre-calender, a soft calender in which a metal roll and an elastic roll are combined is preferable because the surface is highly improved. The pre-calendar can be performed in one stage or a combination of two or more stages as required. By the pre-calender treatment, the surface of the base paper after the application of the water-soluble polymer is flattened, and the excessive calendering treatment is not required in the later calendar, so that the rigidity of the paper is not reduced. The flatness can be improved, and sufficient printability and rigidity as a coated paper can be obtained. Further, by performing the flattening process on the surface of the base paper, it is possible to improve the coating property of the top coating and to suppress the coating unevenness of the coating liquid. The linear pressure of the pre-calender is preferably 10 to 80 kN / m, more preferably 10 to 50 kN / m. If it is less than 10 kN / m, flattening of the base paper after application of the water-soluble polymer does not proceed, and if it exceeds 80 kN / m, the base paper is compressed more than necessary, so that paper strength and rigidity are reduced, which is preferable. Absent.

[Top coating (pigment coating)]
Next, a coating layer containing a pigment and an adhesive is applied to one or both sides of the base paper to provide a coating layer. Conventional pigments can be used, such as kaolin, fine kaolin, calcium carbonate, talc, satin white, calcium sulfite, gypsum, barium sulfate, white carbon, calcined kaolin, structured kaolin, diatomaceous earth, magnesium carbonate, Inorganic pigments such as titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, polystyrene resin fine particles, urea formalin resin fine particles, fine hollow particles, porous One or more of organic pigments such as fine particles may be appropriately selected and blended. Among them, calcium carbonate having a large whiteness improving effect and clay having a high white paper gloss improving effect are preferable.

  There are no particular limitations on the type of adhesive blended in the coating solution together with the above pigments, for example, proteins such as casein and soybean protein; styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, Conjugated diene latex such as styrene-methyl methacrylate-butadiene copolymer latex, acrylic latex such as polymer latex or copolymer latex of acrylate ester and / or methacrylate ester, ethylene-vinyl acetate polymer latex, etc. Vinyl-based latex, or latexes such as alkali partially soluble or insoluble latex obtained by modifying these various copolymer latexes with a functional group-containing monomer such as a carboxyl group; polyvinyl alcohol, olefin-maleic anhydride resin , Me Synthetic resin adhesives such as min resin, urea resin, urethane resin; starches such as oxidized starch, positive starch, esterified starch, dextrin; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, etc. Adhesives used can be mentioned, and one or two or more of these can be appropriately selected and used.

  Although there is no limitation in particular in the ratio of the pigment in a coating agent, and an adhesive agent, Preferably an adhesive agent is 3-17 mass parts by solid content ratio with respect to 100 mass parts of pigments, More preferably, it is 5-15. Part by mass. If the amount of the adhesive is less than 3 parts by mass, the strength of the coating layer is lowered, and the coating layer is easily taken up by the printing ink at the time of printing, so that it is easy to cause troubles that are not printed (white spots). . On the other hand, if it exceeds 17 parts by mass, the effect of improving the surface strength reaches its peak and the economic efficiency deteriorates.

  Furthermore, for example, various commonly used auxiliaries such as a fluorescent brightening agent, a fluorescent brightening agent fixing agent, an antifoaming agent, a release agent, a coloring agent, and a water retention agent are appropriately blended in the coating liquid. You can also.

  The coating of the top coat layer (pigment coating layer) on the base paper is preferably performed, for example, in a coater part between dryer parts which is performed in a plurality of stages, usually two stages of a pre-dryer part and an after-dryer part. . In this coater part, as in the case of undercoat coating, for example, a film transfer type roll such as a 2-roll size press coater, a gate roll coater, a blade metering size press coater, a rod metering size press coater, or a shim sizer or JF sizer. It can apply | coat with coating machines, such as a coater. The film transfer type roll coater is preferable because it has a high surface coverage even at a low coating amount and a coated paper having a high surface strength can be easily obtained. A blade coater is preferable because of its high flatness after coating and excellent printability. Coating machines other than the above, such as air knife coaters, are not preferred because they cannot be applied at low coating amounts, and spray coaters and curtain coaters are capable of coating at low coating amounts, but have a uniform coating surface. Since it cannot be obtained, surface coverage and surface strength tend to be low, which is not preferable.

  In addition, when using an on-machine coater that is integrated with the paper machine, the coating device can produce products in a shorter time than an off-machine coater, so that moisture unevenness in the width direction and flow direction can be reduced. It is preferable because a more uniform coating can be obtained and a uniform surface strength can be obtained. In addition, as a drying method in the dryer part, for example, various heating drying methods such as hot air heating, gas heater heating, and infrared heater heating can be appropriately employed.

The coating amount of the coating liquid into the base paper is per side, preferably ^{3g / m 2 ~10g / m 2} , more preferably ^{5g / m 2 ~9g / m 2} . If the amount of the coating liquid is less than 3 g / m ² per side, an uncoated part is likely to occur on the paper surface, and a part having a low surface strength may be generated. If the coating exceeds 10 g / m ² per side, cracks are likely to occur in the coating layer, and not only the printability but also the cosmetic properties of the coated paper itself are not preferred.

[Calendar part]
For the purpose of imparting glossiness, flatness, and printability to the coating layer, a pair of rolls, at least one of which is a hot roll, preferably a paper is passed between an elastic roll and a metal roll to perform a flattening treatment. it can. The linear pressure of the calendar is preferably 100 to 600 kN / m, and more preferably 100 to 400 kN / m. If it is less than 100 kN / m, flattening of the pigment coating layer does not proceed, and if it exceeds 600 kN / m, the base paper is pressed more than necessary, so that the rigidity is lowered, which is not preferable. 100-300 degreeC is preferable and the temperature of a metal roll has more preferable 100-200 degreeC. If the temperature is lower than 100 ° C, the pigment coating layer will not be flattened. If the temperature exceeds 300 ° C, fiber burn will occur, the coated paper itself will turn yellow due to heat and pressure, and discoloration will occur. Therefore, it is not preferable.

  As the calendar facility, a flattening facility such as a super calendar or a soft calendar can be used. Among them, a multi-nip calender, more desirably a 6-, 8-, or 10-stage multi-nip calender is preferable because it easily adjusts the nip pressure and prevents the decrease in rigidity and easily adjusts the glossiness of blank paper. Moreover, as an installation place of a calendar, an on-machine type integrated with a paper machine and a coating machine is preferable. With the on-machine type, flattening can be performed immediately after coating at a high paper surface temperature, so the glossiness of blank paper is easy to improve, the linear pressure required to obtain the desired coated paper is low, rigidity and paper thickness This is preferable because there is little decrease in the.

Since the coated paper obtained as described above contains a specific flocculant, the coated paper has few foreign matter defects and has a good appearance. The foreign matter defect can be evaluated by a foreign matter area ratio using a foreign matter testing machine, and it is preferable that the foreign matter area ratio is less than 5 mm ² per 1 m ^2, preferably less than 4 mm ^2, more preferably less than 3 mm ^2. preferable. When the foreign matter area ratio exceeds 5 mm ² , not only the sharpness of the image after printing is lowered, but also the visibility of characters in the printed portion is lowered, resulting in a coated paper with poor appearance.

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

  First, as raw material pulp, LBKP, waste paper pulp (MDIP) manufactured from magazine waste paper or leaflet waste paper, and waste paper pulp (NDIP) manufactured from newspaper waste paper are mixed in the ratios (mass ratio) in Tables 1 and 2, and this pulp is mixed. With respect to 100 parts by mass (absolutely dry amount), the cationized starch (product number: Amilofax T-2600, manufactured by Abebe Japan Co., Ltd.) 1% by mass, filler (light calcium carbonate: product number: TP121-), each in solid content 6S, manufactured by Okutama Kogyo Co., Ltd.) 2% by mass, and as shown in Tables 1 and 2, a coagulant and a flocculant were added to obtain a pulp slurry. The chemicals used are as follows.

・ Coagulant (all positively charged and cationic)
a) Polyamine grafted polyethyleneimine (product number: SC924, manufactured by HAimo Co., Ltd.)
b) Polyamine graft polyacrylamide c) Polyamine graft polyDADMAC
d) Polyamine grafted sodium polyacrylate e) PolyDADMAC grafted polyethyleneimine / flocculant a) Cationic PAM (Part No .: ND270, manufactured by Hymo Co., Ltd.)
b) Colloidal silica (product number: NP442, manufactured by Eka Chemicals Co., Ltd.)
c) Polyethyleneimine (Product No .: Polymin PR8150, manufactured by BASF)

Next, after manufacturing a paper sheet through a wire part consisting of a gap former, a straight-through press part without an open draw, and a pre-dryer part consisting of a single deck dryer, 0.5 g of starch coating solution per side is applied to both sides. An undercoat was applied using a film transfer type roll coater at a coating amount of / m ² . After this undercoating, the film was dried by an after dryer part and flattened at a linear pressure of 25 kN / m using a pre-calender composed of a soft calender with two rolls and one stack.

Next, using a blade coater, 30 parts by mass of fine kaolin clay (product number: AMAZON, manufactured by Kadam) as a pigment, and 70 parts by mass of wet heavy calcium carbonate (product number: ESCALON # 90, manufactured by Sankyo Flour Milling Co., Ltd.) A coating liquid containing 10 parts by mass of a styrene-butadiene copolymer latex (product number: PA5036, manufactured by Nippon A & L Co., Ltd.) as an adhesive is applied to the base paper so that the coating amount is 8.0 g / m ² per side. Coated on both sides.

  Next, the base paper with the coating layer formed on both sides was subjected to an after dryer part to dry the coating layer, and planarized at a linear pressure of 150 kN / m and a temperature of 200 ° C. using a multi-nip calender. . Then, it was used for the reel part and the winder part to obtain coated paper.

The weight of the coated paper obtained was 105 g / m ^{2 as} measured according to JIS P 8124. The coated paper was evaluated as follows. The results are shown in Tables 1 and 2.

(A) Contaminant Area Ratio Using a contaminant tester, the contaminant area per 1 m ² (mm ² ) was measured and used as an index of the amount of foreign object defects. The foreign matter tester was manufactured by ESK Create Co., Ltd. (scanner: EPSON ES-2000), and the measurement was performed with a resolution of 1600 DPI, a minimum measurement area of 0.001 mm, and a measurement area of A4.

(B) Agglomerate The degree of occurrence of the agglomerate was visually evaluated on the coated paper based on the following evaluation criteria.
(Double-circle): There is no generation | occurrence | production of the aggregate and it is excellent in appearance.
○: Some agglomerates were generated, but the appearance was good.
Δ: Some agglomerates are generated and the appearance is somewhat inferior.
X: Agglomerates are generated and the appearance is inferior.

(C) Coating property Coating was performed continuously for 24 hours, and coating property was evaluated in the following four stages.
◎: Good ○: Slightly inferior but practical use △: Inferior but practical use ×: Largely inferior, impractical

(D) Rigidity 20 samples of A4 size (210 mm x 297 mm) are stacked, one side of the long side is stapled at 3 locations (top, center, bottom) and placed horizontally, turning 10 sheets in total, The rigidity of the paper was evaluated based on the evaluation criteria.
A: The paper after turning does not sag and has excellent rigidity.
○: The paper after turning slightly sagged and slightly inferior in rigidity.
Δ: The paper after turning is slightly sagged and slightly inferior in rigidity.
X: The paper after turning is sag and inferior in rigidity.

(E) Printing suitability Using an offset printing machine (model number: Lysopia L-BT3-1100, manufactured by Mitsubishi Heavy Industries, Ltd.), color 4 (color: product number: ADVAN, manufactured by Dainippon Ink & Chemicals, Inc.) 5000 copies of color printing were performed. About this printing surface, the printing nonuniformity of the printed matter was observed visually and with a magnifying glass (10 times), and the degree thereof was evaluated based on the following evaluation criteria.
A: There is no printing unevenness, excellent printability, and practical use.
○: Printing unevenness occurs slightly and printability is slightly inferior, but it can be used in practice.
Δ: Some printing unevenness occurs and printability is slightly inferior, but it can be used in practice.
X: Printing unevenness occurs, printability is poor, and actual use is impossible.

表１及び２より、実施例の塗工紙はいずれも、特定の凝結剤を含有しているため、異物欠陥と凝集塊が少なく、塗工適性と剛性に優れた塗工紙であることが分かる。

From Tables 1 and 2, since all of the coated papers of Examples contain a specific coagulant, there are few foreign object defects and agglomerates, and the coated paper is excellent in coating suitability and rigidity. I understand.

  On the other hand, since the coated paper of the comparative example does not contain a predetermined coagulant as in the examples, it is easy to generate foreign matter defects and agglomerates, and is a coated paper with poor coating suitability and rigidity. is there.

  Even when pulp containing a lot of fine fibers such as used paper is used, the occurrence of foreign matter defects due to a decrease in the yield of fine fibers, the generation of agglomerates due to improved yield, and the occurrence of foreign matter defects due to the aggregation of residual ink are suppressed. Therefore, it is possible to obtain a paper that has a good appearance and can obtain a clear image when printed.

Claims (6)

  A paper in which a coagulant is internally added to pulp, wherein the coagulant is a coagulant obtained by graft polymerization of two or more different polymer components.   The paper according to claim 1, wherein the polymer component is selected from the group consisting of polyethyleneimine, polyamine, polydadomac and polyacrylamide.   The paper according to claim 1 or 2, wherein the coagulant has a dendrogram shape.   The paper according to any one of claims 1 to 3, wherein the coagulant has a molecular weight of 500,000 to 3,000,000 and a charge density of 10 to 25 meq / g.   The paper according to any one of claims 1 to 4, wherein 70% by mass or more of the total pulp is deinked pulp (MDIP) regenerated from magazine waste paper or leaflet waste paper.   In addition to the coagulant, the coagulant further contains polyacrylamide having a molecular weight of 12 to 16 million and a charge density of 1 to 10 meq / g. The paper according to item 1.