JP3262047B2 - Coated paper for 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 using deinked pulp as a base paper, and more particularly to a coated paper having excellent whiteness and light resistance for double-sided printing.

[0002]

2. Description of the Related Art Coated paper for double-sided printing is formed by forming a pigment coated layer mainly composed of a white pigment and an adhesive on both sides of a base paper and smoothing it with a super calender or a gloss calender. Printability is improved, and art paper, coated paper and the like are typical examples.

[0003] As the base paper of the coated paper, a paper using 100% of chemical pulp has been mainly used so far in order to upgrade the coated paper. However, in recent years, the recycling of waste paper has become an important theme for paper products from the viewpoint of preserving the global environment. In the market for coated paper for printing, deinked pulp (hereinafter referred to as “DIP”) recycled from waste paper ) Products have been increasingly demanded.

[0004] On the other hand, when a printing coated paper is prepared using a base paper that makes extensive use of DIP, the whiteness is necessarily inferior to that of a printing coated paper using a base paper using 100% chemical pulp. There is a disadvantage. For this reason, applications are limited to special fields at present.
It has been considered unsuitable for application to color and high-grade. Further, in the case of a printing coated paper in which DIP is frequently used for the base paper, there is a serious drawback in terms of preservability that the yellow light browning phenomenon is rapidly caused by the influence of ultraviolet rays and the whiteness is also reduced.

[0005] In order to improve such a drawback that occurs when producing a coated paper for printing using a large amount of DIP on the base paper,
For example, JP-A-49-146297 describes a coated paper for printing in which a colored concealing layer is first formed on a base paper made of DIP, and a pigment coated layer is formed thereon. However, in order to obtain a coated paper of high whiteness in this printing coated paper, the coating amount of the pigment coated layer must necessarily be increased. Therefore, there is a problem that the texture of the paper is lost and the cost is increased.

Japanese Patent Application Laid-Open No. Hei 4-109614 discloses a printing coating in which a coating layer containing a large amount of titanium dioxide is formed before a base paper and a pigment coating layer is further formed on the coating layer. Paper is listed. However, the printing coated paper thus configured uses a large amount of expensive titanium dioxide and has two layers formed on one side. As a result, the process becomes complicated, the texture of the paper itself is lost, and the cost is increased.

[0007]

SUMMARY OF THE INVENTION The present invention has a high whiteness equivalent to that of a printing coated paper using a base paper using 100% of chemical pulp, while using a base paper using a large amount of DIP. An object of the present invention is to provide a coated paper for double-sided printing excellent in storability which does not cause yellowing-browning phenomenon or decrease in whiteness due to ultraviolet rays.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a coated paper for double-sided printing wherein a pigment coated layer mainly composed of a white pigment and an adhesive is formed on both sides of a base paper mainly composed of DIP.
A pulp having a whiteness of 65% or more is used as the DIP, and a fluorescent whitening dye is added to the base paper to the deinked pulp.
And the pigment coating layer contains titanium dioxide in an amount of 3 to 20% by weight of the total pigment, so that coated paper for double-sided printing using 100% base paper of chemical pulp. Thus, a coated paper having the same whiteness and light resistance as in Example 1 was obtained.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The DIP used in the present invention is widely used for relatively low-grade waste paper such as newspapers, magazines, and printing waste paper, and relatively high-grade paper such as high-quality paper, coated paper, and art paper. Printed or unprinted waste paper can be obtained as a raw material.

Specifically, after removing foreign matter from the recovered waste paper as described above, the waste paper is defibrated with a pulper or the like, dust is removed with a screen, a cleaner, or the like, and then bleached with a bleaching agent such as hydrogen peroxide. The whiteness of the DIP in the present invention is preferably at least 65% or more, and more preferably 67% or more. The reason is that it is desirable to use a DIP having as high a whiteness as possible because the effect on the whiteness when the coated paper for printing is finished is large. By the way, when a DIP having a whiteness of less than 65% is used, it is difficult to obtain a target coated printing paper. If a DIP of less than 65% is to be used to finish the coated paper for printing with high whiteness, it is necessary to provide a concealing layer as in the prior art or to increase the coating amount of the pigment coated layer. As a result, the process becomes complicated, the texture of the paper itself is lost, and the cost is increased.

For the above reasons, the present invention has a whiteness of 6
A base paper containing DIP of 5% or more as a main component is used, but softwood bleached kraft pulp (NBK) is used to improve paper strength.
P), conventional chemical pulp such as bleached bleached kraft pulp (LBKP), refiner ground pulp (RGP),
An appropriate amount of mechanical pulp such as thermomechanical pulp (TMP) or stone ground pulp (GP) may be mixed. However, since the feature of the present invention is to use base paper containing DIP as a main component, it is necessary to mix the amount of DIP so that the amount of DIP does not fall below 70% by weight.

One of the features of the present invention is that the base paper contains a fluorescent whitening dye. By the way, in the case of the present invention, a base paper of 100% chemical pulp bleached to a whiteness of 80% or more is used only by including titanium dioxide in the pigment coating layer or simply by including a fluorescent whitening dye in the base paper. It is not possible to obtain a printing coated paper having the same degree of whiteness as that of the printing coated paper obtained as described above and having little yellowish browning. Even if a method of mixing a fluorescent whitening dye and titanium dioxide in the base paper or in the pigment coating layer is employed, the respective functions cannot be sufficiently exhibited, and the coated paper for printing using 100% base paper of chemical pulp. It is difficult to obtain a coated printing paper free from whiteness and yellow-browning phenomena comparable to the above.

Accordingly, the present invention provides a base paper containing DIP as a main component, which contains a fluorescent whitening dye in advance to increase the whiteness of the base paper, and then a pigment coating layer containing titanium dioxide is provided on both sides of the base paper. It is characterized in that the function of the fluorescent whitening dye and the function of titanium dioxide can be extremely effectively exerted on the entire coated paper by being formed. Titanium dioxide has a high concealment rate and UV absorption,
When present in the pigment coating layer, ultraviolet rays are blocked by the coating layer and do not reach the base paper. As a result, it was possible to obtain, for the first time, a printing coated paper having a whiteness similar to that of a coated paper for printing using 100% base paper of chemical pulp and having less yellowish browning.

Thus, the amount of the fluorescent brightening dye contained in the base paper is determined so as to obtain the desired effect of the present invention in relation to the whiteness of DIP and the amount thereof used. Typically, 500 to 1000 for DIP
0 PPm is effective. By the way, if it is less than 500 PPm, the effect of increasing the whiteness of the base paper is not sufficient, and if it is more than 10,000 PPm, the effect becomes saturated and further use increases the cost.

In the base paper, other fillers, a retention aid, a paper strength improver,
It is a matter of course that various auxiliaries such as a sizing agent can be appropriately contained, and in papermaking, an aqueous solution of starch, polyvinyl alcohol or the like is applied in order to improve the surface strength of the base paper in the same manner as in the case of the conventional base paper. It is also possible. Incidentally, as the filler, talc, heavy calcium carbonate, precipitated calcium carbonate kaolin and the like can be used. However, from the viewpoint of improving the whiteness of the base paper, the wire abrasion resistance of the paper machine and the neutral paper making the base paper. Therefore, use of light calcium carbonate is desirable.

The content of titanium dioxide in the pigment coating layer is preferably 3 to 20% by weight based on the total pigment in order to obtain the desired effect of the present invention. By the way, if it is less than 3% by weight, it is difficult to obtain a paper having a high whiteness equivalent to that of a coated printing paper using 100% base paper of chemical pulp, and the effect of blocking ultraviolet rays from entering the base paper is not sufficient. .
On the other hand, if the content exceeds 20% by weight, the effect surface reaches a saturated state, and if the content is more than 20% by weight, the cost becomes high, and the fluidity of the pigment coating composition deteriorates.

As the titanium dioxide used in the pigment coated paper of the present invention, three types of rutile type and anatase type brookite type are known, but practically, rutile type and anatase type are preferable.

Other white pigments include kaolin, clay, and the like used in the production of ordinary coated paper for printing.
Inorganic pigments such as calcium carbonate, aluminum hydroxide, zinc oxide, barium sulfate, calcium sulfate, silica, activated clay, talc, satin white, and lake, and organic pigments such as plastic pigment are appropriately used.

The adhesive used together with the white pigment is not particularly limited, but proteins such as casein, soybean protein and synthetic protein: conjugated diene-based polymer latex such as styrene-butadiene copolymer Acrylic polymer latex such as polymer and / or copolymer of acrylate and / or methacrylate, ethylene
Vinyl-soluble polymer latex such as vinyl acetate copolymer, or alkali-soluble or alkali-insoluble polymer latex obtained by modifying these various polymer latexes with a monomer containing a functional group such as a carboxyl group: polyvinyl alcohol, olefin. Synthetic resin adhesives such as maleic anhydride resin and melamine resin: starches such as positive starch, oxidized starch, enzyme-modified starch, thermochemically modified starch, etherified starch, esterified starch, cold water-soluble starch, etc .: carboxymethyl cellulose, hydroxy An ordinary adhesive for coated paper, such as a cellulose derivative such as ethyl cellulose, may be appropriately selected and used.

The mixing ratio of the adhesive is as follows:
0 to 25 parts by weight, more preferably 10 to 25 parts by weight
It is about 20 parts by weight. In the pigment coating composition, if necessary, a dispersant, a thickener, a water retention agent, a flow modifier, a defoaming agent, a release agent, a waterproofing agent lubricant, a dye, a fluorescent brightener, a pH control Various auxiliaries such as agents can be appropriately compounded.

The pigment coating composition prepared under the above conditions may be, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater curtain coater, a die rod coater, a gravure coater, a champlex coater. The coating is performed by an on-machine or off-coater provided with a known coating device such as a gate roll coater or a size press. In addition,
When finishing coated paper with high gloss, it is preferable to use a blade coater, a rod blade coater, or the like.

At that time, the solid content concentration of the pigment coating composition is as follows:
Generally, it is about 40 to 75% by weight, but considering operability,
A range of 45-70% by weight is preferred.

The coating amount of the pigment coating composition is about 3 to 50 g / m ² per one side in dry weight, but is preferably 8 to 25 g / m ² in consideration of the desired effect of the present invention. By the way, if it is less than 3 g / m ² , it is not possible to obtain a printing coated paper having a whiteness and a yellowish-browning phenomenon that is comparable to a printing coated paper using 100% base paper of chemical pulp, and the printability is also poor. Will be insufficient. On the other hand, when it is 50 g / m ² or more, the texture of the paper itself is lost, which leads to an increase in cost.

After being dried, the pigment coating layer is finished through a finishing device such as a super calender or a gloss calender.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but it is needless to say that the present invention is not limited to these examples. Further, “parts” and “%” in the examples represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 Waste paper consisting of 80% newsprint and 20% leaflets was defibrated with a drum barker, foreign matter was removed with a screen having a slit width of 0.20 mm, deinked with a diffuser-type floatator, and then dried to dry pulp. 2.5% H ₂ O ₂ per pulp
%, At 60 ° C. for 3 hours, and further deinked with a diffuser-type floatator to produce a DIP having a Hunter brightness of 70%. The following fillers and papermaking chemicals were added to 100 parts of the above DIP to obtain a paper stock, and a coating paper having a basis weight of 95 g / m ² was produced by a fourdrinier paper machine.

(Filler / papermaking chemical) (brand name, manufacturer) (addition amount “% of pulp” ) Filler (settling calcium carbonate, self-made) 12% Sizing agent (Fibran 81, Oji National) 0.02% starch ( Ace K100, Oji Cornstarch) 0.8% Acrylic amide polymer (Himoloc NR12MLS, Himo) 0.005% Fluorescent whitening dye (Blanco-Hower BSU-PN, Bayer) (2000PPm)

A pigment coating solution (60%) shown below is applied to both sides of the coating base paper by a blade coater and dried, and then subjected to a smoothing treatment (linear pressure: 200 kg / cm) with a super calender to perform a printing coated paper. It was created. The coating amount was adjusted to be 15 g / m ² (one side). Whiteness of the created coated paper for printing,
The light fastness and the degree of yellowing were as shown in the attached table.

(Coating liquid material) (Product name) (Manufacturer) (Blending amount) Kaolin (UW-90) (Engelbird) 50 parts Heavy calcium carbonate (own) 10 parts Precipitated calcium carbonate (own) 35 parts Dioxide Titanium (FA 55W) (Furukawa Metal) 5 parts Oxidized starch (Ace A) (Oji corn starch) 3 parts SBR latex (latex L-1303) (Asahi Kasei) 10 parts Dispersant (Aron F40) (Toa Gosei) 0.02 parts

Example 2 A DIP having a whiteness of 65% was used, and a fluorescent whitening dye was used for 8000.
A base paper was made in the same manner as in Example 1 except that PPm was contained. Using this base paper, a coated paper for double-sided printing was prepared in the same manner as in Example 1. The whiteness, light fastness, and degree of yellowish browning of the prepared printing coated paper are as shown in the attached table.

Example 3 A base paper was prepared in the same manner as in Example 1 except that 70 parts of DIP having a whiteness of 70% and 30 parts of LBKP having a whiteness of 82% were used. Using this base paper, a coated paper for double-sided printing was prepared in the same manner as in Example 1. The whiteness, light fastness, and degree of yellowish browning of the prepared printing coated paper are as shown in the attached table.

Example 4 A coating liquid was prepared in the same manner as in Example 1 except that 18 parts of titanium dioxide and 37 parts of kaolin were used in the composition of the pigment coating liquid. A coated paper for double-sided printing was prepared in the same manner as in Example 1 except that this coating liquid was used. The whiteness, light fastness and degree of yellowish browning of the prepared coated paper for double-sided printing are as shown in the attached table.

Comparative Example 1 A base paper was prepared in the same manner as in Example 1 except that 100 parts of DIP having a whiteness of 58% was used, and the content of a fluorescent whitening dye was 10,000 ppm. Using this base paper, a coated paper for double-sided printing was prepared in the same manner as in Example 1. The whiteness, light fastness and degree of yellowish browning of the prepared coated paper for double-sided printing are as shown in the attached table.

Comparative Example 2 Example 1 except that the content of the fluorescent whitening dye was added to 400 PPm.
The base paper was made in the same manner as described above. Using this base paper, a coated paper for double-sided printing was prepared in the same manner as in Example 1. The whiteness, light fastness and degree of yellowish browning of the prepared coated paper for double-sided printing are as shown in the attached table.

Comparative Example 3 A coating liquid was prepared in the same manner as in Example 1 except that 2 parts of titanium dioxide and 53 parts of kaolin were used. A coated paper for double-sided printing was prepared in the same manner as in Example 1 except that this coating liquid was used. The whiteness, light fastness and degree of yellowish browning of the prepared coated paper for double-sided printing are as shown in the attached table.

Comparative Example 4 A base paper was prepared in the same manner as in Example 1 except that no fluorescent dye was used for the base paper. Further, a coating liquid was prepared in the same manner as in Example 1, except that 20 parts of titanium dioxide and 35 parts of kaolin were used in the composition of the pigment coating liquid. A coated paper for double-sided printing was prepared using the base paper and the coating liquid. The whiteness, light fastness and degree of yellowish browning of the prepared coated paper for double-sided printing are as shown in the attached table.

Comparative Example 5 A coating solution was prepared in the same manner as in Example 1 except that 55 parts of kaolin was used without using titanium dioxide in the composition of the pigment coating solution. A coated paper for double-sided printing was prepared in the same manner as in Example 1 except that this coating liquid was used. The whiteness, light fastness and degree of yellowish browning of the prepared coated paper for double-sided printing are as shown in the attached table.

Comparative Example 6 A coating solution was prepared in the same manner as in Example 1, except that 25 parts of titanium dioxide and 30 parts of kaolin were used in the composition of the pigment coating solution. An attempt was made to prepare a coated paper for double-sided printing in the same manner as in Example 1 except that this coating liquid was used, but the coating property was poor and could not be prepared.

[0039]

[Table 1]

In the examples and comparative examples, the test method and the evaluation method of the coated paper were performed in the following manner. * Pulp whiteness: Measured using a Hunter whiteness meter (manufactured by Toyo Seiki) in accordance with JIS P 8123. * Whiteness of coated paper: SC-10W according to JIS P 8148
N (manufactured by Suga Test Instruments). * Light resistance of coated paper: coated paper was irradiated for 1 hour using a fading tester model MH-1 (manufactured by Mitsubishi Electric Corporation), the whiteness before processing was W ₁ , and the whiteness after processing. and light resistance measure as whiteness decreases and W ₂ a _{(Point) = (W 1 -W} 2). The smaller the numerical value, the smaller the decrease in whiteness and the better the light resistance. * Degree of yellow-browning: After irradiating coated paper for 1 hour using a fading tester model MH-1 (manufactured by Mitsubishi Electric Corporation), JIS
According to Z 8729, SC-10WN (manufactured by Suga Test Instruments)
^{* The} value was measured and the degree of yellowish brown of the coated paper was measured. B ₁ , after irradiation
The degree of tanning and _{b 2 (Point) = (b} 2 - b 1) as was a measure of tanning. The smaller the value, the less the yellowing is reduced, indicating that the yellowing is more difficult.

[0041]

As is clear from the examples, according to the present invention, while using a base paper using a large amount of DIP, the same height as a coated paper for double-sided printing using a base paper using chemical pulp 100 is obtained. A coated paper for double-sided printing having whiteness, having less yellowish-browning phenomena due to ultraviolet light, and little decrease in whiteness, and having excellent storage stability was obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisao Dasukoshi 1 Oji-cho, Kasugai-shi, Aichi Oji Paper Kasugai Mill Co., Ltd. (56) References JP-A-3-294598 (JP, A) JP-A-3-3 241095 (JP, A) Table 8-8-506860 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (2)

(57) [Claims] 1. A coated paper for double-sided printing wherein a pigment coating layer mainly composed of a white pigment and an adhesive is formed on both sides of a base paper mainly composed of deinked pulp. Use a pulp with a whiteness of 65% or more, and apply a fluorescent whitening dye to the base paper.
Coated paper for double-sided printing characterized in that it contains 0 PPm and that the pigment coated layer contains titanium dioxide in an amount of 3 to 20% by weight of the total pigment. 2. The deinking pulp content is 70% by weight.
2. The coated paper for double-sided printing according to claim 1, wherein: