JPS6329902B2 - - 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. Used for surface 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, methods have been used, such as using a heat-adhesive film that has no adhesiveness or pressure sensitivity at room temperature and requiring heating, or baking PVC paint onto a metal plate. However, it is difficult to perform 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. The deformation rate locally reaches ±50% in the case of highly drawn products such as the ball part of a stainless steel sink. In this case, the process goes through 3 to 6 stages, but each process is basically performed as a continuous operation.
It is required that floating does not occur even if left in the middle for at least one hour, and for one week, including holidays. When observing the floating state when using an adhesive film, it is often the case 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 access the interface due to the molecular structure and cannot exhibit any effect. The present invention was developed as a result of intensive studies in view of the above circumstances, and its purpose is to obtain an adhesive film that does not cause lifting.
A copolymer with a molecular weight of 300,000 or more obtained by copolymerizing 1 to 20 parts by weight of a monomer component having an acidic group consisting of a carboxyl group or a phosphoric acid group per part by weight.
Solubility parameter (SP value) is 9 for 100 parts by weight
A pressure-sensitive adhesive composition for pressure-sensitive adhesive film is characterized in that it contains 5 to 50 parts by weight of the above polar solvent. The polar solvent used in the present invention is one with a solubility parameter, so-called SP value, of 9 or more. Examples include the following. They are usually used alone, but may be used as a mixture of two or more. . That is, methanol, ethanol, isopropanol, acetone, chloroform, dichloromethane, dioxane, dimethylformamide water, and the like. These polar solvents are used in an amount of 5% by weight or more, but 5% by weight or more is used.
% or less, no effect will be obtained. Although a larger amount is preferable, the amount of copolymerized monomer having an acidic group deteriorates compatibility with the acrylic copolymer, so it is preferable to add approximately 50% to avoid clouding. In addition, a surfactant may be added in some cases to ensure compatibility. It is not clear why mixing such polar solvents makes it difficult for floating to occur, but the mixed polar solvent causes the acidic groups in the adhesive to associate with each other through hydrogen bonds, etc., preventing aggregation and preventing them from appearing on the adhesive surface. This is thought to be because it is easy to release and, as a result, exhibits a strong adsorption effect on the metal plate surface. Next, the acrylic copolymer used in the present invention will be explained. The main acrylic esters and methacrylic esters preferably have alkyl groups with 1 to 12 carbon atoms, and particularly advantageous ones include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and methacrylic acid. butyl, which 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 phosphoxypropyl methacrylate, 2-
Acid phosphooxyethyl acrylate, 2-
One type or a mixture of two or more types of acid phosphoxypropyl methacrylate is used and 1 to 20% by weight of the total adhesive component is copolymerized. Other functional monomers such as hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, acrylamide, and N-methylol acrylamide may also be copolymerized to achieve sufficient crosslinking.Other vinyl monomers such as acrylonitrile may also be used. It may also be used to adjust copolymerization reactivity. The copolymer has a molecular weight so high that it does not dissolve in polar solvents, and usually has a molecular weight of 300,000 or more. 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, an epoxy compound, a 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 it is less than % by weight, the object of the present invention cannot be achieved. 20 again
When the amount exceeds % by weight, the copolymerization reaction does not proceed smoothly and low-molecular-weight compounds mainly composed of 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 20% by weight, 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 to acrylic ester copolymers, there are other polymers with free acidic groups such as acrylonitrile-butadiene rubber, chloroprene, and ethylene-vinyl acetate, but it is important to balance appropriate adhesiveness and squeezing properties. It is difficult. It can be cured not only by thermosetting acrylic copolymers such as those mentioned above, but also by ionizing radiation such as electron beams or gamma rays, and active energy rays such as ultraviolet rays. Even the so-called radiation curing type can be used effectively. They are radiation polymerizable monomers (such as glycidyl methacrylate) that have addition reactivity to side chain functional groups such as acidic groups present in the copolymer.
It has one or more reactive unsaturated bonds in one molecule, such as those in which a double bond, which is a functional group, is added to the side chain by reacting with . Hereinafter, this will be specifically explained in Examples. Examples 1 to 4, Comparative Example 1 A mixture consisting of 88 parts of butyl acrylate, 8 parts of acrylic acid, and 4 parts of actronitrile was solution polymerized in toluene in the presence of a catalyst to obtain a 50% concentration acrylic copolymer solution. was synthesized. The obtained solution is
It was ¹⁰⁴ centipoise. To 100 parts of this solution, 2 parts of a melamine compound (trade name Melan X-66, manufactured by Hitachi Chemical Co., Ltd.) and various polar solvents were mixed in amounts shown in Table 1 to prepare an adhesive solution. The solution was applied onto a polyethylene film with a thickness of 60 μm to a dry thickness of 5 μm, and after drying at 100° C. for 3 minutes, an adhesive film was prepared. The adhesive film obtained in this way has a temperature of 0°C to
It had appropriate adhesiveness within the temperature range of 40°C, and could be easily attached to a 0.7 mm thick stainless steel plate with 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.

[Table] 〓 Drilling holes in the water drain area.
Examples 5 to 8, Comparative Example 2 80 parts of 2-ethylhexyl acrylate and 20 parts of acrylic acid were subjected to bulk polymerization in the presence of a catalyst,
A solvent-free acrylic copolymer was synthesized. The viscosity of the resulting solution was ¹⁰⁵ centipoise. Next, 5 parts of glycidyl methacrylate was subjected to an addition reaction to produce a radiation-curable acrylic copolymer having a double bond in the side chain. 100 parts of this copolymer were mixed with various polar solvents in the amounts shown in Table 2 to prepare radiation-curable pressure-sensitive adhesive compositions. The composition was applied to a thickness of 8μ on a 60μ thick polyethylene film at an accelerating voltage of 170kV and a beer current.
Using a 10 mA electron beam accelerator, a 4 Mrad electron beam was irradiated in a nitrogen atmosphere (oxygen concentration 500 ppm) to polymerize and form a reticulate film, thereby producing an adhesive film. Table 2 shows the adhesive properties of the obtained adhesive film and the results of drawing the sink ball.

[Table] Examples 9 to 12, Comparative Example 3 A mixture consisting of 70 parts of 2-ethylhexyl acrylate, 5 parts of maleic acid, and 25 parts of methyl methacrylate was solution polymerized in ethyl acetate in the presence of a catalyst to obtain a 40% concentration. An acrylic copolymer solution was synthesized. The viscosity of the resulting solution was ¹⁰⁴ centipoise. To 100 parts of this solution, 3 parts of polyfunctional isocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) and various polar solvents were mixed in the amounts shown in Table 3.
An adhesive solution was prepared. The solution was applied to a 60μ thick vinyl chloride film with a solid content of 8μ.
After drying at 100°C for 3 minutes, an adhesive film was prepared. Table 3 shows the adhesive properties of the obtained adhesive film and the results of drawing the sink ball.

[Table] As is clear from Tables 2 and 3, the adhesive film using the adhesive of the present invention exhibits sufficient adhesiveness, and since it is radiation-curable, it has high cohesive strength and little change over time. It can be seen that drawing workability is also good.

Claims (1)

[Claims] 1. Polymer 100 with a molecular weight of 300,000 or more obtained by copolymerizing 80 to 99 parts by weight of acrylic ester or methacrylic ester with 1 to 20 parts by weight of a monomer component having a carboxyl group or phosphoric acid group.
1. An adhesive composition for an adhesive film, comprising 5 to 50 parts by weight of a polar solvent having a solubility parameter (SP value) of 9 or more.