JP4622659B2 - Method for producing adhesive film - Google Patents

Description

  The present invention relates to a method for producing a pressure-sensitive adhesive film excellent in surface smoothness without lack of surface printing or distortion as a label attached to a resin molded product.

  Styrenic substrates formed by molding styrene resins such as polystyrene (PS), acrylonitrile butadiene styrene (ABS), and modified polyphenylene ether (modified PPE) are used as housings for OA equipment and home appliances. Yes. A label for displaying a caution or warning is generally attached to these cases, and the label is produced by printing an adhesive film as a raw material. In recent years, by using a styrene-based resin-based adhesive film of the same material as the housing for the base material of the adhesive film that is the label raw material, the label can be crushed, melted, pelletized, and remolded without peeling from the housing. The casing is being recycled. The specific technique is disclosed (for example, refer patent document 1, patent document 2, patent document 3, patent document 4).

  By the way, when a coloring pigment (masterbatch) is added and colored in a thermoplastic resin such as a styrene resin, an aggregate of the pigment tends to be a projection on the film surface due to poor dispersion. If there are protrusions on the film surface, printing ink transfer failure or image distortion will occur during printing, which will be a fatal defect as a label indicating caution or warning. Further, since the styrene-butadiene block copolymer is a block copolymer containing an unsaturated bond in the polymer skeleton, it is thermally unstable, and foreign substances such as gels are likely to be mixed during extrusion film formation. Moreover, when a styrene resin is formed into a film of 50 μm to 120 μm, the size of the gel or foreign matter often exceeds the thickness of the film and often protrudes on both surfaces of the film. A method for producing a styrene resin film with little gel generation has been disclosed (see, for example, Patent Document 5, Patent Document 6, Patent Document 7, and Patent Document 8). However, when a foreign matter such as an aggregate of colored pigments is mixed in, there is no effect, and a sufficient effect as a means for reducing protrusions cannot be obtained.

  As a method for forming a styrene-based resin film, there are an inflation film formation method and a T-die film formation method, and the film is stretched immediately after film formation as necessary. In the T-die film forming machine, a molten film is extruded from a linear slit die, and is brought into close contact with a metal cooling roll to be cooled. However, in order to increase the adhesion between the film and the cooling roll, an air knife cast method, an air chamber method, etc. There are a method of spraying the air and bringing the film into close contact with the cooling roll, and a method of pressing with a rubber roll called a touch roll method to make the film adhere to the cooling roll. The touch roll method may also be used for embossing the film surface by using an embossed and engraved roll. However, nip pressure and rubber roll hardness are not considered in the conventional touch roll method, and an effect of bringing gel or foreign matter to one side is not expected.

  Moreover, the manufacturing method of the film bowl body which winds up while pressing the extruded thermoplastic resin film using the touch roll whose surface layer rubber hardness is 50-90 is disclosed (refer patent document 9). ). However, the technique relates to a method for producing a film-like body having good appearance without involving air, and a method for passing a thermoplastic resin film between a metal roll and a rubber roll and a method for reducing projections on the film surface. It is not disclosed.

JP-A-10-105063 JP-A-11-237840 JP 2000-338882 JP 2003-183604 A Japanese Patent No. 3367053 JP-A-11-292995 JP 2000-186179 A JP2003-14140 JP 2001-180850 A

  Accordingly, an object of the present invention is to provide a method for producing a pressure-sensitive adhesive film excellent in surface smoothness, in which printed images and characters are not chipped or distorted.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by the following method for producing an adhesive film. That is, by sandwiching a thermoplastic resin between a metal roll and a rubber roll having a rubber hardness of 30 to 60 immediately after melt extrusion, the surface of the film base where the gel or foreign matter comes into contact with the rubber roll (the surface on which the adhesive layer is laminated). The present inventors have found that protrusions caused by gels or foreign substances can be eliminated on the surface of the film base material (surface to be printed) that moves and contacts the metal roll on the opposite surface.

  That is, the present invention is a method for producing a pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer is laminated on a resin film substrate, and a melt-kneaded product mainly composed of a thermoplastic resin extruded from a melt extruder is made parallel to an axis. A surface of the resin film substrate that is in contact with the rubber roll is manufactured by passing between the adjusted metal roll and a rubber roll having a surface rubber hardness of 30 to 60 to produce a resin film substrate made of the melt-kneaded product. The present invention provides a method for producing a pressure-sensitive adhesive film, comprising providing a pressure-sensitive adhesive layer thereon.

  Since the pressure-sensitive adhesive film produced according to the present invention is excellent in surface smoothness, chipping or distortion of surface printing does not occur. Therefore, it is suitable as a pressure-sensitive adhesive film for sticking to a resin molded product used for a housing of an electronic device or the like to produce a label indicating a precaution or warning for use. In particular, when a styrene resin is used as the thermoplastic resin, the effect of the present invention is remarkable. Therefore, in the present invention, it is preferable to use a styrene resin as the thermoplastic resin, and the label printed on the surface of the adhesive film produced using the thermoplastic resin is affixed to a molded body of the styrene resin. Suitable for use. As a method for using such a label, a method for recycling the casing by pulverizing, melting, pelletizing, or remolding the label without peeling it from the casing is suitable.

  The thermoplastic resin used in the present invention is not particularly limited, and for example, polyester resin, epoxy resin, polyurethane resin, styrene resin, styrene acrylic resin, acrylic resin, and the like can be used. Among them, in the present invention, it is preferable to use the following styrene resin, and it is more preferable to use a styrene-butadiene resin among the styrene resins.

  As the styrene resin, polystyrene resin (GPPS resin), styrene-butadiene resin, styrene-butadiene copolymer resin, resin obtained by block polymerization of styrene and butadiene, or resin obtained by graft polymerization of styrene to styrene-butadiene resin ( As described above, high-impact polystyrene resin (HIPS resin), high-impact polystyrene resin (MIPS resin) blended with GPPS resin and HIPS resin, styrene-acrylonitrile copolymer resin (AS resin), styrene-methyl methacrylate Examples thereof include a copolymer resin, a styrene-butadiene-acrylonitrile copolymer resin (ABS resin), and a modified polyphenylene ether resin (modified PPE resin) in which GPPS is alloyed with polyphenylene ether. Preferred are flexible HIPS resin and MIPS resin. More preferred is HIPS resin.

  The styrene-butadiene copolymer structure (SBR) in the HIPS resin is added or copolymerized for the purpose of imparting impact resistance and flexibility to the film. The copolymerization ratio of SBR is preferably 30 to 80% by mass, more preferably 35 to 65% by mass. If it is less than 30% by mass, the impact resistance is poor and the film is easily cut, so that the workability such as scrap removal work is poor at the time of adhesive coating or label processing. If it exceeds 80%, the film becomes too soft and the label workability becomes inferior.

  When coloring the film, a colorant (masterbatch) obtained by kneading an inorganic pigment or organic pigment such as titanium oxide with a thermoplastic resin can be added. The addition amount is preferably 10 to 40 parts by mass, more preferably 10 to 40 parts by mass, with the addition of a master batch containing a color pigment to 100 parts by mass of the thermoplastic resin serving as the film base. ˜20 parts by mass. If it is less than 10 parts by mass, the film has poor concealability. If it is 40 parts by mass or more, the impact resistance of the film becomes poor and workability at the time of adhesive coating or label processing is inferior.

  As a method for forming a thermoplastic resin film, a T-die film forming method in which a melt-kneaded material mainly composed of a thermoplastic resin extruded from a melt extruder can be nipped immediately after extrusion is preferable, and the axes are adjusted in parallel. A touch roll method that can nip a metal roll and a rubber roll is preferred. The nip pressure between the metal roll and the rubber roll is preferably 0.5 to 2.5 N / cm, and particularly preferably 1.0 to 2.0 N / cm. The rubber hardness of the rubber roll is preferably from 30 to 60, particularly preferably from 30 to 40, in order to bring the gel or foreign matter in the film to the rubber roll surface side when nipping. The material of the rubber roll is not particularly limited, but a material that can withstand the molten resin temperature is preferable, and a silicone rubber roll that can be used continuously at a high temperature is particularly preferable. When the rubber hardness is in the above range, sufficient nip pressure is obtained, pressure is sufficient to bring gel or foreign matter to one side, elasticity is moderate, and gel or foreign matter returns to the surface side in contact with the metal roll. Or protruding on the film surface is less likely to occur. On the other hand, since the metal roll becomes the printing surface of the thermoplastic resin film substrate, it is preferably a mirror surface so that surface printing is not distorted or chipped. The material of the metal roll is not particularly limited, but a stainless steel roll having a chrome plated surface is preferable. It is preferable that the metal roll is hollow and also serves as cooling of the thermoplastic resin film by internally circulating cooling water.

  The thickness of the thermoplastic resin film substrate is preferably 50 to 120 μm, and more preferably 60 to 80 μm.

  As a surface modification of the thermoplastic resin film substrate, corona treatment is generally applied to the surface. However, when seal printing, offset printing, screen printing, or thermal printing is performed, the ink adhesion is poor, and the housing If it is attached to a body and used as a label for displaying a caution or warning, printing or printing may be lost. Therefore, it is preferable to provide an anchor coat layer for bringing the ink into close contact with the surface of the thermoplastic resin film substrate. In this case, if the anchor coat layer is directly formed on the surface of the thermoplastic resin film substrate, the anchor coat layer is difficult to adhere to the film, so the corona treatment is applied to the film surface and the anchor coat layer is formed thereon. It is preferable.

The anchor coat layer satisfying such conditions is formed by applying a coating agent composed of an ink-accepting resin and a dispersion medium to one side of a thermoplastic resin film substrate and drying it. Anti-blocking agent for the purpose of preventing the uncoated film surface on the opposite side of the coating agent from unnecessarily adhering when a thermoplastic resin film substrate having an anchor coat layer formed on one side is wound into a roll. May be added. Moreover, you may add an antistatic agent, a ultraviolet absorber, etc. to a coating agent as needed in the range which does not inhibit performance. As the ink-accepting resin, a known acrylic resin, polyvinyl alcohol resin, polyurethane resin, nitrocellulose, or the like can be used. A dispersion medium that does not dissolve the styrene resin film substrate is selected. Basically, it is mainly composed of alcohol such as isopropyl alcohol or ethanol. As the anti-blocking agent, publicly known inorganic additives such as synthetic silica, calcium carbonate, and titanium oxide, and organic additives such as polyethylene wax resin can be used. The blending of the coating agent is preferably 20 to 30 parts by mass of the ink-accepting resin, 60 to 70 parts by mass of the dispersion medium, and 1 to 5 parts by mass of the antiblocking agent. The coating amount of the coating agent is preferably 0.5 to 3.0 g / m ² , more preferably 1.0 to 2.0 g / m ² .

  The coating method of the coating agent to the thermoplastic resin film substrate is performed by a known method. For example, it can coat using a knife coater, a gravure coater, a roll coater, etc. A gravure coater is preferable.

  The pressure-sensitive adhesive to be laminated on the thermoplastic resin film substrate is not particularly limited as to the resin composition, and known pressure-sensitive adhesives can be used. Examples thereof include acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. . Examples of the form of the pressure-sensitive adhesive include solvent-based and water-based emulsions.

  In order to increase the cohesive strength of the adhesive, a crosslinking agent may be added to the adhesive. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, chelate crosslinking agents, and the like. Moreover, you may add various additives to an adhesive as needed, in the range which does not inhibit performance. For example, tackifying resins, fillers, pigments, anti-aging agents, ultraviolet absorbers, thickeners and the like can be mentioned. Preferably, the acrylic pressure-sensitive adhesive is excellent in durability and easy to control the adhesive force.

The coating amount of the pressure-sensitive adhesive is preferably in the range of 10 to 30 g / m ² by dry weight. If it is less than 10 g / m < ² >, the gel and the foreign material brought close to one side of the film are not sufficiently buried by the pressure-sensitive adhesive, which causes surface protrusions. On the other hand, if it exceeds 30 g / m ² , it will cause a sticking out of the adhesive during label processing.

  Lamination of the pressure-sensitive adhesive layer in the production of the pressure-sensitive adhesive film of the present invention is performed by a known method such as a transfer method. A known apparatus can be used as the adhesive coating apparatus, and examples thereof include a knife coater, a comma coater, a gravure coater, and a roll coater. The pressure-sensitive adhesive adjusted to a solid content of 20 to 60% by mass is applied to the release liner using a coating apparatus. As the release liner, known ones can be used. For example, polyethylene laminate paper, glassine paper, clay coat paper, polyester film, polypropylene film, etc., on which a release layer of a silicone compound is formed can be suitably used. The pressure-sensitive adhesive applied to the release liner and dried with hot air is bonded to the styrene resin film substrate and wound up, whereby the pressure-sensitive adhesive is transferred to the styrene resin film substrate. On the other hand, the method of directly applying a pressure-sensitive adhesive to a styrene resin film substrate is not suitable for producing a pressure-sensitive adhesive film for this application because deformation or shrinkage of the styrene resin film substrate occurs in a drying furnace.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these. In the examples, “parts” and “%” are based on mass unless otherwise specified.

(1) Preparation of anchor coating agent 30 parts of an acrylic resin (“Thermolac EF-32” manufactured by Soken Chemical) as an ink-accepting resin, 65 parts of a 4: 1 mixed solvent of ethanol and isopropyl alcohol as a dispersion medium, blocking prevention 5 parts of synthetic silica ("Silysia 350" manufactured by Fuji Silysia Chemical) was added as an agent to prepare a total of 100 parts of the mixture. The compounded liquid was dispersed for 20 minutes using a paint conditioner to obtain an anchor coating agent having a solid content of 35%.

(2) In a reaction vessel equipped with a synthetic stirrer, a cold flow cooler, a thermometer, a dropping funnel, and a nitrogen gas inlet for an adhesive main agent, 92.9 parts of n-butyl acrylate, 5 parts of vinyl acetate, 2 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate and 0.2 part of azobisisobutyronitrile (AIBN) as a polymerization catalyst are dissolved in 100 parts of ethyl acetate and polymerized at 80 ° C. for 8 hours to obtain a mass average molecular weight of 700,000. An acrylic copolymer solution was obtained. Next, 15 parts of a special rosin ester-based tackifier resin ("Arakawa Chemical Industries" Superester A100 ") and 100 parts of a rosin ester-based tackifier resin (Arakawa Chemical Industries, Ltd.) with respect to 100 parts of the solid content of the acrylic copolymer solution. 5 parts of “Pencel D135”) was added, and ethyl acetate was added and mixed uniformly to obtain an adhesive main agent a having a solid content of 45%.

(3) Preparation of pressure-sensitive adhesive [pressure-sensitive adhesive (I)] 2.3 parts of an isocyanate-based crosslinking agent (“Coronate L-55” manufactured by Nippon Polyurethane Industry Co., Ltd.) is added to 100 parts by weight of the above-mentioned pressure-sensitive adhesive main agent (a). The mixture was stirred for 15 minutes to obtain a pressure-sensitive adhesive (I).

[Example 1]
[Styrene-based resin film substrate (A)] A compound obtained by adding 40 parts of a master batch containing 50% titanium oxide to 100 parts of HIPS resin graft-polymerized at a ratio of 60 parts of styrene and 40 parts of SBR, A hollow metal roll having a diameter of 500 mm (a mirror drum manufactured by Kano Shoji Co., Ltd.) melted and extruded at 200 ° C. using a die film forming machine, and immediately after cooling water was internally circulated, and a silicone rubber roll having a diameter of 200 mm and a rubber hardness of 30 A non-stretched film having a thickness of 50 μm was obtained by nip (nip pressure 1.0 N / cm) with Toughcon White 930 manufactured by Roller Seisakusho. Next, corona discharge treatment was performed on both surfaces of the film. Further, the anchor coating agent prepared in (1) was applied to the surface of the film substrate that was in contact with the metal roll surface of the double-sided corona discharge treated film using a gravure coater, and the coating amount was 2.5 g / m ^2. An anchor coat layer was provided to obtain a styrene resin film substrate (A).
A release sheet (“OKB-105NC” manufactured by Oji Paper Co., Ltd.) coated with a silicone compound on polyethylene laminated paper was coated with the adhesive (I) and dried at 80 ° C. for 90 seconds to a dry weight of 20 g / m ² . A pressure-sensitive adhesive layer was formed and bonded to the styrene resin film substrate (A) to obtain a pressure-sensitive adhesive sheet.

[Example 2]
[Styrenic resin film substrate (B)] In the production of the styrene resin film substrate (A), a styrene resin film base was prepared under the same conditions as in Example 1 except that the thickness of the unstretched film was 120 μm. Material (B) was obtained.
A pressure-sensitive adhesive sheet was obtained under the same conditions as in Example 1 except that the styrene resin film substrate (B) was used.

Example 3
[Styrene-based resin film substrate (C)] In the production of the above-mentioned styrene-based resin film substrate (A), Example 1 was used except that nipping was performed with a silicone rubber roll having a rubber hardness of 60 (Toughcon White 960 manufactured by Kakkuri Roller Mfg. Co., Ltd.). A styrene resin film substrate (C) was obtained under the same conditions.
A pressure-sensitive adhesive sheet was obtained under the same conditions as in Example 1 except that the styrene resin film substrate (C) was used.

[Comparative Example 1]
[Styrenic resin film substrate (D)] In the production of the styrene resin film substrate (A), a silicone rubber roll (Toughcon Red H970 manufactured by Kakkuri Roller Mfg. Co., Ltd.) having a rubber hardness of 70 is used immediately after extrusion of the T-die. A styrene resin film substrate (D) having a thickness of 50 μm was obtained under the same conditions as in Example 1 except that the nip was performed.
A pressure-sensitive adhesive sheet was obtained under the same conditions as in Example 1 except that the styrene-based resin film substrate (D) was used.

[Comparative Example 2]
[Styrene-based resin film substrate (E)] In the production of the above-mentioned styrene-based resin film substrate (A), except that the metal roll and the rubber roll were not niped immediately after extrusion of the T-die, and cooling was performed by an air knife cast method. A styrene resin film substrate (E) having a thickness of 50 μm was obtained under the same conditions as in Example 1.
A pressure-sensitive adhesive sheet was obtained under the same conditions as in Example 1 except that the styrene resin film substrate (E) was used.

[Comparative Example 3]
[Styrenic resin film substrate (F)] In the production of the styrene resin film substrate (A), styrene having a thickness of 50 μm under the same conditions as in Example 1 except that the film forming method is an inflation method. System resin film base material (F) was obtained.
A pressure-sensitive adhesive sheet was obtained under the same conditions as in Example 1 except that the styrene resin film substrate (F) was used.

<Thickness>
The thickness of the styrene resin film substrate was measured using a thickness meter.

<Number of surface protrusions>
Protrusions with a height of 0.1 mm or more and a width of 0.1 mm or more while 1000 cm candela light is obliquely incident on the surface of a 1 m × 1 m styrene resin film substrate adhesive film at an angle of 60 ° and enlarged with a video microscope. Were visually counted.

<Printability>
Using a letterpress flat pressure printing machine ("OPM-W150-3S" manufactured by Onda Seisakusho), UV curable ink ("Dai Cure MV Seal" manufactured by Dainippon Ink & Chemicals, Inc.) is applied to the surface of the adhesive film wound in a roll. After applying and curing the ink by ultraviolet irradiation, it was punched into a rectangular shape (width 50 mm, length 50 mm), unnecessary parts were removed to produce 100 labels, and printability was evaluated according to the following criteria.
○: There is no lack of printing ink and there is no problem.
Δ: Slightly generated label with missing printing ink.
X: A label with lack of printing ink frequently occurs.
The evaluation results of Examples and Comparative Examples are shown in Table 1.

Claims (7)

A method for producing a pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer is laminated on a resin film substrate, wherein a melt-kneaded material mainly composed of a styrene-butadiene resin extruded from a melt extruder is adjusted in parallel with an axis. A resin film substrate made of the melt-kneaded material is produced by passing between a roll and a rubber roll having a surface rubber hardness of 30 to 60, and an adhesive is formed on the surface of the resin film substrate in contact with the rubber roll. A method for producing an adhesive film, comprising providing a layer.   The method for producing an adhesive film according to claim 1, wherein a nip pressure between the metal roll and the rubber roll is 0.5 to 2.5 N / cm. The method for producing an adhesive film according to claim 1 or 2, wherein the rubber roll has a rubber hardness of 30 to 40. The pressure-sensitive adhesive layer has a dry weight of 10 to 30 g / m. ² The method for producing a pressure-sensitive adhesive film according to claim 1, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer obtained by coating a pressure-sensitive adhesive with the coating amount.   The method for producing an adhesive film according to claim 1, wherein the melt-kneaded product contains 10 to 40 parts by mass of a color pigment. The styrene-butadiene resin is a styrene-butadiene copolymer resin, a resin obtained by block polymerization of styrene and butadiene, or a resin obtained by graft polymerization of styrene to a styrene-butadiene copolymer resin. The manufacturing method of the adhesive film of description. The said rubber roll is a silicone rubber roll, The manufacturing method of the adhesive film in any one of Claims 1-6.