JPS6160877B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pressure-sensitive adhesive composition for pressure-sensitive adhesive film that has excellent drawing processability. It has been known to use adhesive films for surface protection in order to prevent local scratches caused by molds during processing of metal plates such as aluminum plates, stainless steel plates, steel plates, and coated plates thereof. This adhesive film is made by coating a plastic film such as polyethylene, polypropylene, or soft vinyl chloride with an adhesive such as natural rubber, synthetic rubber, or acrylic copolymer, and is generally used on surfaces such as metal, glass, and decorative boards. Used for protection. Although many proposals have been made so far for drawing metal plates, none have sufficient characteristics to withstand high-level drawing processing, and they have only been applied to light processing. The drawing process is generally completed after one or three stages of drawing, followed by trimming, drilling, and mounting the parts, but in each step, the surface protection film generally does not adhere well to the metal plate. In the next process, the film folds over itself and leaves a mark on the metal plate. That is, conventional adhesive films have the disadvantage that they naturally peel off from the periphery (hereinafter this phenomenon is referred to as "lifting") due to various conditions applied during the intermediate process. For this reason, as a surface protection film for drawing processing, a heat-adhesive film is used, which has no adhesiveness or pressure sensitivity at room temperature and requires heating, or a method of baking PVC paint onto a metal plate is used. However, it is difficult to perform either of these methods easily, and there has been a demand for an adhesive film that can be easily applied to metal plates throughout the year between a pair of rolls. Lifting occurs because the metal plate deforms plastically, whereas the base film contains elastic elements, so a stress remains depending on the deformation rate, and the film cannot withstand this stress. In the case of highly drawn products such as the ball part of a stainless steel sink, the deformation rate locally reaches ±50%. In this case, the process goes through 3 to 6 steps, and each step is basically done as a continuous operation, but the float is left in the middle for at least 1 hour, and if holidays are taken into account, it can take up to a week. It is required that it does not occur even if it occurs. When observing the floating state when using an adhesive film, it is often found that the adhesive is not transferred onto the metal plate, and the interface is broken. This indicates that it is necessary to strengthen the interfacial adhesive force between the adhesive and the metal plate in order to suppress floating. Therefore, the present inventors introduced an acidic group, which is generally employed in the adhesive and paint fields, in order to strengthen the interfacial adhesive force with the metal plate. That is, an acrylic acid ester copolymer containing a few percent of a monomer having an acidic group such as acrylic acid or methacrylic acid was used as an adhesive, but no lifting effect was obtained. . The reason for this is thought to be that even if these acidic groups are provided, they cannot easily approach the interface due to the molecular structure and cannot exert any effect. However, the present inventors have discovered that by incorporating a specific amount of a compound having a sulfonic acid group with a molecular weight of 300 or less into these adhesives, an adhesive film that does not cause lifting can be obtained, leading to the present invention. That is, the gist of the present invention is to add 100 parts by weight of an adhesive whose main component is an acrylic ester copolymer copolymerized with 1 to 10 mol% of a monomer having an ethylenically unsaturated bond and an acidic group, and a compound having a molecular weight of 300 or less. A pressure-sensitive adhesive composition in a pressure-sensitive adhesive film is characterized in that it contains 1 to 10% by weight of a compound having a sulfonic acid group. Compounds having a sulfonic acid group with a molecular weight of 300 or less used in the present invention include the following. That is, sulfosalicylic acid, 2-aminoethane-1-sulfonic acid, aminobenzenesulfonic acid, sulfobenzoic acid, para-toluenesulfonic acid,
2-amino-4-toluenesulfonic acid, 2-hydroxyethanesulfonic acid, 2-naphthol-7-
Sulfonic acid, 1-naphthol-8-sulfonic acid,
Hydroxybenzenesulfonic acid, etc. When the mixed number is less than 1%, there is no effect of suppressing floating, and when it is more than 10%, the cohesive force of the adhesive is reduced, and the adhesive tends to float due to cohesive failure during squeezing. The acrylic ester copolymer having an acidic group is a compound having a sulfonic acid group, which mixes well within the range of 1 to 10% to form a transparent film. The mechanism of action of these sulfonic acid group-containing compounds to suppress floating is not clear, but when attached to a metal plate, the sulfonic acid group strongly adsorbs to the metal plate surface.
It is thought that the interfacial force necessary to suppress floating is formed. When the molecular weight is 300 or more, sulfonic acid groups cannot exist on the surface of the adhesive and it does not have this effect. Furthermore, compounds having sulfonic acid groups do not have sufficient solubility with acrylic copolymers which do not have acidic groups, and bloom on the surface after application, causing the adhesive to disappear. Next, the acrylic ester copolymer used in the present invention will be explained. The main components of acrylic ester and methacrylic ester are preferably those in which the alkyl group has 1 to 12 carbon atoms, and particularly advantageous are ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and methacrylate. Butyl acid, etc., provides the basic properties for year-round stickiness. Monomers having acidic groups as essential components of the present invention include acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, acryloyloxyethyl hydrogen phthalate, 3-chloro-2 acid phosphooxyethyl acrylate, -Acid phosphoxypropyl methacrylate or the like is used, and 1 to 10 mol% of the total adhesive component is copolymerized. Polymerization is carried out using these monomers by a conventional solution polymerization method or emulsion polymerization method. When applying the obtained adhesive to a film base material, it is desirable to crosslink the adhesive by adding polyisocyanate, epoxy compound, melamine compound, etc. to the extent that 1% or more of free acidic groups remain. . In addition, the monomer having an acidic group as an essential component is 1
If the amount is less than mol%, the object of the present invention cannot be achieved. 10 again
If it exceeds mol%, the copolymerization reaction will not proceed smoothly,
Low-molecular compounds, mainly acidic monomers, are produced as by-products, and the solution often becomes cloudy and gel-like, making it impossible to apply. Moreover, if it is more than 10 mol%, it will often peel off when it is made into an adhesive film and then attached to a metal plate and immersed in hot water. In addition, there are polymers with free acidic groups other than acrylic ester copolymers, such as acrylonitrile-butadiene rubber, chloroprene, and ethylene-vinyl acetate, but it is important to balance appropriate adhesion and squeezing properties. It is difficult. The adhesiveness of the adhesive film of the present invention is not significantly affected by compounds having sulfonic acid groups, and is compliant with JIS C-
If the adhesive force is set to 150 to 300 g/10 mm based on 2107, it can be easily attached to metal plates throughout the year by pressing between a pair of rubber rollers, and the peeling workability after drawing is completed is also good. be. This will be explained in detail in Examples below. Example 1 A 25% concentration acrylic ester copolymer solution was prepared in toluene, consisting of 83 moles of butyl acrylate, 7 moles of acrylic acid, and 10 moles of acrylonitrile. The resulting solution was 5000 centipoise. For 100 parts of this solution, add 1 part of a melamine compound (manufactured by Hitachi Chemical Co., Ltd., trade name Melan The mixture was mixed and coated onto a 65 micron thick polyethylene film and allowed to dry. The coating thickness of the adhesive after drying was 8 microns. The adhesive film thus obtained is 0℃~
It has suitable adhesion in the range of 40℃, 0.7mm
It was easy to attach to the thick stainless steel plate SUS-304-2B finish. Table 1 shows the results of cutting the affixing board to 830 x 900 mm and drawing it into a sink ball with a depth of 170 mm, a length of 540 mm, and a width of 540 mm. The processing conditions at this time are as follows. Sink bowl squeezing process: Perform the following four processes at intervals of one hour each. 1st step: Narrow down to 80% of the product shape. 2nd process...Narrowing down to almost the shape of the product. 3rd step... Squeezing of the water drain area and finishing squeezing of the entire surface. 4th step: Trimming around the flange and drilling holes in the drain area.

[Table] As is clear from the examples shown in Table 1, according to the present invention, it is possible to provide a pressure-sensitive adhesive film with good pasting workability, drawing workability, and peeling workability.

Claims (1)

[Scope of Claims] 1. To 100 parts by weight of an adhesive whose main component is an acrylic ester copolymer obtained by copolymerizing 1 to 10 mol% of a monomer having an ethylenically unsaturated bond and an acidic group, the following group is added. An adhesive composition for an adhesive film, characterized in that it contains 1 to 10% by weight of a compound having a sulfonic acid group selected from (a). (a) Sulfosalicylic acid, 2-aminoethane-1-
Sulfonic acid, aminobenzenesulfonic acid, sulfobenzoic acid, para-toluenesulfonic acid, 2-amino-4-toluenesulfonic acid, 2-hydroxyethanesulfonic acid, 2-naphthol-7-sulfonic acid, 1-naphthol-8-sulfone acid,
Hydroxybenzenesulfonic acid.