JP2013126743A - Coating film surface protective film and base material film used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film that satisfies both flexibility and nerve, and is excellent in tear resistance by making it multilayers, and improved in lubricity by raising film surface roughness and can be suitably used as a base material film of a coating film surface protective film, and furthermore, a multilayer film that controls a decrease of adhesion by the bleed of a weather resistance agent, and the coating film surface protective film prepared by providing an adhesion layer to the multilayer film.SOLUTION: The are provided a base material film that is used for the coating film surface protective film, and a protective film that is provided by forming an adhesive layer to one side of the base material film. In the coating film surface protective film, an outer layer and an inner layer are layers each containing a resin mixture that mixes a propylene homopolymer (a1) at 70-90 mass% and low density polyethylene (a2) at 10-30 mass%, and an intermediate layer (B) is a layer that contains a propylene polymer (b1) at 15-40 mass% and linear low density polyethylene (b2) at 40-70 mass% to the whole mass of the intermediate layer (B).

Description

  TECHNICAL FIELD The present invention relates to a film that is stuck and used when protecting a coating film surface, and in particular, a coating film surface protection film used for preventing deterioration or scratching of a painted surface when transporting an automobile or the like. And a base film used therefor.

  In recent years, in order to protect the painted surface of automobiles during transportation and storage of finished automobiles, a surface protective film with adhesive applied on one side of a plastic film is applied to protect the painted surface, instead of the conventional method of applying paint. The way to do is taken. Since the protective film is often incinerated and discarded after peeling, a polyolefin-based film that is easily incinerated and discarded is preferably used. However, depending on the type of the plastic film, the film is difficult to follow due to the shape of the adherend, so that the film does not adhere uniformly, and the appearance of the painted surface may become uneven after the film is peeled off. In particular, when the adherend is a curved surface, if the rigidity of the film is large, the area where the bonding portion of the film becomes non-uniform may increase. Moreover, when peeling a protective film, in the case of a film that is easily torn, such as a biaxially stretched film, there is a problem that the film is easily torn in the middle of peeling and the efficiency of the peeling work is reduced.

  As a means of solving such a tearing problem, the adhesive layer is provided on a three-layer substrate film using a polyethylene resin for both outer layers and a polypropylene resin for the intermediate layer, so that the film itself is strained and flexible. Furthermore, it has been reported that the tear resistance can be improved (for example, see Patent Document 1). However, since the film surface having such a structure has low roughness and inferior slipperiness, there is a problem that blocking during winding and storage tends to occur, and processing suitability when forming an adhesive layer is poor.

  In addition, since protective films used for automobile bodies are often stuck to the painted surface of finished vehicles and left outdoors for a long period of time, weather resistance is required. In many cases, the film is whitened in order to add a weathering agent and further suppress ultraviolet attack to the adhesive. In the example of Patent Document 1 as well, titanium oxide and a hindered amine light stabilizer are added to all layers in a three-layer film. Such additives are used on the film surface under long-term use. Because it is easy to bleed, especially when bleeding out between the adhesive layer and the surface layer, it may adversely affect the adhesive used in the adhesive layer. The function may not be performed.

Japanese Patent Laid-Open No. 2001-121661

  An object of the present invention has been made in view of the above-described problems, and by multilayering, both flexibility and waist strength are achieved, tear resistance is good, and the surface roughness of the film is improved. Multilayer film that can be suitably used as a base film for a coating surface protection film with improved slipperiness, and further, a multilayer film that suppresses a decrease in adhesive strength due to weathering bleed, and an adhesive layer therefor It is providing the coating-film surface protection film which provides this.

  As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention are multilayer films having at least a three-layer structure having both surface layers and an intermediate layer, and a specific olefin-based resin mixture is used for each layer. As a result, the inventors have found that the above problems can be solved, and have completed the present invention.

  That is, in the present invention, the outer layer and the inner layer are layers containing a resin mixture in which 70 to 90% by mass of the propylene homopolymer (a1) and 10 to 30% by mass of the low density polyethylene (a2) are mixed. B) is 15-40% by mass of the propylene polymer (b1) and 40-70% by mass of the linear low density polyethylene (b2) with respect to the total mass of the intermediate layer (B). The present invention provides a base film used for a coating film surface protective film, which is a layer to be contained, and a coating film surface protection film provided with an adhesive layer on one surface thereof.

  The base film of the present invention can be a surface protective film that can prevent the coating film surface from being deteriorated and damaged over a long period of time outdoors by providing an adhesive layer on one surface thereof. Since this base film has a certain roughness on the surface, it can be stored even in the state of the multilayer film before providing the pressure-sensitive adhesive layer, and good processing suitability when providing the pressure-sensitive adhesive layer It is. Furthermore, when the light-resistant stabilizer is contained only in the intermediate layer of the base film, the light-resistant stabilizer does not bleed to the surface layer (inner layer and outer layer), so that the adhesive strength is deteriorated. It can also be used suitably for automobiles that are stored outdoors for a long period of time.

  The base film of the present invention is a multilayer film having at least three layers, and mainly uses an olefin-based material for ease of disposal and incineration. By providing a pressure-sensitive adhesive layer on one surface of the substrate film, it can be used as a coating film surface protective film.

  The outer layer and the inner layer of the base film of the present invention are layers containing a resin mixture obtained by mixing 70 to 90% by mass of propylene homopolymer (a1) and 10 to 30% by mass of low density polyethylene (a2). From the viewpoint of strain and heat resistance of the resulting base film, and surface roughness, the resin mixture is preferably contained at 95% by mass or more based on the total mass of the layer.

  The propylene homopolymer (a1) is not particularly limited, and even if it is polymerized using a multi-site catalyst (Ziegler-Natta catalyst), it is polymerized with a single-site catalyst (metallocene catalyst). It may be. As MFR (230 degreeC, 21.18N) of a propylene homopolymer (a1), what is 0.5-30.0 g / 10min is preferable, More preferably, MFR (230 degreeC) is 2.0- 15.0 g / 10 min. When the MFR is in this range, the film formability when producing a base film by the coextrusion lamination method is improved. In addition, the melting point of the propylene homopolymer (a1) is preferably 158 ° C. or higher, particularly preferably 160 ° C. or higher, from the viewpoint of heat resistance of the base film. By using such a highly crystalline propylene homopolymer, even if additives are used, it is possible to effectively suppress bleeding out of the film surface. In the coating film surface protective film provided with the agent layer, the change with time of the adhesive force can be suppressed. In addition, melting | fusing point in this invention says the value of a peak top when it measures with a differential scanning calorimeter (DSC).

The low density polyethylene (a2) has a density of 0.918 to 0 from the viewpoint of easily expressing the roughness of the film surface when used in combination with the propylene homopolymer (a1). The range is preferably 922 g / cm ³ , and the MFR (190 ° C., 21.18 N) is preferably in the range of 0.29 to 0.41 g / 10 min.

  The proportion of the propylene homopolymer (a1) and the low-density polyethylene (a2) used is determined from the viewpoint of the balance between the surface roughness of the obtained base film, heat resistance, strain, and flexibility. a1) 70 to 90% by mass, low density polyethylene (a2) 10 to 30% by mass, preferably (a1) 75 to 85% by mass, (a2) 15 to 25% by mass Is the ratio.

  In the base film of the present invention, the outer layer and the inner layer preferably contain the above-mentioned resin mixture in an amount of 95% by mass or more based on the total mass of the layer. It is not required to be the same resin mixture, and the use ratio of the propylene homopolymer (a1) and the low density polyethylene (a2) and the ratio of the layer to the layer are different within the range specified in the present invention. It does not matter.

  The outer layer and inner layer of the present invention may be used in combination with other olefin-based resins and the like as long as the effects of the present invention are not impaired. From the viewpoint of compatibility and surface roughness, a polypropylene-based resin or a polyethylene-based resin is used. They can be used alone or in combination. When it is set as a coating film surface protective film, it is usual to make a base film white or to add a light-resistant stabilizer etc. especially from a weather-resistant viewpoint. In the base film of the present invention, since a propylene-based homopolymer is used for the outer layer and the inner layer, bleed-out of these additives can be suppressed, and titanium oxide and hindered amine-based light resistance stability can be achieved in these layers. An agent or the like may be added, but it is preferable not to use these additives in the outer layer and the inner layer from the viewpoint of further suppressing the change in the adhesive force with time.

  The surface roughness Ra of the substrate film of the present invention can be easily adjusted in the range of 0.3 to 2.0 μm, particularly 0.5 to 1.3 μm, as measured by JIS-B0601. It is preferable from the viewpoints of blocking prevention, processing suitability when providing the pressure-sensitive adhesive layer, and ease of use when a surface protective film is provided. Such adjustment of the surface roughness includes the above-mentioned mixing ratio of the resin mixture, the use ratio of the resin mixture with respect to the total mass forming the layer, and various conditions when the base film is manufactured by the coextrusion lamination method ( Temperature, speed, etc.) and can be adjusted to the desired roughness.

  The intermediate layer (B) in the base film of the present invention is 15 to 40% by mass of the propylene polymer (b1) and 40 to 70% by mass of the linear low density polyethylene (b2) with respect to the total mass. It is essential to contain in the range of. While maintaining the heat resistance and rigidity (strain) of the base film by using the propylene polymer (b1), the linear low density polyethylene (b2) is equal to or more than the propylene polymer (b1). By using it, the tear resistance of the base film or the protective film provided with the pressure-sensitive adhesive layer can be improved.

  Examples of the propylene polymer (b1) include, in addition to the propylene homopolymer described above, for example, a copolymer of propylene such as a propylene-ethylene copolymer and other olefins. Also, a mixture of two or more may be used. The MFR (230 ° C.) of the propylene polymer (b1) is preferably 0.5 to 30.0 g / 10 minutes, more preferably from the viewpoint of easy coextrusion lamination with the outer layer and the inner layer. Has an MFR (230 ° C.) of 2.0 to 15.0 g / 10 min. Although it does not specifically limit as melting | fusing point, The thing of the range of 120-150 degreeC is preferable from a viewpoint of maintaining the rigidity of a base film, heat resistance, and prevention of bleed-out at the time of using an additive.

The linear low density polyethylene (b2) is usually one density is in the range of 0.880~0.938g / cm ^3, more things density is 0.898~0.925g / cm ³ preferable. Moreover, as MFR (190 degreeC, 21.18N), what is 0.5-30.0 g / 10min is preferable, and what is 2.0-15.0 g / 10min is more preferable. When the density and MFR of the linear low-density polyethylene (b2) are within this range, the compatibility with the propylene polymer (b1) described above is good, and the film formability of the base film is improved.

  As described above, the intermediate layer (B) in the base film of the present invention is in the range of 15 to 40% by mass of the propylene polymer (b1) and 40 to 70% by mass of the linear low density polyethylene (b2). Preferably, (b1) is contained in an amount of 20 to 30% by mass, and (b2) is contained in an amount of 45 to 60% by mass. Other resins, particularly olefin resins may be used in combination, but other resins are preferably used in an amount of less than 15% by mass with respect to the total mass in order to express the effects of the present invention more efficiently.

  Other resins in the intermediate layer (B) can be used as a master batch in the case of using various additives such as titanium oxide and light stabilizer for whitening the base film of the present invention, thereby improving production efficiency. From the point of view, it is preferable. Moreover, you may mix the recycled product of the film used for the use similar to this invention at about 10 mass% or less.

  Moreover, even if the intermediate | middle layer (B) of the base film of this invention consists of a single layer, it may laminate | stack two or more layers. In the case of a multilayer structure, the propylene polymer (b1) is used in the range of 15 to 40% by mass and the linear low density polyethylene (b2) is used in the range of 40 to 70% by mass as the resin component forming each layer. However, if the intermediate layer as a whole is used in this range, the effects of the present invention can be obtained.

  The base film of the present invention has a pressure-sensitive adhesive layer on one side and is used as a coating film surface protective film. It is preferable to use a light-resistant stabilizer and the like, and from the viewpoint of preventing bleeding out, it is preferable to add these additives only to the intermediate layer (B). In the case of a colored film, for example, inorganic fillers such as talc, titanium oxide, calcium carbonate, clay, mica, barium sulfate, whiskers, magnesium hydroxide, etc. can be used, and the average particle size of these fillers The diameter is preferably in the range of 0.1 μm to 10 μm. These fillers and the like can be used in a range of 10 to 20% by mass with respect to the total mass of the intermediate layer (B).

  Examples of the light resistance stabilizer include hindered amine compounds, phosphorus compounds, cyanoacrylate compounds, and the like. Although it does not specifically limit as a usage rate of these stabilizers, It is preferable to use in 0.2-0.3 mass% with respect to the whole mass of an intermediate | middle layer (B).

  Moreover, you may use the various additives used for an olefin resin in the range which does not impair the effect of this invention in the outer layer of the base film of this invention, an intermediate | middle layer, and an inner layer. Examples of additives include lubricants, antiblocking agents, ultraviolet absorbers, antistatic agents, antifogging agents, and coloring agents.

  The base film of the present invention preferably has a total film thickness of 40 to 80 μm. If the thickness of all the films is within this range, the protective properties and adhesion of the adherend, and workability such as sticking and peeling will be good. Moreover, when the thickness ratio with respect to the total thickness of the intermediate layer (B) is in the range of 55 to 85%, the adhesiveness and the film formability of the base film become good, and the tear resistance is also excellent.

  Although it does not specifically limit as a manufacturing method of the base film of this invention, The coextrusion lamination method is preferable. As the coextrusion laminating method, for example, the resin used for each resin layer is melted by using two or more extruders, laminated in a molten state by a coextrusion method such as a coextrusion die method or a feed block method, and then inflation is performed. And a method of processing into a film using a method such as a T-die chill roll method. In the case of the T-die / chill roll method, the melt-laminated film may be nipped and cooled between a rubber touch roll, a steel belt or the like and the chill roll.

  Furthermore, the base film of the present invention may be stretched in at least one axial direction. As the stretching method, a known method such as longitudinal or lateral uniaxial stretching, sequential biaxial stretching, simultaneous biaxial stretching, or tubular method biaxial stretching can be employed. Further, the stretching process may be inline or offline. The stretching method for uniaxial stretching may be a proximity roll stretching method or a rolling method. The stretching ratio of uniaxial stretching is preferably 1.1 to 80 times, more preferably 3 to 30 times in the longitudinal or transverse direction. On the other hand, the stretch ratio of biaxial stretching is preferably 1.2 to 70 times in terms of area ratio, more preferably 4 to 6 times in length, 5 to 9 times in width, and 20 to 54 times in area ratio.

  In addition, the longitudinal or lateral stretching step is not necessarily limited to one-stage stretching, and may be multi-stage stretching. In particular, in longitudinal uniaxial stretching such as longitudinal uniaxial roll stretching and longitudinal uniaxial rolling stretching in sequential biaxial stretching, it is preferable to perform multistage stretching in view of thickness, uniformity of physical properties, and the like. Further, in the proximity roll stretching, either the flat method or the cross method may be used, but multistage proximity cross stretching that can reduce width shrinkage is more preferable. In the case of uniaxial stretching, the stretching temperature is preferably 80 ° C to 160 ° C in any stretching method, and in the case of using tenter stretching in uniaxial stretching, 90 to 165 ° C is preferable. Moreover, as more preferable extending | stretching temperature, they are 110-155 degreeC and 120-160 degreeC, respectively. On the other hand, in the case of biaxial stretching, the stretching temperature range similar to that in the case of uniaxial stretching is preferable in any method. Moreover, you may provide a pre-heating part before an extending process, and a heat setting part after an extending process suitably. In this case, the temperature of the preheating part is preferably in the range of 60 to 140 ° C, and the temperature of the heat fixing part is preferably in the range of 90 to 160 ° C.

  In the case of stretching in at least one uniaxial direction, by stabilizing the structure by heat setting, the orientation crystallization of the resin used for each layer further improves the heat resistance and reduces the change in adhesive force over time.

  By providing the pressure-sensitive adhesive layer on one surface of the base film obtained above, the coating film surface protective film of the present invention is obtained. When the pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive, the surface of the base film on which the pressure-sensitive adhesive layer is provided is improved in wettability by corona treatment, ultraviolet irradiation treatment, flame treatment, plasma treatment, sputter etching treatment, etc. May be.

  The pressure-sensitive adhesive layer is not particularly limited. For example, various thermoplastic elastomers may be used alone or in combination with other tackifiers to form a pressure-sensitive adhesive, which is applied to the surface of the base film. Can be easily formed. The content ratio of the thermoplastic elastomer is preferably in the range of 50 to 95% by mass. When the content ratio of the thermoplastic elastomer in the pressure-sensitive adhesive layer falls within the above range, the obtained surface protective film has sufficient adhesion to the adherend and good interlayer strength between the pressure-sensitive adhesive layer and the substrate film surface. Thus, it is possible to further suppress the occurrence of adhesive residue when peeling off after being attached to the adherend.

  Examples of the thermoplastic elastomer include styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, urethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers. Only one type of thermoplastic elastomer may be used, or two or more types may be used in combination.

  Examples of the styrenic thermoplastic elastomer include styrene-based AB diblock copolymers such as styrene-ethylene-butylene copolymer (SEB); styrene-butadiene-styrene copolymer (SBS), and hydrogenated product of SBS. (Styrene-ethylene-butylene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), hydrogenated product of SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), styrene -Styrenic ABA type triblock copolymer such as isobutylene-styrene copolymer (SIBS); Styrene type ABAB type tetrablock copolymer such as styrene-butadiene-styrene-butadiene (SBSB); Styrene-butadiene-styrene- Butadiene-styrene (SBSBS), etc. Styrene-based ABABA-type pentablock copolymer; Styrene-based multiblock copolymer having AB repeating units higher than these; Hydrogenation of ethylenic double bonds of styrene-based random copolymers such as styrene-butadiene rubber (SBR) And the like. A commercially available styrene thermoplastic elastomer may be used.

  The pressure-sensitive adhesive layer may be a pressure-sensitive adhesive other than such a thermoplastic elastomer. Examples of such adhesives include rubber adhesives, acrylic adhesives, and silicone adhesives.

  The pressure-sensitive adhesive layer may contain other components as necessary. Examples of other components include olefin resins; silicone resins; liquid acrylic copolymers; polyethyleneimines; fatty acid amides; phosphate esters; The type, number and amount of other components contained in the pressure-sensitive adhesive layer can be appropriately set according to the purpose. Examples of additives include tackifiers; softeners; anti-aging agents; hindered amine light stabilizers; ultraviolet absorbers; fillers or pigments such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide; Can be mentioned.

  The formulation of the tackifier is effective for improving the adhesive strength. The amount of the tackifier is appropriately determined to be any appropriate amount depending on the adherend in order to avoid the occurrence of the adhesive residue problem due to the decrease in cohesive force. Usually, it is 0-60 mass parts with respect to 100 mass parts of resin materials which form an adhesive, Preferably it is 0-50 mass parts.

  Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymer systems and alicyclic copolymers, and coumarone-indene resins. Terpene resins, terpene phenol resins, polymerized rosins and other rosin resins, (alkyl) phenol resins, xylene resins or hydrogenated products thereof. Only one type of tackifier may be used, or two or more types may be used in combination.

  In addition, the blending of various softeners is effective for improving the adhesive strength. Examples of the softening agent include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, and derivatives thereof. Examples of the derivative include those having an OH group or a COOH group at one or both ends. Specific examples include hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, and hydrogenated polyisoprene monool. In order to further suppress the improvement in adhesion to the adherend, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, olefinic softeners, and the like are preferable. These softeners may be used alone or in combination of two or more.

  When using a softening agent, the addition amount can employ | adopt arbitrary appropriate amounts. If the amount of the softener added is too large, the adhesive residue tends to increase when exposed to high temperatures or outdoors. Therefore, it is preferably 20 parts by mass or less with respect to 100 parts by mass of the resin material forming the pressure-sensitive adhesive layer. In particular, it is used at 10 parts by mass or less.

  The method of providing the pressure-sensitive adhesive layer is not particularly limited, and a method of hot-melt coating the pressure-sensitive adhesive, an organic solvent coating solution in which the pressure-sensitive adhesive is dissolved on the base film, or an emulsion liquid in which the pressure-sensitive adhesive is dispersed in water. Either the method of coating or the method of laminating the material for forming the pressure-sensitive adhesive layer at the time of production of the base film may be either coextrusion. Examples of the coating method include a method using a bar coater, a gravure coater, a spin coater, a roll coater, a knife coater, an applicator and the like. The pressure-sensitive adhesive layer is formed continuously, but may be formed in a regular or random pattern such as a dot or stripe depending on the purpose and application.

  The thickness of an adhesive layer is not specifically limited, It can determine suitably according to the objective. Usually, it is appropriate to set it as 100 micrometers or less (for example, 1 micrometer-100 micrometers), Preferably they are 1 micrometer-50 micrometers, More preferably, they are 3 micrometers-20 micrometers. For example, the above range can be preferably adopted as the thickness of the pressure-sensitive adhesive layer provided in the automobile paint film protective sheet.

  The present invention will be specifically described below with reference to examples and comparative examples. Unless otherwise specified, parts and% in the examples are based on mass.

Example 1
As outer layer and inner layer, 80 parts of propylene homopolymer (density: 0.90 g / cm ³ , MFR: 9 g / 10 min) and low density polyethylene (density: 0.90 g / cm ³ , MFR: 0.35 g / 10 min) 20 As a middle layer (B), 53 parts of linear low density polyethylene (density: 0.92 g / cm ³ , MFR: 4 g / 10 min) and a propylene-ethylene copolymer [density: 0.90 g / cm ³ , MFR: 7 g / 10 min] 23 parts, 20 parts of a masterbatch based on a propylene-ethylene copolymer containing 70% titanium oxide (TiO ₂ ), a hindered amine light stabilizer (HALS ) Masterbatch based on propylene-ethylene copolymer containing 60000 ppm of [chimasorb 2020FDL] The mixture consisting of 4 parts is fed to each of three extruders and coextruded so that the average thickness ratio of outer layer / intermediate layer (B) / inner layer is 15:70:15, A 60 μm three-layer coextruded multilayer film was formed. Next, the surface of the obtained film was subjected to corona discharge treatment so that the surface energy was 40 mN / m, to obtain a base film.

Example 2
The resin used for the outer layer and inner layer of Example 1 was the same as Example 1 except that 70 parts of propylene homopolymer / 30 parts of low-density polyethylene were used, and a co-extruded multilayer film consisting of three layers having a thickness of 60 μm was used. Obtained. Next, the surface of the obtained coextruded multilayer film was subjected to corona discharge treatment so that the surface energy was 40 mN / m as in Example 1.

Example 3
The resin used for the outer layer and the inner layer of Example 1 was the same as Example 1 except that 90 parts of propylene homopolymer / 10 parts of low density polyethylene were used, and a co-extruded multilayer film consisting of 3 layers having a thickness of 60 μm was used. Obtained. Next, the surface of the obtained coextruded multilayer film was subjected to corona discharge treatment so that the surface energy was 40 mN / m as in Example 1.

Example 4
In the intermediate layer (B) of Example 1, 61 parts of a linear low density polyethylene, 15 parts of a propylene-ethylene copolymer, and 20 master batches based on a propylene-ethylene copolymer containing 70% titanium oxide. A mixture of 4 parts of a masterbatch based on a propylene-ethylene copolymer containing 60000 ppm of hindered amine light stabilizer (chimasorb 2020FDL) and then the surface of the resulting coextruded multilayer film is carried out Corona discharge treatment was performed in the same manner as in Example 1 so that the surface energy was 40 mN / m.

Example 5
The intermediate layer (B) of Example 1 is composed of 41 parts of a linear low density polyethylene, 35 parts of a propylene-ethylene copolymer, and 20 master batches based on a propylene-ethylene copolymer containing 70% titanium oxide. A mixture of 4 parts of a masterbatch based on a propylene-ethylene copolymer containing 60000 ppm of hindered amine light stabilizer (chimasorb 2020FDL) and then the surface of the resulting coextruded multilayer film is carried out Corona discharge treatment was performed in the same manner as in Example 1 so that the surface energy was 40 mN / m.

Comparative Example 1
As an outer layer and an inner layer, 80 parts of propylene-ethylene copolymer [density: 0.90 g / cm ³ , MFR: 7 g / 10 min] and low density polyethylene (density: 0.90 g / cm ³ , MFR: 0.35 g / 10) A mixture consisting of 20 parts per minute, and as an intermediate layer, 53 parts of linear low density polyethylene (density: 0.92 g / cm ³ , MFR: 4 g / 10 min) and a propylene-ethylene copolymer [density: 0.90 g / cm ³ , MFR: 7 g / 10 min] 23 parts, 20 parts of a masterbatch based on a 70% titanium oxide propylene-ethylene copolymer, hindered amine light stabilizer (chimasorb 2020FDL) Using a mixture consisting of 4 parts of a masterbatch based on a propylene-ethylene copolymer containing 60000 ppm In the same manner as in Example 1, a coextruded multilayer film having a three-layer structure having a thickness of 60 μm was formed. Next, a corona discharge treatment was applied so that the surface energy of the obtained film was 40 mN / m, to obtain a laminated film.

Comparative Example 2
Comparative Example 1 was carried out in the same manner as Comparative Example 1 except that only the propylene homopolymer was used for the outer layer and inner layer, to obtain a coextruded multilayer film having a thickness of 60 μm and consisting of 3 layers. Next, the surface of the obtained film was subjected to corona discharge treatment so that the surface energy was 40 mN / m.

Comparative Example 3
The same procedure as in Comparative Example 1 was carried out except that the outer layer and inner layer of Comparative Example 1 were replaced with only 60 parts of propylene homopolymer / 40 parts of low density polyethylene to obtain a coextruded multilayer film consisting of 3 layers having a thickness of 60 μm. . Next, the surface of the obtained film was subjected to corona discharge treatment so that the surface energy was 40 mN / m.

Comparative Example 4
The intermediate layer (B) of Example 1 is composed of 76 parts of a linear low density polyethylene (density: 0.92 g / cm ³ , MFR: 4 g / 10 min) and a propylene-ethylene copolymer having a titanium oxide concentration of 70%. Except that the masterbatch based on propylene-ethylene copolymer containing 20 parts of a masterbatch based on styrene and 60,000 ppm of hindered amine light stabilizer (chimasorb 2020FDL) was replaced with a mixture consisting of 4 parts. In the same manner as in No. 1, a coextruded multilayer film consisting of three layers having a thickness of 60 μm was obtained. Next, the surface of the obtained film was subjected to corona discharge treatment so that the surface energy was 40 mN / m.

Comparative Example 5
An intermediate layer (B) of Example 1 was prepared by using a master batch based on 31 parts of linear low density polyethylene, 45 parts of a propylene-ethylene copolymer, and a propylene-ethylene copolymer containing 70% titanium oxide. The same procedure as in Example 1 was carried out except that the masterbatch based on propylene-ethylene copolymer containing 60 parts by weight of 20 parts hindered amine light stabilizer (chimasorb 2020FDL) was replaced with a mixture of 4 parts. A coextruded multilayer film consisting of 3 layers having a thickness of 60 μm was obtained. Next, the surface of the obtained film was subjected to corona discharge treatment so that the surface energy was 40 mN / m.

Comparative Example 6
The outer layer and inner layer of Example 1 were prepared by adding 78 parts of propylene-ethylene copolymer [density: 0.90 g / cm ³ , MFR: 7 g / 10 min] and low-density polyethylene (density: 0.90 g / cm 3, MI: 0.00). Example 1 except that the masterbatch based on propylene-ethylene copolymer containing 18 parts of 35 g / 10 minutes) and 60000 ppm of hindered amine light stabilizer (chimasorb 2020FDL) was replaced with a mixture of 4 parts. In the same manner, a coextruded multilayer film consisting of three layers having a thickness of 60 μm was obtained. Next, the surface of the obtained film was subjected to corona discharge treatment so that the surface energy was 40 mN / m.

Comparative Example 7
Master batch based on 100 parts of linear low density polyethylene (density: 0.938 g / cm ³ , MFR: 2.1 g / 10 min) and propylene-ethylene copolymer with 70% titanium oxide concentration as outer and inner layers 2 parts, a masterbatch based on a propylene-ethylene copolymer containing 60000 ppm of a hindered amine light stabilizer (HALS) [chimasorb 2020FDL], and an intermediate layer (B) as a propylene-ethylene copolymer [ Density: 0.90 g / cm ³ , MFR: 7 g / 10 min] 100 parts, 2 parts of a masterbatch based on a propylene-ethylene copolymer having a 70% concentration of titanium oxide (TiO ₂ ), a hindered amine light stabilizer (HALS) [chimasorb 2020FDL] 60000p A mixture of 8 parts of a masterbatch based on a propylene-ethylene copolymer containing m is supplied to each of three extruders, and the ratio of the average thickness of the outer layer / intermediate layer (B) / inner layer is It was coextruded so as to have a ratio of 1.5: 3: 1.5 to form a three-layer coextruded multilayer film having a thickness of 60 μm. Next, the surface of the obtained film was subjected to corona discharge treatment so that the surface energy was 40 mN / m, to obtain a base film.

  On one side of the base film obtained in Examples 1 to 5 and Comparative Examples 1 to 7, 100 parts of polyisobutylene as a base polymer and 0.4 part of a tackifier (p-tert-octylphenol resin) A pressure-sensitive adhesive solution was prepared by dissolving in an organic solvent. This pressure-sensitive adhesive solution was applied to one side of the base film obtained above and dried to form a pressure-sensitive adhesive layer having a thickness of 10 μm, thereby obtaining a coating film surface protective film.

<Measurement of rigidity>
Tensilon tensile test using 1% tangent modulus (unit: MPa) at 23 ° C. in the extrusion direction (hereinafter referred to as “MD”) at 23 ° C. using the obtained base film based on ASTM D-882. It was measured using a machine (manufactured by A & D Co., Ltd.).

<Measurement of tear strength>
Using the obtained base film, the sample was held for 6 hours in a temperature-controlled room adjusted to 23 ° C., and then measured using an Elmendorf tear tester (manufactured by Tester Sangyo Co., Ltd.).

<Measurement of friction coefficient value>
Using the obtained base film, the static friction coefficient value and the dynamic friction coefficient value between the side surfaces of the surface layer were measured at 23 ° C. based on ASTM D-1894.

<Measurement of surface roughness>
Using the obtained base film, surface roughness (Ra) was measured using SURFCOM 480A manufactured by Tokyo Seimitsu Co., Ltd. for one film based on JIS B-0601.

<Measurement of residual adhesive strength>
In order to confirm bleeding on the surface of HALS, a two-layer product tape (PET / acrylic adhesive, 31B tape: manufactured by Nitto Denko Corporation) is applied to the obtained base film and pressurized at 70 ° C. for 24 hours. (100 g / cm <2>) After promotion, it was affixed to the adherend of SUS # 360, and the adhesive force after 30 minutes was measured. Regarding pressure-sensitive adhesive strength before and after pressurization, those with a difference of 7% or more were evaluated as ×, those with a difference of 5% or more but less than 7% were evaluated as △, and those with a difference of less than 5% were evaluated as ○. .

<Evaluation after sticking to the coating surface>
The coating film surface protective film obtained above on the surface of a coating film obtained by coating a 45 cm × 30 cm steel plate with an alkydmelamine-based paint (product of Kansai Paint Co., Ltd., trade name “Amirac TM-13 (RC)”) (30 cm × 30 cm × 3 sheets) were pressure-bonded. This was kept at 40 ° C. for 48 hours, and then kept at room temperature of 25 ° C. for 2 hours, and then the film was peeled off from the adherend. The presence or absence of adhesive residue on the adherend surface at this time was visually confirmed. In addition, the presence or absence of tearing of the film during peeling was also confirmed.

  Each evaluation result about the base film and the surface protective film obtained in Examples 1 to 5 and Comparative Examples 1 to 7 is shown in Tables 1 and 2. In the base film obtained in Comparative Example 2, blocking occurred due to the small surface roughness, the adhesiveness between the films was high when the adhesive was applied, and it was difficult to apply uniformly. In addition, the surface of the obtained surface protective film on which the adhesive was not applied and the adhesive layer were closely adhered, making it difficult to handle.

Claims (9)

The outer layer and the inner layer are layers containing a resin mixture in which 70 to 90% by mass of the propylene homopolymer (a1) and 10 to 30% by mass of the low density polyethylene (a2) are mixed.
The intermediate layer (B) is 15 to 40% by mass of the propylene polymer (b1) and 40 to 70% by mass of the linear low density polyethylene (b2) with respect to the total mass of the intermediate layer (B). The base film used for the coating-film surface protection film characterized by being a layer contained in the range. The base film according to claim 1, wherein the resin mixture in the outer layer and the inner layer is contained by 95% by mass or more based on the total mass of the layer. The base film according to claim 1 or 2, wherein the low density polyethylene (a2) has a melt flow rate (MFR) of 0.29 to 0.41 g / 10 min. The base film according to claim 1, wherein the density of the low-density polyethylene (a2) is 0.918 to 0.922 g / cm ³ . The base film according to any one of claims 1 to 4, wherein the outer layer and the inner layer do not contain a light-resistant stabilizer, and the intermediate layer contains a light-resistant stabilizer. The surface roughness (Ra) according to JIS-B0601 of the surface of the outer layer and the inner layer is 0.5 to 1.3 (μm), The base film according to any one of claims 1 to 5. The base film according to claim 1, wherein the total thickness of the base film is in the range of 40 to 80 μm, and the thickness ratio with respect to the total thickness of the intermediate layer is in the range of 55 to 85%. A coating film surface protective film, wherein a pressure-sensitive adhesive layer is provided on one surface of the substrate film according to claim 1. The coating film surface protective film according to claim 8, which is for automobiles.