JP2005281328A - Surface-protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-protective film ensuring a long run in its molding, having few film defects such as fish eyes, exhibiting good initial tack irrespective of whether the desired pressure-sensitive adhesiveness is low or high, does not lift from the surface of an adherend even after heat treatment, showing good release from the adherend after a lapse of time, and is free from the tendency to stain the adherend with, e.g. residual adhesive. <P>SOLUTION: The surface-protective film is one comprising a base layer comprising a thermoplastic resin and a pressure-sensitive adhesive layer comprising an ethylene-methyl methacrylate copolymer resin/non-crystalline polypropylene resin blend and formed on either surface of the base layer, wherein the non-crystalline polypropylene resin has a melt flow rate (MFR) of 2 to 15 g/10 min (230°C) and a weight-average molecular weight of 300,000 to 500,000. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface protective film for protecting plate materials such as a metal plate, a decorative plate, a resin plate, and a glass plate from scratches and dirt.

  Conventionally, a method has been adopted in which a surface protective film is attached to the surface of a metal plate, a decorative plate, a resin plate, a glass plate, or the like to prevent surface scratches or dirt that tend to occur during transportation or processing.

  As such a surface protective film, there is a self-adhesive type by coextrusion molding in which an adhesive layer is formed on one side of a base film. For example, this adhesive layer is made of an ethylene-vinyl acetate copolymer resin. There is something like the 5-98224 gazette.

  However, when this ethylene-vinyl acetate copolymer resin is used for the adhesive layer, acetic acid odor is generated due to its structure, or acetic acid is generated when pyrolysis occurs. There was a problem such as that there is a fear of.

  Also, in order to obtain high initial adhesive properties, it is preferable to use a vinyl acetate content of 20% or more, but the change over time of heating and pressurization is large, and it becomes difficult to peel off over time, and the adhesive residue In addition, there is a problem that the possibility of occurrence of such problems is increased, and fish eyes are increased.

  Further, when the vinyl acetate content is large, there is a problem that the thermal stability is poor and the long run property during molding tends to be lowered.

JP-A-5-98224

  Therefore, the present invention is excellent in long run properties during molding, has few defects in the film such as fish eyes, has good initial adhesive properties from low to high desired adhesive strength, and the film remains after heat treatment. An object of the present invention is to provide a surface protective film that does not float from the surface of the adherend, has good peelability with time, and has no contamination such as adhesive residue on the adherend.

  In order to achieve the above object, a surface protective film of the present invention comprises a base material layer made of a thermoplastic resin, an ethylene-methyl methacrylate copolymer resin and an amorphous polypropylene resin provided on one surface of the base material layer. The non-crystalline polypropylene resin has a melt flow rate (MFR) at 230 ° C. of 2 to 15 g / 10 min and a weight average molecular weight of 300,000 to 500,000. It is characterized by.

  The thermoplastic resin used for the base material layer of the surface protective film of the present invention is preferably a thermoplastic polyolefin resin, for example, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene- α-olefin copolymer, propylene-α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, Examples include polypropylene homopolymers, random copolymers, block copolymers, and the like, or polyethylene terephthalate resins. These may be used alone or in combination of two or more.

  Thus, by using the ethylene-methyl methacrylate copolymer resin as the adhesive layer, the problem of acetic acid odor and the problem of corrosive gas during heating have been solved, Since the ethylene-methyl methacrylate copolymer resin is more stable than the ethylene-vinyl acetate copolymer resin, an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 20% or more in the adhesive layer. This solves the problem of long-running properties that occur when using.

  Further, this ethylene-methyl methacrylate copolymer resin has an amorphous polypropylene having a melt flow rate (MFR) at 230 ° C. of 2 to 15 g / min and a weight average molecular weight of 300,000 to 500,000. By arbitrarily mixing the resin, desired initial adhesive strength can be obtained from low to high adhesive strength.

  If the melt flow rate (MFR) at 230 ° C. is less than 2 g / min, the melt viscosity is too high and it becomes difficult to form a film, and if it exceeds 15 g / min, the melt viscosity is too low to cause holes in the film formation process. A malfunction occurs. Further, when the weight average molecular weight is less than 300,000, since there are more low molecular weight components than necessary, the surface protective film is pasted on the adherend and then peeled off from the adherend. When the weight average molecular weight exceeds 500,000, the remainder is generated, and the low molecular weight component is small, and the adhesive force necessary for the adhesive layer is not exhibited.

  In addition, since the ethylene-methyl methacrylate copolymer that forms this adhesive layer is excellent in long-running properties at the time of molding, it can be used regardless of the amount of methyl methacrylate, but the ethylene-methyl methacrylate copolymer resin. When the amount of the methyl methacrylate component is too small, the tackiness becomes weak, and when the amount is too large, fish eyes are generated. Therefore, the amount of the methyl methacrylate is preferably 3% to 20%.

  Furthermore, in order to improve moldability, it is preferable to mix a small amount of polypropylene resin with amorphous polypropylene resin.

  Moreover, you may provide a recycling layer between a base material layer and an adhesion layer as needed. This recycled layer is formed of, for example, an ear material generated at the time of film formation, thereby enabling effective use of resources.

  This adhesive layer has a tackifier resin, an antioxidant, a softener, an ultraviolet absorber, a heat stabilizer, a weather stabilizer, an antistatic agent and an anti-blocking as long as it does not impair the performance of the adhesive if necessary. Agents, slip agents, pigments, dyes and the like may be added.

  Examples of the tackifying resin include aliphatic petroleum resins, alicyclic hydrogenated petroleum resins, aromatic petroleum resins, C5 petroleum resins, terpene resins, phenol resins, rosin resins, and the like. You may use independently and may use 2 or more types together.

  Although the thickness of the base material layer and the adhesive layer constituting the surface protective film varies depending on applications, the thickness of the base material layer is preferably 10 to 90 μm, and the thickness of the adhesive layer is preferably 2 to 40 μm. If the thickness of the base material layer is less than 10 μm, the strength required for the surface protection film cannot be ensured, and if it exceeds 90 μm, the base material is stiff and sticking to the adherend becomes difficult and wasteful use of resources. It becomes. On the other hand, if the thickness of the adhesive layer is less than 2 μm, it is difficult to ensure a sufficient adhesive force, while if it exceeds 40 μm, the cost becomes high.

  The surface protective film of the present invention comprises a base material layer made of a thermoplastic resin, and an adhesive layer obtained by mixing an ethylene-methyl methacrylate copolymer resin and an amorphous polypropylene resin provided on one side of the base material layer. This non-crystalline polypropylene resin has a melt flow rate (MFR) at 230 ° C. of 2 to 15 g / 10 min and a weight average molecular weight of 300,000 to 500,000. Even after the heat treatment is performed, it has excellent fishiness, has few fish eyes that damage the adherend when applied, has no contamination such as adhesive residue on the adherend, has an appropriate initial adhesive strength according to the purpose. To provide a surface protective film that does not float from the surface of the resin plate, generates no odor, does not generate corrosive gas, and has good peelability over time. You can.

  In addition, the blending amount of methyl methacrylate of the ethylene-methyl methacrylate copolymer forming this adhesive layer is 3% to 20%, so that the adhesiveness becomes weak when the methyl methacrylate component is too small, and the fish eye is It is possible to provide a surface protective film capable of eliminating the problem of occurrence.

  Furthermore, by setting the thickness of the base material layer to 10 to 90 μm and the thickness of the adhesive layer to 2 to 40 μm, the strength required for the surface protection film can be secured, and there is no difficulty in sticking. In addition, it is possible to provide a surface protective film that can secure sufficient adhesive force and is excellent in cost.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not necessarily limited to these Examples.

Linear low-density polyethylene (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumikasen FZ203-0, density: 0.932 g / cm ³ ) is 40 μm thick on the base material layer, and ethylene-methyl methacrylate co-polymerized on the adhesive layer Resin mainly composed of amorphous polypropylene (Sumitomo Chemical Co., Ltd) Product name: Tuff selenium T3712, MFR = 3, weight average molecular weight (hereinafter abbreviated as Mw) = 399,000) 10% by weight mixed with T-die molding at a processing temperature of 170 ° C. to a thickness of 10 μm A surface protective film having a total thickness of 50 μm was produced by coextrusion molding by the method. The evaluation results are shown in Table 1.

  Resin consisting mainly of amorphous polypropylene with 75% by weight of ethylene-methyl methacrylate copolymer (manufactured by Sumitomo Chemical Co., Ltd., trade name: ACRIFTH WH302, MMA content: 15%) in the adhesive layer (Sumitomo Chemical Industries) A product obtained by mixing 25% by weight of a product name (Tafselen T3712) manufactured by Co., Ltd. was used. A surface protective film was produced in the same manner as in Example 1 except for this. The evaluation results are shown in Table 1.

  Resin consisting mainly of amorphous polypropylene (Sumitomo Chemical Co., Ltd.) with 60% by weight of ethylene-methyl methacrylate copolymer (manufactured by Sumitomo Chemical Co., Ltd., trade name: ACRIFTH WH302, MMA content: 15%) in the adhesive layer A 40% by weight mixed product (trade name: Tough Selenium T3712) manufactured by Co., Ltd. was used. A surface protective film was produced in the same manner as in Example 1 except for this. The evaluation results are shown in Table 1.

<Comparative Example 1> The adhesive layer used was an ethylene-vinyl acetate copolymer (manufactured by Sumitomo Chemical Co., Ltd., trade name: Evertate D2021F, VA content: 10%) made 100% by weight. A surface protective film was produced in the same manner as in Example 1 except for this. The evaluation results are shown in Table 2.

<Comparative Example 2> An ethylene-methyl methacrylate copolymer (manufactured by Sumitomo Chemical Co., Ltd., trade name: ACRIFTH WH302, MMA content: 15%) and 75% by weight of amorphous polypropylene resin (Sumitomo) A mixture of 25 wt% of Chemical Industry Co., Ltd., trade name: Tough Selenium X1102, MFR = 0.5, Mw = 658,000) was used. A surface protective film was produced in the same manner as in Example 3 except for this. The evaluation results are shown in Table 2.

<Comparative example 3> What used the ethylene-methylmethacrylate copolymer (Sumitomo Chemical Co., Ltd. brand name: ACLIFT WK307, MMA content: 25%) as 100 weight% for the adhesion layer. A surface protective film was produced in the same manner as in Example 1 except for this. The evaluation results are shown in Table 2.

  The obtained surface protective film was measured for the initial adhesive force by the method described below, and the resin plate surface contamination was visually evaluated for the surface protective films of Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Tables 1 and 2.

  The initial adhesive strength is a force required when a surface protective film is attached to a commercially available acrylic plate having a thickness of 2 mm with a laminator, left at 23 ° C. for 30 minutes, and then peeled off at a peeling width of 25 mm and a peeling angle of 90 °. Was measured.

  The adhesive strength with time was obtained by attaching a surface protective film to a commercially available acrylic plate with a thickness of 2 mm with a laminator, exposing it to a hot-air circulating oven heated to 40 ° C. for one month, taking it out, and cooling it to room temperature. In the same manner as in the previous section, after leaving at 23 ° C. for 30 minutes, it was measured by measuring the force required for peeling at a peeling width of 25 mm and a peeling angle of 90 °.

  In addition, in the measurement of this adhesive force, STROGRAPH-M1 by Toyo Seiki Seisakusho was used.

  Evaluation of the state of fish eye was performed by visually observing the extruded film. The case where fish eyes were hardly seen was evaluated as ○, the case where it was conspicuous was evaluated as ×, and the middle was evaluated as Δ.

  As shown in Tables 1 and 2, it was confirmed that the initial adhesive strength increased in Examples 1 to 3 depending on the amount of tough selenium T3712 added.

  The adhesive strength with time was judged to be good if it did not change significantly from the initial adhesive strength, and poorly peeled if it changed significantly. In Examples 1 to 3, all are within 2 times, which is a level with no problem.

  As shown in Tables 1 and 2, it was confirmed that the adherend was not contaminated in Examples 1 to 3 and Comparative Examples 1 to 3.

  As shown in Tables 1 and 2, it was confirmed that there was no corrosive gas generated during pyrolysis other than Comparative Example 1.

  As shown in Tables 1 and 2, it was confirmed that an amorphous polypropylene resin having a weight average molecular weight exceeding 500,000 does not exhibit initial adhesive strength.

  As shown in Tables 1 and 2, it was confirmed that the fish eyes were good except for Comparative Example 3.

Claims (3)

A base material layer made of a thermoplastic resin;
It is composed of an adhesive layer in which an ethylene-methyl methacrylate copolymer resin and an amorphous polypropylene resin are provided on one side of the base material layer,
This non-crystalline polypropylene resin has a melt flow rate (MFR) at 230 ° C. of 2 to 15 g / 10 min and a weight average molecular weight of 300,000 to 500,000. The surface protection film according to claim 1, wherein the methyl methacrylate component of the ethylene-methyl methacrylate resin forming the adhesive layer is 3% to 20%. The thickness of the said base material layer is 10-90 micrometers, and the thickness of the said adhesion layer is 2-40 micrometers. The surface protection film of Claim 1 or 2 characterized by the above-mentioned.