JP2013204212A - Printing paper containing ground calcium carbonate as filler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide paper to which a high quality and low cost ground calcium carbonate is internally added, that shows excellent strength characteristics such as flexural rigidity, tensile strength, and interlayer strength and has a good balance between strength characteristics and papermaking efficiency such as wire abrasion properties and filler yield, without using or using a small amount of chemicals such as an yield improving agent and a paper strengthening agent.SOLUTION: The printing paper contains as a papermaking filler a ground calcium carbonate that satisfies the following (1) to (3): (1) the BET specific surface area is 1.0 to 10 m/g; (2) the average particle diameter is 2 to 10 μm; and (3) the ratio of the particle diameter of 90 wt.% in a particle size distribution curve to the particle diameter of 50 wt.% in a particle size, (D/D), is 1.0 to 3.0.

Description

  The present invention relates to a method for producing a calcium carbonate-containing paper excellent in strength and bending stiffness.

  In recent years, the demand for cheap paper has increased remarkably in the market, and it is used for coated base paper, newsprint, and electrophotography containing 10% or more of low-priced minerals such as clay, talc, calcium carbonate, and sodium silicate as fillers. Development of printing paper such as transfer paper is rapidly progressing.

  Paper blended with fillers tends to have superior optical properties such as opacity and whiteness compared to unblended paper, but the paper properties required for printing such as bending stiffness, tensile strength, and interlaminar strength are reduced. Therefore, troubles during printing such as paper breakage and poor print transportability frequently occur, so a method for suppressing a decrease in strength is required. There are methods such as the addition of paper strength agents such as cationized starch and PAM for the purpose of optimizing the physical properties of the paper. However, this leads to an increase in chemical costs, which is inconsistent with the trend toward lower prices required by the market.

  Calcium carbonate used for papermaking includes light calcium carbonate synthesized by reacting lime milk with carbon dioxide, and heavy calcium carbonate obtained by grinding limestone with a sand mill. In particular, light calcium carbonate, whose average particle size, particle size distribution, and specific surface area are more easily adjusted than heavy calcium carbonate, is generally used as a filler for many current printing papers. As for heavy calcium carbonate, it is difficult to adjust the particle size distribution, and the production efficiency is reduced due to the occurrence of wire wear during papermaking. Therefore, it is obviously less used as a filler than light calcium carbonate.

  Regarding these problems, for example, Japanese Patent Application Laid-Open No. 56-144296 also presents solutions for problems. However, when the above technique is used for actual papermaking, the calcium carbonate particles are less likely to stay in the paper, and the addition of chemicals such as cationic polyacrylamide used to improve the yield in the paper is weak. . Japanese Patent Application Laid-Open No. 2008-248398 shows a method for producing a high strength paper by pre-treating a filler with an anionic polymer / cationic polymer. However, additional processing and chemical addition are required in the papermaking process.

  As described above, the reduction in paper strength due to the addition of filler has been solved in the techniques of JP-A-56-144296 and 2008-248398. However, it is necessary to reduce the chemical effect and change the papermaking process.

JP-A-56-144296 JP 2008-248398 A

  Under such circumstances, the present invention does not use chemicals such as yield improvers and paper strength agents, or exhibits excellent strength properties such as bending stiffness, tensile strength, and interlayer strength even with a small amount of use. Further, the present invention has been made for the purpose of providing a high-quality and inexpensive heavy calcium carbonate-containing paper having a good balance between strength characteristics and paper-making efficiency such as wire wear resistance and filler yield.

As a result of conducting research using calcium carbonate having various physical properties in order to develop paper having the above-described properties, the present inventors have found that a BET specific surface area, a particle diameter, and a particle size distribution are in a specific range. It has been found that the purpose can be achieved by adding calcium carbonate to paper internally, and the present invention has been made based on this finding.
That is, the present invention has a BET specific surface area of 1 to 10 m ² / g, an average particle size of 2 to 10 μm, a particle size of 90% by weight of the particle size distribution curve and a particle size of 50% by weight of the particle size distribution curve. The base paper contains heavy calcium carbonate having a ratio (D ₉₀ / D ₅₀ ) of 1.0 to 3.0 as a filler. In order to obtain the printing paper of the present invention, only the physical properties of heavy calcium carbonate as a filler are adjusted, the effects of other internal chemicals are not affected, the papermaking process is not changed, and it is simple and low cost. It becomes a measure to improve the strength of printing paper.

  By using the present invention, it is possible to produce a printing paper that does not use a filling chemical such as a yield improver or a paper strength agent, or exhibits strength properties such as excellent bending rigidity, tensile strength, and interlayer strength even with a small amount of use. It is possible. In addition, since it is possible to suppress wire wear during operation that has conventionally occurred by using heavy calcium carbonate, it is also effective in terms of production efficiency and cost.

  In the present invention, heavy calcium carbonate satisfying a specific BET specific surface area, average particle diameter and particle size distribution is used as a filler for papermaking.

BET specific surface area of the calcium carbonate of the present invention is a 1.0~10.0m ² / g, is preferably 1.5~7.0m ² / g. If it is less than 1.0 m ² / g, it is difficult to produce heavy calcium carbonate itself, and if it is more than 10.0 m ² / g, the effect of the additive such as a yield improver used during papermaking may be reduced. There is. The BET specific surface area was measured using Micromeritics Gemini 2360 (manufactured by Shimadzu Corporation).

  The average particle diameter of the heavy calcium carbonate of this invention is 2.0-10.0 micrometers, 3.0-8.0 are preferable and it is more preferable that it is 3.0-5.0 micrometers. The average particle size was measured using a laser diffraction / scattering type particle size distribution analyzer (manufactured by Malvern Co., Ltd., device name: Mastersizer 2000) as the average particle size at the 50% point of the volume cumulative distribution. When the average particle size of the heavy calcium carbonate is 2 to 10 μm, it is possible to prevent the yield rate of the filler on the wire and the wire wear resistance from being lowered during paper making.

In the particle size distribution curve of the heavy calcium carbonate of the present invention, the ratio of the particle size of 90% of the particle size distribution curve to the particle size of 50% of the particle size distribution curve (D ₉₀ / D ₅₀ ) is 1.0 to 3.0. It is preferable that it is 2.3-2.6. When D ₉₀ / D ₅₀ is 1.0 or less, the particle size distribution of heavy calcium carbonate is sharp, but because of its manufacturing process, it is necessary to carry out classification treatment, which is negative in terms of production efficiency of heavy calcium carbonate. There are many factors. On the other hand, when the particle size is 3.0 or more, the particle size distribution becomes broad, which tends to cause a decrease in yield during papermaking.

In the present invention, the particle size distribution curve is obtained by determining the particle size distribution of the heavy calcium carbonate of the present invention using a laser diffraction / scattering type particle size distribution analyzer (manufactured by Malvern Co., Ltd., device name: Mastersizer 2000). When the cumulative curve was determined with the total volume of the calcium carbonate as 100%, the particle diameters at the points where the cumulative curves were 50% and 90% were calculated as D ₅₀ (μm) and D ₉₀ (μm), respectively.
The printing paper of the present invention exhibits excellent strength properties such as bending stiffness, tensile strength, and interlayer strength by satisfying all the properties of heavy calcium carbonate as described above.

  In the present invention, as calcium carbonate, only heavy calcium carbonate having the above properties may be contained, or in addition, light calcium carbonate may be contained. The shape of the light calcium carbonate to be used is not particularly limited, and may be calcite, aragonite, vaterite, or a mixture thereof.

  When light calcium carbonate is used in combination, it is preferable to contain 50% by weight or more of heavy calcium carbonate, more preferably 80% heavy calcium carbonate, out of the total calcium carbonate of heavy calcium carbonate and light calcium carbonate. It is contained by weight% or more.

  The addition amount of the heavy and light calcium carbonate of the present invention can be 10 to 70% by weight based on the weight of the pulp. In consideration of the yield, the addition amount is preferably such that the ash content in the printing paper is 1 to 40% by weight, more preferably 3 to 25% by weight, and 5 to 25% by weight. % Is more preferable. When the ash content exceeds 40% by weight, the strength of the paper is lowered and the operability tends to deteriorate.

  When the ash content in the paper exceeds 35% by weight, the stiffness and strength of the paper are remarkably lowered. Further, when the heavy calcium carbonate of the present invention is used, even if the heavy calcium carbonate has an ash content in the paper of 20% or more, there is little decrease in the stiffness and strength of the paper.

  In general, the ash content indicates the amount of inorganic substances contained in the paper, and thus basically reflects the amount of filler contained in the paper. The ash content of paper is composed of those derived from fresh fillers added to the stock and those brought in by pulp raw materials such as DIP (waste paper pulp, deinked pulp). The amount of ash brought in by DIP is relatively high in calcium carbonate, but inorganic components other than calcium carbonate are also included. The ratio of calcium carbonate to other inorganic components depends on the type and collection of used paper such as used newspaper and magazine used paper. It depends on the situation. In the present invention, the ash content is measured by a method in which the combustion temperature is set to 525 ± 25 ° C. in accordance with the ash test method for paper and paperboard specified in JIS P 8251.

  Examples of the pulp used in the present invention include chemical pulps such as LBKP (hardwood bleached kraft pulp), NBKP (softwood bleached kraft pulp), LBSP (hardwood bleached sulfite pulp), NBSP (coniferous bleached sulfite pulp), and stone ground pulp. (SGP), Pressurized Stone Grand Pulp (PGP), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Chemi Thermomechanical At least one selected from the group consisting of mechanical pulp such as pulp (CTMP) and refiner mechanical pulp (RMP), and waste paper pulp such as deinked pulp (DIP), is blended at an arbitrary ratio, and used appropriately be able to.

  In the present invention, an internal sizing agent can be used in addition to pulp and filler. As the internally added sizing agent, sizing agents such as rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, and neutral sizing agents can be used. In the present invention, it is preferable to use, in combination with these internally added sizing agents, a fixing agent for fibers such as sulfuric acid band and cationized starch. In the present invention, paper-making internal additives such as paper strength enhancers, dyes, pH control agents, antifoaming agents, and pitch control agents can be appropriately added depending on the purpose.

  In producing the printing paper of the present invention, it is possible to make paper using a known apparatus such as a long web paper machine, an on-top twin-wire paper machine, or a gap former as appropriate. As the papermaking conditions, the pulp beating degree, jet wire ratio, profile, press, calendar, and the like are adjusted.

  Depending on the application, various surface sizing agents such as starch, polyvinyl alcohol, latex, maleic anhydride-based size, olefin-based size, styrene-acrylic acid-based size on the surface of the formed paper in the size press process according to the application, A dimensional stabilizer such as ethylene-urea resin, an inorganic conductive agent such as sodium chloride, potassium chloride, or sodium sulfate, an organic conductive agent such as dimethylaminoethyl methacrylate, a surfactant, or the like may be applied. Application methods in the size press process include conventional size presses (two rolls, pound methods), gate roll size presses, rod metering size presses, metalling blade type size presses, bill blades, and short dwell coaters. Can be used.

  In the present invention, there are no particular limitations on the pH, temperature, method of addition to the base paper, etc. when adjusting heavy calcium carbonate. In addition, when making the paper pulp of the present invention, it goes without saying that a known paper making method can be applied as it is.

Basis weight of printing paper The basis weight of the printing paper of the present invention is not particularly limited, but can be about 30 to 200 g / m ² . Since the printing paper of the present invention has high rigidity, the effect is more likely to be exhibited when used for printing paper with a low basis weight of 80 g / m ² or less.

  The printing paper of the present invention can be used for various printing applications such as electrophotography, offset printing, gravure printing, letterpress printing, and intaglio printing.

  The printing paper of the present invention can be suitably used as an electrophotographic transfer paper for use in an electrophotographic copying machine or printer. When the printing paper of the present invention is used as an electrophotographic transfer paper, it can be an electrophotographic transfer paper with good printing operability, which is less likely to cause jamming during printing.

  When used as electrophotographic transfer paper, a clear (transparent) coating layer is provided by applying a clear coating solution containing starch and a conductive agent to one or both sides of the base paper. In the present invention, clear coating means, for example, a coating liquid (surface treatment liquid) using a coater (coating machine) such as a pound type size press, a gate roll coater, a rod metering size press, a curtain coater, or a spray coater. ) On the base paper (size press).

  The printing paper of the present invention can also be suitably used as a base paper for printing coated paper. The coated paper can be used for various printing applications such as offset printing, gravure printing, letterpress printing, and intaglio printing. When the printing paper of the present invention is used as the base paper for the coated paper for printing, the strength of the base paper can be maintained and the ash content in the paper can be highly blended, so printing such as optical suitability such as opacity and ink penetration The suitability is better than the prior art.

  When the base paper of the coated paper is used, at least one surface of the printing paper of the present invention is provided with at least one pigment coating layer mainly composed of a pigment and an adhesive. Moreover, you may provide the above-mentioned clear coating layer in the lower layer of a pigment coating layer.

  As the pigment of the pigment coating layer, those conventionally used for coated paper can be used. For example, kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light carbonate As needed, inorganic pigments such as calcium, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, and satin white, and organic pigments such as solid, hollow, or core-shell types Can be used alone or in admixture of two or more.

  There is no restriction | limiting in particular about the adhesive agent (binder) of a pigment coating layer, The adhesive agent conventionally used for coated paper can be used. For example, as preferred adhesives, various copolymers such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, and polyvinyl alcohol and maleic anhydride copolymers. Synthetic adhesives such as acrylic acid / methyl methacrylate copolymer; Proteins such as casein, soybean protein, synthetic protein; Etherification of oxidized starch, positive starch, urea phosphated starch, hydroxyethyl etherified starch, etc. One or more ordinary adhesives for coated paper such as starches and starches such as dextrin; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and hydroxymethylcellulose can be appropriately selected and used. In addition to pigments and adhesives, pigment coating liquids contain various dispersants, thickeners, water-retaining agents, antifoaming agents, water-proofing agents, and ordinary pigments for coated paper as needed. Auxiliaries can be used as appropriate.

  In the present invention, in order to provide a pigment coating layer, any commonly used coater may be used. An on-machine coater or an off-machine coater may be used, and if it is an on-machine coater, a coater such as a roll coater such as a size press coater or a gate roll coater, a bill blade coater, or a blade metering size press coater can be used. The coating amount of the pigment coating solution is not particularly limited. It can be determined according to the application. After coating, surface treatment can be performed with a calendar such as a super calender or a high temperature soft nip calender.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, these do not limit this invention at all. Unless otherwise specified, parts and% indicate parts by weight and% by weight.
[Evaluation method]
(1) Average particle diameter of pigment: The 50% point of the volume cumulative distribution was defined as the average particle diameter using a laser diffraction / scattering particle size distribution analyzer (manufactured by Malvern, Inc., device name: Mastersizer 2000).
(2) Basis weight: Measured according to JIS P 8124.
(3) Paper thickness: Measured according to JIS P 8118.
(4) Density: Determined from basis weight and paper thickness according to JIS P 8118.
(5) Tensile strength: Measured according to JIS P8113.
(6) Bending stiffness: According to ISO-2493, a bending stiffness with a bending angle of 15 degrees was measured with an L & W Bending Tester (manufactured by Lorentzen & Wettre).
(7) Interlaminar strength: Measured with L & W ZD Tensile Tester (Lorentzen & Wettre) according to ISO-15754 / TAPPI T551.
(8) The ash content was measured according to JIS-P8128 and the ashing temperature was 525 ° C.

Example 1-1
As a raw material pulp, a slurry of 100 parts of LBKP (hardwood bleached kraft pulp) having a freeness of 500 ml was used. A sulfuric acid band as an internally added chemical was added to a pulp weight of 2.0% and stirred. Here, commercially available heavy calcium carbonate (Escalon 800: manufactured by Sanki Flour Milling Co., Ltd.) was added and stirred for 15% of the weight of the pulp. Thereafter, a yield improver (R-101: manufactured by Somar Co., Ltd.) was added to 0.01% by weight. As described above, handmade paper was prepared according to JIS P 8222 using the prepared slurry.
Example 1-2
In Example 1-1, handmade paper was prepared in the same manner as in Example 1 except that the amount of heavy calcium carbonate added was 30% of the pulp weight.
Example 1-3
In Example 1-1, handmade paper was prepared in the same manner as in Example 1 except that the amount of heavy calcium carbonate added was 65% of the pulp weight.

Example 2-1
In Example 1-1, except that heavy calcium carbonate is Escalon 200 (manufactured by Sanki Flour Milling Co., Ltd.) and the amount of heavy calcium carbonate added is 15% to pulp weight, Example 1-1 and Similarly, handmade paper was prepared.
Example 2-2
In Example 2-1, a handmade paper was prepared in the same manner as in Example 2-1, except that the amount of heavy calcium carbonate added was 30% of the pulp weight.
Example 2-3
In Example 2-1, a handmade paper was prepared in the same manner as in Example 2-1, except that the amount of heavy calcium carbonate added was 65% of the pulp weight.

Comparative Example 1-1
In Example 1-1, handmade paper was prepared in the same manner as in Example 1-1, except that heavy calcium carbonate was self-made light calcium carbonate, and the addition amount of light calcium carbonate was 20% to pulp weight. Created.
Comparative Example 1-2
In Comparative Example 1-1, handmade paper was prepared in the same manner as Comparative Example 1-1 except that the amount of light calcium carbonate produced was changed to 40% pulp weight.
Comparative Example 1-3
In Comparative Example 1-1, handmade paper was prepared in the same manner as in Comparative Example 1-1 except that the amount of self-made light calcium carbonate was 70% with respect to pulp weight.

Comparative Example 2-1
In Example 1-1, except that heavy calcium carbonate was FMT-MAT (325 mesh) (manufactured by Phimattek Co., Ltd.) and the amount of heavy calcium carbonate added was 40% to pulp weight. Hand-made paper was prepared in the same manner as in Example 1-1.
Comparative Example 2-2
In Comparative Example 2-1, a handmade paper was prepared in the same manner as Comparative Example 2-1, except that the amount of heavy calcium carbonate added was 100% to pulp weight.
Comparative Example 2-3
In Comparative Example 2-1, a handmade paper was prepared in the same manner as Comparative Example 2-1, except that the amount of heavy calcium carbonate added was 200% to pulp weight.

Comparative Example 3-1
In Example 1-1, heavy calcium carbonate was changed to Cerafil (manufactured by Luck Minerals), which is clay, and the amount of clay added was 10% with respect to the weight of pulp, as in Example 1-1. Handmade paper was made.
Comparative Example 3-2
In Comparative Example 3-1, a handmade paper was prepared in the same manner as Comparative Example 3-1, except that the amount of clay added was 30% with respect to pulp.
Comparative Example 3-3
A handmade paper was prepared in the same manner as in Comparative Example 3-1, except that the amount of clay added was 60% with respect to the pulp weight in Comparative Example 3-1.

  Table 1 shows the quality of each filler, and Table 2 shows the results.

  Table 1 shows the physical properties of the filler. Table 2 shows the physical property values of the paper. In any of the physical properties of Examples 1 and 2 such as bending stiffness, tensile strength, and interlaminar strength, it is clear that a decrease in strength is small compared to the comparative example at an ash content of about 20%. In addition, the printing paper of the present invention satisfies the tensile strength of 2.0 kN / m or more, the interlayer strength of 5.4 kPa or more, and the ISO bending stiffness of 70 μN · m or more even when the ash content is about 30%. It can be seen that the strength and interlayer strength are high.

Claims (4)

Printing paper containing heavy calcium carbonate satisfying the following (1) to (3) as a filler for papermaking.
(1) BET specific surface area of 1.0 to 10 m ² / g
(2) The average particle size is 2 to 10 μm
(3) 50 wt% of the ratio of the particle diameter of 90 wt% of the particle size and particle size distribution curve of the particle size distribution curve _(D 90 _{/ D 50)} is 1.0 to 3.0
The printing paper according to claim 1, wherein the printing paper is electrophotographic transfer paper.
The printing paper according to claim 1, wherein the printing paper is a base paper for coated paper.
  A coated paper for printing in which at least one coating layer mainly composed of a pigment and an adhesive is provided on at least one side of the printing paper according to claim 3.