JP4556468B2 - Surface protection film - Google Patents

Description

  The present invention relates to a surface protective film having a base material layer and an adhesive layer.

Articles such as metal plates such as aluminum and stainless steel used for industrial and architectural purposes, synthetic resin plates such as acrylic and engineering plastic, wood decorative boards, liquid crystal displays, optical film products used for CDs and DVDs, etc. In order to prevent the article from being scratched by contact or friction with an object during processing, storage or transportation of the article, or to prevent the article surface from becoming dirty due to adhesion of dust, etc., a surface protective film is applied to the article. Is being pasted. The surface protective film has an adhesive layer that adheres and adheres to an article and a base material layer that is a non-adhesive layer, and a polyethylene resin is often used for the base material layer. For example, a base material layer linear low density polyethylene and density were blended with high pressure radical polymerization process low-density polyethylene of 0.928 g / cm ³ of density 0.935 g / cm ^3, an adhesive layer comprising the pressure-sensitive adhesive A film having a base layer made of a high-pressure radical polymerization method low-density polyethylene having a density of 0.920 g / cm ³ and an adhesive layer made of a linear low-density polyethylene. (For example, refer to Patent Document 2).

JP-A-5-98219 JP-A-5-229082

However, in the above surface protective film, the slipping property of the film cannot be said to be sufficient, and surface protection is performed during the pasting of the surface protective film to the article or the secondary processing of the article bonded with the surface protective film. The handling property of the article bonded with the film or the surface protection film was not sufficiently satisfactory.
Under such circumstances, the problem to be solved by the present invention is to provide a surface protective film excellent in slipperiness.

  According to the present invention, a surface protective film excellent in slipperiness can be provided.

That is, the present invention is a surface protective film in which one surface is a base material layer and the other surface is an adhesive layer, and the base material layer is applied to a surface protective film containing the following component (A). is there.
(A): an ethylene-α-olefin having a monomer unit based on ethylene and a monomer unit based on an α-olefin having 3 to 20 carbon atoms and having a flow activation energy of 35 kJ / mol or more Copolymer (I)

  Component (A) is an ethylene-α-olefin copolymer (I) obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4 -Methyl-1-pentene, 4-methyl-1-hexene and the like can be mentioned, and 1-butene, 1-hexene and 1-octene are preferable. Moreover, said C3-C20 alpha olefin may be used independently and may use 2 or more types together.

  Examples of the component (A) ethylene-α-olefin copolymer (I) include ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, and ethylene-1- An octene copolymer etc. are mentioned, Preferably they are an ethylene-1-butene copolymer and an ethylene-1-hexene copolymer. An ethylene-1-butene-1-hexene copolymer and an ethylene-1-butene-1-octene copolymer are also preferably used.

  The melt flow rate (MFR) of the ethylene-α-olefin copolymer (I) as the component (A) is usually 0.01 to 100 g / 10 minutes. The MFR is preferably 0.05 g / 10 min or more, more preferably 0.1 g / 10 min or more, and further preferably 0.5 g / 10 min or more from the viewpoint of improving the extrusion moldability. Moreover, from a viewpoint of improving impact strength, it is preferably 20 g / 10 min or less, more preferably 10 g / 10 min or less, and further preferably 6 g / 10 min or less.

The density of the ethylene-α-olefin copolymer (I) as the component (A) is usually 890 to 970 kg / m ³ . The density is preferably 910 kg / m ³ or more, more preferably 920 kg / m ³ or more from the viewpoint of increasing slipperiness, and preferably 940 kg / m ³ or less from the viewpoint of increasing impact strength. More preferably, it is 935 kg / m ³ or less. The density is a value measured according to a method defined in JIS K7112 using a sample subjected to annealing described in JIS K6760.

  The ethylene-α-olefin copolymer (I) of component (A) is an ethylene-α-olefin copolymer having a long chain branch and excellent in melt tension, and such an ethylene-α-olefin copolymer. The polymer has a higher flow activation energy (Ea) as compared with a conventionally known ordinary ethylene-α-olefin copolymer. Conventionally known Ea of a normal ethylene-α-olefin copolymer is usually lower than 35 kJ / mol and may be inferior in slipperiness.

  Ea of the ethylene-α-olefin copolymer (I) of the component (A) is preferably 40 kJ / mol or more, more preferably 50 kJ / mol or more, further preferably, from the viewpoint of further improving the slipperiness. 60 kJ / mol or more. From the viewpoint of enhancing the appearance of the film, Ea is preferably 100 kJ / mol or less, and more preferably 90 kJ / mol or less.

The flow activation energy (Ea) is a master curve indicating the dependence of the melt complex viscosity (unit: Pa · sec) at 190 ° C. on the angular frequency (unit: rad / sec) based on the temperature-time superposition principle. Is a numerical value calculated by the Arrhenius equation from the shift factor (a _T ) at the time of creating the value, and is a value obtained by the following method. That is, the melt complex viscosity-angular frequency curve of the ethylene-α-olefin copolymer at temperatures of 130 ° C., 150 ° C., 170 ° C. and 190 ° C. (T, unit: ° C.) (the unit of melt complex viscosity is Pa · sec. The unit of the angular frequency is rad / sec.), Based on the temperature-time superposition principle, for each melt complex viscosity-angular frequency curve at each temperature (T), The shift factor (a _T ) at each temperature (T) obtained when superposed on the melt complex viscosity-angular frequency curve of the coalescence is obtained, and each temperature (T) and the shift factor at each temperature ( _T ) are obtained. From (a _T ), a first-order approximate expression (formula (I) below) of [ln (a _T )] and [1 / (T + 273.16)] is calculated by the method of least squares. Next, Ea is obtained from the slope m of the linear expression and the following expression (II).
ln (a _T ) = m (1 / (T + 273.16)) + n (I)
Ea = | 0.008314 × m | (II)
a _T : Shift factor Ea: Activation energy of flow (unit: kJ / mol)
T: Temperature (unit: ° C)
For the calculation, commercially available calculation software may be used. As the calculation software, Rheos V. manufactured by Rheometrics is used. 4.4.4.
The shift factor (a _T ) is obtained by moving the logarithmic curve of the melt complex viscosity-angular frequency at each temperature (T) in the log (Y) = − log (X) axis direction (however, the Y axis Is the complex viscosity of the melt, and the X axis is the angular frequency.), And the amount of movement when superposed on the melt complex viscosity-angular frequency curve at 190 ° C., in the superposition, melting at each temperature (T) The logarithmic curve of complex viscosity-angular frequency shifts the angular frequency by a _T times and the melt complex viscosity by 1 / a _T times for each curve. Moreover, the correlation coefficient when calculating | requiring (I) Formula by the least squares method from the value of four points | pieces, 130 degreeC, 150 degreeC, 170 degreeC, and 190 degreeC is usually 0.99 or more.

  The melt complex viscosity-angular frequency curve is measured using a viscoelasticity measuring apparatus (for example, Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), and usually geometry: parallel plate, plate diameter: 25 mm, plate interval: 1. It is performed under the conditions of 5 to 2 mm, strain: 5%, angular frequency: 0.1 to 100 rad / sec. The measurement is performed in a nitrogen atmosphere, and it is preferable that an appropriate amount (for example, 1000 ppm) of an antioxidant is added to the measurement sample in advance.

The ethylene-α-olefin copolymer (I) of component (A) has a melt complex viscosity of η * (unit: Pa · sec) at a temperature of 190 ° C. and an angular frequency of 100 rad / sec from the viewpoint of further improving the extrusion moldability. And the melt flow rate measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N specified in JIS K7210 is MFR (unit: g / 10 min), and preferably satisfies the following formula (1): ,
η * <1550 × MFR ^-0.25 -420 (1)
More preferably, the following formula (1-2) is satisfied,
η * <1500 × MFR ^-0.25 -420 (1-2)
More preferably, the following formula (1-3) is satisfied,
η * <1450 × MFR ^-0.25 -420 (1-3)
It is particularly preferable that the following formula (1-4) is satisfied.
η * <1350 × MFR ^-0.25 -420 (1-4)
Note that η * is measured under the same conditions as in the viscoelasticity measurement for obtaining Ea.

  The molecular weight distribution (Mw / Mn) of the ethylene-α-olefin copolymer (I) of the component (A) is preferably 5 to 30 from the viewpoint of enhancing extrusion moldability, slipperiness, film appearance and transparency. More preferably, it is 7-20, More preferably, it is 8-20. The molecular weight distribution (Mw / Mn) was determined by gel permeation chromatography and calculating polystyrene-reduced weight average molecular weight (Mw) and number average molecular weight (Mn), and Mw divided by Mn (Mw / Mn).

The component (A) ethylene-α-olefin copolymer (I) is measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N, as defined in JIS K7210, from the viewpoint of improving take-up characteristics during molding. It is preferable that the melt flow rate is MFR (unit: g / 10 minutes), the melt tension at 190 ° C. is MT (unit: cN), and the following formula (2) is satisfied.
2 x MFR ^-0.59 <MT <40 x MFR ^-0.59 (2)
The component (A) ethylene-α-olefin copolymer (I) more preferably satisfies the following formula (2-2) from the viewpoint of further improving the take-up property at the time of molding,
2.2 x MFR ^-0.59 <MT (2-2)
It is more preferable to satisfy the following formula (2-3).
2.5 × MFR ^-0.59 <MT (2-3)
More preferably, the ethylene-α-olefin copolymer (I) of the component (A) satisfies the following formula (2-4) from the viewpoint of further improving the high-speed take-up property at the time of molding,
MT <25 × MFR ^-0.59 (2-4)
It is more preferable to satisfy the following formula (2-5).
MT <15 × MFR ^-0.59 (2-5)
In addition, the conventional normal ethylene-alpha-olefin copolymer does not normally satisfy the left side of Formula (2).

The component (A) ethylene-α-olefin copolymer (I) is measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N, as defined in JIS K7210, from the viewpoint of improving slipperiness and extrusion moldability. It is preferable that the melt flow rate is MFR (unit: g / 10 min) and the intrinsic viscosity is [η] (unit: dl / g) to satisfy the following formula (3).
1.02 × MFR ^−0.094 <[η] <1.50 × MFR ^−0.156 (3)
The component (A) ethylene-α-olefin copolymer (I) preferably satisfies the following formula (3-2) from the viewpoint of further improving the slipperiness.
1.05 × MFR ^−0.094 <[η] (3-2)
It is more preferable to satisfy the following formula (3-3).
1.08 × MFR ^−0.094 <[η] (3-3)
The component (A) ethylene-α-olefin copolymer (I) preferably satisfies the following formula (3-4) from the viewpoint of further enhancing the extrusion moldability,
[Η] <1.47 × MFR ^−0.156 (3-4)
It is more preferable to satisfy the following formula (3-5).
[Η] <1.42 × MFR ^−0.156 (3-5)
In addition, the conventional ethylene-α-olefin copolymer having the same melt flow rate measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N as defined in JIS K7210 and ethylene-α- of component (A) When comparing with the olefin copolymer (I), the intrinsic viscosity of the conventional ethylene-α-olefin copolymer is more than the intrinsic viscosity of the ethylene-α-olefin copolymer (I) of the component (A). Usually high.

  As a method for producing the ethylene-α-olefin copolymer (I) of component (A), the following promoter support (A), crosslinked bisindenylzirconium complex (B) and organoaluminum compound (C) are contacted. And a method of copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of the obtained catalyst.

The promoter support (A) comprises (a) diethylzinc, (b) fluorinated phenol, (c) water, (d) silica and (e) trimethyldisilazane (((CH ₃ ) ₃ Si) ₂ NH). It is a carrier obtained by contact.

The amount of each component (a), (b), (c) used is not particularly limited, but the molar ratio of the amount of each component used is the component (a): component (b): component (c) = 1: When y: z, y and z preferably satisfy the following formula.
| 2-y-2z | ≦ 1
Y in the above formula is preferably a number of 0.01 to 1.99, more preferably a number of 0.10 to 1.80, and still more preferably a number of 0.20 to 1.50. Most preferably, the number is 0.30 to 1.00.

  The amount of component (d) used relative to component (a) is such that the number of moles of zinc atoms contained in the particles obtained by contacting component (a) and component (d) is 1 g of the particles. The amount is preferably 0.1 mmol or more, and more preferably 0.5 to 20 mmol. The amount of the component (e) to be used with respect to the component (d) is preferably an amount that makes the component (e) 0.1 mmol or more per 1 g of the component (d), and an amount that becomes 0.5 to 20 mmol. More preferably.

  The cross-linked bisindenyl zirconium complex (B) is preferably racemic-ethylenebis (1-indenyl) zirconium dichloride or racemic-ethylenebis (1-indenyl) zirconium diphenoxide.

  The organoaluminum compound (C) is preferably triisobutylaluminum or trinormaloctylaluminum.

The amount of the bridged bisindenyl zirconium complex (B) used is preferably 5 × 10 ^{−6 to} 5 × 10 ⁻⁴ mol per 1 g of the promoter support (A). The amount of the organoaluminum compound (C) used is preferably such that the aluminum atom of the organoaluminum compound (C) is 1 to 2000 moles per mole of zirconium atoms in the cross-linked bisindenyl zirconium complex (B). is there.

The polymerization method of the ethylene-α-olefin copolymer (I) of component (A) is preferably a polymerization method involving the formation of ethylene-α-olefin copolymer particles, for example, gas phase polymerization, slurry Polymerization and bulk polymerization are preferred, and gas phase polymerization is preferred.
The gas phase polymerization reaction apparatus is usually an apparatus having a fluidized bed type reaction tank, and preferably an apparatus having a fluidized bed type reaction tank having an enlarged portion. A stirring blade may be installed in the reaction vessel.

As a method of supplying each component of the olefin polymerization catalyst used for the production of the component (A) ethylene-α-olefin copolymer (I) to the reaction vessel, usually an inert gas such as nitrogen or argon, hydrogen , A method of supplying ethylene or the like in a moisture-free state, and a method of dissolving or diluting each component in a solvent and supplying in a solution or slurry state. Each component of the catalyst may be supplied individually, or arbitrary components may be supplied in contact in advance in an arbitrary order.
Moreover, it is preferable to carry out prepolymerization before carrying out the main polymerization and to use the prepolymerized prepolymerized catalyst component as a catalyst component or catalyst for the main polymerization.

The polymerization temperature is usually below the temperature at which the copolymer melts, preferably 0 to 150 ° C, more preferably 30 to 100 ° C.
Further, hydrogen may be added as a molecular weight regulator for the purpose of regulating the melt fluidity of the copolymer. An inert gas may coexist in the mixed gas.

  The surface protective film of the present invention is a film having a base material layer containing the component (A) on one surface and an adhesive layer containing an adhesive on the other surface.

As the pressure-sensitive adhesive in which the pressure-sensitive adhesive layer is also used, a known pressure-sensitive adhesive can be used, and examples thereof include the following components (B1), (B2) and (B3), and at least one of them is used.
(B1): Ethylene polymer other than component (A) (B2): Acrylic adhesive (B3): Rubber adhesive

  As the ethylene polymer of component (B1), a polymer obtained by a radical polymerization method using peroxide or oxygen as a catalyst, or a coordination polymerization method using a known Ziegler-Natta catalyst or metallocene catalyst as a catalyst is used. For example, ethylene homopolymer, ethylene-α-olefin copolymer (excluding the copolymer of component (A)), ethylene-vinyl ester copolymer, ethylene-unsaturated carboxylic acid copolymer, ethylene -Unsaturated carboxylic acid ester copolymer etc. are mentioned, Specifically, high-pressure radical polymerization method low density polyethylene, high density polyethylene, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-4 -Methyl-1-pentene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-1-decene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer Examples thereof include a polymer, an ethylene-methacrylic acid copolymer, and an ethylene-methyl methacrylate copolymer. These ethylene polymers may be used alone or in combination of two or more.

As the component (B1), an ethylene-α-olefin copolymer having a flow activation energy (Ea) of less than 35 kJ / mol is suitably used. The density of the ethylene-α-olefin copolymer is preferably 870 to 920 kg / m ³ .

  Examples of the component (B2) include acrylic acid ester monomers such as acrylic acid esters and methacrylic acid esters (such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate), and the like. And a copolymer with a vinyl compound copolymerizable with the monomer (for example, acrylic acid, methacrylic acid, vinyl acetate, styrene, acrylonitrile, etc.). Examples of the component (B3) include polyisobutylene, hydrogenated compounds of styrene-butadiene-styrene rubber (SBS) and styrene-isoprene-styrene rubber (SIS).

  The surface protective film of the present invention may be a film having a base material layer containing the component (A) on one surface and an adhesive layer containing an adhesive on the other surface. Another layer may be provided between the layer and the adhesive layer as necessary.

  In the surface protective film of the present invention, an antioxidant, an antistatic agent, other resins, and the like may be blended into the base material layer, the adhesive layer, and other layers provided as necessary. These may be used alone or in combination of two or more.

  As said antioxidant, a phenolic antioxidant, phosphorus antioxidant, etc. are mentioned. Each may be used alone or in combination of two.

  Examples of the phenolic antioxidant include 2,6-di-t-butyl-4-methylphenol (BHT) and n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl). ) Propionate (trade name Irganox 1076, manufactured by Ciba Specialty Chemicals), pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name Irganox 1010, manufactured by Ciba Specialty Chemicals) ), 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate (trade name Irganox 3114, manufactured by Ciba Specialty Chemicals), 1,3,5-trimethyl-2,4 , 6-Tris (3,5-di-tert-butyl-4-hydroxyben L) benzene, 3,9-bis [2- {3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10 -Tetraoxaspiro [5,5] undecane (trade name Sumilizer GA80, manufactured by Sumitomo Chemical Co., Ltd.) and the like.

  Examples of the phosphorus-based antioxidant include distearyl pentaerythritol diphosphite (trade name ADK STAB PEP8), tris (2,4-di-t-butylphenyl) phosphite (trade name Irgafos 168, manufactured by Ciba Specialty Chemicals) ), Bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) 4,4′-biphenylenediphosphonite (trade name Sandostab P- EPQ (manufactured by Clariant Shapin), bis (2-t-butyl-4-methylphenyl) pentaerythritol diphosphite, 2,4,8,10-tetra-t-butyl-6- [3- (3-methyl -4-hydroxy-5-t-butylphenyl) propoxy] dibenzo [d , F] [1, 3, 2] dioxaphosphine (trade name: Sumilizer GP, manufactured by Sumitomo Chemical Co., Ltd.), and the like.

  Examples of the antistatic agent include glycerin esters and sorbitan acid esters of fatty acids having 8 to 22 carbon atoms, alkyl dialkanolamides of fatty acids having 8 to 22 carbon atoms, polyethylene glycol esters, and alkyldiethanolamines. .

  Examples of other resins include polyolefin resins and the like, for example, high-pressure radical polymerization low-density polyethylene added to improve moldability, and high-density polyethylene added to improve rigidity and heat resistance. And polypropylene resins and olefin-based elastomers added to improve adhesiveness.

  The thickness of the surface protective film of this invention is 20-200 micrometers normally, Preferably it is 25-150 micrometers, More preferably, it is 30-120 micrometers.

  In the surface protective film of the present invention, the ratio of the thickness of the base material layer to the total film thickness (100%) is preferably 20% or more from the viewpoint of enhancing coextrusion moldability and film handling properties.

  As a method for producing the surface protective film of the present invention, for example, the ethylene / α-olefin copolymer (I) of the component (A) is formed into a base film by an inflation film molding method or a T-die cast film molding method. Thereafter, a method of producing by applying an adhesive to the base film (for example, a method in which the adhesive is dissolved in a solvent and then drying, a method in which the adhesive is applied in a molten state, etc.); Examples thereof include a method of producing the ethylene-α-olefin copolymer (I) and the pressure-sensitive adhesive by coextrusion molding such as a coextrusion inflation film molding method and a coextrusion T die cast film molding method. Preferably, it is a coextrusion T die-cast film forming method.

  According to the present invention, it is possible to provide a surface protective film excellent in slipperiness of the substrate surface of the film, particularly in the bonding of the surface protective film to the article and the secondary processing of the article bonded with the surface protective film, Handleability is improved. In addition, compared to conventional surface films, the amount of slipperiness improver such as a lubricant can be reduced or eliminated, so that the transfer of the slipperiness improver to the article on which the surface protective film is bonded is further reduced. Can do. Furthermore, since the protective film of the present invention is excellent in extrudability, when extruding the film through a fine mesh filter for the purpose of further reducing fish eyes and foreign matters of the obtained film, The load is reduced.

Hereinafter, the present invention will be described with reference to examples and comparative examples.
The physical properties in Examples and Comparative Examples were measured according to the following methods.
[Physical properties of polymer]
(1) Melt flow rate (MFR, unit: g / 10 minutes)
According to the method defined in JIS K7210, the measurement was performed under the conditions of a load of 21.18 N and a temperature of 190 ° C.

(2) Density (Unit: Kg / m ³ )
It measured according to the method prescribed | regulated to A method among JISK7112. The sample was annealed according to JIS K6760.

(3) Molecular weight distribution (Mw / Mn)
Using a gel permeation chromatograph (GPC) method, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured under the following conditions (1) to (7), and the molecular weight distribution (Mw / Mn) was determined.
(1) Equipment: Waters 150C manufactured by Water
(2) Separation column: TOSOH TSKgelGMH-HT
(3) Measurement temperature: 145 ° C
(4) Carrier: Orthodichlorobenzene
(5) Flow rate: 1.0 mL / min
(6) Injection volume: 500 μL
(7) Detector: Differential refraction

(4) Flow activation energy (Ea, unit: kJ / mol)
Using a viscoelasticity measuring device (Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics), a melt complex viscosity-angular frequency curve at 130 ° C., 150 ° C., 170 ° C. and 190 ° C. was measured under the following measurement conditions. From the obtained melt complex viscosity-angular frequency curve, calculation software Rhios V. The activation energy (Ea) was determined using 4.4.4.
<Measurement conditions>
Geometry: Parallel plate Plate diameter: 25mm
Plate spacing: 1.5-2mm
Strain: 5%
Angular frequency: 0.1 to 100 rad / sec Measurement atmosphere: Under nitrogen

(5) Melt viscosity (η *, unit: Pa · s)
From the melt viscoelasticity at 190 ° C. measured in the above (4), the melt viscosity at 190 ° C. at an angular frequency of 100 rad / sec was determined.

(6) Melt tension (MT, unit: cN)
Using a melt tension tester manufactured by Toyo Seiki Seisakusho, a molten resin filled in a 9.5 mmφ barrel at a temperature of 190 ° C., a piston descending speed of 5.5 mm / min, a diameter of 2.09 mmφ, and a length of 8 mm The melted resin extruded from the orifice was wound up at a winding speed of 40 rpm / min using a winding roll having a diameter of 150 mmφ, and the tension value immediately before the molten resin broke was measured. It shows that melt tension is so large that this value is large.

(7) Intrinsic viscosity ([η], unit: dl / g)
A tetralin solution (hereinafter referred to as a blank solution) in which 5% by weight of 2,6-di-t-butyl-p-cresol (BHT) is dissolved, and the concentration of the ethylene polymer resin with respect to the blank solution is 1 mg. A 135 ° C. tetralin solution (hereinafter referred to as a sample solution) is prepared, and the falling time of the blank solution and the sample solution at 135 ° C. is measured by an Ubbelohde viscometer. From the following formula, the relative viscosity (ηrel) at 135 ° C. was calculated and calculated from the following formula.
[Η] = 23.3 × log (ηrel)

[Extrudability of surface protective film]
(8) Motor load (Unit: Amps)
In film forming, the motor load of the extruder of the base material layer was measured. The smaller this value, the better the extrusion moldability.

(9) Resin pressure (unit: MPa)
In film forming, the resin pressure of the extruder for the base material layer was measured. The smaller this value, the better the extrusion moldability.

[Physical properties of surface protective film]
(10) Sliding property of substrate layer surface (static friction coefficient μs, dynamic friction coefficient μk)
Using an AB-401 type friction coefficient measuring device manufactured by Tester Sangyo Co., Ltd., measurement was performed in accordance with JIS K7125-1987, except that the 70 mm sliding plate was moved under the condition of a thread weighing 500 g and a sliding speed of 700 mm / min. The smaller this value, the better the slipperiness.

Example 1
(1-1) Preparation of cocatalyst carrier A solid product (hereinafter referred to as an assistant) was prepared in the same manner as the synthesis of component (A) described in Example 10 (1) and (2) of JP-A No. 2003-171415. Catalyst carrier (A) ”was obtained.

(1-2) Prepolymerization Into an autoclave with a stirrer having an internal volume of 210 liters, which was previously purged with nitrogen, 0.7 kg of the above promoter support (A), 100 liters of butane, 0.02 kg of 1-butene, hydrogen at normal temperature and pressure After charging 12 liters, the autoclave was heated to 42 ° C. Further, ethylene was charged at a gas phase partial pressure in the autoclave of 0.1 MPa, and after the system was stabilized, 225 mmol of triisobutylaluminum and 75 mmol of racemic-ethylenebis (1-indenyl) zirconium diphenoxide were added to initiate polymerization. While raising the temperature to 50 ° C. and continuously supplying ethylene and hydrogen, preliminary polymerization was carried out at 50 ° C. for a total of 6 hours. After the polymerization was completed, ethylene, butane, hydrogen gas and the like were purged, and the remaining solid was vacuum-dried at room temperature, and 13 g of ethylene-1-butene copolymer was prepolymerized per 1 g of the promoter support (A). A prepolymerized catalyst component was obtained.

(1-3) Continuous gas phase polymerization Using the above prepolymerization catalyst component, ethylene and 1-butene were copolymerized in a continuous fluidized bed gas phase polymerization apparatus. The polymerization conditions were a temperature of 85 ° C., a total pressure of 2 MPa, a hydrogen molar ratio to ethylene of 1.8%, and a 1-butene molar ratio to ethylene of 3%. During the polymerization, ethylene, 1- Butene and hydrogen were continuously supplied. Further, the pre-polymerization catalyst component and triisobutylaluminum were continuously supplied at a constant rate so that the total powder weight of the fluidized bed was maintained at 80 kg and the average polymerization time was 5 hours. By polymerization, a powder of an ethylene-1-butene copolymer (hereinafter referred to as PE-a1) was obtained with a production efficiency of 16 kg / hr.

(1-4) Granulation of ethylene-1-butene copolymer powder Using the LCM50 extruder manufactured by Kobe Steel, the PE-a1 powder obtained above was fed at a feed rate of 50 kg / hr and a screw rotation speed of 450 rpm. Then, pellets of PE-a1 were obtained by granulation under conditions of a gate opening of 50%, a suction pressure of 0.1 MPa, and a resin temperature of 200 to 215 ° C. Table 1 shows the physical properties of the obtained PE-a1 pellets.

(1-5) Film processing Using a feed block type three-layer coextrusion T-die processing machine (die width 600 mm, lip opening 1.0 mm) composed of three extruders with a screw diameter of 50 mmφ, PE-a1 pellets are supplied to the substrate layer (inner layer) extruder, and commercially available ethylene-1-hexene copolymer (manufactured by Nippon Evolu Co., Ltd., Sumitomo Chemical) is used as the adhesive layer (outer layer) extruder. Industrial Co., Ltd. Sales Sumikasen E FV403; hereinafter referred to as PE-b1, physical properties of PE-b1 are shown in Table 1.), cooling roll temperature is 40 ° C., processing temperature (extruder and die setting temperature) ) At 200 ° C., the extrusion rate of the substrate layer extruder is 20 kg / hr, the extrusion rate of the intermediate layer extruder and the adhesion layer extruder is 10 kg / hr, and the take-up speed is 30 m / min. Extrusion T die cast fill Perform molding to obtain a film having a thickness of 50 [mu] m. As processing data, the resin pressure and motor load of the extruder for base material layer were measured. The processing data and the physical property evaluation results of the obtained film are shown in Table 2.

Example 2
In continuous gas phase polymerization, 1-hexene was used instead of 1-butene, and polymerization was performed at 75 ° C. according to (1-1) to (1-4) of Example 1, and ethylene-1- A pellet of a hexene copolymer (hereinafter referred to as PE-a2) was obtained. Table 1 shows the physical properties of the obtained PE-a2 pellets.
Next, film forming was performed according to (1-5) of Example 1 except that PE-a2 pellets were used instead of PE-a1 pellets. The processing data and the physical property evaluation results of the obtained film are shown in Table 2.

Example 3
The continuous gas phase polymerization is carried out according to (1-1) to (1-4) of Example 1 except that the gas composition is changed, and an ethylene-1-butene copolymer (hereinafter referred to as PE-a3). Pellets were obtained. Table 1 shows the physical properties of the obtained PE-a3 pellets.
Next, film forming was performed according to (1-5) of Example 1 except that PE-a3 pellets were used instead of PE-a1 pellets. The processing data and the physical property evaluation results of the obtained film are shown in Table 2.

Comparative Example 1
A film was formed in accordance with (1-5) of Example 1 except that PE-b1 was used instead of PE-a1 pellets. The processing data and the physical property evaluation results of the obtained film are shown in Table 2.

Comparative Example 2
Instead of pellets of PE-a1, commercially available high-pressure radical polymerization low density polyethylene (Sumitomo Chemical L705, manufactured by Sumitomo Chemical Co., Ltd .; hereinafter referred to as PE-c1. Physical properties of PE-c1 are shown in Table 1). Except that was used, film forming was performed according to (1-5) of Example 1. The processing data and the physical property evaluation results of the obtained film are shown in Table 2.

Claims (3)

A surface protective film having one surface as a base material layer and the other surface as an adhesive layer, wherein the base material layer contains the following component (A).
(A): having a monomer unit based on ethylene and a monomer unit based on an α-olefin having 3 to 20 carbon atoms, and having a flow activation energy of 60 kJ / mol or more ,
Ethylene-α-olefin copolymer (I) having a molecular weight distribution (Mw / Mn) of 7 to 30 The surface protective film according to claim 1, wherein the pressure-sensitive adhesive layer is a layer containing at least one pressure-sensitive adhesive selected from the following components (B1), (B2) and (B3).
(B1): Ethylene polymer other than component (A) (B2): Acrylic adhesive (B3): Rubber adhesive Component (B1) is ethylene -α- olefin copolymer is (II), in claim 1 or 2 activation energy of flow of the ethylene -α- olefin copolymer (Ea) is less than 35 kJ / mol The surface protective film as described.