JPH08266997A - Production of coated paper and coated cardboard by rod type coating apparatus - Google Patents

Abstract

PURPOSE: To eliminate the formation and adhesion of coating refuse or the generation of a coating stripe, in a method for producing coated paper and coated cardboard using a rod type coating apparatus, by specifying the physical properties of coated raw paper and a coating compsn. CONSTITUTION: A coating compsn. 7 of which the viscosity at 10<2> -10<7> sec<-1> is ηcp within a shearing region of a shearing speed prescribed by a capillary diameter h2 mm and a coating speed Sm/min constituted of a rod bar 10 and coating raw paper 1 is adjusted so that the value A of the formula being the characteristic thereof becomes 1-300 to be applied to coating raw paper 1 with water absorbability of 0.05-1.0ml/m and smoothness of 10-10.0ml/m<2> (by a Bristol apparatus). In the formula, Wr is water retention g/m<2> , η is viscosity cp at a shearing speed at a time of coating, Ka is water absorbability ml/m<2> by a Bristol apparatus, T is the thixotropy of paint and S is a coating speed m/min.

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 paper and paperboard which are excellent in operation and quality, and more specifically, in the bar coating in a rod type coating apparatus, coating streaks and coating residues are produced. The present invention relates to a method for producing difficult-to-use coated paper and coated paperboard.

[0002]

2. Description of the Related Art Rod-type coating devices are widely used because they can coat with high-viscosity paints and have excellent operability as compared with air knife-type coating devices. There is a problem that coating streaks and paint dregs are likely to occur during the work.

This is especially a problem in the grooved bar described in JP-A-5-293580 and JP-B-5-74427, which is said to be capable of forming a coating film having excellent surface properties. The reason for this is that the coating dregs are likely to accumulate in the recesses of the groove defined by the diameter of the wire to be wound, the bottom of the acute angle, and the portion of the acute angle where the coating amount is small is likely to be a coating streak.

In order to improve this, various proposals have been made, such as studying the groove shape to make it difficult for the coating dregs to accumulate, or applying a rod having grooves formed on the rod surface by grinding to suppress the occurrence of coating streaks. However, the coating property varies depending on the properties of the coating material to be applied, the coating speed and the absorbability of the base paper to be coated, and the surface properties. .

In high-speed coating, it is obvious that the fluidity such as the viscosity of the coating composition or the viscosity physical properties of the coating composition changes with the absorbability of the base paper. There has been a demand for measures for improving coatability from the aspect of paints and coated base paper, which greatly affect problems such as the occurrence of blemishes.

[0006]

DISCLOSURE OF THE INVENTION In the present invention, when bar coating is carried out with a rod type coater, the coating composition is prepared to have a coating material property suitable for the coating base paper, thereby producing, adhering or It is an object of the present invention to provide a method for coating without causing coating streaks.

[0007]

Means for Solving the Problems After transferring an excessive amount of coating liquid onto a coated base paper, the present inventors scrape off an excessive amount of liquid by a rotating or stationary bar, Water absorption by Bristow's device, which is a basic property of the base paper to be coated in the rod type bar coating method for obtaining the film thickness
Ka (ml / m) and smoothness Vr (ml / m ² ), physical properties of the coating composition to be coated are a capillary diameter h ₂ mm composed of a rod bar and coating base paper, and coating speed S m / min Values of viscosity η (cp) and water retention Wr (g / m ² ), thixotropy T of paint, which are obtained by measurement under shear rate [(1000 × S) / (60 × h ₂ )] specified by It has been found that the above object can be achieved by using a value A of 1 to 300 in the following equation. The capillary diameter h ₂ is approximately equal to the film thickness of the applied coating composition, and for a bar having grooves with a depth of 30 μm, h ₂ = 0.015 mm. A = (Wr × η × Ka × Vr × s × 10 ⁻⁴ ) / T

Here, the smoothness Vr and the water absorbency Ka of the coated base paper are J. The shear rate at the time of coating the coating composition (coating speed / coating speed /
The viscosity η in the capillary diameter composed of the rod bar and the coated base paper) is determined by a high pressure pump viscometer manufactured by SMT Co., Ltd., and the thixotropy index T is determined by a hercules type viscometer. Water retention Wr is TAPPI JOURN
Pekka described in the December issue of AL 1989.
J. Kaltec Sci by the method of Salminen et al.
AA-GWR WATER RE of encific
It was performed using a TENTION METER.

The fluidity-based behavior of the coating material during coating is affected by the absorbency and smoothness of the coated base paper, and the shear rate defined by the coating amount and coating rate. For example, when the absorbability of the base paper is high, the smoothness of the base paper is rough, the viscosity is high at a high shearing speed during coating, or when these are combined and the A value is 300 or more, the coating is accompanied by poor fluidity. Streaks occur.

In order to lower the A value, the coating speed is lowered to lower the shear rate, or the film thickness of the coating composition is reduced.
Whether to increase the (coating amount) or the water retention of the coating composition,
It may be considered that the absorbency of the coated base paper is reduced or the smoothness of the base paper is increased. In particular, in order to reduce the A value to less than 1, it is necessary to take measures such as internal addition, adding a large amount of chemicals such as sizing agents to the undercoat paint to drastically reduce the absorbency or significantly reduce the coating speed. It is not realistic because it involves a huge cost increase. Therefore, it is necessary to further respond to the coating physical properties based on the physical properties of the base paper in order to carry out coating without streaking, and by setting the A value within a certain range as described above, a coated paper with a good coated surface It enables a method of manufacturing coated paperboard. Hereinafter, the present invention will be specifically described.

FIG. 1 is a sectional view of a conventionally known bar coating device. FIG. 1A shows a general bar coating device. Figure (b)
Is a device that can perform both coating and scraping of the coating liquid. FIG. 6 (c) shows a mechanism in which a bar and a backing roll sandwich and press the coated paper to be applied.

FIG. 2 is an explanatory sectional view of the bar. Figure (a)
[Fig. 3] is a cross-sectional view of a bar which is not covered. FIG. 2B is a cross-sectional view of the bar with the wire covered. FIG. 3C is a cross-sectional view of a bar having grooves formed by cutting. The shapes of these grooves are not particularly limited, and the groove depth and the groove interval are not specified.

The rod coater using the bar of the type shown in FIG. 2 (c) can be applied at a higher coating speed than the bars shown in FIGS. 2 (a) and 2 (b). It is suitable for the invention.

The pigment coating composition is not particularly limited, and the pigment is clay, calcium carbonate, calcium sulfate, titanium dioxide, aluminum hydroxide, satin white, magnesium carbonate, barium sulfate, amorphous silica, styrene plastic pigment. As the binder such as urea plastic pigment, starch, casein, polyvinyl alcohol, soybean protein, styrene-butadiene latex, acrylic latex, vinyl acetate latex, urethane latex and the like are used.

Examples of the water retention agent include starch, carboxymethyl cellulose, polyacrylate and the like. Others, dispersants, PH adjusters, lubricants, defoamers, preservatives, fluorescent dyes,
Dyes, color pigments, waterproofing agents and the like can be used as required.

The coated base paper is not particularly limited, and the paper or paperboard may be either neutral papermaking or acid papermaking. The coating may or may not be applied in advance. The coating is not particularly limited, and a size press, gate roll coater, blade coater, rod coater, roll coater, air knife coater, champion coater,
A gravure coater, a simsizer, etc. are optionally used.

Further, any pulp may be used for making the base paper, and examples thereof include chemical pulp, mechanical pulp, waste paper pulp and synthetic pulp. If necessary, internal sizing agent, fixing agent,
Paper strength enhancers, drainage retention improvers, internal fillers, dyes, slime control agents, etc. may be used.

[0018]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. All the compounding parts are effective solids. Parts and% are based on weight.

Example 1 Preparation of Topcoat: Ultra White 90 as Pigment Composition
(Clay, manufactured by Engelhard Co., Ltd.) 40 parts by weight, Carbital 90 (heavy calcium carbonate, manufactured by EC Sea International Co., Ltd.) 15 parts by weight, Brilliant 15 (light calcium carbonate, manufactured by Shiraishi Industry Co., Ltd.) 30 parts by weight, Kronos 15 parts by weight of KA-10 (titanium dioxide, manufactured by Titanium Industry Co., Ltd.) are used, 0.10 parts by weight of these and Aron T-40 (dispersant, manufactured by Toagosei Co., Ltd.), 0.1 part by weight of caustic soda, Formaster AP. (Antifoam, San Nopco)
Add 0.1 parts by weight to the dispersion water, and add 3 by a Choles disperser.
The mixture was stirred for 0 minute to obtain a 70% concentrated pigment slurry.

Then, with respect to 100 parts by weight of the pigment slurry, Penford gum 290 was used as a binder composition.
(Hydroxyethyl etherified starch, manufactured by Penford Co.) 3 parts by weight, SN-307 (carboxy modified SBR latex, manufactured by Sumitomo Dow Co., Ltd.) 12 parts by weight, diluted water was added to these, and the mixture was stirred for 10 minutes to obtain a 57% concentration. A coating composition was obtained. The details of the coating are described in Coating below.

Preparation of undercoat paint: 60 parts by weight of caobrite (clay, manufactured by Seal Co.) as a pigment composition, Softon 22
00 (heavy calcium carbonate, Shiraishi Calcium Co., Ltd.) 40
Parts by weight, MS4600 as a binder composition
(Urea phosphate esterified starch, manufactured by Japan Food Processing Co., Ltd.) 5 parts by weight, JSR0668 (carboxy modified SBR latex, manufactured by JSR Co.) 16 parts by weight The same as the above-mentioned top coating composition except that it is used, and an undercoat of 62% concentration is used. A coating composition for use was obtained. (Undercoat is Examples 1, 2, 4 Comparative Examples 1, 2,
The same conditions with a coating amount of 8 g / m ² common to 4 and 5. )

Example 2 Preparation of top coating composition: A coating composition having a concentration of 45% was prepared in the same manner as in Example 1 above. The undercoat is the same as in Example 1.

Example 3 Preparation of topcoat paint: The same as in Example 1 above, but with a 61% concentration coating composition. The coating composition of the undercoat is the same as in Example 1, and the coating amount is 11
g / m ² .

Example 4 Preparation of Topcoat Paint: The same as in Example 1 above, but with a 61% concentration coating composition. The top coating speed is 200 m / min. The undercoat is the same as in Example 1.

Comparative Example 1 Preparation of top coating composition: A coating composition having the same concentration as that of Example 1 but having a concentration of 61% was prepared. The undercoat is the same as in Example 1.

Comparative Example 2 Preparation of Topcoat Paint: Common to Example 1 and the pigment slurry,
With respect to 100 parts by weight of this pigment slurry, 6 parts by weight of Penford gum 290 (hydroxyethyl etherified starch, manufactured by Penford Co.) as a binder composition, SN-30
7 (carboxy modified SBR latex, manufactured by Sumitomo Dow)
10 parts by weight were used, diluted water was added to these, and the mixture was stirred for 10 minutes to give a coating composition having a concentration of 59%. The undercoat is the same as in Example 1.

Comparative Example 3 Preparation of Topcoat Paint: Same as Example 1 above. The coating composition of the undercoat is the same as in Example 1 and the coating amount is 5 g / m ² .

Comparative Example 4 Preparation of Topcoat Paint: The same as in Example 1 above, but with a 63% concentration coating composition. The undercoat is the same as in Example 1.

Comparative Example 5 Preparation of topcoat paint: The same as in Example 1 above. The coating speed was 900 m / min under the coating conditions. The undercoat is the same as in Example 1.

Comparative Example 6 Preparation of Topcoat Paint: Same as Comparative Example 2 above. Uses a bar different from those used in Examples 1 and 2 and Comparative Examples 1 to 5 under coating conditions. (See coating below) The undercoat is the same as in Example 1.

Coating: Examples 1, 2, 4, Comparative Examples 1, 2,
In Nos. 4, 5 and 6, the undercoating coating composition was
CLC6000 coater (Sens) equipped with ungrooved rod so that the coating amount is 8 g / m ² on uncoated white paperboard of 5 g / m ²
or & Simulation Products)
Was used at a coating speed of 400 m / min. In Example 3 and Comparative Example 3, only the coating amount is changed.

For the top coating, the coating materials described in each of the examples and comparative examples were applied to the above-mentioned base coating paper so that the coating amount was 11 g / m ² , the groove depth was 30 μm, the pitch was 100 μm, and the groove peak length was 30.
C equipped with a rod having a length of μm ((d) in FIG. 3)
An LC6000 coater was used, and in Examples 1 to 3 and Comparative Examples 1 to 4, the coating speed was 400 m / min (the shear rate in this case was 4.4 × 10 ⁵ sec ⁻¹ ), and in Example 4, 2
00 m / min (shear speed is 2.2 × 10 ⁵ sec ⁻¹ ), and in Comparative Example 5 900 m / min (shear speed is 9.9 × 10).
^It was applied for ⁵ sec ^-1 ). Immediately after coating each of the upper and lower coatings, the coating was dried with an infrared dryer attached to a coater.

In Comparative Example 6, the coating material of Comparative Example 2 was used as the top coating material, and the undercoated coated paper had a groove depth of 30 μm and a pitch of 20 so that the coating amount was 11 g / m ^2.
Coating was carried out at a coating speed of 400 m / min using a CLC6000 coater equipped with a rod having a length of 0 μm groove ridges of 30 μm (FIG. 3 (e)). Drying was performed with an infrared dryer attached to a coater immediately after the top coating, as in the other examples and comparative examples. The shear rate in this case is 4.4 x 1
It is 0 ⁵ .

Calender treatment: This pigment coated paper was used for JI
Processed according to SP8111, metal roll surface temperature 1
The coated surface was supercalendered at 00 ° C. and a nip linear pressure of 100 kg / cm. The number of treatments is twice. The coated paper was treated again according to JIS P8111 to evaluate the coating amount and the occurrence of coating streaks. The results are shown in Table 1.

Test method Coating amount measurement: Measured by measuring ash content of coated paper and coated base paper Coating streak: Ammonium chloride solution (ammonium chloride; 10 parts by weight, isopropyl alcohol; 10 parts by weight, water; 100)
The coating sample is dipped in (part by weight) for 10 minutes, and is heat-treated by holding it over an electric heater to carbonize the coated base paper to visually reveal coating unevenness of the coating layer. With this sample, the occurrence of coating stripes is visually evaluated. The product with streaks is judged x. Paint dregs: After coating, the CLC6000 coater's rod bar was observed and evaluated as XX. X is judged if the residue is observed.

Smoothness and absorbency of coated base paper: J. TAPP
It was determined by the liquid absorption test method (Bristow's method) of the paper and paperboard of I paper pulp test method No. 51-87.

Viscosity at coating shear rate
The viscosity at coating (in Table 1) is determined by a high pressure pump viscometer manufactured by SMT Co., Ltd., and the thixotropic index is determined by a Hercules type viscometer.

Water retention is TAPPI JOURNAL 1
989 December issue of Pekka J. et al. Sa
by the method of Lminen et al., Kaltec Science
tiaff's AA-GWR WATER RETE
It was carried out using a NTION METER.

[0039]

[Table 1]

[0040]

As can be seen from the above examples, according to the manufacturing method of the present invention, the calculation formula A = (Wr × η × Ka × V
By adjusting the physical properties of the coating composition according to the coating base paper so that the A value given by r × s × 10 ⁻⁴ ) / T is 1 to 300, a rod type coating device is used. It is possible to manufacture coated paper and coated paperboard without coating streaks.

[Brief description of drawings]

FIG. 1 is a schematic view of a rod-type bar coating device, (a)
Indicates that the coating part and the scraping part are separated, (b) indicates that the coating and scraping can be performed integrally, and (c) indicates that the coated paper is sandwiched between the bar and the backing roll, and that a pressure mechanism is provided.

FIG. 2 is an explanatory cross-sectional view of a bar, each bar has a perfect circle in cross section, and (a) is one not surface-coated,
(B) is coated with wire, (c) is grooved by cutting,

FIG. 3 is an explanatory sectional partial view of a bar, (d) is a partial sectional view of a bar having a pitch of 100 μm, and (e) is a pitch 200.
FIG. 7 is a partial sectional view of a μm bar.

[Explanation of symbols]

 1 Paper 2 Backing Roll 3 Applicator Roll 6 Paint Vat 7 Coating Composition 9 Bar Holder 10 Bar A Depth B Wire L Groove Length d Wire Surface Plating p Pitch h Cutting Depth

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Endo 2-3-2 Higashishinozaki, Edogawa-ku, Tokyo Honshu Paper Co., Ltd.

Claims (1)

[Claims] 1. A method for producing coated paper and coated paperboard using a rod-type coating device, comprising:
a) is a value measured by a Bristow device of 0.05 to 1.0 (ml / m)
Of which the smoothness (Vr) is in the range of 1.0 to 10.0 (ml / m ² ) as measured by Bristow's device, and which has a capillary diameter composed of a rod bar and coated base paper. h ₂ mm and the shear rate [(1000 × S) / (60 × h ₂ )] specified by the coating speed S m / min in the shear rate region of 10 ² to 10 ⁷ sec ^{-1 have} a viscosity of η ( cp) is used, and the characteristics of the coating composition are prepared so that the value of A is in the range of 1 to 300 in the calculation formula shown below, and the coating is performed. The method for producing coated paper and coated paperboard. A = (Wr × η × Ka × Vr × S × 10 ⁻⁴ ) / T where Wr is the water retention (g / m ² ), η is the viscosity at the shear rate during coating (cp), and Ka is Bristow's. Water absorption by the device (ml / m), Vr is smoothness by the Bristow device (ml / m)
m ² ), T is the thixotropy of the paint, S is the coating speed (m / mi
represents n).