JP5289882B2 - Paper manufacturing method - Google Patents

Description

  The present invention relates to a paper manufacturing method. In particular, the present invention relates to a method for producing a well-formed paper with a high stock and ash yield.

  In general, paper is manufactured from pulp raw materials such as wood fibers. In the manufacture of paper, a paper material is prepared by adding fillers and, if necessary, various chemicals such as a sizing agent, a paper strength enhancer, and a retention agent to a pulp raw material obtained from wood chips and waste paper. Foreign matter is removed from the prepared stock using a cleaner or a screen, and the stock from which the foreign matter has been removed is supplied to a head box (also referred to as a stock inlet) of the paper machine. The stock supplied to the head box is jetted from the head box, dehydrated at the wire part to become wet paper, and further squeezed at the press part, and then dried at the dryer part to become paper.

  However, because part of the papermaking raw materials such as fine fibers and fillers are discharged together with water due to dehydration in the wire part and squeezing in the press part, it is important to keep these papermaking raw materials on the paper machine. become. In particular, improving the yield of fine fibers and fillers on the wire can be achieved by reducing the drainage load, reducing the manufacturing cost by reducing the amount of lost material, improving the quality of the paper, such as improving the two-sidedness of the paper. It has important implications in the manufacture of paper because of its improved properties.

  Therefore, a chemical called a yield agent (yield improver) is generally added to the paper stock for the purpose of improving the yield of pulp fibers and fillers in the paper manufacturing process and increasing the productivity. Various types of retention agents have been proposed so far. Basically, the retention of papermaking materials in water is suppressed by the retention agent, thereby suppressing the discharge of papermaking materials in the wire part and press part. This improves the yield of papermaking raw materials.

  By the way, in recent years, in the manufacture of paper, there is a tendency of increasing the ratio of used paper to paper, increasing the speed and neutralization of paper manufacture, making the wire part twin-wire, and high ash differentiation of the paper. However, these technical trends are not preferable from the viewpoint of the yield of papermaking raw materials and fillers (or ash).

  The increase in the ratio of used paper is promoted against the background of rising consumer environmental awareness and cost reductions, and it is not uncommon for the ratio of used paper to exceed 70%. However, waste paper contains a large amount of negatively charged fine particles such as ink components and paint components derived from coated paper. When the waste paper content is increased, these fine particles flow into the papermaking system in large quantities. become. Since the negatively charged particles repel each other and do not easily bind to the negatively charged pulp fiber, the ink component and the paint component pass through the paper machine wire and accumulate in the papermaking system. When the concentration of the negatively charged colloidal particles increases in this way, the effect of the positively charged cationic retention agent added to the papermaking system is significantly reduced.

  The speed of paper production has been promoted from the standpoint of improving production efficiency. In the production of current offset printing paper, the paper making speed is generally 1000 m / min or more, and the speed is about 1500 m / min. It is not uncommon for paper to be produced. As the papermaking speed is increased, the shearing force applied to the raw material fibers and the like in the manufacturing process becomes very strong, which causes problems such as a decrease in paper strength and a significant decrease in paper yield.

  The neutralization of paper manufacturing has been promoted particularly in offset printing paper such as newspaper paper, and the papermaking system has changed from conventional acidic papermaking to neutral papermaking, which also contributes to the deterioration of yield. In acidic papermaking, it is possible to use sulfuric acid band (aluminum sulfate), which is an acidic inorganic coagulant, and it is derived from fine pulp fiber and waste paper in paper stock by using sulfuric acid band and synthetic polymer-based retention agent. The yield of fine particles such as fine particles and fillers was maintained at a level with no problem. In contrast, in the neutral papermaking method, it is common to add calcium carbonate as a filler, but when a sulfuric acid band is added, the sulfuric acid band and calcium carbonate react to form calcium sulfate, which precipitates in the papermaking system. As a result, paper defects such as dirt and holes in the system may be generated, and paper breakage may be caused, so that the amount of sulfuric acid band used is limited. As a result, there arises a problem that the yield of fine particles in the paper is lowered. In particular, newsprint (neutral newsprint) manufactured by neutral papermaking can impart excellent functions in terms of quality such as high whiteness, high opacity, and high opacity after printing to calcium carbonate. The compounding amount of sucrose increases, and the problem of yield reduction is great. Further, when calcium carbonate having a small particle diameter is used, the yield on paper in the paper making process is reduced. Furthermore, in the case of acidic papermaking, the ash content of the deinked pulp decreased due to the dissolution of calcium carbonate among the ash contained in the wastepaper pulp or deinked pulp produced from the used paper. As there is no ash, carry-in ash increases. While this is a great advantage in terms of environment and resource saving, it leads to a decrease in yield, particularly a decrease in ash content.

  The twin wire process has been advanced in order to improve the paper formation, and paper machines equipped with a twin wire former are widely used. The texture of paper is an important quality for printing paper such as offset printing paper. A poor texture causes a decrease in opacity, a decrease in strength and stiffness, and uneven basis weight and thickness. It will be a paper with large occurrence and fluctuation. In addition, when the formation deteriorates, the ink oozes out when printing is performed, leading to problems such as a decrease in the back-through, a non-uniform ink setting property, and a poor setting due to uneven printing. However, many of the paper machines used for making newsprint paper, among other things, have a paper suspension in the gap between the two wires formed in a loop from the head box (gap between the wires) even in the twin wire system. In many cases, a gap former method is employed in which liquid is ejected and immediately dehydrated from both sides at once, but this gap former tends to cause a decrease in yield because dehydration is performed simultaneously with the formation of the paper layer structure.

Thus, in light of recent trends in papermaking technology, the importance of technology for improving the yield of papermaking raw materials is high.
In Patent Document 1 (Japanese Patent Laid-Open No. 2006-16716), for the purpose of improving the yield, a specific yield agent called an emulsion-type cationic polyacrylamide material having a weight average molecular weight of 15 million or more by the intrinsic viscosity method is disclosed. It is described that paper is added to the stock. In the embodiment, the retention agent is added on the suction side of the fan pump.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2002-227090) discloses a polymerized cationic polymer and / or a polycondensation-based cationic substance (A) for the purpose of making a neutral newspaper with a high yield. It is described that the cationic cationic water-soluble polymer (B) is added at the entrance or exit of the screen after being added and treated at the seed box, before the fan pump, or at the entrance of the screen.

In Patent Document 3 (Japanese Patent Application Laid-Open No. 2004-176184), when making paper with a module jet type paper machine, a yield improver is added to the papermaking raw material and the white water returned to the head box. It is described that papermaking is performed after mixing with the papermaking raw material. Patent Document 3 describes that after mixing white water with a fan pump, a yield improver is added before the screen or at the screen exit.
JP 2006-16716 A JP 2002-227090 A JP 2004-176184 A

  With regard to the method of adding the yield agent, if the yield agent is added to the raw material before the screen, the effect of the yield agent may not be fully exerted, and if it is simply added after the screen, it will lead to the head box. Since the time is extremely short and laminar, the formation is extremely deteriorated when a retention agent is simply added, and troubles such as paper breakage occur in some cases. In order to avoid this, special addition / mixing equipment is required so that the retention agent can be mixed uniformly, and it is necessary to select chemicals with particularly good dispersibility. There were problems such as increased costs.

  In view of the situation as described above, an object of the present invention is to provide a method for producing paper with a high yield without deteriorating the formation and operability of the paper.

  As a result of intensive studies on the method of adding a retention agent in order to solve the above-mentioned problems, the present inventor performed screen treatment after distributing the stock to two or more, and added the retention agent to the screen-treated stock. It was found that by adding the paper materials after the addition, a paper with good formation can be produced with a high yield. Specifically, distributing the stock containing the pulp raw material to two or more, removing each foreign material from the stock by passing each of the two or more distributed stock through the screen, and passing through the screen Adding a retention agent to at least one of the subsequent stocks, joining the two or more distributed stocks, and jetting the joined stocks from a headbox to make paper. The present invention has been completed by finding that paper can be produced with a high yield without deteriorating the formation and operability of the paper by the paper production method comprising the above.

The present invention includes, but is not limited to, the following inventions.
(1) Distributing the stock containing pulp raw material to two or more, removing each foreign material from the stock by passing each of the two or more distributed stocks through the screen, and after passing through the screen Adding a retention agent to at least one of the stocks, joining two or more of the distributed stocks, jetting the joined stocks from a headbox to make paper,
A method for producing paper, comprising:
(2) The paper manufacturing method according to (1), wherein the at least one distribution paper to which the retention agent is added is an amount of 80% by weight or less of the whole paper after joining.
(3) For paper stocks that have been distributed after passing through the screen, and that have passed through the screen and have the opportunity to join with other paper stocks more than once The method for producing paper according to (1) or (2), wherein a retention agent is added.
(4) The paper manufacturing method according to any one of (1) to (3), wherein the head box is a concentration dilution type head box.
(5) The paper manufacturing method according to any one of (1) to (4), wherein the paper making speed is 700 m / min or more.
(6) Distributing the stock containing pulp raw material into two or more, removing each foreign material from the stock by passing each of the two or more distributed stocks through the screen, A method of preparing a stock comprising adding a retention agent to at least one of the stock and combining two or more dispensed stocks.

  According to the present invention, paper can be produced with a high stock and ash yield without deteriorating the paper formation and operability.

  In one aspect, the present invention is a method for producing paper, in which a stock containing a pulp raw material is distributed to two or more, and each of the two or more distributed stocks is passed through a screen to form a foreign object. , Adding a retention agent to at least one of the stocks after passing through the screen, merging the two or more distributed stocks, and passing the joined stocks to the headbox And making paper by spraying. According to the present invention as described above, paper can be produced with a high stock and ash yield without deteriorating the formation and operability of the paper. From another point of view, the present invention is a paper preparation method.

Hereinafter, the present invention will be described in five steps.
Distributing Step In the present invention, the stock containing the pulp raw material is distributed into two or more. The method for distributing the paper stock is not particularly limited, and can be distributed by a general method. For example, one paper flow may be sequentially distributed at a plurality of locations to form a plurality of paper flows, or may be distributed to a plurality of paper flows at one location. In a preferred embodiment of the present invention, the stock containing the pulp raw material is sequentially distributed at a plurality of locations. This is because by distributing the paper at a plurality of locations, it becomes easy to control the distribution of the paper, and the paper can be distributed more accurately.

  The paper stock used in the present invention comprises a pulp raw material. There are no particular restrictions on the pulp raw material used. Besides wood pulp, non-wood pulp such as linter pulp, hemp, bagasse, kenaf, esparto grass, and straw, semi-synthetic fibers such as rayon and acetate, polyolefin, polyamide, polyester, etc. Synthetic fibers can be used. Specifically, it is commonly used as a papermaking raw material for printing paper such as mechanical pulp (MP), deinked pulp (DIP, also called waste paper pulp), hardwood kraft pulp (LKP), conifer kraft pulp (NKP), etc. Can be suitably used, and one or two or more of these are suitably used in combination. Examples of the mechanical pulp include groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemiground pulp (CGP), semi-chemical pulp (SCP), and the like. . Deinked pulp includes high-quality paper, medium-quality paper, low-grade paper, newspaper, flyers, magazines, and other sorts of waste paper, unsorted waste paper mixed with these, copy paper, thermal paper, and carbonless paper There is no particular limitation as long as it is a deinked pulp made from waste paper.

  In particular, the effect of the present invention is particularly large because the amount of ash brought in increases when waste paper pulp is highly blended, and therefore it is preferable to apply the present invention to a paper stock blended with pulp. Specifically, it is preferable to mix 20% by weight of waste paper pulp, and more preferably 40% by weight or more based on the total dry weight of pulp. In particular, in printing paper such as newsprint, waste paper pulp is preferably 50% by weight or more with respect to the total pulp dry weight.

  A filler can be blended with the stock of the present invention. The type of filler is not particularly limited, and fillers generally used in acidic papermaking or neutral papermaking can be used. For example, in the present invention, clay, silica, talc, kaolin, calcined kaolin, deramikaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, Inorganic fillers such as aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, titanium oxide, bentonite; organic fillers such as urea-formalin resin, polystyrene resin, melamine resin, phenol resin, and fine hollow particles; Two or more types can be used in combination as appropriate. In addition, recycled fillers made from papermaking sludge, deinking floss, etc. can also be used. In particular, in the present invention, it is preferable to use calcium carbonate as a filler because it is inexpensive and excellent in optical properties. Of these, spindle-shaped and rosetta-type plasma calcium carbonate is preferable. A composite filler such as a calcium carbonate-silica composite (for example, a light calcium carbonate-silica composite described in JP2003-212539A or JP2005-219945A) can also be used. In acidic papermaking, a filler obtained by removing acid-soluble ones from the filler used in the neutral papermaking is used, and used alone or in appropriate combination of two or more.

  As a compounding quantity of a filler, 2-30 weight% is preferable with respect to pulp weight from points, such as opacity. Further, the filler content in paper (ash content in paper) is desirably 10% by weight or more, and desirably 40% by weight or less. In particular, when paper having a high filler content and a high filler content in paper is produced, a decrease in yield becomes a serious problem. According to the present invention, paper having excellent texture with a high ash yield is produced. can do.

  Various internal additives may be added to the stock of the present invention as long as the effects of the present invention are not impaired. Internal additives include, but are not limited to, internal papers such as polyacrylamide polymers, polyvinyl alcohol polymers, cationic starches, various modified starches, urea / formalin resins, melamine / formalin resins, etc. Strength enhancer: Rosin-based sizing agent, AKD-based sizing agent, ASA-based sizing agent, petroleum-based sizing agent, neutral rosin sizing agent, and other internal sizing agents; sulfuric acid band, ultraviolet light inhibitor, anti-fading agent, improved drainage Auxiliaries, coagulants, auxiliaries such as dyes and fluorescent dyes may be added.

Screening Process The present invention includes a process for removing foreign substances from the stock by passing each of the two or more distributed stocks through a screen.

  In general, a paper stock containing pulp, filler and the like is diluted with circulating white water discharged from a wire part and the like, and is fed to a head box of a paper machine after removing foreign matter with a screen or a cleaner. Removal of foreign matter from the paper stock is important for the stable operation of the paper machine as well as improving the quality of the paper. An apparatus for removing foreign matter from paper stock is roughly divided into a screen for removing large foreign matter and a cleaner for removing heavy foreign matter. Usually, these are combined appropriately to remove foreign matter from the stock.

  The screen for removing foreign matter used in the present invention is not particularly limited, and a commonly used screen can be used. For example, a screen basket having openings such as round holes or slits can be used. . Specifically, a plurality of screens having different openings can be used in combination. In one aspect, the screen removes foreign material larger than the screen opening from the paper stock, but the paper stock is accelerated by the rotating blade and the foreign material is pushed out by this centrifugal force. Further, in the present invention, in addition to the screen, other foreign matter removing devices such as a cleaner can be used in combination.

Yield Agent Addition Step In the present invention, a yield agent is added to at least one of the two or more stocks after passing through the screen. That is, in the present invention, a retention agent is added not after the screen treatment but after the screen treatment, whereby the yield of pulp fibers and fillers can be improved.

  Conventionally, since the retention agent can be uniformly dispersed in the paper stock by the stirring action in the screen, it has been common to add the retention agent in front of the screen. This is because if the retention agent is not uniformly dispersed, problems such as the formation of spots and the deterioration of operability such as generation of foreign matter and paper breakage occur.

  In the present invention, details of the reason why an excellent yield effect can be obtained by adding a retention agent in front of the screen is not clear, and the present invention is not limited to this, but is assumed as follows. The Generally, a retention agent improves the yield of papermaking raw materials by aggregating or condensing papermaking raw materials such as pulp fibers and fillers in water, thereby suppressing the falling of the papermaking raw materials in the wire part and press part. When a yield agent is added, a uniform dispersion can be obtained, but agglomeration of the yield agent and papermaking raw material is destroyed by the shear (shearing force) when passing through the screen, and the yield effect is lowered. On the other hand, in the method of the present invention, since the retention agent is added to the stock after passing through the screen, the effect of the retention agent is not suppressed by the share when passing through the screen. It is estimated that the yield effect is obtained. In particular, due to the recent high-speed papermaking, the screen share tends to increase, and the present invention has a great effect in the case of high-speed papermaking. Further, as a countermeasure against foreign matter derived from waste paper pulp, the slit width of the screen tends to be narrowed, and the effect is increased in the case of a paper machine that contains a large amount of waste paper pulp.

  Furthermore, in the present invention, there is a step of joining the respective stocks after the step of adding the retention agent, and at that time, the stock and the retention agent can be uniformly mixed. Deterioration of formation caused by non-uniform dispersion can be suppressed.

  In the present invention, a retention agent is added to at least one of the plurality of distributed paper stocks. Therefore, the retention agent may be added to only one of the distributed paper materials, or the retention agent may be added to all of the distributed paper materials. Further, the retention agent added to the stock in the present invention may be different or the same for each distributed stock.

  In a preferred embodiment of the present invention, the at least one distribution stock to which the retention agent is added is in an amount of 80% by weight or less of the total stock after joining. By adding a retention agent in this way, the retention agent becomes excessive with respect to pulp fibers and fillers at the time when the retention agent is added to the distributed stock. The aggregating action can be sufficiently exhibited, and the effect of the retention agent can be effectively extracted. For example, when the stock is distributed into four streams of 25% by weight, and then merged again after passing through the screen, a retention agent is added to one of the four stocks after passing through the screen. A retention agent is added to 25% by weight of the total stock after joining. When a retention agent is added to two stocks, a retention agent is added to 50% by weight of the total stock after joining. Therefore, when a retention agent is added to the three stocks, the retention agent is added to 75% by weight of the total stock after joining.

  The retention agent used in the present invention is not particularly limited, and conventionally known ones can be used. For example, the retention agent used in the present invention includes a cationic polymer, an anionic polymer, an amphoteric polymer, a nonionic polymer, and the like. For example, polyethylene oxide and a phenol resin (such as a sulfonated phenol formaldehyde resin) are used in combination. It is also possible to use a plurality of drugs in combination like a yield system. Further, for the purpose of increasing the yield, an inorganic coagulant such as sulfuric acid band or polyaluminum chloride may be used in combination.

  The cationic polymer used as a retention agent can be obtained, for example, by copolymerizing a cationic monomer and a nonionic monomer. As the cationic monomer, (meth) acrylic acid which is a cationic vinyl monomer is used. Examples thereof include acrylamide such as dimethylaminoethyl and dimethylaminopropyl (meth) acrylamide. Examples of nonionic monomers include (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N- Examples include vinylpyrrolidone, N-vinylformamide, N-vinylacetamidoacryloylmorpholine, acryloylpiperazine and the like. Of these, acrylamide is most preferred. It can also be used for polyvinylamine and the like produced by polymerizing and then hydrolyzing.

  The amphoteric polymer used as a retention agent can be obtained, for example, by copolymerizing an anionic vinyl monomer and a cationic monomer. As the anionic vinyl monomer, acrylamide 2-methylpropanesulfonic acid is used. Styrene sulfonic acid, (meth) allyl sulfonic acid, vinyl sulfonic acid, (meth) acrylic acid, maleic acid or itaconic acid.

Even when an anionic polymer or a nonionic polymer is used as a retention agent, the type is not particularly limited, and a known polymer can be used.
As a retention agent used in a desirable embodiment of the present invention, a cationic linear or branched polymer is preferable. As a product form, an emulsion type or dispersion type polymer is preferable, and an emulsion type polymer is more preferable. More preferably, it is an emulsion type, cationic, and branched polyacrylamide-based material.

  Among them, as a retention agent that can be preferably used in the present invention, an emulsion-type cationic polyacrylamide-based material having a weight average molecular weight of 10 million or more by an intrinsic viscosity method can be exemplified, and a weight average molecular weight of 15 million or more. More preferred are those having a weight average molecular weight of 20 million or more. The emulsion type cationic polyacrylamide material having a weight average molecular weight of 15 million or more can be appropriately selected from commercially available materials. This emulsion-type cationic polyacrylamide-based material is emulsion-polymerized by a known method, but is preferably synthesized by a water-in-oil type reverse-phase emulsion method. The specific composition is not particularly limited as long as the substance contains an acrylamide monomer unit as a structural unit. For example, a copolymer of quaternary ammonium salt of acrylate ester and acrylamide, or acrylamide And a quaternized ammonium salt after copolymerization of acrylate and acrylate.

  When a cationic polyacrylamide-based material is used as the retention agent of the present invention, the cationic charge density is not particularly limited. However, when making newsprint, the cation requirement of the stock is extremely high, so that the yield is improved. Therefore, the cation charge density is preferably higher, specifically 0.5 meq / g or more, more preferably 1 meq / g or more, further preferably 1.5 meq / g or more, and most preferably 2 meq / g or more.

  The addition amount of the retention agent in the present invention is appropriately determined according to the properties of the stock and the paper making speed, and therefore cannot be generally stated. 005 to 0.05% by weight, preferably 0.01 to 0.03% by weight. If the addition amount of the retention agent is too small, the formation is good, but a sufficient yield of fine components cannot be obtained, and stable operation becomes difficult. On the other hand, when the addition amount of the retention agent is too large, the yield of the fine component is increased, but the formation is deteriorated, and the problem of defective printing such as uneven printing due to uneven formation tends to occur. In the present invention, as described above, since the retention agent is added to the distributed stock, the retention agent is in an excessive state with respect to the pulp fiber and the filler at the time when the retention agent is added. It is possible to sufficiently exhibit the coagulation action of the stock by the retention agent, and to effectively bring out the effect of the retention agent. For example, when the stock is distributed into four streams of 25% by weight and a retention agent is added to one of the four stocks after passing through the screen, 25% of the total stock after joining. The retention agent is added to the weight percent, and the addition amount of the retention agent at that time is 0.02 to 0.2 weight percent with respect to the weight of the solid material.

Merge Step In the present invention, after distributing and passing through the screen, the stock added with the retention agent is merged again. In the present invention, a retention agent is added to the material that has passed through the screen. However, since the materials are mixed when the materials are merged, uniform dispersion of the retention agent can be achieved. . Therefore, it is considered that the present invention can produce a paper having a good formation despite the addition of a retention agent to the stock after the screen treatment.

  In the present invention, the method for joining the distributed paper materials is not particularly limited, and the flow of the distributed paper materials may be sequentially joined or may be joined at one place. In a preferred embodiment of the present invention, each dispensed stock is joined sequentially. This is because, by sequentially merging the distributed paper stock, the number of merging increases, and uniform dispersion is easily achieved.

  Further, in the present invention, when the paper materials after passing through the screen are sequentially joined, it is preferable to add the retention agent to the paper material that has two or more chances of joining with other distribution paper materials. This is because if the stock to which the retention agent is added has a chance to merge with at least two stocks thereafter, the stock is mixed at the opportunity of joining, so that the uniform stock can be easily dispersed. . For example, as shown in FIG. 1, when the paper materials distributed in 25% by weight are sequentially merged into one paper flow, the first and second distribution paper materials merge with other paper materials. The opportunity is three times, the third distribution paper fee has two opportunities to merge with other paper materials, and the fourth distribution paper fee has one opportunity to merge with other paper materials. Therefore, in the case shown in FIG. 1, it is preferable to add a retention agent to the first to third stocks.

Papermaking process When paper is produced using the paper stock of the present invention merged in this manner, the paper stock is sent to the head box, and the paper stock is jetted onto the wire from the head box to make paper. The present invention can be applied to various paper machines and paper making methods.

  The papermaking system of the present invention is not particularly limited and may be neutral papermaking or acidic papermaking. However, neutral papermaking is preferable because the effects of the present invention can be enjoyed more significantly. Specifically, in the present invention, the paper pH at the time of papermaking is preferably 6.0 to 9.0, and more preferably 7.0 to 8.0.

  In the paper production method of the present invention, the papermaking speed is not particularly limited, but in a preferred embodiment of the present invention, the papermaking process of the present invention is performed at a high speed. That is, in high-speed papermaking, the share of the screen increases, so it is easy to enjoy the effect of the present invention of adding a retention agent at the screen exit, and in high-speed papermaking, the stock and dilution water in the headbox Since the merging becomes intense, the stock can be uniformly mixed even if a retention agent is added after the screen, so that a paper with good formation can be produced at a high yield. In the present invention, high-speed papermaking means papermaking at 700 m / min or more, but since the effect obtained by applying the present invention is great, the papermaking speed of the present invention is preferably 800 m / min or more, and 1000 m / min. The above is more preferable, 1200 m / min or more is more preferable, and 1500 m / min or more is most preferable. Although it is expected that the paper machine will continue to increase in speed, the upper limit of the paper making speed is not limited as long as the effects of the present invention can be obtained.

  The head box of the paper machine used in the present invention is not particularly limited, and various types of head boxes can be used. In general, a head box is a device that sprays raw materials onto a wire in a stable state over the entire width of a paper machine, and greatly affects the formation of the paper to be manufactured. In order to produce paper with excellent formation, it is important to uniformly disperse the material sprayed from the head box. In the head box, turbulence is generated in the tube, and the fiber is subjected to shearing action and stirring. By providing the action, the stock is dispersed.

  Examples of the head box used in the present invention include a step diffuser type head box (manufactured by Hitachi Zosen, Escher Wyth, etc.), a high turbulence type head box (manufactured by IHI / Voith, etc.), an axle flow type head box (manufactured by Mitsubishi / Beloit, etc.). ), A module jet type head box (made by IHI / Voith, etc.). Among these, in the present invention, a module jet type head box which is a concentration dilution type head box (also referred to as a density control type head box) can be suitably used. An example of the density dilution type head box is a paper machine equipped with a mixing device as described in JP 2000-512696 A. The concentration dilution type head box has multiple mixing modules that are independent in the width direction. Each of the thick header pipes supplied with high-concentration stock and the thin header pipes supplied with low-concentration stock or white water. Mounted in the module, low density paper stock and high density paper stock are supplied and mixed for each mixing module, and the stock density, that is, the basis weight is determined. Although details of the reason why the concentration dilution type head box can be suitably used in the present invention are not clear, in the concentration dilution type head box, the high concentration paper and dilution water (low concentration paper, white water, etc.) merge in the head box. Therefore, it is presumed that the paper stock containing the retention agent is uniformly dispersed, and a paper with good formation can be produced with a high yield.

  Further, the paper machine used in the present invention is not particularly limited. For example, the paper machine can be appropriately made with a long net paper machine, a twin wire paper machine, a gap former paper machine, a Yankee paper machine, etc., and in particular, a twin wire paper machine. Is preferable in that the effect of the present invention can be exhibited significantly. Examples of twin wire paper machines include gap formers and on-top formers. In the case of a twin wire paper machine, the yield of fine particles decreases, which may cause instability of operation and fluctuation of paper quality, and this problem increases as the paper speed increases. According to this, it is possible to produce a paper with a good yield at a high yield rate.

  The present invention is not limited to the configuration of the wire part of the paper machine, and can be applied to wire parts having various configurations. In general, various dewatering elements and dewatering devices are arranged in the wire part of a paper machine to promote dewatering. Specifically, a foil blade, a suction box or the like is used, and in the case of an on-top twin wire, an upper dewatering device or the like is also installed. Although the yield of fine fibers varies depending on the conditions of these dehydrating elements and dehydrating apparatuses, the type and arrangement of these dehydrating elements and dehydrating apparatuses are not particularly limited in the present invention, and are within the normal operating range. Thus, these dehydrating elements can be appropriately selected and arranged.

  In the wire part, the yield of pulp and filler varies depending on the type of the wire, but the opening and weaving method of the wire used in the present invention is not particularly limited, and a commercially available wire can be used as appropriate. .

  Generally, wet paper (web) formed in a sheet shape by a wire part of a paper machine is sent to a press part and squeezed. In the present invention, the press form of the press part of the paper machine is not limited, and a public apparatus can be used, but it is preferable to use a shoe press in two or more stages. Further, the pressing conditions are not particularly limited, and can be appropriately set within a normal operation range.

  Further, the wet paper whose moisture content has been reduced through the press part of the paper machine is sent to the dryer part and dried to be paper. The paper manufacturing method of the present invention is not limited to the configuration of the dryer part, and can be applied to various apparatuses. Therefore, in the present invention, a public apparatus can be used for both the paper machine pre-dryer and the after-dryer, and the drying conditions are not particularly limited, and can be appropriately set within a normal operating range.

  Furthermore, in the present invention, various surface treatments can be applied to the paper made. As the surface treatment, a surface coating such as a pigment coating or a clear coating can be applied, or a calendar treatment can be performed.

  In the present invention, when a surface treatment agent is applied to the paper surface, for example, a surface coating apparatus installed between a pre-dryer and an after-dryer can be used. As the coating apparatus, a commonly used one can be used. For example, a film transfer type size press such as a gate roll size press is generally used in a newspaper paper machine, and it is preferably used in the present invention. Can do. In the present invention, when clear coating is performed using such a surface coating apparatus, a surface coating agent such as starch, polyacrylamide, or polyvinyl alcohol can be applied to paper. Of course, in the present invention, such clear coating need not be applied.

  The type and composition of the surface coating agent for clear coating are not particularly limited, but as the water-soluble polymer substance for the purpose of enhancing the surface strength, raw starch, oxidized starch, esterified starch, cationized starch, Enzyme-modified starch, aldehyde-modified starch, hydroxyethylated starch, hydroxypropylated starch and other starches; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose and methylcellulose; modified alcohols such as polyvinyl alcohol and carboxyl-modified polyvinyl alcohol; styrene-butadiene copolymer , Polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid ester, polyacrylamide and the like are used alone or in combination. Of these, application of hydroxyethylated starch or hydroxypropylated starch, which is excellent in the effect of improving surface strength, is most preferable. Further, in order to impart water absorption resistance to paper, a general surface sizing agent such as styrene acrylic acid, styrene maleic acid, and olefinic compound can be applied in addition to the water-soluble polymer substance. It is preferable to apply a sizing agent whose ionicity is cationic.

  In the case of applying a surface treatment agent comprising a water-soluble polymer substance and a surface sizing agent, the mixing ratio of the water-soluble polymer substance and the surface sizing agent may be within a public range and is not particularly limited. Further, the application amount of the water-soluble polymer substance and / or the surface sizing agent may be within a public range, and is not particularly limited.

  In the case of pigment coating, the pigments are kaolin, clay, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white and other inorganic pigments; organic pigments such as plastic pigments Can be appropriately selected and used. As the adhesive, synthetic adhesives such as styrene / butadiene latex and polyvinyl alcohol; starches, cellulose derivatives and the like can be conveniently selected and used. The ratio of the pigment and the adhesive may be within a public range and is not particularly limited. As a coating apparatus, a blade coater, a bar coater, an air knife coater, a reverse roll coater, a curtain coater, a rod metering size press coater, a gate roll coater, or the like can be used. Of course, in the present invention, such pigment coating need not be applied.

  In the present invention, the paper surface can be calendered, but the type and processing conditions of the calender device are not particularly limited, and a regular calender made of a metal roll, a soft nip calender, a high-temperature soft nip calender, etc. Devices may be selected as appropriate, and conditions may be set within the controllable range of these devices according to the quality target value.

The paper obtained by the production method of the present invention can be used for various uses such as high-quality or medium-quality printing paper, newsprint, coated base paper such as art paper and cast coated paper, and information recording paper. In the case of printing paper, the printing method is not limited to offset printing, letterpress printing, etc., but since the present invention can be suitably applied to neutral papermaking and high-speed papermaking, the paper produced by the present invention is offset paper such as newsprint paper. Printing paper is preferred. Although there is no limitation also about the basic weight of the paper manufactured by this invention, in the case of a newsprint, Preferably it is 30-60 g / m < ² >, More preferably, it is 35-55 g / m < ² >.

  As described above, according to the production method of the present invention, it is possible to obtain a paper having a good yield and a good formation. The formation can be evaluated by the formation index (see Paper Pulp Technology Times 28 (5), 1985, P30-35) by the laser light transmission fluctuation method. For example, in the case of newsprint, the formation index is 11 0.0 or less is preferable, and 10.5 or less is more preferable. Here, the formation index indicates that the smaller the value is, the better the paper is, and a difference of 0.5 in the formation index can be recognized as a difference in formation by the naked eye.

Embodiments of the Present Invention Hereinafter, examples of preferred embodiments of the present invention will be described with reference to FIG. In FIG. 1, a stock containing pulp raw material is sequentially distributed at 25% by weight at three branch points to form four stock streams, and each distributed stock is passed through four screens # 1 to # 4. Foreign materials are removed, a retention agent is added to the paper material that has passed through the screen, the distributed paper materials are sequentially joined at three joining points, and the joined paper materials are sent to the head box.

  In the prior art, the retention agent is generally added before the screen in anticipation of mixing when passing through the screen, whereas in the present invention, the stock after passing through the screen is used. A retention agent is added. By adding the retention agent according to the present invention, the retention agent is not exposed to a strong shearing force when passing through the screen, so that the effect of the retention agent can be sufficiently exerted.

  First, in FIG. 1, the paper stock is sequentially distributed at a plurality of branch points to form four paper stocks. In the present invention, it is possible to distribute the paper stock to a plurality of paper stocks at one branch point, but it is preferable to sequentially distribute the paper stock at a plurality of branch points because accurate distribution is possible. In FIG. 1, the paper stock is equally divided into four, but it is of course possible to distribute the paper stock at different ratios. Further, in the present invention, the paper stock may be distributed to two or more. Thus, for example, in addition to distributing the paper stock into four as shown in FIG. 1, the paper stock can be distributed into two paper stocks, three paper stocks, and even five or more paper stocks. . A known apparatus can be used for liquid feeding, for example, using a fan pump.

  Next, in the embodiment of the present invention shown in FIG. 1, the distributed paper stock is passed through screens # 1 to 4, respectively, and foreign matters are removed. In the present invention, various screens can be used as the screen. For example, the screen through which the distributed paper is passed may be different or the same for each paper. That is, in the aspect shown in FIG. 1, the same type of screen can be used as the screens # 1 to # 4, or different types of screens can be used. As the screen, for example, a screen plate having openings such as round holes or slits can be used. In one aspect, when passing the stock through the screen, the stock is accelerated by a rotating blade or the like, and foreign matters are pushed out by this centrifugal force.

  In addition, a retention agent is added to the stock treated with the screen. The retention agent can be added from the exit of the screen until all of the dispensed stock joins. In the present invention, a retention agent is added to at least one of the two or more distributed and screened stocks. In the embodiment shown in FIG. 1, a retention agent is added to the stock treated with the # 1 screen, but the retention agent is further added to one or more of the stock treated with the # 2-4 screen. It is also possible to add. At this time, the retention agent added to each paper stock may be the same or different. In another embodiment, for example, a retention agent is not added to the paper material processed with the # 1 screen, and the retention agent is added to one or more of the paper materials processed with the # 2 to 4 screens. Can also be added. Furthermore, in the present invention, a retention agent may be added until all of the two or more screen-treated materials are joined. In the case of the configuration shown in FIG. Yield can be added before the paper material that has exited the # 3 screen joins the paper material that has joined the paper material that has exited the # 2 screen. In another embodiment, a retention agent may be added after the paper materials processed on the screens # 1 to # 3 merge and before the paper materials processed on the screen # 4 merge.

  In one preferred embodiment, the post-screening stock to which the retention agent is added is preferably in an amount of 80% by weight or less based on the stock after all of the dispensed stock has joined. When a retention agent is added in such a manner, the yield can be further improved. The reason for this is not clear, but it is speculated that the addition of a retention agent in this way will temporarily produce a stock with a large amount of retention agent, making it easier to exert the effect of the retention agent. The A preferred embodiment of the present invention will be described with reference to FIG. 1. For example, when a retention agent is added only to the material that has exited the # 1 screen, all the papers after the screen treatment to which the retention agent is added are used. The amount is preferably 25% by weight with respect to the entire paper stock after the materials are joined. Similarly, when a retention agent is added to both the materials treated with the # 1 and # 2 screens or the material that they have joined together, the material after the screen treatment with the addition of the retention agent is all paper. The amount is 50% by weight with respect to the entire paper stock after joining the materials, which is preferable.

  In another preferred embodiment, the retention agent of the present invention is added to the stock that has passed through the screen and has the opportunity to merge with at least two or more distribution stocks. When added in such a manner, the yielding agent is easily dispersed uniformly in the stock, and thus the effect of the retention agent is easily exhibited. Referring to FIG. 1, since the stock that has exited the screen of # 1 or # 2 has three chances to join with other stock (joining points 1 to 3), the retention agent is It is preferable as a paper stock to be added. Similarly, the paper material that exits the # 3 screen, or the paper material that exits the # 1 screen and the paper material that exits the # 2 screen, is then an opportunity to merge with other paper materials. Is at least twice (meeting points 2 and 3), which is preferable as a paper material to which a retention agent is added.

  Further, the paper materials distributed and screened as described above are merged. The joining of the paper materials may be performed sequentially as shown in FIG. 1 or may be performed collectively at one joining point. When two or more stocks are merged, a piping state that facilitates mixing can be obtained, and a device for promoting mixing may be added. In the present invention, a paper material to be sent to the head box is prepared in this way.

  Then, the paper stock prepared in this way is sent to the head box of the paper machine, and the paper stock is ejected from the head box to produce paper. In the present invention, various types of head boxes can be used. In particular, a mixing module in the head box, called a concentration dilution type head box, is used to prepare a paper stock and diluted water (diluted paper stock, clear white water). It is preferred to use a type of headbox that is mixed. In this type of head box, the stock is mixed again in the head box, so that the uniform dispersion of the retention agent in the stock is further promoted, and the effects of the present invention are fully exhibited. .

  Hereinafter, the present invention will be described with reference to examples relating to newsprint for offset printing, but the present invention is not limited thereto. In the examples, unless otherwise specified, “part” and “%” respectively represent “part by weight” and “% by weight”, and the numerical ranges are described as including the end points. In addition, the chemical addition rate indicates the solid content addition rate unless otherwise specified. When it is designated as solid, it indicates the addition rate of the chemical itself, not the solid content. For example, when 0.2% of a 1% chemical is added as a solid content, 20% is added in solid form.

The evaluation test method in the present invention is as follows.
<Measurement method of yield>
Solid content concentration and ash concentration were measured for the stock inlet raw material and white water that had fallen under the wire (described as white water under the wire). Paper yield was measured by the following formula (1), and ash (filler) yield was measured by the following formula (2). In addition, the measurement of the ash content measured the weight about the stock inlet raw material and the white water under a wire, and ashed the solid content at 525 degreeC.

Paper yield = 100 × (A−B) / A (1)
A: Solid content concentration of stock inlet raw material (g / l)
B: Solid content concentration of white water under wire (g / l)
Ash content yield = 100 × (C−D) / C (2)
C: Ash concentration of stock inlet raw material (g / l)
D: Ash concentration of white water under the wire (g / l)
<Measuring method of formation>
The formation index was measured by FMT-MIII (light transmission fluctuation method) manufactured by Nomura Corporation. Here, the smaller the value of the formation index, the better the paper fit. A difference of 0.5 in the formation index can be recognized as a difference in formation with the naked eye.

<Evaluation of operability>
The operability was evaluated in the following four stages from the viewpoint of the difficulty of paper breaks.
A: Very good, B: Good, B: Slightly poor, X: Bad [Example 1]
A pulp slurry prepared by mixing and disaggregating 80 parts of DIP (freezing degree 180 ml), 15 parts of TMP (freezing degree 100 ml), and 5 parts of softwood bleached kraft pulp (NBKP, freezing degree 600 ml) was used as a filler. Light calcium carbonate with a solid content of 20%, cation-modified starch with a solid content of 0.5% as an internal paper strength enhancer, and a liquid sulfuric acid band with a solid content of 0.5% with respect to the solid content of the pulp. The material was prepared.

  As shown in FIG. 1, the stock was distributed into 4 streams in order of 25% by weight, and foreign matters were removed through the screens. A cationic linear linear polyacrylamide-based retention agent (Realizer R-300, manufactured by Somar Co., Ltd.) having a weight average molecular weight of about 20 million at the screen exit is 0.021 with respect to the paper initially divided. Weight percent was added. Thereafter, the four distributed paper stocks were sequentially joined to form one paper stock.

This paper is sent to the module jet type head box, and the paper is sprayed onto the twin wire type paper making wire from the head box, and the neutral paper making so that the basis weight is 42 g / m ² at a paper making speed of 1200 m / min. Newspaper paper was produced.

Using a gate roll coater on this base paper, a surface coating agent comprising a hydroxyethylated starch and a cationic surface sizing agent (styrene / acrylate copolymer) (solid content concentration of hydroxyethylated starch 6.0%, The surface sizing agent solid content concentration of 0.30% was evenly applied to both the felt surface and the wire surface to obtain offset printing newsprint. The coating amounts of hydroxyethylated starch and cationic surface sizing agent were 0.8 g / m ² (both sides total) and 0.04 g / m ² (both sides total), respectively.

[Example 2]
In Example 1, newsprint for offset printing was obtained in the same manner as in Example 1 except that the addition rate of the retention agent was 0.017% by weight.

[Comparative Example 1]
With respect to the stock prepared in the same manner as in Example 1, a retention agent (rearizer R-300, at the outlet of the secondary fan pump (upstream from the branch point 1 in FIG. 1)) immediately before distributing the stock to each screen. Newspaper for offset printing was obtained in the same manner as in Example 1 except that 0.03% by weight was added.

[Comparative Example 2]
Newspaper for offset printing was obtained in the same manner as in Comparative Example 1 except that 0.021% by weight of the retention agent was added in Comparative Example 1.

  Table 1 shows the results of the above examples and comparative examples. As is apparent from the results of Example 1 and Comparative Example 2 in Table 1, when a retention agent is added to the stock at the screen outlet according to the present invention, a paper with a high yield rate of the stock and ash is efficiently produced. I understood that I could do it. Further, from the results of Example 2 and Comparative Example 1, even when the addition rate of the retention agent is reduced by 40% or more by using the present invention, the yield of the same level as the conventional one, and the paper of the formation is a problem in operability. It was found that it can be manufactured without any problems.

FIG. 1 is a schematic diagram illustrating one embodiment of the present invention.

Claims (6)

Distributing the stock containing pulp raw material to two or more;
Passing each of the dispensed two or more stocks through a screen to remove foreign matter from the stock;
Adding a retention agent to at least one of the stocks after passing through the screen;
Merging two or more distributed stocks;
Jetting the combined stock from the headbox to make paper,
A method for producing newsprint , comprising: The basis weight of the newspaper is 30-60 g / m ² The method of claim 1, wherein The method according to claim 1 or 2, wherein the at least one dispensed stock to which the retention agent is added is in an amount of up to 80% by weight of the total stock after merging. Yield for paper stock that has been passed through the screen and that has been distributed through the screen and that has two or more chances to join with other stock. The method according to any one of claims 1 to 3, wherein an agent is added. The method according to claim 1, wherein the head box is a concentration dilution type head box. The method in any one of Claims 1-5 whose papermaking speed is 700 m / min or more.

Images