JP2011132267A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protective film having good adhesiveness of each layer of a base layer, an intermediate layer and a pressure-sensitive adhesive layer in the surface protective film and having low adhesiveness between surface protective films (between the base layer and the pressure-sensitive adhesive layer). <P>SOLUTION: The surface protective film includes at least three layers of a base layer, an intermediate layer and a pressure-sensitive adhesive layer, wherein the base layer is formed of a polymer composition containing 40 to 70 wt.% of a copolymer or a hydrogenated product thereof comprising an aromatic vinyl unit and a conjugate diene unit and 30 to 60 wt.% of an acrylic resin; the intermediate layer is formed of a polymer composition containing 0 to 50 wt.% of a copolymer or a hydrogenated product thereof comprising an aromatic vinyl unit and a conjugate diene unit and 50 to 100 wt.% of a polypropylene resin; and the pressure-sensitive adhesive layer is formed of a polymer composition containing 20 to 90 wt.% of an olefin elastomer and 10 to 80 wt.% of a styrene elastomer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface protective film having at least three layers of a base material layer, an intermediate layer and an adhesive layer.

  For the purpose of preventing damage to building materials, resin products such as acrylic resins for optical applications, metal products such as aluminum, glass products, etc., storage, processing, or contamination, these components and products It is known to apply a surface protective film. The surface protective film is generally composed of a base material layer, an intermediate layer, and an adhesive layer for adhering to the adherend.

  The base material layer is usually formed of a polyolefin resin such as polyethylene and polypropylene, a polyester resin such as polyethylene terephthalate, and the like, and is known as a roll with a release film attached to the adhesive layer. From the viewpoint of not generating a large amount of waste, a surface protective film that can be easily fed out from a roll without a release film is known (Patent Documents 1 to 3).

  By the way, since the surface protective film is generally wound in a roll shape, the adhesive layer and the base material layer in the surface protective film are overlapped, and when the film is unwound from the roll shape, a pattern such as a wrinkle is formed on the film. There is a problem that a zipping phenomenon occurs. In order to prevent such a zipping phenomenon from occurring, it is necessary to reduce the peeling resistance between the base material layer and the adhesive layer between the surface protective films, but if the peeling resistance is reduced, the surface protective film itself There was a problem that peeling of the film occurred. Therefore, there is a demand for a surface protective film having good adhesion between the layers in the surface protective film and having a small peeling resistance between the base material layer and the adhesive layer between the surface protective films.

JP 2003-327936 A JP 2004-2624 A JP 2008-214492 A

  In the present invention, the adhesiveness of each layer of the base material layer, the intermediate layer and the adhesive layer in the surface protective film is good, and the peel resistance (adhesiveness) between the surface protective films (base material layer-adhesive layer) An object of the present invention is to provide a surface protective film having a small thickness.

  In order to solve such problems, as a result of intensive studies, the substrate layer in the surface protective film is a copolymer composed of an aromatic vinyl unit and a conjugated diene unit (hereinafter referred to as an aromatic vinyl-conjugated diene copolymer). Or a hydrogenated product thereof, and a polymer composition containing an acrylic resin in a specific ratio, thereby improving the adhesion of the base layer, intermediate layer and adhesive layer in the surface protective film. And obtained knowledge that it is useful for reducing the adhesiveness between the surface protective films (base material layer-adhesive layer). The present invention has been completed based on such findings.

Item 1. A surface protective film having at least three layers of a base material layer, an intermediate layer and an adhesive layer,
The base material layer is formed from a polymer composition containing 40 to 70% by weight of an aromatic vinyl-conjugated diene copolymer or a hydrogenated product thereof and 30 to 60% by weight of an acrylic resin,
The intermediate layer is formed from a polymer composition containing 0 to 50% by weight of an aromatic vinyl-conjugated diene copolymer or a hydrogenated product thereof and 50 to 100% by weight of a polypropylene resin,
The surface protection film in which an adhesion layer is formed from a polymer composition containing 20 to 90% by weight of an olefin-based elastomer and 10 to 80% by weight of a styrene-based elastomer.

  Item 2. In the polymer composition for forming the base material layer, the content of aromatic vinyl units in the aromatic vinyl-conjugated diene copolymer is 5 to 40% by weight, and the content of conjugated diene units is 60 to 95. Item 2. The surface protective film according to Item 1, which is% by weight.

  Item 3. Item 3. The surface protective film according to Item 1 or 2, wherein the polymer composition forming the adhesive layer further comprises 45 parts by weight or less of polypropylene resin with respect to 100 parts by weight of the total amount of olefin elastomer and styrene elastomer.

Hereinafter, each component in each layer will be described in detail.
Base material layer The base material layer is a layer provided to reduce the peeling force (unwinding force) when unwinding the surface protection film from the product roll, and is an aromatic vinyl-conjugated diene copolymer or its It is formed from a polymer composition containing a hydrogenated product and an acrylic resin.

  By using an aromatic vinyl-conjugated diene copolymer or a hydrogenated product thereof, the adhesion between the base material layer and the intermediate layer in the surface protective film is improved, and between the surface protective films (base material layer- The effect of reducing the peel resistance between the adhesive layers) is obtained.

  Here, the aromatic vinyl is an aromatic hydrocarbon having at least one vinyl group, such as styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene and the like can be mentioned. These can be used individually by 1 type or in mixture of 2 or more types. Among these, styrene is preferable.

  The conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3- Examples thereof include butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, and 1,3-hexadiene. These can be used individually by 1 type or in mixture of 2 or more types. Among these, butadiene and 2-methyl-1,3-butadiene (isoprene) are preferable.

  The hydrogenated aromatic vinyl-conjugated diene copolymer is obtained by saturating a double bond derived from a conjugated diene by hydrogenation (for example, a nickel catalyst) by a known method. Thereby, in addition to the above effects, a more stable resin excellent in heat resistance, chemical resistance, durability and the like can be obtained, which is preferable.

  The hydrogenation rate of the hydrogenated aromatic vinyl-conjugated diene copolymer is preferably 85% or more of double bonds derived from the conjugated diene in the copolymer, more preferably 90% or more, More preferably, it is 95% or more. This hydrogenation rate can be confirmed by measuring using a nuclear magnetic resonance apparatus (NMR).

  The content of aromatic vinyl units in the aromatic vinyl-conjugated diene copolymer or its hydrogenated product is usually 5 to 40% by weight, preferably 5 to 15% by weight. Moreover, the content rate of a conjugated diene unit is 60 to 95 weight% normally, Preferably it is 85 to 95 weight%. The content of aromatic vinyl units can be measured using an ultraviolet spectrophotometer or a nuclear magnetic resonance apparatus (NMR), and the content of conjugated diene units can be measured using a nuclear magnetic resonance apparatus (NMR). it can.

  The hardness (JIS K6253 durometer type A) of the aromatic vinyl-conjugated diene copolymer or its hydrogenated product is usually about 40 to 90, preferably about 55 to 85.

  In addition, the specific gravity (ASTMD 297) of the aromatic vinyl-conjugated diene copolymer or hydrogenated product thereof is usually about 0.85 to 1.0, and MFR (ASTM D1238: 230 ° C., 21.2 N) is Usually, it is about 2 to 6 g / 10 minutes.

  The weight average molecular weight (Mw) of the aromatic vinyl-conjugated diene copolymer or hydrogenated product thereof is, for example, usually about 100,000 to 500,000, preferably about 150,000 to 300,000. The weight average molecular weight can be measured using commercially available standard gel permeation chromatography (GPC).

  The content ratio of the aromatic vinyl-conjugated diene copolymer or the hydrogenated product thereof is preferably 40 to 70% by weight, more preferably 40 to 60% by weight in the polymer composition forming the base layer. More preferably, it is 45 to 55% by weight.

  When the content ratio of the aromatic vinyl-conjugated diene copolymer or the hydrogenated product thereof is less than 40% by weight, the peel resistance tends to increase and zipping tends to occur, and the content ratio is 70% by weight. If it exceeds%, the peel resistance increases, and zipping tends to occur.

(2) Acrylic resin Examples of the acrylic resin include homopolymers or copolymers of (meth) acrylic acid and (meth) acrylic acid alkyl esters.

  Here, (meth) acrylic acid means methacrylic acid or acrylic acid. The alkyl chain in the (meth) acrylic acid alkyl ester preferably has 1 to 6 carbon atoms, and more preferably has 1 to 4 alkyl chains. Specific examples of the (meth) acrylic acid alkyl ester include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, acrylic acid 2 -Ethylhexyl, 2-ethylhexyl methacrylate, etc. are mentioned. The homopolymer or copolymer of (meth) acrylic acid alkyl ester can be produced by a known polymerization method such as solution polymerization method, emulsion polymerization method, suspension polymerization method, bulk polymerization method and the like. Among these, a homopolymer (PMMA) of methyl methacrylate (MMA) is preferable.

  The content of the acrylic resin is preferably 30 to 60% by weight, more preferably 40 to 60% by weight, and still more preferably 45 to 55% by weight in the polymer composition forming the base layer.

  When the content ratio of the acrylic resin is less than 30% by weight, the peeling resistance increases, and zipping tends to occur. When the content ratio exceeds 60% by weight, the peeling resistance increases. Also, zipping tends to occur.

  In addition to the resin, an antioxidant, a light stabilizer, an ultraviolet absorber, a softening agent and the like can be blended to such an extent that the effects of the present invention are not impaired, thereby forming a base material layer.

An intermediate | middle layer intermediate | middle layer is a layer provided in order to provide rigidity (waist) to a surface protection film, and to adhere | attach a base material layer and an adhesion layer.

  Examples of the resin forming the intermediate layer include a polypropylene resin or a polymer composition of a polypropylene resin and an aromatic vinyl-conjugated diene copolymer or a hydrogenated product thereof.

  Examples of the polypropylene resin include polypropylene resin, a mixture of polypropylene resin and polyethylene resin, and the like. The polypropylene resin is preferably a polypropylene resin, that is, a propylene homopolymer (homo PP), from the viewpoint that the rigidity of the film can be increased and good handling properties can be imparted. As a polypropylene resin, an isotactic index (hereinafter referred to as II value) is preferably 95% or more, and more preferably 98% or more.

  Moreover, in a polypropylene resin, it is preferable to add a nucleating agent (crystallization nucleating agent) from the viewpoint that higher rigidity can be obtained. The nucleating agent is not particularly limited, and various inorganic compounds, various carboxylic acids or metal salts thereof, dibenzylidene sorbitol compounds, aryl phosphate compounds, cyclic polyvalent metal aryl phosphate compounds, and aliphatic monocarboxylic acid alkalis. Examples thereof include a metal salt or a mixture of basic aluminum, lithium, hydroxy, carbonate, hydrate, and α crystal nucleating agent such as various polymer compounds. These crystallization nucleating agents can be used alone or in combination of two or more materials.

  The MFR of the polypropylene resin can be measured according to JIS K7210, and is preferably 0.5 to 20 g / 10 min under the measurement conditions of a temperature of 230 ° C. and a load of 21.18 N, and 1.0 to 15 g / More preferably, it is 10 minutes. It is preferable for the MFR of the polypropylene resin to be in the above range because it is suitable for extrusion molding.

  The content rate of the polypropylene resin in the polymer composition in the intermediate layer is 50 to 100% by weight. When the content of the polypropylene resin is less than 50% by weight, the rigidity (waist) is weak and the handling property as a film tends to deteriorate. Moreover, in order to improve the adhesiveness of a base material layer and an intermediate | middle layer, when the content rate of the aromatic vinyl-conjugated diene copolymer in the base material layer or its hydrogenation rate is 50 weight% or less The polymer composition forming the intermediate layer preferably contains an aromatic vinyl-conjugated diene copolymer or its hydrogenation rate. In that case, when the polymer composition is a mixture of a polypropylene resin and an aromatic vinyl-conjugated diene copolymer or a hydrogenation rate thereof, the content of the polypropylene resin is 90 to 50% by weight. Is preferable, and 80 to 60% by weight is more preferable.

  As the aromatic vinyl-conjugated diene copolymer used for forming the intermediate layer, the same aromatic vinyl-conjugated diene copolymer used for forming the base material layer is used. be able to.

The pressure-sensitive adhesive layer is a layer provided for bonding the adherend and the surface protective film. The adhesive layer is formed of a resin composition containing a styrene thermoplastic elastomer and an olefin elastomer.

  The styrene thermoplastic elastomer has a polystyrene phase as a hard segment. Specific examples include styrene-butadiene copolymers, styrene-isobutylene copolymers, and hydrogenated products thereof.

  Examples of the olefin elastomer include an α-olefin copolymer having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and may be a binary copolymer or a ternary copolymer.

  Specific examples include an ethylene-propylene copolymer, an ethylene-1-butene copolymer, a propylene-1-butene copolymer, and a propylene-ethylene-1-butene copolymer.

  The content ratio of the styrene-based thermoplastic elastomer and the olefin-based elastomer that forms the adhesive layer is preferably styrene-based thermoplastic elastomer / olefin-based elastomer = 20 to 90% by weight / 10 to 80% by weight.

  The content of the styrenic thermoplastic elastomer is preferably 20% by weight or more in order to give the necessary adhesive strength, and the adherend is not peeled off when the film is peeled off without reducing the rigidity of the adhesive layer itself. 90 weight% or less is preferable from the point that the sticking trace does not remain on the surface.

  In addition, the content of the olefin-based elastomer is 80% by weight or less from the point that when the film is peeled off from the adherend, the adhesive layer itself does not decrease the rigidity of the pressure-sensitive adhesive layer itself, and no sticking trace remains on the adherend surface. preferable.

  A polypropylene resin can be further added to the adhesive layer.

  Examples of the polypropylene resin include a propylene homopolymer (homo PP), a propylene-ethylene copolymer having a small amount of ethylene as a copolymerization component, and the like. The copolymerization ratio of ethylene in the propylene-ethylene copolymer is preferably 9% by weight or less. Homo PP preferably has an isotactic index of 95% or higher, more preferably 98% or higher. The propylene-ethylene copolymer may be a random copolymer or a block copolymer, and may contain a nucleating agent (crystallization nucleating agent). As the nucleating agent, those mentioned in the intermediate layer can be used.

  Moreover, adhesive force can be adjusted by adding a polypropylene resin.

  The content of the polypropylene resin is preferably 45 parts by weight or less with respect to 100 parts by weight of the resin group composition of the styrene thermoplastic elastomer and olefin elastomer. When the content of the polypropylene resin is 45 parts by weight or less, the adhesive layer can provide the adhesive force required for the surface protective film.

  In the adhesive layer, in addition to the above-mentioned polymer, a known softener, ultraviolet absorber, light stabilizer, if necessary, to the extent that the adhesiveness of the adhesive layer and the contamination to the adherend are not impaired. Additives such as pigments and fillers can also be added.

Surface protective film The surface protective film of the present invention has a structure in which an intermediate layer is sandwiched between a base material layer and an adhesive layer. Although it does not specifically limit as a manufacturing method of a surface protection film, For example, In order to form the resin composition for forming the said base material layer, the resin composition for forming an intermediate | middle layer, and an adhesion layer Each of the resin compositions was dry blended, each composition was supplied to the extruder in this order, extruded into a film at a barrel temperature of about 160 to 250 ° C, and cooled while passing through a cooling roll of about 20 to 40 ° C. And can be obtained. Further, after each layer resin is once obtained as a pellet, it may be extruded as described above.

  The surface protective film of the present invention preferably has a total thickness of 20 to 80 μm.

As a ratio of the thickness of the intermediate layer of the surface protective film, when the thickness of the base material layer is 1, 0.125 to 38 is preferable, and 0.5 to 10 is more preferable. Also,
As a ratio of the thickness of the adhesive layer, when the thickness of the base material layer is 1, 0.5 to 20 is preferable, and 0.5 to 10 is more preferable.

  As for the thickness of the base material layer of a surface protection film, 2-40 micrometers is preferable. The thickness of the intermediate layer is preferably 5 to 76 μm. The thickness of the adhesive layer is preferably 2 to 40 μm. When the thickness of each layer is within this range, excellent film-forming properties are exhibited while having good adhesiveness and peelability.

  The surface protective film of the present invention improves the adhesiveness of each layer of the base material layer, the intermediate layer and the adhesive layer in the surface protective film, particularly by forming the base material layer and the intermediate layer with a specific polymer composition. can do. Furthermore, the adhesiveness between surface protection films (base material layer-adhesion layer) can be reduced.

  The present invention will be described more specifically with reference to the following examples and comparative examples. In addition, this invention is not limited to the following embodiment.

  The resins and elastomers used in the base layer, intermediate layer and adhesive layer produced in the examples and comparative examples are shown below. The MFR was measured according to JIS K7121.

SEBS-1: Kraton MD6945 (hydrogenated product of styrene-butadiene copolymer) manufactured by Kraton Polymer Japan Co., Ltd.
SEBS-2: HIBLER 7311 manufactured by Kuraray Co., Ltd. (hydrogenated product of styrene-isoprene copolymer)
SEBS-3: Tuftec M1913 (acid-modified product of hydrogenated styrene-butadiene copolymer) manufactured by Asahi Kasei Corporation
PMMA: Parapet G (polymethyl methacrylate) manufactured by Kuraray Co., Ltd.
Polypropylene: PC412A manufactured by Sun Allomer Co., Ltd.
Olefin-based elastomer: propylene-ethylene-1-butene copolymer (MFR: 6 g / 10 min, density: 0.868 g / cm ³ )
Styrene elastomer: Styrene-isobutylene copolymer (MFR: 6 g / 10 min, density: 0.946 g / cm ³ )

Examples 1-15 and Comparative Examples 1-5
By dry blending, the resin for the base layer, the resin for the intermediate layer, and the resin for the adhesive layer are formed so that the resin forming each layer of the base layer, the intermediate layer, and the adhesive layer has the ratio shown in Table 1 or 2. Prepared. The prepared base layer resin, intermediate layer resin, and adhesive layer resin were supplied in the same order to each extruder adjusted to a barrel temperature of 160 to 260 ° C. And it extrude | pushed out from T dice | dies heated to 230 degreeC, it solidified by cooling with the take-up roll of 20 degreeC of preset temperature, and wound up in the unstretched state, and obtained the surface protection film. The thickness of the surface protective film obtained at this time was 5 μm for the base material layer, 35 μm for the intermediate layer, 10 μm for the adhesive layer, and the total thickness was 50 μm.

About the obtained surface protection film, peeling resistance, zipping, film forming property, and Young's modulus were measured by the following measuring methods. The evaluation results are shown in Tables 4-6.
-Film-forming property In the manufacturing process of a surface protection film, it evaluated by the following references | standards.

○: A surface protective film could be formed without any problem.
X: Winding around the cooling roll occurred, the sample could not be collected, or a beautiful film could not be formed when the layers were laminated due to different resin flow rates.

・ Peeling resistance [sample pasting]
Two samples having a width of 50 mm and a length of 150 mm were cut out from the sample roll, and bonded together in an atmosphere of 23 ° C. so that the base material layer and the adhesive layer overlapped. Thereafter, the sample was subjected to pressure bonding with a pressure roller under conditions of pressure: 3.0 MPa and speed: 5.0 m / min to obtain a measurement sample.
[Peel resistance measurement]
The measurement sample obtained by the above method was allowed to stand at 40 ° C. under a pressure of 7.14 KPa for 72 hours. Then, using a peeling tester (Peeling TESTER HEIDON-17 manufactured by Shinto Kagaku Co., Ltd.), the peeling resistance between the base material layer and the adhesive layer bonded by the pressure bonding under the setting condition of peeling speed: 1.0 m / min. The force was measured.

  At this time, the average value of 10 local maximum points in the measurement chart was defined as the peel resistance. Those having a peel resistance of 5 N / 25 mm or less were evaluated as good.

[Zipping evaluation]
Using the chart obtained by the measurement of the peeling resistance force, the 10-point average value of the maximum value is the maximum value, the 10-point average value of the minimum value is the minimum value, and the difference is A,
○: 0 ≦ A ≦ 0.5N / 25mm
Δ: 0.5 <A ≦ 1.5 N / 25 mm
×: 1.5N / 25mm <A
It was.

-Young's modulus Young's modulus was measured for the sample for measurement based on ASTM D882-64T. The higher the Young's modulus, the better the waist (rigidity), and the better. The Young's modulus of 50 MPa or less was judged to be inferior in rigidity because it was soft.

Claims (3)

A surface protective film having at least three layers of a base material layer, an intermediate layer and an adhesive layer,
The base material layer is formed from a polymer composition containing 40 to 70% by weight of a copolymer comprising an aromatic vinyl unit and a conjugated diene unit or a hydrogenated product thereof, and 30 to 60% by weight of an acrylic resin.
The intermediate layer is formed from a polymer composition containing 0 to 50% by weight of a copolymer comprising an aromatic vinyl unit and a conjugated diene unit or a hydrogenated product thereof and 50 to 100% by weight of a polypropylene resin,
The surface protection film in which an adhesion layer is formed from a polymer composition containing 20 to 90% by weight of an olefin-based elastomer and 10 to 80% by weight of a styrene-based elastomer. In the polymer composition forming the base material layer, the content of the aromatic vinyl unit in the copolymer comprising the aromatic vinyl unit and the conjugated diene unit is 5 to 40% by weight, and the content of the conjugated diene unit The surface protective film according to claim 1, wherein is from 60 to 95% by weight. The surface protection film according to claim 1 or 2, wherein the polymer composition for forming the adhesive layer further comprises 45 parts by weight or less of polypropylene resin with respect to 100 parts by weight of the total amount of olefin elastomer and styrene elastomer.