JPH09302596A - Lightweight coated paper and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing lightweight coated paper excellent in surface disposition (surface coveredness, luster unevenness) and printing surface strength, excellent in high-speed operability when base paper is to be coated with a pigment coating liquid by use of a film transfer-type coater. SOLUTION: This lightweight coated paper is obtained by preparing a pigment coating liquid followed by coating a sheet of base paper with the coating liquid by use of a film transfer-type coater. The pigment coating liquid has a viscosity of 45-55cPs at a high shear rate of 10<6> s<-1> and comprises (a) 100 pts.wt. of a pigment containing 40-70wt.% of kaolin 0.3-0.7μm in average particle size and (b) an adhesive composed of 4-8 pts.wt. of a starch derivative and 13-18 pts.wt. of a copolymer latex 75-90wt.% in gel content.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a light-weight coated paper, which is excellent in high-speed operability when a base paper is coated with a pigment coating liquid, and has a surface state after coating (base paper coverage). , Uneven gloss, surface smoothness, and printability, and a lightweight coated paper produced by the method.

[0002]

2. Description of the Related Art In recent years, demand for paper in the commercial printing field for the purpose of advertising and advertising such as leaflets, catalogs, pamphlets, and direct mail has been increasing. Although these commercial prints have low commercial value themselves, it is important that the purpose be achieved as an advertising medium, so low-cost, good-quality prints are required, and paper users are becoming more cost-conscious. And the use of paper is also getting lower and lighter. In particular, in the field of coated printing paper, the demand for lightly coated paper, which is relatively inexpensive and has a printing finish comparable to that of conventional coated paper, is remarkable. For the same reason, the demand for lighter coated paper is also increasing in the field of conventional coated paper.

In order to meet such a strong demand for light-weight coated paper, paper makers are promoting widening and speeding up of coating equipment in order to more efficiently produce products and reduce costs. Under such circumstances, achieving both high quality and high productivity is an important technical issue.

The production equipment for coated paper includes an off-machine coating method which is usually used for performing paper making and coating in separate steps, and an on-machine coating method for performing paper making and coating simultaneously by one machine. In comparison with the off-machine coating method, the on-machine coating method has a feature that the manufacturing cost of the product can be suppressed and a product having a price competitiveness can be manufactured. Therefore, as a general production facility for lightweight coated papers, especially lightly coated papers, the on-machine coating method has been adopted, which enables simultaneous efficient papermaking and coating with a single machine. It is manufactured by a short dwell blade coater, a gate roll coater that is a film transfer method, a rod or a blade metalling size press coater, or the like.

However, it is difficult to increase the speed of the on-machine coating device due to the problem of operability, and when the pigment coating liquid is coated on the base paper, the maximum operating speed is about 11 so far.
The limit is 00 m / min. One of the causes of hindering this speed increase is a phenomenon called mist in the case of a rod or blade metalling size press coater, in which the coating liquid is atomized and scattered at the applicator roll nip outlet. Mist is more likely to occur at higher speeds, but especially 1
Under a high speed condition of 100 m / min or more, the degree thereof is remarkably increased and the working environment is deteriorated, and at the same time, the peripheral rolls are soiled and extra labor and time are spent for cleaning work.
Further, when the mist is dried and solidified, it falls on the surface of the paper and becomes a product defect. Also in the case of gate roll coater,
When a similar problem of mist occurs and the mechanical stability of the coating liquid is inferior, between rolls with different roll diameters and peripheral speeds such as between inner roll and outer roll or between inner roll and applicator roll. Due to the shearing force applied to the roll, a phenomenon called "gum-up" in which the coating liquid is solidified and adheres to the surface of the roll occurs to lower the operability.
In addition, the problem that the release of paper from the roll is not stable at the applicator roll nip outlet and streak-like surface unevenness called a peeling pattern or ring pattern occurs is also a problem when applying high speed coating with a film transfer type coating device. It's a common problem. These problems can be reduced by reducing the concentration of the coating liquid, but in addition to increasing the drying load, the quality of the coating liquid causes the base paper to soak into the base paper more often, and the coverage of the base paper is poor and the surface property is reduced. However, there is a problem that gloss unevenness increases and the surface state and printability deteriorate. As mentioned above, paper users are making lower grades of paper, but in particular, so-called high-quality lightweight coated paper consisting of base paper made solely of bleached chemical pulp is one of them, or two in some cases. There is also a large demand for switching from coated paper, which is a grade of. Therefore, it is necessary to maintain a certain level of quality of products that have been commercialized by off-machine blade coaters, and in order to efficiently produce by on-machine coating, a higher concentration of coating liquid is required. Must be applied in quantity. However, the higher the speed, the higher the concentration, and the higher the coating amount, the more problems of quality such as mist, peeling pattern, and surface unevenness become apparent as described above. Is a difficult situation.

The above problems are alleviated in JP-A-7-189188 by controlling the transfer roll coating liquid at a concentration of 58% or more and a B-type viscosity of 1500 cps or less. However, there is no problem when these coating liquids are applied at a low speed, but when applied at a high speed, especially 1100 m
There is a problem that mist is generated and a peeling pattern and gum-up become more remarkable under the high-speed operating condition of not less than / min.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have used a film transfer type coating apparatus as described above and applied a pigment coating solution at a high speed condition, especially at a high speed of 1100 m / min or more. An object of the present invention is to provide a light-weight coated paper which has excellent high-speed operability and excellent surface quality and printability.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, in a pigment coating liquid containing at least a pigment and an adhesive, (a) average particle diameter 40 to 7 of kaolin having a size of 0.3 to 0.7 μm
100 parts by weight of pigment containing 0% by weight, (b) 4 to 8 parts by weight of starch derivative as an adhesive, and gel content of 75 to
A pigment coating liquid containing 13 to 18 parts by weight of a 90% copolymer latex and having a viscosity within a range of 45 to 55 cps at a high shear rate (10 ⁶ sec ^-1 ) is provided. The present invention has been achieved by applying a coating on a base paper with a film transfer type coating device. This makes it possible to obtain a light-weight coated paper which has excellent high-speed operability and excellent surface quality and printability.

The pigment used in the present invention has an average particle size of 0.1.
It is necessary to use 40 to 70% by weight of kaolin having a particle size of 3 to 0.7 μm. Whether the average particle size is less than 0.3 μm,
If the amount used exceeds 70% by weight, the viscosity at a high shear rate becomes too high and mist is generated.
Further, when the average particle size is larger than 0.7 μm or smaller than 40% by weight, the glossiness of the blank paper and the glossiness after printing are deteriorated.

The adhesive used in the present invention must contain 4 to 8 parts by weight of the starch derivative and 13 to 18 parts by weight of the copolymer latex having a gel content of 75 to 90%. If the amount of starch is more than 8 parts by weight, the viscosity under high shear rate becomes too high and mist is generated. When the amount is less than 4 parts by weight, the internal strength of the paper layer is lowered, so that the printing surface strength and the blister resistance during off-wheel printing are deteriorated. In addition, when a pigment coating liquid containing a latex with a gel content of less than 75% is applied, the mechanical stability of the latex is poor, and the coating force is different due to the shearing force applied between the rolls having different roll diameters and peripheral speeds. Liquid coagulation occurs and gum up adheres to the roll surface to reduce operability. This tendency became more remarkable especially at high speeds of 1100 m / min or more. If the gel content exceeds 90%, it generally does not function as an adhesive. On the other hand, when the amount of the latex compounded exceeds 18 parts by weight, the air permeability of the paper is lowered and the blister resistance is deteriorated. Conversely, if less than 13 parts by weight,
The printing surface strength is reduced.

Further, the inventors of the present invention have made extensive studies in order to solve the problems of mist generation, peeling pattern and gum-up, which are more noticeable particularly at high speed operating conditions of 1100 m / min or more, and as a result, the pigment coating liquid High shear rate (10
It admitted that the first generation of mist can be greatly reduced by the viscosity at ⁶ seconds ^-1) under the following 55 cps. When the viscosity is lower than 45 cps, the pigment coating liquid excessively penetrates into the base paper, resulting in poor base paper coverage and surface smoothness, large gloss unevenness, poor surface condition, and poor printability. In the present invention, a high shear rate (10 ⁶ seconds
^-1 ) Viscosity under means the value measured by a high pressure capillary viscometer (manufactured by Anton Paar).

In the present invention, the film transfer type coating apparatus may be a gate roll coater, a blade or a rod metalling size press coater. When using a rod metering size press coater, it is desirable to use a rod with a smooth surface in order to avoid streaking during operation. Further, by setting the diameter of the rod to 30 to 50 mm, more preferable operability and quality can be obtained. 30mm in diameter
With smaller rods, the film-forming ability tends to deteriorate and the surface state tends to be inferior, and with rods larger than 50 mm, the effect does not change, so there is no need to make it particularly large.

Further, the present inventors have applied a pigment coating liquid,
After drying, by soft calendering,
Compared with the case of processing with a calendar having only a normal metal roll, it is possible to suppress the peeling pattern, reduce uneven gloss, obtain excellent surface condition, and further heat the paper with steam to perform soft calendar processing. It was possible to obtain a further effect.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The coating pigment used in the present invention is
Other than kaolin, heavy calcium carbonate, light calcium carbonate, satin white, talc, plastic pigment, titanium dioxide, silica and the like are used without particular limitation.

As the starch derivative used in the present invention, oxidized starch, esterified starch, enzyme-modified starch, etherified starch and flash thereof are generally used in order to maintain the water retention of the coating liquid and increase the internal bond strength of the base paper. Cold water soluble starch obtained by drying is used. Further, as the copolymer latex used in the present invention, styrene-butadiene copolymer, methyl methacrylate
Conjugated diene-based copolymer latex such as butadiene copolymer, acrylic-based polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester, ethylene / vinyl acetate copolymer latex, or various copolymers thereof. A polymer latex in which a functional group such as a carboxyl group is modified is used.

In the coating liquid of the present invention, various auxiliaries such as a dispersant, a thickener, a water retention agent, a defoaming agent and a water resistant agent, which are mixed with a usual pigment for coated paper, are used. Also, as the base paper for coating,
Although high-quality paper and medium-quality paper used for general coated paper for printing are used, high-quality paper with 100% by weight of exposed chemical pulp is more preferable in order to obtain high surface properties and printing quality, and the freeness of pulp is The Canadian standard freeness is preferably 250 to 400 ml. The basis weight of the base paper is preferably 30 to 100 g / m.

The coating amount is 5 to 10 per one side of the base paper.
g / m ² is preferred. A coating amount of less than 5 g / m ² is unavoidable because of the limitation of the apparatus, and the concentration of the pigment coating liquid must be greatly reduced, and as a result, the base paper coatability and surface state are likely to be lowered. 10
On the contrary, when the coating amount is more than g / m ^2, it is necessary to increase the concentration of the pigment coating liquid. In this case, it becomes difficult to control the coating amount on the device, and at the same time, a lot of peeling patterns occur, resulting in orange peel or other satin finish. -Shaped surface roughness tends to occur on the paper surface.

The elastic roll of the soft calender used in the present invention is a roll coated with a special resin having high heat resistance and having a Shore hardness of D80 to 90. The surface roughness of the metal roll is RZ (JIS B0601, 10 point average roughness) is preferably 2 μm or less, and the surface temperature is 50 to 18
It is preferably used in the range of 0 ° C. In the soft calender process, the steam used to humidify and heat the paper is a low pressure and mild heating steam, and the steam pressure used is 1 kg / c.
It is preferable to apply steam at m ² or less, a steam flow rate of 15 to 80 kg / Hr / m width, and a moisture increase rate of paper within a range of 0.3 to 1.5%.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited by these examples. The parts and% in the examples are parts by weight and% by weight, respectively. The quality evaluation method is as follows.

<Quality Evaluation Method> (1) Kaolin Average Particle Size Seishin Enterprise Optical Transmission Type Particle Size Distribution Measuring Device SHC5000
Was measured as the average particle size at the 50% point of the cumulative weight distribution.

(2) Latex gel content About 0.3 g of latex is spread thinly on a slide glass,
It is dried in a dryer at 50 ° C. until it becomes a film. The latex film is immersed in about 50 ml of toluene for a whole day and night, filtered with a glass filter, and the filtrate is dried with a drier at 105 ° C. to measure the weight of toluene-soluble matter. The gel content was calculated from the weight of the toluene-soluble matter obtained here by the following formula.

Gel content (%) = (weight of dry film-weight of toluene-soluble content) × 100 / (weight of dry film) (3) Evaluation of high-speed fluidity The evaluation of high-speed fluidity was carried out by the following capillary viscosity values. The coated liquid was kept at 45 ° C., using an Anton Paar high pressure capillary viscometer HVA-6 type, diameter 0.4 mm, using a capillary tube length 10 mm, conditions of shear rate 1 × 10 ⁶ sec ^-1 Viscosity value measured below.

(4) Glossiness of blank paper: Measured at an angle of 75 degrees in accordance with JIS P-8142.

(5) Glossiness after printing Using an RI-II type printer (manufactured by Akira Seisakusho), an ink for offset printing manufactured by Sakata Inx (trade name: Diatone)
GSL red) was printed using 0.35 cc, and after standing overnight, the glossiness was measured at 75 degrees.

(6) Smoothness According to Japan Tappi No5, the smoothness was measured by an Oken type smoothness tester. (7) Blister resistance Using an RI-II type printer (manufactured by Akira Seisakusho) and TK Mark V New 617 manufactured by Toyo Ink, the amount of ink is 0.8.
After printing at a constant cc, the hair dryer was heated with hot air having different temperatures for 3 seconds, and the degree of blistering generated was visually evaluated.

⊚ = not generated at all, ∘ = not generated at all, Δ = generated, x = remarkably generated (8) Printing surface strength Using a RI-II type printing machine (manufactured by Ming Seisakusho), TV-24 manufactured by Toyo Ink Co., Ltd. Was used to print at a rotation speed of 40 rpm and a constant ink amount of 0.35 cc, and the degree of picking on the printed surface was visually evaluated relative to each other.

⊚ = No occurrence, ◯ = Almost no occurrence, Δ = Occurrence, × = Significant occurrence.

⊚ = No unevenness, ◯ = Almost no unevenness, Δ = Unevenness, × = Significant unevenness (10) Mist generation evaluation The state of mist generation was visually evaluated during coating.

⊚ = No occurrence, ◯ = Almost no occurrence Δ = Occurrence, × = Significant occurrence

⊚ = No occurrence, ◯ = Almost no occurrence Δ = Occurrence, × = Significant occurrence (12) Streak occurrence evaluation The occurrence of streak was visually evaluated during coating.

⊚: No occurrence, ◯: Almost no occurrence Δ: Occurrence, × = Significant occurrence (13) Peeling pattern evaluation The occurrence of the peeling pattern was visually evaluated during coating.

⊚ = not generated at all, ∘ = not generated at all, Δ = generated, x = remarkably generated [Example 1] Kaolin having an average particle size of 0.55 μm (E
Pigment 1 containing 50 parts of CC Co., β-coat and 50 parts of heavy calcium carbonate having an average particle size of 0.60 μm (Shiroishi Calcium Co., Ltd., Hydrocarb 90)
Dispersant (Toa Gosei Co., Ltd., Aron T-4)
0) 0.3 part was added and dispersed in water using a Cowles disperser, and 7 parts of phosphorylated esterified starch as an adhesive and 15 parts of styrene-butadiene latex having a gel content of 80% were blended to obtain a high composition. A pigment coating solution having a concentration of 59% and a viscosity under a shear rate of 49 cps was prepared.

Rod metering having a rod having a smooth surface of 35 mm in diameter as a coating device for coating pigment-blended kraft pulp single-blended base paper having a basis weight of 54 g / m ² and a Canadian standard freeness of 300 ml. Using a size press coater (made by Valmet), coating speed 1300m
/ Min, 9 g / m ² per side was coated on both sides and dried.

Furthermore, using a steam humidifier ("Steamfoil" manufactured by Aikawa Tekko Co., Ltd.), the steam pressure was 0.8 kg / c.
m ^2, the vapor is given to the paper steam flow rate at 50 kg / Hr / m width constant conditions, 1300 m / min, 60 ℃, 250kg /
Soft calendar (made by Minami Senju Seisakusho) with cm processing condition
A treatment was applied to give a glossy finish.

[Example 2] 65 parts of kaolin (ECC, β-coat) having an average particle diameter of 0.55 µm and ground calcium carbonate (Shiraishi Calcium Co., Ltd., hydrocarbo) having an average particle diameter of 0.60 µm 90) To 100 parts of a pigment containing 35 parts, 5 parts of phosphoric esterified starch as an adhesive and 17 parts of a styrene-butadiene latex having a gel content of 80% are blended, and the viscosity at a high shear rate is A pigment coating liquid having a concentration of 58% of 48 cps was prepared, and a gate roll coater (manufactured by IHI) was used as a coating device for coating the pigment, coating speed was 1200 m / min, and 8.0 g / m ² per side. On both sides, then 1200
A coated paper was produced in the same manner as in Example 1 except that the soft calendar treatment was performed at a speed of m / min.

[Example 3] A coated paper was produced in the same manner as in Example 1 except that the steam humidifier was not used and the soft calender treatment was carried out under the treatment conditions of 1300 m / min, 160 ° C and 250 kg / cm.

Comparative Example 1 A coated paper was produced in the same manner as in Example 1 except that 10 parts of phosphate esterified starch was used.

Comparative Example 2 A coated paper was produced in the same manner as in Example 1 except that 2 parts of phosphoric esterified starch was used.

[Comparative Example 3] A coated paper was produced in the same manner as in Example 1 except that 20 parts of a styrene-butadiene latex having a gel content of 80% was used.

[Comparative Example 4] A coated paper was produced in the same manner as in Example 1 except that 10 parts of styrene-butadiene latex having a gel content of 80% was used.

[Comparative Example 5] A gate roll coater (manufactured by IHI) was used as a coating device for coating a pigment, using 15 parts of a styrene-butadiene latex having a gel content of 50%.
And apply at a coating speed of 1200 m / min for 120
Example 1 except that soft calendering was performed at 0 m / min.
A coated paper was produced in the same manner as in.

Comparative Example 6 80 parts of kaolin (ECC Co., β-coat) having an average particle size of 0.55 μm and heavy calcium carbonate having an average particle size of 0.60 μm (Shiraishi Calcium Co., Ltd.) , Hydrocarbo 90) 20
A coated paper was produced in the same manner as in Example 1 except that the parts were used.

Comparative Example 7 20 parts of kaolin (ECC Co., β-coat) having an average particle size of 0.55 μm and heavy calcium carbonate (Shiraishi Calcium Co., Ltd.) having an average particle size of 0.60 μm. , Hydro Carbo 90) 80
A coated paper was produced in the same manner as in Example 1 except that the parts were used.

[Comparative Example 8] 50 parts of kaolin (ECC Co., Ltd., DB coat) having an average particle size of 0.75 μm, and heavy calcium carbonate (Shiraishi Calcium Co., Ltd.) having an average particle size of 0.60 μm. , Hydrocarbo 90) 50
A coated paper was produced in the same manner as in Example 1 except that the parts were used.

The above results are shown in Table 1.

[0046]

[Table 1] As is clear from Table 1, Examples 1, 2, and 3 have high smoothness,
High gloss after printing, excellent surface strength, blister resistance, and blank surface state, and no mist, gum up, streak, or peeling pattern occurs during coating. In contrast, in Comparative Example 1, the occurrence of mist and peeling pattern is remarkable. Comparative Example 2 has a smoothness,
The white paper glossiness and gloss after printing are low, and the white paper surface state is inferior. Also, the blister resistance is slightly inferior. Comparative Example 3 is inferior in blister resistance. Comparative Example 4 is inferior in printing surface strength. Comparative Example 5
Has a lot of gum up. In Comparative Example 6, the generation of mist and peeling pattern is remarkable. In Comparative Example 7, the smoothness, the glossiness of the blank sheet, and the glossiness after printing are low, and the surface state of the blank sheet is also poor. Comparative Example 8 has low smoothness, white paper gloss, and gloss after printing.

Therefore, the light-weight coated paper produced according to the present invention provides unprecedented excellent operability and coated paper quality, and the effect is extremely great.

[0048]

The present invention uses a film transfer type coating apparatus in a method for producing a lightweight coated paper,
By applying a pigment coating liquid on a lightweight coated paper at high speed conditions, especially at a high speed of 1100 m / min or more, a lightweight coated paper excellent in high-speed operability and excellent in surface quality and printability is obtained. be able to.

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[Procedure amendment]

[Submission date] July 23, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Deleted

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

Example 2 65 parts of kaolin (ECC, β-coat) having an average particle size of 0.55 μm and ground calcium carbonate (Shiraishi Calcium Co., Ltd.) having an average particle size of 0.60 μm. Hydrocarbo 90) To 100 parts of pigment containing 35 parts of pigment, 5 parts of phosphate esterified starch as an adhesive agent and 17 parts of styrene-butadiene latex having a gel content of 87% were blended and blended under high shear rate. Using a gate roll coater (manufactured by IHI) as a coating device for preparing a pigment coating liquid having a viscosity of 48 cps and a concentration of 58%, a coating speed of 1200 m / min, 8.0 g / per surface m ² is coated on both sides, then 1200
A coated paper was produced in the same manner as in Example 1 except that the soft calendar treatment was performed at a speed of m / min.

Claims (5)

[Claims] 1. A lightweight coated paper manufacturing method for coated the coated liquid to the base paper, contain the following (a) and (b), and a high shear rate ^{(106 sec-1)} viscosity at lower 45-5
A method for producing a lightweight coated paper, which comprises preparing a pigment coating liquid of 5 cps and then coating the pigment coating liquid on a base paper by a film transfer type coating apparatus. (A) 100 parts by weight of a pigment containing 40 to 70% by weight of kaolin having an average particle size of 0.3 to 0.7 μm. (B) 1 to 4 parts by weight of a starch derivative as an adhesive and 1 to a copolymer latex having a gel content of 75 to 90%
3-18 parts by weight. 2. The method for producing a lightweight coated paper according to claim 1, wherein the coating speed is 1100 m / min or more. 3. The method for producing a lightweight coated paper according to claim 1, wherein the film transfer type coating device is a rod metalling size press coater having a rod having a smooth surface. 4. A light weight coated paper manufacturing method for coated the coated liquid to the base paper, contain the following (a) and (b), and a high shear rate ^{(106 sec-1)} viscosity at lower 45-5
After preparing a pigment coating liquid of 5 cps, the pigment coating liquid is coated on the base paper by a film transfer type coating device,
After drying, the coated paper is humidified and heated by steam and subjected to a soft calender treatment, which is a method for producing a lightweight coated paper. (A) 100 parts by weight of a pigment containing 40 to 70% by weight of kaolin having an average particle size of 0.3 to 0.7 μm. (B) 1 to 4 parts by weight of a starch derivative as an adhesive and 1 to a copolymer latex having a gel content of 75 to 90%
3-18 parts by weight. 5. A lightweight coated paper produced by the production method according to claim 1.