JPH03124900A - Preparation of sheathing material - Google Patents

Abstract

PURPOSE: To manufacture surface-coated cardboard usable as exterior materials by using a printing machine having plural printing stations and coating the cardboard with a specific coating material. CONSTITUTION: The printing machine having at least two printing stations is used and a web of unbleached cardboard having smooth, dense and high strength surfaces is selected. The web is introduced to the first station of the printing machine and coated with the coating material on at least one surface, and then at the second station, the printing is performed on the coated surface of the web. Such a coating material is used as contains 20-25 parts low thermosensitivity binder and 100 parts pigments, and has the viscosity showing 7-11 seconds as the measured value by No.3 Zahn-cap and 50-60% solid content by percentage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing an exterior material. Specifically, the present invention relates to a method for manufacturing an exterior material using a printing machine.

[Prior Art] Exterior packaging materials are generally understood to mean packaging materials for containers such as bottles and cans, transportation cartons, and the like. Most of the exterior packaging materials are made of paper or cardboard, and a typical example is first market paperboard, or corrugated cardboard. Unbleached cardboard is specially manufactured for the exterior of the container. Such cardboard must have high strength, so it is usually manufactured using high-strength IIM, and chemical additives are added during manufacturing to improve moisture resistance.

At least one side of the manufactured cardboard is usually treated with a white coating material or the like. This is because the surface of unbleached cardboard is brown and rough, so a good printing surface cannot be obtained as it is. Coating methods for one side of the cardboard include on-machine coating and off-machine coating using coating materials containing latex, clay, and titanium dioxide. Another method for treating one side of cardboard to improve printability is to coat the cardboard with high quality label paper or plastic film.

There are two types of cases that use unbleached kraft paper with surface treatment (clay coating treatment).

One of them is a cardboard box. When manufacturing such surface-treated corrugated cardboard boxes, cardboard base paper (for example, 1,
Approximately 30 to 65 pounds per 000 square feet, 1 or 9
The outer surface of approximately 135-29.3/(g) per 2.9 m is clay-coated in a vapor mill, on which a high-quality figure is preprinted by flexography, and then this base paper is used as an outer liner in the corrugating process. used. The corrugated board thus formed is formed into a corrugated box. The other one is a drink'8'm8
It is a folding carton made of single layer paper of m. In this case, unbleached cardboard (e.g., about 40 to 100 pounds per 1,000 square feet, or about 18 to 45 pounds per 92.9 m) is coated with a vapor mill and then gravure printed and cut to form the box. be done.

The cardboard used in the latter case must have a higher basis weight and be more durable than the paper used in the former case. At present, clay-coated paper with a large basis weight is expensive because it is in limited supply. Additionally, lightweight coated paper for corrugated board is not often manufactured in the United States. The reason for this is that this paper cannot generally be manufactured in a craft mill, and requires the hands of a specially skilled person to manufacture it. Under these circumstances, many users are turning to expensive laminates using plastic films and label paper.

[Summary of the Invention 1 According to the present invention, cardboard whose surface is coated for use as an exterior material can be manufactured using a printing machine. In the method of this invention, the coated paper is produced by printing unbleached and uncoated kraft base paper, applying a single layer or multiple coatings to one side of the base paper, and then applying a single or multilayer coating to one side of the base paper, and applying the coating to the coated side using the same or another printing machine. It is formed by printing. This method can be applied to both flexo printing machines and gravure printing lines. The coating and printing surface of the coated paper obtained by this method has few scratches and is excellent in smoothness and gloss, and can fully compete with that produced by vapor mills. The method of this invention is dependent on various factors including the nature of the paper surface before coating, the type of coating material, the location of the printing press, etc.

The first step involves selecting an unbleached paper for coating and printing on a printing press. The selection of paper is made taking into consideration whether the final product will be used as a base paper for corrugated boards or as a base paper used in a single layer for folding cartons. No matter what purpose it is used for, the paper surface is smooth! And it has to be durable. Furthermore, the coating material must be of good quality, and it is desirable that the paper surface be highly treated to improve the adhesion of the coating material. The surface roughness of the paper is required to be 300 units or less for cardboard base paper and 330 units or less for single layer cardboard. For normal cardboard base paper and single layer cardboard,
Since the values are 350 or more and 400 or more, respectively, the above conditions are quite strict. Similarly, the density of paper, which is determined by its air permeability, is important. The paper used in this invention must exhibit a high value of 30 seconds or more in the Gurley air permeability test. These properties can be obtained by applying certain techniques during production on a paper machine.

One method is to apply hard wood grains to the paper surface by containing 85% or more of hard wood in the furnish. When this furnish is applied in a secondary headbox, the stock is highly refined and Williams Freeness (14i
11iams rreeness) is 0117 or more and 3
It will be 50 to 400 seconds. Furthermore, a means for removing the binding 13111 and sand from the paper surface using a cleaning agent is also required. The paper produced in this manner is calendered to improve the chef yield roughness of the paper surface. Paper that does not meet the above property criteria has a rough, uneven surface and poor gloss, and cannot be used as the coating and printing paper of the present invention.

The second step involves selecting the printing press and accessory elements for applying the coating. In flexographic printing machines, the anilOX roller is preferably a laser etched roller with a close packed (30 degree) cell arrangement to obtain the most uniform coating. The depth of the cell should not exceed 100 microns (μm). Also 1 inch (2,54 cp
Approximately 120 to 360 lines per screen size (sc
An engraved O-ra with reen s + ze) is preferred.

The printing blanket for flexographic printing is preferably made of a rubber material with a Shore hardness of 55 or less. If the hardness value is too high, the coating weight will decrease, and if it is made of a photopolymerized polymer, it will cause unevenness on the printed surface. Further, in the case of gravure printing, indirect gravure printing using an etching roller and a printing plunket having the same characteristics as in the case of flexographic printing is preferable.

The third step involves preparing the coating material. Typical coating materials commonly used in paper or board manufacturing plants cannot be used on printing presses. The reason is that the fluidity is low and the leveling ability is too high. Furthermore, when a general coating material is used in a printing press, uncoated portions may occur. The properties of coating materials for printing presses can be adjusted by the type of binder, the ratio of binder to pigment and the type of pigment.

Binder selection is important. In printing presses, there is no way to adjust the temperature of the coating material, so the temperature of the coating material is not kept constant and its flow rate varies. Therefore, temperature sensitive binders such as starch cannot be used. Preferred is synthetic latex. For example, polyvinyl acetate (PAvC), styrene butadiene rubber (SBR), and polyacrylate can be used, and these can be used either as a medium or as a mixture. A preferred mixture is 70/30 PAVc/SBR. Furthermore, regarding the binder/pigment ratio, a low binder ratio of 16/100, such as that used in conventional paper surface coatings, is not desirable. The reason for this is that the fluidity of the coating material decreases. The six desirable binder/pigment ratios are 20/100 to 25/100. Furthermore, clay, titanium dioxide, and calcium carbonate can also be used as pigments to improve the brightness of the coating material. The use of pigment mixtures containing titanium dioxide improves the hiding power on unbleached paper surfaces. Other additives can also be added to adjust or improve the flowability and smoothing ability of the coating material. For example, calcium stearate, glycols, small intermolecular water-soluble polymers, etc. can be added. The concentration of these additives is usually less than 5% by weight. The coating material of the present invention does not require pH adjustment, unlike conventional coating materials applied to paper machines.

In addition, the viscosity of the coating material in this invention is NQ
3 (7) Zaankup (Number 31ahn)
When measured with a cup), it is preferably 7 to 11 seconds.

The coating material is applied to the base paper one or more times prior to printing. The number of coatings depends on the nature of the coated surface required and the possible markings; the number of stations. If a very smooth coating surface is required, the weight of the coating material being coated (1 to 1.5 pounds per 1,000 square feet (92,9 TIt) for each coating)
, 45 to 0.611 g).

Factors to obtain the most suitable coated surface for printing include coating weight and coating material brightness (ie, bright pigment concentration). For example, a total coating weight ta of about 2 pounds (0.97 (g)) per 1,000 square feet (929 Tli) is required to ensure sufficient smoothness and gloss of the printed surface. Note that such characteristics of the coated surface are required when there is no white portion on the printed surface, or when there is only a small amount of white portion.

On the other hand, if sufficient brightness (brightness by TAPPI of 78 to 80) is required on the coating surface, titanium dioxide is contained in the coating material at a high concentration (40 to 50%) and the coating weight is 1000%. square foot (9
4 pounds (1,8*y) or more per 2,9 m). It has been found that after the coating has been applied using a printing press, a pigmented white ink can be applied to the printing surface. Finally, there is no need to modify the printing press when applying the method of the invention. By selecting a substrate with optimal smoothness, selecting a printing machine, and preparing a coating material according to the purpose of use, it is possible to obtain a product (coated paper) with a white surface that can be used as an exterior material. can.

[Purpose] The purpose of this invention is to print paper using a printing press.
It is to create. This coated paper is subjected to printing by that printing machine or by another printing machine, allowing high quality printing.

Another object of the invention is to improve the surface quality of at least one side of unbleached cardboard at low cost. The surface of the cardboard is completely coated, bright, uniform and smooth, allowing for high quality printing using any printing method.

Examples The method of the invention can be applied to any type of flexographic or gravure printing press. A typical flexographic printing machine to which this invention applies has a plurality of flexographic printing stations arranged around one or more large diameter impression cylinders. Furthermore, drying units are arranged around the impression cylinder, alternating with flexo printing stations. moreover,
A varnished John is provided in front of the rewind stand. A space is provided after each flexographic printing station for coating, in which a doctor blade is arranged. This smoothes the coated surface after coating and before drying.

A typical gravure printing press to which this invention is applied has two or more gravure middle stations alternating. Direct method (di) in gravure printing presses
It is not possible to obtain a sufficient coated paper with the ink.

Therefore, it is necessary to perform coating by an indirect method in a gravure printing machine.

In FIGS. 1A and 1B, a large basis weight cardboard or cardboard base paper, ie a web W for packaging material, is fed from a roller 10 and guided to a flexographic printing machine. The web W includes a first guide roller 22 and a second guide roller 2.
3, the first flexographic printing station 1
Leads to 2.

Here, the first coating in the present invention is applied to the web W. Flexographic printing station 12 includes an anilox roller 13 arranged to rotate within coating pan 14 .

This roller 13 is partially immersed in the coating material and picks up the coating material and delivers it to the applicator roller 17 . A mesh is formed on the surface of the roller 13, and is set so that the suspension of the coating material pulled up from the coating pan 14 is constant.

The rollers 13 useful in this invention are chrome plated and have approximately 120 to
It has a screen size of 360 lines, and a smaller number indicates a larger capacity. The coating material retained on the meshed surface of roller 13 is transferred to applicator roller 17 . In a typical flexo printing method, a printing pattern to be transferred to the web W is formed on the applicator roller 17. However, in this invention, the applicator roller 17 is used to apply the first coating to the web W and does not have such a pattern. The surface of the back roller 25 acts as a web holding surface and the web W is held between it and the applicator roller 17. After the coating is applied to the web W in this manner, the coating is smoothed by a smoothing blade 20 (see FIG. 2). After passing through this smoothing process, the web W is guided into the drying unit 21. Note that the blade 20 is inclined at an angle of about 900 with respect to the web W in order to exhibit the best smoothing ability.

After passing through the drying unit 21, the tube W is transferred to the back roll 2.
5 and is led roughly to another flexo printing station. In this example, three flexographic printing stations 26, 27 .
28 are provided. In addition, each printing station 26
．． Next to 27.28 are drying units 11.15 and 11.15 respectively.
．． 16 are provided. These printing stations 2
6.27.28 are for applying a coating to the web W in a small manner, so they are the same as the conventional printing process.

After passing through the last drying unit 16, the web W is sent to another back roller 43 (see FIG. 1B) and is coated with another color, ie, printed. in this case,
The web W is guided by idle rollers 34, 35 and is further fed via idle rows 518, 19 to back roller 43 shown in FIG. 1B. The back roller 43 has five flexo printing stations 29°30.
31, 32, and 34a are provided. Also, in the back row 543, each printing station 29, 30, 31, 3
2. Drying units 18a, 19a, in the position following 34a,
24.33.35a are provided. Drying unit 3
The web W that has passed through 5a is guided by idle rollers 36, 37 and further led to a varnish station 39 and a subsequent drying station 40 via an idle roller 38 (see FIG. 1A). Drying station 4
The web W that has left 0 passes through the idle roller 41 to the row 5
42 and is wound around this roller 42. As described above, the method of the present invention can be applied to typical flexo printing machines, and can be applied as is without any changes other than the configuration of the applicator roll (having a printing blanket) in the coating base printing station. . This also applies if the printing machine is a gravure printing machine. Therefore, according to the present invention, there is no need to attach an expensive coating device to the printing machine or to perform separate coating.

Coating tests using a flexo printing machine and a gravure printing machine will be described below.

In the first test, the web was paperboard manufactured by Westvaco Corporation (trade name "KRAFTPA").
ni '°〉 and cardboard base paper (product name "PRINT")
AFT") was used and the coating was carried out by a flexible printing machine. Two formulations were used as coating materials, one containing only polyvinyl acetate latex as a binder and the other containing polyacetic acid as a binder. Contains vinyl and styrene butadiene rubber.

Furthermore, calcium stearate is added to some coating material samples for the purpose of improving the ability to smooth the coating surface. Coating material sample NQ1 was applied to both a flexible photopolymer printing plate and a rubber printing plate. On the other hand, coating material sample 2 was applied only to a rubber printing plate. The RAFTPA is fully calendered and its surface is similar to the polished surface of hardwood, making it ideal for Sheffield.
The roughness is 330 units. The chef yield roughness of the PR[NTKRAF knife shows a value lower than the average chef yield roughness of 230 units.

When each of the above-mentioned coated materials, or webs, were coated by passing them through a printing machine, each coating process yielded 1,000 square feet (92.9 ffl) of the web.
The coating weight per coat was approximately 1 pound (0.45 Kg). The coating number of coating batting order 2 under the same conditions is coating viNo. It was slightly more than 1. Considering the sheaf yield roughness of the web and the surface properties of the coated coating, rubber blankets are found to be superior to photopolymerized blankets of similar hardness and wettability.

Coating materials containing calcium stearate are PR[
NrKlt^[[Coated against. Adding only about 1% calcium stearate on a solids basis improved chef yield roughness by 15 units. Also,
The brightness of the coated web was proportional between coatings as expected. Additionally, the spreading and smoothing ability of the coating material was non-uniform above about 57% solids content.

The print test on the coated web consisted of one coat of bright white ink, one coat of clear sealer over the white ink, and an additional coat of the applied tone print over that. moreover,
A varnish is applied to this coating surface as is customary for exterior materials. The evaluation of the printed surface was based on the quality of the print, the brightness of the coated surface, and a comparison of the printed surface obtained by the method of the invention with the printed surface obtained with the clay coating material of the reprint. As a result, coating material sample No. 2 (mixed binder) was found in coating material sample No. 2 (mixed binder). 1, and the rubber blanket was found to be superior to the photopolymerized polymer blanket. Furthermore, a clear correlation was observed between the quality of the printed surface and the smoothness of the underlying coating surface.

It was also found that the higher the smoothness, the fewer missing dots in the applied color printing, and generally the higher the image quality.

When using a gravure printing machine, the direct method
It has been found that printing with Ct graVtlre DrOCeSS) results in an undesirable split pattern. However, the indirect method (indirC
The split pattern problem was solved by switching to printing with tgravure arrcrngesent).

The range of the coating weight of the coating material in the direct method and indirect method is 1. Goo square foot (92,9
1.1 to 2.1 pounds (0.5 to 0.958
9).

In the indirect method, the coating material is lifted from the coating pan by a row of notched rows. This roller has a doctor blade numbered thereon, which adjusts the amount of coating material. The conditioned coating material is then transferred to a rubber printing roller. The printing roller applies the coating material to the paper by sandwiching the web or cardboard between it and a back roller. The notched roller and printing roller were rotated at the same speed as the web in most tests, but speed differences of up to 20% are allowed.

In the direct method, a notched roller for lifting the coating material from the coating pan has a doctor blade for adjusting the amount of coating material. The coating material on the roller is then coated directly onto the web moving at the same speed. Once the web is coated, it will be approximately 0.5 inch (1,27 cm) in diameter.
) The coating surface is smoothed by the rod. A coating formulation containing a single binder (polyvinyl acetate) was used at a solids content of 56.8% and was applied to cardboard 1
, 42 pounds (1
8, coated at a ratio of 'aKy>. In all cases, a smooth coated surface suitable for printing was obtained.

[Effects of the Invention] As described above, the present invention relates to a coating/printing method carried out using one stamp 81 machine.

According to this method, the quality of unbleached paper and cardboard for exterior packaging can be improved.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1A is a schematic diagram showing a part of the Mark WA machine, FIG. 1B is a schematic diagram showing the remaining part of the Mark S machine, and FIG. 2 is a partially enlarged view of FIG. 1A. It is a diagram. 12.26, 28, 29, 30.3t, 32, 34a・
...Flexographic printing station 13...Roller 17...Applicator roller 20...Blade

Claims (10)

[Claims] (1) A method of manufacturing cladding using a printing press having at least two printing stations, the steps comprising: selecting a web of unbleached cardboard having a smooth, dense, and strong surface; and the printing press. directing the web to a first printing station of the printing press; coating at least one side of the web with a coating material at the first printing station; and applying the coating to a second printing station of the printing press. printing on the surface of the web, wherein the coating material contains a binder with low temperature sensitivity and a pigment in a ratio of 20 to 25 parts of the binder to 10 parts of the pigment.
0 parts, and its viscosity is No. A method in which the Zahnkapp measurement value of No. 3 is 7 seconds to 11 seconds, and the solids content is 50% to 60%. 2. The method of claim 1, wherein said binder is selected from the group consisting of polyvinyl acetate, styrene butadiene rubber, polyacrylate, and mixtures thereof. 3. The method of claim 2, wherein said pigment is selected from the group consisting of clay, titanium dioxide, calcium carbonate, and mixtures thereof. (4) At other printing stations on the same printing press, multiple layers of coating material are applied, and each layer of coating material weighs between 1 pound and 1.5 pounds per 1,000 square feet (92.9 m^2). Pound (0
．． 45Kg to 0.68Kg), and the total weight of the coating material is 4 to 6 pounds (1.8Kg to 2.7Kg) per 1,000 square feet (92.9m^2). The method described in section. (5) the printing machine is a flexo printing machine having a roller at each printing station, the roller being 1 inch (2.
5. The method of claim 4, comprising a blanket made of natural rubber having a screen size of 120 to 360 lines per 54 cm and a shore hardness of 55 or less. (6) The method according to claim 5, wherein the coating surface of the web is adjusted each time after each coating step. (7) The method according to claim 4, wherein the printing machine is a gravure printing machine, and the coating surface of the web is adjusted each time after each coating process. (8) The web is a corrugated paperboard, its weight is 30 pounds to 65 pounds (13.5 kg to 29.3 kg) per 1,000 square feet (92.9 m^2), and its Sheffield roughness is 300 units. 7. The method of claim 6, wherein the Gurley air permeability is at least 30 seconds. (9) The web is a folding carton cardboard, and its weight per 1,000 square feet (92.9 m^2) is 40 pounds to 100 pounds (18 Kg to 45 kg).
7. The method of claim 6, wherein the Sheffield roughness is less than 330 units and the Gurley air permeability is at least 30 seconds. (10) A method of manufacturing an exterior material using a printing machine, the process comprising: selecting a web of unbleached base paper with a Sheffield roughness of 330 units or less and a Gurley air permeability of 30 seconds or less; and applying the web to a printing machine. a printing station; at the printing station, coating at least one side of the web with a coating material; and directing the coated side of the web to a doctor blade positioned at an angle of approximately 90° relative to the web. drying the coated side of the web; and printing the coated side of the web at another printing station of a printing press, the coating material being temperature sensitive. It contains a binder and pigment with a low viscosity of 20 to 25 parts of binder and 100 parts of pigment. 7 based on Zahn cup measurements of 3.
s to 11 s, and its solid content is 50% to 60 s.
%, and the binder is selected from the group consisting of polyvinyl acetate, styrene butadiene rubber, polyacrylate, and mixtures thereof, and the pigment is selected from the group consisting of clay, titanium dioxide, calcium carbonate, and mixtures thereof. Method.