JP2009073968A - Release agent and surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold release agent and a surface protection film, which allows easy rewinding of a rolled body even having a large width while ensuring stable adhesive force for a long period only by being applied and dried. <P>SOLUTION: The mold release agent principally comprises a thermoplastic silicone elastomer having polar bonds, and an n-hexane extraction is 0.6 wt.% or less. The surface protection film is provided with a mold release layer containing the mold release agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mold release agent and a surface protective film, and more specifically, a surface protective film used to prevent adhesion of dust to the surface of the adherend and damage to the surface of the adherend, and a mold release used therein. It relates to the agent.

  Conventionally, for example, when various articles and members such as optical devices, metal plates, painted steel plates, resin plates, glass plates, etc. are transported, processed, or cured, dirt adheres to these surfaces or the surface is damaged. A surface protective film is used to prevent this.

In this type of surface protective film, for example, a pressure-sensitive adhesive layer is laminated on a base material layer made of a synthetic resin or the like by applying a pressure-sensitive adhesive solution containing an elastomer or the like, or co-extrusion of the base material layer and the pressure-sensitive adhesive layer. Configured.
In recent years, surface protective films have been used for optical members for liquid crystal displays. Some optical members have an uneven surface such as a prism sheet or a diffusion film, and when a surface protective film is attached to a predetermined surface, the contact area cannot be obtained, so an appropriate adhesive force cannot be obtained, Therefore, it is necessary to form a pressure-sensitive adhesive layer having a strong adhesive force.

  Generally, the surface protective film is industrially manufactured as a wound body obtained by winding a long film in a roll shape, for example. In the surface protective film as such a wound body, when the wound body is unfolded, the outer surface protective film can be easily peeled off from the inner surface protective film, that is, the wound body is unwound. There is a strong demand for being easy. Therefore, so that the pressure-sensitive adhesive layer having a strong adhesive force does not strongly adhere to the back surface of the base material layer of the surface protection film on the inner side (the opposite surface to the pressure-sensitive adhesive layer lamination side of the base material layer, the same shall apply hereinafter) On the back surface of the base material layer of the surface protective film, a release treatment that exhibits higher release properties than usual is required.

As a method for forming a release layer on the back surface of a substrate layer of the surface protection film, a surface protection film in which a substrate layer made of polyethylene having a polysiloxane as a graft chain and an adhesive layer are laminated is disclosed. (For example, patent document 1). Patent Document 1 also shows a configuration in which an intermediate layer made of a polyolefin-based resin is provided between a base material layer and an adhesive layer. It is said that the wound body can be rewound satisfactorily by constituting the base material layer using polyethylene having a polysiloxane as a graft chain.
Further, as a surface protection film subjected to a release treatment, a surface protection film in which a base material layer made of a polyolefin resin and an adhesive layer are laminated and the back surface of the base material layer is friction-treated with a solid is disclosed. (For example, patent document 2).

On the other hand, in Patent Document 3, a surface layer containing a polyolefin-based resin and a pressure-sensitive adhesive layer containing a thermoplastic elastomer are laminated and formed by a coextrusion method, and then a release agent containing a release agent on the back surface of the surface layer. A surface protective sheet having a mold layer formed by a coating method is disclosed.
Japanese Patent Laid-Open No. 2-252782 JP-A-2-252777 JP 2003-41216 A

  The friction treatment with the solid on the back surface of the base material layer as in Patent Document 2 can be performed inline relatively easily. However, the present situation is that the rewinding property of the wound body has not been sufficiently improved only by the friction treatment. Moreover, the improvement effect of the rewinding property by friction treatment varies depending on the selection of the polyolefin resin constituting the base material layer.

  In general, since the polysiloxane described in Patent Document 1 has high releasability, relatively good releasability can be obtained. However, since free polysiloxane is present in the resin, these are pressure-sensitive adhesives. It moves to the layer, reduces the adhesive strength, and causes peeling.

  Furthermore, as described in Patent Document 3, when a release agent is applied to form a release layer, the thickness of the release layer is reduced to 1 to 1000 nm to reduce contamination on the adherend. It is said that the effect is great. However, long-chain alkyl polymer mold release agents such as those used in the examples of Patent Document 3 have insufficient release properties, and UV curable silicone release agents can provide release properties, Since the UV curing reaction time is required, the line speed cannot be increased freely, resulting in a decrease in productivity.

  The object of the present invention is to allow the wound body to be rewound without difficulty even when it is made into a wide wound body only by coating and drying in view of the above-described conventional state of the art, and coming into contact with the release layer. It is an object of the present invention to provide a mold release agent and a surface protective film with less migration of a bleed component to an adhesive layer.

  As a result of diligent research on the above problems and the existing surface protection sheet, the present inventors have a specific thermoplastic silicone elastomer superior in release properties compared to long-chain alkyl polymer release agents, It has been found that a release layer can be formed only by coating and drying without requiring a reaction time like UV curable silicone, and is a useful release agent. However, when accelerated evaluation of the wound body of the surface protective film produced using this thermoplastic silicone elastomer as a release layer, a decrease in adhesive strength was observed, and in the process of investigating the cause, thermoplastic silicone elastomer It was found that the free siloxane containing the cyclic siloxane component contained in the main component as a main component migrates to the pressure-sensitive adhesive layer in the wound surface protective film. Therefore, the free siloxane containing cyclic siloxane as a main component is regarded as n-hexane extract, and the thermoplastic silicone elastomer with reduced n-hexane extract is used as a mold release agent, so that it has only excellent rewinding properties. In addition, it was found that it was possible to suppress the migration of free siloxane to the pressure-sensitive adhesive layer over a long period of time, and the present invention was completed.

That is, the release agent of the present invention is characterized in that a thermoplastic silicone elastomer having a polar bond is a main component and the amount of n-hexane extracted is 0.6% by weight or less.
In addition, it is preferable that the release agent is one obtained by subjecting a thermoplastic silicone elastomer having a polar bond to a reduced pressure treatment, or one obtained by washing a thermoplastic silicone elastomer having a polar bond with a poor solvent for the thermoplastic silicone elastomer. .
Furthermore, the surface protective film of the present invention is characterized by comprising a release layer containing the above release agent.

According to the release agent of the present invention, in the release agent mainly composed of a thermoplastic silicone elastomer having a polar bond, the amount of n-hexane extracted is set to 0.6% by weight or less, whereby the release agent is reduced. Impurities in the constituent components can be effectively reduced, and high releasability can be ensured continuously.
Further, the surface protective film of the present invention is provided with a release layer with the above-described release agent, thereby ensuring releasability even when the surface protective film is a wound body, particularly a wide wound body. It is possible to rewind the wound body without difficulty. Moreover, the fall of the adhesive force in a wound body can be stopped over the long term to the minimum.

  The release agent of the present invention contains a thermoplastic silicone elastomer having a polar bond as a main component. Here, the main component refers to the component having the largest weight among the components constituting the release agent. The amount is usually 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more with respect to the total weight of the release agent.

Examples of the thermoplastic silicone elastomer having a polar bond include a block copolymer containing polysiloxane and a polar bond. Here, examples of the polar bond include a urea bond, a urethane bond, an amide bond, and an ester bond. In particular, those having a urea bond are preferable.
Examples of the polysiloxane include polydimethylsiloxane, polymethylpropylsiloxane, polydipropylsiloxane, polymethyloctylsiloxane, polydioctylsiloxane, polymethylphenylsiloxane, and polydiphenylsiloxane. These may be used alone or in combination of two or more.

  A commercially available polydimethylsiloxane containing a urea bond (manufactured by Wacker Chemie, product number: GENIOMER series) may be used.

  Specifically, JP-A-2005-179671, JP-A-2005-029795, JP-A-2005-002340, JP-A-2003-247173, JP-A-11-269430, JP-A-10-310628. And other thermoplastic silicone elastomers having various polar bonds, such as known thermoplastic silicone elastomers having polar bonds, which are described in Japanese Patent Publication No. JP-A-2006-521430, JP-T 2006-521420, etc. be able to.

  In such a thermoplastic silicone elastomer having a polar bond, the extraction amount of n-hexane is 0.6% by weight or less, so that the thermoplastic silicone elastomer having a polar bond is stored in a wound body. It is possible to suppress the transfer of contaminants from the release surface using the adhesive to the pressure-sensitive adhesive in contact therewith, and it is possible to suppress a decrease in adhesive strength.

  The extraction amount of n-hexane was obtained by immersing a thermoplastic silicone elastomer having a polar bond in n-hexane at room temperature for 72 hours, and performing a solution GC-MS measurement on the obtained supernatant under the conditions described later, followed by extraction. It means the value obtained by determining the product as n-undecane equivalent concentration.

  In this invention, after preparing or preparing the thermoplastic silicone elastomer which has a polar bond, the extraction amount of n-hexane mentioned above is realizable by processing the elastomer under reduced pressure. Here, the degree of decompression, the temperature, the treatment time, and the like in the decompression treatment are not particularly limited and can be adjusted as appropriate. For example, by setting the degree of vacuum to about 20 mmHg (ab.) Or less, the temperature of about 23 to 150 ° C., and about 1 hour to 1 week, damage to the elastomer, such as thermal decomposition, can be minimized relatively easily. The amount of n-hexane extracted.

  Moreover, even if it wash-processes the prepared or prepared elastomer with the poor solvent with respect to this, the extraction amount of n-hexane mentioned above is realizable. As the poor solvent here, it is preferable to select an organic solvent having a low ability to dissolve the thermoplastic silicone elastomer having a polar bond and a high ability to dissolve the cyclic siloxane contained in the elastomer. For example, an aliphatic hydrocarbon solvent and an aromatic hydrocarbon solvent are preferable. Specifically, n-pentane, n-hexane, n-heptane, etc. are mentioned as an aliphatic hydrocarbon solvent. Examples of the aromatic hydrocarbon solvent include benzene, toluene, xylene and the like. It is particularly preferable to use n-pentane or n-hexane because of the efficiency of the washing treatment and the ease of drying. The conditions for the washing treatment are not particularly limited, and for example, it is suitable to perform the treatment for about 1 hour to about 1 week within 1 to several times within a temperature range from room temperature to the boiling point of the solvent.

In the mold release agent of the present invention, an additive known in the art can be appropriately added as necessary within a range not inhibiting the achievement of the object of the present invention. Examples of such additives include ultraviolet absorbers, antioxidants, light stabilizers, fillers, and the like. Moreover, you may mix | blend well-known things, such as an antistatic agent, a pigment, a plasticizer, an antiblocking agent, suitably.
The ultraviolet absorber is not particularly limited, and examples thereof include commonly used ones such as salicylic acid series, benzophenone series, benzotriazole series, and cyanoacrylate series.
It does not specifically limit as antioxidant, For example, what is used normally, such as a phenol type (monophenol type, bisphenol type | system | group, high molecular type phenol type), sulfur type, phosphorus type, is mentioned.
Examples of the light stabilizer include hindered amine compounds.
Examples of the filler include calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide.

  The release layer is usually formed by coating and drying on the back surface of the base material layer constituting the surface protective film. This is because the silicone elastomer may be thermally decomposed to generate free siloxane when melt-molded at a high temperature. Therefore, it is preferable to use a coating method that can be molded at a lower temperature than melt molding. The surface protective film of the present invention only needs to evaporate the solvent by drying, and does not require crosslinking / curing such as UV irradiation.

When the release layer is applied, the solution concentration of the silicone elastomer used for the application can be appropriately adjusted in consideration of the film thickness after drying, productivity, and the like. Specifically, 0.1-30 wt% is mentioned.
The solvent used is not particularly limited as long as it can dissolve the thermoplastic silicone elastomer uniformly. For example, in the case of polydimethylsiloxane containing urea bond, methyl ethyl ketone, isopropyl alcohol, tetrahydrofuran, chloroform Etc.
The application method of the resin solution is not particularly limited, and a known technique can be used. Examples thereof include a coating method using a roll coater such as a gravure roll and a micro gravure roll, and a spraying method using a spray.

  The thickness of the release layer is not particularly limited, but it is preferable to reduce the thickness in consideration of cost and productivity, for example, 0.001 to 5 μm.

In the surface protective film of the present invention, the base material layer may be either a single layer or a laminate structure of two or more layers.
The material of the base material layer is not particularly limited, and for example, polyolefin-based, polycycloolefin-based, polyester-based, polyamide-based, polyvinyl alcohol-based, ethylene-polyvinyl alcohol-based copolymer, and the like can be used. A polyolefin type is preferable from the viewpoint of cost and moldability.

  The polyolefin-based copolymer is not particularly limited. For example, a propylene-based polymer such as polypropylene or a propylene component and an ethylene component, such as a block system or a random system; an ethylene-based polymer such as a low density, high density, or linear low density polyethylene. An olefin polymer such as an ethylene-α-olefin copolymer, an olefin polymer of an ethylene component such as an ethylene-vinyl acetate copolymer and an ethylene-methyl methacrylate copolymer and other monomers, and the like. These polyolefins may be used alone or in combination of two or more.

  In the surface protective film, each interface of the release layer, the base material layer, and the pressure-sensitive adhesive layer needs to have good adhesion. For example, an easy adhesion layer is provided between the base material layer and the release layer. The substrate layer surface may be subjected to an easy adhesion treatment. A polyurethane-based anchor coat agent, chlorinated polyolefin, or the like may be applied to the easy-adhesion layer, or an easy-adhesion layer containing an acid-modified polymer is in contact with the release layer as part of the base material layer having a laminated structure. You may form by coextrusion etc. so that it may arrange | position to one surface of a base material layer. As the easy adhesion treatment, known means such as corona treatment, ultraviolet treatment, and plasma treatment can be used.

  Here, the acid-modified polymer typically includes acid-modified polyolefin. The acid-modified polyolefin means a modified polyolefin containing a carboxyl group or an acid anhydride group. Examples of the acid-modified polyolefin include a method of graft-modifying an unsaturated carboxylic acid or an anhydride thereof to the polyolefin, a method of copolymerizing an α-olefin with an unsaturated carboxylic acid or an anhydride thereof, and the like. .

As the polyolefin, the above-described polyolefin or the like can be used. These polyolefins may be used alone or in combination of two or more.
Examples of the unsaturated carboxylic acid or its anhydride include anhydrides such as acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid. Of these, maleic anhydride is preferable.
In particular, maleic anhydride-modified polyolefin is preferable as the acid-modified polyolefin.
The maleic anhydride-modified polyolefin is a polyolefin copolymer in which a skeleton of maleic anhydride is introduced into the molecule. Maleic anhydride-modified polyolefins include ethylene-acrylic acid ester-maleic anhydride terpolymer, ethylene-vinyl acetate-maleic anhydride terpolymer, maleic anhydride graft-modified polyethylene, maleic anhydride graft Modified polypropylene, maleic anhydride graft modified ethylene-propylene copolymer, maleic anhydride graft modified ethylene-ethyl acrylate copolymer, maleic anhydride graft modified ethylene-vinyl acetate copolymer, maleic anhydride-α-olefin copolymer Polyethylene etc. are mentioned, These may be used independently and may use 2 or more types together.

You may mix | blend an additive with a base material layer as needed. As such an additive, those similar to those of the mold release agent, and further known additives such as an anti-glare agent and a lubricant can be appropriately blended.
The thickness of the base material layer is not particularly limited, but is preferably about 5 to 180 μm, more preferably about 10 to 130 μm, and more preferably about 20 to 100 μm in consideration of cost and moldability.

Although it does not specifically limit as a material which comprises an adhesive layer, The adhesive composition which has a rubber-type resin component as a main component is used preferably. This is because, particularly, in combination with the release agent of the present invention, excellent release properties can be exhibited.
The rubber-based resin component is not particularly limited, and those used as a base polymer for pressure-sensitive adhesives such as styrene-based elastomers, urethane-based elastomers, ester-based elastomers, and olefin-based elastomers can be used. In particular, when a styrene-based elastomer is used, a surface protective film can be easily formed by coextrusion, and a surface protective film having good temporary adhesion to an adherend can be provided.

  Specific examples of styrene elastomers include styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-ethylene / butylene copolymer-styrene (SEBS), and styrene-ethylene / propylene copolymer. -ABA type block polymer such as styrene (SEPS); styrene-butadiene (SB), styrene-isoprene (SI), styrene-ethylene-butylene copolymer (SEB), styrene-ethylene / propylene copolymer AB block polymer such as (SEP); Styrene random copolymer such as styrene-butadiene rubber (SBR); ABC type such as styrene-ethylene-butylene copolymer-olefin crystal (SEBC) Styrene-olefin crystal block polymer C-B-C type olefin crystal block polymer such as crystal-ethylene / butylene copolymer-olefin crystal (CEBC); ethylene-α-olefin, ethylene-propylene-α-olefin, propylene-α-olefin, etc. Examples thereof include olefin-based elastomers and hydrogenated products thereof. These rubber-based resin components may be used alone or in combination of two or more.

  In particular, when the rubber-based resin component has an unsaturated double bond derived from an olefin, the unsaturated double bond is preferably less from the viewpoint of improving heat resistance and weather resistance, and hydrogenated as necessary. It is preferable that

For example, as a styrene elastomer,
(1) a block copolymer of a styrene-based polymer block and an olefin-based or conjugated diene-based polymer block;
(2) a block copolymer of a styrenic polymer block and a random copolymer block of a styrenic monomer and an olefinic or conjugated diene monomer, and / or (3) a hydrogenated product thereof as a main skeleton In these styrenic elastomers, at least 80% of the double bonds of the conjugated diene moiety in the conjugated diene polymer block or in the random copolymer block of the styrenic monomer and the conjugated diene monomer are present in these styrenic elastomers. Saturated by hydrogenation is preferable. Moreover, it is preferable that it is saturated by hydrogenation 90% or more, and also 95-100%. This is to ensure heat resistance and weather resistance.

  The weight average molecular weight in terms of polystyrene measured by GPC (gel permeation chromatography) of the styrene elastomer is preferably in the range of 30,000 to 400,000, more preferably in the range of 50,000 to 200,000. This is because the cohesive force of the pressure-sensitive adhesive layer is ensured and adhesive residue on the adherend when the surface protective film is peeled off is prevented. Moreover, it is for ensuring a suitable adhesive force and preventing the increase in a solution viscosity and / or a melt viscosity at the time of preparation of an adhesive composition or manufacture of a surface protection film.

  By using a tackifier as a material constituting the pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer can be effectively increased. In this case, it is preferable to use the surface protective film in an amount that can prevent adhesive residue when the surface protective film is peeled off from the adherend. For example, the blending ratio of the tackifier is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and still more preferably 10 parts by weight or less with respect to 100 parts by weight of the rubber-based resin component.

Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymer systems and alicyclic copolymers, and coumarone-indene resins. , Terpene resin, terpene phenol resin, rosin resin such as polymerized rosin, (alkyl) phenol resin, xylene resin or hydrogenated products thereof are generally used for adhesives Things can be used without particular limitation. These tackifiers may be used alone or in combination of two or more.
In order to improve the peelability and weather resistance, it is more preferable to use a hydrogenated tackifier. Moreover, you may use the tackifier marketed as a blend with an olefin resin.

When a softener is further used as the material constituting the pressure-sensitive adhesive layer, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer can be effectively increased.
Examples of the softening agent include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, and derivatives thereof. Examples of these derivatives include those having an OH group or a COOH group at one or both ends. Specific examples include hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, and hydrogenated polyisoprene monool.
Of these, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, and olefinic softeners are preferred. This is because the adhesive strength of the pressure-sensitive adhesive layer can be appropriately increased. These softeners may be used alone or in combination of two or more.

  The number average molecular weight of the softening agent is not particularly limited, but is preferably in the range of 5000 to 100,000, and more preferably in the range of 10,000 to 50,000. This is because the material transfer from the pressure-sensitive adhesive layer to the adherend can be suppressed to prevent heavy peeling and the like, and the improvement of the adhesive strength can be ensured.

  When the pressure-sensitive adhesive composition is composed of a rubber-based resin component and a softening agent, the amount of the softening agent is not particularly limited, but the total amount of the rubber-based resin component and the softening agent is 100 parts by weight. On the other hand, the blending ratio of the softener is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and still more preferably 10 parts by weight or less. It is because the adhesive residue at the time of peeling from an adherend after high temperature or outdoor exposure can be reduced.

In addition, as a material which comprises an adhesive layer, you may mix | blend another additive as needed in the range which does not inhibit achievement of the subject of this invention. Examples of such additives include known ones such as ultraviolet absorbers, antioxidants, and adhesion progress inhibitors.
Examples of the ultraviolet absorber and the antioxidant are the same as described above.
Examples of the adhesion progress preventing agent include fatty acid amides, polyethyleneimine long-chain alkyl grafts, soybean oil-modified alkyd resins (for example, Arakawa Chemical Co., Ltd., trade name “Arachid 251”), tall oil-modified alkyd resins (for example, Arakawa). Chemical name, “Arachid 6300”, etc.).

Although the thickness in particular of an adhesive layer is not restrict | limited, It is about 0.5-50 micrometers, Preferably it is 1-30 micrometers, More preferably, it is 2-30 micrometers.
Accordingly, the total thickness of the surface protective film is suitably about 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm.

The base material layer and the pressure-sensitive adhesive layer of the surface protective film of the present invention can be laminated and integrated by co-extrusion by a known method such as an inflation method or a T-die method.
Moreover, the surface protection film of this invention is manufactured industrially as a wound body which wound the elongate film in roll shape, for example. When the surface protection film is a wound body, the outer peripheral pressure-sensitive adhesive layer adheres to the back surface of the base material layer. In the present invention, even in such a case, and when the surface protective film is, for example, a relatively wide wound body, the pressure-sensitive adhesive layer can be easily peeled from the back surface of the base material layer. it can. That is, the wound body can be easily rewound.

  Hereinafter, examples of the surface protective film of the present invention will be described in detail. However, the present invention is not limited to the following examples.

Example 1
The surface protective film of this example is composed of one base layer and one adhesive layer obtained by coextrusion, and after applying surface treatment to the surface of the base, a release agent is applied. Worked.
First, a block PP (product name: Prime Polypro J704LB, Prime Polymer Co., Ltd.) was prepared as a material constituting the base material layer.
As a material constituting the pressure-sensitive adhesive layer, a styrene-based elastomer (SEBS, manufactured by Kraton Polymer Co., Ltd., product number: G1657) made of a hydrogenated styrene-butadiene copolymer, and Alcon P-125 (Arakawa) as a tackifier A pressure-sensitive adhesive composition containing Chemical Industries, Ltd.) was kneaded with a twin-screw extruder and pelletized.
The base material layer and the pressure-sensitive adhesive layer made of each of the above materials are coextruded by the T-die method, and a pressure-sensitive adhesive film (width 1300 mm) having a two-layer structure of base material layer (thickness 34 μm) / pressure-sensitive adhesive layer (thickness 6 μm) Subsequently, the back surface of the base material layer was subjected to corona treatment.

As a material constituting the release agent, pellets (particle size: 2 to 7 mm) of a thermoplastic silicone elastomer containing a urea bond (manufactured by Wacker Chemie, product number: GENIOMER 200) were dried under reduced pressure at 100 ° C. for 15 hours.
Then, it melt | dissolved in tetrahydrofuran so that it might become 7 weight%, it apply | coated and dried so that the coating film thickness after drying might be set to 0.9 micrometer using the gravure coater, and it was set as the surface protection film. In addition, it sampled before winding up a part, and made the remainder into a wound body.

(Example 2)
A surface protective film having a release layer was prepared in the same manner as in Example 1 except that the thermoplastic silicone elastomer used in Example 1 was immersed in n-hexane at room temperature for 3 days.

(Example 3)
The pressure-sensitive adhesive layer of Example 1 was prepared as maleic anhydride-modified PP (product name: OREVAC G, Arkema Co., Ltd.) as the material constituting the substrate layer.
A surface protective film (width) comprising a base material layer (thickness: 34 μm) / adhesive layer (thickness: 6 μm) having a two-layer structure by coextruding the base material layer made of each of the above materials and the pressure sensitive adhesive layer by a T-die method. 1300 mm) was obtained.
The release layer was formed by coating the release agent of Example 1 in the same manner. At this time, corona treatment is not performed.

Example 4
As a material constituting the base material layer, an equal mixture of maleic anhydride-modified PP and block PP described above was prepared, and the pressure-sensitive adhesive layer of Example 1 was prepared as the pressure-sensitive adhesive layer.
A surface protective film (width) comprising a base material layer (thickness: 34 μm) / adhesive layer (thickness: 6 μm) having a two-layer structure by coextruding the base material layer made of each of the above materials and the pressure-sensitive adhesive layer by a T-die method. 1300 mm) was obtained.
The release layer was formed by coating the release agent of Example 2 in the same manner. At this time, corona treatment is not performed.

(Comparative Example 1)
The surface protective film of this comparative example was composed of one base layer and one adhesive layer obtained by coextrusion, and no release agent was applied.
A block PP was prepared as a material constituting the base material layer. As the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer of Example 1 was prepared.
In the same manner as in Example 1, the base material layer and the pressure-sensitive adhesive layer were coextruded by the T-die method to form a surface protective film.

(Comparative Example 2)
A surface protective film was produced in the same manner as in Example 1 except that the pretreatment (decompression treatment or n-hexane extraction) of the release agent was not performed.

(Comparative Example 3)
A surface protective film was obtained in the same manner as in Example 1 except that a 1% by weight toluene solution of a long-chain alkyl-based release agent (product name: Pyroyl # 1010, manufactured by Yushi Co., Ltd.) was used as the release agent.

(Comparative Example 4)
As a release agent, an ultraviolet curable silicone release agent XS56-A2982 (manufactured by GE Toshiba Silicone) was used, and after application, the release layer was formed by irradiating ultraviolet rays. Thus, a surface protective sheet was produced. The coating thickness after drying was 0.9 μm. Curing conditions were as follows: a light source with a fusion H bulb of 120 W / cm was used, and the film was wound immediately after irradiation at an irradiation distance of 10 cm and a line speed of 15 m / min.

(Evaluation)
(1) Self-back surface peeling force Each surface protection film was affixed on the flat acrylic board from the adhesive layer side. Moreover, what cut out each surface protection film to the magnitude | size of width 25mm x length 150mm was prepared separately.
Using the 2 kg rubber roller from the pressure-sensitive adhesive layer side, cut each surface protective film of Example and Comparative Example to the back surface of the surface layer of each surface protective film of Examples and Comparative Examples affixed to an acrylic plate to 2 m. Affixed at a rate of / min. This was left in a room at 23 ± 2 ° C. for 30 minutes. Thereafter, in accordance with JIS Z 0237, peeling between the surface protective films was performed, and the 180-degree peeling strength was measured at a speed of 30 m / min.

(2) Rewindability of wide winding body The film end of each 1300 mm wide winding body was grasped by hand and pulled, and the winding body was rewound by about 1 m. When rewinding, it was visually observed whether or not the surface protective film had partial elongation or deformation. The case where there was no partial expansion or deformation was judged as “◯”, and the case where there was partial expansion or deformation was judged as “x”.

(3) Transferability The surface protective film sampled from the wound body subjected to heat promotion treatment at 40 ° C. for 7 days after winding as the wound body against the adhesive strength A of the surface protective film sampled before winding as the wound body. The adhesive strength ratio (B / A) of the adhesive strength B was evaluated. That is, using a 2 kg rubber roller, a test piece cut out from each surface protective film to a size of 25 mm wide × 150 mm long was attached to a flat acrylic plate at a speed of 2 m / min from the pressure-sensitive adhesive layer side. . This was left in a room at 23 ± 2 ° C. for 30 minutes. Thereafter, in accordance with JIS Z0237, the surface protective film was peeled off from the acrylic plate, and the 180 ° peel strength was measured at a speed of 300 mm / min. The ratio (B / A) of adhesive strength is expressed as a percentage, where “◯” indicates a case of 85% or more, “Δ” indicates a case of 65% or more and less than 85%, and “x” indicates a case of less than 65%. It was judged.
The results are shown in Tables 1 and 2 below.

(4) Solution GC-MS measurement conditions Apparatus: JMS K-9 (manufactured by JEOL Ltd.)
GC column: ZB-1 (nonpolar), inner diameter 0.25 mm × length 30 m × film thickness 0.25 μm
Inlet temperature: 300 ° C
Injection volume: 1 μL
GC temperature rise: After holding at 40 ° C. for 4 minutes, the temperature is raised at 10 ° C./minute, and after reaching 300 ° C., held for 10 minutes.
Helium flow rate: 1.0 ml / min, split ratio 1:50
MS measurement range: 33-600amu (scan 500ms)
Ionization voltage: 70 eV
MS temperature: ion source, 230 ° C .; interface, 250 ° C.

  Not limited to various articles and members such as optical devices, metal plates, coated steel plates, resin plates, glass plates, etc. For all adherends that require prevention of dirt and scratches during transportation, processing or curing Can be used.

Claims (4)

  A mold release agent comprising a thermoplastic silicone elastomer having a polar bond as a main component and an extraction amount of n-hexane being 0.6% by weight or less.   The mold release agent according to claim 1, wherein the thermoplastic silicone elastomer having a polar bond is subjected to a reduced pressure treatment.   The mold release agent according to claim 1, wherein the thermoplastic silicone elastomer having a polar bond is washed with a poor solvent for the thermoplastic silicone elastomer. A surface protective film comprising a release layer containing the release agent according to claim 1.