JPS61216771A - Method for coating aqueous dispersion liquid - Google Patents

Abstract

PURPOSE:To make it possible to uniformly and stably apply an aqueous dispersion liquid to a base material, by setting the surface roughness of an application roll rotating to the direction reverse to the running direction of the base material. CONSTITUTION:For example, in preparing a final product by applying of a magnetic tape or a photographic film, as an application roll for coating an aqueous dispersion, one with surface roughness of 0.15-1mum as center line average surface roughness Ra is used. If this application roll is used, the surface thereof holds a wet state even if said roll is reversely rotated with respect to the running direction of the base material as a reverse coater and, because of this wetting effect, the omission of the aqueous dispersion at a contact part is not generated to enable uniform coating.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for coating an aqueous dispersion, and more particularly to a method for coating a continuously running flexible substrate with an application roll that is applied in a direction opposite to the running direction. Transfer the aqueous dispersion to form the coating film I! The present invention relates to an improved coating method for coating E-cloths.

Conventional technology Polyester film, or polyethylene terephthalate double-stretched film, has excellent mechanical properties, electrical properties, heat resistance, and chemical resistance, so it is used in magnetic tape, photographic film, packaging films for various types of lumberjacks, and capacitor metallization. , is used for an extremely wide range of applications such as insulation materials and writing materials, and the demand for it has been growing particularly rapidly recently. However, when producing these materials smoothly and applying them to various fields, there are various problems such as adhesiveness, slipperiness, heat sealability, antistatic properties, and others. One way to solve this problem is to prepare a primer layer (undercoat layer) on the biaxially stretched film before obtaining the final product such as magnetic tape or photographic film, so that it has all the necessary functions. After forming a thin surface layer on a sheet, a desired synthetic resin layer is applied to the surface by printing or coating to achieve maximum M
It is known to be a product.

BACKGROUND ART Conventionally, methods of applying a coating liquid to a flexible substrate such as a polyester film have been extensively studied and implemented. For example, air doctor coat, grade coat, C
T-rad coat, knife coat, impregnation coat, reverse coat, gravure coat, kiss roll coat.

Cast coat, curtain coat. Metaling barcodes and the like are known. However, when these coating methods are applied to coating with an aqueous dispersion, various problems occur, such as clogging, which makes it difficult to apply the coating for a long time, and the thin coating layer breaking. Furthermore, to explain the trouble with the reverse coating method, which is suitable for bath liquid type thin layer coating, for example, when the coater uses a chrome-plated application roll, On the other hand, since the rotation of the application roll is reversed, the aqueous dispersion is extracted between the base material and the application roll or between the application roll and the pick-up 7'-- and scum is generated, resulting in dotted JF' A problem arises in that band-like application spots occur.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for uniformly and stably coating an aqueous dispersion onto a moving flexible substrate. Another object of the present invention is to apply a coating film of an easy-to-adhesion stone filler, a slippery treatment agent, an antistatic treatment agent, etc. onto a traveling flexible substrate through an application roll rotating in the opposite direction. An object of the present invention is to provide an improved coating method that stably transfers and coats an aqueous dispersion for a long period of time.

Structure and Effects of the Invention According to the present invention, the object of the present invention is to continuously apply water-dispersed coating to a traveling flexible substrate using an application roll that rotates in the opposite direction to the traveling direction. In this method, the surface roughness of the seven applications is achieved by an aqueous dispersion coating method characterized in that the center line average surface roughness Ra is 0.15 to 1 μm. Here, the aqueous dispersion' is one in which an agent (fine particles) for modifying the surface properties of a flexible substrate is dispersed in an aqueous medium.

Examples of flexible substrates used in the present invention include aluminum foil,
Examples include gold lA foil such as copper foil; thin steel sheets; plastic films such as polyethylene, polyethylene terephthalate, nylon, and the like. Among these, poly(di+lene terephthalate) film in particular has excellent properties such as heat resistance and chemical resistance, so it is useful in high-tech anogy industries such as hunting tape, fat discs, and photographic films. It is a base material and is preferred.

In the present invention, in order to modify the surface properties of these flexible substrates, an aqueous dispersion is coated. Made of Ishizuki, made of vinyl resin, and made of Acrylic.

Emulsions in which fine resin particles such as polynisnal resin, urethane resin, and epoxo group-containing resin are dispersed, alumina,
Examples include colloidal dispersions in which inorganic fine particles such as silica and iron oxide are dispersed. As a more special example, Nananta/I
! ! A water-insoluble lubricant dispersion such as wax or a liquid dispersion may contain a small amount of an organic solvent.

It may also contain a dispersion aid, other film forming agents, and the like.

The solid component concentration of the aqueous dispersion is suitably 5 to iotS.

The application roll to be coated with such an aqueous dispersion has a surface roughness of 0 at the center line average surface roughness Ra.
．． A coolant of 15 to 1 μm is used. Here, 'center mtl[i roughness Ra' is determined by the following method.

First, measure the roughness curve of the surface of the roll to be measured, then cut out a part of measurement length L (2 standard lengths) in the direction of this center line, and set the center width of this cut out part on the X axis and the vertical magnification. When the roughness curve is expressed as Y = f (X) with the direction of Y being the Y axis, it is expressed as a value (unit: 2 μm) given by the following formula.

In this measurement, 8 pieces were measured with a reference length of 0.25 tm, 3 pieces from the direction with the largest value were excluded, and the average value of the 5 pieces was expressed.

When an application roll with a centerline average surface roughness Ra of tlj 5 to 1 μm is used, the surface remains wet even if the application roll is reversed with respect to the running direction of the substrate, such as in a reverse coater, and this 1111
Due to the g effect, the aqueous dispersion does not drain at the contact area, making uniform footing possible. The above Ra is 0.15μm
If it is smaller, the aqueous dispersion will drain between the coolant and the substrate, and various coating spots will occur due to scum, which is not preferable. Moreover, if Ra is larger than 1 μm, the uneven shape of the cooled surface, especially the shape of the convex portions, becomes sharp, which may damage the surface of a flexible substrate such as a plastic film such as a polyethylene terephthalate film, which is not preferable. Ra
Even if the blade is in the range of 0°15 to 1μ, it is preferable to make the contact surface between the base material and the coolant flat and large in order to prevent the surface of the base material from becoming hot, and the shape of the roll surface is such that the convex portion is flat. Therefore, it is preferable that the recessed portion is deep.

It is essential for the cool surface to have the above-mentioned surface roughness in order to maintain the wet state.

In order to maintain this wet state more efficiently, it is preferable that the a-le surface layer be in a porous state.

is preferred. Here, 1 porosity' is determined by the mercury intrusion method.
It is determined from the amount of mercury injected at the pressure zoktt/crl. If the porosity is too large, the mechanical strength of the surface layer decreases and the surface layer is destroyed, and fragments of the surface layer become caught between the application roll and the base material and often damage the base material, which is undesirable. Furthermore, destruction of the surface layer impairs the durability of the coolant and makes uniform application a problem.

The thickness of the porous surface IfI portion is preferably 10 μm or more. If this thickness is too large, the moisturizing effect due to water retention will be reduced, the durability of the surface layer will be insufficient, and it will not be able to withstand long-term use.

Methods for obtaining such a surface include a method of chemically treating a uniform plated surface with an etching solution to create fine recesses;
Examples include a matte roll method in which uniform fine particles of abrasive material are sprayed onto the roll surface together with air or liquid to physically create irregularities, and a method in which a porous surface is obtained by coating a cool surface with ceramic particles.

In particular, the method of coating the surface with ceramic particles is optimal as a method of forming appropriate roughness and porousness on the surface. About the coating method for this ceramic layer! The method is to coat ceramic material and a binder such as acrylic resin together on the surface of the a-ru, gradually raise the temperature to a high temperature, and coat the ceramic while baking the plate. A method of spraying and coating the roll surface is preferred. Ceramic layers can also be formed by chemical vapor deposition or physical vapor deposition (for example, vacuum evaporation, ion blating, sputtering, cluster ion beam, etc.). Among these methods, plasma melt injection is Liquid spraying is a method to obtain a uniform coating layer in a dark manner.The melt spraying method (ceramic materials used are An, O, etc.).

A material containing as a main component is preferable. The Aj? , O, is an advantageous and useful material in terms of solvent resistance, acid resistance, alkali resistance, and cost. In order to further improve this, Si
n,, TiC, WC, B, S.

It is desirable to add one or more of C, ZrC, In, 06*Fe, o, etc. In order to prevent the base material from being corroded by the water dispersion during use of the a-le, it is preferable to plate the base material, such as nickel plating or Kanigen plating, before melting and spraying the ceramic material.

When a porous surface layer is formed by the above method, the a-R surface roughness Ha often becomes larger than 1 μm, but in this case, a part of the surface is polished to reduce the surface roughness Ra to 0.15 to 1 μm.
μsK can be obtained. The a-ru obtained in this way can also be used as an application roll of the present invention. Sanding flattens the sharp tip of the convex part, increases the contact surface with the base material, and prevents damage to the base material surface.
A surface roughness Ra of 1 μm or less is also preferably used.

Such application rolls are used in a state in which they are reversed with respect to the traveling direction of the substrate, for example, a three-roll reverse coater,
4 reverse coaters =? It can be used as an application roll for a sliver coater, especially a Kisurino Kuichi coater with a pumping coolant.

In coating using such a coater, it is desirable that the coating amount before drying be in the range of 1 to 20 Ji/G.

OBJECTS OF THE INVENTION The coating method of the present invention is particularly effective in coating thin layers.

Am cloth spots are likely to occur when the solid content concentration of the aqueous dispersion is high, but in this case, the effects of the present invention are most effective.

Example The present invention will be further explained below with reference to Examples.

In the examples, "1 part" means "part by weight" and "r%J" means "% by weight."

Example 1 Particle size 15-5 on the surface of stainless steel meal with a diameter of 100m+
3 pm ceramic powder (AA!, 0.: Ti
e.

=96:4. Metco's 101NS) was sprayed with plasma ffJ and further polished with an abrasive material to cut large protrusions on the surface to a surface roughness Ra = 0.25μ.
A ceramic coating application ball with a surface layer thickness of 200μ and a porosity of 2 was obtained. Using this ceramic school as an application roll of 4 reverse coaters, Brimal HA-16 (trade name, manufactured by Nippon Acrylic Co., Ltd., 45.5% 7cryl emulsion)
50 copies.

Nonion N 8208.5 (product name manufactured by NOF Corporation).

HLB=12.4. An 8% aqueous dispersion obtained by mixing 1 part (concentration 100% surfactant) and 534 parts of water was 50 μm thick.
5# per ml on a polyester film] 1! When applied with a cloth, a uniform coating with no spots was obtained.

Comparative Example 1 When coating was performed in exactly the same manner as in Example except that the application roll of Example 1 or ROM Plating Cool (surface roughness Ra = 0.1 μm) was used, streaks occurred.

Example 2 The surface of an iron awl with a diameter of 100 m was drilled in a welding process, and then alumina powder with an average particle size of 40 μm (Sumitomo Fluminicum Seirin Seikari trade name A-25) was plasma melted and injected.
After the polishing process, the surface layer thickness is 400μ and the porosity is 3 and 1.
A ceramic coated aru with a surface roughness Ra of 0035 μm was obtained. Used as an application roll for this 4-line reverse coater, Bay@r's back product name Impranil DL)i (emulsion particle size 0
．． 60 parts of water-dispersed sludge obtained by heating 60 parts of 2 μm ta degree 40 or better, aqueous anion-injected polyurethane resin), 1 part of the same nonionic surfactant used in Example 1, and 355.7 parts of water was heated to 30 μm. Kim on polypropylene film
When I applied Portrait 81, I was able to get a uniform coating.

Example 3 In Example 2, the composition of the aqueous dispersion was changed to the same acrylic emulsion as that used in Example 1 (P5 Imul HA-
16) 40 ifB, particle size 10-20 μm,
45.5 parts of colloidal silica water dispersion (trade name: Snowtex-20, manufactured by Nichijo Kagaku Kogyo ■), 1 part of the same nonionic surfactant as used in Example 1, and 196.5 parts of water. An 8% aqueous dispersion obtained by mixing the above was coated in the same manner as in Example 2, except that the IC was changed, and a uniform coating was obtained.

Comparative Examples 2 to 3 7 Pregussion a-ru was chrome plated o-ru (surface roughness Ra = -(1,08 am) Ic except that it was changed).

When coating was carried out in the same manner as in Examples 2 and 3, the film was coated in the direction of flow! There was an outbreak of tanasuji.

Claims (1)

[Claims] 1. In a method of continuously coating a running flexible substrate with an aqueous dispersion using an application roll rotating in the opposite direction to the running direction, the surface roughness of the application roll is The center line average surface roughness Ra is 0.
A method for coating an aqueous dispersion, characterized in that the thickness is 15 to 1 μm. 2. The coating method according to claim 1, wherein the surface layer of the application roll on which the aqueous dispersion is applied has a porosity of 0.1 to 20%.