JP2007161882A - Surface-protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-protective film which is good in initial adhesion to an adherend having irregularities, less in the increase of adhesion with time and free from the presence of the residual adhesive. <P>SOLUTION: The surface-protective film is obtained by integrally laminating an adhesive layer (II) on a substrate layer (I) composed of an olefinic resin. The adhesive layer (II) contains a hydrogenated styrene-conjugated diene copolymer (a) and a polyethylene resin (b), wherein the formulation ratio of both the components is 10-50 pts.wt. of (b), relative to 100 pts.wt. of (a). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface protective film, and more specifically, adherends of various name plates such as synthetic resin plates, metal plates, decorative plywood, coated coated steel plates, painted resin plates, diffusion plates, diffusion films, brightness enhancement films, and the like. An adherend having an uneven surface (having a centerline average surface roughness Ra of 0.1 to 2 μm as defined in JIS B0601) on the surface thereof. The present invention relates to a surface protective film to be protected. The surface protective film referred to in the present invention includes a surface protective sheet and a surface protective tape.

  Conventionally, to prevent the surface from being stained or scratched when processing or transporting various nameplates such as synthetic resin plates, metal plates, decorative plywood, or optical films, Protective films are frequently used.

  Such a surface protective film generally has a configuration in which an adhesive layer is formed on one side of a base material (support) made of thermoplastic resin or paper. And when using it, the surface of the adherend is protected by temporarily attaching to the surface of the adherend such as a synthetic resin plate from the adhesive layer side, and the function of preventing the adhesion and scratches of the adherend is exhibited. .

  The surface protective film must be able to be temporarily attached to the surface of the adherend and have an adhesive strength that is maintained. If the adhesive strength is low, the surface protective film may float immediately after being applied or turn over with time. It is necessary to design adhesive strength. Adhesive strength design is important especially for adherends with uneven surfaces, and it is necessary to consider issues such as adhesive entering the uneven surface over time, increasing the adhesive force, and generating adhesive residue. .

Various attempts have been made to deal with the above problems. For example, in Patent Document 1, a hydrogenated styrene-conjugated diene block copolymer and an ethylene-α-olefin copolymer or a propylene-α-olefin copolymer and an adhesive are used. Although an improvement by a resin composition comprising an imparting resin has been proposed, the centerline average surface roughness Ra is 2 μm or more, although it is effective for adherends with large irregularities, the centerline average surface roughness Ra is For adherends of 2 μm or less, the adhesive strength becomes high and may be difficult to peel off.
JP-A-6-240216

  In view of the above-mentioned problems of the prior art, the object of the present invention is that initial adherence to an adherend is good with respect to an uneven adherend, there is little increase in adhesive strength over time, and there is no adhesive residue. The object is to provide a surface protective film.

  As a result of intensive studies to achieve the above object, the inventor, as a pressure-sensitive adhesive layer, in a surface protective film in which a pressure-sensitive adhesive layer is laminated and integrated with a base material layer made of a polyolefin-based resin, When a hydrogenated styrene-conjugated diene copolymer and a polyethylene resin are used at a specific ratio, they have a good initial adhesive strength when applied to an uneven adherend, and the adhesive strength is good even over time. It has been found that a surface protective film that is stable and has no adhesive residue can be obtained. Further studies were conducted on these findings, and the present invention was completed.

That is, according to the first invention of the present invention, a surface protective film in which a pressure-sensitive adhesive layer (II) is laminated and integrated with a base material layer (I) made of a polyolefin resin,
The pressure-sensitive adhesive layer (II) contains a hydrogenated product (a) of a styrene-conjugated diene copolymer and a polyethylene resin (b), and the blending ratio of both components is that (a) is 100 parts by weight. Thus, a surface protective film is provided in which (b) is 10 to 50 parts by weight.
According to the second invention of the present invention, in the first invention, the hydrogenated product of the styrene-conjugated diene copolymer (a) comprises (i) a styrene polymer block (A), styrene, (AB) n consisting of a random polymer block (B) of a conjugated diene, or a hydrogenated product of an (AB) mX type block copolymer (where n is 1 or more, m is an integer of 2 or more, X represents a coupling agent residue.), (Ii) (AB ′) n, (AB ′) n comprising a styrene polymer block (A) and a conjugated diene polymer block (B ′). -A or (AB ') hydrogenated product of nX type block copolymer (where n is 1 or more, X represents a coupling agent residue), and (iii) styrene polymer block (A ), A random polymer block (B) of styrene and conjugated diene, and conjugated with styrene It is at least one selected from the group consisting of hydrogenated products of an ABC type block copolymer comprising a tapered block (C) in which styrene gradually increases among copolymers with diene. A surface protective film is provided.
Further, according to the third invention of the present invention, in the first or second invention, the hydrogenated product of the styrene-conjugated diene copolymer (a) is a hydrogen of the ABC type block copolymer. A surface protective film characterized by being an additive is provided.

According to a fourth invention of the present invention, in any one of the first to third inventions, the polyethylene resin (b) is a linear low density polyethylene (LLDPE) produced by low pressure ion polymerization. A surface protective film is provided.
According to a fifth aspect of the present invention, there is provided a surface protective film according to any one of the first to fourth aspects, wherein the polyolefin resin used for the base material layer (I) is polyethylene. Provided.
Furthermore, according to the sixth invention of the present invention, in any one of the first to fifth inventions, it is affixed to an adherend having a centerline average surface roughness Ra (JIS B0601) of 0.1 to 2 μm. A surface protective film is provided.
Furthermore, according to the seventh invention of the present invention, in any one of the first to sixth inventions, a surface protective film is provided which is molded by a coextrusion method.

The surface protective film of the present invention can provide a product having a good initial adhesive force when adhered to an uneven adherend, stable adhesive force over time, and no adhesive residue. In addition, since both layers are laminated and integrated by coextrusion, both layers are firmly integrated with chemical bonding by polarity and physical bonding by the anchor effect. The layers do not separate.
Therefore, the surface protective film of the present invention has a strong laminate integration of the base material and the pressure-sensitive adhesive layer in addition to the above-described excellent performance of the pressure-sensitive adhesive layer. There is an excellent effect that no residue is produced and the surface of the adherend is not contaminated.

  Hereinafter, the surface protective film of the present invention will be described in detail.

  The surface protective film of the present invention is a surface protective film in which a pressure-sensitive adhesive layer (II) is laminated and integrated on a base material layer (I) made of a polyolefin resin, and the pressure-sensitive adhesive layer (II) is made of styrene. -Containing dihydrogenated conjugated diene copolymer (a) and polyethylene resin (b), and the blending ratio of both components is (a) 100 parts by weight, (b) 10-50 It is a weight part.

1. Base material layer (I)
The polyolefin resin constituting the substrate of the surface protective film of the present invention is not particularly limited. For example, ethylene homopolymer (low density polyethylene, medium density polyethylene, high density polyethylene), propylene homopolymer, Linear (linear) low density polyethylene, copolymer of ethylene and α-olefin other than ethylene or propylene, propylene and α-olefin copolymer other than ethylene or propylene, propylene-ethylene random copolymer or block copolymer Examples thereof include polymers and polyolefin alloy resins.
Moreover, these polyolefin resin may be used independently and 2 or more types may be used together.
Furthermore, it does not specifically limit as alpha olefins other than the said ethylene or propylene, For example, 1-butene, 1-hexene, 4-methyl-1- pentene, 1-octene etc. are mentioned. These α-olefins may be used alone or in combination of two or more.

  The polyolefin-based resin (or resin composition) includes a filler, a softening agent, a plasticizer, a lubricant, a flame retardant, an antistatic agent, a colorant, an oxidation agent, as necessary, as long as the object of the present invention is not impaired. One kind or two or more kinds of various additives such as an inhibitor (anti-aging agent), a heat stabilizer, a light stabilizer, and an ultraviolet absorber may be blended.

As a method for forming the base material layer (I), for example, a polyolefin resin composition comprising a polyolefin resin and various additives added as necessary is prepared in advance by a conventional method, and then the polyolefin resin composition The material is melt-kneaded in an extruder and extruded, and a method of forming into a film (including a sheet) using a T die or a circular die, or a polyolefin resin composition dissolved in a solvent such as an organic solvent or After the dispersion, a method of forming a film by a casting method, and coextruding a polyolefin resin composition and an adhesive used to form an adhesive layer (II) described later, Examples include a method in which the formation of the layer (I) and the formation of the pressure-sensitive adhesive layer (II) are simultaneously performed, and any method may be adopted, because it is excellent in productivity. It is preferable to adopt a coextrusion method.
The base material layer (I) thus obtained may have a single layer structure or a multilayer structure of two or more layers.

  The thickness of the base material layer (I) varies depending on the purpose of use and is not particularly limited, but is preferably 20 to 120 μm. When the thickness of the base material layer is less than 20 μm, the strength of the surface protective film to be obtained and the peelability after use may be insufficient. On the other hand, when the thickness exceeds 120 μm, The followability to the unevenness of the adherend surface may be insufficient.

2. Adhesive layer (II)
The hydrogenated product (a) of the styrene-conjugated diene copolymer used in the pressure-sensitive adhesive layer (II) of the surface protective film of the present invention is composed of a styrene polymer block (A) and a conjugated diene polymer block (B ′). (AB ′) n, (AB ′) nA, (AB ′) nX type block copolymer hydrogenated product, styrene polymer block (A), styrene and conjugated diene (AB) n consisting of random polymer blocks (B), (AB) mX type block copolymer hydrogenated product, and a taper in which styrene gradually increases among copolymers of styrene and conjugated diene Examples of the hydrogenated product of the ABC type block copolymer comprising the block (C) include a styrene polymer block (A) and a random polymer block (B) of styrene and a conjugated diene. (AB) n, (A-B) Hydrogenated product of mX type block copolymer, and ABC type block copolymer comprising a tapered block (C) in which styrene gradually increases among copolymers of styrene and conjugated diene A hydrogenated product is employed (where n is 1 or more, m is an integer of 2 or more, and X represents a coupling agent residue). A hydrogenated product of an ABC type block copolymer is more preferable.
The conjugated diene is a hydrocarbon having a structure in which two ethylene bonds are directly bonded by a single bond (C═C—C═C). For example, butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and the like can be mentioned, among which butadiene and isoprene are preferably used. These conjugated dienes may be used alone or in combination of two or more.

In the styrene-conjugated diene copolymer, the number of styrene bonding parts (constituent ratio, weight%) is preferably 3 to 50% by weight, more preferably 5 to 40% by weight, and further preferably 5 to 25% by weight of the total monomers. It is. When the styrene bond content is less than 3% by weight, the cohesive strength of the pressure-sensitive adhesive decreases, and thus adhesive residue may occur on the adherend during re-peeling. Adhesive strength may be insufficient, and it may be difficult to attach a surface protective film (adhesion workability) to an adherend having uneven surfaces.
The total bond content of styrene in the styrene-conjugated diene copolymer is preferably at least 2% by weight, more preferably 3 to 20% by weight.
Furthermore, the vinyl bond content of the conjugated diene moiety in the tapered block (C) in which styrene gradually increases in the random polymer block (B) of styrene and conjugated diene and the conjugated diene is 60% by weight of the total monomers. The amount is more preferably 70% by weight or more, and still more preferably 80% by weight or more. When the vinyl bond content is 60% by weight or less, the adhesive strength may be insufficient. The vinyl bond here refers to a monomer block unit in which a conjugated diene bond is polymerized by a double bond at a 1,2- or 3,4-bond position.

  Styrene content in the terminal styrene polymer block (A) which is a constituent component of the styrene-conjugated diene copolymer and the styrene content in the tapered block (C) where styrene gradually increases in the copolymerization of styrene and conjugated diene The amount is preferably 5 to 60% by weight, more preferably 7 to 40% by weight, based on the total amount of monomers. If the styrene content is less than 5% by weight, the cohesive force at the time of adhesion may be insufficient, and adhesive residue may be generated on the adherend at the time of re-peeling. May be difficult to attach to the adherend.

  It is preferable that at least 80% of the double bond of the conjugated diene moiety in the random polymer block (B) of styrene and conjugated diene is saturated by hydrogenation, more preferably 90% or more, and still more preferably 95- 100%. If the ratio of hydrogenation is less than 80%, heat resistance and weather resistance may be inferior.

  The weight average molecular weight of the hydrogenated styrene-conjugated diene copolymer is preferably 50,000 to 400,000, more preferably 80,000 to 200,000 in terms of polystyrene. If the weight average molecular weight is less than 50,000, the cohesive strength of the adhesive is reduced, and adhesive residue may be generated on the adherend during re-peeling. On the other hand, if the weight average molecular weight exceeds 400,000, the adhesive strength is insufficient. In addition, fluidity may deteriorate.

The polyethylene resin (b) of the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer (II) of the surface protective film of the present invention is not particularly limited, but in consideration of compatibility with the styrene-conjugated diene copolymer, the crystallinity A linear (linear) low density polyethylene (LLDPE) produced by low pressure ion polymerization with a low viscosity is desirable. A density of 0.91 to 0.94 g / cm ³ can be used, and when the density is lower than 0.91 g / cm ³ , an increase in adhesive strength over time is observed. A melt mass flow rate (MFR) of 2 to 12 g / 10 minutes can be used. When the melt mass flow rate (MFR) is lower than 2 g / 10 minutes, the moldability may be deteriorated and surface roughness may be observed, while 12 g / 10 minutes. If it exceeds 1, productivity in the extruder may be lowered.

  In the present invention, the pressure-sensitive adhesive used as the pressure-sensitive adhesive layer (II) includes 10 to 50 polyethylene resins (b) with respect to 100 parts by weight of the hydrogenated product (a) of the styrene-conjugated diene copolymer. By including this part by weight, it is the most characteristic, and by using this specific ratio, the centerline average surface roughness Ra (based on JIS B0601) is 0.1 to 2 μm, particularly on the uneven adherend. When applied to an adherend, a surface protective film having good initial adhesive strength, stable adhesive strength over time and no adhesive residue can be obtained.

  If necessary, for example, an antioxidant, a light stabilizer, and an ultraviolet absorber (UVA) can be added to the pressure-sensitive adhesive as long as the performance of the pressure-sensitive adhesive is not impaired.

  Although the thickness of the said adhesive layer is not specifically limited, It is preferable that it is 3-50 micrometers. When the thickness of the pressure-sensitive adhesive layer is less than 3 μm, the surface protection film obtained may have insufficient adhesiveness and adhesive strength, while when it exceeds 50 μm, the obtained surface protection film is used after being used. When peeling from the body, fogging or adhesive residue may occur on the adherend surface.

3. Surface protection film The method for producing the surface protection film of the present invention is, as described above, for example, a method of laminating and integrating a base material layer and an adhesive layer by coextrusion, such as an inflation method and a T-die method, There is a method in which an adhesive solution is applied and dried by a coating method such as casting.
Among these, the hot melt extrusion method by coextrusion is preferable from the viewpoint of quality and economy.
In the case of co-extrusion, it is common to process the pressure-sensitive adhesive compound into pellets that are previously melted and uniformly mixed, and the purpose of preventing blocking is to prevent re-bonding of the pellets. Additive.
Commonly used anti-blocking agents include metal soap lubricants (calcium stearate, zinc stearate, barium stearate, aluminum stearate, magnesium stearate, and composites thereof), fatty acid amide lubricants, higher fats Family lubricants.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples.

[Examples 1 to 5 and Comparative Examples 1 to 4]
For the base material layer, polyethylene (“Mirason 12” manufactured by Mitsui Chemicals, MFR = 3 g / 10 min (190 ° C.)) was used.
In addition, a hydrogenated product (a) and polyethylene (b) of a styrene-conjugated diene copolymer constituting the pressure-sensitive adhesive layer, and an antioxidant (“Irganox 1010” manufactured by Ciba Specialty Chemicals) A pressure-sensitive adhesive pellet-shaped raw material for a pressure-sensitive adhesive layer in which the materials are melt-kneaded in advance with the formulation shown in Table 1 is prepared. In Table 1, SEBS is an abbreviation for styrene-ethylene-butylene-styrene block copolymer.

  Next, using a co-extruder (T-die method), two-layer co-extrusion of the polyethylene “Mirason 12” for the base layer and the pressure-sensitive adhesive pellets for the pressure-sensitive adhesive layer obtained above was performed, and the base layer And a pressure-sensitive adhesive layer were integrated to obtain a surface protective film having a base material layer thickness of 50 μm, a pressure-sensitive adhesive layer thickness of 10 μm, and a total thickness of 60 μm.

(Evaluation):
The surface protective films obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were evaluated by the following methods.

(1) Uneven film adhesive strength:
The obtained surface protective film was cut to a width of 25 mm, and applied to the surface of a 2 mm uneven acrylic film with Ra = 1.0 μm at a speed of 300 mm / min using a 2 kg pressure roller, and left for 30 minutes. 180 ° peel adhesive strength was measured according to JIS Z0237, and this was defined as initial adhesive strength (N / 25 mm). In addition, all the said operation was implemented on the conditions of 23 degreeC x 65%.

(2) Adhesive strength with time:
A sample prepared in the same procedure as the initial adhesive strength was left in a 60 ° C. atmosphere for 1 week, and then the adhesive strength (N / 25 mm) was measured.

(3) Floating over time:
The surface protective film was affixed to the surface of a 2 mm concavo-convex acrylic film with Ra = 1.0 μm, and it was visually evaluated whether or not floating occurred when left in a 60 ° C. atmosphere for 1 week.

(4) Feeling of peeling:
Sensory evaluation was performed on the workability when the surface protective film was attached to the surface of a 2 mm concavo-convex acrylic film with Ra = 1.0 μm and peeled off.

(5) Adhesive residue over time:
The surface protective film was affixed to the surface of a 2 mm concavo-convex acrylic film with Ra = 1.0 μm and left standing in an atmosphere of 60 ° C. for 1 week, and then the workability when peeled was subjected to sensory evaluation.

  The evaluation results are shown in Table 1.

  From the evaluation results in Table 1, the surface protective films obtained in Examples 1 to 5 mainly use a hydrogenated product of a styrene-conjugated diene copolymer and a polyethylene resin as a pressure-sensitive adhesive layer in a specific ratio. Therefore, it has a good initial adhesive strength, the adhesive strength is stable over time, there is no adhesive residue, and the initial and post-use peel feeling is also good. On the other hand, as can be seen from the evaluation results of Table 1, the surface protective films of Comparative Examples 1 to 4, for example, in Comparative Example 1, the adhesive strength with time increased and the feeling of peeling over time was poor (x evaluation), In Comparative Example 2 where the adhesive residue is also poor, the adhesive strength with time increases, the feeling of peeling over time is poor (x evaluation), and the overall evaluation is bad ( × evaluation), and also in Comparative Example 3 that is outside the range of the specific ratio, it is an evaluation of “do not stick” in the time-dependent adhesive strength evaluation. From these results, any of the Comparative Examples The overall evaluation is bad (× evaluation).

Claims (7)

A surface protective film in which a pressure-sensitive adhesive layer (II) is laminated and integrated with a base material layer (I) made of a polyolefin resin,
The pressure-sensitive adhesive layer (II) contains a hydrogenated product (a) of a styrene-conjugated diene copolymer and a polyethylene resin (b), and the blending ratio of both components is that (a) is 100 parts by weight. And (b) is 10 to 50 parts by weight. Hydrogenated product (a) of styrene-conjugated diene copolymer is
(I) Hydrogenated product of (AB) n or (AB) mX block copolymer comprising a styrene polymer block (A) and a random polymer block (B) of styrene and conjugated diene (A-B) Where n is 1 or more, m is an integer of 2 or more, and X represents a coupling agent residue.
(Ii) (AB ′) n, (AB ′) nA, or (AB ′) nX type comprising a styrene polymer block (A) and a conjugated diene polymer block (B ′) A hydrogenated block copolymer (where n is 1 or more and X represents a coupling agent residue), and (iii) a styrene polymer block (A), a random polymer of styrene and a conjugated diene A hydrogenated product of an ABC type block copolymer comprising a block (B) and a tapered block (C) in which styrene gradually increases among copolymers of styrene and conjugated diene,
The surface protective film according to claim 1, wherein the surface protective film is at least one selected from the group consisting of:   The surface protective film according to claim 1 or 2, wherein the hydrogenated product (a) of the styrene-conjugated diene copolymer is a hydrogenated product of an ABC type block copolymer.   The surface protection film according to any one of claims 1 to 3, wherein the polyethylene resin (b) is a linear low density polyethylene (LLDPE) produced by low pressure ion polymerization.   The surface protection film according to claim 1, wherein the polyolefin resin used for the base material layer (I) is polyethylene.   The surface protective film according to claim 1, which is attached to an adherend having a center line average surface roughness Ra (JIS B0601) of 0.1 to 2 μm.   The surface protective film according to claim 1, wherein the surface protective film is molded by a coextrusion method.