JP6248870B2 - Inkjet printing coated paper - Google Patents

Description

  The present invention relates to a coated paper for inkjet printing, and more particularly to a coated paper for inkjet printing having printability of an inkjet commercial printing machine that performs high-speed and continuous printing.

  Ink-jet printing using the ink-jet method is not limited to photo printing, terminal PC printers, fax machines, or copiers, but is also practical in the so-called on-demand printing field that enables multi-product small-lot printing and variable information printing. Is progressing. In recent years, printing speed and image quality have been improved, and offset printing in which the number of copies per printing lot is 5000 copies or less is also spreading. In addition, the application of inkjet commercial printing is also being studied for areas that have been conventionally printed by gravure printing.

The ink jet method is a method in which fine droplets of ink ejected by various methods are attached to paper such as paper to form images and characters. This method is used in many fields because it is easy to increase the speed and full color, has low noise during output, and is inexpensive. In particular, in commercial inkjet printing, since it is necessary to perform high-speed and continuous printing, a line head system has been adopted and spread in inkjet heads that eject inkjet ink.

A serial type head that is often used in a terminal PC printer or the like needs to stop paper conveyance and perform printing, and therefore cannot convey paper continuously. On the other hand, the line-type head is suitable for rotary inkjet commercial printing because it can perform printing while continuously conveying paper. In the recent ink jet commercial printing market, ink jet commercial printing machines appearing at 60 m / min or higher and at a high speed exceeding 200 m / min.

This ink jet commercial printing machine ejects ink droplets from an ink jet head onto a paper surface to form an image, and then dries the printed matter with a drying device. As this drying device, various types of drying methods are adopted. In addition to UV lamps, halogen lamps, LED lamps, hot air dryers, paper is transported to a transport roll (heat roll) whose surface is heated and dried. There is something to make. The temperature during drying is adjusted to an optimum temperature depending on the printing speed and the amount of ink to be printed.

In this way, high-speed ink absorbency is required for printing paper for inkjet printers that are increasing in speed. However, if this ink absorbency is insufficient, uneven printing on the printing surface or different colors may occur. Bleeding occurs at the boundary line of the image, and print quality is degraded. Ink fixation on the paper surface does not proceed, and ink may fall off when the printing surface is rubbed immediately after printing.

Inkjet printers that are also non-printing printing systems can handle variable information, and are widely used in document processing services (DPS) and direct mail (DM) that handle customer information. In this application, in addition to variable information, printing of photographic images and designs that increase the amount of ink shot is also performed. In addition, since a high advertising effect is required for the obtained printed matter, a printing company demands printing on a coated paper for printing, which can obtain a higher printing effect. However, since the current printing coated paper has a lower ink-absorbing property than the non-coated printing paper, the printing company uses an uncoated printing paper that does not provide a high printing effect. After printing or selecting a coated paper for printing with emphasis on a high printing effect, printing a photo or design with a large amount of ink applied with an offset printer, and printing only variable information with an inkjet printer, so-called The current situation is that composite printing is performed, and productivity is reduced by an inkjet printer, and ultra-low speed printing is performed.

Conventional inkjet dedicated papers for photo prints and terminal PC printers have high ink absorbability because they employ an ink receiving layer using a porous pigment. However, since the porous pigment is used, the printing effect such as the gloss of the printing portion is low, and the so-called matte tone is obtained. After applying a porous pigment, the glossy ink jet recording paper that has been cast so that it is in close contact with a chrome-plated metal roll, or a polyethylene resin applied to the surface of the base paper, and then the porous pigment is applied to make it glossy There are so-called RC-based glossy inkjet recording papers that express the above-mentioned, but both of them are high in processing costs and cannot be used as substitutes for the coated paper used for printing while reducing the current productivity.

  Up to now, various studies have been made on coated paper for printing having ink jet printing suitability. For example, in Japanese Patent Application Laid-Open No. H11-228260, the mass ratio of the adhesive of the coating layer adjacent to the support and the smoother air permeability are offset printing paper that has both high-speed and continuous printing suitability for inkjet printing. Defines the range of degrees. In this invention, ink absorbability suitable for inkjet is improved, and variable information, which is mainly character information, can be printed on an inkjet printer, but photographic images and designs with a large amount of ink can be printed. Such an ink absorption level cannot be satisfied.

  Patent Document 2 proposes that calcium chloride is applied to a coating layer in a coating paper having a coating layer mainly composed of a pigment and a binder on at least one side of the base paper. Although the unevenness and the fixing property of the part tend to improve, the ink absorbability is not sufficient, so it is considered that the level is not sufficient for use.

  In Patent Document 3, the surface coating layer and the base material (base paper) contain a calcium compound other than calcium carbonate and the content of the calcium compound is specified. However, although the unevenness of the printed portion and the tendency to improve the ink fixing property are recognized, the ink absorption level required for inkjet commercial printing is not achieved, and as a result, a printed material that can be used is not obtained.

  In patent document 4, in the coated paper for printing which provided the coating layer which has a pigment and a binder as a main component, a calcium compound is contained in a base paper and content of the calcium compound is prescribed | regulated. However, although there is a tendency to improve printing portion unevenness and ink fixability during inkjet printing, the ink absorbability level required for inkjet commercial printing is not achieved, and as a result, a printed material that can be used is not obtained.

  In Patent Document 5, calcium carbonate is specified as a pigment type used in the coating layer, and the ratio, the optimum rice basis weight, and the surface electric resistance value range are specified. It is said that a good printed matter can be obtained even with this printing method. However, high-speed inkjet commercial printing is not sufficient for photographic image printing that requires high ink absorbency.

  Patent Document 6 stipulates that the carboxylic acid is contained in the paper shared by the ink jet recording method and the electrophotographic recording method. However, although it improves printing unevenness and blurring, it is considered that the ink absorbency is not at a sufficient level. .

  In Patent Document 7, agglomerated light calcium carbonate having an average secondary particle size is contained, and the optimum addition amount thereof is specified. However, the ink absorbability level in the terminal PC printer before the high-speed printing is as follows. Although satisfied, it is insufficient for the level of ink absorbency required for an inkjet commercial printing press equipped with a line head.

  In Patent Document 8, mainly silica, alumina, alumina hydrate, alumina silicate, kaolin, clay, calcined clay, zinc oxide, magnesium sulfate, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, smectite, zeolite, Viscosity used in a single or several mixed systems of various publicly known pigments in general coating fields such as magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, urea resin plastic pigment, etc. At least one selected from cellulose derivatives and high molecular weight polysaccharides is used as a modifier to increase viscosity, but the effect is insufficient when focused on size press coating and occurs on rolls specific to roll coating. Ring-shaped paint unevenness (so-called ring pattern Down) occurs, and an excellent coated surface is obtained.

  In Patent Document 9, one or more types of white inorganic pigments such as silica, clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, satin white, aluminum silicate, lithopone, alumina and zeolite are used. ing. However, in order to achieve both coating suitability and ink jet suitability with a size press (roll coater), it is necessary to specify pigment types with different properties and to specify the number of parts, and neither of these properties is sufficient without considering this part. It is. In addition, carboxymethyl cellulose is an example of a water-soluble polymer used as a binder for the white inorganic pigment, but there is no description about the effect of adjusting the coating viscosity obtained using this chemical. In addition, sodium carboxymethyl cellulose that can provide an appropriate coating aptitude improvement effect cannot be specified, and a sufficient effect cannot be obtained.

  In Patent Document 10, it is obtained by copolymerizing at least two types of monomers including at least an aromatic vinyl monomer and a conjugated diene monomer in the presence of a water-soluble polymer containing an alcoholic hydroxyl group. A method for producing a coated paper with a coating liquid containing an aqueous emulsion and a pigment is described. In such a coating solution containing a water-soluble emulsion and a pigment, ring-shaped paint unevenness (so-called ring pattern) occurs on the roll of the transfer roll coater, and a good coating surface cannot be obtained.

JP 2011-246838 A JP 2012-77395 A JP 2012-77393 A JP 2012-77392 A JP 2008-297679 A JP 2005-8993 A JP 2005-8992 A JP 2007-15253 A JP-A-8-104057 JP 2005-290579 A

  An object of this invention is to provide the coated paper for inkjet printing which has the printability of the inkjet commercial printing machine which performs high-speed and continuous printing.

The present inventors provide a pigment-coated paper that has the same surface properties and printing effects as those of conventional coated paper used in offset printing, and is excellent in ink jet printing properties such as ink absorbability and ink fixing properties. Therefore, research on the composition of the pigment coating layer was repeated. As a result, at least one side of the base paper was size-pressed with a coating layer containing a pigment, a binder, and an inkjet ink fixing agent, and applied to 1 g / m ² or more and 8 g / m ² or less per side. It is a coated paper, and it is important that the content ratio of acicular light calcium carbonate and oil-absorbing pigment is specified in a specific range as a pigment of the coating layer, and that carboxymethylcellulose sodium is contained It was found to be an element.

The present invention includes the following inventions.
(1) Coated paper for ink jet printing in which a coating layer containing a pigment, a binder, and an ink jet ink fixing agent is applied to at least one surface of a base paper in an amount of 1 g / m ² or more and 8 g / m ² or less per side. in, as a pigment in coating coating layer, acicular precipitated calcium carbonate 40 parts by mass or more and 80 parts by mass with respect to 100 parts by weight of the pigment, in addition to needle-shaped precipitated calcium carbonate, oil absorbency 80 ml / 100 g or more oil-absorbing pigment 20 parts by mass or more and 60 parts by mass or less, and sodium carboxymethylcellulose, and a styrene-butadiene copolymer latex having a Tg point of 10 ° C. or more and 60 ° C. or less as a part of the binder of the coating layer. Coated paper for inkjet printing.
(2) The coated paper for inkjet printing according to (1), wherein the B-type viscosity of a 1% solution of sodium carboxymethylcellulose (temperature: 25 ° C.) is 50 mPa · s or more and 500 mPa · s or less.
(3) on at least one surface of a base paper, a pigment, a binder, an inkjet fixer, carboxymethyl contain methylcellulose low Sand thorium, pigment is acicular precipitated calcium carbonate and acicular light oil absorption 80 ml / 100 g or more than calcium carbonate An oil-absorbing pigment which is a coating paper for ink-jet printing, wherein a coating liquid containing a styrene-butadiene copolymer latex having a Tg point of 10 ° C. or more and 60 ° C. or less as a part of the binder is applied with a size press. Production method.
( 4 ) The method for producing coated paper for ink-jet printing according to ( 3 ), wherein the size press is a gate roll coater or a shim sizer coater.
(5) B-type viscosity (temperature: 25 ° C.) of the coating solution is 500 mPa · s or more and 4000 mPa · s or less, The production of coated paper for ink jet printing according to (3) or (4) Method.

  The coated paper for inkjet printing of the present invention has a surface gloss comparable to that of coated paper for offset printing, and is excellent in inkjet printing suitability such as ink absorbability and ink fixability in an inkjet commercial printing machine.

[Coating layer]
In the coated paper for inkjet printing of the present invention, a coating layer containing a pigment, a binder, and an inkjet ink fixing agent is applied to at least one surface of a base paper with a size press at 1 g / m ² or more to 8 g / m ^{2 on} one side. ² or less coated paper for inkjet printing, wherein the pigment of the coating layer is 40 to 80 parts by mass of acicular light calcium carbonate, and 20 masses of oil-absorbing pigment other than acicular light calcium carbonate. It is contained in an amount of 60 parts by mass or more and 60 parts by mass or less and contains sodium carboxymethylcellulose.

  In order to obtain good quality in ink absorbability, glossiness of white paper and printed parts, color development of ink, etc. as ink-jet coated paper, in addition to the use of an ink fixing agent, acicular light calcium carbonate as a pigment and Oil-absorbing pigments are required. However, when an ink fixing agent and these pigments are used in combination, the viscosity of the paint is increased and the water retention is reduced, and a good coated surface cannot be obtained. If the coating concentration is lowered to improve this water retention, the required coating amount will not be obtained this time, and as a result, the desired coated surface and ink absorbability will not be obtained, and the desired inkjet coated paper will be obtained. Absent. In order to improve this situation, using carboxymethylcellulose sodium together with an ink fixing agent, acicular light calcium carbonate, and oil-absorbing pigment can ensure good water retention without lowering the paint concentration. An ink-jet coated paper having both a coated surface and ink absorbability can be obtained.

[Pigment]
(Light calcium carbonate)
In the present invention, the coating layer contains acicular light calcium carbonate and an oil-absorbing pigment as pigments, and the ratio of acicular light calcium carbonate to the oil-absorbing pigment is 40 parts by mass: 20 parts by mass to 80 parts by mass. Used in the department.
Light calcium carbonate is available in the shape of needles, cubes, spindles, columns, etc., but it has excellent ink-absorbing ink absorbability, color development, and fixability, which are the effects required in the present invention, and has a white paper gloss on the surface. To obtain excellent quality, acicular light calcium carbonate is preferable. The reason for this is not clear, but when acicular light calcium carbonate and oil-absorbing pigment are present in the coating layer, uneven orientation hardly occurs on the surface of the coating layer and in the coating layer due to the shape of the acicular light calcium carbonate. In addition, when mixed with acicular light calcium carbonate, it seems that when the ink jet ink adheres to the surface with an appropriate gap in the coating layer, an absorption speed increase effect due to the so-called capillary phenomenon that is absorbed instantaneously can be obtained. It is. In addition, the mixture of acicular light calcium carbonate and oil-absorbing pigment in the coating layer increases the water retention of the oil-absorbing pigment, increases the space ratio of the pigment and pigment, and retains the absorbed ink in the coating layer. It is considered that an effect of improving the so-called ink absorption capacity can be obtained. For this reason, it is considered that when an acicular light calcium carbonate and an oil-absorbing pigment are used in combination, ink that is instantaneously absorbed in the coating layer is retained in the coating layer, and an inkjet paper having excellent surface glossiness can be obtained. .

  Acicular light calcium carbonate has better ink absorption in inkjet commercial printers when the particle size measured by an X-ray transmission sedimentation particle size distribution device laser diffraction device is 0.3 μm or more and 0.9 μm or less. In addition, it is possible to provide a coated paper for inkjet commercial printing which has excellent properties, ink color developability, ink fixability, and excellent surface white paper gloss. When the particle size is 0.9 μm or less, ink absorbency and white paper gloss can be improved, and when it is 0.3 μm or more, the coating layer strength is reduced, or guillotine cutting is performed with paper powder. It is possible to prevent deterioration of suitability and adhesion of the coating layer to the paper transport roll in the ink jet printer. When the thickness is 0.3 μm or less, sufficient gaps between the pigments are reduced, and the ink absorbability is lowered. When the particle diameter measured by an X-ray transmission type sedimentation method particle size distribution apparatus laser diffraction apparatus is further 0.4 μm or more and 0.6 μm or less, various qualities are desirably improved. In addition, the particle diameter measured by the X-ray transmissive sedimentation particle size distribution apparatus laser diffraction apparatus in the present invention is 50 volume% particle diameter (D50).

  The method for obtaining acicular light calcium carbonate used in the present invention is not particularly limited, and a conventionally known production method such as a method of reacting calcium hydroxide (slaked lime) with carbon dioxide, calcium chloride and sodium carbonate anhydride ( Soda ash) and a method of reacting slaked lime with soda ash.

  In addition, since the slaked lime slurry temperature at the time of a carbonation start affects the crystal | crystallization shape of the light calcium carbonate which is a product, it is necessary to adjust. When the carbonation start temperature is less than 20 ° C., fine needle-like crystals are aggregated when carbon dioxide or carbon dioxide-containing gas is blown, while when it exceeds 30 ° C., the needle shape gradually changes from a needle shape to a spindle shape. The ratio of will increase. In order to obtain a needle shape, it is necessary to adjust the slaked lime slurry temperature to 30 to 50 ° C.

The amount of carbon dioxide gas or carbon dioxide-containing gas blown is not particularly limited, but it is necessary to adjust the flow rate of 100% carbon dioxide gas (1 atm, converted to 20 ° C.) per kilogram of slaked lime before the start of the reaction in terms of crystal shape. . In order to obtain a needle shape, it is preferably 5 L / min or less, and when this diversion increases, other shapes such as a spindle shape are obtained.

In order to obtain a needle shape, it is necessary to equip the reaction vessel with a stirrer and perform carbonation while stirring. Thereby, the carbon dioxide gas becomes fine, the contact with the slaked lime slurry is improved, the reaction is performed uniformly and efficiently, and a needle shape is obtained. The stirring peripheral speed of the stirrer is preferably 2.0 m / s or more, and more preferably 2.5 m / s or more. As the agitator, a uniaxial or biaxial tank agitator, a coreless mixer, a high-speed agitating disperser, or the like can be used. Furthermore, the shear force of slaked lime slurry can be increased by installing a baffle plate in the reaction tank.

In order to obtain light calcium carbonate having a particle size within the range of the present invention, it is preferable to provide a dispersion step and a pulverization step after the dehydration step. However, when the average particle after the dispersion treatment is in a desired average particle size range, pulverization is performed. You may use as it is, without performing.

The oil-absorbing pigment used together with acicular light calcium carbonate refers to amorphous silica, fine-particle silica, alumina, and calcined kaolin, and one or more of these pigments are used. The higher the oil absorbency of these pigments, the better the ink absorbability, which is preferable. Oil absorption is used as an index indicating oil absorption, but if it exceeds 80 ml / 100 g or more, it is recognized that ink absorption is improved.
However, when an oil-absorbing pigment is used, the paint is easily dried after the paint is applied to the paper from the roll of the roll coater, and the dried paint remains as dirt on the roll, making continuous coating difficult. Thus, when roll dirt occurs, a good coated surface cannot be obtained, and as a result, the ink jet quality deteriorates. In order to suppress such roll dirt, it is common practice to formulate various water retention agents to improve the water retention of the paint. As water-retaining agents, synthetic water-retaining agents such as polycarboxylic acid-based copolymers and natural water-retaining agents such as sodium carboxymethylcellulose, polyethylene glycol, starch, casein, etc. are known, but sodium carboxymethylcellulose, starch, casein, etc. Other water retention agents are not compatible with the ink fixing agent and often aggregate. Even if it can be used without agglomeration using a special mixing method, a decrease in ink absorbency occurs. Starch and casein have good compatibility with the ink fixing agent and are easy to produce paints. However, if an addition amount sufficient to suppress roll stain is added, ink absorbability is lowered. On the other hand, even when sodium carboxymethylcellulose sodium is added in an amount that provides a roll stain inhibiting effect, the ink absorbability is only slightly lowered, and a good ink jet suitability that is required commercially is obtained. In addition, carboxymethylcellulose sodium can improve the coating layer strength. If the amount of chemicals used as a binder is adjusted (decreased), the coated paper has even better quality. Is obtained.

Using a carboxymethyl cellulose sodium 1% solution (temperature: 25 ° C.) having a viscosity of 50 mPa · s to 500 mPa · s, a balance between high roll smear suppression effect and good ink jet aptitude Excellent coated paper can be obtained. The reason why the quality becomes excellent by regulating the viscosity of a 1% solution of sodium carboxymethylcellulose (temperature: 25 ° C.) is not clear, but at 50 mPa · s or less, the water holding power of the paint is weak and the paint on the roll Becomes easy to dry, and a sufficient roll dirt suppressing effect cannot be obtained. In addition, at 500 mPa · s or more, when the coating layer coated on the base paper from the roll is dried, the binder component is retained on the surface, resulting in a decrease in ink absorbability and an excellent inkjet coated paper. Estimated.
The amount of sodium carboxymethylcellulose added is preferably such that the B-type viscosity (25 ° C.) of the coating solution is 500 mPa · s to 4000 mPa · s. More preferably, the added amount is 1500 mPa · s or more and 2500 mPa · s or less. When the addition amount is such that the B-type viscosity (25 ° C.) of the coating liquid is 500 mPa · s or less, unevenness on the ring pattern is likely to occur in the paint on the roll. On the other hand, when the B-type viscosity (25 ° C.) of the coating liquid is 4000 mPa · s or more, the ink-absorbing property tends to decrease.

In the present invention, an ink fixing agent, acicular light calcium carbonate, an oil-absorbing pigment, carboxymethylcellulose sodium, and a binder are used for the coating layer, but when the coated paper for inkjet printing has two or more coating layers, You may make it contain in any of the outermost surface coating layer and the coating layer (undercoat coating layer) below the outermost surface coating layer.
By including these materials in the outermost surface coating layer, it is possible to improve ink fixability, ink absorbability, or white paper glossiness of inkjet ink.
Moreover, the ink absorbability of an inkjet ink and the surface glossiness of an outermost surface coating layer can be improved by containing these materials in an undercoat coating layer.
When these materials are contained and coated by a size press, roll contamination is suppressed in coating of all layers.
When it has two or more layers of a coating layer, it is preferable to contain 90 mass% or more of acicular light calcium carbonate and an oil absorbing pigment with respect to 100 mass parts of pigments of all the coating layers.
In addition, a coating layer may exist only in the single side | surface of a base paper, and may exist in both surfaces.

(Pigments that can be used in combination)
In addition to the acicular light calcium carbonate and oil-absorbing pigment specified in the present invention, the pigment used in the coating layer includes kaolin, heavy calcium carbonate, aggregated calcium carbonate, light calcium carbonate other than the present invention, talc, calcium sulfate. , Barium sulfate, Titanium dioxide, Zinc oxide, Magnesium carbonate, Magnesium oxide, Organic hollow pigment, Composite pigment, Calcium carbonate aluminomagnesium silicate with silica particles combined on the surface, Fine calcium silicate, Fine calcium carbonate, Satin white, Inorganic pigments such as bentonite, zeolite, sericite, smectite, polystyrene resin, styrene / acrylic copolymer resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin, benzoguanamine resin, and these micro hollow particles and through-hole type Or organic material Organic pigment particles or the like made. When kaolin, organic pigment particles, etc. are used in combination, there is an effect of improving white paper glossiness.

[binder]
In the present invention, the binder used in the coating layer is not particularly specified, and styrene / butadiene copolymer, synthetic rubber latex such as methyl methacrylate / butadiene copolymer, oxidized starch, etherified starch, cationized Starch, starch-based starch, starch-based starch such as dextrin, casein, gelatin, protein such as soy protein, cellulose-based such as hydroxyethylcellulose, polyvinyl alcohol, polyvinyl alcohol, vinyl acetate copolymer, Vinyl polymer systems such as acrylic copolymers can be used. Among these binders, a styrene-butadiene copolymer latex binder can exhibit high ink absorbability because a high coating layer strength can be obtained with a small amount. Moreover, starch has the effect | action which adjusts the viscosity of a coating liquid while expressing the coating layer intensity | strength. When the viscosity of the coating liquid is outside the appropriate range, the glossiness of the white paper is reduced. For this reason, it is better to use both a styrene-butadiene copolymer latex binder and starch because high coating layer strength and viscosity adjustment of the coating liquid can be performed while maintaining high ink absorbability. Casein is also applicable as having the same effect as starch. If the Tg point of a part or all of the styrene-butadiene copolymer latex is adjusted to 10 ° C. or more and 60 ° C. or less, the ink absorbability is improved and the white paper gloss is improved. The reason why the quality is improved by adjusting the Tg point of the styrene-butadiene copolymer latex in this way is not clear, but by setting the Tg point of the binder in the coating layer to 10 ° C. or higher, the heat of the binder increases the temperature of the binder. It is considered that, by only melting the part and forming a film and maintaining a partly granular shape, it is possible to achieve both appropriate coating layer strength and pores in the coating layer necessary for ink absorption. When the Tg point is 60 degrees or more, the ink absorbability is improved, but an appropriate coating layer strength cannot be obtained.

As the binder, those described above can be used, and one or more of them can be appropriately selected and used. The amount of binder added depends on the type of binder used, but the P / B ratio is preferably 3 or more and 40 or less. When the P / B ratio is less than 3, the gloss and the coating layer strength of the coated paper for ink jet printing are excellent, but the ink absorbability is low. The P / B ratio for better ink absorbability is preferably 6 or less, and more preferably 5 or less. On the other hand, when the P / B ratio exceeds 35, the ink jet recording suitability is excellent, but the glossiness and coating layer strength of the coated paper for ink jet printing are not at desirable levels. By making it preferably 35 or less, more preferably 30 or less, it is possible to prevent the occurrence of paper dust during guillotine cutting and to enhance various processability.

[Carboxymethylcellulose sodium]
Sodium carboxymethylcellulose is obtained by pulverizing raw material pulp with a pulverizer and then reacting the resulting cellulose in the pulverization treatment with monohaloacetic acid or a salt thereof and an alkali agent in a hydrophilic solvent to obtain sodium carboxymethylcellulose.

  In this case, the raw material pulp that can be used in the present invention includes cotton linter, rice straw pulp, and wood pulp. Specifically, the pulp is mainly N-wood pulp and hardwood wood mainly made of linter pulp and softwood. L material pulp can be used. The shape of the raw material pulp is not particularly limited, but the shape of the raw material pulp is preferably a chip shape.

  As a halogen atom in monohaloacetic acid, an iodine atom, a bromine atom, or a chlorine atom is preferably used, and a chlorine atom is more preferable because of reactivity, versatility, and ease of handling. As the metal capable of forming a salt of monohaloacetic acid, lithium, potassium, and sodium are used from the viewpoint of expressing the water solubility and high aqueous solution viscosity of the obtained carboxymethyl cellulose, and sodium is preferable.

  As the alkali agent, an alkali metal hydroxide or an alkaline earth metal hydroxide is preferable. Examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide and the like, and examples of the alkaline earth metal hydroxide include magnesium hydroxide and calcium hydroxide.

  After completion of the reaction, an aqueous solution of a hydrophilic solvent such as methanol is added to the obtained reaction product, and salts such as NaCl can be removed by filtration after stirring. Carboxymethyl cellulose is obtained as a filter cake, and can be washed with acetone and dehydrated efficiently.

From the viewpoint of improving the mixing property of monohaloacetic acid or a salt thereof and raw pulp, a hydrophilic organic solvent may be used in the pulverization treatment step and / or the reaction step. Examples of the hydrophilic organic solvent include secondary or tertiary lower alcohols such as isopropanol and tert-butanol; diglymes such as 1,4-dioxane, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, ether solvents such as triglyme, dimethyl sulfoxide and the like. The hydrophilic polar solvent is raised, preferably a secondary or tertiary lower alcohol such as isopropanol or tert-butanol.

[Ink fixing agent]
Water-based pigment inks and water-based dye inks are used as inks for ink jet commercial printing presses. For the purpose of improving ink fixability and color development of printed matter with these water-based inks, an ink fixing agent is included in the coating layer. Good. As the ink fixing agent, one or more kinds selected from those listed below can be selected and used. The effect is obtained when 0.1 g / m ² or more is applied per side, and more preferably 0.3 g / m ² or more is applied on one side. If the coating amount per side is less than 0.1 g / m ² , the effect of ink fixability and color developability is diminished. If it is applied at ² g / m ² or more on one side, the ink absorbency is slightly inferior, and the production cost becomes high and the cost effectiveness becomes low.
Further, it is better to contain the ink fixing agent in the base paper, but it is desirable that the ink fixing agent is present on the surface layer of the paper on which the ink is applied, and the effect is greater when it is contained in the coating layer than in the base paper. Incidentally, when adding internally to the base paper, an addition amount of 0.1% by mass or more and 1% by mass or less is desirable with respect to 100% by mass of the pulp to be used. Even when contained in the base paper, the effect obtained can be ensured by setting the content to 0.1% by mass or more. On the other hand, below the lower limit, the desired effect is reduced. If the optimum upper limit value is exceeded, there is a possibility of causing ink absorption unevenness due to profile unevenness on the surface of the base paper of the ink fixing agent.

  The ink fixing agent includes an organic type and an inorganic type. As the organic ink fixing agent, for example, a water-soluble or aqueous emulsion type is used. For example, polyalkylene polyamine resins or derivatives thereof, acrylic resins having tertiary amino groups or quaternary ammonium groups, polyethyleneimine resins, polyamide resins, polyamide epichlorohydrin resins, polydiallylamine resins, polyamine resins And cationic resins such as dicyandiamide condensate, specifically, polyethyleneamine, polypropylene polyamine, cationic polyvinylpyrrolidone, poly-trimethylammonium methacrylate, vinylimidazolium methacrylate-vinylpyrrolidone copolymer, diallyldimethyl quaternary. Ammonium hydrochloride, dicyandiamide-polyethylene polyamine, dimethylaminopropylacrylamide copolymer, polyalkoxydialkyl quaternary ammonium salt, monoa Ruamine-diarylamine hydrochloride copolymer, polyallylamine hydrochloride, dicyandiamide-formalin polycondensate, epichlorohydrin-dimethylamine addition polymer, dimethyldiallylammonium chloride / SO2 copolymer, diallylamine salt / SO2 copolymer, dimethyldiallylammonium A chloride polymer, an allylamine salt polymer, a dialkylaminoethyl (meth) acrylate quaternary salt polymer, an acrylamide-diallylamine salt copolymer, and the like may be used, or one or more may be used in combination. The molecular weight of these cationic resins is not particularly limited. However, since the ink absorptivity decreases when the molecular weight is high, it is desirable to use those having a molecular weight of 30,000 or less.

  Examples of the inorganic ink fixing agent include magnesium, aluminum, calcium, scandium, titanium, vanadium, manganese, iron, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, molybdenum, indium, barium, and lanthanum. Metal salts or complexes selected from cerium, praseodymium, neodymium, samarium, europium, gadolinium, dysproprosium, erbium, ytterbium, hafnium, tungsten, bismuth.

[Auxiliary]
The coating layer may contain various auxiliary agents as necessary.
The auxiliary agent used in the present invention includes polyethylene emulsion, fatty acid salts and derivatives thereof, mold release agents such as microcrystalline wax, dispersants, antifoaming agents, preservatives, and water retention other than sodium carboxymethylcellulose defined in this patent. One type or two or more types can be appropriately selected and used from among property improvers, colorants, lubricants, water resistance agents and the like.
The coating layer may be a single layer or a plurality of layers, and may be present only on one side of the base paper or on both sides.

[Base paper]
The base paper used in the present invention may be in the form of a sheet. For example, a paper support having a basis weight of about 30 to 500 g / m ² used for ordinary inkjet recording paper, printing coated paper, and paperboard is used. It can be suitably used as a base paper. The pulp material of the paper support used as the base paper is not particularly limited, and pulp generally used as a pulp material for paper produced by a normal papermaking method such as deinked pulp, mechanical pulp, chemical pulp, etc. One type or two or more types can be appropriately selected and used from the raw materials. The paper machine for obtaining the base paper is not particularly limited, and is a long net paper machine, a short net paper machine, a circular net paper machine, an on-top former paper machine, a gap former paper machine, a Yankee paper machine. Paper can be appropriately made with a conventionally known paper machine such as a machine. The paper layer may be single-layered or multilayered.

However, in order to reduce the coating amount of the coating layer in consideration of economic effects, it is preferable to use a base material having a cup water absorption (JIS P 8140 Cobb30) adjusted to 50 cc / m ² or more.

  Further, the paper support to be used may be subjected to a surface treatment by applying a clear coating layer as necessary before coating the coating layer defined in this patent. When a clear coating layer is applied to the paper support, conventionally known devices such as a rod metalling size press coater, a gate roll coater, an inline size press coater, and a shim sizer can be used as appropriate.

  This clear coating layer is mainly composed of an adhesive, but as an adhesive, starch such as oxidized starch, enzyme-modified starch, phosphate esterified starch, cationized starch, etc., protein such as casein, soy protein, synthetic protein, etc. System, cellulose-based compounds such as hydroxyethyl cellulose, synthetic compounds such as polyvinyl alcohol, styrene / butadiene copolymers, synthetic rubber systems such as methyl methacrylate / butadiene copolymers, vinyl acetate copolymers, acrylic copolymers, etc. One or two or more types can be selected as appropriate from vinyl polymer systems. Further, the use of an ink fixing agent is more preferable because it improves ink jet aptitude.

  In addition, the paper support used as the base paper can be subjected to a calendar process in advance before the coating liquid is applied to smooth the surface of the paper support.

[Coating and finishing]
The coating liquid was prepared having a solid concentration of about 20 to 60 wt%, 1-8 g / ^{m 2} by dry weight based on paper, more preferably coated so that the 1 to 5 g / ^{m 2,} and dried . Examples of the coating apparatus for forming the coating layer include conventionally known coating apparatuses such as a blade coater, an air knife coater, a bar coater, a curtain coater, a roll coater, a rod coater, a gravure coater, a gate roll coater, and a shim sizer.
Among these, roll coaters, gate roll coaters, and shim sizers that are often used as size presses are more suitable for inkjet printing than blade coaters, air knife coaters, rod coaters, etc. This is because the printing unevenness is reduced and the coating speed is easily increased. The reason why printing unevenness is reduced is not clear, but when the paint is applied to the base paper using a blade coater, air knife coater, rod coater, etc., the penetration of the paint into the base paper becomes uneven due to the influence of the base paper. As a result, it is estimated that the coating layer unevenness occurs. Also, among the coating methods often used as size presses, coated paper obtained by using a gate roll or a shim sizer coating device that transfers the pre-lightweight paint with a roll or winding bar to the base paper The surface gloss and ink jet quality are excellent and even better.

As a method for drying the wet coating layer on the base paper, it can be appropriately selected from conventionally known drying methods such as hot air drying, steam drying, gas heater drying, electric heater drying, infrared heater drying and the like. . Further, the coating layer may be smoothed by a calendar process. Examples of the calendar processing apparatus include a gloss calendar, a super calendar, a soft calendar, and the like, and a thermal calendar that performs a smoothing process while applying heat can also be used.

  The coated paper for ink-jet printing of the present invention is compatible with a higher-speed ink-jet printer than before, and both fixed information and variable information, which are images such as photographs and designs with a large amount of ink, can be processed at once with an ink-jet printer. It becomes possible to print. Of course, the fixed information can be offset printed, and the variable information can be printed separately by an inkjet printer. Further, it can be adapted to inkjet commercial printing such as boxes and envelopes in the packaging field and the logistics field. Furthermore, it can be used for direct postcards (4 or 6 sides, etc.) with an adhesive layer on the surface after printing, various adhesive layers on the back side, pseudo adhesive layers, A known process such as forming a laminated laminate with another sheet can be appropriately performed.

Hereinafter, the present invention will be described with specific examples, but the present invention is not limited by these. In addition, what is with% and a part in a manufacture example, an Example, and a comparative example shows all the mass% and a mass part.
Examples 7, 10 and 11 are reference examples.

Example 1
"Pigment"
Commercially available acicular light calcium carbonate (trade name: TP123CS, manufactured by Okutama Kogyo Co., Ltd., average particle size = 0.45 μm), calcined kaolin (product name: Alphatex, manufactured by Imerizu Minerals Japan, average particle size = 0.48 μm), Kaolin (trade name: Amazon Plus, manufactured by CADEM, average particle size = 0.26 μm),
Amorphous silica (trade name: Fine Seal X-45, manufactured by Tokuyama, average particle size = 4.5 μm) was obtained.

"Particle size measurement" of "Pigment"
The particle size distribution was measured using an X-ray transmission type sedimentation particle size distribution apparatus (SediGraph 5100 manufactured by Micromeritex Corporation). The particle diameter corresponding to 10%, 50%, and 90% of the cumulative volume was defined as D10, D50, and D90, and the particle diameter of 50 volume% (D50) was defined as the average particle diameter.

"Creating a base paper"
After adding talc as a filler to a pulp slurry consisting of 90% LBKP (CSF 450 ml) and 10% NBKP (CSF 400 ml) so that the support ash content becomes 7%, 0.95% aluminum sulfate based on the pulp solid content, Cationic starch 0.22%, alkyl ketene dimer sizing agent (trade name: Size Pine K-287, manufactured by Arakawa Chemical Industries) 0.1%, polyacrylamide (trade name: Realizer R-300, manufactured by Somaru) 0.05 % Were sequentially added to prepare a paper stock. The resulting stock is made with an on-top twin-wire paper machine, and then coated with 2.0 g / m ² (solid content) of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch) on both sides with a gate roll size press. · and dried to give the basis weight 81 g / m ² base paper subjected to smoothing treatment by a machine calender.

"Preparation of coating solution"
40 parts of acicular light calcium carbonate TP-123CS shown in the “pigment” (in terms of solid content), 60 parts of calcined kaolin alphatex (in terms of solid content), oxidized starch (trade name: Ace A, Oji Constarch) 2 parts (solid content) and 20 parts (solid content) of styrene-butadiene copolymer latex (trade name: PB2407, Nippon A & L, Tg point = 40 ° C., particle size = 190 nm), amine fixing agent 5 parts of epichlorohydrin polymer (DK6810 made by Starlight PMC) was added to prepare a coating solution having a solid concentration of 40%. To this was added carboxymethyl cellulose sodium (SG Cellogen WS-C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 1% solution (temperature 25 ° C., B-type viscosity = 200 mPa · s)) as a water retention agent, and the B-type viscosity of the paint was 2000 mPa・ Adjusted to s.

“Preparation of coated paper for inkjet printing”
Using the gate roll coater on the said base paper, the said coating liquid was coated and dried on both surfaces so that the dry mass of one side might be 4 g / m < ² >. Thereafter, using a super calender, smoothing treatment was performed under the conditions of a linear pressure of 60 kg / cm and a 2-nip to obtain a coated paper for inkjet printing having a basis weight of 89 g / m ² .

Example 2
As a pigment used for the coating layer of Example 1, 40 parts of acicular light calcium carbonate (TP-123CS) (in terms of solid content) is 70 parts, and 60 parts of calcined kaolin (alphatex) (in terms of solid content) is 30 parts. A coated paper for ink jet printing was obtained in the same manner as in Example 1 except that the change was made.

Example 3
As a pigment used for the coating layer of Example 1, 40 parts of acicular light calcium carbonate (TP-123CS) (in terms of solid content) is 80 parts, and 60 parts of calcined kaolin (alphatex) (in terms of solid content) is 20 parts. A coated paper for ink jet printing was obtained in the same manner as in Example 1 except that the change was made.

Example 4
Except for changing 30 parts (calculated in terms of solid content) of calcined kaolin (alphatex) of the pigment used in the coating layer of Example 2 to 30 parts of amorphous silica (Fine Seal X-45), the same as in Example 2. A coated paper for inkjet printing was obtained.

Example 5
Sodium carboxymethylcellulose (trade name: SG Serogen PR, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 1% solution (temperature B at 25 ° C., B-type viscosity = 50 mPa · s) is added as a water retention agent used in the coating layer of Example 2 Then, a coated paper for inkjet printing was obtained in the same manner as in Example 2 except that the B-type viscosity of the paint was adjusted to 2000 mPa · s.

Example 6
As a water retention agent used in the coating layer of Example 2, sodium carboxymethylcellulose (trade name: AG gum manufactured by Daiichi Kogyo Seiyaku Co., Ltd., manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1% solution (temperature: 25 ° C.) B-type viscosity = 400 mPa · s ) Was added to adjust the B-type viscosity of the paint to 2000 mPa · s, and a coated paper for inkjet printing was obtained in the same manner as in Example 2.

Example 7
20 parts (solid content) of styrene-butadiene copolymer latex (trade name: PB2407, manufactured by Nippon A & L, Tg point = 40 ° C., particle size = 190 nm) used for the coating layer of Example 2 Coated latex (trade name: OJ3000N, manufactured by JSR, Tg point = −37 ° C., particle size = 90 nm) is changed to 20 parts (solid content), and coated paper for inkjet printing is obtained in the same manner as in Example 2. It was.

Example 8
The basis weight was 83 g / m in the same manner as in Example 2 except that the coating amount of Example 2 was changed from 4 g / m ² on one side to 1 g / m ² on one side and coated and dried. ² coated paper for inkjet printing was obtained.

Example 9
Coating from 4g / m ² coating amount on one surface of the dry weight of the Example 2 in the 7 g / m ² on one surface of the dry weight, except that drying, in the same manner as in Example 2, a basis weight of 96 g / m ² coated paper for inkjet printing was obtained.

Example 10
In the preparation of the coating solution of Example 7, a water retention agent carboxymethylcellulose sodium (trade name: SG Serogen WS-C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1% solution (temperature 25 ° C., B-type viscosity = 200 mPa · s) To adjust the B-type viscosity of the paint to 2000 mPa · s, except that the B-type viscosity of the paint is adjusted to 450 mPa · s. Obtained.

Example 11
In the preparation of the coating solution of Example 7, a water retention agent carboxymethylcellulose sodium (trade name: SG Serogen WS-C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1% solution (temperature 25 ° C., B-type viscosity = 200 mPa · s) To adjust the B-type viscosity of the paint to 2000 mPa · s, except that the B-type viscosity of the paint is adjusted to 4500 mPa · s. Obtained.

Example 12
In the production of the ink-jet printing coated paper of Example 2, the above-mentioned coating solution was coated on both sides and dried using a gate roll coater so that the dry mass on one side was 4 g / m ^2. Using a coater, a coated paper for inkjet printing was obtained in the same manner as in Example 2 except that the coating liquid was coated on both sides so that the dry mass on one side was 4 g / m ² .

Example 13
In the production of the ink-jet printing coated paper of Example 2, using a gate roll coater, the coating liquid was coated on both sides so that the dry mass on one side was 4 g / m ² and dried. Using a coater, a coated paper for inkjet printing was obtained in the same manner as in Example 2 except that the coating liquid was coated on both sides so that the dry mass on one side was 4 g / m ² .

Example 13
In the production of the coated paper for ink jet printing of Example 2, a gate roll coater was used to apply the coating liquid on both sides so that the dry mass on one side was 4 g / m ² Using a coater, a coated paper for inkjet printing was obtained in the same manner as in Example 2 except that the coating liquid was coated on both sides so that the dry mass on one side was 4 g / m ² .

Comparative Example 1
As a pigment used for the coating layer of Example 1, 20 parts of acicular light calcium carbonate (TP-123CS) (in terms of solid content) is 20 parts, and 60 parts of calcined kaolin (alphatex) (in terms of solid content) is 80 parts. A coated paper for ink jet printing was obtained in the same manner as in Example 1 except that the change was made.

Comparative Example 2
As a pigment used for the coating layer of Example 1, 40 parts of acicular light calcium carbonate (TP-123CS) (in terms of solid content) is 100 parts, and 60 parts of calcined kaolin (alphatex) (in terms of solid content) is 0 part ( A coated paper for ink jet printing was obtained in the same manner as in Example 1 except that the content was changed to “No Addition”.

Comparative Example 3
As a pigment used for the coating layer of Example 1, 0 part (no addition) of acicular light calcium carbonate (TP-123CS) 40 parts (solid content conversion), 60 parts of calcined kaolin (alphatex) (solid content conversion) A coated paper for ink jet printing was obtained in the same manner as in Example 1 except that was changed to 100 parts.

Comparative Example 4
As pigments used in the coating layer of Example 1, 70 parts of acicular light calcium carbonate (TP-123CS) (in terms of solid content) is 70 parts, and 60 parts of calcined kaolin (alphatex) (in terms of solid content) is kaolin (product). Name: Amazon Plus, manufactured by CADEM, average particle size = 0.26 μm) A coated paper for inkjet printing was obtained in the same manner as in Example 1 except that the amount was changed to 30 parts.

Comparative Example 5
The basis weight was 82 g in the same manner as in Example 2 except that the coating amount of Example 2 was changed from 4 g / m ² on one side to 0.5 g / m ² on one side and applied and dried. A coated paper for inkjet printing of / m ² was obtained.

Comparative Example 6
The basis weight is 99 g in the same manner as in Example 2 except that the coating amount of Comparative Example 5 is 0.5 g / m ^{2 in} terms of dry weight on one side to 9 g / m ² in terms of dry weight on one side and is coated and dried. A coated paper for inkjet printing of / m ² was obtained.

Comparative Example 7
In the preparation of the coating solution of Example 7, a water retention agent carboxymethylcellulose sodium (trade name: SG Serogen WS-C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1% solution (temperature 25 ° C., B-type viscosity = 200 mPa · s) Was added to adjust the B-type viscosity of the paint to 2000 mPa · s, except that sodium carboxymethylcellulose was not added, and a coated paper for ink jet printing was obtained in the same manner as in Example 7. The B-type viscosity of the coating liquid at this time was 200 mPa · s.

Comparative Example 8
In the adjustment of the coating liquid of Comparative Example 7, a comparative example is obtained except that oxidized starch (trade name: Ace A, manufactured by Oji Constarch Co., Ltd.) is added as a water retention agent and the B-type viscosity of the paint is adjusted to 2000 mPa · s. In the same manner as in Example 7, a coated paper for inkjet printing was obtained. The final amount of oxidized starch added at this time was 15 parts.

  The following evaluation was performed on the coated paper for inkjet printing obtained in Examples and Comparative Examples, and the results are shown in Table 1.

"Inkjet printing aptitude"
(Evaluation of ink absorbency)
The obtained coated paper for inkjet printing is subjected to black solid printing and character printing with a color label printer (LX-P5500 pigment ink model, manufactured by Canon) equipped with a line head. The printed portion was visually evaluated.
A: There is no unevenness in the solid print portion. No blurring on letters and blank pages. Good.
○: Unevenness in the solid print part and slight blurring of the ink from the character part to the blank paper part, but at a level where there is no problem in use.
Δ: Level at which unevenness is observed in the solid print portion and ink blur is observed from the character portion to the blank paper portion.
(A level that can be used by changing the printer settings)
×: Level where the solid print portion is uneven, the characters themselves are crushed, and the shape of the characters cannot be identified.
(Unable to use even if the printer settings are changed)

"Blank gloss"
Based on JIS P8142, the glossiness of the white paper surface at 75 degrees was measured.

"Coating suitability"
(Roll dirt)
Coating was performed with a gate roll coater, and roll contamination due to the paint was visually confirmed.
A: No dirt on the roll. Good.
○: Slight dirt on the roll is observed, but there is no problem in use.
Δ: Slight dirt on the roll is observed, but there is little influence on the coated surface and no problem in use.
X: Dirt on the roll is seen. The level that greatly affects the coated surface and causes problems in use.

"Visual evaluation of coated surface"
The state of the coated surface of the ink-jet printing coated paper produced this time was visually observed, and the following classification was performed according to the surface state.
A: No coating unevenness. Good.
○: Coating unevenness is slightly observed, but there is no problem in use.
Δ: Level at which coating unevenness is observed.
(A level that can be used by changing various settings of the inkjet printer used)
X: Coating unevenness is seen, and in some places, the surface of the base paper is visible. NG level.
(Unable to use even if the printer settings are changed.

  As is clear from Table 1, the coated paper for inkjet printing of the present invention is excellent in inkjet coating suitability (ink absorbability) and white paper gloss, has good coating suitability and a good coated surface. It was.

Claims (5)

In coated paper for inkjet printing, wherein a coating layer containing a pigment, a binder, and an inkjet ink fixing agent is applied to at least one surface of a base paper at a rate of 1 g / m ² or more and 8 g / m ² or less per side, As a pigment in the coating layer, 40 parts by weight or more and 80 parts by weight or less of acicular light calcium carbonate with respect to 100 parts by weight of the pigment, and 20 parts by weight of an oil-absorbing pigment having an oil absorption of 80 ml / 100 g or more other than the acicular light calcium carbonate. The styrene-butadiene copolymer latex containing at least 60 parts by mass and containing sodium carboxymethylcellulose, and having a Tg point of 10 ° C. or more and 60 ° C. or less as a part of the binder of the coating layer, Coated paper for inkjet printing. The coated paper for inkjet printing according to claim 1, wherein the 1% solution of sodium carboxymethylcellulose (temperature 25 ° C) has a B-type viscosity of 50 mPa · s to 500 mPa · s. Oil absorbing pigment containing pigment, binder, inkjet fixing agent, sodium carboxymethyl cellulose on at least one side of the base paper, and the pigment has an oil absorption of 80 ml / 100 g or more other than the acicular light calcium carbonate and the acicular light calcium carbonate der is, styrene as part Tg point of 10 ° C. or higher 60 ° C. or less of the binder - jet printing coating, which comprises coating a coating liquid in a size press you containing butadiene copolymer latex A method of manufacturing paper. The said size press is a gate roll coater or a shim sizer coater, The manufacturing method of the coated paper for inkjet printing of Claim 3 characterized by the above-mentioned. 5. The method for producing a coated paper for ink jet printing according to claim 3, wherein the coating solution has a B-type viscosity (temperature: 25 ° C.) of 500 mPa · s or more and 4000 mPa · s or less.