JP2812016B2 - Coated paper for gravure printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for gravure printing. More specifically, the present invention relates to a coated paper for gravure printing which is obtained at low cost and has excellent suitability for gravure printing.

[0002]

2. Description of the Related Art In recent years, the visualization of the printing and publishing industries,
The tendency of colorization becomes strong, and coated paper such as coated paper (one-side coated amount of 10 to 20 g / m ² ), art paper (one-side coated amount of 20 to 25 g / m ² ), cast coated paper (one-side coated amount) The demand for pigment coated paper such as 25 g / m ² or more, medium coated paper and finely coated paper (15 g / m ² or less on one side) is remarkably growing, and its use is also diversified. It is expanding.

[0003] In particular, in recent years, in recent publications, the use of coated paper for gravure printing having an excellent printing effect is increasing. In particular, demands for medium coated paper containing mechanical pulp, deinked pulp and the like are increasing from the viewpoint of cost reduction and global environmental problems.

Conventionally, softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP) have been mainly used as raw materials for coated paper for gravure printing, but recently refiner ground pulp (RGP) has been used. And mechanical pulp such as thermomechanical pulp (TMP) and stone ground pulp (GP) are also being used for the purpose of cost reduction, improvement of opacity, and the like.

[0005] Further, recycling of used paper has become important in view of the problem of the global environment. Deinked pulp (hereinafter, referred to as DIP) recycled from used paper is also used as raw material pulp for medium coated paper for gravure printing. It is also well known that one of them can be used.

It is necessary to use a neutral sizing agent from the viewpoint of making the coated base paper by the neutral papermaking method. For this purpose, well-known alkenyl succinic anhydride (ASA) and alkyl ketene dimer are used. (AKD) sizing agents are commonly used.

[0007] Further, at the time of papermaking of coated base paper, an internal filler is contained as ash in an amount of about 10% by weight per pulp for the purpose of improving opacity. As the internal filler, talc, clay, heavy calcium carbonate, and light calcium carbonate are used.

[0008] However, there is almost no known literature examining the effect of the internal filler on the gravure printing suitability, and even more, the crystal state of light calcium carbonate for internal addition to the coated base paper of the present invention (X-ray diffraction in the present invention). Value of 2θ of 29 °; C value and intensity value of 2θ of 26 °; ratio of A value; C / A
There is no known literature relating to coated paper for gravure printing mentioned above.

[0009] On the other hand, many proposals have already been made for the coating method and the coating pigment. For example, Tokuho 1-224
00, Japanese Patent Publication 2-58400, Japanese Patent Publication 2-59181,
There are JP-A-3-40897, JP-A-3-40895, JP-A-3-82897, and the like, all of which are related to coating pigments.
6898 and JP-A-3-97997.

As a coating method, a size press, a gate roll coater, an air knife coater, a roll coater, a blade coater and the like well known in the art can be used as appropriate.

However, as described above, no study has been made on the filler used in the coating base paper of the coated paper for gravure printing, or even on the crystalline state of light calcium carbonate.

[0012]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present inventors have proposed light weight calcium carbonate used as an internal filler in coated base paper to reduce the cost of gravure printing coated paper and improve gravure printing suitability. As a result of diligent research on the crystal state of the compound, it was found that the difference in the crystal structure of light calcium carbonate greatly affected the suitability for gravure printing, and the present invention was completed. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a gravure printing coated paper in which the cost of the gravure printing coated paper is reduced and printing suitability such as missing dots is improved.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a gravure printing coated paper in which a coating composition is coated in two steps of undercoating and overcoating on a coated base paper made by a neutral papermaking method. The ratio of the intensity value (C value) when 2θ is 29 ° and the intensity value (A value) when 2θ is 26 ° (C / A ratio) is 20 or less by X-ray diffraction as an internal filler 10 to 25% by weight of calcium carbonate based on pulp;
The coated paper after step coating is calendered to smoothness (JIS
P 8119) for 3000 seconds or more.

As the pulp for coating base paper used in the present invention, the aforementioned LBKP and NBKP can be used. Other pulp includes RGP, TMP,
GP, DIP, etc. can be used. As the type of waste paper for DIP, newspaper waste paper, high-quality waste paper, office waste paper, and the like can be used.

As the DIP, pulp obtained by disintegrating waste paper with a disintegrator such as a pulper, bleaching with a bleach such as hydrogen peroxide or a screen or a cleaner is usually used. These pulp can be used by appropriately changing the mixing ratio.

From the viewpoint of cost reduction, it is desirable to mix as much DIP as possible, mainly composed of used newspaper and the like.

In the coated base paper of the present invention, the DIP can be blended in an amount of from 50% by weight to 95% by weight. NB corresponding to less than 50% by weight of DIP
When KP and LBKP are increased, not only the opacity is reduced but also the cost is increased. If it exceeds 95% by weight, there is a problem that paper breakage occurs during paper making.

As the internal filler, talc, clay, heavy calcium carbonate, titanium dioxide and the like are known. In the present invention, light calcium carbonate is converted to ash based on 10 parts per pulp.
The light calcium carbonate crystals used are X-ray diffracted, and the 2θ of X-ray diffraction is 29 ° and the intensity value (C value) is 2%.
One of the features of the present invention is that the intensity ratio (C / A value) to the intensity value (A value) when θ is 26 ° is 20 or less. C /
The lower limit of the A value is preferably about 5.

When the C / A value exceeds 20, there is a problem that the smoothness is hardly obtained when the undercoating and the overcoating are performed on the coated paper calendering. On the other hand, when the C / A value is 20 or less, the smoothness after the calendering treatment is easily obtained. The degree can be increased to 3000 seconds or more, and there is an advantage that good results are obtained in gravure printing suitability.

Light calcium carbonate can be produced by hydrating quicklime to form slaked lime slurry and introducing waste gas such as caustic kiln waste gas in the pulping process. The desired C / A ratio of the present invention can be changed by adjusting the reaction conditions (concentration of slaked lime slurry, reaction gas introduction speed, stirring conditions, introduction of seed crystals, etc.).

The average particle size of the light calcium of the present invention is desirably 3 to 4 μm from the viewpoint of using as an internal filler and increasing the yield on paper as much as possible. With respect to this particle size, a substantially desired particle size can be obtained by adjusting the above reaction conditions.

The addition rate of the internal filler is determined in relation to the opacity, the softness of the paper, and the like. In the coated paper for gravure printing of the present invention, the addition rate of the filler has a subtle effect. When the coated paper is calendered when ash content of the paper is added in the range of 10% by weight to 25% by weight based on pulp, the smoothness tends to be easily obtained. Therefore, the above-mentioned light calcium carbonate is added to the coated base paper as ash in an amount of 1 to pulp.
It is also an important element of the present invention to contain 0 to 25% by weight.

When the above light calcium carbonate is contained in the coated base paper as ash less than 10% by weight based on pulp,
Even if the coated paper after the coating is calendered, the smoothness becomes difficult to appear. When the content exceeds 25% by weight, there is a problem that the surface strength is reduced.

As the sizing agent for neutral papermaking of the present invention, any of an alkenyl succinic anhydride (ASA) and an alkyl Tekken dimer (AKD) can be used.

As the undercoating composition of the present invention, known coating compositions comprising pigments such as heavy calcium carbonate and kaolin can be used. Has already proposed (Japanese Patent Laid-Open No. 2-2
10096) A coating composition comprising a pigment such as light calcium carbonate and kaolin having an oil absorption of 35 mg / 100 g or more can be used. The coating amount is undercoating (3 to
7 g / m ² single-sided), topcoat (3 to 7 g / m ² single-sided) and also can be appropriately selected.

As the coating device, any of a size press, a gate roll, an air knife coater, a roll coater, a blade coater and the like can be used, but from the viewpoint of gravure printing suitability, which is the object of the present invention, a blade coater is used. It is desirable. The coated paper after the two-step coating can be subjected to a known super calendar treatment to obtain a coated paper for gravure printing of the present invention having excellent smoothness and excellent gravure printing suitability.

[0027]

EXAMPLES The present invention will be described more specifically with reference to comparative examples and examples, but of course, the present invention is not limited thereto. In the following, parts and% mean parts by weight and% by weight, respectively.

The coated base paper made by the neutral papermaking method in Comparative Examples and Examples had a basis weight of 44.0 g / m ^{2 and} a Steckigt sizing degree (according to JIS P8122) of 1 to 3 seconds.
Table 1 shows the types of pulp used in the base paper for coating, and Table 2 shows the chemicals added.

[0029]

[0030]

The undercoat coating composition having the composition shown in Table 3 below and the topcoat coating composition having the composition shown in Table 4 were coated on the base paper by a two-stage coating with a blade coater (undercoat coating composition concentration: 62 %, Overcoating composition concentration 62%) and calendering with a super calender. The linear pressure during the processing of the super calendar was kept constant at 225 kg / cm.
The coating amount was adjusted so that the undercoat was 6.0 g / m ² (one side) and the top coat was 7.0 g / m ² (one side).

[0032]

[0033]

The test methods and evaluation methods used in the following comparative examples and examples are as follows. -X-ray diffraction RINT- 1100 manufactured by Rigaku Corporation (X-ray source: C
The intensity value (A) at 2θ of 26 ° and the intensity value (C) at 2θ of 29 ° were determined using a u-tube) . -Particle size of filler It was determined using SACP-2 type manufactured by Shimadzu Corporation. -Smoothness Calculated according to JIS P-8119.・ White paper glossiness JIS Z-8741 using a glossmeter manufactured by Murakami Color Research Laboratory.
It was determined according to. -Missing dot and halftone dot reproducibility TAPPI paper pulp test method No. Printed matter printed by a 24 m “test method for gravure printing of paper (printing bureau method)” was visually evaluated on the following four scales. ◎: Excellent. : Excellent. Δ: Slightly inferior. ×: Poor.

Comparative Example 1 Light calcium carbonate used as an internal filler when making coated base paper was prepared by reacting quicklime slurry with carbon dioxide gas in the exhaust gas of a causticized kiln. The C / A ratio of light calcium carbonate is 25.6 (X-ray diffractometer RINT-1100 manufactured by Rigaku Corporation), and the average particle size is 3.
4μ (SACP-2 manufactured by Shimadzu Corporation as a particle size analyzer)
Was used).

The C / A ratio is determined by the degree of firing (TAPPI T617).
Hm84 method by) 91.8% hydrated lime slurry (concentration 13%) and 22m ³ charged to the reaction vessel of 30 m ^3, the concentration of carbon dioxide is charged with 19.8% of causticizing kiln gases at a rate of 27m ³ / min, It adjusted by stirring (reaction temperature 75 degreeC) and making it react for 150 minutes.

Ash (when calcined in an electric furnace at 500 ° C. for 3 hours)
Has 8.7% light calcium carbonate per pulp,
It was adjusted to be 0.9% and 15.3%. The smoothness (surface) of the coated base paper was 14 seconds. Table 5 shows the results. Due to the super calender treatment, the smoothness did not reach 3000 seconds on both the front and back sides, and the gravure printing effect was not so good.

COMPARATIVE EXAMPLE 2 In Comparative Example 1, 25 m ^{3 of} causticized kiln gas was introduced into the reactor.
/ Minute, and stirred (reaction temperature 75 ° C.).
As a light calcium carbonate prepared by reacting for 0 minutes, a light calcium carbonate having a C / A ratio of 22.3 and an average particle size of 3.6 μm was used. Manufactured. Table 5 shows the results.

COMPARATIVE EXAMPLE 3 In Comparative Example 1, 20 m ^{3 of} caustic kiln gas was supplied to the reaction vessel.
/ Minute, and stirred (reaction temperature 75 ° C.).
Light calcium carbonate having a C / A ratio of 19.8 and an average particle size of 3.3 μm was used as a light calcium carbonate prepared by reacting for 0 minutes, and the ash content of the base paper for coating was 8.3% with respect to pulp. Other conditions were all the same as Comparative Example 1. Table 5 shows the results.

COMPARATIVE EXAMPLE 4 20 m ³ of the same lime slurry as in Comparative Example 1 was charged into the reaction tank, leaving 2 m ³ of the reacted light calcium carbonate slurry in Comparative Example 1, and the causticized kiln gas was charged at a rate of 20 m ³ / min. Then, the mixture was stirred (reaction temperature: 75 ° C.) and reacted for 200 minutes to obtain C as light calcium carbonate.
A / A ratio of 7.6 and an average particle size of 3.7μ was used and the ash content was 9.1% per pulp. All other conditions were the same as in Comparative Example 1. Table 5 shows the results.

Example 1 Light calcium carbonate having a C / A ratio of 19.8 and an average particle size of 3.3 μm was used.
0.5% and 17.3%. All other conditions were the same as in Comparative Example 3. Table 5 shows the results. The smoothness is easily increased to 3000 seconds or more by the super calendering process, and the gravure printing effect is extremely excellent.

Example 2 Light calcium carbonate having a C / A ratio of 7.6 and an average particle size of 3.7 μm was used, and the ash content was 11.1 per pulp.
5% and 16.3%. All other conditions were the same as Comparative Example 4. Table 5 shows the results. The coated paper for gravure printing having a smoothness easily exceeding 3000 seconds and having a very excellent gravure printing effect was obtained by the super calendering treatment.

[0043]

[Table 5]

[0044]

According to the present invention, it is possible to obtain gravure printing aptitude with extremely excellent smoothness by defining the amount of light calcium carbonate to be added to the base paper for coating by using a specific one having a specific crystal structure. In addition, it also has the effect of reducing costs.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-104795 (JP, A) JP-A-3-234895 (JP, A) JP-A-63-196795 (JP, A) 76898 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) D21H 19/38

Claims (1)

(57) [Claims] 1. In a gravure printing coated paper in which a coating composition is applied to a base paper coated by a neutral papermaking method in two steps of undercoating and overcoating, X-ray diffraction is used as an internal filler of the coated base paper. The intensity value (C value) when 2θ is 29 ° and 2θ is 26
Light calcium carbonate having a strength value (A value) ratio (C / A ratio) of 20 or less at 10 ° is 10% by weight to 2% per pulp.
A coated paper for gravure printing, characterized in that the coated paper after the two-step coating is calendered to have a smoothness (according to JIS P 8119) of 3000 seconds or more.