JPH048557B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to neutral lightweight coated base paper. Specifically, the invention relates to a neutral papermaking base paper for obtaining coated paper that has low basis weight, high opacity, and low density. (B) Problems to be Solved by the Prior Art and the Invention In general, lightweight coated base paper has a low basis weight, so it is required to have high opacity per unit basis weight. Furthermore, lightweight coated paper is mainly used in roll-type products such as offset rotary printing and gravure printing. in this case,
The distortion and thickness in the winding width direction must be uniform. Therefore, it is required to have low density, be easily compressed, and have properties that allow the thickness to be easily recovered upon release of the compressive force, that is, cushioning properties. In particular, gravure products that require good adhesion to the plate require high cushioning properties. Usually, mechanical pulp (GP, RGP, TMP, etc.) is blended to meet these characteristics. However, it is very difficult to incorporate mechanical pulp into a neutral papermaking system due to pitch troubles and the like. Moreover,
Not only lightweight coated paper but also recent coated paper contains a large amount of calcium carbonate in the coating layer, so it is necessary to make the base paper in which the coated paper waste is mixed with a neutral system. On the other hand, if the pulp is only a chemical pulp such as semi-bleached KP, and light calcium carbonate, which has excellent opacity, is added as a filler, a considerable degree of opacity can be obtained. However, low-density base paper cannot be obtained using chemical pulp and fillers alone. An object of the present invention is to overcome the above-mentioned problems and provide a lightweight coated base paper that has high opacity, low density, and can be made in a neutral system. (C) Means for solving the problem The present invention contains 10% by weight or more of sodium sulfite-cooked high-yield pulp whose fiber Runkel ratio is 0.4 or more, 5% by weight or more of light calcium carbonate, and has a pH of 7 or more. This is a neutral, lightweight coated base paper that is manufactured using The sodium sulfite-cooked high-yield pulp used in this neutral lightweight coated base paper is digested with a sodium sulfite chemical solution with a pH of 12 or less, and has a yield of 70% by weight or more and a freeness of 200ml or more. It is said that The above means will be explained in detail below. The sodium sulfite-cooked high-yield pulp referred to in the present invention contains sodium hydroxide (NaOH) and/or
Alternatively, a mixture of sodium sulfite (Na ₂ SO ₃ ) and/or sodium bisulfite (NaHSO ₃ ) is added to the wood chips at a temperature of 105°C to 180°C;
It is a pulp that is digested for 5 to 40 minutes under a steam pressure of 1 to 9 kg/cm ² and then defibrated in a pressurized and normal pressure refiner. This sodium sulfite-cooked high-yield pulp reduces the resin content to 1/3 to 1/10 of mechanical pulp during the cooking and bleaching processes, so it does not cause problems such as pitch trouble even in systems with a pH of 7 or higher. Does not occur. Therefore, unlike mechanical pulps such as GP and TMP, it can be used in neutral papermaking systems that use light calcium carbonate as a filler. This sodium sulfite-cooked high-yield pulp is generally inferior to mechanical pulp (GP, RGP, TMP, etc.) in terms of opacity of the pulp alone. In particular, the specific scattering coefficient, which is an important measure of opacity, is 600 to 700 for GP.
cm ² /g, whereas high-yield pulp cooked with sodium sulfite is 300 to 400 cm ² /g, which is not much different from chemical pulp such as semi-bleached KP. However, when coated base paper is blended with light calcium carbonate, which is a highly opaque filler, and subjected to supercalender treatment after coating, even if the whiteness is the same, there is a high degree of impurity compared to coated paper containing semi-bleached KP. Gives transparency. This is because the density of sodium sulfite-cooked high-yield pulp is as low as that of mechanical pulp, and its cushioning properties are high.
This is due to the fact that the voids in the base paper that scatter light do not decrease as they do with semi-bleached KP blended base paper. Naturally, it is a lightweight coated paper containing sodium sulfite-cooked high-yield pulp and light calcium carbonate.
Contains GP, etc. and mechanical pulp to achieve opacity comparable to lightweight coated base paper made using acidic papermaking systems. Furthermore, when light calcium carbonate is blended with chemical pulp such as semi-bleached KP, the density becomes extremely high and the cushioning properties are poor, making it unsuitable for lightweight coated base paper. On the other hand, when sodium sulfite digested high-yield pulp is blended, mechanical pulp such as GP is blended,
Density and cushioning properties comparable to lightweight coated paper made using acidic papermaking systems can be obtained. If the blending ratio of sodium sulfite-cooked high-yield pulp is less than 10% by weight, the effect of maintaining density will be reduced. Furthermore, if the amount of soft calcium carbonate is less than 5% by weight, the effect on opacity will be reduced. Generally, the yield of sodium sulfite-cooked high-yield pulp is reduced by treatments such as increasing the cooking temperature, lengthening the cooking time, or increasing the pH of the cooking chemical. At that time, the fibrillation force decreases and the strength increases, but the density increases and the specific scattering coefficient decreases, and when the yield is less than 70% by weight (bone-dried pulp/bone-dried wood chips), it becomes comparable to KP. I'm getting used to it. In addition, if the yield is not high, the density will decrease and the specific scattering coefficient will increase, but the fibrillation power will increase.
Strength also decreases. If the pH of the cooking chemical is high and exceeds 12, the density tends to decrease even with the same yield, and becomes comparable to KP. However, thick-walled fiber chips provide relatively high specific scattering coefficients and low densities at low yields. To explain this point in detail, the Runkel ratio (2 x wall thickness/lumen width) of the fiber is required to be 0.4 or more. Conventionally, it has been said that materials with a low Runkel ratio are suitable for producing high-yield pulp. This is because materials with a low Runkel material have flexible fibers that are easy to defibrate and are easy to develop strength. However, when the yield of materials with a low Runkel ratio is less than about 90% by weight, the specific scattering coefficient decreases significantly and becomes less than KP. At a yield of 90% by weight or more, the fibrillation power suddenly increases and becomes comparable to mechanical pulp, but the specific scattering coefficient does not improve. Fibers with a high Runkel ratio are easily obtained from materials with a high apparent specific gravity. Particularly representative materials include domestic materials such as beech and oak, and imported materials such as eucalyptus.
and mixtures of these materials. However, in materials with too high a Runkel ratio, such as some mangrove materials, the material is too hard and the fibers are crushed when they are made into fibers. This sodium sulfite-cooked high-yield pulp made of fibers with a Runkel ratio of 0.4 or more has a yield of 70
% or more, and even if the freeness is lowered to 200 ml CSF, the specific scattering coefficient improves. however,
When the volume drops below 200ml, the specific scattering coefficient suddenly decreases, and at the same time, the density increases rapidly, reaching the same level as KP. On the other hand, in fibers with a low Runkel ratio, the specific scattering coefficient and density decrease as the freeness decreases even from a high yield stage. The light calcium carbonate used in the present invention is a common product and has an average particle size of about 0.3 to 2.0 μm. Also, used in the present invention
NBKP and LBKP are also common products. Furthermore, the effects of the present invention are not impaired by using commonly used retention improvers and the like within a common sense range. (D) Examples The effects of the present invention will be explained in more detail below using examples. Example 1 For hardwood mixed chips with a Runkel ratio of 1.5, PH
A mixed chemical solution of sodium sulfite (Na ₂ SO ₃ ) and sodium bisulfite (NaHSO ₃ ) from No. 7 was added in an amount of 8.3% by weight (as total SO ₂ ), and the chemical liquid ratio (total cooking chemical solution/dry chip amount) was 4.5. Cooking holding temperature 160℃−
After cooking with a holding time of 20 minutes, pressure defibration and normal pressure fibers were performed, yield 85% by weight, freeness 300ml - CSF
A high-yield pulp was obtained by cooking with sodium sulfite. This sodium sulfite digested high yield pulp is 30% by weight, LBKP (350ml/CSF) is 25% by weight,
A 40 g/m ² handmade paper was prepared with a composition ratio of 35% by weight of NBKP (450ml-CSF) and 10% by weight of light calcium carbonate. When light calcium carbonate is added, the pH of the paper stock at the time of paper making becomes 8.4. The hand-made sheet was pressed using a roll press with a linear pressure of 80 kg/cm and dried using a cylinder dryer. The physical properties of the handmade paper are summarized in Table 1. *Runkel ratio: 2 x wall thickness/lumen width Measured from an optical or electron micrograph of the fiber cross section of raw material chips. *Yield: 100 x weight of bone dry pulp/weight% of bone dry chips *Freeness: JIS P8121 *Whiteness: JIS P8123 *Specific scattering coefficient: S cm ² /g S = 10000 x R∞ x 1n ((1 -RO×R
∞)/(1-RO/R∞))/(1- ^R∞2 )/WW: Air-dry basis weight of paper (g/ ^m2 ). The definitions of RO and R∞ are based on TAPPI T519. R.O.
The measurement of R∞ was based on JIS P8138. *Internal bond strength: TAPPI T506-SU68 *Tearing length: JIS P8113 *Density: JIS P8118 Comparative example 1 Semi-bleached LKP with brightness of 60 (unbleached pulp bleached with chlorine, sodium hydroxide, and sodium hypochlorite) pulp) is 30% by weight, NBKP is 35% by weight,
A 40 g/m ² handmade paper was prepared with a composition ratio of 25% by weight of LBKP and 10% by weight of light calcium carbonate. When light calcium carbonate is added, the pH of the paper stock at the time of paper making becomes 8.4. The sheet after hand-sheeting has a linear pressure of 80 kg/
Pressed with cm roll press, cylinder and
Dry with a hair dryer. The constituent raw material ratios and physical property values of the handmade paper are summarized in Table 1. As you can see from this result, the density after calendering is 0.9g/cm ³
As above, the specific scattering coefficient after calendering is also
It is less than 300 cm ² /g, which is not preferable as a lightweight coated base paper. Example 2 Sodium sulfite-cooked high-yield pulp prepared under the same production conditions as in Example 1 was produced.
A 40 g/m ² handmade paper containing 75% by weight and other raw materials in the composition ratios shown in Table 1 was prepared under the same handmade paper preparation conditions as in Example 1. The results are shown in Table 1. Example 3 Sodium sulfite-cooked high-yield pulp prepared under the same production conditions as in Example 1 was produced.
A 40 g/m ² handmade paper was prepared under the same conditions as in Example 1, containing 15% by weight and other raw materials in the composition ratios shown in Table 1. The results are shown in Table 1. Comparative Example 2 7% by weight of sodium sulfite digested high yield pulp prepared under the same production conditions as in Example 1 was blended, and other raw materials were blended in the composition ratios shown in Table 1 at 40 g/m Handmade paper ^{No. 2} was prepared under the same handmade paper preparation conditions as in Example 1. The results are shown in Table 1. As can be seen from these results, the density after calendering is 0.9 g/cm ³ or more, and the specific scattering coefficient after calendering is also 300 cm ² /g or less, which is not preferable as a lightweight coated base paper. Example 4 A 40 g/m ² handmade paper containing 7% by weight of light calcium carbonate and other raw materials in the composition ratios shown in Table 2 was prepared under the same conditions as in Example 1. The results are shown in Table 2. Example 5 A 40 g/m ² handmade paper containing 25% by weight of light calcium carbonate and other raw materials in the composition ratios shown in Table 2 was prepared under the same conditions as in Example 1. The results are shown in Table 2. Comparative Example 3 A 40 g/m ² handmade paper containing 3% by weight of light calcium carbonate and other raw materials in the composition ratios shown in Table 2 was prepared under the same conditions as in Example 1. The results are shown in Table 2. As can be seen from these results, the density after calendering is 0.9 g/cm ³ or more, and the specific scattering coefficient after calendering is 300 cm ² /
g or less, which is not preferable as a lightweight coated base paper. Example 6 Using hardwood chips with a Runkel ratio of 0.4, the third
According to the production conditions shown in the table, the sodium sulfite-cooked high-yield pulp was 30% by weight.
LBKP (350ml−CSF) 25% by weight, NBKP (450ml
- 40 g/m ² handmade paper was prepared with a composition ratio of 35% by weight of calcium carbonate and 10% by weight of light calcium carbonate. When light calcium carbonate is added, the pH of the paper stock at the time of paper making becomes 8.4. The sheet after hand-sheeting has a linear pressure of 80
It was pressed using a roll press of kg/cm and dried using a cylinder dryer. The physical properties of the handmade paper are summarized in Table 3. Example 7 Using hardwood chips with a Runkel ratio of 2.0, the third
Example 6 Using the sodium sulfite-cooked high-yield pulp prepared according to the production conditions shown in the table,
Handmade paper was prepared according to the raw material formulation and handmade paper preparation conditions shown in . The physical properties of the handmade paper are summarized in Table 3. Comparative Example 4 Using hardwood chips with a Runkel ratio of 0.3, the third
Example 6 Using the sodium sulfite-cooked high-yield pulp prepared according to the production conditions shown in the table,
Handmade paper was prepared according to the raw material formulation and handmade paper preparation conditions shown in . The physical properties of the handmade paper are summarized in Table 3. As can be seen from these results, the density after calendering was 0.9 g/cm ³ or more, and the specific scattering coefficient after calendering was also 300 cm ² /g or less, which is not preferable as a lightweight coated base paper. Example 8 Sodium sulfite digested high-yield pulp was prepared according to the production conditions shown in Table 4 so that the yield was 70% by weight, and the raw material composition and hand paper preparation conditions shown in Example 6 were used. Handmade paper was prepared according to the following. The physical properties of the handmade paper are summarized in Table 4. Example 9 Sodium sulfite digested high-yield pulp was prepared according to the production conditions shown in Table 4 so that the yield was 92% by weight, and the raw material composition and hand paper preparation conditions shown in Example 6 were used. Handmade paper was prepared according to the following. The physical properties of the handmade paper are summarized in Table 4. Comparative Example 5 Sodium sulfite-cooked high-yield pulp was prepared according to the production conditions shown in Table 4 so that the yield was 65% by weight, and the raw material composition and handmade paper preparation conditions shown in Example 6 were used. Handmade paper was prepared according to the following. The physical properties of the handmade paper are summarized in Table 4.
As can be seen from these results, the density after calendering is 0.9 g/cm ³ or more, and the specific scattering coefficient after calendering is also 300 cm ² /g or less, which is not preferable as a lightweight coated base paper. Example 10 Using sodium sulfite-cooked high-yield pulp prepared with a chemical solution pH of 4 and other production conditions shown in Table 5, the raw material composition and hand-made paper preparation conditions shown in Example 6 were used. Handmade paper was prepared according to the following. The physical properties of the handmade paper are summarized in Table 5. Example 11 Using sodium sulfite-cooked high-yield pulp prepared with a chemical solution pH of 12 and other manufacturing conditions shown in Table 5, the raw material composition and hand paper preparation conditions shown in Example 6 were used. Handmade paper was prepared according to the following. The physical properties of the handmade paper are summarized in Table 5. Comparative Example 6 Using sodium sulfite-cooked high-yield pulp prepared with a chemical solution pH of 13 and other production conditions shown in Table 5, the raw material composition and hand-made paper preparation conditions shown in Example 6 were used. Handmade paper was prepared according to the following. The physical properties of the handmade paper are summarized in Table 5. As can be seen from these results, the density after calendering is 0.9 g/cm ³ or more, and the specific scattering coefficient after calendering is also 300 cm ² /g or less, which is not preferable as a lightweight coated base paper. Example 12 Sodium sulfite-cooked high-yield pulp was prepared according to the production conditions shown in Table 6 so that the freeness was 200 ml CSF, and the raw material composition and hand paper preparation conditions shown in Example 6 were used. , handmade paper was prepared. The physical properties of the handmade paper are summarized in Table 6. Example 13 Sodium sulfite-cooked high-yield pulp was prepared according to the production conditions shown in Table 6 so that the freeness was 400 ml CSF, and the raw material composition and hand paper preparation conditions shown in Example 6 were used. , handmade paper was prepared. The physical properties of the handmade paper are summarized in Table 6. Comparative Example 7 Sodium sulfite-cooked high-yield pulp was prepared according to the production conditions shown in Table 6 so that the freeness was 180 ml CSF, and the raw material composition and hand paper preparation conditions shown in Example 6 were used. , handmade paper was prepared. The physical properties of the handmade paper are summarized in Table 6. As can be seen from these results, the density after calendering is 0.9 g/cm ³ or more, and the specific scattering coefficient after calendering is also 300 cm ² /g or less, which is not preferable as a lightweight coated base paper. (E) Effects of the Invention By carrying out the present invention, high opacity, low density,
That is, a neutral, lightweight coated base paper with excellent cushioning properties (specifically, a specific scattering coefficient after calendering of over 300 cm ² /g and a density after calendering of 0.9 g/cm ³ or less) is obtained. I can do things. Particularly, the effect of the present invention is remarkable in that it is sustained on lightweight coated paper after being smeared and supercalendered. Therefore, the lightweight coated paper coated with the neutral lightweight coated base paper of the present invention exhibits excellent printability in offset rotary printing, gravure printing, and the like. In addition, the sodium sulfite digested high-yield pulp, which is an important component of the present invention, can be produced with lower fibrillation energy than other mechanical pulps.
Energy consumption can be reduced.

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[Table] *: Sodium sulfite cooking high yield pulp **: Weight % as _SO2
* Calendaring: Linear pressure 200Kg/cm 2
circulation

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Claims (1)

[Claims] 1. 10% by weight or more of sodium sulfite-cooked high-yield pulp having a fiber Runkel ratio of 0.4 or more;
Contains 5% by weight or more of light calcium carbonate and has a pH of 7.
Neutral lightweight coated base paper characterized by being made by the above process. 2 Digested with a sodium sulfite chemical solution with a pH of 12 or less, the yield is 70% by weight or more, and the freeness is 200ml.
The neutral lightweight coated base paper according to claim 1, characterized in that it contains the sodium sulfite digested high-yield pulp as described above.