WO2010016403A1

WO2010016403A1 - Surface protection film

Info

Publication number: WO2010016403A1
Application number: PCT/JP2009/063326
Authority: WO
Inventors: 一範小橋; 貴史森谷; 芳隆佐藤
Original assignee: Dic株式会社
Priority date: 2008-08-05
Filing date: 2009-07-27
Publication date: 2010-02-11
Also published as: CN102112305A; KR101162583B1; TW201008772A; KR20110027721A

Abstract

Provided is a surface protection film that is applied to the surfaces of various resin plates, glass plates, and metal plates that are used as construction materials or in electrical and electronic fields for protection purposes and protects the adherend from being scratched, and contamination or the like during storage, transportation, and post-processing. Specifically, provided is a surface protection film which realizes extremely low contamination on the adherend surface and has excellent suitability for secondary processing that uses the resin, wherein a block copolymer having crystalline olefin blocks and a straight chain low-density polyethylene of 0.880-0.938 g/cm³ density are mixed in a specific proportion, as the major component, for the adhesive layer of the surface protection film.

Description

Surface protection film

The present invention is a surface protective film used for the purpose of protecting the surface of various resin plates, glass plates, metal plates, etc., and in particular, contamination such as adhesive residue on the adherend surface after film peeling is extremely high. The present invention relates to a surface protective film characterized in that the secondary workability of the adherend can be kept small.

Surface protective films are used for the purpose of protecting the surface of adherends from scratches and contamination by sticking to the surface of various resin plates, glass plates, metal plates, etc. used in the building materials and electrical / electronic fields. Is. Many inventions have been reported so far for the purpose of satisfying various performance requirements for the surface protective film. One of the required performances for the surface protective film is minimization of contamination due to adhesive residue on the adherend surface after film peeling. When secondary processing such as printing is performed on the adherend after film peeling, even fine contamination that cannot be visually confirmed affects its workability. Reduction of the remaining is required. Other required performances include that there is no so-called blocking phenomenon that the contact surfaces of the film cannot be easily peeled off when the film is rolled up and then used, and the film is stuck on the adherend. When heat treatment or the like is performed in a worn state, there is no lifting or peeling from the adherend, no increase in adhesive strength with the passage of time after film attachment, so-called no increase in adhesion, etc. It is done. Furthermore, in actual use, after the surface protective film is stored and transported in a state of being adhered to various adherends, the protective film is peeled off from the adherend once, and the surface state of the adherend is determined. After the inspection, the surface protective film may be pasted again and used for post-processing. If the adhesive surfaces adhere to each other at such a use site, and the adhesiveness between the adhesive surfaces is strong, the adhesive surface may be whitened or roughened if the adhesive portions are peeled off. New problems have arisen, such as inferior handling properties that allow the surface to be peeled off and the surface protective film to be adhered to the adherend again. In order to combine these, various technical measures such as selecting an appropriate resin combination in consideration of the affinity between the adhesive layer and the base material layer as well as appropriately adjusting the adhesive performance of the adhesive layer. Ingenuity is required.

As an example of a conventional surface protection film, as an example of suppressing the enhancement of adhesion of the surface protection film, a base material layer made of a thermoplastic resin, an amorphous olefin copolymer, a crystalline olefin polymer, and a crystallinity Coextruded laminated film having a pressure-sensitive adhesive layer made of a block copolymer having an olefin block (for example, see Patent Document 1), and improving heat processability in a state where a surface protective film is adhered to an adherend. As an example, a coextruded laminated film having a base layer mainly composed of a crystalline propylene polymer, and an adhesive layer composed of an amorphous α-olefin copolymer and a crystalline propylene polymer ( For example, refer to Patent Document 2.), heat processability in a state in which the surface protective film is adhered to the adherend, and a block when the film is wound up and used after being rolled up. Examples of king suppression include a surface layer mainly composed of a polypropylene resin composed of a propylene homopolymer and a propylene-ethylene copolymer elastomer, and a base material layer mainly composed of a crystalline propylene polymer. And a coextruded laminated film having an adhesive layer made of an amorphous α-olefin copolymer and a crystalline propylene polymer (for example, see Patent Document 3).

However, in these techniques, there are certainly effects such as suppression of enhancement of adhesion of the film, heat processability when the film is adhered to the adherend, suppression of blocking after winding the film, and the like. However, in any of the techniques, the minimization of contamination due to adhesive residue on the surface of the adherend after film peeling is insufficient, and there is a problem in the secondary processability of the adherend after film peeling. Furthermore, the peelability when the surface protective films are attached to each other is not sufficiently solved.

JP 2006-257247 A Japanese Patent Laid-Open No. 2007-130872 JP 2008-68564 A

Accordingly, the problem to be solved by the present invention is that the surface protection film is capable of maintaining good secondary workability of the adherend with very little contamination such as adhesive residue on the adherend surface after peeling the surface protective film. It is to provide a film, and further to provide a surface protective film having good peelability and excellent handling properties even when the adhesive surfaces of the surface protective film are attached to each other.

As a result of intensive studies to solve the above problems, the present inventors have found that the surface protective film is a block copolymer having a crystalline olefin block and a density of 0.880 to 0.938 g / cm ^3. When having a pressure-sensitive adhesive layer mainly composed of chain-shaped low-density polyethylene, the surface protective film that can keep the secondary workability of the adherend satisfactorily with very little contamination to the adherend surface after film peeling. As a result, the present invention has been completed.

That is, the present invention is a surface protective film in which an adhesive layer (A) and a base material layer (B) are laminated, wherein the adhesive layer (A) is a block copolymer (A1) having a crystalline olefin block. And a linear low density polyethylene (A2) having a density of 0.880 to 0.938 g / cm ³ , in an amount of 50% by mass or more based on the total mass of the components constituting the adhesive layer (A). 5-80% by mass of the total mass of the block copolymer (A1) having a crystalline olefin block and the linear low-density polyethylene (A2) having a density of 0.880-0.938 g / cm ^3. Is a block copolymer (A1) having a crystalline olefin block.

According to the present invention, it is attached to the surface of various resin plates, glass plates, metal plates, etc. used in the building materials and electric / electronic fields, etc., and used for the purpose of protecting these adherend surfaces from scratches and contamination. When the film is rolled up into a roll and then used again after being rolled out, there is no blocking, and the film is stuck to the adherend when heat processing is performed Also has high heat resistance such as no lifting or peeling from the adherend, no adhesion enhancement after film sticking, and very little contamination due to adhesive residue on the adherend surface after film peeling, It is possible to obtain a highly useful surface protective film that can keep the secondary workability of the adherend favorable. In addition, when using a propylene polymer in the adhesive layer, the adhesive surface of the surface protective film is excellent in peelability even when the adhesive surfaces are attached to each other, and the adhesive surface after peeling does not cause surface roughness or whitening. Again, it can be used as a surface protective film.

The pressure-sensitive adhesive layer (A) constituting the surface protective film of the present invention comprises a block copolymer (A1) having a crystalline olefin block and a linear low density polyethylene having a density of 0.880 to 0.938 g / cm ^3. (A2) and the block copolymer (A1) having the crystalline olefin block with respect to the total amount of the components constituting the adhesive layer (A), specifically, The total mass with the chain low density polyethylene (A2) is 50% by mass or more. In particular, when importance is attached to reduction of adhesive residue and low contamination on the adherend, the total mass of the block copolymer (A1) and the linear low-density polyethylene (A2) is 80% by mass or more. It is preferable.

The block copolymer (A1) having a crystalline olefin block used in the present application is a copolymer having a block (I) made of crystalline polyolefin and another block (II) having no crystallinity. Preferably, the other block (II) has a block composed of a conjugated diene polymer. In addition, as the constitution of the copolymer, the adhesiveness and adhesive residue of the surface protective film obtained when used as a resin for the adhesive layer (A) in combination with the linear low density polyethylene (A2) described later At least one of the polymer chains represented by (I-II) _n1 or (I-II) _n2- (I) (n1, n2 is an integer of 1 or more). The terminal is preferably composed of the crystalline olefin block (I).

Examples of the block copolymer (A1) having such a crystalline olefin block include those provided in JP-A-3-128957 and JP-A-8-231786. Specifically, a polybutadiene polymer block having a low 1,2-vinyl bond content (for example, 25% or less) and a polymer mainly composed of a conjugated diene compound, which contains 1,2- and 3,4-bonds. A copolymer composed of a polymer block having a high rate (for example, 50% or more) is synthesized, and the polybutadiene portion is made to have a structure similar to polyethylene by hydrogenating the copolymer to form a crystalline polymer block. And the like.

Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl. 1,3-octadiene, 3-butyl-1,3-octadiene, chloroprene, and the like. From the viewpoint of industrial availability, 1,3-butadiene and isoprene are preferably used. Examples of commercially available products that can be preferably used as such a block copolymer having a crystalline olefin block include a block copolymer having a structure of crystalline olefin-ethylene / butylene copolymer-crystalline olefin (hereinafter referred to as a block copolymer). , Abbreviated as CEBC.) “Dynalon 6200P” manufactured by JSR Corporation.

The pressure-sensitive adhesive layer (A) constituting the surface protective film of the present invention has a linear shape having a density of 0.880 to 0.938 g / cm ³ in combination with the block copolymer (A1) having a crystalline olefin block. Low density polyethylene (A2) is one of the main components. When the linear low density polyethylene (A2) having a density of 0.898 to 0.925 g / cm ³ is used, the balance between the suppression effect of adhesion enhancement and the tackiness of the finally obtained surface protective film is good. This is more preferable. Moreover, the melt flow rate [The value measured at 190 degreeC and 21.18N based on JISK7210: 1999. Hereinafter, it is indicated as “MFR (190 ° C.)”. ] In the range of 0.5 to 30.0 g / 10 min is preferable because the film formability is improved. More preferably, the MFR is in the range of 2.0 to 15.0 g / 10 min.

The pressure-sensitive adhesive layer (A) constituting the surface protective film of the present invention has a block copolymer (A1) having a crystalline olefin block as its main component and a density of 0.880 to 0.938 g / cm ³ . By using together with the linear low density polyethylene (A2), the contamination on the adherend surface after film peeling can be minimized and the secondary processability of the adherend surface can be maintained.

As the use ratio of the block copolymer (A1) having a crystalline olefin block and the linear low density polyethylene (A2) having a density of 0.880 to 0.938 g / cm ³ in the adhesive layer (A). It is essential that 5 to 80% by mass of the total mass of (A1) and (A2) is a block copolymer (A1) having a crystalline olefin block. When the use ratio is within this range, the balance between low contamination and adherence to the adherend surface is maintained. That is, when the use ratio of the block copolymer (A1) is less than 5% by mass, the adhesive strength is insufficient, and peeling or floating after the sticking is likely to occur, and the use ratio of the block copolymer (A1) is If it exceeds 80% by mass, the adhesive strength becomes strong. As a result, blocking during storage in the form of a roll tends to occur, and low contamination to the adherend surface may be insufficient.

As resin used for the adhesive layer (B) of the surface protective film of the present invention, if the above block copolymer (A1) and linear low density polyethylene (A2) are contained in a total amount of 50% by mass or more. In addition, other resins, particularly other olefin polymers may further be included. At this time, it is preferable to use a propylene polymer (A3) in combination from the viewpoint of ease of peeling when the adhesive surfaces are further adhered to each other and reusability after peeling.

Examples of the propylene polymer (A3) include propylene homopolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and metallocene catalyst-based polypropylene. Can be mentioned. These may be used alone or in combination of two or more. These propylene polymers (A3) preferably have an MFR of 230 ° C. of 0.5 to 30.0 g / 10 min and a melting point of 120 to 165 ° C., more preferably an MFR of 230 ° C. Of 2.0 to 15.0 g / 10 min and a melting point of 125 to 162 ° C. If the MFR at 230 ° C. and the melting point are within this range, the film shrinks little even when exposed to a high temperature environment by drying, heat molding or the like after being adhered to the adherend, and thus there is no floating or peeling. There is no warping of the adherend and the film formability is improved.

Of the propylene polymers (A3) used for the adhesive layer (A), metallocene catalyst polypropylene is preferred. The metallocene catalyst polypropylene is a polypropylene polymerized using a metallocene catalyst instead of the conventional Ziegler-Natta catalyst. Examples of the metallocene catalyst include a metallocene homogeneous mixed catalyst containing a metallocene compound and an aluminoxane, a metallocene supported catalyst in which a metallocene compound is supported on a particulate carrier, and the like. The metallocene supported catalysts are disclosed in JP-A-5-155931, JP-A-8-104691, JP-A-8-157515, JP-A-8-231621, and the like. Metallocene catalyst-based polypropylene has high uniformity in molecular weight distribution and composition distribution and low content of low molecular weight components. Therefore, by using metallocene catalyst polypropylene for the propylene polymer (A3), bleeding of low molecular weight components Contamination of the adherend surface due to can be prevented. The metallocene catalyst-based polypropylene may be a propylene homopolymer or a copolymer of propylene and other α-olefins. Examples of copolymers of propylene and other α-olefins include propylene-ethylene copolymer. Coalescence is mentioned.

In the adhesive layer (A), a block copolymer (A1) having a crystalline olefin block, a linear low density polyethylene (A2) having a density of 0.880 to 0.938 g / cm ³ , a propylene-based polymer When combined with (A3), the total mass is 80% by mass or more based on the total mass of the components constituting the adhesive layer (A) because the performance balance of the resulting surface protective film is excellent. preferable.

Moreover, the usage ratio (A1) of each component in a total of 100 parts by mass of the block copolymer (A1), the linear low-density polyethylene (A2), and the propylene polymer (A3): ( A2): (A3) is in the range of 10-50: 10-70: 10-50, it can be easily peeled when the adhesive surfaces are attached to each other while the adhesive force is appropriate, and It is more preferable because it can be reused after peeling. That is, if the use ratio of (A1) is 10% by mass or more, the adhesive strength is sufficient, and if it is 50% by mass or less, adhesive residue after peeling can be prevented. If the use ratio of (A2) is 10% by mass or more, whitening and roughening of the adhesive surface at the time of mutual attachment can be prevented, and if it is 70% by mass or less, appropriate adhesive force can be easily obtained. Further, when the use ratio of (A3) is 10% by mass or more, peeling at the time of mutual attachment is easy, and when it is 50% by mass or less, it is easy to prevent whitening and unevenness after peeling.

In the pressure-sensitive adhesive layer (A) of the present invention, the component (A1) and the component (A3) are combined in order to combine low adhesion to the adherend, blocking resistance, and practical adhesive strength as a surface protective film. Even when used in combination, it has been found that a practical surface protective film can be obtained by controlling the mixing ratio. However, since only the component (A1) and the component (A3) are different in the original properties (flexibility) of the resin, it becomes difficult to control the tackiness, and the degree of freedom in industrial production is narrow and not practical. As a result, it was found that the combined use of the component (A1) and the component (A2) and the combined use of the component (A3) are preferable. As a result, the adhesive layer (A) can be made into a mixture in which other resins, various additives, and the like are used in combination as long as the effects of the present invention are not impaired. As other resins, as long as the effects of the present invention are not impaired, it is possible to use a resin conventionally used for obtaining a film by a coextrusion lamination method, and particularly, various olefin polymers are used. it can.

As resin which comprises the base material layer (B) used together with the adhesion layer (A) which comprises the surface protection film of this invention, it is a thermoplastic resin and co-extrusion with an adhesion layer (A) is possible. Although it will not specifically limit if it exists, the base material layer (B) is comprised from an olefin polymer (B1) from the point that affinity with the adhesion layer (A) which comprises the surface protection film of this invention is favorable. It is preferable to contain 65% by mass or more with respect to the total mass of the components.

Examples of the olefin polymer (B1) include ethylene polymers and crystalline propylene polymers.

Examples of the ethylene polymer include low density polyethylene, linear low density polyethylene, medium density polyethylene, and high density polyethylene. These may be used alone or in combination. When these ethylene-based polymers are used as the base material layer (B), the surface protective film is cut cleanly when the adherend is cut with the surface protective film adhered to the adherend. As a result, good cutting properties that do not cause appearance defects such as stringing and fluffing are exhibited. Of these, low-density polyethylene, high-density polyethylene, or a mixed resin of low-density polyethylene and high-density polyethylene is preferable because of good heat resistance.

In addition, those ethylene polymers having an MFR (190 ° C.) of 0.5 to 30.0 g / 10 min are preferable because of easy extrusion, and more preferably an MFR of 2.0 to 15.0 g / 10 min. Further, when these ethylene polymers have a melting point of 90 to 135 ° C., the film shrinks little even when exposed to a high temperature environment by drying, heat molding or the like after being attached to the adherend. Therefore, it is preferable because it can suppress floating and peeling from the adherend and warpage of the adherend, and more preferably has a melting point of 105 to 130 ° C.

Examples of the crystalline propylene polymer include propylene homopolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and metallocene catalyst-based polypropylene. Can be mentioned. These may be used alone or in combination. When these crystalline propylene-based polymers are used as the base material layer (B), the heat resistance of the surface protective film is improved, and the crystalline propylene-based polymer can be suitably used for applications such as heat processing after sticking. Of these, metallocene catalyst-based polypropylene is preferably used. This is because metallocene-catalyzed polypropylene has high molecular weight distribution and uniform composition distribution and low content of low molecular weight components, so when used as a main component of the base material layer (B), it is due to bleeding of low molecular weight components. This is because contamination of the adherend surface is reduced. In the present application, crystallinity means having a peak of 0.5 J / g or more in the range of 95 to 250 ° C. in DSC (differential scanning calorimetry). The metallocene catalyst-based polypropylene may be a propylene homopolymer or a copolymer of propylene and another α-olefin.

These crystalline propylene polymers preferably have an MFR (230 ° C.) of 0.5 to 30.0 g / 10 min and a melting point of 120 to 165 ° C., more preferably MFR (230 ° C. ) Is 2.0 to 15.0 g / 10 min and the melting point is 125 to 162 ° C. If the MFR and the melting point are within this range, the film shrinks little even when exposed to a high temperature environment by drying, heat molding, or the like after being attached to the adherend, so that it floats or peels off from the adherend. This is preferable because warpage of the adherend can be suppressed, and the film forming property of the laminated film is also improved.

The surface protective film of the present invention may be composed of two layers of the above-mentioned pressure-sensitive adhesive layer (A) and base material layer (B), and a surface layer (C) may be provided in combination therewith. . At this time, the surface layer (C) is placed on the surface opposite to the adhesive layer (A) on the base material layer (B). The resin that is the main component of the surface layer (C) used in the surface protective film of the present invention is a thermoplastic resin, particularly if coextrusion with the adhesive layer (A) and the base material layer (B) is possible. Although not limited, 65 mass% or more of olefin polymer (C1) is contained with respect to the total mass of the component which comprises this surface layer (C) from the point that affinity with the said base material layer (B) is favorable. It is preferable to do. In particular, when the main component of the base material layer (B) is an ethylene polymer, an ethylene polymer is used. When the main component of the base material layer (B) is a crystalline propylene polymer, crystallinity is obtained. It is more preferable to use a propylene polymer.

Examples of the ethylene polymer used as the resin component of the surface layer (C) include those similar to the ethylene polymer used in the base material layer (B). Further, by selecting an ethylene polymer as the resin component of the surface layer (C), the surface protective film finally obtained is the same as in the case of using the ethylene polymer as the resin component of the base layer (B). High cutting ability.

Among the ethylene polymers used as the resin component of the surface layer (C), when low density polyethylene is used, it is easy to modify the surface of the surface layer (C) into a satin finish. By making the surface of the surface layer (C) satin, blocking can be reduced even when the adhesive force of the adhesive layer (A) is designed to be strong. Moreover, when high-density polyethylene is used in combination with low-density polyethylene, the rigidity of the resulting surface protective film can be increased, and workability such as sticking and peeling is improved.

Further, even when a mixed resin of the ethylene polymer and the propylene-ethylene block copolymer is used as the resin component of the surface layer (C), the surface of the surface layer (C) can be modified into a satin finish. Can do. Here, the propylene-ethylene block copolymer may be a resin obtained by block polymerization of propylene and ethylene. For example, ethylene polymerization or ethylene / propylene polymerization is performed in the presence of a propylene homopolymer. And a propylene-ethylene block copolymer obtained in the above manner. Among these, a propylene-ethylene block copolymer having an ethylene-derived component content of 8 to 20% by mass is preferable because the surface can be easily textured, and the ethylene-derived component content is 10 to 10%. A propylene-ethylene block copolymer of 15% by mass is more preferable. The MFR (230 ° C.) of the mixed resin of the ethylene polymer and the propylene-ethylene block copolymer is preferably in the range of 4 to 12 g / 10 minutes from the viewpoint of easy extrusion, and 6 to 10 g / 10. More preferably, it is in the range of minutes. Similarly, the density of the mixed resin is preferably in the range of 0.890 to 0.910 g / cm ^{3 from} the viewpoint of easy extrusion, and more preferably in the range of 0.895 to 0.905 g / cm ^3. preferable.

Examples of the crystalline propylene polymer used as the resin component of the surface layer (C) include the same as the crystalline propylene polymer used as the resin component of the substrate layer (B). Further, by selecting a crystalline propylene polymer as the resin component of the surface layer (C), finally, as in the case of using the crystalline propylene polymer as the resin component of the base layer (B), finally High heat resistance of the obtained surface protective film is expressed.

Further, when a mixed resin of the crystalline propylene polymer and the propylene-ethylene copolymer elastomer (hereinafter referred to as “EPR”) is used as the resin component of the surface layer (C), the surface layer (C) is formed into a satin finish. Can be easily modified. The crystalline propylene polymer used at this time is preferably a highly versatile propylene homopolymer (hereinafter referred to as “HOPP”). On the other hand, as the EPR used at this time, those having a weight average molecular weight in the range of 400,000 to 1,000,000 are preferable in that irregularities can be formed on the film surface and the surface can be modified into a satin finish. A range is more preferable. Further, the content of EPR in the mixed resin is preferably in the range of 5 to 35% by mass from the viewpoint that the film surface can be uniformly modified into a satin finish. The MFR (230 ° C.) of the mixed resin of crystalline propylene polymer and EPR is preferably in the range of 0.5 to 15 g / 10 minutes from the viewpoint of easy extrusion. In addition, the weight average molecular weight of the EPR was obtained by calculating a component extracted from the mixed resin by a cross fractionation method at 40 ° C. using orthodichlorobenzene as a solvent by GPC (gel permeation chromatography). It is. The content of EPR in the mixed resin is obtained from the amount of EPR extracted by cross-fractionation at 40 ° C. using orthodichlorobenzene as a solvent.

The method for producing the mixed resin of the crystalline propylene polymer and EPR is not particularly limited, and specific examples include, for example, a propylene homopolymer and an ethylene-propylene copolymer elastomer, each separately using a Ziegler type catalyst. After producing by a solution polymerization method, a slurry polymerization method, a gas phase polymerization method, etc., after producing a propylene homopolymer in the first stage by a method of mixing both in a kneader or a two-stage polymerization method, Examples include a method of generating EPR in the presence of this polymer in the second stage.

The Ziegler-type catalyst is a so-called Ziegler-Natta catalyst, and is obtained by supporting a transition metal compound such as a titanium-containing compound or a transition metal compound on a support such as a magnesium compound. The combination with the promoter of an organometallic compound is mentioned.

The surface protective film of the present invention preferably has a total film thickness of 20 to 120 μm. When the thickness of all the films is within this range, workability such as sticking and peeling is improved. The thickness of the adhesive layer (A) is preferably 3 to 30 μm, more preferably 5 to 25 μm. If the thickness of the pressure-sensitive adhesive layer (A) is within this range, in addition to the above-mentioned pressure-sensitive adhesive properties, the film formability of the laminated film will be good. Furthermore, when the surface layer (C) is provided on the surface protective film of the present invention, the thickness of the surface layer is preferably 3 to 30 μm, more preferably 5 to 20 μm. When the thickness of the surface layer is within this range, the heat resistance and the film formability of the laminated film are good.

The method for producing the surface protective film of the present invention is not particularly limited as long as it is a coextrusion lamination method. For example, the resin used for each resin layer is melted by using two or more extruders, Examples include a method of laminating in a molten state by a co-extrusion method such as a manifold method or a feed block method, and then processing into a film using a method such as inflation or a T-die chill roll method. In the case of the T-die / chill roll method, the melt-laminated film may be nipped between a rubber touch roll, a steel belt or the like and the chill roll and cooled.

Furthermore, the surface protective film of the present invention may be a uniaxially stretched film or a biaxially stretched film. The base material layer is oriented and crystallized by stretching in at least one axial direction, and the structure is stabilized by heat setting. This is preferable because the heat resistance is improved and the change in adhesive strength with time is reduced.

In addition, a lubricant, an antiblocking agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antifogging agent, and the like may be added as appropriate within a range not impairing the effects of the present invention. As these additives, it is preferable to use various additives for olefin-based resins.

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples.

Example 1
As a resin for the surface layer, a propylene mixed resin [a resin composed of a propylene homopolymer and EPR, MFR (230 ° C.): 4.0 g / 10 min, EPR content: 11 mass%, EPR weight average molecular weight 550,000 As a base layer resin, a metallocene catalyst-based propylene-ethylene random copolymer [density: 0.900 g / cm ³ , MFR (230 ° C., 21.18 N): 7.0 g / 10 min, ethylene single Content rate of the monomer unit: 3.5 mass%; hereinafter referred to as “metallocene catalyst system COPP”. As a resin for the adhesive layer, “Dynalon 6200P” manufactured by JSR Corporation [density: 0.88 g / cm ³ , MFR (230 ° C.): 2.5 g / 10 min: hereinafter referred to as “CEBC”]. ] 10 parts by mass and linear low density polyethylene [density: 0.902 g / cm ³ , MFR (190 ° C.): 3.0 g / 10 min; hereinafter referred to as “LLDPE (1)”. ] Using 90 parts by mass of the mixture, each was supplied to an extruder for surface layer (caliber 30 mm), an extruder for base layer (caliber 40 mm) and an extruder for adhesive layer (caliber 30 mm), and extruded by coextrusion method. After extruding from a T-die at a temperature of 250 ° C. to a surface layer thickness of 10 μm, a base material layer thickness of 30 μm, and an adhesive layer thickness of 10 μm, and cooling with a 40 ° C. water-cooled metal cooling roll The film was wound on a roll to obtain a surface protective film. The obtained film was aged in a aging room at 35 ° C. for 48 hours in order to stabilize physical properties.

(Example 2)
A surface protective film of Example 2 was obtained in the same manner as Example 1 except that a mixture of 30 parts by mass of CEBC and 70 parts by mass of LLDPE (1) was used as the adhesive layer resin.

(Example 3)
As a resin for the adhesive layer, 10 parts by mass of CEBC and linear low density polyethylene [density: 0.920 g / cm ³ , MFR (190 ° C.): 3.0 g / 10 min; hereinafter referred to as “LLDPE (2)”. The surface protective film of Example 3 was obtained in the same manner as in Example 1 except that 90 parts by mass of the mixture was used.

Example 4
A surface protective film of Example 4 was obtained in the same manner as in Example 1 except that a mixture of 30 parts by mass of CEBC and 70 parts by mass of LLDPE (2) was used as the adhesive layer resin.

(Example 5)
The surface protective film of Example 5 was the same as Example 4 except that HOPP [density: 0.900 g / cm ³ , MFR (230 ° C.): 8.0 g / 10 min] was used as the base layer resin. Got.

(Example 6)
As a resin for the surface layer, a propylene-based mixed resin [a resin comprising a propylene homopolymer and EPR, MFR (230 ° C.): 4.0 g / 10 min, EPR content: 30 mass%, EPR weight average molecular weight 550,000 The surface protective film of Example 6 was obtained in the same manner as in Example 1 except that a mixture of 50 parts by mass of CEBC and 50 parts by mass of LLDPE (2) was used as the adhesive layer resin.

(Example 7)
A surface protective film of Example 7 was obtained in the same manner as in Example 6 except that a mixture of 70 parts by mass of CEBC and 30 parts by mass of LLDPE (2) was used as the adhesive layer resin.

(Example 8)
A surface protective film of Example 8 was obtained in the same manner as in Example 7 except that HOPP was used as the base layer resin.

Example 9
As the resin for the surface layer and the resin for the base layer, low density polyethylene [density: 0.920 g / cm ³ , MFR (190 ° C.): 6 g / 10 min; hereinafter referred to as “LDPE (1)”. ], A mixture of 10 parts by weight of CEBC and 90 parts by weight of LLDPE (1) was used as the adhesive layer resin, the surface layer thickness was 14 μm, the base layer thickness was 42 μm, and the adhesive layer thickness A surface protective film of Example 9 was obtained in the same manner as in Example 1 except that the film was extruded so as to be 14 μm.

(Example 10)
A surface protective film of Example 10 was obtained in the same manner as Example 9 except that a mixture of 30 parts by mass of CEBC and 70 parts by mass of LLDPE (1) was used as the adhesive layer resin.

Example 11
A surface protective film of Example 11 was obtained in the same manner as Example 9 except that a mixture of 10 parts by weight of CEBC and 90 parts by weight of LLDPE (2) was used as the adhesive layer resin.

(Example 12)
A surface protective film of Example 12 was obtained in the same manner as in Example 9 except that a mixture of 30 parts by mass of CEBC and 70 parts by mass of LLDPE (2) was used as the adhesive layer resin.

(Example 13)
As the resin for the surface layer, 50 parts by mass of LDPE (1) and high-density polyethylene [density: 0.960 g / cm 3, MFR (190 ° C.): 5.5 g / 10 min; hereinafter referred to as “HDPE (1)”. ] In the same manner as in Example 9, except that 50 parts by mass of the mixture was used, and 50 parts by mass of CEBC and 50 parts by mass of LLDPE (2) were used as the adhesive layer resin. Got.

(Example 14)
The surface layer resin is not used, and a mixture of 70 parts by mass of CEBC and 30 parts by mass of LLDPE (2) is used as the adhesive layer resin so that the thickness of the base layer is 56 μm and the thickness of the adhesive layer is 14 μm. A surface protective film of Example 14 was obtained in the same manner as Example 9 except that the film was extruded.

(Example 15)
Low density polyethylene (density: 0.902 g / cm ³ , MFR (190 ° C., 21.18 N): 4 g / 10 min; hereinafter referred to as “LDPE (2)”) and high density polyethylene (density: 0.960 g / cm ³ , MFR (190 ° C., 21.18 N): 13 g / 10 min; hereinafter referred to as “HDPE (2)”) are mixed so as to have a mass ratio of 50/50, and used as an adhesive layer resin. Using a mixture of 30 parts by mass of CEBC and 70 parts by mass of LLDPE (2), the mixture was supplied to an extruder for a base layer (caliber 50 mm) and an extruder for an adhesive layer (caliber 40 mm), respectively, and an extrusion temperature of 250 by coextrusion method. A surface protective film of Example 15 was obtained in the same manner as in Example 1 except that the substrate layer was extruded from a T-die so that the thickness of the base material layer was 64 μm and the thickness of the adhesive layer was 16 μm.

(Example 16)
As a resin for the surface layer, LDPE (2) and a propylene-ethylene block copolymer are mixed at a mass ratio of 95/5, and LDPE (2) and HDPE (2) are mixed as the base resin. Used as a resin for the adhesive layer, with a mass ratio of 50/50, CEBC and linear low-density polyethylene (density: 0.902 g / cm ³ , MFR (190 ° C., 21.18 N): 6 g / 10 minutes; hereinafter referred to as “LLDPE (3)”) using a mixture having a mass ratio of 5/95, an extruder for surface layer (caliber 50 mm), an extruder for substrate layer (caliber 50 mm), and an adhesive layer To an extruder (40 mm in diameter) and by co-extrusion at an extrusion temperature of 250 ° C., the thickness of the surface layer from the T-die is 16 μm, the thickness of the base material layer is 48 μm, and the thickness of the adhesive layer is 16 μm. Except for extruding In the same manner as in Example 1, to obtain a surface protective film of Example 16.

(Example 17)
HOPP and propylene-ethylene block copolymer are mixed as a surface layer resin in a mass ratio of 95/5, a metallocene catalyst COPP is used as the base layer resin, and CEBC is used as the adhesive layer resin. A surface protective film of Example 17 was obtained in the same manner as in Example 16 except that a mixture of LLDPE (2) at a mass ratio of 30/70 was used.

(Example 18)
A surface protective film of Example 18 was obtained in the same manner as Example 16 except that a mixture of CEBC, LLDPE (3), and metallocene catalyst system COPP having a mass ratio of 25/70/5 was used as the adhesive layer resin. It was.

Example 19
The surface protective film of Example 19 was obtained in the same manner as in Example 15 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 40/40/20 was used as the adhesive layer resin. It was.

(Example 20)
The surface protective film of Example 20 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 40/35/25 was used as the adhesive layer resin. Obtained.

(Example 21)
The surface protective film of Example 21 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 40/30/30 was used as the adhesive layer resin. It was.

(Example 22)
A surface protective film of Example 22 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 35/40/25 was used as the adhesive layer resin. It was.

(Example 23)
A surface protective film of Example 23 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (3), and metallocene catalyst system COPP having a mass ratio of 25/45/30 was used as the adhesive layer resin. It was.

(Example 24)
A surface protective film of Example 24 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (3), and metallocene catalyst system COPP having a mass ratio of 25/50/25 was used as the adhesive layer resin. It was.

(Example 25)
The surface protective film of Example 25 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 40/10/50 was used as the adhesive layer resin. Obtained.

(Example 26)
The surface protective film of Example 26 was obtained in the same manner as in Example 17 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 40/35/25 was used as the adhesive layer resin. Obtained.

(Example 27)
The surface protective film of Example 27 was obtained in the same manner as in Example 17 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 40/30/30 was used as the adhesive layer resin. Obtained.

(Example 28)
The surface protective film of Example 28 was obtained in the same manner as in Example 17 except that a mixture of CEBC, LLDPE (3), and metallocene catalyst system COPP having a mass ratio of 25/50/25 was used as the adhesive layer resin. Obtained.

(Example 29)
The surface protective film of Example 29 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 15/65/20 was used as the adhesive layer resin. It was.

(Example 30)
The surface protective film of Example 30 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 30/60/10 was used as the adhesive layer resin. It was.

(Comparative Example 1)
Example 6 except that a mixture of 57 parts by mass of amorphous propylene-butene-1 copolymer, 3 parts by mass of crystalline propylene-butene-1 copolymer and 40 parts by mass of CEBC was used as the adhesive layer resin. Similarly, the surface protective film of Comparative Example 1 was obtained.

(Comparative Example 2)
As the adhesive layer resin, a mixture of 49.4 parts by mass of an amorphous propylene-butene-1 copolymer, 10.6 parts by mass of a crystalline propylene-butene-1 copolymer and 40 parts by mass of CEBC was used. In the same manner as in Example 6, a surface protective film of Comparative Example 2 was obtained.

(Comparative Example 3)
As the adhesive layer resin, a mixture of 50 parts by mass of styrene-ethylene-propylene-styrene block copolymer (Kuraray Co., Ltd. “Septon 2063”; hereinafter referred to as “SEPS”) and LLDPE (2) 50 parts by mass was used. A surface protective film of Comparative Example 3 was obtained in the same manner as Example 6 except for the above.

(Comparative Example 4)
A surface protective film of Comparative Example 4 was obtained in the same manner as in Example 16 except that a mixture of CEBC, LLDPE (2), and metallocene catalyst system COPP having a mass ratio of 30/10/60 was used as the adhesive layer resin. It was.

(Comparative Example 5)
Comparative Example in the same manner as in Example 16 except that a mixture of CEBC, metallocene catalyst system COPP, and amorphous propylene-butene-1 copolymer having a mass ratio of 40/10/50 was used as the adhesive layer resin. 5 surface protection film was obtained.

(Comparative Example 6)
A surface protective film of Comparative Example 6 was obtained in the same manner as in Example 16 except that a mixture of CEBC and metallocene catalyst system COPP having a mass ratio of 70/30 was used as the adhesive layer resin.

(Evaluation method of surface protective film obtained in Examples and Comparative Examples)
Measurement of Adhesive Strength In a thermostatic chamber at 23 ° C. and 50% RH, the surface protective film obtained above was applied to an acrylic plate having a thickness of 2 mm (mirror finish, Mitsubishi Rayon) in accordance with the adhesive strength evaluation method of JIS Z0237: 2000. It was attached to "Acrylite" manufactured by Co., Ltd. The acrylic plate with the film attached is left in a constant temperature room at 23 ° C. for 24 hours, and then peeled off in the 180 ° direction at a speed of 300 mm / min using a tensile tester (manufactured by A & D Co., Ltd.). The initial adhesive strength was measured. Moreover, after leaving the acrylic board which stuck the film in a 50 degreeC dryer for one day, adhesive force was measured similarly.

Evaluation of adhesiveness When measuring the above-mentioned adhesive strength, the state of adhesion of the surface protective film adhered to the acrylic plate to the acrylic plate was visually confirmed, and the adhesiveness was evaluated according to the following criteria.
◯: Maintaining uniform adhesion to the acrylic plate surface.
X: Insufficient initial adhesive strength, uniform adhesion cannot be maintained, and partly floated.

Evaluation of adhesive residue In a temperature-controlled room at 23 ° C. and 50% RH, a surface protective film is made of an acrylic plate (mirror finish, manufactured by Mitsubishi Rayon Co., Ltd., “Acrylite” in accordance with JIS Z0237: 2000. )). The acrylic plate on which the film was adhered was allowed to stand in a dryer at 60 ° C. for 3 days, and then cooled in a constant temperature room at 23 ° C. for 1 hour. From the cooled test piece, the film was peeled off at a high speed in the direction of 180 °, the state of contamination on the acrylic plate surface was visually confirmed, and the adhesive residue was evaluated according to the following criteria.
○: No cloudiness, white streaks, foreign matter, etc. on the acrylic plate surface.
△: The surface of the acrylic plate is cloudy, white streaks, foreign matter, etc. but can be used for practical use. ×: The surface of the acrylic plate is cloudy, white streaks, foreign matter, etc. What is unsuitable for

Measurement of the wetting tension on the acrylic plate surface Using the test piece before film sticking (the test piece obtained by washing the surface of the acrylic plate with alcohol and drying) and the test piece after film peeling used in the evaluation of the adhesive residue, The wetting tension on the acrylic plate surface was measured by a method based on JIS K6768: 1999. The wetting tension of the test piece before film attachment was 40 mN / m.

Evaluation of printing suitability after surface protective film peeling Using the measured value of wetting tension on the surface of the acrylic plate, the reduction width of wetting tension [(wetting tension of test piece before film sticking: 40 mN / m)-(after film peeling) Was evaluated as a substitute evaluation of printability after peeling off the protective film. The evaluation criteria are as follows.
A: The decrease width of the wetting tension is 2 mN / m or less.
X: The reduction width of the wetting tension exceeds 2 mN / m.

Evaluation of blocking resistance The obtained surface protective film was cut out in the size of A4 (length 297 mm x width 210 mm). At this time, the film was cut out so that the extrusion direction (MD direction) during film formation coincided with the A4 vertical direction. After stacking 10 cut out films, the upper and lower sides were sandwiched between A4 size, 3 mm thick vinyl chloride plates, a weight of 5 kg was placed, and stored in a dryer at 40 ° C. for 14 days, then at 23 ° C. It was stored for 1 hour in a constant temperature room of 50% RH. Next, the film was cut out in a width of 25 mm in the MD direction, and peeled in the direction of 180 ° at a speed of 300 mm / min using a tensile tester (manufactured by A & D Co., Ltd.) to measure the blocking force. From the obtained blocking force, blocking resistance was evaluated according to the following criteria.
A: The blocking force is less than 0.8 N / 25 mm.
X: The blocking force is 0.8 N / 25 mm or more.

Measurement of Adhesive Force Between Adhesive Surfaces In a thermostatic chamber at 23 ° C. and 50% RH, the adhesive surfaces of two surface protective films each having a length of 15 cm and a width of 25 mm were attached by a method in accordance with JIS Z0237: 2000. After the stuck film was allowed to stand for 30 minutes in a constant temperature room at 23 ° C., it was peeled off in the 180 ° direction at a speed of 300 mm / min using a tensile tester (manufactured by A & D Co., Ltd.). The adhesive force between the adhesive surfaces was measured.

Adhesion between adhesive surfaces, adhesive surface state after peeling In a temperature-controlled room at 23 ° C. and 50% RH, the adhesive surfaces of two surface protective films consisting of 15 cm long × 25 mm wide by a method according to JIS Z0237: 2000 Affixed. The stuck film was allowed to stand in a constant temperature room at 23 ° C. for 30 minutes, and then peeled off at high speed. The condition of the adhesive surface was visually confirmed, and the adhesive surface state was evaluated according to the following criteria.
○: The adhesive surface is not whitened or roughened. △: The adhesive surface is whitened or roughened, but it can withstand practical use. ×: The adhesive surface is whitened and roughened. What is

The results of the above evaluations are shown in the table below. In addition, about the surface protection film which has not provided the surface layer, the said location is blank.

Regarding adhesion enhancement, the strength of the adhesive strength of the surface protective film obtained in each example is mainly due to the difference in the adhesion layer, and can take various values depending on the composition of the adhesion layer. There is no significant difference between the values of “50 ° C. × 1 day” and there is little increase in adhesion. On the other hand, the surface protective film obtained in each comparative example has a greater adhesion enhancement than the examples.

Contamination of the adherend surface after peeling of the surface protective film In the surface protective film obtained in each Example, the adhesive residue on the adherend after peeling of the film could not be visually confirmed. In addition, the decrease in the wet tension of the adherend surface before and after the film was peeled was small, and the contamination of the adherend surface could be minimized to the extent that the printability was not lowered. On the other hand, in the surface protective film obtained in each comparative example, the adhesive residue on the adherend after film peeling can be visually confirmed, and the printability of the adherend surface after film peeling is as in each example. An evaluation result that is lower than the above was obtained.

Regarding adhesion between adhesive surfaces, in the case where a propylene-based polymer is further used in the adhesive layer, even when the adhesive surfaces are adhered to each other, peeling is easy, and there is no occurrence of roughness or the like on the adhesive surface. The surface protective film of the present invention can also be used in such a usage method that the surface protective film is attached and detached during the manufacturing process.

The surface protective film of the present invention has a wide range of adhesive strengths ranging from optimum fine adhesion to medium adhesion level, and does not cause floating or peeling after sticking to an acrylic plate. In particular, when the film is peeled off from the attached acrylic plate, there is no visible contamination such as cloudiness, streaks, or foreign matter, and there is very little reduction in the wetting tension on the acrylic plate surface after peeling off the surface protective film. Therefore, it is suitable for applications in which secondary processing such as printing is performed after the surface protective film is peeled off.

Claims

A surface protective film obtained by laminating an adhesive layer (A) and a base material layer (B), wherein the adhesive layer (A)
The pressure-sensitive adhesive layer (A) comprises a block copolymer (A1) having a crystalline olefin block and a linear low-density polyethylene (A2) having a density of 0.880 to 0.938 g / cm 3. A block copolymer (A1) containing 50% by mass or more based on the total mass of the components and having a crystalline olefin block, and a linear low-density polyethylene having a density of 0.880 to 0.938 g / cm 3 A surface protective film, wherein 5 to 80% by mass of the total mass with (A2) is a block copolymer (A1) having a crystalline olefin block.
The surface protective film according to claim 1, wherein the block copolymer (A1) having a crystalline olefin block is a crystalline olefin-ethylene-butylene copolymer-crystalline olefin block copolymer (CEBC).
The surface protective film according to claim 1 or 2, further comprising a propylene-based polymer (A3) in the adhesive layer (A).
The surface protection film according to claim 3, wherein the propylene polymer (A3) is a metallocene catalyst-based polypropylene.
Usage ratio (A1): (A2) of each component in a total of 100 parts by mass of the block copolymer (A1), the linear low-density polyethylene (A2), and the propylene-based polymer (A3): The surface protective film according to claim 3 or 4, wherein (A3) is from 10 to 50:10 to 70:10 to 50.
The base material layer (B) contains the olefin polymer (B1) in an amount of 65% by mass or more based on the total mass of the components constituting the base material layer (B). A surface protective film according to claim 1.
The surface protection film according to claim 6, wherein the olefin polymer (B1) is one or more olefin polymers selected from the group consisting of low density polyethylene, high density polyethylene and crystalline propylene polymer.
The surface protective film according to any one of claims 1 to 7, wherein the surface layer (C) is provided on the base material layer (B) opposite to the adhesive layer (A).
The surface protective film according to claim 8, wherein the surface layer (C) contains the olefin polymer (C1) in an amount of 65% by mass or more based on the total mass of components constituting the surface layer (C).
The surface protection film according to claim 9, wherein the olefin polymer (C1) is one or more olefin polymers selected from the group consisting of low density polyethylene, high density polyethylene and propylene homopolymer.
The olefin polymer (C1) is a mixed resin of at least one olefin polymer selected from the group consisting of low density polyethylene, high density polyethylene and propylene homopolymer, and a propylene-ethylene block copolymer. The surface protective film according to claim 9.