JP2016130387A - Method for manufacturing paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for effectively preparing pulp having characteristics by applying a fiber classification technique, and producing paper having characteristics, especially a strong hardness by using the pulp.SOLUTION: A method for manufacturing paper includes: a step of classifying a pulp slurry containing old paper pulp and having a solid content concentration of 1.5 wt.% or more into a long fiber fraction and a short fiber fraction by using an outward type slit screen having an opening of a slit width of 0.1 mm-0.3 mm; a step of bringing a solid content ratio of the long fiber fraction to the short fiber fraction to (10:90)-(60:40), and a Canada standard freeness difference between the long fiber fraction and the short fiber fraction to 100 ml-300 ml; a step of adding at least one paper-making additive to the pulp slurry of the short fiber fraction; and a step of paper-making using the pulp slurry of the short fiber fraction, added with the paper-making additive.SELECTED DRAWING: None

Description

  The present invention relates to a paper manufacturing method. The present invention relates to a method for efficiently producing a strong paper using a pulp slurry of a short fiber fraction containing a relatively large amount of fine fibers classified by a specific method.

  In order to produce recycled pulp from waste paper at a low cost, it is necessary to efficiently remove ink and adhesive foreign matter contained in the waste paper from the fiber. Since the ink is fixed to the fiber and ash, it is common to treat the fiber with a mechanical ink peeling device to promote ink peeling, and then remove the ink by washing or flotation. Moreover, it is known that it is most effective to remove the low-concentration pulp slurry using a screen having a narrow slit width for removing the adhesive foreign matter.

  On the other hand, recently, diversified prints have increased the number of inks that are difficult to remove, such as UV inks and varnishes, and the presence of sticking foreign substances derived from stickers and adhesive tapes has increased. It tends to get worse. In order to compensate for these deteriorations in quality, the production process of recycled pulp tends to be more heavily equipped, and accordingly, there are problems such as a decrease in yield and an increase in power cost.

  Thus, it has been difficult to achieve both the production of regenerated pulp at a low cost and the good quality while raw material quality deteriorates. In order to solve such problems, attempts have been made to apply fiber classification in the production process of recycled pulp and separately process the fractions after fractionation and blend them into paper.

  In Patent Document 1, a long fiber and a short fiber are fractionated using an inward-type screen, the long fiber side is processed by a selective process, the short fiber side is processed by flotation, and both are combined with a cleaner. Attempts have been made to treat and dehydrate to obtain recycled pulp. As an advantage of this method, the facility is made compact by not performing the flotation treatment on the long fiber side. However, since this method uses an inward-type screen that is easily clogged with raw materials, it is necessary to classify fibers at a low concentration of about 1%, and a large screen is required. When the fiber is processed by flotation, the ink adheres to the fine fibers and ash. Therefore, the yield in the flotation is reduced to remove the ink, and the ink is used to keep the yield good. There was a drawback that the whiteness was lowered without progressing the removal.

  In Patent Document 2, there is a method in which unsorted waste paper is disaggregated and processed with a coarse screen, followed by flotation, and the subsequent suspension is classified using a screen having a slit width of 0.05 to 0.12 mm. Has been tried. In this method, since the flotation is performed before classification, the volume to be processed becomes large and a large flotation facility is required. For example, in order to obtain 100 BD tons / day of regenerated pulp, it is necessary to process a solid content of 4 tons / hour or more, and when flotation is performed at a concentration of about 1% by weight, which is considered to have good flotation efficiency. A large flotation facility capable of processing 400 tons / hour or more as a slurry is required.

In Patent Document 3, an attempt is made to classify pulp into a fine fraction and a coarse fraction using a pressure sorter, a screw press, or a hydrocyclone, and to perform the flotation of these fractions separately under different conditions. However, it is difficult to control the classification conditions with a screw press, and the hydrocyclone has a disadvantage that the separation efficiency is low although the concentration is low and the equipment becomes large and the energy consumption increases. Even in the case of using a pressure sorter, since the flotation in which the yield is most likely to be reduced is performed in both fractions in the production process of the regenerated pulp, there is a problem in that the yield is likely to be reduced and the cost is easily increased. . Furthermore, as in Patent Document 1, flotation is performed at a higher concentration than the coarse fraction without having a means for separating the ink fixed to the fine fibers and ash in the fine infrastructure from these fine fibers and ash. Therefore, the ink separation efficiency is low, and in order to obtain good whiteness, the yield is inevitably reduced.

Japanese Patent No. 29986525 JP 2004-131892 A JP 2006-316400 A

  An object of the present invention is to provide a technique for efficiently preparing a characteristic pulp by applying a fiber classification technique and producing a characteristic paper, particularly a strong paper, using the pulp. is there.

  As a result of intensive studies by the inventor on the above problems, it has been found that a characteristic short fiber fraction can be efficiently obtained by classifying a pulp slurry containing waste paper by a specific method. That is, in the manufacturing process of recycled pulp, the pulp slurry after disintegration of used paper is an outward-type slit having an opening with a slit width of 0.1 mm to 0.3 mm at a high solid content concentration of 1.5% by weight or more. A long fiber fraction and a short fiber fraction are classified using a screen, and the solid content ratio of the long fiber fraction and the short fiber fraction is 10:90 to 60:40, the long fiber fraction and the short fiber fraction. By making the difference in Canadian standard freeness of 100 minutes to 300 ml, a characteristic long fiber fraction and short fiber fraction could be produced with less energy.

  And when further studying, even if using short fibers, the paper strength of which is likely to decrease compared to long fibers, by pre-processing the short fiber fraction with a specific method and then making paper The present inventors have found that high-strength paper can be produced and have completed the present invention.

The present invention includes, but is not limited to, the following inventions.
(1) A pulp slurry containing a waste paper pulp having a solid content concentration of 1.5% by weight or more, using an outward slit screen having an opening with a slit width of 0.1 mm to 0.3 mm, to a long fiber fraction And the short fiber fraction, the solid content ratio of the long fiber fraction to the short fiber fraction is 10:90 to 60:40, and the Canadian standard filter for the long fiber fraction and the short fiber fraction. Using a process in which the difference in water degree is 100 ml to 300 ml, a process of adding one or more papermaking additives to the pulp slurry of the short fiber fraction, and a pulp slurry of the short fiber fraction to which the papermaking additive is added A paper manufacturing method including a paper making process.
(2) The method according to (1), wherein the papermaking additive is an organic polymer.
(3) The method according to (1) or (2), wherein a filler is added together with the papermaking additive to the pulp slurry of the short fiber fraction.
(4) The method according to any one of (1) to (3), wherein the paper slurry is made after mixing the pulp slurry of the short fiber fraction to which the papermaking additive is added with the pulp slurry of the long fiber fraction.
(5) The method according to (4), wherein papermaking is performed after further adding another papermaking additive to the pulp slurry obtained by mixing with the pulp slurry of the long fiber fraction.
(6) The method according to any one of (1) to (5), wherein the filler contains calcium carbonate.
(7) The method according to any one of (1) to (6), wherein the papermaking additive added to the pulp slurry of the short fiber fraction contains polyacrylamide.

  According to the present invention, it is possible to efficiently prepare a characteristic pulp by classifying fibers by a specific method, and to produce a strong paper by performing a specific pretreatment on the pulp. Become.

  In the present invention, a pulp slurry having a solid content concentration including waste paper pulp of 1.5% by weight or more is used as a long fiber by using an outward type slit screen having an opening with a slit width of 0.1 mm to 0.3 mm. Including fractionation into a fraction and a short fiber fraction, the solid content ratio of the long fiber fraction and the short fiber fraction is 10: 90-60: 40, the Canadian standard for the long fiber fraction and the short fiber fraction Classification is performed so that the difference in freeness is 100 to 300 ml.

(Recycled pulp)
In the present invention, the regenerated pulp means pulp regenerated from waste paper, and includes waste paper pulp obtained by breaking up waste paper and deinked pulp from which ink has been removed after waste paper is removed. Examples of the used paper as a raw material include newspapers, flyers, magazines, books, office paper, sealed letters, thermal paper, carbonless paper, cardboard, white paperboard, other copiers, and printing paper generated from OA equipment. Magazine waste paper containing adhesives such as pressure-sensitive adhesives, adhesives, pressure-sensitive adhesive tapes, and magazine back paste can also be used as a raw material for the recycled pulp of the present invention.

  Waste paper used as a raw material for these recycled pulps may contain inorganic particles called ash. Ash content refers to inorganic particles in general, and is a substance that remains when paper is incinerated, such as fillers and pigments added internally or coated during paper manufacture. Examples include calcium carbonate, talc, kaolin, titanium dioxide and the like, but are not limited thereto.

  If necessary, sodium hydroxide, sodium silicate, other alkaline chemicals, deinking agents, oxidizing bleaching agents, and reducing bleaching agents can be added to the recycled pulp. Furthermore, there is no problem even if a dye, a fluorescent brightening agent, a pH adjuster, an antifoaming agent, a pitch control agent, a slime control agent and the like are added as necessary.

  When deinking from waste paper, a deinking agent can be used. Examples of the deinking agent include known or novel surfactants such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, Nonionic surfactants such as higher alcohols, alkylphenols, alkylene oxide adducts such as fatty acids, anionic surfactants, cationic surfactants, amphoteric surfactants, and organic solvents, proteins, enzymes, natural polymers, Examples include, but are not limited to, synthetic polymers. These may be composed of a single component or a mixture of two or more components.

(Classification)
In the present invention, a pulp slurry having a solid content concentration including waste paper pulp of 1.5% by weight or more is used as a long fiber by using an outward type slit screen having an opening with a slit width of 0.1 mm to 0.3 mm. Classify into fraction and short fiber fraction.

The pulp classification means that can be used in the present invention may be any outward slit screen (outward type slit screen), for example, use of a reject screen such as Aikawa Iron Works Max Saver. Is preferred.

  An outward type screen is a type of screen in which raw materials to be processed pass through openings from the inside to the outside of the screen basket. In this type of screen, the area of the opening on the outer side is larger than that on the inner side, the pressure tends to be lower on the outer side than on the inner side, and the centrifugal force acts on the outer side. On the other hand, the inward-type screen is a type of screen in which the raw material passes through the opening from the outside to the inside of the screen basket, and the raw material is less likely to pass than the outward-type screen used in the present invention. This is unsuitable because it tends to clog when the concentration is 1.5% by weight or more. Conventionally, inward screens have been able to classify fibers more accurately than outward screens. In the present invention, however, pulp having a high solid content is obtained by using outward screens. Process the slurry.

  For the classification of the present invention, a slit screen having a slit-like opening is used. Conventionally, a round hole screen having a round hole opening has been generally used for fiber classification, but a slit screen is used in the present invention. In a round hole-shaped opening, if the hole diameter is reduced, the opening area of the basket is reduced, a large facility is required, and raw materials and foreign substances are easily clogged, so that it is difficult to increase the concentration. When the hole diameter is increased, separation of adhesive foreign matters and the like becomes insufficient, which is not suitable for the purpose of the present invention.

  In the present invention, the slit width is 0.1 to 0.3 mm, preferably 0.13 to 0.2 mm, and more preferably 0.13 to 0.15 mm. When the slit width is smaller than 0.1 mm, clogging easily occurs, so that it is difficult to treat with a solid concentration of 1.5% by weight or more, and the operation is performed with a concentration of 2.0% by weight or more as in the present invention. It becomes extremely difficult. On the other hand, when the slit width exceeds 0.3 mm, the separation of the sticky foreign matter becomes insufficient, and the sticky foreign matter increases especially on the short fiber side. Pulp quality is reduced.

  The classification conditions of the present invention are not particularly limited as long as the solid concentration of the pulp slurry to be treated is 1.5% by weight or more. Screen treatment is preferably performed at a concentration of 1.5% by weight or more and less than 4.0%, more preferably by treatment at a concentration of 1.8% by weight or more and less than 3.5%, and a concentration of 2.2% by weight or more and 3.0%. More preferably, the treatment is performed at less than%. In a preferred embodiment, the pulp slurry after waste paper disintegration can be subjected to a coarse screen without being diluted to a solid content concentration of about 1% by weight, and then processed with the above-described outward type screen.

  If the concentration is less than 1.5%, the classification efficiency will improve, but the classification equipment will become larger, the concentration of the short fiber fraction (accepted side) after processing will be lower, the size of the concentrator will be increased, etc. Therefore, the advantage of energy saving and downsizing as obtained by the present invention cannot be obtained. On the other hand, if the concentration is 4% or more, classification on the screen becomes difficult and problems such as clogging are likely to occur, which is not suitable.

  Moreover, since the concentration of the long fiber fraction immediately after classification can be set to 2.0% by weight or more by increasing the concentration of the pulp slurry to be classified as described above, It is efficient because the concentration can be increased using a medium to high concentration concentrator without going through a concentration concentrator, and for example, the long fiber fraction after increasing the concentration to 25% by weight or more is obtained by an ink peeling device. The ink can be peeled off very efficiently.

The operating conditions of the screen in the present invention are different from the so-called normal screening screen operating conditions in an optimum range. That is, the preferred flow velocity of the outward type screen of the present invention is slower than the normal screen, preferably in the range of 0.6 to 1.2 m / s, more preferably in the range of 0.7 to 1.0 m / s. preferable. Furthermore, the peripheral speed of the agitator inside the screen is higher than usual, preferably 14 to 20 m / s, and more preferably 16 to 19 m / s.

(Long fiber fraction and short fiber fraction)
The long fiber fraction in the present invention is a fraction collected as a reject side when the pulp slurry is treated with a screen, and is a fraction containing a lot of relatively long fibers in the pulp slurry before treatment. is there. The short fiber fraction is a fraction collected as the accept side of the screen, and is a fraction containing a lot of relatively short fibers, fine fibers, and ash in the pulp slurry before processing.

  In the present invention, the obtained long fiber fraction / short fiber fraction is classified so that the solid fraction classification ratio is 10:90 to 60:40. The effect of the present invention is that the classification ratio is 20:80 to 50. : 50 is even more remarkable, and it is particularly remarkable when it is 30:70 to 50:50. When the ratio of long fibers to the classification ratio of the long fiber fraction / short fiber fraction is smaller than 10:90, the function is the same as a so-called selective screen used for removing foreign matters, and the long fiber image is also classified. The amount of fibers that are separated in minutes is small, and the merit of performing the subsequent processing separately is reduced. If the ratio of long fibers is larger than 60:40, it is necessary to put more rejects on the screen than accepts, which is not suitable because of problems such as clogging of slits and clogging of reject pipes. .

  In the present invention, classification is performed so that the difference in Canadian standard freeness of the obtained long fiber fraction and short fiber fraction is 100 to 300 ml. The effect of the present invention is that the difference in Canadian standard freeness is This is particularly noticeable in the case of 150 to 200 ml. If the difference in freeness is less than 100 ml, the classification of long fibers and short fibers will not work very well, and the distribution of ink and sticking foreign materials will not work well, leading to a decline in the quality of the finished pulp. Unsuitable. In particular, when the screen treatment is performed only on the long fibers or the flotation treatment is performed only on the short fibers, ink removal of the long fibers and adhesion foreign matter removal of the short fibers are insufficient. On the other hand, in order to set the freeness difference to 300 ml or more, it is necessary to take out only the long fibers. As a result, the proportion of the long fibers in the classification ratio is too small, and the pulp slurry is classified and processed separately. The merit of performing is reduced.

  In the present invention, in the long fiber fraction after classification as described above, in addition to fibers having a relatively long fiber length, there are many coarse dirt and adhesive foreign matter, and conversely, there are few fine inks and ash. For example, refining dirt using a high-concentration ink peeling device and removing sticky foreign matter using a selective screen are particularly effective for the long-fiber fraction, and are suitable for producing high-quality long-fiber finished pulp. It is.

  On the other hand, the short fiber fraction after classification contains relatively short fibers, fine fibers, ink, and ash, and there are few coarse dirt and adhesive foreign matter. It is particularly effective to do and is suitable for producing high quality short fiber finished pulp.

(Long fiber fraction processing)
In the present invention, recycled pulp may be obtained by performing an ink peeling step and a foreign matter removing step on the long fiber fraction. In a preferred embodiment, in the present invention, the pulp slurry is classified with a solid content concentration of 1.5% by weight or more using the screen, so that the concentration of the long fiber fraction immediately after classification is 2.0% by weight or more. The fraction is efficient because it can be concentrated using a medium to high concentration concentrator without going through a low concentration concentrator. For example, the long fiber fraction after dehydration to a solid concentration of 25% or more Can finely remove ink adhered to long fibers and coarse dirt using a high-concentration ink peeling device or the like to exfoliate ink very efficiently, and further, for example, a solid content concentration of 0.5 to 1.2 The finished long fiber pulp can be efficiently obtained by diluting up to 5% and screening and removing foreign matters.

  The low concentration concentrator in the present invention is a preliminary dewatering device that dehydrates and concentrates pulp having a concentration of around 1% to a concentration of about 3% by weight or more. For example, a device that performs filtration and dewatering using a pulp mat such as a disk extract or a dissicener, or a device that performs natural dewatering using a filter or dewatering element such as an SP filter or a trommel may be used. Since these apparatuses process low-concentration slurries, it is necessary to have a large processing capacity, and the maintenance and management costs are high due to clogging of disks and filters.

  In the present invention, the concentration of the long fiber fraction discharged as a reject is obtained by performing the classification using the screen at a solid content concentration of 1.5% by weight or more, thereby concentrating the reject of the screen. Therefore, it is possible to perform post-processing without using a low concentration concentrator, so that the equipment can be made compact and energy can be saved.

  The medium to high concentration dehydrator in the present invention is a device that dehydrates pulp having a concentration of about 2 to 3% by weight to about 10% by weight, such as a screw thickener, an inclined extractor, a screw press or a power press, or about 10% by weight. Is a device for dehydrating a pulp having a concentration of about 25 to 30% by weight.

  Examples of the high concentration ink peeling apparatus in the present invention include a low speed kneader and a high speed disperser. As a kneader, one, two or four axes can be used, and a kneader having two or more kneading portions can also be used. As the disperser, a disc type or a conical type can be used.

  In the present invention, the foreign matter can be separated and removed from the long fiber fraction after classification using the slit screen again. At the time of classification, the long fiber fraction hits the screen reject, so there is a high possibility that a large amount of adhesive foreign matter is mixed in the fraction. Therefore, it is preferable to separate foreign matter using a screen having a slit width of 0.1 to 0.2 mm, preferably 0.13 to 0.15 mm.

  In the screen treatment of the long fiber fraction, since the ratio of long fibers and coarse foreign matters is large, the treatment concentration is preferably 0.5 to 1.2% by weight, and preferably 0.6 to 1.0% by weight. Is more preferable, and 0.6 to 0.8% by weight is particularly preferable. If the treatment concentration is less than 0.5% by weight, the equipment to be treated becomes large, which is disadvantageous because the production cost increases. When the content is higher than 1.2% by weight, the raw material is easily clogged because the ratio of long fibers is large, and the yield is lowered and the cost is increased because a large amount of long fibers are discharged.

  According to the present invention, it is not necessary to perform the flotation with the lowest yield in the process of producing regenerated pulp on the whole pulp slurry, so that the production efficiency can be improved. By removing foreign matter with a screen having a slit width of 0.1 to 0.2 mm, an ink removal step by flotation is not required, and thus the equipment can be made compact and energy-saving while maintaining the quality of the finished pulp.

(Short fiber fraction processing)
In the present invention, a regenerated pulp may be obtained by performing an ink removing step on the short fiber fraction. In a preferred embodiment, in the present invention, the short fiber fraction is completed with less residual ink by performing ink removal by dehydration washing and / or flotation after the ink is peeled off at a solid content concentration of 5% by weight or less. Pulp can be obtained.

  The method of performing ink peeling at a solid content concentration of 5% or less is not particularly limited, and a known ink peeling method can be applied. In a preferred embodiment, cavitation bubbles are actively introduced into the pulp slurry, and finely divided. A method of stripping ink from fibers and ash using bubble collapse energy can be used. Although there is no restriction | limiting in particular about the method of introduce | transducing a cavitation bubble positively, For example, the method of patent 4291819 can be used. That is, cavitation bubbles can be generated using a liquid jet, and the ink can be peeled from the pulp fibers by contacting the bubbles with the pulp suspension.

  According to the present invention, it is possible to process only the short fiber fraction without subjecting the entire pulp slurry to flotation with the lowest yield in the process of producing regenerated pulp. The equipment can be made compact and energy-saving while maintaining it.

(Manufacture of paper)
The long fiber finished pulp and short fiber finished pulp obtained by the present invention can be separately blended as raw materials to produce paper. Further, by mixing at an arbitrary ratio, a characteristic paper can be obtained with respect to the conventional paper obtained by paper making using whole pulp. For example, if the ratio of the long fiber finished pulp is increased, the bulk becomes higher and the tear strength becomes higher. Conversely, when the ratio of the short fiber finished pulp is increased, the paper becomes denser, the tensile strength (breaking length) is increased, and the smoothness / air permeability resistance is increased.

  In the present invention, pretreatment is performed by previously adding a papermaking additive to the short fibers obtained as described above. By performing such pretreatment, short fibers containing fine fibers can be efficiently produced on paper and contribute to the strength of the paper, and a high strength paper can be obtained.

  Although the papermaking additive used in the present invention is not limited to the following, it is an additive added in the papermaking process. For example, generally a paper strength improver and / or a yield improver and / or Or the additive for papermaking used as a coagulant | flocculant can be used conveniently. Such chemicals have been developed as papermaking chemicals and generally have good fixability to pulp fibers. These include those mainly composed of inorganic molecules and those mainly composed of organic polymers, but those composed of organic polymers can be suitably used.

  Examples of inorganic molecular papermaking additives include aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum compounds such as basic aluminum chloride and basic polyaluminum hydroxide, and water-degradable alumina sol. Water-soluble aluminum compounds, polyvalent metal compounds such as ferrous sulfate and ferric sulfate, silica sol and the like.

  Although there is no restriction | limiting in particular in the organic polymer used by this invention, The organic polymer generally used as a paper strength improving agent and / or a yield improving agent can be used conveniently. Such chemicals have been developed as papermaking chemicals and generally have good fixability to pulp fibers.

As the organic polymer, an ionic polymer, that is, a cationic polymer, an anionic polymer, an amphoteric polymer, and a polyion complex composed thereof can be preferably used, and starch and derivatives thereof can also be preferably used. it can. Moreover, in this invention, it is also possible to use in combination of multiple types as an organic polymer. Preferred organic polymers include polyacrylamide, polyvinylamine, starch, guar gum, polyamidoamine epichlorohydrin, carboxymethylcellulose, cellulose nanofiber, chitosan, alginic acid and derivatives thereof, and polyacrylamide polymers and starches are more preferred. More preferred are polyacrylamide polymers. The polyacrylamide polymer preferably has a molecular weight of 1 million or more, and is amphoteric and cation-rich. As starches, raw starch, oxidized starch, esterified starch, cationized starch, enzyme-modified starch, aldehyde-modified starch, hydroxyethylated starch and the like are used. Examples of raw starch materials include corn, tapioca, and potato.

  The amount of the papermaking additive added to the short fiber is not particularly limited, but is preferably added in the range of 0.01 to 6.0%, more preferably 0.01 to 2.0%, and more preferably 0.01 to 0.4% with respect to the weight of the short fiber dry solid content. Is more preferable. Further, the addition in the range of 0.01 to 5.0% with respect to the total solid content of the paper is preferable, 0.01 to 1.0% is more preferable, and 0.01 to 0.3% is more preferable. By adding the papermaking additive in such a range in advance, the strength of the paper can be effectively improved.

  In a preferred embodiment of the present invention, a filler is added together with the papermaking additive to the pulp slurry of the short fiber fraction. By preliminarily fixing the filler to the short fibers containing fine fibers in this manner, the paper strength can be further improved as compared with the case where the papermaking additive is added after the filler is added to the whole pulp.

  There are no particular restrictions on the method of adding the filler and papermaking additive to the short fiber pulp, either adding the papermaking additive after adding the filler to the short fiber, or adding the filler after adding the papermaking additive. Well, it is possible to add a mixture of filler and papermaking additive in advance to the short fiber, but especially when adding the papermaking additive after adding the filler to the short fiber pulp, the short fiber of the filler Since the fixability to pulp is high and the filler can be entangled with fibrils such as fine fibers, the effect is enhanced.

  The filler used for the pretreatment is not particularly limited, and particles generally called inorganic filler and organic filler can be used. For example, as inorganic filler, calcium carbonate (light calcium carbonate, heavy calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay (kaolin, calcined kaolin, deramikaolin) ), Talc, zinc oxide, zinc stearate, titanium dioxide, silica made from sodium silicate and mineral acid (white carbon, silica / calcium carbonate composite, silica / titanium dioxide composite), white clay, bentonite, diatomaceous earth, Examples thereof include calcium sulfate, an inorganic filler that regenerates and uses the ash obtained from the deinking process, and an inorganic filler that forms a complex with silica or calcium carbonate in the process of regeneration. As the calcium carbonate-silica composite, amorphous silica such as white carbon may be used together with calcium carbonate and / or light calcium carbonate-silica composite. Among these, calcium carbonate and light calcium carbonate-silica composite, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used. Organic fillers include urea-formalin resin, polystyrene resin, phenol resin, fine hollow particles, acrylamide composites, wood-derived substances (fine fibers, microfibril fibers, powder kenaf), modified insolubilized starch, ungelatinized starch, etc. Is mentioned. These may be used alone or in combination of two or more.

Preferable fillers include calcium carbonate such as light calcium carbonate and heavy calcium carbonate, kaolin, talc, titanium oxide and the like.
The amount of filler added to the short fiber is not particularly limited, but it is preferably added in the range of 1 to 70 solids by weight, more preferably 10 to 60 solids by weight, based on the short fiber absolutely dry solids, 20 More preferred is -50% solids by weight. In addition, 1 to 50% by weight of the solid content is preferably 10% by weight, 10%
-40% solids by weight is more preferred, and 15-30% solids by weight is more preferred. By adding the filler in such a range in advance, the strength of the paper can be effectively improved.

  In the present invention, paper having excellent paper strength can be obtained by making paper using the pretreated short fiber pulp. The pretreated short fiber pulp may be appropriately blended with other raw materials to prepare a paper stock to produce paper. Other raw materials include softwood or hardwood kraft pulp (NKP or LKP), mechanical pulp using softwood or hardwood, for example, groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermo Coated broke made from disintegrated waste paper including mechanical pulp (CTMP), chemi-ground pulp (CGP), semi-chemical pulp (SCP), waste paper pulp that has been disassembled from corrugated cardboard, coated paper, coated paper, and other paper And a mixture of two or more of these pulps, but is not limited thereto.

  In addition, in a multi-layer paper machine, a multi-layer paper can be produced by blending long fiber finished pulp or short fiber finished pulp obtained by the present invention, or both in an arbitrary ratio into the stock of each layer. it can.

  The finished long fiber or short fiber finished pulp obtained by the present invention can be made by adding chemicals and / or fillers separately. In particular, starch and paper strength agent are added to finished long fiber pulp, filler is added to short fiber pulp, and then a yielding agent, coagulant, paper strength agent, and starch are added and mixed to produce paper. Even if it is ash, a characteristic paper such as a high strength paper can be produced.

  Chemicals to be added include rosin emulsion, neutral rosin, alkyl ketene dimer, alkenyl succinic anhydride, styrene / acrylic copolymer, sizing agent, cationic, amphoteric, anionic polyacrylamide, polyvinylamine, polyamine Acrylic acid-containing resins, dry paper strength enhancers such as guar gum, cationic and amphoteric and anionic modified starches, wet paper strength enhancers such as polyamidoamine epichlorohydrin, carboxymethylcellulose, drainage improvers, Examples thereof include conventionally used internal chemicals such as colorants, dyes and fluorescent dyes, and paper bulking agents for increasing the bulk (lowering the density) of paper.

  Also included as coagulants are polyethyleneimines and modified polyethyleneimines containing tertiary and / or quaternary ammonium groups, polyalkyleneimines, dicyandiamide polymers, polyamines, polyamine / epichlorohydrin polymers, and dialkyldiallyl quaternary ammonium monomers. , Dialkylaminoalkyl acrylate, dialkylaminoalkyl methacrylate, dialkylaminoalkyl acrylamide, polymers of dialkylaminoalkyl methacrylamide and acrylamide, polymers of monoamines and epihalohydrin, polymers having polyvinylamine and vinylamine moieties, and mixtures thereof In addition to the cationic polymer, an anionic group such as a carboxyl group or a sulfone group was copolymerized in the polymer molecule. Chionritchi a zwitterionic polymers, and a mixture of cationic polymer and an anionic or zwitterionic polymer.

  Further, as a retention agent, in addition to a cationic, amphoteric or anionic polymer, in particular, a polyacrylamide-based material or a copolymer containing the same, at least one cationic or anionic drug. It is also possible to use a so-called dual polymer or micropolymer yield system in combination with inorganic fine particles such as at least one kind of anionic bentonite, colloidal silica, polysilicic acid, polysilicic acid or polysilicate microgel, and aluminum modified products thereof. It may be a yield system in which one or more organic fine particles having a particle size of 100 μm or less, which are so-called micropolymers obtained by cross-linking acrylamide, are used. Moreover, the multicomponent yield system which combined these may be sufficient.

In addition to the filler used for the short fiber pretreatment, a filler may be added to the paper. The filler to be added may be particles generally called inorganic filler and organic filler, and is not particularly limited. Specifically, as inorganic fillers, calcium carbonate (light calcium carbonate, heavy calcium carbonate, synthetic calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay ( Kaolin, calcined kaolin, deramikaolin), talc, zinc oxide, zinc stearate, titanium dioxide, silica produced from sodium silicate and mineral acid (white carbon, silica / calcium carbonate composite, silica / titanium dioxide composite) , White clay, bentonite, diatomaceous earth, calcium sulfate, inorganic filler that regenerates and uses ash obtained from the deinking process, and inorganic filler that forms a complex with silica or calcium carbonate in the process of regeneration. As the calcium carbonate-silica composite, amorphous silica such as white carbon may be used together with calcium carbonate and / or light calcium carbonate-silica composite. Among these, calcium carbonate and light calcium carbonate-silica composite, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used. Organic fillers include urea-formalin resin, polystyrene resin, phenol resin, fine hollow particles, acrylamide composites, wood-derived substances (fine fibers, microfibril fibers, powder kenaf), modified insolubilized starch, ungelatinized starch, etc. Is mentioned. These may be used alone or in combination of two or more.

Furthermore, cellulose nanofibers, finely pulverized cellulose, or modified ones thereof may be added.
In the present invention, the pre-treated short fibers can be re-blended with the long fibers of the long fiber fraction obtained by fiber classification to prepare a paper stock. By doing so, it is particularly preferable because the used paper as a raw material can be used effectively. The ratio of re-blending is not particularly limited, and may be appropriately adjusted according to the use of paper and the required quality.

  In the present invention, the paper making method and paper making conditions are not particularly limited, and paper can be produced by a known paper making method. The type of paper to be made, the basis weight, etc. are also free, and if necessary, a clear coating layer of an adhesive or a pigment coating layer containing a pigment can be provided on the paper surface.

  The present invention will be described more specifically with reference to examples of the present invention. However, the present invention is not limited to the following examples. Unless otherwise specified, parts and% are based on weight in the present specification, and numerical ranges are described as including the end points.

Evaluation Method Concentration and freeness of the obtained long fiber fraction and short fiber fraction, electric power required for classification (power intensity), and water usage were evaluated as follows. Further, the ash content, the average fiber length, the sieving fiber composition, and the number of adhesive foreign substances were measured for the fibers before classification, and the long fiber fraction and the short fiber fraction. Further, a handmade sheet having a basis weight of 60 g / m ² was prepared using a round hand machine based on JIS P 8209, and the number of darts, whiteness, and ink amount were measured.
(Drainage degree CSF)
It was measured based on Canadian standard freeness measurement method JIS P 8121: 1995.
(Electric power consumption)
From the motor load during screen operation and the amount of processing per hour, the power required for classification was calculated as the power consumption. The higher this value, the higher the manufacturing cost.
(Water consumption)
The processing flow rate per time during the screen processing was divided by the processing solid content and calculated as the amount of water per ton of pulp. The higher this value is, the more water is needed to process 1 ton of pulp with a solid content, and a larger capacity (volume) is required.
(ash)
Measured according to JIS P 8251: 2003.
(Average fiber length)
The length weighted average fiber length was measured using a fiber tester (manufactured by Lorentzen & Wettre).
(Sieving fiber composition)
According to JIS P 8207: 1976, the fiber composition was measured using sieves of 24 mesh, 42 mesh, 80 mesh, and 150 mesh. In Tables 2 and 3 below, “24 mesh on” indicates the ratio of fibers remaining on the sieve when sieving is performed using a 24-mesh sieve. 42 mesh on indicates the proportion of fibers that pass through the 24 mesh sieve but remains on the 42 mesh sieve (80 mesh on and 150 mesh on have the same meaning). Furthermore, 150 mesh pass indicates the proportion of fibers that pass through a 150 mesh screen.
(Number of dirt)
Using a dust measuring device (Spec Scan 2000: manufactured by Apogee Technology), measure a dart of 0.05 mm ² or more on five different hand-made sheets by image processing and calculate the number of darts per 1 m ^2. did.
(Whiteness)
According to JIS P 8148, it was measured with a color difference meter (Murakami Color).
(Remaining ink amount)
In order to measure the residual ink, the ERIC (effective residual ink density) value was measured for the fine ink using a residual ink measuring device (Color Touch: manufactured by Technidyne).
(Adhesive foreign matter)
About 1 kg of the pulp slurry absolutely dried was precisely weighed, treated with a 6-cut flat screen, the residue remaining on the screen was collected, hot-pressed between filter papers, and then colored with a hydrophobic dye. Foreign matter colored with the dye was counted by image analysis.

Experiment 1: Pulp classification (Example 1)
At Aikawa Iron Works Co., Ltd. pilot test plant, waste paper and magazine waste paper are charged into a high-concentration pulper so that the weight ratio is 7: 3, caustic soda (pure) 1% by weight, sodium silicate (Solid) 1% by weight, hydrogen peroxide (pure) 0.5%, higher alcohol deinking agent (solid) 0.2% were added, and the mixture was disaggregated at a temperature of 40 ° C. for 15 minutes. About the pulp after disaggregation, it processed by the solid content density | concentration 2.5 weight% using the coarse selection screen which has a slit width of 0.2 mm, and removes foreign materials, such as a coarse adhesion foreign material, The pulp slurry containing a waste paper pulp is used. Obtained (used paper pulp slurry A).

Thereafter, the used paper pulp slurry A whose solid content concentration was adjusted to 1.9% by weight was classified into a long fiber fraction and a short fiber fraction using an outward-type slit screen. Specifically, a reject screen manufactured by Aikawa Tekko Co., Ltd. (Max Saver: MXS-1) is used as an outward-type slit screen, and the slit width is 0.15 mm, the passing flow velocity is 1.0 m / s, and the agitator circumferential speed is 16 m / s. To obtain a long fiber fraction and a short fiber fraction. Here, the rejected portion of the screen was the long fiber fraction, the accepted portion was the short fiber fraction, and the solid content ratio (classification ratio) of the long fiber fraction and the short fiber fraction was 21:79.
(Example 2)
The same procedure as in Example 1 was performed except that the classification ratio of the long fiber fraction and the short fiber fraction was changed to 47:53 by adjusting the inlet flow rate and the reject flow rate of the classification screen.
Example 3
The solid content concentration of the waste paper pulp slurry A is adjusted to 1.6% by weight, and is processed under the conditions of a slit width of 0.13 mm, a passing flow velocity of 0.9 m / s, and an agitator peripheral speed of 14 m / s. The same procedure as in Example 1 was performed except that the classification ratio of the long fiber fraction and the short fiber fraction was changed to 22:78 by adjusting the reject flow rate.
Example 4
The classification ratio of the long fiber fraction and the short fiber fraction is set to 26:74 by processing at a flow velocity of 0.7 m / s and an agitator peripheral speed of 13 m / s, and adjusting the inlet flow rate and reject flow rate of the classification screen. The procedure was the same as in Example 3 except that.
(Example 5)
At Aikawa Iron Works Co., Ltd. pilot test plant, waste paper and magazine paper are fed into a high-concentration pulper so that the weight ratio is 8: 2, caustic soda (pure content) 1% by weight, sodium silicate 1% by weight (solid), 0.17% hydrogen peroxide (pure), 0.18% higher alcohol deinking agent (solid) were added, and the mixture was disaggregated at a temperature of 40 ° C. for 15 minutes. About the pulp after disaggregation, it processed by the solid content density | concentration 3.3 weight% using the coarse selection screen which has a slit width of 0.2 mm, and removes foreign matters, such as a coarse adhesion foreign material, and the pulp slurry containing a waste paper pulp is used. Obtained (used paper pulp slurry B).

About the waste paper pulp slurry B which adjusted solid content concentration to 2.4 weight%, using the same outward type slit screen as Example 1, slit width 0.13mm, passage flow velocity 0.8m / s, agitator peripheral speed 18m / S conditions (classification ratio of long fiber fraction and short fiber fraction is 24:76).
(Example 6)
The same procedure as in Example 5 was performed except that the classification ratio of the long fiber fraction and the short fiber fraction was changed to 30:70 by adjusting the inlet flow rate and the reject flow rate of the classification screen.
(Example 7)
The same procedure as in Example 5 was performed except that the classification ratio of the long fiber fraction and the short fiber fraction was set to 44:56 by adjusting the inlet flow rate and the reject flow rate of the classification screen.
(Example 8)
The same procedure as in Example 5 was performed except that the classification ratio of the long fiber fraction and the short fiber fraction was set to 40:60 by adjusting the inlet flow rate and reject flow rate of the classification screen, and the inlet / outlet differential pressure. .
(Comparative Example 1)
The same procedure as in Example 1 was performed except that the classification ratio of the long fiber fraction and the short fiber fraction was set to 65:35 by adjusting the inlet flow rate and the reject flow rate of the classification screen.
(Comparative Example 2)
The classification ratio of the long fiber fraction and the short fiber fraction was set to 22:78 by adjusting the solid content concentration of the waste paper pulp slurry A to 1.3% by weight and adjusting the inlet flow rate and the reject flow rate of the classification screen. Except for this, the procedure was the same as in Example 1.
(Comparative Example 3)
Comparative Example 2 was performed except that the classification ratio of the long fiber fraction and the short fiber fraction was set to 48:52 by adjusting the inlet flow rate and the reject flow rate of the classification screen.
(Comparative Example 4)
The classification ratio of the long fiber fraction and the short fiber fraction was the same as that of Comparative Example 2 except that the ratio was 60:40 by adjusting the inlet flow rate and the reject flow rate of the classification screen.
(Comparative Example 5)
Classification was performed after ink removal by flotation treatment. That is, the waste paper pulp B of Example 5 was subjected to a flotation treatment at 40 ° C. with a solid content concentration of 1% using a Maxell Flotter manufactured by Aikawa Tekko to obtain a flotation accept raw material. Next, for the accept content with a solid content concentration of 0.8% by weight, using the same outward slit screen as in Example 1, the slit width was 0.13 mm, the flow velocity was 0.8 m / s, and the agitator peripheral speed was 16.5 m / It processed on condition of s, and classified so that the classification ratio of a long fiber fraction and a short fiber fraction might be set to 39:61.
(Comparative Example 6)
At Aikawa Iron Works Co., Ltd. pilot test plant, the weight ratio of waste newspaper and magazine paper is 8:
It is charged in a high-concentration pulper so that it becomes 2. Caustic soda (pure) 1% by weight, sodium silicate (solid) 1% by weight, hydrogen peroxide (pure) 0.5%, high grade Alcohol-based deinking agent (solid) 0.2% was added, and the mixture was disaggregated at a temperature of 40 ° C. for 15 minutes. The pulp after the disaggregation is treated with a solid content concentration of 2.3% by weight using a coarse screen having a slit width of 0.2 mm to remove foreign matters such as coarse sticky foreign matters, and further a solid content concentration of 1.2. %, The ink was removed by flotation at 40 ° C. to obtain a pulp slurry containing waste paper pulp (waste paper pulp slurry C).

About the used paper pulp slurry C which adjusted solid content concentration to 0.9 weight%, it classified into the long fiber fraction and the short fiber fraction using the inward type | mold slit screen. Specifically, a screen (FH-400) manufactured by Aikawa Tekko Co., Ltd. was used as an inward-type slit screen, with a slit width of 0.10 mm, a passing flow rate of 1.0 m / s, and an agitator peripheral speed of 16.5 m / s. It processed and classified so that the classification ratio of a long fiber fraction and a short fiber fraction might be set to 64:36.
(Comparative Example 7)
The same as Comparative Example 6 except that the classification ratio of the long fiber fraction and the short fiber fraction was 39:61.

<Evaluation results>
The evaluation results are shown in Tables 1 and 2.
From Examples 1 and 2 and Comparative Examples 2 to 5, when the treatment concentration on the classification screen is lower than 1.5% by weight, since the concentration of the long fiber fraction is reduced, it is necessary to enlarge the equipment in the subsequent process. Yes, the manufacturing cost is high. Moreover, since the amount of water used increases, the manufacturing cost increases, which is disadvantageous.

  From Examples 1 to 8 and Comparative Examples 1 and 4, when the classification ratio of the long fiber fraction is larger than 60%, the freeness difference between the long fiber fraction and the short fiber fraction becomes less than 100 ml, and the sieving fiber composition As the difference between the two is reduced and the distribution of the dirt and ink is also reduced, a dart micronization process is required to remove the ink in both fractions, which increases the manufacturing cost.

  From Example 8 and Comparative Example 5, when the flotation is performed before classification, the concentration for subsequent classification treatment is reduced, the power required for the treatment is increased, and the amount of water used is increased. Moreover, since the density | concentration of a long fiber fraction becomes low, it is necessary to enlarge the apparatus of a post process, and a manufacturing cost becomes high.

  From Examples 1 to 8 and Comparative Examples 6 and 7, when an inward screen is used, the processing density cannot be increased because the clogging easily occurs, and the density of the long fiber fraction is lowered. Moreover, since the electric power which a process requires becomes high and water usage-amount increases, since manufacturing cost becomes high, it is disadvantageous.

Experiment 2: Manufacture of paper Paper was manufactured by the following method, and ash content, thickness, basis weight, density, tearing length, and interlayer strength (strength in the thickness direction of the paper) were measured. In addition, the addition rate in this experiment is a numerical value with respect to the total weight of the paper stock.
-Ash content: According to JIS P 8251: 2003.
-Thickness: According to JIS P 8118: 1998.
-Basis weight: According to JIS P 8124: 1998.
Density: Calculated from measured values of thickness (paper thickness) and basis weight.
-Tensile strength: measured according to JIS P 8113.
-Breaking length: in accordance with JIS P 8113: 1998.
Interlaminar strength: Interlaminar strength was measured with L & W ZD Tensile Tester SE 155 (manufactured by Lorentzen & Wettre). (TAPPI T 541, ISO 15754)
(Example 2-1)
The long fiber fraction is the same as in Example 1 except that the waste paper used is a weight ratio of 8: 2 and the classification ratio of the long fiber fraction and the short fiber fraction is 20:80. A short fiber fraction was obtained.

Dilute the short fiber fraction to a solid content of 0.5%, add and mix 10% of light calcium carbonate (average particle size 2.5μm) while stirring at a speed of 500rpm with a three-one motor. A paper strength agent (polyacrylamide, EX288 manufactured by Harima Chemicals Co., Ltd .: weight average molecular weight of about 4 million, cationic charge density 0.61 meg / g) was added 0.2% as an additive for use, and the short fiber was pretreated.

  The short fiber pretreated in this way has a weight ratio of 20:80 to the pulp slurry (solid content concentration 0.5%) of the long fiber fraction added with 2% sulfuric acid band and the long fiber: short fiber. And a yield improver (ND300 manufactured by Hymo Co., Ltd .: weight average molecular weight of about 15 million, cationic charge density of 2.1 meg / g) is added and mixed so as to be 100 ppm as a papermaking additive. Prepared.

Using this paper material, a handsheet with a basis weight of 60 g / m ² was prepared based on JIS P 8209.
(Example 2-2)
Papermaking was performed in the same manner as in Example 2-1, except that the amount of the paper strength agent was changed to 0.4% by mass.
(Example 2-3)
The short fiber was pretreated in the same manner as in Example 2-1, except that light calcium carbonate was not added to the short fiber.

  The short fiber pretreated in this way has a weight ratio of 20:80 to the pulp slurry (solid content concentration 0.5%) of the long fiber fraction added with 2% sulfuric acid band and the long fiber: short fiber. After adding and mixing 10% light calcium carbonate (average particle size 2.5 μm), further, as a papermaking additive, a yield improver (ND300 manufactured by Hymo Co., Ltd .: weight average molecular weight of about 15 million, cationic charge density 2.1 meg / g) was added and mixed at 100 ppm to prepare a paper stock.

Using this stock, a handmade sheet having a basis weight of 60 g / m ² was made in the same manner as in Example 2-1.
(Example 2-4)
Paper making was performed in the same manner as in Example 2-3 except that the amount of the paper strength agent was changed to 0.4% by mass.
(Comparative Example 2-1)
After mixing long fibers and short fibers at a weight ratio of 20:80, a sulfuric acid band (addition amount 2%), a paper strength agent (polyacrylamide, Harima Chemicals EX288, addition amount 0.2%), light calcium carbonate ( Example 2-1 except that an average particle diameter of 2.5 μm, an addition amount of 10%) and a yield improver (ND300 manufactured by Hymo Co., Ltd., addition amount of 100 ppm) were added in this order to prepare a paper stock. Paper was made in the same manner.
(Comparative Example 2-2)
Papermaking was performed in the same manner as in Comparative Example 2-1, except that the amount of the paper strength agent was changed to 0.4% by mass.
(Comparative Example 2-3)
While stirring the calcium carbonate slurry at a speed of 500 rpm with a three-one motor, a paper strength agent (polyacrylamide, EX288 manufactured by Harima Kasei) was added as an additive for papermaking (Sample A). After mixing the long and short fibers in a weight ratio of 20:80, a sulfuric acid band (added amount 2%), sample A, and a yield improver (added amount 100 ppm) are added in this order to prepare a paper stock. (Calcium carbonate concentration in paper stock was 10%, paper strength agent concentration was 0.2%). Except that, paper was made in the same manner as in Example 2-1.
(Comparative Example 2-4)
Paper making was performed in the same manner as in Comparative Example 2-3 except that the amount of the paper strength agent was changed to 0.4% by mass.

<Evaluation results>
The evaluation results are shown in Table 3. The handmade paper of the example in which the short fibers were previously treated with the papermaking additive tended to have higher tear length and interlayer strength than the comparative example in which the pretreatment was not performed. Further, when pretreatment is performed by adding a paper strength agent and a filler in advance to the short fibers (Examples 2-1 and 2-2), when the short fibers are pretreated with only the papermaking additive (Example 2- The fracture length and interlaminar strength were higher than those in 3,2-4). Furthermore, compared with the case where the filler was pretreated with a papermaking additive (Comparative Examples 2-3 and 2-4), the Examples of the present invention tended to increase both the breaking length and the interlayer strength.

Experiment 3: Production of paper (Example 3-1)
The long fiber fraction is the same as in Example 1 except that the waste paper used is a weight ratio of 8: 2 and the classification ratio of the long fiber fraction and the short fiber fraction is 40:60. A short fiber fraction was obtained. The following chemical treatment was performed on the classified raw material. The addition rate is a value relative to the total solid weight of the stock.
<Sample B> 2% sulfuric acid band was added to and mixed with a long fiber slurry (concentration: 0.5%) while stirring with a three-one motor at a speed of 500 rpm.
<Sample C> 17% light calcium carbonate was added to and mixed with a short fiber slurry (concentration 0.5%) at a speed of 500 rpm with a three-one motor, and then a paper strength agent as an additive for papermaking (Polyacrylamide, EX288 manufactured by Harima Chemicals) was added at 0.2%.

After mixing Sample B and Sample C, a yield improver (ND300 manufactured by Hymo Co., Ltd.) was added and mixed as an additive for papermaking to 100 ppm to prepare a paper stock. Next, JIS P
Based on 8209, 10 handmade sheets with a basis weight of 60 g / m ² were made.
(Example 3-2)
Papermaking was carried out in the same manner as in Example 3-1, except that the addition ratio of light calcium carbonate was changed to 22%.
(Example 3-3)
Paper making was conducted in the same manner as in Example 3-2 except that 0.02% of an anionic yield improver (SP7200 manufactured by Hercules) was added instead of the paper strength agent.
(Example 3-4)
Papermaking was conducted in the same manner as in Example 3-2 except that 0.04% of a coagulant (FR740 manufactured by Hymo Co., Ltd.) was added instead of the paper strength agent.
(Example 3-5)
Example 3 except that 0.02% of a cationic yield improver (ND300 manufactured by Hymo) and 0.02% of an anionic yield improver (FA230 manufactured by Hymo) were used in combination as the yield improver. Paper was made in the same manner as in No. 2. The order of addition of these two types of yield improvers is the order of cationic yield improvers and anionic yield improvers.
(Comparative Example 3-1)
After mixing long fiber slurry (concentration 0.5%) and short fiber slurry (concentration 0.5%), sulfuric acid band, paper strength additive (polyacrylamide, EX288 manufactured by Harima Kasei Co., Ltd.), light carbonate Yield improver (ND300 manufactured by Hymo Co., Ltd.) as an additive for calcium and papermaking
) In this order. Otherwise, paper was made in the same manner as in Example 3-1.
(Comparative Example 3-2)
Paper making was performed in the same manner as in Comparative Example 3-1, except that the addition ratio of light calcium carbonate was changed to 22%.

<Evaluation results>
The evaluation results are shown in Table 4. In Example 3-1, the ash yield was slightly improved and the fracture length and interlaminar strength were increased compared to Comparative Example 3-1. It was the same even when Example 3-2 and Comparative Example 3-2 were compared. In Example 3-3, the ash yield was almost the same as that of Comparative Example 3-2, and both the fracture length and the interlayer strength were increased. In Examples 3-4 and 3-5, although the ash yield decreased, both the fracture length and the interlayer strength increased compared to Comparative Example 3-2. From the above, it has been found that the paper strength is improved by fixing the filler to the short fibers using the papermaking additive. In Example 3 of the present invention, both the breaking length and the interlayer strength tended to increase.

Experiment 4: Production of paper (Example 4-1)
The long fiber fraction is the same as in Example 1 except that the waste paper used is a weight ratio of 8: 2 and the classification ratio of the long fiber fraction and the short fiber fraction is 40:60. A short fiber fraction was obtained. The following chemical treatment was performed on the classified raw material. The addition rate is a value relative to the total solid weight of the stock.
<Sample D> 2% sulfuric acid band was added to and mixed with the long fiber slurry (concentration: 0.5%) while stirring at a speed of 500 rpm with a three-one motor.
<Sample E> 22% of light calcium carbonate was added to and mixed with a short fiber slurry (concentration 0.5%) at a speed of 500 rpm with a three-one motor, and then a paper strength agent ( 0.5% of cationized starch, Nippon 304, Cato 304) was added.

After mixing Sample D and Sample E, a yield improver (ND300 manufactured by Hymo Co., Ltd.) was added and mixed as an additive for papermaking to 100 ppm to prepare a paper stock. Next, JIS P
Based on 8209, 10 handmade sheets with a basis weight of 60 g / m ² were made.
(Example 4-2)
Paper making was performed in the same manner as in Example 4-1, except that the addition ratio of the paper strength agent was 0.3%.
(Comparative Example 4-1)
After mixing long fiber slurry (concentration 0.5%) and short fiber slurry (concentration 0.5%), sulfuric acid band, paper strength agent (cationized starch, Cato304 manufactured by NSC Japan) as an additive for papermaking. 0.5% was added, 22% light calcium carbonate was added, and a yield improver (ND300 manufactured by Hymo Co., Ltd.) was added in order so as to be 100 ppm as an additive for papermaking.
Otherwise, paper was made in the same manner as in Example 4-1.

<Evaluation results>
The evaluation results are shown in Table 5. In Example 4-1, the ash yield was significantly improved and the interlayer strength was higher than that of Comparative Example 4-1. In Example 4-2, compared with Comparative Example 4-1, the ash content yield was improved and the interlaminar strength was increased despite the low addition rate of the papermaking additive. From the above, it has been found that the ash yield and paper strength are improved by fixing the filler to the short fiber using the papermaking additive. Example 4 of the present invention tended to improve the ash yield and increase the interlayer strength. It is clear from the graph below that the ash yield and interlayer strength are improved simultaneously.

Experiment 5: Production of paper (Example 5-1)
The long fiber fraction is the same as in Example 1 except that the waste paper used is a weight ratio of 8: 2 and the classification ratio of the long fiber fraction and the short fiber fraction is 40:60. A short fiber fraction was obtained. The following chemical treatment was performed on the classified raw material. The addition rate is a value relative to the total solid weight of the stock.
<Sample F> 2% sulfuric acid band was added to and mixed with the long fiber slurry (concentration: 0.5%) while stirring at a speed of 500 rpm with a three-one motor.
<Sample G> 17% of light calcium carbonate was added to and mixed with a short fiber slurry (concentration 0.5%) at a speed of 500 rpm with a three-one motor, and then a paper strength agent (cationized starch, Japan) 0.3% of NSSC Cato304) was added.

After mixing Sample F and Sample G, 0.15% of a paper strength agent (polyacrylamide, EX288 manufactured by Harima Chemicals Co., Ltd.) is added as a papermaking additive, and a yield improver (manufactured by Hymo Co., Ltd.) is added as a papermaking additive. ND300) was added and mixed in order so that it might become 100 ppm, and the paper stock was prepared. Next, ten hand-made sheets with a basis weight of 60 g / m ² were made based on JIS P 8209.
(Example 5-2)
Papermaking was carried out in the same manner as in Example 5-1, except that the addition ratio of light calcium carbonate was changed to 22%.
(Example 5-3)
The papermaking additive to be added to sample G is 0.15% of polyacrylamide (EX288 manufactured by Harima Chemicals), and the papermaking additive to be added after mixing sample F and sample G is cationized starch (NSC Japan) Papermaking was carried out in the same manner as in Example 5-1, except that 0.3% of Cato 304) was added.
(Example 5-4)
Papermaking was carried out in the same manner as in Example 5-3 except that the addition ratio of light calcium carbonate was changed to 22%.
(Comparative Example 5-1)
After mixing the long fiber slurry (concentration 0.5%) and the short fiber slurry (concentration 0.5%), 0.3% cationized starch (Cato304 manufactured by Nippon NSC Co., Ltd.) as an additive for sulfuric acid band and papermaking. % Addition, 0.15% addition of polyacrylamide (EX288 manufactured by Harima Chemicals Co., Ltd.), 17% addition of light calcium carbonate, and a yield improver (ND300 manufactured by Hymo Co., Ltd.) as an additive for papermaking to be 100 ppm. The stock was prepared by adding in this order. Using this stock, paper was made in the same manner as in Example 5-1.
(Comparative Example 5-2)
Papermaking was performed in the same manner as in Comparative Example 5-1, except that the addition ratio of light calcium carbonate was changed to 22%.

<Evaluation results>
The evaluation results are shown in Table 6. In Example 5-1 and Example 5-3, the breaking length and the interlayer strength were higher than those in Comparative Example 5-1. This tendency was the same when Example 5-2 and Example 5-4 were compared with Comparative Example 5-2. From the above, it has been found that the paper strength is improved by fixing the filler to the short fibers using the papermaking additive.

Claims (7)

A pulp slurry containing a waste paper pulp having a solid content concentration of 1.5% by weight or more is treated with a long fiber fraction and a short fiber by using an outward type slit screen having an opening with a slit width of 0.1 mm to 0.3 mm. A step of classifying into a fraction, wherein the solid content ratio of the long fiber fraction and the short fiber fraction is 10:90 to 60:40, and the Canadian standard freeness of the long fiber fraction and the short fiber fraction is A step in which the difference is 100 ml to 300 ml;
Adding one or more papermaking additives to the pulp slurry of the short fiber fraction;
A process of making paper using a pulp slurry of a short fiber fraction to which a papermaking additive is added,
A method for producing paper, comprising:   The method according to claim 1, wherein the papermaking additive is an organic polymer.   The method of Claim 1 or 2 which adds a filler with the said papermaking additive with respect to the pulp slurry of a short fiber fraction.   The method according to any one of claims 1 to 3, wherein papermaking is performed after mixing the pulp slurry of the short fiber fraction added with the papermaking additive with the pulp slurry of the long fiber fraction.   The method according to claim 4, wherein papermaking is performed after further adding another papermaking additive to the pulp slurry obtained by mixing with the pulp slurry of the long fiber fraction.   The method according to claim 1, wherein the filler contains calcium carbonate.   The method according to any one of claims 1 to 6, wherein the papermaking additive added to the pulp slurry of the short fiber fraction comprises polyacrylamide.