JP2001064894A - Paper for offset printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a paper for offset printing having few adhesion troubles such as surface adhesion, adhesion curl, etc., and slight COD load in a drain by coating a paper base containing deinked pulp with an inorganic surface treating agent consisting essentially of a silica sol or colloidal silica. SOLUTION: A base paper for offset printing containing >=70 wt.% based on the whole pulp components of deinked pulp and having 37-43 g/m2 weight such as newsprint, etc., is coated with 0.1-1.0 g/m2 solid content on both sides of an inorganic surface treating agent comprising a silica sol or colloidal silica (component A) as a main component and 5-50 wt.% based on the component A of an inorganic pigment (component B) such as titanium oxide to give a paper for offset printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing paper having an improved ink inking property, and in particular, has less adhesion trouble such as surface tackiness and tackiness even though it contains tacky foreign matter. In addition, the present invention relates to an offset printing paper having a low chemical oxygen demand (COD) load in wastewater when recycled.

[0002]

2. Description of the Related Art In recent years, the printing technology has been offset printing,
Significant progress has been made in color printing, high-speed mass printing, and automation. Along with this, for printing paper,
Improvements in various physical properties are required from the viewpoint of workability and printability.

[0003] In particular, newsprint paper (newspaper, newsprint paper) is generally made of mechanical pulp or deinked pulp (hereinafter referred to as "pulp").
“Deinked pulp” is abbreviated as “DIP”. ) Is the main type of paper and is classified as middle or lower grade paper. On the other hand, it is necessary to print the specified number of copies reliably within the specified time of the specified time zone. Is a paper that requires stricter quality than ordinary printing paper. Therefore, newspaper printing paper is a special paper, and is also uniquely classified in terms of paper classification. Recent newsprint papers are required to be reduced in weight and to have a high DIP content, and various improvements need to be made while overcoming these disadvantages.
As described above, it is difficult to improve newsprint paper as compared with general high-quality print paper. Therefore, it is difficult to directly transfer the technology of general printing paper to the technology of newsprint paper. However, conversely, it is relatively easy to divert newsprint paper technology to general print paper technology.
Therefore, problems and improvements as offset printing paper will be described below for newsprint paper.

[0004] In recent years, newspaper printing has also been offset from letterpress printing in conjunction with the introduction of computer systems for newspaper printing, in view of the demand for high-speed printing, the demand for color paper, the demand for various types of printing, and the demand for automation. The switch to printing is progressing rapidly.

[0005] Newsprint paper for offset printing is required to have a different quality from newsprint paper for letterpress printing. For example, 1) low surface adhesiveness, 2) low accumulation of paper powder on the blanket, 3) water absorption resistance is maintained moderately, 4) wet strength, low water drainage, etc., 5) The ink setability is appropriate, 6)
High opacity, no set-off, and 7) moderate friction coefficient. Among the required qualities, in particular, 1) reduction of surface tackiness and 2) improvement of surface strength as a measure against paper dust are important issues.

That is, newsprint paper having a high content of mechanical pulp or DIP is different from general printing paper having a low content of mechanical pulp and a high content of bleached hardwood kraft pulp (hereinafter abbreviated as LBKP). There are many fine fibers, and the problem of paper dust is likely to occur. Further, the bonding force between the fine fibers of the mechanical pulp is weak, and the state of the paper surface is rough, so that the paper powder falls off the paper surface and the paper powder is easily deposited on the blanket during printing.

[0007] In addition, the high blending of DIP causes an increase in fine fibers, fillers and pigments derived from DIP, and in combination with weight reduction, causes problems such as an increase in paper powder and a decrease in paper strength. Furthermore, DIP manufactured from used magazine paper has hot melt adhesives, acrylic adhesives,
Adhesives such as vinyl acetate adhesives are included.
If a large amount of this sticky substance is present on the paper surface, when the paper passes through a paper machine or printing machine, it will adhere to the canvas, belt, roll surface, etc., which comes into contact with the paper, causing a problem of paper breakage or perforation of the paper (adhesion trouble) Occurs. In particular, this tendency is remarkable in an offset rotary printing press of a type in which a steel belt is brought into contact with a winding surface to control the running property of a sheet,
The paper surface adheres to the steel belt, causing troubles such as paper breakage and perforation (stickiness).

[0008] Possible means for suppressing the stickiness include removal and fine dispersion of the sticky substance from the raw material, change of the raw material composition, change of papermaking conditions, and application of a surface treatment agent. However, at present, centrifugal treatment, cleaner treatment, and mechanical dispersion cannot sufficiently remove or disperse. In addition, changes in the raw material composition and the papermaking conditions hardly produced any effect on the adhesive tackle.

On the other hand, as a measure for improving the surface strength, a newsprint paper base paper is coated with a surface treating agent comprising a water-soluble organic polymer such as starch, modified starch (eg, oxidized starch and starch derivatives), polyacrylamide, and polyvinyl alcohol. Engineering (external)
Although it is known to use a large amount of a surface treatment agent to suppress stickiness by this method, then, during offset printing or during production, the surface treatment agent is affected by the dampening solution. The tackiness (a phenomenon called so-called "Nepari") increased and was not practical at all.

Particularly in an offset printing machine used for full-color printing, which has recently been developed in newspaper printing, since the paper surface is moistened with dampening water four times, the problem of Neppari is even more remarkable. A phenomenon in which the black ink is poorly deposited after yellow color printing, that is, poor wet ink deposition is likely to occur.

In addition, when the surface treatment agent is applied by a film transfer method such as a gate roll coater, the surface treatment agent is localized on the surface of the paper as compared with a two-roll size press. Was a more prominent and serious problem.

In this regard, an anti-adhesion agent which is added to a surface treatment agent to improve releasability is disclosed. Japanese Patent Application Laid-Open No. 6-57688 discloses an anti-adhesion agent comprising an organic fluoro compound. Japanese Unexamined Patent Publication (Kokai) No. 6-92995 discloses an anti-tackiness agent containing a substituted succinic acid and / or a substituted succinic acid derivative as an active ingredient.

Further, San Nopco Co., Ltd. introduces the application of ammonium zirconium carbonate as a measure against pitch and sticky substances in the paper industry (Paper Engineering Co., Ltd., VOL.52, NO.2, PAG).
E.184-191, 1998). The feature utilizes metal ions,
It has excellent cross-linking reactivity with carboxyl groups and hydroxyl groups, and reacts with functional groups of pitch, latex and the like to reduce adhesiveness. Furthermore, in HALL JD, etc., it is impossible to remove very small sticky substances with a particle size of 150 microns or less by a mechanical method, and it is necessary to prevent the sticky substances from depositing and clumping, It states that the use of cationic and nonionic polymers is effective but has limitations (TAPPI Proc. Recycl Sym
p. 1998, PAGE. 73-77, 1998).

JP-A-5-59689 and JP-A-5-295693 disclose paper sizing agents comprising polyvinyl alcohol and a polyether compound. In particular, JP-A-5-59689 discloses that when a composition comprising a block copolymer of ethylene oxide and propylene oxide and polyvinyl alcohol is applied to newsprint base paper,
It is disclosed that newsprint paper having improved surface strength and low tackiness during offset printing can be obtained. These surface treatment agents can improve the adhesiveness of the paper surface, that is, Nepali to some extent, as compared with the case where starch or polyvinyl alcohol is applied alone, but it has no effect on the improvement of the adhesive mask, It was not possible to improve the wet ink deposition.

Therefore, when a conventional surface treatment agent is applied by a film transfer system such as a gate roll coater, it is difficult to improve the inking failure and surface tackiness (Nepari) of the ink during offset printing. Also, it has been extremely difficult to prevent troubles such as sticky marks when the sticky substance is mixed into the paper from the raw material and internal addition processes.

In addition, the surface treating agent composed of a water-soluble organic polymer is eluted in wastewater in the recycling process, and the chemical oxygen demand (hereinafter abbreviated as COD) load of the wastewater and the biological oxygen demand (hereinafter referred to as COD). (Abbreviated as BOD) increases the load. Since the eluted surface treatment agent becomes a nutrient source of microorganisms, it promotes the expression of slime, and further causes new problems such as a possibility that the slime, filler and hydrophobic component may become composite particles.

[0017]

Therefore, in the present invention,
Despite containing a DIP containing an adhesive, it has sufficient surface strength, has improved surface adhesiveness (Nepari) and adhesiveness, and has excellent ink-adhesiveness. An object of the present invention is to provide an offset printing paper having a small COD load in drainage.

[0018]

Means for Solving the Problems The present inventors have applied an inorganic surface treatment agent mainly composed of silica sol or colloidal silica (component A) to a printing base paper, so that the adhesive surface and the ink coating The inventors have found that the properties and Nepari are improved, and solved the above-mentioned problems. In addition, it has been found that by adding an inorganic pigment (component B) in addition to component A, opacity can be simultaneously improved.

As an example of using colloidal alumina or colloidal silica or silica sol as a surface treatment agent, Japanese Patent Application Laid-Open No. 4-12879 discloses a method for printing various kinds of printing materials such as synthetic resin films with respect to 100 parts by weight of colloidal alumina.
It is disclosed that an aqueous dispersion to which a surfactant is added by weight or less is applied and printing is performed. JP-A-4-327297 discloses an anti-slip agent comprising whisker and colloidal alumina and colloidal silica. JP
JP-A-6-48022 describes colloidal alumina and silica sol as a coating composition of an inorganic colloid in order to improve the fixation of toner on carbonless copy paper. JP-A-10-131091 discloses newsprint paper for electrocoagulation printing provided with a coating layer mainly composed of silica sol or colloidal silica and a binder. Furthermore, the use of colloidal silica to increase the coefficient of friction of corrugated board to prevent slippage has been described by Inoue et al. (M. Inoue, N. guruna).
gul, and P.Aroca, Tappi Journal, 72 (12), 81-85,199
0). Similarly, C.I. H. Fletcher discusses the use of colloidal silica as a friction-increasing material for paper in a report entitled "Anti-Slip Treatment Using Colloidal Silica" (CHFletcher, Tappi Journal 1973, 56 (8),
81-85).

In addition, there are many documents describing that the addition of colloidal silica to paper stock improves the yield of fillers and fine fibers during papermaking. However, in the above-mentioned known documents, it is possible to improve adhesive tackiness and surface tackiness (Nepari) by applying an inorganic surface treatment agent mainly composed of silica sol to printing paper, especially newsprint, and to improve offset. There is no description for the purpose of improving the ink inking property at the time of printing.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail, but the description has been made by taking as an example the newsprint paper on which the present invention works most effectively.

The component A used in the inorganic surface treating agent of the present invention usually contains 30 to 40% of silicic anhydride, the content of sodium calculated as sodium oxide is 1% or less, and the pH is 9.5 to 9.5. 10.5 colloidal silica or silica sol. Silicic anhydride is used in aqueous dispersions of SiO ₂
XH ₂ O, ultrafine particles having a particle size of 4 to 100 nm, and spherical and linear shapes. Since the particle size is very small, it easily penetrates into the paper layer and has strong adsorption or adhesion between silica fine particles and between silica fine particles and pulp. By applying this silica sol-based inorganic surface treating agent to printing paper base paper, surface tackiness (Nepari) is remarkable due to dampening water during offset printing as compared with the conventional coating of a water-soluble polymer compound. To decline.
This is because the inorganic surface treatment agent composed of silica once dried does not dissolve or swell with water unlike the organic polymer. Further, even if the printing paper contains an adhesive, the adhesive is covered with the coating made of silica, and thus it is considered that the adhesive stickiness is suppressed.

Component B used in the inorganic surface treating agent of the present invention is an inorganic pigment such as calcium carbonate, kaolin, clay, talc, silica, white carbon, titanium oxide or the like, which is usually used as a filler for papermaking and a pigment. is there. As the titanium oxide, titanium oxide and hydrated titanium oxide having a specific gravity of about 3.8 to 4.2, which are usually used for papermaking or condensers, are preferable. As for the form of the crystal, either a rutile type or an anatase type can be used.

The amount of component B relative to component A is
Although it varies depending on the type of the base paper, the composition of the base paper, and the amount and type of the internal additive in the base paper, it is preferable to add 20 to 50% by weight to the component A. By blending the component A in the range of 20 to 50% by weight, the balance between the opacity and the surface tackiness of the printing paper can be made appropriate.

The inorganic surface treating agent of the present invention may be mixed with an inorganic material or a very small amount of an organic material as long as the surface tackiness is not deteriorated.
It should be kept to a minimum as it will increase the load.

The base paper for newsprint used in the present invention is ground pulp (GP) or thermomechanical pulp (TM).
P), mechanical pulp such as semi-chemical pulp (M
P), chemical pulp (CP) typified by kraft pulp (KP), and deinked pulp (DIP) obtained by deinking waste paper containing these pulp or obtained by disintegrating waste paper from the papermaking process. The recovered pulp or the like is used alone or mixed at an arbitrary ratio. Prominent effect of the present invention is a base paper sheet forming the basis weight of ^{37g / m 2 ~43g / m 2} . In the case of base paper having a basis weight of 46 g / m ² or more, the base paper is considered to have sufficient surface strength, and the dimensional change of the paper due to the dampening solution during offset printing or the reduction in strength is ignored. Since it is considered to be possible, it is not always necessary to improve the surface strength by externally adding a chemical.

On the other hand, the blending ratio of DIP of the base paper used in the present invention may be blended in an arbitrary range (0 to 100% by weight). In view of the recent trend of DIP enrichment, the range of 30 to 100% by weight per total pulp component is more preferable.
In particular, the present invention is effective for base paper containing 70% by weight or more of DIP. As described above, it is also possible to use DIP manufactured from magazine wastepaper containing an adhesive.

This newsprint base paper is made of an inorganic filler such as white carbon, clay, kaolin, silica, talc, titanium oxide, calcium carbonate or the like, or a synthetic resin (vinyl chloride resin, polystyrene resin, urea formalin resin, melamine resin). Resin, styrene / butadiene copolymer resin, etc.). In particular, calcium carbonate is effective for neutral papermaking.

If necessary, a paper strength enhancer such as polyacrylamide polymer, polyvinyl alcohol polymer, cationized starch, urea / formalin resin, melamine / formalin resin; copolymerization of acrylamide / aminomethylacrylamide Drainage or retention improver such as salt of the product, cationized starch, polyethyleneimine, polyethylene oxide, acrylamide / sodium acrylate copolymer; reinforced rosin sizing agent (adding maleic anhydride or fumaric anhydride to rosin A partially maleated or fumarated rosin, completely saponified with alkali to form a solution), an emulsion sizing agent (partially maleated or fumarated rosin, a rosin soap or various surfactants as an emulsifier, Dispersed in , Synthetic sizing agent (sizing agent using petroleum resin obtained by copolymerizing C ₃ -C ₁₀ fraction obtained from a naphtha fraction), reactive size (AKD, alkenylsuccinic anhydride) sizing agents and the like; aluminum sulfate (Sulfuric acid band), an auxiliary agent such as a waterproofing agent, an ultraviolet ray inhibitor, and a fading inhibitor. Considering recyclability,
Auxiliaries that can reduce the COD load as much as possible are preferred. The physical properties of the base paper need to be such that it can be printed by an offset printing machine, and may have any properties such as tensile strength, tear strength and elongation comparable to those of ordinary newsprint paper.

The newsprint base paper of the present invention may be an acidic newsprint base paper or a neutral or alkaline newsprint base paper.

The coating amount of the inorganic surface treating agent of the present invention should be determined according to the degree of surface strength required for the printing paper to be produced, and is not particularly limited. From the viewpoint of imparting surface strength, the surface treatment agent of the present invention has a coating amount (in other words, the sum of the solid contents of the components A and B) of 0.1 to 1.0 g / m ² (per surface ), The effect is effectively exhibited. Coating amount
If the amount is less than 0.1 g / m ² , the effect of improving the ink inking property, preventing the paper powder from falling off, and the effect of lowering the adhesion to the sticky substance on the paper surface are insufficient. On the other hand, even if the coating amount is more than 1.0 g / m ² ,
The effect of lowering the tackiness reaches a plateau and is uneconomical in cost due to an increase in the drying load and the like. Considering the application to newsprint paper, as described above, it is desirable to improve the surface strength and adhesiveness in a well-balanced manner using only an inorganic surface treating agent. Is most preferably in the range of 0.3 to 1.0 g / m ² (per side).

The newsprint paper of the present invention is produced by applying a coating solution containing the inorganic surface treating agent of the present invention to one or both sides of the base paper of the newsprint paper using a coating machine. As a coating machine, it is preferable to apply using a coat transfer type coater such as a gate roll coater, a blade metalling coater, a rod metaling coater,
In particular, when a gate roll coater is used, the effect is large. That is, as described above, conventionally used surface treatment agents, in a gate roll coater, had a problem in tackiness when having sufficient surface strength, the surface treatment agent of the present invention, Even in this method, the on-machine coating is performed at a coating speed of 600 to 1800 m / min within the above-described coating amount, and the surface strength is efficiently increased.
It is also possible to improve the surface tack.

In the case of newsprint paper, the smoothness of the paper surface is low, and it is difficult to provide an inorganic barrier layer on the paper surface in a low coating amount region by external addition (particularly, a gate roll coater method). It has been said that. However, the inorganic surface treating agent of the present invention has a papermaking speed of 600 to 1800.
m / min and a relatively low coating amount.
There is an excellent feature that the surface strength with little tackiness and the effect of imparting ink inking property are recognized.

Newsprint paper coated with the inorganic surface treating agent of the present invention does not show a decrease in the coefficient of friction. Therefore,
It is not particularly necessary to mix an anti-slip agent. When applied to newsprint paper, the dynamic friction coefficient of the manufactured newsprint paper is
It is desirable to be in the range of 0.40 to 0.70.

The newspaper printing paper coated with the inorganic surface treating agent of the present invention can control the surface strength in a wide range, so that it can be widely used for various inks used in printing. For example, special inks such as emulsion ink in which dampening water is mixed in oil-based ink, and inks having high tackiness for lithographic printing without water can be used.

As mentioned above, the improvement of newsprint paper is as follows.
Difficult compared to general high quality printing paper. For this reason, it is difficult to divert the technology for general printing paper directly to the technology for newsprint paper, but conversely, the technology for newsprint paper is diverted to the technology for general printing paper. It is easy. Therefore, the inorganic surface treatment agent of the present invention,
The invention can be applied not only to newsprint paper but also to general print paper, and the same effect as that of newsprint paper can be obtained.

[0037]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the description, parts and percentages indicate parts by weight and percentage by weight, respectively.

<Preparation of Coating Solution: Component A> Component A of the present invention
The inorganic surface treatment agent of the present invention was prepared by diluting the aqueous solution of silica sol corresponding to the above to a predetermined concentration. A coating solution that is emulsified or produces an insoluble precipitate when diluted is not preferable when performing gate roll coating. Further, it is not preferable that the coating liquid is suspended while repeatedly passing through the roll for a long time. Therefore, component A
Was subjected to a gum shear test using a Malone test machine (manufactured by Kumagai Riki Co., Ltd.) with a mechanical shear (1000 rpm, 30 minutes), and no gum up was observed. . Therefore, the inorganic surface treating agent containing the silica sol of the present invention had excellent suitability as a gate roll coating solution.

<Manufacture of newsprint base paper> DIP (deinked pulp) 35 parts, TMP (thermomechanical pulp) 30
Parts, 20 parts of GP (ground pulp) and 15 parts of KP (kraft pulp). The mixed pulp having a freeness adjusted to 200 ml was mixed with a Berbe-former type paper machine.
Papermaking at a papermaking speed of 1100 m / min to 1200 m / min,
A no-calendar newsprint base paper was obtained. This base paper has a basis weight of 43 g / m ² , a density of 0.65 g / cm ³ , a whiteness of 51%,
The smoothness is 60 seconds, the static friction coefficient is 0.45, and the dynamic friction coefficient is 0.56.
The base paper was equivalent to general newsprint paper. This base paper did not contain an internal sizing agent, and had a water absorption resistance of 5 to 7 seconds by a drip water absorption method.

[Examples 1 to 3] An aqueous solution of silica sol (trade name: Snowtex 40, manufactured by Nissan Chemical Industries) as component A was diluted to a concentration of 5.0%, 10.0%, 23.6% (solid content% by weight). Three types of coating liquids were prepared. These coating liquids were applied to the F side of the above newsprint base paper at a coating speed of 300 m / min using a gate roll coater.
After the application, a super calender treatment was performed to produce three types of newsprint papers with different coating amounts. The coating amount, peel strength, ink inking property, static friction coefficient, dynamic friction coefficient, and COD of this newsprint paper were measured by the following methods, and the results are shown in Table 2.

Measurement of coating amount: The coating amount of silica sol was calculated assuming that the thickness of the liquid film on the applicator roll was 1.2 μm and the transfer rate was 95%. In the case of starch, the coating amount is 10 cm x 10 cm sample, and 50 ml of distilled water
The mixture was kept in a boiling water bath for 1 hour to extract starch. After filtration, the filtrate was diluted to 100 ml and the 10 m
l. In the case of starch, 2N-hydrochloric acid 2.5m
1) Add 2.5 ml of potassium iodide / iodine solution to dilute the total volume to 50 ml. The absorbance at 580 nm was measured, and the amount of starch was calculated from a previously prepared calibration curve. In the case of polyacrylamide, determine the nitrogen content by the Kjeldahl method,
Converted. Measurement of surface strength: 10,000 copies were printed with an Apollo printing machine, and the amount of paper dust deposited on the non-image area of the blanket was visually evaluated. Evaluation criteria:: Generation of paper dust is slightly observed, but there is no practical problem. : Generation of paper dust is clearly recognized. ×: Paper dust is deposited, and the non-image area of the bun ranket looks white. -Measurement of peel strength: Two pieces of newsprint paper were cut into 4 x 6 cm, and the coated surfaces were immersed in water at a temperature of 20 ° C for 5 seconds, and the coated surfaces were brought into close contact with each other. Newsprint paper base paper is laid on both outer sides and passed through a roll at a pressure of 50 kg / cm.
H was conditioned for 24 hours. After forming a sample piece of 3 × 6 cm, the measurement was performed with a tensile tester at a tensile speed of 30 mm / min. The high value of the initial peel strength was defined as the peak value. Next, the value of the stable peel strength was defined as a stable value. The larger the measured value of the peeling strength, the more difficult it is to peel off (in other words, the stronger the adhesiveness). In the newsprint paper of the present invention, evaluation was made based on the stable value of the peel strength, and those having a stable value of the peel strength of 15.0 gf / 3 cm or less were regarded as “having good peelability, that is, low surface tackiness”. . Evaluation of ink inking property: Using a Prüfbau printing tester, ink: News king Sumi HM, dampening water volume: 80 μl,
Printing is performed under the conditions of printing pressure: 125 N / cm, printing speed: fountain solution portion 3 m / sec, and printing portion 6.8 m / sec (the time from application of the fountain solution to transfer of ink is 0.15 sec.). When the dampening solution is not attached (dry) and the dampening solution is attached (wet), the stamp surface density is measured with a Macbeth densitometer,
The inking property of the ink was evaluated.・ Measurement of COD: JIS K 0101 “17.
Consumption by potassium permanganate (CO2)
D _Mn ) ", 43 g of newsprint paper was redissolved in 1 kg of water, and the COD of the filtrate was measured.

[Comparative Example 1] The base paper for newsprint used in Example 1 was subjected to a supercalender treatment, and the coating amount, peel strength, ink adhesion, static friction coefficient, dynamic friction coefficient, and COD were measured. The results are shown in Table 2.

Comparative Example 2 Instead of the silica sol used in Example 1, polyacrylamide (trade name: P-12)
0, manufactured by Seiko Chemical Co., Ltd.) was applied to the F surface at a coating speed of 300 m / min using a gate roll coater.
After coating, a super calender treatment was performed to obtain newsprint paper. The coating amount, peel strength, ink inking property, static friction coefficient, dynamic friction coefficient and COD of this newsprint paper were measured, and the results are shown in Table 2.

[Comparative Example 3] Instead of the silica sol used in Example 1, a 10% aqueous solution of oxidized starch (trade name: SK-20, manufactured by Nippon Cornstarch) was used as a base material for newsprint paper.
Using a gate roll coater on the surface, coating speed 300m /
Minutes. After coating, a super calender treatment was performed to obtain newsprint paper. About this newsprint paper,
The coating amount, peel strength, ink adhesion, static friction coefficient, dynamic friction coefficient, and COD were measured, and the results are shown in Table 2.

[0045]

[Table 1] The surface strength of the newsprint papers of Examples 1 to 3 had no practical problem. The results of the inking test of newsprint paper are shown in Table 2. As shown in Table 2, the printing surface density when printing was performed without dampening water (dry) and the printing when wet printing was performed with dampening water applied The difference between the densities of the stamped surfaces was small, and the wet ink deposition property was improved. In addition, the wet ink inking property after water adhesion by the Prüfbau of Examples 1 to 3 was compared with Comparative Examples 1 to 3.
The level was higher than that of No. 3. The newsprint papers of Examples 1 to 3 did not show adhesiveness, and the peel strength could not be measured. In addition, the coefficient of static friction and the coefficient of dynamic friction improved. In addition, based on the results of the ink deposition test of these newsprint papers, it was proved that the surface treatment agent containing silica sol as a main component (including other inorganic materials such as titanium) was extremely excellent in terms of printing operability. Was. When the COD of the filtrate of the newsprint papers of Examples 1 to 3 was measured, it was almost the same as Comparative Example 1, and the COD value corresponding to the coating amount did not increase. That is, when recycled, the COD load of the wastewater did not increase. On the other hand, for the newsprint papers of Comparative Examples 1 to 3, the printing surface density and the dampening solution when printing was performed without the dampening solution (dry) were applied (wet).
The difference from the printing surface density at the time of printing was large, and the wet ink deposition was poor. When the COD of the filtrate of the newsprint papers of Comparative Examples 1 to 3 was measured, the COD value corresponding to the coating amount was increased. In other words, if you recycle,
COD load in drainage increased. In addition, although the uncoated newsprint paper of Comparative Example 1 had good wet-adhesiveness, the surface strength was weak, and the amount of paper powder falling off during long-run printing was large, making it practical.

Example 4 A 10% aqueous colloidal silica solution (trade name: Snowtex 40, manufactured by Nissan Chemical Industries, Ltd.) as component A, and titanium oxide (trade name: TYPE-T
(W-10, manufactured by Ishihara Sangyo Co., Ltd., X-ray particle size: 150 nm) was prepared as a solid content and mixed at a ratio of 1: 1 in advance, diluted and diluted to obtain a solid content of 6 containing the two components A and B. % Coating solution was prepared. The obtained coating liquid was applied to the F side of the aforementioned newsprint base paper using a plain Mayer bar.
After coating, a super calendar treatment was performed to produce newsprint paper, and the coating amount, peel strength, and opacity were measured.
It was shown to. Opacity is measured according to JIS P 8138-1
976.

Example 5 A 10% aqueous solution of silica sol (trade name: Snowtex 40, manufactured by Nissan Chemical Industries) was used as the component A, and light calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Kogyo) was used as the component B. To prepare a dispersion mixed at a ratio of 1: 1 and dilute to prepare a mixture of components A and B.
A coating solution having a solid content of 6% including the two was prepared. The obtained coating liquid was applied to the F side of the aforementioned newsprint base paper using a plain Mayer bar. After coating, a super calender treatment was performed to produce newsprint paper, and the coating amount, peel strength, and opacity were measured.

Example 6 A 10% aqueous solution of silica sol (trade name: Snowtex 40, manufactured by Nissan Chemical Industries, Ltd.) was used as component A, and white carbon (trade name: Nipple E-75, manufactured by Nippon Silica) was previously solidified as component B. A dispersion liquid mixed at a ratio of 1: 1 was prepared, diluted and diluted with components A and B.
A coating solution having a solid content of 6% including the two was prepared. The obtained coating liquid was applied to the F side of the aforementioned newsprint base paper using a plain Mayer bar. After coating, a super calender treatment was performed to produce newsprint paper, and the coating amount, peel strength, and opacity were measured.

Comparative Example 4 The base paper for newsprint used in Example 1 was subjected to a supercalender treatment, and the peel strength and the opacity were measured.

[Comparative Example 5] With respect to the base paper for newsprint used in Example 1, an aqueous solution of silica sol having a concentration of 6% (trade name: Snowtex 40, manufactured by Nissan Chemical Industries, Ltd.) was applied to the F side of the base paper for newsprint paper described above. , Using a plain Mayer bar. After coating, a super calender treatment was performed, and the coating amount, peel strength, and opacity were measured.

[0051]

[Table 2] As shown in Table 2, the newsprint papers of Examples 4 to 6 coated with a surface treatment agent composed of silica sol and an inorganic pigment did not show any tackiness, and thus the peel strength could not be measured. The opacity was improved despite the low coating amount. On the other hand, newsprint paper coated with the surface treatment agent consisting of only the silica sol of Comparative Example 5 did not show any tackiness, but did not clearly show an improvement in opacity as compared with Comparative Example 4.

<Evaluation of Anti-stickiness> The following experiment was conducted to show how the surface treating agent of the present invention has an effect of preventing adhesiveness against the adhesive. An acrylic adhesive (trade name: PZ-8) which is usually used as the adhesive material for the backing paper of magazines on the above newsprint base paper
04, manufactured by Seiden Chemical Co., Ltd.) and a vinyl acetate-based adhesive (trade name: GH-451, manufactured by Siden Chemical Co., Ltd.) using a plain bar to give a coating amount of 1.5 g / m ² . Using a plain bar again, an aqueous solution of silica sol (trade name: Snowtex 40, manufactured by Nissan Chemical Industries) was applied to the adhesive-coated surface of the base paper of newsprint paper coated with these two adhesives in an amount of 0.1 g. / M ² and 0.5 g / m ² to prepare newsprint paper. For comparison,
Using a plain bar, an aqueous solution of an adhesive coated with nothing and an aqueous solution of oxidized starch (trade name: SK-20, manufactured by Nippon Cornstarch Co., Ltd.) were applied to a coating amount of 0.5 g / m ² using a plain bar. Coated newsprint papers were prepared, and the coated surfaces of these newsprint papers were passed through a roll at a pressure of 50 kg / m ² and adhered. The test piece was 3 × 6 cm, and the peel strength was measured using a tensile tester at a pulling rate of 30 mm / min. Table 3 shows the stable value of the peel strength.

[0053]

[Table 3] As shown in Table 3, the newsprint paper coated with the silica sol did not show any tackiness, so that it was impossible to measure the peel strength. That is, even if the paper contains a large amount of the adhesive substance, the generation of the adhesive gray can be suppressed.

[0054]

According to the present invention, an inorganic surface treatment agent mainly composed of silica sol is used to obtain newsprint paper in which the peel strength (Nepari) is suppressed and the ink adhesion is improved. By applying the inorganic surface treatment agent of the present invention with a gate roll coater, it has become possible to obtain a printing paper having a good balance of ink deposition and releasability. In particular, newsprint paper suitable for continuous high-speed offset printing is obtained. Furthermore, the coating agent when recycled is greatly reduced or eliminated the adhesiveness of the adhesive foreign matter caused by the acrylic, vinyl acetate and hot melt type back glue mixed in the DIP. The result that the COD load of the wastewater is small is obtained. In addition, by arbitrarily changing the coating amount, the mixing ratio, the type of the material, and the like of the inorganic surface treating agent of the present invention, it is easy to cope with a wide variety of products.

Continued on the front page (72) Inventor Toshiyuki Takano 5-21-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Central Research Laboratory (72) Inventor Toshiaki Minami 5-2-1-1, Oji, Kita-ku, Tokyo Nippon Paper Co., Ltd. F-term in the Central Research Laboratory of the Company (reference) 4L055 AC09 AG12 AG18 AG19 AG97 AH02 AH37 AJ04 BE08 EA04 EA08 EA32 FA15 FA30 GA16 GA19

Claims (6)

[Claims] 1. Offset printing paper obtained by applying an inorganic surface treatment agent mainly composed of silica sol or colloidal silica (component A) to a base paper for offset printing. 2. The offset printing paper according to claim 1, wherein the offset printing base paper is a newsprint base paper. 3. The inorganic surface treating agent according to claim 1, comprising an inorganic pigment (component B).
Or the offset printing paper according to claim 2. 4. The offset according to claim 1, wherein an addition ratio of the component B to the component A is 5 to 50% by weight in the inorganic surface treating agent according to claim 1. Printing paper. 5. The base paper for newspaper printing has a basis weight of 37 g / m ² to 43 g
claim 2 or claim 3 for offset printing newsprint according, characterized in that it is a range of g / m ^2. 6. The newspaper for offset printing according to claim 2, wherein the newsprint base paper contains at least 70% by weight of deinked pulp based on all pulp components. Paper.