JPH0332781A - Production of film coated paper - Google Patents

Abstract

PURPOSE:To obtain a high quality practical product free from streaks in the coated surface by coating a plastic film with a pigment coating liq. contg. wet-pulverized titanium oxide by means of a bar coater. CONSTITUTION:When only rutile or anatase type titanium oxide is used as a pigment, it is dispersed in water and wet-pulverized by means of a wet pulverizer such as a sand grinder, a ball mill or an attriter to prevent secondary coagulation. When the titanium oxide is used in combination with other pigment such as clay or kaolin, they are dispersed in water and pulverized in the same way. After coarse grains are perfectly removed by passing through a filter, the pigment is mixed with an adhesive component and a plastic film such as a PE or PP film is coated with the mixture by means of a bar coater and dried. A product with a uniform pigment coated surface having superior opacity and printability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing high-quality film-coated paper by applying a pigment coating liquid to a plastic film using a bar coater.

[Conventional technology]

In general, synthetic paper based on plastic has superior water resistance compared to general-purpose paper or coated paper made from natural valves, and features such as not tearing easily even when wet. Therefore, it is suitable for use in outdoor posters, etc.

Film-coated paper is one type of synthetic paper that is made printable by coating the surface of a plastic film with an aqueous or solvent-based coating solution containing pigments and adhesives as main components.

Film-coated paper that uses an aqueous coating solution is usually prepared by adding an inorganic or organic pigment and a latex or water-soluble polymer adhesive, and then the pigment coating solution is prepared without treatment or with corona discharge or anchor treatment. It can be obtained by coating the treated plastic film using a coating machine such as a gravure coater, roll coater, bar coater, or air knife coater.

Film-coated paper of the type that uses this water-based coating liquid is described in Japanese Patent Publication No. 33-336 and Japanese Patent Publication No. 50-39700, but it may not be sufficient in terms of performance depending on the materials and manufacturing method used. There are some difficult aspects.

For example, when a relatively large amount of coating is desired, coating with a bar coater is effective, but titanium oxide, which is suitable for increasing the hiding power of the sheet, is used as a pigment for this coating.
As with paper coating, when applying a pigment coating liquid prepared by adding a binder after dispersing the pigment using an agitator such as a coalesce or propeller mixer, streaks tend to appear on the coated surface, resulting in a high quality product that is practical. film-coated paper is difficult to obtain.

[Problem to be solved by the invention]

The purpose of the present invention is to solve the above-mentioned drawbacks of conventional film-coated paper obtained by bar-coating a plastic film with an aqueous pigment coating solution containing titanium oxide.
The present invention provides a method for obtaining a practical, high-quality film-coated paper.

[Means to solve the problem]

The present invention provides a method for producing film-coated paper by bar-coating a plastic film with a pigment coating liquid containing titanium oxide, which is characterized in that wet-pulverized titanium oxide is used as the titanium oxide. It is a method of manufacturing paper.

[Effect]

The inventors of the present invention have conducted extensive studies in order to solve the problem that when bar coating a pigment coating solution containing titanium oxide, streaks tend to appear on the coated surface and it is difficult to obtain a practical, high-quality film-coated paper. . As a result, it was found that the streaking phenomenon was caused by huge secondary aggregation of titanium oxide, which was included to impart concealing properties.

Therefore, the present inventors have found that the shearing force of a normal stirrer is insufficient to break up the secondary agglomeration of titanium oxide, and that wet grinding using a sand grinder or the like is necessary.

Incidentally, the titanium oxide used in the present invention is applicable to both rutile type and anatase type titanium oxide, but as a wet pulverization method, after dispersing in water, grinding with a sand grinder, ball mill, attritor, etc. Secondary agglomeration is broken up by processing with a wet grinder.

In the method for producing film-coated paper according to the present invention, the pigments constituting the coating liquid include not only titanium oxide described above but also clay kaolin, which is commonly known as a pigment for coated paper. , aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate, zinc oxide, satin white, calcium sulfate, talc, plastic pigments, and the like.

In addition, when using titanium oxide and other pigments together, the blending ratio of titanium oxide should be at least 5 to increase the hiding effect.
It is desirable to use % or more together.

To wet-pulverize titanium oxide, use a sand grinder or ball mill after dispersing titanium oxide in water when using it alone, or after dispersing it in water when using titanium oxide in combination with other pigments. , Attritor, or other wet grinder.

In addition, when carrying out the above-mentioned wet pulverization treatment, a dispersant is appropriately used in order to improve the dispersion of the pigment.

The above wet-pulverized pigment dispersion or the pigment coating solution below can be further passed through a filter to completely remove large particles, completely eliminating the risk of streaks forming on the coated surface. be able to. In this case, as for the size of the filter, one cut to 75 microns or more is effective, more preferably one cut to 50 microns or more.

The pigment coating liquid used in the present invention contains the above-mentioned pigment and adhesive as main components, similar to conventional coating liquids for coated paper. Examples of adhesives include conjugated diene polymers such as styrene-butadiene copolymers, methyl methacrylate-butadiene copolymers, and acrylic polymers such as polymers or copolymers of acrylic esters and/or methacrylic esters. Latexes such as coalescing latex, vinyl polymer latex such as ethylene/vinyl acetate copolymer, or modified latex obtained by modifying these various polymer latexes with monomers containing functional groups such as carboxyl groups; casein, soybean protein Starches such as positive starch and oxidized starch; Cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; Conventional coatings such as polyvinyl alcohol, olefin/maleic anhydride copolymer, melamine resin, epoxy resin, etc. One or more types of paper adhesives are appropriately selected and used. Among these, from the viewpoint of water resistance of the coating layer, a system using a latex alone or a system mainly composed of latex is preferable.

In general, the adhesive is used in an amount of 5 to 100 parts by weight per 100 parts by weight of the pigment.
The amount of knots is about 50 parts by weight, more preferably about IO to 30M parts. In addition, various auxiliary agents such as a dispersant, a thickener, an antifoaming agent, a coloring agent, a mold release agent, a preservative, and a crosslinking agent are appropriately blended into the coating liquid as required.

The solid content concentration of the pigment coating liquid thus obtained is generally 30 to 30.
It is about 75% by weight, but considering the operability, it is 40~7% by weight.
A range of 0% by weight is preferred.

In the present invention, examples of the plastic film used for applying the pigment coating solution include polyolefin films such as polyethylene, polypropylene, ethylene propylene copolymer, polybutene-1, polyethylene terephthalate, polystyrene, polyvinyl chloride, nylon, etc. In addition to transparent films, examples include pigment-added polyolefin films.

These plastic films are usually subjected to corona discharge treatment, flame treatment, ionizing radiation treatment, chemical treatment, or anchor treatment in order to increase their receptivity to coating liquids.

As a method for applying the pigment coating liquid to the plastic film, the present invention presupposes application using a bar coater. Here, the term "bar coke" refers to a coater that uses a bar to meter excess paint out of the paint applied to a sheet, thereby bar-coating one or both sides of a plastic film with the pigment coating liquid.

The amount of pigment coating liquid to be applied is generally 3 to 3 per side by dry weight.
It is about 50 g/m2, but considering the quality of the film coated paper obtained, printability, etc., it is 3 to 25 g/m2.
It is desirable to adjust within a range of about 2.

Various conventionally known methods such as steam heating, hot air heating, gas heater heating, electric heating heater, infrared heating heater, high frequency heating, laser heating, electron beam heating, etc. can be used to dry the wet coating layer. Can be adopted.

The film-coated paper thus obtained is subjected to a calender treatment such as a super calender or a gloss calender, if necessary.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

Note that "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 A 60 μm polypropylene film (trade name: Evo ξ-n P-100) obtained by incorporating an antistatic agent of Film Co' and biaxially stretching.
0, manufactured by Nippon Shokubai Chemical Co., Ltd.) (solid content) was diluted with 87 parts of isopropanol, and a polyepoxy compound (
Product name: Epikote 828 (manufactured by Shell Chemical Co.)
An anchor-treated polypropylene film was prepared by coating both sides to a thickness of m2.

Kaolin (trade name: UW-90) was added to water containing 0.2 parts (solid content) of sodium polyacrylate (trade name: Nearon A-9, manufactured by Toagosei Kagaku Kogyo ■) using a Coles disperser.
, made by EMC) 50 parts, light calcium carbonate (product name:
Tama Pearl TPK, manufactured by Okutama Kogyo Of3) 40 parts (solid content), titanium oxide (product name: FA55W, Furukawa Mining ■
After dispersing 10 parts of the pigment, the dispersion was treated with a sand grinder to prepare a pigment slurry with a solid content concentration of 60%.

To this slurry were added 16 parts (solid content) of carboxy-modified styrene-butadiene latex (product name: 5N-307, manufactured by Sumitomo Naugatac), and an epoxy compound (product name: Bunacol, PC-1000, Nagase Chemical) as a crosslinking agent. Add 1 part of
A 3% aqueous pigment coating liquid was obtained.

The pigment coating solution thus obtained was coated on both sides of the anchor-treated propylene film at a dry weight of 20% per side.
A film-coated paper was prepared by bar-coating the film to a concentration of g/m2.

Example 2 A film coated paper was produced in the same manner as in Example 1 except that only the titanium oxide was previously treated with a sand grinder.

Example 3 The pigment slurry with a solid content concentration of 60% obtained in Example 1 was passed through a Kron filter 50 times, and then a film coated paper was prepared in the same manner as in Example 1.

Comparative Example 1 A film coated paper was produced in the same manner as in Example 1 except that the pigment slurry was not subjected to the sand grinder treatment.

The film-coated papers prepared in Examples 1 to 3 and Comparative Example 1 were printed using New Champion G set ink manufactured by Dainippon Ink ■ with an R1 printing machine (Mei Seisakusho), and the condition of the printed surface and print strength were visually observed. evaluated. The evaluation results are shown in Table 1.
It was shown to.

Table note) Condition of the printed surface (surface condition when printed) ◎...Printed surface is extremely uniform○...Printed surface is uniform×...Printing with noticeable streaks on the printed surface Strength (pigment peelability on the surface of the coating layer when printed) O: Pigment peeling is not observed ×: Pigment peeling is observed "Effect" According to the present invention, the pigment coating layer surface is uniform Thus, film-coated paper with excellent opacity and printability (printing strength) can be obtained.

Claims (1)

[Claims] (1) A method for producing film-coated paper by bar-coating a plastic film with a pigment coating liquid containing titanium oxide, characterized in that titanium oxide that has been wet-pulverized is used as the titanium oxide. manufacturing method.