JP2000136497A - Newsprint for offset rotary press printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain newsprint for offset rotary press printing, excellent in blank paper opacity and printing opacity by coating a surface-treating agent consisting essentially of titanium dioxide and/or a hollow organic pigment, and a binder, on both surfaces of a base paper containing an internally added specific hydrated silicic acid. SOLUTION: This newsprint for offset rotary press printing is obtained by coating a surface-treating agent consisting essentially of titanium dioxide having rutile crystal form and covered with aluminum, and/or a hollow organic pigment having 0.7-3 μm average particle diameter and 40-85% porosity, and a binder, on both surfaces of a base paper including >=30 wt.% waste paper pulp containing a hydrated silicic acid having 5-30 μm average particle diameter (based on a laser method), and <=0.25 standard deviation of the distribution of the particle volumes to the particle diameters (in a logarithmic representation), as a filler, expressed in terms of solid content, so that the basis weight of the titanium dioxide and/or the hollow pigment may be 0.1-1.5 g/m2, drying the coated product, and subjecting the dried product to a smoothing finishing by a soft calender.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to newsprint for web offset printing, and more particularly to newsprint for thin web offset printing which is excellent in printing workability and has excellent color printing quality and a high blending ratio of waste paper pulp. is there.

[0002]

2. Description of the Related Art In recent years, newsprint printing has been rapidly advanced in offset rotary printing, color printing, and high-speed printing, and concomitantly with better color printing suitability and printing even on newsprint as a printing medium. Workability is required. In general, newsprint paper is made of a mixture of mechanical pulp and waste paper pulp.In recent years, from the viewpoint of environmental protection, a high proportion of waste paper pulp has been used, and paper weight has been reduced as part of increasing the number of newsprint pages. Has been requested.

[0003] In offset rotary printing, a printing ink having a relatively high tackiness is required to have a high paper surface strength, and furthermore, a water resistance of the paper surface is required to use a dampening solution. Is done. Incidentally, when paper having low printing strength or paper having low or no water resistance is used, troubles such as generation of so-called blurring on a printing surface occur due to accumulation of paper dust on a blanket or mixing with ink.

Further, with the recent reduction in weight of newsprint, high opacity after printing on the newsprint is required. In order to increase the opacity of paper, inorganic pigments such as hydrated silicic acid, titanium oxide and talc and organic pigments such as urea-formaldehyde resin have come to be widely used as papermaking fillers. Above all, hydrated silicic acid represented by so-called white carbon is most widely used because it has an effect on opacity at low cost. Generally, these hydrated silicas have a very small primary particle size and are relatively uniform, but in most cases, a plurality of particles aggregate to form secondary aggregates, and the particles at the time of use The particle size is widely distributed from small particle size to large particle size. When such filler is added to papermaking pulp (paper stock) and papermaking is performed, particles in the small particle size region where the effect of developing opacity is large are paper The yield inside is extremely poor. As a result, the effect of expressing the opacity becomes insufficient, and it is necessary to increase the addition ratio in order to obtain the sufficient opacity desired by the present invention.

[0005] However, these fillers tend to be easily leached out of the paper layer by dampening water used in the printing process at the time of rotary offset printing when the addition ratio is increased, and the main component of the paper powder piled on the blanket. It is one of the ingredients. On the other hand, D which is regarded as important in the environment
The high mixing ratio of IP (deinked waste paper pulp) makes it difficult for DIP to produce opacity compared to mechanical pulp such as GP, RGP, TMP, etc., especially when applied to thin products, it is necessary to improve opacity. In order to achieve a high ratio of DIP,
The situation is extremely difficult.

[0006] Conventionally, in order to cope with the difficulties of such newsprint for rotary offset printing, it has been generally practiced to apply a surface treating agent containing starch, PVA, polyacrylamide or the like as a component to the surface thereof. Have been done. These components have the effect of improving the paper surface strength and adhering the fine fibers and fillers on the paper surface to the pulp fibers, etc., but also increase the tackiness when the newsprint surface is wet (hereinafter referred to as "Nepari property"). Tend to cause
If the slimness increases, the paper surface sticks to the blanket during printing, resulting in running problems such as wrinkles and paper breaks.

[0007] For this reason, various methods have been proposed for newsprint for offset rotary printing in order to exhibit high opacity and obtain good paper surface strength.
For example, the base paper surface has an oil absorption of 65 cc / 100 g to 15
A method of increasing the opacity by providing a coating layer having a filler of 0 cc / 100 g (Japanese Patent Laid-Open No. 1-174697), a method comprising a pigment, a specific latex (SBR), and a composition containing a water-soluble adhesive as a main component. 0.3~3g / m ²
Coating method (JP-A-2-195595), and a method in which a binder containing starch and copolymer latex contains a specific amount of an organic pigment such as PP and BP in a specific amount (JP-A-5-263394) ) Etc. have been proposed. On the other hand, for example, when a low-grain pulverized product of 45 g / m ² or less or a base paper having a waste paper pulp compounding ratio of 40% by weight or more is used, opacity is improved, color printing suitability is improved, and blanket piling is eliminated. There are difficulties such as (reduction), and these difficulties have not been effectively balanced to obtain stable quality.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have studied the use of newsprint for web offset printing, particularly thin newsprint, in which a high proportion of waste paper is blended, the opacity is maintained, and excellent web offset printing suitability is achieved. And earnestly studied to obtain newsprint with. As a result, the present invention solves the above-mentioned difficulties by applying a surface treatment agent containing a specific highly opaque pigment and an adhesive to a base paper containing hydrated silica as an internal filler, and drying it. It is an object of the present invention to provide effectively balanced, high-quality, newsprint paper for offset web offset printing.

[0009]

According to the present invention, a surface treatment agent containing titanium dioxide and / or a hollow organic pigment and an adhesive as main components is applied to both sides of a base paper containing hydrated silica as a filler and dried. This is newsprint paper for web offset printing.

[0010]

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention comprises a base paper containing hydrated silicic acid as an internal additive, a titanium dioxide and / or a hollow organic pigment, a pigment called a so-called highly opaque pigment, and an adhesive as main components. The present invention relates to a lightweight newsprint for web offset printing obtained by applying and drying a surface treating agent. In particular, the present invention is characterized by a combination of hydrated silicic acid used as a base paper filler and a highly opaque pigment which is a component of a surface treating agent applied to the base paper surface.

That is, hydrated silicic acid, specifically, a filler called white carbon is used, which is widely used as a filler for ordinary newsprint, etc., but is particularly preferable in the present invention. As the hydrated silicic acid, the average particle diameter at the time of use is 5 to 30 μm as a value measured by a laser method (measuring device: laser diffraction type particle size distribution analyzer-SALD-2000J / Shimadzu Corporation), and more preferably hydration. As the silicic acid, a hydrated silicic acid that maintains the above average particle diameter and has a standard deviation of a particle volume distribution with respect to the particle diameter when the particle diameter of the hydrated silicic acid is expressed by a logarithm of 0.25 or less is used. It is desirable. By the way, specifying the average particle diameter to 5 to 30 μm is that if it is less than 5 μm, the particles as the internal filler are too small, the yield in paper is extremely poor, and a large amount of addition is required. As a result, paper quality characteristics such as formation deteriorate, which is not preferable. Meanwhile, 3
If the size of the large particles exceeds 0 μm, there is no problem in terms of the yield into paper, but the amount of the fine particles having a high light scattering effect is reduced, so that the effect of improving the opacity cannot be expected.

Regarding hydrated silicic acid, the standard deviation of the particle volume distribution with respect to the particle diameter when the particle diameter (μm) is expressed in logarithm is 0.25 in addition to the above-mentioned specific average particle diameter.
By using the following, a more excellent effect of improving opacity can be obtained, which is a preferred embodiment. As described above, normal hydrated silica is a single fine particle, which has a relatively uniform particle size.
Many entities exist as agglomerates of single particles, and are a mixture of aggregates that have been aggregated from fine particles close to a single particle diameter to a large particle diameter, and such a mixture is usually The body is used as a filler.

Therefore, when such a mixture is used as an internal filler, most of the small to fine particles contributing to the improvement in opacity deviate from the paper layer, while the large particles remain in the paper layer. However, it cannot contribute to improving the opacity of paper. By the way, in the case of hydrated silicic acid having the above standard deviation exceeding 0.25, the ratio of the particles of the small particle diameter portion to the large particle diameter portion increases, and when such a powder slurry is put into paper stock and papermaking is performed. However, there is a concern that improvement in opacity cannot be expected. On the other hand, the lower the standard deviation, the higher the proportion of particles of a certain size. The lower the standard deviation, the more desirable. By the above, the hydrated silica used as the internal filler is not particularly limited, but preferably has an average particle diameter of 5 to 30 μm, more preferably maintains the average particle diameter, and the When the particle diameter is expressed in logarithm, the standard deviation of the particle volume distribution with respect to the particle diameter is 0.25.
It has been found that by using the following hydrated silicic acid, the function as an internal filler desired by the present invention is exhibited extremely efficiently.

The method for obtaining the hydrated silicic acid having a standard deviation of 0.25 or less as described above is not limited. For example, it can be obtained by the following means. That is, poorly soluble in alkali silicate aqueous solution,
And after dispersing the acid-soluble particles, neutralize the aqueous alkali silicate solution by adding a mineral acid, and further, to the precipitated hydrated silicic acid, at least the alkali-insoluble and acid-soluble particles initially dispersed and at least It is produced by adding at least the same mole of mineral acid.

More specifically, SiO ₂ / Na ₂
An aqueous solution of sodium silicate or an aqueous solution of potassium silicate having a molar ratio of O in the range of 2.0 to 3.4 is added in an amount of 0.01 to 10%.
After adding and dispersing 10 to 60% by weight of alkali-soluble and acid-soluble particles such as magnesium hydroxide whose average particle diameter is adjusted to μm with respect to the solid weight in terms of silica in an aqueous solution of alkali silicate, sulfuric acid or the like is added. Mineral acid is added to neutralize the aqueous alkali silicate solution. In this case, the mineral acid may be added all at once or in plural portions. In addition, when adding in several parts, the first addition of mineral acid is performed in the range of 20 to 60 ° C., and 10 to 50% by weight of the amount of mineral acid necessary for neutralizing the aqueous alkali silicate solution. Is added. Further, after the temperature of the aqueous alkali silicate solution is raised to a range of 85 ° C. or higher and lower than the boiling point of the aqueous solution, an aging time is provided if necessary, and then the second and subsequent mineral acids are added at once or continuously. After the addition, an aging time may be provided if necessary.

The hydrated silicic acid thus produced contains particles hardly soluble in alkali and acid-soluble, and a mineral acid is further added to dissolve the particles. The mineral acid is added in an amount of at least the same mole as the initially dispersed particles, and the pH of the slurry containing the hydrated silica is adjusted to a range of 4 to 6. The hydrated silicic acid thus obtained has a standard deviation of 0.25 or less in the distribution of the particle volume with respect to the particle diameter when the particle diameter is expressed in logarithm. Therefore, the hydrated silica slurry thus obtained can be used as it is as a filler for paper according to the present invention.

The average particle size of the above hydrated silica (5 to 30 μm)
For the adjustment of m), if necessary, use a homomixer,
It can be adjusted by using a wet pulverizer such as a colloid mill, a disc refiner, or a sand grinder, and appropriately changing the number of revolutions, the number of treatments, or the diameter and amount of beads used. In addition, even if such a crushing treatment is performed,
It is desirable to adjust the standard deviation after pulverization to be 0.25 or less. Furthermore, the rate of addition of hydrated silica as an internal filler to the pulp fiber is not particularly limited, but is usually 1 to 3 with respect to the solid content with respect to the pulp fiber.
It is adjusted at 0% by weight.

The pulp fibers which are the main components of the base paper according to the present invention include chemical pulp (NBKP, LBKP, etc.) and mechanical pulp (GP, CGP, RGP, PGW, TMP).
Etc.) and known paper pulp (DIP etc.) are appropriately used. In particular, in the case of base paper which is lightweight and has a high content ratio of waste paper pulp, specifically, in the case of base paper containing 30% by weight or more of waste paper pulp in the whole pulp, the desired effect of the present invention is effective. Is obtained. In addition, when the hydrated silicic acid as described above is internally added to the pulp fiber to make paper, an inorganic filler such as talc or clay may be used in addition to the hydrated silicic acid. However, in this case, it is desirable to add the hydrated silicic acid, which is preferable in the present invention, so that it is contained at least 30% by weight or more, preferably 50% by weight or more based on the total filler. By the way, when it is less than 30% by weight,
There is a possibility that the effect of improving the opacity desired by the present invention may not be obtained.

Further, in the paper stock, in addition to the hydrated silicic acid, a paper strength enhancer, a retention enhancer, an internal sizing agent such as a strengthened rosin sizing agent, an emulsion sizing agent, a water-proofing agent, or an ultraviolet ray preventing agent. In general, well-known and publicly-known chemicals for papermaking can also be added. The pulp fibers thus prepared are appropriately adjusted by a beating machine such as a refiner, and then made by a known and publicly used paper machine. As described above, the basis weight of the base paper is a lightweight base paper having many difficulties, specifically, a base paper having a basis weight of 42 to 30 g / m ² (a product basis weight of 45 g / m 2).
² or less). By the way, 42 base paper
If the g / m ² exceeds 45 g / m ² (the product exceeds 45 g / m ² ), the base paper layer is thicker than the initial layer, and improvement in opacity is not so strongly required. On the other hand, 30 g / m ²
If it is less than 1, it is expected that the thickness of the base paper layer will be considerably reduced, and as a result, the paper strength and opacity will be significantly reduced. It is judged that there are too many tasks to be taken and should not be considered.

Next, a surface treatment agent which is another important component of the present invention will be described. That is, as described above, the present invention provides a remarkable effect on opacity by using hydrated silicic acid, especially a hydrated silicic acid (specified average particle diameter and standard deviation). However, on the other hand, due to the fact that it is a thin base paper, the surface strength of the paper is weak, and fillers and fine fibers are deposited on the blanket during offset printing, so it is easy to induce so-called blanket piling troubles. Is the actual situation. As described above, a paper strength enhancer such as starch or polyacrylamide is generally externally applied to the surface of a conventional newsprint for offset rotary printing. All of these external coating agents (surface treatment agents) are effective in preventing the generation of paper dust, but on the other hand, have poor water resistance and are liable to induce trouble of neppari.

The inventors of the present invention have sought to improve the opacity, prevent blanket piling (suppress the generation of paper dust), and improve the quality of newsprint, especially light-weight (for example, products of 45 g / m ² or less) newsprint. In order to simultaneously solve the three problems such as the reduction of the Neppari property and the quality, and to obtain the offset rotary printing aptitude balanced in quality, intensive studies have been made on the components of the surface treatment agent applied to the base paper, particularly on the pigment thereof. As a result, by applying a surface treatment agent containing a specific high opacity pigment and an adhesive as main components on base paper containing the above-mentioned hydrated silica as a filler, and drying, a further improvement in opacity can be achieved. That is, they have found that the occurrence of blanket piling can be extremely effectively prevented (the paper surface strength can be improved) without increasing the nepari property.

That is, titanium dioxide and / or hollow organic pigments are used as highly opaque pigments.
Incidentally, as the conventional highly opaque pigment, there are exemplified kaolins such as structured kaolin and calcined kaolin, inorganic pigments such as titanium dioxide, and organic pigments such as plastic pigment and binder pigment. The present invention is characterized in that titanium dioxide and / or hollow organic pigments are used as the pigment. These pigments are specified not only because both pigments are excellent in opacity, but in particular, the effect is exhibited with a small amount of use, and furthermore, blanket piling is effectively suppressed, and the nepari properties are other pigments. It is understood that it is relatively low compared to etc.
The three requirements to be improved as described above (reducing napping, preventing blanket piling, and improving opacity)
It has been found for the first time that newsprint paper for offset rotary printing having an excellent balance and excellent quality can be obtained.

First, rutile type titanium dioxide is used.
Alternatively, any of the anatase type can be used, but the rutile type is preferable in that the opacity is higher.Moreover, the surface thereof is more preferably because rutile type titanium dioxide whose surface is coated with aluminum is excellent in the effect of expressing opacity. used.

Next, the hollow organic pigment is generally provided as an aqueous dispersion of a styrene-based polymer or a styrene-acrylic-based copolymer, and is a spherical body in which core portions of particles are filled with water. Specifically, HP105
5, HP91 (Rohm & Haas), SX863 (A)
(JSR), MH5055 (Zeon Corporation) and the like. It is known that such a spherical body has a hollow structure due to the dissipation of water by drying, and has an effect of improving opacity and whiteness. On the other hand, hollow organic pigments such as those described above are disadvantageous in that they are expensive, have poor printing strength, etc., and are generally used in practical use by mixing a small amount with commonly used inorganic pigments such as kaolin and calcium carbonate. It is.
Incidentally, in order to increase the opacity of newsprint and the like, the above pigment-mixed system requires a dry coating amount of 5 g / m ² or more. However, there is a drawback that the amount of pulp fibers must be reduced, and as a result, a decrease in paper stiffness cannot be avoided.

As an application example of the hollow organic pigment, for example, Japanese Patent Application Laid-Open No. 2-74698 proposes the use of a hollow organic pigment in a light-weight coated paper. It is said that the size of about 0.7 μm is optimal. On the other hand, a certain thickness is required for the shell part of the particles, and in the above-mentioned particle size range, only a relatively low porosity is obtained. As a result, a small amount of coating can sufficiently improve the opacity. Is difficult to expect. Based on the above, the present inventors have intensively studied the porosity of the hollow organic pigment. As a result, in order to obtain the desired effect of improving the opacity, it is desirable that the porosity is at least 40% or more, and the upper limit is not particularly limited, but it is necessary that the stable hollow state be maintained. Considering 8
It is estimated to be about 5%. By the way, if it is less than 40%, the effect of improving the opacity is insufficient, while if it exceeds 85%, the shell is thin and the hollow is broken by a small impact, so that the desired effect cannot be obtained. There is a fear.

Therefore, in order to stably obtain a hollow organic pigment having a porosity of 40% or more, the average particle size is as follows:
It is desirable that the thickness be adjusted to 0.7 μm or more, preferably 3 μm or less. By the way, when the particle diameter becomes as large as 3 μm or more, when used as a surface treatment agent for lightweight newsprint,
There is a high possibility that the hollow organic pigment is protruded from the surface of the paper layer, and as a result, the hollow state is broken in the papermaking process, and particularly when the coating amount is small, the effect as the hollow organic pigment may not be expected. The porosity of the hollow organic pigment is determined by the following formula based on the inner and outer diameters of the particles. That is,
Assuming that the volume of the void portion is v and the volume of the entire particle including the void is V, the porosity (%) = [v / V] × 100.
Hollow organic pigments with high porosity, which tends to produce opacity, have relatively thin shells, so that hollow particles are formed by mechanical impact during application or drying through a calender. There is a disadvantage that it is easily crushed. Therefore, in order to obtain the initial purpose of using the hollow organic pigment, that is, to obtain the effect of improving opacity, it is essential that the hollow state is maintained. For this purpose, care must be taken to maintain a hollow state until the surface treatment agent containing the hollow organic pigment is applied to the base paper surface, dried, and further subjected to a calendering treatment.

It is important that such a hollow organic pigment is present in a portion near the surface of the base paper. In the present invention, by applying a small amount of a highly opaque pigment (titanium dioxide and / or hollow organic pigment), not only the effect, that is, the effect of improving the so-called opacity can be achieved, but also blanket piling and running troubles (Nepari property) ) Was also reduced or eliminated at the same time. The reason why such an effect is obtained is not clear, but is presumed as follows. That is, the dampening water applied to the paper surface during the offset printing penetrates into the paper layer surface or the inside of the paper layer, and if the wetness with the pulp fiber is too good, the adhesive strength on the paper surface or the inside of the paper layer decreases. However, fine fibers and internal fillers are easily released, causing blanket piling and the like,
By arranging hollow organic pigments having a strong hydrophobicity compared to other inorganic pigments and the like in the portion close to the surface layer, water absorption by dampening water is suppressed, and the emergence of fine fibers and internally added pigments is suppressed. As a result, not only the effect of improving the opacity, but also the generation of paper dust and the like is prevented, and it is considered that blanket piling and running troubles (Nepari property) are improved. In the case of titanium dioxide particles, the reason is not clear, but blanket piling and running trouble (nepari property) are more effectively reduced as compared with other inorganic pigments such as kaolin and calcium carbonate. It turned out to be.

In any case, when the above two types of highly opaque pigments are used in a mixture with a conventionally used water-soluble adhesive such as starch or polyacrylamide, the use of the two types of highly opaque pigments can be compared with the case where the adhesive is used alone. As a result, it was found that the effect of reducing the nepari property and the effect of reducing the blanket piling were large, and the present invention was completed.

As the adhesive used in combination with the highly opaque pigment, various starches, polyacrylamide, etc., as well as carboxymethyl cellulose, methyl cellulose,
Examples include water-soluble cellulose compounds such as hydroxyalkyl cellulose, polyvinyl alcohol and various modified polyvinyl alcohols, and synthetic latexes such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer. Among them, starches and synthetic latexes are particularly preferably used because they have good compatibility with highly opaque pigments and hardly cause aggregation or the like during coating. In addition, in the surface treatment agent, in addition to the specific pigment and the adhesive, a surface sizing agent, an antifoaming agent, a preservative, or an auxiliary agent such as a thickener, which is generally used in the papermaking field, may be appropriately used in combination. Can also.

The mixing ratio of the highly opaque pigment is not particularly limited, but is preferably 30 to 200% by weight based on the total solid content of the adhesive in the surface treatment agent. By the way, if it exceeds 200% by weight, the paper powder may be deteriorated, while if it is less than 30% by weight, the improvement effect desired by the present invention may be insufficient.

The surface treating agent thus obtained is adjusted to a solid concentration of 5 to 30% by weight, and is applied on newsprint base paper to which the above-mentioned hydrated silica is internally added. The dry coating amount is 0.1 to 1.5 g per side of the base paper based on a specific pigment.
/ M ² , preferably 0.2 to 1.0 g / m ² . By the way, when it is less than 0.1 g / m ² , it is difficult to obtain sufficient opacity, and on the other hand, 1.5 g / m ²
If it exceeds, there is a concern that sticking to a blanket or the like due to the nepari property may occur.

According to the above, a surface treating agent containing a specific pigment is applied to the base paper for newsprint and dried. In this case, a coating apparatus is not particularly limited. A blade metering size press, a rod metering size press, a gate roll coater, a blade coater, a bar coater, a rod blade coater, an air knife coater and the like are appropriately used. Above all, when a film transfer type coating device, for example, a coating device using a gate roll coater, a blade metering size press, or a rod metering size press is adopted, the coating film in a film state is transferred to the paper surface, and the surface treating agent is applied to the paper. The preferred embodiment can be a preferred embodiment because it is easy to stay on the surface much, and as a result, the effect of suppressing blanket piling and the effect of reducing the nepari property are large and can contribute to the improvement of the opacity.

The newsprint paper for web offset printing according to the present invention is coated with a surface treating agent on the base paper and dried in the same manner as in the prior art, and then the surface is smoothed to finish the product.
In this case, a calender is usually used for smoothing, but a soft calender having a large smoothing effect without increasing the pressurizing condition is preferably used. Furthermore, the advantage of using a soft calender is that when a soft calender consisting of a metal roll and a resin roll is used, the It is particularly preferably used because it is easy to adjust so as not to crush the sphere.

[0034]

The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to them. The parts and percentages in the examples are unless otherwise specified.
The parts by weight and% by weight are respectively shown.

(Preparation of hydrated silicic acid) [1] Hydrated silicic acid A A silica concentration of 19.7 g prepared from commercially available silicate cullet
/ L, SiO_Two/ Na _TwoNa silicate with a molar ratio of O of 2.84
8390 liters of aqueous lithium solution and 6% w / v sulfuric acid
6850 liter and 8850 liter of sodium aqueous solution
35m of industrial water^ThreeInto the reaction vessel
Umm (# 200 / Kamijima Chemical Industry Co., Ltd.)
0 / IMEX Co., Ltd.) to obtain an average particle size of 0.5 μm.
m (a solid content concentration of 19.1)
(w / v%) was added and the aqueous solution temperature was reduced to 50
° C. While stirring this aqueous solution, the sodium silicate
Sulfuric acid equivalent to 30% of the total sulfuric acid required for neutralization
(20 w / v% concentration, 940 liters) over 12 minutes
Added continuously. 25 minutes after adding sulfuric acid with stirring
Steam to 90 ° C and raise the temperature.
Aged for 10 minutes. Next, neutralize sodium silicate
Dissolves the remaining sulfuric acid and magnesium hydroxide needed to
4550 liters (20
(w / v% concentration) was added continuously over 40 minutes. This
The pH of the slurry at the time of was 5.2. This slurry
After filtration and washing, the obtained hydrated silica was
Average particle size and standard deviation with a particle size analyzer
As a result, they were 19.4 μm and 0.22, respectively.
Was. This hydrated silicic acid sample was designated as hydrated silicic acid A.
A slurry for papermaking having a degree of 10% was obtained.

[2] Hydrated Silicic Acid B In the preparation of Hydrated Silicic Acid A, 940 liters of sulfuric acid added first was changed to 1190 liters without adding magnesium hydroxide, and the remaining amount required to neutralize sodium silicate was added. Except for adding 1000 liters of sulfuric acid, 10% of hydrated silicate B was prepared in the same manner as in the preparation of hydrated silicate A.
A papermaking slurry was obtained. At this time, the average particle diameter and the standard deviation of the hydrated silicate B were 20.3 μm and 0.3 μm, respectively.
It was one.

(Making of base paper for newsprint) A mixture of 7 parts of softwood kraft pulp, 43 parts of thermomechanical pulp, 10 parts of ground pulp, and 40 parts of deinked waste paper pulp was mixed and disintegrated.
S. F. (Canadian Standard Freeness)
A 2% pulp slurry was obtained. The hydrated silicic acid slurries A and B were added to the pulp slurry so that the paper ash content was 3%, and a sulfuric acid band was added at 1% as a solid content per absolute dry pulp to obtain a solid content of 0.5%. %, And used as stocks A and B, respectively. Stock A,
Using B, papermaking was carried out with a twin-wire type paper machine to obtain newsprint base papers A and B each having a rice area of 39 g / m ² .

A mixture of 10 parts of softwood kraft pulp, 20 parts of thermomechanical pulp, 5 parts of ground pulp, and 65 parts of deinked waste paper pulp was mixed and disintegrated. S. F. (Canadian standard freeness) pulp slurry having a concentration of 1.2% was obtained. To the pulp slurry, the above hydrated silica slurry A was added so as to have a paper ash content of 3%, and further, a sulfuric acid band was added at a solid content of 1% per absolute dry pulp so that the solid content concentration was 0.5%. To C. Using the stock C, papermaking was performed with a twin-wire type paper machine to obtain a newsprint base paper C having a rice area of 39 g / m ² .

In addition, talc having an average particle size of 5 μm was added to the above pulp slurry in place of hydrated silicic acid by a paper ash content of 3%.
A newsprint base paper D was obtained in the same manner as in the preparation of the newsprint base paper A, except that it was added so that

Example 1 Oxidized starch dissolved in hot water as an adhesive (trade name: Ace)
A / Oji Cornstarch) 100 parts, average as pigment
In a styrene-acrylic system with a particle diameter of 1 μm and a porosity of 55%
Sky organic pigment (Product name: HP1055 / ROHM & Haas)
Company) 50 parts (as solid content) of 12% solid content
A surface treatment agent was obtained. Use this surface treatment agent for newsprint
Using a gate roll coater on both sides of base paper A,
0.5 g / m in dry weight per surface^TwoCoating so that
After drying, soft curry under the condition of linear pressure 100kg / cm
Underground paper, rice tsubo 40g / m ^TwoOffset web rotation
Newsprint paper for printing was obtained.

Example 2 In Example 1, the pigment (HP 105) in the surface treating agent was used.
Newspaper for rotary offset printing was obtained in the same manner as in Example 1, except that 5) was changed to a hollow organic pigment (trade name: HP91 / Rohm & Haas Co.) having an average particle diameter of 1 μm and a porosity of 50%.

Example 3 In Example 1, the pigment (HP105) in the surface treatment agent was used.
5) was converted to rutile-type titanium dioxide coated with aluminum (trade name: CR50 ... average particle diameter 0.25 μm /
Except for changing to Ishihara Sangyo Co., Ltd., newsprint for offset rotary printing was obtained in the same manner as in Example 1.

Example 4 In Example 1, the pigment (HP105) in the surface treating agent was used.
5) was replaced with anatase type titanium dioxide (trade name: JA-1)
... average particle diameter 0.18 μm / Taika Co., Ltd.), except that newsprint paper for offset rotary printing was obtained in the same manner as in Example 1.

Example 5 Newspaper for offset rotary printing was obtained in the same manner as in Example 1, except that the base paper B was used in place of the base paper A for newsprint.

Example 6 Newspaper for offset rotary printing was obtained in the same manner as in Example 1 except that the base paper C was used in place of the base paper A for newsprint.

Example 7 Newspaper for offset rotary printing was obtained in the same manner as in Example 3, except that the base paper B was used in place of the base paper A for newsprint.

Example 8 A newsprint for offset rotary printing was obtained in the same manner as in Example 3, except that the base paper C was used in place of the base paper A for newsprint.

Example 9 In Example 1, when applying the surface treating agent to the base paper on both sides, a rod metering size press was used, and the amount of application was 0.5 g / m ² per side on a dry weight basis, followed by drying. Thereafter, soft calender paper passing was performed under the condition of a linear pressure of 100 kg / cm to obtain newsprint paper for offset rotary printing of 40 g / m ^{2 in} rice tsubo.

Example 10 The procedure of Example 1 was repeated, except that the machine calender consisting of two metal rolls was subjected to one nip at a linear pressure of 70 kg / cm to perform pressure treatment instead of the soft calender finish. In the same manner as in Example 1, newsprint paper for web offset printing was obtained.

Comparative Example 1 Newspaper for offset rotary printing was obtained in the same manner as in Example 1, except that the base paper D was used in place of the base paper A for newsprint.

Comparative Example 2 A newsprint for offset rotary printing was obtained in the same manner as in Example 3, except that the base paper D was used instead of the base paper A for newsprint.

Comparative Example 3 In Example 1, the pigment (HP105) in the surface treating agent was used.
5) was changed to sedimentable calcium carbonate (trade name: Brilliant S15 / Shiroishi Industry Co., Ltd.), the solid content concentration of the surface treatment agent was 13%, and the dry weight per side was 0.5 g / m ^2.
In the same manner as in Example 1 except that coating and drying were performed, newsprint paper for offset rotary printing was obtained.

Comparative Example 4 In Example 1, the pigment in the surface treating agent was not added.
Newspaper for offset rotary printing was obtained in the same manner as in Example 1 except that the solid content concentration was changed to 6%. Incidentally, the coating amount at this time was 0.3 g / m ² per one side in dry weight.

Comparative Example 5 In Example 5, the pigment in the surface treatment agent was not added.
Newsprint paper for offset rotary printing was obtained in the same manner as in Example 5, except that the solid content concentration was changed to 4%. The coating amount at this time was 0.2 g / m ² per one side in dry weight.

With respect to the thus obtained Examples and Comparative Examples, the newsprint for web offset printing was subjected to the following quality evaluation, and the obtained results are summarized in Table 1.

(Opacity of white paper): The measurement was performed in accordance with ISO2471.

(Print opacity): Printing was performed using an RI printing machine while changing the ink amount of the ink for rotary offset printing (black ink), and when the print surface reflectance was 9%, the back surface reflectance before printing (print surface) The ratio of the back surface reflectivity after printing to the opposite surface) was determined. The reflectance was measured using a spectral whiteness colorimeter (Suga Test Instruments Co., Ltd.).

(Pilling of blanket paper powder): After printing 5,000 copies using an offset printing machine (Komori SYSTEM C-20), four-color printing was performed, and blanket non-image area and image area paper were printed. The degree of powder accumulation was visually determined. : Generation of paper dust is not recognized. △: Generation of paper dust is slightly recognized. ×: A large amount of paper dust is deposited on the blanket.

(Nappari property / blanket adhesive property): Two newsprint samples were cut to an appropriate size, immersed in water for 10 seconds, and then quickly brought into close contact with each other and passed through a calender at a linear pressure of 100 kg / cm. After drying at room temperature for 24 hours, the peel strength of the two sheets of paper was measured using a tensile tester. The higher the value, the stronger the tackiness.

[0060]

[Table 1]

[0061]

As is evident from Table 1, the newsprint for rotary offset printing according to the present invention has little blanket paper powder piling or blanket sticking, is excellent in white paper opacity and print opacity, and has excellent color. It had printability.

Continued on the front page (72) Inventor Hitoshi Matsuda 1-10-6 Shinonome, Koto-ku, Tokyo Oji Paper Co., Ltd. Shinonome Research Center F-term (reference) 4L055 AC09 AG03 AG05 AG19 AG48 AG63 AG71 AG89 AG94 AG98 AH01 AH02 AH37 AJ04 BE02 BE08 CH11 EA04 EA14 EA16 EA18 FA13 FA15 FA21 GA16 GA19

Claims (9)

[Claims] 1. A base paper containing hydrated silica as a filler,
Newspaper for offset rotary printing, which is obtained by applying and drying a surface treatment agent containing titanium dioxide and / or a hollow organic pigment and an adhesive as main components. 2. The newsprint paper for offset rotary printing according to claim 1, wherein the hydrated silicic acid is a hydrated silicic acid having an average particle size of 5 to 30 μm measured according to a laser method. 3. The hydrated silicic acid has an average particle diameter measured by a laser method of 5 to 30 μm, and the standard deviation of the particle volume distribution with respect to the particle diameter when the particle diameter is expressed in logarithm is 0.25.
The newsprint for offset rotary printing according to claim 1 or 2, wherein the following hydrated silica is used. 4. The newsprint for offset rotary printing according to claim 1, wherein the waste paper pulp is contained as a base paper in a solid content ratio of 30% by weight or more based on all pulp constituting the base paper. 5. The newsprint for offset rotary printing according to claim 1, wherein the titanium dioxide is a titanium dioxide having a rutile crystal form and having a surface coated with aluminum. 6. The hollow organic pigment having an average particle diameter of 0.7
The newsprint paper for offset rotary printing according to any one of claims 1 to 5, wherein a hollow organic pigment having a porosity of from 3 to 3 µm and a porosity of from 40 to 85% is used. 7. The coating amount of the titanium dioxide and / or the hollow organic pigment is 0.1 to 1.5 g / m 2 per solid surface.
^The newsprint for offset rotary printing according to any one of claims 1 to 6, which is ² . 8. The method according to claim 1, wherein a film transfer type coating device is used for coating the surface treatment agent.
Newspaper for offset rotary printing according to the above item. 9. The method according to claim 1, wherein after the surface treatment agent is applied and dried, the paper is further passed through a soft calender and smoothed.
The newsprint for offset rotary printing according to any one of Items 1 to 8.