JP2009191103A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protective film with high initial adhesive force, easily peeled off on peeling, hardly generating variation of adhesive force with age, hardly generating remaining of coating, hardly generating peeling off by wind pressure or the like, and further easily performing development from a wound body. <P>SOLUTION: The surface protective film is obtained by laminating a polyolefin-based base material and an adhesive layer by co-extrusion, and the adhesive layer contains a rubber-based resin component, an adhesion-imparting material and a fine particle having an average particle diameter of a primary particle of 100 nm or less. The rubber-based resin component is a block copolymer of a styrene-based polymer block (A) and an isobutylene-based polymer block (B) and/or a block copolymer of the styrene-based polymer block (A) and a random copolymer block (B') of styrene and isobutylene. The surface protective film contains the rubber-based resin composition and 1-30 pts.wt. of the fine particle based on 100 pts.wt. of the rubber-based resin composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface protective film for preventing adhesion of dust to the surface of an adherend and scratching of the surface of the adherend, and in particular, a surface on which a rubber-based adhesive layer is laminated on one side of a polyolefin-based substrate. It relates to a protective film.

  In order to protect various articles and members, a surface protective film is often temporarily attached to the surfaces of the articles and members. For example, various adherends such as synthetic resin plates, metal plates, decorative plywood, painted steel plates, painted resin plates, or various nameplates, especially the surfaces of coated steel plates and painted resin plates, during processing and transportation to these surfaces In order to prevent the adhesion of dirt and scratches on the surface, surface protection films are frequently used.

  This type of surface protective film has a structure in which an adhesive layer is laminated on one side of a film substrate. In general, a film substrate made of a thermoplastic resin is used as the film substrate. The surface protective film is affixed to the adherend surface using the adhesive force of the adhesive layer, thereby protecting the adherend surface. Before the adherend is used, the surface protective film is peeled off from the adherend surface. Therefore, the surface protective film is required to have an appropriate adhesiveness so that it can be easily temporarily attached to the surface of the adherend, and is good enough to be easily peeled off from the adherend surface. It is required to have peelability. Furthermore, there is a strong demand for no adhesive residue or adhesion marks on the adherend surface after peeling.

  By the way, car bodies and parts of automobiles that have been painted may be loaded onto trucks and ships and transferred to remote locations such as overseas. During the transfer, various floating substances such as dust, dust or rain may adhere to the coating film, which may cause the coating film to become dirty or discolored. Moreover, the coating film may be damaged by the collision of another substance or member.

  Therefore, in order to prevent such contamination, discoloration, or damage of the coating film, a surface protective film is temporarily attached to the coating film surface and transferred to a remote place such as overseas.

  In general, a film made of a thermoplastic resin is used as a surface protective film material for protecting this type of coating film.

  Surface protective films used for the surface protection of coating films such as the above-mentioned coated steel sheets and surface protective films for protecting various articles are generally temporarily attached to the surface to be protected by hand attachment and peeled off prior to use. The

  Therefore, the surface protective film has 1) sufficient initial adhesive strength, 2) good stability of adhesive strength with time, 3) difficult to peel off from the adherend due to wind pressure, and 4) deposition during peeling. 5) It is required that the adhesive can be easily peeled off from the body, and 5) adhesive residue is hardly generated on the adherend after peeling.

  As a surface protective film satisfying the above requirements 1) to 5), the following Patent Document 1 discloses a surface protective film composed of a block copolymer of a styrene polymer block and an olefin polymer block. By using a block copolymer of a styrene polymer block and an olefin polymer block as the pressure-sensitive adhesive, the above requirements 1) to 5) are satisfied.

  By the way, when manufacturing the surface protective film described in Patent Document 1, a method of obtaining a long surface protective film by using a melt coextrusion method is preferable in terms of increasing productivity. In the melt coextrusion method, the film substrate and the pressure-sensitive adhesive are coextruded to continuously produce the surface protective film. And the storage of a surface protection film is prepared by winding up this surface protection film and making it a wound body. At the time of use, the surface protective film may be drawn out from the wound body and cut to an appropriate length for use.

  However, in the surface protective film described in Patent Document 1, when the surface protective film is unwound from the wound body in use, that is, the force required for unfolding the wound body is relatively large, and the surface protective film can be smoothly unwound. There was something I couldn't do. Further, when the surface protective film is forcibly drawn out, the surface protective film is stretched and deformed, and the appearance may be impaired at the time of pasting.

  On the other hand, various methods have been proposed in the past in order to reduce the development force from the wound body in the surface protective film produced by the melt coextrusion method. For example, in the following Patent Document 2, after a film base material made of polyethylene and an adhesive layer are laminated by a melt coextrusion method, the surface opposite to the adhesive layer of the film base material, that is, the back surface is subjected to friction treatment. The developing force is reduced by rubbing the back surface of the film substrate.

Moreover, in the following patent document 3, the manufacturing method of the surface protection sheet by which the film base material layer, the adhesion layer, and the mold release layer were laminated | stacked is disclosed. Here, a film base material layer containing a polyolefin resin and an adhesive layer containing a thermoplastic elastomer are laminated by coextrusion. After the lamination, a release layer made of a release agent is continuously formed on the back surface of the film substrate, that is, the surface opposite to the side on which the adhesive layer of the film substrate layer is laminated. Here, the adhesive force between the release layer in the roll and the adhesive layer of the surface protective sheet of the next layer in contact with the release layer is reduced by forming the release layer.
WO2006 / 32183 JP-A-2-252777 JP 2003-41216 A

  As described above, the surface protective film and the surface protective sheet described in Patent Documents 2 and 3 can reduce the developing force from the wound body.

  However, the surface protective film described in Patent Document 1 is designed to have a low shear storage elastic modulus at 23 ° C. of the pressure-sensitive adhesive in order to enhance the adhesion at the initial stage when being applied to an adherend. For this reason, even when the deployment force reduction method described in Patent Document 2 is used, the force required to deploy from the wound body, that is, the deployment force, is difficult to decrease.

  On the other hand, if the release layer is formed using the method of Patent Document 3, sufficient developability can be expected. However, in this method, the release agent can be applied, dried, and cured in a short time until co-extrusion and winding. This process is necessary, and there are many problems to be solved such as equipment space and cost, productivity, and adhesive quality due to poor curing.

  In general, a surface protective film produced by a co-extrusion method has an advantage that the cost can be reduced and an adhesive residue hardly occurs compared to a surface protective film in which an adhesive layer is formed by a solution coating method. However, it has been difficult to design such that it can be easily and stably developed from the roll while maintaining the adhesion of the adherend in the initial stage of application to the adherend.

  An object of the present invention is to provide a surface protective film having good development properties as described above while eliminating the above-mentioned drawbacks of the prior art and maintaining physical properties such as initial adhesive strength and stability over time of adhesive strength. .

  According to the present invention, there is provided a surface protective film in which a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive containing a rubber-based resin component and a tackifier resin is laminated on a polyolefin-based substrate, and the rubber-based resin component and the polyolefin-based substrate. A surface protective film in which an adhesive layer comprising an adhesive containing a tackifier is laminated by a coextrusion method, wherein the rubber-based resin component comprises a styrene polymer block (A) and an isobutylene polymer block ( B) and / or a block copolymer of a styrene polymer block (A) and a random copolymer block (B ′) of styrene and isobutylene, wherein the adhesive is the rubber 1 to 30 parts by weight of fine particles having an average particle size of primary particles of 100 nm or less with respect to 100 parts by weight of the rubber-based resin component and the rubber-based resin component The surface protective film is provided.

In a specific aspect of the surface protective film according to the present invention, the shear storage elastic modulus measured at a frequency of 10 Hz at −30 ° C. and 70 ° C. of the adhesive layer is Ga- ₃₀ and Ga ₇₀ , respectively, and the fine particles are added. except that no shear storage modulus measured at a frequency of 10Hz at -30 ° C. and 70 ° C. of the adhesive layer as well as the cohesive layer when the _{Gb -30} and _{Gb 70, respectively, Ga -30} / _{Gb -30} and _Ga 70 / _{Gb 70} is characterized in that in the ranges of the following formula (1) and (2).

1.0 <Ga ₋₃₀ / Gb ₋₃₀ ≦ 1.5... Formula (1)
1.15 ≦ Ga ₇₀ / Gb ₇₀ ......... Formula (2)

Shear storage modulus Ga _-30 and Ga ₇₀ of the adhesive, by being within the range satisfying the above formula (1) and (2), even in the original low-temperature environment such as winter, the adherend Since the undesired peeling of the surface protective film from the film is more difficult to occur and the expression (2) is satisfied, the variation of the adhesive force contacting the adherend of the surface protective film with time is further suppressed.

Preferably, the shear storage elastic modulus Ga- _{30 at} −30 ° C. measured at a frequency of 10 Hz of the adhesive layer is 5 × 10 ⁶ Pa or less, and the shear storage elastic modulus Ga _{70 at} 70 ° C. is 3.2 × 10 ^5. Pa or higher.

  In another specific aspect of the surface protective film according to the present invention, the fine particles having an average primary particle size of 100 nm or less are silica fine particles. Among the fine particles, silica fine particles have good compatibility with the molded elastomer, so that the transparency of the adhesive layer can be increased.

  Details of the present invention will be described below.

  The inventors of the present application have made extensive studies on a surface protective film in which an adhesive layer comprising an adhesive containing a rubber-based resin component and a tackifier is laminated on the surface of a polyolefin-based substrate. As a component, a block copolymer of a styrene polymer block (A) and an isobutylene polymer block (B), a random copolymer block (B ′) of a styrene polymer block (A), styrene and isobutylene, and In the pressure-sensitive adhesive, and 100 parts by weight of the rubber-based resin component in the pressure-sensitive adhesive, the fine particles having an average primary particle diameter of 100 nm or less are contained in the range of 1 to 30 parts by weight. The present inventors have found that the above problems can be achieved, and have reached the present invention.

(Rubber resin component)
The pressure-sensitive adhesive for the surface protective film according to the present invention contains a rubber-based resin component. The rubber resin component is a block copolymer of a styrene polymer block (A) and an isobutylene polymer block (B) and / or a random copolymer of a styrene polymer block (A), styrene and isobutylene. It is a block copolymer with a block (B '). In other words, the rubber-based resin component contains at least one of the following block copolymers (1) and (2).

(1) A block copolymer of a styrene polymer block (A) and an isobutylene polymer block (B). As the block copolymer is not particularly limited, for example, A-B, A-B- A, copolymers thereof represented by such _{(A-B) n} or _{(A-B) n} X. In addition, n is an integer greater than or equal to 1, and X is a residue by a coupling agent.

  (2) A block copolymer of a styrene polymer block (A) and a random copolymer block (B ′) of styrene and isobutylene. Examples of such a block copolymer include the following (2-1) to (2-4).

(2-1) Block (A) and block (B ′) combined: AB ′ block copolymer (2-2) Among styrene and isobutylene, tapered block (C) in which styrene gradually increases Including: AB′-C block copolymer (2-3) Including styrenic polymer block (A) instead of taper block (C): AB′-A block copolymer ( 2-4) Repeats of (2-1) to (2-3) and those in which these are bonded at an arbitrary ratio: (AB ′) _n , (AB ′) _n X, (AB ′) _-C) n X, such as _{(A-B'-A) n} X.

  In addition, n is an integer greater than or equal to 1, and X is a residue by a coupling agent.

  The rubber-based resin component has polymer blocks (B) and (B ′) containing isobutylene. However, since polyisobutylene does not have an aliphatic unsaturated bond, hydrogenation is unnecessary, Stability and weather resistance can be improved.

  In the rubber-based resin component, the content ratio of the constituent components of styrene and isobutylene is preferably in the range of 5:95 to 60:40, more preferably in the range of 7:93 to 40:60. When the total amount of styrene and isobutylene is 100% by weight, when the content ratio of styrene is less than 5% by weight, the cohesive force of the adhesive layer decreases, and adhesive residue remains on the adherend when the surface protective film is peeled off. If it exceeds 60% by weight, the adhesive strength may be insufficient and sticking to the adherend may be difficult.

  In the rubber-based resin component comprising the block copolymer of (2) above, in the configuration containing the block (C), the styrene content and the block in the block (A) with respect to the total of all monomers constituting the block copolymer The styrene content ratio that is the sum of the styrene content in (C) is preferably in the range of 3 to 50% by weight, more preferably in the range of 5 to 40% by weight, and still more preferably in the range of 5 to 25% by weight. When the styrene content ratio, which is the sum of the styrene contents of the block (A) and the block (C), is less than 3% by weight, the cohesive force of the pressure-sensitive adhesive layer is reduced, and the adhesive is applied to the adherend when the surface protective film is peeled off. When the amount exceeds 50% by weight, the adhesive strength of the pressure-sensitive adhesive layer may be insufficient, and it may be difficult to attach to the adherend. The ratio of the styrene content in the block (A) to the total of all monomers constituting the rubber-based resin component is preferably 3% by weight or more, more preferably 3 to 20% by weight.

  The polystyrene-equivalent weight average molecular weight measured by GPC (gel permeation chromatography) of the rubber-based resin component is preferably in the range of 30000-400000, more preferably in the range of 50000-200000. When the weight average molecular weight is less than 30000, the cohesive force of the adhesive layer is lowered, and thus, adhesive residue may be generated on the adherend when the surface protective film is peeled off. When the weight average molecular weight exceeds 400,000, the adhesive strength is insufficient, and the melt viscosity tends to increase during the production of the surface protective film.

(Tackifier)
The adhesive layer of the surface protective film according to the present invention further includes a tackifier in addition to the specific rubber-based resin component.

  Examples of the tackifier include terpene resin, paraffin process oil, naphthene process oil, aromatic process oil, castor oil, tall oil, natural oil, liquid polyisobutylene resin, polybutene, and the like. Specifically, as the terpene resin, Yashara Chemical Co., Ltd., trade name: Clearon, as the paraffinic process oil, Idemitsu Kosan Co., Ltd., trade name: Diana Process Oil, manufactured by Kobe Oil Chemical Co., Ltd., trade name: SYNTAC, Examples of the liquid polyisobutylene resin include BASF Corp., trade name: Glysopearl, and examples of polybutene include Idemitsu Kosan Co., Ltd., trade name: Idemitsu Polybutene. These may be used independently and 2 or more types may be used together.

  The polystyrene-converted weight average molecular weight measured by GPC (gel permeation chromatography) of the tackifier is preferably in the range of 300 to 5000, more preferably in the range of 300 to 4000. More preferably, it is the range of 300-3000. If the weight average molecular weight is too small, the cohesive force of the pressure-sensitive adhesive layer is reduced, and thus adhesive residue may be generated on the adherend when the surface protective film is peeled off. On the other hand, even if the weight average molecular weight exceeds 5000, the compatibility with the rubber-based resin component is deteriorated, and adhesive residue may be generated on the adherend when the surface protective film is peeled off.

  In the adhesive layer, the tackifier is preferably contained in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the rubber-based resin component. More preferably, it is 10-30 weight part. If the amount is less than 5 parts by weight, the shear storage elastic modulus of the adhesive layer may be too high, and the adhesive force to the adherend may be insufficient. When the amount exceeds 40 parts by weight, the cohesive force of the pressure-sensitive adhesive is insufficient, and adhesive residue may easily occur when the surface protective film is peeled off from the adherend.

(Fine particles)
In the pressure-sensitive adhesive layer of the surface protective film according to the present invention, the pressure-sensitive adhesive further includes fine particles having an average primary particle size of 100 nm or less. By including fine particles having an average particle size of 100 nm or less in the adhesive layer, the developing force can be reduced while maintaining the physical properties of the adhesive.

  This is because when particles of 100 nm or less are added to the pressure-sensitive adhesive, the particles of 100 nm or less strongly interact and coalesce with each other to form a three-dimensional network of particles in the pressure-sensitive adhesive. This is considered to increase the shear storage modulus of the rubber plateau region.

  When the primary particle diameter of the fine particles exceeds 100 nm, it is difficult to form a three-dimensional fine particle network structure in the pressure-sensitive adhesive, and it is difficult to obtain an effect of increasing the shear storage elastic modulus in the rubber plateau region of the pressure-sensitive adhesive layer. Moreover, the smoothness of the surface of the adhesive layer of the surface protective film cannot be ensured, and it is difficult to obtain the adhesive physical properties required for the surface protective film.

  The fine particles are contained in the range of 1 to 30 parts by weight with respect to 100 parts by weight of the rubber-based resin component. Preferably it is 3-25 weight part. If it is less than 1 part by weight, the effect of increasing the shear storage modulus of the rubber plateau region of the adhesive layer cannot be obtained, and the effect of lowering the developing force is not achieved. When it exceeds 30 parts by weight, the shear storage modulus of the rubber plateau region of the adhesive layer becomes too high. Therefore, sufficient adhesive properties necessary for the surface protective film cannot be obtained.

  The particle diameter of the fine particles can be observed and evaluated with a transmission electron microscope. The primary particle diameter is an average value of the particle diameters of 100 primary particles arbitrarily extracted from the visual field observed and evaluated by a transmission electron microscope. The primary particles are the particle diameters of the fine particles supplied to form the pressure-sensitive adhesive, and are the particle diameters before being bonded by the interaction between the fine particles in the pressure-sensitive adhesive.

  Examples of the fine particles include inorganic compounds such as alumina, silica, zirconia, and carbon black, and two or more kinds of fine particles may be used in combination. Specific products include, for example, carbon black such as SEAST 6, SEAST 600, SEAST s (Toyo Carbon Co., Ltd.); Aerosil AER series (Nippon Aerosil Co., Ltd.), Leosir series ( Fine powder silica such as manufactured by Tokuyama Corporation.

  Among these, silica fine particles are preferable. Since the silica fine particles have good compatibility with the rubber-based resin component, the transparency of the pressure-sensitive adhesive can be ensured.

(Other ingredients blended in the adhesive layer)
In the surface protective film according to the present invention, if necessary, a stabilizer such as a light-resistant agent and an antioxidant, an adhesion progress preventing agent, and the like may be added to the pressure-sensitive adhesive layer as long as the adhesive performance is not impaired.

  The light stabilizer is not particularly limited, and examples thereof include ultraviolet absorbers such as salicylic acid, benzophenone, benzotriazole, and cyanoacrylate, and light stabilizers such as hindered amine compounds. The antioxidant is not particularly limited, and examples thereof include phenol-based (monophenol-based, bisphenol-based, polymer-based phenol-based), sulfur-based and phosphorus-based antioxidants.

  Examples of the anti-adhesion progress 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 Co., Ltd., trade name “Arachid 6300”, etc.).

(Polyolefin substrate)
The polyolefin constituting the polyolefin-based substrate is not particularly limited, and polyolefins such as polypropylene and polyethylene, polyolefins mixed with olefin-based elastomers, and the like can be used.

  Although the thickness of the said polyolefin-type base material changes with purposes of use, 20-100 micrometers is preferable. If it is less than 20 μm, for example, the protective performance of the adherend such as a coating film may not be sufficiently exhibited. If it exceeds 100 μm, handling properties and sticking properties may be deteriorated, which is disadvantageous in terms of cost. .

  In this invention, the well-known additive normally mix | blended in this field | area may be mix | blended with the polyolefin-type base material. Examples of additives include stabilizers such as light-proofing agents and antioxidants that can be added to the adhesive layer, as well as lubricants, antistatic agents, rust inhibitors, and pigments. For example, in the case of a surface protective film that is exposed to ultraviolet rays, such as a surface protective film that protects a coating film for automobiles, it is preferable to add a weathering agent to the polyolefin-based substrate.

  As a weathering agent blended in the polyolefin base material, an ultraviolet shielding agent and / or an ultraviolet stabilizer are preferably used.

  Examples of the ultraviolet shielding agent include inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, and carbon black. These may be used alone, or may be used by blending a plurality of them.

  Examples of the UV stabilizer include UV stabilizers such as salicylic acid, benzophenone, benzotriazole, and cyanoacrylate, and light stabilizers such as hindered amine compounds.

  As for these additives, only 1 type may be used and 2 or more types may be used together.

(Surface protection film)
In the surface protective film according to the present invention, the shear storage elastic modulus at a frequency of 10 Hz of the pressure-sensitive adhesive layer is preferably 5 × 10 ⁶ Pa or less at −30 ° C.

  When the surface protective film is temporarily attached to the adherend and stored outdoors in winter, the temperature of the surface protective film may be lower than 0 ° C. In this case, in the conventional surface protective film, the adhesive force of the surface protective film is lowered, and the surface protective film may be peeled off naturally from the adherend. Furthermore, the surface protective film may be peeled off by wind pressure when transported by a carrier car or the like after pasting, and it may be necessary to perform pasting again.

The inventors of the present application have found that the natural peeling phenomenon of the surface protective film when stored outdoors in winter and the peeling due to the wind pressure during transportation are related to the shear storage modulus at −30 ° C. If the shear storage modulus at −30 ° C. of the film is a specific value, that is, 5 × 10 ⁶ Pa or less, the surface protective film does not peel from the adherend when stored outdoors in winter, and is temporarily attached. It was found that peeling was not easily caused by wind pressure during transportation.

  By setting the shear storage modulus at −30 ° C. at a frequency of 10 Hz within the above specific range, the initial adhesive strength is particularly good, and the surface protective film is peeled off from the adherend when stored outdoors in winter. It is difficult to maintain a temporary wearing state. Further, the surface protective film is very difficult to peel off due to the wind pressure during transportation.

In the surface protective film according to the present invention, the shear storage elastic modulus at 10 Hz of the pressure-sensitive adhesive layer is preferably 3.2 × 10 ⁵ Pa or more at 70 ° C. When the shear storage elastic modulus at 70 ° C. is 3.2 × 10 ⁵ Pa or more, the stability with time of the adhesive force is further enhanced, and the adhesive force is more difficult to vary with time. When the shear storage modulus at 70 ° C. is less than 3.2 × 10 ⁵ Pa, the adhesive force may vary with time.

In the present invention, the shear storage modulus at a frequency of 10Hz the adhesive layer preferably is in the range of ^{2.5 × 10 5 ~8 × 10 5} Pa at 23 ° C.. If it exceeds 8 × 10 ⁵ Pa, the surface protective film is easily peeled off from the adherend during transportation due to insufficient adhesive strength, and if it is less than 2.5 × 10 ⁵ , workability in the peeling process may be deteriorated or peeled off. There is a possibility that glue may easily remain.

  By setting the shear storage elastic modulus at −30 ° C. and the shear storage elastic modulus at 23 ° C. and 70 ° C. at a frequency of 10 Hz to the above specific ranges, 1) initial adhesive force and 2) adhesion of the surface protective film Force stability over time and 4) peeling workability can be further improved.

In the present invention, preferably, the shear storage modulus _{Ga -30} and _{Ga 70} at -30 ° C. and 70 ° C. of the adhesive layer, it is preferable to satisfy the following equation (1) and (2) respectively.

1.0 <Ga ₋₃₀ / Gb ₋₃₀ ≦ 1.5... Formula (1)
1.15 ≦ Ga ₇₀ / Gb ₇₀ ......... Formula (2)

In the formula (1), Gb- ₃₀ is a shear storage elastic modulus at −30 ° C. of the adhesive layer similarly configured except that the fine particles are not added. In the formula (2), Gb ₇₀ is the shear storage elastic modulus at 70 ° C. of the pressure-sensitive adhesive layer configured in the same manner as described above except that fine particles are not added. In addition, each said shear storage elastic modulus is a shear storage elastic modulus in frequency 10Hz similarly to the above.

  By satisfying the formulas (1) and (2), the effect of adding fine particles can be ensured.

(Use)
The surface protective film of the present invention can be applied to various adherends. That is, the surface protective film of the present invention can be suitably used for protecting the surface of an adherend made of a synthetic resin such as an acrylic resin or a material having polarity such as a metal. Even in that case, no adhesive residue is likely to occur, and good peeling performance can be obtained. That is, the adherend surface to which the surface protective film of the present invention is applied is not particularly limited.

  As a method for producing the surface protective film, a method of laminating and integrating the polyolefin base material and the pressure-sensitive adhesive composition by coextrusion is employed. As a specific method, a known method such as an inflation method or a T-die method can be used. Among these, a co-extrusion method using a T-die is preferable because quality can be improved and production can be made economically.

  In the surface protective film according to the present invention, an adhesive layer made of an adhesive containing a rubber-based resin component, a tackifier, and primary particles of the specific average particle diameter is laminated on a polyolefin-based substrate. While maintaining various performances such as sticking performance and removability, the deployment force when the surface protective film is deployed from the roll can be sufficiently reduced.

  Hereinafter, the present invention will be clarified by giving examples and comparative examples of the present invention. The present invention is not limited to the following examples.

  In the following examples and comparative examples, a surface protective film in which an adhesive layer was laminated on one side of a polyolefin-based substrate was produced and evaluated by a T-die coextrusion method.

(Materials used)
[Rubber resin component]
SIBS; manufactured by Kaneka Corporation, product number: Shibster 102T, block copolymer of styrene and isobutylene SEBS; manufactured by Kraton Polymer Co., Ltd., product number: G1652, block copolymer of styrene, ethylene, and butylene

[Tackifier]
PA95: Paraffinic process oil manufactured by Kobe Oil Chemical Co., Ltd., trade name: SYNTAC PA95 (weight average molecular weight = 400)
Clearon LH; manufactured by Yashara Chemical Co., Ltd., hydrogenated terpene resin, trade name: Clearon LH (weight average molecular weight = 1000)

[Silica fine particle material]
Fumed silica HM-20L; silica fine particles (average primary particle size 12 nm) manufactured by Tokuyama Corporation
Carplex FPS: silica fine particles (average primary particle size 10 nm) manufactured by DEGUSSA

[Alumina particulate material]
AW50-74; Micron alumina fine particles (average primary particle size 55 μm)
The average primary particle size of the fine particles was observed with a transmission electron microscope (JEM-1200EX II, manufactured by JEOL Ltd.), and the average value of the particle sizes of any 100 particles in the field of view was defined as the average primary particle size.

[Polyolefin base material]
PB170A; block polypropylene PEX6800A manufactured by Sun Allomer Co., Ltd. Titanium oxide manufactured by Tokyo Ink Co., Ltd., trade name: PEX6800A White
UVT-52; a hindered amine light stabilizer manufactured by Tokyo Ink Co., Ltd., trade name: PPM UVT-52

Example 1
A pressure-sensitive adhesive composition containing 100 parts by weight of SIBS (1) as a rubber-based resin component, 20 parts by weight of (PA95) as a tackifier, and 10 parts by weight of silica fine particles (HM-20L), and polypropylene (PB170A) ) 100 parts by weight, titanium oxide (PEX6800A) 20 parts by weight, and light stabilizer (UVT-52) 3 parts by weight dry blended with a polypropylene substrate composition by T-die method. The surface protective film in which a 10 μm thick adhesive layer was laminated on a 50 μm thick polypropylene base material was continuously wound to obtain a wound body.

(Example 2 and Comparative Examples 1 to 4)
A surface protective film was obtained in the same manner as in Example 1 except that the types of rubber-based resin components, tackifiers and fine particles used, and the blending ratio thereof were changed as shown in Table 1 below.

(Evaluation)
The characteristics of each surface protective film obtained as described above were evaluated in the following manner.

(1) Unfolding force Prepare a roll of each surface protective film with a width of 100 mm, and the force (maximum value) required for unwinding when the surface protective film is unwound at each speed of 300 mm / min and 20 m / min. It measured and it was set as deployment force (N / 100mm).

(2) Shear storage elastic modulus A pressure-sensitive adhesive composition corresponding to each pressure-sensitive adhesive layer was pressed to produce a sheet having a thickness of 1 mm, and the shear storage elastic modulus of this sheet sample was measured using a dynamic viscoelasticity spectrum measurement device (IT measurement). Measured in the range of −50 ° C. to + 150 ° C. at a frequency of 10 Hz and a heating rate of 6 ° C./min, and determined for each shear storage modulus at −30 ° C., 23 ° C. and 70 ° C. It was.

(3) Shear storage modulus ratio Each shear storage modulus ratio at −30 ° C. and 70 ° C. before and after blending the fine particles was determined.

That is, the shear storage elastic modulus at −30 ° C. and 70 ° C. of the pressure-sensitive adhesive before mixing the fine particles is Gb- ₃₀ and Gb ₇₀ , respectively, and the shear storage elastic modulus of the pressure-sensitive adhesive to which fine particles are added is Ga- ₃₀ and Ga _70. and then to determine the respective shear storage modulus ratio _Ga -30 _{/ Gb -30} and _{Ga 70} / _Gb 70.

_{Incidentally, Gb -30} and _{Gb 70} were also measured under the same conditions as shear storage modulus (2).

(4) Initial adhesive strength Each surface protective film was applied to a coated steel sheet for automobiles (alkyd melamine coating film, surface gloss 80%) in an environment of room temperature 23 ° C. and relative humidity 65%. In this example, a 2 kg pressure-bonded rubber roller was attached by running at a speed of 300 mm / min and left in that state for 30 minutes. Next, based on JIS Z0237, 180 degree peel strength in a 25 mm width was measured at a speed of 300 mm / min. The peel strength measured in this manner was taken as the initial adhesive strength.

(5) Initial peeling force Each surface protection film is applied to a coated steel sheet for automobiles (alkyd melamine coating, surface gloss 80%) in an environment of room temperature 23 ° C. and relative humidity 65%, and the back surface of the polyolefin substrate. In this example, a 2 kg pressure-bonded rubber roller was attached by running at a speed of 300 mm / min and left in that state for 30 minutes. Next, in accordance with JIS Z0237, the 180 degree peel strength at a width of 25 mm was measured at a speed of 30 m / min. The peel strength measured in this way was taken as the initial peel force.

(6) Adhesive strength with time Each surface protective film was applied to a coated steel sheet for automobiles in the same manner as in the case of measuring the initial peel force in (4), and left in a 70 ° C. gear oven for 7 days in that state. In accordance with JIS Z0237, a 180 degree peel strength at a width of 25 mm was measured at a speed of 300 mm / min.

(7) Contamination evaluation of adherends The adherend surface after the peel test of (4) to (6) was visually observed, and contamination was evaluated based on the presence or absence of adhesive residue.

[Evaluation criteria for adhesive residue]
○: No adhesive residue ×: Adhesive residue generated

(8) Peeling test by wind pressure Each surface protection film is cut to a width of 100 mm, a 2 kg pressure roller is applied to an automotive coated steel sheet (alkyd melamine coating, surface gloss 80%), and 300 mm on the back of the polyolefin substrate. Attached by running at a speed of / min and left in an ambient temperature atmosphere of 0 ° C. for 30 minutes in that state.

  Next, the steel plate obtained above was placed horizontally on a pedestal, and after performing a wind tunnel experiment at a wind speed of 22 m in an ambient temperature atmosphere of 0 ° C. for 2 hours, the distance at which the film was peeled was measured. This was evaluated at n = 10, and the case where it was peeled off by 10 mm or more was regarded as defective, and the peeling performance by wind pressure was evaluated according to the following evaluation criteria.

[Evaluation criteria for peeling performance by wind pressure]
○: Defect rate is 20% or less Δ: Defect rate is over 20% and less than 40% X: Defect rate is 40% or more The results are shown in Table 1 below.

Claims (3)

A surface protective film in which an adhesive layer made of an adhesive containing a rubber-based resin component and a tackifier is laminated on a polyolefin-based substrate by a coextrusion method,
The rubber-based resin component is a block copolymer of a styrene polymer block (A) and an isobutylene polymer block (B) and / or a random copolymer of a styrene polymer block (A), styrene and isobutylene. A block copolymer with a combined block (B ′),
The pressure-sensitive adhesive contains 1 to 30 parts by weight of fine particles having an average particle diameter of primary particles of 100 nm or less with respect to 100 parts by weight of the rubber-based resin component and the rubber-based resin component. Protective film. The shear storage modulus measured at a frequency of 10 Hz at −30 ° C. and 70 ° C. of the adhesive layer is Ga- ₃₀ and Ga ₇₀ , respectively, and is the same as the adhesive layer except that the fine particles are not added. shear storage modulus measured at a frequency of 10Hz at -30 ° C. and 70 ° C. of the adhesive layer when the _{Gb -30} and _{Gb 70, respectively,} Ga _{-30 / Gb} -30 and _Ga 70 / _{Gb 70} is below each The surface protective film according to claim 1, wherein the expressions (1) and (2) are satisfied.
1.0 <Ga ₋₃₀ / Gb ₋₃₀ ≦ 1.5... Formula (1)
1.15 ≦ Ga ₇₀ / Gb ₇₀ ......... Formula (2) The surface protective film according to claim 1, wherein the fine particles are silica.