JP2008105411A - Manufacturing method of surface protective film and surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a surface protective film having a small number of fish eyes and such a surface protective film. <P>SOLUTION: The manufacturing method of the surface protective film comprises forming a molten film by the melt extrusion of a polyolefin resin, then forming a multilayer film by the extrusion coating of the molten film on a substrate, and pressing the surface of the molten polyolefin resin film layer side of the multilayer film with a metal roll and pressing the surface of the substrate layer side with a pressing roll to make the molten polyolefin resin film layer and the substrate layer bonded by pressure. The method is characterized in that the pressing rolls linear pressure by which the multilayer film is pressed by the metal roll and pressing roll is set to be 16-35 kN/m. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a surface protective film and the surface protective film.

  Liquid crystal displays such as mobile phones and liquid crystal televisions, optical film products used for CDs and DVDs, metal plates such as aluminum and stainless steel used for industrial and architectural purposes, synthetic resin plates such as acrylic and engineering plastics, wood decorative plates For articles such as, prevent the article from being scratched by contact or friction with the object during processing, storage, or transportation of the article, or prevent the surface of the article from becoming dirty due to dust adhesion, etc. Therefore, a surface protective film is affixed to the article. As the surface protective film, a multilayer film having a base material layer and an adhesive layer is used, and as a method for producing the multilayer film, for example, low density polyethylene is used as the base material layer resin by an extruder (set temperature). 200.degree. C.), a linear low density polyethylene as an adhesive layer resin is melted with an extruder (set temperature 240.degree. C.), and co-extruded from a T die (set temperature 210.degree. C.) (for example, known) , See Patent Document 1).

JP-A-5-229082

However, the surface protective film manufactured by the above manufacturing method is not sufficiently satisfactory with respect to the number of fish eyes.
Under such circumstances, the problem to be solved by the present invention is to provide a method for producing a surface protective film with a small number of fish eyes and the surface protective film.

  That is, in the first aspect of the present invention, a polyolefin-based resin is melt-extruded to form a molten film, and then the molten film is extrusion-coated on a base material to form a multilayer film. The surface of the base material layer is pressed with a pressing roll, and the surface of the base layer is pressed with a pressing roll, and the molten polyolefin resin film layer and the base material layer are pressure-bonded to each other, comprising a metal roll and a pressing roll. A method for producing a surface protection film, wherein the pressing roll linear pressure for pressing the multilayer film is 16 to 35 kN / m.

  The second of the present invention relates to a surface protective film produced by the above production method.

  According to the present invention, it is possible to provide a method for producing a surface protective film with a small number of fish eyes, and the surface protective film. In addition, the surface protective film provided according to the present invention is also excellent in adhesive properties to adherends.

  Resin, paper, metal, etc. are used as a base material used by this invention. Examples of the resin include polyester resin, nylon resin, polyvinyl alcohol resin, polypropylene resin, polyethylene resin, cellophane, polyvinylidene chloride, polystyrene, polyvinyl chloride, polycarbonate, polymethyl methacrylate, polyurethane, fluororesin, Examples include polyacrylonitrile, polybutene resin, polyimide resin, polyarylate resin, acetylcellulose, and the like, and polyester resin is preferable.

  Examples of the polyester resin used as a base material in the present invention include a polymer having a monomer unit based on dicarboxylic acid and a monomer unit based on glycol. Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid; and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. , Ethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and the like. These can use 1 type, or 2 or more types. The polyester resin may have a monomer unit based on a monomer other than dicarboxylic acid and glycol, and examples of the monomer include p-oxybenzoic acid.

  Examples of the polyester resin include polyethylene terephthalate (PET), polyethylene 2,6-naphthalene dicarboxylate (PEN), polybutylene terephthalate (PBT), and the like.

  The substrate used in the present invention is used in the form of a film or the like, and may be a single layer or a multilayer. The thickness of the substrate is only required to be capable of extrusion coating, and is preferably 5 to 300 μm, more preferably 8 to 250 μm, and still more preferably 12 to 200 μm.

  The polyolefin resin melt-extruded in the present invention contains 70% by weight or more of one or more monomer units based on olefins having 2 to 18 carbon atoms such as ethylene, propylene, 1-butene and 1-hexene. A polyethylene resin which is a polymer containing 50% by weight or more of a monomer unit based on ethylene, a polypropylene resin which is a polymer containing 50% by weight or more of a monomer unit based on propylene, etc. Can be given.

  The polyolefin resin to be melt extruded in the present invention is an ethylene homopolymer, an ethylene-α-olefin copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer, and an ethylene-methacrylic acid ester copolymer. Of these, at least one polyethylene-based resin selected from the above is preferable.

  The ethylene-α-olefin copolymer is a copolymer containing a monomer unit based on ethylene and a monomer unit based on an α-olefin having 3 to 18 carbon atoms. In addition to the monomer unit based on ethylene and the monomer unit based on an α-olefin having 3 to 18 carbon atoms, the ethylene-α-olefin copolymer may be used as long as the effects of the present invention are not impaired. It may have a monomer unit based on the monomer. Examples of the α-olefin monomer having 3 to 18 carbon atoms include propylene, 1-butene, 1-hexene and 1-octene. Examples of other monomers include conjugated dienes (for example, butadiene and isoprene), non-conjugated dienes (for example, 1,4-pentadiene), acrylic acid, acrylic acid esters (for example, methyl acrylate and ethyl acrylate), and methacrylic acid. Methacrylic acid esters (for example, methyl methacrylate and ethyl methacrylate), vinyl acetate and the like.

  The ethylene-vinyl acetate copolymer melt-extruded in the present invention has an ethylene-based monomer unit content of 70 to 98% by weight, and a vinyl acetate-based monomer unit content (vinyl acetate content) of 30. ~ 2 wt% ethylene-vinyl acetate copolymer, preferably 80 to 95 wt% of monomer units based on ethylene, 20 to 5 wt% of monomer units based on vinyl acetate %. In addition, this vinyl acetate content is measured by the method prescribed | regulated to JISK6924.

The ethylene- (meth) acrylic acid ester copolymer melt-extruded in the present invention has a monomer unit content based on ethylene of 70 to 98% by weight, and a monomer unit content based on (meth) acrylic acid ester. An ethylene- (meth) acrylic acid ester copolymer having an amount of 30 to 2% by weight, preferably 72 to 95% by weight of monomer units based on ethylene, and based on (meth) acrylic acid ester The content of the monomer unit is 28 to 5% by weight. In addition, content of the monomer unit based on the (meth) acrylic acid ester in an ethylene- (meth) acrylic acid ester copolymer is measured by the method shown next.
That is, using infrared absorption spectrum analysis, a sample of thickness [t (cm)] from incident light intensity (I ₀ ) and transmitted light intensity (I) at a wave number showing an absorption spectrum derived from (meth) acrylate ester The content (% by weight) of the monomer unit based on (meth) acrylic acid ester is calculated using Formula 1.
Content = a × log (I ₀ / I) / t−b (Formula 1)
For example, when calculating | requiring content of the monomer unit based on methyl methacrylate, JASCO Corporation FT / IR-7300 is used as an apparatus, When measuring a 0.3-mm-thick sheet, a of Formula 1 Is 4.1 and b in formula 1 is 5.3. The wave number indicating the absorption spectrum derived from methyl methacrylate is 3448 cm ⁻¹ . Further, the baseline for obtaining I ₀ is 3510 to 3310 cm ⁻¹ .

  Examples of the ethylene- (meth) acrylate copolymer include ethylene- (meth) methyl acrylate copolymer, ethylene- (meth) ethyl acrylate copolymer, ethylene- (meth) acrylate n-propyl copolymer. Copolymer, ethylene- (meth) acrylic acid isopropyl copolymer, ethylene- (meth) acrylic acid n-butyl copolymer, ethylene- (meth) acrylic acid isobutyl copolymer, ethylene- (meth) acrylic acid t-butyl A copolymer etc. are mentioned.

  The melt flow rate (MFR) of the polyethylene resin to be melt extruded in the present invention is preferably 0.01 to 300 g / 10 minutes, more preferably 0.1 to 100, and further preferably 1 to 30. In addition, this MFR is measured on condition of temperature 190 degreeC and load 21.18N in the method prescribed | regulated to JISK7210-1995.

The density of the polyethylene-based resin to be melt extruded in the present invention is preferably 880 kg / m ³ or more, more preferably 900 kg / m ³ from the viewpoint of improving the handleability of the film and the peelability from the adherend. That's it. Moreover, it said seal degree, from the viewpoint of reducing the white powder generation of adhesive layer resins due to friction between the film and the roll during the film production, preferably is at 960 kg / m ³ or less, more preferably, 940 kg / m ³ or less It is. The density is measured according to the method defined in Method A of JIS K7112-1980 after annealing described in JIS K6760-1995.

  The polyethylene resin to be melt extruded in the present invention is produced by a known polymerization method. For example, in the presence of slurry polymerization method, solution polymerization method, bulk polymerization method, gas phase polymerization method, radical generator using complex catalyst such as Ziegler-Natta catalyst, metallocene complex or nonmetallocene complex And a high-pressure radical polymerization method in which polymerization is performed in the presence or absence of a suitable polymerization solvent or chain transfer agent at a polymerization pressure of 50 to 400 MPa and a polymerization temperature of 100 to 300 ° C.

  Examples of the polypropylene resin to be melt-extruded in the present invention include propylene homopolymer, propylene-ethylene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-ethylene-1- Examples include butene copolymers and propylene-ethylene-1-hexene copolymers, and these are used alone or in combination of two or more. The polypropylene resin preferably has an MFR measured in the range of 1 to 300 g / 10 min under the conditions of a load of 21.18 N and a temperature of 230 ° C. according to the method defined in JIS K7210-1995. These polypropylene resins are produced by a known method, for example, an ionic polymerization method.

  The polyolefin resin to be melt-extruded in the present invention may be added with additives such as an antioxidant, a lubricant, an antistatic agent and an antiblocking agent as long as the effects of the present invention are not impaired.

  In the production method of the present invention, a polyolefin-based resin is melt-extruded to form a molten film, and then the molten film is extrusion-coated on a substrate to form a multilayer film. The surface of the multilayer film on the side of the molten polyolefin-based resin film layer Is pressed with a metal roll, and the surface on the base material layer side is pressed with a pressing roll, and the molten polyolefin resin film layer and the base material layer are pressure-bonded.

  In the present invention, when a polyethylene-based resin is used as an extruded molten resin, the melt-extruded resin temperature immediately below the die is preferably 200 ° C. or higher from the viewpoint of workability and the number of fish eyes. When the polyethylene resin is an ethylene homopolymer or an ethylene-α-olefin copolymer, the temperature of the melt-extruded resin immediately below the die is more preferably 300 ° C or higher. Further, when a polyethylene resin is used as an extruded molten resin, the molten extruded resin temperature immediately below the die is preferably 350 ° C. or less from the viewpoint of suppressing the deterioration of the resin and reducing the cooling roll contamination due to the fuming component. Preferably it is 340 degrees C or less. When the polyethylene-based resin is an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer, or an ethylene-methacrylic acid ester copolymer, the melt extrusion resin temperature immediately below the die is more preferably 300 ° C. or less. .

  In the present invention, as a method for increasing the adhesive strength between the melt-extruded film and the base material, a method using a base material that has been subjected to surface oxidation treatment on the surface of the base material to be pressure-bonded to the melt-extruded film, base For example, a method of performing an anchor coat treatment on the surface of the material to be pressure-bonded to the melt-extruded film. When the anchor coating treatment is performed, a solvent is contained in the anchor coating agent. Therefore, it is preferable to perform the surface oxidation treatment for a field where a cleaner surface protective film is required. Examples of the surface oxidation treatment include corona discharge treatment, plasma treatment, flame plasma treatment, electron beam irradiation treatment, ultraviolet ray irradiation treatment, and the like, and corona discharge treatment is preferable. As a timing for performing the corona discharge treatment, it may be performed off-line in advance of the step of performing the extrusion coating, or may be performed in-line immediately before the substrate after unwinding the substrate and the melt-extruded film. Preferably, it is performed in-line immediately before crimping.

  Various levels of the adhesive strength of the surface protective film to the adherend are required depending on the kind and application of the adherend and the bonding conditions. About the surface protection film manufactured by this invention, it can adjust suitably with the kind and processing conditions of the melt-extrusion film to be used.

  The pressing roll linear pressure when the molten polyolefin resin film layer and the base material layer are pressure-bonded in the production method of the present invention is 16 to 35 kN / m, and preferably 20 kN / m from the viewpoint of reducing the number of fish eyes. m or more and preferably 32 kN / m or less from the viewpoint of uniform pressure bonding.

  The arithmetic average roughness (Ra) of the metal roll in the crimping step is preferably 0.01 to 10 μm, and preferably 0.1 to 1 μm. When the value of Ra is large, the adhesion to the adherend may not be exhibited or the transparency may be inferior. Moreover, when the value of Ra is small, the roll-off property from the cooling roll may be deteriorated during film formation. The Ra is measured by the method defined in JIS B0601-1994.

  The pressing roll in the crimping step is preferably a rubber roll. The hardness of the rubber roll is preferably 60 to 95 from the viewpoint of enhancing the pressure bonding between the melt-extruded film and the substrate. The hardness is measured by a method defined in JIS K6253.

  The adhesive strength between the base material and the melt-extruded film is that the base material and the melt-extruded film may be peeled off when the surface protection film is peeled off from the adherend, so the melt-extruded film after being bonded to the adherend It is preferable that it is larger than the adhesive strength between the substrate and the adherend.

  The surface protective film of the present invention includes liquid crystal displays such as mobile phones and liquid crystal televisions, optical film products used for CDs and DVDs, metal plates such as aluminum and stainless steel, synthetic resin plates such as acrylic and engineering plastics, wood decorative plates, etc. It is suitably used for the surface protection of. The thickness of the surface protective film is preferably 7 to 600 μm, more preferably 10 to 500 μm, and still more preferably 15 to 300 μm.

Hereinafter, the present invention will be described by way of examples.
The physical properties in the examples were measured according to the following methods.

(1) Density (Unit: kg / m ³ )
It measured according to the method prescribed | regulated to A method among JISK7112-1980. The sample was annealed according to JIS K6760-1995.

(2) Vinyl acetate content (unit:%)
It measured according to JIS K6924.

(3) Melt flow rate (MFR, unit: g / 10 min)
According to the method defined in JIS K7210-1995, the measurement was performed by the A method under the conditions of a load of 21.18 N and a temperature of 190 ° C.

(4) Adhesive strength (unit: N / 15 mm width)
A test piece having a width of 15 mm was cut out from the surface protective film. Using a Toyo Seiki Seisakusho Co., Ltd. autostrain type tensile tester, the polyolefin resin layer and the base material layer of the test piece were peeled 180 degrees at a tensile speed of 200 mm / min. The adhesive strength of the material layer was measured.

(5) Adhesive strength (unit: N / 100 mm width)
A 10 cm × 25 cm optical film (Zeonor film ZF-14, manufactured by Optes Co., Ltd., thickness 100 μm) is used as an adherend, and a 10 cm × 25 cm surface protective film is applied to the adherend, and a polyolefin-based resin layer of the surface protective film. Are laminated so as to be on the adherend side, and the laminate is made up of two rolls (the surface protective film side is a rubber roll, under the conditions of a roll temperature of 40 ° C., a pressure of 0.49 MPa, and a speed of 0.5 m / min. By passing the adherend side through a metal roll), the surface protective film and the adherend were bonded and bonded together.
Next, using an autostrain type tensile tester manufactured by Toyo Seiki Seisakusho Co., Ltd., the adherend of the bonded product and the surface protective film are peeled 180 degrees at a tensile speed of 300 mm / min, and the adhesive strength is increased. It was measured.

(6) Arithmetic mean roughness (Ra) (unit: μm)
The arithmetic average roughness of the metal roll was measured according to the method defined in JIS B0601-1994.

(7) Fisheye (Unit: pieces / m ² )
Six A4 large test pieces were cut out from the surface protective film. Fish eyes having a diameter of 0.3 mm or more were detected visually, and the number of fish eyes per 1 m ² was calculated.

(8) Transparency (HAZE) (unit:%)
The method specified in ASTM D1003 was followed. A smaller value indicates higher transparency.

Example 1
High-pressure low-density polyethylene resin [Sumikasen L705 (MFR = 7 g / 10 min, density = 919 kg / m ³ )] manufactured by Sumitomo Chemical Co., Ltd. as a melt-extruded film is melt-kneaded with a φ65 mm extruder and extruded from a T-die and extruded. The melted polyethylene resin film immediately after was extrusion coated onto a base material [biaxially stretched polyethylene terephthalate film (Toyobo Co., Ltd., Toyobo Ester Film E5100) thickness = 50 μm], a metal cooling roll and silicon having an arithmetic average roughness of 0.1 μm A surface protective film was obtained by pressure-bonding the molten polyethylene resin film and the substrate with a pressing roll linear pressure of 19.6 kN / m with a rubber (hardness: 80) pressing roll. In addition, the corona discharge process was performed by the output of 4 kW for the surface crimped | bonded with a molten resin film just before unwinding a base material and crimping | bonding with a molten resin film.
In the extrusion coating process, the temperature of the molten resin immediately below the die was 310 ° C., the air gap was 160 mm, the film width was 500 mm, the coating thickness was 25 μm, and the take-up speed was 80 m / min. Table 1 shows the physical property evaluation results of the obtained surface protective film.

Example 2
A surface protective film was obtained in the same manner as in Example 1 except that a metal cooling roll having an arithmetic average roughness of 1.0 μm was used. Table 1 shows the physical property evaluation results of the obtained surface protective film.

Example 3
An ethylene-α-olefin copolymer resin [Sumikasen Hiα FW401-0 (MFR = 4.8 g / 10 min, density = 923 kg / m ³ )] manufactured by Sumitomo Chemical Co., Ltd. is used as the melt-extruded film, and the molten resin directly under the die. The same operation as in Example 1 was performed except that the temperature was 324 ° C. Table 1 shows the physical property evaluation results of the obtained surface protective film.

Example 4
A surface protective film was obtained in the same manner as in Example 3 except that a metal cooling roll having an arithmetic surface roughness of 1.0 μm was used. Table 1 shows the physical property evaluation results of the obtained surface protective film.

Example 5
Using an ethylene-vinyl acetate copolymer resin [Evalate D3021 (MFR = 7 g / 10 min, vinyl acetate content = 6%) manufactured by Sumitomo Chemical Co., Ltd.] as the melt-extruded film, the molten resin temperature immediately below the die is 240 ° C., The same operation as in Example 2 was performed except that the thickness of the base material was 16 μm. Table 2 shows the physical property evaluation results of the obtained surface protective film.

Example 6
The same procedure as in Example 5 was performed except that an ethylene-vinyl acetate copolymer resin [Evalate D3010 (MFR = 6 g / 10 min, vinyl acetate content = 10%) manufactured by Sumitomo Chemical Co., Ltd.] was used as the melt-extruded film. . Table 2 shows the physical property evaluation results of the obtained surface protective film.

Example 7
The same procedure as in Example 5 was performed except that an ethylene-vinyl acetate copolymer resin [Evalate H3011 (MFR = 6 g / 10 min, vinyl acetate content = 15%) manufactured by Sumitomo Chemical Co., Ltd.] was used as the melt-extruded film. . Table 2 shows the physical property evaluation results of the obtained surface protective film.

Example 8
The same operation as in Example 6 was performed except that the temperature of the molten resin immediately below the die was set to 260 ° C. Table 2 shows the physical property evaluation results of the obtained surface protective film.

Example 9
The same operation as in Example 4 was performed except that the roll linear pressure was 16.5 kN / m, the temperature of the molten resin immediately below the die was 316 ° C., and the thickness of the base material was 16 μm. Table 3 shows the physical property evaluation results of the obtained surface protective film.

Example 10
The same operation as in Example 9 was performed except that the roll linear pressure was 20.7 kN / m. Table 3 shows the physical property evaluation results of the obtained surface protective film.

Example 11
The same operation as in Example 9 was performed except that the roll linear pressure was changed to 24.8 kN / m. Table 3 shows the physical property evaluation results of the obtained surface protective film.

Example 12
The same operation as in Example 9 was performed except that the roll linear pressure was 31.0 kN / m. Table 3 shows the physical property evaluation results of the obtained surface protective film.

比較例１
ロール線圧を１２．０ｋＮ／ｍにした以外は、実施例９と同様に行った。得られた表面保護フィルムの物性評価結果を表４に示す。

Comparative Example 1
The same operation as in Example 9 was performed except that the roll linear pressure was 12.0 kN / m. Table 4 shows the physical property evaluation results of the obtained surface protective film.

Comparative Example 2
The same operation as in Example 9 was performed except that the roll linear pressure was 14.5 kN / m. Table 4 shows the physical property evaluation results of the obtained surface protective film.

Claims (4)

  A polyolefin resin is melt extruded to form a molten film, and then the molten film is extrusion coated onto a substrate to form a multilayer film. The surface of the multilayer film on the side of the molten polyolefin resin film layer is coated with a metal roll. A method for producing a surface protective film that presses a surface of a material layer side with a pressing roll and presses the molten polyolefin resin film layer and the base material layer, and presses the multilayer film with the metal roll and the pressing roll. The manufacturing method of the surface protection film characterized by making 16-35 kN / m.   The method for producing a surface protective film according to claim 1, wherein the polyolefin resin is a polyethylene resin.   The method for producing a surface protective film according to claim 1 or 2, wherein the substrate is a polyester resin.   The surface protection film manufactured by the manufacturing method in any one of Claims 1-3.