JPH10195796A - Material for papermaking and paper for recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain paper for recording, having high absorbing property of ink and high printing concentration, hardly causing oozing of dot and capable of providing dots having a form similar to circle. SOLUTION: This paper for recording comprises a material for papermaking which is a calcium phosphate-based compound (having <=16.7atom ratio Ca/P) having petal-like porous structure using inorganic particles of calcium carbonate as a nucleating agent. The material for papermaking has 0.1-20μm average particle diameter, 1-5 disperse coefficient, 0-2 sharpness, 0.01-1μm average pore of particles, 95-99% stationary porosity, 70-95% porosity under pressure and 50-500m<2> /g BET specific surface area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium having a specific particle shape and a specific particle size. Coating pigment for papermaking which can give an image having the same circular shape and sharp edges and which can obtain a smooth paper surface by using particles having a sharp particle size distribution, and papermaking with good yield The present invention relates to an internal filler and a recording paper containing the same.

[0002]

2. Description of the Related Art In recent years, inkjet recording papers, thermal recording papers, pressure-sensitive recording papers, PPC papers, NIP papers and the like have been developed.
With respect to the A-apparatus paper, colorization has progressed, and coated paper or filled paper having excellent ink absorbency, color developing properties, smoothness and the like has been demanded in order to obtain good recording. For example, in the case of inkjet recording paper, the following characteristics are required. 1) Quick ink absorption. 2) When the ink dots overlap, the ink does not flow or bleed. 3) The diameter of the ink dot does not become larger than necessary. 4) The shape of the ink dot is close to a perfect circle, and its periphery is smooth. 5) The density of the ink dots is high.

[0003] In order to satisfy these demands, in the case of an internally-filled paper, clay, talc, calcium carbonate, sodium silicate, etc. have conventionally been included, and oxidized starch, PVA, Cationic resins, rosin-based sizing agents and the like are used. On the other hand, in the case of coated paper,
Pigments mainly used include calcium carbonate, finely divided silica, calcium silicate, barium sulfate, titanium oxide and the like. As a binder, PVA,
A water-soluble binder such as SBR latex, polyacrylamide, and polyvinylpyrrolidone or an aqueous binder is used.

[0004]

For example, the problem with the ink jet recording paper is that when silica having a large specific surface area is incorporated, the ink absorption becomes large, but on the other hand, there is a problem of fluffing and bleeding. However, there are drawbacks in that it is difficult for an ink droplet to give a perfect circular image and that the print density is reduced. In addition, when coated, it can improve color development and ink absorption, but high-resolution images cannot be obtained on coating-type recording paper without a high degree of uniformity of the coating layer. Was. Further, when calcium carbonate is filled or coated, there is a drawback that the print density often decreases and the print becomes non-uniform due to its optical characteristics.

When a silica-based white pigment, so-called white carbon, is used as the inorganic pigment, the coating layer generally has a flat surface with improved ink absorption.
No. 7-107879 discloses an inorganic pigment (mainly composed of synthetic silica).
And coating and drying a coating liquid composed of an aqueous polymer adhesive and ² to 9 g / m ² on one side with a single coating, and applying the coating and drying step twice or more on the same surface to form a coating layer. However, all of them had problems of writing property (especially pencil writing property) and cracking of the coating layer. The problem of writability can be improved by selecting and using other compounding pigments, but it is necessary to increase the compounding ratio of white carbon and increase the coating amount as long as the aim is to improve ink absorption and resolution. Therefore, the problem of cracking cannot be improved.

[0006] Japanese Patent Application Laid-Open No. 58-16 discloses a method for preventing cracks.
No. 884 describes a method of sequentially laminating a first coating containing zeolite and a second coating containing silicon dioxide on a substrate, but this method requires complicated steps and high cost. There were drawbacks such as not being obtainable.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that particles having a specific particle composition, a specific particle diameter, and a specific specific surface area are intended papermaking. It has a function as a papermaking material such as a coating pigment for papermaking and a filler for papermaking, and it has been found that the recording paper containing the papermaking material has the intended function. Completed the invention.

A first aspect of the present invention is a calcium phosphate compound having a petal-like porous structure containing inorganic particles as a core material, wherein the atomic ratio of Ca / P is 16.7 or less, and the following formula (a) ) To (g). (A) 0.1 ≦ dx1 ≦ 20 (μm) (b) 1 ≦ α ≦ 5 where α = d50 / dx1 (c) 0 ≦ β ≦ 2 where β = (d90−d10) /
d50 (d) 0.01 ≦ dx2 ≦ 1 (μm) (e) 95 ≦ ω1 ≦ 99 (%) (f) 70 ≦ ω2 ≦ 95 (%) (g) 50 ≦ Sw1 ≦ 500 (m ² / g) Here, dx1: average particle diameter (μm) of particles measured by an electron micrograph α: dispersion coefficient d50: 50% average particle diameter (μm) of particles measured by a microtrack FRA laser type particle size distribution analyzer β: sharpness d90: 90% total particle size (μm) of the particles passing through the sieve measured by a Microtrac FRA laser type particle size distribution meter (μm) d10: 10% total particle size (μm) of the particles passing through the sieve measured by a Microtrac FRA laser type particle size distribution meter dx2: Average pore diameter (μm) of particles determined by pore distribution measured by mercury intrusion method ω1: JIS K5101-91 20.1 Static of pigment test method Apparent by law specific volume (ml / g) was measured, static 置空 porosity calculated by the formula (h) below (%) ω2: 0.5 g sample was filled in a cylinder having a cross-sectional area of 2 cm ² , 30
Pressurized at a pressure of kg / cm ² for 30 seconds, the thickness thereof was measured with a vernier caliper, and the pressurized porosity (%) of 30 kg / cm ² calculated from the following formula (i) Sw1: BET specific surface area by nitrogen adsorption method (m ² / g)

[0009]

An important feature of the papermaking material of the present invention is its particle shape and size content. Further, it is not a simple calcium phosphate-based compound but a porous calcium phosphate-based compound having a petal-like structure.
Since it has a petal-like structure, it has a high specific surface and has excellent ink absorbency. Regarding the particle size content, it has excellent dispersibility and sharp particle size distribution, so that a papermaking material having a uniform and smooth surface and excellent yield can be provided.

A second aspect of the present invention is directed to a recording sheet containing the above-mentioned papermaking material. By filling or coating the papermaking material, the ink absorbency is high,
It is possible to provide a recording paper having a high print density, little dot bleeding, and dots having a shape close to a circle.
Hereinafter, the present invention will be described in detail.

The petal-like porous calcium phosphate compound constituting the papermaking material of the present invention is not particularly limited, but amorphous calcium phosphate [ACP, chemical formula Ca]
₃ (PO ₄ ) ₂ .nH ₂ O], fluorapatite [abbreviation FAP, chemical formula Ca ₁₀ (PO ₄ ) ₆ F ₂ ], chlorapatite [abbreviation CAP, chemical formula Ca ₁₀ (PO ₄ ) ₆ C]
l ₂ ], hydroxyapatite [abbreviation HAP, chemical formula C]
_{a 10 (PO 4) 6 (} OH) 2 ], octacalcium phosphate [Symbol OCP, chemical formula _{Ca 8 H 2 (PO 4)} 6 · 5H 2
O], tricalcium phosphate [abbreviation TCP, chemical formula Ca ₃
(PO ₄ ) ₂ ], calcium hydrogen phosphate (abbreviation DCP,
Chemical formula CaHPO ₄ ), calcium hydrogen phosphate dihydrate (abbreviation DCPD, chemical formula CaHPO ₄ .2H ₂ O), etc., may be used alone or in combination of two or more. Among them, hydroxyapatite is preferred from the viewpoint of high composition stability. Octacalcium phosphate, tricalcium phosphate and calcium hydrogen phosphate are preferred, and hydroxyapatite is particularly preferred. As for the content of hydroxyapatite having the highest stability, the content is preferably 10% by weight or more, more preferably 50% by weight, and most preferably 90% by weight, based on the total calcium phosphate compound.

C in the weight of the papermaking material of the present invention
The atomic ratio of a / P is 16.7 or less, and preferably 5.56 or less, more preferably 3.33 from the viewpoint of further improving the affinity between the papermaking material particles and the synthetic resin used in the coating liquid.
The following is more preferable, and 1.85 or less is still more preferable.
When the atomic ratio of Ca / P exceeds 16.7, the ink absorption decreases. Further, the lower limit of the atomic ratio is preferably about 1.60 from the viewpoint of high stability of the composition. In addition, there is no problem even if all the inorganic particles used as the core material are changed to calcium phosphate compounds.

The average particle size d of the papermaking material according to the present invention
x1 is 0.1 ≦ dx1 ≦ 20 (μm). dx1
Is less than 0.1 μm, agglomeration of particles causes a decrease in print density, and also causes a decrease in yield.
If it exceeds 0 μm, it causes the spread of dots. Preferably, 0.2 ≦ dx1 ≦ 10 (μm), more preferably, 0.5 ≦ dx1 ≦ 8 (μm).

The dispersion coefficient α and the sharpness β of the papermaking material of the present invention are 1 ≦ α ≦ 5 and 0 ≦ β ≦ 2, respectively. When α exceeds 5, the proportion of coarse aggregates increases. When α is less than 1, the proportion of fine particles increases, the cohesiveness of the particles increases, and printing unevenness occurs. On the other hand, when β exceeds 2, the particle diameter is non-uniform and, at the same time, the ink absorbency varies. Preferably, 1 ≦ α ≦ 2 and 0 ≦ β ≦ 1.

The average pore diameter dx2 of the papermaking material of the present invention
Satisfies 0.01 ≦ dx2 ≦ 1. When dx2 is less than 0.01, the amount of ink absorption decreases, and when dx2 exceeds 1, the color developability deteriorates.

The stationary porosity ω1 of the papermaking material of the present invention is:
95 ≦ ω1 ≦ 99. When ω1 is less than 95, the amount of ink absorption decreases, and when ω1 exceeds 99, the color developability deteriorates. In addition, handling during storage and transportation becomes difficult.

The pressurized porosity ω2 of the papermaking material of the present invention is:
70 ≦ ω2 ≦ 95. When ω2 is less than 70, the amount of ink absorption decreases, and when ω2 exceeds 95, the color developability deteriorates. In addition, handling during storage and transportation becomes difficult.

BET specific surface area SW of papermaking material of the present invention
1 satisfies 50 ≦ SW1 ≦ 500. If SW1 is less than 50, the amount of ink absorption decreases, and if it exceeds 500, the color developability deteriorates. Preferably 100 ≦ SW1 ≦ 3
50.

The inorganic particles constituting the core material of the papermaking material of the present invention include talc, kaolin, mica, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, calcium silicate, titanium dioxide, barium sulfate, calcium phosphate And white pigments such as hydroxyapatite, and these can be used alone or in combination of two or more. Among them, calcium carbonate is most preferred.

The method for preparing the papermaking material of the present invention is not particularly limited. For example, a water-soluble phosphoric acid or a water-soluble phosphate is gradually reacted in an aqueous system in which calcium carbonate as a core material is dispersed. The petal-like porous calcium phosphate compound is precipitated on the surface of the core material to prepare the papermaking material of the present invention. Specifically, an aqueous suspension dispersion of calcium carbonate as a specific core material and a diluted aqueous solution of phosphoric acid and / or an aqueous suspension dispersion of calcium hydrogen phosphate and / or calcium hydrogen phosphate dihydrate For example, a method of preparing a water suspension dispersion by mixing at a specific ratio under specific mixing conditions, aging under specific aging conditions, and then drying.

The base paper used in the present invention is not particularly limited, but preferably has a cold water extraction pH of 7.5 to 10.0. When used as a filler, the addition amount of the calcium phosphate compound of the present invention is not particularly limited,
Usually, the content is 2 to 35% by weight in the paper.

If necessary, one or more of calcium carbonate, silica, clay, talc, titanium, kaolin, plastic pigment and the like may be used in combination with the paper-making material of the present invention. Amorphous calcium phosphate having no structure, fluorapatite, chlorapatite, hydroxyapatite, octacalcium phosphate, tricalcium phosphate, calcium hydrogen phosphate, calcium hydrogen phosphate dihydrate, etc. One or two or more different calcium phosphate compounds having no petal-like structure may be mixed according to the purpose. Further, a neutral sizing agent such as an alkyl ketene dimer can be used in a range usually used.

When used as a pigment in a coating solution, the papermaking material of the present invention is generally used in a paper coating such as talc, kaolin, satin white, titanium dioxide, pyrophyllite clay, calcium sulfite, calcium sulfate. , Aluminum hydroxide, zinc oxide, zeolite, barium sulfate, amorphous silica, plastic pigment, calcium carbonate, magnesium carbonate, calcium hydroxide, etc., depending on the purpose. Papermaking materials of the present invention such as amorphous calcium phosphate, fluorapatite, chlorapatite, hydroxyapatite, octacalcium phosphate, tricalcium phosphate, calcium hydrogen phosphate, calcium hydrogen phosphate dihydrate having no linear structure Phosphate calcium without petal-like structure No problem be blended singly or in combination depending on the purpose of beam-based compound. Other components of the coating solution include starch, gelatin, casein, gum arabic, sodium alginate, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble polymers such as sodium polyacrylate, polyvinyl butyral, and polyvinyl chloride. Organic solvent soluble resin, and various additives such as dispersant, fluorescent dye, pH adjuster, defoamer, lubricant, preservative, surfactant, water resistant agent, dispersant, surface sizing agent, flow modifier, etc. One or more of these can be used as needed.

[0024] As the coating amount, the not particularly limited, but is a coating liquid having a solid content of 1-50 wt% according to a conventional method by dry coating amount, usually 1 to 50 g / m ^2, preferably 2 to 30 g / m ² A small amount is applied on the substrate. The coating method can be appropriately selected from known coating methods such as gravure coating, air knife coating, size press coating, gate roll coating, and bar coating.

In the following, among the calcium phosphate compounds having a petal-like porous structure, petal-like porous hydroxyapatite, which can be particularly preferably used, is mainly used.
The method for preparing the papermaking material of the present invention when calcium carbonate is used as a core material will be described more specifically. Particle size distribution analyzer (SA-CP manufactured by Shimadzu Corporation)
3) An aqueous suspension dispersion of calcium carbonate having an average particle diameter of 0.1 to 5 μm and a diluted aqueous solution of phosphoric acid and / or a particle size distribution analyzer (SA- manufactured by Shimadzu Corporation)
The average particle diameter (μm) measured by CP3) is 2 to 10.
μm aqueous dispersion of calcium dihydrogen phosphate and / or a particle size distribution analyzer (SA-C manufactured by Shimadzu Corporation)
Average particle diameter (μm) measured by P3) is 2 to 10 μm
m, and an aqueous suspension dispersion of calcium hydrogen phosphate dihydrate in water at a ratio of Ca / P atomic ratio of 1.60 to 16.7 in water under the following mixing conditions, followed by the following aging conditions: After aging at 700 ℃ without dehydration or without dehydration
It is dried under the following drying atmosphere and crushed.

Mixing Conditions Solid Concentration of Water Suspension Dispersion of Calcium Carbonate 1-15% Concentration of Dilute Aqueous Solution of Phosphoric Acid 1-50% Solid Concentration of Water Suspension Dispersion of Calcium Dihydrogen Phosphate 2-15% Hydrogen Phosphate Solid concentration of aqueous dispersion of calcium dihydrate 2-15% Peripheral speed of mixing and stirring blades 0.5 m-50 / sec Mixing time 0.1-150 hours Mixing aqueous suspension temperature 0-80 ° C Aqueous suspension pH of mixed system 5 to 9 Aging condition Ca concentration of aging system 0.4 to 5% Peripheral speed of aging stirring blade 0.5 to 50 m / sec Aging time 0.1 to 100 hours Aging water suspension Liquid temperature 20-80 ° C Aged water suspension pH 6-9

The papermaking material of the present invention may further comprise a coupling agent such as a silane coupling agent or a titanate coupling agent, an organic acid such as a fatty acid, a resin acid, or an acrylic resin, for further improving the dispersibility and stability of the particles. Α, β monoethylenically unsaturated carboxylic acids such as acids and esters thereof, organic acids such as oxalic acid and citric acid, inorganic acids such as tartaric acid and hydrofluoric acid, polymers and copolymers thereof, salts thereof, Or surface treatment agents such as esters thereof, surfactants and sodium hexametaphosphate, pyrophosphate, sodium pyrophosphate, tripolyphosphate, sodium tripolyphosphate, trimetaphosphate, condensed phosphates such as high polyphosphoric acid and the like,
Addition or surface treatment may be performed according to a conventional method.

[0028]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which do not limit the present invention in any way. In the following description, “%”,
“Parts” represent “% by weight” and “parts by weight” unless otherwise specified.

(1) Preparation method of aqueous dispersions A and B of calcium carbonate used in Examples and Comparative Examples Preparation of aqueous dispersion A of calcium carbonate: specific gravity 1.0
At 55, 7000 liters of lime milk (aqueous suspension of calcium hydroxide) at a temperature of 8 ° C. was passed through a furnace gas having a carbon dioxide concentration of 27% by weight at a flow rate of 24 m ³ to carry out a carbonation reaction to pH 9, followed by 40 By carrying out stirring and aging at 時間 50 ° C. for 5 hours, alkalis between the particles are eluted and dispersed to pH 10.8, and the average particle diameter measured from an electron micrograph is 0.05
μm particle size distribution analyzer (SA-C manufactured by Shimadzu Corporation)
An aqueous suspension dispersion A of calcium carbonate having an average particle diameter measured by P3) of 0.48 μm was prepared.

Preparation of water suspension dispersion B of calcium carbonate: Water was added to heavy calcium carbonate "Super SS" (1.2 m ² / g) manufactured by Maruo Calcium Co., Ltd.
The dispersion was stirred and dispersed with a K homomixer (5000 rpm, 15 minutes), and the average particle diameter was 3 μm as measured from an electron micrograph at a solid content of 25%. The average was measured with a particle size distribution analyzer (SA-CP3 manufactured by Shimadzu Corporation). 2. Particle size is 3.
An aqueous suspension dispersion B of calcium carbonate of 4 μm was prepared.

(2) Method for Preparing Kaolin Aqueous Suspension Dispersion C Used in the Examples Water was added to ASP-072 of imported kaolin, mixed, and TK was added.
A kaolin aqueous suspension dispersion C having a solid content of 25% was stirred and dispersed by a homomixer (5000 rpm, 15 minutes).
Was prepared.

Examples 1 to 6 and Comparative Examples 1 to 3 According to the raw materials and mixing conditions described in Tables 1 and 2, a turbine blade 1 having a diameter of 0.6 m was placed in a stainless steel tank with baffles.
Like the stirring machine with a 0.4 m ³ stainless steel tank dilution prepared and the temperature control water suspension dispersion A or B of calcium carbonate were charged, dilute aqueous solution of phosphoric acid under stirring, calcium hydrogen phosphate dihydrate Or an aqueous suspension dispersion of calcium dihydrogen phosphate is dropped and mixed, and the mixture is aged while stirring under the aging conditions described in Table 1. After completion of the ripening, the stirring is stopped, the supernatant is removed by a decantation method, the solid content is concentrated to 8%, and spray drying is performed to obtain a calcium phosphate compound having a petal-like porous structure using calcium carbonate as a core material. Papermaking Materials D1 to D6 of the Present Invention (Examples)
And E1 to E3 (Comparative Examples) were prepared. The total weight of the raw material and water was 400 kg. The spray-drying conditions were as follows: spraying particle size about 0.1 mm, hot air temperature at the entrance 250
℃, drying time about 10 seconds, 200 ℃ of the dried product immediately after drying,
The loss on heating in 2 hours was 5 to 8%. Examples 1 to 6
The physical properties of the papermaking materials D1 to D6 of the present invention prepared in Table 3 and E1 to E prepared in Comparative Examples 1 to 3
Table 4 shows the physical properties of Sample No. 3. Commercially available light calcium carbonate (trade name: light calcium carbonate, manufactured by Maruo Calcium Co., Ltd.), commercially available heavy calcium carbonate (trade name: Super SS, manufactured by Maruo Calcium Co., Ltd.), commercially available synthetic silica (trade name: Aerosil # 130, manufactured by Nippon Aerosil Co., Ltd.), commercially available calcium silicate (trade name: Florite R, manufactured by Tokuyama Soda Co., Ltd.), commercially available hydroxyapatite (trade name: tricalcium phosphate, manufactured by Yoneyama Chemical Industry Co., Ltd.) , F1 to F5 are also shown in Table 4. As can be seen from Table 3, it can be confirmed that the papermaking material of the present invention has a high specific surface area, a high porosity and excellent dispersibility by having a petal-like porous structure. Electron micrographs showing the particle structure of D1 are shown in FIGS. 1 (1000 ×) and 2 (10000 ×).
Shown in 1 and 2, it can be confirmed that the papermaking material of the present invention has a petal-like structure. In addition, powder X-ray diffraction diagrams of the papermaking materials D1, D2, and D3 of the present invention are shown in FIGS. 3, 4, and 5. 1 and 2, D1 and D2 were not recognized except for the calcium phosphate compound and calcium carbonate (calcite). It can be confirmed that the main component of the calcium phosphate compound is hydroxyapatite (HAP) and contains a trace amount of octacalcium phosphate (OCP). As for D3, calcium carbonate was not recognized from FIG. 3, and no compounds other than the calcium phosphate compound were recognized. It can be confirmed that the main component of the calcium phosphate compound is hydroxyapatite (HAP) and contains a trace amount of octacalcium phosphate (OCP).

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3] * 1: Papermaking materials corresponding to the examples

[0036]

[Table 4]

Example 7 In the same manner as in Example 1, a 0.6 m diameter turbine blade having a diameter of 0.6 m was placed in an obstructed stainless steel tank, and a 0.4 m ³ stainless tank with a stirrer was adjusted to a dilution concentration of 8% and the temperature was adjusted to 35 ° C. The aqueous kaolin suspension C thus prepared was charged, and a 10% aqueous solution of sodium hydrogen phosphate and a 5% aqueous solution of calcium chloride were mixed under stirring at a ratio such that the atomic molar ratio of Ca / P became 5.56. After the dropwise addition, the mixture was aged at 35 ° C. for 24 hours to precipitate a calcium phosphate compound on the surface of kaolin as a core material. After washing with water, stirring was stopped, and the supernatant was removed by a decantation method to obtain a solid concentration of 8%. By concentrating and spray-drying, a papermaking material F whose particle surfaces were coated with a calcium phosphate compound was prepared. X
As a result of the line diffraction, no substance other than kaolin (kaolinite) and hydroxyapatite was observed. The total weight of the raw material and water was 400 kg. The spray drying conditions are the same as in Example 1. Table 3 shows the physical properties of the papermaking material D7 prepared in Example 7.

Examples 8 to 14 and Comparative Examples 4 to 11 Papermaking materials D1 to D prepared in Examples 1 to 7 as samples.
7 and the particles E1 to E3 prepared in Comparative Examples 1 to 3, commercially available light calcium carbonate, commercially available heavy calcium carbonate, commercially available synthetic silica, commercially available calcium silicate, and commercially available hydroxyapatite F1 to F5 are described below. Based on the composition of the above, recording paper (filled paper) having a basis weight of 67.0 g / m ² was obtained. LBKP (csf400ml) 90 parts Sample 10 parts Alkenyl succinic anhydride 0.01 parts Cationized starch 0.5 parts

The inner sheets prepared in Examples 8 to 14 and Comparative Examples 4 to 11 were evaluated by the following method under recording conditions of a droplet diameter of 90 μm and a pixel size of 300 × 300. Table 5 shows the results of the evaluation of the recording characteristics. According to Table 5,
It was confirmed that the paper sheets prepared in Examples 8 to 14 had excellent yield and recording characteristics. For comparison with the papermaking material of the present invention, an electron micrograph showing the particle structure of commercially available hydroxyapatite (F5) is shown in FIG.
FIG. 7 (10000 times) and the powder X-ray diffraction diagram are shown in FIG. 6 and 7, it can be confirmed that commercially available hydroxyapatite is fine particles and aggregates of the particles, and does not have a petal-like porous structure. FIG.
According to the powder X-ray diffraction diagram of the above, commercially available hydroxyapatite is different from hydroxyapatite (HAP) as a main component,
It can be confirmed that it contains a trace amount of calcium hydrogen phosphate dihydrate (DCPD).

(Evaluation of Recording Characteristics) 1) Yield: Calculated according to JIS P8129. 2) Evaluation of ink absorptivity: A method was used in which a commercially available inkjet printer was used to measure the number of hit points (number of times of overwriting) until ink bleed (flow) at the hit points.
◎, △, Δ, × were ranked in four stages in order from those having good absorbency. 3) Dot shape: Observe the printed dots with a stereo microscope,
An almost circular one was rated as O, a circular one was slightly broken, and an indefinite one was x. 4) Bleeding degree: The diameter of a printed dot is measured by a stereoscopic microscope,
Indicated by how many times the ink droplets. 5) Color clarity: The clarity of the colors of the ink jet recorded images was compared visually, and the best one was marked with ◎, the worst one was marked with x, and the four levels of ◎, △, Δ and × were classified.

Examples 15 to 21, Comparative Examples 12 to 19 Papermaking materials D1 to D prepared in Examples 1 to 7 as samples.
No. 7 and particles E1 to E3 prepared in Comparative Examples 1 to 3, a commercially available light calcium carbonate, a commercially available heavy calcium carbonate, a commercially available synthetic silica, a commercially available calcium silicate, and a binder using commercially available hydroxyapatite F1 to F5. Was used to prepare an ink-absorbing layer coating composition based on the following composition. Sample 100 parts Polyvinyl alcohol 30 parts SBR latex 3 parts Water 500 parts

On the other hand, high quality paper having a basis weight of 80 g / m ² was used as a substrate, and the above-mentioned coating composition was coated on the substrate by a blade coater method at a dry coating amount of 20 g / m ^2. And dried by a conventional method to obtain recording paper (coated paper).
The coated papers prepared in Examples 15 to 21 and Comparative Examples 11 to 19 were prepared by applying a droplet diameter of 90 μm and a pixel size of 300.
The evaluation was performed by the following method under a recording condition of × 300. Table 6 shows the evaluation results of the recording characteristics. According to Table 6, Example 15 was obtained.
It was confirmed that the coated papers prepared in Nos. To 21 had excellent recording characteristics.

(Evaluation of Recording Characteristics) 1) Evaluation of ink absorptivity: A method was used in which a commercially available ink jet printer was used to measure the number of hit points (number of times of overwriting) until ink bleed (flow) at the hit points.
◎, △, Δ, × were ranked in four stages in order from those having good absorbency. 2) Dot shape: Observe the printed dots with a stereo microscope,
An almost circular one was rated as O, a circular one was slightly broken, and an indefinite one was x. 3) Bleeding degree: The diameter of a printed dot is measured with a stereoscopic microscope,
Indicated by how many times the ink droplets. 4) Color clarity: The clarity of the colors of the ink jet recorded images was compared visually, and the best one was marked with ◎, the worst one was marked with x, and ranked in four stages of ◎, △, Δ, and x.

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

As described above, since the papermaking material of the present invention has a specific particle composition, particle diameter, and specific surface area, the recording paper containing the material has excellent recording characteristics.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (× 1000) showing a particle structure of a particle D1 obtained in Example 1.

FIG. 2 is an electron micrograph (× 10000) showing the particle structure of particle D1 obtained in Example 1.

FIG. 3 is a powder X-ray diffraction diagram of a particle D1 obtained in Example 1.

FIG. 4 is an X-ray powder diffraction diagram of a particle D2 obtained in Example 2.

FIG. 5 is a powder X-ray diffraction diagram of a particle D3 obtained in Example 3.

FIG. 6 is an electron micrograph (× 1000) showing the particle structure of commercially available hydroxyapatite.

FIG. 7 is an electron micrograph (× 10000) showing the particle structure of commercially available hydroxyapatite.

FIG. 8 is a powder X-ray diffraction diagram of a commercially available hydroxyapatite.

Claims (13)

[Claims] 1. A calcium phosphate compound having a petal-like porous structure containing inorganic particles as a core material, comprising Ca / P
Is 16.7 or less, and the following formulas (a) to (a)
A papermaking material characterized by satisfying (g). (A) 0.1 ≦ dx1 ≦ 20 (μm) (b) 1 ≦ α ≦ 5 where α = d50 / dx1 (c) 0 ≦ β ≦ 2 where β = (d90−d10) /
d50 (d) 0.01 ≦ dx2 ≦ 1 (μm) (e) 95 ≦ ω1 ≦ 99 (%) (f) 70 ≦ ω2 ≦ 95 (%) (g) 50 ≦ Sw1 ≦ 500 (m ² / g) Here, dx1: average particle diameter (μm) of particles measured by an electron micrograph α: dispersion coefficient d50: 50% average particle diameter (μm) of particles measured by a microtrack FRA laser type particle size distribution analyzer β: sharpness d90: 90% total particle size (μm) of the particles passing through the sieve measured by a Microtrac FRA laser type particle size distribution meter (μm) d10: 10% total particle size (μm) of the particles passing through the sieve measured by a Microtrac FRA laser type particle size distribution meter dx2: Average pore diameter (μm) of particles determined by pore distribution measured by mercury intrusion method ω1: JIS K5101-91 20.1 Static of pigment test method Apparent by law specific volume (ml / g) was measured, static 置空 porosity calculated by the formula (h) below (%) ω2: 0.5 g sample was filled in a cylinder having a cross-sectional area of 2 cm ² , 30
Pressurized at a pressure of kg / cm ² for 30 seconds, the thickness thereof was measured with a vernier caliper, and the pressurized porosity (%) of 30 kg / cm ² calculated from the following formula (i) Sw1: BET specific surface area by nitrogen adsorption method (m ² / g) 2. The papermaking material according to claim 1, wherein the inorganic particles of the core material are calcium carbonate. 3. The papermaking material according to claim 1, wherein the average particle diameter dx1 comprises particles satisfying the following formula (j). (J) 0.2 ≦ dx1 ≦ 10 (μm) 4. The papermaking material according to claim 1, wherein the average particle size dx1 is a particle satisfying the following formula (k). (K) 0.5 ≦ dx1 ≦ 8 (μm) 5. The papermaking material according to claim 1, wherein the dispersion coefficient α and the sharpness β consist of particles satisfying the following expressions (l) and (m) at the same time. (L) 1 ≦ α ≦ 2 (m) 0 ≦ β ≦ 1.0 6. The BET specific surface area Sw1 is represented by the following formula (n):
The papermaking material according to any one of claims 1 to 5, comprising particles satisfying the following. (N) 100 ≦ Sw1 ≦ 350 (m ² / g) 7. An atomic ratio of Ca / P in particles is 5.5.
The papermaking material according to any one of claims 1 to 6, which has a molecular weight of 6 or less. 8. An atomic ratio of Ca / P in the particles is 3.3.
The papermaking material according to claim 7, which is 3 or less. 9. An atomic ratio of Ca / P in particles is 1.8.
9. The papermaking material according to claim 8, wherein the number is 5 or less. 10. The compound represented by the formula C, wherein the calcium phosphate compound is represented by the following formula:
_{a 10 (PO 4) 6 (} OH) papermaking material according to any one of claims 1 to 9 which is ₂ hydroxyapatite. A recording sheet comprising the papermaking material according to any one of claims 1 to 10. 12. The recording paper according to claim 11, wherein the recording paper is a coated paper. 13. The recording sheet according to claim 11, wherein the recording sheet is an inner sheet.