JP5872048B2 - Surface protective film and propylene copolymer composition for surface protective film - Google Patents

Description

  The present invention relates to a surface protective film and a propylene copolymer composition for a surface protective film. Specifically, the present invention relates to a propylene copolymer composition suitable for producing a surface layer of a surface protective film, and a surface protective film comprising the composition.

  The surface protective film is usually a laminated film having a surface layer on one surface and an adhesive layer on the other surface, and the adhesive layer is attached to an adherend for use. The surface protective film has uses such as a building material use and an optical member use. For example, a surface protective film may be pasted and stored on various optical films (for example, a diffusion film, a polarizing film, a retardation film, etc.) incorporated in a liquid crystal display or a plasma display. Moreover, if it is a transparent surface protection film, it may affix on the display surface of a display.

  In general, a laminated film is produced by coextrusion or by applying an adhesive layer to a base film. According to coextrusion molding, a laminated film can be generally produced at low cost. The laminated film produced by coextrusion is usually wound and stored in a roll shape, and the film is fed out from the roll from which the film is wound when the film is used.

  However, when a surface protective film having an adhesive layer and a surface layer is wound up in a roll shape, the surface layer and the adhesive layer of the film are fixed, and so-called blocking may occur. When blocking occurs, it becomes impossible to feed the film from the roll, or the performance of the fed film deteriorates. For this reason, the surface protective film is usually wound up in a roll shape with the release film superimposed on the adhesive layer. However, the roll of the surface protective film having a release film has a problem that the peeled release film becomes a large amount of waste when the surface protective film is applied to the adherend.

  On the other hand, a surface protective film that does not cause blocking even when it is wound up in a roll shape without overlapping a release film on the adhesive layer has been proposed by imparting peelability to the surface layer of the surface protective film. (See Patent Document 1).

  In addition, when a surface protective film is used for an adherend such as an optical member, when the surface protective film is peeled off, if there is adhesive residue or fish eyes are present on the surface protective film, the optical member may be defective. Therefore, a surface protective film with less adhesive residue and fish eyes is desired.

  Patent Document 2 discloses a surface protective film mainly composed of a polyethylene component. However, although the method according to the publication can be applied to some use members, the adhesive strength is low and the transparency is insufficient, and the use of the adherend is limited.

  Patent Document 3 proposes a surface protective film made of a specific propylene random block copolymer obtained by a metallocene catalyst system, but further improvement is desired.

JP 2008-81709 A JP 2006-116769 A JP 2009-83110 A

  An object of the present invention is to provide a surface protective film having a small amount of fish eyes, excellent in drawability (feeding out property, blocking resistance) of a take-up film, and sufficient transparency.

The present invention relates to the following [1] to [7].
[1] An ethylene-based elastomer satisfying the following requirements (1 ′) to (3 ′): 75% by weight to 97% by weight of the propylene / ethylene block copolymer (A) satisfying the following requirements (1) to (3) It has a film made of a propylene copolymer composition (however, the total of (A) and (B) is 100% by weight) containing 3% by weight to 25% by weight of (B) as a surface layer, Surface protective film;
(1) The intrinsic viscosity [η] _insol in 135 ° C. decalin of a part insoluble in room temperature n-decane (D _insol ) is 1.5 dl / g or more and 2.5 dl / g or less.
(2) The intrinsic viscosity [η] _sol in 135 ° C. decalin of the portion soluble in room temperature n-decane (D _sol ) is 2.5 dl / g or more and 4.5 dl / g or less.
(3) The content of the skeleton derived from ethylene in the portion soluble in room temperature n-decane (D _sol ) is 35% by weight or more and 50% by weight or less.
(1 ′) A melt flow rate (MFR _B ) under a load of 190 ° C. and a load of 2.16 kg is 0.1 g / 10 min or more and 2 g / 10 min or less.
(2 ′) Density is 860 kg / m ³ or more and 890 kg / m ³ or less.
(3 ′) The melt flow rate (MFR _B ) satisfies the following relational expression (1) with respect to [η] _{sol of the} propylene / ethylene block copolymer (A).

[η] _sol ≦ (1.4 / MFR _B ) +2.8 (1)
[2] In the propylene / ethylene block copolymer (A), the content of the skeleton derived from ethylene in the portion insoluble in room temperature n-decane (D _insol ) is 0% by weight or more and 8% by weight or less. The surface protective film as described in [1] above.
[3] The surface protective film as described in [1] or [2] above, which has a surface layer on one surface and an adhesive layer on the other surface.
[4] An ethylene-based elastomer satisfying the following requirements (1 ′) to (3 ′): 75% by weight to 97% by weight of the propylene / ethylene block copolymer (A) satisfying the following requirements (1) to (3) A propylene copolymer composition for a surface protective film, comprising (B) in an amount of 3% by weight to 25% by weight (provided that the total of (A) and (B) is 100% by weight).
(1) The intrinsic viscosity [η] _insol in 135 ° C. decalin of a part insoluble in room temperature n-decane (D _insol ) is 1.5 dl / g or more and 2.5 dl / g or less.
(2) The intrinsic viscosity [η] _sol in 135 ° C. decalin of the portion soluble in room temperature n-decane (D _sol ) is 2.5 dl / g or more and 4.5 dl / g or less.
(3) The content of the skeleton derived from ethylene in the portion soluble in room temperature n-decane (D _sol ) is 35% by weight or more and 50% by weight or less.
(1 ′) A melt flow rate (MFR _B ) under a load of 190 ° C. and a load of 2.16 kg is 0.1 g / 10 min or more and 2 g / 10 min or less.
(2 ′) Density is 860 kg / m ³ or more and 890 kg / m ³ or less.
(3 ′) The melt flow rate (MFR _B ) satisfies the following relational expression (1) with respect to [η] _{sol of the} propylene / ethylene block copolymer (A).

[η] _sol ≦ (1.4 / MFR _B ) +2.8 (1)
[5] The propylene / ethylene block copolymer (A) contains 0% by weight or more and 8% by weight or less of a skeleton derived from ethylene in a portion (D _insol ) insoluble in room temperature n-decane. The propylene copolymer composition for a surface protective film as described in [4] above.
[6] The propylene / ethylene block copolymer (A) polymerizes homopolypropylene or propylene / ethylene random copolymer in the first polymerization step, and polymerizes propylene / ethylene random copolymer in the second polymerization step. The propylene copolymer composition for a surface protective film as described in [4] above, which is produced by
[7] The propylene / ethylene block copolymer (A) is a portion insoluble in room temperature n-decane (D _insol ) by controlling the polymerization amount ratio between the first polymerization step and the second polymerization step. And the propylene copolymer composition for a surface protective film according to [6] above, wherein the mass fraction of the soluble part (D _sol ) is controlled within the above range.

  According to the present invention, less damage to the adherend due to less fisheye, sufficient transparency, excellent functionality as a surface protection film, and roll-like without using a release film Even when wound up and stored, it is possible to provide a surface protective film that is excellent in blocking resistance and excellent in pull-out properties when the wound film is used. The surface protective film according to the present invention can be used without limitation for various uses using the surface protective film, and also exhibits sufficient transparency, so that the surface of an optical film, an optical member, an electrical material, etc. is protected. Can be suitably used.

  Hereinafter, the present invention will be specifically described.

  The surface protective film of this invention has the film formed from the propylene copolymer composition for surface protective films which concerns on this invention as a surface layer. The surface protective film of the present invention may be formed singly, but as a preferred embodiment, it is a laminated film of at least two layers having a surface layer on one surface and an adhesive layer on the other surface.

<Propylene copolymer composition for surface protective film>
The propylene copolymer composition for a surface protective film of the present invention is a composition suitable for forming a surface layer of a surface protective film, and comprises a propylene / ethylene block copolymer (A), an ethylene elastomer ( B).

Propylene / ethylene block copolymer (A)
The propylene / ethylene block copolymer (A) according to the present invention is formed from a part insoluble in room temperature n-decane (D _insol ) and a part soluble in room temperature n-decane (D _sol ).

As long as the propylene / ethylene block copolymer (A) of the present invention satisfies the following requirements (1) to (3), the polymerization catalyst and polymerization conditions used in the production thereof are not particularly limited. Moreover, it can also be used individually by 1 type, and can also be used in combination of 2 or more type.
(1) The intrinsic viscosity [η] _insol in 135 ° C. decalin of the portion insoluble in room temperature n-decane (D _insol ) is 1.5 dl / g or more and 2.5 dl / g or less. The lower limit is preferably 1.7 dl / g, more preferably 1.9 dl / g, and the upper limit is preferably 2.4 dl / g, more preferably 2.3 dl / g.

If the intrinsic viscosity [η] _{insol of the} propylene / ethylene block copolymer (A) is out of the above range, the cast film moldability of the resulting propylene copolymer composition for a surface protective film tends to be inferior.

As a method of controlling within the range satisfying the above requirement (1), homopolypropylene or propylene / ethylene random copolymer may be used in the first polymerization step, as described later in the method for producing the propylene / ethylene block copolymer (A). A portion (D _insol ) insoluble in room temperature n-decane having a coalescence as a main component, and a portion soluble in room temperature n-decane having a propylene / ethylene random copolymer elastomer as a main component in the second polymerization step ( In the case of polymerizing D _sol ), the intrinsic viscosity [η] _insol in 135 ° C. decalin of the part insoluble in room temperature n-decane (D _insol ) is controlled by controlling the hydrogen feed amount in the first polymerization step. Can be controlled within.
(2) The intrinsic viscosity [η] _sol in 135 ° C. decalin of the portion soluble in room temperature n-decane (D _sol ) is 2.5 dl / g or more and 4.5 dl / g or less. The lower limit is preferably 3.0 dl / g, more preferably 3.5 dl / g, and the upper limit is preferably 4.4 dl / g, more preferably 4.3 dl / g.

  If it is more than the said lower limit, it is excellent in blocking resistance of the surface protection film obtained, and if it is below an upper limit, generation | occurrence | production of the fish eye of the surface protection film obtained is fully suppressed.

As a method for controlling within the range satisfying the above requirement (2), as will be described later, a portion insoluble in room temperature n-decane having a main component of homopolypropylene or propylene / ethylene random copolymer in the first polymerization step ( D _insol ) is polymerized, and in the second polymerization step, a portion soluble in room temperature n-decane (D _sol ) containing propylene / ethylene random copolymer elastomer as the main component (D _sol ) is polymerized. By controlling the amount, etc., the intrinsic viscosity [η] _sol in 135 ° C. decalin of the part soluble in room temperature n-decane (D _sol ) can be controlled within the above range.
(3) The content of the skeleton derived from ethylene in the portion soluble in room temperature n-decane (D _sol ) is 35% by weight or more and 50% by weight or less. The lower limit is preferably 45% by weight, more preferably 40% by weight.

  If it is more than the said lower limit, it will be excellent in blocking resistance, and if it is below an upper limit, fish eye will be excellent.

As a method of controlling within the range satisfying the above requirement (3), homopolypropylene or propylene / ethylene random copolymer may be used in the first polymerization step as described later in the method of producing the propylene / ethylene block copolymer (A). A portion (D _insol ) insoluble in room temperature n-decane having a coalescence as a main component, and a portion soluble in room temperature n-decane having a propylene / ethylene random copolymer elastomer as a main component in the second polymerization step ( when polymerizing D _sol), the second ethylene feed amount of the polymerization process and the like by controlling the, within the above range the content of skeletons derived from ethylene in the portion soluble (D _sol) to room temperature n- decane Can be controlled.

The propylene / ethylene block copolymer (A) according to the present invention preferably satisfies the following requirements (4) and (5) in addition to the above requirements (1) to (3).
(4) The mass fraction of the portion soluble in room temperature n-decane (D _sol ) is 5 wt% or more and 40 wt% or less. The lower limit is more preferably 9% by weight, and the upper limit is more preferably 17% by weight.

  If it is more than the said lower limit, it is excellent in blocking resistance of the surface protection film obtained, and if it is below an upper limit, the fish eye of a surface protection film can be suppressed suitably.

As a method for controlling within the range satisfying the above requirement (4), homopolypropylene or propylene / ethylene random copolymer may be used in the first polymerization step, as described later in the method for producing the propylene / ethylene block copolymer (A). A portion (D _insol ) insoluble in room temperature n-decane having a coalescence as a main component, and a portion soluble in room temperature n-decane having a propylene / ethylene random copolymer elastomer as a main component in the second polymerization step ( when polymerizing D _sol), by controlling the polymerization amount ratio of the first polymerization step and the second polymerization step, the mass of the portion insoluble in room temperature n- decane (D _insol) soluble portion (D _sol) The fraction can be controlled within the above range.
(5) The content of the skeleton derived from ethylene in the portion (D _insol ) insoluble in room temperature n-decane is 0% by weight or more and 8% by weight or less. More preferably, it is 0 to 1% by weight.

As a method of controlling to the range satisfying the above requirement (5), it is derived from ethylene in a portion insoluble in D- _sol at room temperature (D _insol ) by adjusting the kind of solid catalyst or electron donating compound used. The content of the skeleton can be controlled within the above range.

  The propylene / ethylene block copolymer (A) according to the present invention satisfying the above requirements (1) to (3), preferably further satisfying the above requirements (4) and (5) is, for example, as follows: It can be manufactured by the method.

Production Method of Propylene / Ethylene Block Copolymer (A) The propylene / ethylene block copolymer (A) according to the present invention is not particularly limited in the polymerization catalyst and polymerization conditions used during production as described above, but is suitably known. In the presence of the Ziegler catalyst or metallocene catalyst, homopropylene or a propylene / ethylene random copolymer composed of propylene and a small amount of ethylene is produced in the first polymerization step ([Step 1]), and then the second polymerization step ( In [Step 2]), a propylene / ethylene copolymer elastomer is produced by copolymerizing propylene and a larger amount of ethylene than in the first step.
Polymerization catalyst Examples of the polymerization catalyst used for the production of the propylene / ethylene block copolymer (A) include (A1) a solid catalyst component containing magnesium atoms, titanium atoms, and halogen atoms as essential components, and (B1). Examples thereof include highly stereoregular catalysts obtained using organoaluminum compounds. Examples of such a catalyst include a highly stereoregular catalyst obtained by using the following components (A1) and (B1).
(A1) Solid catalyst component (B1) organoaluminum compound obtained by using (a) magnesium compound and (b) titanium compound. Preferably, the following (A1) component, (B1) component and (C1) component are also used. And a highly stereoregular catalyst obtained in the above manner.
(A1) Solid catalyst component obtained by using (a) magnesium compound and (b) titanium compound (B1) Organoaluminum compound (C1) Electron donating compound Solid catalyst component (A1) and its preparation method Solid catalyst component ( A1) can be prepared using a magnesium compound (a), a titanium compound (b), and, if necessary, an electron donating compound (c).
(A) Magnesium compound The magnesium compound is not particularly limited, and includes magnesium oxide, magnesium hydroxide, dialkylmagnesium, alkylmagnesium halide, magnesium halide, magnesium dialkoxide, specifically magnesium chloride, magnesium diethoxide, A magnesium dimethoxide etc. can be mentioned. Moreover, as a magnesium compound, the well-known solid product obtained by making metal magnesium, a halogen, and alcohol react can be used conveniently. Here, examples of the alcohol include methanol and ethanol, and those having a water content of 200 ppm or less are easy to obtain a solid product having a good morphology. As halogen, chlorine, bromine, iodine, particularly iodine is preferably used.
(B) Titanium compound As a titanium compound, arbitrary titanium compounds can be used, for example, the titanium compound represented by General formula (1) is mentioned.

TiX ¹ _n (OR ¹ ) _4-n (1)
(In the formula (1), X ¹ is a halogen atom, particularly a chlorine atom, R ¹ is a hydrocarbon group having 1 to 10 carbon atoms, particularly a linear or branched alkyl group, and a plurality of groups R ¹ are present. They may be the same or different from each other, n is an integer from 0 to 4.)
Specifically, Ti (O-i-C 3 H 7) 4, Ti (O-C 4 H 9) 4, TiCl (O-C 2 H 5) 3, TiCl (O-i-C 3 H 7 ) ₃ , TiCl (O—C ₄ H ₉ ) ₃ , TiCl ₂ (O—C ₄ H ₉ ) ₂ , TiCl ₂ O—i—C ₃ H ₇ ) ₂ , TiCl _{4 and the} like.
(C) Electron-donating compound For the preparation of the solid catalyst component (A1), any electron-donating compound (c) can be used as necessary. These electron donating compounds (c) are usually organic compounds containing oxygen, nitrogen, phosphorus or sulfur. For example, amines, amides, ketones, nitriles, phosphines, esters, ethers, Mention may be made of thioethers, alcohols, thioesters, acid anhydrides, acid halides, aldehydes, organic acids, and organosilicon compounds having a Si—O—C bond.

  Specifically, for example, aromatic phthalic acid diesters such as diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, dihexyl phthalate, dimethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, di- Preferred examples include organosilicon compounds such as t-butyldimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, dicyclohexyldimethoxysilane, and dicyclopentyldimethoxysilane.

  The solid catalyst component (A1) can be prepared by a known method using the magnesium compound (a), the titanium compound (b), and, if necessary, the electron donating compound (c). For example, the magnesium compound (a) and the electron donating compound (c) are contacted and then contacted with the titanium compound (b). The contact conditions are not particularly limited, and usually 0.01 to 10 mol, preferably 0.05 to 5 mol of an electron donating compound (c) is added to 1 mol of the magnesium compound (a) in terms of magnesium atom, Contact is performed at 0 to 200 ° C. for 5 minutes to 10 hours, preferably at 30 to 150 ° C. for 30 minutes to 3 hours. In addition, inert hydrocarbons such as pentane, hexane, and heptane can be added to this preparation.

  The conditions for contacting the titanium compound (b) with the magnesium compound (a) or the contact product of the electron donor compound (c) with the magnesium compound (a) are not particularly limited. The titanium compound (b) is added in an amount of 1 to 50 mol, preferably 2 to 20 mol, and contacted at 0 to 200 ° C. for 5 minutes to 10 hours, preferably at 30 to 150 ° C. for 30 minutes to 5 hours. The contact with the titanium compound (b) can be performed in a state where the liquid titanium compound (for example, titanium tetrachloride) is used alone and the other titanium compounds are dissolved in an arbitrary inert hydrocarbon. Further, before the contact between the magnesium compound (a) and, if necessary, the electron donating compound (c), for example, halogenated hydrocarbon, halogen-containing silicon compound, halogen gas, hydrogen chloride, hydrogen iodide Etc. can be brought into contact with the magnesium compound (a). In addition, after completion | finish of contact, it is preferable to wash | clean a product with an inert hydrocarbon.

Organoaluminum compound (B1)
There is no limitation in particular as an organoaluminum compound (B1), For example, the compound represented by following General formula (2) is mentioned.

AlR ² _m X ² _3-m (2)
(In the formula (2), R ² is an alkyl group, a cycloalkyl group or an aryl group having 1 to 10 carbon atoms, m is an integer of 1 to 3, X ² is a halogen atom (chlorine or bromine atom) .)
Specific examples include trialkylaluminum compounds such as trimethylaluminum, triethylaluminum, triisopropylaluminum, and triisobutylaluminum, and dialkylaluminum monochlorides such as diethylaluminum monochloride and dipropylaluminum monochloride.

Electron donating compound (C1)
In the catalyst used for the production of the propylene / ethylene block copolymer (A) according to the present invention, an electron donating compound (C1) can be used in combination as required. As the electron donating compound (C1) in this case, the same electron donating compound (c) used in the preparation of the solid catalyst component (A1) can be used. In this case, it may be the same as or different from that used in the preparation of the solid catalyst component. A preferred electron donating compound (C1) is a silane compound having a SiO—C bond, particularly a compound represented by the following general formula (3).

R ³ _p Si (OR ⁴ ) _4-p (3)
(In the formula (3), R ³ represents a linear or branched hydrocarbon group, an aromatic hydrocarbon group, a cyclic saturated hydrocarbon group or a nitrogen atom-containing hydrocarbon group. R ⁴ is a linear hydrocarbon group or a branched hydrocarbon group, and p is an integer of 0 to 3.)
Specific examples of the compound of the formula (3) include t-butylcyclohexyldimethoxysilane, methylcyclohexyldimethoxysilane, di-t-butyldimethoxysilane, dicyclohexyldimethoxysilane, dicyclopentyldimethoxysilane, diphenyldimethoxysilane, dimethyldiethoxy. Silane, trimethylethoxysilane, methylphenyldimethoxysilane, diethylaminotriethoxysilane, bis (perhydroquinolino) dimethoxysilane, bis (perhydroisoquinolino) dimethoxysilane, ethyl (perhydroquinolino) dimethoxysilane, ethyl (perhydroiso) Quinolino) dimethoxysilane, and the like.
-Polymerization method The propylene / ethylene block copolymer (A) according to the present invention uses a polymerization apparatus in which two or more reaction apparatuses are connected in series, and comprises the following two steps ([Step 1] and [Step 2]. ) Is preferably carried out continuously.

[Step 1] polymerizes propylene alone or copolymerizes propylene and ethylene at a polymerization temperature of 0 to 100 ° C. and a polymerization pressure of normal pressure to 5 MPa gauge pressure. In [Step 1], the amount of ethylene fed relative to propylene is made small so that the polypropylene or the propylene / ethylene random copolymer produced in [Step 1] becomes the main component of D _insol .

In [Step 2], propylene and ethylene are copolymerized at a polymerization temperature of 0 to 100 ° C. and a polymerization pressure of normal pressure to 5 MPa gauge pressure. In [Step 2], the propylene / ethylene copolymer elastomer produced in [Step 2] becomes the main component of D _sol by increasing the amount of ethylene fed to propylene than in [Step 1]. To do.

By doing in this way, requirements (1) and (5) concerning D _insol are adjusted by adjusting the polymerization conditions in [Step 1], and requirements (2) and (3) concerning D _sol are [Step 2]. It can be satisfied by adjusting the polymerization conditions. The requirement (4) relating to the composition ratio between D _insol and D _sol can be controlled by adjusting the amount ratio of the polymer produced in [Step 1] and [Step 2].

The intrinsic viscosity [η] in 135 ° C. decalin of D _insol of requirement (1) can be adjusted by the feed amount of a molecular weight regulator such as hydrogen in [Step 1].

The intrinsic viscosity [η] in 135 ° C. decalin of D _sol of requirement (2) can be adjusted by the feed amount of a molecular weight regulator such as hydrogen in [Step 2].

The content of the skeleton derived from ethylene in D _{sol of} requirement (3) can be adjusted by the amount of ethylene feed in [Step 2].

The composition ratio between D _insol and D _sol of requirement (4) and the melt flow rate of the propylene / ethylene block copolymer (A) are the ratios of the polymers produced in [Step 1] and [Step 2]. It is possible to adjust appropriately by adjusting.

The content of the skeleton derived from ethylene in D _{insol of} requirement (5) can also be adjusted by adjusting the type of solid catalyst or electron donating compound used. It is also possible to adjust by the amount of ethylene feed in [Step 1].

  The propylene / ethylene block copolymer (A) used in the present invention is produced by the propylene / ethylene random copolymer produced in [Step 1] of the above method and [Step 2] of the above method. Propylene / ethylene random copolymer elastomers may be produced individually in the presence of a polymerization catalyst and then blended using these physical means.

Ethylene elastomer (B)
The ethylene-based elastomer is a random copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms of a comonomer type. As long as the ethylene elastomer (B) of the present invention satisfies the following requirements, the polymerization catalyst and polymerization conditions to be used are not particularly limited. Moreover, it can also be used individually by 1 type, and can also be used in combination of 2 or more type.

The ethylene-based elastomer (B) according to the present invention satisfies the following requirements (1 ′) to (3 ′).
(1 ′) The melt flow rate (MFR _B ) under a load of 190 ° C. and a load of 2.16 kg is 0.1 g / 10 min or more and 2 g / 10 min or less. The lower limit is preferably 0.3 g / 10 minutes, more preferably 0.4 g / 10 minutes, and the upper limit is preferably 1.5 g / 10 minutes, more preferably 1.0 g / 10 minutes.

  Exceeding the above lower limit value, the propylene copolymer composition obtained has excellent extrusion characteristics and surface protective film fish eye and blocking resistance, and if the upper limit value or less, the resulting protective eye fish eye and blocking resistance are obtained. Excellent.

As a method for controlling to the above range, a known method can be appropriately employed. Further, for example, by selecting an appropriate one from commercially available ethylene-based elastomers, it can be within the above range.
(2 ′) The density is 860 kg / m ³ or more and 890 kg / m ³ or less. The lower limit is preferably 870 kg / m ³ , more preferably 875 kg / m ³ , and the upper limit is preferably 889 kg / m ³ , more preferably 888 kg / m ³ .

  If the density is within the above range, fish eyes of the obtained surface protective film can be suitably suppressed.

As a method for controlling to the above range, a known method can be appropriately employed. Further, for example, by selecting an appropriate one from commercially available ethylene-based elastomers, it can be within the above range.
(3 ′) The melt flow rate (MFR _B ) satisfies the following relational expression (1) with respect to [η] _{sol of the} propylene / ethylene block copolymer (A).

[η] _sol ≦ (1.4 / MFR _B ) +2.8 (1)
More preferably, the following relational expression (2) is satisfied.

[η] _sol ≦ (1.4 / MFR _B ) +2.0 (2)
Particularly preferably, the following relational expression (3) is satisfied.

[η] _sol ≦ (1.4 / MFR _B ) +1.0 (3)
The relational expression (1) of the requirement (3 ′) indicates the magnitude relationship between the molecular weights of the propylene / ethylene block copolymer (A) and the ethylene-based elastomer (B). In the present invention, for [η] _sol of the propylene / ethylene block copolymer (A), it is found that the fish-eye improvement effect cannot be obtained unless the molecular weight of the ethylene-based elastomer (B) is larger than a certain level. This is specified in the relational expression (1).

  That is, the reason why the surface layer of the surface protective film of the present invention exhibits an average surface roughness as will be described later, is excellent in blocking resistance, and is suppressed in fish eyes is not clear. In the propylene / ethylene block copolymer (A), by blending a high-viscosity ethylene-based elastomer (B) that does not become the core of fisheye, It is considered that the domain size (dispersed particle size) of the ethylene-based elastomer (B) component is large, and forming this makes the surface roughness of the film rough and significantly improves the blocking resistance.

When the melt flow rate (MFR _B ) of the ethylene-based elastomer (B) satisfies the requirement (3 ′) in addition to the requirement (1 ′), fish eyes of the resulting surface protective film are suppressed, and anti-blocking property Excellent in properties.

Other components The propylene copolymer composition for a surface protective film of the present invention has the object of the present invention for the purpose of imparting functions such as impact resistance, transparency, dimensional stability, and high-speed extrusion sheet formability. As long as it is not necessary, it may contain a polyethylene resin (C) or other thermoplastic resin as necessary. That is, the surface layer of the surface protective film of the present invention may contain a polyethylene resin (C) or other thermoplastic resin as necessary, as long as the object of the present invention is not impaired.

  For example, in the case of a propylene-based resin composition comprising a propylene / ethylene block copolymer (A), an elastomer (B), and a polyethylene resin (C), the amount of the polyethylene resin (C) is determined by the amount of the propylene / ethylene block copolymer. (A) It is 0-30 mass parts normally with respect to 100 mass parts, Preferably it is 1-20 mass parts. In addition, the ratio of ethylene-type elastomer (B) and polyethylene resin (C) can be arbitrarily adjusted according to the objective.

  In addition, the propylene copolymer composition for a surface protective film of the present invention is a range that does not impair the object of the present invention, and if necessary, vitamins, antioxidants, heat stabilizers, weathering stabilizers, slip agents, An additive such as an anti-blocking agent and mineral oil may be included. That is, the surface layer of the surface protective film of the present invention may contain the various additives as necessary within a range not impairing the object of the present invention.

Propylene copolymer composition for surface protective film The propylene copolymer composition for a surface protective film of the present invention comprises the propylene / ethylene block copolymer (A) and the ethylene elastomer (B). If necessary, the above-mentioned other components are contained.

  The propylene copolymer composition for a surface protective film of the present invention comprises a propylene / ethylene block copolymer (A) of 75% by weight to 97% by weight and an ethylene elastomer (B) of 3% by weight to 25% by weight. Includes: The lower limit of the content of the propylene / ethylene block copolymer (A) is preferably 76% by weight, more preferably 77% by weight, and the upper limit is preferably 96% by weight, more preferably 95% by weight, still more preferably 93% by weight. It is. Further, the lower limit of the content of the ethylene elastomer (B) is preferably 4% by weight, more preferably 5% by weight, still more preferably 7% by weight, and the upper limit is preferably 24% by weight, more preferably 23% by weight. It is. However, (A) + (B) = 100% by weight.

  When the blending amount of the ethylene-based elastomer (B) is not less than the above lower limit value, the resulting film has excellent blocking resistance, fish eyes are suppressed, and when it is not more than the above upper limit value, the moldability is excellent.

Further, the surface protective film propylene copolymer composition of the present invention, 230 ° C., under a 2.16kg load melt flow rate (MFR _E) is preferably 0.5 g / 10 min or more 50 g / 10 min or less, The lower limit is more preferably 3 g / 10 minutes, and the upper limit is more preferably 6 g / 10 minutes. The above range is preferable because cast film moldability is excellent.

  The propylene copolymer composition for a surface protective film of the present invention can be produced by melt-kneading the above-mentioned propylene / ethylene block copolymer (A) and ethylene elastomer (B), or propylene. -It can manufacture also by dry blending the pellet which granulated the ethylene block copolymer (A), and the pellet of ethylene-type elastomer (B). Preferably, a method of production by melt kneading can be used, and at this time, a continuous extruder or a closed kneader can be used. For example, apparatuses, such as a single screw extruder, a twin screw extruder, a mixing roll, a Banbury mixer, a kneader, can be mentioned. Among these, it is preferable to use a single screw extruder and / or a twin screw extruder from the viewpoints of economy, processing efficiency, and the like.

  The propylene copolymer composition for a surface protective film of the present invention is suitably used as a composition for forming a surface layer of a surface protective film having a surface layer and an adhesive layer.

<Surface protection film>
The surface protective film of the present invention includes at least two layers of a surface layer and an adhesive layer.

Surface layer The surface layer of the surface protective film of the present invention is formed from the propylene copolymer composition for a surface protective film of the present invention.

Adhesive layer The material for forming the adhesive layer of the surface protective film of the present invention is not particularly limited as long as the surface protective film can be attached to an adherend. For example, EVA, SBR, SIS, SBS, Examples thereof include SEBS-based, butyl elastomer-based, natural elastomer-based, and acrylic pressure-sensitive adhesives.

As a material for forming the adhesive layer, linear low density polyethylene (LLDPE) having a density of 0.900 kg / m ³ or less can be used.

  Moreover, as a material for forming the adhesive layer, a propylene-based random block copolymer described in JP-A-2009-185239, which is polymerized with a metallocene catalyst system, can also be used.

  When the pressure-sensitive adhesive is coextruded by a T-die coextrusion molding method, EVA, SEBS, or linear low density polyethylene (LLDPE) can be preferably used. Moreover, when apply | coating an adhesive to a base film, an acrylic adhesive can be used preferably.

  The pressure-sensitive adhesive layer in the surface protective film of the present invention includes additives such as vitamins, antioxidants, heat stabilizers, weather stabilizers, mineral oils, etc., as necessary, as long as the purpose of the present invention is not impaired. May be.

Intermediate layer The surface protective film of the present invention has at least two layers of a surface layer and an adhesive layer, and may be formed of only two layers of a surface layer and an adhesive layer. One or more intermediate layers may be provided therebetween. The intermediate layer may be provided for the purpose of controlling the mechanical strength and transparency of the film. If the adhesive strength between the surface layer and the adhesive layer is insufficient, the intermediate layer may be made of a polyolefin resin, an adhesive resin, or an adhesive. It may be a layer having adhesiveness.

  The intermediate layer is not particularly limited as long as it does not hinder the functions of the surface layer and the adhesive layer, but generally, a crystalline polyolefin such as polypropylene or polyethylene having a melting point of 100 ° C. or higher, polyester, polyamide, polyolefin elastomer, etc. are used. it can.

  When it is desired to impart adhesiveness to the intermediate layer, modified polyolefin, polyolefin elastomer, styrene elastomer, polyester elastomer or the like is used.

  Among these, from the viewpoint of productivity and transparency, it is preferable to use polypropylene or polyolefin elastomer as the intermediate layer.

Surface Protective Film The thickness of the surface protective film of the present invention can be appropriately determined according to the purpose, and can be, for example, 10 to 200 μm. The thickness of the surface layer can be 8 to 150 μm, and the thickness of the adhesive layer can be 2 to 50 μm.

  The surface layer of the surface protective film of the present invention is formed by using the propylene copolymer composition for a surface protective film of the present invention, so that fish eyes are effectively suppressed and usually has good transparency. Have In addition, the surface protective film of the present invention having such a surface layer is less likely to cause blocking with the adhesive layer that comes into contact when the surface protective film is rolled up, has excellent blocking resistance, and is a roll-shaped film. Excellent feedability.

  The exposed surface of the surface layer to be the surface of the surface protective film, that is, the surface opposite to the adhesive layer side preferably has a certain unevenness, and the average surface is a parameter indicating the surface state The roughness Ra (arithmetic mean roughness) is preferably 0.20 to 2.00 μm, more preferably 0.3 to 0.8 μm. When the surface on the surface layer side of the surface protective film of the present invention has such an average surface roughness Ra, the surface protective film overlaps when the surface protective film is rolled up by having certain irregularities. Since the contact with the adhesive layer of the film becomes a point contact and the contact area is reduced, the adhesion with the adhesive layer is suppressed, the surface protection film has excellent blocking resistance, and excellent roll-out property of the roll film It becomes.

  A surface layer having such an average surface roughness can be easily obtained when the propylene / ethylene block copolymer according to the present invention is formed into a film by a conventional method.

  Although the surface layer of the surface protective film of the present invention exhibits such average surface roughness, is excellent in anti-blocking properties, and the fisheye is suppressed, the present inventor is not sure, By blending the propylene / ethylene block copolymer (A) with a high-viscosity ethylene elastomer (B) that does not become the core of fish eye, the ethylene elastomer in the propylene copolymer composition for surface protective film It is considered that the domain size (dispersed particle size) of the component (B) is large, and by molding this, the surface roughness of the film becomes rough and the blocking resistance is remarkably improved.

And, through the ethylene elastomer (B) component, shear stress was transmitted to the fish eye nuclei present in the propylene / ethylene block copolymer (A), and the fish eye nuclei were crushed to reduce the fish eyes. Yes. In order to transmit the shear stress, the effect cannot be obtained unless the molecular weight of the ethylene elastomer (B) is larger than a certain value with respect to [η] _sol of the propylene / ethylene block copolymer (A). It was derived that it can be expressed by the requirement (3 ′) of the propylene copolymer composition for a surface protective film described above.

  In addition, it is thought that a fish eye nucleus is a high-viscosity component resulting from an especially high molecular weight thing among the elastomer components which exist in a propylene ethylene block copolymer (A). Here, the unevenness of the film surface for improving the blocking resistance is on the order of several μm, for example, about 1 to 3 μm, whereas the FE nucleus has an order of magnitude different from the order of several tens of μm, for example, about 10 to 50 μm. .

Production Method of Surface Protective Film Various known methods can be employed to form the surface layer of the surface protective film of the present invention. For example, the above-described propylene copolymer composition for a surface protective film of the present invention is formed into a film form from a T die together with a resin for forming an intermediate layer as necessary, and formed into a tube form from a circular die. By this method, a single layer / multilayer substrate film can be obtained. Moreover, the base film containing the surface layer formed by these methods can be multilayered by a dry lamination method or an extrusion lamination method.

  Moreover, the film formed by the above methods can be appropriately stretched and used.

  The adhesive layer is formed by various known methods. For example, a method of coating a pressure-sensitive adhesive on a substrate including a surface layer with a coating machine, a co-extrusion method in which a substrate and a pressure-sensitive adhesive are formed into a multilayer film form from a T die or a circular die, and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

The measuring method of the physical property in an Example and a comparative example is as follows.
(1) MFR (melt flow rate)
MFR was measured according to ASTM D1238 (230 ° C or 190 ° C, load 2.16 kg).
(2) Room temperature n-decane soluble part (D _sol )
200 ml of n-decane was added to 5 g of a sample of the final product (that is, the propylene random block polymer of the present invention) and dissolved by heating at 145 ° C. for 30 minutes. It was cooled to 20 ° C. over about 3 hours and left for 30 minutes. Thereafter, the precipitate (hereinafter, n-decane insoluble part: D _insol ) was filtered off. The filtrate was put in about 3 times the amount of acetone to precipitate the components dissolved in n-decane (precipitate (A)). The precipitate (A) and acetone were separated by filtration, and the precipitate was dried. Even when the filtrate side was concentrated to dryness, no residue was observed.

  The amount of n-decane soluble part was determined by the following formula.

n-decane soluble part amount (wt%) = [precipitate (A) weight / sample weight] × 100
(3) Content of skeleton derived from ethylene In order to measure the skeleton concentration derived from ethylene in D _insol and D _sol , 20 to 30 mg of sample was subjected to 1,2,4-trichlorobenzene / heavy benzene (2: 1 ) After dissolving in 0.6 ml of the solution, carbon nuclear magnetic resonance analysis ( ¹³ C-NMR) was performed. Propylene, ethylene, and α-olefin were quantitatively determined from the dyad chain distribution.

For example, in the case of propylene-ethylene copolymer,
PP = Sαα, EP = Sαγ + Sαβ, EE = 1/2 (Sβδ + Sδδ) + 1 / 4Sγδ
Was obtained by the following calculation formulas (Eq-1) and (Eq-2).

Propylene (mol%) = (PP + 1 / 2EP) x 100 / [(PP + 1 / 2EP) + (1 / 2EP + EE)] ... (Eq-1)
Ethylene (mol%) = (1 / 2EP + EE) x 100 / [(PP + 1 / 2EP) + (1 / 2EP + EE)] ... (Eq-2)

(4) Intrinsic viscosity [η]
It measured at 135 degreeC using the decalin solvent. About 20 mg of the sample was dissolved in 15 ml of decalin, and the specific viscosity ηsp was measured in an oil bath at 135 ° C. After adding 5 ml of decalin solvent to the decalin solution for dilution, the specific viscosity ηsp was measured in the same manner. This dilution operation was further repeated twice, and the value of ηsp / C when the concentration (C) was extrapolated to 0 was determined as the intrinsic viscosity.

[Η] = lim (ηsp / C) (C → 0)
(5) HAZE
Measurement was performed according to JIS K 7105.
(6) Average surface roughness (Ra)
The average surface roughness Ra in the MD direction of the surface layer of the obtained laminated film (surface protective film) is measured at a measurement speed of 0.15 mm / min using a surface roughness measuring device according to JIS-B0601: 2001. = 3 measured and arithmetically averaged.
(7) Fisheye (FE)
Using the FE counter, the number of FEs with a size of 100 μm or more (pieces / m ² ) was counted.
(8) Peeling force from adhesive layer (N / 25mm)
Using a 2 kg rubber roller, the surface layer film (MD direction) was attached to the adhesive film at a speed of 2 m / min. This was left at room temperature of 23 ° C. ± 2 ° C. for 30 minutes. Thereafter, the adhesive film was peeled from the surface layer film in accordance with JIS Z 0237, and the 180 ° peel strength (T peel method) at 25 mm width was measured at n = 5 at a tensile speed of 300 mm / min, and the arithmetic average was obtained.

[Production Example 1] (Production of propylene / ethylene block copolymer)
(1) Preparation of Magnesium Compound A reactor equipped with a stirrer (with an internal volume of 500 liters) was sufficiently replaced with nitrogen gas, and 97.2 kg of ethanol, 640 g of iodine, and 6.4 kg of magnesium metal were added and refluxed with stirring. The reaction was continued until no hydrogen gas was generated from the system to obtain a solid reaction product. The reaction solution containing the solid reaction product was dried under reduced pressure to obtain the target magnesium compound (solid catalyst carrier).
(2) Preparation of solid catalyst component In a reactor equipped with a stirrer sufficiently substituted with nitrogen gas (with an internal volume of 500 liters), 30 kg of the magnesium compound (not pulverized), 95 liters of purified heptane (n-heptane), four 4.4 liters of silicon chloride and 6.0 liters of di-n-butyl phthalate were added. The system was kept at 90 ° C., 144 liters of titanium tetrachloride was added while stirring and reacted at 110 ° C. for 2 hours, and then the solid components were separated and washed with purified heptane at 90 ° C. Further, 228 liters of titanium tetrachloride was added and reacted at 110 ° C. for 2 hours, and then thoroughly washed with purified heptane to obtain a solid catalyst component.
(3) Preparation of prepolymerization catalyst 230 liters of purified heptane was charged into a reaction tank with an internal volume of 500 liters equipped with a stirrer, 25 kg of the above solid catalyst component and 1.0 mol of triethylaluminum with respect to titanium atoms in the solid catalyst component / Mol, dicyclopentyldimethoxysilane was supplied at a rate of 1.8 mol / mol. Thereafter, propylene was introduced until the partial pressure of propylene reached 0.3 kg / cm ² G and reacted at 25 ° C. for 4 hours. After completion of the reaction, the solid catalyst component was washed several times with purified heptane, and further carbon dioxide was supplied and stirred for 24 hours.
(4) Main polymerization Block polymerization was carried out using two polymerization tanks connected in series.

  As a previous stage, homopolymerization was carried out by supplying propylene at 45 kg / h and hydrogen at 380 Nl / h into a polymerization tank (homopolymerization tank) with a stirring blade having an internal volume of 200 liters. The pre-polymerized solid catalyst component was supplied so that the polymerization rate was 30 kg / hour, triethylaluminum was supplied at 120 mmol / hour, and dicyclopentyldimethoxysilane was supplied at 12 mmol / hour, and the polymerization temperature was 83 ° C., The reaction was carried out at a polymerization tank pressure of 3.0 MPa (Gauge). At this time, it adjusted so that it might become a predetermined molecular weight using hydrogen. Subsequently, powder was continuously extracted from the former polymerization tank and transferred to the latter stage (block polymerization tank).

In the subsequent polymerization tank (block polymerization tank), propylene was supplied at 9.9 kg / h, ethylene at 15.5 kg / h, and hydrogen at 400 NL / h at a polymerization temperature of 60 ° C. Moreover, the catalytic activity controlling agent ethanol supplied from the upper part of the reactor was supplied at 4.4 g / h. The powder was continuously withdrawn from the subsequent polymerization tank to obtain propylene / ethylene block copolymer powder (PP-A). Properties are shown in Table 1.
[Production Examples 2 and 3]
The same procedure as in Production Example 1 was carried out except that propylene, hydrogen, ethylene, and ethanol supplied to each polymerization tank of the main polymerization were adjusted. Table 1 shows the properties of the obtained propylene / ethylene block copolymers (PP-B) and (PP-C).

[Examples 1-9, Comparative Examples 1-6]
100 mass of a resin composition in which the propylene / ethylene block copolymer (A) produced in Production Examples 1 to 3 and the ethylene elastomer (B) shown in Table 2 are blended in the blending amounts shown in Table 3 and Table 4. Heat stabilizer IRGANOX 1010 (Ciba Geigy Co., Ltd.) 0.1 parts by mass, heat stabilizer IRGAFOS168 (Ciba Geigy Co., Ltd.) 0.1 parts by mass, and calcium stearate 0.1 parts by mass in a tumbler After mixing, melt-kneading at 190 ° C using a twin-screw extruder manufactured by Nakatani Machinery Co., Ltd. (same direction twin-screw kneader) to prepare a propylene copolymer composition for a surface protective film in the form of pellets did.

  Using a single-layer T-die molding machine having a die width of 250 mm and a 20 mmφ single-screw extruder as a film molding machine, supplying the prepared propylene copolymer composition for a surface protective film to the extruder, A single layer film having a thickness of 40 μm was formed.

  About the single layer film corresponding to the obtained surface layer, the peeling force from an adhesion layer was evaluated by the measuring method mentioned above. As the evaluation adhesive layer, a commercially available olefin-based adhesive film (A2450, manufactured by Hitachi Chemical Co., Ltd.) was used. The results are shown in Table 3 and Table 4 together.

  In addition, a single layer film corresponding to the surface layer and the adhesive layer were bonded together by a dry laminating method to produce a laminate. Two laminated bodies having the same size are prepared (referred to as laminated bodies 1 and 2), the surface layers of the laminated body 1 and the adhesive layer of the laminated body 2 are opposed to each other, and the laminated bodies are overlapped with each other. Using a 2 kg rubber roller from above, it was attached at a speed of 2 m / min. This was left at room temperature of 23 ° C. ± 2 ° C. for 30 minutes. Thereafter, the laminate 2 was peeled from the laminate 1 according to JISZ0237, and the 180 degree peel strength (T peel method) at 25 mm width was measured at a pulling speed of 300 mm / min, n = 5, and the arithmetic average was obtained. This evaluated the peeling force of the adhesion layer and the base-material surface. The results are shown in Table 3 and Table 4.

  As shown in Tables 3 and 4, Examples 1 to 9 have excellent characteristics such as a large surface roughness and a small fish eye (FE) compared to Comparative Examples 1 to 3 compared with each of them. Show. Further, as the amount of the elastomer component added increases, the surface roughness and FE improve, that is, the surface roughness increases and the FE tends to decrease. In contrast, in Comparative Examples 4 to 6, the surface roughness is not so much improved as compared to Comparative Examples 1 to 3 which are the respective references, and the improvement (suppression) effect of FE is not seen.

  Until now, it has been difficult to obtain a surface protective film having a surface layer of a propylene / ethylene block copolymer satisfying both contradictory properties of high surface roughness and low FE. It was confirmed that such a surface protective film can be obtained.

  The surface protective film of the present invention can be widely used as a surface protective film for optical films, electronic component materials, building members and the like. Moreover, the propylene copolymer composition for surface protection films of this invention can be used suitably for manufacture of such a surface protection film.

Claims (7)

The propylene / ethylene block copolymer (A) satisfying the following requirements (1) to (3): 75 wt% or more and 97 wt% or less, ethylene-based elastomer (B) satisfying the following requirements (1 ') to (3') Surface protection characterized by having as a surface layer a film comprising a propylene copolymer composition containing 3 wt% or more and 25 wt% or less (provided that the sum of (A) and (B) is 100 wt%) the film;
(1) The intrinsic viscosity [η] _insol in 135 ° C. decalin of a part insoluble in room temperature n-decane (D _insol ) is 1.5 dl / g or more and 2.5 dl / g or less.
(2) The intrinsic viscosity [η] _sol in decalin at 135 ° C. of the part soluble in room temperature n-decane (D _sol ) is 2.5 dl / g or more and 4.5 dl / g or less.
(3) The content of the skeleton derived from ethylene in the portion soluble in room temperature n-decane (D _sol ) is 35% by weight or more and 50% by weight or less.
(1 ′) A melt flow rate (MFR _B ) under a load of 190 ° C. and a load of 2.16 kg is 0.1 g / 10 min or more and 2 g / 10 min or less.
(2 ′) Density is 860 kg / m ³ or more and 890 kg / m ³ or less.
(3 ′) The melt flow rate (MFR _B ) satisfies the following relational expression (1) with respect to [η] _{sol of the} propylene / ethylene block copolymer (A).
[Η] _sol ≦ (1.4 / MFR _B ) +2.8 (1) The propylene / ethylene block copolymer (A) is characterized in that the content of the skeleton derived from ethylene in the portion insoluble in room temperature n-decane (D _insol ) is 0 wt% or more and 8 wt% or less. The surface protective film according to claim 1.   The surface protective film according to claim 1, wherein the surface protective film has a surface layer on one surface and an adhesive layer on the other surface. The propylene / ethylene block copolymer (A) satisfying the following requirements (1) to (3): 75 wt% or more and 97 wt% or less, ethylene-based elastomer (B) satisfying the following requirements (1 ') to (3') 3 to 25% by weight (provided that the total of (A) and (B) is 100% by weight), and a propylene copolymer composition for a surface protective film.
(1) The intrinsic viscosity [η] _insol in 135 ° C. decalin of a part insoluble in room temperature n-decane (D _insol ) is 1.5 dl / g or more and 2.5 dl / g or less.
(2) The intrinsic viscosity [η] _sol in decalin at 135 ° C. of the part soluble in room temperature n-decane (D _sol ) is 2.5 dl / g or more and 4.5 dl / g or less.
(3) The content of the skeleton derived from ethylene in the portion soluble in room temperature n-decane (D _sol ) is 35% by weight or more and 50% by weight or less.
(1 ′) A melt flow rate (MFR _B ) under a load of 190 ° C. and a load of 2.16 kg is 0.1 g / 10 min or more and 2 g / 10 min or less.
(2 ′) Density is 860 kg / m ³ or more and 890 kg / m ³ or less.
(3 ′) The melt flow rate (MFR _B ) satisfies the following relational expression (1) with respect to [η] _{sol of the} propylene / ethylene block copolymer (A).
[Η] _sol ≦ (1.4 / MFR _B ) +2.8 (1) The propylene / ethylene block copolymer (A) is characterized in that the content of the skeleton derived from ethylene in the portion insoluble in room temperature n-decane (D _insol ) is 0 wt% or more and 8 wt% or less. The propylene copolymer composition for a surface protective film according to claim 4. The propylene / ethylene block copolymer (A) satisfying the following requirements (1) to (3): 75 wt% or more and 97 wt% or less, ethylene-based elastomer (B) satisfying the following requirements (1 ') to (3') 3% by weight to 25% by weight (provided that the total of (A) and (B) is 100% by weight), a method for producing a propylene copolymer composition for a surface protective film,
In the first polymerization step, homopropylene or propylene / ethylene random copolymer is polymerized, and in the second polymerization step, propylene / ethylene random copolymer is polymerized to produce the propylene / ethylene block copolymer (A). The manufacturing method of the propylene copolymer composition for surface protection films characterized by including a process.
(1) A portion insoluble in room temperature n-decane (D _insol ) In 135 ° C decalin [η] _insol Is 1.5 dl / g or more and 2.5 dl / g or less.
(2) A portion soluble in room temperature n-decane (D _sol ) In 135 ° C decalin [η] _sol Is 2.5 dl / g or more and 4.5 dl / g or less.
(3) A portion soluble in room temperature n-decane (D _sol ) The content of the skeleton derived from ethylene is 35% by weight to 50% by weight.
(1 ′) Melt flow rate (MFR under 190 ° C. and 2.16 kg load) _B ) Is 0.1 g / 10 min or more and 2 g / 10 min or less.
(2 ′) Density is 860 kg / m ^Three 890 kg / m or more ^Three Less than.
(3 ′) Melt flow rate (MFR) _B ) Of the propylene / ethylene block copolymer (A) [η] _sol In contrast, the following relational expression (1) is satisfied.
[Η] _sol ≤ (1.4 / MFR _B ) +2.8 (1) The step of producing the propylene / ethylene block copolymer (A) controls a polymerization amount ratio between the first polymerization step and the second polymerization step, so that a portion insoluble in room temperature n-decane (D _insol ) and manufacturing method of the soluble part (D _sol) mass fraction of the surface protection film for propylene copolymer composition according to claim 6, characterized in that to control within the above range.