JP2009242980A - Paper containing filler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide paper excellent in both opacity and hand touch despite having low basis weight. <P>SOLUTION: In the paper, a filler is added in pulp. The paper can be obtained by adding, in advance, an anionic compound as a filler treatment agent to the filler followed by mixing the resultant filler into pulp and then conducting a papermaking operation. Preferably, the anionic compound is a styrene-acrylic polymer, and the filler is regenerated particles derived from papermaking sludge, a regenerated particle aggregate derived from deinked floss, or a regenerated particle aggregate obtained by coating the deinked floss-derived regenerated particle aggregate with silica. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a paper in which a filler is internally added. More specifically, the present invention relates to a paper having a low hand-weight and high opacity, and can be suitably used for, for example, commercial printed matter, information paper, wrapping paper, newsprint, and paperboard.

  Paper is widely used for commercial printed matter, information paper, wrapping paper, newsprint, paperboard, and the like, but the need for weight reduction is increasing due to environmental problems in recent years and ease of carrying. However, simply reducing the weight not only makes the paper sag easy and smooth, but also reduces the opacity and allows the print on the back to show through. Troubles that make printing unclear.

  When the filler is increased in order to improve the opacity, the filler tends to be agglomerated, the strength of the agglomerated portion is lowered, the hand feeling of the paper is lowered, and the paper breakage is likely to occur. In order to maintain the hand feeling of paper, there is a method of applying a paper strength improver such as starch or polyacrylamide to the paper surface (for example, Patent Document 1), but not only a large-scale coating facility is required. There is a problem that the part not coated becomes wrinkles and becomes foreign matter. In order to improve hand feeling, it is necessary to improve the entanglement between the fibers inside the paper, and a method of promoting fibrillation or reducing the internal filler having an action of inhibiting hydrogen bonding is considered, Fibrilization causes a decrease in hand feeling, and a reduction in internal filler causes a decrease in opacity.

  As a method for obtaining high opacity while reducing the filler content, regenerated particle aggregates, which are fillers with higher opacity, can be used (for example, Patent Document 2). However, common fillers (eg, talc, calcium carbonate) have a high crystal structure and a constant charge, whereas regenerated particle aggregates consist of a mixture of aluminum, calcium and magnesium and are not crystallized. Since the electric charge is not constant, unlike the above-mentioned general fillers, there is a problem in that the yield is poor even when an appropriate flocculant and coagulant that has been conventionally used is used, and it is difficult to obtain the expected improvement in opacity. It was.

  As a method for improving the yield of the filler efficiently, there is a method of mixing the filler with CMC or epichlorohydrin in advance before adding the filler to the pulp which is the raw material of paper (for example, Patent Documents 3 and 4). In this method, the filler tends to be agglomerated, and the opacity and hand feeling cannot be improved efficiently.

As described above, no method has been found that achieves both opacity and hand feeling, especially in low-US paper.
JP 2006-70374 A JP-A-6-73695 JP 2006-249598 A JP-T 09-506397

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a paper excellent in opacity and hand feeling while being low in weight.

The present invention is as follows.
(1) Paper obtained by internally adding a filler to a pulp, the paper being obtained by adding an anionic compound as a filler treatment agent to the filler in advance and then mixing with pulp to make paper.
(2) The paper according to (1), wherein the filler is regenerated particles derived from papermaking sludge.
(3) The paper according to (2), wherein the regenerated particles are regenerated particle aggregates derived from deinking floss.
(4) The paper according to any one of (1) to (3), wherein the anionic compound is a styrene-acrylic polymer.
(5) The paper according to any one of (2) to (4), wherein the filler is a silica-coated regenerated particle aggregate obtained by coating a deinked floss-derived regenerated particle aggregate with silica.
(6) The anionic compound is an anionic polymer compound, and the molecular weight of the anionic polymer compound is 10,000 to 1,000,000, according to any one of (1) to (5), Paper.
(7) The paper according to any one of (1) to (6), wherein the filler and the filler treating agent are mixed in advance and then added to the pulp within one minute.

  According to the present invention, the paper is excellent in opacity and hand feeling while having a low rice floor area.

(Embodiment)
The paper of the present invention is a paper obtained by mixing a pulp with a filler treatment agent in advance, and then mixing the pulp with a filler treatment agent and then mixing with pulp and making paper.

First, the paper according to the present embodiment will be described using a printing coated paper as an example.
<Pulp>
The base paper should just be obtained by papermaking a normal raw material pulp. The raw material pulp is also not particularly limited. For example, chemical pulp such as unbleached softwood pulp (NUKP), unbleached hardwood pulp (LUKP), bleached softwood pulp (NBKP), bleached hardwood pulp (LBKP), etc .; Stone Grand Pulp (SGP) ), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Chemi Thermo Mechanical Pulp ( CTMP), refiner mechanical pulp (RMP) and other mechanical pulp; tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, corrugated waste paper, Kakuhishi waste paper, Kent waste paper, imitation waste paper, Jiju waste paper, Disaggregated waste paper pulp made from recycled paper, etc. Ink waste paper pulp, waste paper pulp such as disaggregation / deinking / bleached waste paper pulp, pulp bleached from these, etc. are selected, one or more of these are appropriately selected, and the ratio is adjusted and used be able to.

<Regenerated particles>
In the present invention, in order to improve opacity, at least one regeneration selected from the group consisting of the following regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates, which are fillers that are particularly excellent in opacity. It is preferred to use particles.

a) Recycled particles derived from paper sludge As regenerated particles derived from paper sludge, for example, those described in JP-A No. 2002-167523 can be used. Specifically, paper sludge is extruded into a string with a diameter of 3 to 10 mm, cut to a length of 8 to 10 cm, then incinerated with a rotary kiln at 500 to 1000 ° C., and the incinerated ash obtained by this incineration is dry-pulverized A white pigment having an average particle diameter of 0.1 to 10 μm obtained by pulverization in the order of wet pulverization can be used.

  As the quality of the regenerated particles derived from papermaking sludge, for example, the whiteness (powder whiteness meter (manufactured by Kett Scientific Laboratory, type C-100)) is 60% or more, and the hardness (plastic wire wear degree) (Nippon Filcon, 3 hours)) of less than 100 mg can be used.

b) Regenerated particle aggregate derived from deinking floss As the regenerated particle aggregate derived from deinking floss, for example, those described in Japanese Patent Application Laid-Open No. 2007-99613 and Japanese Patent Application Laid-Open No. 2007-1000026 may be used. it can. Specifically, a flocculant is added to deinking floss having a moisture content of about 95 to 98% by mass, dehydrated to about 50 to 60% by mass, the dehydrated product is dried with hot air and classified, and then in a range of 450 to 650 ° C. Then, it is baked and agglomerated so that the unburned rate becomes 10 mass% or more and less than 15 mass%. White particles obtained by pulverizing the calcined inorganic particle aggregate so that the primary particles have an average particle diameter of 0.01 to 0.1 μm and the secondary particles in which the primary particles have aggregated have an average particle diameter of 0.1 to 10 μm. Pigments can be used.

As the quality of the regenerated particle aggregate derived from deinking floss, for example, the oil absorption is 30 to 100 ml / 100 g. Moreover, the peak height of the average particle diameter in the differential curve of the particle size distribution by the Coulter counter method is adjusted to 30% or more, and furthermore, calcium, silica and aluminum in the raw material sludge are converted into oxides in an amount of 30 to 82: 9 to By adjusting the mass ratio to 35: 9 to 35, the pore volume of the inorganic particle aggregate is 0.15 to 0.60 cc / g, the pore surface area is 10 to 25 m ² / g, and the pore radius is 300 to White pigments adjusted to 1000 angstroms can also be used.

  In terms of filler quality, regenerated particle aggregates derived from deinked floss are preferred over regenerated particles derived from papermaking sludge. In addition to deinking floss, papermaking sludge contains sludge and heavy foreign matter that have been processed from papermaking wastewater, so firing unevenness is likely to occur, and it cannot be uniformly fired. Increase in objects and decrease in whiteness and opacity are likely to occur.

  In the paper of this embodiment, the above regenerated particles or regenerated particle aggregates can be used as at least an internal filler. Since this recycled particle or recycled particle aggregate can be recycled by baking papermaking sludge or deinked floss, it does not require disposal such as landfill as waste, reducing the environmental burden. This greatly contributes to resource saving. Further, since the raw material is papermaking sludge or deinking floss generated in the used 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.

c) Silica-coated regenerated particle aggregate In the present embodiment, as a suitable regenerated particle to be internally added to the raw material pulp, a silica-coated regenerated particle aggregate in which the surface of the regenerated particle aggregate is coated with silica is particularly preferably used. be able to.

  As the silica-coated regenerated particle aggregate, for example, those described in JP 2007-146354 A or JP 2007-186800 A can be used. Specifically, deinked floss dehydrated to 95 to 98% moisture is further dehydrated to 40% to 70%, and then dried with hot air at 100 to 200 ° C. to a moisture content of 2 to 20% by mass. To do. The dried product is adjusted so that the particle size of 355 to 2000 μm is 70% by mass or more. The dried product is baked and agglomerated in the range of 510 to 750 ° C., and after adjusting the unburned matter, it is finely divided, the primary particles have an average particle diameter of 0.01 to 0.1 μm, and the secondary particles in which the primary particles are aggregated The particles are adjusted so as to have an average particle diameter of 0.1 to 10 μm to obtain regenerated particle aggregates.

In the regenerated particle aggregate, the peak height of the average particle diameter in the differential curve of the particle size distribution by the Coulter counter method is adjusted to 30% or more, and further, calcium, silicon and aluminum in the deinking floss are converted to 30 in terms of oxide. By adjusting the mass ratio to ˜82: 9 to 35: 9 to 35, the pore volume of the inorganic particle aggregate is 0.15 to 0.60 cc / g, the pore surface area is 10 to 25 m ² / g, fine. It is preferable that the white pigment has a pore radius adjusted to 300 to 1000 angstroms.

  After this regenerated particle aggregate is added and dispersed in an aqueous alkali silicate solution to prepare a slurry, a dilute solution of a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid is added at a liquid temperature of 70 to 100 ° C. while stirring with heating, and a silica sol is prepared. The white pigment obtained by generating silica sol particles having a particle diameter of 10 to 20 nm on the regenerated particle aggregate surface by adjusting the pH of the final reaction solution to a range of 8.0 to 11.0. . This silica-coated regenerated particle aggregate improves the oil absorption and opacity due to the silica precipitation effect by making calcium, silicon and aluminum into mass ratios of 30 to 62:29 to 55: 9 to 35 in terms of oxides. Can be made.

  The quality of the silica-coated regenerated particle aggregate is, for example, an oil absorption of 30 to 100 ml / 100 g, and when used as an internal additive in the paper making process, a white pigment having an average particle size adjusted to 0.1 to 10 μm is used. It can also be used.

  The silica-coated regenerated particle agglomerates can be reacted with sodium hydroxide in a used paper processing step in circulation use to contribute to the recycle use of papermaking raw materials and regenerated particles as a buffering agent or bleaching aid. Further, when such silica-coated regenerated particle aggregate is internally added to the raw material pulp as a filler, the whiteness, opacity, and surface strength of the paper are further increased than when the regenerated particle aggregate not coated with silica is used. In addition, the effects of ink drying, ink absorption unevenness, and bulkiness can be further improved.

  In this embodiment, recycled particles (recycled particles derived from paper sludge, recycled particle aggregates derived from deinking floss, and silica-coated recycled paper particle aggregates) are both washed into the raw pulp and recycled particles are washed away into white water. The average particle size is preferably 0.1 μm or more, more preferably 0.3 μm or more, from the viewpoint of preventing foreign matters from being generated inside the paper machine, and from the viewpoint of maintaining printability and preventing clogging of the sword tip. The average particle size is preferably 10 μm or less, more preferably 8 μm or less. If the thickness is less than 0.1 μm, the yield on the paper is poor, and it tends to accumulate inside the paper machine and become a foreign substance. If the thickness exceeds 10 μm, the binding between fibers tends to be inhibited inside the paper, and the hand feeling of the resulting paper is reduced. Therefore, it is not preferable.

  Although the usage-amount of these reproduction | regeneration particles is not specifically limited, 0.2-5.0 mass% is preferable with respect to a pulp total amount, and 0.5-2.0 mass% is more preferable. When the amount is less than 0.2% by mass, the yield of the filler is decreased, and the whiteness and opacity are decreased. When the amount exceeds 5.0% by mass, the filler is excessively agglomerated, and the fibers of the pulp locally. The bond between the hands decreases and the hand feeling and operability decrease.

<Fillers other than regenerated particles>
In addition to the regenerated particles such as the regenerated particles, the regenerated particle aggregates, and the silica-coated regenerated particles, fillers generally used for papermaking can be used. For example, clay, calcined kaolin, deramikaolin, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide Zinc hydroxide and the like, and can be used in combination of one or more as required. Of these, the use of calcium carbonate is preferred.

  The amount of filler used other than regenerated particles is preferably 0.2 to 12% by mass, more preferably 2 to 6% by mass, based on the total amount of pulp. When the amount is less than 0.2% by mass, the filler yield decreases and the whiteness and opacity are decreased. When the amount exceeds 12% by mass, the filler is excessively agglomerated to reduce hand feeling and operability.

<Filler treatment agent>
Anionic compounds are used as the filler treating agent to be added to the above-mentioned recycled particles, recycled particle aggregates, silica-coated recycled particle aggregates, fillers generally used in papermaking applications, and the like. In the case of a cationic compound, it repels these fillers, the filler yield is not improved, and an increase in opacity cannot be obtained. Examples of the anionic compound include colloidal silica; anionic polymer compounds such as polyacrylamide, polyamine, polyacrylate, and derivatives thereof. Among these, polyacrylic polymers and derivatives thereof are preferable, and styrene-acrylic polymers are particularly preferable. Use of polyamine or anionic polyacrylamide (PAM) is not preferable because it has a strong aggregating action and a floc becomes dense, and thus an ash yield is improved, but opacity is lowered.

  When the filler treatment agent is an anionic polymer compound, the molecular weight is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 500,000, and still more preferably in the range of 50,000 to 200,000. . If it is less than 10,000, the yield of the filler will decrease and the whiteness and opacity will decrease. If it exceeds 1,000,000, not only will the filler be over-agglomerated and the hand feeling will be weakened, but the occurrence of defects will increase. The operability is reduced. 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 amount of the filler treating agent used is preferably 0.01 to 1% by mass and more preferably 0.2 to 0.5% by mass with respect to the total amount of filler. When it is less than 0.01% by mass, the yield of the filler is lowered, and the whiteness and opacity are lowered. When the amount exceeds 1% by mass, the filler is excessively agglomerated and the opacity, hand feeling and operability are lowered.

  The time from the addition of the filler treatment agent to the filler until the addition to the pulp (treatment time) is not particularly limited as long as the filler and the filler treatment agent can be mixed and stirred uniformly, but preferably the filler and the filler. It is preferable to add to the pulp within 1 to 10 minutes after mixing with the treatment agent. If it is less than 1 minute, the filler and the filler treating agent cannot be sufficiently mixed, and the yield of the filler is lowered, and the whiteness and opacity may be lowered. Exceeding 10 minutes is not preferable because the bond between the fillers becomes strong, the particle diameter of the fillers becomes large, and the hand feeling and opacity of the resulting paper decrease.

  The filler treatment agent can be added to the filler either by adding the filler treatment agent to the filler cushion tank or directly into the piping, but both must have sufficient agitation to ensure uniform mixing. It becomes.

  When adding a filler processing agent to a cushion tank, it is preferable to provide a stirring device in the tank and stir. As the stirring device, an agitator generally used in papermaking applications such as a raw material dilution tank can be used.

  When the filler treatment agent is added in the filler pipe (in-line), it is preferably added to the suction side of the filler addition pump so that the filler and the filler treatment agent are sufficiently stirred after the addition. Although it may be added to the discharge side of the filler addition pump, unlike the suction side, a stirring force by the pump cannot be obtained, so that it is necessary to allow sufficient time for fixing to the filler. As described above, it is preferable to appropriately adjust the flow rate and the length of the pipe so that the fixing time is 1 minute or more and less than 10 minutes before mixing with the pulp. However, when the piping from the addition of the filler treatment agent to the mixing with the pulp is short, it is necessary to pay attention to the fact that the filler treatment agent cannot be sufficiently fixed to the filler, and it is difficult to improve whiteness and opacity. . Conversely, if the filler and the filler treatment agent can be sufficiently mixed in the pipe, there is no problem even if the filler treatment agent is added to the pump discharge side.

  The place where the filler treated with the filler treatment agent is added to the pulp may be a place where the filler is added as usual, and is not limited to a specific place. Preferably, the suction side of the secondary fan pump is preferable because an agitation effect on the pump and the subsequent screen can be obtained. Addition before the cleaner before the secondary fan pump is not preferable because a part of the raw materials and chemicals are removed by the cleaner and more chemicals than necessary are required.

  In addition, in the case where a filler not treated with a filler treating agent (untreated filler) is used in combination with a filler treated with a filler treating agent (treated filler), the place where the treated filler and the untreated filler are added to the pulp is the same as above. There is no particular limitation. Further, the treated filler and the untreated filler may be added to the pulp at the same time, or may be added at different places.

  Moreover, as an addition order, after adding a coagulant | flocculant and other additives, it is preferable to add the filler processed with the filler processing agent, and finally add a flocculant. If a coagulant is added after the filler treated with the filler treating agent is added to the pulp, it is not preferable because the filler is combined with the coagulant and easily falls off from the pulp fiber, and the ash yield decreases. Moreover, it is not preferable to add a papermaking aid (bulky agent, sizing agent, etc.) after adding a filler-treated filler to the pulp, since the filler and the papermaking aid are easily combined and the effect of the assistant is difficult to obtain. Further, when the flocculant is added to the pulp before the filler, the yield of the filler added later is lowered, and the effect of improving the opacity cannot be obtained. For this reason, the order of addition is preferably the order of coagulant, papermaking aid, filler-treated filler, and flocculant.

  In this embodiment, the raw material pulp is mixed to prepare a papermaking raw material (stock slurry). For example, an internal sizing agent, a bulking agent, a paper strength enhancer, a paper thickness improver, Various additives such as a retention improver, which are usually blended into the base paper of the coated paper, can be internally added by appropriately adjusting the type and blending amount.

  In the present invention, as described above, a specific filler treatment agent is used before processing with pulp fibers to treat regenerated particles, regenerated particle aggregates, and silica-coated regenerated particle aggregates with high opacity. However, paper with excellent opacity and hand feeling can be obtained.

  Further, in the present invention, by making a paper using a specific coagulant and a flocculant, the regenerated particles treated with the filler can be more effectively retained on the paper. Is more preferable because it can effectively improve the opacity and prevent a decrease in hand feeling.

<Coagulant>
In this embodiment, before the treated filler is mixed with the pulp fiber, an anionic trash and fine fibers can be effectively adsorbed to the pulp fiber by adding a coagulant to the pulp fiber slurry, and the opacity Since the improvement effect and the fall prevention effect of a hand feeling are acquired, it is especially preferable. The kind of the coagulant is not particularly limited as long as it can be generally used for papermaking. For example, polyacrylamide (PAM), polyvinylamine (PVAm), polydiallyldimethylammonium chloride (Polydadomac, PDADMAC), polyamine (PAm). ), Polyethyleneimine (PEI), polyethylene oxide (PEO), polyacrylate, methacrylate and the like. Among these, polyamine, polyethyleneimine, and DADMAC are preferable, and polyethyleneimine and DADMAC are more preferable, and DADMAC is most effective in effectively increasing the whiteness and hand feeling of the treated filler. preferable.

  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 filler and pulp fibers tend to collect and the hand feeling is reduced, which is not preferable. If it is less than 0.01% by mass, the filler is easily adsorbed on anionic trash and fine fibers, and the yield of the filler is reduced. Decreases, and opacity cannot be obtained.

  As described above, before adding a specific filler treatment agent to a filler composed of regenerated particles, an anionic trash and fine fibers are adsorbed on pulp fibers using a specific coagulant, and an effect of improving opacity, Increases the effect of preventing hand feeling.

<Flocculant>
In this embodiment, after adding the coagulant and the filler treated with the filler treatment agent to the pulp, further adding a specific flocculant at the pre-stage of the paper making process following the pulp preparation stage, further filler Can improve the opacity by improving the yield and prevent the reduction of hand feeling.

  As a component of the flocculant, a flocculant conventionally used in papermaking applications can be used. For example, inorganic flocculants such as bentonite and colloidal silica, polyacrylamide (PAM), polyvinylamine (PVAm), polyamine ( Any of organic polymer flocculants such as PAm) and polyethylene oxide (PEO) can be used. However, preferred are bentonite, cationic PAM, and anionic PAM, which are highly effective in improving opacity and preventing reduction in hand feeling, more preferably cationic PAM and anionic PAM, and most preferably anionic PAM.

  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. When the amount exceeds 0.30% by mass, the filler and pulp fibers tend to aggregate and the hand feeling decreases, which is not preferable. When the amount is less than 0.05% by mass, the yield of the filler is poor and the opacity and whiteness are not improved.

  Thus, by adjusting the type and amount of the flocculant, it is possible to effectively improve the opacity and prevent the hand feeling from being lowered. Further, when combined with the above-mentioned coagulant, a further effect can be obtained, and a paper excellent in opacity and hand feeling can be obtained particularly in a paper having a low rice floor.

  The pulp slurry thus obtained is made by a wire part, and then subjected to a press part and a pre-dryer part, whereby paper can be produced for the purpose. Moreover, after coating the coating agent mentioned later in a coater part on a base paper, it can use for an after-dryer part, a calendar part, etc., and can also obtain a coated paper.

[Paper making process]
The papermaking equipment that can be used in this embodiment is not particularly limited, but in order to obtain the desired opacity and hand feeling, a wire part made of a gap former, a press part made of a straight-through type without an open draw, a single deck dryer It is preferable to combine a dryer part consisting of

[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 web former, a long web former combined with 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 the dewatering efficiency is good because it dehydrates from both sides, the nip pressure at the press part, which will be described later, can be reduced, and the hand feeling is unlikely to decrease.

[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 high dehydration properties is used, the linear pressure on the paper can be reduced, and hand feeling can be reduced. It is preferable because a decrease in the thickness 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 basis weight of the paper thus obtained is not particularly limited. However, in the present invention, even a paper having a lower weight is high in opacity and hand feeling as described above. Even at / m ² or less, paper that can be suitably used for flyers, pamphlets, books and the like can be obtained. Although the basis weight varies depending on the intended printing application, in the present invention, considering that it is 30 to 80 g / m ² , the basis weight of the base paper is usually about 25 to 75 g / m ^2. It is preferable to adjust so that.

  The base paper may be provided with an undercoat coating layer by applying an undercoat coating agent containing starch or a paper strength improver before providing a pigment coating layer to be described later. By providing the undercoat coating layer, hand feeling can be improved, but in the present invention, it is possible to improve hand feeling and opacity without adding these starch and paper strength improvers. it can.

When applying an undercoating agent (an aqueous solution containing starch or a derivative thereof, a paper strength enhancer, a sizing agent, etc.), the amount of solid content is 1.0 g / m ² or less per side of the base paper. In addition, it is desirable that coating is performed by, for example, a film transfer method in a size press process in the paper making process. In blade coating, the coating amount increases, and the weight reduction that is the object of the present invention cannot be achieved.

  The undercoating agent can be applied by various known methods in the size press step during the paper making process, but is preferably applied by a film transfer method. The film transfer system is a system in which an undercoat film in a wet state is formed on an applicator roll, and this undercoat film is transferred to the surface of the base paper. For example, a transfer roll coater, a rod metering size press coater, etc. Is used. Adopting the film transfer method allows you to apply an undercoat layer with a certain film thickness to the surface of the base paper, so that, for example, a method of forming a coating agent pound such as a two-roll size press In comparison, the amount of application can be minimized and the weight can be further reduced. In the film transfer method, any method may be used for forming the undercoat coating film on the applicator roll.

  The type of sizing agent for forming the undercoat coating layer is not particularly limited. For example, styrene sizing agent, olefin sizing agent, acrylate sizing agent, styrene-acrylic sizing agent, etc. What is used for a use can be used suitably.

  There is no particular limitation on the method for preparing the undercoat coating agent, and it is preferable to add purified water as appropriate to the sizing agent so as to obtain a desired solid content concentration and stir at an appropriate temperature to obtain a uniform aqueous solution. .

  Next, the pigment coating layer formed on the base paper, preferably on the undercoat coating layer provided on the base paper will be described. On the base paper, preferably on the undercoat coating layer provided on the base paper, at least one pigment coating layer mainly composed of a pigment and an adhesive is formed.

  The type of the pigment is not particularly limited, and those generally used as papermaking pigments can be used. Examples of the pigment include heavy calcium carbonate, light calcium carbonate, kaolin clay, delaminated kaolin, talc and the like, and one or more of these can be appropriately selected and blended. Note that white carbon, titanium dioxide, calcium sulfate, and the like can be used as the special pigment having high whiteness. However, in the present invention, the target high pigment can be obtained without using the special pigment having high whiteness. Since white coated paper for printing can be obtained, it is preferable not to add the special pigment because cost can be reduced. Further, satin white, calcium sulfite, gypsum, barium sulfate, diatomaceous earth, magnesium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, as long as the effects of the present invention are not impaired. Inorganic pigments such as bentonite and sericite, and special pigments such as organic pigments such as polystyrene resin fine particles, urea formalin resin fine particles, fine hollow particles, and porous fine particles may be used in combination.

  Among the above pigments, kaolin clay is preferable because it is easy to improve the glossiness and smoothness of the coated paper for printing, and printability is improved under flattening conditions with a lower nip, so that the hand feeling of the paper is hardly lowered. . However, on the other hand, since the whiteness is lower than that of calcium carbonate, the whiteness of the coated paper for printing may be lowered when the amount is high. Therefore, the blending amount of the kaolin clay is preferably 30 to 70 parts by mass, more preferably 40 to 60 parts by mass with respect to 100 parts by mass of the total pigment.

  Moreover, as a pigment suitably used other than clay, it is preferable to use heavy calcium carbonate because of its high whiteness. It is preferable that the compounding quantity of heavy calcium carbonate is 30-70 mass parts with respect to 100 mass parts of all the pigments, More preferably, it is 40-60 mass parts. If the blending amount of heavy calcium carbonate is less than 30 parts by mass, the whiteness of the resulting coated paper for printing may not be sufficiently improved. Conversely, if it exceeds 60 parts by mass, the printability may be reduced. .

  In addition, although there is no limitation in particular in the kind of heavy calcium carbonate, What has an average particle diameter of about 5 micrometers or less which carried out the dry grinding | pulverization or wet grinding | pulverization of white crystalline limestone can be illustrated, for example.

  In addition, light calcium carbonate can be used instead of the heavy calcium carbonate. Examples of the light calcium carbonate include those having an average particle size of about several μm and those having an average particle size of about 0.02 to 0.1 μm, which are chemically produced by baking limestone, for example. Examples of the shape include a columnar shape, a needle shape, and a spindle shape, and a chestnut shape in which crystal structures having these shapes are aggregated and crystallized. Light calcium carbonate is more preferable because the pigment has high flexibility, can form a smoother pigment coating layer surface, and improves printability.

  In addition, high whiteness clay that can be imparted with high whiteness and high whiteness that can be imparted with high whiteness obtained by firing or sufficiently removing impurities in the production process Although fine clay can be blended, in the present invention, the desired high whiteness coated coated paper can be obtained without using these high whiteness clay and high whiteness fine clay. . When these are used, it is particularly preferable that the blending amount is 50 parts by mass or less with respect to 100 parts by mass of the total pigment, as in the case of the kaolin clay.

  There is no particular limitation on the type of adhesive compounded with the pigment, but in order to form a more flexible pigment coating layer, latex having high stability, latex containing a butadiene component as a monomer component is used. It can be particularly preferably used. Among them, in the present invention, it is preferable to use a latex containing a butadiene component in an amount of 50 to 80% by mass, further 55 to 75% by mass, particularly 60 to 70% by mass, based on the total amount of monomer components. When the butadiene component is less than 50% by mass, the flexibility of the pigment coating layer is lowered and printability may be lowered. On the other hand, when the butadiene component exceeds 80% by mass, for example, when performing a flattening process with a super calender, the pigment coating layer may be taken on a metal roll and roll contamination may easily occur.

  In addition to the styrene-butadiene copolymer latex, an adhesive that can be generally used for papermaking can be used in combination with the present invention. Examples of such adhesives include proteins such as casein and soybean protein; conjugated diene latexes such as methyl methacrylate-butadiene copolymer latex and styrene-methyl methacrylate-butadiene copolymer latex, acrylic acid esters and / or Acrylic latex such as polymer latex or copolymer latex of methacrylic acid ester, vinyl latex such as ethylene-vinyl acetate polymer latex, or a monomer containing functional groups such as carboxyl groups of these various copolymer latexes Latexes such as alkali partially soluble or non-soluble latex modified with 1; synthetic resin adhesives such as polyvinyl alcohol, olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin; oxidized starch, positive starch Esthetic Starches such as modified starch and dextrin; examples of adhesives usually used in coated paper such as cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, and one or more of these are appropriately selected and used in combination can do.

  The blending ratio of the pigment and the adhesive in the pigment coating agent is preferably adjusted so that the adhesive is 3 parts by mass or more, more preferably 4 parts by mass or more, with respect to 100 parts by mass of the total pigment. It is preferable to adjust so that it may become 10 parts by mass or less. When the blending amount of the adhesive is less than 3 parts by mass, for example, when performing a flattening process with a super calender, the pigment coating layer may be taken on a metal roll and roll contamination may easily occur. On the other hand, when the blending amount of the adhesive exceeds 12 parts by mass, the adhesive is formed in the pigment coating layer, making it difficult for the ink to transfer, which may reduce the printability.

  Furthermore, in the pigment coating layer, a fluorescent dye generally used for papermaking can be contained for the purpose of further improving the whiteness.

  There are no particular limitations on the type of fluorescent dye, and those generally used for papermaking can be used. Examples of the fluorescent dye include fluorescent dyes such as aminostilbene, imidazole, oxazole, triazole, coumarin, naphthalimide, and pyrazoline, and one or more of these are appropriately selected. Can be used. Among these, aminostilbene fluorescent dyes are preferable, and aminostilbene sulfonic acid derivatives are particularly preferable. Furthermore, hexatypes in which six sulfonic acid groups are coordinated in one molecule and tetratype aminostilbene sulfonic acid derivatives in which four sulfonic acid groups are coordinated in one molecule have a high fluorescent whitening effect. preferable. In particular, hexa-type aminostilbene sulfonic acid derivatives are preferred because they have a higher fluorescent whitening effect.

  The pigment coating agent used in the present embodiment is mainly composed of a pigment and an adhesive, but besides these, for example, a fluorescent dye, a fluorescent dye fixing agent, an antifoaming agent, a release agent, a colorant, water retention Various auxiliary agents generally used in papermaking applications, such as an agent, can be appropriately blended within a range not impairing the object of the present invention.

  The method for preparing the pigment coating agent is not particularly limited, and the blending ratio of the pigment, the adhesive and the softening agent, and the fluorescent dye and various auxiliary agents as necessary is appropriately adjusted, and uniform at an appropriate temperature. What is necessary is just to stir and mix so that it may become a composition. The solid content concentration of the pigment coating agent is not particularly limited, and is preferably adjusted to, for example, about 60 to 75% by mass according to the coating apparatus and the coating amount.

  Next, the pigment coating agent is coated on at least one surface of the base paper, preferably on the primer coating layer provided on the base paper, and at least one pigment coating layer is formed on the base paper. Form.

  The pigment coating agent is preferably applied to the base paper in a coater part between the dryer parts, which is performed in a plurality of stages, usually two stages of a pre-dryer part and an after dryer part. The coater part is divided into one layer or multiple layers on the base paper by an on-machine coater or an off-machine coater equipped with a coating device such as a blade coater, air knife coater, transfer roll coater, rod metering size press coater, curtain coater, etc. The pigment coating agent is applied. Among these, it is preferable to use a blade coater from the viewpoint that high smoothness of the surface of the pigment coating layer is ensured. In addition, as a drying method in the dryer part, for example, various heating drying methods such as hot air heating, gas heater heating, infrared heater heating and the like can be appropriately employed.

The coating amount of the pigment coating agent is preferably 5 g / m ² or more, more preferably 7 g / m ² or more, more preferably 9 g / m ² or more, more preferably 20 g / m ² per side of the base paper in terms of solid content. It is preferably ² or less, more preferably 18 g / m ² or less, and particularly preferably 15 g / m ² or less. When the coating amount is less than 5 g / m ² per side, the pigment coating layer is not sufficiently flattened, and it becomes difficult to obtain good printability. On the other hand, when the coating amount exceeds 20 g / m ² per side, for example, when performing a flattening process with a super calender, the pigment coating layer is peeled off and taken on the roll, and roll contamination troubles are likely to occur. Not only is there a possibility that productivity and quality will be lowered, but it will not meet the object of the present invention of weight reduction.

[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, the pigment coating layer will not be flattened, and if it exceeds 600 KN / m, the base paper will be pressed more than necessary, and the hand feeling will be reduced, which is not preferable. 100-300 degreeC is preferable and the temperature of a metal roll has more preferable 100-200 degreeC. When the temperature is less than 100 ° C, the pigment coating layer does not flatten, and when the temperature exceeds 300 ° C, fiber burns occur, or the coated paper itself turns yellow due to heat and pressure. 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 multi-nip calender of 6, 8, 10 is suitable because it is easy to adjust the nip pressure, easy to adjust hand feeling and white paper gloss, and is excellent in bulkiness. 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 with a high paper surface temperature, making it easier to improve the glossiness of blank paper, lowering the linear pressure required to obtain the desired coated paper, and reducing hand feeling. Is preferable because of a small amount.

The basis weight of the coated paper for printing thus obtained is 30 g / m ² measured in accordance with the method described in JIS P 8124 “Basis weight measurement method” in terms of weight reduction, opacity, and hand feeling. In addition, it is preferably 40 g / m ² or more, more preferably 80 g / m ² or less, and even more preferably 75 g / m ² or less. When the basis weight is less than 30 g / m ^2, it is difficult to sufficiently improve the opacity and hand feeling even with the present invention. Conversely, when the basis weight exceeds 80 g / m ² , the opacity and hand feeling can be sufficiently improved without using the present invention.

  In such low rice paper, opacity is particularly important so that the printing on the back side is not visible from the front side after printing, and specifically the opacity is preferably 85% or more, It is more preferably 87% or more, and most preferably 89% or more. When the opacity is less than 85%, not only the sharpness of the printed image on the surface is impaired, but also a problem that it is difficult to distinguish characters in the printing portion occurs.

  In addition, paper with a low tsubo is generally soft and has a rough texture, which impairs the sense of quality. However, in the present invention, a specific filler and a filler treatment agent are used, so that the paper has an excellent hand feeling. It becomes.

  The degree of whiteness varies slightly depending on the application, but from the viewpoint of obtaining a sufficiently satisfactory aesthetic appearance as a printed matter or recorded matter, a pigment coating layer measured with a color analyzer (model number: Color i5, manufactured by Macbeth Gretag). The surface whiteness is preferably 86% or more, more preferably 88% or more, and particularly preferably 90% or more. The whiteness is preferably 100% or less so that the contrast between the image area and the non-image area becomes too high after printing and the appearance of the printed matter is not deteriorated.

  As described above, the coated paper of the present invention achieves both excellent opacity and hand feeling while reducing the weight of the paper, and is suitably used for, for example, commercial printed matter, information paper, packaging paper, and newspaper. can do.

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

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

  In Examples and Comparative Examples, paper making was performed using a paper machine including a wire part, a press part, a predryer part, an undercoater part, an afterdryer part, a top coater part, a calendar part, and a reel part.

  For 100 parts by mass (absolutely dry amount) of pulp mixed with 20% NBKP and 80% LBKP, 0.001% by mass of an internal sizing agent (part number: FK34 modified, manufactured by Toho Chemical Co., Ltd.) 0.5% by mass of a modified starch (product number: Amylofax T-2600, manufactured by Abebe Japan Co., Ltd.), and a filler preliminarily mixed with a coagulant and a filler treating agent shown in Table 1, or a filler not mixed, and agglomeration The agent was mixed at a ratio shown in Table 1 to obtain a pulp slurry. In addition, calcium carbonate was used for the untreated filler.

The pulp slurry was paper in the wire part, and then subjected the press part, the pre-dryer part, to produce a base paper having a basis weight 49~51g / m ^2. Next, in the undercoater part, undercoat is applied to both sides of the base paper so that the solid content is 1.0 g / m ² per side and dried in the after dryer part. A construction layer was formed.

  When the whiteness of the base paper was measured by the same method as the whiteness of the coated paper for printing described later, it was 83 to 86%.

After that, at the top coater part, the pigment coating agent is applied onto the base coating layer on both sides of the base paper so that the solid content is 9 g / m ² per side. A layer was formed, and a coated paper having a basis weight of 67 to 69 g / m ² was obtained.

  Next, the coated paper was flattened at a calender part at a linear pressure of 200 kN / m, a metal roll temperature of 200 ° C., and a speed of 1000 m / min to obtain a target coated paper for printing.

  The wire part made paper using a gap former, the undercoater part adopted a film transfer system using a rod metering size press coater, and the top coater part used a blade coater. In the calendar part, a multi-nip calendar was used.

  The chemicals used are as follows.

<Regenerated particles>
a) Regenerated particles derived from paper sludge (regenerated particles)
It manufactured by adjusting the particle size by the manufacturing method of Unexamined-Japanese-Patent No. 2002-167523, Test Example 8. Specifically, paper sludge obtained by dehydration to 55-65% with a DIP floater floss or dewatering equipment is cut into a string of 4.5 mm in diameter and 8-10 cm in length, and then incinerated. Regenerated particles having a secondary particle diameter of 3 μm were produced by incineration at 1000 ° C. in a furnace.
b) Regenerated particle aggregate derived from deinking floss (regenerated particle aggregate)
It manufactured by adjusting the particle size by the manufacturing method of Unexamined-Japanese-Patent No. 2007-146354 and Example 3. FIG. 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%. In the first firing step, the unburned portion is 7%, and in the second firing step, the unburned portion is fired to 12 mass% (baking step), so that the particle diameter is 5 μm. Grinding (grinding step) produced regenerated particle aggregates.
c) Silica-coated regenerated particle aggregate (silica coating)
It manufactured by adjusting the particle size by the manufacturing method of Unexamined-Japanese-Patent No. 2007-146354 and Example 15. Specifically, deinked floss discharged from the waste paper processing process is dehydrated to a moisture content of 50% (dehydration process), dried at 130 ° C. (drying process), and the moisture content at the firing process inlet becomes 3%. In the first firing step, the unburned portion is 7%, and in the second firing step, the unburned portion is fired to 12 mass% (baking step), so that the particle diameter is 5 μm. By pulverizing (pulverizing step), a silica-coated regenerated particle aggregate in which silica was deposited on the surface of the regenerated particle aggregate was produced.

<Calcium carbonate>
Product number: TP121-6S, a light calcium carbonate manufactured by Okutama Kogyo Co., Ltd. was used.

<Filler treatment agent>
Styrene-acrylic polymer (product number: FM-8173, manufactured by Seiko PMC)
Anion PAM (Part No .: FA-230, manufactured by Hymo)
Polyamine (Part No .: Cartafix NTC2, Clariant)
Epichlorohydrin (product number: FM-8170, manufactured by Seiko PMC)

<Coagulant>
Polyamine (Product No .: FR740, manufactured by Hymo)
Polyethyleneimine (Part No .: Cassiofast VFH, manufactured by BASF)
DADMAC (Part No .: NR-783, manufactured by Hymo)

<Flocculant>
Bentonite (Product number: Hydrocoal 0, manufactured by Kyowa Sangyo Co., Ltd.)
Cation PAM (Part No .: Percoll E24X, manufactured by Ciba Specialty)
Anion PAM (Part No .: FA-230, manufactured by Hymo)

得られた印刷用塗工紙について、各物性及び特性を以下の方法にて調べた。その結果を表１に示す。

About the obtained coated paper for printing, each physical property and characteristic were investigated with the following method. The results are shown in Table 1.

(1) Opacity It was measured using a color analyzer (model number: color i5, manufactured by Macbeth Gretag Co., Ltd.) by a method based on ISP6149.

(2) Whiteness The whiteness was measured by a method based on JISP8148 using a color analyzer (model number: color i5, manufactured by Macbeth Gretag).

(3) Hand feeling 20 sheets of A4 size (210 mm x 297 mm) coated paper are stacked, and one side of the long side is stapled at 3 locations (top, center, bottom) and placed horizontally, 10 sheets in total On the other hand, hand feeling was evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: The paper after turning does not sag and is particularly excellent in hand feeling.
○: Sag of paper after turning is slight and excellent hand feeling.
Δ: Little paper sagging after turning and good hand feeling.
X: The paper after turning is sagging, and the hand feeling is inferior.

(4) Operability The operation was performed continuously for 24 hours, and the operability was evaluated in the following four stages.
A: There is almost no fluctuation of draw and tension, and operability is particularly excellent.
○: Draw and tension fluctuations are slight, and operability is excellent.
Δ: Draw and tension fluctuations are small and operability is good.
×: Draw and tension fluctuate greatly and operability is poor.

  From Table 1, it can be seen that all of the papers of the examples are papers having high opacity and hand feeling while having a low rice floor because the filler is treated with a predetermined filler treatment agent.

  On the other hand, all the comparative examples are papers with low opacity and hand feeling because no filler is treated with a predetermined filler treatment agent.

  Paper with excellent opacity and hand feeling can be obtained while having a low rice floor.

Claims (7)

  A paper in which a filler is internally added to a pulp, wherein the paper is obtained by adding an anionic compound as a filler treating agent to the filler in advance and then mixing with pulp to make paper.   The paper according to claim 1, characterized in that the filler is recycled particles derived from papermaking sludge.   The paper according to claim 2, wherein the regenerated particles are regenerated particle aggregates derived from deinking floss.   The paper according to any one of claims 1 to 3, wherein the anionic compound is a styrene-acrylic polymer.   The paper according to any one of claims 2 to 4, wherein the regenerated particles are silica-coated regenerated particle aggregates in which regenerated particle aggregates derived from deinked floss are coated with silica.   The paper according to any one of claims 1 to 5, wherein the anionic compound is an anionic polymer compound, and the molecular weight of the anionic polymer compound is 10,000 to 1,000,000.   The paper according to any one of claims 1 to 6, wherein the filler and the filler treating agent are mixed in advance and then added to the pulp within one minute.